复合电解质BaCe_(0.8)Y_(0.2)O_(2.9)–Ce_(0.8)Gd_(0.2)O_(1.9)的化学稳定性

采用溶胶―凝胶燃烧法制备BaCe_(0.8)Y_(0.2)O_(2.9)(BCY)和Ce_(0.8)Gd_(0.2)O_(1.9)(GDC)粉末,并通过机械混合法制备不同摩尔比的BCY―GDC复合电解质粉末,在1 450℃烧结5 h获得BCY―GDC复合电解质。研究了复合电解质的化学稳定性及电化学性能稳定性。结果表明:BCY–GDC复合电解质在CO_2和沸水中的稳定性均高于单相BCY;当BCY―GDC复合电解质中的BCY摩尔分数小于70%时,试样在CO_2气氛和沸水中都具有良好的化学稳定性。基于BCY:GDC摩尔比为1:1的BCY―GDC复合电解质的单电池,在700℃工作20 h内的最大功率密度的稳定性高于基于BCY电解质的单电池。     

过渡金属离子对Ce_(0.8)Sm_(0.2)O_(1.9)电解质离子导电性的影响

本文研究了掺杂过渡金属离子(Ni~(2+)、Cu~(2+)、V~(5+)、Mn~(2+))对Ce_(0.8)Sm_(0.2)O_(1.9)(SDC)材料离子导电性的影响。用电化学阻抗谱、SEM、XEDS等检测手段对样品的离子导电性、显微结构和微区元素进行了检测分析,并对影响机理进行了探讨。结果表明:掺杂过渡金属离子对SDC电解质材料的离子电导率有不同程度的影响,且主要是对晶界离子电导率产生较为显著的影响。Ni、Cu对SDC晶界离子电导率的提高相对较为显著,从而导致其对宏观离子电导率的提高也较为显著;其它过渡金属离子和铝离子对SDC电解质晶界离子电导率提高作用相对较小,故而对其宏观离子电导率的提高作用也较小。     

Al_2O_3掺杂方式对Ce_(0.8)Sm_(0.2)_(1.9)电解质结构和性能的影响

研究了Al_2O_3掺杂方式对Ce_(0.8)Sm_(0.2)_(1.9)(SDC)材料性能的影响。用XRD、SEM、XEDS和热膨胀系数仪等检测手段对样品的晶体结构、力学、热学、显微结构和微区元素进行检测分析。结果表明:采用低温燃烧一步合成法制备的样品其力学性能、烧结性和离子电导率均优于采用铝溶胶直接添加法所制备的样品,其主要原因在于铝溶胶直接添加法会在SDC材料中产生残留Al_2O_3,并富集在晶界处形成晶界夹杂,阻碍了氧离子迁移。     

沉淀剂对胶质溶液喷雾热解Sm_(0.2)Ce_(0.8)O_(1.9)固体电解质结构的影响(英文)

分别采用碳酸铵((NH4)2CO3,AC)和碳酸氢铵(NH4HCO3,AHC)作沉淀剂制备胶质溶液,利用胶质溶液喷雾热解制备纳米晶氧化钐掺杂氧化铈(Sm0.2Ce0.8O1.9,SDC)电解质粉末。通过X射线衍射、热重分析和扫描电镜表征粉末和陶瓷的结构和形貌,探讨沉淀剂对前驱体和SDC粉末形貌、粒径和结晶相的影响及作用机理。结果表明:通过AC途径制备的喷雾热解粉末呈球状,经700℃热处理后,得到的SDC粉末聚集体粒径小于0.5μm,具有很高的烧结活性,经1250℃烧结4h获得的陶瓷密度达到理论密度的96%;通过AHC途径制备的喷雾热解粉末经热处理后仍保持片状,相应的陶瓷呈多孔结构,只有理论密度的79%。     

La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3–δ)–Sm_(0.2)Ce_(0.8)O_(1.9)复合阴极的制备及性能表征

分别采用凝胶浇注法和甘氨酸–硝酸盐法制备La0.6Sr0.4Co0.2Fe0.8O3–δ(LSCF)粉体与Sm0.2Ce0.8O1.9(SDC)粉体,随后制备出不同比例的LSCF–SDC复合阴极。用X射线衍射分析粉体的化学稳定性,用扫描电子显微镜观察复合阴极的微观结构,在500～800℃范围内测量其热膨胀系数和电导率。采用丝网印刷法将LSCF–SDC涂覆在SDC电解质片上,在1100℃烧结4h。用交流阻抗法在600～800℃范围内测量不同成分的LSCF–SDC复合阴极和SDC电解质的交流阻抗谱。结果表明:LSCF和SDC粉体具有良好的化学相容性,烧结体具有多孔结构,LSCF–SDC复合阴极与SDC电解质可形成良好的接触界面。SDC的加入在降低阴极材料的热膨胀系数的同时还保持了其本身较高的电导率,在中温范围内,电导率达到500S/cm以上。复合阴极的极化电阻随着SDC的含量增加而减小,当SDC含量为30%时,复合阴极的极化电阻最小,在700℃空气中测试得到的界面电阻为0.32Ω·cm2。     

Ce_(0.8)Y_(0.2)O_(1.9)氧化物的烧结及晶粒生长动力学研究

通过对Ce0.8Y0.2O1.9(YDC)素坯烧结行为的考察,得到了试样的密度、晶粒大小随烧结温度(1000~1500℃)的变化规律。利用扫描电子显微镜对烧结体的晶粒尺寸分布进行统计分析表明:Ce0.8Y0.2O1.9晶粒生长在两个烧结温度区域内分别遵循不同的速率方程,在1000~1300℃较低的温度范围内,晶粒成长的活化能较小(171.1 kJ/mol),即烧结温度对晶粒成长的影响较小;在1300~1500℃较高的温度范围,晶粒生长的活化能较大(479.8 kJ/mol),即晶粒成长对烧结温度的高低表现为非常敏感,并且晶粒尺寸分布显著宽化。烧结体的密度在1000~1400℃范围内随温度的升高几乎直线上升,在1400℃时相对密度达98.5%,1400℃以上则提高的幅度变得很小。     

溶胶-凝胶法低温制备Ce_(0.8)Sm_(0.2)O_(2-α)及其复合电解质的中温燃料电池性能

以三氧化二钐、浓硝酸、硝酸铈铵、柠檬酸为原料,采用溶胶-凝胶法低温(900℃)制备Ce_(0.8)Sm_(0.2)O_(2-α)(SDC),低于通常高温烧结温度(1400℃),并与(Li/K)_2CO_3共熔体进行复合。采用DSC-TGA确定制备Ce_(0.8)Sm_(0.2)O_(2-α)的烧结温度。XRD结果表明,(Li/K)_2CO_3与Ce_(0.8)Sm_(0.2)O_(2-α)复合后没有发生化学反应。SEM图像表明,SDC粒径均匀一致,(Li/K)_2CO_3作为SDC颗粒黏结剂均匀覆盖SDC颗粒表面。采用电化学工作站研究了复合电解质在400~600℃下干燥氮气气氛中的电导率。结果表明,温度为600℃时,复合电解质在干燥氮气气氛中的电导率达到最大值3.3×10~(-2)S/cm,高于单一二氧化铈材料在相同条件下的电导率。氧分压与电导率关系曲线表明,复合电解质具有良好的氧离子导电性。H_2/O_2燃料电池性能测试表明复合电解质Ce_(0.8)Sm_(0.2)O_(2-α)-(Li/K)_2CO_3(SDC-SG-LK)在600℃开路条件下的电解质阻抗、极化阻抗分别为3.13W·cm~2、0.81W·cm~2,最大输出功率密度为130m W/cm~2。     

Co_3O_4浸渍La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_3-Sm_(0.2)Ce_(0.8)O_(1.9)复合阴极的制备及电化学性能

分别以固相反应法和甘氨酸法合成La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_3(LSCF)阴极粉体和Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)电解质粉体。机械混合后,经压制烧结得到多孔LSCF-SDC复合阴极,通过水热法对多孔LSCF-SDC阴极浸渍Co_3O_4。研究Co_3O_4浸渍后的复合阴极的微观形貌和电化学性能。实验结果表明,对多孔LSCF-SDC阴极浸渍含Co盐溶液,经700℃焙烧后,在阴极表面形成针状Co_3O_4颗粒。浸渍处理使700℃下LSCF-SDC复合阴极的界面阻抗由0.49Ω·cm~2降低至0.19Ω·cm~2,阴极的氧还原反应活化能由1.52 eV降低至1.03 eV。此外,Co_3O_4浸渍阴极使700℃下单电池的功率密度由180 mW·cm~(-2)提高至260 mW·cm~(-2)。实验结果揭示,通过Co_3O_4浸渍,可有效提高LSCF-SDC复合阴极和燃料电池的电化学性能。     

La_2O_3-CaO复合添加对Ni-Sm_(0.2)Ce_(0.8)O_(1.9)阳极电化学和抗积碳性能的影响

通过甘氨酸硝酸盐法合成出添加0~6 mol%La_2O_3-CaO的NiO-SDC(Sm0.2Ce0.8O1.9)复合阳极(La_2O_3-CaO/NiO-SDC)粉体,以SDC为电解质、BSCF(Ba0.5Sr0.5Co0.8Fe0.2O3-δ)为阴极构建SOFC单电池。考察了La_2O_3-CaO添加对Ni-SDC阳极微观组织和电化学性能等的影响;以乙醇为燃料气测定单电池的电化学性能和阳极的抗积碳性能。实验结果表明,La_2O_3-CaO/NiO-SDC复合阳极主要由NiO和SDC相组成,而La_2O_3和CaO的存在状态与其加入量有关。La_2O_3-CaO的加入,使复合阳极的电导率有所降低。添加少量La_2O_3-CaO阳极的SOFC单电池在乙醇燃料中的电池性能有所增加,800℃时添加2 mol%La_2O_3-CaO的Ni-SDC阳极的单电池最大输出功率为377.79 m W·cm-2,而Ni-SDC阳极单电池的最大输出功率仅158.86 m W·cm-2。此外,La_2O_3-CaO的添加有效减少了Ni-SDC阳极单电池在乙醇燃料中的积碳,提高了电池的运行稳定性。     

固体氧化物燃料电池阳极材料Sr_2Fe_(1.5)Mo_(0.5)O_6(SFM)/Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)的研究

采用机械混合法合成了Sr2Fe1.5Mo0.5O6(SFM)和Sm0.2Ce0.8O1.9(SDC)质量比为7∶3的SFM/SDC复合材料。用X射线衍射(XRD)、扫描电镜(SEM)、H2-TPR、EIS等表征手段对其进行了表征,并以SFM/SDC|La0.8Sr0.2Ga0.83Mg0.17O3(LSGM)|Ba0.5Sr0.5Co0.8Fe0.2O3(BSCF)为单电池片进行电化学测试,对其性能进行评价。结果表明,复合材料取得了较好的放电性能,即以氢气为燃料气,850、800、750℃时分别取得了630.6、548.4、426 mW/cm2最大功率密度;以甲醇为燃料,850、800、750℃时分别取得了551.6、426.8、335.3 mW/cm2最大功率密度。     

Aqueous processing of Ce0.8Sm0.2O1.9 green tapes

An aqueous tape casting of Ce_0.8Sm_0.2O_1.9 (SDC) ceramics was developed using poly(acrylic acid) (PAA) as dispersant, poly(vinyl alcohol) (PVA) as binder, poly(ethylene glycol) (PEG) as plasticizer, and deionized water as solvent. Surface properties of SDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The rheology of the SDC slurries was evaluated with a rotary viscometer. The zeta potential measurement showed that the isoelectric point (IEP) for SDC powders in the absence of dispersant corresponds to a pH value of 3.66. The experimental results showed that the pH value greatly affects the rheology of the slurry. The optimum content to get a stable dispersed slurry is 2 wt% PAA in pH value range of 9–10. In presence of 2 wt% PAA dispersant, 55 wt% SDC powders exhibited shear thinning behavior, indicating that SDC slurry was homogenous and well stabilized. Homogeneous, smooth, and defect-free green tapes were successfully obtained by an appropriate slurry formula.     

Preparation of ultra-fine Sm0.2Ce0.8O1.9 powder by a novel solid state reaction and fabrication of dense Sm0.2Ce0.8O1.9 electrolyte film

A novel solid state reaction was adopted to prepare Sm_0.2Ce_0.8O_1.9 (SDC) powder. A mixed oxalate Sm_0.2Ce_0.8(C₂O₄)_1.5·2H₂O was synthesized by milling a mixture of cerium acetate hydrate, samarium acetate hydrate, and oxalic acid for 5 h at room temperature. An ultra-fine SDC powder with the primary particle size of 5.5 nm was obtained at 300 °C. The ultra-low temperature for the formation of SDC phase was due to the atomic level mixture of the Sm³⁺ and Ce⁴⁺ ions. The crystal sizes of SDC powders at 300 °C, 550 °C, 800 °C, and 1050 °C were 5.5 nm, 11.4 nm, 24.1 nm and 37.5 nm, respectively. The sintering curves showed that the powder calcined at lower temperature was easier to be sintered owning to its smaller particle size. A solid oxide electrolytic cell (SOEC), comprising porous La_0.8Sr_0.2Cu_0.1Fe_0.9O_3−δ (LSCF) for substrate, LSCF–SDC for active electrode, SDC for electrolyte, and LSCF–SDC for symmetric electrode, was fabricated by dip-coating and co-sintering techniques. An extremely dense SDC film with the thickness of 20 μm was obtained at only 1200 °C, which was about 100–300 °C lower than the literatures׳ reports. The designed SOEC was proved to work effectively for decomposing NO (3500 ppm, balanced in N₂), 80% NO can be decomposed at 600 °C.     

Sm0.5Sr0.5CoO3–Sm0.2Ce0.8O1.9 Composite Oxygen Electrodes for Solid Oxide Electrolysis Cells

In this paper, a series of Sm_0.5Sr_0.5CoO₃–Sm_0.2Ce_0.8O_1.9 (SSC–SDC) composite with different ratios were prepared and characterized as oxygen electrodes for solid oxide electrolysis cells (SOECs). Yttria‐stabilized zirconia (YSZ) was selected as the electrolyte with a SDC barrier layer to avoid detrimental solid state interaction between SSC and YSZ. At 850 °C, the impedance spectra showed that the optimum SDC content in the composite electrode was found to be about 30 wt.%, which showed a much lower area specific resistance of 0.03 Ω cm². The electrochemical performances of a Ni–YSZ hydrogen electrode supported YSZ membrane SOEC with the SSC–SDC73 oxygen electrode were also measured at 750–850 °C. The hydrogen production rate calculated from the Faraday's law was 327 mL cm^–2 h^–1 at 850 °C at an electrolysis voltage of 1.3 V with a steam concentration of ∼40%, which indicated that the SSC–SDC73 was a promising oxygen electrode candidate for high temperature electrolysis cells.     

Al2O3掺杂方式对Ce0.8Sm0.2O1.9电解质结构和性能的影响

研究了Al2O3掺杂方式对Ce0.8Sm0.2O1.9 (SDC) 材料性能的影响。用XRD、SEM、XEDS和热膨胀系数仪等检测手段对样品的晶体结构、力学、热学、显微结构和微区元素进行检测分析。结果表明：采用低温燃烧一步合成法制备的样品其力学性能、烧结性和离子电导率均优于采用铝溶胶直接添加法所制备的样品,其主要原因在于铝溶胶直接添加法会在SDC材料中产生残留Al2O3,并富集在晶界处形成晶界夹杂,阻碍了氧离子迁移。     

自蔓延低温燃烧-溶胶凝胶合成Ce0.8Sm0.2O1.9及烧结性能

用甘氨酸作还原剂、硝酸盐作氧化剂,采用溶胶-凝胶与自蔓延低温燃烧相结合的方法制备了超细Ce_0.8Sm_0.2O_1.9 (SDC)固溶体,对所合成的粉体分别采用XRD、SEM和BET法进行了表征。结果表明,600℃焙烧产物是具有较高相纯度的单一立方相萤石型结构固溶体,根据XRD估算晶粒度为13～30 nm。甘氨酸与金属硝酸盐(G/N)摩尔比对粉体的微观形貌和烧结性能有很大影响, 当G/N相似文献   

Ce0.8Sm0.1Gd0.1O1.9电解质的制备及其性能

通过共沉淀法制备了Sm、Gd共同掺杂的CeO2的前驱体粉末,并将粉末经煅烧、压制、烧结制作成相应的电解质材料.对煅烧得到的电解质粉末及相应的电解质材料的性能进行了表征.实验结果表明:共沉淀法成功制备出了Sm、Gd共同掺杂的CeO2粉末.煅烧所得的电解质粉末具有良好的烧结活性,1400℃下烧结后相对密度达到93.4%.电导率的测试表明,电解质材料在中温范围有较高的电导率,800℃时,其电导率达到了0.076 S·cm-1,有望成为中温固体氧化物燃料电池的电解质材料.     

草酸盐共沉淀法制备Ce0.8Y0.2O1.9超细氧化物固溶体

实验采用草酸二乙酯、Ce(NO_3)_3·6H_2O、Y(NO_3)_3·6H_2O为原料,以尿素为pH值调节剂,利用均相共沉淀法制备了20%(摩尔分数)Y_2O_3掺杂CeO_2(Ce_(0.8)Y_(0.2)O_(1.9))的氧化物前驱体,通过优化沉淀反应过程中尿素用量、pH值及沉淀物醇洗和干燥处理等制备工艺条件,实现对草酸盐沉淀物的制备过程中的团聚控制,得到分散良好的亚微米级草酸盐共沉淀物,进一步选择合适的热处理温度,得到亚微米级的超细Ce_(0.8)Y_(0.2)O_(1.9)粉体。     

添加Al2O3对Ce0.8Sm0.2O1.9固体电解质烧结行为和性能的影响

通过凝胶浇注法制备了Al2O3掺杂0～3%（按质量计）的Ce0.8Sm0.2O1.9（samarium doped ceria,SDC）粉体.对所得粉体的相组成和粒度等进行了测定.粉体经模压成形,生坯在1 350～1 450℃烧结5 h,制成Al2O3-SDC固体电解质材料,对该材料样品的密度、微结构、电导率及抗弯强度等进行了测试分析.试验结果表明：掺入适量的Al2O3,所得Al2O3-SDC粉体具有良好的烧结性能,并能使Ce0.8Sm0.2O1.9粉体保持立方萤石结构,其烧结样品具有较高电导率,并且力学性能明显提高.未添加和添加1.0%Al2O3的SDC材料在600℃的电导率分别为0.28 S/cm和0.030 S/cm;室温抗弯强度分别为89.3 MPa和109.7 MPa.     

Aqueous tape casting and crystallization kinetics of Ce0.8La0.2O1.9 powder

An aqueous tape casting of Ce_0.8La_0.2O_1.9 (LDC) ceramics was developed using PAA as dispersant, PVA as binder, PEG as plasticizer, and deionized water as solvent. Surface properties of LDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The rheology of the LDC slurries was evaluated with a rotary viscometer. The zeta potential measurement showed that the isoelectric point for LDC powders in the absence of dispersant corresponds to a pH value of 4.02. The experimental results showed the pH value greatly affects the rheology of the slurry. The optimum content to get a stable dispersed slurry is 1.5 wt% PAA at pH value of 9–10. In presence of 1.5 wt% PAA dispersant, 5 wt% PVA binder, 5 wt% PEG plasticizer, and 55 wt% LDC powders exhibited shear thinning behavior, indicating that LDC slurry was homogenous and well stabilized. With an appropriate formulation homogeneous, smooth, and defect-free green tapes were successfully obtained. Moreover, the crystallization kinetics of LDC powders prepared by coprecipitation process also has been investigated in this study. The activation energy of crystallization was calculated on the basis of differential scanning calorimetry (DSC) at different heating rates. From non-isothermal DSC data presented values in the range of 343.3–379.1 kJ/mol and 2.282–2.030 for the activation energy of crystallization and the Avrami exponent, respectively, at specific temperatures ranging from 280 to 285 °C.