Formation of Bulk Nanostructured Materials by Rapid Solidification

Abstract

When a eutectic melt is undercooled below its liquidus T₁ by a critical amount, it undergoes metastable liquid-state spinodal decomposition. The resulting morphologies can be described as intermixing undercooled liquid networks of characteristic wavelength λ. At a temperature substantially below T₁, λ can be <100 nm. When λ ≤ 100 nm, the undercooled liquid networks break up into nanometer-size droplets/strips driven apparently by surface tension. The morphologies of the tiny droplets/strips can be frozen by subsequent crystallization. The as-crystallized specimen is a nanostructured material. It is microvoid free and the size of the constituent grains is rather uniform. Two systems, Pd_40.5Ni_40.5P₁₉ and Pd₈₂Si₁₈, were chosen to illustrate the synthesis process.