CAREER: Aerosol Droplet Combustion Synthesis of Nonequilibrium Nanoscale Materials

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Abstract - Helble This is a fundamental exploration of combustion aerosol synthesis to generate chemically complex nanoscale ceramic materials. In combustion aerosol synthesis, ceramic precursors are dissolved or dispersed in a combustible carrier; when this carrier is atomized into a high-temperature flame, each droplet can become a "microreactor" for nanoscale ceramic particle synthesis. The high temperature, exothermic droplet combustion reactions enable the generation of chemically complex, crystalline materials without need for further heat treatment. The first material to be examined is yttria-stabilized zirconia because of its applicability as a thermal barrier, coating, catalyst, and catalyst support. A range of yttria compositions is considered to determine whether the nanoscale material, with its high concentration of surface atoms, shows the same transitions in phase behavior as does conventional stabilized zirconia. Synthesis issues explored include the control of reacting aerosol droplet size, particle formation through the condensed-phase reaction and nucleation within the reacting droplet, and particle formation through the vaporization and subsequent condensation of ceramic compound vapors. Key issues are the ability to minimize agglomeration of nanoscale particles and the ability to control their chemical composition. Advanced ceramic materials consolidated from nanometer-scale ceramics have the potential to provide improved mechanical, optical, and electronic behavior over their larger-grained counterparts. Potential applications include barrier coatings, catalysts, structural materials, and cores of superconducting wires. Educational efforts include development of an aerosol science course using interactive learning and, in conjunction with the Boston Museum of Science, development of a hands-on interpretive module addressing the nanoscale world as a realm between atomic and macroscopic regimes.