Thermal expansion of nanocrystalline boron carbide

The lattice thermal expansion behaviour of nanocrystalline and microcrystalline boron carbides has been measured by high temperature X-ray diffraction technique in the temperature range 298–1773 K. The lattice parameters of both were found to increase with increase in temperature. The average thermal expansion coefficients in this temperature range for the nanocrystalline and the microcrystalline boron carbides were found to be 7.76 × 10^?6 and 7.06 × 10^?6 K^?1, respectively. The difference observed in the thermal expansion behaviour is probably due to increase in the surface energy of the lattice in the nanocrystalline material.