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May 15,2012
Volume 5,Issue 9
Pages -
Subject Area:Composite Materials,Foundational Subject in Materials Science

Title: Synthesis and photoelectrochemical properties of CdSe/TiO2 nanotubes array coaxial heterojunction

Authors: LIU Yong, ZHU Wen, MA Jian
PP: 883-891
Abstract: The under-potential deposition (UPD) of Cd and Se elements on TiO2 nanotubes array substrate is studied. CdSe, a kind of narrowband gap semiconductor compound, is successfully deposited onto the walls of the highly structured and orderly TiO2 nanotubes array using a combination of UPD and co-deposition at a suitable potential. Field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD), energy dispersive atomic X-ray （EDAX） and transmission electron microscope (TEM) analyses show that CdSe/TiO2 nanotubes array with coaxial heterojunction structure has been formed. The photoelectrochemical properties of the resulting films with the CdSe/TiO2 nanotube-array coaxial heterojunction are discussed. The results show that the maximum photoconversion efficiency can be obtained for the sample with the sensitization layer using the deposition time of 7 h. In addition, the effect of annealing atmosphere on the photoactivity of as-prepared samples also has been investigated. It suggests that the annealing in nitrogen atmosphere can introduce the N atoms to TiO2 lattice, to a certain extent, is conducive to the improvement of photoactivity, however, the efficacy tends to decline in the wake of the increasing deposition time.
Keywords: low-dimensional inorganic non-metallic materials; electrochemical atomic layer epitaxy; TiO2 nanotube arrays; CdSe; under-potential deposition; photoconversion efficiency

Title: Amorphous-nanocrystalline composite cobalt-rich alloys for giant magnetic impedance

Authors: SUN Qiangqiang, SONG Yujun, ZHANG Tao, JIANG Yanwei, FANG Jiancheng
PP: 872-882
Abstract: Co-rich amorphous ribbons with thickness of 20 μm and width of 1-2 mm are fabricated by the rapid-quenching process. Controlled annealing is performed on these ribbons for enhancing giant magnetic impedances (GMI), which are further correlated with their intrinsic crystal structures, magnetic and electric properties. The results indicate that ultra-fine nano-structural alloys are formed by field-annealing the amorphous ribbons at 450℃ for 30 minutes, featured by the formation of primary nano-crystals with size of (3.5±0.4) nm uniformly dispersing in the amorphous residues with inter-spacing of (0.4±0.2) nm. This kind of ultra-fine nano-structural alloys preserves a MI ratio of 520%, much higher than the as-quenched sample with only 84%, and a DC magnetic-field sensitivity of 250×10-4%/T at a given frequency of 10 MHz. Samples annealed without field exhibit a dual peak MI feature with a MI ratio of 324 % and a low-field (0-0.001 T) sensitivity of 133×10-4%/T at 15 MHz.
Keywords: nanocrystalline; cobalt-rich amorphous alloys; annealing; magnetic property; electric property; giant magnetic impedance

Title: Development of a thermodynamic and kinetic combined material modeling platform

Authors: XIONG Hua, HUANG Zhiheng, WU Zhiyong
PP: 865-871
Abstract: The computational interface for thermodynamic calculations software MTDATA has been extended. Based on it, an integrated platform for materials modeling is developed for five programming languages including C, Fortran, Python, Java and Matlab, by calling the dynamic-link libraries of thermodynamic calculations software packages Thermo-Calc and MTDATA, and incorporating COMSOL Multiphysics for kinetic modeling. Thermodynamic modeling, kinetic modeling, combined thermodynamic and kinetic modeling, and microstructure-based multiphysics modeling can be conducted within the platform. The platform solves the governing equations of kinetic processes based on the finite element method, and therefore has advantages on handling complicated geometries, general boundary conditions and nonlinear material properties. Several application examples are presented, including the utilization of the thermodynamic data of typical alloys, and modeling of solidification using both a phase field model and a phase field crystal model.
Keywords: thermodynamics and kinetics of materials; microstructure modeling platform; phase field; phase field crystal

Title: Effect of high current pulsed electron beam on microstructure and properties of Mg67Zn30Y3 quasicrystal alloy

Authors: GAO Bo, JIANG Fei, HAO Yi, ZHANG Wenfeng, LI Shiwei, HU Liang, TU Ganfeng
PP: 858-864
Abstract: In this paper, the Mg67Zn30Y3 quasicrystal alloy was bombarded through high current pulsed electron beam (HCPEB). The surface microstructures of Mg67Zn30Y3 quasicrystal alloy before and after HCPEB treatment were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM), and cross-sectional microhardness was examined using a 401 MVDTM vickers hardness. The results indicate that HCPEB treatment leads to rapid remelting of alloy surface, so the phase boundaries become indistinct, and a large number of tiny nano-quasicrystals are dispersedly distributed in surface layer, and average sizes are about 10~20 nm. The thickness of remelted layer induced by HCPEB increases with the increase of pulse number, and it is increased from 5.20 μm of 2-pulse sample to 7.41 μm of 15-pulse sample. The microstructure variation results in the hardness enhancement. The cross-sectional microhardness of Mg67Zn30Y3 quasicrystal alloy has a growing tendency after HCPEB bombardment compared with initial sample. The maximal hardness appears in 50~100 μm depth range. In summary, the HCPEB treatment is able to effectively improve surface structure and properties of Mg67Zn30Y3 quasicrystal alloy.
Keywords: surface and interface in the materials science; surface treatment; high current pulsed electron beam; nano-quasicrystals; Mg67Zn30Y3; remelted layer; cross-sectional microhardness

Title: Study on mechanical performance evolution of ultra-temperature conductive adhesive co-modified by B4C/graphite

Authors: WANG Jigang, YUAN Hongguan ,ZHANG Shouchun
PP: 852-857
Abstract: In order to realize joining of carbon and graphite materials which is usually used at high temperatures, ultra temperature conductive adhesives were prepared by using phenol formaldehyde (PF) resin as matrix and B4C and graphite powders as additives. The pure PF resin matrix and adhesives were hot-pressed respectively, and then heat-treated at high temperatures ranging from 200 to 1 200°C. The compressive strengths of all the specimens were tested at room temperature. Based on the analysis of obtained data and modification mechanism, double-parabolic evolution of mechanical performance was observed. Below 600°C, the strength of both the pure PF matrix and adhesives kept on decreasing. On the contrary, a re-increase of the mechanical performance occurred with the further elevation of heat-treatment temperatures. The main reinforcement effect should be contributed to boron carbide. Mainly as the conductive component, the excessive addition of graphite powder showed little effect on adhesive strength. The adhesive experiments were also carried out using pure PF resin and adhesive, respectively, and the same regularity of strength evolution was observed, and the optimized ratio for the high-temperature conductive adhesive can be confirmed as PF∶B4C∶graphite powder=100∶75∶25.
Keywords: functional polymer materials; ultra-temperature conductive adhesive; shear strength; phenol formaldehyde; boron carbide; graphite

Title: The effect of different heat treatment process on microstructure and mechanical properties of casting Ti-44Al-4Nb-4Zr-1B alloy

Authors: SUN Hongliang, HUANG Zewen
PP: 847-851
Abstract: The effect of different heat treatment process on microstructure and mechanical properties of casting Ti-44Al-4Nb-4Zr-1B alloy was investigated. The results indicate that at 700℃ the tensile stress is increased by about 130-200 MPa, and the elongation to failure is significantly improved, compared to those at room temperature. The colonies of this cast alloy can be refined to some degree through some heat treatment schemes in the α+γ two-phase region, but the refinement has a little influence on tensile properties and stress rupture life.
Keywords: materials science; TiAl-based alloy; heat treatment; microstructure; mechanical properties

Title: Preparation of Sc2Mo3O12/ZrO2 composites with controllable thermal expansion

Authors: CHENG Xiaonong, ZHU Junjun, YANG Juan
PP: 841-846
Abstract: Sc2Mo3O12 which exhibits excellent anisotropic negative thermal expansion was synthesized using solid-state reaction. Sc2Mo3O12/ZrO2 composites were prepared by mixing ZrO2 and Sc2Mo3O12 at different volume ratios and sintered at 1 000℃ for 10 h. The crystal structure, fracture surface morphology and thermal expansion properties of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and dilatometer. The results indicate that the obtained samples contain only orthorhombic Sc2Mo3O12 and monoclinic ZrO2 phase without other phases. All the thermal expansion properties of Sc2Mo3O12/ZrO2 composites are linear in 30-600℃ and their thermal expansion coefficients can be controlled as positive, negative or even zero by adjusting the volume fraction of Sc2Mo3O12. 50% (volume percentage) Sc2Mo3O12/ZrO2 composite shows almost zero thermal expansion, and its average thermal expansion coefficient is -0.13×10-6℃-1 in 30-600℃.
Keywords: non-metallic inorganic material；solid-state reaction; Sc2Mo3O12; ZrO2; composites; controllable thermal expansion; negative thermal expansion

Title: Thermodynamic conditions of corrosion between oil well cement and H2S

Authors: LIU Weijun, YAO Xiao, ZHU Huajun, ZHANG Liang, HUA Sudong
PP: 835-840
Abstract: The thermodynamic method was applied from the perspective of cement chemistry to calculate the Gibbs free energy and the lowest partial pressure necessary for the corrosion reaction occurring between H2S and oil well cement clinker as well as its hydration products in dry stratum and wet stratum at 50, 80, 150℃. The corrosion conditions and its level of difficulty were studied according to above calculation results. It is found that the corrosion reaction between H2S and oil well cement and its hydration products Ca(OH)2, 3CaO·SiO2, 3CaO·2SiO2·3H2O, 2CaO·SiO2, 3CaO·Al2O3·6H2O, 2CaO·3SiO2·2.5H2O, 3CaO·Al2O3·3CaSO4·31H2O and 3CaO·Al2O3·CaSO4·12H2O only occurs at special temperature and pressure in dry stratum. While in wet stratum, the H2S, in forms of HS- and S2-, will react with Ca2+, causing the decline of pH value of pore solution, which trig the continuous solution of hydration products. The whole cement stone will decay and lose strength as a result.
Keywords: materials physics and chemistry；cementing; oil well cement; H2S corrosion; chemical thermodynamics

Title: Hydrothermal preparation of CuFe2O4 nanoparticles in the magnetic field and the study of their magnetic behavior

Authors: LIU Gang, WU Mingzai, LIU Yanmei, DU Xianzhen, MA Yongqing, LIU Xiansong
PP: 830-834
Abstract: In the presence of applied magnetic field, Spinel structure CuFe2O4 particles were prepared by hydrothermal process using CuCl2 H2O and FeCl3 H2O as starting materials. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were carried out to investigate their structures, morphologies and magnetic properties. The result demonstrates that the introduction of magnetic field during synthesis process could not only influence on the crystallographic orientation, crystalline size and particles dispersion, but also reduce the saturation magnetization significantly. And after annealing treatment, the saturation magnetizations of particles are greatly improved in magnetic field or not.
Keywords: material physics and chemistry; ferrite; magnetic field; hydrothermal; annealing

Title: Preparation and characterization of new tentacle-type chiral stationary phase of β-CD

Authors: WANG Quanyi, ZHU Weixia, CUI Yannan, XIE Shuang, SONG Hang, DU Kaifeng
PP: 825-829
Abstract: To add the amount of β-CD on SiO2, the new tentacle-type β-CD chiral stationary phase (CSP) was prepared. In the study, choosing γ-aminopropyltrimethoxysilane as the coupling agent, PVA was grafted on the surface of SiO2 by using a surface grafting technique, to get more OH on the SiO2 derivant. Finally, β-CD was used to modify the PVA-SiO2 by coupling action of γ-glycidoxypropyltrimethoxysilane, to get β-CD-PVA-SiO2. Using Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Dubois M method and Molisch regents were employed to characterize the properties of the CSPs. The experimental results showed that β-CD was successfully grafted on PVA-SiO2 and the amount was 3 times of conventional CPS.
Keywords: material physics and chemistry; chiral stationary phase; tentacle-type; cyclodextrin

Title: Study on crystallization kinetics of PA6 in confined domains

Authors: JI Yali, LIANG Kai, LIANG Borun
PP: 820-824
Abstract: In this study, the nanoblends of poly (2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 (PPO/PA6) were prepared by the method of in situ polymerization and in situ compatibility, and the confined crystallization behavior of PA6 was studied using differential scanning calorimetry and wide angle X-ray diffraction (WAXD). It was found that there coexisted α-type and a small quantity of γ-type crystals in the micrometer-sized confined domains; however, a large amount of γ-type crystals was formed in the nanometer-sized confined domains. According to non-isothermal crystallization kinetics and Kissinger formula, it was concluded that PA6 was easy to crystallize in the nanoblends.
Keywords: material physics and chemistry; confined crystallization; crystallization kinetics; PA6; nanoblend

Title: Microstructure and magnetic properties of Co and C co-doped LiNbO3

Authors: SHENG Peng, ZENG Fei, CHEN Chao, PAN Feng
PP: 814-819
Abstract: In this paper, Co and C co-doped LiNbO3 was prepared by ion beam implantation with Co atom content of 3.5% and C atom contents of 2%, 3%, 4%, respectively. The microstructure and magnetic properties of the doped LiNbO3 were investigated. With low concentration of C, structure characterization using X-ray absorption near edge structure (XANES) determined that the Co atoms substituted principally the Nb atoms in the LiNbO3 lattice. When the atom concentration of C achieved 4%, Co clusters were precipitated from the LiNbO3 lattice. The magnetic properties of the doped LiNbO3 are enhanced as the increase of C contents. The ferromagnetism in (Co, C)-doped LiNbO3 is proposed to be mediated by the structure defects induced by C doping.
Keywords: materials physics; LiNbO3; diluted magnetic oxides; X-ray absorption near edge structure

Title: Surface-modification effect of magnesium hydroxide on the properties of flame-retarded O-SEBS/PP blends

Authors: LIU Shumei, GE Junjing, ZHAO Jianqing
PP: 808-813
Abstract: This paper presents surface-modification effect of Mg(OH)2 on the properties of flame-retarded blends of styrene-ethylene/butylene-styrene(SEBS)block copolymers filled by paraffin oil and polypropylene (O-SEBS/PP). The flame-retarded rate of the O-SEBS/PP blends attains UL 94@V-0 by the incorporation of mass percent 60% Mg(OH)2, but mechanical properties decrease. The influences of surface-modification of Mg(OH)2 by three kinds of silane couplings (KH550, KH560 and A171) on the combustion, mechanical and processing properties of the O-SEBS/PP/Mg(OH)2 composites are evaluated. The surface-modification of A171 induces the tensile strength of the composites to increase while the surface-modification of KH560 leads to decrease. Scanning electron microscope images of cryogenic fracture sections of the composites by the use of Mg(OH)2 surface-modified by A-171 illustrate a fine encapsulation and the uniform dispersion of particles and strong interfacial bonding between particles and matrix.
Keywords: organic macromolecule materials science; styrene-ethylene/butylene-styrene block copolymer/polypropylene blends; surface-modification; halogen-free flame retardancy; Mg(OH)2

Title: Preparation and characterization of antibacterial CMC/SSD composite membranes

Authors: ZHANG Linghui, ZHANG Lingmin, WANG Qiulan, CAI Jiye, LOU Cui
PP: 801-807
Abstract: A novel composite membrane of carboxymethyl chitosan (CMC)/silver sulfadiazine (SSD) was prepared by mixing CMC water solution with SSD. The structure and the properties of the composite membranes were investigated by atomic force microscopy (AFM), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and so on. AFM images of the composite membrane showed that the average roughness of the composite membrane was larger than the membrane prepared by only CMC. The results of FTIR and XRD showed that SSD was stable in CMC and both of them could exist finely together. The inhibitory rates of solution of the composite membrane against Escherichia coli 8099 and Staphylococcus aureus ATCC 6538 increased with the increasing concentration of solution respectively. It’s a promising wound dressing.
Keywords: foundational subject in materials science; carboxymethyl chitosan; silver sulfadiazine; surface morphology; Fourier transformed infrared spectroscopy; X-ray diffraction; antibacterial property

Title: Advances in preparation and modification of melamine formaldehyde resin foam

Authors: WANG Dongwei, ZHANG Xiaoxian, YANG Danna, LI Sai
PP: 795-800
Abstract: Melamine formaldehyde (MF) resin foam has a variety of splendid properties, which can be widely used. On account of the main disadvantages, its application in wider range is inhibited. In this paper, several kinds of methods of manufacturing MF and its mechanism as well as the modification for instance improving its toughness, intensity, lowing down its water or oil absorbability in recent years is previewed in detail.
Keywords: polymer materials; melamine foam; reviews; preparation; synthesis mechanism; modification; application

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