Synthetische Nano-Verbundkeramiken - maßgeschneiderte Alternativmaterialien aus Hochdruck-Mineralphasen
Zusammenfassung der Projektergebnisse
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, nanopolycrystalline 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. We successfully proved high pressure-high temperature synthesis of nano-polycrystalline geomaterial composites with controlled textures. Nano-polycrystalline aggregates of (i) corundum (Al2O3) and stishovite (SiO2) with variable molar Al2O3:SiO2 proportions from Al2SiO5 glasses, (ii) nanopolycrystalline aggregates of jadeite from NaAlSi2O6 glass, and (iii) nano-polycrystalline aggregates of jadeite and SiO2-high pressure minerals stishovite and coesite, respectively, from NaAlSi3O8 glass were synthesized. Those ceramics have enhanced mechanical and optical properties. In contrast to pressureless crystallization of transparent (glass)ceramics, pressure-assisted synthesis of transparent ceramics will result in enhanced mechanical properties of materials caused by crystallization and aggregate formation processes. In addition, pressure can stabilize phase assemblages that otherwise do not exist at the ambient conditions opening the way to various novel potential technological materials.
Projektbezogene Publikationen (Auswahl)
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(2017) Synthesis of Al2O3/SiO2 nano-nano composite ceramics under high pressure and its inverse Hall-Petch behavior. Journal of the American Ceramic Society 100, 323-332
Gaida NA, Nishiyama N, Masuno A, Holzheid A, Ohfuji H, Schürmann U, Szillus Ch, Kulik E, Bednarcik J, Beermann O, Giehl Ch, Kienle L
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(2017) Transparent polycrystalline cubic silicon nitride. Scientific Reports, Article Number 44755
Nishiyama N, Ishikawa R, Ohfuji H, Marquardt H, Kurnosov A, Taniguchi T, Kim BN, Yoshida H, Masuno A, Bednarcik J, Kulik E, Ikuhara Y, Wakai F, Irifune T
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(2018) Transparent polycrystalline nanoceramics consisting of triclinic Al2SiO5 kyanite and Al2O3 corundum. Journal of the American Ceramic Society 101, 998-1003
Gaida NA, Nishiyama N, Masuno A, Schürmann U, Giehl Ch, Beermann O, Ohfuji H, Bednarcik J, Kulik E, Holzheid A, Irifune T, Kienle L
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(2019) Hardness of polycrystalline SiO2 coesite. Journal of the American Ceramic Society 102, 2251-2256
Kulik E, Nishiyama N, Higo Y, Gaida NA, Katsura T
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(2019) Phase relations in silicon and germanium nitrides up to 98 GPa and 2400°C. Journal of the American Ceramic Society 102, 2195-2202
Nishiyama N, Langer J, Sakai T, Kojima Y, Holzheid A, Gaida NA, Kulik E, Hirao N, Kawaguchi SI, Irifune T, Ohishi Y
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(2019) Thermal expansion and P-V-T equation of state of cubic silicon nitride. Journal of European Ceramic Society 39, 3627-3633
Nishiyama N, Fujii K, Kulik E, Shiraiwa M, Gaida NA, Higo Y, Tange Y, Holzheid A, Yashima M, Wakai F
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(2020) Low temperature heat capacity measurements of β-Si3N4 and γ-Si3N4: determination of the equilibrium phase boundary between β-Si3N4 and γ-Si3N4. Journal of the European Ceramic Society 40, 6309-6315
Nishiyama N, Kitani S, Ohta Y, Kulik E, Netriová Z, Holzheid A, Lenčéš Z, Kawaji H, Wakai F
