SHS-Derived Powders by Reactions’ Coupling as Primary Products for Subsequent Consolidation

Abstract

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.

High-Temperature Wear Performance of hBN-Added Ni-W Composites Produced from Combustion-Synthesized Powders

“…CS or self-propagating high-temperature synthesis (SHS) is an easy and inexpensive technique with tunable thermal settings for the fabrication of Ni-W (1:1 molar or 24:76 mass ratio) composite powder from a NiO-WO 3 -Mg-C powder mixture [ 9 ]. In previous studies, SHS was shown to deliver powders of Mo-Cu and W-Cu in the nano-to-submicron size range using a similar pathway [ 10 , 11 , 12 ]. It was earlier reported [ 13 ] that the incorporation of W into Ni matrix results in grain refinement at micro and nano levels promoted properties such as hardness and wear; however, a higher amount of W induced a decrease in oxidation stability of the sintered materials.…”

Kinetic Highlights of the Reduction of Silver Tungstate by Mg + C Combined Reducer

“…Thus, the development of cost-effective techniques of production of homogenous and fine-grained composite materials, as well as the optimization of their preparation conditions are of current relevance. In recent years, a number of researchers [21][22][23][24][25][26][27] have offered a self-propagating high-temperature synthesis (SHS) method via a thermo-kinetic coupling approach by using an Mg + C combined reducer for producing metal-composite materials. Its essence consists in the coupling of a low exothermic reduction reaction (e.g., Ag 2 WO 4 + C) with a high caloric one (Ag 2 WO 4 + Mg), with a possible change of reaction pathway.…”

New Solvent-Free Melting-Assisted Preparation of Energetic Compound of Nickel with Imidazole for Combustion Synthesis of Ni-Based Materials

“…The literature pays great attention to the method of combustion of organometallic precursors for the synthesis of different dispersed materials. It has resulted in dozens of published reviews [1][2][3][4][5] presenting the economy and flexibility of this approach, since varying the conditions makes it possible to synthesize metals and their alloys, simple and complex oxides, supported catalysts, etc.…”