Influence of hydrothermal exposure on surface characteristics and corrosion behaviors of anodized titanium

Titanium surface was modified by anodization in phosphoric acid solution at the voltages of 100 and 250 V, respectively. Surface characteristics and corrosion behaviors of anodized titanium were investigated before and after hydrothermal exposure in 3.5 wt.% NaCl solution at 160 °C for 24 h. It was found that anodization at 100 and 250 V resulted in the formation of a dense and a porous TiO₂ layer, respectively. The existence of anatase in the oxide layers of the 250‐V samples was confirmed by X‐ray diffraction analysis but not in the oxide layers of the 100‐V samples. After the hydrothermal exposure, the surface morphology of the 100‐V sample changed significantly, and discrete nanorods were formed on the surface. In contrast, the 250‐V sample basically preserved their original surface structures after the exposure except that numerous closely packed nanoparticles emerged on the surface. X‐ray diffraction analysis indicated that the exposure transformed the amorphous oxides into crystalline anatase. The corrosion behavior investigation of anodized titanium showed that the hydrothermal exposure had slight influence on the corrosion resistance of the 100‐V samples but decreased the corrosion resistance of the 250‐V samples significantly. Copyright © 2014 John Wiley & Sons, Ltd.     

Synergistically Interactive Pyridinic-N–MoP Sites: Identified Active Centers for Enhanced Hydrogen Evolution in Alkaline Solution

For electrocatalysts for the hydrogen evolution reaction (HER), encapsulating transition metal phosphides (TMPs) into nitrogen-doped carbon materials has been known as an effective strategy to elevate the activity and stability. Yet still, it remains unclear how the TMPs work synergistically with the N-doped support, and which N configuration (pyridinic N, pyrrolic N, or graphitic N) contributes predominantly to the synergy. Here we present a HER electrocatalyst (denoted as MoP@NCHSs) comprising MoP nanoparticles encapsulated in N-doped carbon hollow spheres, which displays excellent activity and stability for HER in alkaline media. Results of experimental investigations and theoretical calculations indicate that the synergy between MoP and the pyridinic N can most effectively promote the HER in alkaline media.     

A Simple Analysis of Fructooligosaccharides in Two Medicinal Plants by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method for the analysis of seven fructooligosaccharides (FOS, DP3–9) in...     

C18‐bound porous silica monolith particles as a low‐cost high‐performance liquid chromatography stationary phase with an excellent chromatographic performance

Ground porous silica monolith particles with an average particle size of 2.34 μm and large pores (363 Å) exhibiting excellent chromatographic performance have been synthesized on a relatively large scale by a sophisticated sol–gel procedure. The particle size distribution was rather broad, and the d(0.1)/d(0.9) ratio was 0.14. The resultant silica monolith particles were chemically modified with chlorodimethyloctadecylsilane and end‐capped with a mixture of hexamethyldisilazane and chlorotrimethylsilane. Very good separation efficiency (185 000/m) and chromatographic resolution were achieved when the C₁₈‐bound phase was evaluated for a test mixture of five benzene derivatives after packing in a stainless‐steel column (1.0 mm × 150 mm). The optimized elution conditions were found to be 70:30 v/v acetonitrile/water with 0.1% trifluoroacetic acid at a flow rate of 25 μL/min. The column was also evaluated for fast analysis at a flow rate of 100 μL/min, and all the five analytes were eluted within 3.5 min with reasonable efficiency (ca. 60 000/m) and resolution. The strategy of using particles with reduced particle size and large pores (363 Å) combined with C₁₈ modification in addition to partial‐monolithic architecture has resulted in a useful stationary phase (C₁₈‐bound silica monolith particles) of low production cost showing excellent chromatographic performance.     

A Vinyl Cyclopropane Ring Expansion and Iridium-Catalyzed Hydrogen Borrowing Cascade

A vinyl cyclopropane rearrangement embedded in an iridium-catalyzed hydrogen borrowing reaction enabled the formation of substituted stereo-defined cyclopentanes from Ph* methyl ketone and cyclopropyl alcohols. Mechanistic studies provide evidence for the ring-expansion reaction being the result of a cascade based on oxidation of the cyclopropyl alcohols, followed by aldol condensation with the pentamethyl phenyl-substituted ketone to form an enone containing the vinyl cyclopropane. Subsequent single electron transfer (SET) to this system initiates a rearrangement, and the catalytic cycle is completed by reduction of the new enone. This process allows for the efficient formation of diversely substituted cyclopentanes as well as the construction of complex bicyclic carbon skeletons containing up to four contiguous stereocentres, all with high diastereoselectivity.     

Morphological and spectroscopic analyses of poly(alkyl methacrylate)/poly(thiophene) composite nanoparticles prepared by dual initiation system

Poly(alkyl methacrylate)/poly(thiophene) (PAMA/PTh) core/shell nanoparticles were synthesized using a one-pot dual initiation system. A ferric chloride/hydrogen peroxide mixture and sodium vinyl sulfonate were used as an initiator couple and a reactive surfactant, respectively. In the dual initiation, process variables such as the concentration of reactive surfactant, monomer ratio, and monomer type were adjusted to control the particle size of PAMA/PTh core/shell nanoparticles from 192 to 1,172 nm. The inner structure of the core/shell nanoparticles was confirmed in their morphological transition from spherical particles to a crumpled sheath using a solvent extraction method and field-emission scanning electron microscopy. From the spectroscopic data, it was found that the UV-adsorption and fluorescent emission intensity of PAMA/PTh latexes increased with a decrease in the average particle size. The quantum efficiency of all the samples was approximately 12 % and was unaffected by the particle size.     

System mode approach for analysis of horizontal vibration of 3-D two-link flexible manipulators

This paper deals with the system mode analysis of horizontal vibration for 3-D two-link flexible manipulators. For the analysis, we formulate and solve a set of partial differential equations which represent vibration mixed with bending and torsional moment. The inclusion of torsional vibration complicates the analysis, but the results are more precise and realistic. We obtain a number of geometrical and dynamical boundary conditions depending on manipulator configuration. There are two possible boundary conditions at the rotary joint: clamped and pinned with spring condition. We perform a examination and comparison between the two joint conditions. Numerical and experimental tests show the validity and effectiveness of the proposed analysis and modelling.     

The lattice of convex subsemilattices of a semilattice

The convex subsemilattices of a semilattice E form a lattice Co(E) in the natural way. The purpose of this paper is to study how the properties of this lattice relate to the semilattice itself. For instance, lower semimodularity of the lattice is equivalent, along with various properties, to the semilattice being a tree. When E has more than two elements the lattice does, however, fail many common lattice-theoretic tests. It turns out that it is more fruitful to describe those semilattices E for which every “atomically generated” filter of Co(E) satisfies certain lattice-theoretic properties.     

DC-biased AC-electrokinetics: a conductivity gradient driven fluid flow

This paper studies the principles of fluid flow manipulation based on DC-biased AC-electrokinetics. This method makes use of planar parallel electrodes in a microfluidic channel in contact with an electrolyte solution, with a DC biased AC electrical signal applied to the electrode pair. Due to the application of DC bias, incipient Faradaic electrolytic reactions take place resulting in an increase of the ionic content of the bulk solution. The ionic content was found to be dissimilar at the cathodic and anodic sides of the channel and a conductivity difference of approximately 10% was measured for 2 V(DC). Fluid flow is generated by the action of the DC biased AC electric signal acting on the transverse conductivity gradient generated across the microchannel. The induced flow in the form of vortex was characterized experimentally and the results substantiated theoretically. The velocity of the induced flow vortex under the employed experimental conditions was ~600 to 700 μm s(-1) which is faster than those obtained in conventional AC-electroosmosis and AC-electrothermal types of flows.