Sol gel is a colloidal suspension of silicon dioxide that is gelled to form a solid. The resulting porous gel then is chemically purified and fired at high temperatures into high purity silica. The gel can be modified with a number of dopants to produce unique properties in the resultant glass unattainable by other means. It can be used in ceramics manufacturing processes, as an investment casting material, or as a means of producing very thin films of metal oxides for various purposes, including a form superior to teflon. Sol-gel derived materials have diverse applications in optics, electronics, energy, space, sensors and separation technology. A colloid or colloidal dispersion, is a form of matter intermediate between a true solution and a mixture (suspension). ... Flour suspended in water In chemistry, a suspension is a colloidal dispersion (mixture) in which a finely-divided species is combined with another species, with the former being so finely divided and mixed that it doesnt rapidly settle out. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... A gel (from the lat. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... A dopant is an impurity element added to a semiconductor lattice in quite low concentrations in order to alter the optical/electrical properties of the semiconductor. ... This article refers to the material. ... Crown The word ceramic is derived from the Greek word κεραμικος (keramikos, having to do with pottery). The term covers inorganic non-metallic materials whose formation is due to the action of heat. ... The lost wax process is a method that requires the metallurgist to build a wax replica of the item that is desired to be replicated, followed by the coating of the wax sculpted article in a heat resistant yet durable exterior, typically a ceramic, which is then fired to permit... Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ... An oxide is a chemical compound of oxygen with other chemical elements. ... Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910–1994) of DuPont in 1938 and introduced as a commercial product in 1946. ...

The sol-gel process

The sol-gel process is a process for making glass/ceramic materials. The sol-gel process involves the transition of a system from a liquid (the colloidal “sol") into a solid (the "gel") phase. The sol-gel process allows the fabrication of materials with a large variety of properties: ultra-fine powders, monolithic ceramics and glasses, ceramic fibers, inorganic membranes, thin film coatings and aerogels. Solgel chemistry is a remarkably versatile approach for fabricating materials. Scientists have used it to produce the world’s lightest materials and some of its toughest ceramics. This article refers to the material. ... Crown The word ceramic is derived from the Greek word κεραμικος (keramikos, having to do with pottery). The term covers inorganic non-metallic materials whose formation is due to the action of heat. ... A colloid or colloidal dispersion, is a form of matter intermediate between a true solution and a mixture (suspension). ... Look up sol in Wiktionary, the free dictionary. ... A gel (from the lat. ... Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ... A 2. ... Toughness, in material science and metallurgy, is the resistance to fracture of a material when suddenly stressed. ...

The sol is made of solid particles of a diameter of few hundred nm, usually inorganic metal salts, suspended in a liquid phase. In a typical sol-gel process, the precursor is subjected to a series of hydrolysis and polymerization reactions to form a colloidal suspension, then the particles condense in a new phase, the gel, in which a solid macromolecule is immersed in a solvent. Hydrolysis is a chemical process in which a molecule is split into two parts by the addition of a molecule of water. ... Polymerization is a process of reacting monomer molecules together in a chemical reaction to form linear chains or a three-dimensional network of polymer chains [1]. There are many forms of polymerization and different systems exist to categorize them. ... A colloidal suspension consists of a mixture of compounds in which a solid or liquid is suspended in a fluid because of its particle size. ... A macromolecule is a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ...

The beginnings of sol-gel processing can be traced back over 50 years to research done by Rustom Roy at Pennsylvania State University. Roy, born in the Bihar province of India, had come to the United States in 1944 for graduate studies under Elburt F. Osborn. In 1956, he wrote a review paper that became the first citation classic in the field. Sol-gel research grew to be so important that in the 1990s more than 50,000 papers were published worldwide on the process. The Pennsylvania State University The Pennsylvania State University (commonly known as Penn State) is a state-related land-grant university based in State College, Pennsylvania (the university uses a University Park, Pennsylvania to differentiate University addresses from those in town), with over 80,000 students at 24 campuses throughout the... Bihar (बिहार in Devanagari) is a state of the Indian union situated in the eastern part of the country. ... 1944 (MCMXLIV) was a leap year starting on Saturday (link will take you to calendar). ... 1956 (MCMLVI) was a leap year starting on Sunday of the Gregorian calendar. ...

Applications

The applications for sol gel-derived products are numerous. One of the largest application areas is thin films, these can be produced on a piece of substrate by spin-coating or dip-coating. Other methods include spraying, electrophoresis, inkjet printing or roll coating. Optical coatings, protective and decorative coatings, and electro-optic components can be applied to glass, metal and other types of substrates with these methods. Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ... Spin coating is a procedure used to apply uniform thin films to flat substrates. ... Electrophoresis is the movement of an electrically charged substance under the influence of an electric field. ... Ink jet printers are the most common type of computer printer; and industry and commerce also use them extensively for special-purpose applications. ... An optical coating is a thin layer of material placed on an optical component such as a lens or mirror which alters the way in which the optic reflects and transmits light. ...

Cast into a mold, and with further drying and heat-treatment, dense ceramic or glass articles with novel properties can be formed that cannot be created by any other method. Macroscopic optical elements and active optical components as well as large area hot mirrors, cold mirrors, lenses and beam splitters all with optimal geometry can be made quickly and at low cost via the sol-gel route. See also list of optical topics. ... A hot mirror is a specialized dichromatic interference filter often employed to protect optical systems by reflecting heat back into the light source. ... Cold Mirror is a specialized dichromatic interference filter that operates over a very wide temperature range to reflect the entire visible light spectrum while very efficiently transmitting infrared wavelengths. ... A lens. ... A beam splitter is an optical device, that splits a beam of light in two. ...

With the viscosity of a sol adjusted into a proper range, both optical and refractory ceramic fibers can be drawn which are used for fiber optic sensors and thermal insulation, respectively. The pitch drop experiment at the University of Queensland. ...

Ultra-fine and uniform ceramic powders can be formed by precipitation. These powders of single- and multicomponent compositions can be made in submicron particle size for dental and biomedical applications. Composite powders have been patented for use as agrochemicals and herbicides. Also powder abrasives, used in a variety of finishing operations, are made using a sol-gel type process. Agrichemical (or agrochemical) is a generic term for the various synthetic chemical products manufactured and sold for use in agriculture. ... Image:Http://www. ... An abrasive is a usually rough object that is used to smooth another through extensive rubbing. ...

One of the more important aplications of sol-gel processing is to carry out zeolite synthesis. Other elements (metals, metal oxides) can be easily incorporated into the final product and the silicalite sol formed by this method is very stable. Zeolite Zeolites (Greek, zein,to boil;lithos,a stone) are minerals that have a porous structure. ...

Other products fabricated with this process include various ceramic membranes for microfiltration, ultrafiltration, nanofiltration, pervaporation and reverse osmosis. This article or section should include material from Net flux A membrane is a thin, typically planar structure or material that separates two environments. ... Microfiltration is a filtration process which removes contaminants from a fluid or gas by passage through a microporous membrane. ... Ultrafiltration (UF) is a pressure-driven membrane process for purifying and concentrating macromolecular (10^3 - 10^6 Da) solutions, especially protein solutions. ... Pervaporation is a method for the separation of mixtures of liquids by partial vaporization through a non-porous membrane. ... The term reverse osmosis comes from the process of osmosis, the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration if no external pressure is applied. ...

If the liquid in a wet gel is removed under a supercritical condition, a highly porous and extremely low density material called aerogel is obtained. Drying the gel by means of low temperature treatments (25-100 C), it is possible to obtain porous solid matrices called xerogels. In chemistry and condensed matter physics, a critical point specifies the conditions (temperature, pressure) at which the liquid state of the matter ceases to exist. ... A 2. ... A term used for the dried out open structures which have passed a gel stage during preparation (e. ...

Finally of historical note, a sol-gel process was developed in the 1950s for the production of radioactive powders of UO₂ and ThO₂ for nuclear fuels, without generation of large quantities of dust. 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. ...

References

• Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing by C. Jeffrey Brinker, George W. Scherer
• Sol-Gel Materials: Chemistry and Applications by John D. Wright, Nico A.J.M. Sommerdijk
• Sol-Gel Technologies for Glass Producers and Users by Michel A. Aegerter and M. Mennig

External links

• the Sol-Gel Gateway
• Journal of Sol-Gel Science and Technology