COMBUSTION SYNTHESIS is a special thermophysico-chemical process applied for production of intermetallic compounds. In the present work, a reaction–diffusion numerical model was developed to analyze the COMBUSTION SYNTHESIS of aluminide intermetalli(CS) by self-propagating high-temperature SYNTHESIS process. In order to verify the reliability of the numerical model, an experimental setup was designed and used to perform the COMBUSTION SYNTHESIS of nickel and titanium aluminides. The developed model was further used to determine the temperature history of a powder mixture compact during self-propagating high-temperature SYNTHESIS. The effect of compact relative density on COMBUSTION temperature and wave propagation velocity was also studied.

In this investigation, COMBUSTION SYNTHESIS and the mechanochemical SYNTHESIS of chromium carbide (Cr3C2) were studied using chromium oxide, aluminium and carbon powders. XRD technique was used to characterize the product. Without any mechanical activation, ignition of the raw mixture only resulted in aluminothermic reduction of chromites. When the raw powders were mechanically activated for 2 hours, COMBUSTION reactions were completed and Cr3C2 was produced. Results of the mechanochemical process indicated that the aluminothermic reduction of chromites proceed with time and is almost completed after 5 hours. Further milling results in dissolution of carbon in chromium and after 7 hours of milling, distinguished peaks for Cr3C2 appeared in XRD results. No peaks for alumina, a by product of the process, were observed in the XRD pattern which means this phase is amorphous. This was confirmed by annealing of the sample at 1100°C for 1 hr which resulted in a sharp peak for alumina in addition to chromium carbide.

Self-propagating high temperature SYNTHESIS (SHS) is one variety of COMBUSTION, in which, as a result of a fast reaction, the valuable condensed products are formed. Although the reactants in (SHS) may be in various states of solid, liquid or gas, the products after cooling should be in solid state. Molybdenite concentrate from Sarchechme mines (South-east of Iran) with the composition of mainly: 41.5% S, 2.8% Fe, 1.3% Cu and 47.7% Mo by weight was used as a source of molybdenum. It was mixed with different concentration of aluminum, pressed to a briquette of 25.4 mm. in diameter and ignited by use of a microwave oven. Depending on the conditions, different modes of COMBUSTION of the briquettes were observed. The product of the reaction was leached with dilute hydrocholoric acid, and was tested for sulfur, aluminum and molybdenum. The respective effects of aluminum powder size, pellet density and power input to the pellet before ignition on the final product were investigated; in some samples the sulfur was reduced to less than 1%.

Thermal explosion mode of COMBUSTION SYNTHESIS was employed to produce a composite of titanium carbide in nickel aluminide matrix. Nickel titanium (NiTi2) powder was used as a source of both Ni and Ti, which is much cheaper than elemental powders. Phase analysis of the products was carried out using X-ray diffraction with Cu-Ka radiation. Microstructure of the product was also studied by SEM. The results show that a COMBUSTION reaction between Al, C, and NiTi2 powders could be maintained as long as the Ni + Al (the matrix) in the powder mixture is lower than 68 wt%. When the matrix content is higher, the reaction is not sustained due to the low COMBUSTION temperature. XRD results show that all reacted samples consist of TiC and NiAl intermetalic. Microscopic examination of the polished samples revealed a fine dispersion of particulate TiC in the NiAl matrix. The size of the TiC particles were a function of TiC:NiTi ratio in the composites. The lower the weight percent of the matrix phase the larger was the size of TiC particles. This was believed to be due to the higher COMBUSTION temperature in the samples with lower matrix weight percent.