With a thickness of 33 microns, it can shield 99% of the incident electromagnetic waves
Our research team has developed high-performance electromagnetic shielding materials
◎ Li He, reporter of this newspaper
In daily life and work, electromagnetic radiation will be generated during the operation of electronic equipment, which may bring adverse effects to people's health, and electromagnetic interference between devices will also seriously affect the performance of electronic equipment and its normal operation. Therefore, the development of new electromagnetic shielding materials, especially high-performance electromagnetic shielding materials, is the key to solving electromagnetic pollution.
Nowadays, a variety of electronic equipment is increasingly used in people's life and work, but electronic equipment in the process of operation will produce electromagnetic radiation, may bring adverse effects to people's health, electromagnetic interference between the equipment will also cause signal interception, data loss, etc., seriously affecting the performance of electronic equipment and its normal operation. Especially with the development of the Internet of Things, automatic driving, and wearable devices, electronic devices are becoming more and more complex, smaller and smaller, and have higher and higher accuracy requirements, and electromagnetic interference shielding is crucial to ensure the normal operation of these highly integrated and high-power electronic devices.
The development of new electromagnetic shielding materials is the key to solving electromagnetic pollution, especially ultra-thin, lightweight high-performance electromagnetic shielding materials with excellent mechanical strength and reliability. Recently, the team of Heng Liping, a researcher at the School of Chemistry of Beihang University, developed a reduced graphene oxide/liquid metal (S-rGO/LM) heterolayered nanocomposite with an ultra-lubricated interface, which can be used for high-performance and stable electromagnetic shielding. The relevant research results were published in the international academic journal American Chemical Society Nano.
Research and development of high-performance flexible electromagnetic shielding materials using graphene
Electromagnetic shielding materials are functional materials that can attenuate the propagation of electromagnetic wave energy through absorption, reflection, etc., so as to effectively suppress electromagnetic interference and pollution.
People hope that when electronic equipment is working, it is neither interfered by external electromagnetic waves, nor radiates electromagnetic waves to interfere with other equipment or endanger human health, so when electronic devices are running, the electromagnetic waves generated by themselves need to be absorbed, and the external incident electromagnetic waves need to be reflected or absorbed. Copper, aluminum and other metals are commonly used electromagnetic shielding materials, but they are easy to be corroded, dense, heavy, and mainly reflect electromagnetic waves, which will cause secondary electromagnetic pollution. In particular, traditional metal materials are not flexible and are difficult to be applied in the field of flexible electromagnetic shielding.
Gallium-based liquid metal (LM) is currently the most widely used material in flexible electronics manufacturing, mainly due to its physical properties such as low melting point, low viscosity, high electrical conductivity and thermal conductivity. Hengliping said that with the gradual deepening of the research on gallium metal and gallium-based alloy liquid metal materials with room temperature fluidity, it has shown considerable potential in the field of flexible electromagnetic shielding materials.
However, the existing gallium-based liquid metal electromagnetic shielding materials generally need to be blended with insulating polymer substrates to obtain electromagnetic shielding materials with certain mechanical strength and practical applications. The better the conductivity and magnetic permeability of the material, the higher the shielding effect on electromagnetism, and the gallium-based liquid metal electromagnetic shielding material blended with the insulating polymer substrate will lose the conductivity of gallium-based liquid metal, so that the electromagnetic shielding performance cannot reach the best level. The use of a substrate that also has ultra-high conductivity to construct liquid metal flexible composites is the key to improving the performance of liquid metal flexible electromagnetic shielding composites. As a result, graphene entered the sight of Hengliping's team.
Graphene has excellent optical, electrical and mechanical properties, and can maintain good conductivity in itself. Graphene oxide (GO) also plays a good bridging role for gallium-based liquid metals, so a continuous and complete conductive network can be formed inside the S-rGO/LM material. With a thickness of only 33 microns, the material can shield 99% of the incident electromagnetic waves, and the electromagnetic shielding efficiency of the X-band is high.
It can be used as an anti-icing and de-icing functional material
Polydimethylsiloxane (PDMS) has heat resistance, cold resistance, waterproofness, thermal conductivity and good chemical stability, good electrical insulation and hydrophobic properties, and can be used for a long time under -50 °C-200 °C. At present, PDMS has been widely used in insulation lubrication, shockproof, oil dust protection and heat carrier.
The team first dipped the S-rGO/LM material in a diluted PDMS solution, and then rotated it to apply silicone oil to achieve super-lubricating properties. Hengliping said that thanks to the stability of the material itself and the synergistic protection of the ultra-lubricated interface, the S-rGO/LM material can still maintain good electromagnetic shielding ability after severe mechanical wear at the extreme operating temperature.
In addition to excellent electromagnetic shielding properties, S-rGO/LM materials also offer excellent thermal management properties. Experiments have shown that the surface temperature of S-rGO/LM materials can reach 1.100°C within 40 seconds under 47 solar light power (5 mW/cm²). This shows that in low temperature areas, S-rGO/LM can also be used as a material with anti-icing and de-icing functions. (Science and Technology Daily)