渗硼处理对木质碳纤维力学性能的影响

Effect of boron impregnation on tensile strength of wood-based carbon fiber

【目的】针对木材苯酚液化物制备的木质碳纤维存在力学强度低且性能不稳定等问题,对木质碳纤维原丝进行渗硼处理,以改善其力学性能。【方法】分别用质量分数为5%和8%的硼酸溶液浸渍木质碳纤维原丝1h,再于900℃下碳化1h制得木质碳纤维。采用扫描电镜、X射线衍射、红外衍射谱图分析等方法,对改性后的原丝及碳纤维的力学性能及微观构造进行对比分析。【结果】经质量分数5%硼酸溶液改性的木质碳纤维原丝和碳纤维的拉伸强度分别达到0.195和0.468GPa,与未经渗硼处理的对照相比分别增加了40.29%和44.89%;从表面形态看,渗硼后的碳纤维与未经渗硼处理的碳纤维相比,表面缺陷和内部孔隙均明显减少,内部结构也相对致密;不同条件处理的原丝及碳纤维在2θ=20°附近出现了明显的衍射峰,随着炭化过程的进行,衍射峰的位置明显向高角方向移动,半高峰宽有增大的趋势,纤维的微晶参数基本稳定在一定范围内;炭化过程使得碳纤维的结构发生较大变化,几乎所有的特征吸收峰都发生了变化。【结论】渗硼处理能够有效提高碳纤维的力学强度,其原因主要是硼原子通过间隙扩散进入碳层,消除了部分孔洞缺陷,使得碳结构层相互靠近,碳网的聚合度增大。

【Objective】Wood-based carbon fiber derived from liquefied wood has shortcomings such as low mechanical strength and unstable performance.To improve mechanical properties of wood-based carbon fibers,wood-based carbon fiber precursors were impregnated in boric acid aqueous solutions with different concentrations.【Method】Wood-based carbon fiber precursors were impregnated in boric acid solutions with concentrations of 5% and 8%for 1h,before being carbonized at 900℃for 1h.The mechanical properties and microscopic structure of modified wood-based carbon fiber precursors and carbon fibers were studied through SEM,XRD and FTIR infrared analysis.【Result】The tensile strength of wood-based carbon fibers and precursors reached 0.195 GPa and 0.468 GPa,with increases of 40.29% and 44.89%,respectively.Compared with the untreated carbon fibers,the surface defects and internal porosity of impregnated carbon fibers were decreased significantly while the internal structure was denser relatively.There were obvious diffraction peaks in the 2θ=20°range for all precursors under different treatment conditions.The positions of diffraction peaks shifted to high angle direction and the half-height widths of diffractionpeaks had an increasing tendency as the processing of carbonization.Microcrystalline parameters of carbon fibers were stable within a certain range.The carbon fibers had large changes in structure due to carbonization.Almost all the characteristic absorption peaks were changed.【Conclusion】Boron impregnation could improve the tensile strength of carbon fibers mainly because boron atoms permeated through gap into carbon layer,reduced holes in carbon network,made carbon structure layer closer to each other and augmented polymerization degree.