Properties Of Cs Research Articles

A Comparison of Catalytic Properties of Cs x H3−x PW12O40 Salts of Various Cesium Contents in Gas Phase and Liquid Phase Reactions

The cesium salts Cs x H3−x PW12O40 of Cs content x = 2 up to x = 3 were tested as the catalysts in the gas and liquid phase reactions. Dehydration of ethanol and transesterification of triglycerides with methanol were selected as the catalytic reactions. Apart from the standard preparation, the catalysts were prepared by two-stage procedure with methanol or water as a solvent. The Cs-salts were characterized by FT-IR, XRD, scanning electron microscopy and energy dispersive X-ray techniques. In turn, the influence of Cs-salts composition on the pH and conductivity of their aqueous colloidal solutions was investigated. The results obtained by the latter techniques were also characteristic for acidity of surface layer of colloidal particles because of surface layer-solution equilibrium. It has been shown that the secondary structure of acidic cesium salts existing in crystalline samples (solid solution of H3PW12O40 in Cs3PW12O40) changes after contacting with polar medium to the system consisting most probably of Cs3PW12O40 core with epitaxial layer of heteropolyacid. This is result of the protons migration from bulk to surface layer of primary particles enhanced by polar medium. It strongly influences the surface acidity of primary particles as well as the activity of Cs-salts in transesterification of triglycerides with methanol. In such polar medium, Cs2HPW12O40 salt becomes the most active catalyst, more active than Cs2.5H0.5PW12O40. An accumulation of partial glycerides and in particular glycerol on the surface of primary particles of Cs-salts resulted in relatively low maximum conversion of triglycerides, most probably due to partial blockage of the catalytic centers. This effect and the almost constant activity of Cs-salts under recycling use in the transesterification experiments are considered to be experimental evidences that methanolysis over Cs-salts was accomplished with the participation of surface protons.

Symmetry-Dependent Strong Reduction of the Spin Exchange Interactions in Cs2CuCl4 by the 6p Orbitals of Cs+ Ions

Despite a three-dimensional arrangement of its CuCl(4)(2-) ions, the magnetic properties of Cs(2)CuCl(4) are explained by a two-dimensional frustrated triangular antiferromagnetic spin-lattice. The origin of this low-dimensional magnetism was explored by evaluating the spin exchange interactions of A(2)CuCl(4) (A = Cs, Rb, K, Na) on the basis of first principles density functional calculations. The calculated spin exchange parameters agree with experiment only when the Cs(+) ions located between the CuCl(4)(2-) ions are not neglected. The antiferromagnetic spin exchange interaction between adjacent CuCl(4)(2-) ions is strongly reduced by the 6p orbitals of the intervening Cs(+) ions when the arrangement of the CuCl(4)(2-) and Cs(+) ions has either mirror-plane or inversion symmetry. The observed magnetism of Cs(2)CuCl(4) arises from this symmetry-dependent participation of the 6p orbitals of the Cs(+) ions in the spin exchange interactions between CuCl(4)(2-) ions.

Synthesis, Characterization, and Crystal Growth of Cs2Hg3I8: A New Second-Order Nonlinear Optical Material

This paper reports, for the first time, the second-order nonlinear optical (NLO) property of Cs 2 Hg 3 I 8 , a new potential NLO material in the infrared region. The compound exhibits a powder second harmonic generation (SHG) effect as strong as KTiOPO 4 (KTP). It also shows excellent transparency in the range of 0.5-25 μm with relatively high thermal stability. A single crystal up to 25 x 14 x 5 mm 3 in size has been grown in acetone by a slow evaporation technique.

An inorganic/organic self-humidifying composite membranes for proton exchange membrane fuel cell application

With an aim to operate the proton exchange membrane fuel cells (PEMFCs) with dry reactants, an inorganic/organic self-humidifying membrane based on sulfonated polyether ether ketone (SPEEK) hybrid with Cs 2.5H 0.5PW 12O 40 supported Pt catalyst (Pt-Cs2.5 catalyst) has been investigated. The Pt-Cs2.5 catalysts incorporated in the SPEEK matrix provide the site for catalytic recombination of permeable H 2 and O 2 to form water, and meanwhile avoid short circuit through the whole membrane due to the insulated property of Cs 2.5H 0.5PW 12O 40 support. Furthermore, the Pt-Cs2.5 catalyst can adsorb the water and transfer proton inside the membrane for its hygroscopic and proton-conductive properties. The structure of the SPEEK/Pt-Cs2.5 composite membrane was characterized by XRD, FT-IR, SEM and EDS. Comparison of the physicochemical and electrochemical properties, such as ion exchange capacity (IEC), water uptake and proton conductivity between the plain SPEEK and SPEEK/Pt-Cs2.5 composite membrane were investigated. Additive stability measurements indicated that the Pt-Cs2.5 catalyst showed improved stability in the SPEEK matrix compared to the PTA particle in the SPEEK matrix. Single cell tests employing the SPEEK/Pt-Cs2.5 self-humidifying membrane and the plain SPEEK membrane under wet or dry operation conditions and primary 100 h fuel cell stability measurement were also conducted in the present study.

Transparent Top-Emitting Organic Light-Emitting Diodes Using a Cs/Al/Ag/ITO Semi-Transparent Cathode

A top-emitting organic light-emitting diode (TEOLED) was fabricated with a semi-transparent multilayer cathode composed of Cs/Al/Ag and an ITO capping layer. The optical properties of Cs (0.5 nm)/Al (2.0 nm)/Ag (20 nm) at a wavelength of 533 nm exhibited a transmittance of 50 %. The light-output of the TEOELD with the Cs/Al/Ag/ITO showed a maximum luminance of 51,000 cd/m at a current density of 2.32 A/m (corresponding to the forward bias voltage of 11.2 V); the device structure consisted of glass/Ag (100 nm)/ITO (125 nm)/2-TNATA (30 nm)/NPB (15 nm)/Alq3 (55 nm)/Cs (1 nm)/Al (2 nm)/Ag (20 nm)/ITO (100 nm). Also, the external quantum efficiency and the power efficiency at a luminance of 1000 cd/m (corresponding to the forward bias voltage of 6.8 V) were 1.7 % and 2.0 lm/W, respectively. This TEOLED exhibited similar electrical properties, but a little lower light output, compared with a reference TEOLED of the same structure using Alq3 instead of ITO as the capping layer. These characteristics are strongly governed by the thickness, the electrical properties, and optical properties of the semi-transparent multilayer cathode composed of Cs/Al/Ag and by the optical properties of the top capping layer.

Transport properties of Cs doped Pr 2/3(Ba 1− xCs x) 1/3MnO 3 manganites

Magneto-transport behaviour of Pr 2/3Ba 1/3MnO 3 manganite (PBMO) doped with Cs at Ba-site is reported here. The observed decrease in the Curie temperature T C and the two insulator–metal like transitions (at T P1 and T P2) in PBMO with Cs doping have been discussed in the light of the decrease in the carrier concentration emanating due to the change in the Mn 3+/Mn 4+ ratio. While the peak magnetoresistance (MR) value at T P1 (reminiscent of the intra-granular behaviour) remains nearly invariant, the inter-granular (grain boundary) behaviour is clearly reflected through a substantial higher value of MR below T P2. The insulating behaviour above T P1 has been co-related to the decrease in the density of states at the Fermi level and is substantiated by the observed decrease in the resistivity with magnetic field. Electron–magnon scattering process has been invoked to consider the ferromagnetic metallic state below T P2.

High‐Temperature, High‐Pressure Hydrothermal Synthesis, Crystal Structure, and Luminescence Properties of Cs3EuSi6O15, a New Europium(III) Silicate with a Three‐Dimensional Framework Structure.

AbstractFor Abstract see ChemInform Abstract in Full Text.

High-Temperature, High-Pressure Hydrothermal Synthesis, Crystal Structure, and Luminescence Properties of Cs3EuSi6O15, a New Europium(III) Silicate with a Three-Dimensional Framework Structure

The crystal structure and luminescence properties of hydrothermally grown crystals of Cs3EuSi6O15 are reported. The structure consists of loop-branched vierer double chains of silicate with four-, six-, and eight-membered rings, which are connected via 10-membered rings at their interfaces to form a 3-D silicate framework. The six-coordinate europium atoms are located at sites between six-membered silicate rings. This Cs, Eu silicate is the second example of 3-D silicate framework with Si:O = 2:5, which contains only tertiary [SiO4] tetrahedra. The sharp peaks in the emission spectrum are assigned, and the lifetime measurements confirm the presence of one local Eu3+ environment. Crystal data: monoclinic, space group P21/n, a = 7.1664(1) Å, b = 28.4756(6) Å, c = 8.5418(2) Å, β= 104.976(1)°, V = 1683.89(7) Å3, and Z = 4.

The Lone‐Pair Cation I5+ in a Hexagonal Tungsten Oxide‐Like Framework: Synthesis, and Second‐Harmonic Generating Properties of Cs2I4O11.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The lone-pair cation I(5+) in a hexagonal tungsten oxide-like framework: synthesis, structure, and second-harmonic generating properties of Cs(2)I(4)O(11).

The layered iodate Cs2I4O11 has been synthesized and characterized. Its hexagonal tungsten oxide-like framework consists of six-membered rings of corner-sharing IO5 polyhedra with three lone pairs pointing inward and three lone pairs pointing outward (depicted for central ring). Capping of the layer by asymmetric IO3 polyhedra on one side results in a noncentrosymmetric material with highly efficient second-harmonic generating properties.

The Lone‐Pair Cation I5+ in a Hexagonal Tungsten Oxide‐Like Framework: Synthesis, Structure, and Second‐Harmonic Generating Properties of Cs2I4O11

The Lone‐Pair Cation I⁵⁺ in a Hexagonal Tungsten Oxide‐Like Framework: Synthesis, Structure, and Second‐Harmonic Generating Properties of Cs₂I₄O₁₁

Structural and vibrational properties of Cs and {Cs,H,H} complexes in Si

Carbon is a common substitutional impurity in Si. It traps hydrogen, and several {C,H} and {C,H,H} complexes have been observed by electrical and optical techniques. In this paper, we report (preliminary) first-principles molecular-dynamics studies of the structures and energetics of substitutional carbon (Cs) and two {Cs,H,H} complexes. Complete vibrational spectra are obtained from linear response theory. The relative stability of the two {Cs,H,H} complexes is calculated as a function of temperature.

Preparation, Transport Properties, and Structure Analysis by Resonant X-ray Scattering of the Type I Clathrate Cs8Cd4Sn42

Structural and transport properties of Cs 8 Cd 4 Sn 42 are reported. Cs 8 Cd 4 Sn 42 has a thermal conductivity that is unusually low for a crystalline solid (1 W m -1 K -1 at room temperature). This low lattice thermal conductivity is associated with the rattling of cesium in the tetrakaidecahedral cavities, as indicated by the large atomic displacement parameters of Cs in the tretrakaidecahedra. Resonant X-ray powder diffraction measurements indicate that all of the cadmium is located on one of three inequivalent framework sites. There is no evidence for any framework vacancies in the material.

Magnetic Phase Transition and Magnetization Plateau in Cs2CuBr4

The crystal structure of Cs$_2$CuBr$_4$ is the same as that of Cs$_2$CuCl$_4$, which has been characterized as a spin-1/2 quasi-two-dimensional frustrated system. The magnetic properties of Cs$_2$CuBr$_4$ were investigated by magnetization and specific heat measurements. The phase transition at zero magnetic field was detected at $T_{\rm N}=1.4$ K. It was observed that the magnetization curve has a plateau at about one-third of the saturation magnetization for magnetic field $H$ parallel to the $b$- and $c$-axes, while no plateau was observed for $H\parallel a$. The field-induced phase transition to the plateau state appears to be of the first order. The mechanism leading to the magnetization plateau is discussed.

Experimental Cs and Sr sorption on analcime in rock-buffered systems at 250-300°C and Psat and the thermodynamic evaluation of mineral solubilities and phase relations

Experimental studies on replacement of Na by Cs and Sr in analcime-albite bearing buffered assemblages were carried out at 250–300°C and P sat = 39.7-85.8 bars in pure water and in chloride solution. This investigation shows that such ion exchange of Na for Cs and Sr in analcime changes the Si/Al ratio. The compositions of end members for Cs and Sr analcimes at 250°C are shown to be Cs 0.95 Al 0.79 Si 2.17 O6 and Sr 0.645 Al 1.41 Si 1.62 O 6 . Continuous solid solutions between Cs and Na and Sr and Na do not appear to exist. Based on the composition of the aqueous chloride solutions, the thermodynamic properties of Cs, Sr and Na analcimes were determined and used in thermodynamic simulations in Cs and Sr leaching from albite-(Cs, Sr, Na) analcime assemblages at 250°C. In line with the above, the minimum leachability of Cs and Sr from Cs- and Sr-bearing analcimes occurs at pH values above 8 with an analcime-albite-paragonite buffer. The analcime-albite-paragonite assemblage can, therefore, act as a potential sorption barrier to the migration of Cs and Sr from radionuclide contaminated materials owing to the insolubility of Cs and Sr bearing analcimes. These findings have implications for underground High Level Waste storage facilities designed for maximum safety at moderately elevated temperatures.

Liquid phase esterification of acrylic acid with 1-butanol catalyzed by solid acid catalysts

Esterification of acrylic acid with 1-butanol has been studied in a heterogeneous solid–liquid reaction system using a variety of solid acids including an acidic salt of H 3PW 12O 40, Cs 2.5H 0.5PW 12O 40. The catalytic activity (per proton) of liquid acids such as heteropolyacids, H 2SO 4, and para-toluenesulfonic acid increased as the acid strength of the solution increased, but the difference in the activity among them was not significant. In the solid–liquid reaction system, Cs 2.5H 0.5PW 12O 40 exhibited the highest catalytic activity in the unit of catalyst weight among the solid oxide catalysts, while the activity of Cs 2.5H 0.5PW 12O 40 was less than those of organic resins such as Nafion and Amberlyst 15. Contrary to the liquid acids, the specific activity values (per proton) of solid acids were significantly different. It was demonstrated that the activity of Cs 2.5H 0.5PW 12O 40 was almost retained after the addition of water, while the activities of the organic resins greatly decreased. The water-tolerant property of Cs 2.5H 0.5PW 12O 40 is presumed to be due to the hydrophobic nature of the surface.

Caesium hexachlororhodate(IV): An authentic compound of rhodium(IV)

The green solid Cs 2[RhCl 6], generated in aqueous media using acidic ammonium hexanitrocerate(IV), (NH 4) 2[Ce IV(NO 3) 6], is as formulated. It has the d 5 configuration for rhodium. Evidence for the Rh IV ions in the freshly prepared solid—and for Rh III ions in the solid and aqueous solution after decomposition—is given using X-ray powder photographs, vibrational spectra (IR and Raman), ESR, magnetic susceptibility and elemental analysis. The definitive properties of Cs 2[RhCl 6] are compared with those for various chlororhodium(III) compounds. Previous data concerning it, often apparently conflicting, are rationalized.

Complexation of the cations of six alkalides and an electride by mixed crown ethers

It is well-known that crown ethers form sandwich complexes with the cations of many metals, but to date, the same crown ether formed both halves of the sandwich. Six new alkalides and an electride have now been synthesized that contain mixed sandwich complexes of alkali metal cations with 18-crown-6 (18C6), 15-crown-5 (15C5), and 12-crown-4 (12C4). The properties of Cs s + (18C6)(15C5)Na - and Cs + (18C6)(15C5)e - demonstrate the existence of these stoichiometric compounds, but single-crystal X-ray diffraction studies yielded only the crystal systems and cell parameters

Magnetic Properties of CsxC60

Abstract Magnetic properties of Cs x C60 have been studies by the magnetic susceptibility and ESR. The observation of Pauli and Curie-Weiss susceptibilities implies the existence of a metallic phase Cs1C60 and a paramagnetic phase Cs4C60.

Modelling of Cs-137 cycling in forests: recent developments and research needed

After the Chernobyl nuclear reactor accident in April 1986, 137Cs was found to be one of the most abundant radionuclides released and the forest ecosystem was one of the most contaminated environments. Long-term management of the forests to minimize the radiation dose to man requires understanding of the cycles of the 137Cs and the other radionuclides which were also deposited. Thus, the health physicists responsible for remediation programs in the contaminated zones must have information on the long-term behaviour of the deposited radioactivity. The similarity between the chemical properties of Cs and K and the fact that K has been studied previously as a nutrient in forest productivity may provide an analogue to evaluate the long-term mechanism of the deposited radioactivity. One of the goals of this study is to describe the global cycle of K in forests related to the 137Cs contaminant. The first results of an experimental program to measure the deposition of 137Cs in the several forest compartments is presented, together with the complementary K results. These data provide information which is necessary to construct a useable model describing the 137Cs-transfer after atmospheric contamination of a woodland ecosystem.