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作者： Li, Z. Xu, Q. Xiong, J. Li, J. Liu, B. School of Materials Science and Engineering Key Laboratory for Advanced Materials Processing Technology Ministry of Education Tsinghua University Beijing100084 China National Key Laboratory of Science and Technology on Advanced High Temperature Structural Materials Beijing Institute of Aeronautical Materials Beijing100095 China

Modelling and targeted experimentation on the rod casting with ceramic core were used to quantify the plasticity, recrystallisation during the subsequent solution heat treatment, as a result of the different thermal contractions of the metal, ceramic shell and core during directional solidification. Thermal-elastic-plastic analysis was carried out with the high temperature plasticity assumed to be the rate independent, considering the orthotropic characteristics of single crystal nickel base superalloys. The calculation results indicate that the plasticity occurs mainly during two stages: the initial solidification stages (around solidus) owing to its low immediate yield strength, and the later solidification stage (below 800°C) due to the thermal contraction. The influential factors, such as wall and shell thickness, flanges, etc., are analysed. Experimentally, recrystallisation takes place in the thin walled areas due to broken or buckled cores, which agrees well with the plasticity calculations. © W. S. Maney & Son Ltd. 2014.

关键词： Single crystals

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Spin Hall effect by surface roughness

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Physical Review B 2015年第4期91卷 045407-045407页

作者： Lingjun Zhou Vahram L. Grigoryan Sadamichi Maekawa Xuhui Wang Jiang Xiao (萧江) Department of Physics and State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Advanced Science Research Center Japan Atomic Energy Agency Tokai 319-1195 Japan CREST Japan Science and Technology Agency Tokyo 102-0075 Japan King Abdullah University of Science and Technology (KAUST) Physical Science and Engineering Division Thuwal 23955-6900 Saudi Arabia Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

The spin Hall and its inverse effects, driven by the spin orbit interaction, provide an interconversion mechanism between spin and charge currents. Since the spin Hall effect generates and manipulates spin current electrically, to achieve a large effect is becoming an important topic in both academia and industries. So far, materials with heavy elements carrying a strong spin orbit interaction, provide the only option. We propose here a new mechanism, using the surface roughness in ultrathin films, to enhance the spin Hall effect without heavy elements. Our analysis based on Cu and Al thin films suggests that surface roughness is capable of driving a spin Hall angle that is comparable to that in bulk Au. We also demonstrate that the spin Hall effect induced by surface roughness subscribes only to the side-jump contribution but not the skew scattering. The paradigm proposed in this paper provides the second, not if only, alternative to generate a sizable spin Hall effect.

关键词： spin-orbit surface roughness heavy elements Spin spin Hall effect spin-orbit interactions

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Effect of sintering atmosphere on pore properties and microstructure of YAG porous ceramics

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Rengong Jingti Xuebao/Journal of Synthetic Crystals 2015年 44卷 221-224and233页

作者： Song, Jie-Guang Xu, Ming-Han Du, Da-Ming Wang, Fang Li, Shi-Bin Ma, Ming-Liang Ji, Gang-Chang Chen, Fei Engineering and Technology Research Center for Materials Surface Remanufacturing of Jiangxi Province School of Mechanical and Materials Engineering Jiujiang University Jiujiang China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

The YAG porous ceramics were prepared under different sintering atmosphere. The results show that the amount of sintering neck increases as holding time prolonging and sintering temperature increasing, which improves the binding degree among ceramic particles. YAG porous ceramics are sintered at 1550 for 2 h through considering the cost performance. The pore microstructure of prepared YAG porous ceramics via the vacuum sintering method is more homogeneous than that prepared via the atmosphere sintering method and the pore shape is more smooth. In addition, the binding degree of prepared YAG porous ceramics between the ceramic particles via the vacuum sintering method is higher than that prepared via the atmosphere sintering method. © 2015, Chinese Ceramic Society. All right reserved.

关键词： Yttrium aluminum garnet

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Effect of directional solidification condition on interfacial reaction between DD6 single crystal superalloy and zirconia-silica ceramic core

Effect of directional solidification condition on interfacia...

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2014 International Conference on Materials Science and Computational engineering, ICMSCE 2014

作者： Wang, Li Li Li, Jia Rong Tang, Ding Zhong Gu, Guo Hong Li, Xin Yao, Jian Sheng Fan, Hong Na Niu, Shu Xin Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education School of Materials Science and Engineering Tianjin University Tianjin 300072 China

ISBN: (纸本)9783038350996

The characterization of the interfaces between DD6 single crystal superalloy and zirconia-silica (ZrO2-SiO2) ceramic cores was performed by optical microscope (OM), SEM and EDS analysis in order to study the influence of directional solidification condition on the interfacial reaction. The results showed that there were chemical reactions on interfaces between DD6 melt and ZrO2-SiO2 ceramic cores and the main reaction product was Al2O3. The interfacial reaction involved a complex, interdependent system including the oxidation of Al element, the destabilization of calcia stabilization zirconia (CSZ) and the formation of liquid phase with low melting point. The intensity of interfacial reaction increased with the increase of pouring temperature and solidification time, but the number and size of reaction zones could not increase together because of the limited Al content in DD6 alloy. © (2014) Trans Tech Publications, Switzerland.

关键词： Solidification

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Activation of antiferromagnetic domain switching in exchange-coupled Fe/CoO/MgO(001) systems

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Physical Review B 2015年第13期91卷 134428-134428页

作者： Q. Li G. Chen T. P. Ma J. Zhu A. T. N'Diaye L. Sun T. Gu Y. Huo J. H. Liang R. W. Li C. Won H. F. Ding Z. Q. Qiu Y. Z. Wu Department of Physics State Key Laboratory of Surface Physics and Collaborative Innovation Center of Advanced Microstructures Fudan University Shanghai 200433 People's Republic of China NCEM Molecular Foundry Lawrence Berkeley National Laboratory Berkeley California 94720 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Chinese Academy of Sciences Ningbo Institute of Materials Technology and Engineering Key Laboratory of Magnetic Materials and Devices Ningbo 315201 Zhejiang People's Republic of China Department of Physics Kyung Hee University Seoul 130-701 Republic of Korea National Laboratory of Solid State Microstructures Department of Physics and Collaborative Innovation Center of Advanced Microstructures Nanjing University 22 Hankou Road Nanjing 210093 People's Republic of China Department of Physics University of California at Berkeley Berkeley California 94720 USA

In contrast to the extensive study of domain reversal in ferromagnetic materials, the domain switching process in antiferromagnets is much less studied due to the difficulty of probing antiferromagnetic spins. Using a combination of hysteresis loop, Kerr microscope, and x-ray magnetic linear dichroism measurements, we investigated the antiferromagnetic (AFM) domain switching process in single crystalline Fe/CoO bilayers on MgO(001). We demonstrate that the CoO AFM switching is a Kolmogorov-Avrami process in which the thermal activation energy creates AFM domain nucleation centers which further expand by domain wall propagation. From the temperature- and thickness-dependent measurements, we are able to retrieve quantitatively the important parameter of the CoO AFM activation energy, which is shown to increase linearly with CoO thickness.

关键词： ANTIFERROMAGNETIC materials LINEAR dichroism NUCLEATION KOLMOGOROV complexity AVRAMI equation

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Effect of bending speed on forming quality of 0Cr21Ni6Mn9N stainless steel tube NC bending

Effect of bending speed on forming quality of 0Cr21Ni6Mn9N s...

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4th International Symposium on Chemical engineering and Material Properties, ISCEMP 2014

作者： Fang, Jun Lu, Shi Qiang Wang, Ke Lu Yao, Zheng Jun Jiangxi Key Laboratory of Surface Engineering Jiangxi Science and Technology Normal University Nanchang 330013 China School of Aeronautical Manufacturing Engineeringxs Nanchang Hangkong University Nanchang 330063 China Institute of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 211106 China

ISBN: (纸本)9783038352303

Based on the nonlinear FE platform ABAQUS, an elastic plastic 3D-FE model of 0Cr21Ni6Mn9N stainless steel tube was established to simulate the whole process, and its reliability was validated by experiment. Using the model, the effect of bending speed on forming quality was studied and the influence laws of bending speed on wrinkling wave ratio, wall thinning, cross section deformation and springback angle were revealed. The results show that the wrinkling wave ratio and springback angle decrease with the increasing of bending speed, while the effect of bending speed on wall thinning and cross section deformation are not significant. The maximum cross section deformation degree presents in the vicinity of the bending angle 30° along the bending direction and its position is almost unchanged with the variation of bending speed. © (2014) Trans Tech Publications, Switzerland.

关键词： Speed

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Bulging of 1420 Al-Li alloy based on Pulse Current

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Procedia engineering 2014年 81卷 808-812页

作者： Qi Xiong Xiao-tao Han Quan-liang Cao Zhi-peng Lai Qi Chen Tao Niu Zhong-yu Zhou Hong-liang Hou Liang Li Wuhan National High Magnetic Field Center HuaZhong University of Science and Technology WuHan Hubei Province 430074 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology HuaZhong University of Science and Technology WuHan Hubei Province 430074 China AVIC Beijing Aeronautical Manufacturing Technology Research Institute Beijing 100024 China

The pulse current auxiliary forming technology has been widely applied for the fabrication of complex sheet metal parts. However, the potential of high-density pulse current to generate high electromagnetic forces, which can be taken as drive forces in forming process, hasn’t been paid enough attention. Compared with the traditional gas bulging technology, bulging based on pulse current has two main advantages. One is that metal sheets can be formed directly by electromagnetic forces instead of the air pressure, and thus the airtightness of die is not an issue. The other is that the forming performance can be improved by the electro plastic effect induced by pulse currents during deformation. In this paper, to validate the effectiveness of this novel method, a special electromagnetic system for bulging of 1420 Al-Li Alloy has been designed and fabricated, in which a high-density pulse current flows through two parallel 1420 Al-Li Alloy sheets in opposite directions to generate repulsive forces for bulging. Finally, both the numerical and experimental studies are carried out to study the forming behaviour of sheets.

关键词： Electroplastic Bulging Pulse current

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Unstable spin-ice order in the stuffed metallic pyrochlore Pr2+xIr2−xO7−δ

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Physical Review B 2015年第5期92卷 054432-054432页

作者： D. E. MacLaughlin O. O. Bernal Lei Shu Jun Ishikawa Yosuke Matsumoto J.-J. Wen M. Mourigal C. Stock G. Ehlers C. L. Broholm Yo Machida Kenta Kimura Satoru Nakatsuji Yasuyuki Shimura Toshiro Sakakibara Department of Physics & Astronomy University of California Riverside California 92521 USA Institute for Solid State Physics University of Tokyo Kashiwanoha 5-1-5 Kashiwa Chiba 277-8581 Japan Department of Physics & Astronomy California State University Los Angeles California 90032 USA State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Fudan University Shanghai 200433 China Institute for Quantum Matter and Department of Physics and Astronomy The Johns Hopkins University Baltimore Maryland 21218 USA NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Quantum Condensed Matter Division Neutron Sciences Directorate Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Materials Science and Engineering The Johns Hopkins University Baltimore Maryland 21218 USA PRESTO Japan Science and Technology Agency (JST) 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan

Specific heat, elastic neutron scattering, and muon spin rotation (μSR) experiments have been carried out on a well-characterized sample of “stuffed” (Pr-rich) Pr2+xIr2−xO7−δ. Elastic neutron scattering shows the onset of long-range spin-ice “2-in/2-out” magnetic order at TM=0.93 K, with an ordered moment of 1.7(1)μB/Pr ion at low temperatures. Approximate lower bounds on the correlation length and correlation time in the ordered state are 170 Å and 0.7 ns, respectively. μSR experiments yield an upper bound 2.6(7) mT on the local field Bloc4f at the muon site, which is nearly two orders of magnitude smaller than the expected dipolar field for long-range spin-ice ordering of 1.7μB moments (120–270 mT, depending on muon site). This shortfall is due in part to splitting of the non-Kramers crystal-field ground-state doublets of near-neighbor Pr3+ ions by the μ+-induced lattice distortion. For this to be the only effect, however, ∼160 Pr moments out to a distance of ∼14 Å must be suppressed. An alternative scenario, which is consistent with the observed reduced nuclear hyperfine Schottky anomaly in the specific heat, invokes slow correlated Pr-moment fluctuations in the ordered state that average Bloc4f on the μSR time scale (∼10−7s), but are static on the time scale of the elastic neutron scattering experiments (∼10−9s). In this picture, the dynamic muon relaxation suggests a Pr3+4f correlation time of a few nanoseconds, which should be observable in a neutron spin echo experiment.

关键词： SPIN waves PYROCHLORE PRASEODYMIUM INELASTIC neutron scattering MUON spin rotation CRYSTAL field theory GROUND state (Quantum mechanics)

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Synthesis and characterization of zinc oxide hollow and flower likemicrospheres by simple one step solvothermal approach

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2013 3rd International Conference on key engineering Materials, ICKEM 2013

作者： Jamil, Saba Jing, Xiao Yan Jun, Wang Zhang, Mi Lin Key Laboratory of Superlight Material and Surface Technology Ministry of Education Harbin Engineering University 150001 China Institute of Advanced Marine Materials Harbin Engineering University 150001 China

ISBN: (纸本)9783037857045

Zinc oxide with spherical shaped and flower shaped morphology are prepared by simple one step solvothermal method. The product is subjected to characterization to investigate the morphology and size by using X ray diffraction, semi electron microscopy and transmission electron microscopy. The size of the prepared zinc oxide particle is in the range of 1 micrometer to 3 micrometers. The outer surface of the particles is not smooth but it is rough. The possible formation mechanism for the product is investigated that is further justified by means of structural characterization. © (2013) Trans Tech Publications, Switzerland.

关键词： Morphology

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Electrical and mechanical performance of graphene sheets exposed to oxidative environments

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Nano Research 2013年第7期6卷 485-495页

作者： Mario Lanza Yan Wang Teng Gao Albin Bayerl Marc Porti Montserrat Nafria Yangbo Zhou Guangyin Jing Yanfeng Zhang Zhongfan Liu Dapeng Yu Huiling Duan State Key Laboratory for Turbulence and Complex System Department of Mechanics and Aerospace Engineering CAPT College of Engineering Peking University Beijing 100871 China Beijing Aeronautical Science and Technology Research Institute Beijing 10221 I China Center for Nanochemistry (CNC) Beijing National Laboratory for Molecular Sciences State Key Laboratory for Structural Chemistry of Unstable and Stable Species College of Chemistry and Molecular Engineering Academy for Advanced Interdisciplinary Studies Peking University Beijing 100871 China Electronic Engineering Department Universitat Autonoma de Barcelona Cerdanyola del Valles 08193 Spain Department of Physics State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 China Physics Department Northwest University Xi'an 710069 China

Graphene coatings have been shown to protect the underlying material from oxidation when exposed to different media. However, the passivating properties of graphene in air at room temperature, which corresponds to the operating conditions of many electronic devices, still remain undear. In this work, we analyze the oxidation kinetics of graphene/Cu samples in air at room temperature for long periods of time （from I day to 113 days） using scanning electron microscopy, conductive atomic force microscopy and Auger electron microscop3~ and we compare the results with those obtained for similar samples treated in H202. We observe that unlike the graphene sheets exposed to H202, in which the accumulation of oxygen at the graphene domain boundaries evolves in a very controlled and progressive way, the local oxidation of graphene in air happens in a disordered manner. In both cases the oxide hillocks formed at the graphene domain boundaries can propagate to the domains until reaching a limiting width and height. Our results demonstrate that the local oxidation of the underlying material along the domain boundaries can dramatically decrease the roughness, conductivity, mechanical resistance and frictional characteristics of the graphene sheet, which reduces the performance of the whole device.

关键词： graphene local oxidation domain boundary passivating layer

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