Promotion of CO2 methanation activity and CH4 selectivity at low temperatures over Ru/CeO2/Al2O3 catalysts

The effect of CeO₂ loading amount of Ru/CeO₂/Al₂O₃ on CO₂ methanation activity and CH₄ selectivity was studied. The CO₂ reaction rate was increased by adding CeO₂ to Ru/Al₂O₃, and the order of CO₂ reaction rate at 250 °C is Ru/30%CeO₂/Al₂O₃ > Ru/60%CeO₂/Al₂O₃ > Ru/CeO₂ > Ru/Al₂O₃. With a decrease in CeO₂ loading of Ru/CeO₂/Al₂O₃ from 98% to 30%, partial reduction of CeO₂ surface was promoted and the specific surface area was enlarged. Furthermore, it was observed using FTIR technique that intermediates of CO₂ methanation, such as formate and carbonate species, reacted with H₂ faster over Ru/30%CeO₂/Al₂O₃ and Ru/CeO₂ than over Ru/Al₂O₃. These could result in the high CO₂ reaction rate over CeO₂-containing catalysts. As for the selectivity to CH₄, Ru/30%CeO₂/Al₂O₃ exhibited high CH₄ selectivity compared with Ru/CeO₂, due to prompt CO conversion into CH₄ over Ru/30%CeO₂/Al₂O₃.     

Solution-Processable Pure Green Thermally Activated Delayed Fluorescence Emitter Based on the Multiple Resonance Effect

Thermally activated delayed fluorescence (TADF) materials based on the multiple resonance (MR) effect are applied in organic light-emitting diodes (OLEDs), combining high color purity and efficiency. However, they are not fabricated via solution-processing, which is an economical approach toward the mass production of OLED displays. Here, a solution-processable MR-TADF material (OAB-ABP-1), with an extended π-skeleton and bulky substituents, is designed. OAB-ABP-1 is synthesized from commercially available starting materials via a four-step process involving one-shot double borylation. OAB-ABP-1 presents attractive photophysical properties, a narrow emission band, a high photoluminescence quantum yield, a small energy gap between S₁ and T₁, and low activation energy for reverse intersystem crossing. These properties are attributed to the alternating localization of the highest occupied and lowest unoccupied molecular orbitals induced by the boron, nitrogen, and oxygen atoms. Furthermore, to facilitate charge recombination, two novel semiconducting polymers with similar ionization potentials to that of OAB-ABP-1 are synthesized for use as interlayer and emissive layer materials. A solution-processed OLED device is fabricated using OAB-ABP-1 and the aforementioned polymers; it exhibits pure green electroluminescence with a small full-width at half-maximum and a high external quantum efficiency with minimum efficiency roll-off.     

A negative resist,LMR (low molecular weight resist), for deep UV lithography

A negative deep UV resist, LMR, has been developed. LMR is a diazonaphthoquinonesulfonate of cresol novolac resin and possesses a high sensitivity of 15 mJ/cm² and a high resolution up to 0.2 μm by contact printing. An important feature of LMR is the production of negative images with overhung profiles. Such profiles are attributed to LMR possessing a large absorbance in the deep UV region (12 μm^?1 at 250 nm), which is of great advantage to the lift-off process in the fabrication of GaAs-FET, surface acoustic wave (SAW) devices, and so on. Furthermore, because of the good thermal stability of LMR, it can liftoff hard metals such as Ni and Mo. In order to elucidate the phenomenon that deep UV irradiation retards the dissolution rate of LMR, a mechanistic study has been carried out. In both LMR and its analog lacking diazoquinone moiety, their molecular weights Increase upon deep UV irradiation, which suggests that crosslinking occurs in the base resin. This is supported by 13C NMR analyses of photochemical reaction products and by detection of radical species produced from the base resin. The photochemical reaction of the base resin is important to understand the overall lithographic performance of LMR.     

Incorporation of LiNbO3 crystals into tellurite glasses

Transparent tellurite glasses containing 5–10 m diameter LiNbO₃ crystals (3–7 wt%) have been successfully prepared using an incorporation method in which LiNbO₃ crystals are directly dispersed into the 80TeO₂-15Li₂O-5Nb₂O₅ glass. The dissolution behaviour of the LiNbO₃ crystals greatly depends on the Li₂O: Nb₂O₅ ratio in the matrix glasses. In the 80TeO₂-10Li₂O-10Nb₂O₅ matrix glass, the crystals remaining after incorporation have the composition LiNb₃O₈. A small difference in the refractive indices, n, between the TeO₂-based glasses (n=2.07) and the incorporated LiNbO₃ crystals (n=2.296) is a significant reason for the transparency. It is feasible to prepare the highly transparent TeO₂-based glasses containing a large amount of LiNbO₃ crystals by controlling the incorporation process.     

Degradation of poly[bis(ethylamino)phosphazene] in aqueous solution

Three polymers of poly[bis(ethylamino)phosphazene] (PBEAP) containing different amounts of the residual P–Cl moieties, which had been hydrolyzed into P OH in the following sample purification processes, were prepared by substitution of the chlorines on poly(dichlorophosphazene) with ethylamine. Only the polymer which had the highest side-chain content of ethylamino groups (ca. 93°_o) had a film-forming ability and a crystalline nature. The hydrolytic degradation of PBEAP in acidic solutions was investigated using the solution viscosity data obtained as a function of standing time. Acetic acid, 0.5 and 1N, pure acetic acid, and 2.2.2-trifluoroethanol were used as solvents. The degradation was composed of random breaking processes along the polymer chain, especially at the-N=P(OH)₂-and-N=P(OH)(NHC₂H₅)-units, and an unzippering-like breaking process which was started at the chain ends produced by the former random breaking. The random breaking caused an abrupt decrease in viscosity at the beginning of the degradation, and on the contrary, the unzippering-like breaking appeared as a gradual decrease in viscosity at the later stages of degradation. The total rate of degradation depended on the concentration of the ethylamino groups.     

Kinetics of Nonisothermal Crystallization of Bi2Sr2CaCu2Ox Glasses with Different Copper Valence States

The kinetics of the nonisothermal crystallization process in Bi₂Sr₂CaCu₂O_x glasses with different copper valance states, R(Cu⁺) = Cu⁺/(Cu⁺+ Cu²⁺) = 0.79–0.99, were examined by using differential scanning calorimetry. Four different kinetic equations were used for the data analyses. It was found that the values of activation energy for crystal growth, E _a, decreased with increasing Cu⁺ content. The value of E _a, which was estimated from the modified Ozawa equation, for the glass with R(Cu⁺) = 0.79 was 483 kJ·mol^-1 and for the glass with R(Cu⁺) = 0.99 was 353 kJ·mol^-1. In the former glass, the number of crystal nuclei was almost independent of the heating rate. But, in the latter glass, the number of crystal nuclei varied significantly with the heating rate. The crystallization mechanism in the glasses was closely related to the thermal stability and viscosity of glasses: the glass with R(Cu⁺) = 0.99 showing a high thermal stability and a low activation energy for viscous flow had a small value of E _a. The plot of In ( T _p²/α) against 1/ T _p, where T _p and α are crystallization peak temperature and heating rate, respectively, gave a reasonable value of E _a for the glass with R(Cu⁺) = 0.79 but was unsuitable for the evaluation of E _a for crystal growth of the glass with R(Cu⁺) = 0.99.     

Low-temperature chemical synthesis of intermetallic TiFe nanoparticles for hydrogen absorption

Nanosizing of TiFe hydrogen storage alloy is conducted to facilitate its activation. Here, pure intermetallic TiFe nanoparticles (45 nm) were prepared using chemical reduction of oxide precursors at 600 °C, which is the lowest temperature ever used in chemical synthesis. This was achieved using a strong reducing agent (CaH₂) in a molten LiCl. When used for hydrogen absorption, the obtained nanoparticles surprisingly exhibited almost no hydrogen absorption. The results demonstrated that TiFe nanoparticles are more difficult to activate than the bulk powder because the oxidized surface layers of the nanoparticles become stabilized, which prevents the morphological change necessary for their activation.     

Direct Evaluation of the Electrokinetic Properties of Electrolytes in a Nanochannel using Electrical Impedance Spectroscopy

An electric double layer is the local distribution of ions created at any liquid and solid interface. The thickness of the electric double layer is typically in nanometers, so that it is dominant in the nanoscale. Because the size of the nanospace is the same order of magnitude as the thickness of the electric double layer, the nanospace should be partially/totally filled with an electric double layer. Therefore, the investigation of the electrokinetics inside the electric double layer in nanospaces, such as nanopores and nanochannels, is very important for electrical/electrochemical analysis and for the manipulation of molecules and nanoparticles in nanofluidic systems. Here, electrical impedance spectroscopy was used to comprehensively investigate how the ionic concentration and the volume of the nanospace influenced the electrical properties of various ionic solutions in a nanochannel. The electrokinetic properties and the thickness of the electric double layer in the nanospace were determined to be dependent on the hydration diameter, mobility, and ionic strength of the various ion species. The electric double layer overlaps under particular conditions, such as with sufficiently narrow channels, and the qualitative properties of this were consistent with the Debye-Hückel-Onsager equation. These results should be a significant contribution to the improvement of the analysis and manipulation of molecules and particles in nanochannels, which could lead to further development in the application of nanofluidics.     

Hydrogen generation by water radiolysis with immersion of oxidation products of Zircaloy-4

In order to predict the hydrogen gas generation from seawater or water in which debris would be included by the severe accident of nuclear power plant, we investigated the effect of ZrO₂ and the oxidation products of Zircaloy-4 on hydrogen gas generation by radiolysis of water since the radiolytic generation could be affected by materials immersed in water. Powders of well-characterized oxides and oxidation products were immersed in either seawater or distilled water, and irradiated by gamma ray from a Co-60 source. The observed hydrogen yield, G(H₂), was measured as a function of the weight fraction of oxide in water up to 50 wt%. The enhancement of the hydrogen generation by radiolysis of water with the commercial oxides and the oxidation products of Zircaloy-4 was quite small or absent in seawater. But the enhancement was observed in the presence of the oxides or the oxidation products at low weight fraction in distilled water. This enhancement in distilled water seemed to be dependent on specific surface area or particle size, but its dependence on the crystal structure was not apparent in the experimental results. The enhancement was saturated at higher ZrO₂ weight fractions and it was not apparent in the seawater.