(Bi0.5Na0.5)TiO3 and NaNbO3 are ABO3 perovskite ferroelectric materials and they are considered to be promising lead-free ferroelectric materials because of their relatively high piezoelectric properties in lead-free piezoelectric ceramics. Furthermore, disordered rhombohedral phases are included in their phase transition sequences. In these disordered phases it is possible by substituting Na for Li to induce ordered ferroelectric phases. The purpose of this work was to clarify the local structures of Li-substituted (Bi0.5Na0.5)TiO3 and NaNbO3 to elucidate the mechanism of the stabilization of the ordered ferroelectric phases. A local structure analysis was carried out using the X-ray absorption fine structure (XAFS) the X-ray pair-distribution function (PDF) obtained from high-energy synchrotron X-ray diffraction. Although XAFS and PDF are the local structure analysis techniques, the Li substitution effect was observed clearly in PDF, but not observed in XAFS. The difference in the coherence of the local structure analysis in XAFS and PDF indicates that the ordered structure of (Bi0.5Na0.5)TiO3 and NaNbO3 is stabilized by excluded volume effect.
In this paper, we report the synthesis of two fluorinated block-copolymers, namely, poly(TFEMA-co-BMA) (PFB) and poly(HFIMA-co-BMA) (PHFB) using radical polymerization. We studied their ability to function as water-repellent surface coatings using non-woven fabric as substrate by forming dimple morphology on the fabric surface. The compositions of PFB and PHFB were determined using 1H NMR, gel permeation chromatography (GPC), and IR spectroscopy analyses. The dimple morphology was obtained from the fluorinated polymer on non-woven fabric by drop coating in a high-humidity environment, through self-organization. Initially, water droplets were assembled on the coating solution and dried by evaporation of different solvents such as methylene chloride and chloroform. Eventually, a template of dimple morphology was formed on the non-woven fabric. The morphology can be easily tuned, for example, by choice of organic solvent, concentration, and humidity (flow rate of water vapor). The dimple morphology was observed using scanning electron microscopy (SEM). The diameters of the dimples, PFB and PHFB, were roughly 0.63 μm and 2.5 μm, respectively. The wettability on the surface was characterized using static contact angle measurements.
Because of the increased need for higher levels of integration of capacitors and piezoelectric generators, such as in energy harvesting devices, the dielectrics used in capacitors have changed from traditional materials to complex oxides. One important candidate material for future integrated capacitors is (Ba,Sr)TiO3 (BST), because of its high dielectric and piezoelectric constants and its low leakage current. However, growth of BST films requires high temperatures of about 700°C, and the electrical properties of BST can be degraded by patterning processes. In the present study, BST thin films were deposited on sapphire and Pt/sapphire substrates using RF magnetron sputtering. Layered capacitors were then prepared using a metal mask method, and in-plane capacitors with interdigital electrodes were fabricated by lithography and wet etching. The electrical properties of the capacitors were evaluated, and defect energy levels were investigated using thermally stimulated current (TSC) measurements. The TSC results indicated the presence of three kinds of defects in the BST, with activation energies of 0.6, 0.7 and 0.8 eV. An annealing process was carried out in an attempt to remove damage caused by wet processing. This was found to reduce the dielectric loss, and the optimum annealing temperature was determined to be 200°C.
We investigated the photocurrent characteristics for ferroelectric single crystals of non-doped barium titanate (BT) and Mn-doped barium titanate (Mn-BT). The introduction of 90 ° domain structures into the BT crystals markedly raised the photocurrent, which suggests that the separation of photoinduced carriers is significantly enhanced around 90 ° domain walls (DWs). The Mn doping led to a drastic increase in the photocurrent, with photon energy less than the band gap. Density functional theory calculations show that the large photocurrent observed for the Mn-BT crystals originates from the electron excitation from the O-2p valence band to the Mn-eg defect level followed by the carrier (hole) injection.
The technique of secondary ion mass spectrometry (SIMS) using an ion beam with MeV-energy has been developed to visualize the spatial distribution of biological tissues and cells with high spatial resolution. In this analytical technique, low vacuum is essential for keeping the samples wet. The effect of evaporation of volatile samples on the SIMS spectra was investigated under vacuum pressures of 50 and 500 Pa by using two higher alcohols, 1-decanol and 1-dodecanol. The results indicated that secondary ions of monomer and multimer species were generated by different phases in the sample. Moreover, the comparison of mass spectra obtained under the vacuum conditions of 50 and 500 Pa separately demonstrated that the secondary ion yields were affected by the gas flow adjusting the vacuum, whereas analysis at lower vacuum conditions allowed obtaining constant secondary ion intensity from volatile samples. The results clearly indicated the advantage of ambient analysis with the MeV-SIMS apparatus.
Amphiphilic α-cholesteryl poly(ethylene glycol) (CS-050) consists of hydrophilic poly(ethylene glycol) with a hydrophobic cholesteryl group at the polymer chain end. Hydrophobic poly(cholesteryl 6-methacryloyloxyhexanoate) (PChM) was prepared via reversible addition-fragmentation chain transfer radical polymerization. A mixture of PChM and CS-050 in organic solution was dialyzed against pure water to exchange the solvent. These polymers formed vesicles in pure water, which were characterized using dynamic light scattering, scanning electron microscopy, and transmission electron microscopy techniques. The light scattering intensity for the vesicle solution was increased upon increasing the [PChM]/[CS-050] weight ratio. However the diameter of the vesicles remained constant, independent of the [PChM]/[CS-050] weight ratio. The thickness of the vesicles increased with increasing amounts of the cholesteryl group content in the vesicle.
Polyacrylonitrile (PAN) gel was prepared by the freezing and thawing method using the solvents of N,N-dimethylacetamide (DMA) and tetramethylene sulfone(sulfolane). The gelation time after a series of freezing and thawing was examined with varying PAN concentration of DMA solution and the freezing time. Dynamic viscoelasticity was measured in the course of gelation for DMA solution to observe the intermediate state called as the critical gel. Double endothermic peaks appeared in the heating DSC scans for gels prepared from sulfolane solutions.
As the field of regenerative medicine based on stem cell engineering starts to play the important role in the new generation of bioengineering, the cells are starting to be treated as one of the materials to be controlled and optimized rather than those to be observed. Temporal and spatial encapsulation of the cells by the hydrogels are getting an attention as a novel way to handle cells in the three dimensional condition. In this study, cytocompatible and reversible phospholipid polymer hydrogels were prepared by mixing the aqueous solutions of poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-vinylphenylboronic acid) (PMBV) and poly(vinyl alcohol) (PVA). The murine pluripotent stem cell line C3H10T1/2 is known to suppress its proliferation when encapsulated in the PMBV/PVA hydrogel with storage modulus of 1.2 kPa. The cell cycle of the encapsulated cells were unified to G1 phase in cell proliferation cycle after 1 day of encapsulation. The differentiation of C3H10T1/2 to osteogenic cells by bone morphogenetic protein 2 (BMP-2) was evaluated by polymerase chain reaction method after induction of BMP-2 signal for 3 days. The cells encapsulated in the PMBV/PVA hydrogel showed 1.7-hold increase of early-stage osteoblast gene expression with well-defined quality will make substantial contribution to the field of regenerative medicine.
ITO and TiO2 layers were prepared using spin-coating method. TiO2 films were spin-coated on n-type Si(100) substrates with resistivity of 1-10 Ωcm and annealed at 950°C in O2 gas for 60 minutes. ITO films were spin-coated on Si substrates or on TiO2 layers and annealed at 700°C in O2 or N2 gas. They were annealed for 30, 60, 90 or 120 minutes. Properties of the films were investigated using X-ray diffraction (XRD), four-point probe method and thickness monitor. The resistivity of ITO films prepared on Si substrates and annealed in O2 gas was lower than that annealed in N2 gas. The resistivity of the ITO films prepared on TiO2 layers and annealed in O2 gas was almost the same as that for the films prepared on Si substrates and annealed in O2 gas. The resistivity of the ITO films prepared on TiO2 layers and annealed in N2 gas decreased when annealing time was shorter than 60 minutes and began to increase after 60 minutes. These results can be explained by the proposed model for the amount of oxygen vacancies in ITO films
The effect of UV irradiation of electrodes on the discharge starting voltage for arc discharge plasma was studied using a low pressure mercury lamp and an UV-LED. The reduction of breakdown voltage via the photoelectric effect of the low pressure mercury lamp and UV-LED was confirmed because the photon energy of the UV lamps exceed the work function of electrodes. The reduction effects depend on the gas, electrode material electrode shape. The reduction rate of about 30 % was realized in the case of Fe electrodes. Especially, the UV-LED is potential alternative to conventional pre-ignition discharge because it can suppress the total energy consumption of the system drastically.
The thermophotovoltaic (TPV) system has been attracted as the waste heat recovery system. A TPV system consists of the heat source, the selective emitter and the TPV cells. For high conversion efficiency, it needs the wavelength matching between emitter radiation and the bandgap of TPV material. The Yb2O3 emitter is a high temperature resistant material with a selective emission spectrum. The peak wavelength of this spectrum is 980 nm. The bandgap of α- and β-In2Se3 is 1.2-1.3 eV, so that α- and β-In2Se3 are promising as the TPV material for this emitter radiation. We investigated about the crystal growth of In-Se by vapor transport method in two conditions of temperature gradients which were 0.83 and 0.33 Kmm-1. In addition, an effect on substrate which has Si-O layer on the surface was also investigated. The hollow hexagonal cylinders with diagonal dimension of approximately 10 μm were obtained at both growth conditions. The layers with thickness of approximately 200 nm were stacked in a longitudinal direction of the hollow hexagonal cylinder. From the results of powder XRD analysis, it was revealed that these hollow hexagonal cylinders were mixed phase of In2Se3. In addition, the similar morphological crystals as hollow hexagonal cylinder were obtained onto Si-O layer.
Modeling and simulation of non-ideal characteristics of a vertical Mo/diamond Schottky barrier diode ( n= 7.677 and Schottky barrier height= 0.8554 at 298 K) were performed in finite element software. Diode’s measured forward and reverse bias I-V characteristics at different temperature were presented and analyzed based on Metal- Interfacial layer- Semiconductor (MIS) model with interface states charges to explain the high ideality factor and Fermi level pinning at the Schottky metal- diamond interface. Current transport through the interfacial layer was simulated with Non-local tunneling model with Wentzel- Kramers- Brillouin (WKB) approximation. By combining characterization results and numerous simulations, we determined the values of unknown parameters (related to interfacial layer and energy distribution profile of the interface states charges) to best fit the forward and reverse bias I-V-T characteristics simultaneously. Good fittings to the experimental data validate the use of MIS model. The best fitting was obtained with acceptor traps concentration of 1.3x1013 to 2.7x1013 eV-1cm-2. From reverse bias simulations, it was found that high electric field occurs inside the interfacial layer, especially at the corner of Schottky contact (～11.8 MV/cm). To avoid premature breakdown and realize true potential of diamond material, special attention on the metal-diamond interface must be paid.
The β-Ga2O3 films for oxygen (O2) gas sensors were prepared by the RF magnetron sputtering method. The effect of annealing time on the oxygen detection properties was evaluated. The films were annealed at 1000℃ with varying the annealing time from 2 to10h. It was found that sensing properties did not depend on the annealing time. The annealing temperature of 1000℃ is not high enough to vary the sensing properties. It means that Ga2O3 films are stable and long life for high temperature applications, for example O2 gas sensors. The influence of the two kinds of substrates, namely Si (100) and quartz (SiO2) on the oxygen detection properties was evaluated. It was found that the oxygen gas sensor fabricated on a quartz substrate had shorter response time than that on a Si substrate.
Citrus juice processing residues are mainly composed of peel, juice sack and seed. The peel, especially, consists of bioactive compounds such as flavones. Supercritical carbon dioxide (SC-CO2) extraction of flavonoid was carried out at a pressure of 30 MPa and temperature ranging from 80 to 160°C. Ratio of water and ethanol as a co-solvent was varied from 0 to 100%. Flavonoids such as naringin and hesperidin have glycoside group, thus water was a good solvent for extraction of these compounds. Extraction behavior of tangeretin was quite different from those of flavonoid glycosides, and the yield of tangeretin tended to increase with ethanol concentration.
We demonstrated a simple solution synthesis method of ZnO nanoparticles to explorer the probability of controlling diameter and shape by the synthesis conditions. The optimized synthesis condition of ZnO nanoparticles was found for application of NIR scatterer. The ZnO nanoparticles with an average diameter of 370 nm, which is suitable diameter for NIR scatterer, were observed. The diameter of observed 76% nanoparticles was under 500 nm. The synthesized ZnO nanoparticles were hybridized with transparent amorphous polymers (PMMA) for the purpose of film applications as NIR scatterer. The optical properties of ZnO-polymer materials were examined in the UV-VIS and FT-IR. We confirmed that the transmittance of ZnO-polymer (containing 10 wt% of ZnO nanoparticles) in NIR region is clearly reduced. To achieve effective NIR scattering film, ZnO-polymer ratio should be optimized
We prepared amphiphilic peptide, (L-Leu-L-Lys)8, grafted poly(N-isopropylacrylamide) crosslinked membranes which have the pH and thermo-responses in the MF-Millipore support films. The content of grafted peptide was fixed at 4 mol% and the crosslinking degrees of the membranes were 1.5% and 16%, respectively. We investigated the influence of the crosslinking degree on the pH and thermo-induced permeability and permselectivity of L- and D-Phe through the membranes. Under the neutral condition (pH 6.5, at 20 °C), the maximum permselectivity (α=2.6) and relatively high permeability (P=2.86×10-7 cm2 s-1) were achieved in the high crosslinking degree membrane (16%). Meanwhile, the low crosslinking degree membrane showed very high permeability (P=3.2×10-6 cm2 s-1) under this condition. In the high crosslinking degree membrane, the peptide graft chains formed β-sheet domain. The domain acted as the selective permeable path for L-Phe. On the other hand, In the low crosslinking membrane, the grafted peptide chains, which were fixed on the flexible poly(N-isopropylacrylamide) main chains, could not form the β-sheet domain result in the high permeability and low perselectivity of the Phe.
Dye and quantum dot (QD) are representative sensitizers of the photochemical solar cells. Dye has the highest efficiency in the whole sensitizers. QDs have relatively low performance but their multiple exciton generation enhanced theoretical efficiency from 33 to 44% and expected to achieve high efficiency. This work tried to enhance the photovoltaic performance with the co-sensitization of N719 dye and Si QD. The performance of dye and QD co-sensitized solar cell was not much enhanced because of electron loss of charge recombination. Therefore, TiO2 barrier layer was introduced on TiO2 and Si QD. It blocked the charge recombination with redox electrolyte. It also helped better electron injection from excited dye to TiO2 with strengthened dye adsorption. Consequently, the performance of co-sensitized solar cell was enhanced with reduced charge recombination and increased dye adsorption.
This paper describes the output voltage characteristics of the metal-core piezoelectric ceramic fiber/aluminum composites fabricated by the Interphase Forming/Bonding (IF/B) method. Piezoelectric materials are generally used as electric and mechanical energy transducers. When their devices are developed for fulfilling their functions, complicated electrode systems and resin layers for adhesion of the materials and the electrodes are usually needed, where depression of response and reliability, and complication of structure are caused. Additionally, as the metal-core piezoelectric ceramic fiber is brittle and reactive with molten aluminum, general fabrication processes such as diffusion bonding and casting are hard to be applied to embed it into an aluminum matrix. Therefore the IF/B method was used for embedding it in an aluminum matrix without fracturing it. In this study, a thin patch type device developed by the modified IF/B method was evaluated by a vibration test and an impact test. As the result, it was found that the output voltage from the device is proportional to its strain and the square root of the impact energy. In addition, the output voltage varies with its strain direction. Especially, at the strain direction 50.6 degrees, sign of the output voltage changes. Taking the above mentioned characteristics into consideration, this composite was found to be useful for structural health monitoring systems.
MgB2 was mechanically milled by a planetary ball mill. Rotation speeds were selected from 0 to 150 rpm. Magnetization measurements were performed by Quantum design’s SQUID magnetometer. The milled samples above 100 rpm showed ferromagnetism at 300K. The enhancement of flux pinning property at 20K was observed for milled sample at 150 rpm under 0 field and 10 kOe. These results may be due to the oxygen vacancies in the MgO1-δ nano-particles in the MgB2 host material, since the ferromagnetism was weakened by the sintering in air at 573 K.
KNO3 nano-particles with the diameter of about 28 nm were prepared by mechanical milling using planetary ball mill from the commercial KNO3 powder. Rotation speeds of ball mill were 0 to 500 rpm, where the milling time was kept at 15 minutes. Magnetization was measured by SQUID magnetometer. The milled sample at 500 rpm showed same order of saturation magnetization as that of BaTiO3 with vacancies.
In this study, Co nanoparticles were deposited on a substrate in an island pattern using an arc plasma gun (APG). An MgO thin film was then formed on this substrate by metal organic decomposition (MOD), which enables the formation of films in atmosphere, thus yielding a double-layer structure. The MgO thin film on Co nanoparticles deposited using an APG with 500 pulses of arc discharge exhibited improved crystallinity and a photoelectron emission that was at least threefold higher than that of the MgO thin film without Co nanoparticles. It was confirmed that depositing Co nanopaticles and then forming the films on them significantly improves characteristics of the MgO thin films. We successfully established a bottom-up process that requires no ion injection by dispersing Co nanoparticles within the MgO thin film during heat treatment.
Ti implants with two-type surfaces, regular micro-groove and Zn-modification, were prepared in order to assess the effect of the implant surface on the osseointegration between bone and implant. Biomechanical push-out testing was performed to evaluate bone-implant interfacial shear strength at 4, 8 and 12 weeks after implantation to rabbit femora. The results revealed that there was no significant effect of the regular micro-groove on the bone fixation of the implants. On the other hand, Zn-modified implant was found to be effective for producing a stronger bone fixation than those with the regular micro-groove.
Sputtered Pt film, heated the Pt film in H2, and Ti4O7 film on glass substrates were used for counter electrodes of dye sensitized solar cells, and photovoltaic properties of these cells were evaluated. Paste containing Ti4O7 powder, which was prepared by reducing anatase type TiO2 powder at 1200 °C in H2, was used and sintered in H2 to form the Ti4O7 film. It was confirmed that all cells generated electricity. Short circuit current density of the cell using counter electrode of Pt film decreased remarkably, when the Pt film was heated in H2. Comparing the films heated in H2, the cell using Ti4O7 counter electrode showed lower fill factor, but higher short circuit current density than that using Pt counter electrode.
FeSix films were deposited on Si (100) substrates by RF-sputtering method using an FeSi3 target. Total deposition time was 30 min in all cases. Various temperature programs during deposition were employed. After deposition, FeSix films were annealed at 400-900°C for 10min in Ar gas. The crystal quality of the films was analyzed by X-ray diffraction (XRD) measurements, the surface of β-FeSi2 films was observed by an optical microscope and the film thickness was measured by a scanning electron microscope (SEM). It was revealed that the substrate heating at the initial stage of the deposition only for 5 min was enough to reduce cracks on the surface of the β-FeSi2 films.
A polymer-supported terpyridine palladium complex has been prepared. The complex was found to promote the transfer reduction of aryl chlorides with potassium formate in seawater. The terpyridine ligand was prepared from 4-methoxycarbonylbenzaldehyde, 2-acetylpyridine, and NH4OAc according to reported procedures [7-8]. The terpyridine ligand was immobilized on a polystyrene–polyethylene glycol (PS–PEG) resin, and the complexation of the PS–PEG–terpyridine ligand with Pd(II) provided the PS–PEG–terpyridine–Pd(II) complex. The polymeric catalysts showed high catalytic activity and high reusability for the transfer reduction in seawater.
Brain-derived neurotrophic factor (BDNF) has been studied for one of candidate proteins for brain disorder. Its detection has been performed with Enzyme-Linked Immunosorbent Assay (ELISA) at present. However, developments of more rapid BDNF detection system using a small amount blood sample has been demanded and it is important to find the anti-BDNF antibody with highly affinity. In this study, BDNF was rapidly detected with the enhanced fluorescence in the sandwich assay prepared on the Ag/ZnO-coated plasmonic chip. We used protein-protein interaction among two peptides constituting BDNF, Mature-BDNF and Prodomain-BDNF, for detecting Mature-BDNF. As for the capture part, Prodomain-BDNF linked with anti-ZnO antibody was immobilized to the ZnO surface of a plasmonic chip. As the detection part, primary antibody (monoclonal or polyclonal antibody) and secondary labeled IgG antibody were used. The detailed analysis of the primary antibody provided the important information on the BDNF detection. Compared with large nonspecific adsorption between Prodomain-BDNF and primary polyclonal antibody, monoclonal antibody was found to show the specific affinity with Mature-BDNF. Mature-BDNF was quantitatively detected with the monoclonal antibody on the plasmonic chip until the concentration lower than that detectable on the glass slide.
It is known that loaded some metals on the TiO2 surface facilitate their organic decomposition properties. In this study, Cu and Fe were loaded in the TiO2 films. The concentration of Cu- and Fe- loadings was varied from 0.2 to 5wt%, respectively. Their hydrophilic and Methylene blue decomposition properties were evaluated. The hydrophilic property was evaluated by a contact-angle measurement method. We also tried to investigate the difference between Cu loading and Fe loading by using XPS analysis and photo absorbance measurement. We found that pure TiO2 showed best properties in this study. It was shown that the 5wt% of Cu- and Fe- loadings deteriorated the photocatalytic properties.