【百家大讲堂】第192期：MAX相陶瓷中的自主氧化诱导裂纹愈合

　　讲座题目：MAX相陶瓷中的自主氧化诱导裂纹愈合

　　报  告 人：Willem G. Sloof

　　时　   间：2019年5月22日（周三）10:30

　　地　   点：中关村校区5号教学楼502-1

　　主办单位：研究生院、材料学院

　　报名方式：登录北京理工大学微信企业号---第二课堂---课程报名中选择“【百家大讲堂】第192期：MAX相陶瓷中的自主氧化诱导裂纹愈合”

 

【主讲人简介】

  

 Wiiiem G.Sloof，代尔夫特理工大学材料科学与工程系副教授，自1988年起担任表面与界面课题组组长。此外，Wim博士获聘哈尔滨工业大学客座教授，合作关系密切。Wim博士的研究领域主要为金属和陶瓷涂层的性质、化学成分和结构间的耦合关系。目前，Wim博士的研究项目涉及高温热障涂层系统、金属氧化（包括辐射辅助）、高强度钢上的保护涂层和自修复材料，并致力于开发用于材料的详细化学和微观结构表征的方法和技术。他参与并领导的国家和国际资助自愈材料项目，包括SAMBA欧洲自愈热障涂层项目（FP7），以及SHeMat欧洲国际培训网络中的自愈陶瓷项目等。

主讲人简介（英文）

Dr. Ir. Wim G. Sloof, Associate Professor at Delft University of Technology, Department of Materials Science and Engineering and is head of the Surface and Interface Research group since 1988. He received his MSc degree (cum laude) in 1984 and PhD in 1996 in Materials Science at the Delft University of Technology, The Netherlands. He is also visiting professor at Harbin Institute of Technology, Institute for Advanced Ceramics, School of Materials Science and Engineering in China. His research projects involve the relations between properties, chemistry and structure of various metal and ceramic coatings. Out of the many possible subjects, residual stresses, adhesion and layer growth are specialisation areas. Currently, the research program involves high temperature thermal barrier coating systems, oxidation of metals (including radiation assisted), protective coatings on high strength steels and self-healing materials. Research on self-healing materials was initiated in 2003 focused on high temperature metallic coatings, followed by thermal barrier coating systems and MAX-phase ceramics. A substantial part of the research program is devoted to the development of methods and techniques for detailed chemical and microstructure characterization of materials. He participated and led national and international funded projects on self-healing materials, among them a European project (FP7) on self-healing thermal barrier coatings, called SAMBA, and on self-healing ceramics in a European International Training Network, called SHeMat. Recently, a research program on self-healing ceramics was initiated with the Yokohama National University, Japan. Since 2010 a close cooperation on self-healing ceramics exists with Harbin Institute of Technology, Institute for Advanced Ceramics, School of Materials Science and Engineering in China.

【讲座信息】

 英文题目：Autonomous oxidation induced crack healing in MAX phase ceramics

内容简介（中文）

    与许多其他常见的工程陶瓷材料相比，MAX相金属陶瓷更为坚韧的，具有耐损伤性较好，并且在高温下具有稳定性和耐腐蚀性。高导热性使这类材料具有抗热冲击性。此外，它们在高温下可保持静态强度，高于一定温度时温度，蠕变将成为限制因素。 MAX相材料也更易于加工。这些特性使MAX相材料在高温应用中，例如热循环、机械负载和热循环等环境下具有独特的吸引力。动力或推进发电、原料生产等领域普遍存在以上环境。

    MAX相材料的机械、热学和电学特性的独特组合是由于它们的原子层状和六方晶体结构。通式为Mn + 1AXn，其中n等于1,2或3，M为早期过渡金属，A为A族元素（主要为IIIA和IVA，如Al和Si），X为C和/或N。

    近期，已有学者证明Ti3AlC2，Ti2AlC和Cr2AlC MAX相中的裂纹损伤可以通过A元素的选择性氧化来修复。因此，MAX阶段是愈合反应的一部分，并且通过从气体气氛中消耗氧气来形成愈合产物。这些MAX相材料满足裂缝损伤成功愈合的所有要求，即：A元素的优先氧化和快速扩散，氧化时的体积膨胀和氧化产物与基质的粘附。本次讲座将讲解通过上述MAX相的高温氧化来修复裂纹损伤的一些亮点。

内容简介（英文）

In contrast with many other common engineering ceramics, so-called MAX phase metallo-ceramics are tough and therefore damage tolerant. The MAX phase ceramics are stable up to high temperatures and corrosion resistant. The high thermal conductivity makes these ceramics thermal shock resistant. Their static strength is maintained up to high temperatures, above which creep will become the limiting factor. Also MAX phase materials are easy machinable. These properties make MAX phase materials attractive for high temperature applications, where the material is exposed to thermal cycles, mechanical loading and oxidation. These conditions are encountered in e.g. power or propulsion generation, raw material production, recycling facilities etc. 

The unique combination of mechanical, thermal and electric properties of MAX phase material is due to their atomic layered and hexagonal crystal structure . The general formula is Mn+1AXn, where n equals 1, 2 or 3, M is an early transition metal, A is an A group element (mostly IIIA and IVA, like Al and Si), and X is C and/or N. 

Recently, it has been demonstrated that crack damage in Ti3AlC2, Ti2AlC and Cr2AlC MAX phases can be healed by selective oxidation of the A element. Hence, the MAX phase is part the healing reaction and the healing product is formed by consuming oxygen from the gas atmosphere. These MAX phase materials meet all requirements outlined for successful healing of crack damage, viz.: preferential oxidation and fast diffusion of the A-element, volume expansion upon oxidation and adhesion of the oxidation product to the matrix. Some highlights of healing of crack damage by high temperature oxidation of the aforementioned MAX phases are presented.