Immersion‐Angle Dependence of the Resonant‐Frequency Shift of a Quartz Crystal Microbalance in Three Types of Newtonian Liquids

Abstract

The present work reports the new characteristics of the immersion‐angle dependence of the resonant‐frequency shift (ΔF) of the one‐face sealed quartz crystal microbalance (QCM) in three types of Newtonian liquids, i.e., sucrose, glucose, and glycerol solutions. Below some 1.80×10^?2 g cm^?2 · s^?1/2, the ΔF values are dependent on the immersion angles in all solutions. However, we have found that the transition phenomenon of ΔF occurs between 1.78×10^?2 and 4.80×10^?2 g · cm^?2 · s^?1/2 in the sucrose solution, between 1.75×10^?2 and 4.34×10^?2 g · cm^?2 · s^?1/2 in the glucose solution and between 1.83×10^?2 and 3.03×10^?2 g · cm^?2 · s^?1/2 in the glycerol solution, respectively. Moreover, above the concentrations of the end points of the transition phenomenon, the ΔF values of the sucrose solution are equal to those of 90° at all immersion angles. On the other hand, those of the glucose and the glycerol solutions are the same as those of 30°. This difference may be caused by inherent characteristics of adsorption to the surface of the QCM electrode.     

TEM study of Mg-Zn precipitates in Mg-Zn-Y alloys

The precipitates in Mg-Zn-Y alloys in the as-cast state with nominal atomic composition of Mg₉₆Zn₁Y₃, Mg₉₆Zn₂Y₂ and Mg₉₇Zn₁Y₂ were studied by means of TEM as well as XRD techniques. The results show that there is a phase separation of Zn on the nanometer scale in these alloys. Two kinds of nano-sized precipitates were found, namely MgZn and MgZn₂. TEM observation shows that MgZn precipitates are distributed in both the Mg matrix and in Mg₂₄Y₅ grains, which is the typical precipitate in Mg-Zn-Y alloys. There is an inherent crystallographic relationship between MgZn and Mg₂₄Y₅ precipitates: // , // . The size of MgZn₂ precipitates is much smaller than that of MgZn precipitates. They are distributed only in Mg₂₄Y₅ grains, not in the Mg matrix. It is suggested that the nano-sized precipitates, MgZn and MgZn₂, can improve the mechanical properties of the Mg-Zn-Y alloys studied.     

Nano-cube MgO formed on silicon substrate using pulsed laser deposition

Nano-cube MgO particles were formed on Si substrates by deposition of an MgO target using pulsed laser deposition method. An epitaxial film grows on Si(001) substrate with its contraction of lattice constants. In this study, expecting high quality MgO film, the MgO film prepared in the oxygen pressure ranging from 75-400 mTorr at the high temperature of -750 degrees C. The deposited MgO showed the growth of (001) preferred orientation on the Si(001) substrate. However, X-ray Photoelectron Spectroscopy (XPS) indicated the MgO film did not form a continuous film on the Si surface. Interestingly, the surface morphology observed by an Atomic Force Microscopy (AFM) showed nano-cube MgO particles scattered on the smooth surface of Si substrate. After annealing the nano-cube MgO, the shape of MgO particles were changed from nano-cube to round shaped particles. The AFM image of the surface showed round shaped MgO nanoparticles scattered on rough surface. X-ray Diffraction (XRD) revealed the epitaxial growth of MgO(001) with cubic on cubic arrangement on the Si(001) substrate (MgO[100] parallel to Si[100]).     

Self-discharge behavior of polyacenic semiconductor and graphite negative electrodes for lithium-ion batteries

Variations in open-circuit potential (OCP) of artificial graphite and polyacenic semiconductor (PAS) negative electrodes have been investigated as a function of the storage time in alkylcarbonate-based electrolyte solutions after their cathodic charging (electrochemical lithiation) to discuss self-discharge phenomena of these negative electrodes for lithium ion batteries. The OCP of the graphite showed a plateau at ca. 90 mV vs. Li/Li⁺ for a long period (>8 × 10⁵ s), which suggested the retention of a stage structure of lithiated graphite during the storage. The lithiated PAS electrode gave gradual changes in OCP during the storage in the carbonate-based electrolyte solutions, suggesting continuous loss of Li species in the electrode. Variations in the interfacial resistance determined by an ac method, corresponding to the changes in the structure and properties at the electrode/electrolyte interface, also showed different features for the lithiated graphite and PAS electrodes. The mechanisms of self-discharging for these carbonaceous electrodes are discussed from the results of the influences of temperature and additives on the OCP variations.     

Charge-discharge rate of spinel lithium manganese oxide and olivine lithium iron phosphate in ionic liquid-based electrolytes

Rate capability of Li/spinel LiMn₂O₄ or olivine LiFePO₄ positive electrode cells containing mixed imidazolium ionic liquids electrolytes has been investigated under comparison with conventional organic solvent electrolyte and piperidinium ionic liquid. The LiMn₂O₄ electrode provides variation of rate capabilities among the ionic liquid electrolytes, while ionic liquid electrolytes provide similar extent of capacity degradation under high rate compared with organic solvent electrolyte for LiFePO₄ electrode. Such differences in electrolyte dependences of the rate capabilities can be explained in relation to parameters in the high frequency resistances on AC impedance, assumed as interfacial resistances. The rate capability of LiMn₂O₄ is somewhat related to the activation energy of the high frequency resistance, while for LiFePO₄ the resistance value appears to contribute to the rate capability.     

Synthesis of a fullerene/expanded graphite composite and its lubricating properties

A fullerene/expanded graphite composite, in which fullerene crystals were incorporated into the expanded graphite interspaces, was prepared by chemical and thermal treatments and its lubricating properties in commercial grease were investigated. Expanded graphite, which was synthesized from graphite by oxidizing by KMnO₄ in 98% H₂SO₄ containing NaNO₃ and by heating at 400 °C for 3 min, and fullerene were placed in a stainless steel tube, and were heated in a furnace under vacuum at 600 °C for 2 weeks. The fullerene/expanded graphite composite obtained was characterized by X-ray diffraction analysis (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). XRD and FT-IR analyses showed that crystalline fullerene was present in the material and SEM images confirmed that it existed in the expanded graphite interspaces. The composite was blended with a commercial grease, and its lubricating properties were investigated using a four-ball lubricant tester. These properties were evaluated by measuring the wear scar diameter and wear volume loss of the test ball. The combination of composite and grease provided a better lubricating performance than that of pure graphite and grease.     

A study on horizontal stud welding by using steel stud for flat welding

ABSTRACT

In recent years, manufacturing sites have strongly requested for the steel stud with large diameter to be welded in the horizontal position, which is difficult because of gravity. In this study, the steel stud of 19 mm in diameter was welded horizontally to the mild steel plate by using ferrule for usage in flat position. As results two kinds of weld defect were observed; lack of fusion and blowhole. The former occurred in the welding condition of too small or too large heat input, and the latter did in the range of longer arc time. Therefore, the suitable welding condition could be found in the large current and shorter arc time. When the areal ratio of weld defect to the cross section of stud was lower than 10 percent, the welded joint had enough statical strength.     

Photo-induced molecular alignment of azo dye derivative

Photo-induced molecular alignment behavior of azo dye derivative (sodium 4,4′-bis (4-hydroxy-3-carboxy-phenylazo) benzidine-2,2′-disulphonate: SD1) was investigated using SD1 film prepared by spin-coating method. As-prepared SD1 film was composed of an amorphous layer with smooth surface. Upon linearly polarized UV light irradiation, the film surface was roughened slightly and X-ray diffraction measurement and transmittance electron microscope observation indicated that SD1 molecules crystallized with orientation. Molecular plane of SD1 aligned parallel to the substrate surface along the normal to the polarization direction of irradiated UV light through the trans-cis and cis-trans isomerizations of the azobenzene chromophore.     

Isolation and characterization of the ATF2 gene encoding alcohol acetyltransferase II in the bottom fermenting yeast Saccharomyces pastorianus

The ATF2 gene encodes alcohol acetyltransferase II, which catalyses the synthesis of isoamyl acetate from acetyl coenzyme A and isoamyl alcohol. To characterize the ATF2 gene from the bottom fermenting yeast Saccharomyces pastorianus, the S. pastorianus ATF2 gene was cloned by colony hybridization using the S. cerevisiae ATF2 gene as a probe. When an atf1 null mutant strain was transformed with a multi-copy plasmid carrying the S. pastorianus ATF2 gene, the AATase activity of this strain was increased by 2.5-fold compared to the control. The S. pastorianus ATF2 gene has 99% nucleic acid homology in the coding region and 100% amino acid homology with the S. cerevisiae ATF2 gene. Southern blot analysis of chromosomes separated by pulse-field gel electrophoresis indicated that the ATF2 gene probe hybridized to chromosome VII in S. cerevisiae and to the 1100 kb chromosome in S. pastorianus. As S. pastorianus is thought to be a hybrid of S. cerevisiae and S. bayanus, the S. bayanus-type gene, which has a relatively low level of homology with the S. cerevisiae-type gene, is also usually detected. Interestingly, an S. bayanus-type ATF2 gene could not be detected. These results suggested that the cloned ATF2 gene was derived from S. cerevisiae. Analysis using an ATF2-lacZ fusion gene in S. pastorianus showed that expression of the ATF2 gene was relatively lower than that of the ATF1 gene and that it is repressed by aeration but activated by the addition of unsaturated fatty acids. The S. pastorianus ATF1, Lg-ATF1 and ATF2 Accession Numbers in the DDBJ Nucleotide Sequence Database are D63449, D63450 and D86480, respectively.