烧结助剂对固体氧化物电池的质子导体电解质烧结性能和电导率影响的研究进展

质子导体氧化物在600 °C下具有较高的质子导电性,在应用于开发低成本、耐用的中低温固体氧化物电池方面具有显著的优势。目前,BaZr1-xYxO3-δ (BZY),BaCe0.7-xZrxY0.2O3-δ (BCZY)和BaCe0.7-xZrxY0.1Yb0.1O3-δ (BCZYYb)等基于Ba、Ce、Zr、Y和Yb的ABO3型钙钛矿结构的质子导体电解质材料具有最优异的电化学性能。但是这些材料的烧结性能,电导性能和稳定性难以兼得,从而严重限制了它们的应用。为了在较低的烧结温度下获得具有高导电率和长期稳定的致密的电解质,最常用的方法是在质子导体氧化物中添加烧结助剂。而最近报道的研究论文中,烧结助剂对质子导体导电性的影响存在较大的差异。所以本综述全面讨论了近年来烧结助剂改性的质子导电氧化物的研究进展,并详细总结了不同烧结助剂对质子导电氧化物相对密度、晶粒生长、烧结行为、体电导率和晶界电导率的影响,进而提出一些潜在的研究思路。     

碱土金属双掺杂钴铁酸镧的结构和电性能

应用共沉淀法合成了中温固体氧化物燃料电池刚极材料La0.7Sr0.3-xCaxCo0.9Fe01O3-δ(x=0.05,0.10,0.15,0.20)的粉料.采用XRD,SEM和直流四极探针法研究了其晶体结构和电导率随温度变化规律以及其与电解质Ce0.8Sm0.2O2的化学相容性.实验表明Ca2+和Sr2+双掺杂取代La3+进入晶格后,合成的粉料具有六角晶系钙钛矿结构;随着Ca2+含量x增加,La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ晶胞a轴方向缩短c轴方向拉长,晶胞体积减小且样品的电导率也在降低.随温度升高到490℃,电导率出现最大值,温度继续升高晶格氧逸出而导致电导率降低.400℃～700℃时,样品的电导率均高于450S/cm.当x=0.10和0.15时,其电导率基本相等且高于760 S/cm.合成的粉料与电解质Ce0.8Sm0.2O2具有良好的化学相容性.     

纳米SrCe0.95Y0.05O3-x陶瓷粉的制备与烧结

采用基于Pechini法的低温燃烧工艺制备了SrCe0.95Y0.05O3-x(SCY)前驱物.前驱物在900℃经0.5 h的煅烧处理即可得到纯的粒度在7～25 nm范围内的SrCe0.95Y0.05O3-x固体电解质纳米粉.将煅烧的粉体在18 MPa压力下压成片状的素坯,在900～1 500℃的温度范围内于空气中烧结索坯10 h.用X射线衍射(XRD)表征煅烧粉体的晶体结构,用扫描电镜(SEM)和透射电镜(TEM)表征了煅烧粉体和烧结体的形貌和粒度,采用阿基米德法测量了烧结体的密度.结果表明:温度达到1 000℃时,烧结体的径向收缩率和密度随着温度的升高而显著增加;温度达1 300℃时烧结体的径向收缩率和密度趋于恒定,得到相对密度高于96%、平均粒径约为3.68 μm的SrCe095Y0.05O3-x固体电解质陶瓷体.     

BZCY-(Li/Na)2CO3新型复合电解质材料性能研究

BaZr0.1Ce0.7Y0.2O2.9（BZCY）电解质与氧离子传导型电解质相比,质子迁移的电导活化能较氧离子更低,低温下具有更高的离子电导率,在固体氧化物燃料电池低温话发展过程中,质子传导型电解质将会是一个很好的选择。本研究采用均相共沉淀法合成BaZr0.1Ce0.7Y0.2O2.9（BZCY）粉体,并制备不同组成的BZCY- (Li/Na)2CO3复合电解质,初步研究了其结构与性能。实验结果表明,复合电解质中碳酸盐以无定形形态存在,BZCY与碳酸盐发生反应生成BaCO3杂相;复合电解质电导率在空气中600℃和450℃时分别可达到0.095Scm-1和0.071Scm-1,加湿氢气中分别可达到0.126Scm-1和0.075Scm-1。以BZCY- 20%(Li/Na)2CO3为复合电解质的单电池表现出良好输出性能,在600℃和500℃时输出功率密度可达741mWcm-2和258mWcm-2。     

La0．9Sr0．1Ga0．8Mg0．2O2．85固体电解质合成及其性能

在NH4OH-(NH4)2CO3沉淀体系中用相转移分离法制备了La0.9Sr0.1Ga0.8Mg0.2O2.85(LSGM1020)固体电解质前驱体,并在较低的烧结温度得到了纯度较高,杂质含量低的电解质陶瓷.用XRD,Raman光谱,直流四电极,交流阻抗谱和扫描电镜分析了电解质的晶体结构,电化学性能和显微结构.XRD和Raman分析表明LSGM1020电解质具有菱方钙钛矿结构,800oC时测量得到的氧离子电导率达到0.12S?cm-1.SEM和交流阻抗分析表明,烧结体具有良好的微观结构.采用相转移分离法合成LSGM1020有利于降低烧结温度,改善电解质的性能.     

燃料电池用LSGM-碳酸盐复合电解质材料的稳定性

目前研究较多的固体氧化物电池用碳酸盐复合电解质体系中,碳酸盐在工作温度下的熔融状态使其稳定性受到质疑。本文通过聚丙烯酰胺溶胶凝胶法制得La0.9Sr0.1Ga0.8Mg0.2O2.85（LSGM）粉体与二元碳酸盐复合,制备了新型LSGM-碳酸盐复合电解质,从老化、循环和电池输出三方面考察了LSGM- (Li/Na)2CO3复合电解质的稳定性。在600℃、650 h的测试中,复合电解质的电导率长期稳定在0.07~0.09 S?cm-1;在室温~700℃循环中碳酸盐基本没有损失,电导率也较稳定;单电池在0.6 A?cm-2恒流放电,1 h内平均功率密度为256 mW?cm-2。     

BaCe1-xYxO3-α及BaCe0.9Sm0.1O3-α质子导体的表征及组成氢泵对铝熔体的脱氢

采用固相合成法制备了BaCe0.9Y0.1O3-α,BaCe0.85Y0.15O3-α和BaCe0.9Sm0.1O3-α质子导体.XRD结果表明,掺0.1Y的粉体形成了单一的钙钛矿型BaCeO3结构,掺0.15Y和0.1Sm的粉体形成了主相为钙钛矿结构的固溶体;激光粒度分析表明,煅烧后的粉体平均粒径增大,粒度分布比较集中;DSC-TG分析表明,质子导体的合成温度约1360℃;SEM结果显示,质子导体由分布均匀的大小两种晶粒和气孔构成;BaCe0.9Y0.1O3-α和BaCe0.9Sm0.1O3-α脱氢电池对铝液的脱氢结果表明,脱氢电流随着铝液温度的升高,水蒸气分压增大或外加电压增加而分别增大;用自制的CaZr0.9In0.1O3-α氢传感器测得铝液温度为780℃、水蒸气分压分别为4122.8和4366.0 Pa时,100 g铝液中的氢含量分别为0.0536和0.0445mL.     

La_(0.4)Sr_(0.6)Co_(0.2)Fe_(0.7)Nb_(0.1)O_(3-δ)电极应用于YSZ基对称SOFC性能研究

采用固相法合成了钙钛矿型氧化物La_(0.4)Sr_(0.6)Co_(0.2)Fe_(0.7)Nb_(0.1)O_(3-δ)(LSCFN),并采用流延-丝印法制备了以8 mol%Y_2O_3稳定Zr O_2(YSZ)为电解质、Gd_(0.1)Ce_(0.9)O_(2-δ)(GDC)为隔离层、LSCFN同时为阴极和阳极的对称固体氧化物燃料电池。利用X射线衍射对电极材料进行了物相及化学相容性分析,用扫描电镜表征了对称电池的微观形貌。分别以湿H_2(3%H_2O)和湿CH_4(3%H_2O)为燃料气,空气为氧化气测试了单电池的电化学性能,并在850℃湿CH_4下进行了电池的稳定性测试。结果表明:LSCFN与GDC具有良好的化学相容性。以湿H_2和湿CH_4为燃料气的单电池在850℃时最大功率密度分别为254和105 m W/cm~2。在100 h的CH_4稳定性测试中性能无明显衰减,具有良好的稳定性。     

MgS+1.5%ZrS2固体电解质硫浓差电池的实验研究

以金属和升华硫为原料,利用温度梯度法合成硫化物;并用合成的MgS+1.5%ZrS2作为固体电解质,以Mo+MoS2作为参比极研制了硫浓差电池.在1623 K利用该电池对碳饱和铁水(氧的活度a[O]≤2×10-6)中的硫含量进行了测定.进一步优化了硫浓差电池的结构,解决了电解质管的炸裂和漏气问题,同时采用特殊工艺抑制了硫化物水化.结果表明,该硫浓差电池的电动势信号稳定,重现性好且持续时间长.     

用喷雾热分解法制备Gd2O3-Y2O3-ZrO2电解质材料的性能

用喷雾热分解方法制备了2mol%Gd2O3-8YSZ的粉末,用激光粒度分析,X射线衍射(XRD),BET法和扫描电子显微镜(SEM)检测粉末和陶瓷体的性能和结构。结果表明,获得的粉末粒径为12.18μm,晶粒尺寸为100nm,比表面积为25.09m2/g。粉末和陶瓷体材为立方结构。陶瓷体的烧结密度大于98%理论密度。在操作的温度高于600℃下的电导率达2×10-3S/cm。证实Gd2O3-8YSZ材料完全适用于作中温固体氧化物燃料电池(SOFC)的电解质。     

Sm2O3和Nd2O3共同掺杂CeO2基电解质材料的研究

采用柠檬酸-硝酸盐法合成出单一相、均匀的Ce0.8SmxNd0．2-xO19粉体，XRD结果表明该粉体为单相萤石结构，粒径约在11．7nm～20．1nm之间。将粉体干压成型，在1400℃下无压烧结5h可得到高致密度陶瓷。SEM照片显示陶瓷微观结构均匀，晶粒尺寸在2μm～4μm。经直流四端电极法测试得到该样品在500℃时电导率约在0．012 S／cm。该结果说明与单项掺杂相比，两相共掺杂会进一步提高材料的电导率。     

柠檬酸法合成SOFC阴极粉体La_(1-x)Sr_xMnO_(3-δ)的研究

采用柠檬酸法制备了固体氧化物燃料电池钙钛矿型阴极粉体La_(1-x)Sr_xMnO_(3-δ)(0.1＜x＜0.5),研究了pH值、络合剂量、煅烧温度等各工艺参数对络合效果的影响.结果表明:pH值是关键因素,最佳pH值为3.乙二醇能很好地促进柠檬酸络合金属离子,同时适当增加柠檬酸量有利于金属离子的络合.制备阴极粉体La_(1-x)Sr_xMnO_(3-δ)的最佳实验条件为:pH值为3,添加乙二醇,柠檬酸与金属离子的摩尔比为2,煅烧温度为1000 ℃.     

水和乙醇悬浮液等离子喷涂SOFC (Ce0.80Gd0.20)O1.9电解质层的比较

选用水和乙醇两种溶剂配置悬浮液,研究了分散剂含量对(Ce_0.80Gd_0.20)O_1.9 (GDC)悬浮液粘度的影响和pH值对GDC颗粒Zeta电位的影响。结果表明：水悬浮液优化参数是：PAA含量为2.5 wt.%,pH=10;乙醇悬浮液优化参数为：PAA含量2.0 wt.%,pH=10。采用GDC悬浮液等离子喷涂制备固体氧化物燃料电池电解质层。利用XRD、SEM和电子探针分别分析了喷涂前后GDC的相结构、电解质层微观组织及化学成分。研究表明：GDC喷涂前后没有相结构的变化,乙醇悬浮液得到的电解质层结构更精细,水和乙醇悬浮液得到电解质的孔隙率分别为5.64 ％和1.25 %,但是氧化铈有烧损,水和乙醇悬浮液电解质层氧化铈分别烧损了15.8 %和 16.8 %。     

Analysis of macro segregation in twin-roll cast aluminium strips via solidification curves

A porous NiO/yttria-stabilized zirconia (YSZ) anode substrate for zirconia-based tubular solid oxide fuel cells (SOFCs) was prepared by the gelcasting. The effect of the impregnation of SDC in the substrate was studied. Electrochemical impedance spectroscopy and I–V and I–P curves of the cells were measured. Scanning electron microscopy (SEM) was used to observe the microstructures. The results indicate that the performance of the cell can be significantly improved by incorporating the nano-structured SDC particles in the substrate. The peak power density of the cell is increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 °C, compared with the unmodified cells. It is explained as the extended triple-phase boundary (TPB) in the anode substrate and the excellent electrocatalytic property of SDC. It is also found that the nano-scale SDC particles change a lot during the reduction of the anode substrate, and the morphology of the resultant SDC particles on the metal Ni is significantly different from that on the YSZ. After the long-term operation, the morphology of the SDC particles on the Ni changes again, but that on the YSZ keeps almost unchanged.     

流延-共烧法制备掺杂氧化铈基阳极／电解质双层结构

采用甘氨酸／硝酸盐（GNP）法合成了具有较高烧结活性的Ce0.8Gd0.05Y0.15O1.9（GYDC）粉体，通过流延-共烧法制备了NiO—GYDC阳极／GYDC电解质双层结构。结果表明：GYDC电解质薄膜经过1400℃保温4h后可烧结致密，说明GNP法制备的GYDC粉体的烧结活性较高；通过流延．共烧法可以成功制备外观完好、平整的NiO-GYDC／GYDC双层结构，满足SOFC的组装要求。     

钛基SnO2+SbOx电极固溶体生长活化能及作用机制

采用热分解法制备SnO2+SbOx钛基氧化物电极,利用TG/DTA、XRD和XPS等手段对SnO2+SbOx固溶体进行表征,计算SnO2+SbOx固溶体的生长活化能,并探讨SnO2+SbOx固溶体的作用机制,同时采用快速寿命法考察氧化物电极在0.5 mol/L H2SO4溶液中2 A/cm2下的预期使用寿命。结果表明： Sb掺杂SnO2形成的N型半导体和P型半导体产生的自由电子和氧空位使得电极导电性增强,预期使用寿命增加为30 h,晶粒表面氧空位的存在和非常低的晶间旋转驱动力是导致SnO2+SbOx固溶体的生长活化能降低为12.63 kJ/mol的主要原因。因此,Sb掺杂SnO2形成的电极固溶体是一种导电性好和稳定性高的电极材料。     

Observations on the structural degradation of silver during simultaneous exposure to oxidizing and reducing environments

The structural stability of silver (Ag) in dual atmosphere exposure conditions, which are representative of solid oxide fuel cell (SOFC) current collector and gas seals, has been examined in the 600–800 °C temperature range. Experiments conducted on Ag tubular sections exposed to flowing H₂-3% H₂O (inside the tube) and air (outside the tube) showed extensive porosity formation along the grain boundaries in the bulk metal. Similar tubular sections, when exposed to air only (both inside and outside the tube), showed no bulk porosity or structural changes. It is postulated that the porosity formation in the bulk metal is related to the formation of gaseous H₂O bubbles due to simultaneous diffusion of hydrogen and oxygen followed by subsequent interaction resulting in the formation of steam. Thermochemical processes that are responsible for structural degradation are presented and discussed. Based on experimental observations, it is concluded that Ag metal may not provide adequate long-term structural stability under a dual-environment condition that is typical of interconnects or gas seals in intermediate temperature SOFCs. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

Solid reaction mechanism of CaHPO4·2H2O + CaCO3 with and without yttria

The effect ofyttria on the solid reaction mechanism ofa CaHPO4·2H2O + CaCO3 system at different temperatures was experimentally stud-ied. The samples with and without yttria were subjected to thermogravimetric/differential scanning calorimetry measurement. The samples were heat treated at the temperatures corresponding to the peaks on the DSC spectra, and the resulted phase compositions were identified by X-ray diffraction. The transformation mechanism was deduced by comparing the phases obtained at different temperatures. The results show that the transformations at below 1073 K are not affected by yttria, but all those at above 1073 K are completely altered. The formation tem-perature of hydroxyapatite decreases by 134 K, and the decomposition temperature increases by 38 K. The polymorphous transformation of Ca3(PO4)2 from β phase to α phase increases by 47 K. The thermodynamic properties of the transformations at above 1073 K are also modi-fied by the addition of yttria; that is, the endothermal peaks are substituted by exothermal peaks.