Study of Crystallization Process in Se₈₀In₁₀Pb₁₀by Iso-Conversional Methods

The crystallization kinetics of Se80In10Pb10 chalcogenide glass is studied using differential scanning calorimeter (DSC) at different heating rates (5, 10, 15 and 20 K/min) under non-isothermal conditions. Four iso-conversional methods (Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Tang and Straink) were used to determine various kinetic parameters: crystallization temperature (Tα), activation energy of crystallization (Eα), Avrami exponent (nα) in non-isothermal mode. The transformation from amorphous to crystalline phase in Se80In10Pb10 is considered as a single step reaction mechanism.

Thermal Characterization of Se_80-xTe₂₀In_xGlasses Using Iso-Conversional Methods

Alloys of Se80-xTe20Inx glassy system are obtained by quenching technique and crystallization kinetics has been studied using Differential Scanning Calorimetric [DSC] technique. Well defined endothermic and exothermic peaks are ob- served at glass transition temperature (Tg) and crystallization temperature (Tc). From DSC scans, Tc is obtained at dif- ferent heating rates (5, 10, 15, 20, 25 K/min). It is observed that Tc increases with increasing heating rate for a particular glassy alloy. Activation energy of crystallization (Ec) has been calculated by different Non-isothermal Iso-conversional methods, i.e., Kissinger-Akahira-Sunose [KAS], Friedman, Flynn-wall-Ozawa [FWO], Friedman-Ozawa [FO] and Sta-rink methods. It is observed that Ec is dependent on extent of crystallization (α). Activation energy is also found to vary with atomic percentage of In in ternary Se80-xTe20Inx glassy system. The compositional dependence of Ec shows a re-versal in the trend at x = 15 in Se80-xTe20Inx, which is explained in terms of mechanically stabilized structure at this composition.

Thermogravimetric study of combustion of biomass and anthracite coal by iso-conversional method

The combustion characteristics of biomass, anthracite coal and their blends were investigated using thermogravimetry, and the kinetic parameters and combustion reaction mechanisms were tested by combining the iso-conversional method and Avrami method in order to find out the kinetics characteristics responsible for the combustion of samples. In biomass combustion, two peaks were observed at 332.3 and 472.3℃, but the reactive rate curve of coal showed one peak with maximum mass loss rate at 552.8℃. The ignition temperature and burnout temperature of blends decreased, and the ignition index and combustibility index increased with the increase in biomass content. Calculation of kinetic parameters showed that the values of activation energy of blends increased with increasing biomass content from 150.77 to 215.93 kJ/mol. The reaction orders of blends lay in the range of 0.44 and 0.78.

An evaluation equation of TG experiment data based on iso-conversion method for activation energy

The iso-conversion method to could calculate the kinetics parameters effectively, the present paper built an evaluation equation for iso-conversion methods according to the thermo kinetics integral equation and analyses the temperatures of the same degree of conversion for different heating rates by ideal TG （thermo-gravity） curve data. It is obtained that the temperatures of the same degree of conversion for different heating rates＇ TG curve have good linearity connection validating the correction of the evaluation equation for iso-conversion methods and the scope of linear slope for theratio between heating rates being 2 is 1.05 to 1.09.

Effect of demineralization on pyrolysis characteristics of LPS coal based on its chemical structure

The critical issue in developing mature Oxy-Coal Combustion Steam System technology could be the reactivity of deminer-alized coal which,is closely related to its chemical structure.The chemical structures of Liupanshui raw coal(LPS-R)and Liupanshui demineralized coal(LPS-D)were analyzed by FTIR and solid-state 13C-NMR.The pyrolysis experiments were carried out by TG,and the pyrolysis kinetics was analyzed by three iso-conversional methods.FTIR and 13C-NMR results suggested that the carbon structure of LPS coal was not altered greatly,while demineralization promoted the maturity of coal and the condensation degree of the aromatic ring,making the chemical structure of coal more stable.The oxygen-containing functional groups with low bond energy were reduced,and the ratio of aromatic carbon with high bond energy was increased,decreasing the pyrolysis reactivity.DTG curve-fitting results revealed that the thermal weight loss of LPS coal mainly came from the cleavage of aliphatic covalent bonds.By pyrolysis kinetics analysis of LPS-R and LPS-D,the apparent activation energies were 76±4 to 463±5 kJ/mol and 84±2 to 758±12 kJ/mol,respectively,under different conversion rates.The reactivity of the demineralized coal was inhibited to some extent,as the apparent activation energy of pyrolysis for LPS-D increased by acid treatment.

Thermal Stability and Thermal Decomposition Kinetics of 1-Butyl-3-methylimidazolium Dicyanamide

Thermal stability and thermal decomposition kinetics of 1-butyl-3-methylimidazolium dicyanamide ([bmin+][N(CN) ]2-) were investigated using both isothermal and non-isothermal thermogravimetric analyses (TGA) under high pure nitrogen as carrier gas. The long-term thermogravimetric studies revealed that the highest temperature used should be 110 °C, at which [bmin+][N(CN)2-] lost less than 10% by mass in 10 hours. The non-isothermal activation energy values determined using Friedman and ASTM methods were (150±13) and (147±2) kJ·mol –1 , respectively. Multivariate non-linear-regression methods showed that expanded Fn and CnB models were the best fit models with highest correlation coefficient of 0.9994, and the apparent activation energies were consistent with iso-conversional methods.

Kinetic mechanism of magnesium production by silicothermic reduction of CaO·MgO in vacuum

The investigation of silicothermic reduction of CaO·MgO was carried out using a self-developed thermogravimetric analysis(TGA)instrument under vacuum and high temperature conditions.The TG data of pellets prepared with calcined dolomite,ferrosilicon and fluorite were determined at the heating rates of 1.5,2.0,2.5 and 3.0℃/min in 5 Pa vacuum at 300−1400℃,respectively.Model-free analysis and model-based analysis were applied for simulating the kinetic mechanism.By analyzing the characteristics of the initial and final reaction temperatures of TG curve,ratio of half-width of derivative TG curve and kinetic parameters,a conclusion was made that the most probable mechanism function is the first order formal chemical reaction with activation energy of 233.42 kJ/mol and pre-exponential factor of 5.14×1010 s−1.This study provides the basic data of dynamics of silicothermic magnesium production under vacuum conditions.

Green Composite Material Made from Typha latifolia Fibres Bonded with an Epoxidized Linseed Oil/Tall Oil-Based Polyamide Binder System

Here,we report the mechanical and water sorption properties of a green composite based on Typha latifolia fibres.The composite was prepared either completely binder-less or bonded with 10%(w/w)of a bio-based resin which was a mixture of an epoxidized linseed oil and a tall-oil based polyamide.The flexural modulus of elasticity,the flexural strength and the water absorption of hot pressed Typha panels were measured and the influence of pressing time and panel density on these properties was investigated.The cure kinetics of the biobased resin was analyzed by differential scanning calorimetry(DSC)in combination with the iso-conversional kinetic analysis method of Vyazovkin to derive the curing conditions required for achieving completely cured resin.For the binderless Typha panels the best technological properties were achieved for panels with high density.By adding 10%of the binder resin the flexural strength and especially the water absorption were improved significantly.

Investigation on Co-Combustion Kinetics of Anthracite and Waste Plastics by Thermogravimetric Analysis

In order to effectively recycle resource for the benefit of the global environment, the utilization of waste plastics as auxiliary injectant for blast furnaces is becoming increasingly important. Combustion kinetics of plastics-coal blends with 0, 10%, 20% and 40% waste plastics (WP) are investigated separately by thermogravimetric analysis (TGA) from ambient temperature to 900 ℃ in air atmosphere. These blends are combusted at the heating rates of 5, 10 and 20 ℃/min. The results indicate that, with the increase of waste plastics content, the combustion processes of blends could be divided into one stage, two stages and three stages. The waste plastics content and heating rates have important effects on the main combustion processes of blends. With the increase of waste plastics content, the ignition temperature and the final combustion temperature of blends tend to decrease, while the combustion reaction becomes fiercer. With the increase of the heating rate, the ignition temperature, the mass loss rate of the peaks and the final combustion temperature of blends combustion tend to increase. The Flynn-Wall-Ozawa (FWO) iso-conversional method is used for the kinetic analysis of the main combustion process. The results indicate that, when the waste plastics content varied from 0 to 40%, the values of activation energy increase from 126.05 to 184.12 kJ /mol.

Reaction model and cure kinetics of fiber-reinforced phenolic system

Fiber-reinforced phenolic composite has become an ideal material for solid rocket motor’s(SRM)nozzle,because of its excellent high temperature resistance and ablation resistance.The physical and chemical properties of reinforcing fiber would significantly affect the cure reaction of phenolic(PF)resin,which results in the obvious difference between the cure characteristics of the fiberreinforced phenolic system and neat resin.To clarify the difference in cure reaction between fiber-reinforced phenolic system and PF resin,meanwhile,to obtain the kinetics of high silica glass fiber/phenolic(GF-HSi/PF)prepreg and carbon fiber/phenolic(CF/PF)prepreg,the dynamic experiments of PF resin,GF-HSi/PF prepreg and CF/PF prepreg are carried out by differential scanning calorimetry(DSC).Iso-conversional kinetics is proposed,and the activation energy is determined as a function of cure degree.The reaction model f(α)is obtained by introducing the kinetics compensation effect,founding that the f(α)of PF resin is influenced significantly by reinforcing fiber.The kinetics of three materials are determined by the model-fitting method,founding that the kinetic models of PF resin,GF-HSi/PF prepreg and CF/PF prepreg are a one-step autocatalytic model,two-step model from autocatalytic reaction to N-order reaction and three-step model from autocatalytic reaction to N-order reaction respectively.