Calorimetric dynamic differential calorimetry

These authors report the enthalpies of formation of RX3 compounds (R = Y, Th or U X = Ga, In, n, Sn or Pb) as determined by dynamic differential calorimetry (integration of DTA peaks, with a calibration from elements and compounds of known heats of fusion). These studies follow previous studies by the same group on rare earth intermetal-lic compounds having the same general formula. The calorimetric method used is described in one of these earher publications [1973PAL]. 

Differential scanning calorimetry (DSC) is a calorimetric method that finds widespread use in many fields, including protein dynamics, polymers, pharmaceuticals, and inorganic materials. DSC measures energy (heat) flow into a sample and a reference substance as a function of controlled increase or decrease of temperature. In a typical power-compensated DSC (Fig. 3.2), the sample and reference are placed on metal pans in identical furnaces each containing a platinum resistance thermometer (thermocouple) and heater. During a thermal transition (e.g., when a physical change in the sample occurs),... 

In the direct calorimetric determination, (- AH =f nn)T), the amount adsorbed ( ta) is calculated either from the variations of the gas pressure in a known volume (volumetric determination) or from variations of the weight of the catalyst sample in a static or continuous-flow apparatus (gravimetric determination). In a static adsorption system, the gas is brought into contact with the catalyst sample in successive doses, whereas the catalyst is swept by a continuous flow in a dynamic apparatus. Comparative calorimetric studies of the acidity of zeolites by static (calorimetry linked to volumetry) and temperature-programmed (differential scanning calorimetry linked to thermogravimetry) methods of ammonia adsorption and desorption have been performed [23]. 

The variation of the mechanical properties near the glass transition is discussed in Chapter 12, and techniques developed to this end such as dynamic mechanical analysis (DMA) are usually employed. Figure 11.3 illustrates the shape taken by the curve that reflects the variation of the volume of a polymer sample as a function of the temperature this technique is sometimes used but in spite of the simplicity of its principle, it is delicate to handle. The calorimetric technique is preferred, especially differential scanning calorimetry (DSC). The typical shape taken by a thermogram for a noncrystallizable polymer is shown in Figure 11.6. 

Note r , dynamic mechanical peak temperature for glass transition (1 Hz) Tg, calorimetric glass transition temperature Pkww. KWW distribution parameter for glass-rubber relaxation FE V, fractional fiee volume based on density measurements DSC, differential scanning calorimetry. 

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