Non-isothermal crystallization kinetics of Ag-As2S3 semiconductor glasses

Using a differential thermal analysis technique to give single scan thermograms, the transformation mode,n, and the activation energy of crystallization,E, were determined for the chalcogenide glasses of the system Ag _x (As₂S₃)_100–x' withx=6, 15 and 25. Bothn andE were found to be compositionally dependent. The value ofn varies between 2.1 and 3.6, and that ofE between 2.4 and 3.6 eV. The crystallization kinetic data were explained using X-ray diffraction results of amorphous and crystalline structures.     

纳米二氧化硅改性PA6非等温结晶动力学

用DSC手段考察了反应釜内原位聚合制备的含有纳米二氧化硅的PA6的非等温结晶行为，熔体冷却的结晶发生在可结晶温度范围的高温区，冷却速率越快，结晶温度越低，即结晶温度趋向具有最大结晶速率的结晶温度靠近。F-3、F-4与1013B的结晶速率常数Zg也相差不多，△Hc也类似，n也在3～4之间，说明改性F-3、F-4的结晶特性未收到明显影响，保持在与1013B一致的水平。     

The crystallization kinetics of Fe-Ni based metallic glasses

Differential scanning calorimetry is used to study the crystallization kinetics of two commerical Fe-Ni metallic galsses near their glass transition point. For 0.01 <x<0.85 the fraction transformed,x, as a function of time,t, satisfies the Johnson-Mehl-Avrami equation with exponentn varying from 2.8 to 4.3 as the annealing temperature is increased. The activation energies for the crystallization process are estimated from the time to 50% transformation as close to 100 kcal mol^–1 and are interpreted as arising from viscous flow.     

SiO2-聚合物杂化微球改性聚丙烯的非等温结晶动力学

将原位乳液聚合制得的SiO₂-聚合物杂化微球与聚丙烯熔融共混制备了SiO₂/聚丙烯(SiO₂/PP)复合材料, 利用差示扫描量热法(DSC)研究了SiO₂/PP复合材料的非等温结晶动力学行为。结果表明, SiO₂-聚合物杂化微球具有明显的异相成核效应, 提高了PP的结晶温度和结晶速率, 同时降低了PP的结晶度, 提高了PP的结晶活化能。运用Mo法处理纯PP和SiO₂/PP复合材料的非等温结晶动力学, 结果显示SiO₂-聚合物杂化粒子降低了聚丙烯在单位结晶时间内达到一定结晶度时所需的降温速率。     

Ge23Se67Sb10玻璃非等温结晶动力学研究

通过示差扫描量热法(DSC),采用了Kissinger、Augis-Bennett和Matuasita理论对Ge23Se67Sb10玻璃的结晶动力学进行了分析研究.得到Ge23Se67Sb10玻璃的结晶激活能、频率因子和玻璃转变激活能的平均值分别为156.8kJ/mol、1.56×108s-1和420.3kJ/mol;Avrami指数n≈3表明Ge23Se67Sb10玻璃的结晶机制主要为三维形核生长机制.最后采用Lasocka经验公式讨论了玻璃化温度与升温速率的关系.     

SiO2-聚合物杂化微球改性聚丙烯的非等温结晶动力学

将原位乳液聚合制得的SiO2-聚合物杂化微球与聚丙烯熔融共混制备了SiO2/聚丙烯(SiO2/PP)复合材料,利用差示扫描量热法(DSC)研究了SiO2/PP复合材料的非等温结晶动力学行为.结果表明,SiO2-聚合物杂化微球具有明显的异相成核效应,提高了PP的结晶温度和结晶速率,同时降低了PP的结晶度,提高了PP的结晶活化能.运用Mo法处理纯PP和SiO2/PP复合材料的非等温结晶动力学,结果显示SiO2-聚合物杂化粒子降低了聚丙烯在单位结晶时间内达到一定结晶度时所需的降温速率.     

Evaluation of crystallization kinetics of glasses by non-isothermal analysis

Based on Johnson-Mehl-Avrami transition equation, this paper proposes a new non-isothermal method for evaluating the crystallization kinetics of glasses. An equation relating the kinetic parameters of the crystallization activation energy, E, and the frequency factor, v, to the inflection-point temperature, T _f, and the heating rate, , of differential thermal analysis (DTA) experiment is established. The inflection-point temperature, T _f, can be easily determined from the derivative differential thermal analysis (DDTA) curves. The validity of the proposed method is ascertained by applying it to Li₂O·2SiO₂ glass. The acquired values of the crystallization kinetic parameters by this method are excellent agreement with the isothermal analysis results. In contrast, the traditional non-isothermal methods give much higher values.     

Time-scaling and crystallization kinetics of three Fe-B-based metallic glasses

Time-scaling properties of the isothermal transformation kinetics have been tested for three Fe-B-based metallic glasses exhibiting two crystallization stages. The time scale was defined as the time at which crystallization has reached half completion and is derived from calorimetric (DSC) data. The temperature dependence of the time-scaling parameter shows a lowtemperature freezing behaviour and can be described by empirical functions based on free-volume considerations.     

A study of the crystallization kinetics of some Cu-As-Te glasses

The crystallization kinetics of two amorphous alloys in the Cu-As-Te system was studied by differential scanning calorimetry, using continuous heating methods, and applying a new analysis procedure in order to calculate the kinetic parameters which define the crystallization reactions, in the Johnson-Mehl-Avrami model. In this analysis, the crystallized fraction interval at which the characteristic function of said model is constant was taken into account. The values obtained for these parameters made it possible to discuss the glass-forming ability of the compounds under study, and the types of crystalline growths in the alloys.     

Nucleation kinetics of primary crystallization products in FeSiB metallic glasses

Three iron-based metallic glasses in the Fe_96–x Si₄B _x series were examined after various dynamic and isothermal annealing treatments. The number and type of the primary crystallization products formed in these alloys were determined as functions of time and temperature, and the results compared with theoretical models. It has been found that, for certain alloys, a proportion of the primary -iron crystals in the structure are nucleated by particles of the metastable Fe₃B phase. The transformation kinetics of these composite crystals are different from those which do not contain an Fe₃B core, suggesting different nucleation mechanisms for the two types of crystal.     

木粉/低熔点尼龙6复合材料的非等温结晶动力学

利用LiCl改性尼龙6(PA6),并将其与木粉熔融共混制备了木粉/低熔点PA6复合材料,通过DSC法研究了木粉/低熔点PA6复合材料的非等温结晶动力学行为.结果 表明,LiCl降低了PA6的熔点、结晶温度、结晶度和结晶速率,提高了PA6的结晶活化能.木粉是良好的成核剂,能够加快PA6的结晶速率,但却降低了其结晶度.通过...     

Isothermal crystallization kinetics of Ni60Nb4o-xCrx,glasses

Isothermal crystallization kinetics of Ni₆₀Nb_40-xCr_x (x = 0, 5, and 13 at %) glasses was investigated by differential scanning calorimetry. It was possible to separate out the kinetics of formation of various phases which are obtained on crystallization of these glasses. The results are compared with the earlier investigations [1] in which the data were obtained by constant heating rate experiments. The crystallization of M-phase, Ni₃Nb and NbCr₂ phases could be described by Johnson-Mehl-Avrami kinetics. The activation energies for the formation of these phases were found to decrease in the same order. A decreasing activation energy with increasing transformed fraction (time) was also observed. The results are interpreted in light of the values obtained for Avrami exponents.     

双峰聚乙烯非等温结晶行为的研究

采用DSC方法研究了双峰聚乙烯(BPE)和茂金属聚乙烯(mPE)的非等温结晶过程,分别采用Ozawa方程和莫志深方法对所得的数据进行了处理。结果表明:茂金属聚乙烯结晶速率高于双峰聚乙烯。在实验范围内,两种聚乙烯的非等温结晶动力学均符合莫志深方程。     

聚氧化乙烯(PEO)及其与高氯酸锂复合体系的非等温结晶动力学研究

用示差扫描量热法(DSC)研究了PEO及其与高氯酸锂复合体系的非等温结晶过程.分别用Jeziorny方法、一种结合Avrami和Ozawa方程的方法对该体系的非等温结晶过程进行了研究,分别得到PEO进行非等温结晶时的动力学参数.结果表明LiClO4晶粒缩短了PEO的结晶时间,使复合体系中PEO的结晶速率要大于纯PEO;但纯PEO结晶时形成的晶体更完善.为使二者达到相同的相对结晶度,纯PEO体系需要更大的冷却速度.LiClO4微粒能有效地将PEO的结晶相转变成非晶相,也就是说LiClO4可有效地抑制PEO的结晶过程.     

Non-isothermal crystallization and isothermal transformation kinetics of the Ni68.5Cr14.5P17 metallic glass

Non-isothermal crystallization of the Ni_68.5Cr_14.5P₁₇ alloy is characterized by differential scanning calorimetry (DSC) and X-ray techniques. Transformation occurs in two stages at peak temperatures 622±1 and 692±1 K (at 20 K min^–1), with H ₁=1.50+0.1 kJ mol^–1 and H ₂=3.0±0.1 kJ mol^–1. Precipitation of a nickel phase occurs in the first stage and a (NiCr)₃ P phase is formed during the second stage. An approach to the isothermal kinetics of the two crystallization events is derived within the frame work of the Johnson-Mehl-Avrami theory.     

Effect of high-energy heavy ion irradiation on the crystallization kinetics of Co-based metallic glasses

Differential scanning calorimeter (DSC) is employed to study the crystallization kinetics of irradiated (at three different fluences with high-energy heavy ion; Ni¹¹⁺ of 150 MeV) specimens of two Co-based metallic glasses. It is found that the crystallization process in both the glasses is completed in two phases. The DSC data have been analysed in terms of kinetic parameters viz. activation energy (E _c), Avrami exponent (n), dimensionality of growth (m), bdusing two different theoretical models. The results obtained have been compared with that of virgin samples. The lower activation energy in case of second crystallization occurring at higher temperature indicates the easier nucleation of second phase. The abnormally high value of Avrami exponent in Co-Ni glass indicates very high nucleation rate during first crystallization.