Metal Carbide-Carbon Eutectic and Peritectic Fixed Points as High-Temperature Standards

TiC-C eutectic and WC-C peritectic systems were investigated for their potential of serving as high-temperature reference points in thermometry. Mixtures of high-purity graphite powder with Ti and W were filled in graphite crucibles and melting/freezing plateaus were observed by means of a radiation thermometer. The observed melting range of WC-C peritectic was roughly 0.1 K with repeatability of 0.02 K. The melting range of TiC-C eutectic was roughly 0.5 K with repeatability of 0.09 K. The freezing curve of TiC-C showed a sharp peak after recovery from supercool, followed by a gently-sloped curve, probably due to composition of eutectic ingot or impurities. WC-C peritectic seems to have more potential as high-temperature standards, although it is still at a preliminary stage of investigation