White ceramic powder

EINECS 215-225-1 HSDB 6364 Thoria Thorianite Thorium anhydride Thorium dioxide Thorium oxide Thorium oxide (Th02) Thorotrast Thortrast Umbrathor. Used in ceramics, gas mantles, nuclear fuel, medicine and non-silica optical glass. White crystalline powder mp = 3390 d = 10.0 insoluble in H2O carcinogen. 

Sihcon nitride occurs in two forms, a-Si N and P-Si N. Pure Si N is white, but the colors of commercial materials may be tan, gray, or black because of residual siUcon or impurities. Si N may be prepared by nitriding siUcon powder at 1200—1400°C or, for extremely fine-grained Si N, by the reaction of SiCl or SiH and N2 or NH (see also Advanced ceramics). 

Opacifiers are fine inorganic powders, usually white, that are used to reduce the transparency of ceramic gla2es and porcelain enamels. The coating becomes opaque because the particles of the opacifter scatter and reflect the incident light. When inorganic pigments are combined with white opacifiers, pastel colors are obtained. 

Other applications of ceramics require clay, either raw or purified, sand, and feldspar. Brick, porcelain, and white wares are made from these raw materials the main expenditure in making these products is in firing the mixtures of powders to a dense solid. Ordinary brick made from fire-clay requires a small amount of energy even refractory brick for high temperatures and chemical durability, made partly from purified oxides such as alumina or chrome ore,... 

Beryllium Oxide (Bromellite). BeO, mw 25.01, white amorph powd, mp 2530°, bp ca 3900°, d 3.01g/cc. Sol in coned acids and alkalies. V si sol in w. Prepn is by burning BeC03 at 900° in a Pt crucible to the oxide. It is used in nuclear reactor fuels and moderators as well as in powder metallurgy, ceramics, fuel cells and coatings (see above)... 

The polycondensation of 13 is conducted in vacuo using a process similar to that used for the polycondensation of 11. After heating to 150°C, the product becomes solid and the mechanical stirring is stopped to yield polymer 14. This product is a colorless waxy solid at 150°C, which becomes a white powder after cooling to TIoom. DSC and TGA give a 7 g 55°C and a ceramic yield of 47% (at 1000°C). 

Stannic oxide, SnC>2, is a white powder, insoluble in acids and alkalis. It is an excellent glaze opacifier, a component of pink, yellow and maroon ceramic stains and of dielectric and refractory bodies. 

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