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.1144, 北京科技大学学报 第29卷 [5]Sun B.Skyllas-Kazacos M.Modification of graphite electrode ma [8]Kaneko K,Nozaki K.wada Y,et al.Vanadium redox reactions terials for vanadium redox flow battery application I:Thermal and carbon electrodes for vanadium redox flow battery.Elec- treatment.Flectrochim Acta.1992.37(7):1253 trochim Acta.1991.36:1191 [6]Sukkar T.Skyllas-Kazacos M.Modification of membranes using [9]OrijiG.Katayama Y,Miura T.Investigations on V(N)/V polyelectrolytes to improve water transfer properties in the vanadi- (V)and v(II)/V()redox reactions by various electrochemi- um redox battery.J Membr Sci.2003,222:249 cal methods.J Power Sources.2005,139:321 [7]Sun B.Skyllas-Kazacos M.Chemical modification and electro- [10]Gattrell M.Park J,Madougall B.Study of the mechanism of chemical behaviour of graphite fiber in acidic vanadium solution the vanadium 4+/5+redox reaction in acidic solutions.JElec- Electrochim Acta.1991.36:513 tochem Soc.2004.151:A123 Different treatments for positive and negative electrode materials of an all vanadium redox flow battery WANG Wenhong,WA NG Xindong,GUO Min,LI Jianling Metallurgical and Ecological Engineering School.University of science and technology Beijing.Beijing 100083.China ABSTRACT An all-vanadium redox flow battery (VRB)typically uses carbon felt as the electrode material in order to enhance the reactive current.The carbon felt made by polyacrylonitrile-based polymers can be heat- treated to increase the number of surface oxide sites and to improve its crystallinity and conductivity.It was ex- amined in VRB that the over potentiality was mainly caused by positive pole reactions.The heat treatment of positive felt could decrease the cell's resistance dramatically,but that of negative felt induced low hydrogen evo- lution over potentiality and low current efficiency.With raw felt as the negative pole material and heat-treated felt as the positive pole material the test cell could get the optimal energy efficiency. KEY WORDS all vanadium redox flow battery;PAN based carbon felt;over potentiality;cell resistance (上接第1140页) Effect of phase difference between dual laser fields on phonon amplification in a graphene FENG Peng,LI Jiajie Applied Science School.University of Science and Technology Beijing.Beijing 100083.China ABSTRACI Atomic displacement fluctuation in a graphene under dual laser fields was studied by a modified functional integral approach.It was show n that when the field strength and the frequency were fixed,the atom- ic displacement fluctuation was tuned by the phase difference bet ween dual laser fields.It was realized that the rate of change of the atomic displacement fluctuation took its positive value in measurable time ranges.This cor- responded to a phonon amplification effect.The mechanism of generating the phonon amplification was dis- cussed. KEY WORDS atomic displacement fluctuation;laser field;photon electron interaction;electron phonon inter- action［5］ Sun BSkyllas-Kazacos M．Modification of graphite electrode materials for vanadium redox flow battery application Ⅰ：Thermal treatment．Electrochim Acta199237（7）：1253 ［6］ Sukkar TSkyllas-Kazacos M．Modification of membranes using polyelectrolytes to improve water transfer properties in the vanadium redox battery．J Membr Sci2003222：249 ［7］ Sun BSkyllas-Kazacos M．Chemical modification and electrochemical behaviour of graphite fiber in acidic vanadium solution． Electrochim Acta199136：513 ［8］ Kaneko KNozaki Kwada Yet al．Vanadium redox reactions and carbon electrodes for vanadium redox flow battery．Electrochim Acta199136：1191 ［9］ Oriji GKatayama YMiura T．Investigations on V （Ⅳ）／ V （Ⅴ） and V（Ⅱ）／V（Ⅲ） redox reactions by various electrochemical methods．J Power Sources2005139：321 ［10］ Gattrell MPark JMadougall B．Study of the mechanism of the vanadium4＋／5＋ redox reaction in acidic solutions．J Electochem Soc2004151：A123 Different treatments for positive and negative electrode materials of an al-l vanadium redox flow battery WA NG WenhongWA NG XindongGUO MinLI Jianling Metallurgical and Ecological Engineering SchoolUniversity of science and technology BeijingBeijing100083China ABSTRACT An al-l vanadium redox-flow battery （VRB） typically uses carbon felt as the electrode material in order to enhance the reactive current．The carbon felt made by polyacrylonitrile-based polymers can be heattreated to increase the number of surface oxide sites and to improve its crystallinity and conductivity．It was examined in VRB that the over potentiality was mainly caused by positive pole reactions．The heat treatment of positive felt could decrease the cell’s resistance dramaticallybut that of negative felt induced low hydrogen evolution over potentiality and low current efficiency．With raw felt as the negative pole material and heat-treated felt as the positive pole material the test cell could get the optimal energy efficiency． KEY WORDS al-l vanadium redox flow battery；PAN based carbon felt；over potentiality；cell resistance （上接第1140页） Effect of phase difference between dual laser fields on phonon amplification in a graphene FENG PengLI Jiajie Applied Science SchoolUniversity of Science and Technology BeijingBeijing100083China ABSTRACT Atomic displacement fluctuation in a graphene under dual laser fields was studied by a modified functional integral approach．It was shown that when the field strength and the frequency were fixedthe atomic displacement fluctuation was tuned by the phase difference between dual laser fields．It was realized that the rate of change of the atomic displacement fluctuation took its positive value in measurable time ranges．This corresponded to a phonon amplification effect．The mechanism of generating the phonon amplification was discussed． KEY WORDS atomic displacement fluctuation；laser field；photon-electron interaction；electron-phonon interaction ·1144· 北 京 科 技 大 学 学 报 第29卷