Abstract
An isothermal calorimeter was newly designed and constructed to measure the heats of mixing of alloys, in expectation of expansion of the study at steelmaking temperatures.
The calorimeter consists of a cylindrical molybdenum heater with slit, calorimeter block, and isothermal jacket made of beryllia, which is a good thermal conductor. In order to check the accuracy of the constructed calorimeter, copper alloys were applied to measure the heats of mixing under low An isothermal calorimeter was newly designed and constructed to measure the heats of mixing of alloys, in expectation of expansion of the study at steelmaking temperatures.
The calorimeter consists of a cylindrical molybdenum heater with slit, calorimeter block, and isothermal jacket made of beryllia, which is a good thermal conductor. In order to check the accuracy of the constructed calorimeter, copper alloys were applied to measure the heats of mixing under low pressures of argon (0.1-5.0mmHg) at 1120°C. The temperature of the isothermal jacket was. controlled within+0.1C at 1200°C. and the difference of the temperature inside the isothermal jacket was negligible. As socalled “Newton's law of cooling” is valid for heat transfer form the calorimeter block to the isothermal jacket, the obtained data can be calibrated reasonably.
The maximum heat of mixing of the Cu-Ag and the Cu-Sn systems were 970 and-1430cal/g·atom respectively, and the heats of mixing of the Cu-Si system were exothermic up to 0.2 atomic fraction of silicon.
The error in the heats of mixing was estimated approximately as ±8%.
