Abstract
The ZrO2(MgO)/CaAl2O4+CaAl4O7 bilayer structure used for sulfur sensor was fabricated by the laser powder cladding (LPC) method using the MgO partially stabilized zirconia (2.7 wt% MgO-PSZ) as the substrate and the CaAl2O4 + CaAl4O7 composites as the coating material. The microstructure, phase composition and ionic conductivity of this bilayer structure were investigated for better application in the sulfur determination. The results indicated that the structure of the coating was dense and well-distributed with a thickness of 100 μm. The ionic conductivity of the ZrO2(MgO)/CaAl2O4+CaAl4O7 bilayer structure was up to 2.06 × 10−3 S·cm−1 at 850 °C that met the required ionic conductivity of ionic conductor for solid electrolyte sulfur sensor. Furthermore, the sulfur sensor Mo|Cr+Cr2O3| ZrO2(MgO)| CaAl2O4+CaAl4O7|[S]Fe| Mo was assembled used this bilayer structure and tested in carbon-saturated liquid iron at 1773 K and 1823 K. The stability and reproducibility of the sulfur sensor were satisfactory and could be used for sulfur determination in the liquid iron.
Highlights
In the iron and steel metallurgical industry, on-line measurement of sulfur in liquid iron and steel has been a challenge for decades and two types of sulfur sensors have developed
One is the direct sulfur determination sensor by sulfide solid electrolyte [1,2,3,4,5], the other is the indirect sulfur sensor based on ZrO2 with doped oxides and β-Al2 O3 as solid electrolyte and sulfides as auxiliary electrode [6,7,8,9,10,11]
Based on the above principle, a bilayer structure of non-sulfide solid electrolyte with a coating of calcium aluminate has been proposed to use in the sulfur sensor, as this unique structure would solved the disadvantages of the traditional sulfide coating with poor stability and easy oxidation
Summary
In the iron and steel metallurgical industry, on-line measurement of sulfur in liquid iron and steel has been a challenge for decades and two types of sulfur sensors have developed. Based on the above principle, a bilayer structure of non-sulfide solid electrolyte with a coating of calcium aluminate has been proposed to use in the sulfur sensor, as this unique structure would solved the disadvantages of the traditional sulfide coating with poor stability and easy oxidation. This structure would help more effectively to increase the conductivity in the sensor and avoid high electronic conductivity. The application of the bilayer structure in sulfur determination was studied
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