2.Liquid phase coating: coating the powder in liquid phase by chemical method. Ordinary liquid phase coating is to layer the surface of ultrafine powder with metal oxide, metal, polymer and other unconventional modifiers. The chemical modification of the powder particles by liquid phase chemical method is characterized by graft polymerization and emulsion polymerization. Grafting polymerization is to pre-transplant some groups onto the surface of ultrafine powder, which can participate in the polymerization or play an initiating role, or stop the polymerization, and then add monomers and promoters to carry out the polymerization.

3.Microencapsulation: the encapsulation of a solid, liquid or gas in a natural or synthetic polymer material. A core-shell structure with a diameter of less than a few hundred microns and up to a thousand microns is formed. The key to microcapsule preparation lies in the film formation of the encapsulated core, sometimes the film must be solidified. There are 4 ways to prepare microcapsules: interfacial polymerization, physical mechanical, phase separation, emulsion solvent evaporation. Microcapsule coating of ultra-fine heat conducting particles is the use of microcapsule technology to layer an organic film on the surface of the powder, which changes the surface properties of the powder. The coating effect of this method is uniform and the coating efficiency of other coating methods is relatively low. Most microcapsules are covered by the wet process, although the effect is good, but the solvent is wasted and the cycle is long; while the dry microcapsule coating is relatively low cost, it is suitable for industrial production, and it is worth studying and improving.

The surface modification methods of powder by various surface treatment agents are collectively referred to as surface chemical modification. This method is the most widely used method of surface modification of ultrafine powder. It mainly uses the surface treatment agent and powder particles for adsorption and chemical reaction to achieve the purpose of powder surface treatment.