Several engineering processes are powder based, ranging from food processing to engineering ceramic and composite production. In most of these processes, powders of different composition are mixed together in order to produce the final product, and this combining of powders of different density, shape, and surface properties is often very difficult. Mixtures may be quite inhomogeneous. This research focuses on a method of avoiding such problems, by coating individual particles of one material, with a relatively very thick layer of another powder material.
The study is limited to undertaking as a first step, the coating of large, nominally spherical particles with a more fine powder, and consists o f two aspects. Experimental work investigates the principle of coating such particles using a ‘snowball’ process, and presents supporting mathematical models to describe the process.
The experimental study has identified particular media (particles, binders and powder), and processing conditions (speed of rolling) most suited to successful coating of large sized particles as a means of demonstration of the principles. It has been found that the process of a single pass through the coating equipment can be modelled using a simple exponential expression, in which constants represent the total increase in diameter, and the rate at which this is reached.
With further experimentation, the experience gained may be applied to encapsulation of smaller sized ceramic particles with metallic matrix materials using suitably modified experimental equipment and procedures.