Journal articles on the topic 'Oxides'
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1
Gornostaev, Leonid M. "Synthesis of 5-hydroxy-10-R-benzo[a]phenazine-12-oxides by cyclization of 2-arylamino-1,4-naphthoquinone-1-oximes under the action of nitrating mixture." Butlerov Communications 61, no. 2 (February 29, 2020): 12–23. http://dx.doi.org/10.37952/roi-jbc-01/20-61-2-12.
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The synthesis of рolycyclic quinoid compounds, which exhibit a wide range of biological activity is one of the most promising and actively developing areas of the fine organic synthesis. Heterocyclic compounds including those that can be donors of nitrogen oxide NO occupy a special place among biologically active structures. These substances include a number of N-oxides, e.g., 1,2-diazet-1,2-dioxides, furoxanes and their benzo analogs, and N,N′-pyrazole dioxides. The reason for the high biological activity of N-oxides of nitrogenous heterocycles, which cannot easily generate nitrogen oxide NO may be their oxidative properties. Thus, N-oxides of nitrogenous heterocycles are of interest due to their high biological activity. We have developed an approach to the synthesis of 5-hydroxy-10-R-benzo[a]phenazine-12-oxides that contain the N-oxide fragment, which makes these compounds promising for studying their biological activity. We have demonstrated that the treatment of 2-arylamino-1,4-naphthoquinones with hydroxylamine in ethanol at 50-60 °С leads to selective oximation at position 1 and the formation of 2-arylamino-1,4-naphthoquinone-1-oximes. It has been shown that the interaction of 2-arylamino-1,4-naphthoquinone-1-oximes with the nitrating mixture in acetic acid results in the formation of 5-hydroxy-10-R-benzo[a]phenazine-12-oxides. Our work is a continuation of the study on the interactions of 2-arylamino-1,4-naphthoquinones and 4-arylamino-1,2-naphthoquinones with nitrosylsulfuric acid in acetic acid and the interaction of 2-alkyl(benzyl)amino-1,4-naphthoquinones with nitrosylsulfuric acid or nitrating mixture in acetic acid. The former reactions lead to the formation of 3-R-benzo[b]phenazine-6,11-dione-5-oxides and 9-R-benzo[a]phenazine-5,6-dion-7-oxides, respectively. The latter reaction leads to the formation of 2-alkyl(aryl)naphtho[2,1-d][1,3]oxazole-4,5-dione-4-oximes and 2-alkyl(aryl)-1-hydroxy-1H-naphtho[2,3-d]imidazole-4,9-dione as main products.
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Hanhela, PJ, and DB Paul. "Synthesis and Stability of Aryl Bis(nitrile oxides) With Potential as Curing Agents for Polysulfide Sealants." Australian Journal of Chemistry 42, no. 2 (1989): 287. http://dx.doi.org/10.1071/ch9890287.
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Several aromatic bis( nitrile oxides) have been prepared as potential curing agents for sealants produced from thiol -terminated polysulfide liquid polymers. All were obtained by dehydrohalogenation of α-halo oximes and the requisite aldehydes were synthesized from either the dimethyl derivatives or the chloromethylated hydrocarbons. The direct chloromethylation of naphthalene which offered a convenient route to the naphthalene-1,4- and 1,5-bis(carbonitrile oxides) was re-examined. Also prepared were naphthalene-2,6-bis(carbonitri1e oxide), anthracene-9,10-bis(carbonitri1e oxide) and 4,4′-sulfonylbisbenzonitrile dioxide. The course of the reaction between naphthalene-2,3-dicarbaldehyde and hydroxylamine was established and shown to differ from that involving phthalaldehyde. Stabilities of the nitrile oxides at -15�, 4� and 25� were assessed by spectroscopic means.
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Ennis, BC, PJ Hanhela, and DB Paul. "Organic Curing Agents for Polysulfide Sealants. III. A Mechanistic Interpretation of the Thermal Degradation of Nitrile Oxide-Cured Polysulfide Sealants." Australian Journal of Chemistry 43, no. 1 (1990): 109. http://dx.doi.org/10.1071/ch9900109.
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Sealants obtained by cure of polysulfide liquid polymers with aryl bis ( nitrile oxides) possess the thiohydroximic acid ester structural feature. Unexpectedly these materials were found to exhibit poor thermal stability: when heated at 60° they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degraded faster than those produced with equimolar amounts of reagents. Interpretations considered included (A) dissociation of the thiohydroximic acid group, (B) reaction between nitrile oxide and a reactive centre in the polysulfide structure, and (c) addition of nitrile oxide to the side chain. It was shown that neither of the first two possibilities was applicable. Moreover, spectroscopic studies demonstrated that, after an initial rapid addition between nitrile oxide and thiol , a second slower reaction occurred which consumed additional nitrile oxide. Although aldehyde oximes and a- chloro oximes do not participate in such processes unless catalysts are present, thiohydroximic acid derivatives were shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol . For the case of a polysulfide sealant the equivalent rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process would lead to degradation of the sealant. These observations were supported by thermal analysis studies on the polysulfide sealants and model polymers.
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She, Weiqing, Zhenzhen Xu, Lianjie Zhai, Junlin Zhang, Jie Huang, Weiqiang Pang, and Bozhou Wang. "Synthetic Methods Towards Energetic Heterocyclic N-Oxides via Several Cyclization Reactions." Crystals 12, no. 10 (September 25, 2022): 1354. http://dx.doi.org/10.3390/cryst12101354.
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Due to the introduction of oxygen atoms, N-oxide energetic compounds have a unique oxygen balance, excellent detonation properties, and a high energy density, attracting the extensive attention of researchers all over the world. N-oxides are classified into two categories based on the structural characteristics of their skeletons: azine N-oxides and azole N-oxides, whose N→O coordination bonds are formed during cyclization. There are six kinds of azine N-oxides, namely 1,2,3,4-tetrazine-1,3-dioxide, 1,2,3,5-tetrazine-2-oxide, 1,2,3-triazine-3-oxide, 1,2,3-triazine-2-oxide, pyridazine-1,2-dioxide, and pyrazine-1-oxide. Azole N-oxides include 1,2,5-oxadiazole-2-oxide, pyrazole-1-oxide, and triazole-1-oxide. Synthetic strategies towards these two categories of N-oxides are fully reviewed. Corresponding reaction mechanisms towards the aromatic N-oxide frameworks and examples that use the frameworks to create high-energy substances are discussed. Moreover, the energetic properties of N-oxide energetic compounds are compared and summarized.
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Novosyolov, A., I. Olianina, I. Novoselova, Y. Vasina, Y. Ershova, T. Loik, and Yu Kudelina. "RESEARCH OF THE POSSIBILITY OF REDUCING THE CIRCULATION OF SULFUR OXIDE IN THE PRODUCTION OF WHITE CEMENT." Bulletin of Belgorod State Technological University named after. V. G. Shukhov 6, no. 7 (July 10, 2021): 89–98. http://dx.doi.org/10.34031/2071-7318-2021-6-7-89-98.
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The article discusses the possibility of reducing the circulation of sulfur oxide in the production of white cement by introducing alkaline potassium oxides K2O and sodium Na2O. A decrease in the circulation of sulfur oxide SO3 is achieved by increasing its yield in the clinker by transferring SO3 from a more sublimated compound of calcium sulfate CaSO4 to less sublimated potassium sulfates K2SO4 and sodium Na2SO4. Potassium and sodium oxides are introduced in the composition of carbonates and feldspar. The amount of introduced alkali oxides is controlled by the molar ratio A/S between sulfur oxide SO3 and alkaline oxides K2O and Na2O. It is shown that with the same molar ratio between sulfur oxide and alkaline oxides, the amount of SO3 removed with clinker depends on the ratio between potassium and sodium oxides. The higher the sodium oxide content, the more sulfur oxide comes out with the clinker and less remains to circulate in the kiln. The sublimation of sulfur oxide decreases from 70.5% - without the introduction of alkaline oxides, to 38,5 % at the maximum A/S ratio with the addition of potassium and sodium oxides in a ratio of 80:20 %. When potassium and sodium oxides are added in a ratio of 20:80%, the sublimation of sulfur oxide is reduced to
7,7 % at the same A/S ratio.
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Navrotsky, Alexandra, and Anastasia Koryttseva. "Acid–Base Properties of Oxides Derived from Oxide Melt Solution Calorimetry." Molecules 28, no. 12 (June 7, 2023): 4623. http://dx.doi.org/10.3390/molecules28124623.
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The paper analyzes the relationships among acid–base interactions in various oxide systems and their thermodynamics. Extensive data on enthalpies of solution of binary oxides in oxide melts of several compositions, obtained by high-temperature oxide melt solution calorimetry at 700 and 800 °C, are systematized and analyzed. Oxides with low electronegativity, namely the alkali and alkaline earth oxides, which are strong oxide ion donors, show enthalpies of solution that have negative values greater than −100 kJ per mole of oxide ion. Their enthalpies of solution become more negative with decreasing electronegativity in the order Li, Na, K and Mg, Ca, Sr, Ba in both of the commonly used molten oxide calorimetric solvents: sodium molybdate and lead borate. Oxides with high electronegativity, including P2O5, SiO2, GeO2, and other acidic oxides, dissolve more exothermically in the less acidic solvent (lead borate). The remaining oxides, with intermediate electronegativity (amphoteric oxides) have enthalpies of solution of between +50 and −100 kJ/mol, with many close to zero. More limited data for the enthalpies of solution of oxides in multicomponent aluminosilicate melts at higher temperature are also discussed. Overall, the ionic model combined with the Lux–Flood description of acid–base reactions provide a consistent and useful interpretation of the data and their application for understanding the thermodynamic stability of ternary oxide systems in solid and liquid states.
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Nizhnik, Yakov P., Erin Hansen, Cayden Howard, Matthias Zeller, and Sergiy V. Rosokha. "Complexes of Zinc-Coordinated Heteroaromatic N-Oxides with Pyrene: Lewis Acid Effects on the Multicenter Donor–Acceptor Bonding." Molecules 29, no. 14 (July 13, 2024): 3305. http://dx.doi.org/10.3390/molecules29143305.
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4-Nitroquinoline-N-oxide (NQO) and 4-nitropyridine-N-oxide (NPO) are important precursors for the synthesis of substituted heterocycles while NQO is a popular model mutagen and carcinogen broadly used in cancer research; intermolecular interactions are critical for their reactions or functioning in vivo. Herein, the effects of the coordination of N-oxide’s oxygen atom to Lewis acids on multicenter donor–acceptor bonding were explored via a combination of experimental and computational studies of the complexes of NQO and NPO with a typical π-electron donor, pyrene. Coordination with ZnCl2 increased the positive electrostatic potentials on the surfaces of these π-acceptors and lowered the energy of their LUMO. Analogous effects were observed upon the protonation of the N-oxides’ oxygen or bonding with boron trifluoride. The interaction of ZnCl2, NPO, or NQO and pyrene resulted in the formation of dark co-crystals comprising π-stacked Zn-coordinated N-oxides and pyrene similar to that found with protonated or (reported earlier) BF3-bonded N-oxides. Computational studies indicated that the coordination of N-oxides to zinc(II), BF3, or protonation led to the strengthening of the multicenter bonding of the nitro-heterocycle with pyrene, and this effect was related both to the increased electrostatic attraction and molecular–orbital interactions in their complexes.
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Johnson, Haden A., Darby Donaho, Aya Ali, Amisha Parekh, Randall S. Williamson, Mary E. Marquart, Joel D. Bumgardner, Amol V. Janorkar, and Michael D. Roach. "Photocatalytic Activity and Antibacterial Properties of Mixed-Phase Oxides on Titanium Implant Alloy Substrates." Coatings 14, no. 5 (May 9, 2024): 595. http://dx.doi.org/10.3390/coatings14050595.
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Titanium alloys are commonly used for implants, but the naturally forming oxides are bioinert and not ideal for bacterial resistance or osseointegration. Anodization processes are a modification technique that can crystallize the oxides, alter oxide surface topography, and introduce beneficial chemistries. Crystalline titanium oxides are known to exhibit photocatalytic activity (PCA) under UVA light. Anodization was used to create mixed-phase oxides on six titanium alloys including commercially pure titanium (CPTi), Ti-6Al-4V (TAV), Ti-6Al-7Nb (TAN), two forms of Ti-15Mo (TiMo-β and TiMo-αβ), and Ti-35Nb-7Zr-5Ta (TNZT). Combined EDS and XPS analyses showed uptake of the electrolyte and substrate alloying elements into the oxides. The relative oxide PCA was measured using methylene blue degradation assays. CPTi and TAN oxides exhibited increased PCA compared to other alloys. Combined XRD and EBSD oxide phase analyses revealed an unfavorable arrangement of anatase and rutile phases near the outermost surfaces, which may have reduced PCA for other oxides. The relative Staphylococcus aureus attachment to each oxide was also assessed. The CPTi and TiMo-αβ oxides showed significantly reduced S. aureus attachment after 1 h of UVA compared to un-anodized CPTi. Cell culture results verified that the UVA irradiation did not negatively influence the MC3T3-E1 attachment or proliferation on the mixed-phase oxides.
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Takagaki. "Rational Design of Metal Oxide Solid Acids for Sugar Conversion." Catalysts 9, no. 11 (October 29, 2019): 907. http://dx.doi.org/10.3390/catal9110907.
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Aqueous-phase acid-catalyzed reactions are essential for the conversion of cellulose-based biomass into chemicals. Brønsted acid and Lewis acid play important roles for these reactions, including hydrolysis of saccharides, isomerization and epimerization of aldoses, conversion of d-glucose into 5-hydroxymethylfurfural, cyclodehydration of sugar alcohols and conversion of trioses into lactic acid. A variety of metal oxide solid acids has been developed and applied for the conversion of sugars so far. The catalytic activity is mainly dependent on the structures and types of solid acids. Amorphous metal oxides possess coordinatively unsaturated metal sites that function as Lewis acid sites while some crystal metal oxides have strong Brønsted acid sites. This review introduces several types of metal oxide solid acids, such as layered metal oxides, metal oxide nanosheet aggregates, mesoporous metal oxides, amorphous metal oxides and supported metal oxides for sugar conversions.
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Himbert, Gerhard, Dieter Faul, and Michael Barz. "Cycloadditionen, XIX. Umsetzungen von Butadiinyl- und Hexatriinyl-amin-Derivaten mit Nitriloxiden /Cycloadditions, XIX. Reactions of Butadiynyl- and Hexatriynyl-amine Derivatives with Nitrile Oxides." Zeitschrift für Naturforschung B 46, no. 7 (July 1, 1991): 955–68. http://dx.doi.org/10.1515/znb-1991-0715.
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Butadiyn- and hexatriynamines 1 a - g, bearing silyl-, trichlorvinyl- and amino groups, resp. in the ω-position of their acetylenic system add nitrile oxides 3 at their first C/C-triple bond to give the 5-aminoisoxazoles 4, whereas the analogous oligoynamines 1 i-l, bearing a hydrogen in the ω-position, add the nitrile oxides 3 at their terminal C/C-triple bond to give the (5-isoxazolyl)ethynyl- or -1,3-butadiynyl-amines 7. The latter ones react with a second molecule of nitrile oxide 3 to give the bis(isoxazoles) 8. In two cases, keton oximes 6e,j are formed as the products of a 1,3-addition.
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Jiang, She Ming, Shi Jie Feng, Zhen Hua Li, and Qi Fu Zhang. "Influence of Oxide Morphologies on the Galvanizability of the Third Generation Automotive Steel." Advanced Materials Research 887-888 (February 2014): 233–39. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.233.
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Focusing on improving the galvanizability of the third generation automotive steel, the effect of surface oxides morphologies on the galvanizability was studied. The results show that the surface oxide types of sample steels by XPS analysis after annealing in different conditions are the same, only MnO and Cr2O3 were detected and no complex oxides exist on the surface. Morphologies of surface oxides can greatly influence the galvanizability of the third generation automotive steel, nodule-like oxides surface can contribute to better wettability and inhibition layer than vitreous film-like oxides surface. Galvanizing panels of nodule-like oxides surface steels only show pinhole-sized bare spots, while panels galvanized from vitreous film-like oxide surface steels reveal larger areas of bare spots and uncoated areas. Inhibition layer observed in galvanizing panels of nodule-like oxides surface steels are compact but not homogeneous, some inhibition layer grains are fine, and others are coarse. While the inhibition layer grains of panels galvanized from vitreous film-like oxide surface steels have a non-compact morphology with some particularly fine equiaxed crystals which developed deficiently.
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Pincinato, Eder de Carvalho, Patricia Moriel, and Dulcinéia Saes Parra Abdalla. "Cholesterol oxides inhibit cholesterol esterification by lecithin: cholesterol acyl transferase." Brazilian Journal of Pharmaceutical Sciences 45, no. 3 (September 2009): 429–35. http://dx.doi.org/10.1590/s1984-82502009000300007.
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Cholesterol oxides are atherogenic and can affect the activity of diverse important enzymes for the lipidic metabolism. The effect of 7β-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol, cholestan-3β,5α,6β-triol,5,6β-epoxycholesterol, 5,6α-epoxycholesterol and 7α-hydroxycholesterol on esterification of cholesterol by lecithin:cholesterol acyl transferase (LCAT, EC 2.3.1.43) and the transfer of esters of cholesterol oxides from high density lipoprotein (HDL) to low density lipoproteins (LDL) and very low density lipoproteins (VLDL) by cholesteryl ester transfer protein (CETP) was investigated. HDL enriched with increasing concentrations of cholesterol oxides was incubated with fresh plasma as source of LCAT. Cholesterol and cholesterol oxides esterification was followed by measuring the consumption of respective free sterol and oxysterols. Measurements of cholesterol and cholesterol oxides were done by gas-chromatography. 14C-cholesterol oxides were incorporated into HDL2 and HDL3 subfractions and then incubated with fresh plasma containing LCAT and CETP. The transfer of cholesterol oxide esters was followed by measuring the 14C-cholesterol oxide-derived esters transferred to LDL and VLDL. All the cholesterol oxides studied were esterified by LCAT after incorporation into HDL particles, competing with cholesterol by LCAT. Cholesterol esterification by LCAT was inversely related to the cholesterol oxide concentration. The esterification of 14C-cholesterol oxides was higher in HDL3 and the transfer of the derived esters was greater from HDL2 to LDL and VLDL. The results suggest that cholesterol esterification by LCAT is inhibited in cholesterol oxide-enriched HDL particles. Moreover, the cholesterol oxides-derived esters are efficiently transferred to LDL and VLDL. Therefore, we suggest that cholesterol oxides may exert part of their atherogenic effect by inhibiting cholesterol esterification on the HDL surface and thereby disturbing reverse cholesterol transport.
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Doremus, R. H. "Diffusion of water in crystalline and glassy oxides: Diffusion–reaction model." Journal of Materials Research 14, no. 9 (September 1999): 3754–58. http://dx.doi.org/10.1557/jmr.1999.0508.
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Diffusion of water in oxides is modeled as resulting from the solution and diffusion of molecular water in the oxide. This dissolved water can react and exchange with the oxide network to form immobile OH groups and different hydrogen and oxygen isotopes in the oxide. The model agrees with many experiments on water diffusion in oxides. The activation energy for diffusion of water in oxides correlates with the structural openness of the oxide, suggesting that molecular water is the diffusing species.
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Twum, Kwaku, Nicholas Schileru, Bianca Elias, Jordan Feder, Leena Yaqoo, Rakesh Puttreddy, Małgorzata M. Szczesniak, and Ngong Kodiah Beyeh. "Water Soluble Host–Guest Chemistry Involving Aromatic N-Oxides and Sulfonateresorcinarene." Symmetry 12, no. 11 (October 22, 2020): 1751. http://dx.doi.org/10.3390/sym12111751.
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Resorcinarenes decorated with sulfonate groups are anionic in nature and water soluble with a hydrophobic electron-rich interior cavity. These receptors are shown to bind zwitterionic aromatic mono-N-oxides and cationic di-N-oxide salts with varying spacer lengths. Titration data fit a 1:1 binding isotherm for the mono-N-oxides and 2:1 binding isotherm for the di-N-oxides. The first binding constants for the di-N-oxides (K1: 104 M−1) are higher compared to the neutral mono-N-oxide (K: 103 M−1) due to enhanced electrostatic attraction from a receptor with an electron-rich internal cavity and cationic and electron deficient N-oxides. The interaction parameter α reveals positive cooperativity for the di-N-oxide with a four-carbon spacer and negative cooperativity for the di-N-oxides that have spacers with more four carbons. This is attributed to shape complementarity between the host and the guest.
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Liu, Haiyan, Olivier Pourret, Huaming Guo, Raul E. Martinez, and Lahcen Zouhri. "Impact of Hydrous Manganese and Ferric Oxides on the Behavior of Aqueous Rare Earth Elements (REE): Evidence from a Modeling Approach and Implication for the Sink of REE." International Journal of Environmental Research and Public Health 15, no. 12 (December 12, 2018): 2837. http://dx.doi.org/10.3390/ijerph15122837.
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In this study, models were used for the first time to investigate the fate and transport of rare earth elements (REE) in the presence of hydrous manganese and ferric oxides in groundwaters from the coastal Bohai Bay (China). Results showed that REE sorption is strongly dependent on pH, as well as hydrous manganese and ferric oxide content. Higher proportions of REE were sorbed by hydrous manganese oxide as compared to hydrous ferric oxides, for example in the presence of neodymium. In this case, a mean 28% of this element was sorbed by hydrous manganese oxide, whereas an average 7% sorption was observed with hydrous ferric oxides. A contrasting REE sorption behavior was observed with hydrous manganese and ferric oxide for all investigated groundwaters. Specifically, REE bound to hydrous manganese oxides showed decreasing sorption patterns with increasing atomic number. The opposite trend was observed in the presence of hydrous ferric oxides. In addition, these results suggested that light REE (from La to Sm) rather than heavy REE (from Eu to Lu) are preferentially scavenged by hydrous manganese oxide. However, the heavy REE showed a greater affinity for hydrous ferric oxides compared to light REE. Therefore, both hydrous manganese and ferric oxide are important scavengers of REE. This study shows the implication of hydrous manganese and ferric oxide sorption for the sink of REE in groundwater.
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Read, RW, and WP Norris. "The Nucleophilic Substitution Reactions of 5- and 7-Chloro-4,6-dinitrobenzofurazan 1-Oxide by Aromatic Amines." Australian Journal of Chemistry 38, no. 3 (1985): 435. http://dx.doi.org/10.1071/ch9850435.
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7-Chloro-4,6-dinitrobenzofurazan 1-oxide is a powerful electrophile which reacts with a variety of primary and secondary aromatic amines, even those with deactivating substituents , to give arylamino - benzofurazan oxides under mild conditions. Tertiary aromatic amines react through carbon to give aminoarylbenzofurazan oxides. During, or as a consequence of, the substitution reactions, tautomerism occurs to give in all but one example an equilibrium mixture of 5- and 7-substituted 4,6-dinitrobenzofurazan oxides in which the latter predominates. Thus 5-chloro-4,6-dinitrobenzofurazan 1-oxide and 7- chloro-4,6-dinitrobenzofurazan 1-oxide both react with aniline to yield the same isomeric mixture of products: 4,6-dinitro-7- phenylaminobenzofurazan oxide (predominantly 1-oxide) (major) and 4,6- dinitro-5-phenylaminobenzofurazan 1-oxide (minor). The 5- and 7- phenylamino 4,6-dinitrobenzofurazans were prepared to assist in structural assignment of the N-oxides.
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Li, Hui Qing, Rui Xiang Zhang, Hai Wang Liu, Shi Zhi Wang, and Xian Ku Hao. "Effects of Calcination Temperature on Crystal Structure of Pr-Nd Oxides." Advanced Materials Research 233-235 (May 2011): 2918–21. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2918.
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Ammonium hydrogen carbonate is taken as the precipitating agent to prepare Pr-Nd carbonates from the raw material of Pr-Nd chloride solution. Pr-Nd oxides have been prepared at different calcination temperature in the range of 800°C-1500°C. The oxides were characterized by XRD and XPS.Calcination temperature effects on the structure of Pr-Nd oxides and the valence state of Pr in Pr-Nd oxides have been studied; Results showed that praseodymium oxide full entered into the lattices of neodymium oxide. The crystal structure changed from cubic into hexagonal system with increasing calcination temperature.The valence of Pr in Pr-Nd binary oxides are Pr3+ and Pr4+.
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T.Ch.Taghiyeva, T. Ch Taghiyeva. "X-RAY DIFFRACTION STUDY OF BINARY ZINC-OXIDE CATALYSTS." Azerbaijan Journal of Chemical News 04, no. 01 (May 30, 2022): 60–64. http://dx.doi.org/10.32010/ajcn5012022-60.
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The phase composition of binary zinc-containing catalysts was studied by X-ray diffraction. It was found that the formation of two phases of the initial oxides is observed in all the studied catalytic systems. So, samples of the Zr-Zn-O catalytic system consist of phases of zirconium and zinc oxides, samples of the Ce-Zn-O catalytic system consist of phases of cerium and zinc oxides, while samples of the Mg-Zn-O catalytic system consist of phases of magnesium and zinc oxides. It has been established that the crystallinity of binary zinc-containing catalysts varies in the range from 70% to 89%. Keywords: X-ray phase analysis, binary catalysts, zinc oxide, cerium oxide, zirconium oxide, magnesium oxide
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Kajitani, Tsuyoshi, Yuzuru Miyazaki, Kei Hayashi, Kunio Yubuta, X. Y. Huang, and W. Koshibae. "Thermoelectric Energy Conversion and Ceramic Thermoelectrics." Materials Science Forum 671 (January 2011): 1–20. http://dx.doi.org/10.4028/www.scientific.net/msf.671.1.
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Oxide thermoelectrics are relatively new materials that are workable at temperatures in the range of 400K≤T≤1200K. There are several types of thermoelectric oxide, namely, cobalt oxides (p-type semi-conductors), manganese oxides (n-type) and zinc oxides (n-type semi-conductors) for high temperature energy harvesting. The Seebeck coefficient of 3d metal oxide thermoelectrics is relatively high due to either high density of states at Fermi surfaces or spin entropy flow associated with the carrier flow. The spin entropy part dominates the Seebeck coefficient of 3d-metal oxides at temperatures above 300K. Introduction of impurity particles or quantum-well structures to enhance thermionic emission and energy filtering effects for the oxide semiconductors may lead to a significant improvement of thermoelectric performance.
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Ribis, Joël, Isabelle Mouton, Cédric Baumier, Aurélie Gentils, Marie Loyer-Prost, Laurence Lunéville, and David Siméone. "Nano-Structured Materials under Irradiation: Oxide Dispersion-Strengthened Steels." Nanomaterials 11, no. 10 (October 1, 2021): 2590. http://dx.doi.org/10.3390/nano11102590.
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Oxide dispersion-strengthened materials are reinforced by a (Y, Ti, O) nano-oxide dispersion and thus can be considered as nanostructured materials. In this alloy, most of the nanoprecipitates are (Y, Ti, O) nano-oxides exhibiting a Y2Ti2O7 pyrochlore-like structure. However, the lattice structure of the smallest oxides is difficult to determine, but it is likely to be close to the atomic structure of the host matrix. Designed to serve in extreme environments—i.e., a nuclear power plant—the challenge for ODS steels is to preserve the nano-oxide dispersion under irradiation in order to maintain the excellent creep properties of the alloy in the reactor. Under irradiation, the nano-oxides exhibit different behaviour as a function of the temperature. At low temperature, the nano-oxides tend to dissolve owing to the frequent ballistic ejection of the solute atoms. At medium temperature, the thermal diffusion balances the ballistic dissolution, and the nano-oxides display an apparent stability. At high temperature, the nano-oxides start to coarsen, resulting in an increase in their size and a decrease in their number density. If the small nano-oxides coarsen through a radiation-enhanced Ostwald ripening mechanism, some large oxides disappear to the benefit of the small ones through a radiation-induced inverse Ostwald ripening. In conclusion, it is suggested that, under irradiation, the nano-oxide dispersion prevails over dislocations, grain boundaries and free surfaces to remove the point defects created by irradiation.
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Matsumoto, Yasumichi. "Electrochemical and Photoelectrochemical Processing for Oxide Films." MRS Bulletin 25, no. 9 (September 2000): 47–50. http://dx.doi.org/10.1557/mrs2000.179.
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Metal oxides are important materials in industry. For example, there are many kinds of functional oxides: dielectric oxides such as BaTiO3 (perovskite), semiconductor oxides such as ZnO, ionic conductors such as Bi2O3, magnetic oxides such as Fe3−xMxO4 (spinel), and so on. These oxide materials must be prepared as films, nanodots, and layered films to increase their functionality for a wide variety of applications.
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Brash, Alan R., William E. Boeglin, Donald F. Stec, Markus Voehler, Claus Schneider, and Jin K. Cha. "Isolation and Characterization of Two Geometric Allene Oxide Isomers Synthesized from 9S-Hydroperoxylinoleic Acid by Cytochrome P450 CYP74C3." Journal of Biological Chemistry 288, no. 29 (May 24, 2013): 20797–806. http://dx.doi.org/10.1074/jbc.m113.482521.
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Specialized cytochromes P450 or catalase-related hemoproteins transform fatty acid hydroperoxides to allene oxides, highly reactive epoxides leading to cyclopentenones and other products. The stereochemistry of the natural allene oxides is incompletely defined, as are the structural features required for their cyclization. We investigated the transformation of 9S-hydroperoxylinoleic acid with the allene oxide synthase CYP74C3, a reported reaction that unexpectedly produces an allene oxide-derived cyclopentenone. Using biphasic reaction conditions at 0 °C, we isolated the initial products and separated two allene oxide isomers by HPLC at −15 °C. One matched previously described allene oxides in its UV spectrum (λmax 236 nm) and NMR spectrum (defining a 9,10-epoxy-octadec-10,12Z-dienoate). The second was a novel stereoisomer (UV λmax 239 nm) with distinctive NMR chemical shifts. Comparison of NOE interactions of the epoxy proton at C9 in the two allene oxides (and the equivalent NOE experiment in 12,13-epoxy allene oxides) allowed assignment at the isomeric C10 epoxy-ene carbon as Z in the new isomer and the E configuration in all previously characterized allene oxides. The novel 10Z isomer spontaneously formed a cis-cyclopentenone at room temperature in hexane. These results explain the origin of the cyclopentenone, provide insights into the mechanisms of allene oxide cyclization, and define the double bond geometry in naturally occurring allene oxides.
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Zhang, Yuzhe, Bin Wang, Qian Cheng, Xinling Li, and Zhongyu Li. "Removal of Toxic Heavy Metal Ions (Pb, Cr, Cu, Ni, Zn, Co, Hg, and Cd) from Waste Batteries or Lithium Cells Using Nanosized Metal Oxides: A Review." Journal of Nanoscience and Nanotechnology 20, no. 12 (December 1, 2020): 7231–54. http://dx.doi.org/10.1166/jnn.2020.18748.
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How to remove harmful heavy metal ions from waste batteries or lithium cells efficiently has been the focus of scholars. More and more metal oxides had been used to deal with the pollution of heavy metal caused by waste batteries in recent years. Nanostructured metal oxides have great potential because of their large comparative areas. The adsorption for these heavy metal ions can be further improved by using modified metal oxides as adsorbents. At present, iron oxide is widely used in this field. Other metal oxides have also been studied in removing these heavy metal ions. Compared to other metal oxides, the adsorbents made of iron oxide are easy to be separated from the reaction system. pH value in the solution can affect the activity of adsorption sites on metal oxides adsorbents and change the distribution of ions in solution. As a result, pH value can significantly influence the adsorption of metal oxides adsorbents for heavy metal ions from waste batteries or lithium cells.
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Lowther, J. E. "Superhard Ceramic Oxides." MRS Bulletin 28, no. 3 (March 2003): 189–93. http://dx.doi.org/10.1557/mrs2003.61.
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AbstractOxide-based ceramic materials are rapidly proving to have exciting potential for application as hard coatings. The most commonly known oxide material is silica, with a well-known variety of polytypes. Many other oxides, especially those involving metals, are now also proving to be important for a variety of applications where, because of the chemical role played by metal d electrons, large oxygen coordinations can be sustained. Properties of a variety of oxides—from silica to metal-based oxides—are discussed, and the role of predictive computer modeling is shown to be valuable in guiding the search for potentially new superhard oxides.
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Cheung, Kin P. "On the “intrinsic” breakdown of thick gate oxide." Journal of Applied Physics 132, no. 14 (October 14, 2022): 144505. http://dx.doi.org/10.1063/5.0118081.
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The thick gate oxide breakdown mechanism has become an important topic again due to the rising demand for power electronics. The failure of the percolation model in explaining the observed Weibull shape factor, β, seriously hampers the establishment of thick gate oxide breakdown models and the ability to project reliability from measurement data. In this work, lifetime shortening by oxide defects is simulated to produce degraded breakdown distributions that match experimentally observed βs. The result shows that even a low density of defects with the right energy is enough to greatly degrade β for thick oxides. Strong area scaling for thin oxides counters this sensitivity to defects effectively and explains why the percolation model is successful in thin oxides but not in thick oxides. Only defects with the appropriate energy can degrade the breakdown distribution. The required energy is consistent with oxygen vacancy Eγ′ defect after capturing a hole and the concentration required is consistent with very high-quality oxide. This explains the consistent low β values for thick oxides universally reported in the literature.
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JIANG, ZHI, HAIRONG ZHANG, ZHONGPENG WANG, MINGXIA CHEN, and WENFENG SHANGGUAN. "SIMULTANEOUSLY CATALYTIC REMOVAL OF NOx AND SOOT ON RARE EARTH ELEMENT OXIDE LOADED WITH POTASSIUM AND TRANSITION NANOSIZED METAL OXIDES." Nano 03, no. 04 (August 2008): 239–44. http://dx.doi.org/10.1142/s1793292008001088.
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The simultaneous catalytic removal of NO x and soot over the rare earth element (REE) oxide-based mixture oxides loaded with potassium and transition nanosized metal oxide (designated as M/K/REE oxide) was investigated by using temperature-programmed reaction (TPR). The influence of the type of REE oxides together with the type and amount of transitional metal oxides on the catalytic removal activity was discussed. K / Nd 2 O 3 was found to be the most active oxide among the REE oxides to simultaneous remove the NO x and soot under lean conditions. Chromium oxide was more active than the other transition metal oxides on enhancing the activity of soot oxidation of Nd 2 O 3 loaded with potassium. The optimum loading level of chromium was about 10 wt%, with ignition temperature at about 237°C and the conversion ratio NO → N 2 about 24.1%. The Mn -loading on K / Nd 2 O 3 resulted in the biggest conversion efficiency of NO to N 2 at about 30.2%. The increasing catalytic reaction of NO x–soot activities is attributed to the formation of complex crystalline phase in the catalyst together with the improving contacting between catalysts and soot.
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Mańkowska, Ewa, and Michał Mazur. "Gas sensing properties of mixtures of copper and titanium oxides thin films." Bulletin of the Military University of Technology 72, no. 1 (March 31, 2023): 37–46. http://dx.doi.org/10.5604/01.3001.0054.2895.
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The subject of the current studies were mixtures of copper and titanium oxide thin films,with various elemental compositions, deposited by magnetron sputtering and annealed in the postprocess.The effect of elemental composition and annealing temperature on the morphology of thinfilms was determined using scanning electron microscope images. The crystal structure and chemicalcomposition of copper‒titanium oxide (CuTi)Ox mixtures were investigated by X-ray diffraction.Hydrogen gas sensing experiments were performed for hydrogen with concentrations ranging from 100to 1,000 ppm. The resistance of the prepared (CuTi)Ox mixtures increased during hydrogen exposure,demonstrating the applicability of these oxides in hydrogen sensing. In addition, better sensor responseswere obtained for the mixtures in comparison to single copper oxides or titanium oxides. Mixturesof copper oxides and titanium oxides may be promising materials for hydrogen sensor applications.Keywords: mixtures of copper and titanium oxides, hydrogen gas sensors, mixed copper and titaniumoxides, thin films, magnetron sputtering
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Zhang, Yuelin, Jilei Chen, Jinxing Zhang, and Haiming Yu. "Oxide magnonics: Spin waves in functional magnetic oxides." Applied Physics Reviews 9, no. 4 (December 2022): 041312. http://dx.doi.org/10.1063/5.0112794.
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Spin waves or their quanta magnons are collective excitations in magnetically ordered materials. Magnonics have recently attracted tremendous interest for building next-generation nanoscale devices and circuits with low-power consumption. Oxide materials provide an excellent platform for achieving highly efficient spin-wave excitation and transmission for magnonic applications with versatile functionalities. In this article, we review some recent advances for oxide-based magnonics, including both magnetic oxides for hosting spin waves and non-magnetic oxides for manipulating spin waves. First, we introduce recent development on coherent propagation and incoherent transport of magnons in thin-film iron garnets, low-damping ferrimagnetic oxides widely used in magnonics. Then, we discuss spin-wave chirality due to the inversion symmetry broken in magnetic oxides. Magnonics in antiferromagnetic oxides is also presented, where the spin-wave resonance frequency enters THz regime. Nanoscale spin textures, such as magnetic skyrmions, can be stabilized in magnetic oxides, and provide additional versatilities by coupling their dynamics with spin waves. Last but not the least, we highlight the electrical control of spin waves based on multiferroic oxides toward applications for hybrid magnonics.
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Kong, Hui, Xiang Cheng, Shoulin Huang, and Yue Qiu. "Inclusion Characteristics in Steel with CeO2 Nanoparticle Addition." Metals 12, no. 11 (November 21, 2022): 1994. http://dx.doi.org/10.3390/met12111994.
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The application of Ce oxides in oxide metallurgy has received extensive attention, but until now, the direct adding of CeO2 into molten steel to generate Ce oxides has not occurred. In this paper, a mixture of CeO2 and Si nanoparticles were added into molten steel. The resultant formation of micrometer scale Ce-bearing oxides confirmed its adding validity. This behavior may be interpreted as the reactivity between CeO2 and [Al], and the improved wettability between CeO2 and molten steel with the assistance of Si powder. Thus, when the quantity of CeO2 is kept constant, its added yield should increase when increasing the added quantity of Si. This was verified by the larger percentage of Ce-bearing oxides of the total oxides and the greater average content of Ce in Ce-bearing oxides after normalization. Moreover, compared with the blank sample, statistical results indicated that the oxides in CeO2-modified samples were refined, and their dispersion homogeneity was enhanced. This comparison indicates the effectiveness of the external adding method in oxide metallurgy.
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Plemiannikov, Mykola, and Nataliіa Zhdanіuk. "Determination of the influence of temperature, concentration of ferric oxides and oxidative conditions of glass boiling on the displacement of the equilibrium of ferric oxides Fе2O3↔FеO." Technology audit and production reserves 3, no. 1(71) (June 29, 2023): 10–14. http://dx.doi.org/10.15587/2706-5448.2023.283267.
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The object of research is the state of equilibrium of ferrum(II) and ferrum(III) oxides in glass melts at temperatures of 1000–1400 °С, welded in oxidizing, neutral and reducing conditions with a content of ferrum oxides up to 1.5 %. This problem is relevant in the following aspects. The first aspect of this problem is the unwanted coloring of the glass: FeO colors the glass blue, and Fe2O3 – yellow. The combined presence of ferrum(II) oxide and ferrum(III) oxide determines the gradations of glass shades that fall on the green spectrum. The second aspect concerns the thermophysics of processes of boiling glasses containing iron oxides. Ferrum(II) oxide causes a strong absorption band of infrared radiation in the region of 1.1 μm. This becomes an obstacle to the volumetric heating of glass in the processes of cooking, forming, and annealing. The third aspect of the problem concerns the structure of glasses and glass-crystalline materials with an increased content of iron oxides. Iron oxides significantly affect the processes of glass structuring, as ferrum(III) oxide is a typical network former, and ferrum(II) oxide is a typical modifier. The state of FeO↔Fe2O3 equilibrium in glass is significantly influenced by the glass cooking environment, the total amount of iron oxides, and the temperature of the melt. The glass brewing environment has the greatest influence on the balance of iron oxides in the glass. The share of FeO oxide in the total amount of iron oxides (FeO+Fe2O3) increases sharply when moving from an oxidizing medium to a neutral one and then to a reducing one. During thermostating at a temperature of 1400 °С, the proportion of FeO in the glass increases by 1.4–1.7 times during cooking in an oxidizing environment, by 1.2–1.3 times in a neutral environment, and by approximately 1.1 times in a reducing environment. At the same time, this growth is more noticeable in glasses with a lower iron content. Thus, the equilibrium state of FeO↔Fe2O3 in glass significantly affects the technological and operational properties of silicate melts and the final glass. The ratio of formed oxides of trivalent and divalent ferrum was studied by chemical (titrometric) analysis. The research results can be used in practice to develop the composition of glasses with an increased content of iron oxides.
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Gulla, Mahendra, Lars Bierer, Stefan Schmidt, Leo Redcliffe, and Volker Jäger. "Bromocyclization of Unsaturated Oximes. Synthesis of Five-Membered Cyclic Nitrones (Pyrroline N-Oxides)." Zeitschrift für Naturforschung B 61, no. 4 (April 1, 2006): 471–85. http://dx.doi.org/10.1515/znb-2006-0414.
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The cyclization of a ribose-derived pentenose oxime with various halogen electrophiles showed bromine to be the most effective reagent, leading to 80% of L-lyxo/D-ribo-pyrroline N-oxides in an 84:16 diastereomeric ratio. In order to explore the scope of this facile process, several other γ,δ - unsaturated oximes were submitted to this reaction. Depending on the substitution pattern, 23 - 87%, yields of pyrroline N-oxides of were registered. With α-allyl-β -ketoester oximes the alkoxycarbonyl group proved a similar (ethoxy) or even better (t-butoxy) trapping nucleophile, leading preferentially to the corresponding bromolactone oxime. - With 2,2-dimethyl-3-butene aldoxime, the corresponding 3-bromopyrroline N-oxide was formed, due to a formal, unusual N-endo cyclization to the chain terminus. This was exploited for a new access to six-membered nitrones from a γ,δ -pentene aldoxime, with addition of Br/OH to the C=C of the 4-pentenal first, and oximation/cyclization following then
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Pham Thi, Ho, Ngan Pham Thi Thanh, and Binh Nguyen Thanh. "Synthesis, characterization and catalytic activity estimation of WO3/MeO2 (Me: Zr, Ti, Si) oxides for fructose conversion reaction into 5-hydroxymethylfurfural." Vietnam Journal of Catalysis and Adsorption 10, no. 3 (August 20, 2021): xx. http://dx.doi.org/10.51316/jca.2021.054.
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Series of WO3/MeO2(Me: Zr, Ti, Si) oxides were synthesized by impregnationmethod with 1:9 atomic ration of W:Me.The oxides were characterized by various techniques such as XRD, IR. The XRD patterns showed the crystalline structure of ZrO2, TiO2,WO3 and amorphous of SiO2. They were formed in tetragonal, anatase, monoclinic phase structure. All oxide and mixed oxides were estimated its catalytic activity through fructose conversion into 5-hydroxymethylfurfural in DMSO solvent. The results indicated that all mixed oxides owned good catalytic activity for the reaction in comparison with case of only presence DMSO solvent. Especially, The oxide WO3/ZrO2 showed the best HMF yield, 81,6%, at experimental conditions. This property could be due to the well dispersionand acidity of nano cluster WO3 on the surface s of oxides MeO2.
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Grieb, Michael, Masato Noborio, Dethard Peters, Anton J. Bauer, Peter Friedrichs, Tsunenobu Kimoto, and Heiner Ryssel. "Electrical Characterization of MOS Structures with Deposited Oxides Annealed in N2O or NO." Materials Science Forum 615-617 (March 2009): 521–24. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.521.
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In this work, the electrical characteristics and the reliability of 80nm thick deposited oxides annealed in NO and N2O on the 4H-SiC Si-face for gate oxide application in MOS devices is analyzed by C-V, I-V measurements and by constant current stress. Compared to thermally grown oxides, the deposited oxides annealed in N2O or NO showed improved electrical properties. Dit-values lower than 1011cm-2eV-1 have been achieved for the NO sample. The intrinsic QBD-values of deposited and annealed oxides are one order of magnitudes higher than the highest values reported for thermally grown oxides. Also MOSFETS were fabricated with a channel mobility of 20.05 cm2/Vs for the NO annealed deposited oxide. Furthermore annealing in NO is preferred to annealing in N2O regarding µFE- and QBD-values.
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Christopher Braddock, D., Areeb Mahtey, Henry S. Rzepa, and Andrew J. P. White. "Stable bromoallene oxides." Chemical Communications 52, no. 75 (2016): 11219–22. http://dx.doi.org/10.1039/c6cc06395k.
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Grieb, Michael, Dethard Peters, Anton J. Bauer, Peter Friedrichs, and Heiner Ryssel. "Influence of the Oxidation Temperature and Atmosphere on the Reliability of Thick Gate Oxides on the 4H-SiC C(000-1) Face." Materials Science Forum 600-603 (September 2008): 597–602. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.597.
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The reliability of thermal oxides grown on n-type 4H-SiC C(000-1) face wafer has been investigated. In order to examine the influence of different oxidation atmospheres and temperatures on the reliability, metal-oxide-semiconductor capacitors were manufactured and the different oxides were characterized by C-V measurements and constant-current-stress. The N2O-oxides show the smallest flat band voltage shift compared to the ideal C-V curve and so the lowest number of effective oxide charges. They reveal also the lowest density of interface states in comparison to the other oxides grown on the C(000-1) face, but it is still higher than the best oxides on the Si(000-1) face. Higher oxidation temperatures result in smaller flat band voltage shifts and lower interface state densities. Time to breakdown measurements show that the charge-to-breakdown value of 63% cumulative failure for the N2O-oxide on the C(000-1) face is more than one order of magnitude higher than the highest values measured on the Si(000-1) face. Therefore it can be concluded that a smaller density of interface states results in a higher reliability of the oxide.
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Zhang, Lin, Di Lun Sheng, Rui Zhang, En Yi Chu, Ju Peng Liu, and Sheng Li Zhou. "Preparation of Self-Assembled Iron Oxide Nanorings with Nano-Aluminum." Applied Mechanics and Materials 446-447 (November 2013): 210–13. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.210.
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To make fuels and oxides react better, Iron oxide nanoring was synthesized using hydrothermal method and then self-assembled with nano aluminum particles. Iron oxide were characterized by hollow column morphology with outer diameters of 200-240nm, inner diameters of 90-120nm and heights of 120-150nm using SEM and TEM. Iron oxide and aluminum were evenly distributed and contact closely by self-assembly.The touch of fuels and oxides increased effectively.While the ultrasonically-mixed sample scattered randomly and aggregated seriously. Self-assembly is proved to be a effective method for the touch and distribution of oxides and fuels.
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Hubbard, K. J., and D. G. Schlom. "Thermodynamic stability of binary oxides in contact with silicon." Journal of Materials Research 11, no. 11 (November 1996): 2757–76. http://dx.doi.org/10.1557/jmr.1996.0350.
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Using tabulated thermodynamic data, a comprehensive investigation of the thermo-dynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient data exist to conclude that all binary oxides except the following are thermodynamically unstable in contact with silicon at 1000 K: Li2O, most of the alkaline earth oxides (BeO, MgO, CaO, and SrO), the column IIIB oxides (Sc2O3, Y2O3, and Re2O3, where Re is a rare earth), ThO2, UO2, ZrO2, HfO2, and Al2O3. Of these remaining oxides, sufficient data exist to conclude that BeO, MgO, and ZrO2 are thermodynamically stable in contact with silicon at 1000 K. Our results are consistent with reported investigations of silicon/binary oxide interfaces and identify candidate materials for future investigations.
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Rasheed, Sufian, Niamat Ullah, and Amir Ullah. "Chemical analysis of some Pakistani Portland cement/clinker and their compliance with ASTM standards." European Journal of Chemistry 11, no. 3 (September 30, 2020): 194–97. http://dx.doi.org/10.5155/eurjchem.11.3.194-197.1980.
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This is a quality control study and analysis of Portland cement taken from four Pakistani cement plants (Deewan, Kohat, Lucky and Maple Leaf). These four samples were analysed and the determination of major oxides present was carried out. Loss on ignition and the percentage of insoluble residue was also determined. Our research shows percentage of major oxides present in these four samples i.e. calcium oxide, silicon dioxide, aluminium oxide, iron oxide, sulphur trioxide and magnesium oxide. According to the American Society for Testing and Materials Cement (ASTM C150), the percentage of these oxides, loss on ignition and insoluble residue of these four plants are within the specified quality control range. The present study compared the quality of different oxides at the Portland cement brands in Pakistan. The percentages of SiO2,SO3, CaO, Al2O3,MgO and Fe2O3 were calculated according to American Society for Testing and Materials (ASTM C150) uniform standards. The percentages of all of the brands were within the limits specified by the standard (ASTM C150).
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Alam, Mir Waqas, Muhammad Aamir, Mohd Farhan, Maryam Albuhulayqah, Mohamad M. Ahmad, C. R. Ravikumar, V. G. Dileep Kumar, and H. C. Ananda Murthy. "Green Synthesis of Ni-Cu-Zn Based Nanosized Metal Oxides for Photocatalytic and Sensor Applications." Crystals 11, no. 12 (November 26, 2021): 1467. http://dx.doi.org/10.3390/cryst11121467.
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The preparation, characterization, and application of Nickel oxide (NiO)–Copper oxide (CuO)–Zinc oxide (ZnO) transition nanometal oxides have significantly enhanced their tunable properties for superior multifunctional performances compared with well-known metal oxides. NiO–CuO–ZnO nano transition metal oxides were synthesized by a simple eco-friendly solution combustion method. X-ray diffraction studies revealed distinct phases such as monoclinic, cubic, and hexagonal wurtzite for CuO, NiO, and ZnO, respectively, with NiO having the highest composition. The particle sizes were found to be in the range between 25 and 60 nm, as determined by powder X-ray diffraction. The energy bandgap values were found to be 1.63, 3.4, and 4.2 eV for CuO, ZnO, and NiO, respectively. All metal oxides exhibited a moderate degradation efficiency for AR88 dye. The results of ultraviolet–visible absorption spectra helped identify the bandgap of metal oxides and a suitable wavelength for photocatalytic irradiation. Finally, we concluded that the electrochemical studies revealed that the synthesized materials are well suitable for sensor applications.
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Liu, Hong Bo, Wu Ying Zhang, Feng Lin, and Hong Da Cao. "Comparison and Characterization of Two Preparation Methods of Graphene Oxide." Advanced Materials Research 989-994 (July 2014): 125–29. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.125.
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The graphene oxides were prepared form graphite by thermal expansion and ultrasonic dispersion. The structure of graphene oxides was characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectra. The difference of structure of graphene oxides by two preparation methods was compared. The measurement of FTIR and XRD showed the graphite was completely oxidized. The graphene oxide prepared by thermal expansion would lose large number of active functional groups, such as hydroxyl, carboxyl group, et al. However, the graphene oxide prepared by ultrasonic dispersion can retain these active functional groups. These active functional groups will be benefit to chemically modify the graphene oxides and prepare the polymer/graphene nanocomposites.
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Zinchenko, V. F., V. V. Menchuk, and L. V. Sadkovska. "ELECTRONEGATIVITY AS A FACTOR OF STABILIZATION OF VALENCE STATES IN COMPLEX OXIDES OF p- AND d-ELEMENTS." Odesa National University Herald. Chemistry 27, no. 2(82) (November 16, 2022): 35–41. http://dx.doi.org/10.18524/2304-0947.2022.2(82).264883.
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From the thermodynamic standpoint, the stability of valence states in binary and complex oxides of d- and p-metals is considered by the change in the free Gibbs energy in the oxidation-reduction reactions. The presence of a correlation between a valence state of a metal and the electronegativity of its oxide has been established. Thus, metals in the lowest valence state M(II) – (Mn(II), Fe(II), Tl(I), Pb(II)) have low (less than 1.5 еV1/2/O2-) values of electronegativity and reveal predominantly basic properties. Their oxides are undergone to oxidation reactions with increasing valence states of M(III) or M(IV) and, accordingly, electronegativities with conversion to amphoteric oxides. The essence of the stabilization of the lowest state is the binding of binary oxides of metals in complex oxide compounds (oxosalts), and the stabilization can be represented as the difference between the electronegativities of oxides. It is established that with a certain difference of electronegativities the stabilization of the valence state increases significantly, and in some cases complete stability is realized. The motive force of the process of stabilization of the lower valence state is the increase of the ionicity of the bond in the complex oxide compared to the binary oxide. Instead, metal oxides in the highest valence states (M(IV), M(VI)) have high (above 2 еV1/2/O2-) values of electronegativities and exhibit mainly acidic properties. Under reducing conditions, they undergo reduction to lower valence states (M(III), (M(IV)), again acquiring amphoteric properties to form complex oxide compounds with higher oxides. Although the stability values of the valence states of these oxides are quite high at normal amphoteric pressure, their further stabilization is possible. The essence of the process, as in the previous part, is to increase the ionicity of the bonds between the low-valent metal and polyhedron, and most importantly – to increase the covalence of the high-valent metal-oxygen bonds in the latter. It should be noted that the stabilization effect in this case also depends on the difference between the electronegativities of the oxides – basic and stabilizing. Thus, using data from the electronegativities of metal oxides, which show the instability of a valence state, it is possible to effectively carry out the processes of their stabilization.
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Zhao, Yan, Lei Liu, Dengcui Yang, Weinan Li, Jianlin Yu, and Zhengzhi Zhao. "Analysis of the Oxidation Behavior and Formation of an Extremely Thin Oxide Layer with a Novel Hot-Stamped Steel." Metals 14, no. 7 (June 27, 2024): 760. http://dx.doi.org/10.3390/met14070760.
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This study investigates enhancing the high-temperature oxidation resistance of hot-stamped steels by adding the Cr/Mn/Si elements to form an extremely thin oxide layer. Under low oxygen partial pressure conditions and high Cr content in the matrix, the oxide layer of a 38Cr3MnNbVMo hot-rolled plate containing the Mo element and high Si content was further thinned to 0.6 μm after cooling at 900 °C for 5 min. The structure of the ultra-thin oxide layer consists of Fe3O4, Mn oxides, FeCr2O4, Cr2O3, and Fe2SiO4 oxides. Compared to other antioxidant elements, under low oxygen partial pressure conditions, Si is more prone to oxidation, forming ultra-thin (22 nm) Fe2SiO4 oxides at the matrix interface. Combined with Cr2O3, FeCr2O4, and Mn oxides, it collectively inhibits the mutual diffusion of external O ions and matrix Fe ions. Furthermore, the addition of the Mo element improves the oxidation resistance. The synergistic effect of multiple powerful oxidation-resistant elements and oxide products effectively inhibits the growth of the iron oxide scale, enhancing the oxidation resistance of hot-rolled, hot-stamped steel.
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Nelson, Yarrow M., Leonard W. Lion, William C. Ghiorse, and Michael L. Shuler. "Production of Biogenic Mn Oxides by Leptothrix discophora SS-1 in a Chemically Defined Growth Medium and Evaluation of Their Pb Adsorption Characteristics." Applied and Environmental Microbiology 65, no. 1 (1999): 175–80. http://dx.doi.org/10.1128/aem.65.1.175-180.1999.
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Biogenic Mn oxides were produced by the bacterium Leptothrix discophora SS-1 (= ATCC 3182) in a chemically defined mineral salts medium, and the Pb binding and specific surface area of these oxides were characterized. Growth of SS-1 in the defined medium with pyruvate as a carbon and energy source required the addition of vitamin B12. Complete oxidation of Mn(II) within 60 h required the addition of ≥0.1 μM FeSO4. Pb adsorption isotherms were determined for the biogenic Mn oxides (and associated cells with their extracellular polymer) and compared to the Pb adsorption isotherms of cells and exopolymer alone, as well as to abiotic Mn oxides. The Pb adsorption to cells and exopolymer with biogenic Mn oxides (0.8 mmol of Mn per g) at pH 6.0 and 25°C was 2 orders of magnitude greater than the Pb adsorption to cells and exopolymer alone (on a dry weight basis). The Pb adsorption to the biogenic Mn oxide was two to five times greater than the Pb adsorption to a chemically precipitated abiotic Mn oxide and several orders of magnitude greater than the Pb adsorption to two commercially available crystalline MnO2 minerals. The N2Brunauer-Emmet-Teller specific surface areas of the biogenic Mn oxide and fresh Mn oxide precipitate (224 and 58 m2/g, respectively) were significantly greater than those of the commercial Mn oxide minerals (0.048 and 4.7 m2/g). The Pb adsorption capacity of the biogenic Mn oxide also exceeded that of a chemically precipitated colloidal hydrous Fe oxide under similar solution conditions. These results show that amorphous biogenic Mn oxides similar to those produced by SS-1 may play a significant role in the control of trace metal phase distribution in aquatic systems.
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Nowick, Arthur S. "Defects in Ceramic Oxides." MRS Bulletin 16, no. 11 (November 1991): 38–41. http://dx.doi.org/10.1557/s0883769400055500.
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The topic that I am attempting to cover easily requires a whole book to do it justice. To deal with it in a short article, I will focus on a few basic principles that dominate the behavior of defects in oxides and then present some examples taken from well-studied and relatively well-understood materials.The study of defects in oxides differs from the study of defects in metals and alloys or in semiconductors in several important ways. First, oxides generally have very high melting points so that intrinsic point defect concentrations at temperatures below ~1500°C are usually negligibly small. Second, an oxide does not always maintain the composition at which it was fabricated, as alloys do, but can exchange oxygen with the ambient atmosphere, according to the ambient partial pressure of oxygen, P(O2). Thus, the stoichiometry, and accordingly the defect concentration, can be controlled by annealing in a specific P(O2) atmosphere. Third, and most important, oxides have a high degree of ionicity so that most point defects possess an effective charge. The consequences of this fact are far reaching; some of them are as follows:1. In a binary oxide, e.g. a metal oxide (MO), there are two sublattices. The diffusion of cations and of anions proceeds each on its own sublattice, involving different point defects. Accordingly, cation and anion diffusion rates can be very different and, in fact, usually are.
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Saito, Suguru, Yoshiya Hagimoto, Hayato Iwamoto, and Yusuke Muraki. "Mechanism of Plasma-Less Gaseous Etching Process for Damaged Oxides from the Ion Implantation Process." Solid State Phenomena 145-146 (January 2009): 227–30. http://dx.doi.org/10.4028/www.scientific.net/ssp.145-146.227.
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Recently, plasma-less gaseous etching processes have attracted attention for their interesting etching properties. Previously, we reported on the etching properties of theses processes for various kinds of oxides and revealed that they reduce the etch rate of the chemical-vapor-deposited (CVD) oxides more than the conventional wet etching process does [1]. Our results also revealed that depressions called divots in the CVD oxide of the shallow trench isolation (STI) became smaller in size by substituting a plasma-less gaseous etching process for the conventional wet etching process. In semiconductor manufacturing, many processes are used to remove oxides damaged during ion implantation or reactive ion etching on the device surface. Therefore, it is very important to understand the etching properties of plasma-less gaseous etching processes for damaged oxides as well as those for other kinds of oxides. In this report, we evaluate the etching properties of one particular plasma-less gaseous etching process for oxide films damaged during the ion implantation process under various conditions and discuss the mechanism of interesting etching properties for the damaged oxides.
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Kobędza, Piotr, Aleksandra Smejda-Krzewicka, and Krzysztof Strzelec. "The Use of Copper Oxides as Cross-Linking Substances for Chloroprene Rubber and Study of the Vulcanizates Properties. Part I." Materials 14, no. 19 (September 24, 2021): 5535. http://dx.doi.org/10.3390/ma14195535.
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The purpose of this work was to verify the ability to cross-link the chloroprene rubber (CR) by using copper oxides: copper(I) oxide or copper(II) oxide. The use of copper oxides arises from the need to limit the application of ZnO as a cross-linking agent of CR. The obtained results indicate that CR compositions cross-linked with copper oxides are characterized by good mechanical properties and a high cross-linking degree. The results show that the type and the amount of copper oxides influence the cross-linking of the CR and the properties of the vulcanizates. For compositions containing copper(II) oxide, the properties are linearly dependent on the amount of CuO. Such a relationship is difficult to notice in the case of the use of copper(I) oxide—when analyzing individual parameters, the best results are obtained for different samples. Infrared spectroscopy (IR) studies confirmed the possibility of cross-linking of chloroprene rubber with copper oxides. This is evidenced by the characteristic changes in the intensity of the bands. Structural changes in the material during heating were determined by the thermal analysis—differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Regardless of the type and amount of copper oxide, all compositions exhibit similar characteristics, and there are no significant changes in the glass transition temperature of the material.
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Gulkhan, Genjemuratova, and Jumabayeva Janna Mahmud kizi. "THE DISSOLUTION OF ANTIMONY OXIDES, AND LEAD AND OTHER RELATED METALS IN ALKALINE-AQUEOUS ORGANIC SOLUTIONS." International Journal of Pedagogics 03, no. 06 (June 1, 2023): 35–38. http://dx.doi.org/10.37547/ijp/volume03issue06-10.
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Metal oxides such as antimony oxide and lead oxide can be dissolved in alkaline-aqueous organic solutions through various methods, including acid-base reactions, complexation, ion exchange, and redox reactions. These methods involve manipulating factors such as pH, temperature, type of solvent, concentration of metal oxide, and presence of other ions. By dissolving metal oxides, they can be extracted from various materials.
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Miyata, Naoyuki, Yukinori Tani, Kanako Maruo, Hiroshi Tsuno, Masahiro Sakata, and Keisuke Iwahori. "Manganese(IV) Oxide Production by Acremonium sp. Strain KR21-2 and Extracellular Mn(II) Oxidase Activity." Applied and Environmental Microbiology 72, no. 10 (October 2006): 6467–73. http://dx.doi.org/10.1128/aem.00417-06.
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ABSTRACT Ascomycetes that can deposit Mn(III, IV) oxides are widespread in aquatic and soil environments, yet the mechanism(s) involved in Mn oxide deposition remains unclear. A Mn(II)-oxidizing ascomycete, Acremonium sp. strain KR21-2, produced a Mn oxide phase with filamentous nanostructures. X-ray absorption near-edge structure (XANES) spectroscopy showed that the Mn phase was primarily Mn(IV). We purified to homogeneity a laccase-like enzyme with Mn(II) oxidase activity from cultures of strain KR21-2. The purified enzyme oxidized Mn(II) to yield suspended Mn particles; XANES spectra indicated that Mn(II) had been converted to Mn(IV). The pH optimum for Mn(II) oxidation was 7.0, and the apparent half-saturation constant was 0.20 mM. The enzyme oxidized ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (pH optimum, 5.5; Km , 1.2 mM) and contained two copper atoms per molecule. Moreover, the N-terminal amino acid sequence (residues 3 to 25) was 61% identical with the corresponding sequence of an Acremonium polyphenol oxidase and 57% identical with that of a Myrothecium bilirubin oxidase. These results provide the first evidence that a fungal multicopper oxidase can convert Mn(II) to Mn(IV) oxide. The present study reinforces the notion of the contribution of multicopper oxidase to microbially mediated precipitation of Mn oxides and suggests that Acremonium sp. strain KR21-2 is a good model for understanding the oxidation of Mn in diverse ascomycetes.
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Patra, Shanti Gopal, and Dan Meyerstein. "On the Mechanism of Heterogeneous Water Oxidation Catalysis: A Theoretical Perspective." Inorganics 10, no. 11 (October 26, 2022): 182. http://dx.doi.org/10.3390/inorganics10110182.
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Earth abundant transition metal oxides are low-cost promising catalysts for the oxygen evolution reaction (OER). Many transition metal oxides have shown higher OER activity than the noble metal oxides (RuO2 and IrO2). Many experimental and theoretical studies have been performed to understand the mechanism of OER. In this review article we have considered four earth abundant transition metal oxides, namely, titanium oxide (TiO2), manganese oxide/hydroxide (MnOx/MnOOH), cobalt oxide/hydroxide (CoOx/CoOOH), and nickel oxide/hydroxide (NiOx/NiOOH). The OER mechanism on three polymorphs of TiO2: TiO2 rutile (110), anatase (101), and brookite (210) are summarized. It is discussed that the surface peroxo O* intermediates formation required a smaller activation barrier compared to the dangling O* intermediates. Manganese-based oxide material CaMn4O5 is the active site of photosystem II where OER takes place in nature. The commonly known polymorphs of MnO2; α- (tetragonal), β- (tetragonal), and δ-(triclinic) are discussed for their OER activity. The electrochemical activity of electrochemically synthesized induced layer δ-MnO2 (EI-δ-MnO2) materials is discussed in comparison to precious metal oxides (Ir/RuOx). Hydrothermally synthesized α-MnO2 shows higher activity than δ-MnO2. The OER activity of different bulk oxide phases: (a) Mn3O4(001), (b) Mn2O3(110), and (c) MnO2(110) are comparatively discussed. Different crystalline phases of CoOOH and NiOOH are discussed considering different surfaces for the catalytic activity. In some cases, the effects of doping with other metals (e.g., doping of Fe to NiOOH) are discussed.
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Senzaki, Junji, Atsushi Shimozato, Kozutoshi Kajima, Keiko Aryoshi, Takahito Kojima, Shinsuke Harada, Yasunori Tanaka, Hiroaki Himi, and Hajime Okumura. "Electrical Properties of MOS Structures on 4H-SiC (11-20) Face." Materials Science Forum 740-742 (January 2013): 621–24. http://dx.doi.org/10.4028/www.scientific.net/msf.740-742.621.
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Threshold voltage (VTH) instability, channel mobility and oxide reliability have been investigated for meta-oxide-semiconductor (MOS) structures on 4H-SiC (11-20) face using various gate oxidation procedures. Channel mobility of n-channel MOSFET with a gate oxide by pyrogenic oxidation is higher than that by dilute-DRY oxidation followed by a nitrous oxide (N2O) post-oxidation annealing (POA). On the other hand, oxide reliability for the pyrogenic oxides is poor compared with the dilute-DRY/N2O oxides. A Hydrogen POA is effective in an improvement of channel mobility for both oxides, but causes a harmful effect on VTH stability. Temperature dependence of VTH instability indicates that MOS structure grown by dilute-DRY followed by N2O POA is suitable for a practical use of SiC MOS power devices.