溶胶凝胶法制备Ce_(0.8)Y_(0.2-x)Ca_xO_(2-δ)电解质材料及其性能

采用溶胶-凝胶法制备出Ce0.8Y0.2-x Cax O2-δ(0.02≤x≤0.10)系列电解质材料。通过红外、热重、X射线衍射、扫描电子显微镜、透射电子显微镜、交流阻抗和热膨胀系数测试对试样进行分析。结果表明:采用溶胶-凝胶法经600℃煅烧所得粉体形成了单相立方萤石结构,平均晶粒尺寸在5~10nm之间;Ce0.8Y0.2-x Cax O2-δ超细粉体具有较高的烧结活性,在1 400℃烧结得到的Ce0.8Y0.2-x Cax O2-δ系列电解质陶瓷的相对密度均大于96%。在该系列材料中,Ce0.8Y0.1Ca0.1O1.85具有良好的离子导电率、较低的电导活化能和适中的热膨胀性能。它在800℃时的离子电导率为0.041S/cm,电导活化能为0.81eV,热膨胀系数为13.5×10-6 K-1(常温~800℃)。     

甘氨酸-硝酸盐燃烧法制备Ce_(0.8)Y_(0.2-x)Sm_xO_(1.9)电解质材料及其性能

采用甘氨酸-硝酸盐燃烧法合成了中低温固体氧化物燃料电池(SOFCs)的电解质材料Ce_(0.8)Y_(0.2-x)Sm_xO_(1.9)(CYSO,x=0.0～0.20)。通过热重-差热分析(TG-DSC), X射线衍射(XRD),扫描电镜(SEM)及交流阻抗技术分析材料的性能.结果表明:初始粉体经700℃煅烧2 h后形成单相的结晶性能良好的具有萤石结构晶粒尺寸约为25 nm的CYSO纳米粉体,CYSO晶格常数随Sm掺杂量的增加而增大;CYSO纳米粉体烧结性能良好,在1400℃烧结5 h后样品的相对密度均超过95.0%。电化学性能研究表明Sm、Y共掺杂能改善CeO_2基电解质材料的性能,其中Ce_(0.8)Y_(0.2-x)Sm_xO_(1.9)在800℃时电导率高达0.050 S/cm,电导活化能低至0.386 eV。因此,甘氨酸-硝酸盐燃烧法合成CYSO有利于降低烧结温度,提高纯度,改善电解质的性能。     

固体氧化物燃料电池电解质材料 Ce0.8Sm0.2-xCuxO1.9-δ的制备与性能研究

以硝酸铈、硝酸铜、硝酸钐为原料,柠檬酸为络合剂,采用溶胶-凝胶法制备了固体氧化物燃料电池(SOFCs)电解质材料Ce0.8 Sm0.2-x Cux O1.9-δ(x=0、0.02、0.04、0.08、0.12、0.16、0.20),并通过红外光谱(FTIR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、交流阻抗(AC)等技术对样品进行了分析表征.结果表明,采用溶胶-凝胶法经600℃煅烧所得粉体呈现出单相的立方萤石结构,超细粉体Ce0.8 Sm0.2-x Cux O1.9-δ具有较高的烧结活性.经1500℃烧结3 h后得到的Ce0.8 Sm0.2-x Cux O1.9-δ系列电解质陶瓷,其相对密度均大于95％.电化学性能研究表明,Sm、Cu双掺杂可以提高CeO2基电解质的性能.其中,Ce0.8 Sm0.18 Cu0.02 O1.89电导率最大,在800℃时达到0.06 S/cm,活化能为0.33 eV.     

溶胶凝胶法制备Ce_(0.8)Y_(0.15)M_(0.05)O_(2-δ)电解质材料及其性能研究

文章以Ce0.8Y0.15M0.05O2-δ(M=Fe、Co、Mg)为主要研究对象。通过红外、致密度分析、X射线衍射、扫描电镜、交流阻抗、热膨胀等测试方法对试样进行测试和分析,对实验得到的电解质粉及相应的电解质材料的性能进行表征。实验结果表明:溶胶-凝胶法经700℃煅烧成功制备出了单相立方萤石结构的超细粉末,具有良好的烧结活性。1300℃下烧结后相对密度达到97%以上。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,其中,Ce0.8Y0.15Mg0.05O1.9在800℃时,电导率达到了0.0661 S/cm。     

固体氧化物燃料电池复合电解质粉体BaCe0.8Y0.2O3–δ–Ce0.8Gd0.2O1.9的制备及表征

用分步硝酸盐–柠檬酸凝胶燃烧法制备新型混合离子传导复合电解质粉体BaCe0.8Y0.2O3–δ–Ce0.8Gd0.2O1.9[BCY–GDC,摩尔比n(BCY):n(GDC)=1:1],研究不同烧结温度下制备的BCY–GDC电解质片的性能,以及以BCY–GDC为电解质的单电池的电性能。结果表明:采用该法可以获得分布均匀的BCY–GDC粉末,平均晶粒尺寸约为40nm;BCY–GDC复合电解质的相对密度随着烧结温度的升高而不断增大;1450℃烧结5h的电解质片基本达到完全致密,且BCY、GDC两相分布均匀,并且随着烧结温度的升高,复合电解质片的电导率增大;以BCY–GDC为电解质的单电池在450℃的开路电压达到0.95V,700℃的最大功率密度达到0.4W/cm2。     

Ce0.8Nd0.2-xPrxO1.9固溶体的Raman光谱与阻抗谱

用溶胶-凝胶法合成了氧化铈稀土双掺杂Ce0.8Nd0.2-xPrxO1.9(x=0,0.10,0.15)固溶体。用X射线衍射(X-ray diffraction,XRD),Raman光谱和交流阻抗谱研究了固溶体的结构和导电性。XRD结果表明:经800℃焙烧所有的样品都形成了单相立方萤石结构,平均晶粒尺寸为22～32nm。X射线光电子能谱结果表明:样品中镨离子以混合价态(Pr3+和Pr4+)存在。Raman谱结果表明:Ce0.8Nd0.2-xPrxO1.9具有氧缺位的立方萤石结构,Pr离子的掺杂有利于氧缺位增加。阻抗谱表明:稀土双掺杂Ce0.8Nd0.2-xPrxO1.9(x=0.10,0.15)的电导率高于稀土单掺样品Ce0.8Nd0.2O1.9的,Ce0.8Nd0.05Pr0.15O1.9的电导率最大,在600℃时的电导率为2.63×10-2S/cm,导电活化能Ea=0.40eV(600～800℃),Ea=0.62eV(400～600℃),与Ce0.8Nd0.05Pr0.15O1.9材料内部更多的氧离子缺位和小极化子电子导电相关。     

有机泡沫浸渍法制备ZrO2泡沫陶瓷烧结过程研究

采用两种不同添加剂,用有机泡沫浸渍法制备了两种氧化锆泡沫陶瓷试样;用高温电阻炉分别在1300 ℃、1400 ℃、1500℃、1600 ℃下进行烧结制备试样;测试了在各温度下烧结试样的收缩率,用环境扫描电镜和能谱分析仪观察陶瓷的显微结构,用X射线衍射仪分析试样的物相组成.结果表明:试样的收缩主要发生在1300～1500 ℃,在1300 ℃进入烧结中期,1400～1500 ℃进入晶粒成长期,1500-1600 ℃进入晶粒异常长大期.采用MgO、CeO2复合稳定,对促进烧结、生成高温稳定相有一定作用,可以减小试样的收缩.制品中高温相的含量在1300～1500 ℃烧结温度范围内迅速增加,1500℃后逐渐减少.     

固体氧化物燃料电池复合电解质粉体BaCe0.8Y0.2O3–δ-Ce0.8Gd0.2O1.9的制备及表征

用分步硝酸盐-柠檬酸凝胶燃烧法制备新型混合离子传导复合电解质粉体BaCe0.8Y0.2O3-δ-Ce0.8Gd0.2O1.9[BCY-GDC,摩尔比n（BCY）：n（GDC）=1：1],研究不同烧结温度下制备的BCY-GDC电解质片的性能,以及以BCY-GDC为电解质的单电池的电性能。结果表明：采用该法可以获得分布均匀的BCY-GDC粉末,平均晶粒尺寸约为40nm;BCY-GDC复合电解质的相对密度随着烧结温度的升高而不断增大;1450℃烧结5h的电解质片基本达到完全致密,且BCY、GDC两相分布均匀,并且随着烧结温度的升高,复合电解质片的电导率增大;以BCY-GDC为电解质的单电池在450℃的开路电压达到0.95V,700℃的最大功率密度达到0.4W/cm2。     

Ce0.8 Y0.1 Gd0.1 O1.9电解质的制备及其性能研究

通过溶胶凝胶法制备了Y、Gd共同掺杂的CeO2粉末(Ce0.8Y0.1 Gd0.1O1.9,CYG).并将制得的粉末经1400℃下高温烧结4h得到相应的CYG电解质烧结体.对CYG粉末及烧结体进行了相应的性能测试.实验结果表明:用溶胶凝胶法成功制备出了纳米CYG粉末,所得CYG粉末具有良好的烧结活性,1400℃下烧结所得电解质材料烧结体的相对密度达到95.8%.电导率的测试表明,CYG电解质烧结体在中温范围有较高的电导率,800℃时,其电导率达到了0.084S·cm-1.     

La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)-Gd_(0.1)Ce_(0.9)O_(1.95)复相材料的性能

通过干压成型制备了La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O1.95(LSCF-GDC)系列双相复合材料,研究了不同LSCF含量对复合材料电导率及烧结性能的影响,同时对微观结构进行了深入分析。结果表明:LSCF含量越高,材料的电导率越高,LSCF质量含量为65%时,800℃电导率可达141.7S/cm。扫描电子显微镜分析了材料的微观结构,晶粒发育良好,结构致密;LSCF对GDC晶粒增长有抑制作用,LSCF质量含量为65%时,1 350℃烧结5h,GDC晶粒尺寸仅有0.3~0.6μm。因此具有很好的微观结构及电性能的双相复合LSCF-GDC透氧膜材料将具有很好的应用前景。     

外加微波作用下Sm0.15Gd0.05Ce0.8O1.9的制备研究

用Pechini法制备的Sm0.15Gd0.05Ce0.8O1.9在600℃时,立方萤石相己基本形成;在Pechini法的基础上外加微波场作用,制备的粉体粒径分布在14～16 nm之间,经1400℃烧结,烧结致密度达到96.5%,1600℃焙烧4h时,样品的烧结致密度达到99.3%。采用Pechini法(R=1.5)制备的粉体,经1400℃烧结其烧结致密度为理论密度的87%(1600℃时为96.2%)。采用外加微波场作用下制备的粉体具有更小的粒径和高的比表面积,其烧结驱动力要大于热场下Pechini法制备的粉体,能够在相对较低的烧结温度下获得很高的烧结致密度。     

微波法制备纳米铁酸锌及其晶粒生长动力学

纳米铁酸锌广泛应用于催化和材料领域,为了避免传统焙烧法高耗能的缺点,本实验选用高效微波法制备纳米铁酸锌,并与常规焙烧进行对比,研究了铁酸锌晶粒生长动力学。采用FTIR、XRD和SEM对样品进行表征。结果表明,相同焙烧温度和焙烧时间下,微波法制备的铁酸锌比常规制备的样品结晶度高,颗粒大小更均匀。通过谢乐公式计算不同温度下铁酸锌粒径得出,焙烧温度低于500℃时,焙烧方式对铁酸锌粒径影响较大;纳米铁酸锌晶粒生长动力学研究显示,微波焙烧时晶粒的平均生长指数为9.66,低于常规焙烧生长指数(10.6),表明微波焙烧时晶粒的平均生长速率较高,有利于晶粒生长;同时,微波晶粒生长平均活化能为122.1kJ/mol,远低于常规焙烧平均活化能(179.4kJ/mol),说明微波可以降低晶粒生长活化能,且微波的“非热效应”影响晶粒的生长。     

Al_2O_3-Si材料加热过程中物相组成和显微结构研究

以电熔刚玉骨料和细粉为主要原料,引入5%～8%的Si粉,以纸浆废液为结合剂制备了Al_2O_3-Si材料.研究了Al_2O_3-Si材料埋碳加热(1000～1600 ℃)过程中物相组成和显微结构的变化.结果表明: 1200 ℃烧后,Si开始与CO反应生成晶须状SiC,且晶须相互交叉连锁.1300～1400 ℃烧后,SiC晶须生成量明显增加,且发育长大,形成交叉连锁的网络填充在刚玉骨架结构中.1400 ℃烧后试样中还出现少量O'-SiAlON晶体.1500～1600 ℃烧后,SiC晶体发育长大,呈枝杈状和弯曲状.1400～1500 ℃烧后残留Si已熔化,发生塑性变形,起助烧结作用.     

Kinetics and mechanisms for the densification and grain growth of the α-alumina fibers isothermally sintered at elevated temperatures

Understanding the densification and grain growth processes is essential for preparing dense alumina fibers with nanograins. In this study, the alumina fibers were prepared via isothermal sintering at 1200, 1300, 1400, and 1500 °C for 1–30 min. The phase, microstructure, and density of the sintered fibers were investigated using XRD, SEM, and Archimedes methods. It was found that the phase transformation during the isothermal sintering enhances the densification of Al₂O₃ fibers in the initial stage, while the pores generated during the phase transformation retard the densification in the later period. The kinetics and mechanisms for the densification and grain growth of the fibers were discussed based on the sintering and grain growth models. It was revealed that the densification process of the fibers sintered at 1500 °C is dominated by the lattice diffusion mechanism, while the samples sintered at 1200–1400 °C are dominated by the grain boundary diffusion mechanism. The grain growth of the Al₂O₃ fibers sintered at 1200–1300 °C is governed by surface-diffusion-controlled pore drag, and that sintered at 1400 °C is dominated by lattice-diffusion-controlled pore drag.     

晶界相对半透明氮化铝陶瓷透过率的影响

分别添加质量分数为3%的CaF2和Y2O3为烧结助剂,在相同烧结工艺制度下采用放电等离子烧结(spark plasma sintering,SPS),制备了两种半透明AlN陶瓷.两种样品有相近的密实度和晶粒尺寸,但是它们的透过率却相差很大.用扫描电镜,X射线衍射分析和透射电镜结合能量散射型X射线光谱分析仪对样品微观结构进行分析.结果表明:晶界相的存在及分布方式对样品透过率有重要影响.添加CaF2的样品表现出很高的纯度,晶界及三角晶界处观察不到第二相.添加Y2O3的样品中,由于生成的晶界相Y3Al5O12沿AlN晶界分布,阻隔AlN晶粒之间的连接,在晶界处造成光散射,导致样品透过率下降.     

Electrical properties of samaria-doped ceria electrolytes from highly active powders

The correlations of the microstructures and the electrical properties of high reactive Ce_0.8Sm_0.2O_1.9 (SDC) powders, synthesized via an optimal carbonate coprecipitation method, were investigated. Microstructure of the SDC ceramics sintered at 900-1400 °C showed uniform grain and small grain size, compared with those prepared with various methods under similar sintering conditions. These features may be related to high conductivity (σ_600 °C = 0.022 S cm⁻¹) and low activation energy for conduction (0.66 eV). AC impedance spectra were involved to resolve grain interior and grain boundary resistance. Grain boundary contribution to the total resistance showed the values below 1/2 at 200-450 °C, suggesting low grain boundary effect. The motion enthalpy for the grain interior conduction decreased while the association enthalpy increased with sintering temperature up to 1300 °C, which might be possibly originated from the increase in lattice parameters with the sintering temperature.     

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   

Preliminary investigation of hydroxyapatite microstructures prepared by flash sintering

Flash sintering is a novel and emerging route for sintering ceramics within a few seconds, even under pressure-less conditions. In the current study, hydroxyapatite (HA) was fully densified by flash sintering at a furnace temperature of 1020°C. Flash sintering with constant electric fields of 750 and 1000?V?cm^?1 reduced the grain growth rate significantly compared to that sintered in the absence of an electric field at 1400°C. The microstructure of HA consolidated by flash sintering was compared with that of the without electric field sintered samples. The flash-sintered samples showed smaller grains (160?～?320?nm) than the without electric field sintered samples (～15?µm). The samples with a higher applied electric field showed slightly better densification than those with the lower field by flash sintering. Overall, the electric flash reduces the sintering temperature effectively and decreases the holding time to densify highly insulating ceramics, such as HA.     

溶胶-凝胶低温燃烧合成法制备Sm0.15Gd0.05Ce0.8O1.9纳米粉体

采用溶胶-凝胶与低温自蔓延燃烧相结合的方法合成了纳米级超细Sm0.15Gd0.05Ce0.8O1．9粉体，选用的合成体系有：柠檬酸-硝酸盐，甘氨酸-硝酸盐，EDTA络合-硝酸盐等方法。对所合成粉体进行了XRD，TEM及激光Raman光谱仪(laser Raman spectroscope，LRS)检测，研究了不同方法制备的粉体的结构及晶相。结果表明：XRD和LRS相结合能较好地表征固溶体的结构和纯度，几种方法合成的粉体为纯度高的掺杂氧化铈固溶体，晶粒尺寸较均匀，但分散性差。影响最终合成的超细粉体粒径的因素有：有机络合剂的种类、性质，有机络合剂与总金属阳离子比例及形成掺杂固溶体所需的温度。     

Influence of α-Al2O3 addition on sintering and grain growth behaviour of 8 mol% Y2O3-stabilised cubic zirconia (c-ZrO2)

The effect of α-Al₂O₃ addition on sintering and grain growth behaviour of high purity 8 mol% yttria-stabilised cubic zirconia (c-ZrO₂) was investigated. For these purposes, 1 wt.% α-Al₂O₃ was selected as a dopant in c-ZrO₂. The slip-cast specimens were sintered at different temperatures between 1150 and 1400 °C. It was seen that doped c-ZrO₂ had a faster sintering rate and lower sintering temperature than undoped c-ZrO₂. In particular, doped c-ZrO₂ achieved a density of 95% of its theoretical value at 1275 °C, while undoped c-ZrO₂ reached the same value at 1325 °C. The different sinterability of doped c-ZrO₂ and undoped c-ZrO₂ can be attributed to their different behaviour of grain growth. For grain growth measurements, the specimens sintered at 1400 °C were annealed at 1400, 1500 and 1600 °C for 10, 30 and 66 h. It was seen that grain growth rate could be controlled by the deliberate addition of 1 wt.% grain boundary phase of α-Al₂O₃. A grain growth exponent of 2 and activation energy for grain growth of 298 kJ/mol were obtained for undoped c-ZrO₂. The α-Al₂O₃ containing specimens had a grain growth exponent of 3 and activation energy of 361 kJ/mol. The slow grain growth in doped c-ZrO₂ is attributed to solute ions segregation in grain boundary region. The addition of the grain boundary phase results in limiting matter transfer along the grain boundary resulting in slower grain growth.