Decay-dissipative Belousov-Zhabotinsky nanobands and nanoparticles in NiAl

Abstract

A relationship is inferred between dissipative reactions, nanocrystal formation and nanobands in micropyretically synthesized equimolar Ni-Al alloys. Various microkinetic mechanisms may be operative, depending on the chosen processing conditions and alloy chemistry. Time-lapse X-ray reports, microstructural studies, process conditions and combustion calculations are correlated to understand the microkinetics of the synthesis process. Dissipative oscillatory chemical reactions, called Belousov-Zhabotinsky (BZ) reactions, are proposed as one synthesis mechanism, which leads to the formation of the observed nanoscale features such as nanoparticles and nanobands. Nanoband features in a solid-state combustion processes are discussed for the first time. The dissipative oscillations that are a consequence of the nonlinear reaction rate equations create and simultaneously disperse nanoparticles and nanobands depending on the initial temperature, composition and other process conditions chosen. The spatiotemporal structure from a moving geometrical configuration such as a micropyretic solid-state combustion front can contain a decaying dissipative reaction product, e.g. a spin combustion microstructure. Nanoband-forming waves and nanocrystals possibly interact, leading to unique variations in the structure. Such nanostructural possibilities could be advantageously controlled by manipulating the initial conditions. The implications of the BZ finding could be significant, as it offers a method of forming bulk near-net-shaped objects containing nanostructured enhancements. For the NiAl material in particular, this could be a significant technical advantage from a manufacturing viewpoint. Some possible methods to influence the process and the resultant structure on the nanoscale are discussed.