2009 volumne 30卷 Issue 01
LIU Wencai; DONG Jie; ZHAI Chunquan; etc
Abstract: In order to study the changes of the microstructure of the surface deformation layer of high-strength deformed magnesium alloy ZK60 after shot peening treatment and its effect on the high cycle fatigue performance, the round rod poured by semi-continuous casting was first hot extruded with an extrusion ratio of 14, and the extruded rod was processed into a funnel-type fatigue sample after T5 heat treatment, labeled ZK60-T5. The effects of surface roughness, microhardness and residual compressive stress of the deformation layer on the high cycle fatigue properties of ZK60-T5 magnesium alloy after shot peening treatment were studied. The results show that the optimal shot peening process of high-strength deformed magnesium alloy ZK60-T5 is 0.05 mmN, and after shot peening, the microstructure of the deformation layer on the surface of ZK60-T5 magnesium alloy changes, the fatigue strength increases from 150 MPa to 195 MPa, which is increased by 30%, and the fatigue life is significantly improved, while the fatigue crack source is "driven" from the surface to the surface reinforcement layer under the action of the residual compressive stress field of the surface deformation layer.
YU Teng; WANG Lei; ZHAO Yongqing; etc
Abstract: The growth law of Ti-26 alloy under different solution temperature and solution time conditions β was studied, and the growth activation energy Qm of the β grain and the growth index n of 775.880~1 h at 820 °C were calculated when the alloy was kept warm for 0 h in the range of 5~4 °C, and the main reasons affecting the growth activation energy Qm and growth index n of the β grain were analyzed. The results show that when Ti-26 alloy is insulated at different temperatures in the β phase, the growth process of the β grain is controlled by Ti. When the alloy is soluble at 820 °C (Tβ+45 °C), the grain growth index n is only 0.24, which is caused by the drag of the solid solution atoms lagging behind the movement of the β grain boundary, but when the solution temperature exceeds 820 °C, the movement of the β grain boundary can get rid of the shackles of solute atoms.
ZHANG Xiaoning; SONG Jie; FAN Zhiguo
Abstract: Gleeble-3500 thermal simulator was used to test the hot compression set test of Ti-9.8Mo-3.9Nb-2V-3.1Al alloy in the range of room temperature ~ 800 °C, and the strain rate was 0.1 s-1. The results showed that in the range of room temperature ~ 300 °C and 500 ~ 800 °C, the deformation resistance of the alloy decreased with the increase of temperature, but at 300~500 °C, abnormal deformation resistance increased with the increase of temperature. Finally, the influence of thermal compression set behavior on the experimental results is discussed.
CHEN Jie; ZU Fangxuan; HUANG Zhongyue; etc
Abstract: The mechanism of melt superheat treatment on the solidification structure and solidification behavior of CuSn18.7(at.%) and BiPb20.1(at.%) alloys was discussed from the perspective of liquid-liquid structure transition. Experiments show that some physical properties of the alloy melt (such as internal friction, resistivity, thermoelectric potential and heat) change abnormally in specific temperature intervals during the heating process, but there are no abnormal changes during the cooling process, revealing that discontinuous liquid-liquid structure transformations occur in these temperature intervals in the melt. Subsequent solidification experiments showed that the structural transformation had a great impact on the solidification of the alloy, for example, the nucleation subcooling degree increased significantly, the solidification microstructure of CuSn18.7 alloy was significantly refined, and the morphology of the primary phase of BiPb20.1 alloy changed from fishbone dendrites to disordered equiaxed crystals. The change of microstructure of BiPb20.1 alloy is caused by the change of interfacial solute partition coefficient by the transformation of melt structure.
CHE Hongyan; XU Wenfu; CHEN Jianhong
Abstract: TIG welding was used to obtain 6061 aluminum alloy butt welded joints with good weld quality, and static tensile tests were carried out; The test results show that most of the samples are fractured in the softening zone 7~9 mm away from the edge of the weld fusion line. The mechanical properties and loss parameters of each micro-region of the welded joint are obtained by combining the double-hole microshear test with finite element, which is provided to the finite element calculation, and the finite element model of the static tensile test is established, and the correctness of the model is verified by comparison with the actual test results, on this basis, the influence of the relative width of the high-matching and low-matching welded joints and specimens on the failure behavior of the welded joints is studied, and the results show that for low-matching welded joints, the narrower the joint, the easier it is to fail, so the wider welded joints should be selected as much as possible; For high-matching welded joints, the narrower the joint, the less likely it is to fail, so it is recommended that narrower welded joints should be selected as much as possible.
YAO Xusheng; LIU Yandong; JIANG Qiwu; etc
Abstract: In order to explore the variation of grain orientation during the flattening of cylindrical wire, the evolution of the texture of the experimental sample after the secondary treatment of ECAP by asynchronous rolling was studied with the help of XRD texture diffractometer and three-dimensional orientation distribution function (ODF) analysis. The experimental results show that from the fast roll side, the texture orientation density along the thickness of the cold-rolled experimental specimen from the surface layer to the center layer increases with the increase of deformation variables, and the main texture components in the cold-rolled pure iron specimen gradually form a α-fiber texture of <110>//RD (rolling direction) and a γ-fiber texture of <111>//ND (rolling face normal), and the orientation density level of the texture components gradually increases. In addition, through the analysis and quantitative calculation of the reverse polar diagram, it can be seen that the volume fraction of the <110 > texture components shows an increasing trend from the table to the inside under different pressures. < the volume fraction of the 100 > texture components rises first and then decreases from the surface to the inside when the amount is 0%, and 40%. When the amount of pressure down is 80%, the opposite trend occurs. When the amount of pressure is 0%, the volume fraction of the <111 > texture components first decreases and then increases. However, when the indentation amount is 40%, when the amount is 80%, the <volume fraction of the 111 > texture component shows an upward trend, and there is a certain difference along the thickness of the sample.
YAO Xusheng; LIU Yandong; JIANG Qiwu; etc
Abstract: In order to explore the cold deformation microstructure and texture of the precipitated steel, the conformed steel with severe plastic deformation was subjected to certain heat treatment to obtain cementite samples of a certain shape and submicron size, and then the above samples were rolled with different deformation variables to obtain the analysis samples of microstructure and texture, and the microstructure and deformation texture of the rolled samples were analyzed by field emission scanning electron microscopy (FE-SEM) and texture diffractometer (XRD). The results show that the annealing of cold-rolled high-carbon steel shows that the number of lamellar cementite decreases and the number of granular cementite increases, forming a complex microstructure sample in which two shapes of cementite and ferrite coexist. During the cold rolling process, the ferrite grains are elongated and gradually develop into fibrous; The grain size and shape of cementite do not change much, and the distribution is relatively uniform. With the increase of deformation variables, the main textures in the co-analysis steel gradually formed a α-fiber texture consisting of <110>//RD (rolling direction) and γ-fiber texture of <111>// ND (rolling face normal), and the grain orientation gradually gathered to the main texture component types such as {558}<110> and {001}<110>.
WANG Fuqiang; WANG Lei; LIU Yang; etc
Abstract: The high-temperature and high-pressure gas-phase thermal hydrogen charging method was used to introduce hydrogen into GH690 nickel-based superalloy with a concentration of 38.1 mg/kg. The results show that hydrogen has no obvious effect on the yield strength of GH690 alloy, but the yield step of the hydrogen-filled sample disappears, and the tensile strength and elongation at break of the alloy are significantly reduced. Fracture analysis showed that the unhydrogenated samples were mainly characterized by ductility ligament fracture, while the hydrogen-filled samples showed brittle along the crystal fracture. When GH690 alloy is tensile deformed, hydrogen easily migrates to the grain boundary with the movable dislocation in the form of Cottrell air mass, and with the plastic deformation, the dislocation accumulates at the grain boundary, resulting in hydrogen enrichment at the grain boundary. The enrichment of hydrogen at the grain boundary reduces the grain boundary bonding strength of the alloy, so that microcracks are easy to germinate at the grain boundary, resulting in fracture along the grain.
ZHU Shaofeng; WU Yucheng; HUANG Xinmin
Abstract: The electrophoretic Ni-P/nano-TiO2 composite coating was prepared by electrophoretic deposition-electroless plating, the effects of electric field strength, current and electrophoresis time on the electrophoresis process were studied, the appropriate electroless plating process parameters were determined, the structure of the composite coating was analyzed by X-ray diffraction and scanning electron microscopy, the microhardness of the composite coating was tested, and the photocatalytic degradation experiment of the composite coating was carried out with methyl orange as the model reactant. The experimental results show that the nano-TiO2 particles are uniformly distributed in the composite coating, and the microhardness of the composite coating is higher than that of the electroless nickel-phosphorus alloy in the plating state and after heat treatment, and the catalytic effect of the composite coating is comparable to that of the nano-titanium dioxide coating.
REN Huaihui; LI Xudong
Abstract: The metallographic morphology and crystallographic orientation of the microstructure of titanium alloy composites were described by electron backscattering diffraction (EBSD) and OIM analysis systems, and the representative volume units of the microstructure of titanium alloy composites were simulated through the modular and visual design of the microstructure of the composites. On this basis, the finite element method is used to calculate the mesomechanical response of the microstructure of titanium alloy, and according to the calculation results, the "material structure weakness" is identified, the cracking and propagation of microcracks are evaluated, the performance of materials in the microstructure of the material after damage is predicted, and the "virtual failure of microstructure" behavior is deduced.
XU Weichang; DAI Pinqiang
Abstract: Nano-nickel with an average grain size of 27.2 nm and a wide grain size of 5~120 nm was prepared by direct current deposition. The effect of gauge size on the mechanical properties of nano-nickel was studied by unidirectional tensile experiment at room temperature. It is found that the yield strength of nano-nickel increases with the increase of the gauge aspect ratio (r), the elastic and plastic strain decrease with the increase of r, and the gauge size has no effect on the shear fracture behavior in tension. Through TEM’s observation of the structure of tensile fracture and shear band, it is found that the average grain size after the deformation of nano-nickel is significantly coarsed compared with the plating state, and the shear band is caused by further concentrated plastic deformation of the grain area that is first coarsed during the deformation process, and the grain on the shear band is elongated in a specific direction, and the straight grain boundary corresponds to the parallel line observed by SEM.
HUANG Yamin; WU Youming; PAN Chunxu
Abstract: The oxidative corrosion characteristics and failure mechanism of YUS701 high Cr-Ni austenitic stainless steel in long-term service under the environment of ultra-high temperature corrosion medium at 1 200 °C were systematically studied by using modern analytical instruments such as electron microscope and energy spectroscopy. The results show that the oxide film on the surface of stainless steel has a multi-layer structure, and the oxidation environment and the distribution and diffusion of elements at the matrix-oxide interface have important effects on the structure and properties of the oxide film. The failure behavior of the oxide film is mainly manifested as the generation of cracks in the oxide layer and the peeling of the non-dense oxide layer.
YANG Ke; YU Shengfu; TAO Panfeng; etc
Abstract: Hard carbide is obtained by using the developed nitrogen alloy self-protecting hard surface flux cored welding wire on low carbon steel plate. Nb and Ti are added to the hard face alloy as the most efficient carbon-nitrogen alloying elements. The morphology and composition of carbonitride precipitates in hard-sided carbides were studied by optical microscope, scanning electron microscopy and electron probe, and thermodynamic analysis was carried out, and the effects of carbon-nitrogen precipitates on tissues were discussed. The results show that the carbon and nitrogen precipitates in the hard face alloy are MX(M=alloying elements, X=C, N) composite carbonitrides distributed on grain boundaries and dislocations, and have different quantities and sizes under welded state and heat treatment conditions. Primary carbon-nitrogen precipitates are formed during the solidification process of the weld and have a large size; The fine secondary carbon and nitrogen precipitates can be dispersed and precipitated in large quantities after overlay welding heat treatment, which has obvious hardening effect on the matrix. The precipitation of carbon and nitrogen in hard-sided alloy is distributed along dislocation and grain boundary dispersion, which inhibits the formation of Cr-rich precipitated phase and improves the corrosion resistance of grain boundaries.
SUI Yanwei; LIU Aihui; LI Bangsheng; etc
Abstract: In order to study the shrinkage defects of titanium alloy centrifugal casting in depth, microcrystalline wax was used as the physical simulation medium, and the shrinkage defects during the solidification and forming of titanium alloy under centrifugal force field were simulated according to similar criteria, and the influence of rotation speed and centrifugal holding time on shrinkage defects of centrifugal casting was studied. The experimental results show that with the increase of rotation speed, the volume of shrinkage defects at the riser of the microcrystalline wax coagulator increases. Compared with the centrifugation holding time of 900 s, the volume of shrinkage defects at the riser decreases correspondingly after the holding time of 30 s, and the shrinkage effect of the riser is weakened. At the same time, the titanium alloy castings were actually poured, and the test results were consistent with the physical simulation results, which verified the correctness of the physical simulation test results.
CUI Zhixiang; LIU Chuntai; SI Junhui; etc
Abstract: Due to the huge difference between macroscopic part size and micro-feature size, the injection molding filling process with micro-feature is a typical geometric multi-scale structure flow and heat transfer problem. The flow and heat transfer behavior of the injection molding process with microstructure was analyzed by numerical and analytical methods, the macroscopic filling process was dynamically simulated based on the finite element/finite difference method, and the quantitative relationship between the filling distance in the microstructure and the inlet pressure, size, flow velocity and material properties of the microstructure was established by the analytical method, and the effects of macro mold temperature, injection rate and micro-feature size on the micro-feature filling distance were analyzed in detail.
SUN Daoming; JIANG Yiming; GAO Juan; etc
Abstract: Stainless steel often germinates in Cl-containing solutions with porous lacy cover etched holes, and continuous erosion is hidden on the inner surface of the pit under the lace cover, which is an interesting pitting corrosion that often aggravates the failure of the material. Fine 316 ss microelectrode area regulation was used to form a single pitting hole to study pitting corrosion, and the kinetic data of pitting corrosion development were obtained, and according to Fick’s diffusion law, it can be seen that the stable growth condition of pitting corrosion is the product of current density (i) and depth (a) in the pit. The effect of lace cover on the growth of metastable pitting was confirmed by a new ultrasonic electrolytic cell.
WANG Chao; HOU Yudong; WU Ningning; etc
Abstract: Nb2O5 was converted into soluble niobium salt instead of expensive ethanol niobium as the source of niobium, and nano(Li0.06Na0.47K0.47)NbO3 ultrafine powder was synthesized by sol-gel method. The phase structure and micromorphology of (Li0.06Na0.47K0.47)NbO3 nanopowders were characterized by XRD, Raman and TEM. The results show that a (Li500.5Na20.0K06.0)NbO47 nanopowder with an average grain size of 0 nm and a pure tetragonal structure can be prepared by calcination of the dry gel at 47 °C for 3 h, and the synthesis temperature is reduced by more than 350 °C compared with the traditional solid phase method.
HONG Xiaoqin; ZHAO Zhimin; LI Peng; etc
Abstract: The optical fiber is made of self-made light-curing material as the sensing section, and the two ends are coupled with the optical fiber and buried in the light-curing material to form the optical fiber refractive index sensor. With He-Ne laser input fiber, photodetector is used at the output end to receive optical power, and the degree of attenuation of transmitted light characterizes the curing of light-curing materials during the curing process. The critical exposure of the light-curable material was measured as 193.8 s·mw/cm2. The experimental results show that this method can accurately measure the exposure time of the light-curable material at a certain depth, which is simple and easy, and provides a new method for real-time monitoring of the curing degree of the light-curable material.
GONG Dianting; LI Fenghua; FAN Zhanguo; etc
Abstract: Boric acid was prepared by neutralizing borax by acidification of sulfuric acid, combined with recrystallization method and ion exchange resin method, which could improve the quality of boric acid products. The solution after neutralization reaction is mainly H3BO3-Na2SO4-H2O system, and the optimal experimental conditions for boric acid crystallization in the system are obtained through the experimental study of the crystallization kinetics of the system, which provides an experimental basis for the preparation of high-purity boric acid. Through the study of the factors influencing the crystallization process of boric acid in the system, it is found that the crystallization of boric acid is mainly affected by the supersaturation of the solution, crystallization temperature, crystallization time, stirring speed and impurities contained in the solution. Experiments show that for H3BO3-Na2SO4-H2O system, under the condition that other reaction conditions remain unchanged, the concentration increases and the crystallization time prolongs, and the appropriate crystallization temperature and stirring speed are conducive to boric acid crystallization. Compared with the H3BO3-H2O system, the Na3SO3 contained in the H2BO4-Na2SO2-H4O system inhibits the crystallization of boric acid. The crystallization kinetic curve of boric acid in H3BO3-Na2SO4-H2O system was obtained from the experimental data, and the crystallization kinetic equation was established.
LUO Jianlin; DUAN Zhongdong
Abstract: The dispersion effect of polyacrylic acid (PAA) or/and nonylphenol ethoxylate(10) (Tx100) on different multi-walled barky pipes (MWNT) was studied, and then five groups of MWNT-reinforced cementitious composites (MWNT/CMs) were prepared. The results show that it is difficult to obtain good dispersion of MWNT by PAA, especially when the MWNT content is large, SEM shows that it is mostly agglomerated and winding in the matrix, and the distribution uniformity is poor. The resistivity (ρ) value of the corresponding MWNT/CM is high, and the nonlinearity of I-V characteristics is also obvious.PAA and Tx5(Ф(PAA)∶Ф(Tx3)=100) can well disperse the MWNT with higher content, and SEM shows that most MWNTs have good compatibility distribution in the matrix. The ρ of MWNT/CM in the NPT100 group was only about 2.4 Ω·m (ρmax was only 12.7 Ω·m), while the ρ of the NMNT/CM of the NP14 group with the same MWNT content was 8.4 Ω·m, and ρmax was 429 8.1 Ω·m.
XUE Huiqing; DENG Zongcai; LI Jianhui
Abstract: Polyvinyl alcohol (PVA) fiber is a new type of fiber with high tensile resistance, high elasticity, good hydrophilicity, especially good compatibility with Portland cement. In order to prepare high-toughness and large-deformation fiber-reinforced cementitious composites, the uniaxial tensile properties and flexural toughness of PVA fiber-reinforced cementitious composites were introduced, and the test results showed that PVA fibers had good crack resistance and toughening effects, which could significantly improve the crack resistance and deformation ability of cement-based composites. PVA fiber can significantly improve the flexural toughness of concrete, and the flexural toughness index of PVA fiber concrete is significantly higher than that of polypropylene (PP) fiber concrete.
YAO Wu; XU Jing
Abstract: The conductive properties of carbon fiber cement-based (CFRC) materials at different frequencies of alternating current were studied, and the samples with different fiber content were compared and tested. The results show that the impedance-frequency curves of CFRC materials with carbon fiber content below the seepage threshold show similar variation rules with the increase of frequency. And with the increase of carbon fiber content, the trend of impedance change with frequency slows down. An equivalent circuit model inside the CFRC material was established to describe its conductivity under alternating current, and linear regression calculation and correlation analysis were performed on the model to verify the rationality of the model. The results show that the AC resistance of CFRC material is lower than that of DC resistance, and its capacitance value increases with the increase of carbon fiber content.
LIU Xiaogen; BAO Yiwang; SONG Yile; etc
Abstract: The vacuum degree of vacuum glass is detected online by photoelastic method and dynamic method. The experimental test shows that the stress spot caused by stress concentration at the vacuum glass support and the glass support point can be observed by the photoelastic instrument, and the diameter of the stress spot also increases with the increase of the vacuum degree. At the same time, the natural frequency of vacuum glass measured by dynamic method also increases with the increase of its vacuum degree. The principle, detection process and engineering application of the two methods are analyzed, which are characterized by simple operation, intuitive and reliable results, and easy to realize the online detection of vacuum glass actual engineering.
LI Meili; XU Shanshan; QIAN Jueshi; etc
Abstract: A new resistivity method for judging the degree of concrete curing is proposed: using built-in copper electrode and improved resistivity measurement method, three typical conservation systems are selected: natural curing, standard curing and water curing, and the change of resistivity at different depths reflects the humidity gradient change inside concrete, and then reflects the curing status of concrete. The test results show that the resistivity of concrete is significantly affected by the curing conditions, and the curing degree of concrete can be well reflected by the difference in resistivity at different depths from the surface, and different curing systems mainly affect the resistivity of concrete at 3~1 cm from the surface. Based on the resistivity of concrete, the curing quality can be divided into three grades, namely adequate curing, general curing and poor curing. For fly ash high-performance concrete, the resistivity at 3 cm away from the surface of concrete at 28 days < 2 kΩ·cm is fully cured, 15 kΩ·cm~15 kΩ·cm is generally cured, and the > 100 kΩ·cm is poorly maintained. The resistivity method can be effectively applied to on-site concrete engineering testing.
TANG Xian; DAI Jingliang
Abstract: When designing the gradation of asphalt mixture, the practice of first preparing the grading and then conducting performance tests to determine the optimal gradation lacks scientific theoretical basis. Therefore, the basic theory of particle flow is used to simulate the motion law of mixed material particles, the linear contact model of particle flow program is applied, the particle microscopic characteristic parameters and model size are given, the CA0.2, CA0.4, CA0.6 and CA0.8 grads are simulated for contact, and the particle contact force network diagram is drawn, and the simulation results show that the particle contact force of CA0.4 and CA0.6 is relatively uniform, the mixture has good contact force, has good stability during construction, and is not easy to roll. The situation of graded CA0.2 and CA0.8 is the opposite, which provides a certain indoor simulation basis for the grading design of asphalt mixture.
CAO Fabin; TIAN Yanwen; CHEN Yongjie; etc
Abstract: A red LED phosphor CaxSr2-x-3.2yMoO3:yEu2+ with a low-dimensional structure was prepared by using Na3CO1, K1CO5 and Li4CO3 as fluxes (one or several). The results showed that the optimal process conditions were as follows: the optimal dosage molar fraction of 2.3 Na0CO24-2.3K0CO38-2.3Li0CO38 was 2 mol%, Eu3+ concentration was 6 mol%, Ca3+ molar fraction was 8 mol%, reaction temperature was 2 °C and reaction time was 60 h. The spectral test results showed that the fluorescent material could be effectively excited by 900 nm, 2 nm and 311 nm, and the emission peaks were at 395 nm.465 nm and 616 nm nm matches the output light wavelength of ultraviolet and blue LED chips that are currently widely used.
WANG Wenwu; ZHENG Jiagui; FENG Lianghuan; etc
Abstract: In the preparation of CdTe solar cells, the contact characteristics of CdTe solar cells are improved by using Te/Cu/Ni structures with simple processes as contacts. Different temperature combinations were used to annealed CdTe solar cells of this structure. The influence of Te/Cu/Ni contact on device performance was analyzed by changing the performance parameters of the battery before and after heat treatment and the dark I~V and C~V curves. Through the analysis, it can be concluded that the heat treatment of Te/Cu/Ni contact has an important influence on the performance of CdTe solar cells. When the cur annealing temperature is low (130 °C, 160 °C), the reprocessing of Te/Cu/Ni can significantly improve the cell efficiency, so that the final efficiency of the cell is higher than that of the Cu high-temperature annealed battery. However, when the Cu annealing temperature is high (190 °C), the reprocessing of Te/Cu/Ni makes the device performance worse, and the higher the heat treatment temperature of Te/Cu/Ni, the more severe the degradation of battery performance. Experiments show that the Te/Cu/Ni structure as the back contact of CdTe solar cells may improve the performance of the battery after appropriate heat treatment, and the process is relatively simple.
SONG Wenlong; DENG Jianxin; ZHANG Hui
Abstract: MoS14/Zr composite films were prepared on cemented carbide YT2 matrix by composite coating process combining medium frequency magnetron sputtering and multi-arc ion plating. The surface and cross-sectional morphology of the composite film were investigated by scanning electron microscopy (SEM), and the composition of the film was analyzed by energy spectroscopy (EDX). The effects of deposition process parameters such as deposition temperature, negative bias of matrix and Zr current on the adhesion, microhardness and thickness of composite films were studied. The results show that the deposition process parameters have a great influence on the performance of MoS2/Zr composite films, and reasonable selection of deposition process parameters can significantly improve and improve the performance of the composite films, and the influence mechanism of deposition parameters on the properties is analyzed. Under the experimental conditions, the optimal deposition process parameters are: deposition temperature 200 °C, matrix bias 180 V, Zr current 30 A, the structure of the prepared MoS2/Zr composite film is dense, the adhesion is about 60 N, the thickness is about 2.4 μm, and the microhardness is about HV900.
ZHANG Xifeng; YAN Chong; CHENG Xiaonong; etc
Abstract: Using liquid phase chemical reduction method, nickel acetate was used as the precursor, polyethylene glycol 6000 as modifier, hydrazine hydrate as reducing agent, sodium hydroxide as pH adjuster in the aqueous system, microwave irradiation was introduced to synthesize nickel nanowires with a length of 1~3 μm and a diameter of 30~50 nm. Nickel nanowires were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nickel nanowires and spherical nano-nickel were added as base oil liquid paraffin (LP) additives to LP, and the friction and wear properties of LP before and after addition were investigated on UMT-II. friction and wear testing machine and M-2000 ring/block friction and wear testing machine, and the surface morphology and surface film element composition and content were analyzed by scanning electron microscope (SEM) and energy spectrometer (EDS). The results show that compared with the base oil LP, the LP after adding nano-nickel forms a self-healing film, which greatly reduces the friction coefficient, obtains relatively flat grinding marks and significantly improves the friction performance of LP. Compared with spherical nickel nanowires, the addition of nickel nanowires can increase the degree to which they improve the lubrication performance of LP.
LIAN Xiaojie; WANG Song; ZHU Hesun
Abstract: In order to improve the anticoagulant properties of silk fibrous material, it was tried to modify it with Chuanxiong, the active ingredient of the Chinese herbal medicine Chuanxiong. Firstly, the side chain of Chuanxiongzine was structurally modified to introduce the active group hydroxyl, and then the double bond was introduced by esterification reaction, and the obtained intermediate was further grafted and polymerized on the surface of silk fibrous material without initiator. The structure of modified silk was identified by Fourier transform infrared spectroscopy (FTIR), Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). The anticoagulant performance of modified silk pigment was evaluated by partial thromboplastin time (APTT) and platelet adhesion, and compared with unmodified silk pigment, the APTT time of modified silk fibroin was prolonged, and no adhesion platelets were found after 30 minutes of culture in platelet-rich plasma, indicating that the anticoagulant activity of Chuanxiongzine derivative modified silk material in vitro was improved.
YOU Junhua; LIAN Fa Zeng; LI Kyung-da
Abstract: The effects of disproportioned hydrogen pressure, dehydrogenation recombination temperature, dehydrogenation recombination vacuum degree and addition of alloying element Co on the magnetic properties of Nd12.5Fe80.4-xCox Ga0.5 Zr0.1B6.5 (x=0,4,8,12,15,17,20) alloys in d-HDDR process were studied. The phase structure of magnetic particles was characterized by X-ray diffraction (XRD). The results show that the phase transition process of the alloy in the d-HDDR process is: Nd2(Fe,Co)14B+2H2<=>2NdH2+12a-(Fe,Co)+(Fe,Co)2B; The disproportioned hydrogen pressure below 0.025 MPa is the key to the magnetic anisotropy generated by NdFeB magnetic powder, and the system of combining high temperature, low vacuum and high vacuum in the dehydrogenation and recombination stage is the guarantee of high anisotropy of NdFeB magnetic powder. When the disproportioned hydrogen pressure was 0.025 MPa and the dehydrogenation recombination temperature was 840 °C, the anisotropic DOA value of magnetic powder was 0.74. The addition of alloying element Co is beneficial to improve the coercivity and anisotropy of magnetic powder, and when the Co content is 15 at% (atomic fraction), the alloy obtains high comprehensive magnetic properties after the best treatment process: DOA=0.62, Br=1.27T, jHc=754.3 kA/m, (BH)max=245.7 kJ/m3.
CHI Qingguo; LI Weili; Fei Weidong
Abstract: Lanthanum calcium-doped lead titanate (Pb0.8La0.1Ca0.1) Ti0.975O3 (PLCT) pyroelectric films were prepared by pulsed laser (PLD), the phase composition of the films was studied by wide-angle X-ray diffraction (XRD), the thickness of TiO2 seed layer was characterized by X-ray specular reflection, and the effect of TiO2 seed layer on the crystallographic texture of thin film crystallography and its diffusion degree was studied by X-ray diffraction and ω scanning. The results show that PLCT pyroelectric films of pure perovskite phase can be obtained at a suitable crystallization temperature. The introduction of the seed layer changes the texture type of the film, and when there is no seed layer, the film tends to form a (100) texture; The introduction of TiO2 seed layer was conducive to the formation of thin film (301) texture.
ZHANG Chaoyang; CHEN Chaohui; CHENG Haifeng; etc
Abstract: The polarization scattering characteristics of camouflaged coatings were tested by multi-band polarization CCD camera in the optical and infrared bands, and the polarization information was extracted, and the influence of the test conditions on the scattering polarization degree of the coating materials was studied. The results show that the illumination conditions and detection band during the test have a great influence on the scattering polarization degree of the coating. The scattering effect of the coating on the incident light can be divided into two parts: surface scattering and bulk scattering. Area scattering increases the polarization degree and bulk scattering has the effect of depolarization. When the light is incident perpendicularly, bulk scattering plays a major role, and the coating has a small degree of polarization; With the increase of the incidence angle, the proportion of surface scattering in the scattered light gradually increases, which becomes the main influencing factor of the polarization degree of the coating. It is found that the use of appropriate angles and bands for detection in polarization remote sensing is of great significance for the recognition of camouflaged targets in complex backgrounds.
Abstract: The calculation of the relaxation rate of the three—phonon umklapp process in single—walled carbon nanotubes is introduced.Selection rules are determined for the umklapp process.The equations are developed to get the relaxation rate,and the high and low temperature limit approximations.The rate varies linearly with the square of the frequency under the linear phonon dispersion assumption.The rate varies exponentially with the inverse of temperature in the low temperature limit,and linearly with temperature in the high temperature limit,respectively.Inclusion of all the phonon branches leads to the increase of the number of the scattering channels,and the number of the singularities on the total relaxation rate line.Another result is that the rate increases at least one order of magnitude.
MA Xueliang; SUN Zuwang; YANG Donglai
Abstract: Based on the establishment of the dynamic model of oscillating compaction, a large number of field tests were carried out on the amplitude-frequency characteristics of the roller during the oscillation compaction process, and a dynamic identification method for the stiffness and damping of the compacted material in the dynamic model was proposed. The actual test curve is simulated by computer simulation test of the dynamic model, and the fitting curve is obtained by the trial method for different stiffness and damping, so that the stiffness and damping values can be determined. The results show that the change trend of the actual amplitude-frequency characteristics highlights the characteristics of the two degree-of-freedom systems in the theoretical model of the interaction between the oscillating wheel and the hot asphalt mixture, and the stiffness and damping determined by the dynamic identification method are similar to the actual change trend of the compacted material during the compaction process.
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