A detailed comparison of first order transitions by DSC and TMC

Indium was analyzed with both, standard differential scanning calorimetry ( DSC) and temperature-modulated DSC (TMDSC) using sinusoidal and saw-tooth m odulation. Instrument and sample effects were separated during nucleated, r eversible melting and crystallization transitions, and irreversible crystal lization with supercooling. The changes in heat flow, time, and sample and reference temperatures were correlated as functions of heating rate, mass, and modulation parameters. The transitions involve three regions of steady state (an initial and a final region before and after melting/crystallizati on, a region while melting/crystallization is in progress) and one region o f approach to steady state (melting peak to final steady state region). Ana lyses in the time domain show promise when instrument lags, known from DSC, are used for correction of TMDSC A new method of integral analysis is intr oduced for quantitative analysis even when irreversible processes occur in addition to reversible transitions. The information was derived from heat-f lux calorimeters with control at the heater block or at the reference tempe rature sensor.