Enhancing adhesion of ceramic particles by deposition of polymer using supercritical CO2

Abstract

Ceramic particles do not have good adhesion characteristics. Adhesion is usually improved by the introduction of binders on the surface of these particles. However, conventional methods to coat ceramic particles rely on the use of toxic liquid chemicals. Potential candidates to substitute these chemicals include supercritical fluids which are commonly used in many industrial applications. Among its applications, supercritical carbon dioxide (scCO2) stands out as one of the most promising options. ScCO2 has a wide range of applications in industry, spanning from woodwork to pharmaceuticals. As a substitute to traditional chemicals used in industrial applications, scCO2 usually has major advantages because of its non-toxicity, non-flammability, low-cost, and recyclability. Moreover, its supercritical qualities (extremely low surface tension, high diffusivity, and liquid-like density) give scCO2 unrivaled performance when compared to traditional chemicals. Coating particles using supercritical carbon dioxide is commonly used in industry to alter the substrate’s chemical and physical properties. Due to its economic, environmental and physical benefits, scCO2 based coating is a very sought-after method. Despite their wide usage in industry, most processes currently used to coat particles are multi-step procedures and often complicated procedures. A different issue is that bare ceramic particles suffer from low adhesion potential. Thus, to address both these issues, an easy one-step method using Poly(vinylidene fluoride) to coat small LiCoO2 ceramic particles with the assistance of supercritical carbon dioxide is proposed. Three parameters for the process were optimized: temperature, pressure, and dissolution time. The optimal parameters for the process were determined to be 140 °C, 150 bar and 6 hours. Visual evidence of coating was obtained using Scanning Electron Microscopy. The presence of fluorine presence on the surface of the ceramic particles, which is indicative of the polymer, was verified using Energy Dispersive X-ray Spectroscopy. Fourier Transformed Infrared Spectroscopy and X-ray Diffraction were employed as tools to check for chemical integrity of the polymer. To confirm that adhesion was improved, pellets were manufactured with coated ceramic powders and were tested under compression using a universal mechanical testing system. Results show that the pellets made from powders coated under optimal conditions were not only uniformly coated but were also stronger when compared to pellets of products coated under non-optimal conditions and sub-critical conditions.