Controlled transformation rate

J. Rouquerol, Controlled Transformation Rate Thermal Analysis The Hidden Face of Thermal Analysis , Thermochim. Acta, 1989,144, 209. 

Rouquerol J (1989) Controlled transformation rate thermal analysis - the hidden face of thermal analysis. Thermochimica Acta 144 209-224. 

Controlled Transformation Rate Thermal Analysis (CRTA) Method [40,43]... 

In controlled transformation rate thermal analysis (CRTA), instead of controlling the temperature (as in conventional thermal analysis (Fig. 2.8a)), some other physical or chemical property X is modified, which is made to follow a pre-determined programme X = f(t) under the appropriate action of temperature (Fig. 2.8b) [7]. Heating of the sample may be controlled by any parameter finked to the rate of thermally activated transformations, such as total gas flow (EGD control constant decomposition rate thermal analysis [199]), partial gas flow (EGA... 

Table 2.10. Examples of controlled transformation rate thermal analysis linked with another measurement ...

CRTA Controlled transformation rate DLI (1) Direct laser ionisation ... 

A valuable approach for measuring thermal degradation kinetic parameters is controlled-transformation-rate thermal analysis (CRTA) - a stepwise isothermal analysis and quasi-isothermal and quasi-isobaric method. In this method, some parameters follow a predetermined programme as functions of time, this being achieved by adjusting the sample temperature. This technique maintains a constant reaction rate, and controls the pressure of the evolved species in the reaction environment. CRTA is, therefore, characterised by the fact that it does not reqnire the predetermined temperature programmes that are indispensable for TG. This method eliminates the nnderestimation and/or overestimation of kinetic effects, which may resnlt from an incomplete understanding of the kinetics of the solid-state reactions normally associated with non-isothermal methods. 

CONTROLLED TRANSFORMATION RATE THERMAL ANALYSIS (CRTA)... 

Conventional thermal analysis requires that the temperature of the sample follows some predetermined program as a function of time. Controlled transformation rate thermal analysis (CRTA), referred to as the... 

Figure 18. Schematic of apparatus used for controlled transformation rate thermal analysis. (A) sample ( 5 glass orfused-silicacell ( Q furnace fDj thermocouple f ) andfT/), Pirani gauges (G), diaphragm (I), pumping system. ]...

Badens, E., Llewellyn, P., Fulconis, J. M., Jourdon, C., Veesler, S., Boistelle, R., and Rouquerol, F., Study of Gypsirm Dehydration by Controlled Transformation Rate Thermal Analysis (CRTA), J. Solid State Chem., 139 37 4 (1998)... 

An amorphous micioporous silica (previously studied in the scope of an SCI-IUPAC project (ref. 10)) is examined (fractal dimension ca 2.5 (ref. 11)). It is outgassed at increasing temperatures from 423 to 1173 K by Controlled Transformation Rate Thermal Analysis (ref. 12). 

Evolution of the external surface area and the two types of microporosity of atiapulgite (structural and inter-fiber) were examined as a function of a vacuum thermal treatment upt to 500°C. The methods used include controlled transformation rate thermal analysis, N2 and Ar low temperature adsorption calorimetry, water vapor adsorption gravimetry and quasi equilibrium gas adsorption procedure of N2 at 77K and CO2 at 273 and 293K. Depending on the outgassing conditions,i.e. the residual pressure, the structure folds 150 to 70 C. For lower temperature, only a part (18%) of the structural microp< osity is available to N2,13% to argon and 100% to CC>2.With water, the structure can rehydrate after the structure is folded up to an outgassing temperature of 225°C. 

Outgassing for adsorption microcalorimetry and thermal analysis was carried out by controlled transformation rate thermal analysis (CTRTA) (ref. 6). Its interest is both the rather high resolution achieved on the thermal analysis curves (ref. 7) and the possibility of carrying out the experiment directly with the sample bulbs needed for adsorption microcalorimetry. The experimental conditions selected were a sample mass of about 0.260 g, a residual pressure of 2 Pa over the sample and a dehydration rate of 2.77 mg/h. 

Badens, E., P. Llewellyn, J. M. Fulconis, C. Jourdan, S. Veesler, R. Boistelle and F. Rouquerol (1998). Study of gypsum dehydration by controlled transformation rate thermal analysis (CtCTA) . Journal of Solid State Chemistry 139(1) 37-44. 

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