Development and structural investigation for nano-graphite energy storage materials

在氢气气氛下，采用机械研磨法制备了纳米结构石墨。用x射线衍射法对样品的铣削过程进行了研究。随着铣削时间的增加，中间层的长程有序逐渐消失。制粉80 h后，氢浓度达到了7.4质量%。为了更详细地了解石墨中的原子排列和氢原子的位置，用中子衍射法测量了样品的结构因子S(Q)，测量值高达Q=50 A^<-1>。悬空键的产生改变了石墨的构象，石墨中的氢（氘）原子在RDF(r)中明显地观察到新的峰，这是由S(Q)的傅里叶变换得出的。在径向分布函数RDF(r)中发现了两种类型的氘配位。一个是C-D共价键，另一个是位于石墨层之间的氘。在热解吸质谱中观察到两个氢分子的解吸峰，分别从600 K和950 K开始。这一结果表明，纳米结构石墨有望保留两种类型的结构，并具有合适的氢捕获位点。因此，研究结果使我们相信，通过机械铣削制备的纳米结构石墨是吸收和保留大量氢的最有效介质之一。

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.