Advanced Materials Research Vol. 716

Abstract: The present work investigates the surface finishing of two mould tool steels (WNr 1.2738~P20 and WNr 1. 4305) after polishing by conventional method and automatic laboratory equipment. These steels are employed in the fabrication of polymer injection moulds due to its good machinability, homogeneous microstructure and hardness. The polishing process was performed in laboratory by manual and automated processes. The surface finishing was measured by mechanical and optical methods. In the manual polishing, SiC paper grit 320, 600 and 1200 was used. Final polishing was carried out with polishing cloth containing 0.3 μm alumina suspension or 6 μm and 1 μm diamond suspension. Alternately, polishing of steel specimens in the specially developed laboratory automatic equipment was performed using a large rotating disc at 140 rpm, nominal pressures of 0.013 Pa, 0.139 Pa and 0.244 Pa and diamond paste with particle size 1 μm. Surface finish of specimens were compared as a function of the particle size and polishing time by three methods: the roughness parameter Rz (mean of maximum roughness depth) using a stylus probe, light reflectance with an integrating sphere connected to a spectrophotometer, and reflected diffuse light intensity analysis of a He-Ne laser. Specimen surface images were also obtained by an optical microscope to compare the topography after polishing. From the plot of roughness measurements versus particle size and intensity of diffuse light versus particle size, it was observed that both roughness parameter Rz and the intensity of diffuse light decreased linearly with the abrasive particle size for the manual polishing method. The method of light reflectance measurements shows an approximately constant value of 55 % for all particle size. Therefore, the better methods to assess surface finish of tool steels are the roughness parameter Rz and the intensity of diffuse light by laser method. For the automatic polishing, the results show that there is an optimized time for minimum roughness which is 5 minute. Other relevant aspects of surface finish by particle abrasion are also discussed.

Abstract: In this work, micro rod arrays of 50 um and 200 um in diameter, respectively, were fabricated by 316L metal injection molding. Acryl sacrificial mold was used for the 50 um rod array. Aspect ratios were about 8 and 6 in 50 um and 200 um rod arrays, respectively and the bending of the rods occured due to high aspect ratio in debinding and sintering steps. Also, severe grain growth occurred at rod surface by sintering for 3 hrs at 1300°C and the average size was measured to be about 70 um.

Abstract: The wheel/rail contact is chracterized by high contact forces and small contact areas. Although the standard of railway wheel has sustained, the damages of railway wheel have been occurred in service running. The railway wheel damage can be divided into three types; wear, contact fatigue failure and thermal crack due to braking. In curves, especially, large sliding on the contact patch occurs at the wheel tread and flange. Due to this sliding, wear increases in the wheel/rail contact under the dry condition. To reduce wear, more durable wheel steels are required. In order to develop new materials and predict wear, It is important to understand the wear mechanism in wheel steels. In this study, we have investigated the wear characteriscs of RSW1 railway wheel steel using twin disc wear testing. Also the comparative wear behavior of RSW1 and R7 wheel steel under rolling-sliding contact was performed.

Abstract: A convergent synthetic approach was applied to 4-(2, 4-diaminophenoxy) phthalic acid ethyl esters (DAPPAcE) by reacting it with mono-anhydride in each successive step and this approach was found to be highly efficient in getting three generations of PI dendrimers than all known dendritc strategies carried out so far in PI preparation.The structures of prepared PI dendritic anhydride intermediates of three generations, [ and PI dendrimers, [, were all positively characterized by ¹H-NMRFT-IR and mass spectrometry. GPC analyses showed molecular weight distributions are 1.02 (for [G-[B]), 1.04 (for [G-[) and 1.07 (for [G-[) indicating that they all possess narrow molecular distributions. All PI dendrimers have excellent thermal properties. The 5wt % loss temperature of intermediates [G-[ (X=1, 2, and 3) are between 383°C and 390°C, while their respective [G-[ PI dendrimers (X=1, 2, and 3) are between 412°C and 421°C. [G-[ (X=1, 2, and 3).They all exhibit good solubility behaviors in most organic solvents, and their solubility do not show any appreciable difference between generations.

Abstract: Titanium alloys have been applied to aerospacemedical and other fields. The surface roughness of titanium alloy about these areas is very high. Based on the results of orthogonal test, belt grinding surface roughness prediction model of TC4 Titanium alloy is established using linear regression method. The significant tests of regression equation are conducted and proved that the prediction model has a significant. The results indicate that the model has reliability on the prediction of surface roughness, abrasive belt grinding pressure has certain influence on the surface roughness, and grain size of belt and the belt linear speed have high significant influence on surface roughness and the influence coefficient are-0.9378 and-0.2317. While the contact wheel hardness and workpiece axial feeding speed have no significant influence on surface roughness.

Abstract: The antitumor activity of porcine cartilage polysaccharide was evaluated by vivo animal models. The Ca761 tumor-bearing mice were treated with daily intraperitoneal injections of normal saline (control group) or cartilage polysaccharide (1500, 3000 or 4500mg/kg CPS group) for 14 days. The results demonstrated that CPS could effectively inhibit the tumor growth in Ca761 tumor-bearing mice. The tumor weights of the CPS groups were smaller compared to the control group. While the thymus index, spleen index were higher in the high dose 4500mg/kg CPS group than the control group. These results suggest that CPS might be a strong natural immunomodulator and the antitumor effect of this polysaccharide is associated with its potent immunostimulating effect.

Abstract: The present study is aimed to prepare the chitosan-coated alginate microspheres by an internal gelation technique with rutin as model drug. Recovery of microspheres and microspheres morphology were evaluated by determination of rutin encapsulation efficiency and microscope observation, respectively. The interaction between chitosan and alginate was assessed by differential scanning calorimetry (DSC). The microscope observation showed that the microspheres were homogeneous and the surface was spherical and smooth. The result of DSC indicated that the main force of complex formation was electrostatic interactions between ammonium of chitosan and carboxylate groups of alginate. In vitro release of the chitosan-coated alginate gel beads indicated that it had a satisfactory sustained releasing behavior for the drug within 20 h, and still maintain existed within 180 h. The microspheres which were biodegradable, biocompatible, metal ion adsorbable and persistable in environment may be applied to wastewater treatment.

Abstract: Total mercury (T-Hg) concentration was determined to evaluation the distribution, enrichment, accumulation and potential ecological risk of mercury contamination in the surface sediments of southern Kaohsiung Harbor, Taiwan. Sediment samples from 12 locations located between the river mouths (i.e., Jen-Gen River and Salt River) and harbor entrance of southern Kaohsiung Harbor were collected and characterized for T-Hg, aluminum, water content, organic matter, and grain size. Results showed that the T-Hg concentrations varied from 0.190.45 mg/kg with an average of 0.28±0.09 mg/kg. The spatial distribution of T-Hg reveals is relatively high in the river mouth region, and gradually diminishes toward the harbor entrance region. This indicates that upstream industrial and municipal wastewater discharges along the river bank are major sources of Hg pollution; and Hg may drift with sea current to be dispersed into open sea. Results from the enrichment factor (EF) and geo-accumulation index (I_geo) analyses imply that the sediments can be characterized between moderate and moderately severe degree enrichment and between none to medium and moderate accumulation of Hg, respectively. Results of potential ecological risk index indicate that the sediment has higher to high ecological potential risk.

Abstract: A rapid reversed phase highperformance liquid chromatography (RP-HPLC) method was developed for the simultaneous analysis of L-ascorbic acid and L-ascorbylpalmitate (AP). The chromatography was performed on a SSI model 2300-525 high performance liquid chromatographequipped with anAlltechApollo C18 column at 30 oC.The mobile phase was acetonitrile-water (90:10,v/v) with the flow rate of 1.0 mL/min. UV detection wavelength was 250 nm. This method permits the simultaneous determination of ascorbic acid and AP in the synthesis of AP transesterified with methyl palmitate and ascorbic acid. The detection limit of ascorbic acid and AP was 0.07μg/mL and 0.12μg/mL, respectively. The recovery was 90.59 ± 3.04% for ascorbic acid and 101.3 ± 4.81% for AP. The linearity range for ascorbic acid and AP was in the range of 0.1 - 0.7 mg/mL and 0.4 - 4.0 mg/mL, respectively. Correlation coefficients (R2) were 0.9910 for ascorbic acid and 0.9986 for AP. The proposed method could be used for routine quality control of AP synthesis with methyl palmitate and ascorbic acidby enzymatic transesterification.

Abstract: Methaogens performing the final step in the anaerobic conversion of biomass to methane are members of the domain Archaea, which synthesis methane as the major product of their energy metabolism. Both acetotrophic and hydrogenotrophic methanogens are essential for the key step of methanogenesis.