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Effects of Mg substitution on the structural and magnetic properties of Co0.5Ni（0.5-x）MgxFe2O4 nanoparticle ferrites

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Chinese Physics B 2016年第4期25卷 358-364页

作者： r M rosnan z Othaman r Hussin Ali A Ati Alireza Samavati Shadab Dabagh samad zare Centre for Sustainable Nanomaterials Ibnu Sina Institute for Scientific and Industrial Research Universiti Teknologi Malaysia 81310 Skudai Johor Bahru Malaysia

In this study, nanocrystalline Co-Ni-Mg ferrite powders with composition Coo.5Nio.5-xMgxFe2O4 are successfully synthesized by the co-precipitation method. A systematic investigation on the structural, morphological and magnetic properties of un-doped and Mg-doped Co-Ni ferrite nanoparticles is carried out. The prepared samples are characterized using x-ray diffraction （XrD） analysis, Fourier transform infrared spectroscopy （FTIr）, field emission scanning electron microscopy （FESEM）, and vibrating sample magnetometry （VSM）. The XrD analyses of the synthesized samples confirm the formation of single-phase cubic spinel structures with crystallite sizes in a range of - 32 nm to - 36 nm. The lat- tice constant increases with increasing Mg content. FESEM images show that the synthesized samples are homogeneous with a uniformly distributed grain. The results of Ir spectroscopy analysis indicate the formation of functional groups of spinel ferrite in the co-precipitation process. By increasing Mg2- substitution, room temperature magnetic measurement shows that maximum magnetization and coercivity increase from - 57.35 emu/g to - 61.49 emu/g and - 603.26 Oe to 684.11 Oe （l Oe = 79.5775 A.m-l）, respectively. The higher values of magnetization Ms and Mr suggest that the opti- mum composition is Co0.5Ni0.4Mg0.1Fe204 that can be applied to high-density recording media and microwave devices.

关键词： co-precipitation magnetic materials spinel ferrite magnetic properties

remarkably high fracture toughness of HfNbTaTizr refractory high-entropy alloy

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Journal of Materials Science & Technology 2022年第28期123卷 70-77页

作者： X.J.Fan r.T.Qu z.F.zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nano Science and Technology Institute University of Science and Technology of ChinaSuzhou 215132China

High-entropy alloys(HEAs)with face-centered cubic(FCC)phase such as CoCrFeMnNi or CoCrNi generally exhibit ultra-high fracture toughness but relatively low *** contrast,body-centered cubic(BCC)HEAs often display higher strengths,but the few reports on fracture toughness measurement demonstrate low toughness *** we show that the BCC HfNbTaTizr refractory HEA,which possesses a combination of high strength,good tensile ductility and excellent high-temperature properties,also exhibits a remarkably high fracture *** using the"single specimen"compliance method for J-integral measurement according to the ASTM E1820–17 standard,its fracture toughness K_(JIC)was experimentally determined to be 210 MPa m^(1/2),which renders this HEA among the toughest metallic *** excellent damage tolerance makes the HEA promising for applications as high-temperature structural materials such as in aerospace field.

关键词： High-entropy alloys BCC structure Fracture toughness J-integral

High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals

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Journal of Materials Science & Technology 2023年第23期154卷 94-106页

作者： D.F.Shi z.J.zhang Y.H.Yang Y.z.zhou r.Liu P.zhang z.F.zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China

Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.

关键词： Superalloys Bicrystals Grain boundary misorientation Fatigue strength Fatigue crack

Survey of the mechanisms of power take-off(PTO)devices of wave energy converters

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Acta Mechanica Sinica 2020年第3期36卷 644-658页

作者： z.Liu r.zhang H.Xiao X.Wang School of Engineering RMIT UniversityBundooraVIC 3083Australia

Ocean wave energy conversion as one of the renewable clean energy sources is attracting the research interests of many *** review introduces different types of power take-off(PTO)technology of wave energy *** novelty of this paper is to present advantages and disadvantages of the linear direct and indirect drive PTO devices for ocean wave energy *** designs and optimizations of PTO systems of ocean wave energy converters have been studied from reviewing the recently published *** novel mechanical designs of the PTO systems have been compared and investigated in order to increase the energy harvesting efficiency.

关键词： ocean wave energy

Experimental　Study　on　Heat　Transfer　and　Pressure　Drop　Characteristics　of　Four　Types　of　Plate　Fin－and－TUbe　Heat　Exchanger　Surfaces

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Journal of Thermal Science 1994年第1期3卷 34-42页

作者： H.J. kang W. Li H.z. Li r.C. Xin W.Q. Tao(School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China) 1. School of Energy and Power Engineering Xi’an Jiaotong University 710049 Xi’an Shaanxi China

In this paper, air side heat transfer and pressure drop characteristics of twelve three-row plate finandtube heat exchanger cores of four types of fin configurations have been experimentally *** heat transfer and friction factor correlations for'the twelve cores are provided in a wide range ofreynolds number. It is found that in the range of reynolds number tested, the Nusselt number of theslotted fin surface is the largest and that of the plain plate fin is the lowest while the Nusselt numbersof two types of wavy fins are somewhere in between.

关键词： plate fin-and-tube exchanger heat transfer and pressure drop characteristics plain plate fin wavy plate fin slotted plate fin

Structural Damage Detection Using a Modified Artificial Bee Colony Algorithm

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Computer Modeling in Engineering & Sciences 2016年第4期111卷 335-355页

作者： H.J.Xu z.H.Ding z.r.Lu J.K.Liu Department of Mechanics Sun Yat-sen UniversityGuangzhou 510006China

An optimization approach based on Artificial Bee Colony(ABC)algorithm is proposed for structural local damage detection in this *** objective function for the damage identification problem is established by structural parameters and modal assurance criteria(MAC).The ABC algorithm is presented to solve the certain objective *** the Tournament Selection Strategy and chaotic search mechanism is adopted to enhance global search ability of the certain algorithm.A coupled double-beam system is studied as numerical example to illustrate the correctness and efficiency of the propose *** simulation results show that the modified ABC algorithm can identify the local damage of the structural system efficiently even under measurement noise,which demonstrates the proposed algorithm has a higher damage diagnosis precision.

关键词： structural damage detection Artificial Bee Colony algorithm Modal Assurance Criteria coupled double-beam system Tournament Selection Strategy

Effect of post weld artificial aging and water cooling on microstructure and mechanical properties of friction stir welded 2198-T8 Al-Li joints

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Journal of Materials Science & Technology 2022年第28期123卷 92-112页

作者： Y.Tao z.zhang P.Xue D.r.Ni B.L.Xiao z.Y.Ma Institute of Metal research Chinese Academy of SciencesShenyang 110016China

Friction stir welding(FSW)under both air cooling and water cooling conditions with welding parameters of 800-1200 rpm rotation rates and 50-200 mm/min welding speeds was carried out on 2198-T8 Al-Li alloys,and post weld artificial aging was performed on the air cooled *** welding defects other than lazy S were observed in the nugget zone(Nz)for all *** air cooling condition,the lowest hardness zone(LHz)occurred in the heat affected zone(HAz).FSW resulted in gradual dissolution of original T_(1),θ′andδ′/β′from the base material(BM)to the thermo-mechanically affected zone(TMAz),and complete dissolution of all precipitates in the Nz withδ′/β′and Guinier-Preston zones precipitating during *** air cooled joints exhibited no noticeable changes in intrinsic tensile strength with a joint strength reaching 81.3%of the BM,but varied elongation with welding parameters,which was closely related to failure in the Nz and fracture along lazy *** weld artificial aging led to the largest hardness recovery in the TMAz but smaller hardness recovery in the initial LHz and the *** aging kinetics across the joint was determined by volume fraction of both original precipitate dissolu-tion during welding and coarse particles formed during aging,and by dislocation density inherited from *** weld artificial aging greatly enhanced the joint strength with the ultimate tensile strength reaching 87.3%of the *** compared to air cooling condition,water cooling hardly affected the Nz hardness and did not improve the joint strength,and the reason was discussed in light of precipitates,hardness changes and fracture behavior.

关键词： Friction stir welding Aluminum-lithium alloys Microstructure Mechanical properties

Theoretical framework and experimental solution for the air-water interface adsorption problem in cryoEM

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Biophysics reports 2023年第4期9卷 215-229页

作者： Joon S.kang Xueting zhou Yun-Tao Liu Kaituo Wang z.Hong zhou Department of Microbiology Immunology & Molecular Genetics University of California Los Angeles (UCLA) Molecular Biology Institute UCLA California Nano Systems Institute UCLA

As cryogenic electron microscopy(cryoEM) gains traction in the structural biology community as a method of choice for determining atomic structures of biological complexes, it has been increasingly recognized that many complexes that behave well under conventional negative-stain electron microscopy tend to have preferential orientation, aggregate or simply mysteriously “disappear” on cryoEM grids. However, the reasons for such misbehavior are not well understood, which limits systematic approaches to solving the problem. Here, we have developed a theoretical formulation that explains these observations. Our formulation predicts that all particles migrate to the air–water interface(AWI)to lower the total potential surface energy-rationalizing the use of surfactant, which is a direct solution to reduce the surface tension of the aqueous solution. By performing cryogenic electron tomography(cryo ET) on the widely-tested sample, Gro EL, we demonstrate that, in a standard buffer solution, nearly all particles migrate to the AWI. Gradually reducing the surface tension by introducing surfactants decreased the percentage of particles exposed to the surface. By conducting single-particle cryoEM, we confirm that suitable surfactants do not damage the biological complex, thus suggesting that they might provide a practical, simple, and general solution to the problem for high-resolution cryoEM. Applying this solution to a real-world AWI adsorption problem involving a more challenging membrane protein,namely, the Cl C-1 channel, has resulted in its near-atomic structure determination using cryoEM.

关键词： Surface energy Surfactant Sample preparation CryoEM CryoET Air–water interface adsorption

Microstructural refinement mechanism and its effect on toughness in the nugget zone of high-strength pipeline steel by friction stir welding

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Journal of Materials Science & Technology 2021年第34期93卷 221-231页

作者： r.H.Duan G.M.Xie P.Xue z.Y.Ma z.A.Luo C.Wang r.D.K.Misra State Key Laboratory of rolling and Automation Northeastern UniversityNo.3 Wenhua RoadShenyang 110819China Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of Sciences72 Wenhua RoadShenyang 110016China School of Metallurgy Northeastern UniversityNo.3 Wenhua RoadShenyang 110819China Department of Metallurgical Materialsand Biomedical EngineeringUniversity of Texas at El PasoTX 79968USA

High-strength pipeline steel was subjected to friction stir welding(FSW)at rotation rates of 400-700 rpm,and the grain refinement mechanism of the nugget zone(Nz)was *** thermomechanical process during FSW in the Nz was simulated by multi-pass thermal compression,thereby achieving the austenitic non-recrystallization temperature(T_(nr)).The austenitic non-recrystallization in the Nz at the lowest rotation rate of 400 rpm caused a significant grain ***,the reduced rotation rate also resulted in the formation of a high ratio of island-like martensite-austenite(M-A)*** toughness of the Nzs was enhanced as the rotation rate decreased,which is attributed to the fine effective grains and homogeneously distributed fine M-A constituents dramatically inhibiting crack initiation and propagation.

关键词： Pipeline steel Friction stir welding Grain refinement M-A constituent Toughness