Research Areas:
Synthesis of inorganic membranes, films, and powders by aerosol deposition, chemical vapor deposition and chemical vapor infiltration; membrane reactors; chemical physics of aerosols and microparticles

We are currently investigating several techniques for the fabrication of thin supported ceramic and metallic membranes. The objective is to obtain thin, dense, defect-free membrane layers of metals and ceramics on porous supports which allow the permeation of a particular gas, such as H₂ or O₂, with essentially perfect selectivity. Such membranes can be applied in high temperature gas separations or purification, or in the design of "membrane reactors", which may provide better reaction conversion or selectivity, as well as better energy efficiency than conventional reactor technology. We also are involved in lab-scale membrane reactor testing for reactions such as dehydrogenation and hydrocarbon oxidation. The materials being investigated include metals, such as palladium alloys and silver, and ionic/electronic conductors such as doped zirconia, and several perovskite compounds. We utilize primarily aerosol deposition and chemical vapor deposition (CVD) to produce the membrane layers. In the aerosol techniques, very small particles of the desired material are produced by atomization of a solution or gas-phase reaction, followed by collection on a porous support and sintering or other processing. The CVD techniques involve thermal decomposition of metal-organic compounds on a heated support or high temperature reaction of gaseous reactants within the pores of support. For all of the fabrication approaches, we are interested in identifying the conditions for producing desirable membranes, understanding the fundamentals of the fabrication techniques, and evaluation and application of the membranes.
One very important aspect in the production of films and powders by aerosol techniques is the control of the final morphology of particles which undergo a number of physical and chemical transitions during the aerosol production process. For example, a typical synthesis might involve solvent evaporation, salt precipitation, melting, precursor decomposition, and particle sintering. We are currently building an electrodynamic balance which will allow individual particles to be suspended and observed directly while conditions are changed and these various processes occur. This should lead to a better understanding of the processes which control particle morphology. The electrodynamic particle balance is also a useful tool for the study of a variety of other chemical reaction and transport phenomena associated with aerosols and microparticles. These phenomena are important in applications such as combustion and pyrolysis, environmental aerosols, and spray material synthesis.

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