A temperature programmed desorption study of non-thermal plasma modified γ-Al2O3

In this paper, the effect of non-thermal RF plasma modification on the point of zero charge (PZC) of gamma-Al2O3 has been explored. Samples of alumina were first modified with air, CO2, N-2 or Ar plasma and then measurements of the PZC were taken. In order to determine the mechanism behind PZC shift, the surface area and crystal phase were measured for each sample using nitrogen physisorption (BET) and X-ray diffraction (XRD). Additionally, the presence of plasma gas on the surface of alumina was determined qualitatively using a modified temperature programmed desorption (TPD) technique. Air and CO2 modification of alumina powder decreased the PZC from 7.48 to 4.86 and 6.57 respectively. However, N-2 and Ar modification did not result in any PZC shift. BET and XRD measurements showed no significant surface area or phase changes occurred due to non-thermal plasma modification. TPD profiles for air and CO2 modified samples showed new peaks corresponding to the adsorption of plasma ions on the alumina surface. These results demonstrate that PZC changes in a support after plasma treatment is caused by the adsorption of plasma species. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.