Investigation On Electrical Conductivity And Electromagnetic Shielding Effect Of Boron Carbide Composite Material

Boron carbide has many excellent properties, such as low density, high hardness, chemical stability and the neutron absorption characteristics. It has been applied to many industrial fields, such as reactor control rod material, nuclear shielding material, bulletproof armor and anti-corrosion materials. But the application of boron carbide and composites mainly concentrated in the physical properties and neutron absorption properties, and the understanding and application for the conductive mechanism are basically stuck in the experimental stage. Boron carbide has excellent physical properties, electrical conductivity of the semiconductor and the similar structure of carbon black. We can use these characteristics and produce the multifunctional composite material by mixing with a suitable rubber base. This paper discussed the resistance, thermal conductivity, dielectric constant, piezo-resistive properties, voltage characteristics, thermal stability, electromagnetic shielding and absorbing performance of the boron carbide/butyl rubber composites are affected by the process factors, component content, pressure, temperature, and voltage. The research priorities are conductivity and electromagnetic shielding properties of boron carbide/butyl rubber composites.The repeatability conductivity of the polymer is essential during the prepared processing. The specific proportion was determined by the orthogonal analysis. The changes of the resistivity were measured by the electrode presented in the composite during the prepared processing. We analyzed the different batches, components, curing pressure, curing temperature, mixing time and speed of the roller effect on the structure and properties of the conductive network. The optimal process conditions of the conductive properties were determinedThe conductivity of the boron carbide/butyl rubber composites under pressure, temperature and voltage effects had been studied. The resistivities of the composite material reduced with the increasing of the content of boron carbide were found and had a significant linear relationship. The resistivity of boron carbide composite was the minimum value1018Ω·cm when the content of the boron carbide was60%wt. The resistivity of the carbide composite under pressure was tested. The changes of the boron carbide composite resistivity affected on the boron carbide content, pressure and the number of circulating pressurized were analyzed. The temperature of experimental data showed that the boron carbide composites had PTC (Positive Temperature Coefficient) and NTC (Negative Temperature Coefficient) effect, and the mechanisms were discussed and explained. The voltammogram results indicated that boron carbide composite had a "switch" feature. The mechanisms for its generation were studied according to the Joule heat phenomenon in the test. The dielectric constant, thermal conductivity and Seebeck coefficient of the boron carbide composite were tested; the test results had proved that the composite had the characteristic of the P-type semiconductor and excellent electric performance. The thermal gravimetric analysis showed that the thermal stability of boron carbide composites get improved for the adding of the boron carbide. The two-dimensional equivalent circuit and three-dimensional lattice model were raised. The conductive mechanism of the boron carbide/butyl rubber composite affected on the temperature, pressure and voltage are discussed. The explained scope and shortcomings of the model were analyzed.The experiments of the electromagnetic shielding performance showed that the composite had shielding and microwave absorbing properties, and studied the influence of the boron carbide content and sample thickness on them. Combined with the classical electromagnetic theory, the theory of shielding and microwave absorbing properties was analyzed. The shielding efficiency of the sample which has60wt%boron carbide content and2mm thickness is up to-4.6dB in the1800MHz. Therefore the shielding efficiency of the sample which has20wt%boron carbide content and2mm thickness is up to-23.7dB in the5.9GHz.