SBIR-STTR Award

Nanocomposites of carbon nanotubes (CNTs) dispersed in alumina powders and consolidated to near 100% theoretical density at low temperatures have been shown to have a four point bend strength 3 times that of pure alumina ceramics. Recently, in situ synthesized CNTs have been produced in alumina powders containing finely dispersed Fe nanoparticles. The anticipated improvement in mechanical properties had not been realized from the collagen like scaffolding of the CNTs when the nanocomposites were consolidated using hot isostatic pressing (HIP). This disappointing performance was attributed to the destruction of the CNTs by the high temperatures used in the HIPing. HY-Tech proposes to consolidate alumina nanocomposite green bodies containing in situ synthesized CNTs using a low temperature pressureless sintering approach. The characteristics of the CNTs and microstructure of the composite will be measured at different times in the fabrication process by scientists at the University of Missouri-Rolla. The studies will assess the effects of varying fabrication parameters on survivability of the CNTs and the bend strength of the nanocomposite material.

Keywords:
IN SITU SYNTHESIZED CARBON NANOTUBES, NANOCOMPOSITES, REINFORCED ALUMINA

Reinforced tough ceramics that fail gracefully are requied for structural components in airframes and engines of military and commercial airplanes. The expected toughening was not realized when alumina powder, containing carbon nanotubes (CNTs), was consolidated by hot isostatic pressing due to the destruction of the CNTs at the high temperatures encountered. HY-Tech has demonstrated in the Phase I effort that microwave sintering can be used to consolidate alumina/CNT mixtures without destroying the CNTs. HY-Tech proposes to study the relationship between the preparation and consolidation processes with the resulting microstructure and mechanical properties of the nanocomposite material in the Phase II effort. The volume fraction of CNTs, their quality (single walled or multi-walled), and their surface conditions will be varied as widely as possible along with the starting particle size, microwave heating rate and sintering conditions. The mechanical properties will be correlated with the microstructure achieved by University of Missouri/ Rolla investigators to determine the dominant material reinforcement process at play.

Keywords:
Carbon Nanotubes, Nanocomposite Materials, Microwave Sintering, Microstructure, High Temperature, Ar