Synthetic nanocomposite ceramics - tailored alternative materials of high-pressure minerals

最先进的高压技术可以合成纳米多晶材料，如陶瓷，具有优异的机械性能，如高硬度和高断裂韧性，从地球上丰富的地质材料。许多陶瓷、金属和金刚石的晶粒细化与硬度的正相关关系被称为Hall-Petch关系。这一点在辉石中也很明显，辉石是SiO2的高压多晶型，被称为最硬的氧化物。纳米多晶针云石的硬度是单晶针云石的7倍。这说明细化晶粒不仅可以提高材料的硬度，还可以提高材料的断裂韧性。因此，纳米多晶岩土材料具有很大的潜力，可以替代经济的关键金属原材料，这些原材料对于生产具有增强机械性能的普通材料至关重要。特别是纳米多晶岩土材料在创造高硬度和高断裂韧性的材料方面非常有前景，这是迄今为止材料科学的一大挑战。该项目的目标是采用最先进的高压高温技术合成具有优异机械性能的经济非关键材料，由纳米多晶岩土材料复合材料制成，具有可控的纹理。计划从Al2O3-SiO2玻璃中合成具有可变Al2O3:SiO2比例的刚玉（Al2O3）和刚玉（SiO2）纳米多晶聚集体，从MgAl2O4玻璃中合成方石（MgO）和刚玉纳米多晶聚集体，从NaAlSi3O8玻璃中分别合成硬玉（NaAlSi2O6）和高压矿物（NaAlSi2O6和coesite） SiO2纳米多晶聚集体。这种系统实验方法的另一个重要目标是更好地理解由结晶和聚集体形成过程引起的增强材料机械性能的基本机制。

State-of-the-art high pressure technologies allow synthesizing nano-polycrystalline materials, e.g., ceramics, with excellent mechanical properties, as for instance high hardness and high fracture toughness, from Earth s high abundant geomaterials. The positive correlation of grain fining and hardness of many ceramics, metals and diamond is known as the Hall-Petch relation. This is also evident from stishovite, which is a high pressure polymorph of SiO2 and known as the hardest oxide. Nano-polycrystalline stishovite is seven times tougher than single crystal stishovite. This point towards that grain fining not only can enhance material hardness, but also the fracture toughness. Thus, nano-polycrystalline geomaterials have high potential to substitute economical critical metal raw materials that are essential for the production of common materials with enhanced mechanical properties. In particular, nano-polycrystalline geomaterials are very promising in creating materials that combine high hardness and high fracture toughness, which is a great challenge of material science so far. The aim of the proposed project is a state-of-the-art high pressure-high temperature technology synthesis of economical non-critical materials with excellent mechanical properties made out of nano-polycrystalline geomaterial composites with controlled textures. Nano-polycrystalline aggregates of corundum (Al2O3) and stishovite (SiO2) with variable molar Al2O3:SiO2 proportions from Al2O3-SiO2 glasses as well as nano-polycrystalline aggregates of periclase (MgO) and corundum from MgAl2O4 glass and nano-polycrystalline aggregates of jadeite (NaAlSi2O6) and SiO2-high pressure minerals stishovite and coesite, respectively, from NaAlSi3O8 glass are planned to be synthesized. Another important objective of this systematic experimental approach is to better understand fundamental mechanisms that enhance the mechanical properties of materials caused by crystallization and aggregate formation processes.