Advanced Materials Research Vols. 291-294

Abstract: This paper provides an experimental verification of decentralized approach for modal test and analysis of a 30 meters long railway overpass bridge. 11 Imote2 smart sensor nodes were implemented on the WSSN. In order to compare the identification precision of different topologies, acceleration responses were obtained under centralized and 3 different decentralized topologies. Local modal parameters were estimated by NExT/ERA within each local group; true modes were then distinguished from spurious modes by EMAC and finite-element analysis. In order to estimate global mode shape, a least square method was used for calculating the normalization factor. Then the global mode shapes were determined by normalization factors and local mode shapes. The result demonstrates that the more overlapping nodes in each group, the more accurate the global mode shape will be; the decentralized approach is workable for modal test of large-scale bridge.

Abstract: In this study, it was the first attempt to fabricate Ni-P-PTFE composite coatings on titanium alloy (manufactured through electroless composite plating). The effects of suspended PTFE concentration, temperature and surfactant concentration in the plating solution on the PTFE content in the resulting coatings were investigated. In addition, the friction and wear properties of the samples were analyzed. The results showed that co-deposition of Ni-P and PTFE can obviously decrease the friction coefficient of the coatings, reduce wear and improve lubricating property of the coatings.

Abstract: The corrosion behavior of Fe₄₄Cr₁₆Mo₁₆C₁₈B₆ amorphous alloy coating was studied by electrochemical polarization curves and electrochemical impedance spectroscopy (EIS) in different HCl concentration solution at room temperature. Experimental results show that the polarization curves of the coating present a wide passivation range under open circuit potential and i_corr increase from 1.049×10^-5A/cm² to 1.487×10^-5A/cm² with HCl solution from 0.5M to 2.0M. The EIS of coating are composed of high-frequency inductive loop and low-frequency capacitance arc, which is different from the EIS of other amorphous alloys, the Rt is up to 5789Ω·cm² in 2M HCl solution. The especial equivalent circuit model R(RL)(Q(R(QRW))) can better interpret the corrosion behavior of the amorphous alloy coating.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and B₄C-Yb₂O₃ (1:1, in mass) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1250 °C, 1300 °C, 1350 °C and 1400 °C for 1 h. The apparent porosity, bending strength and thermal expansion ratios of the samples were examined and they were analysed by means of XRD and SEM. The results showed that the sample sintered at each temperature with 3% B₄C-Yb₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% B₄C-Yb₂O₃ was conducive to sintering of fused quartz ceramic materials. The results of XRD analysis and thermal expansion ratio analysis showed that 3% B₄C-Yb₂O₃ compound additive had obvious effect on inhibiting crystallization of the samples sintered at various temperatures. It can be deduced that the 3% B₄C-Yb₂O₃ compound additive plays the excellent role in inhibiting crystallization and facilitating sintering of fused quartz ceramic materials.

Abstract: The electrode alloys (Mg_1-xZr_x)₂Ni (x = 0, 0.3) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted by Zr in order to improve the electrochemical hydrogen storage characteristics of the Mg₂Ni-type alloy. The effects of substituting Mg with Zr as well as milling duration on the microstructures and electrochemical performances of the alloys were investigated in detail. The results showed that the substitution of Zr facilitates the formation of amorphous Mg₂Ni-type phase. The electrochemical measurement indicated that the substitution of Zr significantly enhances the discharge capacity and cycle stability of the alloys, and it markedly improved the discharge potential characteristic of the alloys. For a fixed alloy, the electrochemical performances, including the cycle stability and the discharge voltage characteristic as well as discharge capacity, of the alloys were markedly improved with prolonging of the ball-milling duration.

Abstract: The YBa₂Cu₃O_x/Ag and Bi₂Sr₂CaCu₂O_x/Ag self-lubricating composites were prepared using powder metallurgic method. The crystal structure and morphology of the as-synthesized samples were characterized by XRD and SEM. The YBa₂Cu₃O_x/Ag and Bi₂Sr₂CaCu₂O_x/Ag self-lubricating composites were found to compose of superconductor phase and Ag phase. The tribological properties from ultra-low temperature to room temperature of the composites were studied by pin-on-disk friction test. It was found that the friction coefficients of pure YBa₂Cu₃O_x (YBCO) and Bi₂Sr₂CaCu₂O_x (BSCCO) were both dropped abruptly when the temperature cooled below the superconducting transition temperature. At room temperature, the friction coefficient of pure YBa₂Cu₃O_x is 0.68~0.95, when mixing 15wt% Ag, the friction coefficient of the sample decreased to the lowest value 0.11. The friction coefficient of pure Bi₂Sr₂CaCu₂Ox is 0.15~0.17, When Ag content reach 10wt%, the coefficient was lowest (average value is 0.13). The addition of appropriate amount of Ag obviously improve the tribological property of YBCO, while only slightly meliorate that of BSCO. On the other hand, the YBCO/Ag composites exhibit better tribological properties than BSCCO/Ag composites at higher load under the same experimental condition.

Abstract: To ensure the use of oil tank safely, it is necessary that the conductive coating was used in inner oil tank. This paper concentrates on a study of the electrical properties (surface resistance rate) of epoxy resins filled with different types of carbon pigments, such as colloid graphite, carbon black and mixture of colloid graphite/carbon black, as well as on the investigation of some mechanical properties, appearance and morphology .To produce a light grey and conductive coating, titanium oxide and carbon electro-conductive pigments were investigated in this article. The objective of the experiment therefore was to choose the optimal electro-conductive filler and determine the optimal mix ratio of colloid graphite/ carbon black and titanium oxide /colloid graphite and titanium oxide /mixable electro-conductive filler. From the experiment analysis, it was found that the optimized colloid graphite and carbon black mix ratio is 3:1; the optimized titanium oxide and colloid graphite mix ratio is 1:1; the optimized titanium oxide and mixable electro-conductive filler mix ratio is 8:1. In terms of resistance rate and color, we may arrive at the conclusion that 15μm colloid graphite as the optimized electro- conductive pigments and the optimal mix ratio of titanium oxide /colloid graphite is 1:1.

Abstract: An experimental zirconium-based conversion coating on cold rolled steel was investigated in the present work. The following tests on differently pretreated panels, such as bonderite^®NT-1, oxsilan^®9810/1 and lz-4356, were conducted to evaluate corrosion performance include adhesion test, T-bent test, neutral salt spray test and warm salt water dipping test and electrochemical studies were also performed. The whole results showed that the experimental zirconium-based conversion coating had well-pleasing corrosion protection properties and adhesion properties, and similar lever performance as compared to the other industrial coatings. The experimental zirconium-based conversion coating was very hopeful about industrial application.

Abstract: The aim of this work is to investigate the possibility of improvement of surface roughness in the wire-EDMed sample by usinig ultrasonic wave and abrasive particle suspension. For this study, two-type ultrasonic polishing methods were used. Removal of the white layers on surface of EDMed sample depended largely on the movement of the suspended particles : the white layers are removed by the impact of free moving particles due to ultrasonic wave, so-called micro chipping mechanism. Even though the surface roughness was improved very slowly, 3-dimensional fine polishing was achieved in wire-EDMed micro PIM molds. These results indicated that micro polishing by ultrasonic wave using suspension is applicable to improvement of surface roughness of micro parts with 3-dimensional complex shape.