Considered were the thermodynamic and kinetic aspects for different kinds of coupled SHS reactions: thermally coupled, chemically coupled, and thermochemically coupled ones. Thermodynamic calculations confirmed the applicability of coupling as a useful route to materials synthesis in a one-step combustion process.

The capability of self-propagating high-temperature synthesis (SHS) to produce powders that are characterized by a high sintering ability, owing to high heating and cooling rates inherent to the exothermic reaction, is of a special interest for the industry. In particular, SHS-derived powders comprise a significant defect concentration in order to effectively enhance the mass transfer processes during the sintering, which allows for the successful consolidation of difficult-to-sinter materials at relatively low sintering temperatures. From this perspective, the design of precursors suitable for sintering, synthesis in a controlled temperature regime and the optimization of geometrical and structural parameters of SHS powders as a potential feedstock for the consolidation is of key importance. Here, we report on the comparative studies concerning the SHS processing of composites for advanced powder metallurgy techniques. The synthesis and sintering peculiarities of the SHS through coupled reactions in the Me’O₃(WO₃,MoO₃)-Me’’O(CuO,NiO)-Mg-C, Ti-B-Al₁₂Mg₁₇ systems are comparatively reviewed. The SHS coupling approach was used for the preparation of powders with a tuned degree of fineness (a high specific surface area of particles), a high-homogeneity and a controllable distribution of elements via both the regulation of the thermal regime of combustion in a wide range and the matching of the thermal and kinetic requirements of two interconnected reactions. Microstructural features of the powder feedstock greatly contributed to the subsequent consolidation process.

Understanding of the decisive role of non-isothermal treatment on the interaction mechanism and kinetics of the MoO₃-CuO-Mg-C system is highly relevant for the elaboration of optimal conditions at obtaining Mo-Cu composite powder in the combustion processes. The reduction pathway of copper and molybdenum oxides with combined Mg + C reducing agents at high heating rates from 100 to 5200 K min⁻¹ was delivered. In particular the sequence of the reactions in all the studied binary, ternary and quaternary systems contemporaneously demonstrating the effect of the heating rate on products’ phase composition and microstructure was elucidated. The combination of two highly exothermic and speedy reactions (MoO₃ + 3Mg and CuO + Mg vs. MoO₃ + CuO + 4Mg) led to a slow interaction with weak self-heating (dysynergistic effect) due to a change in the reaction mechanism. Furthermore, it has been shown that upon the simultaneous utilization of the Mg and C reducing agents, the process initiates exclusively with carbothermic reduction, and at relatively high temperatures it continues with magnesiothermic reaction. The effective activation energy values of the magnesiothermic stages of the studied reactions were determined by Kissinger isoconversional method.

Functional features of Ni-W composite materials combined with successful performance enabled a breakthrough in their broad application. To disclose the formation pathway of Ni-W composite materials at extreme conditions of combustion synthesis in the NiO-WO₃-Mg-C and NiWO₄-Mg-C systems for the optimization of the synthesis procedure, the process was modeled under programmed linear heating conditions by thermal analysis methods. The reduction kinetics of tungsten and nickel oxides mixture and nickel tungstate by Mg + C combined reducer at non-isothermal conditions was studied at high heating rates (100–1200 °C min⁻¹) by high-speed temperature scanner techniques. It was shown that when moving from low heating to high heating rates, the mechanism of both the magnesiothermic and magnesio-carbothermic reductions of the initial mixtures changes; that is, the transition from a solid-solid scheme to a solid-liquid scheme is observed. The strong influence of the heating rate on the reduction degree and kinetic parameters of the systems under study was affirmed. The simultaneous utilization of magnesium and carbon as reducers allowed the lowering of the starting and maximum temperatures of reduction processes, as evidenced by the synergetic effect at the utilization of a combined reducer. The effective values of activation energy (E_a) for the reactions proceeding in the mixtures NiO + WO₃ + 4Mg, NiO + WO₃ + 2.5Mg + 1.5C, NiWO₄ + 4Mg and NiWO₄ + 2Mg + 2C were estimated by Kissinger isoconversional method and were 146 ± 10, 141 ± 10, 216 ± 15 and 148 ± 15 kJ mol⁻¹, respectively.

Macrokinetic features and mechanism of Mo-Si reaction in conditions of rapid heating on a single particle level (Mo/Si diffusion couple) were studied by high-speed scanning electrothermography. The experiments were conducted in the temperature-time conditions (T = 1000–1600°C, t = 0.01–3.0 s) comparable to those of combustion synthesis of molybdenum disilicide. The rates of chemical heat release (depending on the thickness of silicon layer, δ_Si) were measured and the processes of phase/structure formation were explored. Over a wide range of δ_Si, two-stage chemical heat release was associated with occurrence of solid-solid Mo(s) + Si(s) (for T < T _mp ^Si ) and solid-liquid Mo(s) + Si(l) reactions (for T > T _mp ^Si ), where T _mp ^Si stands for the melting point of Si. Proposed was a new mechanism for siliconization of Mo in non-isothermal conditions.