Denitrification mechanism of NaOH in the presence of carbon

We tested a mixture of NaOH and carbon and found it to react rapidly with NO gas, thus demonstrating a promising new method of flue gas denitrification (FGD). We determined the reaction products: gas phases were analyzed by GC-MS and NOx meter, and solid residues were analyzed by X-ray diffusion (XRD) and chemical analysis. The reaction process was clearly divided into two stages. In the first stage, the reaction proceeded extremely rapidly, with NO almost completely removed. The mechanism describing this stage consists of a series of reactions of NaOH and NO in the presence of carbon. The main conversion of sodium in this stage is proposed to be: NaOH-->NaNO3 (and NaNO2)-->Na2O2-Na2CO3. The pyrolysis of NaNO3 was examined and carbon was found to have the ability to reduce NOx emission during this process. In the second stage, NO reduction proceeds slowly and stabilizes at a constant value. The mechanism behind this stage is considered to be the reaction of carbon with NO in the presence of Na2-CO3 as catalyst. Quantitative study of the reaction system demonstrated that the total amount of denitrified NO is proportional to the amount of carbon and that the denitrified NO in the first stage is proportional to the amount of NaOH.     

Oxygen-reduction activity of silk-derived carbons

Carbonized silk fibroin (CS), which is free of metallic elements, showed high catalytic activity for oxygen-reduction reaction (ORR). The catalytic activity of CS for ORR was greatly enhanced by steam activation forming silk-derived activated carbon (CS-AC). The surface morphology, surface area, pore structure and remaining nitrogen species of the CSs were compared with those of the CS-ACs. The open-circuit potential and the power density of a polymer electrolyte fuel cell using a CS900-AC, which was heat-treated at 900 °C prior to the steam activation, and a platinum/C (C: carbon black) anode under pure oxygen and hydrogen gases, respectively, both at 0.2 MPa, were 0.92 V and 142 mW cm⁻² at 80 °C. The ORR on the activated carbon, CS900-AC, proceeded with a 3.5-electron reaction at 0.6 V (vs. RHE); however, this was improved to a 3.9-electron reaction with the addition of zirconium oxide at 20 wt% to CS900-AC.     

Investigation of grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment

The grain boundary formation in PtRu/C catalyst obtained in a polyol process with post-treatment was investigated by scanning transmission electron microscopy, transmission electron microscopy (TEM) and High resolution TEM. The crystalline structure and surface composition of the PtRu/C catalysts were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical activities were evaluated by CO stripping voltammetry and linear sweep voltammetry measurements in combination with in situ IR reflection-absorption spectroscopy. As-prepared isolated spherical nanoparticles on the carbon support started to interconnect after washing procedure, and the interconnection between the particles was greatly promoted by reduction post-treatment at 80 °C; grain boundary formation occurred in the interconnected particles with increasing reduction temperature to 200 °C, and the particles reconstructed severely with further increasing reduction temperature to 400 °C. The defects at the grain boundary served as active sites for methanol electro-oxidation by weakening CO_ads adsorption on Pt sites and facilitating OH_ads formation, and the PtRu/C catalyst treated in 5% H₂/Ar at 200 °C for 10 h had the greatest catalytic activity for methanol electro-oxidation among the PtRu/C catalysts treated under various atmospheres and temperatures.     

Measurements of polyphosphoric acid on HOPG

As a sample for initial study on biological materials by using scanning tunnelling microscope (STM), we selected phosphoric acid consisting of phosphorous atoms which play biologically an important role. We measured polyphosphoric acid coated on HOPG by STM and scanning tunnelling spectroscopy (STS) in air. In order to identify molecules on STM images, local I-V curves were taken simultaneously. The averaged I-V curves and the normalized conductance spectra of graphite coated with the acid show characteristics different from those of clean graphite surface. Around a step of the substrate, we found domains where normalized conductance spectra were different from those of clean graphite surface and ascribable to that of the adsorbed molecules.     

Heat removal characteristics of vault storage system with cross flow for spent fuel

Since the amount of spent fuel to be stored is expected to steadily increase in Japan, a use of large-scale dry storage facilities is considered to be a promising method in practice at reasonable economic cost. The present study is concerned with the heat removal experiment of vault storage system adopting cross flow with passive cooling, using a 1/5 scale model. The results show that the flow pattern of air in the storage module strongly depends on the ratio of the buoyancy to the inertia force. A simple method to estimate air flow patterns in the storage module was proposed, where the Ri (Richardson) number was considered as the most representative parameter. Then the heat transfer rate from a storage tube to cooling air was estimated, which could apply to the design of a full-scale vault storage system with cross flow, in which dozens of storage tubes were placed. The acquired information was also used to optimize heat removal design of the vault storage system in the present study.     

Heat removal verification tests of full-scale concrete casks under accident conditions

Heat removal verification tests using two kinds of full-scale concrete casks under accident conditions were performed. One is reinforced concrete cask and the other is concrete filled steel cask. From the test results, their safety on heat removal performance under accident conditions was confirmed. Accident conditions for the tests were partial (50%) and complete (100%) blockage of the air inlets. Because the shape of air flow area in the concrete casks are different between two types of the cask, it was found that the change of the temperature distribution and air flow pattern were different for each accident condition.     

Effects of bacteriostatic emulsifiers on stability of milk-based emulsions

For milk-based emulsion products such as canned coffee or tea, the addition of bacteriostatic emulsifiers is necessary to inhibiting the growth of heat-resistant sporeformers. Since bacteriostatic emulsifiers often cause the destabilization of emulsions, other type of emulsifiers, such as stability-enhancing ones, are necessary for the long-term stability of emulsions. Four milk-based emulsions were prepared from powdered milk combined with several types of emulsifiers. The long-term stability of emulsions, which was detected by the occurrence of a creaming layer after 3 months of storage, differed according to the composition of emulsifiers. To understand the reason for the differences in the stability of emulsions, particle size, distribution, ζ-potential, and the amount of proteins and phospholipids present in the cream layer (separated oil droplets) in the emulsions were measured. Only the amount of proteins adsorbed onto oil droplets was found to be closely related to the difference in emulsion stability, that is, the more proteins adsorbed, the higher the emulsion stability. SDS–PAGE analyses revealed that κ-casein and β-lactoglobulin play an important role in emulsion stability by adsorbing onto the oil droplet surface.