Tungsten carbides preparation

Carburization By Fusion. This method is used for the preparation of tungsten carbide for the mineral industry, ie, for coarse-grained powder or castings for welding (qv) onto oil drills and wear-resistant parts. 

These properties make CoTAA a good catalyst for the anodic oxidation of formic acid. Economic application of this catalyst is, however, not anticipated because formic acid is not economically attractive as a fuel. It is certainly possible to prepare electrodes containing a mixture of tungsten carbide and CoTAA as catalyst, with the tungsten carbide catalyzing the first stage of the oxidation of CH2O to HCOOH, and the CoTAA the further oxidation of HCOOH to CO 2, but this possibility does not offer any more favorable prospects. Economic application of CoTAA will only come into question when cheap catalysts are available for the partial oxidization of methanol to formaldehyde or formic acid. 

Although sample preparation was conducted under great care to minimize the analytical error, the potential for contamination does exist. As a precaution, tungsten and cobalt were removed from consideration during the statistical analysis of data because samples were powdered using a tungsten carbide cell grinder in which W is a major component and Co is a minor component. 

The selectivity of alcohol depends on the carbide preparation. A maximum in alcohol is achieved for the sample WC/Ti02 (T3) for which the preparation of the carbide combines reduction and carburization steps at moderate temperatures (respectively, 873 K and 1073 K). In this case, anionic vacancies stabilized by mixed oxides are formed, associated with carbon vacancies in mixed carbides resulting in a better interaction of carbidic and oxidic phases. On silica, ceria and zirconia, the extent of carburization is too high and the interaction of the carbide phase with the oxide support is suppressed giving larger isolated particles of tungsten carbide with low dispersion. 

In order to study the chemical effects on the Auger peaks of tungsten carbides and nitrides by factor analysis, it was necessary to prepare model samples of tungsten nitrides and carbides where the chemical species of nitrogen, carbon and tungsten were separated. A sample where the different chemical species were mixed was also prepared. 

A variety of other ceramics are prepared by pyrolysis of preceramic polymers.32,38 Some examples are silicon carbide, SC, tungsten carbide, WC, aluminum nitride, AIN, and titanium nitride, TiN. In some cases, these materials are obtained by simple pyrolysis in an inert atmosphere or under vacuum. In other cases a reactive atmosphere such as ammonia is needed to introduce some of the atoms required in the final product. Additional details are given in Chapter 9. 

Microcline, albite and labradorite were obtained from Ward s Canada Limited. Cleaved crystal fragments and 60 mesh-sized samples were ultrasonically cleaned prior to use. Powdered samples (particle size < 25 ym) were prepared by grinding in a tungsten carbide ball mill, wet-sieving and washing in water. 

The tungsten carbides (WC and W2C) has also attracted attention. The WC is catalyst of hydrogen oxidation, the W2C is catalyst of oxygen reduction. The technology of WC and W2C preparation is identical. 

Ma, Chun-an Zhang, Wen-kui Chen, Dan-hong Zhou, Bang-xing. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts. Transactions of Nonferrous Metals Society of China 2002 12(6) 1015-1019. 

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