【作者】 蔡爱军；

【导师】 刘洪波；

【作者基本信息】 湖南大学 ， 材料学， 2004， 硕士

【摘要】 过渡金属氯化物-石墨层间化合物（GICs）是一类具有特殊结构和性质的石墨层间化合物。不但具有优异的物理化学性能，如高导电性和高选择催化性，而且具有良好的结构稳定性和性能稳定性，还便于规模化合成，因而成为近二十年来石墨层间化合物研究的热点。但利用过渡金属氯化物的可还原性制备具有磁性和原位催化功能的过渡金属-GICs的研究工作，在国内外都很少开展。作为一种新的制备金属-GICs的方法，它的发展无疑将对石墨层间化合物的研究起良好的促进作用。为此本文在合成三元过渡金属氯化物-GICs的基础上，对以H₂作为还原剂制备三元过渡金属-GICs的可行性及其在流动性的H₂气氛中还原FeCl₃-NiCl₂-GICs的工艺条件进行了初步探讨。 本文采用熔盐法，以天然鳞片石墨为宿主，NiCl₂与FeCl₃的混合物为插层剂合成三元FeCl₃-NiCl₂-GICs。考察了石墨与氯化物的摩尔比、NiCl₂与FeCl₃的摩尔比、反应温度和反应时间等工艺因素对产物阶结构和产物中Ni／Fe摩尔比的影响，探讨了NiCl₂与FeCl₃在石墨层间的插层过程。研究结果表明，改变反应体系中石墨与氯化物的摩尔比、NiCl₂与FeCl₃的摩尔比、反应温度和反应时间，可以得到阶结构和Ni／Fe原子比不同的FeCl₃-NiCl₂-GICs。产物的Ni／Fe原子比随反应体系中NiCl₂与FeCl₃的摩尔比的增大、反应温度的提高而增加。当石墨与氯化物的摩尔比为3：1，NiCl₂与FeCl₃的摩尔比为3：7，反应温度为400℃，反应时间为72h时，所得产物为纯一阶FeCl₃-NiCl₂-GIC。反应过程中存在FeCl₃先插入石墨层间，然后NiCl₂逐渐替换FeCl₃的插层反应机制。 根据熔盐法合成三元FeCl₃-NiCl₂-GICs的特点和对上述实验结果的分析，认为FeCl₃和NiCl₂在石墨层间的插入过程可以分成插入物质的演化形成、插入物在宿主石墨表面（边缘）的吸附、插入物在宿主石墨边缘的插入、插入物在宿主石墨层间的扩散与交换、阶结构的形成与转化等五个反应阶段。FeCl₃和NiCl₂插入石墨层间的驱动力来自于反应体系的温度和Cl₂的分压，它们在宿主石墨层间的扩散与交换控制着插层反应的速率。它们在石墨层间以岛屿的形式存在，岛屿的扩散和石墨层面位错的移动导致阶的形成和转化。 在合成三元FeCl₃-NiCl₂-GICs的基础上，进行了FeCl₃-NiCl₂-GICs的H₂还原工艺研究，期望得到具有磁性和催化活性的三元Fe-Ni-GICs。初步探讨了H₂流量、还原温度、升温制度和还原时间等工艺因素对还原产物的结构和还原产物中CI／（Fe+Ni）摩尔比的影响，确立了适宜的还原FeCl₃-NiCl₂-GICs的工艺条件。研究结果表明，采取降低初始还原温度、梯度升温、分步还原的工艺措施，控制适宜的工艺条件可以在流动性的H₂气氛中使FeCl₃-NiCl₂-GICs部分还原成三元Fe-Ni-GICs，还原产物的Cl/（Fe+Ni）摩尔比随还原温度的提高和还原时间的延长而减小。Cl原子在石墨层间与层面上的:电子形成了牢固的化学键和反应体系中H:的压力过小，H:难以扩散进入石墨层间与己插入石墨层间的过渡金属氯化物反应是还原产物中Cl元素含量过高的主要原因。更多还原

【Abstract】 Transition metal Chloride-graphite intercalation compounds (GICs) are a kind of material with special structure and properties. They become the focus among the research of GICs in the latest 20 years because of good physical and chemical properties, such as high conductivity and catalysis, and good structural and capability stability, including which can be bulkily synthesized. However, it is very scarce the research on transition metal chloride-GICs to be reduced to magnetism and in-situ catalysis transition metal-GICs at home and abroad. As a new method of synthesis of transition metal-GICs, it shall be greatly promoting research process on GICs. So based on the experiment of synthesis of FeCl3-NiCl2-GICs, the possibility of synthesis of transition metals-GICs,which reduced by H2, and the FeCl3-NiCl2-GICs reduction conditions in flowing H2 was basically discussed in our present work.FeCb-NiCb-GICs had been synthesized through molten salts method. The natural graphite powder was used as host material and the mixture of NiCl2 and FeCl3 was as intercalant .The paper discussed the influence of reaction conditions such as temperature and time as well as the chlorides molar ratios on the products stage structure and its Ni/Fe molar ratios. The intercalation process was also discussed. The results showed that with the change of molar ratios among graphite, FeCl3 and NiCl2, and the change of reaction time and temperature, FeCl3-NiCl2-GICs, with different stages and Fe/Ni ratios, could be obtained. The products Ni/Fe molar ratio increased with the increasing of NiCl2/FeCl3 molar ratio and reaction temperature. Under the conditions of C/chlorides=3:l, NiCl2/FeCl3=3:7, 400, 72h, the product was approximately a pure stage one FeCl3-NiCl2-GIC. During the reaction process, NiCl2 partially took the place of FeCl3 which was intercalated preferentially.From the characteristic of synthesis of FeCl3-NiCl2-GICs and the result analysis, it could be concluded that during the process of FeCl3 and NiCl2 being intercalated into the graphite, the reaction process may be divided into several steps as follows: evolution of transportable species; absorption of the intercalate onto the surface (or edge) of the host graphite; insertion of the intercalate into the gallery of the host ; diffusion occurred at the interface between the initial stage and pristine graphite. The dynamic of FeCl3 and NiCl2 intercalation into graphite arose from temperate and C12 pressure in the system, and the two mental chlorides exchange and diffusion among graphite layers controlled the reaction rate .The intercalants remained as islands in graphite layers. The formationiiand transform of stages resulted from the islands diffusion and dislocations remove.After synthesis of FeCla-NiCb-GICs, which were reduced by Fk in hope of getting magnetic and catalyst Fe-Ni-GIC, we basically discussed the influence of flow rate of H2, the means of increasing reaction temperature and reduction time on the stage structure and C/(Fe+Ni) molar ratio. The reduction condition was basically concluded. The results showed that lowering the starting temperature, then gradually upgrading temperature for several steps, FeCU-NiCh-GIC can be partially reduced to Fe-Ni-GICs in flowing Fk. The Cl/(Fe+Ni) molar ratio of the reduction product became smaller with reduction temperature increase and reduction time prolong. The key reason of high proportion Cl in the reduction products was that Cl atoms were combined with graphite electrons to form firm chemical bonds. Another important reason was that H2 pressure in the system was too small.更多还原