激光熔覆制造致密扩散障碍层极限电流型氧传感器的研究

In this project, the diffusion model of oxygen ions in the dense diffusion barrier and the theoretical equation of the dense diffusion barrier limiting current oxygen sensor will be established from the viewpoint of electrochemistry. The dense diffusion barrier material has been synthesized by solid state reaction. The influence rule and function mechanism of the chemical composition of the dense diffusion barrier on its properties will be revealed, and the dense diffusion barrier material that is compatible with LSGM will be determined. The dense diffusion barrier limiting current oxygen sensor has been fabricated by a laser cladding technique. Based on the relationship between the laser cladding parameters and the microstructure and microhardness of the cladding layer, and the study of heat and mass transfer under the interaction between laser and material, the laser cladding parameters will be optimized. Based on the analysis of composition, morphology and structure of the dense diffusion barrier, the formation mechanism of the dense diffusion barrier will be revealed, and the structure model of the dense diffusion barrier will be established. The formation and diffusion process of the dense diffusion barrier will be illustrated from the viewpoint of thermodynamics and dynamics. The electrochemical property, combination and thermal shock resistance performance of the dense diffusion barrier/LSGM will be studied, and the mechanism will be discussed. The influence rule and function mechanism of structure dimension, temperature and ambience on performance indicators of oxygen sensor will be revealed, and the optimum structure dimension and using conditions of the oxygen sensor will be determined. The successful implementation of the project is of great importance to realize energy-saving, emission reduction and the automatic control of combustion process in metallurgical industry.

本项目从电化学角度建立氧离子在致密扩散障碍层内的扩散模型和致密扩散障碍层极限电流型氧传感器的测氧理论方程。采用固相法合成致密扩散障碍层材料，揭示材料化学组成对其性能的影响规律和作用机制，确定与LSGM相匹配的致密扩散障碍层材料。利用激光熔覆技术制造致密扩散障碍层极限电流型氧传感器，通过研究激光熔覆工艺参数与熔覆层显微组织和显微硬度间的关系以及激光与材料相互作用下的传热、传质过程来优化激光熔覆工艺参数。研究致密扩散障碍层的成分、形貌和结构，掌握致密扩散障碍层的形成机制和结构模型，从热力学和动力学角度阐明致密扩散障碍层形成和扩散等过程。研究致密扩散障碍层/LSGM的电化学性能、结合性能和抗热震性能，探讨其性能产生机制。揭示结构尺寸、温度和气氛等对氧传感器性能指标的影响规律和作用机制，确定氧传感器最佳结构尺寸和使用条件。本项目的成功实施对实现冶金企业节能减排以及燃烧过程的自动化控制具有重要意义。

从电化学原理出发建立了致密扩散障碍层极限电流型氧传感器的理论方程。利用激光熔覆技术在LSGM固体电解质表面制备了与LSGM具有优良物理、化学相容性的过渡金属（Fe、Cr、Co）掺杂的LSGM（LSGMN）混合导体材料。通过研究激光熔覆工艺与熔覆层显微组织的关系以及激光与材料相互作用下的传热、传质过程来优化激光熔覆工艺参数。研究致密扩散障碍层的成分、形貌和结构，掌握致密扩散障碍层的形成机制及其与LSGM具有优良结合性能的原因。揭示温度、O2、CO2、CO、H2S和致密扩散障碍层厚度对氧传感器性能指标的影响规律。结果表明：激光熔覆最佳工艺参数为：输出功率29W，光斑直径1mm，扫描速度1mm/s，预置层厚度2mm。熔覆层组织具有明显的梯度渐变特征，外表面和结合区附近的组织均匀细小而中部组织粗大。在界面结合处混合导体成分（La、Sr、Ga、Mg、过渡金属和O）与基体成分（La、Sr、Ga、Mg和O）相互扩散，具有明显的反应界面特征。熔覆层/LSGM界面处形成稳定的复杂晶体结构，其结合力主要依靠强烈的化合键作用，实现了牢固的冶金结合。氧传感器对CO2、CO和H2S等气体具有优良的稳定性，极限电流与致密扩散障碍层的厚度和氧含量均呈线性关系，与温度的倒数呈指数关系，这与氧传感器的测氧理论方程一致。