关键词： Foams (Chemistry)   Lakes   Elasticity   Composite materials   Poisson ratio  

摘要： Materials with negative Poisson's ratio are peculiar in that they expand laterally when stretched. Examples of such type of behavior have been discovered with foams by Lakes (1987);however, it is only recently that isotropic materials with negative Poisson's ratio have been shown by Milton (1992) to exist within the framework of classical theory of elasticity. In this Note, we demonstrate qualitatively that a composite material with a reentrant microstructure can also have a negative Poisson's ratio, even though the composite may be isotropic owing to a completely random distribution of the microstructure.

关键词： 无机材料-显微结构-图册  

ISBN: (纸本)7562909466

关键词： 氧化锆   氧化铝   结构   陶瓷复合材料  

摘要： 用透射电镜研究了（ＺｒＯ２＋ｘｍｏｌ％Ｙ２Ｏ３）－２０ｗｔ％Ａｌ２Ｏ３陶瓷复合材料的显微结构，发现在Ｙ２Ｏ３含量为２．０ｍｏｌ％～２．５ｍｏｌ％成分下，较大的（可达１μｍ）未转变颗粒仅限于嵌在Ａｌ２Ｏ３晶内的ＺｒＯ２（ｔ），当Ｙ２Ｏ３含量为３．０ｍｏｌ％时不嵌在Ａｌ２Ｏ３晶内的ＺｒＯ２（ｔ）颗粒（可达１．３μｍ）也可保持四方相结构。因此３．０ｍｏｌ％Ｙ２Ｏ３成分下四方相的急增及其最佳相交增韧效果归因于基体弹性模量的增加和适量稳定剂（Ｙ２Ｏ３）加入的共同作用结果。

关键词： SiN结合碳化硅   硅加入量   AlO添加物   抗氧化抗碱侵蚀法   抗渣侵蚀性   Sialon相  

关键词： 镁碳铝系   耐火材料   铝   结构  

摘要： 1.前言 为了改进含碳耐火材料在高温下容易氧化和高温强度低等缺点,对其添加了金属、合金及碳化物这样的非氧化物。在镁碳系耐火材料中,Al是最常用的金属,至今对其使用效果等仍在研究。其中,京田等人报道说,把Al-C系混合压制成型的试样。

关键词： 棉花   花粉   发育时期   超微结构   三系配套  

摘要： ＭＡ不育系是洞Ａ不育系×ＭＢ（保持系）获得的全不育系。本试验以ＭＡ不育系和洞Ａ不育系为材料，采用石蜡切片扫描电镜观察技术，研究了两个材料的花粉在不同发育时期的败育表现。观察到花粉母细胞外的胼胝质沉积过多，溶解较慢。单核期败育的花粉细胞质完全解体，但核留下不同程度解体的残体，核膜仍清晰可见。败育花粉壁发育不完全，壁上刺状突起小而稀，无萌发孔。因花粉败育花药壁绒毡层出现各种异常变化。

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。