Five nanopowders—common electromagnetic shielding materials
At present, the mostly used is composite electromagnetic shielding coatings, composition of which is mainly film-forming resin, conductive filler, diluent, coupling agent and other additives. Among them, conductive filler is an important component. Silver powder and copper powder , nickel powder, silver coated copper powder, carbon nanotubes, graphene, nano ATO and so on are commonly used.
Carbon nanotubes have great aspect ratio and excellent electrical and magnetic properties, and exhibit excellent performance in electrical and absorbing shielding. Therefore, increasing importance is attached to research and development of conductive fillers as electromagnetic shielding coatings. This has high requirements on the purity, productivity and cost of carbon nanotubes. The carbon nanotubes produced by Hongwu Nano Factory, including single-walled and multi-walled CNTs, have a purity of up to 99%. The dispersion of carbon nanotubes in the matrix resin and whether it has good affinity with the matrix resin become a direct factor affecting the shielding performance. Hongwu Nano also supplies a dispersed carbon nanotube dispersion solution.
2. Low Bulk Density and low SSA flake silver powder
The earliest publicly available conductive coatings were patented in the United States in 1948 to make conductive adhesives made of silver and epoxy. The electromagnetic shielding paint prepared by the ball-milled silver powder produced by Hongwu Nano has the characteristics of small electric resistance, good electrical conductivity, high shielding efficiency, strong environmental resistance and convenient construction. Widely used in communications, electronics, medical, aerospace, nuclear facilities and other fields of shielding paint is also suitable for ABS, PC, ABS-PCPS and other engineering plastic surface coating. The performance indicators include wear resistance, high and low temperature resistance, heat and humidity resistance, adhesion, electrical resistivity, and electromagnetic compatibility.
3. Copper powder and nickel powder
Copper powder conductive coatings are low in cost, easy to apply, have good electromagnetic shielding effect, and are widely used. They are especially suitable for electromagnetic wave interference of electronic products with engineering plastics as the shell, because copper powder conductive paint can be conveniently sprayed or brushed on Various shapes of plastic are used to make the surface, and the plastic surface is metalized to form an electromagnetic shielding conductive layer, so that the plastic can achieve the purpose of shielding electromagnetic waves. The shape and amount of copper powder have a great influence on the conductivity of the coating. The copper powder has a spherical shape, a dendritic shape, a sheet shape and the like. The sheet is much larger than the spherical contact area and shows better conductivity. In addition, copper powder (silver-coated copper powder) is coated with inactive metal silver powder, which is not easy to be oxidized. Generally, the content of silver is 5-30%. Copper powder conductive coating is used to solve electromagnetic shielding of engineering plastics and wood such as ABS, PPO, PS, etc. And conductive problems, have a wide range of applications and promotion value.
In addition, the electromagnetic shielding effectiveness measurement results of electromagnetic shielding coatings mixed with nano-nickel powder and nano-nickel powder and micro-nickel powder show that the addition of nano-nickel powder can reduce the electromagnetic shielding effectiveness, but it can increase the absorption loss due to the increase. The magnetic loss tangent reduces the damage caused by electromagnetic waves to the environment and equipment and the harm to human health.
4. Nano ATO Tin Oxide
As a unique filler, nano-ATO powder has high transparency and conductivity, and has wide applications in display coating materials, conductive antistatic coatings, transparent thermal insulation coatings and other fields. Among the optoelectronic device display coating materials, ATO materials have anti-static, anti-glare and anti-radiation functions, and were first used as electromagnetic shielding coating materials for displays. Nano ATO coating materials have good light color transparency, good electrical conductivity, mechanical strength and stability. It is one of the most important industrial applications of ATO materials in display equipment. Electrochromic devices, such as displays or smart windows, are an important aspect of current nano ATO applications in the display field.
5. Graphene
As a new carbon material, graphene is more likely to be a new effective electromagnetic shielding or microwave absorbing material than carbon nanotubes. The main reasons include the following:
The improvement in the performance of electromagnetic shielding and absorbing materials depends on the content of the absorbing agent, the properties of the absorbing agent and the good impedance matching of the absorbing substrate. Graphene not only has a unique physical structure and excellent mechanical and electromagnetic properties, but also has good microwave absorption properties. When combined with magnetic nanoparticles, a new absorbing material can be obtained, which has both magnetic loss and electrical loss. It has a good application prospect in the field of electromagnetic shielding and microwave absorption.