Advanced Materials Research Vols. 47-50

Abstract: The present study aimed at the development of new artificial golden-colored pigments which are thermally stable up to 900 oC and can be used for coloring ceramics wares. Silver was used as a base material with bright metallic luster. Silver with the larger lamellar structure was indispensable to maintain the metallic luster, and it was successfully obtained by the heat-treatment of as-obtained silver powder at 200-400 oC in air and subsequently dry ball-milling at 300 rpm for 1 h. The surface of the lamellar-structured silver was coated with small particles of hydroxides, oxyhydroxides and oxides of Fe, Co, Ni, Ce and Pr. Appearance of golden color depended on the combination of metal species and heat-treatment temperature, and CeO2-coated silver gave golden color after calcination at 800 and 900 oC. The golden color of CeO2-coated silver could be controlled by the loading amount and particle size of CeO2 for color tone and relative area of naked surface of Ag for luster.

Abstract: Corrosion-resistant nickel-based Alloy 600 is susceptible to a lead-induced stress corrosion cracking (PbSCC) in aqueous solutions. The lead species incorporated into the oxide at the alloy surface degraded the passivity, and caused the PbSCC. Effects of lead on the properties of the surface passive films were investigated. The cross sections of the surface films were examined by the transmission electron microscopy and the species present in the films were analyzed with the energy dispersive x-ray spectroscopy and the x-ray photoelectron spectroscopy. In-depth concentration profiles of the species were analyzed by using an ion sputtering technique. The electrochemical impedance spectroscopy technique was used to characterize the electrochemical behaviors. Effectiveness of a nickel boride inhibitor was evaluated. The boride inhibitor altered the properties of the passive film, and significantly reduced the susceptibility to the PbSCC.

Abstract: The contact in the valve train system is known to be the part subject to significant load in an automobile engine. For such reason, the wear of the contact accounts for the greatest portion of entire friction loss of an engine, leading to the occurrence of abnormal wear. In order to reduce the wear in the valve train, this study first formed a crn layer to increase the bonding force with the base metal using the pvd coating method and then applied a 2-layer coating that formed the wc/c layer with low friction/wear resistance characteristics. In addition, it examined the friction characteristics occurring between the cam and tappet by using the dedicated wear tester and found that the friction torque value was reduced significantly through comparison testing with the existing part when the crn+wc/c coating was applied.

Abstract: Tris(2,2’-bipyridyl)ruthenium (II) (Ru(bpy)3 2+) electrogerated chemiluminescence (ECL) sensor was fabricated by immobilization of Ru(bpy)3 2+) complex on the functionalized MWCNT-Nafion composite film coated on surface of glass carbon electrode. The functionalized MWCNT was prepared by coating of polythiophene (PTh), polyaniline (PANI), and poly(3-thiophene acetic acid) [P(3-TAA)] on the surface of the carboxylic acid-modified MWCNT. The sensitivity and reproducibility of the prepared ECL sensor to tripropylamine (TPA) was evaluated. As results, the carboxylic acid-modified MWNT composite electrode was high sensitivity and good reproducibility than that of other functionalized MWNT composite electrode.

Abstract: Pt-Ru@CP-MWNT catalysts were prepared by radiolytic deposition of Pt-Ru nanoparticles on conduction polymer (CP) coated multi walled carbon nanotubes (MWNTs) surfce. Three different types of conducting polymers; polypyrrole(PPy), polyaniline(PANI), and polythiophene (PTh), were coated on the MWNTs surface by in situ polymerization. Then Pt-Ru nanoparticles were deposited onto CP-MWNTs composite by the reduction of metal ions using gamma-irradiation to obtain Pt-Ru@CP-MWNT catalysts. The size, morphology and composition of Pt-Ru@CP-MWNT catalysts were characterized by SEM, TEM and elemental analysis. The catalytic efficiency of Pt-Ru@CP-MWNT catalyst was examined for CO stripping. Pt-Ru@PPy-MWNT and Pt-Ru@PANI-MWNT electrodes show enhanced activity for electrooxidation of CO and methanol over Pt-Ru@PTh-MWNT catalyst.

Abstract: In this paper, (C,N) alloyed austenitic stainless steel coatings (or hybrid S-phase with both carbon and nitrogen) were produced by a magnetron sputtering deposition process combined with ion implantation (CMSII). This technique involves a periodical high energy ion bombardment of the coating during its growth, which has a beneficial effect on the structure and properties of the deposited coating. The influence of the nitrogen and carbon addition to the deposition atmosphere on the structure, chemical composition and coating morphology was investigated using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Glow Discharge Optical Spectrometry (GDOS) techniques. Wear tests were carried out and the results were compared with low temperature plasma nitrided austenitic stainless steel.

Abstract: This paper describes a mechanical mechanism of chemical mechanical polishing (CMP) and the model is applied to the polishing of silicon substrates by polyurethane pads and slurries containing fumed silica as is typically done in the manufacture of integrated circuits. The model utilizes the concept that the polishing pad surface contains asperities that support the normal load on the wafer, and that friction and hydrodynamic forces influence wear. The interfacial fluid pressure can significantly influence the normal pressures on the wafers and its effects modify the wear rate predictions.

Abstract: The frictional coefficient and wear rate of CDC layer were significantly lowered by chlorine gas treatment at high temperatures due to the formation of a carbon layer. A severe to mild wear transition occurred, depending on the reaction temperature. In this study, the effect of the fraction of transformed carbon layer on the tribological properties has been investigated. The fraction of transformed carbon layer was controlled by varying the reaction temperature of the hydrogen and chlorine gas mixture. The degree of the transformed layer was measured using Energy Dispersive X-ray (EDX) and Raman spectroscopy. The mechanical properties of the partially transformed layer were measured by using a micro-Vickers hardness tester. The variation of the fraction of the transformed carbon was correlated with the tribological and mechanical properties.

Abstract: Ceria based slurries with and without PVP were prepared for the polishing of patterned and blanket wafers. The changes in the cross-sectional profiles of the oxide as a function of the polishing time and surfactant concentration were analyzed, in order to understand the mechanism by which the step height of the oxide is reduced during the CMP process. The reduction in the thickness as a function of the polishing time varied with the PVP surfactant concentration in the patterned wafer. When the surfactant concentration was increased to 0.8wt%, the material removal rate of oxide in the patterned wafer approached a maximum. The maximum removal rate observed at a surfactant concentration of 0.8wt% was explained by the competing effects of the increasing number of active particles and the increasing thickness of the viscous layer due to the addition of surfactant.

Abstract: CrN/AlSiN multilayer coatings with bilayer period (Λ) between 2.3 nm and 8.0 nm were synthesized from Cr and AlSi (Si=20 and 66 at.%) targets by using a closed-field unbalanced magnetron sputtering (CFUBMS) and their crystal structure, chemical composition and mechanical properties have been investigated by glow discharge optical emission spectroscopy (GDOES), Xray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and nano-indenter. In order to evaluate the thermal stability of the coatings annealing treatments for 30 min at temperature between 800 °C and 1000 °C were performed in air. The thermal stability of the CrN/AlSiN multilayer coatings was improved with increasing Si content. In case of the coating with Si content of 18.2 at.%, a superior thermal stability was exhibited even after annealed at 1000 °C and the relatively high hardness of 25 GPa was maintained without a significant decrease in hardness. The reduced oxidation rate of the coatings at high temperature could be attributed to the formation of the amorphous Si3N4 phase around the crystalline AlN phase.