Advanced Materials Research Vols. 239-242

Abstract: In this work percolation range for Al₂O₃-Ni interpenetrating phase composite (IPC) was studied to find the optimal combination of electrical conductivity and coefficient of thermal expansion (CTE). The impedance spectroscopy and scanning electron spectroscopy were used to study the percolation limit.

Abstract: New 1-D zigzag chain coordination polymer {[HgBr₂(pbbm)]^.DMF}_n (1) has been successfully constructed with the aim of exploiting new and potent ion-exchange materials. Remarkably, the coordinated Br^- anions in the title polymer can be replaced completely by F^-, Cl^- and I^- anions when the crystals are immersed in the aqueous solutions of the corresponding potassium salts, respectively. This exchange is quantified by FT-IR spectra, the PXRD pattern as well as EDS analyses.

Abstract: Silane surface technology have been rapidly developed in the field of anti-corrosion of metals as one of the “green” replacements for conventional chromizing. The article introduced the corrosion prevention mechanism of silane treatment; factors affecting performance of the silane film(including silane categories, the concentration and pH of the silane solution, and deposition methods); modified technologies(such as loading nanoparticles, doping corrosion inhibitor and adding suitable dyes and colorants); analytical and characterization techniques of the silanizing film. The shortage that existed currently in silane treatment is also discussed. All above are aimed to promote the research of environmental friendly surface passivation technology on aluminum alloy.

Abstract: Blank holder force of box deep drawing is studied changes with time and displacement by DYNAFORM numerical simulation software. The results shows that, when the straight edge part of the blank holder force is constant, rounded part adopts small blank holder force can significantly improve the forming limit of box deep drawing, but the wrinkle is still evident. If the straight edge and rounded part of the blank holder force changes with time, not only deep drawing limit increase, wrinkles are also significantly reduced, indicating that the forming limit of the box shaped part is more effective on the blank holder force changes over time than with the position variation.

Abstract: Lauric acid-N-quinazolin-4-one methylester was synthesized as potential lubricating oil additive. The friction and wear behaviors of the synthesized compound as an additive in liquid paraffin on 12.7mm diameter steel ball bearing specimen were evaluated with a four-ball machine. The worn surfaces of the steel balls were observed using a scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the novel compound as an additive in liquid paraffin was effective in improving the tribological performance.

Abstract: Based on heat transfer theory, thermodynamics steady state equation of hydrostatic bearing, thermal mathematical model of hydrostatic bearing and boundary condition of numerical simulation is established. Temperature field distribution of hydrostatic bearing at different velocity is numerical simulated. Regularity of the influence of velocity on temperature field of heavy hydrostatic thrust bearing is revealed. The results show that, velocity impacted a significant influence on heat transfer and temperature field distribution of hydrostatic bearing. Average temperature of workbench steadily declined as velocity increasing, while average temperature of base gradually increased; both of them emerged serious heat concentration, but the cooling situation of workbench is better than base. The numerical simulation results could provide theoretical basis for temperature control scheme design which will improve the stability and reliability during hydrostatic bearing operation.

Abstract: Based on the principle that chlorophyll’s photodegradation occurs in the presence of oxygen, high-oxygen-barrier polyvinyl alcohol (PVA) films comprising chlorophyll are prepared without photodegradation of chlorophyll by a facile procedure. The photostability of the films are characterized by the absorption spectra. The result shows that the chlorophyll in the films can keep photostable at least for six months whereas the photostability of chlorophyll in ethanol is less than one day. The absorption maxima of chlorophyll/PVA films at red band, which are at 668nm due to the chlorophyll and consist with that of chlorophyll in ethanol (666 nm), shift blue after the sunlight treatment. The shift extent increases with the time of sunlight treatment and decreases with the content of chlorophyll in samples. The method proposed in the study could greatly improve the photostability of chlorophyll and can be used in the field of photocatalysis.

Abstract: 6-arm star-shaped Poly (ε-caprolactone)-dextran (sPCL-dextran) was synthesized and characterized. The core of the star polymer is dipentaerythritol, the inner block in the arm is hydrophobic poly (ε-caprolactone) (PCL), and the outer block in the arm is hydrophilic dextran. The synthesis involves three steps: (1) The ring-opening polymerization of ε-caprolactone (CL) initiated by dipentaerythritol produces 6-arm star-shaped PCL (sPCL-OH). (2) The sPCL-OH reacts with acryloyl chloride to get star-shaped PCL with acrylate end group (sPCL-CH=CH₂). (3) The amino ended dextran (dextran-NH₂) is then attached to sPCL-CH=CH₂ terminus by Micheal addition to form star-shaped sPCL-dextran. The architecture of products was characterized with ¹H NMR, GPC and element analysis. Micellization of sPCL-dextran in aqueous solutions was investigated by DLS. The results showed that the micelle size (R_h) and size distribution are related to the concentration of the sPCL-dextran. Salt, pH value and temperature have no obvious influence on the R_h.

Abstract: The bamboo pulp fiber fabric was treated by chitosan with low molecular weight in aqueous citric acid. The effect of citric acid concentration, chitosan concentration, treatment time and reaction temperature on anti-creasing and mechanical properties of the fabric were studied, respectively. Meanwhile, the optimal finishing condition was obtained. The anti-wrinkle and hygroscopic properties of all processed fabrics improved markedly at the optimal technology. However, the breaking strength of the fabric decreased slightly after the optimal treatment. FT-IR characterization of the treated fabric showed that the chitosan was crosslinked on the bamboo pulp fiber fabric and the ester linkage was formed between the citric acid and bamboo pulp cellulose. The antibacterial property of the chitosan treated fabric increased dramatically. The resulting bamboo pulp fiber fabric treated by chitosan is a natural ecological textile product, having the various application and more potential chemical modification.

Abstract: How to uniformly disperse carbon nanotubes (CNTs) and densely sinter green body are the key issues to prepare carbon nanotubes reinforced alumina (Al₂O₃) composite. We prepare CNTs-Al₂O₃ powder by shearing extruding dispersion method, and then obtain CNTs-Al₂O₃ composite by hydrogen atmosphere pressureless sintering. 93% of the relative increased fracture toughness can be achieved, when the CNTs content of composite is 1%. Because of Absorbing energy by pulling CNTs out from alumina matrix and refining grain by CNTs bundles sitting along alumina grain, the fracture toughness is improved obviously. By XRD and SEM analysis, the residual tensile stress which is caused by embedding CNTs into alumina matrix also plays an important role for the increase of fracture toughness.