【作者】 刘晓光；

【导师】 陈大明；

【作者基本信息】 北京航空材料研究院 ， 材料学， 2004， 博士

【摘要】 本文深入、系统地研究了水基注模凝胶法制备固体氧化物燃料电池用氧化锆基电解质薄片的工艺过程,利用XRD、SEM、TEM等技术对材料的相结构和微观组织进行了分析。系统研究了ZrO₂-Y₂O₃和ZrO₂-Y₂O₃-Al₂O₃体系的力学性能和电性能,从而展示了这一材料的良好工业化应用前景。系统研究了注模凝胶成型用ZrO₂水基料浆的制备及其稳定性和流变性,确定了pH值、分散剂、固含量及球磨时间对ZrO₂水基料浆的稳定性和流变性的影响规律,最终优化出本材料体系的最佳实验参数,即pH=8～10,分散剂含量为2vol%,球磨时间为20～24h。首次配制出高固含量（56vol%）、低粘度（0.5Pa·s）的ZrO₂水基料浆。并首次用水基注模凝胶法制备出100mm×100mm,厚度仅为0.2mm的光滑、平整,致密度高达98.1%的ZrO₂固体电解质薄片,为进一步工业化批量生产奠定了基础。研究了加热凝胶、催化剂凝胶和氧化还原凝胶三种凝胶方式中各参数对ZrO₂水基料浆凝胶化成型的影响,以及温度、湿度和厚度对水基注模凝胶坯体的干燥过程的影响规律;研究了排胶前后坯体中颗粒的结合及分布状态,并与干压坯体进行比较,发现水基注模凝胶坯体的断口较平整,颗粒分布均匀,没有大的团聚体存在;此外通过对烧结工艺的研究表明,烧结温度、保温时间、升温速率、坯体密度等均对烧结过程有很大影响。1600℃×4h烧结时,瓷体晶界平直,晶粒发育较好。本文系统研究了水基注模凝胶法制备的Al₂O₃-Y₂O₃-ZrO₂体系氧化锆基固体电解质的综合力学性能和电性能,并与Y₂O₃-ZrO₂体系进行对比。结果表明,Al₂O₃/YSZ的σ和K_1c均随Al₂O₃含量的增加而增大。Y₂O₃-ZrO₂陶瓷随Y₂O₃含量的增加,σ是先增加后减小,而K_1c是一直降低的;3mol%的Y₂O₃-ZrO₂陶瓷的抗弯强度最高,可达891Mpa,其断裂韧性可达9.2MPa·m^1/2,综合力学性能最佳。随着Y₂O₃含量的增加,Y₂O₃-ZrO₂体系材料的电导率呈现出了先增加后减小的趋势。离子电导率随着温度的升高而增大,1nσ-1/T曲线基本上是呈线性关系。Al₂O₃-Y₂O₃-ZrO₂体系的电导率则随Al₂O₃增加呈现先增大后减小的趋势,1wt%Al₂O₃-YSZ材料电导率最大,此时电导率高于YSZ电解质材料的电导率。本文对此现象进行了认真的分析研究,并首次制得在1000℃时的电导率可以达到0.15S/cm的Al₂O₃-YSZ大面积固体电解质薄片,其电导激活能为0.821eV,这为实用化提供了可能。更多还原

【Abstract】 In present paper, the process of zirconia solid electrolyte in solid oxide fuel cell prepared by aqueous gel-casting technique was studied thoroughly. Microstructure and phase configuration were analyzed by XRD, SEM, TEM and so on. The mechanic properties and electric performances of ZrO₂-Y₂O₃ and ZrO₂-Y₂O₃-Al₂O₃ systems were studied thoroughly, these opened up a bright prospect for their industrial applications.Stability and rheological characteristics of aqueous zirconia slurry were studied firstly. The effects of pH value, dispersant, solid loading and milling time on stability and rheological characteristics were determined. The ultimately optimized pH value is from 8 to 10, the content of dispersant is 2% in volume, and milling time is from 20h to 24h. Zirconia aqueous slurries of high solid loading（56vol%） and low viscosity（0.5Pa.s） were first prepared. And YSZ electrolyte thin substrate, which thickness is 200μm and areas are 100×100 mm², was also first fabricated. When sintering is carried out at 1600℃for 4h, crystal boundaries are straight, crystal particles grow rightly and relative density reaches 98.1 percent, these give a base for industrial production.Secondly the effects of some parameters such as temperature, catalyst, humidity and sample thickness on gel forming and drying process were also investigated. Moreover, the distribution of particles in green bodies before and after binder burnt-out was studied. Compared with drying pressing green body, AGC green body has narrow pore distribution and high dispersible particles. Lastly, sintering progress was studied. The results show that sintering temperature, holding time, increasing temperature rate and density of green body have a great influence on sintering progress.The mechanic properties and electric performances of ZrO₂-Y₂O₃ and ZrO₂-Y₂O₃-Al₂O₃ systems prepared by aqueous gel casting method were also studied in this thesis. Results show that bending strength and fracture toughness of Al₂O₃-YSZ increase with increasing alumina content. Bending strength increases firstly, then decreases with increasing yittra content, but fracture toughness decreases straightly. When yittra content is 3 mol percent. bending strength reaches as high as 891MPa and fracture toughness is 9.2 MPa·m^1/2, its general mechanic properties are best of all.Ionic electric conductivity increases firstly, then decreases with increasing yittra content. Electric conductivity increases with increasing temperature, and is linearity. Ionic electric conductivity also increases firstly, then decreases with increasing alumina content. Electric conductivity of 1 weight percent ratio-YSZ is higher than that of YSZ. Ionic electric conductivity of zirconia solid electrolyte thin substrate using aqueous gel casting technique reaches 0.15 S/cm at 1000℃, and its activation energy for ionic conduction is 0.821eV. This provides the possibility of applications.更多还原