NSF-Europe Materials Collaboration: Atomic Structure of Nanosize Crystalline Grains in Diamond-SiC Composites

非技术描述：这项由材料研究部和国际科学与工程办公室共同资助的研究计划将重点研究金刚石-碳化硅(碳化硅)复合材料的合成、结构和性能之间的关系。在高温高压条件下制备的金刚石基复合材料具有硬度高、耐磨性好的特点。在生产方案中加入纳米级钻石将如何影响复合材料的结构和性能。超硬金刚石复合材料可以应用于许多行业；其中一个可能的应用是石油和天然气勘探，其中金刚石复合材料可以用作钻头的刀具。钻头寿命的增加将降低天然气/石油钻井的成本。由于更换钻头的频率降低，潜在井喷期间环境污染风险降低，很难确定其货币价值，但这将是巨大的。该项目是与匈牙利布达佩斯的Eotvos大学和波兰华沙的波兰科学院高压研究中心合作进行的。学生们将在匈牙利和波兰的顶尖科学家的监督下，长时间访问这些机构。同样，匈牙利和波兰的科学家将访问TCU并在国家实验室进行高压实验。技术细节：复合材料的微观结构可以通过表征金刚石和碳化硅相的微晶尺寸和粒度分布以及由晶体缺陷引起的晶格应变来描述。最有可能的缺陷是层错和晶体之间的界面。重点是了解纳米结构碳化硅基质的形成机理，它的结构和机械稳定性，以及它的机械和物理性能的表征。这种结合的方法将指导选择制备超硬金刚石-碳化硅纳米复合材料的前驱体的最佳制备工艺和工艺条件。由X射线和中子衍射图确定纳米晶体的颗粒尺寸和原子结构的缺陷表征新方法将进一步发展和完善，并应用于纳米材料的表征。一旦开发出来，它们可以用来表征其他金属、介电或半导体纳米晶和纳米复合材料。具体地说，研究在微晶表面/界面形成的结构将能够评估这些材料的化学反应能力，以及纳米结构基质中的晶界结构及其与材料性能的关系。基本了解纳米晶体中的原子排列，特别是界面附近的原子排列，对于纳米技术的进一步发展是绝对必要的。有关复合材料结构的补充信息将从其他技术中获得。与纳米技术有关的研究和拟议的教育活动的跨学科性质将使学生和年轻专业人员为未来的挑战做好准备。国际合作、研究活动的整合、知识和实用技能的分享、研究生和博士后研究员的交流以及来访的高级研究人员提供的一系列讲座将为学生提供新的教育体验。

NON-TECHNICAL DESCRIPTION:This research program, co-funded between the Division of Materials Research and the Office of International Science and Engineering, will focus on relationship between synthesis, structure and properties of diamond-silicon carbide (SiC)composites. Diamond-based composites manufactured under high-pressure and high-temperature conditions are characterized by high hardness and very good wear resistance. How the structure and properties of the composites are influenced by inclusion of nanosize diamonds in the production protocol will be examined. Superhard diamond composites can be applied by many industries; one possible application is in oil and gas exploration where diamond composites could be used as cutting inserts in drill bits. An increase in the lifetime of drill bits will lower the cost of gas/oil drilling wells. It is difficult to assign the monetary value to the diminished risk of environmental pollution during potential blowouts by reduced frequency of drill bits replacements, but it would be substantial. This project is being carried out in collaborations with Eotvos University, Budapest, Hungary and High Pressure Research Center of Polish Academy of Sciences, Warsaw, Poland. Students will visit these institutions for extended periods of time and work under supervision of the leading Hungarian and Polish scientists. Likewise, Hungarian and Polish scientists will visit TCU and conduct high-pressure experiments at national laboratories.TECHNICAL DETAILS: The microstructure of composites can be described by characterizing diamond and silicon carbide phases in terms of their crystallite size and size distribution, and lattice strain caused by crystal defects. The most likely defects are stacking faults and interfaces between the crystallites. The emphasis is on understanding the formation mechanism of the nanostructured silicon carbide matrix, its structural and mechanical stability, and on characterization of its mechanical and physical properties. This combined approach will guide in selection of the optimum preparation procedures of precursors and technological conditions leading to sintering of superhard diamond-SiC nanocomposites. Novel methodologies of defects characterization, determination of grain sizes and atomic structure of nanocrystals from x-ray and neutron diffractograms, will be further developed and refined, and applied to characterize nanomaterials. When developed they could be used to characterize other metal, dielectric, or semiconductor nanocrystals and nanocomposites. Specifically, examination of the structures formed at the crystallite surfaces/interfaces will enable assessing chemical reactivity of these materials, and the structure of grain boundaries in nanostructured matrix and its relation to the material properties. Fundamental understanding of the atomic arrangements in nanosize crystals, especially near the interface, is absolutely necessary for further progress in nanotechnology. Supplementary information on structure of composites will be obtained from other techniques. The interdisciplinary nature of the nanotechnology-related research and proposed education activities will prepare students and young professionals for future challenges. International collaboration, integration of research activities, sharing of knowledge and practical know-how, the exchange of graduate students and post-doctoral fellows, and series of lectures offered by visiting senior researchers will offer students a new educational experience.