Al2O3基陶瓷材料增韧的研究进展

Al_2O_3基陶瓷材料具有高的化学稳定性,有较好的应用前景,但其脆性限制了它的推广应用,对氧化铝陶瓷进行增韧是解决其脆性问题的一条重要途径。简要介绍了目前氧化铝陶瓷的增韧方法和增韧机理,综述了氧化铝陶瓷增韧的研究现状,分析了氧化铝陶瓷增韧研究中存在的主要问题,展望了氧化铝陶瓷增韧的发展方向,提出了原位生长及复合增韧是高性能Al_2O_3基陶瓷材料的研究重点。     

晶须增韧陶瓷复合材料

综述了晶须增韧陶瓷复合材料的制备方法和分类;讨论了影响增韧效果的各种因素及对陶瓷材料力学性能、抗热震性和耐磨性等方面的影响;并将近年来有关晶须增韧陶瓷基复合材料机理方面的研究进展,晶须在陶瓷材料中的应用及今后的发展趋势等作以介绍.     

SiC陶瓷增韧的研究进展

碳化硅陶瓷以其优异的性能被广泛利用于各种领域，但其脆性限制了其性能的发挥，因此其增韧技术得到广泛研究并取得良好效果。综合评述了碳化硅陶瓷增韧机理和增韧方法的研究进展，包括晶须或纤维增韧、颗粒弥散增韧、表面改性技术增韧、自增韧、层状结构复合增韧的增韧机理和方法进。     

连续纤维补强增韧碳化硅基陶瓷复合材料研究进展

连续纤维补强增韧碳化硅基陶瓷复合材料具有密度低、强度和韧性高、抗氧化、耐高温等综合性能,已在国外宇航领域得到了广泛的应用.综述了国内外连续纤维补强增韧C/SiC陶瓷复合材料的研究进展,主要包括国内外在增韧机理、基体复合技术、界面技术以及应用等方面的研究进展情况.     

纳米氧化锆复合陶瓷在牙科上的应用发展

纳米氧化锆复合陶瓷由于具有良好的相变增韧性能而被作为新型义齿材料。本文介绍了被广泛应用于牙科界的两种纳米氧化锆复合陶瓷及其制备方法：纳米增韧复合陶瓷（ZTA）、四方相氧化锆多晶体（TZP）,以及纳米氧化锆复合陶瓷的增韧机理与机制;概述了氧化锆复合陶瓷在牙科的研究现状以及氧化锆复合陶瓷材料的发展前景及应用限制。     

颗粒增韧陶瓷的研究进展

综述了几种主要的颗粒增韧陶瓷的增韧机理，并从晶界应力设计、纳米颗粒增韧、金属及金属间化合作增韧陶瓷等几方面对颗粒增韧陶瓷的最新进展进行了评述。     

纤维增强陶瓷复合材料的制造技术

工程陶瓷的开发是目前国内外甚为重视的新型材料研究领域。纯陶瓷材料因其脆性,不能满足苛刻条件下的使用要求。因此,目前广泛采取增韧技术来提高陶瓷的使用性能。纤维和晶须增韧陶瓷是一类有效的方法。用纤维来增韧陶瓷的技术是七十年代以后开始的,最初是用碳纤维增强陶瓷,八十年代以来又开发了用陶瓷纤维和晶须增韧陶瓷,增韧效果不断取得进展,增韧技术也不断有所创新。纤维增强陶瓷复合材料的加工技术主要有四种类型,下面分别加以介     

齿科用氧化锆陶瓷韧性研究进展

氧化锆陶瓷具有高强度、高韧性、高硬度、耐磨损、生物相容性好等优点, 广泛应用于齿科修复。但氧化锆陶瓷相变增韧会缩短其服役寿命, 尤其在极潮湿的口腔唾液等复杂的生物化学条件下, 因承受咀嚼力、温度的频繁变化, 而导致其失效断裂。本文概述了氧化锆陶瓷在齿科修复领域的应用研究进展, 总结了氧化锆陶瓷的增韧机理以及常用齿科氧化锆陶瓷的研究现状, 并对临床服役中氧化锆陶瓷的韧性老化现象进行分析, 总结了韧性老化机理及其预防措施和方法。随着齿科氧化锆陶瓷综合力学性能的提高以及健康功能化的未来需求, 其在生物医用领域的应用将会越来越广泛。     

碳化硼陶瓷增韧补强和致密化研究现状及其展望

碳化硼陶瓷具有极高的硬度,然而其低韧性、低抗弯强度、难以致密化限制了它的广泛应用.已有一些研究集中于碳化硼陶瓷增韧补强和致密化,对这一方面国内外研究进展进行了归纳与评述,阐明各种增韧补强和致密化方法的优缺点,提出碳化硼陶瓷增韧补强和致密化研究值得发展的一些方向.     

层状复合陶瓷材料的研究现状与发展趋势

层状复合陶瓷材料是目前陶瓷增韧的最有效途径之一,有着广泛的应用前景,是陶瓷增韧研究的热点,近年来发展很快。综述了层状复合陶瓷材料的起源、设计及国内外的研究现状,展望了层状复合陶瓷材料未来的发展方向。     

马氏体时效钢的强韧化设计

马氏体时效钢是用途最为广泛的超高强度钢,其强韧化设计是研究的主要内容。在回顾超高强度钢至马氏体时效钢的强韧化发展历程和总结马氏体时效钢的强韧化元素的作用与强韧化机制的基础上,提出了一些马氏体时效钢的强韧化设计原理,并对马氏体时效钢未来的强韧化设计进行了展望。     

环氧树脂的增韧改性研究进展

综述了环氧树脂增韧的研究进展。主要介绍了环氧树脂的增韧方法(热塑性树脂增韧、热致性液晶聚合物增韧、核壳聚合物粒子增韧、原位聚合增韧等)及相关增韧机理,展望了今后环氧树脂增韧改性的发展趋势。     

From Biomimetic Concept to Engineering Reality – A Case Study on the Design of Ceramic Reinforcement

The applications of ceramics are limited by their brittleness. Though the toughness of ceramics can be improved by adding hard and strong toughening agents, their damage tolerance is still poor. Novel concept derives from fish scale is explored and used to design alternative toughening agent. The microstructure of fish scale exhibits hierarchical complexity and many weak layers are present. As fish scales are used directly as the toughening agent, the toughness of ceramics can be enhanced. Furthermore, a new toughening mechanism involving crack deflection within fish scale is observed. Based on such observation, the toughening agents with internal weak interfaces are recommended as the toughening agent. Many ceramic/metal interfaces are present within the multilayer ceramic capacitors (MLCCs). The addition of MLCCs into brittle glass improves its crack resistance considerably.     

晶须增韧陶瓷基复合材料裂纹扩展行为模型

在考虑晶须桥联和裂纹转两种增韧机理的基础上，建立了晶须增韧陶瓷复合材料裂纹扩展行为的理论模型，利用该型计算了单边切口梁三点弯曲的Ｒ－阻力曲线和载荷－位移曲线。     

晶须增韧补强陶瓷基复合材料的若干关键技术研究(Ⅲ):纤维独石结构和层状结构的设计

为了进一步提高晶须增韧陶瓷基复合材料的断裂韧性，提出了纤维独石结构和层状结构的复合材料的设计思路，这两类特殊结构的复合材料都具有非常高的断裂韧性和断裂功。在这两类材料的设计中，都基于一种多级增韧机制的思想，即在材料中引进相对较弱的界面将一个个结构单元（纤维或薄层）结合起来，结构单元之间的弱界面层作为一级增韧机制，是这两类复合材料具有很高断裂韧性的主要增韧机制；在结构单元内部，晶须增韧体作为二级增韧机制；长柱状的基体晶粒作为三级增韧机制。这三级增韧机制的协同作用，使得这类复合材料具有非常高的断裂韧性和断裂功。     

晶须和相变复合增韧陶瓷的复合增韧模型

建立了晶须和相变复合增韧陶瓷的复合增韧模型,其中晶须增韧考虑了裂纹桥联和裂纹偏转两种机理;相变增韧在考虑体膨胀作用的基础上,用切应变影响因子来考虑切应变增韧效应．计算结果表明,相变增韧、桥联增韧和裂纹偏转增韧存在相干性,相变增韧降低晶须增韧效果,而晶须增韧促进相变增韧效果,SiC_w／ZrO₂（2mol％Y₂O₃）／Al₂O₃断裂韧性的计算结果与实验结果吻合．     

Toughening mechanisms and properties of mullite matrix composites reinforced by the addition of SiC particles and Y-TZP

Mullite matrix composites reinforced by SiC particles and Y-TZP, were fabricated by hot-pressing. The effects of adding SiC particles and Y-TZP to mullite or mullite-based materials on properties and toughening mechanisms in the composites were investigated. Crack deflection is proposed as the principal toughening mechanism, produced by the addition of SiC particles. Transformation and microcrack toughening are the two main toughening mechanisms caused by Y-TZP addition. However, the magnitude of their contribution varied with increasing Y-TZP addition. With low Y-TZP addition, the transformation toughening dominated, while at a higher Y-TZP content, the microcrack toughening was dominant. The simultaneous addition of SiC particles and Y-TZP to mullite resulted in higher increases in both flexural strength and fracture toughness, than the simple sum of those obtained by the separate processes. It appears that the two toughening processes were coupled, thereby leading to synergistic toughening and strengthening effects in the mullite composites.     

耐超高温铱合金强韧化技术研究进展

概括地论述了铱的特点,说明了探索研究铱的强韧化技术的重要性.系统地综述了国内外在铱强韧化技术方面的研究思路、取得的研究结果以及最近的研究焦点,对耐超高温铱合金强韧化技术提出了新的研究思路,阐明理论计算的方法将是铱的强韧化技术研究的热点和有效方法.最后展望了耐超高温铱合金的发展和应用前景.     

Effects of deleterious impurities and cerium modificationon intrinsic and extrinsic toughening levels of AI-Li based alloys

Abstract

The toughness of AI-Li-Cu-Zr and AI-Li-Cu-Mg-Zr sheets containing various impurities and cerium concentrations, and AI-Li-Mg-Zr sheets containing various cerium concentrations under two aged conditions has been investigated by establishing the variabilities of intrinsic and extrinsic toughening levels and by determining the fracture toughness and the tensile ductility. The relationships of intrinsic and extrinsic toughening levels with fracture morphologies and microstructural parameters have been discussed. Iron and silicon impurities detract from the intrinsic toughening level although they do not have any important influence on the extrinsic toughening level. Sodium and potassium impurities significantly degrade the intrinsic toughening level although they may benefit the extrinsic toughening level to a certain degree. Cerium modification increases the intrinsic and extrinsic toughening levels of AI-Li-Cu-Zr alloy containing higher concentrations of iron and silicon impurities, resulting in an improvement of the fracture toughness. A small amount of cerium addition in Al-Li-Cu-Mg-Zr alloy rich in either Fe + Si or Na + K increases the intrinsic toughening level but decreases the extrinsic toughening level so that, overall, the fracture toughness is hardly affected. A certain amount of cerium addition in AI-Li-Cu-Mg-Zr alloy rich in iron and silicon improves the fracture toughness because both the intrinsic toughening level and the extrinsic toughening level are enhanced. However, for the AI-Li-Mg-Zr alloy, cerium modification does not bring about any improvement in the fracture toughness as the extrinsic toughening level is generally damaged. When impurities result in increased crack branching or when cerium addition promotes more marked lamellar type splitting, the extrinsic toughening level can usually be increased.