检索结果-南通市图书馆

New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints

在线全文

学校读者我要写书评

暂无评论

Journal of materials science & Technology 2002年第6期18卷 527-531页

作者： Wenxian WANG, Lixing HUO, Yufeng ZHANG, Dongpo WANG and Hongyang JINGcollege of material science and engineering, Tianjin university, Tianjin 300072, china Coll. of Mat. Sci. and Eng. Tianjin Univ. Tianjin 300072 China

A new welding electrode, low transformation temperature electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods. It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.

关键词： Low transformation temperature electrode Compressive residual stress Fatigue strength Welded joints

Cycloaddition mechanism for the resin-OsO_4-catalyzed of styrene: A DFT study

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 2008年第1期51卷 19-24页

作者： ZHANG XingHui1, WANG KeTai1 & FANG Ran2 1 college of chemical engineering, Gansu Unite university, Lanzhou 730000, china 2 college of Chemistry and chemical engineering, Sun Yat-sen university, Guangzhou 510275, china college of chemical engineering Gansu Unite UniversityLanzhou 730000China college of Chemistry and chemical engineering Sun Yat-sen UniversityGuangzhou 510275China

The postulated intermediates in the base-free and base-assisted addition of OsO4 to styrene have been investigated at the B3LYP/6-311G** level of the theory. N(CH3)2(Ph) was chosen as the base of the resin-OsO4. According to our model calculations the [2+3] addition was found to be favorable with an activation of 45.00 kJ/mol. In contract, the reaction barriers for the [2+2] cycloaddition remain high (>155.00 kJ/mol). In addition, the electronic structure analysis of the molecules was carried out by na- ture bond orbital (NBO). The computational results were in reasonable agreement with experimental results.

关键词： cycloaddition resin-OsO4 density functional theory

Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

在线全文

学校读者我要写书评

暂无评论

Journal of materials science & Technology 2001年第1期17卷 135-136页

作者： He YANG and Zhichao SUN college of materials science and engineering, Northwestern Polytechnical university, Xi’an 710072, china NW Polytech Univ Coll Mat Sci & Engn Xian 710072 Peoples R China

The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp1.

关键词： Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

Theoretical studies of the transport property of oligosilane

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 2010年第12期53卷 2571-2580页

作者： ZHANG GuiLing 1,YUAN HongLiang 1,ZHANG Hui 1,SHANG Yan 1,SUN Miao 1,LIU Bo 1 & LI ZeSheng 2 1 college of chemical and Environmental engineering,harbin university of science and Technology,harbin 150080,china 2 State Key Laboratory of Theoretical and Computational Chemistry Institute of Theoretical Chemistry,Jilin university,Changchun 130023,china 1. college of chemical and Environmental engineering Harbin University of Science and Technology Harbin 150080 China2. State Key Laboratory of Theoretical and Computational Chemistry Institute of Theoretical Chemistry Jilin University Changchun 130023 China

The transport mechanisms of four-conjugated systems were comparatively studied by combining ATK and Gaussian 03 *** was found that the charge-doped oligosilane behaved in a different way from the boron doped and phosphorus doped oligosilanes in terms of the transmission *** charge-doped oligosilane showed almost no conductivity owing to the damage of the electron transfer path by *** contrast,the boron doped and phosphorus doped oligosilanes were demonstrated to be good semiconductors and NDR behavior was observed for *** is a reasonable result after the analysis of the transmission spectra,MPSH states,energy gap,conjugation effect,and scattering effect.

关键词： theoretical study transport property oligosilane

Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3-BaTiO_3 Complex Perovskite Ferroelectric Ceramics with High Dielectric Constant and Low Firing Temperature

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and materials 2000年第2期14卷 115-117页

作者： Zhen Ji Zhhong Xiao Xuqing Liu Zhaozeng Ma Zongsen Yu(material science and engineering School, university of science and Technology Bejing, Beijing 100083, china) material science and engineering School University of Science and Technology Beijing Beijing 100083 China

The effects of different firing temperatures on the stability of perovskite phase, grain size, and dielectric properties were investigated by XRD, TEM, SEM and dielectric measurements. The dielectric ceramics of Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system were obtained by chemical coprecipitation in water. The ceramics have higher dielectric constant (7003-9714), lower firing temperature(950-1150℃), quite uniform microstructure with grain size less than 2.5 mp, and lower temperature coefficients of capacitance. As a re-sult, it was confirmed that the simple and low cost chemical route used namely coprecipitation in water is a desired method for preparinghigh property dielectfic materials applicable to multilayer capacitors.

关键词： PMN-PT-BT coprecipitation dielectric property

Synthesis and photochromic properties of WO_3 powder induced by oxalic acid

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 2009年第5期52卷 609-614页

作者： SHEN Yi1, ZHU Hua1, HUANG Rong1, ZHAO Li2 & YAN ShaNing1 1 Faculty of material science and chemical engineering, china university of Geosciences, Wuhan 430074, china 2 Faculty of materials science and engineering, Hubei university, Wuhan 430062, china 1. Faculty of material science and chemical engineering China University of Geosciences Wuhan 430074 China 2. Faculty of materials science and engineering Hubei University Wuhan 430062 China

Tungsten trioxide powder with the novel morphology was prepared via the hydrothermal method with oxalic acid as the organic inducer, the structure and shape of which were detected by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET. Furthermore, photochromic properties of the as-prepared powder samples were tested by an ultraviolet-visible spectrophotometer combined with a color difference meter. The corresponding results indicated that the induced product was still hexagonal WO3, made up of regularly spindle particles with 200-300 nm in length and 30-50 nm in width. The ratio of the length and width was from 4 to 10. Moreover, the special morphology improved its absorptive capacity to the excitation light source, resulting in its high photochromic properties.

关键词： WO3 powder photochromism oxalic acid organic inducer

Electrochemical characteristics of amorphous MgTi_xNi(x = 0,0.1,and 0.2) hydrogen storage alloys

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2010年第5期29卷 486-490页

作者： LIU Suqin,ZHAO Wenjuan,HUANG Kelong,and HUANG Hongxia college of Chemistry and chemical engineering,Central South university,Changsha 410083,china college of Chemistry and chemical engineering Central South University Changsha China

MgTixNi （x = 0, 0.1, and 0.2） alloys were successfully prepared by mechanical alloying （MA）, and the influence of milling time on the electrochemical characteristics of the electrodes was discussed. MgTixNi alloys after 90 h milling displayed the best electrochemical performance The X-ray diffraction patterns showed that the alloy ball-milled for 90 h was amorphous with a widened diffraction peak. The charge-discharge tests indicated that these alloys had good electrochemical activation properties, and the MgTi0.2Ni alloy electrode exhibited the best cycle performance. The initial discharge capacity of the MgTi0.2Ni alloy reached up to 401.1 mAh·g^-1, and the retention rate of capacity was 31.0% after 30 cycles, much higher than that of MgNi （17.3%）. The Tafel polarization curves revealed that Ti addition could enhance the anticorrosion performance of these alloys in alkali solution, which was responsible for the ameliorated cyclic stability of these alloy electrodes.

关键词： hydrogen storage alloys titanium electrochemical properties mechanical alloying

SYNTHESIS AND OPTICAL PROPERTIES OF A NOVEL ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL POLYMER VIA SOL-GEL PROCESS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer science 2001年第4期19卷 421-427页

作者： Hong-xia Xi Zhong Li Zhao-xi Liang The Institute of chemical engineering South china university Guangzhou 510640 china The Institute of Polymer science, Zhongshan university Guangzhou 510275, china S china Univ Inst Chem Engn Canton 510640 Peoples R China Zhongshan Univ Inst Polymer Sci Canton 510275 Peoples R China

A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of an alkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4 ' -hydroxy azobenzene was covalently bonded to the triethoxysilane derivative, i.e, gamma -isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gel derived NLO polymer were studied and characterized by SEM, FTIR,H-1-NMR, UV-Vis, DSC and second harmonic generation (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO2 networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showed that the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r(33)) of 7.1 pm/V at 1.1 mum wavelength, and exhibit good SHG stability, the r(33) values can maintain about 92.7% of its initial value at room temperature for 90 days, and can maintain about 59.3% at 100 degreesC for 300 min.

关键词： sol-gel process nonlinear optical material alkoxysilane dye dipole alignment relaxation chromophore

Electrochemical synthesis of ammonia using a cell with a Nafion membrane and SmFe_(0.7)Cu_(0.3-x)Ni_xO_3(x=0―0.3) cathode at atmospheric pressure and lower temperature

在线全文

学校读者我要写书评

暂无评论

science china Chemistry 2009年第8期52卷 1171-1175页

作者： XU GaoChao,LIU RuiQuan & WANG Jin college of Chemistry and chemical engineering,Xinjiang university,Urumqi 830046,china college of Chemistry and chemical engineering Xinjiang University Urumqi 830046 China

Samaria-doped ceria Ce0.8Sm0.2O2-δ(SDC) and SmFe0.7Cu0.3-xNixO3 have been synthesized by the sol-gel method and characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM) and scanning electron microscopy(SEM).The electrochemical synthesis of ammonia was investigated at atmospheric pressure and low temperature,using the SFCN materials as the cathode,a Nafion membrane as the electrolyte,nickel-doped SDC(Ni-SDC) as the anode and silver-platinum paste as the current *** was synthesized from 25 to 100℃ when the SFCN materials were used as cathode,with SmFe0.7Cu0.1Ni0.2O3 giving the highest rates of ammonia *** maximum rate of evolution of ammonia was 1.13 × 10-8 mol·cm-2·s-1 at 80℃,and the current efficiency reached as high as 90.4%.

关键词： electrochemical synthesis of ammonia ammonia synthesis at atmospheric pressure and low temperature Nafion membrane metal oxide