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Sample records for ammonolysis

  1. Ammonolysis-induced solvent removal: a facile approach for solidifying emulsion droplets into PLGA microspheres.

    Science.gov (United States)

    Kim, Jayoung; Hong, Dasom; Chung, Younglim; Sah, Hongkee

    2007-12-01

    An ammonolysis-based microencapsulation technique useful for the preparation of biodegradable microspheres was described in this study. A dispersed phase consisting of poly- d, l-lactide- co-glycolide, progesterone, and methyl chloroacetate was emulsified in an aqueous phase. Upon addition of ammonia solution, the emulsion droplets were quickly transformed into poly- d, l-lactide- co-glycolide microspheres laden with progesterone. Rapid solvent removal was accompanied by ammonolysis. The chemical reaction converted water-immiscible methyl chloroacetate to water-miscible chloroacetamide and methanol. Chloroacetamide formation was proved by (1)H NMR and ESI-MS studies. Thermogravimetric analysis showed that the microspheres contained only small amounts of residual methyl chloroacetate. Incorporation efficiencies of progesterone ranged from 64.3 +/- 1.1 to 72.8 +/- 0.3%, depending upon microsphere formulations. X-ray powder diffractometry analysis substantiated that no polymorphic transition of progesterone occurred during microencapsulation. To evaluate the feasibility of this new method against the commonly used microencapsulation method, microspheres were also prepared by a typical dichloromethane-based solvent evaporation process. The important attributes of microspheres prepared from both methods were characterized for comparison. The new ammonolysis-based microencapsulation process showed interesting features distinct from those of the solvent evaporation process. The microencapsulation process reported in this study might be applicable in loading pharmaceuticals into various polymeric microspheres.

  2. Synthesis and ammonolysis of nickel and cobalt tungstates and their characterisation

    Directory of Open Access Journals (Sweden)

    J.L. Rico

    2016-07-01

    Full Text Available The synthesis and characterization of NiW and CoW compounds are herein reported. The NiWO4 and CoWO4 samples, successfully synthesised by the hydrothermal method, were treated under NH3 to obtain the metal nitride. The SEM micrographs show that this transformation is a topotactic process. Tungsten trioxide was also treated under NH3 at similar operating conditions, and used as a reference. High nitrogen contents after ammonolysis were calculated, however, the percentages were below the theoretical values assuming the formation of pure NiWN, CoWN and WN. The XRD pattern indicates that WON is likely formed after ammonolysis of tungsten oxide whereas phase segregation was observed on the nickel and cobalt samples. Furthermore, the reactivity of the nitride samples as function of temperature was measured under argon and the results show that most of the nitrogen is removed from the cobalt and nickel samples whereas it was partially released from the tungsten specimen.

  3. Structural study of gallium oxynitrides prepared by ammonolysis of different oxide precursors

    Energy Technology Data Exchange (ETDEWEB)

    Cailleaux, Xavier; Merdrignac-Conanec, Odile; Tessier, Franck [UMR CNRS 6226 Sciences Chimiques de Rennes, Equipe Verres et Ceramiques, Universite de Rennes 1, 35042 Rennes Cedex (France); De Lucas, MarIa del Carmen Marco [Institut Carnot de Bourgogne, UMR 5209 CNRS-Universite de Bourgogne, 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex (France); Nagasaka, Kazuteru; Kikkawa, Shinichi [Graduate School of Engineering, Hokkaido University, N13W8, Kita-ku Sapporo 060-8628 (Japan)

    2009-02-21

    A comparative structural study has been carried out on gallium oxynitride powders using XRD and Raman spectroscopy. Gallium oxynitrides have been prepared by ammonolysis of either NiGa{sub 2}O{sub 4} ternary oxide or the citrate method-derived amorphous oxide. Their crystal chemistry is different and appears to be influenced by the nature of the oxide precursor: whereas gallium oxynitride obtained from amorphous gallium oxide crystallizes with the common wurtzite structure, gallium oxynitride obtained from NiGa{sub 2}O{sub 4} crystallizes with an original structure that we have identified as the carborundum II (B6) structure type or 6H-SiC. As far as we know, this is the first 6H-SiC structure found in gallium oxynitride powders.

  4. Catalytic activity of oxide cerium-molybdenum-tellurium catalysts in oxidation ammonolysis

    International Nuclear Information System (INIS)

    Dzhordano, N.; Bart, D.; Madzhori, R.

    1984-01-01

    A commercial catalyst containing a mixture of Ce-, Mo-, Te oxides deposited on SiO 2 is shown to manifest a high efficiency in oxidative ammonolysis of propylene (C 3 - ) to acrylonitrile (AN). The dependence of the catalytic properties on the catalyst composition and reaction conditions is studied. It is established that three-component mixtures are more active and selective than the systems with a lesser number of components. Using the catalyst with the optimum ratio of constituent oxides in a microreactor at 440 deg enabled one to achieve initial selectivity in terms of AN equal to 82.5% at 97% conversion of C 3 - . Acrolein, acetonitrile, HCN and nitrogen oxides are the reaction by-products. A supposition is made that the reaction proceeds via the formation of π-compleXes on the centres of Te(4). Setective oxidation occurs on oxygen atoms bonded with the Mo(6) ions. Tellurium enhances the molybdenum reducibleness due to delocalization of electrons, whereas the cerium addition to the mixture of tellurium- and molybdenum oxides increases the rate of molybdenum reoxidation and thus enhances the catalytic system stability

  5. Enhanced enzymatic hydrolysis and acetone-butanol-ethanol fermentation of sugarcane bagasse by combined diluted acid with oxidate ammonolysis pretreatment.

    Science.gov (United States)

    Li, Hailong; Xiong, Lian; Chen, Xuefang; Wang, Can; Qi, Gaoxiang; Huang, Chao; Luo, Mutan; Chen, Xinde

    2017-03-01

    This study aims to propose a biorefinery pretreatment technology for the bioconversion of sugarcane bagasse (SB) into biofuels and N-fertilizers. Performance of diluted acid (DA), aqueous ammonia (AA), oxidate ammonolysis (OA) and the combined DA with AA or OA were compared in SB pretreatment by enzymatic hydrolysis, structural characterization and acetone-butanol-ethanol (ABE) fermentation. Results indicated that DA-OA pretreatment improves the digestibility of SB by sufficiently hydrolyzing hemicellulose into fermentable monosaccharides and oxidating lignin into soluble N-fertilizer with high nitrogen content (11.25%) and low C/N ratio (3.39). The enzymatic hydrolysates from DA-OA pretreated SB mainly composed of glucose was more suitable for the production of ABE solvents than the enzymatic hydrolysates from OA pretreated SB containing high ratio of xylose. The fermentation of enzymatic hydrolysates from DA-OA pretreated SB produced 12.12g/L ABE in 120h. These results suggested that SB could be utilized efficient, economic, and environmental by DA-OA pretreatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Synthesis of uranium fluorides from uranium dioxide with ammonium bifluoride and ammonolysis of uranium fluorides to uranium nitrides

    Science.gov (United States)

    Yeamans, Charles Burnett

    This work presents the chemical conversion of uranium oxides to uranium fluorides, and their subsequent conversion to uranium nitrides. Uranium dioxide reacts with ammonium bifluoride at 20°C to form compound in the ammonium-uranium fluoride chemical system. This reaction occurs between solid uranium dioxide at the surface of the particles and ammonium fluoride vapor. A shrinking-sphere model demonstrated surface reaction kinetics, not mass transport by diffusion through the product layer, limit the reaction rate when the starting material consists of 100 mum uranium dioxide particles. Powder x-ray diffraction showed the reaction to be complete within 8 hours, with (NH4) 4UF8 the reaction product. High-resolution electron microcopy revealed the product is largely amorphous on a micrometer-scale, but contains well-formed crystal domains on the order of 10x10 nm. X-ray diffraction showed the reaction progresses though beta-NH4UF5, delta-(NH 4)2UF6, and gamma-(NH4)2UF6 intermediate phases before finally forming (NH4)4UF 8. Modeling the system as a series of first-order reaction suggested a fourth intermediate, possibly UF4, is likely to occur. The reaction of (NH4)4UF8 with ammonia gas at 800°C forms alpha-U2N3/UN2 solid solution products with a composition of UN1.83. The x-ray powder diffraction pattern of this product is the fcc pattern commonly referenced as that of UN2 and the lattice parameter was 0.53050 nm. Surface area increased by a factor of ten during ammonolysis, consistent with the action of a hydriding agent. The alpha-U2N 3/UN2 solid solution system formed contained 1 wt% UO 2 as an impurity. Upon subsequent heating to 1150°C for 4.5 hours under argon, the nitride sample formed UN with a UO2 impurity of 9 wt%. Based on the HRTEM images, oxidation in the UN product appears to be limited to within 20 nm of particle surfaces and grain boundaries.

  7. Biocatalytic ammonolysis of (5S)-4,5-dihydro-1H-pyrrole-1,5-dicarboxylic acid, 1-(1,1-dimethylethyl)-5-ethyl ester: preparation of an intermediate to the dipeptidyl peptidase IV inhibitor Saxagliptin.

    Science.gov (United States)

    Gill, Iqbal; Patel, Ramesh

    2006-02-01

    An efficient biocatalytic method has been developed for the conversion of (5S)-4,5-dihydro-1H-pyrrole-1,5-dicarboxylic acid, 1-(1,1-dimethylethyl)-5-ethyl ester (1) into the corresponding amide (5S)-5-aminocarbonyl-4,5-dihydro-1H-pyrrole-1-carboxylic acid, 1-(1,1-dimethylethyl)ester (2), which is a critical intermediate in the synthesis of the dipeptidyl peptidase IV (DPP4) inhibitor Saxagliptin (3). Candida antartica lipase B mediates ammonolysis of the ester with ammonium carbamate as ammonia donor to yield up to 71% of the amide. The inclusion of Ascarite and calcium chloride as adsorbents for carbon dioxide and ethanol byproducts, respectively, increases the yield to 98%, thereby offering an efficient and practical alternative to chemical routes which yield 57-64%.

  8. Synthesis of InN nanoparticles by rapid thermal ammonolysis

    Czech Academy of Sciences Publication Activity Database

    Šimek, P.; Sedmidubský, D.; Klimová, K.; Huber, Š.; Brázda, Petr; Mikulics, M.; Jankovský, O.; Sofer, Z.

    2014-01-01

    Roč. 16, č. 12 (2014), "2805-1"-"2805-11" ISSN 1388-0764 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 Keywords : InN * nanoparticles * nanocrystals Subject RIV: CA - Inorganic Chemistry Impact factor: 2.184, year: 2014

  9. Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

    International Nuclear Information System (INIS)

    Jackson, Andrew W.; Shebanova, Olga; Hector, Andrew L.; McMillan, Paul F.

    2006-01-01

    Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe 2 ) 4 ) and ammonia yield precipitates with composition TiC 0.5 N 1.1 H 2.3 . Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH 3 yields nearly stoichiometric TiN. However, heating in N 2 atmosphere leads to isostructural carbonitrides, approximately TiC 0.2 N 0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC 0.22 N 1.01 H 0.07 , or Ti 3 (C 0.17 N 0.78 H 0.05 ) 3.96 , close to Ti 3 (C,N) 4 . Previous workers have suggested that the intermediate compound was an amorphous form of Ti 3 N 4 . TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

  10. Thermodynamics of Ternary Nitride Formation by Ammonolysis: Application to LiMoN2, Na3WN3 and Na3WO3N

    Science.gov (United States)

    1992-01-01

    oxidation of a nitride or oxynitride to a well defined solid or molten oxide. The enthalpies of formation of LiMoN2, Na3WN3 and U Na3WO3N have been measured...the Feasibility of Nitride Synthesis Oxide Precursors Ternary solid state compounds, as well as ionic salts and coordination compounds, are potential... MOx + 2/3x NH 3 -+ MNy + xH20 + (x/3 - y/ 2 ) N2 (1) Because nitrides frequently contain the metals in a lower formal oxidation state than oxides

  11. Phase formation, structural and microstructural characterization of novel oxynitride- perovskites synthesized by thermal ammonolysis of (Ca,Ba)MoO.sub.4./sub. and (Ca,Ba)MoO.sub.3./sub..

    Czech Academy of Sciences Publication Activity Database

    Logvinovich, D.; Aguirre, M.H.; Hejtmánek, Jiří; Aguiar, R.; Ebbinghaus, S.G.; Reller, A.; Weidenkaff, A.

    2008-01-01

    Roč. 181, č. 9 (2008), s. 2243-2249 ISSN 0022-4596 Institutional research plan: CEZ:AV0Z10100521 Keywords : oxynitride * molybdate * crystal Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.910, year: 2008

  12. 21 CFR 173.400 - Dimethyldialkylammonium chloride.

    Science.gov (United States)

    2010-04-01

    ...) The food additive is produced by one of the following methods: (1) Ammonolysis of natural tallow fatty... used as a processing solvent. (2) Ammonolysis of natural tallow fatty acids to form amines that are... Administration, 5100 Paint Branch Pkwy., College Park, MD 20740, and from the American Oil Chemists' Society, P.O...

  13. Rapid thermal synthesis of GaN nanocrystals and nanodisks

    Czech Academy of Sciences Publication Activity Database

    Sofer, Z.; Sedmidubský, D.; Huber, Š.; Šimek, P.; Šaněk, F.; Jankovský, O.; Gregorová, E.; Fiala, R.; Matějková, Stanislava; Mikulics, M.

    2013-01-01

    Roč. 15, č. 1 (2013), 1411/1-1411/7 ISSN 1388-0764 Institutional support: RVO:61388963 Keywords : gallium nitride * thermal ammonolysis * nanodisks * nanocrystals Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.278, year: 2013

  14. Synthesis Of A Precursor Of Silicon Nitride

    Science.gov (United States)

    Philipp, Warren H.; Cornell, Linda; Lin, Y. C.

    1994-01-01

    Promising route toward production of highly pure, finely divided, easily sinterable silicon nitride (Si3N4) involves thermal decomposition of silicon diimide {Si(NH)2} prepared by ammonolysis of Si(SCN)4 in CH3CN and purified by complete extraction of byproduct NH4SCN by use of ammonia at temperature and pressure above critical point.

  15. Lipase-catalyzed synthesis of fatty acid amide (erucamide) using fatty acid and urea.

    Science.gov (United States)

    Awasthi, Neeraj Praphulla; Singh, R P

    2007-01-01

    Ammonolysis of fatty acids to the corresponding fatty acid amides is efficiently catalysed by Candida antartica lipase (Novozym 435). In the present paper lipase-catalysed synthesis of erucamide by ammonolysis of erucic acid and urea in organic solvent medium was studied and optimal conditions for fatty amides synthesis were established. In this process erucic acid gave 88.74 % pure erucamide after 48 hour and 250 rpm at 60 degrees C with 1:4 molar ratio of erucic acid and urea, the organic solvent media is 50 ml tert-butyl alcohol (2-methyl-2-propanol). This process for synthesis is economical as we used urea in place of ammonia or other amidation reactant at atmospheric pressure. The amount of catalyst used is 3 %.

  16. Studies on the use of supercritical ammonia for ceramic nitride synthesis and fabrication

    Science.gov (United States)

    Cornell, Linda; Lin, Y. C.; Philipp, Warren H.

    1990-01-01

    The extractability of ammonia halides (including ammonium thiocyanate) formed as byproducts from the synthesis of Si(NH)2 via ammonolysis of the corresponding silicon tetrahalides using supercritical NH3 as the extraction medium was investigated. It was found that the NH4SCN byproduct of ammonolysis of Si(SCN)4 can be almost completely extracted from the insoluble Si(NH)2 forming a promising system for the synthesis of pure Si(NH)2, one of the best precursors for Si3N4. In addition it was found that Si3N4, AlN, BN, and Si(NH)2 are insoluble in SC ammonia. Also discussed are design considerations for a supercritical ammonia extraction unit.

  17. Synthesis of niobium nitride by pyrolysis of niobium pentachloride ammines

    International Nuclear Information System (INIS)

    Grebtsova, O.M.; Shulga, Y.M.; Troitskii, V.N.

    1986-01-01

    This paper investigates the conditions for the preparation of niobium nitride in the thermal decomposition of niobium nitride in the thermal decomposition of niobium pentachloride ammines. The synthesis of the ammines was accomplished by the reaction of powdered NbC1 5 with dry ammonia at 210 K. Thermography and x-ray diffraction, spectral, and chemical analyses were used to identify the ammonolysis products. It was established that the products of ammonolysis of NbC1 5 are a mixture of the x-ray-amorphous complex Nb (NH 2 ) /SUB 5-x/ - (NG 3 ) 3 CL 3 (x≅) and 2 moles of NH 4 C1. The steps in the thermal decomposition of this mixture were studied. The phase transition that is observed in the case of further vacuum heat treatment at 1100-1300 K is presented

  18. The Process of Acetonitrile Synthesis over γ-Al2O3 Promoted by Phosphoric Acid Catalysts

    OpenAIRE

    Galanov, Sergey I.; Sidorova, Olga I.; Gavrilenko, Mikhail A.

    2014-01-01

    The influence of principal parameters (reaction temperature, ratio of acetic acid and ammonia, composition of reactionary mixture and promotion of catalysts) on the selectivity and yield of the desired product was studied in the reaction of catalytic acetonitrile synthesis by ammonolysis of acetic acid. The processing of [gamma]-Al[2]O[3] by phosphoric acid increases amount of the centers, on which carries out reaction of acetamide dehydration. The kinetic model of a limiting stage of reactio...

  19. tert-Butyl 4-carbamoyl-3-methoxyimino-4-methylpiperidine-1-carboxylate

    Directory of Open Access Journals (Sweden)

    Yucheng Wang

    2008-12-01

    Full Text Available The title compound, C13H23N3O4, was prepared starting from ethyl N-benzyl-3-oxopiperidine-4-carboxylate through a nine-step reaction, including hydrogenation, Boc (tert-butoxycarbonyl protection, methylation, oximation, hydrolysis, esterification and ammonolysis. In the crystal structure, molecules are linked by intermolecular N—H...O hydrogen bonds to form a porous three-dimensional network with solvent-free hydrophobic channels extending along the c axis.

  20. Synthesis of ternary nitrides by mechanochemical alloying

    DEFF Research Database (Denmark)

    Jacobsen, C.J.H.; Zhu, J.J.; Lindelov, H.

    2002-01-01

    Ternary metal nitrides ( of general formula MxM'N-y(z)) attract considerable interest because of their special mechanical, electrical, magnetic, and catalytic properties. Usually they are prepared by ammonolysis of ternary oxides (MxM'O-y(m)) at elevated temperatures. We show that ternary...... nitrides by mechanochemical alloying of a binary transition metal nitride (MxN) with an elemental transition metal. In this way, we have been able to prepare Fe3Mo3N and Co3Mo3N by ball-milling of Mo2N with Fe and Co, respectively. The transformation sequence from the starting materials ( the binary...

  1. Investigation of iron-bismuth-molybdenum catalysts

    International Nuclear Information System (INIS)

    Ven'yaminov, S.A.; Barannik, G.B.; Pitaeva, A.N.; Sazonova, N.N.; Plyasova, L.M.

    1977-01-01

    The catalytic properties of an oxide iron-bismuth-molybdenum system in reactions of oxidative ammonolysis of propylene and oxidative dehydrogenation of butene-1 are investigated. It is shown that catalysts containing double molybdate of bismuth and iron (the X-phase) exhibit an increased catalytic activity as compared with bismuth molybdate (Bi 2 O 3 x3MoO 3 ). Preliminary reduction of such specimens increases their activity and selectivity in subsequent work under conditions of a stationary course of the oxidation reaction. The activity and selectivity of catalysts containing only bismuth molybdate and iron molybdate are due to the additivity of the properties of the separate molybdates

  2. Bandgap tuning in SrTi(N,O,F)3 by anionic-lattice variation

    International Nuclear Information System (INIS)

    Yoon, Songhak; Maegli, Alexandra E.; Karvonen, Lassi; Matam, Santhosh K.; Shkabko, Andrey; Riegg, Stefan; Großmann, Thomas; Ebbinghaus, Stefan G.; Pokrant, Simone; Weidenkaff, Anke

    2013-01-01

    Polycrystalline SrTiO 3 and SrTi(O,F) 3 powders were synthesized by a solid-state reaction. A partial substitution of oxygen by nitrogen was subsequently carried out using thermal ammonolysis resulting in SrTi(N,O) 3 and SrTi(N,O,F) 3 . Powder X-ray diffraction (XRD) revealed a cubic perovskite structure with space group Pm-3m for all samples. The thermal ammonolysis slightly increased the lattice parameters, crystallite sizes and strain. As a result from the co-substitution of oxygen with nitrogen and fluorine for SrTi(N,O,F) 3 , highly distorted TiO 6 octahedra were detected using X-ray absorption near edge structure (XANES) spectroscopy. The weakening of all active modes of the Raman spectra after thermal ammonolysis also indicated enhanced distortions in the local crystal structure. SrTi(N,O,F) 3 has the largest amount of nitrogen as well as fluorine among all four samples as determined by thermogravimetric analysis (TGA), elemental analysis and X-ray photoelectron spectroscopy (XPS). In the UV–vis spectra a distinctive shift of the absorption-edge energy was observed exclusively for the SrTi(N,O,F) 3 sample from 390 to 510 nm corresponding to a bandgap narrowing from 3.18 to 2.43 eV. - Graphical abstract: Figure shows the shift of the absorption-edge energy for the SrTi(N,O,F) 3 sample from 390 to 510 nm corresponding to a bandgap narrowing from 3.18 to 2.43 eV. Display Omitted - Highlights: • Synthesis of phase-pure SrTi(N,O,F) 3 via solid-state reaction. • The incorporated nitrogen contents increase by the presence of fluorine in SrTi(N,O,F) 3 . • Co-substitution with nitrogen and fluorine is beneficial for the bandgap narrowing compared to by only nitrogen or fluorine substitution

  3. Bandgap tuning in SrTi(N,O,F){sub 3} by anionic-lattice variation

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Songhak; Maegli, Alexandra E.; Karvonen, Lassi; Matam, Santhosh K.; Shkabko, Andrey [Laboratory for Solid State Chemistry and Catalysis, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Riegg, Stefan [Lehrstuhl für Experimentalphysik 5, EKM, Universität Augsburg, Universitätsstraße 1, 86135 Augsburg (Germany); Großmann, Thomas; Ebbinghaus, Stefan G. [Institut für Chemie, Martin-Luther Universität Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle/Saale (Germany); Pokrant, Simone [Laboratory for Solid State Chemistry and Catalysis, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland); Weidenkaff, Anke, E-mail: anke.weidenkaff@empa.ch [Laboratory for Solid State Chemistry and Catalysis, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf (Switzerland)

    2013-10-15

    Polycrystalline SrTiO{sub 3} and SrTi(O,F){sub 3} powders were synthesized by a solid-state reaction. A partial substitution of oxygen by nitrogen was subsequently carried out using thermal ammonolysis resulting in SrTi(N,O){sub 3} and SrTi(N,O,F){sub 3}. Powder X-ray diffraction (XRD) revealed a cubic perovskite structure with space group Pm-3m for all samples. The thermal ammonolysis slightly increased the lattice parameters, crystallite sizes and strain. As a result from the co-substitution of oxygen with nitrogen and fluorine for SrTi(N,O,F){sub 3}, highly distorted TiO{sub 6} octahedra were detected using X-ray absorption near edge structure (XANES) spectroscopy. The weakening of all active modes of the Raman spectra after thermal ammonolysis also indicated enhanced distortions in the local crystal structure. SrTi(N,O,F){sub 3} has the largest amount of nitrogen as well as fluorine among all four samples as determined by thermogravimetric analysis (TGA), elemental analysis and X-ray photoelectron spectroscopy (XPS). In the UV–vis spectra a distinctive shift of the absorption-edge energy was observed exclusively for the SrTi(N,O,F){sub 3} sample from 390 to 510 nm corresponding to a bandgap narrowing from 3.18 to 2.43 eV. - Graphical abstract: Figure shows the shift of the absorption-edge energy for the SrTi(N,O,F){sub 3} sample from 390 to 510 nm corresponding to a bandgap narrowing from 3.18 to 2.43 eV. Display Omitted - Highlights: • Synthesis of phase-pure SrTi(N,O,F){sub 3} via solid-state reaction. • The incorporated nitrogen contents increase by the presence of fluorine in SrTi(N,O,F){sub 3}. • Co-substitution with nitrogen and fluorine is beneficial for the bandgap narrowing compared to by only nitrogen or fluorine substitution.

  4. Synthesis and antitumor activity of 2-beta-D-ribofuranosyloxazole-4-carboxamide (oxazofurin).

    Science.gov (United States)

    Franchetti, P; Cristalli, G; Grifantini, M; Cappellacci, L; Vittori, S; Nocentini, G

    1990-10-01

    Condensation of 3,4,6-tri-O-benzoyl-2,5-anhydro-D-allonyl chloride (4) with ethyl 2-amino-2-cyanoacetate (5) provided 2-[(3',4',6'-tri-O-benzoyl-2',5'-anhydroallonyl)amino]-2-cyanoa cetate (6). Compound 6 was treated with hydrogen chloride gas to give ethyl 5-amino-2-(2',3',5'-tri-O-benzoyl-beta-D- ribofuranosyl)oxazole-4-carboxylate (8). Reductive dediazotization of blocked nucleoside 8 provided ethyl 2-(2',3',5'-tri-O- benzoyl-beta-D-ribofuranosyl)oxazole-4-carboxylate (10), which after deblocking with sodium methoxide and ammonolysis was converted to 2-beta-D-ribofuranosyl-oxazole-4-carboxamide (oxazofurin, 3), an analogue of the antitumor and antiviral C-nucleoside tiazofurin (1). Oxazofurin (3) was found to be cytotoxic toward B16 murine melanoma cells in culture but inactive against murine leukemia P388 and L1210.

  5. Preparation and optical spectroscopy of Eu3+-doped GaN luminescent semiconductor from freeze-dried precursors

    International Nuclear Information System (INIS)

    El-Himri, Abdelouahad; Perez-Coll, Domingo; Nun-tilde ez, Pedro; Martin, Inocencio R.; Lavin, Victor; Rodriguez, Vicente D.

    2004-01-01

    Pure and 0.5% and 5mol% Eu 3+ doped GaN nanoparticles have been prepared by ammonolysis of the corresponding freeze-dried precursors. A single hexagonal phase with the wurtzite structure was obtained as determined by X-ray Powder Diffraction. The crystallite size determined by XRD was lower than 10nm. From optical spectroscopy characterization, it is found that the Eu 2 O 3 formation is avoided by using nitrates as starting reagent. Fluorescence line narrowing spectra show excitation wavelength dependence, which is indicative that the Eu 3+ ions are well dispersed in the prepared samples. The environment distribution occupied by the Eu 3+ ions has been analyzed by crystal-field calculation and the results are compared with those for other materials

  6. Enhanced Charge Transport in Tantalum Nitride Nanotube Photoanodes for Solar Water Splitting.

    Science.gov (United States)

    Wang, Lei; Nguyen, Nhat Truong; Zhou, Xuemei; Hwang, Imgon; Killian, Manuela S; Schmuki, Patrik

    2015-08-24

    In the present work we grow anodic self-organized Ta2O5 nanotube layers, which are converted by ammonolysis to Ta3 N5 nanotubes, and then are used as photoanodes for photoanalytic water splitting. We introduce a two-step anodization process that not only improves order (reduced growth defects) and overall light absorption in the nanotube layers, but also provides a significantly reduced interface charge resistance at the nitride/metal interface due to subnitride (TaNx ) formation. As a result, such nanotube anodes afford a 15-fold increase of the photocurrent compared with conventional nanotubular Ta3 N5 electrodes under AM 1.5 G simulated sunlight (100 mW cm(-2)) conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

    DEFF Research Database (Denmark)

    Meyer, Simon; Beyer, Hans; Köhler, Klaus

    2015-01-01

    For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of W2......N inside the pores of ordered mesoporous silica SBA-15 offers a possibility to reduce sintering phenomena and thus to obtain smaller particles, porous structures and a higher surface area material. The preparation was pursued in a two-step approach. First, WO3 was introduced into the channels of SBA......-15 and second, ammonolysis was conducted for its conversion to W2N. When performed in the presence of the exo-template, SBA-15 acts as a stabilizer and small W2N particles (6-7 nm) with a high specific surface area (40 m(2) g(-1)) are obtained after template removal. When the template is, however...

  8. Silicon oxynitrides of KCC-1, SBA-15 and MCM-41 for CO 2 capture with excellent stability and regenerability

    KAUST Repository

    Patil, Umesh

    2012-01-01

    We report the use of silicon oxynitrides as novel adsorbents for CO 2 capture. Three series of functionalized materials based on KCC-1, SBA-15 and MCM-41 with Si-NH 2 groups were prepared using a simple one-step process via thermal ammonolysis using ammonia gas, and they demonstrated excellent CO 2 capture capabilities. These materials overcome several limitations of conventional amine-grafted mesoporous silica. They offer good CO 2 capture capacity, faster adsorption-desorption kinetics, efficient regeneration and reuse, more crucially excellent thermal and mechanical stability even in oxidative environments, and a clean and green synthesis route, which allows the overall CO 2 capture process to be practical and sustainable. This journal is © The Royal Society of Chemistry 2012.

  9. Multifaceted characterization of cell wall decomposition products formed during ammonia fiber expansion (AFEX) and dilute acid based pretreatments.

    Science.gov (United States)

    Chundawat, Shishir P S; Vismeh, Ramin; Sharma, Lekh N; Humpula, James F; da Costa Sousa, Leonardo; Chambliss, C Kevin; Jones, A Daniel; Balan, Venkatesh; Dale, Bruce E

    2010-11-01

    Decomposition products formed/released during ammonia fiber expansion (AFEX) and dilute acid (DA) pretreatment of corn stover (CS) were quantified using robust mass spectrometry based analytical platforms. Ammonolytic cleavage of cell wall ester linkages during AFEX resulted in the formation of acetamide (25mg/g AFEX CS) and various phenolic amides (15mg/g AFEX CS) that are effective nutrients for downstream fermentation. After ammonolysis, Maillard reactions with carbonyl-containing intermediates represent the second largest sink for ammonia during AFEX. On the other hand, several carboxylic acids were formed (e.g. 35mg acetic acid/g DA CS) during DA pretreatment. Formation of furans was 36-fold lower for AFEX compared to DA treatment; while carboxylic acids (e.g. lactic and succinic acids) yield was 100-1000-fold lower during AFEX compared to previous reports using sodium hydroxide as pretreatment reagent. Copyright 2010 Elsevier Ltd. All rights reserved.

  10. Bixbyite-type phases in the system Ta-Zr-O-N

    Energy Technology Data Exchange (ETDEWEB)

    Luedtke, Tobias; Orthmann, Steven; Lerch, Martin [Technische Univ. Berlin (Germany). Inst. fuer Chemie

    2017-06-01

    Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3). The nitrogen content of these compounds has a significant influence on the cell parameters, the atomic positions, and the optical band gap. The results extend the already well-studied Ta-Zr-O-N system by new oxide nitrides in addition to the already known baddeleyite- and anosovite-type phases. TaZrN{sub 3} can be considered as a thermodynamically stable ternary variant of metastable Ta{sub 2}N{sub 3}.

  11. Synthesis of a Novel Polyethoxysilsesquiazane and Thermal Conversion into Ternary Silicon Oxynitride Ceramics with Enhanced Thermal Stability.

    Science.gov (United States)

    Iwase, Yoshiaki; Horie, Yoji; Daiko, Yusuke; Honda, Sawao; Iwamoto, Yuji

    2017-12-05

    A novel polyethoxysilsesquiazane ([EtOSi(NH) 1.5 ] n , EtOSZ) was synthesized by ammonolysis at -78 °C of ethoxytrichlorosilane (EtOSiCl₃), which was isolated by distillation as a reaction product of SiCl₄ and EtOH. Attenuated total reflection-infra red (ATR-IR), 13 C-, and 29 Si-nuclear magnetic resonance (NMR) spectroscopic analyses of the ammonolysis product resulted in the detection of Si-NH-Si linkage and EtO group. The simultaneous thermogravimetric and mass spectrometry analyses of the EtOSZ under helium revealed cleavage of oxygen-carbon bond of the EtO group to evolve ethylene as a main gaseous species formed in-situ, which lead to the formation at 800 °C of quaternary amorphous Si-C-N with an extremely low carbon content (1.1 wt %) when compared to the theoretical EtOSZ (25.1 wt %). Subsequent heat treatment up to 1400 °C in N₂ lead to the formation of X-ray amorphous ternary Si-O-N. Further heating to 1600 °C in N₂ promoted crystallization and phase partitioning to afford Si₂N₂O nanocrystallites identified by the XRD and TEM analyses. The thermal stability up to 1400 °C of the amorphous state achieved for the ternary Si-O-N was further studied by chemical composition analysis, as well as X-ray photoelectron spectroscopy (XPS) and 29 Si-NMR spectroscopic analyses, and the results were discussed aiming to develop a novel polymeric precursor for ternary amorphous Si-O-N ceramics with an enhanced thermal stability.

  12. Synthesis of a Novel Polyethoxysilsesquiazane and Thermal Conversion into Ternary Silicon Oxynitride Ceramics with Enhanced Thermal Stability

    Directory of Open Access Journals (Sweden)

    Yoshiaki Iwase

    2017-12-01

    Full Text Available A novel polyethoxysilsesquiazane ([EtOSi(NH1.5]n, EtOSZ was synthesized by ammonolysis at −78 °C of ethoxytrichlorosilane (EtOSiCl3, which was isolated by distillation as a reaction product of SiCl4 and EtOH. Attenuated total reflection-infra red (ATR-IR, 13C-, and 29Si-nuclear magnetic resonance (NMR spectroscopic analyses of the ammonolysis product resulted in the detection of Si–NH–Si linkage and EtO group. The simultaneous thermogravimetric and mass spectrometry analyses of the EtOSZ under helium revealed cleavage of oxygen-carbon bond of the EtO group to evolve ethylene as a main gaseous species formed in-situ, which lead to the formation at 800 °C of quaternary amorphous Si–C–N with an extremely low carbon content (1.1 wt % when compared to the theoretical EtOSZ (25.1 wt %. Subsequent heat treatment up to 1400 °C in N2 lead to the formation of X-ray amorphous ternary Si–O–N. Further heating to 1600 °C in N2 promoted crystallization and phase partitioning to afford Si2N2O nanocrystallites identified by the XRD and TEM analyses. The thermal stability up to 1400 °C of the amorphous state achieved for the ternary Si-O-N was further studied by chemical composition analysis, as well as X-ray photoelectron spectroscopy (XPS and 29Si-NMR spectroscopic analyses, and the results were discussed aiming to develop a novel polymeric precursor for ternary amorphous Si–O–N ceramics with an enhanced thermal stability.

  13. Perovskite-type SrTi1-xNbx(O,N)3 compounds: Synthesis, crystal structure and optical properties

    International Nuclear Information System (INIS)

    Maegli, Alexandra; Yoon, Songhak; Otal, Eugenio; Karvonen, Lassi; Mandaliev, Peter; Weidenkaff, Anke

    2011-01-01

    The synthesis, crystal structure, thermal stability and absorbance spectra of perovskite-type oxynitrides with the general formula SrTi 1-x Nb x (O,N) 3 (x=0.05, 0.10, 0.20, 0.50, 0.80, 0.90, 0.95) have been investigated. Oxide samples were prepared by a polymerized complex synthesis route and post-treated under ammonia at 850 o C for 24 h to substitute nitrogen for oxygen. Synchrotron X-ray powder diffraction (XRD) evidenced that the mixed oxide phases were all transformed into oxynitrides with perovskite-type structure during a thermal ammonolysis. SrTi 1-x Nb x (O,N) 3 with compositions x≤0.80 crystallized in a cubic and samples with x≥0.90 in a tetragonal structure. The Rietveld refinement indicated a continuous enlargement of the lattice parameters towards higher niobium content of the samples. Thermogravimetric analysis (TGA) and hotgas extraction revealed the dependence of the nitrogen incorporation upon the degree of niobium substitution. It showed that more nitrogen was detected in the samples with higher niobium content. Furthermore, TGA disclosed stability for all oxynitrides at T≤400 o C. Diffuse reflectance spectroscopy indicated a continuous decrease of the band gap's width from 3.24 eV (SrTi 0.95 Nb 0.05 (O,N) 3 ) to 1.82 eV (SrTi 0.05 Nb 0.95 (O,N) 3 ) caused by the increasing amount of nitrogen towards the latter composition. -- Graphical Abstract: The system SrTi 1-x Nb x (O,N) 3 is described and the changes in crystal structure, nitrogen content and width of the band gap are discussed. Display Omitted Research highlights: → Synthesis of SrTi 1-x Nb x (O,N) 3 perovskite-type oxynitrides via thermal ammonolysis. → Co-substitution of Nb 5+ enabled to adjust the amount nitrogen insertion. → Tuning of the optical band gap through nitrogen.→ Changes of crystal structure from cubic to tetragonal with increasing niobium content.

  14. A novel LaFeO3−XNX oxynitride. Synthesis and characterization

    International Nuclear Information System (INIS)

    Sierra Gallego, G.; Marín Alzate, N.; Arnache, O.

    2013-01-01

    Highlights: ► LaFeO 3 perovskite synthesized by auto combustion method. ► LaFeO 3−X N X oxynitride produced by ammonolysis reaction. ► Oxynitride characterized by XRD, Rietveld, SEM, EDX, BET, Raman, TGA and FTIR. ► Partial replacement of oxygen by nitrogen increases slightly the cell parameters. ► TGA shows that oxynitride start to decompose in air above 550 °C. Evolution of N 2 and NO was detected. - Abstract: A perovskite LaFeO 3 was synthesized by auto combustion method and then LaFeO 3−X N X oxynitride was produced by ammonolysis reaction. The synthesized LaFeO 3−X N X oxynitride was characterized by X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET) nitrogen adsorption, particle size distribution, Raman spectroscopy, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Nitrogen effect into the perovskite structure was confirmed by DRX. The structure refinement using the Rietveld method indicates that partial replacement of oxygen by nitrogen increases slightly the cell parameters of the LaFeO 3 perovskite. FTIR analysis show that bands at 995 and 1070 cm −1 in the oxynitrides spectra could be assigned to the stretching vibration modes of Fe–N bonds in the FeO 6−X N X octahedral. Thermogravimetric analysis (TGA) showed that LaFeO 3−X N X oxynitride series start to decompose in air above 550 °C. During the decomposition it was found that some amount of nitrogen stays retained in the structure forming intermediate compounds. MS analysis of the gaseous products reveals the evolution of N 2 and NO, suggesting a complex reaction mechanism. To our knowledge, there are no reports on the synthesis and characterization of the LaFeO 3−X N X oxynitrides.

  15. Synthesis of [{sup 18}F]-labelled nebivolol as a β{sub 1}-adrenergic receptor antagonist for PET imaging agent

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Taek Soo; Park, Jeong Hoon; Lee, Jun Young; Yang, Seung Dae [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute (KAERI), Jeongeup (Korea, Republic of); Chang, Dong Jo [College of pharmacy, Sunchon National University, Suncheon (Korea, Republic of)

    2017-02-15

    Selective β{sub 1}-agonist and antagonists are used for the treatment of cardiac diseases including congestive heart failure, angina pectoris and arrhythmia. Selective β{sub 1}-antagonists including nebivolol have high binding affinity on β{sub 1}-adrenergic receptor, not β{sub 2}-receptor mainly expressed in smooth muscle. Nebivolol is one of most selective β{sub 1}-blockers in clinically used β{sub 1}- blockers including atenolol and bisoprolol. We tried to develop clinically useful cardiac PET tracers using a selective β{sub 1}-blocker. Nebivolol is C{sub 2}-symmetric and has two chromane moiety with a secondary amino alcohol and aromatic fluorine. We adopted the general synthetic strategy using epoxide ring opening reaction. Unlike formal synthesis of nebivolol, we prepared two chromane building blocks with fluorine and iodine which was transformed to diaryliodonium salt for labelling of {sup 18}F. Two epoxide building blocks were readily prepared from commercially available chromene carboxylic acids (1, 8). Then, the amino alcohol building block (15) was prepared by ammonolysis of epoxide (14) followed by coupling reaction with the other building block, epoxide (7). Diaryliodonium salt, a precursor for {sup 18}F-aromatic substitution, was synthesized in moderate yield which was readily subjected to {sup 18}F-aromatic substitution to give {sup 18}F-labelled nebivolol.

  16. CALB-Catalyzed Two-Step Alcoholytic Desymmetrization of 3-Methylglutaric Diazolides in MTBE.

    Science.gov (United States)

    Wu, Ting-Yi; Lai, Yuan-Rong; Tsai, Shau-Wei

    2017-12-15

    Optically pure 3-substituted glutarates can be prepared from the alcoholic ring-opening of cyclic anhydride derivatives, esterification of 3-substituted glutaric acid, and hydrolysis, alcoholysis, aminolysis, and ammonolysis of the diester derivatives via hydrolases or organocatalysts. Unfortunately, most of them mainly focus on the first-step desymmetrization, leading to the difficulty on producing optically pure enantiomers. As a general trend in lipase-catalyzed desymmetrization of 3-methylglutarates, poorer enantiomeric excesses with lower chemical yields were found, as the methyl substituent is relatively small to induce a high enzyme stereodiscrimination. The two-step desymmetrization for CALB-catalyzed alcoholysis of 3-methylglutaric di-1,2,4-triazolide 1a in anhydrous MTBE is first developed to increase the enzyme activity in each reaction step. The enantioselectivity for the second-step kinetic resolution is furthermore improved by using 3-methylglutaric dipyrazolide 1b as the substrate. The kinetic and thermodynamic analysis is, moreover, addressed for shedding insights into the desymmetrization process.

  17. Microporosity and CO₂ Capture Properties of Amorphous Silicon Oxynitride Derived from Novel Polyalkoxysilsesquiazanes.

    Science.gov (United States)

    Iwase, Yoshiaki; Horie, Yoji; Honda, Sawao; Daiko, Yusuke; Iwamoto, Yuji

    2018-03-13

    Polyalkoxysilsesquiazanes ([ROSi(NH) 1.5 ] n , ROSZ, R = Et, nPr, iPr, nBu, sBu, nHex, sHex, cHex, decahydronaphthyl (DHNp)) were synthesized by ammonolysis at -78 °C of alkoxytrichlorosilane (ROSiCl₃), which was isolated by distillation as a reaction product of SiCl₄ and ROH. The simultaneous thermogravimetric and mass spectrometry analyses of the ROSZs under helium revealed a common decomposition reaction, the cleavage of the oxygen-carbon bond of the RO group to evolve alkene as a main gaseous species formed in-situ, leading to the formation of microporous amorphous Si-O-N at 550 °C to 800 °C. The microporosity in terms of the peak of the pore size distribution curve located within the micropore size range (derived from DHNpOSZ having an SSA of 750 m²·g -1 . The CO₂ capture properties were further discussed based on their temperature dependency, and a surface functional group of the Si-O-N formed in-situ during the polymer/ceramics thermal conversion.

  18. Synthesis, structure, and antiproliferative activity of selenophenfurin, an inosine 5'-monophosphate dehydrogenase inhibitor analogue of selenazofurin.

    Science.gov (United States)

    Franchetti, P; Cappellacci, L; Sheikha, G A; Jayaram, H N; Gurudutt, V V; Sint, T; Schneider, B P; Jones, W D; Goldstein, B M; Perra, G; De Montis, A; Loi, A G; La Colla, P; Grifantini, M

    1997-05-23

    The synthesis and biological activity of selenophenfurin (5-beta-D-ribofuranosylselenophene-3-carboxamide, 1), the selenophene analogue of selenazofurin, are described. Glycosylation of ethyl selenophene-3-carboxylate (6) under stannic chloride-catalyzed conditions gave 2- and 5-glycosylated regioisomers, as a mixture of alpha- and beta-anomers, and the beta-2,5-diglycosylated derivative. Deprotected ethyl 5-beta-D-ribofuranosylselenophene-3-carboxylate (12 beta) was converted into selenophenfurin by ammonolysis. The structure of 12 beta was determined by 1H- and 13C-NMR, crystallographic, and computational studies. Selenophenfurin proved to be antiproliferative against a number of leukemia, lymphoma, and solid tumor cell lines at concentrations similar to those of selenazofurin but was more potent than the thiophene and thiazole analogues thiophenfurin and tiazofurin. Incubation of K562 cells with selenophenfurin resulted in inhibition of IMP dehydrogenase (IMPDH) (76%) and an increase in IMP pools (14.5-fold) with a concurrent decrease in GTP levels (58%). The results obtained confirm the hypothesis that the presence of heteroatoms such as S or Se in the heterocycle in position 2 with respect to the glycosidic bond is essential for both cytotoxicity and IMP dehydrogenase inhibitory activity in this type of C-nucleosides.

  19. Mesoporous VN prepared by solid-solid phase separation

    Energy Technology Data Exchange (ETDEWEB)

    Yang Minghui, E-mail: m.yang@cornell.edu [Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 (United States); Ralston, Walter T. [Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 (United States); Tessier, Franck [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , Equipe ' Verres et Ceramiques' , Universite de Rennes 1, F-35042 Rennes cedex (France); Allen, Amy J. [Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 (United States); DiSalvo, Francis J., E-mail: fjd3@cornell.edu [Department of Chemistry, Cornell University, Ithaca, New York 14853-1301 (United States)

    2013-01-15

    We recently reported a simple route to prepare mesoporous, conducting nitrides from Zn containing ternary transition metal oxides. Those materials result from the condensation of atomic scale voids created by the loss of Zn by evaporation, the replacement of 3 oxygen anions by 2 nitrogen anions, and in most cases the loss of oxygen to form water on the reduction of the transition metal. In this report, we present a different route to prepare mesoporous VN from K containing vanadium oxides. In this case, ammonolysis results in a multiphase solid product that contains VN, and other water soluble compounds such as KOH or KNH{sub 2}. On removing the K containing products by washing with degassed water, only mesoporous VN remains. VN materials with different pore sizes (10 nm-20 nm) were synthesized at 600 Degree-Sign C by varying the reaction time, while larger pores are obtained at higher temperatures (50 nm at 800 Degree-Sign C). - Graphical Abstract: The synthesis process of mesoporous VN from solid-solid separation. Highlights: Black-Right-Pointing-Pointer Mesoporous VN has been prepared by solid-solid phase separation. Black-Right-Pointing-Pointer Mesoporous VN was characterized by Rietveld refinement of PXRD, SEM and nitrogen physisorption. Black-Right-Pointing-Pointer VN materials with different pore sizes (10 nm-50 nm) were synthesized.

  20. Mechanical Properties of Titanium Nitride Nanocomposites Produced by Chemical Precursor Synthesis Followed by High-P,T Treatment

    Directory of Open Access Journals (Sweden)

    Paul F. McMillan

    2011-10-01

    Full Text Available We investigated the high-P,T annealing and mechanical properties of nanocomposite materials with a highly nitrided bulk composition close to Ti3N4. Amorphous solids were precipitated from solution by ammonolysis of metal dialkylamide precursors followed by heating at 400–700 °C in flowing NH3 to produce reddish-brown amorphous/nanocrystalline materials. The precursors were then densified at 2 GPa and 200–700 °C to form monolithic ceramics. There was no evidence for N2 loss during the high-P,T treatment. Micro- and nanoindentation experiments indicate hardness values between 4–20 GPa for loads ranging between 0.005–3 N. Young's modulus values were measured to lie in the range 200–650 GPa. Palmqvist cracks determined from microindentation experiments indicate fracture toughness values between 2–4 MPa·m1/2 similar to Si3N4, SiC and Al2O3. Significant variations in the hardness may be associated with the distribution of amorphous/crystalline regions and the very fine grained nature (~3 nm grain sizes of the crystalline component in these materials.

  1. Synthesis and electrochemical characterization of Ti{sub x}Ta{sub y}Al{sub z}N{sub 1-δ}O{sub γ} for fuel cell catalyst supports

    Energy Technology Data Exchange (ETDEWEB)

    Wakabayashi, Ryo H.; Abruña, Héctor D., E-mail: hda1@cornell.edu; DiSalvo, Francis J., E-mail: fjd3@cornell.edu

    2017-02-15

    Quinary Ti{sub x}Ta{sub y}Al{sub z}N{sub 1-δ}O{sub γ} of various compositions have been prepared by a co-precipitation method followed by ammonolysis. The nitride samples were examined as potential catalyst supports in polymer electrolyte membrane fuel cells. The nitride products crystallized in the rock salt (NaCl) structure over a wide range of compositions. The addition of Ta and Al was highly beneficial towards improving the chemical and electrochemical stability of TiN, without a significant loss of electrical conductivity. Platinum particles were successfully deposited on the (oxy)nitride samples, and the composite samples at some compositions were found to be comparable to Pt/carbon in their stability and catalytic activity even without optimizing the Pt deposition and dispersion processes. - Graphical abstract: The effect of additions of Ta and Al into TiN structure. Shifts the lattice constant, and increases its chemical stability in acidic environment.

  2. Synthesis, crystal structure, electric and magnetic properties of LaVO{sub 2.78}N{sub 0.10}

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Songhak; Maegli, Alexandra E.; Karvonen, Lassi; Shkabko, Andrey; Populoh, Sascha; Sagarna, Leyre; Aguirre, Myriam H.; Pokrant, Simone [Laboratory for Solid State Chemistry and Catalysis, Empa - Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland); Galazka, Krzysztof [Laboratory for Solid State Chemistry and Catalysis, Empa - Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland); Department of Chemistry and Biochemistry, University of Berne (Switzerland); Jakes, Peter; Eichel, Ruediger A. [Institut fuer Energie und Klimaforschung IEK-9, Forschungszentrum Juelich (Germany); Ebbinghaus, Stefan G. [Institut fuer Chemie, Martin-Luther Universitaet Halle-Wittenberg, Halle/Saale (Germany); Weidenkaff, Anke [Laboratory for Solid State Chemistry and Catalysis, Empa - Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland); Institute for Materials Science, University of Stuttgart (Germany)

    2014-04-15

    Perovskite-type LaVO{sub 2.78}N{sub 0.10} powder was synthesized by thermal ammonolysis of the oxide precursor LaVO{sub 4}. By X-ray, neutron, and electron diffraction an orthorhombic crystal structure with space group Pnma was identified. XANES spectra showed that the oxidation state of vanadium changes from 5+ in LaVO{sub 4} to approximately 3+ in LaVO{sub 2.78}N{sub 0.10}. The temperature dependence of the electrical conductivity revealed an Arrhenius-type behavior with an activation energy of 0.103 eV in the temperature range of 119-302 K indicating that the conduction process is thermally activated band transition. Based on the positive Seebeck coefficient, holes were identified as the dominant charge carriers in the temperature range of 100-302 K. Both the Seebeck coefficient and the thermal conductivity showed an anomaly at 138 K, which is attributed to the Neel temperature for antiferromagnetic ordering according to magnetic susceptibility measurements. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Synthesis, crystal structure, electric and magnetic properties of LaVO2.78N0.10

    International Nuclear Information System (INIS)

    Yoon, Songhak; Maegli, Alexandra E.; Karvonen, Lassi; Shkabko, Andrey; Populoh, Sascha; Sagarna, Leyre; Aguirre, Myriam H.; Pokrant, Simone; Galazka, Krzysztof; Jakes, Peter; Eichel, Ruediger A.; Ebbinghaus, Stefan G.; Weidenkaff, Anke

    2014-01-01

    Perovskite-type LaVO 2.78 N 0.10 powder was synthesized by thermal ammonolysis of the oxide precursor LaVO 4 . By X-ray, neutron, and electron diffraction an orthorhombic crystal structure with space group Pnma was identified. XANES spectra showed that the oxidation state of vanadium changes from 5+ in LaVO 4 to approximately 3+ in LaVO 2.78 N 0.10 . The temperature dependence of the electrical conductivity revealed an Arrhenius-type behavior with an activation energy of 0.103 eV in the temperature range of 119-302 K indicating that the conduction process is thermally activated band transition. Based on the positive Seebeck coefficient, holes were identified as the dominant charge carriers in the temperature range of 100-302 K. Both the Seebeck coefficient and the thermal conductivity showed an anomaly at 138 K, which is attributed to the Neel temperature for antiferromagnetic ordering according to magnetic susceptibility measurements. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Prophylactic Modulation of Methane and Nitrous Oxide Emitted from Ruminants Livestock for Sustainable Animal Agriculture

    Directory of Open Access Journals (Sweden)

    J. Takahashi

    2014-12-01

    Full Text Available Major greenhouse gases (GHG attributed to animal agriculture sector are methane (CH4 and nitrous oxide (N2O, either generated from enteric fermentation or manure. The abatement mechanism of rumen CH4 emission may be divided to direct and indirect suppression to methanogens in the rumen.The most significant strategy to mitigate ruminal CH4 emission in indirect manner is to promote alternative metabolic pathway to dispose of the reducing power, competing with methanogenesis for H2 uptake. This includes prebiotics and probiotics (mostly propionate enhancers which consume metabolic hydrogen (H2 compete with methanogens and abate rumen methanogenesis in indirect manner. With regard to mitigate GHG emissions from manure, such waste has been proposed as a renewable energy and nitrogen sources through biogas plant. Furthermore, in advanced new biogas system, the ammonia stripping from digested slurry of livestock manure in biogas plant has been examined to apply to nitrogen recycling-options mitigating N2O emission. These options are: (1 ammonolysis on fiber-rich feedstuffs, (2 saccharification of the NH3 treated cellulose biomass to produce bio-ethanol, and (3 reformed hydrogen into NH3 fuel cell to generate electricity with proton exchange membrane fuel cell (PEM.

  5. Incorporating different vegetable oils into an aqueous dispersion of hybrid organic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Samyn, Pieter, E-mail: Pieter.Samyn@fobawi.uni-freiburg.de [Albert-Luedwigs-University Freiburg, Institute for Forest Utilization (Germany); Schoukens, Gustaaf [Ghent University, Department of Textiles (Belgium); Stanssens, Dirk; Vonck, Leo; Van den Abbeele, Henk [Topchim N.V. (Belgium)

    2012-08-15

    Different vegetable oils including soy oil, high-oleic sunflower oil, corn oil, castor oil (CO), rapeseed oil, and hydrogenated CO were added to the imidization reaction of poly(styrene-maleic anhydride) or SMA, with ammonium hydroxide in aqueous medium. The oils favorably reduce viscosity during ammonolysis of the anhydride moieties and increase the maximum solid content of the dispersed imidized SMA to at least 50 wt%, compared to a maximum of 35 wt% for pure imidized SMA. The viscosity of imidized SMA with polyunsaturated oils was generally larger than for monosaturated oils, but it was highest for COs due to high contents of hydroxyl groups. Depending on the oil reactivity, homogeneous or core-shell nanoparticles with 20-60 nm diameters formed. The interactions of oil and organic phase were studied by Fourier-transform infrared spectroscopy, indicating qualitative variances between different oils, the fraction imidized SMA and remaining fraction of ammonolyzed SMA without leakage of oil upon diluting the dispersion and precipitation at low pH. A quantitative analysis with calculation of imide contents, amounts of reacted oil and chemical interactions was made by Fourier-transform-Raman spectroscopy suggesting that most interactions take place around the unsaturated oil moieties and ammonolyzed anhydride.

  6. Green House Gas Control and Agricultural Biomass for Sustainable Animal Agriculture in Developing Countries

    Directory of Open Access Journals (Sweden)

    J Takahashi

    2010-06-01

    Full Text Available Important green house gases (GHG attributed to animal agriculture are methane (CH4 and nitrous oxide (N2O, though carbon dioxide (CO2 contributes almost half of total greenhouse effect. Rumen CH4 production in an enteric fermentation can be accounted as the biggest anthropogenic source. Some of prebiotics and probiotics have been innovated to mitigate rumen CH4 emission. The possible use of agricultural biomass consisted of non-edible parts of crop plants such as cellulose and hemi cellulose and animal wastes was proposed as a renewable energy and nitrogen sources. The ammonia stripping from digested slurry of animal manure in biogas plant applied three options of nitrogen recycling to mitigate nitrous oxide emission. In the first option of the ammonia stripping, the effect of ammonolysis on feed value of cellulose biomass was evaluated on digestibility, energy metabolism and protein utilization. Saccharification of the NH3 treated cellulose biomass was confirmed in strictly anaerobic incubation with rumen cellulolytic bacteria, Ruminoccous flavefaciens, to produce bio-ethanol as the second option of ammonia stripping. In an attempt of NH3 fuel cell, the reformed hydrogen from the NH3 stripped from 20 liter of digested slurry in thermophilic biogas plant could generate 0.12 W electricity with proton exchange membrane fuel cell (PEM as the third option.

  7. Ba{sub 1.63}La{sub 7.39}Si{sub 11}N{sub 23}Cl{sub 0.42}:Ce{sup 3+} - a nitridosilicate chloride with a zeolite-like structure

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter; Oeckler, Oliver [Institute of Mineralogy, Crystallography and Materials Science, Faculty of Chemistry and Mineralogy, Leipzig University, Scharnhorststrasse 20, 04275 Leipzig (Germany); Durach, Dajana; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich (Germany)

    2016-05-15

    The nitridosilicate chloride Ba{sub 1.63}La{sub 7.39}Si{sub 11}N{sub 23}Cl{sub 0.42}:Ce{sup 3+} was synthesized by metathesis reaction starting from LaCl{sub 3}, BaH{sub 2}, CeF{sub 3} and the product of the ammonolysis of Si{sub 2}Cl{sub 6}. The title compound is stable towards air and moisture. Diffraction data of a microcrystal were recorded using microfocused synchrotron radiation. X-ray spectroscopy confirms the chemical composition of the crystal. IR spectra corroborate absence of N-H bonds. The compound is homeotypic to Ba{sub 2}Nd{sub 7}Si{sub 11}N{sub 23} and crystallizes in space group Cmmm with a = 11.009(3), b = 23.243(8), c = 9.706(4) Aa and Z = 4, R{sub 1}(all) = 0.0174. According to bond valence sum calculations, some crystallographic positions show complete occupancy by Ba or La whereas others contain significant amounts of both elements. In contrast to the structure prototype Ba{sub 2}Nd{sub 7}Si{sub 11}N{sub 23}, Ba{sub 1.63}La{sub 7.39}Si{sub 11}N{sub 23}Cl{sub 0.42}:Ce{sup 3+} contains chloride ions in channels of the SiN{sub 4} tetrahedra network, hinting at various substitution possibilities of the complex zeolite-like structure. (Copyright copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Synthesis of nanocrystalline Gd{sub 2}O{sub 2}NCN from a versatile single-source precursor

    Energy Technology Data Exchange (ETDEWEB)

    Ionescu, Emanuel; Wiehl, Leonore; Mera, Gabriela; Riedel, Ralf [Fachbereich Material- und Geowissenschaften, Technische Universitaet Darmstadt (Germany); Li, Wenjie [Fachbereich Material- und Geowissenschaften, Technische Universitaet Darmstadt (Germany); Center for Energy Harvesting Materials and Systems, Mechanical Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA (United States)

    2017-11-17

    Nanocrystalline Gd{sub 2}O{sub 2}NCN (P anti 3m1, crystallite size 30-40 nm) was synthesized upon ammonolysis of bis[[(N-carboxymethyl,N-carboxy-κO-methyl)amino-κN-ethyl]-glycinato( 3-)-κN,κO]gadolinium(III) (diethylenetriamine pentaacetic acid gadolinium(III) dihydrogen salt or gadopentetic acid, Gd-H{sub 2}DTPA hereafter) at 900 C. The conversion of Gd-H{sub 2}DTPA into Gd{sub 2}O{sub 2}NCN takes place in several steps, probably via transient formation of iminodiacetate-, glycinate-, and carbamate-containing complexes of Gd. Thermal treatment in air of Gd-H{sub 2}DTPA at 750 and 1300 C delivers nanocrystalline bixbyite-type Gd{sub 2}O{sub 3} (Ia anti 3, crystallite size 30-70 nm); in an argon or nitrogen atmosphere the formation of monoclinic Gd{sub 2}O{sub 3} (C2/m) was observed at 1300 C. The synthesized Gd{sub 2}O{sub 2}NCN converts upon thermal treatment in air, nitrogen, or argon atmosphere into monoclinic Gd{sub 2}O{sub 3} (C2/m). In ammonia atmosphere, Gd{sub 2}O{sub 2}NCN seems to be stable against decomposition, even upon prolonged exposure to 1000 C. This study indicates that Gd-H{sub 2}DTPA may be a robust, low-cost, and flexible precursor for nanoscaled Gd-based nanopowders. Moreover, precursor approaches based on metal complexes using H{sub 5}DTPA as a ligand are suggested as promising access pathways towards nanocrystalline materials in the M/O/C/N system. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Tuning the bimetallic amide-imide precursor system to make paramagnetic GaMnN nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Drygas, Mariusz [AGH University of Science and Technology, Faculty of Energy and Fuels, Al. Mickiewicza 30, 30-059 Krakow (Poland); Janik, Jerzy F., E-mail: janikj@agh.edu.pl [AGH University of Science and Technology, Faculty of Energy and Fuels, Al. Mickiewicza 30, 30-059 Krakow (Poland); Musial, Michal [AGH University of Science and Technology, Faculty of Energy and Fuels, Al. Mickiewicza 30, 30-059 Krakow (Poland); Gosk, Jacek [Warsaw University of Technology, Faculty of Physics, Koszykowa 75, 00-662 Warszawa (Poland); Twardowski, Andrzej, E-mail: andrzej.twardowski@fuw.edu.pl [University of Warsaw, Faculty of Physics, Pasteura 5, 02-093 Warszawa (Poland)

    2016-09-01

    A bimetallic molecular system made of gallium (III) tris(dimethyl)amide Ga(NMe{sub 2}){sub 3} and manganese (II) bis(trimethylsilyl)amide Mn[N(SiMe{sub 3}){sub 2}]{sub 2} (Me = CH{sub 3}, fixed initial Mn-content 10 at.%) was subjected to ammonolysis in refluxing/liquid ammonia. Upon isolation at room temperature, the amide-imide mixed metal precursor was pyrolyzed at elevated temperatures under an ammonia flow by two different routes. Route 1 consisted of a direct nitridation at high temperatures of 500, 700 or 900 °C. In route 2, a low temperature pyrolysis at 150 °C was applied prior to nitridation at the same final temperatures as in route 1. All nanopowders were characterized by XRD diffraction, FT-IR spectroscopy, and SEM/EDX microscopy and analysis. Thorough magnetization measurements in function of magnetic field and temperature were carried out with a SQUID magnetometer. In all samples, the paramagnetic phase of GaMnN was accompanied by an antiferromagnetic by-product linked to a Mn-containing species from decomposition and oxidation of Mn-precursor excess. The Mn-contents in the crystalline GaMnN, i.e., Mn-incorporated in GaN crystal lattice, were of the order of 2–3 at.% mostly independent on the nitridation route whereas the latter had a pronounced effect on amounts of the antiferromagnetic by-product. - Highlights: • New bimetallic precursor system for conversion to GaN/Mn nanopowders was designed. • Two conversion routes were applied with precursor nitridation at 500, 700 or 900 °C. • Prepared nanopowders were thoroughly characterized including magnetic measurements. • The major product was the gallium nitride Mn-doped phase GaMnN with 2–3 at.% of Mn.

  10. Investigations of inorganic and hybrid inorganic-organic nanostructures

    Science.gov (United States)

    Kam, Kinson Chihang

    This thesis focuses on the exploratory synthesis and characterization of inorganic and hybrid inorganic-organic nanomaterials. In particular, nanostructures of semiconducting nitrides and oxides, and hybrid systems of nanowire-polymer composites and framework materials, are investigated. These materials are characterized by a variety of techniques for structure, composition, morphology, surface area, optical properties, and electrical properties. In the study of inorganic nanomaterials, gallium nitride (GaN), indium oxide (In2O3), and vanadium dioxide (VO2) nanostructures were synthesized using different strategies and their physical properties were examined. GaN nanostructures were obtained from various synthetic routes. Solid-state ammonolysis of metastable gamma-Ga2O 3 nanoparticles was found to be particularly successful; they achieved high surface areas and photoluminescent study showed a blue shift in emission as a result of surface and size defects. Similarly, In2O3 nanostructures were obtained by carbon-assisted solid-state syntheses. The sub-oxidic species, which are generated via a self-catalyzed vapor-liquid-solid mechanism, resulted in 1D nanostructures including nanowires, nanotrees, and nanobouquets upon oxidation. On the other hand, hydrothermal methods were used to obtain VO2 nanorods. After post-thermal treatment, infrared spectroscopy demonstrated that these nanorods exhibit a thermochromic transition with temperature that is higher by ˜10°C compared to the parent material. The thermochromic behavior indicated a semiconductor-to-metal transition associated with a structural transformation from monoclinic to rutile. The hybrid systems, on the other hand, enabled their properties to be tunable. In nanowire-polymer composites, zinc oxide (ZnO) and silver (Ag) nanowires were synthesized and incorporated into polyaniline (PANI) and polypyrrole (PPy) via in-situ and ex-situ polymerization method. The electrical properties of these composites are

  11. Kinetic modeling of the polymer-derived ceramics route: investigation of the thermal decomposition kinetics of poly[B-(methylamino)borazine] precursors into boron nitride.

    Science.gov (United States)

    Bernard, Samuel; Fiaty, Koffi; Cornu, David; Miele, Philippe; Laurent, Pierre

    2006-05-11

    A complete kinetic modeling of the polymer-derived ceramics (PDCs) route is achieved for the first time through the investigation of the solid-state decomposition of a typical melt-spinnable poly[B-(methylamino)borazine] into boron nitride fibers at various heating rates. Through the use of the Lorentz fitting approach, it is shown that the two-step weight loss associated with the polymer-to-ceramic conversion is governed by a complex interplay of five diffusion-type transport mechanisms that are independent of the applied heating schedule. The application of the Friedman method to dynamic thermogravimetry data yields Ea and ln A values that are seen to increase with the extent of the ceramic conversion from region one (Ea = 38.73 kJ mol(-1)) to region five (Ea = 146.64 kJ mol(-1)). This fact indicates that both the mechanisms within those regions are parallel routes to the formation of the final solid-state material and their complexity increases with the conversion progress. The cross-linking process (first weight loss) of the polymer is governed by three dependent poorly energetic mechanisms. The first weight loss is activated by ammonolysis reactions that provide a modified polymer capable of undergoing condensation reactions in regions two and three to yield a highly cross-linked polymer. A large evolution of methylamine is identified during this process. Mineralization (region four) and ceramization (region five) steps are represented by two highly energetic multistep mechanisms. The mineralization step is associated with a large evolution of methylamine and occurs during the transition between the cross-linking and ceramization processes through the cleavage of the inter-ring B-N bonds. Ceramization represents the end of the polymer-to-ceramic conversion in which the planar consolidation of BN hexagons occurs through complex structural rearrangements of the borazine units (cleavage of the intraring B-N bonds) accompanied with an ammonia evolution. Finally

  12. Synthesis of oxynitride materials for solar water splitting: investigations with ambient pressure and high pressure synthesis techniques

    Science.gov (United States)

    Dharmagunawardhane, Hingure Arachchilage Naveen

    be formed by direct ammonolysis of gallium nitrate hydrate at ambient pressure. The formed product was nanocrystalline and exhibited an indirect band gap of 2.5 eV. The material photocatalytically evolved H 2 at an initial rate 8 ?mol/ h, but the activity diminished after five hours due to degradation forming gallium oxide hydroxide.

  13. Synthesis and Characterization of LaTiO2N

    Science.gov (United States)

    Rugen, Evan E.

    Photocatalysts offer an excellent opportunity to shift the global energy landscape from a fossil fuel-dependent paradigm to sustainable and carbon-neutral solar fuels. Oxynitride materials such as LaTiO2N are potential photocatalysts for the water splitting reaction due to their high oxidative stability and their narrow band gaps, which are suitable for visible light absorption. However, facile synthetic routes to metal oxynitrides with controlled morphologies are rare, and the local structures of these materials are under-characterized. Ultrasonic spray synthesis (USS) offers a facile method toward complex metal oxides which can potentially be converted to oxynitrides with preservation of the microsphere structures that typify the products from such aerosol routes. Here, La-Ti-O microspheres were facilely produced by USS and converted by ammonolysis to LaTiO2N microspheres with porous shells and hollow interiors. This particle architecture is accounted for by coupling suitable combustion chemistry with the aerosol technique, producing precursor particles where the La3+ and Ti4+ are well-mixed at small length scales; this feature enables preservation of the microsphere morphology during nitridation despite the crystallographic changes that occur. The LaTiO2N microspheres are comparable oxygen evolving photocatalysts to samples produced by conventional solid state methods. Pair distribution function (PDF) analysis is a local probe designed to examine the structure of disordered crystalline materials, and is an ideal technique for characterizing the ordering of anions in oxynitrides. Preliminary studies using PDF analysis to determine the presence of anion ordering and local structure in LaTiO2N produced by solid state methods are presented here. Future experiments are proposed that will grant detailed insight into the factors driving the degree of anion ordering in these types of materials. These results demonstrate the utility of USS as a facile, potentially

  14. Composition-induced structural, electrical, and magnetic phase transitions in AX-type mixed-valence cobalt oxynitride epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jumpei; Oka, Daichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); Hirose, Yasushi, E-mail: hirose@chem.s.u-tokyo.ac.jp; Yang, Chang; Fukumura, Tomoteru; Hasegawa, Tetsuya [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado, Takatsu, Kawasaki 213-0012 (Japan); CREST, Japan Science and Technology Agency, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Harayama, Isao; Sekiba, Daiichiro [University of Tsukuba Tandem Accelerator Complex (UTTAC), 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8577 (Japan)

    2015-12-07

    Synthesis of mid- to late-transition metal oxynitrides is generally difficult by conventional thermal ammonolysis because of thermal instability. In this letter, we synthesized epitaxial thin films of AX-type phase-pure cobalt oxynitrides (CoO{sub x}N{sub y}) by using nitrogen-plasma-assisted pulsed laser deposition and investigated their structural, electrical, and magnetic properties. The CoO{sub x}N{sub y} thin films with 0 ≤ y/(x + y) ≤ 0.63 grown on MgO (100) substrates showed a structural phase transition from rock salt (RS) to zinc blend at the nitrogen content y/(x + y) ∼ 0.5. As the nitrogen content increased, the room-temperature electrical resistivity of the CoO{sub x}N{sub y} thin films monotonically decreased from the order of 10{sup 5} Ω cm to 10{sup −4} Ω cm. Furthermore, we observed an insulator-to-metal transition at y/(x + y) ∼ 0.34 in the RS-CoO{sub x}N{sub y} phase, which has not yet been reported in Co{sup 2+}/Co{sup 3+} mixed-valence cobalt oxides with octahedral coordination. The low resistivity in the RS-CoO{sub x}N{sub y} phase, on the 10{sup −3} Ω cm order, may have originated from the intermediate spin state of Co{sup 3+} stabilized by the lowered crystal field symmetry of the CoO{sub 6−n}N{sub n} octahedra (n = 1, 2,…5). Magnetization measurements suggested that a magnetic phase transition occurred in the RS-CoO{sub x}N{sub y} films during the insulator-to-metal transition. These results demonstrate that low-temperature epitaxial growth is a promising approach for exploring novel electronic functionalities in oxynitrides.

  15. Multifaceted metabolomics approaches for characterization of lignocellulosic biomass degradation products formed during ammonia fiber expansion pretreatment

    Science.gov (United States)

    Vismeh, Ramin

    Lignocellulosic biomass represents a rather unused resource for production of biofuels, and it offers an alternative to food sources including corn starch. However, structural and compositional impediments limit the digestibility of sugar polymers in biomass cell walls. Thermochemical pretreatments improve accessibility of cellulose and hemicellulose to hydrolytic enzymes. However, most pretreatment methods generate compounds that either inhibit enzymatic hydrolysis or exhibit toxicity to fermentive microorganisms. Characterization and quantification of these products are essential for understanding chemistry of the pretreatment and optimizing the process efficiency to achieve higher ethanol yields. Identification of oligosaccharides released during pretreatment is also critical for choosing hydrolases necessary for cost-effective hydrolysis of cellulose and hemicellulose to fermentable monomeric sugars. Two chapters in this dissertation describe new mass spectrometry-based strategies for characterization and quantification of products that are formed during ammonia fiber expansion (AFEX) pretreatment of corn stover. Comparison of Liquid Chromatography Mass Spectrometry (LC/MS) profiles of AFEX-treated corn stover (AFEXTCS) and untreated corn stover (UTCS) extract shows that ammonolysis of lignin carbohydrate ester linkages generates a suite of nitrogenous compounds that are present only in the AFEXTCS extract and represent a loss of ammonia during processing. Several of these products including acetamide, feruloyl, coumaroyl and diferuloyl amides were characterized and quantified in the AFEXTCS extracts. The total amount of characterized and uncharacterized phenolic amides measured 17.4 mg/g AFEXTCS. Maillard reaction products including pyrazines and imidazoles were also identified and measured in the AFEXTCS extract totaling almost 1 mg/g AFEXTCS. The total of quantified nitrogenous products that are formed during AFEX was 43.4 mg/g AFEXTCS which was equivalent