Figure 2 (IMAGE) Tohoku University Caption Optical micrographs of the polyaniline layer on pure Ni. Because hydrogen atoms diffuse in pure Ni with time, the flow of hydrogen atoms is visualized as a color change of the polyaniline layer (from purple to white). The color-changed area of the polyaniline layer corresponded to the grain boundaries of pure Ni, meaning that the grain boundaries are the preferential hydrogen diffusion path in pure Ni. Credit Acta Materialia Usage Restrictions Credit must be given to the creator. License CC BY Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.