In-Situ High-Temperature Ferroelastic Phase Transformations in Oxide Ceramics

氧化物陶瓷中的原位高温铁弹性相变

• 批准号: 0211139
• 负责人: Waltraud Kriven
• 金额: $ 32.73万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0211139&HistoricalAwards=false
• 关键词: Situ; Temperature; Ferroelastic; Phase; Transformations

A compact, thermal-image furnace has been developed in conjunction with synchrotron radiation to collect in situ high-temperature powder diffraction data on selected oxide ceramics in air up to 2400 C. The experimental data is analysed and compared with theoretical predictions by the Rietveld crystallographic, profile fitting technique. The ultimate aim of this research project is to investigate detailed mechanisms of crystal structure changes involved in ferroelastic phase transformations in selected materials, using in situ synchrotron XRD, hot stage optical microscopy and TEM techniques. Specifically, phase transformations involving negligible or zero volume changes, but possibly some unit cell shape changes will be focused upon. Phase transformations in tantalum oxide (Ta2O5) and lanthanide tantalates (LnTaO4), as well as lanthanide aluminates will be studied. In this manner, the structure-property relationships of the materials could be better understood and tailored for application, e.g., in toughening mechanisms, large force actuation and shape memory ceramics. Preliminary studies will be made on some of the mechanical properties of key ferroelastic materials This objective of this project is to undertake in-situ high-temperature studies of phase transformations in oxide ceramics, using our newly-invented, thermal-image furnace, capable of 2400 C in air, in conjunction with synchrotron radiation. The emphasis is on oxide materials exhibiting polymorphic phase transformations, especially of a ferroelastic nature, at elevated temperatures. This is inline with our on-going research efforts in identifying potential materials with new, energy absorbing mechanisms, which have applications in the design of tough, high-temperature composites. Furthermore, as a result of domain rearrangement by ferroelastic mechanisms, potential applications are possible in large force actuation and shape memory behavior.

研制了一台紧凑的热像炉，与同步辐射相结合，对选定的氧化物陶瓷在2400℃以下的空气中进行了高温粉末衍射数据的现场采集。用Rietveld结晶学、轮廓拟合技术对实验数据进行了分析，并与理论预测进行了比较。本研究项目的最终目的是利用同步辐射X射线衍射仪、热台光学显微镜和透射电子显微镜等技术，详细研究选定材料中铁弹性相变过程中晶体结构变化的详细机制。具体地说，涉及可忽略或零体积变化的相变，但可能涉及一些单位晶胞形状的变化。将研究氧化钽(Ta2O5)和稀土钽酸盐(LnTaO4)以及稀土铝酸盐中的相变。通过这种方式，可以更好地理解和定制材料的结构-性能关系以用于例如增韧机制、大力驱动和形状记忆陶瓷中。这个项目的目标是利用我们新发明的、能够在空气中达到2400摄氏度的热像炉，结合同步辐射，对氧化物陶瓷中的相变进行原位高温研究。重点是氧化物材料在高温下表现出多晶型相变，特别是铁弹性性质的相变。这与我们正在进行的具有新的能量吸收机制的潜在材料的研究工作是一致的，这些材料在坚韧的高温复合材料的设计中具有应用价值。此外，由于铁弹性机制的磁区重排，在大力驱动和形状记忆行为中可能有潜在的应用。