Electrode Specimen Research Articles

Active-Passive Transition of an Fe-6 mass% Cr Surface in Acidic Sodium Sulfate Solutions Under a Laminar Flow Condition Evaluated by Ellipso-Microscopy and Channel Flow Electrode Method

Electrochemical ellipso-microscopy was combined with the channel flow triple electrode method to evaluate the active-passive transition behavior of Fe-6 mass% Cr in acidic sodium sulfate solutions under the control of mass-transport reaction. During potentiodynamic polarization of the Fe-6 mass% Cr specimen electrode (SE), the SE surface was monitored by ellipso-microscopy and generated Fe(II) and Cr(III) species from the SE were detected at two detector electrodes arranged downstream in parallel. Forced convection of the electrolyte solution affected the mass-transport process of Cr(III) species on the SE surface in the latter half of the active region. In addition, the electrolyte solution flow resulted in enhancement of the passivation process and Cr enrichment on the passive surface. The effects of the electrolyte solution flow on active-passive transition and improvement of the passive film resistance are discussed.

The Investigation of Insulation Breakdown Strength for the Nano-composite Oxide Doped Epoxy Resin Insulator by Using Positive Impulse Voltage in Comparison with Negative Impulse Voltage

This article presents the nano-composite oxides in dielectric materials which are suitable for increasing the efficiency of the destruction of strength and durability against voltage. Tests were conducted to compare the characteristics and details of epoxy resin materials doped with nano zinc oxides by using positive and negative impulse standard voltage to test the destruction of specimen in order to make insulators more efficient and durable against the positive and the negative impulse voltage. This research also studied the abilities of nano-composite oxides to be used as electrical insulators - epoxy resin doped with zinc oxides nano-composite in ratios of 0, 5, 10, 15 and 20% by weight. After that, there were destruction tests by using impulse voltage at levels of 75, 90, 98, and 115 kV connected to the specimen's electrodes immersed in oil transformer by using each voltage level against specimen usage in each of the aforementioned ratios to investigate the damages on insulator surfaces and the number of breakdowns. In viewing damages on insulator surfaces, microscopes with magnification levels of 20-800X were used. From experimental results, it was found that regarding specimens used to doped an epoxy resin with zinc oxides nano-composite and each level of standard positive impulse voltage, in the first round of voltage feeding it was observed that the period of specimens surface destruction was higher than when negative impulse voltage were used, and the breakdown occurrences were also faster increasing than that the of standard negative impulse voltage were used. In conclusion, a 5% doped epoxy resin with nano-composite zinc oxides tested with negative impulse voltage has better properties as an insulator than other samples in ratios of 0, 10, 15, and 20%, respectively, as the 5% ratio has a breakdown occurrences also happened later with smaller periods of insulator surface destruction in the first round of voltage feeding than the other cases.