Development and structural investigation for nano-graphite energy storage materials

采用机械球磨法在氢气气氛下制备了纳米石墨。用X射线衍射法对球磨过程中的样品进行了研究。随着球磨时间的增加，中间层的长程有序性不断消失。在研磨80小时后，氢浓度达到7.4质量%。为了获得更多的详细原子排列和氢原子在石墨中的位置信息，用中子衍射测量了样品的结构因子S（Q），直到Q=50 A^<-1>。石墨中的构象通过悬挂键的产生而改变，并且在RDF（r）中明显观察到由于石墨中的氢（氘）原子而产生的新峰，RDF（r）由S（Q）的傅立叶变换导出。在径向分布函数RDF（r）中发现了两种氘配位形式。在氢气气氛下机械球磨80 h后，石墨的热脱附性质得到了进一步的研究。热脱附质谱中观察到了两个氢分子的脱附峰，分别出现在600和950 K附近。这一结果表明，纳米结构石墨有望保留两种类型的结构，并具有合适的储氢捕集位置，因此，我们认为，通过机械研磨制备的纳米结构石墨是最有效的大量储氢介质之一。

Nano-structured graphite was prepared by mechanical milling under hydrogen gas atmosphere. The sample during the milling process was studied by X-ray diffraction. The long-range ordering of the interlayer disappears continuously with increasing milling time. The hydrogen concentration reached up to 7.4 mass% after milling 80 hours. In order to get more information of the detailed atomic arrangement and the location of hydrogen atoms in the graphite, the structure factors S(Q) of the samples were measured up to Q=50 A^<-1> by neutron diffraction. The conformation in the graphite was changed by the creation of dangling bonds and the new peaks due to the hydrogen (deuterium) atoms in the graphite were apparently observed in RDF(r), which was derived from the Fourier transformation of S(Q). Two types of the deuterium coordinations were found in radial distribution function RDF(r). One is the C-D covalent bond and the other is deuterium located between layers of the graphite.The next work was carried out to clarify the thermal desorption property for the sample mechanically milled for 80 h under hydrogen atmosphere Two desorption peaks of hydrogen molecule, starting at about 600 and 950 K, respectively, were observed in thermal desorption mass spectroscopy. This result indicates that the nano-structured graphite is expected to retain two types of structures with suitabl e trapping sites for hydrogen storage.Therefore, the results lead us to believe that nano-structured graphite prepared by mechanical milling constitutes one of the most effective media for the absorption and retention of large quantities of hydrogen.