Application of Flame Jet Spray Technique to Manufacture of Oxygen Sensor

作为直接测量熔融金属中的氧含量和大气中的氧分压的方法，使用固体电解质的电化学方法是众所周知的。该方法的原理基于氧浓度电池，如等式（1）所示。该电池由已知氧电位的参比电极、氧离子导体固体电解质和未知氧电位的电极组成，然后通过式（2）表示的电动势（E）计算未知氧分压Po_2。为了方便现有氧传感器的操作并降低其成本，改善响应特性和大规模生产是必不可少的。为了满足这些要求，研制了一种新型的微型氧浓差电池，采用喷涂技术，以Fe/FeO涂层为参比电极，稳定氧化锆涂层为固体电解质。固体电解质是在基底上热喷涂一层。在开发阶段，研究了基体的形状和涂层厚度，以提高测量精度，因为测量精度会受到热冲击或氧气泄漏引起的涂层剥落的影响。作为参比电极的Fe/FeO涂层的厚度是决定传感器性能的主要因素。测试性能表明，用热喷涂技术制成的氧传感器与传统的管式氧传感器性能相当。

As a method of direct measurement of oxygen content in molten metal and oxygen partial pressure in Atmosphere, the electorochemical method by use of solid electorolyte is well known. The principle of this method is based on an oxygen concentration cell, as shown in Equation (1). This cell is composed of a reference electrode of known oxygen potential, a solid electrolyte which is an oxygen ion conductor, and an electrode with unknown oxygen potential.The unknown oxygen partial pressure, Po_2, is then calculated by the EMF (E) represented by Equation (2). To facilitate the handling of the existing oxygen sensor and to reduce its cost, improved response character and mass-production are essential. To meet these demands, a new type of miniaturized oxygen concentration cell has been developed, using a spraying technique.The new oxygen concentration cell utilizes Fe/FeO coating as the reference electrode, and stabilized zirconia coating as the solid electrolyte. The solid electrolyte are the thermal sprayed one layer on the substrate. During the development stage, the shape of the substrate and the coating thickness were investigated to improve the measurement accuracy which is influenced by spalling of the coating due to thermal shock or by a leakage of oxygen gas. The thickness of Fe/FeO coating as the reference electrode is a leading factor to determine the senor properties. The test performance has revealed that the oxygen sensor made by the thermal spray technique, is in the same performance level as the conventional tubular type cell.