Nanophase Composite Materials for Magnetic Refrigeration

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The objectives of the proposed program are (1) to generate relatively monodispersed nanoparticles containing Fe and Cr by laser-induced gas-phase particle formation processes, (2) to effectively remove particles by a surface discharge/liquid nitrogen electrode assembly , (3) to consolidate nanoparticles into nanophase composites and measure their enhanced magnetocaloric effect under varying external magnetic field, and (4) to compare the experimental data with theory for maximum magnetocaloric refrigerating capacity. Three techniques are used for the generation of nanometer- sized particles: laser ablation, photolytic dissociation, and pyrolysis. For both the laser ablation and photolytic dissociation experiments, excimer lasers operating in the ultraviolet frequency range will be used. The reaction chamber configuration, gas pressure and flow patterns will be optimized for controlled generation of monodispersed nanoparticles. The photolytic pyrolysis technique using CO2 lasers will be developed for the eventual scale-up production of nanocomposite at high rates. Using CO2 laser-induced pyrolytic process, the proposed new nanocomposite material may be prepared in large quantities for the construction of prototype magnetic refrigerators operating near room temperature. The creation of nanocomposite refrigerant particles by gas- phase nucleation processes and their consolidation into superparamagnetic materials with enhanced magnetic moments will result in significant materials with increases of the magnetocaloric effect.