Rh nanoparticle catalysts were prepared via liquid phase reduction assisted by microwave-heating. Different kinds of alcohols as reductant including Rh precursor and stabilizer (Polyvinylpyrrolidone) were equally and quickly heated by microwave-heating. Conventional liquid phase reduction using electric heater requires long-heating time (2-3 h) . However,microwave-heating leads to formation of uniform Rh nanoparticles within 15 min. In EXAFS analyses, local structure of prepared Rh nanoparticles was identical to that of pure Rh powder, indicating that Rh atoms were reduced to metallic state.Coordination number (Rh-Rh) decreased from 12.5±1.1 to 9.4±0.7 when Rh particle size determined by TEM decreased from 6.7 nm to 3.3 nm. It was revealed that smaller Rh nanoparticles which have low coordination number (i.e., many dangling bond)show higher catalytic activity in CO oxidation reaction
Microwave (MW) heating techniques have been paid attention by many technological researches and developers because MW dielectric heating is selective and rapid. However, metals cannot be heated by the electric field because of the spark phenomenon.We developed novel MW soldering system by using cylindrical cavity and single-mode TM110 mode that separate electric and magnetic field distribution of MW. Furthermore, we developed a novel short-time melting technology for solder paste using MW dielectric heating. In particular, we found that only solder paste on polyethyleneterephtalate (PET) substrate can absorb MW energy, and can be melted without damage on the substrate using the developed system. Furthermore, we succeeded in mounting a temperature and humidity sensor array using the novel MW heating system without damage to the electric component and electric circuits of the device. The distortion of PET substrate was less than 0.01 %.
A comparative study was carried out on degradation of methyl orange (MO) by TiO2, Au/TiO2, and Ag/TiO2 photocatalysts in neutral and acidic solutions. Au/TiO2, and Ag/TiO2 photocatalysts were prepared by microwave-polyol method in the presence of P25 TiO2 . The Au/Ti and Ag/Ti atomic ratio in Au/TiO2 and Ag/TiO2 catalysts was 1.5%. Initial degradation rates of MO by TiO2,Au/TiO2, and Ag/TiO2 at pH=7 were 0.13, 0.22, and 0.12 min-1, whereas those at pH=2 were 0.96, 3.1, 2.9 min-1, respectively.These results indicate that the degradation rates are enhanced for TiO2, Au/TiO2, and Ag/TiO2 by factors of 7.4, 14, and 24 in acidic conditions, respectively. On the basis of effects of additions of isopropyl alcohol, oxalic acid, and p-benzoquinone as scavengers of ･OH, h+, and ･O2-, major active species for the degradation of MO using TiO2, Au/TiO2, and Ag/TiO2 were determined. Results show that all three active species take part in the degradation of MO in neutral conditions and their contribution was ･OH < h+ < ･O2- . On the other hand, major active species in acidic solution was ･O2-. Combining these results with mass spectroscopic studies on the degradation products led us to conclude that the great enhancement of degradation rates using Au/TiO2 and Ag/TiO2 photocatalysts in acidic conditions arises from a great increase in the ･O2- concentration due to electron trapping effects of Au and Ag nanoparticles loaded on TiO2 under UV irradiation. Mass spectroscopic data suggested that major product channels are ring opening and carboxylation in the reactions of ･O2- with MO in acidic conditions.
Since a quarter-century ago, many researchers reported the rapid decomposition a glass fiber reinforced plastic (GFRP) resin by either high pressure or catalyst. We have been investigating the decomposition of GFRP by both microwave and high pressure. As using a catalyst, the microwave reactor became uncontrollable. On the other hand, in the absence of catalyst, the alcoholysis of GFRP resin under pressurized conditions could almost completely decompose the GFRP resin. Ethylene glycol mono-allyl ether (EGMA) with cross-linking functional group also easily decomposed GFRP resin with adding the prevention condition of the oligomerization of EGMA. In the present study, cross-linking functional groups were introduced to the resin decomposition product of the GFRP-made bathtub waste generated by the Kumamoto earthquake by using this method. And since the decomposed resin product has the allyl groups, the product could easily cure with unsaturated polyester. As a result, it was suggested that about 50% by weight of the crosslinking agent (styrene) can be substituted. The re-production of GFRP was also successful.
We have developed a new waveguide for 2.45GHz microwave which is equipped an aluminum block jacket thermostat, and built up a novel microwave synthesizer which can perform chemical reactions even at low temperatures with continuous microwave irradiation. Applying this for solid-phase peptide synthesis (SPPS), we successfully obtained some advantages. Reactions were accelerated even at lower temperatures. Microwave unique effect could be clearly observed. Only small excess reagents (ex. 1.2 equivalent of Fmoc-amino acids and condensation reagents) were enough in microwave supported SPPS even at low temperatures, though large excess (more than five equivalent) of reagents are commonly used. As glycosylated amino acid synthons are expensive and relatively unstable, also as glycopeptides are potentially suffered epimerization and are easily to be decomposed by elimination of sugars, microwave supported SPPS at low temperatures gave big advantages for glycopeptide synthesis.
The heating properties were investigated for Al4SiC4 powders with various particle sizes (3.0 μm to 1-2 mm) to develop 2.45GHz microwave well absorber. The single-mode cavity, which is able to separate electric field heating and magnetic field heating, was employed as microwave heating systems and the heating behavior was investigated at separated electrical field employing a radiation thermometer. Their electrical permittivity for 2.45GHz were measured by the cavity perturbation method. Al4SiC4 were compared with Al2O3 in both heating behavior and electrical permittivity. The microwave absorption of Al4SiC4 powders increases with their grain size, 1-2 mm particles powders indicates higher temperature than 3 μm in their microwave heating.
Previous studies revealed that microwaves have particular effects on the interfacial tension of the decane/water interface in the presence of Triton X-100. This study investigated the reasons for the hysteresis during and after microwave irradiation by varying the concentration and type of Triton surfactants: X-100 and X-405. As before, physiochemical changes were found to persist after the irradiation of Triton X-100. Interestingly, no hysteresis was observed for Triton X-405. The difference of temperature dependency was caused by different hydrophilicity of Triton X-100 and X-405. Desorption at the interface during the irradiation is easier for the shorter surfactant (Triton X-100) than its longer surfactant (Triton X-405), due to the length of the hydrophilic group. Moreover, the shorter surfactant has a stronger hysteresis during the heating/cooling cycles due to higher adsorption. The dynamic surfactant behaviour between two phases during the irradiation might be promisingly applicable to industrial processes such as de-emulsification.