Experimental Determination of the Enthalpy, Temperature, and Heat of Phase Transition of the alpha-Modification of A1203 in the Temperature Range of 1200 to 2500 Degrees K

摘要

An investigation was made of the enthalpy of the alpha-modification of A12O3 (corundum) at high temperatures with a view toward using it as a heat-capacity 'standard' for high-temperature calorimeter research. Corundum may be obtained in pure form, has high chemical and thermal stability, and a high specific heat. Corundum has several crystalline modifications, of which the alpha-modification is the most widely distributed natural form, and may be produced synthetically. An investigation was made of samples of colorless corundum, consisting of crystals 30 mm long and 2 mm in diameter, and of 99.99% purity. Molybdenum capsules were employed in the experiments. It was shown that no reactions occur in the system Mo-Al2O3 at temperatures up to 2100K. It was also found (within experimental accuracy) that no reaction occurred in the hermetically sealed molybdenum capsules during measurements of the enthalpy of liquid corundum.