最佳晶粒尺寸和介观效应

理论研究表明：存在最佳晶粒尺寸是一种新的介观效应,它来自当晶粒尺寸缩小到一定程度时反映吸附氧负离子的Fermi统计失效;根据当晶粒尺寸缩小到特征长度rm时晶粒将保持电中性的Kubo理论,对Fermi统计公式进行修改,从而给出了最佳晶粒尺寸最佳晶粒尺寸等于2rm的理论结果.用Kubo理论电子逸出功公式估算了rm与最佳晶粒尺寸r*0的数值,其结果与实验一致.     

介观RLC电路的量子效应

在电荷不连续的前提下,利用介观电路的量子化方法,得到了介观RLC电路的有限差分薛定谔方程。在广义动量表象中,通过幺正变换,系统的薛定谔方程转化为标准的马丢(Mathieu)方程的形式,在WKM近似下,计算了系统的能谱和电流的量子涨落。本文的结果将对高度集成电路设计中量子噪声的控制提供理论依据。     

纳米氧化镁晶粒微结构的尺寸效应

我们对纳米氧化镁微晶的系列样品进行了差热分析（ＤＴＡ）、红外（ＦＴ－ＩＲ）测量以及Ｘ射线衍射（ＸＲＤ）分析研究。结合所获得的晶粒度和ＸＲＤ微结构参数,我们发现：纳米晶氧化镁的晶粒组元中存在晶格膨胀,纳米氧化镁晶粒随着温度的升高而长大,且其微呈现出明显的变化,其晶格畸变与晶粒尺寸有关。     

动态断裂介观判据的解析表达

提出了积分形式的应力的动态断裂的介观判据，由此裂纹尖端应力分布的奇异性问题得到了解决．原子半径作为微观参量引入到判据中，同时在描述材料惯性效应时提出了特征时间的概念．该判据同时反映了加载速率、缺陷和试样的几何因素，以及包括微观结构参数在内的材料常数的影响．     

介孔氧化硅薄膜合成及酸根离子对介观相影响

在不同种类酸的存在下，以非离子型烷基聚氧乙烯表面活性剂为模板分别制备出有序三维立方、二维六方和无序结构的介孔氧化硅薄膜。采用小角X射线衍射和高分辨率透射电镜研究了不同酸根离子对产物介孔结构的影响。结果表明，以盐酸为介质易得到立方介孔结构，以硝酸为介质易得到六方介孔结构，而以醋酸为介质却得到无序的介孔结构。并对酸根阴离子的作用机理进行了探讨。     

高纯铝晶粒尺寸与晶粒拓扑学参数定量关系研究

本文采用晶界渗镓剥离晶粒技术实现了三维晶粒尺寸及其拓扑学参数（晶粒界面数N2）的直接实验测量,利用回归分析,得出了晶粒尺寸与晶粒拓扑学参数定量关系;晶粒界面数N2与晶粒尺寸R^-间存在线性对应关系。     

晶粒尺寸对等静压铍材力学性能的影响

用冲击研磨方法制备了６种不同粒度低氧含量的铍粉,并进行了冷、热等静压成形固结,对材料的抗拉强度,屈服强度、延伸率和微屈服强度的测试结果表明,随晶粒细化,材料强度尤其是屈服强度和微屈服强度得到显著提高;Ｘ射线衍射和电镜观察结果表明,细而弥散分布的氧化铍是较高纯度等静压铍材强化的主要原因。     

纳米金属材料的强度与晶粒尺寸的关系

传统多晶金属材料的强度与晶粒尺寸的关系符合H—P关系，然而，对于纳米金属材料，随着晶粒尺寸的减小，强度与晶粒尺寸的关系不符合H—P关系．这与纳米材料晶界（包括三叉晶界、四方晶界或晶隅）所占的体积分数有很大关系．对此，通过几种修正模型对该问题进行了分析．     

三维晶粒尺寸计算误差的分析及其消除

本文分析了用传统球模型计算三维晶粒尺寸所导致的系统误差、分组误差和随机误差，提出了多面体模型和基小二乘法原理的分布参数拟合法（ＤＰＦ法），根据测量的一维或二维数据计算三维晶粒尺寸分布。实验结果表明，ＤＰＰ法基本上消除了系统误差以及人为因素对计算结果的干扰，并有效地降低了测量随机误差的影响，可在不降低精度的前提下减少测量数据的需求量。     

Characteristic grain size: Part I description and definition

Characteristic grain size, G _c, is defined in the present paper. It indicates an intrinsic size of grain for a given system, and has the following advantages over the average grain size which is based on a statistical mean value of the linear intercept length of grains: (1) The characteristic grain size G _c has clear and determined geometric meaning, i. e. G _c refers to two times of the area-weighted average height of the surface elements to the centroid of grain or the average length of the chord through the centroid of grain; (2) The value of G _c can be directly obtained without introducing any correcting factors such as grain shape or grain size distribution factors. Generally, G _c is larger than the average grain size G when the Heyn intercept method is adopted for the grain size measurement. Project supported by the British Council Academic Link Scheme Synopsis of the first author Cao Shunhua, lecturer, born in Jan. 1965, strong interest in the following research areas: ceramic composites, FGMs, prototype design of WC-Co alloys, and preparation of β-SiC and sialon powders.     

超微颗粒尺寸测量方法比较研究

应用x射线衍射线线宽法、透射电镜法、比表面积法和激光粒度分析法对自制的Ni(OH)2超微粉及标准颗粒度的样品进行比较分析,探讨了分析原理、颗粒形状等因素对粒径测试准确度的影响．实验结果表明：由球形颗粒组成的超微粉,透射电镜法和激光粒度分析法分析的结果均比较准确;4种方法对由不规则形状颗粒组成的超微粉分析结果相差悬殊,应采用不同的测试方法比较以得出可信的颗粒尺寸．实验证实,样品在分散介质中的分散程度对超微颗粒尺寸测量结果有较大影响,测量前对超微粉进行充分的分散是得出准确结果的前提．     

Derivation of Hillert-type 3D grain growth rate model with topological considerations and discussion on its grain size parameter

A Hillert-type three-dimensional grain growth rate model was derived through the grain topology-size correlation model, combined with a topology-dependent grain growth rate equation in three dimensions. It shows clearly that the Hillert-type 3D grain growth rate model may also be described with topology considerations of microstructure. The size parameter bearing in the model is further discussed both according to the derived model and in another approach with the aid of quantitative relationship between the grain size and the integral mean curvature over grain surface. Both approaches successfully demonstrate that, if the concerned grains can be well approximated by a space-filling convex polyhedra in shape, the grain size parameter bearing in the Hillert-type 3D grain growth model should be a parameter proportional to the mean grain tangent radius.     

深度还原工艺对铁颗粒粒度影响规律研究

采用深度还原技术处理浸染微细粒度的复杂难选铁矿石,控制铁颗粒粒度是分选出合格产品的关键.根据深度还原物料中铁颗粒的球形特征,通过测量铁颗粒二维截面参数,求取了其累计粒度特性曲线,定性地描述了不同深度还原工艺对铁颗粒粒度的影响规律.结果表明:适当的提高还原温度、延长还原时间、增大配碳系数,都有利于铁颗粒的长大,但还原温度过高、配碳系数过大将阻碍铁颗粒长大;适宜的工艺条件为:还原温度1 225℃,还原时间30min,配碳系数2.0,获得铁颗粒的d50为278.88μm.     

Reanalysis of the 3D quasi-stationary grain size distribution based on Hillert's grain growth rate equation

Based on Hillert's 3D grain growth rate equation, the grain growth continuity equation was solved. The results show that there are an infinite number of 3D quasi-stationary grain size distributions. This conclusion has gained strong supports from results of different computer simulations reported in the literature.     

Grain size distribution and topology in 3D grain growth simulation with large-scale Monte Carlo method

Three-dimensional normal grain growth was appropriately simulated using a Potts model Monte Carlo algorithm. The quasi-stationary grain size distribution obtained from simulation agreed well with the experimental result of pure iron. The Weibull function with a parameter β=2.77 and the Yu-Liu function with a parameter ν =2.71 fit the quasi-stationary grain size distribution well. The grain volume distribution is a function that decreased exponentially with increasing grain volume. The distribution of bounda...     

Effect of relative grain size on the flow stress of polycrystalline FCC sheets

A dynamic explicit finite element code and rate-dependent elastic-viscoplastic polycrystalline model were used to simulate the simple tension test of annealing FCC polycrystal and 6111-T4 aluminum alloy sheet metal. The variability of flow stress was investigated, which was induced by various grain boundary constraints when the ratio of thickness-to-grain size was changed. The simulated results show that, when the relative grain size increases, the constraint of grain boundary will increase accordingly, which results in the increase of the flow stress of polycrystal. The results agree with experiments.     

奥氏体不锈钢晶粒度对晶间腐蚀速度的影响

晶间腐蚀是诱导奥氏体不锈钢产生破坏的主要原因,而晶粒度对晶间腐蚀速度的影响不容忽视。通过在敏化温度和固溶处理温度对奥氏体不锈钢进行相应的热处理,利用草酸电解腐蚀法观察金相组织,并评定其晶粒度大小,通过极化曲线腐蚀实验,比较了奥氏体不锈钢晶粒度对晶间腐蚀速度地影响。实验结果表明奥氏体不锈钢在不同热处理条件下,其晶粒大小随保温时间延长而增大。随着奥氏体不锈钢组织的晶粒粗大,其晶粒度越小,奥氏体晶粒的晶间腐蚀的速度减慢。