Microwave sintering of MoSi₂-SiC composites

Abstract

Microwave preparation of MoSi₂-SiC composites has been studied using several strategies. Direct sintering of MoSi₂ and SiC mixtures using 2.45 GHz microwaves has been found to be the most successful approach. Sintered composites exhibit higher than 96.4% of theoretical density. Sintering times required are very short and of the order of only 10 min. The observed accelerated sintering has been discussed in the context of unique microwave effects. Vickers hardnesses and fracture toughnesses of the composites are in the range of 9.25-13.2 GPa and 3.2-4.5 MPa m^1/2, respectively. Microwave sintered composites do not exhibit any pesting tendency at 550 °C even after 72 h of exposure to air. Reactive sintering of elemental powders and partially reactive sintering based on the use of one of the compounds (MoSi₂ or SiC) in the premix, do not result in good sintering and lead to the formation of unintended products such as Mo₅Si₃, Si₃N₄ and Si₂ON₂.