Structural disorder in Ba0.6Sr0.4Al2O4

The structural disorder in Ba_0.6Sr_0.4Al₂O₄ (space group P6₃22) was investigated by X-ray powder diffraction and selected-area electron diffraction (SAED). The initial structural model was determined using direct methods, and it was further modified by the combined use of Rietveld method and maximum-entropy method (MEM). MEM-based pattern fitting method was subsequently applied, resulting in the final reliability indices of R_wp=9.61%, R_p=6.96%, R_B=1.40% and S=1.25. The electron density distribution was satisfactorily expressed by the split-atom model in which the strontium/barium and oxygen atoms were split to occupy the lower symmetry sites. The diffuse scattering in SAED was mainly attributable to the positional disorder of oxygen atoms.     

Photocatalytic activity of divalent ion (copper,zinc and magnesium) doped NiAl2O4

Nickel aluminate (NiAl₂O₄) and doped nickel aluminate (Ni_1-xM_xAl₂O₄; M = Mg, Zn, Cu; x = 0.1) were prepared by sol-gel method using citric acid. The synthesized compounds were analyzed by various techniques such as powder XRD, FTIR, SEM-EDAX and UV-DRS. The lattice parameter was found to increase with the copper, zinc and magnesium doping in nickel aluminate. The band gap was decreased from 3.0 eV (NiAl₂O₄) to 2.9 (zinc doped), 2.7 eV (magnesium doped) and increased to 3.1 eV in the case of copper doping. The catalytic study was carried out for a cationic (methylene blue) and an anionic dye (methyl orange). The percentage degradation of methyl orange using Zn_0.1Ni_0.9Al₂O₄ and Mg_0.1Ni_0.9Al₂O₄ was found to be 92% (180 min) and 96% (90 min). 93% (120 min) and 97% (120 min) degradation of methylene blue was observed using zinc doped and magnesium doped nickel aluminate respectively. These results are comparatively higher than its parent analogue (94% (180 min) degradation against methyl orange and 91% (120 min) against methylene blue). Whereas the percentage degradation was found to be less in the case of Cu_0.1Ni_0.9Al₂O₄ (83% (180 min) against methyl orange and 90% (120 min) against methylene blue).     

Calix[4]pyrrolato Aluminates: The Effect of Ligand Modification on the Reactivity of Square-Planar Aluminum Anions

Structural constraint represents an attractive tool to modify p-block element properties without the need for unusual oxidation or valence states. The recently reported methyl-calix[4]pyrrolato aluminate established the effect of forcing a tetrahedral aluminum anion into a square-planar coordination mode. However, the generality of this structural motif and any consequence of ligand modification remained open. Herein, a systematic ligand screening was launched, and the class of square-planar aluminum anions was extended by two derivatives that differ in the meso-substitution at the calix[4]pyrrolato ligand. Strikingly, this modification provoked opposing trends in the preference for a Lewis acidic binding mode with σ-donors versus the aluminum-ligand cooperative binding mode with carbonyls. Insights into the origin of these counterintuitive experimental observations were provided by computation and bond analysis. Importantly, this rationale might allow to exploit mode-selective binding for catalytic rate control.     

Effect of ultrasound on the synthesis of low-modulus zeolites from a metakaolin

It was studied the effect of ultrasonic processing (22 kHz) of the aqueous suspension of metakaolin, sodium hydroxide and alumina with a molar ratio 2Al₂Si₂O₇:12NaOH:2Al₂O₃ on the low-modulus zeolite synthesis processes. To investigate the XRD, SEM, IR, EDS had been used. It was shown that after ultrasonic processing, sodium aluminates are formed, what leads to a change in process of further synthesis. It was found that without ultrasonic processing on the stage of thermal treatment at 650 °C, SOD zeolite (|Na₆|[Al₆Si₆O₂₄]) and sodium aluminosilicate (Na₆Al₄Si₄O₁₇) are synthesized. In the sample after ultrasound during thermal treatment, only sodium aluminosilicates of cubic syngony (Na₆Al₄Si₄O₁₇ and Na₈Al₄Si₄O₁₈) are formed. It was demonstrated that sodium aluminosilicates are precursors for the formation of LTA zeolite (|Na₁₂|[Al₁₂Si₁₂O₄₈]). As a result zeolitization of sodium aluminosilicates after the hydrothermal crystallization in alkaline solution, the sonicated sample contained 97 wt% LTA. Without ultrasonic processing, the product of synthesis contained 50 wt% SOD and 40 wt% LTA.     

经Opuntia dilenii haw植物提取液绿色合成制备的纳米铝酸锌的催化性质(英文)

Various nanosized zinc aluminate(ZnAl2O4) samples were prepared by a conventional and a mi- crowave method both with and without using Opuntia dilenii haw plant extract,and were charac- terized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),high resolution scanning electron microscopy(HRSEM),energy dispersion scanning(EDX),temperature dependent conductance measurements, thermoelectric power measurements, ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy,and photoluminescence spectroscopy.The formation of a pure ZnAl2O4 phase was confirmed by XRD and FT-IR.A change in morphology from nanosized plates to nanosized sheets with,respectively,the conventional and microwave heating methods was clearly shown by HRSEM.UV-Vis diffusion reflectance spectroscopy measured the band gaps of ZnAl2O4 nanosized plates and nanosized sheets as 3.5 and 3.9 eV,respectively.The synthesized ZnAl2O4 was single crystalline and has three photoluminescence emissions at 482,528,and 540 nm.ZnAl2O4 nanosized sheets prepared by the microwave method showed higher catalytic activity for the oxida- tion of benzyl alcohol(85% conversion) than ZnAl2O4 nanosized plates prepared by the convention- al method(60% conversion).     

Synthesis, Characterization, Spectroscopy and Study of Antimicrobial Properties of Two New Substituted Trichloroaluminate（Ⅲ） Complexes [AlCl3X]- （X = SCN-, CN-）

The synthesis and characterization of two new aluminate(Ⅲ) complexes with general formula K[AlCl3X] are reported. These compounds derived from aluminate trichloride and related salts. Potassium trichlorothiocyanoaluminate, PCTA, and potassium trichlorocyanatoalu-minate, PCCA, are two new ionic aluminate complexes. They can be easily synthesized in a nearly quantitative yield by using the direct reaction of AlCl3 and KX. The complexes were characterized by physico-chemical and spectroscopic methods. Theoretical calculations have been used for the extraction of structural and spectroscopic data of these new synthesized complexes. The antibacterial activities of such compounds were studied against the Staphylococcus aureus, Escherichia coli, Staphylococcus Epidermidis, Estreptococo B and Shigella.     

ZnAl2O4 SiO2纳米复合催化剂用于无溶剂条件下乙酸酐与醇、酚和胺的乙酰化反应简

A ZnAl₂O₄@SiO₂ nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N₂ adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhydride over the ZnAl₂O₄@SiO₂ nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH₂ group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl₂O₄@SiO₂ nanocomposite was higher than that of pure ZnAl₂O₄. The method gives high yields, and is clean, cost effective, compatible with substrates having other functional groups and it is suitable for practical organic synthesis.     

ZnAl_2O_4@SiO_2纳米复合催化剂用于无溶剂条件下乙酸酐与醇、酚和胺的乙酰化反应(英文)

A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process,and characterized by X-ray diffraction,Fourier transform infrared,transmission electron microscopy,and N2 adsorption-desorption measurements.The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols,phenols,and amines under solvent-free conditions.Under optimized conditions,efficient acetylation of these substrates with acetic anhydride over the ZnAl2O4@SiO2 nanocomposite was obtained.Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature,while the reaction time was longer for the acetylation of alcohols and phenols,showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups.The catalyst can be reused without obvious loss of catalytic activity.The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4.The method gives high yields,and is clean,cost effective,compatible with substrates having other functional groups and it is suitable for practical organic synthesis.     

Spectral and defect analysis of Cu-doped combustion synthesized new SrAl4O7 phosphor

A simple solution combustion synthesis route for preparation of Cu-doped SrAl₄O₇ has been described. Average particle size of 33 nm and platelet-like morphology has been observed. ESR studies confirm the presence of Cu in polycrystalline SrAl₄O₇. Bright-green luminescence under near-UV irradiation arising due to transition between Cu⁺ levels with microsecond level decay time makes it suitable for application in phosphor converted light emitting diode (LED). TL measurements show broad glow peaks which when deconvoluted indicate activation energies in the range of 0.6-1.1 eV and elucidate the trapping dynamics.     

The use of alumatrane for the preparation of high‐surface‐area nickel aluminate and its activity for CO oxidation

Supported nickel has been used in a wide range of applications for industrial reactions, such as steam reforming, hydrogenation and methanation. In this work, nickel aluminate was prepared by the sol–gel process using alumatrane as the alkoxide precursor, directly synthesized from the reaction of inexpensive and available compounds, aluminum hydroxide and TIS (triisopropanolamine) via the oxide one pot synthesis (OOPS) process. Various conditions of the sol–gel process, such as pH, calcination temperature, hydrolysis ratio and ratio of nickel to aluminum, were studied. All samples were characterized using FTIR, TGA, XRD, TPR, DR‐UV and BET. The BET surface area was in the range of 340–450 m²/g at the calcination temperature of 500 °C with a mesoporous pore size distribution. Catalyst activity testing in CO oxidation reaction depended on Ni:Al ratio and calcination temperature. Higher activity was obtained from higher Ni content and lower calcination temperature. In addition, catalysts prepared using alumatrane precursor had higher percentage conversion than those prepared using aluminum hydroxide precursor. Copyright © 2005 John Wiley & Sons, Ltd.