木材苯酚液化生成物碳素纤维化材料的制备及结构性能表征

木材苯酚液化生成物碳素纤维化材料的制备及结构性能 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 征 (作者:马晓军，导师:赵广杰教授) 摘要 为了实现碳纤维原料资源的可持续利用，用木质生物资源替代化石资源，改良生物质碳纤维的工艺缺陷，本论文以速生人工林杉木木材为原料，通过一步法合成法将其苯酚液化产物制备成纺丝原液，熔融纺丝后直接炭化成功获得通用级木材液化物碳纤维。同时利用扫描电子显微镜、红外光谱、X射线衍射、拉曼光谱、元素 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 等多种手段对碳纤维的形貌、结构进行了表征，并对木材液化物原丝及其碳纤维的炭化机理、力学性能、热力学特性以及比表面积、孔隙分布等物理性能进行了系统研究。 得到主结论如下: 1. 以木材苯酚液化物为原料，加入六次甲基四胺后熔融纺丝，将熔纺纤维置于甲醛和盐酸溶液中固化处理后制成最大拉伸强度达365MPa的碳纤维原丝，并研究了纺丝液合成因素和拉丝工艺因素对木材液化物原丝性能的影响。结果表明，原丝的拉伸强度随苯酚/木材比、合成温度以及收丝辊的转速的增加而增加;随着合成剂用量的增加而逐渐减小;随着纺丝液合成升温时间、固化液中盐酸浓度以及固化时间的增加而先增加后减小。 2. 研究了木材苯酚液化物纺制碳纤维原丝的分子转化过程和反应机理。液化物中加入的甲醛给与体(六次甲基四胺)与液化中未反应完全的游离苯酚进行加成反应形成新的羟甲基，同时羟甲基之间或羟甲基和苯环上活波H之间发生缩合反应，形成次甲基醚键和亚甲基键，分子内交联程度较低，形成具有可拉丝的线性结构的纺丝液; +初始纤维经过酸性固化液处理后，纤维中芳环与固化液中的CHOH离子发生了交联2 反应，苯环上的活波氢原子数量减少，同时次甲基醚键转化为亚甲基键，以及酚羟基 +之间、酚羟基与固化液中生成的CHOH离子之间发生了脱水缩合反应，纤维的交联2 度增大，初步形成网状结构，原丝纤维的力学性能大幅度增加 3. 对木材苯酚液化物、纺丝液、原丝的热力学特性进行了综合评价。150,600?是液化物、纺丝液、原丝的主要热失重区间，其热失重分别达到36.9%、41.3%、43.3%;600?以后，原丝在此阶段发生了明显的二次热解重组;三种材料的残余重量的比率说明原丝和纺丝液比液化物的热稳定性好。木材苯酚液化物原丝的DSC曲线上在0,600?之间存在两个明显的放热峰，且随着升温速率的增加，原丝的放热峰向高温方向移动，放热峰的峰形加宽变大;利用Kissinger和Crane公式，求得原丝的第一个放热 -1 峰的表观活化能为69.36 KJ?mol，反应级数为0.862;第二个放热峰的表观活化能 -159.02KJ?mol;反应级数为0.734。 4. 研究了炭化因素对木材液化物碳纤维力学性能的影响。木材液化物碳纤维的力学性能随炭化温度和炭化时间的增加而显著提高;随着炭化升温速率的增加而逐渐下降。同时，原料中木材/苯酚比越大，其碳纤维的拉伸强度和拉伸模量增幅比例越大，且直径收缩越小。优化炭化工艺后，木材液化物碳纤维的拉伸强度、模量、炭化率可分别达到1.7GPa、159GPa和60%。 5. 研究了木材液化物碳纤维的微晶结构及在炭化过程中的变化规律。炭化温度400?以上，原丝的X射线衍射(002)衍射峰随着炭化温度的提高而明显增强;同时碳丝出现了较明显的(100)衍射峰。木材液化物碳纤维的微结构d、d值随炭化()()002100温度的升高逐渐减小，La、Lc、Lc/d值先减小后增大，表征材料石墨化程度的g值()002 由小变大。另外，500?以上得到的碳丝其拉曼光谱谱图中都出现了具有类石墨炭材料典型马鞍状的表征无序结构的D峰和表征石墨微晶的G峰。随着炭化温度的提高，D峰衍射强度逐渐减小，G峰衍射强度逐渐增大，材料的无序化度R值逐渐减小。 6. 研究了炭化过程中木材液化物原丝的结构变化。在炭化处理过程中木材苯酚液化 -1-1-1-1-1物纤维的红外光谱其3444cm、2924,2852cm、1632 cm、1454cm、900,650cm处的吸收峰都发生了明显的减弱，说明随炭化温度的提高，纤维的结构发生了较大的改 -1-1变;但1632 cm、1454cm处芳环骨架中碳碳双键吸收峰的减弱速度较慢，并且在1000?以下的炭化处理中没有消失，表明1000?以下木材苯酚液化物原丝炭化处理是一个难石墨化的过程;红外光谱的变化显示500?和800?附近成为其炭化处理的两个关键温度 -1段;另外，2378,2311cm处出现与P-H伸缩振动相关吸收峰成为木材苯酚液化物碳纤维具有较强荧光的佐证，其原因主要是木材液化时加入的磷酸催化剂所致。 7. 研究了木材液化物原丝的炭化机理。1000?以下木材苯酚液化物原丝的炭化过程较为复杂，可分为三个阶段，第一阶段为300?以下，主要表现为分子内部分醚键断裂和脱羟甲基，产物以CO、CO、、CHO等低分子物质及游离苯酚为主;第二阶段300?,22 600?之间是炭化的关键区间，分子内的网状交联结构被破坏，分子结构体系发生重排，碳网结构初步形成，分解产物除了苯酚、甲苯酚、二甲苯酚等酚类物质和CO、CO、2CH等低分子物质外，苯、甲苯以及部分大分子产物的含量也很高，其主要在500?附4 近逸出;第三阶段为700?以上，碳网结构继续成长，碳网聚合度进一步提高，分子结构在800?附近出现二次调整，分解产物主要以CO和甲苯为主。 2 8. 研究了木材液化物碳纤维的比表面积和孔隙分布特征。木材液化碳纤维的比表面积、BET表面积、微孔面积、总孔容积、微孔容积随着炭化温度的提高呈增大趋势，而孔隙半径却逐渐下降，其中600,800?是木材苯酚液化物碳纤维孔隙结构发生变化的关键温度区间。随着炭化温度的提高，碳纤维的吸附等温线从具有清晰平稳部分的I-A型向I-B型过渡，吸附滞后回线从A类管状毛细孔回线向B类狭缝状毛细孔回线过渡。 关键词:碳纤维，木材液化物，微结构，力学性能，炭化机理 Preparation and Characterization of Carbon Fibrous Material from Liquefied Wood in Phenol (Ma Xiaojun Directed by Prof. Zhang Guangjie) Abstract In order to release the shortage of fossil resource, realize the sustainable development of carbon fiber, change the process defects of tradition biomass-based carbon fiber and efficiently improve the utilization of wood-based resource, carbon fibers (LWCFs) from the phenolated Chinese Fir (Cunninghamia Lanceolata) were prepared by direct carbonization, after the melt-spinning of spinning solution synthesized with one-step reaction. Morphologies, structures of LWCFs have been characterized by scanning electron microscope (SEM), FT-IR spectrometer, X-ray diffraction (XRD), Raman spectroscopy, Elemental analysis, etc. The carbonization mechanisms, mechanical property, thermodynamic behavior and physical properties (including specific surface area and pore distribution) have been investigated. 1. The phenolated wood was modified to spinning solution by adding hexamethylenetetramine, melt-spinning then cured in combined solution of hydrochloric acid and formadehyde to obtain carbon fiber precursors (LWCFPs) with tensile strength 356MPa. The effect factors of spinning solution and spinning process on mechanical properties of LWCFPs have been studied. The tensile strength of LWCFPs increased obviously with increasing the phenol/wood ratio, the synthesis temperature, and the spinning speed, but decreased with increasing synthetics agent content. In addition, the tensile strength of LWCFPs firstly increased and then decreased with increasing synthesis temperature rise time, concentration of HCl, and the curing time. 2. The molecular transformation and reaction mechanism of LWCFPs have been studied. Firstly, formaldehyde (HCHO) from hexamethylenetetramine (HMTA) combined with unreacted phenol during wood liquefaction to produce new hydroxymethyl. At the same time, hydroxymethyl or hydroxymethyl reacting with alive hydrogen of aromatic ring formed diphenyl ether linkage and carbonyl brigdes, so that spinning solution with the low degree of crosslinkage and linearity structure was prepared. Secondly, many aromatic ring of fiber +reacted with CHOH in curing solution during curing reaction; the relative intensity of the 2 out-of-plane CH deformation band decreased; the crosslinkage of fibers were improved; the precursors preliminary had net-crosslinking structure and good mechanical properties. 3. The thermodynamic properties of liquefied wood, spinning solution, and LWCFPs have been comprehensive evaluated. Temperature rang 150~600? was the main weight loss stage for three materials, which were 36.9%, 41.3% and 43.3% respectively. Weight retention ratio illustrated that thermal stability of LWCFPs and spinning solution was better than that of liquefied wood. There were two exothermic decomposition peaks on DSC curves of LWCFPs from 0? to 600?. The location of these peaks move to high temperature with increasing heating rate and the shape of peaks became larger and wider. According to Kissinger and -1-1Crane formula, the activation energy of two peaks were 69.36kJ?mol and 59.02kJ?mol; the reaction order were 0.862 and 0.734, respectively. 4. The influence of carbonization condition on the mechanical properties of LWCFs has been investigated. The mechanical properties of LWCFs increased obviously with increasing carbonization temperature and time, and decreased with increasing the heating rate. The trend of the breaking elongation was opposite to that of tensile strength and modulus. It was also found that, the higher the wood/phenol ratio, the higher the increasing amplitude of mechanical properties, and the smaller the dimension shrinkage. LWCFs with tensile strength of 1.7GPa, modulus of 159GPa and yield of 60% were reached at optimal carbonization conditions. 5. The Variation of microcrystalline structure of LWCFs during carbonization has been studied. Above carbonization temperature 400?, the (002) crystal plane diffraction peak of the precursors at were obviously heighten with the rise of carbonization temperature, and gradually approached to the (002) plane peak of graphitoidal. LWCFs showed obvious (100) crystal plane diffraction peak, which illustrated that this material changed from non-crystal to crystal structure. With temperature rising，the value of dand d decreasd; Values of the ()()002100 crystallite sizes La and Lc, the Lc/drate reduced then increased. The g value corresponding ()002 to the change degree of graphitoidal structure increased. Above 500?, the Raman spectra of carbon fibers appeared the known D band which is related to disorder carbon and G band which corresponds to graphite with varying characteristics that are similar to other graphitoidal material. With carbonization temperature rising, intensity of the D band decreased and that of G band increased; the integrated intensity ratio R=I/I (R-value) which D G is the degree of disorder of material gradually decreased with increasing carbonization temperature. 6. The structure changes of LWCFPs during carbonization have been investigated in -1detail. FTIR absorded band of LWCFPs were evidently weakened in 3444cm，2924, -1-1-1-12852cm，1632 cm，1454cm，900,650cm during carbonization, which indicated that the structure of carbon fiber changed. The intensity of the carbon-carbon double bond at 1632 -1 -1cmand 1454cm, which is corresponding to the characteristic vibrations of aromatic ring, decreased slowly, but both bands did not disappear under 1000?. It indicated that carbonization process of LWCFPs was a typical non-graphitizing course. 500? and 800? are the critical temperature section during carbonization of LWCFPs. The infrared absorption -1band in 2378,2311cm is believed to be P-H stretching vibration band, which is caused by phosphoric acid during wood liquefaction. 7. The carbonization mechanisms of LWCFPs have been studied. The complex carbonization of the precursors was divided into three phases. In the first stage, the carbonization temperature was lower than 350?, the cleavage of intramolecular ether linkage and the removal of end hydroxymethyl mainly occurred, and some molecules such as HO, 2 CO , CHOH and free phenol were found. In the second stage, 300,600 ? was the main 22 rang of carbonization; the bond cleavage occurred at different positions of the most molecule chain; many substance were observed at around 500?, such as phenol, methyl-phenol, dimethyl-phenol, CO, CO,CH, benzene, methylbenzene and so on. In the third stage, the 24 carbon net structure continually developed above 700?; molecule structure took place a further reaction at around 800? accompanying the production of CO and methylbenzene. 2 8. The characteristics on specific surface area and pore distribution of LWCFs have been studied. With increasing heat-treatment temperature, specific surface area, BET surface area， micropore area, total pore volume and micropore volume of carbon fibers increased, but pore radius decline. Temperature rang 600,800? was the critical stage at which the pore structure of carbon fiber changed. The adsorption isotherms of carbon fibers transformed type I-A to type I-B during carbonization, and the desorption isotherms converted from type A with tubular capillary to type B with capillary. Key words: Carbon Fiber, Liquefied Wood, Microstructure, Mechanical Properties, Carbonization Mechanism