The analysis of first order transitions by TMDSC
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
First order transitions are increasingly investigated with the new temperature-modulated DSC technique (TMDSC). In order to separate the instrument and sample effects during a nucleated reversible melting transition, indium is analyzed with both, standard DSC and TMDSC. All temperature signals are used in the time domain to analyze the temperatures within the DSC cell. The sample-mass dependence of standard DSC determined earlier is used as basis for the analysis. Indium is an ideal calibration substance because of its sharp melting and ease of crystal nucleation (no superheating, easy availability of pure samples, quick crystallization to sufficiently perfect crystals, and relatively small supercooling). It can be used for both DSC and TMDSC. The melting during a standard heating DSC experiment occurs isothermally until the sample is completely melted. The melting and crystallization during a saw-tooth TMDSC are segments of a series of standard DSC experiments. The change of heating to cooling during incomplete melting is a possible method to determine the melting temperature of a pure, sharp melting substance and calibrate the TMDSC on cooling. It avoids the use of fully reversible transitions of liquid crystals. The more complicated behavior of sinusoidally modulated TMDSC is easily understood based on the experience gathered from DSC and saw-tooth TMDSC.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 548636
- Report Number(s):
- ORNL/CP-95002; CONF-9709121-; ON: DE98000989; CNN: Grant DMR-9703692; TRN: AHC29724%%37
- Resource Relation:
- Conference: North American Thermal Analysis Society (NATNAS) meeting, Washington, DC (United States), 7-9 Sep 1997; Other Information: PBD: [1997]
- Country of Publication:
- United States
- Language:
- English
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