导　　师： 黄正宏

学科专业： 0805

授予学位： 硕士

作　　者： ;

机构地区： 清华大学

摘　　要： 电容式脱盐是利用多孔电极材料在直流电场作用下产生的电吸附作用去除溶液中带电离子的一种新兴脱盐技术，具有能耗低、无污染、可再生等优点。作为电容式脱盐装置的核心，高比表面积、自支撑而且为柔性的电极材料具有更高的脱盐性能。静电纺丝制备的酚醛基碳纤维具有酚醛基碳材料碳产率和比表面积较高的优势，又因为其直径更细，可以改善传统酚醛基碳纤维力学性能较差的缺点，因而有可能具有更优异的电容式脱盐性能。但是目前见于报道的电纺制备酚醛基碳纤维依然存在力学性能差、制备工艺繁琐、制备成本高等问题。因此，有必要对其制备工艺进行优化，以获得低成本高柔韧性的自支撑酚醛基碳纤维毡，使其成为更具竞争力的电容式脱盐用电极材料。 本文采用市售的低分子量可溶性酚醛树脂作为前驱体，分别以热塑性酚醛树脂、热固性酚醛树脂及其混合物的溶液，通过电纺工艺制备出了均匀连续的酚醛纤维。对其固化工艺的研究表明：热固性酚醛树脂的比例较高时，可以通过浸渍固化液和分阶加热实现其固化。浸渍固化液后，纤维紧密堆叠在一起，导致固化纤维毡的柔韧性降低；而分阶加热时，纤维既能充分交联，又能保持疏松的网络结构，因而具有非常优异的柔韧性。 对热固性酚醛树脂电纺工艺的深入研究表明：在热固性酚醛树脂中掺入少量聚乙烯醇缩丁醛（PVB）可以有效改善其可纺性，当调节溶液的浓度在35wt/%以下，而粘度在15-30mpa s之间时，可以获得均匀连续的带状酚醛纤维。针对带状纤维成因的分析表明：热固性酚醛树脂的非线性分子结构及其溶液较高的导电性有利于获得带状纤维，而溶剂的挥发速率过高或者过低都不利于带状纤维的形成。 电纺酚醛纤维的碳化产物具有良好的柔韧性，其比表面积在1000℃时达到最大值，为858m2//g。采用水蒸气在900℃活化30min可以获得比表面积在1300m2//g的活性碳纤维，同时保持了较好的宏观力学性能。对其电容式脱盐性能测试表明，酚醛基活性碳纤维在初始浓度100mg//L的NaCl溶液中的物理吸附量较高，一定程度上降低了可逆吸附量。但是活化样品的孔径大，比表面积高，而且为柔性自支撑结构，因而具有更快的电吸附速率和电容式脱盐容量，其可逆吸附量达到了7.6mg//g，高于相同条件下的其他材料。 Capacitive deionization /(CDI/) is a newly developed desalination method byadsorbing charged ions from aqueous solution onto the surface of porous electrodematerials under external power supply, which has many advantages like energy-saving,regenerative, pollution-free and etc. According to literatures, the choice of flexible andfree-standing electrode materials with high specific surface area is the critical issue forthe success of CDI. Compared to conventional phenolic resin-based carbon fibers, electrospun phenolicresin-based carbon fibers not only retain the high carbon yield and high specific surfacearea, but also will improve the mechanical properties due to smaller fiber diameter. Butup to now, electrospun phenolic resin-based carbon fibers reported in the literatures stillhave some disadvantages like poor mechanical properties, complex procedures, and etc.Thus it is necessary to optimize the preparation method of electrospun phenolicresin-based carbon fibers. Free-standing phenolic resin-based carbon mats with highflexibility and low cost could be competitive electrode materials for CDI. In this work, we prepared uniform and continuous phenolic resin fibers byelectrospinning solutions of thermosetting phenolic resin /(resol/), or thermoplasticphenolic resin /(novolac/), or their mixture. All of them are commercially available, thushave low cost. It was found that as the ratio of resol increased, electrospun phenolicresin fibers could be cured by immersing in curing solutions, or by stepped-heating atlow temperature in air. After immersed in curing solutions, the fibers closely stackedtogether, resulting in poor flexibility of the mats. But for stepped-heating, the fibermats can completely cross-linked while maintaining a loose network structure, and thushas excellent flexibility. In-depth study of electrospinning process of resol solutions showed that by addinglittle amount of polyvinyl alcohol butyral /(PVB/), its spinnability was effectivelyimproved. While the solution concentration is less than35wt/%, and the viscosity isbetween15-30mpa s, uniform and continuous beads-free phenolic resin ribbons couldbe obtained. Further study indicates that the non-linear molecular structure of resol andits relatively high solution conductivity is in favor of the formation of ribbons, while the solvent with too high or too low evaporation rate is not conducive to the formation ofribbons. After being stepped-heated, the cured electrospun phenolic resin fiber mats werefurther carbonized and activated. All of the carbonized samples show great flexibility,and the maximum specific surface area858m2//g was obtained at1000℃. For steamactivation, while activated at900℃for30min, carbon mats with good mechanicalproperties and high specific surface area of1343m2//g was obtained. Capacitive deionization characterization shows that, while the initial concentrationof NaCl solution is100mg//L and the applied voltage is1.2V, the physical adsorptioncapacity of electrospun phenolic resin-based activated carbon fibers is very high, whichmay reduce the reversible adsorption capacity. But the larger pore width, higher specificsurface area, flexible and free-standing structure, still lead to faster adsorption rate andhigher reversible adsorption capacity, which reaches7.6mg//g，higher than that of othermaterials tested under similar conditions.

关 键 词： 酚醛树脂 静电纺丝 带状碳纤维 酚醛纤维 电容式脱盐

分 类 号： [TQ342.742]

领　　域： [化学工程]