Coprecipitation Synthesis of a Superconductor via Multi‐Precipitants

A precipitation process has been developed to prepare precursor powders, which can be calcined and sintered to form high‐Tc superconductors such as YBa₂Cu₃O_y. Precursor powders are prepared using a mixed‐precipitants system in which a solution contains precipitating anions such as hydroxide, oxinate and oxalate ions. A theoretical study on the conditions of mixed‐precipitants coprecipitation is performed. The solution pH of complete precipitation of the title system is extended and is maintained between 4.46 and 12.0. A series of experiments were conducted to confirm the as‐derived optimal condition. Finally, characterization of the properties of the YBa₂Cu₃O_y obtained after high temperature treatment is reported.     

Surface‐initiated atom transfer radical polymerization from porous poly(tetrafluoroethylene) membranes using the C?F groups as initiators

This work reports the surface‐initiated atom transfer radical polymerization (ATRP) from hydrogen plasma‐treated porous poly(tetrafluoroethylene) (PTFE) membranes using the C? F groups as initiators. Hydrogen plasma treatment on PTFE membrane surfaces changes their chemical environment through defluorination and hydrogenation reactions. With the hydrogen plasma treatment, the C? F groups of the modified PTFE membrane surface become effective initiators of ATRP. Surface‐initiated ATRP of poly(ethylene glycol) methacrylate (PEGMA) is carried out to graft PPEGMA chains to PTFE membrane surfaces. The chain lengths of poly(PEGMA) (PPEGMA) grafted on PTFE surfaces increase with increasing the reaction time of ATRP. Furthermore, the chain ends of PPEGMA grown on PTFE membrane surfaces then serve as macroinitiators for the ATRP of N‐isopropylacrylamide (NIPAAm) to build up the PPEGMA‐b‐PNIPAAm block copolymer chains on the PTFE membrane surfaces. The chemical structures of the modified PTFE membranes are characterized using X‐ray photoelectron spectroscopy. The modification increases the surface hydrophilicity of the PTFE membranes with reductions in their water‐contact angles from 120° to 60°. The modified PTFE membranes also show temperature‐responsive properties and protein repulsion features owing to the presence of PNIPAAM and PPEGMA chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2076–2083, 2010     

The role of pyrrhotite (Fe7S8) and the sample texture in the hydrothermal transformation of pentlandite ((Fe,Ni)9S8) to violarite ((Ni,Fe)3S4)

The catalytic role of pyrrhotite (Fe₇S₈) in the reaction kinetics of the hydrothermal transformation of pentlandite ((Fe,Ni)₉S₈) to violarite ((FeNi₂S₄) was found to depend on the physical form of pyrrhotite. Pyrrhotite in fine scale intergrown with pentlandite boosts the reaction, whereas in a mechanical mixture of pyrrhotite and pentlandite, it plays the opposite role. This phenomenon was interpreted as result of dissolution of pyrrhotite under reaction conditions.     

Frequency-tripled Nd:YAG laser ablation in laser structuring process

With the increasing demand for finer lines/spaces on PCB boards, a new technology—laser structuring—has emerged in recent years. In this research, the frequency-tripled Nd:YAG laser is selected as the laser source in laser structuring; this laser is often used in miniaturization machining. This paper describes in detail the processing parameters’ influences, such as laser power, numbers of repetition, repetition rate and bite size, on laser structuring results. From the research results, it can be concluded that the line width and depth are increased with increases in the laser power and numbers of repetition. Repetition rate, bite size and velocity are related to one another. When the bite size is fixed, the velocity increases with the repetition rate and the depth of the line is decreased at the same time. When the repetition rate is fixed, velocity increases with the bite size.     

Thermal Cyclization of Copper Carbenoid of α‐Dizao α‐Phosphorylacetate: Unexpected and Novel Access to Oxaphosphirane

Under the catalysis of Cu(OTf)₂ in refluxing CH₂Cl₂, ethyl α‐dizao α‐(diethylphosphoryl)acetate was shown to undergo a new cyclization reaction to afford a pentacovalent oxaphosphirane product. The reaction is proposed to occur through the addition of the P=O double bond to the copper carbenoid, followed by the hydrolysis of the ylide intermediate. Our finding represents the first example on producing oxaphosphiranes from dizao phosphoryl compounds. On the other hand, the corresponding rhodium carbenoid displayed the different reactivity under the same thermal conditions, to produce the β‐propiolactone through the well‐recognized C‐H insertion pathway.     

Structural investigation of high‐transmittance aluminum oxynitride films deposited by ion beam sputtering

Aluminum oxynitride films were deposited by ion beam sputtering technique at room temperature. The optical properties and morphologies of the aluminum oxynitride films were studied and reported previously. It was found that the optical properties are closely related to the O contents in the films. In this study, the structures of the films were investigated by X‐ray diffractometer and XPS. Three oxidation states of N_1s in oxynitride films, N⁺, N²⁺ and N³⁺, were clearly deduced from N_1s spectra in the amorphous films fabricated under various oxygen partial pressures (P_O2). To our knowledge, three oxidation states of N_1s have not been simultaneously observed and reported in the aluminum oxynitride films previously. Corresponding bonding variations in Al_2p and O_1s spectra indicated more oxygen in oxynitride in the film as P_O2 increases. Three aluminum oxynitride networks, AlO₂N, AlO_2.5N and AlO₃N were deduced. Optical properties of aluminum oxynitride films resemble those of AlN and Al₂O₃ films when P_O2 is low and high during the deposition. The refractive indices and extinction coefficients of the aluminum oxynitride films can be adjusted by using proper P_O2 during the film depositions. Copyright © 2010 John Wiley & Sons, Ltd.     

Study on tribological behaviors of short glass fiber and polytetrafluoroethylene reinforced polycarbonate composites via a d‐optimal mixture design

This study analyzed variations of tribological behaviors that depend on the injection molding techniques during the blending of short glass fiber (SGF) and polytetrafluoroethylene (PTFE) reinforced polycarbonate (PC) composites. The proposed planning of blending experiments is to use a D‐optimal mixture design (DMD). The tribological behaviors of friction coefficient and wear mass loss were selected for discussion. Nine experimental runs, based on a DMD method, utilized to train the back‐propagation neural network (BPNN) and then the simulated annealing algorithm (SAA) approach is applied to search for an optimal mixture ratio setting. In addition, the result of BPNN integrating SAA was also compared with response surface methodology (RSM) approach. The results of confirmation experiment show that DMD, RSM, and BPNN integrating SAA method are effective tools for the optimization of reinforced process. Furthermore, the scanning electron microscope (SEM) images show that the abundant debris are peeled off from the matrix materials and predominant delamination mechanisms and plastic deformation are shown on the worn surface after tribological behavior tests. Copyright © 2010 John Wiley & Sons, Ltd.     

Hybrid evolutionary algorithms in a SVR traffic flow forecasting model

Accurate urban traffic flow forecasting is critical to intelligent transportation system developments and implementations, thus, it has been one of the most important issues in the research on road traffic congestion. Due to complex nonlinear data pattern of the urban traffic flow, there are many kinds of traffic flow forecasting techniques in literature, thus, it is difficult to make a general conclusion which forecasting technique is superior to others. Recently, the support vector regression model (SVR) has been widely used to solve nonlinear regression and time series problems. This investigation presents a SVR traffic flow forecasting model which employs the hybrid genetic algorithm-simulated annealing algorithm (GA-SA) to determine its suitable parameter combination. Additionally, a numerical example of traffic flow data from northern Taiwan is used to elucidate the forecasting performance of the proposed SVRGA-SA model. The forecasting results indicate that the proposed model yields more accurate forecasting results than the seasonal autoregressive integrated moving average (SARIMA), back-propagation neural network (BPNN), Holt-Winters (HW) and seasonal Holt-Winters (SHW) models. Therefore, the SVRGA-SA model is a promising alternative for forecasting traffic flow.     

Effect of oxygen evolution catalysts on hematite nanorods for solar water oxidation

Photochemical deposition of Co and Ni based oxygen evolution catalysts on hematite nanorods cathodically shifted the onset potential of photocurrent near to the flat band potential of hematite. A 9.5 fold enhancement in the photocurrent density at 0.86 V vs. RHE compared to the parent hematite photoanode was observed with the Ni-Bi/Fe(2)O(3) photoanode.