Papers by Author: Yu Jiang Wang

Abstract: Ferrite is frequently employed as a high-efficiency microwave absorption material (MAM). Herein, a novel and prospective high-temperature mechanochemical (HTMC) method was employed to fabricate pure-phase spinel zinc ferrite powders with a spherical structure. After that, the chemical compositions and structures, microscopic morphology, static magnetic characteristics, and microwave absorption properties of the powders were examined. The powder achieves a minimum reflection loss of -54.7 dB at a matching thickness of 4.4 mm, at which time the effective absorption bandwidth approaches 3.9 GHz. The superior microwave absorption ability of the powders is attributable to the favorable cooperative impact between dielectric and magnetic losses. Therefore, the as-prepared zinc ferrite powders can be utilized as high-efficiency MAM. The HTMC method has considerable potential for the large-scale preparation of high-performance MAM.

Abstract: A metal coating corrosion monitoring system (CMS) based on corrosion potential was introduced. It’s working principle, especially the design and selection of soft and hardware and the main technical specifications. The system has the characters of real-time monitoring of changes in corrosion potential status of coatings, automatically storing corrosion information and alarming according to corrosion degree in monitoring sites.

Abstract: We have studied the anodization behavior of an Al film electrodeposited on the 316L stainless steel (316L SS) substrate and demonstrated an effective approach to fabricate the micro-cavities on the conducting substrate through anodic aluminum oxide (AAO) template. The morphologies and composition of the electroplating aluminum layers and the micro-cavities were evaluated by SEM and energy dispersive X-ray analysis (EDXA) respectively. The results indicated that different shapes of cavities with size ranging from 0.6 to 2 mm were come into being directly on 316L SS substrates. The size of cavities could be controlled by adjusting the anodizing voltage and time. And the morphologies of the initial aluminum films were found to be critical factors for successfully anodizing the Al film on 316L SS surface.

Abstract: The corrosion behavior of Al-RE coating in copper accelerated acetic acid salt spray test (CASS) was studied by electrochemical impedance spectroscopy (EIS). Typical EIS spectral changes were clearly observed during the CASS process. The EIS was shown to be a very useful tool for studying corrosion resistance mechanism. Scanning electron microscope and X-ray energy dispersive spectroscopy were used to analyze the microstructure of Al-RE coatings before and after CASS test. The results revealed that the corrosion behavior of Al-RE coating could be divided into two different stages. In the first stage of CASS, there were two capacitive impedance semicircles in the complex plane plots. The high frequency semicircle responded to barrier layer, the low frequency semicircle responded to the electrochemical reaction of Al-RE coating. In the second stage of CASS, porous layer began to influence the electrochemical behavior.

Abstract: The most severe corrosion of offshore steel structure occurs in splash zone. There are many factors affecting the steel structure corrosion in the splash zone, such as corrosion problems caused by seawater and effect of impacted brought by the ocean wave. Considering the corrosion characteristics in splash zone and the corrosion invalidity behaviors of offshore steel structure, the Zn-15Al, Al-RE, Zn-Al-Mg-RE and FeBSiNb uncrystal coatings were prepared by automatic high velocity arc spraying. The different anti-corrosion behaviors of the four coatings were studied through the corrosion comparative tests and the microstructures analyzed of the coatings before and after the corrosion tests. The anti-corrosion coating systems suitable for using on surface of steel structure corrosion in the splash zone were found, which provided technique guarantee for extending the using life of offshore steel structures.

Abstract: A series of a-C:H films have been prepared by plasma-based ion implantation (PBII) with acetylene on AISI 321 substrates. The effect of negative bias pulse on the characteristics of these films was investigated. The structures of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The surface hardness was measured by microindentation tests. The results indicated that the characteristics of these films are strongly depended on the negative bias pulse. When the bias pulse ranges from -10kV to -40kV, the films are typical diamond like carbon (DLC) films, while the films deposited at -5kV are polymer films. The peak intensity ratio of the D-band to that of the G-band (ID/IG) of the DLC films changes with the negative bias pulse. The minimum value of ID/IG (1.02) was gotten at -10kV.

Abstract: In this paper, the micro pits were fabricated on 316L stainless steel surface, and the influence of pits topography on the platelets adhesion was investigated. For initial steel, large platelets agglomeration and long pseudopodia are observed. It is found that the pits on stainless steel surface can effectively prevent pseudopodia spreading; as a result the aggregation of platelets is fully restrained. The resistance of platelets adhesion increase with the coverage rate of pits area () on total steel surface.