Self-Propagating High-Temperature Centrifugal Processing of Cu2O-Cu-Al and Cu2O-Al Systems

Abstract

Solid-solid and gas-solid chemical reactions are being exploited for interesting and relatively new technological applications based on the so-called Self-propagating High-temperature Synthesis (SHS) technique. As schematically shown in Figure 1, this technique, which belongs to the more general category of Combustion Synthesis (CS), is characterized by the fact that once ignited, a relatively strong exothermic reaction is able to propagate as a combustion wave through the entire reacting mixture, without requiring any other energy supply. The main characteristics of the SHS technique are its simplicity, relatively low power requirements, high combustion temperature (up to 4000 K) and front propagation velocities up to about 25 cm per second, often permitting one to obtain final products with purity and mechanical properties better than those prepared by conventional methods.e.g., 1-7 This is because SHS processes are characterized by very high temperature gradients (about 105 K/cm) and large reaction rates, so that volatile impurities adsorbed on the reactants are eliminated (“self-cleaning”) during the reaction, thus leading to materials with high purity. Furthermore, the temperature gradients combined with rapid cooling may form metastable phases and unique structures not possible by conventional methods of furnace synthesis.