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New world of plasma research
Meet the team at Deakin making it happen.
Dr Xiujuan Jane Dai
+61 3 522 72427
Plasma can be used to make better performing materials and processes to address challenges in key research areas, such as energy capture or energy storage, biomedicine, lighter and stronger composites and textile and food industries.
As the fourth state of matter, plasma shows its splendour in nature, e.g. shimmering aurora and lightning flashes; but plasma also brings convenience to human life, e.g. plasma TV and fluorescent lamps. It is at the heart of Tokamaks for fusion energy and also in many environmentally friendly and more benign scientific and industrial applications.
What is plasma and how does it work are questions often asked by newcomers to the technology. The plasma, used by our group, is a partially (or weakly) ionised gas generated by an electric or electromagnetic field. It is electrically neutral (the number of positive charges is equal to the number of negative charges). It is a 'cold' or nonequilibrium plasma where electrons get energy directly from the field and so can have a much higher temperature (~104 K) than the gas, including the ions, which have the ambient temperature of 300 K. Therefore it is possible to avoid thermal damage of materials during the process.
In this weakly ionised gas, the electrons mostly collide with neutral molecules and atoms which results in ionisation, excitation, and dissociation (gas phase reactions). During these reactions, various reactive species are generated, including charged particles (positive and negative ions and electrons), free radicals, neutral particles, and UV photons. These species will react with the material surface (top down) so that the surface/interface will be changed (gas-interface reactions), or the reactive species will link and grow into a nanostructured material (bottom up).
In a plasma process, the electron energy distribution function (f(ε)) and electron number (Ne) play critical roles. They are determined by the external parameters (frequency, power, pressure etc.), and they determine what chemically reactive species are generated. The reactive species are chosen to match the application (or final product). The gas used may also be the vapour of a monomer, typically a larger chemical unit containing a desired functional group.
The key issue and challenge is how to design the parameters, and hence select and control the reactive species for a specific application. This demands a deep understanding of plasma physics, plasma chemistry, material science, biology, devices, and requires different experts working harmoniously together.
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