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Improving creep strength of the fine-grained heat-affected zone of novel 9Cr martensitic heat-resistant steel via modified thermo-mechanical treatment 被引量:1
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作者 Jingwen Zhang liming yu +6 位作者 Yongchang Liu Ran Ding Chenxi Liu Zongqing Ma Huijun Li Qiuzhi Gao Hui Wang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第5期1037-1047,共11页
The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional the... The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling,i.e.,normalizing,cold rolling,and tempering (NCT),which was developed to improve the creep strength of the FGHAZ in G115 steel weldments.The NCT treatment effectively promoted the dissolution of preformed M_(23)C_(6)particles and relieved the boundary segregation of C and Cr during welding thermal cycling,which accelerated the dispersed reprecipitation of M_(23)C_(6) particles within the fresh reaustenitized grains during post-weld heat treatment.In addition,the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations.As a result,the interacting actions between precipitates,dislocations,and boundaries during creep were reinforced considerably.Following this strategy,the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%,which can further push the application of G115 steel in USC power plants. 展开更多
关键词 G115 steel fine-grained heat-affected zone creep strength element segregation nano-sized precipitates
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Effect of two-step solid solution on microstructure andδphase precipitation of Inconel 718 alloy
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作者 Enyu Liu Qingshuang Ma +5 位作者 Xintong Li Aoxue Gao Jing Bai liming yu Qiuzhi Gao Huijun Li 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第10期2199-2207,共9页
Inconel 718 is the most popular nickel-based superalloy and is extensively used in aerospace,automotive,and energy indus-tries owing to its extraordinary thermomechanical properties.The effects of different two-step s... Inconel 718 is the most popular nickel-based superalloy and is extensively used in aerospace,automotive,and energy indus-tries owing to its extraordinary thermomechanical properties.The effects of different two-step solid solution treatments on microstructure andδphase precipitation of Inconel 718 alloy were studied,and the transformation mechanism fromγ″metastable phase toδphase was clarified.The precipitates were statistically analyzed by X-ray diffractometry.The results show that theδphase content firstly increased,and then decreased with the temperature of the second-step solid solution.The changes in microstructure andδphase were studied by scanning electron microscopy and transmission electron microscopy.An intragranularδphase formed in Inconel 718 alloy at the second-[100]_(δ)[011]γ step solid solution temperature of 925℃,and its orientation relationship withγmatrix was determined as//and(010)_(δ)//(111)γ.Furthermore,the Vickers hardness of different heat treatment samples was measured,and the sample treated by second-step solid solution at 1010℃ reached the maximum hardness of HV 446.84. 展开更多
关键词 Inconel 718 alloy two-step solid solution treatment δphase γ″-δtransformation
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Optical design of vertical edge Thomson scattering on HL-2M tokamak
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作者 龚少博 石中兵 +9 位作者 周艺轩 张通川 高金明 郑典麟 孙平 于利明 陈伟 钟武律 许敏 段旭如 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第7期97-103,共7页
A vertical edge Thomson scattering(ETS) diagnostic system on HL-2M tokamak has been designed.The ETS system collects the scattered light from Nd:YAG laser(1064 nm,2 J,30 Hz,15 ns).The laser beam propagates vertically ... A vertical edge Thomson scattering(ETS) diagnostic system on HL-2M tokamak has been designed.The ETS system collects the scattered light from Nd:YAG laser(1064 nm,2 J,30 Hz,15 ns).The laser beam propagates vertically through the plasma region and the polarization is parallel to the toroidal magnetic field.A special designed Galileo-type telescope with long Rayleigh length is applied to focus the laser size and ensure collimation.A group of doubleGaussian collection lenses image the 600 mm vertical scattered region onto rectangular fiber arrays with a spatial resolution of 10 mm.The 2.20 mm × 2.86 mm fiber optic bundle consists of 130 low hydroxyl(OH) 200/220 μm(core/cladding) diameter fibers with numerical aperture NA=0.22,carrying the light to remotely located multi-channel polychromators.Effect of oblique incidence on narrow band filter has been analyzed.The designed electron temperatures range from 5 to 1000 eV and electron densities from 5 × 10^(18) to 1×10^(20) m^(-3). 展开更多
关键词 edge Thomson scattering optical design HL-2M
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Exercise-induced irisin in bone and systemic irisin administration reveal new regulatory mechanisms of bone metabolism 被引量:26
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作者 Jin Zhang Paloma Valverde +9 位作者 Xiaofang Zhu Dana Murray yuwei Wu liming yu Hua Jiang Michel M Dard Jin Huang Zhiwei Xu Qisheng Tu Jake Chen 《Bone Research》 SCIE CAS CSCD 2017年第1期49-62,共14页
Irisin is a polypeptide hormone derived from the proteolytic cleavage of fibronectin-type III domain- containing 5 (FNDC5) protein. Once released to circulation upon exercise or cold exposure, irisin stimulates brow... Irisin is a polypeptide hormone derived from the proteolytic cleavage of fibronectin-type III domain- containing 5 (FNDC5) protein. Once released to circulation upon exercise or cold exposure, irisin stimulates browning of white adipose tissue (WAT) and uncoupling protein I (UCP1) expression, leading to an increase in total body energy expenditure by augmented UCPl-mediated thermogenesis. It is currently unknown whether irisin is secreted by bone upon exercise or whether it regulates bone metabolism in vivo. In this study, we found that 2 weeks of voluntary wheel-running exercise induced high levels of FNDC5 messenger RNA as well as FNDC5/irisin protein expression in murine bone tissues. Increased immunoreactivity due to exercise-induced FNDC5/irisin expression was detected in different regions of exercised femoral bones, including growth plate, trabecular bone, cortical bone, articular cartilage, and bone-tendon interface. Exercise also increased expression of osteogenic markers in bone and that of UCP1 in WAT, and led to bodyweight loss. Irisin intraperitoneal (IP) administration resulted in increased trabecular and cortical bone thickness and osteoblasts numbers, and concurrently induced UCP1 expression in subcutaneous WAT. Lentiviral FNDC5 IP administration increased cortical bone thickness. In vitro studies in bone cells revealed irisin increases osteoblastogenesis and mineralization, and inhibits receptor activator of nuclear factor-kB ligand (RANKL)- induced osteoclastogenesis. Taken together, our findings show that voluntary exercise increases irisin production in bone, and that an increase in circulating irisin levels enhances osteogenesis in mice. 展开更多
关键词 Exercise-induced irisin in bone and systemic irisin administration reveal new regulatory mechanisms of bone metabolism BONE
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Observation of Multiple Broadband Alfvénic Chirping Modes in HL-2A NBI Plasmas 被引量:1
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作者 liming yu Wei Chen +11 位作者 Xiaoquan Ji Peiwan Shi Xuantong Ding Zhongbing Shi Ruirui Ma yumei Hou Yonggao Li Jiaxian Li Jianyong Cao Wulyu Zhong Min Xu Xuru Duan 《Chinese Physics Letters》 SCIE CAS CSCD 2021年第5期41-45,共5页
Multiple broadband Alfvenic chirping modes(CMs),with frequencies in the wide range of f-35-150 kHz and chirping down rapidly,are found in HL-2A neutral beam injection plasmas,and the CMs can even coexist.The frequency... Multiple broadband Alfvenic chirping modes(CMs),with frequencies in the wide range of f-35-150 kHz and chirping down rapidly,are found in HL-2A neutral beam injection plasmas,and the CMs can even coexist.The frequency chirping down process can be completed within-1 ms,and the frequency shift can reach 30-50 kHz.The CMs propagate in ion diamagnetic drift directions poloidally.The toroidal mode number is confirmed to be n=1,2,3 and 4 for the f-35-65,55-90,70-120 and 100-150 kHz CMs,respectively.The CMs are more like to be energetic-particle continuum modes(EPMs),since the modes almost locate on the Alfven continuum. 展开更多
关键词 kHz Observation of Multiple Broadband Alfv nic Chirping Modes in HL-2A NBI Plasmas NBI
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Myocardin-related transcription factor A cooperates with brahmarelated gene 1 to activate P-selectin transcription 被引量:2
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作者 Mingzi Song Mingming Fang +1 位作者 liming yu Yong Xu 《The Journal of Biomedical Research》 CAS CSCD 2016年第1期60-66,共7页
Expression of P-selectin in injured or activated endothelia cells serves as a permissive step towards leukocyte recruitment and perpetuation of inflammation in the pathogenesis of atherosclerosis.P-selectin can be ind... Expression of P-selectin in injured or activated endothelia cells serves as a permissive step towards leukocyte recruitment and perpetuation of inflammation in the pathogenesis of atherosclerosis.P-selectin can be induced by pro-inflammatory stimuli via the transcription factor NF-κB,but the epigenetic mechanisms remain incompletely understood.Previously we reported that myocardin-related transcription factor A(MRTF-A)mediates the transactivation of a slew of adhesion molecules by oxidized low-density lipoprotein(oxLDL),likely through a crosstalk with brahma-related gene 1(BRGl),a chromatin remodeling protein.Here,we show that MRTF-A was both sufficient and necessary for the transactivation of P-selectin gene in endothelial cells treated with TNF-α.Depletion of MRTF-A using small interfering RNA(siRNA)abrogated the binding of BRGl on the P-selectin promoter.Overexpression of BRG1 up-regulated the activity of P-selectin promoter activity while BRGl knockdown attenuated P-selectin expression.Finally,BRGl silencing suppressed the accumulation of acetylated histone H3 and methylated histone H3K4,and altered the binding of NF-κB on the P-selectin promoter.Therefore,our data demonstrate an essential role for MRTF-A and BRGl in P-selectin transactivation in endothelial cells. 展开更多
关键词 myocardin-related transcription factor A(MRTF-A) brahma-related gene 1(BRG1) P-selectin endothelial cell
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Nonlinear Simulations of the Bump-on-Tail Instabilities in Tokamak Plasmas
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作者 yumei Hou Wei Chen +3 位作者 liming yu yunpeng Zou Min Xu Xuru Duan 《Chinese Physics Letters》 SCIE CAS CSCD 2021年第4期67-70,共4页
We reproduce nonlinear behaviors,including frequency chirping and mode splitting,referred to as bump-on-tail instabilities.As has been reported in previous works,the generation and motion of phase-space hole-clump pai... We reproduce nonlinear behaviors,including frequency chirping and mode splitting,referred to as bump-on-tail instabilities.As has been reported in previous works,the generation and motion of phase-space hole-clump pairs in a kinetically driven,dissipative system can result in frequency chirping.We provide examples of frequency chirping,both with and without pure diffusion,in order to illustrate the role of the diffusion effect,which can suppress holes and clumps;Asymmetric frequency chirpings are produced with drag effect,which is essential to enhance holes,and suppress clumps.Although both diffusion and drag effect suppress the clumps,downward sweepings are observed,caused by a complicated interaction of diffusion and drag.In addition,we examine the discrepancies in frequency chirping between marginally unstable,and far from marginally unstable cases,which we elucidate by means of a dissipative system.In addition,mode splitting is also produced via BOT code for a marginal case with large diffusion. 展开更多
关键词 DIFFUSION SPLITTING DISSIPATIVE
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不同温度对含与不含位错α-Fe中He原子行为的影响 被引量:3
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作者 王瑾 余黎明 +3 位作者 李冲 黄远 李会军 刘永长 《金属学报》 SCIE EI CAS CSCD 北大核心 2019年第2期274-280,共7页
采用分子动力学模拟了不同温度下0.1%He (原子分数)浓度下含与不含位错α-Fe中He原子偏聚行为和拉伸变形行为。结果表明,当温度为300 K时,预置的位错影响较弱,含与不含位错α-Fe模型中He原子均容易发生自吞噬形成He团簇,He团簇分布弥散... 采用分子动力学模拟了不同温度下0.1%He (原子分数)浓度下含与不含位错α-Fe中He原子偏聚行为和拉伸变形行为。结果表明,当温度为300 K时,预置的位错影响较弱,含与不含位错α-Fe模型中He原子均容易发生自吞噬形成He团簇,He团簇分布弥散且尺寸较小,位错环数目较少;当温度为600 K时,He原子热扩散行为加剧,较多的He原子偏聚到位错,He团簇分布离散且尺寸较大,位错环数目增加。在拉伸变形过程中,位错的存在能够加速He团簇演变成He泡,降低了模型的屈服应力和应变。在低温300 K时,弥散分布的小He团簇容易合并,发生脆性断裂,整个变形过程位错密度较低;在高温600 K时,离散分布的大He泡展现出较好的延展性,发生塑性断裂,整个变形过程中位错大量增殖,塑性较好。 展开更多
关键词 Α-FE 位错 温度 HE 分子动力学
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Design and performance analysis of position-based impedance control for an electrohydrostatic actuation system 被引量:12
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作者 Yongling FU Xu HAN +4 位作者 Nariman SEPEHRI Guozhe ZHOU Jian FU liming yu Rongrong YANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第3期584-596,共13页
Electrohydrostatic actuator(EHA) is a type of power-by-wire actuator that is widely implemented in the aerospace industry for flight control, landing gears, thrust reversers, thrust vector control, and space robots.... Electrohydrostatic actuator(EHA) is a type of power-by-wire actuator that is widely implemented in the aerospace industry for flight control, landing gears, thrust reversers, thrust vector control, and space robots. This paper presents the development and evaluation of positionbased impedance control(PBIC) for an EHA. Impedance control provides the actuator with compliance and facilitates the interaction with the environment. Most impedance control applications utilize electrical or valve-controlled hydraulic actuators, whereas this work realizes impedance control via a compact and efficient EHA. The structures of the EHA and PBIC are firstly introduced. A mathematical model of the actuation system is established, and values of its coefficients are identified by particle swarm optimization. This model facilitates the development of a position controller and the selection of target impedance parameters. A nonlinear proportional-integral position controller is developed for the EHA to achieve the accurate positioning requirement of PBIC. The controller compensates for the adverse effect of stiction, and a position accuracy of 0.08 mm is attained.Various experimental results are presented to verify the applicability of PBIC to the EHA. The compliance of the actuator is demonstrated in an impact test. 展开更多
关键词 Actuation system AEROSPACE Electrohydrostatic actuator Force control Nonlinear dynamics Particle swarm optimization Position control
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Multi-level virtual prototyping of electromechanical actuation system for more electric aircraft 被引量:13
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作者 Jian FU Jean-Charles MARE +1 位作者 liming yu Yongling FU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第5期892-913,共22页
Electromechanical actuators(EMAs) are becoming increasingly attractive in the field of more electric aircraft because of their outstanding benefits, which include reduced fuel burn and maintenance cost, enhanced sys... Electromechanical actuators(EMAs) are becoming increasingly attractive in the field of more electric aircraft because of their outstanding benefits, which include reduced fuel burn and maintenance cost, enhanced system flexibility, and improved management of fault detection and isolation. However, electromechanical actuation raises specific issues when being used for safetycritical aerospace applications like flight controls: huge reflected inertia to load, jamming-type failure, and increase of backlash with service due to wear and local dissipation of heat losses for thermal balance. This study proposes an incremental approach for virtual prototyping of EMAs. It is driven by a model-based system engineering process in order to enable simulation-aided design.Best practices supported by Bond graph formalism are suggested to develop a model's structure efficiently and to make the model ready for use(or extension) by addressing the above mentioned issues. Physical effects are progressively introduced, and the realism of lumped-parameter models is increased step-by-step. In particular, multi-level component models are architected to ensure continuity between engineering activities. The models are implemented in the AMESim simulation environment, and simulation responses are given to illustrate how they can be used for preliminary sizing, control design, thermal balance verification, and faults to failure analysis. The proposed best practices intend to provide engineers with fast, reusable, and efficient means to assess performance virtually and enhance maturity, performance, and robustness. 展开更多
关键词 Bond graph Electromechanical actuator Flight control Model-based system engi-neering More electric aircraft Power-by-wire
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Tailoring the secondary phases and mechanical properties of ODS steel by heat treatment 被引量:6
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作者 Qian Zhao Zongqing Ma +4 位作者 liming yu Huijun Li Chenxi Liu Chong Li Yongchang Liu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2019年第6期1064-1073,共10页
The oxide dispersion strengthened(ODS) steel with the nominal composition of Fe–14 Cr–2 W–0.3 Ti–0.2 V–0.07 Ta–0.3 Y2O3(wt%) was fabricated by mechanical alloying and hot isostatic pressing(HIP). In order to opt... The oxide dispersion strengthened(ODS) steel with the nominal composition of Fe–14 Cr–2 W–0.3 Ti–0.2 V–0.07 Ta–0.3 Y2O3(wt%) was fabricated by mechanical alloying and hot isostatic pressing(HIP). In order to optimize the relative volume fraction of secondary phases, the as-HIPed ODS steel was annealed at 800°C, 1000°C, 1200°C for 5 h, respectively. The microstructures and different secondary phases of the as-HIPed and annealed ODS samples were identified by scanning electron microscopy(SEM), transmission electron microscopy(TEM), and X-ray diffraction(XRD). The tensile properties of all the ODS steels at room temperature were also investigated. The results indicate that annealing is an effective way to control the microstructure and the integral secondary phases. The annealing process promotes the dissolution of M23C6 particles, thus promoting the precipitation of TiC.No obvious coarsening of Y2Ti2O7 nanoparticles can be observed during annealing. The tensile results indicate that the annealed ODS sample with the optimized secondary phases and high density possesses the best mechanical properties. 展开更多
关键词 ODS steel ANNEALING SECONDARY phase MECHANICAL property
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Synthesis of W-Y2O3 alloys by freeze-drying and subsequent low temperature sintering:Microstructure refinement and second phase particles regulation 被引量:6
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作者 Weiqiang Hu Zhi Dong +2 位作者 liming yu Zongqing Ma Yongchang Liu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2020年第1期84-90,共7页
In this work,W-Y2 O3 alloys are prepared by freeze-drying and subsequent low temperature sintering.The average size of reduced W-Y2 O3 composite powders prepared by freeze-drying method is only 18.1 nm.After low tempe... In this work,W-Y2 O3 alloys are prepared by freeze-drying and subsequent low temperature sintering.The average size of reduced W-Y2 O3 composite powders prepared by freeze-drying method is only 18.1 nm.After low temperature sintering of these composite nanopowders,the formed W-Y2 O3 alloys possess a smaller grain size of 510 nm while maintaining a comparatively higher density of 97.8%.Besides a few submicron Y2 O3 particles(about 100-300 nm)with a W-Y-O phase diffusion layer on their surface distribute at W grain boundaries,lots of nano Y2 WO6 particles(<20 nm)exist in W matrix.Moreover,many Y6 WO12(<10 nm)particles exist within submicron Y2 O3 particles.The formation of these ternary phases indicates that some oxygen impurities in the W matrix can be adsorbed by ternary phases,resulting in the purification of W matrix and the strengthening of phase boundaries.The combined action of the above factors makes the hardness of the sintered W-Y2 O3 alloys in our work as high as 656.6±39.0 HV0.2.Our work indicates that freeze-drying and subsequent low temperature sintering is a promising method for preparing high performance W-Y2 O3 alloys. 展开更多
关键词 W-Y2O3 ALLOYS FREEZE-DRYING Low temperature SINTERING ULTRAFINE grains
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Effect of W addition on phase transformation and microstructure of powder metallurgic Ti-22Al-25Nb alloys during quenching and furnace cooling 被引量:5
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作者 Junpeng YANG Qi CAI +4 位作者 Zongqing MA yuan HUANG liming yu Huijun LI Yongchang LIU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2019年第5期1343-1351,共9页
Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by wa... Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by water quenching and furnace cooling. Comparisons of phase and microstructure between quenched and furnace-cooled W-modified alloys are carried out to illustrate the phase transformation and microstructure evolution during the cooling process. Furthermore, a comparison is also made between W-modified and W-free alloys, to reveal the function of the W alloying.W addition accelerates the solutions of a_2 and O phases during the high-temperature holding, and a Widmannsta¨tten B2 + O structure, which contributes to the properties, is induced by furnace cooling from all the phase regions. The Widmannsta¨tten structure includes a B2 matrix, primary O, and secondary O precipitates. However, W alloying refines the Widmannsta¨tten structure only when the alloys are solution-treated and then cooled from the single B2 phase. Although the hardness of the W-modified alloys is lower than that of the W-free alloys sintered in the same phase region, an enhancement of hardness, 489 ± 18 HV, is obtained in the alloy solution-treated in the single B2 phase region for only 0.5 h. 展开更多
关键词 Hardness Phase formation Ti2AlNb-based alloy W ADDITION Widmannsta¨tten MICROSTRUCTURE
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Ultra-Thin Double-Walled Carbon Nanotubes: A Novel Nanocontainer for Preparing Atomic Wires 被引量:5
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作者 Lei Shi Leimei Sheng +3 位作者 liming yu Kang An Yoshinori Ando Xinluo Zhao 《Nano Research》 SCIE EI CAS CSCD 2011年第8期759-766,共8页
Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and mo... Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner diameters in the range 0.6-1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission current density of DWCNTs reached 1 A/cm2 at an applied field of about 4.3 V/~tm. After high-temperature treatment of DWCNTs, long linear carbon chains (C-chains) can be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter. 展开更多
关键词 Arc discharge carbon chains double-walled carbon nanotubes field electron emission NANOCONTAINER NANOWIRES
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Refined microstructure and enhanced mechanical properties in Mo-Y_(2)O_(3)alloys prepared by freeze-drying method and subsequent low temperature sintering 被引量:5
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作者 Weiqiang Hu Tao Sun +3 位作者 Chenxi Liu liming yu Tansir Ahamad Zongqing Ma 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第29期36-44,共9页
The ultrafine Mo-Y_(2)O_(3)composite powders were successfully synthesized by innovative freeze-drying method.Consequently,the freeze-dried Mo-Y_(2)O_(3)composite powders with high sintering activities possess an aver... The ultrafine Mo-Y_(2)O_(3)composite powders were successfully synthesized by innovative freeze-drying method.Consequently,the freeze-dried Mo-Y_(2)O_(3)composite powders with high sintering activities possess an average grain size of 54 nm.After low temperature sintering at 1600°C,the Mo-Y_(2)O_(3)alloys maintaining a high density(99.6%)have the finest grain size(620 nm)comparing with available literature about oxide dispersion strengthened molybdenum alloy(ODS-Mo).The oxide particles remain their small size(mainly<50 nm)within Mo grains and at Mo grain boundaries.Furthermore,the Y_(5)MO_(2)O_(12)particles were firstly observed within Mo matrix,and its formation can absorb nearby oxygen impurities,which involves the purification of Mo matrix.The mechanical properties show that Mo-Y_(2)O_(3)alloy possess a high hardness of 487±28 HV_(0.2),a high yield strength of 902 MPa,a high compressive strength of1110 MPa,respectively.Our work suggests that freeze-drying and subsequent low temperature sintering can shed light on the preparation of ultrafine ODS-Mo alloys with high performance. 展开更多
关键词 Mo-Y_(2)O_(3) FREEZE-DRYING Low temperature sintering Ultrafine grains Y_(5)MO_(2)O_(12)particles
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Influence of Yttrium Addition on the Reduction Property of Tungsten Oxide Prepared via Wet Chemical Method 被引量:4
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作者 Nan Liu Zhi Dong +4 位作者 Zongqing Ma Zhu Qian Lei Ma liming yu Yongchang Liu 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2020年第2期275-280,共6页
W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hy... W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO3(c-WO3),and the c-WO3 particles have c-WO3 whiskers attached to the surface.This kind of whiskers is essential for c-WO3 to be reduced directly to tungsten and also helpful to obtain W-Y2O3 powders with small size and good uniformity. 展开更多
关键词 W–Y2O3 NANOPOWDERS WET chemical method REDUCTION PROPERTY
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The simultaneous improvements of strength and ductility in additive manufactured Ni-based superalloy via controlling cellular subgrain microstructure 被引量:4
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作者 Yanan Zhao Zongqing Ma +2 位作者 liming yu Ji Dong Yongchang Liu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第9期184-190,共7页
Fine cellular subgrain structure was formed in the Selective Laser Melting(SLM) manu factured IN718 alloy via optimizing the processing parameters.During the subsequent homogenization heat treatment process,the Laves ... Fine cellular subgrain structure was formed in the Selective Laser Melting(SLM) manu factured IN718 alloy via optimizing the processing parameters.During the subsequent homogenization heat treatment process,the Laves phase dispersed at the subgrain boundaries can be eliminated while the cellular subgrain structure is reserved in the printed samples after holding at 1080℃ for 50 min.With the prolongation of the holding time,the subgrain boundaries undergo low angle rotation via the motion ofdislocation,which leads to the annihilation of the cellular subgrain structure.Moreover,during the subsequent double aging heat treatment process,the reserved cellular subgrain structure in the homogenized samples promotes the precipitation of γ" second phase nanoparticles,and these precipitated γ" phase nanoparticles prefer to distribute at subgrain boundaries.It was found that these unique subgrain boundaries with γ" phase precipitates can hinder but not fully terminate the motion of dislocation during the plastic deformation process,which contributes to increasing the strength as well as holding the stable plastic flow.Hence,the strength and ductility of final prepared IN718 alloy with cellular subgrain microstructure were improved simultaneously compared to the prepared alloy without cellular subgrain structure,which even exceed the mechanical properties standards(AMS 5662) of wrought IN718 alloy.These results in our work suggest that controlling the subgrain structure is a promising effective strategy to improve the mechanical properties of SLM manu factured nickel-based superalloy. 展开更多
关键词 Selective laser melting SUPERALLOY Subgrain structure Strengthening and toughening
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Digital fixed-frequency hysteresis current control of a BLDC motor applied for aerospace electrically powered actuators 被引量:3
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作者 Jian FU Yongling FU +3 位作者 liming yu Jianwen GUO Rongrong YANG Mingkang WANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第6期1287-1297,共11页
In the conventional cascade control structure of aerospace electrically powered actuators, the current(or electromagnetic torque) loop plays a critical role in realizing a rapid response for a digitally controlled B... In the conventional cascade control structure of aerospace electrically powered actuators, the current(or electromagnetic torque) loop plays a critical role in realizing a rapid response for a digitally controlled Brush Less Direct Current(BLDC) motor. Hysteresis Current Control(HCC) is an effective method in improving the performance of current control for a BLDC motor.Nevertheless, the varying modulating frequency in the traditional HCC causes severe problems on the safety of power devices and the electromagnetic compatibility design. A triangular carrier-based fixed-frequency HCC strategy is expanded by relaxing the constraints on the rising and descending rates of the winding current to advance the capability of HCC to realize fixed-frequency modulation in the steady state. Based on that, a new flexible-bound-size quasi-fixed-frequency HCC is proposed, and the range feasible to realize fixed-frequency modulation control can cover the entire running process in the steady state. Meanwhile, a corresponding digital control strategy is designed,and four digitalization rules are proposed to extend the capacity to achieve fixed-frequency modulation control to the unsteady working state, that is, a novel fixed-frequency modulation is realized.Simulation and experimental results prove the effectiveness of this improved fixed-frequency HCC strategy. 展开更多
关键词 BLDC motor Current control Fixed-frequency modulation Flexible bound size Hysteresis current control PWM Triangular carrier
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Phase Transformation Behavior and Microstructural Control of High-Cr Martensitic/Ferritic Heat-resistant Steels for Power and Nuclear Plants: A Review 被引量:27
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作者 Xiaosheng Zhou Chenxi Liu +2 位作者 liming yu Yongchang Liu Huijun Li 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2015年第3期235-242,共8页
The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic an... The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic analysis of the martensite formation and microstructural control of high-Cr martensitic/ferritic steels are reviewed. A modular approach, incorporating Fisher partitioning nucleation and anisotropic growth for impingement, was proposed to describe the martensite formation kinetics under different cooling rates.The kinetic analysis suggested a thermal-activated growth feature occurring during the martensitic transformation of martensitic steels. The microstructure can be tuned by composition optimization and various combinations of heat treatment parameters(temperature, time, severe and minor deformation).For the application in power plant, the potential of boundary-design, refinement of original austenite grain size and the final martensitic lath, pinning effect of stable carbides, in improving the performances of martensitic/ferritic steels at elevated temperatures should be investigated more thoroughly.Furthermore, efforts should be made to explore the effects of retained austenite on the improvement of high-temperature creep strength. For the application of nuclear plants, attempts should also be made to produce Fe powders with uniformly distributed oxide particles by chemical reactions. 展开更多
关键词 Martensitic/ferritic steels Microstructural contro
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Selected multiferroic perovskite oxides containing rare earth and transition metal elements 被引量:2
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作者 Shunbo Hu Lei Chen +5 位作者 Yabei Wu liming yu Xinluo Zhao Shixun Cao Jincang Zhang Wei Ren 《Chinese Science Bulletin》 SCIE EI CAS 2014年第36期5170-5179,共10页
Multiferroic materials are currently the subject of intensive research worldwide, because of both their fundamental scientific problems and also possible technological applications. Among a number of candidates in the... Multiferroic materials are currently the subject of intensive research worldwide, because of both their fundamental scientific problems and also possible technological applications. Among a number of candidates in the laboratories, compounds consisting of rare earth and transition metal perovskite oxides have very unusual structural and physical properties. In contrast to the so-called type I multiferroics, ferroelectricity may be induced by magnetic ordering or by applying external fields. In this review, the recent progress on the experimental and theoretical studies of some selected type II multiferroics is presented, with a focus on the perovskite oxides containing rare earth and transition metal elements. The rare earth orthoferrite crystals, rare earth titanate strained film, and rare earthbased superlattices are systematically reviewed to provide a broad overview on their promising electric, magnetic, and structural properties. The recent experimental advances in single-crystal growth by optical floating zone method are also presented. First-principles investigations, either supported by experimental results or awaiting for experimental verifications, are shown to offer useful guidance for the future applications of unconventional multiferroics. 展开更多
关键词 钙钛矿型氧化物 过渡金属元素 稀土元素 铁电性 钙钛矿氧化物 外部磁场 结构特性 实验室
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