Other Effects of Combustion Conditions

In addition to the main variables already considered, other parameters also influence the combustion synthesis process. These include the ignition conditions, initial temperature of the green mixture, sample dimensions, and their effects and they are discussed next. 

A recent review by Barzykin (1992) summarizes experimental and theoretical studies on the initiation of CS systems. In this section, we focus only on the effects of initiation conditions on the reaction pathway during CS. 

It has been shown theoretically that for the case of two competing parallel reactions, two stable combustion modes can exist (Khaikin and Khudiaev, 1979), where the reaction route depends on the ignition conditions. This effect was first observed experimentally by Martirosyan et al. (1983) for the Zr-C-H2 system (Fig. 50). Using relatively low ignition temperatures (1300 K), the combustion 

Experimental data for the combustion velocity dependence on initial temperature for different systems are presented in Fig. 52. Examples of intermetallic systems (Al-Ni and Co-Ti) with melting of both reactants show a general trend in which U increases with increasing Tq. The same behavior was obtained for the Mo-Si (Kumar et ai, 1988b), Ti-C (Kirdyashkin et al., 1981) and 3Ni-Al (Lebrat and Varma, 1992a) systems, which are characterized by melting of only one reactant. 

For gas-solid systems, this effect has not been studied well. In the only example available, which involves combustion of silicon in nitrogen, it was observed 

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