【作者】 顾安妍；

【导师】 张胜涛；

【作者基本信息】 重庆大学 ， 化学， 2010， 硕士

【摘要】 膨胀石墨（EG）是由天然鳞片石墨经氧化、插层、水洗、干燥及高温膨胀而得到的一种疏松多孔的物质,是一种新型的导电材料。本论文研究以HNO3和H2SO4共同插入法、分步插层法和电解氧化法制备EG的工艺路线,探讨主要因素对膨胀体积的影响规律,正交试验优化EG的制备条件,测试优化条件下制得石墨层间化合物（GICs）的各项技术指标,并采用扫描电镜、X射线衍射、红外光谱和热分析等现代分析技术对优化的工艺条件得到的GICs进行表征,确定其结构、形貌等相关信息。将制得的EG与丙烯酸树脂复配,分析了填料的含量与涂层表面电阻率的关系。本论文的主要研究结果如下:1)采用HNO₃、H₂SO₄共同插入法制备了在900℃下膨胀体积达到290ml/g的EG。优化的工艺条件为:混酸量为60g,KMnO4用量为1.8g,硝酸与硫酸的质量比为1:3,反应时间是50min。制得的EG具有蠕虫状蓬松结构,石墨蠕虫由许多微胞连接在一起组成。微胞间的狭缝宽度为40⁵0μm。插入剂破坏了鳞片石墨晶体结构,但是未破坏石墨的C-C键,X射线衍射峰对应2θ为29.5°处的特征峰是插层物结晶区引起的。GICs片层间存在SO₄²⁺和NO₃^-,500℃前热失重达21.452%,这是由插层物的气化、分解所致。2)采用分步插层法制备的EG在900℃下膨胀体积可达300mL/g。分步插层法是一次插层后再插入低沸点甲酸,有利于得到更高膨胀体积的EG,同时降低了GICs的含硫量。优化工艺条件为:混酸量为60g,KMnO4用量为2.2g,硝酸与硫酸比为1:3,反应时间为50min,在甲酸中浸泡2小时。分步插层法获得的GICs石墨层比较疏松,层间距离较大。EG有良好的孔隙结构,从表面观察为许多网状的多边形孔,孔隙开口比HNO₃、H₂SO₄共同插层EG的深。插入剂破坏了鳞片石墨晶体结构,但是未破坏石墨的C-C键,X射线衍射峰对应2θ为28.5°处的特征峰是插层物结晶区引起的。GICs片层间存在SO₄²⁺、NO₃^-和COOH^-,500℃前热失重达15.156%。3)采用电解氧化法制备的EG在900℃下膨胀体积达到200ml/g。硫酸的质量分数控制在75 %左右最佳,优化的电流密度为0.75 A/m2 ,m（H₂SO₄）:m（KMnO4）=90:1为宜,较好的电解氧化时间为5小时。电解氧化后的EG层间显得较为松散,呈层状开裂。插入剂破坏了鳞片石墨晶体结构,但是未破坏石墨的C-C键,X射线衍射峰对应2θ为29.6°处的特征峰是插层物结晶区引起的。GICs片层间存在SO₄²⁺,500℃前热失重达10.766%。4)以鳞片石墨做导电填料的涂层渗滤阈值为33.33 wt.%,表面电阻率最低为1.76×10⁴Ω·cm^-2,当含量大于41.18 wt.%,表面电阻率有所回升。以EG为导电填料的涂层渗滤阈值（0.5 wt.%）很低。当填料含量大于2 wt.%后,相同质量分数条件下EG为填料的涂层电阻率比鳞片石墨为填料的涂层低约10个数量级,并且非常稳定。更多还原

【Abstract】 Exfoliated graphite （EG） is a porous and conductive material which is produced by natural flake graphite by means of oxidation, inserting, watering, dryness and expansion. In this thesis, what to study was to synthesize EG by chemical and electrochemical methods. The influence factors were discussed in detail,and the best reaction conditions were obtained by orthogonal tests. Specifications of graphite intercalation compounds （GICs） were tested. In addition, the structure and apparent performance of GICs were studied by means of XRD, SEM, TGA, and IR. In the present investigation,three acrylic resin / graphite conductive coatings were prepared from natural flake graphite, EG prepared by chemical method and EG prepared by electrochemical method, respectively. Surface resistivity was tested, and relationships of content and surface resistivity were investigated. The main research work was as follows:1) EG were prepared by a chemical method from natural flake graphite, using sulfuric acid and nitric acid mixing as intercalation agent and potassium permanganate as oxidant. EG with 290 ml/g exfoliation volume at 900℃was obtained in the best process condition. The optimum conditions of processing were obtained as follows: the amount of mixed acid was 60g, weight ratio of nitric acid to sulfuric acid in mixed acid was 1:3, 2.5 g of KMnO₄ was the best amount, and reaction time was 50 min. The exfoliated domain had a multilayer structure with many diamond-shaped pores. EG is worm-like or accordion-like and microcells are held together at their edges. Crystalline of graphite was damaged because of oxidation intercalation, but the C-C bond was not undermined. The medial strength feature diffraction peak of GICs at 2θ=29.5o was also determined by the damaged graphite crystalline. Sulfuric acid and nitric acid were intercalated into the graphite layers. The thermal event in GICs occurred at 71 500℃,which attained 21.45%, which seemed to be evidence for a removal of the intercalate from GICs.2) EG with 300 ml/g exfoliation volume at 900℃was obtained, which was prepared by the step method in the best process condition. The optimum technological conditions are as follows: the amount of mixed acid was 60g, weight ratio of nitric acid to sulfuric acid in mixed acid was 1:3, 2.2 g of KMnO4 was the best amount, reaction time was 50 min, and it was dipped in formic acid for two hours. Graphite layers of GICs appeared relatively looser than that of natural flake graphite,and EG possessed better pore structure. Crystalline of graphite was damaged because of oxidation intercalation, but the C-C bond was not undermined. The medial strength feature diffraction peak of GICs at 2θ=28.5o was also determined by the damaged graphite crystalline. Sulfuric acid, nitric acid and formic acid were intercalated into graphite layers. The thermal event in GICs occurred at 89 500℃,which attained 21.45%, which seemed to be evidence for a removal of the intercalate from GICs.3) EG with 200 ml/g exfoliation volume at 900℃was obtained, which was prepared by the electrochemical method in the best process condition. Experimental results show that the best process conditions were following: the current intensity was 0.75 A/m2, the sulfuric acid concentration was 75%,m（H2SO4）:m（KMnO4）=90:1,and reaction time was 5 hours. Graphite layers of GICs appeared relatively looser than that of natural flake graphite. Crystalline of graphite was damaged because of oxidation intercalation, but the C-C bond was not undermined. The medial strength feature diffraction peak of GICs at 2θ=29.6o was also determined by the damaged graphite crystalline. Sulfuric acid was intercalated into the graphite layers. The thermal event in GICs occurred at 266 500℃,which attained 10.766%, which seemed to be evidence for a removal of the intercalate from GICs.4) When natural flake graphite was used as conductive filler, percolation threshold of coating was 33.33 wt. % and surface resistivity was decreased obviously to 1.76×10⁴Ω·cm^-2. The coating with EG as conductive filler possessed a lower percolation threshold （0.5 wt. %） and a better electrical conductivity, reaching about 20.8Ω·cm^-2Ω, which was nearly independent of the amount of the EG.更多还原