STUDY ON THE PREPARATION OF MANGANESE DIOXIDE VIA CATHODIC ELECTROLYSIS

A novel synthesis method was developed to prepare manganese dioxide via cathodic electrolysis in potassium permanganate solution. The morphology and the composition of the synthesized products were analyzed by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The electrolyzed products include two kinds of materials: amorphous and crystalline manganese dioxide. The manganese dioxides were formed by cathodic reduction via two reaction mechanisms: direct and indirect electrochemical reactions. The electrolysis current performance strongly depends on the electrolyte solution temperature, applied voltage and not clearly depends on electrolyte solution concentration. With high current performance and uniformity products, the cathodic reduction of potassium permanganate is promising method for manganese dioxide fabrication.

Influence of Hydrogen-Charging on Oxidation of SUSF316L in Simulated BWR Environment

In order to clarify the effect of hydrogen on oxidation, the austenitic stainless steel SUSF316L was charged with hydrogen by the means of cathodic electrolysis and then the hydrogen-charged steel was subjected to the oxidation test in simulated BWR environment. Experimental results revealed that the size of oxide particle formed on the outer layer increased with increasing hydrogen content, resulting in the hydrogen accelerated oxidation (HAO). Additionally, the oxide of the hydrogen-charged steel was mainly NiFe2O4, whereas Fe3O4 was predominantly formed on the non-charged one. The effect of hydrogen on the oxidation was almost equivalent to that of applied stress.

Microstructure Evaluation of High Chromium Ferritic Steels Based on Hydrogen Desorption Profile Analysis

The thermally aged 10Cr-1Mo-1W-VNbN steels were charged with hydrogen by cathodic electrolysis and then were subjected to the thermal desorption spectroscopic analyses to examine an applicability of hydrogen as a tracer for evaluating the microstructure. The variation in hydrogen desorption characteristics with aging was discussed from the view points of microstructural changes. Experimental results revealed that the amount of hydrogen desorbed, CH, decreased monotonously as the aging proceeded and there was a relatively good correlation between the CH and Vickers hardness. The CH was expected to be a useful indicator for the material degradation. Additionally, the decomposition of the profile was attempted to understand the metallurgical meaning of hydrogen profile and apply the present method to the microstructural evaluation. As the result, it was suggested that the changes in two decomposed profiles with aging might reflect the variation of dislocation density and the precipitation process of M23C6 carbide and/or Laves phase, respectively.