The Preparation And Process Optimization Of Gadolinium Oxide Doped Cerium Oxide Powders

Solid Oxide Fuel Cells(SOFC)is considered to be one of the most promising technology for the future energy and environmental crsis,because of its high energy conversion efficience,fuel gas flexible,have no use for noble metal and other advantage.Traditional SOFC operate under high temperature,cause high performance requirements for component materials,and need long time to start up,which limit its application.In order to lower its operation temperature,a bunch of materials with excellent electrochemical properties at medium and low temperatures have been investigate,as the core component of SOFC electrolyte material is the hotspot in recent years.Among the many electrolyte materials,gadolinium oxide doped cerium oxide(GDC)is considered to be one of the most promising materials for medium and low temperature SOFC electrolytes.However,the poor sintering performance is a crucial problem for GDC electrolytes.According to the sintering theory,in order to obtain a dense electrolyte membrane at low temperature,the electrolyte particle size should be as small as possible with narrow particle size distribution.Around this issue,this paper through theoretical and experimental research,carried out the following work:(1)The effect of preparation method and preparation process parameters on the performance of GDC powder was investigated by single factor experiment.The prepared electrolyte powder was characterized by XRD,SEM and PSD,and the preparation process of GDC powder was optimized by response surface experiment.The optimum preparation scheme was as follows: the concentration of cerium nitrate was 0.55 mol/L,the concentration of oxalic acid was 0.05 mol/L,the reaction temperature was 28 ?,the aging temperature was 20 ?,the aging time was 1 h,the calcination temperature was 600 ?.Under this condition,the average particle size D50 of the powder is 1.091 ?m,which is close to the predicted value,indicating that the mathematical model obtained by the response surface method is accurate and reliable.(2)The crystallization kinetics of GDC powder was studied by experiment with oxalate coprecipitation method,and the effects of nitrate concentration,reaction temperature and stirring rate on crystal nucleation rate B and growth rate G were investigated.The experimental results show that the nucleation rate B and the growth rate G are sensitive to the change of nitrate concentration,all increased with the increase of nitrate concentration,but the growth rate G growth rate is growing and the nucleation rate B slowed down.The nucleation rate B and the growth rate G decrease with the increase of reaction temperature.Appropriate increase in stirring speed,promote the nucleation and nucleation growth,but when the stirring speed exceed 400 rpm,the growth rate of G decreased.(3)Respectively,using physical,chemical and two methods of combining the means to deal with powder agglomeration,the effects of ultrasonic treatment time and the amount of surfactant on the agglomeration of powder in the preparation process were investigated.The experimental results show that the optimal ultrasonic treatment time is 25 min at a frequency of 20 kHz and a power of 0.3 kW.The best addition of nonionic surfactant PEG-400 was 0.4%,the best addition amount of cationic surfactant CTAB was 0.15%,and the optimum amount of anionic surfactant SDS was 0.6%.Ultrasonic treatment and anionic surfactants have a synergistic effect,can further eliminate powder agglomeration.