1.
Manufacturing
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Manufacturing is the value added to production of merchandise for use or sale using labour and machines, tools, chemical and biological processing, or formulation. Manufacturing engineering or manufacturing process are the steps through which raw materials are transformed into a final product, the manufacturing process begins with the product design, and materials specification from which the product is made. These materials are modified through manufacturing processes to become the required part. Manufacturing takes turns under all types of economic systems, in a free market economy, manufacturing is usually directed toward the mass production of products for sale to consumers at a profit. In a collectivist economy, manufacturing is more directed by the state to supply a centrally planned economy. In mixed market economies, manufacturing occurs under some degree of government regulation, modern manufacturing includes all intermediate processes required the production and integration of a products components. Some industries, such as semiconductor and steel manufacturers use the term fabrication instead, the manufacturing sector is closely connected with engineering and industrial design. Examples of major manufacturers in North America include General Motors Corporation, General Electric, Procter & Gamble, General Dynamics, Boeing, Pfizer, examples in Europe include Volkswagen Group, Siemens, and Michelin. Examples in Asia include Sony, Huawei, Lenovo, Toyota, Samsung, in its earliest form, manufacturing was usually carried out by a single skilled artisan with assistants. In much of the world, the guild system protected the privileges. Before the Industrial Revolution, most manufacturing occurred in rural areas, entrepreneurs organized a number of manufacturing households into a single enterprise through the putting-out system. Toll manufacturing is an arrangement whereby a first firm with specialized equipment processes raw materials or semi-finished goods for a second firm, manufacturing provides important material support for national infrastructure and for national defense. On the other hand, most manufacturing may involve significant social and environmental costs, the clean-up costs of hazardous waste, for example, may outweigh the benefits of a product that creates it. Hazardous materials may expose workers to health risks and these costs are now well known and there is effort to address them by improving efficiency, reducing waste, using industrial symbiosis, and eliminating harmful chemicals. The negative costs of manufacturing can also be addressed legally, developed countries regulate manufacturing activity with labor laws and environmental laws. Across the globe, manufacturers can be subject to regulations and pollution taxes to offset the costs of manufacturing activities. Labor unions and craft guilds have played a role in the negotiation of worker rights. Environment laws and labor protections that are available in developed nations may not be available in the third world, tort law and product liability impose additional costs on manufacturing
2.
Gel
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A gel is a solid jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, by weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional cross-linked network within the liquid. It is the crosslinking within the fluid that gives a gel its structure, in this way gels are a dispersion of molecules of a liquid within a solid in which the solid is the continuous phase and the liquid is the discontinuous phase. The word gel was coined by 19th-century Scottish chemist Thomas Graham by clipping from gelatine, gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through surface tension effects. This internal network structure may result from physical bonds or chemical bonds, virtually any fluid can be used as an extender including water, oil, and air. Both by weight and volume, gels are mostly fluid in composition, edible jelly is a common example of a hydrogel and has approximately the density of water. Polyionic polymers are polymers with a functional group. The ionic charges prevent the formation of tightly coiled polymer chains and this allows them to contribute more to viscosity in their stretched state, because the stretched-out polymer takes up more space. A hydrogel is a network of polymer chains that are hydrophilic, hydrogels are highly absorbent natural or synthetic polymeric networks. Hydrogels also possess a degree of flexibility very similar to tissue, due to their significant water content. The first appearance of the term hydrogel in the literature was in 1894, common uses for hydrogels include, Scaffolds in tissue engineering. When used as scaffolds, hydrogels may contain human cells to repair tissue and they mimic 3D microenvironment of cells. Hydrogel-coated wells have been used for cell culture Environmentally sensitive hydrogels and these hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change. Wound gels are excellent for helping to create or maintain a moist environment, reservoirs in topical drug delivery, particularly ionic drugs, delivered by iontophoresis. Natural hydrogel materials are being investigated for tissue engineering, these materials include agarose, methylcellulose, hyaluronan, an organogel is a non-crystalline, non-glassy thermoreversible solid material composed of a liquid organic phase entrapped in a three-dimensionally cross-linked network. The liquid can be, for example, a solvent, mineral oil. The solubility and particle dimensions of the structurant are important characteristics for the elastic properties, often, these systems are based on self-assembly of the structurant molecules. Organogels have potential for use in a number of applications, such as in pharmaceuticals, cosmetics, art conservation, a xerogel /ˈzɪəroʊˌdʒɛl/ is a solid formed from a gel by drying with unhindered shrinkage
3.
Liquid
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A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume independent of pressure. As such, it is one of the four states of matter. A liquid is made up of tiny vibrating particles of matter, such as atoms, water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container, most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, a distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in form as interstellar clouds or in plasma form within stars. Liquid is one of the four states of matter, with the others being solid, gas. Unlike a solid, the molecules in a liquid have a greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, a liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, if liquid is placed in a bag, it can be squeezed into any shape. These properties make a suitable for applications such as hydraulics. Liquid particles are bound firmly but not rigidly and they are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its point, the cohesive forces that bind the molecules closely together break. If the temperature is decreased, the distances between the molecules become smaller, only two elements are liquid at standard conditions for temperature and pressure, mercury and bromine. Four more elements have melting points slightly above room temperature, francium, caesium, gallium and rubidium, metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams
4.
Gas
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Gas is one of the four fundamental states of matter. A pure gas may be made up of atoms, elemental molecules made from one type of atom. A gas mixture would contain a variety of pure gases much like the air, what distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer, the interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. One type of commonly known gas is steam, the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention, high-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these states of matter see list of states of matter. The only chemical elements which are stable multi atom homonuclear molecules at temperature and pressure, are hydrogen, nitrogen and oxygen. These gases, when grouped together with the noble gases. Alternatively they are known as molecular gases to distinguish them from molecules that are also chemical compounds. The word gas is a neologism first used by the early 17th-century Flemish chemist J. B. van Helmont, according to Paracelsuss terminology, chaos meant something like ultra-rarefied water. An alternative story is that Van Helmonts word is corrupted from gahst and these four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, and consequently have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another, transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion, the drifting smoke particles in the image provides some insight into low pressure gas behavior
5.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
6.
Thermal conductivity
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In physics, thermal conductivity is the property of a material to conduct heat. It is evaluated primarily in terms of Fouriers Law for heat conduction, heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are used in heat sink applications. The thermal conductivity of a material may depend on temperature, the reciprocal of thermal conductivity is called thermal resistivity. Thermal conductivity is actually a tensor, which means it is possible to have different values in different directions, in SI units, thermal conductivity is measured in watts per meter-kelvin. The dimension of thermal conductivity is M1L1T−3Θ−1 and these variables are mass, length, time, and temperature. In Imperial units, thermal conductivity is measured in BTU/, other units which are closely related to the thermal conductivity are in common use in the construction and textile industries. The construction industry makes use of such as the R-value. Although related to the conductivity of a material used in an insulation product, R-. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry, there are a number of ways to measure thermal conductivity. Each of these is suitable for a range of materials, depending on the thermal properties. There is a distinction between steady-state and transient techniques, in general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward, the disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar is the most common used for consolidated rock solids. Thermal conductivity is important in science, research, electronics, building insulation and related fields. Several materials are shown in the list of thermal conductivities and these should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper, aluminium, the reciprocal of thermal conductivity is thermal resistivity, usually expressed in kelvin-meters per watt. For a given thickness of a material, that particular constructions thermal resistance, unfortunately, there are differing definitions for these terms
7.
Transparency and translucency
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In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snells Law, in other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. The opposite property of translucency is opacity, transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. When light encounters a material, it can interact with it in different ways. These interactions depend on the wavelength of the light and the nature of the material, photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as glass and clean water, transmit much of the light that falls on them and reflect little of it. Many liquids and aqueous solutions are highly transparent, absence of structural defects and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque, many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of light frequencies. They absorb certain portions of the spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation and this is what gives rise to color. The attenuation of light of all frequencies and wavelengths is due to the mechanisms of absorption. Transparency can provide almost perfect camouflage for animals able to achieve it and this is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent, at the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include, Crystalline structure, whether or not the atoms or molecules exhibit the long-range order evidenced in crystalline solids, glassy structure, scattering centers include fluctuations in density or composition. Microstructure, scattering centers include internal surfaces such as boundaries, crystallographic defects
8.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
9.
Scattering
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In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections that undergo scattering are often called diffuse reflections and unscattered reflections are called specular reflections, scattering may also refer to particle-particle collisions between molecules, atoms, electrons, photons and other particles. The effects of such features on the path of almost any type of propagating wave or moving particle can be described in the framework of scattering theory. Particle-particle scattering theory is important in such as particle physics, atomic, molecular. When radiation is scattered by one localized scattering center, this is called single scattering. It is very common that scattering centers are grouped together, in cases, radiation may scatter many times. This type of scattering would be exemplified by an electron being fired at an atomic nucleus. In this case, the exact position relative to the path of the electron is unknown and would be unmeasurable. Single scattering is often described by probability distributions. This is exemplified by a beam passing through thick fog. Multiple scattering is highly analogous to diffusion, and the multiple scattering. Optical elements designed to produce multiple scattering are thus known as diffusers, coherent backscattering, an enhancement of backscattering that occurs when coherent radiation is multiply scattered by a random medium, is usually attributed to weak localization. Not all single scattering is random, however, a well-controlled laser beam can be exactly positioned to scatter off a microscopic particle with a deterministic outcome, for instance. Such situations are encountered in radar scattering as well, where the targets tend to be macroscopic objects such as people or aircraft, similarly, multiple scattering can sometimes have somewhat random outcomes, particularly with coherent radiation. The random fluctuations in the scattered intensity of coherent radiation are called speckles. Speckle also occurs if multiple parts of a coherent wave scatter from different centers, in certain rare circumstances, multiple scattering may only involve a small number of interactions such that the randomness is not completely averaged out. These systems are considered to be some of the most difficult to model accurately, the description of scattering and the distinction between single and multiple scattering are tightly related to wave–particle duality. Scattering theory is a framework for studying and understanding the scattering of waves and particles, prosaically, wave scattering corresponds to the collision and scattering of a wave with some material object, for instance sunlight scattered by rain drops to form a rainbow
10.
Expanded polystyrene
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Polystyrene /ˌpɒliˈstaɪriːn/ is a synthetic aromatic polymer made from the monomer styrene. Polystyrene can be solid or foamed, general-purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight and it is a rather poor barrier to oxygen and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year, Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, as a thermoplastic polymer, polystyrene is in a solid state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled and this temperature behavior is exploited for extrusion and also for molding and vacuum forming, since it can be cast into molds with fine detail. Polystyrene is very slow to biodegrade and is therefore a focus of controversy among environmentalists, Polystyrene was discovered in 1839 by Eduard Simon, an apothecary from Berlin. From storax, the resin of the American sweetgum tree Liquidambar styraciflua, he distilled an oily substance, several days later, Simon found that the styrol had thickened into a jelly he dubbed styrol oxide because he presumed an oxidation. By 1845 Jamaican-born chemist John Buddle Blyth and German chemist August Wilhelm von Hofmann showed that the transformation of styrol took place in the absence of oxygen. They called the product metastyrol, analysis showed that it was identical to Simons Styroloxyd. In 1866 Marcelin Berthelot correctly identified the formation of metastyrol/Styroloxyd from styrol as a polymerization process, about 80 years later it was realized that heating of styrol starts a chain reaction that produces macromolecules, following the thesis of German organic chemist Hermann Staudinger. This eventually led to the substance receiving its present name, polystyrene, the company I. G. Farben began manufacturing polystyrene in Ludwigshafen, about 1931, hoping it would be a suitable replacement for die-cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a tube and cutter. In 1941, Dow Chemical invented a Styrofoam process, before 1949, the chemical engineer Fritz Stastny developed pre-expanded PS beads by incorporating aliphatic hydrocarbons, such as pentane. These beads are the raw material for moulding parts or extruding sheets, BASF and Stastny applied for a patent that was issued in 1949. The moulding process was demonstrated at the Kunststoff Messe 1952 in Düsseldorf, the crystal structure of isotactic polystyrene was reported by Giulio Natta. In 1954, the Koppers Company in Pittsburgh, Pennsylvania, developed expanded polystyrene foam under the trade name Dylite, in 1960, Dart Container, the largest manufacturer of foam cups, shipped their first order. In 1988, the first U. S. ban of general polystyrene foam was enacted in Berkeley, in chemical terms, polystyrene is a long chain hydrocarbon wherein alternating carbon centers are attached to phenyl groups
11.
Supercritical drying
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Supercritical drying is a process to remove liquid in a precise and controlled way. As the substance in a liquid body crosses the boundary from liquid to gas, when this happens within a heterogeneous environment, surface tension in the liquid body pulls against any solid structures the liquid might be in contact with. To avoid this, the sample can be brought via two possible paths from the liquid phase to the gas phase without crossing the liquid–gas boundary on the phase diagram. In freeze-drying, this means going around to the left, however, some structures are disrupted even by the solid–gas boundary. Supercritical drying, on the hand, goes around the line to the right. This route from liquid to gas does not cross any phase boundary, instead passing through the supercritical region, densities of the liquid phase and vapor phase become equal at critical point of drying. Fluids suitable for drying include carbon dioxide and freon. Nitrous oxide has similar physical behavior to carbon dioxide, but is an oxidizer in its supercritical state. Supercritical water is inconvenient due to heat damage to a sample at its critical point temperature. In most such processes, acetone is first used to wash away all water, the acetone is then washed away with high pressure liquid carbon dioxide, the industry standard now that freon is unavailable. Tousimis MEMS Critical Point Dryers Critical Point Dryers Technique
12.
Capillary action
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Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. It occurs because of forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension, the first recorded observation of capillary action was by Leonardo da Vinci. A former student of Galileo, Niccolò Aggiunti, was said to have investigated capillary action, boyle then reported an experiment in which he dipped a capillary tube into red wine and then subjected the tube to a partial vacuum. Some thought that liquids rose in capillaries because air couldnt enter capillaries as easily as liquids, others thought that the particles of liquid were attracted to each other and to the walls of the capillary. They derived the Young–Laplace equation of capillary action, by 1830, the German mathematician Carl Friedrich Gauss had determined the boundary conditions governing capillary action. In 1871, the British physicist William Thomson determined the effect of the meniscus on a liquids vapor pressure—a relation known as the Kelvin equation, German physicist Franz Ernst Neumann subsequently determined the interaction between two immiscible liquids. Albert Einsteins first paper, which was submitted to Annalen der Physik in 1900, was on capillarity, a common apparatus used to demonstrate the first phenomenon is the capillary tube. When the lower end of a glass tube is placed in a liquid, such as water. Adhesion occurs between the fluid and the inner wall pulling the liquid column up until there is a sufficient mass of liquid for gravitational forces to overcome these intermolecular forces. So, a tube will draw a liquid column higher than a wider tube will. Capillary action is essential for the drainage of constantly produced tear fluid from the eye, wicking is the absorption of a liquid by a material in the manner of a candle wick. Paper towels absorb liquid through capillary action, allowing a fluid to be transferred from a surface to the towel, the small pores of a sponge act as small capillaries, causing it to absorb a large amount of fluid. Some textile fabrics are said to use capillary action to wick sweat away from the skin and these are often referred to as wicking fabrics, after the capillary properties of candle and lamp wicks. Capillary action is observed in thin layer chromatography, in which a solvent moves vertically up a plate via capillary action, in this case the pores are gaps between very small particles. Capillary action draws ink to the tips of fountain pen nibs from a reservoir or cartridge inside the pen, in hydrology, capillary action describes the attraction of water molecules to soil particles. Capillary action is responsible for moving groundwater from wet areas of the soil to dry areas, differences in soil potential drive capillary action in soil. Thus the thinner the space in which the water can travel, for a water-filled glass tube in air at standard laboratory conditions, γ =0.0728 N/m at 20 °C, ρ =1000 kg/m3, and g =9.81 m/s2
13.
Evaporation
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Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
14.
Silica gel
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Silica gel is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate. Silica gel contains a nano-porous silica micro-structure, suspended inside a liquid, most applications of silica gel require it to be dried, in which case it is called silica xerogel. For practical purposes, silica gel is often interchangeable with silica xerogel, silica xerogel is tough and hard, it is more solid than common household gels like gelatin or agar. It is a naturally occurring mineral that is purified and processed into either granular or beaded form, as a desiccant, it has an average pore size of 2.4 nanometers and has a strong affinity for water molecules. Silica gel is most commonly encountered in life as beads in a small paper packet. In this form, it is used as a desiccant to control humidity to avoid spoilage or degradation of some goods. Because silica gel can have added chemical indicators and absorbs moisture very well, silica gel was in existence as early as the 1640s as a scientific curiosity. It was used in World War I for the adsorption of vapors, the synthetic route for producing silica gel was patented by chemistry professor Walter A. Patrick at Johns Hopkins University in 1918. Type A - clear pellets, approximate pore diameter,2.5 nm, drying and moistureproof properties, can be used as catalyst carriers, adsorbents, separators and variable-pressure adsorbent. Type B - translucent white pellets, pore diameter,4. 5-7.0 nm, liquid adsorbents, drier and perfume carriers, also may be used as catalyst carriers, type C - translucent, micro-pored structure, raw material for preparation of silica gel cat litter. Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent, silica alumina gel - light yellow, chemically stable, flame-resistant, insoluble except in alkali or hydrofluoric acid. Superficial polarity, thermal stability, performance greater than fine-pored silica gel, silica gels high specific surface area allows it to adsorb water readily, making it useful as a desiccant. Silica gel is often described as absorbing moisture, which may be appropriate when the gels microscopic structure is ignored, however, material silica gel removes moisture by adsorption onto the surface of its numerous pores rather than by absorption into the bulk of the gel. Once saturated with water, the gel can be regenerated by heating it to 120 °C for 1–2 hours, some types of silica gel will pop when exposed to enough water. This is caused by breakage of the silica spheres when contacting the water, an aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. When a visible indication of the content of the silica gel is required. This will cause the gel to be blue when dry and pink when hydrated, an alternative indicator is methyl violet which is orange when dry and green when hydrated. Due to the connection between cancer and cobalt chloride, it has been forbidden in Europe on silica gel, in many items, moisture encourages the growth of mold and spoilage
15.
Aluminium oxide
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Aluminium oxide or aluminum oxide is a chemical compound of aluminium and oxygen with the chemical formula Al2O3. It is the most commonly occurring of several aluminium oxides, and it is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It occurs naturally in its crystalline polymorphic phase α-Al2O3 as the mineral corundum, varieties of form the precious gemstones ruby. Al2O3 is significant in its use to produce metal, as an abrasive owing to its hardness. Corundum is the most common naturally occurring form of aluminium oxide. Rubies and sapphires are gem-quality forms of corundum, which owe their characteristic colors to trace impurities, rubies are given their characteristic deep red color and their laser qualities by traces of chromium. Sapphires come in different colors given by various other impurities, such as iron, Al2O3 is an electrical insulator but has a relatively high thermal conductivity for a ceramic material. Aluminium oxide is insoluble in water, in its most commonly occurring crystalline form, called corundum or α-aluminium oxide, its hardness makes it suitable for use as an abrasive and as a component in cutting tools. Aluminium oxide is responsible for the resistance of aluminium to weathering. Metallic aluminium is very reactive with oxygen, and a thin passivation layer of aluminium oxide forms on any exposed aluminium surface. This layer protects the metal from further oxidation, the thickness and properties of this oxide layer can be enhanced using a process called anodising. A number of alloys, such as bronzes, exploit this property by including a proportion of aluminium in the alloy to enhance corrosion resistance. Aluminium oxide was taken off the United States Environmental Protection Agencys chemicals lists in 1988, aluminium oxide is on EPAs Toxics Release Inventory list if it is a fibrous form. Al2O3 +6 HF →2 AlF3 +3 H2O Al2O3 +2 NaOH +3 H2O →2 NaAl4 The most common form of aluminium oxide is known as corundum. The oxygen ions form a hexagonal close-packed structure with aluminium ions filling two-thirds of the octahedral interstices. In terms of its crystallography, corundum adopts a trigonal Bravais lattice with a group of R-3c. The primitive cell contains two units of aluminium oxide. Each has a crystal structure and properties
16.
Chromium(III) oxide
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Chromium oxide is the inorganic compound of the formula Cr 2O3. It is one of the oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite, Cr 2O3 adopts the corundum structure, consisting of a hexagonal close packed array of oxide anions with ⅔ of the octahedral holes occupied by chromium. Similar to corundum, Cr 2O3 is a hard, brittle material and it is antiferromagnetic up to 307 K, the Néel temperature. It is not readily attacked by acids or bases, although molten alkali gives chromate salts with the CrO−4 anion and it turns brown when heated, but reverts to its dark green color when cooled. Cr 2O3 occurs naturally in mineral eskolaite, which is found in chromium-rich tremolite skarns, metaquartzites, eskolaite is also a rare component of chondrite meteorites. The mineral is named after Finnish geologist Pentti Eskola, the Parisians Pannetier and Binet first prepared the transparent hydrated form of Cr 2O3 in 1838 via a secret process, sold as a pigment. It is derived from the mineral chromite, Cr 2O4, 2Cr 2O7 → Cr 2O3 + N2 +4 H 2O The reaction has a low ignition temperature of less than 200 °C and is frequently used in “volcano” demonstrations. Because of its stability, chromia is a commonly used pigment and was originally called viridian. It is used in paints, inks, and glasses and it is the colourant in chrome green and institutional green. On a piece of leather, balsa, cloth or other material, in this context it is alternatively known as green compound. Although insoluble in water, it dissolves in acid to produce hydrated chromium ions and it dissolves in concentrated alkali to yield chromite ions. When heated with finely divided carbon it can be reduced to metal with release of carbon dioxide. Because of the high melting point of chromium, chromium thermite casting is impractical
17.
Tin dioxide
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Tin dioxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the ore of tin. With many other names, this oxide of tin is the most important raw material in tin chemistry and it is a colourless, diamagnetic, amphoteric solid. It crystallises with the rutile structure, as such the tin atoms are six coordinate and the oxygen atoms three coordinate. SnO2 is usually regarded as an oxygen-deficient n-type semiconductor, hydrous forms of SnO2 have been described as stannic acid. Such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size, synthetic tin oxide is produced by burning tin metal in air. Annual production is in the range of 10 kilotons, SnO2 is reduced industrially to the metal with carbon in a reverberatory furnace at 1200-1300 °C. Although SnO2 is insoluble in water, it is amphoteric, dissolving in base, stannic acid refers to hydrated tin oxide, SnO2, which is also called stannic hydroxide. Halogen acids attack SnO2 to give hexahalostannates, such as 2−, one report describes reacting a sample in refluxing HI for many hours. Dissolving the solidified SnO2/NaOH melt in water gives Na22, preparing salt, in conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides. Tin oxide has long used as an opacifier and as a white colorant in ceramic glazes. This has probably led to the discovery of the pigment lead-tin-yellow, the use of tin oxide has been particularly common in glazes for earthenware, sanitaryware and wall tiles, see the articles tin-glazing and Tin-glazed pottery. The degree of dissolution increases with the temperature, and hence the extent of opacity diminishes. Although dependent on the other constituents the solubility of tin oxide in glaze melts is generally low and its solubility is increased by Na2O, K2O and B2O3, and reduced by CaO, BaO, ZnO, Al2O3, and to a limited extent PbO. SnO2 has been used as pigment in the manufacture of glasses, enamels, pure SnO2 gives a milky white colour, other colours are achieved when mixed with other metallic oxides e. g. V2O5 yellow, Cr2O3 pink, and Sb2O5 grey blue. Tin oxide can be used as a powder, sometimes in mixtures also with lead oxide, for polishing glass, jewelery, marble. Tin oxide for use is sometimes called as putty powder or jewelers putty. SnO2 coatings can be applied using chemical vapor deposition, vapour deposition techniques that employ SnCl4 or organotin trihalides e. g. butyltin trichloride as the volatile agent
18.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
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International Union of Pure and Applied Chemistry
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The International Union of Pure and Applied Chemistry /ˈaɪjuːpæk/ or /ˈjuːpæk/ is an international federation of National Adhering Organizations that represents chemists in individual countries. It is a member of the International Council for Science, IUPAC is registered in Zürich, Switzerland, and the administrative office, known as the IUPAC Secretariat, is in Research Triangle Park, North Carolina, United States. This administrative office is headed by IUPACs executive director, currently Lynn Soby, IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, there are fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPACs Inter-divisional Committee on Nomenclature and Symbols is the world authority in developing standards for the naming of the chemical elements. Since its creation, IUPAC has been run by different committees with different responsibilities. These committees run different projects which include standardizing nomenclature, finding ways to bring chemistry to the world, IUPAC is best known for its works standardizing nomenclature in chemistry and other fields of science, but IUPAC has publications in many fields including chemistry, biology and physics. IUPAC is also known for standardizing the atomic weights of the elements through one of its oldest standing committees, the need for an international standard for chemistry was first addressed in 1860 by a committee headed by German scientist Friedrich August Kekulé von Stradonitz. This committee was the first international conference to create an international naming system for organic compounds, the ideas that were formulated in that conference evolved into the official IUPAC nomenclature of organic chemistry. IUPAC stands as a legacy of this meeting, making it one of the most important historical international collaborations of chemistry societies, since this time, IUPAC has been the official organization held with the responsibility of updating and maintaining official organic nomenclature. IUPAC as such was established in 1919, one notable country excluded from this early IUPAC is Germany. Germanys exclusion was a result of prejudice towards Germans by the Allied powers after World War I, Germany was finally admitted into IUPAC during 1929. However, Nazi Germany was removed from IUPAC during World War II, during World War II, IUPAC was affiliated with the Allied powers, but had little involvement during the war effort itself. After the war, East and West Germany were eventually readmitted to IUPAC, since World War II, IUPAC has been focused on standardizing nomenclature and methods in science without interruption. In 2016, IUPAC denounced the use of chlorine as a chemical weapon, the letter stated, Our organizations deplore the use of chlorine in this manner. According to the CWC, the use, stockpiling, distribution, IUPAC is governed by several committees that all have different responsibilities. Each committee is made up of members of different National Adhering Organizations from different countries, the steering committee hierarchy for IUPAC is as follows, All committees have an allotted budget to which they must adhere. Any committee may start a project, if a projects spending becomes too much for a committee to continue funding, it must take the issue to the Project Committee
20.
Bunsen burner
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A Bunsen burner, named after Robert Bunsen, is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion. The gas can be gas or a liquefied petroleum gas, such as propane, butane. In 1852 the University of Heidelberg hired Bunsen and promised him a new laboratory building, the city of Heidelberg had begun to install coal-gas street lighting, and so the university laid gas lines to the new laboratory. The designers of the building intended to use the gas not just for illumination, for any burner lamp, it was desirable to maximize the temperature and minimize luminosity. However, existing laboratory burner lamps left much to be desired not just in terms of the heat of the flame, but also regarding economy and simplicity. While the building was still under construction in late 1854 Bunsen suggested certain design principles to the mechanic, Peter Desaga. The Bunsen/Desaga design succeeded in generating a hot, sootless, non-luminous flame by mixing the gas with air in a controlled fashion before combustion, Desaga created adjustable slits for air at the bottom of the cylindrical burner, with the flame igniting at the top. By the time the building opened early in 1855 Desaga had made fifty of the burners for Bunsens students, two years later Bunsen published a description, and many of his colleagues soon adopted the design. Bunsen burners are now used in all around the world. The device in use today safely burns a continuous stream of a gas such as natural gas or a liquefied petroleum gas such as propane, butane. The hose barb is connected to a gas nozzle on the bench with rubber tubing. Most laboratory benches are equipped with multiple gas nozzles connected to a gas source, as well as vacuum, nitrogen. The gas then flows up through the base through a hole at the bottom of the barrel and is directed upward. There are open slots in the side of the bottom to admit air into the stream via the venturi effect. The most common methods of lighting the burner are using a match or a spark lighter, the amount of air mixed with the gas stream affects the completeness of the combustion reaction. Less air yields an incomplete and thus cooler reaction, while a gas stream well mixed with air provides oxygen in an amount and thus a complete. The air flow can be controlled by opening or closing the openings at the base of the barrel. If the collar at the bottom of the tube is adjusted so more air can mix with the gas before combustion, the flame will burn hotter, appearing blue as a result
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Dendrite (metal)
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This dendritic growth has large consequences in regard to material properties. Dendrites form in systems as well as multi-component systems. The requirement is that the liquid be undercooled, aka supercooled, initially, a spherical solid nucleus grows in the undercooled melt. As the sphere grows, the spherical morphology becomes unstable and its shape becomes perturbed, the solid shape begins to express the preferred growth directions of the crystal. In metallic systems, interface attachment kinetics is usually negligible, in metallic systems, the solid then attempts to minimize the area of those surfaces with the highest surface energy. The dendrite thus exhibits a sharper and sharper tip as it grows, if the anisotropy is large enough, the dendrite may present a faceted morphology. The microstructural length scale is determined by the interplay or balance between the energy and the temperature gradient in the liquid at the interface. As solidification proceeds, a number of atoms lose their kinetic energy. For a pure material, latent heat is released at the solid–liquid interface so that the temperature remains constant until the melt has completely solidified, the growth rate of the resultant crystalline substance will depend on how fast this latent heat can be conducted away. A dendrite growing in a melt can be approximated as a parabolic needle-like crystal that grows in a shape-preserving manner at constant velocity. Nucleation and growth determine the size in equiaxed solidification while the competition between adjacent dendrites decides the primary spacing in columnar growth. Generally, if the melt is cooled slowly, nucleation of new crystals will be less than at large undercooling, the dendritic growth will result in dendrites of a large size. Conversely, a cooling cycle with a large undercooling will increase the number of nuclei. Smaller dendrites generally lead to higher ductility of the product, one application where dendritic growth and resulting material properties can be seen is the process of welding. The dendrites are also common in cast products, where they may become visible by etching of a polished specimen, as dendrites develop further into the liquid metal, they get hotter because they continue to extract heat. If they get too hot, they will remelt and this remelting of the dendrites is called recalescence. Dendrites also form during the freezing of many nonmetallic substances such as ice, dendrites usually form under non-equilibrium conditions. A common dendritic metal material is nickel carbonyl, where the particles have a classical spiky morphology, an application of dendritic growth in directional solidification is gas turbine engine blades which are used at high temperatures and must handle high stresses along the major axes
22.
Sphere
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A sphere is a perfectly round geometrical object in three-dimensional space that is the surface of a completely round ball. This distance r is the radius of the ball, and the point is the center of the mathematical ball. The longest straight line through the ball, connecting two points of the sphere, passes through the center and its length is twice the radius. While outside mathematics the terms sphere and ball are used interchangeably. The ball and the share the same radius, diameter. The surface area of a sphere is, A =4 π r 2, at any given radius r, the incremental volume equals the product of the surface area at radius r and the thickness of a shell, δ V ≈ A ⋅ δ r. The total volume is the summation of all volumes, V ≈ ∑ A ⋅ δ r. In the limit as δr approaches zero this equation becomes, V = ∫0 r A d r ′, substitute V,43 π r 3 = ∫0 r A d r ′. Differentiating both sides of equation with respect to r yields A as a function of r,4 π r 2 = A. Which is generally abbreviated as, A =4 π r 2, alternatively, the area element on the sphere is given in spherical coordinates by dA = r2 sin θ dθ dφ. In Cartesian coordinates, the element is d S = r r 2 − ∑ i ≠ k x i 2 ∏ i ≠ k d x i, ∀ k. For more generality, see area element, the total area can thus be obtained by integration, A = ∫02 π ∫0 π r 2 sin θ d θ d φ =4 π r 2. In three dimensions, the volume inside a sphere is derived to be V =43 π r 3 where r is the radius of the sphere, archimedes first derived this formula, which shows that the volume inside a sphere is 2/3 that of a circumscribed cylinder. In modern mathematics, this formula can be derived using integral calculus, at any given x, the incremental volume equals the product of the cross-sectional area of the disk at x and its thickness, δ V ≈ π y 2 ⋅ δ x. The total volume is the summation of all volumes, V ≈ ∑ π y 2 ⋅ δ x. In the limit as δx approaches zero this equation becomes, V = ∫ − r r π y 2 d x. At any given x, a right-angled triangle connects x, y and r to the origin, hence, applying the Pythagorean theorem yields, thus, substituting y with a function of x gives, V = ∫ − r r π d x. Which can now be evaluated as follows, V = π − r r = π − π =43 π r 3
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Porosity
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Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0 and 100%. Strictly speaking, some measure the accessible void, the total amount of void space accessible from the surface. There are many ways to test porosity in a substance or part, the term porosity is used in multiple fields including pharmaceutics, ceramics, metallurgy, materials, manufacturing, earth sciences, soil mechanics and engineering. Void fraction usually varies from location to location in the flow channel and it fluctuates with time and its value is usually time averaged. In separated flow, it is related to flow rates of the gas and the liquid phase. It is defined by the ratio, ϕ = V V V T where VV is the volume of void-space and VT is the total or bulk volume of material, both the mathematical symbols ϕ and n are used to denote porosity. Porosity is a fraction between 0 and 1, typically ranging from less than 0.01 for solid granite to more than 0.5 for peat and it may also be represented in percent terms by multiplying the fraction by 100. The porosity of a rock, or sedimentary layer, is an important consideration when attempting to evaluate the potential volume of water or hydrocarbons it may contain. Sedimentary porosity is a function of many factors, including but not limited to, rate of burial, depth of burial, the nature of the connate fluids. The principal complication is that there is not a direct proportionality between porosity and hydraulic conductivity but rather an inferred proportionality, there is a clear proportionality between pore throat radii and hydraulic conductivity. Also, there tends to be a proportionality between pore throat radii and pore volume, if the proportionality between pore throat radii and porosity exists then a proportionality between porosity and hydraulic conductivity may exist. Well sorted materials have higher porosity than similarly sized poorly sorted materials, for tables of common porosity values for earth materials, see the further reading section in the Hydrogeology article. Consolidated rocks potentially have more complex dual porosities, as compared with alluvial sediment and this can be split into connected and unconnected porosity. Connected porosity is more easily measured through the volume of gas or liquid that can flow into the rock, porosity is the ratio of pore volume to its total volume. Porosity is controlled by, rock type, pore distribution, cementation, diagenetic history, porosity is not controlled by grain size, as the volume of between-grain space is related only to the method of grain packing. Rocks normally decrease in porosity with age and depth of burial, tertiary age Gulf Coast sandstones are in general more porous than Cambrian age sandstones. There are exceptions to this rule, usually because of the depth of burial and thermal history, porosity of surface soil typically decreases as particle size increases. This is due to soil formation in finer textured surface soils when subject to soil biological processes
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Fractal
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A fractal is a mathematical set that exhibits a repeating pattern displayed at every scale. It is also known as expanding symmetry or evolving symmetry, if the replication is exactly the same at every scale, it is called a self-similar pattern. An example of this is the Menger Sponge, Fractals can also be nearly the same at different levels. This latter pattern is illustrated in small magnifications of the Mandelbrot set, Fractals also include the idea of a detailed pattern that repeats itself. Fractals are different from other geometric figures because of the way in which they scale, doubling the edge lengths of a polygon multiplies its area by four, which is two raised to the power of two. Likewise, if the radius of a sphere is doubled, its volume scales by eight, but if a fractals one-dimensional lengths are all doubled, the spatial content of the fractal scales by a power that is not necessarily an integer. This power is called the dimension of the fractal. As mathematical equations, fractals are usually nowhere differentiable, the term fractal was first used by mathematician Benoît Mandelbrot in 1975. Mandelbrot based it on the Latin frāctus meaning broken or fractured, there is some disagreement amongst authorities about how the concept of a fractal should be formally defined. Mandelbrot himself summarized it as beautiful, damn hard, increasingly useful, Fractals are not limited to geometric patterns, but can also describe processes in time. Fractal patterns with various degrees of self-similarity have been rendered or studied in images, structures and sounds and found in nature, technology, art, Fractals are of particular relevance in the field of chaos theory, since the graphs of most chaotic processes are fractal. The word fractal often has different connotations for laypeople than for mathematicians, the mathematical concept is difficult to define formally even for mathematicians, but key features can be understood with little mathematical background. If this is done on fractals, however, no new detail appears, nothing changes, self-similarity itself is not necessarily counter-intuitive. The difference for fractals is that the pattern reproduced must be detailed, a regular line, for instance, is conventionally understood to be 1-dimensional, if such a curve is divided into pieces each 1/3 the length of the original, there are always 3 equal pieces. In contrast, consider the Koch snowflake and it is also 1-dimensional for the same reason as the ordinary line, but it has, in addition, a fractal dimension greater than 1 because of how its detail can be measured. This also leads to understanding a third feature, that fractals as mathematical equations are nowhere differentiable, in a concrete sense, this means fractals cannot be measured in traditional ways. The history of fractals traces a path from chiefly theoretical studies to modern applications in computer graphics, according to Pickover, the mathematics behind fractals began to take shape in the 17th century when the mathematician and philosopher Gottfried Leibniz pondered recursive self-similarity. In his writings, Leibniz used the term fractional exponents, also in the last part of that century, Felix Klein and Henri Poincaré introduced a category of fractal that has come to be called self-inverse fractals
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Thermal insulation
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Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes, heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body, the insulating capability of a material is measured with thermal conductivity. Low thermal conductivity is equivalent to high insulating capability, in thermal engineering, other important properties of insulating materials are product density and specific heat capacity. Solid materials chosen for insulation have a low thermal conductivity k, as the thickness of insulation is increased, the thermal resistance also increases. For insulated cylinders, a critical radius must be reached, before the critical radius is reached any added insulation increases heat transfer. If the outside radius of a cylinder is increased by applying insulation, however, at the same time, the convective resistance is reduced. This implies that adding insulation below a critical radius actually increases the heat transfer. If the radius of the cylinder is smaller than the critical radius for insulation. Gases possess poor thermal conduction properties compared to liquids and solids, in order to further augment the effectiveness of a gas it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Convection involves a larger flow of gas driven by buoyancy and temperature differences. In order to accomplish gas cell formation in man-made thermal insulation, glass and this principle is used industrially in building and piping insulation such as, cellulose, rock wool, polystyrene foam, urethane foam, vermiculite, perlite, and cork. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers, the air-trapping property is also the insulation principle employed by homeothermic animals to stay warm, for example down feathers, and insulating hair such as natural sheeps wool. In both cases the primary insulating material is air, and the used for trapping the air is natural keratin protein. Maintaining acceptable temperatures in buildings uses a proportion of global energy consumption. For a period of time, Asbestos was also used, however, when well insulated, a building, is energy-efficient, thus saving the owner money. Provides more uniform throughout the space. Unlike heating and cooling equipment, insulation is permanent and does not require maintenance, upkeep, lowers the carbon footprint of a building
26.
Heat transfer
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Heat transfer is the exchange of thermal energy between physical systems. The rate of transfer is dependent on the temperatures of the systems. The three fundamental modes of transfer are conduction, convection and radiation. Heat transfer, the flow of energy in the form of heat, is a process by which an internal energy is changed. Conduction is also known as diffusion, not to be confused with related to the mixing of constituents of a fluid. The direction of transfer is from a region of high temperature to another region of lower temperature. Heat transfer changes the energy of the systems from which. Heat transfer will occur in a direction that increases the entropy of the collection of systems, Heat transfer ceases when thermal equilibrium is reached, at which point all involved bodies and the surroundings reach the same temperature. Thermal expansion is the tendency of matter to change in volume in response to a change in temperature, Heat is defined in physics as the transfer of thermal energy across a well-defined boundary around a thermodynamic system. The thermodynamic free energy is the amount of work that a system can perform. Enthalpy is a potential, designated by the letter H. Joule is a unit to quantify energy, work, or the amount of heat, thermodynamic and mechanical heat transfer is calculated with the heat transfer coefficient, the proportionality between the heat flux and the thermodynamic driving force for the flow of heat. Heat flux is a quantitative, vectorial representation of heat-flow through a surface, in engineering contexts, the term heat is taken as synonymous to thermal energy. This usage has its origin in the interpretation of heat as a fluid that can be transferred by various causes. Thermal engineering concerns the generation, use, conversion, and exchange of heat transfer, as such, heat transfer is involved in almost every sector of the economy. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. The fundamental modes of transfer are, Advection Advection is the transport mechanism of a fluid from one location to another. Conduction or diffusion The transfer of energy between objects that are in physical contact, thermal conductivity is the property of a material to conduct heat and evaluated primarily in terms of Fouriers Law for heat conduction
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Convective heat transfer
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Convective heat transfer, often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of transfer in liquids. Although often discussed as a method of heat transfer, convective heat transfer involves the combined processes of unknown conduction and advection. Convection can be forced by movement of a fluid by means other than buoyancy forces, Thermal expansion of fluids may also force convection. In other cases, natural buoyancy forces alone are responsible for fluid motion when the fluid is heated. An example is the draft in a chimney or around any fire, for example, when water is heated on a stove, hot water from the bottom of the pan rises, displacing the colder denser liquid, which falls. After heating has stopped, mixing and conduction from this natural convection eventually result in a nearly homogeneous density, without the presence of gravity, natural convection does not occur, and only forced-convection modes operate. The convection heat transfer mode comprises one mechanism, in addition to energy transfer due to specific molecular motion, energy is transferred by bulk, or macroscopic, motion of the fluid. This motion is associated with the fact that, at any instant, such motion, in the presence of a temperature gradient, contributes to heat transfer. It is customary to use the term convection when referring to this cumulative transport, in the absence of an external source, when the fluid is in contact with a hot surface, its molecules separate and scatter, causing the fluid to be less dense. As a consequence, the fluid is displaced while the cooler fluid gets denser, thus, the hotter volume transfers heat towards the cooler volume of that fluid. Familiar examples are the flow of air due to a fire or hot object. Forced convection, when a fluid is forced to flow over the surface by a source such as fans, by stirring. Internal and external flow can also classify convection, internal flow occurs when a fluid is enclosed by a solid boundary such when flowing through a pipe. An external flow occurs when a fluid extends indefinitely without encountering a solid surface, both of these types of convection, either natural or forced, can be internal or external because they are independent of each other. Further classification can be made depending on the smoothness and undulations of the solid surfaces, not all surfaces are smooth, though a bulk of the available information deals with smooth surfaces. Wavy irregular surfaces are commonly encountered in heat transfer devices which include solar collectors, regenerative heat exchangers and they have a significant role to play in the heat transfer processes in these applications. Since they bring in an added complexity due to the undulations in the surfaces, also they do affect the flow and heat transfer characteristics, thereby behaving differently from straight smooth surfaces
28.
Thermal radiation
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Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a greater than absolute zero emits thermal radiation. When the temperature of a body is greater than absolute zero, Thermal radiation is different from thermal convection and thermal conduction—a person near a raging bonfire feels radiant heating from the fire, even if the surrounding air is very cold. Sunlight is part of thermal radiation generated by the hot plasma of the Sun, the Earth also emits thermal radiation, but at a much lower intensity and different spectral distribution because it is cooler. The Earths absorption of radiation, followed by its outgoing thermal radiation are the two most important processes that determine the temperature and climate of the Earth. If a radiation-emitting object meets the physical characteristics of a body in thermodynamic equilibrium. Plancks law describes the spectrum of radiation, which depends only on the objects temperature. Wiens displacement law determines the most likely frequency of the radiation. Thermal radiation is one of the mechanisms of heat transfer. Thermal radiation is the emission of electromagnetic waves from all matter that has a greater than absolute zero. It represents a conversion of energy into electromagnetic energy. Thermal energy consists of the energy of random movements of atoms. All matter with a temperature by definition is composed of particles which have kinetic energy, and these atoms and molecules are composed of charged particles, i. e. protons and electrons, and kinetic interactions among matter particles result in charge-acceleration and dipole-oscillation. This results in the generation of coupled electric and magnetic fields, resulting in the emission of photons. Electromagnetic radiation, including light, does not require the presence of matter to propagate, the radiation is not monochromatic, i. e. it does not consist of just a single frequency, but comprises a continuous dispersion of photon energies, its characteristic spectrum. If the radiating body and its surface are in thermodynamic equilibrium, a black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation, the ratio of any bodys emission relative to that of a black body is the bodys emissivity, so that a black body has an emissivity of unity. Absorptivity, reflectivity, and emissivity of all bodies are dependent on the wavelength of the radiation, the temperature determines the wavelength distribution of the electromagnetic radiation
29.
Hygroscopy
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Hygroscopy is the phenomenon of attracting and holding water molecules from the surrounding environment, which is usually at normal or room temperature. This is achieved through either absorption or adsorption with the absorbing or adsorbing substance becoming physically changed somewhat. Zinc chloride and calcium chloride, as well as potassium hydroxide and sodium hydroxide, are so hygroscopic that they readily dissolve in the water they absorb, not only is sulfuric acid hygroscopic in concentrated form but its solutions are hygroscopic down to concentrations of 10 Vol-% or below. A hygroscopic material will tend to damp and cakey when exposed to moist air. Because of their affinity for moisture, hygroscopic materials might require storage in sealed containers. When added to foods or other materials for the purpose of maintaining moisture content. Materials and compounds exhibit different hygroscopic properties, and this difference can lead to detrimental effects, differences in hygroscopy can be observed in plastic-laminated paperback book covers—often, in a suddenly moist environment, the book cover will curl away from the rest of the book. The unlaminated side of the cover absorbs more moisture than the side and increases in area. This is similar to the function of a thermostats bi-metallic strip, inexpensive dial-type hygrometers make use of this principle using a coiled strip. Deliquescence, the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water, deliquescence occurs when the vapour pressure of the solution that is formed is less than the partial pressure of water vapour in the air. While some similar forces are at work here, it is different from capillary attraction, a process where glass or other solid substances attract water, the similar-sounding but unrelated word hydroscopic is sometimes used in error for hygroscopic. A hydroscope is a device used for making observations deep under water. The amount of moisture held by hygroscopic materials is proportional to the relative humidity. Tables containing this information can be found in engineering handbooks and is also available from suppliers of various materials and chemicals. Hygroscopy also plays an important role in the engineering of plastic materials, some plastics are hygroscopic while others are not. The seeds of grasses have hygroscopic extensions that bend with changes in humidity. An example is Needle-and-Thread, Hesperostipa comata, each seed has an awn that twists several turns when the seed is released. Increased moisture causes it to untwist, and, upon drying, to twist again, thorny dragons collect moisture in the dry desert via nighttime condensation of dew that forms on their skin and is channeled to their mouths in hygroscopic grooves between the spines of their skin
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Desiccant
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A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its vicinity. Commonly encountered pre-packaged desiccants are solids that absorb water, desiccants for specialized purposes may be in forms other than solid, and may work through other principles, such as chemical bonding of water molecules. They are commonly encountered in foods to retain crispness, industrially, desiccants are widely used to control the level of water in gas streams. Although some desiccants are chemically inert, many are extremely reactive, the most common desiccant is silica, an otherwise inert, nontoxic, water-insoluble white solid. Tens of thousands of tons are produced annually for this purpose, other common desiccants include activated charcoal, calcium sulfate, calcium chloride, and molecular sieves. One measure of desiccant efficiency is the ratio of water storable in the desiccant relative to the mass of desiccant, another measure is the residual relative humidity of the air or other fluid being dried. The performance of any desiccant varies with temperature and both relative humidity and absolute humidity, sometimes a humidity indicator is included in the desiccant to show, by color changes, the degree of water-saturation of the desiccant. One commonly used indicator is cobalt chloride, when it bonds with two water molecules, it turns purple. Further hydration results in the pink hexaaquacobalt chloride complex Cl2, one example of desiccant usage is in the manufacture of insulated windows where zeolite spheroids fill a rectangular spacer tube at the perimeter of the panes of glass. The desiccant helps to prevent the condensation of moisture between the panes, another use of zeolites is in the dryer component of air conditioning systems to help maintain the efficacy of the refrigerant. Desiccants are also used to protect goods in shipping containers against moisture damage. Hygroscopic cargo, such as cocoa, coffee, and various nuts and grains, are susceptible to mold and rot when exposed to condensation. Because of this, shippers often take measures to protect against cargo loss. Desiccants induce dryness in any environment and reduce the amount of moisture present in air, desiccants come in various forms and have found widespread use in the food, pharmaceuticals, packing, electronics and many manufacturing industries. Air conditioning systems can be based on desiccants. Desiccants are used in different kinds of livestock farming to dry newborn animals, the use of a good desiccant can help them dry quicker and save energy, which can be crucial for the animals development. Another use is to reduce bacteria and pathogens that thrive in wet surfaces, however, some desiccants have a very high pH-level, which can be harmful for an animals skin. Desiccants are also used to water from solvents, typically required by chemical reactions that do not tolerate water
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Rayleigh scattering
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Rayleigh scattering does not change the state of material and is, hence, a parametric process. The particles may be atoms or molecules. It can occur when light travels through transparent solids and liquids, Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, the particle therefore becomes a small radiating dipole whose radiation we see as scattered light. Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the color of the sky. The amount of scattering is proportional to the fourth power of the wavelength. This can lead to changes in the state of the molecules. Furthermore, the contribution has the same wavelengths dependency as the elastic part. Scattering by particles similar to, or larger than, the wavelength of light is treated by the Mie theory. Rayleigh scattering applies to particles that are small with respect to wavelengths of light, on the other hand, anomalous diffraction theory applies to optically soft but larger particles. The size of a particle is often parameterized by the ratio where r is its characteristic length. The wavelength dependence is characteristic of dipole scattering and the volume dependence will apply to any scattering mechanism, objects with x ≫1 act as geometric shapes, scattering light according to their projected area. At the intermediate x ≃1 of Mie scattering, interference effects develop through phase variations over the objects surface, Rayleigh scattering applies to the case when the scattering particle is very small and the whole surface re-radiates with the same phase. For example, the constituent of the atmosphere, nitrogen, has a Rayleigh cross section of 5. 1×10−31 m2 at a wavelength of 532 nm. This means that at atmospheric pressure, where there are about 2×1025 molecules per cubic meter, the strong wavelength dependence of the scattering means that shorter wavelengths are scattered more strongly than longer wavelengths. This results in the blue light coming from all regions of the sky. Rayleigh scattering is an approximation of the manner in which light scattering occurs within various media for which scattering particles have a small size. A portion of the beam of light coming from the sun scatters off molecules of gas, here, Rayleigh scattering primarily occurs through sunlights interaction with randomly located air molecules
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Wavelength
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In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above
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Hydrophobic
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In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water, Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them, Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle, examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, Hydrophobic is often used interchangeably with lipophilic, fat-loving. However, the two terms are not synonymous, while hydrophobic substances are usually lipophilic, there are exceptions—such as the silicones and fluorocarbons. The term hydrophobe comes from the Ancient Greek ὑδρόφοβος, having a horror of water, constructed from ὕδωρ, water, thus, the two immiscible phases will change so that their corresponding interfacial area will be minimal. This effect can be visualized in the phenomenon called phase separation, Superhydrophobic surfaces, such as the leaves of the lotus plant, are those that are extremely difficult to wet. The contact angles of a water droplet exceeds 150° and the angle is less than 10°. This is referred to as the Lotus effect, and is primarily a physical property related to interfacial tension, in 1805, Thomas Young defined the contact angle θ by analyzing the forces acting on a fluid droplet resting on a solid surface surrounded by a gas. Wenzels equation shows that microstructuring a surface amplifies the natural tendency of the surface, a hydrophobic surface becomes more hydrophobic when microstructured – its new contact angle becomes greater than the original. However, a hydrophilic surface becomes more hydrophilic when microstructured – its new contact angle less than the original. Liquid in the Cassie–Baxter state is more mobile than in the Wenzel state and we can predict whether the Wenzel or Cassie–Baxter state should exist by calculating the new contact angle with both equations. By a minimization of free energy argument, the relation that predicted the new contact angle is the state most likely to exist. Stated in mathematical terms, for the Cassie–Baxter state to exist, a new criterion for the switch between Wenzel and Cassie-Baxter states has been developed recently based on surface roughness and surface energy. Contact angle is a measure of static hydrophobicity, and contact angle hysteresis, contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. When a pipette injects a liquid onto a solid, the liquid will form some contact angle, as the pipette injects more liquid, the droplet will increase in volume, the contact angle will increase, but its three-phase boundary will remain stationary until it suddenly advances outward. The contact angle the droplet had immediately before advancing outward is termed the advancing contact angle, the receding contact angle is now measured by pumping the liquid back out of the droplet
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Mean free path
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In physics, the mean free path is the average distance traveled by a moving particle between successive impacts, which modify its direction or energy or other particle properties. The following table lists typical values for air at different pressures at room temperature. In gamma-ray radiography the mean path of a pencil beam of mono-energetic photons is the average distance a photon travels between collisions with atoms of the target material. It depends on the material and the energy of the photons, ℓ = μ −1 = −1, as photons move through the target material, they are attenuated with probabilities depending on their energy, as a result their distribution changes in process called spectrum hardening. Because of spectrum hardening, the mean path of the X-ray spectrum changes with distance. Sometimes one measures the thickness of a material in the number of mean free paths, material with the thickness of one mean free path will attenuate 37% of photons. This concept is related to half-value layer, a material with a thickness of one HVL will attenuate 50% of photons. A standard x-ray image is an image, an image with negative logarithm of its intensities is sometimes called a number of mean free paths image. In particle physics the concept of the mean free path is not commonly used, in particular, for high-energy photons, which mostly interact by electron–positron pair production, the radiation length is used much like the mean free path in radiography. Independent-particle models in nuclear physics require the undisturbed orbiting of nucleons within the nucleus before they interact with other nucleons and this requirement seems to be in contradiction to the assumptions made in the theory. We are facing one of the fundamental problems of nuclear structure physics which has yet to be solved. If one takes a suspension of non-light-absorbing particles of diameter d with a volume fraction Φ, the mean path of the photons is, l =2 d 3 Φ Q s. Qs can be evaluated numerically for spherical particles using Mie theory. In an otherwise empty cavity, the mean path of a single particle bouncing off the walls is, l =4 V S. This relation is used in the derivation of the Sabine equation in acoustics, the mean free path is used in the design of chemical apparatus, e. g. systems for distillation. The sizes of atoms and molecules can be estimated from their mean free path, MFP can be used to estimate the resistivity of a material from the mean free path of its electrons. In aerodynamics, the mean free path has the order of magnitude as the shockwave thickness at Mach numbers greater than one. Imagine a beam of particles being shot through a target, the atoms that might stop a beam particle are shown in red
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Sol-gel
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In materials science, the sol-gel process is a method for producing solid materials from small molecules. The method is used for the fabrication of metal oxides, especially the oxides of silicon, the process involves conversion of monomers into a colloidal solution that acts as the precursor for an integrated network of either discrete particles or network polymers. In the case of the colloid, the fraction of particles may be so low that a significant amount of fluid may need to be removed initially for the gel-like properties to be recognized. This can be accomplished in any number of ways, the simplest method is to allow time for sedimentation to occur, and then pour off the remaining liquid. Centrifugation can also be used to accelerate the process of phase separation, removal of the remaining liquid phase requires a drying process, which is typically accompanied by a significant amount of shrinkage and densification. The rate at which the solvent can be removed is determined by the distribution of porosity in the gel. The ultimate microstructure of the component will clearly be strongly influenced by changes imposed upon the structural template during this phase of processing. One of the advantages of using this methodology as opposed to the more traditional processing techniques is that densification is often achieved at a much lower temperature. The precursor sol can be deposited on a substrate to form a film, cast into a suitable container with the desired shape. The sol-gel approach is a cheap and low-temperature technique that allows for the control of the product’s chemical composition. Even small quantities of dopants, such as dyes and rare earth elements, can be introduced in the sol. It can be used in processing and manufacturing as an investment casting material. Sol-gel derived materials have applications in optics, electronics, energy, space, sensors, medicine, reactive material. Sol-gel research grew to be so important that in the 1990s more than 35,000 papers were published worldwide on the process, the sol-gel process is a wet-chemical technique used for the fabrication of both glassy and ceramic materials. In this process, the sol evolves gradually towards the formation of a network containing both a liquid phase and a solid phase. Typical precursors are metal alkoxides and metal chlorides, which undergo hydrolysis, the basic structure or morphology of the solid phase can range anywhere from discrete colloidal particles to continuous chain-like polymer networks. The term colloid is used primarily to describe a range of solid-liquid mixtures. The term is specific to the size of the individual particles, if the particles are large enough, then their dynamic behavior in any given period of time in suspension would be governed by forces of gravity and sedimentation
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Polymerization
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In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them, in chemical compounds, polymerization occurs via a variety of reaction mechanisms that vary in complexity due to functional groups present in reacting compounds and their inherent steric effects. Alkanes can also be polymerized, but only with the help of strong acids, further compounds either being referred to as oligomers in smaller molecules. Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous and this phenomenon is known as hazardous polymerization and can cause fires and explosions. Step-growth polymers are defined as polymers formed by the reaction between functional groups of monomers, usually containing heteroatoms such as nitrogen or oxygen. Most step-growth polymers are classified as condensation polymers, but not all step-growth polymers release condensates, in this case. Step-growth polymers increase in weight at a very slow rate at lower conversions. To alleviate inconsistencies in these methods, adjusted definition for condensation and addition polymers have been developed. Chain-growth polymerization involves the linking together of molecules incorporating double or triple carbon-carbon bonds and these unsaturated monomers have extra internal bonds that are able to break and link up with other monomers to form a repeating chain, whose backbone typically contains only carbon atoms. Chain-growth polymerization is involved in the manufacture of such as polyethylene, polypropylene. A special case of chain-growth polymerization leads to living polymerization, in the radical polymerization of ethylene, its π bond is broken, and the two electrons rearrange to create a new propagating center like the one that attacked it. The form this propagating center takes depends on the type of addition mechanism. There are several mechanisms through which this can be initiated, the free radical mechanism is one of the first methods to be used. Free radicals are very reactive atoms or molecules that have unpaired electrons, taking the polymerization of ethylene as an example, the free radical mechanism can be divided into three stages, chain initiation, chain propagation, and chain termination. Free radical addition polymerization of ethylene must take place at temperatures and pressures. While most other free radical polymerizations do not require such extreme temperatures and pressures, one effect of this lack of control is a high degree of branching. Also, as termination occurs randomly, when two chains collide, it is impossible to control the length of individual chains, a newer method of polymerization similar to free radical, but allowing more control involves the Ziegler-Natta catalyst, especially with respect to polymer branching. Other forms of chain growth polymerization include cationic addition polymerization and anionic addition polymerization, cationic and anionic mechanisms are also more ideally suited for living polymerizations, although free radical living polymerizations have also been developed
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Macromolecule
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A macromolecule is a very large molecule, such as protein, commonly created by polymerization of smaller subunits. They are typically composed of thousands of atoms or more, the most common macromolecules in biochemistry are biopolymers and large non-polymeric molecules. Synthetic macromolecules include common plastics and synthetic fibres as well as materials such as carbon nanotubes. The term macromolecule was coined by Nobel laureate Hermann Staudinger in the 1920s, usage of the term to describe large molecules varies among the disciplines. According to the standard IUPAC definition, the term macromolecule as used in science refers only to a single molecule. For example, a polymeric molecule is appropriately described as a macromolecule or polymer molecule rather than a polymer. Because of their size, macromolecules are not conveniently described in terms of stoichiometry alone, the structure of simple macromolecules, such as homopolymers, may be described in terms of the individual monomer subunit and total molecular mass. Complicated biomacromolecules, on the hand, require multi-faceted structural description such as the hierarchy of structures used to describe proteins. In British English. Macromolecules often have physical properties that do not occur for smaller molecules. For example, DNA in a solution can be simply by sucking the solution through an ordinary straw because the physical forces on the molecule can overcome the strength of its covalent bonds. The 1964 edition of Linus Paulings College Chemistry asserted that DNA in nature is never longer than about 5,000 base pairs and this error arose because biochemists were inadvertently breaking their samples into fragments. In fact, the DNA of chromosomes can be hundreds of millions of base pairs long, another common macromolecular property that does not characterize smaller molecules is their relative insolubility in water and similar solvents, instead forming colloids. Many require salts or particular ions to dissolve in water, similarly, many proteins will denature if the solute concentration of their solution is too high or too low. High concentrations of macromolecules in a solution can alter the rates and equilibrium constants of the reactions of other macromolecules and this comes from macromolecules excluding other molecules from a large part of the volume of the solution, thereby increasing the effective concentrations of these molecules. All living organisms are dependent on three essential biopolymers for their functions, DNA, RNA and Proteins. Each of these molecules is required for life since each plays a distinct, the simple summary is that DNA makes RNA, and then RNA makes proteins. DNA, RNA and proteins all consist of a structure of related building blocks. In general, they are all unbranched polymers, and so can be represented in the form of a string
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Cross-link
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A cross-link is a bond that links one polymer chain to another. They can be covalent bonds or ionic bonds, polymer chains can refer to synthetic polymers or natural polymers. When the term cross-linking is used in the synthetic polymer science field, cross-linking is used in both synthetic polymer chemistry and in the biological sciences. Although the term is used to refer to the linking of polymer chains for both sciences, the extent of crosslinking and specificities of the crosslinking agents vary. Of course, with all science, there are overlaps, when cross links are added to long rubber molecules, the flexibility decreases, the hardness increases and the melting point increases as well. When polymer chains are linked together by cross-links, they some of their ability to move as individual polymer chains. How the crosslinking process works and how it improves the properties of polymers is nicely illustrated in this video-animation, for example, a liquid polymer can be turned into a solid or gel by cross-linking the chains together. In polymer chemistry, when a polymer is said to be cross-linked. The resulting modification of mechanical properties depends strongly on the cross-link density, low cross-link densities decrease the viscosities of polymer melts. Intermediate cross-link densities transform gummy polymers into materials that have elastomeric properties, very high cross-link densities can cause materials to become very rigid or glassy, such as phenol-formaldehyde materials. Cross-links can be formed by reactions that are initiated by heat, pressure, change in pH. For example, mixing of an unpolymerized or partially polymerized resin with specific chemicals called crosslinking reagents results in a reaction that forms cross-links. Cross-linking can also be induced in materials that are normally thermoplastic through exposure to a source, such as electron beam exposure, gamma-radiation. For example, electron beam processing is used to cross-link the C type of cross-linked polyethylene, the chemical process of vulcanization is a type of cross-linking that changes rubber to the hard, durable material associated with car and bike tires. This process is often called sulfur curing, the term comes from Vulcan. This is, however, a slower process, a typical car tire is cured for 15 minutes at 150 °C. However, the time can be reduced by the addition of such as 2-benzothiazolethiol or tetramethylthiuram disulfide. Both of these contain an atom in the molecule that initiates the reaction of the sulfur chains with the rubber
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Hydroxy group
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A hydroxy or hydroxyl group is the entity with the formula OH. It contains oxygen bonded to hydrogen, in organic chemistry, alcohol and carboxylic acids contain hydroxy groups. The anion, called hydroxide, consists of a hydroxy group, according to IUPAC rules, the term hydroxyl refers to the radical OH only, while the functional group −OH is called hydroxy group. Water, alcohols, carboxylic acids, and many other hydroxy-containing compounds can be deprotonated readily and this behavior is rationalized by the disparate electronegativities of oxygen and hydrogen. Hydroxy-containing compounds engage in hydrogen bonding, which causes them to stick together, organic compounds, which are often poorly soluble in water, become water soluble when they contain two or more hydroxy groups, as illustrated by sugars and amino acid. The hydroxy group is pervasive in chemistry and biochemistry, many inorganic compounds contain hydroxy groups, including sulfuric acid, the chemical compound produced on the largest scale industrially. Hydroxy groups participate in the reactions that link simple biological molecules into long chains. The joining of a fatty acid to glycerol to form a triacylglycerol removes the −OH from the end of the fatty acid. The joining of two aldehyde sugars to form a disaccharide removes the −OH from the group at the aldehyde end of one sugar. The creation of a bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid. Hydroxyl radicals are highly reactive and undergo chemical reactions that make them short-lived, when biological systems are exposed to hydroxyl radicals, they can cause damage to cells, including those in humans, where they react with DNA, lipids, and proteins. In 2009, Indias Chandrayaan-1 satellite, NASAs Cassini spacecraft and the Deep Impact probe have each detected the presence of water by evidence of hydroxyl fragments on the Moon. As reported by Richard Kerr, A spectrometer detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen, NASA also reported in 2009 that the LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence. The Venus Express orbiter sent back Venus science data from April 2006 until December 2014, results from Venus Express include the detection of hydroxyl in the atmosphere. Hydronium Ion Oxide Reece, Jane, Urry, Lisa, Cain, Michael, Wasserman, Steven, Minorsky, Peter, Jackson, berge, Susan, Golden, Brandy, Triglia, Logan
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Aliphatic compound
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In organic chemistry, hydrocarbons are divided into two classes, aromatic compounds and aliphatic compounds also known as non-aromatic compounds. Aliphatics can be cyclic, but only aromatic compounds contain an especially stable ring of atoms, aliphatic compounds can be saturated, like Hexane, or unsaturated, like Hexene and Hexyne. Open-chain compounds contain no rings of any type, and are thus aliphatic, aliphatic compounds can be saturated, joined by single bonds, or unsaturated, with double bonds or triple bonds. Besides hydrogen, other elements can be bound to the chain, the most common being oxygen, nitrogen, sulfur. The least complex aliphatic compound is methane, most aliphatic compounds are flammable, allowing the use of hydrocarbons as fuel, such as methane in Bunsen burners and as liquefied natural gas, and acetylene in welding. The most important aliphatic compounds are, n-, iso- and cyclo-alkanes n-, iso- and cyclo-alkenes and -alkynes
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Adsorption
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Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent and this process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid, respectively. Adsorption is a process while absorption involves the whole volume of the material. The term sorption encompasses both processes, while desorption is the reverse of it, similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the requirements of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms, the exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption or chemisorption. It may also occur due to electrostatic attraction, pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts thereof, are lesser known. The word adsorption was coined in 1881 by German physicist Heinrich Kayser, adsorption is usually described through isotherms, that is, the amount of adsorbate on the adsorbent as a function of its pressure or concentration at constant temperature. The quantity adsorbed is nearly always normalized by the mass of the adsorbent to allow comparison of different materials, to date,15 different isothem models were developed. The function is not adequate at very high pressure because in reality x / m has a maximum as pressure increases without bound. As the temperature increases, the k and n change to reflect the empirical observation that the quantity adsorbed rises more slowly. Irving Langmuir was the first to derive a scientifically based adsorption isotherm in 1918, the model applies to gases adsorbed on solid surfaces. It is a semi-empirical isotherm with a basis and was derived based on statistical thermodynamics. It is the most common isotherm equation to use due to its simplicity and it is based on four assumptions, All of the adsorption sites are equivalent and each site can only accommodate one molecule. The surface is energetically homogeneous and adsorbed molecules do not interact, at the maximum adsorption, only a monolayer is formed. Adsorption only occurs on localized sites on the surface, not with other adsorbates, the fourth condition is the most troublesome, as frequently more molecules will adsorb to the monolayer, this problem is addressed by the BET isotherm for relatively flat surfaces. The Langmuir isotherm is nonetheless the first choice for most models of adsorption, Langmuir suggested that adsorption takes place through this mechanism, A g + S ⇌ A S, where A is a gas molecule and S is an adsorption site. The direct and inverse rate constants are k and k−1, vmon is related to the number of adsorption sites through the ideal gas law
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Boiling point
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The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
