Effect of increasing disorder on superconductivity of Mo/Nb superlattices

Science.gov (United States)

Pereiro, Juan; Saerbeck, Thomas; Schuller, Ivan K.

2015-08-01

We investigated the superconducting properties of Nb/Mo superlattices (SLs). The structural changes as a function of Nb and Mo layer thickness allow us to investigate the effect of disorder on the superconducting properties in a controlled fashion. Systematic structural studies provide quantitative measures of disorder parameters, such as roughness, interdiffusion, and strain, which allow separating their effect on the individual superconducting layers. The Mo critical temperature does not change as the layer thickness decreases below its coherence length. Thus, the SL critical temperatures in the presence of disorder and proximity effects can be modeled by considering only the effects of the Nb mean free path and coherence length. With increasing layer thickness, the SL critical temperatures approach Nb bulk values. Contrary to expectations the Tc of Mo remains below the Nb Tc. We discuss the results using existing theories based on Coulomb repulsion or changes in the density of states at the Fermi surface as a function of disorder. Questions about current understanding of the effect of disorder on superconductivity arise from the results.

Development of Ti-12Mo-3Nb alloy for biomedical application; Desenvolvimento da liga Ti-12Mo-3Nb para aplicacao biomedica

Energy Technology Data Exchange (ETDEWEB)

Panaino, J.V.P.; Gabriel, S.B., E-mail: josevicentepanaino@hotmail.co [Centro Universidade de Volta Redonda (UNIFOA), RJ (Brazil); Mei, P. [Universidade Estadual de Campinas (DEMa/UNICAMP), SP (Brazil). Dept. de Materiais; Brum, M.V. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Programa de Engenharia Metalurgica e de Materiais; Nunes, C.A. [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia

2010-07-01

The titanium alloys are quite satisfactory for biomedical applications due to their physical, mechanical and biological properties. Recent studies focuses on the development of beta type titanium alloys, composed of toxic elements (Nb, Mo, Ta ,...), because they have more advantages than alpha and alpha + beta (Ti- 6Al-4V) alloys such as lower modulus of elasticity, better plasticity and, moreover, the process variables can be controlled to produce selected results. This project focused on the development and characterization of Ti-12Mo-3Nb alloy in the condition 'as cast' and after thermomechanical treatment. The material was characterized in different conditions by X-ray diffraction, optical microscopy, microhardness measurements and elasticity modulus. The results showed that the forged Ti-12Mo-3Nb alloy showed the best combination of properties, being a promising candidate for use as implant. (author)

MoS{sub 2} on an amorphous HfO{sub 2} surface: An ab initio investigation

Energy Technology Data Exchange (ETDEWEB)

Scopel, W. L., E-mail: wlscopel@if.uff.br [Departamento de Física, Universidade Federal do Espírito Santo, Vitória, Brazil and Departamento de Ciências Exatas, Universidade Federal Fluminense, Volta Redonda, Rio de Janerio (Brazil); Miwa, R. H., E-mail: hiroki@infis.ufu.br; Schmidt, T. M., E-mail: tome@infis.ufu.br [Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Minas Gerais (Brazil); Venezuela, P., E-mail: vene@if.uff.br [Instituto de Física, Universidade Federal Fluminense, Niterói, Rio de Janerio (Brazil)

2015-05-21

The energetic stability, electronic and structural properties of MoS{sub 2} adsorbed on an amorphous a-HfO{sub 2} surface (MoS{sub 2}/HfO{sub 2}) are examined through ab initio theoretical investigations. Our total energy results indicate that the formation of MoS{sub 2}/HfO{sub 2} is an exothermic process with an adsorption energy of 34 meV/Å{sup 2}, which means that it is more stable than similar systems like graphene/HfO{sub 2} and MoS{sub 2}/SiO{sub 2}. There are no chemical bonds at the MoS{sub 2}-HfO{sub 2} interface. Upon formation of MoS{sub 2}/HfO{sub 2}, the electronic charge distribution is mostly localized at the interface region with no net charge transfer between the adsorbed MoS{sub 2} sheet and –HfO{sub 2} surface. However, the MoS{sub 2} sheet becomes n-type doped when there are oxygen vacancies in the HfO{sub 2} surface. Further investigation of the electronic distribution reveals that there are no electron- and hole-rich regions (electron-hole puddles) on the MoS{sub 2} sheet, which makes this system promising for use in high-speed nanoelectronic devices.

Photorefractive features of non-stoichiometry codoped Hf:Fe:LiNbO3 single crystals

International Nuclear Information System (INIS)

Liu, Bo; Li, Chunliang; Bi, Jiancong; Sun, Liang; Xu, Yuheng

2008-01-01

Hf(2mol%):Fe(0.05wt%):LiNbO 3 crystals with various [Li]/[Nb] ratios of 0.94, 1.05, 1.2 and 1.38 have been grown. The photorefractive resistant ability increases with the accretion of [Li]/[Nb] ratio. When the ratio of [Li]/[Nb] is 1.20 or 1.38, the OH - absorption band shifts to about 3477cm -1 . The mechanisms of the photorefractive resistant ability increase and the absorption band shift have been discussed. The exponential gain coefficient (Γ) of the crystals was measured with two-beam coupling method and the effective charge carrier concentration (N eff ) was calculated. The results show that Γ and N eff increase with the accretion of [Li]/[Nb] ratio. The temperature effect of codoped Hf:Fe:LiNbO 3 crystals was also studied, it was found that the exponential gain coefficient increase dramatically at about 55 C, 70 C and 110 C, this is due to the inner electric field which is resulted from structure phase change. (copyright 2007 WILEY -VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Mechanical Properties of TiTaHfNbZr High-Entropy Alloy Coatings Deposited on NiTi Shape Memory Alloy Substrates

Science.gov (United States)

Motallebzadeh, A.; Yagci, M. B.; Bedir, E.; Aksoy, C. B.; Canadinc, D.

2018-04-01

TiTaHfNbZr high-entropy alloy (HEA) thin films with thicknesses of about 750 and 1500 nm were deposited on NiTi substrates by RF magnetron sputtering using TiTaHfNbZr equimolar targets. The thorough experimental analysis on microstructure and mechanical properties of deposited films revealed that the TiTaHfNbZr films exhibited amorphous and cauliflower-like structure, where grain size and surface roughness increased concomitant with film thickness. More importantly, the current findings demonstrate that the TiTaHfNbZr HEA films with mechanical properties of the same order as those of the NiTi substrate constitute promising biomedical coatings effective in preventing Ni release.

Mechanical Properties of TiTaHfNbZr High-Entropy Alloy Coatings Deposited on NiTi Shape Memory Alloy Substrates

Science.gov (United States)

Motallebzadeh, A.; Yagci, M. B.; Bedir, E.; Aksoy, C. B.; Canadinc, D.

2018-06-01

TiTaHfNbZr high-entropy alloy (HEA) thin films with thicknesses of about 750 and 1500 nm were deposited on NiTi substrates by RF magnetron sputtering using TiTaHfNbZr equimolar targets. The thorough experimental analysis on microstructure and mechanical properties of deposited films revealed that the TiTaHfNbZr films exhibited amorphous and cauliflower-like structure, where grain size and surface roughness increased concomitant with film thickness. More importantly, the current findings demonstrate that the TiTaHfNbZr HEA films with mechanical properties of the same order as those of the NiTi substrate constitute promising biomedical coatings effective in preventing Ni release.

Enhanced photorefractive properties in Hf, Ce and Cu co-doped LiNbO{sub 3} crystals for holographic application

Energy Technology Data Exchange (ETDEWEB)

Zhang, Tao, E-mail: tzhang_hit02@yahoo.com [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China); Wang, Xin; Geng, Tao; Tong, Chengguo [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Kang, Chong [Key Laboratory of In-fiber Integrated Optics, Ministry of Education of China, Harbin Engineering University, Harbin 150001 (China); College of Science, Harbin Engineering University, Harbin 150001 (China); Postdoctoral Research Station of Mechanical Engineering, College of Mechanical and Electrical Engineering, Harbin Engineering University, Harbin 150001 (China)

2015-04-25

Graphical abstract: Correlation spots of 200 holograms in a Hf, Ce and Cu co-doped LiNbO{sub 3}. - Highlights: • Several doped LiNbO{sub 3} crystals with various level of Hf doping were grown by Cz method. • IR peak shift is attributed to the complex defect change at different level of Hf. • Enhanced photorefractive properties have been got with higher Hf-doping level. • Reduced defect and increased photoconductivity are responsible for optical properties. • 200 holograms’ experiment is realized in a coherent volume 0.073 cm{sup 3}. - Abstract: Hf, Ce and Cu co-doped LiNbO{sub 3} crystals with various level of Hf doping were grown in air by a conventional Cz method. The infrared spectra were measured to discuss the defect structures and the mechanism of the absorption peak shift in these crystals. The light-induced scattering of the crystals was evaluated by the transmitted light method. The influence of the Hf-doping level on the photorefractive properties of Hf, Ce and Cu co-doped LiNbO{sub 3} crystals was studied via two-beam coupling. It is found that proper doping Hf is an efficient method to enhance the comprehensive photorefractive properties of the LiNbO{sub 3}. Using one of these crystals as medium, 200 holograms storage and correlation experiments based on angle fractal multiplexing have been realized in a coherent volume 0.073 cm{sup 3}. Moreover the diffraction efficiency is uniform and the storage density has reached 2.2 Gb/cm{sup 3}.

A survey of the mechanical properties of uranium alloys U-5Mo-3Nb wt.% and U-3Mo-3Nb wt.%

Energy Technology Data Exchange (ETDEWEB)

Dupont, G.

1969-04-15

In a continuing program on the development of soft and ductile uranium alloys for armament applications, two compositions were studied. These gamma extruded uranium alloys were U-5Mo-3Nb wt.% and U-3Mo-3Nb wt.%. This study was carried out to determine the influence of tempering heat treatments associated with extrusion on the ductility of these uranium alloys. The mechanical properties of both alloys were measured in the extruded condition, in the extruded and annealed condition and in the quenched and tempered condition. A maximum elongation of 13.7% in tension with a low amount of work hardening was obtained for the U-3Mo-3Nb wt.% alloy after 1 1/2 hours anneal at 1200 deg F (650 deg C) followed by a rapid cooling in water at 70 deg F (21 deg C). A maximum elongation of 17.3% with a large amount of work hardening was obtained for alloy U-5Mo-3Nb wt.% after vacuum annealing, normalizing, gamma phase solubilizing at 1500 deg F (815 deg C) and quenching in water at 700 deg F (210 deg C). The maximum ductility achieved in these two alloys by our approaches is low compared with the ductility of Armco Iron employed for the same applications in the field of ballistics.

Phase formation in the K2MoO4-Lu2(MoO4)3-Hf(MoO4)2 system and the structural study of triple molybdate K5LuHf(MoO4)6

International Nuclear Information System (INIS)

Romanova, E.Yu.; Bazarov, B.G.; Tushinova, Yu.L.; Fedorov, K.N.; Bazarova, Zh.G.; Klevtsova, R.F.; Glinskaya, L.A.

2007-01-01

Interactions in the ternary system K 2 MoO 4 -Lu 2 (MoO 4 ) 3 -Hf(MoO 4 ) 2 have been studied by X-ray powder diffraction and differential thermal analysis. A new triple (potassium lutetium hafnium) molybdate with the 5 : 1 : 2 stoichiometry has been found. Monocrystals of this molybdate have been grown. Its X-ray diffraction structure has been refined (an X8 APEX automated diffractometer, MoK α radiation, 1960 F(hkl), R = 0.0166). The trigonal unit cell has the following parameters: a = 10.6536(1) A, c = 37.8434(8) A, V=3719.75(9) A, Z = 6, space group R3-bar c. The mixed 3D framework of the structure is built of Mo tetrahedra sharing corners with two independent (Lu,Hf)O 6 octahedra. Two sorts of potassium atoms occupy large framework voids [ru

Performance of Nb protective diffusion coating on U-Mo/Al dispersion fuel

Energy Technology Data Exchange (ETDEWEB)

Kim, Ji-Hyeon; Sohn, Dong-Seong [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Kim, Sunghwan; Nam, Ji Min; Lee, Kyu Hong; Park, Jong Man [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

To achieve this aim, it is necessary to increase the volume fraction of fuel particles inside the meat. However, the technical limit is reached at approximately 55 vol.% of fuel particles in the aluminum matrix. As a solution, an uranium compound with an higher uranium density than existing U3Si2 fuel has to be selected. Also alloying the uranium must stabilize γ-phase of uranium at room temperature because adequate properties of the γ -phase of uranium showed a good irradiation behavior in the past. Hence, U-Mo alloys were selected as the best candidates. The formation of interaction phase is a critical problem to apply U-Mo alloys to the high performance research reactor. Different means have been proposed to reduce the interaction between U-Mo fuel and Al matrix. There are three means. : 1. Addition of a diffusion limiting element to the matrix 2. Insertion of a diffusion barrier at the interface between the U-Mo and the Al 3. Alloying of the U-Mo with a third element Here we present the effect of Nb coating as diffusion barrier on formation of interaction layers between UMo powders and Al matrix. We present the effect of Nb coating on formation of interaction layers between U-Mo powders and Al matrix. Centrifugally atomized U-7 wt.% Mo powders were used, and Nb was coated on the surface of U-7 wt.% Mo by sputtering. Subsequently, the Nb-coated U-7 wt.% Mo powders were mixed with pure Al powders, and were made into compacts. The compacts were annealed at 550 .deg. C for 1, 3, 5 hours, respectively, and the result showed that the Nb coating on U-7 wt.% Mo effectively suppressed the growth of interaction layers between U-7 wt.% Mo and Al matrix.

Phase formation in the Rb2MoO4-Li2MoO4-Hf(MoO4)2 system and the crystal structure of Rb5(Li1/3Hf5/3)(MoO4)6

International Nuclear Information System (INIS)

Solodovnikov, S.F.; Zolotova, E.S.; Balsanova, L.V.; Bazarov, B.G.; Bazarova, Zh.G.

2003-01-01

Phase formation in the Rb 2 MoO 4 -Li 2 MoO 4 -Hf(MoO 4 ) 2 system is studied in subsolidus region in air by the method of crossing sections. Three ternary molybdates are detected in the system. Compositions of two of them are corroborated by selection of isostructural analogues [ru

Internal friction peaks observed in explosively deformed polycrystalline Mo, Nb, and Cu

Science.gov (United States)

Rieu, G. E.; Grimes, H. H.; Romain, J. P.; Defouquet, J.

1974-01-01

Explosive deformation (50 kbar range) induced, in Cu, Mo and Nb, internal friction peaks identical to those observed after large normal deformation. The variation of the peaks with pressure for Mo and Nb lead to an explanation of these processes in terms of double kink generation in screw and edge dislocations.

Study on soft magnetic properties of Finemet-type nanocrystalline alloys with Mo substituting for Nb

Energy Technology Data Exchange (ETDEWEB)

Jiang, Dehui; Zhou, Bingwen; Jiang, Boyu; Ya, Bin; Zhang, Xingguo [School of Materials Science and Engineering, Dalian University of Technology, Dalian (China)

2017-10-15

The thermal stability, microstructure, and soft magnetic properties as a function of annealing time were studied for Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 3-x}Mo{sub x} (x = 0, 1, 2, 3) (atom percent, at.%,) ribbons. It was found that substituting Nb by Mo reduced the thermal stability. After 15 min short time vacuum annealing, Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 2}Mo{sub 1} and Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1}Mo{sub 2} samples obtained higher permeability and similar coercivity compared to the original Finemet alloy (Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 3}), Mo substituting Nb reduced the optimum annealing time in Finemet-type alloys, and meanwhile marginally increased the saturation magnetization. Substituting all Nb by Mo led to the earlier formation of non-soft magnetic phase, thus deteriorated the soft magnetic properties. XRD and TEM structural analysis showed that in Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 2}Mo{sub 1} and Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1}Mo{sub 2} samples (annealed for 15 min), nanocrystals ∝10 nm in size were obtained, and the good soft magnetic properties of these alloys could be attributed to the small grain size. The relationship between annealing time, soft magnetic properties, and microstructure was established. Reducing annealing time and temperature to obtain best soft magnetic properties could cut down the production costs of Finemet-type alloys. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

On the stabilization of NbV-solutions by ZrIV and HfIV

International Nuclear Information System (INIS)

Soerensen, E.; Bjerre, A.B.

1987-11-01

Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as Cl- and SO 4 --. This is ascribed to the copolymerisation of Nb v and the hydrolyzed ionic species of Zr IV v and Hf IV by which the colloidal particles are masked as Zr- and Hf-compounds. In HCl the particles are positively charged as opposed to when they are in sulphate solution where the Zr- and Hf- sulphate complexes confer a negative charge. The two cases are considered separately. (author)

{sup 91}Nb(p,γ) or there and back again

Energy Technology Data Exchange (ETDEWEB)

Thomas, Benedikt; Glorius, Jan; Reich, Markus; Reifarth, Rene; Sonnabend, Kerstin [Goethe University Frankfurt a.M. (Germany); Blazhev, Andrey; Zell, Karl-Oscar [University of Cologne (Germany); Dressler, Rugard; Schumann, Dorothea [Paul-Scherrer Institute, Villigen (Switzerland); Giesen, Ulrich [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Kritcka, Milan [Charles University, Prague (Czech Republic)

2016-07-01

The cross section of the reaction {sup 91}Nb(p,γ){sup 92}Mo is of special interest to answer questions about the production of the most abundant p nucleus {sup 92}Mo. With {sup 91}Nb being a radioactive nucleus the measurement of this reaction in standard kinematics is a big challenge. To produce a sufficient number of {sup 91}Nb isotopes an enriched {sup 92}Mo target was activated by protons at E{sub p} = 19 MeV. Afterwards the produced {sup 91}Nb isotopes are separated chemically and applied onto a tungsten backing. This leads to approximately 10{sup 16} {sup 91}Nb isotopes. The high proton current delivered by the HF-linear-accelerator FRANZ currently built at Goethe University Frankfurt, Germany, enables the execution of measurement with such limited amount of target material. The goal of our investigation is the determination of the cross section of the {sup 91}Nb(p,γ){sup 92}Mo reaction at 2 MeV proton energy and thereby in the astrophysical relevant energy region. We present the current status and the next steps towards the measurement of this cross section.

Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

KAUST Repository

Ahmed, Bilal; Anjum, Dalaver H.; Hedhili, Mohamed N.; Alshareef, Husam N.

2015-01-01

It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanistic Insight into the Stability of HfO2-Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

KAUST Repository

Ahmed, Bilal

2015-06-01

It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g-1, respectively, at current density of 100 mA g-1. These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2. Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Ti-12Mo-3Nb alloy for biomedical application

International Nuclear Information System (INIS)

Panaino, J.V.P.; Gabriel, S.B.; Mei, P.; Brum, M.V.; Nunes, C.A.

2010-01-01

The titanium alloys are quite satisfactory for biomedical applications due to their physical, mechanical and biological properties. Recent studies focuses on the development of beta type titanium alloys, composed of toxic elements (Nb, Mo, Ta ,...), because they have more advantages than alpha and alpha + beta (Ti- 6Al-4V) alloys such as lower modulus of elasticity, better plasticity and, moreover, the process variables can be controlled to produce selected results. This project focused on the development and characterization of Ti-12Mo-3Nb alloy in the condition 'as cast' and after thermomechanical treatment. The material was characterized in different conditions by X-ray diffraction, optical microscopy, microhardness measurements and elasticity modulus. The results showed that the forged Ti-12Mo-3Nb alloy showed the best combination of properties, being a promising candidate for use as implant. (author)

Anion exchange behaviour of Zr, Hf, Nb, Ta and Pa as homologues of RF and Db in fluoride medium

International Nuclear Information System (INIS)

Monroy G, F.; Trubert, D.; Brillard, L.; Hussonnois, M.; Constantinescu, O.; Le Naour, C.

2010-01-01

Studies of the chemical property of trans actinide elements are very difficult due to their short half-lives and extremely small production yields. However it is still possible to obtain considerable information about their chemical properties, such as the most stable oxidation states in aqueous solution, complexing ability, etc., comparing their behaviour with their lighter homologous in the periodic table. In order to obtain a better knowledge of the behaviour of rutherfordium, RF (element 104), dub nium, Db (element 105) in HF medium, the sorption properties of Zr, Hf, Nb, Ta an Pa, homologues of RF and Db, were studied in NH 4 F/HClO 4 medium in this work. Stability constants of the fluoride complexes of these elements were experimentally obtained from K d obtained at different F - and H + concentrations. The anionic complexes: [Zr(Hf)F 5 ] - , [Zr(Hf)F 6 ] 2- , [Zr(Hf)F 7 ] 3- , [Ta(Pa)F 6 ] - , [Ta(Pa)F 7 ] 2- , [Ta(Pa)F 8 ] 3- , [NbOF 4 ] - and [NbOF 5 ] 2- are present as predominant species in the HF range over investigation. (Author)

Microstructure control of Zr-Nb-Sn alloy with Mo addition for HWR pressure tube application

International Nuclear Information System (INIS)

Hwang, S. K.; Kim, M. H.; Kim, J. H.; Kwon, S. I.; Kim, Y. S.

1997-01-01

As a basic research to develop the material for heavy water reactor pressure tube application the effect of Mo addition to Zr-Nb-Sn alloy was studied for the purpose of minimizing the amount of cold working while maintaining a high strength. To select the target alloy system we first designed various alloy compositions and chose Zr-Nb-Sn and Zr-Nb-Mo through multi-regression analysis of the relationship between the basic properties and the compositions. Plasma arc melting was used to produce the alloys and the microstructure change introduced by the processing steps including hot forging, beta-heat treatment, hot rolling, cold rolling and recrystallization heat treatment was investigated. Recrystallization of Zr-Nb-Sn was retarded by adding Mo and this resulted in a fine grain structure in Zr-Nb-Sn-Mo alloy. Beside the retarding effect recrystallization, Mo increased the amount of residual beta phase and showed an indication of precipitation hardening, which added up to the possibility of applying the alloy for the desired usage. (author)

Anion exchange behaviour of Zr, Hf, Nb, Ta and Pa as homologues of RF and Db in fluoride medium

Energy Technology Data Exchange (ETDEWEB)

Monroy G, F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Trubert, D.; Brillard, L.; Hussonnois, M.; Constantinescu, O.; Le Naour, C., E-mail: fabiola.monroy@inin.gob.m [Institut de Physique Nucleaire, F-91406 Orsay, France (France)

2010-07-01

Studies of the chemical property of trans actinide elements are very difficult due to their short half-lives and extremely small production yields. However it is still possible to obtain considerable information about their chemical properties, such as the most stable oxidation states in aqueous solution, complexing ability, etc., comparing their behaviour with their lighter homologous in the periodic table. In order to obtain a better knowledge of the behaviour of rutherfordium, RF (element 104), dub nium, Db (element 105) in HF medium, the sorption properties of Zr, Hf, Nb, Ta an Pa, homologues of RF and Db, were studied in NH{sub 4}F/HClO{sub 4} medium in this work. Stability constants of the fluoride complexes of these elements were experimentally obtained from K{sub d} obtained at different F{sup -} and H{sup +} concentrations. The anionic complexes: [Zr(Hf)F{sub 5}]{sup -}, [Zr(Hf)F{sub 6}]{sup 2-}, [Zr(Hf)F{sub 7}]{sup 3-}, [Ta(Pa)F{sub 6}]{sup -}, [Ta(Pa)F{sub 7}]{sup 2-}, [Ta(Pa)F{sub 8}]{sup 3-}, [NbOF{sub 4}]{sup -} and [NbOF{sub 5}]{sup 2-} are present as predominant species in the HF range over investigation. (Author)

Structure and physical properties of ternary uranium transition-metal antimonides U3MSb5 (M = Zr, Hf, Nb)

International Nuclear Information System (INIS)

Tkachuk, Andriy V.; Muirhead, Craig P.T.; Mar, Arthur

2006-01-01

The ternary uranium transition-metal antimonides U 3 MSb 5 (M = Zr, Hf, Nb) were prepared by arc-melting reactions followed by annealing at 800 deg. C, or by use of a Sn flux. These compounds extend the previously known series U 3 MSb 5 (M = Ti, V, Cr, Mn) and RE 3 MSb 5 (RE = La, Ce, Pr, Nd, Sm; M = Ti, Zr, Hf, Nb). The crystal structures of U 3 MSb 5 were determined by single-crystal X-ray diffraction data (Pearson symbol hP18, hexagonal, space group P6 3 /mcm, Z = 2; U 3 ZrSb 5 , a = 9.2223(3) A, c = 6.1690(2) A; U 3 HfSb 5 , a = 9.2084(4) A, c = 6.1629(3) A; U 3 NbSb 5 , a = 9.1378(4) A, c 6.0909(6) A). U 3 TaSb 5 has also been identified in microcrystalline form (a = 9.233(3) A, c = 6.142(3) A). Four-probe electrical resistivity measurements on single crystals and dc magnetic susceptibility measurements on powders indicated prominent transitions that are attributed to ferromagnetic ordering. The Curie temperatures, T C , located from ac magnetic susceptibility curves, are 135 K for U 3 ZrSb 5 , 141 K for U 3 HfSb 5 , and 107 K for U 3 NbSb 5

Effects of substitution of Mo for Nb on less-common properties of Finemet alloys

International Nuclear Information System (INIS)

Butvin, P.; Butvinova, B.; Silveyra, J.M.; Chromcikova, M.; Janickovic, D.; Sitek, J.; Svec, P.; Vlasak, G.

2010-01-01

Particular properties of Fe-Nb/Mo-Cu-B-Si rapidly quenched ribbons were examined. Apart from minor variation, no significant difference due to the Mo for Nb substitution was observed in alloy density and its annealing-induced changes. The same holds for the anisotropic thermal expansion of as-cast ribbon when annealed and for induced anisotropy when annealed under stress. The Mo-substituted ribbons show only slightly higher crystallinity and lower coercivity if annealed in inert gas ambience than in vacuum. Some diversity in surface to interior heterogeneity of the differently annealed ribbons can still be distinguished. Preserving a minor percentage of Nb together with Mo does not seem substantiated to obtain favorable soft magnetic properties of ribbons annealed in inert gas.

Effects of substitution of Mo for Nb on less-common properties of Finemet alloys

Energy Technology Data Exchange (ETDEWEB)

Butvin, P., E-mail: pavol.butvin@savba.s [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Butvinova, B. [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Silveyra, J.M. [Instituto de Technologias y Ciencias de la Ingenieria H.F. Long, Facultad de Ingenieria, UBA-CONICET, Buenos Aires (Argentina); Chromcikova, M. [Vitrum Laugaricio - Joint Glass Centre of the Inst. of Inorg. Chem., SAS Bratislava and A. Dubcek University of Trencin, 911 50 Trencin (Slovakia); Janickovic, D. [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Sitek, J. [Dept. of Nuclear Phys. and Technol., FEI, Slovak University of Technology, 812 19 Bratislava (Slovakia); Svec, P.; Vlasak, G. [Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia)

2010-10-15

Particular properties of Fe-Nb/Mo-Cu-B-Si rapidly quenched ribbons were examined. Apart from minor variation, no significant difference due to the Mo for Nb substitution was observed in alloy density and its annealing-induced changes. The same holds for the anisotropic thermal expansion of as-cast ribbon when annealed and for induced anisotropy when annealed under stress. The Mo-substituted ribbons show only slightly higher crystallinity and lower coercivity if annealed in inert gas ambience than in vacuum. Some diversity in surface to interior heterogeneity of the differently annealed ribbons can still be distinguished. Preserving a minor percentage of Nb together with Mo does not seem substantiated to obtain favorable soft magnetic properties of ribbons annealed in inert gas.

Effects of substitution of Mo for Nb on less-common properties of Finemet alloys

Science.gov (United States)

Butvin, P.; Butvinová, B.; Silveyra, J. M.; Chromčíková, M.; Janičkovič, D.; Sitek, J.; Švec, P.; Vlasák, G.

2010-10-01

Particular properties of Fe-Nb/Mo-Cu-B-Si rapidly quenched ribbons were examined. Apart from minor variation, no significant difference due to the Mo for Nb substitution was observed in alloy density and its annealing-induced changes. The same holds for the anisotropic thermal expansion of as-cast ribbon when annealed and for induced anisotropy when annealed under stress. The Mo-substituted ribbons show only slightly higher crystallinity and lower coercivity if annealed in inert gas ambience than in vacuum. Some diversity in surface to interior heterogeneity of the differently annealed ribbons can still be distinguished. Preserving a minor percentage of Nb together with Mo does not seem substantiated to obtain favorable soft magnetic properties of ribbons annealed in inert gas.

Crystal structure and ion conducting properties of La5NbMo2O16

KAUST Repository

Vu, T.D.

2016-01-29

The new compound La5NbMo2O16 with high ionic conduction has been discovered during the study of the ternary phase diagram of La2O3-MoO3-Nb2O5. The material crystallizes in the cubic space group Pn 3n (no 222) with the unit cell parameter a=11.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex impedance spectroscopy. © 2016 Elsevier Inc. All rights reserved.

First-principles evaluation of electronic and optical properties of (Mo, C) codoped BaHfO3 for applications in photocatalysis

Science.gov (United States)

Akhtar, Shaheen; Alay-e-Abbas, Syed Muhammad; Abbas, Syed Muhammad Ghulam; Arshad, Muhammad Imran; Batool, Javaria; Amin, Nasir

2018-04-01

In this paper, we report first-principles spin-polarized density functional theory calculations for exploring the effect of aliovalent Mo and C dopants on the electronic properties and photocatalysis potential of doped modifications of wide-bandgap cubic perovskite oxide BaHfO3 for water splitting. The structural and thermodynamic properties are computed by using the generalized gradient approximation, whereas the modified Becke-Johnson local density approximation is used to calculate the electronic structures of pristine, cation (Mo), and anion (C) monodoped and cation-anion (Mo, C) codoped BaHfO3. The spin-polarized calculations reveal that substitutional dopants CO and MoHf in the BaHfO3 lattice are thermodynamically stable. The incorporation of C in the O site reduces the bandgap of BaHfO3 and acts as a double-acceptor system, whereas a metallic character is obtained when Mo is doped into the Hf site giving rise to a double-donor system. We show that the acceptor and donor states of the C- and Mo-monodoped BaHfO3 can be passivated by (Mo, C) codoping at nearest-neighbor Hf and O sites of the BaHfO3 lattice, respectively. Analysis of the calculated electronic structure and optical absorption of (Mo, C) codoped BaHfO3 with reference to the H2O oxidation and reduction potentials reveals that this system is a suitable candidate for efficient splitting of water through photocatalysis in the visible region of the electromagnetic spectrum.

Effect of alloying Mo on mechanical strength and corrosion resistance of Zr-1% Sn-1% Nb-1% Fe alloy

International Nuclear Information System (INIS)

Sugondo

2011-01-01

It had been done research on Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy. The ingot was prepared by means of electrical electrode technique. The chemical analysis was identified by XRF, the metallography examination was perform by an optical microscope, the hardness test was done by Vickers microhardness, and the corrosion test was done in autoclave. The objective of this research were making Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy with Mo concentration; comparing effect of Mo concentration to metal characteristics of Zr-1%Sn-1%Nb-1%Fe which covered microstructure; composition homogeneity, mechanical strength; and corrosion resistance in steam, and determining the optimal Mo concentration in Zr-1%Sn-1%Nb-1%Fe-(x)% Mo alloy for nuclear fuel cladding which had corrosion resistance and high hardness. The results were as follow: The alloying Mo refined grains at concentration in between 0,1%-0,3% and the concentration more than that could coarsened grains. The hardness of the Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy was controlled either by the flaw or the dislocation, the intersection of the harder alloying element, the solid solution of the alloying element and the second phase formation of ZrMo 2 . The corrosion rate of the Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy was controlled by the second phase of ZrMo 2 . The 0.3% Mo concentration in Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy was the best for second phase formation. The Mo concentration in between 0,3-0,5% in Zr-1%Sn-1%Nb-1%Fe-(x)%Mo alloy was good for the second phase formation and the solid solution. (author)

The effect of niobium morphology on the fracture behavior of MoSi2/Nb composites

International Nuclear Information System (INIS)

Alman, D.E.; Stoloff

1995-01-01

The morphology of the niobium reinforcement added to MoSi 2 affected the fracture behavior (and hence toughness) of MoSi 2 /20 vol pct Nb composites. The addition of discontinuous random niobium in the form of particles or short fibers deflected cracks that propagated through the MoSi 2 matrix. However, this did not result in any improvements in toughness, as matrix cracks preferentially propagated through the Nb/MoSi 2 interphase region. The addition of aligned niobium fibers, oriented perpendicular to the direction of matrix crack propagation, directly participated in the fracture of the composite. Depending on the diameter of Nb embedded in the MoSi 2 matrix, these fibers either fractured in a brittle manner or ruptured in a ductile manner. Small (400-μm) diameter continuously aligned Nb fibers fractured by brittle cleavage during testing. Therefore, the addition of these fibers was not as effective in improving the toughness of MoSi 2 as the addition of larger (800-μm) diameter continuously aligned Nb fibers, which ruptured in a ductile manner. It was observed that the larger diameter fibers had separated from the matrix through the propagation of cracks in the reaction zone adjacent to the fibers and that these cracks formed prior to yielding of these fibers. In contrast, the smaller diameter fibers remained well bonded to the matrix and, thus, were constrained by the MoSi 2 matrix from yielding. This resulted in brittle fracture behavior of the Nb fiber. There appeared to be an effect of aspect ratio on the fracture of the ductile embedded fibers

Preparation and Oxidation Resistance of Mo-Si-B Coating on Nb-Si Based Alloy Surface

Directory of Open Access Journals (Sweden)

PANG Jie

2018-02-01

Full Text Available Mo-Si-B coating was prepared on Nb-Si alloys to improve the high-temperature oxidation. The influence of the halide activators (NaF and AlF3 on Si-B co-depositing to obtain Mo-Si-B coating on Nb-Si alloys was analyzed by thermochemical calculations. The results show that NaF proves to be more suitable than AlF3 to co-deposit Si and B. Then Mo-Si-B can be coated on Nb-Si based alloys using detonation gun spraying of Mo followed by Si and B co-deposition. The fabricated coatings consist of outer MoSi2 layer with fine boride phase and inner unreacted Mo layer. The mass gain of the Mo-Si-B coating is 1.52mg/cm2 after oxidation at 1250℃ for 100h. The good oxidation resistance results in a protective borosilicate scale formed on the coating.

Effect of Sn addition on the microstructure and superelasticity in Ti-Nb-Mo-Sn alloys.

Science.gov (United States)

Zhang, D C; Yang, S; Wei, M; Mao, Y F; Tan, C G; Lin, J G

2012-09-01

Ti-7.5Nb-4Mo-xSn (x=0-4at%) alloys were developed as the biomedical materials. The effect of the Sn content on the microstructure and superelasticity of the alloys was investigated. It is found that Sn is a strong stabilizer of the β phase, which is effective in suppressing the formation of α″ and ω phases in the alloys. Moreover, the Sn addition has a significant impact on the mechanical properties of the alloys. With the increase of Sn addition, the yield stress of the alloys increase, but their elastic modulus, the fracture strength and the ductility decrease, and the deformation mode of the alloys changes from (322) twining to α″ transformation and then to slip. The Ti-7.5Nb-4Mo-1Sn and Ti-7.5Nb-4Mo-3Sn alloys exhibit a good superelasticity with a high σ(SIM) due to the relatively high athermal ω phases containing or the solution hardening at room temperature. Under the maximum strain of 5%, Ti-7.5Nb-4Mo-3Sn (at%) alloy exhibits higher super elastic stability than that of Ti-7.5Nb-4Mo-1Sn alloy. Copyright © 2012 Elsevier Ltd. All rights reserved.

Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

Directory of Open Access Journals (Sweden)

Gorka Larzabal

2017-02-01

Full Text Available Low carbon microalloyed steels show interesting commercial possibilities by combining different “micro”-alloying elements when high strength and low temperature toughness properties are required. Depending on the elements chosen for the chemistry design, the mechanisms controlling the strengths and toughness may differ. In this paper, a detailed characterization of the microstructural features of three different microalloyed steels, Nb, Nb-Mo and Ti-Mo, is described using mainly the electron backscattered diffraction technique (EBSD as well as transmission electron microscopy (TEM. The contribution of different strengthening mechanisms to yield strength and impact toughness is evaluated, and its relative weight is computed for different coiling temperatures. Grain refinement is shown to be the most effective mechanism for controlling both mechanical properties. As yield strength increases, the relative contribution of precipitation strengthening increases, and this factor is especially important in the Ti-Mo microalloyed steel where different combinations of interphase and random precipitation are detected depending on the coiling temperature. In addition to average grain size values, microstructural heterogeneity is considered in order to propose a new equation for predicting ductile–brittle transition temperature (DBTT. This equation considers the wide range of microstructures analyzed as well as the increase in the transition temperature related to precipitation strengthening.

Representation of the properties 10 CrMoNiNb 9 10

International Nuclear Information System (INIS)

Dette, M.; Hahn, H.; Nieuwland, H.C.D.; Tichler, J.W.

The high-temperature ferritic steal 10 CrMoNiNb 9 10 is used as structural material in nuclear steam generators. It is exposed to loads within the creep range. In order to resist safety also loads caused by incidents after long temperature stress, the time-independent stability parameters must not fall below specified minimum values. The material is characterised by the stability degree Nb/C+N and the niobium excess δ Nb. (orig.) [de

Surface Characterization, Corrosion Resistance and in Vitro Biocompatibility of a New Ti-Hf-Mo-Sn Alloy

Science.gov (United States)

Ion, Raluca; Drob, Silviu Iulian; Ijaz, Muhammad Farzik; Vasilescu, Cora; Osiceanu, Petre; Gordin, Doina-Margareta; Cimpean, Anisoara; Gloriant, Thierry

2016-01-01

A new superelastic Ti-23Hf-3Mo-4Sn biomedical alloy displaying a particularly large recovery strain was synthesized and characterized in this study. Its native passive film is very thick (18 nm) and contains very protective TiO2, Ti2O3, HfO2, MoO2, and SnO2 oxides (XPS analysis). This alloy revealed nobler electrochemical behavior, more favorable values of the corrosion parameters and open circuit potentials in simulated body fluid in comparison with commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy taken as reference biomaterials in this study. This is due to the favorable influence of the alloying elements Hf, Sn, Mo, which enhance the protective properties of the native passive film on alloy surface. Impedance spectra showed a passive film with two layers, an inner, capacitive, barrier, dense layer and an outer, less insulating, porous layer that confer both high corrosion resistance and bioactivity to the alloy. In vitro tests were carried out in order to evaluate the response of Human Umbilical Vein Endothelial Cells (HUVECs) to Ti-23Hf-3Mo-4Sn alloy in terms of cell viability, cell proliferation, phenotypic marker expression and nitric oxide release. The results indicate a similar level of cytocompatibility with HUVEC cells cultured on Ti-23Hf-3Mo-4Sn substrate and those cultured on the conventional CP-Ti and Ti-6Al-4V metallic materials. PMID:28773939

Control of the interfacial reactions in Nb-toughened MoSi2

International Nuclear Information System (INIS)

Shaw, L.; Abbaschian, R.

1993-01-01

Toughening of MoSi 2 for high-temperature applications can be achieved by incorporating ductile refractory-metal reinforcements, provided that a coating is applied to prevent interdiffusion and reaction between the matrix and the reinforcements. In the present study, three different coating techniques for applying a thin Al 2 O 3 film on Nb reinforcements as a diffusion barrier have been studied. The techniques consisted of (1) sol-gel coating; (2) physical vapor deposition (PVD); (3) hot dipping in molten Al, followed by anodizing Al to form Al 2 O 3 . The processing parameters for the techniques were evaluated and the effectiveness of each coating as a diffusion barrier was assessed. For the present MoSi 2 matrix which contains SiO 2 , PVD coatings provided the most effective diffusion barrier for processing MoSi 2 /Nb composites

Interplay between lattice distortions, vibrations and phase stability in NbMoTaW high entropy alloys

NARCIS (Netherlands)

Kormann, F.H.W.; Sluiter, M.H.F.

2016-01-01

Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions. For BCC NbMoTaW,

TiZrNbTaMo high-entropy alloy designed for orthopedic implants: As-cast microstructure and mechanical properties.

Science.gov (United States)

Wang, Shao-Ping; Xu, Jian

2017-04-01

Combining the high-entropy alloy (HEA) concept with property requirement for orthopedic implants, we designed a Ti 20 Zr 20 Nb 20 Ta 20 Mo 20 equiatomic HEA. The arc-melted microstructures, compressive properties and potentiodynamic polarization behavior in phosphate buffer solution (PBS) were studied in detail. It was revealed that the as-cast TiZrNbTaMo HEA consisted of dual phases with bcc structure, major bcc1 and minor bcc2 phases with the lattice parameters of 0.3310nm and 0.3379nm, respectively. As confirmed by nanoindentation tests, the bcc1 phase is somewhat harder and stiffer than the bcc2 phase. The TiZrNbTaMo HEA exhibited Young's modulus of 153GPa, Vickers microhardness of 4.9GPa, compressive yield strength of σ y =1390MPa and apparent plastic strain of ε p ≈6% prior to failure. Moreover, the TiZrNbTaMo HEA manifested excellent corrosion resistance in PBS, comparable to the Ti6Al4V alloy, and pitting resistance remarkably superior to the 316L SS and CoCrMo alloys. These preliminary advantages of the TiZrNbTaMo HEA over the current orthopedic implant metals in mechanical properties and corrosion resistance offer an opportunity to explore new orthopedic-implant alloys based on the TiZrNbTaMo concentrated composition. Copyright © 2016 Elsevier B.V. All rights reserved.

Alloy Design and Property Evaluation of Ti-Mo-Nb-Sn Alloy for ...

African Journals Online (AJOL)

Ti-Mo alloy containing Nb and Sn were arc melted and composition analyzed by EDX. The XRD analysis indicates that the crystal structure and mechanical properties are sensitive to Sn concentration. A combination of Sn and Nb elements in synergy hindered formation athermal w phase and significantly enhanced b phase ...

Metastable beta Ti-Nb-Mo alloys with improved corrosion resistance in saline solution

International Nuclear Information System (INIS)

Chelariu, R.; Bolat, G.; Izquierdo, J.; Mareci, D.; Gordin, D.M.; Gloriant, T.; Souto, R.M.

2014-01-01

Graphical abstract: - Highlights: • Microstructural and electrochemical characterization of metastable beta Ti-Nb-Mo alloys for biomedical implantation. • Corrosion resistance was established in 0.9 wt% NaCl saline solution at 25 °C using conventional and microelectrochemical techniques. • The materials spontaneously form passivating oxide films on their surface. • Surface films are stable for polarizations more positive than those encountered in the human body. • The addition of niobium to Ti12Mo enhances the capacitive characteristics of the passivating oxide layers. - Abstract: The present study explores the microstructural characteristics and electrochemical responses of four metastable beta Ti-Nb-Mo alloys for biomedical implantation. They were synthesized by the cold crucible levitation melting technique, and compositions were selected to keep the molybdenum equivalency close to 12 wt% Mo eq . For the sake of comparison, Ti12Mo was also investigated. Microstructural characterization reveals that all the alloys are β (body-centred cubic structure), and the surface is composed by β equiaxial grains with dimensions in the range of tens to hundreds μm. The corrosion resistance (potentiodynamic polarization and electrochemical impedance spectroscopy) of the alloys was determined in 0.9 wt% NaCl saline solution at 25 °C. The materials spontaneously form a passivating oxide film on their surface, and they are stable for polarizations up to +1.0 V SCE . No evidence of localized breakdown of the oxide layers is found for polarizations more positive than those encountered in the human body. The passive layers show dielectric characteristics, and the wide frequency ranges displaying capacitive characteristics occur for both higher niobium contents in the alloy and longer exposures to the saline solution. The insulating characteristics of the oxide-covered surfaces were investigated by scanning electrochemical microscopy operated in the feedback mode

Measurement of cross-sections for the 93Nb(p,n)93mMo and 93Nb(p,pn)92mNb reactions up to ∼20 MeV energy

Science.gov (United States)

Lawriniang, B.; Ghosh, R.; Badwar, S.; Vansola, V.; Santhi Sheela, Y.; Suryanarayana, S. V.; Naik, H.; Naik, Y. P.; Jyrwa, B.

2018-05-01

Excitation functions of the 93Nb(p,n)93mMo and 93Nb(p,pn)92mNb reactions were measured from threshold energies to ∼ 20MeV by employing stacked foil activation technique in combination with the off-line γ-ray spectroscopy at the BARC-TIFR Pelletron facility, Mumbai. For the 20 MeV proton beam, the energy degradation along the stack was calculated using the computer code SRIM 2013. The proton beam intensity was determined via the natCu(p,x)62Zn monitor reaction. The experimental data obtained were compared with the theoretical results from TALYS-1.8 as well as with the literature data available in EXFOR. It was found that for the 93Nb(p,n)92mMo reaction, the present data are in close agreement with some of the recent literature data and the theoretical values based on TALYS-1.8 but are lower than the other literature data. In the case of 93Nb(p,pn)93mNb reaction, present data agree very well with the literature data and the theoretical values.

New intermetallic MIrP (M=Ti, Zr, Nb, Mo) and MgRuP compounds related with MoM'P (M'=Ni and Ru) superconductor

Science.gov (United States)

Kito, Hijiri; Iyo, Akira; Wada, Toshimi

2011-01-01

Using a cubic-anvil high-pressure apparatus, ternary iridium phosphides MIrP (M=Ti, Zr, Nb, Mo) and MgRuP have been prepared by reaction of stoichiometric amounts of each metal and phosphide powders at around 2 Gpa and above 1523 K for the first time. The structure of these compounds prepared at high-pressure has been characterized by X-ray powder diffraction. Diffraction lines of these compounds are assigned by the index of the Co2Si-type structure. The electrical resistivity and the d.c magnetic susceptibility of MIrP (M=Ti, Zr, Nb, Mo) have measured at low temperatures. Unfortunately, no superconducting transition for MIrP (M=Ti, Zr, Nb, Mo) and MgRuP are observed down to 2 K.

New intermetallic MIrP (M=Ti, Zr, Nb, Mo) and MgRuP compounds related with MoM'P (M'=Ni and Ru) superconductor

International Nuclear Information System (INIS)

Kito, Hijiri; Iyo, Akira; Wada, Toshimi

2011-01-01

Using a cubic-anvil high-pressure apparatus, ternary iridium phosphides MIrP (M=Ti, Zr, Nb, Mo) and MgRuP have been prepared by reaction of stoichiometric amounts of each metal and phosphide powders at around 2 Gpa and above 1523 K for the first time. The structure of these compounds prepared at high-pressure has been characterized by X-ray powder diffraction. Diffraction lines of these compounds are assigned by the index of the Co 2 Si-type structure. The electrical resistivity and the d.c magnetic susceptibility of MIrP (M=Ti, Zr, Nb, Mo) have measured at low temperatures. Unfortunately, no superconducting transition for MIrP (M=Ti, Zr, Nb, Mo) and MgRuP are observed down to 2 K.

Atomic displacements in dilute alloys of Cr, Nb and Mo

Indian Academy of Sciences (India)

physics pp. 497–514. Atomic displacements in dilute alloys of Cr, Nb and Mo ... used to calculate dynamical matrix and the impurity-induced forces up to second nearest ... origin, the lattice is strained, and the host atoms get displaced to new ...

Metal-metal bonding and aromaticity in [M2(NHCHNH)3]2 (μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh).

Science.gov (United States)

Yan, Xiuli; Meng, Lingpeng; Sun, Zheng; Li, Xiaoyan

2016-02-01

The nature of M-M bonding and aromaticity of [M2(NHCHNH)3]2(μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh) was investigated using atoms in molecules (AIM) theory, electron localization function (ELF), natural bond orbital (NBO) and molecular orbital analysis. These analyses led to the following main conclusions: in [M2(NHCHNH)3]2(μ-E)2 (E = O, S; M = Nb, Mo, Tc, Ru, Rh), the Nb-Nb, Ru-Ru, and Rh-Rh bonds belong to "metallic" bonds, whereas Mo-Mo and Tc-Tc drifted toward the "dative" side; all these bonds are partially covalent in character. The Nb-Nb, Mo-Mo, and Tc-Tc bonds are stronger than Ru-Ru and Rh-Rh bonds. The M-M bonds in [M2(NHCHNH)3]2(μ-S)2 are stronger than those in [M2(NHCHNH)3]2(μ-O)2 for M = Nb, Mo, Tc, and Ru. The NICS(1)ZZ values show that all of the studied molecules, except [Ru2(NHCHNH)3]2(μ-O)2, are aromaticity molecules. O-bridged compounds have more aromaticity than S-bridged compounds. Graphical Abstract Left Molecular graph, and right electron localization function (ELF) isosurface of [M2(NHCHNH)3]2(μ-E)2(E = O, S; M = Nb, Mo, Tc, Ru, Rh).

Electric field gradient at the Nb3M(M = Al, In, Si, Ge, Sn) and T3Al (T = Ti, Zr, Hf, V, Nb, Ta) alloys by perturbed angular correlation method

International Nuclear Information System (INIS)

Junqueira, Astrogildo de Carvalho

1999-01-01

The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb 3 M (M = Al, Si, Ge, Sn) and at the T site in the intermetallic compounds T 3 Al (T = Ti, Zr, Hf, V, Nb, Ta) was measured by Perturbed Angular Correlation (PAC) method using the well known gamma-gamma cascade of 133-482 keV in 181 Ta from the β - decay of 181 Hf. The compounds were prepared by arc melting the constituent elements under argon atmosphere along with radioactive 181 Hf substituting approximately 0.1 atomic percent of Nb and T elements. The PAC measurements were carried out at 295 K for all compounds and the efg was obtained for each alloy. The results for the efg in the T 3 Al compounds showed a strong correlation with the number of conduction electrons, while for the Nbs M compounds the efg behavior is influenced mainly by the p electrons of the M elements. The so-called universal correlation between the electronic and lattice contribution for the efg in metals was not verified in this work for all studied compounds. Measurements of the quadrupole frequency in the range of 100 to 1210 K for the Nb 3 Al compound showed a linear behaviour with the temperature. Superconducting properties of this alloys may probably be related with this observed behaviour. The efg results are compared to those reported for other binary alloys and discussed with the help of ab-initio methods. (author)

Design of Refractory High-Entropy Alloys

Science.gov (United States)

Gao, M. C.; Carney, C. S.; Doğan, Ö. N.; Jablonksi, P. D.; Hawk, J. A.; Alman, D. E.

2015-11-01

This report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties for liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.

Shape memory and superelastic behavior of Ti-7.5Nb-4Mo-1Sn alloy

International Nuclear Information System (INIS)

Zhang, D.C.; Lin, J.G.; Jiang, W.J.; Ma, M.; Peng, Z.G.

2011-01-01

Research highlights: → A Ti-based shape memory alloy, Ti-7.5Nb-4Mo-1Sn, was designed. → The martensitic transformation start temperature of the alloy, M s , is 261 K. → The alloy exhibits good shape memory and superelastic behaviors. → The alloy also shows a good superelastic stability at room temperature. → The Ti-5Mo-7.5Nb-1Sn alloy has a potential application as a biomedical material. -- Abstract: In the present work, a Ti-based shape memory alloy with the composition of Ti-7.5Nb-4Mo-1Sn was designed based on the d-electron orbit theory. The shape memory and superelastic behavior of the alloy were investigated. It is found that the martensitic transformation temperature of the alloy is near 261 K. The tensile and the thermal cycling testing results show that the alloy exhibits the stable shape memory effect and superelasticity at room temperature. The maximum recovered strain of the alloy is 4.83%.

Thermodynamic calculation and an experimental study of the combustion synthesis of (Mo{sub 1−x}Nb{sub x})Si{sub 2} (0 ⩽ x ⩽ 1)

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaohong, E-mail: matinbow@163.com; Lu, Qiong; Wu, Guangzhi; Shi, Jialing; Sun, Zhi

2015-08-25

Highlights: • (Mo{sub 1−x}Nb{sub x})Si{sub 2} alloys were synthesized by a simple and energy-saving process of SHS. • Theoretical adiabatic temperature of (Mo{sub 1−x}Nb{sub x})Si{sub 2} was calculated for the first time. • The variation of the actual temperature is consistent with theoretical temperature. - Abstract: The theoretical adiabatic temperature of (Mo{sub 1−x}Nb{sub x})Si{sub 2} (0 ⩽ x ⩽ 1) is calculated. The results indicate that the theoretical adiabatic temperature of (Mo{sub 1−x}Nb{sub x})Si{sub 2} increases with an increasing Nb content when (Mo{sub 1−x}Nb{sub x})Si{sub 2} is of a single-phase structure, but decreases with an increasing Nb content when (Mo{sub 1−x}Nb{sub x})Si{sub 2} is of a double-phase structure. All of the temperatures are higher than 1800 K, indicating that (Mo{sub 1−x}Nb{sub x})Si{sub 2} (0 ⩽ x ⩽ 1) can be prepared by the combustion synthesis method. In this work, (Mo{sub 1−x}Nb{sub x})Si{sub 2} (0 ⩽ x ⩽ 1) alloys are successfully synthesized by the combustion synthesis process from elemental powders of Mo, Nb, and Si. The highest combustion temperature and combustion product structure are studied. The results confirm that the variation of the experimental maximum combustion temperature of (Mo{sub 1−x}Nb{sub x})Si{sub 2} is consistent with that of the theoretical adiabatic temperature. The combustion products are non-equilibrium species, and a supersaturated solid solution of C11{sub b} type (Mo{sub 1−x}Nb{sub x})Si{sub 2} forms during combustion synthesis.

Structure and properties of heat-treated Ti-(40-4X)%Nb-X%Mo alloys with IE (SME)

International Nuclear Information System (INIS)

Silva, Marcia Almeida; Matlakhova, Lioudmila Aleksandrovna; Matlakhov, Anatoliy Nikolaevich; Paes Junior, Herval Ramos; Goncharenko, Boris Andreevich

2010-01-01

Whereas the inelastic effects (IE) are related with reversible martensitic transformation, in this work, was analyzed the structure and properties of heat treated Ti-(40-4x)%Nb-x%Mo alloys, where the contents of niobium and molybdenum are between 24-40%Nb and 0-4%Mo (% weight). The structural and phase analysis were done through optical microscopy and X-rays diffraction. The properties measured in this study were electrical resistivity and density. The Ti-40%Nb alloy shows a structure consisting of the β phase and αα’’ martensite with a minor participation of the α’ and ω. The alloys with 1 to 4%Mo have similar structures consisting of the β phase and traces of the α’’ phase. Thus, was observed greater capacity of Mo as a β stabilizer. The increase in Mo content in the composition of the alloys causes an increase in electrical resistivity of these. The samples may have undergone change in volume, caused by phase transformation, what possibly caused the difference between the density values calculated (theoretical) and experimental. (author)

Optical properties of Nb and Mo calculated from augmented-plane-wave band structures

International Nuclear Information System (INIS)

Pickett, W.E.; Allen, P.B.

1975-01-01

Nonrelativistic band calculations of Mattheiss for Nb and Petroff and Viswanathan for Mo are used to calculate the imaginary part epsilon 2 of the dielectric function for these metals. The structure resulting from interband transitions in the frequency range 0.1--0.5 Ry is found to give fairly good agreement with experiment. The calculation indicates that structure in epsilon 2 can arise from transitions away from symmetry points and lines in the Brillouin zone. The difficulty in distinguishing between the direct and indirect transition models for epsilon 2 is shown to arise from a lack of strong optical critical points. Predictions of the rigid-band model for the optical properties of Nb-Mo alloys are presented

Creep-fatigue-environment interaction of 9Cr-1Mo-V-Nb steel

International Nuclear Information System (INIS)

Shibata, Hiroyuki; Ishikawa, Akiyoshi; Asada, Yasuhide

1996-01-01

An extension of the creep-fatigue damage model has been conducted in the present study. The original damage model has been developed to the predict the creep-fatigue life of 9Cr-1Mo-V-Nb steel (Modified 9Cr-1Mo steel) in a very high vacuum environment. The present study is to extend an applicability of the model to the creep-fatigue damage accumulation in the air environment. (orig.)

Mechanical characterization of Ti-12Mo-13Nb alloy for biomedical application hot swaged and aged

Energy Technology Data Exchange (ETDEWEB)

Gabriel, Sinara Borborema; Rezende, Monica Castro; Almeida, Luiz Henrique de, E-mail: sinara@metalmat.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Departamento de Engenharia Metalurgica e de Materiais; Dille, Jean [Universite Libre de Bruxelles, Brussels (Belgium); Mei, Paulo [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Departamento de Engenharia Mecanica; Baldan, Renato; Nunes, Carlos Angelo [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Departamento de Engenharia de Materiais

2015-07-01

Beta titanium alloys were developed for biomedical applications due to the combination of its mechanical properties including low elasticity modulus, high strength, fatigue resistance, good ductility and with excellent corrosion resistance. With this perspective a metastable beta titanium alloy Ti-12Mo-13Nb was developed with the replacement of both vanadium and aluminum from the traditional alloy Ti-6Al-4V. This paper presents the microstructure, mechanical properties of the Ti-12Mo-13Nb hot swaged and aged at 500 deg C for 24 h under high vacuum and then water quenched. The alloy structure was characterized by X-ray diffraction and transmission electron microscopy. Tensile tests were carried out at room temperature. The results show a microstructure consisting of a fine dispersed α phase in a β matrix and good mechanical properties including low elastic modulus. The results indicate that Ti-12Mo-13Nb alloy can be a promising alternative for biomedical application. (author)

Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

Directory of Open Access Journals (Sweden)

Andrii Kostryzhev

2018-02-01

Full Text Available Steel product markets require the rolled stock with further increasing mechanical properties and simultaneously decreasing price. The steel cost can be reduced via decreasing the microalloying elements contents, although this decrease may undermine the mechanical properties. Multi-element microalloying with minor additions is the route to optimise steel composition and keep the properties high. However, this requires deep understanding of mutual effects of elements on each other’s performance with respect to the development of microstructure and mechanical properties. This knowledge is insufficient at the moment. In the present work we investigate the microstructure and mechanical properties of bainitic steels microalloyed with Cr, Mo, Nb and V. Comparison of 0.2 wt. % Mo and Cr additions has shown a more pronounced effect of Mo on precipitation than on phase balance. Superior strength of the MoNbV-steel originated from the strong solid solution strengthening effect. Superior ductility of the CrNbV-steel corresponded to the more pronounced precipitation in this steel. Nature of these mechanisms is discussed.

Application of NiMoNb adhesion layer on plasma-treated polyimide substrate for flexible electronic devices

Energy Technology Data Exchange (ETDEWEB)

Bang, S.-H.; Kim, K.-K.; Jung, H.-Y.; Kim, T.-H.; Jeon, S.-H. [Metal and Material Technology Group, R and D Center, LS Mtron Ltd., Gyeonggi 431-080 (Korea, Republic of); Seol, Jae-Bok, E-mail: zptkfm20@hanmail.net [Max-Planck-Insititut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany)

2014-05-02

A thin film, NiMoNb, was introduced as an adhesion layer between the Cu metal and the insulator polyimide substrate in a flexible Cu-clad laminated structure. Using 90° peel test, we evaluated the peel strength of the system as a function of the thickness of the adhesion layer. An increase in the NiMoNb thickness from 7 to 40 nm enhanced the peel strength of the deposited systems. After plasma treatment by the roll-to-roll method, the multilayer structure showed an outstanding peel strength of ∼ 529 N/m, even after thermal annealing at 150 °C for 168 h. We also studied the role of plasma treatment of the polyimide substrate on the adhesion strength and microstructure of a flexible Cu-clad laminated structure by peel strength, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. These experimental observations showed that the plasma-treated polyimide substrate with the deposition of NiMoNb showed the enhanced adhesion of ∼ 656 N/m, because of the change of functional groups, which affected the bonding force and crystallinity of the thin films deposited on polyimide, rather than an increase in the surface roughness. - Highlights: • NiMoNb film on polyimide substrate was employed for higher peel strength. • Plasma-treated substrate enhances the peel strength of multilayer. • Even when annealed at 150 °C, plasma-treated films showed enhanced peel strength.

Application of NiMoNb adhesion layer on plasma-treated polyimide substrate for flexible electronic devices

International Nuclear Information System (INIS)

Bang, S.-H.; Kim, K.-K.; Jung, H.-Y.; Kim, T.-H.; Jeon, S.-H.; Seol, Jae-Bok

2014-01-01

A thin film, NiMoNb, was introduced as an adhesion layer between the Cu metal and the insulator polyimide substrate in a flexible Cu-clad laminated structure. Using 90° peel test, we evaluated the peel strength of the system as a function of the thickness of the adhesion layer. An increase in the NiMoNb thickness from 7 to 40 nm enhanced the peel strength of the deposited systems. After plasma treatment by the roll-to-roll method, the multilayer structure showed an outstanding peel strength of ∼ 529 N/m, even after thermal annealing at 150 °C for 168 h. We also studied the role of plasma treatment of the polyimide substrate on the adhesion strength and microstructure of a flexible Cu-clad laminated structure by peel strength, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. These experimental observations showed that the plasma-treated polyimide substrate with the deposition of NiMoNb showed the enhanced adhesion of ∼ 656 N/m, because of the change of functional groups, which affected the bonding force and crystallinity of the thin films deposited on polyimide, rather than an increase in the surface roughness. - Highlights: • NiMoNb film on polyimide substrate was employed for higher peel strength. • Plasma-treated substrate enhances the peel strength of multilayer. • Even when annealed at 150 °C, plasma-treated films showed enhanced peel strength

Characterization of hydrogenation behavior on Mo-modified Zr-Nb alloys as nuclear fuel cladding materials

International Nuclear Information System (INIS)

Yang, H.L.; Shibukawa, S.; Abe, H.; Satoh, Y.; Matsukawa, Y.; Kido, T.

2014-01-01

The effects of Mo in Zr-Nb alloys are investigated in terms of their mechanical properties associated with microstructure, as well as their behavior under hydrogen environment. Zr-Nb-Mo alloys were fabricated by arc melting and subsequently cold rolling and annealing below the eutectoid temperature. Hydrogen was absorbed in a furnace under argon and hydrogen gas flow environment at high temperature. X-Ray diffraction, electron backscatter diffraction, and tensile test were jointly utilized to carry out detailed microstructural characterization and mechanical properties. Results showed that fcc-δ-ZrH 1.66 was formed in all hydrogen-absorbed alloys, and the amount of hydride enhanced with increasing of hydrogen content. In addition, it was clear that δ-ZrH 1.66 was precipitated both in grain boundary and interior, and preferential precipitation was observed on the habit planes of (0001) and {101-bar7}. Moreover, the strengthening effect by Mo addition was observed. The ductility loss by hydrogen absorption was found from fracture surface observation. Large area cleavage facets were found in Mo-free specimen, and less cleavage facets was observed in Mo-containing specimen, showing an appropriate addition of Mo can increase the tolerance to hydrogen embrittlement. (author)

Solution chemistry of element 105. Pt. III. Hydrolysis and complex formation of Nb, Ta, Db and Pa in HF and HBr solutions

International Nuclear Information System (INIS)

Pershina, V.; Bastug, T.

1999-01-01

Calculations of the electronic structure of MF 6 - and MBr 6 - complexes of Nb, Ta, Pa and element 105, Db, formed in HF and HBr solutions have been performed using the Dirac-Slater Discrete Variational method. On the basis of results of these calculations, relative values of the free energy change of reactions of complex formation have been determined. The order of the complex formation for both acids is shown to be Pa >> Nb > Db > Ta. Such a sequence is defined by a predominant electrostatic energy of the metal-ligand interaction. The hydrolysis of compounds, as a reverse process, proved to change as Ta > Db > Nb >> Pa. Using the theory of metal extraction by anion exchange, the following trend in the extraction of the anionic species from both the HF and HBr aqueous solutions has been predicted: Pa >> Nb ≥ Db > Ta. The strength of the ML 6 - complexes is shown to decrease from MF 6 , to MCl 6 and further to MBr 6 - which is reflected by shifting the complex formation process to the area of higher acid concentrations. (orig.)

Crystal structure and ion conducting properties of La5NbMo2O16

KAUST Repository

Vu, T.D.; Krichen, F.; Barre, M.; Busselez, R.; Adil, Karim; Jouanneaux, A.; Suard, E.; Goutenoire, F.

2016-01-01

.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex

Mo-V-Te-Nb oxides as catalysts for ethene production by oxidative dehydrogenation of ethane

Energy Technology Data Exchange (ETDEWEB)

Hartmann, D. [Technische Universitaet Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center; Meiswinkel, A.; Thaller, C.; Bock, M.; Alvarado, L. [Linde AG, Pullach (Germany)

2013-11-01

The availability of ethane in shale gas, as well as the interest in valorising previously underutilized carbon feedstocks, makes the oxidative dehydrogenation (ODH) of ethane an attractive alternative to the industrially established processes for production of ethylene. Mo-V-Te-Nb mixed oxide has been chosen as catalyst for the ODH reaction in view of its outstanding ability to activate alkane molecules. Catalytic test results showed that this type of catalyst can selectively oxidize ethane to ethene at moderate temperatures (350-400 C) with minor production of CO{sub x}. The catalytic performance of Mo-V-Te-Nb mixed-oxide is mainly attributable to the crystalline phase 'M1'. Rietveld analysis of the X-Ray diffractograms allowed us to quantify the amount of MoVTeNb oxide that has crystallized as M1. In this way, it was possible to find a linear correlation of the reaction rate with the abundance of M1 in the solid. Therefore, it is clear that for improving the efficiency of MoVTeNb oxide in ODH, the amount of M1 in the catalyst should be maximized. With this purpose, several MoVTeNb oxides were subject to different thermal treatments prior to the catalytic test. Structural changes in the catalyst were monitored by in-situ XRD technique. Under oxidative atmosphere, it was observed a recrystallization of M2 and possibly, amorphous oxide, into M1 phase, leading to correspondingly more active and selective catalysts (selectivities above 95 % for ethane conversions up to 40 % under industrially relevant conditions). The active site of M1 involves V species, likely with redox properties enhanced by the proximity of Mo and Te species, while the function of the crystalline structure itself is to provide the spatial configuration that allows interaction between these species. However, ethene formation rate was observed to be independent of the V content of the samples. The vanadium species exposed at the surface were studied by LEIS and by IR spectroscopy of CO

Band alignment of HfO{sub 2}/multilayer MoS{sub 2} interface determined by x-ray photoelectron spectroscopy: Effect of CHF{sub 3} treatment

Energy Technology Data Exchange (ETDEWEB)

Liu, Xinke; He, Jiazhu; Tang, Dan; Jia, Fang; Lu, Youming, E-mail: ymlu@szu.edu.cn; Zhu, Deliang; Liu, Wenjun; Cao, Peijiang; Han, Sun [College of Materials Science and Engineering, Shenzhen Engineering Laboratory for Advanced Technology of Ceramics, Nanshan District Key Lab for Biopolymer and Safety Evaluation, Shenzhen University, 3688 Nanhai Ave, Shenzhen 518060 (China); Liu, Qiang; Wen, Jiao; Yu, Wenjie, E-mail: casan@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, CAS,865 Chang Ning Road, Shanghai 200050 (China); Pan, Jisheng [Institute of Materials Research and Engineering, Agency for Science Technology and Research, Singapore 117602 (Singapore); He, Zhubing [Department of Materials Science and Engineering, South University of Science and Technology of China, 1088 Xueyuan Road, Shenzhen 518055 (China); Ang, Kah-Wee [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583 (Singapore)

2015-09-07

The energy band alignment between HfO{sub 2}/multilayer (ML)-MoS{sub 2} was characterized using high-resolution x-ray photoelectron spectroscopy. The HfO{sub 2} was deposited using an atomic layer deposition tool, and ML-MoS{sub 2} was grown by chemical vapor deposition. A valence band offset (VBO) of 1.98 eV and a conduction band offset (CBO) of 2.72 eV were obtained for the HfO{sub 2}/ML-MoS{sub 2} interface without any treatment. With CHF{sub 3} plasma treatment, a VBO and a CBO across the HfO{sub 2}/ML-MoS{sub 2} interface were found to be 2.47 eV and 2.23 eV, respectively. The band alignment difference is believed to be dominated by the down-shift in the core level of Hf 4d and up-shift in the core level of Mo 3d, or the interface dipoles, which caused by the interfacial layer in rich of F.

Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

Science.gov (United States)

Isasti, Nerea; Jorge-Badiola, Denis; Taheri, Mitra L.; Uranga, Pello

2013-08-01

A complete microstructural characterization and phase transformation analysis has been performed for several Nb and Nb-Mo microalloyed low-carbon steels using electron backscattered diffraction (EBSD) and dilatometry tests. Compression thermomechanical schedules were designed resulting in the undeformed and deformed austenite structures before final transformation. The effects of microalloying additions and accumulated deformation were analyzed after CCT diagram development and microstructural quantification. The resulting microstructures ranged from polygonal ferrite and pearlite at slow cooling ranges, to a combination of quasipolygonal ferrite and granular ferrite for intermediate cooling rates, and finally, to bainitic ferrite with martensite for fast cooling rates. The addition of Mo promotes a shift in the CCT diagrams to lower transformation start temperatures. When the amount of Nb is increased, CCT diagrams show little variations for transformations from the undeformed austenite and higher initial transformation temperatures in the transformations from the deformed austenite. This different behavior is due to the effect of niobium on strain accumulation in austenite and its subsequent acceleration of transformation kinetics. This article shows the complex interactions between chemical composition, deformation, and the phases formed, as well as their effect on microstructural unit sizes and homogeneity.

Transmission electron microscopy of Ti-12Mo-13Nb Alloy aged after heat forging; Microscopia eletronica de transmissao da liga Ti-12Mo-13Nb envelhecida apos forjamento a quente

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Nathalia Rodrigues [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Baldan, Renato [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Nunes, Carlos Angelo; Mei, Paulo Roberto [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil); Gabriel, Sinara Borborema [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil)

2014-06-15

Metastable β-Ti alloys possess mechanical properties, in particular a elastic modulus that depends not only on its composition but also the applied thermomechanical treatments. These alloys require high mechanical strength and a low Young’s modulus to avoid stress shielding. Preliminary studies on the development of Ti- 13Nb-12Mo alloy showed than the better properties were obtained at aged at 500 ° C / 24 h after cold forging , whose microstructure consisted of bimodal α phase in the β matrix. In this work, Ti-12Mo-13Nb alloy was heat forged and aged at 500 deg C for 24h and the microstructure was analyzed by employing X-ray diffraction and transmission electron microscopy. According to the results, while the cold forging resulted in bimodal α phase in the β matrix, hot forging resulted in a fine and homogeneous α phase in the β matrix. (author)

MO-HF-C alloy composition

International Nuclear Information System (INIS)

Whelan, E.P.; Kalns, E.

1987-01-01

This patent describes, as an article of manufacture, a cast ingot of a molybdenum-hafnium-carbon alloy consisting essentially by weight of about 0.6% to about 1% Hf, about 0.045% to about 0.08% C, and the balance essentially molybdenum. The amount of Hf and C present are substantially stoichiometric with respect to HfC and within about +-15% of stoichiometry. The ingot is characterized in that it has a substantially less tendency to crack compared to alloys containing Hf in excess of about 1% by weight and carbon in excess of 0.08% by weight, without substantial diminution in strength properties of the alloy

Phase diagrams for the M2MoO4–Ln2(MoO43–Hf(MoO42 systems, where M = Li–Cs, Tl and Ln = La–Lu

Directory of Open Access Journals (Sweden)

Zh. G. Bazarova

2017-12-01

Full Text Available In this paper, the results of systematic studies of complex molybdate systems M2MoO4–Ln2(MoO43–Hf(MoO42 (M = Li–Cs, Tl; Ln = La–Lu are presented. Subsolidus phase diagrams of ternary systems were constructed and new triple molybdates were obtained. The optimum synthesis conditions for poly- and monocrystalline form were determined. According to single-crystal data, the structure of one of the representatives of triple molybdates was determined.

Study of the interface stability of the metal (Mo, Ni, Pd/HfO2/AlN/InGaAs MOS devices

Directory of Open Access Journals (Sweden)

Huy Binh Do

2017-08-01

Full Text Available The degeneration of the metal/HfO2 interfaces for Mo, Ni, and Pd gate metals was studied in this paper. An unstable PdOx interfacial layer formed at the Pd/HfO2 interface, inducing the oxygen segregation for the Pd/HfO2/InGaAs metal oxide capacitor (MOSCAP. The low dissociation energy for the Pd-O bond was the reason for oxygen segregation. The PdOx layer contains O2− and OH− ions which are mobile during thermal annealing and electrical stress test. The phenomenon was not observed for the (Mo, Ni/HfO2/InGaAs MOSCAPs. The results provide the guidance for choosing the proper metal electrode for the InGaAs based MOSFET.

A new type of Nb (Ta)-Zr(Hf)-REE-Ga polymetallic deposit in the late Permian coal-bearing strata, eastern Yunnan, southwestern China: Possible economic significance and genetic implications

Energy Technology Data Exchange (ETDEWEB)

Dai, Shifeng; Wang, Xibo; Luo, Yangbing; Song, Zhentao; Ren, Deyi [State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083 (China); Zhou, Yiping; Zhang, Mingquan; Wang, Jumin; Song, Xiaolin; Yang, Zong [Yunnan Institute of Coal Geology Prospection, Kunming 650218 (China); Jiang, Yaofa [Xuzhou Institute of Architectural Technology, Xuzhou 221116 (China)

2010-07-01

This paper describes a new type of Nb(Ta)-Zr(Hf)-REE-Ga polymetallic deposit of volcanic origin in the late Permian coal-bearing strata of eastern Yunnan, southwestern China. Well logging data (especially natural gamma-ray), geochemical data (high concentrations of Nb, Ta, Zr, Hf, REE, and Ga) and mineralogical compositions (Nb(Ta)-, Zr(Hf)-, or REE-bearing minerals rarely observed), together with the volcanic lithological characteristics indicate that there are thick (1-10 m, mostly 2-5 m) ore beds in the lower Xuanwei Formation (late Permian) in eastern Yunann of southwestern China. The ore beds are highly enriched in (Nb,Ta){sub 2}O{sub 5} (302-627 ppm), (Zr,Hf)O{sub 2} (3805-8468 ppm), REE (oxides of La-Lu + Y) (1216-1358 ppm), and Ga (52.4-81.3 ppm). The ore beds are mainly composed of quartz, mixed-layer illite-smectite, kaolinite, berthierine, and albite. Four types of ore beds in the study area were identified, namely, clay altered volcanic ash, tuffaceous clay, tuff, and volcanic breccia. Preliminary studies suggest that the high concentrations of otherwise rare metals were mainly derived from the alkalic pyroclastic rocks. The modes of occurrence, spatial distribution, and enrichment mechanism of the rare metals, however, require further study. (author)

M₅Si₃(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

Energy Technology Data Exchange (ETDEWEB)

Tang, Zhihong [Iowa State Univ., Ames, IA (United States)

2007-01-01

Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti₅Si₃-based alloys was investigated. Oxidation behavior of Ti₅Si₃-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti₅Si₃ by nucleation and growth of nitride subscale. Ti₅Si_3.2and Ti₅Si₃C_0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi₂ coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo₃Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo₃Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb_ss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} Nb_SS + NbB was determined to occur at 2104 ± 5 C by DTA.

Transmission electron microscopy of aged Ti-10Mo-20Nb alloy after hot swaging; Microscopia eletronica de transmissao da liga Ti-10Mo-20Nb envelhecida apos forjamento a quente

Energy Technology Data Exchange (ETDEWEB)

Gabriel, Sinara Borborema, E-mail: sinarab@msn.com [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil); Baldan, Renato, E-mail: renatobaldan@gmail.com [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Torres, Juliana; Oliveira, Nathalia Rodrigues, E-mail: juliana_torres_5@hotmail.com, E-mail: nathalia_roliveira@yahoo.com.br [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Mei, Paulo Roberto, E-mail: cnunes@demar.eel.usp.br, E-mail: pmei@fem.unicamp.br [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil)

2014-08-15

Ti alloys are widely used in biomedical applications. Within this class, metastable β -Ti alloys stand, because through thermomechanical processing it is possible to obtain mechanical properties and in particular one suitable Young's modulus for biomedical applications. These alloys require high mechanical strength and a low Young's modulus to avoid stress shielding. Preliminary studies showed that the microstructure of the Ti-10Mo- 20Nb alloy after cold forging and aging 500 °C/24 h consisted in bimodal distribution of α phase in the β matrix. The aim of this study was to characterize the microstructure of Ti-10Mo-20Nb alloy after hot forging and aging at 500 °C for 24 hours. Microstructural characterization consisted of analyzes by X-ray diffraction and transmission electron microscopy. According to the results, while the cold forging resulted in a bimodal α distribution in the β matrix, hot forging resulted in a thin and homogeneous α precipitation in the β matrix. (author)

Phase diagrams for pseudo-binary carbide systems TiC-NbC, TiC-TaC, ZrC-NbC, ZrC-TaC and HfC-TaC

International Nuclear Information System (INIS)

Gusev, A.I.

1985-01-01

Parameters of interaction and energy of mutual exchange in the liquid and solid phases of pseudobinary TiC-NbC, TiC-TaC, ZrC-NbC, ZrC-TaC, HfC-TaC systems are calculated with account of dependence on composition and temperature. Positions of liquidus-solidus phase boundaries on the phase diagrams of the mentioned systems are calculated on the basis of the determined mutual exchange energies in approximati.on of subregular solutions. The existance of latent decomposition ranges in the solid phase on the phase diagrams of the investgated systems is established

Combined ion beam and hyperfine interaction studies of LiNbO3 single crystals

International Nuclear Information System (INIS)

Marques, J.G.; Kling, A.; Soares, J.C.; Rebouta, L.

1999-01-01

A review of recent studies of LiNbO 3 crystals doped with Hf and Mg,Hf combining high precision RBS/channelling, PIXE/channelling and hyperfine interaction techniques is presented. The lattice location of Hf was found to depend strongly on the dopant concentration, crystal stoichiometry and Mg co-doping level. At low concentrations Hf occupies Li sites in congruent crystals, while it occupies both Li and Nb sites for higher doping levels or in near-stoichiometric crystals. Co-doping with Mg also forces a split location of Hf in Li and Nb sites and when the MgO amount exceeds 4.5 mol% Hf occupies only Nb sites. Neutron irradiation of these crystals displaces Hf from its initial lattice site and leads to a strong decrease of the Nb site fraction. The results are discussed in the framework of the Li and Nb vacancy models currently proposed in the literature for the defect structure of LiNbO 3 . (author)

Impact and Origin of Interface States in MOS Capacitor with Monolayer MoS2 and HfO2 High-k Dielectric.

Science.gov (United States)

Xia, Pengkun; Feng, Xuewei; Ng, Rui Jie; Wang, Shijie; Chi, Dongzhi; Li, Cequn; He, Zhubing; Liu, Xinke; Ang, Kah-Wee

2017-01-13

Two-dimensional layered semiconductors such as molybdenum disulfide (MoS 2 ) at the quantum limit are promising material for nanoelectronics and optoelectronics applications. Understanding the interface properties between the atomically thin MoS 2 channel and gate dielectric is fundamentally important for enhancing the carrier transport properties. Here, we investigate the frequency dispersion mechanism in a metal-oxide-semiconductor capacitor (MOSCAP) with a monolayer MoS 2 and an ultra-thin HfO 2 high-k gate dielectric. We show that the existence of sulfur vacancies at the MoS 2 -HfO 2 interface is responsible for the generation of interface states with a density (D it ) reaching ~7.03 × 10 11  cm -2  eV -1 . This is evidenced by a deficit S:Mo ratio of ~1.96 using X-ray photoelectron spectroscopy (XPS) analysis, which deviates from its ideal stoichiometric value. First-principles calculations within the density-functional theory framework further confirms the presence of trap states due to sulfur deficiency, which exist within the MoS 2 bandgap. This corroborates to a voltage-dependent frequency dispersion of ~11.5% at weak accumulation which decreases monotonically to ~9.0% at strong accumulation as the Fermi level moves away from the mid-gap trap states. Further reduction in D it could be achieved by thermally diffusing S atoms to the MoS 2 -HfO 2 interface to annihilate the vacancies. This work provides an insight into the interface properties for enabling the development of MoS 2 devices with carrier transport enhancement.

Upper critical fields in multifilamentary NbTi alloy superconducting wires

International Nuclear Information System (INIS)

Watanabe, Kazuo; Muto, Yoshio; Noto, Koshichi.

1991-01-01

In order to improve the high field performance of superconducting magnets, the upper critical field B c2 for practical multifilamentary alloy wires of NbTi, NbTiTa and NbTiHf were examined in respect with the usage of a pressurized superfluid cooling technique. The addition of Ta or Hf to NbTi enhanced by 0.5 T for B c2 at 1.8 K. Although the addition of a heavy element such as Ta or Hf has been regarded as suppressing Pauli-paramagnetism so far, it was found that the mechanism for B c2 enhancement by Hf addition is different from that by Ta addition. (author)

MoSx-coated NbS2 nanoflakes growth on glass carbon: an advanced electrocatalyst for the hydrogen evolution reaction

KAUST Repository

Zhou, Xiaofeng; Lin, Shi-Hsin; Yang, Xiulin; Li, Henan; Hedhili, Mohamed N.; Li, Lain-Jong; Zhang, Wenjing; Shi, Yumeng

2018-01-01

Recent experimental and theoretical studies have demonstrated that two-dimensional (2D) transition metal dichalcogenide (TMDC) nanoflakes are one of the most promising candidates for non-noblemetal electrocatalysts for hydrogen evolution reaction (HER). However, it is still demanding to optimize their conductivity and enrich active sites for the high efficient electrochemical performance. Herein, we report a chemical vapor deposition (CVD) and thermal annealing two-step strategy to controllably synthesize hybrid electrocatalysts consisting of metallic NbS2 nanoflake backbones and highly catalytic active MoSx nanocrystalline shell on polished commercial glass carbon (GC). In addition, the amounts of MoSx in the hybrids can be easily adjusted, we first demonstrate that small amount of MoSx obviously promotes the HER activity of 2D NbS2 nanoflakes, which is in good consistence with the density functional theory (DFT) calculation results. Meanwhile, the optimized MoSx@NbS2/GC electrocatalyst displays a superior HER activity with an overpotential of -164 mV at -10 mA/cm2, a small Tafel slope of 43.2 mV/dec, and prominent electrochemical stability. This study provides a new path for enhancing the HER performance of 2D TMDC nanoflakes.

MoSx-coated NbS2 nanoflakes growth on glass carbon: an advanced electrocatalyst for the hydrogen evolution reaction

KAUST Repository

Zhou, Xiaofeng

2018-01-19

Recent experimental and theoretical studies have demonstrated that two-dimensional (2D) transition metal dichalcogenide (TMDC) nanoflakes are one of the most promising candidates for non-noblemetal electrocatalysts for hydrogen evolution reaction (HER). However, it is still demanding to optimize their conductivity and enrich active sites for the high efficient electrochemical performance. Herein, we report a chemical vapor deposition (CVD) and thermal annealing two-step strategy to controllably synthesize hybrid electrocatalysts consisting of metallic NbS2 nanoflake backbones and highly catalytic active MoSx nanocrystalline shell on polished commercial glass carbon (GC). In addition, the amounts of MoSx in the hybrids can be easily adjusted, we first demonstrate that small amount of MoSx obviously promotes the HER activity of 2D NbS2 nanoflakes, which is in good consistence with the density functional theory (DFT) calculation results. Meanwhile, the optimized MoSx@NbS2/GC electrocatalyst displays a superior HER activity with an overpotential of -164 mV at -10 mA/cm2, a small Tafel slope of 43.2 mV/dec, and prominent electrochemical stability. This study provides a new path for enhancing the HER performance of 2D TMDC nanoflakes.

Thermal and electric conductivity of Cu50Zr35Ti8Hf5Nb2 volume amorphous alloy

International Nuclear Information System (INIS)

Gavrenko, O.A.; Merisov, B.A.; Mikhajlova, T.N.; Molokanov, V.V.; Sologubenko, A.V.; Khadzhaj, G.Ya.

1996-01-01

The temperature dependences of thermal conductivity and electric resistance of the Cu 50 Zr 35 Ti 8 Hf 5 Nb 2 volume amorphous alloy experimentally studied within the temperature range of 1.8-240 K. The temperature dependence of electrical resistance is well described by the ratio, taking into account the electron scattering on the phonons and in the two-level systems

First principles study the stability and mechanical properties of MC (M = Ti, V, Zr, Nb, Hf and Ta) compounds

International Nuclear Information System (INIS)

Liu, YangZhen; Jiang, YeHua; Zhou, Rong; Feng, Jing

2014-01-01

Highlights: • The stability and elastic constants of carbides are studied by first principles. • The rules of modulus of MC compounds are discussed by their group. • The hardness of carbides is estimated in this paper at the first time. -- Abstract: The first principles calculations based on density functional theory (DFT) were adopted to investigate the stability, elastic constants, chemical bonding, Debye temperature and hardness of MC (M = Ti, V, Zr, Nb, Hf and Ta) compounds. The cohesive energy and formation enthalpy of these carbides indicate that they are thermodynamically stable structures. The population analysis was used to discuss the chemical bonding of these carbides. The elastic constants and moduli of these compounds were calculated. The results show that the bulk moduli of the carbides of transition metals from the fourth group (TiC, ZrC, HfC) are lower than the fifth group (VC, NbC, TaC). However, the Young’s moduli of the carbides from fourth group are higher than the fifth group. The hardness of compounds was estimated using a semi empirical hardness theory

Transmission electron microscopy of Ti-12Mo-13Nb Alloy aged after heat forging

International Nuclear Information System (INIS)

Oliveira, Nathalia Rodrigues; Baldan, Renato; Gabriel, Sinara Borborema

2014-01-01

Metastable β-Ti alloys possess mechanical properties, in particular a elastic modulus that depends not only on its composition but also the applied thermomechanical treatments. These alloys require high mechanical strength and a low Young’s modulus to avoid stress shielding. Preliminary studies on the development of Ti- 13Nb-12Mo alloy showed than the better properties were obtained at aged at 500 ° C / 24 h after cold forging , whose microstructure consisted of bimodal α phase in the β matrix. In this work, Ti-12Mo-13Nb alloy was heat forged and aged at 500 deg C for 24h and the microstructure was analyzed by employing X-ray diffraction and transmission electron microscopy. According to the results, while the cold forging resulted in bimodal α phase in the β matrix, hot forging resulted in a fine and homogeneous α phase in the β matrix. (author)

Corrosion behavior of Nb-based and Mo-based super heat-resisting alloys in liquid Li

International Nuclear Information System (INIS)

Saito, J.; Kano, S.; Morinaga, M.

1998-07-01

Research on structural materials which will be utilized even in the severe environment of high-temperature liquid alkali metals has been promoted in order to develop the frontiers of materials techniques. The super-heat resisting alloys which are based on refractory metals, Nb and Mo, are aimed as promising materials used in such an environment. The corrosion resistance in liquid Li and the mechanical properties such as creep and tensile strengths at high temperatures are important for these structural materials. On the basis of many experiments and analyses of these properties at 1473 K, the material design of Nb-based and Mo-based alloys has been carried out successfully. In this report, all the previous experimental results of corrosion tests in liquid Li were summarized systematically for Nb-based and Mo-based alloys. The corrosion mechanism was proposed on the basis of a series of analyses, in particular, focussing on the deposition mechanism of corrosion products on the surface and also on the initiation and growth mechanism of cracks on the corroded surface of Nb-based alloys. The principal results are as follows. (1) For the deposition mechanism, a reaction took place first between dissolved metallic elements and nitrogen which existed as an impurity in liquid Li and then corrosion products (nitrides) precipitated on the metal surface. Subsequently, another reaction took place between dissolved metallic elements in liquid Li, and corrosion products (intermetallic compounds) precipitated on the metal surface. The composition of deposited corrosion products could be predicted on the basis of the deposition mechanism. (2) For the crack initiation mechanism, the chemical potential diagrams were utilized in order to understand the formation of Li-M-O ternary oxides which caused cracks to be formed on the corroded surface. Consequently, it was evident that not only the concentration of the dissolved oxygen in the alloy but also the concentration of Li which

Improvement of NiMoNb to polyimide adhesion by inductively coupled nitrogen plasma treatment

Energy Technology Data Exchange (ETDEWEB)

Bang, S.-H., E-mail: zxclucy@snu.ac.kr

2016-01-01

Graphical abstract: - Highlights: • NiMoNb was introduced as the adhesion layer for flexible Cu-clad laminate structure. • The effect of sputtering and plasma power on the peel strength was studied. • Plasma pretreatment in inductively coupled plasma greatly affects the peel strength. • FCCL with NiMoNb adhesion layer show outstanding peel strength. - Abstract: In this study, the effect of sputtering power on the peel strength of the flexible copper clad laminate (FCCL) was evaluated before and after heat treatment using 180° peel test. An increase in the sputtering powers from 200 W to 600 W increased film density and improved peel strength. To enhance peel strength much more, an inductively coupled plasma (ICP) was treated on the PI surface using N{sub 2} gas with Ar as a function of RF power. A dramatic enhancement of the peel strength, 923 N/m was achieved, especially after heat treatment by changing ICP power from 200 W to 900 W. The reduction ratio of the peel strength for the 900 W plasma-treated FCCL was only 12%, whereas that for the 200 W plasma-treated FCCL was 43%. The root mean square (RMS) surface roughness with PIs exposed to both 200 W and 900 W plasma treatments was rarely changed, while X-ray photoelectron spectroscopy (XPS) showed the substantial increase of C–N functional groups. To obtain insight the film characteristics, the NiMoNb/PI interfaces were investigated by a high resolution transmission electron microscopy (HR-TEM).

Precipitation hardening and microstructure evolution of the Ti-7Nb-10Mo alloy during aging.

Science.gov (United States)

Yi, Ruowei; Liu, Huiqun; Yi, Danqing; Wan, Weifeng; Wang, Bin; Jiang, Yong; Yang, Qi; Wang, Dingchun; Gao, Qi; Xu, Yanfei; Tang, Qian

2016-06-01

A biomedical β titanium alloy (Ti-7Nb-10Mo) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and aging. Age-hardening behavior, microstructure evolution and its influence on mechanical properties of the alloy during aging were investigated, using X-ray diffraction, transmission electron microscopy, tensile and hardness measurements. The electrochemical behavior of the alloy was investigated in Ringer's solution. The microstructure of solution-treated (ST) alloy consists of the supersaturated solid solution β phase and the ωath formed during athermal process. The ST alloy exhibits Young's modulus of 80 GPa, tensile strength of 774 MPa and elongation of 20%. The precipitation sequences during isothermal aging at different temperatures were determined as β+ωath→β+ωiso (144 h) at Taging=350-400 °C, β+ωath→β+ωiso+α→β+α at Taging=500°C, and β+ωath→β+α at Taging=600-650 °C, where ωiso forms during isothermal process. The mechanical properties of the alloy can be tailored easily through controlling the phase transition during aging. Comparing with the conventional Ti-6Al-4V alloy, the Ti-7Nb-10Mo alloy is more resistant to corrosion in Ringer's solution. Results show that the Ti-7Nb-10Mo alloy is promising for biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Zr, Hf, Mo and W-containing oxide phases as pinning additives in Bi-2212 superconductor

International Nuclear Information System (INIS)

Makarova, M.V.; Kazin, P.E.; Tretyakov, Yu.D.; Jansen, M.; Reissner, M.; Steiner, W.

2005-01-01

Phase formation was investigated in Bi-Sr-Ca-Cu-M-O (M = Mo, W) systems at 850-900 deg C. It was found that Sr 2 CaMO 6 phases were chemically compatible with Bi-2212. The composites Bi-2212-Sr 2 CaMO 6 and Bi-2212-SrAO 3 (A = Zr, Hf) were obtained from a sol-gel precursor using crystallisation from the melt. The materials consisted of Bi-2212 matrix and submicron or micron grains of the corresponding dispersed phase. T c was equal or exceeded that for undoped Bi-2212, reaching T c = 97 K in the Mo-containing composite. The composites exhibited enhanced pinning in comparison with similar prepared pure Bi-2212, especially at T = 60 K. The best pinning parameters were observed for the Bi-2212-Sr 2 CaWO 6 composite

Effect of annealing temperature on microstructure and superelastic properties of a Ti-18Zr-4.5Nb-3Sn-2Mo alloy.

Science.gov (United States)

Fu, Jie; Kim, Hee Young; Miyazaki, Shuichi

2017-01-01

In this study a new superelastic Ti-18Zr-4.5Nb-3Sn-2Mo alloy was prepared by adding 2at% of Mo as a substitute for Nb to the Ti-18Zr-11Nb-3Sn alloy, and heat treatment at different temperatures was conducted. The temperature dependence of superelasticity and annealing texture was investigated. Texture showed a dependence of annealing temperature: the specimen annealed at 923K for 0.3ks exhibited {113} β β type texture which was similar to the deformation texture, while specimens annealed at 973, 1073K, and 1173K showed {001} β β type recrystallization texture which was preferable for recovery strain. The largest recovery strain of 6.2%, which is the same level as that of the Ti-18Zr-11Nb-3Sn alloy, was obtained in the specimen annealed at 1173K for 0.3ks due to the well-developed {001} β β type recrystallization texture. The Ti-18Zr-3Nb-3Sn-2Mo alloy presented a higher tensile strength compared with the Ti-18Zr-11Nb-3Sn alloy when heat treated at 1173K for 0.3ks, which was due to the solid solution strengthening effect of Mo. Annealing at 923K for 0.3ks was effective in obtaining a good combination of a high strength as 865MPa and a large recovery strain as 5.6%. The high recovery strain was due to the high stress at which the maximum recovery stain was obtained which was attributed to the small grain size formed at low annealing temperature. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis of MoVTeNb Oxide Catalysts with Tunable Particle Dimensions

DEFF Research Database (Denmark)

Kolenko, Yury V.; Zhang, Wei; d'Alnoncourt, Raoul Naumann

2011-01-01

Reliable procedures for the controlled synthesis of phase-pure MoVTeNb mixed oxides with M1 structure (ICSD 55097) and tunable crystal dimensions were developed to study the structure sensitivity of the selective oxidation of propane to acrylic acid. A series of powdered M1 catalysts...... catalysts were studied in the selective oxidation of propane to acrylic acid, revealing that active sites appear on the entire M1 surface and illustrating the high sensitivity of catalyst performance on the catalyst synthesis method....

Determination of Nb and Zr in U-Nb-Zr alloys by ICP-AES

International Nuclear Information System (INIS)

Wang Cuiping; Dong Shizhe; Li Lin; He Meiying

2003-01-01

The U-Nb-Zr alloy sample is dissolved by HNO 3 , H 2 O 2 and HF, and the contents of Nb and Zr in the sample are determined on the JY-70 II type ICP-AES by using the internal standard synchronous dilution method. The range of determination is 1%-10% and 0.33%-3.33%, respectively for Nb and Zr. The relative standard deviation is better than 3.2% for Nb, and 2.5% for Zr. The method is rapid and convenient for determining Nb and Zr in U-Nb-Zr alloy sample

The Structure and Magnetic Properties of Pr 3MO7 with M = Nb, Ta, and Sb

Science.gov (United States)

Vente, J. F.; Helmholdt, R. B.; IJdo, D. J. W.

1994-01-01

The crystal structure of the fluorite-related praseodymium compounds with the composition Pr 3MO7, M = Nb, Ta, and Sb, have been determined using Rietveld refinement from X-ray and neutron powder diffraction data at 293 and 4 K. The structure described is orthorhombic with space group Cmcm (No. 63). It is a superstructure of the cubic fluorite structure with unit cell parameters a orth ≈ 2a c, b orth ≈ c orth ≈ a c2, as in La 3NbO 7. This structure consists of chains of corner linked MO 6 octahedra parallel with the c-axis. The magnetic susceptibility was measured between 4 and 300 K. The compounds obey the Curie-Weiss law including a Van Vleck temperature independent term. Pr 3SbO 7 shows a small deviation from this law below 25 K.

MoNbTaV Medium-Entropy Alloy

Directory of Open Access Journals (Sweden)

Hongwei Yao

2016-05-01

Full Text Available Guided by CALPHAD (Calculation of Phase Diagrams modeling, the refractory medium-entropy alloy MoNbTaV was synthesized by vacuum arc melting under a high-purity argon atmosphere. A body-centered cubic solid solution phase was experimentally confirmed in the as-cast ingot using X-ray diffraction and scanning electron microscopy. The measured lattice parameter of the alloy (3.208 Å obeys the rule of mixtures (ROM, but the Vickers microhardness (4.95 GPa and the yield strength (1.5 GPa are about 4.5 and 4.6 times those estimated from the ROM, respectively. Using a simple model on solid solution strengthening predicts a yield strength of approximately 1.5 GPa. Thermodynamic analysis shows that the total entropy of the alloy is more than three times the configurational entropy at room temperature, and the entropy of mixing exhibits a small negative departure from ideal mixing.

Hyperfine Interaction Studies on Y, Zr, Nb, Mo, Rh, In and Xe in Co

International Nuclear Information System (INIS)

Seewald, G.; Zech, E.; Ratai, H.; Schmid, R.; Stadler, R.; Schramm, O.; Koenig, C.; Hinfurtner, B.; Hagn, E.; Deicher, M.; Eder, R.; Forkel-Wirth, D.

2004-01-01

Nuclear magnetic resonance on oriented nuclei and modulated adiabatic fast passage on oriented nuclei measurements were performed on several 4d and 5sp impurities in polycrystalline Co(fcc) foils and Co(hcp) single crystals. The hyperfine fields of Y and Zr in Co(fcc), the hyperfine fields of Y, Zr, Nb, Mo, Rh, In and Xe in Co(hcp), the electric field gradients of Zr, Nb and In in Co(hcp), and the nuclear spin-lattice relaxations of Zr, Nb, Rh and In in Co(hcp) were determined. The dependence of the hyperfine fields and electric field gradients in Co(hcp) on the angle between the magnetization and the c axis was investigated in most cases. The magnetic-field dependence of the spin-lattice relaxation was studied for Nb, Rh and In in Co(hcp), applying the magnetic field perpendicular to the c axis. The known hyperfine interaction parameters of the4d and 5sp impurities in Co(fcc) and Co(hcp) are summarized. The new results provide a more detailed picture of the hyperfine interaction in Co.

MoRe-based and NbN-based tunnel junctions and their characteristics

International Nuclear Information System (INIS)

Shaternik, V.E.; Noskov, V.L.; Chubatyy, V.V.; Larkin, S.Yu.; Sizontov, V.M.; Miroshnikov, A.M.; Karmazin, A.A.

2007-01-01

Full text: Perspective [1] Josephson Mo-Re alloy-oxide-Pb, Mo-Re alloy-normal metal-oxide-Pb and Mo-Re alloy-normal metal-oxide- normal metal-Mo-Re alloy junctions have been fabricated and investigated. Thin (∼50-100 nm) MoRe superconducting films are deposited on Al 2 O 3 substrates by using a dc magnetron sputtering of MoRe target. Normal metal (Sn, Al) thin films are deposited on the MoRe films surfaces by thermal evaporation of metals in vacuum and oxidized to fabricate junctions oxide barriers. Quasiparticle I-V curves of the fabricated junctions were measured in wide range of voltages. To investigate a transparency spread for the fabricated junctions barriers the computer simulation of the measured quasiparticle I-V curves have been done in framework of the model of multiple Andreev reflections in double-barrier junction interfaces. It's demonstrated the investigated junctions can be described as highly asymmetric double-barrier Josephson junctions with great difference between the two barrier transparencies [2,3]. The result of the comparison of experimental quasiparticle I-V curves and calculated ones is proposed and discussed. Results of computer simulation of quasiparticles I-V curves of NbN-based junctions are presented and discussed. Also I-V curves of the fabricated junctions have been measured under microwave irradiation with 60 GHz frequency , clear Shapiro steps in the measured I-V curves were observed and discussed. (authors)

History-dependent thermal expansion in NbO{sub 2}F

Energy Technology Data Exchange (ETDEWEB)

Wilkinson, Angus P., E-mail: angus.wilkinson@chemistry.gatech.edu [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 (United States); Josefsberg, Ryan E.; Gallington, Leighanne C.; Morelock, Cody R.; Monaco, Christopher M. [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States)

2014-05-01

Materials with cubic ReO{sub 3}-type structures are of interest for their low or negative thermal expansion characteristics. TaO{sub 2}F is known to display almost zero thermal expansion over a wide temperature range. On heating NbO{sub 2}F, its volume coefficient of thermal expansion decreases from ∼+45 ppm K{sup −1} at 100 K to almost zero at 400 K. NbO{sub 2}F is cubic between 100 and 500 K. Samples of “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying contain hydroxyl defects and metal vacancies. On heating, they can undergo irreversible chemical changes while maintaining a cubic ReO{sub 3}-type structure. The possibility of hydroxyl defect incorporation should be considered when preparing oxyfluorides for evaluation as battery materials. - Graphical abstract: “NbO{sub 2}F” prepared by the digestion of Nb{sub 2}O{sub 5} in HF contains cation vacancies and hydroxyl groups. It undergoes irreversible changes on heating to low temperatures, unlike NbO{sub 2}F prepared by the solid state reaction of Nb{sub 2}O{sub 5} and NbF{sub 5}. - Highlights: • The digestion of Nb{sub 2}O{sub 5} in aqueous HF followed by mild drying does not produce NbO{sub 2}F. • The ReO{sub 3}-type product from the HF digestion of Nb{sub 2}O{sub 5} contains metal vacancies and hydroxyl. • The thermal expansion coefficient of NbO{sub 2}F decreases on heating and approaches zero at ∼400 K.

Behaviour at the indicator scale of the elements Zr, Hf and 104, Nb,Ta and Pa (105) in very complexation media; Comportement a l`echelle des indicateurs des elements Zr, Hf, et 104, Nb, Ta, et Pa (105) en milieux tres complexants

Energy Technology Data Exchange (ETDEWEB)

Monroy Guzman, F. [Institut de Physique Nucleaire, CNRS - IN2P3 Universite Paris Sud, 91406 Orsay Cedex (France)

1997-12-31

In order to determine the chemical properties of the trans-actinide elements of Z = 104 and 105 in aqueous solutions we studied their behaviour to ion exchange resin in different complex media. Due to the very short lifetimes (some tens of seconds) et to the low yield of these elements (a few atoms per irradiation hour) only very fast radiochemical techniques can be used. These severe constraints impose comparative studies of these elements with their most likely homologues to be carried out. The corresponding homologues were the elements of group 4 (Zr and Hf) for the element 104 and the elements of group 5 (Nb and Ta) and also Pa for the element 105. The complexation properties of the elements at indicator scale were determined in the media of HF, NH{sub 4}/HClO{sub 4}, NH{sub 4}SCN/HClO{sub 4}, NH{sub 4}SCN/HF and HCl/HF by ion exchange chromatography. The studies in fluorides media allowed us to identify the complexes in solution and to explain the shape of the experimentally observed sorption curves. The decrease of sorption for higher acid concentration in case of HF/HCl medium was interpreted by formation of chloro-fluoro-complexes. In case of the mixture NH{sub 4}SCN/HF, the particularly pronounced anti-synergic effects were observed and discussed. At the same time studies of the Hf and Ta short-lived isotopes were carried out by means of the RACHEL facility operating by the Orsay Tandem accelerator. These realistic simulations allowed optimization of different production, transportation and separation stages of the trans-actinide elements. The two experiments of 104 element production showed that this element forms in HF very stable anionic complexes similarly to its homologues Zr and Hf. (authors). 181 refs.

Behaviour at the indicator scale of the elements Zr, Hf and 104, Nb,Ta and Pa (105) in very complexation media; Comportement a l`echelle des indicateurs des elements Zr, Hf, et 104, Nb, Ta, et Pa (105) en milieux tres complexants

Energy Technology Data Exchange (ETDEWEB)

Monroy Guzman, F [Institut de Physique Nucleaire, CNRS - IN2P3 Universite Paris Sud, 91406 Orsay Cedex (France)

1998-12-31

In order to determine the chemical properties of the trans-actinide elements of Z = 104 and 105 in aqueous solutions we studied their behaviour to ion exchange resin in different complex media. Due to the very short lifetimes (some tens of seconds) et to the low yield of these elements (a few atoms per irradiation hour) only very fast radiochemical techniques can be used. These severe constraints impose comparative studies of these elements with their most likely homologues to be carried out. The corresponding homologues were the elements of group 4 (Zr and Hf) for the element 104 and the elements of group 5 (Nb and Ta) and also Pa for the element 105. The complexation properties of the elements at indicator scale were determined in the media of HF, NH{sub 4}/HClO{sub 4}, NH{sub 4}SCN/HClO{sub 4}, NH{sub 4}SCN/HF and HCl/HF by ion exchange chromatography. The studies in fluorides media allowed us to identify the complexes in solution and to explain the shape of the experimentally observed sorption curves. The decrease of sorption for higher acid concentration in case of HF/HCl medium was interpreted by formation of chloro-fluoro-complexes. In case of the mixture NH{sub 4}SCN/HF, the particularly pronounced anti-synergic effects were observed and discussed. At the same time studies of the Hf and Ta short-lived isotopes were carried out by means of the RACHEL facility operating by the Orsay Tandem accelerator. These realistic simulations allowed optimization of different production, transportation and separation stages of the trans-actinide elements. The two experiments of 104 element production showed that this element forms in HF very stable anionic complexes similarly to its homologues Zr and Hf. (authors). 181 refs.

Non-destructive Residual Stress Analysis Around The Weld-Joint of Fuel Cladding Materials of ZrNbMoGe Alloys

Directory of Open Access Journals (Sweden)

Parikin

2003-08-01

Full Text Available The residual stress measurements around weld-joint of ZrNbMoGe alloy have been carried out by using X-ray diffraction technique in PTBIN-BATAN. The research was performed to investigate the structure of a cladding material with high temperature corrosion resistance and good weldability. The equivalent composition of the specimens (in %wt. was 97.5%Zr1%Nb1%Mo½%Ge. Welding was carried out by using TIG (tungsten inert gas technique that completed butt-joint with a current 20 amperes. Three region tests were taken in specimen while diffraction scanning, While diffraction scanning, tests were performed on three regions, i.e., the weldcore, the heat-affected zone (HAZ and the base metal. The reference region was determined at the base metal to be compared with other regions of the specimen, in obtaining refinement structure parameters. Base metal, HAZ and weldcore were diffracted by X-ray, and lattice strain changes were calculated by using Rietveld analysis program. The results show that while the quantity of minor phases tend to increase in the direction from the base metal to the HAZ and to the weldcore, the quantity of the ZrGe phase in the HAZ is less than the quantity of the ZrMo2 phase due to tGe element evaporation. The residual stress behavior in the material shows that minor phases, i.e., Zr3Ge and ZrMo2, are more dominant than the Zr matrix. The Zr3Ge and ZrMo2 experienced sharp straining, while the Zr phase was weak-lined from HAZ to weldcore. The hydrostatic residual stress ( in around weld-joint of ZrNbMoGe alloy is compressive stress which has minimum value at about -2.73 GPa in weldcore region

Development of the dentistry alloy Ni-Cr-Nb; Desenvolvimento de ligas odontologicas Ni-Cr-Nb

Energy Technology Data Exchange (ETDEWEB)

Souza, M.A.; Ramos, A.S.; Hashimoto, T.M., E-mail: mari_sou@hotmail.co [UNESP/FEG, Guaratingueta, SP (Brazil). Fac. de Engenharia. Dept. de Materiais e Tecnologia

2010-07-01

This work reports on the structural characterization of Ni-Cr-Mo and Ni-Cr-Nb alloys produced by arc melting. Samples were characterized by means of optical microscopy, X-ray diffraction, scanning electron microscopy, and EDS analysis. Results indicated that the arc melting process was efficient to produce homogeneous structures in Ni-Cr-Mo and Ni-Cr-Nb alloys. The nickel dissolved large amounts of Cr, Mo and Nb, which was detected by EDS analysis and X-ray diffraction. The alloy containing molybdenum indicated the presence of structure based on Ni{sub SS}, while that the alloys containing niobium presented primary grains of Ni{sub SS} and precipitates formed by the simultaneous transformation of the Ni and Ni{sub 3}Nb phases. (author)

Correlation between hardness and stress in Al-(Nb, Mo, Ta) thin films

Energy Technology Data Exchange (ETDEWEB)

Car, T., E-mail: car@irb.h [Rudjer Boskovic Institute, Division of Materials Science, Bijenicka cesta 54, 10000 Zagreb, P.O.B. 1016 (Croatia); Radic, N. [Rudjer Boskovic Institute, Division of Materials Science, Bijenicka cesta 54, 10000 Zagreb, P.O.B. 1016 (Croatia); Panjan, P.; Cekada, M. [Jozef Stefan Institute, Ljubljana (Slovenia); Tonejc, A. [Department of Physics, Bijenicka cesta 32, 10000 Zagreb, P.O.B. 331 (Croatia)

2009-06-30

The thin films of Al{sub x}Nb{sub 1-x} (95 {>=} x {>=} 20), Al{sub x}Mo{sub x} (90 {>=} x {>=} 20) and Al{sub x}Ta{sub 1-x} (95 {>=} x {>=} 20) were prepared by magnetron codeposition at room temperature. The average film thickness was from 325 to 400 nm, depending on the film composition. The structure of the as-deposited films was examined by the X-ray diffraction. The stress of the films was determined from the substrate deformation by the profilometer, and the microhardness (load 2 mN) was examined by the micro- and nano-hardness device. For the purpose of the examination of the hardness, the samples were deposited onto the sapphire wafers, while the examination of the film stress, was performed by using thin glass substrates. For all the Al-(Nb, Mo, Ta) alloy compositions, the microhardness is predominantly under the influence of the harder element, and monotonically decreases with the increase of the aluminum content. However, the microhardness of the amorphous AlTa films was higher than the bulk value of a harder element (Ta) in the alloy. A simple empirical linear relationship between the Vickers hardness, the bulk value hardness of the transition metal (harder element) and the elastic energy fraction of the identation deformation, was established. The elastic energy fraction in the microhardness is also linearly correlated with the stress in films.

Mechanical properties of steel 8 CrMoNiNb 9 10 in dependence on the microstructural condition

International Nuclear Information System (INIS)

Fabritius, H.; Schnabel, E.

1976-01-01

Tension tests at room temperature to 600 0 C and creep-rupture tests at 500 to 600 0 C lasting up to about 75,000 h on two casts of steel 8 CrMoNiNb 9 10 with about 0.08% C, 0.3% Si, 0.7% Mn, 0.012% N, 0.005% Al, 2.34% Cr, 0.95% Mo, 0.8% Nb and 0.64% Ni in bainitic and ferritic microstructural condition. Influence of annealing at 650 to 800 0 C on the properties in the tension test. Influence of aging at 500 to 600 0 C lasting up to 30,000 h with and without mechanical stress on the properties in the tension test at aging temperature and on the toughness behaviour in the notched bar impact bend test at room temperature. (orig.) [de

Lifetime measurements of nuclear states in 92,91,90Mo, 89,88Nb

International Nuclear Information System (INIS)

Chakrawarthy, R.S.; Singh, Pragya; Pillay, R.G.; Devare, H.G.

1993-01-01

In order to test the correctness of the wave functions calculated by the shell-model calculations, the knowledge of transition probabilities is important. This, in turn, requires the determination of half lives of these states. We have performed two different experiments, based on Recoil Distance Method (RDM), to measure the lifetime in picosecond range, of states belonging to 92,91,90 Mo and 89,88 Nb nuclei. (author). 3 refs., 1 tab., 1 fig

4p-5s transitions in YVII, VIII, ZrVIII, IX, NbIX, X and MoX, XI

International Nuclear Information System (INIS)

Rahimullah, K.; Chaghtai, M.S.Z.; Khatoon, S.

1976-01-01

The spectra of Y VII, VIII, Zr VIII, IX, Nb X and Mo X, XI are studied for the first time and the 1971 analysis of Nb IX is improved. By analyses of the transitions 4s 2 4psup(k)-4s 2 4psup(k-1)5s all the levels of the configurations 4p 3 , 4p 2 5s, 4p 2 and 4p5s are established in the spectra concerned. (Auth.)

New Layered Oxide-Fluoride Perovskites: KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+

Directory of Open Access Journals (Sweden)

Rachelle Ann F. Pinlac

2011-03-01

Full Text Available KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+, three new layered oxide-fluoride perovskites with the general formula ABB’X6, form from the combination of a second-order Jahn-Teller d0 transition metal and an alkali metal (Na+ on the B-site. Alternating layers of cation vacancies and K+ cations on the A-site complete the structure. The K+ cations are found in the A-site layer where the fluoride ions are located. The A-site is vacant in the adjacent A-site layer where the axial oxides are located. This unusual layered arrangement of unoccupied A-sites and under bonded oxygen has not been observed previously although many perovskite-related structures are known.

Bridge toughening enhancement in double-notched MoSi2/Nb model composites

International Nuclear Information System (INIS)

Pickard, S.M.; Ghosh, A.K.

1996-01-01

Single-ply composites containing both laminate and continuous Nb fiber reinforcement coated with Al 2 O 3 debond coatings in an MoSi 2 matrix are used as model systems for investigating bridge toughening concepts for various precrack configurations., When cracks are introduced symmetrically on either side of the ductile phase with zero crack offset spacing (S = 0), a minimum amount of energy is expended in plastic deformation and the local rupture process in the metal, as measured by the area of the force displacement curve in tension. For asymmetric precracks introduced on either side of the ductile reinforcement, as the offset spacing, S, was varied from 1 to 20 R (R being the ductile phase half-thickness), the overall extension continuously increased within the bridging ligament. The effective ligament gage length was nearly equal to the crack spacing in the limiting case of a weak interface. However, the ductile Nb phase developed a Nb 5 Si 3 reaction layer on its surface which was strongly bonded to the Nb and was found to undergo periodic cracking, leading to numerous shear bands within the ductile phase. This unique and previously unreported mode of metal deformation in shear loading has been analyzed using a simple geometric model. The results indicate that the profusion of shear bands is the primary source of toughening enhancement in the case of asymmetric crack geometry, which was not recognized in prior work of this type

A comparison of the microstructure and high temperature tensile properties of a novel P/M Mo-Hf-Zr-Ta-C alloy and TZM

International Nuclear Information System (INIS)

Warren, J.; Reznikov, G.

2001-01-01

The microstructure and elevated temperature quasi-static tensile yield and ultimate strength observed in a novel, forged Mo-based alloy (Mo-0.25 Hf-0.25 Zr-0.25 Ta-0.025 C) has been analyzed and compared to a standard forged TZM composition (Mo-0.50 Ti-0.08 Zr-0.02 C). The novel material exhibits the desirable forging characteristics typical of the widely used TZM composition yet possess a higher ultimate strength and 0.2 % offset yield strength in both the stress-relieved and recrystallized conditions over a 400 o -1200 o C temperature range. The greater strength measured in the novel composition has been attributed to the combined effects of precipitation of Hf, Zr and Mo-(carbide) precipitates that strengthen the matrix in the classical Orowan fashion and improved resistance to recrystallization after high temperature exposure. Elevated temperature creep behavior, not addressed in the study presented here, will be reported on in a subsequent analysis. (author)

Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

OpenAIRE

Fan Zhang; Oleg N. Senkov; Jonathan D. Miller

2013-01-01

Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively....

The structural and electronic properties of cubic AgMO{sub 3} (M=Nb, Ta) by first principles calculations

Energy Technology Data Exchange (ETDEWEB)

Prasad, K. Ganga; Niranjan, Manish K.; Asthana, Saket [Department of Physics, Indian Institute of Technology Hyderabad, India, 502205 (India)

2016-05-06

We report the electronic structure of the AgMO{sub 3}(M=Nb, Ta) within the frame work of density functional theory and calculations are performed within the generalized gradient approximation (GGA) by using ultrasoft pseudopotentials. The calculated equilibrium lattice parameters and volumes are extracted from fitting of Birch third order equation of state and which are reasonable agreement with the available experimental results. The density of states,band structure of Ag(Nb,Ta)O{sub 3} reveals that the valance bands mostly occupied with O-2p and O-2s states and whereas conduction band occupied with Nb (Ta) 4d(5d) states including less contribution from Ag 5s states.

Superconductivity in dense Mg1–xMxB2 (M= Zr, Nb, Mo; x= 0⋅ 05 ...

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 28; Issue 3. Superconductivity in dense Mg1–MB2 (M = Zr, Nb, Mo; = 0.05) materials sintered under pressure. S Kalavathi C Divakar. Superconductors Volume 28 Issue 3 June 2005 pp 249-252 ...

Magnetic and surface properties of Fe-Nb (Mo, V)-Cu-B-Si ribbons

International Nuclear Information System (INIS)

Butvinova, B.; Butvin, P.; Svec, P. Sr.; Matko, I.; Svec, P.; Janickovic, D.; Kadlecikova, M.

2014-01-01

The rapidly quenched Finemet (FeNbCuBSi) ribbons prepared by planar flow casting of the melt are very variable to obtain very good soft-magnetic properties. An appropriate thermal treatment leading to ultra-fine grain structure enables to attain such properties as desired for practical use. Increasing Fe percentage to the detriment of non-magnetic components lifts saturation induction above 1.3 T, preserves low coercivity and makes the alloy even cheaper to suit its mass production for use in power electronics. Apart from the plenty of benefits the ribbons show some risks. One of them is macroscopic heterogeneity, which often manifests via differences between surfaces and interior of a ribbon [3]. The surfaces squeeze (by in-plane force) the interior of many such ribbons and if engaged in magnetoelastic interaction, the force affects the resulting magnetic anisotropy [4]. Current research shows that changes of hysteresis loop shape come rather from surface crystallization and not from oxides namely in positively magnetostrictive alloys FeNbCuBSi known as low- Si Finemets. The object of this work is to verify whether the substitution of another element instead of Nb (usually incorporated as the grain-growth blocker) can change surface properties and affects the resulting magnetic properties. We chose V and Mo instead of Nb. Oxides, oxyhydroxides and a possible squeezing layer was looked for after higher temperature annealing which ensures partially nanocrystalline structure. (authors)

Self-diffusion of Er and Hf inpure and HfO2-doped polycrystalline Er2O3

International Nuclear Information System (INIS)

Scheidecker, R.W.

1979-01-01

Using a tracer technique, self-diffusion of Er and Hf was measured over the approximate temperature interval of 1600 to 1970 0 C in pure and HfO 2 -doped polycryatalline Er 2 O 3 . Up to about 10 m/o HfO 2 dopant level, the Er self-diffusion coefficients followed a relationship based on cation vacancies. Above 10 m/o HfO 2 , deviation from this relationship occurred, apparently due to clustering of cation vacancies and oxygen interstitials around the dopant hafnia ion. The activation energy for the self-diffusion of Er in pure Er 2 O 3 was 82.2 Kcal/mole and increased with the HfO 2 dopant level present. Self-diffusion of Hf was measured in pure Er 2 O 3 having two impurity levels, and a separation of the grain boundary. The volume diffusion of Hf showed both extrinsic and intrinsic behavior with the transition temperature increasing with the impurity level present in Er 2 O 3 . The activation energy for Hf volume diffusion in the intrinsic region was high, i.e. 235 -+ 9.5 Kcal/mole. The grain boundary diffusion was apparently extrinsic over the entire temperature interval Very low Hf self diffusion rates were found in both pure and HfO 2 doped Er 2 O 3 compositions. Despite a clustering effect, the HfO 2 dopant increased the Hf volume diffusion coefficients

Deposition and cyclic oxidation behavior of a protective (Mo,W)(Si,Ge) 2 coating on Nb-base alloys

International Nuclear Information System (INIS)

Mueller, A.; Wang, G.

1992-01-01

A multicomponent diffusion coating has been developed to protect Nb-base alloys from high-temperature environmental attach. A solid solution of molybdenum and tungsten disilicide (Mo, W)Si 2 , constituted the primary coating layer which supported a slow-growing protective silica scale in service. Germanium additions were made during the coating process to improve the cyclic oxidation resistance by increasing the thermal expansion coefficient of the vitreous silica film formed and to avoid pesting by decreasing the viscosity of the protective film. In this paper, the development of the halide-activated pack cementation coating process to produce this (Mo,W)(Si,Ge) 2 coating on Nb-base alloys is described. The results of cyclic oxidation for coupons coated under different conditions in air at 1370 degrees C are presented. Many coupons have successfully passed 200 1 h cyclic oxidation tests at 1370 degrees C with weight-gain values in the range of 1.2 to 1.6 mg/cm 2

Anomalous temperature dependence of the superelastic behavior of Ti-Nb-Mo alloys

International Nuclear Information System (INIS)

Al-Zain, Y.; Kim, H.Y.; Koyano, T.; Hosoda, H.; Nam, T.H.; Miyazaki, S.

2011-01-01

The effect of test temperature on the superelasticity of Ti-27Nb and various Ti-Nb-Mo alloys is investigated. A deviation in the stress at which martensitic transformation starts (σ β-α'' ) from the behavior expected from the Clausius-Clapeyron relationship is confirmed in all alloys. The degree of deviation is found to be in inverse proportion to the electron-to-atom ratio. However, no deviation is observed in the stress at which the reverse transformation finishes (σ α''-β ). All alloys exhibit anomalous electrical resistivity during cooling. X-ray diffraction (XRD) and transmission electron microscopy investigations show that the volume fraction of the athermal ω (ω ath ) phase increases with a decrease in temperature. An in situ XRD experiment obtained during a loading-unloading cycle shows that the β and ω ath phases transform into the α'' phase during loading. The annihilation of the ω ath phase within the α'' phase allows σ α''-β to obey the Clausius-Clapeyron relationship. As a result, a large hysteresis loop is produced.

Synthesis and characterization of V, Mo and Nb incorporated micro-mesoporous MCM-41 materials

Energy Technology Data Exchange (ETDEWEB)

Solmaz, Arzu, E-mail: arzu.solmaz@rshm.gov.tr [Gazi University, Faculty of Engineering, Chemical Engineering Department, 06570 Ankara (Turkey); Balci, Suna, E-mail: sunabalci@gazi.edu.tr [Gazi University, Faculty of Engineering, Chemical Engineering Department, 06570 Ankara (Turkey); Dogu, Timur, E-mail: tdogu@metu.edu.tr [Middle East Technical University, Faculty of Engineering, Chemical Engineering Department, 06531 Ankara (Turkey)

2011-01-01

Highly microporous metal-MCM-41 ordered mesoporous structure catalysts having different metal/Si (V, Mo, Nb) atomic ratios and combinations of metal sources were hydrothermally synthesized. The structural properties estimated using different techniques were found to be in agreement with each other. Metals were successfully incorporated into MCM-41 without deteriorating the ordered hexagonal structure. The metal ions in the synthesis solutions probably settled on the hydrophilic end of the template hence the metal incorporation resulted improvements in the micropore structure. Low loading of metals caused an increase in the surface area and pore volume values of the catalysts. The highest total (1310 m{sup 2} g{sup -1}) and micropore surface area values (1083 m{sup 2} g{sup -1}) were obtained by Nb incorporation. The micro- and mesopore dimensions of MCM-41 increased from 0.5 to 1.1 nm and from 2.5 to 2.8 nm, respectively, with metal incorporation. Low V/Si ratios and presence of Nb in the starting solution enhanced narrow mesopore size distribution. The pore dimension and wall thickness values estimated from nitrogen adsorption and X-ray diffraction methods were consistent with the corresponding values obtained using transmission electron microscopy.

Role of Nb in glass formation of Fe–Cr–Mo–C–B–Nb BMGs

Energy Technology Data Exchange (ETDEWEB)

Zhai, Fuqiang, E-mail: fuqiangzhai@gmail.com [Departament Física Aplicada, EETAC, Universitat Politècnica Catalunya-BarcelonaTech, Esteve Terradas 5, 08860 Castelldefels (Spain); Pineda, Eloi [Departament Física i Enginyeria Nuclear, ESAB, Universitat Politècnica Catalunya- BarcelonaTech, Esteve Terradas 8, 08860 Castelldefels (Spain); Duarte, M. Jazmín [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf (Germany); Crespo, Daniel [Departament Física Aplicada, EETAC, Universitat Politècnica Catalunya-BarcelonaTech, Esteve Terradas 5, 08860 Castelldefels (Spain)

2014-08-01

Highlights: • The Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4} BMG of 3 mm Ø was produced for the first time. • The compressive strength of Fe–Cr–Mo–C–B–Nb BMG is reported. • The fragility parameter of Fe–Cr–Mo–C–B–Nb BMG was studied. • The microscopic mechanism is explained by E{sub g}, E{sub x}, E{sub p} and m parameters. - Abstract: A new Fe-based bulk metallic glass with superior glass-forming ability (GFA), Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4}, was developed based on the Fe–Cr–Mo–C–B alloy system by minor addition of Nb. The effects of Nb addition on glass formation of the Fe{sub 50−x}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub x} (x = 0, 2, 4 and 6 at.%) alloys were investigated. The optimum addition content of Nb was determined as 4 at.% by X-ray diffraction and differential scanning calorimeter analysis. A fully amorphous rod sample with 3 mm in diameter was produced by using commercial-grade raw materials and a copper mold casting technique. This alloy shows an ultimate compressive strength of 1920 MPa and Vicker’s hardness 1360 H{sub V}, which is two to three times that of conventional high strength steel and suggests a promising potential for applications combining outstanding corrosion and wear resistance properties. The crystallization kinetics studies found that the activation energies for glass transition, onset of crystallization and crystallization peak were higher than those of other reported Fe-based bulk metallic glasses. The value of the fragility parameter m for the Fe{sub 46}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Nb{sub 4} alloy was calculated to be 34, indicating that the Fe–Cr–Mo–C–B–Nb alloy system is a strong glass former according to the Angell’s classification scheme. It is inferred that the more sequential change in the atomic size, the generation of new atomic pairs with large negative heats of mixing and the amount of oxygen in the molten liquid

Electrochemical etching of a niobium foil in methanolic HF for electrolytic capacitor

International Nuclear Information System (INIS)

Kim, Kyungmin; Park, Jiyoung; Cha, Gihoon; Yoo, Jeong Eun; Choi, Jinsub

2013-01-01

Electrochemical etching of niobium foil in order to enlarge the surface area for the application in electrolytic capacitor was carried out in a methanolic electrolyte. We found that the pit density and depth are not linearly proportional to concentration of HF and applied potential: there is the optimal concentration of HF at each applied potential. The optimal etching condition was obtained at 50 V in 0.99 vol.% HF, which exhibited the capacitance of 350 μF cm −2 . Pit density and depth of pits on electrochemical etched Nb foil under different conditions were counted from SEM images and electrochemical impedance spectroscopy (EIS) of the etched Nb foils was carried out for the capacitance measurement. Equivalent circuit model showing less than 5% error was suggested for applying to the etched niobium foil. - Highlights: • Surface enlargement of Nb foil can be achieved by electrochemical etching in methanolic HF. • Electrolytic capacitor of etched niobium foil exhibits a capacitance of 350 μF cm −2 . • The method provides a way of developing commercially viable process

Effect of Carbon Content on the Microstructure and Mechanical Properties of NbC-Ni Based Cermets

Directory of Open Access Journals (Sweden)

Shuigen Huang

2018-03-01

Full Text Available The aim of this work was to correlate the overall carbon content in NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo starting powders with the resulting microstructure, hardness, and fracture toughness of Ni-bonded NbC cermets. A series of NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo cermets with different carbon content were prepared by conventional liquid phase sintering for 1 h at 1420 °C in vacuum. Microstructural analysis of the fully densified cermets was performed by electron probe microanalysis (EPMA to assess the effect of carbon and VC or Mo additions on the NbC grain growth and morphology. A decreased carbon content in the starting powder mixtures resulted in increased dissolution of Nb, V, and Mo in the Ni binder and a decreased C/Nb ratio in the NbC based carbide phase. The Vickers hardness (HV30 and Palmqvist indentation toughness were found to decrease significantly with an increasing carbon content in the Mo-free cermets, whereas an antagonistic correlation between hardness and toughness was obtained as a function of the Mo-content in Mo-modified NbC cermets. To obtain optimized mechanical properties, methods to control the total carbon content of NbC-Ni mixtures were proposed and the prepared cermets were investigated in detail.

Ternary alloying study of MoSi2

International Nuclear Information System (INIS)

Yi, D.; Li, C.; Akselsen, O.M.; Ulvensoen, J.H.

1998-01-01

Ternary alloying of MoSi 2 with adding a series of transition elements was investigated by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Iron, Co, Ni, Cr, V, Ti, and Nb were chosen as alloying elements according to the AB 2 structure map or the atomic size factor. The studied MoSi 2 base alloys were prepared by the arc melting process from high-purity metals. The EDS analysis showed that Fe, Co, and Ni have no solid solubility in as-cast MoSi 2 , while Cr, V, Ti, and Nb exhibit limited solid solubilities, which were determined to be 1.4 ± 0.7, 1.4 ± 0.4, 0.4 ± 0.1, and 0.8 ± 0.1. Microstructural characterization indicated that Mo-Si-M VIII (M VIII = Fe, Co, Ni) and Mo-Si-Cr alloys have a two-phase as-cast microstructure, i.e., MoSi 2 matrix and the second-phase FeSi 2 , CoSi, NiSi 2 , and CrSi 2 , respectively. In as-cast Mo-Si-V, Mo-Si-Ti, and Mo-Si-Nb alloys, besides MoSi 2 and C40 phases, the third phases were observed, which have been identified to be (Mo, V) 5 Si 3 , TiSi 2 , and (Mo, Nb) 5 Si 3

Ionic conductivity in new perovskite type oxides: NaAZrMO6 (A = Ca or Sr; M = Nb or Ta)

International Nuclear Information System (INIS)

Rajendran, Deepthi N.; Ravindran Nair, K.; Prabhakar Rao, P.; Sibi, K.S.; Koshy, Peter; Vaidyan, V.K.

2008-01-01

New oxides of the type, NaAZrMO 6 (M = Ca or Sr; M = Nb or Ta), have been prepared by the solid-state reaction technique. Phase identification by powder X-ray diffraction (XRD) shows that NaCaZrMO 6 has orthorhombic perovskite type structure (Pnma) and NaSrZrMO 6 has cubic perovskite type structure (Pm3m). The grain morphology observation by scanning electron microscope (SEM) shows well-sintered grains. ac impedance spectra and electrical conductivity measurements in air, oxygen and nitrogen atmospheres indicate that they are probable oxide ion conductors with ionic conductivities of the order of 10 -3 S cm -1 at 750 deg. C

91Mo and 89Nb high-spin states

International Nuclear Information System (INIS)

Baktybaev, K.; Kojlyk, N.; Ramankulov, K.E.

2003-01-01

In the work the shell-model calculation for 91 Mo and 89 Nb nuclei high-spin states with several valente nucleons is worked out. The nucleons have been arranged in the {2p 1/2 1g 9 / 2 } configurations above the 88 Sr twice magic frame. Using of formalism of generalized quasi-spin with H=H 0 +H pp +H nn +H pn Hamiltonian in which H pp , H nn , H pn the residual nucleon interactions have being written through generalized quasi-spin operators. The obtained scheme well reproduces experimental data for examined nuclei up to 31/2 + , 33/2 - levels with seniority ν=3.5. Similarity of the spectroscopic structures of the nucleus levels with different protons and neutrons numbers above inert frame shows independence of nucleon-nucleon interactions from isotope spins of particles. There are analogous comparison of some negative yrast bands parity levels. The theory well transmits intensity values for electromagnet transitions between states. Besides the observed nuclei's properties does not give any indication on presence of valent nucleons collective motion in the both nuclei

Formation and Applications of Bulk Glassy Alloys in Late Transition Metal Base System

International Nuclear Information System (INIS)

Inoue, Akihisa; Shen Baolong

2006-01-01

This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Fe- and Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials

Neutron Activation Resonance Integrals of 64Zn, 68Zn, 85Rb, 100Mo, 102Ru, 113In, 123Sb, and 180Hf

International Nuclear Information System (INIS)

Ricabarra, M. D.; Turjanski, R.; Ricabarra, G. H.

1969-01-01

The ratio of resonance integral to thermal activation cross sections of the isotopes 64 Zn, 68 Zn, 85 Rb, 100 Mo, 102 Ru, 113 In, 123 Sb, and 180 Hf relative to gold has been determined by measuring cadmium ratios. The standard gold or a secondary standard was mixed uniformly in the samples and the activities resolved with a lithium-drift germanium γ-ray spectrometer. Expressed as Westcott S 0 values the results were: 64 Zn = 2.06 ± 0.03, 68 Zn = 3.72 ± 0.14, 85 Rb = 18.4 ± 0.6, 100 Mo = 21.7 ± 0.8, 102 Ru = 3.76 ± 0.03, 113 In = 24.7 ± 0.5, 123 Sb = 28.3 ± 2.1, 180 Hf = 2.17 ± 0.09. All measurements are relative to S 0 = 17.7 for gold. (author)

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)

Comparison of U-Pu-Mo, U-Pu-Nb, U-Pu-Ti and U-Pu-Zr alloys; Comparaison des alliages U-Pu-Mo, U-Pu-Nb, U-Pu-Ti, U-Pu-Zr

Energy Technology Data Exchange (ETDEWEB)

Boucher, R; Barthelemy, P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-07-01

The data concerning the U-Pu, U-Pu-Mo and U-Pu-Nb are recalled. The results obtained with U-Pu-Ti and U-Pu-Zr alloys containing 15-20 per cent Pu and 10 wt. per cent ternary element are reported. The transformation temperatures, the expansion coefficients, the nature of phases, the thermal cycling behaviour have been determined. A list of the principal properties of these different alloys is presented and the possibilities of their use as fast reactor's fuel element are considered. The U-Pu-Ti alloys seem to be quite promising: easiness of fabrication, large thermal stability, excellent behaviour in air, small quantity of zeta phase, temperature of solidus superior to 1100 deg. C. (authors) [French] On rappelle brievement les connaissances acquises sur les alliages U-Pu, U-Pu-Mo et U-Pu-Nb. On presente les resultats obtenus avec les alliages U-Pu-Ti et U-Pu-Zr pour des teneurs de 15 a 20 pour cent de plutonium et 10 pour cent en poids d'element ternaire. On a determine les temperatures de transformation, les coefficients de dilatation, la nature des phases, la conductibilite thermique a 20 deg. C, la tenue au cyclage thermique et diverses autres proprietes. Un tableau resume les principales proprietes des divers alliages. On considere les possibilites d'emploi de ces alliages comme combustibles de reacteur rapide. Les alliages U-Pu-Ti paraissent particulierement interessants: facilite d'elaboration, stabilite thermique etendue, tenue dans l'air excellente, faible quantite de la phase U-Pu zeta, temperature de fusion commencante superieure a 1100 deg. C. (auteurs)

Structure and magnetic properties of NdFeB thin films with Cr, Mo, Nb, Ta, Ti, and V buffer layers

International Nuclear Information System (INIS)

Jiang, H.; O'Shea, M.J.

2000-01-01

Layers of NdFeB of the form A(20 nm)/NdFeB(d nm)/A(20 nm) where A represents Cr, Mo, Nb, Ta, Ti, V were prepared on a silicon substrate by magnetron sputtering. The purpose is to determine how (i) the chosen buffer layer and (ii) NdFeB layer thickness d (especially d 2 Fe 14 B with no preferred crystalline orientation. Our highest coercivities occur for buffer layer elements from row five of the periodic table, 20 kOe (1600 kA/m) in a Nb buffered sample with d of 180 nm and 17 kOe (1350 kA/m) in a Mo buffered sample with d of 180 nm. Buffer layers from row four (Ti, V, and Cr) and row six (Ta) all give lower coercivities. Our largest energy product, 10.3 MG-Oe (82 kJ/m 3 ), is obtained for the Mo buffered sample. Average Nd 2 Fe 14 B crystallite size for this sample is 27 nm. Only the Cr and Ti buffered films show a large coercivity (≥2 kOe) for d of 54 nm with the Cr films showing the highest coercivity, 2.7 kOe (215 kA/m). In films subjected to a rapid thermal anneal (anneal time 30 s) we find that both the coercivity and energy product are larger than in samples subjected to a 20 min anneal. In our Nb buffered systems we obtain coercivities as high as 26.3 kOe (2090 kA/m) after a rapid thermal anneal

Some properties of low-vapor-pressure braze alloys for thermionic converters

Science.gov (United States)

Bair, V. L.

1978-01-01

Density, dc electrical resistivity, thermal conductivity, and linear thermal expansion are measured for arc-melted rod-shaped samples of binary eutectics of Zr, Hf, Ru, Nb, Ir, Mo, Ta, Os, Re, and W selected as very-low-pressure braze fillers for thermionic converters. The first two properties are measured at 296 K for Zr-21.7 at% Ru, Zr-13 wt% W, Zr-19 wt% W, Zr-22.3 at% Nb, Nb-66.9 at% Ru, Hf-25.3 wt% Re, Zr-25.7 at% Ta, Hf-22.5 at% W, and Nb-35 wt% Mo. The last property is measured from 293 K to 2/3 melting point for specified alloys of different compositions. Resistivities of 0.000055 to 0.000181 ohm-cm are observed with the alloys having resistivities about ten times that of the less resistive constituent metal and about three times that of the more resistive constituent metal, except for Zr-19 wt% W and Nb-35 wt% Mo (greater resistivities). Thermal expansion coefficients vary from 0.000006 to 0.0000105/K. All brazes exhibit linear thermal expansion near that of their constituent metals.

Effect of Cold Deformation and Annealing on the Microstructure and Tensile Properties of a HfNbTaTiZr Refractory High Entropy Alloy

Science.gov (United States)

Senkov, O. N.; Pilchak, A. L.; Semiatin, S. L.

2018-05-01

The microstructure and tensile properties of HfNbTaTiZr after cold working and annealing were investigated. Cold work was introduced by axial compression followed by rolling resulting in a total thickness reduction of 89 pct without any evidence of cracking. The cold-worked material retained a single-phase microstructure and had a room temperature tensile yield stress σ 0.2 = 1438 MPa, peak true stress σ p = 1495 MPa, and true fracture strain ɛ f = 5 pct. Annealing at 800 °C for up to 256 hours resulted in the precipitation of Nb and Ta rich particles with a BCC crystal structure inside a Hf-and-Zr-enriched BCC matrix. The second phase particles nucleated heterogeneously inside deformation bands and slip lines and coarsened during annealing. Analysis of the coarsening behavior suggested that kinetics were controlled by the diffusion of Nb and Ta. In the two-phase material, σ 0.2 and σ p decreased from 1159 to 1071 MPa and from 1174 to 1074 MPa, respectively, with an increase in particle diameter from 0.18 to 0.72 μm, while ɛ f remained between 5 and 8 pct. Full recrystallization and normal grain growth, with the activation energy of 238 kJ/mol and activation volume of 5.3 to 9.6 m3/mol, occurred during annealing above 1000 °C. After heat treatment at this temperature, the alloy was characterized by a single-phase BCC structure with σ 0.2 = 1110 to 1115 MPa, σ p = 1160 to 1195 MPa, and ɛ f = 12 to 19 pct with the maximum values attained after annealing for 1 hour.

Welded joint properties of steel 2.25Cr1MoNiNb

International Nuclear Information System (INIS)

Gladis, R.; Ivanek, J.; Gottwald, M.

1981-01-01

Welded joints of steel 08Cr2.25Mo1NiNb for fast reactor steam generators made using manual arc welding with electrodes of identical compositions attain short-term mechanical properties and times to fracture when creep tested that match those of the base material. The reduction of the carbidic phase content in the steel and the welded joint metal did not adversely affect the tensile properties of the welded joint while increasing notch toughness of the heat-affected zone. Reduced carbon and niobium contents in the steel and the welded joint resulted in significant reduction in the proportion of carbidic eutectic particles in both the heat-affected zone and the weld metal. (Ha)

Trace- and rare-earth element geochemistry and Pb-Pb dating of black shales and intercalated Ni-Mo-PGE-Au sulfide ores in Lower Cambrian strata, Yangtze Platform, South China

Science.gov (United States)

Jiang, Shao-Yong; Chen, Yong-Quan; Ling, Hong-Fei; Yang, Jing-Hong; Feng, Hong-Zhen; Ni, Pei

2006-08-01

The Lower Cambrian black shale sequence of the Niutitang Formation in the Yangtze Platform, South China, hosts an extreme metal-enriched sulfide ore bed that shows >10,000 times enrichment in Mo, Ni, Se, Re, Os, As, Hg, and Sb and >1,000 times enrichment in Ag, Au, Pt, and Pd, when compared to average upper continental crust. We report in this paper trace- and rare-earth-element concentrations and Pb-Pb isotope dating for the Ni-Mo-PGE-Au sulfide ores and their host black shales. Both the sulfide ores and their host black shales show similar trace-element distribution patterns with pronounced depletion in Th, Nb, Hf, Zr, and Ti, and extreme enrichment in U, Ni, Mo, and V compared to average upper crust. The high-field-strength elements, such as Zr, Hf, Nb, Ta, Sc, Th, rare-earth elements, Rb, and Ga, show significant inter-element correlations and may have been derived mainly from terrigenous sources. The redox sensitive elements, such as V, Ni, Mo, U, and Mn; base metals, such as Cu, Zn, and Pb; and Sr and Ba may have been derived from mixing of seawater and venting hydrothermal sources. The chondrite-normalized REE patterns, positive Eu and Y anomalies, and high Y/Ho ratios for the Ni-Mo-PGE-Au sulfide ores are also suggestive for their submarine hydrothermal-exhalative origin. A stepwise acid-leaching Pb-Pb isotope analytical technique has been employed for the Niutitang black shales and the Ni-Mo-PGE-Au sulfide ores, and two Pb-Pb isochron ages have been obtained for the black shales (531±24 Ma) and for the Ni-Mo-PGE-Au sulfide ores (521±54 Ma), respectively, which are identical and overlap within uncertainty, and are in good agreement with previously obtained ages for presumed age-equivalent strata.

Phase transformations in Mo-doped FINEMETs

Energy Technology Data Exchange (ETDEWEB)

Silveyra, Josefina M., E-mail: jsilveyra@fi.uba.a [Lab. de Solidos Amorfos, INTECIN, FIUBA-CONICET, Paseo Colon 850, (C1063ACV) Buenos Aires (Argentina); Illekova, Emilia; Svec, Peter; Janickovic, Dusan [Institute of Physics SAS, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Rosales-Rivera, Andres [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Manizales (Colombia); Cremaschi, Victoria J. [Lab. de Solidos Amorfos, INTECIN, FIUBA-CONICET, Paseo Colon 850, (C1063ACV) Buenos Aires (Argentina)

2010-06-15

In this paper, the phase transformations occurring during the crystallization process of FINEMETs in which Nb has been gradually replaced by Mo have been studied by a variety of techniques including DSC, DTA, TGA, XRD and TEM. The thermal stability of the alloy was deteriorated as a consequence of Mo's smaller atomic size. The gradual replacement of Nb by Mo reduced the onset temperature of Fe-Si and of the borides. The Curie temperature of the amorphous phase slightly decreased from 594 K for x=0 to 587 K for x=3. The borides compounds Fe{sub 2}B and Fe{sub 23}B{sub 6} as well as the (Nb,Mo){sub 5}Si{sub 3} phase were found to precipitate in the second and third crystallization.

An investigation of the fatigue and fracture behavior of a Nb-12Al-44Ti-1.5Mo intermetallic alloy

International Nuclear Information System (INIS)

Soboyejo, W.O.; Dipasquale, J.; Ye, F.; Mercer, C.

1999-01-01

This article presents the results of a study of the fatigue and fracture behavior of a damage-tolerant Nb-12Al-44Ti-1.5Mo alloy. This partially ordered B2 + orthorhombic intermetallic alloy is shown to have attractive combinations of room-temperature ductility (11 to 14 pct), fracture toughness (60 to 92 MPa√m), and comparable fatigue crack growth resistance to IN718, Ti-6Al-4V, and pure Nb at room temperature. The studies show that tensile deformation in the Nb-12Al-44Ti-1.5Mo alloy involves localized plastic deformation (microplasticity via slip-band formation) which initiates at stress levels that are significantly below the uniaxial yield stress (∼9.6 pct of the 0.2 pct offset yield strength (YS)). The onset of bulk yielding is shown to correspond to the spread of microplasticity completely across the gage sections of the tensile specimen. Fatigue crack initiation is also postulated to occur by the accumulation of microplasticity (coarsening of slip bands). Subsequent fatigue crack growth then occurs by the unzipping of cracks along slip bands that form ahead of the dominant crack tip. The proposed mechanism of fatigue crack growth is analogous to the unzipping crack growth mechanism that was suggested originally by Neumann for crack growth in single-crystal copper. Slower near-threshold fatigue crack growth rates at 750 C are attributed to the shielding effects of oxide-induced crack closure. The fatigue and fracture behavior are also compared to those of pure Nb and emerging high-temperature niobium-based intermetallics

Ionic conductivity in new perovskite type oxides: NaAZrMO{sub 6} (A = Ca or Sr; M = Nb or Ta)

Energy Technology Data Exchange (ETDEWEB)

Rajendran, Deepthi N.; Ravindran Nair, K. [Regional Research Laboratory (CSIR), Trivandrum 695019 (India); Prabhakar Rao, P. [Regional Research Laboratory (CSIR), Trivandrum 695019 (India)], E-mail: padala_rao@yahoo.com; Sibi, K.S.; Koshy, Peter [Regional Research Laboratory (CSIR), Trivandrum 695019 (India); Vaidyan, V.K. [Department of Physics, University of Kerala, Trivandrum 695581 (India)

2008-06-15

New oxides of the type, NaAZrMO{sub 6} (M = Ca or Sr; M = Nb or Ta), have been prepared by the solid-state reaction technique. Phase identification by powder X-ray diffraction (XRD) shows that NaCaZrMO{sub 6} has orthorhombic perovskite type structure (Pnma) and NaSrZrMO{sub 6} has cubic perovskite type structure (Pm3m). The grain morphology observation by scanning electron microscope (SEM) shows well-sintered grains. ac impedance spectra and electrical conductivity measurements in air, oxygen and nitrogen atmospheres indicate that they are probable oxide ion conductors with ionic conductivities of the order of 10{sup -3} S cm{sup -1} at 750 deg. C.

Detailed investigation of the β-decay of the 9/2+ ground state of 99Nb to levels in 99Mo

International Nuclear Information System (INIS)

Lhersonneau, G.; Persson, J.R.; Suhonen, J.; Dendooven, P.; Wang, J.C.; Aeystoe, J.

1997-01-01

The decay of 99 Nb to 99 Mo has been investigated. The use of the ion-guide technique for on-line mass separation and of a Ge-array for γ-ray detection have allowed the observation of decay branchings lower than 10 -3 . Medium-spin levels, some already known from reaction studies and new ones at high energy, are populated. The β-feeding patterns of the decays of the 9/2 + states in 99 Nb and in its isotones 97 Y, and 101 Tc are qualitatively reproduced by QRPA calculations. (orig.). With 5 figs., 7 tabs

The transitions 4p-5s in Y VI, Zr VII, Nb VIII and Mo IX

International Nuclear Information System (INIS)

Chaghtai, M.S.Z.; Rahimullah, K.; Khatoon, S.

1976-01-01

With the help of the spectra recorded in the Physics Department of Lund University, Y VI, Zr VII, Nb VIII and Mo IX are freshly analysed. The five 4s 2 4p 4 ground levels and the ten 4s 2 4p 3 5s levels of previous analyses are confirmed in the first three spectra, except for revising in Y VI the 4p 4 1 S 0 and 4p 3 5s( 4 Ssub(3/2)) 2 levels and interchanging 5s( 2 Dsub(3/2)) 1 with 5s( 2 Dsub(3/2)) 2 . All level values are improved due to the new measurements. A new analysis of Mo IX establishing all the 4p 4 and 4p 3 5s levels is being reported. (Auth.)

Polymorphism in the Laves-phase precipitates of a quinternary Nb-Mo-Cr-Al-Si alloy

International Nuclear Information System (INIS)

Hu Yanling; Vasiliev, Alexandre; Zhang Lichun; Song, Kai; Aindow, Mark

2009-01-01

Transmission electron microscopy has been used to study the precipitates that develop in the A2 phase of an Nb-Mo-Cr-Al-Si alloy upon heat treatment. The precipitates include a Laves-phase that adopts the cubic C15 structure initially and the hexagonal C14 structure in the later stages of precipitation. The morphologies, orientation relationships and defect microstructures indicate that the metastable C15 phase arises due to tensile coherency stresses and that a synchroshear polymorphic transformation to the equilibrium C14 phase occurs as these relax

Isothermal cross-sections of Hf-Sc-Ga(800 deg C) and Hf-Ti-Ga (750 deg C) phase diagrams

International Nuclear Information System (INIS)

Markiv, V.Ya.; Belyavina, N.N.

1981-01-01

Isothermal cross sections of Hf-Sc-Ga (800 deg C) and Hf-Ti-Ga (750 deg C) state diagrams are plotted. The existence of two ternary Hfsub(0.1-0.8)Scsub(0.9)-sub(0.2)Ga and Hfsub(0.8)Scsub(0.2)Gasub(3) phases is stated in the Hf-Sc-Ga system. The crystal structure of these compounds investigated by the powder method belongs to the structural α-MoB and ZrAl 3 types respectively. Continuous rows of (Hf, Sc 5 Ga 5 , (Hf, Ti)Ga 3 and (Hf, Ti)Ga 2 solid solutions are formed in the investigated systems. Essential quantity of the third component dissolve binary Sc 5 Ga 4 , Sc 2 Ga 3 (15 and 30 at % Hf respectively), Hf 5 Ga 4 , HfGa 2 (20, 10 at. % Sc), Hf 5 Ga 4 , HfGa, Hf 5 Ga 3 , Hf 2 Ga 3 (48, 30, 46, 20 at. % Ti) gallides [ru

High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

Science.gov (United States)

Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

2010-07-13

An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments

International Nuclear Information System (INIS)

Gaffard, V.

2004-12-01

Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also

Phase Composition of a CrMo0.5NbTa0.5TiZr High Entropy Alloy: Comparison of Experimental and Simulated Data

Directory of Open Access Journals (Sweden)

Fan Zhang

2013-09-01

Full Text Available Microstructure and phase composition of a CrMo0.5NbTa0.5TiZr high entropy alloy were studied in the as-solidified and heat treated conditions. In the as-solidified condition, the alloy consisted of two disordered BCC phases and an ordered cubic Laves phase. The BCC1 phase solidified in the form of dendrites enriched with Mo, Ta and Nb, and its volume fraction was 42%. The BCC2 and Laves phases solidified by the eutectic-type reaction, and their volume fractions were 27% and 31%, respectively. The BCC2 phase was enriched with Ti and Zr and the Laves phase was heavily enriched with Cr. After hot isostatic pressing at 1450 °C for 3 h, the BCC1 dendrites coagulated into round-shaped particles and their volume fraction increased to 67%. The volume fractions of the BCC2 and Laves phases decreased to 16% and 17%, respectively. After subsequent annealing at 1000 °C for 100 h, submicron-sized Laves particles precipitated inside the BCC1 phase, and the alloy consisted of 52% BCC1, 16% BCC2 and 32% Laves phases. Solidification and phase equilibrium simulations were conducted for the CrMo0.5NbTa0.5TiZr alloy using a thermodynamic database developed by CompuTherm LLC. Some discrepancies were found between the calculated and experimental results and the reasons for these discrepancies were discussed.

DFT investigation of electronic structures and magnetic properties of halides family MeHal3 (Me=Ti, Mo,Zr,Nb, Ru, Hal=Cl,Br,I) one dimensional structures

Science.gov (United States)

Kuzubov, A. A.; Kovaleva, E. A.; Popova, M. I.; Kholtobina, A. S.; Mikhaleva, N. S.; Visotin, M. A.; Fedorov, A. S.

2017-10-01

Using DFT GGA calculations, electronic structure and magnetic properties of wide family of transition metal trihalides (TMHal3) (Zr, Ti and Nb iodides, Mo, Ru, Ti and Zr bromides and Ti or Zr chlorides) are investigated. These structures consist of transition metal atoms chains surrounded by halides atoms. Chains are connected to each other by weak interactions. All TMHal3 compounds were found to be conductive along chain axis except of MoBr3 which is indirect gap semiconductor. It was shown that NbI3 and MoBr3 have large magnetic moments on metal atoms (1.17 and 1.81 μB, respectively) but other TMHal3 materials have small or zero magnetic moments. For all structures ferromagnetic and anti-ferromagnetic phases have almost the same energies. The causes of these properties are debated.

In vitro performance assessment of new beta Ti–Mo–Nb alloy compositions

Energy Technology Data Exchange (ETDEWEB)

Neacsu, Patricia [University of Bucharest, Department of Biochemistry and Molecular Biology, 91–95 Spl. Independentei, 050095 Bucharest (Romania); Gordin, Doina-Margareta [INSA Rennes, UMR CNRS 6226 ISCR/Chimie-Métallurgie, 20 avenue des Buttes de Coësmes, F-35043 Rennes, Cedex (France); Mitran, Valentina [University of Bucharest, Department of Biochemistry and Molecular Biology, 91–95 Spl. Independentei, 050095 Bucharest (Romania); Gloriant, Thierry [INSA Rennes, UMR CNRS 6226 ISCR/Chimie-Métallurgie, 20 avenue des Buttes de Coësmes, F-35043 Rennes, Cedex (France); Costache, Marieta [University of Bucharest, Department of Biochemistry and Molecular Biology, 91–95 Spl. Independentei, 050095 Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91–95 Spl. Independentei, 050095 Bucharest (Romania)

2015-02-01

New β-titanium based alloys with low Young's modulus are currently required for the next generation of metallic implant materials to ensure good mechanical compatibility with bone. Several of these are representatives of the ternary Ti–Mo–Nb system. The aim of this paper is to assess the in vitro biological performance of five new low modulus alloy compositions, namely Ti12Mo, Ti4Mo32Nb, Ti6Mo24Nb, Ti8Mo16Nb and Ti10Mo8Nb. Commercially pure titanium (cpTi) was used as a reference material. Comparative studies of cell activity exhibited by MC3T3-E1 pre-osteoblasts over short- and long-term culture periods demonstrated that these newly-developed metallic substrates exhibited an increased biocompatibility in terms of osteoblast proliferation, collagen production and extracellular matrix mineralization. Furthermore, all analyzed biomaterials elicited an almost identical cell response. Considering that macrophages play a pivotal role in bone remodeling, the behavior of a monocyte-macrophage cell line, RAW 264.7, was also investigated showing a slightly lower inflammatory response to Ti–Mo–Nb biomaterials as compared with cpTi. Thus, the biological performances together with the superior mechanical properties recommend these alloys for bone implant applications. - Highlights: • Ti–Mo–Nb compositions show a fully β-microstructural state by XRD analysis. • Similar osteoblast growth and differentiation is displayed by β-Ti alloys and cpTi. • Ti–Mo–Nb alloys elicit a slightly lower inflammatory response than cpTi.

In vitro performance assessment of new beta Ti–Mo–Nb alloy compositions

International Nuclear Information System (INIS)

Neacsu, Patricia; Gordin, Doina-Margareta; Mitran, Valentina; Gloriant, Thierry; Costache, Marieta; Cimpean, Anisoara

2015-01-01

New β-titanium based alloys with low Young's modulus are currently required for the next generation of metallic implant materials to ensure good mechanical compatibility with bone. Several of these are representatives of the ternary Ti–Mo–Nb system. The aim of this paper is to assess the in vitro biological performance of five new low modulus alloy compositions, namely Ti12Mo, Ti4Mo32Nb, Ti6Mo24Nb, Ti8Mo16Nb and Ti10Mo8Nb. Commercially pure titanium (cpTi) was used as a reference material. Comparative studies of cell activity exhibited by MC3T3-E1 pre-osteoblasts over short- and long-term culture periods demonstrated that these newly-developed metallic substrates exhibited an increased biocompatibility in terms of osteoblast proliferation, collagen production and extracellular matrix mineralization. Furthermore, all analyzed biomaterials elicited an almost identical cell response. Considering that macrophages play a pivotal role in bone remodeling, the behavior of a monocyte-macrophage cell line, RAW 264.7, was also investigated showing a slightly lower inflammatory response to Ti–Mo–Nb biomaterials as compared with cpTi. Thus, the biological performances together with the superior mechanical properties recommend these alloys for bone implant applications. - Highlights: • Ti–Mo–Nb compositions show a fully β-microstructural state by XRD analysis. • Similar osteoblast growth and differentiation is displayed by β-Ti alloys and cpTi. • Ti–Mo–Nb alloys elicit a slightly lower inflammatory response than cpTi

Studies on advanced superconductors for fusion device. Pt. 2. Metallic superconductors other than Nb{sub 3}Sn

Energy Technology Data Exchange (ETDEWEB)

Tachikawa, K.; Yamamoto, J.; Mito, T. [eds.

1997-03-01

A comprehensive report on the present status of the development of Nb{sub 3}Sn superconductors was published as the NIFS-MEMO-20 in March, 1996 (Part 1 of this report series). The second report of this study covers various progress so far achieved in the research and development on advanced metallic superconductors other than Nb{sub 3}Sn. Among different A15 crystal-type compounds, Nb{sub 3}Al has been fabricated into cables with large current-carrying capacity for fusion device referring its smaller sensitivity to mechanical strain than Nb{sub 3}Sn. Other high-field A15 superconductors, e.g. V{sub 3}Ga, Nb{sub 3}Ge and Nb{sub 3}(Al,Ge), have been also fabricated through different novel processes as promising alternatives to Nb{sub 3}Sn conductors. Meanwhile, B1 crystal-type NbN and C15 crystal-type V{sub 2}(Hf,Zr) high-field superconductors are characterized by their excellent tolerance to mechanical strain and neutron irradiation. Chevrel-type PbMo{sub 6}S{sub 8} compound has gained much interests due to its extremely high upper critical field. In addition, this report includes the recent progress in ultra-fine filamentary NbTi wires for AC use, and that in NbTi/Cu magnetic shields necessary in the application of high magnetic field. The data on the decay of radioactivity in a variety of metals relating to fusion superconducting magnet are also attached as appendices. We hope that this report might contribute substantially as a useful reference for the planning of fusion apparatus of next generation as well as that of other future superconducting devices. (author)

Refining of cast intermetallic alloy Ti - 43 % Al - X (Nb, Mo, B) microstructure using heat treatment

International Nuclear Information System (INIS)

Imaev, R.M.; Imaev, V.M.; Khismatullin, T.G.

2006-01-01

The microstructure and high temperature mechanical properties are studied in a cast alloy Ti - 43 % Al - X (Nb, Mo, B) using methods of optical and scanning electron microscopy, X ray spectrum microanalysis and differential thermal analysis. The alloy belongs to a new class of β-solidifying γ-TiAl+α 2 -Ti 3 Al alloys. The alloy is investigated as cast and after heat treatment that promotes grain refinement. Mechanical properties are determined on tensile tests at 1000 and 1100 deg C in the air [ru

Effect of aluminum on the microstructure and properties of two refractory high-entropy alloys

International Nuclear Information System (INIS)

Senkov, O.N.; Senkova, S.V.; Woodward, C.

2014-01-01

The microstructure, phase composition and mechanical properties of the AlMo 0.5 NbTa 0.5 TiZr and Al 0.4 Hf 0.6 NbTaTiZr high-entropy alloys are reported. The AlMo 0.5 NbTa 0.5 TiZr alloy consists of two body-centered cubic (bcc) phases with very close lattice parameters, a 1 = 326.8 pm and a 2 = 332.4 pm. One phase was enriched with Mo, Nb and Ta and another phase was enriched with Al and Zr. The phases formed nano-lamellae modulated structure inside equiaxed grains. The alloy had a density of ρ = 7.40 g cm −3 and Vickers hardness H v = 5.8 GPa. Its yield strength was 2000 MPa at 298 K and 745 MPa at 1273 K. The Al 0.4 Hf 0.6 NbTaTiZr had a single-phase bcc structure, with the lattice parameter a = 336.7 pm. This alloy had a density ρ = 9.05 g cm −3 , Vickers microhardness H v = 4.9 GPa, and its yield strength at 298 K and 1273 K was 1841 MPa and 298 MPa, respectively. The properties of these Al-containing alloys were compared with the properties of the parent CrMo 0.5 NbTa 0.5 TiZr and HfNbTaTiZr alloys and the beneficial effects from the Al additions on the microstructure and properties were outlined. A thermodynamic calculation of the solidification and equilibrium phase diagrams was conducted for these alloys and the calculated results were compared with the experimental data

Regularities in electroconductivity and thermo-emf in systems of binary continuous solid solutions of metals

International Nuclear Information System (INIS)

Vedernikov, M.V.; Dvunitkin, V.G.; Zhumagulov, A.

1978-01-01

Given are new experimental data about specific electric resistance of 10 systems of binary continuous solid metal solutions at the temperatures of 293 and 4.2 K: Cr-V, Mo-Nb, Mo-V, Cr-Mo, Nb-V, Ti-Zr, Hf-Zr, Hf-Ti, Sc-Zr, Sc-Hf. For the first time a comparative analysis of all available data on the resistance dependence on the composition of systems of continuous solid solutions, which covers 21 systems, is carried out. The ''resistance-composition'' dependence for such alloy systems is found to be of two types. The dependence of the first type is characteristic of the systems, formed by two isoelectronic metals, the dependence of the second type - for the systems, formed by non-isoelectronic metals. Thermo-emf of each type of solid solutions differently depends on their compositions

Preparation and electrical properties of MoO{sub 3}-modified SrBi{sub 2}Nb{sub 2}O{sub 9}-based lead-free piezoelectric ceramics

Energy Technology Data Exchange (ETDEWEB)

Yao, Zhongran, E-mail: ruiqingchu@sohu.com [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Chu, Ruiqing, E-mail: rqchu@lcu.edu.cn [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Xu, Zhijun; Hao, Jigong; Wei, Denghu; Cheng, Renfei [College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Li, Guorong [The State Key Lab of High Performance Ceramics and Superfinemicrostructure, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 200050 (China)

2016-05-05

Lead-free piezoelectric ceramics, SrBi{sub 2}(Nb{sub 1-x}Mo{sub x}){sub 2}O{sub 9} (SBNM-x), were prepared by a conventional solid-state reaction method. The crystal structure, microstructure and electrical properties were systematically investigated. The X-ray diffraction analysis suggested that the substitution formed layered perovskite structure. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed for all the samples. The excellent electrical properties (e.g., d{sub 33}∼18 pC/N, 2P{sub r}∼20.34 μC/cm{sup 2}) and a high Curie temperature (e.g., T{sub c}∼458 °C) are simultaneously obtained in the ceramics with x = 0.12. Additionally, thermal annealing studies indicated that piezoelectric constant (d{sub 33}) of SBNM-0.12 ceramic remains almost unchanged (16 pC/N, only decrease by 12%) at temperatures below 400 °C, demonstrating that the Mo-modified SBN-based ceramics are the promising candidates for high-temperature applications. - Highlights: • Higher valent cation Mo{sup 6+} substituted for B-site Nb{sup 5+} in the perovskite layers ions. • The piezoelectric constant (d{sub 33}) of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramic is increased to be 18 pC/N. • The remnant polarization (2P{sub r}) of SrBi{sub 2}Nb{sub 2}O{sub 9} ceramic is increased to be 20.34 μC cm{sup −2}. • SBNM-x ceramics show good temperature stability for high temperature applications.

Vanadium Oxide Thin Films Alloyed with Ti, Zr, Nb, and Mo for Uncooled Infrared Imaging Applications

Science.gov (United States)

Ozcelik, Adem; Cabarcos, Orlando; Allara, David L.; Horn, Mark W.

2013-05-01

Microbolometer-grade vanadium oxide (VO x ) thin films with 1.3 Nb, Mo, and Zr using a second gun and radiofrequency (RF) reactive co-sputtering to probe the effects of the transition metals on the film charge transport characteristics. The results reveal that the temperature coefficient of resistance (TCR) and resistivity are unexpectedly similar for alloyed and unalloyed films up to alloy compositions in the ˜20 at.% range. Analysis of the film structures for the case of the 17% Nb-alloyed film by glancing-angle x-ray diffraction and transmission electron microscopy shows that the microstructure remains even with the addition of high concentrations of alloy metal, demonstrating the robust character of the VO x films to maintain favorable electrical transport properties for bolometer applications. Postdeposition thermal annealing of the alloyed VO x films further reveals improvement of electrical properties compared with unalloyed films, indicating a direction for further improvements in the materials.

XPS study on the electronic structure of hydrided Ti-V, Ti-Nb and Ti-Mo alloys

International Nuclear Information System (INIS)

Tanaka, Kazuhide; Aoki, Hiromasa

1989-01-01

Effects of hydrogenation on the core and valence electronic structures of β(bcc)-stabilized Ti-25at%V, Ti-50at%Nb and Ti-20at%Mo alloys are studied with XPS technique using monochromatized Al K α radiation. Small but uniform binding-energy shifts are observed upon hydrogenation for all the core spectra measured. Their valence-band spectra are significantly distorted, providing an evidence of the formation of metal-hydrogen bonding bands in these Ti alloys. Interrelations between the core binding-energy shifts and the valence-band distortion are discussed. (orig.)

Zircon U-Pb geochronology and Sr-Nd-Pb-Hf isotopic constraints on the timing and origin of Mesozoic granitoids hosting the Mo deposits in northern Xilamulun district, NE China

Science.gov (United States)

Shu, Qihai; Lai, Yong; Zhou, Yitao; Xu, Jiajia; Wu, Huaying

2015-12-01

Located in the east section of the Central Asian orogen in northeastern China, the Xilamulun district comprises several newly discovered molybdenum deposits, primarily of porphyry type and Mesozoic ages. This district is divided by the Xilamulun fault into the southern and the northern parts. In this paper, we present new zircon U-Pb dating, trace elements and Hf isotope, and/or whole rock Sr-Nd-Pb isotopic results for the host granitoids from three Mo deposits (Yangchang, Haisugou and Shabutai) in northern Xilamulun. Our aim is to constrain the age and petrogenesis of these intrusions and their implications for Mo mineralization. Zircon U-Pb LA-ICP-MS dating shows that the monzogranites from the Shabutai and Yangchang deposits formed at 138.4 ± 1.5 and 137.4 ± 2.1 Ma, respectively, which is identical to the molybdenite Re-Os ages and coeval well with the other Mo deposits in this region, thereby indicating an Early Cretaceous magmatism and Mo mineralization event. Zircon Ce/Nd ratios from the mineralized intrusions are significantly higher than the barren granites, implying that the mineralization-related magmas are characterized by higher oxygen fugacity. These mineralized intrusions share similar zircon in-situ Hf and whole rock Sr-Nd isotopic compositions, with slightly negative to positive εHf(t) ranging from - 0.8 to + 10.0, restricted εNd(t) values from - 3.7 to + 1.6 but a little variable (87Sr/86Sr)i ratios between 0.7021 and 0.7074, indicative of formation from primary magmas generated from a dominantly juvenile lower crust source derived from depleted mantle, despite diverse consequent processes (e.g., magma mixing, fractional crystallization and crustal contamination) during their evolution. The Pb isotopes (whole rock) also show a narrow range of initial compositions, with (206Pb/204Pb)i = 18.03-18.88, (207Pb/204Pb)i = 15.48-15.58 and (208Pb/204Pb)i = 37.72-38.28, in agreement with Sr-Nd-Hf isotopes reflecting the dominance of a mantle component

Self-propagating high temperature synthesis as a method of determination of formation heat of refractory compounds

International Nuclear Information System (INIS)

Maslov, V.M.; Neganov, A.S.; Borovinskaya, I.P.; Merzhanov, A.G.

1978-01-01

Determination possibility of formation heats of refractory compounds in the process of direct synthesis from elements in a special calorimeter in the combustion regime is studied. Determined are formation heats of carbides - ZrCsub(0.92), Hf Csub(0.93), TaCsub(0.86), borides - ZrB 2 , HfB 2 NbB, NbB 2 , TaB, TaB 2 , MoB and silicides - ZrSi, ZrSi 2 , MoSi 2 . The results of chemical and x-ray phase analyses of the synthesized compounds are also given. Total error of formation heat determination methods does not surpass 2.0%

Further investigations of the upper critical field and the high field critical current density in Nb-Ti and its alloys

International Nuclear Information System (INIS)

Hawksworth, D.G.; Larbalestier, D.C.

1980-09-01

This paper reports further measurements of Hc 2 in the Nb-Ti-Ta and Nb-Ti-Hf systems. Whilst we find only small enhancements of approx. 0.3 Tesla in μ 0 Hc 2 (4.2 0 K) compared to binary Nb-Ti, at 2 0 K there is a wide composition range in the Nb-Ti-Ta system where μ 0 Hc 2 (2 0 K) exceeds 15 Tesla, reaching a maximum of 15.5 Tesla. This represents an enhancement of 1.3 Tesla over unalloyed Nb-Ti. By comparison alloys in the Nb-Ti-Hf system show a maximum enhancement in μ 0 Hc 2 (2 0 K) of only 0.3 Tesla. The reasons both for the enhancements in Hc 2 and for the differences in behavior shown by alloys containing Ta and Hf are briefly discussed. This paper also discusses common features in the behavior of the high field critical current density, J/sub c/, of four commercial Nb-Ti composites and upon the basis of this behavior predict the enhancements in high field J/sub c/ to be expected from using Nb-Ti-Ta and its alloys

Experimental study and modelling of high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steel weldments; Etude experimentale et modelisation, du comportement, de l'endommagement et de la rupture en fluage a haute temperature de joint soudes en acier 9Cr1Mo-NbV

Energy Technology Data Exchange (ETDEWEB)

Gaffard, V

2004-12-15

Chromium martensitic stainless steels are under development since the 70's with the prospect of using them as structural components in thermal and nuclear power plants. The modified 9Cr1Mo-NbV steel is already used, especially in England and Japan, as a material for structural components in thermal power plants where welding is a commonly used joining technique. New generations of chromium martensitic stainless steels with improved mechanical properties for high pressure and temperature use are currently under development. However, observations of several in-service premature failures of welded components in 9Cr1Mo-NbV steel, outline a strong need for understanding the high temperature creep flow and damage behaviour of 9Cr1Mo-NbV steels and weldments. The present study aimed at experimentally determining and then modelling the high temperature creep flow and damage behaviour of both 9Cr1Mo-NbV steels and weldments (typically in the temperature range from 450 C to 650 C). The base metal was first studied as the reference material. It was especially evidenced that tempered chromium martensitic steels exhibit a change in both creep flow and damage behaviour for long term creep exposure. As a consequence, the classically performed extrapolation of 1,000 hours creep data to 100,000 hours creep lifetime predictions might be very hazardous. Based on experimental observations, a new model, integrating and coupling multiple creep flow and damage mechanisms, was developed in the framework of the mechanics of porous media. It was then successfully used to represent creep flow and damage behaviour of the base metal from high to low stress levels even for complex multiaxial loading conditions. Although the high temperature creep properties of the base metal are quite good, the occurrence of premature failure in weldments in high temperature creep conditions largely focused the attention of the scientific community. The lower creep strength of the weld component was also

Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying

Energy Technology Data Exchange (ETDEWEB)

Guo, Lili; Qin, Lin, E-mail: qinlin@tyut.edu.cn; Kong, Fanyou; Yi, Hong; Tang, Bin

2016-12-01

Highlights: • The Mo alloyed layers were successfully prepared on TLM surface by DG-PSA. • The surface microhardness of TLM is remarkably enhanced by Mo alloying. • The TLM samples after Mo alloying exhibit good wettability. • The Mo alloyed TLM samples show excellent tribological properties. - Abstract: Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000 °C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000 °C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.

A comparative study on top-gated and bottom-gated multilayer MoS2 transistors with gate stacked dielectric of Al2O3/HfO2.

Science.gov (United States)

Zou, Xiao; Xu, Jingping; Huang, Hao; Zhu, Ziqang; Wang, Hongjiu; Li, Borui; Liao, Lei; Fang, Guojia

2018-06-15

Top-gated and bottom-gated transistors with multilayer MoS 2 channel fully encapsulated by stacked Al 2 O 3 /HfO 2 (9 nm/6 nm) were fabricated and comparatively studied. Excellent electrical properties are demonstrated for the TG transistors with high on-off current ratio of 10 8 , high field-effect mobility of 10 2 cm 2 V -1 s -1 , and low subthreshold swing of 93 mV dec -1 . Also, enhanced reliability has been achieved for the TG transistors with threshold voltage shift of 10 -3 -10 -2 V MV -1 cm -1 after 6 MV cm -1 gate-biased stressing. All improvement for the TG device can be ascribed to the formed device structure and dielectric environment. Degradation of the performance for the BG transistors should be attributed to reduced gate capacitance density and deteriorated interface properties related to vdW gap with a thickness about 0.4 nm. So, the TG transistor with MoS 2 channel fully encapsulated by stacked Al 2 O 3 /HfO 2 is a promising way to fabricate high-performance ML MoS 2 field-effect transistors for practical electron device applications.

Erosion and mass transfer of Mo, W and Nb under neutron irradiation of high temperature materials

International Nuclear Information System (INIS)

Berzhatyj, V.I.; Luk'yanov, A.N.; Zavalishin, A.A.; Tkach, V.N.; Fedorenko, A.I.

1980-01-01

Studies have been made of the medium composition in thermionic fuel elements of two types during reactor tests; erosion and mass transfer of electrode materials have been investigated in the after-reactor analysis of the tested fuel elements. The studies of electrode material evaporation at the conditions approaching (in environment temperature and composition) those of reactor tests of thermionic fuel elements have shown that the process proceeds in the form of metal oxides. Evaporation rates are determined, the mechanism of evaporation is discussed, and the analytical dependences are obtained for calculating the evaporation rates of Mo and W at certain temperature and gaseous medium composition. It is found that the main contribution to the material transfer off the Mo and Nb surfaces under a high-temperature reactor irradiation comes through the thermal evaporation; in the case of tungsten at the same experimental conditions the rates of mass transfer due to thermal evaporation and neutron sputtering are nearly the same [ru

Zirconium Zr and hafnium Hf

International Nuclear Information System (INIS)

Busev, A.I.; Tiptsova, V.G.; Ivanov, V.M.

1978-01-01

The basic methods for extracting and determining Zr(4) and Hf(4) are described. Diantipyrinemethane and its alkyl homologs selectively extract Zr and Hf from HNO 3 solutions in the presence of nitrates. Zr is selectively extracted with tetraethyldiamide of heptyl phosphoric acid (in benzene) as well as with 2-thenoyltrifluoroacetone (in an acid). The latter reagents is suitable for rapid determination of 95 Zr in a mixture with 95 Nb and other fragments. The complexometric determination of Zr is based on formation of a stable complex of Zr with EDTA. The titration is carried out in the presence of n-sulfobenzene-azo-pyrocatechol, eriochrome black T. The determination is hindered by Hf, fluoride-, phosphate-, oxalate- and tartrate-ions. The method is used for determining Zr in zircon and eudialyte ore. Zr is determined photometrically with the aid of xylenol orange, arsenazo 3 and pyrocatechol violet (in phosphorites). Hf is determined in the presence of Zr photometrically with the aid of xylenol orange or methyl-thymol blue. The method is based on Zr being masked with hydrogen peroxide in the presence of sulfate-ions

Petrogenesis of the Yaochong granite and Mo deposit, Western Dabie orogen, eastern-central China: Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes

Science.gov (United States)

Chen, Wei; Xu, Zhaowen; Qiu, Wenhong; Li, Chao; Yu, Yang; Wang, Hao; Su, Yang

2015-05-01

The Dabie orogen is among the most famous continent-continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U-Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re-Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87Sr/86Sr ratios of 0.7087-0.7096, and Pb isotopic ratios of (206Pb/204Pb)i = 16.599-16.704, (207Pb/204Pb)i = 15.170-15.618 and (208Pb/204Pb)i = 36.376-38.248. The granite has εNd(t) of -18.0 to -16.3 and εHf(t) values of -26.5 to -20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8-74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region.

Search for chemical separations of the element 106 homologues in HF and HF-HCl media

International Nuclear Information System (INIS)

Trubert, D.; Monroy-Guzman, F.; Hussonnois, M.; Brillard, L.; Le Naour, C.; Constantinescu, O.

1996-01-01

In order to study the chemical properties of element 263 106 in aqueous media, fast, efficient and reproducible chromatographic separations were tested on its assumed homologous: Mo, W and U. Corroborative static and dynamic off-line experiments have shown that after fixation of these three elements on anion-exchange resin in HF medium, selective elution could be achieved by using suitable concentration of HCl - HF and HCl solutions. Separations of short-lived W isotopes, produced through heavy ion irradiation were also performed on-line. (author). 27 refs., 14 figs

Surface Passivation of MoO3 Nanorods by Atomic Layer Deposition Towards High Rate Durable Li Ion Battery Anodes

KAUST Repository

Ahmed, Bilal; Shahid, Muhammad; Nagaraju, Doddahalli H.; Anjum, Dalaver H.; Hedhili, Mohamed N.; Alshareef, Husam N.

2015-01-01

We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in Lithium (Li) ion batteries at high rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2 coated MoO3 electrodes is 68% higher than bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2 coated MoO3 electrodes exhibited specific capacity of 657 mAh/g, on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2 coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li–ions through the passivation layer to the active material. Furthermore, ex–situ HRTEM, X–ray photoelectron spectroscopy (XPS), Raman spectroscopy and X–ray diffraction was carried out to explain the capacity retention mechanism after HfO2 coating.

Surface Passivation of MoO3 Nanorods by Atomic Layer Deposition Towards High Rate Durable Li Ion Battery Anodes

KAUST Repository

Ahmed, Bilal

2015-06-03

We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in Lithium (Li) ion batteries at high rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2 coated MoO3 electrodes is 68% higher than bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2 coated MoO3 electrodes exhibited specific capacity of 657 mAh/g, on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2 coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li–ions through the passivation layer to the active material. Furthermore, ex–situ HRTEM, X–ray photoelectron spectroscopy (XPS), Raman spectroscopy and X–ray diffraction was carried out to explain the capacity retention mechanism after HfO2 coating.

4s24p3--4s4p4 and 4s24p3--4s2fp25s transitions in Y VII, Zr VIII, Nb IX, and MoX

International Nuclear Information System (INIS)

Reader, J.; Acquista, N.

1981-01-01

Spectra of ionized Y, Zr, Nb, and Mo have been observed in sliding-spark and triggered-spark discharges on 10.7-m normal- and grazing-incidence spectrographs at the National Bureau of Standards in Washington, D. C. From these observations the 4s 2 4p 3 --4s4p 4 transitions in Y VII, Zr VIII, Nb IX, and Mo X have been identified. The 4s 2 4p 3 --4s 2 4p 2 5s transitions in Y VII-Mo X, previously identified by Rahimullah et al. [Phys. Scr. 14, 221--223 (1976); 18, 96--106 (1978)], have been confirmed. In Y VII the 4s 2 4p 3 --4s 2 4p 2 6s and 4s4p 4 --4p 5 transition also have been found. The parameters obtained from least-squares fits to the energy levels are compared with Hartree--Fock calculations. Preliminary values of the ionization energies have been determined as 110.02 +- 0.15 eV for Y VII, 133.7 +- 0.5 eV for Zr VIII, 159.2 +- 0.7 eV for Nb IX, and 186.4 +- 1.2 eV for Mo X

Directional crystallization of B4C-NbB2 and B4C-MoB2 eutectic compositions

International Nuclear Information System (INIS)

Paderno, Varvara; Paderno, Y.B.; Filippov, Vladimir; Liashchenko, Alfred

2004-01-01

We studied the directional crystallization of different compositions in B 4 C-NbB 2 and B 4 C-MoB 2 systems. The eutectic compositions for both systems are evaluated. It is shown that in the first system the rod-like eutectic structure is formed, in second, the 'Chinese hieroglyphics'. In both cases high hardness and high microplasticity are observed, which are much more than for individual component phases. These compositions may be considered as a new kind of self-strengthening composite materials

Non-stoichiometry in the KMo2P3O12-tunnel structure: The oxide K0.75MoNbP3O12

International Nuclear Information System (INIS)

Leclaire, A.; Borel, M.M.; Grandin, A.; Raveau, B.

1990-01-01

K 0.75 MoNbP 3 O 12 , M r =503.009, orthorhombic, Pbcm, a=8.8518 (5), b=9.1453 (11), c=12.5174 (11) A, V=1013.3 (3) A 3 , Z=4, D x =3.300 Mg m -3 , λ(Mo Kα)=0.71073 A, μ=3.13 mm -1 , F(000)=953, T=294 K, R=0.029, wR=0.033 for 1235 observed reflections. This compound is isostructural with KMo 2 P 3 O 12 -type oxides. Its framework is built up from MoO 6 octahedra and PO 4 tetrahedra which delimit tunnels running along b. Different from KMo 2 P 3 O 12 , the tunnels are partly occupied by the potassium ions which are distributed at random. (orig.)

Anodic Fabrication of Ti-Nb-Zr-O Nanotube Arrays

Directory of Open Access Journals (Sweden)

Qiang Liu

2014-01-01

Full Text Available Highly ordered Ti-Nb-Zr-O nanotube arrays were fabricated through pulse anodic oxidation of Ti-Nb-Zr alloy in 1 M NaH2PO4 containing 0.5 wt% HF electrolytes. The effect of anodization parameters and Zr content on the microstructure and composition of Ti-Nb-Zr-O nanotubes was investigated using a scanning electron microscope equipped with energy dispersive X-ray analysis. It was found that length of the Ti-Nb-Zr-O nanotubes increased with increase of Zr contents. The diameter and the length of Ti-Nb-Zr-O nanotubes could be controlled by pulse voltage. XRD analysis of Ti-Nb-Zr-O samples annealed at 500°C in air indicated that the (101 diffraction peaks shifted from 25.78° to 25.05° for annealed Ti-Nb-Zr-O samples with different Zr contents because of larger lattice parameter of Ti-Nb-Zr-O compared to that of undoped TiO2.

Threshold current reduction for the metal–insulator transition in NbO2−x-selector devices: the effect of ReRAM integration

International Nuclear Information System (INIS)

Nandi, Sanjoy Kumar; Liu, Xinjun; Venkatachalam, Dinesh Kumar; Elliman, Robert Glen

2015-01-01

The threshold current for inducing the metal–insulator transition in a NbO 2−x selector element is shown to be affected by the properties of an adjacent memory element when integrated into a hybrid selector-memory device structure. Experimental results are reported for homogeneous NbO 2−x /Nb 2 O 5−y and heterogeneous NbO 2−x /HfO 2 device structures, and show that the threshold current is lower in both hybrid structures than in the selector element alone, and is lower in the heterogeneous structure than in the homogeneous structure. Finite element modeling of the selector-memory structure shows that this results primarily from current confinement produced by the filamentary conduction path in the resistive-switching memory layer (i.e. Nb 2 O 5−y or HfO 2 ), an observation that further implies a smaller diameter filament in HfO 2 than in Nb 2 O 5−y . The thermal and electrical conductivities of the memory layer are also shown to influence the threshold current, but to a lesser extent. (paper)

Low electron density of states at the boron site of TMB{sub 2} (TM = Ti, Zr, Hf, and Nb): a {sup 11}B NMR study

Energy Technology Data Exchange (ETDEWEB)

Paluch, S.; Zogal, O.J.; Peshev, P

2004-11-30

The local density of states at the boron site in TMB{sub 2} (TM=Ti, Zr, Hf, and Nb) has been examined using the solid-state {sup 11}B NMR technique. The magic angle spinning (MAS) NMR spectra at room temperature and the spin-lattice relaxation rates have been measured as functions of temperature (30-293 K). The resonance line shifts are small and become more negative in the direction from 3d- to 5d-elements. The relaxation rates follow a linear law characteristic of hyperfine magnetic interaction with conduction electrons. With borides of IV group metals the data can be understood in terms of a very low s-electron density of states and absence of a p-character of the conduction electron wave function at the Fermi level while in the case of NbB{sub 2} a small partial p-electron density of states is assumed. Then, the results are in good agreement with the earlier theoretical prediction.

Electronic energy states of HfSe/sub 2/ and NbSe/sub 2/ by low energy electron loss spectroscopy study

Energy Technology Data Exchange (ETDEWEB)

Ito, T; Iwami, M; Hiraki, A [Osaka Univ., Suita (Japan). Faculty of Engineering

1981-06-01

Low energy electron loss spectroscopy (ELS) study was performed on 1T-HfSe/sub 2/ (group IVB metal compound) and 2H-NbSe/sub 2/ (group VB metal compound) by using incident electron energies of 30-250 eV. From the loss data in the second derivative form, maxima in density-of-states in the conduction band of the compounds were deduced through the information on the filled core states by X-ray photoelectron spectroscopy. The conduction band of the transition-metal dichalcogenides could be divided into two parts. The results are discussed in relation to the previous work on WS/sub 2/ (group VIB metal compound), and also to proposals based on band calculations and experimental studies on the transition-metal dichalcogenides with constituent metals of group IVB, VB and VIB.

Selective oxidation of i-butene and i-butene to methacrolein and methacrylic acid over Keggin-type polyoxometalate and MoVTeNbOx catalysts. A comparative catalytic and in situ-spectroscopic study

Energy Technology Data Exchange (ETDEWEB)

Bentrup, U.; Brueckner, A.; Kant, M.; Kolf, S.; Dingerdissen, U. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V. (Germany); Jansen, S.; Maschmeyer, D.; Sieger, H.; Zanthoff, H.W. [Degussa AG, Marl (Germany)

2005-07-01

An alternative to overcome the drawbacks connected with POM catalysts may be the development of suitable mixed metal oxide catalysts. MoVTeNbO{sub x} materials could be promising candidates since they revaled remarkable performance in the selective oxidation of propane to acrylic acid. However, up to now their behaviour in the selective oxidation of i-butane has rarely been studied. The investigations presented in this paper are focused on the interaction of feed components (i-butane / i-butene, O{sub 2}, H{sub 2}O) with Keggin-type polyoxometalate and MoVTeNbO{sub x} catalysts. FTIR spectroscopy was used to identify adsorbed intermediates and products while the novel simultaneous operando-EPR/UV-vis/Raman/GC technique revealed to be an excellent tool to follow the behaviour of V and Mo sites. In relation to the results of catalytic tests, structure-reactivity relationships are derived. (orig.)

Corrosion resistance of tantalum base alloys

International Nuclear Information System (INIS)

Gypen, L.A.; Brabers, M.; Deruyttre, A.

1984-01-01

The corrosion behaviour of substitutional Ta-Mo, Ta-W, Ta-Nb, Ta-Hf, Ta-Zr, Ta-Re, Ta-Ni, Ta-V, Ta-W-Mo, Ta-W-Nb, Ta-W-Hf and Ta-W-Re alloys has been investigated in various corrosive media, i.e. (1) concentrated sulfuric acid at 250 0 C and 200 0 C, (2) boiling hydrochloric acid of azeotropic composition, (3) concentrated hydrochloric acid at 150 0 C under pressure, (4) HF-Containing solutions and (5) 0.5% H 2 SO 4 at room temperature (anodisation). In highly corrosive media such as concentrated H 2 SO 4 at 250 0 C and concentrated HCl at 150 0 C tantalum is hydrogen embrittled, probably by stress induced precipitation of β-hydride. Both corrosion rate and hydrogen embrittlement in concentrated H 2 SO 4 at 250 0 C are strongly influenced by alloying elements. Small alloying additions of either Mo or Re decrease the corrosion rate and the hydrogen embrittlement, while Hf has the opposite effect. Hydrogen embrittlement in concentrated H 2 SO 4 at 250 0 C is completely eliminated by alloying Ta with 1 to 3 at % Mo (0.5 to 1.5 wt % Mo). These results can be explained in terms of oxygen deficiency of the Ta 2 O 5 film and the electronic structure of these alloys. (orig.) [de

Unidirectional solidification of a Nbss/Nb5Si3 in-situ composite

International Nuclear Information System (INIS)

Guo, X.P.; Ding, X.; Zhang, J.; Fu, H.Z.; Guan, P.; Kusabiraki, K.

2005-01-01

The directionally solidified specimens of Nb-13.52 Si-22.60 Ti-6.88 Hf-2.54 Cr-2.24 Al alloy were prepared in an electron beam floating zone melting furnace at the withdrawing rate of 0.1, 0.3, 0.6, 1.0, 2.4 and 6.0 mm/min. All the primary Nb solid solution (Nb ss ) columns, Nb ss + (Nb) 3 Si/(Nb) 5 Si 3 eutectic colonies and divorced (Nb) 3 Si/(Nb) 5 Si 3 plates or chains align well along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the microstructure is gradually refined, and the amount of Nb ss + (Nb) 3 Si/(Nb) 5 Si 3 eutectic colonies increases. Both the room temperature ultimate tensile strength σ b and fracture toughness K Q are improved for the directionally solidified specimens. The tensile fracture occurs in a cleavage way. (orig.)

Acoustic modes of the phonon dispersion relation of NbD/sub x/ alloys

International Nuclear Information System (INIS)

Rowe, J.M.; Vagelatos, N.; Rush, J.J.; Flotow, H.E.

1975-01-01

The acoustic modes of the phonon dispersion relation in Nb, NbD 0 . 15 , and NbD 0 . 45 were measured at 473 0 K for phonons with wave vectors along the [100], [110], and [111] axes by coherent neutron scattering. The observed neutron groups for both alloys were well defined, with little or no apparent broadening. Results are compared to similar data for Nb--Mo alloys and with previous lattice-dynamics results for PdD 0 . 63 . This comparison shows that despite differences in detail, the general features of the dispersion relations of NbD/sub x/ and Nb--Mo are similar after allowing for the differences in lattice parameters for the two alloys. The measured dispersion curves and derived phonon frequency distributions for the Nb--D alloys are quite different from the analogous results for PdD 0 . 63 in that the average acoustic phonon frequencies increase with increasing deuterium concentration and lattice parameter

Crystal structure and X-ray photoemission spectroscopic study of A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta

Energy Technology Data Exchange (ETDEWEB)

Dutta, Alo, E-mail: alo_dutta@yahoo.com [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Saha, Sujoy [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Kumari, Premlata [Department of Chemistry, Government P.G. College, Lansdowne, Pauri-Garhwal 246139 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Shannigrahi, Santiranjan [Institute of Materials Research and Engineering, Agency for Science Technology and Research, 3 Research Link, Singapore 117602 (Singapore)

2015-09-15

The X-ray photoemission spectroscopic (XPS) study of the double perovskite oxides A{sub 2}LaMO{sub 6} [A=Ba, Ca; M=Nb, Ta] synthesized by the solid-state reaction technique has been carried out to investigate the nature of the chemical state of the constituent ions and the bonding between them. The Rietveld refinement of the X-ray diffraction patterns suggests the monoclinic crystal structure of all the materials at room temperature. The negative and positive chemical shifts of the core level XPS spectrum of O-1s and Nb-3d{sub 3/2}/Ta-4f{sub 5/2} respectively suggest the covalent bonding between Nb/Ta cations and O ion. The change of the bonding strength between the anion and the cations from one material to another has been analyzed. The vibrational property of the materials is investigated using the room temperature Raman spectra. A large covalency of Ta-based compound than Nb compound is confirmed from the relative shifting of the Raman modes of the materials. - Graphical abstract: Crystal structure of two perovskite oxides CLN and CLT is investigated. XPS study confirms the two different co-ordination environments of Ca and covalent bonding between B-site cations and O-ion. - Highlights: • Ordered perovskite structure obtained by Rietveld refinement of XRD patterns. • Study of nature of chemical bonding by X-ray photoemission spectroscopy. • Opposite chemical shift of d-states of Nb/Ta with respect to O. • Covalent bonding between d-states of Nb/Ta and O. • Relative Raman shifts of CLN and CLT substantiate the more covalent character of Ta than Nb.

Comparison of U-Pu-Mo, U-Pu-Nb, U-Pu-Ti and U-Pu-Zr alloys

International Nuclear Information System (INIS)

Boucher, R.; Barthelemy, P.

1964-01-01

The data concerning the U-Pu, U-Pu-Mo and U-Pu-Nb are recalled. The results obtained with U-Pu-Ti and U-Pu-Zr alloys containing 15-20 per cent Pu and 10 wt. per cent ternary element are reported. The transformation temperatures, the expansion coefficients, the nature of phases, the thermal cycling behaviour have been determined. A list of the principal properties of these different alloys is presented and the possibilities of their use as fast reactor's fuel element are considered. The U-Pu-Ti alloys seem to be quite promising: easiness of fabrication, large thermal stability, excellent behaviour in air, small quantity of zeta phase, temperature of solidus superior to 1100 deg. C. (authors) [fr

Analysis of hot rolling and hot forging effects on mechanical properties and microstructure of ZrNbMoGe alloy

International Nuclear Information System (INIS)

AH Ismoyo; Parikin; Bandriyana

2014-01-01

Research on formation technique by a combined method of rolling and forging has been carried out in order to improve the mechanical properties of ZrNbMoGe alloy to be used as fuel cladding in NPP (Nuclear Power Plant) application. The effects of rolling and forging were analyzed several tests. The tests were conducted for zirconium alloy specimen with a composition of (in % wt.) 97% Zr, 0,5% Mo, 2% Nb and 0,5% Ge, where the specimen was melted with an arc-furnace. The hot rolling and forging were conducted at 900 °C and 950 °C respectively. Hardness test was carried out by using a microhardness testing machine, while microstructure examination and crystal structure analysis were conducted with an optical microscope and an X-ray diffractometer. The results show that the hardness of the alloy increase from 141.21 HV (starting material) to 210.47 HV (hot rolled material) and 365.75 HV (hot forged material). Texturing phenomenon is clearly figured on the microstructure due to hot rolling and forging process. Analysis by diffractogram also indicates that the hot rolling and forging process has influence on the crystal orientation of dominant preferred direction in the reflection plane of (10ī1), recorded from the rise of intensity counting from about 2500 to 3000. In summary, hot forging and rolling process can change the mechanical properties (hardness and texture) and microstructure of materials. (author)

Superconductivity in U-T alloys (T = Mo, Pt, Pd, Nb, Zr stabilized in the cubic γ-U structure by splat-cooling technique

Directory of Open Access Journals (Sweden)

N.-T.H. Kim-Ngan

2016-06-01

Full Text Available We succeed to retain the high-temperature (cubic γ-U phase down to low temperatures in U-T alloys with less required T alloying concentration (T = Mo, Pt, Pd, Nb, Zr by means of splat-cooling technique with a cooling rate better than 106 K/s. All splat-cooled U-T alloys become superconducting with the critical temperature Tc in the range of 0.61 K–2.11 K. U-15 at.% Mo splat consisting of the γ-U phase with an ideal bcc A2 structure is a BCS superconductor having the highest critical temperature (2.11 K.

Effect on Al:MO{sub 2}/In{sub 0.53}Ga{sub 0.47}As interface (M = Hf, Zr) of trimethyl-aluminum pre-treatment during atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Lamperti, A., E-mail: alessio.lamperti@mdm.imm.cnr.it [Laboratorio MDM, IMM-CNR, via C. Olivetti 2, 20864 Agrate Brianza, MB (Italy); Molle, A.; Cianci, E.; Wiemer, C.; Spiga, S. [Laboratorio MDM, IMM-CNR, via C. Olivetti 2, 20864 Agrate Brianza, MB (Italy); Fanciulli, M. [Laboratorio MDM, IMM-CNR, via C. Olivetti 2, 20864 Agrate Brianza, MB (Italy); Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Milano (Italy)

2014-07-31

For the fabrication of n-type metal–oxide–semiconductor field-effect transistor based on high mobility III–V compound semiconductors as channel materials, a major requirement is the integration of high quality gate oxides on top of the III–V substrates. A detailed knowledge of the interface between the oxide layer and the substrate is mandatory to assess the relevance of interdiffusion and related defects, which are detrimental. Here we grow high dielectric constant (k) Al:MO{sub 2} (M = Hf, Zr) gate materials on In{sub 0.53}Ga{sub 0.47}As substrates by atomic layer deposition, after an Al{sub 2}O{sub 3} pre-treatment based on trimethylaluminum is performed to properly passivate the substrate surface. Time of flight secondary ion mass spectrometry depth profiles reveal not only the film integrity and the chemical composition of the high-k oxide but also well elucidate the effect of the Al{sub 2}O{sub 3} pre-treatment on Al:MO{sub 2}/In{sub 0.53}Ga{sub 0.47}As interface. Even though the chemical profile is well defined in both cases, a broader interface is detected for Al:ZrO{sub 2}. X-ray photoemission spectroscopy evidenced the presence of As{sup 3+} states in Al:ZrO{sub 2} only. Accordingly, preliminary capacitance–voltage measurements point out to a better field effect modulation in the capacitor incorporating Al:HfO{sub 2}. Based on the above considerations Al:HfO{sub 2} looks as a preferred candidate with respect to Al:ZrO{sub 2} for the integration on top of In{sub 0.53}Ga{sub 0.47}As substrates. - Highlights: • Al:MO{sub 2} (M = Hf, Zr) thin films are grown on In{sub 0.53}Ga{sub 0.47}As substrates. • Trimethylaluminum (TMA) pre-treatment properly passivates the substrate surface. • ToF-SIMS depth profiles reveal the chemical composition of the high-k films. • Depth profiles well elucidate the effect of TMA on Al:MO{sub 2}/In{sub 0.53}Ga{sub 0.47}As substrates. • XPS evidences the presence of As{sup 3+} state in Al:ZrO{sub 2}/In{sub 0

Niobium Nb and tantalum Ta

International Nuclear Information System (INIS)

Busev, A.I.; Tiptsova, V.G.; Ivanov, V.M.

1978-01-01

The basic methods for determining niobium and tantalum in various objects are described. Nb and Ta are separated with the aid of N-benzoyl-N-phenylhydroxylamine by precipitating Nb(5) from a tartaric acid solution with subsequent precipitation of Ta from the filtrate. The gravimetric determination of Nb and Ta in steels is based on their quantitative separation from a diluted solution by way of hydrolysis with subsequent after-precipitation with phenylarsonic acid (in the absence of W). The gravimetric determination of Nb in the presence of W is carried out with the aid of Cupferron. To determine Nb in its carbide, Nb(5) reduced to Nb(3) is titrated with a solution of K 2 Cr 2 O 7 in the presence of phenyl-anthranilic acid. The photometric determination of Nb in tungsten-containing steels and in ores containing Ti, W, Mo and Cr is based on the rhodanide method. Nb is determined in alloys with Zr and Ti photometrically with the aid of 4-(2-pyridylazo)-resorcin and in alloyed steels with the aid of benzhydroxamic acid. The latter complex is extracted with chloroform. This method is used to determine Nb in rocks. The photometric determination of Ta in TiCl 4 is carried out with the aid of pyrogallol, in commercial niobium with the aid of methyl violet, and in steel with the aid of 4-(-pyridylazo)-resorcin. Also described is the polarographic determination of Nb in tantalum pentoxide

Reduced activation calculations for the STARFIRE first wall

International Nuclear Information System (INIS)

Mann, F.M.

1983-10-01

The activation of 27 elements (Li, Be, B, C, N, O, Mg, Al, Si, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Sn, Hf, Ta, W, and Pb) was calculated for a two-year exposure at the STARFIRE first-wall position. Based on a reasonable extension of current NRC regulations for near-surface land disposal, restrictions on N, Al, Ni, Cu, Nb, Mo, and Pb concentrations in first-wall materials may be required

A high-throughput reactor system for optimization of Mo–V–Nb mixed oxide catalyst composition in ethane ODH

KAUST Repository

Zhu, Haibo; Laveille, Paco; Rosenfeld, Devon C.; Hedhili, Mohamed N.; Basset, Jean-Marie

2015-01-01

75 Mo-V-Nb mixed oxide catalysts with a broad range of compositions were prepared by a simple evaporation method, and were screened for the ethane oxidative dehydrogenation (ODH) reaction. The compositions of these 75 catalysts were systematically changed by varying the Nb loading, and the Mo/V molar ratio. Characterization by XRD, XPS, H2-TPR and SEM revealed that an intimate structure is formed among the 3 components. The strong interaction among different components leads to the formation of a new phase or an "intimate structure". The dependency of conversion and selectivity on the catalyst composition was clearly demonstrated from the results of high-throughput testing. The optimized Mo-V-Nb molar composition was confirmed to be composed of a Nb content of 4-8%, a Mo content of 70-83%, and a V content of 12-25%. The enhanced catalytic performance of the mixed oxides is obviously due to the synergistic effects of the different components. The optimized compositions for ethane ODH revealed in our high-throughput tests and the structural information provided by our characterization studies can serve as the starting point for future efforts to improve the catalytic performance of Mo-V-Nb oxides. This journal is © The Royal Society of Chemistry.

A long-term ultrahigh temperature application of layered silicide coated Nb alloy in air

Science.gov (United States)

Sun, Jia; Fu, Qian-Gang; Li, Tao; Wang, Chen; Huo, Cai-Xia; Zhou, Hong; Yang, Guan-Jun; Sun, Le

2018-05-01

Nb-based alloy possessed limited application service life at ultrahigh temperature (>1400 °C) in air even taking the effective protective coating strategy into consideration for last decades. In this work a long duration of above 128 h at 1500 °C in air was successfully achieved on Nb-based alloy thanked to multi-layered silicide coating. Through optimizing interfaces, the MoSi2/NbSi2 silicide coating with Al2O3-adsorbed-particles layer exhibited three-times higher of oxidation resistance capacity than the one without it. In MoSi2-Al2O3-NbSi2 multilayer coating, the Al2O3-adsorbed-particles layer playing as an element-diffusion barrier role, as well as the formed porous Nb5Si3 layer as a stress transition zone, contributed to the significant improvement.

Resistencia a la corrosión a alta temperatura de recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por APS

Directory of Open Access Journals (Sweden)

José Luis Tristancho-Reyes

2014-12-01

Full Text Available La corrosión a alta temperatura de las tuberías utilizadas en equipos generadores de vapor (calderas ha sido reconocida como un grave problema que trae consigo el adelgazamiento de éstas y, por consiguiente, la falla de los equipos. En la última década se han incrementado las investigaciones que involucran recubrimientos protectores que ayudan de alguna manera a prolongar la vida útil de estos equipos. Esta investigación determinó el comportamiento de los recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por proyección térmica asistida por plasma (APS sobre la aleación SA213 – T22 (2¼Cr – 1Mo, en un ambiente corrosivo de 80%V2O5–20%K2SO4 a 800°C. Los valores de la cinética de corrosión fueron determinados mediante resistencia a la polarización lineal (RPL y espectroscopia de impedancia electroquímica (EIE. Los resultados obtenidos muestran una menor cinética de corrosión en el recubrimiento NiCrFeNbMoTiAl que la presentada por el recubrimiento NiCrAlY, corroborado por Microscopia Electrónica de Barrido (MEB.

Subduction Contributions in the Trans-Mexican Volcanic Belt: Implications from Lava Chemistry and Hf-Nd-Pb Isotopes

Science.gov (United States)

Cai, Y.; Goldstein, S. L.; Langmuir, C. H.; Gómez-Tuena, A.; Lagatta, A.; Straub, S. M.; Martín Del Pozzo, A.

2007-05-01

Despite thick continental crust, near primitive lavas erupt throughout the Trans-Mexican Volcanic Belt (TMVB). In order to distinguish and better constrain subduction contributions and effects of crustal contamination, we analyzed samples representing subducting sediments from DSDP Site 487, and Quaternary lavas from stratovolcanoes and cinder cones, including alkaline "high-Nb" lavas from the Sierra Chichinautzin Volcanic Field (SCVF) showing negligible subduction signature in its trace element chemistry and representing melts of the mantle wedge. Our primary observations and implications are: (1) The high-Nb SCVF `intraplate' lavas define a linear trend along the "Nd-Hf mantle-crust array", defining the composition of the mantle wedge. (2) Popocatepetl and Nevado de Toluca stratovolcanoes show the highest Nd and Hf isotope ratios, higher than the `intraplate' lavas, indicating their sources are more "depleted mantle-like" than the regional mantle wedge. (3) The Popo and Toluca chemical and isotopic trends sharply contrast with Pico de Orizaba, which shows classic indications of crustal contamination (e.g. high 207Pb/204Pb, low Nd-Hf isotope ratios), consistent with contamination by local Precambrian crust. (4) Higher Nd-Hf isotopes in Popo and Toluca lavas also correlate with lower Pb isotope ratios, and lower Lu/Hf and Zr/Hf. Together, these data indicate contributions from subducted Pacific oceanic crust and hydrothermal sediment. (5) Popo and Toluca are also enriched in Th/LREE compared with `intraplate' lavas, reflecting subducted sediment contributions. (6) Nd-Hf isotope ratios of hydrothermal sediment from DSDP Site 487 lie on the "seawater array", with high Hf isotope ratios compared to the "mantle-crust array". Popo and Toluca Nd-Hf isotopes display a shallower slope than the "intraplate lava Nd-Hf array", reflecting contributions from hydrothermal sediment. Popocatepetl and Toluca lavas therefore avoid substantial crustal contamination of mantle wedge

Electrochemical conversion of solid Nb{sub 2}O{sub 5} to Nb in sodium chloride melt as proof of oxygen ionisation mechanism of electrodeoxidation

Energy Technology Data Exchange (ETDEWEB)

Sri Maha Vishnu, D., E-mail: smvd2@cam.ac.uk [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India); Presently with Materials Chemistry Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS (United Kingdom); Sanil, N.; Mohandas, K.S. [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 (India)

2016-08-25

The direct electrochemical reduction of a solid metal oxide (MO{sub x}) to metal (M) in calcium chloride melt (FFC Cambridge process) has been proposed to take place via. oxygen ionisation mechanism, MO{sub x} + 2xe{sup −} → M + xO{sup 2−}. However, generation of calcium metal and reduction of the oxide with it too becomes possible under the applied potential condition (3.1 V) of an FFC cell. The unique chemistry of calcium chloride melt, upon cathodic polarisation, makes it difficult to distinguish between the reduction by electrons and calcium metal. Hence in order to confirm the oxygen ionisation theory of electro-deoxidation, electrochemical deoxidation experiments were carried out with sintered Nb{sub 2}O{sub 5} pellet electrodes in molten sodium chloride at 1173 K. The pellets were found reduced to Nb metal. Sodiothermic reduction of Nb{sub 2}O{sub 5} is thermodynamically not feasible (Nb{sub 2}O{sub 5} + 10Na → 5Na{sub 2}O + 2Nb, ΔG°{sub 1173K} = 102.1 kJ) and hence the observed reduction of the oxide is attributed to electrons. This study, for the first time, gives reliable experimental evidence to the oxygen ionisation mechanism of electro-reduction of solid oxides in the FFC process. The experimental results also prove that the electro-reduction of oxides can occur in melts, which otherwise were considered unsuitable from thermodynamic considerations. - Highlights: • In NaCl melt: Negligible O{sup 2−} ion solubility & Na reduction of Nb{sub 2}O{sub 5} to Nb – absent. • Nb{sub 2}O{sub 5} could be electrochemically reduced to spongy Nb in NaCl melt at 1173 K. • Mechanism: Nb{sub 2}O{sub 5} → Na−Nb−O compounds + suboxides of Nb → Na{sub x}NbO{sub y} → Nb. • Metallothermic reduction of oxide in melt - not mandatory for electrodeoxidation. • In FFC Cambridge process: Metallothermic reduction is not essential but desirable.

Phonon broadening in high entropy alloys

Science.gov (United States)

Körmann, Fritz; Ikeda, Yuji; Grabowski, Blazej; Sluiter, Marcel H. F.

2017-09-01

Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation high-temperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In contrast to perfect crystals and ordered alloys, the inherently present mass and force constant fluctuations in multi-component random alloys (high entropy alloys) can induce significant phonon scattering and broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of 12 body-centered cubic random alloys, from binaries up to 5-component high entropy alloys, addressing the key question of how chemical complexity impacts phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability considerations. The set of studied alloys includes MoTa, MoTaNb, MoTaNbW, MoTaNbWV, VW, VWNb, VWTa, VWNbTa, VTaNbTi, VWNbTaTi, HfZrNb, HfMoTaTiZr.

Analysis of local regions near the interfaces in nanostructured multicomponent cathodic – arc – vapor – deposition (CAVD) coatings (Ti-Zr-Hf-V-Nb)N

International Nuclear Information System (INIS)

Kraus-Rekhberg, R.; Pogrebnyak, A. D.; Borisyuk, V. N.; Kaverin, M. V.; Belokur, M.A.; Ponomarev, G.; Ojoshi, K.; Takeda, J.; Beresnev, V. M.; Sobol', O. V.

2013-01-01

Multicomponent, nanostructure (Ti- Zr-Hf-V-Nb)N coatings derived using cathodic – Arc – Vapor – Deposition method, were characterized by applying SPB, (μ-PIXE), EDS and SEM-analysis), XRD methods, including ''a-sin 2 φ'' procedure. It was found that through the creation of high elastic strains of compression in coating it is possible to a significant extent enhance its oxidation resistance under high-temperature annealing. During the characterization of coatings the elements and defects’ redistribution was discovered, its segregation through thermally-stimulated diffusion and the spinoidal segregation process end, in the neighborhood of the interfaces, around grains and subgrains, without substantial change of the average nanograin dimension. (authors)

Growth and photo-response of NbSe2 and NbS2 crystals

Science.gov (United States)

Patel, Kunjal; Solanki, G. K.; Pataniya, Pratik; Patel, K. D.

2018-05-01

Transition metal dichalcogenides(TMDCs) have attracted intense research efforts due to their drastic properties change as we move towards ultra-thin crystalline layers from their bulk counterparts. Many well studied members of this family such as MoS2, WS2, WSe2, WS2 etc. have shown potential for flexible electronic devices including photovoltaic applications. The TMDCs like NbSe2 and NbS2 are relatively less studied layered compounds consisting of staked sandwiches of Se-Nb-Se/S-Nb-Se tri-layers with strong covalent/ionic intra layer bonds and weak Van der Waals interlayer interactions. In the present work, author have grown the crystals of NbSe2 and NbS2 by Direct Vapour Transport (DVT) technique and the material composition is confirmed using EDAX data. Photoelectrochemical (PEC) solar cell measurements are performed under monochromatic light illumination at different intensities and various solar cell parameters are calculated. These crystalline semiconductor electrodes were also analysed by photocurrent-voltage characteristics in a PEC solar cell structure (Cu/NbSe2/(0.1M K4Fe(CN)6 + 0.1M K3Fe(CN)6) and Cu/NbS2/(0.1M K4Fe(CN)6 +0.1M K3Fe(CN)6)). Blue coloured light gave the maximum efficiency. For further analysis of photodetection properties of the grown crystals, Ag painted broad low contact resistance electrical contacts were drawn from the crystals and its transient photoresponse was studied to evaluate different detector parameters.

Structure of steel 8 CrMoNiNb 9 10 and its variations in long-term thermal stress

International Nuclear Information System (INIS)

Fabritius, H.; Schnabel, E.

1976-01-01

On four casts of steel 8 CrMoNiNb 9 10 with about 0.06% C, 0.25; Si, 0.7% Mn, 0.012% N, 0.002 to 0.020% Al, 2.25% Cr, 0.94% Mo, 0.63 to 0.91% Nb and 0.67% Ni, transformation behaviour and structural changes during long-time annealing at 500 to 750 degC lasting up to 30,000 h were studied in unformed condition and after previous cold forming. The carbon content was largely bound in form of primary niobium carbonitrides so that during quenching and tempering low-carbon bainite was formed, or at very slow cooling a ferritic structure without pearlite. Martensite occurred only after fast cooling from temperatures above 1200 degC. Bainite exhibited a very high dislocation density and a large number of coherent niobium carbonitrides. During tempering, the precipitates overaged, and the dislocations started to arrange themselves to subgrain boundaries. Hardness and strength in quenched and tempered condition were essentially governed by dislocation density and size of subgrains. In the whole range of bainite transformation, they are only slightly dependent upon the cooling rate and hence upon the dimensions of the products. The structural changes which occurred in bainitic material during long-time aging and led to a ferritic structure in the final state were interpreted as recovery and recrystallization. In unformed and slightly formed material recrystallization led to a very coarse-grained structure. In highly formed material a very fine-grained structure was achieved by recrystallization. By a high degree of cold forming the recrystallization process was considerably promoted. With an annealing time of 10 5 h, no recrystallization is to be expected for unformed specimens of the studied cast up to 580 degC, but above 650 degC complete recrystallization. (author)

Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M=Li, Na, or Rb)

International Nuclear Information System (INIS)

Bazarov, B.G.; Chimitova, O.D.; Bazarova, Ts.T.; Arkhincheeva, S.I.; Bazarova, Zh.G.

2008-01-01

Phase equilibria in the systems M 2 MoO 4 -Cr 2 (MoO 4 ) 3 -Zr(MoO 4 ) 2 (M=Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb 2 MoO 4 -Cr 2 (MoO 4 ) 3 -Zr(MoO 4 ) 2 system with the molar ratios of the starting components equal to 5:1:1 (S 2 ) and 1:1:1 (S 1 ). Proceeding from isostructural character of Rb 5 FeHf(MoO 4 ) 6 and S 2 , the unit cell parameters are determined for S 2 [ru

Microstructure and creep behavior of an orthorhombic Ti-25Al-17Nb-1Mo alloy

International Nuclear Information System (INIS)

Zhang, J.W.; Zou, D.X.; Li, S.Q.; Lee, C.S.; Lai, J.K.L.

1998-01-01

Microstructural evolution during three heat-treatment schedules and the terminal microstructures in an orthorhombic alloy of Ti-25Al-17Nb-1Mo were observed and analyzed with optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The creep behavior of the alloy with three different microstructures (a coarse-lath, fine-lath, and fine equiaxed microstructure) was studied over a temperature range of 600 C to 750 C and over a stress range of 150 to 400 MPa in air. The steady-state creep rates, apparent stress exponents, and apparent creep activation energies of the various samples have been determined. The results show that creep behaviors in the alloy are strongly influenced by microstructure. The effect on creep by some of the microstructural features, such as the multivariants within the coarse laths and the interfaces of the laths and the equiaxed grains, is also discussed

Phase composition of Al-Ti-Nb-Mo γ alloys in the heat-treatment temperature range: Calculation and experiment

Science.gov (United States)

Belov, N. A.; Dashkevich, N. I.; Bel'tyukova, S. O.

2015-07-01

The phase composition of TNM-type Al-Ti-Nb-Mo γ alloys at heat-treatment temperatures is quantitatively studied using the Thermo-Calc program package and experimental methods. Isothermal cross sections are calculated and the joint influence of two alloying elements on the phase composition of the alloy is determined at the mean concentration of a third component. Based on the calculations of vertical cross sections, the boundaries of the four-phase eutectoid reaction α → α2 + β + γ are found. The temperature is shown to significantly influence the phase compositions of the γ alloys, among them the mass fractions of various phases (α, β, γ,α2) and the element concentration in them.

Basic research for alloy design of Nb-base alloys as ultra high temperature structural materials; Chokoon kozoyo niobuki gokin no gokin sekkei no tame no kisoteki kenkyu

Energy Technology Data Exchange (ETDEWEB)

Miura, E [Tohoku University, Sendai (Japan); Yoshimi, K; Hanada, S [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals

1997-02-01

This paper describes an influence of additional elements on the high temperature deformation behavior of Nb-base solid solution alloys. Highly concentrated solid solution single crystals of Nb-Ta and Nb-Mo alloys were prepared. Compression test and strain rate sudden change test were conducted in the vacuum at temperatures ranging from 77 to 1773 K, to determine the strain rate sensitivity index. Yield stress of the Nb-Ta alloy was similar to that of Nb alloy at temperatures over 0.3{times}T{sub M}, where T{sub M} is fusing point of Nb. While, the yield stress increased with increasing the impurity oxygen concentration at temperatures below 0.3{times}T{sub M}. The yield stress became much higher than that of Nb alloy. The strain rate sensitivity index showed positive values in the whole temperature range. On the other hand, the yield stress of Nb-Mo alloy was higher than that of Nb alloy in the whole temperature range, and increased with increasing the Mo concentration. The strain rate sensitivity index showed negative values at the temperature range from 0.3{times}T{sub M} to 0.4{times}T{sub M}. It was found that serration occurred often for Nb-40Mo alloys. 1 ref., 4 figs., 1 tab.

Precision measurement of the half-life of {sup 90m}Nb and {sup 99m}Tc

Energy Technology Data Exchange (ETDEWEB)

Kikunaga, H.; Fujisawa, H.; Ooe, K. [Osaka Univ., Toyonaka (Japan). Graduate School of Science] [and others

2011-07-01

We have produced {sup 90m}Nb and {sup 99m}Tc in the reactions of {sup nat}Zr(p, xn){sup 90m}Nb and {sup 100}Mo({gamma}, n){sup 99}Mo, followed by disintegration to {sup 99m}Tc, respectively, and measured the halflives of these nuclides by using a reference source method. In order to determine the short half-lives of {sup 90m}Nb precisely, an on-line gas-jet system has been employed. As a result, the half-lives of these nuclides were determined with good precision on the order of magnitude of 0.1%. (orig.)

Superconductivity of Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} high entropy alloy from first principles calculations

Energy Technology Data Exchange (ETDEWEB)

Jasiewicz, K.; Wiendlocha, B.; Korben, P.; Kaprzyk, S.; Tobola, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059, Krakow (Poland)

2016-05-15

The Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) is applied to study the first superconducting high entropy alloy (HEA) Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} (discovered in 2014 with T{sub c}=7.3 K), focusing on estimations of the electron-phonon coupling constant λ. The electronic part of λ has been calculated using the rigid muffin-tin approximation (RMTA), while the phonon part has been approximated using average atomic mass and experimental Debye temperature. The estimated λ=1.16 is close to the value determined from specific heat measurements, λ=0.98, and suggests rather strong electron-phonon coupling in this material. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Recent Advances in Nb-silicide in-situ composites

International Nuclear Information System (INIS)

Bewlay, B.P.; Jackson, M.R.; Subramanian, P.R.; Briant, C.L.

2001-01-01

In-situ composites based on Nb silicides have great potential for future high-temperature applications. These Nb-silicide composites combine a ductile Nb-based matrix with high-strength silicides. With the appropriate combination of alloying elements, such as Ti, Hf, Cr, AI, it is possible to achieve a promising balance of fracture toughness, high-temperature creep performance, and oxidation resistance. This paper will describe the effect of volume fraction of silicide on microstructure, high-temperature creep performance, and oxidation resistance. The ratio of Nb:(W+Ti) is critical in determining both creep rate and oxidation performance. If this ratio goes below ∼1.5, the creep rate increases substantially. In more complex silicide-based systems, other intermetallics, such as laves phases and a boron-rich T-2 phase, are added for oxidation resistance. To understand the role of each phase on the creep resistance and oxidation performance of these composites, we determined the creep and oxidation behavior of the individual phases and composites at temperatures up to 1200 o C. These data allow quantification of the load-bearing capability of the individual phases in the Nb-silicide based in-situ composites. (author)

Effect of ternary alloying elements on microstructure and mechanical property of Nb-Si based refractory intermetallic alloy

International Nuclear Information System (INIS)

Kim, W.Y.; Kim, H.S.; Kim, S.K.; Ra, T.Y.; Kim, M.S.

2005-01-01

Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting points, atomic sizes smaller than Nb. Both ternary alloying elements were found to have a significant role in modifying the microstructure from dispersed structure to eutectic-like structure in Nb solid solution/Nb 5 Si 3 intermetallic composites. The 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb 5 Si 3 . At 1773 K, Mo addition has a positive role in increasing the yield strength. On the other hand, V addition has a role in decreasing the yield strength. The fracture toughness of ternary alloys was superior to binary alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase, and the microstructure. (orig.)

Superconductivity and NMR investigations of amorphous Be-Nb-Zr and Be-Mo-Zr alloys

International Nuclear Information System (INIS)

Goebbels, J.; Lueders, K.; Freyhardt, H.C.; Reichelt, J.

1981-01-01

9 Be NMR investigations and measurements of the superconducting properties and the resistivity are reported for amorphous Besub(32.5)Nbsub(x)Zrsub(67.5-x) and Besub(32.5)Mosub(x)Zrsub(67.5-x) alloys (x = 2.5; 5; 7). Line width analysis suggests an enlarged Nb concentration around the Be sites for the Be-Nb-Zr alloys. Comparing the two types of alloys the Knight shifts are of the same order of magnitude whereas the Tsub(c) and Bsub(c) 2 (0) values are slightly smaller than for the Nb alloys. For Be-Nb-Zr Tsub(c) and K increases with the Nb content. The results are discussed in connection with the density of states N(Esub(F)). (orig.)

Excitation functions of the 98Mo+d reactions

International Nuclear Information System (INIS)

Zarubin, P.P.; Padalko, V.Yu.; Khrisanfov, Yu.V.; Lebedev, P.P.; Podkopaev, Yu.N.

The excitation functions of the 98 Mo+d reactions were studied. The energy dependence of (d,p),(d,n) and (d,α) reactions was investigated by the activation analysis. The energies of deuterons in the range (6-12) MeV were determined by means of the aluminium filters. 98 Mo foils with surface densities of 1.02, 0.23 and 0.14 mgxcm -2 with 98 Mo enrichment of 94.1% were used as targets. The gamma spectra were measured by a Ge(Li) detector. The 98 Mo(d,p) 99 Mo reaction excitation function was determined via detection of 739 and 181 keV γ-radiation of 99 Mo (Tsub(1/2)=66.47h); 140 keV γ-radiation of 99 Tc (Tsub(1/2)=6h) was detected for the 98 Mo(d,n) 99 Tc reaction excitation function determination and 460, 568, 1091, 1200 and 1492 keV γ-quanta of 96 Nb (Tsub(1/2)=23.35h) - for the 98 Mo(d,α) 96 Nb reaction. In the excitation function the wide extremum was observed at Esub(d) approximately 10 MeV. The ratio of cross sections σsup(m)(d,n)/σ(d,p) on the 98 Mo target was determined. The ratio σsup(m)(d,n)/σ(d,p) was found to be decreasing function of the deuteron energy. The relative cross sections were determined with an accuracy of +-5%, while for the absolute values of cross sections the accuracy was +-15%

Characterization of a High Strength, Refractory High Entropy Alloy, AlMo0.5NbTa0.5TiZr

Science.gov (United States)

Jensen, Jacob

High entropy alloys (HEAs) are a relatively new class of materials that have garnered significant interest over the last decade due to their intriguing balance of properties including high strength, toughness, and corrosion resistance. In contrast to conventional alloy systems, HEAs are based on four or more principal elements with near equimolar concentrations and tend to have simple microstructures due to the preferential formation of solid solution phases. HEAs appear to offer new pathways to lightweighting in structural applications, new alloys for elevated temperature components, and new magnetic materials, but more thorough characterization studies are needed to assess the viability of the recently developed multicomponent materials. One such HEA, AlMo0.5NbTa0.5TiZr, was selected to be the basis for this characterization study in part due to its strength at elevated temperatures (sigma0.2 = 1600 MPa at T = 800 °C) and low density compared with commercially available Ni-based superalloys. The refractory element containing HEA composition was developed in order to balance the high temperature strength of the refractory elements with the desirable properties achieved by the high entropy alloying design approach for potential use in aerospace thermal protection and structural applications. Ingots of AlMo0.5NbTa0.5TiZr were cast by vacuum arc melting followed by hot isostatic pressing (HIP) and homogenization at 1400 °C for 24 hrs with a furnace cool of 10 °C/min. The resulting microstructure was characterized at multiple length scales using x-ray diffraction (XRD), scanning transmission electron microscopy (SEM), conventional and scanning transmission electron microscopy (TEM and STEM), and x-ray energy dispersive spectroscopy (XEDS). The microstructure was found to consist of a periodic, coherent two phase mixture, where a disordered bcc phase is aligned orthogonally in an ordered B2 phase. Through microstructural evolution heat treatment studies, the

Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (10{sup 18} cm{sup −2}): Their structure and mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Pogrebnjak, A.D., E-mail: alexp@i.ua [Sumy State University, Department of Nanoelectronics, 40007, R.-Korsakova 2, Sumy (Ukraine); Bondar, O.V., E-mail: oleksandr.v.bondar@gmail.com [Sumy State University, Department of Nanoelectronics, 40007, R.-Korsakova 2, Sumy (Ukraine); Borba, S.O. [Sumy State University, Department of Nanoelectronics, 40007, R.-Korsakova 2, Sumy (Ukraine); Abadias, G. [Institut Pprime, CNRS, Université de Poitiers, ISAE-ENSMA, F86962 Futuroscope Chasseneuil (France); Konarski, P. [Tele and Radio Research Institute, Ratuszowa 11, 03-450 Warsaw (Poland); Plotnikov, S.V. [D. Serikbaev East-Kazakhstan State Technical University, 070004, Ust-Kamenogorsk, 69 Protozanov St. (Kazakhstan); Beresnev, V.M. [V.N. Karazin Kharkiv National University, 61022, Svobody Sq. 4, Kharkiv (Ukraine); Kassenova, L.G. [Kazakh University of Economics, Finance and International Trade, St. Zhubanov 7, 010005 Astana (Kazakhstan); Drodziel, P. [Lublin University of Technology, Nadbystrzycka 36, 20-618 Lublin (Poland)

2016-10-15

Highlights: • (TiZrHfVNbTa)N coatings were deposited by vacuum–arc evaporation of a cathode. • Nanostructured coatings were investigated experimentally and by MD simulations. • Good correlation between experimental data and simulation results is observed. • Ion implantation formed amorphous, nanocrystalline and nanostructured layers. • Hardness changed from 12 GPa in the implanted layer to 38 GPa with the depth. - Abstract: Multielement high entropy alloy (HEA) nitride (TiHfZrNbVTa)N coatings were deposited by vacuum arc and their structural and mechanical stability after implantation of high doses of N{sup +} ions, 10{sup 18} cm{sup −2}, were investigated. The crystal structure and phase composition were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy, while depth-resolved nanoindentation tests were used to determine the evolution of hardness and elastic modulus along the implantation depth. XRD patterns show that coatings exhibit a main phase with fcc structure, which preferred orientation varies from (1 1 1) to (2 0 0), depending on the deposition conditions. First-principles calculations reveal that the presence of Nb atoms could favor the formation of solid solution with fcc structure in multielement HEA nitride. TEM results showed that amorphous and nanostructured phases were formed in the implanted coating sub-surface layer (∼100 nm depth). Concentration of nitrogen reached 90 at% in the near-surface layer after implantation, and decreased at higher depth. Nanohardness of the as-deposited coatings varied from 27 to 38 GPa depending on the deposition conditions. Ion implantation led to a significant decrease of the nanohardness to 12 GPa in the implanted region, while it reaches 24 GPa at larger depths. However, the H/E ratio is ⩾0.1 in the sub-surface layer due to N{sup +} implantation, which is expected to have beneficial effect on the wear properties.

The genesis of Mo-Cu deposits and mafic igneous rocks in the Senj area, Alborz magmatic belt, Iran

Science.gov (United States)

Nabatian, Ghasem; Li, Xian-Hua; Wan, Bo; Honarmand, Maryam

2017-11-01

The geochemical and isotopic investigations were provided on the Upper Eocene Senj mafic intrusion and Mo-Cu mineralization to better understand the tectono-magmatic evolution and metallogeny of the central part of the Alborz magmatic belt. The Senj mafic intrusion is composed of gabbro to monzodiorite and monzonite in lithology, and intruded as a sill into volcano-sedimentary rocks of the Eocene Karaj Formation. The Karaj Formation consists of volcano-sedimentary rocks, such as altered crystalline to shaly tuffs. The Senj intrusion (39.7 ± 0.4 Ma) shows LILE and LREE enrichment and negative anomaly of Nb, Ta and Ti, the geochemical signatures similar to those from subduction-related mafic magmas. The Hf-O zircon analyses yield ɛHf(t) values of + 4.1 to + 11.1 and δ18O values of + 4.8 to + 6.2‰. The zircon isotopic signatures together with shoshonitic affinity in the Senj mafic samples suggest partial melting of an enriched lithospheric mantle that had already been metasomatized by slab-derived melts and fluids. The Mo-Cu mineralization mainly occurs as veins and veinlets in the volcano-sedimentary rocks of the Karaj Formation and is dominated by molybdenite with minor amounts of chalcopyrite, bornite, pyrite and tetrahedrite-tennantite. The associated gangue minerals are tremolite, actinolite, quartz, calcite, chlorite and epidote. The Senj Mo-Cu deposit formed in volcano-sedimentary rocks following the emplacement of the Late Eocene Senj sill. The source of molybdenite in the Senj deposit is dominantly from crustal materials as it is revealed by Re contents in the molybdenite minerals (0.5 to 0.7 ppm). In fact, the molybdenite occurrence may be a remobilization process related to the emplacement of the Senj mafic magma.

Determination of trace amount of titanium in 2.5% Nb-Zr alloy by anion exchange separation and sulfo salicylic acid photometry

International Nuclear Information System (INIS)

Sakai, Fumiaki; Wachi, Isamu; Tsuji, Nobuo; Satoh, Hitoshi

1973-01-01

A trace amount of Ti in 2.5% Nb-Zr alloy can be determined by a combined method of the characteristic anion exchange separation of Ti from Nb and the absorption photometry of Ti with sulfo salicylic acid. The alloy (1g) was dissolved in 5 ml of HF (1 + 1), and 5 ml of HNO 3 was added to them. The resultant 5M HF - 6M HNO 3 mixed acid solution was passed into an anion exchange resin column with 10 mm internal diameter and 100 mm high, at the rate of 1 to 2 ml/min. Niobium was adsorbed on to the column, through which Ti passed. The collected passing and washing solutions were converted into H 2 SO 4 medium by twice successive fuming treatments. The solution was transferred into a volumetric flask of 50 ml, and 10 ml of 10% sulfo salicylic acid in H 2 SO 4 was added. Diluting to a mark with H 2 SO 4 , the solution was allowed to stand for 15 min. Titanium was then determined by measuring absorption intensity at the wavelength of 410 mm. The influence of coexisting elements on the coloration of Ti and some adsorption conditions of Nb was experimentally investigated by using 95 Nb as a tracer. The experiment revealed that the removal of Nb is essential, and that higher HF concentration and lower HNO 3 concentration contribute to higher Nb adsorption. A variable rate type cockless column is useful for this routine analysis. The standard deviation and the coefficient of variation of analysis are 1.3 and 4.06% respectively for the concentration level of 32 ppm Ti (NZ-3). (Iwakiri, K.)

Porous p-NiO/n-Nb{sub 2}O{sub 5} nanocomposites prepared by an EISA route with enhanced photocatalytic activity in simultaneous Cr(VI) reduction and methyl orange decolorization under visible light irradiation

Energy Technology Data Exchange (ETDEWEB)

Hashemzadeh, Fatemeh, E-mail: Fa.hashemzadeh@gmail.com [Young Researchers and Elite Clube, Marand Branch, Islamic Azad University, Marand (Iran, Islamic Republic of); Gaffarinejad, Ali, E-mail: Ghaffarinejad@iust.ac.ir [Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of); Rahimi, Rahmatollah, E-mail: Rahimi_Rah@iust.ac.ir [Department of Chemistry, Iran University of Science and Technology, Tehran 16846-13114 (Iran, Islamic Republic of)

2015-04-09

Highlights: • EISA synthesis of NiO/Nb{sub 2}O{sub 5} composites (NiNbx; x = Ni/Nb = 0.0, 0.4, 0.8, 1.2). • 200–400 nm extension in absorption edge to visible region compared to NiNb0.0. • Simultaneous Cr(VI)–MO redox photoreactions on NiNbx in visible light at pH 2. • NiNb0.4, the most active sample, due to low E{sub g} & e{sup −}–h{sup +} separation by p–n junction. • More efficiency of Cr(VI)–MO system than that of single ones, showing synergism effect. - Abstract: Porous NiO/Nb{sub 2}O{sub 5} nanocomposites with Ni/Nb molar ratio of 0.4, 0.8 and 1.2 have been obtained via the EISA route using P123 copolymer as organic template, and are assigned as NiNb0.4, NiNb0.8 and NiNb1.2, respectively. For comparison, pure Nb{sub 2}O{sub 5} sample assigned as NiNb0.0 was also synthesized by the same method. Structural and textural features of the as prepared samples were investigated by XRD, FTIR, FE-SEM, EDX, UV–vis DRS and BET techniques. The results indicated that the porous p-NiO/n-Nb{sub 2}O{sub 5} junction nanocomposites were formed and coupling of NiO with Nb{sub 2}O{sub 5} resulted a remarkable red shift in the optical response of the nanocomposite samples. The photocatalytic properties of the nanocomposite samples, and also synthesized pure Nb{sub 2}O{sub 5} (NiNb0.0) and commercial Nb{sub 2}O{sub 5} as reference catalysts were evaluated for the first time by simultaneous Cr(VI) reduction and MO decolorization in aqueous suspension under visible light irradiation at pH 2. NiNb0.4 was found to be the most active photocatalyst, which might be attributed to the extended absorption in the visible light region and the effective photogenerated electron–hole separation by the photosynergistic effects of the p-NiO/n-Nb{sub 2}O{sub 5} composite powder. The photocatalytic efficiency of the most active photocatalyst, NiNb0.4, was found to be rather low for either single Cr(VI) solution or single MO solution. However, the photocatalytic reduction of

Evaluation of Some (n,n'), (n,γ), (n,p), (n,2n) and (n,3n) Reaction Excitation Functions for Fission and Fusion Reactor Dosimetry Applications; Evaluation of the Excitation Functions for the 54Fe(n,p)54Mn, 58Ni(n,2n)57Ni, 67Zn(n,p)67Cu, 92Mo(n,p)92mNb, 93Nb(n,γ)94Nb, 113In(n,n')113mIn, 115In(n,γ) 116mIn, and 169Tm(n,3n)167Tm Reactions. Progress Report on Research Contract No 16242

International Nuclear Information System (INIS)

Zolotarev, K.I.; Zolotarev, P.K.

2013-12-01

Cross section data for the 54 Fe(n,p) 54 Mn, 58 Ni(n,2n) 57 Ni, 67 Zn(n,p) 67 Cu, 92 Mo(n,p) 92m Nb, 93 Nb(n,γ) 94 Nb, 113 In(n,n') 113m In, 115 In(n,γ) 116m In, 169 Tm(n,3n) 167 Tm reactions are needed to solve a wide spectrum of scientific and technical tasks. Activation detectors based on these reactions may be used in the field of reactor dosimetry. Furthermore, the 54 Fe(n,p) 54 Mn reaction is often used in experimental nuclear physics as a monitor reaction for measurements of unknown cross sections by means of the activation method over the neutron energy range from 5 to 15 MeV. The 93 Nb(n,γ) 94 Nb reaction is also very promising for using in retrospective neutron dosimetry for determination of total neutron fluence during a campaign of a reactor. In the existing version of the International Reactor Dosimetry File and the new extended version named as IRDFF data for excitation functions of 67 Zn(n,p) 67 Cu, 92 Mo(n,p) 92m Nb, 113 In(n,n') 113m In, and 169 Tm(n,3n) 167 Tm reactions are absent. Data for these reactions are also absent in the JENDL/D-99 dosimetry file. Excitation functions of 67 Zn(n,p) 67 Cu and 169 Tm(n,3n) 167 Tm are presented in the TENDL-2012, EAF-2010, JENDL-4.0, JEFF-3.1/A, MENDL-2 libraries. Cross section data for the 67 Zn(n,p) 67 Cu reaction up to 20 MeV are given also in the JENDL/HE-2007 library. Excitation functions of the 92 Mo(n,p) 92m Nb and 113 In(n,n') 113m In reactions are evaluated in the EAF-2010 and JEFF-3.1/A libraries. Cross section data for the 113 In(n,n') 113m In reaction are given also in the TENDL-2010 library. It is necessary to note that neutron data in the JEFF-3.1/A and JENDL-4.0 libraries were evaluated up to 20 MeV. Neutron data in the TENDL-2012, EAF-2010, MENDL-2 and TENDL-2010 libraries had been evaluated up to 30 MeV, 60 MeV, 100 MeV and 200 MeV, respectively. Neutron cross sections in the MENDL-2, TENDL-2010 and TENDL-2012 libraries had been obtained on the basis of pure theoretical model calculations

Geochronology, geochemistry, and Sr-Nd-Pb-Hf isotopes of the Zhunsujihua granitoid intrusions associated with the molybdenum deposit, northern Inner Mongolia, China: implications for petrogenesis and tectonic setting

Science.gov (United States)

Zhang, Xiaojun; Lentz, David R.; Yao, Chunliang; Liu, Rui; Yang, Zhen; Mei, Yanxiong; Fan, Xianwang; Huang, Fei; Qin, Ying; Zhang, Kun; Zhang, Zhenfei

2018-03-01

The Zhunsujihua porphyry molybdenum deposit, located in northern Inner Mongolia of China that belongs to Central-Asian Orogenic Belt (CAOB), is the only Mo deposit formed in the late Carboniferous in this area so far. Its mineralization is mainly restricted to the Zhunsujihua granitoid intrusions, which are composed of the main granodiorite (GD) and crosscutting, virtually coeval minor syn-ore leucogranite (LG) and diorite porphyry (DP) dykes. LA-ICP-MS zircon U-Pb dating yields crystallization ages of 300.0 ± 2.0, 299.3 ± 2.0, and 299.0 ± 2.6 Ma for the GD, LG, and DP, respectively. The major and trace element lithogeochemical data show that the GD and LG are metaluminous to weakly peraluminous, high-K calc-alkaline series with I-type granite characteristics, strongly oxidized, with low concentrations of Ba, Nb, Sr, P, and Ti and elevated K and Rb contents, indicating typical arc magmatic features. The LG is a product derived by extensive fractional crystallization of a parental magma similar to the GD as evident from the lower Eu/Eu*, Nb/Ta, Zr/Hf, and T Zr. The moderately altered DP exhibits high concentrations of K, Rb, Cs, LREE, Y, and low Sr/Y, with a positive ɛ Nd (300 Ma), which indicates a mantle or juvenile source associated with an arc setting. The Sr-Nd-Hf isotope data show low I Sr (0.70406-0.70461) and moderate ɛ Nd (300 Ma) (-0.9 to 1.5) for the GD and LG, and relatively high ɛ Hf (300 Ma) values (-3.6 to +11.2) for the GD, suggesting the magma mainly originated from the juvenile lower crust that was derived from depleted mantle, with a minor component of ancient continental crust. Lead isotope data have characteristics of a lower crust source with minor contamination by upper crustal material. Combined with previous research, the Zhunsujihua granitoid intrusions developed in an intracontinental volcanic arc (Uliastai) associated with northward subduction of the Paleo-Asian Ocean plate during late Carboniferous to early Permian; this suggests

Oxidation behavior of U-2wt%Nb, Ti, and Ni alloys in air

International Nuclear Information System (INIS)

Ju, J. S.; Yoo, K. S.; Jo, I. J.; Gug, D. H.; Su, H. S.; Lee, E. P.; Bang, K. S.; Kim, H. D.

2003-01-01

For the long term storage safety study of the metallic spent fuel, U-Nb, U-Ti, U-Ni, U-Zr, and U-Hf simulated metallic uranium alloys, known as corrosion resistant alloys, were fabricated and oxidized in oxygen gas at 200 .deg. C-300 .deg. C. Simulated metallic uranium alloys were more corrosion resistant than pure uranium metal, and corrosion resistance increases Nb, Ni, Ti in that order. The oxidation rates of uranium alloys determined and activation energy was calculated for each alloy. The matrix microstructure of the test specimens were analyzed using OM, SEM, and EPMA. It was concluded that Nb was the best acceptable alloying elements for reducing corrosion of uranium metal considered to suitable as candidate

Nonvolatile ferroelectric memory based on PbTiO3 gated single-layer MoS2 field-effect transistor

Science.gov (United States)

Shin, Hyun Wook; Son, Jong Yeog

2018-01-01

We fabricated ferroelectric non-volatile random access memory (FeRAM) based on a field effect transistor (FET) consisting of a monolayer MoS2 channel and a ferroelectric PbTiO3 (PTO) thin film of gate insulator. An epitaxial PTO thin film was deposited on a Nb-doped SrTiO3 (Nb:STO) substrate via pulsed laser deposition. A monolayer MoS2 sheet was exfoliated from a bulk crystal and transferred to the surface of the PTO/Nb:STO. Structural and surface properties of the PTO thin film were characterized by X-ray diffraction and atomic force microscopy, respectively. Raman spectroscopy analysis was performed to identify the single-layer MoS2 sheet on the PTO/Nb:STO. We obtained mobility value (327 cm2/V·s) of the MoS2 channel at room temperature. The MoS2-PTO FeRAM FET showed a wide memory window with 17 kΩ of resistance variation which was attributed to high remnant polarization of the epitaxially grown PTO thin film. According to the fatigue resistance test for the FeRAM FET, however, the resistance states gradually varied during the switching cycles of 109. [Figure not available: see fulltext.

Effect of Nb aggregates on Zr2Fe

International Nuclear Information System (INIS)

Ramos, Cinthia P.

2001-01-01

The binary Zr-Fe phase diagram revision, performed by Arias et al., accepted the intermetallic Zr 2 Fe crystalline structure as tetragonal and determined that the presence of a third element like oxygen, nitrogen or carbon, stabilizes a cubic phase. Nevitt et al. studying Ti, Zr and Hf alloys with transition metals as second or third element and ternary systems with oxygen as third element, systematized the occurrence of phases with a cubic Ti 2 Ni type crystalline structure. From previous studies in the Zr-Nb-Fe system, it is an agreed fact that Nb presence in the Zr 2 Fe intermetallic stabilizes a cubic Ti 2 Ni type phase. The purpose of the present work is to determine the stability range of the Zr 2 Fe intermetallic with Nb contents, the existence range of the ternary cubic Ti 2 Ni type phase (designated Λ) and the corresponding two-phase region. We analyze as cast and heat treated (800 C degrees) Zr-Nb-Fe alloys with 35 atomic % Fe and Nb contents between 0.5 and 15 atomic %. The determination and characterization of the phases is made by optical and scanning electron microscopy, X-ray diffraction microprobe analysis and Moessbauer Spectroscopy. Joining these techniques together it is found, among many other things, that the Zr 2 Fe phase would accept up to around 0.5 atomic % Nb in solution and that the two-phase region Zr 2 Fe+Λ would be stable in the (0.5 - 3.5) Nb atomic % range. It is proposed as well a 800 C degrees section of the ternary (Zr-Nb-Fe) in the studied region. (author) [es

Impact of ambient gases on the mechanism of [Cs8Nb6O19]-promoted nerve-agent decomposition.

Science.gov (United States)

Kaledin, Alexey L; Driscoll, Darren M; Troya, Diego; Collins-Wildman, Daniel L; Hill, Craig L; Morris, John R; Musaev, Djamaladdin G

2018-02-28

The impact of ambient gas molecules (X), NO 2 , CO 2 and SO 2 on the structure, stability and decontamination activity of Cs 8 Nb 6 O 19 polyoxometalate was studied computationally and experimentally. It was found that Cs 8 Nb 6 O 19 absorbs these molecules more strongly than it adsorbs water and Sarin (GB) and that these interactions hinder nerve agent decontamination. The impacts of diamagnetic CO 2 and SO 2 molecules on polyoxoniobate Cs 8 Nb 6 O 19 were fundamentally different from that of NO 2 radical. At ambient temperatures, weak coordination of the first NO 2 radical to Cs 8 Nb 6 O 19 conferred partial radical character on the polyoxoniobate and promoted stronger coordination of the second NO 2 adsorbent to form a stable diamagnetic Cs 8 Nb 6 O 19 /(NO 2 ) 2 species. Moreover, at low temperatures, NO 2 radicals formed stable dinitrogen tetraoxide (N 2 O 4 ) that weakly interacted with Cs 8 Nb 6 O 19 . It was found that both in the absence and presence of ambient gas molecules, GB decontamination by the Cs 8 Nb 6 O 19 species proceeds via general base hydrolysis involving: (a) the adsorption of water and the nerve agent on Cs 8 Nb 6 O 19 /(X), (b) concerted hydrolysis of a water molecule on a basic oxygen atom of the polyoxoniobate and nucleophilic addition of the nascent OH group to the phosphorus center of Sarin, and (c) rapid reorganization of the formed pentacoordinated-phosphorus intermediate, followed by dissociation of either HF or isopropanol and formation of POM-bound isopropyl methyl phosphonic acid (i-MPA) or methyl phosphonofluoridic acid (MPFA), respectively. The presence of the ambient gas molecules increases the energy of the intermediate stationary points relative to the asymptote of the reactants and slightly increases the hydrolysis barrier. These changes closely correlate with the Cs 8 Nb 6 O 19 -X complexation energy. The most energetically stable intermediates of the GB hydrolysis and decontamination reaction were found to be Cs 8 Nb 6 O

Chromatographic purification of neutron capture molybdenum-99 from cross-contaminant radionuclides

International Nuclear Information System (INIS)

Mostafa, M.A.M.

2011-01-01

Technetium-99m is called the work horse, for many reasons, in nuclear medicine diagnostic purposes. It is produced as the β - decay of 99 Mo radionuclide. Molybdenum-99 gel type generators are considered as a suitable alternative of the conventional chromatographic alumina columns loaded with fission molybdenum-99. 99 Mo neutron-capture is cross-contaminated with radionuclides originated from activation of chemical impurities in the Mo target such 60 C0, 65 Zn, 95 Zr, 175 Hf, 181 Hf, 86 Rb, 134 Cs, 141 Ce, 152 Eu, 140 La, 51 Cr, 124 Sb, 46 Sc, 54 Mn, 59 Fe and / or fast neutrons interactions with the stable isotopes of molybdenum such as 92m Nb, 95 Nb and 95 Zr. To prevent contamination of the eluted 99m Tc, successive purification methods were made. After complete dissolution of the irradiated target wrapped with thin Al foil in 5 M NaOH solution, hydrogen peroxide was added to start precipitation of Fe(OH) 3 . The formed Fe (III) minerals allow complete elimination of some radio contaminants from the molybdate solute such as 152 Eu, 140 La, 141 Ce, 45 Mn and 92m Nb in addition to partial elimination of 46 Sc, 60 Co and 59 Fe radionuclides. The remaining supernatant was acidified by concentrated nitric acid to ph 9.5 for precipitation of Al(OH) 3 with complete elimination of radio contaminants such as 95 Zr 175 Hf, 181 Hf, 65 Zn, 124 Sb, 51 Cr, 46 Sc, 60 Co and 59 Fe. 134 Cs and 86 Rb radionuclides were not affected by precipitation of Fe(OH) 3 or Al(OH) 3 . Chromatographic column of potassium nickel hexacyanoferrate (II) (KNHCF) has high affinity towards elimination of 134 Cs and 86 Rb radionuclides. Highly pure molybdate- 99 Mo solution was processed for preparation of zirconium molybdate gel generator with 99m Tc eluate of high radionuclidic, radiochemical and chemical purity suitable for use in medical purposes.

Determination of trace amount of titanium in 2. 5% Nb-Zr alloy by anion exchange separation and sulfo salicylic acid photometry

Energy Technology Data Exchange (ETDEWEB)

Sakai, F; Wachi, I; Tsuji, N; Satoh, Hitoshi [Power Reactor and Nuclear Fuel Development Corp., Tokyo (Japan)

1973-04-01

A trace amount of Ti in 2.5% Nb-Zr alloy can be determined by a combined method of the characteristic anion exchange separation of Ti from Nb and the absorption photometry of Ti with sulfo salicylic acid. The alloy (1g) was dissolved in 5 ml of HF (1 + 1), and 5 ml of HNO/sub 3/ was added to them. The resultant 5M HF - 6M HNO/sub 3/ mixed acid solution was passed into an anion exchange resin column with 10 mm internal diameter and 100 mm high, at the rate of 1 to 2 ml/min. Niobium was adsorbed on to the column, through which Ti passed. The collected passing and washing solutions were converted into H/sub 2/SO/sub 4/ medium by twice successive fuming treatments. The solution was transferred into a volumetric flask of 50 ml, and 10 ml of 10% sulfo salicylic acid in H/sub 2/SO/sub 4/ was added. Diluting to a mark with H/sub 2/SO/sub 4/, the solution was allowed to stand for 15 min. Titanium was then determined by measuring absorption intensity at the wavelength of 410 mm. The influence of coexisting elements on the coloration of Ti and some adsorption conditions of Nb was experimentally investigated by using /sup 95/Nb as a tracer. The experiment revealed that the removal of Nb is essential, and that higher HF concentration and lower HNO/sub 3/ concentration contribute to higher Nb adsorption. A variable rate type cockless column is useful for this routine analysis. The standard deviation and the coefficient of variation of analysis are 1.3 and 4.06% respectively for the concentration level of 32 ppm Ti (NZ-3).

Influence of Annealing on Microstructure and Mechanical Properties of Refractory CoCrMoNbTi0.4 High-Entropy Alloy

Science.gov (United States)

Zhang, Mina; Zhou, Xianglin; Zhu, Wuzhi; Li, Jinghao

2018-04-01

A novel refractory CoCrMoNbTi0.4 high-entropy alloy (HEA) was prepared via vacuum arc melting. After annealing treatment at different temperatures, the microstructure evolution, phase stability, and mechanical properties of the alloy were investigated. The alloy was composed of two primary body-centered cubic structures (BCC1 and BCC2) and a small amount of (Co, Cr)2Nb-type Laves phase under different annealing conditions. The microhardness and compressive strength of the heat-treated alloy was significantly enhanced by the solid-solution strengthening of the BCC phase matrix and newborn Laves phase. Especially, the alloy annealed at 1473 K (1200 °C) achieved the maximum hardness and compressive strength values of 959 ± 2 HV0.5 and 1790 MPa, respectively, owing to the enhanced volume fraction of the dispersed Laves phase. In particular, the HEAs exhibited promising high-temperature mechanical performance, when heated to an elevated temperature of 1473 K (1200 °C), with a compressive fracture strength higher than 580 MPa without fracture at a strain of more than 20 pct. This study suggests that the present refractory HEAs have immense potential for engineering applications as a new class of high-temperature structural materials.

Effect of plastic deformation on the supercooled austenite transformations of the Cr-Mo steel with Nb, Ti and B microadditions

International Nuclear Information System (INIS)

Adamczyk, J.; Opiela, M.

1998-01-01

Effect of plastic deformation at austenizing temperature was investigated on phase transformations, structure and hardness of the supercooled austenite transformation products of the Cr-Mo constructional steel with Nb, Ti and B microadditions. Basing on the analysis of the phase transformation plots of the supercooled undeformed austenite and of the supercooled and plastically deformed one, it was found out that direct cooling of specimens after completing their plastic deformation in the above mentioned conditions, results in significant acceleration of the α→β, and ferritic and pearlitic transformations, and in the decrease of transformation products hardness. These phenomena are of great importance for working out of the thermo-mechanical treatment of products made from the heat-treated microalloyed steel. (author)

Nonequilibrium synthesis of Nb-Al alloys by laser processing

International Nuclear Information System (INIS)

Tewari, S.K.; Mazumder, J.

1993-01-01

The technique of laser surface modification provides a unique means of synthesizing novel nonequilibrium materials in near net shape. Claddings of several NbAl 3 alloys with Ti, B and Hf as a ternary alloy addition were prepared using a CW CO 2 laser. Isothermal oxidation behavior of the clads were examined in air. Oxidation tests at 800, 1,200 and 1,400 C. Alternating layers of alumina and NbAlO 4 were not observed in any of the samples as reported in literature for conventionally processed NbAl 3 oxidized under similar conditions. The parabolic rate constants for all the alloys, except 0 B, were comparable to that for isothermal oxidation of β-NiAl, at 1,200 and 1,400 C in 0.1 atm oxygen, which is a known alumina former. Ternary alloying additions for improved oxidation resistance at 1,400 C accompanied with improved ductility were identified

Glycerol oxidehydration into acrolein and acrylic acid over W/V/Nb bronzes with hexagonal structure

Energy Technology Data Exchange (ETDEWEB)

Basile, F.; Cavani, F.; Chieregato, A. [Bologna Univ. (Italy). Dipt. di Chimica Industriale e dei Materiali; CIRI Energia e Ambiente, Bologna (Italy); Concepcion, P.; Lopez Nieto, J.M.; Soriano, M.D. [Univ. Politecnica de Valencia (Spain). Inst. de Tecnologia Quimica; Liosi, G.; Trevisanut, C. [Bologna Univ. (Italy). Dipt. di Chimica Industriale e dei Materiali

2012-07-01

This paper deals with an investigation of hexagonal W-V-Nb-O and W-V-Mo-O bronzes as catalysts for the one-pot oxidehydration of glycerol into acrylic acid. In a previous work, we reported a study on a bi-component bronze W-V-O that allowed us to obtain a 25% acrylic acid selectivity; in the current work, the incorporation of either Nb or Mo in a tri-component bronze structure allowed us to tune the acid and redox properties of the catalyst, so as to study their influence on the overall reaction scheme. (orig.)

Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

Science.gov (United States)

Qi, Yaping; Ni, Hao; Zheng, Ming; Zeng, Jiali; Jiang, Yucheng; Gao, Ju

2018-05-01

Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K). These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to "light OFF" and "light ON" states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons) could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

Directory of Open Access Journals (Sweden)

Yaping Qi

2018-05-01

Full Text Available Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K. These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to “light OFF” and “light ON” states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

Integrated design of Nb-based superalloys: Ab initio calculations, computational thermodynamics and kinetics, and experimental results

International Nuclear Information System (INIS)

Ghosh, G.; Olson, G.B.

2007-01-01

An optimal integration of modern computational tools and efficient experimentation is presented for the accelerated design of Nb-based superalloys. Integrated within a systems engineering framework, we have used ab initio methods along with alloy theory tools to predict phase stability of solid solutions and intermetallics to accelerate assessment of thermodynamic and kinetic databases enabling comprehensive predictive design of multicomponent multiphase microstructures as dynamic systems. Such an approach is also applicable for the accelerated design and development of other high performance materials. Based on established principles underlying Ni-based superalloys, the central microstructural concept is a precipitation strengthened system in which coherent cubic aluminide phase(s) provide both creep strengthening and a source of Al for Al 2 O 3 passivation enabled by a Nb-based alloy matrix with required ductile-to-brittle transition temperature, atomic transport kinetics and oxygen solubility behaviors. Ultrasoft and PAW pseudopotentials, as implemented in VASP, are used to calculate total energy, density of states and bonding charge densities of aluminides with B2 and L2 1 structures relevant to this research. Characterization of prototype alloys by transmission and analytical electron microscopy demonstrates the precipitation of B2 or L2 1 aluminide in a (Nb) matrix. Employing Thermo-Calc and DICTRA software systems, thermodynamic and kinetic databases are developed for substitutional alloying elements and interstitial oxygen to enhance the diffusivity ratio of Al to O for promotion of Al 2 O 3 passivation. However, the oxidation study of a Nb-Hf-Al alloy, with enhanced solubility of Al in (Nb) than in binary Nb-Al alloys, at 1300 deg. C shows the presence of a mixed oxide layer of NbAlO 4 and HfO 2 exhibiting parabolic growth

Ba3NbAs3O: synthesis, crystal structure, Raman spectroscopy and bonding analysis

International Nuclear Information System (INIS)

Monconduit, L.; Tillard, M.; Favier, F.; Belin, C.

1999-01-01

The crystal structure of Ba 3 NbAs 3 O has been solved by crystal X-ray analysis (CAD-4 automatic diffractometer, Mo Kα radiation). The compound crystallizes in space group Pnma, a=6.724(2), b=11.100(2), c=13.462(3) A, V=1004.7(4) A 3 , Z=4. The structure has been refined to R1=0.0343 for 964 independent reflections, it can be described as packing of nearly tetrahedral NbAs 3 O 6- anions, their coordination by Ba 2+ cations forming interconnected trigonal prisms. The chemical bonding has been analyzed by MO calculations and Raman spectroscopy. (orig.)

Two-dimensional Haeckelite NbS{sub 2}. A diamagnetic high-mobility semiconductor with Nb{sup 4+} ions

Energy Technology Data Exchange (ETDEWEB)

Ma, Yandong; Kuc, Agnieszka; Jing, Yu; Heine, Thomas [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Universitaet Leipzig (Germany); Philipsen, Pier [Scientific Computing and Modelling NV, Amsterdam (Netherlands)

2017-08-14

In all known Group 5 transition-metal dichalcogenide monolayers (MLs), the metal centers carry a spin, and their ground-state phases are either metallic or semiconducting with indirect band gaps. Here, on grounds of first-principles calculations, we report that the Haeckelite polytypes 1S-NbX{sub 2} (X=S, Se, Te) are diamagnetic direct-band-gap semiconductors even though the Nb atoms are in the 4+ oxidation state. In contrast, 1S-VX{sub 2} MLs are antiferromagnetically coupled indirect-band-gap semiconductors. The 1S phases are thermodynamically and dynamically stable but of slightly higher energy than their 1H and 1T ML counterparts. 1S-NbX{sub 2} MLs are excellent candidates for optoelectronic applications owing to their small band gaps (between 0.5 and 1 eV). Moreover, 1S-NbS{sub 2} shows a particularly high hole mobility of 2.68 x 10{sup 3} cm{sup 2} V{sup -1} s{sup -1}, which is significantly higher than that of MoS{sub 2} and comparable to that of WSe{sub 2}. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Nanoporous niobium nitride (Nb2N) with enhanced electrocatalytic performance for hydrogen evolution

Science.gov (United States)

Li, Yan; Zhang, Jianli; Qian, Xingyue; Zhang, Yue; Wang, Yining; Hu, Rudan; Yao, Chao; Zhu, Junwu

2018-01-01

The transition metal nitrides (TMNs) with nanoporous structure have shown great promise as potential electrocatalysts for the hydrogen evolution reaction (HER). Herein, self-organized nanoporous Nb2N was first successfully synthesized through the anodization of niobium in mixed oxalic acid/HF electrolyte, followed by a simple annealing treatment in the ammonia atmosphere. Due to the highly ordered nanoporous structure with abundant active sites and the enhanced electrical conductivity, the Nb2N exhibits a high catalytic current (326.3 mA cm-2) and low onset potential (96.3 mV), which is almost 3.9 times and 4.2 times better than that of Nb2O5, respectively. Meanwhile, the Nb2N also presents low Tafel slope (92 mV dec-1), and excellent cycling durability. More importantly, this study will provide more opportunities for designing and fabricating niobium compounds as an innovative HER catalysts.

Highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf

Energy Technology Data Exchange (ETDEWEB)

Kim, Jeong-Jae; Byeon, In-Seop [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, & Research Center for Oral Disease Regulation of the Aged, College of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative Sciences and Prosthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, & Research Center for Oral Disease Regulation of the Aged, College of Dentistry, Chosun University, Gwangju (Korea, Republic of)

2015-12-01

The purpose of this study was to investigate the highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf, examining the roles of niobium, zirconium, tantalum and hafnium alloying elements. The Ti–25Nb–xZr and Ti–25Ta–xHf ternary alloys contained 0, 7 and 15 wt.% of these alloying elements and were manufactured using a vacuum arc-melting furnace. Cast ingots of the alloys were homogenized in Ar atmosphere at 1050 °C for 2 h, followed by quenching into ice water. Formation of nanotubular films was achieved by an electrochemical method in 1 M H{sub 3}PO{sub 4} + 0.8 wt.% NaF at 30 V and 1 h for the Ti–25Nb–xZr alloys and 2 h for the Ti–25Ta–xHf alloys. Microstructures of the Ti–25Ta–xHf alloys transformed from α″ phase to β phase, changing from a needle-like structure to an equiaxed structure as the Hf content increased. In a similar manner, the needle-like structure of the Ti–25Nb–xZr alloys transformed to an equiaxed structure as the Zr content increased. Highly ordered nanotubes formed on the Ti–25Ta–15Hf and Ti–25Nb–15Zr alloys compared to the other alloys, and the nanotube layer thickness on Ti–25Ta–15Hf and Ti–25Nb–15Zr was greater than for the other alloys. Nanotubes formed on Ti–25Ta–15Hf and Ti–25Nb–15Zr showed two sizes of highly ordered structures. The diameters of the large nanotubes decreased and the diameters of the small nanotubes increased as Zr and Hf contents increased. It was found that the layer thickness, diameter, surface density and growth rate of nanotubes on the Ti–25Ta–xHf and Ti–25Nb–xZr alloys can be controlled by varying the Hf and Zr contents. X-ray diffraction analyses revealed only weak peaks for crystalline anatase or rutile TiO{sub 2} phases from the nanotubes on the Ti–25Nb–xZr and Ti–25Ta–xHf alloys, indicating a largely amorphous condition. - Highlights: • Nanotubular film formation on anodized Ti-25Nb-xZr and Ti-25Ta-xHf (x = 0, 7 and

Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10 alloys

Directory of Open Access Journals (Sweden)

Rzącki Jakub

2015-03-01

Full Text Available As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confirmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one.

Excitation function and isomeric ratio of Tc-isotopes from the 93Nb(α, xn) reaction

International Nuclear Information System (INIS)

Kim, K.; Kim, G.N.; Naik, H.; Zaman, M.; Yang, S.-C.; Song, T.-Y.; Guin, R.; Das, S.K.

2015-01-01

The excitation functions of 94–96 Tc isotopes and independent isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc from the 93 Nb(α, xn) reaction within the energy range below 40 MeV have been determined by using a stacked-foil activation and an off-line γ-ray spectrometric technique at the Variable Energy Cyclotron Center, Kolkota, India. The excitation function of 94–96 Tc in the 93 Nb(α, xn) reaction was also calculated by using the computer code TALYS 1.6. The present data are found to be in general agreement with the literature data but have similar trend with some deviation from calculated data of the TALYS 1.6 code. The isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc in the 93 Nb(α, xn) reactions from the present work and literature data were compared with similar data in the 93 Nb( 3 He, xn) and 96 Mo(p, xn) reactions. In all the three reactions, the isomeric ratios increase with the increasing excitation energy. However, at all excitation energies, the isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc in the 93 Nb(α, xn) and 93 Nb( 3 He, xn) reactions are higher than those in the 96 Mo(p, xn) reactions, which indicate the role of input angular momentum besides excitation energy. Above the excitation energy of 35–55 MeV, the isomeric ratios of 95m, g Tc, 94m, g Tc, and 93m, g Tc decrease in all the 93 Nb(α, xn), 93 Nb( 3 He, xn) and 96 Mo(p, xn) reactions. This decreasing trend at higher excitation energy indicates the starting of pre-equilibrium reaction, which depends on the target, projectile, and type of reaction products

Evidence for Slab Melt Contributions to the Mexican Volcanic Belt and Other Young Hot Slab Arcs from Lu-Hf Isotopes

Science.gov (United States)

Goldstein, S. L.; Cai, Y. M.; Langmuir, C. H.; Lagatta, A.; Straub, S. M.; Gomez-Tuena, A.; Martin Del Pozzo, A.

2007-12-01

Despite major advances in delineating the processes that govern magma generation at convergent margins, the problem persists of distinguishing slab, mantle wedge, and crustal contributions. A corrollary question is whether there is significant melting of subducted ocean crust. Especially in thick crust regions, the importance of crustal versus mantle contributions to lavas represents a long-standing fundamental issue in arc magma geochemistry. We show that frontal arc magmas from the Central Mexican Volcanic Belt (CMVB), including the large andesitic stratovolcanoes Popocatepetl and Nevado de Toluca, display negligible crustal contamination, and contain substantial contributions from melting of subducted Pacific ocean crust. Despite ca. 50 km thick continental crust, the CMVB erupts near primitive lavas including "high-Nb" alkaline basalts that show negligible "subduction signatures" in their trace element patterns. These "high-Nb" basalts define the regional mantle wedge composition in isotope-trace element space. The "normal" calcalkaline lavas form a negative correlation between Hf isotopes and Lu/Hf. One endmember is like the high Nb basalts representing the regional mantle wedge. The other endmember has higher Hf isotopes (approaching values of Pacific MORB) and very low Lu/Hf of less than 0.04 (e.g. compared to typical values of ca. 0.2 in Pacific MORB). The low Lu/Hf values require low degree partial melting of a source rich in garnet. The high Hf isotopes require a depleted mantle source with isotopes like Pacific MORB. Together the Lu-Hf data indicate a substantial component derived from melting of eclogitic Pacific ocean crust. A key feature of the data is that the stratovolcano lavas showing the largest slab melt signature also show the highest Hf isotope ratios and thus are more "depleted mantle-like" than the regional mantle wedge. Thus, the integrated data allow us to clearly distinguish between mantle and crustal sources in the CMVB and point to

Mechanical and electronic properties of Janus monolayer transition metal dichalcogenides

Science.gov (United States)

Shi, Wenwu; Wang, Zhiguo

2018-05-01

The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y  =  S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16–1.91 and 0.94–1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M  =  Ti, Zr and Hf). The monolayers MXY (M  =  V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M  =  Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m‑1. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.

Investigation of the generation of several long-lived radionuclides of importance in fusion reactor technology: Report on a Coordinated Research Program sponsored by the International Atomic Energy Agency

International Nuclear Information System (INIS)

Smith, D.L.; Pashchenko, A.B.

1994-01-01

The IAEA initiated a Coordinated Research Program (CRP) in 1988 to obtain reliable information for 16 long-lived activation reactions of special importance to fusion reactor technology: 27 Al (n, 2n) 26 Al, 63 Cu(n,p) 63 Ni, 94 Mo(n,p) 94 Nb, 109 Ag(n,2n) 108m Ag, 179 Hf(n,2n) 178m2 Hf, 182 W(n,n ' a) 178m2 Hf, 151 Eu(n,2n) 150 gEu, 153 Eu(n,2n) 152+m2 Eu, 159 Tb(n, 2n) 158 Tb, 158 Dy(n,p) 158 Tb, 193 Ir(n,2n) 192m2 Ir, 187 Re(n,2n) 186m Re, 62 Ni(nγ) 63 Ni, 98 Mo(n,γ) 99 Mo(β-) 99 Tc, 165 Ho(n,γ) 166m Ho and 191 Ir(n,γ) 192m2 Ir. this paper documents progress achieved from the start of the program through mid- 1993

Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

Science.gov (United States)

Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

2002-01-01

Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

Effect of Dielectric Interface on the Performance of MoS2 Transistors.

Science.gov (United States)

Li, Xuefei; Xiong, Xiong; Li, Tiaoyang; Li, Sichao; Zhang, Zhenfeng; Wu, Yanqing

2017-12-27

Because of their wide bandgap and ultrathin body properties, two-dimensional materials are currently being pursued for next-generation electronic and optoelectronic applications. Although there have been increasing numbers of studies on improving the performance of MoS 2 field-effect transistors (FETs) using various methods, the dielectric interface, which plays a decisive role in determining the mobility, interface traps, and thermal transport of MoS 2 FETs, has not been well explored and understood. In this article, we present a comprehensive experimental study on the effect of high-k dielectrics on the performance of few-layer MoS 2 FETs from 300 to 4.3 K. Results show that Al 2 O 3 /HfO 2 could boost the mobility and drain current. Meanwhile, MoS 2 transistors with Al 2 O 3 /HfO 2 demonstrate a 2× reduction in oxide trap density compared to that of the devices with the conventional SiO 2 substrate. Also, we observe a negative differential resistance effect on the device with 1 μm-channel length when using conventional SiO 2 as the gate dielectric due to self-heating, and this is effectively eliminated by using the Al 2 O 3 /HfO 2 gate dielectric. This dielectric engineering provides a highly viable route to realizing high-performance transition metal dichalcogenide-based FETs.

High-performance liquid ion-pair chromatography in inorganic analysis

International Nuclear Information System (INIS)

Alimarin, I.P.; Basova, E.M.; Bol'shova, T.A.; Ivanov, V.M.

1990-01-01

In literature review for the recent 15 years theoretical foundations, regularities and mechanisms of ionized compound retention in reverse-phase ion-pair chromatography are considered, possibilities and prospects of its application in inorganic analysis being demonstrated. Analytic characteristics of the methods for the determination of inorganic anions (I - , IO 3 - , MoO 4 2- , etc.), as well as metals (Zr, Hf, V, Nb, Mo, W, Ru, lanthanides, etc.) in the form of chelates, are given

Effect of Nb Addition to Ti-Bearing Super Martensitic Stainless Steel on Control of Austenite Grain Size and Strengthening

Science.gov (United States)

Ma, Xiaoping; Langelier, Brian; Gault, Baptiste; Subramanian, Sundaresa

2017-05-01

The role of Nb in normalized and tempered Ti-bearing 13Cr5Ni2Mo super martensitic stainless steel is investigated through in-depth characterization of the bimodal chemistry and size of Nb-rich precipitates/atomic clusters and Nb in solid solution. Transmission electron microscopy and atom probe tomography are used to analyze the samples and clarify precipitates/atom cluster interactions with dislocations and austenite grain boundaries. The effect of 0.1 wt pct Nb addition on the promotion of (Ti, Nb)N-Nb(C,N) composite precipitates, as well as the retention of Nb in solution after cooling to room temperature, are analyzed quantitatively. (Ti, Nb)N-Nb(C,N) composite precipitates with average diameters of approximately 24 ± 8 nm resulting from epitaxial growth of Nb(C,N) on pre-existing (Ti,Nb)N particles, with inter-particle spacing on the order of 205 ± 68 nm, are found to be associated with mean austenite grain size of 28 ± 10 µm in the sample normalized at 1323 K (1050 °C). The calculated Zener limiting austenite grain size of 38 ± 13 µm is in agreement with the experimentally observed austenite grain size distribution. 0.08 wt pct Nb is retained in the as-normalized condition, which is able to promote Nb(C, N) atomic clusters at dislocations during tempering at 873 K (600 °C) for 2 hours, and increases the yield strength by 160 MPa, which is predicted to be close to maximum increase in strengthening effect. Retention of solute Nb before tempering also leads to it preferentially combing with C and N to form Nb(C, N) atom clusters, which suppresses the occurrence of Cr- and Mo-rich carbides during tempering.

Precipitation Kinetics in a Nb-stabilized Ferritic Stainless Steel

Science.gov (United States)

Labonne, M.; Graux, A.; Cazottes, S.; Danoix, F.; Cuvilly, F.; Chassagne, F.; Perez, M.; Massardier, V.

2017-08-01

The precipitation occurring in a Nb-stabilized ferritic stainless steel, containing initially Nb(C, N) carbonitrides and Fe3Nb3X precipitates, was investigated during aging treatments performed between 923 K and 1163 K (650 °C and 890 °C) by combining different techniques, (thermoelectric power (TEP), scanning/transmission electron microscopy (SEM/TEM), and atom probe tomography (APT)), in order to determine the precipitation kinetics, the nature and morphology of the newly formed precipitates as well as the chemistry of the initial Fe3Nb3X precipitates, where X stands for C or N. The following composition was proposed for these precipitates: (Fe0.81 Cr0.19)3 (Nb0.85 Si0.08 Mo0.07)3 (N0.8 C0.2), highlighting the simultaneous presence of N and C in the precipitates. With regard to the precipitation in the investigated temperature range, two main phenomena, associated with a hardness decrease, were clearly identified: (i) the precipitation of Fe2Nb precipitates from the niobium initially present in solution or coming from the progressive dissolution of the Fe3Nb3X precipitates and (ii) the precipitation of the χ-phase at grain boundaries for longer aging times. From the TEP kinetics, a time-temperature-precipitation diagram has been proposed.

Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

International Nuclear Information System (INIS)

Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S.V.

2015-01-01

Highlights: • Microstructural development during laser cladding has been studied. • In this multi component system Cr 7 C 3 is found to be the stable carbide phase. • Phases were identified by EBSD since XRD results were not conclusive. • Increase in laser power and/or scanning speed reduced the carbide content. • Hardness seems to depend on phase content as well as microstructure. - Abstract: Microstructural development in laser clad layers of Chromium carbide (Cr x C y )-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr 3 C 2 and Cr 7 C 3 , the clad layers showed only the presence of Cr 7 C 3 . Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr 7 C 3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr 7 C 3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ 2 ) of the Cr 7 C 3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

Density of thermal vacancies in γ-Ti-Al-M, M = Si, Cr, Nb, Mo, Ta or W

International Nuclear Information System (INIS)

Woodward, C.; Kajihara, S.

1999-01-01

Modifications to alloy chemistry are often used to tailor the intrinsic flow behavior of structural materials. Models of creep in intermetallic alloys must account for the influence of chemistry on the available intrinsic creep mechanisms. As in simple metals the presence of vacancies strongly influences bulk diffusion processes in these materials. Limiting the density of constitutional and thermal vacancies by alloying may produce materials with enhanced creep properties. The energy of intrinsic and substitutional point defects in L1 0 TiAl is calculated within a first principles, local density functional theory framework. Relaxed structures and energies for vacancies, antisites and solid solutions are calculated using a plane-wave-pseudopotential method. Calculated defect energies are used within a canonical ensemble formalism to estimate the point defect densities as a function of temperature and composition. The density of vacancies is found to be sensitive to the underlying stoichiometry of TiAl. The dependence of the vacancy concentration for solid solutions of Si, Cr, Nb, Mo, Ta and W is also predicted

Substitution-induced near phase transition with Maxwell-Wagner polarization in SrBi{sub 2}(Nb{sub 1-x}A{sub x}){sub 2}O{sub 9} ceramics [A = W, Mo and x = 0, 0.025

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Prasun; Franco, Adolfo Jr. [Instituto de Fisica, Universidade Federal de Goias, Goiania (Brazil)

2017-10-15

The synthesis, micro-structure, spectroscopic, and dielectric properties of SrBi{sub 2}(Nb{sub 1-x}A{sub x}){sub 2}O{sub 9} [with A=W, Mo and x = 0, 0.025] ceramics were systematically studied. A relative density of ≥98% was obtained for all the samples using a two-step solid state sintering process. XRD images showed that a single phase layered perovskite structure of SrBi{sub 2}Nb{sub 2}O{sub 9} (SBN) was formed. The orthorhombic structure with A2{sub 1}am phase group was found up to ∝2.5 at.% substitution of W and Mo into the SBN matrix. SEM revealed the rod-like grain structure similar to the Maxwell-Wagner (MW) parallel plate capacitor model in SBN ceramic, whereas smaller heterogeneous grain structure was observed in W and Mo donor doped ceramics. The initial high value of real and imaginary part of relative permittivity also indicated the presence of interfacial MW relaxation in the SBN ceramics. The experimental data fit well to the theoretical data obtained from MW polarization model in SBN ceramics. The possible origin of the difference of the properties present in the doped sample has been explained based on grain size, orientation, and modification done in the ceramic matrices. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Obtainment of tantalum oxide from national ores

International Nuclear Information System (INIS)

Pinatti, D.G.; Ribeiro, S.; Martins, A.H.

1988-01-01

The experimental results of tantalum oxides (Ta 2 O 5 ) obtainment from Brazilian ores of tantalite and columbite are described. This study is a part of the technologic and scientific research design of refractory metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W) and correlate ceramics. (C.G.C.) [pt

Na2MoO2As2O7

Directory of Open Access Journals (Sweden)

Raja Jouini

2012-12-01

Full Text Available Disodium molybdenum dioxide diarsenate, Na2MoO2As2O7, has been synthesized by a solid-state reaction. The structure is built up from MoAs2O12 linear units sharing corners to form a three-dimensional framework containing tunnels running along the a-axis direction in which the Na+ cations are located. In this framework, the AsV atoms are tetrahedrally coordinated and form an As2O7 group. The MoVI atom is displaced from the center of an octahedron of O atoms. Two Na+ cations are disordered about inversion centres. Structural relationships between different compounds: A2MoO2As2O7 (A = K, Rb, AMOP2O7 (A = Na, K, Rb; M = Mo, Nb and MoP2O7 are discussed.

TbNb6Sn6: the first ternary compound from the rare earth–niobium–tin system

Directory of Open Access Journals (Sweden)

Viktor Hlukhyy

2010-12-01

Full Text Available The title compound, terbium hexaniobium hexastannide, TbNb6Sn6, is the first ternary compound from the rare earth–niobium–tin system. It has the HfFe6Ge6 structure type, which can be analysed as an intergrowth of the Zr4Al3 and CaCu5 structures. All the atoms lie on special positions; their coordination geometries and site symmetries are: Tb (dodecahedron 6/mmm; Nb (distorted icosahedron 2mm; Sn (Frank–Caspar polyhedron, CN = 14–15 6mm and overline{6}m2; Sn (distorted icosahedron overline{6}m2. The structure contains a graphite-type Sn network, Kagome nets of Nb atoms, and Tb atoms alternating with Sn2 dumbbells in the channels.

2,3,4-Trihydroxyflourones immobilized on cellulose matrices in test methods for determining rare elements

International Nuclear Information System (INIS)

Amelin, V.G.; Abramenkova, O.I.

2008-01-01

It was shown that 2,3,7-trihydroxyfluorones immobilized by adsorption on cellulose matrices can be used as reagents for the test determination of Mo(Vl), Ti(lV), Ge(lV), Hf(lV), Nb(V), Ta(V), W(VI), Bi(III), V(IV), and Zr(IV). The change of the protolytic and complexing properties of trihydroxyfluorones immobilized on cellulose matrices was considered in comparison to corresponding properties in a solution. It was found that the reactions of trihydroxyfluorones with rare elements on cellulose matrices and in a solution exhibit similar effects upon the addition of cetylpyridinium. These effects are the bathochromic shift of the absorption maxima of the reagents and their complexes with analytes and the extension of the range of optimum acidity for complex formation. The complexation of salicylfluorones with the titanium(IV) in solution and on cellulose paper was studied by IR spectrometry. Phenylfluorone immobilized on a mixed-fiber cloth as used in test determinations of (mg/L) 0.05-5 Ti(IV), V(IV), Hf(IV), Nb(V), and Mo(VI); 0.01-5 Ge(IV) and Zr(IV); 0.05-1 Bi(III) and W(VI); and 0.1-5 Ta(V) by the color intensity of the indicator matrix after passing through 20 mL of a analyzable solution. It was shown that phenylfluorone immobilized on cellulose paper can be used to determine (mg/L) 0.05-50 Ti(IV), 0.5-1000 Ge(IV), 0.5-500 Zr(IV), 5-200 Bi(III), 0.1-50 Mo(VI), 0.1-1000 V(IV), 0.1-100 Nb(V), 0.1-800 Hf(IV), 1-100 Ta(V), and 1-800 W(VI) by the length of the colored zone of a test strip after it was brought into contact with a test solution [ru

Metal Oxide-Supported Platinum Overlayers as Proton-Exchange Membrane Fuel Cell Cathodes

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Abild-Pedersen, Frank; Studt, Felix

2012-01-01

We investigated the activity and stability of n=(1, 2, 3) platinum layers supported on a number of rutile metal oxides (MO2; M=Ti, Sn, Ta, Nb, Hf and Zr). A suitable oxide support can alleviate the problem of carbon corrosion and platinum dissolution in Pt/C catalysts. Moreover, it can increase t...

Evidence for Nb-Ta Occurrences in the Syn-Tectonic Pan-African Mayo Salah Leucogranite (Northern Cameroon: Constraints from Nb-Ta Oxide Mineralogy, Geochemistry and U-Pb LA-ICP-MS Geochronology on Columbite and Monazite

Directory of Open Access Journals (Sweden)

Periclex Martial Fosso Tchunte

2018-04-01

Full Text Available The Mayo Salah pluton, which is located in the North-Cameroon domain of Central African Bold Belt (CAFB, is emplaced as a laccolith in volcano-sedimentary schists of Poli series, and displays features of Rare-metal Granite (RMG. It is made of two main rock groups: (1 the metaluminous barren muscovite granite (MsG and (2 the Nb-Ta bearing peraluminous leucogranite (MsL which expresses four subtypes. The evolved Rare-element MsL is subalkaline, slightly peraluminous (ASI = 1.01–1.21, and it displays flat REE chondrite-normalized patterns with a strong negative Eu anomaly (Eu/Eu* = 0.02–0.20. It belongs to the peraluminous low phosphorus Rare-element Granites and L-type igneous rocks, as shown by the relatively low Zr/Hf (4.8–14 and Nb/Ta (1.4–9.0 ratios and the positive slope of the Zr-Hf-Nb-Ta profile in spider diagrams. The rare-element-bearing mineral is represented by columbite-group minerals (CGM and other Nb-Ta-oxides (Nb-rutile and pyrochlore supergroup minerals. The CGM is classified as Mn-columbite, with Ta# and Mn# ratios increasing from core to rim. Two stages of mineralization are identified; the earliest stage (CGM-I consists in scattered tabular or prismatic euhedral grains that were related to magmatic fractionation. The latest stage (CGM-II is expressed as a Ta-rich Mn hydrothermal CGM episode represented as rims and/overgrowths around and/or as veinlet crosscutting CGM-I or in cleavage planes of muscovite. The U-Pb dating of columbite and monazite of the Mayo Salah leucogranite indicates a late-Neoproterozoic magmatic-hydrothermal mineralization event from 603.2 ± 5.3 to 581.6 ± 7.2 Ma, as consistent with both late D2 to D3 events that were recorded in the CAFB in Cameroon, and the associated continental collision environment. The Nb-Ta mineralization of the Mayo Salah pluton provides evidence for the presence of RMG in Northern Cameroon of CAFB, and its temporal association with the youngest period of metallogenic epoch

Photocatalytic activity of TiO2/Nb2O5/PANI and TiO2/Nb2O5/RGO as new nanocomposites for degradation of organic pollutants.

Science.gov (United States)

Zarrin, Saviz; Heshmatpour, Felora

2018-06-05

In this study, highly active titanium dioxide modified by niobium oxide (Nb 2 O 5 ), polymer (PANI) and reduced graphene oxide (RGO) were successfully prepared. The morphology, structure, surface area and light absorption properties of the present nanocomposites for removal of methylene blue (MB) and methyl orange (MO) were investigated and compared with those of TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. The characterization techniques such as XRD, FT-IR, UV-vis, SEM, EDX, BET and TEM were employed in order to identify the nanocomposites. Also, photocatalytic properties of TiO 2 /Nb 2 O 5 /PANI and TiO 2 /Nb 2 O 5 /RGO nanocomposites under visible light irradiation were studied. In this way, the obtained results were compared to each other and also compared to TiO 2 /Nb 2 O 5 and TiO 2 nanoparticles. In this context, the chemical oxygen demand (COD) removal follows the photodegradation in observed performance. The results indicate that reduced TiO 2 /Nb 2 O 5 nanocomposite is effectively modified by graphene oxide to give TiO 2 /Nb 2 O 5 /RGO composite. The TiO 2 /Nb 2 O 5 /RGO exhibits significantly higher photocatalytic activity in degradation of organic dyes under visible light rather than that of TiO 2 /Nb 2 O 5 /PANI, TiO 2 /Nb 2 O 5 and pure TiO 2 . Copyright © 2018 Elsevier B.V. All rights reserved.

Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

Energy Technology Data Exchange (ETDEWEB)

Venkatesh, L., E-mail: venkatesh@arci.res.in [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India); Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Samajdar, I. [Department of Metallurgical Engineering & Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Tak, Manish [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India); Doherty, Roger D. [Department of Materials Engineering, Drexel University, Philadelphia, PA 19104 (United States); Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S.V. [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur, Hyderabad 500005 (India)

2015-12-01

Highlights: • Microstructural development during laser cladding has been studied. • In this multi component system Cr{sub 7}C{sub 3} is found to be the stable carbide phase. • Phases were identified by EBSD since XRD results were not conclusive. • Increase in laser power and/or scanning speed reduced the carbide content. • Hardness seems to depend on phase content as well as microstructure. - Abstract: Microstructural development in laser clad layers of Chromium carbide (Cr{sub x}C{sub y})-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr{sub 3}C{sub 2} and Cr{sub 7}C{sub 3}, the clad layers showed only the presence of Cr{sub 7}C{sub 3}. Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr{sub 7}C{sub 3} with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr{sub 7}C{sub 3} is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ{sub 2}) of the Cr{sub 7}C{sub 3} dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

Interference-free determination of sub ng kg-1 levels of long-lived 93Zr in the presence of high concentrations (μg kg-1) of 93Mo and 93Nb using ICP-MS/MS.

Science.gov (United States)

Petrov, Panayot; Russell, Ben; Douglas, David N; Goenaga-Infante, Heidi

2018-01-01

Long-lived high abundance radionuclides are of increasing interest with regard to decommissioning of nuclear sites and longer term nuclear waste storage and disposal. In many cases, no routine technique is available for their measurement in nuclear waste and low-level (ng kg -1 ) environmental samples. Recent advances in ICP-MS technology offer attractive features for the selective and sensitive determination of a wide range of long-lived radionuclides. In this work, inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS)-based methodology, suitable for accurate routine determinations of 93 Zr at very low (ng kg -1 ) levels in the presence of high levels (μg kg -1 ) of the isobaric interferents 93 Nb and 93 Mo (often present in nuclear waste samples), is reported for the first time. Additionally, a novel and systematic strategy for method development based on the use of non-radioactive isotopes is proposed. It relies on gas-phase chemical reactions for different molecular ion formation to achieve isobaric interference removal. Using cell gas mixtures of NH 3 /He/H 2 or H 2 /O 2 , and suitable mass shifts, the signal from the 93 Nb and 93 Mo isobaric interferences on 93 Zr were suppressed by up to 5 orders of magnitude. The achieved limit of detection for 93 Zr was 1.3 × 10 -5  Bq g -1 (equivalent to 0.14 ng kg -1 ). The sample analysis time is 2 min, which represents a significant improvement in terms of sample throughput, compared to liquid scintillation counting methods. The method described here can be used for routine measurements of 93 Zr at environmentally relevant levels. It can also be combined with radiometric techniques for use towards the standardisation of 93 Zr measurements. Graphical abstract Interference-free determination of 93 Zr in the presence of high concentrations of isobaric 93 Mo and 93 Nb by ICP-MS/MS.

First- and second-chance proton emission in the interactions of fast neutrons with 92Mo

International Nuclear Information System (INIS)

Qaim, S.M.; Wolfle, R.; Strohmaier, B.

1989-01-01

Cross sections were measured radiochemically for the 92 Mo(n,p) 92 Nb m and 92 Mo(n,n'p +pn+d) 91 Nb m reactions over the neutron energy range of 9.0--10.6 MeV, and for the latter reaction also between 12.6 and 14.4 MeV. Use was made of high-resolution γ-ray and x-ray spectroscopy. Statistical-model calculations taking into account precompound effects were performed for fast neutron induced reactions on 92 Mo. The calculational results agree well with the experimental data on emitted proton spectra as well as on the excitation functions of various reaction channels. The second-chance proton emission is significant for incident neutron energies above 11 MeV; between 13 and 14 MeV it is comparable to the first-chance proton emission

Thermal analysis of precipitation reactions in a Ti-25Nb-3Mo-3Zr-2Sn alloy

International Nuclear Information System (INIS)

Kent, Damon; Wang, Gui; Dargusch, Matthew S.; Pas, Steven; Zhu, Suming

2012-01-01

A study was undertaken on a Ti-25Nb-3Mo-3Zr-2Sn alloy using differential scanning calorimetry (DSC) in order to improve understanding of the precipitation reactions occurring during aging heat treatments. The investigation showed that isothermal ω phase can be formed in the cast and solution treated alloy at low aging temperatures. An exothermic peak in the temperature range of 300 to 400 C was detected for precipitation of the ω phase, with approximate activation energy of 176 kJ/mol. The ω phase begins to dissolve at temperatures around 400 C and precipitation of the α phase is favoured at higher temperatures between 400 C and 600 C. An exothermic peak with activation energy of 197 kJ/mol was measured for precipitation of the α phase. Deformation resulting in the formation of the stress induced α'' phase altered the DSC heating profile for the solution treated alloy. The exothermic peak associated with precipitation of the ω phase was not detected during heating of the deformed material and increased endothermic heating associated with recovery and recrystallisation was observed. (orig.)

Effects of cold-working on pinning behaviour and critical current densities in NbTi-based superconductors

International Nuclear Information System (INIS)

Yamada, Y.; Murase, S.; Wada, H.; Tachikawa, K.

1985-01-01

The effects of cold-working on high-field pinning behaviour at 1.8 K and 4.2 K have been studied for multifilamentary NbTi, NbTiHf and NbTiTa superconductors, which were subjected to cold-working, heat treatment and cold-working, in sequence. It is found that the cold-working, either before or after heat treatment, shifts the peak in pinning force density to a higher field, while the maximum pinning force value is first increased with increasing amount of cold-working, and then decreased. This result can not be predicted by existing pinning theories, and we conclude that for pinning behaviour induced by cold-working, not only the introduction of pinning centres but also their size and spacing must be taken into account. (author)

Thermo-mechanical treatment of the Cr-Mo constructional steel plates with Nb, Ti and B additions

International Nuclear Information System (INIS)

Adamczyk, J.; Opiela, M.

2002-01-01

Results of investigations of the influence of parameters of thermomechanical treatment, carried out by rolling with controlled recrystallization, on the microstructure and mechanical properties of Cr-Mo constructional steel with Nb, Ti and B microadditions, destined for the manufacturing of weldable heavy plates, are presented. These plates show a yield point of over 960 MPa after heat treatment. Two variants of thermomechanical treatment were worked out, based on the obtained results of investigations, when rolling a plate 40 mm thick in several passes to a plate 15 mm thick in a temperature range from 1100 to 900 o C. It was found that the lack of complete recrystallization of the austenite in the first rolling variant, leads to localization of plastic deformation in form of shear bands. There exists a segregation of MC-type carbides and alloying elements in these bands, causing a distinctive reduction of the crack resistance of the steel, as also a disadvantageous anisotropy of plastic properties of plate after tempering. For plates rolled under the same conditions, using a retention shield, a nearly three times higher impact energy in - 40 o C was obtained, as also only a slight anisotropy of plastic properties, saving the required mechanical properties. (author)

Improved Mo-Re VPS Alloys for High-Temperature Uses

Science.gov (United States)

Hickman, Robert; Martin, James; McKechnie, Timothy; O'Dell, John Scott

2011-01-01

Dispersion-strengthened molybdenum- rhenium alloys for vacuum plasma spraying (VPS) fabrication of high-temperature-resistant components are undergoing development. In comparison with otherwise equivalent non-dispersion-strengthened Mo-Re alloys, these alloys have improved high-temperature properties. Examples of VPS-fabricated high-temperature-resistant components for which these alloys are expected to be suitable include parts of aircraft and spacecraft engines, furnaces, and nuclear power plants; wear coatings; sputtering targets; x-ray targets; heat pipes in which liquid metals are used as working fluids; and heat exchangers in general. These alloys could also be useful as coating materials in some biomedical applications. The alloys consist of 60 weight percent Mo with 40 weight percent Re made from (1) blends of elemental Mo and Re powders or (2) Re-coated Mo particles that have been subjected to a proprietary powder-alloying-and-spheroidization process. For most of the dispersion- strengthening experiments performed thus far in this development effort, 0.4 volume percent of transition-metal ceramic dispersoids were mixed into the feedstock powders. For one experiment, the proportion of dispersoid was 1 volume percent. In each case, the dispersoid consisted of either ZrN particles having sizes <45 m, ZrO2 particles having sizes of about 1 m, HfO2 particles having sizes <45 m, or HfN particles having sizes <1 m. These materials were chosen for evaluation on the basis of previously published thermodynamic stability data. For comparison, Mo-Re feedstock powders without dispersoids were also prepared.

Study of the 93Mo nucleus

International Nuclear Information System (INIS)

Mittal, V.K.; Avasthi, D.K.; Kumar, A; Govil, I.M.

1981-01-01

The level structure of 93 Mo has been studied through 93 Nb(p,nγ) reaction at incident proton energy of 4.2 MeV. Spin assignments and multipole mixing ratios for various levels and transitions have been deduced from the analysis of angular distributions of singles γ-ray spectra. Lifetimes of various levels have been obtained using Doppler Shift Attenuation (DSA) method. (author)

High-energy neutron irradiation of superconducting compounds

International Nuclear Information System (INIS)

Sweedler, A.R.; Snead, C.L.; Newkirk, L.; Valencia, F.; Geballe, T.H.; Schwall, R.H.; Matthias, B.T.; Corenswit, E.

1975-01-01

The effect of high-energy neutron irradiation (E greater than 1 MeV) at ambient reactor temperatures on the superconducting properties of a variety of superconducting compounds is reported. The materials studied include the A-15 compounds Nb 3 Sn, Nb 3 Al, Nb 3 Ga, Nb 3 Ge and V 3 Si, the C-15 Laves phase HfV 2 , the ternary molybdenum sulfide Mo 3 Pb 0 . 5 S 4 and the layered dichalcogenide NbSe 2 . The superconducting transition temperature has been measured for all of the above materials for neutron fluences up to 5 x 10 19 n/cm 2 . The critical current for multifilamentary Nb 3 Sn has also been determined for fields up to 16 T and fluences between 3 x 10 17 n/cm 2 and 1.1 x 10 19 n/cm 2

Nonequilibrium theory of flame propagation

International Nuclear Information System (INIS)

Merzhanov, A.G.

1995-01-01

The nonequilibrium theory of flame propagation is considered as applied to the following three processes of wave propagation: the combustion waves of the second kind, the combustion waves with broad reaction zones, and the combustion waves with chemical stages. Kinetic and combustion wave parameters are presented for different in composition mixtures of boron and transition metals, such as Zr, Hf, Ti, Nb, Ta, Mo, as well as for the Ta-N, Zr-C-H, Nb-B-O systems to illustrate specific features of the above-mentioned processes [ru

Microstructures and phase relationships in the Ti3Al + Nb system

International Nuclear Information System (INIS)

Kestner-Weykamp, H.T.; Kaufman, M.J.

1989-01-01

Alloys based on the α 2 -Ti 3 Al compound (hexagonal) DO 19 are currently experiencing limited use as advanced aerospace materials. To date, the alloys with the most desirable properties contain additions of β stabilizers, such as Nb, Mo and V, which promote the formation of a two-phase mixture of α 2 +β or α 2 +B2 (where B2 refers to the ordered CsCl structure). Unfortunately, the phase relationships in these systems have not been established in sufficient detail to allow their more widespread application. Recently, there has been a series of investigations aimed at alleviating this deficiency in the ternary Ti-Al-Nb system. These studies have clearly indicated the existence of the ordered B2 phase, which, in the higher Nb alloys, can be retained at room temperature by rapid cooling from the liquid or solid state. The authors describe (TiNb) 3 Al alloys (from 0 to 30 at. pct. Nb) were studies after conventional and nonequilibrium (i.e., rapid solidification) processing with an emphasis on providing further insight into the transformation sequences and phase equilibria in these alloys

Geochronology of the Thompson Creek Mo Deposit: Evidence for the Formation of Arc-related Mo Deposits

Science.gov (United States)

Lawrence, C. D.; Coleman, D. S.; Stein, H. J.

2016-12-01

The Thompson Creek Mo deposit in central ID, has been categorized as an arc-related Mo deposit due to the location, grade of Mo, and relative lack of enrichments in F, Rb, and Nb, compared to the Climax-type Mo deposits. Geochronology from this arc-related deposit provides an opportunity to compare and contrast magmatism, and mineralization to that in Climax-type deposits. Distinct pulses of magmatism were required to form the Thompson Creek Mo deposit, which is consistent with recent geochronology from Climax-type deposits. Molybdenite Re-Os geochronology from five veins requires at least three pulses of magmatism and mineralization between 89.39 +/- 0.37 and 88.47 +/- 0.16 Ma. Zircon U-Pb ages from these mineralized samples overlap with molybdenite mineralization, but show a much wider range (91.01 +/- 0.37 to 87.27 +/- 0.69). Previous work from Climax-type Mo deposits suggest a correlation between a super eruption, and the subsequent rapid (<1 Ma) onset, and completion of Mo mineralizing intrusions. The longer life (3-4 Ma) for the Thompson Creek Mo deposit suggests that the mineralizing intrusions for arc-related Mo deposits may not need to have as high [Mo] as the Climax-type deposits. This study also finds a shift in the source of magmatism from the pre- to syn-mineralizing intrusions. Zircons from pre-mineralizing intrusions have much higher (15-60 pg) concentrations of radiogenic Pb than zircons from mineralized intrusions, which all have less than 15 pg, though whole rock [U] are similar.

Superconductivity and specific heat measurements in V--Nb--Ta ternary alloys

International Nuclear Information System (INIS)

Wang, R.Y.P.

1977-01-01

The correlation between the superconducting transition temperature T/sub c/ with electronic specific heat coefficient γ and Debye temperature theta/sub D/ in some isoelectronic ternary V--Nb--Ta alloys is investigated. It has been known that the variation of theta/sub D/ with concentration in both V--Nb and V--Ta systems is clearly of the same curvature as that of T/sub c/ and γ. In Ta--Nb alloys, however, over most of the concentration range theta/sub D/ seems to have a slight negative curvature while T/sub c/ and γ curve upwards. (But beyond approx. 80 at. % Nb theta/sub D/ rises rapidly to the pure Nb value.) By choosing alloys along a line connecting Ta and V 25 --Nb 75 which is close to the Nb--Ta side of the Gibb's triangle the extent to which the Nb--Ta type of behavior persists in this ternary system can be estimated. A model proposed by Miedema that takes into account the variation of properties caused by possible charge transfer among constituent atoms in an alloy has been found to apply almost quantitatively for nearly all binary alloy systems whose experimental data are available, including those for which Hopfield's method fails. A previous test of the extension of Miedema's empirical model into ternary alloys shows qualitatively correct behavior for intra-row Zr/sub x/Nb/sub 1-2x/Mo/sub x/ alloys. The good agreement between the predicted values of γ and T/sub c/ and the experimental values in the inter-row ternary V--Nb--Ta system studied here gives another and better test of the application of Miedema's model

Specific heat of Nb3Sn and V2Zr compounds irradiated with high fluences fast neutrons

International Nuclear Information System (INIS)

Kar'kin, A.E.; Mirmel'shtejn, A.V.; Arkhipov, V.E.; Goshchitskij, B.N.

1987-01-01

Specific heat of Nb 3 Sn (structure A15) and V 2 Zr (C15) specimens irradiated with high fluences of bast neutrons has been measured. It is shown that in these compounds the temperature reduction of superconducting transition T c under neutron irradiation is accompanied with high decrease of N(E F ). Phonon spectrum of the irradiated V 2 Zr (amorphous phase) on the whole is harder, than at an initial state, for irradiated Nb 3 Sn state (disordered crystalline structure) phonon spectrum is differ weakly from initial one. General regularities of parameter change of electron and phonon subsystems for A15 compounds investigated here and earlier (V 3 Si, Mo 3 Si, Mo 3 Ge) have been analysed

Studies on {sup 99}Mo-{sup 99m}Tc adsorption and elution behaviors using the inorganic sorbent ceric tungstate and conventional organic resins

Energy Technology Data Exchange (ETDEWEB)

El-Sweify, Fatma H.; Fattah, Alaa El-Din A. Abdel; Aly, Shorouk M.; Ghamry, Mohamed A. [Atomic Energy Authority, Cairo (Egypt). Hot Laboratories Center; El-Sheikh, Ragaa [Zagazig Univ. (Egypt). Chemistry Dept.

2017-09-01

Adsorption behavior of {sup 99}Mo(VI) and {sup 99m}Tc(VII) was studied on ceric tungstate (CeW) and compared with the adsorption on the conventional cation and anion exchangers Dowex-50X8 and AG-2X8, respectively. The studies were carried out under static and dynamic conditions. The effect of contact time and pH on the adsorption was investigated under static conditions. High K{sub d}-values for sorption of {sup 99}Mo(VI) on (CeW) were obtained over the investigated pH range. {sup 99m}Tc was adsorbed with much lower K{sub d}-values. The K{sub d}-values were pH dependent. K{sub d}-values of {sup 99}Mo-adsorption on AG-2X8 were lower than those on (CeW) and vice versa for {sup 99m}Tc. Ionic species of both elements were not adsorbed on Dowex-50X8, indicating the absence of cationic species and the adsorption of both elements on AG-2X8 and (CeW) as anionic species. The loading and elution behaviors of {sup 99}Mo and {sup 99m}Tc on (CeW) were studied using different eluents. {sup 99}Mo remained strongly adsorbed under all conditions whereas {sup 99m}Tc was easily eluted. Adsorption of some fission products, i.e. {sup 95}Zr(IV) and {sup 95}Nb(V), in addition to {sup 123m}Te(IV) and {sup 75}Se(IV), as representatives of their corresponding fission product isotopes, as well as {sup 181}Hf, as probable radioactive contaminant was also studied. Solutions of the ionic species of those metals were loaded in mixtures together with {sup 99}Mo on (CeW) columns. Strong adsorption of those ionic species and {sup 99}Mo on (CeW) was found whereas {sup 99m}Tc was easily eluted. Different eluents were investigated for eluting {sup 99m}Tc from {sup 99}Mo-adsorbed on (CeW).

Nb nanoSQUIDs for detection of small spin systems

Energy Technology Data Exchange (ETDEWEB)

Woelbing, R.; Nagel, J.; Kemmler, M.; Kleiner, R.; Koelle, D. [Physikalisches Institut, Universitaet Tuebingen (Germany); Kieler, O.; Weimann, T.; Kohlmann, J.; Zorin, A. [Fachbereich 2.4 ' ' Quantenelektronik' ' , PTB Braunschweig (Germany); Buchter, A.; Xue, F.; Poggio, M. [Department of Physics, University of Basel (Switzerland); Rueffer, D.; Russo-Averchi, E.; Fontcuberta i Morral, A. [Laboratoire des Materiaux Semiconducteurs, EPF Lausanne (Switzerland); Huber, R.; Berberich, P. [Physik-Department E10, Technische Universitaet Muenchen (Germany); Grundler, D. [Laboratoire des Materiaux Semiconducteurs, EPF Lausanne (Switzerland); Physik-Department E10, Technische Universitaet Muenchen (Germany)

2013-07-01

We report on the realization of highly sensitive dc nanoSQUIDs for the investigation of small spin systems in moderate magnetic fields. The Nb SQUIDs are based on normal metal Josephson junctions made of HfTi and patterned by e-beam lithography. We demonstrate stable operation up to B = ± 50 mT without degradation of rms flux noise (S{sub Φ}{sup 1/2} ≤ 280 nΦ{sub 0}/√(Hz)). We also present a multifunctional system combining a Nb nanoSQUID and a low-temperature magnetic force microscope (LTMFM) with a Ni nanotube as a scanning tip. This system allows for magnetization measurements of the Ni tube by using both, LTMFM and SQUID readout. Furthermore, the measurement of magnetic flux Φ vs. position of the particle provides an experimental determination of the coupling factor φ{sub μ} = Φ/μ between SQUID and Ni tube with magnetic moment μ. The results confirm our predictions from numerical simulations, taking into account the SQUID geometry.

Hf-Nd isotope constraints on the origin of the Cretaceous Caribbean plateau and its relationship to the Galápagos plume

Science.gov (United States)

Thompson, P. M. E.; Kempton, P. D.; White, R. V.; Kerr, A. C.; Tarney, J.; Saunders, A. D.; Fitton, J. G.; McBirney, A.

2004-01-01

Formation of the Cretaceous Caribbean plateau, including the komatiites of Gorgona, has been linked to the currently active Galápagos hotspot. We use Hf-Nd isotopes and trace element data to characterise both the Caribbean plateau and the Galápagos hotspot, and to investigate the relationship between them. Four geochemical components are identified in the Galápagos mantle plume: two 'enriched' components with ɛHf and ɛNd similar to enriched components observed in other mantle plumes, one moderately enriched component with high Nb/Y, and a fourth component which most likely represents depleted MORB source mantle. The Caribbean plateau basalt data form a linear array in Hf-Nd isotope space, consistent with mixing between two mantle components. Combined Hf-Nd-Pb-Sr-He isotope and trace element data from this study and the literature suggest that the more enriched Caribbean end member corresponds to one or both of the enriched components identified on Galápagos. Likewise, the depleted end member of the array is geochemically indistinguishable from MORB and corresponds to the depleted component of the Galápagos system. Enriched basalts from Gorgona partially overlap with the Caribbean plateau array in ɛHf vs. ɛNd, whereas depleted basalts, picrites and komatiites from Gorgona have a high ɛHf for a given ɛNd, defining a high- ɛHf depleted end member that is not observed elsewhere within the Caribbean plateau sequences. This component is similar, however, in terms of Hf-Nd-Pb-He isotopes and trace elements to the depleted plume component recognised in basalts from Iceland and along the Reykjanes Ridge. We suggest that the Caribbean plateau represents the initial outpourings of the ancestral Galápagos plume. Absence of a moderately enriched, high Nb/Y component in the older Caribbean plateau (but found today on the island of Floreana) is either due to changing source compositions of the plume over its 90 Ma history, or is an artifact of limited sampling. The

A search for superconductivity below 1 K in transition metal borides

International Nuclear Information System (INIS)

Leyarovska, L.; Leyarovski, E.

1979-01-01

Some AlB 2 -type (C32 structure) boron compounds were examined for superconductivity down to 0.42 K; the compounds have the formula MeB 2 (Me equivalent to Ti, Zr, Hf, V, Nb, Ta, Cr, Mo) (the atomic ratio of metal to boron was 0.5). Only NbB 2 was found to be superconducting with Tsub(c) = 0.62 K and a surprisingly high value of Hsub(c)(0), about 1600 Oe. Other transition metal as well as non-transition metal boron phases were also tested for superconductivity down to 0.42 K; these compounds were MeB 2 (Me equivalent to Ca, Sr, Ba), W 2 B 5 , CrB, Cr 5 B 3 , UB 2 , UB 4 and UB 12 . None of these compounds proved to be superconducting above 0.42 K; nor was any trace of superconductivity down to 0.42 K observed in MoB and NbB. (Auth.)

Improved method for Hf separation from silicate rocks for isotopic analysis using Ln-spec resin column

International Nuclear Information System (INIS)

Shinjo, Ryuichi; Ginoza, Yuko; Meshesha, Daniel

2010-01-01

An improved chemical separation method for Hf isotope ratio measurement using both the thermal ionization mass spectrometer (TIMS) and the multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS) is presented in this paper. In the first column (2.5-ml Eichrom Ln-spec resin), Hf cut was collected with 2M HCl-0.2M HF after washing the major elements, HREE, Ti, Nb, and Zr. For further Hf purification, the second column (1-ml Ln-spec resin) chemistry was conducted in a manner similar to that of the first column. The first column is designed for treatment with a 0.5-g silicate rock sample for TIMS analysis. Thus, because the Hf amount required for MC-ICP-MS analysis is much lesser than that required for TIMS analysis, the column chemistry for MC-ICP-MS analysis can be scaled down, depending on the amount of digested sample. Although there is a need to improve the TIMS technique, the TIMS Hf data obtained for geological reference rocks and Ethiopian flood basalts after the application of the proposed separation methods are consistent, within analytical error, with the previously reported data obtained using the MC-ICP-MS. The advantages of the proposed method include a reduction in the amount of reagents used (hence, a consequent reduction in the blank contribution), reduction in the time required, and a simplified preparation requiring a fewer number of acids. (author)

(V,Nb)-doped half Heusler alloys based on {Ti,Zr,Hf}NiSn with high ZT

International Nuclear Information System (INIS)

Rogl, G.; Sauerschnig, P.; Rykavets, Z.; Romaka, V.V.; Heinrich, P.; Hinterleitner, B.; Grytsiv, A.; Bauer, E.; Rogl, P.

2017-01-01

Half Heusler alloys are among the most promising materials for thermoelectric generators as they can be used in a wide temperature range and their starting materials are abundant and cheap, the latter as long as no hafnium is involved. For Sb-doped Ti 0.5 Zr 0.25 Hf 0.25 NiSn Sakurada and Shutoh in 2008 have published ZT max  = 1.5 at 690 K, a value that hitherto was never reproduced independently. In this paper we successfully prepared Ti 0.5 Zr 0.25 Hf 0.25 NiSn with ZT max  = 1.5, however, at higher temperature (825 K). As the main goal is to produce hafnium – free half Heusler alloys, we investigated the influence of niobium or vanadium dopants on Ti x Zr 1−x NiSn 0.98 Sb 0.02 , reaching ZTs > 1.2 and thermal-electric conversion efficiencies up to 13.1%. For Hf-free n-type TiNiSn-based half Heusler alloys these values are unsurpassed. In order to further improve our thermoelectric materials our study is completed by electrical resistivity and thermal conductivity data in the low temperature range but also by mechanical properties (elastic moduli, hardness) at room temperature. The electrical properties have been discussed in comparison with DFT calculations.

Abrasive wear resistance and microstructure of Ni-Cr-B-Si hardfacing alloys with additions of Al, Nb, Mo, Fe, Mn and C

International Nuclear Information System (INIS)

Berns, H.; Fischer, A.; Theisen, W.

1987-01-01

The development of new Ni-base hardfacing alloys for filler wire welding or metal spraying should result in materials with a good resistance against high temperature corrosion and abrasive wear. The first step is to design microstructures, which obtain a satisfactory abrasive wear behaviour at room temperature. Thus, different alloys are melted and scrutinized as to their microstructure and their abrasive wear resistance in laboratory. Compared to commercial Ni-base hardfacing alloys they show a higher volume fraction of coarse hard phases due to the additional, initial solidification of Nb-carbides and Cr-, and Mo-borides. Thus, the abrasive wear resistance is improved. For hard abrasive particles, such as corundum, the Ni-base alloys are more wear resistant than harder Fe-base alloys investigate earlier. This is due to the tougher Ni metal matrix that results in microcracking not to be the most significantly acting wear mechanism

Magnetic hyperfine fields on 181Ta at the Nb and V sites in Heusler alloys CO2YAL (Y=NB,V)

International Nuclear Information System (INIS)

Pendl Junior, W.

1990-01-01

Magnetic hyperfine fields (MHF) acting on sup(181)Ta at the Nb and V sites have been determined in the Heusler alloys Co sub(2) NbA1 and Co sub(2) VA1 by the time differential perturbed angular correlation (TDPAC) technique utilizing the well known 133-482 Kev gamma cascade in sup(181)Ta. The measurement were carried out using an automatic spectrometer consisting of three NaI(T1) detectors and a fast-slow coincidence system. The measurements were performed at 77 K with and without an externally applied magnetic field ( ∼ 4.5 KGauss) to determine the sign as well as the magnitude of the hyperfine fields in both alloys. For the alloy Co sub(2) NbA1 a unique field of -138(4) KOe was observed whereas in the case of Co sub(2)VA1 two distinct magnetic sites were observed. The present result show that approximately 24% of the sup(181)Ta atoms in this alloy probe a field of -116(4) KOe while the other ∼ 76% of the atoms feel -83(3) KOe. Present data along with the existing results on similar alloys Co sub(2)T1,Hf,Zr (Al,Ga,Sn) are discussed and compared with the magnetic hyperfine field systematics in Heusler alloys. (author)

Petrogenesis of the late Early Cretaceous granodiorite - Quartz diorite from eastern Guangdong, SE China: Implications for tectono-magmatic evolution and porphyry Cu-Au-Mo mineralization

Science.gov (United States)

Jia, Lihui; Mao, Jingwen; Liu, Peng; Li, Yang

2018-04-01

Comprehensive petrological, zircon U-Pb dating, Hf-O isotopes, whole rock geochemistry and Sr-Nd isotopes data are presented for the Xinwei and Sanrao intrusions in the eastern Guangdong Province, Southeast (SE) China, with an aim to constrain the petrogenesis, tectono-magmatic evolution and evaluate the implication for porphyry Cu-Au-Mo mineralization. The Xinwei intrusion is composed of granodiorite and quartz diorite, whilst the Sanrao intrusion consists of granodiorite. Zircon U-Pb ages show that both intrusions were emplaced at ca. 106-102 Ma. All rocks are metaluminous to weakly peraluminous, high-K calc-alkaline in composition, and they are characterized by LREEs enrichment, depletion in Nb, Ta, P, and Ti, and strongly fractionated LREEs to HREEs. The initial 87Sr/86Sr ratios range from 0.7055 to 0.7059, and εNd(t) values range from -3.9 to -3.0. Together with the relatively high εHf(t) values (-3.2 to 3.3) and low δ18O values (4.9‰ to 6.6‰), these data suggest that the Xinwei and Sanrao intrusions were derived from a mixed source: including the mantle-derived mafic magmas and lower continental crustal magmas. Fractional crystallization played an important role in the magmatic evolution of the Xinwei and Sanrao intrusions. The elemental and isotopic compositions of the Xinwei and Sanrao intrusions, as well as the high water content and oxidation state of their parental magmas, are similar to those of the ore-bearing granodiorites of the Luoboling porphyry Cu-Mo deposit in the Fujian Province, neighbouring east to the Guangdong Province, indicating that the late Early Cretaceous granodioritic intrusions in the eastern Guangdong Province may also have Cu-Au-Mo mineralization potential. The late Early Cretaceous magmatic event is firstly reported in eastern Guangdong, and represents a positive response of large-scale lithosphere extension and thinning, triggered by the changing subduction direction of the Paleo-Pacific plate from oblique subduction to

Ferromagnetic bulk glassy alloys

International Nuclear Information System (INIS)

Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

2000-01-01

This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

Direct flow separation strategy, to isolate no-carrier-added {sup 90}Nb from irradiated Mo or Zr targets

Energy Technology Data Exchange (ETDEWEB)

Radchenko, Valery; Roesch, Frank [Mainz Univ. (Germany). Inst. of Nuclear Chemistry; Filosofov, Dmitry V.; Dadakhanov, Jakhongir [Joint Institute of Nuclear Research, Dubna (Russian Federation). Dzhelepov Laboratory of Nuclear Problems; Karaivanov, Dimitar V. [Joint Institute of Nuclear Research, Dubna (Russian Federation). Dzhelepov Laboratory of Nuclear Problems; Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. for Nuclear Research and Nuclear Energy; Marinova, Atanaska [Joint Institute of Nuclear Research, Dubna (Russian Federation). Dzhelepov Laboratory of Nuclear Problems; Sofia Univ. (Bulgaria). Faculty of Chemistry and Pharmacy; Baimukhanova, Ayagoz [Joint Institute of Nuclear Research, Dubna (Russian Federation). Dzhelepov Laboratory of Nuclear Problems; Institute of Nuclear Physics of the Republic of Kazakhstan, Almaty (Kazakhstan)

2016-11-01

{sup 90}Nb has an intermediate half-life of 14.6 h, a high positron branching of 53% and optimal β{sup +} emission energy of only E{sub mean} 0.35 MeV per decay. These favorable characteristics suggest it may be a potential candidate for application in immuno-PET. Our recent aim was to conduct studies on distribution coefficients for Zr{sup IV} and Nb{sup V} in mixtures of HCl/H{sub 2}O{sub 2} and HCl/oxalic acid for anion exchange resin (AG 1 x 8) and UTEVA resin to develop a ''direct flow'' separation strategy for {sup 90}Nb. The direct flow concept refers to a separation accomplished using a single eluent on multiple columns, effectively streamlining the separation process and increasing the time efficiency. Finally, we also demonstrated that this separation strategy is applicable to the production of the positron emitter {sup 90}Nb via the irradiation of molybdenum targets and isolation of {sup 90}Nb from the irradiated molybdenum target.

HAZ microstructure in joints made of X13CrMoCoVNbNB9-2-1 (PB2 steel welded with and without post-weld heat treatment

Directory of Open Access Journals (Sweden)

M. Łomozik

2016-07-01

Full Text Available The article presents the results of research butt welded joints made of X13CrMoCoVNbNB9-2-1 steel. The joints were welded with post-weld heat treatment PWHT and without PWHT, using the temper bead technique TBT. After welding the joint welded with PWHT underwent stress-relief annealing at 770 °C for 3 hours. The scope of structural tests included the microstructural examination of the coarse-grained heat affected zone (HAZ areas of the joints, the comparison of the morphology of these areas and the determination of carbide precipitate types of the coarse grain heat affected zone (CGHAZ of the joints welded with and without PWHT.

Hf layer thickness dependence of resistive switching characteristics of Ti/Hf/HfO2/Au resistive random access memory device

Science.gov (United States)

Nakajima, Ryo; Azuma, Atsushi; Yoshida, Hayato; Shimizu, Tomohiro; Ito, Takeshi; Shingubara, Shoso

2018-06-01

Resistive random access memory (ReRAM) devices with a HfO2 dielectric layer have been studied extensively owing to the good reproducibility of their SET/RESET switching properties. Furthermore, it was reported that a thin Hf layer next to a HfO2 layer stabilized switching properties because of the oxygen scavenging effect. In this work, we studied the Hf thickness dependence of the resistance switching characteristics of a Ti/Hf/HfO2/Au ReRAM device. It is found that the optimum Hf thickness is approximately 10 nm to obtain good reproducibility of SET/RESET voltages with a small RESET current. However, when the Hf thickness was very small (∼2 nm), the device failed after the first RESET process owing to the very large RESET current. In the case of a very thick Hf layer (∼20 nm), RESET did not occur owing to the formation of a leaky dielectric layer. We observed the occurrence of multiple resistance states in the RESET process of the device with a Hf thickness of 10 nm by increasing the RESET voltage stepwise.

Extraction of scandium by aromatic carboxylic acids

Energy Technology Data Exchange (ETDEWEB)

Kamenev, V F; Fadeeva, V I [Moskovskij Gosudarstvennyj Univ. (USSR)

1977-04-01

Extraction of complex compounds af scandium with salicylic, phenyl- and diphenylacetic acids with chloroform solutions of tetraethyldiamideheptylphosphate as a donor-active additive in relation to the pH and reagent concentration has been studied. Extraction of salicylates of some elements (Ta, Nb, Zr, Hf, Mo) by solutions of tetraethyldiamideheptylphosphate in chloroform has been investigated, and the possibility of their extraction separation from scandium is shown.

Extraction of scandium by aromatic carboxylic acids

International Nuclear Information System (INIS)

Kamenev, V.F.; Fadeeva, V.I.

1977-01-01

Extraction of complex compounds af scandium with salicylic, phenyl- and diphenylacetic acids with chloroform solutions of tetraethyldiamideheptylphosphate as a donor-active additive in relation to the pH and reagent concentration has been studied. Extraction of salicylates of some elements (Ta, Nb, Zr, Hf, Mo) by solutions of tetraethyldiamideheptylphosphate in chloroform has been investigated, and the possibility of their extraction separation from scandium is shown

Possible doping strategies for MoS 2 monolayers: An ab initio study

KAUST Repository

Dolui, Kapildeb

2013-08-14

Density functional theory is used to systematically study the electronic properties of doped MoS2 monolayers, where the dopants are incorporated both via S/Mo substitution or as adsorbates. Among the possible substitutional dopants at the Mo site, Nb is identified as suitable p-type dopant, while Re is the donor with the lowest activation energy. When dopants are simply adsorbed on a monolayer we find that alkali metals shift the Fermi energy into the MoS2 conduction band, making the system n type. Finally, the adsorption of charged molecules is considered, mimicking an ionic liquid environment. We find that molecules adsorption can lead to both n- and p-type conductivity, depending on the charge polarity of the adsorbed species. © 2013 American Physical Society.

Possible doping strategies for MoS 2 monolayers: An ab initio study

KAUST Repository

Dolui, Kapildeb; Rungger, Ivan; Das Pemmaraju, Chaitanya; Sanvito, Stefano

2013-01-01

Density functional theory is used to systematically study the electronic properties of doped MoS2 monolayers, where the dopants are incorporated both via S/Mo substitution or as adsorbates. Among the possible substitutional dopants at the Mo site, Nb is identified as suitable p-type dopant, while Re is the donor with the lowest activation energy. When dopants are simply adsorbed on a monolayer we find that alkali metals shift the Fermi energy into the MoS2 conduction band, making the system n type. Finally, the adsorption of charged molecules is considered, mimicking an ionic liquid environment. We find that molecules adsorption can lead to both n- and p-type conductivity, depending on the charge polarity of the adsorbed species. © 2013 American Physical Society.

Binary and tertiary reaction cross-sections of V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes

International Nuclear Information System (INIS)

Garg, S.B.

1982-01-01

Neutron induced binary and tertiary reaction cross-sections have been evaluated for V, Cr, Mn, Fe, Ni, Cu, Zr, Nb, Mo, Ta, W, Pt and their isotopes in the 'energy range 0.5 MeV to 20 MeV using the nuclear statistical empirical model. The reactions considered are (n,n'), (n,2n), (n,3n), (n,p), (n,d), (n,t), (n, 3 He), (n,α), (n,np), (n,nd), (n,nt), (n,n 3 He), (n,nα), (n,pn), (n,2p), (n,ν), (n,αp), (n,dn) and (n,pα). Most of the above mentioned elements are used as structural materials in nuclear reactors and the measured cross-section data for the above listed reactions are seldom available for the radiation damage and safety analysis. With a view to providing these data, this nuclear model based evaluation has been undertaken. The associated uncertainties in the cross-sections and their fission averages have also been evaluated. (author)

Comparison of HfCl4, HfI4, TEMA-Hf, and TDMA-Hf as precursors in early growing stages of HfO2 films deposited by ALD: A DFT study

International Nuclear Information System (INIS)

Cortez-Valadez, M.; Fierro, C.; Farias-Mancilla, J.R.; Vargas-Ortiz, A.; Flores-Acosta, M.; Ramírez-Bon, R.; Enriquez-Carrejo, J.L.

2016-01-01

Highlights: • Hafnium oxide growth on Si(100) by atomic layer deposition was simulated. • The interface structure was considered as silicate and silicide. • The interface was studied employing DFT. • TDMA-Hf precursor show better interface stability. - Abstract: The final structure of HfO 2 films grown by atomic layer deposition (ALD) after reaction with OH − ions has been analyzed by DFT (density functional theory). The interaction of the precursors: HfCl 4 (hafnium tetrachloride), HfI 4 (hafnium tetraiodide), TEMA-Hf (tetrakis-ethylmethylamino hafnium), and TDMA-Hf (tetrakis-dimethylamino hafnium) with HO–H was studied employing the B3LYP (Becke 3-parameter, Lee–Yang–Parr) hybrid functional and the PBE (Perdew–Burke–Ernzerhof) generalized gradient functional. The structural evolution at the Si(100) surface has been analyzed by LDA (local density approximation). The structural parameters: bond length and bond angle, and the vibrational parameters for the optimized structures are also reported. The presence of hafnium silicate at the interface was detected. The infrared spectra and structural parameters obtained in this work agree with previously reported experimental results.

Comparison of HfCl4, HfI4, TEMA-Hf, and TDMA-Hf as precursors in early growing stages of HfO2 films deposited by ALD: A DFT study

Science.gov (United States)

Cortez-Valadez, M.; Fierro, C.; Farias-Mancilla, J. R.; Vargas-Ortiz, A.; Flores-Acosta, M.; Ramírez-Bon, R.; Enriquez-Carrejo, J. L.; Soubervielle-Montalvo, C.; Mani-Gonzalez, P. G.

2016-06-01

The final structure of HfO2 films grown by atomic layer deposition (ALD) after reaction with OH- ions has been analyzed by DFT (density functional theory). The interaction of the precursors: HfCl4 (hafnium tetrachloride), HfI4 (hafnium tetraiodide), TEMA-Hf (tetrakis-ethylmethylamino hafnium), and TDMA-Hf (tetrakis-dimethylamino hafnium) with HO-H was studied employing the B3LYP (Becke 3-parameter, Lee-Yang-Parr) hybrid functional and the PBE (Perdew-Burke-Ernzerhof) generalized gradient functional. The structural evolution at the Si(100) surface has been analyzed by LDA (local density approximation). The structural parameters: bond length and bond angle, and the vibrational parameters for the optimized structures are also reported. The presence of hafnium silicate at the interface was detected. The infrared spectra and structural parameters obtained in this work agree with previously reported experimental results.

Liquidus projection of the Nb-Cr-Al system near the Al3(Nb,Cr) + Cr(Al,Nb) eutectic region

International Nuclear Information System (INIS)

Souza, S.A.; Ferrandini, P.L.; Nunes, C.A.; Coelho, A.A.; Caram, R.

2006-01-01

The system Nb-Cr-Al was investigated in the region near the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic and the liquidus projection of that region was determined based on the microstructural characterization of arc melted alloys. The characterization utilized scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results allowed one to determine three primary solidification liquidus surfaces ((Cr,Al) 2 Nb, Cr(Al,Nb) and Al 3 (Nb,Cr)), that are originated from the binary systems Cr-Nb, Cr-Al and Al-Nb. It is proposed the occurrence of the invariant reaction L + (Cr,Al) 2 Nb ↔ Al 3 (Nb,Cr) + Cr(Al,Nb) and of a point of minimum, which involves a three phase reaction, L ↔ Al 3 (Nb,Cr) + Cr(Al,Nb). All alloys studied showed formation of the Al 3 (Nb,Cr) + Cr(Al,Nb) eutectic as the last solidification step with Al(Nb)Cr 2 precipitating from Cr(Al,Nb)

Microstructural investigations of fatigued 12% Cr-steel 1.4914 (X 18 Cr Mo V Nb 12 1)

International Nuclear Information System (INIS)

Gersinska, R.

1992-10-01

The low cycle fatigue properties of a tempered steel X18 Cr Mo V Nb 12 1 (DIN 1.4914) have been investigated at different temperatures, strain amplitudes, mean strains and strain rates. The role of martensite lath structure and of precipitates and dislocations on the strengthening mechanisms and fatigue damage have been analysed. Plastic deformation results in a slip band formation on the surface and in a cellular dislocation structure in the interior of the specimens. A reduced strain rate is causing lower stress amplitudes and greater cells at higher temperatures. At lower temperatures the influence of strain rate is small. Fatigue mechanisms are soon dominant at lower strain rates. REM-investigations of the specimen surfaces are revealing the development of cracks at slip bands. The cracks start always at the surfaces of the specimen, and they are transcristalline in nature. The influence of the ageing temperature has been investigated. A reduced ageing temperature of 600degC results in a higher dislocation density and a lower martensite lath distance in the undeformed material. Strain ageing was initially observed in tensile experiments. The influence of dynamic strain ageing on the mechanical properties and the microstructure of tempered steel 1.4914 is investigated. A correlation of mechanical and microstructural data has been performed. (orig./MM) [de

CVD growth of large-area and high-quality HfS2 nanoforest on diverse substrates

Science.gov (United States)

Zheng, Binjie; Wang, Zegao; Qi, Fei; Wang, Xinqiang; Yu, Bo; Zhang, Wanli; Chen, Yuanfu

2018-03-01

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted burgeoning attention due to their various properties and wide potential applications. As a new TMD, hafnium disulfide (HfS2) is theoretically predicted to have better electrical performance than widely studied MoS2. The experimental researches also confirmed the extraordinary feature in electronics and optoelectronics. However, the maximal device performance may not be achieved due to its own limitation of planar structure and challenge of transfer without contamination. Here, through the chemical vapor deposition (CVD) technique, inch-size HfS2 nanoforest has been directly grown on diverse objective substrates covering insulating, semiconducting and conducting substrates. This direct CVD growth without conventional transfer process avoids contamination and degradation in quality, suggesting its promising and wide applications in high-quality and multifarious devices. It is noted that all the HfS2 nanoforests grown on diverse substrates are constructed with vertically aligned few-layered HfS2 nanosheets with high crystalline quality and edge orientation. Moreover, due to its unique structure, the HfS2 nanoforest owns abundant exposed edge sites and large active surface area, which is essential to apply in high-performance catalyst, sensor, and energy storage or field emitter.

A model for Nb-Zr-REE-Ga enrichment in Lopingian altered alkaline volcanic ashes: Key evidence of H-O isotopes

Science.gov (United States)

Dai, Shifeng; Nechaev, Victor P.; Chekryzhov, Igor Yu.; Zhao, Lixin; Vysotskiy, Sergei V.; Graham, Ian; Ward, Colin R.; Ignatiev, Alexander V.; Velivetskaya, Tatyana A.; Zhao, Lei; French, David; Hower, James C.

2018-03-01

Clay-altered volcanic ash with highly-elevated concentrations of Nb(Ta), Zr(Hf), rare earth elements (REE), and Ga, is a new type of critical metal deposit with high commercial prospects that has been discovered in Yunnan Province, southwest China. Previous studies showed that the volcanic ashes had been subjected to hydrothermal fluids, the nature of which, however, is not clear. Here we show that the volcanic ashes were originated from alkaline magmatism, followed by a continuous hydrothermal-weathering process. Heated meteoric waters, which were sourced from acidic rains and mixed with CO2 from degassing of the Emeishan plume, have caused partial, but widespread, acidic leaching of Nb, Ta, Zr, Hf, REE, and Ga into ground water and residual enrichment of these elements, along with Al and Ti, in the deeply altered rocks. Subsequent alteration occurring under cooler, neutral or alkaline conditions, caused by water-rock interaction, resulted in precipitation of the leached critical metals in the deposit. Polymetallic mineralization of similar origin may be found in other continental regions subjected to explosive alkaline volcanism associated with deep weathering in humid conditions.

Electrical and materials properties of AlN/ HfO{sub 2} high-k stack with a metal gate

Energy Technology Data Exchange (ETDEWEB)

Reid, Kimberly G. [Tokyo Electron U.S., 14338 FM 1826, Austin, TX 78737 (United States)], E-mail: kim@ireid.com; Dip, Anthony [Tokyo Electron U.S., 2400 Grove Blvd., Austin, TX 78747 (United States)], E-mail: anthony.dip@us.tel.com; Sasaki, Sadao [Tokyo Electron U.S. (United States)], E-mail: Sadao.sasaki@us.tel.com; Triyoso, Dina [Freescale Semiconductor Inc., 3501 Ed Bluestein Blvd, Austin, TX 78721 (United States)], E-mail: Dina.Triyoso@freescale.com; Samavedam, Sri [Freescale Semiconductor Inc., 3501 Ed Bluestein Blvd, Austin, TX 78721 (United States)], E-mail: Sri.Samavedam@freescale.com; Gilmer, David [SEMATECH 2706 Montopolis Drive, Austin, TX 78741 (United States)], E-mail: David.Gilmer@sematech.org; Gondran, Carolyn F.H. [Process Characterization Laboratory, ATDF/SEMATECH, 2706 Montopolis Drive, Austin, Texas 78741 (United States)], E-mail: Carolyn.Gondran@atdf.com

2009-02-27

In this study, aluminum nitride (AlN) was grown by molecular layer deposition on HfO{sub 2} that had been deposited on 200 mm Si (100) substrates. The AlN was grown on HfO{sub 2} using sequential exposures of trimethyl-aluminum and ammonia (NH{sub 3}) in a batch vertical furnace. Excellent thickness uniformity on test wafers from the top of the furnace to the bottom of the furnace (across the furnace load) was obtained. The equivalent oxide thickness was 16.5-18.8 A for the AlN/HfO{sub 2} stack on patterned device wafers with a molybdenum oxynitride metal gate with leakage current densities from low 10{sup -5} to mid 10{sup -6} A/cm{sup 2} at threshold voltage minus one volt. There was no change in the work function with the AlN cap on HfO{sub 2} with the MoN metal gate, even with a 1000 deg. C anneal.

Novel elastic, lattice dynamics and thermodynamic properties of metallic single-layer transition metal phosphides: 2H-M 2P (Mo2P, W2P, Nb2P and Ta2P)

Science.gov (United States)

Yin, Jiuren; Wu, Bozhao; Wang, Yanggang; Li, Zhimi; Yao, Yuanpeng; Jiang, Yong; Ding, Yanhuai; Xu, Fu; Zhang, Ping

2018-04-01

Recently, there has been a surge of interest in the research of two-dimensional (2D) phosphides due to their unique physical properties and wide applications. Transition metal phosphides 2H-M 2Ps (Mo2P, W2P, Nb2P and Ta2P) show considerable catalytic activity and energy storage potential. However, the electronic structure and mechanical properties of 2D 2H-M 2Ps are still unrevealed. Here, first-principles calculations are employed to investigate the lattice dynamics, elasticity and thermodynamic properties of 2H-M 2Ps. Results show that M 2Ps with lower stiffness exhibit remarkable lateral deformation under unidirectional loads. Due to the largest average Grüneisen parameter, single-layer Nb2P has the strongest anharmonic vibrations, resulting in the highest thermal expansion coefficient. The lattice thermal conductivities of Ta2P, W2P and Nb2P contradict classical theory, which would predict a smaller thermal conductivity due to the much heavier atom mass. Moreover, the calculations also demonstrate that the thermal conductivity of Ta2P is the highest as well as the lowest thermal expansion, owing to its weak anharmonic phonon scattering and the lowest average Grüneisen parameter. The insight provided by this study may be useful for future experimental and theoretical studies concerning 2D transition metal phosphide materials.

Electrodeposition of Ge/C composite anode for lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang Wan; Ngo, Duc Tung; Pak, Chan Jin [Junnam National Univ., Gwangju (Korea, Republic of)

2014-06-15

As a result, new titanium alloys are now being studies for application as biomaterials and interesting choice is the β-type titanium alloys. In order to overcome these weakness of Ti-6Al-4V alloy, many Ti alloys consisting of non-toxic elements such as Nb, Ta, Zr, Hf, Mo and Sn, have been developed for biomedical applications. They are mostly β type alloys composed of non-toxic elements. This newly developed Ti-25Ta-xHf (x = 0, 3, 7, 10, and 15 wt.%) alloy is expected to demonstrate better biocompatibility. The purpose of this research was to investigate electrochemical characteristics of Ti-Ta alloys containing HA for biomaterials. Electrochemical characteristics of Ti-25Ta-xHf alloys were improved by Hf addition and it can be an important factor for the improvement of corrosion resistance.

Obtaining of U-2.5Zr7.5Nb and U-3Zr-9Nb alloys by sintering process

International Nuclear Information System (INIS)

Mazzeu, Thiago de Oliveira; Paula, Joao Bosco de; Ferraz, Wilmar Barbosa; Santos, Ana Maria Matildes dos; Brina, Jose Giovanni Mascarenhas

2011-01-01

The development of metallic fuels with low enrichment to be used in research and test reactors, as well in the future pressurized water reactors, focuses on the search for uranium alloys of high density. Alloying elements such as Zr, Nb and Mo are added to uranium to improve fuel performance in reactors. In this context, the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN) in Belo Horizonte is developing the U-2.5Zr-7.5Nb and U- 3Zr-9Nb (weight %) alloys by the innovative process of sintering that utilizes raw materials in the form of powders. The powders were pressed at 400MPa and then sintered under a vacuum of about 5 x 10-6 Torr at temperatures ranging from 1050 deg to 1300 deg C. The densities of the alloys were measured geometrically and by hydrostatic method using water. The microstructures of the pellets were observed by scanning electron microscopy (SEM) and the elements of alloying were identified by energy dispersive X-ray spectroscopy (SEM/EDS) analysis. The obtained results showed a small increasing density with rising sintering temperature. The highest density achieved was approximately 80% of theoretical density. It was also qualitatively observed that the superficial oxidation of the pellets increased with increasing sintering temperature thus avoiding the fusion of the alloys at higher temperatures. (author)

Maximisation of the ratio of microhardness to the Young's modulus of Ti-12Mo-13Nb alloy through microstructure changes.

Science.gov (United States)

Gabriel, Sinara B; de Almeida, Luiz H; Nunes, Carlos A; Dille, Jean; Soares, Glória A

2013-08-01

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable β titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti-12Mo-13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000°C for 24h, water quenching, cold forging to reduce 80% of the area, and ageing at 500°C for 24h, where the final microstructure consisted of an α phase dispersed in a β matrix. The α phase appeared in two different forms: as fine lamellas (with 240±100 nm length) and massive particles of 200-500 nm size. Copyright © 2013 Elsevier B.V. All rights reserved.

Molybdenite Re-Os dating of Mo-Th-Nb-REE rich marbles: pre-Variscan processes in Moldanubian Variegated Group (Czech Republic

Directory of Open Access Journals (Sweden)

Drábek Milan

2015-06-01

Full Text Available In an effort to contribute to the discussion concerning the age of rocks of the Moldanubian Variegated Group, we have undertaken Re-Os dating of molybdenite of banded carbonatite-like marbles (CLM from the graphite mine Václav at Bližná (Southern Bohemia, which belong to the metamorphic sequence of this group. The Re-Os model ages for the molybdenites range between 493 and 497 Ma and apparently correspond to the early stages of metamorphism connected with pre-Variscan rift-related tectono-metamorphic events, which affected and recrystallized sedimentary CLM material rich in Mo-Th-Nb-REE. The molybdenite bearing carbonatite like marbles situated in the footwall of Bližná graphite mine have been interpreted as carbonates with a large share of volcano-detritic material derived from contemporaneous primitive alkaline (carbonatite-like volcanism deposited in a shallow marine lagoonal environment. There is no geological evidence for the participation of fluids mobilized from host rocks in the formation of the CLM. Because the Re-Os chronometer in molybdenite is demonstrably stable through later Variscan facies metamorphism, the molybdenite chronometer has not been affected by subsequent thermal overprints associated with the Variscan orogeny.

Substitution of modified 9 Cr-1 Mo steel for austentic stainless steels

International Nuclear Information System (INIS)

Sikka, V.K.

1982-04-01

This report describes the current program to develop a high-strength ferritic-martensitic steel. The alloy is essentially Fe-9% Cr-1% Mo with small additions of V and Nb and is known as modifed 9 Cr-1 Mo steel. Its elevated-temperature properties and design allowable stresses match those of type 304 stainless steel for temperatures up to 600 0 C and exceed those of other ferritic steels by factors of 2 to 3. The improved strength of this alloy permits its use in place of stainless steels for many applications

HF i dag

DEFF Research Database (Denmark)

Lindstrøm, Maria Duclos; Simonsen, Birgitte

2008-01-01

Notatet er lavet på baggrund af uddannelsesbiografiske dybdeinterviews med kursister på toårigt HF. Indenfor rammerne af en pilotundersøgelse identificerer notatet fire gennemgående profiler: De pragmatiske, de fagligt usikre, second chance-kursisterne, og de HF-kursister, som har HF som first...

X-ray and neutron diffraction studies of the formation and structure of hydrogen intercalated 2H-NbSe2 phases

International Nuclear Information System (INIS)

Kulikov, L.M.; Skolozdra, R.V.; Fruchart, D.; Soubeyroux, J.L.

1996-01-01

Intercalated compounds of H 0.07 NbSe 2 and D x NbSe 2 (x = 0.41; 0.49) composition have been prepared and investigated by powder X-ray and neutron diffraction. Rietveld analysis of the data showed that hydrogen (deuterium) atoms occupy the 2(c) site with coordinates (1/3 2/3 1/4) (structure type 2H-TaS 2 for H 0.07 NbSe 2 ) and the 2(b) site with coordinates (0 0 1/3) (structure type 2H-MoS 2 for D 0.41 NbSe 2 and D 0.49 NbSe 2 ). According to crystallographic results it is suggested that the nature of the quasi-two-dimensional layer plays a key role in the unusual location of the hydrogen atoms, the intercalation processes and the maximum uptake of hydrogen. The results are compared with the available literature data. (orig.)

Peierls-distorted Ru-chains and boron dumbbells in Nb{sub 2}RuB{sub 2} and Ta{sub 2}RuB{sub 2} from first-principles calculations and experiments

Energy Technology Data Exchange (ETDEWEB)

Touzani, Rachid S.; Mbarki, Mohammed; Chen, Ximeng [Institute of Inorganic Chemistry, RWTH Aachen University (Germany); Fokwa, Boniface P.T. [Institute of Inorganic Chemistry, RWTH Aachen University (Germany); Department of Chemistry, University of California Riverside (UCR), Riverside, CA (United States)

2016-09-15

Nb{sub 2}RuB{sub 2} and Ta{sub 2}RuB{sub 2} phases were recently predicted by GGA-VASP structure optimization to crystallize in the Nb{sub 2}OsB{sub 2}-type structure. Although the Fe-based (Mo{sub 2}FeB{sub 2} type) and Os-based (Nb{sub 2}OsB{sub 2} type, superstructure variant of Mo{sub 2}FeB{sub 2} type) analogues have been synthesized and characterized successfully, the Ru-based phases remained unknown. Crystal structure prediction of Nb{sub 2}RuB{sub 2} and Ta{sub 2}RuB{sub 2} phases, using an evolutionary algorithm, led to the AlMn{sub 2}B{sub 2}-type structure in contrast to the aforementioned optimization; however, phonon calculations showed that the Nb{sub 2}OsB{sub 2}-type phases are dynamically more stable than the AlMn{sub 2}B{sub 2}-type phases. A slightly modified synthetic strategy finally led to the successful preparation of the predicted phases. The extremely quick arc-melting procedure, under argon atmosphere, not only led to a quantitative amount of the phases but also to single crystals suitable for structure determination. Powder and single-crystal X-ray diffraction as well as EDX analysis of the metal ratio have confirmed the GGA-VASP structure optimization: Nb{sub 2}RuB{sub 2} and Ta{sub 2}RuB{sub 2} compounds indeed crystallize isotypically with Nb{sub 2}OsB{sub 2} structure, a superstructure variant of Mo{sub 2}FeB{sub 2} type, in which B-dumbbells and Peierls-distorted Ru-chains are found. Susceptibility measurements on a Ta{sub 2}RuB{sub 2} single crystal reveal no superconducting transition down to 2 K, even though some features in the band structures of both phases, similar to those reported in superconducting NbRuB, hinted at possible superconductivity. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The creep and stress-rupture behaviour under internal pressure of tubes made from austenitic stainless steel X8 CrNiMoNb 1616 (Material No. 1.4981)

International Nuclear Information System (INIS)

Schaefer, L.; Polifka, F.; Kempe, H.

1979-05-01

Creep and stress rupture tests have been performed at 600, 650, 700 and 750 0 C on tubes made from three different heats from the austenitic stainless steel X8 CrNiMoNb 1616 (Material No. 1.4981). The tubes were loaded by internal pressure and the tangential (hoop) creep strain was measured continuously. The results are presented in form of creep curves, stress-time to rupture curves and curves for a creep limit. The average and minimum creep rates as a function of the applied stress have been evaluated and are described with a creep law analogous to Norton's creep law. An interpolation and extrapolation of the stress-rupture-strength and the creep strength are possible using the time-temperature-parameter-plot after Larson and Miller. (orig.) [de

Synthesis and molecular structures of niobocene derivatives containing Nb-Sn-Nb metallochain

International Nuclear Information System (INIS)

Skripkin, Yu.V.; Volkov, O.G.; Pasynskij, A.A.

1985-01-01

The [Cp 2 Nb(CO)] 2 SnCl 2 (1) complex is synthesized in the form of crystals with 63% yield by the Cp 2 Nb(CO)H reaction wih SnCl 4 in THF in the presence of Et 3 N. The complex 1 is also prepared by interaction of Cp 2 Nb(CO)H with Cp 2 Nb(CO)SnCl 3 with 16% yield. The crystalline more sluble analog [(CH 3 C 5 H 4 ) 2 Nb(CO)] 2 ShCl 2 (2) is extracted, which contains the chain of Nb-Sn-Nb with short Nb-Sn(2.840)2)A bonds and 140.69(5) deg angle between them. The (Cp 2 NbH) 2 Sn(Cl)Et (3) complex is prepared wih 12% yield, possessing the structure analogous to type 2. In 3 each fragment CpNb is connected with the terminal hydride (Nb-H, 1.66(1) and 1.69(1)A) atom forms shortened bond with tin atom Nb-Sn 2.868(1) and 2.856(1) A, NbSnNb angle is 129.44(5)

Comparison of HfCl{sub 4}, HfI{sub 4}, TEMA-Hf, and TDMA-Hf as precursors in early growing stages of HfO{sub 2} films deposited by ALD: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Cortez-Valadez, M. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190 Hermosillo, Son. (Mexico); Fierro, C.; Farias-Mancilla, J.R. [Instituto de Ingeniería y Tecnología, Departamento de Física y Matemáticas, Universidad Autónoma de Ciudad Juárez, Av. del Charro 450, Cd. Juárez C.P. 32310, Chihuahua (Mexico); Vargas-Ortiz, A. [Universidad Autónoma de Sinaloa, Facultad de Ingeniería Mochis, Ciudad Universitaria, C.P. 81223 Los Mochis, Sinaloa (Mexico); Flores-Acosta, M. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190 Hermosillo, Son. (Mexico); Ramírez-Bon, R. [Centro de Investigación y Estudios Avanzados del IPN, Unidad Querétaro, Apdo. Postal 1-798, 76001 Querétaro, Qro. (Mexico); Enriquez-Carrejo, J.L. [Instituto de Ingeniería y Tecnología, Departamento de Física y Matemáticas, Universidad Autónoma de Ciudad Juárez, Av. del Charro 450, Cd. Juárez C.P. 32310, Chihuahua (Mexico); and others

2016-06-15

Highlights: • Hafnium oxide growth on Si(100) by atomic layer deposition was simulated. • The interface structure was considered as silicate and silicide. • The interface was studied employing DFT. • TDMA-Hf precursor show better interface stability. - Abstract: The final structure of HfO{sub 2} films grown by atomic layer deposition (ALD) after reaction with OH{sup −} ions has been analyzed by DFT (density functional theory). The interaction of the precursors: HfCl{sub 4} (hafnium tetrachloride), HfI{sub 4} (hafnium tetraiodide), TEMA-Hf (tetrakis-ethylmethylamino hafnium), and TDMA-Hf (tetrakis-dimethylamino hafnium) with HO–H was studied employing the B3LYP (Becke 3-parameter, Lee–Yang–Parr) hybrid functional and the PBE (Perdew–Burke–Ernzerhof) generalized gradient functional. The structural evolution at the Si(100) surface has been analyzed by LDA (local density approximation). The structural parameters: bond length and bond angle, and the vibrational parameters for the optimized structures are also reported. The presence of hafnium silicate at the interface was detected. The infrared spectra and structural parameters obtained in this work agree with previously reported experimental results.

Wet etching characteristics of a HfSiON high-k dielectric in HF-based solutions

International Nuclear Information System (INIS)

Li Yongliang; Xu Qiuxia

2010-01-01

The wet etching properties of a HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing, the etch rate of HfSiON annealed at 900 0 C for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interfacial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of Si-N bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N 2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case. (semiconductor technology)

Microhardness evaluation alloys Hf-Si-B; Avaliacao de microdureza de ligas Hf-Si-B

Energy Technology Data Exchange (ETDEWEB)

Gigolotti, Joao Carlos Janio; Costa, Eliane Fernandes Brasil [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Rocha, Elisa Gombio; Coelho, Gilberto Carvalho, E-mail: carlosjanio@uol.com.br, E-mail: eliane-costabrasi@hotmail.com, E-mail: cnunes@demar.eel.usp.br, E-mail: elisarocha@alunos.eel.usp.br, E-mail: coelho@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil)

2014-08-15

The technological advance has generated increasing demand for materials that can be used under high temperature, what includes intermetallic MR-Si-B (MR = refractory metal) alloys with multiphase structures, that can also be applied in oxide environments. Thus, this work had for objective the micro hardness study of the Hf-Si-B system alloys, heat treated at 1600 deg C, in the Hf rich region. Hf-Si-B alloys had been produced with blades of Hf (min. 99.8%), Si (min. 99.998%) and B (min. 99.5%), in the voltaic arc furnace and heat treated at 1600 deg C under argon atmosphere. The relationship of the phases had been previously identified by X-ray diffraction and contrast in backscattered electron imaging mode. The alloys had their hardness analyzed by method Vickers (micro hardness) with load of 0.05 kgf and 0.2 kgf and application time of 20 s. The results, obtained from the arithmetic mean of measurements for each alloy on the heterogeneous region, showed a mean hardness of 11.08 GPA, with small coefficient of variation of 3.8%. The borides HfB2 (19.34 GPa) e HfB - 11.76 GPa, showed the hardness higher than the silicides Hf2Si (8.57 GPa), Hf5Si3 (9.63 GPa), Hf3Si2 (11.66 GPa), Hf5Si4 (10.00 GPa), HfSi (10.02 GPa) e HfSi2 (8.61 GPa). (author)

The use of extraction and electronic diffraction replicas for precipitates characterization in welded Cr-Mo Steels

International Nuclear Information System (INIS)

Gutierrez de Saiz-Solabarria, S.; San Juan Nunez, J.M.

1997-01-01

The precipitates and phases found in the structure of welded joints of Heat Interchanges Tubes were studied and identified. The base material satisfied the requirements of ASME Sec II, SA 213 Gr T22 (2 1/4 Cr 1 Mo). Compositions of Filler Metals were: 2 1/4 Cr 1 Mo and 2 1/4 Cr 1 Mo 1/4 Nb. The chemical composition of base and weld materials were analyzed by atomic emission spectroscopy in high vacuum electric discharge and by inductive plasma coupled. For the constituents characterization extraction and diffraction microscopy replicas were used. (Author) 65 refs

Effects of temperature and Mo2C layer on stress and structural properties in CVD diamond film grown on Mo foil

International Nuclear Information System (INIS)

Long, Fen; Wei, Qiuping; Yu, Z.M.; Luo, Jiaqi; Zhang, Xiongwei; Long, Hangyu; Wu, Xianzhe

2013-01-01

Highlights: •Polycrystalline diamond films were grown on Mo foil substrates by HF-CVD. •We investigated the temperature dependence of the film stress for each sample. •We show that how the thermal stress and intrinsic stress affects the total stress. •The stress of Mo foil substrate obtained by XRD was investigated in this study. •The effect of Mo 2 C interface layer for stress of multilayer system was considered. -- Abstract: Polycrystalline diamond films have been prepared by hot-filament-assisted chemical vapor deposition (HFCVD) on Mo foils. The morphology, growth rate, phase composition, element distribution and residual stress of the films at different temperature were investigated by field-emission scanning electron microscopy, Raman spectrum, field emission electron probe microanalysis and X-ray diffraction. Results show that the residual stress of the diamond films is compressive. The thermal stress plays a decisive role in the total stress, while the intrinsic stress can change the trend of the total stress. The residual stress of substrate gradually changes from tensile stress to compressive stress with the increase of the deposited temperature. A Mo 2 C interlayer is formed during deposition process, and this layer has an important influence on the stresses of films and substrates

Pressure induced Amorphization of Ln1/3(Nb,Ta)O3

International Nuclear Information System (INIS)

Melchior, A.; Noked, O.; Sterer, E.; Shuker, R.

2014-01-01

The research focuses on the phenomenon of pressure induced amorphization (PIA) in Ln1/3MO3, Ln - La,Pr,Nd and M-Nb,Ta. In most pressure induced phase transitions the material changes from a crystalline phase to another crystalline phase. However, if this transition is kinetically hindered, the increased free energy due to the applied pressure will result in a structural collapse to an amorphous intermediate phase. This phenomenon is known as pressure induced amorphization

Comparison of results analysis of chemical composition of alloys inside the U-Zr-Nb by XRF and AAS techniques

International Nuclear Information System (INIS)

Masrukan; Tri Yulianto; Anwar Muchsin

2011-01-01

U-Zr-Nb alloy chemical composition analysis using X Ray Fluorescence (XRF) and Atomic Absorption Spectroscopy (AAS) techniques have been conducted, where U-Zr- Nb alloy was chosen as candidates for new high-density fuel for future research reactors . Composition analysis is necessary because the composition of elements in the fuel will determine the characteristics of fuel during the fabrication process and in the reactor. The use of two kinds of analysis techniques were designed to obtain accurate analysis results. The experiment was conducted to determine the major element composition and impurities in the alloy U-Zr-Nb. First U-Zr-Nb varying alloy composition Nb were respectively 1%, 4%, 7% (U10% Zr1% Nb, U10% Zr4% Nb and U10% 7% Nb) as results of the melting process of measuring the diameter of 120 mm crushed on the surface bottom. Once on the bottom surface is smooth, then analyzed using XRF techniques. To analyze the elements using AAS techniques, alloy U-Zr-Nb cut into 10 mm x 5 mm then dissolved using HF and nitric acid. Solution that occurred were analyzed using AAS technique. From the analysis using the XRF technique is obtained the alloy U-10% Zr-1% Nb, U-10% Zr-4% Nb and Zr-10% U-7% Nb) had a content of each element as follows: U (87.8858%), Zr (2.6097%) and Nb (0.2206%), U (87.8556%), Zr (2.6302%), and Nb (0.6573%); U (84.6334%), Zr (2.5773%), and Nb (1.0940) weight. Results of analysis using AAS techniques on samples obtained third consecutive Zr content of 9.25%, 8.90% and 9.80% while the content of Nb was not detected. Meanwhile, the results of elemental analysis of impurities in all three samples showed that almost all the elements are still qualify as fuel except Zn element. Element Zn at the three samples of each alloys U-10% Zr-1% Nb, U-10% Zr-4% Nb and U-10% Zr-7%Nb is 1.3266%, 3.2756% and 1.0927% weight. It could be concluded that the results of analysis of elemental content and impurities in the alloy U-Nb-Zr using both XRF and AAS visible

Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

International Nuclear Information System (INIS)

Han, Jian; Li, Huijun; Barbaro, Frank; Jiang, Laizhu; Zhu, Zhixiong; Xu, Haigang; Ma, Li

2014-01-01

The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe 2 Nb (Laves phase) and Cr 23 C 6 formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe 2 Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe 2 Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe 2 Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe 2 Nb particles

Precipitation and impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel during isothermal aging

Energy Technology Data Exchange (ETDEWEB)

Han, Jian, E-mail: jh595@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Li, Huijun [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Barbaro, Frank [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); CBMM Technology Suisse, 14, Rue du Rhone, Geneve 1204 (Switzerland); Jiang, Laizhu [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China); Zhu, Zhixiong [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia); Xu, Haigang; Ma, Li [Baoshan Iron and Steel Co., Ltd., Shanghai 200431 (China)

2014-08-26

The effect of isothermal aging on precipitation behaviour and Charpy impact toughness of Nb–V stabilised 18Cr–2Mo ferritic stainless steel was investigated by means of Thermo-Calc prediction, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Charpy impact toughness testing. The results show that, niobium, vanadium carbides and nitrides, Fe{sub 2}Nb (Laves phase) and Cr{sub 23}C{sub 6} formed after 2 h aging at 800 °C, and the equilibrium solvus temperature of Fe{sub 2}Nb phase increases to above 750 °C, higher than the calculated temperature (730 °C) using Thermo-Calc. After isothermal aging at 750–950 °C, 2 h aging resulted in a decrease in toughness due to the formation of precipitation, especially (Nb,V)(C,N) and Fe{sub 2}Nb. When isothermally aged at 800 °C for up to 24 h, the coarsening rate of Fe{sub 2}Nb particle is much higher than that of (Nb,V)(C,N), and the impact toughness of the steel is dependent on quantity and sizes of (Nb,V)(C,N) and Fe{sub 2}Nb particles.

Preparation, composition, and solid state investigations of TiN, ZrN, NbN, and compounds from the pseudobinary systems NbN-NbC, NbN-TiC, and NbN-TiN

International Nuclear Information System (INIS)

Christensen, A.N.; Fregerslev, S.

1977-01-01

Single crystals of the cubic phases TiN, ZrN, delta-NbN and of compounds from the pseudobinary systems NbN-NbC, NbN-TiC, and NbN-TiN were obtained by zone melting, zone annealing and annealing of the metal carbides in nitrogen gas of 2 MPa. Single crystals of the tetragonal phase gamma-NbN were obtained in a similar way by annealing of niobium. The nitrides are non-stochiometric. TiN was obtained in the composition range TiNsub(0.99) to TiNsub(0.50), ZrN in the range ZrNsub(1.00) to ZrNsub(0.63), and in niobium nitrides were obtained in the composition range NbNsub(0.90) to NbNsub(0.69). The compounds from the pseudobinary systems have up to 35% vacant sites in the nitrogen-carbon sublattice. TiN and ZrN have only vacant sites in the nitrogen sublattice. A correlation is found between the unit cell parameters for titanium nitride and zirconium nitride and the nitrogen-metal ratios. (orig.) [de

The Effect of Simulated Thermomechanical Processing on the Transformation Behavior and Microstructure of a Low-Carbon Mo-Nb Linepipe Steel

Science.gov (United States)

Cizek, P.; Wynne, B. P.; Davies, C. H. J.; Hodgson, P. D.

2015-01-01

The present work investigates the transformation behavior of a low-carbon Mo-Nb linepipe steel and the corresponding transformation product microstructures using deformation dilatometry. The continuous cooling transformation (CCT) diagrams have been constructed for both the fully recrystallized austenite and that deformed in uniaxial compression at 1148 K (875 °C) to a strain of 0.5 for cooling rates ranging from 0.1 to about 100 K/s. The obtained microstructures have been studied in detail using electron backscattered diffraction complemented by transmission electron microscopy. Heavy deformation of the parent austenite has caused a significant expansion of the polygonal ferrite transformation field in the CCT diagram, as well as a shift in the non-equilibrium ferrite transformation fields toward higher cooling rates. Furthermore, the austenite deformation has resulted in a pronounced refinement in both the effective grain (sheaf/packet) size and substructure unit size of the non-equilibrium ferrite microstructures. The optimum microstructure expected to display an excellent balance between strength and toughness is a mix of quasi-polygonal ferrite and granular bainite (often termed "acicular ferrite") produced from the heavily deformed austenite within a processing window covering the cooling rates from about 10 to about 100 K/s.

HF/DF chemical labs

International Nuclear Information System (INIS)

Meinzer, R.A.

1987-01-01

This paper provides the essential details to understand and design HF/DF and related types of chemical lasers. The basic operation of the HF/DF chemical laser is described. The details of the excitation chemistry are presented and the pertinent laser physics is described. A description of the various laser components is given and the analytical models for the HF/DF chemical laser are discussed. A brief description of the chain reaction HF/DF chemical laser is offered

Toughening MoSi2 with Niobium metal -- Effects of size and orientation of ductile laminae

International Nuclear Information System (INIS)

Shaw, L.; Abbaschian, R.

1994-01-01

Effects of size and orientation of ductile laminae on the toughness of brittle matrix composites have been evaluated using MoSi 2 composites reinforced with Nb laminae. Nb laminae with thicknesses ranging from 0.127 to 1.0 mm were hot pressed with MoSi 2 powder to prepare the composites. Toughness of the composites was measured using four-point bend test on chevron-notched specimens. It was found that the toughness of the composites increased with increasing size of the niobium laminae. Furthermore, toughening was observed at crack propagation directions perpendicular to the laminae plane, indicating that ductile laminae offer two dimensional toughening. A model based on the bridging contribution of the ductile phase has been proposed to analyze the chevron-notched specimens of the ductile-phase-reinforced brittle matrix composites. The analysis showed that the dependence of the toughness of the composites on the size and orientation of the ductile laminae could be interpreted in terms of their bridging capability and bending contributions

Influence of microstructural development during annealing at 780oC on creep resistance of ferritic-martensitic T91 (9%Cr-1%Mo-V-Nb) steel

International Nuclear Information System (INIS)

De Cicco, H; Zavaleta Gutierrez, N; Marrero, J; Luppo, M.I; Danon, C.A

2006-01-01

Due to its good properties of creep resistance, toughness and rust resistance, martensitic-ferritic 9%Cr-1%Mo steels are widely used for the production of heating plant components, boilers, heat exchangers, piping and tubing, etc. The effectiveness in steels of MX carbonitrides such as (Nb,V) (C,N) on improving creep resistance at high temperatures is well known. Controlling the behavior of the MX phases to precipitation, during annealing, is essential for obtaining a stable microstructure that can resist high temperatures. This study investigates the relationship between creep resistance and the microstructural changes that occur at different annealing times at a temperature of 780 o C -used industrially during the production and post-welding- in T91 steel. Creep trials were carried out at 600 o C and 190 MPa, and the samples were characterized using optic microscopy (OM), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and transmission electron microscopy (TEM), the latter including a facility for energy dispersive spectroscopy (EDS). Based on its morphological characteristics, the MX precipitates are classified into three types, types I, II and III. Tempering time at 780 o C has been found to be one of the factors that determines which MX is dominant in the annealed steel. The presence of type MX-III, formed by the secondary precipitation of a VN particle adhering to a NbX, commonly called 'wing', seems to favor creep resistance in these steels. This type of of precipitate, then, fills an effective role in the anchoring of dislocations during creep (cw)

HF laser

International Nuclear Information System (INIS)

Suzuki, Kazuya; Iwasaki, Matae

1977-01-01

A review is made of the research and development of HF chemical laser and its related work. Many gaseous compounds are used as laser media successfully; reaction kinetics and technological problems are described. The hybrid chemical laser of HF-CO 2 system and the topics related to the isotope separation are also included. (auth.)

Comparing Thermal Stability of NbTi and Nb$_3$Sn Wires

CERN Document Server

Breschi, M; Bottura, L; Devred, A; Trillaud, F

2009-01-01

The investigation of quenching in low temperature superconducting wires is of great relevance for a proper design of superconductive cables and magnets. This paper reports the experimental results of a vast measurement campaign of quench induced by laser pulses on NbTi and Nb$_{3}$Sn wires in pool boiling Helium I. A comparison of the quench behavior of two typical NbTi and Nb$_{3}$Sn wires is shown from different standpoints. Different qualitative behaviors of the voltage traces recorded during quenches and recoveries on NbTi and Nb$_{3}$Sn wires are reported and analyzed. It is shown that the Nb$_{3}$Sn wire exhibits a quench or no-quench behavior, whereas quenches and recoveries are exhibited by the NbTi wire. The two wires are also compared considering the behaviors of the two main parameters describing quench, i.e. quench energies and quench velocities, with respect to operation current and pulse duration and magnetic field. It is shown that the Nb$_{3}$Sn wire exhibits a ‘kink’ of the quench energy ...

Thermodynamics of superconducting Nb3Al, Nb3Ge, Nb3Sn, and V3Ga

Science.gov (United States)

Mitrović, B.; Schachinger, E.; Carbotte, J. P.

1984-06-01

We have calculated the superconducting thermodynamic properties for several high-transition-temperature A15 compounds: Nb-Al, Nb-Ge, Nb-Sn, and V-Ga. In our calculations we have used the tunneling electron-phonon-coupling spectra α2F for all four systems considered, and in the case of Nb-Al and Nb-Ge we have also used α2F=CG, where G is the measured generalized phonon density of states and C is a constant. We find that all Nb-based A15 compounds display similar thermodynamic properties, which do not depend explicitly on the band density of states: 2Δ0κBTc≅4.6, ΔCγTc≅2.5-2.6,-Tc[dHc(T)dT]TcHc(0)≅2.1, γ[TcHc(0)]2≅0.134, and positive D(t)'s with the maximum value around 0.02. For Nb3Sn we find good agreement between the calculated properties and the old specific-heat experimental results (γ≅52 mJ/mol K2). The same applies to V3Ga, where the theoretical results have been compared with the experiments of Junod et al. However, we do not find good agreement between calculated ΔCγTc, - Tc[dHc(T)dT]TcHc(0), γ[TcHc(0)]2, and experimental values for Nb3Al and Nb3Ge, presumably due to broadened transitions. It is argued that the tunneling experiments underestimate the value of the gap which should be associated with the inverted α2F.

Chemistry of the elements

International Nuclear Information System (INIS)

Greenwood, N.N.; Earnshaw, A.

1984-01-01

This textbook presents an account of the chemistry of the elements for both undergraduate and postgraduate students. It covers not only the 'inorganic' chemistry of the elements, but also analytical, theoretical, industrial, organometallic;, bio-inorganic and other areas of chemistry which apply. The following elements of special nuclear interest are included: Rb, Cs, Fr, Sr, Ba, Ra, Po, At, Rn, Sc, Y, Zr, Hf, V, Nb, Ta, Mo, Tc, Ru, the Lanthanide Elements, the Actinide Elements. (U.K.)

Omega phase in materials

International Nuclear Information System (INIS)

Sikka, S.K.; Vohra, Y.K.; Chidambaram, R.

1982-01-01

The subject is reviewed under the headings: introduction; occurrence and some systematics of omega phase; crystallography; physical properties; kinetics of formation, synthesis and metastability of omega phase; electronic structure of omega phase; electronic basis for omega phase stability; omega phase formation under combined thermal and pressure treatment in alloys; transformation mechanisms and models for diffuse omega phase; conclusion. The following elements of nuclear interest (or their alloys) are included: Zr, Hf, Nb, V, Mo. (U.K.)

Large Area Deposition of MoS2 by Pulsed Laser Deposition with In-Situ Thickness Control

KAUST Repository

Serna, Martha I.

2016-05-24

A scalable and catalyst-free method to deposit stoichiometric Molybdenum Disulfide (MoS2) films over large areas is reported with the maximum area limited by the size of the substrate holder. The method allows deposition of MoS2 layers on a wide range of substrates without any additional surface preparation including single crystals (sapphire and quartz), polycrystalline (HfO2), and amorphous (SiO2). The films are deposited using carefully designed MoS2 targets fabricated with excess of sulfur (S) and variable MoS2 and S particle size. Uniform and layered MoS2 films as thin as two monolayers, with an electrical resistivity of 1.54 × 104 Ω cm-1 were achieved. The MoS2 stoichiometry was as confirmed by High Resolution Rutherford Backscattering Spectrometry (HRRBS). With the method reported here, in situ graded MoS2 films ranging from ~1 to 10 monolayers can also be deposited.

Large Area Deposition of MoS2 by Pulsed Laser Deposition with In-Situ Thickness Control

KAUST Repository

Serna, Martha I.; Yoo, Seong H.; Moreno, Salvador; Xi, Yang; Oviedo, Juan Pablo; Choi, Hyunjoo; Alshareef, Husam N.; Kim, Moon J.; Minary-Jolandan, Majid; Quevedo-Lopez, Manuel A.

2016-01-01

A scalable and catalyst-free method to deposit stoichiometric Molybdenum Disulfide (MoS2) films over large areas is reported with the maximum area limited by the size of the substrate holder. The method allows deposition of MoS2 layers on a wide range of substrates without any additional surface preparation including single crystals (sapphire and quartz), polycrystalline (HfO2), and amorphous (SiO2). The films are deposited using carefully designed MoS2 targets fabricated with excess of sulfur (S) and variable MoS2 and S particle size. Uniform and layered MoS2 films as thin as two monolayers, with an electrical resistivity of 1.54 × 104 Ω cm-1 were achieved. The MoS2 stoichiometry was as confirmed by High Resolution Rutherford Backscattering Spectrometry (HRRBS). With the method reported here, in situ graded MoS2 films ranging from ~1 to 10 monolayers can also be deposited.

Micro-structural study and Rietveld analysis of fast reactor fuels: U-Mo fuels

Science.gov (United States)

Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K. B.; Kumar, Arun

2015-12-01

U-Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U-Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U-Mo alloys as fast reactor fuel.

Cross sections for nuclide production in proton- and deuteron-induced reactions on 93Nb measured using the inverse kinematics method

Directory of Open Access Journals (Sweden)

Nakano Keita

2017-01-01

Full Text Available Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113 MeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249 MeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections.

SEMICONDUCTOR TECHNOLOGY: Wet etching characteristics of a HfSiON high-k dielectric in HF-based solutions

Science.gov (United States)

Yongliang, Li; Qiuxia, Xu

2010-03-01

The wet etching properties of a HfSiON high-k dielectric in HF-based solutions are investigated. HF-based solutions are the most promising wet chemistries for the removal of HfSiON, and etch selectivity of HF-based solutions can be improved by the addition of an acid and/or an alcohol to the HF solution. Due to densification during annealing, the etch rate of HfSiON annealed at 900 °C for 30 s is significantly reduced compared with as-deposited HfSiON in HF-based solutions. After the HfSiON film has been completely removed by HF-based solutions, it is not possible to etch the interfacial layer and the etched surface does not have a hydrophobic nature, since N diffuses to the interface layer or Si substrate formation of Si-N bonds that dissolves very slowly in HF-based solutions. Existing Si-N bonds at the interface between the new high-k dielectric deposit and the Si substrate may degrade the carrier mobility due to Coulomb scattering. In addition, we show that N2 plasma treatment before wet etching is not very effective in increasing the wet etch rate for a thin HfSiON film in our case.

Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

Science.gov (United States)

Muralidharan, Govindarajan

2017-09-05

An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

Phase stability in the Nb-rich region of the Nb-B-Si system

Energy Technology Data Exchange (ETDEWEB)

Nunes, C.A.; Coelho, G.C.; Pinto, D.M. Jr.; Camargo Gandolpho, K.C. de; Borges, L.A. Jr.; Rodrigues, G. [Polo Urbo-Ind., Gleba, Lorena (Brazil). Dept. de Engenharia de Materiais

2000-07-01

Alloys of the Me-B-Si systems (Me-refractory metal) have been evaluated due to their potential for use as high temperature structural materials (T>1400 C). In the present study, the phase stability in the Nb-rich region of the Nb-B-Si system has been evaluated in terms of the current information associated to the Nb-Si, Nb-B and Nb-B-Si systems as well as our own data. For the experiments several as-cast and heat-treated alloys of the Nb-B and Nb-B-Si systems were investigated by X-ray diffraction and scanning electron microscopy. Concerning the Nb-B system the results indicated the existence of the eutectic reaction L ({proportional_to} 16 at%B) <=> Nb{sub ss}+NbB. The Nb{sub 3}B{sub 2} phase was not observed in the microstructure of as-cast alloys with composition in the range of 0 to 50 at%B. The analysis of heat-treated ternary alloys at 1600 C and 1750 C confirmed the existence of the Nb{sub ss}+T{sub 2} two-phase field at those temperatures. This T{sub 2}-phase is isomorphous of the {alpha}Nb{sub 5}Si{sub 3} and is formed through the partial substitution of Si atomos for B atoms in the lattice of the {alpha}Nb{sub 5}Si{sub 3}-phase. All ternary alloys prepared in the present study presented either Nb{sub ss} or T{sub 2} primary phases in the as-cast microstructures. In addition, those alloys presented an eutectic-like microstructure formed by the Nb{sub ss} and T{sub 2} phases in the interdendritic region. (orig.)

Thermodynamics of superconducting Nb3Al, Nb3Ge, Nb3Sn, and V3Ga

International Nuclear Information System (INIS)

Mitrovic, B.; Schachinger, E.; Carbotte, J.P.

1984-01-01

We have calculated the superconducting thermodynamic properties for several high-transition-temperature A15 compounds: Nb-Al, Nb-Ge, Nb-Sn, and V-Ga. In our calculations we have used the tunneling electron-phonon--coupling spectra α 2 F for all four systems considered, and in the case of Nb-Al and Nb-Ge we have also used α 2 F = CG, where G is the measured generalized phonon density of states and C is a constant. We find that all Nb-based A15 compounds display similar thermodynamic properties, which do not depend explicitly on the band density of states: 2Δ 0 /k/sub B/T/sub c/approx. =4.6, ΔC/γT/sub c/approx. =2.5--2.6, -T/sub c/[dH/sub c/(T)/dT]c/ H/sub c/(0)approx. =2.1, γ[T/sub c//H/sub c/(0)] 2 approx. =0.134, and positive D(t)'s with the maximum value around 0.02. For Nb 3 Sn we find good agreement between the calculated properties and the old specific-heat experimental results (γapprox. =52 mJ/mol K 2 ). The same applies to V 3 Ga, where the theoretical results have been compared with the experiments of Junod et al. However, we do not find good agreement between calculated ΔC/γT/sub c/, -T/sub c/[dH/sub c/(T)/dT]c/H/sub c/(0), γ[T/sub c//H/sub c/(0)] 2 , and experimental values for Nb 3 Al and Nb 3 Ge, presumably due to broadened transitions. It is argued that the tunneling experiments underestimate the value of the gap which should be associated with the inverted α 2 F

HF-laser program

International Nuclear Information System (INIS)

Anon.

1978-01-01

Sandia's HF-laser program for FY 77 and FY 78 was revised in June 1977 in order to meet several new program milestones. Research progress is reported on: objective of HF oscillator-amplifier studies using H 2 -F 2 gas mixtures; characteristics of large-volume oscillator using H 2 -F 2 mixtures; characteristics of large-volume amplifier using H 2 -F 2 mixtures; experimental results of the oscillator-amplifier study; objective of high-quality discharge-initiated SF 6 -HI oscillator-preamplifier system; pin-discharge-initiated oscillator and first beam expander; fast-discharge-initiated preamplifiers; reflecting beam expanders for oscillator-preamplifier system; beam quality of discharge-initiated oscillator-preamplifier system; short pulse option for discharge initiated SF 6 -HI system; H 2 -F 2 electron-beam-initiated oscillator-preamplifier system; chamber for HF-laser focusing experiments; computer study of parasitic oscillations in HF amplifiers and oscillators; kinetics upgrade of HF-laser code; repetitivey ignited flowing H 2 -F 2 -O 2 mixtures; spontaneous detonations in multiatmosphere H 2 -F 2 -O 2 mixtures; high-pressure H 2 -F 2 laser studies; and time sequenced energy extraction on the high xenon laser

High-aspect-ratio HfC nanobelts accompanied by HfC nanowires: Synthesis, characterization and field emission properties

Energy Technology Data Exchange (ETDEWEB)

Tian, Song, E-mail: tiansong22@126.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Zhang, Yulei; Ren, Jincui; Qiang, Xinfa; Zhang, Shouyang [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Hejun, E-mail: lihejun@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China)

2017-04-30

Highlights: • HfC naobelts accompanied by HfC nanowires were synthesized by a catalytic CVD method. • HfC nanobelts as a novel structure of HfC ceramic are reported for the first time. • HfC nanobelts have 100–200 μm in lengths and reach up to 10 μm in widths. • The synthesized product is promising field nanoemitters. - Abstract: As a key refractory carbide, hafnium carbide (HfC) is commonly used as structural materials while the field emission (FE) application of HfC in the field of vacuum microelectronics is almost the only one for functional material purposes. Based on its outstanding physical and chemical characteristics, HfC is identified as a potential candidate with satisfactory mechanical properties and long-term and/or high-temperature FE stability for future applications in high-performance field emitters. However, the development of HfC in various FE applications is hindered because it is not facile to fabricate large-scale low-dimensional HfC field nanoemitters. Herein, High-aspect-ratio HfC nanobelts accompanied by HfC nanowires were synthesized on a large scale by a traditional and simple catalytic chemical vapor deposition (CVD) method. Classical vapor–liquid–solid (VLS) theory was employed to explain the growth of the HfC nanowires and nanobelts along axial direction. The thin HfO{sub 2} shell and thin C layer surrounding the nanostructures might give rise to the diameter fluctuation of HfC nanowires and the width increase of HfC nanobelts in lateral direction. Field emission results show that the high-aspect-ratio HfC nanobelts accompanied by the nanowires are promising field nanoemitters, which exhibit excellent field emission properties with a fairly low turn-on field of ∼1.5 V μm{sup −1} and a low current fluctuation less than ∼10%. This suggests that HfC ceramics with high-aspect-ratio nanostructures are ideal cathode material for various field emission applications.

Determination of the rate of HF hydration and the effects of HF on moisture condensation

International Nuclear Information System (INIS)

McCulla, W.H.

1982-01-01

There were four basic questions addressed in this report that relate to the HF interaction in the environment. As to whether HF hydrates in the vapor phase and what the rate of that hydration is, there seems ample evidence that HF hydrates readily in the vapor phase and the rate of that hydration is very fast, i.e., dHF/dt greater than or equal to 25 torr sec -1 . Concerning under what conditions condensation of the hydrate will occur and whether a third body is required for condensation, it was found that HF does effect the dew point or condensation of water and data was presented indicating the extent of that effect. It was also determined that condensation will occur without a third body present. Thus, in attempting to model an HF release for the Safety Analysis Report the hydration of HF and the subsequent heat released may be treated as occurring instantaneously; but the ultimate disposition of the HF will be strongly dependent upon the environmental conditions at the time of the release

Determination of the rate of HF hydration and the effects of HF on moisture condensation

Energy Technology Data Exchange (ETDEWEB)

McCulla, W H

1982-04-30

There were four basic questions addressed in this report that relate to the HF interaction in the environment. As to whether HF hydrates in the vapor phase and what the rate of that hydration is, there seems ample evidence that HF hydrates readily in the vapor phase and the rate of that hydration is very fast, i.e., dHF/dt greater than or equal to 25 torr sec/sup -1/. Concerning under what conditions condensation of the hydrate will occur and whether a third body is required for condensation, it was found that HF does effect the dew point or condensation of water and data was presented indicating the extent of that effect. It was also determined that condensation will occur without a third body present. Thus, in attempting to model an HF release for the Safety Analysis Report the hydration of HF and the subsequent heat released may be treated as occurring instantaneously; but the ultimate disposition of the HF will be strongly dependent upon the environmental conditions at the time of the release.

High-K rotational bands in {sup 174}Hf and {sup 175}Hf

Energy Technology Data Exchange (ETDEWEB)

Gjoerup, N L; Sletten, G [The Niels Bohr Institute, Roskilbe (Denmark); Walker, P M [Surrey Univ., Guildford (United Kingdom). Dept. of Physics; Bentley, M A [Daresbury Lab. (United Kingdom); Cullen, D M; Sharpey-Schafer, J F; Fallon, P; Smith, G [Liverpool Univ. (United Kingdom). Oliver Lodge Lab.

1992-08-01

High sensitivity experiments with {sup 48}Ca, {sup 18}O and {sup 9}Be induced reactions using the ESSA-30, TESSA-3 and NORDBALL arrays have provided extensive new information on the high spin level structures of {sup 174}Hf and {sup 175}Hf. During the series of experiments, several new bands have been found and most known bands have been extended considerably. Spin and excitation energy ranges for {sup 174}Hf are now {approx} 35 {Dirac_h} and {approx} 13 MeV, respectively, and for {sup 175}Hf ranges are {approx} 30 {Dirac_h} and {approx} 7 MeV. respectively. Several new high-K structures have been found in {sup 174}Hf and the structure of these and the already known high-K bands in both nuclei together with the new Tilted Axis Cranking approach might explain the small K-hindrances observed for K-isomers in this region. (author). 8 refs., 2 figs.

Suppression of superconductivity in Nb by IrMn in IrMn/Nb bilayers

KAUST Repository

Wu, B. L.

2013-10-10

Effect of antiferromagnet on superconductivity has been investigated in IrMn/Nb bilayers. Significant suppression of both transition temperature (Tc) and lower critical field (Hc1) of Nb is found in IrMn/Nb bilayers as compared to a single layer Nb of same thickness; the suppression effect is even stronger than that of a ferromagnet in NiFe/Nb bilayers. The addition of an insulating MgO layer at the IrMn-Nb interface nearly restores Tc to that of the single layer Nb, but Hc1 still remains suppressed. These results suggest that, in addition to proximity effect and magnetic impurity scattering, magnetostatic interaction also plays a role in suppressing superconductivity of Nb in IrMn/Nb bilayers. In addition to reduced Tc and Hc1, the IrMn layer also induces broadening in the transition temperature of Nb, which can be accounted for by a finite distribution of stray field from IrMn.

Isovector excitations in 100Nb and their decays by neutron emission studied via the Mo100(t,He3+n reaction at 115 MeV/u

Directory of Open Access Journals (Sweden)

K. Miki

2017-06-01

Full Text Available Spin–isospin excitations in Nb100 were studied via the Mo100(t,He3 charge-exchange reaction at 115 MeV/u with the goal to constrain theoretical models used to describe the isovector spin response of nuclei. The experiment was performed with a secondary beam of tritons, and 3He particles were analyzed in the S800 magnetic spectrometer. Decay by neutron emission from excited states in Nb100 was observed by using plastic and liquid scintillator arrays. Differential cross sections were analyzed and monopole excitations were revealed by using a multipole decomposition analysis. The Gamow–Teller transition strength observed at low excitation energies, which is important for estimating the electron-capture rate in astrophysical scenarios, was strongly fragmented and reduced compared to single-particle and spherical mean-field models. The consideration of deformation in the theoretical estimates was found to be important to better describe the fragmentation and strengths. A strong excitation of the isovector spin giant monopole resonance was observed, and well reproduced by the mean-field models. Its presence makes the extraction of Gamow–Teller strengths at high excitation energies difficult. The branches for statistical and direct decay by neutron emission were identified in the spectra. The upper limit for the branching ratio by direct decay (integrated over all observed excitations was determined to be 20±6%. Even though the statistical uncertainties in the neutron-coincident data were too large to perform detailed studies of the decay by neutron emission from individual states and resonances, the experiment demonstrates the feasibility of the method.

Record high-nuclearity polyoxoniobates. Discrete nanoclusters {Nb_1_1_4}, {Nb_8_1}, and {Nb_5_2}, and extended frameworks based on {Cu_3Nb_7_8} and {Cu_4Nb_7_8}

Energy Technology Data Exchange (ETDEWEB)

Jin, Lu; Zhu, Zeng-Kui; Wu, Yan-Lan; Qi, Yan-Jie; Li, Xin-Xiong; Zheng, Shou-Tian [State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fujian (China)

2017-12-18

A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114-nuclear {Li_8 is contained in Nb_1_1_4O_3_1_6}, one 81-nuclear {Li_3K is contained in Nb_8_1O_2_2_5}, and one 52-nuclear {H_4Nb_5_2O_1_5_0}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high-nuclearity PONbs (≤32). Furthermore, the introduction of 3d Cu{sup 2+} ions can lead to the generation of extended inorganic-organic hybrid frameworks built from novel, high-nuclearity, nanoscale heterometallic PONb building blocks {H_3Cu_3Nb_7_8O_2_2_2} or {H_3Cu_4(en)Nb_7_8O_2_2_2}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new-type PONbs has long been a challenging subject in PONb chemistry. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Multi-component solid solution alloys having high mixing entropy

Science.gov (United States)

Bei, Hongbin

2015-10-06

A multi-component high-entropy alloy includes a composition selected from the following group: VNbTaTiMoWRe, VNbTaTiMoW, VNbTaTiMoRe, VNbTaTiWRe, VNbTaMoWRe, VNbTiMoWRe, VTaTiMoWRe, NbTaTiMoWRe, VNbTaTiMo, VNbTaTiW, VNbTaMoW, VNbTiMoW, VTaTiMoW, NbTaTiMoW, VNbTaTiRe, VNbTaMoRe, VNbTiMoRe, VTaTiMoRe, NbTaTiMoRe, VNbTaWRe, VNbTiWRe, VTaTiWRe, NbTaTiWRe, VNbMoWRe, VTaMoWRe, NbTaMoWRe, VTiMoWRe, NbTiMoWRe, TaTiMoWRe, wherein relative amounts of each element vary by no more than .+-.15 atomic %.

The effect of microstructure on the deformation modes and mechanical properties of Ti-6Al-2Nb-1Ta-0.8Mo: Part II. Equiaxed structures

Science.gov (United States)

Lin, Fu-Shiong; Starke, E. A.; Gysler, A.

1984-10-01

The Ti-6Al-2Nb-lTa-0.8Mo alloy was processed to develop both near-basal and transverse textures. Samples were annealed at different temperatures to vary the equiaxed alpha grain size and the thick-ness of the grain boundary beta, and subsequently quenched in order to transform the beta phase to either martensite, tempered martensite, or Widmanstätten alpha + beta. The effect of microstructure and texture on tensile properties and on fracture toughness was investigated. In addition, yield locus diagrams were constructed in order to study the texture strengthening effect. The yield strength was found to be strongly dependent on the thickness and Burgers relationship of the transformed beta phase surrounding the alpha grains. A texture hardening effect as large as 60 pct was found for the basal-texture material but only 15 pct for the transverse texture material. These variations are asso-ciated with differences in deformation behavior.

Production of superconducting Nb3Sn wire using Nb or Nb(Ti) and Sn(Ga) solid solution powders

International Nuclear Information System (INIS)

Thieme, C.L.H.; Foner, S.

1991-01-01

This paper reports on superconducting Nb 3 Sn wire produced by the powder metallurgy method using Nb or Nb-2.9 at% Ti powder in combination with Sn-x at% Ga powders (x = 3, 4.2, 6.2 and 9.0). Ga additions to the Sn caused considerable solid solution hardening which improved its workability. It made the Nb-Sn(Ga) powder combinations convenient for swaging and extensive wire drawing. Anneals at 950 degrees C produced wires with an overall J c of 10 4 A/cm 2 at 21.9 T for wires with both Ti in the Nb and 6.2 at% Ga in the Sn. Comparison of this wire with the best Nb(Ti)-Cu-internal Sn(Ti) shows a higher J c per A15 areas, especially in fields of 22T and above

Comparing the thermal stability of NbTi and Nb3Sn wires

International Nuclear Information System (INIS)

Breschi, M; Trevisani, L; Bottura, L; Devred, A; Trillaud, F

2009-01-01

The investigation of quenching in low temperature superconducting wires is of great relevance for a proper design of superconductive cables and magnets. This paper reports the experimental results of a vast measurement campaign of quench induced by laser pulses on NbTi and Nb 3 Sn wires in pool boiling helium I. A comparison of the quench behavior of two typical NbTi and Nb 3 Sn wires is shown from different standpoints. Different qualitative behaviors of the voltage traces recorded during quenches and recoveries on NbTi and Nb 3 Sn wires are reported and analyzed. It is shown that the Nb 3 Sn wire exhibits a quench or no-quench behavior, whereas quenches and recoveries are exhibited by the NbTi wire. The two wires are also compared by considering the behaviors of the two main parameters describing quench, i.e. quench energies and quench velocities, with respect to operating current, pulse duration, and magnetic field. It is shown that the Nb 3 Sn wire exhibits a 'kink' of the quench energy versus current curve that makes the quench energy of Nb 3 Sn lower than that of NbTi at some intermediate current levels. Both the qualitative differences of the voltage traces and the different behaviors of quench energies and velocities are interpreted through a coupled electromagnetic-thermal model, with special emphasis on the detailed description of heat exchange with liquid helium.

Optical and electrical experiments at some transition-metal oxide foil-electrolyte interfaces

International Nuclear Information System (INIS)

Sari, S.O.; Ahlgren, W.L.

1977-01-01

Metal-oxide layers formed from transition-metal foils oxidized by heating in air have been examined for their photoelectrolytic response. The metals examined are Y, Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Pt. Weak photoeffects are observed for oxide layers of all of these metals. Sizable light-dependent oxygen gas evolution rates are found in Ti and also in W oxides. The spectral dependence of the oxygen response in these compounds is investigated, and interpretation is given of these experiments

Development of Nb nanoSQUIDs based on SNS junctions for operation in high magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Morosh, Viacheslav; Kieler, Oliver; Weimann, Thomas; Zorin, Alexander [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Mueller, Benedikt; Martinez-Perez, Maria Jose; Kleiner, Reinhold; Koelle, Dieter [Physikalisches Institut and Center for Quantum Science in LISA+, Universitaet Tuebingen (Germany)

2016-07-01

Investigation of the magnetization reversal of single magnetic nanoparticles requires SQUIDs with high spatial resolution, high spin sensitivity (a few Bohr magneton μ{sub B}) and at the same time sufficient stability in high magnetic fields. We fabricated dc nanoSQUIDs comprising overdamped SNS sandwich-type (Nb/HfTi/Nb) Josephson junctions using optimized technology based on combination of electron beam lithography and chemical-mechanical polishing. Our nanoSQUIDs have Josephson junctions with lateral dimensions ≤ 150 nm x 150 nm, effective loop areas < 0.05 μm{sup 2} and the distance between the Josephson junctions ≤ 100 nm. The feeding strip lines of the width ≤ 200 nm have been realized. The nanoSQUIDs have shown stable operation in external magnetic fields at least up to 250 mT. Sufficiently low level of flux noise resulting in spin sensitivity of few tens μ{sub B}/Hz{sup 1/2} has been demonstrated. A further reduction of the nanoSQUID size using our technology is possible.

High resolution TDPAC measurements on 181Ta in Hf2Fe, Hf2Co and Hf2Rh at high temperature

International Nuclear Information System (INIS)

Cekic, B.; Koicki, S.; Ivanovic, N.; Manasijevic, M.; Koteski, V.; Marjanovic, D.

1998-01-01

The time differential perturbed angular correlation measurements (TDPAC-method ) on 181 Ta ion probe in Hf 2 Co, Hf 2 Fe and Hf 2 Rh intermetallic compounds have been performed at 1170 K, using a fast - slow time spectrometer consisting of two BaF 2 detectors. The results of the measurements show the presence of two independent electric quadrupole interactions, compatible with the crystalline structure of these polycrystalline compounds. (authors)

High-temperature x-ray diffraction study of HfTiO4-HfO2 solid solutions

International Nuclear Information System (INIS)

Carpenter, D.A.

1975-01-01

High-temperature x-ray diffraction techniques were used to determine the axial thermal expansion curves of HfTiO 4 -HfO 2 solid solutions as a function of composition. Data show increasing anisotropy with increasing HfO 2 content. An orthorhombic-to-monoclinic phase transformation was detected near room temperature for compositions near the high HfO 2 end of the orthorhombic phase field and for compositions within the two-phase region (HfTiO 4 solid solution plus HfO 2 solid solution). An orthorhombic-to-cubic phase transformation is indicated by data from oxygen-deficient materials at greater than 1873 0 K. (U.S.)

Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

Science.gov (United States)

Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

2018-03-01

In this work, the Nb-rich ternary eutectic in the Nb-Si-Cr system has been experimentally determined to be Nb-10.9Si-28.4Cr (in at. pct). The eutectic is composed of three main phases: Nb solid solution (Nbss), β-Cr2Nb, and Nb9(Si,Cr)5. The ternary eutectic microstructure remains stable for several hundred hours at a temperature up to 1473 K (1200 °C). At 1573 K (1300 °C) and above, the silicide phase Nb9(Si,Cr)5 decomposes into α-Nb5Si3, Nbss, and β-Cr2Nb. Under creep conditions at 1473 K (1200 °C), the alloy deforms by dislocation creep while the major creep resistance is provided by the silicide matrix. If the silicide phase is fragmented and, thus, its matrix character is destroyed by prior heat treatment [ e.g., at 1773 K (1500 °C) for 100 hours], creep is mainly controlled by the Laves phase β-Cr2Nb, resulting in increased minimum strain rates. Compared to state of the art Ni-based superalloys, the creep resistance of this three-phase eutectic alloy is significantly higher.

Heavy metal distribution at dump-field Ľubietová – Podlipa

Directory of Open Access Journals (Sweden)

Peter Andráš

2009-09-01

Full Text Available The article present the results of the environmental study at the Ľubietová Podlipa dump-field. The distribution of the selectedelements and heavy metals is unequal and depend on the geochemical behaviour of the elements (mainly on their migration ability.The present natural sorbents are predominantly the clay minerals (illite, muscovite, caolinite, smectite and hydrogoethite. The clay mineralsare good sorbents of K, Na, Li, Al, Rb, Sr, Hf, V, Cr, Ti, W, Zr, Nb, Ta a Th and at the hydrogoethite of Cu, Zn, Mo, Mn, Mg, P (± Fe, Cd,Co, Ca. In the case of the Fe, As, Sb, Ag, Pb, Zn, Mn, Mo, Bi, U was proved also the free sorption capacity.

Excitation functions of deuteron induced nuclear reactions on natMo up to 21 MeV. An alternative route for the production of 99mTc and 99Mo

International Nuclear Information System (INIS)

Sonck, M.; Hermanne, A.; Takacs, S.; Szelecsenyi, F.; Tarkanyi, F.

1999-01-01

Cross sections of deuteron induced nuclear reactions on natural molybdenum have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions of 92m,95 Nb-, 93,94g,94m,95g,95m,96,99m Tc- and 99 Mo were measured up to 21 MeV deuteron energy by using stacked foil technique and activation method. The goal of this work was to study the production possibility of the medical important 94m,99m Tc- and 99 Mo-nuclides. Production of 99m Tc and 99 Mo is of importance for their use in nuclear medicine, whereas 94m Tc is of interest regarding quantification of kinetics of well-established 99m Tc-radiopharmaceuticals. The production possibilities of 99m Tc and 99 Mo above 20 MeV deuteron energies up to 50 MeV were estimated and was found that beside the proton induced reactions the deuteron induced reactions on enriched molybdenum target are very promising. (author)

Structure and wear behavior of AlCrSiN-based coatings

Energy Technology Data Exchange (ETDEWEB)

Chen, Yun [School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chengdu Tool Research Institute Co., Ltd., Chengdu 610500 (China); Du, Hao [School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065 (China); Chen, Ming, E-mail: mchen@sjtu.edu.cn [School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Yang, Jun [Chengdu Tool Research Institute Co., Ltd., Chengdu 610500 (China); Xiong, Ji [School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610065 (China); Zhao, Haibo [The Analysis and Testing Centre, Sichuan University, Chengdu 610065 (China)

2016-05-01

Graphical abstract: - Highlights: • AlCrSiN based coating showed amorphous structure. • AlCrSiN/Me{sub x}N coatings obtained better wear resistance. • Molybdenum and niobium increased the coating hardness and wear resistance. - Abstract: AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC–Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N{sub 2} mixtures. Al{sub 0.6}Cr{sub 0.4}, Al{sub 0.6}Cr{sub 0.3}Si{sub 0.1}, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiN{sub x} peak were formed in the AlCrSiN/Me{sub x}N coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H{sup 3}/E{sup 2} ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

Suppression of superconductivity in Nb by IrMn in IrMn/Nb bilayers

KAUST Repository

Wu, B. L.; Yang, Y. M.; Guo, Z. B.; Wu, Y. H.; Qiu, J. J.

2013-01-01

Effect of antiferromagnet on superconductivity has been investigated in IrMn/Nb bilayers. Significant suppression of both transition temperature (Tc) and lower critical field (Hc1) of Nb is found in IrMn/Nb bilayers as compared to a single layer Nb

Microstructural effects of ductile phase toughening of Nb-Nb silicide composites

International Nuclear Information System (INIS)

Lewandowski, J.J.; Dimiduk, D.; Kerr, W.; Menddiratta, M.G.

1988-01-01

In the Nb-Si system, the terminal Nb phase and Nb 5 Si 3 phase are virtually immiscible up to approximately 2033k. This system offers the potential of producing composites consisting of a ductile refractory metal phase and a strong intermetallic phase. In-situ composites containing different volume fractions of the ductile Nb phase were produced via vacuum arc-casting. Microhardness testing as well as smooth bend bar testing was conducted at temperatures ranging from 298k to 1673k in an attempt to determine microstructural effects on the yield strength and smooth bar fracture strength. Notched bend specimens were similarly tested to determine the effects of the ductile phase (i.e. Nb) on enhancing the notched bend toughness. It is shown that Nb phase often behaves in a ductile manner during testing, thereby toughening the in-situ composite. The mechanism of toughening appears to be due to crack bridging

The functionally graded sintered steel WC-Co-NbC matrix

Energy Technology Data Exchange (ETDEWEB)

Santos, A.A.A.; Silva Junior, J.F. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil)

2009-07-01

Full text: The high speed steels are used for machining, including cutting tools at high speeds because their wear resistance, high temperature properties and excellent hardness. They are ferrous based alloys of the Fe-C-X component system where X represents a group of elements comprising Cr, W or Mo, V and Co. The aim of this work was to study the feasibility of powder metallurgy technique to develop functionally graded alloy material added by WC, Co and NbC. The morphology of the composite powders and sintered MMC were characterized by scanning electron microscopy and XRD measurements. (author)

Semiquantitative spectrographic analysis of nuclear interest minerals and of various products

International Nuclear Information System (INIS)

Alvarez Gonzalez, F.; Roca Adell, M.; Fernandez Cellini, R.

1958-01-01

Because the great number of samples of various kinds receiving in the Chemical Division, minerals in the most part, for its complete analysis, a rapid spectrographic method has been developed. It permits the determination of the following elements with a semiquantitative character. Al, As, Ag, Au, B, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf, Hn, In, K, La, Li, Mg, Mn, Mo, Na, Nb, P, Pb, Pt, Sb, Si, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr. (Author) 14 refs

Semiquantitative spectrographic analysis of nuclear interest minerals and of various products; Analisis espectrografico semicuantitativo de minerales de interes nuclear y productos diversos

Energy Technology Data Exchange (ETDEWEB)

Alvarez Gonzalez, F; Roca Adell, M; Fernandez Cellini, R

1958-07-01

Because the great number of samples of various kinds receiving in the Chemical Division, minerals in the most part, for its complete analysis, a rapid spectrographic method has been developed. It permits the determination of the following elements with a semiquantitative character. Al, As, Ag, Au, B, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Ga, Ge, Hf, Hn, In, K, La, Li, Mg, Mn, Mo, Na, Nb, P, Pb, Pt, Sb, Si, Sn, Sr, Ta, Ti, V, W, Y, Zn and Zr. (Author) 14 refs.

Niobium alloys production with elements of high steam pressure and high ductilidate Nb46,5%Ti, Nb 1%Zr, Nb 1%Ti and Nb20% Ta

International Nuclear Information System (INIS)

Pinatti, D.G.; Baldan, C.A.; Dainesi, C.R.; Sandim, H.R.Z.

1988-01-01

The melting technology of niobium alloys with high ductilidade and high steam pressure, having the Ti, Zr and Ta as alloying elements is described. The electron beam technique for production of Nb 46,5%Ti, Nb 1%Zr and Nb 20%Ta alloys is analysed, aiming a product with high grade and low cost. (C.G.C.) [pt

Impact of Nb vacancies and p-type doping of the NbCoSn-NbCoSb half-Heusler thermoelectrics.

Science.gov (United States)

Ferluccio, Daniella A; Smith, Ronald I; Buckman, Jim; Bos, Jan-Willem G

2018-02-07

The half-Heuslers NbCoSn and NbCoSb have promising thermoelectric properties. Here, an investigation of the NbCo 1+y Sn 1-z Sb z (y = 0, 0.05; 0 ≤ z ≤ 1) solid-solution is presented. In addition, the p-type doping of NbCoSn using Ti and Zr substitution is investigated. Rietveld analysis reveals the gradual creation of Nb vacancies to compensate for the n-type doping caused by the substitution of Sb in NbCoSn. This leads to a similar valence electron count (∼18.25) for the NbCo 1+y Sn 1-z Sb z samples (z > 0). Mass fluctuation disorder due to the Nb vacancies strongly decreases the lattice thermal conductivity from 10 W m -1 K -1 (z = 0) to 4.5 W m -1 K -1 (z = 0.5, 1). This is accompanied by a transition to degenerate semiconducting behaviour leading to large power factors, S 2 /ρ = 2.5-3 mW m -1 K -2 and figures of merit, ZT = 0.25-0.33 at 773 K. Ti and Zr can be used to achieve positive Seebeck values, e.g. S = +150 μV K -1 for 20% Zr at 773 K. However, the electrical resistivity, ρ 323K = 27-35 mΩ cm, remains too large for these materials to be considered useful p-type materials.

Reconciliation of the excess 176Hf conundrum in meteorites: Recent disturbances of the Lu-Hf and Sm-Nd isotope systematics

Science.gov (United States)

Bast, Rebecca; Scherer, Erik E.; Sprung, Peter; Mezger, Klaus; Fischer-Gödde, Mario; Taetz, Stephan; Böhnke, Mischa; Schmid-Beurmann, Hinrich; Münker, Carsten; Kleine, Thorsten; Srinivasan, Gopalan

2017-09-01

The long-lived 176Lu-176Hf and 147Sm-143Nd radioisotope systems are commonly used chronometers, but when applied to meteorites, they can reveal disturbances. Specifically, Lu-Hf isochrons commonly yield dates up to ∼300 Myr older than the solar system and varying initial 176Hf/177Hf values. We investigated this problem by attempting to construct mineral and whole rock isochrons for eucrites and angrites. Meteorites from different parent bodies exhibit similar disturbance features suggesting that a common process is responsible. Minerals scatter away from isochron regressions for both meteorite classes, with low-Hf phases such as plagioclase and olivine typically being most displaced above (or left of) reference isochrons. Relatively Hf-rich pyroxene is less disturbed but still to the point of steepening Lu-Hf errorchrons. Using our Lu-Hf and Sm-Nd data, we tested various Hf and Lu redistribution scenarios and found that decoupling of Lu/Hf from 176Hf/177Hf must postdate the accumulation of significant radiogenic 176Hf. Therefore early irradiation or diffusion cannot explain the excess 176Hf. Instead, disturbed meteorite isochrons are more likely caused by terrestrial weathering, contamination, or common laboratory procedures. The partial dissolution of phosphate minerals may predominantly remove rare earth elements including Lu, leaving relatively immobile and radiogenic Hf behind. Robust Lu-Hf (and improved Sm-Nd) meteorite geochronology will require the development of chemical or physical methods for removing unsupported radiogenic Hf and silicate-hosted terrestrial contaminants without disturbing parent-daughter ratios.

Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

Science.gov (United States)

Stein, Frank; Philips, Noah

2018-03-01

High-melting Nb-based alloys hold significant promise for the development of novel high-temperature materials for structural applications. In order to understand the effect of alloying elements Al and Fe, the Nb-rich part of the ternary Nb-Al-Fe system was investigated. A series of Nb-rich ternary alloys were synthesized from high-purity Nb, Al, and Fe metals by arc melting. Solidification paths were identified and the liquidus surface of the Nb corner of the ternary system was established by analysis of the as-melted microstructures and thermal analysis. Complementary analysis of heat-treated samples yielded isothermal sections at 1723 K and 1873 K (1450 °C and 1600 °C).

Geochronology, geochemistry and Hf–Sr–Nd isotopes of the ore-bearing syenite from the Shapinggou porphyry Mo deposit, East Qinling-Dabie orogenic belt

Directory of Open Access Journals (Sweden)

Tao He

2016-12-01

Full Text Available The Shapinggou Mo deposit is located in the western Dabie mountains, the eastern part of the Qinling-Dabie molybdenum orogenic belt. Shapinggou Mo deposit is a concealed deposit with the ore body mainly hosted by explosive breccia of Gaijing and the granite porphyry as well as the syenite of Shapinggou. Geochemistry study show that the SiO2 contents of Shapinggou syenite range from 61.74 to 69.93%, and the A/CNK from 0.95 to 1.06, classified as metaluminous to weak peraluminous, belonging to alkalic to shoshonitic series. The Mo deposits in Qinling Mo belt formed in two main periods, i.e., the first period occurred in to the Early Cretaceous (145–130 Ma, the second period in the late Early Cretaceous (130–110 Ma. Most of the Mo deposits in Dabie region formed in the second period. The results of zircon U–Pb show that the age of the Shapinggou syenite is 111.3 ± 1.2 Ma, which belongs to the second period. Proterozoic-Archean inherited zircons suggest that it may include some more ancient crustal material like Kongling group. The ɛHf(t values of Shapinggou syenite range from −15.6 to −8.0, TDM2(Hf from 1.7 to 2.16 Ga, respectively. The ɛNd(t values of the Shapinggou syenite range from −12.29 to −11.76, TDM2(Nd from 1.85 to 1.89 Ga, the 87Sr/86Sr from 0.709 to 0.710, respectively. Results of zircon Hf isotope and whole rock Sr–Nd isotope of Shapinggou syenite indicate that the Mo ore-forming materials were mainly generated from old Yangtze craton, e.g., gneiss from Dabie orogeny, mixed with some juvenal mantle materials. The geodynamics of the Shapinggou Mo deposit corresponded to an extension period in Eastern China, which caused by large scale lithospheric thinning. The delamination caused asthenosphere upwelling and crust-mantle interaction, which provided the ore-forming material and heat.

Clinical trials update from the Heart Failure Society of America Meeting 2009: FAST, IMPROVE-HF, COACH galectin-3 substudy, HF-ACTION nuclear substudy, DAD-HF, and MARVEL-1.

Science.gov (United States)

Lainscak, Mitja; Coletta, Alison P; Sherwi, Nasser; Cleland, John G F

2010-02-01

This article presents findings and a commentary on late-breaking trials presented during the meeting of the Heart Failure Society of America in September 2009. Unpublished reports should be considered as preliminary, since analyses may change in the final publication. The FAST trial showed somewhat better performance of intrathoracic impedance for prediction of deterioration in patients with heart failure (HF) when compared with daily weighing. The IMPROVE-HF study reported the benefits of education on the management of patients with systolic HF. Galectin-3 appeared a useful method for improving risk stratification of patients with chronic HF in a substudy of the COACH trial. A nuclear substudy of the HF-ACTION trial failed to demonstrate that resting myocardial perfusion imaging, a measure of myocardial scar and viability, was clinically useful. A small randomized controlled trial (DAD-HF) suggested that the use of low-dose dopamine in patients with acutely decompensated HF was associated with less deterioration in renal function and less hypokalaemia. The MARVEL-1 trial raises further concerns about the safety of myoblast transplantation in ischaemic HF.

AC loss time constant measurements on Nb3Al and NbTi multifilamentary superconductors

International Nuclear Information System (INIS)

Painter, T.A.

1988-03-01

The AC loss time constant is a previously univestigated property of Nb 3 Al, a superconductor which, with recent technological developments, shows some advantages over the more commonly used superconductors, NbTi and Nb 3 Sn. Four Nb 3 Al samples with varying twist pitches and one NbTi sample are inductively measured for their AC loss time constants. The measured time constants are compared to the theoretical time constant limits imposed by the limits of the transverse resistivity found by Carr [5] and to the theoretical time constants found using the Bean Model as well as to each other. The measured time constants of the Nb 3 Al samples fall approximately halfway between the theoretical time constant limits, and the measured time constants of the NbTi sample is close to the theoretical lower time constant limit. The Bean Model adequately accounts for the variance of the permeability of the Nb 3 Al superconductor in a background magnetic field. Finally, the measured time constant values of the Nb 3 Al samples vary approximately according to the square of their twist pitch. (author)

Properties of carbides and hard metals. Pt. 1

International Nuclear Information System (INIS)

Nazare, S.; Ondracek, G.

1977-01-01

Measurements of the electrical resistivity and of the Young modulus are reported for the carbides TiC, HfC, NbC, and TaC. The investigations included the solid solutions TiC-HfC, HfC-NbC, TaC-NbC, and TiC-NbC. For the solid solutions, measurements of the thermal expansion in the range 293-1173 K are also reported. All the samples were prepared by hot pressing of the commercial powders in graphite dies. The chemical composites are also presented. The measurement results are shown in figures. (GSC) [de

Ab initio theoretical study of dipole-bound anions of molecular complexes: (HF)3- and (HF)4- anions

Science.gov (United States)

Ramaekers, Riet; Smith, Dayle M. A.; Smets, Johan; Adamowicz, Ludwik

1997-12-01

Ab initio calculations have been performed to determine structures and vertical electron detachment energy (VDE) of the hydrogen fluoride trimer and tetramer anions, (HF)3- and (HF)4-. In these systems the excess electron is bound by the dipole field of the complex. It was determined that, unlike the neutral complexes which prefer the cyclic structures, the equilibrium geometries of the anions have "zig-zag" shapes. For both complexes the predicted VDEs are positive [210 meV and 363 meV for (HF)3- and (HF)4-, respectively], indicating that the anions are stable systems with respect to the vertical electron detachment. These results were obtained at the coupled-cluster level of theory with single, double and triple excitations [CCSD(T) method; the triple-excitation contribution in this method is calculated approximately using the perturbation approach] with the anion geometries obtained using the second-order Møller-Plesset perturbation theory (MP2) method. The same approach was also used to determine the adiabatic electron affinities (AEA) of (HF)3 and (HF)4. In addition to the electronic contribution, we also calculated the contributions (using the harmonic approximation) resulting from different zero-point vibration energies of the neutral and anionic clusters. The calculations predicted that while the AEA of (HF)3 is positive (44 meV), the AEA for (HF)4 is marginally negative (-16 meV). This suggests that the (HF)3- anion should be a stable system, while the (HF)4- is probably metastable.

High current density 2D/3D MoS2/GaN Esaki tunnel diodes

Science.gov (United States)

Krishnamoorthy, Sriram; Lee, Edwin W.; Lee, Choong Hee; Zhang, Yuewei; McCulloch, William D.; Johnson, Jared M.; Hwang, Jinwoo; Wu, Yiying; Rajan, Siddharth

2016-10-01

The integration of two-dimensional materials such as transition metal dichalcogenides with bulk semiconductors offer interesting opportunities for 2D/3D heterojunction-based device structures without any constraints of lattice matching. By exploiting the favorable band alignment at the GaN/MoS2 heterojunction, an Esaki interband tunnel diode is demonstrated by transferring large area Nb-doped, p-type MoS2 onto heavily n-doped GaN. A peak current density of 446 A/cm2 with repeatable room temperature negative differential resistance, peak to valley current ratio of 1.2, and minimal hysteresis was measured in the MoS2/GaN non-epitaxial tunnel diode. A high current density of 1 kA/cm2 was measured in the Zener mode (reverse bias) at -1 V bias. The GaN/MoS2 tunnel junction was also modeled by treating MoS2 as a bulk semiconductor, and the electrostatics at the 2D/3D interface was found to be crucial in explaining the experimentally observed device characteristics.

The optimization of NbTi-Nb/sub 3/Sn high field superconducting magnet used for physics experiments

International Nuclear Information System (INIS)

Han, B.; Han, S.; Feng, Z.X.

1989-01-01

The approach to the optimum cost design of multigraded NbTi-Nb/sub 3/Sn high field superconducting magnet is proposed. Investigation shows that by reasonably choosing the contribution of NbTi and Nb/sub 3/Sn coils to the central field required and properly increasing the parameters β of both NbTi and Nb/sub 2/Sn coils, the optimum cost design of the NbTi-Nb/sub 3/Sn solenoid magnet can be obtained. This is the base on which the minimum cost design of multi-graded NbTi-Nb/sub 3/Sn high field superconducting magnet is reached. As an example, a calculation of a 14T three graded NbT-Nb/sub 3/Sn superconducting magnet with a bore of 31mm in diameter is given

Effect of Nb element content in U-Zr-Nb alloy on hardness, microstructure and phase formation

International Nuclear Information System (INIS)

Masrukan; M Husna Al Hasa; Jan Setiawan; Slamet Pribadi

2015-01-01

Experiments to determine the effect of Nb element in the U-Zr alloys on hardness, microstructure and phase formation has been done. The addition of Nb element would effect the hardness, microstructure and phase which formed. The U-Zr-Nb alloy was made with the variation of Nb 2%, 5% and 8% by melting in an electric arc melting furnace that equipped with water cooling and the argon atmosphere. The U-Zr-Nb alloy to be cut divided to some testing, such as hardness test, microstructure, and phase analysis. Hardness testing was done by Vickers hardness testing equipment, microstructure by an optical microscope, and diffraction pattern by XRD and phase analysis was done by GSAS. Hardness testing results showed that the addition of 2% to 5% Nb element in U-Zr alloys will increased in hardness, but the addition of Nb element over 5% the hardness was decreased. Observations the microstructure showed that the addition of 2% to 5% Nb element, grains were formed from fine into coarse. Phase analysis for diffraction pattern showed that the phase changed from αU and γU (Zr,Nb)at 2% Nb to be αU, γU (Zr,Nb) and δ1 (UZr_2) phase at 5% and 8% Nb. Phase changes was followed by changes in its compositions. The composition of αU at 2% Nb was 40% increased to 81% at 5% Nb and decreased to 3.9% at 8% Nb. The composition of γU decreased from 59,86% to 14,91% with increased Nb from 2% to 5% and further increased to 52,74% at 8% Nb. (author)

Searching for Next Single-Phase High-Entropy Alloy Compositions

Directory of Open Access Journals (Sweden)

David E. Alman

2013-10-01

Full Text Available There has been considerable technological interest in high-entropy alloys (HEAs since the initial publications on the topic appeared in 2004. However, only several of the alloys investigated are truly single-phase solid solution compositions. These include the FCC alloys CoCrFeNi and CoCrFeMnNi based on 3d transition metals elements and BCC alloys NbMoTaW, NbMoTaVW, and HfNbTaTiZr based on refractory metals. The search for new single-phase HEAs compositions has been hindered by a lack of an effective scientific strategy for alloy design. This report shows that the chemical interactions and atomic diffusivities predicted from ab initio molecular dynamics simulations which are closely related to primary crystallization during solidification can be used to assist in identifying single phase high-entropy solid solution compositions. Further, combining these simulations with phase diagram calculations via the CALPHAD method and inspection of existing phase diagrams is an effective strategy to accelerate the discovery of new single-phase HEAs. This methodology was used to predict new single-phase HEA compositions. These are FCC alloys comprised of CoFeMnNi, CuNiPdPt and CuNiPdPtRh, and HCP alloys of CoOsReRu.

Structural high-temperature and (βNiAl+γ)-alloys based on Ni-Al-Co-Me systems with an improved low-temperature ductility

International Nuclear Information System (INIS)

Povarova, K.B.; Kazanskaya, N.K.; Drozdov, A.A.; Lomberg, B.S.; Gerasimov, V.V.

2001-01-01

The βNiAl-based alloys (B2) have lower density higher resistance to oxidation, and higher melting temperature relative to those of Ni-superalloys or γ'Ni 3 Al-base alloys. An improved low-temperature ductility of advanced Ni-AI-Co-M β+γ alloys(El=9-16 % at 293-1173 K is achieved due to the formation γ-Ni solid solution intergranular interlayers of eutectic origin. Secondary γ and/or γ' precipitates form in the grains of the supersaturated β-solid solution upon heat treatment at 1473-1573 K and 1073-1173 K. The limiting contents of alloying elements (Ti, Hf, Nb, Ta, Cr, Mo) for the (β+γ) alloys Ni - (19-29) % AI - (22-35) % Co, are determined which allowed to avoid the formation of primary γ'-phase (decrease solidus temperature ≤1643 K) and hard phases of the types σ, η and δ (decrease ductility). Alloying affects the morphology of the secondary γ and γ' precipitates: globular equiaxed precipitates are formed in the alloys containing Cr, Mo, and needle precipitates are formed in alloys alloys containing γ'-forming elements Nb, Ta and, especially, Ti and Hf. After directional solidification, (β+γ')-alloys have directed columnar special structure with a low extension of transverse grain boundaries. This microstructure allows one to increase UTS, by a factor 1,5-2 and long-term strength (time to rupture increase by a factor of 5-10 at 1173 K). (author)

NbN-AlN-NbN Josephson junctions on different substrates

Energy Technology Data Exchange (ETDEWEB)

Merker, Michael; Bohn, Christian; Voellinger, Marvin; Ilin, Konstantin; Siegel, Michael [KIT, Karlsruhe (Germany)

2016-07-01

Josephson junction technology is important for the realization of high quality cryogenic devices such as SQUIDs, RSFQ or SIS-mixers. The material system based on NbN/AlN/NbN tri-layer has gained a lot of interest, because it offers higher gap voltages and critical current densities compared to the well-established Nb/Al-AlOx/Nb technology. However, the realization of high quality Josephson junctions is more challenging. We developed a technology of Josephson junctions on a variety of substrates such as Silicon, Sapphire and Magnesium oxide and compared the quality parameters of these junctions at 4.2 K. The gap voltages achieved a range from 4 mV (for the junctions on Si) to 5.8 mV (in case of MgO substrates) which is considerably higher than those obtained from Nb based Josephson junctions. Another key parameter is the ratio of the subgap resistance to the normal state resistance. This so-called subgap ratio corresponds to the losses in a Josephson junction which have to be minimized. So far, subgap ratios of 26 have been achieved. Further careful optimization of the deposition conditions is required to maximize this ratio, The details of the optimization of technology and of characterization of NbN/AlN/NbN junctions will be presented and discussed.

Thermodynamic analysis and evaluation of the nitrogen solubility in liquid Nb and Fe-Nb alloys

International Nuclear Information System (INIS)

Qiu Caian

1994-01-01

Experimental information on the nitrogen solubility in liquid Nb and Fe-Nb alloys has been critically analysed and then utilized to evaluate the thermodynamic properties of the Nb-N and Fe-Nb-N liquid phases on the basis of thermodynamic models of Gibbs energy. A thermodynamic description of the Fe-Nb-N liquid phase was obtained, which has been used to calculate the N solubility in comparison with experimental results. The effect of an addition of Nb on the temperature dependence of the N solubility in liquid Fe has been examined by comparing with the effect of the Cr and V additions. It has been shown that the N solubility in liquid Nb and Fe-Nb alloys under various conditions is well described by the present calculation. (orig.)

Superconductor (Nb)-charge density wave (NbSe sub 3) point-contact spectroscopy

CERN Document Server

Sinchenko, A A

2003-01-01

Measurements of differential current-voltage (I-V) characteristics of point contacts between Nb and the charge density wave (CDW) conductor NbSe sub 3 formed along the conducting chain direction are reported. Below the superconducting transition of Nb, we have clearly observed Andreev reflection of the gapless electrons of NbSe sub 3. Analysis of the spectra obtained indicates that when the energy of injected particles exceeds the superconducting energy gap, the superconductivity near the S-CDW interface is suppressed because of non-equilibrium effects.

Oxidation kinetics of some zirconium alloys in flowing carbon dioxide at high temperatures

International Nuclear Information System (INIS)

Kohli, R.

1980-01-01

The oxidation kinetics of three zirconium alloys (Zr-2.2 wt% Hf, Zr-2.5 wt% Nb, and Zr-3 wt% Nb-1 wt% Sn) have been measured in flowing carbon dioxide in the temperature range from 873 to 1173 K to 120 ks (2000 min). At all oxidation temperatures, Zr-2.5 Nb and Zr-3 Nb-1 Sn showed a transition to rapid linear kinetics after initial parabolic oxidation. The Zr-2.2 Hf showed this transition at temperatures in the range from 973 to 1173 K; at 873 K, no transition was observed within the oxidation times reported. The Zr-2.2 Hf showed the smallest weight gains, followed in order by Zr-2.5 Nb and Zr-3 Nb-1 Sn. Increased oxidation rates and shorter times-to-rate-transition of Zr-2.2 Nb and Zr-1 Sn as compared with Zr-2.2 Hf can be attributed to the presence of niobium, tin, and hafnium in the alloys. This is considered in terms of the Nomura-Akutsu model, according to which hafnium should delay the rate transition, while niobium and tin lead to shorter times-to-rate-transition. The scale on Zr-2.2 Hf was identified as monoclinic zirconia, while the tetragonal phase, 6ZrO 2 .Nb 2 O 5 , was contained in the monoclinic zirconia scales on both other alloys

High-qualitative face Josephson transitions Nb-Sisup(ast)-Nb

International Nuclear Information System (INIS)

Gudkov, A.L.; Likharev, K.K.; Makhov, V.I.

1985-01-01

Preliminary results of investigation into characteristics of face transitions on the basis of refractory materials (niobium and polycrystalline silicon) are reported. Measured values of characteristic voltage and normal resistance are given; typical current-voltage characteristics of Josephson transitions Nb-Sisub(*)-Nb are presented too

Piezoelectric ceramic material, containing PbNb2O6, K2Nb2O6

International Nuclear Information System (INIS)

Fesenko, E.G.; Filip'ev, V.S.; Razumovskaya, O.N.; Cherner, Ya.E.; Rudkovskaya, L.M.; Zav'yalov, V.P.; Molchanova, R.A.; Kryshtop, V.G.; Panich, A.E.; Servuli, V.A.

1984-01-01

A new piezoelectric ceramic material including PbNb 2 O 6 , K 2 Nb 2 O 6 is prepared. Above the new material contains Nb 2 O 5 . The invention relates to piezotechnique. The principal advantage of this material for acoustic converters is high anisotropy of piezoelectric properties as well as high Curie temperature (T C =539-553 deg C). The composition containing 93.96 mole% PbNb 2 O 6 ; 2.48 mole% K 2 Nb 2 O 6 and 3.56 mole% Nb 2 O 5 has optimum content of parameters

The rotational excitation of HF by H

Science.gov (United States)

Desrousseaux, Benjamin; Lique, François

2018-06-01

The HF molecule is a key tracer of molecular hydrogen in diffuse interstellar medium (ISM). Accurate modelling of the HF abundance in such media requires one to model its excitation by both radiation and collisions. In diffuse ISM, the dominant collisional partners are atomic and molecular hydrogen. We report quantum time-independent calculations of collisional cross-sections and rate coefficients for the rotational excitation of HF by H. The reactive hydrogen exchange channels are taken into account in the scattering calculations. For the first time, HF-H rate coefficients are provided for temperature ranging from 10 to 500 K. The strongest collision-induced rotational HF transitions are those with Δj = 1, and the order of magnitude of the new HF-H rate coefficients is similar to that of the HF-H2 ones previously computed. As a first application, we simulate the excitation of HF by both H and H2 in typical diffuse ISM. We show that, depending on the rotational transition, hydrogen atoms increase or decrease the simulated excitation temperatures compared to collisional excitation only due to H2 molecules. Such results suggest that the new HF-H collisional data have to be used for properly modelling the abundance of HF in diffuse ISM.

Dependence of the elastic properties of the early-transition-metal monoborides on their electronic structures: A density functional theory study

Energy Technology Data Exchange (ETDEWEB)

Xu, Xuewen, E-mail: xuxuewen@hebut.edu.cn [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Fu, Kun [School of Computer Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li, Lanlan; Lu, Zunming; Zhang, Xinghua; Fan, Ying; Lin, Jing; Liu, Guodong; Luo, Hongzhi; Tang, Chengchun [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)

2013-06-15

We systematically investigated the crystal structure, stability, elastic properties, chemical bonding and electronic properties of the early-transition-metal monoborides (TMBs, where TM=Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Mo, and W) using the ab initio calculations based on the density functional theory. The results indicated that all 11 TMBs crystallized to a CrB-type structure are thermodynamically and mechanically stable. The elastic constants were calculated using the finite strain method. The correlation between the electronic structure and elastic properties was discussed. YB was found to have high machinability (B/C{sub 44}=1.73) and low hardness (C{sub 44}=43 GPa). The weak interaction between the interleaved yttrium planes and weak pd bonding resulted in the good machinability of YB.

Gaerttner LINAC Laboratory report on international nuclear data measurements

International Nuclear Information System (INIS)

Mesh, D.W.; Block, R.C.

1999-04-01

The Gaerttner LINAC Laboratory has made neutron transmission and capture measurements up to several hundred eV on samples of Zr, Nb, Mo, Sm, Nd, Ho, Er, Tm, Hf, and W. A new neutron time-of-flight target has been built and installed and a new 6 Li glass transmission detector is under construction. The electron linear accelerator is being refurbished with new klystrons, a new RF transport system and the reinstallation of the ninth accelerating section. These improvements are intended to provide a more powerful and monoenergetic electron beam

Ab initio study of adsorption and diffusion of lithium on transition metal dichalcogenide monolayers

OpenAIRE

Sun, Xiaoli; Wang, Zhiguo

2017-01-01

Using first principles calculations, we studied the stability and electronic properties of transition metal dichalcogenide monolayers of the type MX2 (M = Ti, Zr, Hf, V, Nb, Ta, Mo, Cr, W; X= S, Se, Te). The adsorption and diffusion of lithium on the stable MX2 phase was also investigated for potential application as an anode for lithium ion batteries. Some of these compounds were found to be stable in the 2H phase and some are in the 1T or 1T' phase, but only a few of them were stable in bot...

Simultaneous analysis of rotational and vibrational-rotational spectra of DF and HF to obtain irreducible molecular constants for HF

International Nuclear Information System (INIS)

Horiai, Koui; Uehara, Hiromichi

2011-01-01

Graphical abstract: Available rotational and vibrational-rotational spectral lines of DF and HF are analyzed simultaneously using a non-Born-Oppenheimer effective Hamiltonian. Research highlights: → Simultaneous analysis of DF and HF spectral data. → Application of a non-Born-Oppenheimer effective Hamiltonian. → Twenty irreducible molecular constants for HF have been determined. - Abstract: Analytic expressions of corrections for the breakdown of the Born-Oppenheimer approximation to Dunham's Y ij with optimal parameters, i.e., determinable clusters of expansion coefficients, are applied to a data analysis of the rotational and vibrational-rotational transitions of HF reported in the literature. All the available spectral lines of the two isotopologues, DF and HF, are simultaneously fitted to a single set of molecular parameters of HF within experimental errors. Fitting of a data set of 595 spectral transitions for DF and HF has generated only 20 minimal independent parameter values, i.e., 'irreducible' molecular constants of HF, that are sufficient to precisely generate 82 Y ij coefficients and 144 band constants in total: 41 Y ij and 72 band constants each for DF and HF.

Technology development of fabrication NbTi and Nb3 Sn superconducting wires

International Nuclear Information System (INIS)

Rodrigues Junior, D.; Bormio, C.; Baldan, C.A.; Ramos, M.J.; Pinatti, D.G.

1988-01-01

The technology development of NbTi and Nb 3 Sn superconducting wires are studied, mentioning the use of fluxes capture theory in the sizing of wires fabrication. The fabrication process, the thermal treatment and the experimental datas of critical temperature and current of Nb 3 Sn wires are described. (C.G.C.) [pt

Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys.

Science.gov (United States)

Han, Mi-Kyung; Kim, Jai-Youl; Hwang, Moon-Jin; Song, Ho-Jun; Park, Yeong-Joon

2015-09-09

In this paper, the effects of Nb addition (5-20 wt %) on the microstructure, mechanical properties, corrosion behavior, and cytotoxicity of Ti-Nb alloys were investigated with the aim of understanding the relationship between phase/microstructure and various properties of Ti-xNb alloys. Phase/microstructure was analyzed using X-ray diffraction (XRD), SEM, and TEM. The results indicated that the Ti-xNb alloys (x = 10, 15, and 20 wt %) were mainly composed of α + β phases with precipitation of the isothermal ω phase. The volume percentage of the ω phase increased with increasing Nb content. We also investigated the effects of the alloying element Nb on the mechanical properties (including Vickers hardness and elastic modulus), oxidation protection ability, and corrosion behavior of Ti-xNb binary alloys. The mechanical properties and corrosion behavior of Ti-xNb alloys were found to be sensitive to Nb content. These experimental results indicated that the addition of Nb contributed to the hardening of cp-Ti and to the improvement of its oxidation resistance. Electrochemical experiments showed that the Ti-xNb alloys exhibited superior corrosion resistance to that of cp-Ti. The cytotoxicities of the Ti-xNb alloys were similar to that of pure titanium.

Magnetic properties improvement of melt spun Co{sub 86.5}Hf{sub 11.5}B{sub 2} nanocomposites by refractory elements substitution

Energy Technology Data Exchange (ETDEWEB)

Chang, H.W. [Department of Applied Physics, Tunghai University, Taichung 407, Taiwan (China); Lin, Y.H.; Shih, C.W.; Liao, M.C.; Lee, Y.I. [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); Chang, W.C., E-mail: phywcc@ccu.edu.tw [Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan (China); Yang, C.C. [Department of Physics, Chung-Yuan Christian University, Chungli 320, Taiwan (China); Shaw, C.C. [Superrite Electronics Co. Ltd., Taipei 111, Taiwan (China)

2016-03-01

Magnetic properties of melt spun Co{sub 86.5}Hf{sub 10.5}MB{sub 2} ribbons with refractory elements substitution (M=Cr, Nb, Ti, Zr) have been studied. For ternary Co{sub 86.5}Hf{sub 11.5}B{sub 2} ribbon, permanent magnetic properties of B{sub r}=0.71 T, {sub i}H{sub c}=192 kA/m, and (BH){sub max}=34.4 kJ/m{sup 3} are obtained, and they are significantly improved to B{sub r}=0.73–0.76 T, {sub i}H{sub c}=136–216 kA/m and (BH){sub max}=38.4–52.8 kJ/m{sup 3} with M substitution. Summarized with the results of x-ray diffraction refinement, thermal magnetic analysis, and transmission electron microscopy, the Co{sub 86.5}Hf{sub 10.5}MB{sub 2} nanocomposites following the optimal crystallization treatment mainly consist of orthorhombic 7:1 and face-center-cubic Co phases. Fine microstructure with average grain size in the range of 12.5−19.6 nm promotes exchange coupling effect between magnetic grains, thus improving permanent magnetic properties. The magnetic field dependence of coercivity reveals that coercivity of the studied Co{sub 86.5}Hf{sub 10.5}MB{sub 2} nonocomposites is mainly governed by the reverse domain nucleation mechanism. - Highlights: • M substitution refines the grain size. • M substitution strengthens the exchange coupling effect between grains. • M substitution improves hard magnetic properties of Co{sub 86.5}Hf{sub 10.5}MB{sub 2} ribbons. • The coercivity is mainly governed by the reverse domain nucleation mechanism. • Co{sub 86.5}Hf{sub 10.5}MB{sub 2} ribbons are relevant candidate for RE free permanent magnets.

Alloy 33: A new material for the handling of HNO3/HF media in reprocessing of nuclear fuel

International Nuclear Information System (INIS)

Koehler, M.; Heubner, U.; Eichenhofer, K.W.; Renner, M.

1997-01-01

Alloy 33, an austenitic 33Cr-32Fe-31Ni-1.6Mo-0.6Cu-0.4N material shows excellent resistance to corrosion when exposed to highly oxidizing media as e.g. HNO 3 and HNO 3 /HF mixtures which are encountered in reprocessing of nuclear fuel. According to the test results available so far, resistance to corrosion in boiling azeotropic (67%) HNO 3 is about 6 and 2 times superior to AISI 304 L and 310 L. In higher concentrated nitric acid it can be considered corrosion resistant up to 95% HNO 3 at 25 C, up to 90% HNO 3 at 50 C and up to somewhat less than 85% HNO 3 at 75 C. In 20% HNO 3 /7% HF at 50 C its resistance to corrosion is superior to AISI 316 Ti and Alloy 28 by factors of about 200 and 2.4. Other media tested with different results include 12% HNO 3 with up to 3.5% HF and 0.4% HF with 32 to 67.5% HNO 3 at 90 C. Alloy 33 is easily fabricated into all product forms required for chemical plants (e.g. plate, sheet, strip, wire, tube and flanges). Components such as dished ends and tube to tube sheet weldments have been successfully fabricated facilitating the use of Alloy 33 for reprocessing of nuclear fuel

Stability, elastic properties and fracture toughness of Al0.75X0.75B14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo) investigated using ab initio calculations

International Nuclear Information System (INIS)

Emmerlich, Jens; Thieme, Niklas; To Baben, Moritz; Music, Denis; Schneider, Jochen M

2013-01-01

The effect of the transition metal valence electron concentration on the energy of formation, effective charge of B icosahedra, elastic properties, surface energy and fracture toughness was calculated using density functional theory for icosahedral transition metal borides of AlXB 14 (X=Sc, Ti, V, Cr, Y, Zr, Nb, Mo). Consistent with previous work on AlYB 14 (Kölpin et al 2009 J. Phys.: Condens. Matter 21 355006) it is shown that phase stability is generally dependent on the effective charge of the icosahedral transition metal borides. Also, ionization potential and electronegativity are identified as parameters affecting the effective charge of B icosahedra suitable for use in predicting the phase stability. Al 0.75 Y 0.75 B 14 , Al 0.75 Sc 0.75 B 14 and Al 0.75 Zr 0.75 B 14 have been identified as promising phases for application as protective coatings as they exhibit high phase stability and stiffness combined with a comparatively high fracture toughness. (paper)

Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

International Nuclear Information System (INIS)

Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K.B.; Kumar, Arun

2015-01-01

U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U_2Mo phase shows lower hardness than two phase microstructures in annealed alloys.

Micro-structural study and Rietveld analysis of fast reactor fuels: U–Mo fuels

Energy Technology Data Exchange (ETDEWEB)

Chakraborty, S., E-mail: sibasis@barc.gov.in [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Choudhuri, G. [Atomic Fuels Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Banerjee, J. [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Agarwal, Renu [Product Development Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India); Khan, K.B.; Kumar, Arun [Radiometallurgy Division, Bhabha Atomic Research Centre, Mumbai, 400085 (India)

2015-12-15

U–Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U–Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U–Mo alloys as fast reactor fuel. - Highlights: • U–Mo alloys in as-cast as well as in annealed conditions have been studied using Optical Microscope, SEM, XRD. • The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. • The dendritic microstructure of γ-(U,Mo) and B.C.C. ‘Mo’ phase of 33 at.% U–Mo alloy have been analysed. • Rietveld analysis has been done to optimize lattice parameters and calculate phase fractions in annealed alloys. • The Vickers microhardness of U{sub 2}Mo phase shows lower hardness than two phase microstructures in annealed alloys.

HNbO3 and HTaO3: new cubic perovskites prepared from LiNbO3 and LiTaO3 via ion exchange

International Nuclear Information System (INIS)

Rice, C.E.; Jackel, J.L.

1982-01-01

The synthesis of HNbO 3 and HTaO 3 from LiNbO 3 via ion exchange in hot aqueous acid solutions is reported. This reaction is accompanied by a topotactic structural transformation from the rhombohedral LiNbO 3 structure to the cubic perovskite structure; cell constants are a = 3.822(1) angstrom for HNbO 3 and 3.810(2) angstrom for HTaO 3 . These new compounds have been characterized by powder X-ray diffraction, thermogravimetric analysis, and solid-state NMR. They are electronic insulators and have low ionic conductivity. Evidence of partially proton-exchange phases Li/sub 1-x/H/sub x/MO 3 was also seen. The possible significance of this ion exchange reaction for devices using LiNbO 3 or LiTaO 3 is discussed

On friction of Nb-Nb pair in He1 and He2

International Nuclear Information System (INIS)

Zinenko, S.A.; Karapetyan, S.S.; Silin, A.A.

1990-01-01

Peculiarities of manifestation of the effect of anomalous friction of superconductors (AFS) in He1 and He2 are studied. Helium thermodynamic state effect on the character of friction interaction of Nb-Nb pair velocity and reduction ratio for friction coefficient is studied. The intensity of heat removal released from friction contact region is estimated, the necessary and sufficient conditions for AFC effect manifestation are ascertained using characteristic relaxation time concept. Dependences for Nb-Nb pair friction coefficient in a superconducting state on the time of friction interaction in gaseous helium, He1, He2 are presented

Development of HF-systems for electron storage systems

International Nuclear Information System (INIS)

Androsov, V.P.; Karnaukhov, I.M.; Popkov, Yu.P.; Reva, S.N.; Telegin, Yu.N.

1999-01-01

Development of HF systems for electron storages is described. Its final task is construction of 100 kW HF station at 699,3 MHz frequency consisting from low-power HF system, klystron amplifier, wave line for HF power transmission and accelerating section. Functional parameters of HF station are given

Strengthening from Nb-rich clusters in a Nb-microalloyed steel

International Nuclear Information System (INIS)

Xie, Kelvin Y.; Zheng, Tianxiao; Cairney, Julie M.; Kaul, Harold; Williams, James G.; Barbaro, Frank J.; Killmore, Chris R.; Ringer, Simon P.

2012-01-01

We demonstrate that a Nb-microalloyed ultra-thin cast strip steel can be strengthened substantially without compromising ductility by performing a simple heat treatment at 700 °C for 4 min. The strengthening was attributed to a fine dispersion of Nb-rich solute atom clusters. These clusters had an average size of ∼60 atoms at peak hardness and resembled Guinier–Preston zones in Al–Cu alloys. The application of the Ashby–Orowan equation indicates that these clusters are potent strengthening agents when compared to conventional Nb(C,N) precipitation strengthening.

Simple thermodynamic model of the extension of solid solution of Cu-Mo alloys processed by mechanical alloying

International Nuclear Information System (INIS)

Aguilar, C.; Guzman, D.; Rojas, P.A.; Ordonez, Stella; Rios, R.

2011-01-01

Highlights: → Extension of solid solution in Cu-Mo systems achieved by mechanical alloying. → Simple thermodynamic model to explain extension of solid solution of Mo in Cu. → Model gives results that are consistent with the solubility limit extension reported in other works. - Abstract: The objective of this work is proposing a simple thermodynamic model to explain the increase in the solubility limit of the powders of the Cu-Mo systems or other binary systems processed by mechanical alloying. In the regular solution model, the effects of crystalline defects, such as; dislocations and grain boundary produced during milling were introduced. The model gives results that are consistent with the solubility limit extension reported in other works for the Cu-Cr, Cu-Nb and Cu-Fe systems processed by mechanical alloying.

Coulomb-nuclear interference measurements of 168Yb, 176Hf, 178Hf, and 180Hf and lifetime measurements in 186Hg

International Nuclear Information System (INIS)

Nettles, W.G.

1979-01-01

Alpha scattering measurements were performed at center-of-mass energies near the Coulomb barrier. These energies allow for nuclear as well as pure Coulomb forces to play a significant role in the excitation process. The interference of these two forces is very sensitive to the sign of the E4 ground-state moment, whereas pure Coulomb excitation is not. Systematics of the E4 moments of the rare earth mass region indicate a transition in the magnitude and sign of the reduced matrix element of the M(E4) operator between 0 + and 4 + states from small and positive to large and negative between Yb and W. Previous Coulomb-nuclear interference measurements show that this reduced matrix element for 180 Hf is large and negative. The present results agree with that conclusion. It is also shown that the above reduced matrix element for 178 Hf, like that of 180 Hf, is large and negative. The small and positive moment (matrix element) for 168 Yb is seen to be consistent with the experimental data. No conclusions are drawn for the E4 moment in 176 Hf. The measurement of nuclear lifetimes shorter than 500 ps requires the use of plastic scintilltor detectors. These detectors, however have very poor energy resolution. A system is described that uses plastic scintillators with a magnetic lens spectrometer for energy selection. The system was used to measure the lifetime of the 522-keV 0 + sate in 186 Hf. A data analysis method using higher-order distribution moments is also presented

Single-layer MoS2 electronics.

Science.gov (United States)

Lembke, Dominik; Bertolazzi, Simone; Kis, Andras

2015-01-20

CONSPECTUS: Atomic crystals of two-dimensional materials consisting of single sheets extracted from layered materials are gaining increasing attention. The most well-known material from this group is graphene, a single layer of graphite that can be extracted from the bulk material or grown on a suitable substrate. Its discovery has given rise to intense research effort culminating in the 2010 Nobel Prize in physics awarded to Andre Geim and Konstantin Novoselov. Graphene however represents only the proverbial tip of the iceberg, and increasing attention of researchers is now turning towards the veritable zoo of so-called "other 2D materials". They have properties complementary to graphene, which in its pristine form lacks a bandgap: MoS2, for example, is a semiconductor, while NbSe2 is a superconductor. They could hold the key to important practical applications and new scientific discoveries in the two-dimensional limit. This family of materials has been studied since the 1960s, but most of the research focused on their tribological applications: MoS2 is best known today as a high-performance dry lubricant for ultrahigh-vacuum applications and in car engines. The realization that single layers of MoS2 and related materials could also be used in functional electronic devices where they could offer advantages compared with silicon or graphene created a renewed interest in these materials. MoS2 is currently gaining the most attention because the material is easily available in the form of a mineral, molybdenite, but other 2D transition metal dichalcogenide (TMD) semiconductors are expected to have qualitatively similar properties. In this Account, we describe recent progress in the area of single-layer MoS2-based devices for electronic circuits. We will start with MoS2 transistors, which showed for the first time that devices based on MoS2 and related TMDs could have electrical properties on the same level as other, more established semiconducting materials. This

Creep properties of Nb-1Zr and Nb-1Zr-0.1C

International Nuclear Information System (INIS)

Horak, J.A.; Egner, L.K.

1994-12-01

In the early 1980s a compact, lithium cooled, fast-energy spectrum nuclear reactor was selected for space applications requiring prolonged uninterrupted electrical power. This reactor was to be capable of generating up to 100 kilowatts of electricity for times up to seven years in space and thus was given the acronym SP-100. The material selected for the fuel cladding, reactor heat transport systems and structural components was Nb-1 wt % Zr (Nb-1Zr). In addition to commercial Nb-1Zr, modified alloys containing 100--200 wt ppM each of carbon and nitrogen and 900 ± 150 wt ppM carbon were also included, Type B Nb-1Zr and PWC-11, respectively. The SP-100 reactor was designed to operate at temperatures of 1290--1425 K. At these temperatures the principal mode of deformation for Nb-1Zr is creep, and creep strain of the fuel cladding limits the useful reactor lifetime. To develop a creep data base for design, safety and reliability analyses, uniaxial creep testing of Nb-1Zr, Type B Nb-1Zr and PWC-11 was conducted from 1250--1450 K at stresses from 5.0 MPa to 41.4 MPa. Methodology and test results are presented

Effect of Carbide Dissolution on Chlorine Induced High Temperature Corrosion of HVOF and HVAF Sprayed Cr3C2-NiCrMoNb Coatings

Science.gov (United States)

Fantozzi, D.; Matikainen, V.; Uusitalo, M.; Koivuluoto, H.; Vuoristo, P.

2018-01-01

Highly corrosion- and wear-resistant thermally sprayed chromium carbide (Cr3C2)-based cermet coatings are nowadays a potential highly durable solution to allow traditional fluidized bed combustors (FBC) to be operated with ecological waste and biomass fuels. However, the heat input of thermal spray causes carbide dissolution in the metal binder. This results in the formation of carbon saturated metastable phases, which can affect the behavior of the materials during exposure. This study analyses the effect of carbide dissolution in the metal matrix of Cr3C2-50NiCrMoNb coatings and its effect on chlorine-induced high-temperature corrosion. Four coatings were thermally sprayed with HVAF and HVOF techniques in order to obtain microstructures with increasing amount of carbide dissolution in the metal matrix. The coatings were heat-treated in an inert argon atmosphere to induce secondary carbide precipitation. As-sprayed and heat-treated self-standing coatings were covered with KCl, and their corrosion resistance was investigated with thermogravimetric analysis (TGA) and ordinary high-temperature corrosion test at 550 °C for 4 and 72 h, respectively. High carbon dissolution in the metal matrix appeared to be detrimental against chlorine-induced high-temperature corrosion. The microstructural changes induced by the heat treatment hindered the corrosion onset in the coatings.

Conductivity ageing studies on 1M10ScSZ (M4+=Ce, Hf)

DEFF Research Database (Denmark)

Omar, Shobit; Bin Najib, Waqas; Bonanos, Nikolaos

2011-01-01

The long-term conductivity stability is tested on zirconia based electrolyte materials for solid oxide fuel cell applications. The ageing studies have been performed on the samples of ZrO2 co-doped with 10mol% of Sc2O3 and 1mol% MO2, where M = Ce or Hf (denoted respectively 1Ce10ScSZ and 1Hf10Sc......SZ) in oxidising and reducing atmospheres, at 600°C for 3000h. At 600°C, these compositions show initial conductivity of around 9–12mS∙cm−1 in air. After 3000h of ageing, no phase transitions are observed in any of the samples. For the first 1000h, the degradation rate is higher than in the subsequent 2000h......; thereafter, conductivity degrades linearly with time for all samples. In air, the loss in the conductivity is lower than in reducing conditions. The 1Ce10ScSZ shows the highest degradation rate of 3.8%/1000h in wet H2/N2 after the first 1000h of ageing. A colour change of the 1Ce10ScSZ sample from white...

High-pressure phases of Weyl semimetals NbP, NbAs, TaP, and TaAs

Science.gov (United States)

Guo, ZhaoPeng; Lu, PengChao; Chen, Tong; Wu, JueFei; Sun, Jian; Xing, DingYu

2018-03-01

In this study, we used the crystal structure search method and first-principles calculations to systematically explore the highpressure phase diagrams of the TaAs family (NbP, NbAs, TaP, and TaAs). Our calculation results show that NbAs and TaAs have similar phase diagrams, the same structural phase transition sequence I41 md→ P6¯ m2→ P21/ c→ Pm3¯ m, and slightly different transition pressures. The phase transition sequence of NbP and TaP differs somewhat from that of NbAs and TaAs, in which new structures emerge, such as the Cmcm structure in NbP and the Pmmn structure in TaP. Interestingly, we found that in the electronic structure of the high-pressure phase P6¯ m2-NbAs, there are coexistingWeyl points and triple degenerate points, similar to those found in high-pressure P6¯ m2-TaAs.

Evolution of Si-2N2Nb island configuration on NbN (0 0 1) surface: A first-principles calculation

International Nuclear Information System (INIS)

Ren, Yuan; Xia, Qing; Zhang, Chao; Liu, Xuejie; Li, Zhi; Zhang, Fucheng

2015-01-01

Graphical abstract: - Highlights: • We investigate the separation and gathering of Nb, Si and N atom around come to NbN grain. • The adsorption and diffusion of single atom around 2N2Nb island were calculated by DFT. • The adsorption behavior of Si-2N2Nb island on NbN (0 0 1) surface were investigated. • The evolution of Si-2N2Nb island on NbN (0 0 1) were calculated by nudged elastic band. - Abstract: The separation and aggregation of Nb, Si, and N atoms around the NbN grain during the deposition of the Nb–Si–N nanocomposite film were discussed. The evolution behavior of the 2N2Nb island and the adsorption and diffusion energy of Nb, Si, and N atoms around the island on the NbN (0 0 1) surface were investigated using the first-principles method based on density functional theory. Results indicated that the most stable configuration of the Nb–Si–N island was the combination of Nb and N atoms to form the island and the possible aggregation of the Si atom to diagonal Nb atom outside the island. Substitution solid solution was eventually formed, in which the Nb atom of the 2N2Nb island was replaced by the Si atom during deposition. However, the Si atom was easily replaced by the Nb atom at the site with abundant Nb atoms. The diffusion energy of the evolution from Nb-2N1Nb1Si to Si-2N2Nb was 1.58 eV, and the total energy of the configuration decreased. Moreover, the interface of Si and NbN grains tended to separate. The highest energy adsorption sites for Nb, Si, N atoms adsorbed on the NbN (0 0 1) surface around the 2N2Nb island were P3, P1, and P2, respectively. The adsorption energies of Nb, Si, and N atoms on the NbN (0 0 1) surface around the 2N2Nb island were 7.3067, 5.3521, and 6.7113 eV, respectively, and their diffusion energies around the 2N2Nb island were 2.62, 1.35, and 5.094 eV, respectively. The low adsorption and diffusion energies of active Si atoms promoted the distribution of Nb and N atoms during deposition. Furthermore, the Nb

Hf på VUC

DEFF Research Database (Denmark)

Pless, Mette; Hansen, Niels-Henrik Møller

. Konkret har forskningsprojektet 3 mål: At afdække hf-kursisternes tidligere uddannelsesforløb og -erfaringer, før de starter på hf på VUC.At afdække, hvordan mødet med uddannelsens studiemiljø opleves af kursisterne, og ikke mindst kursisternes oplevelse af undervisningsformer, lærere mm.At afdække, hvad...

Reactive Fabrication and Effect of NbC on Microstructure and Tribological Properties of CrS Co-Based Self-Lubricating Coatings by Laser Cladding.

Science.gov (United States)

Fang, Liuyang; Yan, Hua; Yao, Yansong; Zhang, Peilei; Gao, Qiushi; Qin, Yang

2017-12-28

The CrS/NbC Co-based self-lubricating composite coatings were successfully fabricated on Cr12MoV steel surface by laser clad Stellite 6, WS₂, and NbC mixed powders. The phase composition, microstructure, and tribological properties of the coatings ware investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS), as well as dry sliding wear testing. Based on the experimental results, it was found reactions between WS₂ and Co-based alloy powder had occurred, which generated solid-lubricant phase CrS, and NbC play a key role in improving CrS nuclear and refining microstructure of Co-based composite coating during laser cladding processing. The coatings were mainly composed of γ-Co, CrS, NbC, Cr 23 C₆, and CoC x . Due to the distribution of the relatively hard phase of NbC and the solid lubricating phase CrS, the coatings had better wear resistance. Moreover, the suitable balance of CrS and NbC was favorable for further decreasing the friction and improving the stability of the contact surfaces between the WC ball and the coatings. The microhardness, friction coefficient, and wear rate of the coating 4 (Clad powders composed of 60 wt % Stellite 6, 30 wt % NbC and 10 wt % WS₂) were 587.3 HV 0.5 , 0.426, and 5.61 × 10 -5 mm³/N·m, respectively.

Reactive Fabrication and Effect of NbC on Microstructure and Tribological Properties of CrS Co-Based Self-Lubricating Coatings by Laser Cladding

Directory of Open Access Journals (Sweden)

Liuyang Fang

2017-12-01

Full Text Available The CrS/NbC Co-based self-lubricating composite coatings were successfully fabricated on Cr12MoV steel surface by laser clad Stellite 6, WS2, and NbC mixed powders. The phase composition, microstructure, and tribological properties of the coatings ware investigated by means of X-ray diffraction (XRD, scanning electron microscopy (SEM, and energy dispersive spectrometer (EDS, as well as dry sliding wear testing. Based on the experimental results, it was found reactions between WS2 and Co-based alloy powder had occurred, which generated solid-lubricant phase CrS, and NbC play a key role in improving CrS nuclear and refining microstructure of Co-based composite coating during laser cladding processing. The coatings were mainly composed of γ-Co, CrS, NbC, Cr23C6, and CoCx. Due to the distribution of the relatively hard phase of NbC and the solid lubricating phase CrS, the coatings had better wear resistance. Moreover, the suitable balance of CrS and NbC was favorable for further decreasing the friction and improving the stability of the contact surfaces between the WC ball and the coatings. The microhardness, friction coefficient, and wear rate of the coating 4 (Clad powders composed of 60 wt % Stellite 6, 30 wt % NbC and 10 wt % WS2 were 587.3 HV0.5, 0.426, and 5.61 × 10−5 mm3/N·m, respectively.

Comparison of the costs of superconducting accelerator dipoles using NbTi, Nb3Sn and NbTiTa

International Nuclear Information System (INIS)

Hassenzahl, W.

1981-03-01

The present study, which is based on the assumption that future, high-energy accelerators will use superconductors, is a comparison of the costs of 5 to 12 Tesla NbTi, Nb 3 S/sub n/, and NbTiTa accelerator magnets operating at 4.2 K or 1.8 K. The object of this evaluation is not to determine the actual cost of future accelerators, rather, its purpose is to provide some rationale for research on the next generation of superconducting accelerator magnets. Thus, though the actual costs of accelerator magnets may be different from those given here, the comparisons are valid

Continuous, flexible, and high-strength superconducting Nb3Ge and Nb3Sn filaments

International Nuclear Information System (INIS)

Ahmad, I.; Heffernan, W.J.

1976-01-01

Fabrication of continuous, flexible, and high-strength (1600 MN/m 2 ) composite filaments of Nb 3 Ge (T/subc/ 18 0 K) and Nb 3 Sn is reported, involving chemical vapor deposition of these compounds on Nb-coated high-strength W--1% ThO 2 filaments

Outstanding compressive creep strength in Cr/Ir-codoped (Mo0.85Nb0.15)Si2 crystals with the unique cross-lamellar microstructure.

Science.gov (United States)

Hagihara, Koji; Ikenishi, Takaaki; Araki, Haruka; Nakano, Takayoshi

2017-06-21

A (Mo 0.85 Nb 0.15 )Si 2 crystal with an oriented, lamellar, C40/C11 b two-phase microstructure is a promising ultrahigh-temperature (UHT) structural material, but its low room-temperature fracture toughness and low high-temperature strength prevent its practical application. As a possibility to overcome these problems, we first found a development of unique "cross-lamellar microstructure", by the cooping of Cr and Ir. The cross-lamellar microstructure consists of a rod-like C11 b -phase grains that extend along a direction perpendicular to the lamellar interface in addition to the C40/C11 b fine lamellae. In this study, the effectiveness of the cross-lamellar microstructure for improving the high-temperature creep deformation property, being the most essential for UHT materials, was examined by using the oriented crystals. The creep rate significantly reduced along a loading orientation parallel to the lamellar interface. Furthermore, the degradation in creep strength for other loading orientation that is not parallel to the lamellar interface, which has been a serious problem up to now, was also suppressed. The results demonstrated that the simultaneous improvement of high-temperature creep strength and room temperature fracture toughness can be first accomplished by the development of unique cross-lamellar microstructure, which opens a potential avenue for the development of novel UHT materials as alternatives to existing Ni-based superalloys.

Nonequilibrium synthesis of NbAl3 and Nb-Al-V alloys by laser cladding. II - Oxidation behavior

Science.gov (United States)

Haasch, R. T.; Tewari, S. K.; Sircar, S.; Loxton, C. M.; Mazumder, J.

1992-01-01

Isothermal oxidation behaviors of NbAl3 alloy synthesized by laser cladding were investigated at temperatures between 800 and 1400 C, and the effect of vanadium microalloying on the oxidation of the laser-clad alloy was examined. The oxidation kinetics of the two alloys were monitored using thermal gravimetric weight gain data, and the bulk and surface chemistries were analyzed using XRD and XPS, respectively. It was found that NbAl3 did not form an exclusive layer of protective Al2O3. The oxidation products at 800 C were found to be a mixture of Nb2O5 and Al2O3. At 1200 C, a mixture of NbAlO4, Nb2O5, and Al2O3 formed; and at 1400 C, a mixture of NbAlO4, Al2O3, NbO2, NbO(2.432), and Nb2O5 formed. The addition of V led to a dramatic increase of the oxidation rate, which may be related to the formation of (Nb, V)2O5 and VO2, which grows in preference to protective Al2O3.

Ab initio characterization of the structure and energetics of the ArHF complex

International Nuclear Information System (INIS)

van Mourik, T.; Dunning, T.H. Jr.

1997-01-01

The ArHF complex has been investigated using correlation consistent basis sets at several levels of theory, including Mo/ller endash Plesset perturbation theory (MP2, MP3, MP4) and coupled cluster techniques [CCSD, CCSD(T)]. The three stationary points (the primary linear Ar endash HF minimum, the secondary linear Ar endash FH minimum, and the interposed transition state TS) on the counterpoise-corrected potential energy surface have been characterized. Calculations with the aug-cc-pV5Z basis set predict D e for the Ar endash HF minimum to be (with estimated complete basis set limits in parentheses) -215 (-218)cm -1 for MP4 and -206 (-211)cm -1 for CCSD(T). For the Ar endash FH minimum and the TS, calculations with the d-aug-cc-pVQZ sets predict D e close-quote s (and CBS limits) of -97 (-99) and -76 (-78)cm -1 (MP4) and -93 (-94) and -75 (-76)cm -1 [CCSD(T)], respectively. The corresponding values for the H6(4,3,2) potential of Hutson [J. Chem. Phys. 96, 6752 (1992)] are -211.1±4cm -1 , -108.8±10cm -1 , and -82.6±10cm -1 . While the agreement of our CCSD(T) estimate with Hutson close-quote s value is excellent for the global minimum, it is less so for the other two stationary points, suggesting that the H6(4,3,2) potential may be too attractive around the secondary minimum and the transition state. copyright 1997 American Institute of Physics

Test of RIPL-2 cross section calculations

International Nuclear Information System (INIS)

Herman, M.

2002-01-01

The new levels and optical segments and microscopic HF-BCS level densities (part of the density segment) were tested in practical calculations of cross sections for neutron induced reactions on 22 targets (40-Ca, 47-Ti, 52-Cr, 55-Mn, 58-Ni, 63-Cu, 71-Ga, 80-Se, 92-Mo, 93-Nb, 100-Mo, 109-Ag, 114-Cd, 124-Sn, 127-I, 133-Cs, 140-Ce, 153-Eu, 169-Tm, 186-W, 197-Au, 208-Pb). For each target all reactions involving up to 3 neutron, 1 proton and 1 α-particle emissions (subject to actual reaction thresholds) were considered in the incident energy range from 1 keV up to 20 MeV (in some cases up to 27 MeV). In addition, total, elastic, and neutron capture cross sections were calculated

FY 1998 annual report on the improvement of toughness of silicide-based intermetallic compounds by controlling their composite structures; 1998 nendo fukugo soshikika ni yoru shirisaidokei kinzokukan kagobutsu no kyojinsei kaizen chosa hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-03-01

Intermetallic compounds, although attracting much attention as most promising materials serviceable at superhigh temperature, are very fragile at normal temperature, which is one of their major disadvantages. Structures of these compounds prepared by the melting method are controlled to improve their toughness by, e.g., changing phase ratio of the initial crystal for the Mo-Si-Nb system to prevent cracking during the melting and casting stages, addition of a third element (e.g., Zr, Ti or Hf) or a mixed component of Nb and Zr to control the structure of Mo{sub 5}Si{sub 3} considered to be a cause for the cracking, and controlling melting and solidification rates for the FZ melting method. The three-phase microstructures with added Hf or Zr show improved toughness, but need additional procedures for controlling solidification and cooling conditions. For the powder method, the MA conditions are investigated with a two-element system, and the effects of Al or Zr as the third element added to the base composition on the composite microstructures and constituent phases are also investigated. Unlike the melting method, the powder method causes no cracking problems during the stock preparation stage and hence is expected to be applicable to production of larger stocks. However, the products by this method are found to be insufficient both in toughness and high-temperature strength. It is necessary to develop methods for cutting down and controlling oxides in the grain boundaries, in order to prevent deterioration of their strength at high temperature. (NEDO)

Aqueous corrosion behaviour of Zr-1 Nb and Zr-20 Nb with different heat treatments

International Nuclear Information System (INIS)

Jaime Solis, F.; Bordoni, Roberto; Olmedo, Ana M.; Villegas, Marina; Miyagusuku, Marcela

2003-01-01

The corrosion behaviour of Zr-1 Nb and Zr-20 Nb coupons annealed at 850 C degrees during 1 hour and afterwards aged at different temperatures and time periods was studied. The Zr-1 Nb samples were aged at 400 and 500 C degrees and the Zr-20 Nb samples at 265 and 550 C degrees. The results have shown that ageing increases the corrosion resistance because the aged microstructure is somewhat closer to the equilibrium one. This was not the case of Zr-1 Nb aged 72 hs at 400 C degrees. The presence of the ω-phase does not have a deleterious effect in the corrosion behaviour of Zr-20 Nb. Also, an ageing of 2200 h at 265 C degrees induced a relevant decrease in the corrosion rate of Zr-20 Nb indicating a decomposition of the β- Zr phase. This effect was observed at the inlet of pressure tubes in CANDU reactors. The results obtained will be used to establish the relative importance of the α-Zr and β-Zr phases in the corrosion behaviour of pressure tubes. (author)

Magnetization anomaly of Nb3Al strands and instability of Nb3Al Rutherford cables

International Nuclear Information System (INIS)

Yamada, Ryuji; Kikuchi, Akihiro; Wake, Masayoshi

2006-01-01

Using a Cu stabilized Nb 3 Al strand with Nb matrix, a 30 meter long Nb 3 Al Rutherford cable was made by a collaboration of Fermilab and NIMS. Recently the strand and cable were tested. In both cases instability was observed at around 1.5 Tesla. The magnetization of this Nb 3 Al strand was measured first using a balanced coil magnetometer at 4.2 K. Strands showed an anomalously large magnetization behavior around at 1.6 T, which is much higher than the usual B c2 ∼ 0.5 Tesla (4.2 K) of Nb matrix. This result is compared with the magnetization data of short strand samples using a SQUID magnetometer, in which a flux-jump signal was observed at 0.5 Tesla, but not at higher field. As a possible explanation for this magnetization anomaly, the interfilament coupling through the thin Nb films in the strands is suggested. The instability problem observed in low field tests of the Nb 3 Al Rutherford cables is attributed to this effect