TPRL has two different pieces of equipment available for the direct measurement of the specific heats of materials. Depending on the temperature range needed and the atmosphere conditions required, either one or the other or sometime both pieces of equipment will be used.
A Perkin-Elmer Differential Scanning Calorimeter is used to measure the specific heats of a material from room temperature to 725 C. The glove box surrounding the sample holder is used to protect this area from moisture condensation when measurements are made. Both the reference and sample holders are equipped with heaters and temperature sensors. These sensors detect fluctuations of the sample holder with respect to the reference holder as both are heated. A high gain, closed-loop electronic system provides differential electrical power to read out directly in millicalories per second and is equivalent to the rate of energy absorption or evolution of the sample. By comparing this rate with the rate measured during the heating of a known mass of sapphire, the specific heat is calculated. The experiments are performed under computer control and specific heat is calculated in Joules/(gm K) and BTU/(lb F) (which equals Cal/(gm C) ) at the related temperature intervals. The DSC is periodically checked by running either NIST sapphire or alumium as a sample and the results are compared to the NIST values.
A Netzsch Model 404 differential scanning calorimeter (DSC) is used to measure specific heats from 50 to 1400 C. Energetics of transformations and reactions can also be determined over the temperature range of 25 to 1500 C. The system is vacuum tight and therefore samples can be tested under pure inert, reducing or oxidizing atmospheres as well as under vacuum.
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