Materials Science Forum Vols. 783-786

Abstract: Diamond-like carbon (DLC) films were synthesized on a p-type silicon wafer using radio-frequency plasma composed of a mixture of Ar and C₂H₂ (ratio of 7 to 28). NH₃ plasma treatment of as-grown DLC substrate was carried out to generate surface-terminal amino groups while oxidation of as-grown DLC was performed in O₂ plasma. X-ray photoelectron spectroscopy (XPS) was used to characterize the different surface functions formed on DLC surfaces. Water contact angle measurements indicate different wetbility of modified surfaces. The cell (Mouse MC₃T₃-E₁ pre-osteoblasts) morphology and proliferation were monitored to evaluate the biocompatibility of the modified DLC surfaces. A cell count kit-8 (CCK-8 Beyotime) was employed to determine quantitatively the viable pre-osteoblasts. The cell viability assay shows that osteoblast proliferation are improved on NH₃ and O₂ plasma-treated DLC surface after culturing for 1day, 2days and 3 days. The cell-surface interactions are studied by fluorescence microscopy. There are more osteoblasts as well as better spreading on the aminated and oxidized surfaces after culturing for 3 days. In summary, compared to the as-grown sample, the modified DLC shows better biocompatibility.

Abstract: Several electroless nickel deposits, on steel substrate, of varying chemistry were investigated in the as-plated and heat-treated condition: 3 nickel-phosphorous (low, mid and high P) and 2 nickel-boron (nickel-boron (lead) and nickel-boron (thallium)). Samples were characterized by SEM and X-ray diffraction. They were then submitted to Knoops microhardness testing and Taber abrasion tests, with abrasive CS-10 wheels, as well as scratch testing to investigate their mechanical properties and wear resistance. Hardness and wear resistance of all deposits were improved by heat treatment, but the best candidate was the Nickel-boron (lead), with a hardness over 1100 hk50 after heat treatment and a Taber Wear Index of 6. Scratch testing allowed identifying the damage mechanisms of the coated systems.

Abstract: Shot peening is widely utilized to improve the fatigue property of mechanical parts for transportation equipment such as cars and airplanes. Also, this technology is being applied as a film-forming technology in order to improve surface quality. The authors have recently proposed new joining methods using shot peening, shot lining. In this method, the metals are bonded with the dissimilar metal by applying plastic deformation and the pressure. The thin foil can be joined to the substrate surface by the pressure generated by the hit of the shots. In this study, the formation of an Fe-Al intermetallic compound film on high-speed tool steel by shot lining and heat treatment was investigated. In the experiment, a centrifugal-type peening machine with an electrical heater was employed. The shot medium was high-carbon cast steel. The substrate was a commercial high-speed tool steel JIS-SKH51, and the foil was commercially available pure aluminium. The shot lining process of tool steel with an aluminium foil was carried out at 573K in air using a peening machine. Heat treatment was performed at diffusion temperatures from 923 to 1573K in vacuum. The lined substrates exhibited a harder layer of aluminium-rich intermetallics in the diffusion temperature range of 923 to 1173K. When the temperature of the lined substrates was more than 1273K, the surface was covered with thicker and highly anticorrosive layers of iron-rich intermetallics. We found that the present method could be used for the formation of functional films on high-speed tool steel.

Abstract: Zinc-nickel-SiO2 electrodeposits have been produced from an acid sulphate bath. Thecodeposition behavior of SiO2 and the homogeneity of platings were examined. The presence ofSiO2 nanoparticles in the plating bath appears to change the alloy deposition behavior. Rate ofnickel deposition was considerably decreased with SiO2 nanoparticles in the bath. The homogeneityof platings between zinc and nickel were improved by adding the SiO2 nanoparticles in the bath. Atan early stage of electrodeposition, it seems that the SiO2 nanoparticle acts as a nucleus of theprecipitation. The SiO2 nanoparticle has not uniformly dispersed in a plating film, but distributedonly in the SiO2 rich layer with about 50 nm in thickness formed beneath the surface. In addition,this SiO2 rich layer can improve the anticorrosive performance. Therefore, the zincic use can besuppressed, because film thickness can be more thinned, compared with zinc and zinc-nickel alloyelectroplating.

Abstract: TiAlSiN coatings were deposited on WC-Co metal by using a cathodic arc ion deposition method of cylindrical cathode. We used Ti / Al (50 / 50 at.%) arc target and silicon sputter target. The influence of the nitrogen pressure, TiAl cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The structural features of the films were investigation in detail using X-ray diffraction. And coatings were characterized by means of FE-SEM, nanoindentation, Scratch tester, Tribology tester, XRD and XPS. The hardness of the film reached 43 GPa at the cathode arc current of 230 A and decreased with a further increase of the arc current. And the adhesion of the film reached 34 N. The results showed that the TiAlSiN coating exhibited an excellent mechanical properties which application for tools and molds.

Abstract: Hybrid organic-inorganic nanocomposites can be prepared by the sol-gel process. An attribute of the sol-gel process is that organic and inorganic components can be linked together on the nanoscale through chemical reactions at room temperature. Functionalized siloxanes can be mixed and reacted to form nanocomposites with a wide range of mechanical, optical and dielectric properties.

Abstract: The effect of Cu-Sn coating on steel towards improving the adhesion between steel and typical styrene butadiene rubber (SBR) based tyre bead composition has been investigated in this work. Steel coupons were coated with varying compositions of Cu-Sn via immersion coating, where the electrolyte bath composition was varied. Chemical analysis of the coatings using ICP-OES confirmed increase in Sn content with increasing SnSO₄ concentration in the coating baths, keeping other parameters constant. No change in the coating weight was observed with change in Sn concentration in the coatings. Bare spots on the coating surface was observed under SEM XPS analysis confirmed formation of Fe oxide at the bare locations. The coated steel plates were vulcanized with SBR based rubber and peel strength was measured. The results confirmed an optimum Sn concentration of 3 - 4 wt% in the coatings up to which an increase (~ 25%) in adhesion strength was exhibited compared to only Cu coatings. Stereo-microscopic analysis of the peel tested samples validated mixed mode i.e. both adhesive and cohesive modes of failure.

Abstract: Cubic boron nitride (cBN) has significant technological potential for use in high-temperature high-power electronic applications. And S and Zn were reported to be potential n-and p-type dopants. In this study, influences of vacancies, S and Zn impurity atoms on the electronic properties of cBN were investigated by first-principle approaches. The computation results are in good agreement with our experimental approach.

Abstract: The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina layers, under an oxygen potential gradient ΔP_O2 was evaluated at a temperature of 1873 K. When mutual grain boundary (GB) diffusion of oxygen and aluminum occurred in wafers subjected to a steep ΔP_O2, the oxygen and aluminum fluxes at the inflow side of the wafer were significantly smaller than those at the outflow side. It was noteworthy that Lu and Hf segregation at the GBs selectively reduced the mobility of oxygen and aluminum, respectively. It was found that a wafer with a bilayer structure, in which a Lu-doped layer was exposed to a low partial oxygen pressure (P_O2) and a Hf-doped layer was exposed to a high P_O2, exhibited excellent oxygen shielding properties at high temperatures.

Abstract: Electrodeposited silver layers obtained from high-cyanide silver plating solution are widely applied for connectors and switches of automobiles. However, few groups have discussed the relationship between the crystal structure of silver layers and their properties. In this study, the effect of the concentration of Se, added as a brightener to high-cyanide silver plating solution, was investigated by XRD and EBSD analysis for electrodeposited silver layers with {200} orientation. By optimizing the concentration of Se in the silver plating solution, the {200} orientation ratio of the silver layer was increased to as high as 94%. Since the diffusion of Cu from the Cu substrate used in this study into the silver layer was inhibited, the silver layer with the high {200} orientation ratio exhibited good electrical contact resistance of the surface of 1.3mΩ after a heating test performed at 200°C for 74h. In addition, the silver layer had good bend formability. The results of XRD analysis confirmed that the recrystallization of the electrodeposited silver layer occurred at room temperature within several hours, thus increasing the {200} orientation ratio of the silver layer.