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      20 July 2012, Volume 0 Issue 7 Previous Issue    Next Issue
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    Preparation of PS@Au Nano-catalyst and Its Catalytic Performance
    LIU Da-bo, QI Hong-fei, CHENG Bo
    2012, 0 (7): 1-4,91.  
    Abstract ( 707 ( PDF (1831KB)( 377 Citation
    PS@Au nano-catalyst with excellent catalytic performance was prepared by electroless plating technology, and the diameters of Au nanoparticles were around 16 nm with a narrow distribution. The influence of adding order for raw materials on the catalytic performance was investigated by SEM, UV-Vis spectrometer, and the detection of catalytic performance. It was found that larger surface area was responsible for the improvement of degradation rate of MB chromophore and the excellent catalytic performance of PS@Au nano-catalyst. An increase in the loading and surface roughness of Au nanoparticles could help to promote the catalytic performance of the PS@Au nano-catalyst.
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    Densification and Properties of Continuous Carbon Fiber Reinforced Contact Strip
    YUAN Hua, WANG Cheng-guo, LU Wen-bo, ZHANG Shan, CHEN Yang, XIE Ben
    2012, 0 (7): 5-9.  
    Abstract ( 787 ( PDF (1961KB)( 336 Citation
    In current-carrying wear condition,the temperature increase of material could affect the thermal reliability of resin-based contact strip greatly. The carbonization-liquid impregnation on the contact strip for thermal stability and densification was adopted. The influence of this method on the contact strip was investigated, meanwhile, the densification effect was evaluated, and SEM was used to analyze friction and wear mechanism. The results showed that the thermal reliability of phenolic resin are enhanced after 800°C heat treatment; the contact strip specimen resistivity decreases significantly (about 100% after carbonization) and the impact strength decreased; and friction coefficient and wear volume increased. After four times densification treatment, the porosity is decreased about 45%, and the impact property and wear performance are both improved. The mechanical wear of contact strip specimen are abrasive wear, adhesive wear and accompanied by oxidation without heat treatment; while after heat treatment, abrasive wear is the main wear form.
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    Numerical Simulation and Influential Factors Analysis of Density Distribution in High Velocity Compaction
    ZHENG Zhou-shun, XU Dan, LEI Xiang-yuan, YING Ren-ren, ZHOU Wen, ZHANG Meng-xuan
    2012, 0 (7): 10-14,19.  
    Abstract ( 935 ( PDF (2907KB)( 447 Citation
    Discrete element method which is used for studying mechanical behaviors of discontinuance is applied to studying the process of powder densification in high velocity compaction. Considering the powder as viscoelastic discrete particles, the contact model of particle flow and the equation of motion of each particle are established, constitutive model of viscoelastic powder in high velocity compaction described by force-displacement is deduced in detail. Based on computing software PFC for discrete element method, the process of the two-dimensional particle flow and density distribution during high velocity compaction are simulated. The density distribution of numerical simulation results coincide well with experiments in engineering application. The factors which affect the density distribution including friction coefficient, height-diameter ratio and two-directional compaction are analyzed.
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    Analytical Studies for Deep Drawing Formability of DP590 Tailor-welded Blanks on Warm Sheet Metal Forming
    CHEN Wei, HE Zhen-liang, GUO Yu-qin, LIU Zheng, WANG Tong
    2012, 0 (7): 15-19.  
    Abstract ( 530 ( PDF (6168KB)( 477 Citation
    The warm forming process has been widely applied as a promising alternative, which can be applied to the forming of dual phase steel (DP) laser tailor-welded blanks (TWBs) to improve their drawing formability. The deep drawing formability of DP-TWBs on warm sheet forming has been investigated by the square cup. Tensile tests, finite element and experimental analysis on deep drawing of square cup, metallographic tests were used to investigate the formability of DP-TWBs at various temperatures ranging from room temperature to 500℃. The results show that the forming temperature has great effect on the formability of DP-TWBs, and the formability is much better when they are formed at the temperature from 400℃ to 500℃.
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    Study on the Synthesis of N,N-di-2, 3-epoxypropyl Dodecylamine
    LIU Yun-fei, CHEN Yu, SHI Liang, YAO Wei-shang, CHEN Yang
    2012, 0 (7): 20-23,28.  
    Abstract ( 536 ( PDF (1082KB)( 419 Citation
    N,N-di-2,3-epoxypropyl dodecylamine (EDA), an important intermediate of the surfactants with good chemical reactivities, was synthesized via ring-closing reaction of the chlorohydrin, which was prepared through the ring-opening reaction of the epichlorohydrin with dodecylamine, in the KOH-H2O solutions. The structure of the products were characterized through FTIR, 1H-NMR and 13C-NMR spectrum. Influence of the reaction conditions, such as temperature and time of the ring-closing reaction, amount of the alkali and epichlorohydrin, types of the alkali, etc. on the content of EDA in the produces were studied, and then the optimal conditions for synthesizing N,N-di-2,3-epoxypropyl dodecylamine was defined.
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    Study on Superplasticity of Extruded FGH96 Alloy
    WANG Shu-yun, ZHANG Min-cong, DONG Yun-peng, LIU Chen-yi, CHEN You-hong, SUN Xing
    2012, 0 (7): 24-28.  
    Abstract ( 617 ( PDF (2074KB)( 450 Citation
    The superplasticity of extruded FGH96 alloy was studied. The results show that the extruded FGH96 alloy exhibits excellent superplasticity at temperatures of 1050℃ and 1100℃. Superplastic elongation rate reaches 405% and flow stress is decreased to 32MPa at temperature of 1100℃ with the initial strain rate of 3.33×10-4s-1. The metallographic analysis indicates that the relatively large size of γ' phase and the large distance between different γ' phases in FGH96 alloy can promote dynamic recrystallization, and the grain growth can be restrained in the subsequent deformation. Evident dynamic recrystallization in FGH96 alloy has been occurred during the extrusion deformation. But due to the insufficient dynamic recrystallization in extrusion deformation, a large quantity of substructures still exists in the interior of the grain. The unstable substructures would cause finer, stable and uniform grains, the mean size of which is about 10μm, through dynamic recovery and dynamic recrystallization in superplastic deformation, thus resulting in excellent superplasticity of FGH96 alloy.
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    Microstructures and Properties of Thickness Aluminium Alloy Eleocellarium Repairing Welding Joint by Friction Stir Welding
    LIU Jie, YANG Jing-hong, HAN Feng-wu, GONG Wen-biao
    2012, 0 (7): 29-33.  
    Abstract ( 859 ( PDF (2465KB)( 434 Citation
    The welding technology of 35mm thickness aluminium alloy eleocellarium repairing welding was investigated. Microstructures and properties of the welding joint have been studied by using optical microscope, scanning electron microscope, energy spectrum analysis, micro-hardness tester and electron tensile testing machine. Experimental results show that the formation of weld is good and there are no defects of tunnel, hole and groove defect by FSW after filling eleocellarium with aluminum alloy block, and there are groove defects by FSW without filling eleocellarium. The visible clear kiss defect was formed between weld nugget zone and thermal-mechanical affected zone in advencing side when welding with FSW once; The transition zone of advancing and retreating side were formed well between weld nugget zone and thermal-mechanical affected zone in advancing side when welding with FSW twice and thrice. The microhardness of once and twice welding distributing was W model and reached 56HV and 60HV in heat affected zone of advancing side. The joint tensile strength of welding once, twice and thrice reached 173, 210MPa and 205MPa at rotation speed of 720r/min and welding speed of 180mm/min.
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    Research on a Theoretical Model of Anode in Pure Titanium Microarc Oxidation Process
    WANG Hong-yuan, ZHU Rui-fu, WANG Zhi-gang, LU Yu-peng, XIAO Gui-yong, ZHU Xian-jun
    2012, 0 (7): 34-38.  
    Abstract ( 754 ( PDF (2041KB)( 370 Citation
    Experiments on the ceramic coating with different growth stages were conducted in the process of pure titanium microarc oxidation (MAO). The surface morphology, thickness and phase component in different stages were also analysed. Based on the equivalent circuit of MAO anode, a theoretical model was established to investigate the influences of process parameters on the properties of coatings, which include electrical voltage, current density, frequency, duty ratio and time.The analysis results of the model show that the relative content of rutile TiO2 increases with the increase of the thickness after the ceramic coatings are finished; it indicates the MAO process complete as the thickness does not change. All the analysis agrees with the experimental results, and the model can provide a theoretical base for improving the performance of coating as well as MAO technologies.
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    Study on Modification of Coal Tar Pitch and Structure of Mesophase
    XIE Xiao-ling, ZHAO Cai-xia, CAO Qing, JIN Li-e, ZHANG Huai-ping
    2012, 0 (7): 39-43.  
    Abstract ( 704 ( PDF (1444KB)( 411 Citation
    Coal tar pitch (CTP) has been successfully modified with modifier benzaldehyde in the presence of p-toluene sulfonic acid as catalyst. The main influence factors such as the mass ratio of benzaldehyde to CTP, the temperature and reaction time on optical microstructure of mesophase formed by modified coal tar pitch (MCTP) were observed. The results showed that the optical microstructure of mesophase formed by carbonized MCTP, which was produced when the mass ratio of benzaldehyde to CTP was 0.3, the modified reaction kept for 15 h at 150 ℃, has the characteristic with incomplete fibrous structure. The result of XRD revealed that order of optical microstructure of mesophase was enhanced through modifying coal tar pitch. The results from FT-IR analysis indicated that the degree of condensation of aromatic ring increased according to the increment of vibration frequency of aromatic ring. The spectra from 1H-NMR indicated that the polymerization reaction mainly occurred in the HA position of aromatic rings. The possible reaction mechanism was proposed.
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    Preparation and Thermal Properties of α-Hydroxy, ω-Epoxide Polycaprolactone/Epoxy Resin Composites
    LIU Ying, LIU Ping-gui, HE Li-hua, LIANG Xing-quan
    2012, 0 (7): 44-49.  
    Abstract ( 828 ( PDF (1657KB)( 394 Citation
    α-Hydroxyl, ω-epoxide polycaprolactone oligomer (ETPCL) was synthesized from ε-caprolactone monomer and glycidol via enzyme catalyzed ring-opening polymerization. Then ETPCL grafted epoxy resin copolymer (PCL-g-GY250) was synthesized via —OH and —NCO nucleophilic addition reaction through urethane route. Through directly blending PCL-g-GY250 and epoxy resin GT7071 having higher molecular mass, and curing them with amine curing agent, a series of epoxy resin composites (PCL-g-GY250/GT7071) containing different content of PCL-g-GY250 were prepared. The thermal degradation and cross-linking density of the amine-cured epoxy composites were investigated by thermogravimetry analysis (TGA) and swelling in toluene, respectively. The results show that the cross-linking network density decreased with increasing PCL-g-GY250 content. And from TGA analysis, it can be concluded that incorporating PCL-g-GY250 into the epoxy resin improved the thermal resistance of the composites. When the mass ratio of PCL-g-GY250 and GT7071 was 4∶1, the characteristic degradation temperature at 5% mass loss (Td5%) was increased from 145.0℃ of amine-cured epoxy to 216.3℃ of amine-cured PCL-g-GY250/ GT7071. And Td5% of amine-cured PCL-g-GY250 reached 293.9℃, which was 148.9℃ higher than that of amine-cured epoxy.
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    Influence of Continuous Annealing on Microstructure and Properties High-strength IF Steel
    HU Kuan-hui, TIAN De-xin, FENG Guan-wen, DUAN Xiao-ping, YAN Long
    2012, 0 (7): 50-54.  
    Abstract ( 874 ( PDF (2285KB)( 329 Citation
    The influence of continuous annealing on the properties and microstructure and particle of second phase of high-strength IF steel was studied. The hot simulation of different temperature and different holding time continuous annealing was performed on EU AV hot dip process simulator. Universal testing machine,optical microscope and transmission electron microscope were used to examine the annealed samples. It was proved that there is a close relationship between the mechanical properties, the microstructure, the second phase’s shape. The effect of continuous annealing on the mechanical properties and the microstructure and the second phases was obtained.
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    Study on Precipitates of Grain-oriented Silicon Steel Produced by Acquired Inhibitor Method
    WU Zhong-wang, ZHAO Yu, LI Jun, LI Bo
    2012, 0 (7): 55-58.  
    Abstract ( 766 ( PDF (2047KB)( 413 Citation
    The grain-oriented silicon steels were produced by acquired inhibitor method. The type and distribution of precipitates in grain-oriented silicon steel were investigated by transmission electron microscopy. The results show that a little of AlN particles are precipitated in hot-rolled, normalized and decarburizing annealing strip, and a mass of amorphous Si3N4 particles are formed after nitriding. There are two different types of amorphous Si3N4 particles in nitriding strip. One is polygonal block, and another is small square. Polygonal block Si3N4 particles are distributed in grain boundary, and the square Si3N4 particles are distributed in the matrix.
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    Research of the Relationship Between Pore Morphology and Ultrasonic Attenuation Coefficient in CFRP
    GAO Xiao-jin, ZHANG Zheng
    2012, 0 (7): 59-63,70.  
    Abstract ( 779 ( PDF (1804KB)( 342 Citation
    Pores in CFRP samples were characterized by metallography and ultrasonic attenuation coefficient. The effect of pore morphology on ultrasonic attenuation was researched. The results show that ultrasonic attenuation coefficient is increasing with the increase of pore geometric morphology parameter; the slope of average pore length-porosity is bigger than of width-porosity; ultrasonic attenuation coefficient is decreasing with the increase of the percentage of pores in main sizes; ultrasonic attenuation coefficient is increasing with the increase of the percentage of big pores at the same porosity. In short, the pore morphology has some influence on ultrasonic attenuation and can not be ignored.
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    Effect of SO42- Concentration on 304 Stainless Steel Pitting Corrosion in NaCl Solution
    DU Nan, TIAN Wen-ming, ZHAO Qing, MENG Bao-li
    2012, 0 (7): 64-70.  
    Abstract ( 779 ( PDF (2198KB)( 373 Citation
    Effect of SO42- concentration on 304 stainless steel pitting corrosion in 3.5%NaCl solution was investigated by means of dynamic potential polarization, electrochemical impedance spectroscopy (EIS) and electronic speckle pattern interferometer (ESPI). The pitting induction time τ under 0.3V (vs SCE) polarization was detected by means of ESPI and chronoamperometry. The results showed that the stainless steel corrosion resistance was the worst when the SO42- concentration was 0.5%. When the SO42- concentration was below 1%, the corrosion resistance was worse than that having no SO42-. When the SO42- concentration was beyond 1%, the corrosion resistance was better. The pitting induction time τ of the 304 stainless steel were 4s, 9s and 94s in 0.5%NaCl+0.5%Na2SO4 solution, 3.5%NaCl solution and 3.5%NaCl+4%Na2SO4 solution respectively.
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    Preparation and Electrical Properties of PVPy/MWNTs Nanocomposites
    WANG Pan, ZHENG Yu-ying, LI Bao-ming, ZHANG Tong
    2012, 0 (7): 71-75.  
    Abstract ( 945 ( PDF (1920KB)( 313 Citation
    Conducting poly(3-valerylpyrrole)(PVPy)/multi-wall carbon nanotubes (MWNTs) nanocomposites have been prepared by in-situ polymerization of 3-valerylpyrrole (VPy) on MWNTs. The structure and properties of the resulting samples are studied by FT-IR, 1H NMR, XRD, SEM, TEM and TGA. FT-IR,SEM and TEM indicate that no chemical reaction occurred between PVPy and MWNTs, and only the MWNTs serve as a template for VPy polymerization. PVPy is only coated on the external surface of MWNTs and the thickness of the PVPy coating on each nanotube depends on the feed ratio of VPy to MWNTs. XRD patterns of the nanocomposites are investigated, it is clear that the intensity of the peaks at around 25.82° and 43.10° decreases with the increase of the mass ratio of VPy to MWNTs. Furthermore, the electrical conductivity of the samples is measured at room temperature, and the results exhibit that MWNTs can enhance the conductivity of PVPy/MWNTs nanocomposites compared to PVPy. The conductivity of PVPy/MWNTs nanocomposites is 1.42S/cm (VPy/MWNTs=2.5/1) and 0.22S/cm (VPy/MWNTs=5/1), respectively.
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    R-curve Behavior of Si3N4/TiC Nanocomposite Ceramic Materials
    LU Zhi-jie, ZHAO Jun
    2012, 0 (7): 76-80.  
    Abstract ( 670 ( PDF (1353KB)( 450 Citation
    Si3N4/TiC nanocomposite ceramic materials were fabricated via hot pressing technique by adding submicro Si3N4 and nano-TiC powders and with Al2O3 and Y2O3 as additives. The crack growth resistance behavior (R-curve) of ceramic materials was evaluated using the indentation-strength method. The results indicate that the ceramic materials possess rising R-curve behavior, which exhibits an excellent crack growth resistance. The sample with 10%(mass fraction) submicro-Si3N4 and 15% nano-TiC has a steepest rising R-curve. Observation and analysis indicate that these phenomena can be attributed mainly to the synergetic toughening mechanism caused by pull-out and bridging of the Si3N4 quasiwhiskers, the elastic modulus and thermal expansion mismatch between Si3N4 and TiC particles.
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    Correlation Between Properties of Carbon Fibers and Interfacial Fracture Energy of Carbon Fiber/Epoxy Resin
    ZHANG Li-jiao, GU Yi-zhuo, LI Min, LIU Hong-xin, ZHANG Zuo-guang
    2012, 0 (7): 81-85.  
    Abstract ( 644 ( PDF (1311KB)( 454 Citation
    By using the single fiber fragmentation test (SFFT) based on Wagner-Nairn-Detassis (WND) energy model, the interfacial fracture energy of five kinds of homemade and two kinds of foreign carbon fibers/epoxy resin systems for aeronautical structures was measured. The surface physical and chemical characteristics of the seven carbon fibers were analyzed by means of SEM, AFM, IR and XPS. Moreover, the correlation between the characteristics of carbon fibers and the interfacial fracture energy was studied. The results indicate that the interfacial fracture energy decreases due to the removal of the sizing agent on the carbon fiber surfaces, which means that the sizing agent may improve the interface toughness to some extent. Furthermore, within the laboratory experiments, the obtained results of the interfacial fracture energy are higher with the higher tensile strength and surface roughness of carbon fibers, which demonstrates the tensile strength and surface roughness have significant influences on the interfacial toughness. Comparing with these two factors, the type of sizing agent has a relatively small effect.The results have instructive significance for the studies of homemade high performance carbon fibers and the matching of carbon fiber/epoxy resin.
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    Study on Infiltration Alloying of Tungsten Surface
    YANG Zong-hui, SHEN Yi-fu, MENG Qing-bei
    2012, 0 (7): 86-91.  
    Abstract ( 863 ( PDF (1659KB)( 402 Citation
    W-Ni-Fe alloying layer on tungsten was prepared by infiltration Ni-Fe melt. The microstructures and the depths of alloying layer with different infiltration holding time were analyzed. Results showed that W-Ni-Fe alloying layer depths were 530μm and 700μm when the infiltration holding time was 10min and 20min, and the NiFe-rich phase region embedded in tungsten phase was very small. When the infiltration holding time increased to 30min and 40min, the W-Ni-Fe alloying layer depths were 750μm and 770μm, the NiFe-rich phase region significantly enlarged, and the shape of partial tungsten phase became spheroid. The forming mechanism of W-Ni-Fe alloying layer on tungsten was explained based on experimental results and W-Ni phase diagram.
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    TiN/NbN Multilayers Prepared by Asymmetrical Bipolarpulsed Reactive Magnetron Sputtering
    HEI Li-fu, XU Jun-bo, CHEN Liang-xian, LI Cheng-ming, LU Fan-xiu
    2012, 0 (7): 92-96.  
    Abstract ( 699 ( PDF (1731KB)( 393 Citation
    TiN /ZrN multilayers with different modulation periods were prepared by asymmetrical bipolar pulsed reactive magnetron sputtering. The microstructure, mechanical properties and fracture characteristics of multilayers were investigated by X-ray diffraction, scanning electron microscopy and nonoindentation. The results show that the nanohardness reaches to 43GPa at modulation period 19.86nm. The fracture morphology of TiN/NbN multilayer was observed by SEM after three-point bending test, which reveals that the cracks in the multilayer have a tendency of deflection at the interfaces and thus a higher cracking resistance of the multilayer can be induced.
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