研究领域

Inorganic & Materials Chemistry/Physical Chemistry

Idealized crystal structure and nanoindentation damage of a layered perovskite being considered as a “soft-ceramic” My research group focuses on the physical chemistry of ceramics, glasses and wide band-gap semiconductors. We seek to find new compounds, or modifications of known materials, with special properties suitable for electronic, optic, electrochemical and mechanical applications. The approach is to design new materials by manipulating both crystal chemistry and microstructure of solids. A wide variety of synthetic techniques are employed, ranging from the soft chemical approaches of solution and vapor chemistry to the hard chemical approaches of extreme temperatures and pressures. Icosahedral morphology of a single grain of boron suboxide, B12O2, made at high pressures and temperatures The manipulation of microstructures implies the introduction and control of grain boundaries and phase boundaries, which often impart radically different physical properties to solids than would have been expected of single crystals. Taken to the extreme of nanoscaled organization, we are developing “soft-ceramics” that combine high temperature stability in oxidizing and corrosive environments with mechanical toughness. To achieve this, one project investigates the crystal chemical alteration of layered perovskites to produce mica-like materials that are stable to greater than 1500°C, but yet can be easily machined into complex shapes. Another project is devoted to investigating the chemistry of very high temperature glasses as precursors to forming ductile-like nanocomposites. Paradoxically, this is achieved by developing finely divided microstructures of two brittle solids. With respect to electronic materials, we are investigating the chemistry of icosahedral boride compounds for use as wide bandgap semiconductor materials. Beginning with our early work on B12O2 that produced elegant icosahedral morphologies of individual grains (as shown), we have expanded our research to examine the physical and chemical properties of other compositions of the general formula fo B12X 2, where X is typically a main group element. Another project focuses on the thermochemistry and phase chemistry of electroceramics that are targeted for use in piezoelectric, ferroelastic and optical transducers. The importance of this work relates to controlling the crystal growth of complex oxides.

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"Melt and glass structure in the Al2O3-CaO-LaPO4 system studied by 27Al and 31 P NMR, and by Raman scattering," S. Boucher, J. Piwowarczyk, R.F. Marzke, R.F.B. Takulapalli, G.H. Wolf, P.F. McMillan and W.T. Petuskey, Journal of the European Ceramic Society 25 1333-1340 (2005) "Phase equilibria of the lead-magnesium-titanate and lead-niobium-titanate systems at 1000C, and 1 atm," R. Mangham and W.T. Petuskey, Ceramic Transactions 169 139-149 (2005) "Hardness, elasticity, and fracture toughness of polycrystalline spinel germanium nitride and tin nitride," M.P. Shemkunas, W.T. Petuskey, A.V.G. Chezmeshya, K. Leinenweber, G.H. Wolf and J. Mater, Res. 19 (5) 1392-1399 (2004) "Phase Equilibria in the Lead-Magnesium-Niobium-Oxygen System at 1000C," P. Lucas and W.T. Petuskey, Am. Ceram. Soc 84 (9) 2150-52 (2001) "Layered Perovskites as 'Soft-Ceramics'," G. Fair, M. Shemkunas, W.T. Petuskey and S. Sambasivan, J. Eur. Ceram. Soc. 19 2437-2447 (1999) "Nucleation and Growth of Icosahedral Boron Suboxide Clusters at High Pressure," P.F. McMillan, H. Hubert, A. Chiszmeshya, W.T. Petuskey, L.A.J. Garvie and B. Devouard, J. Solid State Chemistry 147 281-290 (1999) "Nanoindentation of a Layered Crystal Structure Oxide," M.P. Shemkunas and W.T. Petuskey, Fundamentals of Nanoindentation and Nanotribology, Materials Research Society Symposium Series 522 275-280 (1998)