Advanced Materials Research Vols. 148-149

Abstract: Preparation of membranes from stimuli-responsive polymers, copolymers, and polymer-additive mixtures is an important approach in the design of responsive membranes. N-isopropylacrylamide(NIPPAm) was dispersed in polyurethane(PU) solution, crosslinked with N,N’-methylene bisacrylamide(BIS) and then cast in bathes to get a thermosensitive microporous film. The ratio of NIPAAm with BIS amount and the cast medium were varied. The structure, surface and cross-section images of polyurethane/poly(N-isopropylacrylamide) (PU/PNIPPAm) semi- interpenetrating networks (semi-IPNs) were characterized by FT-IR and SEM. The swelling behavior of pure PU films and PU/PNIPPAm semi-IPNs were compared. The results showed that incorporation of PNIPPAm had great effect on the structure and swelling behavior of composite films. This approach enables fabrication of membranes with the desired pore structure.

Abstract: Flower like Bi2WO6 powders were synthesized via a mild hydrothermal method. Analysis of X-ray diffraction (XRD) revealed that optimal calcination temperature was believed to be 400 °C at which the photocatalyst displayed high surface area and small crystallite size. Scanning electron microscope (SEM) showed that obtained Bi2WO6 with a flower like shape, which greatly enhance the surface area of catalyst and increase the contact area with dyes. The photocatalytic activity of as-prepared catalyst was investigated using Rhodamine B as a model compound under solar light irradiation. Results showed that the prepared photocatalyst was an effective photocatalyst and exhibited high photocatalytic performance. In the presence of 1 g/L Bi2WO6, 80.76% decolorization efficiency of RhB could be achived after 150 min irradiation

Abstract: In this paper, Polymer Plus of Aspen Tech Inc. is used to establish a styrene-butadiene rubber (SBR) polymerization process model; the sensitivity analysis method is used to analyze concentration of the initiator, reaction temperature and other factors which influence production and molecular weight of product. It is concluded that increasing amount of initiator can improve production, while the molecular weight would increase at first and then decline; and along with the increasing temperature, weight-average molecular weight would lower and production of polymer PBS would increase; molecular weight of polymer and production of polymer would magnify along with increase of amount of emulsifier and volume of the reactor.

Abstract: The attapulgite / natural rubber (NR) micro-nano composites were prepared by co-coagulating rubber latex and clay aqueous suspension. The vulcanization behavior, mechanical properties and microcosmic structure of the composites were investigated. The field emission scanning electron microscope (FESEM) micrographs of the composites showed that the attapulgite stick particles inserted into the rubber. The interaction between the attapulgite and natural rubber could be improved by using the attapulgite pre-modified with cetyltrimethylammonium bromide (CTAB). The properties of the composites filled with CTAB-modified attapulgite are better than that of the composites filled with carbon black N330. The best properties, which the tensile strength, the 300% tensile modulus and the tear strength increase by 46.9%, 269.7%, 102.0%, respectively, compared with the composites with the unmodified attapulgite, can be obtained, when 20 phr CTAB-modified attapulgite was added.

Abstract: The variation discipline of turbulence motion locus during the process of bearing’s strengthening grinding is a difficult point in the research fields of fluid theory. For the purpose of obtaining accurate discipline of turbulence motion, the fitting curve’s characteristics of turbulence motion locus based on image projection transformation and light stream vector is investigated. Through tracing particles be equally-distributed scattered into flow field, they reflect turbulence’s motion discipline accurately. After each particle’s movement has been shot from different orientations in continuous time-points, thus sequential conjugate images have been obtained. Relationship of image projecting transformation is established for determining these particles’ absolute three-dimensional coordinates. Combining with light stream vector, these particles’ motion vectors in each instantaneous moment can be deducted and mathematical models of motion locus can be gotten. Then correlative mathematical characteristics are built, their variation tendency is analyzed in different flow velocities. This experiment provides theoretical foundation and technical preparation for research of complicated turbulence and selection of fluid signal sampling’s condition.

Abstract: On the basis of conventional hot-top casting and Casting, Refining and Electromagnetic process, a lower frequency electromagnetic field was applied during the hot-top casting process. A comprehensive two-dimensional (2-D) mathematical model based upon the ANSYS and FLUENT has been developed for the computation of the electromagnetic field, solidification, fluid flow and heat transport during conventional and low frequency electromagnetic hot-top casting processes. The results show that there is a good agreement between the experimental results and calculated results.

Abstract: The extrusion die is of great importance in the quality control of profile production. Yet in practice, the design of extrusion die is mainly dependent on the experience and intuition of die designers, which is difficult to guarantee product quality and productivity. In this paper, a numerical model was developed based on HyperXtrude with an attempt to investigate the effects of the shape of the welding chamber on metal flow and weld quality. The porthole dies with different steps of welding chamber were designed and applied to extrude an identical profile. Numerical results showed that with an increasing step of welding chamber, more uniform velocity and temperature distributions in the cross-section of the extrudate were observed. In addition, the weld quality was improved owing to increasing welding pressure, when adopting the multi-step welding chamber.

Abstract: Friction stir processing (FSP) was applied to modify the surface of a hypereutectic Al-30wt.%Si alloy, the influence of the parameters on the size and morphology of Si particles, the microhardness of the mateials in the stir zone was investigated. All samples were preheated to research the influence of the pure heat input on Si. With the preheating temperature increasing from 100°C to 400°C, the average diameter increases gradually, but the shape factor decreases, the microhardness of the materials decreases. With the rotation rate increasing from 375rpm to 1050rpm, both the average diameter and shape factor increase, but the microhardness decreases. With the FSP passes increasing from 2 to 6, the average diameter decreases, and both the shape factor and the microhardness increases. Linear regression lines in most cases are presented to reveal the quantitative relationship between the FSP parameters and the Si particles and the microhardness. The reasons of the refinement and the spheroidization of the Si particles are carefully discussed. The microhardness variation of the materials is attributed to the size change of the Si particles with the FSP parameters.

Abstract: The phase equilibria at 900 °C and B2/L21 order-disorder transition in the Ni-Mn-Ga ternary system were investigated by analyzing the equilibrated alloys and diffusion couples using a combination of techniques. It was confirmed that a bcc single phase region exists in a wide composition range at 900 °C, and the critical temperatures of B2/L21 order-disorder transition were determined in Ni-50 at.% section, which exhibits a maximal ordering transition temperature of 796 at Mn content of 25 at.%. The obtained results will be helpful for the preparation and annealing of Ni-Mn-Ga alloys in the specific temperature.

Abstract: This paper analyzed the microstructure evolution and grain-refining mechanism in producing ultra-fine grained steel sheet by heavy rolling of lath martensite. The results show that this technique is composed of three processes with different grain-refining mechanism respectively: i) austenite grains subdivide into homogeneous and tiny martensite laths during quenching; ii) martensite laths are thinned and damaged during heavy rolling; iii) equiaxed ultra-fine ferrite forms during low temperature recrystallization annealing.