微細周期構造の付与で検出特性を改善した気泡センサ

Abstract

In solid oxide fuel cell, carbon dioxide is generated in the water circulator and tends to accumulate in the reformer. If the air bubble forms a fair size, it disturbs the water flow and gives damage to the water circulator. For practical applications, long-term operation with an air bubble detection capability is needed. The purpose of this paper is to enhance the sensitivity of the air-bubble sensor by increasing the physical water repellency of its detecting surface using micro- and nano-periodic structures. The air-bubble sensor comprised a cylindrical sleeve with two coil shaped-electrodes and a ground electrode. Four types of sleeves for the air-bubble sensor with different micro- and nano-periodic structures on the surface of a detection area were fabricated. As the results, it was found that i) a micro-periodic structure increased the apparent contact angle of air bubble from 50° to 89°, and ii) a V-shaped micro-periodic structure could degrease the accidental error by improving the wettability. The electrode voltage was increased toward the detection threshold level and the detected time was prolonged when the apparent contact angle of water was small, showing that which increase the probability of false detection. Additionally, the detecting sensitivity of the air-bubble sensor was increased by forming a micro-periodic structure on the surface. In summary, a micro-periodic structure has the effects improving the detecting precision of air-bubble sensor.