调制MDSC技术原理

Modulated DSC (MDSC) can be easily understood by comparing it to its well-established precursor, differential
scanning calorimetry (DSC). Conventional DSC is an analytical technique in which the difference in heat flow between
a sample and an inert reference is measured as a function of time and temperature as both the sample and reference are
subjected to a controlled environment of time, temperature, atmosphere and pressure. The schematic of a typical heat
flux DSC cell is shown in Figure 1. In this design, a metallic disk (made of constantan alloy) is the primary means of
heat transfer to and from the sample and reference. The sample, contained in a metal pan, and the reference (an empty
pan) sit on raised platforms formed in the constantan disk. As heat is transferred through the disk, the differential heat
flow to the sample and reference is measured by area thermocouples formed by the junction of the constantan disk and
chromel wafers which cover the underside of the platforms. Chromel and alumel wires attached to the chromel wafers
form thermocouples which directly measure sample temperature. Purge gas is admitted to the sample chamber through
an orifice in the heating block wall midway between the raised platforms. The gas is preheated by circulation through
the block before entering the sample chamber. The result is a uniform, stable thermal environment which assures
excellent baseline flatness and exceptional sensitivity (signal-to-noise). In conventional DSC, the temperature regime
seen by the sample and reference is linear heating or coo领 at rates from as fast as 200°C/minute to rates as slow as
0°C/minute (isothermal). DISCOVERY 差示扫描量热仪