As a method to strengthen and modify the solid surface, the coating has been widely used in mechanics, electronics, chemical engineering, aerospace and other fields. With the development of science and technology, materials are required to serve under special conditions, such as ultra-high temperature, ultra-low temperature, ultra-high pressure, high vacuum, strong redox or corrosive environment, and environment in which exist radiation, sound absorption signal shielding, point load, etc. All these situations put forward higher requirements for traditional coating.
Studies have shown that when a certain geometrical size (grain size, diameter, film thickness, grain size) of a certain phase in a material is nanoscale, the characteristics of the material tend to mutate. Due to the effects of surface effects, small size effects and quantum effects, many physical and mechanical properties of nanomaterials appear to be different from those of macroscopic materials, such as high strength, high toughness, high specific heat, high thermal expansion rate, high electrical conductivity, high permeability, high wave absorption, etc. These properties have become an important research field at the forefront of the development of science and technology in the 21st century. Nano-materials are combined with surface coating technology to make nano-coatings, which is conducive to expanding the application of nano-materials, and at the same time it can further improve coating technology.
The nano-material coating is a nano-composite system coating that contains nano-material in the surface coating. Nano-coatings can be implemented either on traditional materials or powder particles and fibers. It is one of the hot topics in nanomaterials science research in recent years. The main researches are focused on functional coatings, including coating that on traditional materials, fiber coating and particle coating. The performance of nano-coating is reflected in the following aspects:
1. Adding nano-phase can increase the hardness and wear resistance of the coating, and maintain high toughness.
2. Improve the material's high temperature resistance and oxidation resistance.
3. Improve the anti-corrosion properties of the substrate to achieve the purpose of surface modification and decoration.
4. Achieve the effect of reducing the friction coefficient to form R lubricant material.
5. Nanomaterial coatings have widely varying optical properties and excellent electromagnetic properties.
Nano-coating can be divided into the following categories according to the composition:
1. 0-0 composites. It refers to nano solids that composed of nanoparticle in different components, different phases or different types. Usually it is obtained by in-situ briquetting, phase transformation and other methods. Also, it has nano-non-uniform structure, also known as aggregate type.
2. 0-3 complex. It means that nanoparticles disperse in a conventional three-dimensional solid. In addition, mesoporous solids can also be used as composite precursors to physically or chemically fill nanoparticles in mesopores to form mesoporous composite nanocomposites.
3. 0-2 composites, that is, the nano-particles are dispersed in two-dimensional thin film materials, which can be divided into uniform dispersion and non-uniform dispersion, called nano-composite thin film materials.
The 0-0 composite, 0-3 composite nanomaterial coating is still far from commercialization. With the help of traditional coating technology and the addition of nano-materials, 0-2 compounding nano-composite coating can be obtained, so that the function of the traditional coating can be greatly improved. Also, there is no need to add too much cost to the technology, so it has been rapidly developed in recent years.