Multiple heating rate methods

One reason for the higher values obtained using the single constant heating rate method (e.g., Eq. 9.3, [70]) is probably due to the different reactions proceeding in a mixed and complex manner. If this is true, it is difficult to evaluate the correct value of each elementary reaction, because the E value is calculated as an apparent value from the slope of the total plot made up of multiple reactions. 

By applying multiple heating rate DSC measurements and Ozawa s isoconver-sional model free method, an activation energy of 34.2 kcal mol1 and pre-exponential factor of 1.99 1012 s 1 were calculated from the DSC peak maximum temperature - heating rate relationship. 

The kinetics of the cure of ATS at 130°C in nitrogen determined by various methods are shown in Figure 1. The dashed curve represents the prediction based on kinetic parameters determined by analysis of scanning DSC data by the method of multiple heating rates described previously (8). This method utilizes a rate equation of the form ... 

Charrier et al. accurately measured the equilibrium temperature of the solid-solid phase transition of high purity caesium nitrate by stepwise heating and by the method of extrapolation to zero heating rate. The authors reported a mean value of 154.3 0.1 C, that was obtained by using two different heat-flux DSC instruments. Because the transition temperature of caesium nitrate is close to that of the fusion of indium, indium can be used as a single-point calibrant. This approach decreases the error that may arise when the calibration value for the material of interest is determined by interpolation between two-point or multiple-point calibrations [66],... 

Popescu is a non-model kinetic analysis method which is based on multiple scanning rates two temperature values T = and T = will determine a pair of values of a on each curve of different heating rate (a l, (a ,3, a ), and also... 

Transferring of the gas into the tank by the heat pump method was at a rate of about 0.4 kg of UF per hour with a 50°C temperature differential. The system multiplication was nil with the UF in solid form, all probably at the bottom of the tank. The increase in multiplication as the complete gaseous phase was obtained was sinooth but upon cooling of the tank, the initial condensation on the walls created a small positive transient reactivity increase that rapidly turned negative as the condensate thickened. 

The calculation of the activation energy is based on multiple scan methods where several measurements at different heating rates are needed, i.e. the iso-conversion methods the Ozawa-Flynn-Wall method, the Kissinger-Akahira-Sunose method and the expanded Friedman method. The first two are described in Section 3.3.1. The expanded Friedman method is expressed in the form... 

Kinetic analyses of multiple nonisothermal, also referred to as multiple heating rate, runs are most commonly performed by using the methods of Friedman, Ozawa, and Flynn and Wall. However, application of the Kissinger method (Kissinger 1957) is discouraged because the method yields a single value of... 

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