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1.
Zn-doped LiNi0.8Co0.2O2 exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi0.8Co0.15Zn0.05O2 as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al2O3 layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al2O3-coated LiNi0.8Co0.15Zn0.05O2 cathode delivers a highly reversible capacity of 182 mA h g?1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi0.8Co0.15Zn0.05O2 cathode. The enhanced electrochemistry performance can be attributed to the Al2O3-coated protective layer, which prevents the direct contact between the LiNi0.8Co0.15Zn0.05O2 and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al2O3-coated LiNi0.8Co0.15Zn0.05O2, which rationally illuminates the protection mechanism of the Al2O3-coated layer.  相似文献   

2.
New barium bismuth oxides have been synthesized under an argon atmosphere at 530 and 430°C, respectively: a Ba: Bi = 1 : 4 phase has a tetragonal perovskite structure, and a 1 : 15 phase has a rhombohedral structure. For the 1 : 4 phase, the unit cell parameters are a = 4.297(2) Å and c = 4.472(2) Å as determined by powder X-ray diffraction (XRD). Electron diffraction (ED) patterns show superstructure reflections with the vectors q 1= 1/17[530], q 2 = 1/17[3\(\bar 5\)0], and q 3 = 1/5[002]. These reflections point to an ordered arrangement of barium and bismuth ions in the supercell with the parameters √17a and 5c. The supercell of the 1 : 4 phase includes a ten-layer stack of metal-oxygen planes along the c axis. The rhombohedral 1 : 15 phase has the following hexagonal unit cell parameters as determined by XRD: a= 6.018(2) Å, c = 4.070(2) Å. In view of the superstructure on the ED patterns, the supercell parameters of the rhombohedral phase are 4a and 2c. The supercell of the 1 : 15 phase contains a six-layer stack of planes along the c axis.  相似文献   

3.
The carbon cages composed of pentagons and heptagons (F5F7 isomers) are the analogs of fullerenes composed of pentagons and hexagons (F5F6 isomers). To provide insight into the structures and stability of the hydrides of F5F6 and F5F7 isomers, systematical density functional theory calculations are performed on all the 1,812 F5F6–C60H60 and 56 F5F7–C60H60. The calculated results demonstrate that the isomer with lowest/highest energy has most/fewest fused pentagons for both F5F6 and F5F7 hydrides and the stability of these hydrides increase with the number of fused pentagons roughly. The lowest energy F5F6–C60H60 and F5F7–C60H60 are 237.1 and 152.5 kcal/mol lower in energy than the isolated pentagon rule (IPR) C60H60, respectively; however, these two parent cages are 529.6 and 660.0 kcal/mol higher in energy than the IPR C60. The calculations suggest that heptagon-containing cages, not only those violating the IPR can be the candidate cages for fullerene derivatives and the possible repulsion between the added atoms may play an important role in determining the structures and stability of the hydrides of carbon cages.  相似文献   

4.
Thermodynamic properties of melts of the CaB2O4-CaSiO3 and Ca2B2O5-CaSiO3 systems were determined by the method of high-temperature mass-spectrometry. The melts of these systems are characterized by negative deviations from the ideal behavior at 1800 K.  相似文献   

5.
A novel metal chalcogenide HgCd4S5 (1) was synthesized from solid-state reactions and structurally characterized. Compound 1 crystallizes in the space group C2221 of the orthorhombic system with four formula units in a cell: a = 12.5661(5) Å, b = 7.2551(5) Å, c = 10.7520(7) Å, V = 980.2(1) Å3, Cd4HgS5, M r = 810.49, D c = 5.492 g/cm3, S = 1.010, μ(MoK α) = 25.128 mm?1, F(000) = 1408, R = 0.0611 and wR = 0.1495. Compound 1 is characterized by a 3-D cadmium sulfide framework structure with the infinite mercury sulfide chains located in the cavities.  相似文献   

6.
The present research work reports the study on crystal structure, vibrational spectroscopy and thermal analysis of organic-inorganic hybrid compound (C6H5(CH2)2NH3)2CdCl4. Single crystals of bis(phenethylammonium)tetrachlorocadmate (C6H5(CH2)2NH3)2CdCl4 (PEA–Cd) were obtained by diffusion at room temperature. This compound crystallizes in the orthorhombic space group C2cb with unit cell parameters a = 7.4444(2) Å, b = 38.8965(3) Å, c = 7.3737(2) Å and Z = 4. Single crystal structure has been solved and refined to R = 0.036 and wR = 0.092. The structure consists of an extended [CdCl4]2– network and two [C6H5(CH2)2NH3]+ cations to form a two-dimensional perovskite system. The infrared (IR) spectrum of the title compound was recorded at room temperature. Differential scanning calorimetry (DSC) was used to investigate the phase transition; this compound exhibits a reversible single solid-solid phase transition.  相似文献   

7.
Phase equilibria in the three-component systems LiBr-LiVO3-Li2MoO4 and LiBr-Li2SO4-Li2MoO4 have been studied using differential thermal analysis (DTA). Eutectic compositions have been determined (mol %): in the system LiBr-LiVO3-Li2MoO4, 56.0 LiBr, 22.0 LiVO3, and 22.0 Li2MoO4 with a melting temperature of 413°C; and in the system LiBr-Li2SO4-Li2MoO4, 65.0 LiBr, 14.0 Li2SO4, and 21.0 Li2MoO4 with a melting temperature of 421°C. Phase fields have been demarcated.  相似文献   

8.
This is the first study of the NaBO2-Na2CO3-Na2MoO4-Na2WO4 quaternary system by differential thermal analysis. Na2[MoO4(x)WO4(1 − x)] solid solutions in the quaternary system are found to not decompose.  相似文献   

9.
The crystal structure of a new bismuth aluminoborate Bi0.96Al2.37(B4O10)O is studied by single-crystal X-ray diffraction. The Bi0.96Al2.37(B4O10)O single crystals are hexagonal (space group \(P\bar 6\) 2m). The unit cell parameters are as follows: a = b = 4.587(4) Å, c = 2.253(9) Å, α = β = 90°, γ = 120°, V = 168.60 Å3, Z = 1.  相似文献   

10.
The accuracy of various computational methods (Hartree–Fock, MP2, CCSD, CAS-SCF, and several types of DFT) for predicting relative intensities in Raman spectra for C6H6, C6D6, and C6F6 was compared. The predicted relative intensities for ν1 and ν2 were compared with relative intensities measured by an FT-Raman spectrometer. While none of these methods excelled at this prediction, Hartree–Fock with a large basis set was most successful for C6H6 and C6D6, while PW91PW91 was the most successful for C6F6.  相似文献   

11.
New metal-rich mixed nickel-silicon and nickel-germanium chalcogenides, Ni5.68SiSe2, Ni5.46GeSe2, and Ni5.42GeTe2, were synthesized by high-temperature ceramic techniques. The X-ray diffraction study of single crystals grown from a molten flux revealed that the compounds are isostructural and crystallize in the tetragonal system (space group I4/mmm, Z = 2). These compounds are the first members of the family of M7−δEX2-type (M = Ni or Pd; E = Sn or Sb; X is chalcogen) intergrowth structures containing “light” p elements E. Resistivity measurements on pressed textured pellets showed that both selenides are anisotropic metallic conductors in the directions parallel and perpendicular to the heterometallic bond systems. The geometric criteria of stability of the intergrowth structure type under consideration are discussed. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1632–1638, September, 2007.  相似文献   

12.
A physicochemical study of glasses based on the MO-Bi2O3-B2O3 and SrO-Bi2O3-B2O3 systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal behavior of the glasses, were studied.  相似文献   

13.
A procedure for the synthesis of carbon-encapsulated multilayer magnetite and zirconium oxide–magnetite nanoparticles that form porous nanostructures, for use as biocompatible sorbents, is proposed. The properties, composition, dimensions, particle shapes, surface morphology, and magnetic characteristics of the products are studied.  相似文献   

14.
The structure of (C3H6N3)4Bi2Cl10 was determined by single crystal X-ray diffraction at room temperature. It crystallizes in the orthorhombic space group Pcmn, with a = 9.430 (1) Å, b = 17.426 (3) Å, c = 19.883(5) Å, V = 3267.3 (11) Å3 and Z = 4. The structure consists of discrete binuclear [Bi2Cl10]4– anions and 3-aminopyrazolium cations. The crystal packing is governed by weak N–H···Cl hydrogen bonds, π–π and electrostatic Cl···Cl interactions. Infrared spectrum is used to gain more information on the title compound. An assignment of the observed vibration modes is reported. The crystal morphology is studied using the BFDH laws. The calculated HOMO and LUMO energies show that charge transfer occur within organic and inorganic molecules. The optical absorption of the zero-dimensional hybrid was also investigated.  相似文献   

15.
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%.  相似文献   

16.
The effect of the method used for the synthesis of NH4V3O7 on its morphology, textural parameters, and optical properties was studied. Ammonium vanadate NH4V3O7 was prepared by treating NH4VO3 in the presence of citric acid under hydrothermal (4.0 ≤ pH ≤ 5.5, T = 180–200°C, 48 h) and microwave–hydrothermal (3.5 ≤ pH ≤ 5.0, T = 180–220°C, 20 min) conditions. Self-assembled NH4V3O7 microcrystals crystallizing in monoclinic system with unit cell parameters a = 12.247(5) Å, b = 3.4233(1) Å, c = 13.899(4) Å, β = 89.72(3)°, and V = 582.3(4) Å3 (space group P21) were shown to be formed independently of the method used to treat the reaction mixture. The morphology of NH4V3O7 particles was shown to depend on рН of the reaction mass and the method of synthesis. The structural features of NH4V3O7 were studied by IR, UV, and Vis spectroscopy, and the optical bandgap was determined.  相似文献   

17.
The subsolidus phase composition of the M2O-CdO-V2O5 systems with M = Li or Na is studied. Double orthovanadates MCdVO4 and MCd4(VO4)3 form solid solutions of composition Li1 ? 2x/3Cd x/3CdVO4 (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na3 ? 2x Cd3 + x (VO4)3 (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn21 a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.  相似文献   

18.
19.
The quaternary thioselenochloride complex Os2S6Se2Cl8 (I) was obtained by a reaction of OsO4 with a solution of Se in S2Cl2 at 100°C and identified by combination of X-ray diffraction (polycrystalline approach) and cluster framework isolation. A reaction of complex I with melted 4-cyanopyridine (4-CNPy) at 165°C gave the complex Os2S2Cl4(4-CNPy)4, which confirms the integrity of the binuclear cluster frame-work [Cl2OsS2OsCl2] in complex I.  相似文献   

20.
Silica/titania binary xerogels were prepared by joint hydrolysis of the ingredients. Gels of various compositions were characterized by 1H NMR spectroscopy, IR spectroscopy, and thermogravimetry. The spectral characteristics of binary systems differ considerably from mere superposition of the spectra of the two constituent compounds and the spectrum of a mechanical mixture. A feasibility was demonstrated for controlling the acid properties of binary oxide gels via varying the component mole ratio.  相似文献   

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