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通过全谱拟合法对碳纤维制备过程中不同阶段纤维的XRD谱图进行处理,得到不同阶段纤维的微观结构参数,研究了聚丙烯腈(PAN)基碳纤维制备过程中晶态结构的演变.全谱拟合法基于晶体衍射的严格物理理论,拟合目标为整个衍射谱,并不是个别衍射峰,所得结果具有更高的可信度.研究结果表明:PAN原丝中的高分子链沿纤维轴高度取向,表观晶粒尺寸为6.5 nm左右;经过预氧化处理,纤维中的有序结构遭到破坏,表观晶粒尺寸锐减.纤维中逐渐形成梯形结构并沿纤维轴取向,从而形成新的有序结构;经过碳化处理后,环状梯形结构转变为碳的层状结
关键词:
碳纤维
晶体结构
XRD
全谱拟合法 相似文献
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聚丙烯腈基碳纤维及其原丝中的微孔尺寸分布 总被引:1,自引:0,他引:1
利用二维小角X射线散射技术(SAXS)研究了聚丙烯腈基碳纤维及其原丝的微孔结构。结合逐级切线法、对数正态分布及麦克斯韦分布函数对2类实验样品内部微孔的尺寸分布进行了分析。结果表明,2类样品中的孔结构具有显著差别,原丝微孔在4~8 nm范围内分布比较集中,碳纤维中微孔的分布区域则移向1.3~1.8 nm。散射数据显示出明显的分形特征,碳纤维与其原丝的孔分形维数分别为1.33和1.55,表明原丝中具有较大的孔隙缺陷。相对于原丝,碳纤维微孔尺寸分布走向均匀和集中,前者则表现出比后者更宽的尺寸分布。就拟合方法而言,逐级切线法的解析手段容易引入误差,低角区的纤维表面散射和高角区的噪音容易对其结果造成影响。正态分布得到了比较窄的尺寸分布,但对于低尺寸区域孔隙的拟合不理想。麦氏分布在一定程度上弥补了以上不足,能够较好地拟合两类纤维样品中微孔的分布状况。 相似文献
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The nanopore structures in precursors are crucial to the performance of PAN-based carbon fibers. Four carbon-fiber precursors are prepared. They are bath-fed filaments (A), water-washing filaments (B), hot-stretching filaments (C) and drying-densification filaments (D). Synchrotron radiation small angle X-ray scattering is used to probe and compare the nanopore structures of the four fibers. The nanopore size, discrete volume distribution, nanopore orientation degree along the fiber axis and the porosity are obtained. The results demonstrate that the nanopores are mainly formed in the water-washing stage. During the processes of the subsequent production technologies, the slenderness ratio of nanopores and their orientation degree along the fiber axis increase further and simultaneously, the porosity decreases. These results are helpful for improving the performance of the final carbon fibers. 相似文献
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Spherical polyelectrolyte brushes(SPBs) consisting of polystyrene(PS) core and poly(2-aminoethyl methacrylate hydrochloride)(PAEMH) shell were prepared by photo-emulsion polymerization. Au nanoparticles(Au-NPs) with controlled size and size distribution were synthesized in situ using SPBs as nanoreactors. Via layer-by-layer deposition technique on the surface of SPBs, nano-composite particles with Au/Ag-NPs bilayer and Au/Ag/Au-NPs trilayer were prepared. The structures of the as-prepared Au/Ag multilayer SPBs were characterized by UV-Vis spectroscopy, TEM, ICP-AES and DLS. The charge reversal of the nano-composite particles observed by zeta potential confirmed the success of layer-by-layer assembly. The Au/Ag-NPs bilayer nano-composite particles showed high catalytic efficiency with an apparent activation energy of about 41.2 k J/mol in the reduction reaction of 4-nitrophenol to 4-aminophenol in the existence of sodium borohydride monitored. The catalytic activity of Au/Ag-NPs multilayer SPBs close to that of Au-NPs SPBs and much higher than that of Ag-NPs SPBs reveals its potential applications in cost-effective catalysts with high-performance. 相似文献
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Chemical degradation of diglycidyl ether of bisphenol A(DGEBA) epoxy resin cured with an aliphatic amine in supercritical 1-propanol was investigated under different reaction temperature and time. The combination of GC-MS and LC-MS proved that the epoxy resin was decomposed to five main products including phenol, 4-isopropylphenol, 4-isopropenylphenol, bisphenol A, and 4,4’-(cyclopropane-1,1-diyl)diphenol. The 13C-NMR results verified the chemical structures of the degradation products. The change of the products′ yield with time was evaluated by an effective means of HPLC. In addition, the GPC analysis confirmed the formation of soluble low molecular weight clusters during the degradation reaction. A possible free-radical reaction mechanism was proposed for chemical depolymerization of the epoxy resin in supercritical 1-propanol. After the homolytic cleavage of the aromatic ether linkages, the resulting bisphenol A biradical either produced 4,4’-(cyclopropane-1,1-diyl)diphenol after intramolecular rearrangement or generated bisphenol A after capturing hydrogen from 1-propanol. 相似文献