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of picoseconds. On cooling, several phase transitions take place in these compounds [ 7 – 11 ]. For example, [Ni(NH 3 ) 6 ](NO 3 ) 2 displayed four low temperature phases [ 8 – 10 ]. The phase transition at T C1 , associated with the largest change

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stellerite, with two close peaks one by one. The first one (∼200 °C) is narrow and high and the second one (∼250 °C) is broader and smaller. The first peak was reported to be the first-order phase transition with the step change of 3.24% in the UC volume and

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There are several approaches for the description of phase transitions (PT). leading to different classification schemes:Approach Classification scheme bythermodynamicorder (after Ehrenfest)kineticreversibility, quenchability, hysteresisstructuralrelationship of crystallographic axes before and after PTmechanisticactual migration path of atoms during PT The most important techniques for investigating PT include DTA and DSC thermo-optical analysis, melastic neutron scattering, IR and Raman spectroscopy and elastic X-ray and neutron diffraction. The latter, as dependent on the temperature, can give indications on the mechanism of PT. The appropriate application of these techniques is demonstrated on the example of the polymorphism of KPO3.

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. Thermodynamics and introduction to thermostatistics 1985 Brokate M., Sprekels J. Hysteresis and phase transitions , Springer

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Abstract  

The phase transition and the crystal structures of CuITe were investigated by differential thermal analysis and X-ray powder diffraction measurements in the temperature range between 300 and 683 K. The new phase transition in CuITe was observed at 592 K. The enthalpy of transition is ΔH=0.125 kJ mol-1. The new phase above 592 K belongs to tetragonal system with the space group I41 /amd.

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Journal of Thermal Analysis and Calorimetry
Authors: George G. G. de Oliveira, Humberto G. Ferraz, Patrícia Severino, and Eliana B. Souto

]. The aim of this article was to analyse the phase transition and dehydration processes of nevirapine using DSC and thermogravimetry differential thermal analysis (TG-DTA). Materials and methods Nevirapine was provided by the

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Abstract  

The aim of this study was to correlate the results of experimental data using DTA method and predictions of artificial neural network (ANN) and multivariate linear regression (MLR). Thermal decomposition of polymers was analyzed by simultaneous DTA method, and kinetic parameters (critical points, the change of enthalpy and entropy) of polymers were investigated. A computer model based on multilayer feed forwarding back propagation and multilayer linear regression model were used for the prediction of critical points, phase transitions of low-density polyethylene (LDPE) and mid-density polyethylene. As a result of our study, we concluded that ANN model is more suitable than MLR about prediction of experimental data.

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Abstract  

Yttrium orthoborate crystallizes in the vaterite-type structure and has two polymorphous forms, viz. a low- und a high temperature one. DTA measurements of YBO3 confirmed a reversible phase transition with a large thermal hysteresis. The phase transition has been accurately characterized by the application of different heating and cooling rates (β). Consequently, the extrapolation of the experimental data to zero β yields the transition points at 986.9C for the heating up and at 596.5C for the cooling down cycle. These values correspond to samples just after treatment at 1350C. For samples with a different ‘thermal history’ other phase transition temperatures are observed, (e.g. after having performed several heating and cooling cycles). The linear relationship between the associated DTA signal ΔT=T onsetT offset and the square root of the heating rate β was confirmed, but the relation between T onset and square root of β is not found here. From the empirical data a good linear fitting between T onset and ln(β+1) can be derived. From the kinetic analysis (Kissinger method) of the phase transformation of YBO3 an apparent activation energy of about 1386 kJ mol–1 for heating and of about 568 kJ mol–1 for cooling can be determined

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Journal of Thermal Analysis and Calorimetry
Authors: Bedřich Smetana, Simona Zlá, Aleš Kroupa, Monika Žaludová, Jaromír Drápala, Rostislav Burkovič, and Daniel Petlák

investigation is focused on the area close to the monovariant line in the phase diagram of Sn–Zn–Al ternary system ( Fig. 1 ). As this region of the Sn–Zn–Al phase diagram still deserves a lot of attention [ 3 – 11 ], the temperatures of phase transitions were

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]. Although several research groups have experimental and theoretically investigated the pressure induced phase transitions in TiN using different methods. For example, Zhao et al. [ 13 ] investigated the behavior of TiN using axial X-ray diffraction under

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