Abstract
Modeling the self-sustained high-temperature synthesis (SHS) reaction via thermal dilution and transformation of the reaction heterogeneous media into a moderate exothermic one has unlimited potential for designing inorganic powders of a certain morphology beneficial for advanced consolidation. Thermal/inert dilution of the high-exothermic mixtures leads to the fluent decrease of both the combustion temperature and velocity, thus allowing to tailor the thermal regime of the combustion process, therewith contributing to high yield of reaction and governing the microstructural features of the combustion products. In the current review, we shed on light on the possibilities of this effective strategy to control the thermal behavior of the SHS process for the preparation of applicable powder precursors for the subsequent successful sintering. Since the SHS process of some refractory ceramics (MoSi2, TiB2, TiC, etc.) involves a relatively violent reaction rate and high combustion temperature, achieving a high level of microstructure control in these systems is often challenging. The challenge was tackled with a thermal dilution approach, attaining considerable enhancement in the homogeneity among phases with an increase of diluent content along with microstructure refinement.
Highlights
Self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) is one of the attractive but challenging approaches for the synthesis of advanced inorganic materials, including refractory ceramic-based composites [1,2]
Smolyakov investigated the role of inert low melting additive in SHS processes from another stance [25] considering various combustion regimes induced by phase transformations, where the combustion wave propagation velocity is not conditional on the amount of inert diluent
We aimed to demonstrate the effect of diluent or additive not on the combustion parameters, but on the microstructure evolution and sinterability of powders based on the available literature
Summary
Self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) is one of the attractive but challenging approaches for the synthesis of advanced inorganic materials, including refractory ceramic-based composites [1,2]. After local ignition of the reactive mixture, the self-sustaining mode is achieved due to heat released at the chemical interaction converting reagents into products without the need for any external energy In this scenario, the products’ characteristics are primarily influenced by temperaturetime history of the reaction, which, in turn, accounts for thermodynamics, kinetics, and different physical phenomena associated with ignition of reaction [3,4,5,6,7]. There are two different phenomena that should be considered during the dilution of violent combustion reactions: temperature limit (combustion wave does not propagate due to high energy consumption by diluents) and concentration limit (no further improvement in the extent of conversion or product microstructure is observed). We aimed to demonstrate the effect of diluent or additive not on the combustion parameters, but on the microstructure evolution and sinterability of powders based on the available literature
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