Research Project

Nucleation with Steep Composition Gradients

This NSF project aims to build on our previous work and established capability using nanocalorimeters to study intermetallic reactions. The theory developed in the project will be a notable improvement on our existing understanding of how nucleation occurs in sharp concentration gradients, with the experiments representing the first rigorous and systematic verification of such a model.

A simple example of a nanocalorimetry result, here showing the heat capacity spike associated with the melting of Al nanoparticles. Note the sensitivity of the nanocalorimeter with absolute heat capacity in micro-Joules per Kelvin.

A simple example of a nanocalorimetry result, here showing the heat capacity spike associated with the melting of Al nanoparticles. Note the sensitivity of the nanocalorimeter with absolute heat capacity in micro-Joules per Kelvin.

The NSF project titled “Nucleation in Solid Metallic Solutions with Steep Composition Gradients” aims to build on our previous work and established capability using nanocalorimeters to study intermetallic reactions. This project is a continuing collaboration with Dr. David LaVan of the National Institute of Standards and Technology.

Nanocalorimeters are small, microfabricated devices which enable rapid heating and precise thermal measurement of small samples. Our previous project utilized the nanocalorimeter as a unique test platform for examining the reaction mechanism of Ni/Al bilayers under the unique combination of rapid heating and low maximum temperature (forced solid-state mixing). This system is ideal for studying nucleation conditions as it offers precise control of both thermal history (via the nanocalorimeter) and concentration gradient (through the precision layering possible using physical vapor deposition). The experimental component of the project studies the roles of concentration gradient and nucleation temperature in determining the first phase to form in Ni/Al bilayers. This will be coupled with an analytical modeling effort aimed at predicting phase nucleation. The theory developed in the project will be a notable improvement on our existing understanding of how nucleation occurs in sharp concentration gradients, with the experiments representing the first rigorous and systematic verification of such a model.

Nanocalorimeter Chip: (a) Cross-sectional schematic and (b) top-down micrograph of a fabricated nanocalorimeter chip.

Nanocalorimeter Chip: (a) Cross-sectional schematic and (b) top-down micrograph of a fabricated nanocalorimeter chip.

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