Silica oxide ceramics

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

Stober A process for making metal oxides in the form of small spheres of uniform diameter by the controlled hydrolysis of metal alkoxides. First used in 1968 to make silica spheres from alkyl silicates. The products can be used to make high quality oxide ceramics. See also Sol-Gel. 

The use of certain vanadium compounds as catalysts has been increasing. Vanadium oxy trichloride is a catalyst in making ediylene-propylene rubber. Ammonium metavanadate and vanadium pentoxide aie used as oxidation catalysts, particularly in the production of polyamides, such as nylon, in the manufacture of H>S04 by the contact process, in the production of phdialic and maleic anhydrides, and in numerous other oxidation reactions, such as alcohol to acetaldehyde, anthracene to anthraquinone, sugar to oxalic acid, and diphenylamine to carbazole. Vanadium compounds have been used for many years 111 die ceramics field for enamels and glazes. Colors are produced by various combinations of vanadium oxide and silica, zirconia, zinc, lead, tin, selenium, and cadmium. Vanadium intermediate compounds also are used in the making of aniline Mack used by the dye industry... 

Figure 2. The proposed reaction of the bifunctional APS molecule when serving as an adhesion promoter or coupling agent for polyimide thin films on native-oxide ceramics such as silica and alumina.

In the following sections some examples are given of the ways in which these principles have been utilized. The first example is the use of these techniques for the low temperature preparation of oxide ceramics such as silica. This process can also be used to produce alumina, titanium oxide, or other metal oxides. The second example describes the conversion of organic polymers to carbon fiber, a process that was probably the inspiration for the later development of routes to a range of non-oxide ceramics. Following this are brief reviews of processes that lead to the formation of silicon carbide, silicon nitride, boron nitride, and aluminum nitride, plus an introduction to the synthesis of other ceramics such as phosphorus nitride, nitrogen-phosphorus-boron materials, and an example of a transition metal-containing ceramic material. 

Luthra KL (1994) Theoretical Aspects of the Oxidation of Silica-Forming Ceramics. In Nickel KG (ed) Corrosion of Advanced Ceramics - Measurement and Modelling. Kluwer Academic Publishers, Dordrecht, p 23... 

As to ceramic membranes [3,4] the focus has been so frir in particular on amorphous porous aluminas and silicas. Other inorganics studied include titania, zirconia, non-oxide ceramics (carbides), and microporous carbons. 

Aluminium fluoride Aluminium fluorure Aluminum fluoride (AIF3) Aluminum trifluoride CCRIS 2282 EINECS 232-051-1 Fluorid hlinity HSDB 600. Used mixed with aluminum oxide and silica for use as an electrolyte in reduction of alumina to aluminum metal as flux in remelting and refining of aluminum and its alloys opacifier aid In production of ceramic enamels, glass, and glazes. Crystals sublimes 1272 soluble in H20 (0.559 g/100 ml). Alcan Chem. 

Aluminum oxide (AI2O3, alumina, corundum) is the most widely used inorganic chemical for ceramics and is produced from the mineral bauxite using the Bayer process. Bauxite is a mixture of hydrated aluminum oxide with iron oxide (Fe203), silica (SiOi), and titania (TiOi) impurities. It results from the decay and weathering of aluminous rocks, often igneous, under tropical conditions. Like kaolin, bauxite occurs as both primary deposits and secondary deposits. 

Luthra, K.L. 1994. Theoretical aspects of the oxidation of silica-forming ceramics. Pp. 23-34 in Corrosion of Advanced Ceramics Measurement and Modeling Proceedings of the NATO Advanced Research Workshop, Tubingen, Germany August 30-September 3, 1993. Klaus G. Nickel (ed.). Norwell, Mass. Kluwer Academic Publications. 

Rosenthal, A. B. and Garofalini S. H. (1987) Structural Role of Zinc Oxide in Silica and Soda-Silica Glasses, J. Am. Ceram. Soc., 70, 821-826. 

Ceramic oxides represent the most extensive group of ceramic materials produced today. Traditionally, but rather artificially, the oxide ceramics are divided into traditional and advanced groups. The traditional ceramics include mostly silica-based products prepared from natural raw materials (clays), including building parts (bricks, tiles), pottery, sanitaryware, and porcelain, but also ceramics with other main components (e.g., alumina, magnesia), which are applied in the field of electroceramics (insulators), or industrial refractories. 

Depending on the oxidation conditions, the oxidation of silicon-rich non-oxide ceramics proceeds by passive or active oxidation. At low temperatures and high oxygen partial pressures, a protective layer of silica is formed by passive oxidation (Equations 20a and 20b). 

Ceramic Oxide Alumina Silica Zirconia Mullite High temperature Tension Creep... 

Coated silica oxide ceramic Tubular reactor 300% increase in yield Terry (1999)... 

Terry, P. A. (1999). Catalytic dehydrogenation of cyclohexene using coated silica oxide ceramic membrane. Journal of Porous Material, 6, 267—274. 

C.700 HIGH ALUMINA ceramics C.800 OXIDE CERAMICS The standard also defines six classes of glass insulating materials, based on composition G.lOO alkali-lime-silica G.200 and G.300, borosilicates (chemically and electrically resistant respectively) G.400 alumina-lime-silicates G.500 lead oxide alkali silica G.600 barium oxide alkali silica. 

Lead Silicate. A material obtained by fritting lead oxide with silica in various ratios. The usual ratio approximates to Pb0.2Si02 and a frit of this composition is known as lead bisilicate a specification (Trans. Brit. Ceram. Soc., 50,255,1951) is 63-66% PbO, 2-3.5% AI2O3, and PbO + Si02 + AI2O3 to exceed 98%. A lead solubility test (q.v.) is also specified. The bisilicate is used in pottery glazes. 

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