Materials Science Forum Vols. 675-677

Abstract: In this study, two kinds of NiCr/Cr3C2-BN composite powders were prepared with individual cladding (FKBN) and low pressure spray granulation (YLBN) methods, and the derived NiCr/Cr3C2-BN coatings were fabricated by plasma spraying technology. The microstructure, mechanical and tribological properties of the two coatings were systematically investigated. Both NiCr/Cr3C2-BN coatings have relatively high adhesive strength and microhardness, but the porosity of YLBN coating is much lower than that of FKBN coating. With comparison to FKBN coating, YLBN coating showed lower friction coefficient and better wear resistance, which was attributed to the more compact microstructure and uniform distribution of BN in the coating.

Abstract: The competitive reactions in atomic layer deposition (ALD) of HfO2, ZrO2 and Al2O3 on the hydroxylated Si(100) surfaces are investigated by using density functional theory. The surface reactions in ALD of HfO2 and ZrO2 show large similarities in energetics and geometrical structures. However, both of them show discrepancies with the surface reactions in ALD of Al2O3. In addition, by comparing with the self-termination reactions, we could find that the further growth reactions are both kinetically and thermodynamically more favorable in ALD of HfO2, ZrO2 and Al2O3.

Abstract: W-Mo and W-Mo-N surface-modified layers on Ti6Al4V alloy were obtained using a double glow plasma surface alloying technique. The morphology, microstructure, and chemical composition distribution of the modified layers were analyzed by scanning electron microscope, Xray diffraction, and glow discharge optical emission spectrometry. The hardness and toughness of the modified layers were measured using a micro-hardness tester, and dynamic repeating press equipment. The wear resistance in ambient air and the corrosive wear resistance in NaCl solution were evaluated using a ball-on-disk wear tester. The results show that W-Mo and W-Mo-N surface modified layers are composed of the alloying layers which vary in composition and phase form along the depth. A microhardness gradient was observed in the modified-surface layers. The surface hardness of the W-Mo-N and W-Mo modified layers was 25.3 and 14.2 GPa, which is seven-fold and 3.9-fold harder than the Ti6Al4V substrate, respectively. W-Mo and W-Mo-N surface-modified layers significantly improved the wear and corrosion resistance of Ti6Al4V. It seems that the wear resistance of W-Mo and W-Mo-N surface-modified layers in NaCl solution is better than that in ambient air owing to the strong lubricating effect of NaCl solution and the excellent corrosion resistance of the modified layers.

Abstract: Preferred orientation of AlN films has been improved to c-axis using a highly (111) textured Pt layer. The highly textured (111) Pt layer is obtained by inserting an AlN layer between the Pt layer and substrate. Thus, Pt/AlN/substrate could be termed a substrate for preferred orientation controlled AlN films. X-ray diffraction (XRD) profiles reveal that the degree of preferred orientation of such highly (111) textured Pt layer surpasses the one originated from the crystal structure of Pt. The (2θ, ψ) intensify maps of diffracted X-ray collected as a function of the diffraction angle (2θ) and the tilting angle (ψ) exhibit that the films are perfectly (111) preferred orientated, however, they do not show in-plane texture. The (2θ, ψ) maps also demonstrate that a residual stress in films is subject to compressive.

Abstract: We have used ferromagnet/antiferromagnet/ferromagnet sandwich structure to probe the antiferromagnetic layer thickness dependence of exchange bias in sputter-deposited Co/CoO/Co trilayer. The exchange coupling occurring at the upper ferromagnetic/antiferromagnetic interface is always found to be stronger than the one at the lower antiferromagnetic/ferromagnetic interface. The grain growth with increasing antiferromagnetic layer thickness can lead to a gradient of grain size distribution through the whole antiferromagnetic layer. Consequently, the relatively large grains at the upper interface would results in a rougher interface which we treat as structural defects and can significantly enhance exchange bias through domain state model. The slightly decrease of exchange coupling with increasing antiferromgnetic layer thickness indicates that the exchange bias is only governed by the grains that are thermally stable but whose anisotropy energy is low enough to be set.

Abstract: Because of clear image, bright color, high saturation of the color printing on coated paper, the ink-jet printing on coated paper catches more and more people’s eyes. In order to solve the problem of the ink-jet ink (cyan, magenta, yellow and black) on coated paper already developed out, whose yellow ink slants red and gloomy, different dyes are used to produce ink-jet ink. The inks were printed on the R-230 ink-jet printer on matt coated paper. The chromatic aberration is obtained on the basis of the colorimetric values in the ISO 12647-2:1996 eqv GB/T 17934.2-1999. It is found that the aberration of the Y79 is lower and its saturation is higher. The ink is filtered with 0.20 μm filter membrane and it can be used on ink-jet printing. The ink was used to print on the coated paper together with the previous cyan, magenta and black ink already developed out. The colorimetric values were measured and chromatic aberration and saturation is computed. The Color gamut graph of original inks and improved inks combination are made and compared to the standard of the ISO 12647-2:1996. It is found that the problems of hue unjust and gloomy color are improved compared to the previous four colors together. The cyan and magenta still stay away from perfect and it should be improved in future.

Abstract: TiAlCrN coating was deposited on a stainless steel using unbalanced magnetron sputtering technique. The erosion wear resistance of the TiAlCrN coating was investigated by comparison with that of the TiN coating deposited by filtered vacuum arc deposition. SEM was used for observing the surface morphologies of coatings both the un-eroded and eroded. Scratch test was used to evaluate the adhesion of the coatings. The erosion wear was tested with a gas blast apparatus at room temperature. In the test, the coatings were impacted at an impingement angle of 90° by angular SiC solid particles with an average diameter of 124um. The maximum depth of the erosion scar measured by the optical profiler was used to evaluate the erosion wear loss of the coatings. TiAlCrN coating proved to have much lower erosion rate than TiN coating. Unlike TiN coating, the TiAlCrN coating behaved like semi-brittle material.

Abstract: ZnO:Al thin films were deposited on glass substrates by r. f. magnetron sputtering. The crystal structures were characterized using X-ray diffraction. The electrical property and the light transmission of the ZnO:Al thin films were investigates utilizing Hall system and UV/Vis/NIR spectrophotometer. The results show that the ZnO:Al thin films prepared with the sputtering power of 100W, working pressure of 0.3Pa and substrate temperature of 250°C have the resistivity as low as 3.1×10-3Ω⋅cm and transmittance over 90% in visible region. From the GIXRD patterns, higher electrical conductivity is related to the higher ratio of I2 (103)/I(002), which is a new reasonable structure parameter to estimate the electrical property of ZnO:Al thin films.

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 work, YAG: Ce phosphors coated with ZnO nanoparticles were prepared based on the wet chemical method in ethanol solution at low temperature. The surface character was characterized by XPS and SEM. The XPS spectra showed that the peak positions corresponding to the Zn 2p3/2 , Zn 2p1/2 and O 1s are 1022.08 eV, 1044.88 eV and 530. 8 eV, respectively. The SEM images showed that the surface of YAG:Ce were coated with ZnO nanoparticles. The thickness is about 25 nm. The luminescence properties of YAG:Ce phosphors coated with ZnO nanoparticles were studied. It is found that the photoluminescence intensity of coated phoshors increases a maximum at 12% compared with that of the uncoaed YAG: Ce phosphors and the enhancement of photoluminescence intensity depends on the consistency of ZnO nanoparticles. Finally, the YAG: Ce phosphors coated with ZnO nanoparticles were used for LED package. The results show that the luminescent intensity increases 6.8 % and the quantity of phosphors decreases 1 %. It is important for the lighting product to improve the luminescence intensity of white LED and decrease the cost of package.