The synthesis and application of fine particles for coatings and composites

A variety of coating methods are presented for producing titanium and zirconium oxide coatings on spherical α-alumina substrates. Some methods did not completely coat the alumina substrate leaving surface areas exposed. Techniques such as surface modifications with PDVB and 4-VP did produce coatings of metal oxides of very high quality. The best metal oxide coatings are produced from pre-treatment of the alumina microspheres followed by the acid catalyzed hydrolysis of the metal tetra-alkoxides.; Methods to investigate converting titanium oxide and zirconium oxide coated alumina microspheres to the corresponding metal carbide coated alumina microspheres have been done. The methods involving direct reduction of the metal oxides by methane and methane-hydrogen gas proved inefficient in producing high quality metal carbide coatings. It is evident higher processing temperatures are required to achieve good metal carbide yield by these methods.; Metal oxide coated products carbided by ART (Buffalo, NY) proved the carbiding can be accomplished at higher temperatures and with a different carburizing gas. In addition to the ART carbiding method, the magnesium thermite reaction is a promising method in converting metal oxides to metal carbides at much lower temperatures and shorter processing times.; The electrophoretic deposition of Bi₂Sr₂CaCu ₂O₈ powder was in ethanol. Of critical consequence were the design of the cathode geometry and the arrangement of the electrodes so that all faces and edges of the silver anode were coated simultaneously. This was achieved by shaping the platinum cathode into a configuration that allowed the silver tape to be completely surrounded by the platinum. The electrophoretic cell was set up to keep the electrodes stationary thereby maintaining a constant distance from the cathode and anode (3 mm).; The relationship between deposition time and coating thickness was determined for various powder loadings for a given electric field strength (62 V). For low powder loadings (10 and 20 g/L), the thickness of the coating increases with increasing deposition time (6, 12, and 24 hours). At a powder loading of 30 g/L, the thickness of the BSCCO layer decreases from a deposition time of 6 to 12 hours. At 24 hours, the layer thickness increases. Very high powder loadings (40 g/L) showed a linear decrease in the BSCCO layer thickness with increasing deposition time.; Analysis by XRD showed the EPD superconductor exhibited preferential orientation on the silver tape. The degree of orientation was related to the layer thickness and hence the deposition times. Thermal treatment at 800°C in 90% Ar-10% O₂ improved the orientation effects. A marked improvement in the surface texture was also observed by SEM.; Carbon nanotubes were synthesized via Fe catalysis in an aerosol column in the presence of Ar, CO, and H₂ gas. Fe particles were generated by the thermal decarbonylation of Fe(CO)₅. Multiwalled and single-walled carbon nanotubes were grown from the decomposition of CO gas on the forming Fe particles. Optimal conditions were determined for producing high yields of single-walled nanotubes. A growth theory is proposed based on the results. (Abstract shortened by UMI.)...