A particle may be defined as a single entity comprising part of a solid or liquid discontinuous phase. According to this definition a particle may have any size. It is common to refer to a suspension of particles in a gas as an Aerosol and to particles in suspension in a liquid as a sol (hydrosol if the liquid is water). Clearly, when we are considering the stability of a suspension, particle size becomes important. For example, a suspension of 1 μm (one micrometer = 1 μm = 10–6 m) particles in air may remain stable for many minutes, whereas 100 μm particles will settle out in seconds. Similarly, flow rates of particles from hoppers and bins, reaction rates of particles in reactors, separation efficiencies in filters and separators and most other aspects of particle behavior depend on particle size.
Methods of producing particles, which meet a predetermined specification, expressed in terms of size distribution and shape distribution, by such processes as are appropriate including growth from the liquid phase and the gas phase.
Methods of producing composite particles by such processes as agglomeration and encapsulation.
The relationship between bulk properties of assemblies of particles and the measurable parameters of the individual particles.
The relationship between such properties as size, shape, their distribution and optimal range for the variables, which control production, handling, processing and utilization of particulate material.
Overall design of particulate processes. This could include the use of microprocessor and automatic control in general, in conjunction with on-line measurement devices.
Health and safety considerations of the production, handling, processing and utilization of particulate materials including, for example, explosion risks and inhalation risks.