DOCSLIB.ORG

Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-1973 Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates Gann Ting University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Chemistry Commons Recommended Citation Ting, Gann, "Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates. " PhD diss., University of Tennessee, 1973. https://trace.tennessee.edu/utk_graddiss/3261 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Gann Ting entitled "Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Chemistry. G. Mamantov, Major Professor We have read this dissertation and recommend its acceptance: Charles Baes, G. P. Smith, J. O. Chambers Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) July 31, 1973 To the Graduate Council: I am submitting herewith a dissertation written by Gann Ting entitled "Thermodynamic and Electrochemical Studies of Niobium in Molten Fluorides and Chloroaluminates." I recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy , with a major in Chemistry. r Professor fo ma-. We have read this dissertation f!.f. and recommend its acceptance : Accepted for the Council: Vice Chancellor for Graduate Studies and Research THERMODYNAMIC AND ELECTROCHEMICAL STUDIES OF NIOBIUM IN MOLTEN FLUORIDES AND CHLOROALUMINATES A Dissertation Presented to the Graduate Council of The University of Tennessee In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy by Gann Ting August 1973 ACKNOWLEDGMENT The author wishes to express his appreciation to Drs. G. Mamantov and C. F. Baes, Jr. for their guidance and encouragement throughout this investigation. Appreciation is expressed to Drs. c. E. Bamberger and K. w. Fung for their valuable assistance and suggestions in the labora­ tory, to D. L. Manning for making his instruments available for this work and for helpful discussions , to G. M. Begun for assistance with the Raman experiments, and to J. P. Young for performing the UV spectrometric analysis. Thanks are also expressed to the Oak Ridge National Laboratory operated for the United States Atomic Energy Commission by Union Carbide Corporation, especially to its Reactor Chemistry Division, for allowing the author to do this research, for providing equipment, materials, and facilities , and to the members of the Analytical Chemistry Division for sample analysis . Support of the National Science Foundation, Grant GP-32433X, for work carried out at the Department of Chemistry, University of Tennessee, is gratefully acknowledged. I would also like to thank Mrs . J. Wallace for typing this manuscript , and to s. C. Lin for drawing the figures. Financial support from the Institute of Nuclear Energy Research , Chinese Atomic Energy Council, Republic of China, is gratefully acknowledged. ii 11190:1.9 ABSTRACT The oxide chemistry of niobium(V) has been studied in molten LiF-BeF2 mixtures. The stoichiometry of an oxygen-containing niobium(V) F) has been established in molten Li species (Nb02 2BeF4 from the hetero­ geneous equilibrations of NiNb206 and NiO with the melt containing NiF2 , the equilibrium quotient for the reaction was determined. The equili- brium quotient for the heterogeneous reaction of Nb2o5 and BeO with mo lten LiF-BeF2 mixtures (67-33 and 52-48 mole %) was also determined, and the effect of the melt composition on the solubility of Nb2o5 (c) and on the activity coefficient of Nb02F(d) have been examined. The free energies of formation of Nb02F(d) and NiNb206 (c) has been estimated from the experimental results. A Pourbaix diagram for niobium in molten Li2BeF4 at 500° and a phases diagram at 600° involving Nb02F and NiF2 and the equilibrium oxide phases (Nb2o5 , NiNb2o6, NiO, and BeO) in molten Li2BeF4 were constructed. The electrochemical reduction of Nb (V) in molten LiF-BeF2-ZrF4 (65.6-29.4-5.0 mole %) has been studied by linear sweep voltammetry with pyrolytic graphite and platinum electrodes. Potentials were measured with respect to a Ni(II) (saturated)/Ni reference electrode. Nb (V) was found to form Nb02F. The results at the pyrolytic graphite electrode were reproducible; three reduction steps were observed at low scan rates (< 0.5 V/sec) and one reduction step was observed at high scan rates (> 5 V/sec). Mechanisms are proposed for the reduction of niobium(V). The results with platinum electrode were complicated and irreproducible. The electrochemical reduction of Nb (V) chloride and Nb (V) oxychloride in molten AlCl3-NaCl mixtures (63-37 to 50-50 mole %) has iii iv been examined by means of chronoamperometry, differential pulse polaro- graphy , chronopotentiometry and linear sweep voltammetry using platinum and tungsten electrodes. Potentials were measured with respect to an Al (III) (AlC13-NaCl, 63-37 mole %) /Al reference electrode. The effect of the melt composition, temperature and Nb (V) concentration on the reduc- tion steps was studied. The results show that the stability of the niobium species and the electrode reduction mechanisms of Nb (V) chloride and oxychloride are very sensitive to the melt composition and to the temperature. The number of reduction steps, the redox potentials, and the stability of the various niobium species at different melt composi- tiona and temperatures are reported. Reduction mechanisms of niobium(V) chloride and oxychloride are proposed. Some vibrational spectroscopic studies of solid Nb20s and NiNb20s were performed; the results indicate that the symmetric stretching fre­ -1 quencies of Nb-0 in Nb20s and NiNb2o6 are 992 and 882 em • respectively. TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION . • • . 1 A. Review of the Literature • • • . 2 1. Oxide chemistry in molten Li2BeF4 and 2 LiF-BeF2-ThF4 ••••••, , • , , • , , , • • 2 , Chemistry of niobium oxides, fluorides, oxyfluorides and oxo-fluoro complexes • • • • • 5 3, Chemistry of niobium chlorides and oxychlorides 10 4. Electrochemistry of niobium in molten chlorides and fluor ides • • • • • • • • • • • • • 14 B, Review of Basic Principles • . 19 1. Acid-base concepts in molten chlorides and fluorides . 19 2 . EMF measurements • • • • • • • • • . 21 3. Representation of equilibria by Pourbaix diagrams . 23 4. Linear sweep voltammetry • • • • . 26 5. Chronopotentiometry • • . 30 6. Chronoamperometry and construction of stationary electrode polarograms • • • • • • • • 43 7. Pulse polarography • • • • • • 43 8, Studies of adsorption by linear sweep voltammetry and chronopotentiometry . 46 c. Proposed Research . • • • • • • • • • • • 49 II. EXPERIMENTAL • 0 Q • 0 0 • • • . • • . 51 v vi CHAPTER PAGE A. Ma terials e • • • • • • • • • • ' • • • • • • • • • • 51 1. Materials for equilibria and electrochemical studies in mo lten fluorides • • • • • • • • • • 51 2. Materials for electrochemical studies in molten chloroaluminates • • • • • • • • • • • • . 52 B. Apparatus 0 • • • • • . 53 1. Apparatus for equilibria studies in molten fluorides . 53 2. Apparatus for electrochemical studies in molten chloroaluminates • • • • • • • • • • • . 58 3. Apparatus for electrochemical studies in molten fluorides • • . • • • • . 61 c. Procedures • . • • • • • • • • • • 64 1. Procedure for equilibria studies • • . 64 2. Procedure for electrochemical studies in molten chloroaluminates . 66 3. Procedure for electrochemical studies in molten fluorides . 68 III. RESULTS AND DISCUSSION • • • • • . 69 A. The Oxide Chemistry of Niobium in Molten LiF-BeF2 Mixtures • • • • • • • • • • • • • • • • • 69 Equilibrations of and BeO with molten 1. Nb20s LiF-BeF 2 mixtures • • • • • • • • • • • 70 2. Equilibrations involving nickel niobates in mo lten Li2BeF4 • • • • • • • • • • • • • • • • • • • • 80 vii CHAPTER PAGE 3. Equilibrations of NiNb o and NiO with molten Li BeF 2 6 2 4 and determination of the stoichiometry of an oxygen-containing niobium species in the melt. 87 4. Estimation of the heat of formation and the lattice energy of NiNb2o6 • • • • • • • • • • 97 B. Studies of Nb (V) in Molten LiF-BeF2-zrF4 (65. 6-29. 4-5.0 Hole %) ••••••••. 102 c. Electrochemistry of Niobium Pentachloride in Holten AlC1 -NaCl Hixtures • • • • • • • • • • • • 114 3 1. Electrochemistry of Nb (V) in molten AlC13-NaCl (63-37 mole %) • • • • • • • • • • • • • • • • 114 2. Electrochemistry of Nb (V) in molten AlC13-NaCl (61-39 mole %) • • • • • • • . • • • • • • • • 127 3. Electrochemistry of Nb (V) in molten AlC13-NaCl (55-45 mole%) ••••••••••• o 0<0 o o 130 4o Electrochemistry of Nb (V) in molten AlC13-NaCl (50-50 mole %) • • • • • o o o oeooae•• 141 So Effect of melt composition and temperature on the reduction of Nb (V) in molten AlC13-NaCl mixtures • o o • • • 0 0
Load more

Recommended publications
  • Chemistry of the Corrosion of Metals in Presence of Molten Vanadium Pentoxide
    CHEMISTRY OF THE CORROSION OF METALS IN PRESENCE OF MOLTEN VANADIUM PENTOXIDE THESIS Submitted for the Degree of DOCTOR OF PHILOSOPHY THE UNIVERSITY OF LONDON by KAILATHUVALAPPIL INNIRI VASU February, 1964 Department of Metallurgy, Royal School of Mines, Imperial College, London, S.W.7. The author is grateful to Dr. D. A. Pantony, who supervised this research project, for his constant encouragement, numerous suggestions and stimulating discussions; to his colleagues and the members of the teaching and technical staff of the Department of Metallurgy, Imperial College, for their helpful co—operation; and to the British Petroleum Company Limited for financial assistance. CONTENTS ABSTRACT NOMENCLATURE vi I. INTRODUCTION A. HISTORY 1 B. NATURE OF CORROSION 2 C. ACTIVATION - AND DIFFUSION - CONTROLLED PROCESSES 4 D. RELEVANT PREVIOUS INVESTIGATIONS 6 E. APPROACH TO THE PROBLEM 9 (a) PHYSICAL-CHEMICAL STUDIES ON VANADIC MELTS (1)Dissociation Equilibrium 10 (2)Kinetics of the Oxidation of Vanadium Dioxide 11 (3)Cryoscopy 11 (4)Conductivity of Vanadic Melts 11 (5)Viscosity and Density 12 (b) CORROSION OF METALS IN THE PRESENCE OF MOLTEN VANADIUM PENTOXIDE (1)General Nature 12 (2)In Relation to Gas-Turbine Corrosion 13 (3)A Model for Study 14 (3a) The Corrosion Layer 19 (4)Metal Surface and Corrosion 23 (5)Prevention of Corrosion 23 II. EXPERIMENTAL A. MATERIALS (a)Vanadium Pentoxide 25 (b)Metals 25 (c)Metal Oxides 27 (d)Oxygen, Nitrogen, and Oxygen- Nitrogen Mixtures 28 B. SPECIMENS FOR CORROSION STUDIES 30 C. EXPERIMENTAL PROCEDURE (a)Container
    [Show full text]
  • S42004-019-0231-3.Pdf — Adobe
    ARTICLE https://doi.org/10.1038/s42004-019-0231-3 OPEN Niobium pentoxide nanomaterials with distorted structures as efficient acid catalysts Kai Skrodczky1, Margarida M. Antunes2, Xianying Han1, Saveria Santangelo 3, Gudrun Scholz1, Anabela A. Valente 2*, Nicola Pinna 1* & Patrícia A. Russo1* 1234567890():,; Niobium pentoxides are promising acid catalysts for the conversion of biomass into fuels and chemicals. Developing new synthesis routes is essential for designing niobium pentoxide catalysts with improved activity for specific practical processes. Here we show a synthesis approach in acetophenone, which produces nanostructured niobium pentoxides with varying structure and acidity that act as efficient acid catalysts. The oxides have orthorhombic structures with different extents of distortions and coordinatively unsaturated metal atoms. A strong dependence is observed between the type and strength of the acid sites and specific structural motifs. Ultrasmall niobium pentoxide nanoparticles, which have strong Brønsted acidity, as well as Lewis acidity, give product yields of 96% (3 h, 140 °C, 100% conversion), 85% (3 h, 140 °C, 86% conversion), and 100% (3 h, 110 °C, 100% conversion) in the reac- tions of furfuryl alcohol, 5-(hydroxymethyl)furfural, and α-angelica lactone with ethanol, respectively. 1 Institut für Chemie and IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany. 2 Department of Chemistry, CICECO, University of Aveiro, Aveiro, Portugal. 3 Dipartimento di Ingegneria Civile, dell’Energia, dell’Ambiente e dei Materiali (DICEAM), Università “Mediterranea”, Reggio Calabria, Italy. *email: [email protected]; [email protected]; [email protected] COMMUNICATIONS CHEMISTRY | (2019) 2:129 | https://doi.org/10.1038/s42004-019-0231-3 | www.nature.com/commschem 1 ARTICLE COMMUNICATIONS CHEMISTRY | https://doi.org/10.1038/s42004-019-0231-3 iobium pentoxides show high potential as acid catalysts will also allow getting insights into the structure–acidity–activity Nfor the sustainable production of fuels and chemicals from relationships.
    [Show full text]
  • Enrichment Strategies for Phosphoproteomics: State-Of-The-Art
    Rev Anal Chem 31 (2012): 29–41 © 2012 by Walter de Gruyter • Berlin • Boston. DOI 10.1515/revac-2011-0025 Enrichment strategies for phosphoproteomics: state-of-the-art Barbora Salovska 1,2, *, Ales Tichy 1,2 , Martina MIP molecularly imprinted polymer Rezacova 1 , Jirina Vavrova 2 and Eva Novotna 2 MOAC metal oxide affi nity chromatography MS mass spectrometry 1 Department of Medical Biochemistry , Faculty of NTA nitriloacetic acid Medicine in Hradec Kralove, Charles University in PTMs post-translational modifi cations Prague, Hradec Kr á lov é , Czech Republic , pS phosphoserine e-mail: [email protected] pT phosphothreonine 2 Department of Radiobiology , Faculty of Military Health pY phosphotyrosine Sciences, University of Defence, Hradec Kralove , RPLC reversed phase liquid chromatography Czech Republic SAX strong anion-exchange chromatography SCX strong cation-exchange chromatography * Corresponding author Introduction Abstract Protein phosphorylation is a key regulator in many biological The human genome involves approximately 30,000 protein- processes, such as homeostasis, cellular signaling and com- coding genes; the human proteome contains several million munication, transcriptional and translational regulation, and different protein effectors. This is due to alternative splic- apoptosis. The defects in this tightly controlled reversible post- ing of genes and post-translational modifi cations (PTMs). translational modifi cation have been described to contribute Several hundred PTMs are currently known, among them to genesis and
    [Show full text]
  • Niobium(V) Oxide Patinal®
    Product Information Niobium(V) Oxide Patinal ® GENERAL INFORMATION Niobium pentoxide is especially suited for IAD processes and a suitable alternative to TiO 2 with its high refractive index and low absorption. However the layers may show some absorption when deposited by conventional thermal evaporation. Similar to tantalum pentoxide, niobium pentoxide emits oxygen during melting and evaporation, requiring reactive evaporation. Due to the similarities in the process for those two materials, Nb 2O5 is a close alternative to Ta 2O5 and, in contrary to tantalum, not included on the list of “conflict minerals” mentioned in the Dodd-Franck Wall Street Reform and Consumer Protection Act. AREAS OF APPLICATION • Multi-layer coatings for laser mirrors and beam splitters • Anti-reflection coatings on glass in VIS and NIR THIN FILM PROPERTIES Chemical Formula Nb 2O5 Range of Transparency 380 nm – 7 µm Refractive index at 500 nm • conventional T s = 300 °C / no IAD ~ 2.25 – 2.30 • IAD – Ts = RT ~ 2.30 – 2.35 Thin film stress Compressive The optical properties of the thin film are strongly dependent on the deposition rate, substrate temperature and oxygen partial pressure. Strict control of these parameters allows excellent reproducibility. wavl / nm 375 450 550 700 900 1200 n - IAD 2.495 2.341 2.266 2.220 2.196 2.181 k - IAD 2.5E-03 4.6E-04 2.0E-04 1.1E-04 6.9E-05 4.6E-05 Status: 02 / 2018, Page 1 of 4 EMD Performance Materials* One International Plaza Suite 300 / Philadelphia, PA / 19113 USA +888 367 3275 / [email protected] / patinal.com
    [Show full text]
  • Niobium Pentoxide Based Materials for High Rate Rechargeable Electrochemical Energy Storage Cite This: Mater
    Materials Horizons View Article Online REVIEW View Journal | View Issue Niobium pentoxide based materials for high rate rechargeable electrochemical energy storage Cite this: Mater. Horiz., 2021, 8, 1130 Fei Shen,a Zhongti Sun,ab Qinggang He, *c Jingyu Sun, abd Richard B. Kaner *e and Yuanlong Shao*abd The demand for high rate energy storage systems is continuously increasing driven by portable electronics, hybrid/electric vehicles and the need for balancing the smart grid. Accordingly, Nb2O5 based materials have gained great attention because of their fast cation intercalation faradaic charge storage that endows them with high rate energy storage performance. In this review, we describe the crystalline features of the five main phases of Nb2O5 and analyze their specific electrochemical characteristics with an emphasis on the intrinsic ion intercalation pseudocapacitive behavior of T-Nb2O5. The charge Received 14th September 2020, storage mechanisms, electrochemical performance and state-of-the-art characterization techniques for Accepted 9th December 2020 Nb2O5 anodes are summarized. Next, we review recent progress in developing various types of Nb2O5 DOI: 10.1039/d0mh01481h based fast charging electrode materials, including Nb2O5 based mixed metal oxides and composites. Finally, we highlight the major challenges for Nb2O5 based materials in the realm of high rate rechargeable rsc.li/materials-horizons energy storage and provide perspectives for future research. 1. Introduction Due to the increasing demand for rapid charging and high power a College of Energy, Soochow Institute for Energy and Materials InnovationS delivery for portable electronics and electricvehicles,highrate (SIEMIS), Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and energy storage systems (ESSs) that can store/release charge in Wearable Energy Technologies, Soochow University, 215006 Suzhou, P.
    [Show full text]
  • Synthesis, Characterization of Nb2o5\Cdsnanocomposites, And
    International Journal of ChemTech Research CODEN (USA): IJCRGG, ISSN: 0974-4290, ISSN(Online):2455-9555 Vol.9, No.10 pp 149-156, 2016 Synthesis, Characterization of Nb2O5\Cds Nanocomposites and Study of High Photo Catalytic Activity of Transition Metal Ion Zena T Omran, and Nada Y Fairooz* Department of Chemistry, College of Science, University of Babylon,Hilla-Iraq Abstract : This work includes the study of preparing the new Nb2O5/CdS coupled photocatalyst was prepare by wet commixing method at different ratios of (0.75:0.25, 0.6:0.4,0.5:0.5, 0.85:0.15,0:1 ,1:0) and calcinations at different temperature 200 0C,500 0C and8000C for4 hours .The prepared powder was characterized by X-ray diffraction, and Fourier Transform Technique (FT-IR).The photocatalytic activity was estimated under mercury high pressure lamp for degradation Co(NO3)2 solution after find the wavelength at λ max510nm . The result showed that (0.85:0.15) percentage at 800 0C has high activity than other ratio at different temperature. After this study some measure such as best of mass for the catalyst, initial of concentration for Co(NO3)2, effect of temperature, effect of PH. Keywords: Co(NO3)2, couple Nb2o5/CdS, Degradation, photocatalytic. Introduction: Niobium pentoxide (Nb2O5) is considered one of the most committed transition metal oxides (TMO) for 1 pseudocapacitive energy storage. Nb2O5 is to a great degreestudied in lithium-ion batteries (LIB) , electrochemical hydrogenation catalysts2.gas sensing3, electrochromic devices4 and solar cells5. Nb2O5 exhibits a different of crystalline allotropes,with orthorhombic (T-Nb2O5), pseudo-hexagonal 6,7 (TT-Nb2O5), tetragonal (M-Nb2O5) and monoclinic(H-Nb2O5) .
    [Show full text]
  • 1 Thermodynamic Evaluation of the Propensity of Niobium to Absorb
    Thermodynamic Evaluation of the Propensity of Niobium to Absorb Hydrogen During Fabrication of Superconducting Radio Frequency Accelerator Cavities Richard E. Ricker Materials Performance Group Metallurgy Division Materials Science and Engineering Laboratory National Institute of Standards and Technology US Department of Commerce Gaithersburg, MD 20899-8553 ABSTRACT During the fabrication of niobium superconducting radio frequency (SRF) particle accelerator cavities procedures are used that chemically or mechanically remove the passivating surface film of niobium pentoxide (Nb2O5). Removal of this film will expose the underlying niobium metal and allow it to react with the processing environment. If these reactions produce hydrogen at sufficient concentrations and rates, then hydrogen will be absorbed and diffuse into the metal. High hydrogen activities could result in supersaturation and the nucleation of hydride phases. If the metal repassivates at the conclusion of the processing step and the passive film blocks hydrogen egress, then the absorbed hydrogen or hydrides could be retained and alter the performance of the metal during subsequent processing steps or in-service. This report examines the feasibility of this hypothesis by identifying the postulated events, conditions, and reactions and determining if each is consistent with accepted scientific principles, literature, and data. Established precedent for similar events in other systems was found in the scientific literature and thermodynamic analysis found that the postulated reactions were not only energetically favorable, but produced large driving forces. The hydrogen activity or fugacity required for the reactions to be at equilibrium was determined used to indicate the propensity for hydrogen evolution, absorption, and hydride nucleation. The influence of processing conditions and kinetics on the proximity of hydrogen surface coverage to these theoretical values is discussed.
    [Show full text]
  • Formation of Niobium Oxides by Electrolysis from Acidic Aqueous Solutions on Glassy Carbon
    Macedonian Journal of Chemistry and Chemical Engineering, Vol. 38, No. 1, pp. 39–48 (2019) MJCCA9 – 767 ISSN 1857-5552 e-ISSN 1857-5625 Received: November 13, 2018 DOI: 10.20450/mjcce.2019.1623 Accepted: February 1, 2019 Original scientific paper FORMATION OF NIOBIUM OXIDES BY ELECTROLYSIS FROM ACIDIC AQUEOUS SOLUTIONS ON GLASSY CARBON Nataša M. Vukićević1*, Vesna S. Cvetković1, Ljiljana S. Jovanović2, Miroslav M. Pavlović1, Jovan N. Jovićević1 1Institute of Chemistry, Technology and Metallurgy, National Institute, Department of Electrochemistry, University of Belgrade, Njegoševa 12, Serbia 2Faculty of Science, Department of Chemistry, Biochemistry and Environmental Protection, University of Novi Sad, Trg Dositeja Obradovića 3, Serbia [email protected] In this study niobium oxide films were formed without peroxo-precursors from three different mixed acidic aqueous solutions on glassy carbon. Linear sweep voltammetry and potential step were techniques used for electrochemical experiments. The simultaneous and consecutive electrochemical re- duction of water, nitrate and sulphate ions provided an alkaline environment with oxygen in the near vi- cinity of the working cathode, which in combination with the present niobium ions, produced niobium oxides and/or oxyhydroxides on the glassy carbon substrate. The formed deposits were analyzed using scanning electron microscopy and energy dispersive spectroscopy and appear to consist of NbO, NbO2 and Nb2O5. Both the niobium and acid concentration of the electrolytes used influenced the morphology and particle size of the deposits. The formation of niobium-fluoride and hydrogen-niobiumoxide com- plexes is addressed. Key words: electrochemical deposition; niobium oxides; acidic solution; glassy carbon ФОРМИРАЊЕ НА ФИЛМОВИ ОД ОКСИДИ НА НИОБИУМ СО ЕЛЕКТРОЛИЗА ОД КИСЕЛИ РАСТВОРИ НА СТАКЛЕСТА ГРАФИТНА ЕЛЕКТРОДА Во овој труд е изучувано формирањето на филмови на оксиди од ниобиум што се одвива без пероксидни медијатори од три различни водни раствори со различни рН вредности на стаклеста графитна електрода.
    [Show full text]
  • Study of Large Molecular Weight Poly(Isoprene-B-Styrene-B- Ethylene Oxide) and of Its Hybrid Oxides and Nitrides
    STUDY OF LARGE MOLECULAR WEIGHT POLY(ISOPRENE-B-STYRENE-B- ETHYLENE OXIDE) AND OF ITS HYBRID OXIDES AND NITRIDES A Thesis Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Master of Science By Ji-yeob Kim August 2014 © 2014 Ji-yeob Kim ABSTRACT In this study, poly(isoprene-block-styrene-block-ethylene oxide) (ISO) with molecular weight of 93,496 g mol-1 was synthesized to investigate the effect of large molecular weight on polymer phase behavior. This polymer was used to direct aluminosilicate hybrids and results compared with a 23,180 g mol-1 ISO- aluminosilicate hybrid system, i.e. with work of previous Wiesner group member, Juho Kim. Results showed that, despite the occurrence of more mixed phases with the larger ISO, both ISO-aluminosilicate hybrid systems display the same sequence of phases with those of the 93,496 g mol-1 ISO aluminosilicate hybrid structures shifted down to lower O + inorganic volume fractions as compared to the 23,180 g mol-1 ISO. Subsequently, several other metal oxide hybrids derived from 93,496 g mol-1 ISO were studied. The goal of the study was, again to learn about the structure- directing behavior of large molecular weight polymer, and identify ways to obtain uniform phases. This is usually a challenge as a result of the much slower chain dynamics observed for large molecular weight polymer. Uniform structures from large polymers enable access to large pore and strut size mesoporous materials desirable for a numbers of applications.
    [Show full text]
  • Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production
    catalysts Review Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production Barbara Nascimento Nunes 1,2 , Osmando Ferreira Lopes 2 , Antonio Otavio T. Patrocinio 2,* and Detlef W. Bahnemann 1,3,* 1 Institute of Technical Chemistry, Leibniz University Hannover, 30167 Hannover, Germany; [email protected] 2 Laboratory of Photochemistry and Materials Science, Institute of Chemistry, Federal University of Uberlandia, Uberlandia 38400-902, Brazil; [email protected] 3 Laboratory ‘Photoactive Nanocomposite Materials’, Saint-Petersburg State University, Saint-Petersburg 199034, Russia * Correspondence: [email protected] (A.O.T.P.); [email protected] (D.W.B.) Received: 15 December 2019; Accepted: 11 January 2020; Published: 16 January 2020 Abstract: The search for renewable and clean energy sources is a key aspect for sustainable development as energy consumption has continuously increased over the years concomitantly with environmental concerns caused by the use of fossil fuels. Semiconductor materials have great potential for acting as photocatalysts for solar fuel production, a potential energy source able to solve both energy and environmental concerns. Among the studied semiconductor materials, those based on niobium pentacation are still shallowly explored, although the number of publications and patents on Nb(V)-based photocatalysts has increased in the last years. A large variety of Nb(V)-based materials exhibit suitable electronic/morphological properties for light-driving reactions. Not only the extensive group of Nb2O5 polymorphs is explored, but also many types of layered niobates, mixed oxides, and Nb(V)-doped semiconductors. Therefore, the aim of this manuscript is to provide a review of the latest developments of niobium based photocatalysts for energy conversion into fuels, more specifically, CO2 reduction to hydrocarbons or H2 eVolution from water.
    [Show full text]
  • THE EVOLUTION of Fenb MANUFACTURING
    THE EVOLUTION OF FeNb MANUFACTURING Clóvis Antonio de Faria Sousa CBMM - Companhia Brasileira de Metalurgia e Mineração Córrego da Mata s/n – P.O. Box 08 38.183-970 - Araxá, MG, Brazil Abstract This paper describes ferro-niobium manufacturing technology, and comments on alternative methods of production. A brief history of niobium illustrates the evolution of its applications and, as a consequence, the evolution of ferro-niobium manufacturing. The execution of industrial projects by the major niobium supplier, CBMM, is described, including the recent expansion plan, which has increased ferro-niobium production capacity to 45,000 t/y. CBMM’s future plans regarding ferro-niobium manufacturing technology are also discussed. Introduction In less than two centuries niobium has evolved from being an unknown metal to a rare and high-priced material in the market, and then to the opposite extreme, becoming readily available, with an excess of supply and reduced price. In 1801, Charles Hatchett, a British chemist, discovered an element that he named columbium, since the mineral sample he was working with came from New England in the United States. However, Hatchett did not isolate the element. This was done by Heinrich Rose, a German, who separated an impure Nb2O5 from tantalite in 1844. Thinking that he had found a new element, Rose renamed it niobium, which remained a laboratory curiosity for nearly 100 years. In 1948, niobium was adopted as the name for the element by the International Union of Chemists, although the original name columbium is still widely used by metallurgists in North America. Applications of niobium began around 1925 when it was added to tool steels as a partial substitute for tungsten, and later in 1933 when it was first used to stabilise interstitial in austenitic stainless steels.
    [Show full text]
  • Platinum Metals Review
    PLATINUM METALS REVIEW A quarterly survey of research on the platinum metals and of developments in their applications in industry VOL. 11 OCTOBER 1967 NO. 4 Contents Ruthenium Oxide Glaze Resistors Cobalt-Platinum Alloy Magnets The Platinum Metals in Fuel Cells Further Expansion in Platinum Production The Platinum-Molybdenum System Electron Configuration and Crystal Structure of Platinum Metal Alloys Brazing Graphite to Metals The Structure of Supported Platinum Catalysts Thc Platinum Metals in Catalysis Iridium Coatings in Ion Engines Carbonyl Halide Complexes of the Platinum Metals Performance of Platinised Titanium Anodes Abstracts New Patents Index to Volume 11 Communications should be addressed to The Editor, Platinum Metals Revimv Johnson, Matthey & Co., Limited, Hatton Garden, London, E.C.1 Ruthenium Oxide Glaze Resistors NEW SCREEN PRINTING PREPARATIONS FOR THICK FILM CIRCUITRY By G. S. Iles and Miss M. E. A. Casale, B.s~. Research Laboratories, Johnson Matthey & Co Limited many years for discrete component manu- The rapid deoelnpment of thick jlrn facture, and these are now employed in integrated circuits has created a need for thick film integrated circuit production for preparations that will provide resistor connections and interconnections. Probably Jilrns on a variety of substrates. In the the most important new requirement for decelopment of the new rangp of integrated circuits was a preparation capable rnateriuls described in this urticle of producing resistive films. This problem adimntagr has bern takpn ofthr complex has been approached by developing suspen- rnrrhanisrn of conduction through sions, usually of powdered glaze (frit) and ruthenium dioxide. powders of one or more noble metals dis- persed in an organic medium.
    [Show full text]