【作者】 张建辉；

【导师】 赵广杰；

【作者基本信息】 北京林业大学 ， 木材科学与技术， 2011， 博士

【摘要】 碳纤维可采用PAN纤维、沥青纤维等经过氧化、低温碳化、高温碳化制成。由PAN纤维制备碳纤维,工艺简单、产品力学性能良好。但是近年来石油能源的短缺使得PAN纤维原丝日趋紧张,其制造成本上升,因此碳纤维原料的开发已成为当前研究的重点之一。近年来竹材液化技术的研究,为竹材成为碳纤维的替代原料奠定了基础。本论文以竹材为原料,通过正交实验,系统的研究了原丝的优化制备工艺以及原丝的优化炭化工艺；利用扫描电镜(SEM)、X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FTIR)、热失重分析仪(TGA)对原丝的形态结构及晶体结构、原丝制备过程中的化学基团变化以及原丝的热失重过程等进行了研究；并利用SEM、XRD、拉曼光谱仪、压汞仪、电子单纤维强力仪、FTIR、热重—质谱联用分析仪(TG-MS)、微观构造与元素分析仪(SEM-EDAX)等对炭化过程中竹材液化物碳纤维的形态结构、微晶结构、比表面积、孔隙结构、电学性能以及内部化学成分等的变化进行了详细的研究,得出以下主要结论：(1)原丝的优化制备工艺：纺丝速率为800r/min、合成温度为120℃、合成剂用量为5%、合成升温时间为30min；磷酸浓度为18.5%、升温速率为5℃/h、稳定化温度为85℃、稳定化时间为2h；可制备出平均直径28μm、拉伸强度为148.26MPa、拉伸模量为34.68 GPa、断裂伸长率为1.62%的原丝。(2)竹材液化为竹材液化物后,其结晶度减小；竹材液化物生成纺丝液后,其结晶度增加；纺丝液纺制成原丝后,其结晶度继续增加。原丝的表面平滑,其断面边部结构紧密,芯部结构疏松并有孔隙存在,某些原丝存在明显的“皮芯”结构,部分原丝出现变形或节状物。(3)竹材液化过程中,竹材中的纤维素、半纤维素以及木质素等与苯酚交联反应产生更多的芳环衍生物。原丝制备过程中,首先合成剂与游离苯酚加成反应形成羟甲基离子,同时部分羟甲基之间或部分羟甲基与芳环上未反应的活泼氢原子之间发生缩合反应,分别形成次甲基醚键和亚甲基键桥。然后随温度的升高,部分酚羟基之间也发生了缩合反应,可纺制出初始纤维。最后初始纤维中的芳环与羟甲基离子发生交联反应,同时部分次甲基醚键和羟甲基转化为亚甲基键,较多的酚羟基之间、酚羟基与羟甲基离子之间缩合反应形成次甲基醚键,初步形成网状结构的原丝。(4)原丝炭化的优化工艺：原丝直径为24μm、升温速率为2℃/min、炭化温度为1000℃、恒温时间为80min,可制备出平均拉伸强度为982.60MPa、拉伸模量为98.76GPa、断裂伸长率为4.98%、炭化得率55.68%的碳纤维。(5)竹材液化物碳纤维表面较平滑,无明显缺陷；断面为椭圆形,断面边部结构致密且无明显孔隙,中心部分结构稀疏且孔隙较多。它也存在皮芯结构,且部分为中空碳纤维。(6)300℃-1000℃之间,竹材液化物碳纤维属于类石墨的无定型碳结构。随炭化温度的升高,碳纤维中C的含量增加,其比孔容与比表面积呈增大趋势；而碳纤维中0的含量下降,其平均孔径逐渐减小,其电阻率不断下降,其类石墨微晶结构逐渐趋于规整和有序。在同一炭化温度下,随炭化时间的延长,碳纤维中c的含量逐渐增加,0的含量呈现减少的趋势,其电阻率不断下降,并且其电阻率随晶体结构参数(La、Lc及d002)的减小而减小。(7)300℃以下,原丝的热失重率为5.07%,其热解产物主要有CO、CO2、苯酚、CH2O；300℃-600℃,原丝的热失重率达到41.20%,热解产物包括CO、C02、CH4、苯、甲苯、苯酚、甲苯酚、二甲苯酚以及部分大分子产物；600℃-1000℃,原丝的热失重率仅为3.33%,原丝在700℃-800℃之间发生热解产生CO2和甲苯。更多还原

【Abstract】 Carbon fiber can be made by PAN fiber or pitch fiber via oxidation, low-temperature carbonization, high-temperature carbonization process. The process used by PAN fiber is simpler and mechanical properties of carbon fibers are better. However, the shortage of fossil resource caused precursors of PAN fiber to become fewer and fewer in recent years, which caused the cost rise of carbon fibers, so the material development for carbon fibers has been one of important study fields. The research on bamboo liquefication in recent years, base on which it can be used as replaced material for materials of carbon fiber.In this Paper, the reproducible bamboo was used to be material, the optimized preparation process and carbonization process of precursors were studied detailedly by orthogonal tests; The configuration, change of chemical groups during precursor preparation and weight loss process were studied and analyzed by SEM, XRD, FTIR and TGA etc.; The change rule of interior configuration, micro-crystal structure, specific surface area, porous structure, electricity properties during carbonization was studied by SEM, XRD, Laser Raman Spectrometry, mercury indicator, Electronic Tensile Tester for Single Fiber, FTIR, TG-MS and SEM-EDAX etc., based on which the following conclusions were obtained.1) The optimized preparation process of precursors:Spinning velocity is 800r/min, synthetic temperature is 120℃, synthetic agent content is 5%, temperature-rising time is 30min:Phosphoric acid chroma is 18.5%, temperature-rising speed is 5℃/h, stabilizing temperature is 85℃and stabilizing time is 2h. Based on which the precursors could be prepared, its average diameter is 28μm, average tensile strength is 148.26MPa, average tensile modulus is34.68GPa, average breaking elongation is 1.62%.2) After bamboo was liquefied to liquefied bamboo, its crystal became lower. When the liquefied bamboo became spinning solution, its crystal became higher. The crystal became higher after the spinning solution was changed into precursors.The precursor surface was smooth, it had smooth cross-sections, and its border is more compact than the center, many fine pores were mainly observed around the center of the cross-section of carbon fibers. Some precursor s had skin-core structure, and there were distortions and nodes in Partial precursor s.3) The cellulose, hemi-cellulose and lignin in bamboo combined with phenol during bamboo liquefication, which could produce more aryl-ramifications.During the course of precursor preparation, firstly, synthetic agent combined with phenol to make new hydroxymethyl, simultaneously, Partial hydroxymethyl reacted with each other or Partial hydroxymethyl reacted with alive hydrogen on aromatic ring to form (-CH2O-) and methylene bridges respectively. Then With the rising of temperature, Partial hydroxyketone reacted with each other to form original fibers. Finally, the aromatic ring of original fibers reacted with +CH2OH simultaneously, Partial (-CH2O-) and hydroxymethyl transformed to methylene, more hydroxyketone reacted with each other or more hydroxyketone reacted with+CH2OH to form (-CH2O-), thus netty structure precursors formed primarily.4) The optimization process of precursor carbonization:fiber diameter is 24μm, temperature-rising speed is 2℃/min, carbonization temperature is 1000℃, temperature-keeping time is 80min, based on which the better carbon fiber from liquefied bamboo can be prepared, its average tensile strength is 982.60MPa, average tensile modulus is 98.76GPa, average breaking elongation is 4.98%, average yield ration is 55.68%.5) The surface of carbon fibers from liquefied bamboo was more smooth, there were no obvious disfigurements; They had ellipse cross-sections and its border is more compact than the center. Many fine pores were mainly observed around the center of the cross-section of carbon fibers. It also had skin-core structure, moreover, some carbon fibers could form hollow fibers during carbonization.6) Between 300℃and 1000℃, carbon fibers from liquefied bamboo belonged to graphite-like amorphous carbon structure. With the rising of carbonization temperature, the content of carbon element increased, its specific pore volume and specific surface appeared increasing tendency; However, the content of oxygen element decreased, its average porous diameter became smaller and smaller, its resistivity decreased gradually, and its graphite-like crystal structure became regular and orderly. At the same carbonization temperature, with the increasing of carbonization time, the content of carbon element increased gradually, the content of oxygen element appeared decreasing tendency, its resistivity decreased gradually, moreover, its resistivity decreased accompanied with the lower of crystal structure Parameters(La、Lc、d002)7) Below 300℃, the rate of weight loss of precursor was 5.07%, pyrolysates of precursors included CO, CO2, phenol and CH2O; Between 300℃and 600℃, its rate of weight loss reached 41.20%, pyrolysates of precursors included CO, CO2, CH4, benzene, methylbenzene, phenol, methylphenol,2-methylphenol and Partial polymers; Between 600℃and 1000℃, the rate of weight loss was only 3.33%, the precursors were decomposed to CO2 and methylbenzene.更多还原