【作者】 高晓月；

【导师】 贾虎生；

【作者基本信息】 太原理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 在众多形式各异、功能独特的碳材料中,碳微球以其结构形貌规整、导热系数高、耐热性能良好、物理与化学性能稳定等优越性,引起研究人员的广泛关注,在电磁学、生物、物理、化学化工、材料学等多个领域具有巨大的应用价值。因此,碳微球的制备与研究工作具有重要意义。在众多的制备方法中,水热法具有原料价廉易得、成本投入低、生产能耗少、工艺绿色环保、设备简单易操作等优点,成为近年来制备碳微球的研究热点。本论文以纤维素为原料,分别以去离子水和添加不同质量分数的乙醇溶液为分散剂,采用水热法成功制备了碳微球材料。通过单因素实验,研究了碳化温度、反应时间、原料投料比以及助剂(无水乙醇)添加量等参数对碳微球微观形貌、晶态结构及表面官能团的影响规律,同时对纤维素水热碳化的机理作了分析和探讨,并对添加乙醇助剂所得碳微球的电化学性能进行了初步测试。研究工作得出的主要结果如下：(1)选取纤维素棉浆为原料、去离子水作分散剂,采用水热法制备得到微米级的碳微球,通过碳化温度和反应时间可调节微观形貌、晶态结构及粒径尺寸。碳化起始温度为230℃,此后随温度升高纤维素转变为无定形的碳粉末材料；随着反应时间的延长,产物的球化趋势随之增大,碳微球的形貌良好,但同时球颗粒的粒径均匀度降低。(2)以纤维素为碳源、乙醇水溶液为分散剂,利用水热碳化法制得碳微球材料。最佳反应参数为：原料与分散剂的投料比为1.Og/25mL、助剂乙醇的质量分数为60wt%、碳化温度为320℃、保温时间为24h。在此实验条件下,可合成出形貌良好、粒径均匀、成球率高的碳微球。(3)利用水热法制得的碳微球,其表面可直接生成羟基、羰基、羧基、醛基及末端炔基等官能团,且反应过程有一定的芳构化。即：碳化过程与表面功能化改性可一步完成,省却了传统碳材料制备工艺中的表面修饰和改性工作。(4)添加乙醇助剂制得的碳微球材料呈现一定的石墨化,在循环伏安性能测试中表现出可逆电容量的改善和提高。乙醇百分量达到60%时,碳微球材料的电容量和充放电时间达到最佳。同时发现,成球数量越高,石墨化度越大,电极材料的比容量的衰减程度越低。更多还原

【Abstract】 In recent years, much attention has been attracted to the carbonaceous microshperes for many investigators, owing to the trim structure, morphology, unique thermodynamical properties, physical and chemical stabilities. Compared to different forms of functional carbonaceous materials, carbon microspheres have been motivated by the potential applications in various fields ranging from electromagnetism, biological sciences, physics, chemical industry, and materialogy. Accordingly, the synthesis of carbon spheres attracts considerable significance for both academic and industrial fields. A process, termed hydrothermal carbonization (HTC), appears especially important contributed to the low cost, renewable resource, simplicity facility, economic and environmental procedure, and has generated widespread interest recently.The thesis focused on the preparation of carbonaceous spheres materials via hydrothermal carbonization. Cellulose as raw materials was dispersed in deionized water and different mass percents of ethanol solution, respectively. The effects of various reaction parameters on superficial morphology, crystalline structure and functional group were evaluated, including carbonization temperature, reaction time, rate of charge and additive amount. Meanwhile, the carbonization mechanism of cellulose and electrochemical performance of carbon spheres through alcohol additions preliminarily were investigated.The main conclusions are summarized as follows:(1) Using cellulose as precursor and deionized water as dispersant agent, carbon microspheres were synthesized by means of hydrothermal process. Superficial morphology, crystalline structure and partical size were modulated through carbonization temperature and reaction time. The result suggest the onset of hydrothermal reaction occurred at around230℃. In the wake of reaction time lengthening, the spheroidization and morphology of products became well, whereas the partical homogeneity got low.(2) Carbonaceous spheres materials were prepared via hydrothermal method, with cellulose was dispersed in ethanol solution. The optimal reaction parameter was as follows:the ratio of charge was1.0g/25mL, mass fraction of ethanol was60wt%, carbonization temperature was320℃and time was24h. In this condition, regular morphology and uniform grain size could be synthesized successfully.(3) The shell of carbonaceous microspheres possessed directly reactive functional group, such as hydroxyl, carbonyl, carboxyl and aldehyde. Even it generated aromatization in the core. That is, not only carbonization but also functional modification could be achieved concurrently. It dispensed with the surface modification treatment in the traditional preparation of carbon materials.(4) Carbon micro-spheres which were produced by means of ethanol additives displayed graphitization and presented the improvement of reversible electric capacity in cyclic voltammetry. The electric capacity and charge-discharge time attained optimum while mass fraction of ethanol was60wt%. Meanwhile the result showed specific capacity attenuation weakened with carbon spheres got more and the degree of graphitization became higher.更多还原