Nobuhiro Matsushita

Preparation of graphitic carbon nitride (g-C3N4)/WO3 composites and enhanced visible-light-driven photodegradation of acetaldehyde gas

Novel visible-light-driven graphitic carbon nitride (g-C₃N₄)/WO₃ composite photocatalysts were prepared, and the acetaldehyde (CH₃CHO) degradation activity of these composites was evaluated. The prepared g-C₃N₄/WO₃ composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflection spectroscopy (UV-vis), and the N₂ gas adsorption Brunauer-Emmett-Teller (BET) method (N₃-BET). The WO₃ particles, which were 100-300 nm in size, were in direct contact with the g-C₃N₄ sheet surface. The optical band gap and specific surface area of the g-C₃N₄/WO₃ composites were in the range of 2.65-2.75 eV and 4-7 m(2)/g, respectively. The g-C₃N₄/WO₃ composites exhibited higher activity for the photodegradation of CH₃CHO under visible light irradiation compared to g-C₃N₄. The optimal WO₃ content for the CH₃CHO photodegradation activity of the heterojunction structures was determined. The synergistic effect of g-C₃N₄ and WO₃ was considered to lead to improved photogenerated carrier separation. A possible degradation mechanism of CH₃CHO over the g-C₃N₄/WO₃ composite photocatalyst under visible light irradiation was proposed. These results should usefully expand applications of g-C₃N₄ as a visible-light-driven photocatalyst.

Conducted noise suppression effect up to 3 GHz by NiZn ferrite film plated at 90 °C directly onto printed circuit board

A NiZn ferrite film (3 μm thick) was deposited at 90 °C by the spin-spray ferrite plating from an aqueous solution onto a 50 Ω microstrip line formed on an epoxy printed circuit board (PCB). A strong magnetic loss was caused by the ferrite film in a GHz range, ΔPloss reaching 67% attenuation at 3 GHz, the upper limit of our measurement. Furthermore, the reflection loss was very weak, S11 being smaller than 7%. Thus plated NiZn ferrite films hold strong promise to be actually applied to a type of thin film electromagnetic noise suppressors; the films can be directly deposited onto noise sources (semiconductor elements or electronic circuits) to attenuate conducted-electromagnetic noises in the GHz range. Because the plated NiZn ferrite film was magnetically isotropic in film plane, the noise suppressors will be isotropic, attenuating noise electromagnetic waves radiated from any directions. The NiZn ferrite film was also plated on a flat glass substrate as a standard, which exhibited natural resonance freq...

Heating ability of magnetite nanobeads with various sizes for magnetic hyperthermia at 120kHz, a noninvasive frequency

We synthesized four kinds of magnetite particles having average sizes of 7, 18, 40, and 80nm and investigated their heating ability when they were dispersed in an agar gel and exposed to an ac magnetic field at 120kHz, a noninvasive frequency for anticancer hyperthermia. The particles 18nm in average diameter gave the highest heating ability, though they exhibited narrow hysteresis loops as compared to the particles having average diameters of 40 and 80nm. This indicates that hysteresis loss does not contribute much to the heat rise by the 120kHz ac field, and Neel relaxation is dominantly contributing to the heat rise by the 18nm sized particles. A calculation based on Neel relaxation loss gave a plausible explanation.

Ni-Zn ferrite films with high permeability (μ' = ∼30, μ = ∼30) at 1 GHz prepared at 90 °C

Ni–Zn ferrite films were prepared by spin-spray ferrite plating method at 90 °C on glass substrates from a reaction solution of FeCl2(+FeCl3)+NiCl2+ZnCl2 and an oxidizing solution of NaNO2+CH3COONH4. The complex permeability μ=μ′−iμ″ values of the as-plated films were measured at frequencies up to 3 GHz. The Ni0.28Zn0.18Fe2.54O4 film 0.40 μm in thickness plated using the mixture of Fe2+ and Fe3+ as iron ions exhibited a high μ′ of around 42 and a resonance frequency fr of 1.2 GHz. This fr value is about nine times as high as the 130 MHz that was estimated from Snoek’s limit for the Ni–Zn ferrite bulk ceramics. Since μ′ also exhibited a maximum value of about 35, the films prepared in this study will be applicable to both rf inductors and wave absorbers for electromagnetic interference suppression.

Spin-sprayed Ni–Zn–Co ferrite films with high μr″>100 in extremely wide frequency range 100 MHz–1 GHz

Ni–Zn–Co ferrite films were deposited by the spin-spray ferrite plating from an aqueous solution. Film with optimized Zn and Co contents (i.e., Ni0.22Zn0.52Co0.03Fe2.23O4) exhibited the real permeability μr′ higher than 260 at frequencies up to 130 MHz, and the imaginary permeability μr″ higher than 100 in the extremely wide frequency range from 100 MHz to 1 GHz. Prepared at the very low temperature of 90 °C without postdeposition annealing, these films are promising to be actually applied to electromagnetic noise suppressors which directly cover the noise source elements on printed circuit boards.

Method for synthesizing ferrite nanoparticles ∼30 nm in diameter on neutral pH condition for biomedical applications

Nanosized ferrite spherical particles, ∼30 nm in diameter as revealed by scanning electron microscopy, were synthesized from an aqueous Fe(OH)2 suspension (pH=7.6–8.0) at 25 °C by oxidizing it with H2O2. The nanoparticles were of a spinel structure of an intermediate between Fe3O4 and γ-Fe2O3, as revealed by x-ray diffraction. Compared to the nanoparticles synthesized by our previous method in which an aqueous solution of Fe2++Fe3+ was oxidized by air (oxygen), the nanoparticles increased in size, from ∼10 nm (previous method) to 30 nm. Also saturation magnetization increased, though slightly, from 76 emu/g (previous method) to 80 emu/g (present method). Therefore, the ferrite nanoparticles synthesized by this method will improve the efficiency of magnetic separation. Because synthesis is performed at room temperature and neutral conditions (pH=7.1–7.8), which are compatible with most bioactive molecules (e.g., antibodies and proteins), these molecules will be immobilized onto the surface of the nanoparti...

Bioactive titanate nanomesh layer on the Ti-based bulk metallic glass by hydrothermal–electrochemical technique

Titanate nanomesh layers were fabricated on Ti-based bulk metallic glass (BMG) to induce bioactivity in the form of apatite-forming ability. Titanate nanomesh layers were prepared by hydrothermal-electrochemical treatment at 90 degrees C for 2 h, with an aqueous solution of NaOH as an electrolyte. A constant electric current of 0.5 mA cm(-2) was applied between the BMG substrate and a Pt electrode acting as the anode and cathode, respectively. A nanomesh layer, consisting of nanowires (approximately 20 nm in diameter) formed on the BMG. An immersion test in simulated body fluid for 12 days revealed that the titanate nanomesh layer on the BMG promoted the growth of bone-like hydroxyapatite.

Design of an active and durable catalyst for oxygen reduction reactions using encapsulated Cu with N-doped carbon shells (Cu@N-C) activated by CO2 treatment

Cu@N-C with the Cu particles encapsulated in N-doped carbon shells, which was activated by CO2 treatment, is an excellent electrocatalyst for the oxygen reduction reaction (ORR) with a high activity and durability.

High-frequency transport properties of spin-spray plated Ni–Zn ferrite thin films

The frequency and temperature variation of magnetoimpedance in Ni–Zn ferrite thin films fabricated by spray plating method were studied. It is observed that the frequency induces a metal–insulator crossover behavior in impedance spectra. The frequency behavior of the electrical properties of the film can be modeled by an equivalent circuit composed of resistance and capacitance. The relaxation time and activation energy of the conductivity were calculated. The result suggests that the high-frequency conductivity of the spin-spray plating of a Ni–Zn ferrite film is predominantly associated with the dielectric, rather than by magnetization, dynamics. Mechanisms underlying high-frequency transport are discussed.

Ba ferrite films with large saturation magnetization and high coercivity prepared by low‐temperature sputter deposition

Ba ferrite films were deposited in a mixture of Xe, Ar, and O2 by using facing targets sputtering apparatus with sintered targets of Fe‐excessive BaM ferrite. By using Xe as sputtering gas, the bombardment of energetic Ar atoms recoiled from target to film surface was sufficiently suppressed and Fe content in Ba ferrite crystallites was significantly increased. It was found that the segregation of spinel crystallites among BaM ones were not observed and these BaM crystallites revealed the excellent c‐axis orientation normal to film plane and clear perpendicular magnetic anisotropy. At substrate temperature Ts of 600 °C, saturation magnetization 4πMs of 5.1 kG, which is larger than that of BaM ferrite single crystal, and perpendicular coercivity Hc⊥ of 2.4 kOe were obtained. BaM ferrite films composed of well c‐axis oriented crystallites with large perpendicular magnetic anisotropy constant, large saturation magnetization 4πMs of 4.7 kG and high perpendicular coercivity Hc⊥ of 2.4 kOe were obtained at subs...