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A measuring technique has been developed whereby thermodilatometric examinations can be carried out at a strictly constant rate, slower by one or two orders of magnitude than that of conventional measurements. Under the special conditions the temperature of the sample changes in a special way. The TD curve recorded as a function of this temperature yields new information about the kinetics and mechanism of the structural changes taking place within the sample.

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Simultaneous volume and enthalpy relaxation

The effect of experimental conditions

Journal of Thermal Analysis and Calorimetry
Authors: M. Liška and M. Chromčíková
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Abstract  

In this work the (α + γ1) complex phase formation reaction in the Cu-10mass% Al-6mass% Ag alloy was studied using Differential Scanning Calorimetry (DSC), Differential Thermodilatometry (DTD), X-ray diffractometry (XRD), Optical (OM) and Scanning Electron Microscopies (SEM). The results indicated the presence of two different processes, related to a change in the Ag diffusion route from the α matrix to the (α + γ1) complex phase.

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Abstract  

The author gives a detailed survey on thermogravimetric investigations under quasi-isothermal — quasi-isobaric conditions (Q-TG). According to the principle of the technique the heating of the sample is governed by the transformation itself according to the feed-back principle in a way that the transformations should take place at a strictly constant rate, slower by orders of magnitude than in the case of the conventional techniques. Due to this, the transformations take place under ideal conditions, near to physico-chemical requirements.Based on the obtained advantageous results further methods were elaborated, like thermo-dilatometry (Q-TD), evolved gas analysis (Q-EGA) and microdistillation under quasi-isothermal conditions.The second part of the present review deals with DTA and DSC techniques under quasi-isothermal conditions elaborated recently

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Abstract  

The silica waste originating from a geothermal power plant in Mexico was investigated with the aim of finding its applicability as a raw secondary material for ceramics production. The thermal behaviour of the original silica waste (containing NaCl and KCl from marine brine) and of the purified silica was characterized by means of DTA/TG, emanation thermal analysis (ETA) and thermodilatometry (TD). The reactivity of the purified silica waste mixed with CaCO3 (1.8 mass%) was characterized by means of ETA, DTA and TG. The microstructures and phase compositions of the final products prepared by heating in air were tested by means of X-ray diffraction and of scanning electron microscopy coupled with electron probe X-ray microanalysis. The thermal analysis methods allowed determination of the optimal conditions for thermal treatment of the silica waste in order to obtain partly sintered porous materials for use as refractory bricks.

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Abstract  

La2Mo2O9 (LMO) was synthesized at lower temperature 973 K (LT-phase) by ceramic route. Differential thermal analysis (DTA) scan of LT-phase of LMO showed α→β transition at 843 K during heating and β→α conversion via a metastable γ-phase during cooling. This was also confirmed by thermo-dilatometry and impedance spectroscopy. La2Mo1.95V0.05O9-δ (LMVO), La1.96Sr0.04Mo2O9-δ (LSMO) and La1.96Sr0.04Mo1.95V0.05O9-δ (LSMVO) were prepared in a similar way. These compounds exhibited α→β transition on heating with shift in transition temperature, but the existence of γ-phase during cooling disappeared. Substitution increased the ionic conductivity of α-phase and reduced that of β-phase.

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Abstract

The effect of TeO2 additions on the thermal behaviour of zinc borophosphate glasses were studied in the compositional series (100 − x)[0.5ZnO–0.1B2O3–0.4P2O5]–xTeO2 by differential scanning calorimetry, thermodilatometry and heating microscopy thermal analysis. The addition of TeO2 to the starting borophosphate glass resulted in a linear increase of glass transition temperature and dilatometric softening temperature, whereas the thermal expansion coefficient decreased. Most of glasses crystallize under heating within the temperature range of 440–640 °C. The crystallization temperature steeply decreases with increasing TeO2 content. The lowest tendency towards crystallization was observed for the glasses containing 50 and 60 mol% TeO2. X-ray diffraction analysis showed that major compounds formed by annealing of the glasses were Zn2P2O7, BPO4 and α-TeO2. Annealing of the powdered 50ZnO–10B2O3–40P2O5 glass leads at first to the formation of an unknown crystalline phase, which is gradually transformed to Zn2P2O7 and BPO4 during subsequent heating.

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Abstract  

The thermal decomposition behavior of hard coal fly ash (HCA2), obtained from the combustion of an Australian hard coal in thermoelectric power plants, in different atmospheres (air, N2 and N2-H2 mixture), was studied using thermogravimetry (TG), infrared-evolved gas analysis (IR-EGA), differential scanning calorimetry (DSC) and thermodilatometry (DIL) techniques. It was found that changing of the applied atmosphere affects the carbon content of the ash which results in different thermal decomposition behaviors. In air, the carbon content was oxidized to carbon dioxide before the decomposition of carbonate. In N2 or in N2-H2 atmospheres, the carbon content acts as a spacer causing a fewer points of contact between calcium carbonate particles, thus increasing the interface area which results in a decrease of the carbonate decomposition temperature. Following the carbonate decomposition, the iron oxide content of the ash undergoes a reductive decomposition reaction with the unburned carbon. This oxidation-reduction reaction was found to be fast and go to completion in presence of the N2-H2 mixture than in the pure nitrogen atmosphere due to the reducing effect of the hydrogen. The kinetics of the carbonate decomposition step, in air and N2-H2 mixture was performed under non-isothermal conditions using different integral methods of analysis. The dynamic TG curves obeyed the Avrami-Erofeev equation (A2) in air, and phase boundary controlled reaction equation (R2) in N2-H2 mixture. The change in the reaction mechanism and the difference in the calculated values of activation parameters with the change of the atmosphere were discussed in view of effect of the atmosphere on the carbon content of the ash.

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