Thermophysical Properties of Rh3X for Ultra-High Temperature Applications

Thermal conductivity and thermal expansion were measured for the Lbeta intermetallic compounds Rh3X (X = Ti, Zr, Hf,V, Nb, Ta) in the temperature range 300-1100 K to evaluate the feasibility of applying the compounds as ultra-high temperature structural materials. The thermal conductivities of Rh3X are widely distributed over the range 32-103 W m(-1) K(-1) at 300 K, but the differences between the thermal conductivities diminish at higher temperatures. A trend is observed in that the thermal conductivity ofRh3X is greater if the constituent X belongs to Group 5 rather than to Group 4 in the Periodic Table. The coefficient of thermal expansion (CTE) values of Rh3X increase slightly with increasing temperature; values are concentrated around 10*10(6)K(-1) at 800K. CTE values of Rh3X decrease as X appears lower in the Periodic Table. It is demonstrated that Rh3Nb and Rh3Ta are suitable for ultra-high temperature structural applications due to their higher thermal conductivities and smaller CTE values.