Materials Science Forum Vols. 510-511

Abstract: Electrospinning represents an attractive approach for polymer processing. In the present study, gelatin and poly (propylene carbonate)(PPC) were electrospun successfully and collected on a rotating mandrel to form tubulose scaffolds. Furthermore, to mimic the real structure of animal blood vessels, the polymers were employed in a single tube as distinct layers by the technique of alternate electrospinning. Scanning electronic microscopy (SEM) was used to analyze the morphology and diameter of the fibers, and the porosity of the scaffold. The tubes were seeded with rat bone marrow derived mesenchymal stem cells (BMSCs) and cultured for 2 weeks to evaluate their biocompatibility. The growth and distribution of the cells were observed directly under the fluorescent microscope. The interaction between cells and scaffold was analyzed by SEM and H&E staining. After two weeks culture, the fibers were almost embedded by growing BMSCs. H&E staining and green fluorescent image showed that BMSCs uniformly grew inside the scaffolds. The results showed that electrospun tubes with uniform pores and fibers of smaller diameter were appropriate for BMSCs attachment and proliferation. These primary data indicated that scaffolds fabricated by ectrospinning are structurally biocompatible. The PPC scaffolds may be useful in vascular tissue engineering if they were further modified chemically or with appropriate therapeutic molecules.

Abstract: In this paper, we suggest PCH as a method of joining alloys. The temperature distribution in the samples during the joining process was analyzied. From the temperature distribution profiles in PCH joining, it is concluded that PCH for the joining has two advantages: (1) There is a temperature distribution peak along the sample. The contacting surfaces which need high temperature happen to obtain the highest temperature; (2) The parts to be joined at relatively lower temperatures can avoid the damage of heat attack. The optimal joining conditions were discussed. The PCH and HP techniques were compared for the joining of alloys. It was found that the high tensile strength joined structure of alloys can be fabricated by PCH method at lower joining temperature, shorter holding time, and lower pressure, compared with that by HP method. The PCH process was considered to be an eco-friendly process compared with the traditional heat diffusion joining methods.

Abstract: Nano-hydroxyapatite (n-HA) slurry was synthesized at normal pressure, and (Cu2+, Zn2+)-bearing nano-hydroxyapatite (Cu-Zn-HA) was prepared by ion exchange reaction in water medium. The properties of n-HA and Cu-Zn-HA were characterized by AAS, TEM, XRD and FTIR. The results of XRD analysis indicate that Cu2+ and Zn2+ can occupy Ca2+ sites and enter the crystal lattice of hydroxyapatite. Through the antibacterial experiments, it was found that Cu-Zn-HA had better antibacterial ability on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). After heat treatment at 400°C for an hour, the materials still had good antibacterial effect. The accelerated aging method was employed to test antibacterial durability of the material and the results indicated that the durability was good. The results of the security assessment, including skin stimulation test of rabbit, acute toxicity test by stomach filling and the micronucleus test in bone marrow polychromatic erythrocytes of mice, showed that the security of the material was excellent.

Abstract: A new method was studied for improving stainless steel antibacterial capability. The Na2FeO4 coating was prepared on steel surface throughout NaOH treatment, then steel samples were immersed into the solution coantaining Ag+, Zn2+ and TiO2. The antibacterial-ions were fixated firmly on the stainless steel with chemical bond. Scanning electronic microscopy(SEM), X-ray(XRD) and atomic absoption spectroscopy(AAS) were employed to analyze the materials, and the results showed that the antibacterial membrane included silver citrate and silver peroxide. Quinn test was also carried out, in which Staphylococus and E.coli. the results showed that the steel has a bacteriostasis rate of 99.48% to Staphylococus, and 99.09% to E.coli.

Abstract: The crystallization behavior of n-HA/PA66 biocomposites at different processing pressure and annealing temperature were investigated by XRD and DSC. The results showed that increasing annealing temperature would weaken the crystalline intensities of pure PA66 and its composites. For n-HA/PA66 composites, the peaks of α1 crystals of PA66 disappeared, only α2 crystals existed, and with the increase of injection pressure and annealing temperature, the crystalline intensity of PA66 decreased. The degree of crystallinity (Xc) of PA66 in composites increased with the increase of injection pressure, however, annealing temperature had no obvious effects on crystalline degree. The mechanical properties had close relationship with the crystallization behavior of the materials.

Abstract: Al-Mg alloy foam used in this study was prepared, and Al-Mg alloy was melted by using a high-frequency induction furnace. Thickening and foaming agent were added to the molten Al-Mg alloy at a specific temperature, which was stirred. For uniform distribution of thickening and foaming agent, the impeller was rotated with high-speed about 400-1000rpm. When left in a furnace for a specific period after uniform dispersion of the foaming agent, gas was generated from the foaming agent and the cell size and distribution inside. We determined the structure of Al-Mg alloy foam using CT(Computed Tomography). The structure of Al-Mg alloy foam has homogeneous cell size at the bottom, larger cell size in the middle, and oalescence cell in the top part. To prevent this phenomenon, the viscosity and surface tension of the melt of Al-Mg alloy were controlled.

Abstract: Porous clay materials with columnar type pore channels were fabricated from water-based clay slurry and a specially designed mold by using a freeze casting technique. Ice was stimulated to grow vertical direction, and aligned macro pores were formed to the same direction. The phase separation between the ice and clay particles might be responsible for the formation of the columnar type pores. It appears that it is possible to control the size and morphology of pores by modifying a freezing mold, refrigerant temperature, and the weight fraction of clay in slurry.

Abstract: Hydrophobic silica aerogels were synthesized by an ambient pressure drying method from silicic acid with a different pH value, which was prepared from sodium silicate solution (water glass). In this study we chose various hydrocarbon class solvents such as pentane, hexane, heptane, and toluene, and performed surface modification in TMCS (trimethylchlorosilane)/solvent solutions in order to improve reproducibility in aerogel production. Densities of the aerogels were about 0.1 ~ 0.3 g/cm3 , and apparent porosities were 88 ~ 96 %, depending on the processing conditions. Specific surface area was approximately 730 ~ 950 m2/g, and average pore size around 10 nm.

Abstract: The creation of large impervious surface in urban and urbanizing areas commonly leads to multiple impacts on the stream systems including higher peak runoff, reduced infiltration, and increased pollutant loads to streams. Permeable pavements made up of a matrix of concrete blocks with voids offer one solution to the problem of increased stormwater runoff and decreased stream water quality. Experiment results indicate that lower pore size pavement showed a higher runoff reduction rate compared with other pavement. Also, water absorption capability of pavement will drop the surface temperature of pavement. Compared to runoff, the turbidity and phosphorus concentration were lower than 27 [NTU] and 0.5 [mg/L], respectively. It appears that turbidity and hosphorus are concentrated in the pavement void.

Abstract: The pollutants in urban stormwater runoff, which lead to non-point source contamination of water environment around cities, are of great concern. Lignocellulose fiber filters have potential to treat urban stormwater runoff because they are cheap and environmentally friendly, and can effectively remove particulate pollutants. However, the fiber filters alone cannot sufficiently remove soluble pollutants including heavy metals, nitrogen compounds, and phosphate. In this study, techniques for chemical modification of lignocellulose fiber filter were implemented to enhance the treatment efficiency of soluble pollutants in urban stormwater runoff. Using these chemically modified fiber filters together with polymer filter media, a new treatment device was examined to control the pollutants in first flush of stormwater. The results indicated that the filters incorporated into the treatment unit allow the control of urban stormwater runoff with minimal cost and high efficiency.