检索结果-南通市图书馆

Effects of Na/K ratio on the phase structure and electrical properties of Na_xK_(1-x)NbO_3 lead-free piezoelectric ceramics

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2010年第2期29卷 220-225页

作者： ZHANG Qian, ZHANG Boping, Li Haitao, and SHANG Pengpeng school of materials science and engineering, university of science and Technology Beijing, Beijing 100083, china school of materials science and engineering University of Science and Technology Beijing

Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 *** and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na *** grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3 *** MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 *** temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.

关键词： lead-free piezoelectric ceramics NKN sintering morphotropic phase boundary(MPB)

Effect of Ca addition on the as-cast microstructure and creep properties of Mg-5Zn-5Sn magnesium alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2009年第6期28卷 576-581页

作者： YANG Mingbo CHENG Liang SHEN Jia PAN Fusheng materials science and engineering College Chongqing University of Technology Chongqing 400050 China materials science and engineering College Chongqing University Chongqing 400030 China

The effect of Ca addition on the as-cast micmstructure and creep properties of Mg-5Zn-5Sn magnesium alloy was investigated. The results indicate that adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can effectively refine the as-cast microstructure of the alloy, and the CaMgSn phase with high thermal stability is formed in the alloy. In addition, adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy can also improve the creep properties of the alloy. After adding 1.0 wt.% Ca to Mg-5Zn-5Sn alloy, the second creep rate of the alloy at 150℃ and 50 MPa for 100 h decreases from 4.67 ×10^-8 to 1.43 × 10^-8 s^-1. The strengthening mechanism is mainly attributed to the microstructural refinement and the formation of CaMgSn phase.

关键词： magnesium alloys Ca addition creep properties microstructure

Phase transition in the Zr_(60)Al_(15)Ni_(25) bulk metallic glass subjected to rolling at room temperature

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2006年第6期49卷 655-662页

作者： YAN Zhijie1, 2, LI Jinfu1, ZHOU Yaohe1 & WU Yanqing3 1. State Key Laboratory of Metal Matrix Composites, school of materials science and engineering, Shanghai Jiao Tong university, Shanghai 200030, china 2. school of materials science and engineering, Taiyuan university of science and Technology, Taiyuan 030024, china 3. school of Environmental science and engineering, Shanghai Jiao Tong university, Shanghai 200030, china State Key Laboratory of Metal Matrix Composites School of Materials Science engineering Shanghai Jiao Tong University Shanghai 200030 China school of materials science engineering Taiyuan University of Science Technology Taiyuan 030024 China school of Environmental science engineering Shanghai Jiao Tong University Shanghai 200030 China

The microstructure evolution of the Zr60Al15Ni25 metallic glass during rolling at room temperature is investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC); high-resolution transmission electron microscopy (HREM). The results show that the values of full width at half maximum (FWHM) of the XRD patterns; exothermic enthalpy ΔH of DSC plots do not monotonically change with the variation of deformation degrees . As is not large than 20%, the values of FWHM; ΔH are lower than that of the as-cast state. When reaches 30%, the values of FWHM; ΔH become larger than that of the as-cast state, while their values begin to decrease again as reaches about 85%. These results indicate that the reversible transitions between ordered; disordered atomic configurations occur during rolling, which is further verified by the HREM images. The reversible phase transition can be explained by the competition between the diffusion controlled reordering; shear-induced disordering during rolling.

关键词： metallic glasses, plastic deformation, phase transformations, shear bands.

Microstructure evolution in the high temperature compression of Ti-5.6Al-4.8Sn-2.0Zr alloy

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 533-537页

作者： LI Miaoquan,LUO Jiao,and PAN Hongsi school of materials science and engineering,Northwestern Polytechnical university,Xi’an 710072,china school of materials science and engineering Northwestern Polytechnical University Xi’an China

Isothermal compression of a Ti-5.6Al-4.8Sn-2.0Zr alloy was conducted on a Thermecmaster-Z simulator at the deformation temperatures ranging from 960 to 1060℃, the strain rates ranging from 0.001 to 10.0 s^-1, and the maximum height reduction of 70.0%. In the two-phase region of the Ti-5.6Al-4.8Sn-2.0Zr alloy, the volume fraction of α phase decreases with an increase in deformation temperature, but the grain size has a slight variation with deformation temperature. The strain rate affects both morphologies and grain size of the α phase in the isothermal compression of the Ti-5.6Al-4.8Sn-2.0Zr alloy. The optimal height reduction also contributes to the small and well-distributed α phase in the isothermal compression of Ti-5.6Al-4.8Sn-2.0Zr alloy.

关键词： titanium alloys isothermal compression microstructure mechanism

Effects of Er on the microstructure and properties of AZ31 magnesium alloy prepared via the EMS process

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2010年第4期29卷 339-345页

作者： MA Yutao,ZHANG Xingguo,LIU Hongbin,and MENG Linggang school of materials science and engineering,Dalian university of Technology,Dalian 116023,china school of materials science and engineering Dalian University of Technology Dalian China

The effects of small amounts of the rare-earth element erbium on the microstructure and the mechanical properties of AZ31 magnesium alloy via the electromagnetic stirring （EMS） process have been studied. It has been shown that AZ31-Er alloys are mainly composed of α-Mg solid solution and β-Mg17TA112 phases. When the Er content reaches 0.12 wt.%, the characteristic peaks of A12Er can be observed. The micro- structure is obviously refined and the tensile strength of the AZ31-based alloy at ambient temperature is significantly improved by contents of 0.03 wt.% Er, especially the elongation （8= 19%）. More addition of Er obviously decreases the tensile strength and elongation of the AZ31-based alloy because of the grain coarsening and the reduction of β-Mg17A112 phases.

关键词： AZ31 magnesium alloy microstructure mechanical properties erbium

Study on rare earth/alkaline earth oxide-doped CeO_2 solid electrolyte

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2007年第4期26卷 311-316页

作者： YAN Kai ZHEN Qiang Song Xiwen school of materials science and engineering Shanghai University Shanghai 200072 China Research Center of Nanoscience and Nanotechnology Shanghai Univeesity Shanghai 200444 China school of materials science and engineering Inner Mongolia University of Science and Technology B aotou 014010 China

Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the SmzO3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Srno.2oCe0.8Ol.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the An＇henius equation. Then the SmzO3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.

关键词： doped ceria rare earth/alkaline earth oxide solid electrolyte conductivity effective index

Electrochemical Study of Hypophosphite

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and materials 1998年第1期12卷 23-25页

作者： Yuguo Yang Dongbai Sun Dongbai Sun Dejun Yang (materials science and engineering school, university of science and Technology Beijing, Beijing 100083, china) materials science and engineering school University of Science and Technology Beijing Beijing 100083 China

Electrochemical behavior of hypophosphite was studied with cyclic voltammogram in acidic solution(pH = 4.6) at 80℃. Two anodic peaks were observed on gold electrode at - 0.44V and - 0.59 V (SCE),respectively, and no corresponding cathodic peaks were obtained. The one at - 0.44 V wits ascribed to the oxidation oftautomeric form of hypophosphite, the other at - 0.59 V was due to the oxidation of absorbed form of hypophosphite. The two oxidation reactions were believed to be the electron source of nickel ion reduction in electrolessnickel processes.

关键词： cyclic voltammogram electroless nickel plating gold electrode hypophosphite

Refinement of packet size in low carbon bainitic steel by special thermo-mechanical control process

在线全文

学校读者我要写书评

暂无评论

Journal of university of science and Technology Beijing 2004年第3期11卷 221-224页

作者： Chengjia Shang Xuemin Wang Shanwu Yang Xinlai He materials science and engineering school, university of science and Technology Beijing, Beijing 100083, china Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The packet size of bainitic steel can be refined by a specialrelaxation-precipitation-control phase transformation (RFC) technology. When processed by RPCprocess, the low carbon bainitic steel composes of two kinds of main intermediate transformationphases. One is ultra-fine lath-like bainitic ferrite and the lath is less than 1μm in width andabout 6 μm in length; the alignment of laths forms a refined packet, and the size of packets isabout 5-7 μm in length and about 3-4μm in width. The other is acicular structure. The morphologyand distribution of these acicular structures are influenced by relaxation process, the thin andshort acicular structures cut the prior austenite grain and refine the bainitic packet size. For theoptimum relaxation time, the packet size can be refined to the finest. The mechanical propertiesare influenced by relaxation time and the 800 MPa grade low carbon bainitic steel with excellenttoughness can be obtained by RPC process.

关键词： packet size refinement bainitic steel RPC process

Magnetic properties and structure of very thin permalloy films

在线全文

学校读者我要写书评

暂无评论

Journal of university of science and Technology Beijing 2004年第3期11卷 225-229页

作者： Guanghua Yu Haifeng Li Tao Yang Fengwu Zhu materials science and engineering school, university of science and Technology Beijing, Beijing 100083, china Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

In order to study the magnetic properties and structure of very thinpermalloy films, Ni_(81)Fe_(19) films of 12 nm in thickness were prepared by different instrumentsat an ultrahigh base vacuum and a lower base vacuum. The anisotropic magnetoresistance coefficients(ΔR/R) of Ni_(81)Fe_(19) (12 nm) films reached 1.6 % and 0.6 %, and the coercivities were 127 and334 A/m, respectively. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were usedto study the structure and surface chemical state. The experimental results show that the filmsprepared at the ultrahigh base vacuum have a smoother surface, a bigger grain size and a denserstructure with fewer defects than those prepared at the lower base vacuum.

关键词： NiFe film anisotropic magnetoresistance (AMR) coercivity structure