The preparation of a coating consisting of a Ni aluminide layer and Ni-Hf alloy layer on a Ni-Cr-Al alloy was attempted by the four-step electrodeposition of Ni, Hf, Ni and Al. In this study, the Ni electrodeposition was carried out using an aqueous solution, while the Hf and Al electrodepositions were carried out using a molten salt at 1023 K. The cyclic oxidation resistance for the alloy covered with the coting was then evaluated in air at 1373 K. This estimation was carried out by comparison of the alloy covered with a single Ni aluminide layer. For the alloy covered with the single Ni aluminide layer, a decrease in the mass gain of the alloy due to scale spalling was observed, while for the alloy covered with the bilayer coating, such a decrease was not observed. It was found from the observation of a cross-section of the alloy covered with the single Ni aluminide layer that the Al concentration in the surface region of the Ni aluminide layer decreased due to the diffusion of Al from the Ni aluminide layer to the substrate alloy. On the other hand, for the alloy covered with the bilayer coating, the diffusion of Al from the Ni aluminide layer to the substrate alloy was inhibited by the diffusion barrier effect of the Ni-Hf alloy layer. After the 10-cycle oxidation, the decomposition of the Ni-Hf alloy layer proceeded, and as a result, Hf in the Ni-Hf alloy layer diffused into the surface region of the Ni aluminide layer. The Hf in the surface region of the Ni aluminide layer led to the formation of an adhesive scale having a spiked shape.
Ruthenium oxide powders were produced by the reaction of an RuCl3 solution with H2O2, followed by heating of the resulting precursor at a temperature between 200°C and 600°C in air. Pb-based anodes containing these heated products of 1.0 mass% were prepared by the powder-rolling method, and the effect of the heated product as an electrode catalyst on lowering the anode potential was investigated in order to develop an energy-saving insoluble anode for Zn electrowinning. Based on XPS results, RuO2 with a signifi cant amount of RuO2･nH2O was produced by heating the precursor at 250°C or lower. The ratio of RuO2 to RuO2･nH2O increased remarkably above 300°C and the potential of the Pb-based anode decreased in inverse proportion to the RuO2 content of the heated product. The lowest anode potential of 1.72 V vs. NHE, which was about 360 mV lower than that of the anode with the unheated precursor, was observed for the Pb-based anode containing the product heated at 400°C. However, the anode potential of the Pb-based anode increased again when the heating temperature was 500°C or higher. The subsequent increase in the anode potential was probably caused by a decrease in the active sites of the oxygen evolution reaction, that is, the grain growth of the heated product decreased the effective reaction area of the RuO2 catalyst.
In this study, 4-butylaniline-impregnated resins (BuIRs) were prepared by soaking hydrophobic porous resins in aqueous solutions of 4-butylaniline hydrochloride. Rh(III) was successfully adsorbed by BuIRs from10 ppm Rh(III) solutions (6 M HCl). The quantitative desorption of Rh(III) accompanied with 4-butylaniline hydrochloride from BuIRs was also achieved by Soxhlet extraction using methanol. UV-Vis absorption measurements of Rh(III)-containing solutions showed that the equilibrium shift of Rh(III)-based species in HCl solutions is slow, and heating of the solutions is effective for equilibrating. The BuIRs obtained in this study effectively recovered the Rh(III) chloro-complex anion ([RhCl6]3－) from low Rh(III) concentration solutions, and can be useful in the Rh(III) recovery process.
We propose a quick and controlled cracking method for industrial ceramic waste by applying a steam pressure cracking (SPC) agent. The agent is a non-explosive and low-vibration-type chemical, which was developed by one of the authors of this study. We prepared a concrete specimen that had a diameter and cylinder height of 150 mm. Several grams of the agent cracked the specimen. We could control the cracking better in water than air when the air and water conditions were compared. When tested in water, the agent was placed in the hole of the concrete specimen and ignited, and the specimen could be split into two or three pieces of the same size. However, using another SPC agent that was explosive, the concrete specimen was broken into small fragments and size of the concrete pieces could not be controlled. The crushing mechanism was different for the two cases. The explosive crushed the concrete mainly through elastic shock waves. However, the steam pressure cracking agent breaks the specimen using the steam pressure and shock waves. We demonstrated that the cracking can also be controlled using guide holes. This steam pressure method can be applied to industrial waste as a safe and well-controlled method.
The thermal self-polycondensation of 4-(3,5-bis(4-aminophenoxy)phenoxy)phthalic acid, an AB2 type monomer, proceeded successfully at 140°C to form a hyperbranched poly(amic acid). The subsequent chemical imidization of the poly(amic acid) afforded hyperbranched aromatic polyimides bearing acetylamide (HBPI-Ac) or imide terminal (HBPI-Im) groups. The formation of high molecular weight polymers was confirmed by gel permeation chromatography measurements using a light scattering detector. The resulting polymers exhibited good solubility and low solution viscosity, which is typical for hyperbranched polymers. The degree of branching of HBPI-Ac was determined to be 0.48. Moreover, the 1H NMR measurement of the model phthalic acid compound at 120°C suggested that the formation of carboxyl anhydride units facilitated the amide bond formation, resulting in the hyperbranched poly(amic acid). HBPI-Im showed the temperature for a 5 % weight loss at 470°C, which was much higher than that of HBPI-Ac (400°C). HBPI-Im film, coated on a glass plate, became insoluble in amide solvents after heating at 280 °C for 10 min, indicating that it could be applied as a solvent-resistant and thermally stable coating in the microelectronics industry.