Mg1-xZnxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8) nanoparticles encapsulated in amorphous SiO2 were prepared using a wet chemical method, and their magnetic properties were studied. The diameters of these particles were estimated from X-ray diffraction (XRD) patterns as ranging near 4.5 nm. Magnetization measurements were carried out for all samples under a ±50 kOe field. The blocking temperature TB was determined to be approximately 20-60 K from the temperature dependence of the field-cooled (FC) and the zero-field-cooled (ZFC) magnetizations. The M-H curve indicated ferromagnetic behavior at 5 K and superparamagnetic (x = 0 － 0.6) and paramagnetic (x = 0.8) behavior at 300 K. The sample with x = 0.4 had the largest maximum magnetization MS under an applied field of 50 kOe at 5 K, and the sample with x = 0.2 has the largest MS at 300 K among all the samples.
Structure of the C60 nanowhiskers (C60NWs) heat-treated at high temperatures was investigated by high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), Raman spectrometry, thermogravimetric analysis, Brunauer-Emmett-Teller (BET) method, and so forth. Although the C60NWs heated at 800 °C in vacuum showed a remaining of C60 molecules, the C60NWs became amorphous by heating at 900 °C in vacuum, exhibiting the highest specific surface area of 195.2 m2g-1.The porous nanofibers synthesized by heating C60NWsat high temperatures are new candidates of superconductive graphitic carbon.
KNbO3 (KNO) nano-particles with the diameter of about 20 nm were prepared by mechanical milling using planetary ball mill from the commercial KNO powder. Rotation speeds of ball mill were 0 to 300 rpm, where the milling time was kept at 15 minutes. Magnetization was measured by SQUID magnetometer. The 250 rpm milled sample showed a tenth larger saturation magnetization than that of BaTiO3 with vacancies.
Direct-current (dc)-driven inorganic electroluminescent (EL) devices were fabricated with rare-earth (RE) doped ZnO as the light emitting layer (RE = Tm, Eu). The suitability of several polycrystalline materials for the substrate was examined. Among the examined materials of yttria-stabilized zirconia (YSZ), alumina (Al2O3) and magnesia (MgO), YSZ was preferable with respect to the similarity of the thermal expansion coefficient and the chemical inertness with ZnO. On the other hand, the chemical affinity of zirconia with RE3+ became a problem. When RE = Eu, a by-product phase of Eu2Zr2O7 was formed during heat-treatment at a high temperature. Coating a MgO thin-layer on YSZ (MgO-coated YSZ) did not alleviate the formation of Eu2Zr2O7. The dc-driven EL devices fabricated on the YSZ and MgO-coated YSZ substrates successfully revealed EL from the bare RE-doped ZnO layers between the electrodes. A sharp line emission due to Tm3+ and Eu3+ was obtained from Tm3+- and Eu3+-doped ZnO on YSZ, respectively, whereas the RE-doped ZnO layers formed on MgO-coated YSZ emitted a broad luminescence due to the luminescent defects in ZnO.
TiO2 films were prepared by RF magnetron sputtering method. Cu and Fe films were loaded on the TiO2 films by ion coater to improve the photocatalytic properties. The organic-decomposition properties could be improved by the photocatalytic activity of these materials. An optimum thickness of each material was examined through this study. The highest photocatalytic properties for Cu and Fe loaded films were obtained at the thicknesses of 600 and 141 Å, respectively. In the case of hydrophilicity, the contact angles of the Cu and Fe–deposited films are 3 and 5 degrees, respectively after 1hour-UV irradiation. The organic-decomposition properties could be improved without deteriorating the hydrophilicity.
The simulation code to study the dielectric property of nuclei and electrons in nanosize materials based on Rigged QED is developed in our group. In this article, the progress of our code is reported. As the first target, the dependence of dielectric response on the frequency of external electric fields is shown for simple atoms. In addition, for its basic data, the electronic contribution to local polarizability of molecules with covalent bonds, particularly some simple hydride, such as CH4 and NH3 are studied for wave packet derived by ab initio computations. This is also for the purpose of the systematic comprehension of the local dielectric property of nanosize materials, particularly high-k materials, for example HfO2. The relations between the pattern of the local polarizability density on the bonding axis, the bond length, and the atomic radius are paid attention to.
Strain-rate sensitivity (SRS) and shape memory effect were investigated in Ti-Cr-Sn β(bcc)-Ti shape memory alloys using strain-rate dip test. There was a trade-off relation between shape recovery strain and SRS. This means that SRS becomes more significant, whereas the shape recovery strain decreases with increasing Cr content. This change in SRS is considered to be a transition of deformation mechanism from non-thermal activation process to thermal activation process with increasing stability of β phase.
We have prepared the PtCo bimetallic catalysts on Marimo carbon by the modified nanocolloidal solution method. The Marimo carbon is a kind of carbon with a spherical shape and consists of carbon nanofilaments (CNFs). The Pt-Co bimetallic alloy particle size was approximately 2-5 nm in for Pt85Co15. The X-ray diffraction peak of the deposited Pt-Co bimetallic alloy particle shifted to a higher angle than that of Pt, suggesting the formation of a Pt-Co bimetallic solid solution phase. The CV analysis suggested that the Pt85Co15/Marimo carbon can be a good candidate for the PEFC system.
Thermal conductivity is a basic property in material manufacture. Materials show unique physical properties by making it thin. It is expected that the character of a thin film completely differs from that of the bulk. In order to evaluate the thermal conductivity of thin film, we have developed "Thermal Conductivity meter in thin film at Nano scale by 2ω method; TCN-2ω". In this study, we report the result of thermal conductivity evaluation of polymeric thin film measured by using TCN-2ω. With increasing the values of the thin film thickness, those values of thermal resistance (the reciprocal of thermal conductivity) are increasing, too. When the values of the thin film thickness have the range from 100 to 200 nm, the values of thermal conductivity of PI were about 0.3 W m-1 K-1.
Platinum (Pt) nanodots were prepared by applying a heating process to organometallic solutions containing different concentrations of Pt. We investigated how size and crystallinity of Pt nanodots depend on the concentration of Pt in the organometallic solution. The average diameter of Pt nanodots was found to depend on Pt content, and Pt nanodots with a minimum diameter of 33 nm were obtained using a solution containing 2.4% Pt. However, the crystallinity of Pt nanodots was hardly affected by Pt content; all Pt nanodots prepared in this study had high crystallinity. The Pt content was controlled by the dilution ratio between the organometallic and dilute solutions. Therefore, solutions with low viscosity spread thinly and evenly on a substrate, compared to solutions with high viscosity. In addition, we calculated the volumes of individual Pt nanodots using three-dimensional scanning electron microscopy and image processing.
Crystalline perfection in organic charge-transfer complex single crystals, κ-(BEDT-TTF)2Cu[N(CN)2]Br, was characterized by means of synchrotron X-ray topography. Single crystals of κ-(BEDT-TTF)2Cu[N(CN)2]Br were grown electrochemically using a relatively large glass cell in order to scale up the synthesis. The quality of the crystals was examined using white and monochromatic X-ray topography. There was no asterism of each spot in the Laue photographs, though the defect image in the spot was not resolved because of low-resolution power of the white beam topography. We also obtained monochromatic X-ray topographs with 1.0 Å X-rays and were able to observe line images of dislocations. Dislocation density of the specimen was approximately 7 x 103 cm-2 on an average in the whole area of crystal. However, dislocation lines were annihilated in the topograph taken after annealing at room temperature for 5 months. Furthermore, new lattice defects were generated in the crystal after similar room temperature annealing for 15 months. The change of defect structure was caused by X-ray irradiation because dislocations in the un-irradiated crystal were observed by the monochromatic X-ray topography even after 2 years annealing at room temperature. Point defects formed by the X-ray irradiation probably interacted with grown-in dislocations and secondary defects were formed in the specimen crystal, though a long time was needed for this reaction at room temperature.
In this work, we use HfO2 nanoparticles (np-HfO2, embedded in a spin-on glass SOG oxide matrix) as charge trapping layer (CTL) in Metal/Oxide/High-κ/Oxide/Silicon (MOHOS)-type non-volatile memory structures. By depositing the same CTL on an ultra-thin layer of chemical oxide (SiOx ≤ 2 nm), a distinctive trade-off is observed in both writing/erasing and data retention time characteristics when different thicknesses are used for the tunneling oxide. Specifically, better writing/erasing times are obtained while the data retention characteristics worsen when the tunneling oxide thickness decreases to less than 2 nm. The best memory performance is obtained for a CTL (～120nm, based on np-HfO2) deposited on a tunneling oxide of 1.5nm ＜ SiOx ＜ 2nm.
Oxide electrode materials have been studied for use in lithium secondary batteries. Carbon black is added to the oxide electrode as a conductive additive. However, it is very difficult to uniformly disperse the nano-size carbon. We applied the Marimo carbon as a new carbon material for making a new composite. This carbon is a kind of carbon nanofilament (CNF). The Marimo carbon consists of many CNFs, and the CNFs are interwoven to form a spherical secondary shape. The Marimo carbon has a sufficient space volume between the CNFs. We prepared TiO2 from a liquid phase using a hydrothermal synthesis method to compose with the carbon. The prepared sample is anatase TiO2, and it contains carbon. The charge and discharge characteristics were measured at the 0.1 C rate between 1.0 V and 3.0 V vs. Li using a coin-type cell. The cell was able to be charged and discharged. The charge capacity was 172 mAhg-1 and discharge capacity was 200 mAhg-1.
The effect of laser irradiation on few-layer graphene in air was investigated by Raman spectroscopy. The irradiation results in an increase of D band intensity and a concomitant drop in 2D band intensity. Furthermore, both frequencies of G and 2D bands increase. For bilayer and trilayer graphenes, the shape of the 2D band is also changed after the irradiation. Namely, the high-frequency components decrease. From these results, it is suggested that the laser irradiation in air leads to the thermal oxidation with the hole doping and the change in the stacking sequence in the decomposed few-layer graphene with smaller size.
The growth of single-walled carbon nanotubes (SWNTs) was carried out on SiO2/Si substrates with Pt catalysts between 500 and 800ºC under various ethanol pressures using an alcohol gas source method, a type of cold-wall chemical vapor deposition (CVD). The grown SWNTs were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Irrespective of the growth temperature, the optimal ambient ethanol pressures were between 1×10-4 and 1×10-2 Pa. In the SWNT growth at 700ºC, Raman results showed that the diameters of SWNTs grown with Pt catalysts were below 1.4 nm, which was much smaller than that grown with conventional Co catalyst, and that the diameters of SWNTs from Pt decreased as the growth temperature was reduced. In addition, we observed that the catalyst lifetime of Pt was longer than Co. We demonstrated that Pt is an efficient catalyst to grow SWNTs with small diameters.
Methyl cellulose (MC) and Polyethylene Glycol (PEG) were considered to be environmentally and biologically friendly materials, and have been applied to industrial or biological use as a highly hydrophilic and viscous polymer. PEG-water systems in various molar ratios of ethylene oxide (constitutional repeating unit of PEG) to H2O were investigated by DSC, NIR (Near infrared spectroscopy) and 17O NMR, in order to investigate the behavior of water molecules in PEG hydrogel. The melting behavior of eutectic of PEG and water by DSC shows good agreement with those of NIR, NMR measurements. Alkali chloride aqueous solution forms a eutectic at low temperature. In this study, we focused on the MC -PEG- water system and MC-alkali chloride- water system at the water-rich region. The water state or the dynamic mechanical property was investigated. The PEG-MC-water system and MC-alkali chloride-water system form thermo reversible gel in the heating process. We found that the memory of the gel state was kept for 3 days after gelation at room temperature. The period of keeping the memory of the gel state after gelation agreed with the strength of PEG or Alkali chloride -water interaction. It was found that the interaction was detectable by DSC.
In this report, an amorphous indium gallium zinc oxide (a-IGZO) thin-film was fabricated by DC-sputtering at different oxygen partial pressure values. The transmittance of the thin films could be enhanced by treated with oxygen during sputtering and greater than 90% at 300～700 nm. It has been found that the oxide semiconductor properties are highly dependent on oxygen content, because oxygen vacancies provide the needed free carriers for electrical conduction. Therefore, the conductivity could be controlled by adjusting the flux of the mixture oxygen during film deposition. With the increasing amount of oxygen, the IGZO thin film would change from conductor to semiconductor, and finally become an insulator. During this tunable characteristic, one can adjust the resistivity according to different kinds of IGZOs, such as InGaZnO4, In1.1Ga1.1Zn0.9O4, In1.5Ga1.5Zn0.5O5, and In2Ga2Zn1O7. In the case of In2Ga2Zn1O7, we can get an amorphous, transparent thin film with the mobility around 6 cm2/V-s and the resistivity around 106 ohm when the oxygen to argon ratio is 0.66%.
The drug delivery material was developed from mesoporous silica grafted with pH-responsive poly (acrylic acid) (PAA). The mesoporous silica was prepared from rice husk ash via the surfactant assisted sol-gel method, obtaining the 2D hexagonal porous structure. PAA was grafted on mesoporous silica surface by UV-induced graft polymerization. The irradiation time and monomer concentration on the graft polymerization were investigated and the results revealed that increasing the irradiation time as well as the monomer concentration enhanced the grafting percentage due to an increase in the extent of polymerization. Finally, the loading and releasing behaviors of Indigocarmine as drug model from the PAA-grafted mesoporous silica studied at various pHs. The PAA-grafted mesoporous silica showed slower drug releasing as increasing the grafting amount.
Natural materials have been reviewed from the perspective of conservation of Earth’s environment. Bamboo attracts interest not only in Japan but also overseas because bamboo presents many advantages in application as a building material. It is cheap, light, and fast-growing, with excellent tensile and compression strength. For increasing demand of bamboo, its utilization for buildings is necessary. For that purpose, we investigated efficient drying conditions for bamboo without cracks for increasing the durability of bamboo as a structural material through some experimentation. We also proposed a new construction method for building a dome. The main characteristic is that the dome is configured not with strip members but with round straight members having no special joint parts.
Ag added bulk FeSe0.5Te0.5 single crystal like samples Agx(FeSe0.5Te0.5)1-x were prepared by solid-state reaction. The x, nominal concentration of Ag, was ranged between 0 and 8%. The pure Ag or Ag compound was not observed in the X-ray diffraction patterns of Ag doped samples. The temperature and magnetic field dependences of magnetizations of prepared samples were measured using a superconducting quantum interference device (SQUID) magnetometer. The Tc was about 14K up to x=4%, but the Tc decreased gradually to 11K above x=5%. The calculated lattice parameter a is approximately constant with Ag addition. On the other hand, the c is nearly constant in the sample of x≤5%, but it decreases rapidly in x≥6%. The x dependence of Tc corresponds to the lattice parameter c. It means that, Ag might replace Fe and partially distorts a tetragonal FeSe0.5Te0.5 crystal structure in x>6%. The magnetization decreased with increasing of x, but the fishtail-like humps were observed in the magnetization curves. The maximal Jc(x)/Jc(0) was about 1.5 at x=5% and 5T under the applied magnetic field H perpendicular to the c-axis. The pinning potentials (U0) were estimated from relaxation measurement of the magnetization at 5K when H was parallel to the c-axis. As a result, the sample of x=5% is considered to be more susceptible to flux creep than the sample of x=0%.
We investigate resonant wavelength control of optical metamaterials consisting of split ring resonators (SRRs) with inductance variable structures in the optical wavelength region toward the realization of tunable optical metamaterial devices. The metamaterials consist of SRRs, cut wires, and connecting bars. There are air gaps between the SRRs and the cut wires. The cut wires supported by the connecting bars are located over the SRRs with constant gap distance. The resonant wavelength can be controlled by inductance changes in coil structures of the metamaterial, because the inductance depends on positions of the cut wires. On the other hand, capacitance in the metamaterial is not affected by the position of the cut wires. Numerical simulations using rigorous coupled-wave analysis show that the resonant wavelengths shifts between 1025 nm and 805 nm and varies approximately linearly according to the position of the cut wire. At the resonant wavelength, the transmittance decreases to about 10% and quality factors of around 4.5 are obtained. At non-resonant wavelength, on the other hand, the transmittances of around 70% are obtained. Therefore, the metamaterial functions as band-stop filter, in which the center wavelength can be controlled by the positions of the cut wires over the SRRs.
Diamondoids are sp3-hybridized carbon nanomaterials that hold promise for application in biotechnology, medicine, and opto- and nanoelectronics. While difficult or even impossible to realize by conventional organic synthesis methods, the synthesis of larger diamondoids was demonstrated by plasmas generated in supercritical fluids, however, the reaction mechanisms that lead to their formation are not clear. Here, we investigated the synthesis of diamondoids from adamantane and present a simple model that predicts the reaction rates of diamantane, triamantane, and tetramantane. The diamondoids were synthesized by micro dielectric barrier discharges arranged in arrays, generated at frequencies of 7 kHz and applied voltages of 5 − 10 kVp−p in supercritical xenon (pressure 5.56 − 8.22 MPa, temperature 290.0 − 310.2 K). The collected samples were analyzed and quantified by gas chromatography - mass spectrometry measurements. The reaction yields of diamantane increase with increasing precursor density and longer reaction times. Experimental data also suggests a stepwise reaction of higher diamondoids from lower diamondoids, and predicts lower reaction rates for higher diamondoids when compared to lower diamondoids.
Device working in ambient environment, which will generate plasma of parameters enabling treatment and sterilization of inanimate materials and living tissues was developed. Features of the proposed plasma jet are ability to work with various feed-gases in several gas flow, frequency and current- voltage regimes. LabVIEW virtual measurement sub-system for monitoring and measurement process was applied. Electrical characteristics of plasma reactor, temperature measurement results are presented, and achieved ozone concentrations are given.
Amphiphilic graft copolymers were synthesized using N-hydroxyethyl acrylamide (HEAA) as the hydrophilic main chain and poly(trimethylene carbonate) (PTMC) as the hydrophobic side chain. This amphiphilic poly(HEAA-graft-PTMC) (PHT) copolymers self-aggregated because of hydrogen bonds and hydrophobic interaction. The PTMC side chain was incorporated into the hydroxyl group on HEAA via ring-opening polymerization of a trimethylene carbonate monomer using an organic catalyst at room temperature. Enzymatic degradation of PHT was performed using the polymer gel and colloid samples in the presence of lipase in phosphate buffered saline (PBS) solution (pH 7.1) at 37°C. The degradation behavior of this polymer colloid was observed by dynamic light scattering. The surface morphology of PHT was evaluated by scanning electron microscopy. The PHT copolymer was slightly degraded by lipase in PBS, indicating its potential as a carrier of drug delivery systems.
Thermally induced gelation of polyacrylonitrile(PAN) solution in dimethylacetamide was studied through dynamic viscoelasticity measurements. PAN gel were prepared by the freezing(–50°C) and thawing(25°C) method. The evolution of G'(ω) and G"(ω) data in the process of gelation is observed and the critical behaviour is obtained around the sol-gel threshold in which the power law of G'(ω)～G"(ω)∝ωn holds. The evolution in the gelation can be interpreted through the dynamic viscosity, in which characteristic frequency window is defined in connection with the formation of PAN network. The relation between the frequency and the correlation length is also found. The correlation length characterise the size of the cluster formed by the aggregation of PAN chain in pre-gel state, and also characterise the size of regions within the network to follow the power law.
2-Methacryloyloxyethyl phosphorylcholine (MPC), which is known to exhibit excellent blood compatibility, was copolymerized with n-butyl methacrylate (BMA). The poly(MPC-co-BMA) copolymer (PMB) obtained was dissolved in aqueous media and aggregated into PMB polymer colloids. PMB50 and PMB30 (containing 50 and 30 mol% of MPC units in the feed, respectively) were evaluated. Aggregation of MPC polymer colloids was studied by dynamic light scattering, showing a diameter of 15–30 nm, where it was found that the diameter was dependent on the MPC-BMA monomer composition. 8-Anilino-1-naphthalenesulfonic acid sodium salt (ANS), as a fluorescence probe, was included into the hydrophobic domains formed through hydrophobic interactions between BMA units in the PMB colloid. The maximum fluorescence wavelength of ANS was in good agreement with a change in concentration of PMB, as reported in some previous studies. Pyrene as a fluorescence probe was incorporated in the hydrophobic domain as well, and the maximum excitation wavelength of pyrene varied with the concentration of PMB. By using the fluorescence intensity ratio of at a wavelength of λex = 334 and 338 (I334/I338), the critical association concentration (CAC) of the PMB polymer was determined to be 5 × 10-3 g/L for PMB30 and 1 × 10-2 g/L for PMB50. The partition equilibrium constant (Kv) was calculated, which was larger for PMB30 than for PMB50. Thus, hydrophobic molecules could easily dissolve into the hydrophobic domains, which could be regulated by the percentage of BMA units in the PMB polymer. In conclusion, the PMB polymer could be used as a bio-based material in drug delivery systems.
2,2,2-Trifluoroethyl methacrylate (TFEMA) and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIMA) are fluorinated monomers, and water repellency is expected. The monomers are copolymerized with conventional methacrylic acid derivatives for versatile synthesis. In this study, a fluorinated polymer was used to achieve water repellent properties. As fluorinated monomers, TFEMA or HFIMA were copolymerized with n-butyl methacrylate (BMA) by conventional radical polymerization to make poly(TFEMA-co-BMA) (PFB) and poly(HFIMA-co-BMA) (PHFB), respectively. Monomer composition and the molecular weights of PFB and PHFB were characterized by 1H NMR and GPC. We evaluated the surface functionality by making a self-organized dimple pattern. Spin coating of the polymer solution was carried out on the substrate, and then, the solvent was evaporated under a humid environment. After that, a self-organized dimple pattern was formed. The resulting surface structure was regulated by the concentration of the polymer solution, its composition, and the solvent. The surface morphology was observed by optical microscopy, scanning electron microscopy, and atomic force microscopy. The diameters of the dimples of PFB and PHFB were roughly 0.8 μm and 0.5 μm, respectively. Homogeneous dimpled morphology was observed on the polymer-coated surfaces. The surface hydrophobicity is reported in terms of the surface morphology.
We investigated the bioconjugation on polymer colloids covered with a bioinert poly(ethylene glycol) chain. The polymer colloids would be expected to carry out a specific enzymatic reaction by conjugation of a substance at the shell part of the colloids. Therefore, the conjugated polymer colloid surface needs to possess a property for the conjugation of functional molecules. In this study, a water-soluble amphiphilic graft polymer with a substrate specific to the enzyme was designed to possess surface modification of the enzyme-substrate complex. The graft copolymer composed of hydrophilic and hydrophobic side chains was created by a new molecular design. The macromonomer with an oligo hydrophilic chain was modified by using p-nitrophenyl chloroformate to obtain the macromonomer with an active ester group (MEONP). The graft copolymer was prepared by conventional radical polymerization using poly(propylene glycol) methacrylate and MEONP. Their solution properties in an aqueous medium were also analyzed by using fluorescence measurement of sodium 8-anilino-1-naphthalene sulfonate (ANS) as a fluorescence probe to evaluate the hydrophobic domain in the polymer colloids, and were also measured by dynamic light scattering to determine the particle size. The conjugation efficiency was determined by UV-Vis spectroscopy at 400 nm.
Viscoelastic behavior of thermo-responsive polymer hydrogel during temperature swing process was observed by means of quartz crystal microbalance with admittance analysis (QCM-A). The phase behavior of hydrogel was evaluated from the viscoelastic point of view based on the resonant parameters of the QCM, measuring the serial resonant frequency (ƒs), the frequency at Bmin (ƒ2) and the resonant resistance R. The change of resonance parameters at the coil-globule transition point and globule phase at above the LCST of the polymer hydrogel was monitored. The mass effect and/or elasticity of the hydrogel that is independent of viscosity influence of the gel were monitored by the ƒ2 to identify the phenomena of temperature responsive phase behavior of the gel. The viscoelastic behavior was successfully obtained with high resolution by the QCM-A.
We study the electronic states of graphene nanoribbons whose edge structures are modified in the manner that Klein’s bearded bonds are periodically distributed. In the triply periodic system, complete flat bands are obtained in the case that two Klein’s bonds are attached to edge per unit cell. However, there is no flat band in one Klein’s bond case. We discuss the existence of flat bands in the triple periodicity system in relation to the linkage between wavefunctions; the analytic expression of the wavefunction is consecutively derived by the transfer matrix method.
As a means of improving the generating efficiency of the compact SOFC system with a rated AC power of 700 W, we introduced the heat exchanger which is integrated with CoSb3, SiGe thermoelectric materials, namely TEG-HEX, instead of the air preheater in the SOFC system simulation model. We investigated the influences of changes of materials thermoelectric properties and the thermoelectric element size in the TEG-HEX. The results of simulation indicated that using low thermal conductivity materials and high aspect ratio, in other words, long and thin, elements can withdraw larger temperature difference and larger TEG output power under realistic heat transfer conditions. To enhance the SOFC’s power generation efficiency, it is important to design the TEG-HEX using low thermal conductivity materials.
We develop a new tight-binding (TB) approximation method that enables us to calculate electronic structures of materials immersed in the uniform magnetic field. Since the present method is based on the Dirac equation, relativistic effects are inherently taken into account. Due to the Zeeman effect and the translational property of the wave function in the uniform magnetic field, matrix elements of the Hamiltonian explicitly depend on the magnetic field. Relativistic TB parameters, which are needed for actual calculations, can be evaluated by using results of relativistic energy-band calculations of zero magnetic field as the reference data.
Magnetic particle testing (MT) was performed with microcapsules containing magnetic particles with fluorescent pigment adhering to their surfaces. These particles gradually separated into fluorescent pigments and magnetic particles with time. To apply the particles, emulsions of inner water and oil were made by hand shaking. Then, these emulsions were heated and stirred with the outer water in a beaker. The solvent of the oil phase evaporated as a result. Thus, microcapsules of inner water/oil/outer water were formed. MT was demonstrated using microcapsules containing 6.8 wt% fluorescent pigment magnetic particles. These microcapsules were placed into a crack in the dark and observed using a fiber. In addition, elemental analysis measurements of the surface were made by a coupling device consisting of a composite-type optical fiber, spectroscope, and pulse laser. A pure metal and an alloy were measured. The spectra of the pure metal were identified using the electronic database of the National Institute of Standards and Technology. These spectra were then compared with those of the alloy. This analysis method may be useful for elemental analysis at certain locations, such as narrow areas, where conventional methods cannot be employed.
The effect of spatial distribution of local magnetization vectors on variant selection in L10-type ferromagnetic alloys under a magnetic field has been investigated by micromagnetics in conjunction with phase-field modeling. The magnetic energy components, including Zeeman, exchange, anisotropy and dipole-dipole interaction energies resulting from spatial distribution of local magnetization vectors are separately evaluated to clarify which energy component is dominant during microstructure evolution of the alloys. The dependence of the local magnetization vector distribution on the amplitude of the external magnetic field is also carefully examined. It is found that, under an external magnetic field, the anisotropy and Zeeman energies are relatively large and dominant factors affecting the alignment of local magnetization vectors which completely align in the direction of the external field when its amplitude is as high as 6 T. This indicates that the distribution of magnetization is not important for the variant selection in L10-type ferromagnetic alloys since it requires a high magnetic field. In fact, microstructure evolution examined using phase-field modeling remains unchanged by taking into account the spatial distribution of local magnetization vectors, suggesting that only the scalar magnitude of the external magnetic field and the uniaxial magnetic anisotropy are sufficient to form the microstructure.
Thin films of amorphous carbon nitrides (a-CNx) were synthesized using parallel-plate radio-frequency (RF) magnetron plasma chemical vapor deposition (CVD) system. The gas mixture of Ar and N2 with the total pressure of 0.3 Torr was excited by an RF discharge of 50 W where a trace amount of BrCN vapor was added. Films were deposited onto Si substrates set on the powered and grounded electrodes. Using an X-ray photoelectron spectroscopic analysis, the [N]/([N]+[C]) ratios of the films were in the range of 0.35-0.50; a maximum value (≈0.50) was obtained for the partial pressures of Ar and N2 of 0.1 and 0.2 Torr, respectively. A positive correlation was observed between the CN(B2Σ+−X2Σ+) optical emission intensity and the [N]/([N]+[C]) ratio, indicating that the dominant mechanism of the “recovery” of the [N]/([N]+[C]) ratio upon the addition of N2 is the increase of the gas-phase reaction to produce CN radicals; the effect of the increase of N atoms may be minor. This result may suggest an effective methodology to synthesize a-CNx films with high [N]/([N]+[C]) ratios.
The inclusion complex formation of epigallocatechin gallate (EGCg) in γ-cyclodextrin (γ-CD) was investigated. There are already several reports about the complex formation of several kinds of catechin in β- or γ-CD, but no report about EGCg in γ-CD. 1H-NMR spectra and UV absorption spectra gave the proof of the inclusion complex formation of EGCg in γ-CD and the binding constant EGCg in γ-CD was similar to that of gallocatechin gallate (GCg) in γ-CD, which was previously reported. The effect of the complex formation on the antioxidant activity of EGCg was also investigated. The antioxidant activity of EGCg against DPPH radical was not inhibited but slightly enhanced by the complex formation in γ-CD. These data gave the proof of the inclusion complex formation of EGCg in γ-CD for the first time. As EGCg shows the strongest antioxidant activity among the series of catechins and γ-CD adapts highly to the food safety regulation compared with other CDs, the inclusion complex formation of EGCg in γ-CD is valuable in the field of pharmaceutics, cosmetics and food industries.
Photocatalytic decomposition reaction of linoleic acid and oleic acid on rutile TiO2 single crystals were studied by measuring the weight of acid. UV light with maximum intensity at the wavelength of 366 nm was used as light source. Single crystals were oriented at (100), (114), (101) and (001) surfaces. For both acids, decomposition at (001) surface was the fastest and the decomposition at (114) surface was the slowest. The difference might be related to unstableness of (001) surface. The decomposition of linoleic acid was faster than that of oleic acid. This difference in reaction rate is related to the number of unsaturated bond in the acid molecule.