Wan Jun Hao

Electromagnetic Wave Absorption Properties of Cement Filled with Carbon Black

Using the dielectric loss property of carbon black , cement-based composites were prepared by introducing carbon black into cement. The reflection losses were studied using arched testing method in the frequency range of 2~18 GHz. The results showed that the absorption properties were improved in high frequency. The filling ratio of carbon black as well as the thickness of samples had influence on the absorption properties. The lowest reflection loss of-10.6 dB was obtained at 18 GHz of 5wt.% carbon black filled cement with thickness of 20mm. The new material can be used for building indoor electromagnetic radiation protection.

Double-Layered Cement Composites with Superior Electromagnetic Wave Absorbing Properties Containing Carbon Black and Expanded Polystyrene

This paper reported that, using the method of double layer composite successfully prepared high performance of electromagnetic wave absorption materials. Such a composite is composed of a cement matching layer filled with expanded polystyrene (EPS) beads and an absorbing cement layer made of EPS beads and carbon black. The samples were tested by arching method in the frequency range of 8~18GHz. The reflectivities were revealed to be excellent, the lowest being-17dB. The new material can be used for building indoor electromagnetic radiation protection.

Electromagnetic Wave Absorption Properties and Mechanical Properties of Aramid Fiber Reinforced Cement

To solve more and more serious electromagnetic radiations, cement-based composites were prepared by introducing aramid fiber into cement. The reflection losses were studied using arched testing method in the frequency range of 1.7~18 GHz. The results showed that the absorption properties and mechanical properties were all improved preferably. The mechanisms were discussed, which indicated that the space network structure lapped into mutually by aramid fiber played an important role. The filling ratio of aramid fiber as well as the length of fiber had influence on the absorption properties, the breaking strength and the compressive strength of cement. The lowest reflection loss of -12.2 dB was obtained at 18 GHz, the effective absorption bandwidth (less than -8 dB) reached 9.15 GHz ,and the compressive strength was twice than that of cement paste when the specimen was filled with 8 vol. % aramid fiber with length of 3mm.

Preparation and Electromagnetic Properties of CIP/ZnO Composites

CIP/ZnO electromagnetic functional composites with core-shell structure were prepared by chemical precipitation method, and then the morphology, structure and electromagnetic properties in 2-18GHz were characterized by X-ray diffraction, scanning electron microscopy and vector network analyzer, respectively. In process by controlling the component ratio between core and shell, it has been found that the more ZnO particles were coated on the CIP surface, the smaller electromagnetic parameters become. Based with the Electromagnetic Wave Absorption (EMWA) Theory, the composites could prepare EMWA building coating by monolayer design, the theoretical simulation results show that the minimum RL of CIP/ZnO composites is-10.25dB, better than pure CIP particles, exhibiting excellent EMWA properties in 2-18GHz. The magnetic loss of CIP and the dielectric loss of ZnO were the main mechanisms of EMWA for the CIP/ZnO composites, which could be used for electromagnetic radiation protection.

The Thinning Study of λ/4 Type Absorber Made of Carbon Fiber Membrane and Gypsum Board

large thickness of λ/4 type absorber has been an important issue, which affects its application and urges to address. In this paper, λ/4 Type absorber made of carbon fiber membrane, instead of resistive film, and Gypsum board. Its designed for thinning and we took Simulation analysis and experimental testing for it. Results show that, while carbon fiber membrane with a length of 2mm and content of 2.8%, λ/4 type gypsum composite absorber has better absorbing in S-band. Compared with the resistive film, absorber achieved thinning of 10.6%.

The Design and Preparation of X Band Absorbing Insulation Coatings

According to the principle of electromagnetic wave absorption, functionally reforming thermal insulating materials for building, through designing and theoretically simulating of the λ/4 model, using carbon fiber film, the article has successfully prepared insulation coatings for X-band electromagnetic wave absorption. Result shows, with the thickness of 3.0 mm in 8 ~ 12 GHz band, 100% of bandwidth below-10 dB can be reached. New materials can be used such as the surface of the thermal insulation of buildings and X-band electromagnetic interference protection.

The Design and Preparation of Composite Gypsum Boards Absorber Based on Phase Modulation Membrane

According to the principle of electromagnetic wave absorption, functionally reforming thermal insulating materials for building, through designing and theoretically simulating of the λ/4 model, the article has successfully prepared EPS composite gypsum boards for electromagnetic wave absorption. The result shows that, a maximum absorption of-18.7dB at 3GHz and 85% of bandwidth below-10dB was achieved under following conditions: using 380Ω/□ resistive film, specimen thickness of 1.50cm. However, by using phase modulation membrane (PMM),it achieved a maximum absorption of-20dB and 100% of bandwidth below-10dB. This new composite materials can be used for electromagnetic interference protection for WLAN and indoor electromagnetic radiation pollution control.

The Impact of λ/4 Type Absorber Protective Layer 's Thickness on Absorbing Properties

Abstract .Electromagnetic radiation affects normal operation of electronic devices and causes harm to human health, the use of electromagnetic radiation protective material, especially the electromagnetic wave absorption material, is an effective method for interference control and radiation protection, λ / 4 type dielectric absorber with a simple and practical nature, the protective layer should be added to ensure its durability in practice, this article discusses the gypsum board as the substrate, the thickness of conventional protective layers material impacts on the absorbing properties. Studies show that: the position of absorption peak moves to lower frequency with increase of the protective layers thickness by the theory and experiment, this paper puts forward the protective layers thickness criterions impact on the absorption characteristics, the thickness less than 0.05 cm has little effect on absorption characteristics in S band , which can simplify theoretical calculation and be convenient to select a material; when the thickness of the protective layer has a significant effect on absorption, the relationship among the parameters of absorber can be found according to theoretical simulation, thereby reducing or eliminating the impact of protective layer thickness on absorption characteristics.

Broadening Design and Preparation of MDF Absorber for Electromagnetic Pollution Control in S-Band

This paper reported a new type MDF absorber of high absorption and Broadband was successfully prepared, according to the Electromagnetic Wave Absorbing Theory, by means of the theoretical design and simulation analysis by using MDF as the dielectric material and And with the resistance film composite. Results shown that the resistance of resistive film was 195Ω/□, the monolayer combined sample with thickness as 1.4cm in 2~4 GHz frequency bands, the range of absorbing over -20dB could achieve 50%, and all absorption could exceed -15dB in the whole S-band, the maximum absorption peak was -25dB, moreover, the absorption bandwidth of MDF was more than λ/4 Type EWM-absorber. The new materials could be used to improve residential electromagnetic environment and control pollution.

Study on Magnetorheological Fluid Damper

Magnetorheological Fluid Damper has recently received considerable attention. This paper is focused in typical models, the strongpoints and application status of magnetorheological damper. In the meantime, the paper introduce the basic working principle of the smart passive damper using magnetorlogical fluid damper and the Faraday law how to be used in the magnetorlogical fluid damper with the electromagnetic induction part.