Evaluation of the Temperature Range Suitable for the Synthesis of B4C–TiB2 and B4C–ZrB2 Powder Composite Materials

Based on analysis of phase diagram data and thermodynamic modeling, we have evaluated the optimal temperature ranges of the processes underlying the preparation of B4C–TiB2 and B4C–ZrB2 composite powders via boron carbide reactions in the presence of excess boron carbide: 2MO2 + (n + 1)B4C + 3C = 2MB2 + 4CO + nB4C (M = Ti, Zr). The values of n have been taken so as to obtain composite powders with the following compositions (mol %): 90B4C–10MB2 (n = 19), 80B4C–20MB2 (n = 9), 75B4C–25MB2 (n = 7), and 70B4C–30MB2 (n = 5.67). We have found temperatures that ensure the preparation of composite powders with tailored composition at various CO pressures. At a CO pressure of 0.0773 MPa, these temperatures for both reactions are 1816 K (~1540°C), independent of the composition of the synthesized powders. The eutectic temperature in the B4C–TiB2 system is ~2200°C and that in the B4C–ZrB2 system is ~2280°C. Thus, at a nearly atmospheric pressure in the reactor, the optimal synthesis temperature of B4C–TiB2 composite powder lies in the range 1540–2200°C and that of B4C–ZrB2 composite powder lies in the range 1540–2280°C. Such powders are potentially attractive for the fabrication of ceramics with improved performance parameters.