沥青中间相炭微球制备高密高强石墨的工艺与性能研究

发布时间：2018-03-17 22:00

  本文选题：煤沥青　切入点：中间相炭微球　出处：《湖南大学》2016年硕士论文　论文类型：学位论文

【摘要】：沥青中间相炭微球(MCMB)是一种制造高密高强石墨材料的优质前驱体,有关其改性处理和制备工艺的理论研究在实验室和工厂得到了广泛深入的研究并取得较为丰硕的成果。大量研究表明,β树指含量为5%-9%的MCMB因具有良好的自烧结性能和随机取向性,适合于制备高性能高强高密石墨材料。由于本研究所选用的商用MCMB中挥发份含量仅为7.68wt%且β树指含量较低(2.9wt%),自烧结性能较差,因此本文提出了首先采用溶液混合法制备煤沥青改性MCMB,克服粘结剂添加量较少而分散不均匀的问题并改善MCMB自烧结性能,然后再采用常规等静压成型工艺制备高密高强MCMB基石墨材料的新思路,期望能为低挥发份含量MCMB在高强高密石墨材料制备中的应用提供理论与实验指导。首先考察了煤沥青改性前后MCMB的结构与热失重性能变化规律,研究了煤沥青改性MCMB的烧结行为及其对石墨材料性能的影响。结果表明,以THF为溶剂,采用溶液混合法可在MCMB粉体表面均匀包覆一层煤沥青,改性后的粉体中仍有少量残余的THF。在焙烧(炭化)过程中,生坯试样随热处理温度的升高均呈先膨胀后收缩的变化趋势,且收缩率远大于膨胀率。与纯MCMB压制的生坯试样相比,煤沥青改性MCMB压制的生坯试样膨胀阶段的温度上限由450℃C提高至600℃C。600℃C-1100℃之间生坯试样的收缩率、失重率不断增大,电阻率也随着有序度的提高而急剧下降,在焙烧过程中应减小该温度范围内的升温速率以防止产品开裂。适当增加沥青含量可通过增大高温热处理过程中的收缩率提高石墨材料的致密度。其次研究了煤沥青种类和含量对改性MCMB粉体及其所制备的石墨材料结构和性能的影响。实验表明,MCMB粉体中的沥青主要以铺展或超细微粒的形式附着在颗粒表面,少量以大颗粒的形式随机分散在MCMB颗粒之间,其中MS改性MCMB颗粒的表面较粗糙,附着物的覆盖面积最大。三种沥青对MCMB的改性效果排序为：中温沥青(MS)改质沥青(MP)高温沥青(HS),当沥青含量为10wt%、成型压力为150MPa时,所得石墨材料的抗折强度分别为56.9MPa、42.7MPa和27.7MPa。适当提高成型压力和沥青含量可进一步提升石墨材料的强度、密度、硬度及导电性能。最后研究了溶剂种类、脱溶剂温度和时间对石墨材料性能的影响。结果表明,当脱溶剂温度为90℃和脱溶剂时间为12h时,以THF作溶剂、改质沥青改性MCMB制备的石墨材料的抗折强度和体积密度分别为41.0MPa和1.85g/cm3。以THF作溶剂的沥青改性MCMB基石墨材料性能优于以甲苯(TOL)作溶剂的沥青改性MCMB基石墨材料的性能,甲苯等挥发物的大量排除延迟到了300℃之后,即生坯膨胀和致密化重排效应最为剧烈的阶段,阻碍了颗粒间的融并,导致炭/石墨材料孔隙率提高及力学性能和电学性能的下降。
[Abstract]:Pitch mesophase carbon microsphere (MCMB) is a high quality precursor for manufacturing high density and high strength graphite materials. The theoretical research on the modification treatment and preparation process has been extensively and deeply studied in laboratory and factory. A large number of studies have shown that MCMB with 尾 -tree index content of 5- 9% has good self-sintering property. Energy and random orientation, It is suitable for the preparation of high performance high strength and high density graphite materials. Because the volatile content in commercial MCMB is only 7.68 wt% and the 尾 -tree finger content is lower than 2.9 wtC, the self-sintering property is poor. In this paper, firstly, the coal bitumen modified MCMB is prepared by solution mixing method, which can overcome the problem of less binder addition and uneven dispersion, and improve the self-sintering performance of MCMB. Then the conventional isostatic pressing process was used to prepare high density and high strength graphite materials based on MCMB. It is expected to provide theoretical and experimental guidance for the application of low volatile content MCMB in the preparation of high strength and high density graphite materials. Firstly, the structure and thermogravimetric properties of MCMB before and after modification of coal pitch were investigated. The sintering behavior of coal bitumen modified MCMB and its effect on the properties of graphite materials were studied. The results showed that a layer of coal pitch could be uniformly coated on the surface of MCMB powder by solution mixing method with THF as solvent. There is still a small amount of residual THF in the modified powder. During the calcination (carbonization) process, the green samples show a tendency of first expansion and then shrinkage with the increase of heat treatment temperature, and the shrinkage rate is much larger than that of the pure MCMB compacted green sample. The upper limit of the temperature in the expansion stage of the raw green sample pressed by MCMB modified by coal asphalt is increased from 450 鈩，

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