コウシュウハ イオンプレーティング ホウ ニ ヨル ハクマク ケイセイ ニ カンスル ケンキュウ

The nanostructural hydrogenated graphite (CnanoHx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (―CH, ―CH2, and ―CH3) are realized in the nanoscale. By synthesizing the composite of CnanoHx and lithium hydride (LiH), known as the Li―C―H system, hydrogen was desorbed at 350 °C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C―H groups in CnanoHx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li―C―H system, it is an important issue to investigate the change in the C―H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C―D and Li―D correlations are found from the radial distribution function [RDF(r)] obtained by the neutron diffraction for the CnanoDx and LiD composite. After dehydrogenation, C―C triple bond and Li―C bond, ascribed to lithium carbide (Li2C2), are observed. Furthermore, the RDF(r) corresponding to rehydrogenated composite indicates the presence of not only the Li―D correlation but also the C―D one

Anomalous hydrogen absorption on non-stoichiometric iron-carbon compound

On the synthesis of nano-structural hydrogenated graphite by ball-milling under H-2 atmosphere, iron contamination was mingled from steel balls during ball-milling. It is clarified by spectroscopic measurements that the mingled iron formed a non-stoichiometric iron-carbon (Fe-C) compound. The Fe-C phase was transformed to a well-ordered phase with H-2 desorption at 450 degrees C, suggesting that the hydrogen atoms were anomalously trapped at the Fe-C phase. With respect to hydrogen absorbing properties, the mingled iron enhanced the hydrogen capacity by about 50% compared with iron free hydrogenated graphite, where H/Fe was about 13 mass%. Therefore, if the hydrogen absorption site originated in the Fe-C phase could be synthesized independently, it should be recognized as a promising hydrogen storage system