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

• Applicant: Professorin Dr. Astrid Holzheid
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324039096

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.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Norimasa Nishiyama