Titanium silicon carbide processing

Titanium isotopic data for mainstream silicon carbide grains versus 829Si. The correlation between excesses of minor titanium isotopes and minor silicon isotopes most likely reflects galactic chemical evolution. The offset of the S50Ti trend to pass above the solar composition probably reflects 5-process nucleosynthesis in the parent stars, which most strongly affects 50Ti. Data from Huss and Smith (2007) and references therein. 

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. 

This process is carried out in Japan by Nippon Carbon Co. to make NICALON silicon carbide fibers, with high tensile strength and excellent temperature and oxidation resistance. It can also be used to generate coatings and solid objects. Modifications of the basic process include the addition of borosiloxanes as catalysts, and the incorporation of titanium, in the form of titanium alkoxides, to produce fibers containing titanium and oxygen as well as silicon and carbon. 

Silicon of exceptional purity for semiconductor and photovoltaic industries is obtained from metallurgical-grade silicon or liquid silicon tetrachloride. At least four of six steps involve fluidized beds. In Osaka Titanium s process, step 1 (obtaining SiHCls from Si and HCl) takes place at 300°C, whereas in the Union Carbide process, SiHCls is obtained by hydrogenating gaseous SiCU over CUCI2 catalyst at 500°C. Other... 

The catalyst systems employed are based on molybdenum and phosphorus. They also contain Various additives (oxides of bismuth, antimony, thorium, chromium, copper, zirconium, etc.) and occur in the form of complex phosphomolybdates, or preferably heteropolyacids deposited on an inert support (silicon carbide, a-alumina, diatomaceous earths, titanium dioxide, etc.). This makes them quite different from the catalysts used to produce acrylic acid, which do not offer sufficient activity in this case. With residence times of 2 to 5 s, once-through conversion is better than 90 to 95 per cent, and the molar yield of methacrylic acid is up to 85 to 90 per cent The main by-products formed are acetic add, acetone, acrylic add, CO, C02, etc. The major developments in this area were conducted by Asahi Glass, Daicel, Japan Catalytic Chemical, Japanese Gem, Mitsubishi Rayon, Nippon Kayaku, Standard Oil, Sumitomo Chemical, Toyo Soda, Ube, etc. A number of liquid phase processes, operating at about 30°C, in die presence of a catalyst based on silver or cobalt in alkaline medium, have been developed by ARCO (Atlantic Richfield Co,), Asahi, Sumitomo, Union Carbide, etc. 

Diamond, silicon carbide, titanium carbide, and gallium nitride are materials that do not have wet etch processes, but RIE processes do... 

Until recently, the great majority of ceramic fibers were made from oxides such as alumina or mullite. But in the last few years, much woric has been done to develop practical processes for the production of other fiber materials, especially the refr actory carbides and nitrides. This work is beginning to bear results especially with silicon carbide fibers vt4iich have now reached full-scale production. Other materials such as silicon nitride, boron nitride, aluminum nitride, titanium carbide, hafriium carbide, and hafiiium nitride are at die development stage or in pre-production.l d... 

For most of applications, it is required to purity BPA from the mentioned byproducts before its further processing. Therefore, the BPA production line consists of a condensation reactor and the units responsible for the BPA purification. Among them, there is usually a unit for crystallization of the BPA-phenol adduct and stripping tower, where the adduct is cracked and phenol is recovered (as it was described earlier). There are also a recrystallization unit, a cracker for the o,p-isomers of BPA and a wastewater treatment facility. Additionally, there may be an isomerization unit, where the mother liquor is contacted with an acidic or amine-based ion-exchange resin as the isomerization catalyst under the conditions effective to convert the BPA byproducts to BPA. Next, the effluent from the isomerization zone can be contacted with a solid particle guard bed, composed of alumina, titanium oxide, silica, zirconium oxide, tin oxide, charcoal or silicon carbide [55]. This guard... 

Toughened Alumina. Numerous researchers have reported that the addition of a second phase, a process referred to as toughening, can increase the strength and toughness of alumina. Schwartz discusses the properties of alumina toughened by additions of various forms of zirconia, and by additions of silicon carbide. Saito discusses alumina toughened by addition of titanium carbide, TiC. 

PROCESSING AND CHARACTERIZATION OF DIFFUSION-BONDED SILICON CARBIDE JOINTS USING MOLYBDENUM AND TITANIUM INTERLAYERS... 

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