Daiki Nakajima

Ultra-High Density Single Nanometer-Scale Anodic Alumina Nanofibers Fabricated by Pyrophosphoric Acid Anodizing

Anodic oxide fabricated by anodizing has been widely used for nanostructural engineering, but the nanomorphology is limited to only two oxides: anodic barrier and porous oxides. Therefore, the discovery of an additional anodic oxide with a unique nanofeature would expand the applicability of anodizing. Here we demonstrate the fabrication of a third-generation anodic oxide, specifically, anodic alumina nanofibers, by anodizing in a new electrolyte, pyrophosphoric acid. Ultra-high density single nanometer-scale anodic alumina nanofibers (10(10) nanofibers/cm(2)) consisting of an amorphous, pure aluminum oxide were successfully fabricated via pyrophosphoric acid anodizing. The nanomorphologies of the anodic nanofibers can be controlled by the electrochemical conditions. Anodic tungsten oxide nanofibers can also be fabricated by pyrophosphoric acid anodizing. The aluminum surface covered by the anodic alumina nanofibers exhibited ultra-fast superhydrophilic behavior, with a contact angle of less than 1°, within 1 second. Such ultra-narrow nanofibers can be used for various nanoapplications including catalysts, wettability control, and electronic devices.

Spontaneous colloidal metal network formation driven by molten salt electrolysis

The molten salt-based direct reduction process for reactive solid metal outperforms traditional pyrometallurgical methods in energy efficiency. However, the simplity and rapidity of this process require a deeper understanding of the interfacial morphology in the vicinity of liquid metal deposited at the cathode. For the first time, here we report the time change of electrode surface on the sub-millisecond/micrometre scale in molten LiCl-CaCl2 at 823 K. When the potential was applied, liquid Li-Ca alloy droplets grew on the electrode, and the black colloidal metal moved on the electrode surface to form a network structure. The unit cell size of the network and the number density of droplets were found to depend on the applied potential. These results will provide important information about the microscale mixing action near the electrode, and accelerate the development of metallothermic reduction of oxides.