Cellular Automata法模拟材料微观组织结构

用CA(Cellular Automata,CA)法模拟材料微观组织结构的形成过程.模拟过程中考虑了形核过程的随机性与晶粒生长的确定性.采用连续形核模型来描述液相中的自发形核.基于简化的晶粒形状,建立了模拟晶粒生长的二维数学物理模型,开发了模拟程序并进行了二维模拟计算.     

在三元溶液低温相变过程中细胞反应的数值模拟

应用多组分相变系统的连续体模型，对三元溶液（NaCl-H2O-CPA)低温相变过程中的细胞反应进行数值模拟。为了检验数值分析的结果，在特定条件下，提出一种解决多组分系统相变问题的近似分析方法，并在相同条件下，将此结果与数值分析的结果进行比较，两者基本一致。     

二元正烷烃液态混合物加压时的过热极限

建立了适用于链烷烃类系统的过热极限的动力学计算方法。采用发展的动态液滴技术，测定了正戊烷与正庚烷，正辛烷、正壬烷二元混合物的过热极限温度。实验结果表明，过热极限温度随外压的增加而升高，且过热极限温度与外压基本呈线性关系，与组分的摩尔分数也基本呈线性关系。     

Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment meth-ods:conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a dif-ferential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier trans-form infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron micros-copy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the proc-essing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.     

外加电场下脉冲激光烧蚀制备纳米硅晶粒成核生长

采用脉冲激光烧蚀技术,在引入垂直于烧蚀羽辉轴线外加直流电场的前后,分别在1,3,5Pa的室温氩气环境下沉积制备了一系列纳米硅晶薄膜,其中衬底与羽辉轴线平行.扫描电子显微镜(SEM)的检测结果表明,在同一直流电压下制备的纳米Si晶粒平均尺寸和面密度均随气体压强的增加而增大.保持气压不变,引入电场后所制备的纳米Si晶粒平均尺寸相对于无外加电场时增大,而面密度减小.结合纳米晶粒气相成核生长动力学,对实验结果进行了定性分析.     

Ni—Ti合金的R相变及其对形状记忆效应的影响

采用电阻测量和X-射线衍射研究了Ti-54.91wt%Ni合金发生R相变的固溶和有序化处理条件。比较了不同残余应变量下经过 R 相变和只经过熟知的马氏体相变两种试样间的形状记忆特性。在近似等原子的 Ni-Ti 合金中 R 相变的发生取决于热处理条件。除非在最有利的固溶和有序化组合条件下,通常并不存在 R 相变。延长有序化时间总是促进 R 相变。随着马氏体应变量的增大,不论是否附加 R 相变,形状回复温区加宽,单程形状回复率增高并出现极大值,而双程记忆效应单调地升高。在该合金中 R 相变的发生对于单程回复是有益的,但对于双程记忆则稍有削弱。形成 R相的热处理条件可以用声子形核的概念来解释。R 相变在单程和双程记忆上的不同效果可归因于加热(仅 M→B_2)和冷却(B_2→R 和 R→M)中经历不同的相变。     

过热现象的动力学：液体过热亚稳态研究之一

将将相成核动力学理论应用于液体，得出液体内部形成临界气泡的均相成核速率表达式，使用液技术装置了测量了环戊蛇，正己烷等８种元混合物的过热极限，并根据动力学理论作了预测，对于多数体系，二者符合较好。     

硬、软磁多层膜体系成核的解析分析

我们运用微磁学方法,解析地推导了交换耦合多层膜的成核场公式,得到了成核场分别随软、硬磁相厚度变化的曲线,并给出了成核时磁矩角度的空间分布．我们发现成核场随软磁相厚度L^s增加而单调减小,随硬磁相厚度L^h增加而单调增加,没有出现一些文献中所发现的平台和峰值．当L^h〉5nm时,L^h对成核场的影响可以忽略,L^s对成核场起主导作用．成核点磁矩分布并不唯一,但角度满足一定的比值关系．随着薄膜厚度（主要是L^s）的减小,软、硬磁间交换耦合作用逐渐增强,复合磁体由退耦合磁体逐步过渡到交换弹簧,并最后过渡到刚性磁体．即使是刚性磁体,也不会出现完全一致转动的成核模式．     

Liquid exploding emission during boiling nucleation in capillary tubes

A series of experiments was conducted to visually observe boiling nucleation phenomena in micro capillary tubes employing a high speed CCD. At a higher heat flux the liquid in capillary tubes was emitted instantaneously rather than generating nucleate boiling, which is referred as liquid exploding emission in this paper. Both critical emission heat flux and temperature corresponding to this phenomenon were measured for tubes with different heating lengths and arrangements of two end sections. Boiling nucleation and liquid film evaporation played critical roles in different stages during exploding emission. Dimensionless critical emission volumetric heat was introduced to describe the conditions of the emission instead of heat flux, and theoretical discussions were conducted to explore the influences of thermal properties and geometrical configuration, particularly heating length and asymmetry of two end sections of tubes.     

高应变率拉伸下纳米空洞的成核与早期生长

利用分子动力学方法研究了单晶铜中纳米空洞的成核与早期生长过程.研究结果表明：高应变率拉伸作用下,在缺陷原子或空位密集区首先启动（111）-[211],（111）-[211],（111）-[211],（111）-[211]4个滑移系的位错.空洞在特定滑移系层错交叠,即（111）-[211]和（111）-[211]滑移系的层错交叠以及（111）-[211]和（111）-[211]滑移系的层错交叠形成的空穴串处成核.这些空穴串分别沿[011]和[011]方向,与加载方向垂直.相对于其他的滑移系交叠,这种滑移系交叠形成的空穴串的截面积最大.此后,空洞通过发射位错长大,形状类似长条形;伴随其他类型位错的生长,空洞逐渐演化为柱形-椭球形-类球形.对于含双空洞的单晶铜体系,受已存空洞周围应力分布的影响,多个滑移体系同时启动,空洞在3个滑移系的层错交汇点的空穴处成核,其形状受交汇处位错线运动方向的影响,类似扁三角形,并在位错的滑移和攀移作用下逐渐演化为类球形.我们根据畸变场计算了3个层错面交叠处的空穴体积,发现108个不同交叠构型中,只有4种构型的交叠引起的空穴体积最大,空洞成核容易,其他情况不能使空洞成核.