Hardness Characteristics of Unidirectional Nanowire-Alumina Nanocomposites

This work explores the fabrication and characterization of very high interfacial area unidirectional nanowire based nanocomposites. Both sol gel deposition techniques and catalyst assisted chemical vapor deposition (CVD) techniques were used to fabricate the nanowire-based nanocomposites within porous alumina templates. Zirconia-alumina and zinc oxide-alumina nanocomposites were fabricated using sol gel methods while silicon-alumina and germanium-alumina nanocomposites were fabricated using CVD methods. The hardness of the different nanocomposites was established by means of microindentation. Hardness testing of fabricated nanocomposites was performed at room temperature, following a single annealing step and following thermal cycling at elevated temperatures. The hardness values were compared to expected values based on tabulated hardness values and the volumetric percentage of each of the components in the composite. All of the nanocomposites show an increase in hardness following the anneal process. The zinc oxide based nanocomposites consistently show a significant deviation from expected values. Hardness values following the cyclic testing do not illustrate a consistent trend across the various nanocomposites.