共查询到20条相似文献,搜索用时 15 毫秒
1.
Hua Ma Zhanliang Tao Feng Gao Jun Chen Huatang Yuan 《Frontiers of Chemistry in China》2006,1(3):260-263
The structure, morphology and hydrogen-storage capacity of MS2 (M = Mo, Ti) nanotubes prepared by different experimental methods were studied. It was found that the MoS2 nanotubes treated by KOH displayed the gaseous storage capacity of 1.2 wt% hydrogen (under the hydrogen pressure of 3 MPa
and 25°C) and the electrochemical discharge capacity of 262 mAh/g (at the discharge current density of 50 mA/g and 25°C) that
corresponds to about 1.0 wt % hydrogen. In comparison, TiS2 nanotubes can store 2.5 wt% hydrogen under the hydrogen pressure of 4 MPa and 25°C. The results show that MS2 compound nanotubes are promising materials for hydrogen storage.
__________
Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2005, 38(4) (in Chinese) 相似文献
2.
Single crystals of Ln5Ru2O12 (Ln=Pr, Nd, Sm-Tb) were grown out of either NaOH or KOH fluxes in sealed silver tubes. The crystals of all the phases were observed to be twinned as confirmed by TEM studies. The series crystallize in the C2/m monoclinic system with lattice parameters, a=12.4049(4)-12.7621(6) Å, b=5.8414(2)-5.9488(3) Å, c=7.3489(2)-7.6424(4) Å, β=107.425(3)-107.432(2)° and Z=2. The crystal structure is isotypic with the defect/disorder model of Ln5Re2O12 (Ln = Y, Gd) and consists of one dimensional edge shared RuO6 octahedral chains separated by a two dimensional LnOx polyhedral framework. Magnetic measurements indicate paramagnetic and antiferromagnetic behavior for Ln=Nd, Sm-Gd and Ln=Tb, respectively. 相似文献
3.
4.
Robin T. MacalusoJ.L. Sarrao P.G. PagliusoN.O. Moreno R.G. GoodrichD.A. Browne Frank R. FronczekJulia Y. Chan 《Journal of solid state chemistry》2002,166(1):245-250
The compounds CeMIn5 (M=Co, Rh, Ir) have been shown to exhibit heavy fermion behavior. In order to better understand this effect and the nature of the observed superconductivity, we have synthesized and characterized the non-magnetic analogs, LaMIn5 (M=Co, Rh, Ir). The structures of LaCoIn5, LaRhIn5, and LaIrIn5 were determined by single-crystal X-ray diffraction. CeMIn5 and LaMIn5 compounds are isostructural and adopt a tetragonal structure with space group P4/mmm, Z=1. Lattice parameters are a=4.6399(4) and c=7.6151(6) Å for LaCoIn5, a=4.6768(3) and c=7.5988(7) Å for LaRhIn5, and a=4.6897(6) and c=7.5788(12) Å for LaIrIn5. We compare these experimental data with band structure computations and examine structural trends that affect the magnetic and transport properties of these compounds. 相似文献
5.
Rolf W Winter 《Journal of fluorine chemistry》2004,125(4):549-552
Several significant and useful syntheses of pentafluorothiobenzene (SF5C6H5) from SF5halides (SF5X, X=Cl, Br) and cyclohexene or derivatives of cyclohexene are presented. 相似文献
6.
G. Henkel 《Fresenius' Journal of Analytical Chemistry》1980,304(4):265
7.
采用密度泛函理论(DFT)中的UB3LYP方法全参数优化了(IrO_2)n(n=1~5)纳米团簇的几何构型,并对能量、频率、电子性质以及相对稳定性进行了研究。结构优化表明,当n=1,2时,团簇为平面结构,n2时为三维结构。计算结果表明,桥位O原子与Ir原子之间有更多的电荷发生转移;通过计算解离能可知(IrO_2)n(n=2~5)纳米团簇中Ir4O8为稳定分子;经计算垂直电离能和垂直电子亲和势可知n=2,4为团簇的幻数。 相似文献
8.
The thermoanalytical curves of (C6H5)4AsCl (I) and (C6H5)4PCl (II) were generated simultaneously by using a Netzsch simultaneous thermal analyser 409 under static air and dynamic argon atmospheres. The ranges of thermal stability of I and II were found to be 145–310°C and 137–365°C, respectively, and their melting points to be 261 and 278°C. The DTA profiles of I and II differ and can be used for their distinction. 相似文献
9.
Hafiz Hamid Raza G. Murtaza Umm-e-Hani Nawaz Muhammad Shahid M. Ramay 《International journal of quantum chemistry》2020,120(24):e26419
Hydrogen can be utilized as an energy source; therefore, hydrogen storage has received the most appealing examination interest in recent years. The investigations of hydrogen storage applications center fundamentally around the examination of hydrogen capacity abilities of recently presented compounds. XSrH3 (X = K and Rb) compounds have been examined by density functional theory (DFT) calculations to uncover their different characteristics, as well as hydrogen capacity properties, for the first time. Studied compounds are optimized in the cubic phase, and optimized lattice constants are obtained as 4.77 and 4.99 Å for KSrH3 and RbSrH3, respectively. These hydrides have shown negative values of formation enthalpies as they are stable thermodynamically. XSrH3 might be used in hydrogen storage applications because of high gravimetric hydrogen storage densities, which are 2.33 and 1.71 wt% for KSrH3 and RbSrH3, respectively. Moreover, electronic properties confirm the semiconductor nature of these compounds having indirect band gaps of values 1.41 and 1.23 eV for KSrH3 and RbSrH3, respectively. In addition, mechanical properties from elastic constants such as Young modulus and Pugh's ratio, also have been investigated, and these compounds were found to satisfy born stability conditions. Furthermore, Pugh's ratio and Cauchy pressure show that these hydrides have a brittle nature. Furthermore, thermodynamic properties such as entropy and Debye temperature have been examined using the quasiharmonic Debye model for different temperatures and pressures. 相似文献
10.
Alexander Gribanov Andriy Grytsiv Yurii Seropegin 《Journal of solid state chemistry》2010,183(6):1278-1289
Two series of intermetallic alloys, RT2Si and RTSi2, have been synthesized from stoichiometric compositions. The crystal structures of EuPt1+xSi2−x (CeNiSi2-type), CeIr2Si (new structure type), YbPd2Si and YbPt2Si (both YPd2Si-type) have been elucidated from X-ray single crystal CCD data, which were confirmed by XPD experiments. The crystal structures of LaRh2Si and LaIr2Si (CeIr2Si-type), {La,Ce,Pr,Nd}AgSi2 (all TbFeSi2-type), and EuPt2Si (inverse CeNiSi2-type) were characterized by XPD data. RT2Si/RTSi2 compounds were neither detected in as-cast alloys Sc25Pt50Si25, Eu25Os25Si50 and Eu25Rh25Si50 nor after annealing at 900 °C. Instead, X-ray single crystal data prompted Eu2Os3Si5 (Sc2Fe3Si5-type) and EuRh2+xSi2−x (x=0.04, ThCr2Si2-type) as well as a new structure type for Sc2Pt3Si2 (own type). 相似文献
11.
研究了混合稀土储氢合金中氧和氮的测定方法。针对稀土金属高温易挥发、分解的特点,选择适宜的加热温度,使用镍浴,选择高温座坩埚进行试验:选择出了合适的助熔剂的预处理方法。方法已用于实际样品。对含氧0.43%、含氮0.018%的试样,分析精密度为氧4.3%,氮5.9%,加标回收率氧为93%~104%,氮为92%~110%。 相似文献
12.
The reduced Ruddlesden-Popper phases, Sr3Co2O5+δ with δ=0.91, 0.64 and 0.38, have been prepared in a nitrogen atmosphere. The crystal structures were determined by powder neutron diffraction. Oxygen vacancies are found both in O(3) and O(4) sites but the majority are along one crystallographic axis in the CoO2 plane, inducing an orthorhombic distortion of the normally tetragonal n=2 Ruddelsden-Popper structure. Superstructures due to oxygen ordering are observed by electron microscopy. The magnetic measurements reveal complex behavior with some ferromagnetic interactions present for Sr3Co2O5.91 and Sr3Co2O5.64. 相似文献
13.
M. Retuerto M.J. Martínez-Lope M.T. Fernández-Díaz 《Journal of solid state chemistry》2011,184(9):2428-2433
The title compounds have been synthesized by a citrate technique followed by thermal treatments in air (BiFe0.5Mn1.5O5) or under high oxygen pressure conditions (BiFeMnO5), and characterized by X-ray diffraction (XRD), neutron powder diffraction (NPD) and magnetization measurements. The crystal structures have been refined from NPD data in the space group Pbam at 295 K. These phases are isostructural with RMn2O5 oxides (R=rare earths) and contain infinite chains of Mn4+O6 octahedra sharing edges, linked together by (Fe,Mn)3+O5 pyramids and BiO8 units. These units are strongly distorted with respect to those observed in other RFeMnO5 compounds, due to the presence of the electronic lone pair on Bi3+. It is noteworthy the certain level of antisite disorder exhibited in both samples, where the octahedral positions are partially occupied by Fe cations, and vice versa. BiFexMn2−xO5 (x=0.5, 1.0) are short-range magnetically ordered below 20 K for x=0.5 and at 40 K for x=1.0. The main magnetic interactions seem to be antiferromagnetic (AFM); however, the presence of a small hysteresis in the magnetization cycles indicates the presence of some weak ferromagnetic (FM) interactions. 相似文献
14.
Ferenc W. Bocian B. Walków-Dziewulska A. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):179-192
The conditions of the formation of yttrium(III) and lanthanide(III) 2-chloro-5-nitrobenzoates were studied and their quantitative
composition and solubilities in water at 298 K were determined. The compounds are dihydrates and their solubilities are of
the order of 10-3 mol dm-3. The FTIR, FIR and X-ray spectra for the complexes were recorded. All complexes are crystalline compounds. Their thermal
decomposition was studied only in the range 293-523 K since on heating above 523 K the complexes decompose explosively. Hydrated
2-chloro-5-nitrobenzoates of rare earth elements lose two crystallization water molecules in one step. The enthalpy of dehydration
process was established and the magnetic moments of the complexes were determined in the range 77-300 K. The compounds obey
the Curie-Weiss law. The 4f electrons do not participate in the formation of the Ln-O bonds.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Phase equilibria studies of the CaO:TiO2:Nb2O5 system confirmed the formation of six ternary phases: pyrochlore (A2B2O6O′), and five members of the (110) perovskite-slab series Can(Ti,Nb)nO3n+2, with n=4.5, 5, 6, 7, and 8. Relations in the quasibinary Ca2Nb2O7−CaTiO3 system, which contains the Can(Ti,Nb)nO3n+2 phases, were determined in detail. CaTiO3 forms solid solutions with Ca2Nb2O7 as well as CaNb2O6, resulting in a triangular single-phase perovskite region with corners CaTiO3-70Ca2Ti2O6:30Ca2Nb2O7-80CaTiO3:20CaNb2O6. A pyrochlore solid solution forms approximately along a line from 42.7:42.7:14.6 to 42.2:40.8:17.0 CaO:TiO2:Nb2O5, suggesting formulas ranging from Ca1.48Ti1.48Nb1.02O7 to Ca1.41Ti1.37Nb1.14O7 (assuming filled oxygen sites), respectively. Several compositions in the CaO:TiO2:Ta2O5 system were equilibrated to check its similarity to the niobia system in the pyrochlore region, which was confirmed. Structural refinements of the pyrochlores Ca1.46Ti1.38Nb1.11O7 and Ca1.51Ti1.32V0.04Ta1.10O7 using single-crystal X-ray diffraction data are reported (Fd3m (#227), a=10.2301(2) Å (Nb), a=10.2383(2) Å (Ta)), with Ti mixing on the A-type Ca sites as well as the octahedral B-type sites. Identical displacive disorder was found for the niobate and tantalate pyrochlores: Ca occupies the ideal 16d position, but Ti is displaced 0.7 Å to partially occupy a ring of six 96g sites, thereby reducing its coordination number from eight to five (distorted trigonal bipyramidal). The O′ oxygens in both pyrochlores were displaced 0.48 Å from the ideal 8b position to a tetrahedral cluster of 32e sites. The refinement results also suggested that some of the Ti in the A-type positions may occupy distorted tetrahedra, as observed in some zirconolite-type phases. The Ca-Ti-(Nb,Ta)-O pyrochlores both exhibited dielectric relaxation similar to that observed for some Bi-containing pyrochlores, which also exhibit displacively disordered crystal structures. Observation of dielectric relaxation in the Ca-Ti-(Nb,Ta)-O pyrochlores suggests that it arises from the displacive disorder and not from the presence of polarizable lone-pair cations such as Bi3+. 相似文献
16.
A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb2O5-SiO2), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 μg l−1, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 μg l−1 of copper and 10 μg l−1 of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples. 相似文献
17.
Water-soluble conducting poly(2-(3thienyloxy)ethanesulfonic acid) (PTOESA)/V2O5 nanocomposite, (PTOESA)xV2O5, was prepared by simply mixing PTOESA with V2O5 wet gel at room temperature. XRD data showed that the interlayer spacings of (PTOESA)xV2O5 films are 14.0±1.5 Å and increased as the polymer content increased. These values are consistent with the insertion of polythiophene chains into the V2O5 layer gallery. The formation of alternative layers of PTOESA and V2O5 was further supported by depth profile SIMS analyses. Cyclic voltammograms of (PTOESA)xV2O5 film showed two pairs of redox peaks with colors varying from orange, yellowish green, green, to purple blue, depending on the stoichiometry of the nanocomposites. Moreover, a synergetic effect was observed on the electrochromic properties of these nanocomposites. It was found that the optical contrast (ΔOD) of the composites is better than those of PTOESA and V2O5 at the film thickness from 150 to 500 nm. The oxidation optical response time of (PTOESA)xV2O5 is independent of the stoichiometry and falls in between those of PTOESA and V2O5. At higher polymer content (x>0.5), the reduction optical response time of (PTOESA)xV2O5 is smaller than those of PTOESA and V2O5. Variable temperature conductivity data showed that the conductivity of (PTOESA)xV2O5 films increased as temperature increased, characteristic of thermal activated behavior, which was dominated by the interparticle contact resistance. The room-temperature conductivity of water-soluble (PTOESA)xV2O5 films was in between those of PTOESA and V2O5 xerogel and higher conductivity was found in the composite with lower polymer content. The anomalous conductivity of (PTOESA)xV2O5 with high PTOESA content may be due to the reason that the higher the polymer content, the bigger the grain size of (PTOESA)xV2O5 film as revealed with scanning electron microscopy and AFM micrographs. 相似文献
18.
The subsolidus phase relations of R2O3-CaO-CuO ternary systems (R=Nd, Sm, Gd, Tm) have been investigated by X-ray powder diffraction. All samples were synthesized at about 950° in air. There exists a ternary compound Ca14−xRxCu24O41 (x = 4 for R=Nd, Gd and x = 5 for R = Sm) and a ternary solid solution Ca2+xR2−xCu5O10 (R=Nd, Sm, Gd, Tm) with a wide composition range Δx of about 0.6. The compound Ca14−xRxCu24O41 possesses a layered orthorhombic structure and is isostructural to Sr14−xCaxCu24O41. The lattice parameters a and c of the compound are basically independent of the ionic radius of R, while the lattice parameter b and unit-cell volume V decrease substantially with the decrease of the ionic radii of R. The Ca2+xR2−xCu5O10 solid solution is isostructural to Ca2+xY2−xCu5O10, the structure of which is based on an orthorhombic “NaCuO2-type” subcell containing infinite one-dimensional chains of edge-shared square planar cuprate groups crosslinked by the layered cations Ca and R that locate in the inter-chain tunnels. 相似文献
19.
Oksana Sologub Leonid Salamakha Gerfried Hilscher Gerald Giester 《Journal of solid state chemistry》2010,183(5):1013-1037
Phase equilibria and crystal structures of ternary compounds were determined in the systems Ce-Pd-B and Yb-Pd-B at 850 °C in the concentration ranges up to 45 and 33 at% of Ce and Yb, respectively, employing X-ray single crystal and powder diffraction. Phase relations in the Ce-Pd-B system at 850 °C are governed by formation of extended homogeneity fields, τ2-CePd8B2−x (0.10<x<0.48); τ3-Ce3Pd25−xB8−y (1.06<x<1.87; 2.20<y<0.05), and CePd3Bx (0<x<0.65) the latter arising from binary CePd3. Crystallographic parameters for the new structure type τ2-CePd8B2−x (space group C2/c, a=1.78104(4) nm, b=1.03723(3) nm, c=1.16314(3), β=118.515(1)° for x=0.46) were established from X-ray single crystal diffraction. The crystal structures of τ2-CePd8B2−x and τ3-Ce3Pd25−xB3−y are connected in a crystallographic group-subgroup relationship. Due to the lack of suitable single crystals, the novel structure of τ1-Ce6Pd47−xB6 (x=0.2, C2/m space group, a=1.03594(2) nm, b=1.80782(3) nm, c=1.01997(2) nm, β=108.321(1)°) was determined from Rietveld refinement of X-ray powder diffraction data applying the structural model obtained from single crystals of homologous La6Pd47−xB6 (x=0.19) (X-ray single crystal diffraction, new structure type, space group C2/m, a=1.03988(2) nm, b=1.81941(5) nm, c=1.02418(2) nm, β=108.168(1)°).The Yb-Pd-B system is characterized by one ternary compound, τ1-Yb2Pd14B5, forming equilibria with extended solution YbPd3Bx, YbB6, Pd5B2 and Pd3B. The crystal structures of both Yb2Pd14B5 and isotypic Lu2Pd14B5 were determined from X-ray Rietveld refinements and found to be closely related to the Y2Pd14B5-type (I41/amd). The crystal structure of binary Yb5Pd2−x (Mn5C2-type) was confirmed from X-ray single crystal data and a slight defect on the Pd site (x=0.06) was established.The three structures τ1-Ce6Pd47−xB6, τ2-CePd8B2−x and τ3-Ce3Pd25−xB8−y are related and can be considered as the packings of fragments observed in Nd2Fe14B structure with different stacking of common structural blocks.Physical properties for Yb2Pd13.6B5 (temperature dependent specific heat, electrical resistivity and magnetization) yielded a predominantly Yb-4f13 electronic configuration, presumably related with a magnetic instability below 2 K. Kondo interaction and crystalline electric field effects control the paramagnetic temperature domain. 相似文献
20.
Francesco Malatesta Roberto Zamboni Luciano Lepori 《Journal of solution chemistry》1987,16(9):699-714
The apparent molar volumes of Mg, Ca, Sr, and Ba hexacyanocobaltates (III) have been determined from 1×104 to 0.2M (mol-dm–3), using both vibrating tube densimeter and dilatometric methods. The semiempirical Pitzer equation has been used to reproduce the experimental data. Positive deviations from the Debye-Hueckel limiting law (DHLL) have been observed at C<0.01M and are compared with the predictions of two other electrostatic approaches, the DHLL+B2 approximation of the Mayer theory and the numerical integration of the exponential Poisson-Boltzmann equation. A least squares procedure has been used to obtain the best fit parameters, including the apparent molar volume at infinite dilution. 相似文献