Ex situ and in situ characterization studies of spin-coated TiO2 film electrodes for the electrochemical ozone production process

An electrode composed of silicon/titanium oxide/platinum/titanium dioxide (Si/TiO_X/Pt/TiO₂) was fabricated by spin-coating TiO₂ multilayers on a Si/TiO_X/Pt substrate and was used in electrochemical ozone production (EOP). EOP was realized when the Si/TiO_X/Pt substrate was completely covered with the TiO₂ film and a current efficiency of 7% was achieved at a low current density of 26.7 mA cm⁻² in 0.01 M HClO₄ at 15 °C. The TiO₂ film was found to be of an anatase-type TiO₂ and that to comprise aperture structures from the X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations. Moreover, the fabricated TiO₂ film was found to be an n-type semiconductor by photoelectrochemical measurements. The high efficiency at a low current density of EOP on the TiO₂ n-type semiconductor was explained to result from the electron transfer through the TiO₂/HClO₄ interface as tunneling current. When the tunneling current passes through a depletion layer of TiO₂, the electrode potential is necessarily high enough to facilitate EOP.     

Fabrication and Evaluation of Porous Piezoelectric Ceramics and Porosity–Graded Piezoelectric Actuators

Porous ceramics of lead zirconate titanate (PZT) were prepared by sintering powder compacts consisting of PZT and stearic acid powders in an air atmosphere; stearic acid was added as a pore-forming agent (PFA). The dielectric, elastic and piezoelectric properties of uniformly porous PZT ceramics were investigated as a function of the porosity volume fraction. Furthermore, a beam-shaped PZT actuator sample with a graded porosity content across its thickness was fabricated by sintering PFA-graded powder compacts. The electric-field-induced bending displacement characteristics of the actuator samples were measured by using strain gauges and were found to be in good agreement with the theoretical predication based on a classical lamination theory.     

New types of hydrous titanium oxides obtained by homogeneous precipitation from (titanium (III) chloride + urea) solutions

Four kinds of hydrous titanium oxide (HTiO) were prepared by refluxing 1 mol dm⁻³ titanium (III) chloride (TiCl₃) solutions containing urea (urea to titanium mole ratio=2.0, 3.0, 4.5, and 6.0; the (TiCl₃ + urea) system) at 371 K. Their physicochemical properties were investigated by means of X-ray diffraction (XRD), differential thermal analysis (DTA-TG), electronmicroscopy, colour measurement, and nitrogen adsorption-desorption at 77K. A rod-like sample 0.2 μ wide and 1.0 μm long was obtained in the case of urea to titanium mole ratio of 2.0. The transmission electronmicrograph showed that the rods were aggregates of acicular crystals in a parallel arrangement. Blue samples of microcrystalline rutile were obtained in the case of an urea to titanium mole ratio above 3.0. The electron spin resonance (ESR) measurement showed that the blue colouration was ascribed to the presence of stable paramagnetic titanium (III) ions. A chemical mechanism for the formation of rod-like and blue-coloured HTiOs is proposed.     

Calculation and uncertainty evaluation of conductance of a precise orifice for orifice-flow method

For the realization of an accurate vacuum standard by the orifice-flow method in high and ultra-high vacuum, it is important to determine the conductance of an orifice accurately. Since the shape of the edge of the orifice significantly influences the conductance, a new orifice with thin tapered edge was designed and fabricated to measure its dimension and shape precisely with microscopy techniques.The area of the aperture was determined with the relative standard uncertainty, u_r, of 0.011% from the diameter measurement. The transmission probability, W, was estimated with u_r of 0.039% using a Monte Carlo calculation from the geometry. Influences of a deviation from cosine distribution of incident molecules due to the geometry of a vacuum chamber and the specular reflection at the orifice edge on the value of W were also discussed.As a result, the conductance was calculated with u_r of 0.041%. The main source of the uncertainty was that of W and originated from its geometry, which verifies that the measurement of orifice edge is important for the accurate evaluation of the conductance.     

A model for membrane bioreactor process based on the concept of formation and degradation of soluble microbial products

A mathematical model of soluble microbial products (SMPs) formation-degradation was established based on the activated sludge model no. 1 and was applied to the membrane bioreactor process with high concentration of activated sludge under intermittent aerobic operational condition. The simulation results were in good agreement with the experimental data which indicated that the coefficients used in the model could successfully describe the treatment performance. The most advantage of this modified model over the conventional one was that the significant importance of SMP existence was demonstrated and the model provided an reasonable comprehension for SMP concept. The present study demonstrated that SMPs contributed most to the organic matter in the effluent, and the results coincided well with the observations of many other researchers.     

Thermosensitive properties of semi-IPN gel composed of amphiphilic gel and zwitterionic thermosensitive polymer in buffer solutions containing high concentration salt

In this study, a semi-interpenetrating polymer network (semi-IPN) gel, which consists of an amphiphilic N,N-dimethylacrylamide-co-N-isopropylacrylamide (DMAA-co-NIPAM) gel and an interpenetrating zwitterionic thermosensitive poly(N-isopropylacrylamide-co-N,N-dimethyl(acrylamidopropyl)ammonium propane sulfonate) (poly(NIPAM-co-DMAAPS)) was prepared. The thermosensitive behavior of the semi-IPN gel was investigated in a buffer solution composed of a relatively high concentration of sodium chloride and sodium citrate as salts, and sodium dodecyl sulfate as a surfactant, which are generally used as a buffer solution in biochips. At low temperatures, the semi-IPN gel in the buffer solution was absolutely transparent; however, when the gel was heated, the gel became milky white or opaque without a large change in the gel size. The network of the transparent gel is homogeneous, whereas that of the opaque gel consists of coarse and dense parts. Such a structural change in the gel network was confirmed by the temperature dependence of the permeability of the buffer solution through the semi-IPN gel membrane. The permeability increased drastically when the gel became opaque because of heating.     

Anthracene derivatives as efficient emitting hosts for blue organic light-emitting diodes utilizing triplet–triplet annihilation

The molecular design strategies for the host materials suitable for highly efficient, blue fluorescent organic light-emitting diodes (OLEDs) are demonstrated. The device characteristics of blue fluorescent OLEDs are compared with different host materials. Some devices exhibit a highly efficient blue electroluminescence with a high external quantum efficiency of more than 7%. The correlation between OLED efficiency and triplet–triplet annihilation is characterized by measuring the up-conversion of triplet excited states into singlet ones. The host materials require an anthracene unit and a bulky molecular structure to prevent the overlap of anthracene units between adjacent molecules in the film.