Dry coating method for surface modification of particulates

Abstract

Surface modified particulates have many potential industrial applications, ranging from new technologies such as rechargeable batteries and fiat panel displays to a wide variety of unit operation processes such as dispersion, transport and handling, and separation of particulate systems. Owing to environmental constraints, there has recently been a strong interest in the development of dry methods (chemical and/or water free) for particulate coatings. This paper reports on the feasibility of a novel dry method based on a magnetically assisted impaction process for synthesis of surface modified particulates. In this process magneticparticles in the coating system accelerate and collide with the core and secondary particles to form composite particles. Experiments have been conducted on a variety of particle systems such as Si0₂–SiC, CoO–Ni(OH)₂, Al₂0₃–PMMA, and Ti0₂–Al₂0₃. The composite particles were subjected to high frequency ultrasound so that weakly adhering particles could be removed from the surface. The experiments showed that adherent uniformly distributed coatings could be formed in a wide variety of systems. Magnetically assisted impaction coatings were found to be more adherent and possess a higher surface coverage than coatings produced by standard blending methods. Preliminary experiments have also been conducted to investigate the effects of variations in materials parameterssuch as hardness of core and secondary particles.