Temperature dependence of the mechanical and thermal expansion behaviors of MoSi2-RSiC composites with a three-dimensionally (3D) interpenetrated network structure

Abstract

In this paper, microstructure and temperature dependence of mechanical properties and thermal expansion coefficient (TEC) of the MoSi2–RSiC composites was investigated via XRD, SEM, mechanical and thermal behaviors test, etc. three-dimensionally fracture photographs confirm the 3D interpenetrating network structure of the composites, main compositions of the composites are 6H-SiC and tetragonal-MoSi2, a small amount of Mo4.8Si3C0.6 mainly exists on the interface between RSiC and MoSi2; With the increase of tested temperatures, flexural strength and fracture toughness of the composites both increase, fracture toughness of M-S-2.30 reaches 2.05 MPa m1/2 (1400 °C), showing the highest improvement of 57.69% as compared to that of RT value, the interface cracks self-healing behavior occurred at higher temperatures helps to improve the interface compressive stresses and increase the fracture toughness of the composites; With the increase of volume fraction of MoSi2, TEC values of the composites increase, mainly being due to the bond energy difference between Mo-Si (76.020 kJ mol−1) and Si-C(285.0 kJ mol−1) bonds. Theoretical analysis exhibits that modified Kerner model is fitter to express the temperature dependence of thermal expansion behavior of 3D interpenetrated network structure composites than that of modified Kerner and Schapery bound model.