石墨烯被动锁模光纤激光器的研究进展_宋浩青
以二维材料构筑纳米片膜研究进展
Material Sciences 材料科学, 2018, 8(6), 736-741Published Online June 2018 in Hans. /journal/mshttps:///10.12677/ms.2018.86087Progress in Fabrication of NanosheetMembranes with Two-DimensionalMaterialsLukang Zheng, Zhihui Zhou, Yunqin Wu, Qi Chen, Huiling Tang, Haoyi Zhang, Qiang Xiao* Institute of Advanced Fluorine-Containing Materials, Zhejiang Normal University, Jinhua ZhejiangReceived: May 14th, 2018; accepted: May 28th, 2018; published: Jun. 14th, 2018AbstractTwo-dimensional materials, as a new type of materials, exhibit superior advantages in the fabrica-tion of membrane materials due to their high aspect ratio and specific surface areas. In recent years, some two-dimensional materials such as graphene nanosheets, MOF and COF nanosheets have been widely used in the preparation of nanosheets membrane as basic structural units. In this paper, two-dimensional nanosheet materials for preparing nanosheet membranes are intro-duced, with emphasis on two-dimensional zeolite nanosheet materials. Zeolite molecular sieve has wide application prospect in separation membrane field because of its microporous, high temperature resistant, swelling resistant and molecular sieve grading characteristics.KeywordsTwo-Dimensional Nanosheets, Separation Property, MFI Nanosheet以二维材料构筑纳米片膜研究进展郑璐康，周智慧，吴云琴，陈琦，汤会玲，张豪益，肖强*浙江师范大学含氟新材料研究所，浙江金华收稿日期：2018年5月14日；录用日期：2018年5月28日；发布日期：2018年6月14日摘要二维材料作为一类新兴材料，具有较高的面厚比和比表面积，在构筑膜材料方面具有天然优势。
石墨烯超导热管散热性能实验研究
石墨烯超导热管散热性能实验研究
刘泽珙
【期刊名称】《化工机械》
【年(卷),期】2024(51)2
【摘要】为优化室内地暖的散热效果,应用石墨烯超导冷暖技术,设计石墨烯超导热管,并通过实验研究石墨烯超导热管散热性能。
选取石墨烯超导热管、铝极干式热管和传统湿式热管,构建热管实验装置,分别对3种热管的散热性能进行测试,并将测试结果通过数据处理与误差分析方法进行处理。
经实验可知:传统湿式热管在热管启动时启动温度上升速度最慢,且在不同充液率下始终保持较低的导热系数、较高的热阻,说明该热管的散热性能较弱;而铝极干式热管在测试时虽然具备一定的散热能力,但依然弱于石墨烯超导热管;在石墨烯超导热管测试过程中,其在不同启动温度下均能迅速达到相应温度,且总热阻较低、导热系数较高,可迅速实现散热。
当导管的充液率较高时,热管的冷凝段和蒸发段的温差较低,具有较好的散热效果,且石墨烯超导材料还能够提高热管强化作用率,使热管散热效果更强。
【总页数】7页(P201-206)
【作者】刘泽珙
【作者单位】清华大学社科院人类命运共同体研究中心
【正文语种】中文
【中图分类】TK79
【相关文献】
1.石墨烯复合材料对功率器件散热性能影响的仿真与实验研究
2.石墨烯纳米片-水纳米流体重力热管的传热性能实验研究
3.基于石墨烯涂层的热管散热器散热性能研究
4.氧化石墨烯-水重力热管传热性能实验研究
5.氧化石墨烯脉动热管传热性能实验研究
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石墨烯纤维：制备、性能与应用
物 理 化 学 学 报Acta Phys. -Chim. Sin. 2022, 38 (2), 2007093 (1 of 18)Received: July 31, 2020; Revised: August 24, 2020; Accepted: August 24, 2020; Published online: August 27, 2020.*Correspondingauthor.Email:*************.cn;Tel.:+86-10-62758600.The project was supported by the National Key Basic Research Program of China (2016YFA0200103), the National Natural Science Foundation of China(51432002, 51290272, 51672153, 21975141, 51972184), the Beijing National Laboratory for Molecular Sciences (BNLMS-CXTD-202001) and the ChinaPostdoctoral Science Foundation (2019M660322).国家重点基础研究发展规划项目(973) (2016YFA0200103), 国家自然科学基金(51432002, 51290272, 51672153, 21975141, 51972184), 北京分子科学国家研究中心(BNLMS-CXTD-202001)及中国博士后科学基金(2019M660322)资助 © Editorial office of Acta Physico-Chimica Sinica[Review] doi: 10.3866/PKU.WHXB202007093 Graphene Fibers: Preparation, Properties, and ApplicationsMuqiang Jian 1,2, Yingying Zhang 3, Zhongfan Liu 1,2,*1 Center of Nano Chemistry, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.2 Beijing Graphene Institute (BGI), Beijing 100095, China.3 Key Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education, Department of Chemistry,Tsinghua University, Beijing 100084, China.Abstract: Graphene fiber is a macroscopic carbonaceous fiber composed ofmicroscopic graphene sheets, and has attracted extensive attention. Graphenebuilding blocks form a highly ordered structure, resulting in fibers with the sameproperties as graphene, such as superior mechanical and electrical performance, lowweight, excellent flexibility, and ease of functionalization. Moreover, graphene fibers arecompatible with traditional textile technologies, facilitating the development of wearableelectronics, flexible energy devices, and smart textiles. Graphene fibers were firstprepared in 2011 by wet spinning of graphene oxide (GO) solution, which wasdispersed in water. Various fabrication methods have been developed to assemblegraphene sheets into fibers since then and different strategies have been proposed tooptimize their structure and performance. Graphene fibers have applications innumerous fields, including conductors, sensors, actuators, smart textiles, and flexible energy devices. This review aims to provide a comprehensive picture of the preparation approaches, properties, and applications of graphene fibers. Firstly, the preparation processes, unique structures, and properties of three typical carbonaceous fibers—carbon fibers, carbon nanotube (CNT) fibers, and graphene fibers—are compared. It can be seen that graphene fibers possess the unique structures, such as the large grain sizes and highly aligned structure, endowing them with the outstanding properties. Then a variety of fabrication techniques have been summarized, including wet spinning, dry spinning, dry-jet wet spinning, space-confined hydrothermal assembly, film conversion approach, and template-assisted chemical vapor deposition (CVD). Wet spinning is a common method to fabricate high-performance graphene fibers and is promising for the large-scale production of graphene fibers. Besides, various strategies for improving the mechanical, electrical, and thermal properties of graphene fibers are introduced in detail, including well-chosen graphene building blocks, optimized fabrication processes, and high-temperature treatments. Although the electrical and thermal transport properties of typical graphene fibers are better than those of carbon fibers, the strength and modulus of graphene fibers are inferior. Therefore, the enhancement of the mechanical properties of graphene fibers by optimizing the composition of precursors, controlling and adjusting the assembly processes, and exploring feasible post-treatment procedures are essential. Meanwhile, the review outlines the applications of graphene fibers in high-performance conductors, functional fabrics, flexible sensors, actuators, fiber-shaped supercapacitors and batteries. Finally, the persisting challenges and the future scope of graphene fibers are discussed. We believe that graphene fibers will become a new structural and functional material that can be applied in numerous fields in the future, aided by the continuous development of materials and techniques.Key Words: Graphenefiber; Preparation; Spinning; Property; Application. All Rights Reserved.石墨烯纤维：制备、性能与应用蹇木强1,2，张莹莹3，刘忠范1,2,*1北京大学化学与分子工程学院，北京分子科学国家研究中心，北京大学纳米化学研究中心，北京 1008712北京石墨烯研究院，北京 1000953清华大学化学系，有机光电子与分子工程教育部重点实验室，北京 100084摘要：石墨烯纤维是一种由石墨烯片层紧密有序排列而成的一维宏观组装材料。
石墨烯表面等离激元特性研究
学位论文作者签名： 签字日期： 年 月 日
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目 录
摘 要 ........................................................................................................................ 1 ABSTRACT ............................................................................................................ 3 第一章 引言 ......................................................................................................... 5
第三章
石墨烯表面等离激元特性研究 ................................................ 39
3.1 FDTD 研究方法及仿真软件介绍 .................................................................... 39 3.1.1 FDTD 研究方法........................................................................................ 39 3.1.2 FDTD Solutions 仿真软件简介............................................................ 40 3.2 石墨烯表面等离激元的产生 ........................................................................... 40 3.2.1 石墨烯的介质特性.................................................................................... 40 3.2.2 多层石墨烯表面等离激元的 Kretschmann 模型仿真和分析............... 44 3.2.3 单层石墨烯的表面等离激元研究........................................................... 51 3.2.2.1 自由空间内的单层石墨烯的表面等离激元 .................................... 51 3.2.2.2 基底上的单层石墨烯的表面等离激元 ............................................ 55 3.2.2.3 自由空间内的单层石墨烯条带阵列的表面等离激元 .................... 60 3.2.2.4 基底上的单层石墨烯条带阵列的表面等离激元 ............................ 62 本章小结 .................................................................................................................. 64
基于分子动力学的氧化石墨烯对PVA纤维-CSH界面影响机理研究
第42卷第11期2023年11月硅㊀酸㊀盐㊀通㊀报BULLETIN OF THE CHINESE CERAMIC SOCIETY Vol.42㊀No.11November,2023基于分子动力学的氧化石墨烯对PVA 纤维-CSH界面影响机理研究臧㊀芸,王㊀攀,王慕涵,王鑫鹏,侯东帅,赵铁军(青岛理工大学土木工程学院,青岛㊀266520)摘要:纤维增强混凝土的宏观力学性能与纤维/基体的界面结合密切相关㊂本文通过分子动力学模拟,研究氧化石墨烯(GO)对聚乙烯醇纤维(PVA)/基体界面结合的影响㊂结果表明,当GO 与PVA 纤维以共价键连接时,PVA 纤维从混凝土中被拉出所需的拉力最大,GO 的存在能提升纤维与基体的界面黏结性能㊂混凝土基体与GO 主要以钙氧键和氢键连接,其中钙氧键数量多且化学键强度高㊂但GO 与PVA 纤维物理连接时,GO 与PVA 纤维仅依靠强度较弱的氢键连接,对界面的黏结性能带来负面作用㊂此外,GO 受到更多离子键和氢键的束缚,原子平移运动减少,与基体的界面黏结性能提高㊂关键词:氧化石墨烯;PVA 纤维;混凝土;界面;分子动力学中图分类号:TU528㊀㊀文献标志码:A ㊀㊀文章编号:1001-1625(2023)11-3799-08Influence Mechanism of Graphite Oxide on PVA Fiber-CSH Interface Based on Molecular DynamicsZANG Yun ,WANG Pan ,WANG Muhan ,WANG Xinpeng ,HOU Dongshuai ,ZHAO Tiejun (Department of Civil Engineering,Qingdao University of Technology,Qingdao 266520,China)Abstract :The macroscopic mechanical properties of fiber reinforced concrete are closely related to the interfacial bonding of fiber /matrix.In this paper,the effect of graphene oxide (GO)on the interfacial bonding of polyvinyl alcohol fiber (PVA)/matrix was studied by molecular dynamics simulation.The results show that when GO and PVA fiber are connected by covalent bond,the tensile force required for PVA fiber to be pulled out from concrete is the largest,and the presence of GO can improve the interfacial bonding performance between fiber and matrix.The concrete matrix and GO are mainly connected by calcium-oxygen bonds and hydrogen bonds,in which the number of calcium-oxygen bonds is large and the strength of chemical bonds is high.However,when GO and PVA fiber are physically connected,GO and PVA fiber are only connected by weak hydrogen bonds,which has a negative effect on the bonding performance of interface.In addition,GO is bound by more ionic bonds and hydrogen bonds,the atomic translational motion is reduced,and the interfacial bonding performance with matrix is improved.Key words :graphene oxide;PVA fiber;concrete;interface;molecular dynamics 收稿日期:2023-06-01;修订日期:2023-08-12基金项目:国家自然科学基金(U2006224,51978352,51908308)作者简介:臧㊀芸(1986 ),女,博士研究生㊂主要从事土木工程材料方面的研究㊂E-mail:zangyun001@通信作者:侯东帅,博士,教授㊂E-mail:dshou@ 0㊀引㊀言水泥基材料是应用最广泛的建筑材料之一,然而它存在脆性大㊁韧性差㊁易发生突然破坏和耐久性差等缺点㊂添加纤维是提高水泥基材料抗拉强度和韧性的常用方法[1],纤维的主要作用是在断裂区起到桥接作用㊂聚乙烯醇(polyvinyl alcohol,PVA)纤维因其优异的耐碱性能㊁高强度和高弹性而备受关注,已被广泛应用于应变硬化水泥基材料(strain hardening cementitious composites)的制造[2]㊂然而,PVA 纤维尚未被证明可以防止微裂纹的形成或细化孔隙结构,它不能显著提高水泥基材料的耐久性㊂随着纳米技术的兴起,将纳米3800㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷材料(如碳纳米管(carbon nanotubes,CNTs)[3-5]㊁石墨烯和氧化石墨烯(graphene oxide,GO)[6-8])应用于水泥基材料来提高性能已成为近年来新的研究热点㊂与疏水碳纳米管和石墨烯不同,氧化石墨烯引入了含氧基团,如羟基㊁羰基和羧基,是一种优秀的亲水材料[9-10]㊂研究表明,氧化石墨烯的加入可以提高混凝土的抗压抗折强度[11]和耐久性[12-14]㊂因此,利用PVA纤维和氧化石墨烯的协同效应,有望大幅提高水泥基材料的综合性能㊂李相国等[15]研究证明GO复掺PVA纤维可以显著改善水泥基材料孔结构,降低孔隙率,提高水泥基材料抗氯离子渗透性能并降低水泥基材料收缩率㊂Jiang等[16]研究发现在水泥基材料中添加氧化石墨烯可以起到细化孔隙结构的作用,同时提高水化产物在PVA纤维上的黏附性,有利于PVA纤维与水泥基体的结合㊂氧化石墨烯与PVA纤维耦合改性的水泥基材料表现出优异的力学强度和耐久性㊂Yao等[17]利用氧化石墨烯对PVA纤维表面改性,使其化学键能提高80倍以上,混凝土试样抗拉强度提高35.6%㊂然而,GO的存在打破了原有的界面结构,纤维与基体之间的界面变成纤维与GO之间的界面和GO与基体间的界面,界面中化学键的键合也发生了改变㊂在纤维增强水泥基复合材料中,纤维和基体分担载荷,应力通过纤维和基体间的界面传递㊂因此,界面的组成和性能是决定纤维增强水泥基复合材料性能的关键㊂Wang等[18]通过分子动力学分析发现,PVA纤维中的羟基与水化产物中的钙离子可以形成稳定的离子键,因此PVA纤维与水化产物有较好的黏结力㊂GO对界面的影响尚不清晰,而这将直接影响纤维增强水泥基材料的性能㊂本文先通过拉拔模拟计算纤维从界面中拉出所需要的拉拔力,借助力学响应描述界面黏附行为㊂通过静态结构和动态结构分析,探究GO对PVA/CSH界面黏结性能的影响机理㊂本研究有助于指导GO和PVA 在水泥基复合材料中发挥最佳的协同作用㊂1㊀模拟方法1.1㊀模型建立依据Pellenq等[19]和Manzano等[20]提出的方法,基于托贝莫来石(11Å)结构构建了Ca/Si比值为1.7的水化硅酸钙(CSH)模型㊂选取无水托贝莫来石(11Å)层状结构作为建模的初始构型㊂根据硅链的Q n分布结果,随机删除桥接的SiO2和二聚体结构(Si2O4),得到复合硅链的钙硅骨架和层状结构㊂再通过巨正则蒙特卡洛法(GCMC)模拟水分子逐渐吸附在钙硅骨架孔隙上直至饱和这一过程㊂根据液态水在室温下的性质,设定化学势为0,温度为300K,成功建立CSH初始模型,如图1(a)所示㊂根据Allington等[21]提出的方法构建氧化石墨烯模型㊂将石墨烯的单位单元(x=4.62Å,y=3.69Å,z=3.40Å,α=β=γ=90ʎ)在x和y 方向分别扩大,再将环氧( O )㊁羟基( OH)和羧基( COOH)三个官能团修饰到石墨烯上㊂其中 O 和 OH基团分布在石墨烯表面, COOH基团分布在石墨烯边缘,如图1(b)所示㊂氧化石墨烯薄片的化学成分为C10O1(OH)1(COOH)0.5,符合氧化石墨烯典型官能团覆盖率,即含氧量为20%~30%[22]㊂PVA纤维模型如图1(c)所示,每个PVA纤维链具有50个碳原子㊂参照文献[23]结果,本文建立了两种GO/PVA模型:第一种PVA模型如图1(d)所示,GO物理附着在PVA表面,无共价键连接;第二种PVA模型如图1(e)所示,GO与PVA纤维通过脱水缩聚,形成酯基 COO ,使GO与PVA纤维以共价键形式连接㊂因模型中含有多种氧原子和氢原子,为了方便后面的分析将其进行区分㊂O s表示CSH中硅氧四面体中的非桥接氧原子,O hs表示CSH的羟基氧原子,O hp表示PVA纤维中的氧原子,O o表示GO片中C O C中的氧原子, O hg表示GO片中 OH中的氧原子㊂此外, COOH中有两种位置的氧原子,O 表示以双键连接碳的氧原子,O hg表示以单键连接碳的氧原子㊂H op表示PVA纤维中的羟基氢原子,H og表示GO片中含氧官能团中的氢原子㊂从所建立的CSH分子模型层间处切开,并向外平移以预留足够空间插入GO和PVA纤维,并在y方向预留足够的空间保证纤维可以拉出㊂将PVA纤维插入CSH形成的纤维界面定义为界面CP,如图1(f)所示㊂将PVA/GO(物理附着)插入CSH,纤维与GO形成的界面定义为界面CGP1,如图1(g)所示㊂将PVA-GO(形成共价键)插入CSH,纤维与GO成为一体后与CSH形成的界面定义为界面CGP2,如图1(h)所示㊂三个模拟盒子尺寸大小一致,均为x=44.10Å,y=160.70Å,z=67.47Å,α=β=γ=90ʎ㊂㊀第11期臧㊀芸等:基于分子动力学的氧化石墨烯对PVA纤维-CSH界面影响机理研究3801图1㊀氧化石墨烯㊁PVA纤维㊁CSH的结构及连接方式Fig.1㊀Structures and connection modes of graphene oxide,PVA fiber and CSH1.2㊀力㊀场力场的选择对模拟的准确性十分关键,CSH基底采用CLAYFF力场,此力场已被成功用于黏土㊁水泥水化产物㊁多组分矿物体系的模拟[24-25]㊂PVA纤维采用CVFF力场,CVFF已被广泛应用于有机物建模[26-27]㊂CLAYFF与CVFF联合力场已证明适用于模拟胶凝材料与聚合物㊁有机物之间的界面特性[28]㊂此联合力场3802㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷采用Lorentz-Berthelot 混合规则[29]㊂1.3㊀模拟过程模拟过程分为预平衡阶段㊁平衡阶段和拉拔阶段㊂所有模拟均采用大尺度原子/分子大规模并行模拟器(LAMMPS)平台进行计算㊂所有原子在NPT 系统中弛豫1000ps,时间步长设置为1fs,温度为300K㊂平衡后再运行1000ps,此阶段保持系统与环境变量均不变,每1ps 记录一次轨迹数据,收集到1000帧原子轨迹,用于平衡状态下界面结构和动力学行为分析㊂此后,在NVT 系综下对已经平衡的模型进行拉拔模拟,每根纤维链最右侧的碳原子作为外力的位置[30],时间步长设置为1fs㊂外力和界面能每100s 记录一次㊂拉拔力计算如式(1)所示㊂F =K [(x 0+vt )-x com ](1)式中:F 为拉拔力,x 0为所选碳原子在纤维y 方向上的初始质心,K 为弹簧常数,v 为拉力的速度,t 为模拟时间,x com 为所选碳原子质心沿y 方向的动态位置㊂2㊀结果与讨论2.1㊀拉拔过程图2㊀三个界面的拉力-时间关系Fig.2㊀Pull-out force-time relations of three interfaces 通过拉拔模拟计算得到拉拔力-时间曲线,如图2所示㊂在没有GO 的情况下纤维与CSH 形成界面CP㊂加入GO 后,纤维与GO 形成了新的界面CP1㊂从图2中可以清楚地看到,PVA 纤维从CSH 中被拉出所需要的拉力明显高于PVA /GO 从CSH 中被拉出所需要的拉力,这说明PVA /CSH 的界面黏结力优于PVA /GO界面的黏结力㊂此外,三个界面的拉拔力均波动较大,呈锯齿形逐渐减小㊂在模拟初期,拉拔力逐渐增大,主要原因是化学键的伸长㊂当化学键被过度拉伸直至断裂,拉力会突然下降,在松弛阶段又形成新的化学键,导致拉力再次增大,因此拉拔力呈波动状态㊂随着纤维拉出长度增加,界面处化学键减少,拉拔力逐渐减小㊂由此得出,纤维的拔出过程伴随化学键的断裂和重组㊂图3为拉拔过程第1000ps 快照,从图3(a)中可以发现,GO 与PVA 以物理方式连接时,纤维会从GO 之间很轻易地被拉出,说明GO /PVA 界面的黏结性能很差,GO 的加入对界面的黏结性能起到消极作用㊂如图3(b)所示,在PVA 纤维和GO 以共价键形式连接时,PVA 纤维和GO 作为一个整体同时被拉出㊂PVA-GO 与CSH 形成界面CGP2,此时纤维被拉出所需要的拉力最大,说明CGP2界面的黏结性能最好,GO 的加入对界面的黏结性能起到增强作用㊂图3㊀拉拔过程第1000ps 快照Fig.3㊀Snapshots of pull-out process at 1000ps㊀第11期臧㊀芸等:基于分子动力学的氧化石墨烯对PVA纤维-CSH界面影响机理研究3803 2.2㊀界面静态结构分析径向分布函数(radial distribution function,RDF)表示周围原子出现在中心原子一定范围内的可能性,是原子局部密度与系统的平均密度比值㊂RDF曲线可定性表征配位原子之间的空间相关性,曲线出现峰值的距离越近,表明两原子之间排列更规则,形成的化学键更强,峰值越高说明两原子相关性更高㊂同时,RDF也揭示了界面的连接机制㊂图4为径向分布函数计算结果㊂在CP界面中Ca O hp和氢键的RDF曲线均存在明显的峰值,说明在CSH与PVA纤维之间既存在Ca O hp离子键连接也存在氢键连接,如图4(a)所示㊂而在CP1界面(GO与PVA纤维之间),GO中的氧与PVA纤维中的氢形成脆弱的氢键,如图4(b)所示㊂与氢键相比,离子键的键能远大于氢键㊂键能越大,化学键越牢固,含有该键的分子越稳定,这充分说明了CSH与PVA纤维之间的联系远强于GO与PVA纤维的联系㊂图4㊀CGP1界面㊁CGP2界面和CP界面的径向分布函数Fig.4㊀RDF of CGP1,CGP2and CP interfaces在PVA纤维与GO以共价键连接时,PVA纤维与GO形成一个整体,与CSH之间形成了界面CGP2㊂Ca O o㊁Ca O hg㊁Ca O RDF曲线均存在明显的峰值,如图4(c)所示,这说明GO中的含氧官能团均可以与CSH中的钙离子形成离子键,钙离子与GO中氧原子连接,充当了GO与CSH之间的桥梁㊂其中Ca O hg 和Ca O o的RDF曲线峰值更高,说明离子键中的氧位主要由 OH和 O 提供㊂与CP界面相比,CGP2界面中的Ca O的RDF曲线峰值更高,这是因为在GO中拥有更多能够与CSH中阳离子形成有效化学键的极性位点㊂除了离子键外,界面CP和CGP2中氢键的RDF曲线都有明显的峰值,但在CGP2界面中氢键RDF曲线位置更为靠左,峰值更尖锐,这充分说明在这个界面中有更强的界面成键相互作用,如图4(d)所示㊂根据以上分析可以得出结论,在水泥基质中掺入的GO片可以通过离子键和氢键连接硅酸盐骨架,从而加强了有机相和无机相之间的界面连接㊂在拉拔模拟阶段,纤维从CSH中被拉出的过程中,大量的化学键会被拉伸甚至断裂㊂键长越短,原子核之间的距离越小,键能越大,化学键越稳定,破坏这种化学键需要克服的能量就越多㊂化学键越稳定,对原子3804㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷运动的阻碍就越大,化学键越难断裂㊂根据前面的分析,在CGP2界面中形成的Ca O离子键和氢键数量最多,稳定性高,这意味着需要克服很大的键能才能将纤维从CSH中拉出㊂而PVA纤维与GO之间只有较弱的氢键,键能很小,较小的拉力就能将纤维拉出㊂拉拔仿真结果与本节分析结果一致㊂键合结构图如图5所示㊂图5㊀界面键合示意图Fig.5㊀Interface bonding diagrams化学键的稳定性可以通过时间相关函数(temporal correlation function,TCF)来描述㊂TCF值接近1,表明化学键稳定㊂如果TCF的值降至零,则说明化学键易断开且不稳定㊂根据前面章节的分析可知,CP界面和CGP2界面是通过Ca O离子键和氢键连接,而CGP1界面仅仅通过氢键将PVA纤维与CSH连接㊂本小节计算了三种界面间的化学键的时间相关函数,计算结果如图6(a)所示㊂在CGP2界面中Ca O键的TCF 值略高于CP界面,这意味着PVA和CSH之间形成的化学键更频繁地断裂和重组㊂在CGP2界面中, Ca O 键㊁Ca O o键和Ca O hg键的TCF值分别稳定在0.80㊁0.90和0.98左右,略有波动㊂与Ca O hg键和Ca O o键的TCF曲线相比,Ca O 键的TCF曲线下降更快,这表明连接GO和CSH的离子键主要由羟基提供氧位㊂这一结果与RDF分析结果一致㊂此外,Ca O键的TCF曲线大都在最初略有下降,然后几乎保持不变㊂这表明CSH中Ca和氧形成的离子键可以长时间连接㊂图6㊀Ca O键和H O键的时间相关函数Fig.6㊀Time correlation function of Ca O and H O bond第11期臧㊀芸等:基于分子动力学的氧化石墨烯对PVA 纤维-CSH 界面影响机理研究3805㊀三个界面中的氢键的TCF 曲线如图6(b)所示㊂相比于Ca O 键,氢键的TCF 曲线明显下降得更快,这也证明了离子键在界面连接中起到主导作用㊂界面之间化学键稳定性的差异解释了纤维与基体之间相互作用的差异㊂PVA 纤维和GO 之间没有稳定的离子键连接,导致PVA 纤维更容易被拉出㊂界面动态分析表明,三种界面结合强度依次为:CGP2>CP >CGP1,这说明如果GO 与PVA 纤维之间没有形成共价键,而只是以物理形式附着在PVA 纤维表面,不利于提升界面黏结性能,当PVA 纤维与GO 以共价键形式连接时,GO 才能发挥拥有更多极性氧位的优势,对界面的黏结性能才能起到增强作用㊂这与试验中的结果保持一致[23]㊂图7㊀不同界面的黏附能Fig.7㊀Adhesion energy of different interfaces 作用在PVA 纤维上的恢复力来自界面的相互作用,由黏附能提供[31]㊂在分子水平上,黏附能也可以用作表征界面黏结性能的参数㊂在CSH /PVA 模型中,只有存在CP (CSH /PVA)界面㊂而在CSH /GO /PVA 模型中虽然存在两个界面CSH /GO 和GO /PVA,但根据2.1节的分析,当纤维被拔出时,对纤维拉出行为产生影响的是GO /PVA 界面,所以仅计了CGP1(GO /PVA)界面的黏附能㊂在CSH /GO-PVA 模型中,GO 与PVA 纤维以共价键连接,只有界面CGP2(GO /CSH)影响到纤维被拉出行为㊂界面黏附能计算结果如图7所示,CGP1界面的黏附能仅为1979.3kcal /mol(1kJ =4.184kcal),而CP 界面的黏附能为3780.7kcal /mol,明显比界面CGP1要高出很多,这说明CSH /PVA 界面有更强的相互作用㊂CGP2界面的黏附能绝对值最大,为5515.9kcal /mol,这意味着当GO 与PVA 纤维形成共价键连接时,GO 对界面黏结性能起到增强作用㊂3㊀结㊀论1)PVA /CSH 界面主要是以钙氧离子键和氢键连接,而PVA /GO 界面仅依靠氢键连接㊂2)CGP2界面的黏结性能优于CP 界面和CGP1界面,其中CGP1界面的黏结性能最差㊂3)当PVA 纤维与GO 以共价键方式连接时,GO 发挥多极性氧位的优势,与CSH 之间形成更强的键合作用,从而加强了有机相和无机相之间的界面连接㊂当GO 以物理形式附着在PVA 纤维表面时,对界面的黏结性能起负面作用㊂参考文献[1]㊀杨宇林.纤维混凝土复合材料耐久性能研究综述[J].混凝土,2012(2):78-80+85.YANG Y L.Review on durability of complex fiber concrete[J].Concrete,2012(2):78-80+85(in Chinese).[2]㊀KANDA T,LI V C.Practical design criteria for saturated pseudo strain hardening behavior in ECC [J].Journal of Advanced ConcreteTechnology,2006,4(1):59-72.[3]㊀KONSTA-GDOUTOS M 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石墨烯动态调控太赫兹表面等离激元
第 21 卷 第 8 期2023 年 8 月Vol.21，No.8Aug.，2023太赫兹科学与电子信息学报Journal of Terahertz Science and Electronic Information Technology石墨烯动态调控太赫兹表面等离激元张葆青，冯明明，张翼飞*，宋爱民(山东大学微电子学院，山东济南250100)摘要：太赫兹表面等离激元(SPPs)是利用亚波长周期性结构在太赫兹频段模拟的具有与可见光频段表面等离激元相似的光学特性的电磁波，分为传输型和局域型2种。
本文将石墨烯引入太赫兹表面等离激元结构作为动态激励源，通过外加偏压改变石墨烯的电导率，分别实现了对传输型表面等离激元的幅度、频率、相位和对局域表面等离激元共振强度的动态调控。
本文方法为表面等离激元的动态调控提供了新的思路，拓宽了表面等离激元在太赫兹频段的应用。
关键词：表面等离激元；太赫兹；石墨烯；动态调控中图分类号：TN29；O441.4文献标志码：A doi：10.11805/TKYDA2022163Active modulation of terahertz Surface Plasmons Polaritons with grapheneZHANG Baoqing，FENG Mingming，ZHANG Yifei*，SONG Aimin(School of Microelectronics，Shandong University，Jinan Shandong 250100，China)AbstractAbstract：：Terahertz(THz) Surface Plasmons Polaritons(SPPs) can mimic optical Surface Plasmons (SPs) and obtain similar optical properties with periodic sub-wavelength structures, which typicallyconsist of propagating SPPs and Localized Surface Plasmons(LSPs). In this work, graphene is utilized asthe active stimuli to dynamically control the amplitude, frequency, and phase of SPPs and reconfigure theresonant modes of LSPs at various bias voltages. Such design provides new solutions for active control ofSPPs and LSPs at THz frequencies.KeywordsKeywords：：Surface Plasmons Polaritons；terahertz；graphene；active modulation表面等离激元(SPPs)是金属和介质交界面上的自由电荷集体振荡形成的一种电磁表面波，具有局域电场增强和突破光学衍射极限的特点，在生物传感、超分辨力成像、高效光伏等领域应用广泛[1]。