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Suchanek W.L.,Sawyer Technical Materials LLC | Garces J.M.,Consultant LLC | Fulvio P.F.,Kent State University | Fulvio P.F.,Oak Ridge National Laboratory | Jaroniec M.,Kent State University
Chemistry of Materials | Year: 2010

Novel alpha alumina (α-Al2O3) nanosheets with controlled chemical compositions were synthesized at 450 °C under 10.3 MPa pressure by the hydrothermal treatment of boehmite powder (γ-AlOOH) in the presence of soluble salts of metal dopants, α-Al2O3 seeds, and 5% SiO2 morphology modifier. Detailed XRD, SEM, HRTEM, STEM, and XEDS characterization was performed and it was found that the as-synthesized nanosheets were in most cases the phase-pure α-Al 2O3 crystals exhibiting very strong (001) faceting, thicknesses of 10-50 nm, aspect ratios up to a few hundreds, and specific surface areas up to 35 m2/g. Metal dopants from nearly every group of the Periodic Table were present in these α-Al2O3 nanosheets in concentrations up to ∼0.5 atom % either as solid solutions or as nanosized inclusions. A thorough surface analyses using X-ray photoelectron spectroscopy (XPS), measurements of nitrogen adsorption isotherms at -196 °C, temperature-programmed desorption (TPD), and zeta potential measurements, revealed a very wide range of control of the surface charge, surface purity, and acid-base properties of the α-Al2O 3 nanosheets by selection of different dopants and controlling their distribution within the nanosheets. The BET surface area values of the hydrothermally synthesized nanosheets were stable up to 1200 °C. Such novel doped α-Al2O3 nanomaterials can be useful in a variety of applications such as catalysis, chemical-mechanical planarization, composites, and ceramics. © 2010 American Chemical Society. Source

Suchanek W.L.,Sawyer Technical Materials LLC | Garces J.M.,Consultant LLC
CrystEngComm | Year: 2010

Following a strong demand for novel α-Al 2O 3 nano-materials with unique properties, both pure and doped nano-sheets, nano-needles, and nanosized equiaxed particles (reference) of 100% phase-pure α-Al 2O 3, were synthesized at 430-450 °C under 10.3 MPa pressure by the hydrothermal treatment of boehmite powder (γ-AlOOH) in the presence of α-Al 2O 3 seeds and 1-10% morphology modifiers. SiO 2 and H 3BO 3 were used as morphology modifiers to produce phase pure α-Al 2O 3 nano-sheets and nano-needles, respectively, that exhibited strong crystallographic c- and a-faceting and BET surface areas up to 40 m 2 g -1 stable above 1000 °C. A mesocrystal growth mechanism of the α-Al 2O 3 nano-particles was observed. Unprecedented flexibility to control the sizes and morphologies of α-Al 2O 3 enabled fabrication of 90% porous ceramics with unique pore geometries and pore volumes up to 1.5 cm 3 g -1. These novel α-Al 2O 3 nano-materials can be useful in a variety of catalytic applications, nano-filtration, chemical-mechanical planarization, composites, etc. © 2010 The Royal Society of Chemistry. Source

Suchanek W.L.,Sawyer Technical Materials LLC
Journal of the American Ceramic Society | Year: 2010

Alpha alumina (α-Al2O3) powders and α-Al2O3/boehmite (γ-AlOOH) mixtures with controlled γ-AlOOH contents were synthesized hydrothermally under alkaline or acidic conditions at 380-435C for 1-10 days, under 6.9-14.5 MPa pressure, from concentrated precursors without stirring. The precursors were formed by mixing different types of aluminum hydroxides with water, and optionally with α-Al2O3 seeds, hydrogen peroxide, sulfuric acid, dopants (i.e., KMnO4), and/or other additives. The experiments were performed on industrial scale in large production autoclaves. The synthesized α-Al2O3 powders exhibited up to 100% phase purity, 99.98% chemical purity, equiaxed morphology, low aggregation levels, narrow crystallite size distributions with primary particle sizes ranging between 100 nm and 40 μm, and high reproducibility. Precursor types, seeds, chemical additives, and temperature/time of the hydrothermal synthesis were found to govern properties of the powders. Different growth mechanisms for nanosized and rough powders are discussed. Results of this study enable the use of hydrothermal α-Al2O3 powders in a multitude of applications, and make their hydrothermal production a commercial reality. © 2009 The American Ceramic Society. Source

Gorka J.,Kent State University | Jaroniec M.,Kent State University | Suchanek W.L.,Sawyer Technical Materials LLC
Nanoscale | Year: 2010

Novel α-alumina crystalline nanosheets are used for the preparation of alumina-carbon composites, in which the latter component is phenolic resin-based ordered mesoporous carbon. A unique feature of these composites is perpendicular orientation of ordered mesopores of the carbon to the (001) facets of nonporous α-alumina nanosheets accompanied by significant enlargement of these mesopores in comparison to those present in the bulk carbon. © 2010 The Royal Society of Chemistry. Source

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