Plasma Enhanced Chemical Vapor Deposition on Particulate Solid‐State Materials for Improved Powder Processing

Abstract

Abstract The surface of fine lactose powder particulates was modified by direct‐plasma exposure in a radio frequency (RF) discharge, in a mixture of oxygen and hexamethyldisiloxane (HMDSO) diluted in argon. Besides, the RF power (100–500 W) and the HMDSO flow rate (0–68 sccm) at constant oxygen‐to‐HMDSO flow rate ratio of 10 was varied in this study. Apart from the relatively high pressure of 2 mbar, the plasma process adopted is very much alike the plasma enhanced chemical vapor deposition of silica‐like material descending from the plasma‐chemical reaction of oxygen and HMDSO. With respect to the processability of powders in production lines to be solely gravity‐driven, as for instance in the event of dye‐filling, compression ratios (based on the powder bulk and mass density) were measured for solely gravity‐driven filling of a graduated glass. A jolting volumeter was used to provide the compressibility of the compacted powder bulk. Higher compressibility of about 20% (improvement rate) was found for both experimental series: variation of HMDSO flow rate and variation of the discharge power. In both cases, an enhancement of the flowability of the powder was found to cause the compressibility improvement.