Advanced Materials Research Vol. 905

Abstract: The hydrogen embrittlement behavior of sensitized types 304, 316 and 310 in boiling saturated magnesium chloride solutions was explained in more details in terms of an inhibiting effect of chloride ions, martensite transformation, Cr depletion, HELP, and the degree of corrosiveness through the comparison with those for the solution annealed steels. Furthermore, a transgranular HE (TG-HE) cracking mode that was not observed for the solution annealed steels was discussed as well as IG-HE. Then a TG-HE mechanism for sensitized austenitic stainless steels was proposed, while the IG-HE mechanism for solution annealed austenitic stainless steels was discussed in details and was applied to IG-HE of sensitized austenitic stainless steels. It was also pointed out that the occurrence of both TG-HE and IG-HE was explained with an identical concept.

Abstract: Chemically and mechanically protective coatings are formed on surface of Magnesium alloys by micro-arc oxidation (MAO) methods. Modification of the obtained MAO surfaces was made in two aspects. Firstly, the protection is enhanced by forming super-hydrophobic surfaces, with water contact angle higher than 120^o, attributed to hierarchical nanomicro structures. The overall process involves alkaline etching to form nanoscale structures on top of micro-porous surface achieved during micro-arc oxidation processes. Secondly, the electrical property of the MAO surfaces is modified. A film with electrical conductivity of 2.4Ω/sq is achieved by Ni deposition and characterized by four point probe measurement. The morphology, phase, and chemical composition of all surfaces are investigated by SEM, AFM, and XRD analysis.

Abstract: The role of plasmids in hydrocarbon-degrading bacteria Acinetobacter calcoaceticus A1 survival to UV-radiation and hydrocarbons was studied. Natural plasmids-containing A. calcoaceticus A1 showed high resistance to UV-radiation. A. calcoaceticus A1 showed active growth under exposed to UV-radiation for up to 30 minutes. Combined effects of UV-radiation and petroleum hydrocarbons did not considerably reduce the growth of strains. It was shown a stimulating effect of UV-radiation on the growth curves of strains of A. calcoaceticus A1. Constructed recombinant strain (E.coli XL blue Rec) showed the ability to grow on medium with addition petroleum hydrocarbons. Combined effects of UV-radiation and petroleum hydrocarbons have had a negative effect on the growth of E.coli XL blue Rec. Thus, results showed that the plasmid DNA of natural hydrocarbon-degrading bacteria A. calcoaceticus A1 may contain genes of microbial resistance to UV - radiation and petroleum hydrocarbons.

Abstract: This study aimed at investigating positive and negative potential effect on phospholipid lubrication for artificial joint. Surface potentials of CoCrMo in saline were measured once per day for 1 week to simulate corrosion of implanted artificial joint. Both +250 mV and-250 mV were applied on CoCrMo. 2mg/ml DPPC liposome was fabricated to produce lipidic adsorption on CoCrMo. Friction tests were carried out on cartilage vs. CoCrMo and UHMWPE vs. CoCrMo. The results showed that superficial potential of CoCrMo in saline changed from-177 mV at 1^st day to 133mV at 7^th day. Lubrication performance of DPPC liposome without potential was declined gradually. Liposome@-250 mV sustained low friction coefficient of both tribopairs whereas liposome@+250 mV greatly increased friction coefficient of UHMWPE vs. CoCrMo from 0.041 to 0.076. It demonstrated that negative potential enhanced adsorption of DPPC liposome, and promoted its lubrication. In contrast, positive potential on CoCrMo due to corrosion deteriorated liposome lubrication.

Abstract: Different grades of several thermoplastic elastomer types were selected and are investigated over a wide frequency/time, temperature and loading range in a research project of the authors. Relevant material models are selected for different loading situations and based on these experimental data the material model parameters were determined either directly or by applying fitting procedures. These models along with the proper data were used for modeling the deformation and the failure behavior of typical engineering thermoplastic elastomer components. Furthermore, based on the modeling of various elastomers under different service relevant loading situation several design proposals were formulated.

Abstract: Chemical converted graphene (CCG) were coated on 316L stainless steel as a bipolar plate which is a component of proton exchange membrane fuel cell (PEMFC) by electro spray coating (ESC). Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to examine the thickness and surface properties of coating layer. Electrochemical potentiodynamic test was conducted in acidic atmosphere (0.1N H₂SO₄+2ppm F^-) at 80°C using Versastat 4 and analysis program for corrosion resistance measurement. After packing bipolar plates for PEMFC stack, the electrical performances of graphite, bare SS316L and graphene coated SS316L bipolar plates were evaluated by PEMFC evaluating device. The chemical converted graphene was founded on the surface of coated SS316L, and the thickness was 12μm. Graphene coated bipolar plate showed high corrosion resistance of 1.32×10^-7A/cm² beside bare SS316L bipolar plate. In electrical performance evaluation, the graphene coated bipolar plate was shown 0.978V on Voc and 0.5A/m² on the reduction potential (0.6V). Although the electrical performance of the graphene coated bipolar plate is lower than graphite bipolar plate, the thickness and weight is lower than graphite bipolar plate. These advantages can enable the PEMFC system more efficiently and economically.

Abstract: Abstract. Wire electrical discharge machining (WEDM) is a widespread technique used in manufacturing industry for high precision machining of all types of conductive materials such as metals and its alloys of any hardness which are difficult to machine with traditional techniques. In order to get a precise workpiece with good surface quality, some extra repetitive finish cuts along the rough cutting contour are necessary. The selected parameters are servo voltage (SV) and voltage (V). The goal of the research was to obtain accurate dimension (10 + 0.005 mm and surface roughness < 0.46 microns). The experiment material is SKD-11 steel. The experiments are designed by 3k full factorial experimental design at 3 level 2 factors and 9 experiments with 2 replicates. The experiment determines the significant effective factor at confidential interval 95%. The SV factor is the significant effective factor and voltages parameter affects to the average roughness surface. Experimental results show that a surface roughness under 0.46 micron and accurate dimension value + 5 micron of 10 x 10 millimeters can be obtained.

Abstract: The rubbery materials play an important role in the acoustic metamaterials composed of locally resonant structures. To determine the unusual behavior of the dynamic mass density and bulk modulus in acoustic metamaterials in detail, better understanding of the viscoelasticity of rubbery materials is necessary. In the present work, we demonstrated the difference between the fractional and integer constitutive models in describing the viscoelastic behaviors in terms of the natural rubber (NR) and silicone rubber (SR). Test results for the relaxation modulus show that the Maxwell model is not suitable for NR and SR. The fractional Scott-Blair model gave a better estimation for the relaxation modulus but had a more sophisticated relation than the classical Maxwell model did. Compared with the other constitutive models, the fractional Maxwell model gave a better description of the mechanical properties for NR and SR, but it involved four independent parameters to be determined experimentally. By fitting test results in the double logarithmic plot of the modulus and loading time, all the parameters of the fractional Maxwell model were obtained. The present work provided a base for the analysis of the membrane-type acoustic metamaterials.

Abstract: The new azo benzene polyurethane (CAPU) was synthesized by diazo coupling reaction with 1,4-Diaminobenzene, sodium nitrite, and R(-)-3-chloro-1,2-propanediol. The solubility was measured with several organic solvents. Some mechanical properties of CAPU, such as tensile strength and ratio of elongation at break, were investigated. The good thermal stability of the CAPU was shown by its absorption spectrum characterized by UV-Vis spectroscopy and its melting point of 113.5°C. Moreover, the refractive index of CAPU was obtained by the attenuated total reflection (ATR) method at different temperature and wavelength, by which the materials thermo-optic coefficient was calculated. It is shown that the material has a large thermo-optic coefficient and an obvious birefringence phenomena. And the dispersion coefficient was also calculated by the Sellmeyer equation. Because of thermo-optical properties mentioned above, the CAPU could be used to design and generate the thermo-optic switch and even all-optical switch.

Abstract: With the purpose of proposing a construction waste forecasting method specialized for construction phase, this study suggested a forecasting method based on material loss rate to forecase construction wastes with diverse properties. Loss rate of 124 construction materials found in South Korea and Japan was provided. Also to review applicability of construction waste forecasting method using material loss rate, the amount of construction waste found using existing construction waste forecasting method and forecasing method proposed in this study was comparatively analyzed on apartment houses.