Interpenetrating phase ceramic/polymer composite coatings: Fabrication and characterization

The goals of this thesis research were to fabricate interpenetrating phase composite (IPC) ceramic/polymer coatings and to investigate the effect of the interconnected microstructure on the physical and wear properties of the coatings. IPC coatings with an interpenetrating phase microstructure were successfully fabricated by first forming a porous ceramic with an interconnected microstructure using a chemical bonding route (mainly reacting {dollar}alpha{dollar}-alumina (0.3 {dollar}mu{dollar}m) with orthophosphoric acid to form a phosphate bond). Porosity within these ceramic coatings was easily controlled between 20 and 50 vol. % by phosphoric acid addition, and was measured by a new porosity measurement technique (thermogravimetric volatilization of liquids, or TVL) which was developed. The resulting ceramic preforms were infiltrated with a UV and thermally curable cycloaliphatic epoxide resin and cured. This fabrication route resulted in composite coatings with thicknesses ranging from {dollar}sim{dollar}1{dollar}mu{dollar}m to 100 {dollar}mu{dollar}m with complete filling of open pore space.; The physical properties of the composite coatings, including microhardness, flexural modulus and wear resistance, were evaluated as a function of processing variables, including orthophosphoric acid content and ceramic phase firing temperature, which affected the microstructure and interparticulate bonding between particles in the coatings. For example, microhardness increased from {dollar}sim{dollar}30 on the Vicker's scale to well over 200 as interparticulate bonding was increased in the ceramic phase. Additionally, Taber wear resistance in the best TPC coatings was found to approach that of fully-densified alumina under certain conditions.; Several factors were found to influence the wear mechanism in the IPC coating materials. Forming strong connections between ceramic particles led to up to an order of magnitude increase in the wear resistance. Additionally, coating microhardness and ceramic/polymer interfacial strength were studied and found to be important in determining the wear mechanism and wear resistance of IPC composite coatings. A qualitative theory for wear mechanisms in these coatings was developed.; Finally, a series of transparent coatings were developed via a similar processing route, using smaller ({dollar}sim{dollar}90 nm) boehmite particles instead of 0.3 {dollar}mu{dollar}m {dollar}alpha{dollar}-alumina. Physical property control was found to mimic that found in opaque coatings, and showed increasing surface adsorption characteristics with increasing phosphoric acid content.