PAN基碳纤维长周期结构的温度依赖性
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摘要
采用SAXS和HRTEM方法从倒易空间和实空间分别研究了PAN纤维碳化及石墨化过程中长周期结构及其变化。通过HRTEM测试发现碳纤维中存在由石墨微晶的有序堆砌结构,无序堆砌结构及过渡区形成的层状长周期结构,同时碳纤维的SAXS赤道方向散射曲线中出现肩峰,说明这种长周期结构沿纤维径向堆砌。通过SAXS研究发现,在PAN纤维碳化过程中长周期结构从700℃时开始出现且其尺寸随热处理温度的变化呈先增大后减小的趋势,转折温度区域约为1350℃左右。通过一维相关函数分析,计算了长周期结构中石墨微晶有序堆砌结构尺寸(Lo)、无序堆砌结构尺寸(Ld)、过渡区尺寸(Ltr)随热处理温度的变化:1350℃之前,Lo、Ld趋于增大,而Ltr趋于减小;1350℃之后3个参数均呈减小的趋势。
The periodical structure of PAN based carbon fiber during carbonization and graphitization was firstly detected and investigated by SAXS and HRTEM from reciprocal and direct space,respectively. From HRTEM observation,the periodical structure of carbon fiber is composed of the ordered and disordered stacking of crystalline structure of graphite as well as transition region. According to SAXS analysis,the scattering curves along the equatorial direction of carbon fiber show shoulder peaks,which indicates that the periodical structure is alternately arranged perpendicular to the fiber axis. The generation and evolution of this periodical structure during carbonization was also investigated. The periodical structure starts to appear at about 700 ℃ in the process of carbonization for the carbon fiber. The length of long period structure increases up to about 1350 ℃ and after that it is decreased. The electronic density correlation function analysis was also applied to get the detail parameters of the periodical structure,such as the length of the ordered stacking of graphite crystallite structure( Lo),disordered stacking of graphite crystallite structure( Ld) and transition region( Ltr). During carbonization and graphitization,Loand Ldincrease,Ltrdecreases before about 1350 ℃ and after the temperature,all of the three parameters decrease.
The periodical structure of PAN based carbon fiber during carbonization and graphitization was firstly detected and investigated by SAXS and HRTEM from reciprocal and direct space,respectively. From HRTEM observation,the periodical structure of carbon fiber is composed of the ordered and disordered stacking of crystalline structure of graphite as well as transition region. According to SAXS analysis,the scattering curves along the equatorial direction of carbon fiber show shoulder peaks,which indicates that the periodical structure is alternately arranged perpendicular to the fiber axis. The generation and evolution of this periodical structure during carbonization was also investigated. The periodical structure starts to appear at about 700 ℃ in the process of carbonization for the carbon fiber. The length of long period structure increases up to about 1350 ℃ and after that it is decreased. The electronic density correlation function analysis was also applied to get the detail parameters of the periodical structure,such as the length of the ordered stacking of graphite crystallite structure( Lo),disordered stacking of graphite crystallite structure( Ld) and transition region( Ltr). During carbonization and graphitization,Loand Ldincrease,Ltrdecreases before about 1350 ℃ and after the temperature,all of the three parameters decrease.
引文
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[22]王梦梵,李龙,陈旺,等.PAN基碳纤维碳化过程反应动力学研究[J].化工新型材料,2013(5):79-81.WANG Meng-fan,LI Long,CHEN Wang,et al.Kinetics analysis of the PAN based carbon fiber during carbonization[J].New Chemical Matericals,2013(5):79-81.
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[2]王成国,井敏,王延相,等.碳纤维用聚丙烯腈基预氧丝碳化裂解过程研究进展[J].现代化工,2008(7):22-26.WANG Cheng-guo,JING-min,WANG Yan-xiang,et al.Advances in carbonization and pyrolysis of polyacrylonitrile-based stabilized fiber for preparing carbon fiber[J].Modern Chemical Industry,2008(7):22-26.
[3]Ruland W.Carbon fibers[J].Advanced Materials,1990,2(11):528-536.
[4]Chand S.Review-carbon fibers for composites[J].Journal of Material Science,2000,35(6):1303-1313.
[5]陈晓,查刘生,朱育平.高强度、高模量聚丙烯腈基碳纤维的微晶取向研究[J].化工新型材料,2010(7):85-88.CHEN Xiao,CHA Liu-sheng,ZHU Yu-ping.Microstructure of high tensile strength and high tensile modulus PAN-based carbon fibers determined by X-ray diffraction[J].New Chemical Matericals,2010(7):85-88.
[6]Zhu C Z,Yu X L,Liu X F,et al.2D SAXS/WAXD analysis of pan carbon fiber microstructure in organic/inorganic transformation[J].Chinese Journal of Polymer Science,2013,31(5):823-832.
[7]Wu G P,Li D H,Yang Y,et al.Carbon layer structures and thermal conductivity of graphitized carbon fibers[J].Journal of Materials Science,2012,47(6):2882.
[8]Qin X Y,Lu Y G,Xiao H,et al.A comparison of the effect of graphitization on microstructures and properties of polyacrylonitrile and mesophase pitchbased carbon fibers[J].Carbon,2012,50(12):4459-4469.
[9]Zhou G H,Liu Y Q,He L L,et al.Microstructure difference between core and skin of T700 carbon fibers in heat-treated carbon/carbon composites[J].Carbon,2011,49(9):2883-2892.
[10]Perret R,Ruland W.The microstructure of PAN-base carbon fibres[J].Journal of Applied Crystallography,1970,3(6):525-532.
[11]侯锋辉,邓红兵,李崇俊,等.碳纤维结构的常用表征技术[J].纤维复合材料,2008,25(3):18-20.HOU Feng-hui,DENG Hong-bing,LI Chong-jun,et al.Common characterization methods of carbon-fiber structures[J].Fiber Composites,2008,25(3):18-20.
[12]曹维宇,高爱君,徐樑华.聚丙烯腈基碳纤维高温处理过程中石墨微晶的生长[J].宇航材料工艺,2011(1):61-65.CAO Wei-yu,GAO Ai-jun,XU Liang-hua.Evolution of crystallite size of Laof PAN-based carbon fiber during heat-treatment process[J].Aerospace Materials and Technology,2011(1):61-65.
[13]何东新,王成国,王延相,等.表征PAN纤维和炭纤维微细结构的HRTEM样品制备方法[J].理化检验:物理分册,2005,41(3):124-127.HE Dong-xin,WANG Cheng-guo,WANG Yan-xiang,et al.Sample preparation methods for characterizing HRTEM microstructure of PAN and carbon fibers[J].Physical Testing and Chemical Analysis part B:Chemical Analysis,2005,41(3):124-127.
[14]Rahaman M S A,Ismail A F,Mustafa A.A review of heat treatment on polyacrylonitrile fiber[J].Polymer Degradation and Stability,2007,92(8):1421-1432.
[15]朱育平.小角X射线散射[M].北京:化学工业出版社,2008.
[16]Hammersley A P.FIT2D:An introduction and overview,European Synchrotron Radiation Facility Internal Report[R].ESRF97HA02T,1997.
[17]Glatter O,Kratky O.Small Angle X-ray Scattering[M].London:Academic Press,1982.
[18]Guinier A,Fournet G,Yudowitch K L.Small-angle Scattering of X-rays[M].New York:Wiley,1955.
[19]Shioya M,Kawazoe T,Kojima J,et al.Small-angle X-ray scattering of long-period structures forming bundles[J].Polymer,2006,47(10):3616-3628.
[20]Thünemann A F,Ruland W,Lamellar mesophases in polyacrylonitrile:a synchrotron small-angle X-ray scattering study[J].Macromolecules,2000,33(7):2626-2631.
[21]Ruland W,Smarsly B.SAXS of self-assembled oriented lamellar nanocomposite films:an advanced method of evaluation[J].Journal of Applied Crystallography,2004,37(4):575-584.
[22]王梦梵,李龙,陈旺,等.PAN基碳纤维碳化过程反应动力学研究[J].化工新型材料,2013(5):79-81.WANG Meng-fan,LI Long,CHEN Wang,et al.Kinetics analysis of the PAN based carbon fiber during carbonization[J].New Chemical Matericals,2013(5):79-81.
[23]Strobl G R.The Physics of Polymers:Concepts for Understanding Their Structures and Behavior[M].Berlin:Springer,2007.