Development and characterization of covalently cross-linked SPEEK/Cs-TPA/CeO2 composite membrane and membrane electrode assembly for water electrolysis

Covalently cross-linked SPEEK/Cs-TPA/CeO₂ composite membrane was prepared for the polymer electrolyte membrane water electrolysis. Tungstophosphoric acid (TPA) with a cesium was added to the SPEEK to increase proton conductivity. CeO₂ was used to scavenge free radicals which attack the membrane in the water electrolysis and to improve the durability of the membrane. The composite membrane featured the electrochemical characteristics, such as 0.130 S/cm of proton conductivity at 80 °C, and 2.324 meq./g-dry-memb. of ion-exchange capacity. Pt(NH₃)₄Cl₂, Pd(NH₃)₄Cl₂, RhCl₃ and Co(NH₆)₄Cl₃ were used to prepare a variety of the membrane electrode assemblies (MEAs) as electrocatalytic precursors. Electrochemical activity surface area (ESA) of the Pt–Pd electrode prepared with 2 mM Pt(NH₃)₄Cl₂ and 2 mM Pd(NH₃)₄Cl₂ showed the best properties of 26.2 m²/g with CL-SPEEK/Cs-TPA/CeO₂ membrane. In water electrolysis performance, the cell voltage of Pd/PEM/Pt–Pd MEA with CL-SPEEK/Cs-TPA/CeO₂(1%) composite membrane showed cell property of 1.82 V at 1 A cm⁻² and 80 °C.     

Characteristics of polystyrene/polyethylene/clay nanocomposites prepared by ultrasound‐assisted mixing process

In this study, polymer‐clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt‐mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano‐scale dispersion during melt‐mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X‐ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound‐assisted process successfully generated exfoliated nanocomposites and promoted in‐situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198–1204, 2004. © 2004 Society of Plastics Engineers.     

Effect of substrate on the phase transformation of TiO2 in pearlescent pigment

The TiO₂/substrate pearlescent pigments were prepared by the hydrolysis of TiOCl₂ on the substrate followed by a calcinations process. The natural mica (muscovite), synthetic mica (fluorophlogopite) and -alumina flake were selected as the substrates for pearlescent pigments. The effect of substrate on the anatase to rutile (A–R) phase transformation of TiO₂ was studied. The A–R phase transformation of TiO₂ during the preparation of pearlescent pigments and their proportion in the TiO₂ layer have been analyzed by XRD measurements. The phase compositions of TiO₂ layer in each pearlescent pigment are quite different depending on the substrates. The TiO₂ layer deposited on -alumina has higher rutile fraction than those on the natural and synthetic mica. The XPS analysis showed that the cations originally present in the substrates diffused into the TiO₂ layer. The TiO₂ layer deposited on -alumina contains Al, while those on the natural and synthetic mica substrates contain Si and K in addition to Al. The metal cations diffusing from the substrate into TiO₂ layer might retard the A–R phase transformation of TiO₂. The suppressing effect on the A–R transformation of TiO₂ by mixed cations seems to be much stronger than that of single cation, resulting in relatively higher rutile fraction in the case of TiO₂ layer deposited on -alumina.     

TEM investigations of MN nitride phases in a 9% chromium ferritic/martensitic steel with normalization conditions for nuclear reactors

The investigations on the precipitate phases in a 9%Cr ferritic/martensitic steel under different normalization conditions have been made by using a transmission electron microscope and an energy-dispersive X-ray spectroscopy. Hot-rolled steel samples were normalized at 1050-1200 °C for 1-2 h followed by an air cooling to room temperature. MN vanadium nitride precipitates with a plate-like morphology and a chemical formula of about (V_0.4Nb_0.4Cr_0.2)N have been observed at triple junctions, grain boundaries and within matrix in the steel samples normalized at 1050-1150 °C for 1-2 h, but they were dissolved out at 1200 °C within 1 h. Vanadium nitride is a stable phase at 1050 °C according to thermocalc prediction of equilibrium phases in the steel. With increasing normalizing temperature and time, there was no a striking change in the chemical composition of metallic elements in the MN phase, but a considerable increase in the size of the MN precipitate.     

Precipitate phases of a ferritic/martensitic 9% Cr steel for nuclear power reactors

One of the reasons that ferritic/martenstic steels have been considered as candidate materials for nuclear power reactors is their superior creep resistance at elevated temperature. The creep rupture strength of 9% chromium steel could be improved by a fine dispersion of secondary precipitate phase. The precipitate phases in extra-low carbon 9% chromium steel with tempered conditions were investigated by transmission electron microscope and energy-dispersive X-ray analysis. The steel specimens were normalized and then tempered at different temperatures. Niobium-rich MN nitrides (Nb_0.6V_0.3Cr_0.1)N, and two kinds of vanadium nitrides, (V_0.6Nb_0.2Cr_0.2)N and (V_0.45Nb_0.45Cr_0.1)N having a f.c.c. crystal structure, were identified in the steel specimens tempered at 600-780 °C, and 750 or 780 °C respectively. Hexagonal chromium-rich M₂N precipitate phases with different lattice parameters, a = 2.80 Å/c = 4.45 Å and a = 7.76 Å/c = 4.438 Å, were determined in the tempered steel specimens. The M₂N phase showed a decrease/an increase in its chromium/vanadium content as the tempering temperature was increased. The influence of precipitates and heat treatment conditions on the high temperature properties of 9% Cr steel was discussed.     

Purification of novel anti-inflammatory peptides from enzymatic hydrolysate of the edible microalgal Spirulina maxima

Natural bioactive peptides have been known as ingredients in nutraceuticals and pharmaceuticals. In this study, the potential anti-inflammatory peptides were purified from enzymatic hydrolysate of the edible microalgae Spirulina maxima using gastrointestinal endopeptidases (trypsin, α-chymotrypsin, and pepsin). Purification of the hydrolysate resulted in two peptides with amino acid sequences of LDAVNR (P1, 686 Da) and MMLDF (P2, 655 Da). It was found that peptides P1 and P2 exhibited significant inhibition on the release and production of histamine from antigen-stimulated RBL-2H3 mast cells. Moreover, the suppressive effect of P1 and P2 on production as well as expression of interleukin-8 in histamine-stimulated EA.hy926 endothelial cells was determined. Notably, the production of intracellular reactive oxygen species from mast cells and endothelial cells was decreased in the presence of P1 or P2. Collectively, the peptides P1 and P2 from S. maxima could be used as functional ingredients with potent anti-inflammatory benefits.     

Biochemical characterisation of a glycogen branching enzyme from Streptococcus mutans: Enzymatic modification of starch

A gene encoding a putative glycogen branching enzyme (SmGBE) in Streptococcus mutans was expressed in Escherichia coli and purified. The biochemical properties of the purified enzyme were examined relative to its branching specificity for amylose and starch. The activity of the approximately 75 kDa enzyme was optimal at pH 5.0, and stable up to 40 °C. The enzyme predominantly transferred short maltooligosyl chains with a degree of polymerization (dp) of 6 and 7 throughout the branching process for amylose. When incubated with rice starch, the enzyme modified its optimal branch chain-length from dp 12 to 6 with large reductions in the longer chains, and simultaneously increased its branching points. The results indicate that SmGBE can make a modified starch with much shorter branches and a more branched structure than to native starch. In addition, starch retrogradation due to low temperature storage was significantly retarded along with the enzyme reaction.     

Microbial removal of Fe(III) impurities from clay using dissimilatory iron reducers

Fe(III) impurities, which detract refractoriness and whiteness from porcelain and pottery, could be biologically removed from low-quality clay by indigenous dissimilatory Fe(III)-reducing microorganisms. Insoluble Fe(III) in clay particles was leached out as soluble Fe(II), and the Fe(III) reduction reaction was coupled to the oxidation of sugars such as glucose, maltose and sucrose. A maximum removal of 44-45% was obtained when the relative amount of sugar was 5% (w/w; sugar/clay). By the microbial treatment, the whiteness of the clay was increased from 63.20 to 79.64, whereas the redness was clearly decreased from 13.47 to 3.55.     

Photoluminescence and LED application of β-SiAlON:Eu2+ green phosphor

We successfully prepared β-SiAlON:Eu²⁺ phosphors with composition of Eu_xSi_6?zAl_zO_yN_8?y (y = z ? 2x, x = 0.018, z = 0.23) by gas-pressured synthesis for application to LED. The crystal phase, microstructure, PL emission and thermal quenching properties were investigated in detail. The β-SiAlON:Eu²⁺ phosphors absorbed broad UV–vis spectral region, and showed a single intense broadband emission near 538 nm. The Stokes shift and zero-phonon line were calculated mathematically, and also estimated from the spectral data. The β-SiAlON:Eu²⁺ green phosphor showed superior thermal quenching properties compared to commercial silicate (SrBaSiO₄:Eu²⁺) green phosphor. The white light-emitting diode (LED) using the prepared β-SiAlON:Eu²⁺ green phosphor exhibited high color gamut, and good optical stability in high working temperature.     

Fabrication and Characterization of Nanoscale Ferroelectric Honeycombs

Nanoscale ferroelectric honeycombs, comprised of vertically aligned PbTiO₃ nanotubes, are fabricated by vapor phase reaction between lead acetate‐infiltrated TiO₂ nanotubes and PbO vapor. PbTiO₃ nanohoneycombs converted by vapor phase reaction at 550°C showed well‐aligned nanoscale structure with alignment angle less than 1° and well‐defined ferroelectric properties with the effective piezoelectric coefficient of 44 pm/V. This novel nanoscale structure is expected to facilitate high efficiency sensing of electromechanical and electrochemical stimuli.