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1.
Vlase T. Vlase G. Chiriac A. Doca N. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):839-845
The thermal decomposition in non-isothermal conditions of formates, acetates, propionates and butyrates of Mn, Co, Zn, Cd,
Eu, Sm and Ni was studied. The observed compensation effect allows us to calculate the isokinetic temperature. A selective
activation mechanism was suggested. This leads to a good agreement between kinetic and spectroscopic data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
T. Vlase Gabriela Vlase A. Chiriac N. Doca 《Journal of Thermal Analysis and Calorimetry》2005,80(1):87-90
Summary In order to obtain catalysts, the thermal decomposition of the precursors is a compulsory step. However, kinetic analysis of the decomposition data obtained under non-isothermal conditions lead very seldom to the intimate reaction mechanism. There is also a lack of information because in non-isothermal kinetics, the compensation effect, is rather a rule and unfortunately a source of debate. In order to discriminate between these processes, and the influence of conversion, respectively temperature on the reaction rate, the NPK (non-parametric kinetic - Sempere and Nomen) method was used. This method is based on the singular value decomposition algorithm (SVD) applied on the matrix of reaction rate at corresponding conversion and temperature. This method allows a less speculative determination of the conversion functions and of the kinetic parameters. 相似文献
3.
Summary The thermal behavior of KH2PO4, NaH2PO4 and Na2HPO4 under non-isothermal conditions using TG method with different heating rates was studied. The values of the reaction rate were processed by means of Friedmans differential-isoconversional method. A dependence of the activation energy vs. conversion was observed. Therefore a procedure based on the compensation effect (suggested by Budrugeac and Segal) was applied. A less speculative data processing protocol was offered by the non-parametric kinetics method suggested by Serra, Nomen and Sempere. Three steps were observed by non-isothermal heating: a dehydration, a dimerization and a polycondensation. The differences in the intimate reaction mechanism are determined by the initial number of water molecules. 相似文献
4.
T. Vlase Gabriela Vlase N. Doca C. Bolcu 《Journal of Thermal Analysis and Calorimetry》2005,80(1):59-64
Decomposition of dichlorodifluoromethane in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixtures involving carbon, chlorine and fluorine in presence of argon (which is assumed to be the main plasma gas) and/or in addition of hydrogen and calcium together with hydrogen. The calculations were carried out for the temperature range between 500 and 6000 K and for the total pressure of the system of 1 bar. Use is made of the fact that a thermal plasma is a plasma in (local) thermal equilibrium, which makes possible the theoretical determination of its equilibrium composition at definite temperature by employing Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state. The results of calculations show that toxic molecules and radicals can be, under convenient conditions (appropriate temperature and amount of added substances), converted into stable non-toxic species like CaF2 and CaCl2. 相似文献
5.
Adriana Popa Smaranda Iliescu Nicolae Doca Titus Vlase Gabriela Vlase 《International Journal of Polymer Analysis and Characterization》2017,22(1):43-50
A commercial styrene–divinylbenzene copolymer was functionalized by multistep reactions with alpha-isopropylaminophosphonic acid groups. Three different functionalized copolymers were obtained in which the phosphonic groups are in meta (1E), para (2E), and ortho (3E) positions. The thermal behavior was studied using the TG/IR hyphenated technique and kinetic analysis of thermo-oxidation under nonisothermal conditions. The evolved gas analysis confirms the partial thermo-oxidative degradation of polymeric materials, with significant preservation of the aromatic ring. The kinetic analysis was performed by three methods: Friedman, Flynn–Wall–Ozawa, and nonparametric kinetic. 相似文献
6.
7.
Compensation effect as a consequence of vibrational energy transfer in homogeneous and isotropic heat field 总被引:1,自引:1,他引:0
Nicolina Pop Gabriela Vlase T. Vlase N. Doca A. Mogoş A. Ioiţescu 《Journal of Thermal Analysis and Calorimetry》2008,92(1):313-317
By kinetics of decomposition of solids in both isothermal and non-isothermal conditions, the compensation effect (CE) is rather
a rule.
The topic of this work is to suggest an activation mechanism which leads to the dependences similar with CE.
The solid is assimilated to a system of the harmonic oscillator with a Bose-Einstein energy distribution.
Considering an activation process due to a vibrational energy transfer from a homogeneous and isotropic field of thermic oscillators
to the solid-state oscillator, the thermodynamic functions are in the relationship
where ΔH* and ΔS* are the activation functions and T
is is the isokinetic temperature.
Taking into account the definitions of H and S by means of the partition function, the isokinetic temperature is assimilated with the characteristic temperature
An important consequence, a correlation between the isokinetic temperature and the spectroscopic wavenumber of the activated
bond, is illustrated by a number of decomposition reactions under non-isothermal conditions. 相似文献
8.
A multibody frictional mortar contact formulation (Gitterle et al., 2010) is extended for the simulation of solids undergoing finite strains with inelastic material behavior. The framework includes the modeling of finite strain inelastic deformation, the numerical treatment of frictional contact conditions and specific finite element technology. Several well-established and recent models are employed for each of these building blocks to capture the distinct physical aspects of the deformation behavior. The approach is based on a mortar formulation and the enforcement of contact constraints is realized with dual Lagrange multipliers. The introduction of nonlinear complementarity functions into the frictional contact conditions combined with the global equilibrium leads to a system of nonlinear equations, which is solved in terms of the semi-smooth Newton method. The resulting method can be interpreted as a primal–dual active set strategy (PDASS) which deals with contact nonlinearities, material and geometrical nonlinearities in one iterative scheme. The consistent linearization of all building blocks of the framework yields a robust and highly efficient approach for the analysis of metal forming problems. The effect of finite inelastic strains on the solution behavior of the PDASS method is examined in detail based on the complementarity parameters. A comprehensive set of numerical examples is presented to demonstrate the accuracy and efficiency of the approach against the traditional node-to-segment penalty contact formulation. 相似文献
9.
Alexandra Ioiţescu Gabriela Vlase T. Vlase G. Ilia N. Doca 《Journal of Thermal Analysis and Calorimetry》2009,96(3):937-942
The synthesis of four types of hydroxyapatite synthesized from calcium chloride and four different organic phosphites is presented.
The method of synthesis chosen is the sol–gel route, which has a number of advantages compared to other methods, like the
intimate contact between reactants and the milder synthesis conditions. The samples were thermally treated, the TG/DTG/DTA
curves being obtained at four heating rates, namely: 7, 10, 12 and 15 °C min−1. The samples were characterized before and after the thermal treatment using FT-IR analysis. The FT-IR spectra certified
that the formed compounds represent hydroxyapatite. Based on the information from the TG curves and IR spectra interpretation,
a reaction mechanism was proposed. 相似文献
10.
The thermal decompositions of ammonium metavanadate, molybdic acid and ammonium phosphomolybdate supported on carborundum
or silica were subjected to non-isothermal kinetic study. The compensation effect is discussed in connection with the quantitative
estimation of the support effect.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献