高电导率低热膨胀系数针状焦的制备
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摘要
将不同量的中间相炭微球(MCMB)引入煤沥青后经过二次生长、融并和中间相重排,制备出层状结构良好和性能优异的针状焦(NCs)。用偏光显微镜观察和分析了所得中间相和半焦组织的结构;用X射线衍射仪和扫描电镜分析了NCs的微观结构;用高精度电阻率测试仪测试了电阻率;用热机械分析仪测定了热膨胀系数。结果表明:加入适量的MCMB有利于提高焦的有序性,促进针状焦石墨片层结构的形成,显著降低针状焦的电阻率和热膨胀系数值;MCMB的添加量(质量分数)低于50%时,NCs结构有序性随着添加量的提高而提高;MCMB的添加量超过50%,则焦的质量下降。MCMB的添加量为50%时电阻率和热膨胀系数值(0°～100℃)分别降低27.9%和45.7%,石墨化度提高46.2%。
Needle-cokes(NCs) were synthesized via a two-step process, namely mesocarbon microbeads(MCMB) were firstly blended with coal tar pitch(CTP) at 180 oC for ca 30 min, and which was then calcined in an autoclave filled with 0.5 MPa nitrogen at 1500 oC for 5 h. The microstructure of mesophase, semi-cokes and the final product NCs was characterized by means of polarizing microscope, XRD and SEM. The resistivity and coefficient of thermal expansion(CTE) were measured by resistivity meter and thermal mechanical analyzer, respectively. The results show that the addition of moderate amount of MCMB could affect the formation of NCs, so that promote the formation of graphite-like layered structure,which significantly reduced the resistivity and CTE value of NCs. The structure of needle-cokes could be effectively improved with the increase of MCMB content(≤50 mass fraction%). However, the quality of needle-cokes began to decline as the content of MCMB exceeded 50%. The resistivity and CTE value(at0-100oC) of NCs decreased by 27.9% and 45.7%, respectively, when the content of MCMB is 50% in feedstock, meanwhile, the corresponding graphitization degree increased by 46.2%, as comparing with the parent needle-coke.
Needle-cokes(NCs) were synthesized via a two-step process, namely mesocarbon microbeads(MCMB) were firstly blended with coal tar pitch(CTP) at 180 oC for ca 30 min, and which was then calcined in an autoclave filled with 0.5 MPa nitrogen at 1500 oC for 5 h. The microstructure of mesophase, semi-cokes and the final product NCs was characterized by means of polarizing microscope, XRD and SEM. The resistivity and coefficient of thermal expansion(CTE) were measured by resistivity meter and thermal mechanical analyzer, respectively. The results show that the addition of moderate amount of MCMB could affect the formation of NCs, so that promote the formation of graphite-like layered structure,which significantly reduced the resistivity and CTE value of NCs. The structure of needle-cokes could be effectively improved with the increase of MCMB content(≤50 mass fraction%). However, the quality of needle-cokes began to decline as the content of MCMB exceeded 50%. The resistivity and CTE value(at0-100oC) of NCs decreased by 27.9% and 45.7%, respectively, when the content of MCMB is 50% in feedstock, meanwhile, the corresponding graphitization degree increased by 46.2%, as comparing with the parent needle-coke.
引文
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[12] Sun S, Wang C, Chen M, et al. A method to observe the structure of the interface between mesocarbon microbeads and pitch[J].Journal of Colloid and Interface Science, 2014, 426:206
[13] Mochida I, Oyama T, Korai Y, et al. Study of carbonization using a tube bomb:evaluation of lump needle coke, carbonization mecha‐nism and optimization[J]. Fuel, 1988, 67(9):1171
[14] Cao Q, Xie X, Li J, et al. A novel method for removing quinoline insolubles and ash in coal tar pitch using electrostatic fields[J]. Fu‐el, 2012, 96:314
[15] Im U S, Kim J, Lee S H, et al. Effects of Two-stage Heat Treat‐ment on Delayed Coke and Study of Their Surface Texture Charac‐teristics[J]. JOM, 2017, 69(12):2460
[16] Im Ji S, Lee C W, Halim H P. Preparation of needle coke from pe‐troleum by-products[J]. Carbon Letters, 2013, 14(3):152
[2] Kang H G, Park J K, Han B S, et al. Electrochemical characteris‐tics of needle coke refined by olten caustic leaching as an anode material for a lithium-ion battery[J]. Journal of Power Sources,2006, 153(1):170
[3] Wang J, Wang L, Chen M, et al. Nanoporous carbons from oxi‐dized green needle coke for use in high performance supercapaci‐tors[J]. New Carbon Materials, 2015, 30(2):141
[4] Tang X Y, Wei X H, et al. Removal of QI from medium-tempera‐ture coal tar pitch and preparation of needle coke through carbon‐ization[J]. Chinese Journal of Materials Research, 2016, 30(6):448(唐闲逸,魏晓慧,许德平等.中温煤沥青喹啉不溶物的脱除及炭化制备针状焦[J].材料研究学报, 2016, 30(6):448)
[5] Cai Chuang, Chen Ying, Wang Fu, et al. The prospects for the de‐velopment of coal based needle coke industry[J]. Fuel&Chemi‐cal Processes, 2017, 48(6):1(蔡闯,陈莹,王伏等.煤系针状焦行业发展前景[J].燃料与化工, 2017, 48(6):1)
[6] Alvarez P, Diez N, Santamaría R, et al. Novel coal-based precur‐sors for cokes with highly oriented microstructures[J]. Fuel, 2012,95:400
[7] Cheng X, Zha Q, Li X, et al. Modified characteristics of meso‐phase pitch prepared from coal tar pitch by adding waste polysty‐rene[J]. Fuel Processing Technology, 2008, 89(12):1436
[8] Brzozowska T, Zielinski J, Machnikowski J. Effect of polymeric additives to coal tar pitch on carbonization behaviour and optical texture of resultant cokes[J]. Journal of Analytical and Applied Py‐rolysis, 1998, 48(1):45
[9] Lin Q, Li T, Ji Y, et al. Study of the modification of coal-tar pitch with p-methyl benzaldehyde[J]. Fuel, 2005, 84(2):177
[10] Lin Q, Li T, Zheng C, et al. Carbonization behavior of coal-tar pitch modified with divinylbenzene and optical texture of resultant semi-cokes[J]. Journal of Analytical and Applied Pyrolysis, 2004,71(2):817
[11] Xu D P, Tang S B, Tang X Y, et al. Research advances of compos‐ites in feedstock on formation of mesophase in needle coke prepa‐ration[J]. Carbon Techniques, 2016, 35(1):34(许德平,唐世波,唐闲逸等.针状焦制备过程中原料组分对中间相影响的研究进展[J].炭素技术, 2016, 35(1):34)
[12] Sun S, Wang C, Chen M, et al. A method to observe the structure of the interface between mesocarbon microbeads and pitch[J].Journal of Colloid and Interface Science, 2014, 426:206
[13] Mochida I, Oyama T, Korai Y, et al. Study of carbonization using a tube bomb:evaluation of lump needle coke, carbonization mecha‐nism and optimization[J]. Fuel, 1988, 67(9):1171
[14] Cao Q, Xie X, Li J, et al. A novel method for removing quinoline insolubles and ash in coal tar pitch using electrostatic fields[J]. Fu‐el, 2012, 96:314
[15] Im U S, Kim J, Lee S H, et al. Effects of Two-stage Heat Treat‐ment on Delayed Coke and Study of Their Surface Texture Charac‐teristics[J]. JOM, 2017, 69(12):2460
[16] Im Ji S, Lee C W, Halim H P. Preparation of needle coke from pe‐troleum by-products[J]. Carbon Letters, 2013, 14(3):152