Zirconium sulfide is the inorganic compound with the formula ZrS2. It is a violet-brown solid, it adopts a layered structure similar to that of cadmium iodide. Like the related titanium disulfide, ZrS2 is prepared by heating sulfur and zirconium metal, it can be purified by vapor transport using iodine
Glass is a non-crystalline, amorphous solid, transparent and has widespread practical and decorative uses in, for example, window panes and optoelectronics. The most familiar, the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica, the primary constituent of sand; the term glass, in popular usage, is used to refer only to this type of material, familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of 75% silicon dioxide, sodium oxide from sodium carbonate, calcium oxide called lime, several minor additives. Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit and refract light. Glass can be coloured by adding metallic salts, can be painted and printed with vitreous enamels; these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows.
Although brittle, silicate glass is durable, many examples of glass fragments exist from early glass-making cultures. Because glass can be formed or moulded into any shape, it has been traditionally used for vessels: bowls, bottles and drinking glasses. In its most solid forms it has been used for paperweights and beads; when extruded as glass fiber and matted as glass wool in a way to trap air, it becomes a thermal insulating material, when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass. Some objects were so made of silicate glass that they are called by the name of the material, such as drinking glasses and eyeglasses. Scientifically, the term "glass" is defined in a broader sense, encompassing every solid that possesses a non-crystalline structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state. Porcelains and many polymer thermoplastics familiar from everyday use are glasses.
These sorts of glasses can be made of quite different kinds of materials than silica: metallic alloys, ionic melts, aqueous solutions, molecular liquids, polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass. Silicon dioxide is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites. Fused quartz is a glass made from chemically-pure silica, it has excellent resistance to thermal shock, being able to survive immersion in water while red hot. However, its high melting temperature and viscosity make it difficult to work with. Other substances are added to simplify processing. One is sodium carbonate; the soda makes the glass water-soluble, undesirable, so lime, some magnesium oxide and aluminium oxide are added to provide for a better chemical durability. The resulting glass is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.
Most common glass contains other ingredients to change its properties. Lead glass or flint glass is more "brilliant" because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses. Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs ultraviolet wavelengths; the following is a list of the more common types of silicate glasses and their ingredients and applications: Fused quartz called fused-silica glass, vitreous-silica glass: silica in vitreous, or glass, form. It has low thermal expansion, is hard, resists high temperatures, it is the most resistant against weathering. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc.
Soda-lime-silica glass, window glass: silica + sodium oxide + lime + magnesia + alumina. Is transparent formed and most suitable for window glass, it has a high thermal expansion and poor resistance to heat. It is used for windows, some low-temperature incandescent light bulbs, tableware. Container glass is a soda-lime glass, a slight variation on flat glass, which uses more alumina and calcium, less sodium and magnesium, which are more water-soluble; this makes it less susceptible to water erosion. Sodium borosilicate glass, Pyrex: silica + boron trioxide + soda + alumina. Stan
Lanthanum oxide known as lanthana, chemical formula La2O3, is an inorganic compound containing the rare earth element lanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, is a feedstock for certain catalysts, among other uses. Lanthanum oxide is an odorless, white solid, insoluble in water, but soluble in dilute acid. Depending on the pH of the compound, different crystal structures can be obtained. La2O3 is hygroscopic. Lanthanum oxide has p-type semiconducting properties and a band gap of 5.8 eV.. Its average room temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. La2O3 has the lowest lattice energy of the rare earth oxides, with high dielectric constant, ε = 27. At low temperatures, La2O3 has an A-M2O3 hexagonal crystal structure; the La3+ metal atoms are surrounded by a 7 coordinate group of O2−atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above one of the octahedral faces.
On the other hand, at high temperatures lanthanum oxide converts to a C-M2O3 cubic crystal structure. The La3+ ion is surrounded by six O2− ions in a hexagonal configuration. Several elements were discovered as a consequence of lengthy analysis and decomposition of the ore Gadolinite; as the ore was progressively analysed, the residue was first given the label ceria and lanthana and subsequently yttria and terbia. In order of date discovered, the list of elements includes Cerium 58, Lanthanum 57, Erbium 68, Terbium 65, Yttrium 39, Ytterbium 70, Holmium 67, Thulium 69, Scandium 21, Praseodymium 59, Neodymium 60 and Dysprosium 66. Several of these new elements were either discovered or isolated by Carl Gustaf Mosander in the 1830s and 1840s. Lanthanum oxide can be crystallized in several polymorphs. To produce hexagonal La2O3, a 0.1 M solution of LaCl3 is sprayed onto a preheated substrate made of metal chalcogenides. The process can be viewed as occurring in two steps – hydrolysis followed by dehydration: 2 LaCl3 + 3 H2O → La3 + 3 HCl2 La3 → La2O3 + 3 H2OAn alternative route to obtaining hexagonal La2O3 involves precipitation of nominal La3 from aqueous solution using a combination of 2.5% NH3 and the surfactant sodium dodecyl sulfate followed by heating and stirring for 24 hours at 80 °C: 2 LaCl3+ 3 H2O + 3 NH3 → La3 + 3 NH4Cl LaCl3·3H2O → La2O3Other routes include: 2 La2S3 + 3 CO2 → 2 La2O3 + 3 CS2 2 La23 + heat → 2 La2O3 + 6 SO3 Lanthanum oxide is used as an additive to develop certain ferroelectric materials, such as La-doped Bi4Ti3O12.
Lanthanum oxide is used in optical materials. 3 B2O3 + La2O3 → 2 La3When this 1:3 reaction is mixed into a glass composite, the high molecular weight of the lanthanum causes an increase of the homogeneous mixture of the melt which leads to a lower melting point. The addition of the La2O3 to the glass melt leads to a higher glass transition temperature from 658 °C to 679 °C; the addition leads to a higher density and refractive index of the glass. La2O3 is used to make optical glasses, to which this oxide confers increased density, refractive index, hardness. Together with oxides of tungsten and thorium, La2O3 improves the resistance of the glass to attack by alkali. La2O3 is an ingredient for the manufacture of thermoelectric materials. Automobile exhaust-gas converters contain La2O3. La2O3 is used in X-ray imaging intensifying screens, phosphors as well as dielectric and conductive ceramics. Gives off bright glow. La2O3 has been examined for the oxidative coupling of methane. La2O3 films can be deposited by many different methods, including chemical vapor disposition, atomic layer deposition, thermal oxidation and spray pyrolysis.
Depositions of these films occur in a temperature range of 250–450 °C. Polycrystalline films are formed at 350 °C. La2O3 tungsten electrodes are replacing thoriated tungsten electrodes in Gas tungsten arc welding due to safety concerns with thorium's radioactivity
Zirconium chloride known as zirconium tetrachloride, is an inorganic compound used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes in humid air. Unlike molecular TiCl4, solid ZrCl4 adopts a polymeric structure wherein each Zr is octahedrally coordinated; this difference in structures is responsible for the disparity in their properties: TiCl4 is distillable, but ZrCl4 is a solid. In the solid state, ZrCl4 adopts a tape-like linear polymeric structure—the same structure adopted by HfCl4; this polymer degrades upon treatment with Lewis bases, which cleave the Zr-Cl-Zr linkages. This conversion entails treatment of the oxide with carbon as chlorine. ZrO2 + 2 C + 2 Cl2 → ZrCl4 + 2 COA laboratory scale process uses carbon tetrachloride in place of carbon and chlorine: ZrO2 + 2 CCl4 → ZrCl4 + 2 COCl2 ZrCl4 is an intermediate in the conversion of zirconium minerals to metallic zirconium by the Kroll process. In nature, zirconium minerals invariably exist as oxides.
For their conversion to bulk metal, these refractory oxides are first converted to the tetrachloride, which can be distilled at high temperatures. The purified ZrCl4 can be reduced with Zr metal to produce zirconium chloride. ZrCl4 is the most common precursor for chemical vapor deposition of zirconium dioxide and zirconium diboride. In organic synthesis zirconium tetrachloride is used as a weak Lewis acid for the Friedel-Crafts reaction, the Diels-Alder reaction and intramolecular cyclisation reactions, it is used to make water-repellent treatment of textiles and other fibrous materials. Hydrolysis of ZrCl4 gives the hydrated hydroxy chloride cluster called zirconyl chloride; this reaction is rapid and irreversible, consistent with the high oxophilicity of zirconium. For this reason, manipulations of ZrCl4 require air-free techniques. ZrCl4 is the principal starting compound for the synthesis of many organometallic complexes of zirconium; because of its polymeric structure, ZrCl4 is converted to a molecular complex before use.
It forms a 1:2 complex with tetrahydrofuran: CAS, mp 175–177 °C. NaC5H5 reacts with ZrCl42 to give zirconocene dichloride, ZrCl22, a versatile organozirconium complex. One of the most curious properties of ZrCl4 is its high solubility in the presence of methylated benzenes, such as durene; this solubilization arises through the formation of π-complexes. The log of the vapor pressure of zirconium tetrachloride is given by the equation: log10 = −5400/T + 11.766, where the pressure is measured in torrs and temperature in kelvins. The log of the vapor pressure of solid zirconium tetrachloride is given by the equation log10 = −3427/T + 9.088. The pressure at the melting point is 14,500 torrs