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Investigation of the free volume and ionic conducting mechanism of poly(ethylene oxide)-LiClO_4 polymeric electrolyte by positron annihilating lifetime spectroscopy

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Chinese Physics B 2012年第10期21卷 478-484页

作者：龚静宫振丽闫晓丽高舒张忠良王波 School of Physics and Key Laboratory of Nuclear Solid State Physics Wuhan University

The positron annihilation lifetime and ionic conductivity are each measured as a function of organophilic rectorite（OREC） content and temperature in a range from 160 K to 300 K.According to the variation of ortho-positronium（o-Ps） lifetime with temperature,the glassy transition temperature is determined.The continuous maximum entropy lifetime（MELT） analysis clearly shows that the OREC and temperature have important effects on o-Ps lifetime and free volume distribution.The experimental results show that the temperature dependence of ionic conductivity obeys the Vogel-Tammann-Fulcher（VTF） and Williams-Landel-Ferry（WLF） equations,implying a free-volume transport mechanism.A linear least-squares procedure is used to evaluate the apparent activation energy related to the ionic transport in the VTF equation and several important parameters in the WLF equation.It is worthwhile to notice that a direct linear relationship between the ionic conductivity and free volume fraction is established using the WLF equation based on the free volume theory for nanocomposite electrolyte,which indicates that the segmental chain migration and ionic migration and diffusion could be explained by the free volume theory.

关键词： positron free volume polymeric electrolyte ionic conduction

A new model for electromigration grain boundary noise based on free volume

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Chinese Physics B 2010年第9期19卷 525-530页

作者：何亮杜磊庄奕琪陈华陈文豪李伟华孙鹏 School of Technical Physics Xidian University School of Microelectronics Xidian University

Grain boundary plays a key role in electromigration process of polycrystal interconnection. We take a free volume to represent a ＇vacancy-ion complex＇ as a function of grain boundary specific resistivity, and develop a new characterisation model for grain boundary noise. This model reveals the internal relation between the boundary scattering section and electromigration noise. Comparing the simulation result with our experimental result, we find the source as well as the form of noise change in the electromigration process. In order to describe the noise enhancement at grain boundary quantitatively, we propose a new parameter--grain boundary noise enhancement factor, which reflects that the grain boundary noise can characterise the electromigration damage sensitively.

关键词： free volume electromigration grain boundary noise

Comparison of the free volume of LiCl-Added SPPO Membrane and SPPO-PES Blend Membrane by Positron Annihilation Method

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Plasma Science and Technology 2007年第5期9卷 575-577页

作者： Htwe Htwe YIN 黄环唐世彪马庆力 Department of Modern Physics University of Science and Technology of ChinaHefei 230026China Center of Physical Experiment and Teaching School of ScienceUniversity of Science and Technology of ChinaHefei 230026China Electronics Department Electronic Engineering InstituteHefei 230038China

Positron annihilation lifetime spectroscopy （PALS） is a powerful technique for the study of free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size, while the intensity can be used to characterize the number of pores. Based on the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes of sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide）（SPPO） membranes with added LiCl and SPPO-PES （Polyethersulfone） blend were compared. free volume radii in both kinds of membranes are discussed.

关键词： positron annihilation free volume pore size SPPO polymer blend

Gas Permeability and free volume Hole Properties of Interpenetrating Polymer Network Studied by Positrons

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Wuhan University Journal of Natural Sciences 2007年第2期12卷 271-274页

作者： QI Ning GONG Wei WANG Zhifen WANG Bo YANG Yurun HU Chunpu School of Physics and Technology Wuhan University Wuhan 430072 Hubei China Institute of Material Science and Engineering East China University of Science and Technology Shanghai 200237 China

A series of polyurethane/epoxy resin interpenetrating polymer networks （PU/ER IPN） were studied by positron annihilation lifetime spectroscopy （PALS）. The effects of epoxy resin type and content on the free volume properties in IPN were investigated. We found that in PU/ER IPN, the free volume hole size and fractional free volume showed a negative deviation due to closer segmental chain packing through some chemical bonding between PU and epoxy resin. Direct relationship between the gas permeability and the free volume has been established based on the free volume theory. Experimental results revealed that the free volume plays an important role in determining the gas diffusion and permeability.

关键词： interpenetrating polymer network positron annihilation free volume gas permeability

On the Structure and free volume Properties of Poly（3-hydroxybutyrate-co-3-hydroxyvalerate） Membranes via Various Crystallization Conditions

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On the Structure and Free Volume Properties of Poly（3-hydro...

Resolving aging dynamics of a 3D colloidal glass

2009年全国高分子学术论文报告会

作者：程美玲孫一明 Department of Chemical Engineering and Materials Science Yuan Ze University

＜正＞The crystalline structure and the free volume properties within the amorphous phase of poly（3-hydroxybutyrate-co-3-hydroxyvalerate）（PHBV） membranes depend on the preparation conditions.The difference of free volume properties among various PHBV membranes was created according to the crystalline structure of the polymer from different thermal history.free volume properties in the amorphous region of a series of PHBV membranes,which were prepared by cold-and melt-crystallization processes,were investigated using

关键词： positron annihilation lifetime free volume crystallization temperature rigid amorphous fraction long period

来源： cnki会议评论

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Science China(Physics,Mechanics & Astronomy) 2024年第3期67卷 110-118页

作者： XiaoJuan Wang Jun Duan Gan Ding YunZhuo Lu Xing Lu LanHong Dai MinQiang Jiang State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Materials Science and Engineering Dalian Jiaotong UniversityDalian 116028China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Physical aging is an inherent property of glassy matter, but understanding its microscopic mechanism remains a challenge particularly at the particle level. In this work, we use a confocal microscope to in-situ trace the particle trajectories in a 3D colloidal glass for 73000 s, aiming at resolving the aging dynamics. By calculating the mean square displacement of particle motions, we find that the glass aging with time can be divided into three stages: β relaxation, α relaxation and free diffusion. The system's mean square displacement at each aging state is quantitatively resolved into three contributions of particle dynamics modes: vibration within the nearest-neighbor cages, hopping between cages and cooperative rearrangement. We further calculate the particle's free volume and find that the β-to-α transition is accompanied by the temporary increase of the system-averaged free volume due to pronounced hops of particles. Nevertheless, the temporal autocorrelation of the free volume spatial distribution still obeys a monotonically stretched exponential decay with an exponent of 0.76, which is related to the sub-diffusion dynamics of cooperative rearrangements and hops mixed in α relaxation. According to the resolved vibrational displacements,we calculate the vibrational density of states of this 3D glass, and the characteristic boson peak is reproduced at low frequencies.Our findings shed insight into the particle-level aging dynamics of a real glass under purely thermal activation.

关键词： colloidal glass physical aging particle dynamics free volume boson peak

Modification strategies for non-aqueous, highly proton-conductive benzimidazole-based high-temperature proton exchange membranes

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Chinese Chemical Letters 2024年第4期35卷 43-51页

作者： Yunfa Dong Shijie Zhong Yuhui He Zhezhi Liu Shengyu Zhou Qun Li Yashuai Pang Haodong Xie Yuanpeng Ji Yuanpeng Liu Jiecai Han Weidong He National Key Laboratory of Science and Technology on Advanced Composites in Special Environments and Center for Composite Materials and StructuresHarbin Institute of TechnologyHarbin 150080China School of Petroleum Engineering Chongqing University of Science and TechnologyChongqing 401331China School of Physics University of Electronic Science and Technology of ChinaChengdu 610054China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin 150001China Chongqing Research Institute Harbin Institute of TechnologyChongqing 401151China School of Mechanical Engineering Chengdu UniversityChengdu 610106China

High-temperature proton exchange membranes(HT-PEMs) possess excellent thermal and outstanding electrochemical stability, providing an avenue to realize high-temperature proton exchange membranes fuel cells(HT-PEMFCs) with both superior power density and long-term durability. Unfortunately, polybenzimidazole(PBI), a typical material for conventional HT-PEMs, fails to compromise the high nonaqueous proton conductivity and high mechanical properties, thus hindering their practical applications.Achieving efficient nonaqueous proton conduction is crucial for HT-PEMFC, and many insightful research works have been done in this area. However, there still lacks a report that integrates the host-guest interactions of phosphoric acid doping and the structural stability of polymers to systematically illustrate modification strategies. Here, we summarize recent advancements in enhancing the nonaqueous proton conduction of HT-PEMs. Various polymer structure modification strategies, including main chain and side group modification, cross-linking, blocking, and branching, are reviewed. Composite approaches of polymer, including compounding with organic porous polymers, filling the inorganic components and modifying with ionic liquids, etc., are also covered in this work. These strategies endow the HT-PEMs with more free volume, nanophase-separated structure, and multi-stage proton transfer channels, which can facilitate the proton transportation and improve their performance. Finally, current challenges and future directions for further enhancements are also outlined.

关键词： Benzimidazole Nonaqueous proton conduction free volume Nanophase-separated structure Structure modification

A Thermodynamic Perspective on Polymer Glass Formation

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Chinese Journal of Polymer Science 2023年第9期41卷 1329-1341,I0004页

作者： Wen-Sheng Xu Zhao-Yan Sun State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China

The dynamics of polymeric and other glass-forming liquids dramatically slows down upon cooling toward the glass transition temperature without any obvious significant change in their static structure.A quantitative understanding of this extraordinary dynamic slowdown remains one of the most significant challenges in condensed matter physics.Historically,extensive efforts have been devoted to explaining the dynamics of glass-forming liquids in terms of thermodynamic properties,leading to a number of semi-empirical models emphasizing distinct thermodynamic properties.Here,a thermodynamic perspective is provided on the glass formation of polymeric and other materials.We begin with an overview of the thermodynamic models of glass formation,including the intuitively appealing“free volume”models,enthalpy models originally emphasized by Goldstein and later by others,and the highly influential configurational entropy-based models.The review of these models is followed by a discussion of the advances that attempt to bring together some of the seemingly disparate thermodynamic viewpoints on glass formation by revealing a close interrelation between thermodynamic properties.We conclude this review with remarks on several key topics in this field,along with our viewpoint for future work.

关键词： Glass formation Entropy free volume Enthalpy

Effective Energy Density of Glass Rejuvenation

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Acta Mechanica Solida Sinica 2022年第5期35卷 746-754页

作者： Gan Ding Feng Jiang Lanhong Dai Minqiang Jiang State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Science University of Chinese Academy of SciencesBeijing100049China

Glasses with rejuvenated structures usually exhibit improved room-temperature plasticity,which facilitates their applications.However,glass rejuvenation requires external energy injection to“shake up”the frozen-in disordered structure.In this work,we give the answer to how much the required energy is.According to the constitutive model of amorphous plasticity,we find that the applied stress higher than the steady-state flow value can effectively induce the structural disordering in terms of the generation of free volume.Therefore,the effective energy density(EED)of structural rejuvenation is defined as the integral of this effective stress on the corresponding strain.By tailoring the applied strain,strain rate,temperature and initial free volume,different degrees of structural rejuvenation are achieved,which show a generally linear correlation with the defined EED.This work deepens the understanding of glass rejuvenation from an energy perspective.

关键词： Glass Structural rejuvenation Effective energy density Shear transformations free volume