关键词： 锆刚玉莫来石   氮化硼   力学性能  

摘要： 研究了锆刚玉莫来石对氮化硼材料显微结构及力学性能的影响。试验结果表明，氮化硼呈编织状结构构成基体的骨架，氧化物颗粒分布于编织状结构的空隙处，起弥散强化和韧化的作用。随锆刚玉莫来石引入量的加大，材料的韧性、室温及高温抗折强度提高。材料内生成的９Ａｌ＿２Ｏ＿３·２Ｂ＿２Ｏ＿３（Ａ＿９Ｂ＿２），呈细条状存在，在材料断裂时会产生拔出效应。同时，对材料在空气和氮气中的高温强度变化规律进行了研究。

关键词： Microscopic examination  

摘要： We live and work in a world of materials. Modern technology depends critically on the availability of advanced materials, e.g., in transportation, communications, data processing, production systems, etc., and more and more emphasis is being placed on research and development of materials. In order to tailor materials to meet specific performance requirements (mechanical/physical properties), it is essential to understand the relationships Synthesis and Processing - Structure - Performance. Processing develops microstructure, mesostructure and chemical distribution of the components. These in turn determine properties. In order to characterize these features, high resolution techniques such as electron microscopy, microdiffraction and microanalysis are required. This paper, dedicated to Professor H. Hashimoto who has made so many outstanding contributions to the field, gives two examples of the applications of electron microscopy to understanding and developing advanced ceramics, viz. silicon nitride and aluminum nitride.

关键词： 氮化硼   锆刚玉莫来石   显微结构  

摘要： 研究了锆刚玉莫来石－氮化硼夏合材料的显微结构及力学性能，结果表明：在锆刚玉莫来石基质中引入氮化硼，降低材料的抗折强度，但可提高断裂韧性。这是氮化硼的微裂纹增韧作用所致。氮化硼的编织状结构可阻碍晶界的滑移，降低材料高温强度的衰减率。材料内生成的针状９Ａｌ＿２Ｏ＿３·２Ｂ＿２Ｏ＿３，在断裂过程中产生拔出效应，有利于力学性能的提高。

摘要： The egg capsules of dogfish are largely constructed from laminae of parallel orientated collagenous fibrils arranged longitudinally, near-diagonally, and near-transversely. The fibrils show an axial (D) period of about 40 nm. These characteristics facilitated the observation of fibril rotation and strain and the construction of an exploratory model of the mechanical behaviour based on composite theory. Low angle X-ray diffraction demonstrated reversible changes in material strained up to 24%;the D period extended by 5% with a loss in transverse order. Electron microscopy confirmed this fibril strain and demonstrated that failure of the interfibrillar matrix at moderate global strains was conspicuous in the near-transverse laminae and less marked in the near-diagonal ones. Light microscopy demonstrated that rotation of the near-diagonal fibrils occurred during global strain. The results of mechanical testing are described. The model helps to explain the double S-shaped stress/strain and unrecoverable deformation plots. The tensile behaviour up to strains of 10% appeared dominated by failure of the interfibrillar matrix in the near-transverse laminae. The behaviour of the material at strains in excess of this was thought to result from a combination of rotation and straining of matrix and fibrils in the near-longitudinal and near-diagonal laminae. The egg capsule is thought to function as an efficient shock absorber reducing the likelihood of injury from both wave action and attempted predation by fish. (C) 1994 Academic Press, Inc.

关键词： 纳米材料   氧化铁   正电子湮灭   缺陷  

摘要： 用Ｘ射线衍射确定了纳米材料Ｆｅ＿２Ｏ＿３的平均粒径。测量了正电子的寿命。给出了平均粒径随退火温度的变化和短寿命成分τ＿１、中等寿命成分τ＿２以及它们的强度比Ｉ＿２／Ｉ＿１随平均粒径的变化。讨论了纳米材料Ｆｅ＿２Ｏ＿３的界面结构、平均正电子寿命τ与多普勒展宽谱Ｓ参效间的对应关系。

关键词： 掺杂   氧化   结构   电性能   压敏陶瓷  

摘要： 探讨了多种金属氧化物对ＺｎＯ－Ｂｉ＿２Ｏ＿３－ＴｉＯ＿２系材料的改性作用和对其显微结构的影响，为得到预定性能的材料提供了掺杂方面的实验依据。

关键词： 陶瓷复合材料   晶须增韧陶瓷   界面   显微结构  

摘要： 本文报道了碳化硅晶须增韧氟化硅陶瓷复合材料的界面设计模型和界面的显微结构状态，分析了晶须的加入对陶瓷韧性提高的作用。

关键词： 超导体   超导电性   铋系   显微结构  

摘要： Bi系氧化物超导体从发现至今,人们对其显微结构与超导电性间的内在联系已有所了解.研究表明:这类超导体中,多组分混合欠均匀化、弱连接及弱钉扎是影响临界电流密度(Jc)提高的主要因素.因此传统工艺方法制备的块材在强电领域中应用遇到困难.近几年在努力探求工艺上的突破,以改善其均匀化、弱连接、弱钉扎和可加工性,使之尽快进入实用化.工艺上改进可归纳为如下几方面: