Preparation of Nanostructured Membranes by Reactive Depositions from Supercritical Fluids NSF Functional Nanostructures Grant 9811088
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چکیده
Introduction: The fabrication of structured materials for applications in optics, microelectronics, sensors, membranes, and catalysis often requires the deposition of metal or metal oxides onto or within supports or templates. Due to various fundamental constraints of deposition reactions in vapor and liquid media, current metallization techniques are typically impractical for supports with complex surface topographies when the size of the features drops below 100 nm or when the desired deposition must occur deep within a macro or mesoporous substrate. These constraints are relieved by a novel deposition technique developed in our laboratories. The process, called Chemical Fluid Deposition (CFD), involves the reduction of organometallic compounds in supercritical carbon dioxide to yield high-purity deposits. The enabling advantages of CFD are derived from the physicochemical properties of the supercritical solvent, which lie intermediate to those of liquids and gases. Transport and reduction in solution offer low process temperatures, high reagent concentrations and eliminates precursor volatility requirements associated with vapor phase techniques. Moreover the absence of surface tension and low viscosity of supercritical fluid (SCF) solutions are ideally suited to the delivery of relatively high concentrations of organometallic precursor(s) within porous environments. In this report we describe the utility of CFD for the preparation of dense, nanostructured Pd membranes of prescribed thickness at controlled depths within Al2O3 supports using an opposed reactants geometry. Membrane position is predicted by a simple transport model. A detailed simulation is under development to describe membrane structure and evolution.
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Synthesis of Nanostructured Films for Friction and Wear Resistance NSF Functional Nanostructures Grant 9871863
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تاریخ انتشار 2001