我国纳米复相陶瓷制备研究达到国际水平

由中科院上海硅酸盐研究所高濂研究员主持完成的———晶内型氧化物基纳米复相陶瓷的制备科学与性能研究 ,由于在纳米复相陶瓷的制备研究方面达到国际领先水平 ,最近荣获 2 0 0 3年上海市科学技术进步一等奖。课题组开创性地提出了陶瓷材料晶内型纳米增强增韧的新概念 ,首次采用原位包裹法合成高均匀性、高烧结活性的复合纳米陶瓷粉体 ,首创用放电等离子体烧结技术 (SPS)实现了陶瓷材料的超快速烧结 ,制备出了多种高性能晶内型氧化物基纳米复相陶瓷。其中 ,采用上述技术制备的SiC Al2 O3纳米复相陶瓷 ,其抗弯强度由基体材料的 35 0MPa提…     

SiC纳米及晶须增强Si_3N_4基复相陶瓷断裂行为的研究

用扫描电镜、透射电镜及努氏压痕法研究了添加SiC晶须、纳米颗粒及晶须和纳米颗粒的三种Si3N4基复相陶瓷在外力作用下的断裂行为。这三种材料断裂的主要方式是沿晶断裂 ,偶尔可见穿晶断裂。在裂纹发展的路径上当裂纹尖端遇到了晶须、集聚的纳米颗粒及类晶须时 ,会产生扭转、偏转、断裂、拔出和终止 ,从而使裂纹能量消耗 ,抑制和阻碍了裂纹的扩展和传播 ,起到了增韧补强的作用。     

陶瓷基复合材料增韧技术的研究进展

本文综述了陶瓷基复合材料的纤维增韧、晶须增韧、相变增韧、颗粒增韧、纳米复合陶瓷增韧、自增韧陶瓷增韧补强的方法、增韧效果及相关的增韧机理.最后,指出了陶瓷基复合材料增韧技术的研究现状和今后的发展方向.     

颗粒补强锆英石复相陶瓷的增韧行为与其残余应力的关系

采用X射线衍射方法测定了颗粒补强锆英石基复相陶瓷基体中残余应力的大小,并结合力学性能测试和显微结构观察讨论了残余应力与增韧行为之间的关系。结果表明:在基体热膨胀系数小于补强颗粒的情况下,适当增大补强颗粒与基体间热膨胀失配能够提高复相陶瓷的增韧效果。其增韧机制主要为补强颗粒所引起的裂纹偏转和分支。利用残余应力场增韧模型计算得到的复相陶瓷断裂韧性增量与实际值能够较好地吻合。     

SiC纳米及晶须增强Si3N4基复相陶瓷断裂行为的研究

用扫描电镜、透射电镜及努氏压痕法研究了添加ＳｉＣ晶须、纳米颗粒及晶须和纳米颗粒的三种Ｓｉ３Ｎ４基复相陶瓷在外力作用下的断裂行为。这三种材料断裂的主要方式是沿晶断裂,偶尔可见穿晶断裂。在裂纹发展的路径上当裂纹尖端遇到了晶须、集聚的纳米颗粒及类晶须时,会产生扭转、偏转、断裂、拔出和终止,从而使裂纹能量消耗,抑制和阻碍了裂纹的扩展和传播,起到了增韧补强的作用。     

纳米/微米Al2O3-ZrO2内衬复相陶瓷的自蔓延高温合成

采用SHS重力分离技术制备出内衬Al2O3-ZrO2复相陶瓷.复相陶瓷基体主要由纤维状(Al2O3+ZrO2)共晶体组成,其中共晶体的ZrO2纤维直径达到纳米/微米尺度.经Vickers压痕法测试其断裂韧度为15.96MPa·m1/2,SEM观察和陶瓷材料断裂韧度测试得出裂纹的扩展主要受共晶体中Al2O3-ZrO2纳米/微米相增韧机制控制,迫使裂纹沿共晶体边界或层片共晶体Al2O3-ZrO2相界偏转,从而维持了该复相陶瓷较高的断裂韧度.     

精细陶瓷的特性,应用及发展

综述了精细陶瓷的研究范畴、特性、应用、市场及目前的研究状况。重点介绍了复相陶瓷、纳米陶瓷、高强度高韧性陶瓷及生物陶瓷。     

延性相增韧的陶瓷材料中相界面对韧性的作用

论述了相界面结合与延性相的几何形态之间的匹配关系对延性相增韧的陶瓷基复合材料韧性的影响。对于连续延性相,例如网状、纤维或片状的延性相,界面结合较弱对增韧非常有益,因为裂纹扩展过程中相界面可发生部分分离,使桥接裂纹的延性相发生很大的塑性变形,消耗大量能量。而对于颗粒状的延性相,由于其球形形状及小的连续程度,经常导致断裂时断口上的延性相被完全拔出,几乎没有发生塑性变形,增韧效果较差,因此强的相界面结合强度是非常重要的。     

热等静压原位合成SiC–TiC复相陶瓷的微观组织与性能研究

采用纳米级β-SiC粉末、Si粉末、C粉末以及微米级TiH_2粉末为原料,利用热等静压原位合成工艺制备了SiC–TiC复相陶瓷,研究了不同原位合成反应和烧结工艺对复相陶瓷微观组织及力学性能的影响。结果表明:以SiC、TiH_2、C粉末为原料的原位合成反应,无明显副反应发生,更有益于制备成分符合预期、致密度良好且性能优秀的SiC–TiC复相陶瓷。在1600℃,120 MPa,4 h等静压烧结工艺下原位合成得到的体积分数为SiC–32%TiC复相陶瓷具有最好的致密度、硬度、三点弯曲强度以及良好的断裂韧性,分别达到98.7%、21.2 GPa、428 MPa和5.5 MPa·m1/2。提高热等静压压力有助于提高材料的烧结扩散活性,从而提高材料的致密度,有益于力学性能的提升。     

SiC晶须增韧Ti(C,N)基金属陶瓷复合材料的研究

主要研究了不同的SiC晶须(简称SiCw)加入量和真空烧结温度对Ti(C,N)基金属陶瓷复合材料性能的影响,并对SiCw的增韧机理进行了探讨.结果表明:在SiCw的质量分数为15%、真空烧结温度为1470℃时,SiCw增韧Ti(C,N)基金属陶瓷复合材料的综合力学性能最佳;材料中存在裂纹偏转、裂纹桥接和晶须拔出等增韧机理.     

碳化硅材料及其应用研究进展

通过对碳化硅材料工业制备与应用、新技术发展及应用的综述,认为碳化硅材料是目前最具产业化前景的工程结构陶瓷,在国民经济和高技术领域具有重要的应用前景。应积极做好碳化硅材料的研制、开发与推广工作,加速形成我国自己的碳化硅材料产业。     

Ceramic-Metal Composite Coating by Laser Cladding

Ｃｅｒａｍｉｃ－ＭｅｔａｌＣｏｍｐｏｓｉｔｅＣｏａｔｉｎｇｂｙＬａｓｅｒＣｌａｄｄｉｎｇＷａｎｇＰｅｎｇｚｈｕ；ＱｕＪｉｎｘｉｎｇ；ＳｈａｏＨｅｓｈｅｎｇＡｂｓｔｒａｃｔ：Ｆｏｕｒｋｉｎｄｓｏｆｃｅｒａｍｉｃｓ（ｓｉｌｉｃｏｎｃａｒｂｉｄｅ，ｂｏｒｏ...     

Peculiarities of the Synthesis of High-Temperature TaSi2–SiC Ceramics Reinforced in situ by Discrete Silicon Carbide Nanofibers

Russian Journal of Non-Ferrous Metals - The possibility of increasing the mechanical properties of the ceramic material of the TaSi2–SiC system by reinforcing it with silicon carbide...     

Investigation on the preparation of Si/mullite/Yb_2Si_2O_7 environmental barrier coatings onto silicon carbide

With the development of aero-engine,gas import temperatures of hot section structural materials are increasingly higher.Metal alloy materials due to the rapidly decreased mechanical properties at relative high temperature are gradually replaced with silicon-based non-oxide silicon carbide ceramics.However,silicon carbide ceramic materials tend to spall and deform in engine combustion environment,need environmental barrier coatings for the protection of the matrix.The preparation of Si/mullite/Yb2Si2O7 envir...     

纳米复合陶瓷材料的增韧补强机理研究进展

纳米复合陶瓷材料可以极大地提高抗弯强度和断裂韧性。综述了目前相关的增韧补强机理的研究情况，主要包括基体晶粒的细化及由沿晶断裂向穿晶断裂模式的转变，热处理对微裂纹的愈合作用；指出了研究中尚需解决的问题。     

Investigation into the compaction of nanopowders and micropowders of silicon carbide in high-pressure apparatus

The results of the investigation into the compaction (sintering) of silicon carbide nanopowders and micropowders in a DO-138 high-pressure apparatus are presented. Compaction modes for both types of materials are identical (a pressure of 3.5–4.0 GPa, a temperature of 1600—1700°C, and a holding time of 10 s). The influence of cladding of SiC nanopowders and micropowders with titanium and titanium nitride on the properties of compacts (cakes) formed under the same sintering modes is investigated. It is established that, when compacting the silicon carbide nanopowder, cakes differ in regards to higher density, hardness, and lower porosity compared with the samples made of finely dispersed technical silicon carbide. A higher activity of titanium relative to SiC makes it possible to chemically associate the grains of the latter due to the formation of intermediate layers of titanium carbide between them. The resulting ceramics possesses a higher density, hardness, and wear resistance. The wear resistance of synthesized composites based on nano-SiC is higher than for a polycrystalline material based on silicon carbide micropowder by a factor of 4.5.     

Mechanical alloying of Cu–SiC materials prepared with utilisation of copper waste chips

Abstract

The aim of this work was to study the structure and particle size of copper based composite materials reinforced with a high content (15–35 wt-%) of silicon carbide and prepared by mechanical alloying in the high energy planetary mill. Raw materials consisted of grinded copper chips with a size of <5000 μm and reinforcing particles with an initial size of 10 μm. Duration of milling was 20–80 min. It was shown that the formation of Cu–(15–25 wt-%)SiC composites occurred successfully. With an increase in the silicon carbide content of above 25 wt-% (48 vol.-%), the efficiency of mechanical alloying was decreased. The average size of composite particles was ～20 μm.     

Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550 ℃ and 28 MPa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.     

制备工艺对碳化硼陶瓷性能的影响

以活性炭和碳化硅为烧结助剂,采用真空热压工艺,制备了碳化硼陶瓷材料.研究了真空热压工艺、烧结助剂对碳化硼陶瓷性能及断口的影响,结果表明,以活性炭和碳化硅为烧结助剂的碳化硼陶瓷随热压压力增加,开口孔隙度减小,相对密度和抗弯强度增加.添加活性炭的碳化硼陶瓷在热压压力为35MPa下,开口孔隙度有最小值(1.7%),相对密度(91.7%)和抗弯强度(277.6MPa)达最大值;以碳化硅为烧结助剂的碳化硼陶瓷在热压压力为30MPa下,开口孔隙度有最小值(0.66%),相对密度(91.9%)和抗弯强度(173.6MPa)达最大值.添加活性炭的碳化硼陶瓷随保温时间由30min增加到90min,开口孔隙度逐渐减小而相对密度逐渐增加(90min时分别达到0.19%、99.6%),抗弯强度先增加后减小,在保温时间为60min时抗弯强度达到最大值(351.7MPa).在相同的真空热压工艺下,添加活性炭的碳化硼陶瓷与添加碳化硅的碳化硼陶瓷相比,其开口孔隙度低,抗弯强度高.初步探讨了真空热压工艺以及添加剂促进碳化硼陶瓷烧结的机理.     

Fiber-Matrix interactions in brittle matrix composites

Brittle matrix composites, including carbon-carbon (C-C) and ceramic matrix, offer a new dimension in the area of high-temperature structural materials. Fiber-matrix interactions determine the mechanism of the load transfer between the fiber and matrix and resulting mechanical properties. Composites studied in this work include a C-C composite densified with a chemical vapor infiltration (CVI) pyrolytic carbon, silicon carbide fiber-silicon carbide matrix composite, and carbon fiber-silicon carbide matrix composites densified by the CVI technique. The type of the interfacial carbon in C-C composites was found to control their mechanical properties. The presence of the compressive stress exerted by the matrix on the carbon fibers was attributed to an increase in flexural strength. The transverse matrix cracking in C/SiC composites was believed to cause a lowering in the flexural strength value. Brittle fracture behavior of SiC/SiC composites was correlated with the presence of an amorphous silica layer at the fiber-matrix interface. This invited paper is based on a presentation made in the symposium “Structure and Properties of Fine and Ultrafine Particles, Surfaces and Interfaces” presented as part of the 1989 Fall Meeting of TMS, October 1–5, 1989, in Indianapolis, IN, under the auspices of the Structures Committee of ASM/MSD.