Papers by Author: Yao Sun

Abstract: A new kind of the electromagnetic shielding composite coatings with high performance was prepared using the Ni-Cu-coated glass fibers and nickel powders as fillers and using epoxy resin as binder. The effects of the fibers on the conductivity and electromagnetic shielding effectiveness of the coatings were studied. The study results show as follows: 1) when the optimum ratio of the fillers to epoxy resin is 4:1, the coatings containing 6 wt% the Ni-Cu-coated glass fibers has best conductivity and electromagnetic shielding effectiveness; when the coating layer thickness is 300 μm, the shielding effectiveness of the coatings is up to 43.71-52.31 dB and increased an average of 13.94 dB compared with the nickel powders/ epoxy resin electromagnetic shielding coatings in the frequency range of 0.3-1000 MHz. This offers a new idea to enhance the added value of the glass fibers and the prevention of electromagnetic environmental pollution.

Abstract: Coal gangue is a kind of solid waste which is discharged from coal mining and coal washing. Dumped gangues do not only take a large land occupation but also pollute air and water. Treatment and utilizing of coal gangues has become the major issue for the coal industry to resolve. As major experimental material in this study, the coal gangue from Dawukou, Shizuishan, Ningxia province, China had been analyzed to have high-alumina content, and it could been used as alumina constituent for the preparation of sulphoaluminate cement. In this paper, alite-sulphoaluminate cements were prepared at 1330°C using coal gangue, limestone and gypsum as major main materials, fluorite and barite as minor materials. The result shows that major clinker minerals of the cement are sulphoaluminate, alite and belite, while major hydrate is ettringite, compressive strength of the cement is 48.9MPa after 7d. These experiments provide a new method of coal gangue comprehensive utilization.

Abstract: A new kind of the micron-sized flaky silver-coated copper powder was prepared by electroless silver plating in this paper. Its plating structures were characterized by XRD, SEM and EDS. And a new kind of the electromagnetic shielding composite coatings containing 60 wt% the micron-sized flaky silver-coated copper powders and 40 wt% epoxy resin was prepared. Its electromagnetic shielding properties were analyzed by coaxial transmission line equipment. The study results show the micron-sized flaky silver-coated copper powders are composed of 91.35 wt% Cu and 8.65 wt% Ag and have high width-thickness ratio and crystal structure characteristics. In the frequency range of 0.3-1000 MHz, the shielding effectiveness of the coatings is up to 70.15-77.46 dB and increased an average of 22.18 dB compared with the coatings containing 60 wt% micron-sized flaky copper powders when the coating layer thickness is 300 μm. It is seen that the electroless silver plating method effectively improves the inoxidizability, conductivity and electromagnetic shielding properties of copper powders.

Abstract: A new kind of Ni-Cu-coated calcium-magnesium silicate whiskers was prepared by electroless plating and characterized by EDS, SEM and XRD. And the preparation and shielding performance of a new kind of Ni-Cu-coated calcium-magnesium silicate whisker/nickel powder/epoxy resin electromagnetic shielding coatings were explained. The study results show the Ni-Cu-coated whisker with micro-sized spinal structure contains 12.4 wt% Ni and 1.35 wt% Cu. When the coating layer thickness is 300 μm, the shielding effectiveness of the coatings containing 4 wt% Ni-Cu-coated calcium-magnesium silicate whisker is up to 39.24-48.52 dB and increased an average of 10.38 dB compared with the nickel powder/epoxy resin electromagnetic shielding coatings in the frequency range of 0.3-1000 MHz. This offers a new idea to raise the levels of the comprehensive utilization of mineral resources and the prevention of electromagnetic environmental pollution.