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phase Behaviors of Multi-tailed B_(2)AB_(2)-Type Regio-isomeric Giant Surfactants at the Columnar-Spherical Boundary

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Chinese Journal of Chemistry 2021年第12期39卷 3261-3268页

作者： Yu Shao Di Han Xiaojin Yan Bo Hou Yiwen Li Jinlin He Qiang Fu Wen-Bin Zhang Beijing National Laboratory for Molecular Sciences Key Laboratory of Polymer Chemistry&Physics of Ministry of EducationCenter for Soft Matter Science and EngineeringCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China College of Polymer Science&Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengduSichuan 610065China College of Chemistry Chemical Engineering and Materials ScienceState and Local Joint Engineering Laboratory for Novel Functional Polymeric MaterialsJiangsu Key Laboratory of Advanced Functional Polymer Design and ApplicationSuzhou Key Laboratory of Macromolecular Design and Precision SynthesisSoochow UniversitySuzhouJiangsu 215123China

We report herein the precision synthesis and phase behaviors of multi-tailed B_(2)AB_(2)-type regio-isomeric giant surfactants consisting of a hydrophilic polyhedral oligomeric silsesquioxane(POSS)head tethered with four hydrophobic polystyrene(PS)tails.The synthesis was accomplished through two sequential"click"reactions to give a series of regio-isomeric giant surfactants S2DS2(where S is short for PS tails and D for hydroxyl-functionalized POSS)in para-,meta-,and ortho-configurations.Their phase structures and phase be-haviors at the columnar-spherical boundary were investigated with a single PS tail molecular weight of 1.4 kDa.Specifically,the para-and meta-isomers show hexagonally packed cylinders phases with slightly different order-disorder transition temperatures(~120℃ and~130℃)and the ortho-isomer exhibits an order-order transition from a kinetically favored,metastable dodecagonal quasi-crystal phase to a thermodynamically stable sigma phase at~120℃,as well as a further transition into the disordered state at~140℃.The phase diagram was constructed and their differences were rationalized based on the calculated interfacial area per molecule.This work demonstrates that tiny structural disparity could not only lead to unconventional phase formation in single-component macro-molecules,but also render dynamic and rich phase behaviors in these macromolecular assemblies.

关键词： Isomers Self-assembly Giant surfactants phase transitions Frank-Kasper phase

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Influence of sintering temperature on the structure and piezoelectric properties of ZnO-modified (Li, Na, K)NbO_(3) lead-free ceramics

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International Journal of Minerals,Metallurgy and Materials 2012年第9期19卷 843-848页

作者： Hai-tao Li Bo-ping Zhang Wei-gang Yang Nan Ma School of Materials Science and Engineering He'nan University of Science and Technology Luoyang 471003 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

ZnO-modified (Li, Na, K)NbO3 lead-free ceramics with a nominal composition of Li0.06(Na0.535K0.48)0.94NbO3+0.7mol% ZnO (LNKN-ZT) was synthesized normally at 930-1000℃. The Zn ions incorporated into the A-site at a higher sintering temperaVare, which changed LNKN-Z7 to soft piezoelectric ceramics with the mechanical quality factor decreasing from 228 to 192. A phase transition from tetragonal to orthorhombic symmetry was identified by XRD analysis, and the corresponding calculation of lattice parameters was conducted at 970-980℃. Because of such transitional behavior and fine microstructure, the optimized values of piezoelectric coefficient, planar electromechanical coupling coefficient, and relative dielectric constant were obtained.

关键词： piezocemmics niobates zinc oxide modification phase transitions piezoelectricity sintering

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Fluorocarbon and Hydrocarbon Benzodioxocycloalkane （C8-Cl0） End Groups： Effects on Mesomorphism

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Chinese Journal of Chemistry 2013年第7期31卷 933-938页

作者： Wanwan Cao Peilian Liu Hongren Chen Yaohang Zhu Rihao Chen Qifang Zhou Zhuo Zeng College of Chemistry & Environment South China Normal University Guangzhou Guangdong 510006 China Key Laboratory of Organofluorine Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032 China

A new class of benzodioxocycloalkane-based （C8-C10） liquid crystals were prepared. The impact of ring （C8- C10） as end group was investigated. The 8--9 membered ring derivatives, 3a--3b, exhibited the nematic phases （N） The mesomorphic behaviors were weakened with increasing the size of the ring. For the fluorinated medium ring （C8--C10） 3d--3f, it was found only the fluorinated ten membered ring 3f showed the LC phases behaviours. Modification of the ring size with different length alkyl groups and variation of the alkyl to polyfluoroalkyl markedly influenced the properties of these compounds.

关键词： fluorine heterocycles liquid crystals mesophases phase transitions

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In situ measured growth rates of bainite plates in an Fe-C-Mn-Si superbainitic steel

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International Journal of Minerals,Metallurgy and Materials 2014年第4期21卷 371-378页

作者： Zhang-wei Hu Guang Xu Hai-jiang Hu Li Wang Zheng-liang Xue Key Laboratory for Ferrous Metallurgy and Resources Utilization of the Ministry of Education Wuhan University of Science and Technology State Key Laboratory of Development and Application Technology of Automotive Steels (Baosteel Group)

The growth rates of bainite plates in an Fe-C-Mn-Si superbainitie steel were investigated by in situ observation. The lengthening rates of ferrite bainite during both cooling and isothermal holding processes were observed and the growth rates of bainite plates nucleating at grain boundaries, within grains and on preformed bainite were measured. It is indicated that the lengthening rates of bainite plates during the cooling and isothermal processes were different, and that the growth rates of bainite plates nucleating at different types of sites also demon- strated diversity. The bainite plates initiating at [vain boundaries during cooling grew the fastest, while the plates nucleating on preformed bainite did the slowest. However, the growth rate of the bainite plates nucleating at grain boundaries during isothermal transformation de- creased the most, whereas the bainite plates initiating within grains grew the fastest. In addition, the growth rate of ferrite bainite in the study supported the diffusion transformation mechanism of bainite from the viewooint of ~rowth rate.

关键词： bainitic steel bainite growth rate cooling isothermal treatment phase transitions

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Solidification microstructure formation in HK40 and HH40 alloys

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International Journal of Minerals,Metallurgy and Materials 2016年第4期23卷 442-448页

作者： Xian-fei Ding Dong-fang Liu Pei-liang Guo Yun-rong Zheng Qiang Feng National Center for Materials Service Safety University of Science and Technology Beijing Beijing Key Laboratory of Special Melting and Preparation of High-end Metal University of Science and Technology Beijing State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Melting and Casting Center Beijing Institute of Aeronautical Materials

The microstructure formation processes in HK40 and HH40 alloys were investigated through JmatP ro calculations and quenching performed during directional solidification. The phase transition routes of HK40 and HH40 alloys were determined as L → L ＋ γ→ L ＋ γ ＋ M_7C_3 →γ ＋ M_7C_3 →γ ＋ M_7C_3 ＋ M_（23）C_6→γ ＋ M_（23）C_6 and L → L ＋ δ→ L ＋ δ ＋ γ→ L ＋ δ ＋ γ ＋ M_（23）C_6→δ ＋ γ ＋ M_（23）C_6, respectively. The solidification mode was determined to be the austenitic mode（A mode） in HK40 alloy and the ferritic–austenitic solidification mode（FA mode） in HH40 alloy. In HK40 alloy, eutectic carbides directly precipitate in a liquid and coarsen during cooling. The primary γ dendrites grow at the 60° angle to each other. On the other hand, in HH40 alloy, residual δ forms because of the incomplete transformation from δ to γ. Cr_（23）C_6 carbide is produced in solid delta ferrite δ but not directly in liquid HH40 alloy. Because of carbide formation in the solid phase and no rapid growth of the dendrite in a non-preferential direction, HH40 alloy is more resistant to cast defect formation than HK40 alloy.

关键词： iron chromium nickel alloys solidification phase transitions carbides

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Anisotropic character of atoms in a two-dimensional Frenkel-Kontorova model

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Chinese Physics B 2011年第1期20卷 426-434页

作者：王苍龙段文山陈建敏石玉仁 College of Physics and Electronic Engineering Northwest Normal Universityand Laboratory of Atomic and Molecular Physics in Lanzhou Institute of Modern Physics Chinese Academy of Sciences State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of Sciences

The dynamics of a certain density of interacting atoms arranged on a two-dimensional square lattice, which is made to slide over a two-dimensional periodic substrate potential with also the quare lattice symmetry, in the presence of dissipation, by an externally applied driving force, is studied. By rotating the misfit angle θ, the dynamical behaviour displays two different tribological regimes： one is smooth, the other becomes intermittent. We comment both on the nature of the atomic dynamics in the locked-to-sliding transition, and on the dynamical states displayed during the atom motion at different values of the driving force. In tribological applications, we also investigate how the main model parameters such as the stiffness strength and the magnitude of the adhesive force affect the static friction of the system. In particular, our simulation indicates that the superlubricity will appear.

关键词： nanotribology Prenkel-Kontorova model phase transitions

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Stochastic systems with cross-correlated Gaussian white noises

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Chinese Physics B 2010年第11期19卷 510-515页

作者：王成玉高云宋玉敏周鹏杨海 Physics Department Yunnan Normal University Editorial Department Journal of Yunnan Normal University

This paper theoretically investigates three stochastic systems with cross-correlation Gaussian white noises. Both steady state properties of the stochastic nonlinear systems and the nonequflibrium transitions induced by the cross- correlated noises are studied. The stationary solutions of the Fokker-Planck equation for three specific examples are analysed. It is shown explicitly that the cross-correlation of white noises can induce nonequilibrium transitions.

关键词： phase transitions fluctuation phenomenon stochastic processes

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A Fresh Look at the Structures of Nylons and the Brill Transition

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Advanced Fiber Materials 2021年第4期3卷 203-209页

作者： Bernard Lotz Institut Charles Sadron CNRS and Universitéde Strasbourg23Rue du Loess67034 StrasbourgFrance

The common knowledge of the crystal structures of nylons dates back to the early 1950s with the work of Bunn and Garner.It describes the packing of sheets made of hydrogen-bonded stems in an extended chain conformation.These alpha phase structures have a specific powder X-ray diffraction pattern with reflections at 4.4Åand 3.7Å.On heating,reflections trans-form progressively and merge at≈4.2Åat the so-called“Brill transition”.Other diffraction patterns have been recorded for different types of nylons and thermal histories.These patterns were interpreted only as indicating the existence of“variants”of the alpha phase.However,neither their structure,nor the origin of the Brill transition were established.Recent structural analyses and molecular modeling approaches have provided new insights in these long-standing structural puzzles.The“variants”feature chain conformations that are“pleated”.The Brill transition does not involve the standard extended chains of the alpha phase but corresponds to a dynamic interconversion(≈10^(10)/s)between mirror conformations of these pleated stems.

关键词： Nylons Crystal structures phase transitions Brill transition

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Successive inverse and normal magnetocaloric effects in the Mn-vacancy compound Mn0.95Co0.75Cu0.25Ge

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Science China(Physics,Mechanics & Astronomy) 2020年第7期63卷 109-113页

作者： FengXia Liu Hu Zhang He Zhou DaoYong Cong RongJin Huang LiChen Wang Yi Long School of Materials Science and Engineering University of Sc ience and Technology of BeijingBejing 100083.China State Key Laboratory for Advanced Metals and Materials University of Science and Technology of BeijingBejing 100083China Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Ferromagnetic-structural transformation has been studied widely in MnCoGe-based materials. However, the magnetostructural transition(MST) from antiferromagnetic(AFM) orthorhombic phase to ferromagnetic(FM) hexagonal phase, which may lead to a large inverse magnetocaloric effect(MCE), has rarely been reported. Here, the introduction of Mn vacancy lowers the structural transition temperature while retains the AFM state in the orthorhombic phase, thus successfully realizing the AFM-FM MST in Mn0.95Co0.75Cu0.25Ge. Moreover, successive inverse and normal MCEs are observed around the first-order AFM-FM MST and the second-order FM-paramagnetic(PM) transition, respectively. A thermostat is proposed based on this special feature, which could release heat above the critical temperature while absorb heat below the critical temperature by simply applying the same magnetization/demagnetization cycles. This thermostat can be very useful in many applications where a constant temperature is required, such as cryostats and incubators.

关键词： magnetocaloric magnetically ordered materials phase transitions

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Carrier behavior of Hg Te under high pressure revealed by Hall effect measurement

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Chinese Physics B 2015年第11期24卷 363-366页

作者：胡廷静崔晓岩李雪飞王婧姝吕秀梅王棱升杨景海高春晓 Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education Jilin Normal University State Key Laboratory of Superhard Materials Jilin University

We investigate the carrier behavior of HgTe under high pressures up to 23 GPa using in situ Hall effect measurements. As the phase transitions from zinc blende to cinnabar, then to rock salt, and finally to Cmcm occur, all the parameters change discontinuously. The conductivity variation under compression is described by the carrier parameters. For the zinc blende phase, both the decrease of carrier concentration and the increase of mobility indicate the overlapped valence band and conduction band separates with pressure. Pressure causes an increase in the hole concentration of HgTe in the cinnabar phase, which leads to the carrier-type inversion and the lowest mobility at 5.6 GPa. In the phase transition process from zinc blende to rock salt, Te atoms are the major ones in atomic movements in the pressure regions of 1.0-1.5 GPa and 1.8-3.1 GPa, whereas Hg atoms are the major ones in the pressure regions of 1.5-1.8 GPa and 3.1-7.7 GPa. The polar optical scattering of the rock salt phase decreases with pressure.

关键词： electrical properties phase transitions transport properties scattering mechanism

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