Ceramic Quasicrystals

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NON-TECHNICAL DESCRIPTION: Quasicrystals are made from building blocks of regular size and shape that can fill up the space but do not have a repeatable pattern. Macroscale quasicrystals have been known since ancient times to mathematicians and artists who made are mosaics with such patterns. Molecular quasicrystals are very rare. They are found only for limited number of alloys and some meteorites. This unusual structure (tiling) makes them promising candidates for exceptionally strong materials because the lack of periodicity prevents the propagation of cracks. Vast majority of load-bearing structures built today are from ceramic materials but ceramic quasicrystals are not known. This project is aimed at developing general methods for preparation of quasicrystalline ceramics from nanoparticles that can make it both simple and diverse. Such ceramics materials may be of value for national defense, automotive industry, aviation, and electronics. The project includes an integrated multifaceted training of students in the cutting edge materials engineering and computer simulation technologies. It also includes an integral Outreach and Education Program, centered on early science education and quasicrystalline tilings which unite scientific and aesthetic values.TECHNICAL DETAILS: The key to the preparation of ceramic and composite quasicrystals will be self-organization of ceramic nanoparticles into quasicrystalline phases. This approach will allow the manufacturers to avoid extremely high temperatures and pressures. The nanoparticles selected for the project are spherical SiO2 modified with a polymer. Such nanoparticles feature two competing long-range interactions that inhibit crystallization in traditional phases in favor of quasicrystals. The synergy of experiment (Kotov) and simulations (Glotzer) make it possible to experimentally realize bulk ceramic quasicrystals from SiO2 under mild conditions. Quasicrystal phases simulated initially on the computer are assembled in aqueous dispersions. Following the three-dimensional crystallization into aperiodic structures, the initially soft materials are annealed to make robust bulk monoliths interconnected by strong covalent bonds. The composite quasicrystals are being made by monomer infiltration or layer-by-layer assembly. Different quasicrystalline ceramics are being comparatively investigated for mechanical properties and crack propagation mechanisms. They are expected to reveal set of properties previously unseen for any other materials. The combination of toughness, transparency and simplicity of preparation may lead to transformative changes in ceramics and their applications.