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31.
Yudan Wei Shuguo Zhang Shuangfeng Yin Chang Zhao Shenglian Luo Chak-tong Au 《Catalysis communications》2011,12(14):1333-1338
We report for the first time the synthesis of a novel solid superbase that was derived from lanthanum–magnesium composite oxide and KOH through thermal treatment. The as-prepared material shows base strength (H–) above 26.5 and is a high-efficiency catalyst for solvent-free Knoevenagel condensation at room temperature. The results of the present study open up a new dimension for the use of composite oxides as new support materials in the synthesis of superbases. 相似文献
32.
Sung Min Shin Byoung Young Yoon Jung Hyun Kim Joong Myeon Bae 《International Journal of Hydrogen Energy》2013
In this study, the performance improvement of the SOFC single cell and its underlying mechanism was investigated. Furthermore, an application of the identified electrochemical mechanism is proposed and tested experimentally. The deposition of Platinum (Pt) at electrochemically active sites for the oxygen reduction reaction is determined to be responsible for the improved performance. Pt migration from a current collector to the cathode active sites originates from the oxygen partial pressure difference between current collector and triple phase boundary, and the electrochemical reduction reaction. It is supported by the confirmation of Pt particles at the cathode active sites by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and calculations of the thermodynamic equilibrium partial pressure values. In addition, correlation of the initial performance change and the quantities of Pt deposition are investigated. This selective Pt deposition mechanism at the active sites is applied to the LSCF cathode, as well. 相似文献
33.
Improvement of Fracture Toughness Lanthanum Zirconate 总被引:1,自引:0,他引:1
Thermalbarriercoatings(TBCs)havefoundan increasingnumberofapplicationsinprotectinghigh temperaturemetalliccomponents,forexample,TBCsaredepositedontransitionpieces,combustion lines,first stagebladesandvanes,andotherhot pathcomponentsofgasturbineseithertoincreasethe inlettemperaturewithaconsequentimprovementof theefficiencyortoreducetherequirementsfora coolingsystem[1].Thereareseveralceramicsthat havebeenevaluatedasTBCmaterials[2].Lanthanum zirconatewasrecentlyproposedasapromisingTBC materia… 相似文献
34.
StudyonMonoxideEmisionSpectrometryofRareEarthElementsⅠ.DeterminationofSminRareEarthConcentratebyDualWavelengthMethodZhangZaiz... 相似文献
35.
Dispersion conditions for slip (slurry) formulation of a powder mixture of lanthanum strontium manganite (La0.84Sr0.16MnO3 - LSM) and carbon (pore former) in water was studied through detailed zeta-potential and rheological measurements. The zeta potential variation with pH for the aqueous suspensions of only LSM or carbon exhibited a maximum value in alkaline medium (−40 mV to −50 mV at a pH of 10-11), establishing the pH window for their co-dispersion for slurry formulation. A study of the viscosity variation with shear rate for the slurries with varying solid content (in the range of 45-65 wt.%) exhibited pseudo-plastic flow behavior, indicating presence of flocculates in them. The yield stress values obtained from the Casson equation reduced with decreasing solid content, indicating reduction in the flocculate strength. The slip with solid content of 50 wt.% exhibited optimum flow characteristics to form long tubes with uniform wall thickness (wall thickness 2-4 mm and length of 150-200 mm). The tubular specimens formed after controlled carbon burn out and sintering at 1400 °C for 1 h possessed about 35% open porosity. The porosity remained the same upon further sintering at 1400 °C for 8 h. 相似文献
36.
Abbas Saeed Hakeem Jekabs Grins Saeid Esmaeilzadeh 《Journal of the European Ceramic Society》2007,27(16):4783-4787
Vickers hardness and refractive index have been determined for a series of La-Si-O-N oxy-nitride glasses containing 30–62 e/o of La and 9–68 e/o of N. The hardness varies between 7.7 and 11.5 GPa at a load of 1 kg and is dependent of the N content, while the La content does not influence it significantly. The increase of the hardness with N content is, contrary to reported findings for other oxy-nitride glasses, found not to be linear over the whole compositional range. The refractive index varies between 1.8 and 2.3 and increases non-linearly with increasing N content. The compositional variations of hardness and refractive index are compared with previously published results. 相似文献
37.
Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions
of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals
of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this
method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with
two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)
support that LSO loses water around 120°C, and CO and CO2 around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C2 O4)2− ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic
(XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has
been proposed on the basis of these findings. 相似文献
38.
利用差示扫描量热仪(DSC)考察了氧化镧(La2O3)/低密度聚乙烯(LDPE)复合材料的非等温结晶行为。通过Jeziorny法、Ozawa法及莫志深法研究了复合材料的非等温结晶动力学。结果表明:在添加La2O3后,LDPE成核速率降低,结晶度下降,晶体粒径分布变宽。在非等温结晶动力学分析中,Jeziorny法lg[-ln(1-Xt)]~lgt关系曲线在结晶前期和中期具有较好的线性关系,结晶后期产生较大偏离;Ozawa法并不适用;而莫志深法适用于该体系的研究,表明La2O3的加入使LDPE结晶速率增大。 相似文献
39.
《International Journal of Hydrogen Energy》2023,48(47):17838-17851
Sustainable energy innovation is spearheading the way to achieve decarbonisation through commercially viable and highly competitive renewable technologies for green hydrogen. Photocatalytic water splitting has received global attention, as it promotes the direct conversion of solar energy to chemical energy and hydrogen production. Lanthanum orthoferrite (LaFeO3) has been selected due to its narrow bandgap perovskite-oxides (ABO3) type nature, low cost and high chemical stability but it is limited with fast charge recombination. To circumvent its constraint of fast charge recombination, an efficient graphene-based nanocomposite has been prepared by employing reduced graphene oxide (RGO) nanosheets as charge separators for visible light driven photocatalytic water splitting. Here, we present a thorough physical and spectroscopic characterization of the Lanthanum orthoferrite/Reduced Graphene oxide (LaFeO3/RGO) nanocomposites, and investigate its photocatalytic and photoelectrochemical performance. The photocurrent density of the nanocomposites demonstrated ∼21 times higher in comparison to pure LaFeO3. The as-prepared nanocomposites have been successfully used as photocatalysts for H2 generation through water reduction under visible light. A significant enhancement in H2 generation has been recorded for nanocomposites (∼82 mmol g−1 h−1) as compared to that of bare LaFeO3 (∼9 mmol g−1 h−1) which is among the highest values obtained using noble-metal-free graphene-based photocatalytic nanocomposites. This work offers a facile approach for fabricating highly efficient 1D-2D heterostructure for photocatalysis application. 相似文献
40.
Parveen Kumar Sangeeta Singh J.K. Juneja Chandra Prakash K.K. Raina 《Materials Chemistry and Physics》2011
Lanthanum modified Ba0.80Pb0.20Ti0.90Zr0.10O3 (BPZT) ceramics with composition Ba0.80−xLax Pb0.20Ti0.90Zr0.10O3; x = 0–0.01 in steps of 0.0025 were prepared by conventional solid state method. All the samples were sintered at 1325 °C after compacting in circular discs. Detailed structural and ferroelectric properties were carried out for sintered specimens. X-ray diffraction analysis for all the sintered specimens shows tetragonal structure with perovskite. Coercive field (Ec) and remanent polarization (Pr) to spontaneous polarization (Ps) ratio (Pr/Ps) was found to decrease with increase in temperature. Pr/Ps ratio was found to decrease with increase in x, except x = 0.0025. 相似文献