Alleviation of the adhesive protrusion problem at the bonding interface of free-standing microstructures

The vertically allocated free-standing SU-8 microstructures are typically bonded to a glass cover by the usage of uncrosslinked SU-8 adhesives. Such a phenomenon can easily cause SU-8 protrusion and eventually result in the SU-8 cantilever to be immovable. Traditional methods are sensitive to the bonding conditions and have a short bondable thickness of SU-8 adhesives. In this study, we propose an approach, that is, improved structural features, to alleviate the protrusion problem while extending the bondable thickness for the freestanding SU-8 microstructures in an enclosed channel. We used concave and moat microstructures as solutions of the improved structural features. We investigated the influence of both microstructures on the bonding quality and compared the bondable thickness with the previous one. THB-151N was used in another example to demonstrate the availability of our method. The bonding quality at the interfaces was evaluated by SEM images and direct inspection through a transparent glass cover. The bonding method is advantageous to other microfluidic systems, particularly those with long narrow channels.

     

Effect of silane coupling on the joint characteristics of friction lap joined Al alloy/CFRP

Dissimilar materials joining of an A5052 plate and a carbon fibre reinforced thermoplastic (CFRTP), which consisted of polyamide 6 (PA6) with 20 wt% carbon fibre addition, was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the CFRTP plate as a bottom. The joint characteristics were evaluated to investigate effects of the surface treatment by the silane coupling treatment for A5052 and the joining speed on the joining properties. The joint strength was increased by inducing the silane coupling treatment for the A5052 plate surface. The tensile shear fracture load of the silane coupling treated FLJ joint increased by increasing the joining speed up to 6.67 mm/s and then decreased. The maximum tensile shear fracture load of 5.0 kN was obtained at the joining speed of 6.67 mm/s, and the fracture occurred at the CFRTP base plate with the joint efficiency of 97%. The shear strength of the joint interface of the joint formed at the joining speed of 1.67 mm/s, which fractured at the joining interface by the tensile shear test, was estimated to be about 19 MPa. The covalent bondings between the A5052 plate and the silane coupling layer, and the silane coupling layer and the CFRTP plate were indicated by inducing the silane coupling treatment.     

Preparation of ZSM-5 nanoparticles supported on carbon substrate

Influences of the pore structure and the surface functionality of carbon substrates on the formation of ZSM-5 nanoparticles were studied. The inorganic substance formed on these carbons were identified as ZSM-5 by X-ray diffraction, which also revealed the presence of an amorphous silica phase. The fraction of crystalline phase, which was evaluated from XRD, was not affected by the pore structure; however, inorganic content depended on the pore structure of carbon: i.e. 14-17% for non- and microporous carbons, and 40-55% for mesoporous carbons. TEM observation revealed that the ZSM-5 deposited on these carbon substrates was in the form of nanoparticles with 10-20 nm of diameters. The influence of the surface functionality on the formation of ZSM-5 nanoparticles was also studied with an activated carbon, of which surface functionality was modified by heat-treatment and nitric acid-treatment. A strong dependence of the fraction of crystalline phase on the treatments was observed; i.e. the heat-treatment increased the fraction and the acid-treatment decreased it. Finally, we clarified the controlling factors for the formation of ZSM-5 on carbon materials; the mesoporous surface area of carbon strongly affects the inorganic content and the total acidity of carbon influences the selectivity to ZSM-5 formation.     

Asymmetrical dicationic ionic liquids based on both imidazolium and aliphatic ammonium as potential electrolyte additives applied to lithium secondary batteries

Asymmetrical dicationic ionic liquids based on the combination of imidazolium and aliphatic ammonium cations with TFSI anion, MIC_nN₁₁₁-TFSI₂, have been synthesized for the first time, wherein MI represents imidazolium cation, N₁₁₁ represents trimethylammonium cation, and C_n represents spacer length. The physical and electrochemical properties of this family of ionic liquids were studied. 1-(3-Methylimidazolium-1-yl)ethane-(trimethylammonium) bi[bis(trifluoromethane-sulfonyl) imide] (MIC₂N₁₁₁-TFSI₂) shows solid-solid transition characteristics. 1-(3-Methylimidazolium-1-yl)pentane-(trimethylammonium) bi[bis(trifluoromethan-esulfonyl)imide] (MIC₅N₁₁₁-TFSI₂) has one of the lowest solid-liquid transformation temperatures among analogues, and belongs to the greatest thermal stable ionic liquids. Additionally, it has an order of conductivity of 10⁻¹ ms cm⁻¹, and electrochemical window of about 3.7 V at room temperature. To evaluate the potential of MIC₅N₁₁₁-TFSI₂ as an additive of electrolyte for lithium secondary batteries, cells composed of LiMn₂O₄ cathode/1 M LiPF₆ in EC:DMC (1:1, v/v) electrolytic solution containing 5 wt% of MIC₅N₁₁₁-TFSI₂/lithium metal anode have been prepared. The charge-discharge cycling test reveals that unlike the cases of Li/LiMn₂O₄ cells employing a conventional electrolyte with a monocationic ionic liquid, such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EtMeImTFSI) as an additive, the performances of Li/LiMn₂O₄ cells do not drop with the addition of MIC₅N₁₁₁-TFSI₂ at 1C rate, moreover, the cell exhibits better discharge capacity and cycle durability compared with the cell using the conventional electrolyte.     

Effects of Ozonated Water Application on the Population Density of Fusarium oxysporum f. sp. lycopersici in Soil Columns

The potential of ozonated water was investigated as an alternative to soil disinfectants in reducing the population densities of Fusarium oxysporum f. sp. lycopersici in artificially infested quartz sand and Kuroboku soil columns. Significant reductions in the population density were observed with dissolved ozone concentrations (DOCs) of 6 and 12 mg L^?1 in infested quartz sand but not in infested Kuroboku soil. The results indicate that repetitive application of ozonated water with higher DOCs should be required for reducing the population density of F. oxysporum in soils with high content of organic substances and large surface area.     

Optimization of reaction conditions for the production of DAG using immobilized 1,3-regiospecific lipase lipozyme RM IM

Oils with a high DAG (1,3-DAG) content have attracted considerable attention as a healthful food oil component. In this study, we report on the synthesis of 1,3-DAG from a mixture of FA, constituted largely of oleic and linoleic acids, using an immobilized 1,3-regioselective lipase from Rhizomucor miehei in a solvent-free system. The kinetics of 1,3-DAG production from FA and glycerol were investigated on the basis of a simplified model, taking into consideration the acyl migration reaction, the removal of water, and glycerol dissolution in the oil phase in addition to the esterification reactions. Both the yield of 1,3-DAG and the purity of DAG were evaluated under a variety of experimental conditions, including reaction temperature, pressure, and amount of enzyme present. When either the reaction temperature or the amount of enzyme used was increased, the 1,3-DAG production rate increased, but yield remained relatively constant. The 1,3-DAG yield as well as the purity of DAG gradually decreased because of the enhancement of acyl migration at later stages of the reaction after the 1,3-DAG concentration reached a maximum. Vacuum was important for attaining high yields of 1,3-DAG. Under conditions of a high vacuum (1 mm Hg) at 50°C, 1.09 M 1,3-DAG was produced from 1.29 M glycerol and 2.59 MFA in an 84% yield and in 90% purity.     

Device scaling of pseudo-vertical diamond power Schottky barrier diodes

Device size scaling of pseudo-vertical diamond Schottky barrier diodes (SBDs) has been characterized for high-power device applications based on the control of doping concentration and thickness of the p^? CVD diamond layer. Decreasing parasitic resistance on the p⁺ layer utilising lithography and etching realises a constant specific on-resistance of less than 20 mΩ cm² with increasing device size up to 200 µm. However, the leakage current under low reverse bias conditions is increased markedly. Due to the increase in the leakage current, the reverse operation limit is decreased from 2.4 to 1.3 MV/cm when the device size is increased from 30 to 150 µm. If defects induce an increase in leakage current under the reverse conditions, the density of the defects can be estimated to be 10⁴–10⁵/cm². This value is 5–10 times larger than the density of dislocations in single crystal diamond Ib substrate.     

A novel ∈-lysine acylase from <Emphasis Type="Italic">Streptomyces mobaraensis</Emphasis> for synthesis of <Emphasis Type="Italic">N∈</Emphasis>-acyl-<Emphasis Type="SmallCaps">l</Emphasis>-lysines

A novel ∈-lysine acylase (N ₆-acyl-l-lysine amidohydrolase; EC 3.5.1.17) was isolated from Streptomyces mobaraensis and purified to homogeneity by SDS-PAGE from the culture broth. The purified enzyme was monomeric, with a molecular mass of approximately 60 kDa. The enzyme was inactivated by the presence of 1,10-phenanthroline and activated in the presence of Co²⁺ and Zn²⁺. The enzyme showed a pH optimum of 8.0 and was stable at temperatures of up to 50°C for 1 h at pH 8.0. The enzyme specifically catalyzed the hydrolysis of the amide bond of various N∈-acyl-l-lysines. Furthermore, the enzyme efficiently catalyzed the synthesis of N∈-acyl-l-lysines with fatty and aromatic acyl groups in an aqueous buffer. In the syntheses of N∈-decanoyl-l-lysine, N∈-lauroyl-l-lysine, and N∈-myristoyl-l-lysine, the product precipitated and the yield was 90% or higher using 10 mM FA and 0.5 M l-lysine as the substrate.     

III-Nitride grating grown on freestanding HfO2 gratings

We report here the epitaxial growth of III-nitride material on freestanding HfO2 gratings by molecular beam epitaxy. Freestanding HfO2 gratings are fabricated by combining film evaporation, electron beam lithography, and fast atom beam etching of an HfO2 film by a front-side silicon process. The 60-μm long HfO2 grating beam can sustain the stress change during the epitaxial growth of a III-nitride material. Grating structures locally change the growth condition and vary indium composition in the InGaN/GaN quantum wells and thus, the photoluminescence spectra of epitaxial III-nitride grating are tuned. Guided mode resonances are experimentally demonstrated in fabricated III-nitride gratings, opening the possibility to achieve the interaction between the excited light and the grating structure through guided mode resonance.PACS: 78.55.Cr; 81.65.Cf; 81.15.Hi.     

The atomic structure of disordered ion tracks in magnesium aluminate spinel

Atomic resolution transmission-electron microscopy (TEM) observations and analysis have been undertaken on magnesium aluminate spinel to understand the structure of ion tracks induced by swift heavy ions. A combination of TEM techniques, which includes high-resolution and bright-field (BF) imaging, and high angular resolution electron channeling spectroscopy (HARECXS) analysis, disclosed the atomic structure of ion tracks. Swift heavy ions induce cation disordering along the latent tracks for a widespread region of 10 nm in diameter, which is much larger than a strained region detected by BF diffraction contrast. A preferential migration of cations is induced from the tetrahedral to octahedral interstitial site at the core regions of ion tracks under a condition of higher electronic excitation of (dE/dx)_e = 35 keV/nm.