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​Magnetoresistive Nanocomposites for Electrochemical Energy Storage;Individual molecular motion in the flow of entangled polymeric liquids;

发布时间:2017年11月13日 15:44    作者:    来源:     点击率:次

学术讲座一:Magnetoresistive Nanocomposites for Electrochemical Energy Storage;报告人:郭占虎;时间:2017年11月15日上午8:00;地点:11205H;

报告人介绍:

    郭占虎 (男,博士生导师)是美国田纳西州大学化学和生物分子工程系副教授,1996年本科毕业于山东科技大学化学工程专业;1999年硕士毕业于北京化工大学化学工程专业;1999-2000在北京化工研究院任工程师设计。2000-2005年博士毕业于美国路易斯安那州立大学化学工程专业;2005-2008年在加利福尼亚大学洛杉矶分校机械和航空航天工程系博士后。2008年-2014年在美国德克萨斯州拉马尔大学任助理教授,2015年至今在美国田纳西州大学诺克斯维尔分校任副教授。上海高校东方学者特聘教授,2016年四川千人和2017山西百人。已在Chemical Society Reviews,Advanced Materials,Advanced Functional Materials, Angewandte Chemie, Energy & Environmental Science,Journal of Materials Chemistry,等国外SCI主流期刊杂志发表研究论文350余篇, SCI他引12000余次,h-index为63 (google scholar)。有些文章被刊物封面和新闻媒体重点突出报道,并有多项美国专利。同时是Advanced Composites and Hybrid Materials期刊主编及多家SCI杂志的特约审稿人,承担多项美国国家科学基金项目,与其它国内高校合作申请多项国际合作项目。研究领域涉及:多功能纳米复合材料,高级纳米复合膜,提高燃油效率和提高能源使用效率,变色及应变传感和磁场传感装置,电磁波屏蔽材料,环境可持续性和补救,污染物处理和回收,工业/民用安全材料及阻燃材料等。

报告内容简介:

Electrochemical capacitors (ECs) have been in urgent demand for utilizing sustainable and renewable energy sources due to the concerns over both the depletion of fossil fuels and climate changes. However, the current ECs have some challenges, for example, high power but low energy densities for electric double layer capacitors or high energy but low power densities for pseudocapacitors. Main efforts have been focused on developing new electrode materials (for example, highly conductive composites with high capacitance), or designing hierarchical nanomaterials (for example, microstructures with shortened low-resistive pathways for electron transport and ion diffusion). Recently, a small magnetic field of about 0.072 T was reported to significantly enhance the capacitance by 155% in a novel magnetic graphene nanocomposite electrode. However, the measured positive giant magnetoresistance (GMR, a large resistance change upon applying a magnetic field) of the electrode materials failed to interpret the capacitance enhancement. Therefore, how the magnetic field affects the electrochemical energy storage remains unclear. In this talk, the lab-made conductive polymer based- nanocomposites have been designed and synthesized to disclose this puzzle.

学术讲座二:Individual molecular motion in the flow of entangled polymeric liquids;报告人:Brian J. Edwards;时间:2017年11月15日上午9:00;地点:11205H;

报告人介绍:

    Brian Edwards received a B.S. degree in chemical engineering from the University of Illinois in 1986, and a Ph.D. in chemical engineering from the University of Delaware in 1991. He joined the faculty of the Chemical and Biomolecular Engineering Department at the University of Tennessee-Knoxville as an associate professor in 2001. He was promoted to the rank of professor in 2009, and has served as the associate department head since 2006. His areas of expertise lie in the theoretical modeling and atomistic simulation of polymeric fluids, and has also recently worked on modeling self-assembly and transport in nanoporous membranes and applications of graphenic materials. In 2015, he cofounded Celtig LLC, an international producer of graphene, and currently serves as the company’s CEO. He is the co-author of the textbook Thermodynamics of Flowing Systemsand has published over 100 papers in journals and delivered approximately 200 technical presentations on these topics.

报告内容简介:

Dense liquids of entangled polymer macromolecules are processed into a wide range of high-tech and low-tech consumer products, such as plastic bottles, artificial joints, purification membranes, proton exchange membranes, automobile components, and an almost infinite number more. The plastics industry comprises about $100,000,000 in global sales per year, comprising one of the top 10 most important industries in the world economy. In order to drive efficiencies in this market, understanding the flow properties of dense liquids of entangled polymer macromolecules provides critical information to aid the processing of materials with improved mechanical and physiochemical properties.

The dynamics of individual molecule that comprise a dense entangled liquid have been shown to influence significantly the bulk rheological and microstructural properties of the liquid undergoing high strain-rate flows. The objective of this work was to study these individual molecular dynamics using Nonequilibrium Molecular Dynamics simulations of a polyethylene liquid using the well-established potential model of Siepmannet al.for a wide range of flow strength under steady shear flow. It was found that the polyethylene liquid displays multiple timescales associated with not only the decorrelation of the end-to-end vector (commonly related to the Rouse time or disengagement time, depending on the entanglement density of the liquid), but also ones associated with the retraction and rotation cycles of the individual molecules. Brownian Dynamics (BD) simulations were also performed on an analogous free-draining bead-rod chain model to compare the rotation and retraction dynamics of a single chain in dilute solution with individual molecular motions in the dense liquid. These BD simulations revealed that the dynamics of the free-draining chain are qualitatively and quantitatively similar to those of the individual chains comprising the entangled polyethylene melt at strain rates beyond the linear viscoelastic regime, implying a possible breakdown of reptation theory in the high shear limit. An examination of the bulk-average properties revealed the effects of the chain rotation and retraction cycles upon commonly modeled microstructural properties, such as the distribution function of the chain end-to-end vector and the entanglement number density. These findings allow for the development of new models to quantify the dynamics of dense polymeric liquids under flow, which will ultimately enable better end-products to be developed using more economical methods.