Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      15 February 2014, Volume 30 Issue 2 Previous Issue    Next Issue
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    Type Inversion and Certain Physical Properties of Spray Pyrolysed SnO2:Al Films for Novel Transparent Electronics Applications
    K. Ravichandran, K. Thirumurugan
    J. Mater. Sci. Technol., 2014, 30 (2): 97-102.  DOI: 10.1016/j.jmst.2013.09.019
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    Aluminium doped tin oxide films have been deposited onto glass substrates by using a simplified and low cost spray pyrolysis technique. The Al doping level varies between 0 and 30 at.% in the step of 5 at.%. The resistivity (ρ) is the minimum (0.38 Ω cm) for 20 at.% of Al doping. The possible mechanism behind the phenomenal zig-zag variation in resistivity with respect to Al doping is discussed in detail. The nature of conductivity changes from n-type to p-type when the Al doping level is 10 at.%. The results show that 20 at.% is the optimum doping level for good quality p-type SnO2:Al films suitable for transparent electronic devices.

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    Magnetic and Transport Properties of Mn0.98Cr0.02Te Epitaxial Films Grown on Al2O3 Substrates
    Z.H. Wang, D.Y. Geng, J. Li, Y.B. Li, Z.D. Zhang
    J. Mater. Sci. Technol., 2014, 30 (2): 103-106.  DOI: 10.1016/j.jmst.2013.07.009
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    The epitaxial Mn0.98Cr0.02Te films on single crystal Al2O3 (0001) substrates were prepared by pulsed laser deposition. The X-ray diffraction and scanning electron microscopy results showed that the good continuous epitaxial film was obtained with substrate temperature of 500 °C. When the substrate temperature reached 700 °C, the film was island growth and the manganese oxides phase appeared. The temperature dependence of both the magnetization and electrical resistance showed a sharp rise at around 60 K due to the magneto-elastic coupling. The temperature dependence of the electrical resistance of Mn0.98Cr0.02Te provided evidence for a transition from the metallic to semiconducting state at 305 K due to the spin disorder scattering with a large contribution from the influence of magnon drag.

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    Effects of Polymeric Stabilizers on the Synthesis of Gold Nanoparticles
    Eun Jung Kim, Jeong Hyun Yeum, Jin Hyun Choi
    J. Mater. Sci. Technol., 2014, 30 (2): 107-111.  DOI: 10.1016/j.jmst.2013.11.012
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    Gold nanoparticles (AuNPs) stabilized with sodium alginate (SA), glycol chitosan (GC), polyvinyl alcohol (PVA), and polyethyleneimine (PEI) were synthesized in aqueous solutions at room temperature. Different sizes and size distributions of AuNPs were obtained according to the polymeric stabilizers. The mean particle diameters of AuNPs synthesized with GC and PVA as stabilizers were about 5.1 and 5.3 nm, respectively, while those of AuNPs stabilized with SA and PEI were 8.4 and 10.8 nm, respectively. When SA was used, relatively large particles aggregated to form large clusters. In the case of GC, a number of small particles built up large clusters. When PVA was used, the size and the number of nanoparticles were estimated small with a low weight content of Au. For this reason, the PVA-stabilized AuNPs formed clusters with a small hydrodynamic size. The AuNPs synthesized in the aqueous solution of PEI without a reducing agent, sodium borohydride, were uniform in size and formed the smallest nanoclusters (67.4 nm). In this case, the highest Au content was obtained. Sufficiently grown nanoparticles with a high Au content and a limited hydrodynamic size are considered to be suitable for a variety of applications.

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    One Step Synthesis and Growth Mechanism of Carbon Nanotubes
    Akshay Kumar, K. Singh, O.P. Pandey
    J. Mater. Sci. Technol., 2014, 30 (2): 112-116.  DOI: 10.1016/j.jmst.2013.09.005
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    A simple one step, reproducible, synthesis route for carbon nanotubes was proposed. No external catalyst was used for the synthesis. These nanotubes were obtained after decomposition of acetone at 650 °C in a specially designed autoclave. The pressure generated due to decomposition of acetone played a vital role in the synthesis. The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3–14 nm. The thermo gravimetric analysis showed 3% weight loss below 500 °C; the content of amorphous carbon is very less. The growth mechanism of CNTs was also proposed in the present paper.

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    Preparation of Ferrioxalate Submicrorods/Graphene Composites and Their Photocatalytic Properties
    Min Fu, Yun Zhao, Qingze Jiao
    J. Mater. Sci. Technol., 2014, 30 (2): 117-122.  DOI: 10.1016/j.jmst.2013.08.022
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    Ferrioxalate submicrorods/graphene composites were synthesized through a simple solvothermal process in a mixture of ethylene glycol and water. The in situ growth of ferrioxalate submicrorods and the reduction of graphene oxide (GO) were completed in a one-step reaction. Fourier transform infrared and Raman spectroscopy confirmed the reduction of GO. Uniform rod-like ferrioxalates with diameter of about 600 nm and length of several micrometers were well distributed on the graphene sheets. As-obtained composites exhibited better photocatalytic properties than pure ferrioxalate submicrorods. The influence of different contents of GO on photocatalytic performance was also investigated. A possible photocatalytic mechanism of ferrioxalate submicrorods/graphene composites was proposed.

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    Oxidation and Mechanical Properties of SiC/SiC–MoSi2–ZrB2 Coating for Carbon/Carbon Composites
    Xiyuan Yao, Hejun Li, Yulei Zhang, Yongjie Wang
    J. Mater. Sci. Technol., 2014, 30 (2): 123-127.  DOI: 10.1016/j.jmst.2013.09.006
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    To improve oxidation resistance of carbon/carbon (C/C) composites, a SiC/SiC–MoSi2–ZrB2 double-layer ceramic coating was prepared on C/C composites by two-step pack cementation. The phase compositions and microstructures of as-prepared multilayer coating were characterized by X-ray diffraction and scanning electron microscopy. The oxidation resistance at 1773 K and the effect of thermal shock between 1773 K and room temperature on mechanical performance of coated specimens were investigated. The results show that the SiC/SiC–MoSi2–ZrB2 coating exhibits dense structure and is composed of SiC, Si, MoSi2 and ZrB2. It can protect C/C composites from oxidation at 1773 K for more than 510 h with weight loss of 0.5%. The excellent anti-oxidation performance of the coating is due to the formation of SiO2–ZrSiO4 complex glassy film. The coating can also endure the thermal shocks between 1773 K and room temperature for 20 times with residual flexural strength of 86.1%.

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    Effects of Heat Treatments on Microstructures and Precipitation Behaviour of Mg94Y4Zn2 Extruded Alloy
    Huan Liu, Feng Xue, Jing Bai, Jian Zhou, Yangshan Sun
    J. Mater. Sci. Technol., 2014, 30 (2): 128-133.  DOI: 10.1016/j.jmst.2013.04.002
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    Microstructures and precipitation behaviours of Mg94Y4Zn2 (at.%) extruded alloy during solution treatment and ageing processes were investigated. Three major phases were observed in the as-cast Mg94Zn2Y4 alloy: α-Mg, block shaped 18R long period stacking ordered (LPSO) phase and Mg24Y5 cuboid particles. After homogenization and extrusion, the block shaped LPSO phase changed into plate-like shape aligned along the direction of extrusion. During solution treatment, a small fraction of LPSO phase was transformed from 18R structure to 14H type. The nano-scale β′ phase with its close-packed planes being perpendicular to the direction of both α-Mg and LPSO structure was precipitated at ageing stage. The coexistence of β′ and LPSO phase contributes to the strengthening of the alloy, with microhardness for the matrix and LPSO structures reaching 145.8 and 155.0 HV, respectively.

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    Mechanical and Microstructural Properties of Ultra-fine Grained AZ91 Magnesium Alloy Tubes Processed via Multi Pass Tubular Channel Angular Pressing (TCAP)
    G. Faraji, P. Yavari, S. Aghdamifar, M. Mosavi Mashhadi
    J. Mater. Sci. Technol., 2014, 30 (2): 134-138.  DOI: 10.1016/j.jmst.2013.08.010
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    Ultra-fine grained (UFG) cylindrical tubes were produced via recently developed tubular channel angular pressing (TCAP) process through different passes from as-cast AZ91 magnesium alloy. The microstructure and mechanical properties of processed tube through one to four passes of TCAP process at 200 °C were investigated. Microhardness of the processed tube was increased to 98.5 HV after one pass from an initial value of 67 HV. An increase in the number of passes from one to higher number of passes has no more effect on the microhardness. Yield and ultimate strengths were increased by 4.3 and 1.4 times compared to those in as-cast condition. Notable increase in the strength was achieved after one pass of TCAP while higher number of passes has no more effect. Microstructural investigation shows notable decrease in the grain size to around 500 nm from the primary value of ∼150 μm. Dissolution and distribution of hard Mg17Al12 phase in the grain boundaries of dynamically recrystallized UFG AZ91 with a mean grain size of ∼500 nm was an interesting issue of TCAP processing at 200 °C compared to other severe plastic deformation processes.

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    In-situ Observation of Tensile Fracture in A357 Casting Alloys
    Zhongwei Chen, Xiaolei Hao, Yu Wang, Kai Zhao
    J. Mater. Sci. Technol., 2014, 30 (2): 139-145.  DOI: 10.1016/j.jmst.2013.04.014
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    The mechanism of damage evolution and fracture in A357 casting alloys was investigated by in-situ scanning electron microscopy (SEM) tensile testing. Different microstructures of A357 casting alloys were produced by eutectic Si modification and T6 heat treatment. It is shown that microcracks in these alloys are predominantly formed in eutectic Si particles. Large and elongated eutectic Si particles in unmodified alloy show the greater tendency to cracking, whereas cracking of small and round eutectic Si particles in Sr modified and T6 heat treated alloys is relatively lag. The crack mainly propagates along the broken eutectic Si particles in unmodified and Sr modified alloys or along the deepened shear bands in T6 heat treated alloy with accumulating the applied strain. The results were discussed in terms of Weibull statistics and the fracture models were established.

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    Effects of Strontium, Magnesium Addition, Temperature Gradient, and Growth Velocity on Al–Si Eutectic Growth in a Unidirectionally-solidified Al–13 wt% Si Alloy
    Hengcheng Liao, Wanru Huang, Qigui Wang, Fang Jia
    J. Mater. Sci. Technol., 2014, 30 (2): 146-153.  DOI: 10.1016/j.jmst.2013.05.003
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    Al–Si eutectic growth mechanism was investigated in a directionally-solidified Al–13 wt% Si alloy with different strontium (Sr) and magnesium (Mg) additions, growth velocities and temperature gradients. Macro- and micro-scale metallographic analyses revealed that addition level of Sr and Mg, temperature gradient and growth velocity are important factors affecting stability of solidifying Al–Si eutectic front and the final morphology of eutectic grains in the solidified Al–13 wt% Si alloys. By varying (tailoring) these factors, a variety of eutectic grain structures and morphologies such as planar front, cellular structure, a mix of cellular and columnar, or equiaxed dendrites, can be obtained. Increasing temperature gradient, reducing growth velocity, or decreasing Sr and Mg contents is beneficial to stabilizing planar growth front of eutectic grains, which is qualitatively in accordance with constitutional supercooling criterion for binary eutectic growth. In contrast, adding more Sr and Mg, increasing growth velocity, or decreasing temperature gradient produces large constitutional supercooling, leading to columnar-equiaxed transition (CET) of eutectic structure, which can be interpreted on the basis of Hunt's Model. It is also found that both solute concentration and solidification variables have significant impact not only on eutectic growth, but also on gas porosity formation.

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    Role of Double Oxide Film Defects in the Formation of Gas Porosity in Commercial Purity and Sr-containing Al Alloys
    Batool Farhoodi, Ramin Raiszadeh*, Mohammad-Hasan Ghanaatian
    J. Mater. Sci. Technol., 2014, 30 (2): 154-162. 
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    The role of double oxide film (bifilm) defects in the formation of gas porosity in commercial purity and Sr-containing Al alloys was investigated by means of a reduced pressure test (RPT) technique. The liquid metal was poured from a height into a crucible to introduce oxide defects into the melt. The melt was then subjected to different “hydrogen addition” and “holding in liquid state” regimes before RPT samples were taken. The RPT samples were then characterized by determining their porosity parameters and examining the internal surfaces of the pores formed in them by scanning electron microscopy. The results indicated oxide defects as the initiation sites for the growth of gas porosity, both in commercial purity and Sr-containing Al alloys. The results also rejected reduction of the surface tension of the melt, increase in the volumetric shrinkage and reduction in interdendritic feeding as the possible causes of an increase in the porosity content of the Al castings modified with strontium. The change in the composition of the oxide layers of double oxide film defects was suggested to be responsible for this behaviour.

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    Electrochemical Study of Diffusion Bonded Joints between Micro-duplex Stainless Steel and Ti6Al4V Alloy
    Shaily M. Bhola, Sukumar Kundu, Rahul Bhola, Brajendra Mishra, Subrata Chatterjee
    J. Mater. Sci. Technol., 2014, 30 (2): 163-171.  DOI: 10.1016/j.jmst.2013.09.017
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    In the present study, corrosion behavior of diffusion bonded joints formed between micro-duplex stainless steel (MDSS) and Ti6Al4V alloy (TiA) (at 900 °C for 60 min under 4 MPa uniaxial pressure in vacuum) was investigated in 1 mol/L HCl and 1 mol/L NaOH solutions using various electrochemical measurements such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD). For comparison, corrosion behavior of base metals (MDSS and TiA) was also evaluated. Bonded joint was characterized by light optical microscopy and scanning electron microscopy using backscattered electron mode. The layer wise σ phase and λ + FeTi phase mixture has been observed at the bond interface and the bond tensile strength and shear strength were ∼556.4 MPa and ∼420.2 MPa, respectively.

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    Principles Giving High Penetration under the Double Shielded TIG Process
    Dongjie Li, Shanping Lu, Dianzhong Li, Yiyi Li
    J. Mater. Sci. Technol., 2014, 30 (2): 172-178.  DOI: 10.1016/j.jmst.2013.09.002
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    A new welding method named double shielded tungsten inert gas (TIG) has been developed to improve the TIG weld penetration. The main principles to increase the weld depth have been discussed. Results show that the critical oxygen content in the weld pool is around 100 × 10−6 as the temperature coefficient of surface tension changes from negative to positive. The tracer test using pure silver shows that the direction of Marangoni convection changes as the oxygen content increases in the weld pool. The effect of arc constriction on the weld depth has been evaluated on a water-cooled copper plate, and the result indicates that the torch of double shielded can give a more powerful arc. Heavy oxide on the pool surface has undesirable impacts on the increasing of weld depth as the oxygen excessively accumulates in weld pool. It is possible to form chromium oxide in the weld process, while the iron oxide may form as the weld surface exposes to the air after the shielded gas moving away.

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    Evaluation of Pitting Behavior on Solution Treated Duplex Stainless Steel UNS S31803
    Yiming Jiang, Tao Sun, Jin Li, Jie Xu
    J. Mater. Sci. Technol., 2014, 30 (2): 179-183.  DOI: 10.1016/j.jmst.2013.12.018
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    The pitting corrosion resistance of duplex stainless steels UNS S31803 annealed at different temperatures ranging from 1050 °C to 1200 °C for 24 h has been investigated by means of potentiostatic critical pitting temperature (CPT). The microstructural evolution and pit morphologies of the specimens were studied through optical microscopy and scanning electron microscopy. The potentiostatic CPT measurements show that the CPT was elevated with the annealing temperature increased from 1050 °C to 1150 °C and decreased as the temperature further increased to 1200 °C. The specimens annealed at 1150 °C exhibited the highest CPT and the best pitting corrosion resistance. The pit morphologies show that the pit initiation sites transfer from austenite phase to ferrite phase as the annealing temperature increases. The results were explained by the variation of pitting resistance equivalent number (PREN) of ferrite and austenite phases as the annealing temperature was varied.

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    Effect of Transverse Grain Boundary on Microstructure, Texture and Mechanical Properties of Drawn Copper Wires
    Jian Chen, Xiaoguang Ma, Wen Yan, Feng Xia, Xinhui Fan
    J. Mater. Sci. Technol., 2014, 30 (2): 184-191.  DOI: 10.1016/j.jmst.2013.04.018
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    In the present study, microstructure and texture of drawn copper wires with a large number of transverse grain boundaries have been characterized and their mechanical properties have been analyzed. The results show that the texture evolution is accelerated by transverse grain boundary and the saturation value 60% of volume fraction of <111> fiber texture component is reached rapidly with increasing strain. For the microstructure of drawn wires with a large number of transverse grain boundaries, the critical strain, where lamellar boundaries form, is less than that for wires with equiaxed grains or columnar grains (all grain boundaries parallel to axis direction). Since transverse grain boundary accelerates grain subdivision and dislocation density increases rapidly in drawn wires with a large number of transverse grain boundaries, there are a higher flow stress and a higher work hardening rate.

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    Visible Light Photocatalytic Properties of Metastable γ-Bi2O3 with Different Morphologies
    Weichang Hao, Yuan Gao, Xi Jing, Wen Zou, Yan Chen, Tianmin Wang
    J. Mater. Sci. Technol., 2014, 30 (2): 192-196.  DOI: 10.1016/j.jmst.2013.09.023
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    The metastable γ-Bi2O3 photocatalysts with different morphologies were fabricated by means of a chemical precipitation method. The microstructure of as-prepared samples was characterized by X-ray diffraction, transmission electron microscopy and ultraviolet-visible diffusion reflectance spectroscopy. The photocatalytic performance of Bi2O3 powder was evaluated using rhodamine B as a model pollutant under visible light irradiation. The visible light photocatalytic activity of Bi2O3 with different morphologies is as follows, nanorod > nanorod/nanoflake > N doped TiO2 > irregular particle > agglomerated particle. The γ-Bi2O3 shows the best photocatalytic performance and it can effectively degrade 97% RhB within 60 min.

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    Annealing Effect of ZnO on the Performance of Inverted Organic Photovoltaic Devices
    Wenjing Qin, Guojing Ding, Xinrui Xu, Liying Yang, Shougen Yin
    J. Mater. Sci. Technol., 2014, 30 (2): 197-202. 
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    ZnO nanoparticles films were prepared via sol–gel process and incorporated into inverted organic photovoltaic devices with a structure of ITO/ZnO/P3HT:PCBM/MoO3/Ag, in which ZnO film served as an electron selective layer. The effects of annealing temperature of ZnO film on the device performance were investigated. When the annealing temperature was 300 °C, a well-arranged ZnO thin film was obtained, and the optimized device had doubled short circuit current density (JSC) and seven-fold higher power conversion efficiency (PCE) compared to the devices without ZnO film. This improvement could be attributed to the enlarged interfacial area of ZnO/active layer and better energy band matching which causes an efficient electron extraction and a decreased interface energy barrier. At particularly high annealing temperature, dramatically increased sheet resistance of indium tin oxide (ITO) was found to cause PCE deterioration. Our finding indicates that it is highly important to investigate both morphology and electrical effects for understanding and optimizing organic photovoltaic (OPV) performance.

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ISSN: 1005-0302
CN: 21-1315/TG
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