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Direct writing of reactive inks based on electroless nickel deposition on pure aluminium powders

Direct writing of reactive inks based on electroless nickel deposition on pure aluminium powders

தேதி10th Nov 2022

Time03:00 PM

Venue Google meet

PAST EVENT

Details

Reactive multilayers constitute a class of materials that have high energy densities and are capable of releasing heat in a short period of time. Generally, they are composed of two reactants of either metals or alloys. They are inert under normal conditions but release heat when ignited. Heat propagation in these multilayers occurs in a self-sustained manner. In a self-sustained reaction, an external source is used to initiate reaction at one point, which mixes a small volume of reactants and generates heat locally. A self-propagating wave is generated by spreading the heat to other unreacted portions. The heat generated by these multilayers can be used as innovative heat sources for various joining applications. Reactive multilayers have found their way in various technological applications such as welding, brazing and thermal batteries. Of the available bilayer systems, Ni-Al bilayers are widely studied. Traditionally, they are produced by vapor deposition, ball milling or rolling. Vapor deposition is vacuum intensive, expensive and time consuming. Rolling produces films with low bilayer thickness and ball milling produces multilayers with irregular shaped particles and non – uniform mixing.

In this work, electroless nickel (EN) deposition, an autocatalytic chemical reduction technique, is used to produce Ni-Al bilayers, using a pure Al substrate. Al requires surface activation prior to deposition due to the presence of its inherent oxide layer. We show that by using a basic bath, this oxide layer can be removed and hence EN deposits can be obtained on aluminium without surface activation. Mass change is used to study the deposition kinetics and activation energies at two different pH values are extracted. Extending the work further, EN deposition is used to produce Ni-Al core shell structures at different pH values. Increasing the pH increases the Ni content and we optimise the deposition time and parameters. The obtained deposits are then converted into stable dispersion (inks) by dispersing them in various solvents. 1.5 wt.% sodium carboxymethylcellulose as a solvent gives a stable dispersion. This dispersion is printed on a glass substrate and the printed pattern will be used to demonstrate a sealing application.

Speakers

Meghna Narayanan

Metallurgical and Materials Engineering