基于非等温热重法的氟化石墨热分解动力学研究
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摘要
针对氟化石墨热分解动力学机理不确定和动力学预测信息不足的问题,通过测量多组非等温热重曲线,并利用无模型动力学方法分析(CF)n热分解反应动力学机理.热重曲线显示(CF)n热分解经历一步失重,产生的平均气相成分为CF2.95.动力学分析结果表明机理函数随转化率依次变化:α<0.1,机理函数为JMA方程f (α)=1.5 (1-α)[-ln (1-α)]1/3;0.15<α<0.3,机理函数为二维AvramiErofeyev方程f(α)=2(1-α)[-ln(1-α)]1/2;0.3<α<0.8,机理函数为譒esták-Berggren方程f(α)=7.5α1.2·(1-α)2;0.85<α,机理函数为一维Avrami-Erofeyev方程f(α)=(1-α).推荐的动力学预测参量活化能为264.23±7.82 kJ/mol,指前因子为(8.70±0.21)×10~(14)/s.另外,动力学机理反映出(CF)n分解过程存在碳核的链生长以及与分支链的相互作用的特征,这可能是反应产物形成非晶态结构碳的重要因素.
Aiming at the problem of uncertain mechanism of kinetics of thermal decomposition of fluorinated graphite and insufficient information of kinetic prediction,the dynamic mechanism of(CF)nthermal decomposition reaction was analyzed by measuring multiple sets of non-isothermal thermogravimetric curves and using model-free kinetics.The thermogravimetric curve shows that(CF)nthermal decomposition undergoes one step of weight loss,resulting in an average gas phase composition of CF2.95.The results of kinetic analysis show that the mechanism function changes with the conversion rate:α<0.1,the mechanism function is JMA equation f(α)=1.5(1-α)[-ln(1-α)]1/3;0.15<α< 0.3,the mechanism function is two-dimensional Avrami-Erofeyev equation f(α)=2(1-α)[-ln(1-α)]1/2;0.3<α<0.8,the mechanism function is Sesták-Berggren equation f(α)=7.5α1.2(1-α)2;0.85<α,the mec hanism function is the one-dimensional Avrami-Erofeyev equation f(α) =(1-α).The recommended kinetic prediction parameter activation energy is 264.23±7.82 kJ/mol,and the pre-exponential factor is(8.70±0.21)×10~(14)/s.In addition,the kinetic mechanism reflects the existence of carbon chain chain growth and interaction with the branching chain in the(CF)ndecomposition process,which may be an important factor in the formation of amorphous structural carbon in the reaction product.
Aiming at the problem of uncertain mechanism of kinetics of thermal decomposition of fluorinated graphite and insufficient information of kinetic prediction,the dynamic mechanism of(CF)nthermal decomposition reaction was analyzed by measuring multiple sets of non-isothermal thermogravimetric curves and using model-free kinetics.The thermogravimetric curve shows that(CF)nthermal decomposition undergoes one step of weight loss,resulting in an average gas phase composition of CF2.95.The results of kinetic analysis show that the mechanism function changes with the conversion rate:α<0.1,the mechanism function is JMA equation f(α)=1.5(1-α)[-ln(1-α)]1/3;0.15<α< 0.3,the mechanism function is two-dimensional Avrami-Erofeyev equation f(α)=2(1-α)[-ln(1-α)]1/2;0.3<α<0.8,the mechanism function is Sesták-Berggren equation f(α)=7.5α1.2(1-α)2;0.85<α,the mec hanism function is the one-dimensional Avrami-Erofeyev equation f(α) =(1-α).The recommended kinetic prediction parameter activation energy is 264.23±7.82 kJ/mol,and the pre-exponential factor is(8.70±0.21)×10~(14)/s.In addition,the kinetic mechanism reflects the existence of carbon chain chain growth and interaction with the branching chain in the(CF)ndecomposition process,which may be an important factor in the formation of amorphous structural carbon in the reaction product.
引文
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[26]胡荣祖.热分析动力学[M].2版.北京:科学出版社,2008:163-164.
[2]SATO Y,ITOH K,HAGIWARA R,et al.Short-range structures of poly(dicarbon monofluoride)(C2F)nand poly(carbon monofluoride)(CF)n[J].Carbon,2004,42(14):2897-2903.
[3]LAZAR P,OTYEPKOVE,KARLICKY F,et al.The surface and structural properties of graphite fluoride[J].Carbon,2015,94:804-809.
[4]TH OMAS P,DELBK,HIMMEL D,et al.Tribological properties o low-temperature graphite fluorides.Influence of the structure on the lubricating performances[J].Journal of Physics&Chemistry of Solids,2006,67(5/6):1095-1099.
[5]MIAO X,YANG J,PAN W,et al.Graphite fluoride as a cathode material for primary magnesium batteries with high energy density[J].Electrochimica Acta,2016,210:704-711.
[6]房亚楠,刘栓,赵文杰,等.石墨/氟碳涂层与氟化石墨/氟碳涂层腐蚀行为的研究[J].电镀与涂饰,2016,35(14):747-754.
[7]康文泽,李尚益.氟化石墨烯制备与研究进展[J].炭素,2016(3)12-16.
[8]黄海平,徐亮,岳亚锋,等.基于石墨烯量子点修饰电极的亚硝酸根电化学传感器[J].有色金属科学与工程,2017,8(2):47-51.
[9]CRASSOUS I,GROULT H,LANTELME F,et al.Study of the fluorination of carbon anode in molten KF-2HF by XPS and NMRinvestigations[J].Journal of Fluorine Chemistry,2009,130(12):1080-1085.
[10]ZHU H M,SADOWAY D R.Anode reaction in aluminium electrolysis prior to and during anode effect[C]//ANJIER J L.Light Metals 2003.New York:John Wiley&Sons,Inc.,2003:343-349.
[11]HAVERKAMP R G.An XPS study of the fluorination of carbon anodes in molten NaF-AlF3-CaF2[J].Journal of Materials Science,2012,47(3):1262-1267.
[12]CHEN G,SHI Z N,WANG Z W,et al.Mechanism of graphite electrode fluorinated in 2.4 NaF/AlF3-Al2O3melt at 1 373 K[J].Journal of the Electrochemical Society,2014,161(14):C587-C593.
[13]WATANABE N,KOYAMA S,IMOTO H.Thermal decomposition of graphite fluoride.I.Decomposition products of graphite fluoride,(CF)nin a vacuum[J].Bulletin of the Chemical Society of Japan,1980,53(10):2731-2734.
[14]BETTINGER H F,PENG H.Thermolysis of fluorinated singlewalled carbon nanotubes:Identification of gaseous decomposition products by matrix isolation infrared spectroscopy[J].Journal of Physical Chemistry B,2005,109(49):23218-23224.
[15]CHEN G,SHI Z,YU J,et al.Kinetic analysis of the non-isothermal decomposition of carbon monofluoride[J].Thermochimica Acta,2014,589(10):63-69.
[16]KAMARCHIK P,MARGRAVE J L.A study of thermal decomposition of the solid-layered fluorocarbon,poly(carbon monofluoride)[J].Journal of Thermal Analysis,1977,11(2):259-270.
[17]WATANABE N,KOYAMA S.Thermal decomposition of graphite fluoride.II.Kinetics of thermal decomposition of(CF)nin a vacuum[J].Bulletin of the Chemical Society of Japan,1980,53(11):3093-3099.
[18]杨序纲,吴琪琳.拉曼光谱的分析与应用[M].北京:国防工业出版社,2008:158-163.
[19]VYAZOVKIN S,BURNHAM A K,CRIADO J M,et al.ICTACkinetics committee recommendations for performing kinetic computations on thermal analysis data[J].Thermochimica Acta,2011,520(1):1-19.
[20]VYAZOVKIN S.Model-free kinetics:staying free of multiplying entities without necessity[J].Journal of Thermal Analysis&Calorimetry,2006,83(1):45-51.
[21]吴易燃,姜恒,宫红,等.氢氧化镧的热分解动力学[J].稀土,2015,36(4):116-119.
[22]MLEK J.The kinetic-analysis of nonisothermal data[J].Thermochimica Acta,1992,200(8):257-269.
[23]KHAWAM A,FLANAGAN D R.Solid-state kinetic models:basics and mathematical fundamentals[J].Journal of Physical Chemistry B,2006,110(35):17315-17328.
[24]ESTK J,BERGGREN G.Study of the kinetics of the mechanism of solid-state reactions at increasing temperature[J].Thermochimica Acta,1971,3(1):1-12.
[25]IMON P.Fourty years of theesták-Berggren equation[J].Thermochimica Acta,2011,520(1):156-157.
[26]胡荣祖.热分析动力学[M].2版.北京:科学出版社,2008:163-164.