Advanced Materials Research Vols. 391-392

Abstract: The present work investigated the variation of internal structure, molecular orientation, crystallinity and mechanical characteristics of polypropylene(PP) after rolling process. The materials plate became narrow when rolled from entrance to exit, and the internal crystalline gradually deformed and at last destroyed. Plastic deformation was discovered along the rolling direction. In this direction, the crystallinity and vickers hardness were decreased, and molecular orientation was increased. Moreover, molecular orientation had a sharp increase at the second half part of rolling sample. The tensile stress of rolled samples increased by 80% parallel to rolling direction and decreased by 22% perpendicular to rolling direction.

Abstract: The biodegradable composites were prepared with the oyster shell particles (OSP) and poly(lactic acid)(PLA) by injection molding. The mechanical and thermal properties were investigated. The degradation temperature of the composites decreased by increasing the content of OSP compared with PLA. From the results of tensile test, the tensile strength and the fracture strain of the composites decreased because of exist of OSP. However, the Young’s moduli of the composites increased compared with PLA. The SEM observation of morphology confirmed that the interface between PLA and OSP had poor adhesion.

Abstract: In this work, the spring back, dimensional change, internal structure and morphology of extruded polypropylene were investigated in order to consider the rolling characteristic. It was found that the internal structure, molecular orientation and crystallinity were changed a little by high spring back under low reduction in thickness. Crystal structure was extended along the rolling direction with high reduction in thickness due to the increase of plastic deformation. As a result, molecular orientation increased and crystallinity decreased at over 30% of reduction in thickness. Crystalline structure of surface was similar to the center part in cross-section at 70% reduction in thickness, and molecular orientation was constant.

Abstract: In this paper, two kinds of rubber surface modifying methods were studied. One was bis[3-(triethoxysilyl) propyl] tetrasulfide (Si-69) silicon alkane coupling agent and the other was crylic acid coupling agent. The mechanical properties of cement concrete with modified rubber crumb and with non-modified rubber crumb were tested respectively. The results show that as the rubber crumb addition rises, the toughness of concrete with non-modified rubber crumb increases while the compressive strength decreases, and both thoughness and compressive strength of cement concrete with modified rubber crumb increase. The chloride impermeability of the rubber concrete are much better than that of the Portland cement concrete. After surface modification the chloride impermeability can be improved more. The thermoanalysis proves that the surface of modified rubber crumb is grafted by polar function groups, so the surface changes from hydrophobic to hydrophilic. The scanning electron microscopy (SEM) analysis confirms that the interface between rubber crumb and cement matrix is improved.

Abstract: The oxidation behavior of Co-10Cr-5Al-0.3Y alloy in 1 atm of pure O₂ at 700°C was investigated. The addition of 0.3 at.%Y significantly increased the oxidation rate of the alloy and changed the oxidation behavior from the approximate parabolic rate law to linear rate law. The scale grown on the surface at 700°C was porous with many small voids and cracks, and was composed of an outer CoO layer and an inner complex layer rich in Al₂O₃ and Cr₂O₃ which were intermingled with yttric oxide and spinel Co(Cr, Al)₂O₄.

Abstract: The oxidation behavior of thin layers of Fe-15Cu-5Al-0.3Y alloy with grain size in nanometer range, prepared by magnetron sputtering deposition on cast alloy of the same composition, was studied at700oC in 0.1MPa O2. The scales grown on the coatings consist of two layers. The outer layer is composed of an external continuous Fe oxides scale free from copper and aluminum oxides. The inner layer is very complicated, with formation of dark oxides of Fe and Al, coupled with light un-oxidized Cu-rich stringers elongated perpendicularly to the alloy surface. Some degree of internal oxidation of Fe and Al is also present within the coating layer. A grain size reduction can effectively promote the selective external oxidation of Fe.

Abstract: The effect of the addition of 0.3 at.% Y on high temperature oxidation resistance of ternary Co-10Cr-5Si alloy in 0.1MPa O2 at 800°C was investigated. The addition of 0.3 at.% Y greatly increased the oxidation rate of the alloy and changed the approximate parabolic rate law into linear rate law. The scale formed on Co-10Cr-5Si-0.3Y alloy was double-layered, with formation of an outer layer of CoO and an inner region containing a mixture of CoO, Cr₂O₃, SiO₂ and a trace of yttric oxide, coupled to the internal oxidation region of Si.

Abstract: 65Mn spring steel is mainly used for rotary blade which is a vulnerable part of farming machinery. The experiment of the wear-resistance property for 65Mn spring steel under different heat treatments is conducted. The results are discussed based on the regression orthogonal design. The wear-resistance property of 65Mn steel has been discussed by applying diverse heat treatment technology and the optimum parameters of heat treatment for the best anti-wear property are obtained through experiments. The influence of the parameters on anti-wear property is studied by applying the regression orthogonal design. The relation between the wear mass loss and diverse heat treatment parameters has been given by using planar and contour figure. The optimum heat treatment parameter for maximum anti-wear ability is obtained as following: 852.64 for quenching temperature, 18.36min for quenching time, and 145.44 for tempering temperature, respectively.

Abstract: Hydroxyapatite (HAP) is known as a kind of bioactive and biocompatible material, HAP coatings are used to improve the biocompatibility of substrate by some researchers. In this paper, homogenous precipitation of hydroxyapatite was formed in the system of CaNa₂EDTA -(NH₄)₂HPO₄-NH₄OH-H₂O, and HAP powder was obtained after calcinations at 800 and grinding. Add HAP in UHMWPE o-xylene solution to get dipping solution and prepare HAP/UHMWPE-coated titanium by dipping coating process. Scratch test demonstrated that Ti-HAP/UHMWPE material started to shine metallic luster under 1.03 N, and adhesive strength is 32MPa. UHMWPE not only simplified the process of preparing HAP-coated material, but also enhanced the adhesive strength, which shows great potential in biomedical areas.

Abstract: Multi-tubular stirred reactor is an efficient pressure reactor. It is designed and developed to strengthen the mixing and mass transfer process. In order to research the flow characteristics in this reactor, the residence time distribution is measured at different rotation speeds from 50rpm to 350rpm and different flow rates from 1.8m3/h to 3.9m3/h. The relationship among mean residence time, flow flux and rotate speed is obtained.