Solid is one of the four fundamental states of matter. It is characterized by structural rigidity and resistance to changes of shape or volume, unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to other, either in a regular geometric lattice or irregularly. The branch of physics deals with solids is called solid-state physics. Materials science is concerned with the physical and chemical properties of solids. Solid-state chemistry is concerned with the synthesis of novel materials, as well as the science of identification. The atoms, molecules or ions which make up solids may be arranged in a repeating pattern. Materials whose constituents are arranged in a regular pattern are known as crystals, in some cases, the regular ordering can continue unbroken over a large scale, for example diamonds, where each diamond is a single crystal. Almost all common metals, and many ceramics, are polycrystalline, in other materials, there is no long-range order in the position of the atoms.
These solids are known as amorphous solids, examples include polystyrene, whether a solid is crystalline or amorphous depends on the material involved, and the conditions in which it was formed. Solids which are formed by slow cooling will tend to be crystalline, the specific crystal structure adopted by a crystalline solid depends on the material involved and on how it was formed. While many common objects, such as an ice cube or a coin, are chemically identical throughout, for example, a typical rock is an aggregate of several different minerals and mineraloids, with no specific chemical composition. Wood is an organic material consisting primarily of cellulose fibers embedded in a matrix of organic lignin. In materials science, composites of more than one constituent material can be designed to have desired properties, the forces between the atoms in a solid can take a variety of forms. For example, a crystal of sodium chloride is made up of sodium and chlorine. In diamond or silicon, the atoms share electrons and form covalent bonds, in metals, electrons are shared in metallic bonding.
Some solids, particularly most organic compounds, are together with van der Waals forces resulting from the polarization of the electronic charge cloud on each molecule. The dissimilarities between the types of solid result from the differences between their bonding, metals typically are strong and good conductors of both electricity and heat
Antifreeze proteins or ice structuring proteins refer to a class of polypeptides produced by certain vertebrates, plants and bacteria that permit their survival in subzero environments. AFPs bind to small ice crystals to inhibit growth and recrystallization of ice that would otherwise be fatal, There is increasing evidence that AFPs interact with mammalian cell membranes to protect them from cold damage. This work suggests the involvement of AFPs in cold acclimatization, unlike the widely used automotive antifreeze, ethylene glycol, AFPs do not lower freezing point in proportion to concentration. Rather, they work in a noncolligative manner and this phenomenon allows them to act as an antifreeze at concentrations 1/300th to 1/500th of those of other dissolved solutes. Their low concentration minimizes their effect on osmotic pressure, the unusual properties of AFPs are attributed to their selective affinity for specific crystalline ice forms and the resulting blockade of the ice-nucleation process.
AFPs create a difference between the point and freezing point known as thermal hysteresis. The addition of AFPs at the interface between ice and liquid water inhibits the thermodynamically favored growth of the ice crystal. Ice growth is inhibited by the AFPs covering the water-accessible surfaces of ice. Thermal hysteresis is easily measured in the lab with a nanolitre osmometer, organisms differ in their values of thermal hysteresis. The maximum level of thermal hysteresis shown by fish AFP is approximately -1.5 °C, insect antifreeze proteins are 10–30 times more active than fish proteins. This difference probably reflects the lower temperatures encountered by insects on land, in contrast, aquatic organisms are exposed only to -1 to -2 °C below freezing. During the extreme winter months, the spruce budworm resists freezing at temperatures approaching -30 °C, the Alaskan beetle Upis ceramboides can survive in a temperature of -60 °C by using antifreeze agents that are not proteins. The rate of cooling can influence the thermal hysteresis value of AFPs, rapid cooling can substantially decrease the nonequilibrium freezing point, and hence the thermal hysteresis value.
Consequently, organisms cannot necessarily adapt to their subzero environment if the temperature drops abruptly, species containing AFPs may be classified as Freeze avoidant, These species are able to prevent their body fluids from freezing altogether. Generally, the AFP function may be overcome at extremely cold temperatures, Freeze tolerant, These species are able to survive body fluid freezing. Some freeze tolerant species are thought to use AFPs as cryoprotectants to prevent the damage of freezing, the exact mechanism is still unknown. However, it is thought AFPs may inhibit recrystallization and stabilize cell membranes to prevent damage by ice and they may work in conjunction with protein ice nucleators to control the rate of ice propagation following freezing. There are many known types of AFPs
The Verneuil process, called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in 1902 by the French chemist Auguste Verneuil. It is primarily used to produce the ruby and sapphire varieties of corundum, as well as the diamond simulants rutile, the principle of the process involves melting a finely powdered substance using an oxyhydrogen flame, and crystallising the melted droplets into a boule. The process is considered to be the step of modern industrial crystal growth technology. By 1877, chemist Edmond Frémy had devised a method for commercial ruby manufacture by using molten baths of alumina. One of Verneuils sources of inspiration for developing his own method was the appearance of synthetic rubies sold by an unknown Genevan merchant in 1880. These Geneva rubies were dismissed as artificial at the time, but are now believed to be the first rubies produced by flame fusion, after examining the Geneva rubies, Verneuil came to the conclusion that it was possible to recrystallise finely ground aluminium oxide into a large gemstone.
He announced his work in 1902, publishing details outlining the process in 1904, by 1910, Verneuils laboratory had expanded into a 30-furnace production facility, with annual gemstone production by the Verneuil process having reached 1,000 kg in 1907. By 1912, production reached 3,200 kg, and would go on to reach 200,000 kg in 1980 and 250,000 kg in 2000, led by Hrand Djevahirdjians factory in Monthey, founded in 1914. The most notable improvements in the process were made in 1932, by S. K. Popov, who helped establish the capability for producing high-quality sapphires in the Soviet Union through the next 20 years. A large production capability was established in the United States during World War II, when European sources were not available. The process was designed primarily for the synthesis of rubies, which became the first gemstones to be produced, thanks to the efforts of Fremy. Other alternatives to the process emerged in 1957, when Bell Labs introduced the process, and in 1958. In 1989 Larry P Kelley of ICT, Inc.
developed a variant of the Czochralski process where natural ruby is used as the feed material. One of the most crucial factors in successfully crystallising an artificial gemstone is obtaining highly pure starting material, in the case of manufacturing rubies or sapphires, this material is alumina. The presence of impurities is especially undesirable, as it makes the crystal opaque. Depending on the colouration of the crystal, small quantities of various oxides are added, such as chromium oxide for a red ruby, or ferric oxide. Other starting materials include titania for producing rutile, or titanyl double oxalate for producing strontium titanate, small, valueless crystals of the desired product can be used. This starting material is powdered, and placed in a container within a Verneuil furnace
Crystal bar process
The crystal bar process was developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925. This process was the first industrial process for the production of pure ductile metallic zirconium. It is used in the production of quantities of ultra-pure titanium and zirconium. It primarily involves the formation of the iodides and their subsequent decomposition to yield pure metal. This process was superseded commercially by the Kroll process, as seen in the diagram below, impure titanium, hafnium, thorium or protactinium is heated in an evacuated vessel with a halogen at 50–250 °C. The patent specifically involved the intermediacy of TiI4 and ZrI4, which were volatilized, at atmospheric pressure TiI4 melts at 150 °C and boils at 377 °C, while ZrI4 melts at 499 °C and boils at 600 °C. The boiling points are lower at reduced pressure, the gaseous metal tetraiodide is decomposed on a white hot tungsten filament. As more metal is deposited the filament conducts better and thus an electric current is required to maintain the temperature of the filament.
The process can be performed in the span of hours or several weeks. The only metals it has used to purify on an industrial scale are titanium and hafnium. Several metals purified via this process
Zone melting is a group of similar methods of purifying crystals, in which a narrow region of a crystal is melted, and this molten zone is moved along the crystal. The molten region melts impure solid at its edge and leaves a wake of purer material solidified behind it as it moves through the ingot. The impurities concentrate in the melt, and are moved to one end of the ingot and this process is known as the float zone process, particularly in semiconductor materials processing. The principle is that the coefficient k is usually less than one. Therefore, at the boundary, the impurity atoms will diffuse to the liquid region. When high purity is required, such as in industry, the impure end of the boule is cut off. In zone refining, solutes are segregated at one end of the ingot in order to purify the remainder, in zone leveling, the objective is to distribute solute evenly throughout the purified material, which may be sought in the form of a single crystal. For example, in the preparation of a transistor or diode semiconductor, a small amount of antimony is placed in the molten zone, which is passed through the pure germanium.
With the proper choice of rate of heating and other variables and this technique is used for the preparation of silicon for use in computer chips. A variety of heaters can be used for melting, with their most important characteristic being the ability to form short molten zones that move slowly and uniformly through the ingot. Induction coils, ring-wound resistance heaters, or gas flames are common methods, when the liquid zone moves by a distance d x, the number of impurities in the liquid change. Impurities are incorporated in the liquid and freezing solid. The bulk charge carrier lifetime in float-zone silicon is the highest among various manufacturing processes, float-zone carrier lifetimes are around 1000 microseconds compared to 20-200 microseconds with Czochralski process, and 1–30 microseconds with cast multi-crystalline silicon. A longer bulk lifetime increases the efficiency of solar cells significantly, another related process is zone remelting, in which two solutes are distributed through a pure metal.
This is important in the manufacture of semiconductors, where two solutes of opposite conductivity type are used, by melting a portion of such an ingot and slowly refreezing it, solutes in the molten region become distributed to form the desired n-p and p-n junctions. Hermann Schildknecht Zone Melting, Verlag Chemie, georg Müller Crystal growth from the melt Springer-Verlag, Science 138 pages ISBN 3-540-18603-4, ISBN 978-3-540-18603-8
A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, the scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification, the word crystal derives from the Ancient Greek word κρύσταλλος, meaning both ice and rock crystal, from κρύος, icy cold, frost. Examples of large crystals include snowflakes and table salt, most inorganic solids are not crystals but polycrystals, i. e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, ceramics, a third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass and many plastics, Crystals are often used in pseudoscientific practices such as crystal therapy, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements.
The scientific definition of a crystal is based on the arrangement of atoms inside it. A crystal is a solid where the form a periodic arrangement. For example, when liquid water starts freezing, the change begins with small ice crystals that grow until they fuse. Most macroscopic inorganic solids are polycrystalline, including almost all metals, ice, solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids, called glassy, vitreous, or noncrystalline. These have no periodic order, even microscopically, there are distinct differences between crystalline solids and amorphous solids, most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure is characterized by its cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal, the symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps.
There are 219 possible crystal symmetries, called space groups. These are grouped into 7 crystal systems, such as cubic crystal system or hexagonal crystal system, Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. Euhedral crystals are those with obvious, well-formed flat faces, anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces of a crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal. This occurs because some surface orientations are more stable than others, as a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces
By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder. The method revealed the structure and function of biological molecules, including vitamins, proteins. X-ray crystallography is still the method for characterizing the atomic structure of new materials. In a single-crystal X-ray diffraction measurement, a crystal is mounted on a goniometer, the goniometer is used to position the crystal at selected orientations. The crystal is illuminated with a finely focused monochromatic beam of X-rays, poor resolution or even errors may result if the crystals are too small, or not uniform enough in their internal makeup. X-ray crystallography is related to other methods for determining atomic structures. Similar diffraction patterns can be produced by scattering electrons or neutrons, for all above mentioned X-ray diffraction methods, the scattering is elastic, the scattered X-rays have the same wavelength as the incoming X-ray.
By contrast, inelastic X-ray scattering methods are useful in studying excitations of the sample, though long admired for their regularity and symmetry, were not investigated scientifically until the 17th century. Johannes Kepler hypothesized in his work Strena seu de Nive Sexangula that the symmetry of snowflake crystals was due to a regular packing of spherical water particles. The Danish scientist Nicolas Steno pioneered experimental investigations of crystal symmetry, William Hallowes Miller in 1839 was able to give each face a unique label of three small integers, the Miller indices which remain in use today for identifying crystal faces. In the 19th century, a catalog of the possible symmetries of a crystal was worked out by Johan Hessel, Auguste Bravais, Evgraf Fedorov, Arthur Schönflies. Wilhelm Röntgen discovered X-rays in 1895, just as the studies of crystal symmetry were being concluded, physicists were initially uncertain of the nature of X-rays, but soon suspected that they were waves of electromagnetic radiation, in other words, another form of light.
Single-slit experiments in the laboratory of Arnold Sommerfeld suggested that X-rays had a wavelength of about 1 angstrom, however, X-rays are composed of photons, and thus are not only waves of electromagnetic radiation but exhibit particle-like properties. Albert Einstein introduced the concept in 1905, but it was not broadly accepted until 1922. Therefore, these properties of X-rays, such as their ionization of gases. Nevertheless, Braggs view was not broadly accepted and the observation of X-ray diffraction by Max von Laue in 1912 confirmed for most scientists that X-rays were a form of electromagnetic radiation, Crystals are regular arrays of atoms, and X-rays can be considered waves of electromagnetic radiation. Atoms scatter X-ray waves, primarily through the atoms electrons and this phenomenon is known as elastic scattering, and the electron is known as the scatterer
Nuclear magnetic resonance spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei. This type of spectroscopy determines the physical and chemical properties of atoms or the molecules in which they are contained and it relies on the phenomenon of nuclear magnetic resonance and can provide detailed information about the structure, reaction state, and chemical environment of molecules. Suitable samples range from small compounds analyzed with 1-dimensional proton or carbon-13 NMR spectroscopy to large proteins or nucleic acids using 3 or 4-dimensional techniques. The impact of NMR spectroscopy on the sciences has been substantial because of the range of information, NMR spectra are unique, well-resolved, analytically tractable and often highly predictable for small molecules. Thus, in organic chemistry practice, NMR analysis is used to confirm the identity of a substance, different functional groups are obviously distinguishable, and identical functional groups with differing neighboring substituents still give distinguishable signals. NMR has largely replaced traditional wet chemistry tests such as reagents or typical chromatography for identification. A disadvantage is that a large amount, 2–50 mg, of a purified substance is required.
Preferably, the sample should be dissolved in a solvent, because NMR analysis of solids requires a dedicated MAS machine, the timescale of NMR is relatively long, and thus it is not suitable for observing fast phenomena, producing only an averaged spectrum. NMR spectrometers are relatively expensive, universities usually have them, modern NMR spectrometers have a very strong and expensive liquid helium-cooled superconducting magnet, because resolution directly depends on magnetic field strength. There are even benchtop NMR spectrometers, the Purcell group at Harvard University and the Bloch group at Stanford University independently developed NMR spectroscopy in the late 1940s and early 1950s. Edward Mills Purcell and Felix Bloch shared the 1952 Nobel Prize in Physics for their discoveries, when placed in a magnetic field, NMR active nuclei absorb electromagnetic radiation at a frequency characteristic of the isotope. The resonant frequency, energy of the absorption, and the intensity of the signal are proportional to the strength of the magnetic field, for example, in a 21 Tesla magnetic field, protons resonate at 900 MHz.
It is common to refer to a 21 T magnet as a 900 MHz magnet, spinning the sample is necessary to average out diffusional motion. Whereas, measurements of diffusion constants are done the sample stationary and spinning off, the vast majority of nuclei in a solution would belong to the solvent, and most regular solvents are hydrocarbons and would contain NMR-reactive protons. The most used deuterated solvent is deuterochloroform, although deuterium oxide and deuterated DMSO are used for hydrophilic analytes, the chemical shifts are slightly different in different solvents, depending on electronic solvation effects. NMR spectra are often calibrated against the known solvent residual proton peak instead of added tetramethylsilane, to detect the very small frequency shifts due to nuclear magnetic resonance, the applied magnetic field must be constant throughout the sample volume. High resolution NMR spectrometers use shims to adjust the homogeneity of the field to parts per billion in a volume of a few cubic centimeters.
In order to detect and compensate for inhomogeneity and drift in the magnetic field, in modern NMR spectrometers shimming is adjusted automatically, though in some cases the operator has to optimize the shim parameters manually to obtain the best possible resolution
Fractional freezing is a process used in process engineering and chemistry to separate substances with different melting points. The initial sample is thus fractionated, fractional freezing is generally used to produce ultra-pure solids, or to concentrate heat-sensitive liquids. Such enrichment parallels enrichment by true distillation, where the evaporated and re-condensed portion is richer than the portion left behind. The detailed situation is the subject of thermodynamics, a subdivision of physics of importance to chemistry, without resorting to mathematics, the following can be said for a mixture of water and alcohol, Freezing in this scenario begins at a temperature significantly below 0 °C. The first material to freeze is not the water, but a solution of alcohol in water. The liquid left behind is richer in alcohol, and as a consequence, the frozen material, while always poorer in alcohol than the liquid, becomes progressively richer in alcohol. Further stages of removing material and waiting for more freezing will come to naught once the liquid uniformly cools to the temperature of whatever is cooling it.
The best-known freeze-distilled beverages are applejack and ice beer, ice wine is the result of a similar process, but in this case, the freezing happens before the fermentation, and thus it is sugar, not alcohol, that gets concentrated. For an in depth discussion of the physics and chemistry, see eutectic point, when a pure solid is desired, two possible situations can occur. If the contaminant is soluble in the solid, a multiple stage fractional freezing is required. If, however, a system forms, a very pure solid can be recovered. When the requirement is to concentrate a liquid phase, fractional freezing can be due to its simplicity. Fractional freezing is used in the production of fruit juice concentrates and other heat-sensitive liquids. Fractional freezing can be used to desalinate sea water, in a process that naturally occurs with sea ice, frozen salt water, when partially melted, leaves behind ice that is of a much lower salt content. Because sodium chloride lowers the point of water, the salt in sea water tends to be forced out of pure water while freezing.
Likewise, the water with the highest concentration of salt melts first. Either method decreases the salinity of the water left over. Fractional freezing can be used as a method to increase the alcohol concentration in fermented alcoholic beverages
This article deals with melting/freezing point depression due to very small particle size. For depression due to the mixture of compound, see freezing-point depression. Melting-point depression is the phenomenon of reduction of the point of a material with reduction of its size. This phenomenon is very prominent in nanoscale materials, which melt at temperatures hundreds of degrees lower than bulk materials, the melting temperature of a bulk material is not dependent on its size. However, as the dimensions of a material decrease towards the atomic scale, the decrease in melting temperature can be on the order of tens to hundreds of degrees for metals with nanometer dimensions. Melting-point depression is most evident in nanowires and nanoparticles, changes in melting point occur because nanoscale materials have a much larger surface-to-volume ratio than bulk materials, drastically altering their thermodynamic and thermal properties. This article focuses on nanoparticles because researchers have compiled a large amount of size-dependent melting data for near spherical nanoparticles, nanoparticles are easiest to study due their ease of fabrication and simplified conditions for theoretical modeling.
The melting temperature of a nanoparticle decreases sharply as the particle reaches critical diameter, Figure 1 shows the shape of a typical melting curve for a metal nanoparticle as a function of its diameter. Melting point depression is an important issue for applications involving nanoparticles. Nanoparticles are currently used or proposed for prominent roles in catalyst, medicinal, magnetic, electronic, nanoparticles must be in the solid state to function at elevated temperatures in several of these applications. Two techniques allow measurement of the point of nanoparticle. As described above, the beam of the transmission electron microscope can be used to melt nanoparticles. The melting temperature is estimated from the intensity, while changes in the diffraction conditions to indicate phase transition from solid to liquid. This method allows direct viewing of nanoparticles as they melt, making it possible to test, the TEM limits the pressure range at which melting point depression can be tested.
More recently, researchers developed nanocalorimeters that directly measure the enthalpy, nanocalorimeters provide the same data as bulk calorimeters, however additional calculations must account for the presence of the substrate supporting the particles. A narrow size distribution of nanoparticles is required since the procedure does not allow users to view the sample during the melting process, there is no way to characterize the exact size of melted particles during experiment. Melting point depression was predicted in 1909 by Pawlow, takagi first observed melting point depression of several types of metal nanoparticles in 1954. A variable intensity electron beam from an electron microscope melted metal nanoparticles in early experiments
The skull crucible process was developed at the Lebedev Physical Institute in Moscow to manufacture cubic zirconia. It was invented to solve the problem of cubic zirconias melting-point being too high for even platinum crucibles, in essence, by heating only the center of a volume of cubic zirconia, the material forms its own crucible from its cooler outer layers. The term skull refers to these outer layers forming a shell enclosing the molten volume, zirconium oxide powder is heated gradually allowed to cool. Heating is accomplished by radio frequency using a coil wrapped around the apparatus. The outside of the device is water-cooled in order to keep the RF coil from melting and to cool the outside of the zirconium oxide and thus maintain the shape of the zirconium powder. Since zirconium oxide in its solid state does not conduct electricity, as the zirconium melts it oxidizes and blends with the now molten zirconium oxide, a conductor, and is heated by RF induction. When the zirconium oxide is melted on the inside the amplitude of the RF induction coil is gradually reduced, normally this would form a monoclinic crystal system of zirconium oxide.
In order to maintain a cubic crystal system a stabilizer is added, magnesium oxide, after the mixture cools the outer shell is broken off and the interior of the gob is used to manufacture gemstones