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A comprehensive understanding of grain selection in spiral grain selector during directional solidification

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Journal of Materials Science & Technology 2022年第7期102卷 204-212页

作者： Binqiang Wang long zeng Neng Ren Mingxu Xia Jianguo Li School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China

It is of great importance to further investigate grain selection mechanism for the production of single crystal(SX) turbine blade because a single crystal with optimized crystal orientation will enhance service performance of the blade *** this paper,single crystals with different deviation angles,i.e.6°,12° and 29°, were obtained using directional solidification under the same casting *** has been found that the grain selection in spiral selector is a coupling process where high order dendrites branch in the front side and primary dendrites disappear in the back side based on the metallographic analysis and electron back scatter diffraction(EBSD).Considering the development of liquid/solid interface by numerical simulation,a combination effect with space expansion,geometrical restriction and grain competition was proposed for spiral grain *** space expansion mechanism dominates the process as it provides growth space and driving force for high order dendrites ***,the smaller the take-off angle(θ) is,the larger space and the stronger driving force high order dendrites will get,and the higher efficient the selector will be. The competitive growth between the secondary dendrites plays more contribution than that of primary dendrites,*** with preferred secondary dendrites instead of preferred primary dendrites could outcompete during grain selection,and this is the reason why spiral grain selector cannot optimize the orientation of the primary *** findings provide experimental evidence for spatial control of SX growth,and benefit the sophistic casting fields such as turbine blade casting for improved yield.

关键词： Ni-based superalloy Spiral grain selector Space expansion Geometrical restriction Grain competition

The possibility of isolated target 3-D position estimation and optimal receiver position determination in SS-BSAR

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Science in China(Series F) 2008年第9期51卷 1372-1383页

作者： HU Cheng long Teng zeng Tao Radar Research Lab Department of Electronic Engineering Beijing Institute of Technology Beijing 100081China

Starting from the generalized ambiguity function of bistatic SAR （BSAR）, it is shown that 3-D point target estimation can be carried out in space-surface bistatic SAR （SS-BSAR）. Appropriate analytical equations, based on maximum likelihood estimation （MLE）, are derived and confirmed via computer simulation. Furthermore, the performance of the estimate using the Crammer-Rao bound is analyzed for the case in question, thus further revealing the possibility and potential of target 3-D position estimation. Setting the determinant maximum of the information matrix as the criterion, the optimal receiver position and multi-receiver configuration are analytically determined in the SS-BSAR system. Simulation results also validate the correctness of the analytical calculation.

关键词： SS-BSAR position estimation MLE Crammer-Rao bound optimal receiver position

Crystal Structure of a New Cembranolide Diterpene

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Chemical Research in Chinese Universities 2002年第2期18卷 189-191页

作者： LIN Cui wu SU Jing yu zeng long mei School of Chemistry and Chemical Engineering Zhongshan UniversityGuangzhou 510275P.R.China Department of Chemistry Guangxi UniversityNanning 530004P.R.China

A new cembranoide deterpene was isolated from the soft coral Sinularia Tenella . The crystal and chemical structure of the title compound were determined by means of spectroscopic methods and X ray diffraction analysis as ( 1R *,4R *,5S *,12S *,12R * ) 9 acetoxy cembr 8\%E\%,15(17) dien 16,4 olide. It shows a moderate cytotoxicity against P 388 and L 1210 cell lines.

关键词： Crystal structure Cembranolide diterpene X ray diffraction Sinularia tenella

Hot deformation characteristics of as-cast high-Cr ultra-super-critical rotor steel with columnar grains

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International Journal of Minerals,Metallurgy and Materials 2016年第11期23卷 1275-1285页

作者： Zong-ye Ding Qiao-dan Hu long zeng Jian-guo Li School of Materials Science and Engineering Shanghai Jiao Tong University Laboratory of Advanced Materials and Solidification Shanghai Jiao Tong University

Isothermal hot compression tests of as-cast high-Cr ultra-super-critical（USC） rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^（-1）. The softening mechanism was dynamic recovery（DRV） at 950°C and the strain rate of 1 s^（-1）, whereas it was dynamic recrystallization（DRX） under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ ×mol^（-1）. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate（θ）–flow stress（σ） and-θ/σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^（-1）, with a power dissipation efficiency η greater than 31%.

关键词： rotor steel columnar grains dynamic recrystallization constitutive models critical conditions processing maps

Phase,microstructure and compressive properties of refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi

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International Journal of Minerals,Metallurgy and Materials 2022年第6期29卷 1231-1236页

作者： Jiaojiao Yi Fuyang Cao Mingqin Xu Lin Yang Lu Wang long zeng Laboratory of Advanced Multicomponent Materials School of Mechanical EngineeringJiangsu University of TechnologyChangzhou 213001China School of Materials Science and Engineering Jiangsu UniversityZhenjiang 212013China School of Materials Science and Engineering Jiangsu University of TechnologyChangzhou 213001China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China

New refractory high-entropy alloys,CrHfNbTaTi and CrHfMoTaTi,derived from the well-known HfNbTaTiZr alloy through principal element substitution were prepared using vacuum arc *** phase components,microstructures,and compressive properties of the alloys in the as-cast state were *** showed that both alloys were composed of BCC and cubic Laves *** terms of mechanical properties,the yield strength increased remarkably from 926 MPa for HfNbTaTiZr to 1258 MPa for CrHfNbTaTi,whereas a promising plastic strain of around 15.0%was retained in *** morphology and composition of the network-shaped interdendritic regions were closely related to the improved mechanical properties due to elemental *** were surrounded by an incompact interdendritic shell after Mo incorporation,which deteriorated yield strength and accelerated brittleness.

关键词： refractory high-entropy alloys phase structure microstructure yield strength plastic strain

Tricyclic Sesquiterpene from Laurencia Majuscula

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Chemical Research in Chinese Universities 1997年第2期13卷 84-86页

作者： XU Xiao Hua zeng long Mei SU Jing Yu Department of Chemistry Zhongshan UniversityGuangzhou510275

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关键词： Tricyclic sesquiterpene Laurencia majuscula Terpenoid Majusin

Synthesis of Hydroxylated Sterols(Ⅱ)——Synthesis of 24-Methylenecholest-4-en-3β,6α-diol

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Chemical Research in Chinese Universities 2000年第3期16卷 271-272页

作者： zeng long mei CUI Jian guo SU Jing yu Department of Chemistry Zhongshan UniversityGuangzhou 510275P.R.China Department of Chemistry Guangxi Teachers CollegeNaning 530001P.R.China

In a study on the soft coral, Alcyonuim patagonicum, a new hydroxylated sterol, 24-methylenecholest-4-en-3β,6α-diol exhibiting a potent activity to murine leukemia cells (IC50 = 1 μg/mL) was isolated and synthesized. The relationship between the chemical structure and the biological activity of the hydroxylated sterols, the synthesis of 24-methylenecholest-4-en-3β,6α-diol were presented. The melting point were determined on a X4 apparatus and were uncorrected. The infrared spectra were measured with a Nicolet 205 FT-IR and Nicolet FT-360 spectrophotometer. The H NMR spectra were recorded on a Varian Unity Inova 500 NB spectrometer in CDCl3 using tetramethylsilane (TMS) as the internal standard.

关键词： Synthesis Reduction 24-Methylenecholest-4-en-3u,6T-diol

Glucose Biosensor Based on Carbon/PVC-COOH/Ferrocene Composite with Covalently Immobilized Enzyme

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Chinese Chemical Letters 2005年第10期16卷 1357-1360页

作者： Chun Xiang LI Yun long zeng Chun Ran TANG Chemistry and Chemical Engineering College Hunan University of Science and Technology Xiangtan 411201

A carbon/PVC-COOH/ferrocene composite electrode used for the determination of glucose has been prepared. The ferrocene acted as mediator was incorporated into the PVC-COOH polymer and the leakage could be prevented. The presence of carboxyl groups on the electrode surface allowed immobilizing enzyme via EDC and NHS. The ratio of PVC-COOH to graphite powder （w/w） has been studied. Amperometric determination of glucose has been performed at potential of 0.30 V vs SCE. The response time was 〈 15 s. The linear response range was of 0.1-20 mmol/L with a detection limit of 48μmol/L.

关键词： PVC-COOH ferrocene glucose oxidase glucose.

Defect-induced Surface and Interface Reconstruction in Novel Two-dimensional Materials Revealed by Low Voltage Scanning Transmission Electron Microscopy

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Chinese Journal of Structural Chemistry 2020年第3期39卷 401-414,375页

作者： WANG Gang GUO zeng-long NIU Kang-Di LIN Jun-Hao Department of Physics Southern University of Science and TechnologyShenzhen 518055China

Two-dimensional(2 D) materials attracted substantial attention due to their extraordinary physical properties resulting from the unique atomic thickness. 2 D materials could be considered as material systems with flat surfaces at both sides, while the van der Waals gap is a natural out-of-plane interface between two monolayers. However, defects are inevitably presented and often cause significant surface and interface reconstruction, which modify the physical properties of the materials being investigated. In this review article, we reviewed the effort achieved in probing the defect structures and the reconstruction of surface and interface in novel 2 D materials through aberration corrected low voltage scanning transmission electron microscopy(LVSTEM). The LVSTEM technique enables us to unveil the intrinsic atomic structure of defects atom-by-atom, and even directly visualize the dynamical reconstruction process with single atom precision. The effort in understanding the defect structures and their contributions in the surface and interface reconstructions in 2 D materials shed light on the origin of their novel physical phenomenon, and also pave the way for defect engineering in future potential applications.

关键词： two-dimensional materials defects surface and interface reconstruction low voltage scanning transmission electron microscopy