With the development of nanotechnology, the combination of nanotechnology and coating technology can give full play to its comprehensive advantages, achieve excellent properties of mechanics, heat, electromagnetism and other aspects of materials, and meet the needs of structural properties (strength, toughness, etc.) and environmental properties (wear resistance, corrosion resistance, high temperature resistance, etc.). Nano ceramic coating has special physical and chemical properties of the coating, which makes the coating in the functional protection of conventional materials do not have the characteristics. Therefore, nano-ceramic coatings have broad application prospects in heat insulation, corrosion and rust prevention, insulation protection, self-cleaning and antifouling, absorption and energy saving, sealing and high temperature resistance, etc.

Properties of nano-ceramic coatings

Fracture toughness
Fracture toughness is a property index reflecting the resistance to crack instability propagation. There is a two-phase structure in the nano-ceramic coating, which is composed of the matrix phase obtained by the melting and solidification of the nano-particles and the incomplete melted nano-particles. When the crack expands to the interface between the unmelted or semi-melted particles and the matrix phase, the particles can not only absorb the crack growth energy, but also prevent and deflect the crack growth. In the conventional ceramic coatings, the interlamellar tissue bonding is poor, and the crack is easy to propagate along the interlamellar tissue, so the toughness of the nano-ceramic coatings is better than that of the conventional ceramic coatings.

hardness
Hardness is one of the important properties of ceramic coatings. The hardness of nano-coating has low dependence on the spraying process parameters and the heterogeneity of coating structure. The grain refinement makes the hardness of nano-ceramic coating significantly greater than that of micron ceramic coating.

Wear resistance
The improvement of hardness and toughness of nanostructured coatings is the main reason for the increase of wear resistance. During the wear process of nano-ceramic coating, there may be micro-convex shear or incomplete melting particles from the surface of the coating. These fine particles disperse in the lubricating oil film between the coating and the friction parts, and play the role of "micro-bearing", which reduces the friction coefficient of the coating and improves the wear resistance.

Bonding strength
The bond strength of ceramic coating includes the interface bond strength between coating and substrate and the bond strength of coating itself. The release of residual stress by unextended interlayer cracks and the higher flight speed of nanostructured feed during spraying are beneficial to improve the bonding strength. After nano spraying powder, the melting state of particles can be improved, and the pores of coating can be significantly reduced, and some pores are located in the deformed particles, which is helpful to improve the binding strength of coating.

porosity
Suitable coating pores are beneficial for lubrication friction and high temperature heat insulation workpiece, but harmful for corrosion resistance, high temperature oxidation resistance and high temperature erosion resistance workpiece. It is found that the porosity is related to the flame temperature and velocity. It is also related to the particle velocity. With the increase of particle velocity, the pore has a downward trend.

Thermal conductivity
Thermal conductivity is the main performance index of thermal barrier coatings, and decreases with the decrease of grain size. As the grain size decreases, the number of microscopic interfaces inside the coating increases and the distance between the interfaces decreases, so the mean free path of particles decreases during heat conduction, and the thermal conductivity of the material also decreases.


For more information on nano-ceramics, please click:IOTA ST3 Highest hardness Nano-coating in room temp. cured-IOTA (siliconeresin.net)
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