Abstract
We propose a novel technique for the large-scale synthesis of aligned-plate nanostructures that are self-assembled and self-supporting. The synthesis technique involves developing nanoscale two-phase microstructures through discontinuous precipitation followed by selective etching to remove one of the phases. The method may be applied to any alloy system in which the discontinuous precipitation transformation goes to completion. The resulting structure may have many applications in catalysis, filtering and thermal management depending on the phase selection and added functionality through chemical reaction with the retained phase. The synthesis technique is demonstrated using the discontinuous precipitation of a γ′ phase, (Ni, Co)3Al, followed by selective dissolution of the γ matrix phase. The production of the nanostructure requires heat treatments on the order of minutes and can be performed on a large scale making this synthesis technique of great economic potential.
Highlights
We propose a novel technique for the large-scale synthesis of aligned-plate nanostructures that are self-assembled and self-supporting
The process to produce a complete discontinuous or cellular precipitation (DP) transformation can be of short duration and there is potential for the large scale synthesis of aligned plate nanostructures
In many cases DP transformations do not go to completion due to a decreasing driving force resulting from continuous precipitation (CP) ahead of the advancing DP interface[12]
Summary
We propose a novel technique for the large-scale synthesis of aligned-plate nanostructures that are self-assembled and self-supporting. As the Cobalt content increases, there is a rotation of the tie line so that at the limit of the 2 phase field bordering the γ+γ′+βphase field there is 35 at.% Co in Ni3Al (γ′) and 86 at.% Co in the Ni solid solution (γ) phase with which it is in equilibrium Another possibility for the increased propensity for DP is a change in the γ/γ′lattice mismatch causing a change in the interfacial energy favoring discontinuous over continuous precipitation[9]. Further fundamental understanding of the kinetics of the DP transformation is needed so that appropriate heat treatment parameters may be selected for other alloy systems that have potential for complete DP transformations
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