Fe2O3掺杂Ce0.8Nd0.2O1.9固体电解质的结构与导电性能

采用溶胶-凝胶法合成SiO2含量小于50×10-6的Ce0.8Nd0.2O1.9(NDC)陶瓷粉体,并将少量Fe2O3加入到NDC体系中,讨论Fe2O3的掺杂对其微观结构及电性能的影响。通过X射线衍射(XRD)等手段对氧化物进行结构表征,交流阻抗谱(AC)测试电性能。研究表明,Fe2O3的掺杂显著提高NDC陶瓷材料的致密度;相比于NDC而言,加入Fe2O3后材料的晶界电导率提高约12倍,总电导率提高约6倍。     

La0.8Sr0.2Ga0.8Mg0.2O3与La0.8Sr0.2Ga0.8Mg0.15Co0.05O3电导的对比

采用固相合成法制备了La0.8Sr0.2Ga0.8Mg0.2O3(LSGM8282)和La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5), 利用四电极交流阻抗法和Hebb-Wagner 极化法对比研究了两种材料的总电导率和电子电导率. 实验结果表明, LSGM8282 的总电导率与氧分压无明显依赖关系, 而LSGMC5 的总电导率在高氧分压区随氧分压降低而增加,在中等氧分压区域基本保持不变. 在973-1173 K的温度范围内, LSGM8282的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和1/4.在1073-1173 K的温度范围内, LSGMC5的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和约为1/8, 表明LSGMC5的空穴产生机制可能与LSGM8282不同. LSGM8282 的氧离子电导率与氧分压无关, 而LSGMC5 的氧离子电导率在高氧分压区随氧分压的减小而增加.     

ET类分子导体3d轨道对晶体能带及导电性的影响

采用扩展休克尔 -紧束缚方法 (EHTB)研究了ET类分子导体 [ET =bis (ethylenedithio) tetrathiafulvalene]的能带 .讨论了硫原子 3d轨道对能带结构的影响 ,添加 3d轨道导致ET分子柱间的横向作用大为增强 ,并与纵向作用处于同一数量级 ,这一结论解释了晶体二维导电性的实验结果 .计算得到 (ET) 2 C3 H5SO3 ·H2 O ,(ET) 2 HgCl3 ·TCE两个晶体的带隙分别为0 5 79,0 .5 72eV ,与实验得到的导电激活能 0 .3 19,0 .3 0 8eV符合较好 .     

MgO或Fe2O3掺杂Ce0.8Nd0.2O1.9固体电解质的结构和电性能

采用溶胶-凝胶法合成SiO2含量为0.05%(w,质量分数)的Ce0.8Nd0.2O1.9(NDC)粉体(NDCSi).分别将0-2.0%(x,摩尔分数)的MgO或FeO1.5添加到NDCSi粉体中,经10MPa压片后于1300°C烧结6h.采用X射线衍射(XRD)、拉曼(Raman)光谱和场发射扫描电子显微镜(FE-SEM)对样品进行结构表征.采用交流(AC)阻抗谱测试样品导电性能.结果表明:所有样品均呈现单一立方萤石结构.MgO或Fe2O3掺杂于NDCSi体系,均可提高材料的致密度,降低烧结温度,提高材料的晶界电导率和总电导率.掺杂MgO或Fe2O3样品的相对密度(>93%)高于NDC或NDCSi(约86%),有效促进了样品致密化.掺杂Fe2O3或MgO的样品(NDCSi+0N.D5FCeSOi样1.5或品总ND电C导Si率+2(.10.M1×g1O0)-具3S有·c最m高-1)电的导5.7率和,525.60倍°C.M时g总O电或导Fe率2O分3掺别杂是于6.N3D×C10S-i3样或品2.对9×晶10界-3电S·导c率m-的1,是影响比晶粒电导率更明显.MgO或Fe2O3掺杂于NDCSi均具有烧结助剂和晶界清除剂的双重作用,但清除杂质SiO2的机制不同.     

Effects of MoO3 Amounts on Sintering and Electrical Properties of Ce0.8Nd0.2O1.9

The high purity (Ce_0.8Nd_0.2O_1.9)_1-x(MoO₃)_x(x=0, 0.005, 0.010, 0.020; Ce_0.8Nd_0.2O_1.9=NDC) solid solutions were prepared by modified sol-gel method. The structures and electric conductivities were characterized by X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM) and electrochemical impedance spectroscopy( EIS). The XRD results show that the materials were pure phase with a cubic fluorite structure. Compared to the undoped-NDC samples, MoO3 doped-NDC showed higher sintered density(over 96%) at reduced sintering temperature. The electric conductivity(σ_t) of (Ce_0.8Nd_0.2O_1.9)_1-x(MoO₃)_x at 400 ℃ was 9.58×10^–4 S/cm when x=0.010, which was higher than that of undoped-NDC samples(σ_t=3.29×10^–4 S/cm). The obtained optimal amount of the MoO₃ was x=0.010 in this system.     

制备方法及焙烧温度对Co3O4/CeO2催化剂上CO低温氧化反应的影响

 分别采用沉淀氧化法、均匀沉淀法及络合燃烧法制备了Co3O4/CeO2复合氧化物催化剂,并在干燥及湿气条件下进行了CO氧化反应. 结果表明,采用沉淀氧化法经538 K焙烧制得的Co3O4/CeO2催化剂具有优异的CO低温氧化活性和较高的抗湿性能. 在196 K条件下,该催化剂上CO氧化的转化率为99%, 并且可连续保持400 min以上; 当温度上升到298 K时,经过 2400 min反应后, CO的转化率仍可达到94%; 当反应气中含3.1%湿气,温度为383 K时,经过2400 min反应后, CO的转化率仍保持在79%. 实验表明, Co3O4/CeO2催化剂的制备方法及焙烧温度对Co3O4与CeO2之间的相互作用有显著的影响,进而影响催化剂催化CO低温氧化的活性.     

掺杂MoO_3对Ce_(0.8)Nd_(0.2)O_(1.9)固体电解质结构与电性能的影响

采用溶胶凝胶方法将过渡金属氧化物MoO3加入到Ce0.8Nd0.2O1.9体系中,讨论MoO3的掺杂对微观结构及电性能的影响。通过X-射线衍射(XRD)、场发射扫描电镜(FE-SEM)等手段对氧化物进行结构表征,交流阻抗谱测试电性能。结果表明:烧结过程中MoO3在晶粒边缘形成液相,增加了晶粒间浸润性,晶粒间位置重排并接触,晶界滑移加快,促使材料致密化,晶界体积分数降低;总电导率和晶界电导率因晶界电阻减少而提高。600℃时,NDC的σt和σgb分别为6.42×10-3和2.03×10-2S·cm-1,加入MoO3后材料的σt提高约1.5倍,σgb提高约4倍。MoO3是NDC体系理想的烧结助剂。     

Characterization of Ru/CeO2-Al2O3 catalysts and their Performance in CO2 Methanation

Ru/Al₂O₃ and Ru/CeO₂-Al₂O₃ samples were used as catalysts in CO₂ methanation. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction. The promoting effect of ceria on the cataytic activity of the catalysts under study in CO₂ methanation was observed.     

Y2O3和CeO2对氮化硅烧结性能的影响

研究了Y2O3,CeO2的添加量在不同烧结温度下对Si3N4烧结性能的影响，分析了其助烧作用及晶界二次小晶粒形成的机制。结果表明，添加Y2O3,CeO2的Si3N4其烧结性能良好。Y2O3添加5％（此时Al2O3含量为4％）及CeO2为8％时对制品烧结促进作用最大。热处理后在Si3N4晶界获得结晶完美的二次小晶粒，使晶界玻璃相大为下降，为Si3N4高温力学性能的提高奠定结构基础。     

有效主量子数拓扑指数与分子总键能和晶格能的关系

作者定义ＡｊＢｋ分子的有效主量子数拓扑指数（Ｐ）为：Ｐ＝∑（ｎＡ·ｎＢ）－０．５。它与化合物的总键能（ΔＥ）、晶格能（Ｕ）呈现高度相关性,其直线回归方程为：ΔＥ＝－２８．４５１８＋１１１７．８９８Ｐ,Ｒ＝０．９３５４Ｕ＝１９６．６７０３＋１６６５．６２６６Ｐ,Ｒ＝０．９８８２用它预测ΔＥ、Ｕ,估算值与实验值基本吻合     

Phase composition, electroconductivity, oxygen ion transport number, and microhardness of Ln1 ? xSrxGa0.5 ? y/2Al0.5 ? y/2MgyO3 ? δ (Ln = La, Pr, Nd; x, y = 0.10, 0.15)

Phase composition, electroconductivity, oxygen ion transport number, and microhardness of samples of Ln_{1 − x} Sr_xGa_{0.5 − y/2}Al_{0.5 − y/2}Mg_yO_{3 − δ} (Ln = La, Pr, Nd; x, y = 0.10, 0.15) synthesized by a ceramic methods are studied. Methods of x-ray diffraction analysis and scanning electron microscopy reveal the La-containing samples to be homogeneous and have a perovskite structure. Magnesium does not dissolve in Pr-and Nd-containing systems but forms an individual phase based on magnesium oxide. Apart from magnesium oxide, in these systems there form extrinsic phases, specifically, LnSrGa₃O₇ and an unknown phase. The electroconductivity of La_{1 − x} Sr_xGa_{1 − y} Mg_yO_{3 − δ} decreases after substituting Al for Ga. Ceramic La_{1 − x} Sr_xGa_{0.5 − y/2}Al_{0.5 − y/2}Mg_yO_3−δ is a purely ionic conductor in the temperature interval 500 to 1000°C; Nd_xSr_xGa_{0.5 − y/2}Al_{0.5 − y/2}Mg_yO_{3 − δ} has predominantly ionic conduction; and the predominant type of conduction in Pr_{1 − x} Sr_xGa_{0.5 − y/2}Al_{0.5 − y/2}Mg_yO_{3 − δ} is electronic below 700–800°C, with the contribution of ionic conduction increasing at higher temperatures. Substituting Al for Ga raises the hardness of ceramics under study. Among the compositions studied, La_0.85Sr_0.15Ga_0.45Al_0.45Mg_0.10O_{3 − δ} and La_0.85Sr_0.15Ga_0.425Al_0.425Mg_0.15O_{3 − δ} exhibit a combination of electroconductivity and hardness that is optimal for application as electrolyte at reduced temperatures (600–800°C). The Pr_{1 − x} Sr_xGa_{0.5 − y/2}Al_{0.5 − y/2}Mg_yO_{3 − δ} system possesses mixed ionic-electronic conduction and high hardness, which makes it appealing for application as oxygen-penetrable membranes. Original Russian Text ? Yu.V. Danilov, A.D. Neuimin, L.A. Dunyushkina, L.A. Kuz’mina, N.S. Zybko, Z.S. Martem’yanova, A.A. Pankratov, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 1, pp. 57–65.     

Effect of post-annealing in air on optical and XPS spectra of Y2O3 ceramics doped with CeO2

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A Highly Reactive and Sinter-Resistant Catalytic System Based on Platinum Nanoparticles Embedded in the Inner Surfaces of CeO(2) Hollow Fibers

Ceria (CeO(2) ) hollow fibers with Pt nanoparticles (Pt?NPs) embedded in their inner surfaces were prepared by sequentially depositing Pt?NPs and CeO(2) sheaths on electrospun fibers of polystyrene, followed by calcination in air at 400?°C. Despite a relatively low Pt loading in this system, the turnover frequency for CO oxidation was 2-3 orders of magnitude higher than those of other systems, and the reactivity was also stable up to 700?°C.     

Identifying the O2 diffusion and reduction mechanisms on CeO2 electrolyte in solid oxide fuel cells: A DFT + U study

The interactions and reduction mechanisms of O₂ molecule on the fully oxidized and reduced CeO₂ surface were studied using periodic density functional theory calculations implementing on‐site Coulomb interactions (DFT + U) consideration. The adsorbed O₂ species on the oxidized CeO₂ surface were characterized by physisorption. Their adsorption energies and vibrational frequencies are within ?0.05 to 0.02 eV and 1530–1552 cm^?1, respectively. For the reduced CeO₂ surface, the adsorption of O₂ on Ce⁴⁺, one‐electron defects (Ce³⁺ on the CeO₂ surface) and two‐electron defects (neutral oxygen vacancy) can alter geometrical parameters and results in the formation of surface physisorbed O₂, O₂^a? (0 < a < 1), superoxide (O₂^?), and peroxide (O₂^2?) species. Their corresponding adsorption energies are ?0.01 to ?0.09, ?0.20 to ?0.37, ?1.34 and ?1.86 eV, respectively. The predicted vibrational frequencies of the peroxide, superoxide, O₂^a? (0 < a < 1) and physisorbed species are 897, 1234, 1323–1389, and 1462–1545 cm^?1, respectively, which are in good agreement with experimental data. Potential energy profiles for the O₂ reduction on the oxidized and reduced CeO₂ (111) surface were constructed using the nudged elastic band method. Our calculations show that the reduced surface is energetically more favorable than the unreduced surface for oxygen reduction. In addition, we have studied the oxygen ion diffusion process on the surface and in bulk ceria. The small barrier for the oxygen ion diffusion through the subsurface and bulk implies that ceria‐based oxides are high ionic conductivity at relatively low temperatures which can be suitable for IT‐SOFC electrolyte materials. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

The standard transported entropy of chloride ion in H2O and D2O

Transported entropies of the chloride ion, , in H₂O and in D₂O at 25°C and at concentrations ranging from 0.001 to 0.04m have been determined from the measurements of the steady-state (final) thermoelectric powers of the silver-silver chloride thermocell. Experimental data was extrapolated to infinite dilution to obtain the standard transported entropy . The concentration dependence of is examined and the solvent-isotope effect on the transported entropy is investigated. Thermodynamic data on the entropy of transfer of chloride ion from H₂O to D₂O is used to estimate the difference of the standard ionic entropy of transport in H₂O and D₂O for chloride ion.     

Thermal analysis and epr studies of carbon black oxidation in the presence of copper loaded Y2O3-CeO2-ZrO2 catalyst

The activity of copper-free and copper-loaded 10Y₂O₃-10CeO₂-80ZrO₂ solid solutions towards carbon black combustion was studied using simultaneous thermogravimetric analysis and differential thermal analysis techniques coupled with gas chromatography. It was demonstrated that all studied catalysts lower the temperature of carbon black combustion. The selectivity of the catalytic reaction in CO₂ formation was 100%. The comparison of electron paramagnetic resonance (EPR) spectra of pure catalysts with those of the samples (catalysts mixed with carbon black) after catalysis allowed to evidence, despite of the strong oxidizing atmosphere, a thermal reduction by carbon of Fe³⁺ (impurities), Cu²⁺ and Zr⁴⁺ during the reaction. Moreover a new EPR signal appeared after catalytic test and was attributed to the presence of paramagnetic metal-carbon or/and metal-sulphur complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enhanced Electron Transfer and Ion Transport by Binary and Multidimensional CuCo2S4/Fe2O3 on Carbon Cloth for Water Oxidation

The behavior of electron transfer and ion transport plays a significant role in the electrocatalytic activity. However, the improvement of CuCo₂S₄ electrocatalytic activity has been a difficult problem owing to lack of effective electron transfer and ion transport. Herein, the unique structure connected CuCo₂S₄ nanosheets and carbon cloth (CC) with Fe₂O₃ nanoparticles to form CuCo₂S₄/Fe₂O₃/CC. Compared with CuCo₂S₄/CC, the resistances of electron transfer and ion transport were decreased by 65 and 84 %, respectively. The electrochemical surface area of CuCo₂S₄/Fe₂O₃/CC was 2.76 times larger than that of CuCo₂S₄/CC due to the high double-layer capacitance. For the oxygen evolution reaction, CuCo₂S₄/Fe₂O₃/CC could achieve an overpotential of 273 mV and a Tafel slope of 67 mV dec⁻¹ in alkaline solution.     

极化效应指数与脂肪酯类化合物沸点的定量构效关系研究

基于烷基极化效应指数(PEI)构建了有效碳原子数(N_Ceff)用于定量表示烷基碳链相对长度. 用最佳子集回归方法建立了脂肪酯沸点与PEI, N_Ceff参数的定量构效关系模型, 该模型对训练集计算值与实验值的相关系数R²为0.9958, 标准偏差s为3.98 K, 对测试集预测值与实验值的相关系数R²分别为: 0.9958, 标准偏差s为3.92 K, 计算结果表明基于参数PEI和N_Ceff所建立的脂肪酯类化合物的沸点定量构效关系模型具有良好的预测能力.     

Y3+对LiMn2O4的结构和电化学性能的影响

以Li2CO3、电解MnO2和Y2O3为原料,采用固相法合成了Li1.02YxMn2-xO4(x=0,0.005,0.01,0.02,0.04,0.1)。XRD测试表明,不同Y3 掺杂量的Li1.02YxMn2-xO4晶型发育良好。Y3 的加入使Li1.02YxMn2-xO4晶格常数和晶胞体积变小。循环伏安测试结果表明,少量Y3 的加入没有改变锂离子脱嵌过程,但随着掺杂量的增加,锂离子脱嵌过程趋于容易,能有效地避免能级分裂。电化学性能测试表明,当掺杂量x=0.02时,初始容量为117.2mAh.g-1,20次循环容量衰减至113.6mAh.g-1,容量保持率为96.90%;Y3 的加入很好地起到了稳定晶体结构,有效抑制Jahn-Teller效应的作用。交流阻抗测试结果表明,Y3 的加入能改善材料的导电性能。