Reactants self-propagating synthesis

Rice, R. W, Richardson, G. Y., Kunetz, J. M., Schroeter, T., and McDonough, W. J., Effects of self-propagating synthesis reactant compact character on ignition, propagation and microstructure. Adv. Ceramic Mater., 2,222 (1987). 

Combustion synthesis (CS) can occur by two modes self-propagating high-temperature synthesis (SHS) and volume combustion synthesis (VCS). A schematic diagram of these modes is shown in Fig. 1. In both cases, reactants may be pressed into a pellet, typically cylindrical in shape. The samples are then heated by an external source (e.g., tungsten coil, laser) either locally (SHS) or uniformly (VCS) to initiate an exothermic reaction. 

C. S. Raymond, A. Bayliss, B. J. Matkowsky, and V. A. Volpert, Transitions to chaos in condensed phase combustion with reactant melting, Int l J. Self-Propagating High-Temperature Synthesis, 10 (2001), pp. 133-149. 

The first attempt was aimed to synthesize the different UHTCs by SHS according to reactions (l)-(6), when starting from simply blended powder mixtures. While the ZrB - and HfB -based systems were found to clearly exhibit a self-propagating behaviour, both TS and TTS compositions did not. This fact could be readily explained on the basis of the relatively lower heat of reactions (3) and (6) (cf. Table 3). Thus, the mechano-chemical activation of the related starting reactants under the conditions reported in the experimental section was required to induce the SHS character in the synthesis reactions. 

---