Conductive adhesive with transient liquid‐phase sintering technology for high‐power device applications

A highly reliable conductive adhesive obtained by transient liquid‐phase sintering (TLPS) technologies is studied for use in high‐power device packaging. TLPS involves the low‐temperature reaction of a low‐melting metal or alloy with a high‐melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag‐coated Cu, a Sn96.5‐Ag3.0‐Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 °C, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.     

Acute aortic outflow obstruction by diminution of bulboventricular foramen size after volume unloading in univentricular physiology

A young child with [S, L, L] segmental anatomy, double-inlet left ventricle, transposition of the great arteries, rudimentary right ventricle, and mildly restrictive bulboventricular foramen is reported, in whom intraoperative temporary snaring of the modified Blalock-Taussig shunt resulted in instantaneous and dramatic volume contraction of the left ventricle, decrease in bulboventricular foramen size, and increase of the gradient across the latter from 10 mm Hg preoperatively to 50 mm Hg. A modified Damus-Stansel-Kaye procedure using autogenous aortic tissue resulted in unobstructed aortic outflow; in addition, a bidirectional cavopulmonary shunt was performed. The importance of early relief of actual or potential aortic outflow obstruction in hearts with restrictive bulboventricular foramen is emphasized.     

Hydrogen production in fluidized bed by chemical-looping cycle

To investigate the feasibility of a chemical-looping hydrogen generation system, we investigated the reduction and water splitting reaction characteristics for three mediators and two reducing gas in a bubbling fluidized bed reactor (0.02 m I.D.). For three oxygen carrier particles (NiO/bentonite, Fe₂O₃/bentonite, (NiO:Fe₂O₃)/bentonite), hydrogen was used as a reduction gas and water was used as an oxidation gas. For (NiO: Fe₂O₃)/bentonite particle, carbon monoxide, which is the main component in the syngas from coal or heavy residue, was used as a reducing gas to check reactivity for the carbon containing fuels and carbon deposition characteristics. Based on the reactivity tests, (NiO: Fe₂O₃)/bentonite particle was selected as the best mediator for the chemical-looping hydrogen generation system to achieve stable continuous operation. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Hazardous acid detection based on chitosan‐grafted‐polyaniline copolymer

Polyaniline (PANI) has been utilized very well as an active material for hazardous acid detection device. Because its electrical conductivity is developing when it is doped with the protonic acid. However, a critical disadvantage of this material is its insolubility in general solvents so its processability is very poor. In this work, we prepared a Chitosan‐g‐PANI (Cs‐g‐PANI) copolymer to improve its solubility and prossability using common solvents and use film form of the final product to develop a sensitive device, which responds to the presence of hazardous acids. The synthetic Cs‐g‐PANI showing good solubility and excellent film forming properties was characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, as well as X‐ray diffraction analysis, and scanning electron microscopy. The physical properties of Cs‐g‐PANI films were optimized by controlling the Cs composition. Constant potential was applied to this material for detecting the existence of hazardous acids such as hydrochloric acid (HCl), nitric acid, formic acid, and acetic acid. Our findings suggest that this device responds to the presence of HCl faster than any other acids. The detection mechanism is discussed in detail. POLYM. ENG. SCI., 59:E105–E110, 2019. © 2018 Society of Plastics Engineers     

关于Filon算法的一点注记

本文对谐波分析中数值积分的Filon公式提出了一点改进,改进后的算法在微机上得到实现,经实算表明,计算结果满足工程精度要求。     

Rearrangement of Multiferroic BiFeO3 Nanodots Smaller than 15 nm Using Atomic Force Microscopy

In this study, we demonstrate an atomic force microscopy process for manipulating multiferroic BiFeO₃ nanodots smaller than 15 nm to desired positions on a Nb‐doped SrTiO₃ substrate. For formation of the BiFeO₃ nanodot array, nanocrystal movement was achieved using a +1.2 V biased conducting atomic force microscopy (CAFM) followed by nanocrystal attachment to the tip. Using this method, high‐density BiFeO₃ nanodot arrays with a density greater than 0.5 Tb/in.² can be achieved. Perfectly flipped ferroelectric polarization with an external electric field was observed for each BiFeO₃ nanodot, whose ferroelectric properties were confirmed using piezoelectric force microscopy.     

Phosphaannulation of Aryl‐ and Benzylphosphonic Acids with Unactivated Alkenes via Palladium‐Catalyzed C?H Activation/Oxidative Cyclization Reaction

An efficient phosphaannulation via palladium(II)‐catalyzed C H activation/oxidative cyclization by the 6‐endo mode is reported for the synthesis of 3‐substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α‐disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)‐alkylidenyl groups via anti‐phosphoryloxypalladation by the 6‐exo mode.

     

Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering

Zinc sulfide [ZnS] thin films were deposited on glass substrates using radio frequency magnetron sputtering. The substrate temperature was varied in the range of 100°C to 400°C. The structural and optical properties of ZnS thin films were characterized with X-ray diffraction [XRD], field emission scanning electron microscopy [FESEM], energy dispersive analysis of X-rays and UV-visible transmission spectra. The XRD analyses indicate that ZnS films have zinc blende structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM data also reveal that the films have nano-size grains with a grain size of approximately 69 nm. The films grown at 350°C exhibit a relatively high transmittance of 80% in the visible region, with an energy band gap of 3.79 eV. These results show that ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se₂ solar cells.