Coexistence of Flexo- and Ferro-Electric Effects in an Ordered Assembly of BaTiO Nanocubes.

It has been reported that the flexoelectric effect could be dominant in the nanoscale. The discrepancy between theory and experiments on the frequency dependence of the dielectric constant of an ordered assembly of BaTiO nanocubes is nearly resolved by assuming the coexistence of flexo- and ferro-electric effects. Although flexoelectric polarizations perpendicular to the applied alternating electric field contribute to the dielectric constant, those parallel to the electric field do not contribute because the magnitude of the flexoelectric polarization does not change due to the mismatch of strain at the interface of the nanocubes.

Dynamic dielectric-response model of flexoelectric polarization from kHz to MHz range in an ordered assembly of BaTiO nanocubes.

Due to the strain gradient near each surface of a BaTiO nanocube in their ordered assembly, electric polarization appears due to flexoelectric effect. The magnitude of the flexoelectric polarization could be one order of magnitude larger than that of ferroelectric spontaneous polarization of BaTiO. Thus, dielectric response of an assembly could be dominated by that of the flexoelectric polarization if there is no ferroelectric domain-wall motion.

Nanoarchitectonics of Acicular Nanocrystal Assembly and Nanosheet Assembly for Lithium-Ion Batteries.

Nanoarchitectonics of metal oxide nanocrystal electrodes were developed for lithium-ion batteries. The electrodes included copper nanoparticles and doped fluorine. For the acicular nanocrystals, charge-discharge reactions progressed at 1.

Electrospray Deposition of {200} Oriented Regular-Assembly BaTiO Nanocrystal Films under an Electric Field.

Highly oriented, regularly assembled nanocrystalline films have recently emerged as attractive new functional materials. In this study, we deposited a BaTiO (BT) nanocube dispersion on a Si substrate by electrospraying, resulting in a dense, regularly assembled BT nanocrystalline film. X-ray diffraction analysis revealed that applying a voltage between the electrospray nozzle and the Si substrate during electrospraying caused the BT nanocubes to form a regular array in the 200 plane aligned perpendicularly to the substrate.

Extra Surfactant-Assisted Self-Assembly of Highly Ordered Monolayers of BaTiO₃ Nanocubes at the Air⁻Water Interface.

Assembly of nanocrystals into ordered two- or three-dimensional arrays is an essential technology to achieve their application in novel functional devices. Among a variety of assembly techniques, evaporation-induced self-assembly (EISA) is one of the prospective approaches because of its simplicity. Although EISA has shown its potential to form highly ordered nanocrystal arrays, the formation of uniform nanocrystal arrays over large areas remains a challenging subject.

Spatial Control of Crystallographic Direction in 2D Microarrays of Anisotropic Nanoblocks on Trenched Substrates.

Elaborate two-dimensional (2D) microarrays of tetragonal MnO nanocuboids 10-20 nm in size were constructed with parallel trenches 500 nm wide and 500 nm deep on a silicon substrate. By adjusting the conditions, including the dispersion medium, particle concentration, and evaporation rate, the a-face and c-face 2D arrays were selectively deposited on the upper and lower stages of the trenches, respectively. The crystallographic direction of the tetragonal crystal was alternately switched in the 2D microarrays under these specific conditions at the optimal particle concentration and evaporation rate.

Dynamic Equilibrium Model for a Bulk Nanobubble and a Microbubble Partly Covered with Hydrophobic Material.

The dynamic equilibrium model for a bulk nanobubble partly covered with hydrophobic material in water is theoretically and numerically studied. The gas diffusion into a bubble near the peripheral edge of the hydrophobic material on the bubble surface balances that out of the bubble from the other part of the uncovered bubble surface. In the present model, gas diffusion in quiescent liquid is assumed and there is no liquid flow.

Numerical simulations of sonochemical production and oriented aggregation of BaTiO nanocrystals.

Numerical simulations of sonochemical production and oriented attachment of BaTiO nanocrystals are performed in aqueous solution with pH 14. It is suggested that most significant effect of ultrasound is the dissolution of Ti-based gel in aqueous solution. It results in the dissolution-precipitation mechanism in the production of BaTiO nanoparticles, while with mechanical stirring without ultrasound it is the in situ mechanism that BaTiO is gradually formed on Ti-based gel.

SnO2 Nanosheet/Nanoparticle Detector for the Sensing of 1-Nonanal Gas Produced by Lung Cancer.

A sensor has been developed for detecting 1-nonanal gas present in the breath of lung cancer patients by combining SnO2 nanosheets with SnO2 nanoparticles and noble metal catalysts. A significant change in the electrical resistance of this sensor was observed with increasing 1-nonanal gas concentration; the resistance decreased by a factor of 1.12 within the range of 1 to 10 ppm at 300 °C.

Advanced dynamic-equilibrium model for a nanobubble and a micropancake on a hydrophobic or hydrophilic surface.

The dynamic-equilibrium model for stabilization of a nanobubble on a hydrophobic surface by Brenner and Lohse [M. P. Brenner and D.

Effect of surfactants on single bubble sonoluminescence behavior and bubble surface stability.

The effect of surfactants on the radial dynamics of a single sonoluminescing bubble has been investigated. Experimentally, it is observed that an increase in the surfactant concentration leads to a decline in the oscillation amplitude and hence light emission intensity. Numerical simulations support this result, showing that under the driving pressures required to achieve single bubble sonoluminescence (SBSL), the surface properties, namely, the surface elasticity and dilatational viscosity, contribute to the damping of the radial amplitude in the bubble oscillation.

Water bath synthesis of tin oxide nanostructure coating for a molecular sensor.

Tin oxide nanostructures were fabricated using a water bath technique. The structures were modified with dye-labeled DNAs for a molecular sensor. Sensing mechanism of the sensor was based on a photoelectric conversion effect.

Halogen- and acid-free syntheses of TiO2 nanocrystal coatings and high surface area TiO2 nanocrystal-assembled particles.

Halogen- and acid-free aqueous solutions were developed to synthesize TiO2 nanocrystal coatings and high surface area TiO2 nanocrystal-assembled particles. Fluorine doped tin oxide substrates were covered with TiO2 nanocrystal coatings in the solutions containing titanium(IV) potassium oxalate, 2-hydrate (K2[TiO(C2O4)2] x 2H2O) at 90 degrees C for 3 days. The substrates changed color by the coatings.

Long term synthesis of needle crystal assembled TiO2 films in an aqueous solution.

Crystals of TiO2 grew on substrates in aqueous solutions at 50 degrees C for 180 day. Long term synthesis brought us nano-structured films and information of crystal growth. The films showed 101 diffraction peak of anatase phase.

One dimensional spindle titanium oxide nanocrystals.

Anatase TiO2 nanocrystals of 10 nm were formed in aqueous solutions at 90 degrees C for 1 day. The solutions contained ammonium hexafluorotitanate (5 mM) and boric acid (15 mM). The nanocrystals connected each other to form particles of about 100-500 nm.

Liquid phase deposited titania coating to enable in vitro apatite formation on Ti6Al4V alloy.

A recently developed "GRAPE(®) technology" provides titanium or titanium alloy implants with spontaneous apatite-forming ability in vitro, which requires properly designed gaps and optimum heat treatment in air. In this study, titanium alloy and commercially pure (cp) titanium substrates were thermally oxidized in air before aligning pairs of specimens in the GRAPE(®) set-up, i.e.

Bubble dynamics and sonoluminescence from helium or xenon in mercury and water.

Numerical simulations of bubble pulsation and sonoluminescence (SL) have been performed for helium or xenon bubbles in mercury and water under the experimental conditions of Futakawa et al. [M. Futakawa, T.

Fabrication of dielectric nanocubes in ordered structure by capillary force assisted self-assembly method and their piezoresponse properties.

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT/ST nanocubes mixture were directly fabricated on Si and Pt-coated Si substrates using a capillary force assisted assembly method. The morphology of self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop multilayer and monolayer regions at the surface of substrates.

Low-temperature fabrication of bunch-shaped ZnO nanowires using a sodium hydroxide aqueous solution.

Bunch-shaped ZnO nanowires film was successfully fabricated by the forced-hydrolysis-initiated-nucleation of anhydrous zinc acetate in an aqueous solution of zinc acetate and sodium hydroxide at low temperature. X-ray diffraction and a field emission scanning electron microscope clarified their formation mechanism and morphology development. The morphology was controllable by adjusting the solution temperature and deposition time.

Tin oxide nanosheet assembly for hydrophobic/hydrophilic coating and cancer sensing.

Tin oxide nanosheets were crystallized on transparent conductive oxide substrates of fluorine-doped tin oxide in aqueous solutions. The nanosheets had chemical ratio of Sn:O:F = 1:1.85:0.

In situ growth BaTiO3 nanocubes and their superlattice from an aqueous process.

Ordered aggregated BaTiO(3) nanocubes with a narrow size distribution were obtained in an aqueous process by using bis(ammonium lactate) titanium dihydroxide (TALH) as Ti source in the presence of oleic acid and tert-butylamine. Kinetics of the formation of BaTiO(3) nanocubes indicated that an in situ growth mechanism was dominant and the superlattice of nanocubes formed in situ through the growth of BaTiO(3) nanoparticles in Ti-based hydrous gel. The size and morphology of nanocubes were controlled by tuning the concentration and molar ratio of surfactants.

Effect of static pressure on acoustic energy radiated by cavitation bubbles in viscous liquids under ultrasound.

The effect of static pressure on acoustic emissions including shock-wave emissions from cavitation bubbles in viscous liquids under ultrasound has been studied by numerical simulations in order to investigate the effect of static pressure on dispersion of nano-particles in liquids by ultrasound. The results of the numerical simulations for bubbles of 5 μm in equilibrium radius at 20 kHz have indicated that the optimal static pressure which maximizes the energy of acoustic waves radiated by a bubble per acoustic cycle increases as the acoustic pressure amplitude increases or the viscosity of the solution decreases. It qualitatively agrees with the experimental results by Sauter et al.

Connectivity of PS-b-PEO templated spherical pores in titanium oxide films.

Titania films having relatively uniform spherical pores were successfully fabricated using polystyrene-block-poly(ethylene oxide) (PS(n)-b-PEO(m)) diblock copolymers. Depending on the molecular weight of PS(n)-b-PEO(m), the spherical pores were varied from large mesopores (n = 40,000, m = 53,000; ∼40 nm) to macropores (n = 58,600, m = 71,000; ∼60 nm, n = 100,000, m = 150,000; ∼100 nm) in diameter. It was confirmed that the porous structures were thermally stable with crystallization of the titania frameworks.

Influence of degree of gas saturation on multibubble sonoluminescence intensity.

The influence of the degree of saturation (DOS) of a gas in a solution on the intensity of multibubble sonoluminescence (MBSL) excited by ultrasound with a frequency of 261 kHz is investigated at various ultrasonic powers and with different concentrations of ethanol, which is added as a volatile solute. At relatively low powers and a high DOS, low ethanol concentrations give higher sonoluminescence (SL) intensities than those obtained with pure water. This intensity enhancement decreases as sonication proceeds because the SL intensity for pure water increases with time, whereas it remains almost constant or decreases slightly in solutions containing ethanol.