High-temperature synthesis

The technique, now named self-sustaining high-temperature synthesis (SHS) - on the grounds that long names drive out short ones - was later taken up in the West, and has gradually become more sophisticated. The synthesis of TiC, by Holt and Munir (1986) marks the beginning of detailed analysis of heat generation and... 

In many respects the SMDS process (Figure 18.8) precipitated a change in the Fischer-Tropsch community with respect to the preferred catalyst for Fischer-Tropsch synthesis and the approach to product workup. It is therefore instructive to understand why Shell moved away from iron-based Fischer-Tropsch catalysts (and as a consequence also high-temperature synthesis) and opted for a Co-LTFT process with an uncomplicated refinery design that does not produce... 

International Journal of Self-propagating High-temperature Synthesis, Allerton Press, New York, from 1992. 

Hexachloroethane does not occur naturally in the environment. It is made by adding chlorine to tetrachloroethylene. Hexachloroethane is no longer made in the United States, but it is formed as a byproduct in the production of some chemicals. For example, it is a by-product in the high temperature synthesis of tetrachloroethylene from carbon tetrachloride. Some hexachloroethane can be formed by incinerators when materials containing chlorinated hydrocarbons are burned. Hexachloroethane itself does not easily catch fire. Some hexachloroethane can also be formed when chlorine reacts with carbon compounds in drinking water. 

Intermetallic compound formation may be observed as the result from the diffusion across an interface between the two solids. The transient formation of a liquid phase may aid the synthesis and densification processes. A further aid to the reaction speed and completeness may come from the non-negligible volatility of the component(s). An important factor influencing the feasibility of the reactions between mixed powders is represented by the heat of formation of the desired alloy the reaction will be easier if it is more exothermic. Heat must generally be supplied to start the reaction but then an exothermic reaction can become self-sustaining. Such reactions are also known as combustion synthesis, reactive synthesis, self-propagating high-temperature synthesis. 

Combustion Synthesis. Besides solid-state reactions requiring heating even for several days at high temperatures to be completed, fast reactions are also known which give their products in minutes or seconds. Several nearly equivalent names are used for these reactions such as solid-state combustion, combustion synthesis, self-propagating (self-sustained) high-temperature synthesis. Solid state direct combinations and solid-state metathesis have been described. 

Figure 6.12. Self-propagating high-temperature synthesis of NiAl (Fan etal. 2001). The temperature- time profile observed during the passage of a combustion wave is shown.

TABLE 9.5 Compounds Produced by Self-Propagating, High-Temperature Synthesis (SHS)a... 

Under the optimum condition for SAN formation, where the samples prior to high temperature synthesis were washed with Dl-water and DCB, the nanoparticle density was much lower. In this case, fewer SiNW were produced at 1100°C. An SEM image of the sample before growth is shown in Fig. 10.4. The cleanliness of the surface was due to the DI-water wash and the DCB rinse. Individual and strings of nanoparticles are clearly seen. 

Very recently, Solozhenko [540] reported the high-pressure-high-temperature synthesis of cubic BC2N with in situ control of the reaction by x-ray diffraction measurement. The first high-density product has been obtained in a laser-heated diamond anvil cell (DAC). The starting material was g-BC N, prepared... 

Iron oxide (Fe Oj) and tungsten oxide (WO ) films have been studied and developed as candidate semiconductor materials for the PEC junction (photoanode). High-temperature synthesis methods, as reported for some high-performance metal oxides, have been found incompatible with multijunction device fabricatioa A low-temperature reactive sputtering process has been developed instead. In the parameter space investigated so far, the optoelectronic properties of WO3 films were superior to those of Fe Oj films, which showed high recombination of photogenerated carriers (Miller et al., 2004). 

SIDMT. Metal Hydrides Manufacturing. Coals Increase the Hydrogen content in the Metallic Hydrides. Synthesize Metallic Hydrides by conventional techniques and by Self-propagation High Temperature Synthesis. 

Glagovsky, E. M., Yudintsev, S. V., Kuprin, A. V., Pelevin, L. P., Konovalov, E. E., Velichkin, V. I. Myasoedov, B. F. 2001. A study of actinide crystalline matrices produced by self-sustaining high-temperature synthesis. Radiochemistry, 43, 557-562 (in Russian). 

Postnikov, A. Yu., Levakov, E. V., Gavrilov, P. I., Glagovsky, E. V. Kuprin, A. V. 2001. Self-sustaining high temperature synthesis of zirco-nolite-based materials for radioactive waste immobilization. Physics and Chemistry of Materials Treatment, 5, 58-63 (in Russian). 

Combustion synthesis, also known as self-propagating high temperature synthesis,... 

A more promising way of obtaining more uniform degradation products is pyrolysis at high temperature. Synthesis gas is obtained at ever higher temperatures (700-1000°C), but according to Nimz, at the present it is not competitive with the corresponding processes based on coal (2). 

However, because they require high-temperature synthesis, they cannot be prepared in a dispersed form and their catalytic activity is low. 

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