Self-propagating high temperature synthesis (SHS) of ZrC-TiC nanocomposites: Comparison of Mg and Al reductant usage and process optimization

This study investigated the production of ZrC-TiC composite nanopowders by SHS process in TiO₂-ZrO₂-C-Mg/Al systems. Mg and Al charge stoichiometries and composite charge stoichiometries were optimized for SHS processes. The most precise procedural stages were identified for refining the SHS product; acid concentrations were optimized for Mg usage and an innovative chemical method was developed to eliminate and/or decrease the amount of Al₂O₃ by-product, enabling the utilization of Al. Thermochemical simulations were conducted for thermodynamic evaluations (adiabatic temperature and specific heat) and characterizations were performed by XRD and SEM-EDS analysis. The findings indicated that utilizing both reductants allowed for the synthesis of ZrC-TiC-(Al₂O₃) particles that have considerable surface area and commercial purity. The outcomes demonstrated that Magnesium is a more effective reductant, yet Aluminium, also serves as a viable reductant, even though leading to an increase in process steps, but enabling in-situ formation of sinterability and toughness enhancing Al₂O₃. A novel chemical route including pre-acid leaching, NaOH fusion, water leaching, HCl leaching was identified for the synthesis of ZrC-TiC-Al₂O₃ composite powder where the amount of Al₂O₃ could be organized (according to the desired mechanical properties) by optimization.