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      20 October 2016, Volume 44 Issue 10 Previous Issue    Next Issue
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    Droplets Deposition Based on Pulsated Orifice Ejection
    DONG Wei, WEI Yu-ting, KANG Shi-wei, GAI Ru-kun, XU Fu-min, LU Dong
    2016, 44 (10): 1-7.   DOI: 10.11868/j.issn.1001-4381.2016.10.001
    Abstract ( 874 ( PDF (8541KB)( 164 Citation
    A novel equipment based on pulsated orifice ejection method was developed, which can be used to three-dimensional fabrication by depositing uniform micro-droplets one by one. The position accuracy of micro droplets in vertical deposition and the influence of velocity of working platform on lines deposition were carried out. The good reproducibility and accuracy of droplets deposition were proved by high speed camera and micro-structure observation. The results show that the overlapping with no obvious defects between adjacent droplets is obtained when the speed of working platform reaches around 600μm/s in lines deposition. Based on the above results, several thin wall components with good flatness were successfully obtained. Therefore this work provides a novel method for metal micro-droplets deposition manufacture.
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    Microstructure and Room Temperature Fracture Toughness of Nb-Si Materials Alloyed by Rare Earth Elements (La,Sm,Tb)
    GUO Feng-wei, KANG Yong-wang, XIAO Cheng-bo
    2016, 44 (10): 8-16.   DOI: 10.11868/j.issn.1001-4381.2016.10.002
    Abstract ( 684 ( PDF (10516KB)( 122 Citation
    Nb-20Ti-16Si-3Al-3Cr-2Hf alloy was prepared by non-consumable electrode arc-melting, alloyed with different content of rare earth elements La, Sm and Tb. Microstructures and phase composition were analyzed. The results show that (Nb,Ti) and Nb5Si3 are the main phases. Diverse microstructures in different position of the ingots and coarse phase concentration are observed; eutectic grains and lath-like grains with large Nb5Si3 phase as the core widely exist in these ingots; the eutectic grain contains lamellar structure internal and coarse "teeth like" structure external; the Nb5Si3 phase in the center of lath-like grains persists straight interfaces and regular edges, which is surrounded by fine niobium silicide network and coarse dendritic niobium solid solution (Nbss) phase. Multiple linear regression is used to analyze the relationship of REEs' content and room temperature fracture toughness of the alloy,result indicates that room temperature fracture toughness of these ingots is 11-15 MPa·m1/2. The regression equation of REEs' content (Sm, La, Tb) to room temperature fracture toughness Kq is Kq=10.344+6.896La+2.993Sm.
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    Cure Kinetics and TTT-diagram of Toughed Bismaleimide Resin with Double-heating Wave Reaction Characteristics
    ZHANG Chen-qian, CHEN Wei, YE Hong-jun, GUAN Zhi-dong, LI Zeng-shan
    2016, 44 (10): 17-23.   DOI: 10.11868/j.issn.1001-4381.2016.10.003
    Abstract ( 877 ( PDF (911KB)( 135 Citation
    The phenomenological model of 5429 resin was established by cure kinetic parameters of the bismaleimide (5429) with double-heating wave reaction characteristics gained by dynamic DSC analysis combining with the phenomenological model. Also, based on the DSC experimental data of 5429 resins at 180℃ with different heating time, the relationship between curing degree and heating time of 5429 resin was investigated with DiBenedetto equation under isothermal condition, and the equation of glass transition temperature and curing time were obtained. The gel time of 5429 resin was gained at different time by gelation disk. The functional relationship between conversion at gelation and glass transition temperature of 5429 resin was also obtained. Then, the time-temperature-transition (TTT) diagram was presented based on the above results. The optimum curing curve of 5429 resin concluded from TTT diagram is consistent with the standard curing curve.
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    Nickel/Diamond Composite Coating Prepared by High Speed Electrodeposition
    ZHANG Yan, FEI Jing-yin, LI Bei, ZHAO Fei-fan, PENG Qiu-yan
    2016, 44 (10): 24-32.   DOI: 10.11868/j.issn.1001-4381.2016.10.004
    Abstract ( 685 ( PDF (14263KB)( 149 Citation
    Nickel/diamond composite coatings were prepared on the basis of a new high speed electroplating bath. The influence of additives, plating parameters and diamond concentration on internal stress was investigated in order to find the solution to decrease the stress introduced by high current density; the micro morphology of the coatings were observed by SEM. The bath and depositing parameters were optimized that thick nickel/diamond composite coatings with low internal stress can be high speed electroplated with a high cathode current density of 30A/dm2. The results show that when plated with bath composition and parameters as follows: sodium dodecyl sulfate 0.5g/L, ammonium acetate 3g/L, sodium citrate 1.5g/L, diamond particles 30g/L; pH value 3-4, temperature 50℃, the composite coatings prepared in high speed have the lowest internal stress.
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    Electrochemical Behavior and Hydrophobic Properties of CrN and CrNiN Coatings in Simulated Proton Exchange Membrane Fuel Cell Environment
    JIN Jie, HAN Sui-wu, AN Teng, MA Jun-jie, ZHANG Wei
    2016, 44 (10): 33-40.   DOI: 10.11868/j.issn.1001-4381.2016.10.005
    Abstract ( 863 ( PDF (6999KB)( 299 Citation
    The CrN and CrNiN coatings were prepared on the surface of 304 stainless steel by closed field unbalanced magnetron sputtering.X ray diffraction and field emission scanning electron microscopy were used to characterize the structure and morphology of the coatings.The electrochemical corrosion properties under the simulated proton exchange membrane fuel cell(PEMFC) environment, interfacial contact resistance and hydrophobic properties of the two kinds of different coatings were investigated by electrochemical methods,contact resistance test and hydrophobic test,respectively.The results indicate that CrN coating mainly consists of CrN and Cr2N phase,CrN and Cr2N phases in the CrNiN coating are less compared to CrN film, and Ni exist as element in CrNiN coating; dynamic polarization tests show the coating is of better corrosion resistance,whereas the corrosion resistance of CrNiN coating is worse than that of CrN coating,constant potential polarization test shows the corrosion current density of CrN and CrNiN coatings are equivalent; CrN and CrNiN coatings significantly reduce the interfacial contact resistance of the 304 stainless steel,among which CrN coating has the smallest contact resistance; and CrNiN coating which has better hydrophobicity than that of CrN coating is more beneficial for the water management in proton exchange membrane fuel cell.
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    Tribological Properties of Attapulgite/Oil-soluble Nano-Cu Composite Lubricating Additive
    XU Yi, NAN Feng, XU Bin-shi
    2016, 44 (10): 41-46.   DOI: 10.11868/j.issn.1001-4381.2016.10.006
    Abstract ( 650 ( PDF (4541KB)( 97 Citation
    The tribological properties of attapulgite/oil-soluble nano-Cu composite lubricating additive were investigated by a SRV-Ⅳfriction wear tester. The worn surfaces were characterized by SEM and XPS. The results show that the two single additives can both improve the tribological properties of the base oil for a steel-steel friction pair,whereas the composite lubricating additive possesses more excellent friction-reduction and anti-wear properties than the single additives. The higher the load is, the better tribological properties the composite lubricating additive will show. In the effect of composite additive, a compact and smooth protective tribofilm composed by FeS2,Fe2O3,SiO2,Cu,FeOOH and organic compounds was formed on the worn surface.
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    Microstructure and Tribological Property of MWCNTs/Al Composites by Rotational Friction Extrusion Process
    FAN Hao, XING Li, YE Yin, KE Li-ming, FU Xu-rong
    2016, 44 (10): 47-53.   DOI: 10.11868/j.issn.1001-4381.2016.10.007
    Abstract ( 643 ( PDF (7347KB)( 91 Citation
    The aluminum matrix composites reinforced with the multi-walled carbon nanotubes (MWCNTs) were fabricated by rotational friction extrusion (RFE) process and the microstructure, hardness and tribological property of the composites were investigated. The results show that the bulk composites with certain dimension can be fabricated by the RFE process. The microstructure of the composites appears as fine equiaxed grain after dynamic recrystallization and the quality is good. The MWCNTs are uniformly distributed in the composites. The hardness of the composites increases firstly and then decreases with the increase of MWCNTs. When the volume fraction of MWCNTs is about 4%, its hardness is about 20% higher than that of the original Al matrix material by RFE process. The lubrication and wear resistance of the composites are changed with the addition of MWCNTs. With the increase of the MWCNTs, the wear rate of the composites is decreased at first, and when the volume fraction of MWCNTs is more than 3%, the wear rate varies little. The wear mechanism is changed, which is from adhesion wear and mild abrasive wear to the delamination wear and abrasive wear with the increase of the MWCNTs.
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    Influence of Sn on Microstructure and Performance of Electric Vacuum Ag-Cu Filler Metal
    SHI Lei, CUI Liang, ZHOU Fei, GU Xiao-long, HE Peng
    2016, 44 (10): 54-59.   DOI: 10.11868/j.issn.1001-4381.2016.10.008
    Abstract ( 649 ( PDF (13546KB)( 97 Citation
    Influence of Sn on microstructure, melting characteristic and brazing performance of electric vacuum Ag-Cu filler metal was studied by using scanning electronic microscope (SEM) with energy disperse spectroscopy (EDS), differential scanning calorimetry (DSC) and contrast tests. The results show that, while the addition of Sn is 4% (mass fraction,the same below), there is no brittle β-Cu phase in Ag60Cu filler metal,the effect on the processing performance is not obvious; with the increase of Sn content, the liquidus temperature of Ag60Cu filler metal decreases gradually, but the solidus temperature drops drastically,resulting in wider melting temperature range, and worse gap filling ability of filler metal. The Ag60Cu filler metal with Sn content of 4% has good spreading and metallurgical bonding abilities on copper plates, which are closer to that of BAg72Cu filler metal, and it can be processed into flake filler metal to replace the BAg72Cu flake filler metal to be used.
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    Effect of Hot-isostatic Pressing on Microstructure and Mechanical Properties of Second Generation Single Crystal Superalloy DD6
    GUO Hui-ming, ZHAO Yun-song, ZHENG Shuai, XU Jian-wei, ZHANG Jian, LUO Yu-shi, DONG Jian-xin
    2016, 44 (10): 60-67.   DOI: 10.11868/j.issn.1001-4381.2016.10.009
    Abstract ( 733 ( PDF (16095KB)( 536 Citation
    Effects of the hot-isostatic pressing (HIP) temperature (1280,1300,1320℃) on microstructures and mechanical properties of a second generation single crystal superalloy DD6 were investigated. The results show that the HIP treatment significantly decrease the cast porosity number of DD6 compared with standard treated specimens. Especially, the cast porosity volume fraction is deceased from 0.31% to 0.04% after the HIP treatment of 1300℃/100MPa, 4h. The cast eutectic volume fractions are remarkably reduced with increasing HIP temperature. The HIP treatments nearly unchanged the creep lives, While they greatly promote the low cycle fatigue lives. The elimination of cast microspores using the HIP treatment of 1300℃/100MPa, 4h result in the inhibition of crack initiation during fatigue and improve the low cycle fatigue lives one order of magnitude larger than that after standard heat treatment.
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    Effect of Glucose on Structure and Properties of LiFePO4 Cathode Material Prepared by Microwave Hydrothermal Method
    XIA Ao, YU Wan-ru, TAN Guo-qiang
    2016, 44 (10): 68-73.   DOI: 10.11868/j.issn.1001-4381.2016.10.010
    Abstract ( 599 ( PDF (3620KB)( 80 Citation
    Orthorhombic LiFePO4/C composite material with olivine structure was prepared by microwave hydrothermal method using FeSO4·7H2O, LiOH·H2O and H3PO4 as raw materials, with glucose as carbon source and modifier. The influence of glucose on the composition, structure, morphology and electrochemical performance of LiFePO4 was investigated by means of XRD, SEM, EDS and constant current charge-discharge cycling. The results show that the as-obtained LiFePO4/C exhibits stronger bonding among Fe, P and O atoms, finer particle size and improved electrochemical properties than the pristine LiFePO4. From the SEM image, the LiFePO4 is coated by carbon in the LiFePO4/C composite. The LiFePO4/C shows the initial discharge capacity of 125.6mAh/g at 0.1C. Even at a rate of 1.0C, it still can deliver a discharge capacity of 106.2mAh/g, the capacity retention is 91.3% after 30 cycles.
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    Simultaneous Inversion of Thickness and Ultrasonic Longitudinal Velocity for Thin Layered Structure Based on Ultrasonic Reflection Coefficient Amplitude Spectrum Matching Analysis
    ZHANG Wei, MA Zhi-yuan, HE Li-hua, GAO Jian-ying, LUO Wen, LIN Li, LEI Ming-kai
    2016, 44 (10): 74-79.   DOI: 10.11868/j.issn.1001-4381.2016.10.011
    Abstract ( 570 ( PDF (1316KB)( 99 Citation
    For the overlapped signal and unknown longitudinal velocity leading to difficulty in measuring the thickness of thin layers, a method based on ultrasonic reflection coefficient amplitude spectrum (URCAS) matching analysis technique was proposed to characterize thickness and ultrasonic longitudinal velocity of thin layered structure simultaneously. An inverse algorithm based on the correlation coefficient method was introduced. The thickness and velocity were then determined by matching the theoretical and experimental URCAS within the effective frequency band of ultrasonic probe and inversing the ultrasonic testing parameters which corresponding to the maximum correlation coefficient. Experimental validation was conducted on the radar absorbing coatings (RAC) on the aluminum alloy substrates. The results show that this method can realize extraction of the ultrasonic parameters from the overlapped signal effectively, the relative errors between ultrasonic and micrometer measurement are in the range of 2.53%-3.72% for the thickness, and 2.51%-3.75% for the longitudinal velocity.
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    Microstructure Anisotropy Effect on Stress and Hydrogen Distribution in Micro Area for Martensitic Stainless Steel
    ZHONG Zhen-qian, TIAN Zhi-ling, YANG Chun
    2016, 44 (10): 80-87.   DOI: 10.11868/j.issn.1001-4381.2016.10.012
    Abstract ( 660 ( PDF (5937KB)( 126 Citation
    Elastic stiffness distribution of martensite microstructure was analyzed by using Electron Back Scatter Diffraction(EBSD) experiment, based on which the coupled finite element model of stress-hydrogen interaction was established to study the influence of martensitic microstructure anisotropy on the micro local stress and hydrogen distribution. The results show that misorientation between adjacent Block Laths is 60°, and different Block Laths have different elastic stiffness in the same loading direction, which resulted in the heterogeneous distribution of micro stress and hydrogen, and micro stress can be characterized by microstructure element of Block Lath.Elastic stiffness gradient and Block size play a significant role in stress concentration among microstructures, and while stress concentration can affect hydrogen distribution. High elastic stiffness gradient and large size of Block Lath cause high stress concentration, accumulate high concentration of hydrogen, which initiate crack of hydrogen embrittlement in the end. The above results are consistent with micro fracture morphology and EBSD experiment on crack region.
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    Surface State of Domestic 800-grade Carbon Fibers and Interface Property of Composites
    LIU Wei-dan, CHEN Jun-lin, LI Yang, YANG Zhe, ZHAO Yan
    2016, 44 (10): 88-93.   DOI: 10.11868/j.issn.1001-4381.2016.10.013
    Abstract ( 699 ( PDF (4501KB)( 160 Citation
    The surface and micro-interface property of three domestic 800-grade carbon fibers (1#, 2#, 3#) were characterized by Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), X-ray Photoelectron Spectroscopy (XPS), multifilament stretching method and single fiber fragmentation test. The results show that the surfaces of these three fibers are all smooth and the roughness is between 9-17nm. They all possess high content of oxygen, and the ratio of O/C of the three carbon fibers is between 0.23-0.27. The multifilament tensile property is similar, which reveals the domestic carbon fibers have stable quality control, and the breaking elongation rate of about 1.9 revealing that the fiber and resin matrix matching is good. The tensile strength of single fiber is unstable, meanwhile the high tensile surface active functional group has big influence on the interface shear strength of carbon fibers.
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    Effect of Silicon Powder on Properties of SiO2 Gel/Alumina-silica Fibers Composites
    ZHANG Jing, TIAN Geng, LIU Jia-chen
    2016, 44 (10): 94-99.   DOI: 10.11868/j.issn.1001-4381.2016.10.014
    Abstract ( 600 ( PDF (4849KB)( 78 Citation
    SiO2 gel/alumina-silica fibers composites were prepared by impregnation method. Silicon powder with different mass fractions of 0%, 0.2%, 0.4%, 0.6% and 0.8% was added in the slurry, and the effects of silicon powder on the microstructure, bulk density, compression-resilience ratio and phase compositions of the SiO2 gel/alumina-silica fiber composites were investigated. The results show that when the mass fraction of the silicon powder is lower than 0.6%, the volume expansion of silicon resulting from the silicon oxidation fills the cracks between fibers and gel, the volume density of the composites increases from 0.468g/cm3 to 0.723g/cm3, and the resilience ratios increase from 43.1% to 59.6%. Besides, it is found that the mechanical property is improved and the degree of high-temperature damage for the composites is decreased by the silicon crystallization, which restrains the fibers crystallization and facilitates the generation of pyroxene. However, when the mass fraction of silicon powder is 0.8%,the compression-resilience ratio of the composites significantly declines to 44.5%, which is attributed to the big cracks generated from the excessive volume expansion of silicon powder at high temperature.
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    Corrosion of X65 Pipeline Steel Under Deposit and Effect of Corrosion Inhibitor
    XU Yun-ze, HUANG Yi, YING Liang, WANG Xiao-na, YANG Fei
    2016, 44 (10): 100-108.   DOI: 10.11868/j.issn.1001-4381.2016.10.015
    Abstract ( 764 ( PDF (9084KB)( 121 Citation
    Effect of the deposit on the electrochemical parameters of X65 pipeline steel in oxygen contained sodium chloride solution was studied by EIS and PDS methods. The galvanic corrosion behavior under deposit and effect of different concentration of corrosion inhibitor PBTCA were studied by electrical resistance (ER) method combined with ZRA. The results show that the corrosion potential of X65 steel shifts negatively as SiO2 covering its surface and the corrosion rate becomes lower. When the galvanic couple specimen with deposit is electrically connected with the specimen without deposit, anodic polarization occurs on X65 steel under deposit and the galvanic current density decreases from 120μA/cm2 to 50μA/cm2 and keeps stable. As 5×10-5, 8×10-5 and 3×10-4 PBTCA were introduced into the solution, the galvanic current density reaches the highest 1300μA/cm2 and then decreases to 610μA/cm2 keeping stable around 610μA/cm2, corrosion rate of X65 steel under deposit reaches 6.11mm/a. PBTCA accelerates the corrosion of X65 steel under deposit in oxygen contained solution. Through the investigation on the surface of the specimens, serious local corrosion occurs on the X65 steel surface under deposit.
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    Progress in Research on Lightweight Graphene-based EMI Shielding Materials
    WANG Chan-yuan, WANG Xi-xi, CAO Mao-sheng
    2016, 44 (10): 109-118.   DOI: 10.11868/j.issn.1001-4381.2016.10.016
    Abstract ( 1593 ( PDF (9352KB)( 411 Citation
    With rapid progresses on the advanced electronic science and technology, electromagnetic irradiations have led to considerable issues, including electromagnetic pollutions, electromagnetic interference and security concerns, in electronics, aeronautics, astronautics, information technology, communication systems and etc. Based on the fundamentals of the electromagnetic interference shielding and general methods for preparing graphene nanosheets, this review involves the recent advances in the electromagnetic interference shielding materials of various applications in four morphologies, which include bulk, lightweight foams, flexible films and those for operation at high temperature. Meanwhile, the major strategical methods and general concept for designing and fabricating graphene-based electromagnetic interference shielding materials have been overviewed, and fundamental issues of electromagnetic interference technology have been further discussed. The perspectives for fabricating novel electromagnetic interference shielding materials, including ultrathin and transparent configuration, and future development have been proposed based on the practical applications, which suggest significant conception for designing next generation lightweight EMI shielding materials.
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    Research Progress on Preparation and Application of Graphene Oxide/ Chitosan Biocomposites
    LYU Sheng-hua, LI Ying, YANG Wen-qiang, CUI Ya-ya
    2016, 44 (10): 119-128.   DOI: 10.11868/j.issn.1001-4381.2016.10.017
    Abstract ( 1145 ( PDF (6073KB)( 220 Citation
    Graphene oxide/chitosan is a new type of biocomposites which was developed in recent years, it possesses the unique mechanical, adsorptive, electrochemical and antibacterial properties. The research progress of graphene oxide/chitosan composites was summarized in this paper. The preparation methods of the biocomposites were introduced briefly. Meanwhile, the application of the biocomposites in the field of high mechanical strength of materials, waste water treatment, electrochemical sensor and biomedical materials were illustrated in details. At last, the low cost and large scale preparation, structure and properties of composite materials and its application in new areas of graphene oxide/chitosan biocomposites were prospected.
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