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Innovative Materials Processing Using Non-Equilibrium Plasmas

Final Report Summary - IMPUNEP (Innovative Materials Processing Using Non-Equilibrium Plasmas)

Plasma is sometimes called the fourth state of matter. It is created by adding energy to a gas so that some of the atoms in the gas lose electrons, therebey becoming ionised. Once in that state it is possible to accelerate and/or deflect them using electrical or magnetic fields. When incorporated in to a coating process, the accelerated species can impart advantageous advantageous into the growing surface film, such as higher density and the creation of non-equilibrium phases. Whilst these advantages have been widely used in recent decades to obtain enhanced coatings, the method has rarely been used to create bulk materials.

This ERC Advanced Grant utilised plasma creation to achieve improvement in bulk material properties in a range of types of plasmas; these were in-liquid plasmas, vacuum plasmas, and atmospheric plasmas.

The in-liquid plasma studies utilised the electrolytic plasmas which create localised discharges on the surface of metals, converting them to, for example, oxide states. We have improved our understanding of this method and we are now able to create bulk material shapes in metallic form and convert them into bulk ceramics, or metal-ceramic composites.

Our work on vacuum plasmas has investigated a range of metal and oxide coatings. The reseach focus on this has been on the effect of thickness on the morphology, phase and properties of the coatings. For example, we carried out extensive studies into plasma-deposited transparent conducting oxides, revealing unusual strcutural characteristics. Also, we have looked at the plasma-assisted deposition of hydroxyapatite (HA), a synthetic form of bone, to understand the influence of the plasma process on the structure and crystalline state of HA.

The atmospheric plasma studies have focused on controlling the wettability of carbon fibres used in carbon-fibre composite bulk materials with the objective of improving the bonding to the matrix phase of the composite.

The project has involved leading-edge plasma process development (including for example pulsed-plasmas), as well as advanced diagnostic and control systems. In addition, advanced analysis and characterisation methods have been judiciously implemented to fulfill the evaluation requirements for the different material systems studied.