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排序方式: 共有655条查询结果,搜索用时 37 毫秒
1.
为寻求新型热障涂层用陶瓷材料,本文采用高温固相烧结法制备了(Sm0.5Gd0.2Nd0.3)2(Hf0.3Ce0.7)2O7复合氧化物。利用XRD分析了其晶体结构,SEM分析其显微组织,膨胀仪测试其热膨胀性能,激光热导仪测试其热扩散系数。结果表明,成功制备了具有单一萤石晶体结构的(Sm0.5Gd0.2Nd0.3)2(Hf0.3Ce0.7)2O7复合氧化物。其显微组织结构致密,晶界清晰无其他相存在。由于复杂的元素组成和较大的原子量,其热导率明显低于7YSZ和Sm2Ce2O7。其较低的热膨胀系数则归因于B位离子较小的离子半径,但其热膨胀系数依然满足热障涂层的要求。 相似文献
2.
Xiong Sun Dr. Wei Su Kaiying Shi Zhuoyi Xie Prof. Dr. Congqing Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5354-5359
Rare-earth metal cations have been used rarely as Lewis-acidic components in the chemistry of frustrated Lewis pairs (FLPs). Herein, we report the first cerium/phosphorus system ( 2 ) employing a heptadentate N4P3 ligand, which exhibits triple FLP-type reactivity towards a series of organic substrates, including isocyanates, isothiocyanates, diazomethane, and azides on a single rare-earth Lewis acidic Ce center. This result shows that the Ce center and three P atoms in 2 could simultaneously activate three equivalents of small molecules under mild conditions. This study broadens the diversity of FLPs and demonstrates that rare earth based FLP exhibit unique properties compared with other FLP systems. 相似文献
3.
Lianghao Song Tiantian Xu Daowei Gao Prof. Xun Hu Prof. Cuncheng Li Prof. Shun Li Prof. Guozhu Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(26):6621-6627
CeO2-based catalysts are widely studied in catalysis fields. Developing one novel synthetic approach to increase the intimate contact between CeO2 and secondary species is of particular importance for enhancing catalytic activities. Herein, an interfacial reaction between metal–organic framework (MOF)-derived carbon and KMnO4 to synthesize CeO2−MnO2, in which carbon is derived from the pyrolysis of Ce-MOFs under an inert atmosphere, is described. The MOF-derived carbon is found to restrain the growth of CeO2 crystallites under a high calcination temperature and, more importantly, intimate contact within CeO2/C is conveyed to CeO2/MnO2 after the interfacial reaction; this is responsible for the high catalytic activity of CeO2−MnO2 towards CO oxidation. 相似文献
4.
Thammadihalli Nanjundaiah Ravishankar Thippeswamy Ramakrishnappa Ganganagappa Nagaraju Hanumanaika Rajanaika 《ChemistryOpen》2015,4(2):146-154
CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm−1 due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa. 相似文献
5.
The present study describes the simple and fast preparation of Cerium (III) hexacyanoferrate (II) (CeHCF) solid nanoparticles at three different water/formamide (%) ratios used as solvent (v/v) (100:0, 80:20, 0:100). CeHCF nanoparticles (Nps) were characterized by fourier transform infrared pectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), zeta potential and cyclic voltammetry (CV). Electrodes modified with CeHCF presented a well-defined redox pair with formal potential (Eo′) of approximately 0.29 V (vs. Ag/AgCl(sat) attributed to the Fe2 +/Fe3+ redox pair in the presence of cerium (III)). The Nps in the three systems investigates, presents a random size distribution to different surface, where most were distributed between 20 and 160 nm. Considering the three investigated systems, only CeHCF-1 (100:0) was sensitive to L-dopamine, presenting a linear signal region as a function of L-dopamine concentrations, with a limit of detection (LD) of 0.125 mmol L−1, limit of quantification (LQ) of 0.419 mmol L−1 and amperometric sensitivity (S) of 148.16 μA mmol L−1. 相似文献
6.
Amivi Felicite Amoudji Sylvie Arpigny Philippe Moisy Fethi Bedioui 《Electroanalysis》2021,33(8):1871-1876
In this work we report on the electrochemical behavior of Ce(IV)/Ce(III) redox couple in pure N,N-dialkyl amides (N,N-DA), namely N,N-di(2-ethylhexyl)-n-butanamide (DEHBA), N,N-di(2-ethylhexyl)-iso-butanamide (DEHiBA), and N,N-di(2-ethylhexyl)-3,3-dimethyl butanamide (DEHDMBA) equilibrated with nitric aqueous solutions as an entry to the direct electrochemical characterization of plutonium in these extractants. Ce(IV)/Ce(III) redox process was used as a model. Its potential (E1/2≅1.02 V/SCE) is not affected by the temperature and the nature of the N,N-DA and this clearly indicates that the functionalities of these extractants produce the same relative effect on both +IV and +III oxidation states of the cerium cation. Linear variations of the current intensity of the reduction peak of Ce(IV) with the concentration of Ce(IV)/N,N-DAs/HNO3(5 M) solutions were obtained from cyclic voltammograms recorded at 25 °C and 40 °C. Due to the poor definition of the voltammograms in DEHiBA and DEHDMBA, such characterization allows only the evaluation of the performances of the chemical extraction of Ce(IV) from aqueous nitric acid solution by the undiluted DEHBA. To our knowledge, the electrochemical behavior of Ce(IV)/Ce(III) in N,N-DAs was not previously studied and our findings will for sure open the door for further investigations in this field. 相似文献
7.
Parmish Kaur Lukas Mai Arbresha Muriqi David Zanders Ramin Ghiyasi Dr. Muhammad Safdar Nils Boysen Manuela Winter Prof. Michael Nolan Prof. Maarit Karppinen Prof. Anjana Devi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(15):4913-4926
Owing to the limited availability of suitable precursors for vapor phase deposition of rare-earth containing thin-film materials, new or improved precursors are sought after. In this study, we explored new precursors for atomic layer deposition (ALD) of cerium (Ce) and ytterbium (Yb) containing thin films. A series of homoleptic tris-guanidinate and tris-amidinate complexes of cerium (Ce) and ytterbium (Yb) were synthesized and thoroughly characterized. The C-substituents on the N-C-N backbone (Me, NMe2, NEt2, where Me=methyl, Et=ethyl) and the N-substituents from symmetrical iso-propyl (iPr) to asymmetrical tertiary-butyl (tBu) and Et were systematically varied to study the influence of the substituents on the physicochemical properties of the resulting compounds. Single crystal structures of [Ce(dpdmg)3] 1 and [Yb(dpdmg)3] 6 (dpdmg=N,N'-diisopropyl-2-dimethylamido-guanidinate) highlight a monomeric nature in the solid-state with a distorted trigonal prismatic geometry. The thermogravimetric analysis shows that the complexes are volatile and emphasize that increasing asymmetry in the complexes lowers their melting points while reducing their thermal stability. Density functional theory (DFT) was used to study the reactivity of amidinates and guanidinates of Ce and Yb complexes towards oxygen (O2) and water (H2O). Signified by the DFT calculations, the guanidinates show an increased reactivity toward water compared to the amidinate complexes. Furthermore, the Ce complexes are more reactive compared to the Yb complexes, indicating even a reactivity towards oxygen potentially exploitable for ALD purposes. As a representative precursor, the highly reactive [Ce(dpdmg)3] 1 was used for proof-of-principle ALD depositions of CeO2 thin films using water as co-reactant. The self-limited ALD growth process could be confirmed at 160 °C with polycrystalline cubic CeO2 films formed on Si(100) substrates. This study confirms that moving towards nitrogen-coordinated rare-earth complexes bearing the guanidinate and amidinate ligands can indeed be very appealing in terms of new precursors for ALD of rare earth based materials. 相似文献
8.
Magnetic Relaxation in Single‐Electron Single‐Ion Cerium(III) Magnets: Insights from Ab Initio Calculations 下载免费PDF全文
Saurabh Kumar Singh Tulika Gupta Dr. Liviu Ungur Prof. Dr. Gopalan Rajaraman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13812-13819
Detailed ab initio calculations were performed on two structurally different cerium(III) single‐molecule magnets (SMMs) to probe the origin of magnetic anisotropy and to understand the mechanism of magnetic relaxations. The complexes [CeIII{ZnII(L)}2(MeOH)]BPh4 ( 1 ) and [Li(dme)3][CeIII(cot′′)2] ( 1 ; L=N,N,O,O‐tetradentate Schiff base ligand; 2 ; DME=dimethoxyethane, COT′′=1,4‐bis(trimethylsilyl)cyclooctatetraenyldianion), which are reported to be zero‐field and field‐induced SMMs with effective barrier heights of 21.2 and 30 K respectively, were chosen as examples. CASSCF+RASSI/SINGLE_ANISO calculations unequivocally suggest that mJ|±5/2〉 and |±1/2〉 are the ground states for complexes 1 and 2 , respectively. The origin of these differences is rooted back to the nature of the ligand field and the symmetry around the cerium(III) ions. Ab initio magnetisation blockade barriers constructed for complexes 1 and 2 expose a contrasting energy‐level pattern with significant quantum tunnelling of magnetisation between the ground state Kramers doublet in complex 2 . Calculations performed on several model complexes stress the need for a suitable ligand environment and high symmetry around the cerium(III) ions to obtain a large effective barrier. 相似文献
9.
Inside Back Cover: Isolation of CeLu2N@Ih‐C80 through a Non‐Chromatographic,Two‐Step Chemical Process and Crystallographic Characterization of the Pyramidalized CeLu2N within the Icosahedral Cage (Chem. Eur. J. 29/2015) 下载免费PDF全文
10.
Yu. Zorenko V. Gorbenko T. Zorenko O. Sidletskiy A. Fedorov P. Bilski A. Twardak 《固体物理学:研究快报》2015,9(8):489-493
We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd3–xLux Al5–yGay O12:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.75–2Ga2.25–3O12:Ce SCF show the light yield (LY) comparable with that of high‐quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5–1.6 times the values previously reported for SCF scintillators.