Norimitsu Hirose

Effect of Ni‐Al Precursor Alloy on the Catalytic Activity for a Raney‐Ni Cathode

Raney-Ni cathodes were prepared by leaching aluminum from Ni-Al precursor alloys (NiAl 3 , Ni 2 Al 3 , NiAl, and Ni 3 Al). The catalytic activity for the hydrogen evolution reaction was investigated in I M NaOH at 303 K. The hydrogen overpotentials of Raney-Ni electrodes obtained from NiAl 3 and Ni 2 Al 3 were lower than those from nickel rich alloys (NiAl and Ni 3 Al). Especially, NiAl 3 yielded the most active Raney-Ni cathode. This is because the fast aluminum leaching from NiAl 3 phase gives large surface area of the electrode, the formation of small micropores, and the appearance of the Ni phase.

Degradation evaluation of corrosion protective coatings by electrochemical, physicochemical and physical measurements

In various aqueous salt solution systems with a metal specimen, it has been found that the current density (i) measured by scanning vibrating electrode technique (SVET) increases in the order NaCl<Na2SO4<K2CO3<H3PO4<HCOOH. A linear correlation exists in various aqueous solution systems between i and the film resistance Rf, or lifetime ts measured by electrochemical impedance spectroscopy (EIS). A growth of defects or disbonded area of the coating film from the steel substrate was observed with increasing immersion time in NaCl solution. A good correlation can be seen between the percentage (%) of disbonded area measured by the scanning acoustic microscope (SAM) and the Rf, Young’s modulus (E) and hardness (H) measured by nanoindentation of the pigmented long oil alkyd resin paint (LAR-P) film on steel increased soon after immersion, then decreased with further immersion. The spread of lower E area and growth of blister with immersion time, which are difficult to observe by optical method, can be brought into vision by SAM. The % of corroded and uncorroded areas determined by O1s spectra of X-ray photoelectron spectroscopy (XPS) correspond well to the Rf.

The Preparation of Porous TiO2 by Immersing Ti in NaOH Solution

The formation of a porous TiO 2 layer by immersing Ti in 5 M NaOH at 303 K was investigated using electrochemical measurements, a scanning electron microscope, and grazing incident X-ray diffraction. The porous layer was readily obtained in the case of the presence of titanium hydride (TiH 2 ) on the surface before immersion. The crystalline structure of the porous layer is composed of a mixture of the rutile and anatase type TiO 2 . The porous layer is hard to produce without the presence of TiH 2 . TIte TiH 2 is directly changed to TiO 2 by a dissolution reaction in alkaline solution. The presence of TiH 2 on the surface is an important factor for the preparation of the porous TiO 2 layer.

Effect of Hydrogen on the Formation of Porous TiO2 in Alkaline Solution

The influence of hydrogen on the formation of porous TiO 2 in alkaline solution was investigated using an electrochemical measurement, a scanning electron microscope, and a grazing incident X-ray diffraction technique. The porous TiO 2 was not obtained on the surface of titanium in 5 M NaOH solution at 303 K for 3 h. When the titanium was charged with hydrogen in I M H 2 SO 4 at 303 K for I h before immersion, the porous TiO 2 was readily produced on the surface under the same experimental conditions. The anodic polarization measurement indicated that the hydrogen-charged titanium was more readily dissolved in alkaline solution than the titanium. The cathodic reaction was the hydrogen evolution reaction on both the titanium and the hydrogen-charged titanium. For titanium, although the hydrogen penetrated into the inside of the material due to the side reaction of hydrogen evolution, the hydrogen content in the inside was so small that porous TiO 2 was not produced under this condition.

Evaluation of Raney‐Nickel Cathodes Prepared with Aluminum Powder and Titanium Hydride Powder

Raney-nickel (Ni) cathodes were prepared on nickel wire from aluminum powder and titanium hydride powder by heat-treatment. The influence of the addition of titanium to the Raney-Ni electrode on the polarization characteristics of the hydrogen evolution reaction was studied in 1 M NaOH at 303 K. Although the coated layer was composed of nickel with a small amount of aluminum and titanium, the titanium was enriched the most. The relative surface area of the Raney-Ni cathodes was about 3500 independent of the presence of titanium, but titanium could decrease the hydrogen overpotential.

Effect of the Temperature and Concentration of NaOH on the Formation of Porous TiO2

The influence of the temperature and concentration of NaOH on the formation of porous TiO 2 was investigated. The porous TiO 2 was obtained only after a 24-h immersion in 5 M NaOH at 353 K. The X-ray diffraction pattern indicated that the porous layer consisted of a mixture of anatase and rutile types of TiO 2 . During immersion in the NaOH solution, the anodic and cathodic reactions proceed at the same time on the titanium. From the cathodic polarization measurements, the cathodic reaction proceeded mainly the hydrogen evolution reaction. Therefore, a part of the adsorbed hydrogen penetrated into the titanium. The penetration of hydrogen confirmed with a glow discharge optical emission spectroscopy. The hydrogen evolution reaction continues during immersion in the 5 M NaOH solution at 353 K. However, the hydrogen evolution did not proceed in the low concentration of NaOH solution or at below 283 K. In addition, although the hydrogen evolution continues during immersion in 5 M NaOH solution at 303 or 333 K. As a result, the content of hydrogen in the titanium is insufficient to form the porous TiO 2 layer so that the porous layer is not produced on the titanium.

The effect of tin ingredients on electrocatalytic activity of Raney-Ni prepared by mechanical alloying

Abstract Sn was added to the conventional Raney-Ni precursor powder by the mechanical alloying in order to improve the catalytic activity for hydrogen evolution reaction (HER). After leaching Al, the cathodic performance of the modified powder was investigated in 1 M NaOH at 303 K. Sn was incorporated in the Raney-Ni precursor alloy after mechanical alloying. This was confirmed by differential thermal analysis (DTA) and energy-dispersive X-ray spectroscopy (EDX). However, the appearance of a new phase due to the mechanical alloying was not observed by X-ray diffraction analysis (XRD). The Sn-containing Raney-Ni cathode indicated a decrease of the hydrogen overvoltage. This is because the Tafel slope of the Sn-containing Raney-Ni cathode decreases from 180 to 95 mV / decade . The Raney-Ni cathode prepared by electrochemical codeposition could increase the electrocatalytic activity when the mechanical alloyed powder substitutes for the conventional Raney-Ni precursor powder.

In Situ Observation of Sintered Iron and Carbon Steel Compacts Using a Low-Temperature Acoustic Microscope

Sintered iron compacts and carbon steel compacts (0.3 mass% carbon) were observed in situ using a low-temperature acoustic microscope (LTSAM). The effects of structure, pore distribution, tensile load and testing temperature were evaluated by using the acoustic images. Before the tensile test was conducted, initial inner defects, such as pores and cracks, existed in the specimens and the conditions of the defect distribution were different for each specimen. As the tensile load increased, the newly generated defect area was extended where expansion, deformation and connection of pores occurred. As the testing temperature was lowered, the area became more localized. In different structures, for example, in ferrite and in ferrite-pearlite, the trend of the acoustic images also differed, and the defect area of the latter was sharper than that of the former. These results are consistent with elongation data obtained by tensile tests and observations using an optical microscope. Therefore, the LTSAM is useful for understanding the low-temperature brittleness of sintered iron and carbon steel compacts.

Effect of Film Thickness on Coated Film Degradation by Scanning Acoustic Microscope and Nanoindentation Tester

The effect of film thickness from 33 to 211 μm on the degradation of pigmented long oil alkyd resin paint film coated on a steel plate in a 3% NaCI solution was investigated by use of a scanning acoustic microscope (SAM) and a nanoindentation tester. The growth speed and progress pattern of blisters observed by SAM were classified as three types. In the case of a type A blister, at first a lower Youngs modulus (E) area generated partially, a lot of fine blisters initiated in the area at the initial stage that connected with each other and became large. In the case of a type B blister, the initiation time of blistering was long, and the blisters grew rapidly and became large once they appeared. In the case of a type C blister, the initiation time of blistering was long, and blisters grew slowly if they appeared. The blister of 33 μm film showed type A, the blister of 47 μm film showed type A or type B, the blisters of 119, 154, and 211 mm film showed type B and/or type C blistering. Furthermore, type A initiated before the immersion time of maximum E peak value (T EP ), and type B and type C initiated after T EP .

Ultrasonic Measurement of Lipid Bilayer Transition in The Presence of Melittin

Ultrasonic relaxation was measured for suspensions of sonicated dimyristoyl phosphatidylcholine (DMPC) vesicles in the presence of melittin, the lipid/melittin ratio being 100/1. The results showed that a DMPC/melittin suspension at pH 5 was characterized by much larger relaxation strength and relaxation time than a pure DMPC vesicle suspension. The relaxation phenomenon indicated anomalous enhancement in the vicinity of a gel-to-liquid crystal transition point, which was the characteric feature of a critical phenomenon. The transition temperature increased by about 1°C with the addition of melittin.