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      20 August 2015, Volume 43 Issue 8 Previous Issue    Next Issue
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    Mechanical Property and Enhancement Mechanism of Aluminum 5083 Composites with Carbon Nanotubes
    LI Zheng, CAI Xiao-lan, ZHOU Lei, YI Feng, YU Ming-jun, ZHANG Wen-zhong, GUO Li
    2015, 43 (8): 1-6.   DOI: 10.11868/j.issn.1001-4381.2015.08.001
    Abstract ( 1132 ( PDF (3510KB)( 320 Citation
    The composite materials of 3%(mass fraction)carbon nanotubes(CNTs)/Al5083 were fabricated by high-energy ball milling and cold rolling. The surface morphology of the composite powder of ball milled was observed using SEM and TEM, the phase of composite powder and composite material were analyzed by Raman spectrum and XRD.Finally, the mechanical properties of composite material were tested.The results show that, the CNTs have a good structure and are well-distributed in the for 1.5h milled aluminum matrix. The composite material exhibits high strength for the tensile strength of 278MPa, yield strength of 247MPa and elongation rate of 0.07, Vickers hardness of 95. Compared with the predicted value of yield strength by thermal mismatch model and Orowan model, the experiment value indicates that the mechanism of CNTs/Al5083 accords with Orowan mechanism.
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    Superplastic Process and Deformation Mechanism of Asymmetrically Rolled AZ31 Magnesium Alloy
    JIANG Hai-tao, DUAN Xiao-ge, CAI Zheng-xu, WANG Dan
    2015, 43 (8): 7-12.   DOI: 10.11868/j.issn.1001-4381.2015.08.002
    Abstract ( 1029 ( PDF (3521KB)( 270 Citation
    AZ31 magnesium alloy sheet was prepared by asynchronous rolling process. From 300℃ to 450℃, tensile test was conducted with different strain rates of 5×10-3, 1×10-3s-1 and 5×10-4s-1 respectively to investigate the superplastic deformation behavior of AZ31 magnesium alloy. The value of the strain rate sensitive index m, the superplastic deformation activation energy Q and the threshold stress σwere also calculated. The superplastic deformation mechanism of AZ31 was investigated through observation of the fracture morphology of the tensile specimens by EBSD and SEM.The results show that the plastic deformation capacity of AZ31 magnesium alloy enhances with increasing deformation temperature and decreasing strain rate. AZ31 magnesium alloy exhibits good superplasticity, and maximum elongation-to-failure of 206% at 400℃ when the strain rate is 5×10-4s-1, and the m value is 0.72. Furthermore, the superplastic deformation of the asynchronous rolled AZ31 magnesium alloy at 400℃ relies on the joint effects of grain boundary sliding (GBS) controlled by lattice diffusion and basal slip.0
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    Effects of Heat Treatment on Microstructure and Properties of 7A85 Aluminium Alloy
    HE Zheng-lin, GAO Wen-li, LU Zheng, FENG Zhao-hui
    2015, 43 (8): 13-18.   DOI: 10.11868/j.issn.1001-4381.2015.08.003
    Abstract ( 1195 ( PDF (3079KB)( 497 Citation
    The influence of heat treatment on microstructure, mechanical properties and intergranular corrosion(IGC) of 7A85 aluminum alloy was investigated by tensile testing, conductivity testing, intergranular corrosion testing and transmission electron microscope. The results show that tensile strength, elongation and conductivity of 7A85 aluminium alloy aged at 120℃/24h are 760.8MPa, 8.9% and 29.7%IACS respectively;the main strengthening precipitates in the alloy are GP zones.While the tensile strength and the conductivity of 7A85 aluminium alloy reach 597.7MPa and 38.1%IACS respectively, after duplex aging at 120℃/8h+165℃/12h, and with increase of aging time, the precipitates in the matrix become coarser and PFZs become broaden, resulting in the susceptibility to IGC decreasing. Therefore, the alloy after duplex aging at 120℃/8h+165℃/12h shows good comprehensive performance.
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    Influence Factors and Photocatalytic Activity of ZnO Nanoarrays Synthesized via Solution Method
    BAO Yan, ZHANG Yong-hui, MA Jian-zhong
    2015, 43 (8): 19-24.   DOI: 10.11868/j.issn.1001-4381.2015.08.004
    Abstract ( 767 ( PDF (4251KB)( 240 Citation
    ZnO nanoarrays were fabricated through solution method using nano ZnO as seeds, which were hydrolyzed in-situ by anhydrous zinc acetate. The effects of various factors on the morphologies of ZnO nanoarrays during the reaction process, and the photocatalytic activity of the obtained ZnO nanoarrays was investigated. The results indicate that ZnO nanoarrays, which are obtained from ZnO seeds fabricated by dip-coating, distribute uniformly and densely;ZnO nanoarrays, which are obtained from ZnO seeds fabricated by spray coating, appears with larger blank area;the addition of diethanolamine or formamide into the seeds precursor solution, will result in the aggregation of nano ZnO nucleation, which is not conducive to gain the uniform distribution of ZnO nanoarrays. When the solution pH is 6.7, the uniform and dense ZnO nanoarrays with good vertical orientation can be obtained. When using ZnO nanoarrays based on stainless steel wire mesh for the photocatalytic degradation of methyl orange of about 15mg/L, methyl orange is completely eliminated after 3h. Moreover, the ZnO nanoarrays exhibit good photocatalytic activity after three times continuous photocatalytic degradation in succession.
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    Effect of Anion(NO3-/Cl-/SO42-) on Crystal Type and Structural Stability of Ni(OH)2
    HAN Quan-yong, ZHU Yan-juan, MIAO Cheng-cheng, LUO Jie, ZHANG Wei, ZHAO Teng-qi, ZHANG Chun-hua
    2015, 43 (8): 25-30.   DOI: 10.11868/j.issn.1001-4381.2015.08.005
    Abstract ( 709 ( PDF (1784KB)( 341 Citation
    Nanometer nickel hydroxide with three kinds of nickel sources were synthesized by ultrasonic-assisted precipitation under single, double and no doping condition. The effect of three anions (NO3-, Cl-, SO42-) which comes from nickel sources on the crystal structure and stability of samples were investigated. The results indicate that the larger ion radius SO42- is more in favor of the formation of α-Ni(OH)2 in the case of undoping. In the single doped Co samples(Ni2+:Co2+=1:0.20), NO3- anion is not only conducive to form α-Ni(OH)2, but also can keep high stability of α-Ni(OH)2 in alkali solution. When co-doped Co/Cu(Ni2+:Co2+:Cu2+=1:0.15:0.05), the samples which were prepared using three nickel sources are all pure α-Ni(OH)2 structures, however, the stability of the nickel nitrate doped α-Ni(OH)2 in alkali solution is higher, which is using Ni(NO3)2 as nickel source, NiCl2 is lower, NiSO4 is the lowest. It can be concluded that the structure and stability of α-Ni(OH)2 is not only related to doping condition, but also related with anions.
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    Preparation and Characterization of Hydrophobic SiO2-glass Fibers Aerogels via Ambient Pressure Drying
    YU Yu-xi, WU Xiao-yun, SAN Hai-sheng
    2015, 43 (8): 31-36.   DOI: 10.11868/j.issn.1001-4381.2015.08.006
    Abstract ( 738 ( PDF (1942KB)( 418 Citation
    Hydrophobic SiO2-glass fibers aerogels were prepared by sol-gel process with tetraethoxysiliane (TEOS) and methyltriethoxysilane (MTES) as the silica source, glass fibers as reinforcement, followed by ambient pressure drying. The physical properties and microstructure of silica aerogels were characterized by nitrogen adsorption/desorption tests, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis, scanning electron microscopy, high resolution transmission electron microscopy, contact angle measurement and mechanical testing. The influences of acid concentration and soaking time during pretreatment of glass fibers on the densities of SiO2-glass fibers aerogels were investigated. The results show that when the pretreatment condition of glass fibers is soaking 0.5h at 2.5mol/L hydrochloric acid, the obtained monolithic SiO2-glass fibers aerogels exhibit the lowest density of 0.12g·cm-3 and pore size is in the range of 2-50nm, the water contact angle is 142°, the thermal stability temperature reaches 500℃, the compressive strength is 0.05MPa, and the elastic modulus is 0.5MPa.
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    Effect of Carbon Sources on Synthesis of AlON Powder and Fabrication of Transparent Ceramics
    LEI Jing-xuan, SHI Ying, XIE Jian-jun, SHI Jian-bo, WU Hao, ZHAO Zhong-jian, HU Wei
    2015, 43 (8): 37-42.   DOI: 10.11868/j.issn.1001-4381.2015.08.007
    Abstract ( 835 ( PDF (2083KB)( 296 Citation
    Nanosized carbon black and micron carbon powder were used as the carbon sources to synthesize AlON powders by carbothermal reduction method and prepare transparent AlON ceramics by the synthesized AlON powders through pressureless sintering. Effects of the carbon sources on the synthesis of the AlON powder and the fabrication of the transparent ceramics were investigated by XRD, SEM, particle size analyzer and spectrometer. The results show that the size and the morphology of the carbon sources are closely related with the calcining synthetic temperature, the morphology and the particle size of the obtained AlON powder greatly. The addition of the nanosized carbon black decreases the calcination temperature to 1730℃ at which the single phase AlON powders are synthesized. High purity AlON powders prepared by the micron carbon powders calcined at 1750℃ for 2 hours are used to fabricate the highly transparent AlON ceramics. The in-line optical transmittance at 1000-5000nm wavelength of the AlON ceramic sample (1mm-thick) is almost 80%, with the max transmittance of 83.7% at 3.93μm wavelength. The average grain size of the obtained AlON transparent ceramics is in range of 110-120μm.
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    Influences of Substrate Negative Bias Voltage on Microstructure and Performance of DLC Coatings
    JI Xi-wang, XU Zhen-hua, HE Li-li, HE Li-min, HAO Jun-wen, ZHEN Hong-bin
    2015, 43 (8): 43-49.   DOI: 10.11868/j.issn.1001-4381.2015.08.008
    Abstract ( 992 ( PDF (4192KB)( 540 Citation
    A series of diamond-like-carbon coatings (DLC) were deposited on top of YG8 cemented carbides by direct current plasma enhanced chemical vapor deposition (DC-PECVD) in different substrate negative bias voltage. Scanning electron microscopy, atomic force microscopy, roughness tester, micro-hardness tester, scratch tester, Raman spectroscopy, X-ray photoelectron spectroscopy were used to study the composition, surface morphology, micro-hardness and interfacial adhesion performance of the DLC coatings. The results show that the coatings' surface morphology gradually becomes smooth and dense with the increasing of the substrate negative bias voltage.Meanwhile, the number and size of particles decrease. The DLC coatings exhibit typical diamond-like characteristics from Raman spectroscopy. The fraction belonging to sp3 valence bond is approach to a maximum value at 1000V and then decreases with the increase of the substrate negative bias voltage. The maximum value of the sp3 valence bond is determined to be about 67.9%.Micro-hardness varying pattern is consistent with sp3 content change low, sp3 content determines the micro-hardness of the DLC coatings. Ions sputtering could lead to the decrease of the thickness when the substrate negative bias voltage increases excessively. The best adhesive strength is gained among the coatings when the substrate negative bias voltage is near to 1100V.
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    Effect of Cold Rolling on Microstructures and Mechanical Properties of Al10Cu25Co20Fe20Ni25 High-entropy Alloys
    WANG Zhong, LIN Wan-ming, MA Sheng-guo, YANG Hui-jun, LIANG Hong-yu, QIAO Jun-wei
    2015, 43 (8): 50-55.   DOI: 10.11868/j.issn.1001-4381.2015.08.009
    Abstract ( 1223 ( PDF (1909KB)( 422 Citation
    The tensile testing of as-cast Al10Cu25Co20Fe20Ni25 high-entropy alloys after cold rolling was conducted upon at room temperature. The phase structure, microstructural morphology, and tensile fracture were investigated by the combination of X-ray diffraction(XRD) and scanning electron microscope(SEM). The results reveal that by cold-rolling processing, the Al10Cu25Co20Fe20Ni25 high-entropy alloy hardness reaches the maximum up to 285HV, increases by 51.6% compared with the as-cast sample. Moreover, the tensile strength reaches the maximum up to 638MPa, when deformation amount is 40%, is 2.7 times of the as-cast alloy.Tensile fracture analysis shows that the fracture mode of as-cast alloy is dendrits intergranular fracture and ductile dimple fracture, and the cold-rolled alloys fracture mode is mainly ductile dimple fracture.
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    Crack Closure Behavior and Crack Propagation Characteristic of FGH95 Powder Metallurgy Superalloy
    ZUO Ping, WEI Da-sheng, WANG Yan-rong
    2015, 43 (8): 56-61.   DOI: 10.11868/j.issn.1001-4381.2015.08.010
    Abstract ( 926 ( PDF (1875KB)( 329 Citation
    Plasticity-induced crack closure effect of compact tension (CT) specimen of FGH95 powder metallurgy superalloy was investigated by using finite element method. The stress distribution in crack surface was analyzed. The effects of three principal factors, the constitutive model, mesh density and stress ratio, on the crack closure behavior were studied, to further establish crack propagation life analysis model of CT specimens with considering crack closure, and to predict life. The results show that crack closure in elastic-perfectly plastic constitutive model appears more sensitive to grid cell than that in multi-linear kinematic hardening constitutive model. Crack closure trends to be stable with the number of crack tip elements in the plastic zone reach to 20. Crack closure decreases with the increase of stress ratio, and disappears as stress ratio reaches to 0.5. The revised life prediction model shows higher prediction accuracy than traditional model for CT specimens.
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    Stress Analysis and Fatigue Behavior Assessment of Components with Defect Based on FEM and Lock-in Thermography
    FAN Jun-ling, GUO Qiang, ZHAO Yan-guang, GUO Xing-lin
    2015, 43 (8): 62-71.   DOI: 10.11868/j.issn.1001-4381.2015.08.011
    Abstract ( 947 ( PDF (5717KB)( 220 Citation
    The relationships between the stress concentration factor Kt with the depth h and diameter φ of the blind hole were investigated based on the FEM. The thermo-elastic analysis mode (E-Mode) built-in the lock-in thermography was utilized to study the stress distribution around the blind hole, and to predict the variation of Kt of different depth. Good predictions were achieved between the thermography and FEM. The variations of the intrinsic dissipation and the temperature signal during fatigue process were studied respectively using the dissipation mode (D-Mode) of Altair Li and Altair software, to evaluate fatigue damage evolution. These two signals were considered as fatigue damage markers to rapidly predict the fatigue limit and the fatigue notch factor Kf of the component with blind hole. The theoretical result validates the capability of the lock-in thermography.
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    Influence of Sn4+ Substitution on Magnetic Properties of NiZn Power Ferrites
    MA Yu-qi, LIU Xian-song, FENG Shuang-jiu, HUANG Xin, HUANG Feng
    2015, 43 (8): 72-76.   DOI: 10.11868/j.issn.1001-4381.2015.08.012
    Abstract ( 714 ( PDF (1775KB)( 303 Citation
    The stoichiometric Ni0.65Zn0.35SnxFe2-xO4 (x=0.00-0.08) power ferrites soft magnetic material was prepared by the solid-state reaction method. The structural characteristics and electromagnetic properties were investigated by X-ray diffraction(XRD), SEM, LCR tester, B-H analyzer, respectively. The results indicate that with increasing Sn4+ substitution amount, lattice constant a increases gradually, grain size varies not much, saturation magnetic flux density Bs continuously decreases, initial permeability μi of the ferrites increases initially and then decreases, and power loss Pcv has an opposite change with μi.The power loss Pcv has a minimum value when the Sn4+ substitution amount is 0.04 and Pcv decreases gradually when the temperature increases.
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    Contact Fatigue Life and Failure Mode of Plasma Sprayed Coating Based on Statistical Analysis
    ZHANG Zhi-qiang, LI Guo-lu, WANG Hai-dou
    2015, 43 (8): 77-83.   DOI: 10.11868/j.issn.1001-4381.2015.08.013
    Abstract ( 854 ( PDF (2052KB)( 342 Citation
    The rolling contact fatigue(RCF) life and failure modes of coatings, prepared by plasma sprayed Ni-based alloy, were investigated under different stress levels, and were analyzed and discussed by statistical analysis methods (including variance analysis, regression analysis and discrimination analysis) with R-3.1.1 software as a platform. The results show that the RCF life of the coatings exhibits normal distribution form. In addition, the mean and variance of the coatings' life decreases as the contact stress increases, and the distribution of the fatigue life becomes more concentrated. Furthermore, variance analysis indicates that the contact stress has a significant influence on the RCF life of the coatings. And the mean life of the coatings is linear associated with the contact stress. The discrimination criterion for the failure modes of the coatings is also established. The failure modes of the coatings can be predicted if the contact stress and the fatigue life are designated. And the prediction accuracy of the failure mode is above 65%. Furthermore, the contribution proportion of the fatigue life for the failure mode is obviously higher than that of the contact stress, thus the fatigue life is the main factor determining the failure mode of the coating.
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    Research Progress in Preparation and Application of TEMPO-oxidized Cellulose Nanofibers
    DAI Lei, LONG Zhu, ZHANG Dan
    2015, 43 (8): 84-91.   DOI: 10.11868/j.issn.1001-4381.2015.08.014
    Abstract ( 2777 ( PDF (1259KB)( 999 Citation
    The recent progress on TEMPO-oxidized cellulose nanofibers(TOCNs) was reviewed. Research progress on fabrication of TOCNs was discussed, including development of TEMPO-mediated oxidation system, research on various of cellulose raw materials, and factor influencing the homogenization of TEMPO-oxidized cellulose. The latest application of TOCNs in composite materials, films, nanopapers and other fields was discussed. Furthermore, the development status was evaluated, the existing problems and developing trend of TOCNs were also introduced.
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    Research and Application Development of Microbe Cement
    QIAN Chun-xiang, WANG Xin, YU Xiao-niu
    2015, 43 (8): 92-103.   DOI: 10.11868/j.issn.1001-4381.2015.08.015
    Abstract ( 1362 ( PDF (3849KB)( 842 Citation
    Microbiologically induced calcium carbonate precipitation(MICP) was a biological process of calcium carbonate precipitation resulting from bio-mineralization during metabolic activities of microorganisms. Microbe cement, a kind of novel biological cementitious material, was developed due to the special cementation of calcium carbonate via microbe. Research and progress in recent years were discussed in detail from three aspects of mineralization mechanisms, cementation function and applications in geotechnical engineering of microbe cement. The problems existing at present were analyzed, and ways of thinking and suggestions for further research on microbe cement were put forward.
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    Recent Progress on Flame Retardance of Polymer/Layered Silicate Nanocomposites
    CHEN Ge-gu, GUAN Ying, QI Xian-ming, PENG Feng, YAO Chun-li, SUN Run-cang
    2015, 43 (8): 104-112.   DOI: 10.11868/j.issn.1001-4381.2015.08.016
    Abstract ( 896 ( PDF (3233KB)( 277 Citation
    The preparation methods of polymer/layered silicate nanocomposites were summarized, based on the research progress on the flame retardance of layer silicate(clay) reinforced polymer nanocomposites. It is pointed out that melt intercalation is a highly effective and environmental friendly production method. The flame retardance mechanism of layered silicates in nanocomposites was discussed in details from three aspects, including barrier effect, network structure and radical trapping, which produced by silicates in nanocomposites. At last, it is pointed out that there are still problems existing in the current flame retardance research of polymer/layered silicate nanocomposites, and the future development of flame retarded polymer nanocomposites is prospected.
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