Collaborative Research: Bulk synthesis of stishovite near ambient pressure and temperature

合作研究：接近环境压力和温度的石英石的批量合成

• 批准号: 1463948
• 负责人: Kai Landskron
• 金额: $ 14.61万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1463948&HistoricalAwards=false
• 关键词: Collaborative; Research; Bulk; synthesis; stishovite

NON-TECHNICAL DESCRIPTION: The project targets synthesis of stishovite, a form of SiO2 (silica) and one of the hardest materials known to mankind at hydrothermal conditions. Presently, this precious form of silica can only be attained at extremely high pressure (ca. 100,000 times atmospheric pressure) in a technically very difficult and expensive process that yields only small quantities. The new approach of this project mimics geological conditions, and grows the crystals from aqueous solutions in bulk quantities. The process occurs close to ambient pressure and temperature conditions, and consequently, will be inexpensive and scalable. This facilitates new applications of stishovite as an abrasive, in cutting tools, and as a hard ceramic material in other applications. TECHNICAL DETAILS: Stishovite, a polymorph of silica (SiO2), is - together with cubic boron nitride - only second in hardness to diamond. Moreover, among the hardest materials known it is the only oxide, thus naturally resistant against degradation through oxidation. Despite these outstanding properties, stishovite is not used as an engineering material, because it can be synthesized only at pressures above 8 GPa. Although technically feasible, the high-pressure route is not scalable and rather expensive. In this project, a kinetically controlled hydrothermal synthesis approach for stishovite is being developed. The process occurs near ambient pressure and temperature conditions and is similar to the industrial production of quartz crystals. The difference to industrial quartz growth is that instead of quartz seed crystals, stishovite seed crystals are employed. The temperature gradient in the autoclave system allows for the supersaturation of the silicate solution in the growth chamber and the kinetically controlled growth of the stishovite seed crystals from the supersaturated solution. The experiments are guided by computations that explore and predict optimal synthesis conditions. The research is a seminal approach to synthesize high pressure phases near ambient conditions from solution which suggests a transformational impact on the synthesis of high-pressure phases. The project is training graduate students in high-pressure and hydrothermal synthesis techniques and computational materials chemistry. The results from the research are part of the graduate level course "Solid State Chemistry".

非技术描述：该项目的目标是合成石英石，石英石是 SiO2（二氧化硅）的一种形式，也是人类已知的在水热条件下最坚硬的材料之一。目前，这种珍贵形式的二氧化硅只能在极高的压力（约 100,000 倍大气压）下通过技术上非常困难且昂贵的工艺获得，且产量很小。该项目的新方法模仿地质条件，并从水溶液中大量生长晶体。该过程发生在接近环境压力和温度条件下，因此成本低廉且可扩展。这促进了石英石作为磨料、切削工具以及其他应用中的硬质陶瓷材料的新应用。技术细节：Stishovite 是二氧化硅 (SiO2) 的多晶型物，与立方氮化硼一起，硬度仅次于金刚石。此外，在已知的最硬材料中，它是唯一的氧化物，因此天然能够抵抗氧化降解。尽管具有这些突出的特性，石英石并不用作工程材料，因为它只能在高于 8 GPa 的压力下合成。尽管技术上可行，但高压路线不可扩展且相当昂贵。在该项目中，正在开发一种动力学控制的硅铁矿水热合成方法。该过程发生在接近环境压力和温度条件下，类似于石英晶体的工业生产。与工业石英生长的不同之处在于，使用石英晶种代替石英晶种。高压釜系统中的温度梯度允许生长室中硅酸盐溶液的过饱和以及硅酸盐晶种从过饱和溶液中的动力学控制生长。实验以探索和预测最佳合成条件的计算为指导。该研究是一种从溶液中合成接近环境条件的高压相的开创性方法，这表明对高压相的合成具有变革性的影响。该项目正在培训高压和水热合成技术以及计算材料化学方面的研究生。研究结果是研究生课程“固态化学”的一部分。