Nov 2016, Volume 10 Issue 4

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    Weimin MAO

    Grain orientation evolutions and texture formation based on the Taylor principles offer important references to reveal crystallographic mechanisms of deformation behaviors. Strain equilibrium between grains is achieved in Taylor theory, however, stress equilibrium has not yet been reached perfectly even in many modifications of the theory though the textures predicted become very close to those of experimental observations. A reaction stress model is proposed, in which mechanical interactions between grains are considered in details and grain deformation is conducted by penetrating and non-penetrating slips. The new model offers both of the stress and strain equilibria and predicts the same textures indicated by Taylor theory. The rolling texture simulated comes very close to the experimental observations if the relaxation effect of the non-penetrating slips on the up-limits of reaction stresses is included. The reaction stress principles open theoretically a new field of vision to consider deformation behaviors of polycrystalline materials, whereas the Taylor principles become unnecessary both theoretically and practically. Detailed engineering conditions have to be included in simulations if the deformation textures of industrial products should be predicted.

    Xuran GUO,Kaile ZHANG,Mohamed EL-AASSAR,Nanping WANG,Hany EL-HAMSHARY,Mohamed EL-NEWEHY,Qiang FU,Xiumei MO

    Urethral strictures were common disease caused by over-expression of extracellular matrix from fibroblast. In this study, we compare two nanoyarn scaffolds for improving fibroblasts infiltration without inhibition the?over-expression of extracellular matrix. Collagen/poly(L-lactide-co-caprolactone)?(Col/P(LLA-CL)) nanoyarn scaffolds were prepared by conjugated electrospinning and dynamic liquid electrospinning, respectively. In addition, co-axial electrospinning technique was combined with the nanoyarn fabrication process to produce nanoyarn scaffolds loading?Wnt?signaling pathway inhibitor. The mechanical properties of the scaffolds were examined and morphology was observed by SEM. Cell morphology, proliferation and infiltration on the scaffolds were investigated by SEM, MTT assay and H&E staining, respectively. The release profiles?of different scaffolds were?determined using?HPLC. The results indicated that cells showed an organized morphology along the?nanoyarns and considerable infiltration?into the nanoyarn scaffolds prepared by dynamic liquid electrospinning (DLY). It was also observed that the DLY significantly facilitate cell proliferation. The D-DLY could facilitate the infiltration of the fibroblasts and could be a promising scaffold for the treatment of urethra stricture while it may inhibit the collagen production.

    Dong YAN,Zhong-Zheng ZHOU,Chang-Qing JIANG,Xiao-Jie CHENG,Ming KONG,Ya LIU,Chao FENG,Xi-Guang CHEN

    A water absorption biomaterial, sodium carboxymethylation-functionalized chitosan fibers (Na-NOCC fibers) were prepared, applied for cutaneous wound repair, and characterized by FTIR and NMR. The water absorption of Na-NOCC fibers increased significantly with substitution degree rising, from 3.2 to 6.8 g/g, and higher than that of chitosan fibers (2.2 g/g) confirmed by swelling behavior. In the antibacterial action, the high degree of substitution of Na-NOCC fibers exhibited stronger antibacterial activities against E. coli (from 66.54% up to 88.86%). The inhibition of Na-NOCC fibers against S. aureus were above 90%, and more effective than E. coli. The cytotoxicity assay demonstrated that Na-NOCC2 fibers were no obvious cytotoxicity to mouse fibroblasts. Wound healing test and histological examination showed that significantly advanced granulation tissue and capillary formation in the healing-impaired wounds treated with Na-NOCC fibers, as compared to those treated with gauze, which demonstrated that Na-NOCC fibers could promote skin repair and might have great application for wound healing.

    Tao JIN,Fan-mei KONG,Rui-qin BAI,Ru-liang ZHANG

    In this study, anti-corrosion coatings were prepared and coated successfully on magnesium alloy substrates by mixing nanopowders, solvent, curing agent with epoxy resin. The effect of the amount of iron trioxide (Fe2O3) on the adhesion strength and corrosion resistance on magnesium alloy was investigated with standard protocols, and electrochemical measurements were also made in 3.5 wt.% NaCl solutions. The surface morphology and corrosion mechanism after corrosion tests was characterized using FESEM analysis. Nanoparticles in matrix acted as filler, and interstitial cross-linked spaces and other coating artifacts regions (micro cracks and voids) would all affect the anti-corrosion properties of coating. The results showed the proper powder content not only provided adhesion strength to these coatings but also improved obviously their anti-corrosion. Hydrogen bound to the amine nitrogen (1N) could take part in the curing process rather than hydrogen of the amide site due to the smaller ΔG and the more stable configuration.

    Javier Esteban Enríquez MONTENEGRO and Dinesh Pratap SINGH

    Controlled growth of nano/micro structures by controlling the effective parameters is the basic requirement for the application point of view in various areas. Here we report the facile growth of silver molybdate nano/micro rods by mixing the solution of silver nitrate and ammonium molybdate at ambient condition followed by hydrothermal treatment at various temperatures for 12 h. To achieve the goal for the synthesis of long, high yield and homogeneous nanorods various effective parameters have been studied to set the most effective conditions for the growth. Among possible effective parameters first the temperature of the furnace was set by warring the temperature and then at the set temperature the concentration of reactants (NH4)6Mo7O24 and silver nitrate are varied respect to each other. The pH and temperature values were monitored during the mixing of the reactants. Structural/microstructural characterization revealed the optimum condition of 150°C of the furnace and the concentration of (NH4)6Mo7O24 and silver nitrate as described in various tables.

    Hassan Rayat AZIMI,Mahmood GHORANNEVISS,Seyed Mohammad ELAHI,Mohammad Reza MAHMOUDIAN,Farid JAMALI-SHEINI,Ramin YOUSEFI

    ZnS/graphene nanocomposites with different graphene concentrations (5, 10 and 15 wt.%) were synthesized using L-cysteine as surfactant and graphene oxide (GO) powders as graphene source. Excellent performance for nanocomposites to remove methylene blue (MB) dye and hexavalent?chromium (Cr(VI)) under visible-light illumination was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide (rGO) during the synthesis process. Photocurrent measurements under a visible-light source indicated a good chemical reaction between ZnS NPs and rGO sheets.


    In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a unique frequency of microwave irradiation. The sphere sizes were controlled by the microwave power level and the concentration of dissolved precursor. Structural and morphological characterization was performed by SEM, HRTEM, EELS and XRD. The results demonstrated that rhombohedral zero valent Bi spheres were synthesized after microwave radiation at 600 and 1200 W. However, if the power level is decreased to 120 W, a monoclinic phase of Bi2O3 is obtained with a flake-like morphology. In comparison with a conventional hydrothermal process, the microwave-assisted solvothermal approach provides many advantages such as shorter reaction time, optimum manipulation of morphologies and provides a specific chemical phase and avoids the mixture of structural phases and morphologies which is essential for further applications such as drug delivery or functionalization with organic materials, thanks to its biocompatibility.

    Dongthanh NGUYEN,Wei WANG,Haibo LONG,Hongqiang RU

    This work demonstrated that mesoporous TiO2 (meso-TiO2) with controllable mesoporous and crystalline structures can be facilely prepared by using poly(ethylene glycol) (PEG) as structure-directing (SD) agent and peroxotitanic acid (PTA) as precursor. Meso-TiO2 with high specific surface area (157 m2·g−1), pore volume (0.45 cm3·g−1) and large mesopore size of 13.9 nm can be obtained after calcination at 450°C. Such meso-TiO2 also shows relatively high thermal stability. BET surface area still reaches 114 m2·g−1 after calcination at 550°C. In the synthesis and calcination process, PEG that plays multiple and important roles in delivering thermally stable and tunable mesoporous and crystalline structures shows to be a suitable low-cost SD agent for the controllable preparation of nanocrystalline meso-TiO2. The photocatalytic activity tests show that both high surface area and bi-crystallinity of obtained meso-TiO2 are important in enhancing the performance in photo-decomposing Rhodamine B in water.

    Bao YANG,Hong ZHANG,Jia GUO,Ya LIU,Zhicheng LI

    The Ti/Y modified CuO-based negative temperature coefficient (NTC) thermistors, Cu0.988−2yY0.008TiyO (TYCO; y= 0.01, 0.015, 0.03, 0.05 and 0.07), were synthesized through a wet-chemical method followed by a traditional ceramic sintering technology. The related phase component and electrical properties were investigated. XRD results show that the TYCO ceramics have a monoclinic structure as that of CuO crystal. The TYCO ceramics can be obtained at the sintering temperature 970°C–990°C, and display the typical NTC characteristic. The NTC thermal-sensitive constants of TYCO thermistors can be adjusted from 1112 to 3700 K by changing the amount of Ti in the TYCO ceramics. The analysis of complex impedance spectra revealed that both the bulk effect and grain boundary effect contribute to the electrical behavior and the NTC effect. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the TYCO thermistors.

    Yajing ZHAO,Yan CHEN,Kepi CHEN

    In this paper, the effects of doping with GeO2 on the synthesis temperature, phase structure and morphology of (K0.5Na0.5)NbO3 (KNN) ceramic powders were studied using XRD and SEM. The results show that KNN powders with good crystallinity and compositional homogeneity can be obtained after calcination at up to 900°C for 2 h. Introducing 0.5 mol.% GeO2 into the starting mixture improved the synthesis of the KNN powders and allowed the calcination temperature to be decreased to 800°C, which can be ascribed to the formation of the liquid phase during the synthesis.

    Qianli HUANG,Ningmin HU,Xing YANG,Ranran ZHANG,Qingling FENG

    Selective laser melting (SLM) was used in fabricating the dense part from pre-alloyed Ti–6Al–4V powder. The microstructural evolution and inclusion formation of as-fabricated part were characterized in depth. The microstructure was characterized by features of columnar prior β grains and acicular martensite α'. High density defects such as dislocations and twins can be produced in SLM process. Investigations on the inclusions find out that hard alpha inclusion, amorphous CaO and microcrystalline Al2O3 are three main inclusions formed in SLM. The inclusions formed at some specific sites on melt pool surface. The microstructural evolution and inclusion formation of as-fabricated material are closely related to the SLM process.