Materials Science Forum Vols. 675-677

Abstract: P-type microcrystalline silicon films prepared by electron cyclotron resonance（ECR）PECVD are studied here. Silane diluted with Ar (SiH4/Ar=1/19) is used as a source gas and diborane (B2H6) diluted with H2 (100ppm) as doping gases. The effect of flow rate of doping gas on the microstructures and electrical properties of the films were investigated. Raman spectroscopy and X-ray diffraction were used to determine the film structure; AFM was employed to characterize the film surface topography; Hall measurements were carried out on the doped films to determine the carrier type, carrier concentration, and Hall mobility. The optical quality was measure by transmission spectrum.

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: In this study, 304 stainless steel particles were deposited on IF steel substrates by cold dynamic spray technology. The effect of gas temperature on bonding features and deposition critical velocity were studied and compared. The results demonstrated that the successful bonding between 304SS particle and substrate could be attributed to the adiabatic shear instability mechanism, increasing gas temperature led to enhance the particle interface bonding, deduce the deposition critical velocity, and also increase both deposition efficiency and density of coatings.

Abstract: In this paper, WC-Ni60 alloy composite coating with different contents of WC particles was prepared on the 45steel substrate by high frequency induction cladding. The Composition and microstructure were characterized by X-ray diffraction (XRD) and electron probe X-ray microanalysis (EPMA), the abradability and hardness were tested by UMT-2 tribometer and HV-50A durometer, respectively. The results showed that the hardness and wear resistance of coating were enhanced with the increasing of WC content. WC-Ni60 coating obtained the best wear resistance with the content of 50% WC. The hardness of the coating got the highest when the content of WC was 60%, but wear resistance decreased. The WC-Ni60 coating was reinforced for various hard phases and the metallurgical bonding layer about 10μm was formed between coating and 45steel substrate.

Abstract: Detailed studies on Photoluminescence (PL) of porous silicon (PS) with copper deposition were presented. PS was prepared via double electrobath, and then copper was deposited on PS surface by chemical plating. Atomic force microscopy (AFM) measurement indicates that there are different surface morphologies of PS samples with hemispherical, mountain, and tubes-like shape in different etching conditions. PL results show that the PL spectrum intensity of PS with Cu post-deposition increases 50% and do not decay after being laid 4 months than that of PS with pre-deposition. And the peak position from the PL spectrum with Cu deposition has a 14nm blue shift due to the surface stress effect of Cu to PS.

Abstract: TiN coating with thickness of 2.5μm was deposited on high-speed steel (HSS) substrate by pulsed bias cathodic arc ion plating. The surface and cross-section morphologies, composition depth profile and phase structure were characterized by FESEM, GDOES and XRD, respectively. Scratch test for adhesion evaluation, microhardness test for hardness measurement, and potentiodynamic polarization for corrosion resistance test were used. The results show that the TiN coating exhibits smooth surface, dense columnar grain structure and an obviously preferred orientation of TiN(111). The adhesion of the coating to substrate is exceeded more than 100N. The hardness of the coating is about 26 GPa. The low corrosion current density (Icorr) and rather high corrosion potential (Ecorr) value imply that the TiN coating displays a good corrosion resistance in 0.5mol/l NaCl solution. However, pitting is still existed due to the defects in the coating.

Abstract: The Si3N4 protective coating has an important impact on avoiding melting silicon from contacting with the crucible wall directly. A mixed Si/Si3N4 layer was formed on the interface of silicon and Si3N4 coating, and the declination of N content was observed in this mixed layer. With the ingots condition of 1500oC for 2 h, the large Si3N4 and SiC particles appeared in the mixed layer and the formation mechanism was discussed. The Si3N4 coating had significantly increased the lifetime of minority carriers by decreasing impurity content.

Abstract: The present paper presents the first results of an ongoing research dedicated to the analysis of microstructure in steels surfaces treated by Low Energy High Current Pulsed Electron Beam (LEHCPEB). Various steels - 316L (a stainless steel), D2 (a cold-worked die steel) and 4Cr13 (a martensitic steel) - have been treated by LEHCPEB in order to improve the understanding of the surface microstructure modifications induced by this treatment. The microstructures in the modified surface were characterized by microscopy and diffraction techniques.