Phase separation temperatures in the polystyrene—poly(α-methyl styrene)—methylcyclohexane system

The phase separation temperatures (PST) in the ternary system polystyrene (PS) (M_w = 1.75 × 10⁴ g mol⁻¹ — poly(α-methyl styrene) (PαMS) (M_w = 6.0 × 10⁴) — methylcyclohexane (MCH) and the binary systems PS-MCH and PαMS-MCH have been determined by using a He---Ne laser light-scattering apparatus over the total polymer weight fraction (W_{PS + PαMS}) range of 0.018 to 0.80 and various polymer blend ratios. The PST determined at a scattering angle of 0° agreed with those at 90° for the binary systems over polymer concentrations of 0.1 to 0.7 and for the ternary over W_{PS + PαMS} of higher than 0.3. Deviations of the PST determined at an angle of 90° from those at 0° were observed in the ternary system when W_{PS + PαMS} was lower than 0.3. Two phase separation temperatures, at which the intensity scattered from zero angle changed discontinuously, are observed at concentrations lower than W_{PS + PαMS} = 0.042 in the ternary system. The PST in the ternary system decreases monotonically with increasing W_{PS + PαMS} over 0.3 to 0.7. The phase diagram for the PS-PαMS-MCH system at W_{PS + PαMS} = 0.8 is characterized by a maximum PST around − 14°C.     

Improving the oxygen permeability of Ba0.5Sr0.5Co0.8Fe0.2O3−δ membranes by a surface-coating layer of GdBaCo2O5+δ

A GdBaCo₂O_5+δ layer was coated on the Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ membranes to enhance their oxygen permeability by employing the fast oxygen adsorption/desorption surface-exchange properties of the GdBaCo₂O_5+δ material. The oxygen flux of the coated and uncoated Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ membranes was measured in the temperature range of 600–850 °C. The results reveal that the oxygen-permeation flux of the Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ membranes coated by a GdBaCo₂O_5+δ layer shows significant enhancement. The GdBaCo₂O_5+δ layer coated on the oxygen desorption side (He side) has much effect than that coated on the oxygen adsorption side (air side). At 850 °C, the oxygen flux with a single coating layer on the air side can rise 16%, while a single coating on the helium side will result into a rise of 23%.     

Determination of the β ↔ αL′ transition in Ca2SiO4 to 7 KBAR

Differential thermal analysis in hydrostatic apparatus to 7 kbar shows that the β → α_L′ transition temperature in Ca₂SiO₄ linearly increases from 701° ± 2°C at 1 bar at the rate of 10.5 ± 0.5 deg kbar⁻¹. The α_L′ → β transition temperature is observed some 20°–30° lower in temperature than the β → α_L′ transition and no variation in this hysteresis with pressure is indicated.     

Photocatalytic reduction of Ag2SO4 by the Dawson anion α-[P2W18O62] and tetracobalt sandwich complexes

The photocatalytic behaviours of the Dawson salt α-K₆[P₂W₁₈O₆₂] and two isomers of the tetracobalt Dawson-derived sandwich complexes, αββα-Na₁₇[Co₄(H₂O)(OH)(P₂W₁₅O₅₆)₂]·51H₂O·2NaCl and ααβα-Na₁₆[Co₄(H₂O)₂(P₂W₁₅O₅₆)₂]·51H₂O (abbreviated ββ-{Co₄P₄W₃₀} and αβ-{Co₄P₄W₃₀}, respectively), are described and compared.The direct photochemical excitation of the polyoxometalates (POM) in the presence of propan-2-ol as electron donor leads to their reduction. With polyoxometalates as photocatalyst and propan-2-ol as sacrificial electron donor, the reduction of Ag^I₂SO₄ from aqueous solutions is observed leading to metallic Ag_n⁰ clusters and colloidal metal nanoparticles stabilized by POM.In the case of both {Co₄P₄W₃₀}, TEM experiments reveal that most of the Ag_n particles obtained with a slight excess of Ag⁺ are spherical with a quite large distribution in size between 10 and 100 nm.     

A zirconium-containing sandwich-type dimer based on trivacant α- and β-[GeW9O34] units, [Zr3O(OH)2(α-GeW9O34)(β-GeW9O34)]

A new zirconium-containing sandwich-type dimer based on trivacant α- and β-[GeW₉O₃₄]¹⁰⁻ units, [Zr₃O(OH)₂(α-GeW₉O₃₄)(β-GeW₉O₃₄)]¹²⁻, was synthesized and characterized by IR spectroscopy, UV electronic spectroscopy and single crystal X-ray diffraction. The central bent of the polyanion contains three oxygen atoms alternating with the three zirconium atoms. The polyanion represents a rare example of the sandwich POMs containing two different isomer subunits.     

钙钛矿型混合导体透氧膜SrFe0.6Cu0.3Ti0.1O3－δ的制备与表征

Dense membrane with the composition of SrFe0.6Cu0.3Ti0.1O3-δ （SFCTO） was prepared by solid state reaction method. Oxygen permeation flux through this membrane was investigated at operating temperature ranging from 750℃ to 950℃ and different oxygen partial pressure. XRD measurements indicated that the compound was able to form single-phased perovskite structure in which part of Fe was replaced by Cu and Ti. The oxygen desorption and the reducibility of SFCTO powder were characterized by thermogravimetric analysis and temperature programmed reduction analysis, respectively. It was found that SFCTO had good structure stability under low oxygen pressure at high temperature. The addition of Ti increased the reduction temperature of Cu and Fe. Performance tests showed that the oxygen permeation flux through a 1.5 mm thick SFCTO membrane was 0.35-0.96 ml·min ^-1·cm^-2 under air/helium oxygen partial pressure gradient with activation energy of 53.2 kJ·mol^-1. The methane conversion of 85%, CO selectivity of 90% and comparatively higher oxygen permeation flux of 5 ml·min^-1·cm^- 2 were achieved at 850℃, when a SFCTO membrane reactor loaded with Ni-Ce/Al2O3 catalyst was applied for the partial oxidation of methane to syngas.     

Synthesis of onion-like mesoporous silica from sodium silicate in the presence of α,ω-diamine surfactant

Mesoporous silicas with vesicular and onion-like morphologies were assembled through hydrogen-bonding pathway from sodium silicate as silica source and electrically neutral α,ω-diamine, Jeffamine D2000 surfactant (H₂NCH(CH₃)CH₂[OCH₂CH(CH₃)]₃₃NH₂) as template in aqueous media at different synthesis temperatures (25, 60 and 100 °C). Assembling the material at 100 °C afforded onion-like core shell mesoporous silica, while at relatively lower temperature, e.g. 25 and 60 °C, multilamellar vesicles were obtained. Mesoporous silica with onion-like morphology was also obtained by a two-step synthesis involving an aging period of 20 h at room temperature followed by a hydrothermal stage (1–12 h) at 100 °C. The heavily cross-linked (Q⁴/Q³ ratio of 4.43) onion-like mesophase silica exhibited high hydrothermal stability. The BET surface area, pore volume and KJS (Kruk-Jaroniec-Sayari) pore diameter of the onion-like mesoporous silica were found to be 464 m² g⁻¹, 1.16 m³ g⁻¹ and 7.2 nm, respectively.     

Ferromagnetic mixed tribridged dinuclear copper(II) complex [Cu2(OAc)2(OH)(dpa)2]PF6 · H2O (dpa = 2,2′-dipyridylamine): 3D superstructure based on hydrogen bond and π…π interaction

A new dinuclear complex [Cu₂(OAc)₂(OH)(dpa)₂] PF₆ · H₂O (1) is prepared and structurally and magneto-structurally characterized. The monocationic core contains one acetate in familiar bidentate η¹:η¹:μ₂-bridge and another in the rare monoatomic bridge along with one hydroxo intermediary. 1 packs through N–H…O and O–H…O hydrogen bonds and π…π interaction resulting a 3D supramolecular continuum and displays high-energy intraligand ¹(π − π^*) fluorescence and intraligand ³(π − π^*) phosphorescence in glassy solution.     

Uptake of heavy metal ions from aqueous solution using Mg–Al layered double hydroxides intercalated with citrate, malate, and tartrate

Mg–Al layered double hydroxide (Mg–Al LDH) was modified with organic acid anions using a coprecipitation technique, and the uptake of heavy metal ions from aqueous solution by the Mg–Al LDH was studied. Citrate·Mg–Al LDH, malate·Mg–Al LDH, or tartrate·Mg–Al LDH, which had citrate³⁻ (C₆H₅O₇³⁻), malate²⁻ (C₄H₄O₅²⁻), or tartrate²⁻ (C₄H₄O₆²⁻) anions intercalated in the interlayer, was prepared by dropwise addition of a mixed aqueous solution of Mg(NO₃)₂ and Al(NO₃)₃ to a citrate, malate, or tartrate solution at a constant pH of 10.5. These Mg–Al LDHs were found to take up Cu²⁺ and Cd²⁺ rapidly from an aqueous solution at a constant pH of 5.0. This capacity was mainly attributable to the formation of the citrate–metal, malate–metal, and tartrate–metal complexes in the interlayers of the Mg–Al LDHs. The uptake of Cu²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH < citrate·Mg–Al LDH. The uptake of Cd²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH = citrate·Mg–Al LDH. These differences in Cu²⁺ and Cd²⁺ uptake were attributable to differences in the stabilities of the citrate–metal, malate–metal, and tartrate–metal complexes. These results indicate that citrate³⁻, malate²⁻, and tartrate²⁻ were adequately active as chelating agents in the interlayers of Mg–Al LDHs.     

Poly(t-butyl-3α-(5-norbornene-2-carbonyloxy)-7α,12α-dihydroxy-5β-cholan-24-oate-co-maleic anhydride) for a 193-nm photoresist

A copolymer of t-butyl-3α-(5-norbornene-2-carbonyloxy)-7α,12α-dihydroxy-5β-cholan-24-oate and maleic anhydride was synthesized as a matrix polymer for ArF excimer laser lithography. The polymer has an excellent transmittance at 193 nm and possesses good thermal stability up to 255°C. The resist formulated with the polymer showed better dry-etching resistance than the conventional KrF excimer laser resist for chlorine and oxygen mixed gas. A 0.15 μm line and space patterns were obtained at a dose of 18 mJ cm⁻² using an ArF excimer laser stepper.     

气溶胶溶剂萃取技术制备β-谷甾醇亚微粒

The submicroparticles of β-sitosterol were produced by using an aerosol solvent extraction system (ASES) and characterized by scanning electronic microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) analysis. The effects of operational parameters including pressure, temperature, solution concentration, and ratio of flow rate (CO2/solution, r) on particle size (PS), yield, and morphology were investigated. The results showed that microparticles of β-sitosterol (less than 1000 nm size and larger than 70% yield) could be obtained at 10-15 MPa, 35-50°C, 15 mg&#8226;ml－1, 10/1(r); β-sitosterol particles were found to occur as three mophologies: flakes, rods, and spheres by varying ratio of flow rate or solution concentration. In contrast, the crystallinity of β-sitosterol decreased, whereas its molecular structure remained almost unchanged after being ASES-treated. Therefore, ASES was an effective method to produce submicroparticles of β-sitosterol.     

Low-temperature synthesis of La0.6Sr0.4Co0.2Fe0.8O3−δ perovskite powder via asymmetric sol–gel process and catalytic auto-combustion

La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ powder was synthesized by a combined EDTA-citrate complexing process via low-temperature auto-combustion synthesis with NH₄NO₃ as an oxidizer and a combustion trigger. Two novel methods were explored to improve this auto-combustion technology with reduced NH₄NO₃ addition: the use of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ as the combustion catalyst and the application of asymmetric sol–gel process to provide the precursor with different NH₄NO₃ concentrations. The prepared perovskite powder was characterized by BET, SEM, XRD and iodometric titration techniques. The catalytic performance of the powder was also examined in the decomposition of peroxide hydrogen. Experimental results indicate that powders from catalytic combustion and asymmetric precursor routes have more advantages in terms of better crystallites, higher specific surface area, higher B-site valence state, improved sintering capability and better catalytic performance in peroxide hydrogen decomposition than that from the synthesis with uniform NH₄NO₃ distribution.     

Preparation and characterization of an unusual tetracobalt-complex; X-ray crystal structure of [Co2(CO)5{μ-P,P(μ-PPh2CCPPh2)}][Co2(CO)4{μ-P-(μ-PPh2CCPPh2)}]

The reaction of bis(diphenylphosphino)acetylene(DPPA) with Co₂(CO)₈ in toluene at 80 °C for 24 h resulted in an alkyne-bridged, diphosphine-chelated tetracobalt-complex, [Co₂(CO)₅{μ-P,P-(μ-PPh₂CCPPh₂)}][Co₂(CO)₄{μ-P-(μ-PPh₂CCPPh₂)}] 3. The X-ray structural studies of 3 reveals that it can be regarded as a dimerized form of two DPPA bridged dicobalt complex, [Co₂(CO)₆(μ-PPh₂CCPPh₂)] 1.     

A peculiar heterotrimetallic Mn–Co–Ni complex: Synthesis, crystal structure and magnetic properties

The first complex [Mn(H₂O)₆][NiCo(TTHA)(H₂O)₂] · 4H₂O 1 (TTHA⁶⁻ = triethylenetetraminehexaacetate) containing Mn^II–Co^II–Ni^II three different 3d metal ions is synthesized and magnetic measurement suggests that ferromagnetic interactions occur between Ni²⁺ ions and rarely found low-spin Co²⁺ ions.     

β-MnO2 nanowires: A novel ozonation catalyst for water treatment

Using Mn(NO₃)₂ and ozone as raw materials, β-MnO₂ nanowires with diameters of about 6–12 nm, lengths of 2–5 μm and surface area of 73.54 m² g⁻¹ were synthesized by a simple hydrothermal process. The influences of synthesis conditions such as hydrothermal temperature, reaction time and ozone were investigated, and the growth process of β-MnO₂ nanowires was discussed. The catalytic properties of β-MnO₂ nanowires for the degradation of phenol were evaluated. β-MnO₂ nanowires revealed good separability and remarkable catalysis for the degradation of phenol.     

Orientation of β-Ca2SiO4 solid solution lamellae formed in the host α-phase

The cystalline textures of belite consisting of multidirectional lamellae of the β-phase with the α-phase as host (what is called the Type I belite) have been studied by means of the optical microscope, TEM and XRD. The orientation relationship the β- and α-phases is, in agreement with the results of previous studies, and <0001>_α // <010>_β. From combined use of X-ray diffraction and optical microscopy all the lamellae have been found to occur in parallel with the a_α^*-axes and make an angle of 27±3° with {0001}_α. The most probable face indices of the habit planes are and different from by Yamaguchi and Ono (1).     

Oxidation of catechol and l-ascorbic acid by [Ru(tpy)(pic)(OH)] (tpy = 2,2′6′,2″-terpyridine; pic = picolinate): Kinetic and mechanistic studies

Kinetics of oxidation of catechol (H₂cat) to benzoquinone (BQ) and, ascorbate (HA⁻) to dehydroascorbic acid (A) by [Ru^III(tpy)(pic)(OH)]⁺ (1) (tpy = 2,2’6’,2”-terpyridine; pic⁻ = picolinate) have been studied as function of [H₂cat] (or [HA⁻]), ionic strength (0.01 − 0.25 M), temperature (10–30 °C) at a constant pH = 3.2, using stopped-flow and rapid-scan diode array spetrophotometric techniques. The rate of reaction of 1 with HA⁻ was found to be very fast as compared to that of with H₂cat. The kinetic data and activation parameters are interpreted in terms of an associative interchange mechanism. Analysis of spectral and kinetic data revealed that the reaction of 1 with catechol proceeds by a straightforward outer-sphere electron transfer pathway, whereas, reduction of 1 with HA⁻ involves ion-pair formation.     

Electrochemical polymerisation of thiophene derivative induced by Lewis acid: Electrosynthesis of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate]

Films of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate] were deposited on ITO electrodes by potentiodynamic, potentiostatic and galvanostatic methods using a (C₄H₉)₄NBF₄/CH₃CN electrolyte system containing 20% boron trifluoride diethyl etherate. Polymerisation occurred as a charge dependent process at a potential of 1.4 V vs. Ag/Ag⁺(CH₃CN). The surface morphologies of the films so-formed were examined using atomic force microscopy. The film deposited by the galvanostatic method displayed more homogeneous grain geometry and a larger superficial area than those formed by the other methods. Cyclic voltammetry revealed a well defined redox couple at the anodic region, attributable to polymer p-doping, and a poorly defined redox pair at the cathodic region, attributable to the reduction of the nitro group. The polymeric films obtained were yellow in colour (λ_max 425 nm) in the reduced state and light blue (λ_max 745 nm) in the oxidised state.     

Thermal and chemical stability of Cu–Zn–Cr-LDHs prepared by accelerated carbonation

Layered double hydroxides Cu_xZn_6 − xCr₂(OH)₁₆(CO₃)·4H₂O with different molar ratios of Cu/Zn/Cr were synthesized by accelerated carbonation. The products were characterized by XRD, SEM, FT-IR and TG-DTG-DSC-MS. The chemical stability was tested by the modified Toxicity Characteristic Leaching Procedure (TCLP). The results showed that the products were the mixture of Cu_xZn_6 − xCr₂(OH)₁₆(CO₃)·4H₂O and (CuZn)₂(CO₃)(OH)₂, with similar thermal behavior. All products were chemically stable with reduced leaching at pH > 6 (Cu²⁺, Zn²⁺) or > 5 (Cr³⁺).     

An α-K3PMo3W9O40 film loaded with silver nanoparticles: Fabrication, characterization and properties

A composite film consisting of the mixed-addenda Keggin-type polyoxometalate α-K₃PMo₃W₉O₄₀ (PMo₃W₉) and silver nanoparticles (AgNPs) was fabricated on quartz, silicon, and ITO by the layer-by-layer self-assembly method. The regular growth of the multilayer film was monitored by UV–vis spectroscopy, and the morphology was measured by atomic force microscopy (AFM). The multilayer film embedded by AgNPs exhibited the photo-luminescence ascribed to electronic transitions from excited states to d levels of the silver nanoparticles. The composite film also showed electrocatalytic activity towards reduction of NO₂⁻, H₂O₂, ClO₃⁻, BrO₃⁻, and IO₃⁻ attributed to tungsten-centered and molybdenum-centered redox processes of PMo₃W₉.