The effect of different plasma gas environments on vermiculite layer

Abstract

This work presents the first results of a broader research project aimed at the development or modifications of clays with increased properties for technological purposes and novel applications. This first step addresses on the chemical and physical properties of vermiculite treated with several ionised gasses in controlled plasma environments. Vermiculite is a 2:1 layered silicate with well-known chemical-exchange and surface properties useful in many industrial applications. The improving of these properties, in particular at the nanoscale level, can in principle enhance its application in known technological fields and extend its use in novel research and applicative areas as well as in nanotechnology. Vermiculite was treated with argon, air, water vapour and hydrogen radio frequency plasmas at room temperature for few minutes. As a general rule, plasma gasses induced various layer modifications. Chemical analyses evidenced a significant decrease in the interlayer cation content, especially for hydrogen and water vapour treated specimens. X-ray diffraction showed both a decrease of peak intensity and a halving of (001) reflection, thus suggesting the formation of layer defects along the layer stacking direction and onto (00l) planes as well. Thermal analysis showed modifications of the temperature-activated reactions induced by the plasma treatments. Finally Fourier Transformed Infra-Red spectroscopy (FTIR) showed that different bonding of H 2O occurred after the treatment, in particular for vermiculite treated with hydrogen plasma.