Structural studies of some new lamellar magnesium,manganese and calcium phosphonates

Layered phosphonate salts of divalent metal ions (Mg, Ca and Mn) are prepared by combining solutions of soluble metal salts and alkyl- or arylphosphonic acids. In this way the compounds Mg(O₃PC_{nH2n+1)·H2O (n=1−12), Mg(O3PC6H5)·H2O, Mg(HO3PCH(C6H5)2)2·8 H2O, Mn(O3PCH3)·H2O, Mn(O3PC6H5)·H2O, Ca(O3PCnH2n+1)·H2O (n⩽5), Ca(HO3PC6H5)2 and Ca(HO3PCnH2n+1)2 (n⩾6) were prepared. The M(O3PC6H5)·H2O compounds show good thermal stability, losing lattice water at 250–300°C without further decomposition below 550°C. Compounds derived from alkylphosphonic acids decompose at lower temperatures. The Mg(O3PCnH2n+1)·H2O series, Mg(O3PC6H5)·H2O, and Mn(O3PC6H5)·H2O group Pmn21; for the latter compound unit cell dimensions (Å) are a=5.733, b=14.298, c=4.931. The structure consists of roughly coplanar layers of metal atoms coordinated by phenylphosphonate groups above and below. Each metal atom is coordinated by five phosphonate oxygens and one lattice water molecule. Mg(O3PCnH2n+1}·H₂O adopts a similar structure; infrared spectra indicate all-trans alkyl chains. In Mg(HO₃PCH(C₆H₅)₂)₂·8 H₂O, Mg(H₂O)²⁺₆ ions and lattice water lie in hydrogen-bonded sheets; the benzhydryl groups lie above and below and make van-der-Waals contacts between layers.     

Impedance of nonuniform distributed solid protonic electrolyte - polymer systems

The conductivity of mixtures of the solid electrolytes H₃[PMo₁₂O₄₀]·13H₂O and Cs₂H[PW₁₂O₄₀] · 13H₂O follows the predictions of the percolation theory, whereas the electrode impedance in the high frequency range fits well the model of double layer adsorption relaxation. It is concluded that both the adsorption relaxation and the reversibility of the electrodes are related to oxygen transfer, the oxygen ions being the minority charge carriers. Fast oxygen dispersion may occur at the polymer-solid electrolyte interface. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995     

Effect of vanadium-containing activating additives on the oxidation of aluminum powders

The effect of vanadium-containing activating additives on the oxidation of an ASD-4 aluminum powder subjected to low-rate heating in the air is studied. The tests are conducted for a number of activators introduced by impregnating the metal powder with vanadium-containing gels with the following compositions: Li₂V₁₂O₃₁ · nH₂O, Na₂V₁₂O₃₁ · nH₂O, Na₂MoV₁₁O₃₁ · nH₂O, V₂O₅ · nH₂O, and 6V₂O₅ · B₂O₃ · nH₂O. A gel-preparation method based on the instantaneous cooling of melts of the respective reagents in cold water is proposed. It is found that the oxidation of the activated powders is shifted to a low-temperature region.     

Analysis of IR and Raman spectra of transition metal telluromolybdates

The work presents the IR and Raman spectra in the range 400–4000 cm^?1 of simple and double salts of hexamolybdotelluric (VI) acid of the general formula M₃[TeMo₆O₂₄]·nH₂O and (NH₄)_2xM_3?x [TeMo₆O₂₄]·mH₂O respectively, and of substitutive telluromolybdates with the wolframite structure MTe_yMo_1?yO₄, where M = Co, Zn, Ni and Mn. In this range the modes have been assigned to stretching vibrations of appropriate Mo-O bonds. Approximate values of force constants for these bonds have been computed and compared with the literature values reported for transition metal molybdates and ammonium heptamolybdate.     

KxCoO2·yH2O(x<0.2,y≤0.8)的晶体结构、输运及磁学性质

利用熔融KOH和Co₃O₄在较低温度(480℃)下反应制备出K_0.36CoO₂，然后用高锰酸钾溶液和饱和的过硫酸钾溶液进行氧化处理.氧化的同时伴随有水分子嵌入.K_0.36CoO₂用高锰酸钾和过硫酸钾溶液处理后分别得到K_0.12CoO₂·0.8H₂O和K_0.16CoO₂·0.6H₂O.这两种化合物都属于六角晶系，表现出金属行为，脱水后主相变为正交结构并且呈现出半导体特性.K_0.16CoO₂·0.6H₂O在56K附近可能存在自旋玻璃转变行为或其他涨落.随着钾含量的减少和水含量的增多，样品的自旋玻璃行为受到抑制或发生磁性相分离.样品K_0.12CoO₂·0.8H₂O在零场冷却和有场冷却曲线上的分叉现象基本上消失.还讨论了产生K_xCoO₂与Na_xCoO₂体系结构和物性差别的原因. 关键词： xCoO₂')" href="#">K_xCoO₂ 晶体结构 自旋玻璃态 磁性     

Features of the local structure of hydrated fluorine-substituted solid solutions based on Ba2In2O5

It is found for hydrated solid solutions of Ba_2?0.5x In₂O_5?x F _x · nH₂O, Ba₂In₂O_5?0.5y F _y · nH₂O (0 ≤ x ≤ 0.30; 0 ≤ y ≤ 0.24) that increasing the concentration of fluorine lowers the degree of hydration. The composition of proton-containing groups and the places of their localization in the structure of hydrated oxyfluorides are determined. The presence of fluorine in the complex oxide’s structure helps increase the mobility of protons.     

Evidence for a Peierls-Fröhlich state of one-dimensional platinum complex,K1.81Pt(C2O4)2·2H2O

Chemical analyses and electrical conductivity measurements were made on K_xPt(C₂O₄)₂·nH₂O (KDOX). X os 1.62 for α-KDOX and 1.81 for γ-KDOX. 2k_F calculated from the degree of partial oxidation shows that the lattice modulation wave in the superstructure of γ-KDOX is produced by the condensation of 2k_F phonon.     

The influence of PEO on the synthesis and electrochemical properties of VO2 and V3O7·nH2O nanobelts as a cathode for lithium battery

In this paper, we report the hydrothermal synthesis of VO₂, poly(ethylene oxide) (PEO)/VO₂,V₃O₇·nH₂O and PEO/V₃O₇·nH₂O nanobelts by using 1,2-propylene carbonate (1,2-PC (C₄H₆O₃)) and poly(ethylene glycol) (PEG) as templates, respectively. Structure and morphology of the samples were investigated by XRD, FTIR, SEM, and TEM. The vanadium oxide (VO₂) nanobeltcomposite show the initial specific capacity 152?mA?h?g^?1, whereas PEO/VO₂ shows 182?mA?h?g^?1. The pure V₃O₇·nH₂O nanobelts shows the initial specific capacity 192?mA?h?g^?1, while PEO/V₃O₇·nH₂O nanobelts show 297?mA?h?g^?1. It was found that PEO/VO₂ and PEO/V₃O₇·nH₂O nanocomposites show better cyclic performance and high discharge stability compared to pure vanadium oxide nanomaterials. The role of the polymeric PEO component of the hybrid material seems to be the stabilization and improvement of the specific capacity due to probable homogeneous distribution between the nanobelts. The TEM images indicate that PEO works as a surfactant to decrease the dimensions of nanobelts.     

Thermal expansion of the one-dimensional conductor K2Pt(CN)4Br0.3·xH2O and K2Pt(CN)4·xH2O

Measurements of the thermal expansion coefficients of K₂Pt(CN)₄Br_0.3· xH₂O and K₂Pt(CN)₄·xH₂O show a large anisotropy of the a-and c- directions. Their temperature dependence could be described by a simple Grüneisen theory. In the range from 80–330°K no anomaly indicating a Kohn-Peierls transition could be found.     

Effect of (H2O)n (n = 1–3) clusters on H2O2 + HO → HO2 + H2O reaction in tropospheric conditions: competition between one-step and stepwise routes

ABSTRACT

Effects of (H₂O)_n (n?=?1–3) on the H₂O₂?+?HO?→?HO₂?+?H₂O reaction have been investigated by the reactions of H₂O₂L(H₂O)_n (n?=?1–3)?+?HO and H₂O₂?+?HOL(H₂O)_n (n?=?1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H₂O)_n (n?=?1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H₂O₂···H₂O?+?HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H₂O₂···(H₂O)₂?+?HO (k'(R_WD1)) and H₂O₂···(H₂O)₃?+?HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/k_tot) is only 0.28% at 240?K, while at high temperature (such as at 425?K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.     

The n-butyl amine TPD measurement of Brönsted acidity for solid catalysts by simultaneous TG/DTG-DTA

The method for Brönsted acidity measurement based on TPD of alkyl amines desorption by gas-chromatography or thermogravimetry was adapted for simultaneous TG/DTG-DTA analysis. The acidity measurements were focused on the 12-tungstophosphoric acid (H₃PW₁₂O₄₀) and its salts, especially with Cesium since these posses the highest Brönsted acidity and they are among the most interesting catalysts. The n-butyl amine (NBA) desorption takes place in three steps for Cs_xH_3−xPW₁₂O₄₀, x = 0-2, and four steps for the Cs_2.5H_0.5PW₁₂O₄₀. The steps of desorption correspond to the release of NBA molecules in stages, as NBA or butene molecules resulted from the Hofmann elimination reaction and NH₃ + H₂O formed by decomposition of ammonium salt. The quantities of desorption products, C₄H₈ and NH₃ + H₂O, corresponding to the stages with the maximum desorption rates at 400-420 °C, respectively 560-600 °C, are in the stoichiometric ratio with the Brönsted acidity.     

The stability of K2[Pt(CN)4]Cl0·3·x.H2O in wet and dry atmosphere

The behavior of the one-dimensional electrical conductor K₂[Pt(CN)₄Cl_0·3·x.H₂O is studied at several temperatures in both wet and dry atmospheres using chemical analysis, X-ray diffraction and magnetic susceptibility data. It is concluded that the material is a series of hydrates with x between 2.5 and 3, and that a variation in x might influence its physical properties.     

Electrochemical characterization on layered lithium ruthenate for electrochemical supercapacitors

Electrochemical characteristics of lithium ruthenate (Li_xRuO_2+0.5x·nH₂O) for electrochemical capacitors' electrode material were first examined in this paper by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Results show that Li_xRuO_2+0.5x·nH₂O has electrochemical capacitive characteristic within the potential range of − 0.2–0.9 V (vs. SCE) in 1 M Li₂SO₄ solution. The capacitance mainly arises from pseudo-capacitance caused by lithium ions' insertion/extraction into/out of the Li_xRuO_2+0.5x·nH₂O electrode. The specific capacitance of 391 F g^− 1 can be delivered at 1 mA charge–discharge current for Li_xRuO_2+0.5x·nH₂O electrode with an energy density of 65.7 W h kg^− 1. This material also exhibits an excellent cycling performance and there is no attenuation of capacitance over 600 cycles.     

Studies on partially oxidised one-dimensional bis(oxalato)platinate salts containing divalent cations

The preparation and electrical conduction properties of the isostructural one-dimensional conductors Ni_0.84[Pt(C₂O₄)₂]·6H₂O(Ni-OP) and Mn_0.81[Pt(C₂O₄)₂]·6H₂O(Mn-OP) are described. Ni-OP exhibits a similar tem dependence of conductivity to the isostructural compounds Co_0.83[Pt(C₂O₄)₂]·6H₂O(Co-OP) and Zn_0.81[Pt(C₂O₄)₂]·6H₂O whereas the behaviour of Mn-OP is rather like that of K₂[Pt(CN)₄]Br_0.3·3H₂O. These differences are discussed in terms of the variation from compound to compound of the critical temperature for the formation of the “non-Peierls” superstructure (T_c) and the temperature at which the CDW/PD on adjacent conducting chains undergo three-dimensional ordering (T_3D). The variation of thermopower with temperature for Co-OP and Mg_0.82[Pt(C₂O₄)₂]·6H₂O is reported and related to the conduction properties and phase changes which have been observed for these compounds. For the isostructural series M_0.8[Pt(C₂O₄)₂]·6H₂O (M = Mg, Mn, Co, Ni or Zn) the variation of (T_3D) from compound to compound is related to differences in the polarizing power of the cations.     

Structural and thermoelectric power properties of Na-doped V2O5·nH2O nanocrystalline thin films

X-ray diffraction (XRD), thermoelectric power (S) and at room temperature electrical conductivity (σ) of Na⁺¹-doped V₂O₅·nH₂O nanocrystalline thin films fabricated by sol gel technique (colloid route) were studied. XRD showed that the Na₂O–V₂O₅·nH₂O thin films are highly oriented nanocrystals. The average value of particle size was found to be about 7.5 nm. The thermoelectric power showed that the thermoelectric power for all present nanocrystalline thin films samples decreased with increasing Na⁺¹ content. However, the electrical conductivity increased with increasing Na⁺¹ content. There is evidence that small polarons are responsible for determining the transport properties of the Na⁺¹ doped V₂O₅·nH₂O nanocrystalline thin films samples. The high value of electrical conductivity and small value of thermoelectric power is ideal for device applications, where device to device variation of the thermoelectric power must be small. This preparation technique was demonstrated to fabricate high quality Na₂O–V₂O₅·nH₂O nanocrystalline thin films for thermoelectric device applications. However, this may be further used for deposition with an ink-jet printer.     

Rigid lattice NMR spectra of fast proton conductors H2Sb4O11-nH2O

Hydrated antimonic acids H₂Sb₄O₁₁ · 2H₂O and H₂Sb₄O₁₁ · 3H₂O are fast proton conductors with the same (Sb₄O₁₁)^2-covalent framework delimiting intercrossing channels. Using proton magnetic resonance in the very low temperature rigid-lattice regime we show that the channels of the structure are occupied by three species: oxonium ions (H₃O⁺), water molecules (H₂O) and hydroxylic protons (OH) attached to the framework. Quantitative analysis of the experimental spectra lead to a rewriting of the chemical formula, as (H₃O)_xSb₄O_11-y(OH)_y · zH₂O with x,y and z depending on the hydration state. Coexistence of oxonium ions and water molecules is compatible with the assumption of a Grotthuss-type mechanism for proton diffusion. Nuclear magnetic resonance of the completely dehydrated compound H₂Sb₄O₁₁ is also reported. The value of the second moment of the proton resonance line indicates that in this compound all the protons are attached to the (Sb₄O₁₁)^2- framework.     

Characterization of pure and copper-doped iron tartrate crystals grown in silica gel

Single crystal growth of pure and copper-doped iron tartrate crystals bearing composition Cu _x Fe_(1???x)C₄H₄O₆·nH₂O, where x = 0, 0.07, 0.06, 0.05, 0.04, 0.03, is achieved using gel technique. The elemental analysis has been done using energy-dispersive X-ray analysis (EDAX) spectrum. The characterization studies such as Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), magnetic analysis and thermal analysis have been done for crystals with x = 0 for pure iron tartrate and with x = 0.05 for copper-mixed iron tartrate crystals. A detailed comparison has been made between pure and doped crystals.     

Structure of ZnZrF<Subscript>6</Subscript> · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 6–2) and ZnZrF<Subscript>6</Subscript> crystallohydrates according to vibrational spectroscopy data

Fluoridezirconate crystallohydrates ZnZrF₆ · nH₂O (n = 6–2) and anhydrous ZnZrF₆ are investigated by vibrational spectroscopy and thermography. The influence of the hydrate number on the structure of the cationic and anionic sublattices of the crystallohydrates is studied. The changes in the strength of HOH···F and HOH···O hydrogen bonds of coordinated and outer-sphere water molecules occurring with variations in the hydrate number are determined by changes in the IR spectra. The IR spectra of ZnZrF₆ · nH₂O (n =6, 4) compounds, which have isolated complex anions [ZrF₆]^2– in their structure, revealed a band with two peaks in the range of 3470–3430 cm^–1, which corresponds to stretching vibrations of coordinated water molecules. The spectra of ZnZrF₆ · nH₂O (n = 5, 3, 2, 1) crystallohydrates with a polymeric structure show a high-frequency shift of this band, which corresponds to weakening of hydrogen bonds. The vibrations of crystallization water molecules involved in the network of strong O–H···F and O–H···O hydrogen bonds manifest themselves in the spectra of ZnZrF₆ · nH₂O (n =5, 3) crystallohydrates by broad structureless bands in the region of stretching, bending, and libration vibrations.     

Silica–zirconium phosphate–phosphoric acid composites: preparation,proton conductivity and use in gas sensors

Mesoporous composites made of silica and α-zirconium phosphate (SiO₂·xZrP) were synthesized starting from mixtures of delaminated ZrP dispersions and tetrapropylammonium oligosilicate solutions. The surface area of the composites reaches a maximum of 700 m²/g for x≈0.02, while the average pore diameter is about 40 Å for x in the range 0.05–0.35. In order to increase proton conductivity at low relative humidity (r.h.), SiO₂·xZrP·yH₃PO₄ composites were prepared and characterised by ²⁹Si and ³¹P MAS NMR and conductivity measurements. At 100 °C and 6% r.h., the conductivity of the composites, with H₃PO₄ loadings of 80% of the pore volume, rises from 5×10⁻⁴ to 2×10⁻² S/cm for x decreasing between 0.35 and 0.05, as a consequence of the concomitant increase of pore volume. For the composite with x=0.18, the dependence of conductivity on H₃PO₄ loading was also investigated at different temperatures and r.h. values. The combined increase of humidity, temperature and H₃PO₄ loading results in an increase of conductivity from 1×10⁻⁷ S/cm (y=0.09, T=25 °C, 0% r.h.) to 4×10⁻² S/cm (y=0.61, T=100 °C, 30% r.h.). SiO₂·0.18ZrP·0.61H₃PO₄ was also tested as a proton electrolyte in an oxygen sensor consisting of a disk of the composite sandwiched between a platinum sensing electrode and a reference electrode based on Ni_1−xO. The sensor is able to detect O₂ at room temperature in a dry environment with a response time of 20–30 s.     

Indication from NMR of Grotthuss mechanism for proton conduction in H2Sb4O11·nH2O

We have measured the second moment, the linewidth and the relaxation times T₁ and T₂ of the ¹H magnetic resonance signal from 4.2 to 380 K in the fact proton conductors H₂Sb₄O₁₁·nH₂O. Our results reveal that the high ionic conductivity of these materials is due to a Grotthuss-type proton diffusion mechanism with succession of molecular reorientations of H₃O⁺ ions or H₂O molecules and of proton jumps from H₃O⁺ to H₂O.