Optical properties of single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses

International Nuclear Information System (INIS)

Rodriguez-Mendoza, U.R.; Speghini, A.; Jaque, D.; Zambelli, M.; Bettinelli, M.

2004-01-01

The optical properties for single doped Cr 3+ and co-doped Cr 3+ -Nd 3+ aluminum tantalum tellurite glasses have been studied as a function of temperature. For the single doped glass, the existence of two bands in the emission spectra at low temperature indicates the presence of two different sites for the Cr 3+ ions, labelled as usual as low- and high-field sites. The broad band centred in the Near Infrared region, corresponds to low-field sites transition 4 T 2 → 4 A 2 , and the narrow band centred at approximately 715 nm to the high-field sites transition 2 E→ 4 A 2 . The emission intensity for both high- and low-field sites shows a strong decrease with increasing temperature, with the emission for the former sites vanishing at RT. In both cases the quenching observed with the increase of temperature can be ascribed to the presence of non-radiative relaxation mechanisms. Experimental observations for the co-doped glass show that both radiative and non-radiative energy transfer processes from Cr 3+ to Nd 3+ are present

The extraction of trace amounts of tantalum(V) from different mineral acid solutions by 4-(5-nonyl) pyridine oxide and trioctylamine oxide

International Nuclear Information System (INIS)

Ejaz, M.; Carswell, D.J.

1976-01-01

Data are presented on the distribution of trace amounts of tantalum(V) between different mineral acid solutions and 0.1M solutions of N-oxides of 4-(5-nonyl) pyridine and trioctylamine. The optimal acidity is 0.01-0.5M, depending on the nature of the acid. Common anions have little effect on extraction. Possible mechanism of extraction are suggested making use of slope analysis data. Separation factors for a number of metal ions with respect to tantalum are reported for the 0.1M 4-(5-nonyl)pyridine oxide - 1M sulphuric acid extraction system. Separation from uranium(VI), thorium(IV) and a number of fission products is suggested. The conclusions are unique as follows: Amine oxides are as unique as oxygen-donor extractants in their extraction of tantalum(V) from weakly acid solutions; tantalum is almost completely extracted from weakly nitric, hydrochloric and sulphuric acid solutions by both of the amine oxides; the extraction in low acidity solutions is independent of the nature of the anion of the acids present, indicating the ability of amine oxides to extract the product of hydrolysis of hydrolysable elements. In this respect amine oxides are much better than tributyl phosphate. (T.G.)

A study for an electrolytic reduction of tantalum oxide in a LiCl-Li2O molten salt

International Nuclear Information System (INIS)

Park, Sung Bin; Park, Byung Heung; Seo, Chung Seok; Kang, Dae Seung; Kwon, Seon Gil; Park, Seong Won

2005-01-01

Korea Atomic Energy Research Institute (KAERI) has developed the Advanced Spent Fuel Conditioning Process (ACP) to be an innovative technology for handling the PWR spent fuel. As part of ACP, the electrolytic reduction process (ER process) is the electrochemical reduction process of uranium oxide to uranium metal in a molten salt. The ER process has advantages in a technical stability, an economic potential and a good proliferation resistance. KAERI has reported on the good experimental results of an electrochemical reduction of the uranium oxide in a 20 kg HM/batch lab-scale. The ER process can be applicable to the reduction of other metal oxides. Metal tantalum powder has attracted attention for a variety of applications. A tantalum capacitor made from superfine and pliable tantalum powders is very small in size and it has a higher-capacitance part, therefore it is useful for microelectronic devices. By the ER process the metal tantalum can be obtained from tantalum pentoxide. In this work, a 40 g Ta 2 O 5 /batch electrochemical reactor was used for the synthesis of the metal tantalum. From the results of the cyclic voltammograms for the Ta 2 O 5 -LiCl-Li 2 O system, the mechanism of the tantalum reduction in a molten LiCl-Li 2 O salt system was investigated. Tantalum pentoxide is chemically reduced to tantalum metal by the lithium metal which is electrochemically deposited into an integrated cathode assembly in the LiCl-Li 2 O molten salt. The experiments for the tantalum reduction were performed with a chronopotentiometry in the reactor cell, the reduced products were analyzed from an analysis of the X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray (SEM-EDX). From the results, the electrolytic reduction process is applicable to the synthesis of metal tantalum

Structural and photoluminescent properties of a composite tantalum oxide and silicon nanocrystals embedded in a silicon oxide film

International Nuclear Information System (INIS)

Díaz-Becerril, T.; Herrera, V.; Morales, C.; García-Salgado, G.; Rosendo, E.; Coyopol, A.; Galeazzi, R.; Romano, R.; Nieto-Caballero, F.G.; Sarmiento, J.

2017-01-01

Tantalum oxide crystals encrusted in a silicon oxide matrix were synthesized by using a hot filament chemical vapor deposition system (HFCVD). A solid source composed by a mixture in different percentages of Ta 2 O 5 and silicon (Si) powders were used as reactants. The films were grown at 800 °C and 1000 °C under hydrogen ambient. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) at room temperature. From the XPS results it was confirmed the formation of a mixture of Tantalum oxide, silicon oxide and Si nanoparticles (Ta 2 O 5- SiO 2 -Si(nc)) as seen from the Si (2p) and Ta (4f) lines corresponding to Si + and Ta + states respectively. Ta 2 O 5 and Si nanocrystals (Si-NCs) embedded in the silicon oxide films were observed on HRTEM images which corroborate the XPS results. Finally the emission properties of the films exhibited a broad band from 400 to 850 nm caused by the independent PL properties of tantalum oxide and Si-NCs that compose the film. The intensity of the emissions was observed to be dependent on both temperature of deposition and the ratio Ta 2 O 5 /Si, used as initial reactants. Results from this work might supply useful data for the development of future light emitter devices.

Synthesis, Consolidation and Characterization of Sol-gel Derived Tantalum-Tungsten Oxide Thermite Composites

Energy Technology Data Exchange (ETDEWEB)

Cervantes, O [Univ. of California, Davis, CA (United States)

2010-06-01

Energetic composite powders consisting of sol-gel (SG) derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition-tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the SG derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The SG derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO3) energetic composite was consolidated to a density of 9.17 g·cm-3 or 93% relative density. In addition, those samples were consolidated without significant pre-reaction of the constituents, thus retaining their stored chemical energy.

Structural and photoluminescent properties of a composite tantalum oxide and silicon nanocrystals embedded in a silicon oxide film

Energy Technology Data Exchange (ETDEWEB)

Díaz-Becerril, T., E-mail: tomas.diaz.be@gmail.com; Herrera, V.; Morales, C.; García-Salgado, G.; Rosendo, E.; Coyopol, A., E-mail: acoyopol@gmail.com; Galeazzi, R.; Romano, R.; Nieto-Caballero, F.G.; Sarmiento, J.

2017-04-15

Tantalum oxide crystals encrusted in a silicon oxide matrix were synthesized by using a hot filament chemical vapor deposition system (HFCVD). A solid source composed by a mixture in different percentages of Ta{sub 2}O{sub 5} and silicon (Si) powders were used as reactants. The films were grown at 800 °C and 1000 °C under hydrogen ambient. The deposited films were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) at room temperature. From the XPS results it was confirmed the formation of a mixture of Tantalum oxide, silicon oxide and Si nanoparticles (Ta{sub 2}O{sub 5-}SiO{sub 2}-Si(nc)) as seen from the Si (2p) and Ta (4f) lines corresponding to Si{sup +} and Ta{sup +} states respectively. Ta{sub 2}O{sub 5} and Si nanocrystals (Si-NCs) embedded in the silicon oxide films were observed on HRTEM images which corroborate the XPS results. Finally the emission properties of the films exhibited a broad band from 400 to 850 nm caused by the independent PL properties of tantalum oxide and Si-NCs that compose the film. The intensity of the emissions was observed to be dependent on both temperature of deposition and the ratio Ta{sub 2}O{sub 5}/Si, used as initial reactants. Results from this work might supply useful data for the development of future light emitter devices.

Transparent conducting oxide films of group V doped titania prepared by aqueous chemical solution deposition

International Nuclear Information System (INIS)

Elen, Ken; Capon, Boris; De Dobbelaere, Christopher; Dewulf, Daan; Peys, Nick; Detavernier, Christophe; Hardy, An; Van Bael, Marlies K.

2014-01-01

Transparent conducting oxide (TCO) films of titania doped with vanadium (V), niobium (Nb) and tantalum (Ta) are obtained by aqueous Chemical Solution Deposition (CSD). The effect of the dopant on the crystallization and microstructure of the resulting films is examined by means of X-ray diffraction and electron microscopy. During annealing of the thin films, in-situ characterization of the crystal structure and sheet resistance is carried out. Niobium doped anatase films, obtained after annealing in forming gas, show a resistivity of 0,28 Ohm cm, which is the lowest resistivity reported for a solution deposited anatase-based TCO so far. Here, we demonstrate that aqueous CSD may provide a strategy for scalable TCO production in the future. - Highlights: • Aqueous chemical solution deposition of doped titanium dioxide • Doping delays the phase transition from anatase to rutile • Lowest resistivity after doping with niobium and annealing in Forming Gas • Transparency higher than 80% in the visible range of optical spectrum

Transparent conducting oxide films of group V doped titania prepared by aqueous chemical solution deposition

Energy Technology Data Exchange (ETDEWEB)

Elen, Ken [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Strategisch Initiatief Materialen (SIM), SoPPoM Program (Belgium); Capon, Boris [Strategisch Initiatief Materialen (SIM), SoPPoM Programm (Belgium); Coating and Contacting of Nanostructures, Ghent University, Krijgslaan 281 S1, B-9000 Ghent (Belgium); De Dobbelaere, Christopher [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Dewulf, Daan [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Peys, Nick [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw, Kapeldreef 75, B-3001 Heverlee (Belgium); Detavernier, Christophe [Coating and Contacting of Nanostructures, Ghent University, Krijgslaan 281 S1, B-9000 Ghent (Belgium); Hardy, An [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Van Bael, Marlies K., E-mail: marlies.vanbael@uhasselt.be [Inorganic and Physical Chemistry, Institute for Materials Research, Hasselt University, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium)

2014-03-31

Transparent conducting oxide (TCO) films of titania doped with vanadium (V), niobium (Nb) and tantalum (Ta) are obtained by aqueous Chemical Solution Deposition (CSD). The effect of the dopant on the crystallization and microstructure of the resulting films is examined by means of X-ray diffraction and electron microscopy. During annealing of the thin films, in-situ characterization of the crystal structure and sheet resistance is carried out. Niobium doped anatase films, obtained after annealing in forming gas, show a resistivity of 0,28 Ohm cm, which is the lowest resistivity reported for a solution deposited anatase-based TCO so far. Here, we demonstrate that aqueous CSD may provide a strategy for scalable TCO production in the future. - Highlights: • Aqueous chemical solution deposition of doped titanium dioxide • Doping delays the phase transition from anatase to rutile • Lowest resistivity after doping with niobium and annealing in Forming Gas • Transparency higher than 80% in the visible range of optical spectrum.

Electrorecovery of tantalum in molten fluorides

International Nuclear Information System (INIS)

Espinola, A.; Dutra, A.J.B.; Silva, F.T. da

1988-01-01

Considering the privileged situation of Brazil as a productor of tantaliferous minerals, the authors have in view the development of a technology for production of metallic tantalum via molten salts electrolysis; this has the advantage of improving the aggregate value of exportation products, additionally to tantalum oxide and tantalum concentrates. Having in view the preliminary determintion of better conditions of temperature, electrolyte composition and current density for this process, electrolysis were conducted with a solvent composed of an eutetic mixture of lithium, sodium and potassium fluoride for dipotassium fluotantalate and occasionally for tantalum oxide. Current efficiencies as high as 83% were obtained in favoured conditions. (author) [pt

The effect of yttrium addition on oxidation of a sputtered nanocrystalline coating with moderate amount of tantalum in composition

International Nuclear Information System (INIS)

Wang, Jinlong; Chen, Minghui; Yang, Lanlan; Liu, Li; Zhu, Shenglong; Wang, Fuhui; Meng, Guozhe

2016-01-01

Graphical abstract: - Highlights: • Effect of Y addition on oxidation of nanocrystalline coating is studied. • Y addition delays transformation of q-Al_2O_3 to a-Al_2O_3 during oxidation. • Y addition prevents scale rumpling. • Y segregates at grain boundaries of the nanocrystalline coating. • Y retards the transportation of Ta thus reduces its oxidation. - Abstract: The effect of yttrium addition on isothermal oxidation at 1050 °C of a sputtered nanocrystalline coating with moderate amount of tantalum in composition was investigated. Results indicate that yttrium addition delays transformation of metastable θ-Al_2O_3 to equilibrium α-Al_2O_3 grown on the nanocrystalline coatings. It prevents scale rumpling and promotes the formation of oxide pegs at interface between the oxide scale and the underlying coating. Besides, yttrium prefers to segregate at grain boundaries of the nanocrystalline coating and retards the outward transportation of tantalum from coating to oxide scale, thus reducing the excessive oxidation of tantalum.

Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Denny, Yus Rama [Department of Physics Education, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Firmansyah, Teguh [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Yang, Dong-Seok [Department of Physics Education, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Heo, Sung; Chung, JaeGwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 16678 (Korea, Republic of)

2016-10-15

Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

International Nuclear Information System (INIS)

Huang, Heng-Li; Chang, Yin-Yu; Chen, Hung-Jui; Chou, Yu-Kai; Lai, Chih-Ho; Chen, Michael Y. C.

2014-01-01

Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta 2 O 5 and Ta 2 O 5 -Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility

Antibacterial properties and cytocompatibility of tantalum oxide coatings with different silver content

Energy Technology Data Exchange (ETDEWEB)

Huang, Heng-Li [School of Dentistry, China Medical University, Taichung 404, Taiwan (China); Chang, Yin-Yu, E-mail: yinyu@mail2000.com.tw; Chen, Hung-Jui; Chou, Yu-Kai [Department of Mechanical and Computer-Aided Engineering, National Formosa University, Yunlin 632, Taiwan (China); Lai, Chih-Ho [School of Medicine, China Medical University, Taichung 404, Taiwan (China); Chen, Michael Y. C. [Division of Oral and Maxillofacial Surgery, China Medical University Hospital, Taichung 404, Taiwan (China)

2014-03-15

Tantalum (Ta) oxides and their coatings have been proved to increase their applications in the biomedical fields by improving osseointegration and wear resistance. In this study, Ta oxide coatings containing different proportions of Ag are deposited on SS304 materials. A twin-gun magnetron sputtering system is used to deposit the tantalum oxide-Ag coating. In this study, Staphylococcus aureus, which exhibits physiological commensalism on the human skin, nares, and mucosal and oral areas, is chosen as the model for in vitro antibacterial analyses via a fluorescence staining method using Syto9. The cytocompatibility and adhesive morphology of human skin fibroblast cells (CCD-966SK) on the coatings are also determined by using the microculture tetrazolium assay. This study shows that Ta{sub 2}O{sub 5} and Ta{sub 2}O{sub 5}-Ag coatings with 12.5 at. % of Ag exhibit improved antibacterial effects against S. aureus and have good skin fibroblast cell cellular biocompatibility.

High performance fuel electrode for a solid oxide electrochemical cell

DEFF Research Database (Denmark)

2013-01-01

perovskite oxides selected from the group consisting of niobium-doped strontium titanate, vanadium-doped strontium titanate, tantalum-doped strontium titanate and mixtures thereof, thereby obtaining a porous anode backbone, (b) sintering the coated electrolyte at a high temperature, such as 1200 DEG C...

Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

International Nuclear Information System (INIS)

Maho, Anthony; Detriche, Simon; Delhalle, Joseph; Mekhalif, Zineb

2013-01-01

Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH) 2 ). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum/carbon nanotube

Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

Energy Technology Data Exchange (ETDEWEB)

Maho, Anthony [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Fonds pour la Formation à la Recherche dans l' Industrie et dans l' Agriculture (FRIA), Rue d' Egmont 5, B-1000 Bruxelles (Belgium); Detriche, Simon; Delhalle, Joseph [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Mekhalif, Zineb, E-mail: zineb.mekhalif@fundp.ac.be [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium)

2013-07-01

Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH){sub 2}). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum

Ion beam and dual ion beam sputter deposition of tantalum oxide films

Science.gov (United States)

Cevro, Mirza; Carter, George

1994-11-01

Ion beam sputter deposition (IBS) and dual ion beam sputter deposition (DIBS) of tantalum oxide films was investigated at room temperature and compared with similar films prepared by e-gun deposition. Optical properties ie refractive index and extinction coefficient of IBS films were determined in the 250 - 1100 nm range by transmission spectrophotometry and at (lambda) equals 632.8 nm by ellipsometry. They were found to be mainly sensitive to the partial pressure of oxygen used as a reactive gas in the deposition process. The maximum value of the refractive index of IBS deposited tantalum oxide films was n equals 2.15 at (lambda) equals 550 nm and the extinction coefficient of order k equals 2 X 10-4. Films deposited by e-gun deposition had refractive index n equals 2.06 at (lambda) equals 550 nm. Films deposited using DIBS ie deposition assisted by low energy Ar and O2 ions (Ea equals 0 - 300 eV) and low current density (Ji equals 0 - 40 (mu) A/cm2) showed no improvement in the optical properties of the films. Preferential sputtering occurred at Ea(Ar) equals 300 eV and Ji equals 20 (mu) A/cm2 and slightly oxygen deficient films were formed. Different bonding states in the tantalum-oxide films were determined by x-ray spectroscopy while composition of the film and contaminants were determined by Rutherford scattering spectroscopy. Tantalum oxide films formed by IBS contained relatively high Ar content (approximately equals 2.5%) originating from the reflected argon neutrals from the sputtering target while assisted deposition slightly increased the Ar content. Stress in the IBS deposited films was measured by the bending technique. IBS deposited films showed compressive stress with a typical value of s equals 3.2 X 109 dyn/cm2. Films deposited by concurrent ion bombardment showed an increase in the stress as a function of applied current density. The maximum was s approximately equals 5.6 X 109 dyn/cm2 for Ea equals 300 eV and Ji equals 35 (mu) A/cm2. All

Ion-beam and dual-ion-beam sputter deposition of tantalum oxide films

Science.gov (United States)

Cevro, Mirza; Carter, George

1995-02-01

Ion-beam sputter deposition (IBS) and dual-ion-beam sputter deposition (DIBS) of tantalum oxide films was investigated at room temperature and compared with similar films prepared by e-gun deposition. The optical properties, i.e., refractive index and extinction coefficient, of IBS films were determined in the 250- to 1100-nm range by transmission spectrophotometry and at (lambda) equals 632.8 nm by ellipsometry. They were found to be mainly sensitive to the partial pressure of oxygen used as a reactive gas in the deposition process. The maximum value of the refractive index of IBS deposited tantalum oxide films was n equals 2.15 at (lambda) equals 550 nm and the extinction coefficient of order k equals 2 X 10-4. Films deposited by e-gun deposition had refractive index n 2.06 at (lambda) equals 550 nm. Films deposited using DIBS, i.e., deposition assisted by low energy Ar and O2 ions (Ea equals 0 to 300 eV) and low current density (Ji equals 0 to 40 (mu) A/cm2), showed no improvement in the optical properties of the films. Preferential sputtering occurred at Ea(Ar) equals 300 eV and Ji equals 20 (mu) A/cm2 and slightly oxygen deficient films were formed. Different bonding states in the tantalum-oxide films were determined by x-ray spectroscopy, whereas composition of the film and contaminants were determined by Rutherford backscattering spectroscopy (RBS). Tantalum oxide films formed by IBS contained relatively high Ar content (approximately equals 2.5%) originating from the reflected argon neutrals from the sputtering target whereas assisted deposition slightly increased the Ar content. Stress in the IBS-deposited films was measured by the bending technique. IBS-deposited films showed compressive stress with a typical value of s equals 3.2 X 109 dyn/cm2. Films deposited by concurrent ion bombardment showed an increase in the stress as a function of applied current density. The maximum was s approximately equals 5.6 X 109 dyn/cm2 for Ea equals 300 eV and Ji equals

Process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy

International Nuclear Information System (INIS)

Deweck, J.; Van, H.

1980-01-01

In a process for the production of a tantalum and niobium bearing concentrate from a tantalum and niobium bearing ferro-alloy containing tantalum and niobium as carbide, by treating the ferro-alloy in molten state with a controlled amount of an oxidizing agent in order to slag at least most of the tantalum and at least part of the niobium and by separting the so obtained slag phase from the metal phase, the improvement which comprises using air, oxygen enriched air or oxygen as oxidizing agent and adjusting the iron content to the ferro-alloy by adding at least 70% by weight of iron prior to the step of forming the slag so that at least most of the tantalum carbide is dissolved in the molten ferro-alloy

Nonlinear I-V characteristics of doped SnO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Dhage, S.R.; Choube, Vandana; Ravi, V

2004-07-15

When tin oxide is doped with Sb{sub 2}O{sub 3} and CoO, it shows highly nonlinear current (I)-voltage (V) characteristics. Addition of CoO leads to creation of oxygen vacancies and helps in sintering of SnO{sub 2}. Antimony oxide acts as a donor and increases the conductivity. The results are nearly same when antimony oxide is replaced by tantalum oxide. The grain size of these sintered ceramics varies from 5 to 7 {mu}m and the grain boundary barrier height (PHI{sub B}) is in the range of 0.5 eV. The observed nonlinear coefficient ({alpha}) is 25 and 27 for antimony and tantalum oxide, respectively and the breakdown field is in the range of 1250 V cm{sup -1}.

Formation of oxide layers on aluminum, niobium, and tantalum in molten alkali metal carbonates

Science.gov (United States)

Nikitina, E. V.; Kazakovtseva, N. A.

2013-08-01

The electrochemical synthesis of niobium, tantalum, and aluminum oxide nanolayers is studied in the melt of lithium, sodium, and potassium carbonates with various additives to a salt phase in an oxidizing atmosphere at a temperature of 773 and 873 K. A scheme is proposed for high-temperature anion local activation of the process.

Tantalum-based semiconductors for solar water splitting.

Science.gov (United States)

Zhang, Peng; Zhang, Jijie; Gong, Jinlong

2014-07-07

Solar energy utilization is one of the most promising solutions for the energy crises. Among all the possible means to make use of solar energy, solar water splitting is remarkable since it can accomplish the conversion of solar energy into chemical energy. The produced hydrogen is clean and sustainable which could be used in various areas. For the past decades, numerous efforts have been put into this research area with many important achievements. Improving the overall efficiency and stability of semiconductor photocatalysts are the research focuses for the solar water splitting. Tantalum-based semiconductors, including tantalum oxide, tantalate and tantalum (oxy)nitride, are among the most important photocatalysts. Tantalum oxide has the band gap energy that is suitable for the overall solar water splitting. The more negative conduction band minimum of tantalum oxide provides photogenerated electrons with higher potential for the hydrogen generation reaction. Tantalates, with tunable compositions, show high activities owning to their layered perovskite structure. (Oxy)nitrides, especially TaON and Ta3N5, have small band gaps to respond to visible-light, whereas they can still realize overall solar water splitting with the proper positions of conduction band minimum and valence band maximum. This review describes recent progress regarding the improvement of photocatalytic activities of tantalum-based semiconductors. Basic concepts and principles of solar water splitting will be discussed in the introduction section, followed by the three main categories regarding to the different types of tantalum-based semiconductors. In each category, synthetic methodologies, influencing factors on the photocatalytic activities, strategies to enhance the efficiencies of photocatalysts and morphology control of tantalum-based materials will be discussed in detail. Future directions to further explore the research area of tantalum-based semiconductors for solar water splitting

Synthesis of Monodispersed Tantalum(V) oxide Nanospheres by an Ethylene Glycol Mediated Route

Science.gov (United States)

Tantalum(V) oxide (Ta2O5) nanospheres have been synthesized by a very simple ethylene glycol mediated route. The two-step process involves the formation of glycolate nanoparticles and their subsequent hydrolysis and calcination to generate the final Ta2O5 nanospheres. The synthes...

Some organoperoxo complexes of antimony, niobium and tantalum and their oxidation properties

International Nuclear Information System (INIS)

Tarafder, M.T.H.

1999-05-01

Several novel organoperoxo complexes of Nb(V), Ta(V) and Sb(V) have been synthesized and characterized. The complexes have the compositions [M(O 2 ) 2 L Cl] and [M(O 2 ) 2 L'] [L = monodentate and bidentate, neutral ligand; L' = bidentate, uninegative ligand]. These complexes are very reactive to both organic and inorganic substrates. Niobium and tantalum complexes were found to oxidize phosphines and arsines to their oxides. These also oxidize olefins to epoxides under stoichiometric conditions while under catalytic conditions, ring opening of the epoxides occur producing α-hydroxyketone when the substrate is trans-stilbene. The antimony complexes are decidedly inert towards oxidation. (author)

Rapid synthesis of tantalum oxide dielectric films by microwave microwave-assisted atmospheric chemical vapor deposition

International Nuclear Information System (INIS)

Ndiege, Nicholas; Subramanian, Vaidyanathan; Shannon, Mark A.; Masel, Richard I.

2008-01-01

Microwave-assisted chemical vapor deposition has been used to generate high quality, high-k dielectric films on silicon at high deposition rates with film thicknesses varying from 50 nm to 110 μm using inexpensive equipment. Characterization of the post deposition products was performed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy and Raman spectroscopy. Film growth was determined to occur via rapid formation and accumulation of tantalum oxide clusters from tantalum (v) ethoxide (Ta(OC 2 H 5 ) 5 ) vapor on the deposition surface

PREPARATION OF TANTALUM CARBIDE FROM AN ORGANOMETALLIC PRECURSOR

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C. P. SOUZA

1999-03-01

Full Text Available In this work we have synthesized an organometallic oxalic precursor from tantalum oxide. This oxide was solubilized by heating with potassium hydrogen sulfate. In order to precipitate Ta2O5.nH2O, the fused mass obtained was dissolved in a sulfuric acid solution and neutralized with ammonia. The hydrated tantalum oxide precipitated was dissolved in an equimolar solution of oxalic acid/ammonium oxalate. The synthesis and the characterization of the tantalum oxalic precursor are described. Pyrolysis of the complex in a mixture of hydrogen and methane at atmospheric pressure was studied. The gas-solid reaction made it possible to obtain tantalum carbide, TaC, in the powder form at 1000oC. The natural sintering of TaC powder in an inert atmosphere at 1400°C during 10 hours, under inert atmosphere made it possible to densify the carbide to 96% of the theoretical value.

III-V group compound semiconductor light-emitting element having a doped tantalum barrier layer

International Nuclear Information System (INIS)

Oanna, Y.; Ozawa, N.; Yamashita, M.; Yasuda, N.

1984-01-01

Disclosed is a III-V Group compound semiconductor light-emitting element having a III-V Group compound semiconductor body with a p-n junction and including a p-type layer involved in forming the p-n junction; and a multi-layer electrode mounted on the p-type layer of the semiconductor body. The electrode comprises a first layer of gold alloy containing a small amount of beryllium or zinc and formed in direct contact with the p-type layer of the semiconductor body and an uppermost layer formed of gold or aluminum. A tantalum layer doped with carbon, nitrogen and/or oxygen is formed between the first layer and the uppermost layer by means of vacuum vapor deposition

Study of electrochemical behaviour of tantalum in molten alkali metal chlorides

International Nuclear Information System (INIS)

Bajmakov, A.N.; Ezrokhina, A.M.; Sashinina, O.A.; Shkol'nikov, S.N.

1985-01-01

Equilibrium potentials of metallic tantalum in the melt TaCl 5 +KCl-NaCl are studied. Are average degree of tantalum ion oxidation, which are in equilibrium with metallic tantalum, is determined. Anodic behaviour of tantalum in equimolar mixture of potassium and sodium chlorides with Ta and F ion additions is considered. An average degree of oxidation of Ta ions, which transfer into the melt, depending on current density, is determined. It is established that tantalum is dissolved in the regime of diffusional kinetics. It is shown that tantalum corrodes in equimolar mixture of potassium and sodiUm chlorides, at that, corrosion rate increases with introdUction of Ta and F ions into solution. The corrosion is of electrochemical nature and it proceeds in the regime of diffusional kinetics

Niobium and tantalum

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Schulz, Klaus J.; Piatak, Nadine M.; Papp, John F.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

Niobium and tantalum are transition metals that are almost always found together in nature because they have very similar physical and chemical properties. Their properties of hardness, conductivity, and resistance to corrosion largely determine their primary uses today. The leading use of niobium (about 75 percent) is in the production of high-strength steel alloys used in pipelines, transportation infrastructure, and structural applications. Electronic capacitors are the leading use of tantalum for high-end applications, including cell phones, computer hard drives, and such implantable medical devices as pacemakers. Niobium and tantalum are considered critical and strategic metals based on the potential risks to their supply (because current production is restricted to only a few countries) and the significant effects that a restriction in supply would have on the defense, energy, high-tech industrial, and medical sectors.The average abundance of niobium and tantalum in bulk continental crust is relatively low—8.0 parts per million (ppm) niobium and 0.7 ppm tantalum. Their chemical characteristics, such as small ionic size and high electronic field strength, significantly reduce the potential for these elements to substitute for more common elements in rock-forming minerals and make niobium and tantalum essentially immobile in most aqueous solutions. Niobium and tantalum do not occur naturally as pure metals but are concentrated in a variety of relatively rare oxide and hydroxide minerals, as well as in a few rare silicate minerals. Niobium is primarily derived from the complex oxide minerals of the pyrochlore group ((Na,Ca,Ce)2(Nb,Ti,Ta)2(O,OH,F)7), which are found in some alkaline granite-syenite complexes (that is, igneous rocks containing sodium- or potassium-rich minerals and little or no quartz) and carbonatites (that is, igneous rocks that are more than 50 percent composed of primary carbonate minerals, by volume). Tantalum is derived mostly from the

Material removal mechanisms in electrochemical-mechanical polishing of tantalum

International Nuclear Information System (INIS)

Gao, F.; Liang, H.

2009-01-01

Material removal mechanisms in tantalum chemical-mechanical polishing (CMP) and electrochemical-mechanical polishing (ECMP) were investigated using the single frequency electrochemical impedance spectroscopy (EIS). Through measuring the impedance of the tantalum surface, the single frequency EIS scan made it possible to observe the CMP and ECMP processes in situ. The impedance results presented competing mechanisms of removal and formation of a surface oxide layer of tantalum. Analysis indicated that the thickness of the oxide layer formed during polishing was related to the mechanical power correlated to the friction force and the rotating speed. Furthermore, the rate of growth and removal of the oxide film was a function of the mechanical power. This understanding is beneficial for optimization of CMP and ECMP processes.

Composition dependence of the kinetics and mechanisms of thermal oxidation of titanium-tantalum alloys

International Nuclear Information System (INIS)

Park, Y.S.; Butt, D.P.

1999-01-01

The oxidation behavior of titanium-tantalum alloys was investigated with respective concentrations of each element ranging from 0 to 100 wt.%. Alloys were exposed to argon-20% oxygen at 800 to 1400 C. The slowest oxidation rates were observed in alloys with 5--20% Ta. The oxidation kinetics of alloys containing less than approximately 40% Ta were approximately parabolic. Pure Ta exhibited nearly linear kinetics. Alloys containing 50% or more Ta exhibited paralinear kinetics. The activation energies for oxidation ranged between 232 kJ/mole for pure Ti and 119 kJ/mole for pure Ta, with the activation energies of the alloys falling between these values and generally decreasing with increasing Ta content. The activation energies for oxidation of the end members, Ti and Ta, agree well with published values for the activation energies for diffusion of oxygen in α-Ti and Ta. Scale formation in the alloys was found to be complex exhibiting various layers of Ti-, Ta-, and TiTa-oxides. The outermost layer of the oxidized alloys was predominantly rutile (TiO 2 ). Beneath the TiO 2 grew a variety of other oxides with the Ta content generally increasing with proximity to the metal-oxide interface. It was found that the most oxidation-resistant alloys had compositions falling between Ti-5Ta and Ti-15Ta. Although Ta stabilizes the β-phase of Ti, the kinetics of oxidation appeared to be rate limited by oxygen transport through the oxygen-stabilized α-phase. However, the kinetics are complicated by the formation of a complex oxide, which cracks periodically. Tantalum appears to increase the compositional range of oxygen-stabilized α-phase and reduces both the solubility of oxygen and diffusivity of Ti in the α- and β-phases

Rare earth oxide doping in oxide cathodes

International Nuclear Information System (INIS)

Engelsen, Daniel den; Gaertner, Georg

2006-01-01

The effect on life performance and poisoning with O 2 by doping oxide cathodes with rare earth oxides and pseudo rare earth oxides, notably yttria, is qualitatively explained in terms of electrolysis of BaO during emission of electrons. Doped cathodes show less electrolysis and consume therefore less Ba during life: consequently, doped cathodes have a better life performance. However, the lower Ba-production makes doped cathodes more sensitive to oxygen poisoning. The experimentally found relation between conductivity and yttria concentration was the motive to propose a new model for the crystal imperfections in BaO. In this new imperfection model most Y 3+ -ions will combine with barium vacancies, therefore, the increase of the conductivity is modest and also the effect on the position of the Fermi level is modest. By assuming a combination of bulk and surface conductivity, the agreement between experiment and theory can be improved further

Direct electroplating of copper on tantalum from ionic liquids in high vacuum: origin of the tantalum oxide layer.

Science.gov (United States)

Schaltin, Stijn; D'Urzo, Lucia; Zhao, Qiang; Vantomme, André; Plank, Harald; Kothleitner, Gerald; Gspan, Christian; Binnemans, Koen; Fransaer, Jan

2012-10-21

In this paper, it is shown that high vacuum conditions are not sufficient to completely remove water and oxygen from the ionic liquid 1-ethyl-3-methylimidazolium chloride. Complete removal of water demands heating above 150 °C under reduced pressure, as proven by Nuclear Reaction Analysis (NRA). Dissolved oxygen gas can only be removed by the use of an oxygen scavenger such as hydroquinone, despite the fact that calculations show that oxygen should be removed completely by the applied vacuum conditions. After applying a strict drying procedure and scavenging of molecular oxygen, it was possible to deposit copper directly on tantalum without the presence of an intervening oxide layer.

STRUCTURAL CHARACTERISTICS & DIELECTRIC PROPERTIES OF TANTALUM OXIDE DOPED BARIUM TITANATE BASED MATERIALS

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Md. Fakhrul Islam

2013-01-01

Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mole % Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90 % was achieved for 0.5 and 1.0 mole %Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0.5 mole % Ta2O5. Although fine grain size down to 200 - 300 nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000 - 14000 was found in the temperature range of 55 to 80 °C, for 1.0 mole % Ta2O5 doped samples with corresponding shift of Curie point to ~82 °C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

Structural Characteristics & Dielectric Properties of Tantalum Oxide Doped Barium Titanate Based Materials

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Rubayyat Mahbub

2012-11-01

Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mol% Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90% was achieved for 0.5 and 1.0 mol% Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0·5 mol% Ta2O5. Although fine grain size down to 200-300nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000-14000 was found in the temperature range of  55 to 80°C, for 1.0 mol% Ta2O5 doped samples with corresponding shift of Curie point to ~82°C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

Surface Roughness and Grain Size Characterization of Annealing Temperature Effect For Growth Gallium and Tantalum Doped Ba0.5 Sr0.5TiO3Thin Film

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Irzaman

2009-01-01

Full Text Available Thin films 10 % gallium oxide doped barium strontium titanate (BGST and 10 % tantalum oxide doped barium strontium titanate (BTST were prepared on p-type Si (100 substrates using chemical solution deposition (CSD method with 1.00 M precursor. The films were deposited by spin coating method with spinning speed at 3000 rpm for 30 seconds. The post deposition annealing of the films were carried out in a furnace at 200oC, 240oC, 280oC (low temperature for 1 hour in oxygen gas atmosphere. The surface roughness and grain size analysis of the grown thin films are described by atomic force microscope (AFM method at 5000 nm x 5000 nm area. The rms surface roughness BGST thin films at 5000 nm x 5000 nm area are 0.632 nm, 0.564 nm, 0.487 nm for temperature 200oC, 240oC, 280oC, respectively, whereas the grain size (mean diameter are 238.4 nm, 219.0 nm, 185.1 nm for temperature 200oC, 240oC, 280oC, respectively. In fact, to increase annealing temperature from 200oC to 280oC would result in decreasing the rms roughness and grain size. Therefore, rms roughness and grain size would have the strong correlation annealing temperature.

Tantalum: A strategic metal; Tantalo: Un metal estrategico

Energy Technology Data Exchange (ETDEWEB)

Lopez-Lopez, G.; Lopez-Lopez, J.; Garcia-Yagues, M. R.

2009-07-01

In nature, the main source of tantalum is an isomorphous series of minerals containing oxides of tantalum, niobium, iron and manganese, which are collectively known as columbine-tantalite (coltan). Upgraded Ta{sub 2}O{sub 5}-containing tin slags are also used as a secondary source of tantalum. Coltan, either naturally occurring or synthetically produced as concentrates from tin slags, are digested with hydrofluoric and sulphuric acid at an elevated temperature. the aqueous solution of ta-Nb in hydrofluoric acid is extracted in several continuously operating mixer-settler systems or extraction columns with an organic solvent like methyl isobutyl ketone. The organic phase is then scrubbed with 6-15 N H{sub 2}SO{sub 4} to separate the niobium from the tantalum by selective stripping. The tantalum salt is extracted from the organic phase with water or diluted aqueous ammonium fluoride solution, the demands of the solid tantalum capacitor industry for high quality, high surface area tantalum powders have driven improvements in the sodium reduction of K{sub 2}TaF{sub 7}. The much-improved chemistry reflects the many modifications to the process put in place after 1990 and the subsequent improvements in the electrical quality as measured by the performance of tantalum capacitors. (Author) 5 refs.

Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

Science.gov (United States)

Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

2009-08-15

Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).

IR-doped ruthenium oxide catalyst for oxygen evolution

Science.gov (United States)

Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2012-01-01

A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

Titrimetric determination of tungsten in its alloys with tantalum

International Nuclear Information System (INIS)

Elinson, S.V.; Nezhnova, T.I.

1982-01-01

Titrimetric method of tungsten determination in tantalum base alloys has been developed. The method permits to determine 5-10% tungsten in the alloys with relative standard deviation of 0.013. The conditions are created by application of precipitation from homogeieous solutions or by the method of appearing reagents at pH values, which condition gradual hydrolytic precipitation of tantalum, and sodium tungstate remains in the solution and is not sorbed on tantalum hydroxide. After separation of tantalum oxide tungsten is precipitated in the form of lead tungstate by the excess of ti trated solution of lead salt during boiling and then at the background of lead tungstate precipitate without its separation lead excess is titrated by EDTA in the presence of mixed indicator-4-(2-pyridylazo)resocinol and xylenole orange in acetate buffer solution

XPS and GDOES Characterization of Porous Coating Enriched with Copper and Calcium Obtained on Tantalum via Plasma Electrolytic Oxidation

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Krzysztof Rokosz

2016-01-01

Full Text Available XPS and GDOES characterizations of porous coatings on tantalum after Plasma Electrolytic Oxidation (PEO at 450 V for 3 minutes in electrolyte containing concentrated (85% phosphoric acid with calcium nitrate and copper (II nitrate are described. Based on the obtained data, it may be concluded that the PEO coating consists of tantalum (Ta5+, calcium (Ca2+, copper (Cu2+  and Cu+, and phosphates (PO43-. It has to be pointed out that copper and calcium are distributed throughout the volume. The authors also propose a new model of PEO, based on the derivative of GDOES signals with sputtering time.

Structural and dielectric characterization of sputtered Tantalum Titanium Oxide thin films for high temperature capacitor applications

Energy Technology Data Exchange (ETDEWEB)

Rouahi, A., E-mail: rouahi_ahlem@yahoo.fr [Univ. Grenoble Alpes, G2Elab, F-38000 (France); Laboratoire Matériaux Organisation et Propriétés (LMOP), Université de Tunis El Manar, 2092 Tunis (Tunisia); Challali, F. [Laboratoire des Sciences des Procédés et des Matériaux (LSPM)-CNRS-UPR3407, Université Paris13, 99 Avenue Jean-Baptiste Clément, 93430, Villetaneuse (France); Dakhlaoui, I. [Laboratoire Matériaux Organisation et Propriétés (LMOP), Université de Tunis El Manar, 2092 Tunis (Tunisia); Vallée, C. [CNRS, LTM, CEA-LETI, F-38000 Grenoble (France); Salimy, S. [Institut des Matériaux Jean Rouxel (IMN) UMR CNRS 6502, Université de Nantes, 2, rue de la Houssinière, B.P. 32229, 44322, Nantes, Cedex 3 (France); Jomni, F.; Yangui, B. [Laboratoire Matériaux Organisation et Propriétés (LMOP), Université de Tunis El Manar, 2092 Tunis (Tunisia); Besland, M.P.; Goullet, A. [Institut des Matériaux Jean Rouxel (IMN) UMR CNRS 6502, Université de Nantes, 2, rue de la Houssinière, B.P. 32229, 44322, Nantes, Cedex 3 (France); Sylvestre, A. [Univ. Grenoble Alpes, G2Elab, F-38000 (France)

2016-05-01

In this study, the dielectric properties of metal-oxide-metal capacitors based on Tantalum Titanium Oxide (TiTaO) thin films deposited by reactive magnetron sputtering on aluminum bottom electrode are investigated. The structure of the films was characterized by Atomic Force Microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric properties of TiTaO thin films were studied by complex impedance spectroscopy over a wide frequency range (10{sup -2} - to 10{sup 5} Hz) and temperatures in -50 °C to 325 °C range. The contributions of different phases, phases’ boundaries and conductivity effect were highlighted by Cole – Cole diagram (ε” versus ε’). Two relaxation processes have been identified in the electric modulus plot. A first relaxation process appears at low temperature with activation energy of 0.37 eV and it is related to the motion of Ti{sup 4+} (Skanavi’s model). A second relaxation process at high temperature is related to Maxwell-Wagner-Sillars relaxation with activation energy of 0.41 eV. - Highlights: • Titanium Tantalum Oxide thin films are grown on Aluminum substrate. • The existence of phases was confirmed by X-ray photoelectron spectroscopy. • Conductivity effect appears in Cole-Cole plot. • At low temperatures, a relaxation phenomenon obeys to Skanavi’s model. • Maxwell-Wagner-Sillars polarization is processed at high temperatures.

Multistate Memristive Tantalum Oxide Devices for Ternary Arithmetic

Science.gov (United States)

Kim, Wonjoo; Chattopadhyay, Anupam; Siemon, Anne; Linn, Eike; Waser, Rainer; Rana, Vikas

2016-11-01

Redox-based resistive switching random access memory (ReRAM) offers excellent properties to implement future non-volatile memory arrays. Recently, the capability of two-state ReRAMs to implement Boolean logic functionality gained wide interest. Here, we report on seven-states Tantalum Oxide Devices, which enable the realization of an intrinsic modular arithmetic using a ternary number system. Modular arithmetic, a fundamental system for operating on numbers within the limit of a modulus, is known to mathematicians since the days of Euclid and finds applications in diverse areas ranging from e-commerce to musical notations. We demonstrate that multistate devices not only reduce the storage area consumption drastically, but also enable novel in-memory operations, such as computing using high-radix number systems, which could not be implemented using two-state devices. The use of high radix number system reduces the computational complexity by reducing the number of needed digits. Thus the number of calculation operations in an addition and the number of logic devices can be reduced.

Experimental and Theoretical Studies on Corrosion Inhibition of Niobium and Tantalum Surfaces by Carboxylated Graphene Oxide

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Valbonë Mehmeti

2018-05-01

Full Text Available The corrosion of two different metals, niobium and tantalum, in aqueous sulfuric acid solution has been studied in the presence and absence of carboxylated graphene oxide. Potentiodynamic measurements indicate that this nanomaterial inhibits corrosion due to its adsorption on the metal surfaces. The adsorbed layer of carboxylated graphene hinders two electrochemical reactions: the oxidation of the metal and the transport of metal ions from the metal to the solution but also hydrogen evolution reaction by acting as a protective barrier. The adsorption behavior at the molecular level of the carboxylated graphene oxide with respect to Nb, NbO, Ta, and TaO (111 surfaces is also investigated using Molecular Dynamic and Monte Carlo calculations.

La doping effect on TZM alloy oxidation behavior

International Nuclear Information System (INIS)

Yang, Fan; Wang, Kuai-She; Hu, Ping; He, Huan-Cheng; Kang, Xuan-Qi; Wang, Hua; Liu, Ren-Zhi; Volinsky, Alex A.

2014-01-01

Highlights: • The oxidation can be resisted by doping La into TZM alloy. • La doped TZM alloy has more compact organization. • It can rise the starting temperature of severe oxidation reaction by more than 50 °C. • Effectively slow down the oxidation rate. • Provide guidance for experiments of improving high-temperature oxidation resistance. - Abstract: Powder metallurgy methods were utilized to prepare lanthanum-doped (La-TZM) and traditional TZM alloy plates. High temperature oxidation experiments along with the differential thermal analysis were employed to study the oxidation behavior of the two kinds of TZM alloys. An extremely volatile oxide layer was generated on the surface of traditional TZM alloy plates when the oxidation started. Molybdenum oxide volatilization exposed the alloy matrix, which was gradually corroded by oxygen, losing its quality with serious surface degradation. The La-TZM alloy has a more compact structure due to the lanthanum doping. The minute lanthanum oxide particles are pinned at the grain boundaries and refine the grains. Oxide layer generated on the matrix surface can form a compact coating, which effectively blocks the surface from being corroded by oxidation. The oxidation resistance of La-TZM alloys has been enhanced, expanding its application range

Swelling and tensile properties of EBR-II-irradiated tantalum alloys for space reactor applications

International Nuclear Information System (INIS)

Grossbeck, M.L.; Wiffen, F.W.

1985-01-01

The tantalum alloys T-111, ASTAR-811C, Ta-10 W, and unalloyed tantalum were examined following EBR-II irradiation to a fluence of 1.7 x 10 26 neutrons/m 2 (E > 0.1 MeV) at temperatures from 650 to 950 K. Swelling was found to be negligible for all alloys; only tantalum was found to exhibit swelling, 0.36%. Tensile testing revealed that irradiated T-111 and Ta-10 W are susceptible to plastic instability, but ASTAR-811C and tantalum were not. The tensile properties of ASTAR-811C appeared adequate for current SP-100 space nuclear reactor designs. Irradiated, oxygen-doped T-111 exhibited no plastic deformation, and the abrupt failure was intergranular in nature. The absence of plastic instability in ASTAR-811C is encouraging for alloys containing carbide precipitates. These fine precipitates might prevent dislocation channeling, which leads to plastic instability in many bcc metals after irradiation. 10 refs., 13 figs., 8 tabs

Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

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Kuparowitz Martin

2017-06-01

Full Text Available High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential

Vapor deposition of tantalum and tantalum compounds

International Nuclear Information System (INIS)

Trkula, M.

1996-01-01

Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition

Stability aspects of hydrogen-doped indium oxide

OpenAIRE

Jost, Gabrielle; Hamri, Alexander Nordin; Köhler, Florian; Hüpkes, Jürgen

2015-01-01

Transparent conductive oxides play an important role as contact layers in various opto-electronic devices such as solar cells or LEDs. Whilst crystalline materials e.g. zinc oxide (ZnO), tin oxide (Sn2O3) or tin doped indium oxide (ITO) have already been vastly investigated and applied [1] hydrogen doped indium oxide (In2O3:H) entered the scene a while ago as a new material with a superior trade-off between electrical and optical performance. In2O3:H is commonly deposited at room temperature...

Optimum deposition, structure, and properties of tantalum oxide films

International Nuclear Information System (INIS)

Lin, Y.C.

1985-01-01

Amorphous, ductile, and uniform Ta 2 O 5 films that acted as diffusion barriers were developed by sputter depositing Ta metal on Al single crystals (99.99%) and subsequently anodizing these thin films. The morphology, microstructure, composition and properties were characterized by scanning and transmission electron microscopy, surface and Fourier transform infrared spectroscopy, X-ray diffraction, and fluorescence. Superior corrosion resistance in a water saturated Cl 2 atmosphere was provided by Ta 2 O 5 coating on Al single crystal substrates but not on Al alloys. The strong Ta-O bond, the non-porous nature of the film and good adhesion to the substrate are attributed to the outstanding corrosion resistance of these oxide coatings. Al alloy surfaces are not protected, since the anodic film formed over grain boundaries, processing lines and emergent precipitates is poorly adherent, thus providing loci for corrosion. These problems were eliminated by casting a 400 A layer of tantalum oxyhydroxide polymer from ethanol solution onto Al substrate and curing to a Ta 2 O 5 layer that effectively resisted attack by wet Cl 2 . The mechanical properties of Ta 2 O 5 films on Al alloys were studied at various pH's by in-situ fatigue loading coupled with electrochemical measurements of corrosion potential and corrosion current. These results indicate the fatigue resistance of this oxide film effectively protects the underlying metal from strong HCl solution attack. The very unusual ductility and high corrosion resistance of Ta 2 O 5 films could be related to the graphite-like structure that exists in the amorphous state of this oxide

Scandium-doped zinc cadmium oxide as a new stable n-type oxide thermoelectric material

DEFF Research Database (Denmark)

Han, Li; Christensen, Dennis Valbjørn; Bhowmik, Arghya

2016-01-01

Scandium-doped zinc cadmium oxide (Sc-doped ZnCdO) is proposed as a new n-type oxide thermoelectric material. The material is sintered in air to maintain the oxygen stoichiometry and avoid instability issues. The successful alloying of CdO with ZnO at a molar ratio of 1 : 9 significantly reduced...... is a good candidate for improving the overall conversion efficiencies in oxide thermoelectric modules. Meanwhile, Sc-doped ZnCdO is robust in air at high temperatures, whereas other n-type materials, such as Al-doped ZnO, will experience rapid degradation of their electrical conductivity and ZT....

Tantalum X-ray contrast media, by M.G. Zuev and L.P. Larionov (Ekaterinburg: UrO RAN, 2002. 155 p.)

International Nuclear Information System (INIS)

Zhuravleva, E.Yu.

2004-01-01

The monograph of M.G. Zuev and L.P. Larionov Tantalum X-ray contrast media (Solid state chemistry for medicine series) is discussed. The monograph includes information on physical and chemical properties of tantalum, rare earths, and their oxides, phase compositions and phase diagrams of M 2 O 3 -Ta 2 O 5 (M - rare earths) systems is performed. Data on preclinical tests of yttrium orthotantalate and lanthanum orthotantalate as X-ray contrast media are given. Procedures for the production of X-ray contrast media involving tantalum oxide, rare earth tantalate and tantalum powder are described [ru

Corrosion resistance of high-performance materials titanium, tantalum, zirconium

CERN Document Server

2012-01-01

Corrosion resistance is the property of a material to resist corrosion attack in a particular aggressive environment. Although titanium, tantalum and zirconium are not noble metals, they are the best choice whenever high corrosion resistance is required. The exceptionally good corrosion resistance of these high–performance metals and their alloys results from the formation of a very stable, dense, highly adherent, and self–healing protective oxide film on the metal surface. This naturally occurring oxide layer prevents chemical attack of the underlying metal surface. This behavior also means, however, that high corrosion resistance can be expected only under neutral or oxidizing conditions. Under reducing conditions, a lower resistance must be reckoned with. Only very few inorganic and organic substances are able to attack titanium, tantalum or zirconium at ambient temperature. As the extraordinary corrosion resistance is coupled with an excellent formability and weldability these materials are very valua...

Tantalum(V) impurity extraction by octanol from niobium(V) fluoride solutions

International Nuclear Information System (INIS)

Majorov, V.G.; Nikolaev, A.I.; Kopkov, V.K.

2002-01-01

The conditions of the niobium and tantalum extraction separation by octanol in the fluoride solutions, depending on the metals and free hydrofluoric acid concentration as well as on the organic and water phases voluminous relation, are studied for the purpose of developing the technology of niobium deep purification from the tantalum impurities. The technological scheme of the niobium solutions(V) extraction purification from the tantalum impurities(V), which provides for obtaining the niobium oxide(V), containing less than 0.005 mass % Ta 2 O 5 , is proposed on the basis of the established optimal separation conditions. The possibility of using the developed technology by the pyrochlore reprocessing is indicated [ru

Nanoporous titanium niobium oxide and titanium tantalum oxide compositions and their use in anodes of lithium ion batteries

Science.gov (United States)

Dai, Sheng; Guo, Bingkun; Sun, Xiao-Guang; Qiao, Zhenan

2017-10-31

Nanoporous metal oxide framework compositions useful as anodic materials in a lithium ion battery, the composition comprising metal oxide nanocrystals interconnected in a nanoporous framework and having interconnected channels, wherein the metal in said metal oxide comprises titanium and at least one metal selected from niobium and tantalum, e.g., TiNb.sub.2-x Ta.sub.xO.sub.y (wherein x is a value from 0 to 2, and y is a value from 7 to 10) and Ti.sub.2Nb.sub.10-vTa.sub.vO.sub.w (wherein v is a value from 0 to 2, and w is a value from 27 to 29). A novel sol gel method is also described in which sol gel reactive precursors are combined with a templating agent under sol gel reaction conditions to produce a hybrid precursor, and the precursor calcined to form the anodic composition. The invention is also directed to lithium ion batteries in which the nanoporous framework material is incorporated in an anode of the battery.

TRANSPARENT CONDUCTING OXIDE SYNTHESIS OF ALUMINIUM DOPED ZINC OXIDES BY CHEMICAL COPRECIPITATION

Directory of Open Access Journals (Sweden)

Silvia Maioco

2013-03-01

Full Text Available Aluminium doped zinc oxides (AZO are promising replacements for tin doped indium oxides (ITO but thin films show a wide range of physical properties strongly dependent on deposition process conditions. Submicrometric 1% aluminum doped zinc oxide ceramics (AZO are examined, prepared by coprecipitation, from Zn(NO32 and Al(NO33 aqueous solutions, sintered at 1200°C and subsequently annealed in 10-16 atm controlled oxygen fugacity atmospheres, at 1000°C. Electrical resistivity diminishes by two orders of magnitude after two hours of annealing and the Seebeck coefficient gradually changes from -140 to -50 µV/K within 8 h. It is concluded that increased mobility is dominant over the increased carrier density, induced by changes in metal-oxygen stoichiometry

Growth study and photocatalytic properties of Co-doped tungsten oxide mesocrystals

International Nuclear Information System (INIS)

Sun, Shibin; Chang, Xueting; Li, Zhenjiang

2012-01-01

Cobalt-doped tungsten oxide mesocrystals with different morphologies have been successfully generated using a solvothermal method with tungsten hexachloride and cobalt chloride salts as precursors. The resulting mesocrystals were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmet–Teller analysis of nitrogen sorptometer, and UV–vis diffuse reflectance spectroscopy. The photocatalytic properties of the cobalt-doped tungsten oxide mesocrystals were evaluated on the basis of their ability to degrade methyl orange in an aqueous solution under simulated sunlight irradiation. Results showed that the cobalt doping had obvious effect on the morphologies of the final products, and lenticular and blocky cobalt-doped tungsten oxide mesocrystals could be obtained with 1.0 wt.% and 2.0 wt.% cobalt doping, respectively. The cobalt-doped tungsten oxides exhibited superior photocatalytic activities to that of the undoped tungsten oxide. - Graphical abstract: Schematic illustrations of the growth of the bundled nanowires, lenticular mesocrystals, and blocky mesocrystals. Highlights: ► Co-doped W 18 O 49 mesocrystals were synthesized using a solvothermal method. ► The Co doping has obvious effect on the morphology of the final mesocrystals. ► The Co-doped W 18 O 49 exhibited superior photocatalytic activity to the undoped W 18 O 49 .

Properties of Polydisperse Tin-doped Dysprosium and Indium Oxides

Directory of Open Access Journals (Sweden)

Malinovskaya Tatyana

2017-01-01

Full Text Available The results of investigations of the complex permittivity, diffuse-reflectance, and characteristics of crystal lattices of tin-doped indium and dysprosium oxides are presented. Using the methods of spectroscopy and X-ray diffraction analysis, it is shown that doping of indium oxide with tin results in a significant increase of the components of the indium oxide complex permittivity and an appearance of the plasma resonance in its diffuse-reflectance spectra. This indicates the appearance of charge carriers with the concentration of more than 1021 cm−3 in the materials. On the other hand, doping of the dysprosium oxide with the same amount of tin has no effect on its optical and electromagnetic properties.

Growth study and photocatalytic properties of Co-doped tungsten oxide mesocrystals

Energy Technology Data Exchange (ETDEWEB)

Sun, Shibin [College of Logistics Engineering, Shanghai Maritime University, Shanghai 200135 (China); College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061 (China); Chang, Xueting, E-mail: xuetingchang@yahoo.cn [College of Logistics Engineering, Shanghai Maritime University, Shanghai 200135 (China); Li, Zhenjiang [College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061 (China)

2012-11-15

Cobalt-doped tungsten oxide mesocrystals with different morphologies have been successfully generated using a solvothermal method with tungsten hexachloride and cobalt chloride salts as precursors. The resulting mesocrystals were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller analysis of nitrogen sorptometer, and UV-vis diffuse reflectance spectroscopy. The photocatalytic properties of the cobalt-doped tungsten oxide mesocrystals were evaluated on the basis of their ability to degrade methyl orange in an aqueous solution under simulated sunlight irradiation. Results showed that the cobalt doping had obvious effect on the morphologies of the final products, and lenticular and blocky cobalt-doped tungsten oxide mesocrystals could be obtained with 1.0 wt.% and 2.0 wt.% cobalt doping, respectively. The cobalt-doped tungsten oxides exhibited superior photocatalytic activities to that of the undoped tungsten oxide. - Graphical abstract: Schematic illustrations of the growth of the bundled nanowires, lenticular mesocrystals, and blocky mesocrystals. Highlights: Black-Right-Pointing-Pointer Co-doped W{sub 18}O{sub 49} mesocrystals were synthesized using a solvothermal method. Black-Right-Pointing-Pointer The Co doping has obvious effect on the morphology of the final mesocrystals. Black-Right-Pointing-Pointer The Co-doped W{sub 18}O{sub 49} exhibited superior photocatalytic activity to the undoped W{sub 18}O{sub 49}.

Conductivity study of nitrogen-doped calcium zinc oxide prepared by spray pyrolysis

International Nuclear Information System (INIS)

Hsu, Yu-Ting; Lan, Wen-How; Huang, Kai-Feng; Lin, Jia-Ching; Chang, Kuo-Jen

2016-01-01

In this study, the spray pyrolysis method was used to prepare unintentionally doped and nitrogen-doped calcium zinc oxide films by using zinc acetate, calcium nitrate precursor, and ammonium acetate precursor. Morphological and structural analyses were conducted using scanning electron microscopy and X-ray diffraction. The results indicated that film grain size decreased as the nitrogen doping was increased. Both calcium oxide and zinc oxide structures were identified in the unintentionally doped calcium zinc oxide. When nitrogen doping was introduced, the film mainly exhibited a zinc oxide structure with preferred (002) and (101) orientations. The concentration and mobility were investigated using a Hall measurement system. P-type films with a mobility and concentration of 10.6 cm"2 V"−"1 s"−"1 and 2.8×10"1"7 cm"−"3, respectively, were obtained. Moreover, according to a temperature-dependent conductivity analysis, an acceptor state with activation energy 0.266 eV dominated the p-type conduction for the unintentionally doped calcium zinc oxide. By contrast, a grain boundary with a barrier height of 0.274–0.292 eV dominated the hole conduction for the nitrogen-doped calcium zinc oxide films.

Surface Characterization and Electrochemical Oxidation of Metal Doped Uranium Dioxide

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeongmook; Kim, Jandee; Youn, Young-Sang; Kim, Jong-Goo; Ha, Yeong-Keong; Kim, Jong-Yun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Trivalent element in UO{sub 2} matrix makes the oxygen vacancy from loss of oxygen for charge compensation. Tetravalent element alters lattice parameter of UO{sub 2} due to diameter difference between the tetravalent element and replaced U. These structural changes have significant effect on not only relevant fuel performance but also the kinetics of fuel oxidation. Park and Olander explained the stabilization of Ln (III)-doped UO{sub 2} against oxidation based on oxygen potential calculations. In this work, we have been investigated the effect of Gd{sup 3+} and Th{sup 4+} doping on the UO{sub 2} structure with Raman spectroscopy and X-ray diffraction to characterize the surface structure of nuclear fuel material. For Gd doped UO{sub 2}, its electrochemical oxidation behaviors are also investigated. The Gd and Th doped uranium dioxide solid solution pellets with various doping level were investigated by XRD, Raman spectroscopy, SEM, electrochemical experiments to investigate surface structure and electro chemical oxidation behaviors. The lattice parameter evaluated from XRD spectra indicated the formation of solid solutions. Raman spectra showed the existence of the oxygen vacancy. SEM images showed the grain structure on the surface of Gd doped uranium dioxide depending on doping level and oxygen-to-metal ratio.

Plasma Deposition and Characterization of Copper-doped Cobalt Oxide Nanocatalysts

Directory of Open Access Journals (Sweden)

Jacek TYCZKOWSKI

2013-09-01

Full Text Available A series of pure and copper-doped cobalt oxide films was prepared by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD. The effect of Cu-doping on the chemical structure and morphology of the deposited films was investigated. Raman and FTIR spectroscopies were used to characterize the chemical structure and morphology of the produced films. The bulk composition and homogeneity of the samples were investigated by energy dispersive X-ray microanalysis (EDX, and X-ray photoelectron spectroscopy (XPS was employed to assess the surface chemical composition of pure and doped materials. The obtained results permit to affirm that the PEMOCVD technique is a simple, versatile and efficient method for providing homogeneous layers of cobalt oxides with a different content of copper. It has been found that pure cobalt oxide films mainly contain Co3O4 in the form of nanoclusters whereas the films doped with Cu are much more complex, and CoOx (also Co3O4, mixed Co-Cu oxides and CuOx nanoclusters are detected in them. Preliminary catalytical tests show that Cu-doped cobalt oxide films allow to initiate catalytic combustion of n-hexane at a lower temperature compared to the pure cobalt oxide (Co3O4 films. From what has been stated above, the plasma-deposited thin films of Cu-doped cobalt oxides pave the way towards a new class of nanomaterials with interesting catalytic properties. DOI: http://dx.doi.org/10.5755/j01.ms.19.3.2320

Characterization of anodic barrier films on tantalum and 1100 aluminum by ISS/SIMS

International Nuclear Information System (INIS)

McCune, R.C.

1978-01-01

Ion scattering spectrometry (ISS) and concurrent secondary ion mass spectrometry (SIMS) were used to determine the depth profiles of anodic barrier oxide films grown on tantalum and type 1100 aluminum. The sputter rate in each case was determined from the film thickness measured by the anodic overvoltage, and the penetration time determined by the decrease in intensity of the metal oxide fragment observed using SIMS. A mixture of helium and neon ions was used to sputter aluminum oxide films in order to observe ion scattering of helium by oxygen, while taking advantage of the higher sputtering rate available with neon. A comparison of sputter rates for helium and neon on tantalum oxide indicated that neon sputtered the film at a rate eight times that of helium. SIMS depth profiling of the residual boron in the anodic aluminum oxide indicated a mixing effect which did not permit adequate resolution of the interface between the oxide film and the underlying metal

Structural and electrical characterization of zinc oxide doped with antimony

Directory of Open Access Journals (Sweden)

G. Juárez Díaz

2014-08-01

Full Text Available In this work we report the results of structural and electrical characterization realized on zinc oxide single crystal samples with (001 orientation, which were doped with antimony. Doping was carried out by antimony thermal diffusion at 1000 °C for periods of 1 and 2 hours under nitrogen environment from a solid source formed by antimony oxide. Electrical characterization by I-V curves and Hall effect shown an increase in acceptor concentration which demonstrates that doping is effective and create holes in zinc oxide samples.

Copper Doping of Zinc Oxide by Nuclear Transmutation

Science.gov (United States)

2014-03-27

Copper Doping of Zinc Oxide by Nuclear Transmutation THESIS Matthew C. Recker, Captain, USAF AFIT-ENP-14-M-30 DEPARTMENT OF THE AIR FORCE AIR...NUCLEAR TRANSMUTATION THESIS Presented to the Faculty Department of Engineering Physics Graduate School of Engineering and Management Air Force...COPPER DOPING OF ZINC OXIDE BY NUCLEAR TRANSMUTATION Matthew C. Recker, BS Captain, USAF Approved: //signed// 27 February 2014 John W. McClory, PhD

Tantalum Nitride Electron-Selective Contact for Crystalline Silicon Solar Cells

KAUST Repository

Yang, Xinbo

2018-04-19

Minimizing carrier recombination at contact regions by using carrier‐selective contact materials, instead of heavily doping the silicon, has attracted considerable attention for high‐efficiency, low‐cost crystalline silicon (c‐Si) solar cells. A novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties to the silicon surface, due to their small conduction band offset and large valence band offset. Thin TaNx interlayers provide moderate passivation of the silicon surfaces while simultaneously allowing a low contact resistivity to n‐type silicon. A power conversion efficiency (PCE) of over 20% is demonstrated with c‐Si solar cells featuring a simple full‐area electron‐selective TaNx contact, which significantly improves the fill factor and the open circuit voltage (Voc) and hence provides the higher PCE. The work opens up the possibility of using metal nitrides, instead of metal oxides, as carrier‐selective contacts or electron transport layers for photovoltaic devices.

Tantalum-doped hydroxyapatite thin films: Synthesis and characterization

International Nuclear Information System (INIS)

Ligot, S.; Godfroid, T.; Music, D.; Bousser, E.; Schneider, J.M.; Snyders, R.

2012-01-01

To achieve a good bioactivity, magnetron-sputtered (MS) hydroxyapatite (HA) coatings have to be stoichiometric and crystalline. It has also been suggested that doping HA with metallic elements improves its bioactivity but frequently reduces its Young’s modulus. Therefore, efforts are still necessary to identify adequate growth conditions, good doping elements and finally to grow doped HA films. In a first attempt, HA films have been synthesized by MS. Our conditions enabled us to grow at ∼10 nm min −1 stoichiometric and crystallized HA coatings that presented a strong texture. The latter is discussed in view of the competitive growth of the material under the strong electron and ion bombardments used here. Based on ab initio calculations identifying Ta as a promising doping element, we then investigated the growth of Ta-doped hydroxyapatite (HA:Ta) by magnetron co-sputtering. The HA:Ta films were in situ crystallized. Our data reveals that for Ta contents <4.5 at.%, Ta could substitute Ca in the HA cell. For higher doping contents, a deviation from the stoichiometric compound is observed and CaO appears. By nanoindentation, we have measured an elastic modulus of 120 ± 9 GPa for a Ta content of 3 at.%. This value is very close to the value of 110 GPa calculated by ab initio calculations, supporting the substitution scenario. The elasticity drop may be understood by screening of the ionic interaction between constituents in HA upon Ta incorporation.

A study of nitride formation during the oxidation of titanium-tantalum alloys

International Nuclear Information System (INIS)

Hanrahan, R.J. Jr.; Lu, Y.C.; Kung, H.; Butt, D.P.

1996-01-01

The oxidation rates of Ti rich titanium-tantalum alloys are significantly lower in air than in oxygen. This nitrogen effect has been shown to be associated with the formation of a nitride layer at or near the scale-metal interface. In the present work the authors used transmission electron microscopy and microdiffraction to identify the nitrides formed on Ti5Ta and Ti40Ta (5 and 40 weight percent Ta alloys) during identical exposures. In both alloys the nitride develops in contact with the oxygen stabilized α-phase in the substrate. In Ti5Ta a continuous layer of TiN forms, while in Ti40Ta a discontinuous layer of Ti 2 N interspersed with Ta 2 O 5 (formed from the Ta rich β-phase) is formed. The nitride layer acts as an oxygen diffusion barrier, reducing the dissolution of oxygen in the substrate

Long-Term Stability of Oxide Nanowire Sensors via Heavily Doped Oxide Contact.

Science.gov (United States)

Zeng, Hao; Takahashi, Tsunaki; Kanai, Masaki; Zhang, Guozhu; He, Yong; Nagashima, Kazuki; Yanagida, Takeshi

2017-12-22

Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO 2 (ATO) contacts on SnO 2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO 2 nanowire sensors while maintaining the sensitivity for both NO 2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.

Gas-generated thermal oxidation of a coordination cluster for an anion-doped mesoporous metal oxide.

Science.gov (United States)

Hirai, Kenji; Isobe, Shigehito; Sada, Kazuki

2015-12-18

Central in material design of metal oxides is the increase of surface area and control of intrinsic electronic and optical properties, because of potential applications for energy storage, photocatalysis and photovoltaics. Here, we disclose a facile method, inspired by geochemical process, which gives rise to mesoporous anion-doped metal oxides. As a model system, we demonstrate that simple calcination of a multinuclear coordination cluster results in synchronic chemical reactions: thermal oxidation of Ti8O10(4-aminobenzoate)12 and generation of gases including amino-group fragments. The gas generation during the thermal oxidation of Ti8O10(4-aminobenzoate)12 creates mesoporosity in TiO2. Concurrently, nitrogen atoms contained in the gases are doped into TiO2, thus leading to the formation of mesoporous N-doped TiO2. The mesoporous N-doped TiO2 can be easily synthesized by calcination of the multinuclear coordination cluster, but shows better photocatalytic activity than the one prepared by a conventional sol-gel method. Owing to an intrinsic designability of coordination compounds, this facile synthetic will be applicable to a wide range of metal oxides and anion dopants.

KAJIAN SIFAT OPTIK FILM TIPIS BST DIDADAH NIOBIUM DAN TANTALUM

Directory of Open Access Journals (Sweden)

Farida Huriawati

2016-11-01

Full Text Available In this research thin films of Barium Strontium Titanate (BST has been synthesis with different compositions Ba0,5Sr0,5TiO3 and Ba0,25Sr0,75TiO3 which doped by Nb2O5 (Niobium and Ta2O5 (Tantalum on Si (100 type-p substrate. Thin films were produced by chemical solution deposition technique (CSD and spin coating technique with annealing temperature at 850oC, 900oC dan 950oC. Rotation velocity at 3000 rpm and time of rotation is 30 seconds. Characterization of Films is optic Characterization (absorbance ana reflectance. From the Characterizations were obtained BNST thin film with 5% doping and anneling temperature at 8500C as photodiode light sensor which applied in electronic circuit.

Redox Chemisty of Tantalum Clusters on Silica Characterized by X-ray Absorption Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nemana,S.; Gates, B.

2006-01-01

SiO{sub 2}-supported clusters of tantalum were synthesized from adsorbed Ta(CH{sub 2}Ph){sub 5} by treatment in H{sub 2} at 523 K. The surface species were characterized by X-ray absorption spectroscopy (extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near edge spectroscopy (XANES)) and ultraviolet-visible spectroscopy. The EXAFS data show that SiOO{sub 2}-supported tantalum clusters were characterized by a Ta-Ta coordination number of approximately 2, consistent with the presence of tritantalum clusters, on average. When these were reduced in H{sub 2} and reoxidized in O{sub 2}, the cluster nuclearity remained essentially unchanged, although reduction and oxidation occurred, respectively, as shown by XANES and UV-vis spectra; in the reoxidation, the tantalum oxidation state change was approximately two electronic charges per tritantalum cluster. The data demonstrate an analogy between the chemistry of group 5 metals on the SiO{sub 2} support and their chemistry in solution, as determined by the group of Cotton.

Electrodepositions on Tantalum in Alkali Halide Melts

DEFF Research Database (Denmark)

Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

2013-01-01

Surface layers of tantalum metal were electrodeposited on steel from K2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO3 melts carbonate ions seems to be reduced to carbon in...

Electrodepositions on Tantalum in alkali halide melts

DEFF Research Database (Denmark)

Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

2012-01-01

Surface layers of tantalum metal were electrodeposited on steel from K 2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO 3 melts carbonate ions seems to be reduced to carbon ...

Upgrading tantalum and niobium oxides content in Bangka tin slag with double leaching

Science.gov (United States)

Soedarsono, J. W.; Permana, S.; Hutauruk, J. K.; Adhyputra, R.; Rustandi, A.; Maksum, A.; Widana, K. S.; Trinopiawan, K.; Anggraini, M.

2018-03-01

Tantalum has become one of the 14 types of critical materials where the level of its availability is assumed as the midterm critical metal. Benefits of the element tantalum in the electronics field increased the deficit balance of supply / demand, as more variations of electronic products developed. The tantalum experts calculated the level of availability until 2020. Base on the previous studies, tin slag is a secondary source of tantalum and niobium. This study uses tin slag from Bangka, Indonesia, abbreviated, Bangka Tin Slag (BTS). BTS was roasted, water quenched and sieved, abbreviated BTS-RQS.BTS was roasted, water quenched and sieved, abbreviated BTS-RQS.BTS-RQS was roasted at a temperature 700□C given sample code BTS-R700QS, while roasted at 800°C given sample code BTS-R800QS.A variable leaching experiment on BTS-R700QS was solvent concentration variable and on BTS-R800QS was time variable. The entire residue was characterized by X-Ray Fluorescence (XRF), and the optimum results are on the BTS-R800QS leaching into 5 M NaOH for 20 min followed by 5M HCl for 50 min, with content of Ta2O5 and Nb2O51.56% and 1.11%, respectively. The result of XRF measurement showed was the increasing of TNO content due to the increasing solvent concentration and time of acid leaching. The discussion of thermodynamics this study used was HSC Chemistry 6 as a supporting data.

Enhanced oxidation resistance of carbon fiber reinforced lithium aluminosilicate composites by boron doping

International Nuclear Information System (INIS)

Xia, Long; Jin, Feng; Zhang, Tao; Hu, Xueting; Wu, Songsong; Wen, Guangwu

2015-01-01

Highlights: • C f /LAS composites exhibit enhanced oxidation resistance by boron doping. • Boron doping is beneficial to the improvement of graphitization degree of carbon fibers. • Graphitization of carbon fibers together with the decrease of viscosity of LAS matrix is responsible to the enhancement of oxidation resistance of C f /LAS composites. - Abstract: Carbon fiber reinforced lithium aluminosilicate matrix composites (C f /LAS) modified with boron doping were fabricated and oxidized for 1 h in static air. Weight loss, residual strength and microstructure were analyzed. The results indicate that boron doping has a remarkable effect on improving the oxidation resistance for C f /LAS. The synergism of low viscosity of LAS matrix at high temperature and formation of graphite crystals on the surface of carbon fibers, is responsible for excellent oxidation resistance of the boron doped C f /LAS.

Spray deposited gallium doped tin oxide thinfilm for acetone sensor application

Science.gov (United States)

Preethi, M. S.; Bharath, S. P.; Bangera, Kasturi V.

2018-04-01

Undoped and gallium doped (1 at.%, 2 at.% and 3 at.%) tin oxide thin films were prepared using spray pyrolysis technique by optimising the deposition conditions such as precursor concentration, substrate temperature and spraying rate. X-ray diffraction analysis revealed formation of tetragonally structured polycrystalline films. The SEM micrographs of Ga doped films showed microstructures. The electrical resistivity of the doped films was found to be more than that of the undoped films. The Ga-doped tin oxide thin films were characterised for gas sensors. 1 at.% Ga doped thin films were found to be better acetone gas sensor, showed 68% sensitivity at 350°C temperature.

Improving superconducting properties of YBCO high temperature superconductor by Graphene Oxide doping

Energy Technology Data Exchange (ETDEWEB)

Dadras, S., E-mail: dadras@alzahra.ac.ir; Dehghani, S.; Davoudiniya, M.; Falahati, S.

2017-06-01

In this research, we report the synthesis and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-δ} (YBCO) high temperature superconductor prepared by sol-gel method and doped with Graphene Oxide (GO) in different weight percentages, 0, 0.1, 0.7 and 1 % wt. The x-ray diffraction (XRD) analysis confirms the formation of orthorhombic phase of superconductivity for all the prepared samples. We found that GO doping reduces the crystalline size of the samples. We evaluated the effects of GO doping on the normal state resistivity (ρ), superconducting transition temperature (T{sub c}) and critical current density (J{sub c}). The results show that the GO doping has a positive effect on these properties. Also, the highest J{sub c} is obtained for the 0.7 %wt GO doped YBCO compound that its critical current density is about 15 times more than the J{sub c} of pure one in 0.4 T magnetic field. The scanning electron microscope (SEM) analysis shows that there are better connections between the grains of GO doped samples. - Highlights: • Graphene Oxide doping increased the YBCO critical current density. • Graphene Oxide creates a better connection between the YBCO grains. • The normal resistivity of samples were decreased by GO doping to YBCO compounds. • Graphene Oxide doping has a positive effect on the critical transition temperature.

Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells

OpenAIRE

Ding Ding; Youtao Xie; Kai Li; Liping Huang; Xuebin Zheng

2018-01-01

Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs), a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were co...

Surface chemistry and cytotoxicity of reactively sputtered tantalum oxide films on NiTi plates

Energy Technology Data Exchange (ETDEWEB)

McNamara, K. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Kolaj-Robin, O.; Belochapkine, S.; Laffir, F. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Gandhi, A.A. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland); Tofail, S.A.M., E-mail: tofail.syed@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Department of Physics & Energy, University of Limerick, Limerick (Ireland)

2015-08-31

NiTi, an equiatomic alloy containing nickel and titanium, exhibits unique properties such as shape memory effect and superelasticity. NiTi also forms a spontaneous protective titanium dioxide (TiO{sub 2}) layer that allows its use in biomedical applications. Despite the widely perceived biocompatibility there remain some concerns about the sustainability of the alloy's biocompatibility due to the defects in the TiO{sub 2} protective layer and the presence of high amount of sub-surface Ni, which can give allergic reactions. Many surface treatments have been investigated to try to improve both the corrosion resistance and biocompatibility of this layer. For such purposes, we have sputter deposited tantalum (Ta) oxide thin films onto the surface of the NiTi alloy. Despite being one of the promising metals for biomedical applications, Ta, and its various oxides and their interactions with cells have received relatively less attention. The oxidation chemistry, crystal structure, morphology and biocompatibility of these films have been investigated. In general, reactive sputtering especially in the presence of a low oxygen mixture yields a thicker film with better control of the film quality. The sputtering power influenced the surface oxidation states of Ta. Both microscopic and quantitative cytotoxicity measurements show that Ta films on NiTi are biocompatible with little to no variation in cytotoxic response when the surface oxidation state of Ta changes. - Highlights: • Reactive sputtering in low oxygen mixture yields thicker better quality films. • Sputtering power influenced surface oxidation states of Ta. • Cytotoxicity measurements show Ta films on NiTi are biocompatible. • Little to no variation in cytotoxic response when oxidation state changes.

Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

International Nuclear Information System (INIS)

Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

2016-01-01

Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO_2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

Anodic oxidation with doped diamond electrodes: a new advanced oxidation process

International Nuclear Information System (INIS)

Kraft, Alexander; Stadelmann, Manuela; Blaschke, Manfred

2003-01-01

Boron-doped diamond anodes allow to directly produce OH· radicals from water electrolysis with very high current efficiencies. This has been explained by the very high overvoltage for oxygen production and many other anodic electrode processes on diamond anodes. Additionally, the boron-doped diamond electrodes exhibit a high mechanical and chemical stability. Anodic oxidation with diamond anodes is a new advanced oxidation process (AOP) with many advantages compared to other known chemical and photochemical AOPs. The present work reports on the use of diamond anodes for the chemical oxygen demand (COD) removal from several industrial wastewaters and from two synthetic wastewaters with malic acid and ethylenediaminetetraacetic (EDTA) acid. Current efficiencies for the COD removal between 85 and 100% have been found. The formation and subsequent removal of by-products of the COD oxidation has been investigated for the first time. Economical considerations of this new AOP are included

Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells.

Science.gov (United States)

Ding, Ding; Xie, Youtao; Li, Kai; Huang, Liping; Zheng, Xuebin

2018-04-03

Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs), a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were comprehensively studied by employing scanning electron microscopy (SEM), X-ray diffraction (XRD) as well as transmission electron microscopy (TEM). The effects of hierarchical structures as well as micro-porous structure of tantalum coating on the behavior for human bone marrow stem cells (hBMSCs) were evaluated and compared at both cellular and molecular levels in vitro. The experimental results show that a hierarchical micro/nano structure with Ta₂O₅ nanotubes spread onto a micro-scale tantalum coating has been fabricated successfully, which is confirmed to promote cell adhesion and spreading. Besides, the hierarchical micro/nano tantalum coating can provide 1.5~2.1 times improvement in gene expression, compared with the micro-porous tantalum coating. It demonstrates that it can effectively enhance the proliferation and differentiation of hBMSCs in vitro.

Micro/Nano Structural Tantalum Coating for Enhanced Osteogenic Differentiation of Human Bone Marrow Stem Cells

Directory of Open Access Journals (Sweden)

Ding Ding

2018-04-01

Full Text Available Recently, tantalum has been attracting much attention for its anticorrosion resistance and biocompatibility, and it has been widely used in surface modification for implant applications. To improve its osteogenic differentiation of human bone marrow stem cells (hBMSCs, a micro/nano structure has been fabricated on the tantalum coating surface through the combination of anodic oxidation and plasma spraying method. The morphology, composition, and microstructure of the modified coating were comprehensively studied by employing scanning electron microscopy (SEM, X-ray diffraction (XRD as well as transmission electron microscopy (TEM. The effects of hierarchical structures as well as micro-porous structure of tantalum coating on the behavior for human bone marrow stem cells (hBMSCs were evaluated and compared at both cellular and molecular levels in vitro. The experimental results show that a hierarchical micro/nano structure with Ta2O5 nanotubes spread onto a micro-scale tantalum coating has been fabricated successfully, which is confirmed to promote cell adhesion and spreading. Besides, the hierarchical micro/nano tantalum coating can provide 1.5~2.1 times improvement in gene expression, compared with the micro-porous tantalum coating. It demonstrates that it can effectively enhance the proliferation and differentiation of hBMSCs in vitro.

Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

Energy Technology Data Exchange (ETDEWEB)

Bi, Kedong, E-mail: lishi@mail.utexas.edu, E-mail: kedongbi@seu.edu.cn [Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189 (China); Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Weathers, Annie; Pettes, Michael T.; Shi, Li, E-mail: lishi@mail.utexas.edu, E-mail: kedongbi@seu.edu.cn [Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Matsushita, Satoshi; Akagi, Kazuo [Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510 (Japan); Goh, Munju [Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510 (Japan); Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Eunha-ri san 101, Bondong-eup, Wanju-gun, Jeolabuk-do 565-905 (Korea, Republic of)

2013-11-21

Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m{sup −1} K{sup −1} near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, the PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion.

Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

International Nuclear Information System (INIS)

Bi, Kedong; Weathers, Annie; Pettes, Michael T.; Shi, Li; Matsushita, Satoshi; Akagi, Kazuo; Goh, Munju

2013-01-01

Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m −1  K −1 near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, the PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion

Electrical Transport Ability of Nanostructured Potassium-Doped Titanium Oxide Film

Science.gov (United States)

Lee, So-Yoon; Matsuno, Ryosuke; Ishihara, Kazuhiko; Takai, Madoka

2011-02-01

Potassium-doped nanostructured titanium oxide films were fabricated using a wet corrosion process with various KOH solutions. The doped condition of potassium in TiO2 was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Nanotubular were synthesized at a dopant concentration of 0.27%, these structures disappeared. To investigate the electrical properties of K-doped TiO2, pseudo metal-oxide-semiconductor field-effect transistor (MOSFET) samples were fabricated. The samples exhibited a distinct electrical behavior and p-type characteristics. The electrical behavior was governed by the volume of the dopant when the dopant concentration was 0.18%.

Enhance the Pyroelectricity of Polyvinylidene Fluoride by Graphene-Oxide Doping

Directory of Open Access Journals (Sweden)

Yuh-Chung Hu

2014-04-01

Full Text Available The high quality properties and benefits of graphene-oxide have generated an active area of research where many investigations have shown potential applications in various technological fields. This paper proposes a methodology for enhancing the pyro-electricity of PVDF by graphene-oxide doping. The PVDF film with graphene-oxide is prepared by the sol-gel method. Firstly, PVDF and graphene-oxide powders are dispersed into dimethylformamide as solvent to form a sol solution. Secondly, the sol solution is deposited on a flexible ITO/PET substrate by spin-coating. Thirdly, the particles in the sol solution are polymerized through baking off the solvent to produce a gel in a state of a continuous network of PVDF and graphene-oxide. The final annealing process pyrolyzes the gel and form a β-phase PVDF film with graphene-oxide doping. A complete study on the process of the graphene oxide doping of PVDF is accomplished. Some key points about the process are addressed based on experiments. The solutions to some key issues are found in this work, such as the porosity of film, the annealing temperature limitation by the use of flexible PET substrate, and the concentrations of PVDF and graphene-oxide.

Atomic layer deposition of high-mobility hydrogen-doped zinc oxide

NARCIS (Netherlands)

Macco, B.; Knoops, H.C.M.; Verheijen, M.A.; Beyer, W.; Creatore, M.; Kessels, W.M.M.

2017-01-01

In this work, atomic layer deposition (ALD) has been employed to prepare high-mobility H-doped zinc oxide (ZnO:H) films. Hydrogen doping was achieved by interleaving the ZnO ALD cycles with H2 plasma treatments. It has been shown that doping with H2 plasma offers key advantages over traditional

Different magnetic properties of rhombohedral and cubic Ni2+ doped indium oxide nanomaterials

Directory of Open Access Journals (Sweden)

Qingbo Sun

2011-12-01

Full Text Available Transition metal ions doped indium oxide nanomaterials were potentially used as a kind of diluted magnetic semiconductors in transparent spintronic devices. In this paper, the influences of Ni2+ doped contents and rhombohedral or cubic crystalline structures of indium oxide on magnetic properties were investigated. We found that the magnetic properties of Ni2+ doped indium oxide could be transferred from room temperature ferromagnetisms to paramagnetic properties with increments of doped contents. Moreover, the different crystalline structures of indium oxide also greatly affected the room temperature ferromagnetisms due to different lattice constants and almost had no effects on their paramagnetic properties. In addition, both the ferromagnetic and paramagnetic properties were demonstrated to be intrinsic and not caused by impurities.

Self-limited kinetics of electron doping in correlated oxides

International Nuclear Information System (INIS)

Chen, Jikun; Zhou, You; Jiang, Jun; Shi, Jian; Ramanathan, Shriram; Middey, Srimanta; Chakhalian, Jak; Chen, Nuofu; Chen, Lidong; Shi, Xun; Döbeli, Max

2015-01-01

Electron doping by hydrogenation can reversibly modify the electrical properties of complex oxides. We show that in order to realize large, fast, and reversible response to hydrogen, it is important to consider both the electron configuration on the transition metal 3d orbitals, as well as the thermodynamic stability in nickelates. Specifically, large doping-induced resistivity modulations ranging several orders of magnitude change are only observed for rare earth nickelates with small ionic radii on the A-site, in which case both electron correlation effects and the meta-stability of Ni 3+ are important considerations. Charge doping via metastable incorporation of ionic dopants is of relevance to correlated oxide-based devices where advancing approaches to modify the ground state electronic properties is an important problem

A simple model to estimate the optimal doping of p - Type oxide superconductors

Directory of Open Access Journals (Sweden)

Adir Moysés Luiz

2008-12-01

Full Text Available Oxygen doping of superconductors is discussed. Doping high-Tc superconductors with oxygen seems to be more efficient than other doping procedures. Using the assumption of double valence fluctuations, we present a simple model to estimate the optimal doping of p-type oxide superconductors. The experimental values of oxygen content for optimal doping of the most important p-type oxide superconductors can be accounted for adequately using this simple model. We expect that our simple model will encourage further experimental and theoretical researches in superconducting materials.

Thermoelectric material comprising scandium doped zinc cadmium oxide

DEFF Research Database (Denmark)

2016-01-01

There is presented a composition of scandium doped Zinc Cadmium Oxide with the general formula ZnzCdxScyO which the inventors have prepared, and for which material the inventors have made the insight that it is particularly advantageous as an n-type oxide material, such as particularly advantageous...

Genetic algorithm based approach to investigate doped metal oxide materials: Application to lanthanide-doped ceria

Science.gov (United States)

Hooper, James; Ismail, Arif; Giorgi, Javier B.; Woo, Tom K.

2010-06-01

A genetic algorithm (GA)-inspired method to effectively map out low-energy configurations of doped metal oxide materials is presented. Specialized mating and mutation operations that do not alter the identity of the parent metal oxide have been incorporated to efficiently sample the metal dopant and oxygen vacancy sites. The search algorithms have been tested on lanthanide-doped ceria (L=Sm,Gd,Lu) with various dopant concentrations. Using both classical and first-principles density-functional-theory (DFT) potentials, we have shown the methodology reproduces the results of recent systematic searches of doped ceria at low concentrations (3.2% L2O3 ) and identifies low-energy structures of concentrated samarium-doped ceria (3.8% and 6.6% L2O3 ) which relate to the experimental and theoretical findings published thus far. We introduce a tandem classical/DFT GA algorithm in which an inexpensive classical potential is first used to generate a fit gene pool of structures to enhance the overall efficiency of the computationally demanding DFT-based GA search.

Ytterbia doped nickel–manganese mixed oxide catalysts for liquid phase oxidation of benzyl alcohol

Directory of Open Access Journals (Sweden)

S.S.P. Sultana

2017-11-01

Full Text Available Nickel–manganese mixed oxides doped with 1, 3, 5 mol% ytterbia have been prepared by co-precipitation method and used in the catalytic oxidation of benzyl alcohol. Catalytic activity of these oxides calcined at 400 °C and 500 °C was studied for selective oxidation of benzyl alcohol to the corresponding aldehyde using molecular oxygen as an oxidizing agent. The results showed that thermally stable 5 mol% ytterbia doped nickel–manganese oxide [Yb2O3-(5%-Ni6MnO8] exhibited highest catalytic performance when it was calcined at 400 °C. A 100% conversion of the benzyl alcohol was achieved with >99% selectivity to benzaldehyde within a reaction period of 5 h at 100 °C. The mixed oxide prepared has been characterized by scanning election microscopy (SEM and energy dispersive X-ray analysis (EDXA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, thermogravimetric analysis (TGA, Brunauer–Emmett–Teller (BET and temperature programed reduction (H2-TPR.

Combined influence of fluorine doping and vacuum annealing on the electrical properties of ZnO:Ta films

Energy Technology Data Exchange (ETDEWEB)

Subha, K. [Materials Science Research Laboratory, PG and Research Department of Physics, AVVM Sri Pushpam College (Autonomous), Poondi, Thanjavur, 613 503, Tamil Nadu (India); Research Department of Physics, Kunthavai Naachiyaar Govt. Arts College for Women (Autonomous), Thanjavur, 613 007, Tamil Nadu (India); Ravichandran, K., E-mail: kkr1365@yahoo.com [Materials Science Research Laboratory, PG and Research Department of Physics, AVVM Sri Pushpam College (Autonomous), Poondi, Thanjavur, 613 503, Tamil Nadu (India); Sriram, S. [School of Electrical and Electronics Engineering, SASTRA University, Thanjavur, 613 401, Tamil Nadu (India)

2017-07-01

Highlights: • First report on combined effect of F doping and annealing on resistivity of ZnO:Ta films. • Various possible incorporation mechanisms of tantalum and fluorine are addressed. • Theoretical validation of Ta and F incorporation by DFT analysis is done. • Quality factor comparable with those obtained by physical methods is achieved.. - Abstract: In this study, our main focus is to investigate the effects of F doping and post deposition annealing (air and vacuum) on the optical and electrical characteristics of tantalum doped zinc oxide films (ZnO:Ta). A cost-effective, automated jet nebulizer spray pyrolysis technique is adopted to deposit the ZnO:Ta:F films. The doping level of Ta is kept constant (1 at.%) and that of F is varied from 5 to 20 at.% in steps of 5 at.%. The electrical resistivity of the as-deposited films decreases for 10 at.% of F concentration. The resistance increases thereafter. The same trend is also observed in annealed films. The reasons for these variations are addressed based on the effective F incorporation into the ZnO lattice and annealing atmosphere with the help of XRD, FESEM, AFM and PL studies. The incorporation of the dopants was confirmed from XPS and EDX analyses and the DFT studies show that the incorporation of the dopants does not affect the stability of the ZnO lattice. Vacuum-annealed films show better electrical properties over the as-deposited and air-annealed counterparts, though their transparency is affected marginally. A minimum resistivity of 0.81 × 10{sup −3} Ω cm and an enhanced quality factor of 2.265 × 10{sup −4} (Ω/sq){sup −1} are achieved for the vacuum-annealed films having Ta + F doping levels as 1 + 10 at.%. These results make this sample a desirable candidate for transparent electrode applications.

Multifunctional hybrid coating on titanium towards hydroxyapatite growth: Electrodeposition of tantalum and its molecular functionalization with organophosphonic acids films

International Nuclear Information System (INIS)

Arnould, Christelle; Delhalle, Joseph; Mekhalif, Zineb

2008-01-01

Titanium and its alloys are base materials used in the dental and orthopaedic fields owing to suitable intrinsic properties: good biocompatibility, high corrosion resistance and excellent mechanical properties. However, the bonding between titanium and bone tissue is not always strong enough and can become a critical problem. In this context, the two main objectives of this paper are the increase of the corrosion resistance and the improvement of the hydroxyapatite (HAp) growth. The surface modification considered here is achieved in three main steps and consists in the elaboration of different inorganic and organic coatings. The first step is the elaboration of electrodeposition of tantalum on the titanium oxide film of a titanium substrate. The second step is the modification of the tantalum oxide coating with organophosphonic acids. The last step is the nucleation and growth of HAP on the outermost layer of the system by immersion in a simulated body fluid. The hybrid coating tantalum oxide/organophosphonic acids/molecular layer is shown to be promising for orthopaedic implants

Optical and electrochromic properties of sol-gel deposited Ti- doped vanadium oxide films

International Nuclear Information System (INIS)

Oezer, N.; Sabuncu, S.

1997-01-01

Because of the yellowish color, vanadium oxide films in the as deposited state is not as favorable as transparent coatings for most elector chromic devices. an interesting possibility to alter the yellowish colours is the doping with other non-absorbing metal oxides. Ti doped vanadium oxide films with various amounts of titanium were synthesized and investigated as transparent counter electrodes for electrochromic transmissive device application. Electrochromic titanium doped vanadium pentoxide (V sub 2 O 5) coatings were prepared by the sol-gel dip coating technique. The coating solutions were synthesized from vanadium tri(isopropoxide) precursors. X-ray diffraction (XRD) studies showed that the sol-gel deposited doped films heat treated at temperatures below 350 degree centigrade, were amorphous, whereas hose heat treated at higher temperatures were slight y crystalline. The optical and electrochemical properties of the Ti doped vanadium oxide films has been investigated in 0.1 m LiClO sub 4 propylene carbonate solution color changes by dropping were noted for all investigated films exhibits good electrochemical cycling (CV) measurements also showed that Ti doped V sub 2 O sub 5 films exhibits good electrochemical cycling reversibility, 'in situ' optical measurement revealed that those films exhibits good electrochemical cycling the spectra range 300 < lambda < 800 nm and change color between yellow and light green. The change in visible transmittance was 25 % for 5% Ti doped film. (author)

Effect of tungsten doping on catalytic properties of niobium oxide

Energy Technology Data Exchange (ETDEWEB)

Cardoso, Franciane P.; Nogueira, Andre E. [Departamento de Quimica, Universidade Federal de Lavras, Lavras-MG (Brazil); Patricio, Patricia S.O., E-mail: patriciapatricio@cefetmg.br [Centro Federal de Educacao Tecnologica, CEFET, Belo Horizonte, MG (Brazil); Oliveira, Luiz C.A. [Departamento de Quimica, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil)

2012-04-15

A novel material based on niobia (Nb{sub 2}O{sub 5}) was synthesized to oxidize an organic compound in aqueous medium in the presence of H{sub 2}O{sub 2} after chemical modifications. Niobia was modified by doping with tungsten and also treating with H{sub 2}O{sub 2} in order to maximize the oxidative properties of this oxide. The analysis of the products from methylene blue dye oxidation with electro spray ionization mass spectrometry (ESI-MS) showed that the dye was successively oxidized to different intermediate compounds. The successive hydroxylation during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated involving H{sub 2}O{sub 2} on the W-doped niobia grain surface. These results strongly suggest that the H{sub 2}O{sub 2} can regenerate in situ the peroxo group remaining active the system. (author)

Electron tunneling in tantalum surface layers on niobium

International Nuclear Information System (INIS)

Ruggiero, S.T.; Track, E.K.; Prober, D.E.; Arnold, G.B.; DeWeert, M.J.

1986-01-01

We have performed electron tunneling measurements on tantalum surface layers on niobium. The tunnel junctions comprise 2000-A-circle Nb base electrodes with 10--100-A-circle in situ--deposited Ta overlayers, an oxide barrier, and Ag, Pb, or Pb-Bi alloy counterelectrodes. The base electrodes were prepared by ion-beam sputter deposition. The characteristics of these junctions have been studied as a function of Ta-layer thickness. These include the critical current, bound-state energy, phonon structure, and oxide barrier shape. We have compared our results for the product I/sub c/R versus tantalum-layer thickness with an extended version of the Gallagher theory which accounts for both the finite mean free path in the Ta overlayers and suppression of the I/sub c/R product due to strong-coupling effects. Excellent fits to the data yield a value of the intrinsic scattering probability for electrons at the Ta/Nb interface of r 2 = 0.01. This is consistent with the value expected from simple scattering off the potential step created by the difference between the Fermi energies of Ta and Nb. We have found a universal empirical correlation in average barrier height phi-bar and width s in the form phi-bar = 6 eV/(s-10 A-circle) for measured junctions which holds both for our data and results for available data in the literature for oxide-barrier junctions. The latter are composed of a wide variety of base and counterelectrode materials. These results are discussed in the general context of oxide growth and compared with results for artificial tunnel barriers

Ductility of Mo–12Si–8.5B alloys doped with lanthanum oxide by the liquid–liquid doping method

Energy Technology Data Exchange (ETDEWEB)

Li, Wenhu [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); School of Materials Science & Engineering, Shaanxi University of Technology, Hanzhong 723000 (China); Zhang, Guojun, E-mail: zhangguojun@xaut.edu.cn [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); Wang, Shixiong [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Bin; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)

2015-09-05

Highlights: • Alloys doping lanthanum oxide by L–L doped method were prepared by hot pressing. • The compression strength of alloys are superior. • The fracture toughness of alloys is improved by L–L doped method. - Abstract: Mo–12Si–8.5B (Mo–Si–B) alloys doped with different mass fractions (0.3 wt%, 0.6 wt%, and 0.9 wt%) of lanthanum oxide (La{sub 2}O{sub 3}) were prepared by liquid–liquid (L–L) doping, mechanical alloying and hot pressing sintering techniques. The observation of the microstructures of the Mo–Si–B alloys reveals that the grain sizes of the alloys were refined with the increase in La{sub 2}O{sub 3} doping. The fracture toughness values of the alloys of over 10 MPa m{sup 1/2} reveal that the addition of La{sub 2}O{sub 3} via the L–L doping method can obviously improve the alloy fracture toughness compared to the alloys doped with La{sub 2}O{sub 3} via the solid–solid (S–S) doping method. In addition, compression tests indicate that the compression strength of the alloys was improved compared to Mo–12Si–8.5B alloys.

Plasma diagnostics during magnetron sputtering of aluminum doped zinc oxide

DEFF Research Database (Denmark)

Stamate, Eugen; Crovetto, Andrea; Sanna, Simone

2016-01-01

Plasma parameters during magnetron sputtering of aluminum-doped zinc oxide are investigated with optical emission spectroscopy, electrostatic probes and mass spectrometry with the aim of understanding the role of negative ions of oxygen during the film growth and improving the uniformity of the f......Plasma parameters during magnetron sputtering of aluminum-doped zinc oxide are investigated with optical emission spectroscopy, electrostatic probes and mass spectrometry with the aim of understanding the role of negative ions of oxygen during the film growth and improving the uniformity...

Vanadium Doped Tungsten Oxide Material - Electrical Physical and Sensing Properties

Directory of Open Access Journals (Sweden)

Shishkin N. Y.

2008-05-01

Full Text Available The electrical physical and sensing (to VOCs and inorganic gases properties of vanadium doped tungsten oxide in the regions of phase transition temperature were investigated. Vanadium oxide (II dimerization was observed in the doped material, corresponding to new phase transition. The extreme sensitivity and selectivity to chemically active gases and vapors in small concentrations: CO, NOx, NH3 acetone, ethanol near phase transitions temperature was found. Sensor elements were manufactured for the quantitative detection (close to 1 ppm of alcohol and ammonia.

Bioactivity and mechanical behaviour of cobalt oxide-doped ...

Indian Academy of Sciences (India)

tive base glass and cobalt oxide-doped glass were prepared by the addition of cobalt oxide (0, ... and 1 N HCl at 37. ◦. C as compared with the ... SO2−. 4. Cl. −. Simulated body fluid. 142.0. 5.0. 1.5. 2.5. 4.2. 1.0. 0.5. 147.8. Human blood plasma ...

Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

Directory of Open Access Journals (Sweden)

Yu Fu

2017-04-01

Full Text Available Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4, was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(IIN bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0% of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-doping

Sulphur mustard degradation on zirconium doped Ti-Fe oxides

Energy Technology Data Exchange (ETDEWEB)

Stengl, Vaclav, E-mail: stengl@iic.cas.cz [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR v.v.i 250 68 Husinec-Rez (Czech Republic); Grygar, Tomas Matys [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR v.v.i 250 68 Husinec-Rez (Czech Republic); Oplustil, Frantisek; Nemec, Tomas [Military Technical Institute of Protection Brno Veslarska 230, 628 00 Brno (Czech Republic)

2011-09-15

Highlights: {yields} New stechiometric materials for sulphur mustard degradation. {yields} High degree of degradation, more then 95% h{sup -1}. {yields} One-pot synthesis procedure. - Abstract: Zirconium doped mixed nanodispersive oxides of Ti and Fe were prepared by homogeneous hydrolysis of sulphate salts with urea in aqueous solutions. Synthesized nanodispersive metal oxide hydroxides were characterised as the Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) microanalysis, and acid-base titration. These oxides were taken for an experimental evaluation of their reactivity with sulphur mustard (chemical warfare agent HD or bis(2-chloroethyl)sulphide). The presence of Zr{sup 4+} dopant tends to increase both the surface area and the surface hydroxylation of the resulting doped oxides in such a manner that it can contribute to enabling the substrate adsorption at the oxide surface and thus accelerate the rate of degradation of warfare agents. The addition of Zr{sup 4+} to the hydrolysis of ferric sulphate with urea shifts the reaction route and promotes formation of goethite at the expense of ferrihydrite. We discovered that Zr{sup 4+} doped oxo-hydroxides of Ti and Fe exhibit a higher degradation activity towards sulphur mustard than any other yet reported reactive sorbents. The reaction rate constant of the slower parallel reaction of the most efficient reactive sorbents is increased with the increasing amount of surface base sites.

Cellular Automata Modelling of Photo-Induced Oxidation Processes in Molecularly Doped Polymers

Directory of Open Access Journals (Sweden)

David M. Goldie

2016-11-01

Full Text Available The possibility of employing cellular automata (CA to model photo-induced oxidation processes in molecularly doped polymers is explored. It is demonstrated that the oxidation dynamics generated using CA models exhibit stretched-exponential behavior. This dynamical characteristic is in general agreement with an alternative analysis conducted using standard rate equations provided the molecular doping levels are sufficiently low to prohibit the presence of safe-sites which are impenetrable to dissolved oxygen. The CA models therefore offer the advantage of exploring the effect of dopant agglomeration which is difficult to assess from standard rate equation solutions. The influence of UV-induced bleaching or darkening upon the resulting oxidation dynamics may also be easily incorporated into the CA models and these optical effects are investigated for various photo-oxidation product scenarios. Output from the CA models is evaluated for experimental photo-oxidation data obtained from a series of hydrazone-doped polymers.

A novel tantalum-based sol-gel packed microextraction syringe for highly specific enrichment of phosphopeptides in MALDI-MS applications.

Science.gov (United States)

Çelikbıçak, Ömür; Atakay, Mehmet; Güler, Ülkü; Salih, Bekir

2013-08-07

A new tantalum-based sol-gel material was synthesized using a unique sol-gel synthesis pathway by PEG incorporation into the sol-gel structure without performing a calcination step. This improved its chemical and physical properties for the high capacity and selective enrichment of phosphopeptides from protein digests in complex biological media. The specificity of the tantalum-based sol-gel material for phosphopeptides was evaluated and compared with tantalum(V) oxide (Ta2O5) in different phosphopeptide enrichment applications. The tantalum-based sol-gel and tantalum(V) oxide were characterized in detail using FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and also using a surface area and pore size analyzer. In the characterization studies, the surface morphology, pore volume, crystallinity of the materials and PEG incorporation into the sol-gel structure to produce a more hydrophilic material were successfully demonstrated. The X-ray diffractograms of the two different materials were compared and it was noted that the broad signals of the tantalum-based sol-gel clearly represented the amorphous structure of the sol-gel material, which was more likely to create enough surface area and to provide more accessible tantalum atoms for phosphopeptides to be easily adsorbed when compared with the neat and more crystalline structure of Ta2O5. Therefore, the phosphopeptide enrichment performance of the tantalum-based sol-gels was found to be remarkably higher than the more crystalline Ta2O5 in our studies. Phosphopeptides at femtomole levels could be selectively enriched using the tantalum-based sol-gel and detected with a higher signal-to-noise ratio by matrix-assisted laser desorption/ionization-mass spectrometer (MALDI-MS). Moreover, phosphopeptides in a tryptic digest of non-fat bovine milk as a complex real-world biological sample were retained with higher yield using a tantalum-based sol-gel. Additionally, the sol-gel material

Mechanical Properties and Electronic Structure of N and Ta Doped TiC: A First-Principles Study

International Nuclear Information System (INIS)

Ma Shi-Qing; Liu Ying; Ye Jin-Wen; Wang Bin

2014-01-01

The first principles calculations based on density functional theory (DFT) are employed to investigate the mechanical properties and electronic structure of N and Ta doped TiC. The result shows that the co-doping of nitrogen and tantalum dilates the lattice constant and improves the stability of TiC. Nitrogen and tantalum can signiβcantly enhance the elastic constants and elastic moduli of TiC. The results of B/G and C 12 –C 44 indicate tantalum can markedly increase the ductility of TiC. The electronic structure is calculated to describe the bonding characteristic, which revealed the strong hybridization between C-p and Ta-d and between N-p and Ti-d. The hardnessis is estimated by a semi-empirical model that is based on the Mulliken overlap population and bond length. While the weakest bond takes determinative role of the hardness of materials, the addition of Ta sharply reduces the hardness of TiC. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Formation of nickel-tantalum compounds in tantalum fluoride halide melts

International Nuclear Information System (INIS)

Matychenko, Eh.S.; Zalkind, O.A.; Kuznetsov, B.Ya.; Orlov, V.M.; Sukhorzhevskaya, S.L.

2001-01-01

Interaction of nickel with NaCl-K 2 TaF 7 melt (14 mol.%) at 750 deg C was studied, the composition of intermetallic compounds formed in Ni-Ta system being analyzed, using the methods of chemical and X-ray phase analyses, IR spectroscopy. It was ascertained that composition of intermetallic compounds (Ni 3 Ta, Ni 2 Ta) depends on K 2 TaF 7 concentration in the melt, metallic tantalum additions, nickel substrate thickness and experiment duration. The mechanism of currentless deposition of tantalum on nickel was considered and the assumption was made that disproportionation reaction lies in the basis of the process [ru

Effect of Reverse Bias Stress on Leakage Currents and Breakdown Voltages of Solid Tantalum Capacitors

Science.gov (United States)

Teverovsky, Alexander A.

2011-01-01

The majority of solid tantalum capacitors are produced by high-temperature sintering of a fine tantalum powder around a tantalum wire followed by electrolytic anodization that forms a thin amorphous Ta2O5 dielectric layer and pyrolysis of manganese nitrite on the oxide to create a conductive manganese dioxide electrode. A contact to tantalum wire is used as anode terminal and to the manganese layer as a cathode terminal of the device. This process results in formation of an asymmetric Ta -- Ta2O5 -- MnO2 capacitor that has different characteristics at forward (positive bias applied to tantalum) and reverse (positive bias applied to manganese cathode) voltages. Reverse bias currents might be several orders of magnitude larger than forward leakage currents so I-V characteristics of tantalum capacitors resemble characteristics of semiconductor rectifiers. Asymmetric I-V characteristics of Ta -- anodic Ta2O5 systems have been observed at different top electrode materials including metals, electrolytes, conductive polymers, and manganese oxide thus indicating that this phenomenon is likely related to the specifics of the Ta -- Ta2O5 interface. There have been multiple attempts to explain rectifying characteristics of capacitors employing anodic tantalum pentoxide dielectrics. A brief review of works related to reverse bias (RB) behavior of tantalum capacitors shows that the mechanism of conduction in Ta -- Ta2O5 systems is still not clear and more testing and analysis is necessary to understand the processes involved. If tantalum capacitors behave just as rectifiers, then the assessment of the safe reverse bias operating conditions would be a relatively simple task. Unfortunately, these parts can degrade with time under reverse bias significantly, and this further complicates analysis of the I-V characteristics and establishing safe operating areas of the parts. On other hand, time dependence of reverse currents might provide additional information for investigation of

Structural, optical and electrochemical properties of F-doped vanadium oxide transparent semiconducting thin films

Energy Technology Data Exchange (ETDEWEB)

Mousavi, M.; Khorrami, G.H. [University of Bojnord, Department of Physics, Faculty of Basic Science, Bojnord (Iran, Islamic Republic of); Kompany, A. [Ferdowsi University of Mashhad, Department of Physics, Mashhad (Iran, Islamic Republic of); Yazdi, S.T. [Payame Noor University (PNU), Department of Physics, Tehran (Iran, Islamic Republic of)

2017-12-15

In this study, F-doped vanadium oxide thin films with doping levels up to 60 at % were prepared by spray pyrolysis method on glass substrates. To measure the electrochemical properties, some films were deposited on fluorine-tin oxide coated glass substrates. The effect of F-doping on the structural, electrical, optical and electrochemical properties of vanadium oxide samples was investigated. The X-ray diffractographs analysis has shown that all the samples grow in tetragonal β-V{sub 2}O{sub 5} phase structure with the preferred orientation of [200]. The intensity of (200) peak belonging to β-V{sub 2}O{sub 5} phase was strongest in the undoped vanadium oxide film. The scanning electron microscopy images show that the samples have nanorod- and nanobelt-shaped structure. The size of the nanobelts in the F-doped vanadium oxide films is smaller than that in the pure sample and the width of the nanobelts increases from 30 to 70 nm with F concentration. With increasing F-doping level from 10 to 60 at %, the resistivity, the transparency and the optical band gap decrease from 111 to 20 Ω cm, 70 to 50% and 2.4 to 2.36 eV, respectively. The cyclic voltammogram (CV) results show that the undoped sample has the most extensive CV and by increasing F-doping level from 20 to 60 at %, the area of the CV is expanded. The anodic and cathodic peaks in F-doped samples are stronger. (orig.)

The oxidation of carbon monoxide over transition metal doped lanthanum manganates nanoparticles

International Nuclear Information System (INIS)

Fal Desai, M.S.; Salker, A.V.

2012-01-01

Lanthanum manganates perovskites (ABO 3 ) has been widely studied and applied. Many perovskites with A and B sites doped with different metals show good catalytic activity in many oxidation reactions than the individual perovskite. In present study, an attempt has been made to show comparative account of CO oxidation by doping the B site with different cations using sol-gel method

Nitrogen-doped graphene: effect of graphite oxide precursors and nitrogen content on the electrochemical sensing properties.

Science.gov (United States)

Megawati, Monica; Chua, Chun Kiang; Sofer, Zdenek; Klímová, Kateřina; Pumera, Martin

2017-06-21

Graphene, produced via chemical methods, has been widely applied for electrochemical sensing due to its structural and electrochemical properties as well as its ease of production in large quantity. While nitrogen-doped graphenes are widely studied materials, the literature showing an effect of graphene oxide preparation methods on nitrogen quantity and chemical states as well as on defects and, in turn, on electrochemical sensing is non-existent. In this study, the properties of nitrogen-doped graphene materials, prepared via hydrothermal synthesis using graphite oxide produced by various classical methods using permanganate or chlorate oxidants Staudenmaier, Hummers, Hofmann and Brodie oxidation methods, were studied; the resulting nitrogen-doped graphene oxides were labeled as ST-GO, HU-GO, HO-GO and BR-GO, respectively. The electrochemical oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine, nicotinamide adenine nucleotide and DNA free bases, was carried out using cyclic voltammetry and differential pulse voltammetry techniques. The nitrogen content in doped graphene oxides increased in the order ST-GO graphene followed this trend, as shown in the cyclic voltammograms. This is a very important finding that provides insight into the electrocatalytic effect of N-doped graphene. The nitrogen-doped graphene materials exhibited improved sensitivity over bare glassy carbon for ascorbic acid, uric acid and dopamine detection. These studies will enhance our understanding of the effects of graphite oxide precursors on the electrochemical sensing properties of nitrogen-doped graphene materials.

Influence of process parameters on plasma electrolytic surface treatment of tantalum for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Sowa, Maciej, E-mail: maciej.sowa@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Woszczak, Maja; Kazek-Kęsik, Alicja [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland); Dercz, Grzegorz [Institute of Materials Science, University of Silesia, 75 Pułku Piechoty Street 1A, 41-500 Chorzów (Poland); Korotin, Danila M. [M.N. Mikheev Institute of Metal Physics of the Ural Branch of Russian Academy of Sciences, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Zhidkov, Ivan S. [Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Kurmaev, Ernst Z. [M.N. Mikheev Institute of Metal Physics of the Ural Branch of Russian Academy of Sciences, S. Kovalevskoi Street 18, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Cholakh, Seif O. [Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Basiaga, Marcin [Faculty of Biomedical Engineering, Silesian University of Technology, Gen. de Gaulle’a Street 66, 41-800 Zabrze (Poland); Simka, Wojciech, E-mail: wojciech.simka@polsl.pl [Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego Street 6, 44-100 Gliwice (Poland)

2017-06-15

Highlights: • 2-step plasma electrolytic oxidation (PEO) of tantalum was investigated. • PEO coatings surface composition were reflected by the composition of anodizing baths. • Hydrophobic surfaces were obtained from acetate and formate containing baths. • Bioactive phases were identified. - Abstract: This work aims to quantify the effect of anodization voltage and electrolyte composition used during DC plasma electrolytic oxidation (PEO), operated as a 2-step process, on the surface properties of the resulting oxide coatings on tantalum. The first step consisted of galvanostatic anodization (150 mA cm{sup −2}) of the tantalum workpiece up to several limiting voltages (200, 300, 400 and 500 V). After attaining the limiting voltage, the process was switched to voltage control, which resulted in a gradual decrease of the anodic current density. The anodic treatment was realized in a 0.5 M Ca(H{sub 2}PO{sub 2}){sub 2} solution, which was then modified by the addition of 1.15 M Ca(HCOO){sub 2} as well as 1.15 M and 1.5 M Mg(CH{sub 3}COO){sub 2}. The increasing voltage of anodization led to the formation of thicker coatings, with larger pores and enriched with electrolytes species to a higher extent. The solutions containing HCOO{sup −} and CH{sub 3}COO{sup −} ions caused the formation of coatings which were slightly hydrophobic (high contact angle). In the case of the samples anodized up to 500 V, scattered crystalline deposits were observed. Bioactive phases, such as hydroxyapatite, were detected in the treated oxide coatings by XRD and XPS.

Role of aluminum doping on phase transformations in nanoporous titania anodic oxides

Energy Technology Data Exchange (ETDEWEB)

Bayata, Fatma [Istanbul Bilgi University, Department of Mechanical Engineering, 34060, Eyup, Istanbul (Turkey); Ürgen, Mustafa, E-mail: urgen@itu.edu.tr [Istanbul Technical University, Department of Metallurgical and Materials Engineering, 34469, Maslak, Istanbul (Turkey)

2015-10-15

The role of aluminium doping on anatase to rutile phase transformation of nanoporous titanium oxide films were investigated. For this purpose pure and aluminum doped metal films were deposited on alumina substrates by cathodic arc physical deposition. The nanoporous anodic oxides were prepared by porous anodizing of pure and aluminum doped titanium metallic films in an ethylene glycol + NH{sub 4}F based electrolyte. Nanoporous amorphous structures with 60–80 nm diameter and 2–4 μm length were formed on the surfaces of alumina substrates. The amorphous undoped and Al-doped TiO{sub 2} anodic oxides were heat-treated at different temperatures in the range of 280–720 °C for the investigation of their crystallization behavior. The combined effects of nanoporous structure and Al doping on crystallization behavior of titania were investigated using X-ray diffraction (XRD) and micro Raman analysis. The results indicated that both Al ions incorporated into the TiO{sub 2} structure and the nanoporous structure retarded the rutile formation. It was also revealed that presence or absence of metallic film underneath the nanopores has a major contribution to anatase-rutile transformation. - Highlights: • Al-doped TiO{sub 2} nanopores were grown on alumina substrates using anodization method. • The crystallization behavior of nanoporous Al-doped TiO{sub 2} were investigated. • Al doping into nanoporous TiO{sub 2} retarded the anatase-rutile transformation. • Nanostructuring has significant role in controlling rutile formation temperature. • The absence of the metallic film under the nanopores delayed the rutile formation.

Technological challenges in extractive metallurgy and refining of niobium, tantalum and preparation of their alloys

International Nuclear Information System (INIS)

Mirji, K.V.; Sheela; Saibaba, N.

2016-01-01

Manufacturing of refractory and reactive metals, their alloys and fabricated products has been always difficult due to their high affinity with atmospheric gases, stringent specifications and exhaustive quality requirements. In the field of development of these materials, Nuclear Fuel Complex (NFC), Hyderabad has been at the fore front in accepting the challenges for the advancement of technological growth. Extensive developments have been carried out during the last few decades in the field of niobium, tantalum, zirconium etc in the form of pure metal, their compounds and alloys. Over the period of time, efforts have been made for developing sophisticated facilities along with trained man power for manufacturing of critical items for which technical knowhow is not available either with private industries or any other organizations in the country. In the field of reactive metals, though general theory is well established, production is intriguing and requires expert handling on the field. At NFC, efforts were put towards industrial adoptability of the useful knowledge gained from lab scale to reliable production scale. Comprehensive study was conducted to systematically study the effects of various process parameters starting from ore to the metals and their alloys, equipment were modified for ease of operation with stress on recycling/reusing of the waste and handling of effluents. However scale of operation and therefore cost of production has been matter of concern in the field of tantalum and niobium. Electron beam refining is used for production of highly pure reactive and refractory metals like tantalum, niobium, zirconium etc. and their alloys under high vacuum. Special Materials Plant (SMP) at Nuclear Fuel Complex, Hyderabad has developed processes for production of niobium oxide, tantalum oxide, tantalum metal powder, tantalum anodes/capacitors, potassium tantalum fluoride, Nb thermit, Nb metal granules, RRR grade niobium, Nb base alloys such as Zr

Synthesis, Characterization, and Evaluation of Boron-Doped Iron Oxides for the Photocatalytic Degradation of Atrazine under Visible Light

Directory of Open Access Journals (Sweden)

Shan Hu

2012-01-01

Full Text Available Photocatalytic degradation of atrazine by boron-doped iron oxides under visible light irradiation was investigated. In this work, boron-doped goethite and hematite were successfully prepared by sol-gel method with trimethylborate as boron precursor. The powders were characterized by XRD, UV-vis diffuse reflectance spectra, and porosimetry analysis. The results showed that boron doping could influence the crystal structure, enlarge the BET surface area, improve light absorption ability, and narrow their band-gap energy. The photocatalytic activity of B-doped iron oxides was evaluated in the degradation of atrazine under the visible light irradiation, and B-doped iron oxides showed higher atrazine degradation rate than that of pristine iron oxides. Particularly, B-doped goethite exhibited better photocatalytic activity than B-doped hematite.

Hydride Olefin complexes of tantalum and niobium

NARCIS (Netherlands)

Klazinga, Aan Hendrik

1979-01-01

This thesis describes investigations on low-valent tantalum and niobium hydride and alkyl complexes, particularly the dicyclopentadienyl tantalum hydride olefin complexes Cp2Ta(H)L (L=olefin). ... Zie: Summary

Cobalt doped CuMnOx catalysts for the preferential oxidation of carbon monoxide

Science.gov (United States)

Dey, Subhashish; Dhal, Ganesh Chandra; Mohan, Devendra; Prasad, Ram; Gupta, Rajeev Nayan

2018-05-01

Carbon monoxide (CO) is a poisonous gas, recognized as a silent killer for the 21st century. It is produced from the partial oxidation of carbon containing compounds. The catalytic oxidation of CO receives a huge attention due to its applications in different fields. In the present work, hopcalite (CuMnOx) catalysts were synthesized using a co-precipitation method for CO oxidation purposes. Also, it was doped with the cobalt by varying concentration from 1 to 5wt%. It was observed that the addition of cobalt into the CuMnOx catalyst (by the deposition-precipitation method) improved the catalytic performance for the low-temperature CO oxidation. CuMnOx catalyst doped with 3wt% of cobalt exhibited most active performance and showed the highest activity than other cobalt concentrations. Different analytical tools (i.e. XRD, FTIR, BET, XPS and SEM-EDX) were used to characterize the as-synthesized catalysts. It was expected that the introduction of cobalt will introduce new active sites into the CuMnOx catalyst that are associated with the cobalt nano-particles. The order of calcination strategies based on the activity for cobalt doped CuMnOx catalysts was observed as: Reactive calcinations (RC) > flowing air > stagnant air. Therefore, RC (4.5% CO in air) route can be recommended for the synthesis of highly active catalysts. The catalytic activity of doped CuMnOx catalysts toward CO oxidation shows a correlation among average oxidation number of Mn and the position and the nature of the doped cobalt cation.

Human bone ingrowth into a porous tantalum acetabular cup

Directory of Open Access Journals (Sweden)

Gregory N. Haidemenopoulos

2017-11-01

Full Text Available Porous Tantalum is increasingly used as a structural scaffold in orthopaedic applications. Information on the mechanisms of human bone ingrowth into trabecular metal implants is rather limited. In this work we have studied, qualitatively, human bone ingrowth into a retrieved porous tantalum monoblock acetabular cup using optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis. According to the results and taking into account the short operational life (4 years of the implant, bone ingrowth on the acetabular cup took place in the first two-rows of porous tantalum cells to an estimated depth of 1.5 to 2 mm. The bone material, grown inside the first raw of cells, had almost identical composition with the attached bone on the cup surface, as verified by the same Ca:P ratio. Bone ingrowth has been a gradual process starting with Ca deposition on the tantalum struts, followed by bone formation into the tantalum cells, with gradual densification of the bone tissue into hydroxyapatite. A critical step in this process has been the attachment of bone material to the tantalum struts following the topology of the porous tantalum scaffold. These results provide insight to the human bone ingrowth process into porous tantalum implants.

Boron-doped cadmium oxide composite structures and their electrochemical measurements

Energy Technology Data Exchange (ETDEWEB)

Lokhande, B.J., E-mail: bjlokhande@yahoo.com [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Ambare, R.C. [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Mane, R.S. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India); Bharadwaj, S.R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2013-08-01

Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

Methanol electrocatalytic oxidation on Pt nanoparticles on nitrogen doped graphene prepared by the hydrothermal reaction of graphene oxide with urea

International Nuclear Information System (INIS)

Xu, Xiao; Zhou, Yingke; Yuan, Tao; Li, Yawei

2013-01-01

A facile hydrothermal reaction of graphene oxide with urea was used to produce nitrogen doped graphene, and Pt nanoparticles were deposited on the obtained nitrogen doped graphene by the NaBH 4 reduction route. The morphology and microstructure of the synthesized catalysts were characterized by transmission electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy, while the functional groups on the surface of the catalysts were investigated by the Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectra. Cyclic voltammetry, chronoamperometry and electrochemical impedance techniques were carried out to evaluate the methanol electrocatalytic oxidation activity and durability of Pt catalysts supported on the nitrogen doped graphene. The results showed that nitrogen doping and reduction of GO were achieved simultaneously by the facile hydrothermal reaction, which had beneficial effects for the deposition process and electrocatalytic activity of Pt nanoparticles. The Pt catalysts supported on the nitrogen doped graphene substrate presented excellent activity and durability of methanol oxidation reaction, which might be promising for application in direct methanol fuel cells

Preparation of potassium-reduced tantalum powders

International Nuclear Information System (INIS)

Kolosov, V.N.; Miroshnichenko, M.N.; Orlov, V.M.; Prokhorova, T.Yu.

2005-01-01

Characteristics of tantalum powders prepared by reduction of molten potassium heptafluorotantalate with liquid potassium are studied in a temperature range of 750 - 850 deg C using potassium chloride as a flux at a ratio of K 2 TaF 7 : KCl = 1, 2, and 3. The use of potassium as a reducing agent facilitates washing of tantalum powders for impurity salt removal, reduces sodium content and leakage currents in the anodes. As compared to sodium process, the potassium reduction results in a high yield of sponge material, a decrease in the specific surface area and yield of tantalum powder suitable for manufacture of capacitor anodes [ru

A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles: Imaging, Biological, and Physicochemical Performance.

Science.gov (United States)

FitzGerald, Paul F; Butts, Matthew D; Roberts, Jeannette C; Colborn, Robert E; Torres, Andrew S; Lee, Brian D; Yeh, Benjamin M; Bonitatibus, Peter J

2016-12-01

The aim of this study was to produce and evaluate a proposed computed tomography (CT) contrast agent based on carboxybetaine zwitterionic (CZ)-coated soluble tantalum oxide (TaO) nanoparticles (NPs). We chose tantalum to provide superior imaging performance compared with current iodine-based clinical CT contrast agents. We developed the CZ coating to provide biological and physical performance similar to that of current iodinated contrast agents. In addition, the aim of this study was to evaluate the imaging, biological, and physicochemical performance of this proposed contrast agent compared with clinically used iodinated agents. We evaluated CT imaging performance of our CZ-TaO NPs compared with that of an iodinated agent in live rats, imaged centrally located within a tissue-equivalent plastic phantom that simulated a large patient. To evaluate vascular contrast enhancement, we scanned the rats' great vessels at high temporal resolution during and after contrast agent injection. We performed several in vivo CZ-TaO NP studies in healthy rats to evaluate tolerability. These studies included injecting the agent at the anticipated clinical dose (ACD) and at 3 times and 6 times the ACD, followed by longitudinal hematology to assess impact to blood cells and organ function (from 4 hours to 1 week). Kidney histological analysis was performed 48 hours after injection at 3 times the ACD. We measured the elimination half-life of CZ-TaO NPs from blood, and we monitored acute kidney injury biomarkers with a kidney injury assay using urine collected from 4 hours to 1 week. We measured tantalum retention in individual organs and in the whole carcass 48 hours after injection at ACD. Carboxybetaine zwitterionic TaO NPs were synthesized and analyzed in detail. We used multidimensional nuclear magnetic resonance to determine surface functionality of the NPs. We measured NP size and solution properties (osmolality and viscosity) of the agent over a range of tantalum concentrations

Microstructure and mechanical properties of multi-components rare earth oxide-doped molybdenum alloys

International Nuclear Information System (INIS)

Zhang Guojun; Sun Yuanjun; Zuo Chao; Wei Jianfeng; Sun Jun

2008-01-01

Pure molybdenum and molybdenum alloys doped with two- or three-components rare earth oxide particles were prepared by powder metallurgy. Both the tensile property and fracture toughness of the pure molybdenum and multi-components rare earth oxide-doped molybdenum alloys were determined at room temperature. The multi-components rare earth oxide-doped molybdenum alloys are fine grained and contain a homogeneous distribution of fine particles in the submicron and nanometer size ranges, which is why the molybdenum alloys have higher strength and fracture toughness than pure molybdenum. Quantitative analysis is used to explain the increase in yield strength with respect to grain size and second phase strengthening. Furthermore, the relationship between the tensile properties and microstructural parameters is quantitatively established

Synthesis, characterization and photocatalytic activity of porous manganese oxide doped titania for toluene decomposition

International Nuclear Information System (INIS)

Jothiramalingam, R.; Wang, M.K.

2007-01-01

The present study describes the photocatalytic degradation of toluene in gas phase on different porous manganese oxide doped titanium dioxide. As synthesized birnessite and cryptomelane type porous manganese oxide were doped with titania and tested for photocatalytic decomposition of toluene in gas phase. The effects of the inlet concentration of toluene, flow rate (retention time) were examined and the relative humidity was maintained constantly. Thermal and textural characterization of manganese oxide doped titania materials were characterized by X-ray diffraction (XRD), thermogravemetry (TG), BET and TEM-EDAX studies. The aim of the present study is to synthesize the porous manganese oxide doped titania and to study its photocatalytic activity for toluene degradation in gas phase. Cryptomelane doped titania catalyst prepared in water medium [K-OMS-2 (W)] is shown the good toluene degradation with lower catalysts loading compared to commercial bulk titania in annular type photo reactor. The higher photocatalytic activity due to various factors such as catalyst preparation method, experimental conditions, catalyst loading, surface area, etc. In the present study manganese oxide OMS doped titania materials prepared by both aqueous and non-aqueous medium, aqueous medium prepared catalyst shows the good efficiency due to the presence of OH bonded groups on the surface of catalyst. The linear forms of different kinetic equations were applied to the adsorption data and their goodness of fit was evaluated based on the R 2 and standard error. The goodness to the linear fit was observed for Elovich model with high R 2 (≥0.9477) value

Electrokinetic properties of tantalum oxide deposited on model substrate in NaCl and LiCl solutions

International Nuclear Information System (INIS)

Sidorova, M.P.; Bogdanova, N.F.; Ermakova, L.Eh.; Bobrov, P.V.

1997-01-01

Electrokinetic characteristics of tantalum oxide have been studied using a model system - a plane-parallel capillary in chloride solutions containing monocharge (H + , Na + , Li + ) counterions in a wide range of pH and concentrations. It is shown that position of isoelectric point (IEP) of Ta 2 O 5 depends on concentration and type of counterion, moreover, the dependence is not explained in the framework of classical notions of the influence of counterion specific adsorption on IEP position. Electrokinetic potential of Ta 2 O-5 surface at the background of diluted LiCl solutions is higher in its absolute value, than at the background of NaCl solutions according to direct lyotropic series. The results of measurements of the capillary resistance dependence on pH at the background of NaCl and LiCl solutions 10 -3 -10 -1 M are used for the calculation of efficiency and specific surface conductivity factors

Supercapacitors based on nitrogen-doped reduced graphene oxide and borocarbonitrides

Science.gov (United States)

Gopalakrishnan, K.; Moses, Kota; Govindaraj, A.; Rao, C. N. R.

2013-12-01

Nitrogen-doped reduced graphene oxide (RGO) samples with different nitrogen content, prepared by two different methods, as well as nitrogen-doped few-layer graphene have been investigated as supercapacitor electrodes. Two electrode measurements have been carried out both in aqueous (6M KOH) and in ionic liquid media. Nitrogen-doped reduced graphene oxides exhibit satisfactory specific capacitance, the values reaching 126F/g at a scan rate of 10mV/s in aqueous medium. Besides providing supercapacitor characteristics, the study has shown the nitrogen content and surface area to be important factors. High surface-area borocarbonitrides, BxCyNz, prepared by the urea route appear to be excellent supercapacitor electrode materials. Thus, BC4.5N exhibits a specific capacitance of 169F/g at a scan rate of 10mV/s in aqueous medium. In an ionic liquid medium, nitrogen-doped RGO and BC4.5N exhibit specific capacitance values of 258F/g and 240F/g at a scan rate of 5mV/s. The ionic liquid enables a larger operating voltage range of 0.0-2.5V compared to 0.0-1V in aqueous medium.

Decorating Mg/Fe oxide nanotubes with nitrogen-doped carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Cao Yong, E-mail: caoyangel@126.com [Institute of Environment and Municipal Engineering, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450011 (China); Jiao Qingze, E-mail: jiaoqz@bit.edu.cn [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Zhao Yun [School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081 (China); Dong Yingchao [Materials and Surface Science Institute (MSSI), University of Limerick, Limerick (Ireland)

2011-09-22

Graphical abstract: Highlights: > Mg/Fe oxide nanotubes arrayed parallel to each other were prepared by an AAO template method. > The Mg/Fe oxide nanotubes decorated with CN{sub x} were realized by CVD of ethylenediamine on the outer surface of oxide nanotubes. > The magnetic properties of Mg/Fe oxide nanotubes were highly improved after being decorated. - Abstract: Mg/Fe oxide nanotubes decorated with nitrogen-doped carbon nanotubes (CN{sub x}) were fabricated by catalytic chemical vapor deposition of ethylenediamine on the outer surface of oxide nanotubes. Mg/Fe oxide nanotubes were prepared using a 3:1 molar precursor solution of Mg(NO{sub 3}){sub 2} and Fe(NO{sub 3}){sub 3} and anodic aluminum oxide as the substrate. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The XRD pattern shows that the oxide nanotubes are made up of MgO and Fe{sub 2}O{sub 3}. TEM and SEM observations indicate the oxide nanotubes are arrayed roughly parallel to each other, and the outer surface of oxide nanotubes are decorated with CN{sub x}. XPS results show the nitrogen-doped level in CN{sub x} is about 7.3 at.%. Magnetic measurements with VSM demonstrate the saturated magnetization, remanence and coercivity of oxide nanotubes are obvious improved after being decorated with CN{sub x}.

Alkaline earth metal doped tin oxide as a novel oxygen storage material

Energy Technology Data Exchange (ETDEWEB)

Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Yin, Shu; Yoshida, Mizuki; Wu, Xiaoyong; Liu, Bin [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro [Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Miyamae cho-7, Kofu 400-8511 (Japan); Sato, Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan)

2015-09-15

Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.

Fabrication of a tantalum-clad tungsten target for KENS

International Nuclear Information System (INIS)

Kawai, Masayoshi; Kikuchi, Kenji; Kurishita, Hiroaki; Li, J.-F.; Furusaka, Michihiro

2001-01-01

Since the cold neutron source intensity of KENS (the spallation neutron source at High Energy Accelerator Research Organization) was decreased into about a third of the designed value because a cadmium liner at the cold neutron source deformed and obstructed the neutron beam line, the target-moderator-and-reflector assembly (TMRA) has been replaced by a new one aimed at improving the neutron performance and recovering the cold neutron source. The tantalum target has also been replaced by a tantalum-clad tungsten one. In order to bond the tantalum-clad with the tungsten block, a hot isostatic press (HIP) process was applied and optimized. It was found that gaseous interstitial impurity elements severely attacked tantalum and embrittled, and that the getter materials such as zirconium and tantalum were effective to reduce the embrittlement

Oxidation Characteristics and Electrical Properties of Doped Mn-Co Spinel Reaction Layer for Solid Oxide Fuel Cell Metal Interconnects

Directory of Open Access Journals (Sweden)

Pingyi Guo

2018-01-01

Full Text Available To prevent Cr poisoning of the cathode and to retain high conductivity during solid oxide fuel cell (SOFC operation, Cu or La doped Co-Mn coatings on a metallic interconnect is deposited and followed by oxidation at 750 °C. Microstructure and composition of coatings after preparation and oxidation is analyzed by X-ray diffraction (XRD and scanning electron microscopy (SEM. High energy micro arc alloying process, a low cost technique, is used to prepare Cu or La doped Co-Mn coatings with the metallurgical bond. When coatings oxidized at 750 °C in air for 20 h and 100 h, Co3O4 is the main oxide on the surface of Co-38Mn-2La and Co-40Mn coatings, and (Co,Mn3O4 spinel continues to grow with extended oxidation time. The outmost scales of Co-33Mn-17Cu are mainly composed of cubic MnCo2O4 spinel with Mn2O3 after oxidation for 20 h and 100 h. The average thickness of oxide coatings is about 60–70 μm after oxidation for 100 h, except that Co-40Mn oxide coatings are a little thicker. Area-specific resistance of Cu/La doped Co-Mn coatings are lower than that of Co-40Mn coating. (Mn,Co3O4/MnCo2O4 spinel layer is efficient at blocking the outward diffusion of chromium and iron.

Metal Oxides Doped PPY-PVA Blend Thin Films Based Gas Sensor

Directory of Open Access Journals (Sweden)

D. B. DUPARE

2009-02-01

Full Text Available Synthesis of metal oxides doped polypyrrole–polyvinyl alcohol blend thin films by in situ chemical oxidative polymerization, using microwave oven on glass substrate for development of Ammonia and Trimethyl ammine hazardous gas sensor. The all experimental process carried out at room temperature(304 K. These polymer materials were characterized by Chemical analyses, spectral studies (UV-visible and IR and conductivity measurement by four –probe technique. The surface morphology as observed in the SEM image was observed to be uniformly covering the entire substrate surface. The sensor was used for different concentration (ppm of TMA and Ammonia gas investigation at room temperature (304 k. This study found to possess improved electrical, mechanical and environmental stability metal oxides doped PPY-PVA films.

Corrosion of oxide dispersion strengthened iron–chromium steels and tantalum in fluoride salt coolant: An in situ compatibility study for fusion and fusion–fission hybrid reactor concepts

International Nuclear Information System (INIS)

El-Dasher, Bassem; Farmer, Joseph; Ferreira, James; Serrano de Caro, Magdalena; Rubenchik, Alexander; Kimura, Akihiko

2011-01-01

Highlights: ► ODS steel corrosion in molten fluoride salts was studied in situ using electrochemical impedance spectroscopy. ► Steel/coolant interfacial resistance increases from 600 to 800 °C due to an aluminum enriched layer forming at the surface. ► The addition of tungsten to ODS steels increases corrosion resistance measurably at 600 °C. - Abstract: Primary candidate classes of materials for future nuclear power plants, whether they be fission, fusion or hybrids, include oxide dispersion strengthened (ODS) ferritic steels which rely on a dispersion of nano-oxide particles in the matrix for both mechanical strength and swelling resistance, or tantalum alloys which have an inherent neutron-induced swelling resistance and high temperature strength. For high temperature operation, eutectic molten lithium containing fluoride salts are attractive because of their breeding capability as well as their relatively high thermal capacity, which allow for a higher average operating temperature that increases power production. In this paper we test the compatibility of Flinak (LiF–NaF–KF) salts on ODS steels, comparing the performance of current generation ODS steels developed at Kyoto University with the commercial alloy MA956. Pure tantalum was also tested for comparative purposes. In situ data was obtained for temperatures ranging from 600 to 900 °C using a custom-built high temperature electrochemical impedance spectroscopy cell. Results for ODS steels show that steel/coolant interfacial resistance increases from 600 to 800 °C due to an aluminum enriched layer forming at the surface, however an increase in temperature to 900 °C causes this layer to break up and aggressive attack to occur. Performance of current generation ODS steels surpassed that of the MA956 ODS steel, with an in situ impedance behavior similar or better than that of pure tantalum.

Synergistic helium and deuterium blistering in tungsten–tantalum composites

International Nuclear Information System (INIS)

Dias, M.; Mateus, R.; Catarino, N.; Franco, N.; Nunes, D.; Correia, J.B.; Carvalho, P.A.; Hanada, K.; Sârbu, C.

2013-01-01

Abstruct: Tungsten–tantalum composites with 10 and 20 at.% Ta were prepared by ball milling W powder with Ta fibers and by consolidating the milled materials with spark plasma sintering. The composites were implanted at room temperature with He + (30 keV with a fluence 5 × 10 21 at/m 2 ) and/or D + (15 keV with a fluence 5 × 10 21 at/m 2 ) ion beams. The materials were studied by scanning and high-resolution transmission electron microscopy, both coupled with energy dispersive X-ray spectroscopy, and by X-ray diffraction, Rutherford backscattering spectrometry and nuclear reaction analysis. The microstructure observations revealed that the milling operation resulted in severe fragmentation of the Ta fibers. Furthermore, during the consolidation process the Ta phase acted as oxygen getter and reduced the W oxide present in the original material. The surface of the tungsten–tantalum composites implanted with D + remained essentially unaltered, while the materials implanted with He + evidenced blisters on the Ta-rich regions. D retention in the composites increased with He + pre-implantation

Synthesis and characterization of nickel oxide doped barium strontium titanate ceramics

Energy Technology Data Exchange (ETDEWEB)

Banerjee, M. [Dept. of Electrical Engineering, Bengal Institute of Technology Kolkata (India); Mukherjee, S. [Dept. of Metallurgical Engineering, Jadavpur University, Kolkata (India); Maitra, S. [Govt. College of Engg. and Ceramic Technology, Kolkata (India)

2012-01-15

Barium strontium titanate (BST) ceramics (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} were synthesized by solid state sintering using barium carbonate, strontium carbonate and rutile as the precursor materials. The samples were doped with nickel oxide in different proportions. Different phases present in the sintered samples were determined from X-ray diffraction investigation and the distribution of different phases in the microstructure was assessed from scanning electron microscopy study. It was observed that the dielectric properties of BST were modified significantly with nickel oxide doping. These ceramics held promise for applications in tuned circuits. (author)

21 CFR 886.3100 - Ophthalmic tantalum clip.

Science.gov (United States)

2010-04-01

... blood vessels in the eye. (b) Classification. Class II (special controls). The device is exempt from the...) MEDICAL DEVICES OPHTHALMIC DEVICES Prosthetic Devices § 886.3100 Ophthalmic tantalum clip. (a) Identification. An ophthalmic tantalum clip is a malleable metallic device intended to be implanted permanently...

Sonochemically synthesized iron-doped zinc oxide nanoparticles: Influence of precursor composition on characteristics

International Nuclear Information System (INIS)

Roy, Anirban; Maitra, Saikat; Ghosh, Sobhan; Chakrabarti, Sampa

2016-01-01

Highlights: • Sonochemical synthesis of iron-doped zinc oxide nanoparticles. • Green synthesis without alkali at room temperature. • Characterization by UV–vis spectroscopy, FESEM, XRD and EDX. • Influence of precursor composition on characteristics. • Composition and characteristics are correlated. - Abstract: Iron-doped zinc oxide nanoparticles have been synthesized sonochemically from aqueous acetyl acetonate precursors of different proportions. Synthesized nanoparticles were characterized with UV–vis spectroscopy, X-ray diffraction and microscopy. Influences of precursor mixture on the characteristics have been examined and modeled. Linear correlations have been proposed between dopant dosing, extent of doping and band gap energy. Experimental data corroborated with the proposed models.

Electrical properties of tin-doped zinc oxide nanostructures doped at different dopant concentrations

International Nuclear Information System (INIS)

Nasir, M. F.; Zainol, M. N.; Hannas, M.; Mamat, M. H.; Rusop, Mohamad; Rahman, S. A.

2016-01-01

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 °C. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 10"3 Ωcm"−"1. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.

Electrical properties of tin-doped zinc oxide nanostructures doped at different dopant concentrations

Energy Technology Data Exchange (ETDEWEB)

Nasir, M. F., E-mail: babaibaik2002@yahoo.com; Zainol, M. N., E-mail: nizarzainol@yahoo.com; Hannas, M., E-mail: mhannas@gmail.com [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my; Rusop, Mohamad, E-mail: rusop@salam.uitm.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Rahman, S. A., E-mail: saadah@um.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Low Dimensional Materials Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2016-07-06

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 °C. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 10{sup 3} Ωcm{sup −1}. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.

Electrical Properties of Electrospun Sb-Doped Tin Oxide Nanofibers

International Nuclear Information System (INIS)

Leon-Brito, Neliza; Melendez, Anamaris; Ramos, Idalia; Pinto, Nicholas J; Santiago-Aviles, Jorge J

2007-01-01

Transparent and conducting tin oxide fibers are of considerable interest for solar energy conversion, sensors and in various electrode applications. Appropriate doping can further enhance the conductivity of the fibers without loosing optical transparency. Undoped and antimony-doped tin oxide fibers have been synthesized by our group in previous work using electrospinning and metallorganic decomposition techniques. The undoped tin oxide fibers were obtained using a mixture of pure tin oxide sol made from tin (IV) chloride : water : propanol : isopropanol at a molar ratio of 1:9:9:6, and a viscous solution made from poly(ethylene oxide) (PEO) and chloroform at a ratio of 200 mg PEO/10 mL chloroform. In this work, antimony doped fibers were obtained by adding a dopant solution of antimony trichloride and isopropanol at a ratio of 2.2812 g antimony trichloride/10 ml isopropanol to the original tin oxide precursor solution. The Sb concentration in the precursor solution is 1.5%. After deposition, the fibers were sintered 600deg. C in air for two hours. The electrical conductivity of single fibers measured at room temperature increases by up to three orders of magnitude when compared to undoped fibers prepared using the same method. The resistivity change as a function of the annealing temperature can be attributed to the thermally activated formation of a nearly stoichoimetric solid. The resistivity of the fibers changes monotonically with temperature from 714Ω-cm at 2 K to 0.1Ω-cm at 300 K. In the temperature range from 2 to 8 K the fibers have a positive magnetoresistance (MR) with the highest value of 155 % at 2 K and ±9 T. At temperatures of 10 and 12 K the sign of MR changes to negative values for low magnetic fields and positive for high magnetic fields. For higher temperatures (15 K and above) the MR becomes negative and its magnitude decreases with temperature

Microwave synthesis of nanostructured oxide sorbents doped with lanthanides

Energy Technology Data Exchange (ETDEWEB)

Mitrofanov, Andrey A., E-mail: mitrofanov-a@icloud.com; Silyavka, Elena S.; Shilovskikh, Vladimir V.; Kolonitckii, Petr D.; Sukhodolov, Nikolai G.; Selyutin, Artem A., E-mail: selutin@inbox.ru [Saint Petersburg State University, 7/9, Universitetskaya nab., St. Petersburg, 199034 (Russian Federation)

2016-06-17

A number of nanostructured mesoporous oxide systems based on aluminum oxide, doped with lanthanide ions have been obtained in this study. Structure and morphology of oxides obtained have been examined by X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy. The surface area of the samples was determined by the BET method. The dependence of the adsorption of insulin on synthesized oxides from the concentration was investigated. The containing of insulin in solutions after adsorption was determined by the Bradford method. The isotherms of adsorption of insulin on resulting oxide sorbents were plotted, the dependence capacity of the sorption of insulin from the lanthanide dopant was determined.

Optoelectronic Characterization of Ta-Doped ZnO Thin Films by Pulsed Laser Deposition.

Science.gov (United States)

Koo, Horng-Show; Peng, Jo-Chi; Chen, Mi; Chin, Hung-I; Chen, Jaw-Yeh; Wu, Maw-Kuen

2015-11-01

Transparent conductive oxide of Ta-doped ZnO (TZO) film with doping amount of 3.0 wt% have been deposited on glass substrates (Corning Eagle XG) at substrate temperatures of 100 to 500 degrees C by the pulsed laser deposition (PLD) technique. The effect of substrate temperature on the structural, optical and electronic characteristics of Ta-doped ZnO (TZO) films with 3.0 wt% dopant of tantalum oxide (Ta2O5) was measured and demonstrated in terms of X-ray diffraction (XRD), ultraviolet-visible spectrometer (UV-Vis), four-probe and Hall-effect measurements. X-ray diffraction pattern shows that TZO films grow in hexagonal crystal structure of wurtzite phase with a preferred orientation of the crystallites along (002) direction and exhibits better physical characteristics of optical transmittance, electrical conductivity, carrier concentration and mobility for the application of window layer in the optoelectronic devices of solar cells, OLEDs and LEDs. The lowest electrical resistivity (ρ) and the highest carrier concentration of the as-deposited film deposited at 300 degrees C are measured as 2.6 x 10(-3) Ω-cm and 3.87 x 10(-20) cm(-3), respectively. The highest optical transmittance of the as-deposited film deposited at 500 degrees C is shown to be 93%, compared with another films deposited below 300 degrees C. It is found that electrical and optical properties of the as-deposited TZO film are greatly dependent on substrate temperature during laser ablation deposition.

Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

Energy Technology Data Exchange (ETDEWEB)

Stone, D. S.; Bischof, M.; Aouadi, S. M., E-mail: samir.aouadi@unt.edu [Department of Material Science and Engineering, University of North Texas, Denton, Texas 76207 (United States); Gao, H.; Martini, A. [School of Engineering, University of California Merced, Merced, California 95343 (United States); Chantharangsi, C.; Paksunchai, C. [Department of Physics, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand)

2014-11-10

Silver tantalate (AgTaO{sub 3}) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application.

Reconstruction mechanisms of tantalum oxide coatings with low concentrations of silver for high temperature tribological applications

International Nuclear Information System (INIS)

Stone, D. S.; Bischof, M.; Aouadi, S. M.; Gao, H.; Martini, A.; Chantharangsi, C.; Paksunchai, C.

2014-01-01

Silver tantalate (AgTaO 3 ) coatings have been found to exhibit outstanding tribological properties at elevated temperatures. To understand the mechanisms involved in the tribological behavior of the Ag-Ta-O system, tantalum oxide coatings with a small content of silver were produced to investigate the metastable nature of this self-lubricating material. The coatings were produced by unbalanced magnetron sputtering, ball-on-disk wear tested at 750 °C, and subsequently characterized by X-ray diffraction, Scanning Auger Nanoprobe, cross-sectional Scanning Electron Microscopy, and Transmission Electron Microscopy. Complementary molecular dynamic simulations were carried out to investigate changes in the chemical and structural properties at the interface due to sliding for films with varying silver content. Both the experimental characterization and the theoretical modeling showed that silver content affects friction and wear, through the role of silver in film reconstruction during sliding. The results suggest that the relative amount of silver may be used to tune film performance for a given application

Valence electronic structure of tantalum carbide and nitride

Institute of Scientific and Technical Information of China (English)

FAN; ChangZeng

2007-01-01

The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.……

Valence electronic structure of tantalum carbide and nitride

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

@@ The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.

Efficacy of Tantalum Tungsten Alloys for Diffusion Barrier Applications

Science.gov (United States)

Smathers, D. B.; Aimone, P. R.

2017-12-01

Traditionally either Niobium, Tantalum or a combination of both have been used as diffusion barriers in Nb3Sn Multi-filament wire. Vanadium has also been used successfully but the ultimate RRR of the copper is limited unless an external shell of Niobium is included. Niobium is preferred over Tantalum when alternating current losses are not an issue as the Niobium will react to form Nb3Sn. Pure Tantalum tends to deform irregularly requiring extra starting thickness to ensure good barrier qualities. Our evaluations showed Tantalum lightly alloyed with 3 wt% Tungsten is compatible with the wire drawing process while deforming as well as or better than pure Niobium. Ta3wt%W has been processed as a single barrier and as a distributed barrier to fine dimensions. In addition, the higher modulus and strength of the Tantalum Tungsten alloy improves the overall tensile properties of the wire.

Uptake and retention of insufflated tantalum by lymph nodes

International Nuclear Information System (INIS)

Kilpper, R.W.; Bianco, A.; Gibb, F.R.; Landman, S.; Morrow, P.E.

1976-01-01

A nonsacrifice, radiographic technique is presented for evaluating the lymph node uptake of radiographically dense materials from the lungs of beagle dogs into which the material was insufflated. With tantalum as the contrast agent, lymph nodes sometimes become visible within 2 days after exposure when the insufflation resulted in radiographic ''alveolarization'' of some of the tantalum. Localization of the material within the nodes was observed in subsequent radiographs as well as persistent retention after as much as 1 year. Through the use of preinsufflation control films and tantalum foils of varying thickness, densitometric methods for determining the amount of tantalum within the lymph nodes are being investigated. Tantalum-182 is being used to follow the lung retention of the material as well as to verify estimates of burdens in harvested nodes. Preliminary lymphokinetic data are presented from experiments utilizing powders of 1 and 5 μm (mean) particle sizes

Extraction of Tantalum from locally sourced Tantalite using ...

African Journals Online (AJOL)

acer

Extraction of Tantalum from locally sourced Tantalite using ... ABSTRACT: The ability of polyethylene glycol solution to extract tantalum from locally .... metal ion in question by the particular extractant. ... Loparite, a rare-earth ore (Ce, Na,.

Effects of donor doping and acceptor doping on rutile TiO2 particles for photocatalytic O2 evolution by water oxidation

Science.gov (United States)

Amano, Fumiaki; Tosaki, Ryosuke; Sato, Kyosuke; Higuchi, Yamato

2018-02-01

Crystalline defects of photocatalyst particles may be considered to be the recombination center of photoexcited electrons and holes. In this study, we investigated the photocatalytic activity of cation-doped rutile TiO2 photocatalysts for O2 evolution from an aqueous silver nitrate solution under ultraviolet light irradiation. The photocatalytic activity of rutile TiO2 was enhanced by donor doping of Ta5+ and Nb5+ with a valence higher than that of Ti4+, regardless of increased density of electrons and Ti3+ species (an electron trapped in Ti4+ sites). Conversely, acceptor doping of lower valence cations such as In3+ and Ga3+ decreased photocatalytic activity for O2 evolution by water oxidation. The doping of equal valence cations such as Sn4+ and Ge4+ hardly changed the activity of non-doped TiO2. This study demonstrates that Ti3+ species, which is a crystalline defect, enhanced the photocatalytic activity of semiconductor oxides, for example rutile TiO2 with large crystalline size.

Modeling the mechanical behavior of tantalum

International Nuclear Information System (INIS)

Lee, B.J.; Ahzi, S.

1997-01-01

A crystal plasticity model is proposed to simulate the large plastic deformation and texture evolution in tantalum over a wide range of strain rates. In the model, a modification of the viscoplastic power law for slip and a Taylor interaction law for polycrystals are employed, which account for the effects of strain hardening, strain-rate hardening, and thermal softening. A series of uniaxial compression tests in tantalum at strain rates ranging from 10 -3 to 10 4 s -1 were conducted and used to verify the model's simulated stress-strain response. Initial and evolved deformation textures were also measured for comparison with predicted textures from the model. Applications of this crystal plasticity model are made to examine the effect of different initial crystallographic textures in tantalum subjected to uniaxial compression deformation or biaxial tensile deformation

Reaction of tantalum-alkyne complexes with isocyanates or acyl cyanides

International Nuclear Information System (INIS)

Kataoka, Yasutaka; Oguchi, Yoshiyuki; Yoshizumi, Kazuyuki; Miwatashi, Seiji; Takai, Kazuhiko; Utimoto, Kiitiro

1992-01-01

Treatment of alkynes with low-valent tantalum derived from TiCl 5 and zinc produces tantalum-alkyne complexes (not isolated), which react in situ with phenyl isocyanate (or butyl isocyanate) to give (E)-α, β-unsaturated amides stereoselectively. The tantalum-alkyne complexes also react with acyl cyanides in the presence of BF 3 ·OEt 2 to give α-cyanohydrins. In both reactions, filtration of the reaction mixture containing the tantalum-alkyne complexes before addition of isocyanates (or acyl cyanides) is indispensable to obtain good yields. (author)

The effect of Bi3+ and Li+ co-doping on the luminescence characteristics of Eu3+-doped aluminum oxide films

International Nuclear Information System (INIS)

Padilla-Rosales, I.; Martinez-Martinez, R.; Cabañas, G.; Falcony, C.

2015-01-01

The incorporation of Bi 3+ and Li + as co-dopants in Eu 3+ -doped aluminum oxide films deposited by the ultrasonic spray pyrolysis technique and its effect on the luminescence characteristics of this material are described. Both Bi 3+ and Li + do not introduce new luminescence features but affect the luminescence intensity of the Eu 3+ related emission spectra as well as the excitation spectra. The introduction of Bi 3+ generates localized states in the aluminum oxide host that result in a quenching of the luminescence intensity, while Li + and Bi 3+ co-doping increase the luminescence intensity of these films. - Highlights: • Li and Bi co-doping increase the luminescence. • Bi creates localized states in the Al 2 O 3 host. • Li was incorporated as a co-activator

Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation

Energy Technology Data Exchange (ETDEWEB)

Al-Hamdi, Abdullah M.; Sillanpää, Mika [Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli (Finland); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 17, 123 Al-Khoudh (Oman)

2015-01-05

Highlights: • A sol–gel method used to synthesize tin oxide nanoparticles. • Nanoparticles of tin oxide doped with different iodine concentrations. • Degradation studies carried up with UV–vis, TOC, HPLC and GC instruments. • 1% iodine doped tin dioxide showed maximum photodegradation efficiency. - Abstract: Iodine doped tin oxide (SnO{sub 2}:I) nanoparticles were prepared by sol–gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO{sub 2}:I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO{sub 2} nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO{sub 2} nanoparticles under similar illumination conditions.

Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation

International Nuclear Information System (INIS)

Al-Hamdi, Abdullah M.; Sillanpää, Mika; Dutta, Joydeep

2015-01-01

Highlights: • A sol–gel method used to synthesize tin oxide nanoparticles. • Nanoparticles of tin oxide doped with different iodine concentrations. • Degradation studies carried up with UV–vis, TOC, HPLC and GC instruments. • 1% iodine doped tin dioxide showed maximum photodegradation efficiency. - Abstract: Iodine doped tin oxide (SnO 2 :I) nanoparticles were prepared by sol–gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO 2 :I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO 2 nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO 2 nanoparticles under similar illumination conditions

Spectroscopic and luminescent properties of Co2+ doped tin oxide thin films by spray pyrolysis

Directory of Open Access Journals (Sweden)

K. Durga Venkata Prasad

2016-07-01

Full Text Available The wide variety of electronic and chemical properties of metal oxides makes them exciting materials for basic research and for technological applications alike. Oxides span a wide range of electrical properties from wide band-gap insulators to metallic and superconducting. Tin oxide belongs to a class of materials called Transparent Conducting Oxides (TCO which constitutes an important component for optoelectronic applications. Co2+ doped tin oxide thin films were prepared by chemical spray pyrolysis synthesis and characterized by powder X-ray diffraction, SEM, TEM, FT-IR, optical, EPR and PL techniques to collect the information about the crystal structure, coordination/local site symmetry of doped Co2+ ions in the host lattice and the luminescent properties of the prepared sample. Powder XRD data revealed that the crystal structure belongs to tetragonal rutile phase and its lattice cell parameters are evaluated. The average crystallite size was estimated to be 26 nm. The morphology of prepared sample was analyzed by using SEM and TEM studies. Functional groups of the prepared sample were observed in the FT-IR spectrum. Optical absorption and EPR studies have shown that on doping, Co2+ ions enter in the host lattice as octahedral site symmetry. PL studies of Co2+ doped SnO2 thin films exhibit blue and yellow emission bands. CIE chromaticity coordinates were also calculated from emission spectrum of Co2+ doped SnO2 thin films.

Trap state passivation improved hot-carrier instability by zirconium-doping in hafnium oxide in a nanoscale n-metal-oxide semiconductor-field effect transistors with high-k/metal gate

International Nuclear Information System (INIS)

Liu, Hsi-Wen; Tsai, Jyun-Yu; Liu, Kuan-Ju; Lu, Ying-Hsin; Chang, Ting-Chang; Chen, Ching-En; Tseng, Tseung-Yuen; Lin, Chien-Yu; Cheng, Osbert; Huang, Cheng-Tung; Ye, Yi-Han

2016-01-01

This work investigates the effect on hot carrier degradation (HCD) of doping zirconium into the hafnium oxide high-k layer in the nanoscale high-k/metal gate n-channel metal-oxide-semiconductor field-effect-transistors. Previous n-metal-oxide semiconductor-field effect transistor studies demonstrated that zirconium-doped hafnium oxide reduces charge trapping and improves positive bias temperature instability. In this work, a clear reduction in HCD is observed with zirconium-doped hafnium oxide because channel hot electron (CHE) trapping in pre-existing high-k bulk defects is the main degradation mechanism. However, this reduced HCD became ineffective at ultra-low temperature, since CHE traps in the deeper bulk defects at ultra-low temperature, while zirconium-doping only passivates shallow bulk defects.

First-principles study of doping effect on the phase transition of zinc oxide with transition metal doped

International Nuclear Information System (INIS)

Wu, Liang; Hou, Tingjun; Wang, Yi; Zhao, Yanfei; Guo, Zhenyu; Li, Youyong; Lee, Shuit-Tong

2012-01-01

Highlights: ► We study the doping effect on B4, B1 structures and phase transition of ZnO. ► We calculate the phase transition barrier and phase transition path of doped ZnO. ► The transition metal doping decreases the bulk modulus and phase transition pressure. ► The magnetic properties are influenced by the phase transition process. - Abstract: Zinc oxide (ZnO) is a promising material for its wide application in solid-state devices. With the pressure raised from an ambient condition, ZnO transforms from fourfold wurtzite (B4) to sixfold coordinated rocksalt (B1) structure. Doping is an efficient approach to improve the structures and properties of materials. Here we use density-functional theory (DFT) to study doped ZnO and find that the transition pressure from B4 phase to B1 phase of ZnO always decreases with different types of transition metal (V, Cr, Mn, Fe, Co, or Ni) doped, but the phase transition path is not affected by doping. This is consistent with the available experimental results for Mn-doped ZnO and Co-doped ZnO. Doping in ZnO causes the lattice distortion, which leads to the decrease of the bulk modulus and accelerates the phase transition. Mn-doped ZnO shows the strongest magnetic moment due to its half filled d orbital. For V-doped ZnO and Cr-doped ZnO, the magnetism is enhanced by phase transition from B4 to B1. But for Mn-doped ZnO, Fe-doped ZnO, Co-doped ZnO, and Ni-doped ZnO, B1 phase shows weaker magnetic moment than B4 phase. These results can be explained by the amount of charge transferred from the doped atom to O atom. Our results provide a theoretical basis for the doping approach to change the structures and properties of ZnO.

Radioluminescence of rare-earth doped aluminum oxide

Energy Technology Data Exchange (ETDEWEB)

Santiago, M.; Molina, P. [Universidad Nacional del Centro de la Provincia de Buenos Aires, Instituto de Fisica Arroyo Seco, Pinto 399, 7000 Tandil (Argentina); Barros, V. S.; Khoury, H. J.; Elihimas, D. R., E-mail: msantiag@exa.unicen.edu.ar [Universidade Federal de Pernambuco, Departamento de Energia Nuclear, Av. Prof. Luiz Freire 1000, Recife, PE 50740-540 (Brazil)

2011-10-15

Carbon-doped aluminum oxide (Al{sub 2}O{sub 3}:C) is one of the most used radioluminescence (Rl) materials for fiberoptic dosimetry due to its high efficiency and commercial availability. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, the radioluminescence response of rare-earth doped Al{sub 2}O{sub 3} samples has been evaluated. The samples were prepared by mixing stoichiometric amounts of aluminum nitrate, urea and dopants with different amounts of terbium, samarium, cerium and thulium nitrates varying from 0 to 0.15 mo 1%. The influence of the different activators on the Rl spectra has been investigated in order to determine the feasibility of using these compounds for Rl fiberoptic dosimetry. (Author)

Radioluminescence of rare-earth doped aluminum oxide

International Nuclear Information System (INIS)

Santiago, M.; Molina, P.; Barros, V. S.; Khoury, H. J.; Elihimas, D. R.

2011-10-01

Carbon-doped aluminum oxide (Al 2 O 3 :C) is one of the most used radioluminescence (Rl) materials for fiberoptic dosimetry due to its high efficiency and commercial availability. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, the radioluminescence response of rare-earth doped Al 2 O 3 samples has been evaluated. The samples were prepared by mixing stoichiometric amounts of aluminum nitrate, urea and dopants with different amounts of terbium, samarium, cerium and thulium nitrates varying from 0 to 0.15 mo 1%. The influence of the different activators on the Rl spectra has been investigated in order to determine the feasibility of using these compounds for Rl fiberoptic dosimetry. (Author)

Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal–support interactions

International Nuclear Information System (INIS)

Durgasri, D. Naga; Vinodkumar, T.; Lin, Fangjian; Alxneit, Ivo; Reddy, Benjaram M.

2014-01-01

Graphical abstract: - Highlights: • Supported Ce-Gd-oxides are applied for soot oxidation for the first time. • Gd 2 O 3 doping facilitates enhanced extrinsic oxygen vacancy concentration in ceria. • The Ce-Gd/TiO 2 exhibited the highest soot oxidation activity. • Key parameters that involved in tuning the activity are discussed. - Abstract: The aim of the present investigation was to ascertain the role of Al 2 O 3 , SiO 2 , and TiO 2 supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al 2 O 3 , Ce-Gd/SiO 2 , and Ce-Gd/TiO 2 catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H 2 -TPR, and UV–vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F 2g mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV–vis DRS measurements. The H 2 -TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO 2 catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support

Phenomenological effets of tantalum incorporation into diamond films: Experimental and first principle studies

Energy Technology Data Exchange (ETDEWEB)

Ullah, Mahtab, E-mail: mahtabullah@bzu.edu.pk [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Rana, Anwar Manzoor; Ahmad, E. [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Raza, Rizwan [Department of Physics, COMSATS Institute of Information Technology, Lahore-54000 (Pakistan); Hussain, Fayyaz [Department of Physics, Bahauddin Zakariya University Multan (Pakistan); Hussain, Akhtar; Iqbal, Muhammad [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

2016-09-01

Graphical abstract: - Highlights: • Fabrication of tantalum incorporated diamonds films using HFCVD technique. • Decrease in resistivity by increasing tantalum content in diamond thin films. • Electronic structure calculations of tantalum incorporated diamonds films through VASP code. • A rise of bond length and bond angles by addition of tantalum in the diamond lattice. • Confirmation of decrease of resistivity by adding tantalum due to creation of impurity states in the bandgap. - Abstract: Tantalum (Ta) incorporated diamond films are synthesized on silicon substrate by chemical vapor deposition under gas mixture of CH{sub 4} + H{sub 2}. Characterizations of the resulting films indicate that morphology and resistivity of as-grown diamond films are significantly influenced by the process parameters and the amount of tantalum incorporated in the diamond films. XRD plots reveal that diamond films are composed of TaC along with diamond for higher concentration of tantalum and Ta{sub 2}C phases for lower concentration of tantalum. EDS spectra confirms the existence of tantalum in the diamond films. Resistivity measurements illustrate a sudden fall of about two orders of magnitude by the addition of tantalum in the diamond films. Band structure of Ta-incorporated diamond has been investigated based on density functional theory (DFT) using VASP code. Band structure calculations lead to the semiconducting behavior of Ta-incorporated diamond films because of the creation of defects states inside the band gap extending towards conduction band minimum. Present DFT results support experimental trend of resistivity that with the incorporation of tantalum into diamond lattice causes a decrease in the resistivity of diamond films so that tantalum-incorporated diamond films behave like a good semiconductor.

Synergistic helium and deuterium blistering in tungsten–tantalum composites

Energy Technology Data Exchange (ETDEWEB)

Dias, M., E-mail: marta.dias@itn.pt [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Mateus, R.; Catarino, N.; Franco, N. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Nunes, D. [CENIMAT-I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Correia, J.B. [LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); Carvalho, P.A. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); ICEMS, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Hanada, K. [AIST, National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba, 305-8564 Ibaraki (Japan); Sârbu, C. [National Institute of Materials and Physics, 105bis Atomistilor street, 077125 Magurele-Ilfov (Romania); and others

2013-11-15

Abstruct: Tungsten–tantalum composites with 10 and 20 at.% Ta were prepared by ball milling W powder with Ta fibers and by consolidating the milled materials with spark plasma sintering. The composites were implanted at room temperature with He{sup +} (30 keV with a fluence 5 × 10{sup 21} at/m{sup 2}) and/or D{sup +} (15 keV with a fluence 5 × 10{sup 21} at/m{sup 2}) ion beams. The materials were studied by scanning and high-resolution transmission electron microscopy, both coupled with energy dispersive X-ray spectroscopy, and by X-ray diffraction, Rutherford backscattering spectrometry and nuclear reaction analysis. The microstructure observations revealed that the milling operation resulted in severe fragmentation of the Ta fibers. Furthermore, during the consolidation process the Ta phase acted as oxygen getter and reduced the W oxide present in the original material. The surface of the tungsten–tantalum composites implanted with D{sup +} remained essentially unaltered, while the materials implanted with He{sup +} evidenced blisters on the Ta-rich regions. D retention in the composites increased with He{sup +} pre-implantation.

Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study

International Nuclear Information System (INIS)

Nilius, Niklas

2015-01-01

Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce.In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O 2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are

Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study

Science.gov (United States)

Nilius, Niklas

2015-08-01

Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce. In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are

A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

Directory of Open Access Journals (Sweden)

Daniela Lehr

2015-11-01

Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.

The effect of material composition of 3-dimensional graphene oxide and self-doped polyaniline nanocomposites on DNA analytical sensitivity.

Science.gov (United States)

Yang, Tao; Chen, Huaiyin; Yang, Ruirui; Wang, Xinxing; Nan, Fuxin; Jiao, Kui

2015-09-01

Until now, morphology effects of 2-dimensional or 3-dimensional graphene nanocomposites and the effect of material composition on the biosensors have been rarely reported. In this paper, the various nanocomposites based on graphene oxide and self-doped polyaniline nanofibres for studying the effect of morphology and material composition on DNA sensitivity were directly reported. The isolation and dispersion of graphene oxide were realized via intercalated self-doped polyaniline and ultrasonication, where the ultrasonication prompts the aggregates of graphite oxide to break up and self-doped polyaniline to diffuse into the stacked graphene oxide. Significant electrochemical enhancement has been observed due to the existence of self-doped polyaniline, which bridges the defects for electron transfer and, in the mean time, increases the basal spacing between graphene oxide sheets. Different morphologies can result in different ssDNA surface density, which can further influence the hybridization efficiency. Compared with 2-dimensional graphene oxide, self-doped polyaniline and other morphologies of nanocomposites, 3-dimensional graphene oxide-self-doped polyaniline nanowalls exhibited the highest surface density and hybridization efficiency. Furthermore, the fabricated biosensors presented the broad detection range with the low detection limit due to the specific surface area, a large number of electroactive species, and open accessible space supported by nanowalls. Copyright © 2015 Elsevier B.V. All rights reserved.

Tantalum strength model incorporating temperature, strain rate and pressure

Science.gov (United States)

Lim, Hojun; Battaile, Corbett; Brown, Justin; Lane, Matt

Tantalum is a body-centered-cubic (BCC) refractory metal that is widely used in many applications in high temperature, strain rate and pressure environments. In this work, we propose a physically-based strength model for tantalum that incorporates effects of temperature, strain rate and pressure. A constitutive model for single crystal tantalum is developed based on dislocation kink-pair theory, and calibrated to measurements on single crystal specimens. The model is then used to predict deformations of single- and polycrystalline tantalum. In addition, the proposed strength model is implemented into Sandia's ALEGRA solid dynamics code to predict plastic deformations of tantalum in engineering-scale applications at extreme conditions, e.g. Taylor impact tests and Z machine's high pressure ramp compression tests, and the results are compared with available experimental data. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Effective improvement of interface modified strontium titanate based solid oxide fuel cell anodes by infiltration with nano-sized palladium and gadolinium-doped cerium oxide

DEFF Research Database (Denmark)

Abdul Jabbar, Mohammed Hussain; Høgh, Jens Valdemar Thorvald; Zhang, Wei

2013-01-01

The development of low temperature solid oxide fuel cell (SOFC) anodes by infiltration of Pd/Gd-doped cerium oxide (CGO) electrocatalysts in Nb-doped SrTiO3 (STN) backbones has been investigated. Modification of the electrode/electrolyte interface by thin layer of spin-coated CGO (400-500 nm) con...

The global tantalum industry and Sons of Gwalia Ltd

International Nuclear Information System (INIS)

Paull, D.

2002-01-01

Sons of Gwalia Ltd., in Perth Australia is a long-term supplier of tantalum (Ta), a valuable rare metal with adequate supply. Tantalum is soft and ductile with high melting and boiling points and a low co-efficient of thermal expansion. It has excellent capacity to store and release electrical charge and offers exceptional resistance to corrosion. Its' main use is in consumer electronics such as mobile phones, laptop computers, DVD players, personal video recorders and MP-3 players. For automotive electronics, tantalum is used for air-bags, audio systems, navigation systems, anti-lock break systems and under the hood vehicle management systems. The super alloy is also in demand by the aerospace industry and for turbine blades for power stations. The total demand of Tantalum in 2000 was 5 million lbs. Demand growth has increased steadily since 1993 with perhaps a slight increase in the past 5 years. Resources are estimated at a 125 year supply based on year 2000 production rates. 41 per cent of the world supply of tantalum is obtained from Australia, 13 per cent from Africa, 16 per cent from America, 22 per cent from Asia. The Greenbushes mine in Australia is the world's largest tantalum mine with 80 million lbs Ta, followed by Australia's Wodgina Mine with 50 million lbs Ta. Both mines are expected to be operational for the next 25 years. 12 figs

CO_2 capture in Mg oxides doped with Fe and Ni

International Nuclear Information System (INIS)

Sanchez S, I. F.

2016-01-01

In this work the CO_2 capture-desorption characteristics in Mg oxides doped with Fe and Ni obtained by the direct oxidation of Mg-Ni and Mg-Fe mixtures are presented. Mixtures of Mg-Ni and Mg-Fe in a different composition were obtained by mechanical milling in a Spex-type mill in a controlled atmosphere of ultra high purity argon at a weight / weight ratio of 4:1 powder using methanol as a lubricating agent, for 20 h. The powders obtained by mechanical milling showed as main phase, the Mg with nanocrystalline structure. Subsequently, the mixtures of Mg-Ni and Mg-Fe were oxidized within a muffle for 10 min at 600 degrees Celsius. By means of X-ray diffraction analysis, the Mg O with nano metric grain size was identified as the main phase, which was determined by the Scherrer equation. In the Mg O doped with Ni, was identified that as the Ni amount 1 to 5% by weight dispersed in the Mg O matrix was increased, the main peak intensity of the Ni phase increased, whereas in the Mg O doped with Fe was observed by XRD, that the Fe_2O_3 phase was present and by increasing the amount of Fe (1 to 5% by weight) dispersed in the crystalline phase of Mg O, the intensity of this impurity also increased. Sem-EDS analysis showed that the Ni and Fe particles are dispersed homogeneously in the Mg O matrix, and the particles are porous, forming agglomerates. Through energy dispersive spectroscopy analysis, the elemental chemical composition obtained is very close to the theoretical composition. The capture of CO_2 in the Mg O-1% Ni was carried out in a Parr reactor at different conditions of pressure, temperature and reaction time. Was determined that under the pressure of 0.2 MPa at 26 degrees Celsius for 1 h of reaction, the highest CO_2 capture of 7.04% by weight was obtained, while in Mg O-1% Fe the CO_2 capture was 6.32% by weight. The other magnesium oxides doped in 2.5 and 5% by weight Ni and Fe showed lower CO_2 capture. The different stages of mass loss and thermal

Plasma-induced high efficient synthesis of boron doped reduced graphene oxide for supercapacitors

DEFF Research Database (Denmark)

Li, Shaobo; Wang, Zhaofeng; Jiang, Hanmei

2016-01-01

In this work, we presented a novel route to synthesize boron doped reduced graphene oxide (rGO) by using the dielectric barrier discharge (DBD) plasma technology under ambient conditions. The doping of boron (1.4 at%) led to a significant improvement in the capacitance of rGO and supercapacitors ...

Sulfur-doped graphene via thermal exfoliation of graphite oxide in H2S, SO2, or CS2 gas.

Science.gov (United States)

Poh, Hwee Ling; Šimek, Petr; Sofer, Zdeněk; Pumera, Martin

2013-06-25

Doping of graphene with heteroatoms is an effective way to tailor its properties. Here we describe a simple and scalable method of doping graphene lattice with sulfur atoms during the thermal exfoliation process of graphite oxides. The graphite oxides were first prepared by Staudenmaier, Hofmann, and Hummers methods followed by treatments in hydrogen sulfide, sulfur dioxide, or carbon disulfide. The doped materials were characterized by scanning electron microscopy, high-resolution X-ray photoelectron spectroscopy, combustible elemental analysis, and Raman spectroscopy. The ζ-potential and conductivity of sulfur-doped graphenes were also investigated in this paper. It was found that the level of doping is more dramatically influenced by the type of graphite oxide used rather than the type of sulfur-containing gas used during exfoliation. Resulting sulfur-doped graphenes act as metal-free electrocatalysts for an oxygen reduction reaction.

Smart methanol sensor based on silver oxide-doped zinc oxide nanoparticles deposited on microchips

International Nuclear Information System (INIS)

Rahman, Mohammed M.; Khan, Sher Bahadar; Asiri, Abdullah M.

2014-01-01

We have prepared calcined silver oxide-doped zinc oxide nanoparticles (NPs) by a hydrothermal method using reducing agents in alkaline medium. The doped NPs were characterized by UV/vis, FTIR, and X-ray photoelectron spectroscopy, and by X-ray powder diffraction and field-emission scanning electron microscopy. The NPs were deposited on microchips to result in a sensor that has a fast response to methanol in the liquid phase. Features include high sensitivity, low-sample volume, reliability, reproducibility, ease of integration, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r 2  = 0.9981) over the 0.25 mmolL −1 to 0.25 molL −1 methanol concentration range. The sensitivity is ∼7.917 μA cm −2 mmolL −2 , and the detection limit is 71.0 ± 0.5 μmolL −1 at a signal-to-noise-ratio of 3. (author)

Preparation and enhanced oxidation performance of a Hf-doped single-phase Pt-modified aluminide coating

International Nuclear Information System (INIS)

Yang, Y.F.; Jiang, C.Y.; Yao, H.R.; Bao, Z.B.; Zhu, S.L.; Wang, F.H.

2016-01-01

Graphical abstract: Tiny Hf particles were successfully incorporated into Pt plating via simple electro-plating method. The hafnium particles were either nipped at Pt grain boundaries or wrapped inside Pt grains, and most of them were below 3 μm in size, showing a uniform distribution within the Pt plating. - Highlights: • A Hf-rich belt formed between outer (Ni,Pt)Al and IDZ after aluminisation. • Hf-doped coating showed much decreased mass gain and oxidation rate constant k_p. • Hf-rich belt acted as diffusion barrier by restraining diffusions of Al and W. • Degradation of β was effectively postponed by the unique Hf addition. • Hf-doped coating exhibited lighter oxide scale rumpling tendency. - Abstract: A Hf-doped β-(Ni,Pt)Al coating was prepared by co-deposition of a Pt-Hf composite plating and successive aluminisation. Then, a distinct Hf-rich belt was formed internally between the outer additive (Ni,Pt)Al coating and interdiffusion zone. An isothermal oxidation test at 1100 °C revealed a relatively lower oxidation rate constant and decreased oxide scale rumpling tendency for the Hf-doped coating during which the Hf-rich belt partly acted as an effective diffusion barrier. The unique addition of Hf into a β-(Ni,Pt)Al coating can delay the transitional oxidation period from transient alumina to stable one and postpone the degradation from β to γ'.

Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal–support interactions

Energy Technology Data Exchange (ETDEWEB)

Durgasri, D. Naga; Vinodkumar, T. [Inorganic and Physical Chemistry Division, CSIR–Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007 (India); Lin, Fangjian; Alxneit, Ivo [Solar Technology Laboratory, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Reddy, Benjaram M., E-mail: bmreddy@iict.res.in [Inorganic and Physical Chemistry Division, CSIR–Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007 (India)

2014-09-30

Graphical abstract: - Highlights: • Supported Ce-Gd-oxides are applied for soot oxidation for the first time. • Gd{sub 2}O{sub 3} doping facilitates enhanced extrinsic oxygen vacancy concentration in ceria. • The Ce-Gd/TiO{sub 2} exhibited the highest soot oxidation activity. • Key parameters that involved in tuning the activity are discussed. - Abstract: The aim of the present investigation was to ascertain the role of Al{sub 2}O{sub 3}, SiO{sub 2}, and TiO{sub 2} supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al{sub 2}O{sub 3}, Ce-Gd/SiO{sub 2}, and Ce-Gd/TiO{sub 2} catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H{sub 2}-TPR, and UV–vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F{sub 2g} mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV–vis DRS measurements. The H{sub 2}-TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO{sub 2} catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support.

Preparation of tantalum targets of known thicknesses

International Nuclear Information System (INIS)

Alexander, J.R.; Wirth, H.L.

1985-01-01

A series of carbon-backed tantalum targets were produced in a heavy ion sputtering system with a Penning ion source. The target thicknesses were then measured using the alpha-ray energy loss method. The resulting tabulated measurements were reproducible and make possible the production of carbon-backed tantalum targets with pre-determined thicknesses ranging from 20 μg/cm 2 to 1 mg/cm 2 . (orig.)

Processing, characterization, and bactericidal activity of undoped and silver-doped vanadium oxides

Energy Technology Data Exchange (ETDEWEB)

Tousley, M.E.; Wren, A.W.; Towler, M.R. [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States); Mellott, N.P., E-mail: mellott@alfred.edu [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States)

2012-12-14

Vanadium oxide (V) and silver-doped vanadium oxide (Ag-V) powders were prepared via sol-gel processing. Structural evolution and bactericidal activity was examined as a function of temperature ranging from 250, 350, 450 and 550 Degree-Sign C. Powders were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy. Results from all techniques showed vanadium pentoxide (V{sub 2}O{sub 5}) is the predominant phase regardless of heat treatment temperature or the addition of silver (Ag). XRD analysis suggests Ag is present as AgCl in samples heat treated to 250, 350, and 450 Degree-Sign C and as AgV{sub 6}O{sub 15} at 550 Degree-Sign C. Bactericidal activity was evaluated against Escherichia coli using the agar disk diffusion method considering both Ag-V and undoped, V powders. While the addition of Ag significantly increased bactericidal properties, the specific Ag valency, or crystal structure and morphology formed at higher temperatures, had little effect on functionality. -- Highlights: Black-Right-Pointing-Pointer Vanadium and silver-doped vanadium oxide powders were prepared via sol-gel. Black-Right-Pointing-Pointer Powders were characterized using advanced, complementary structural techniques. Black-Right-Pointing-Pointer Bactericidal activity was evaluated against E. coli. Black-Right-Pointing-Pointer Both vanadium and silver doped vanadium oxide show bactericidal activity.

Effect of nitrogen doping of graphene oxide on hydrogen and hydroxyl adsorption

Energy Technology Data Exchange (ETDEWEB)

Min, Byeong June; Jeong, Hae Kyung [Daegu University, Kyungsan (Korea, Republic of)

2014-05-15

We investigate how nitrogen-doping affects the hydrogen (H) and the hydroxyl (OH) adsorption on graphene oxide (GO) and on nitrogen-doped GO (NGO) via pseudopotential plane wave density functional calculations within the local spin density approximation. We find that the nitrogen doping brings about drastic changes in the hydrogen and the hydroxyl adsorption energetics, but its effects depend sensitively on the nitrogen configuration in NGO. The H and the OH adsorption energies are comparable only for pyrrolic NGO. In GO and quarternary NGO, the H adsorption energy is greater than the OH adsorption energy while the trend is reversed in pyridinic NGO. Also, the OH adsorption process is less affected by nitrogen-doping than the H adsorption is.

Producing tantalum or columbium powder

International Nuclear Information System (INIS)

Rerat, C.F.

1979-01-01

A process is described for the production of tantalum or columbium powder with a high yield within a desired range of particle sizes. A molten salt bath of a double salt comprising either an alkali metal tantalum fluoride or an alkali metal columbium fluoride and a relatively large amount of alkali metal halide diluent salt to act as a heat sink is initially maintained at a temperature a little above the liquidus temperature of the salt mixture. A liquid alkali metal at a comparatively low temperature is added to the continuously stirred bath at a high mass flow rate, and reduces the double salt, producing tantalum or columbium. The reaction is exothermic and causes the temperature to rise rapidly to a desired final reaction temperature within the range 760 to 1000 0 . The liquid alkali metal is thereafter fed at a high mass flow rate to complete the reaction quickly at the final reaction temperature. Forced cooling at a heat extraction rate not less than 42 kilojoules/min./kg. of double salt is used during at least a portion of the reaction cycle at a rate sufficient to maintain the final reaction temperature within a desired range. (author)

Bacterial adherence to tantalum versus commonly used orthopedic metallic implant materials.

Science.gov (United States)

Schildhauer, Thomas A; Robie, Bruce; Muhr, Gert; Köller, Manfred

2006-07-01

Evaluation of bacterial adhesion to pure tantalum and tantalum-coated stainless steel versus commercially pure titanium, titanium alloy (Ti-6Al-4V), and grit-blasted and polished stainless steel. Experimental in vitro cell culture study using Staphylococcus aureus and Staphylococcus epidermidis to evaluate qualitatively and quantitatively bacterial adherence to metallic implants. A bacterial adhesion assay was performed by culturing S. aureus (ATCC 6538) and S. epidermidis (clinical isolate) for one hour with tantalum, tantalum-coated stainless steel, titanium, titanium alloy, grit-blasted and polished stainless steel metallic implant discs. Adhered living and dead bacteria were stained using a 2-color fluorescence assay. Adherence was then quantitatively evaluated by fluorescence microscopy and digital image processing. Qualitative adherence of the bacteria was analyzed with a scanning electron microscope. The quantitative data were related to the implant surface roughness (Pa-value) as measured by confocal laser scanning microscopy. Bacterial adherence of S. aureus varied significantly (p = 0.0035) with the type of metallic implant. Pure tantalum presented with significantly (p titanium alloy, polished stainless steel, and tantalum-coated stainless steel. Furthermore, pure tantalum had a lower, though not significantly, adhesion than commercially pure titanium and grit-blasted stainless steel. Additionally, there was a significantly higher S. aureus adherence to titanium alloy than to commercially pure titanium (p = 0.014). S. epidermidis adherence was not significantly different among the tested materials. There was no statistically significant correlation between bacterial adherence and surface roughness of the tested implants. Pure tantalum presents with a lower or similar S. aureus and S. epidermidis adhesion when compared with commonly used materials in orthopedic implants. Because bacterial adhesion is an important predisposing factor in the development of

Influence of Rare Earth Doping on the Structural and Catalytic Properties of Nanostructured Tin Oxide

Directory of Open Access Journals (Sweden)

Maciel Adeilton

2008-01-01

Full Text Available AbstractNanoparticles of tin oxide, doped with Ce and Y, were prepared using the polymeric precursor method. The structural variations of the tin oxide nanoparticles were characterized by means of nitrogen physisorption, carbon dioxide chemisorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The synthesized samples, undoped and doped with the rare earths, were used to promote the ethanol steam reforming reaction. The SnO2-based nanoparticles were shown to be active catalysts for the ethanol steam reforming. The surface properties, such as surface area, basicity/base strength distribution, and catalytic activity/selectivity, were influenced by the rare earth doping of SnO2and also by the annealing temperatures. Doping led to chemical and micro-structural variations at the surface of the SnO2particles. Changes in the catalytic properties of the samples, such as selectivity toward ethylene, may be ascribed to different dopings and annealing temperatures.

Carbochlorination kinetics of tantalum and niobium pentoxides

International Nuclear Information System (INIS)

Allain, E.; Gaballah, I.; Garcia, F.; Ferreira, S.; Ayala, J. N.; Hernandez, A.

1999-01-01

The carbochlorination kinetics of pure Nb 2 O 5 and Ta 2 O 5 by gas mixture (CL 2 +CO+N 2 ) between 380 and 1,000 degree centigree is studied. A calculation of the standard free energy of the carbochlorination reactions is made. A diagram of the phases stability is drawn. The influence of the gas flow, temperature and the partial pressure of Cl 2 and Co at temperatures below 650 degree centigree on the reaction rate is studied. The apparent activation energy is approximately 75 and 110 kJ/mol for Nb 2 O 5 and Ta 2 O 5 , respectively. At temperatures above 650 degree centigree the Arrhenius diagram presents and anomaly which may be attributed to the decomposition of the COCL 2 formed in situ. The apparent reaction order of the carbochlorination of these oxides against Cl 2 +CO is approximately 2. The carbochlorination rates of these oxides are much greater than those of chlorination by Cl 2 +N 2 . The carbochlorination kinetics of tin furnace slag leaching concentrates containing tantalum and niobium compounds are also studied and compared with the carbochlorination kinetics of the pure oxides. (Author) 14 refs

Tantalum markers in radiography

International Nuclear Information System (INIS)

Aronson, A.S.; Jonsson, N.; Alberius, P.

1985-01-01

The biocompatibility of two types of radiopaque tantalum markers was evaluated histologically. Reactions to pin markers (99.9% purity) and spherical markers (95.2% purity) were investigated after 3-6 weeks in rabbits and 5-48 weeks in children with abnormal growth. Both marker types were firmly attached to bone trabeculae; this was most pronounced in rabbit bone, and no adverse macroscopic reactions were observed. Microscopically, no reactions or only slight fibrosis of bone tissue were detected, while soft tissues only demonstrated a minor inflammatory reaction. Nevertheless, the need for careful preparation and execution of marker implantations is stressed, and particularly avoidance iof the use of emery in sharpening of cannulae. The bioinertness of tantalum was reconfirmed as was its suitability for use as skeletal and soft tissue radiographic markers. (orig.)

Optoelectronic properties of expanding thermal plasma deposited textured zinc oxide : effect of aluminum doping

NARCIS (Netherlands)

Groenen, R.; Kieft, E.R.; Linden, J.L.; Sanden, van de M.C.M.

2006-01-01

Aluminum-doped zinc oxide films exhibiting a rough surface morphol. are deposited on glass substrates utilizing expanding thermal plasma. Spectroscopic ellipsometry is used to evaluate optical and electronic film properties. The presence of aluminum donors in doped films is confirmed by a shift in

Surfactant-assisted ultrasonic spray pyrolysis of nickel oxide and lithium-doped nickel oxide thin films, toward electrochromic applications

Energy Technology Data Exchange (ETDEWEB)

Denayer, Jessica [Group of Research in Energy and Environment for MATerials (GREENMAT), University of Liège, allée de la chimie 3, 4000 Liège (Belgium); Bister, Geoffroy [Environmental and Material Research Association (CRIBC-INISMa), avenue gouverneur cornez 4, 7000 Mons (Belgium); Simonis, Priscilla [Laboratory LPS, University of Namur, rue de bruxelles 61, 5000 Namur (Belgium); Colson, Pierre; Maho, Anthony [Group of Research in Energy and Environment for MATerials (GREENMAT), University of Liège, allée de la chimie 3, 4000 Liège (Belgium); Aubry, Philippe [Environmental and Material Research Association (CRIBC-INISMa), avenue gouverneur cornez 4, 7000 Mons (Belgium); Vertruyen, Bénédicte [Group of Research in Energy and Environment for MATerials (GREENMAT), University of Liège, allée de la chimie 3, 4000 Liège (Belgium); Henrist, Catherine, E-mail: catherine.henrist@ulg.ac.be [Group of Research in Energy and Environment for MATerials (GREENMAT), University of Liège, allée de la chimie 3, 4000 Liège (Belgium); Lardot, Véronique; Cambier, Francis [Environmental and Material Research Association (CRIBC-INISMa), avenue gouverneur cornez 4, 7000 Mons (Belgium); Cloots, Rudi [Group of Research in Energy and Environment for MATerials (GREENMAT), University of Liège, allée de la chimie 3, 4000 Liège (Belgium)

2014-12-01

Highlights: • Surfactant-assisted USP: a novel and low cost process to obtain high quality nickel oxide films, with or without lithium dopant. • Increased uniformity and reduced light scattering thanks to the addition of a surfactant. • Improved electrochromic performance (coloration efficiency and contrast) for lithium-doped films by comparison with the undoped NiO film. - Abstract: Lithium-doped nickel oxide and undoped nickel oxide thin films have been deposited on FTO/glass substrates by a surfactant-assisted ultrasonic spray pyrolysis. The addition of polyethylene glycol in the sprayed solution has led to improved uniformity and reduced light scattering compared to films made without surfactant. Furthermore, the presence of lithium ions in NiO films has resulted in improved electrochromic performances (coloration contrast and efficiency), but with a slight decrease of the electrochromic switching kinetics.

Dynamic material properties of refractory metals: tantalum and tantalum/tungsten alloys

International Nuclear Information System (INIS)

Furnish, M.D.; Lassila, D.H.; Chhabildas, L.C.; Steinberg, D.J.

1996-01-01

We have made a careful set of impact wave-profile measurements (16 profiles) on tantalum and tantalum-tungsten alloys at relatively low stresses (to 15 GPa). Alloys used were Ta 96.5 W 3.5 and Ta 86.5 W 13.5 (wt%) with oxygen contents of 30 endash 70 ppm. Information available from these experiments includes Hugoniot, elastic limits, loading rates, spall strength, unloading paths, reshock structure and specimen thickness effects. Hugoniot and spall properties are illustrated, and are consistent with expectations from earlier work. Modeling the tests with the Steinberg-Guinan-Lund rate-dependent material model provides for an excellent match of the shape of the plastic loading wave. The release wave is not well modeled due to the absence of the dynamic Bauschinger effect. There is also a discrepancy between experiments and calculations regarding the relative timing of the elastic and plastic waves that may be due to texture effects. copyright 1996 American Institute of Physics

Thermoluminescence study of aluminium oxide doped germanium prepared by combustion synthesis method

Directory of Open Access Journals (Sweden)

Saharin Nurul Syazlin Binti

2017-01-01

Full Text Available The present paper reports the optimum concentration of germanium (Ge dopant in aluminium oxide (AhO3 samples prepared by combustion synthesis (CS method for thermoluminescence (TL studies. The samples were prepared at various Ge concentration i.e. 1 to 5% mol. The phase formation of un-doped and Ge-doped Al2O3 samples was determined using X-ray Diffraction (XRD. The sharp peaks present in the XRD pattern confirms the crystallinity of the samples. The samples were then exposed to 50 Gy Cobalt-60 sources (Gamma cell 220. TL glow curves were measured and recorded using a Harshaw Model 3500 TLD reader. Comparison of TL peaks were observed to obtain the best composition of Ge dopants. A simple glow curves TL peak at around 175̊C for all composition samples was observed. It was also found that the composition of aluminium oxide doped with 3.0% of germanium exhibits the highest thermoluminescence (TL intensity which is 349747.04 (a.u.

Promoting mechanism of N-doped single-walled carbon nanotubes for O2 dissociation and SO2 oxidation

Science.gov (United States)

Chen, Yanqiu; Yin, Shi; Chen, Yang; Cen, Wanglai; Li, Jianjun; Yin, Huaqiang

2018-03-01

Although heteroatom doping in carbon based catalysts have recently received intensive attentions, the role of the intrinsically porous structure of practical carbon materials and their potential synergy with doping atoms are still unclear. To investigate the complex effects, a range of N-doped single-walled carbon nanotubes (SWCNTs) were used to investigate their potential use for O2 dissociation and the subsequent SO2 oxidation using density functional theory. It is found that graphite N doping can synergize with the outer surface of SWCNTs to facilitate the dissociation of O2. The barrier for the dissociation on dual graphite N-doped SWCNT-(8, 8) is as low as 0.3 eV, and the subsequent SO2 oxidation is thermodynamically favorable and kinetically feasible. These results spotlight on developing promising carboncatalyst via utilization of porous gemometry and heteroatom-doping of carbon materials simultaneously.

Effect of Zinc Oxide Doping on Electroluminescence and Electrical Behavior of Metalloporphyrins-Doped Samarium Complex

Science.gov (United States)

Janghouri, Mohammad; Amini, Mostafa M.

2018-02-01

Samarium complex [(Sm(III)] as a new host material was used for preparation of red organic light-emitting diodes (OLEDs). Devices with configurations of indium-doped tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):(poly(styrenesulfonate) (PEDOT:PSS (50 nm)/polyvinyl carbazole (PVK):[zinc oxide (ZnO)] (50 nm)/[(Sm(III)]:[zinc(II) 2,3-tetrakis(dihydroxyphenyl)-porphyrin and Pt(II) 2,3-dimethoxyporphyrin] (60 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (15 nm)/Al (150 nm) have been fabricated and investigated. An electroplex occurring at the (PVK/Sm: Pt(II) 2,3-dimethoxyporphyrin) interface has been suggested when ZnO nanoparticles were doped in PVK. OLED studies have revealed that the photophysical characteristics and electrical behavior of devices with ZnO nanoparticles are much better than those of devices with pure PVK. The efficiency of devices based on [(Sm(III)] was superior than that of known aluminum tris(8-hydroxyquinoline) (Alq3) and also our earlier reports on red OLEDs under the same conditions.

Electrical properties of vacuum-annealed titanium-doped indium oxide films

NARCIS (Netherlands)

Yan, L.T.; Rath, J.K.; Schropp, R.E.I.

2011-01-01

Titanium-doped indium oxide (ITiO) films were deposited on Corning glass 2000 substrates at room temperature by radio frequency magnetron sputtering followed by vacuum post-annealing. With increasing deposition power, the as-deposited films showed an increasingly crystalline nature. As-deposited

Fabrication of a Tantalum-Based Josephson Junction for an X-Ray Detector

Science.gov (United States)

Morohashi, Shin'ichi; Gotoh, Kohtaroh; Yokoyama, Naoki

2000-06-01

We have fabricated a tantalum-based Josephson junction for an X-ray detector. The tantalum layer was selected for the junction electrode because of its long quasiparticle lifetime, large X-ray absorption efficiency and stability against thermal cycling. We have developed a buffer layer to fabricate the tantalum layer with a body-centered cubic structure. Based on careful consideration of their superconductivity, we have selected a niobium thin layer as the buffer layer for fabricating the tantalum base electrode, and a tungsten thin layer for the tantalum counter electrode. Fabricated Nb/AlOx-Al/Ta/Nb and Nb/Ta/W/AlOx-Al/Ta/Nb Josephson junctions exhibited current-voltage characteristics with a low subgap leakage current.

Effect of aluminum oxide doping on the structural, electrical, and optical properties of zinc oxide (AOZO) nanofibers synthesized by electrospinning

International Nuclear Information System (INIS)

Lotus, A.F.; Kang, Y.C.; Walker, J.I.; Ramsier, R.D.; Chase, G.G.

2010-01-01

Zinc oxide nanofibers doped with aluminum oxide were prepared by sol-gel processing and electrospinning techniques using polyvinylpyrrolidone (PVP), zinc acetate and aluminum acetate as precursors. The resulting nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy, and current-voltage (I-V) properties. The nanofibers had diameters in the range of 60-150 nm. The incorporation of aluminum oxide resulted in a decrease in the crystallite sizes of the zinc oxide nanofibers. Aluminum oxide doped zinc oxide (AOZO) nanofibers exhibited lower bandgap energies compared to undoped zinc oxide nanofibers. However, as the aluminum content (Al/(Al + Zn) x 100%) was increased from 1.70 at.% to 3.20 at.% in the electrospinning solution, the bandgap energy increased resulting in lower conductivity. The electrical conductivity of the AOZO samples was found to depend on the amount of aluminum dopant in the matrix as reflected in the changes in oxidation state elucidated from XPS data. Electrospinning was found to be a productive, simple, and easy method for tuning the bandgap energy and conductivity of zinc oxide semiconducting nanofibers.

A genetic algorithm approach for evaluation of optical functions of very thin tantalum pentoxide films on Si substrate

International Nuclear Information System (INIS)

Sharlandjiev, P S; Nazarova, D I

2013-01-01

The optical characteristics of tantalum pentoxide films, deposited on Si(100) substrate by reactive sputtering, are studied. These films are investigated as high-kappa materials for the needs of nano-electronics, i.e. design of dynamic random access memories, etc. One problem in their implementation is that metal oxides are thermodynamically unstable with Si and an interfacial layer is formed between the oxide film and the silicon substrate during the deposition process. Herein, the center of attention is on the optical properties of that interfacial layer, which is studied by spectral photometric measurements. The evaluation of the optical parameters of the structure is fulfilled with the genetic algorithm approach. The spectral range of evaluation covers deep UV to NIR. The equivalent physical thickness (2.5 nm) and the equivalent refractive index of the interfacial layer are estimated from 236 to 750 nm as well as the thickness of the tantalum pentoxide film (9.5 nm). (paper)

Improved optical response and photocatalysis for N-doped titanium oxide (TiO2) films prepared by oxidation of TiN

International Nuclear Information System (INIS)

Wan, L.; Li, J.F.; Feng, J.Y.; Sun, W.; Mao, Z.Q.

2007-01-01

In order to improve the photocatalytic activity, N-doped titanium oxide (TiO 2 ) films were obtained by thermal oxidation of TiN films, which were prepared on Ti substrates by ion beam assisted deposition (IBAD). The dominating rutile TiO 2 phase was found in films after thermal oxidation. According to the results of X-ray photoelectron spectroscopy (XPS), the residual N atoms occupied O-atom sites in TiO 2 lattice to form Ti-O-N bonds. UV-vis spectra revealed the N-doped TiO 2 film had a red shift of absorption edge. The maximum red shift was assigned to the sample annealed at 750 deg. C, with an onset wavelength at 600 nm. The onset wavelength corresponded to the photon energy of 2.05 eV, which was nearly 1.0 eV below the band gap of pure rutile TiO 2 . The effect of nitrogen was responsible for the enhancement of photoactivity of N-doped TiO 2 films in the range of visible light

Growth of Li doped bismuth oxide nanorods and its electrochemical performance for the determination of L-cysteine

Energy Technology Data Exchange (ETDEWEB)

Wen, Yong, E-mail: yongwen1982@163.com [School of Civil Engineering and Architecture, Xinjiang University (China); Pei, Li-zhai; Wei, Tian [chool of Materials Science and Engineering, Anhui University of Technology (China)

2017-05-15

Li doped bismuth oxide nanorods have been prepared using sodium bismuthate and Li acetate. X-ray diffraction (XRD) pattern shows that the nanorods are composed of monoclinic Bi{sub 2}O{sub 4} and cubic LiBi{sub 12}O{sub 18.50} phases. Scanning electron microscopy (SEM) observation shows that the nanorods have the length and diameter of 1-5 μm and 50-350 nm, respectively. The formation of the Li doped bismuth oxide nanorods is closely relative to the hydrothermal conditions. The electrochemical performance for the determination of L-cysteine based on a Li doped bismuth oxide nanorods modified glassy carbon electrode (GCE) has been developed. The CV peak current increases obviously and linearly with increasing the scan rate. Under the optimal conditions, Li doped bismuth oxide nanorods modified GCE exhibits good analytical performance with good reproducibility and stability. The linear range of L-cysteine is 0.0001-2 mM and the detection limit is 0.36 μM and 0.17 μM for cvp1 and cvp2, respectively. (author)

Growth of Li doped bismuth oxide nanorods and its electrochemical performance for the determination of L-cysteine

International Nuclear Information System (INIS)

Wen, Yong; Pei, Li-zhai; Wei, Tian

2017-01-01

Li doped bismuth oxide nanorods have been prepared using sodium bismuthate and Li acetate. X-ray diffraction (XRD) pattern shows that the nanorods are composed of monoclinic Bi_2O_4 and cubic LiBi_1_2O_1_8_._5_0 phases. Scanning electron microscopy (SEM) observation shows that the nanorods have the length and diameter of 1-5 μm and 50-350 nm, respectively. The formation of the Li doped bismuth oxide nanorods is closely relative to the hydrothermal conditions. The electrochemical performance for the determination of L-cysteine based on a Li doped bismuth oxide nanorods modified glassy carbon electrode (GCE) has been developed. The CV peak current increases obviously and linearly with increasing the scan rate. Under the optimal conditions, Li doped bismuth oxide nanorods modified GCE exhibits good analytical performance with good reproducibility and stability. The linear range of L-cysteine is 0.0001-2 mM and the detection limit is 0.36 μM and 0.17 μM for cvp1 and cvp2, respectively. (author)

Zirconium doped nano-dispersed oxides of Fe, Al and Zn for destruction of warfare agents

International Nuclear Information System (INIS)

Stengl, Vaclav; Houskova, Vendula; Bakardjieva, Snejana; Murafa, Nataliya; Marikova, Monika; Oplustil, Frantisek; Nemec, Tomas

2010-01-01

Zirconium doped nano dispersive oxides of Fe, Al and Zn were prepared by a homogeneous hydrolysis of the respective sulfate salts with urea in aqueous solutions. Synthesized metal oxide hydroxides were characterized using Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). These oxides were taken for an experimental evaluation of their reactivity with sulfur mustard (HD or bis(2-chloroethyl)sulfide), soman (GD or (3,3'-Dimethylbutan-2-yl)-methylphosphonofluoridate) and VX agent (S-[2-(diisopropylamino)ethyl]-O-ethyl-methylphosphonothionate). The presence of Zr 4+ dopant can increase both the surface area and the surface hydroxylation of the resulting doped oxides, decreases their crystallites' sizes thereby it may contribute in enabling the substrate adsorption at the oxide surface thus it can accelerate the rate of degradation of warfare agents. Addition of Zr 4+ converts the product of the reaction of ferric sulphate with urea from ferrihydrite to goethite. We found out that doped oxo-hydroxides Zr-FeO(OH) - being prepared by a homogeneous hydrolysis of ferric and zirconium oxo-sulfates mixture in aqueous solutions - exhibit a comparatively higher degradation activity towards chemical warfare agents (CWAs). Degradation of soman or VX agent on Zr-doped FeO(OH) containing ca. 8.3 wt.% of zirconium proceeded to completion within 30 min.

Zirconium doped nano-dispersed oxides of Fe, Al and Zn for destruction of warfare agents

Energy Technology Data Exchange (ETDEWEB)

Stengl, Vaclav, E-mail: stengl@uach.cz [Institute of Inorganic Chemistry AS CR v.v.i., 250 68 Rez (Czech Republic); Houskova, Vendula; Bakardjieva, Snejana; Murafa, Nataliya; Marikova, Monika [Institute of Inorganic Chemistry AS CR v.v.i., 250 68 Rez (Czech Republic); Oplustil, Frantisek; Nemec, Tomas [Military Technical Institute of Protection Brno, Veslarska 230, 628 00 Brno (Czech Republic)

2010-11-15

Zirconium doped nano dispersive oxides of Fe, Al and Zn were prepared by a homogeneous hydrolysis of the respective sulfate salts with urea in aqueous solutions. Synthesized metal oxide hydroxides were characterized using Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). These oxides were taken for an experimental evaluation of their reactivity with sulfur mustard (HD or bis(2-chloroethyl)sulfide), soman (GD or (3,3'-Dimethylbutan-2-yl)-methylphosphonofluoridate) and VX agent (S-[2-(diisopropylamino)ethyl]-O-ethyl-methylphosphonothionate). The presence of Zr{sup 4+} dopant can increase both the surface area and the surface hydroxylation of the resulting doped oxides, decreases their crystallites' sizes thereby it may contribute in enabling the substrate adsorption at the oxide surface thus it can accelerate the rate of degradation of warfare agents. Addition of Zr{sup 4+} converts the product of the reaction of ferric sulphate with urea from ferrihydrite to goethite. We found out that doped oxo-hydroxides Zr-FeO(OH) - being prepared by a homogeneous hydrolysis of ferric and zirconium oxo-sulfates mixture in aqueous solutions - exhibit a comparatively higher degradation activity towards chemical warfare agents (CWAs). Degradation of soman or VX agent on Zr-doped FeO(OH) containing ca. 8.3 wt.% of zirconium proceeded to completion within 30 min.

Manganese doped-iron oxide nanoparticle clusters and their potential as agents for magnetic resonance imaging and hyperthermia

KAUST Repository

Casula, Maria F.

2016-06-10

A simple, one pot method to synthesize water-dispersible Mn doped iron oxide colloidal clusters constructed of nanoparticles arranged into secondary flower-like structures was developed. This method allows the successful incorporation and homogeneous distribution of Mn within the nanoparticle iron oxide clusters. The formed clusters retain the desired morphological and structural features observed for pure iron oxide clusters, but possess intrinsic magnetic properties that arise from Mn doping. They show distinct performance as imaging contrast agents and excellent characteristics as heating mediators in magnetic fluid hyperthermia. It is expected that the outcomes of this study will open up new avenues for the exploitation of doped magnetic nanoparticle assemblies in biomedicine. © the Owner Societies 2016.

Manganese doped-iron oxide nanoparticle clusters and their potential as agents for magnetic resonance imaging and hyperthermia

KAUST Repository

Casula, Maria F.; Conca, Erika; Bakaimi, Ioanna; Sathya, Ayyappan; Materia, Maria Elena; Casu, Alberto; Falqui, Andrea; Sogne, Elisa; Pellegrino, Teresa; Kanaras, Antonios G.

2016-01-01

A simple, one pot method to synthesize water-dispersible Mn doped iron oxide colloidal clusters constructed of nanoparticles arranged into secondary flower-like structures was developed. This method allows the successful incorporation and homogeneous distribution of Mn within the nanoparticle iron oxide clusters. The formed clusters retain the desired morphological and structural features observed for pure iron oxide clusters, but possess intrinsic magnetic properties that arise from Mn doping. They show distinct performance as imaging contrast agents and excellent characteristics as heating mediators in magnetic fluid hyperthermia. It is expected that the outcomes of this study will open up new avenues for the exploitation of doped magnetic nanoparticle assemblies in biomedicine. © the Owner Societies 2016.

Physical properties of pyrolytically sprayed tin-doped indium oxide coatings

NARCIS (Netherlands)

Haitjema, H.; Elich, J.J.P.

1991-01-01

The optical and electrical properties of tin-doped indium oxide coatings obviously depend on a number of production parameters. This dependence has been studied to obtain a more general insight into the relationships between the various coating properties. The coatings have been produced by spray

Work hardening and plastic equation of state of tantalum

International Nuclear Information System (INIS)

Gypen, L.A.; Aernoudt, E.; Deruyttere, A.

1983-01-01

The influence of cold deformation on the thermal and athermal components of the flow stress of tantalum was investigated. Up to high deformation levels the strain hardening is due only to the development of internal stress fields; the effective stress remains almost constant. The athermal strain hardening of tantalum is parabolic at low deformation levels (epsilon < 0.5) and linear at high deformation levels, as for other bcc metals. Hart's plastic equation of state is shown to be valid for tantalum at room temperature in the whole deformation range investigated (from epsilon = 0.005 to epsilon = 2.8). (author)

Aluminum-doped zinc oxide films as transparent conductive electrode for organic light-emitting devices

International Nuclear Information System (INIS)

Jiang, X.; Wong, F.L.; Fung, M.K.; Lee, S.T.

2003-01-01

Highly transparent conductive, aluminum-doped zinc oxide (ZnO:Al) films were deposited on glass substrates by midfrequency magnetron sputtering of metallic aluminum-doped zinc target. ZnO:Al films with surface work functions between 3.7 and 4.4 eV were obtained by varying the sputtering conditions. Organic light-emitting diodes (OLEDs) were fabricated on these ZnO:Al films. A current efficiency of higher than 3.7 cd/A, was achieved. For comparison, 3.9 cd/A was achieved by the reference OLEDs fabricated on commercial indium-tin-oxide substrates

Oxidation-resistant Ge-doped silicide coating on Cr-Cr2Nb alloys by pack cementation

International Nuclear Information System (INIS)

He Yirong

1997-01-01

The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on Cr-Cr 2 Nb alloys in a single processing step. The morphology and composition of the coating depended both on the pack composition and processing schedule and also on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi 2 and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. Under cyclic and isothermal oxidation conditions, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation and from pesting by the formation of a Ge-doped silica film. (orig.)

Li-doped MgO as catalysts for oxidative coupling of methane: A positron annihilation study

Science.gov (United States)

Dai, G. H.; Yan, Q. J.; Wang, Y.; Liu, Q. S.

1991-08-01

Magnesium oxides intentionally doped with lithium (with a maximum Li content of 40 tool%) for use as catalysts for oxidative coupling of methane were characterized by means of positron annihilation. The positron lifetime spectra, which could be reasonably well interpreted within the framework of the well-known trapping model, depend on the amount of Li doping of the MgO suggesting that positrons are trapped at dispersed small Li 2CO 3 precipitates. Very similar dependencies on lithium doping of the C 2 selectivity and the positron trapping rate ϰ imply an intimate relationship between the concentration of [Li] 0-centers (also referred to as [Li +O -] centers) and the selective activity of Li/MgO during catalytic reactions.

Advances in the chemical vapor deposition (CVD) of Tantalum

DEFF Research Database (Denmark)

Mugabi, James Atwoki; Eriksen, Søren; Christensen, Erik

2014-01-01

The chemical stability of tantalum in hot acidic media has made it a key material in the protection of industrial equipment from corrosion under such conditions. The Chemical Vapor Deposition of tantalum to achieve such thin corrosion resistant coatings is one of the most widely mentioned examples...

Effect of tantalum content of titanium oxide film fabricated by magnetron sputtering on the behavior of cultured human umbilical vein endothelial cells (HUVEC)

International Nuclear Information System (INIS)

Chen, J.Y.; Leng, Y.X.; Zhang, X.

2006-01-01

In this work, we synthesized titanium oxide thin films containing different tantalum using magnetron sputtering to meet the challenge of enhanced biocompatibility. The structure characteristics of the films were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The biological behavior of human umbilical vein endothelial cells (HUVECs) on the film surface was investigated by in vitro cell culture. Study of cultured HUVEC onto films revealed that the growth and proliferation behavior of EC were varied significantly due to the different Ta content which resulting the characterization of films is different. The adherence, growth, shape and proliferation of EC on Ti-O film with high Ta content and smoother surface was excellent

Plasma-induced highly efficient synthesis of boron doped reduced graphene oxide for supercapacitors.

Science.gov (United States)

Li, Shaobo; Wang, Zhaofeng; Jiang, Hanmei; Zhang, Limei; Ren, Jingzheng; Zheng, Mingtao; Dong, Lichun; Sun, Luyi

2016-09-21

In this work, we presented a novel route to synthesize boron doped reduced graphene oxide (rGO) by using the dielectric barrier discharge (DBD) plasma technology under ambient conditions. The doping of boron (1.4 at%) led to a significant improvement in the capacitance of rGO and supercapacitors based on the as-synthesized B-rGO exhibited an outstanding specific capacitance.

Nitrogen Doped Ordered Mesoporous Carbon as Support of PtRu Nanoparticles for Methanol Electro-Oxidation

Directory of Open Access Journals (Sweden)

David Sebastián

2018-04-01

Full Text Available The low oxidation kinetics of alcohols and the need for expensive platinum group metals are still some of the main drawbacks for the commercialization of energy efficient direct alcohol fuel cells. In this work, we investigate the influence of nitrogen doping of ordered mesoporous carbon (CMK as support on the electrochemical activity of PtRu nanoparticles. Nitrogen doping procedures involve the utilization of pyrrole as both nitrogen and carbon precursor by means of a templating method using mesoporous silica. This method allows obtaining carbon supports with up to 14 wt. % nitrogen, with an effective introduction of pyridinic, pyrrolic and quaternary nitrogen. PtRu nanoparticles were deposited by sodium formate reduction method. The presence of nitrogen mainly influences the Pt:Ru atomic ratio at the near surface, passing from 50:50 on the bare (un-doped CMK to 70:30 for the N-doped CMK catalyst. The electroactivity towards the methanol oxidation reaction (MOR was evaluated in acid and alkaline electrolytes. The presence of nitrogen in the support favors a faster oxidation of methanol due to the enrichment of Pt at the near surface together with an increase of the intrinsic activity of PtRu nanoparticles.

Multi-scale Modeling of Plasticity in Tantalum.

Energy Technology Data Exchange (ETDEWEB)

Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carroll, Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Buchheit, Thomas E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Boyce, Brad [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Weinberger, Christopher [Drexel Univ., Philadelphia, PA (United States)

2015-12-01

In this report, we present a multi-scale computational model to simulate plastic deformation of tantalum and validating experiments. In atomistic/ dislocation level, dislocation kink- pair theory is used to formulate temperature and strain rate dependent constitutive equations. The kink-pair theory is calibrated to available data from single crystal experiments to produce accurate and convenient constitutive laws. The model is then implemented into a BCC crystal plasticity finite element method (CP-FEM) model to predict temperature and strain rate dependent yield stresses of single and polycrystalline tantalum and compared with existing experimental data from the literature. Furthermore, classical continuum constitutive models describing temperature and strain rate dependent flow behaviors are fit to the yield stresses obtained from the CP-FEM polycrystal predictions. The model is then used to conduct hydro- dynamic simulations of Taylor cylinder impact test and compared with experiments. In order to validate the proposed tantalum CP-FEM model with experiments, we introduce a method for quantitative comparison of CP-FEM models with various experimental techniques. To mitigate the effects of unknown subsurface microstructure, tantalum tensile specimens with a pseudo-two-dimensional grain structure and grain sizes on the order of millimeters are used. A technique combining an electron back scatter diffraction (EBSD) and high resolution digital image correlation (HR-DIC) is used to measure the texture and sub-grain strain fields upon uniaxial tensile loading at various applied strains. Deformed specimens are also analyzed with optical profilometry measurements to obtain out-of- plane strain fields. These high resolution measurements are directly compared with large-scale CP-FEM predictions. This computational method directly links fundamental dislocation physics to plastic deformations in the grain-scale and to the engineering-scale applications. Furthermore, direct

Environmental and energy gains from using molten magnesium–sodium–potassium chlorides for electro-metallisation of refractory metal oxides

Directory of Open Access Journals (Sweden)

Wei Li

2015-12-01

Full Text Available The molten eutectic mixture of magnesium, sodium and potassium chlorides (MgCl2–NaCl–KCl has inappreciable solubility for oxide ions, and can help disengage a carbon anode from the oxide ions generated at a metal oxide cathode, and effectively avoid carbon dioxide formation. This “disengaging strategy” was successfully demonstrated in electro-reduction of solid oxides of zirconium and tantalum. It has led to significantly higher current efficiency (93%, and lower energy consumption (1.4 kW h kg−1 in electrolysis of tantalum oxide to tantalum metal compared to the conventional electrolysis in molten calcium chloride (e.g. 78% and 2.4 kW h/kg-Ta.

Highly conducting and crystalline doubly doped tin oxide films fabricated using a low-cost and simplified spray technique

Energy Technology Data Exchange (ETDEWEB)

Ravichandran, K., E-mail: kkr1365@yahoo.co [P.G. and Research Department of Physics, AVVM. Sri Pushpum College, Poondi, Thanjavur District, Tamil Nadu 613503 (India); Muruganantham, G.; Sakthivel, B. [P.G. and Research Department of Physics, AVVM. Sri Pushpum College, Poondi, Thanjavur District, Tamil Nadu 613503 (India)

2009-11-15

Doubly doped (simultaneous doping of antimony and fluorine) tin oxide films (SnO{sub 2}:Sb:F) have been fabricated by employing an inexpensive and simplified spray technique using perfume atomizer from aqueous solution of SnCl{sub 2} precursor. The structural studies revealed that the films are highly crystalline in nature with preferential orientation along the (2 0 0) plane. It is found that the size of the crystallites of the doubly doped tin oxide films is larger (69 nm) than that (27 nm) of their undoped counterparts. The dislocation density of the doubly doped film is lesser (2.08x10{sup 14} lines/m{sup 2}) when compared with that of the undoped film (13.2x10{sup 14} lines/m{sup 2}), indicating the higher degree of crystallinity of the doubly doped films. The SEM images depict that the films are homogeneous and uniform. The optical transmittance in the visible range and the optical band gap of the doubly doped films are 71% and 3.56 eV respectively. The sheet resistance (4.13 OMEGA/square) attained for the doubly doped film in this study is lower than the values reported for spray deposited fluorine or antimony doped tin oxide films prepared from aqueous solution of SnCl{sub 2} precursor (without using methanol or ethanol).

One - Step synthesis of nitrogen doped reduced graphene oxide with NiCo nanoparticles for ethanol oxidation in alkaline media.

Science.gov (United States)

Kakaei, Karim; Marzang, Kamaran

2016-01-15

Development of anode catalysts and catalyst supporting carbonaceous material containing non-precious metal have attracted tremendous attention in the field of direct ethanol fuel cells (DEFCs). Herein, we report the synthesis and electrochemical properties of nitrogen-doped reduced graphene oxide (NRGO) supported Co, Ni and NiCo nanocomposites. The metal NRGO nanocomposites, in which metal nanoparticles are embedded in the highly porous nitrogen-doped graphene matrix, have been synthesized by simply and one-pot method at a mild temperature using GO, urea choline chloride and urea as reducing and doping agent. The fabricated NiCo/NRGO exhibit remarkable electrocatalytic activity (with Tafel slope of 159.1mVdec(-1)) and high stability for the ethanol oxidation reaction (EOR). The superior performance of the alloy based NRGO is attributed to high surface area, well uniform distribution of high-density nitrogen, metal active sites and synergistic effect. Copyright © 2015 Elsevier Inc. All rights reserved.

Use of sulfoxides for extraction-gravimetric determination of niobium and tantalum

International Nuclear Information System (INIS)

Nikolaev, A.I.; Babkin, A.G.; Tkachenko, V.G.

1977-01-01

An extraction-gravimetrical technique has been developed for determination of niobium and tantalum. The technique permits simultaneous extraction of tantalum and its concentrating in the aqueous phase; the range of Ta concentrations determined is essentially wider than in case of the routine gravimetric methods. The technique is based upon the fact, that tantalum is extracted by sulfoxides from fluorine-sulphate solutions at lower concentration of Hf and at lower ratios between the volumes of organic and aqueous phases than niobium. Two subsequent extractions by 1M sulfoxide solutions provide for practically complete transfer of tantalum into the organic phase, whereas extraction of niobium is only 3-20%. Sufficient recovery of Ta and Nb from organic phases is provided by re-extraction by NH 4 F solution. The technique is suitable for niobium and tantalum determination at the ratios of their pentoxides from 1:100 to 100:1. The disturbing influence of Fe(3) is suppressed by reductions to Fe(2)

Magnetron sputtered gadolinia-doped ceria diffusion barriers for metal-supported solid oxide fuel cells

DEFF Research Database (Denmark)

Sønderby, Steffen; Klemensø, Trine; Christensen, Bjarke H.

2014-01-01

Gadolinia-doped ceria (GDC) thin films are deposited by reactive magnetron sputtering in an industrial-scale setup and implemented as barrier layers between the cathode and electrolyte in metal-based solid oxide fuel cells consisting of a metal support, an electrolyte of ZrO2 co-doped with Sc2O3...

Improved oxidation resistance of group VB refractory metals by Al+ ion implantation

International Nuclear Information System (INIS)

Hampikian, J.M.

1996-01-01

Aluminum ion implantation of vanadium, niobium, and tantalum improved the metals' oxidation resistances at 500 C and 735 C. Implanted vanadium oxidized only to one-third the extent of unimplanted vanadium when exposed at 500 C to air. The oxidative weight gains of implanted niobium and tantalum proved negligible when measured at 500 C and for times sufficient to fully convert the untreated metals to their pentoxides. At 735 C, implantation of vanadium only slightly retarded its oxidation, while oxidative weight gains of niobium and tantalum were reduced by factors of 3 or more. Implanted niobium exhibited weight gain in direct proportion to oxidation time squared at 735 C. Microstructural examination of the metals implanted with selected fluences of the 180 kV aluminum ions showed the following. The solubility limit of aluminum is extended by implantation, the body centered cubic (bcc) phases being retained to ∼60 at. pct Al in all three metals. The highest fluence investigated, 2.4 x 10 22 ions/m 2 , produced an ∼400-nm layer of VAl 3 beneath the surface of vanadium, and ∼300-nm layers of an amorphous phase containing ∼70 at. pct Al beneath the niobium and tantalum surfaces. All three metals, implanted to this fluence and annealed at 600 C, contained tri-aluminides, intermetallic compounds known for their oxidation resistances. Specimens implanted to this fluence were thus selected for the oxidation measurements

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

Science.gov (United States)

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

Reduced graphene oxide decorated with Fe doped SnO{sub 2} nanoparticles for humidity sensor

Energy Technology Data Exchange (ETDEWEB)

Toloman, D. [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293 Cluj-Napoca (Romania); Popa, A., E-mail: popa@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293 Cluj-Napoca (Romania); Stan, M.; Socaci, C.; Biris, A.R. [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293 Cluj-Napoca (Romania); Katona, G. [Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, 11 Arany Janos Street, 400028 Cluj-Napoca (Romania); Tudorache, F. [Interdisciplinary Research Department – Field Science & RAMTECH, Al. I. Cuza University, 11 Carol I Blvd., 7000506 Iasi (Romania); Petrila, I. [Interdisciplinary Research Department – Field Science & RAMTECH, Al. I. Cuza University, 11 Carol I Blvd., 7000506 Iasi (Romania); Faculty of Automatic Control and Computer Engineering, Gheorghe Asachi Technical University, 27 Dimitrie Mangeron Street, 700050 Iasi (Romania); Iacomi, F. [Faculty of Physics, Al. I. Cuza University, 11 Carol I Blvd., 7000506 Iasi (Romania)

2017-04-30

Highlights: • Reduced graphene oxide decorated with Fe doped SnO{sub 2} nanoparticles were synthesized. • The decoration of rGO layers with SnO{sub 2}:Fe nanoparticles was highlited by TEM. • The reduction of graphene oxide was evidenced using XRD and FT-IR. • Sensitivity tests for relative humidity (RH) were carried out. • The composite sensor exhibited enhanced sensing response as compared with Fe:SnO{sub 2}. - Abstract: Reduced graphene oxide (rGO) decorated with Fe doped SnO{sub 2} nanoparticles were fabricated via the electrostatic interaction between positively charged modified Fe-doped SnO{sub 2} oxide and negatively charged graphene oxide (GO) in the presence of poly(allylamine) hydrochloride (PAH). The decoration of rGO layers with SnO{sub 2}:Fe nanoparticles was highlited by TEM microsopy. For composite sample the diffraction patterns coincide well with those of SnO{sub 2}:Fe nanoparticles. The reduction of graphene oxide was evidenced using XRD and FT-IR spectroscopy. The formation of SnO{sub 2}:Fe-PAH-graphene composites was confirmed by FT-IR, Raman and EPR spectroscopy. Sensitivity tests for relative humidity (RH) measurements were carried out at five different concentrations of humid air at room temperature. The prepared composite sensor exhibited a higher sensing response as compared with Fe:SnO{sub 2} nanoparticles.

Low Temperature Synthesis and Properties of Gadolinium-Doped Cerium Oxide Nanoparticles

DEFF Research Database (Denmark)

Machado, M. F. S.; Moraes, L. P. R.; Monteiro, N. K.

2017-01-01

Gadolinium-doped cerium oxide (GDC) is an attractive ceramic material for solid oxide fuel cells (SOFCs) both as the electrolyte and in composite electrodes operating at low and intermediate temperatures. GDC exhibits high oxygen ion conductivity at a wide range of temperatures and displays a high...... resistance to carbon deposition when hydrocarbons are used as fuels. However, an inconvenience of ceria-based oxides is the high sintering temperature needed to obtain a fully dense ceramic body. In this study, a green chemistry route for the synthesis of 10 mol% GDC nanoparticles is proposed. The aqueous...

Electrochemical Impedance and Polarization Corrosion Studies of Tantalum Surface Modified by DC Plasma Electrolytic Oxidation

Directory of Open Access Journals (Sweden)

Maciej Sowa

2018-04-01

Full Text Available Tantalum has recently become an actively researched biomaterial for the bone reconstruction applications because of its excellent corrosion resistance and successful clinical records. However, a bare Ta surface is not capable of directly bonding to the bone upon implantation and requires some method of bioactivation. In this study, this was realized by direct current (DC plasma electrolytic oxidation (PEO. Susceptibility to corrosion is a major factor determining the service-life of an implant. Therefore, herein, the corrosion resistance of the PEO coatings on Ta was investigated in Ringer’s solution. The coatings were formed by galvanostatic anodization up to 200, 300 and 400 V, after which the treatment was conducted potentiostatically until the total process time amounted to 5 min. Three solutions containing Ca(H2PO22, Ca(HCOO2 and Mg(CH3COO2 were used in the treatment. For the corrosion characterization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques were chosen. The coatings showed the best corrosion resistance at voltages low enough so that the intensive sparking was absent, which resulted in the formation of thin films. The impedance data were fitted to the equivalent electrical circuits with two time constants, namely R(Q[R(QR] and R(Q[R(Q[RW

Temperature dependent selective detection of hydrogen and acetone using Pd doped WO3/reduced graphene oxide nanocomposite

Science.gov (United States)

Kaur, Jasmeet; Anand, Kanica; Kohli, Nipin; Kaur, Amanpreet; Singh, Ravi Chand

2018-06-01

Reduced graphene oxide (RGO) and Pd doped WO3 nanocomposites were fabricated by employing electrostatic interactions between poly (diallyldimethylammonium chloride) (PDDA) modified Pd doped WO3 nanostructures and graphite oxide (GO) and studied for their gas sensing application. XRD, Raman, FTIR, FESEM-EDX, TEM, TGA, XPS and Photoluminescence techniques were used for characterization of as-synthesized samples. Gas sensing studies revealed that the sensor with optimized doping of 1.5 mol% Pd and 1 wt% GO shows temperature dependent selectivity towards hydrogen and acetone. The role of WO3, Pd and RGO has been discussed in detail for enhanced sensing performance.

Ni-doped zinc oxide nanocombs and phonon spectra properties

International Nuclear Information System (INIS)

Zhang Bin; Zhang Xingtang; Gong Hechun; Wu Zhishen; Zhou Shaomin; Du Zuliang

2008-01-01

Ni-doped comb-like zinc oxide (ZnO) semiconductor nanostructures have been synthesized by a simple chemical vapor-deposition method (CVD) at relatively low temperature. The as-synthesized ZnO nanocombs consist of an array of very uniform, perfectly aligned, evenly spaced and long single-crystalline nanobelts (nanowires) with periods of about several tens of nanometers. X-ray diffraction and Raman spectra results provide the evidence that Ni is incorporated into the ZnO lattice at Zn site. Photoluminescence spectra of the as-obtained samples have been detected, in which the incorporation of donor Ni leads to the increases of the ultraviolet emission intensity and a blueshift of emission peak. This technique can be used to prepare other semiconductors and morphology-controlled doping nanocombs

Effect of self purification on the structural optical and electrical properties of copper doped oxidized Zn films

International Nuclear Information System (INIS)

Koshy, Obey; Abdul Khadar, M.

2015-01-01

The effect of self purification mechanism is studied on oxidized Cu–Zn thin films. Oxidized Cu–Zn thin films were prepared by thermal evaporation on glass substrates. XRD studies indicate that the oxidized Cu–Zn thin films are of hexagonal wurtzite structure. AFM images shows that with increase in copper wt. percent the nanoparticle morphology of oxidized Zn film turned to one dimensional nanorod morphology. XPS spectra of the oxidized Cu–Zn thin films shows the oxidized state of zinc and copper. The PL spectra of oxidized Zn film showed a strong and narrow near band edge emission at 380 nm whereas in the case of oxidized Cu–Zn thin films the emission showed peak near 410 nm corresponding to peak related to copper. With increase in copper content, the intensity of the defect emission decreased due to the self purification mechanism in nanomaterials. In addition the resistivity of doped films increased due to the self purification mechanism in nanomaterials. - Highlights: • Copper doping in ZnO resulted in the increase in blue emission due to defect levels formed. • The intensity of the luminescence peak of the doped film sample decreased and resistivity increased due to the self purification mechanism in nanomaterials.

Thermoelectric Properties of the Yttrium-Doped Ceramic Oxide SrTiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Khan, Tamal Tahsin; Ur, Soon-Chul [Korea National University of Transportation, Chungju (Korea, Republic of)

2017-01-15

The doping dependence of the thermoelectric figure of merit, ZT, of the ceramic oxide SrTiO{sub 3} at high temperature has been studied. In this study, yttrium was used as the doping element. A conventional solid-state reaction method was used for the preparation of Y-doped SrTiO{sub 3}. The doping level in SrTiO{sub 3} was controlled to be in the doping range of 2 - 10 mole%. Almost all the yttrium atoms incorporated into the SrTiO{sub 3} provided charge carriers, as was observed by using X-ray diffraction pattern. The relative densities of all the samples varied from 98.53% to 99.45%. The thermoelectric properties, including the electrical conductivity σ, Seebeck coefficient S, thermal conductivity k, and the figure of merit, ZT, were investigated at medium temperatures. The ZT value showed an obvious doping level dependence, in which a value as high as 0.18 is realized at 773 K for a doping of 8 mole%.

Separation of niobium and tantalum by paper chromatography and their following spectrographic determination

International Nuclear Information System (INIS)

Moroshkina, T.M.; Peres Sanfiel', F.

1975-01-01

The paper presents the results of an investigation into the use of water-saturated furfural to separate niobium and tantalum in a 1:1 ratio by means of ascending paper chromatography. The influence of sulphuric acid, ammonium fluoride and hydrofluoric acid concentrations on the completeness of the niobium and tantalum separation was investigated, the extent of the separation being checked by a spectral method. The results indicate that the use of furfural creates favourable conditions for niobium and tantalum separation. The purest tantalum is obtained at concentrations of sulphuric acid 600 k/l, hydrofluoric acid 4.6% and ammonium fluoride 30 g/l. To obtain pure niobium the acid concentrations remain the same but the quantity of ammonium fluoride is doubled. The fluoride ion concentration has a significant effect on the completeness of niobium and tantalum separation. The variation coefficient for the niobium determination is 14%, for the tantalum determination 1O% (author)

Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis

International Nuclear Information System (INIS)

Hartner, Sonja; Schulz, Christof; Wiggers, Hartmut; Ali, Moazzam; Winterer, Markus

2009-01-01

Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis.

Science.gov (United States)

Hartner, Sonja; Ali, Moazzam; Schulz, Christof; Winterer, Markus; Wiggers, Hartmut

2009-11-04

Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

Doping profile measurements in silicon using terahertz time domain spectroscopy (THz-TDS) via electrochemical anodic oxidation

Science.gov (United States)

Tulsyan, Gaurav

Doping profiles are engineered to manipulate device properties and to determine electrical performances of microelectronic devices frequently. To support engineering studies afterward, essential information is usually required from physically characterized doping profiles. Secondary Ion Mass Spectrometry (SIMS), Spreading Resistance Profiling (SRP) and Electrochemical Capacitance Voltage (ECV) profiling are standard techniques for now to map profile. SIMS yields a chemical doping profile via ion sputtering process and owns a better resolution, whereas ECV and SRP produce an electrical doping profile detecting free carriers in microelectronic devices. The major difference between electrical and chemical doping profiles is at heavily doped regions greater than 1020 atoms/cm3. At the profile region over the solubility limit, inactive dopants induce a flat plateau and detected by electrical measurements only. Destructive techniques are usually designed as stand-alone systems to study impurities. For an in-situ process control purpose, non-contact methods, such as ellipsometry and non-contact capacitance voltage (CV) techniques are current under development. In this theses work, terahertz time domain spectroscopy (THz-TDS) is utilized to achieve electrical doping profile in both destructive and non-contact manners. In recent years the Terahertz group at Rochester Institute Technology developed several techniques that use terahertz pulses to non-destructively map doping profiles. In this thesis, we study a destructive but potentially higher resolution version of the terahertz based approach to map the profile of activated dopants and augment the non-destructive approaches already developed. The basic idea of the profile mapping approach developed in this MS thesis is to anodize, and thus oxidize to silicon dioxide, thin layers (down to below 10 nm) of the wafer with the doping profile to be mapped. Since the dopants atoms and any free carriers in the silicon oxide thin

Catalytic activity of metall-like carbides in carbon oxide oxidation reaction

International Nuclear Information System (INIS)

Kharlamov, A.I.; Kosolapova, T.Ya.; Rafal, A.N.; Kirillova, N.V.

1980-01-01

Kinetics of carbon oxide oxidation upon carbides of hafnium, niobium, tantalum, molybdenum, zirconium and chromium is studied. Probable mechanism of the catalysts action is suggested. The established character of the change of the carbide catalytic activity is explained by the change of d-electron contribution to the metal-metal interaction

HIP (hot isostatic pressing) sintering of Tantalum (Ta) and tantalum carbide (TaC) powder mixture: relations between microstructure and properties

International Nuclear Information System (INIS)

Valin, F.; Schnedecker, M.

1994-01-01

HIP sintering at 1630 C and 195 MPa, during 2 hours, can be used for complete densification of mixtures of commercial tantalum carbide and tantalum powders. HIPed material properties are depending upon initial compositions. For C/Ta ratios inferior to 80%, the monocarbide structure is preserved. A partial ordering of the carbon vacancies will result, for TaC(0.80), in microhardness maximization. The microstructurally homogenous TaC(0.45) shows an excellent toughness. 2 figs., 2 refs

Electro-catalytic oxidation of reactive Orange 107 using cerium doped oxides of Nd3+ nanoparticle

International Nuclear Information System (INIS)

Rajkumar, K.; Muthukumar, M.; Mangalaraja, R.V.

2011-01-01

A new rare earth doped cerium oxide powder was used as a catalyst to investigate the removal of colour and TOC from simulated wastewater of Reactive Orange 107. The electro oxidation process was carried out in the reactor in presence of an electrolyte NaCl. Graphite electrode was used as anode and cathode and electrolysis were carried out at a current density of 34.96 mAcm -2 with a catalyst concentration of 0.05g L -1 . In order to find the efficiency of nanocatalyst, experiments were also conducted without catalyst. From the experiment, it was found that complete colour removal was achieved on electrocatalytic oxidation as well as electro oxidation. When comparing the above processes, catalytic oxidation shows more efficient than electro oxidation. With respect to the degradation of the dye, catalytic oxidation shows more TOC removal than the oxidation taken place without catalyst. It infers that even though the electro-catalytic oxidation process achieves complete decolouration but it does not achieve complete mineralisation. The FTIR and GCMS studies confirmed the formation of by-products. (author)

Preparation of potassium tantalum fluoride from tantalum hydroxide

International Nuclear Information System (INIS)

Silva, F.T. da; Espinola, A.; Dutra, A.J.B.

1987-01-01

Potassium tantalum fluoride (K 2 TaF 7 ) is an intermediary product in the processing of tantaliferous materials; it is the basic raw material for both reduction processes in use presently: reduction by metallic sodium and electrolysis in molten halides. It is normally obtained from a fluorotantalic acid solution to which potassium ions are added the precipitation of white acicular crystals of K 2 TaF 7 . The conditions for precipitation and recrystallization were studied, and crystal characterization were done by scanning electron microscopy, X-ray diffraction and thermogravimetric and thermodifferential analyses. (Author) [pt

Mineral-deposit model for lithium-cesium-tantalum pegmatites

Science.gov (United States)

Bradley, Dwight C.; McCauley, Andrew D.; Stillings, Lisa L.

2017-06-20

Lithium-cesium-tantalum (LCT) pegmatites comprise a compositionally defined subset of granitic pegmatites. The major minerals are quartz, potassium feldspar, albite, and muscovite; typical accessory minerals include biotite, garnet, tourmaline, and apatite. The principal lithium ore minerals are spodumene, petalite, and lepidolite; cesium mostly comes from pollucite; and tantalum mostly comes from columbite-tantalite. Tin ore as cassiterite and beryllium ore as beryl also occur in LCT pegmatites, as do a number of gemstones and high-value museum specimens of rare minerals. Individual crystals in LCT pegmatites can be enormous: the largest spodumene was 14 meters long, the largest beryl was 18 meters long, and the largest potassium feldspar was 49 meters long.Lithium-cesium-tantalum pegmatites account for about one-fourth of the world’s lithium production, most of the tantalum production, and all of the cesium production. Giant deposits include Tanco in Canada, Greenbushes in Australia, and Bikita in Zimbabwe. The largest lithium pegmatite in the United States, at King’s Mountain, North Carolina, is no longer being mined although large reserves of lithium remain. Depending on size and attitude of the pegmatite, a variety of mining techniques are used, including artisanal surface mining, open-pit surface mining, small underground workings, and large underground operations using room-and-pillar design. In favorable circumstances, what would otherwise be gangue minerals (quartz, potassium feldspar, albite, and muscovite) can be mined along with lithium and (or) tantalum as coproducts.Most LCT pegmatites are hosted in metamorphosed supracrustal rocks in the upper greenschist to lower amphibolite facies. Lithium-cesium-tantalum pegmatite intrusions generally are emplaced late during orogeny, with emplacement being controlled by pre-existing structures. Typically, they crop out near evolved, peraluminous granites and leucogranites from which they are inferred to be

Studies on the optoelectronic properties of the thermally evaporated tin-doped indium oxide nanostructures

Energy Technology Data Exchange (ETDEWEB)

Pan, Ko-Ying [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan, ROC (China); Lin, Liang-Da [Institute of Materials Science and Nanotechnology, Chinese Culture University, Taipei 111, Taiwan, ROC (China); Chang, Li-Wei [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan, ROC (China); Shih, Han C., E-mail: hcshih@mx.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan, ROC (China); Institute of Materials Science and Nanotechnology, Chinese Culture University, Taipei 111, Taiwan, ROC (China)

2013-05-15

Indium oxide (In{sub 2}O{sub 3}) nanorods, nanotowers and tin-doped (Sn:In = 1:100) indium oxide (ITO) nanorods have been fabricated by thermal evaporation. The morphology, microstructure and chemical composition of these three nanoproducts are characterized by FE-SEM, HRTEM and XPS. To further investigate the optoelectronic properties, the I–V curves and cathodoluminescence (CL) spectra are measured. The electrical resistivity of In{sub 2}O{sub 3} nanorods, nanotowers and ITO nanorods are 1.32 kΩ, 0.65 kΩ and 0.063 kΩ, respectively. CL spectra of these three nanoproducts clearly indicate that tin-doped (Sn:In = 1:100) indium oxide (ITO) nanorods cause a blue shift. No doubt ITO nanorods obtain the highest performance among these three nanoproducts, and this also means that Sn-doped In{sub 2}O{sub 3} nanostructures would be the best way to enhance the optoelectronic properties. Additionally, the growing mechanism and the optoelectronic properties of these three nanostructures are discussed. This study is beneficial to the applications of In{sub 2}O{sub 3} nanorods, nanotowers and ITO nanorods in optoelectronic nanodevices.

Cobalt Oxide on N-Doped Carbon for 1-Butene Oligomerization to Produce Linear Octenes

Energy Technology Data Exchange (ETDEWEB)

Zhao, Dongting [Department; Xu, Zhuoran [Department; Chada, Joseph P. [Department; Carrero, Carlos A. [Department; Rosenfeld, Devon C. [The Dow Chemical Company, 2301 N. Brazosport Boulevard, Freeport, Texas 77541-3257, United States; Rogers, Jessica L. [The Dow Chemical Company, 2301 N. Brazosport Boulevard, Freeport, Texas 77541-3257, United States; Hermans, Ive [Department; Huber, George W. [Department

2017-10-02

Cobalt oxide supported on N-doped carbon catalysts were investigated for 1-butene oligomerization. The materials were synthesized by treating activated carbon with nitric acid and subsequently with NH3 at 200, 400, 600, and 800 °C, followed by impregnation with cobalt. The 1-butene oligomerization selectivity increased with ammonia treatment temperature of the carbon support. The oligomerization selectivity of cobalt oxide on N-doped carbon synthesized at 800 °C (800A-CoOx/N-C) is 2.6 times higher than previously reported cobalt oxide on N-doped carbon synthesized with NH4OH (2A-CoOx/N-C). Over 70% of the butene dimers were linear C8 olefins for all catalysts. The oligomerization selectivity increased with 1-butene conversion. The catalysts were characterized by elemental analysis, N2 adsorption, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS). The nitrogen content of the catalysts increases with ammonia treatment temperature as confirmed by elemental analysis. The surface content of pyridinic nitrogen with a binding energy of 398.4 ± 0.1 eV increased with ammonia treatment temperature as evidenced by deconvolution of N 1s XPS spectra.

Corrosion evaluation of zirconium doped oxide coatings on aluminum formed by plasma electrolytic oxidation.

Science.gov (United States)

Bajat, Jelena; Mišković-Stanković, Vesna; Vasilić, Rastko; Stojadinović, Stevan

2014-01-01

The plasma electrolytic oxidation (PEO) of aluminum in sodium tungstate (Na(2)WO(4) · (2)H(2)O) and Na(2)WO(4) · (2)H(2)O doped with Zr was analyzed in order to obtain oxide coatings with improved corrosion resistance. The influence of current density in PEO process and anodization time was investigated, as well as the influence of Zr, with the aim to find out how they affect the chemical content, morphology, surface roughness, and corrosion stability of oxide coatings. It was shown that the presence of Zr increases the corrosion stability of oxide coatings for all investigated PEO times. Evolution of EIS spectra during the exposure to 3% NaCl, as a strong corrosive agent, indicated the highest corrosion stability for PEO coating formed on aluminum at 70 mA/cm(2) for 2 min in a zirconium containing electrolyte.

Bronchography by tantalum aerosols, an experimental investigation of lung clearance and retention

International Nuclear Information System (INIS)

Causse, Andre.

1974-01-01

Lung clearance of tantalum used as contrast medium has been studied in three animal species: rat, monkey and cat. In rats and monkeys, 80 to 90 percent of the inhaled tantalum was removed with a half life of 10 to 30 hr, but the residual fraction was removed with a half life longer than 100 days; consequently persistent roentgenographic pictures could be observed. These results were in accordance with those obtained by other authors studying dogs and men (accidental inhalation of radioactive tantalum). In cats, about 98 percent was removed with a half life of 15 hr and the remaining fraction with a half life of 18 days. In the three species, the physiological lung clearance mechanisms did not seem disturbed. Microscopic examination showed the peribronchiolar localisation of remaining tantalum in rats and monkeys, with proliferation of granulomes and fibrotic reaction. These results must induce to the greatest care when using tantalum in man in order to outline peripheral airways [fr

Graphene Oxide-Based Q-Switched Erbium-Doped Fiber Laser

International Nuclear Information System (INIS)

Yap, Y. K.; Harun, S. W.; Ahmad, H.; Huang, N. M.

2013-01-01

We demonstrate a pulsed ring erbium-doped fiber laser based on graphene oxide (GO), employing a simplified Hummer's method to synthesize the GO via chemical oxidation of graphite flakes at room temperature. By dipping a fiber ferrule end face onto the GO suspension, GO is successfully coated onto the end face, making it a simple saturable absorption device. A stable Q-switched pulsed fiber laser is achieved with a low pump threshold of 9.5 mW at 980 nm. The pulse repetition rate ranges from 16.0 to 57.0 kHz. The pulse width and the pulse energy are studied and discussed

Photo field emission spectroscopy of the tantalum band structure

International Nuclear Information System (INIS)

Kleint, Ch.; Radon, T.

1978-01-01

Photo field emission (PFE) currents of clean and barium covered tantalum tips have been measured with single lines of the mercury arc spectrum and phase-sensitive detection. Field strength and work function were determined from Fowler-Nordheim plots of the FE currents. Shoulders in the PFE current-voltage characteristics could be correlated to transitions in the band structure of tantalum according to a recently proposed two-step PFE model. A comparison with the relativistic calculations of Mattheiss and the nonrelativistic bands of Petroff and Viswanathan shows that Mattheiss' bands are more appropriate. Beside direct transitions several nondirect transitions from the different features composing the upper two density of states maxima below the Fermi edge of tantalum have been found. (Auth.)

An anode with aluminum doped on zinc oxide thin films for organic light emitting devices

International Nuclear Information System (INIS)

Xu Denghui; Deng Zhenbo; Xu Ying; Xiao Jing; Liang Chunjun; Pei Zhiliang; Sun Chao

2005-01-01

Doped zinc oxides are attractive alternative materials as transparent conducting electrode because they are nontoxic and inexpensive compared with indium tin oxide (ITO). Transparent conducting aluminum-doped zinc oxide (AZO) thin films have been deposited on glass substrates by DC reactive magnetron sputtering method. Films were deposited at a substrate temperature of 150-bar o C in 0.03 Pa of oxygen pressure. The electrical and optical properties of the film with the Al-doping amount of 2 wt% in the target were investigated. For the 300-nm thick AZO film deposited using a ZnO target with an Al content of 2 wt%, the lowest electrical resistivity was 4x10 -4 Ωcm and the average transmission in the visible range 400-700 nm was more than 90%. The AZO film was used as an anode contact to fabricate organic light-emitting diodes. The device performance was measured and the current efficiency of 2.9 cd/A was measured at a current density of 100 mA/cm 2

Well-dispersed NiO nanoparticles supported on nitrogen-doped carbon nanotube for methanol electrocatalytic oxidation in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Wang, Pengcheng; Zhou, Yingke, E-mail: zhouyk888@hotmail.com; Hu, Min; Chen, Jian

2017-01-15

Highlights: • Nitrogen-doped carbon nanotube supporting ultrafine NiO nanoparticles with high dispersity are facile synthesized. • The nitrogen doping, calcination temperature and NiO loading present great effects on the catalyst morphology, structure and electrochemical performance. • NiO-NCNT-3x-400 demonstrates remarkable catalytic activity and stability for the methanol electrolytic oxidation reaction. - Abstract: Nitrogen-doped carbon nanotube supporting NiO nanoparticles were synthesized by a chemical precipitation process coupled with subsequent calcination. The morphology and structure of the composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performance was evaluated using cyclic voltammetry and chronoamperometric technique. The effects of nitrogen doping, calcination temperature and content of NiO nanoparticles on the electrocatalytic activity toward methanol oxidation were systematically studied. The results show that the uniformly dispersed ultrafine NiO nanoparticles supported on nitrogen-doped carbon nanotube are obtained after calcination at 400 °C. The optimized composite catalysts present high electrocatalytic activity, fast charge-transfer process, excellent accessibility and stability for methanol oxidation reaction, which are promising for application in the alkaline direct methanol fuel cells.

Tantalum coating on TiO2 nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

International Nuclear Information System (INIS)

Frandsen, Christine J.; Brammer, Karla S.; Noh, Kunbae; Johnston, Gary; Jin, Sungho

2014-01-01

Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO 2 ) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO 2 nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO 2 nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO 2 nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface

Effect of barium doping on the physical properties of zinc oxide ...

Indian Academy of Sciences (India)

2015-11-27

Home; Journals; Pramana – Journal of Physics; Volume 87; Issue 1. Effect of barium doping on the physical properties of zinc oxide ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015. Guest Editors: ...

Thermoelectric Properties of Hot-Pressed and PECS-Sintered Magnesium-Doped Copper Aluminum Oxide

Science.gov (United States)

Liu, Chang; Morelli, Donald T.

2011-05-01

Copper aluminum oxide (CuAlO2) is considered as a potential candidate for thermoelectric applications. Partially magnesium-doped CuAlO2 bulk pellets were fabricated using solid-state reactions, hot-pressing, and pulsed electric current sintering (PECS) techniques. X-ray diffraction and scanning electron microscopy were adopted for structural analysis. High-temperature transport property measurements were performed on hot-pressed samples. Electrical conductivity increased with Mg doping before secondary phases became significant, while the Seebeck coefficient displayed the opposite trend. Thermal conductivity was consistently reduced as the Mg concentration increased. Effects of Mg doping, preparation conditions, and future modification on this material's properties are discussed.

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

International Nuclear Information System (INIS)

Alver, Ü.; Tanrıverdi, A.

2016-01-01

Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Alver, Ü., E-mail: ualver@ktu.edu.tr [Karadeniz Technical University, Dept. of Metallurgical and Materials Engineering, 61080 Trabzon (Turkey); Tanrıverdi, A. [Kahramanmaras Sutcu Imam University, Department of Physics, 46100 Kahramanmaraş (Turkey)

2016-08-15

Highlights: • Boron doped ZnO particles are fabricated and embedded into reduced graphene oxide (RGO) by hydrothermal method. • RGO/ZnO:B composites are used as electrodes for supercapacitors. • Presence of boron in RGO/ZnO composites caused increasing the stability and specific capacitance of electrodes. - Abstract: In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Development of technology of high-purity compounds of tantalum and niobium with octanol use

International Nuclear Information System (INIS)

Majorov, V.G.; Nikolaev, A.I.; Kopkov, V.K.; Baklanova, I.V.; Safonova, L.A.

2001-01-01

Effect of composition of solutions and extractant expenditure on tantalum and niobium distribution during extraction by octanol and purification of tantalum and niobium extracts from impurities was studied. Scheme was developed according to which samples of high-pure tantalum and niobium pentaoxides were prepared [ru

Development of Doped Microcrystalline Silicon Oxide and its Application to Thin‑Film Silicon Solar Cells

NARCIS (Netherlands)

Lambertz, A.

2015-01-01

The aim of the present study is the development of doped microcrystalline silicon oxide (µc‑SiOx:H) alloys and its application in thin‑film silicon solar cells. The doped µc‑SiOx:H material was prepared from carbon dioxide (CO2), silane (SiH4), hydrogen (H2) gas mixtures using plasma enhanced

The Chemical Vapour Deposition of Tantalum - in long narrow channels

DEFF Research Database (Denmark)

Mugabi, James Atwoki

protective layers of tantalum because of the process’ ability to coat complex geometries and its relative ease to control. This work focuses on studying the CVD of tantalum in long narrow channels with the view that the knowledge gained during the project can be used to optimise the commercial coating...... and that there is a major change in morphology between 850 – 900 °C. The effects of system pressure and precursor partial pressure are also studied, and were found to have relevance to the tantalum distribution along the substrates but little effect on the structural morphology of the deposited layer. In the implemented...

Role of Zn doping in oxidative stress mediated cytotoxicity of TiO2 nanoparticles in human breast cancer MCF-7 cells

Science.gov (United States)

Ahamed, Maqusood; Khan, M. A. Majeed; Akhtar, Mohd Javed; Alhadlaq, Hisham A.; Alshamsan, Aws

2016-07-01

We investigated the effect of Zn-doping on structural and optical properties as well as cellular response of TiO2 nanoparticles (NPs) in human breast cancer MCF-7 cells. A library of Zn-doped (1-10 at wt%) TiO2 NPs was prepared. Characterization data indicated that dopant Zn was incorporated into the lattice of host TiO2. The average particle size of TiO2 NPs was decreases (38 to 28 nm) while the band gap energy was increases (3.35 eV-3.85 eV) with increasing the amount of Zn-doping. Cellular data demonstrated that Zn-doped TiO2 NPs induced cytotoxicity (cell viability reduction, membrane damage and cell cycle arrest) and oxidative stress (reactive oxygen species generation & glutathione depletion) in MCF-7 cells and toxic intensity was increases with increasing the concentration of Zn-doping. Molecular data revealed that Zn-doped TiO2 NPs induced the down-regulation of super oxide dismutase gene while the up-regulation of heme oxygenase-1 gene in MCF-7 cells. Cytotoxicity induced by Zn-doped TiO2 NPs was efficiently prevented by N-acetyl-cysteine suggesting that oxidative stress might be the primarily cause of toxicity. In conclusion, our data indicated that Zn-doping decreases the particle size and increases the band gap energy as well the oxidative stress-mediated toxicity of TiO2 NPs in MCF-7 cells.

Iron Oxide Doped Alumina-Zirconia Nanoparticle Synthesis by Liquid Flame Spray from Metal Organic Precursors

Directory of Open Access Journals (Sweden)

Juha-Pekka Nikkanen

2008-01-01

Full Text Available The liquid flame spray (LFS method was used to make iron oxide doped alumina-zirconia nanoparticles. Nanoparticles were generated using a turbulent, high-temperature (Tmax⁡∼3000 K H2-O2 flame. The precursors were aluminium-isopropoxide, zirconium-n-propoxide, and ferrocene in xylene solution. The solution was atomized into micron-sized droplets by high velocity H2 flow and introduced into the flame where nanoparticles were formed. The particle morphology, size, phase, and chemical composition were determined by TEM, XRD, XPS, and N2-adsorption measurements. The collected particulate material consists of micron-sized aggregates with nanosized primary particles. In both doped and undoped samples, tetragonal phase of zirconia was detected in room temperature while alumina was found to be noncrystalline. In the doped powder, Fe was oxidized to Fe2O3. The primary particle size of collected sample was approximately from 6 nm to 40 nm. Doping was observed to increase the specific surface area of the powder from 39 m2/g to 47 m2/g.

Synthesis and characterization of tantalum organometallic complexes. Catalytic activity for olefins

International Nuclear Information System (INIS)

Baley, A.S.

1990-11-01

Synthesis of monoaryloxy (alcoxy) neopentyl compounds is investigated. The tantalum-oxygen bond is formed by two parallel ways from TaCl 5 or TaR 2 Cl 3 with R = neopentyl and the tantalum carbon bond from a neopentyl derivative of the main series. Some compounds were isolated and characterized by NMR, elemental analysis and sometimes X-ray structure, some others are characterized in solution only. Catalytic effect is tested by ethylene dimerization and olefin polymerization. Reactivity of tantalum aryloxy neopentyl in respect to complexing and chelating ligands is studied for preparation of neopentylidene complexes

Copper doping enhanced the oxidative stress-mediated cytotoxicity of TiO2 nanoparticles in A549 cells.

Science.gov (United States)

Ahmad, J; Siddiqui, M A; Akhtar, M J; Alhadlaq, H A; Alshamsan, A; Khan, S T; Wahab, R; Al-Khedhairy, A A; Al-Salim, A; Musarrat, J; Saquib, Q; Fareed, M; Ahamed, M

2018-05-01

Physicochemical properties of titanium dioxide nanoparticles (TiO 2 NPs) can be tuned by doping with metals or nonmetals. Copper (Cu) doping improved the photocatalytic behavior of TiO 2 NPs that can be applied in various fields such as environmental remediation and nanomedicine. However, interaction of Cu-doped TiO 2 NPs with human cells is scarce. This study was designed to explore the role of Cu doping in cytotoxic response of TiO 2 NPs in human lung epithelial (A549) cells. Characterization data demonstrated the presence of both TiO 2 and Cu in Cu-doped TiO 2 NPs with high-quality lattice fringes without any distortion. The size of Cu-doped TiO 2 NPs (24 nm) was lower than pure TiO 2 NPs (30 nm). Biological results showed that both pure and Cu-doped TiO 2 NPs induced cytotoxicity and oxidative stress in a dose-dependent manner. Low mitochondrial membrane potential and higher caspase-3 enzyme (apoptotic markers) activity were also observed in A549 cells exposed to pure and Cu-doped TiO 2 NPs. We further observed that cytotoxicity caused by Cu-doped TiO 2 NPs was higher than pure TiO 2 NPs. Moreover, antioxidant N-acetyl cysteine effectively prevented the reactive oxygen species generation, glutathione depletion, and cell viability reduction caused by Cu-doped TiO 2 NPs. This is the first report showing that Cu-doped TiO 2 NPs induced cytotoxicity and oxidative stress in A549 cells. This study warranted further research to explore the role of Cu doping in toxicity mechanisms of TiO 2 NPs.

Structural and optical properties of pure and copper doped zinc oxide nanoparticles

Science.gov (United States)

Sajjad, Muhammad; Ullah, Inam; Khan, M. I.; Khan, Jamshid; Khan, M. Yaqoob; Qureshi, Muhammad Tauseef

2018-06-01

Pure and copper-doped zinc oxide nanoparticles (NPs) have been synthesized via chemical co-precipitation method where hydrazine is used as reducing agent and aqueous extract of Euphorbia milii plant as capping agent. Main objectives of the reported work are to investigate the effect of copper doping on crystal structure of ZnO nanoparticles; to study the effect of copper doping on optical band gap of ZnO nanoparticles and photoluminescence (PL) study of pure and copper-doped ZnO nanoparticles. To achieve the aforementioned objectives, XRD and SEM tests were performed for the identification and confirmation of crystal structure and morphology of the prepared samples. From XRD data the average grain size for pure ZnO was observed to be 24.62 nm which was first decreased to 18.95 nm for 5 wt% Cu-doped sample and then it was found to increase up to 37.80 nm as the Cu doping was increased to 7 wt%. Optical band gap of pure and Cu-doped ZnO nanoparticles was calculated from diffuse reflectance spectroscopy (DRS) spectra and was found to decrease from 3.13 eV to 2.94 eV as the amount of Cu increases up to 7 wt%. In photoluminescence study, PL technique was used and enhanced visible spectrum was observed. For further characterization FT-IR and EDX tests were also carried out.

Additively manufactured porous tantalum implants

NARCIS (Netherlands)

Wauthle, Ruben; Van Der Stok, Johan; Yavari, Saber Amin; Van Humbeeck, Jan; Kruth, Jean Pierre; Zadpoor, Amir Abbas; Weinans, Harrie; Mulier, Michiel; Schrooten, Jan

2015-01-01

The medical device industry's interest in open porous, metallic biomaterials has increased in response to additive manufacturing techniques enabling the production of complex shapes that cannot be produced with conventional techniques. Tantalum is an important metal for medical devices because of

The evolution mechanism of the dislocation loops in irradiated lanthanum doped cerium oxide

International Nuclear Information System (INIS)

Miao, Yinbin; Aidhy, Dilpuneet; Chen, Wei-Ying; Mo, Kun; Oaks, Aaron; Wolf, Dieter; Stubbins, James F.

2014-01-01

Cerium dioxide, a non-radioactive surrogate of uranium dioxide, is useful for simulating the radiation responses of uranium dioxide and mixed oxide fuel (MOX). Controlled additions of lanthanum can also be used to form various levels of lattice oxide or anion vacancies. In previous transmission electron microscopy (TEM) experimental studies, the growth rate of dislocation loops in irradiated lanthanum doped ceria was reported to vary with lanthanum concentration. This work reports findings of the evolution mechanisms of the dislocation loops in cerium oxide with and without lanthanum dopants based on a combination of molecular statics and molecular dynamics simulations. These dislocation loops are found to be b=1/3〈111〉 interstitial type Frank loops. Calculations of the defect energy profiles of the dislocation loops with different structural configurations and radii reveal the basis for preference of nucleation as well as the driving force of growth. Frenkel pair evolution simulations and displacement cascade overlaps simulations were conducted for a variety of lanthanum doping conditions. The nucleation and growth processes of the Frank loop were found to be controlled by the mobility of cation interstitials, which is significantly influenced by the lanthanum doping concentration. Competition mechanisms coupled with the mobility of cation point defects were discovered, and can be used to explain the lanthanum effects observed in experiments

Influence of VB group doped TiO2 on photovoltaic performance of dye-sensitized solar cells

International Nuclear Information System (INIS)

Liu, Jia; Duan, Yandong; Zhou, Xiaowen; Lin, Yuan

2013-01-01

Dye-sensitized solar cell with V B group (vanadium (V), niobium (Nb) and tantalum (Ta)) doped TiO 2 prepared by hydrothermal method shows a higher photovoltaic efficiency compared with the undoped TiO 2 . All the V B doping shift the flat band potential positively and increase the doping density which is investigated by Mott–Schottky plot. The positive shift of flat band potential improves the driving force of injecting electron from the LUMO of dye to the conduction band of TiO 2 and the photocurrent. On the other hand, the increase of doping density accelerates transfer rate of electrons in TiO 2 than the un-doped, which is confirmed by intensity-modulated photocurrent. V-, Nb-, Ta-doped TiO 2 exhibited photovoltaic performance with 7.80%, 8.33%, 8.18%, respectively, compared with that of the cells based on pure TiO 2 (7.42%).

Compliance-Free, Digital SET and Analog RESET Synaptic Characteristics of Sub-Tantalum Oxide Based Neuromorphic Device.

Science.gov (United States)

Abbas, Yawar; Jeon, Yu-Rim; Sokolov, Andrey Sergeevich; Kim, Sohyeon; Ku, Boncheol; Choi, Changhwan

2018-01-19

A two terminal semiconducting device like a memristor is indispensable to emulate the function of synapse in the working memory. The analog switching characteristics of memristor play a vital role in the emulation of biological synapses. The application of consecutive voltage sweeps or pulses (action potentials) changes the conductivity of the memristor which is considered as the fundamental cause of the synaptic plasticity. In this study, a neuromorphic device using an in-situ growth of sub-tantalum oxide switching layer is fabricated, which exhibits the digital SET and analog RESET switching with an electroforming process without any compliance current (compliance free). The process of electroforming and SET is observed at the positive sweeps of +2.4 V and +0.86 V, respectively, while multilevel RESET is observed with the consecutive negative sweeps in the range of 0 V to -1.2 V. The movement of oxygen vacancies and gradual change in the anatomy of the filament is attributed to digital SET and analog RESET switching characteristics. For the Ti/Ta 2 O 3-x /Pt neuromorphic device, the Ti top and Pt bottom electrodes are considered as counterparts of the pre-synaptic input terminal and a post-synaptic output terminal, respectively.

Electrochemistry behavior of endogenous thiols on fluorine doped tin oxide electrodes

Energy Technology Data Exchange (ETDEWEB)

Rojas, Luciana; Molero, Leonard; Tapia, Ricardo A.; Rio, Rodrigo del; Valle, M. Angelica del; Antilen, Monica [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile); Armijo, Francisco, E-mail: jarmijom@uc.cl [Departamento de Quimica Inorganica, Facultad de Quimica, Pontificia Universidad Catolica de Chile, Av Vicuna Mackenna 4860, Casilla 306, Correo 22, Macul, Santiago (Chile)

2011-10-01

Highlights: > The first time that fluorine doped tin oxide electrodes are used for the electrooxidation of endogenous thiols. > Low potentials of electrooxidation were obtained for the different thiols. > The electrochemical behavior of thiols depends on the pH and the ionic electroactive species, the electrooxidation proceeds for a process of adsorption of electroactive species on FTO and high values the heterogeneous electron tranfer rate constant of the reaction were obtained. - Abstract: In this work the electrochemical behavior of different thiols on fluorine doped tin oxide (FTO) electrodes is reported. To this end, the mechanism of electrochemical oxidation of glutathione (GSH), cysteine (Cys), homocysteine (HCys) and acetyl-cysteine (ACys) at different pH was investigated. FTO showed electroactivity for the oxidation of the first three thiols at pH between 2.0 and 4.0, but under these conditions no acetyl-cysteine oxidation was observed on FTO. Voltammetric studies of the electro-oxidation of GSH, Cys and HCys showed peaks at about 0.35, 0.29, and 0.28 V at optimum pH 2.4, 2.8 and 3.4, respectively. In addition, this study demonstrated that GSH, Cys and HCys oxidation occurs when the zwitterion is the electro-active species that interact by adsorption on FTO electrodes. The overall reaction involves 4e{sup -}/4H{sup +} and 2e{sup -}/2H{sup +}, respectively, for HCys and for GSH and Cys and high heterogeneous electron transfer rate constants. Besides, the use of FTO for the determination of different thiols was evaluated. Experimental square wave voltammetry shows a linear current vs. concentrations response between 0.1 and 1.0 mM was found for HCys and GSH, indicating that these FTO electrodes are promising candidates for the efficient electrochemical determination of these endogenous thiols.

Nitrogen Doped Graphene Supported Pt Nanoflowers as Electrocatalysts for Oxidation of Formaldehyde.

Science.gov (United States)

Xie, Aijuan; Zhou, Wenting; Luo, Shiping; Chen, Yu; Zhou, Xiaoqing; Chao, Yao

2017-02-01

A facile Pt nanoflowers/nitrogen-doped graphene (PtNFs/NG) electrocatalyst was prepared via depositing Pt nanoflowers (PtNFs) onto the nitrogen-doped graphene (NG) matrix with urea as the nitrogen source and PtNFs/NG modified glassy carbon electrode (GCE) was prepared by electro-chemical method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscope, X-ray photoelectron spectroscopy (XPS) and Scanning electron microscope (SEM) were used to characterize the resulting composites. Also oxidation of formaldehyde on the resulting PtNFs/NG modified electrode was investigated. The influence of deposition time, electrodeposition potential and formaldehyde concentration on electrooxidation of formaldehyde was detected, the experimental results indicate the high performance of PtNFs/NG catalyst for formaldehyde oxidation is at electrodeposition time of 300 s with the applied potential of −0.3 V. Electrochemical process, electrocatalytic stability and chronoamperometry were also inspected, it was indicated that formalde-hyde oxidation reaction on the PtNFs/NG electrode is diffusion-controlled and PtNFs/NG exhibits a high catalytic activity, stability as well as excellent poisoning-tolerance towards formaldehyde oxidation, which is attributed to the synergistic effect of PtNFs and NG. It turns out that PtNFs/NG can be used in direct liquid-feed fuel cells as a promising alternative catalyst.

Influence of pentavalent dopant addition to polarization and bioactivity of hydroxyapatite

International Nuclear Information System (INIS)

Dhal, Jharana; Bose, Susmita; Bandyopadhyay, Amit

2013-01-01

Influence of pentavalent tantalum doping in bulk hydroxyapatite (HAp) ceramics has been investigated for polarizability and bioactivity. Phase analysis from X-ray diffraction measurement indicates that increasing dopant concentration decreased the amount of HAp phase and increased β-TCP and/or α-TCP phases during sintering at 1250 °C in a muffle furnace. Results from thermally stimulated depolarization current (TSDC) measurements showed that doping hindered charge storage ability in HAp ceramics, and doped samples stored fewer charge compared to pure HAp. However, doping enhanced wettability of HAp samples, which was improved further due to polarization. In vitro human osteoblast cell–material interaction study revealed an increase in bioactivity due to dopant addition and polarization compared to pure HAp. This increase in bioactivity was attributed to the increase in wettability due to surface charge and dopant addition. - Highlights: • Tantalum doping makes HAp unstable during sintering at 1250 °C and forms TCP. • Tantalum doping reduces charge storage ability of HAp ceramics. • Even with lower charge storage ability tantalum doping improves wettability. • Tantalum doping enhances bioactivity of calcium phosphate based sintered compacts

Tribological performance of polycrystalline tantalum-carbide-incorporated diamond films on silicon substrates

Science.gov (United States)

Ullah, Mahtab; Rana, Anwar Manzoor; Ahmed, E.; Malik, Abdul Sattar; Shah, Z. A.; Ahmad, Naseeb; Mehtab, Ujala; Raza, Rizwan

2018-05-01

Polycrystalline tantalum-carbide-incorporated diamond coatings have been made on unpolished side of Si (100) wafer by hot filament chemical vapor deposition process. Morphology of the coatings has been found to vary from (111) triangular-facetted to predominantly (111) square-faceted by increasing the concentration of tantalum carbide. The results have been compared to those of a diamond reference coating with no tantalum content. An increase in roughness has been observed with the increase of tantalum carbide (TaC) due to change in morphology of the diamond films. It is noticed that roughness of the coatings increases as grains become more square-faceted. It is found that diamond coatings involving tantalum carbide are not as resistant as diamond films with no TaC content and the coefficient of friction for such coatings with microcrystalline grains can be manipulated to 0·33 under high vacuum of 10-7 Torr. Such a low friction coefficient value enhances tribological behavior of unpolished Si substrates and can possibly be used in sliding applications.

Investigation of the Optoelectronic Properties of Ti-doped Indium Tin Oxide Thin Film.

Science.gov (United States)

Pu, Nen-Wen; Liu, Wei-Sheng; Cheng, Huai-Ming; Hu, Hung-Chun; Hsieh, Wei-Ting; Yu, Hau-Wei; Liang, Shih-Chang

2015-09-21

: In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO) thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The Ti-doped ITO thin films exhibited superior thin-film resistivity (1.5 × 10 - ⁴ Ω/cm), carrier concentration (4.1 × 10 21 cm - ³), carrier mobility (10 cm²/Vs), and mean visible-light transmittance (90%) at wavelengths of 400-800 nm at a deposition temperature of 400 °C. The superior carrier concentration of the Ti-doped ITO alloys (>10 21 cm - ³) with a high figure of merit (81.1 × 10 - ³ Ω - ¹) demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices.

Kinetic Study of the Chemical Vapor Deposition of Tantalum in Long Narrow Channels

DEFF Research Database (Denmark)

Mugabi, James Atwoki; Eriksen, Søren; Petrushina, Irina

2016-01-01

A kinetic study of the chemical vapor deposition of tantalum in long narrow channels is done to optimize the industrial process for the manufacture of tantalum coated plate heat exchangers. The developed model fits well at temperatures between 750 and 850 °C, and in the pressure range of25–990 mbar....... According to the model, the predominant tantalum growth species is TaCl3. The temperature is shown to have a pronounced effect onthe morphology and rate of deposition of the tantalum and an apparent change in deposition mechanism occurs between 850–900 °C, resulting in the deposition rate at 900 °C being...

Structural and optical studies of Mg doped nanoparticles of chromium oxide (Cr2O3) synthesized by co-precipitation method

Science.gov (United States)

Singh, Jarnail; Verma, Vikram; Kumar, Ravi

2018-04-01

We present here the synthesization, structural and optical studies of Mg doped nanoparticles of Chromium oxide (Cr2O3) prepared using co-precipitation method. These samples were characterized using powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV-Vis spectroscopy techniques. We have demonstrated that there is negligible change in optical band gap with the Mg doping. The prepared Cr2O3 nanoparticles are spherical in shape, but they are transformed into platelets when doped with Mg. The XRD studies reveal that the Mg doping in Cr2O3 doesn't affect the structure of Chromium oxide (Cr2O3).

An investigation of tantalum and niobium contents by nuclear technique

International Nuclear Information System (INIS)

Patmasiriwat, N.

1981-01-01

The objective of this experimental study was to find suitable nuclear techniques to determine the quantities of niobium and tantalum in columbite. The study has been performed by using radioisotope X-ray fluorescent technique (X RF) and neutron activation analysis (NAA). The results showed a good agreement between these two techniques. Nevertheless, with NAA, if there is uranium in the sample, the spectrum of niobium will be interfered. So practically, on the basis of accuracy and speed of determination, X-ray fluorescence is more suitable than NAA to determine the quantity of niobium while tantalum is preferable to use NAA. The detection limit of niobium and tantalum using the above techniques are 0.661% and 0.1 mg respectively

Sequential Electrodeposition of Platinum-Ruthenium at Boron-Doped Diamond Electrodes for Methanol Oxidation

Directory of Open Access Journals (Sweden)

Ileana González-González

2011-01-01

Full Text Available Sequential electrodeposition of Pt and Ru on boron-doped diamond (BDD films, in 0.5 M H2SO4 by cyclic voltammetry, has been prepared. The potential cycling, in the aqueous solutions of the respective metals, was between 0.00 and 1.00 V versus Ag/AgCl. The catalyst composites, Pt and PtRu, deposited on BDD film substrates, were tested for methanol oxidation. The modified diamond surfaces were also characterized by scanning electron microscopy-X-ray fluorescence-energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The scanning Auger electron spectroscopy mapping showed the ruthenium signal only in areas where platinum was electrodeposited. Ruthenium does not deposit on the oxidized diamond surface of the boron-doped diamond. Particles with 5–10% of ruthenium with respect to platinum exhibited better performance for methanol oxidation in terms of methanol oxidation peak current and chronoamperometric current stability. The electrogenerated •OH radicals on BDD may interact with Pt surface, participating in the methanol oxidation as shown in oxidation current and the shift in the peak position. The conductive diamond surface is a good candidate as the support for the platinum electrocatalyst, because it ensures catalytic activity, which compares with the used carbon, and higher stability under severe anodic and cathodic conditions.

Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

Science.gov (United States)

Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

2014-02-14

Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.

Boron-Doped Diamond Electrodes for the Electrochemical Oxidation and Cleavage of Peptides

NARCIS (Netherlands)

Roeser, Julien; Alting, Niels F. A.; Permentier, Hjalmar P.; Bruins, Andries P.; Bischoff, Rainer

2013-01-01

Electrochemical oxidation of peptides and proteins is traditionally performed on carbon-based electrodes. Adsorption caused by the affinity of hydrophobic and aromatic amino acids toward these surfaces leads to electrode fouling. We compared the performance of boron-doped diamond (BDD) and glassy

Tuning the Electrical and Thermal Conductivities of Thermoelectric Oxides through Impurity Doping

Science.gov (United States)

Torres Arango, Maria A.

Waste heat and thermal gradients available at power plants can be harvested to power wireless networks and sensors by using thermoelectric (TE) generators that directly transform temperature differentials into electrical power. Oxide materials are promising for TE applications in harsh industrial environments for waste heat recovery at high temperatures in air, because they are lightweight, cheaply produced, highly efficient, and stable at high temperatures in air. Ca3Co4O9(CCO) with layered structure is a promising p-type thermoelectric oxide with extrapolated ZT value of 0.87 in single crystal form [1]. However the ZT values for the polycrystalline ceramics remain low of ˜0.1-0.3. In this research, nanostructure engineering approaches including doping and addition of nanoinclusions were applied to the polycrystalline CCO ceramic to improve the energy conversion efficiency. Polycrystalline CCO samples with various Bi doping levels were prepared through the sol-gel chemical route synthesis of powders, pressing and sintering of the pellets. Microstructure features of Bi doped ceramic bulk samples such as porosity, development of crystal texture, grain boundary dislocations and segregation of Bi dopants at various grain boundaries are investigated from microns to atomic scale. The results of the present study show that the Bi-doping is affecting both the electrical conductivity and thermal conductivity simultaneously, and the optimum Bi doping level is strongly correlated with the microstructure and the processing conditions of the ceramic samples. At the optimum doping level and processing conditions of the ceramic samples, the Bi substitution of Ca results in the increase of the electrical conductivity, decrease of the thermal conductivity, and improvement of the crystal texture. The atomic resolution Scanning Transmission Electron Microscopy (STEM) Z-contrast imaging and the chemistry analysis also reveal the Bi-segregation at grain boundaries of CCO

Hydrogen adsorption on skeletal rhodium-tantalum electrodes-catalysts

International Nuclear Information System (INIS)

Tsinstevich, V.M.; Krejnina, N.M.

1975-01-01

Skeleton rhodium-tantalic catalyst electrodes with a tantalum mass percentage of 0 to 100 have been obtained by the methodology of Crupp and others. The hydrogen adsorption is studied through the method of removing the galvano-static and potentiodynamic curves of charging in sulfuric acid and potassium hydroxide. It has been discovered that the maximum adsorption ability relatively to the hydrogen can be observed in an alloy with a 5% tantalum contents. The energetic characteristics of the alloys are higher in alkali than in acid

Investigations of white light emitting europium doped zinc oxide nanoparticles

International Nuclear Information System (INIS)

Ashtaputre, S S; Nojima, A; Marathe, S K; Matsumura, D; Ohta, T; Tiwari, R; Dey, G K; Kulkarni, S K

2008-01-01

Europium doped zinc oxide nanoparticles have been synthesized using a chemical route. The amount of doped europium was varied which shows the changes in the photoluminescence (PL) intensity. The post synthesis annealing effect on the properties of ZnO nanoparticles has also been investigated. In general, PL is broad and a white light is emitted which originates from ZnO and the intra-4f transitions of Eu 3+ ions. The x-ray diffraction patterns do not show any Eu-related peaks for as-synthesized ZnO nanoparticles as well as for annealed samples. X-ray absorption spectroscopy reveals that europium ions are present on the surface of the core of ZnO and inside the shell of zinc hydroxide [Zn(OH 2 )] after annealing

Tantalum coating on TiO{sub 2} nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

Energy Technology Data Exchange (ETDEWEB)

Frandsen, Christine J.; Brammer, Karla S. [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Noh, Kunbae [Corporate Research Institute, Cheil Industries, Inc., Gocheon-Dong, Uiwang-Si, Gyeonggi-Do, 437-711 (Korea, Republic of); Johnston, Gary [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Jin, Sungho, E-mail: jin@ucsd.edu [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093 (United States)

2014-04-01

Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO{sub 2}) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO{sub 2} nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO{sub 2} nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO{sub 2} nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface.

Comparative study of zinc oxide and aluminum doped zinc oxide transparent thin films grown by direct current magnetron sputtering

International Nuclear Information System (INIS)

Suchea, M.; Christoulakis, S.; Katsarakis, N.; Kitsopoulos, T.; Kiriakidis, G.

2007-01-01

Pure and aluminum (Al) doped zinc oxide (ZnO and ZAO) thin films have been grown using direct current (dc) magnetron sputtering from pure metallic Zn and ceramic ZnO targets, as well as from Al-doped metallic ZnAl2at.% and ceramic ZnAl2at.%O targets at room temperature (RT). The effects of target composition on the film's surface topology, crystallinity, and optical transmission have been investigated for various oxygen partial pressures in the sputtering atmosphere. It has been shown that Al-doped ZnO films sputtered from either metallic or ceramic targets exhibit different surface morphology than the undoped ZnO films, while their preferential crystalline growth orientation revealed by X-ray diffraction remains always the (002). More significantly, Al-doping leads to a larger increase of the optical transmission and energy gap (E g ) of the metallic than of the ceramic target prepared films

High-temperature oxidation of ion-implanted tantalum

International Nuclear Information System (INIS)

Kaufmann, E.N.; Musket, R.G.; Truhan, J.J.; Grabowski, K.S.; Singer, I.L.; Gossett, C.R.

1982-01-01

The oxidation of ion-implanted Ta in two different high temperature regimes has been studied. Oxidations were carried out at 500 0 C in Ar/O 2 mixtures, where oxide growth is known to follow a parabolic rate law in initial stages, and at 1000 0 C in pure O 2 , where a linear-rate behavior obtains. Implanted species include Al, Ce, Cr, Li, Si and Zr at fluences of the order of 10 17 /cm 2 . Oxidized samples were studied using Rutherford backscattering, nuclear reaction analysis, Auger spectroscopy, secondary-ion mass spectroscopy, x-ray diffraction and optical microscopy. Significant differences among the specimens were noted after the milder 500 0 C treatment, specifically, in the amount of oxide formed, the degree of oxygen dissolution in the metal beneath the oxide, and in the redistribution behavior of the implanted solutes. Under the severe 1000 0 C treatment, indications of different solute distributions and of different optical features were found, whereas overall oxidation rate appeared to be unaffected by the presence of the solute. 7 figures

Standard specification for tantalum and tantalum alloy plate, sheet, and strip. ASTM standard

International Nuclear Information System (INIS)

1998-09-01

This specification is under the jurisdiction of ASTM Committee B-10 on Reactive and Refractory Metals and Alloys and is the direct responsibility of Subcommittee B10.03 on Niobium and Tantalum. Current edition approved May 10, 1998 and published September 1998. Originally published as B 708-82. Last previous edition was B 708-92

Microstructural and electrical characteristics of rare earth oxides doped ZnO varistor films

Science.gov (United States)

Jiao, Lei; Mei, Yunzhu; Xu, Dong; Zhong, Sujuan; Ma, Jia; Zhang, Lei; Bao, Li

2018-02-01

ZnO-Bi2O3 varistor films doped with two kinds of rare earth element oxides (Lu2O3 and Yb2O3) were prepared by the sol-gel method. The effects of Lu2O3/Yb2O3 doping on the microstructure and electrical characteristics of ZnO-Bi2O3 varistor films were investigated. All samples show a homogenized morphology and an improved nonlinear relationship between the electric field (E) and current density (I). Both Yb2O3 and Lu2O3 doping can decrease the grain size of ZnO-Bi2O3 varistor films and improve the electrical properties, which have a positive effect on the development of ZnO varistor ceramics. Yb2O3 doping significantly increases the dielectric constant at low frequency. 0.2 mol. % Yb2O3 doped ZnO-Bi2O3 varistor films exhibit the highest nonlinear coefficient (2.5) and the lowest leakage current (328 μA) among Lu2O3/Yb2O3 doped ZnO-Bi2O3 varistor films. Similarly, 0.1 mol. % Lu2O3 doping increases the nonlinear coefficient to 1.9 and decrease the leakage current to 462 μA.

Effect of sputtering parameters and substrate composition on the structure of tantalum thin films

Energy Technology Data Exchange (ETDEWEB)

Hallmann, Lubica, E-mail: lubica.hallmann@zzm.uzh.c [Clinic of Fixed and Removable Prosthodontics and Dental Material Science, Center of Dental Medicine, University of Zürich (Switzerland); Ulmer, Peter [Institute of Geochemistry and Petrology, ETH Zürich (Switzerland)

2013-10-01

The crystallographic properties of tantalum films deposited as a bioactive coating on Co–Cr–Mo and Ti–Al–Nb alloys have been investigated. The desired tough and ductile alpha phase of tantalum has been obtained by DC magnetron sputtering on Co–Cr–Mo and Ti–Al–Nb substrates. The thickness of the tantalum layer was between 20 and 600 nm. The crystallographic structure of tantalum thin film was dependent on the sputtering parameters such as DC power, bias voltage and gas impurities. Oxygen is an important factor for the stabilization of the tantalum alpha phase on Co–Cr–Mo substrate. The crystallographic structure and texture of tantalum thin films was found to be additionally dependent on the substrate composition. For Ti–Al–Nb substrate, oxygen content was not an important factor for the stabilization of the alpha phase. The observed shift of X-ray diffraction peaks to lower 2(θ) is an indication of stress evolving during the sputtering process and was dependent on bias voltage and oxygen content of the carrier gas.

Conducting metal oxide and metal nitride nanoparticles

Science.gov (United States)

DiSalvo, Jr., Francis J.; Subban, Chinmayee V.

2017-12-26

Conducting metal oxide and nitride nanoparticles that can be used in fuel cell applications. The metal oxide nanoparticles are comprised of for example, titanium, niobium, tantalum, tungsten and combinations thereof. The metal nitride nanoparticles are comprised of, for example, titanium, niobium, tantalum, tungsten, zirconium, and combinations thereof. The nanoparticles can be sintered to provide conducting porous agglomerates of the nanoparticles which can be used as a catalyst support in fuel cell applications. Further, platinum nanoparticles, for example, can be deposited on the agglomerates to provide a material that can be used as both an anode and a cathode catalyst support in a fuel cell.

Pd- and Ca-doped iron oxide for ethanol vapor sensing

International Nuclear Information System (INIS)

Neri, G.; Bonavita, A.; Ipsale, S.; Rizzo, G.; Baratto, C.; Faglia, G.; Sberveglieri, G.

2007-01-01

Iron oxide thin films doped with Ca and Pd, prepared by a liquid-phase deposition method (LPD) from aqueous solution, have been investigated as potential ethanol gas sensors. SEM and XRD analyses were used to characterize Fe 2 O 3 LPD films. Hematite (α-Fe 2 O 3 ), having an average crystallite size in the range between 20 and 30 nm, was the only crystalline phase detected on all undoped and doped films. The electrical response towards ethanol (100-500 ppm) has been studied in the temperature range of 300-500 deg. C. Both Ca and Pd promoters have shown a positive effect on the sensitivity of Fe 2 O 3 films at the lower temperature investigated, whereas at higher temperature the undoped Fe 2 O 3 film has shown better performances. The sensing properties of undoped and doped Fe 2 O 3 thin films towards different interfering gases like NO 2 , CO and NH 3 have been also investigated, showing that the selectivity to ethanol benefits of the Ca addition

Facile synthesis of antimony-doped tin oxide nanoparticles by a polymer-pyrolysis method

International Nuclear Information System (INIS)

Li, Yuan-Qing; Wang, Jian-Lei; Fu, Shao-Yun; Mei, Shi-Gang; Zhang, Jian-Min; Yong, Kang

2010-01-01

In this article, antimony-doped tin oxide (ATO) nanoparticles was synthesized by a facile polymer-pyrolysis method. The pyrolysis behaviors of the polymer precursors prepared via in situ polymerization of metal salts and acrylic acid were analyzed by simultaneous thermogravimetric and differential scanning calorimetry (TG-DSC). The structural and morphological characteristics of the products were studied by powder X-ray diffraction (XRD) and transmission electron microscope (TEM). The results reveal that the ATO nanoparticles calcined at 600 o C show good crystallinity with the cassiterite structure and cubic-spherical like morphology. The average particle size of ATO decreases from 200 to 15 nm as the Sb doping content increases from 5 mol% to 15 mol%. Electrical resistivity measurement shows that the resistivity for the 10-13 mol% Sb-doped SnO 2 nanoparticles is reduced by more than three orders compared with the pure SnO 2 nanoparticles. In addition, due to its versatility this polymer-pyrolysis method can be extended to facile synthesis of other doped n-type semiconductor, such as In, Ga, Al doped ZnO, Sn doped In 2 O 3 .

Reduction of a dimeric tantalum(III) compound in acetonitrile solution by pulse radiolysis

International Nuclear Information System (INIS)

Koulkes-Pujo, A.-M.; Le Motais, B.; Hubert-Pfalzgraf, L.G.

1986-01-01

The reduction of the compound [Ta 2 Cl 6 (4Me-py) 4 ] (4Me-py 4-methylpyridine), having a metal-metal double bond, has been achieved by pulse radiolysis in dry oxygen-free acetonitrile. The reduction occurs by CH 3 CN - which leads to a transient species assigned to a tantalum dimer in a 2.5 oxidation state. The spectrum of this species has been established. It decays by a first-order process to give a new transient species which in turn decays more slowly by a second-order reaction. (author)

Design and characterization of Ga-doped indium tin oxide films for pixel electrode in liquid crystal display

International Nuclear Information System (INIS)

Choi, J.H.; Kang, S.H.; Oh, H.S.; Yu, T.H.; Sohn, I.S.

2013-01-01

Indium tin oxide (ITO) thin films doped with various metal atoms were investigated in terms of phase transition behavior and electro-optical properties for the purpose of upgrading ITO and indium zinc oxide (IZO) films, commonly used for pixel electrodes in flat panel displays. We explored Ce, Mg, Zn, and Ga atoms as dopants to ITO by the co-sputtering technique, and Ga-doped ITO films (In:Sn:Ga = 87.4:6.7:5.9 at.%) showed the phase transition behavior at 210 °C within 20 min with high visible transmittance of 91% and low resistivity of 0.22 mΩ cm. The film also showed etching rate similar to amorphous ITO, and no etching residue on glass surfaces. These results were confirmed with the film formed from a single Ga-doped ITO target with slightly different compositions (In:Sn:Ga = 87:9:4 at.%). Compared to the ITO target, Ga-doped ITO target left 1/4 less nodules on the target surface after sputtering. These results suggest that Ga-doped ITO films could be an excellent alternative to ITO and IZO for pixel electrodes in thin film transistor liquid crystal display (TFT-LCD). - Highlights: ► We report Ga-doped In–Sn–O films for a pixel electrode in liquid crystal display. ► Ga-doped In–Sn–O films show phase transition behavior at 210 °C. ► Ga-doped In–Sn–O films show high wet etchability and low resistivity

Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides

Energy Technology Data Exchange (ETDEWEB)

Boltz, Janika

2011-12-12

Alternative transparent conductive oxides to tin doped indium oxide have been investigated. In this work, antimony doped tin oxide and niobium doped titanium oxide have been studied with the aim to prepare transparent and conductive films. Antimony doped tin oxide and niobium doped titanium oxide belong to different groups of oxides; tin oxide is a soft oxide, while titanium oxide is a hard oxide. Both oxides are isolating materials, in case the stoichiometry is SnO{sub 2} and TiO{sub 2}. In order to achieve transparent and conductive films free carriers have to be generated by oxygen vacancies, by metal ions at interstitial positions in the crystal lattice or by cation doping with Sb or Nb, respectively. Antimony doped tin oxide and niobium doped titanium oxide films have been prepared by reactive direct current magnetron sputtering (dc MS) from metallic targets. The process parameters and the doping concentration in the films have been varied. The films have been electrically, optically and structurally analysed in order to analyse the influence of the process parameters and the doping concentration on the film properties. Post-deposition treatments of the films have been performed in order to improve the film properties. For the deposition of transparent and conductive tin oxide, the dominant parameter during the deposition is the oxygen content in the sputtering gas. The Sb incorporation as doping atoms has a minor influence on the electrical, optical and structural properties. Within a narrow oxygen content in the sputtering gas highly transparent and conductive tin oxide films have been prepared. In this study, the lowest resistivity in the as deposited state is 2.9 m{omega} cm for undoped tin oxide without any postdeposition treatment. The minimum resistivity is related to a transition to crystalline films with the stoichiometry of SnO{sub 2}. At higher oxygen content the films turn out to have a higher resistivity due to an oxygen excess. After post

Investigation of the Optoelectronic Properties of Ti-doped Indium Tin Oxide Thin Film

Directory of Open Access Journals (Sweden)

Nen-Wen Pu

2015-09-01

Full Text Available : In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The Ti-doped ITO thin films exhibited superior thin-film resistivity (1.5 × 10−4 Ω/cm, carrier concentration (4.1 × 1021 cm−3, carrier mobility (10 cm2/Vs, and mean visible-light transmittance (90% at wavelengths of 400–800 nm at a deposition temperature of 400 °C. The superior carrier concentration of the Ti-doped ITO alloys (>1021 cm−3 with a high figure of merit (81.1 × 10−3 Ω−1 demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices.

Low Temperature Synthesis and Properties of Gadolinium-Doped Cerium Oxide Nanoparticles

DEFF Research Database (Denmark)

Machado, Marina F. S.; P. R. Moraes, Leticia; Monteiro, Natalia K.

2017-01-01

Gadolinium-doped cerium oxide (GDC) is an attractive ceramic material for solid oxide fuel cells (SOFCs) both as the electrolyte or in composite electrodes. The Ni/GDC cermet can be tuned as a catalytic layer, added to the conventional Ni/yttria-stabilized zirconia (YSZ), for the internal steam...... sintering temperature needed to obtain a fully dense ceramic body, which can result in undesired reactions with YSZ. In this study, a green chemistry route for the synthesis of 10 mol% GDC nanoparticles is proposed. Such a low temperature synthesis provides control over particle size and sinterability...

Thermochemistry of rare earth doped uranium oxides LnxU1-xO2-0.5x+y (Ln = La, Y, Nd)

Science.gov (United States)

Zhang, Lei; Navrotsky, Alexandra

2015-10-01

Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10-50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

Experimental lumbar spine fusion with novel tantalum-coated carbon fiber implant

DEFF Research Database (Denmark)

Li, Haisheng; Zou, Xuenong; Woo, Charlotte

2007-01-01

the possibility of coating a biocompatible metal layer on top of the carbon fiber material, to improve its biological performance. Tantalum was chosen because of its bone compatibility, based on our previous studies. A novel spinal fusion cage was fabricated by applying a thin tantalum coating on the surface...

Fabrication of nickel oxide and Ni-doped indium tin oxide thin films using pyrosol process

International Nuclear Information System (INIS)

Nakasa, Akihiko; Adachi, Mami; Usami, Hisanao; Suzuki, Eiji; Taniguchi, Yoshio

2006-01-01

Organic light emitting diodes (OLEDs) need indium tin oxide (ITO) anodes with highly smooth surface. The work function of ITO, about 4.8 eV, is generally rather lower than the optimum level for application to OLEDs. In this work, NiO was deposited by pyrosol process on pyrosol ITO film to increase the work function of the ITO for improving the performance of OLEDs. It was confirmed that NiO was successfully deposited on pyrosol ITO film and the NiO deposition increased the work function of pyrosol ITO, using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and atmospheric photoelectron spectroscopy. Furthermore, doping ITO with Ni succeeded in producing the Ni-doped ITO film with high work function and lower sheet resistance

Effect of Sr-doping of LaMnO3 spacer on modulation-doped two-dimensional electron gases at oxide interfaces

DEFF Research Database (Denmark)

Chen, Yunzhong; Gan, Yulin; Christensen, Dennis Valbjørn

2017-01-01

Modulation-doped oxide two-dimensional electron gas formed at the LaMnO3 (LMO) buffered disorderd-LaAlO3/SrTiO3 (d-LAO/LMO/STO) heterointerface provides new opportunities for electronics as well as quantum physics. Herein, we studied the dependence of Sr-doping of La1-xSrxMnO3 (LSMO, x = 0, 1/8, ...... of LSMO during the deposition of disordered LAO or that the energy levels of Mn 3d electrons at the interface of LSMO/STO are hardly varied even when changing the LSMO composition from LMO to SrMnO3....

Enhancing the water oxidation activity of Ni2P nanocatalysts by iron-doping and electrochemical activation

International Nuclear Information System (INIS)

Liu, Guang; He, Dongying; Yao, Rui; Zhao, Yong; Li, Jinping

2017-01-01

Highlights: •A sol-gel method for synthesis of Fe-doping Ni 2 P nanocatalysts was present. •Fe-doping Ni 2 P sample exhibited high OER activity after electrochemical activation. •In situ formed Fe-NiOOH layer on activated Fe-Ni 2 P provided more active OER sites. -- Abstract: In this work, we reported a facile and safe route for synthesis of Ni 2 P nanocatalysts by sol-gel method and demonstrated that the oxygen evolution reaction (OER) activity of Ni 2 P nanocatalysts can be dramatically enhanced by iron-doping and electrochemical activation. Compared with the fresh Fe-doped Ni 2 P nanocatalysts, a stable Fe-NiOOH layer was formed on the surface of Fe-doped Ni 2 P nanoparticles by electrochemical activation, thus promoting the charge transfer ability and surface electrochemically active sites generation for the electrochemical activated Fe-doped Ni 2 P nanocatalysts, ultimately accounting for the improvement of water oxidation activity, which was evidenced by cyclic voltammograms (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectra (XPS) as well as high-resolution transmission electron microscopy (HR-TEM) measurements. For water oxidation reaction in 1 M KOH solution, the electrochemical activated Fe-doped Ni 2 P nanocatalysts can attain 10 mA/cm 2 at an overpotential of 292 mV with Tafel slope of 50 mV/dec, which was also much better than that of individual Ni 2 P, Fe 2 P nanocatalysts as well as commercial RuO 2 electrocatalyst. Moreover, long-term stability performance by chronoamperometric and chronopotentiometric tests for the activated Fe-doped Ni 2 P nanocatalysts exhibited no obvious decline within 56 h. It was demonstrated that modulating the OER catalytic activity for metal phosphide by iron-doping and electrochemical activation may provide new opportunities and avenues to engineer high performance electrocatalysts for water splitting.

Power loss and energy density of the asymmetric ultracapacitor loaded with molybdenum doped manganese oxide

International Nuclear Information System (INIS)

Wang, Yue-Sheng; Tsai, Dah-Shyang; Chung, Wen-Hung; Syu, Yong-Sin; Huang, Ying-Sheng

2012-01-01

Highlights: ► Mo-doping (15 mol%) enhances capacitance and diminishes oxide resistance. ► Influences of Mo-doped MnO 2 are analyzed at the level of capacitor power and energy. ► Polarization loss of the asymmetric capacitor is more than that of the symmetric one. ► Pseudocapacitance benefit on energy is evaluated with power and current densities. - Abstract: Ultracapacitors of asymmetric configuration have been prepared with activated carbon (AC) and undoped or Mo-doped manganese oxide (MnO 2 ) in 1.0 M Na 2 SO 4 electrolyte. Phase analysis shows the AC powder, 1–15 μm in size, contains both disordered and graphitic structures, and the undoped and Mo-doped oxide powder, 0.05–0.20 μm in particle size, mainly involves amorphous MnO 2 and MoO 2 . CV results indicate the single electrode of AC plus 10 wt% Mo-doped MnO 2 (A9O M 1) is superior to the electrode with undoped MnO 2 or high content of doped MnO 2 , exhibiting features of double layer capacitance at high scan rate and pseudocapacitance characteristics at low scan rate. When assembled with a negative electrode of AC, the capacitor of positive A9O M 1 electrode demonstrates the least power loss among three asymmetric capacitors. This asymmetric capacitor also shows a higher capacitance than the symmetric AC capacitor when the current density is less than 8.0 A g −1 in 1.8 V potential window. But a higher electrode resistance of A9O M 1, in contrast with AC, compromises its capacitance plus. When the energy density of A9O M 1 asymmetric capacitor is compared with that of symmetric AC capacitor at the same power level, the capacitance benefit on energy density is restricted to current density ≤ 3.0 A g −1 .

Behaviour of tantalum- and ceramics implants in the organism

International Nuclear Information System (INIS)

Reich, M.

1987-01-01

Studies of human and animal tissues after the use of orthopaedic implants were carried out by means of instrumental neutron activation analysis (INAA), as well as studies on the corrosion behaviour of tantalum by means of tracer techniques. After the use of an Al 2 O 3 -ceramic-metal compound prosthesis of the hip joint samples from the joint capsule and the Fascia Lata of 9 patients were studied. The measured Al amounts in the capsule tissues were greater than the normal values by up to 3 orders of magnitude. The corrosion experiment with tantalum was carried out in Ringer's solution as a model of body fluids. Local and systemic changes because of tantalum implants in animal experiments showed massive local stress of the contact tissue as a result of corrosion. Along with this, increased values of Ta were found in the spleen and the liver. (orig./RB) [de

Carbon monoxide and carbon dioxide interaction with tantalum

International Nuclear Information System (INIS)

Belov, V.D.; Ustinov, Yu.K.; Komar, A.P.

1978-01-01

The adsorption of carbon monoxide and carbon dioxide on tantalum and the dissolution of these gases in the adsorbent at T >= 300 K have been studied. The flash-filament method (FFM) in a monopole mass-spectrometer and a field emission microscopy was used in the same apparatus. Carbon monoxide and carbon dioxide dissociate on the tantalum surface, carbon monoxide being desorbed in both cases during the flash. The desorption curves of CO reveal three different binding states: two of them (α and β' 1 ) for the adsorbed particles whereas the high temperature desorption state relates to the adsorbate dissolved in the metal. For the β' 1 state of CO the activation energy, the pre-exponential factor and the kinetic order in the kinetic equation of desorption have been estimated. They turned out to be E = 110 kcal/mol, C = 3 X 10 12 sec -1 , and γ = 1. The activation energy of diffusion for CO in tantalum and the energy of outgassing for the metal were found to be 9.4 and 49 kcal/mole, respectively. (Auth.)

Carbon monoxide and carbon dioxide interaction with tantalum

Energy Technology Data Exchange (ETDEWEB)

Belov, V D; USTINOV, YU K; KOMAR, A P [AN SSSR, LENINGRAD. FIZIKO-TEKHNICHESKIJ INST.

1978-03-01

The adsorption of carbon monoxide and carbon dioxide on tantalum and the dissolution of these gases in the adsorbent at T >= 300 K have been studied. The flash-filament method (FFM) in a monopole mass-spectrometer and a field emission microscopy was used in the same apparatus. Carbon monoxide and carbon dioxide dissociate on the tantalum surface, carbon monoxide being desorbed in both cases during the flash. The desorption curves of CO reveal three different binding states: two of them (..cap alpha.. and ..beta..'/sub 1/) for the adsorbed particles whereas the high temperature desorption state relates to the adsorbate dissolved in the metal. For the ..beta..'/sub 1/ state of CO the activation energy, the pre-exponential factor and the kinetic order in the kinetic equation of desorption have been estimated. They turned out to be E = 110 kcal/mol, C = 3 X 10/sup 12/ sec/sup -1/, and ..gamma.. = 1. The activation energy of diffusion for CO in tantalum and the energy of outgassing for the metal were found to be 9.4 and 49 kcal/mole, respectively.

Study of defects and vacancies in structural properties of Mn, co-doped oxides: ZnO

Science.gov (United States)

Kumar, Harish; Kaushik, A.; Alvi, P. A.; Dalela, B.; Dalela, S.

2018-05-01

The paper deals with the Structural properties on Mn, Co doped oxides ZnO samples using XRD, Positron Annihilation Lifetime (PAL) Spectra and Raman Spectra. The Mn, Co doped ZnO samples crystallize in a wurtzite structure without any impurity phases in XRD Spectra. The defect state of these samples has been investigated by using positron annihilation lifetime (PAL) spectroscopy technique in which all the relevant lifetime parameters are measured for all the spectra. The results are explained in the direction of doping concentration in these samples in terms of defects structure on Zn lattice site VZn and oxygen defects Vo.

Niobium and tantalum

International Nuclear Information System (INIS)

Polupanova, L.I.; Volkova, G.A.

1983-01-01

General mineralogical-geochemical and analytical characteristics of niobium and tantalum are presented. Potentialities of any analytical methods for determining these elements in various geologic samples are estimated. The following specific techniques are described: neutron + activation determination of Ta, fluorescence X-radiometric determination of Nb and Ta, fluorescence X-ray spectral determination of Nb and Ta, spectrographic determination of Nb and Ta, gravimetric determination of Nb and Ta, their extraction-photometric determination with various reagents (crystal violet, rhodamine 6 Y, butylrhodamine B)

Luminescence properties of calcium doped zinc oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

El Mir, L., E-mail: Lassaad.ElMir@fsg.rnu.tn [Al Imam Mohammad Ibn Saud Islamic University (IMSIU), College of Sciences, Department of Physics, Riyadh 11623 (Saudi Arabia); Laboratory of Physics of Materials and Nanomaterials Applied at Environment (LaPhyMNE), Gabes University, Faculty of Sciences in Gabes, Gabes (Tunisia)

2017-06-15

Aerogel nanopowder of calcium-doped zinc oxide (ZnO:Ca) was synthesized by modified sol-gel method. In this process, hydrolyses was slowly released and followed by a thermal drying in supercritical conditions or ethyl alcohol. The obtained nanopowder was characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Cathodoluminescence (CL) and photoluminescence (PL). XRD data showed that Ca-doped ZnO sample has a hexagonal wurtzite structure with a slight distortion of ZnO lattice and no extra secondary phases, suggesting the substitution of Ca ions in the ZnO structure. SEM micrograph shows spherical microparticles having a rough porous fine-grained. From TEM micrograph, the samples are composed by single particles having an inhomogeneous size distribution, with most of them having a dimension in the range between 20 and 50 nm. This powder presents a strong photoluminescence band in the visible range. From photoluminescence excitation (PLE) the energy position of the obtained PL band depends on the wavelength of excitation. The luminescence results are also confirmed by cathodoluminescence technique and suggests the presence of photo-active centers in ZnO:Ca as deduced from new published works for visible photo-activated gas sensors and photo-catalysis of dyes degradation. We hope that this work provides some answers to the scientific community concerning the effect of doping in the creation of optical active centers in ZnO, promising for many technological applications.

Durability of adhesive bonds to uranium alloys, tungsten, tantalum, and thorium

International Nuclear Information System (INIS)

Childress, F.G.

1975-01-01

Long-term durability of epoxy bonds to alloys of uranium (U-Nb and Mulberry), nickel-plated uranium, thorium, tungsten, tantalum, tantalum--10 percent tungsten, and aluminum was evaluated. Significant strengths remain after ten years of aging; however, there is some evidence of bond deterioration with uranium alloys and thorium stored in ambient laboratory air

Optical and electrical properties of zinc oxide thin films with low resistivity via Li-N dual-acceptor doping

Energy Technology Data Exchange (ETDEWEB)

Zhang Daoli, E-mail: zhang_daoli@mail.hust.edu.cn [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Zhang Jianbing [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Guo Zhe [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Miao Xiangshui [Department of Electronic Science and Technology, Huazhong University of Science and Technology, No. 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China); Wuhan National Laboratory for Optoelectronics, 1037 Luoyu Road, Hongshan District, Wuhan City, Hubei Province 430074 (China)

2011-05-19

Highlights: > Zinc oxide films have been deposited on glass substrates by Li-N dual-acceptor doping method via a modified SILAR method. > The resistivity of ZnO film was found to be 1.04 {Omega} cm with a Hall mobility of 0.749 cm{sup 2} V{sup -1} s{sup -1}, carrier concentration of 8.02 x 1018 cm{sup -3}, and transmittance of about 80% in visible range showing good crystallinity with prior c-axis orientation. > A shallow acceptor level of 91 meV is identified from free-to-neutral-acceptor transitions. > Another deep level of 255 meV was ascribed to Li{sub Zn}-Li{sub i} complex. - Abstract: Zinc oxide thin films with low resistivity have been deposited on glass substrates by Li-N dual-acceptor doping method via a modified successive ionic layer adsorption and reaction process. The thin films were systematically characterized via scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, ultraviolet-visible spectrophotometry and fluorescence spectrophotometry. The resistivity of zinc oxide film was found to be 1.04 {Omega} cm with a Hall mobility of 0.749 cm{sup 2} V{sup -1} s{sup -1} and carrier concentration of 8.02 x 10{sup 18} cm{sup -3}. The Li-N dual-acceptor doped zinc oxide films showed good crystallinity with prior c-axis orientation, and high transmittance of about 80% in visible range. Moreover, the effects of Li doping level and other parameters on crystallinity, electrical and ultraviolet emission of zinc oxide films were investigated.

Microstructures and phase transformations in interstitial alloys of tantalum

International Nuclear Information System (INIS)

Dahmen, U.

1979-01-01

The analysis of microstructures, phases, and possible ordering of interstitial solute atoms is fundamental to an understanding of the properties of metal-interstitial alloys in general. As evidenced by the controversies on phase transformations in the particular system tantalum--carbon, our understanding of this class of alloys is inferior to our knowledge of substitutional metal alloys. An experimental clarification of these controversies in tantalum was made. Using advanced techniques of electron microscopy and ultrahigh vacuum techology, an understanding of the microstructures and phase transformations in dilute interstitial tantalum--carbon alloys is developed. Through a number of control experiments, the role and sources of interstitial contamination in the alloy preparation (and under operating conditions) are revealed. It is demonstrated that all previously published work on the dilute interstitially ordered phase Ta 64 C can be explained consistently in terms of ordering of the interstitial contaminants oxygen and hydrogen, leading to the formation of the phases Ta 12 O and Ta 2 H

Structural characterisation of oxygen diffusion hardened alpha-tantalum PVD-coatings on titanium.

Science.gov (United States)

Hertl, C; Koll, L; Schmitz, T; Werner, E; Gbureck, U

2014-08-01

Titanium substrates were coated with tantalum layers of 5 μm thickness using physical vapour deposition (PVD). The tantalum layers showed a (110)-preferred orientation. The coated samples were hardened by oxygen diffusion. Using X-ray diffraction the crystallographic structure of the tantalum coatings was characterised, comparing untreated and diffusion hardened specimen conditions. Oxygen depth profiles were determined by glow discharge spectrometry. The hardening effect of the heat treatment was examined by Vickers microhardness testing. The increase of surface hardness caused by oxygen diffusion was at least 50%. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and characterization of cobalt doped nickel oxide thin films by spray pyrolysis method

Science.gov (United States)

Sathisha, D.; Naik, K. Gopalakrishna

2018-05-01

Cobalt (Co) doped nickel oxide (NiO) thin films were deposited on glass substrates at a temperature of about 400 °C by spray pyrolysis method. The effect of Co doping concentration on structural, optical and compositional properties of NiO thin films was investigated. X-ray diffraction result shows that the deposited thin films are polycrystalline in nature. Surface morphologies of the deposited thin films were observed by FESEM and AFM. EDS spectra showed the incorporation of Co dopants in NiO thin films. Optical properties of the grown thin films were characterized by UV-visible spectroscopy. It was found that the optical band gap energy and transmittance of the films decrease with increasing Co doping concentration.

Electrochemical Capacitors Based on Aligned Carbon Nanotubes Directly Synthesized on Tantalum Substrates

International Nuclear Information System (INIS)

Kim, Byung Woo; Chung, Hae Geun; Kim, Woong; Min, Byoung Koun; Kim, Hong Gon

2010-01-01

We demonstrate that vertically aligned carbon nanotubes can be synthesized directly on tantalum substrate via waterassisted chemical vapor deposition and evaluate their properties as electrochemical capacitors. The mean diameter of the carbon nanotubes was 7.1 ± 1.5 nm, and 70% of them had double walls. The intensity ratio of G-band to D-band in Raman spectra was as high as 5, indicating good quality of the carbon nanotubes. Owing to the alignment and low equivalent series resistance, the carbon nanotube based supercapacitors showed good rate performance. Rectangular shape of cyclic voltammogram was maintained even at the scan rate of > 1 V/s in 1 M sulfuric acid aqueous solution. Specific capacitance was well-retained (∼94%) even when the discharging current density dramatically increased up to 145 A/g. Consequently, specific power as high as 60 kW/kg was obtained from as-grown carbon nanotubes in aqueous solution. Maximum specific energy of ∼20 Wh/kg was obtained when carbon nanotubes were electrochemically oxidized and operated in organic solution. Demonstration of direct synthesis of carbon nanotubes on tantalum current collectors and their applications as supercapacitors could be an invaluable basis for fabrication of high performance carbon nanotube supercapacitors

Iron carbide on titania surface modified with group VA oxides as Fischer-Tropsch catalysts

International Nuclear Information System (INIS)

Wachs, I.E.; Fiato, R.A.; Chersich, C.C.

1986-01-01

A catalyst is described comprising iron carbide supported on a surface modified titania wherein the support comprises an oxide of a metal selected form the group consisting of niobium, vanadium, tantalum or mixture thereof supported on the titania wherein at least a portion of the supported oxide of niobium, vanandium, tantalum or mixture is in a non-crystalline form. The amount of the supported oxide ranges from about 0.5 to 25 weight percent metal oxide on the titania support based on the total support composition and the catalyst contains at least about 2 milligrams of iron, calculated as Fe/sub 2/O/sub 3/, per square meter of support surface

Biological Response of Human Bone Marrow-Derived Mesenchymal Stem Cells to Commercial Tantalum Coatings with Microscale and Nanoscale Surface Topographies

Science.gov (United States)

Skoog, Shelby A.; Kumar, Girish; Goering, Peter L.; Williams, Brian; Stiglich, Jack; Narayan, Roger J.

2016-06-01

Tantalum is a promising orthopaedic implant coating material due to its robust mechanical properties, corrosion resistance, and excellent biocompatibility. Previous studies have demonstrated improved biocompatibility and tissue integration of surface-treated tantalum coatings compared to untreated tantalum. Surface modification of tantalum coatings with biologically inspired microscale and nanoscale features may be used to evoke optimal tissue responses. The goal of this study was to evaluate commercial tantalum coatings with nanoscale, sub-microscale, and microscale surface topographies for orthopaedic and dental applications using human bone marrow-derived mesenchymal stem cells (hBMSCs). Tantalum coatings with different microscale and nanoscale surface topographies were fabricated using a diffusion process or chemical vapor deposition. Biological evaluation of the tantalum coatings using hBMSCs showed that tantalum coatings promote cellular adhesion and growth. Furthermore, hBMSC adhesion to the tantalum coatings was dependent on surface feature characteristics, with enhanced cell adhesion on sub-micrometer- and micrometer-sized surface topographies compared to hybrid nano-/microstructures. Nanostructured and microstructured tantalum coatings should be further evaluated to optimize the surface coating features to promote osteogenesis and enhance osseointegration of tantalum-based orthopaedic implants.

The oxidation states of elements in pure and Ca-doped BiCuSeO thermoelectric oxides

International Nuclear Information System (INIS)

Hsiao, Chun-Lung; Qi, Xiaoding

2016-01-01

Bi 1−x Ca x CuSeO (x = 0–0.3) was synthesized at 650 °C in an air-tight system flowing with pure argon. The Ca doping resulted in an increase in the thermoelectric figure of merit (ZT) as the consequence of increased carrier concentration. X-ray photoelectron spectroscopy (XPS) was carried out to check the oxidation states in Bi 1−x Ca x CuSeO. The results indicated that in addition to the expected Bi 3+ and Cu 1+ , there existed Bi 2+ and Cu 2+ in the undoped BiCuSeO, whereas in the Ca-doped BiCuSeO, Bi 4+ , Cu 3+ and Cu 2+ were observed. The Ca dopant was confirmed to be in the 2+ oxidation state. Two broad peaks centered at 54.22 and 58.59 eV were recorded in the vicinity around the binding energy of Se 3d. The former is often observed in the Se-containing intermetallics while the latter is often found in the Se-containing oxides, indicating that along with the expected Se–Cu bonding, a bonding between Se and O may also exist. Based on the XPS results, the charge compensation mechanisms were proposed for Bi 1−x Ca x CuSeO, which may shed some light on the origins of charge carriers. BiCuSeO based oxides have recently be discovered to have a large ZT comparable to the best alloys currently in use, because of the large Seebeck coefficient and small thermal conductivity. However, their electrical conductivity is lower compared to the best thermoelectrics. This work may provide some hints for the further improvement of ZT in BiCuSeO based oxides. - Graphical abstract: The oxidation states, charge compensation mechanisms, and origins of charge carriers in Bi 1−x Ca x CuSeO thermoelectrics. Display Omitted

Defect-mediated magnetism of transition metal doped zinc oxide thin films

Science.gov (United States)

Roberts, Bradley Kirk

Magnetism in transition metal doped wide band-gap materials is of interest to further the fundamental science of materials and future spintronics applications. Large inter-dopant separations require mediation of ferromagnetism by some method; carrier-mediated mechanisms are typically applicable to dilute magnetic semiconductors with low Curie temperatures. Dilute magnetic oxides, commonly with poor conductivity and TC above room temperature, cannot be described within this theory. Recent experiment and theory developments suggest that ferromagnetic exchange in these materials can be mediated by defects. This research includes experimental results justifying and developing this approach. Thin films of Cr doped ZnO (band gap ˜3.3 eV) were deposited with several processing variations to enhance the effects of either 0-dimensional (vacancy, hydrogen-related defect) or two-dimensional defects (surface/interface) and thereby affect magnetism and conductivity. We observe surface magnetism in dielectric thin films of oxygen-saturated ZnO:Cr with spontaneous magnetic moment and conductance dropping approximately exponentially with increasing thickness. Uniform defect concentrations would not result in such magnetic ordering behavior indicating that magnetism is mediated either by surface defects or differing concentrations of point defects near the surface. Polarized neutron reflectivity profiling confirms a magnetically active region of ˜8 nm at the film surface. Hydrogen is notoriously present as a defect and carrier dopant in ZnO, and artificial introduction of hydrogen in dielectric ZnO:Cr films results in varying electronic and magnetic behavior. Free carriers introduced with hydrogen doping are not spin-polarized requiring an alternative explanation for ferromagnetism. We find from positron annihilation spectroscopy measurements that hydrogen doping increases the concentration of an altered VZn-related defect (a preliminary interpretation) throughout the film, which

The evaluation of hydroxyapatite (HA) coated and uncoated porous tantalum for biomedical material applications

International Nuclear Information System (INIS)

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-01-01

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications

Science.gov (United States)

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-04-01

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

Tuning the properties of visible-light-responsive tantalum (oxy)nitride photocatalysts by non-stoichiometric compositions: A first-principles viewpoint

KAUST Repository

Harb, Moussab

2014-01-01

Finding an ideal photocatalyst for achieving efficient overall water splitting still remains a great challenge. By applying accurate first-principles quantum calculations based on DFT with the screened non-local hybrid HSE06 functional, we bring rational insights at the atomic level into the influence of non-stoichiometric compositions on essential properties of tantalum (oxy)nitride compounds as visible-light-responsive photocatalysts for water splitting. Indeed, recent experiments show that such non-stoichiometry is inherent to the nitridation methods of tantalum oxide with unavoidable oxygen impurities. We considered here O-enriched Ta3N5 and N-enriched TaON materials. Although their structural parameters are found to be very similar to those of pure compounds and in good agreement with available experimental studies, their photocatalytic features for visible-light-driven overall water splitting reactions show different behaviors. Further partial nitration of TaON leads to a narrowed band gap, but partially oxidizing Ta3N5 causes only subtle changes in the gap. The main influence, however, is on the band edge positions relative to water redox potentials. The pure Ta3N5 is predicted to be a good candidate only for H+ reduction and H2 evolution, while the pure TaON is predicted to be a good candidate for water oxidation and O2 evolution. Non-stoichiometry has here a positive influence, since partially oxidized tantalum nitride, Ta(3-x)N(5-5x)O5x (for x ≥ 0.16) i.e. with a composition in between TaON and Ta3N5, reveals suitable band edge positions that correctly bracket the water redox potentials for visible-light-driven overall water splitting reactions. Among the various explored Ta(3-x)N(5-5x)O5x structures, a strong stabilization is obtained for the configuration displaying a strong interaction between the O-impurities and the created Ta-vacancies. In the lowest-energy structure, each created Ta-vacancy is surrounded by five O-impurity species substituting

Electron transport investigation of layered MoO3 oxides doped with different concentrations of Nb2O5 oxide

International Nuclear Information System (INIS)

Al-Khawaja, S.; Kasem, M.

2008-07-01

The dc and ac electric conductivity has been studied for numerous samples of molybdenum oxide MoO 3 doped with niobium oxide Nb 2 O 5 elaborated via the solid state reactions. By means of the electric resistivity and dielectricity curves obtained as a function of temperature, and according to the dopant concentration, the behaviour of these compounds has been allocated. Most of the investigated samples, which are insulating at room temperature, have been witnessed to exhibit simultaneously two different electric comportments; metallic and semiconducting within the range of low and high temperatures respectively, designated by a critical temperature related to the nature of the material. Both of these behaviours are attributed electronically to ionic conduction mechanism, occurring in the solid material formed upon doping with Nb 2 O 5 , which is utterly diffused into the layered structure of MoO 3 particularly for x≥40% concentrations and accompanied by relaxation in the dielectric function between 5 Hz and 13 M Hz.(Authors)

Structure and oxygen storage capacity of Pr-doped Ce0.26Zr0.74O2 mixed oxides

Institute of Scientific and Technical Information of China (English)

RAN Rui; WENG Duan; WU Xiaodong; FAN Jun; WANG Lei; WU Xiaodi

2011-01-01

Binary Ce-Zr (CZ),Pr-Zr (PZ) and ternary Ce-Zr-Pr (CZP) mixed oxides were prepared by an ammonia-aided co-precipitation method,and were aged in a steam/air flow at 1050 ℃.X-my diffraction (XRD),Raman spectra,X-photon spectra (XPS) and CO temperature programmed reduction (TPR) were carried out to characterize the micro-structure and reducibility of catalysts.The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas.The results showed that a pseudo cubic structure was formed for the Zr-rich ceria-zirconia mixed oxides with Pr doping.The insertion of Pr prevented the phase segregation of the mixed oxides during the hydrothermal ageing.The Pr doped samples showed better redox performances in comparison with CZ,and the sample doped with 5 wt.％ Pr showed the most remarkably promoted dynamic oxygen storage capacity.This phenomenon was closely related to both the reducibility and oxygen mobility of the mixed oxides.The introduction of praseodymium into ceria-zirconia could accelerate the oxygen migration by increasing the amount of oxygen vacancies,although it was difficult for Pr3+ ions themselves to participate in the oxygen exchange process.

Evaluation of residual stress in sputtered tantalum thin-film

Energy Technology Data Exchange (ETDEWEB)

Al-masha’al, Asa’ad, E-mail: asaad.al@ed.ac.uk; Bunting, Andrew; Cheung, Rebecca

2016-05-15

Highlights: • Tantalum thin-films have been deposited by DC magnetron sputtering system. • Thin-film stress is observed to be strongly influenced by sputtering pressure. • Transition towards the compressive stress is ascribed to the annealing at 300 °C. • Expose thin-film to air ambient or ion bombardment lead to a noticeable change in the residual stress. - Abstract: The influence of deposition conditions on the residual stress of sputtered tantalum thin-film has been evaluated in the present study. Films have been deposited by DC magnetron sputtering and curvature measurement method has been employed to calculate the residual stress of the films. Transitions of tantalum film stress from compressive to tensile state have been observed as the sputtering pressure increases. Also, the effect of annealing process at temperature range of 90–300 °C in oxygen ambient on the residual stress of the films has been studied. The results demonstrate that the residual stress of the films that have been deposited at lower sputtering pressure has become more compressive when annealed at 300 °C. Furthermore, the impact of exposure to atmospheric ambient on the tantalum film stress has been investigated by monitoring the variation of the residual stress of both annealed and unannealed films over time. The as-deposited films have been exposed to pure Argon energy bombardment and as result, a high compressive stress has been developed in the films.

Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

KAUST Repository

Abutaha, Anas I.; Sarath Kumar, S. R.; Alshareef, Husam N.

2013-01-01

We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature

Enhancement of organic light-emitting device performances with Hf-doped indium tin oxide anodes

International Nuclear Information System (INIS)

Chen, T.-H.; Liou, Y.; Wu, T.J.; Chen, J.Y.

2004-01-01

We have enhanced the luminance and the power efficiency of organic light-emitting devices with Hf-doped indium tin oxide (ITO) anodes instead of a CuPc layer. The Hf-doped ITO layer with a thickness of 15 nm was deposited on top of the ITO anode. Less than 10 mol. % of Hf was doped in ITO films by adjusting the sputtering rates of both sources. The highest work function of the Hf-doped ITO layers was 5.4 eV at the Hf concentrations about 10 mol. %. The driving voltages of the device have been reduced by 1 V. A luminance of 1000 cd/m 2 at 7 mA/cm 2 , a current efficiency of 14 cd/A, and a power efficiency of 6 lm/W at 6 mA/cm 2 have been achieved in the device with a 4 mol. % Hf-doped ITO layer (work function=5.2 eV). In general, the performance was about 50% better than the device with a CuPc buffer layer

Proceedings of IEEE International Conference on Nanotechnology (4th) held at the Technische Universitat Muenchen, Munich, Germany on 17-19 Aug 2004.

Science.gov (United States)

2004-08-01

Based Membranes: A Platform for Studying Nanofluidics , J.K. Holt, H.G. Park, A. Noy, T. Huser, D. Eaglesham, and O. Bakajin, (Chemistry and Materials...56122 Pisa, Italy, 2IEIIT-CNR, Pisa, Italy) TH2_3_4 How Quantum Effects and Unintentional Doping Affect the Threshold Voltage of Narrow-Width SOI...Hafnium Doped Tantalum Oxide High k Film, J. Lu and Y. Kuo, (The Thin Film Nano and Microelectronics Research Laboratory, Texas A&M University, College

High electrocatalytic performance of nitrogen-doped carbon nanofiber-supported nickel oxide nanocomposite for methanol oxidation in alkaline medium

Energy Technology Data Exchange (ETDEWEB)

Al-Enizi, Abdullah M. [Department of Chemistry, King Saud University, PO Box: 2455, Riyadh 11451 (Saudi Arabia); Elzatahry, Ahmed A., E-mail: aelzatahry@ksu.edu.sa [Materials Science and Technology Program, College of Arts and Science, Qatar University, Doha 2713 (Qatar); Advanced Technology and New Materials Research Institute, City of Scientific Research and Technology Applications, New Borg El-Arab City, Alexandria 21934 (Egypt); Abdullah, Aboubakr M., E-mail: bakr@qu.edu.qa [Center for Advanced Materials, Qatar University, Doha 2713 (Qatar); Vinu, Ajayan [Future Industries Institute, University of South Australia, Building X-X2-09, Mawson Lakes Campus, Mawson Lakes 5095 SA (Australia); Iwai, Hideo [Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047 (Japan); Al-Deyab, Salem S. [Petrochemical Research Chair, Department of Chemistry, King Saud University, PO Box: 2455, Riyadh 11451 (Saudi Arabia)

2017-04-15

Highlights: • A mixture of Polyvinylpyrrolidone (PVP), graphene and emeraldine base polyaniline (PANi) was electrospun and used as starting materials to prepare a nitrogen-doped carbon nanofiber (N-CNF). • Nickel oxide was loaded on the N-CNF to form a nanocomposite which was calcined later at different temperatures. • The effect of calcination temperature on the electrocatalytic behavior of the nanocomposite was studied which shows that the nanocomposite calcined at 500 °C was proved to be very high compared to the other calcination temperatures. • The stability of catalyst was excellent and its resistance to the adsorption of the intermediates generated from the methanol oxidation was very high. - Abstract: Nitrogen-Doped Carbon Nanofiber (N-CNF)–supported NiO composite was prepared by electrospinning a sol-gel mixture of graphene and polyaniline (PANi) with aqueous solutions of Polyvinylpyrrolidone (PVP) followed by a high-temperature annealing process. The electrospun was stabilized for 2 h at 280 °C, carbonized for 5 h at 1200 °C then loaded by 10% NiO. The electrocatalytic activities of the produced nanocomposite have been studied using cyclic voltammetry, and chronoamperometry. Also, N-CNF was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and scanning-electron microscopy (SEM). The obtained N-doped carbon nanofiber was found to have a nitrogen content of 2.6 atomic% with a diameter range of (140–160) nm, and a surface area (393.3 m{sup 2} g{sup −1}). In addition, it showed a high electrocatalytic behavior towards methanol oxidation reaction in alkaline medium and high stability and resistivity to the adsorption of intermediates.

Facile synthesis of aluminium doped zinc oxide-polyaniline hybrids for photoluminescence and enhanced visible-light assisted photo-degradation of organic contaminants

Energy Technology Data Exchange (ETDEWEB)

Mitra, Mousumi [Department of Physics, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, West Bengal (India); Ghosh, Amrita; Mondal, Anup [Department of Chemistry, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, West Bengal (India); Kargupta, Kajari [Department of Chemical Engineering, Jadavpur University, Kolkata 700032, West Bengal (India); Ganguly, Saibal [Department of Chemical Engineering, BITS Pilani, K K Birla Goa Campus, NH 17 B Bypass Road, Zuarinagar, Sancoale, Goa 403726 (India); Banerjee, Dipali, E-mail: dipalibanerjeebesu@gmail.com [Department of Physics, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, West Bengal (India)

2017-04-30

Graphical abstract: The present work focuses on the synergistic effect of a novel hybrid hetero structure (n-type aluminum doped zinc oxide and p-type polyaniline), combining both sol-gel and in-situ oxidative polymerization method and studying its photoluminescence (PL), photocatalytic, electrochemical impedance spectroscopy (EIS), linear scan voltammetry (LSV) and photocurrent properties. - Highlights: • Aluminium doped zinc oxide-polyaniline (PAZ) hybrids were prepared by polymerization of aniline using aluminium doped zinc oxide nanorod templates. • The hybrids were used as visible light photocatalysts for methyl orange (MO) and rose bengal (RB) dye degradation. • First order rate constants of the photocatalytic process were evaluated as 1.77 × 10{sup −2} min{sup −1} and 2.61 × 10{sup −2} min{sup −1} for MO and RB dyes respectively. • Photoluminescence and electrochemical properties were in accord with the photocatalytic performance of the hybrid. - Abstract: The emergence of organic-inorganic photoactive materials has led to marked progress in the field of heterogeneous visible-light photocatalysis. Visible-light active aluminium doped zinc oxide-polyaniline (PAZ) hybrid was prepared employing in-situ oxidative polymerization of polyaniline (PANI) in the presence of aluminium doped zinc oxide (AlZnO) nanorods, synthesized via sol-gel route. The compositions, structural and optical properties of the synthesized hybrids were characterized. Among various samples, the 22 wt% aluminium doped zinc oxide-polyaniline (PAZ 3) hybrid show the best photocatalytic action for the degradation of methyl orange (MO) and rose bengal (RB) dyes under visible-light illumination, even after repeated use. The performance of the photocatalytic process was determined by the first order rate constant, 1.77 × 10{sup −2} min{sup −1} and 2.61 × 10{sup −2} min{sup −1} for MO and RB dyes, respectively. Scavenger test was used to determine the role of active

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Energy Technology Data Exchange (ETDEWEB)

Jiang Baojiang [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Tian Chungui; Wang Lei; Sun Li; Chen Chen; Nong Xiaozhen [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Qiao Yingjie, E-mail: qiaoyingjie@hrbeu.edu.cn [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Fu Honggang, E-mail: fuhg@vip.sina.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China)

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 Degree-Sign C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Science.gov (United States)

Jiang, Baojiang; Tian, Chungui; Wang, Lei; Sun, Li; Chen, Chen; Nong, Xiaozhen; Qiao, Yingjie; Fu, Honggang

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 °C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Phosphate-Doped Carbon Black as Pt Catalyst Support: Co-catalytic Functionality for Dimethyl Ether and Methanol Electro-oxidation

DEFF Research Database (Denmark)

Yin, Min; Huang, Yunjie; Li, Qingfeng

2014-01-01

). The supported Pt catalysts show significant improvement in catalytic activity towards the direct oxidation of methanol and DME, attributable to the enhanced adsorption and dehydrogenation of methanol and DME, as well as the presence of activated OH species in the catalysts. The latter is demonstrated......Niobium-phosphate-doped (NbP-doped) carbon blacks were prepared as the composite catalyst support for Pt nanoparticles. Functionalities of the composite include intrinsic proton conductivity, surface acidity, and interfacial synergistic interactions with methanol and dimethyl ether (DME...... to facilitate the removal of CO intermediates formed during the oxidation reactions....

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

Science.gov (United States)

Alver, Ü.; Tanrıverdi, A.

2016-08-01

In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20 wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6 M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20 wt% B) display the specific capacitance as high as 230.50 F/g at 5 mV/s, which is almost five times higher than that of RGO/ZnO (52.71 F/g).

Zn2+-Doped Polyaniline/Graphene Oxide as Electrode Material for Electrochemical Supercapacitors

Science.gov (United States)

Xu, Hui; Tang, Jing; Chen, Yong; Liu, Jian; Pu, Jinjuan; Li, Qi

2017-10-01

Electrodes based on Zn2+-doped polyaniline/graphene oxide (Zn2+/PANI/GO) were synthesized on stainless steel mesh substrates in H2SO4 solution via electrochemical codeposition. Different concentrations of graphene oxide (GO) were incorporated into the films to improve the electrochemical performance of the electrodes. Electrochemical properties of the films were tested by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy, in a three-electrode system. The maximum specific capacitance of the Zn2+/PANI/GO film with a GO concentration of 15 mg L-1 was found to be 1266 F g-1 at a scan rate of 3 mV s-1. This value was higher than that of a Zn2+ doped polyaniline (Zn2+/PANI) film (814 F g-1). The Zn2+/PANI/GO film also showed good cycling stability, retaining over 86% of its initial capacitance after 1000 cycles. These results indicate that the Zn2+/PANI/GO composites can be applied as high performance supercapacitor electrodes.

Electrostatic tuning of Kondo effect in a rare-earth-doped wide-band-gap oxide

KAUST Repository

Li, Yongfeng; Deng, Rui; Lin, Weinan; Tian, Yufeng; Peng, Haiyang; Yi, Jiabao; Yao, Bin; Wu, Tao

2013-01-01

As a long-lived theme in solid-state physics, the Kondo effect reflects the many-body physics involving the short-range Coulomb interactions between itinerant electrons and localized spins in metallic materials. Here we show that the Kondo effect is present in ZnO, a prototypical wide-band-gap oxide, doped with a rare-earth element (Gd). The localized 4f electrons of Gd ions do not produce remanent magnetism, but interact strongly with the host electrons, giving rise to a saturating resistance upturn and negative magnetoresistance at low temperatures. Furthermore, the Kondo temperature and resistance can be electrostatically modulated using electric-double-layer gating with liquid ionic electrolyte. Our experiments provide the experimental evidence of tunable Kondo effect in ZnO, underscoring the magnetic interactions between localized and itinerant electrons and the emergent transport behaviors in such doped wide-band-gap oxides.

Electrostatic tuning of Kondo effect in a rare-earth-doped wide-band-gap oxide

KAUST Repository

Li, Yongfeng

2013-04-29

As a long-lived theme in solid-state physics, the Kondo effect reflects the many-body physics involving the short-range Coulomb interactions between itinerant electrons and localized spins in metallic materials. Here we show that the Kondo effect is present in ZnO, a prototypical wide-band-gap oxide, doped with a rare-earth element (Gd). The localized 4f electrons of Gd ions do not produce remanent magnetism, but interact strongly with the host electrons, giving rise to a saturating resistance upturn and negative magnetoresistance at low temperatures. Furthermore, the Kondo temperature and resistance can be electrostatically modulated using electric-double-layer gating with liquid ionic electrolyte. Our experiments provide the experimental evidence of tunable Kondo effect in ZnO, underscoring the magnetic interactions between localized and itinerant electrons and the emergent transport behaviors in such doped wide-band-gap oxides.

Spark Plasma Sintering and Densification Mechanisms of Antimony-Doped Tin Oxide Nanoceramics

Directory of Open Access Journals (Sweden)

Junyan Wu

2013-01-01

Full Text Available Densification of antimony-doped tin oxide (ATO ceramics without sintering aids is very difficult, due to the volatilization of SnO2, formation of deleterious phases above 1000°C, and poor sintering ability of ATO particles. In this paper, monodispersed ATO nanoparticles were synthesized via sol-gel method, and then ATO nanoceramics with high density were prepared by spark plasma sintering (SPS technology using the as-synthesized ATO nanoparticles without the addition of sintering aids. The effect of Sb doping content on the densification was investigated, and the densification mechanisms were explored. The results suggest that ATO nanoparticles derived from sol-gel method show good crystallinity with a crystal size of 5–20 nm and Sb is incorporated into the SnO2 crystal structure. When the SPS sintering temperature is 1000°C and the Sb doping content is 5 at.%, the density of ATO nanoceramics reaches a maximum value of 99.2%. Densification mechanisms are explored in detail.

Structural, optoelectronic, luminescence and thermal properties of Ga-doped zinc oxide thin films

International Nuclear Information System (INIS)

Shinde, S.S.; Shinde, P.S.; Oh, Y.W.; Haranath, D.; Bhosale, C.H.; Rajpure, K.Y.

2012-01-01

Highlights: ► The ecofriendly deposition of Ga-doped zinc oxide. ► Influence of Ga doping onto physicochemical properties in aqueous media. ► Electron–phonon coupling by Raman. ► Chemical bonding structure and valence band analysis by XPS. - Abstract: Ga-doped ZnO thin films are synthesized by chemical spray pyrolysis onto corning glass substrates in aqueous media. The influence of gallium doping on to the photoelectrochemical, structural, Raman, XPS, morphological, optical, electrical, photoluminescence and thermal properties have been investigated in order to achieve good quality films. X-ray diffraction study depicts the films are polycrystalline and fit well with hexagonal (wurtzite) crystal structure with strong orientations along the (0 0 2) and (1 0 1) planes. Presence of E 2 high mode in Raman spectra indicates that the gallium doping does not change the wurtzite structure. The coupling strength between electron and LO phonon has experimentally estimated. In order to understand the chemical bonding structure and electronic states of the Ga-doped ZnO thin films XPS analysis have been studied. SEM images shows the films are adherent, compact, densely packed with hexagonal flakes and spherical grains. Optical transmittance and reflectance measurements have been carried out. Room temperature PL spectra depict violet, blue and green emission in deposited films. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant in these polycrystalline films.

Synthesis and Characterization of Nanocomposites Tin Oxide-Graphene Doping Pd Using Polyol Method

Directory of Open Access Journals (Sweden)

Aminuddin Debataraja

2018-05-01

Full Text Available This paper report on polyol method for Pd doped tin oxide-graphene nanocomposite thin film. XRD result shows sharp peaks at certain 2θ value and match with tin oxide, graphene, and Pd database. FTIR result shows peak from alcohol chain for –OH strong bonded absorption (3444 cm-1, also there are aldehyde and ketone which are indicated by C=O strong absorption (1751 cm-1. Moreover, alkene is also formed for decreasing symmetry intensity C=C (1616 cm-1, while alkyne is formed at strong deformation absorption at 646 and 613 cm-1. SEM and TEM result show SnO2 particles are attached uniformly on graphene surface layer. The composition for C, O, Sn, and Pd are 33.13, 25.58, 35.35 and 5.94%, respectively. This result indicated that the good composition is formed for Pd doped SnO2-graphene nanocomposite. The nanocomposite is promising materials for toxic gas sensor application at low temperature.

Alcohol vapor sensing by cadmium-doped zinc oxide thick films based chemical sensor

Science.gov (United States)

Zargar, R. A.; Arora, M.; Chackrabarti, S.; Ahmad, S.; Kumar, J.; Hafiz, A. K.

2016-04-01

Cadmium-doped zinc oxide nanoparticles were derived by simple chemical co-precipitation route using zinc acetate dihydrate and cadmium acetate dihydrate as precursor materials. The thick films were casted from chemical co-precipitation route prepared nanoparticles by economic facile screen printing method. The structural, morphological, optical and electrical properties of the film were characterized relevant to alcohol vapor sensing application by powder XRD, SEM, UV-VIS and DC conductivity techniques. The response and sensitivity of alcohol (ethanol) vapor sensor are obtained from the recovery curves at optimum working temperature range from 20∘C to 50∘C. The result shows that maximum sensitivity of the sensor is observed at 25∘C operating temperature. On varying alcohol vapor concentration, minor variation in resistance has been observed. The sensing mechanism of sensor has been described in terms of physical adsorption and chemical absorption of alcohol vapors on cadmium-doped zinc oxide film surface and inside film lattice network through weak hydrogen bonding, respectively.

Pyroelectricity of silicon-doped hafnium oxide thin films

Science.gov (United States)

Jachalke, Sven; Schenk, Tony; Park, Min Hyuk; Schroeder, Uwe; Mikolajick, Thomas; Stöcker, Hartmut; Mehner, Erik; Meyer, Dirk C.

2018-04-01

Ferroelectricity in hafnium oxide thin films is known to be induced by various doping elements and in solid-solution with zirconia. While a wealth of studies is focused on their basic ferroelectric properties and memory applications, thorough studies of the related pyroelectric properties and their application potential are only rarely found. This work investigates the impact of Si doping on the phase composition and ferro- as well as pyroelectric properties of thin film capacitors. Dynamic hysteresis measurements and the field-free Sharp-Garn method were used to correlate the reported orthorhombic phase fractions with the remanent polarization and pyroelectric coefficient. Maximum values of 8.21 µC cm-2 and -46.2 µC K-1 m-2 for remanent polarization and pyroelectric coefficient were found for a Si content of 2.0 at%, respectively. Moreover, temperature-dependent measurements reveal nearly constant values for the pyroelectric coefficient and remanent polarization over the temperature range of 0 ° C to 170 ° C , which make the material a promising candidate for IR sensor and energy conversion applications beyond the commonly discussed use in memory applications.

X-ray absorption spectroscopy on phosphoric-salt pellets. Determination of the geometric and electronic structure of metal-oxide doped sodium-phosphate glasses

International Nuclear Information System (INIS)

Brendebach, B.

2004-02-01

Sodium metaphosphate glasses doped with transition metal oxides show characteristic colors. X-ray absorption spectroscopy (XAS) investigations provide information whether the coloration stems from different electronic transitions or changes in the geometrical structure of the glasses. Even though the violet color of MnO y -doped glasses is considered as an evidence for Mn 3+ -ions, Mn K-XAS reveals that the majority of the manganese ions are in the oxidation state +II and have a mixed coordination of four and six oxygen atoms, respectively. The oxygen coordination around the nickel ions in NiO-doped glasses with different metall oxide concentrations is always six. The change of color from citreous to auburn with increasing nickel oxide content is attributed to a systematic change in the bonding characteristic from mainly ionic-like to a small but significant contribution of covalent-like bonding. Analysis of higher coordination shells provides no indication of the formation of metal oxide clusters. (orig.)

Improvement in R{sub off}/R{sub on} ratio and reset current via combining compliance current with multilayer structure in tantalum oxide-based RRAM

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiaorong; Feng, Jie [Shanghai Jiao Tong University, Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Department of Micro/Nano Electronics, Shanghai (China)

2015-07-15

Improvements in the R{sub off}/R{sub on} ratio and reset current are required prior to the practical application of RRAM. To achieve this improvement, tantalum oxide-based RRAM devices with multilayer structure (bi-layer and tri-layer) were fabricated and various compliance currents were adopted. The reset current of 40 μA was observed; the R{sub off}/R{sub on} ratio increased to more than 20 in the tri-layer structure device. Resistance changes in two types of devices under voltage pulses with different pulse width were also conducted. The tri-layer device exhibited lower reset voltage and higher R{sub off}/R{sub on} ratio than the bi-layer device under voltage pulses. X-ray photoelectron spectroscopy demonstrated the formation of Ta{sub 2}O{sub 5} via plasma oxidation, and there was an oxygen gradient in the multilayer devices. The results demonstrated that the tri-layer structure with oxygen gradient was an effective method for achieving better device performance. Additionally, it is implied that reasonable control of the proportion of TaO{sub 2} and Ta{sub 2}O{sub 5} and compliance current can improve device performance. (orig.)

Comparison of iron and copper doped manganese cobalt spinel oxides as protective coatings for solid oxide fuel cell interconnects

Science.gov (United States)

Talic, Belma; Molin, Sebastian; Wiik, Kjell; Hendriksen, Peter Vang; Lein, Hilde Lea

2017-12-01

MnCo2O4, MnCo1.7Cu0.3O4 and MnCo1.7Fe0.3O4 are investigated as coatings for corrosion protection of metallic interconnects in solid oxide fuel cell stacks. Electrophoretic deposition is used to deposit the coatings on Crofer 22 APU alloy. All three coating materials reduce the parabolic oxidation rate in air at 900 °C and 800 °C. At 700 °C there is no significant difference in oxidation rate between coated samples and uncoated pre-oxidized Crofer 22 APU. The cross-scale area specific resistance (ASR) is measured in air at 800 °C using La0.85Sr0.1Mn1.1O3 (LSM) contact plates to simulate the interaction with the cathode in a SOFC stack. All coated samples have three times lower ASR than uncoated Crofer 22 APU after 4370 h aging. The ASR increase with time is lowest with the MnCo2O4 coating, followed by the MnCo1.7Fe0.3O4 and MnCo1.7Cu0.3O4 coatings. LSM plates contacted to uncoated Crofer 22 APU contain significant amounts of Cr after aging, while all three coatings effectively prevent Cr diffusion into the LSM. A complex Cr-rich reaction layer develops at the coating-alloy interface during oxidation. Cu and Fe doping reduce the extent of this reaction layer at 900 °C, while at 800 °C the effect of doping is insignificant.

Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

Science.gov (United States)

Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

2016-02-18

Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

Recent advances in P/M-tantalum products

International Nuclear Information System (INIS)

Kumar, P.; Uhlenhut, H.

2001-01-01

The metallurgical grade tantalum powder is used for producing parts and mill products. Some of the key requirements include purity, physical characteristics (flow, fill density and compressibility) and interstitial contents. A process to produce 99.99 % pure tantalum powder with less than 150 ppm oxygen has been developed. This powder was consolidated into metallurgical products via conventional P/M processing; resulting products had high purity and low oxygen. It also retained fine grain-size and uniform properties inherent in P/M-derived products. In addition, the desired crystallographic texture was obtained by controlled thermo-mechanical processing (TMP) of the consolidated powder. Fully dense products of this powder were tested for various applications, such as deep drawing, sputtering, ballistics and capacitors. Critical functional requirements in these applications along with the results of evaluations are discussed. (author)

Tantalum and niobium carbides obtention by carbothermic reduction of columbotantalite ores

International Nuclear Information System (INIS)

Gordo, E.; Garcia-Carcedo, F.; Torralba, J.M.

1998-01-01

Tantalum and niobium carbides are characterized by its high hardness and chemical corrosion resistance. Both carbides, but mainly TaC, are used in hard metals (sintered carbides), together with their carbides, to manufacture cutting tools and dies in special machining applications involving mechanical shock at high temperature. Its use as reinforcement of wear resistant materials through powder metallurgy techniques are being investigated. However, the use of TaC is usually limited because of its high cost. Therefore tantalum carbide with niobium content, which is cheaper, is used. In this work the obtention of complex tantalum and niobium carbides from a Spanish columbotantalite ore is studied through relatively cheap and simple process as it is carbothermic reduction. Concentration of the ore, its reduction and the characterization of products are described. (Author) 11 refs

Natively textured surface hydrogenated gallium-doped zinc oxide transparent conductive thin films with buffer layers for solar cells

Energy Technology Data Exchange (ETDEWEB)

Chen, Xin-liang, E-mail: cxlruzhou@163.com; Wang, Fei; Geng, Xin-hua; Huang, Qian; Zhao, Ying; Zhang, Xiao-dan

2013-09-02

Natively textured surface hydrogenated gallium-doped zinc oxide (HGZO) thin films have been deposited via magnetron sputtering on glass substrates. These natively textured HGZO thin films exhibit rough pyramid-like textured surface, high optical transmittances in the visible and near infrared region and excellent electrical properties. The experiment results indicate that tungsten-doped indium oxide (In{sub 2}O{sub 3}:W, IWO) buffer layers can effectively improve the surface roughness and enhance the light scattering ability of HGZO thin films. The root-mean-square roughness of HGZO, IWO (10 nm)/HGZO and IWO (30 nm)/HGZO thin films are 28, 44 and 47 nm, respectively. The haze values at the wavelength of 550 nm increase from 7.0% of HGZO thin film without buffer layer to 18.37% of IWO (10 nm)/HGZO thin film. The optimized IWO (10 nm)/HGZO exhibits a high optical transmittance of 82.18% in the visible and near infrared region (λ ∼ 400–1100 nm) and excellent electrical properties with a relatively low sheet resistance of 3.6 Ω/□ and the resistivity of 6.21 × 10{sup −4} Ωcm. - Highlights: • Textured hydrogenated gallium-doped zinc oxide (HGZO) films were developed. • Tungsten-doped indium oxide (IWO) buffer layers were applied for the HGZO films. • Light-scattering ability of the HGZO films can be improved through buffer layers. • Low sheet resistance and high haze were obtained for the IWO(10 nm)/HGZO film. • The IWO/HGZO films are promising transparent conductive layers for solar cells.

Al-doped TiO{sub 2} mesoporous material supported Pd with enhanced catalytic activity for complete oxidation of ethanol

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jing, E-mail: mlczjsls123@163.com; Mu, Wentao, E-mail: mwt15035687833@163.com; Su, Liqing, E-mail: suliqing0163@163.com; Li, Xingying, E-mail: lixingying0479@link.tyut.edu.cn; Guo, Yuyu, E-mail: guoyuyu0455@link.tyut.edu.cn; Zhang, Shen, E-mail: zhangshen0472@link.tyut.edu.cn; Li, Zhe, E-mail: lizhe@tyut.edu.cn

2017-04-15

Pd catalysts supported on Al-doped TiO{sub 2} mesoporous materials were evaluated in complete oxidation of ethanol. The catalysts synthesized by wet impregnation based on evaporation-induced self-assembly were characterized by X-ray diffraction, measurement of pore structure, XPS, FT-IR, temperature programmed reduction and TEM. Characteristic results showed that the aluminium was doped into the lattice of mesoporous anatase TiO{sub 2} to form Al-O-Ti defect structure. Catalytic results revealed that Al-doped catalysts were much more active than the pristine one, especially at low temperature (≤200 °C). This should be ascribed to the introduction of aluminium ions that suppressed the strong metal-support interaction and increased the active sites of Pd oxides, enhanced the stabilized anatase TiO{sub 2}, improved well dispersed high valence palladium species with high reducibility and enriched chemisorption oxygen. - Graphical abstract: Al-doped Pd/TiO{sub 2} exhibited optimal catalytic performance for ethanol oxidation and CO{sub 2} yield by the suppression of SMSI. - Highlights: • Palladium catalysts supported on Al-doped TiO{sub 2} mesoporous materials were studied. • The introduction of Al can enhance anatase stabilization and increase defect TiO{sub 2}. • The Pd/Al-TiO{sub 2} catalysts show higher ethanol conversion and CO{sub 2} yield than Pd/TiO{sub 2}. • The influence of Al on SMSI and catalytic performance were evaluated by TPR and XPS.

Random Vibration Testing of Advanced Wet Tantalum Capacitors

Science.gov (United States)

Teverovsky, Alexander

2015-01-01

Advanced wet tantalum capacitors allow for improved performance of power supply systems along with substantial reduction of size and weight of the systems that is especially beneficial for space electronics. Due to launch-related stresses, acceptance testing of all space systems includes random vibration test (RVT). However, many types of advanced wet tantalum capacitors cannot pass consistently RVT at conditions specified in MIL-PRF-39006, which impedes their use in space projects. This requires a closer look at the existing requirements, modes and mechanisms of failures, specifics of test conditions, and acceptance criteria. In this work, different lots of advanced wet tantalum capacitors from four manufacturers have been tested at step stress random vibration conditions while their currents were monitored before, during, and after the testing. It has been shown that the robustness of the parts and their reliability are mostly due to effective self-healing processes and limited current spiking or minor scintillations caused by RVT do not increase the risk of failures during operation. A simple model for scintillations events has been used to simulate current spiking during RVT and optimize test conditions. The significance of scintillations and possible effects of gas generation have been discussed and test acceptance criteria for limited current spiking have been suggested.

Pt/XC-72 catalysts coated with nitrogen-doped carbon (Pt/XC-72@C–N) for methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Cao, Jun; Chu, Yuanyuan; Tan, Xiaoyao, E-mail: cestanxy@aliyun.com

2014-03-01

Pt/XC-72 catalysts coated with N-doped carbon (denoted as Pt/XC-72@C–N) for the electro-oxidation of methanol are prepared through a combined microwave-assisted polyol with in-situ carbonization of N-doped carbon coating process using polyvinylpyrrolidone (PVP), 1-vinyl-3-ethylimidazolium nitrate (VEIN) or 1-ethyl-3-methylimidazolium dicyanamide (EMID) ionic liquid as the N-doped carbon precursor. X-ray diffraction, energy dispersive of X-ray, transmission electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammograms and accelerated aging test techniques are applied to characterize the structure and the electro-catalytic activity of the catalysts. The results show that the Pt particles with the average size of around 2.5 nm are highly dispersed in face-centered cubic crystal structure in the carbon support. The structure of the N-doped carbon coating precursor has considerable influence on the electro-catalytic performance of the catalysts. The resultant catalyst with EMID ionic liquid as the N-doped carbon source exhibits 115.9 m{sup 2} g{sup −1}Pt electrochemical surface area (ESA) and 0.66 A mg{sup −1}Pt catalytic activity towards the electro-oxidation of methanol, which are 1.37 times the ESA and 1.35 times the catalytic activity of the PVP-derived catalyst, and 2.02 times the electrochemical surface area and 1.94 times the catalytic activity of the VEIN-derived catalyst. The appropriate amount of the EMID ionic liquid used in the catalyst synthesis process is around 10 uL for 100 mg XC-72 support so as to obtain the highest electro-catalytic activity. - Highlights: • N-doped carbon coated Pt/C catalyst is prepared for methanol electro-oxidation. • Pt/XC-72@C–N exhibits excellent electrocatalytic activity over uncoated catalysts. • Ionic liquid with anionic cyano groups is most suitable as N-doped carbon precursor. • The appropriate amount of ionic liquid for coating is around 10 μL for 100 mg carbon.

Superconducting properties and uniaxial strain characteristics of Nb3Sn fiber-reinforced superconductors with tantalum reinforcement fibers

International Nuclear Information System (INIS)

Arai, Kazuaki; Umeda, Masaichi; Agatsuma, Koh; Tateishi, Hiroshi

1998-01-01

We have been developing fiber-reinforced superconductors (FRS) for high-field and large-scale magnets. Tungsten fibers have been selected as the reinforcement fiber for FRS so far because tungsten has the highest elastic modulus of approximately 400 GPa which can minimize the strain from electromagnetic force. The preparation process of FRS consists of sputtering deposition and heat treatment because it may be difficult to apply drawing methods to materials of high-elastic modulus such as tungsten. Tantalum has high elastic modulus of 178 GPa and its thermal expansion coefficient that is closer to that of Nb 3 Sn than tungsten's, which means prestrain in Nb 3 Sn in FRS is reduced by adopting tantalum fibers. Tantalum has been used as barriers between bronze and copper in conventional Nb 3 Sn superconductors which are usually prepared with drawing process despite of the tantalum's high elastic modulus. That implies drawing process may be applied to prepare FRS with tantalum reinforcement fibers. In this paper, FRS using tantalum fibers prepared with sputtering process are described with making comparison with FRS of tungsten to clarify the basic properties of FRS using tantalum fibers. Depth profiles in Nb 3 Sn layer in FRS were measured to examine reaction between superconducting layers and reinforcement fibers. Superconducting properties including strain and stress characteristics were shown. Those data will contribute to design of FRS using tantalum reinforcement fibers with adopts the drawing processes. (author)

Screen-printed Tin-doped indium oxide (ITO) films for NH3 gas sensing

International Nuclear Information System (INIS)

Mbarek, Hedia; Saadoun, Moncef; Bessais, Brahim

2006-01-01

Gas sensors using metal oxides have several advantageous features such as simplicity in device structure and low cost fabrication. In this work, Tin-doped indium oxide (ITO) films were prepared by the screen printing technique onto glass substrates. The granular and porous structure of screen-printed ITO are suitable for its use in gas sensing devices. The resistance of the ITO films was found to be strongly dependent on working temperatures and the nature and concentration of the ambient gases. We show that screen-printed ITO films have good sensing properties toward NH 3 vapours. The observed behaviors are explained basing on the oxidizing or the reducer nature of the gaseous species that react on the surface of the heated semi-conducting oxide

Plasma electrolytic oxidation of metals

Directory of Open Access Journals (Sweden)

Stojadinović Stevan

2013-01-01

Full Text Available In this lecture results of the investigation of plasma electrolytic oxidation (PEO process on some metals (aluminum, titanium, tantalum, magnesium, and zirconium were presented. Whole process involves anodizing metals above the dielectric breakdown voltage where numerous micro-discharges are generated continuously over the coating surface. For the characterization of PEO process optical emission spectroscopy and real-time imaging were used. These investigations enabled the determination of electron temperature, electron number density, spatial density of micro-discharges, the active surface covered by micro-discharges, and dimensional distribution of micro-discharges at various stages of PEO process. Special attention was focused on the results of the study of the morphology, chemical, and phase composition of oxide layers obtained by PEO process on aluminum, tantalum, and titanium in electrolytes containing tungsten. Physicochemical methodes: atomic force microscopy (AFM, scanning electron microscopy (SEM-EDS, x-ray diffraction (XRD, x-ray photoelectron spectroscopy (XPS, and Raman spectroscopy served as tools for examining obtained oxide coatings. Also, the application of the obtained oxide coatings, especially the application of TiO2/WO3 coatings in photocatalysis, were discussed.

Electromigration of hydrogen and deuterium in vanadium, niobium, and tantalum

International Nuclear Information System (INIS)

Jensen, C.L.

1977-10-01

The electric mobility and effective valence of hydrogen and deuterium in vanadium, niobium, tantalum and three niobium-tantalum alloys were measured. A resistance technique was used to directly determine the electric mobility of hydrogen and deuterium at 30 0 C while a steady-state method was used to measure the effective valence. The use of mass spectrographic techniques on a single specimen which contained both hydrogen and deuterium greatly increased the precision with which the isotope effect in the effective valence could be measured

Comparison of the mechanical properties between tantalum and nickel-titanium foams implant materials for bone ingrowth applications

International Nuclear Information System (INIS)

Sevilla, P.; Aparicio, C.; Planell, J.A.; Gil, F.J.

2007-01-01

Metallic porous materials are designed to allow the ingrowth of living tissue inside the pores and to improve the mechanical anchorage of the implant. In the present work, tantalum and nickel-titanium porous materials have been characterized. The tantalum foams were produced by vapour chemical deposition (CVD/CVI) and the NiTi foams by self-propagating high temperature synthesis (SHS). The former exhibited an open porosity ranging between 65 and 73% and for the latter it ranged between 63 and 68%. The pore sizes were between 370 and 440 μm for tantalum and between 350 and 370 μm for nickel-titanium. The Young's modulus in compression of the foams studied, especially for tantalum, were very similar to those of cancellous bone. This similitude may be relevant in order to minimize the stress shielding effect in the load transfer from the implant to bone. The strength values for NiTi foam are higher than for tantalum, especially of the strain to fracture which is about 23% for NiTi and only 8% for tantalum. The fatigue endurance limit set at 10 8 cycles is about 7.5 MPa for NiTi and 13.2 MPa for tantalum. The failure mechanisms have been studied by scanning electron microscopy

Ultrabroadband terahertz characterization of highly doped ZnO and ITO

DEFF Research Database (Denmark)

Wang, Tianwu; Zalkovskij, Maksim; Iwaszczuk, Krzysztof

2015-01-01

The broadband complex conductivities of transparent conducting oxides (TCO), namely, aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by using THz-TDS from 0.5 to 18 THz. The complex conductivities were accurately calculated using...

Epitaxy-enabled vapor-liquid-solid growth of tin-doped indium oxide nanowires with controlled orientations

KAUST Repository

Shen, Youde; Turner, Stuart G.; Yang, Ping; Van Tendeloo, Gustaaf; Lebedev, Oleg I.; Wu, Tao

2014-01-01

challenges in reliably achieving these goals of orientation-controlled nanowire synthesis and assembly. Here we report that growth of planar, vertical and randomly oriented tin-doped indium oxide (ITO) nanowires can be realized on yttria-stabilized zirconia

Spectrochemical determination of tantalum in plutonium metal using direct current plasma emission spectrometry

International Nuclear Information System (INIS)

Fadeff, S.K.; Morris, W.F.

1983-01-01

Tantalum is determined by direct current plasma spectrometry after separation of plutonium from solution as PuF 3 . After centrifugation of the PuF 3 precipitate, a low level of plutonium remains in solution in sufficient quantity to cause spectral interferences. It is necessary to determine the plutonium by dc plasma spectrometry and apply a correction to determine low tantalum concentrations with good accuracy and precision. Tantalum can be determined down to 0.4 ppM in solution with a relative standard deviation of 10 percent. Better precision can be achieved at higher concentrations. The procedure is simple and convenient for glovebox work. 5 references, 1 figure, 1 table

Bone remodeling around cementless tantalum cups

NARCIS (Netherlands)

Grillo, J. -C.; Flecher, X.; Bouvenot, J.; Argenson, J. -N.

2008-01-01

Purpose of the study.-Most studies have reported a significant decrease in periacetabular bone stock one year after implantation of a cementless cup. The purpose of this work was to study the bone-implant interface of the tantalum cup using plain X-rays and dual-energy X-ray absorptiometry (DEXA).

The recovery of tin, and the production of niobium pentoxide and potassium tantalum fluoride, from a tin slag

International Nuclear Information System (INIS)

Iorio, G.; Tyler, M.S.

1987-01-01

This report describes the results of testwork on the recovery of tin, niobium, and tantalum from a tin slag. The slag, which consisted mainly of amorphous silica, with varying amounts of calcuim, magnesium, manganese, iron, and aluminium, contained an average of 8,8 per cent niobium pentoxide and 6,2 per cent tantalum pentoxide. The metallic tin-ion phase was removed from the crushed slag by magnetic separation. The slag was then leached with hydrochloric acid to remove magnesium, calcium, aluminium, iron, manganese, and the remainder of the tin. Leaching with sodium hydroxide for the removal of silica and phosphorous was followed by a final leach with hydrochloric acid for the removal of sodium. The upgraded concentrate thus obtained was purified by leaching with hydrofluoric acid, solvent extraction of niobium and tantalum into tri-n-butyl phosphate and methyl isobutyl ketone, and selective stripping of niobium with sulphuric acid and tantalum with ammonium floride. Niobium pentoxide and potassium tantalum fluoride were then precipitated by the addition of ammonium hydroxide and potassium fluoride to the respective strip liquors. The overall recoveries in the upgraded concentrate were 98 per cent for tantalum and 92 per cent for niobium. Dissolutions and recoveries of over 99 per cent were obtained for both tantalum and niobium in the purification steps. The niobium pentoxide and potassium tantalum fluoride precipitates obtained were of high purity

Actinide oxide photodiode and nuclear battery

Energy Technology Data Exchange (ETDEWEB)

Sykora, Milan; Usov, Igor

2017-12-05

Photodiodes and nuclear batteries may utilize actinide oxides, such a uranium oxide. An actinide oxide photodiode may include a first actinide oxide layer and a second actinide oxide layer deposited on the first actinide oxide layer. The first actinide oxide layer may be n-doped or p-doped. The second actinide oxide layer may be p-doped when the first actinide oxide layer is n-doped, and the second actinide oxide layer may be n-doped when the first actinide oxide layer is p-doped. The first actinide oxide layer and the second actinide oxide layer may form a p/n junction therebetween. Photodiodes including actinide oxides are better light absorbers, can be used in thinner films, and are more thermally stable than silicon, germanium, and gallium arsenide.

Optoelectronic properties of sprayed transparent and conducting indium doped zinc oxide thin films

International Nuclear Information System (INIS)

Shinde, S S; Shinde, P S; Bhosale, C H; Rajpure, K Y

2008-01-01

Indium doped zinc oxide (IZO) thin films are grown onto Corning glass substrates using the spray pyrolysis technique. The effect of doping concentration on the structural, electrical and optical properties of IZO thin films is studied. X-ray diffraction studies show a change in preferential orientation from the (0 0 2) to the (1 0 1) crystal planes with increase in indium doping concentration. Scanning electron microscopy studies show polycrystalline morphology of the films. Based on the Hall-effect measurements and analysis, impurity scattering is found to be the dominant mechanism determining the diminished mobility in ZnO thin films having higher indium concentration. The addition of indium also induces a drastic decrease in the electrical resistivity of films; the lowest resistivity (4.03 x 10 -5 Ω cm) being observed for the film deposited with 3 at% indium doping. The effect of annealing on the film properties has been reported. Films deposited with 3 at% In concentration have relatively low resistivity with 90% transmittance at 550 nm and the highest value of figure of merit 7.9 x 10 -2 □ Ω -1

Laser welding of a beryllium/tantalum collimator

International Nuclear Information System (INIS)

Lingenfelter, A.C.; Anglin, C.D.

1985-01-01

This report describes the methods utilized in the fabrication of a collimator from 0.001 inch thick beryllium and tantalum foil. The laser welding process proved to be an acceptable method for joining the beryllium in a standing edge joint configuration

Intercalated compounds of niobium and tantalum dicalcogenides

International Nuclear Information System (INIS)

Wypych, F.

1988-01-01

The synthesis of niobium and tantalum lamellar compounds and its intercalated derivatives is described. The intercalated compounds with lithium, with alkaline metal and with metals of the first-row transition are studied, characterized by X-ray diffraction. (C.G.C.) [pt

Electrochemical oxidation of biological pretreated and membrane separated landfill leachate concentrates on boron doped diamond anode

Energy Technology Data Exchange (ETDEWEB)

Zhou, Bo, E-mail: 357436235@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yu, Zhiming, E-mail: zhiming@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Wei, Qiuping, E-mail: qiupwei@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Long, HangYu, E-mail: 55686385@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xie, Youneng, E-mail: 1187272844@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Yijia, E-mail: 503630433@qq.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

2016-07-30

Highlights: • High quality boron-doped diamond film electrodes were synthesized on Nb substrates. • Electrochemical oxidation on boron-doped diamond anode is an effective method for treating landfill leachate concentrates. • Optimal operating conditions for electrochemical oxidation of landfill leachate concentrates is determined. • 87.5% COD removal and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment. - Abstract: In the present study, the high quality boron-doped diamond (BDD) electrodes with excellent electrochemical properties were deposited on niobium (Nb) substrates by hot filament chemical vapor deposition (HFCVD) method. The electrochemical oxidation of landfill leachate concentrates from disc tube reverse osmosis (DTRO) process over a BDD anode was investigated. The effects of varying operating parameters, such as current density, initial pH, flow velocity and cathode material on degradation efficiency were also evaluated following changes in chemical oxygen demand (COD) and ammonium nitrogen (NH{sub 3}−N). The instantaneous current efficiency (ICE) was used to appraise different operating conditions. As a result, the best conditions obtained were as follows, current density 50 mA cm{sup −2}, pH 5.16, flow velocity 6 L h{sup −1}. Under these conditions, 87.5% COD and 74.06% NH{sub 3}−N removal were achieved after 6 h treatment, with specific energy consumption of 223.2 kWh m{sup −3}. In short, these results indicated that the electrochemical oxidation with BDD/Nb anode is an effective method for the treatment of landfill leachate concentrates.

A preliminary deposit model for lithium-cesium-tantalum (LCT) pegmatites

Science.gov (United States)

Bradley, Dwight; McCauley, Andrew

2013-01-01

This report is part of an effort by the U.S. Geological Survey to update existing mineral deposit models and to develop new ones. We emphasize practical aspects of pegmatite geology that might directly or indirectly help in exploration for lithium-cesium-tantalum (LCT) pegmatites, or for assessing regions for pegmatite-related mineral resource potential. These deposits are an important link in the world’s supply chain of rare and strategic elements, accounting for about one-third of world lithium production, most of the tantalum, and all of the cesium.

Catalytic Oxidation of Soot on a Novel Active Ca-Co Dually-Doped Lanthanum Tin Pyrochlore Oxide

Directory of Open Access Journals (Sweden)

Lijie Ai

2018-04-01

Full Text Available A novel active Ca-Co dually-doping pyrochlore oxide La2−xCaxSn2−yCoyO7 catalyst was synthesized by the sol-gel method for catalytic oxidation of soot particulates. The microstructure, atomic valence, reduction, and adsorption performance were investigated by X-ray powder diffraction (XRD, scanning electron microscope (SEM, Fourier-transform infrared spectroscopy (FT-IR, X-ray photoelectron spectroscopy (XPS, H2-TPR (temperature-programmed reduction, and in situ diffuse reflection infrared Fourier transformed (DRIFTS techniques. Temperature programmed oxidation (TPO tests were performed with the mixture of soot-catalyst under tight contact conditions to evaluate the catalytic activity for soot combustion. Synergetic effect between Ca and Co improved the structure and redox properties of the solids, increased the surface oxygen vacancies, and provided a suitable electropositivity for oxide, directly resulting in the decreased ignition temperature for catalyzed soot oxidation as low as 317 °C. The presence of NO in O2 further promoted soot oxidation over the catalysts with the ignition temperature decreased to about 300 °C. The DRIFTS results reveal that decomposition of less stable surface nitrites may account for NO2 formation in the ignition period of soot combustion, which thus participate in the auxiliary combustion process.

Electrical and optical properties of reactive dc magnetron sputtered silver-doped indium oxide thin films: role of oxygen

International Nuclear Information System (INIS)

Subrahmanyam, A.; Barik, U.K.

2006-01-01

Silver-doped indium oxide thin films have been prepared on glass and quartz substrates at room temperature (300 K) by a reactive dc magnetron sputtering technique using an alloy target of pure indium and silver (80:20 at. %). During sputtering, the oxygen flow rates are varied in the range 0.00-2.86 sccm keeping the magnetron power constant at 40 W. The resistivity of these films is in the range 10 0 -10 -3 Ωcm and they show a negative temperature coefficient of resistivity. The films exhibit p-type conductivity at an oxygen flow rate of 1.71 sccm. The work function of these silver-indium oxide films has been measured by a Kelvin probe technique. The refractive index of the films (at 632.8 nm) varies in the range 1.13-1.20. Silver doping in indium oxide narrows the band gap of indium oxide (3.75 eV). (orig.)

Electrical and optical properties of reactive dc magnetron sputtered silver-doped indium oxide thin films: role of oxygen

Energy Technology Data Exchange (ETDEWEB)

Subrahmanyam, A; Barik, U K [Indian Institute of Technology Madras, Semiconductor Physics Laboratory, Department of Physics, Chennai (India)

2006-07-15

Silver-doped indium oxide thin films have been prepared on glass and quartz substrates at room temperature (300 K) by a reactive dc magnetron sputtering technique using an alloy target of pure indium and silver (80:20 at. %). During sputtering, the oxygen flow rates are varied in the range 0.00-2.86 sccm keeping the magnetron power constant at 40 W. The resistivity of these films is in the range 10{sup 0}-10{sup -3} {omega}cm and they show a negative temperature coefficient of resistivity. The films exhibit p-type conductivity at an oxygen flow rate of 1.71 sccm. The work function of these silver-indium oxide films has been measured by a Kelvin probe technique. The refractive index of the films (at 632.8 nm) varies in the range 1.13-1.20. Silver doping in indium oxide narrows the band gap of indium oxide (3.75 eV). (orig.)

One-step synthesis of N-doped activated carbon with controllable Ni nanorods for ethanol oxidation

International Nuclear Information System (INIS)

Shi, Wenjuan; Gao, Haiyan; Yu, Jianguo; Jia, Miaomiao; Dai, Tangming; Zhao, Yongnan; Xu, Jingjing; Li, Guodong

2016-01-01

N-doped activated carbons with controllable Ni nanorods (NiNC) catalysts were fabricated by a facile one-pot method for electrocatalytic oxidation of ethanol. The effects of carbon source and Ni precursor for the different microstructures of the forming Ni are discussed in this work. The sucrose and chloride ion are the key factors for forming nanorod-like nickel catalyst. The sizes of Ni nanorods can be controlled by the reactant ratios and influence the catalytic performance for ethanol oxidation. The doped N atoms are also used to improve the catalytic performance for ethanol oxidation. The NiNC–3 catalyst with the proper content and size of Ni exhibits an improved catalytic activity toward ethanol oxidation with a 5 times current density and 16 times rate constant in comparison with the NiNC–1 catalysts. A current density of 47.5 mA cm −2 is generated on NiNC–3 electrode. Furthermore, current density retention of 80.7% suggests an excellent cyclic stability after 1500 cycle on the NiNC–3 electrode. All of these elevated performances can be attributed to the relatively uniform nanorods size, as well as the excellent electrical conductivity and stability of the carbon support.

Improved thermal stability of methylsilicone resins by compositing with N-doped graphene oxide/Co3O4 nanoparticles

International Nuclear Information System (INIS)

Jiang, Bo; Zhao, Liwei; Guo, Jiang; Yan, Xingru; Ding, Daowei; Zhu, Changcheng; Huang, Yudong; Guo, Zhanhu

2016-01-01

Nanoparticles play important roles in enhancing the thermal-resistance of hosting polymer resins. Despite tremendous efforts, developing thermally stable methylsilicone resin at high temperatures is still a challenge. Herein, we report a strategy to increase the activation energy to slow down the decomposition/degradation of methylsilicone resin using synergistic effects between the Co 3 O 4 nanoparticles and the nitrogen doped graphene oxide. The N-doped graphene oxides composited with Co 3 O 4 nanoparticles were prepared by hydrolysis of cobalt nitrate hexahydrate in the presence of graphene oxide and were incorporated into the methylsilicone resin. Two-stage decompositions were observed, i.e., 200–300 and 400–500 °C. The activation energy for the low temperature region was enhanced by 47.117 kJ/mol (vs. 57.76 kJ/mol for pure resin). The enhanced thermal stability was due to the fact that the nanofillers prevented the silicone hydroxyl chain ends ‘‘biting’’ to delay the degradation. The activation energy for high-temperature region was enhanced by 11.585 kJ/mol (vs. 171.95 kJ/mol for pure resin). The nanofillers formed a protective layer to isolate oxygen from the hosting resin. The mechanism for the enhanced thermal stability through prohibited degradation with synergism of these nitrogen-doped graphene oxide nanocomposites was proposed as well.Graphical Abstract

Effect of nitrogen precursors on the electrochemical performance of nitrogen-doped reduced graphene oxide towards oxygen reduction reaction

International Nuclear Information System (INIS)

Soo, Li Ting; Loh, Kee Shyuan; Mohamad, Abu Bakar; Daud, Wan Ramli Wan; Wong, Wai Yin

2016-01-01

A series of nitrogen-doped reduced graphene oxides (NGs) with different ratios are synthesized by thermal annealing of graphene oxide with melamine or urea. The total nitrogen content in NG is high, with values of up to 5.88 at.%. The NG samples prepared by melamine exhibited thin transparent graphene sheets structure, with consist of higher nitrogen doping level and quaternary N content compared to those NG samples prepared from urea. Electrochemical characterizations show that NG is a promising metal-free electrocatalyst for an oxygen reduction reaction (ORR). Incorporation of nitrogen atoms into graphene basal plane can enhances its electrocatalytic activity toward ORR in alkaline media. The onset potential and mean number of electron transfers on NG 1 are −0.10 V and 3.80 respectively, which is higher than that of reduced graphene oxide (−0.15 V, 3.52). This study suggests that quaternary-N of the NG samples is the active site which determines the ORR activity Moreover, the NG samples with the transparent layer of graphene-like structure have better ORR performances than that of bulk graphite-like NG samples. - Highlights: • Synthesis of nitrogen-doped graphene (NG) via thermal annealing. • The effects of the nitrogen precursors on the synthesized NG are discussed. • Electrochemical performances of the NG are correlated to N doping and EASA. • Graphitic-N is proposed to be the active site for ORR.

Effect of nitrogen precursors on the electrochemical performance of nitrogen-doped reduced graphene oxide towards oxygen reduction reaction

Energy Technology Data Exchange (ETDEWEB)

Soo, Li Ting, E-mail: nicolesoo90@gmail.com [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Loh, Kee Shyuan, E-mail: ksloh@ukm.edu.my [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Mohamad, Abu Bakar, E-mail: drab@ukm.edu.my [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Daud, Wan Ramli Wan, E-mail: wramli@ukm.edu.my [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); Wong, Wai Yin, E-mail: waiyin.wwy@gmail.com [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi UKM, Selangor (Malaysia); School of Engineering, Taylor' s University' s Lakeside Campus, No. 1, Jalan Taylor' s, 46500 Subang Jaya, Selangor (Malaysia)

2016-08-25

A series of nitrogen-doped reduced graphene oxides (NGs) with different ratios are synthesized by thermal annealing of graphene oxide with melamine or urea. The total nitrogen content in NG is high, with values of up to 5.88 at.%. The NG samples prepared by melamine exhibited thin transparent graphene sheets structure, with consist of higher nitrogen doping level and quaternary N content compared to those NG samples prepared from urea. Electrochemical characterizations show that NG is a promising metal-free electrocatalyst for an oxygen reduction reaction (ORR). Incorporation of nitrogen atoms into graphene basal plane can enhances its electrocatalytic activity toward ORR in alkaline media. The onset potential and mean number of electron transfers on NG 1 are −0.10 V and 3.80 respectively, which is higher than that of reduced graphene oxide (−0.15 V, 3.52). This study suggests that quaternary-N of the NG samples is the active site which determines the ORR activity Moreover, the NG samples with the transparent layer of graphene-like structure have better ORR performances than that of bulk graphite-like NG samples. - Highlights: • Synthesis of nitrogen-doped graphene (NG) via thermal annealing. • The effects of the nitrogen precursors on the synthesized NG are discussed. • Electrochemical performances of the NG are correlated to N doping and EASA. • Graphitic-N is proposed to be the active site for ORR.

Facile fabrication of palladium-ionic liquids-nitrogen-doped graphene nanocomposites as enhanced electro-catalyst for ethanol oxidation

Science.gov (United States)

Li, Shuwen; Yang, Honglei; Ren, Ren; Ma, Jianxin; Jin, Jun; Ma, Jiantai

2015-10-01

The palladium-ionic liquids-nitrogen-doped graphene nanocomposites are facile fabricated as enhanced electro-catalyst for ethanol oxidation. First, the ionic liquids functionalized nitrogen-doping graphene nanosheets (PDIL-NGS) with few layers is synthesized through a facile and effective one-pot hydrothermal method with graphene oxide as raw material, urea as reducing-doping agents and ionic liquids (ILs) derived from 3,4,9,10-perylene tetracarboxylic acid as functional molecules. The results of systematic characterization reveal that the PDIL molecules not only can functionalize NGS by π-π stacking with no affecting the nitrogen doping but also prevent the agglomeration of NGS. More importantly, the processing performance and the property of electron transfer are remarkably enhanced duo to introducing a large number of ILs groups. Then, the enhanced electrocatalytic Pd nanoparticles are successfully anchored on PDIL-NGS by a facile and surfactant-free synthetic technique. As an anode catalyst, the novel catalyst exhibits better kinetics, more superior electrocatalytic performance, higher tolerance and electrochemical stability than the other catalysts toward ethanol electrooxidation, owing to the role of PDIL molecules. Therefore, the new catalyst is believed to have the potential use for direct alcohol fuel cells in the future and the functionalized NGS is promising useful materials applied in other fields.

Recovery of hafnium radioisotopes from a proton irradiated tantalum target

International Nuclear Information System (INIS)

Taylor, W.A.; Garcia, J.G.; Hamilton, V.T.; Heaton, R.C.; Jamriska, D.J.; Ott, M.A.; Philips, D.R.; Radzinski, S.D.

1998-01-01

The 178m2 Hf nucleus, with its long half-life (31 y) and high-spin isomeric state (16 + ) is desired for new and exotic nuclear physics studies. The Los Alamos Radioisotope Program irradiated a kilogram of natural tantalum at the Los Alamos Meson Physics Facility in early 1981. After fifteen years of decay, this target was ideal for the recovery of 178m2 Hf. There was more than a millicurie of 178m2 Hf produced during this irradiation and there has been a sufficient period of time for most of the other hafnium radioisotopes to decayed away. Traditionally, separation techniques for recovering hafnium isotopes from tantalum targets employ solvent extractions with reagents that are considered hazardous. These techniques are no longer condoned because they generate a mixed-waste (radioactive and hazardous components) that can not be treated for disposal. In this paper we describe a new and unique procedure for the recovery of hafnium radioisotopes from a highly radioactive, proton irradiated, tantalum target using reagents that do not contribute a hazardous waste component. (author)

Enhancing photovoltaic performance of dye-sensitized solar cell by rare-earth doped oxide of Lu2O3:(Tm3+, Yb3+)

International Nuclear Information System (INIS)

Li Qingbei; Lin Jianming; Wu Jihuai; Lan Zhang; Wang Yue; Peng Fuguo; Huang Miaoliang

2011-01-01

Highlights: → Tm 3+ /Yb 3+ codoped oxide is introduced into the TiO 2 film in dye-sensitized solar cell. → The RE improves light harvest via conversion luminescence and increases photocurrent. → The RE elevates the oxide film energy level and increases the cell photovoltage. → The cell efficiency is increased by 11.1% compared to the cell lacking of RE doping. - Abstract: In order to increase of the photocurrent, photovoltage and energy conversion efficiency of dye-sensitized solar cell (DSSC), rare-earth doped oxide of Lu 2 O 3 :(Tm 3+ , Yb 3+ ) is prepared and introduced into the TiO 2 film in the DSSC. As a luminescence medium, Lu 2 O 3 :(Tm 3+ , Yb 3+ ) improves incident light harvest via a conversion luminescence process and increases photocurrent; as a p-type dopant, the rare-earth ions elevate the energy level of the oxide film and increase the photovoltage. Under a simulated solar light irradiation of 100 mW cm -2 , the light-to-electric energy conversion efficiency of the DSSC with Lu 2 O 3 :(Tm 3+ , Yb 3+ ) doping reaches 6.63%, which is increased by 11.1% compared to the DSSC without Lu 2 O 3 :(Tm 3+ , Yb 3+ ) doping.

Structural and Optical Studies of Magnesium Doped Zinc Oxide Thin Films

OpenAIRE

Arpana Agrawal; Tanveer Ahmad Dar; Pratima Sen

2013-01-01

The paper describes the structural and optical properties of Magnesium doped Zinc Oxide (Mg  3.5 %, 6 %, 9 %, 12 % by weight) thin films prepared by pulsed laser deposition technique. The samples are characterized by X-ray diffraction technique, Ultra-violet visible absorption spectroscopy, X-ray photoelectron spectroscopy. X-ray diffraction results reveal the polycrystalline nature of samples with no impurity or secondary phase formation. Ultra-violet visible absorption spectroscopy studies...

A Novel Method for Assessment of Polyethylene Liner Wear in Radiopaque Tantalum Acetabular Cups

DEFF Research Database (Denmark)

Troelsen, Anders; Greene, Meridith E; Ayers, David C

2015-01-01

Conventional radiostereometric analysis (RSA) for wear is not possible in patients with tantalum cups. We propose a novel method for wear analysis in tantalum cups. Wear was assessed by gold standard RSA and the novel method in total hip arthroplasty patients enrolled in a randomized controlled...

Catalytic Hydroamination of Alkynes and Norbornene with Neutral and Cationic Tantalum Imido Complexes

Science.gov (United States)

Anderson, Laura L.; Arnold, John; Bergman, Robert G.

2005-01-01

Several tantalum imido complexes have been synthesized and shown to efficiently catalyze the hydroamination of internal and terminal alkynes. An unusual hydroamination/hydroarylation reaction of norbornene catalyzed by a highly electrophilic cationic tantalum imido complex is also reported. Factors affecting catalyst activity and selectivity are discussed along with mechanistic insights gained from stoichiometric reactions. PMID:15255680

Sputter deposition of tantalum-nitride films on copper using an rf-plasma

International Nuclear Information System (INIS)

Walter, K.C.; Fetherston, R.P.; Sridharan, K.; Chen, A.; Shamim, M.M.; Conrad, J.R.

1994-01-01

A tantalum-nitride film was successfully deposited at ambient temperature on copper with a modified ion-assisted-deposition (IAD) technique. The process uses an argon and nitrogen plasma to sputter deposit from a tantalum rf-cathode and ion implant the deposited film simultaneously. Both argon and nitrogen ions are used for sputtering and ion implantation. Auger spectroscopy and x-ray diffraction were used to characterize the resulting film

Review of tantalum and niobium alloy production

International Nuclear Information System (INIS)

Buckman, R.W. Jr.

1984-01-01

This paper concentrates on the current state of niobium- and tantalum-base alloy production. The materials requirements, alloy compositions of interest, and production status are discussed. Finally, a list of developments needed to support the SP-100 program will be identified. A bibliography is included

Effect of tin doping on the optical properties of indium oxide films by a spray pyrolysis method

International Nuclear Information System (INIS)

Ibrahim Abu Talib; Muhammad Mat Salleh; Muhammad Yahya; Mod Noor Bader Sher

1993-01-01

Thin films of stannum doped indium oxide were deposited on glass by a X-ray pyrolysis method. The substrate temperature and the rate of flow of the carrier gas were fixed at 450 0 C and 2.5 litre/minute respectively during deposition. The dependence of the optical properties of the films on the doping concentration was studied. It is found that the transmission of the visible wavelengths (300 to 800 nm) through the films increases around 5% from 74.9% as the film was doped with 10% stannum. It is also found that the optical energy bandgap increases 0.2 eV from 3.16 to 3.36 eV by doping the film with 10% stannum. The increase is attributed to the Bernstein-Moss (1) and self-energy (2) effects

Thermal transport properties of polycrystalline tin-doped indium oxide films

International Nuclear Information System (INIS)

Ashida, Toru; Miyamura, Amica; Oka, Nobuto; Sato, Yasushi; Shigesato, Yuzo; Yagi, Takashi; Taketoshi, Naoyuki; Baba, Tetsuya

2009-01-01

Thermal diffusivity of polycrystalline tin-doped indium oxide (ITO) films with a thickness of 200 nm has been characterized quantitatively by subnanosecond laser pulse irradiation and thermoreflectance measurement. ITO films sandwiched by molybdenum (Mo) films were prepared on a fused silica substrate by dc magnetron sputtering using an oxide ceramic ITO target (90 wt %In 2 O 3 and 10 wt %SnO 2 ). The resistivity and carrier density of the ITO films ranged from 2.9x10 -4 to 3.2x10 -3 Ω cm and from 1.9x10 20 to 1.2x10 21 cm -3 , respectively. The thermal diffusivity of the ITO films was (1.5-2.2)x10 -6 m 2 /s, depending on the electrical conductivity. The thermal conductivity carried by free electrons was estimated using the Wiedemann-Franz law. The phonon contribution to the heat transfer in ITO films with various resistivities was found to be almost constant (λ ph =3.95 W/m K), which was about twice that for amorphous indium zinc oxide films

Spray pyrolysis of doped-ceria barrier layers for solid oxide fuel cells

DEFF Research Database (Denmark)

Szymczewska, Dagmara; Chrzan, Aleksander; Karczewski, Jakub

2017-01-01

Gadolinium doped ceria (Ce0.8Gd0.2O2 − x-CGO) layer fabricated by spray pyrolysis is investigated as the diffusion barrier for solid oxide fuel cell. It is deposited between the La0.6Sr0.4FeO3 − δ cathode and the yttria stabilized zirconia electrolyte to mitigate harmful interdiffusion...

Change in lattice parameter of tantalum due to dissolved hydrogen

Directory of Open Access Journals (Sweden)

Gyanendra P. Tiwari

2012-06-01

Full Text Available The volume expansion of tantalum due to the dissolved hydrogen has been determined using Bragg equation. The hydrogen was dissolved in the pure tantalum metal at constant temperature (360 °C and constant pressure (132 mbar by varying the duration of hydrogen charging. The amount of dissolved hydrogen was within the solid solubility limit. The samples with different hydrogen concentration were analyzed by X-ray diffraction technique. Slight peak shifts as well as peak broadening were observed. The relative changes of lattice parameters plotted against the hydrogen concentration revealed that the lattice parameters varied linearly with the hydrogen concentration.

[Short-term curative effects of Tantalum rod treatment in early avascular necrosis].

Science.gov (United States)

Ye, Fu-Sheng; Ni, Zhe-Ji; Chu, Xiao-Bing; He, Bang-Jian; Li, Ju; Tong, Pei-Jian

2013-08-01

To explore the recent clinical curative effect of Tantalum rod in treating the early avascular necrosis. From January 2008 to November 2008, the 25 patients (39 hips) with early avascular necrosis accepted tantalum rod placement and included 9 males (11 hips) and 16 females (28 hips) with an average age of 37 years old ranging from 18 to 74 years old. Four patients (6 hips) caused by Alcoholic, 6 patients (8 hips) by hormone, 2 cases (2 hips) by traumatic, 13 cases (23 hips) by idiopathic. Steinberg preoperative stage involved 7 hips in period I, 24 hips in period II, 8 hips in period III. Curative effect analysis included preoperative and postoperative Harris score, radiographic changes and hip replacement for follow-up to accept the end of the femoral head survival rate. All patients were followed up for 6 to 47 months (averaged 37.4 months). All 12 hips imaging appeard progress,including tantalum rod exit in 1 hip, hip hemiarthroplasty collapse in 3 hips, the area increased to avascular necrosis in 8 hips. Six hips accepted total hip replacement, including imaging progress in 5 hips (41.7%, 5/12), no imaging progress in 1 hip (3.7%,1/27). All hips' Kaplan-Meier survival curves showed 6-month survival rate was (97.4 +/- 2.5)% after tantalum stick insertion, 1-year survival rate was (94.7 +/- 3.6), and 2-year survival rate was (88.6 +/- 5.4)%, 3-year survival rate was (72.5 +/- 11.2). It is effective for treatment of avascular necrosis of femoral head in Steinberg I and II by Tantalum rod, and it can effectively relieve femoral head replacement time.

Photocatalytic and electrochemical performance of three-Dimensional reduced graphene Oxide/WS{sub 2}/Mg-doped ZnO composites

Energy Technology Data Exchange (ETDEWEB)

Yu, Weiwei [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Chen, Xi’an [Zhejiang Key Laboratory of Carbon Materials, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325027 (China); Mei, Wei [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Chen, Chuansheng, E-mail: 1666423158@qq.com [College of Materials Science and Engineering, Changsha University of Science and Technology, Changsha, 410114 (China); Tsang, Yuenhong [Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, 999077 (China)

2017-04-01

Highlights: • 3D graphene oxide/WS{sub 2}/Mg-doped ZnO composites were prepared by electrostatic self-assembly and coprecipitation methods. • A significant photocatalytic activity enhancement of rGWMZ was observed. • The enhancement for photocatalytic activity is ascribed to the synergistic effect of rGO and WS{sub 2} nanosheets. - Abstract: To improve the dispersion of reduced graphene oxide and enhance the photocatalytic property of reduced graphene oxide/Mg-doped ZnO composites (rGMZ), the reduced graphene oxide/WS{sub 2}/Mg-doped ZnO composites (rGWMZ) were prepared by electrostatic self-assembly and coprecipitation methods. The effects of mass ratio of WS{sub 2} nanosheets to reduced graphene oxide (WS{sub 2}/rGO wt.%) and calcination temperature on the photocatalytic and electrochemical property of rGWMZ composites were investigated. Experimental results showed that the photocatalytic efficiency of rGWMZ composites is three-fold compared with that of rGMZ composites when the WS{sub 2}/rGO wt.% is 20.8% and calcination temperature is 500 °C, in which the degradation ratio Rhodamin B (RhB) can reach 95% within 15 min under the UV light and 90% within 90 min under simulated solar light. In addition, the rGWMZ show larger capacitance and smaller resistance than rGMZ. The enhancement for photocatalytic activity and electrochemical performance of rGWMZ is ascribed to improving the specific surface area, electrical conductivity and electronic storage capability because of the synergistic effect of rGO and WS{sub 2} nanosheets.

The effects of argon ion bombardment on the corrosion resistance of tantalum

Science.gov (United States)

Ramezani, A. H.; Sari, A. H.; Shokouhy, A.

2017-02-01

Application of ion beam has been widely used as a surface modification method to improve surface properties. This paper investigates the effect of argon ion implantation on surface structure as well as resistance against tantalum corrosion. In this experiment, argon ions with energy of 30 keV and in doses of 1 × 1017-10 × 1017 ions/cm2 were used. The surface bombardment with inert gases mainly produces modified topography and morphology of the surface. Atomic Force Microscopy was also used to patterned the roughness variations prior to and after the implantation phase. Additionally, the corrosion investigation apparatus wear was applied to compare resistance against tantalum corrosion both before and after ion implantation. The results show that argon ion implantation has a substantial impact on increasing resistance against tantalum corrosion. After the corrosion test, scanning electron microscopy (SEM) analyzed the samples' surface morphologies. In addition, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. The purpose of this paper was to obtain the perfect condition for the formation of tantalum corrosion resistance. In order to evaluate the effect of the ion implantation on the corrosion behavior, potentiodynamic tests were performed. The results show that the corrosion resistance of the samples strongly depends on the implantation doses.

Effects of reduction temperature on the optoelectronic properties of diodes based on n-type Si and reduced graphene oxide doped with a conductive polymer

International Nuclear Information System (INIS)

Zeng, Jian-Jhou; Lin, Yow-Jon; Ruan, Cheng-He; Lin, Jian-Huang

2013-01-01

The effect of reduction temperature on the optoelectronic properties of diodes based on n-type Si and reduced graphene oxide (RGO) doped with a conductive polymer [poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS)] was examined in this study. It is found that conductivity of RGO-doped PEDOT:PSS films increases with increasing reduction temperature of graphene oxide (GO) sheets. The improvement of electrical conductivity is considered to mainly come from the carrier mobility enhancement. In addition, the ideality factor of n-type Si/RGO-doped PEDOT:PSS diodes decreases with increasing reduction temperature of GO sheets. The device-performance improvement originates from high-mobility hole transport combined with long-lifetime electron trapping in the RGO-doped PEDOT:PSS film. In addition, note that a suitable reduction temperature is an important issue for improving the device performance. (paper)

An exploration in mineral supply chain mapping using tantalum as an example

Science.gov (United States)

Soto-Viruet, Yadira; Menzie, W. David; Papp, John F.; Yager, Thomas R.

2013-01-01

This report uses the supply chain of tantalum (Ta) to investigate the complexity of mineral and metal supply chains in general and show how they can be mapped. A supply chain is made up of all the manufacturers, suppliers, information networks, and so forth, that provide the materials and parts that go into making up a final product. The mineral portion of the supply chain begins with mineral material in the ground (the ore deposit); extends through a series of processes that include mining, beneficiation, processing (smelting and refining), semimanufacture, and manufacture; and continues through transformation of the mineral ore into concentrates, refined mineral commodities, intermediate forms (such as metals and alloys), component parts, and, finally, complex products. This study analyses the supply chain of tantalum beginning with minerals in the ground to many of the final goods that contain tantalum.

Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

Science.gov (United States)

Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

2015-09-14

Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

Studies on the electrical properties of reactive DC magnetron-sputtered indium-doped silver oxide thin films: The role of oxygen

Energy Technology Data Exchange (ETDEWEB)

Subrahmanyam, A [Semiconductor Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Barik, Ullash Kumar [Semiconductor Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

2007-03-15

Indium ({approx}10 at.%)-doped silver oxide (AIO) thin films have been prepared on glass substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target made of pure (99.99%) silver and indium (90:10 at.%) metals. The oxygen flow rates have been varied in the range 0.00-3.44 sccm during sputtering. The X-ray diffraction data on these indium-doped silver oxide films show polycrystalline nature. With increasing oxygen flow rate, the carrier concentration, the Hall mobility and the electron mean free path decrease. These films show a very low positive temperature coefficient of resistivity {approx}3.40x10{sup -8} ohm-cm/K. The work function values for these films (measured by Kelvin probe technique) are in the range 4.81-5.07 eV. The high electrical resistivity indicate that the films are in the island state (size effects). Calculations of the partial ionic charge (by Sanderson's theory) show that indium doping in silver oxide thin films enhance the ionicity.

Studies on the electrical properties of reactive DC magnetron-sputtered indium-doped silver oxide thin films: The role of oxygen

International Nuclear Information System (INIS)

Subrahmanyam, A.; Barik, Ullash Kumar

2007-01-01

Indium (∼10 at.%)-doped silver oxide (AIO) thin films have been prepared on glass substrates at room temperature (300 K) by reactive DC magnetron sputtering technique using an alloy target made of pure (99.99%) silver and indium (90:10 at.%) metals. The oxygen flow rates have been varied in the range 0.00-3.44 sccm during sputtering. The X-ray diffraction data on these indium-doped silver oxide films show polycrystalline nature. With increasing oxygen flow rate, the carrier concentration, the Hall mobility and the electron mean free path decrease. These films show a very low positive temperature coefficient of resistivity ∼3.40x10 -8 ohm-cm/K. The work function values for these films (measured by Kelvin probe technique) are in the range 4.81-5.07 eV. The high electrical resistivity indicate that the films are in the island state (size effects). Calculations of the partial ionic charge (by Sanderson's theory) show that indium doping in silver oxide thin films enhance the ionicity

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus.

Science.gov (United States)

Kramer, Nicolaas J; Schramke, Katelyn S; Kortshagen, Uwe R

2015-08-12

Degenerately doped silicon nanocrystals are appealing plasmonic materials due to silicon's low cost and low toxicity. While surface plasmonic resonances of boron-doped and phosphorus-doped silicon nanocrystals were recently observed, there currently is poor understanding of the effect of surface conditions on their plasmonic behavior. Here, we demonstrate that phosphorus-doped silicon nanocrystals exhibit a plasmon resonance immediately after their synthesis but may lose their plasmonic response with oxidation. In contrast, boron-doped nanocrystals initially do not exhibit plasmonic response but become plasmonically active through postsynthesis oxidation or annealing. We interpret these results in terms of substitutional doping being the dominant doping mechanism for phosphorus-doped silicon nanocrystals, with oxidation-induced defects trapping free electrons. The behavior of boron-doped silicon nanocrystals is more consistent with a strong contribution of surface doping. Importantly, boron-doped silicon nanocrystals exhibit air-stable plasmonic behavior over periods of more than a year.

Low-temperature CO oxidation over Cu/Pt co-doped ZrO2 nanoparticles synthesized by solution combustion.

Science.gov (United States)

Singhania, Amit; Gupta, Shipra Mital

2017-01-01

Zirconia (ZrO 2 ) nanoparticles co-doped with Cu and Pt were applied as catalysts for carbon monoxide (CO) oxidation. These materials were prepared through solution combustion in order to obtain highly active and stable catalytic nanomaterials. This method allows Pt 2+ and Cu 2+ ions to dissolve into the ZrO 2 lattice and thus creates oxygen vacancies due to lattice distortion and charge imbalance. High-resolution transmission electron microscopy (HRTEM) results showed Cu/Pt co-doped ZrO 2 nanoparticles with a size of ca. 10 nm. X-ray diffraction (XRD) and Raman spectra confirmed cubic structure and larger oxygen vacancies. The nanoparticles showed excellent activity for CO oxidation. The temperature T 50 (the temperature at which 50% of CO are converted) was lowered by 175 °C in comparison to bare ZrO 2 . Further, they exhibited very high stability for CO reaction (time-on-stream ≈ 70 h). This is due to combined effect of smaller particle size, large oxygen vacancies, high specific surface area and better thermal stability of the Cu/Pt co-doped ZrO 2 nanoparticles. The apparent activation energy for CO oxidation is found to be 45.6 kJ·mol -1 . The CO conversion decreases with increase in gas hourly space velocity (GHSV) and initial CO concentration.

Transparent indium-tin oxide/indium-gallium-zinc oxide Schottky diodes formed by gradient oxygen doping

Science.gov (United States)

Ho, Szuheng; Yu, Hyeonggeun; So, Franky

2017-11-01

Amorphous InGaZnO (a-IGZO) is promising for transparent electronics due to its high carrier mobility and optical transparency. However, most metal/a-IGZO junctions are ohmic due to the Fermi-level pinning at the interface, restricting their device applications. Here, we report that indium-tin oxide/a-IGZO Schottky diodes can be formed by gradient oxygen doping in the a-IGZO layer that would otherwise form an ohmic contact. Making use of back-to-back a-IGZO Schottky junctions, a transparent IGZO permeable metal-base transistor is also demonstrated with a high common-base gain.

New Sesame equation of state for tantalum

International Nuclear Information System (INIS)

Greeff, C. W.; Johnson, J. D.

2000-01-01

A new Sesame equation of state (EOS) table has been created for tantalum. This EOS incorporates new high pressure Hugoniot data and diamond anvil cell compression data. The new EOS gives better agreement with this data as well as with sound speeds and Hugoniot curves of porous samples

Communication: Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene

Energy Technology Data Exchange (ETDEWEB)

Cantatore, Valentina, E-mail: valcan@chalmers.se; Panas, Itai [Department of Chemistry and Chemical Engineering, Energy & Materials, Chalmers University of Technology, Gothenburg (Sweden)

2016-04-21

We use density functional theory to describe a novel way for metal free catalytic reduction of nitric oxide NO utilizing boron doped graphene. The present study is based on the observation that boron doped graphene and O—N=N—O{sup −} act as Lewis acid-base pair allowing the graphene surface to act as a catalyst. The process implies electron assisted N=N bond formation prior to N—O dissociation. Two N{sub 2} + O{sub 2} product channels, one of which favoring N{sub 2}O formation, are envisaged as outcome of the catalytic process. Besides, we show also that the N{sub 2} + O{sub 2} formation pathways are contrasted by a side reaction that brings to N{sub 3}O{sub 3}{sup −} formation and decomposition into N{sub 2}O + NO{sub 2}{sup −}.

Effects of concentration of reduced graphene oxide on properties of sol–gel prepared Al-doped zinc oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Chou, Ching-Tian; Wang, Fang-Hsing, E-mail: fansen@dragon.nchu.edu.tw; Chen, Wei-Chun

2016-04-30

Reduced-graphene-oxide-incorporated aluminum-doped zinc oxide (AZO:rGO) composite thin films were synthesized on glass substrates by using the sol–gel method. The effect of the rGO concentration (0–3 wt%) on structural, electrical, and optical properties of the composite film was investigated by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Hall-effect measurement, and ultraviolet–visible spectrometry. All of the composite films showed a typical hexagonal wurtzite structure, and the films incorporated with 1 wt% rGO showed the highest (0 0 2) peak intensity. The sheet resistance of the films was effectively reduced by a factor of more than two as the rGO ratio increased from 0 to 1 wt%. However, the sheet resistance increased with a further increase in the rGO ratio. The optical transmittance of the composite film monotonically decreased with increasing the rGO ratio from 0 to 3 wt%. The average optical transmittance (400–700 nm) of the AZO:rGO thin film within 1 wt% rGO was above 81%. - Highlights: • Reduced-graphene-oxide-doped ZnO:Al composite films are synthesized by sol–gel. • All AZO:rGO thin films show a typical hexagonal wurtzite structure. • Sheet resistance of AZO:rGO(1 wt%) film decreases by a factor of more than two. • The average visible transmittance of the AZO:rGO(1 wt%) film was 81%.

Liquid Phase Plasma Synthesis of Iron Oxide Nanoparticles on Nitrogen-Doped Activated Carbon Resulting in Nanocomposite for Supercapacitor Applications.

Science.gov (United States)

Lee, Heon; Lee, Won-June; Park, Young-Kwon; Ki, Seo Jin; Kim, Byung-Joo; Jung, Sang-Chul

2018-03-25

Iron oxide nanoparticles supported on nitrogen-doped activated carbon powder were synthesized using an innovative plasma-in-liquid method, called the liquid phase plasma (LPP) method. Nitrogen-doped carbon (NC) was prepared by a primary LPP reaction using an ammonium chloride reactant solution, and an iron oxide/NC composite (IONCC) was prepared by a secondary LPP reaction using an iron chloride reactant solution. The nitrogen component at 3.77 at. % formed uniformly over the activated carbon (AC) surface after a 1 h LPP reaction. Iron oxide nanoparticles, 40~100 nm in size, were impregnated homogeneously over the NC surface after the LPP reaction, and were identified as Fe₃O₄ by X-ray photoelectron spectroscopy and X-ray diffraction. NC and IONCCs exhibited pseudo-capacitive characteristics, and their specific capacitance and cycling stability were superior to those of bare AC. The nitrogen content on the NC surface increased the compatibility and charge transfer rate, and the composites containing iron oxide exhibited a lower equivalent series resistance.

Three-dimensional Nitrogen-Doped Reduced Graphene Oxide/Carbon Nanotube Composite Catalysts for Vanadium Flow Batteries

Energy Technology Data Exchange (ETDEWEB)

Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Song, Junhua [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Engelhard, Mark H. [Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354 USA.; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Lin, Yuehe [School of Mechanical and Materials Engineering, Washington State University, WA, 99164 USA.; Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354 USA.

2017-02-22

The development of vanadium redox flow battery is limited by the sluggish kinetics of the reaction, especially the cathodic VO2+/VO2+ redox couples. Therefore, it is vital to develop new electrocatalyst with enhanced activity to improve the battery performance. Herein, we first synthesized the hydrogel precursor by a facile hydrothermal method. After the following carbonization, nitrogen-doped reduced graphene oxide/carbon nanotube composite was obtained. By virtue of the large surface area and good conductivey, which are ensured by the unique hybrid structure, as well as the proper nitrogen doping, the as-prepared composite presents enhanced catalytic performance toward the VO2+/VO2+ redox reaction. We also demonstrated the composite with carbon nanotube loading of 2 mg/mL exhibits the highest activity and remarkable stability in aqueous solution due to the strong synergy between reduced graphene oxide and carbon nanotubes, indicating that this composite might show promising applications in vanadium redox flow battery.

Cast and hipped gamma titanium aluminum alloys modified by chromium, boron, and tantalum

International Nuclear Information System (INIS)

Huang, Shyhchin.

1993-01-01

A cast body is described of a chromium, boron, and tantalum modified titanium aluminum alloy, said alloy consisting essentially of titanium, aluminum, chromium, boron, and tantalum in the following approximate atomic ratio: Ti-Al 45-50 Cr 1-3 Ta 1-8 B 0.1-0.3 , and said alloy having been prepared by casting the alloy to form said cast body and by HIPping said body

Corrosion studies of tantalum in oxidizing media - intercomparison of data obtained in model media and in a test facility

International Nuclear Information System (INIS)

Vehlow, J.; Wieczorek, H.

1989-01-01

The suitability of tantalum as a material for wet incineration of combustible wastes has been tested in model mixtures of sulfuric and nitric acid at about 250deg C. In addition parts of a semi-technical test facility have been investigated, which had been in operation for more than 3000 h. In general there is good correspondence between predicted wall losses and those found under real conditions. (orig.) [de

Tantalum-based multilayer coating on cobalt alloys in total hip and knee replacement

Energy Technology Data Exchange (ETDEWEB)

Balagna, C., E-mail: cristina.balagna@polito.it [Institute of Materials Engineering and Physics, Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24,10129 Torino (Italy); Faga, M.G. [Istituto di Scienza e Tecnologia dei Materiali Ceramici, Consiglio Nazionale delle Ricerche, Strada delle Cacce 73, 10135 Torino (Italy); Spriano, S. [Institute of Materials Engineering and Physics, Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24,10129 Torino (Italy)

2012-05-01

Cobalt-chromium-molybdenum (CoCrMo) alloys are widely used in total hip and knee joint replacement, due to high mechanical properties and resistance to wear and corrosion. They are able to form efficient artificial joints by means of coupling metal-on-polymer or metal-on-metal contacts. However, a high concentration of stress and direct friction between surfaces leads to the formation of polyethylene wear debris and the release of toxic metal ions into the human body, limiting, as a consequence, the lifetime of implants. The aim of this research is a surface modification of CoCrMo alloys in order to improve their biocompatibility and to decrease the release of metal ions and polyethylene debris. Thermal treatment in molten salts was the process employed for the deposition of tantalum-enriched coating. Tantalum and its compounds are considered biocompatible materials with low ion release and high corrosion resistance. Three different CoCrMo alloys were processed as substrates. An adherent coating of about 1 {mu}m of thickness, with a multilayer structure consisting of two tantalum carbides and metallic tantalum was deposited. The substrates and modified layers were characterized by means of structural, chemical and morphological analysis. Moreover nanoindentation, scratch and tribological tests were carried out in order to evaluate the mechanical behavior of the substrates and coating. The hardness of the coated samples increases more than double than the untreated alloys meanwhile the presence of the coating reduced the wear volume and rate of about one order of magnitude. - Highlights: Black-Right-Pointing-Pointer Thermal treatment in molten salts deposits a Ta-based coating on Co-based alloys. Black-Right-Pointing-Pointer Coating is composed by one or two tantalum carbides and/or metallic tantalum. Black-Right-Pointing-Pointer The coating structure depends on thermal temperature and substrates carbon content. Black-Right-Pointing-Pointer Coating is able to

Homo-junction ferroelectric field-effect-transistor memory device using solution-processed lithium-doped zinc oxide thin films

KAUST Repository

Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Bhansali, Unnat. S.; Alshareef, Husam N.

2012-01-01

High performance homo-junction field-effect transistor memory devices were prepared using solution processed transparent lithium-doped zinc oxide thin films for both the ferroelectric and semiconducting active layers. A highest field-effect mobility

Efficient polymer:fullerene bulk heterojunction solar cells with n-type doped titanium oxide as an electron transport layer

Energy Technology Data Exchange (ETDEWEB)

Choi, Youna [Heeger Center for Advanced Material & Research Institute of Solar and Sustainable Energies, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Geunjin [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Heejoo, E-mail: heejook@gist.ac.kr [Heeger Center for Advanced Material & Research Institute of Solar and Sustainable Energies, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Kim, Sun Hee [School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Lee, Kwanghee, E-mail: klee@gist.ac.kr [Heeger Center for Advanced Material & Research Institute of Solar and Sustainable Energies, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

2015-05-29

We have reported a highly n-type doped solution-processed titanium metal oxide (TiO{sub x}) for use as an efficient electron-transport layer (ETL) in polymer:fullerene bulk heterojunction (BHJ) solar cells. When the metal ions (Ti) in TiO{sub x} are partially substituted by niobium (Nb), the charge carrier density increased, by an order of magnitude, because of the large electronegativity of Nb compared to that of Ti. Therefore, the work function (WF) of Nb-doped metal oxide (Nb-TiO{sub x}) decreases from 4.75 eV (TiO{sub x}) to 4.66 eV (Nb-TiO{sub x}), leading to an enhancement in the power conversion efficiency (PCE) of BHJ solar cells with a Nb-TiO{sub x} ETL (from 7.99% to 8.40%). - Highlights: • Solution processable Nb-doped TiO{sub x} was developed by simple sol-gel synthesis. • Charge carrier density in TiO{sub x} is significantly increased by introducing Nb element. • The work function value of Nb-doped TiO{sub x} is reduced by introducing Nb element. • A charge recombination inside of PSC with Nb-TiO{sub x} was effectively suppressed.

Fabrication and use of zircaloy/tantalum-sheathed cladding thermocouples and molybdenum/rhenium-sheathed fuel centerline thermocouples

International Nuclear Information System (INIS)

Wilkins, S.C.; Sepold, L.K.

1985-01-01

The thermocouples described in this report are zircaloy/tantalum-sheathed and molybdenum/rhenium alloy-sheathed instruments intended for fuel rod cladding and fuel centerline temperature measurements, respectively. Both types incorporate beryllium oxide insulation and tungsten/rhenium alloy thermoelements. These thermocouples, operated at temperatures of 2000 0 C and above, were developed for use in the internationally sponsored Severe Fuel Damage test series in the Power Burst Facility. The fabrication steps for both thermocouple types are described in detail. A laser-welding attachment technique for the cladding-type thermocouple is presented, and experience with alternate materials for cladding and fuel therocouples is discussed

Poisoning Experiments Aimed at Discriminating Active and Less-Active Sites of Silica-Supported Tantalum Hydride for Alkane Metathesis

KAUST Repository

Saggio, Guillaume

2010-10-04

Only 50% of the silica-supported tantalum hydride sites are active in the metathesis of propane. Indeed, more than 45% of the tantalum hydride can be eliminated by a selective oxygen poisoning of inactive sites with no significant decrease in the global turnover. Conversely, cyclopentane induces no such selective poisoning. Hence, the active tantalum hydride sites that show greater resistance to oxygen poisoning correspond to the νTa-H bands of higher wavenumbers, particularly that at 1860cm-1. These active tantalum hydride sites should correspond to tris- or monohydride species relatively far from silica surface oxygen atoms. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recovery of metal values and hydrofluoric acid from tantalum and columbium waste sludge

International Nuclear Information System (INIS)