Plasma Surface Treatment Principles and Applications
Plasma surface treatment utilizes ionized gas plasmas to modify and enhance the surface properties of materials. The plasma is generated by supplying energy to a neutral gas to create a mixture of ions, electrons, reactive species, and ultraviolet radiation. The energetic species in the plasma react with and alter the chemical structure of the material surface.
There are several device configurations used to generate plasmas for surface treatment. Dielectric barrier discharge uses a high voltage AC power source applied to electrodes with a dielectric material separating them. The alternating electric field ionizes the gas to produce a non-thermal plasma discharge. Radio frequency inductively coupled plasmas utilize an RF power source to induce currents in a coil, which couples energy into a plasma. Microwaves can also be used to couple energy into a plasma cavity resonator. In general, these devices use a vacuum chamber, gas delivery system, plasma generator, and pumping system.
Plasma treatment has several functions and applications for industrial materials:
- Cleaning - Plasmas can remove organic contaminants, oxides, and absorbed gases from material surfaces through sputtering and chemical reactions. This activates and enhances adhesion.
- Etching - Plasmas chemically or physically etch surfaces to increase roughness, remove weak boundary layers, and expose fresh material underneath. This improves adhesion.
- Hydrophobicity - Plasma treatment with fluorine-containing gases deposits hydrophobic fluorocarbon films, reducing friction and improving fluid flow.
- Hydrophilicity - Oxygen plasma exposure increases surface energy and wettability through the introduction of oxygen-containing polar functional groups. This is useful for improving printability and coating adhesion.
- Sterilization - Plasmas containing oxygen and hydrogen peroxide neutralize bacteria and viruses, disinfecting surfaces. This has applications in food packaging and medical device manufacture.
In summary, plasma surface modification is widely used in industrial production of plastics, metals, textiles, and other materials. Carefully tailored plasma exposure provides a versatile tool for optimizing surface properties.