25 June 2010, Volume 41 Issue 06
    

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    研究与开发
  • Study on Vibration Control of Thin Plate by Using Piezoelectric Material
    ;;
    . 2010, 41(06): 1-0.
    Abstract ( ) Knowledge map Save
    For intelligent laminated plates, a complete piezothermoelasticity system includes electromechanical coupling, pyroelectric effect and thermo-mechanical coupling, its order is very high generally and the solving controller is difficult. Based on the balancing reduction, H∞ vibration control is studied. For some problems directly related to the realization of vibration control, such as the non-observability of system, the uncontrollability of temperature variation, the physical meaning of state variable of reduced system, the construction method of auxiliary signal and the definition of weight matrices, their effect mechanism on control is studied in detail, and the corresponding solutions or techniques are proposed respectively. Numerical example shows that these works are benefit to the realization of H∞ vibration control from the point of mechanics.
  • Influence of high-energy shot peening on microstructure of titanium and bioactive titania coating followed by Micro-arc oxidation
    Zaiqi Yao;min qiGE ZHEN DONG;;
    . 2010, 41(06): 2-0.
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    To improve the bioactivity of Ti surfaces, porous titania coating were prepared on the high-energy shot peenig treated (HESP) and commercial pure (CP) titanium by micro-arc oxidation (MAO). By OM and TEM observation, the equiaxed grain structural layer with thickness of about 40 μm and diameter of 100-200 nm formed on the HESP titanium surface. The phase identification, thickness, composition and morphology of the coating were analyzed by X-ray diffraction, Scanning electron microscope equipped with Energy-dispersive X-ray spectroscopy. The amounts of Ca, P and Ca/P ratio of the MAO coating formed on the HESP-treated Ti were higher than those of CP Ti obviously. The α-Ca3(PO4)2 phase appeared in H10 MAO coating. Due to surface roughness of HESP Ti increased, the oxidation rate is different in different locations, which leads the micro-mechanical occlusion and cohesion improvement between substrate and coating.
  • Synthesis of Li2FeSiO4/C cathode materials by microwave carbothermal reduction method
    CAO Yan Bing;;;;
    . 2010, 41(06): 3-0.
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    In this study, preparation of Li2FeSiO4/C composites were accomplished by a microwave carbon thermal reduction method, with Li2CO3、FeOOH and nano-SiO2 as the starting materials, polyvinyl alcohol (PVA) and super-P carbon as the carbon sources. The prepared samples were characterized by X-ray diffractometry, SEM, and galvanostatic charge-discharge test. The results show that highly pure Li2FeSiO4 material with uniform and fine particle size is quickly and successfully synthesized at 650 ℃ for 12 min. The initial discharge capacity of the obtained sample delivers 127.5 mAh?g-1 at C/20 rate between 4.5 to1.8 V, and after 20 cycles the discharge capacity maintains 121.6mAh?g-1, indicating good electrochemical capacity and cycling stability.
  • Microwave assisted synthesis of ZnO nanorods in ionic liquid solution and their optical properties
    ;Qing LI ;;;
    . 2010, 41(06): 4-0.
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    ZnO nanorods have been synthesized via a microwave-assisted way by the reaction between Zn(NO3)2?6H2O and NaOH in the ionic liquid 1-butyl-3-methyl imidazole six hexafluorophosphoric acid salts ([BMIM][PF6]) aqueous solution. The as-prepared samples were characterized by XRD, EDX, FESEM, UV and PL techniques. The results showed that the as-prepared ZnO nanorods have a diameter of about 20 nm and a length of 400-500 nm, and the ionic liquid [BMIM][PF6] played a key role. The effects of experimental parameters on the formation of the nanorods were explored, and a plausible three-step mechanism was proposed to explain the formation of ZnO nanorods. This facile and environment-friendly synthetic strategy many open new route to the preparation of other 1D functional nanomatericals.
  • Effect of Rare Earth Elements on the glass-forming abilities of FeCrMoCB alloys
    Ping Jun Tao
    . 2010, 41(06): 5-0.
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    In recent years, with the continue breakthroughs being made in the preparation dimensions of the Fe-based amorphous alloys, the development and researches of non-magnetic amorphous steels have attracted increasingly widespread attention. However, the glass-forming abilities of Fe50Cr15Mo14C15B6 amorphous steel families are limited, of which the maximum diameter is only 1.5mm. In present paper, the copper-mold suction casting method was adopted to study the effect of rare earth elements, Y, Pr, Gd and Tb, on the glass-forming abilities of Fe48Cr15Mo14C15B6M2 (M=RE) alloys. The experimental results showed that substituting 2at.% of Fe in the Fe50Cr15Mo14C15B6 with Y, Pr, Gd and Tb, respectively, a series of Fe48Cr15Mo14C15B6M2 (M = RE) amorphous steel rods can be prepared. The maximum diameters of Fe48Cr15Mo14C15B6M2 (M=Pr, Y, Gd, Tb) amorphous steel rods can be enhanced up to 3mm, 8mm, 12mm and 12mm, respectively.
  • Investigation of Anisotropic Nd12.5Fe68.9-xCo12Gax Zr0.1B6.5 Magnetic Powder
    YOU Jun Hua
    . 2010, 41(06): 6-0.
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    Nd12.5Fe68.9-xCo12GaxZr0.1B6.5(x=0，0.1，0.3，0.5，0.7) permanent magnetic powder was fabricated by the d-HDDR process (Hydrogenation at room temperature-Hydrogenation –Disproportionation-Desorption-Recombination). The investigation focuses on the effects of disproportionation hydrogen pressure, desorption recombination temperature, desorption recombination vacuum and element Ga on magnetic properties of Nd12.5Fe68.9-xCo12GaxZr0.1B6.5 alloys. The phase structure was characterized by X-ray diffraction(XRD). The results indicate that: the reactions [Nd2(Fe,Co)14B+2H2<=>2NdH2+12α-(Fe,Co)+(Fe,Co)2B] occur in the d-HDDR process; 0.03Mpa disproportionation hydrogen pressure is the key to spurring the alloy on to anisotropy, and applying the (low-vacuum& high-vacuum) high-temperature schedule to the desorption-recombination step will make sure that the alloy is anisotropic; Element Ga can improve the jHc and DOA. When Ga content is 0.3at%, the optimum properties of Nd12.5Fe68.6Co12Ga0.3Zr0.1B6.5 magnetic powder are as follows: (BH)max=218.3kJ/m3，Br=1.22T，jHc=751.2kA/m，DOA=0.52。 Key words: d-HDDR; Anisotropy; NdFeB; magnetic powder；Element Ga；magnetic properties
  • Determination of Reactivity Ratio of Copolymerization of Acrylic Acid and Acrylamide and Research on the Moisture Absorption Properties of Copolymer
    . 2010, 41(06): 7-0.
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    In this paper, poly[acrylic acid –co-acrylamide] was synthesized by means of aqueous solution polymerization. The factors such as monomer ratios,monomer concentration, urea content ,temperature and so on influencing on moisture absorption property were investigated. The optimum moisture absorbency of PAA/U reached 1.05 g/g based on the orthogonal experiment results .Copolymer composition was determined by infrared spectroscopy method and then monomer reactivity ratios were obtained according to Fineman-Ross equation.The calculation results indicated that the reactivity ratio of acrylic acid ( r1) was higher than acrylamide’s (r2) and both values were less than 1,which demonstrated the obvious tendency of alternatihg copolymerization between AA and AM.The SEM photograph revealed that copolymer had porous structure and its specific surface area was increased ,after urea added. TGA analysis verified the formation of copolymer. The moisture absorption ability of poly[acrylic acid –co-acrylamide] was superior to corresponding homopolymers and traditional inorganic moisture absorbents .
  • Coupled Heat Transfer and Thermal Stress Analysis of Composite Lattice Core Sandwich Structure
    ;Yin Sha;
    . 2010, 41(06): 8-0.
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    A simulation was carried out for the coupled conduction and radiation heat transfer in the all-composite lattice core sandwich structure. The cavity radiation method was used firstly to detect the radiation contribution to the heat transfer, and then a discussion for the effect factors of this contribution was followed, such as the participation of the lattice truss core and the surface emissivity of the composite materials. Finally, the thermal deformation and thermal stress was calculated on the basis of the known temperature field by coupled simulation. It was shown that the radiation effect was obvious when the structural temperature was higher than 350℃, and this effect was enhanced as the emissivity increased; the contribution of lattice truss core to the heat radiation was small. As the upper and under sheets fixed, thermal stress happened mainly in the upper facesheet and at the endwalls where the cylinders contacted with the upper facesheet. The distribution of thermal stress field depends on the restriction forms, and the max thermal stress is smallest only as the upper sheet is fixed.
  • The convective heat transfer characteristics of nanofluids under the laminar flow conditions
    ; ;;
    . 2010, 41(06): 9-0.
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    This article performed a numerical study by using single phase method on the effects of the Reynolds number、volume fraction and type of based fluid and nanoparticle on the convective heat transfer characteristics of nanofluids under the laminar flow conditions. The results show that the convective heat transfer coefficient of nanofluids is higher than that of the based liquid, however, which is closely related to properties of the based liquid and nanoparticle, and the volume fraction. The heat transfer coefficient of nanofluids increases with an increase in the thermal conductivity of nanoparticles and base fluid, and increases with an increase in the volume fraction of nanoparticles. The heat transfer coefficient of nanofluids almost keeps constant for Cu-water nanofluids with a fixed volume fraction, which has nothing to do with the Reynolds number.
  • Preparation of shell-core structure nano-Fe coated cenosphere composites
    xian-feng Meng ;
    . 2010, 41(06): 10-0.
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  • Study on preparation and surface modification of precipitated silica obtained from fly ash
    ;
    . 2010, 41(06): 11-0.
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    The fly ash, as a starting material, was subjected to alkaline fusion with sodium carbonate and formed nepheline. The resultlant reacted with HCl solution and the filtration was undertaken sol-gel transition process to obtain precipitated silica. Then, the surface modification of precipitated silica was conducted using silane coupling agent γ-MPS and stearic acid. The precipitated silica before and after modification were characterized by XRD, TG-DTA, FT-IR spectroscopy and nitrogen adsorption isotherms measurements. The results showed that the specific surface area and maximum size value were 364.80 m2/g and 6.02 nm, respectively. The TG-DTA analysis and FT-IR spectroscopy indicated that modification agent had been successfully grafted onto the surface of precipitated silica. The γ-MPS showed good modification effect compared with that of stearic acid.
  • Stabilities and Applications of Magnetorheolodical Fluids
    zhangping
    . 2010, 41(06): 12-0.
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    Abstract:The rheological and magnetic properties, antisedimentation and aggregation stability,friction properties,and temperature stability of several magnetorheolodical fluids are presented. Some contemporary applications with ideal performence and durability are introduced briefly. Key words：magnetorheological fluid; damper; polishing; seal; durability
  • Synthesis of Gallium Nitride Nanowires by ammoniating Ga2O3/Pd/Sapphire films
    Xue Chengshan ;;;SUN Hai Bo;;Guo Yongfu
    . 2010, 41(06): 14-0.
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    GaN nanowires have been synthesized by ammoniating technique under flowing ammonia atmosphere on C-plane Al2O3 (sapphire) substrate with Pd Catalysis. Studies by using X-ray diffraction and X-ray photoelectron spectroscopy indicate that the nanowires are hexagonal GaN. Observations by using scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy show that GaN is single-crystal structure. The diameter of the nanowires is in the range of 10~60 nm with the lengths up to several tens of micrometers.Photoluminescence spectrum shows a distinct blueshift comparison to bulk GaN.Finally, The growth mechanism of GaN nanowires is also discussed.
  • Preparation and Photoelectrochemical Properties Zn/ZnO nanorod arrays / Polythiophene film
    PANG Qi
    . 2010, 41(06): 15-0.
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    The ZnO nanorod arrays were synthesized on zinc foil By using the hydrothermal method. The ZnO nanorod arrays were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). X-ray diffraction(XRD) analysis of the product layer on the Zn substrate suggests a hexagonal ZnO phase (JCPDS: 36-1451).SEM shows The whole surface of the Zn foil is completely covered with the nanorods. More important, the nanorods grow oriented perpendicular to the Zn substrate surface. The photo voltaic conversion properties of Zn/ZnO nanorod arrays film and Zn/ZnO nanorod arrays / Polythiophene (PTh) film were studied by using the photocurrent action spectra. The photovoltaic conversion efficiency of Zn/ZnO nanorod arrays / Polythiophene (PTh) film could be improved with 4 times.
  • Electrochemically Deposited Ca-P Coatings on Magnesium Alloy
    ZHANG Chun Yan;Gao Jiao Cheng
    . 2010, 41(06): 16-0.
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    Calcium phosphate coatings were deposited on AZ31 magnesium alloys by virtue of electrochemical deposition. The compositions, phase structures and morphologies of the coatings in different deposition time were investigated by means of X-ray diffractometer (XRD), energy dispersive spectroscopy(EDS) and scanning electron microscope (SEM). The potentiodynamic electrochemical technique was employed to study the corrosion behavior of Ca-P coatings on AZ31 magnesium alloys in Hank’s solutions. The results showed that coatings' morphology changed with deposition time in the deposition process in a bath containing Ca(NO3)2 and NH4H2PO4. The coatings were flake–shape crystals composed of Brushite (DCPD, CaHPO4?2H2O). Significant increase in free corrosion potentials and decrease in corrosion current density indicated that the Ca-P coatings improved corrosion resistance of the AZ31 alloy. The morphologies and the degrees of crystallization of the coatings have obvious influence on corrosion property.
  • Effects of substrate negative bias voltages on preferred orientation and surface morphology of CrN films deposited by DC reactive magnetron sputtering
    TAN Shu-Yong ;
    . 2010, 41(06): 17-0.
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    CrN films were prepared under different substrate negative bias voltages by DC magnetron sputtering. The preferred orientation, composition and surface morphology were explored by X-ray diffraction, EDS and SEM, respectively. The mechanism of bias voltages was also discussed.The results showed that the variation of bias voltages did not affect the phase composition of CrN films. However, when Ar and N2 flux were 6 ml?min-1and 30 ml?min-1 respectively, the preferred growth of CrN films changed from (111) to (200), then no clear preferred growth with the increase of bias voltages from -50 V to -225 V. In addition, as negative bias voltages increased, surface morphology of CrN films also changed from irregular shape with angular structure to globular structure gradually and the grain size decreased.
  • Synthesis and chiral recognition of amylose phenylcarbamate derivative coated onto silica gel as chiral stationary phase for HPLC
    Qu Hai-Tao
    . 2010, 41(06): 18-0.
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    The hybrid-type 3,5-dichloro and 3,5-dimethyl-subsituted phenylcarbamate derivative of amylose was synthesized and coated onto wide pore aminopropylsilanized silica gel as the chiral stationary phase (CSP-2) of high-performance liquid chromatography (HPLC). The structures of the obtained chiral packing materials (CPMs) were characterized by 1H nuclear magnetic resonance (1H NMR) and infrared spectroscopy (IR); 7 racemates were used for evaluating CSP-2 recognition abilities by HPLC with n-hexane/2-propanol (9:1, v/v) solution as the eluent. The results show that CSP-2 exhibits superior and integrated chiral recognition ability compared to single substituted derivate of amylose, and the stability of CPMs is improved.
  • The Effect of Magnetic Field on the structure and catalytic activity of TiCoxO2+x photocatalyst
    ;zhang kun feng
    . 2010, 41(06): 19-0.
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    A Co-doped TiO2 photocatalyst was prepared by sol-gel method under magnetic field and characterized by XRD, SEM, Uv-vis, and PL techniques. The effect of external magnetic field on the degradation of aqueous methyl orange was evaluated under visible light irradiation. The results revealed that the photocatalyst exhibited enhanced visible-light photocatalytic activity under magnetic field. The method not only decreased crystalline size of modified TiO2 and distributed particles uniformity, but also reduced the band gap of the catalyst and improved the separation efficiency of the electron-hole pairs.
  • Microwave Synthesis of MIL-101 and its adsorption heat of Benzene
    HUANG si Si
    . 2010, 41(06): 20-0.
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    In this work, a chromium terephthalate MIL-101 was synthesized using microwave irradiation method, and effects of reaction temperature on synthesis of MIL-101 were investigated, then MIL-101 was characterized. The adsorption isotherms of benzene on the MIL-101 at 288K, 298K and 308K were separately measured by gravimetric method, and the adsorption heat of benzene on the MIL-101 was estimated. Results showed that, the surface area MIL-101 was up to 2089.2 m2?g-1. The isotherm of benzene on MIL-101 was of typeⅠisotherm, and the amounts adsorbed of benzene on the MIL-101 decreased with temperature rising, indicating that the adsorption process is mainly physisorption. Langmuir equation fit well the isotherms of benzene on the MIL-101. The adsorption capacity of the MIL-101 for benzene was up to 9.44 mmol/g at T = 298 K and p / p0 = 0.5, much higher than the adsorption capacity of an conventional activated carbon and activated carbon fiber. Meantime, the isosteric adsorption heat of benzene on the MIL-101 varied in the range from 45.4 kJ / mol to 41.6 kJ / mol. This amplitude of variation in isosteric adsorption heat was less compared to that of activated carbon fiber. It suggested that the surface adsorptive free energy of the MIL-101 was more evenly distributed in comparison with the activated carbon fiber.
  • Carbon sphere prepared by catalytic-free CVD method
    WU Hai Feng
    . 2010, 41(06): 21-0.
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    The effect of temperature and carbon source on preparation of carbon sphere by non-catalytic CVD method is reviewed in this paper, the results are characterized using scanning electron microscopy (SEM)、High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The study shows that: temperature and carbon source has an important impact on the size、uniformity and dispersion of carbon sphere. When use methane as carbon source and keep the preparation temperature at 1200℃, we can get the carbon sphere with better dispersion property and size uniformity. Furthermore, the growth mechanism of carbon sphere prepared by catalytic-free CVD method is discussed.
  • Study for optical performance degradation of ZnO Thermal Control Coatings under electronic irradiation based on monolayer model
    li dan ming
    . 2010, 41(06): 22-0.
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    A color center generation model of monomolecular layer has been presented, and the expression of color center concentration and the relationship of material optical performance degradation vs. irradiation dose have been deduced on basis of mechanics analysis for optical performance degradation of ZnO-type thermal control coatings under electronic irradiation. The fitting results of the solar absorptance change Δαs for S781 white paint under 100keV electronic irradiation using this theory show that the monomolecular layer model can primely predict the optical performance degradation tendency of ZnO-type thermal control coatings under electronic irradiation environment. This theory can also be extended to the optical performance degradation prediction for other thermal control material under different space irradiation environments. Key words: monomolecular layer model ；ZnO white paint；color center concentration ；optical performance degradation
  • Study of The Giant Magnetic Impedance Effect of Co60,15Fe4.35Si12.5B15 Amorphous Alloy Ribbons By low—Frequency Magnetic Pulsing
    . 2010, 41(06): 23-0.
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    Amorphous Co60,15Fe4.35Si12.5B15 alloys have been treated by low frequency magnetic pulsing. The results showed that nano-crystallization of specimens can occur by M?ssbauer spectroscopy and TEM. The temperature rise ?T≤5℃ in the course. The ?Z/Z was greater than 255% under the conditions: external magnetic field 0.296kAm-1;Ac current frequency 2MHz. The quantity of GMI effect has relation to the frequency of low-frequency pulsating magnetic field、intensity .The magneto-nanocrystallization of amorphous alloy is a new processing technique gaining GMI effect .
  • Study on Intrinsic Pyroelectric Property of Mn doped BST Ceramics
    ;
    . 2010, 41(06): 24-0.
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    Abstract：Mn-doped BST ceramics were prepared by citric acid sol-gel method. Using this method，the sintering temperature of BST-based ceramics could be decrease to 1250℃. The obvious degradation of ferroelectric property of BST-based ceramics was found as Mn bringing in. However，with proper content of Mn doping，favor dielectric constant，low dielectric loss，favor pyroelectric property and figure of merit of BST-based ceramics were obtained at room temperature. The intrinsic pyroelectric coefficient γint of 1% Mn-doped BST ceramics reaches 610 nC?cm-2?k-1，and the figure of merit Fd of 1% Mn-doped BST ceramics measured at low frequency was 88.4×10-6Pa-1/2，which can completely meet the need of pyroelectric detectors. In addition，the mechanism of domain switching was discussed during the study.
  • Study on Microwave Absorbing Materials Made of FeSiAlCr Nano-flakes Modified by SrCO3
    LIANWEN DENG;
    . 2010, 41(06): 25-0.
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    FeSiAlCr flaky absorber materials were synthesized by gas atomization and high energy ball milling process in combination with SrCO3 composite technology. The microstructure and morphology of the samples were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM) respectively, and the complex permittivity and complex permeability of samples in the frequency range of 2~18GHz were measured by the vector networks analyzer system. The microwave absorbing ability was calculated based on the measured electromagnetic parameters of FeSiAlCr composite material modified by SrCO3. Results show that the FeSiAlCr powder with nano-crystalline microstructure and flaking morphology can be acquired by gas atomization process and high-energy ball milling technology. The doping SrCO3 can reduce effectively the permittivity of the FeSiAlCr composite material and thus improve the matching capability. The coating in 1.2 mm thickness made of SrCO3/ FeSiAlCr composite material has good absorbing performance (lower than -5 dB) in the frequency range of 2-6 GHz.
  • Synthesis of Nanocrystalline Y2O2S:Eu3+,Mg2+,Ti4+ Long-lasting Phosphorescent Materials
    ;Li Yi Dong;;
    . 2010, 41(06): 26-0.
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    A red long-lasting phosphorescent materials, nanocrystals Y2O2S:Eu3+,Mg2+,Ti4+ were prepared by solvothermal-high temperature solid state method. The products were characterized by the X-ray diffraction (XRD) patterns, transmission electron microscopy (TEM) images and photoluminescence (PL) spectra. The results of XRD indicated that the nanocrystals Y2O2S:Eu3+,Mg2+,Ti4+ possessed pure phase, hexagonal crystal structure. The results of TEM revealed that the single phase Y2O2S:Eu3+,Mg2+,Ti4+ had small size with narrow distribution. Excitation and Emission spectrum showed that Eu3+ could be incorporated into yttrium oxysulfides effectively, and had good luminescent properties. The afterglow test indicated that nanocrystals Y2O2S:Eu3+,Mg2+,Ti4+ had red afterglow color and good afterglow effect.
  • Influences of spark plasma sintering temperature on magnetic properties of both hot pressing and hot deforming NdFeB magnets
    LI Chao-ying
    . 2010, 41(06): 27-0.
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    Abstract: Both hot-pressed and hot-deformed NdFeB magnets were prepared by spark plasma sintering technique. Effects of variable sintering temperatures on microstructures and magnetic properties of both hot-pressed and hot-deformed magnets were studied. The results showed that the density of the hot-pressed magnets increased with the sintering temperature, and reached 99.7% of theoretical density at 680℃. Besides, the grain grew up with the temperature. The remanence and the maximum energy product were influenced by the interaction of the density and grain size , which the maximum value appeared at 650℃: (BH)m=129kJ/m3, Br=0.87T, Hcj=914kA/m. After hot deformation, the c-axis of the tetragonal structure gradually shifted to the direction which paralleled with pressing direction, and formed magnetocrystalline anisotropy, as a result, the remanence and the maximum energy product of the magnets increased significantly. The hot-pressed temperature has great impacts on the magnetic properties of hot-deformed magnets. With the hot-pressed temperature increasing, the remanence and the maximum energy product rose at first ,and then decreased. And the hot-deformed magnets, which were hot pressed at 650℃ ，achieved the best magnetic properties：（BH）m=339kJ/m3，Br=1.49T，Hci=576kA/m.
  • Study on the magnetic property of Fe-Ni based nanocrystalline dust core
    Zhenghou Zhu
    . 2010, 41(06): 28-0.
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    the dust core of Fe-Ni based crystalline have been successfully fabricated by compression molding method. The effects of annealing temperature and time, the grain size and the forming pressure on the magnetic property of dust cores and its temperature stability and frequency stability were investigated. The results show that the permeability and quality factor of dust core first increase and then decrease with the increase of annealing temperature, the μe to the maximum of 31.5 at 600 oC, and its best annealing time is 2h. the bigger of grain size and molding pressure, the better of magnetic property of dust core. When the test frequency changes from 100KHz to 1000KHz, the core shows the optimal stability of frequency. The μe gradually decrease as soon as increasing environmental temperature in the range of 25 to 100 oC. Especially in the range of 25 oC to 40 oC, its μe changes greatly, and its temperature coefficient is -1.95×10-3 oC-1, however, when the environmental temperature over 40 oC it is only -2.48×10-4 oC-1.
  • Skin-core Structure of Polyacrylonitrile Preoxidized Fibers and the Preventing Measures
    Meijie YuQifen Wang; ;
    . 2010, 41(06): 29-0.
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    Three polyacrylonitrile fibers of different titre and different cross-section shape were preoxidized under two kinds of heating modes-isothermal and step-wise rising. Scanning electron microscope, optical microscope and elemental analysis technologies were used to investigate the skin-core structure and diffusion of oxygen. The results show that as for isothermal heating mode, the peroxidized fibers exhibit obvious skin-core structure at 250℃ for 1 hour; but as for step-wise rising mode, the skin-core structure didn’t appear until the temperature is higher than 275℃. The diffusion of oxygen is not affected by the cross-section shape of precursor fibers. Under the same conditions, the skin thickness of round shape fibers is equal to that of kidney-like shape fibers. The thinner precursor fibers are liable to obtain uniform prestabilized fibers. Therefore, fining of precursor fibers and proper process of step-wise rising temperature are the essential guarantee for high quality proxidized fibers.
  • The preparation and characterization of MnO2 coated Co nanoparticles
    jing An ;jun he
    . 2010, 41(06): 30-0.
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    Nano-sized Co particles had been synthesized by chemical reduction method, and coated with a layer of MnO2 to form Co-MnO2 particles with core-shell structure. Three kinds of different structure of core-shell samples were obtained through changing heat treatments. XRD, TEM and SEM were used to analyze their structures. The magnetic properties of these Co/MnO2 particles were also studied. Exchange bias effect was observed for the sample that was coated by MnO2 layer after the Co particles were annealed at 673 K under H2 atmosphere for 1 h.
  • Effect of Al Addition and Icosahedral Clusters on Glass-Forming Ability and Local Structure of Zr50-xCu50Alx (x = 0 ~ 25) Alloys
    Yong Xu ;;;
    . 2010, 41(06): 31-0.
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    The effects of Al addition on glass-forming ability and local structure, as well as phase evolution, in Zr50-xCu50Alx (x = 0 ~ 25) alloys are investigated by means of XRD and SEM. The main phases of Zr45Cu50Al5 alloy are ZrCu + I-phase for d = 5~10 mm and ZrCu + glassy phase for d = 3 mm, respectively. The Bragg peaks of icosahedral phase in Zr45Cu50Al5 alloys decreases quickly by increasing cooling rate and finally dissolves into the dispersion peaks. These results suggest that there is a strong correlation between the I-phase and glassy phase in Zr-Cu-Al alloys during rapid solidification. The glassy phase in Zr-Cu-Al alloys is of the same short-range order, an icosahedron structure, with I-phase. The icosahedron, with five-fold symmetry, is incompatible with lattice periodicity, which will present a barrier for crystallization and improve the glassy formability.
  • Direct Growth of Aligned Carbon Nanotubes on Metal Thin Film Substrate
    . 2010, 41(06): 32-0.
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    In this paper, the effects of pretreatment and temperature on mechanism of direct growth of aligned carbon nanotubes are studied and discussed. Vertically aligned carbon nanotubes (CNT) are grown on the monocrystal line silicon by plasma enhanced chemical vapor deposition (PECVD), and Fe thin film acts as catalyst. Given the conditions of different pretreatment time and temperature, carbon nanotubes are deposited on the Fe/Si substrate. After observed by the scanning electron microscope (SEM), carbon nanotubes that are grown in different conditions are contrasted. The result shows that carbon nanotubes of better directivity and higher purity can be grown in a proper condition.
  • The Structure and Properties of PMAA/MMT and PMAA/MMT/SiO2 nanocomposite
    ;
    . 2010, 41(06): 33-0.
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    In this paper, polymethacrylic/montmorillonite (PMAA/MMT) nanocomposite and polymethacrylic/montmorillonite/silicon dioxide (PMAA/MMT/SiO2) nanocomposite were prepared via in-situ polymerization. The structures and properties of two kinds of nanocomposites were compared. The results show that a coexistence of exfoliated and intercalated MMT layers was found in the PMAA/MMT nanocomposite. The characteristic diffraction peak of MMT has already disappered and the nano materials are well dispersed in the polymer matrix in PMAA/MMT/SiO2 nanocomposite. PMAA/MMT and PMAA/MMT/SiO2 nanocomposites have tanning properies. In contrast, the tanning effect of PMAA/MMT/SiO2 nanocomposite was better.
  • Dielectric and mangetic properties in Ba- and Mn-substituted BiFeO3 ceramics
    . 2010, 41(06): 34-0.
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    The Bi1-xBaxFe1-yMnyO3 ceramic samples were prepared by sol-gel process. XRD analysis showed that it was the single-phase rhombohedral perovskite structure. Magnetic hysteresis loops were observed in substituted specimens , and Ba and/or Mn substitution transformed anti-ferromagnetic (weak ferromagnetic ) BiFeO3 into ferromagnetic . The dielectric constant measured in BiFeO3 and Bi0.9Ba0.1FeO3 showed two phase transitions below room temperature，which were 200k and 230k . The dielectric constant under the external magnetic field showed that the Ba-Mn codoped BFO sample has greater magneto-dielectric effects.
  • Effect of HPMC on the Dispersibility of Carbon Fiber
    ;
    . 2010, 41(06): 35-0.
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    With the tests of the variation coefficient of fresh cement paste, the conductivity of hardened cement paste, and the scanning electron microscope (SEM), the effects of HPMC on the dispersibility of carbon fiber in cement paste are evaluated. The results of the tests show that the adding of HPMC can significantly improve the fiber dispersibility. With the increasing of the adding amount of HPMC, the coefficient of variation and the electric resistivity are both increased firstly and then declined. In the range of 0.2% ~ 0.4% adding of HPMC, the dispersibility of carbon fiber is the best. The mechanism of the positive effect of HPMC on the dispersibility of carbon fiber is that hydrogen bonds are formed between the polar hydroxide radicals in its molecule structure and on the surface of the carbon fiber, and the water. Therefore the hydrophilicity and the wetting ability of the surface of carbon fiber can be increased, and then its dispersibility is improved. However, at higher admixture content, HPMC may increase the air pore content in the hardened cement paste and induce negative effect on the conductivity.
  • Effect of counterface surface roughness on the friction and wear properties of Ultra-high molecular weight polyethylene
    ;
    . 2010, 41(06): 36-0.
    Abstract ( ) Knowledge map Save
    Ultra-high molecular weight polyethylene (UHMWPE) and metal（or ceramic） had been widely used in total joint replacement as acetabular and femoral head materials. The wear of artificial joints mainly occurred in ultra-high molecular weight polyethylene acetabular, and its wear debris could induce tissue reactions and bone resorption that might lead to the joint loosening. It was reported that counterface surface roughness was one of the most important factors affecting the friction and wear properties of ultra-high molecular weight polyethylene. This paper reviewed ultra-high molecular weight polyethylene wear mechanisms. The effect of counterface surface roughness on UHMWPE wear rate, wear debris size and artificial joints lubrication mechanism were mainly discussed.
  • Adsorption and photocatalytic performance of thermosensitive hydrogel supported zinc phthalocyanine on α-naphthol
    ; ;
    . 2010, 41(06): 37-0.
    Abstract ( ) Knowledge map Save
    The thermosensitive property of poly(N-isopropylacrylamide) hydrogel supported zinc phthalocyanine (GE-ZnPc) was studied by differential scanning calorimetry, and the volume phase transition temperature (VPTT) was 34.3 °C. In this paper, α-naphthol was chosen as the substrate, and the results of adsorption thermodynamics showed that the adsorption process of α-naphthol on GE-ZnPc was in accordance with the Freundlich isotherm model. The adsorption of α-naphthol on GE-ZnPc below VPTT was an endothermic process and the temperature increasing is conducive to adsorption. The adsorption above VPTT was an exothermic process and the temperature increasing is not conducive to adsorption. In addition, the photocatalytic activity of GE-ZnPc for the oxidation of α-naphthol was determined. The result showed that GE-ZnPc exhibited a high photocatalytic activity under the visible light irradiation. The effect of reaction temperature on the adsorption and photocatalytic oxidation was also studied. The result indicated that when the temperature was closed to the VPTT, both adsorption and photocatalytic removal of α-naphthol reached the maximum values. Thus, the adsorption behavior of GE-ZnPc plays an important role in the enhancement of photocatalytic activity.
  • strontium-calcium sulfate/multi-(amino acid) copolymer composite： Preparation and in vitro degradation
    ;Yong-Gang YAN ;
    . 2010, 41(06): 38-0.
    Abstract ( ) Knowledge map Save
    In this study, a novel composite: strontium-calcium sulfate/multi-(amino acid) copolymer composite has been synthesized by in-situ polymerization, then the degradation behavior of composite and influence of added strontium to the composite degradation property were investigated in vitro. The results suggested that calcium sulfate/multi-(amino acid) copolymer composite degraded too fast, the degradation products influenced on the pH of PBS significantly in the early stage of degradation. Strontium-calcium sulfate/multi-(amino acid) copolymer composite exhibited excellent degradation behaviors, the total weight loss reached 26.62% after 12 weeks soaking in PBS. In the first week, the material degraded fast with a weight loss of 14.5%, and the dissolution of Ca2+，Sr2+ in soaking medium increased rapidly, meanwhile the pH of PBS was the lowest and reached 5.83. As degradation time prolonged, the degradation velocity and the concentration of Ca2+, Sr2+ tended to be stable, the pH of PBS increased gradually and maintained at 7.4. The hydroxyapatite was found by analyzing the superficial deposition on the non-rinsing composites, suggesting the material have favorable bioactivity.
  • Effect of substrate temperature on surface morphology and photoluminescence of N-Al co-doped ZnO thin films
    . 2010, 41(06): 39-0.
    Abstract ( ) Knowledge map Save
    N-Al co-doped ZnO films were deposited on glass substrate at various substrate temperature by ultrasonic spray pyrolysis (USP). The crystalline microstructure, photoluminescence properties and morphologies of the ZnO films were characterized by X-ray diffraction (XRD), Fluorescense Spectrometer, Scanning electron microscope (SEM) and Atomic force microscopy (AFM). The AFM images show that the size of ZnO particles increased gradually as the increasing of substrate temperature. According to the photoluminescence (PL) spectra, it is obvious that PL property of the films are extremely sensitive to the substrate temperature, and PL spectra of the films deposited at low temperature shows strong defect-related emission, indicating that the films were deposited with low crystalline quality and high defects concentration. When the film deposited at 450℃ only ultraviolet emission is observed in the PL spectra. The disappearance of green emission caused by oxygen vacancy (Vo?) or interstitial zinc ( Zni) implies that the concentration of donated defects decreased as the increasing of substrate temperature, which will benefit the preparation of high quality p type ZnO.
  • Preparation of Ultra-lightweight ceramic from sewage sludge used for fillers
    ;Qinyan Yue;;;;
    . 2010, 41(06): 40-0.
    Abstract ( ) Knowledge map Save
    The purpose of this study was using dehydrated sewage sludge, fly ash and clay to prepare lightweight ceramics for fillers. The Ultra-lightweight sludge ceramics (LWSC) were experimentally produced with various mass ratios of sludge, clay and fly ash, and then the suitable mass ratios and the suitable process were determined. The Optimum conditions (additions of clay, sludge and fly ash, preheating temperature and time, sintering temperature and time) which used for fillers were selected by orthogonal experiment L18 (37). Properties (physical properties, microstructure and toxic metal leaching) were tested at last. The results shows that the LWSC used for fillers are light (bulk density is 365kg/m-3), high hydroscopic (water absorption is 49.46%), nontoxic(contents of toxic metal leaching test are all below the detection limit)and porous(more pores than the commercial lightweight ceramics).
  • Preparation of new affinity membrane and it used for adsorption of bilirubin
    Maoqiang Xue
    . 2010, 41(06): 41-0.
    Abstract ( ) Knowledge map Save
    Microporous polyamide membranes were activated by formaldehyde and subsequently bound with chitosan to amplify reactive groups. Then polylysine (PLL) as ligand was immobilized onto the chitosan-coated nylon membranes. The contents of chitosan and PLL of PLL-attached membranes were 112.4 and 92.3 mg/g nylon membrane, respectively. Such PLL-chitosan affinity membranes were used to adsorb bilirubin from the bilirubin-phosphate solution and albumin- bilirubin solution. The adsorption mechanism of bilirubin and the effects of temperature and ionic strength on adsorption were investigated by batch experiments. The results showed that the adsorption capacity increased with increasing the temperature and bilirubin initial concentration while decreased with increasing the NaCl concentration and the adsorption isotherm fitted the Freundlich model well. The result of dynamic experiment showed PLL-attached membranes can well remove the bilirubin from the albumin-bilirubin solutions.
  • Anti-scaling performance of PPS composite coatings in a circulated and simulated geothermal environment
    Liu Hui Cong;;
    . 2010, 41(06): 42-0.
    Abstract ( ) Knowledge map Save
    In the process of drawing out and transporting geothermal water from the geothermal wells, scaling on the surface of the metal pipes and pump is a common problem. In this paper, the methods of binary images of morphology, scanning electron microscopy (SEM), energy dispersion spectrometry (EDS) and X-ray diffraction (XRD) were used to study the anti-scaling performance of polyphenylenesulfide (PPS) coating, PPS/ polyfluorinated ethylene propylene ( FEP) and PPS/ polytetrafluoroethylene(PTFE) coating in a circulated and simulated geothermal water environment. The results indicated that the surface energy of fluorinated resin-blended PPS coating was lower than pure PPS coating, and their anti-scaling effects were also better than PPS coating. At the same time, the growth appearance of scaling nucleus was affected by the eroding of running water and debasing of surface energy. Furthermore, the results of AC impedance diagrams showed that PPS/FEP coating had a better anti-corrosion performance in the geothermal water environment.
  • THE SYNTHESIS OF PHENOTHIAZINE DERIVATIVES AND THEIR ELECTROCHROMIC PROPERTY
    TU XI;;
    . 2010, 41(06): 43-0.
    Abstract ( ) Knowledge map Save
    In order to develop novel electrochromic materials, a series of N-substituted phenothiazine derivatives (PDs) were synthesized via SN2 reaction and characterized by 1HNMR, 13CNMR, and IR. Their electrochemical properties and spectrachemical properties were examined by cyclic voltammetry and UV-vis. It was found that PDs as anodic electrochromic material and viologen as cathode electrochromic material in the composite electrochromic devices (ECDs) showed reversible, clear color changes on electrochemical doping and dedoping process, and electrochromic effect was observed a color change from blue to red. The PDs synthesized are promising candidate materials for visible ECDs, for their outstanding electrochromic behaviors plus the cheap original stuff and short synthetic routes.
  • Influence of support layer of composite PDMS pervaporation membrane on acetic acid/water separation
    . 2010, 41(06): 44-0.
    Abstract ( ) Knowledge map Save
    Three types of composite PDMS membranes were prepared by using PTFE, PES, and PVDF as support materials and used to separate acetic acid from water by pervaporation. The experimental results evidently demonstrated that the support layer had a significant impact on the flux and selectivity of composite PDMS membranes. The effect of support layer on the performance of composite PDMS membranes depended on many factors such as the physico-chemical properties of skin layers or supports and the preparation methods of composite membranes. The total flux of acetic acid-water mixture through each composite PDMS membrane increased with increasing feed concentration. In contrast, the relation between selectivity and feed concentration was different due to various supports. With increasing temperature, the flux through each composite PDMS membrane increased quickly while the selectivity decreased. With increasing feed velocity, the flux through each composite PDMS membrane increased and then stabilized while the selectivity decreased and then stabilized.
  • Effects of magnesium electrolyte on rheological properties of alumina slurry
    ;Ying Zhang
    . 2010, 41(06): 45-0.
    Abstract ( ) Knowledge map Save
    Abstract: Effects of magnesium electrolyte on the rheological properties of ultra-pure alumina slurries at different pH values were investigated by examining the viscosity and zeta (?) potential. The results showed that the introduction of magnesium ions reduced the rheological properties of alumina slurries. Under the condition of existence of magnesium ions, favorable rheological properties of alumina slurry without adding dispersants was obtained at pH=6.5. When added PAA, the slurry with better rheological properties was prepared at pH =9.5. The best adding amount of PAA increased as magnesium ions were introduced. When no magnesium ion and 0.05 mol/L magnesium ions were introduced, the best adding amount of PAA in the slurries were 0.5 % and 0.9 % respectively.
  • Influence of A/C to Anti-crystallization Ability and Luminescence Properties in Al-Ca-Ba Glass Activated by Ce3+
    zhu yong chang
    . 2010, 41(06): 46-0.
    Abstract ( ) Knowledge map Save
    The Al-Ca-Ba glass system with good chemical durability was investigated as the scintillators host, influence of A/C（Al2O3/CaO）to anti-crystallization ability and luminescence properties were studied. The obvious red shift and larger stokes shift in this glass with respect to others system were observed，the reason is related with its higher optical basicity. The study also show anti-crystallization ability and luminescence properties are the best when A/C within 12CaO.7 Al2O3 low-melting region.
  • Synthesis and characterization of ZnO multipod whiskers
    Li-Bing FENG; ;;
    . 2010, 41(06): 47-0.
    Abstract ( ) Knowledge map Save
    ZnO multipod whiskers were synthesized on Zn-coated Si(1 1 1) substrates by a thermal evaporation oxidation metallic Zn powder method in tube furnace at 900℃. The predeposited Zn films on the substrate were deposited by pulsed laser deposition(PLD). X-ray diffraction(XRD), fourier transformed infrared spectrum(FTIR),scanning electron microscopy(SEM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM) and photoluminescence spectrum (PL) are used to characterize the structure, morphology as well as optical characteristic of the as-synthesized ZnO multipod whiskers.The results reveal that multipod whiskers are pure hexagonal ZnO wurtzite structure with a length of about several microns. The root diameters of the whiskers are in the range of 200–500nm, while the tips have an average diameter about 40nm. The pre-deposited Zn films on the substrates can effectively promote the growth of the ZnO multipod whisker. Finally，the growth mechanism of ZnO multipod whiskers is discussed briefly.
  • Luminescent characteristics of Ca2SiO3Cl2:Eu3+ phosphor
    . 2010, 41(06): 48-0.
    Abstract ( ) Knowledge map Save
    Ca2SiO3Cl2:Eu3+ phosphor was synthesized by high temperature solid state reaction. CaCO3 (A. R.), SiO2 (A. R.), NH4Cl (A. R.), Li2CO3 (A. R.) and Eu2O3 (99.99%) were used for starting materials. After these individual materials were blended and grounded thoroughly in an agate mortar, the homogeneous mixture was heated at 850℃ for 3 h, and the phosphor was obtained. The phase present of the samples was characterized by powder x-ray diffraction (XRD) (D/max-rA, Cu K?, 40 kV, 40 mA, λ=0.15406 nm). The excitation and emission spectra of these phosphors were measured by a SHIMADZU RF-540 fluorescence spectrophotometer. The phosphor shows five major emission peaks locating at 582, 599, 623, 655 and 691 nm, which correspond to the 5D0→7F0, 7F1, 7F2, 7F3 and 7F4 characteristics transport of Eu3 +, respectively. The influence of the concentration of Eu3+ ions to the emission intensity was investigated. Firstly, the intensities increase with increasing Eu3+ concentration, then, decrease because of concentration quenching. It reaches the maximum content of 1% Eu3+, and the concentration self-quenching is the dipole– dipole interaction based on the Dexter theory. The emission intensity of Ca2SiO3Cl2:Eu3+ phosphor was enhanced by doping Li+. The results show that Ca2SiO3Cl2:Eu3+ phosphor is a promising red phosphor for white light emitting diode(w-LED) based on UV InGaN chip.
  • Preparation and Characterization of Y-type hexagonal ferrite Ba2Co2-xZnxFe12O22 via a soft chemical method
    ZHANG Chun-Xiang
    . 2010, 41(06): 49-0.
    Abstract ( ) Knowledge map Save
    Y-type hexagonal ferrite with composition Ba2Co2-xZnxFe12O22 was prepared by a complexing process using corresponding metal nitrates as raw materials and ethylene diamine tetraacetic acid (EDTA) as complexing agent. The effects of calcination temperature and Zn2+ concentration on the crystal structure and magnetic properties were studied. The crystallization behavior, structure and magnetic properties were characterized by XRD, FT-IR, VSM and impednce analyzer. The results indicated the formation of single phase Y-type hexagonal ferrrite was achieved at a relatively low temperature 1000℃. The Zn2+ substitution for Co2+ results in the expansion of crystal lattice and the variation of saturation magnetization and coercivity. The resonance peaks shift towards lower frequency and the real part of permeability increases with the decrease of the magnetic anisotropy.
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