Problems and suggestions associated with a progress of particle technology toward better-defined materials – engineered particulates – are presented.
In the first part of this review, coating technology was categorized from various angles, e.g., purpose, principle, methodology or instrumentation.
Dry, physical methods are divided into mechanical and sputtering, and spray coating inbetween. Typical machines and techniques are displayed. Emphasis is laid on the mechanochemical effects involved in the mechanical treatments. Deliberate introduction of mechanochemical reaction during coating is explained with some concrete examples.
Wet chemical methods are then described in detail. After explaining surface modification by surfactants or coupling agents, various colloid chemical routes are explained. Use of in situ reactions and related micro encapsulation are then referred.
Importance of characterization from non-conventional points of view, e.g., homogeneity of the coating between a lot, within a lot, within a treating chamber or vessel in a machine or even within a single particle is emphasized with concrete examples of analyses. Evaluation of chemical interaction at the host-guest interface and within a guest or shell layer are refined as well.
Examples of particle coating application are given from various area including electronics, optonics, magnetic materials and pharmaceutics. Representative case studies carried out in the author’s own laboratory are introduced. They will cover most of the categories of coating referred above.
Throughout the entire review, the author pays special attention on the microscopic and chemical views to fabricate and to evaluate the well-defined coated products to fulfill the concept of the modern engineered particulates.