Fabrication of a dense La0.2Sr0.8CoO3−δ/CoO composite membrane by utilizing the electroless cobalt plating technique

Fabrication of dense ceramic electrolyte membranes on porous supports is a key step towards performing gas separations (H₂ or O₂) through the electrochemical pathway. This research develops an approach by making use of the electroless plating method for the preparation of metal-ceramic composite membrane, which is used as the precursor to a metal-oxide composite membrane. As a model of the composite membrane, metallic cobalt is incorporated into a powder-packed layer of La_0.2Sr_0.8CoO_3−δ (LSCO-80), which is pre-coated on a porous MgO disk. When this composite membrane is subjected to sintering at 1000 °C in air, an interpenetrating laminar structure consisting of CoO and LSCO-80 phases is formed according to the cross-section EDX profiles. The oxidation of Co during sintering causes a structure expansion, which exerts a compressive stress on LSCO-80 phase, thus effectively buffering a tensile stress applied by the support. As a result, the composite membrane LSCO-80/CoO can achieve almost gas-tight at ambient temperature.     

Preparation and characterization of Ag~+ ion-exchanged zeolite-Matrimid~5218 mixed matrix membrane for CO_2/CH_4 separation

In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of microsized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ion-exchanged zeolite, was then embedded into the Matrimid~5218 matrix to form novel mixed matrix membranes(MMMs). The particles and MMMs were characterized by ultraviolet-visible diffuse reflectance spectroscopy(UV–vis DRS), N_2 adsorption–desorption isotherm, X-ray diffraction(XRD), Fourier transform infrared(FTIR) and scanning electron microscopy(SEM). Furthermore, the effects of filler content(0–20wt%) on pure and mixed gas experiments, feed pressure(2–20 bar) and operating temperature(35–75 oC)on CO_2/CH_4 transport properties of Matrimid/Ag Y MMMs were considered. Characterization results confirmed an appropriate ion-exchange treatment of the zeolites. The SEM results confirmed the superior interfacial adhesion between polymer and zeolites, particularly in the case of Matrimid/Ag Y membranes.This is due to the proper silverous zeolite/Matrimid functional groups' interactions. The gas permeation results showed that the CO_2 permeability increased about 123%, from 8.34 Barrer for pure Matrimid to18.62 Barrer for Matrimid/Ag Y(15 wt%). The CO_2/CH_4 selectivity was improved about 66%, from 36.3 for Matrimid to 60.1 for Matrimid/Ag Y(15 wt%). The privileged gas separation performance of Matrimid/Ag Y(15 wt%) was the result of a combined effect of facilitated transport mechanism of Ag+ions as well as the intrinsic surface diffusion mechanism of Y-type zeolite. In order to survey the possibility of using the developed MMMs in industry, the CO_2-induced plasticization effect and mixed gas experiment were accomplished. It was deduced that the fabricated MMMs could maintain the superior performance in actual operating conditions.     

Preparation,characterization and catalytic behavior of hierachically porous CuO/α-Fe_2O_3/SiO_2 composite material for CO and o-DCB oxidation

Hierachically porous (HP) CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support.The resulting material was characterized by N2 adsorption-desorption,X-ray diffraction and scanning electron microscopy.The as-prepared CuO/Fe2O3/HP-SiO2 sample,with α-Fe2O3 and CuO nanocrystals,possessed a co-continuous skeleton,through-macroporous and mesoporous structure.Its catalytic behavior for CO and o-DCB oxidation was investigated.The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation,indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.     

Preparation and application in oil–water separation of ZrO2/α-Al2O3 MF membrane

The composite tubular membranes were prepared by applying suspensions of zirconia particles to form separation top-layers on two different porous α-alumina supports and heating the coated supports to partly sinter the particles of top-layers. The conditions of synthesizing the ZrO₂/α-Al₂O₃ membranes were investigated systematically. The mean pore diameter of zirconia membrane was about 0.2 μm by gas bubble pressure method, and the pure water flux was about 400 and 1500 l/(m² h bar) for ZrO₂ membrane on symmetric and asymmetric Al₂O₃ support, respectively. Zirconia membrane and three different alumina membranes were applied to separate oil–water emulsion obtained from steelworks to evaluate the permeability and separation characteristics, the ZrO₂/α-Al₂O₃ MF membrane in this work was the preferred membrane.     

Microstructure and electrical properties of IrO2 prepared by thermal decomposition of IrCl3·x H2O: Role played by the conditions of thermal treatment

Some features of the thermal decomposition of IrCl₃·3 H₂O in an oxygen atmosphere are presented. The formation of IrO₂ phases has been followed by X-ray diffractometry, and the onset of definite reflections has been documented for samples pyrolyzed at 350° C, although moderate weight losses are observed by thermogravimetry at this temperature. The effect of the thermal history of iridium oxide coatings on their structure has been studied by means of electrical resistance measurements. An explanation of the results has been attempted in terms of impurity segregation to the oxide grain boundaries.     

Fabrication and characterization of highly crystalline mordenite membranes on α-alumina disks via a seeded in situ template-free hydrothermal treatment

A template-free seeded short-time in situ hydrothermal treatment was carried out in a brass autoclave to synthesize crystalline mordenite (MOR) membranes on alumina-silicate disk supports with micro-scale pores. According to XRD analysis, MOR was the only zeolitic material present in the membrane layers on the supports. SEM examination of the membranes showed three different layers of the membrane thickness: (i) support sub-layer, (ii) mix penetrated mid-layer, the MOR crystals filling the pores among the support (about 4–5 μm), and (iii) MOR top-layer (about 4–5 μm). The crystalline bonds between MOR crystals of the membrane top-layer and the crystals of the support were clearly observed within the mid-layer. The continuous top-layer of zeolitic membrane was formed by many large and well-shaped crystals. The seeding treatment significantly enhanced the formation of MOR crystals onto the surface of the supports. EDAX analysis showed a Si/Al ratio of 6.8 for the MOR layer of the membrane. Due to their hydrophilic natures, the polycrystalline MOR membranes were found to be selective for continuous dehydration of different EtOH–water mixtures through an adsorption–diffusion–desorption mechanism. Both total permeation flux and separation factor of the membrane were found to increase by increasing temperature and water concentration of feed. The continuity and high crystallinity of the membrane top-layer led to the fairly high dehydration of EtOH. It was found that there was no pinhole within the layer and the morphology of the membrane was almost defect-free.     

Influence of the thermal treatment conditions and composition of bimetallic catalysts Fe—Pd/SiO2 on the catalytic properties in phenylacetylene hydrogenation

The supported bimetallic Fe—Pd/SiO₂ catalysts with the different Fe (0.025—8 mass.%) and Pd (0.05—3.2 mass.%) loadings were synthesized by the incipient wetness impregnation of support. The samples were heat-treated under different conditions (calcination in air at 240—350 °C or reduction in an H₂ flow at 400 °C). The X-ray phase analysis revealed the formation of Pd⁰, α-Fe₂O₃ and Fe₃O₄ phases after calcination of the samples at 240—260 °C. The reduction of the calcined Fe—Pd samples in an H₂ flow at 400 °C enables the formation of Fe⁰ nanoparticles of size 17—20 nm. The synthesized catalytic systems were studied in the selective hydrogenation of phenylacetylene at room temperature and atmospheric pressure in a solvent (ethanol, propanol). The catalytic properties of the Fe—Pd catalysts depend on the nature of solvent, catalyst composition, and thermal treatment conditions. The application of the Fe—Pd bimetallic catalysts with a low Pd loading of 0.05—0.1 mass.% made it possible to reach the high activity and selectivity to styrene (91%) at the complete conversion of phenylacetylene.     

Preparation of 2CaO·3B2O3·H2O nanomaterials and evaluation of their flame retardant properties by a thermal analysis method

Different morphologies of calcium borate 2CaO·3B₂O₃·H₂O, nanoribbon, bundle-like nanostructure and fan-shaped non-nanostructure, have been prepared under hydrothermal conditions, which were characterized by XRD, FT-IR, TGA and SEM. Their flame retardant properties to the polypropylene were investigated by thermal analysis method (including TG, DSC and non-isothermal decomposition kinetics) and oxygen index method. With the decrease in TG mass loss, the increase in heat absorption for DSC in N₂ atmosphere, the increase in LOI values, and the increase in apparent activation energy E_a, the flame retardant properties of prepared 2CaO·3B₂O₃·H₂O samples increased gradually from non-nanostructure to bundle-like nanostructure and then to nanoribbon. This trend may be ascribed to their sizes being decreased accordingly. The flame retarding mechanism has been proposed. The mechanical property of polypropylene/2CaO·3B₂O₃·H₂O composite material has also been evaluated. It can be predicted that 2CaO·3B₂O₃·H₂O nanoribbon could serve as an excellent flame retardant.

     

Preparation of LiZnPO4·H2O via a novel modified method and its non-isothermal kinetics and thermodynamics of thermal decomposition

The single phase ??-LiZnPO₄·H₂O was directly synthesized via solid-state reaction at room temperature using LiH₂PO₄·H₂O, ZnSO₄·7H₂O, and Na₂CO₃ as raw materials. XRD analysis showed that ??-LiZnPO₄·H₂O was a compound with orthorhombic structure. The thermal process of ??-LiZnPO₄·H₂O experienced two steps, which involved the dehydration of one crystal water molecule at first, and then the crystallization of LiZnPO₄. The DTA curve had the one endothermic peak and one exothermic peak, respectively, corresponding to dehydration of ??-LiZnPO₄·H₂O and crystallization of LiZnPO₄. Based on the iterative iso-conversional procedure, the average values of the activation energies associated with the thermal dehydration of ??-LiZnPO₄·H₂O, was determined to be 86.59?kJ?mol^?1. Dehydration of the crystal water molecule of ??-LiZnPO₄·H₂O is single-step reaction mechanism. A method of multiple rate iso-temperature was used to define the most probable mechanism g(??) of the dehydration step. The dehydration step is contracting cylinder model (g(??)?=?1?(1???)^1/2) and is controlled by phase boundary reaction mechanism. The pre-exponential factor A was obtained on the basis of E _a and g(??). Besides, the thermodynamic parameters (??S ^??, ??H ^??, and ??G ^??) of the dehydration reaction of ??-LiZnPO₄·H₂O were determined.     

Preparation of zirconium diboride ultrafine hollow spheres by a combined sol–gel and boro/carbothermal reduction technique

In this work, we introduce a modified novel silica sol–gel process to synthesize hexagonal close-packed (hcp) and face-centered cubic (fcc) nickel (Ni) nanoparticles supported on amorphous carbon and silica matrix. The supporting of amorphous carbon and silica can prevent the Ni nanoparticles from aggregating and being oxided which would result in the loss of their magnetism and dispersibility. The phase structure of the Ni nanoparticles which were obtained from the gels pyrolyzed from 250 to 350 °C is hcp structure, whereas that of the Ni nanoparticles pyrolyzed at 750 °C is fcc structure. The grain sizes of the hcp Ni nanoparticles calcined at 250 °C range from 5 to 20 nm in diameter, and that of the fcc Ni nanoparticles calcined at 750 °C range in 7–35 nm. The studies of magnetic properties of the hcp and fcc Ni nanoparticles show that both have quite different magnetic behaviors.     

Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.     

Role of entropy generation on thermal management of a porous solar collector using Al2O3–Cu/water nanofluid and magnetic field

Journal of Thermal Analysis and Calorimetry - The purpose of this study is a presentation of the thermal management of a flat plate solar collector via employing entropy generation analysis. The...     

Correction to: A phase-field study on polymerization-induced phase separation occasioned by diffusion and capillary flow—a mechanism for the formation of porous microstructures in membranes

Journal of Sol-Gel Science and Technology -     

Studies on Oxidation of Active α-H of Aromatic Hydrocarbon by CAN/NaBrO3/H2O System

Cerium ammonium nitrate (CAN) is an expensive and powerful selective oxidant. It has played an important role in organic synthesis. Because it is a single electron oxidant,many organic reactions need large quantities of it. The application of CAN in organic synthesis in the oxidation of alkyl aromatics has so far been limited. In this paper, we wish to report a new method of oxidation of active α-H of aromatic hydrocarbon by CAN/NaBrO₃/H₂O system. Only catalytic amount of CAN was needed in this method and the selectivity was improved as well.     

2H1NA/β-cyclodextrin inclusion complex: Preparation,characterization and chemosensory application for detecting Ag+

The inclusion complex of 2-hydroxy-1-naphthoic acid (2H1NA) with β-cyclodextrin (β-CD) has been investigated using UV-visible and fluorescence spectral techniques in liquid states, FTIR, NMR, XRD and SEM techniques in solid state, molecular docking techniques in virtual states. The binding constants of for the formation of 1:1 2H1NA:β-CD inclusion complex is estimated by UV-visible and fluorescence spectral techniques. The chemosensory power of 2H1NA:β-CD complex was investigated thoroughly for various metal cations and we found the emission of complex showed a drastic increase in the intensity for Ag⁺. Competition experiments of 2H1NA:β-CD complex with Ag⁺ in presence of other metal ions (Na⁺, K⁺, Hg⁺, Al²⁺, Ca²⁺, Ba²⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Sn²⁺, Ti²⁺, Zn²⁺, Cr³⁺, Fe³⁺) showed that no significant variation was found in the fluoresce intensity of 2H1NA:β-CD complex upon adding all other cations. The linearity range, LOD and LOQ are determined from the selectivity and sensitivity studies for Ag⁺. Our result suggests that the 2H1NA:β-CD inclusion complex would be promising material for developing solid state sensory device for sensing Ag⁺.     

Fabrication of an electrochemical immunosensor for α-fetoprotein based on a poly-L-lysine-single-walled carbon nanotubes/Prussian blue composite film interface

Single-walled carbon nanotubes functionalized with poly-L-lysine (PLL-SWCNTs) were successfully prepared and were used as a biocompatible platform to immobilize α-fetoprotein antibody (anti-AFP) which was labeled with horseradish peroxidase (HRP). Then, anti-AFP-HRP/PLL-SWCNT nanocomposites were coated onto a Prussian blue (PB) film-modified glassy carbon electrode surface. Glutaraldehyde was used to further stabilize the biosensing interface through a cross-linking step. All unspecific sites were blocked by bovine serum albumin to fabricate a novel electrochemical immunosensor for α-fetoprotein determination. The immunosensor was characterized by voltammetry and electrochemical impedance spectroscopy. Based on the catalytic current response of H₂O₂, the experimental conditions for α-fetoprotein determination were optimized. Under optimal conditions, the current response was linearly related to α-fetoprotein concentration in the range of 0.05～10.0 and 10.0～50.0 ng/mL with a detection limit of 0.011 ng/mL. The immunosensor was successfully used for the determination of α-fetoprotein in human blood plasma. The results were satisfied with that obtained with ELISA, demonstrating a good accuracy of the immunosensor.     

Preparation,characterization, and properties of a Ag(I) coordination polymer {[Ag(H3bptc)(bpe)] · 2H2O} n

A new coordination polymer, {[Ag(H₃bptc)(bpe)]?·?2H₂O} _n (1) (H₄bptc?=?3,3′,4,4′-benzophenonetetracarboxylic acid, bpe?=?1,2-bis(4-pyridyl)ethene), has been synthesized through a hydrothermal technique and structurally characterized. The crystal structure of 1 exhibits a 2-D hydrogen-bonding sheet between H₃bptc^? and two free water molecules. Fluorescent property, TG analysis, and X-ray powder diffraction for 1 were also measured and discussed.     

Preparation and characterization of magnetic TiO2/ZnFe2O4 photocatalysts by a sol–gel method

A magnetic TiO₂/ZnFe₂O₄ photocatalyst was prepared by a sol-gel method, and X-ray diffraction (XRD), magnetic and photocatalytic properties analysis were employed to characterize this photocatalyst. The XRD results show that ZnFe₂O₄ can prevent the transformation of titania from anatase to rutile. The magnetic properties analysis indicates that TiO₂/ZnFe₂O₄ is of large saturation magnetization value and low coercivity. The photocatalytic experimental results show that TiO₂/ZnFe₂O₄=3 and 4 are superior in photocatalytic reactivity to other proportions. TEM shows that TiO₂/ZnFe₂O₄ has a fine core-shell fabric. After being used for four times during the photocatalytic reaction, the TiO₂/ZnFe₂O₄ nanoparticles have good photocatalytic stability.