Oxidation of benzothiazole, 2‐mercaptobenzothiazole and 2‐hydroxybenzothiazole in aqueous solution by means of H2O2/UV or photoassisted Fenton systems

Oxidative treatments of benzothiazole and benzothiazole derivatives (2‐mercaptobenzothiazole, 2‐hydroxybenzothiazole) in aqueous solution have been studied by using H₂O₂/UV and iron(III) photoassisted Fenton techniques. Experimental runs have been carried out in the pH range 3.0 –8.0 by means of annular reactors and proper UV lamps. The effect of pH, the initial concentration of hydrogen peroxide, the substrate, and the iron(III) concentrations have been investigated. A suitable model has been developed and used for the best estimation of kinetic constants for HO radical attack on the target molecules with the H₂O₂/UV system. The values obtained with this model are consistent with those reported in the literature for other heterocyclic compounds. © 2001 Society of Chemical Industry     

Polymerization of epoxides catalyzed by a mixed‐valent iron trifluoroacetate [Fe3O(O2CCF3)6(H2O)3]

The readily available mixed‐valent iron trifluoroacetate complex [Fe₂^IIIFe^II(µ₃‐O)(O₂CCF₃)₆(H₂O)₃] is an effective catalyst for the polymerization of epoxides. A very small amount of the catalyst (1.0–0.01 mol%) could initiate the polymerization of cyclohexene oxide, cyclopentene oxide and epichlorohydrin. Based on quantitative end‐group analysis by ¹⁹F NMR spectroscopy, a Lewis acid (LA^⊕) catalyzed anionic reaction mechanism is proposed. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of polyimide‐γ‐Fe2O3 nanocomposites

Novel polyimide‐γ‐Fe₂O₃ hybrid nanocomposite films (PI/γ‐Fe₂O₃) has been developed from the poly(amic acid) salt of oxydianiline with different weight percentages (5, 10, 15 wt %) of γ‐Fe₂O₃ using tetrahydrofuran (THF) and N,N‐dimethylacetamide (DMAc) as aprotic solvents. The prepared polyimide‐γ‐Fe₂O₃ nanocomposite films were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), transmission electron micrograph (TEM), X‐ray diffraction (XRD), ¹³C‐NMR, and thermal analysis (TGA/DSC) techniques. These studies showed the homogenous dispersion of γ‐Fe₂O₃ in the polyimide matrix with an increase in the thermal stability of the composite films on γ‐Fe₂O₃ loadings. Magnetization measurements (magnetic hysteresis traces) have shown very high values of coercive force indicating their possible use in memory devices and in other related applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 834–840, 2007     

Constrained Sintering of a Low‐Fire,Polycrystalline Bi2(Zn1/3Nb2/3)2O7 Dielectric

The densification behavior of a low‐fire, polycrystalline Bi₂(Zn_1/3Nb_2/3)₂O₇ (BZN) dielectric under constrained sintering at 800°C–900°C is investigated. Although the constrained densification is retarded in relative to free sintering, a high sintered density of >95% is obtained at 900°C. No significant anisotropy with similar grain sizes is developed under free and constrained sintering. The densification behavior and stress development during constrained sintering of BZN is thus analyzed by using the well‐known isotropic constitutive laws.     

First X-ray crystal structure of cation [cis-Co(en)2(H2O)Cl]2+: Synthesis,spectroscopic and X-ray structural study of [cis-Co(en)2(H2O)Cl](C6H5SO3)2·H2O

A new cobalt(III) complex salt, [cis-Co(en)₂(H₂O)Cl](C₆H₅SO₃)₂ · H₂O] (I) has been synthesized and characterized by single crystal X-ray structure determination and NMR spectroscopy. This is a first report of the cobalt(III) cation in cis-configuration. The crystal lattice of the complex salt is stabilized by electrostatic forces of attraction and hydrogen bonding interactions.     

Structural features and thermoelectric properties of Al‐doped (ZnO)5In2O3 homologous phases

In this work, we investigated the influence of Al doping on the structure of the (ZnO)₅In₂O₃ homologous phase and the thermoelectric characteristics of (ZnO)₅(In_1?xAl_x)₂O₃ ceramics for x=0, 0.01, 0.03, 0.05, 0.1, and 0.2, prepared using a classic ceramic procedure and sintering at 1500°C for 2 hours. The Al substituted for In on both the primary sites in the Zn₅(In_1?xAl_x)₂O₈ homologous phase, the octahedral sites in the basal‐plane inversion boundaries and the trigonal bi‐pyramidal sites in the zig‐zag inversion boundaries, which resulted in a uniformly increased shrinkage of the unit cell with the additions of Al. The a and c parameters were reduced for x=0.2 by a maximum 0.8%. All the samples had similar microstructures, so the differences in the TE characteristics mainly resulted from the effects of the substitution of Al for In, decreasing the charge‐carrier concentration and affecting their mobility. Slightly improved TE characteristics were only observed for Al additions with x=0.01‐0.05, while larger additions of Al only resulted in a reduced electrical conductivity and decreased ZT values in comparison to the un‐doped composition.     

Synthesis,characterizations, and crystal structure of a novel 2D metal phosphonate: Na2[Cd2(H2O)3(O3PCH(OH)CO2)2] · 2H2O

A novel cadmium phosphonate compound Na₂[Cd₂(H₂O)₃(O₃PCH(OH)CO₂)₂] · 2H₂O (1) has been synthesized by hydrothermal reaction at 120 °C and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. The structure of compound 1 comprises CdO₆ octahedra and CdO₇ pentagonal bipyramid connected by [O₃PCH(OH)CO₂]³⁻ to form a 2D layered structure with a one-dimensional channel system and the charge-compensating Na⁺ cations being located between two adjacent layers.     

Synthesis and Anti-Candida Activity of Cobalt(II) Complexes of Benzene-1,2-Dioxyacetic Acid (bdoaH(2)). X-Ray Crystal Structures of [Co(bdoa)(H(2)O)(3)] 3.5H(2)O and {[CO(phen)(3)](bdoa)}(2)24H(2)O (phen = 1,10-Phenanthroline)

Co(CH(3)CO(2))(2)4H(2)O reacts with benzene-1,2-dioxyacetic acid (bdoaH(2)) to give the Co(2+) complexes [Co(bdoa)(H(2)O)(3)]H(2)O (1a) and [Co(bdoa)(H(2)O)(3)] 3.5H(2)O (1b). Subsequent reaction of 1a with 1,10- phenanthroline produces [CO(phen)(3)] bdoa10H(2)O (2a) and {[CO(phen)(3)](bdoa)}(2)24H(2)O (2b). Molecular structures of 1b and 2b were determined crystallographically. In 1b the bdoa(2-)- ligates the metal by two carboxylate oxygens and two ethereal oxygens, whereas in 2b the bdoa(2-) is uncoordinated. The Mn(2+) and Cu(2+) complexes [Mn(bdoa)(phen)(2)]H(2)O (3) and [Cu(pdoa)(imid)(2)] (4) were also synthesised, 1a-4 and other metal complexes of bdoa H(2) (metal = Mn(2+), Co(2+) ,Cu(2+), Cu(+) ) were screened for their ability to inhibit the growth ofhe yeast Candida albicans. Complexes incorporating the 1,10-phenanthroline ligand were the most active.     

Degradation of benzene,toluene ethylbenzene and p‐xylene (BTEX) in aqueous solutions using UV/H2O2 system

The homogeneous degradation of benzene (B), toluene (T), ethylbenzene (E) and p‐xylene (X) (BTEX) was studied in aqueous solutions, at pH 3.0, of hydrogen peroxide (5.8 mM ) under UV irradiation in a photoreactor equipped with a 300 nm lamp of light intensity 3.5 × 10^?5 Ein L^?1 min^?1. BTEX was substantially degraded by the H₂O₂/UV system, with >90% disappearing in 10 min of irradiation. The decomposition of BTEX was studied either as single or as multi‐component systems. The effects of irradiation time, amounts of H₂O₂ in molar ratios, rate of degradation and competition between components were thoroughly examined. It can be stated that the rate of BTEX degradation in mixture was higher than those for the individual components due to external effects of the absorption of UV light by the mixture, and their effects on enhancing the formation of OH^? radicals. The appropriate figure of merit, the electrical energy per mass (EE/M), was estimated at various molar ratios and it was confirmed that the best value was the one depicted for p‐xylene (0.065 kWh kg^?1). A theoretical model for the degradation pathway was proposed. Copyright © 2004 Society of Chemical Industry     

[{W(O)(O2)2(H2O)}2(μ‐O)]2–‐Catalyzed Epoxidation of Allylic Alcohols in Water with High Selectivity and Utilization of Hydrogen Peroxide

A dinuclear peroxotungstate, K₂[{W(O)(O₂)₂(H₂O)}₂(μ‐O)]⋅2 H₂O, exhibits high catalytic performance for the epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide at 305 K in water solvent. The effectiveness of this system is evidenced by high chemo‐, regio‐, and diastereoselectivity, and stereospecificity for the epoxidation of allylic alcohols. Furthermore, products/catalyst separation can be easily carried out by simple extraction and the catalyst recovered can be reused with the maintenance of the catalytic performance.     

Low‐Temperature Sintering and Microwave Dielectric Properties of ZnNb2O6–TiO2 Ceramics with BaCu(B2O5) Additions

The influence of BaCu(B₂O₅) (BCB) on densification, phases, microstructure and microwave dielectric properties of ZnNb₂O₆–xTiO₂ (x = 1.70–1.90) composite ceramics have been investigated. Undoped ZnNb₂O₆–1.8TiO₂ ceramics sintered at 1200°C exhibit temperature coefficient of resonant frequency (τ_f) ~9.25 ppm/°C. When BaCu(B₂O₅) was added, the sintering temperature of the ZnNb₂O₆–1.8TiO₂ composite ceramics was effectively reduced to 950°C. The results indicated that the permittivity and Q × f were dependent on the sintering temperature and the amounts of BaCu(B₂O₅). Addition of 3.0 wt% BaCu(B₂O₅) in ZnNb₂O₆–1.8TiO₂ ceramics sintered at 950°C showed excellent dielectric properties of ε_r = 40.9, Q × f = 12,200 GHz (f = 5.015 GHz) and τ_f = +0.3 ppm/°C.     

Low‐firing and temperature stable microwave dielectric ceramics: Ba2LnV3O11 (Ln = Nd,Sm)

Low‐firing and temperature stable microwave dielectric ceramics of Ba₂LnV₃O₁₁ (Ln = Nd, Sm) were prepared by solid‐state reaction. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the phase purity, crystal structure, sintering behavior, and microstructure. The XRD patterns indicated that Ba₂LnV₃O₁₁ (Ln = Nd, Sm) ceramics belong to monoclinic crystal system with P2₁/c space group in the whole sintering temperature range (800°C ‐900°C). Both ceramics could be well densified at 880°C for 4 hours with relative densities higher than 96%. The Ba₂LnV₃O₁₁ (Ln = Nd, Sm) samples sintered at 880°C for 4 hours exhibited excellent microwave dielectric properties: ε_r = 12.05, Q × f = 23 010 GHz, τ_f = ?7.7 ppm/°C, and ε_r = 12.19, Q × f = 27 120 GHz, τ_f = ?16.2 ppm/°C, respectively. Besides, Ba₂LnV₃O₁₁ (Ln = Nd, Sm) ceramics could be well co‐fired with the silver electrode at 880°C.     

Use of the axial dispersion model to describe the O3 and O3 /H2O2 advanced oxidation of alachlor in water

Experiments on alachlor degradation by ozonation alone and combined with hydrogen peroxide using different surface waters have been conducted in a reactor bubble column and a kinetic model of the advanced oxidation process has been proposed. Variables studied were the nature of the surface water (four surface waters were treated), pH (3.5–9.7) and hydrogen peroxide to ozone mass ratio at the column inlet (0.1–1.85 g g^?1). Data on residence time distribution, rate constants and the absorption kinetic regime were considered to prepare the kinetic model, which was also based on the axial dispersion model of non‐ideal flow. The model gives good predictions of alachlor and hydrogen peroxide conversions and the fraction of dissolved ozone (deviations were lower than ±15%) although it fails, in some cases, to yield accurate estimates of the observed experimental trends of concentrations in water at the reactor column outlet. The calculated results were close to those obtained from the more classical N well‐mixed tanks‐in‐series model (deviations with this model were lower than ±20%). It is concluded that quantitative deviations from experimental observations were likely due to the lack of rate data on ozone reactions with organic matter present in the surface waters investigated. © 2002 Society of Chemical Industry     

两种基于DMBA原位分解的配位聚合物{[Y(C_2O_4)_(1.5)(H_2O)_2]·H_2O}_n和{[Y(C_2O_4)_(1.5)(H_2O)_3]·2H_2O}_n的合成及结构研究

以DMBA(1,3-二甲基巴比妥酸)为底物,通过其原位分解产物H2C2O4(草酸)的自组装,分别制备了两种新颖的由压力调控的二维层状配位聚合物{[Y(C2O4)1.5(H2O)2]·H2O}n(1)和{[Y(C2O4)1.5(H2O)3]·2H2O}n(2)。在水热合成条件下,考察了不同阳离子、阴离子及溶剂对终产物分离的影响。结果显示,配合物(1)的构筑需在Y(Ⅲ)离子及去离子水同时存在的条件下完成。在此基础上,对反应机理进行了初步探究,发现氧化反应、亲核加成反应及消除反应等多种有机转化过程或可诱导原位开环产物的形成。     

Hydrothermal synthesis,crystal structure and photoluminescent property of a novel 3-D [La2(C2O4)2(NO3)(OH)(H2O)] · 3H2O

A novel 3D [La₂(C₂O₄)₂(NO₃) (OH)(H₂O)] · 3H₂O 1 has been synthesized under hydrothermal conditions and characterized by elemental analyses, IR, TGA, X-ray powder diffraction, X-ray single crystal diffraction and photoluminescence. The bridging modes of both nitrates and oxalates in compound 1 are uncommon. We have unexpectedly generated an unusual compound by using the simplest ligands, oxalates and nitrates in the presence of nicotinate (HIN).     

Structure and optical properties of Er‐doped CaO‐Al2O3 (Ga2O3) glasses fabricated by aerodynamic levitation

We fabricated a series of stable Er‐doped CaO‐Al₂O₃(Ga₂O₃) glasses by aerodynamic levitation (ADL) method. Using thermal analysis, we studied the influence of composition on the thermal stability of the glasses. The results unraveled the significance of composition on the stability of glasses. Magic angle spinning nuclear magnetic resonance (MAS‐NMR) and Raman spectra were used to analyze the glass microstructure. The optical and spectroscopic properties were examined by UV‐Vis absorption, steady‐state fluorescence spectroscopy, transient state fluorescence spectroscopy, and luminescence quantum yield measurements. The results unraveled a clear concentration‐dependent up‐conversion and NIR emissions of Er³⁺, with obvious spectral broadening and redshift. The related mechanisms of decrease in fluorescent lifetime (from about 9 ms to 2 ms) and quantum yield (from about 75% to 5%) are discussed.     

Electrical/mechanical properties and activation energies of some poly(2‐vinylpyridine)‐metal complexes

Poly(2‐vinylpyridine) (P2VP) and its metal‐based complexes have been synthesized and characterized through analytical measurements, such as thermal analysis and IR‐ spectroscopy. The electrical conductivity of these complexes was studied as a function of temperature. The conductivity of P2VP is seen to increase by many orders of magnitude on complexation with some metal chlorides such as BaCl₂, ZnCl₂, NiCl₂, or CoCl₂. The activation energy for electrical conductivity of either of these complexes is found to be lower than that of the host polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3537–3549, 2006     

Controllable Preparation of Al2O3‐MgO·Al2O3‐CaO·6Al2O3 (AMC) Composite with Improved Slag Penetration Resistance

Compact Al₂O₃‐MgO·Al₂O₃‐CaO·6Al₂O₃ (AMC) composite was obtained by melting technology using industrial alumina, light‐burned magnesia, and quick lime as raw materials based on the Al₂O₃‐MgO‐CaO ternary phase diagram. The results show that the phases of MgO·Al₂O₃ and Al₂O₃ are formed as the main framework with plate‐like CaO·6Al₂O₃ crystals mainly discontinuously embedded in MgO·Al₂O₃. The bulk density of AMC composite is up to 3.42 g/cm³, equivalent to 90.5% of the theoretical density. The synthesized compact AMC composite in the work also exhibits better slag penetration resistance than the castable based on tabular corundum due to the formation of liquid phase.