Non-isothermal annealing of a cold rolled commercial twin roll cast 3003 aluminum alloy

It is shown that the recrystallization behavior of a cold rolled twin roll cast, commercial 3003 aluminum alloy under non-isothermal conditions, can be satisfactorily modeled by combining the approaches developed by Semiatin et al. and Puchi et al. The first approach allows the determination of the apparent activation energy for recrystallization without any ambiguity, information that can then be used in the second approach to define clearly the search range for the value of the apparent activation energy for recrystallization and to determine simultaneously the Avrami constants, from experiments conducted at a single heating rate. It is also shown that the apparent activation energy for recrystallization in this alloy varies between approximately 34 and 79 kJ/mol, with the trend being to find smaller values of this parameter as the strain applied to the material increases. Such low values of this energy were corroborated by isothermal experiments conducted in samples of the same material. The microstructural evolution of the samples annealed under non-isothermal conditions indicates that the rate of growth of the recrystallized grains in the rolling direction is significantly higher that in the short transverse direction, due to the pinning effect of the second phase particles aligned along the rolling direction, which leads to recrystallized structures with an aspect ratio significantly higher than 1. The effect of the strain applied to the material on the recrystallization kinetics is quantified by expressing the time required to achieve a given recrystallized fraction as a function of the effective strain, by a simple parametric relationship that involves three numerical constants. Recrystallization experiments conducted under non-isothermal conditions are found to be more suitable for the evaluation of the effect of the strain applied on the recrystallization kinetics in comparison with isothermal tests, since larger strains can be applied to material before the annealing treatment.     

基于DSC技术的铜基非晶合金变温动力学的研究

基于大块非晶合金优异性能以及广阔的工程应用前景．采用DSC技术对大块铜基非晶合金Cu50Zr43A17进行了变温晶化动力学研究研究结果表明：晶化转变温度点与加热速度的立方根成正比．随着加热速度的增加．终了温度与晶化开始温度之差越大．晶化发生的温度区间越宽。     

Characterization of melt-quenched and milled amorphous solids of gatifloxacin

The objectives of this study were to characterize and investigate the differences in amorphous states of gatifloxacin. We prepared two types of gatifloxacin amorphous solids coded as M and MQ using milling and melt-quenching methods, respectively. The amorphous solids were characterized via X-ray diffraction (XRD), nonisothermal differential scanning calorimetry (DSC) and time-resolved near-infrared (NIR) spectroscopy. Both the solids displayed halo XRD patterns, the characteristic of amorphous solids; however, in the non-isothermal DSC profiles, these amorphous solids were distinguished by their crystallization and melting temperatures. The Kissinger–Akahira–Sunose plots of non-isothermal crystallization temperatures at various heating rates indicated a lower activation energy of crystallization for the amorphous solid M than that of MQ. These results support the differentiation between two amorphous states with different physical and chemical properties.     

反应性挤出制备PP-St-MAH共混物及其结晶性能

通过双螺杆挤出机对聚丙烯(PP)、马来酸酐(MAH)和苯乙烯(St)进行反应性挤出制备聚丙烯-苯乙烯-马来酸酐(PP-St-MAH)共混物。用傅立叶红外光谱仪、旋转流变仪研究St用量对PP-St-MAH共混物接枝率和复数黏度的影响。结果表明,St的加入使1 780 cm-1与840 cm-1处峰的面积比(吸光比)由0.88上升至3.94,表明MAH的接枝率提高,同时体系黏度增大,说明St抑制了PP的自由基降解。采用差示扫描量热仪分析不同降温速率和St用量下PP-St-MAH共混物的非等温结晶过程。分别采用Jeziorny法、Ozawa法和莫志深法进行数据处理,发现Jeziorny法和莫志深法都适合分析其非等温结晶动力学,而Ozawa法的结果线性关系不明显,不适合分析PP-StMAH共混物的动力学。随着St用量增加,采用Jeziorny法得到的Avrami指数、结晶速率参数总体呈上升趋势,表明St的引入在一定程度上产生异相成核效果,改变了PP-St-MAH共混物的结晶方式,结晶方式从一维向二维、三维转变,同时加快结晶速率。莫志深法的结果也支持此结论。     

可熔融加工聚乙烯醇的非等温结晶分析

通过差示扫描量热法(DSC)测试了成核剂对可熔融加工改性聚乙烯醇(PVA)结晶行为的影响,并在DSC的基础上用Ozawa法、Jeziorny法以及莫志深方法分析了改性PVA以及改性PVA/成核剂两种材料的非等温结晶动力学。结果表明:结晶度、结晶峰温度、结晶半衰期、结晶速率对降温速率有很强的依赖性;随着降温速率的增加,结晶速率常数增大,结晶度提高;在相同的降温速率下,复合体系的结晶速率常数较大,即成核剂的加入使改性PVA的结晶速率增加,具有异相成核的作用;其中莫志深方法能够较好地解释改性PVA的非等温结晶过程。     

A finite element model of the ventilation pattern inside an industrial building: Non-isothermal case

A finite element investigation of the ventilation conditions in a heated building in which the flow is characterized by the existence of a strong effect of natural convection at high Grashof number is presented. The computation of the velocity and the temperature pattern is performed in an intertwined manner, the coupling being performed by a time stepping technique. The proposed solution strategy allows computations at a very reasonable cost. Numerical predictions are compared to experimental data, and exhibit a very good agreement for the velocity field and a fairly good agreement for the temperature.     

一种新型磷酸硼的制备方法

用常温常压的方法制备了磷酸硼 ,用红外光谱与 X-射线粉末衍射确认了所制备的化合物 ,同时用差热热重分析研究了此化合物的热稳定性。     

新型酚醛树脂固化过程的表征研究

主要利用DSC、TG及IR技术研究了新型S157酚醛树脂体系的固化反应及其动力学、树脂体系中改性剂含量对固化反应的影响及固化过程中树脂体系结构变化规律，为确定新型S157酚醛树脂体系的固化工艺提供依据。新型S157酚醛树脂体系的固化反应表观活化能约为82kJ/mol，固化反应级数为0.91；有机硅改性剂的加入及其含量对树脂基体固化反应表现活化能、固化反应级数和热分解温度基本无影响，但失重率有所降低；在树脂基体等温固化过程中，活性羟甲基指数逐渐降低，树脂在高温固化过程中由于受到氧化而产生羰基吸收。     

废轮胎燃烧特性的热重分析

利用热分析方法研究废轮胎胶粉的燃烧特性,分析试样燃烧的TG/DTG曲线,得出试样的燃烧特性参数,计算出能够反映试样燃烧特性的各项指数(着火稳燃特性综合判别指标、燃烧特性指数等),同时得出胶粉和煤粉的燃烧动力学参数。研究表明,废轮胎胶粉比煤粉具有更好的燃烧性能。     

PVC膜材涂层的热稳定性和表面形貌研究

采用溶液共混法制备了PVC膜材涂层,通过TG、DSC、SEM和动态光散射粒度分析仪等研究DINP、Ba-Zn和CaCO3粒子对涂层性能的影响。结果表明:PVC膜材涂层中添加DINP可减小涂层的粘度;Ba-Zn可提高涂层的热稳定性能;采用超声法对超微细CaCO3/乙醇共混体系进行处理减小了团聚程度;PVC膜材涂层中添加超细重质CaCO3粒子时,与添加超微细CaCO3粒子时相比,涂层表面平整性较好。