Horikoshi Satoshi

This is a specialized book for researchers and technicians of universities and companies who are interested in the fundamentals of RF power semiconductors, their applications and market penetration. Looking around, we see that products using vacuum tube technology are disappearing. For example, branch tube TVs have changed to liquid crystal TVs, and fluorescent light have turned into LED. The switch from vacuum tube technology to semiconductor technology has progressed remarkably. At the same time, high-precision functionalization, miniaturization and energy saving have advanced. On the other hand, there is a magnetron which is a vacuum tube device for generating microwaves. However, even this vacuum tube technology has come to be replaced by RF power semiconductor technology. In the last few years the price of semiconductors has dropped sharply and its application to microwave heating and energy fields will proceed. In some fields the transition from magnetron microwave oscillator to semiconductor microwave oscillator has already begun. From now on this development will progress remarkably. Although there are several technical books on electrical systems that explain RF power semiconductors, there are no books yet based on users’ viewpoints on actual microwave heating and energy fields. In particular, none have been written about exact usage and practical cases, to answer questions such as “What are the advantages and disadvantages of RF power semiconductor oscillator?", “What kind of field can be used?" and the difficulty of the market and application. Based on these issues, this book explains the RF power semiconductors from the user’s point of view by covering a very wide range of fields.

For the first time, this comprehensive handbook presents the emerging field of microwave technology for the synthesis of nanoparticles. Divided into three parts--fundamentals, methods, and applications--it covers topics including microwave theory, scale-up, microwave plasma synthesis, characterization, and more. This offers both an important volume for academic researchers, and a resource for those in industry exploring the applications of nanoparticles in semiconductors, electronics, catalysis, sensors, and more. © 2013 Wiley-VCH Verlag GmbH &amp Co. KGaA.

Formation of .OH radicals during TiO2 photocatalyzed oxidations driven by simultaneous UV and microwave radiation was probed by the electron spin resonance technique employing a novel setup in which the ESR sample (contained the DMPO spin-trap agent and P-25 TiO2 or pure anatase or pure rutile in aqueous media) could be irradiated by both UV light and microwave radiation; the microwave generator was coupled through an N connector to the ESR sample cavity and to a photoreactor in which phenol was photooxidized by simultaneous irradiation with UV light and microwaves to assess whether the photooxidative process correlated with the concentration of OH radicals formed. (C) 2003 Elsevier B.V. All rights reserved.

The photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) taking place in UV irradiated aqueous TiO2 dispersions was revisited to obtain mechanistic details on the basis of similar degradation of the related 2,3-dichlorophenoxyacetic acid (2,3-D), 4-chlorophenoxyacetic acid (4-M) and phenoxyacetic acid (PhA). Mechanistic changes were inferred from the different positions of the chlorine substituents. As well, the compounds were compared for differences in degradation rate and initial adsorption on the TiO2 surface as a function of the number of chlorines. The initial mechanistic sequence(s) in the TiO2-photocatalyzed oxidation of each substrate was predicted theoretically by molecular orbital ( MO) calculations of frontier electron densities and point charges of all the atoms in the phenoxyacetic acid structures.

Simulated wastewaters that contain methylene blue (MB) were bleached in a photocatalytic aqueous TiO2 dispersion illuminated by concentrated sunlight using a parabolic round concentrator reactor (PRCR). The kinetic analysis was carried out well when the temporal concentration variation was a function of the concentrated light energy irradiated. The photocatalyzed N-demethylation of NIB takes place concurrently with photocatalytic decomposition of MB by pseudo-first-order kinetics. The dependence of the photo-decomposition kinetics on the initial concentration of MB is consistent with the Langmuir-Hinshelwood model. Elimination of TOC (total organic carbon) also occurs by pseudo-first-order kinetics prior to full bleaching of the aqueous TiO2 dispersion, after which the TOC level decreases only slightly. Also, compared with the open to air, the photodegradation of MB is not influenced by molecular oxygen bubbling continuously through the reactant suspensions during illumination. TiO2 loadings and flow rates markedly affect the degradation of MB. Under concentrated sunlight, the relative photonic efficiency of MB photodegradation is zeta(rel) = 0.49 (relative to phenol). The efficiency zeta(rel) for the degradation of MB is independent of photoreactor geometry (cylindrical bottle reactor versus round-bottomed flask), of light sources (solar light concentrator versus a Hg lamp) and of the operating mode used (flow versus batch operation). (C) 2002 Elsevier Science B.V. All rights reserved.

In an attempt to improve the understanding of the basic mechanisms on the degradation of pollutants in water by TiO(2) photocatalysis, we discussed the primary degradation mechanism of three triazolidine derivatives, such as 1,2,4-triazolidine-3,5-dione (TRIANE), 4-hydroxy-1,2,4-triazolidine-3,5-dione (OH-TRIANE) and 4-phenyl-1,2,4-triazolidine-3,5-dione (Ph-TRIANE) and one triazole derivative of the 4-phenyl-1,2,4-triazole-2,5-dione (Ph-TRIOLE), on the basis of the experimental results together with molecular orbital (MO) calculation of frontier electron density and partial charge. The above four heterocycles were selected as molecular probe, principally because the highest frontier electron density was situated at different places of the molecule, while their structures were very similar, two major pathways have been revealed by LC/MS analysis for each heterocyclic compound. The pathway (a) corresponded to the hydroxylation of the atom bearing the highest electron density, via oxidation on nitrogen atom of azo group with respect to the photodegradation of TRIANE, OH-TRIANE and Ph-TRIOLE and opening of aromatic ring when Ph-TRIANE was used. This initial attack occurred with the preferential electrophilic attack of OH(circle) radicals. The pathway (b) was caused by the attack of active species on to carbon atom of carbonyl group. Considering the calculation of the relative electrophilic density of this carbon atom for the four heterocyclics and the evolution of large amount of N(2) gas at the initial degradation step, it has been suggested that this step (b) was favored by adsorption of carbonyl group on TiO(2) surface as theoretically determined by partial charge and confirmed by IR analysis. The participation of hole (h(+)) to form R-C=O(+circle) was envisaged in this step. The presence of 1,2,4,5-tetrazixane-3,6-dione also agrees with the participation of TiO(2) surface. The nitrogen inorganic analysis (N(2), NH(4)(+) and NO(3)(-)) determined by gas chromatography and ion liquid chromatography, show that the hydrazo group were photoconverted mainly into N(2) gas and partially to NH(4)(+) ions. No nitrate ions were observed at the beginning of the degradation even when a OH substituent was present on one nitrogen atom (case of OH-TRIANE). However, the presence of -OH group increased the NO(3)(-) /NH(4)(+) ratio observed after a few hours of irradiation. The presence of OH also improved the total mineralization of carbon atom into CO(2), which was attributed to mesomeric effect of -OH group. (C) 2002 Elsevier Science B.V. All rights reserved.

The photodegradation of p-nonylphenol polyethoxylate (NPE-9) has been examined in a large-scale circulating photoreactor to assess a set of different procedures to construct hybrid TiO(2) films immobilized on a flexible fiberglass cloth (TiO(2)-FGC). The method consisted of pasting active TiO(2) particles onto the fiberglass cloth support (PA method; 0.24 nm thick; weight, 210 g m(-2)), followed by a number of dip-coatings in a titania sol-gel solution (SG method). Various TiO(2) particulates from different sources have been screened. The Degussa P-25 titania exhibited the greater photocatalytic activity. The hybrid TiO(2)-FGC specimens retained a greater quantity of the TiO(2) catalyst on the FGC support than did the corresponding PA and SG samples. Comparison of the photodegradation of NPE-9 taking place in the various hybrid TiO(2)-FGC specimens with processes occurring in TiO(2) aqueous dispersions, on PA TiO(2)-FGC and SG Ti02-FGC specimens reveals that the hybrid TiO(2)-FGC specimens were the more photocatalytically active. Formic and acetic acids are two of the photo-oxidation intermediates identified in the degradation of NPE-9. Experimental conditions used in the present study to assess the cylindrical photoreactor containing the hybrid TiO(2)-FGC specimens show that such a reactor can be useful in a large-scale treatment of wastewaters. (C) 2002 Elsevier Science B.V. All rights reserved.

Photocurrent is generated during the photooxidation of nonylphenol polyethoxylate surfactants (NPE-n; n = 1, 5, 7, 9 and 10), precursors of 4-nonylphenol (NP), on illuminated TiO2/OTE electrodes on which TiO2 semiconductor particles were immobilized by a pasting (PA), a sol gel (SG), or both techniques (HY). The photooxidative process of NP and NPEs was examined by absorption spectroscopic methods monitoring the cleavage of the benzene ring moiety, and by the evolution of CO2 gas. The kinetics of photooxidation and the magnitude of the generated photocurrent scaled with the length of the ethoxyl side-chain for NPEs where n = 0, 1, 5, 7 and 10. The relative order of adsorption of NPEs on the positive TiO2 surface was predicted from calculated partial negative point charges of all the C and O atoms in the NPEs using molecular orbital methods. Both photodegradation and photocurrent generation were enhanced for the NPE-9 substrate using the HY TiO2/OTE electrode compared to the PA and SG electrodes. Although, biodegradation of NPEs yields NP in rivers, no formation of NP was observed during the photooxidation of NPE-9 because of predominant opening of the benzene ring. Photooxidation of NPEs is facilitated under an applied bias of +0.3 V and scales with the number of ethoxylate groups.

The photocatalytic degradation of six-membered heteroaromatics (pyridazine, pyrimidine and pyrazine) in aqueous TiO(2) suspension was investigated. The initial mechanistic sequence(s) in the TiO(2)-photocatdyzed oxidation of the constituent heterorings was predicted theoretically by molecular orbital (MO) calculations such as frontier electron densities and point charges on all the atoms. The cleavage of the heterocyclic moiety was examined by UV-VIS spectroscopy. The evolution of N(2) and CO(2) gas was determined by gas chromatography. The formation of NH(4)(+) and NO(3)(-) ions was assessed by ion-HPLC, and that of carboxylic acid intermediates by HPLC. The disappearance of six-membered heteroaromatics and the formation of intermediates were observed by LC-MSD. The heterorings containing an N=N fragment lead to the evolution of Nz gas, and those containing a C-N=C fragment lead to the generation of a large amount of NH(4)(+) ions and a minor amount of NO(3)(-) ions. The photodegradation of these heteroaromatics is closely related to the position of the nitrogen in the heterorings. The mechanism of the photodecomposition of the heterocyclic aromatics was revealed through comparison of experimental data with the analytical simulation. (C) 2001 Elsevier Science B.V. Ail rights reserved.

In this study we focus on elucidating the mechanism of the photocatalyzed transformation of the primary, secondary and tertiary amines found in ethanolamine, diethanolamine and triethanolamine when present in illuminated aqueous titania dispersions. Photodecomposition of these ethanolamines leads to the evolution of CO2 through prior formation of various intermediate species. Ammonium (NH4+) and nitrate ions (NO3-) are the ultimate products formed in the photoconversion of the amine nitrogen atoms, with NH4+ cations produced in greater quantity than NO3- anions for all three ethanolamines. Photooxidation of triethanolamine yields various intermediates, including a 3-pyrrolidone derivative, diethanolamine, and then ethanolamine, before complete mineralization occurs. The nature of the initial steps in the photodegradation was predicted by computer-aided molecular orbital (MO) calculations of point charges, and by frontier electron densities of all atoms in the ethanolamine structures.

Sodium benzene sulfonate (BS) was decomposed in aqueous TiO(2) dispersions under highly concentrated solar light illumination to examine the photocatalytic characteristics of a parabolic round concentrator (PRC) reactor to degrade the pollutant without visible light absorption. The effects of such operational parameters as initial concentration, volume of the aqueous BS solution, oxygen purging, and TiO(2) loading on the kinetics of decomposition of BS were investigated. An effective photodegradation necessitates a suitable combination of initial volume and concentration of BS solution. Relative to atmospheric air, oxygen purging significantly accelerates the degradation process at high initial concentrations of BS (0.40 mM or 1.0 mM). Optimal TiO(2) loading was 9 g l(-1), greater than previously reported. Elimination of TOC (total organic carbon) followed pseudo first-order kinetics in the initial stages of the photodegradation process. The relative photonic efficiency for the photodegradation of BS is zeta (rel) = 1.0. (C) 2001 Elsevier Science Ltd. All rights reserved.

This study reports on a comparative assessment of the efficiencies of TiO2/SnO2-doped OTE thin film electrodes fabricated by three different deposition methods. Process efficiencies, as measured by the kinetics of degradation, were examined by monitoring the photo-oxidative fate of two test substrates, namely the anionic surfactant sodium dodecylbenzenesulfonate (DBS) and the model compound sodium benzenesulfonate (BS). Methods chosen to fabricate the TiO2/OTE electrodes comprised (i) pulsed laser deposition, (ii) deposition of a TiO2 paste on the OTE plate, and (iii) sol-gel deposition. Both DBS and BS are readily photo-oxidized and, under our conditions, were partially mineralized to CO2 with the process being made particularly more efficient when the TiO2/OTE electrodes were anodically biased at +0.3 V, which generated a photocurrent during the photoelectrolysis. The sol-gel {C} and anatase {B1} electrodes proved especially useful under the +0.3 V bias. In the absence of any bias, however, DBS photodegraded faster on the TiO2-pasted electrode. Under otherwise similar conditions, the pulsed laser rutile TiO2/OTE electrode showed very little photoactivity. Some of the characteristics of the TiO2 film, such as the TiO2 crystalline form, film thickness, surface roughness, and film transparency appear to have some effect on the overall photodegradative process efficiency. (C) 2001 Elsevier Science B.V. All rights reserved.

In this study we focus on elucidating the mechanism of the photocatalyzed transformation of the primary, secondary and tertiary amines found in ethanolamine, diethanolamine and triethanolamine when present in illuminated aqueous titania dispersions. Photodecomposition of these ethanolamines leads to the evolution of CO2 through prior formation of various intermediate species. Ammonium (NH4 +) and nitrate ions (NO3 -) are the ultimate products formed in the photoconversion of the amine nitrogen atoms, with NH4 + cations produced in greater quantity than NO3 - anions for all three ethanolamines. Photooxidation of triethanolamine yields various intermediates, including a 3-pyrrolidone derivative, diethanolamine, and then ethanolamine, before complete mineralization occurs. The nature of the initial steps in the photodegradation was predicted by computer-aided molecular orbital (MO) calculations of point charges, and by frontier electron densities of all atoms in the ethanolamine structures.

The photocatalytic oxidation of oxalyldihydrazide, N, N'-bis(hydrazocarbonyl)hydrazide, N, N'-bis(ethoxycarbonyl)hydrazide, malonyldihydrazide, N-malonyl-bis[(N'-ethoxycarbonyl)hydrazide] was examined in aqueous TiO2 dispersions under UV illumination. The photomineralization of nitrogen and carbon atoms in the substrates into N-2 gas, NH4+ (and/or NO3-) ions, and CO2 gas was determined by HPLC and GC analysis. The formation of carboxylic acid intermediates also occurred in the photooxidation process. The photocatalytic mechanism is discussed on the basis of the experimental results, and with molecular orbital (MO) simulation of frontier electron density and point charge. Substrate carbonyl groups readily adsorb on the TiO2 surface, and the bonds between carbonyl group carbon atoms and adjacent hydrate group nitrogen atoms are cleaved predominantly in the initial photooxidation process. The hydrate groups were photoconverted mainly into N-2 gas (in mineralization yields above 70%) and partially to NH4+ ions (below 10%). The formation of NO3- ions was scarcely recognized. (C) 2000 Elsevier Science Ltd. All rights reserved.

The photocatalytic oxidation of oxalyldihydrazide, N, N'-bis(hydrazocarbonyl)hydrazide, N, N'-bis(ethoxycarbonyl)hydrazide, malonyldihydrazide, N-malonyl-bis[(N'-ethoxycarbonyl)hydrazide] was examined in aqueous TiO2 dispersions under UV illumination. The photomineralization of nitrogen and carbon atoms in the substrates into N-2 gas, NH4+ (and/or NO3-) ions, and CO2 gas was determined by HPLC and GC analysis. The formation of carboxylic acid intermediates also occurred in the photooxidation process. The photocatalytic mechanism is discussed on the basis of the experimental results, and with molecular orbital (MO) simulation of frontier electron density and point charge. Substrate carbonyl groups readily adsorb on the TiO2 surface, and the bonds between carbonyl group carbon atoms and adjacent hydrate group nitrogen atoms are cleaved predominantly in the initial photooxidation process. The hydrate groups were photoconverted mainly into N-2 gas (in mineralization yields above 70%) and partially to NH4+ ions (below 10%). The formation of NO3- ions was scarcely recognized. (C) 2000 Elsevier Science Ltd. All rights reserved.

The biodegradation of 4-nonylphenol polyethoxylate (NPE-n) nonionic surfactant through bacteria results in the formation of toxic 4-nonylphenol (NP) that has been identified as an endocrine disruptor by EPA. NP persists in nature for long periods, and consequently, new wastewater treatment should be established to ensure aquatic environmental protection.<BR>The photodegradation of NPE-n, NP and mixture solutions at the TiO₂/water interface was investigated. The photodecomposition of NP solution and NP/NPE-n mixed solutions (each 0.1mM) in aqueous TiO₂ (100mg) suspensions under UV-irradiation (320nm<λ<387nm) was monitored. After filtering TiO₂ particles, photodegradation kinetics were examined by surface tension, UV-absorbance, CO₂ evolution, TOC, FT-IR, ¹H-NMR and GC-MS. The aggregation of TiO₂ particles (studied by dynamic light scattering) and the formation of carboxylic acid intermediates (with HPLC) were examined. Surface photocatalytic reactions of NPE-n and/or NP structures on the TiO₂ semiconductor were studied by molecular orbital (MO) simulation. Efficient adsorption of the ethoxyl group on the TiO₂ surface was initially noted, followed by cleavage of the aromatic ring and the ethoxyl moiety by direct photooxidation and attack of OH radicals. No NP formation was detected in the photodecomposition of NPE. The photomineralization of the ethoxyl moiety proceeded via formic acid, and other alkyl groups and benzene rings were converted to acetic acids. The photooxidation of hydrophobic NP material proceeded as follows : (i) adsorption of the OH moiety in NP on the TiO₂ surface, (ii) facile ring-opening cleavage of phenol and (iii) CO₂ gas evolution for mineralization of NP. The photooxidation of mixed NPE-n and NP solution could be predicted from TiO₂ photooxidation results with pure NPE-n and/or NP solutions, photocatalytic degradation is thus shown to be a promising route for wastewater treatment of surfactants.

The photoelectrical degradation of the amino acids L-aspartic acid (L-Asp), L-glutamic acid (L-Glu), L-leucine (L-Leu), L-alpha-alanine (L-alpha-Ala) and beta-alanine (beta-Ala) was examined on TiO2/OTE electrodes prepared by a pulse laser deposition method. The disappearance of amino acids and their mineralization into CO2 were determined with and without an applied anionic bias of 0.3 V. The generation of photocurrent was also measured during the photoelectrical degradation of substrates on the TiO2/OTE electrode assembly considering it as a possible type of solar cell. The relationship between the photoelectrodegradation rate, the photocurrent and the structure of the amino acids was established.

The photooxidative degradation of a TiO2-blended poly(vinyl chloride) (PVC) film and other PVC specimens was carried out under UV light and under solar exposure to test the feasibility that such polymeric materials can be mineralized. The effects of the degree of polymerization and the presence of a plasticizer (o-dioctyl phthalate DOP) in the PVC on the photooxidation process were examined by scanning electron microscopy (SEM), by X-ray photoelectron spectroscopy (XPS), by gel permeation chromatography, and by gas chromatography for CO2 evolution. The TiO2-blended PVC thin film is more easily decomposed than PVC particles (or film) alone in a TiO2 particulate dispersion. The collapse phenomena of polymeric films are closely dependent on the photodegradation rate of DOP in the PVC film. Ames mutagenic assays for the photodegraded solution in aqueous TiO2/PVC dispersions showed a slight mutagenic activity in TA98 without S9 mix for products formed during the photodegradative oxidation.

The pathway to the photomineralization of the three amino acids L-serine (L-Ser), L-phenylalanine (L-Phe) and L-a-alanine (L-Ala) is described experimentally on the basis of CO2 evolution and conversion of the amino group to NH4+ and NO3- ions, and theoretically on the basis of molecular orbital calculations to define frontier electron densities and point charges on all the individual atoms. The relatively high negative point charges on the carboxylate oxygens are consistent with adsorption of the amino acids to the TiO2 particle surface through the carboxylate function. Mineralization to carbon dioxide is complete for L-Ser (similar to 98%) and nearly so for L-Ala (similar to 90%), whereas for L-Phe the extent of mineralization is 59% corresponding to the total photooxidation of the phenyl ring carbons; for the amine function the extent of conversion is 87% for L-Ser, 97% for L-Ala and 91% for L-Phe. Relative formation yields of NH4+ and NO3- ions depend on the structural fragment R attached to the a-amino carboxylic acid functions, R-CH(NH2)COOH. Primary attack of the amino acids by the (OH)-O-. radical is correlated with the frontier electron densities. Ammonia is formed through a photoreductive step by electron attachment onto the zwitterionic form of the amino acids, whereas nitrate is produced through a photooxidative step implicating a very tortuous series of events. (C) 1998 Elsevier Science S.A. All rights reserved.

The fate of DNA, RNA and their pyrimidine and purine bases was examined on exposure to WA and UVB radiation in the presence of a physical sunscreen agent (TiO(2), anatase/rutile particles) to assess the potential damage that such an agent may cause on contact with such substrates. DNA and RNA were partially decomposed and the bases were converted to carbon dioxide (nitrogen atoms to ammonia and nitrate ions) in a Pyrex reactor under conditions simulating UVA and UVB sunlight. The physical and chemical damage inflicted on DNA and RNA was also confirmed by scanning electron microscopy and gel permeation chromatography. (C) 1997 Elsevier Science S.A.

Titanium dioxide (TiO2) has been noted (US Federal Register, 43FR38206, 25 August 1978) to be a safe physical sunscreen because it reflects and scatters UVB and UVA in sunlight. However, TiO2 absorbs about 70% of incident UV, and in aqueous environments this leads to the generation of hydroxyl radicals which can initiate oxidations, Using chemical methods, we show that all sunscreen TiO2 samples tested catalyse the photo-oxidation of a representative organic substrate (phenol), We also show that sunlight-illuminated TiO2 catalyses DNA damage both in vitro and in human cells, These results may be relevant to the overall effects of sunscreens. (C) 1997 Federation of European Biochemical Societies.

The photoelectrochemical degradation of amino acids and derivatives such as glutamic acid, glutamine, glutaric acid, lysine, beta-alanine, 8-aminooctanoic acid and phenylalanine has been examined on an irradiated TiO2/OTE particulate film electrode. The photooxidative disappearance of the substrates ultimately transforms the nitrogen into NO3- and NH3 (as ammonium ions under our conditions), whereas the carbonaceous residues are converted into CO2. Variations in photocurrent were observed during the temporal course of the photodegradative process. The rates of conversion and the quantity of degraded products depend on the external applied bias and appear to be closely related to the molecular structure of the substrates. A photoelectrochemical degradative pathway is discussed briefly on the basis of the experimental observations. (C) 1997 Elsevier Science S.A.

The fate of nitrogen in various amino acids was examined following their photooxidative (and/or reductive) transformation catalyzed by UV-A and UV-B illuminated aqueous TiO2 dispersions. The nitrogens in the amino acids are photoconverted predominantly into NH, (analyzed as NH4+) and to a lesser extent into NO3- ions; NH4+/NO3- ratios span the range 3-12 after ca. 8 h irradiation. Extensive evolution of CO2 is also observed; in some cases it is quantitative. Variations in the NH4+/NO3- ratio in the transformation of amino acids are dependent on the substrates molecular structure. Some of the steps in an otherwise complex mechanism of the heterogeneous photocatalyzedmineralization are described. (C) 1997 Elsevier Science S.A.

The photo-oxidative degradation of sodium benzene sulfonate, 2-phenoxyethanol, ethyleneglycol, diethyleneglycol, acetic acid and formic acid, was examined on a TiO2 particulate film immobilized on a transparent conductive oxide (TCO) glass electrode assembly. The photocurrents generated during the photodegradation of these organic compounds were monitored. Formation of intermediate species (acetic acid and formic acid) during the temporal course of the photo-oxidative process(es) appears to have a direct effect on the photocurrents.