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.

Sedimentological reconstruction of the recent pattern of mercury pollution in the Niagara River

International Nuclear Information System (INIS)

Breteler, R.J.; Bowen, V.T.; Schneider, D.L.; Henderson, R.

1984-01-01

Since 1952 there have been a number of sharp changes in the rates of delivery, or in the ratios delivered, of several long-lived artificial radionuclides distributed worldwide from atmospheric nuclear tests. Analyses of these nuclides in suitably selected, and collected, aquatic sediment cores indicate several dated horizons that can yield more refined estimates of recent pollution history than are otherwise available. This approach has been applied to several cores in eastern Lake Erie, the Niagara River, and its delta in Lake Ontario, and a selection of the sediments so dated have been analyzed for total mercury. On the basis of the assigned, and verified, data horizons of several sediment cores, the history of mercury pollution in the Niagara River has been reconstructed

Split double factorial with additional treatment and the post-harvest of Niagara grapes

Directory of Open Access Journals (Sweden)

Pórtya Piscitelli Cavalcanti

2015-09-01

Full Text Available ABSTRACTThis study aims to discuss and explain how to deal with the analysis of experiments conducted in completely randomized design (CRD and subdivided into double factorial with additional treatment in the plot. In addition it was illustrate the discussion by analyzing data from an experiment on post-harvest of Niagara grapes. The sums of squares for each source of variation are presented, while discussing how the additional treatment affects the whole variation. Niagara grapes were treated in the pre-harvest with three preservatives (calcium chloride, calcium nitrate and calcium lactate at 0%, 0.5%, 1% and 2% and stored for 0, 10, 20 and 30 days.All the preservatives evaluated at 0% represented the control (additional treatment.

Intelligent transportation system (ITS) study for the Buffalo and Niagara Falls metropolitan area, Erie and Niagara Counties, New York : objectives, performance criteria & user service plan, working paper #3

Science.gov (United States)

1997-06-18

This paper is the third in a series that together will comprise an Intelligent Transportation System Study (ITS) for the Buffalo/Niagara Falls region. In this document, the problems identified in Working Paper #1 are critically reviewed to develop go...

New technology and organizational innovation: Niagara Mohawk Power Corporation and nuclear power

International Nuclear Information System (INIS)

Stacey, J.E. Jr.

1981-01-01

Questions with regard to organization behavior and decision theory are explored in relation to the decision-making process of a major private electric utility, Niagara Mohawk Power Corp., that chose to innovate with nuclear power. The character of the firm is such, relative to size, service area, organizational structure, and socio-political environment, that its experience is important for the further development of theories of organizational innovation. The research attempts to understand the political, economic, and social constraints that limited the set of solutions available to the utility in its search for a suitable electricity-generating mode from the early 1950's to the early 1960's. Two contrasting models of organizational decision-making behavior are used to interpret case-study findings. The initial model is from the electric-utility literature and consists essentially of an economic or benefit/cost model of organizational decision making. The second model is developed from the organizational theory literature and is more complex in the sense that factors other than economics such as organizational inertia, the corporate structure of the utility, fuel-supply history and fuel diversification, electricity-demand-growth expectations, the financial environment, and the psychological appeal of the new technology had important influences on Niagara Mohawk's decision to build Nine Mile Point One. Findings of the case study tend to support the second model in that economics was a necessary but not sufficient reason for Niagara Mohawk to have innovated with nuclear power plants

77 FR 60901 - Safety Zone; Battle of Queenston Heights Bicentennial, Niagara River, Lewiston, NY

Science.gov (United States)

2012-10-05

..., Docket Operations, telephone 202-366-9826. SUPPLEMENTARY INFORMATION: Table of Acronyms DHS Department of... Lower Niagara River near the Silo Restaurant, Lewiston, NY. The Captain of the Port Buffalo has...

Host-Sensitized and Tunable Luminescence of GdNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Tm3+) Nanocrystalline Phosphors with Abundant Color.

Science.gov (United States)

Liu, Xiaoming; Chen, Chen; Li, Shuailong; Dai, Yuhua; Guo, Huiqin; Tang, Xinghua; Xie, Yu; Yan, Liushui

2016-10-17

Up to now, GdNbO 4 has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO 4 nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors were synthesized by a Pechini-type sol-gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO 4 nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO 4 :Ln 3+ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f-f transitions of the doping Eu 3+ , Tb 3+ , and Tm 3+ ions. The luminescence color of GdNbO 4 :Ln 3+ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO 4 host lattice. A single-phase white-light-emission has been realized in Eu 3+ /Tb 3+ /Tm 3+ triply doped GdNbO 4 nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) are updated.

New multifunctional materials obtained by the intercalation of anionic dyes into layered zinc hydroxide nitrate followed by dispersion into poly(vinyl alcohol) (PVA).

Science.gov (United States)

Marangoni, Rafael; Ramos, Luiz Pereira; Wypych, Fernando

2009-02-15

Different anionic blue and orange dyes have been immobilized on a zinc hydroxide nitrate (Zn(5)(OH)(8)(NO(3))(2)nH(2)O--Zn-OH-NO(3)) by anion exchange with interlayer and/or outer surface nitrate ions of the layered matrix. Orange G (OG) was totally intercalated, orange II (OII) was partially intercalated, while Niagara blue 3B (NB) and Evans blue (EV) were only adsorbed at the outer surface. Several composite films of poly(vinyl alcohol)--PVA were prepared by casting through the dispersion of the hybrid material (Zn-OH-OG) into a PVA aqueous solution and evaporation of water in a vacuum oven. The obtained composite films were transparent, colored, and capable of absorbing UV radiation. Improved mechanical properties were also obtained in relation to the nonfilled PVA films. These results demonstrate the onset of a new range of potential applications for layered hydroxide salts in the preparation of polymer composite multifunctional materials.

Preparation of graphene/nile blue nanocomposite: Application for oxygen reduction reaction and biosensing

International Nuclear Information System (INIS)

Shervedani, Reza Karimi; Amini, Akbar

2015-01-01

Highlights: •New nanocomposite is synthesized by electrochemical polymerization of Nile blue and reduction of GO on GCE. •The nanocomposite is characterized by SEM, UV–vis and electrochemical methods. •High electrocatalytic activity was observed for O 2 reduction on GNs-NB nanocomposite. •GCE-GNs-NB poly was tested successfully for immobilization of GOx and detection of glucose. -- Abstract: Nile blue/graphene (NB-GNs) nanocomposite was synthesized for the first time via a green and effective one-step electrochemical method, allowing to reduce graphene oxide (GO) and NB on the glassy carbon electrode (GCE) simultaneously and construct GCE-GNs-NB poly composite. The composite was characterized by scanning electron microscopy (SEM), UV–Vis spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical results obtained in the absence of any redox probe, where NB was active, allowed to trace step-by-step addition of the NB-GNs nanocomposite onto the GCE electrode surface, supporting formation of the GCE-GNs-NB poly composite. The electrocatalytic activity of the as-prepared GCE-GNs-NB poly towards O 2 reduction was studied in neutral medium. The results revealed excellent electrocatalytic performance for two-electron reduction of oxygen, suggesting its potential application as metal-free electrocatalysts for O 2 reduction reaction. Application of the GCE-GNs-NB poly in electrochemical biosensing was demonstrated by immobilization of glucose oxidase (GOx) on the surface of GCE-GNs-NB poly , and then, using it for sensing of glucose. The biosensor exhibited a linear response, from 0.2 to 2.0 mM glucose, with a low detection limit, 2.1 μM, and high sensitivity, 67.0 μA mM −1 cm −2 , obtained by cyclic voltammetry method. The proposed biosensor was successfully tested for determination of glucose in blood serum samples

Vývoj grafického editoru pro zásuvný modul BJ2NB do NetBeans

OpenAIRE

Müller, Martin

2011-01-01

This bachelor thesis is part of a project whose goal is to create a plug-in BJ2NB to NetBeans. It aims to bring into the NetBeans some approaches and possibilities of BlueJ environment, widely used for educational purposes, and to simplify the transition from simple BlueJ IDE to extensive and professional NetBeans for novice programmers. The goal of this work is to design and implement a graphical editor for plug-in BJ2NB that would display the current class diagram of the project and allow t...

Niagara pumping generation station inundation mapping and consequence analysis with ArcGIS and Mike 21

Energy Technology Data Exchange (ETDEWEB)

Grover, Patrick; Khayer, Yasmin; Naumov, Aleksey [4DM Inc., Toronto, (Canada); Zhang, Yibing [Ontario Power Generation, Toronto, (Canada)

2010-07-01

Inundation mapping is a key factor of Ontario Power Generation's dam safety program. It is the basis for determining the hazard potential classification of the dam by modelling the consequences of a hypothetical dam failure. This paper presented the project for updating the inundation mapping and consequence analysis study at the Niagara Pump generating station (PGS) reservoir. A complete hydrotechnical assessment of the Niagara PGS reservoir was conducted. The modelling of various breach scenarios was carried out using the 2-D hydrodynamic software MIKE 21 in order to provide the hydraulic data necessary for producing the inundation maps. Updated EPRP maps were produced and a consequence analysis was performed which confirmed the existing hazard classification. The ArcGIS system was used as the underlying framework for all major components of the project. It was found that the use of GIS technologies improve the efficiency of both modelling and analysis.

Variações na anatomia foliar de videira Niagara em diferentes sistemas de condução

Directory of Open Access Journals (Sweden)

Rachel Benetti Queiroz-Voltan

2011-01-01

Full Text Available Alterações na anatomia de folhas são causadas por diversos fatores ambientais, principalmente a disponibilidade de radiação, podendo causar mudanças na capacidade fotossintética e afetando a produção final. Este trabalho objetivou identificar alterações na estrutura anatômica de folhas de videiras 'Niagara Rosada' e 'Niagara Branca' em três diferentes sistemas de condução: espaldeira (ESP, manjedoura em 'Y' (Y e manjedoura em 'Y' coberto com plástico (YPLA. Os estudos anatômicos foram realizados em folhas, externas em relação ao dossel, retiradas em três diferentes alturas da planta (superior, mediana e inferior. Para a caracterização anatômica, as amostras foram fixadas em FAA, emblocadas em parafina, seccionadas em micrótomo e coradas com safranina e azul de alciã. As lâminas foram analisadas com o auxílio de um microscópio óptico acoplado a uma câmera de captura de imagens. As espessuras da epiderme das faces adaxial e abaxial, dos parênquimas paliçádico e esponjoso, da espessura total da folha e da razão entre parênquimas paliçádico e esponjoso foram estimadas em uma amostra ao acaso de dez segmentos de cada tratamento, totalizando 1800 observações. Realizaram as análises de variância pelo teste F, sendo as médias dos tratamentos comparadas pelo Tukey a 5% de probabilidade. Observaram-se nas cultivares Niagara Branca e Niagara Rosada conduzidas em ESP uma espessura média de limbo maior, porém foram menos produtivas, quando comparados com Y e YPLA; folhas expostas a maiores intensidades luminosas tiveram limbo mais espesso devido ao maior desenvolvimento do parênquima paliçádico, independentemente do sistema de condução.

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.

Determination of potential sources of PCBs and PBDEs in sediments of the Niagara River

Energy Technology Data Exchange (ETDEWEB)

Samara, Fatin [Department of Chemistry, 611 Natural Science Complex, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (United States); Tsai, Christina W. [Department of Civil, Structural and Environmental Engineering, 233 Jarvis Hall, University at Buffalo, State University of New York, Buffalo, NY 14260-4400 (United States); Aga, Diana S. [Department of Chemistry, 611 Natural Science Complex, University at Buffalo, The State University of New York, Buffalo, NY 14260-3000 (United States)]. E-mail: dianaaga@buffalo.edu

2006-02-15

Sediments from Niagara River, an important waterway connecting two of the Great Lakes (Lake Erie to Lake Ontario), were analyzed for 14 congeners of polychlorinated biphenyls (PCBs) and 9 congeners of polybrominated diphenyl ethers (PBDEs) using accelerated solvent extraction and gas chromatography/mass spectrometry. Total concentrations of PCBs ranged from 1.7 to 124.6 ng/g were PCBs 138 and 153 were found in all samples. All sites but one showed PBDE in sediments with total concentrations as high as 148 ng/g, suggesting that PBDE is becoming an important class of POP. A land-use and coverage map was used to trace potential localized sources of PCB and PBDE contamination. Results indicate that the highest levels of PCBs and PBDEs were found in sediments collected from areas closest to the discharge locations of municipal wastewater treatment plants (WWTP) and local industries. This is the first study that suggests the importance of WWTP discharges as a potential source of PBDE contamination in the Great Lakes. - Wastewater treatment plant discharges are a main source of PCBs and PBDEs to Niagara River sediments.

77 FR 62510 - Niagara Wind Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

Science.gov (United States)

2012-10-15

... Wind Power, LLC's application for market-based rate authority, with an accompanying rate schedule... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER13-17-000] Niagara Wind Power, LLC; Supplemental Notice That Initial Market- Based Rate Filing Includes Request for Blanket...

Balanço de energia em vinhedo de 'Niagara Rosada' Energy balance on 'Niagara Rosada' vineyard

Directory of Open Access Journals (Sweden)

José Ricardo Macedo Pezzopane

2003-01-01

Full Text Available O método do balanço de energia foi utilizado para caracterizar a variação horária do saldo de radiação e dos fluxos de calor latente, sensível e no solo, em vinhedo cultivado com a cultivar NiagaraRosada', conduzida no sistema de espaldeira, em Jundiaí (SP. Além disso, foram determinadas as relações entre o saldo de radiação (SR no vinhedo e a radiação solar global (RG e a partição da energia disponível ao sistema nos fluxos de calor latente (LE, sensível (H e no solo (G. Em um dia característico de período seco, o LE representou 44% do SR e o H, 48%. Em um dia chuvoso, o LE representou 86% do SR e o H, 21%. Em um dia ensolarado, após um período de chuvas, LE e H foram, respectivamente, 68% e 29% do SR. O G foi, em média, 5,7% e 1,3% do SR para as ruas mantidas capinadas e com forro, respectivamente.The energy balance method was used to characterize the hourly variation of the net radiation, latent and sensible fluxes and soil heat flux on a mature vineyard grown at Jundiaí, São Paulo, Brazil. The grapevines, cv. Niagara Rosada, in the vineyard were wrapped to trellis wires, creating compact hedgerows 2 m apart, 1.7 m height and 0.4 wide, with the foliage 1m above the soil surface. Also, the net and incoming radiation relationships and the partioning of the available energy to the system into latent and heat flux, and soil heat flux were determined for the vineyard. During a sunny day (dry period the latent heat flux was 44% of the net radiation and the sensible heat flux, 48%. However during a rainy day, the latent heat flux was 86% of the net radiation and the sensible heat flux, 21%. During a sunny day, after the occurrence of rain, the latent and sensible heat fluxes were, respectively, 68% and 29% of the net radiation. The soil heat flux was 5.7 an 1.3% of the net radiation, for bare soil and mulched rows, respectively.

Hexagonal-like Nb2O5 Nanoplates-Based Photodetectors and Photocatalyst with High Performances

Science.gov (United States)

Liu, Hui; Gao, Nan; Liao, Meiyong; Fang, Xiaosheng

2015-01-01

Ultraviolet (UV) photodetectors are important tools in the fields of optical imaging, environmental monitoring, and air and water sterilization, as well as flame sensing and early rocket plume detection. Herein, hexagonal-like Nb2O5 nanoplates are synthesized using a facile solvothermal method. UV photodetectors based on single Nb2O5 nanoplates are constructed and the optoelectronic properties have been probed. The photodetectors show remarkable sensitivity with a high external quantum efficiency (EQE) of 9617%, and adequate wavelength selectivity with respect to UV-A light. In addition, the photodetectors exhibit robust stability and strong dependence of photocurrent on light intensity. Also, a low-cost drop-casting method is used to fabricate photodetectors based on Nb2O5 nanoplate film, which exhibit singular thermal stability. Moreover, the hexagonal-like Nb2O5 nanoplates show significantly better photocatalytic performances in decomposing Methylene-blue and Rhdamine B dyes than commercial Nb2O5.

Radiological Survey Results for the Niagara Mohawk Right-of-Way, Tonawanda, New York (TNY004)

International Nuclear Information System (INIS)

McKenzie, S.P.; Uziel, M.S.

1998-01-01

At the request of the U.S. Department of Energy (DOE), a team from Oak Ridge National Laboratory conducted a radiological survey of a small portion of the Niagara Mohawk Power Corporation right-of-way in Tonawanda, New York. The purpose of the survey was to determine if radioactive residuals had migrated from or been redistributed onto the Niagara Mohawk right-of-way from the former Linde property to the west. The Linde Air Products Division of Union Carbide Corporation, Tonawanda New York, had used radioactive materials at that location for work performed under government contract from 1942 through 1948. The survey was performed in May 1996 in response to Formerly Utilized Sites Remedial Action Program (FUSRAP) requirements. These requirements dictate that the radiological status of certain vicinity properties shall be assessed and documented according to prescribed procedures prior to certification of the property for release for unrestricted use. Such release can only be granted if the property is found to be within current applicable authorized limits. The survey included a gamma scan of accessible areas and the collection and radionuclide analysis of soil samples from the portion of right-of-way located east of the former Linde plant site and north of the railway spur entrance gate. Results of the survey indicate that radioactive material probably originating from the Linde plant is located on the Niagara Mohawk right-of-way in the area surveyed. Surface gamma exposure rates were elevated above typical background levels. Four scattered surface soil samples exceeded DOE guideline values for 238 U, and 8 of 13 surface soil samples exceeded DOE guideline values for 226 Ra. The radionuclide distribution in these samples was similar to that found in materials resulting from former processing activities at the Linde site. It is recommended that the property be designated for remedial action by DOE

Preparation of niobium thioiodide NbSsub(4)Isub(0,33)(Nbsub(3)Ssub(12)I)

International Nuclear Information System (INIS)

Fedorov, V.E.; Evstaf'ev, V.K.

1981-01-01

A new niobium thioiodide is prepared by the interaction of Nb 3 I 8 with sulphur at 350-360 deg for several days. The thioiodide NbSsub(4)Isub(0.33) is crystallized in the form of green-blue long fibres. However, the X-ray graphic identification of the thioiodide prepared is hampered as fibrous crystals are difficult to grind and their powder pattern is very texturized. During the heating in the sealed ampoule NbSsub(4)Isub(0.33) decomposes in the range of 650-680 deg C, during the heating in helium flux the decomposition starts considerably earlier and ends with the formation of niobium disulphide [ru

Dynamics of turbidity plumes in Lake Ontario. [Welland Canal and Niagara, Genesee, and Oswego Rivers

Science.gov (United States)

Pluhowski, E. J. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Large turbidity features along the 275 km south shore of Lake Ontario were analyzed using LANDSAT-1 images. The Niagara River plume, ranging from 30 to 500 sq km in area is, by far, the largest turbidity feature in the lake. Based on image tonal comparisons, turbidity in the Welland Canal is usually higher than that in any other water course discharging into the lake during the shipping season. Less turbid water enters the lake from the Port Dalhousie diversion channel and the Genesee River. Relatively clear water resulting from the deposition of suspended matter in numerous upstream lakes is discharged by the Niagara and Oswego Rivers. Plume analysis corroborates the presence of a prevailing eastward flowing longshore current along the entire south shore. Plumes resulting from beach erosion were detected in the images. Extensive areas of the south shore are subject to erosion but the most severely affected beaches are situated between Fifty Mile Point, Ontario and Thirty Mile Point, New York along the Rochester embayment, and between Sodus Bay and Nine Mile Point.

Nuclear at Niagara. 32nd Annual Canadian Nuclear Society conference and 35th CNS/CNA student conference

International Nuclear Information System (INIS)

2011-01-01

The 32nd Annual Canadian Nuclear Society Conference and 35th CNS/CNA Student Conference was held in Niagara Falls, Ontario, Canada on June 5-8, 2011. The theme of the conference, 'Nuclear at Niagara', brought together scientists, engineers, technologists, senior management, government officials, and students interested in all aspects of nuclear science and technology and its applications, including nuclear power generation, fuel production, uranium mining and refining, management of radioactive wastes and used fuel. Other topics include medical and industrial uses of radionuclides, occupational and environmental radiation protection, the science and technology of nuclear fusion, and associated activities in research and development. and applications of energy from the atom. The central objective of this conference was to exchange views on how nuclear science and technology can best serve the needs of humanity, now and in the future. Over 400 delegates from across Canada and other nuclear countries were in attendance.

Photoluminescence of rare-earth ion (Eu3+, Tm3+, and Er3+)-doped and co-doped ZnNb2O6 for solar cells

Science.gov (United States)

Gao, Sen-Pei; Qian, Yan-Nan; Wang, Biao

2015-08-01

Visible converted emissions produced at an excitation of 286 nm in ZnNb2O6 ceramics doped with rare-earth ions (RE = Eu3+, Tm3+, Er3+ or a combination of these ions) were investigated with the aim of increasing the photovoltaic efficiency of solar cells. The structure of RE:ZnNb2O6 ceramics was confirmed by x-ray diffraction patterns. The undoped ZnNb2O6 could emit a blue emission under 286-nm excitation, which is attributed to the self-trapped excitons’ recombination of the efficient luminescence centers of edge-shared NbO6 groups. Upon 286-nm excitation, Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 ceramics showed blue, green, and red emissions, which correspond to the transitions of 5D0 → 7FJ (J = 1-4) (Eu3+), 1G4 → 3H6 (Tm3+), and 2H11/2/4S3/2 → 4I15/2 (Er3+), respectively. The calculated CIE chromaticity coordinates of Eu:ZnNb2O6, Tm:ZnNb2O6, and Er:ZnNb2O6 are (0.50, 0.31), (0.14, 0.19), and (0.29, 0.56), respectively. RE ion-co-doped ZnNb2O6 showed a combination of characteristic emissions. The chromaticity coordinates of Eu/Tm:ZnNb2O6, Eu/Er:ZnNb2O6, and Tm/Er:ZnNb2O6 were calculated to be (0.29, 0.24), (0.45, 0.37), and (0.17, 0.25). Project supported by the National Natural Science Foundation of China (Grant Nos. 10572155 and 10732100) and the Research Fund for the Doctoral Program of Ministry of Education, China (Grant No. 20130171130003).

Nuclear at Niagara. 32nd Annual Canadian Nuclear Society conference and 35th CNS/CNA student conference

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-07-01

The 32nd Annual Canadian Nuclear Society Conference and 35th CNS/CNA Student Conference was held in Niagara Falls, Ontario, Canada on June 5-8, 2011. The theme of the conference, 'Nuclear at Niagara', brought together scientists, engineers, technologists, senior management, government officials, and students interested in all aspects of nuclear science and technology and its applications, including nuclear power generation, fuel production, uranium mining and refining, management of radioactive wastes and used fuel. Other topics include medical and industrial uses of radionuclides, occupational and environmental radiation protection, the science and technology of nuclear fusion, and associated activities in research and development. and applications of energy from the atom. The central objective of this conference was to exchange views on how nuclear science and technology can best serve the needs of humanity, now and in the future. Over 400 delegates from across Canada and other nuclear countries were in attendance.

Comprehensive characterization and hazard assessment of the DOE-Niagara Falls storage site

International Nuclear Information System (INIS)

Anderson, T.L.; Dettorre, J.F.; Jackson, D.R.; Ausmus, B.S.

1981-06-01

A comprehensive radioecological and nonradiological characterization and hazards assessment was conducted on DOE-Niagara Falls Storage Site. Pitchblende residues and other low-level nuclear waste have been stored on the site since 1944. The most highly radioactive residues were stored in four abandoned buildings, while other wastes were deposited in pits or piled on surface soils on the Site. Several ditches were constructed on the Site to facilitate drainage or excess precipitation. Results of the study will permit the US DOE to form an appropriate remedial action plan for the Site

Niagara Falls Storage Site annual environmental report for calendar year 1991, Lewiston, New York. [Niagara Falls Storage Site

Energy Technology Data Exchange (ETDEWEB)

1992-09-01

This document describes the environmental monitoring program at the Niagara Falls Storage Site (NFSS) and surrounding area, implementation of the program, and monitoring results for 1991. Environmental monitoring at NFSS began in 1981. The site is owned by the US Department of Energy (DOE) and is assigned to the DOE Formerly Utilized Sites Remedial Action Program (FUSRAP). FUSRAP is a program to decontaminate or otherwise control sites where residual radioactive materials remain from the early years of the nation's atomic energy program or from commercial operations causing conditions that Congress has authorized DOE to remedy. The environmental monitoring program at NFSS includes sampling networks for radon concentrations in air; external gamma radiation exposure; and total uranium and radium-226 concentrations in surface water, sediments, and groundwater. Additionally, several nonradiological parameters including seven metals are routinely measured in groundwater. Monitoring results are compared with applicable Environmental Protection Agency (EPA) standards, DOE derived concentration guides (DCGs), dose limits, and other requirements in DOE orders. Environmental standards are established to protect public health and the environment.

Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions

Directory of Open Access Journals (Sweden)

Caterine Daza Gomez

2015-08-01

Full Text Available The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR, Raman spectroscopy, X-ray diffraction (XRD, and transmission electron microscopy (TEM. The photodegradation capacity of the powders was studied using the organic molecule, methylene blue. The effect of both the method of synthesis and the percentage of niobium present in the sample on the photodegradation action of the solids was determined. The mesoporous Nb-MCM-41 that produced the greatest photodegradation response was obtained using the sol-gel method and 20% niobium incorporation.

Photosynthetic capacity of 'Niagara Rosada' grapes grown under transparent plastic covering

Directory of Open Access Journals (Sweden)

Bruna Corrêa da Silva de Deus

2016-06-01

Full Text Available ABSTRACT: New techniques in tropical regions such as use of transparent plastic covering (TPC, have been employed in grapes to avoid the wetting leaves and fruits, which can reduce the occurrence of fungal diseases, reduce the use of sprays, and reduce damage caused by hail and high winds. TPC may significantly affect the photosynthetic rates of grapevines cultivated in tropical regions, and thus have strong effects on plant productivity and improve fruit quality. However, in the North of Rio de Janeiro region there are lacks of studies related to TPC effects on photosynthetic capacity. The objective of this study was to evaluate the photosynthetic capacity in 'Niagara Rosada' vines grown under TPC and without transparent plastic covering (WTPC. The experiment was conducted between April and June 2013, on Tabuinha farm, located in the 3rd district of São Fidélis, Rio de Janeiro State, Brazil. A completely randomized block design was used with two treatments (TPC and WTPC and twelve replications. Evaluations consisted of climatological variables, gas exchange and maximum quantum efficiency of open photosystem II centers-quantum yield (Fv/Fm It was possible to observe that under TPC maximum temperature increase of 2.3°C, relative humidity reduced 1.5%, vapor pressure deficit increase 0.4kPa, and light intensity reduced 47.7%. These changes did not cause photochemical damage to the leaves. The TPC promoted higher net photosynthetic rate at 800h, which was associated with higher stomatal conductance. Thus, the TPC used in the northern region of Rio de Janeiro State did not impair the photosynthetic capacity of 'Niagara Rosada' vines.

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)

Accessibility and use of primary healthcare for immigrants living in the Niagara Region.

Science.gov (United States)

Lum, Irene D; Swartz, Rebecca H; Kwan, Matthew Y W

2016-05-01

Although the challenges of accessing and using primary healthcare for new immigrants to Canada have been fairly well documented, the focus has primarily been on large cities with significant immigrant populations. The experiences of immigrants living in smaller, less diverse urban centres remain largely unknown. The purpose of this study was to examine the lived experiences of immigrants living in a small urban centre with regards to the primary healthcare system. A total of 13 immigrants living in the Greater Niagara Region participated in semi-structured interviews. All interviews were recorded, transcribed, and then coded and analyzed for emergent themes using NVivo. Five factors were found to impact primary care access and use: lack of social contacts, lack of universal healthcare coverage during their initial arrival, language as a barrier, treatment preferences, and geographic distance to primary care. Overall findings suggest that immigrants moving to smaller areas such as the Niagara Region face similar barriers to primary care as those moving into large cities. Some barriers, however, appear to be specific to the context of smaller urban centres, further exacerbated by living in a small city due to a smaller immigrant population, fewer services for immigrants, and less diversity in practicing physicians. More research is required to understand the contextual factors inhibiting primary care access and use among immigrants moving to smaller urban centres, and determine effective strategies to overcome these barriers. Copyright © 2016 Elsevier Ltd. All rights reserved.

A fast atom bombardment study of the lead isotope ratios in early nineteenth century Niagara Peninsula pottery glazes

International Nuclear Information System (INIS)

Miller, J.M.; Jones, T.R.B.; Kenney, Tina; Rupp, D.W.

1986-01-01

The application of fast atom bombardment (FAB) mass spectrometry to the determination of lead isotope ratios in nineteenth century pottery glazes from the Niagara Peninsula has been investigated with the aim of determining the source of the lead used in the glazes. Methods of sampling have been compared, including direct analysis of glass chips, analysis of powdered glaze scrapings, analysis of acid extracts of the former, and simple acid leaching of the surface of a piece of pottery. The latter method gave the best results. The FAB data, as obtained on an older mass spectrometer, can distinguish lead from igneous vs. sedimentary deposits, but is not adequate to determine specific mining locations. Although newer FAB instrumentation can narrow this range, the overlap of data from the Niagara Peninsula and England precludes a simple answer to the archeological question as to English vs. Canadian origin of the lead used in the Jordan pottery glazes. However, the data do suggest that the potter used a local source for the lead

Approaches to the Cataract: Butor's Niagara

Directory of Open Access Journals (Sweden)

Elinor S. Miller

1977-09-01

Full Text Available Michel Butor's 6 810 000 litres d'eau par seconde bears certain similarities to each of his earlier stereophonic works, but is much more than a reworking of established techniques. Generally thought to be difficult, as indicated by the title, which arouses interest without revealing the subject matter, the work has a complex and masterful structure. Against a background of gradually accelerated time, emphasized by appropriate sound effects, an Announcer leads a tour of Niagara Falls. Alphabetically identified characters play out predictable roles as newlyweds, second honeymooners, and the lonely ones. A Reader recites throughout Chateaubriand's classic description of the Falls, constantly recombining the original words in canon form. The initially forbidding typography with three typefaces and three margins creates the possibility of multiple readings. Each part is preceded by directions enabling the reader to alter the text, increasing the volume for some characters, drowning out others. Thus, theoretically, one could read any one of ten texts: "mobile readings," revealing each a different work. This mobility, with the typography, creates an "intellectual chord," not possible otherwise except in music. The subtly colored polyphonic mobile brilliantly serves to express Butor's view of the human condition, reflected in his stereophonic vision of the Falls.

Influence of Nb dopant on the structural and optical properties of nanocrystalline TiO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Kaleji, Behzad Koozegar, E-mail: bkaleji@yahoo.com [Department of Materials Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box:14115-143, Tehran (Iran, Islamic Republic of); Sarraf-Mamoory, Rasoul, E-mail: rsarrafm@modares.ac.ir [Department of Materials Engineering, Faculty of Engineering, Tarbiat Modares University, P.O. Box:14115-143, Tehran (Iran, Islamic Republic of); Fujishima, Akira [Photo-catalyst Group, Kanagawa Academy of Science and Technology, KSP East 412, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012 (Japan)

2012-01-16

Highlights: Black-Right-Pointing-Pointer We coated Nb-doped TiO{sub 2} films on glazed porcelain via sol-gel dip coating method. Black-Right-Pointing-Pointer We examined coatings by degradation of MB solution and optical light transmittance. Black-Right-Pointing-Pointer Coatings show enhanced photo-catalytic activity in 1 mol% Nb. Black-Right-Pointing-Pointer Nb doping inhibited the grain growth, and which are found to inhibit the anatase to rutile phase transformation. - Abstract: In this study, preparation of Nb-doped (0-20 mol% Nb) TiO{sub 2} dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of Nb on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films was examined by atomic force microscope and X-ray photoelectron spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The photo-catalytic activity of the film was tested on degradation of methylene blue. Best photo-catalytic activity of Nb-doped TiO{sub 2} thin films were measured in the TiO{sub 2}-1 mol% Nb sample. The average optical transmittance of about 47% in the visible range and the band gap of films became wider with increasing Nb doping concentration. The Nb{sup 5+} dopant presented substitutional Ti{sup 4+} into TiO{sub 2} lattice.

Niagara Falls Storage Site environmental report for calendar year 1989, Lewiston, New York

International Nuclear Information System (INIS)

1990-05-01

The environmental monitoring program, which began in 1981, was continued during 1989 at the Niagara Falls Storage Site (NFSS), a United States Department of Energy (DOE) surplus facility located in Niagara County, New York, that is currently used for interim storage of radioactive residues, contaminated soils, and rubble. The monitoring program is being conducted by Bechtel National, Inc. The monitoring program at NFSS measures radon concentrations in air; external gamma radiation levels; and uranium and radium concentrations in surface water, groundwater, and sediment. Additionally, several nonradiological parameters are measured in groundwater. To verify that the site is in compliance with the DOE radiation protection standard and to assess its potential effect on public health, the radiation dose was calculated for a hypothetical maximally exposed individual. Based on the conservative scenario described in this report, this hypothetical individual receives an annual external exposure equivalent to approximately 2 percent of the DOE radiation protection standard of 100 mrem/yr. This exposure is less than a person receives during a one-way flight from New York to Los Angeles (because of the greater amounts of cosmic radiation at higher altitudes). The cumulative dose to the population within an 80-km (50-mi) radius of NFSS that results from radioactive materials present at the site is indistinguishable from the dose that the same population receives from naturally occurring radioactive sources. Results of the 1989 monitoring show that NFSS is in compliance with applicable DOE radiation protection standards. 18 refs., 26 figs., 18 tabs

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)

PRODUCTION COSTS AND PROFITABILITY OF ‘NIAGARA ROSADA’ TABLE GRAPE GROWN IN DIFFERENT REGIONS OF SÃO PAULO STATE

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FERNANDO PEREZ CAPPELLO

2017-10-01

Full Text Available ABSTRACT Niagara Rosada is the main cultivar of table grapes produced in São Paulo state. Its production is concentrated mainly in the regions of Campinas, Itapetininga and Jales, where it is grown under different production systems. The aim of this study was to analyze the economic viability of cv. Niagara Rosada at main regions producers of São Paulo State. Therefore, case studies were made with grape growers for each region to assess the production cost and calculate profitability. In the Campinas region, for two cycles per year, the main crop and the second crop were evaluated, and the Total Cost (TC obtained was US$ 0.81/Kg, with US$ 0.23/Kg of Total Net Revenue (TNR. Considering only the main crop, the decrease of grape production increased the production cost and reduced profitability, the TC reached was US$ 0.93/Kg and TNR US$ 0.08/Kg. In the Itapetininga region, for two cycles per year, in main crop the TC was US$ 0.68/Kg and the TNR was US$ 0.32/Kg. Meanwhile, in the second crop, the lower productivity increased TC to US$ 1.05/Kg, but the higher price caused a TNR of US$ 0.38/Kg. In the Jales region, only one cycle per year, TC was increased to US$ 1.21/Kg, however, the high selling prices in the off-season in São Paulo State resulted in TNR of US$ 0.43/Kg. According to the results, the production of cv. Niagara Rosada in different regions of São Paulo State is profitable and has a positive return for family agriculture. Nevertheless, each region has its own characteristics in terms of production and commercialization of table grapes.

Leading Change: A Case Study of Leadership Practices from the Development of the Niagara County Community College Culinary Institute

Science.gov (United States)

Caton, Jazmin; Mistriner, Mark

2016-01-01

The purpose of this case study was to evaluate the lessons learned from the development of a project that set out to revitalize an economically depressed area with an innovative approach to workforce development through partnerships. The focus was to utilize the development of the Niagara County Community College Culinary Institute as an example…

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

Caracterização de filmes finos de Nb2O5 com propriedades eletrocrômicas Caracterization of OF Nb2O5 thin films with electrochromic properties

Directory of Open Access Journals (Sweden)

C. O. Avellaneda

1998-06-01

Full Text Available The sols for thin electrochromic coatings of Nb2O5 were obtained by synthesis of the niobium butoxide from BuONa and NbCl5. The ~300nm thick films were deposited by dip-coating technique from the alkoxide solution and calcined at 560ºC in O2 atmosphere during 3 hours. The particles size of niobium oxide (V powder (~20mm was obtained from x-ray diffraction using the Scherrer equation. The coatings were characterized by cyclic voltammetry and cronoamperommetry techniques. The spectral variation of the optical transmittance were determined in situ as a function of the cyclical potencial and memory effect. The insertion process of lithium is reversible and change the film color from transparent (T=80% to dark blue (T=20%.

Factors Impacting Student Service Utilization at Ontario Colleges: Key Performance Indicators as a Measure of Success: A Niagara College View

Science.gov (United States)

Veres, David

2015-01-01

Student success in Ontario College is significantly influenced by the utilization of student services. At Niagara College there has been a significant investment in student services as a strategy to support student success. Utilizing existing KPI data, this quantitative research project is aimed at measuring factors that influence both the use of…

Stability analysis of waterfall cliff face at Niagara Falls: An implication to erosional mechanism of waterfall

OpenAIRE

Hayakawa, Yuichi S.; Matsukura, Yukinori

2010-01-01

Although recession of waterfalls or knickpoints in bedrock rivers is a common geomorphological process, detailed mechanics of waterfall recession has only been examined in a few cases. Caprock recession model at Niagara Falls, in which gravitational collapse of caprock induced by undercutting notch plays a significant role, has been one of the well-known models describing the waterfall erosion, but the validity of the model has hardly been examined in a quantitative context. Here we assess th...

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.

CNTs-Modified Nb3O7F Hybrid Nanocrystal towards Faster Carrier Migration, Lower Bandgap and Higher Photocatalytic Activity.

Science.gov (United States)

Huang, Fei; Li, Zhen; Yan, Aihua; Zhao, Hui; Liang, Huagen; Gao, Qingyu; Qiang, Yinghuai

2017-01-06

Novel semiconductor photocatalysts have been the research focus and received much attention in recent years. The key issues for novel semiconductor photocatalysts are to effectively harvest solar energy and enhance the separation efficiency of the electron-hole pairs. In this work, novel Nb 3 O 7 F/CNTs hybrid nanocomposites with enhanced photocatalytic activity have been successfully synthesized by a facile hydrothermal plus etching technique. The important finding is that appropriate pH values lead to the formation of Nb 3 O 7 F nanocrystal directly. A general strategy to introdue interaction between Nb 3 O 7 F and CNTs markedly enhances the photocatalytic activity of Nb 3 O 7 F. Comparatively, Nb 3 O 7 F/CNTs nanocomposites exhibit higher photodegradation efficiency and faster photodegradation rate in the solution of methylene blue (MB) under visible-light irradiation. The higher photocatalytic activity may be attributed to more exposed active sites, higher carrier migration and narrower bandgap because of good synergistic effect. The results here may inspire more engineering, new design and facile fabrication of novel photocatalysts with highly photocatalytic activity.

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.)

Histomorphologic evaluation of Ti-13Nb-13Zr alloys processed via powder metallurgy. A study in rabbits

International Nuclear Information System (INIS)

Bottino, M.C.; Coelho, P.G.; Yoshimoto, M.; Koenig, B.; Henriques, V.A.R.; Bressiani, A.H.A.; Bressiani, J.C.

2008-01-01

This study presents the in-vivo evaluation of Ti-13Nb-13Zr alloy implants obtained by the hydride route via powder metallurgy. The cylindrical implants were processed at different sintering and holding times. The implants' were characterized for density, microstructure (SEM), crystalline phases (XRD), and bulk (EDS) and surface composition (XPS). The implants were then sterilized and surgically placed in the central region of the rabbit's tibiae. Two double fluorescent markers were applied at 2 and 3 weeks, and 6 and 7 weeks after implantation. After an 8-week healing period, the implants were retrieved, non-decalcified section processed, and evaluated by electron, UV light (fluorescent labeling), and light microscopy (toluidine blue). BSE-SEM showed close contact between bone and implants. Fluorescent labeling assessment showed high bone activity levels at regions close to the implant surface. Toluidine blue staining revealed regions comprising osteoblasts at regions of newly forming/formed bone close to the implant surface. The results obtained in this study support biocompatible and osseoconductive properties of Ti-13Nb-13Zr processed through the hydride powder route

Histomorphologic evaluation of Ti-13Nb-13Zr alloys processed via powder metallurgy. A study in rabbits

Energy Technology Data Exchange (ETDEWEB)

Bottino, M.C. [Department of Materials Science and Engineering, University of Alabama at Birmingham, BEC 254 1530 3rd Avenue South, Birmingham, AL, 35294 (United States); Coelho, P.G. [Department of Biomaterials and Biomimetics, New York University, College of Dentistry, 345 East 24th Street, Room 804S, New York, NY, 10100 (United States)], E-mail: pgcoelho@nyu.edu; Yoshimoto, M. [Materials Science and Technology Center, Institute for Energy and Nuclear Research, Av. Prof. Lineu Prestes, 2242, Sao Paulo, SP, 05508-000 (Brazil); Koenig, B. [Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo (ICB-USP) Av. Prof. Lineu Prestes, 2415, Sao Paulo, SP, 05508-900 (Brazil); Henriques, V.A.R. [Materials Division (AMR/IAE), CTA Brazilian Aerospace Technical Center, Sao Jose dos Campos, SP, 12228-904 (Brazil); Bressiani, A.H.A.; Bressiani, J.C. [Materials Science and Technology Center, Institute for Energy and Nuclear Research, Av. Prof. Lineu Prestes, 2242, Sao Paulo, SP, 05508-000 (Brazil)

2008-03-10

This study presents the in-vivo evaluation of Ti-13Nb-13Zr alloy implants obtained by the hydride route via powder metallurgy. The cylindrical implants were processed at different sintering and holding times. The implants' were characterized for density, microstructure (SEM), crystalline phases (XRD), and bulk (EDS) and surface composition (XPS). The implants were then sterilized and surgically placed in the central region of the rabbit's tibiae. Two double fluorescent markers were applied at 2 and 3 weeks, and 6 and 7 weeks after implantation. After an 8-week healing period, the implants were retrieved, non-decalcified section processed, and evaluated by electron, UV light (fluorescent labeling), and light microscopy (toluidine blue). BSE-SEM showed close contact between bone and implants. Fluorescent labeling assessment showed high bone activity levels at regions close to the implant surface. Toluidine blue staining revealed regions comprising osteoblasts at regions of newly forming/formed bone close to the implant surface. The results obtained in this study support biocompatible and osseoconductive properties of Ti-13Nb-13Zr processed through the hydride powder route.

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

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.

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)

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

Towards an adaptation action plan : climate change and health in the Toronto-Niagara region : summary for policy makers

International Nuclear Information System (INIS)

Chiotti, Q.; Morton, I.; Maarouf, A.

2002-10-01

The current science regarding climate change and its potential health effects was assessed in an effort to provide information to decision-makers dealing with health infrastructure in the Toronto-Niagara region. This report also presents an assessment of how the health care system can adapt to handle the increased demand for services resulting from the projected negative human health effects of climate change. The first part of the report presents some background information on climate change and health issues and demonstrates how the current health care infrastructure cannot deal effectively with the full range of health effects that may occur in heavily populated areas such as the Toronto-Niagara region. The second part of the report summarizes the scientific knowledge about the expected impacts of climate change and associated health effects, such as heat stress, extreme weather events, poor air quality, vector-borne diseases, food and water-borne diseases, and increased exposure to ultra-violet radiation. It was noted that children and the elderly are most vulnerable. The final part of the report outlines an adaptation action plan to improve the health care infrastructure through public education and communication, surveillance and monitoring, ecosystem intervention, infrastructure development, technical engineering, and medical intervention. 100 refs., 1 fig

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.

Results of radiological measurements taken in the Niagara Falls, New York, area (NF002)

International Nuclear Information System (INIS)

Williams, J.K.; Berven, B.A.

1986-11-01

The results of a radiological survey of 100 elevated gamma radiation anomalies in the Niagara Falls, New York, area are presented. These radiation anomalies were identified by a mobile gamma scanning survey during the period October 3-16, 1984, and were recommended for an onsite survey to determine if the elevated levels of radiation may be related to the transportation of radioactive waste material to the Lake Ontario Ordnance Works for storage. In this survey, radiological measurements included outdoor gamma exposure rates at 1 m above the surface; outdoor gamma exposure rates at the surface, range of gamma exposure rates during scan; and uranium, radium, and thorium concentrations in biased surface soil samples. The results show 38 anomalies (35 located along Pletcher Road and 3 associated with other unreleated locations) were found to exceed Formerly Utilized Sites Remedial Action Program (FUSRAP) remedial action guidelines and were recommended for formal characterization surveys. (Since the time of this survey, remedial actions have been conducted on the 38 anomalies identified as exceeding FUSRAP guidelines, and the radioactive material above guidelines has been removed.) The remaining 62 anomalies are associated with asphalt driveways and parking lots, which used a phosphate slag material (previously identified as cyclowollastonite, synthetic CaSiO 3 ). This rocky-slag waste material was used for bedding under asphalt surfaces and in general gravel applications. Most of the contaminated soil and rock samples collected at the latter anomalies had approximately equal concentrations of 226 Ra and 238 U and, therefore, are not related to materials connected with the Niagara Falls Storage Site (NFSS), including material that was transported to the NFSS. 13 refs., 7 figs., 14 tabs

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.

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

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

Spatial variability of leaf wetness duration in a 'Niagara Rosada' vineyard Variabilidade espacial da duração do período de molhamento em vinhedo de 'Niagara Rosada'

Directory of Open Access Journals (Sweden)

Jorge Lulu

2008-03-01

Full Text Available Despite considerable efforts to develop accurate electronic sensors to measure leaf wetness duration (LWD, little attention has been given to studies about how is LWD variability in different positions of the crop canopy. In order to evaluate the influence of 'Niagara Rosada' (Vitis labrusca grapevine structure on the spatial variability of LWD, the objective of this study was to determine the canopy position of the ‘Niagara RosadaÂ’ table grape with longer LWD and its correlation with measured standard LWD over turfgrass. LWD was measured in four different canopy positions of the vineyard (sensors deployed at 45º with the horizontal: at the top of the plants, with sensors facing southwest and northeast (Top-SW and Top-NE, and at the grape bunches height, with sensors facing southwest and northeast (Bottom-SW and Bottom-NE. No significant difference was observed between the top (1.6 m and the bottom (1.0 m of the canopy and also between the southwest and northeast face of the plants. The relationship between standard LWD over turfgrass and crop LWD in different positions of the grape canopy showed a define correlation, with R² ranging from 0.86 to 0.89 for all period, from 0.72 to 0.77 for days without rain, and from 0.89 to 0.91 for days with rain.Apesar dos esforços consideráveis para se desenvolverem sensores eletrônicos acurados para medir a duração do período de molhamento (DPM, pouca atenção tem sido dada às pesquisas sobre a variabilidade da DPM no interior do dossel das culturas. A fim de avaliar a influência da estrutura da cobertura vegetal da videira 'Niagara Rosada' (Vitis labrusca na variabilidade espacial da DPM, o objetivo do presente estudo foi determinar a posição da videira com a maior DPM e sua relação com a DPM medida em condição-padrão (no gramado. Para tanto, a DPM foi medida em quatro diferentes posições da planta, com os sensores inclinados em 45º em relação à horizontal: topo da planta

Synthesis, characterization and photocatalytic activity of NaNbO{sub 3}/ZnO heterojunction photocatalysts

Energy Technology Data Exchange (ETDEWEB)

Xu Hui; Liu Chengtang [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of the Environment, Jiangsu University, Zhenjiang 212013 (China); Li Huaming, E-mail: lihm@ujs.edu.cn [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xu Yuanguo; Xia Jiexiang; Yin Sheng; Liu Ling [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Wu Xiangyang [School of the Environment, Jiangsu University, Zhenjiang 212013 (China)

2011-09-15

Highlights: > There was no report to investigate the photocatalytic activity of NaNbO3/ZnO heterojunction. > The relationship between the photocatalytic activity and the structural features of the prepared catalysts was investigated through a systematic characterization analysis. > The possible photocatalytic mechanism was proposed. - Abstract: A series of NaNbO{sub 3}/ZnO heteronanostructures were synthesized with the hydrothermal method. Various characterization methods such as X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and energy dispersive X-ray spectrometer (EDS), transmission electron microscope (TEM), X-ray photoelectron spectra (XPS) and diffuse reflectance spectra (DRS) were employed to investigate the structure, morphology and photocatalytic properties. The photocatalytic activity of the catalysts was evaluated by the degradation of methylene blue dye and the highest photocatalytic efficiency was observed when the content of NaNbO{sub 3} was 10 wt.%. The photocatalytic mechanism of the heterojunction was also discussed. The effective transformation of the photoexcited electron and holes restricted the recombination of charges, which was regarded as the main reason of the high photocatalytic activity.

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.

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).

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)

DNA Electrochemistry with Tethered Methylene Blue

Science.gov (United States)

Pheeney, Catrina G.

2012-01-01

Methylene blue (MB′), covalently attached to DNA through a flexible C12 alkyl linker, provides a sensitive redox reporter in DNA electrochemistry measurements. Tethered, intercalated MB′ is reduced through DNA-mediated charge transport; the incorporation of a single base mismatch at position 3, 10, or 14 of a 17-mer causes an attenuation of the signal to 62 ± 3% of the well-matched DNA, irrespective of position in the duplex. The redox signal intensity for MB′–DNA is found to be least 3-fold larger than that of Nile blue (NB)–DNA, indicating that MB′ is even more strongly coupled to the π-stack. The signal attenuation due to an intervening mismatch does, however, depend on DNA film density and the backfilling agent used to passivate the surface. These results highlight two mechanisms for reduction of MB′ on the DNA-modified electrode: reduction mediated by the DNA base pair stack and direct surface reduction of MB′ at the electrode. These two mechanisms are distinguished by their rates of electron transfer that differ by 20-fold. The extent of direct reduction at the surface can be controlled by assembly and buffer conditions. PMID:22512327

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)

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.

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

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.

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

CONTROLE QUÍMICO E CULTURAL DAS PLANTAS DANINHAS NA VIDEIRA 'NIAGARA ROSADA'

Directory of Open Access Journals (Sweden)

PAULO EDISON MARTINS

1997-01-01

Full Text Available Estudou-se o controle das plantas daninhas e a seletividade dos herbicidas diclobenil, diuron e simazine à cultura da videira `Niagara Rosada', procurando-se separar os efeitos da cobertura morta sobre os fatores de produção e o teor de sólidos solúveis do suco da uva. O delineamento experimental utilizado foi de blocos ao acaso com quatro repetições. Verificou-se que os herbicidas diuron (2,0 kg/ha, simazine (2,4 kg/ha e diclobenil (3,04; 4,05 e 5,06 kg/ha foram seletivos à cultura da videira e eficientes no controle das plantas daninhas capim-colchão (Digitaria horizontalis Willd., caruru (Amaranthus hibridus L., guanxuma (Sida spp. e picão-preto (Bidens pilosa L.. A cobertura vegetal de capim-gordura (Melinis minutiflora L. foi eficiente no controle das plantas daninhas.

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

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.

Optical properties of Mg2+, Yb3+, and Ho3+ tri-doped LiNbO3 crystals

Science.gov (United States)

Dai, Li; Liu, Chun-Rui; Tan, Chao; Yan, Zhe-Hua; Xu, Yu-Heng

2017-04-01

A series of LiNbO3 crystals tri-doped with Mg{}2+, Yb{}3+, and Ho{}3+ are grown by the conventional Czochraski technique. The concentrations of Mg{}2+, Yb{}3+, and Ho{}3+ ions in Mg:Yb:Ho:LiNbO3 crystals are measured by using an inductively coupled plasma atomic emission spectrometry. The x-ray diffraction is proposed to determine the lattice constant and analyze the internal structure of the crystal. The light-induced scattering of Mg:Yb:Ho:LiNbO3 crystal is quantitatively described via the threshold effect of incident exposure energy flux. The exposure energy ({E}{{r}}) is calculated to discuss the optical damage resistance ability. The exposure energy of Mg(7 mol):Yb:Ho:LiNbO3 crystal is 709.17 J/cm2, approximately 425 times higher than that of the Mg(1 mol):Yb:Ho:LiNbO3 crystal in magnitude. The blue, red, and very intense green bands of Mg:Yb:Ho:LiNbO3 crystal are observed under the 980-nm laser excitation to evaluate the up-conversion emission properties. The dependence of the emission intensity on pumping power indicates that the up-conversion emission is a two-photon process. The up-conversion emission mechanism is discussed in detail. This study indicates that Mg:Yb:Ho:LiNbO3 crystal can be applied to the fabrication of new multifunctional photoluminescence devices. Project supported by the National Natural Science Foundation of China (Grant No. 51301055), the Youth Science Fund of Heilongjiang Province, China (Grant No. QC2015061), the Special Funds of Harbin Innovation Talents in Science and Technology Research, China (Grant No. 2015RQQXJ045 ), and the Science Funds for the Young Innovative Talents of Harbin University of Science and Technology, China (Grant No. 201501).

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

Niagara Falls Storage Site, Annual site environmental report, Lewiston, New York, Calendar year 1986: Surplus Facilities Management Program (SFMP)

International Nuclear Information System (INIS)

1987-06-01

During 1986, the environmental monitoring program was continued at the Niagara Falls Storage Site (NFSS), a US Department of Energy (DOE) surplus facility located in Niagara County, New York, presently used for the interim storage of radioactive residues and contaminated soils and rubble. The monitoring program is being conducted by Bechtel National, Inc. The monitoring program at the NFSS measures radon gas concentrations in air; external gamma radiation levels; and uranium and radium concentrations in surface water, groundwater, and sediment. To verify that the site is in compliance with the DOE radiation protection standard and to assess its potential effect on public health, the radiation dose was calculated for the maximally exposed individual. Based on the conservative scenario described in the report, this individual would receive an annual external exposure approximately equivalent to 6% of the DOE radiation protection standard of 100 mrem/yr. By comparison, the incremental dose received from living in a brick house versus a wooden house is 10 mrem/yr above background. The cumulative dose to the population within an 80-km (50-mi) radius of the NFSS that would result from radioactive materials present at the site would be indistinguishable from the dose that the same population would receive from naturally occurring radioactive sources. Results of the 1986 monitoring show that the NFSS is in compliance with the DOE radiation protection standard. 14 refs., 11 figs., 14 tabs

Niagara Falls Storage Site, Annual site environmental report, Lewiston, New York, Calendar year 1986: Surplus Facilities Management Program (SFMP)

Energy Technology Data Exchange (ETDEWEB)

1987-06-01

During 1986, the environmental monitoring program was continued at the Niagara Falls Storage Site (NFSS), a US Department of Energy (DOE) surplus facility located in Niagara County, New York, presently used for the interim storage of radioactive residues and contaminated soils and rubble. The monitoring program is being conducted by Bechtel National, Inc. The monitoring program at the NFSS measures radon gas concentrations in air; external gamma radiation levels; and uranium and radium concentrations in surface water, groundwater, and sediment. To verify that the site is in compliance with the DOE radiation protection standard and to assess its potential effect on public health, the radiation dose was calculated for the maximally exposed individual. Based on the conservative scenario described in the report, this individual would receive an annual external exposure approximately equivalent to 6% of the DOE radiation protection standard of 100 mrem/yr. By comparison, the incremental dose received from living in a brick house versus a wooden house is 10 mrem/yr above background. The cumulative dose to the population within an 80-km (50-mi) radius of the NFSS that would result from radioactive materials present at the site would be indistinguishable from the dose that the same population would receive from naturally occurring radioactive sources. Results of the 1986 monitoring show that the NFSS is in compliance with the DOE radiation protection standard. 14 refs., 11 figs., 14 tabs.

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

Estimating leaf wetness duration over turfgrass, and in a 'Niagara Rosada' vineyard, in a subtropical environment Estimativa da duração do período de molhamento sobre o gramado e em vinhedo de 'Niagara Rosada' em condição subtropical

Directory of Open Access Journals (Sweden)

Jorge Lulu

2008-12-01

Full Text Available Leaf wetness duration (LWD is a key parameter in agrometeorology because it is related to plant disease occurrence. As LWD is seldomly measured in a standard weather station it must be estimated to run warning systems for schedule chemical disease control. The objective of the present study was to estimate LWD over turfgrass considering different models with data from a standard weather station, and to evaluate the correlation between estimated LWD over turfgrass and LWD measured in a 'Niagara Rosada' vineyard, cultivated in a hedgerow training system, in Jundiaí, São Paulo State, Brazil. The wetness sensors inside the vineyard were located at the top of the plants, deployed at an inclination angle of 45º and oriented southwest, with three replications. The methods used to estimate LWD were: number of hours with relative humidity above 90% (NHRH > 90%, dew point depression (DPD, classification and regression tree (CART and Penman-Monteith (PM. The CART model had the best performance to estimate LWD over turfgrass, with a good precision (R² = 0.82 and a high accuracy (d = 0.94, resulting in a good confidence index (c = 0.85. The results from this model also presented a good correlation with measured LWD inside the vineyard, with a good precision (R² = 0.87 and a high accuracy (d = 0.96, resulting in a high confidence index (c = 0.93, showing that LWD in a 'Niagara Rosada' vineyard can be estimated with data from a standard weather station.A duração do período de molhamento (DPM é uma variável agrometeorológica chave para a ocorrência de doenças de plantas. Como a DPM é raramente medida nas estações meteorológicas, ela deve ser estimada quando se pretende empregar sistemas de alerta de controle químico. Desse modo, o objetivo do presente estudo foi avaliar a estimativa da DPM sobre gramado por diferentes modelos a partir de dados meteorológicos obtidos em uma estação meteorológica padrão e verificar as relações entre a DPM

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

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.

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

Mechanism of generation of large (Ti,Nb,V)(C,N)-type precipitates in H13 + Nb tool steel

Science.gov (United States)

Xie, You; Cheng, Guo-guang; Chen, Lie; Zhang, Yan-dong; Yan, Qing-zhong

2016-11-01

The characteristics and generation mechanism of (Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of (Ti,Nb,V)(C,N) phases exist—a Ti-V-rich one and an Nb-rich one—in the form of single or complex precipitates. The sizes of the single Ti-V-rich (Ti,Nb,V)(C,N) precipitates are mostly within 5 to 10 μm, whereas the sizes of the single Nb-rich precipitates are mostly 2-5 μm. The complex precipitates are larger and contain an inner Ti-V-rich layer and an outer Nb-rich layer. The compositional distribution of (Ti,Nb,V)(C,N) is concentrated. The average composition of the single Ti-V-rich phase is (Ti0.511V0.356Nb0.133)(C x N y ), whereas that for the single Nb-rich phase is (Ti0.061V0.263Nb0.676)(C x N y ). The calculation results based on the Scheil-Gulliver model in the Thermo-Calc software combining with the thermal stability experiments show that the large phases precipitate during the solidification process. With the development of solidification, the Ti-V-rich phase precipitates first and becomes homogeneous during the subsequent temperature reduction and heat treatment processes. The Nb-rich phase appears later.

Degradation of superconducting Nb/NbN films by atmospheric oxidation

Energy Technology Data Exchange (ETDEWEB)

Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

2017-03-01

Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

Phase transformations on Zr-Nb alloys

International Nuclear Information System (INIS)

Doi, Sergio Norifumi

1980-01-01

This research intended the laboratory scale experimental development of Zr-Nb alloys with adequate characteristics for use as fuel element cladding or for the making of irradiation capsules. Zr-Nb alloys with different Nb contents were melted and the resulting material was characterised. The following metallurgical aspects were considered: preparation of Zr-Nb alloys with various Nb contents; heat and thermomechanical treatments; microstructural characterization; mechanical properties; oxidation properties. The influence of the heat treatment and thermomechanical treatment, on the out-of-pile mechanical and oxidation properties of the Zr-Nb alloys were studied. It was found that the alloy microhardness increases with the Nb content and/or with the thermomechanical treatment. Mechanical properties such as yield and ultimate tensile strength as well as elongation were determined by means of compression tests. The results showed that the alloy yield stress increases with the Nb content and with the thermomechanical treatment, while its elongation decreases. Thermogravimetric analysis determined the alloy oxidation kinetics, in the 400 - 800 deg C interval, at 1 atm. oxygen pressure. The results showed that the alloy oxidation rate increases with the temperature and Nb content. It was also observed that the oxidation rate increases considerably for temperatures higher than 600 deg C.(author)

3-D MnNb{sub 2}O{sub 6} nanogears from 1-D Nb{sub 2}O{sub 5} nanorods

Energy Technology Data Exchange (ETDEWEB)

Hu Weibing, E-mail: w.hu@tom.com [School of Chemical and Environmental Engineering, Hubei Institute for Nationalities, Enshi 445000 (China); Cui Zhicai [School of Chemical and Environmental Engineering, Hubei Institute for Nationalities, Enshi 445000 (China); Mi Yuanzhu [School of Chemistry and Environmental Engineering, Yangtze University, Nanhuan Road 1, Jingzhou 434023 (China)

2012-04-16

Graphical abstract: The geometry morphology of Nb-based nanomaterial evolved from long Nb{sub 2}O{sub 5} nanorods to a mixture of short Nb{sub 2}O{sub 5} nanorods and MnNb{sub 2}O{sub 6} 6-teeth nanogears, and eventually to fully developed pure 3-D nanogears. Highlights: Black-Right-Pointing-Pointer MnNb{sub 2}O{sub 6} nanogears have been generated by a simple solvothermal process when the Mn: Nb ratio was 1:1. Black-Right-Pointing-Pointer MnNb{sub 2}O{sub 6} 6-teeth nanogears accompanied with MnNb{sub 2}O{sub 6} 5-teeth nanogears are got when the Mn:Nb ratio reached 1:2. Black-Right-Pointing-Pointer The nanomaterial consists of nanorods and 6-teeth nanogears at low Mn:Nb molar ratio(1:4). Black-Right-Pointing-Pointer Pure long Nb{sub 2}O{sub 5} nanorods are achieved by only using NbCl{sub 5} - Abstract: MnNb{sub 2}O{sub 6} nanogears have been generated by using mixed NbCl{sub 5} and MnCl{sub 2} at an optimized ratio of 1:1 in a cyclohexanol solvent in a simple solvothermal process. It has shown that the Mn:Nb ratio determines the shape of the products. Detailed characterization by electron microscopy has shown that increasing the Mn{sup +2} concentration during the solvo-thermal synthesis promotes a morphological evolution from relatively long Nb{sub 2}O{sub 5} nanorods to a mixture of short Nb{sub 2}O{sub 5} nanorods and MnNb{sub 2}O{sub 6} 6-teeth nanogears, then to a mixture of short Nb{sub 2}O{sub 5} nanorods and more MnNb{sub 2}O{sub 6} 6-teeth nanogears, then to more and more MnNb{sub 2}O{sub 6} 6-teeth nanogears that are occasionally accompanied with under-developed MnNb{sub 2}O{sub 6} 5-teeth nanogears, and eventually to fully developed pure 3-D nanogears. The driving force for such interesting geometry transformations is attributed to the inclusion of Mn{sup 2+} into the Nb{sub 2}O{sub 5} template at low Mn{sup 2+} concentrations, which introduces internal stresses to the Nb{sub 2}O{sub 5} nanorods. At high Mn{sup 2+} concentrations, close to the

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

Estimativa de área foliar da videira 'Niagara Rosada' conduzida em sistema de latada, região norte fluminense

Directory of Open Access Journals (Sweden)

Miquéias Permanhani

2014-12-01

Full Text Available Com o objetivo de estabelecer um modelo matemático para estimar de forma precisa a área foliar da videira 'Niagara Rosada' na região de Cardoso Moreira-RJ, realizou-se este trabalho em vinhedo particular do sítio pioneiro, implantado no ano de 2002, em sistema de latada. Foram coletadas aleatoriamente, no ciclo de produção iniciado em 2011, 70 folhas de diversos tamanhos, completamente expandidas e sem danos aparentes para determinar a relação entre a área foliar (AF e a área do círculo (AC, considerando seu diâmetro igual à largura da folha. Por meio da análise de regressão, obteve-se a equação linear (AFes = 0,82*AC + 16,12 que, juntamente com mais outras duas, foram utilizadas para comparar a área foliar estimada com a área foliar medida em 30 folhas do ciclo de produção posterior (Março de 2012. Constatou-se que as equações apresentadas permitem estimar de forma precisa a área foliar da videira 'Niagara Rosada/IAC 572' conduzida em sistema de latada, na região de Cardoso Moreira-RJ, com apenas uma dimensão foliar: a largura da folha, sendo que o modelo de regressão obtido (AFes = 0,82*AC + 16,12 foi o que menos subestimou a área da folha comparada (coeficiente angular = 0,99, seguido pelo modelo indicado por Pedro Jr. et al. (1986.

Comparison Between Nb3Al and Nb3Sn Strands and Cables for High Field Accelerator Magnets

Energy Technology Data Exchange (ETDEWEB)

Yamada, R.; Kikuchi, A.; Barzi, E.; Chlachidze, G.; Rusy, A.; Takeuchi, T.; Tartaglia, M.; Turrioni, D.; Velev, V.; Wake, M.; Zlobin, A.V.; /Fermilab

2010-01-01

The Nb{sub 3}Al small racetrack magnet, SR07, has been successfully built and tested to its short sample limit beyond 10 Tesla without any training. Thus the practical application of Nb{sub 3}Al strands for high field accelerator magnets is established. The characteristics of the representative F4 strand and cable, are compared with the typical Nb{sub 3}Sn strand and cable. It is represented by the OST high current RRP Nb{sub 3}Sn strand with 108/127 configuration. The effects of Rutherford cabling to both type strands are explained and the inherent problem of the Nb{sub 3}Sn strand is discussed. Also the test results of two representative small racetrack magnets are compared from the stand point of Ic values, and training. The maximum current density of the Nb{sub 3}Al strands is still smaller than that of the Nb{sub 3}Sn strands, but if we take into account of the stress-strain characteristics, Nb{sub 3}Al strands become somewhat favorable in some applications.

Solidification processing of intermetallic Nb-Al alloys

Science.gov (United States)

Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

1992-01-01

Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

Evaluation of the nuclear cross sections for the reactions: /sup 93/Nb(n,2n)sup(92M)Nb and /sup 93/Nb(n,2n)/sup 92/Nb from threshold to 20 MeV

Energy Technology Data Exchange (ETDEWEB)

Philis, C; Young, P G

1975-07-01

A preliminary evaluation of the nuclear cross section for the reactions /sup 93/Nb(n,2n)sup(92M)Nb and /sup 93/Nb(n,2n)/sup 92/Nb has been completed from threshold to 20 MeV. The evaluation is based entirely on experimental results. The recommended values were determined after analysis, selection, and normalization of the measurements to a consistent set of standards. The evaluated data are discussed and compared with theoretical values and estimates of the uncertainty in the adopted data are provided.

Creep properties of annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe cladding tubes and their performance comparison

International Nuclear Information System (INIS)

Ko, S.; Hong, S.I.; Kim, K.T.

2010-01-01

Creep properties of annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe cladding tubes were studied and compared. The creep rates of the annealed Zr-Nb-O alloy were found to be greater than those of the stress-relieved Zr-Nb-Sn-Fe alloy. Zr-Nb-O alloy was found to have stress exponents of 5-7 independent of stress level whereas Zr-Nb-Sn-Fe alloy exhibited the transition of the stress exponent from 6.5 to 7.5 in the lower stress region to ∼4.2 in the higher stress region. The reduction of stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained in terms of the dynamic solute-dislocation effect caused by Sn atoms. The constancy of stress exponent without the transition was observed in Zr-Nb-O alloy, supporting that the decrease of the stress exponent with increasing stress in Zr-Nb-Sn-Fe is associated with Sn atoms. The difference of creep life between annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe is not large considering the large difference of strength level between annealed Zr-Nb-O and annealed stress-relieved Zr-Nb-Sn-Fe. The better-than-expected creep life of annealed Zr-Nb-O alloy can be attributable to the combined effects of creep ductility enhancement associated with softening and the decreased contribution of grain boundary diffusion due to the increased grain size.

Effectiveness of interim remedial actions at the Niagara Falls Storage Site

International Nuclear Information System (INIS)

Devgun, J.S.; Beskid, N.J.; Seay, W.M.; McNamee, E.

1990-01-01

There are 190,000 m 3 of contaminated soils, wastes, and residues stored at the Niagara Falls Storage Site (NFSS). The residues have a volume of 18,000 m 3 and contain about 1,930 Ci of 226 Ra, which accounts for most of the radioactivity. Since 1980, actions have been taken to minimize potential radiological risks and prevent radionuclide migration. Interim actions included capping vents, sealing pipes, relocating the perimeter fence (to limit radon risk), transferring and consolidating wastes, upgrading storage buildings, constructing a clay cutoff wall (to limit potential ground-water transport of contaminants), treating and releasing contaminated water, using a synthetic liner, and using an interim clay cap. An interim waste containment facility was completed in 1986. Environmental monitoring showed a decrease in radon concentrations and in external gamma radiation from 1982 to 1986; levels have been stable since 1986. Uranium and radium concentrations in surface water have decreased; very low concentrations have been detected in stream sediments, and concentrations in ground water have remained stable. Recent monitoring showed that NFSS is in compliance with the U.S. Department of Energy's (DOE's) radiation protection standards

Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Directory of Open Access Journals (Sweden)

Rui Sun

2016-06-01

Full Text Available We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100 substrates with a TiN buffer layer. A 50-nm-thick (200-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large IcRN product of 3.8 mV, a sharp quasiparticle current rise with a ΔVg of 0.4 mV, and a small subgap leakage current. The junction quality factor Rsg/RN was about 23 for the junction with a Jc of 47 A/cm2 and was about 6 for the junction with a Jc of 3.0 kA/cm2. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200-orientated TiN buffer layer and had a highly crystalline structure with the (200 orientation.

Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

Energy Technology Data Exchange (ETDEWEB)

Sun, Rui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Makise, Kazumasa; Terai, Hirotaka [Advanced ICT Research Institute, National Institute of Information and Communications Technology (Japan); Zhang, Lu [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Wang, Zhen, E-mail: zwang@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Shanghai Tech University, Shanghai 201210 (China)

2016-06-15

We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100) substrates with a TiN buffer layer. A 50-nm-thick (200)-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large I{sub c}R{sub N} product of 3.8 mV, a sharp quasiparticle current rise with a ΔV{sub g} of 0.4 mV, and a small subgap leakage current. The junction quality factor R{sub sg}/R{sub N} was about 23 for the junction with a J{sub c} of 47 A/cm{sup 2} and was about 6 for the junction with a J{sub c} of 3.0 kA/cm{sup 2}. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200)-orientated TiN buffer layer and had a highly crystalline structure with the (200) orientation.

Cu-Nb3Sn superconducting wires prepared by ''Copper Liquid Phase Sintering method'' using the Nb-H

International Nuclear Information System (INIS)

Resende, A.T. de.

1985-01-01

Cu-30% Nb in weighting were prepared by the method of Copper sintering liquid phase the method was improved by substitution of Nb power by Nb-H powder, obtaining a high density material with good mechanical properties, which was reduced to fine. Wire, Without heat treatment. The Cu-Nb 3 Sn wires were obtained by external diffusion process depositing tin in the Cu-30%Nb wires, and by internal diffusion process using the Sn-8.5% Cu in weighting, which was reduced to rods of 3.5 mm. These Cu-30%Nb rods were enclosed in copper tubes and deformed mechanically by rotary swaging and drawing. During the drawing step some wires were fractured, that were analysed and correlated with the microstructure of the Sn-8.5 Wt% Cu alloy. External and internal diffusion samples; after a fast thermal treatment for Sn diffusion, were submited to the temperature of 700 0 C to provide the reaction between Sn and Nb, leading to the Nb 3 Sn phase. Samples with several reaction times, and its influence on T c and J c critical parameters and normal resistivity were prepared and analysed. (author) [pt

Biological Properties of Ti-Nb-Zr-O Nanostructures Grown on Ti35Nb5Zr Alloy

Directory of Open Access Journals (Sweden)

Zhaohui Li

2012-01-01

Full Text Available Surface modification of low modulus implant alloys with oxide nanostructures is one of the important ways to achieve favorable biological behaviors. In the present work, amorphous Ti-Nb-Zr-O nanostructures were grown on a peak-aged Ti35Nb5Zr alloy through anodization. Biological properties of the Ti-Nb-Zr-O nanostructures were investigated through in vitro bioactivity testings, stem cell interactions, and drug release experiments. The Ti-Nb-Zr-O nanostructures demonstrated a good capability of inducing apatite formation after immersion in simulated body fluids (SBFs. Drug delivery experiment based on gentamicin and the Ti-Nb-Zr-O nanostructures indicated that a high drug loading content could result in a prolonged release process and a higher quantity of drug residues in the oxide nanostructures after drug release. Quick stem cell adhesion and spreading, as well as fast formation of extracellular matrix materials on the surfaces of the Ti-Nb-Zr-O nanostructures, were found. These findings make it possible to further explore the biomedical applications of the Ti-Nb-Zr-O nanostructure modified alloys especially clinical operation of orthopaedics by utilizing the nanostructures-based drug-release system.

Studies of the transition temperature and normal state resistivity of Nb3Ge and Nb films

International Nuclear Information System (INIS)

Lutz, H.; Weismann, H.; Gurvitch, M.; Goland, A.N.; Kammerer, O.F.; Strongin, M.

1976-01-01

Correlations between T/sub c/ and specific features of the normal state resistance vs temperature curves are discussed for both Nb 3 Ge and ion damaged Nb films. Of particular interest is the correlation between T/sub c/ and rho 0 in Nb 3 Ge films

Formation of Nb3Al in powder processed Nb-Al superconductors

International Nuclear Information System (INIS)

Johnson, P.E.

1987-05-01

In high magnetic fields, the critical current density is strongly dependent on the upper critical field, which is determined primarily by the stoichiometry of the Nb 3 Al. The critical temperature (T/sub c/), like the upper critical field, is considered to be a measure of the ''intrinsic'' quality of the superconductor, indicating the stoichiometry, order, and strain. If the A15 phase is stoichiometric and well ordered, a high T/sub c/ (and high H/sub C 2 /) is expected, regardless of the volume fraction of superconductor. On the other hand, if sigma phase is present with the A15, the resultant composition gradient across the sigma-A15 interface(s) requires that some of the A15 be off-stoichiometric, and therefore that the T/sub c/ (and H/sub C 2 /) be low. Thus the extent of the A15 (Nb 3 Al) reaction and the quality of the A15 formed are interdependent. This work focuses on the factors that control the extent of Nb 3 Al formation in Nb/Al powder wires. The morphology and content of the reacted and unreacted wires are studied in optical, SEM, and TEM micrographs. Critical current density data and its dependence on processing are explained in terms of the unreacted microstructure and its effect on the extent of Nb 3 Al formation. As a method of improving the critical current density, a new variation of the conventional powder process for wire manufacturing is developed and tested

The crystal structure of (Nb$_{0.75}$Cu$_{0.25}$)Sn$_{2}$ in the Cu-Nb-Sn system

CERN Document Server

Martin, Stefan; Nolze, Gert; Leineweber, Andreas; Leaux, Floriane; Scheuerlein, Christian

2017-01-01

During the processing of superconducting Nb$_{3}$Sn wire, several intermediate intermetallic phases including a previously encountered Cu-Nb-Sn phase show up. The yet unknown crystal structure of this phase is now identified by a combination of different experimental techniques and database search to be of the hexagonal NiMg2 type with a proposed composition of about (Nb0.75Cu0.25)Sn2. The structure determination started from an evaluation of the lattice parameters from EBSD Kikuchi patterns from quenched material suggesting hexagonal or orthorhombic symmetry. A database search then led to the hexagonal NiMg2 type structure, the presence of which was confirmed by a Rietveld analysis on the basis of high energy synchrotron X-ray powder diffraction data. Assuming a partial substitution of Nb in orthorhombic NbSn2 by Cu, the change of the valence electron concentration provokes a structural transformation from the CuMg2 type for NbSn2 to the NiMg2 type for (Nb0.75Cu0.25)Sn2. In the previous literature the (Nb0.7...

Effect of [Li]/[Nb] ratio on composition and defect structure of Zr:Yb:Tm:LiNbO3 crystals

Science.gov (United States)

Liu, Chunrui; Dai, Li; Wang, Luping; Shao, Yu; Yan, Zhehua; Xu, Yuheng

2018-04-01

Zr:Yb:Tm:LiNbO3 crystals with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38) were grown by the Czochralski technique. Distribution coefficients of Zr4+, Yb3+ and Tm3+ ions were analyzed by the inductively coupled plasma-atomic emission spectrometer (ICP-AES). The influence of [Li]/[Nb] ratio on the composition and defect structure of Zr:Yb:Tm:LiNbO3 crystals was investigated by X-ray diffraction and IR transmission spectrum. The results show that as the [Li]/[Nb] ratio increases in the melt, the distribution coefficients of Yb3+ and Tm3+ ions both increase while that of Zr4+ ion deceases. When the [Li]/[Nb] ratio increases to 1.20 in the melt, Zr:Yb:Tm:LiNbO3 crystal is nearly stoichiometric. In addition, when the [Li]/[Nb] ratio reaches up to 1.38, NbLi4+ are completely replaced and Li+ starts to impel the Zr4+, Yb3+ and Tm3+ into the normal Li sites.

Fabrication-process-induced variations of Nb/Al/AlOx/Nb Josephson junctions in superconductor integrated circuits

International Nuclear Information System (INIS)

Tolpygo, Sergey K; Amparo, Denis

2010-01-01

Currently, superconductor digital integrated circuits fabricated at HYPRES, Inc. can operate at clock frequencies approaching 40 GHz. The circuits present multilayered structures containing tens of thousands of Nb/Al/AlO x /Nb Josephson junctions (JJs) of various sizes interconnected by four Nb wiring layers, resistors, and other circuit elements. In order to be fully operational, the integrated circuits should be fabricated such that the critical currents of the JJs are within the tight design margins and the proper relationships between the critical currents of JJs of different sizes are preserved. We present experimental data and discuss mechanisms of process-induced variations of the critical current and energy gap of Nb/Al/AlO x /Nb JJs in integrated circuits. We demonstrate that the Josephson critical current may depend on the type and area of circuit elements connected to the junction, on the circuit pattern, and on the step in the fabrication process at which the connection is made. In particular, we discuss the influence of (a) the junction base electrode connection to the ground plane, (b) the junction counter electrode connection to the ground plane, and (c) the counter electrode connection to the Ti/Au or Ti/Pd/Au contact pads by Nb wiring. We show that the process-induced changes of the properties of Nb/Al/AlO x /Nb junctions are caused by migration of impurity atoms (hydrogen) between the different layers comprising the integrated circuits.

Nb(C,N) precipitation kinetics in the bainite region of a low-carbon Nb-microalloyed steel

International Nuclear Information System (INIS)

Park, J.S.; Lee, Y.K.

2007-01-01

Nb(C,N) precipitation in the bainite region (580-660 deg. C) of a low-carbon Nb-microalloyed steel was investigated by electrical resistivity and transmission electron microscopy. Nb(C,N) particles started precipitating after 100-200 s at isothermal temperatures after bainite transformation and cementite formation, and precipitation finished in 1000-2000 s. The precipitation-time-temperature diagram of Nb(C,N) in the bainite region of a low-carbon microalloyed steel was a type of C-curve, with a nose temperature of about 615 deg. C

Solid solution cermet: (Ti,Nb)(CN)-Ni cermet.

Science.gov (United States)

Kwon, Hanjung; Jung, Sun-A

2014-11-01

Solid solution powders without W, (Ti,Nb)(CN) powders with a B1 structure (NaCl like), were synthesized by high energy milling and carbothermal reduction in nitrogen. The range of molar ratios of Ti/Nb for forming complete (Ti,Nb)(CN) phase was broader than that of Ti/W for the (Ti,W)(CN) phase because carbide or carbonitride of Nb had a B1 crystal structure identical to Ti(CN) while WC had a hexagonal crystal structure. The results revealed that the hardness of (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,W)(CN)-Ni cermets. The lower density of the (Ti,Nb)(CN) powder contributed to the higher hardness compared to (Ti,W)(CN) because the volumetric ratio of (Ti,Nb)(CN) in the (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,Nb)(CN) in the (Ti,W)(CN)-Ni cermets at the same weight ratio of Ni. Additionally, it was assumed that intrinsic the properties of (Ti,Nb)(CN) could also be the cause for the high hardness of the (Ti,Nb)(CN)-Ni cermets.

The grand leap of the whale up the Niagara Falls: converting philosophical conclusions into policy prescriptions.

Science.gov (United States)

Holm, Søren

2015-04-01

This article analyzes a neat conjuring trick employed in bioethics, that is, the immediate conversion of a philosophical conclusion into a policy prescription, and compares it to the "grand leap of the whale up the Niagara Falls" mentioned by Benjamin Franklin. It is shown that there is no simple and easy way to achieve the conversion, by considering arguments falling under four headings: (1) reasonable disagreement about values and theories, (2) general jurisprudential arguments, (3) the differences between policymaking and philosophy, and (4) the messy world of implementation. The particular issue used to illustrate the difficulties in moving from philosophical conclusion to policy description is infanticide of healthy infants, but the analysis is general, and the conclusion that the immediate move to policy is illegitimate is quite general.

Influence of Li/Nb ratios on defect structure and photorefractive properties of Zn: In: Fe: LiNbO 3 crystals

Science.gov (United States)

Dai, Li; Su, Yan-Qing; Wu, Shi-Ping; Guo, Jing-Jie; Xu, Chao; Xu, Yu-Heng

2011-04-01

A series of Zn: In: Fe: LiNbO3 crystals are grown by the Czochralski technique with various ratios of Li/Nb = 0.94, 1.05, 1.20 and 1.38 in the melt. The Zn, In, Fe, Nb and Li concentrations in the crystals are analyzed by inductively coupled plasma (ICP) spectrometry. The results indicate that with increasing the [Li]/[Nb] ratio in melt, [Li]/[Nb] ratio increases and goes up continuously in the crystal, the segregation coefficients of both Zn and In ions decrease. The absorption spectra measurement and two-wave coupling experiment are employed to study the effect of [Li]/[Nb] ratio on photorefractive properties of Zn: In: Fe: LiNbO3 crystals. It is found that the [Li]/[Nb] ratio increases, the write time is shortened and the photorefractive sensitivity is improved.

Local tunneling spectroscopy of a Nb/InAs/Nb superconducting proximity system with a scanning tunneling microscope

International Nuclear Information System (INIS)

Inoue, K.; Takayanagi, H.

1991-01-01

Local tunneling spectroscopy for a Nb/In/As/Nb superconducting proximity system was demonstrated with a low-temperature scanning tunneling microscope. It is found that the local electron density of states in the InAs region is spatially modulated by the neighboring superconductor Nb

A new silver metaniobate semiconductor of Ag0.5La0.5Nb2O6 with defect-perovskite structure

Science.gov (United States)

Mi, Longqing; Feng, Yongyi; Cao, Lei; Xue, Mingqiang; Huang, Yanlin; Qin, Lin; Seo, Hyo Jin

2018-03-01

Silver-containing lanthanum metaniobate Ag0.5La0.5Nb2O6 nanoparticles were synthesized by sol-gel polymerized complex method. A typical defect-perovskite structure was confirmed by XRD Rietveld refinements. The surface characteristics of the sample were tested by SEM, TEM and EDS measurements. SEM and TEM show that the sample presents ball-like particles with the diameters of 100 nm to 400 nm. The sample shows both self-activated luminescence and photocatalytic activities. Ag0.5La0.5Nb2O6 has a direct transition with band energy of 2.85 eV. The Ag4d-O2p hybridization in the valence band contributes to the narrowed band gap. The luminescence properties of Ag0.5La0.5Nb2O6 have been investigated for the first time. The luminescence is characterized by two emission centers with maximum wavelength near 460 and 530 nm. The emission and excitation spectra, decay curves and the thermal quenching mechanism were discussed. Ag0.5La0.5Nb2O6 shows the efficient photocatalytic activities and the photodegradation rate for methylene blue dye (MB) can reach about 95% under visible light (> 420 nm) irradiation in 5 h. The trapped experiments for the active species were tested and discussed, which verified that rad OH radicals could be the major active species in photocatalysis.

X-ray investigation of Nb/O interfaces

International Nuclear Information System (INIS)

Delheusy, Melissa

2008-01-01

X-ray free electron lasers and the future International Linear Collider project are based on the performance of niobium superconducting rf cavities for efficient particle acceleration. A remarkable increase of the rf accelerating field is usually achieved by low-temperature annealing of the cavities (T 2 O 5 , NbO 2 and NbO, from the surface to the interface. It reduces progressively upon heating from Nb 2 O 5 to NbO 2 at low temperatures, and to NbO at 300 C. The Nb(110)/NbO(111) interface presents a Nishiyama-Wassermann epitaxial orientation relationship. The depth-distribution of interstitial oxygen has been established indicating that most of the oxygen is located in the direct vicinity of the oxide/niobium interface. No evidence of oxygen depletion below the oxide layer has been observed for the low temperature thermal treatments and surface preparations investigated in this study. (orig.)

Multifilamentar superconductor wires of Cu-Nb-Al and Cu-Nb3Sn obtained by a new method

International Nuclear Information System (INIS)

Lima, O.F. de

1985-01-01

A new method to prepare multifilamentar wires of Cu-Nb 3 Sn which is based on power metallurgy is developed. Wires of Cu+xw%Nb++2wt%Al (x =10,30) were tinned and heat treated for Sn diffusion and reaction (T = 700 0 C), leading to the Nb 3 Sn A 15 phase. Final wires showed microfilament density around 8 x 10 4 mm -2 . The superconducting properties (T sup(c), J sup(c) x H), mechanical properties (tau x epsilon) and eletrical resistivity for Cu-Nb-Al wires were as normally expected. The Cu-Nb 3 Sn wires showed high T sub(c) approx. 17.9 K, very near that for the pure A 15 phase. J sub(c) x H curves were approx. 4 times lower than typical published results for wires prepared by other methods. The experimental evidence shows that J sub(c) increases when decreases the initial Nb particle size. (Author) [pt

Phase transition and piezoelectric properties of K0.48Na0.52NbO3-LiTa0.5Nb0.5O3-NaNbO3 lead-free ceramics

International Nuclear Information System (INIS)

Gao Feng; Liu Liangliang; Xu Bei; Cao Xiao; Deng Zhenqi; Tian Changsheng

2011-01-01

Highlights: → The evolution of the crystal structure for the new phase K 3 Li 2 Nb 5 O 15 was described. → The dielectric relaxor behavior would be strengthened by increasing plate-like NN. → k p and d 33 decrease with increasing amount of plate-like NN. → 0.01-0.03 mol of plate-like NN is a proper content for texturing ceramics by RTGG. - Abstract: Plate-like NaNbO 3 (NN) particles were used as the raw material to fabricate (1 - x)[0.93 K 0.48 Na 0.52 Nb O 3 -0.07Li(Ta 0.5 Nb 0.5 )O 3 ]-xNaNbO 3 lead-free piezoelectric ceramics using a conventional ceramic process. The effects of NN on the crystal structure and piezoelectric properties of the ceramics were investigated. The results of X-ray diffraction suggest that the perovskite phase coexists with the K 3 Li 2 Nb 5 O 15 phase, and the tilting of the oxygen octahedron is probably responsible for the evolution of the tungsten-bronze-typed K 3 Li 2 Nb 5 O 15 phase. The Curie temperature (T C ) is shifted to lower temperature with increasing NN content. (1 - x)[0.93 K 0.48 Na 0.52 NbO 3 -0.07Li(Ta 0.5 Nb 0.5 )O 3 ]-xNaNbO 3 ceramics show obvious dielectric relaxor characteristics for x > 0.03, and the relaxor behavior of ceramics is strengthened by increasing NN content. Both the electromechanical coupling factor (k p ) and the piezoelectric constant (d 33 ) decrease with increasing amounts of NN. 0.01-0.03 mol of plate-like NaNbO 3 in 0.93 K 0.48 Na 0.52 NbO 3 -0.07Li(Ta 0.5 Nb 0.5 )O 3 gives the optimum content for preparing textured ceramics by the RTGG method.

Diffusion behavior in the films of Nb-Ti systems

International Nuclear Information System (INIS)

Yoshitake, Michiko; Yoshihara, Kazuhiro

1990-01-01

The diffusion behavior of substrate element into a deposited film was investigated. The observed systems were a Nb film/Ti substrate and a Ti film/Nb substrate. When the Nb film/Ti substrate was heated in a vacuum, Ti diffused very rapidly in the Nb film. The pre-exponential factor of the diffusion constant of Ti in the Nb film was 5.6x10 -2 m 2 s -1 , and the activation energy was 220 kJmol -1 . The observed activation energy is about 60% of that of Ti in the bulk Nb. On the other hand, when the Ti film/Nb substrate was heated in a vacuum, Nb did not diffuse so rapidly. Titanium diffused through the Nb film rapidly and was concentrated on the surface of the Nb film. The chemical state of the concentrated Ti was metallic, and neither titanium oxides nor titanium carbide was observed. Therefore, the driving force of the rapid diffusion of Ti in the Nb film is considered as the reduction of the surface energy of Nb film. The difference in the diffusion behavior between Ti through the Nb film and Nb through the Ti film is explained supposing that the segregation of Ti reduces the surface energy of the Nb film but the segregation of Nb does not reduce the surface energy of the Ti film. After heating of the Nb film/Ti substrate for a long time, a new phase was formed at the interface between the Nb film and the Ti substrate. The chemical composition of the new phase is about 50% of Ti and 50% of Nb. This phase has not been reported in the phase diagram of the bulk Ti-Nb system. The surface area of the Nb film is considered to be quite large, so the contribution of surface energy to the thermodynamic state of the Nb film cannot be neglected. Therefore, the chemical potential of the film is different from that of the bulk. Then, the new phase, which does not exist in the phase diagram of the bulk system, is formed by an interaction of the films. (author)

XPS study of Li/Nb ratio in LiNbO{sub 3} crystals. Effect of polarity and mechanical processing on LiNbO{sub 3} surface chemical composition

Energy Technology Data Exchange (ETDEWEB)

Skryleva, E.A., E-mail: easkryleva@gmail.com; Kubasov, I.V., E-mail: kubasov.ilya@gmail.com; Kiryukhantsev-Korneev, Ph.V., E-mail: kiruhancev-korneev@yandex.ru; Senatulin, B.R., E-mail: borisrs@yandex.ru; Zhukov, R.N., E-mail: rom_zhuk@mail.ru; Zakutailov, K.V., E-mail: zakkonst@gmail.com; Malinkovich, M.D., E-mail: malinkovich@yandex.ru; Parkhomenko, Yu.N., E-mail: parkh@rambler.ru

2016-12-15

Highlights: • XPS Li/Nb ratio measurement uncertainty in LNbO3 specimens was obtained. • The effect of polarization on surface chemistry was observed only on cleaves. • Li/Nb ratio on positive cleave surface is higher than on negative one. • The positive cleave surface adsorbs fluorine more efficiently than negative one. • Mechanical processing of crystals reduces surface Li/Nb. - Abstract: Different sections of congruent lithium niobate (CLN) crystals have been studied using X-ray photoelectron spectroscopy (XPS). We have developed a method for measuring the lithium-to-niobium atomic ratio Li/Nb from the ratio of the Li1s and Nb4s spectral integral intensities with an overall error of within 8 %. Polarity and mechanical processing affect the Li/Nb ratio on CLN crystal surfaces. The Li/Nb ratio is within the tolerance (0.946 ± 0.074) on the negative cleave surface Z, and there is excess lithium (Li/Nb = 1.25 ± 0.10) on the positive surface. The positive surfaces of the 128° Y cut plates after long exposure to air exhibit LiOH formation indications (obvious lithium excess, higher Li1s spectral binding energy and a wide additional peak in the O1s spectrum produced by nonstructural oxygen). XPS and glow discharge optical electron spectroscopy showed that mechanical processing of differently oriented crystals (X, Z and 128° Y) and different polarities dramatically reduces the Li/Nb ratio. In situ fluorine adsorption experiments revealed the following regularities: fluorine adsorption only occurred on crystal cleaves and was not observed for mechanically processed specimens. Positive cleave surfaces have substantially higher fluorine adsorption capacity compared to negative ones.

Low temperature properties of spin filter NbN/GdN/NbN Josephson junctions

Energy Technology Data Exchange (ETDEWEB)

Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Caruso, R. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Pal, A. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, New York 11961 (United States); Pepe, G.P. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy); Blamire, M.G. [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Tafuri, F. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, via Roma 29, 81031 Aversa (CE) (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, via Cinthia, 80126 Napoli (Italy)

2017-02-15

Highlights: • We study the phase dynamics of ferromagnetic NbN/GdN/NbN Josephson junctions. • The ferromagnetic insulator GdN barrier generates spin-filtering properties. • Spin filter junctions fall in the underdamped regime. • MQT occurs with the same phenomenology as in conventional Josephson junctions. • Dissipation is studied in a wide range of critical current density values. - Abstract: A ferromagnetic Josephson junction (JJ) represents a special class of hybrid system where different ordered phases meet and generate novel physics. In this work we report on the transport measurements of underdamped ferromagnetic NbN/GdN/NbN JJs at low temperatures. In these junctions the ferromagnetic insulator gadolinium nitride barrier generates spin-filtering properties and a dominant second harmonic component in the current-phase relation. These features make spin filter junctions quite interesting also in terms of fundamental studies on phase dynamics and dissipation. We discuss the fingerprints of spin filter JJs, through complementary transport measurements, and their implications on the phase dynamics, through standard measurements of switching current distributions. NbN/GdN/NbN JJs, where spin filter properties can be controllably tuned along with the critical current density (J{sub c}), turn to be a very relevant term of reference to understand phase dynamics and dissipation in an enlarged class of JJs, not necessarily falling in the standard tunnel limit characterized by low J{sub c} values.

Study of superconducting Nb{sub 3}Sn coils; Etude de bobinages supraconducteurs en Nb{sub 3}Sn

Energy Technology Data Exchange (ETDEWEB)

Vivet, B

1963-07-01

Composite superconducting Nb{sub 3}Sn wires with a diameter of 0.5 mm and a length of about 100 m were made, and Hc-Ic diagrams were plotted up to fields of 80 kgauss for short lengths. Two solenoids producing fields of about 20 kgauss were studied. Nb{sub 3}Sn solenoids, as opposed to those of Nb-Zr or Nb-Ti, appear to have a predictable behavior. Solenoids with less insulation produced stronger fields than heavily insulated solenoids. (author) [French] Une etude des fils composites supraconducteurs de Nb{sub 3}Sn a ete entreprise au C.E.N. Saclay, en collaboration avec la Societe S.O.D.E.R.X. Des fils de 0,5 mm de diametre et d'une centaine de metres de longueur ont ete produits de facon experimentale. Des diagrammes Hc-Ic ont pu etre traces, jusqu'en des champs de 80 kG, sur des echantillons de petite longueur. Deux solenoides ont ete etudies produisant les champs de l'ordre de 20 kg. Il semble que, contrairement aux alliages Nb-Zr ou Nb-Ti, les solenoides en Nb{sub 3}Sn aient un comportement previsible d'apres les tests sur des echantillons courts. On montrera d'autre part qu'un bobinage a faible isolement peut produire un champ notablement plus eleve qu'un bobinage isole. Une production plus extensive permettra, dans les semaines a venir, la fabrication de solenoides de plus grosse dimension et produisant des champs plus eleves. (auteur)

Microstructures and room temperature fracture toughness of Nb/Nb5Si3 composites alloyed with W, Mo and W–Mo fabricated by spark plasma sintering

International Nuclear Information System (INIS)

Xiong, Bowen; Cai, Changchun; Wang, Zhenjun

2014-01-01

Highlights: • Microstructure of Nb/Nb 5 Si 3 composite alloyed with W and Mo is change obviously. • W and Mo elements can solid solution in Nb and Nb 5 Si 3 phase respectively. • Alloyed with W and Mo together, the solid solubility of Nb 5 Si 3 phases is undetected. • The Nb/Nb 5 Si 3 composite alloyed with W and Mo together has high fracture toughness. - Abstract: Microstructures and room temperature fracture toughness of Nb/Nb 5 Si 3 composites alloyed with W, Mo and W–Mo fabricated by spark plasma sintering were investigated. The microstructures were examined using scanning electron microscope (SEM). X-ray diffraction (XRD) was performed on the bulk specimens for identification of phases. The chemical species were analyzed using electron-probe micro-analysis (EPMA). Results indicated that the microstructures of Nb/Nb 5 Si 3 composites alloyed with W or Mo is unaltered, including primary Nb and eutectic mixtures of Nb and Nb 5 Si 3 , and the coarse and fine eutectic mixtures. The W and Mo elements solid solution in Nb and Nb 5 Si 3 phase are detected. But that alloyed with W and Mo together, The microstructures are change obviously, including Nb phase, the solid solubility phases of W and Mo atoms in Nb, and the solid solubility phases of Nb atoms in W are also found, but the solid solubility phenomenon of Nb 5 Si 3 phases is not detected. The microhardness of Nb and Nb 5 Si 3 phases increases obviously because of solid solution strengthening. The Nb/Nb 5 Si 3 composite alloyed with W and Mo together hashing high fracture toughness is attributable to the big eutectic Nb and interface of eutectic phases, which can bear large deformation to absorb the crack energy and form the decohesion between eutectic phases

Comparative study of heat transfer from Nb-Ti and Nb_{3}Sn coils to He II

Directory of Open Access Journals (Sweden)

Marco La China

2008-08-01

Full Text Available In superconducting magnets, the energy deposited or generated in the coil must be evacuated to prevent temperature rise and consequent transition of the superconductor to the resistive state. The main barrier to heat extraction is represented by the electric insulation wrapped around superconducting cables. In the LHC, insulation improvement is a key point in the development of interaction region magnets and injector chain fast-pulsed magnets for luminosity upgrade; the high heat load of these magnets, in fact, is not compatible with the use of current insulation schemes. We review the standard insulation schemes for Nb-Ti and Nb_{3}Sn technology from the thermal point of view. We implement, in an analytical model, the strongly nonlinear thermal resistances of the different coil components including the permeability to superfluid helium of Nb-Ti insulations, measured during the LHC main dipole development. We use such a model to compare Nb-Ti and Nb_{3}Sn technologies by taking into account their specific operating margin in different working conditions. Finally, we propose an insulation scheme to enhance the heat transfer capability of Nb-Ti coils.

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)

Niagara Falls Storage Site environmental surveillance report for calendar year 1993

International Nuclear Information System (INIS)

1994-06-01

This report summarizes the results of environmental surveillance activities conducted at the Niagara Falls Storage Site (NFSS) during calendar year 1993. It includes an overview of site operations, the basis for radiological and nonradiological monitoring, a summary of the results, and the estimated dose to the offsite population. Environmental surveillance activities were conducted in accordance with the site environmental monitoring plan, which describes the rationale and design criteria for the surveillance program, the frequency of sampling and analysis, specific sampling and analysis procedures, and quality assurance requirements. NFSS is in compliance with National Emission Standards for Hazardous Air Pollutants (NESHAPs) Subpart H of the Clean Air Act as well as the requirements of the National Pollutant Discharge Elimination System (NPDES) under the Clean Water Act. Located in northwestern New York, the site covers 191 acres. From 1944 to the present, the primary use of NFSS has been storage of radioactive residues that were by-products of uranium production. Most onsite areas of residual radioactivity above regulatory guidelines were remediated during the early 1980s. Additional isolated areas of onsite contamination were remediated in 1989, and the materials were consolidated into the waste containment structure in 1991. Remediation of the site has now been completed

Nuclear quadrupole resonance of 93Nb in ternary phases on the bases of Nb3Al compound

International Nuclear Information System (INIS)

Matukhin, V.L.; Safin, I.A.; Shamraj, V.F.

1980-01-01

Results of investigations into concentration dependences of 93 Nb spectrum parameters of nuclear quadrupole resonance (n.g.r.) (frequencies of n.g.r. transitions, rates of nuclear spin - lattice relaxation R) in triple phases which appear as a result of Nb 3 Al compound alloying with Zr, Ga, Sn, are presented. Nb 3 Al alloying with gallium does not considerably change the R value (R-rate of nuclear spin - lattice relaxation, while alloying with zirconium decreases it to a noticeable extent. It is 30% less in the triple phase than in the Nb 3 Al compound. R alterations, frequency reduction in the 93 Nb n.q.r. spectrum and the decrease of constant of the quadrupole bond point to the alteration of the spatial electron distribution around a niobium atom during alloying [ru

Comparative Study of Heat Transfer from Nb-Ti and Nb$_3$Sn coils to He II

CERN Document Server

La China, M

2008-01-01

In superconducting magnets, the energy deposited or generated in the coil must be evacuated to prevent temperature rise and consequent transition of the superconductor to the resistive state. The main barrier to heat extraction is represented by the electric insulation wrapped around superconducting cables. In the LHC, insulation improvement is a key point in the development of interaction region magnets and injector chain fast-pulsed magnets for luminosity upgrade; the high heat load of these magnets, in fact, is not compatible with the use of current insulation schemes. We review the standard insulation schemes for Nb-Ti and Nb$_{3}$Sn technology from the thermal point of view. We implement, in an analytical model, the strongly nonlinear thermal resistances of the different coil components including the permeability to superfluid helium of Nb-Ti insulations, measured during the LHC main dipole development. We use such a model to compare Nb-Ti and Nb$_{3}$Sn technologies by taking into account their specific...

X-ray investigation of Nb/O interfaces

International Nuclear Information System (INIS)

Delheusy, M.

2008-01-01

X-ray free electron lasers and the future International Linear Collider project are based on the performance of niobium superconducting RF cavities for efficient particle acceleration. A remarkable increase of the RF accelerating field is usually achieved by low-temperature annealing of the cavities (T≤150 C, several hours). The microscopic origin of this effect has remained unclear; however, it has been argued that a redistribution of subsurface interstitial oxygen into niobium is involved. In this study, the near surface structure of oxidized niobium single crystals and its evolution upon vacuum annealing has been studied by means of non-destructive in-situ surface sensitive x-ray techniques: x-ray reflectivity (XRR), grazing incidence x-ray diffraction (GIXD), diffuse scattering (GIDXS), crystal truncation rods measurements (CTRs), and high-resolution core-level spectroscopy (HRCLS). A first insight into the interplay between the oxide formation/dissolution and the occurrence of 181 subsurface interstitial oxygen has been given. The natural oxide on Nb(110) and Nb(100) surfaces is constituted of Nb 2 O 5 , NbO 2 and NbO, from the surface to the interface. It reduces progressively upon heating from Nb 2 O 5 to NbO 2 at low temperatures, and to NbO at 300 C. The Nb(110)/NbO(111) interface presents a Nishiyma-Wassermann epitaxial orientation relationship. The depth-distribution of interstitial oxygen has been established indicating that most of the oxygen is located in the direct vicinity of the oxide/niobium interface. No evidence of oxygen depletion below the oxide layer has been observed for the low temperature thermal treatments and surface preparations investigated in this study. (author) [fr

X-ray investigation of Nb/O interfaces

Energy Technology Data Exchange (ETDEWEB)

Delheusy, Melissa

2008-07-07

X-ray free electron lasers and the future International Linear Collider project are based on the performance of niobium superconducting rf cavities for efficient particle acceleration. A remarkable increase of the rf accelerating field is usually achieved by low-temperature annealing of the cavities (T<150 C, several hours). The microscopic origin of this effect has remained unclear; however, it has been argued that a redistribution of subsurface interstitial oxygen into niobium is involved. In this study, the near surface structure of oxidized niobium single crystals and its evolution upon vacuum annealing has been studied by means of non-destructive in-situ surface sensitive X-ray techniques: X-ray reflectivity (XRR), grazing incidence X-ray diffraction (GIXD), diffuse scattering (GIDXS), crystal truncation rods measurements (CTRs), and high-resolution core-level spectroscopy (HRCLS). A first insight into the interplay between the oxide formation/dissolution and the occurrence of subsurface interstitial oxygen has been given. The natural oxide on Nb(110) and Nb(100) surfaces is constituted of Nb{sub 2}O{sub 5}, NbO{sub 2} and NbO, from the surface to the interface. It reduces progressively upon heating from Nb{sub 2}O{sub 5} to NbO{sub 2} at low temperatures, and to NbO at 300 C. The Nb(110)/NbO(111) interface presents a Nishiyama-Wassermann epitaxial orientation relationship. The depth-distribution of interstitial oxygen has been established indicating that most of the oxygen is located in the direct vicinity of the oxide/niobium interface. No evidence of oxygen depletion below the oxide layer has been observed for the low temperature thermal treatments and surface preparations investigated in this study. (orig.)

Prehistory effect on dielectric properties of NaNbO3-Gd1/3NbO3

International Nuclear Information System (INIS)

Burkhanov, A.I.; Bondarenko, P.V.; Shil'nikov, A.V.; Raevskaya, S.I.; Raevskij, I.P.

2006-01-01

One studied the low- and the infralow-frequency dielectric response of 0.9NaNbO 3 -0.1Gd 1/3 NbO 3 (NNG10) composition ceramics and single crystal at the material different prehistory. One revealed the differences in the nature of dielectric aging in NaNbO 3 antiferroelectric base material with a diffused phase transition in contrast to manifestation of similar phenomena in ferroelectrics-relaxors [ru

Reactive synthesis of NbAl3 matrix composites

International Nuclear Information System (INIS)

Lu, L.; Kim, Y.S.; Gokhale, A.B.; Abbaschian, R.

1990-01-01

NbAl 3 matrix composites were synthesized in-situ via reactive hot compaction (RHC) of elemental powders. It was found that the simultaneous application of pressure during synthesis was effective in attaining a near-theoretical density matrix at relatively low temperatures and pressures. Using this technique, two types of composites were produced: matrices containing a uniform dispersion of second phase particles (either Nb 3 Al or Nb 2 Al with an Nb core or Nb 2 Al) and matrices reinforced with coated or uncoated ductile Nb filaments. It was found that a limited amount of toughening is obtained using the first approach, while composites containing coated Nb filaments exhibited a significant increase in the ambient temperature fracture toughness. In this paper, various aspects of RHC processing of NbAl 3 matrix composites, the effect of initial stoichiometry and powder size on the microstructure, as well as the mechanical behavior of the composites are discussed

Development of High Resolution Resonance Ionization Mass Spectrometry for Neutron Dosimetry Technique with93Nb(n,n'93mNb Reaction

Directory of Open Access Journals (Sweden)

Tomita Hideki

2016-01-01

Full Text Available We have proposed an advanced technique to measure the 93mNb yield precisely by Resonance Ionization Mass Spectrometry, instead of conventional characteristic X-ray spectroscopy. 93mNb-selective resonance ionization is achievable by distinguishing the hyperfine splitting of the atomic energy levels between 93Nb and 93mNb at high resolution. In advance of 93mNb detection, we could successfully demonstrate high resolution resonant ionization spectroscopy of stable 93Nb using an all solid-state, narrow-band and tunable Ti:Sapphire laser system operated at 1 kHz repetition rate.

Fabrication of Nb3Al superconducting wires by utilizing the mechanically alloyed Nb(Al)ss supersaturated solid-solution with low-temperature annealing

International Nuclear Information System (INIS)

Pan, X.F.; Yan, G.; Qi, M.; Cui, L.J.; Chen, Y.L.; Zhao, Y.; Li, C.S.; Liu, X.H.; Feng, Y.; Zhang, P.X.; Liu, H.J.

2014-01-01

Highlights: • This paper reported superconducting properties of the powder-in-tube Nb 3 Al wires. • The Nb 3 Al wires were made by using Nb(Al) ss supersaturated solid solution powders. • The Cu-matrix Nb 3 Al superconducting wires have been successfully fabricated. • The transport J c of Nb 3 Al wires at 4.2 K, 10 T is up to 12,700 A/cm 2 . - Abstract: High-performance Nb 3 Al superconducting wire is a promising candidate to the application of high-field magnets. However, due to the production problem of km-grade wires that are free from low magnetic field instability, the Nb 3 Al wires made by rapid heating, quenching and transformation (RHQT) are still not available to the large-scale engineering application. In this paper, we reported the properties of the in situ powder-in-tube (PIT) Nb 3 Al superconducting wires, which were made by using the mechanically alloyed Nb(Al) ss supersaturated solid solution, as well as the low temperature heat-treatment at 800 °C for 10 h. The results show that Nb 3 Al superconductors in this method possess very fine grains and well superconducting properties, though a little of Nb 2 Al and Nb impurities still keep being existence at present work. At the Nb 3 Al with a nominal 26 at.% Al content, the onset T c reaches 15.8 K. Furthermore, a series of Nb 3 Al wires and tapes with various sizes have been fabricated; for the 1.0 mm-diameter wire, the J c at 4.2 K, 10 T and 14 T have achieved 12,700 and 6900 A/cm 2 , respectively. This work suggests it is possible to develop high-performance Cu-matrix Nb 3 Al superconducting wires by directly using the Nb(Al) ss supersaturated solid-solution without the complex RHQT heat-treatment process

Self-selection bipolar resistive switching phenomena observed in NbON/NbN bilayer for cross-bar array memory applications

International Nuclear Information System (INIS)

Kim, Hee-Dong; Yun, Min Ju; Kim, Tae Geun

2014-01-01

In this letter, to integrate bipolar resistive switching cells into cross bar array (CBA) structure, we study one-selector (1S) and one-resistor (1R) behavior of a niobium oxynitride (NbON) and niobium nitride (NbN) bilayer for the applications of resistive random access memory (RRAM). In this structure, a NbN layer exhibits bipolar switching characteristics while a NbON layer acts as the selector. The NbN-based 1S1R devices within a single RRAM memory cell can be directly integrated into a CBA structure without the need of extra diodes; this can significantly reduce the fabrication complexity

Investigation of short and ballistic coupling in vertical NbSe2 - graphene - NbSe2 Josephson junctions

Science.gov (United States)

Kim, Minsoo; Park, Geon-Hyoung; Yi, Jongyoon; Lee, Jae Hyeong; Park, Jinho; Lee, Hu-Jong

2H-NbSe2 is a layered two-dimensional superconducting material, which can be constructed into a van der Waals heterostructure with versatile functionality. Here we fabricated a vertically stacked NbSe2 - graphene - NbSe2 heterostructure by the dry transfer technique, where defect-free contact via van der Waals force provides the high interfacial transparency. Insertion of an atomically thin graphene layer between two NbSe2 flakes ensures the formation of highly coherent proximity Josephson coupling. Observed temperature dependence of the junction critical current (Ic) and large value of IcRn product (as large as 2.3ΔNbSe 2) reveal the short and ballistic Josephson coupling characteristics. Large junction critical current density of 104 A/cm2, multiple Andreev reflection in the subgap structure of the differential conductance, and magnetic field modulation of Ic also suggest the strong Josephson coupling via the graphene layer.

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.

Fatigue and strain effects in NbTi, Nb3Sn, and V2(Hf, Zr) multifilamentary superconductors

International Nuclear Information System (INIS)

Kuroda, T.; Wada, H.; Tachikawa, K.

1988-01-01

The effects of cyclic strain on critical current were studied in NbTi, bronze processed Nb 3 Sn, and composite diffusion processed V 2 (Hf,Zr) multifilamentary wires. No appreciable changes in critical current were found in NbTi wires until just prior to fatigue-induced fracture. Critical current degradation was also not observed in Nb 3 Sn or V 2 (Hf,Zr) as long as the wires were strained below the reversible limit strain. For strains beyond this limit strain the critical current was first degraded by an increasing number of cycles and then remained constant after a certain cycle number was passed

Emprego da poda verde para a obtenção de duas safras por ciclo vegetativo em 'Niagara Branca' Green pruning to obtain two harvests by vegetative cicle on Niagara grapevine

Directory of Open Access Journals (Sweden)

Paulo Vitor Dutra de Souza

2007-01-01

Full Text Available Avaliou-se o efeito de épocas de poda verde em dois anos consecutivos visando obter a segunda safra de uva em um mesmo ciclo vegetativo na cv. Niágara Branca (Vitis labrusca L., cultivada no sistema em espaldeira. O experimento foi realizado na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul (RS, nas safras de 2003/2004 e 2004/2005. Os tratamentos constaram de três épocas de poda verde, realizadas imediatamente após a quarta folha acima do último cacho, e dois anos consecutivos de avaliação. Todas as plantas foram submetidas à superação de dormência mediante aplicação de cianamida hidrogenada a 2%. Analisou-se a duração dos estádios fenológicos, o período de maturação, a produção por planta, a massa fresca do cacho, o teor de sólidos solúveis totais e a acidez total titulável. Observou-se que a época de realização da poda verde não afetou a quantidade, nem a qualidade da uva produzida na primeira colheita, apenas atrasando-a em uma semana. A poda verde realizada no início de novembro possibilitou a segunda colheita de uva, realizada entre março e abril, sendo uma alternativa de ampliação do período de oferta do produto no mercado.The aim of this study was to evaluate the effects of green prunings on two consecutive years to obtain a second harvest of 'Niagara Branca' (Vitis labrusca grapevine in the same season. The experiment was carried out at Estação Experimental Agronômica of Universidade Federal do Rio Grande do Sul, located at Eldorado do Sul, State of Rio Grande do Sul, Brazil in 2003/2004 and 2004/2005 growth seasons. The grapevines were conducted by cordon training. The treatments involved three dates of green pruning, performed at fourth leaf situated above the last grape, and two seasons. All the plants were sprayed with hidrogenate cianamide (2% to overcome dormency. Fenology, plant production, weight of grapes, °Brix and titratable acid were evaluated. The green pruning time

Study of superconducting Nb3Sn coils

International Nuclear Information System (INIS)

Vivet, B.

1963-01-01

Composite superconducting Nb 3 Sn wires with a diameter of 0.5 mm and a length of about 100 m were made, and Hc-Ic diagrams were plotted up to fields of 80 kgauss for short lengths. Two solenoids producing fields of about 20 kgauss were studied. Nb 3 Sn solenoids, as opposed to those of Nb-Zr or Nb-Ti, appear to have a predictable behavior. Solenoids with less insulation produced stronger fields than heavily insulated solenoids. (author) [fr

Fe3Nb3N precipitates of the Fe3W3C type in Nb stabilized ferritic stainless steel

International Nuclear Information System (INIS)

Malfliet, A.; Van den Broek, W.; Chassagne, F.; Mithieux, J.-D.; Blanpain, B.; Wollants, P.

2011-01-01

Highlights: → The precipitation in Nb stabilized ferritic stainless steel at 950 deg. C is investigated. → We characterized the Fe 3 Nb 3 X precipitates with SAED, EELS, WDS and AES. → We found that Fe 3 Nb 3 X precipitates are stabilized by N and not by C or O. → This insight is new and important for future development of this type of steel grade. - Abstract: A Nb stabilized ferritic stainless steel with 0.45 wt.%Nb, 82 ppm C and 170 ppm N is investigated to reveal the nature of the precipitates present at 950 deg. C. In particular, Fe 3 Nb 3 X precipitates of the Fe 3 W 3 C type are analyzed with WDS and EELS to determine the light elements X stabilizing this phase in the steel. According to WDS on large precipitates after 500 h at 950 deg. C, the Fe 3 Nb 3 X phase contains 10.4 at.% N, 1.2 at.% O and 1.0 at.% C. Auger Electron Spectroscopy on the same precipitates confirms the presence of N. In addition, it is revealed that the C and O peaks observed with WDS result from surface contamination as they disappear after Ar sputtering. The presence of a N peak in the EELS spectra of small Fe 3 Nb 3 X precipitates which have formed after 6 min at 950 deg. C indicate that N stabilizes this phase already from the initial precipitation stage. With this analysis it is demonstrated that N is an effective stabilizer of Fe 3 Nb 3 X precipitates in ferritic stainless steels. The formation of this phase should therefore be considered when predicting the precipitation behavior of Nb in industrial Nb stabilized ferritic stainless steels containing residual N.

Zr-Sn-Nb alloys. Preliminary studies

International Nuclear Information System (INIS)

Danon, C.A.; Arias, D.E.

1993-01-01

Studies of the Zr-Sn-Nb diagram have been started, focussing on the Zr-rich corner, near the composition of Zirlo commercial alloy, Zr-1Sn-1Nb, and with Fe and O contents usual in nuclear grade materials. Three alloys were melted, namely Zr-4Sn-2.4Nb (A), Zr-1Sn-3Nb (B) and Zr-2.1Sn-1Nb (C). α/β transformation temperatures were measured through the variation of electrical resistivity(p) vs temperature (T). Values of 560 deg C, 670 deg C and 750 deg C were measured for the α→α+β reaction and 980 deg C, 910 deg C and 1000 deg C for the α+β→β reaction, for the A, B and C alloys, respectively in that order. Some samples were submitted to heat treatments (62 and 216 hours at 825 deg C, 120 hours at 875 deg C). Optical and scanning electronic microscopy of those samples confirmed our resistivity results. (Author)

Cs0.49NbPS6

Directory of Open Access Journals (Sweden)

Hoseop Yun

2011-01-01

Full Text Available The quaternary thiophosphate, Cs0.49NbPS6, caesium hexathioniobiophosphate(V, has been synthesized by the reactive halide flux method. The title compound is isotypic with Rb0.46TaPS6 and is made up of a bicapped trigonal–biprismatic [Nb2S12] unit and a tetrahedral [PS4] group. The [Nb2S12] units linked by the [PS4] tetrahedra form infinite chains, yielding a three-dimensional network with rather large van der Waals gaps along the c axis in which the disordered Cs+ ions reside. The electrons released by the Cs atoms are transferred to the pairwise niobium metal site and there are substantial intermetallic Nb—Nb bonding interactions. This leads to a significant decrease of the intermetallic distance in the title compound compared to that in TaPS6. The classical charge balance of the title compound may be represented as [Cs+]0.49[Nb4.51+][P5+][S2−]4[S22−].

Improvements in the critical current densities of Nb3Sn by solid solution additions of Sn in Nb

International Nuclear Information System (INIS)

Luhman, T.; Suenaga, M.

1975-01-01

The effectiveness of solid solution additions of Sn to Nb in improving the superconducting properties of diffusion processed Nb 3 Sn conductors was examined. It was found that an increase in the superconducting critical current density, Jc, as function of layer thickness (d) may be obtained for thick Nb 3 Sn layers by solid solution additions of Sn in Nb. A large increase in J/sub c/ (d) is also achieved by increasing the Sn content in the bronze matrix material. In addition to uses of this material in magnet fabrications a potential application of these improved J/sub c/(d) values may lie in the use of Nb 3 Sn in power transmission lines. Here, a high superconducting critical current density is necessary throughout the material to carry the increased current during fault conditions. The magnetic field dependence of J/sub c/ is a function of alloy content but the alloying changes studied here do not increase the high field critical current capability of Nb 3 Sn. (auth)

Li diffusion in NbSe/sub 2/ and Ag/sub 0.25/NbSe/sub 2/ single crystals

International Nuclear Information System (INIS)

Folinsbee, J.T.; Simpson, A.M.; Jericho, M.H.

1986-01-01

Measurements are reported of the diffusion of Lithium into NbSe/sub 2/ and into NbSe/sub 2/ preintercalated with silver. Diffusion parallel to the layers is found to be at least 2 orders of magnitude greater than perpendicular to the layers, but not to be greatly affected by the presence of intercalated silver. The activation energy for Li hopping in NbSe/sub 2/ is estimated to be 520 meV. The staging structure of Ag/sub x/NbSe/sub 2/ is also reported. These results have implications for the characterization of cathode materials in intercalation batteries

The preparation and testing of Nb-Zr and Nb-ZrO2 single crystals for deformation studies

International Nuclear Information System (INIS)

Botta Filho, W.J.; Christian, J.W.; Taylor, G.

1987-01-01

The difficulties to obtain adequate single crystals of Nb-Zr and Nb-ZrO 2 alloys for deformation studies are discussed. Low-temperature internal oxidation of Nb-Zr alloys followed by ageing at higher temperatures resulted in the precipitation of ZrO 2 particles. However, the effect of this treatment on the particles size and distribution and on the crystallographic structure of the particle was not completely understood. Compression tests in the temperature range 4.2K to 373K showed a small effect of zirconia particles on the mechanical properties of Nb-Zr solid solutions and a significative effect of the amount of oxygen remaining in solid solution after the oxidation treatment. (author) [pt

Thermal stability of nano structured iron powder as a function of amount and nature of reinforcement (Nb or NbC); Estudio de la estabilidad termica de polvo de hierro nanoestructurado en funcion del tipo de refuerzo (Nb, NbC) y de su contenido

Energy Technology Data Exchange (ETDEWEB)

Fuentes-Pacheco, L.; Campos, M.; Torralba, J. M.

2011-07-01

In structural steels, an effective strategy to succeed in increasing both strength and toughness is the grain refining, like in microalloyed steels. To delay or even inhibit the grain growth there are two basic mechanisms: particle pinning and solute drag. The effect of the presence of small particles of NbC to inhibit the austenitic grain growth is well known. However, it is not so clear which mechanism will be more effective to delay ferritic grain growth. In order to confirm it, nano structured iron powders reinforced with Nb and NbC have been prepared by mechanical alloying. The main objective of this work is, therefore, to study the thermal stability of the nano structured powder as a function of the reinforce type (elemental Nb or NbC) and its content. (Author) 19 refs.

Niagara Falls Storage Site annual environmental report for calendar year 1991, Lewiston, New York

International Nuclear Information System (INIS)

1992-09-01

This document describes the environmental monitoring program at the Niagara Falls Storage Site (NFSS) and surrounding area, implementation of the program, and monitoring results for 1991. Environmental monitoring at NFSS began in 1981. The site is owned by the US Department of Energy (DOE) and is assigned to the DOE Formerly Utilized Sites Remedial Action Program (FUSRAP). FUSRAP is a program to decontaminate or otherwise control sites where residual radioactive materials remain from the early years of the nation's atomic energy program or from commercial operations causing conditions that Congress has authorized DOE to remedy. The environmental monitoring program at NFSS includes sampling networks for radon concentrations in air; external gamma radiation exposure; and total uranium and radium-226 concentrations in surface water, sediments, and groundwater. Additionally, several nonradiological parameters including seven metals are routinely measured in groundwater. Monitoring results are compared with applicable Environmental Protection Agency (EPA) standards, DOE derived concentration guides (DCGs), dose limits, and other requirements in DOE orders. Environmental standards are established to protect public health and the environment

Phase analysis of superconducting Nb-Sn materials by Moessbauer spectroscopy

International Nuclear Information System (INIS)

Sitek, J.; Tomasich, M.; Cirak, J.; Prejsa, M.; Kruzliak, J.

1978-01-01

Moessbauer spectroscopy is used for the optimalization of superconducting Nb-Sn samples preparation in the form of foils. Pure phases of Nb 3 Sn, Nb 6 Sn 5 , and NbSn 2 are determined. Two series of samples are studied at 750 and 900 0 C tinning temperature respectively, and at 750, 860, 900, and 960 0 C heating temperatures. In the samples the phases Nb 3 Sn, Nb 6 Sn 5 , NbSn 2 , and the solid solution Nb-Sn phase are observed. The results from the phase analysis lead to the assumption that the percentage amount of the phases is preferentially dependent on the tinning temperature. (author)

Synthesis of anatase nanoparticles with extremely wide solid solution range and ScTiNbO6 with α-PbO2 structure

International Nuclear Information System (INIS)

Hirano, Masanori; Ito, Takaharu

2009-01-01

Anatase-type nanoparticles Sc X Ti 1-2X Nb X O 2 with wide solid solution range (X=0-0.35) were hydrothermally formed at 180 deg. C for 5 h. The lattice parameters a 0 and c 0 , and the optical band gap of anatase gradually and linearly increased with the increase of the content of niobium and scandium from X=0 to 0.35. Their photocatalytic activity and adsorptivity by the measurement of the concentration of methylene blue (MB) that remained in the solution in the dark or under UV-light irradiation were evaluated. The anatase phase existed stably up to 900 deg. C for the samples with X=0.25-0.30 and 750 deg. C for that with X=0.35 during heat treatment in air. The phase with α-PbO 2 structure and the rutile phases coexisted in the samples with X=0.25-0.30 after heated at temperatures above 900-950 deg. C. The α-PbO 2 structure having composition ScTiNbO 6 with possibly some cation order similar to that seen in wolframite existed as almost completely single phase after heat treatment at temperatures 900-1500 deg. C through phase transformation from anatase-type ScTiNbO 6 . - Graphical abstract: Anatase-type Sc X Ti 1-2X Nb X O 2 solid solutions with wide solid solution range (X=0-0.35) were hydrothermally formed as nanoparticles from the precursor solutions of Sc(NO 3 ) 3 , TiOSO 4 , NbCl 5 at 180 deg. C for 5 h using the hydrolysis of urea. Anatase-type ScTiNbO 6 was synthesized under hydrothermal condition. ScTiNbO 6 having α-PbO 2 structure with possibly some cation order similar to that seen in wolframite was formed through phase transformation above 900 deg. C.

Microstructure evolution and mechanical properties of Ti−22Al−25Nb alloy joints brazed with Ti−Ni−Nb alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Y.; Cai, X.Q.; Yang, Z.W., E-mail: tjuyangzhenwen@163.com; Qiu, Q.W.; Wang, D.P.; Liu, Y.C.

2016-10-01

Ti{sub 45}Ni{sub 45}Nb{sub 10} (at.%) brazing alloy, fabricated by arc melting, was successfully used to braze Ti−22Al−25Nb (at.%) alloy. The microstructures of Ti{sub 45}Ni{sub 45}Nb{sub 10} brazing alloy and Ti−22Al−25Nb alloy brazed joints were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and micro-area X-ray diffraction (XRD). The effects of the brazing parameters on the interfacial microstructure and mechanical properties of the Ti−22Al−25Nb alloy brazed joints were investigated. The results showed that the joint was primarily comprised of two characteristic zones: diffusion zone I and central zone II, and the reaction phases formed in the brazed joint were the B2, O, τ{sub 3}, and Ti{sub 2}Ni phase. The crystal orientation of B2 phase in diffusion zone I was consistent with that in the Ti−22Al−25Nb substrate. The O phase was precipitated from the B2 phase. As the brazing temperature or holding time increased, τ{sub 3} was gradually replaced by the B2 phase, and the Ti{sub 2}Ni phase decreased and ultimately disappeared. The maximum shear strength achieved at room temperature was 318 MPa when the joint was brazed at 1180 °C for 20 min, whereas it was 278 MPa at 650 °C. Crack primarily propagated in the τ{sub 3} compound, which was extremely hard and brittle, and partially traversed the B2 and O phases. - Highlights: • Ti{sub 45}Ni{sub 45}Nb{sub 10} alloy was successfully developed to braze Ti−22Al−25Nb alloy. • Ti−22Al−25Nb alloy was transformed from B2 phase into the O + B2 duplex phase after brazing. • Crystal orientation of B2 in joint was dependent on metal substrate. • Correlation between joint microstructure and mechanical properties was revealed. • Ti−22Al−25Nb brazed joint had excellent ambient and high temperature strength.

Effect of excess Mg and Excess Nb incorporation into the B-site of pyrochlore in the Pb-Mg-Nb-O system

Directory of Open Access Journals (Sweden)

Mergen, A.

2002-12-01

Full Text Available In the Pb-Mg-Nb-O system, excess Mg and excess Nb incorporation into the B-site of PMN pyrochlore were investigated along the compositons of Pb1.83Mg0.29+xNb1.71-xO6.39-1.5x where x=0.1, 0.2, 0.3, 0.4, 0.522 and Pb1.83Mg0.29-xNb1.71+xO6.39+1.5x where x=0.1, 0.2, 0.29 respectively. Excess Mg incorporation led to the formation of perovskite and excess Nb resulted in formation of Pb2Nb2O7 monoclinic pyrochlore. The densities of the PMN pyrochlore-PMN perovskite mixtures decreased with an increase in Mg concentration. The relative permittivity of the mixtures increased with decreasing pyrochlore content. The effect of pyrochlore on the permittivity follows the Weiner’s mixture rule up to a pyrochlore content of 50 vol%.

Se investigó la incorporación en lugares B de pirocloro PMN de un exceso de Mg y un exceso de Nb. En el sistema Pb-Mg-Nb-O2 las composiciones analizadas fueron Pb1.83Mg0.29+xNb1.71-xO6.39-1.5x donde x=0.1, 0.2, 0.3, 0.4, 0.522 y en Pb1.83Mg0.29-xNb1.71+xO6.39+1.5x donde x= 0.1, 0.2,0.29. El exceso de Mg condujo a la formación de perovskita y el exceso de Nb resultó en la formación del pirocloro monolínico, Pb2Nb2O7. La densidad de la mezcla de PMN pirocloro-perovskita dismunuye con el aumento de la concentración de Mg. La permitividad dieléctrica de las mezclas aumenta con la disminución del contenido de pirocloro. El efecto del pirocloro sobre la permitividad sigue la regla de mezclas de Weiner hasta conenidos de pirocloro del 50%.

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.

Fabrication of Nb{sub 3}Al superconducting wires by utilizing the mechanically alloyed Nb(Al){sub ss} supersaturated solid-solution with low-temperature annealing

Energy Technology Data Exchange (ETDEWEB)

Pan, X.F. [National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd., Xi’an 710018 (China); Superconducting Materials Center, Northwest Institute for Nonferrous Metal Research, Xi’an 710016 (China); Yan, G., E-mail: gyan@c-nin.com [National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd., Xi’an 710018 (China); Superconducting Materials Center, Northwest Institute for Nonferrous Metal Research, Xi’an 710016 (China); Qi, M. [Superconducting Materials Center, Northwest Institute for Nonferrous Metal Research, Xi’an 710016 (China); Cui, L.J. [National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd., Xi’an 710018 (China); Chen, Y.L.; Zhao, Y. [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains (Ministry of Education of China), Superconductivity and New Energy R and D Center, Southwest Jiaotong University, Chengdu 610031 (China); Li, C.S. [Superconducting Materials Center, Northwest Institute for Nonferrous Metal Research, Xi’an 710016 (China); Liu, X.H. [National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd., Xi’an 710018 (China); Feng, Y.; Zhang, P.X. [National Engineering Laboratory for Superconducting Material, Western Superconducting Technologies (WST) Co., Ltd., Xi’an 710018 (China); Key Laboratory of Magnetic Levitation Technologies and Maglev Trains (Ministry of Education of China), Superconductivity and New Energy R and D Center, Southwest Jiaotong University, Chengdu 610031 (China); Liu, H.J. [Institute of Plasma Physics, Chinese Academy of Sciences (CAS), Hefei 230031 (China); and others

2014-07-15

Highlights: • This paper reported superconducting properties of the powder-in-tube Nb{sub 3}Al wires. • The Nb{sub 3}Al wires were made by using Nb(Al){sub ss} supersaturated solid solution powders. • The Cu-matrix Nb{sub 3}Al superconducting wires have been successfully fabricated. • The transport J{sub c} of Nb{sub 3}Al wires at 4.2 K, 10 T is up to 12,700 A/cm{sup 2}. - Abstract: High-performance Nb{sub 3}Al superconducting wire is a promising candidate to the application of high-field magnets. However, due to the production problem of km-grade wires that are free from low magnetic field instability, the Nb{sub 3}Al wires made by rapid heating, quenching and transformation (RHQT) are still not available to the large-scale engineering application. In this paper, we reported the properties of the in situ powder-in-tube (PIT) Nb{sub 3}Al superconducting wires, which were made by using the mechanically alloyed Nb(Al){sub ss} supersaturated solid solution, as well as the low temperature heat-treatment at 800 °C for 10 h. The results show that Nb{sub 3}Al superconductors in this method possess very fine grains and well superconducting properties, though a little of Nb{sub 2}Al and Nb impurities still keep being existence at present work. At the Nb{sub 3}Al with a nominal 26 at.% Al content, the onset T{sub c} reaches 15.8 K. Furthermore, a series of Nb{sub 3}Al wires and tapes with various sizes have been fabricated; for the 1.0 mm-diameter wire, the J{sub c} at 4.2 K, 10 T and 14 T have achieved 12,700 and 6900 A/cm{sup 2}, respectively. This work suggests it is possible to develop high-performance Cu-matrix Nb{sub 3}Al superconducting wires by directly using the Nb(Al){sub ss} supersaturated solid-solution without the complex RHQT heat-treatment process.

Amorphous-crystalline transition in thermoelectric NbO2

International Nuclear Information System (INIS)

Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W

2015-01-01

Density functional theory was employed to design enhanced amorphous NbO 2 thermoelectrics. The covalent-ionic nature of Nb–O bonding is identical in amorphous NbO 2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO 2 , which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO 2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO 2 possesses enhanced transport properties at all temperatures. Amorphous NbO 2 , reaching  −173 μV K −1 , exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions. (paper)

Estudo da previsibilidade das medidas P-NB e 1-NB na elaboração da análise cefalométrica de Steiner Assessing the predictability of the P-NB and 1-NB values by the Steiner’s cephalometric analysis

Directory of Open Access Journals (Sweden)

Célia Regina Maio Pinzan

2004-05-01

Full Text Available O propósito deste trabalho consistiu na avaliação longitudinal da previsibilidade das medidas P-NB e 1-NB na elaboração da análise de Steiner. A amostra compôs-se de 148 pacientes, divididos em três grupos de acordo com o padrão de crescimento: horizontal, equilibrado e vertical. Os valores propostos durante a individualização da análise de Steiner foram comparados com os obtidos ao final do tratamento ortodôntico e nos últimos controles realizados (em média, 4 anos e 9 meses pós-tratamento. A análise dos resultados revelou: 1 os valores propostos para a medida P-NB apresentaram-se significantemente maiores do que os obtidos ao final do tratamento nos grupos horizontal e equilibrado, e, quando comparados aos obtidos nos controles, não se verificou diferença estatisticamente significante para nenhum dos grupos avaliados; 2 os valores propostos para a medida 1-NB demonstraram diferenças estatisticamente significantes em relação aos obtidos ao final do tratamento para o grupo vertical e em relação aos obtidos nos controles, para os grupos equilibrado e vertical. Conclui-se, portanto, que se torna necessário rever as estimativas para o P-NB para pacientes com padrões de crescimento horizontal e equilibrado. Quanto à medida 1-NB, os resultados confirmaram que os valores da tabela de compromissos preconizada por Steiner subestimam o posicionamento final dos incisivos inferiores, tornando-se necessário estabelecer tabelas de compromissos aceitáveis para jovens brasileiros leucodermas com ascendência mediterrânea, de acordo com os padrões distintos de crescimento.The Steiner´s cephalometric analysis has been clinically used worldwide and since its first introduction in the literature, the P-NB rationale has deemed to be essential to properly match all measures at the end of the treatment. However, the factors upon which it is estimated has so far remained uncertain and no guidelines concerning the clinical experience

Solid-state synthesis in the system Na0.8NbyW1-yO3 with 0≤y≤0.4: A new phase, Na0.5NbO2.75, with perovskite-type structure

International Nuclear Information System (INIS)

Debnath, Tapas; Ruescher, Claus H.; Gesing, Thorsten M.; Koepke, Juergen; Hussain, Altaf

2008-01-01

Series of compounds in the system Na x Nb y W 1-y O 3 were prepared according to the appropriate molar ratio of Na 2 WO 4 , WO 3 , WO 2 and Nb 2 O 5 with x=0.80 and 0.0≤y≤0.4 at 600 deg. C in evacuated silica glass tubes. These compounds were investigated by X-ray powder diffraction, optical microscopy, microprobe analysis, Raman and optical microspectroscopy. A y-dependent separation into three distinct coloured crystallites with cubic perovskite-type structures is observed: (i) red-orange crystallites with composition Na x WO 3 with slightly decreasing x (i.e. 0.8-0.72) with increasing nominal y, (ii) bluish solid solution of composition Na x Nb y W 1-y O 3 and (iii) white crystallites of a new phase having defect perovskite-type structure with composition Na 0.5 NbO 2.75 . - Graphical abstract: Optical micrograph of a polished sample of nominal composition Na 0.8 Nb 0.4 W 0.6 O 3 showing a mixture of three different coloured crystals: red, light blue and white. The scale bar is 30 μm

Low-field Instabilities in Nb$_{3}$Sn Multifilamentary Wires the Possible Role of Unreacted Nb

CERN Document Server

Devred, A; Celentano, G; Fabbricatore, P; Ferdeghini, C; Greco, M; Gambardella, U

2007-01-01

We report an experimental study aiming to demonstrate the not negligible role of unreacted Nb on the magnetic instabilities in superconducting Nb$_{3}$Sn multifilamentary wires, observable through partial flux jumps at magnetic field values below 0.5 T. The analysed wires were recently developed for use as dipoles required in future high-energy proton accelerators and are based on powder-in-tube technology. We studied both unreacted (only involving Nb filaments) and reacted wires, finding flux jump instabilities in both cases when performing magnetic measurements. The results can be interpreted on the basis of the critical state model and are coherent with the intrinsic stability criterion.

A quantitative atom probe study of the Nb excess at prior austenite grain boundaries in a Nb microalloyed strip-cast steel

International Nuclear Information System (INIS)

Felfer, Peter J.; Killmore, Chris R.; Williams, Jim G.; Carpenter, Kristin R.; Ringer, Simon P.; Cairney, Julie M.

2012-01-01

Most modern HSLA steels rely on the effect of Nb in steels to achieve the properties desired for a specific application. While the role of Nb in forming precipitates has been well characterized, its role in a solid solution is less well understood due to the difficulty of obtaining quantitative experimental data. In the current work, site-specific atom probe tomography was used to quantify the amount of Nb present at prior austenite grain boundaries in a commercial strip-cast steel, produced via the Castrip ® process. This was compared to the amount of Nb found at ferrite–ferrite grain boundaries that had formed during the transformation from austenite to ferrite. With the interfacial excess Nb measured, thermodynamic calculations were carried out and compared to the change in transformation temperature obtained by dilatometry, with reference to a comparable Nb free, strip-cast steel.

Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]- layers

Science.gov (United States)

Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

2013-01-01

A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]- layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

Tunneling spectroscopy in NbN based Josephson junctions

International Nuclear Information System (INIS)

Chicault, R.; Villegier, J.C.

1984-08-01

Tunneling spectroscopy in high quality NbN-oxide-Pb(In) diodes offers a direct observation of various NbN and Pb phonon frequences as other vibrating modes existing near the tunnel barrier. The large number of peaks attribuated to dips in the transverses and longitudinal acoustic branches of NbN dispersion curves are found to confirm the previous theory developing the contribution of these modes to the strong coupling and high Tc behavior of NbN

Microstructure and mechanical properties of the NiNbZrTiAl amorphous alloys with 10 and 25 at.% Nb content.

Science.gov (United States)

Czeppe, T; Ochin, P; Sypień, A; Major, L

2010-03-01

The results of investigation of two different Ni-based glasses with compositions Ni(58)Nb(10)Zr(13)Ti(12)Al(7) and Ni(58)Nb(25)Zr(8)Ti(6)Al(3) are presented. The structure of the melt spun ribbons was amorphous. The supercooled liquid range decreased and primary crystallization temperature increased with increasing Nb content while the parameter T(g)/T(m) slightly increased. The crystallization process proceeded in a different way. The ribbon containing 10 at.% Nb showed typical primary crystallization of the 50 nm grains of the NiTi(Nb) cubic phase; the ribbon containing 25 at.% of Nb revealed high thermal stability of the amorphous phase, which crystallized only in a small amount in the range of primary crystallization, preserving large fraction of the amorphous phase even high above the end of the crystallization. The tensile load-displacement curves were also different. In both cases, the ribbons revealed quite a large range of the plastic elongation. The ribbon containing 10% Nb showed stress relaxation and was maximally elongated up to 0.6. The ribbon with 25 at.% Nb revealed a hardening effect and the slightly smaller maximal elongation following it. The microstructure of the deformed specimens showed deformation bands parallel to the tensile axis, microcracks formation along shear bands and river-like pattern at the fracture surfaces. In both cases, high resolution electron microscope did not reveal any crystallization after deformation.

Carrier compensation mechanism in heavily Nb-doped anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} epitaxial thin films

Energy Technology Data Exchange (ETDEWEB)

Nogawa, H; Chikamatsu, A; Hirose, Y; Hasegawa, T [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Nakao, S [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Kumigashira, H; Oshima, M, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, Tokyo 113-8656 (Japan)

2011-09-14

We investigated the electronic structures of anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} (TNO) thin films as a function of Nb concentration x using photoemission spectroscopy (PES) measurements to elucidate the origin of the abrupt decrease in carrier activation in heavily Nb-doped regime. The existing intensity ratio of Nb{sup 5+} evaluated from Nb 3d core-level PES spectra maintained a constant value of {approx}0.8 at x = 0.06-0.3, implying that electron carriers generated by Nb doping are compensated by p-type defects. Ti 2p-3d and O1s-2p resonant PES measurements of x = 0.06-0.3 films revealed that the in-gap states positioned {approx}1 eV below the Fermi level (E{sub F}) have a mixed character of Ti 3d and O 2p orbitals, whereas the states at E{sub F} mainly have a Ti 3d nature. We proposed a carrier compensation mechanism that interstitial oxygen atoms strongly combined with surrounding Nb atoms kill conduction electrons in heavily Nb-doped anatase TiO{sub 2}.

Moessbauer spectroscopy characterization of Zr-Nb-Fe phases

Energy Technology Data Exchange (ETDEWEB)

Ramos, C.P. [CONICET, Av. Gral. Paz 1499, 1650 Buenos Aires (Argentina)]. E-mail: ciramos@cnea.gov.ar; Granovsky, M.S. [CAC-CNEA, Av. Gral. Paz 1499, 1650 Buenos Aires (Argentina); Saragovi, C. [CAC-CNEA, Av. Gral. Paz 1499, 1650 Buenos Aires (Argentina)

2007-02-01

The aim of this work was the characterization of the ternary phases and of those coming from the corresponding binary systems in the Zr-Nb-Fe diagram by means of Moessbauer spectroscopy. This is part of a complete study involving a tentative isothermal section at 900 deg. C of the center of the Zr-Nb-Fe diagram which will be published elsewhere. Zr-Nb-Fe alloys with Nb contents between 5 and 50 at% and Fe contents between 10 and 60 at% were analyzed after a heat treatment at 900 deg. C for 4 month. Moessbauer characterization of the phases was complemented by optical and scanning electron microscopies, X-ray diffraction and electron microprobe analysis. From the obtained results it can be inferred that Fe in both of the Laves phases present in this system (Zr(FeNb){sub 2} and (ZrNb)Fe{sub 2}) sees different environments, producing quadrupole splitting and hyperfine field distributions, respectively. Two types of body centered cubic {beta} phases (Zr-rich and Nb-rich) were found having noticeable differences in their Moessbauer parameters. Furthermore it was shown that the ternary Fe(NbZr){sub 2} compound would show magnetic character at low temperatures. Concentration dependence of the hyperfine parameters and their relations with the lattice parameters contributed to the structural characterization of the phases.

Moessbauer spectroscopy characterization of Zr-Nb-Fe phases

International Nuclear Information System (INIS)

Ramos, C.P.; Granovsky, M.S.; Saragovi, C.

2007-01-01

The aim of this work was the characterization of the ternary phases and of those coming from the corresponding binary systems in the Zr-Nb-Fe diagram by means of Moessbauer spectroscopy. This is part of a complete study involving a tentative isothermal section at 900 deg. C of the center of the Zr-Nb-Fe diagram which will be published elsewhere. Zr-Nb-Fe alloys with Nb contents between 5 and 50 at% and Fe contents between 10 and 60 at% were analyzed after a heat treatment at 900 deg. C for 4 month. Moessbauer characterization of the phases was complemented by optical and scanning electron microscopies, X-ray diffraction and electron microprobe analysis. From the obtained results it can be inferred that Fe in both of the Laves phases present in this system (Zr(FeNb) 2 and (ZrNb)Fe 2 ) sees different environments, producing quadrupole splitting and hyperfine field distributions, respectively. Two types of body centered cubic β phases (Zr-rich and Nb-rich) were found having noticeable differences in their Moessbauer parameters. Furthermore it was shown that the ternary Fe(NbZr) 2 compound would show magnetic character at low temperatures. Concentration dependence of the hyperfine parameters and their relations with the lattice parameters contributed to the structural characterization of the phases

Luminescence properties of novel red-emitting phosphor InNb1-xPxO4:Eu3+ for white light emitting-diodes

Directory of Open Access Journals (Sweden)

Tang An

2015-06-01

Full Text Available InNb1-xPxO4:Eu3+ red phosphors were synthesized by solid-state reaction and their luminescence properties were also studied through photoluminescence spectra. The excitation and emission spectra make it clear that the as-prepared phosphors can be effectively excited by near-ultraviolet (UV 394 nm light and blue 466 nm light to emit strong red light located at 612 nm, due to the Eu3+ transition of 5D0 → 7F2. The luminescence intensity is dependent on phosphorus content, and it achieves the maximum at x = 0.4. Excessive phosphorus in the phosphors can result in reduction of luminescence intensity owing to concentration quenching.With the increasing content of phosphorus, the phosphors are prone to emit pure red light. This shows that the InNb1.6P0.4O4:0.04Eu3+ phosphor may be a potential candidate as a red component for white light emitting-diodes.

Corrosion Behavior and Oxide Properties of Zr-Nb-Cu and Zr-Nb-Sn Alloy in High Dissolved Hydrogen Primary Water Chemistry

Energy Technology Data Exchange (ETDEWEB)

Lee, Yun Ju; Kim, Tae Ho; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of)

2016-05-15

The water-metal interface is regarded as rate-controlling site governing the rapid oxidation transition in high burn-up fuel. And the zirconium oxide is made in water-metal interface and its structure and phase do an important role in terms of oxide properties. During oxidation process, the protective tetragonal oxide layer develops at the interface due to accumulated high stress during oxide growth, and it turns into non-protective monoclinic oxide with increasing oxide thickness, thus decreasing the stress. It has been reported that Nb addition was proven to be very beneficial for increasing the corrosion resistance of the zirconium alloys. From a more recent study, Cu addition in Nb containing Zirconium alloy was reported to be effective for increasing corrosion resistance in water containing B and Li. According to the previous research conducted, Zr-Nb-Cu shows better corrosion resistance than Zircaloy-4. The dissolved hydrogen (DH) concentration is the key issue of primary water chemistry, and the effect of DH concentration on the corrosion rate of nickel based alloy has been researched. However, the effect of DH on the zirconium alloy corrosion mechanism was not fully investigated. In this study, the weight gain measurement, FIB-SEM analysis, and Raman spectroscopic measurement were conducted to investigate the effects of dissolved hydrogen concentration and the chemical composition on the corrosion resistance and oxide phase of Zr-Nb-Cu alloy and Zr-Nb-Sn alloy after oxidizing in a primary water environment for 20 d. The corrosion rate of Zr-Nb-Cu alloy is slow, when it is compared to Zr-Nb-Sn alloy. In SEM images, the oxide thickness of Zr-Nb-Cu alloy is measured to be around 1.06 μm it of Zr-Nb-Sn alloy is measured to be 1.15 μm. It is because of the Segregation made by Sn solute element when Sn solute element oxidized. And according to ex situ Raman spectra, Zr-Nb-Cu alloy oxide has more tetragonal zirconium oxide fraction than Zr-Nb-Sn alloy oxide.

Voltage spikes in Nb3Sn and NbTi strands

International Nuclear Information System (INIS)

Bordini, B.; Ambrosio, G.; Barzi, E.; Carcagno, R.; Feher, S.; Kashikhin, V.V.; Lamm, M.J.; Orris, D.; Tartaglia, M.; Tompkins, J.C.; Turrioni, D.; Yamada, R.; Zlobin, A.V.; Fermilab

2005-01-01

As part of the High Field Magnet program at Fermilab several NbTi and Nb 3 Sn strands were tested with particular emphasis on the study of voltage spikes and their relationship to superconductor instabilities. The voltage spikes were detected under various experimental conditions using voltage-current (V-I) and voltage-field (V-H) methods. Two types of spikes, designated ''magnetization'' and ''transport current'' spikes, have been identified. Their origin is most likely related to magnetization flux jump and transport current redistribution, respectively. Many of the signals observed appear to be a combination of these two types of spikes; the combination of these two instability mechanisms should play a dominant role in determining the minimum quench current

Creep behavior of Ti3Al-Nb intermetallic alloys

International Nuclear Information System (INIS)

Yu, T.H.; Yue, W.J.; Koo, C.H.

1997-01-01

It is well known that Ti 3 Al-Nb alloys are potential materials for aerospace applications. The creep property is an important consideration when materials are used at high temperature. In this article, the effect of microstructure of Ti-25Al-10Nb alloy on the creep property was investigated, and the creep property of Ti-25Al-10Nb alloy modified by small addition of silicon 0.2 at.% or carbon 0.1 at.% was observed. The alloy with the addition of molybdenum to replace part of niobium 2 at.% was also studied. The experimental results show that the furnace-cooled Ti-25Al-10Nb alloy has superior creep resistance to the air-cooled Ti-25Al-10Nb alloy at 200 MPa, but exhibits poor creep resistance at 250 MPa or above. Small addition of silicon to the Ti-25Al-10Nb alloy may increase creep resistance. Small addition of carbon to the Ti-25Al-10Nb alloy may reduce creep resistance but raise rupture strain. Molybdenum is the most effective alloying element to increase creep resistance for the Ti-25Al-10Nb alloy. The creep mechanism of Ti-25Al-10Nb alloy is governed by dislocation climb. (orig.)

Characterization of the Nb-B superlattice system

Energy Technology Data Exchange (ETDEWEB)

Franco, D.G.; Sarmiento-Chavez, A.; Schenone, N.; Llacsahuanga Allcca, A.E.; Gómez Berisso, M.; Fasano, Y.; Guimpel, J., E-mail: jguimpel@cab.cnea.gov.ar

2016-12-15

Highlights: • In this manuscript we study the crystalline and superconducting properties of this system, as a possible material to be used in solid state neutron detector sensors. • The results show that this superlattice system can be grown even for very thin layers, in spite of the Nb-B binary system showing many possible compounds, which could enhance interdifussion at the interfaces. • Also, the superconducting properties are not degraded, and they are even enhanced with respect to those of single Nb films of the same thickness. • In conclusion, we find that this system is a good potential candidate for the design and construction of solid state neutron Transition Edge Sensors. - Abstract: We study the growth, stacking and superconducting properties of Nb and B thin films and superlattices. The interest in these resides in their possible use in transition edge neutron sensors. The samples were grown by magnetron sputtering over Si (1  0  0) substrates. The X-ray diffraction patterns for all Nb containing samples show a Nb (1  1  0) preferential orientation. From the low-angle X-ray reflectivity we obtain information on the superlattice structure. The superconducting transition temperatures of the superlattices, obtained from the temperature dependence of the magnetization, are higher than those of single Nb films of similar thickness. The temperature dependence of the perpendicular and parallel upper critical fields indicate that the superlattices behave as an array of decoupled superconducting Nb layers.

Characterization of the Nb-B superlattice system

International Nuclear Information System (INIS)

Franco, D.G.; Sarmiento-Chavez, A.; Schenone, N.; Llacsahuanga Allcca, A.E.; Gómez Berisso, M.; Fasano, Y.; Guimpel, J.

2016-01-01

Highlights: • In this manuscript we study the crystalline and superconducting properties of this system, as a possible material to be used in solid state neutron detector sensors. • The results show that this superlattice system can be grown even for very thin layers, in spite of the Nb-B binary system showing many possible compounds, which could enhance interdifussion at the interfaces. • Also, the superconducting properties are not degraded, and they are even enhanced with respect to those of single Nb films of the same thickness. • In conclusion, we find that this system is a good potential candidate for the design and construction of solid state neutron Transition Edge Sensors. - Abstract: We study the growth, stacking and superconducting properties of Nb and B thin films and superlattices. The interest in these resides in their possible use in transition edge neutron sensors. The samples were grown by magnetron sputtering over Si (1  0  0) substrates. The X-ray diffraction patterns for all Nb containing samples show a Nb (1  1  0) preferential orientation. From the low-angle X-ray reflectivity we obtain information on the superlattice structure. The superconducting transition temperatures of the superlattices, obtained from the temperature dependence of the magnetization, are higher than those of single Nb films of similar thickness. The temperature dependence of the perpendicular and parallel upper critical fields indicate that the superlattices behave as an array of decoupled superconducting Nb layers.

The liquidus surface of the Cr–Al–Nb system and re-investigation of the Cr–Nb and Al–Cr phase diagrams

International Nuclear Information System (INIS)

Stein, F.; He, C.; Wossack, I.

2014-01-01

Highlights: • Liquidus surface and reaction scheme of the Cr–Al–Nb system experimentally determined. • Solidification paths of the ternary alloys derived from as-cast microstructures. • Compositions and temperatures of the invariant points. • Revised versions of the phase diagrams of the Cr–Nb and Al–Cr boundary systems. - Abstract: The liquidus surface and corresponding reaction scheme of the ternary Cr–Al–Nb system were determined experimentally. The solidification paths of a series of more than 40 ternary alloys were deduced from investigation of their as-cast microstructures and measurement of all reaction temperatures applying scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and differential thermal analysis (DTA). The hexagonal C14-type Laves phase Nb(Cr,Al) 2 , which is not stable in any of the binary boundary systems and which is the only ternary compound, forms the most extended primary crystallization field of the ternary system dominating the centre of the liquidus surface. A ternary eutectic was found near the Al–Nb boundary composed of the three intermetallic phases C14 + Nb 2 Al + NbAl 3 . Besides the ternary liquidus surface, the solidus and liquidus curves of the Cr–Nb boundary system and of the Cr-rich part of the Al–Cr system were determined resulting in revised binary phase diagrams

A submillimetre-wave SIS mixer using NbN/MgO/NbN trilayers grown epitaxially on an MgO substrate

CERN Document Server

Uzawa, Y; Saito, A; Takeda, M; Wang, Z

2002-01-01

We have designed, fabricated and tested a quasi-optical superconductor-insulator-superconductor (SIS) mixer employing distributed NbN/MgO/NbN tunnel junctions and NbN/MgO/NbN microstriplines at submillimetre-wave frequencies. These trilayers were fabricated by dc- and rf-magnetron sputtering on an MgO substrate at ambient temperature so that the NbN and MgO films were grown epitaxially. Our SIS mixer consists of an MgO hyperhemispherical lens with an antireflection cap and a self-complementary log-periodic antenna made of a single-crystal NbN film, on which the distributed SIS junctions and the two-section impedance transformers were mirror-symmetrically placed at the feed point of the antenna. As designed, the junctions are 0.6 mu m wide and 15.5 mu m long, which is sufficient to absorb the incoming signal along this lossy transmission line, assuming a current density of 10 kA cm sup - sup 2. The mixer showed good I-V characteristics, with subgap-to-normal resistance ratios of about 13, although weak-link br...

Results of the radiological survey at the Niagara-Mohawk property, Railroad Avenue, Colonie, New York (AL218)

International Nuclear Information System (INIS)

Marley, J.L.; Carrier, R.F.

1987-12-01

A number of properties in the Albany/Colonie area have been identified as being potentially contaminated with uranium originating from the former National Lead Company's uranium forming plant in Colonie, New York. The Niagara-Mohawk property on Railroad Avenue in Colonie, New York, was the subject of a radiological investigation initiated June 11, 1987. This commercial property is an irregularly shaped lot partially occupied by an electric power substation and associated transmission lines. Portions of the property that were swampy and heavily vegetated were inaccessible to the survey team. There are no buildings on the property. A diagram showing the approximate boundaries and the 15-m grid network established for measurements on the property is shown. The lot included in the radiological survey was /approximately/45 m wide by 246 m deep. Two views of the property are shown. 13 refs., 6 figs., 4 tabs

Dissolving of Nb and Ti carbonitride precipitates in microalloyed steels

Institute of Scientific and Technical Information of China (English)

Wenjin Nie; Shanwu Yang; Shaoqiang Yuan; Xinlai He

2003-01-01

The dissolving behaviour of Nb and Ti carbonitride precipitates in microalloyed steels during isothermal holding at 1300℃ was investigated by Transmission electron microscopy (TEM) and energy dispersion x-ray spectrum (EDX). It was found that all precipitates in Nb-Ti microalloyed steel are (Nb, Ti)(C,N). With holding time increasing, the atomic ratio of Nb/Ti in precipitates decrease gradually. These precipitates still existe even after holding for 48 h at 1300℃ while Nb(C,N) precipitates dissolve away in Nb microalloyed steel only after 4 h at the same temperature. These results show that formation and thermostability of precipitates are considerably influenced by interaction between Nb and Ti.

Effect of Nb-doped TiO{sub 2} on nanocomposited aligned ZnO nanorod/TiO{sub 2}:Nb for dye-sensitized solar cells

Energy Technology Data Exchange (ETDEWEB)

Saurdi, I., E-mail: saurdy788@gmail.com; Ishak, A. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); UiTM Sarawak Kampus Kota Samarahan Jalan Meranek, Sarawak (Malaysia); Shafura, A. K.; Azhar, N. E. A.; Mamat, M. H. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); Malek, M. F.; Rusop, M. [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM),40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), (Centre for Nano-Science and Nano-Technology), Institute of Science, Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Alrokayan, A. H. Salman; Khan, Haseeb A. [Department of Biochemistry, College of Science, Bldg. 5, King Saud University (KSU) P.O: 2455 Riyadh 1145 (Saudi Arabia)

2016-07-06

The Nb-doped TiO{sub 2} films were deposited on glass substrate at different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively and their electrical and structural properties were investigated. Subsequently, the Nb-doped TiO{sub 2} films were deposited on top of aligned ZnO Nanorod on ITO glass substrates using spin coating technique. The nanocomposited aligned ZnO nanorod/Nb-doped TiO{sub 2} (TiO{sub 2}:Nb) were coated with different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively. The Dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO{sub 2}:Nb photoanodes and their effects on the performance of the DSSCs were investigated. From the solar simulator measurement of DSSC the solar energy conversion efficiency (η) of 5.376% under AM 1.5 was obtained for the ZnO nanorod/TiO{sub 2}:Nb-5at.%.

Studying superconducting Nb3Sn wire

CERN Multimedia

AUTHOR|(CDS)2099575

2015-01-01

Studying superconducting Nb3Sn wire. From the current experience from LHC and HL-LHC we know that the performance requirements for Nb3Sn conductor for future circular collider are challenging and should exceed that of present state-of-the-art materials.

Studying superconducting Nb$_{3}$Sn wire

CERN Multimedia

AUTHOR|(CDS)2099575

2015-01-01

Studying superconducting Nb$_{3}$Sn wire. From the current experience from LHC and HL-LHC we know that the performance requirements for Nb$_{3}$Sn conductor for future circular collider are challenging and should exceed that of present state-of-the-art materials.

Nanoscale decomposition of Nb-Ru-O

Science.gov (United States)

Music, Denis; Geyer, Richard W.; Chen, Yen-Ting

2016-11-01

A correlative theoretical and experimental methodology has been employed to explore the decomposition of amorphous Nb-Ru-O at elevated temperatures. Density functional theory based molecular dynamics simulations reveal that amorphous Nb-Ru-O is structurally modified within 10 ps at 800 K giving rise to an increase in the planar metal - oxygen and metal - metal population and hence formation of large clusters, which signifies atomic segregation. The driving force for this atomic segregation process is 0.5 eV/atom. This is validated by diffraction experiments and transmission electron microscopy of sputter-synthesized Nb-Ru-O thin films. Room temperature samples are amorphous, while at 800 K nanoscale rutile RuO2 grains, self-organized in an amorphous Nb-O matrix, are observed, which is consistent with our theoretical predictions. This amorphous/crystalline interplay may be of importance for next generation of thermoelectric devices.

Formerly utilized MED/AEC sites, Remedial Action Program: radiological survey of the Hooker Chemical Company, Niagara Falls, New York. Final report

International Nuclear Information System (INIS)

1977-01-01

Results of a radiological survey of a portion of the Hooker Chemical Company, Niagara Falls, New York, are presented. The survey was conducted over 5.5-acres in which uranium-bearing materials were handled in the early 1940's. The survey included direct measurements of alpha, beta-gamma, and external gamma radiation throughout the site, measurement of transferable alpha and beta contamination levels in the buildings, determination of uranium and radium concentrations in the soild on the site, measurement of radon and radon daughter concentrations in the buildings, and determination of radionuclide concentrations in surface water samples. The results of the survey indicate that radiation levels throughout the site are within pertinent guidelines for unrestricted release of the property

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.

Role of alkali carbonate and salt in topochemical synthesis of K1/2Na1/2NbO3 and NaNbO3 templates

Science.gov (United States)

Lee, Jae-Seok; Jeon, Jae-Ho; Choi, Si-Young

2013-11-01

Since the properties of lead-free piezoelectric materials have thus far failed to meet those of lead-based materials, either chemical doping or morphological texturing should be employed to improve the piezoelectric properties of lead-free piezoelectric ceramics. The goal of this study was to synthesize plate-like K1/2Na1/2NbO3 and NaNbO3 particles, which are the most favorable templates for morphological texturing of K1/2Na1/2NbO3 ceramics. To achieve this goal, Bi2.5Na3.5Nb5O18 precursors in a plate-like shape were first synthesized and subsequently converted into K1/2Na1/2NbO3 or NaNbO3 particles that retain the morphology of Bi2.5Na3.5Nb5O18. In this study, we found that sodium or potassium carbonate does not play a major role in converting the Bi2.5Na3.5Nb5O18 precursor to K1/2Na1/2NbO3 or NaNbO3, on the contrary to previous reports; however, the salt contributes to the conversion reaction. All synthesis processes have been performed via a molten salt method, and scanning electron microscopy, scanning probe microscopy, and inductively coupled plasma mass spectroscopy were used to characterize the synthesized K1/2Na1/2NbO3 or NaNbO3 templates.

Comparison of ASME Code NB-3200 and NB-3600 results for fatigue analysis of B31.1 branch nozzles

International Nuclear Information System (INIS)

Nitzel, M.E.; Ware, A.G.; Morton, D.K.

1996-01-01

Fatigue analyses wre conducted on two reactor coolant system branch nozzles in an operating PWR designed to the B31.1 Code, for which no explicit fatigue analysis was required by the licensing basis. These analyses were performed as part of resolving issues connected with NRC's Fatigue Action Plan to determine if the cumulative usage factor (CUF) for these nozzles, using the 1992 ASME Code and representative PWR transients, were comparable to nozzles designed and analyzed to the ASME Code. Both NB-3200 and NB-3600 ASME Code methods were used. NB-3200 analyses included the development of finite element models for each nozzle. Although detailed thermal transients were not available for the plant analyzed, representative transients from similar PWRs were applied in each method. CUFs calculated using NB-3200 methods were significantly less than using NB-3600. The paper points out differences in analysis methods and highlights difficulties and unknowns in performing more detailed analyses to reduce conservative assumptions

Effect of quenching in the Ti-Nb-2%Al alloys structure; Efeito da tempera na estrutura das ligas Ti-Nb-2%Al

Energy Technology Data Exchange (ETDEWEB)

Santos, L.C.O.; Matlakhova, L.A.; Matlakhov, A.N.; Toledo, R. [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacazes, RJ (Brazil). Centro de Ciencias e Tecnologia. Lab. de Materiais Avancados (LAMAV)], e-mail: lucascunhasantos@terra.com.br

2006-07-01

In the present work, the Ti-Nb-2%Al alloys, with the rate varied Nb from 15 to 40%, they were submitted to the quenched since 1000 deg C, in water, to verify the influence of Nb in the structure and phase composition. The alloys were obtained in a process of five coalitions in an oven to electric arch and, soon afterwards, wrought the hot and homogenized to 1200 deg C, for 10 hours. After the quenching and conventional metallographic preparation of the samples obliquely cut, the alloys were examined through the optic microscopic, diffraction of ray-X and Vickers hardness. The very defined correlation was shown between the niobium rate and the structure resulting from the quenched alloys. The phase martensitic was revealed in the alloy with 15% Nb, the phases martensitic and beta metastable in the alloys containing above 30% Nb and the phase beta in the alloys with 38% Nb and 40% Nb. the hardness of the phase martensitic increases with the increment of the niobium rate. (author)

Efeito do porta-enxerto e da época de poda na duração das fases fenológicas e no acúmulo de graus-dia pela videira 'Niagara Rosada'

Directory of Open Access Journals (Sweden)

Marco Antonio Tecchio

2013-12-01

Full Text Available Avaliaram-se a influência dos porta-enxertos 'IAC 766', 'IAC 572', 'IAC 313', 'IAC 571-6' e 'Ripária do Traviú' e da época de poda na duração dos estádios fenológicos e no acúmulo de graus-dia pela videira 'Niagara Rosada'. O experimento foi realizado em Louveira-SP. Os tratamentos consistiram na combinação de cinco porta-enxertos e três épocas de poda, sendo utilizado o delineamento experimental em blocos inteiramente casualizados, com parcelas subdivididas e cinco repetições, sendo as parcelas representadas pelos porta-enxertos,e as subparcelas, pelas épocas de poda. Após a poda da videira, foram realizadas avaliações dos estádios fenológicos, utilizando-se do critério de Eichhon e Lorenz (1984. Nas três épocas de poda, baseado nos estádios fenológicos, calculou-se a duração dos períodos: poda ao início da brotação; poda ao pleno florescimento; poda ao início da frutificação; poda ao início da maturação dos cachos, e poda à colheita. Tomando-se por base a duração do ciclo da videira e as temperaturas médias diárias, calculou-se o acúmulo de graus-dia. Os dados foram submetidos à análise de variância e teste Tukey, a 5% de significância. Obteve-se, na poda de verão, redução na duração dos estádios fenológicos da videira 'Niagara Rosada' enxertada sobre o porta-enxerto 'Ripária do Traviú. A maior duração do ciclo e do acúmulo de graus-dia da cultivar Niagara Rosada foi obtida com os porta-enxertos 'IAC 572' e 'IAC 313' nas podas de inverno.

Reactive diffusion and superconductivity of Nb3Al multilayer films

International Nuclear Information System (INIS)

Vandenberg, J.M.; Hong, M.; Hamm, R.A.; Gurvitch, M.

1985-01-01

Thin films of A15 Nb 3 Al have been prepared by reactive diffusion of sputter-deposited Nb/Al multilayers. The diffusion reactions were studied by in situ annealing x-ray diffraction in the temperature range 50--950 0 C. Initially the Nb and Al sublayers react to form the phase NbAl 3 . This interface reaction prevents the formation of the sigma-phase Nb 2 Al, frequently found as a second phase in A15 Nb 3 Al materials; NbAl 3 reacts with the remaining Nb to form the A15 phase. The highest T/sub c/, 16.2 K measured resistively and 15.2 K inductively, was found in a Nb/Al multilayer with an A15 cell parameter a 0 = 5.195 A which corresponds to approx.20 at. % Al. From a comparison with previous investigations of the T/sub c/ dependence on Al concentration and A15 cell parameter, it is concluded that a small amount of the A15 phase has a higher composition of 22--23 at. % Al

Effect of Nb on plasticity and oxidation behavior of TiA1Nb intermetallic compound by density functional theory

Institute of Scientific and Technical Information of China (English)

LI Yan-feng; XU Hui; SONG Zhao-quan; MA Song-shan

2010-01-01

Based on the pseudo potential plane-wave method of density functional theory(DFT),Ti1-xNbxA1(x=0,0.062 5,0.083 3,0.125,0.250)crystals' geometry structure,elastic constants,electronic structure and Mulliken populations were calculated,and the effects of doping on the geometric structure,electronic structure and bond strength were systematically analyzed.The results show that the influence of Nb on the geometric structure is little in terms of the plasticity,and with the increase of Nb content,the covalent bond strength remarkably reduces,and Ti-A1,Nb-M(M=Ti,A1)and other hybrid bonds enhance; meanwhile,the peak district increases and the pseudo-energy gap first decreases and then increases,the overall band structure narrows,the covalent bond and direction of bonds reduce.The population analysis also shows that the results are consistent with the electronic structure analysis.The density of states of TiAlNb shows that Nb doping can enhance the activity of Al and benefit the form of Al2O3 film.All the calculations reveal that the room temperature plasticity and the antioxidation properties of the compounds can be improved with the Nb content of 8.33%-12.5%(mole fraction).

Voltage spikes in Nb3Sn and NbTi strands

Energy Technology Data Exchange (ETDEWEB)

Bordini, B.; Ambrosio, G.; Barzi, E.; Carcagno, R.; Feher, S.; Kashikhin, V.V.; Lamm, M.J.; Orris, D.; Tartaglia, M.; Tompkins, J.C.; Turrioni, D.; Yamada, R.; Zlobin,; /Fermilab

2005-09-01

As part of the High Field Magnet program at Fermilab several NbTi and Nb{sub 3}Sn strands were tested with particular emphasis on the study of voltage spikes and their relationship to superconductor instabilities. The voltage spikes were detected under various experimental conditions using voltage-current (V-I) and voltage-field (V-H) methods. Two types of spikes, designated ''magnetization'' and ''transport current'' spikes, have been identified. Their origin is most likely related to magnetization flux jump and transport current redistribution, respectively. Many of the signals observed appear to be a combination of these two types of spikes; the combination of these two instability mechanisms should play a dominant role in determining the minimum quench current.

Effect of Nb on phase transformations and microstructure in high Nb titanium aluminides

International Nuclear Information System (INIS)

Bean, Glenn E.; Kesler, Michael S.; Manuel, Michele V.

2014-01-01

Highlights: • Thermodynamically-guided design of heat treatment schedules. • Linking chemistry and heat treatment to phase morphology. • Strong dependence of phase transformation behavior on Nb concentration. - Abstract: Titanium aluminides are of interest due to their high specific strength and performance up to 750 °C. Research into high-Nb γ-TiAl based titanium aluminides has shown promising improvements in performance by introduction of the σ-Nb 2 Al phase. However, one current challenge is improving mechanical properties at room and elevated temperatures in order to enable their further implementation. These properties are closely tied with microstructural refinement, and thus phase evolution and microstructural development is the focus of this work. Phase transformation temperatures and stability ranges were determined experimentally through DSC analysis of arc melted alloys, then compared with predictions based upon computational models, and investigated through heat treatment of experimental alloys to develop an ultrafine γ + σ microstructure

Effect of Nb on phase transformations and microstructure in high Nb titanium aluminides

Energy Technology Data Exchange (ETDEWEB)

Bean, Glenn E.; Kesler, Michael S.; Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu

2014-11-15

Highlights: • Thermodynamically-guided design of heat treatment schedules. • Linking chemistry and heat treatment to phase morphology. • Strong dependence of phase transformation behavior on Nb concentration. - Abstract: Titanium aluminides are of interest due to their high specific strength and performance up to 750 °C. Research into high-Nb γ-TiAl based titanium aluminides has shown promising improvements in performance by introduction of the σ-Nb{sub 2}Al phase. However, one current challenge is improving mechanical properties at room and elevated temperatures in order to enable their further implementation. These properties are closely tied with microstructural refinement, and thus phase evolution and microstructural development is the focus of this work. Phase transformation temperatures and stability ranges were determined experimentally through DSC analysis of arc melted alloys, then compared with predictions based upon computational models, and investigated through heat treatment of experimental alloys to develop an ultrafine γ + σ microstructure.

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.

Radiation detection with Nb/Al-AlOx/Al/Nb superconducting tunnel junctions

International Nuclear Information System (INIS)

Matsumura, Atsuki; Takahashi, Toru; Kurakado, Masahiko

1992-01-01

Superconductor radiation detectors have the possibility of 20-30 times better energy resolution than that of a high resolution Si detector. We fabricated Nb/Al-AlOx/Al/Nb superconducting tunnel junctions with low leakage current. X rays were detected with large area junctions of 178x178 μm 2 . High energy resolution of 160 eV for 5.9 keV was obtained. We also fabricated series connected junctions which covers a rather large area of 4x4 mm 2 . α particles injected into the rear substrate were detected using nonthermal phonons induced by the radiations in the substrate. (author)

Structural stability of characteristic interface for NiTi/Nb Nanowire: First-Principle study

Science.gov (United States)

Li, G. F.; Zheng, H. Z.; Shu, X. Y.; Peng, P.

2016-01-01

Compared with some other conventional interface models, the interface of NiTi(211)/Nb(220) in NiTiNb metal nanocomposite had been simulated and analyzed carefully. Results show that only several interface models, i.e., NiTi(100)/Nb(100)(Ni⃡Nb), NiTi(110)/Nb(110) and NiTi(211)/Nb(220), can be formed accordingly with their negative formation enthalpy. Therein the cohesive energy Δ E and Griffith rupture work W of NiTi(211)/Nb(220) interface model are the lowest among them. Density of states shows that there exists only one electronic bonding peak for NiTi(211)/Nb(220) interface model at -2.5 eV. Electron density difference of NiTi(211)/ Nb(220) shows that the Nb-Nb, Nb-Ti and Nb-Ni bonding characters seem like so peaceful as a fabric twisting every atom, which is different from conventional metallic bonding performance. Such appearance can be deduced that the metallic bonding between Nb-Nb, Nb-Ti and Nb-Ni in NiTi(211)/Nb(220) may be affected by its nanostructure called nanometer size effect. Thus, our findings open an avenue for detailed and comprehensive studies of nanocomposite.

Oxide impedance characteristics of the Zr-xNb alloys

International Nuclear Information System (INIS)

Park, S. Y.; Choi, B. K.; Jung, Y. H.; Jung, Y. H.

2002-01-01

To elucidate the correlation between the oxide impedance and corrosion characteristics of the Zr-xNb alloys, the long term corrosion test in high temperature / high pressure aqueous solution and the impedance test in the room temperature sulfate solution were performed. β-quenched plate specimens were heat-treated at 570 .deg. C for 500 hours to get the α+β Nb phase and the at 640 .deg. C for 10 hours to get the α+β Zr phase. The impedance test was conducted in sulfate solution for the initial corrosion test specimen (WG = 30 mg/dm 2 ). To evaluate the impedance date, 4 types of equivalent circuits were constructed by 5 parallel and serial RC elements. By using the equivalent circuits, the thickness of the inner and outer layers were calculated and the electric resistance of each layers were estimated. The corrosion behaviour of Zr-xNb alloys were quite different depending of the annealing condition and Nb-content. The corrosion resistance of the β Nb phase contained high Nb alloys were excellent rather than β Zr phase contained high Nb alloys. The electric resistance of the outer layer of β Zr phase contained high Nb alloy was twice larger than that of β Zr phase contained high Nb alloy, and in the case of outer layer 30% larger. So, the long term corrosion behaviors in high temperature could be estimated well by using the impedance test results

PTA hardfacing of Nb/Al coatings Revestimentos Nb/Al depositados por PTA

Directory of Open Access Journals (Sweden)

Karin Graf

2012-06-01

Full Text Available Hardfacing is widely applied to components yet the majority of the welding techniques available restrain the variety of hard alloys that can be deposited. Plasma Transferred Arc hardfacing offsets this drawback by using powdered feedstock offering the ability to tailor the chemical composition of the coating and as a consequence its properties. The high strength and chemical inertia of aluminide alloys makes them very suitable to protect components. However, the strong interaction with the substrate during hardfacing requires analysis of each alloy system to optimize its properties and weldability. This work analyzed coatings processed with a cast and ground Nb40wt%Al alloy and the effect of Fe and C on the coatings features. It confirmed that sound Nb aluminide coatings can be processed by plasma Transferred arc hardfacing and will have a strong interaction with the substrate, which determines the final microstructure and properties of coatings. Final remarks point out that during Nb-Al coating tailoring the interaction with the substrate has to be considered at the early stages of design process.Revestimentos soldados são amplamente usados para proteger componentes mecânicos entretanto a maioria das técnicas de soldagem disponíveis restringe a variedade de ligas de alta resistência que podem ser depositadas. O processo de plasma por arco transferido permite ultrapassar esta limitação ao utilizar material de adição na forma de pó, oferecendo a possibilidade de se customizar a composição dos revestimentos e em consequências as suas propriedades. A elevada resistência mecânica e inercia química das ligas de aluminetos tornam estas ligas atrativas para a proteção de componentes diversos. Entretanto a grande interação com o substrato que ocorre quando do processamento exige que para a otimização das propriedades e soldabilidade seja realizada uma a análise de cada sistema liga e substrato. Neste trabalho foram processados e

Microstructure and mechanical behavior of superelastic Ti-24Nb-0.5O and Ti-24Nb-0.5N biomedical alloys.

Science.gov (United States)

Ramarolahy, A; Castany, P; Prima, F; Laheurte, P; Péron, I; Gloriant, T

2012-05-01

In this study, the microstructure and the mechanical properties of two new biocompatible superelastic alloys, Ti-24Nb-0.5O and Ti-24Nb-0.5N (at.%), were investigated. Special attention was focused on the role of O and N addition on α(″) formation, supereleastic recovery and mechanical strength by comparison with the Ti-24Nb and Ti-26Nb (at.%) alloy compositions taken as references. Microstructures were characterized by optical microscopy, X-ray diffraction and transmission electron microscopy before and after deformation. The mechanical properties and the superelastic behavior were evaluated by conventional and cyclic tensile tests. High tensile strength, low Young's modulus, rather high superelastic recovery and excellent ductility were observed for both superelastic Ti-24Nb-0.5O and Ti-24Nb-0.5N alloys. Deformation twinning was shown to accommodate the plastic deformation in these alloys and only the {332} twinning system was observed to be activated by electron backscattered diffraction analyses. Copyright © 2012 Elsevier Ltd. All rights reserved.

Refining U-Zr-Nb alloys by remelting

International Nuclear Information System (INIS)

Aguiar, B.M.; Kniess, C.T.; Riella, H.G.; Ferraz, W.B.

2011-01-01

The high density U-Zr-Nb and U-Nb uranium-based alloys can be employed as nuclear fuel in a PWR reactor due to their high density and nuclear properties. These alloys can stabilize the gamma phase, however, according to TTT diagrams, at the working temperature of a PWR reactor, all gamma phase transforms to α'' phase in a few hours. To avoid this kind of transformation during the nuclear reactor operation, the U-Zr-Nb alloy and U-Nn are used in α'' phase. The stability of α'' phase depends on the alloy composition and cooling rate. The alloy homogenization has to be very effective to eliminate precipitates rich in Zr and Nb to avoid changes in the alloying elements contents in the matrix. The homogenization was obtained by remelting the alloy and keeping it in the liquid state for enough time to promote floating of the precipitates (usually carbides, less dense) and leaving the matrix free of precipitates. However, this floating by density difference may result in segregation between the alloying elements (Nb and Zr, at the top) and uranium (at the bottom). The homogenized alloys were characterized in terms of metallographic techniques, optical microscopy, scanning electronic microscopy, EDS and X-ray diffraction. In this paper, it is shown that the contents of Zr and Nb at the bottom and at the top of the matrix are constant. (author)

Smooth Nb surfaces fabricated by buffered electropolishing

International Nuclear Information System (INIS)

Wu, Andy T.; Mammosser, John; Phillips, Larry; Delayen, Jean; Reece, Charles; Wilkerson, Amy; Smith, David; Ike, Robert

2007-01-01

It was demonstrated that smooth Nb surfaces could be obtained through buffered electropolishing (BEP) employing an electrolyte consisting of lactic, sulfuric, and hydrofluoric acids. Parameters that control the polishing process were optimized to achieve a smooth surface finish. The polishing rate of BEP was determined to be 0.646 μm/min which was much higher than 0.381 μm/min achieved by the conventional electropolishing (EP) process widely used in the superconducting radio frequency (SRF) community. Root mean square measurements using a 3D profilometer revealed that Nb surfaces treated by BEP were an order of magnitude smoother than those treated by the optimized EP process. The chemical composition of the Nb surfaces after BEP was analyzed by static and dynamic secondary ion mass spectrometry (SIMS) systems. SIMS results implied that the surface oxide structure of Nb might be more complicated than what usually believed and could be inhomogeneous. Preliminary results of BEP on Nb SRF single cell cavities and half-cells were reported. It was shown that smooth and bright surfaces could be obtained in 1800 s when the electric field inside a SRF cavity was uniform during a BEP process. This study showed that BEP is a promising technique for surface treatment on Nb SRF cavities to be used in particle accelerators

Climate change, energy and sustainability: lessons from the Toronto-Niagara region

International Nuclear Information System (INIS)

Chiotti, Q.

2001-01-01

(electricity and natural gas), and the demand for energy. Climate factors considered include changes in the mean, but more importantly variability in temperatures and changes in extreme weather events. This part of the discussion draws upon extensive research in the Toronto-Niagara Region, which has been supported through the Federal Interdepartmental Panel on Energy Research and Development (PERD). Emphasis is placed on identifying what aspects of current climate have had the greatest impact on the energy sector, and the adaptation options that will be necessary to reduce future vulnerability in face of inevitable climate variability and change. In section three, the emphasis shifts towards actions to reduce GHG plus related emissions, within the context of environmental and health benefits. The co-benefits of reducing GHG plus related emissions includes the implications for ecosystems and biodiversity, environmental health (managed (forestry) and unmanaged (agriculture) systems), social welfare and human health. This discussion is based on research conducted on co-benefits as part of the multi-stakeholder process to develop a national strategy on climate change. The paper concludes by providing a preliminary assessment of the various mitigation options currently being proposed to help reach emission targets set out in the Kyoto Protocol, as they apply to the Toronto-Niagara Region. The assessment, which will be undertaken in greater depth as part of Phases III through V of the PERD supported project, considers the vulnerability of an altered energy system to climate change impacts, and the potential co-benefits for environment and health This includes changes brought about by fossil fuel switching, the inter-provincial transmission of electricity, alternative technologies, and energy efficiency, amongst other mitigation actions. (author)

Hydrogen absorption in epitaxial W/Nb(001) and polycrystalline Fe/Nb(110) multilayers studied in-situ by X-ray/neutron scattering techniques and X-ray absorption spectroscopy

International Nuclear Information System (INIS)

Klose, F.; Rehm, C.; Fieber-Erdmann, M.; Holub-Krappe, E.; Bleif, H. J.; Sowers, H.; Goyette, R.; Troger, L.; Maletta, H.

1999-01-01

Hydrogen can be absorbed in large quantities by 100 A thin Nb layers embedded in epitaxial W/Nb and polycrystalline Fe/Nb multilayers. The solubility and the hydrogen-induced structural changes of the host lattice are explored in-situ by small-angle neutron/X-ray reflectometry and high-angle diffraction. These measurements reveal for both systems that the relative out-of-plane expansion of the Nb layers is considerably larger than the relative increase of the Nb interplanar spacing indicating two distinctly different mechanisms of hydrogen absorption. In Fe/Nb multilayers, hydrogen expands the Nb interplanar spacing in a continuous way as function of the external pressure. In contrast, the Nb lattice expansion is discontinuous in epitaxial W/Nb multilayers: A jump in the Nb(002) Bragg reflection position occurs at a critical hydrogen pressure of 1 mbar. In-situ EXAFS spectroscopy also exhibits an irreversible expansion of the Nb lattice in the film plane for p H2 > 1 mbar. This can be regarded as a structural phase transition from an exclusively out-of-plane to a three-dimensionally expanded state at low and high hydrogen pressures, respectively

The influence of Zr substitution for Nb on the corrosion behaviors of the Ni-Nb-Zr bulk metallic glasses

Science.gov (United States)

Li, DengKe; Zhu, ZhengWang; Zhang, HaiFeng; Wang, AiMin; Hu, ZhuangQi

2012-12-01

The influence of Zr content on corrosion behaviors of the Ni61.5Nb38.5- x Zr x ( x=1, 3, 5, 7, 9 at.%) bulk metallic glasses (BMGs) in 1 M HCl aqueous solution was investigated by potentiodynamic polarization measurements and X-ray photo-electron spectroscopy (XPS). It was found that these BMG alloys possess superior corrosion resistance, that is, with large passive region of about 1.5 V and low passive current density (as low as 0.05 Am-2 for Ni61.5Nb31.5Zr7). XPS analysis indicates that the high corrosion resistance is attributed to the formation of Nb- and Zr-enriched surface films formed in the aggressive acid solution. The Zr substitution for Nb effectively reduces the Ni content, particularly the metallic state Ni content in the surface films, which depresses the electrical conduction of the surface films and reduces the passive current density, thus leading to the enhancement of the corrosion resistance of these Ni-Nb-Zr BMGs. These alloys may potentially be useful for engineering applications.

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.)

In situ NiTi/Nb(Ti) composite

International Nuclear Information System (INIS)

Jiang, Daqiang; Cui, Lishan; Jiang, Jiang; Zheng, Yanjun

2013-01-01

Graphical abstract: - Highlights: • In situ NiTi/Nb(Ti) composites were fabricated. • The transformation temperature was affected by the mixing Ti:Ni atomic ratios. • The NiTi component became micron-scale lamella after forging and rolling. • The composite exhibited high strength and high damping capacity. - Abstract: This paper reports on the creation of a series of in situ NiTi/Nb(Ti) composites with controllable transformation temperatures based on the pseudo-binary hypereutectic transformation of NiTi–Nb system. The composite constituent morphology was controlled by forging and rolling. It is found that the thickness of the NiTi lamella in the composite reached micron level after the hot-forging and cold-rolling. The NiTi/Nb(Ti) composite exhibited high damping capacity as well as high yield strength

Facile synthesis and characterization of hexagonal NbSe2 nanoplates

International Nuclear Information System (INIS)

Zhang, Xianghua; Zhang, Du; Tang, Hua; Ji, Xiaorui; Zhang, Yi; Tang, Guogang; Li, Changsheng

2014-01-01

Graphical abstract: - Highlights: • Uniform hexagonal NbSe 2 nanoplates were prepared by a simple solid state reaction. • The possible formation mechanism of the NbSe 2 nanoplates was discussed. • The formation of NbSe 2 nanoplates undergoes a series of phase transition. - Abstract: The NbSe 2 nanoplates with hexagonal morphology have been successfully prepared by a facile, environmentally friendly reaction in closed reactor at moderate temperature. The thermal (750 °C) solid-state reaction between the ball-milled mixture of micro-sized Nb and Se yielded a high yield of NbSe 2 nanoplates. The as-prepared products were characterized by XRD, EDS, and SEM. The results showed that the as-prepared products were hexagonal phase NbSe 2 nanoplates with uniform sizes and the formation of NbSe 2 nanoplates underwent a series of phase transition. On the basis of experimental results obtained at different temperatures, a reasonable reaction process and a formation mechanism were proposed. Moreover, the ball milling time played a crucial role in acquiring the homogeneous distribution nanoplates

Effect of nitrogen addition on superelasticity of Ti-Zr-Nb alloys

International Nuclear Information System (INIS)

Tahara, Masaki; Kim, Hee Young; Miyazaki, Shuichi; Inamura, Tomonari; Hosoda, Hideki

2008-01-01

Recently, the Ti-Zr-Nb alloys have been developed as Ni-free shape memory and superelastic alloys. In this study, the effect of Nb and nitrogen (N) contents on martensitic transformation behavior, shape memory effect and superelasticity in Ti-18Zr-(12-16)Nb-(0-1.0)N (at%) alloys were investigated using tensile tests, optical microscopy and X-ray diffraction. Shape memory effect was observed in Ti-18Zr-(12-13)Nb and Ti-18Zr-12Nb-0.5N alloys at room temperature. The superelastic behavior appeared by the increase of Nb or N content. The Ti-18Zr-(14-15)Nb, Ti-18Zr-(13-14)Nb-0.5N and Ti-18Zr-(12-14)Nb-1.0N alloys exhibited the superelasticity at room temperature. The martensitic transformation start temperature (M s ) decreased by 75 K with 1 at% increase of N content for Ti-18Zr-13Nb alloy. The critical stress for slip deformation and the stress for inducing the martensitic transformation increased with increasing N content. The superelastic recovery strain was also increased by adding N. The maximum recovery strain of 5.0% was obtained in the Ti-18Zr-14Nb-0.5N alloy. (author)

Tuning electronic structure and optical properties of SrTiO{sub 3} by site-specific doping by Nb with N/B from hybrid functional calculations

Energy Technology Data Exchange (ETDEWEB)

Liu, Yanyu; Zhou, Wei; Wu, Ping, E-mail: pingwu@tju.edu.cn

2017-07-01

In this study, the extensive density functional theory calculations are performed to modify the electronic structure of perovskite SrTiO{sub 3} by doping with Nb and N/B. The unoccupied states induced by the Nb monodoping at the Sr or Ti site, which were passivated in the codoped systems (the substitution of Nb at Ti site with the replacement of N at O site: Nb@Ti/N@O and the substitution of Nb at Sr site with the replacement of B at O site: Nb@Sr/B@O). The charge-compensated donor-acceptor pair codoping creates the new occupied states within the band gap, which yields the absorption edge extend to visible light. And the calculated defect formation energy implies that the codoped systems are energetically favorable under the O-rich condition. Moreover, the band-edge alignment confirmed that the Nb@Ti/N@O system is desirable for the spontaneous water splitting under visible light and the Nb@Sr/B@O system can split water into hydrogen in presence of sacrificial agent. - Highlights: • A systematical study has been employed on SrTiO{sub 3} with the donor-acceptor codoping. • The donor-acceptor pair codoping yields the absorption edge extend to visible light. • The formation energy implies that the codoped systems are favorable under the O-rich condition. • The Nb@Ti/N@O system is desirable for the spontaneous water splitting under visible light. • The Nb@Sr/B@O system can split water into hydrogen in presence of sacrificial agent.

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

On the role of Nb-related sites of an oxidized β-TiNb alloy surface in its interaction with osteoblast-like MG-63 cells

Energy Technology Data Exchange (ETDEWEB)

Jirka, Ivan, E-mail: Ivan.Jirka@jh-inst.cas.cz [J. Heyrovský Institute of Physical Chemistry, Acad. Sci. CR, v.v.i. Dolejškova 3, 182 23 Prague 8 (Czech Republic); Vandrovcová, Marta [Institute of Physiology, Acad. Sci. CR, v.v.i., Vídeňská 1083, Prague 4 (Czech Republic); Frank, Otakar [J. Heyrovský Institute of Physical Chemistry, Acad. Sci. CR, v.v.i. Dolejškova 3, 182 23 Prague 8 (Czech Republic); Tolde, Zdeněk [Faculty of Mechanical Engineering, Czech Technical University in Prague, Institute of Materials Engineering, Karlovo nám. 13, Prague 2 (Czech Republic); Plšek, Jan [J. Heyrovský Institute of Physical Chemistry, Acad. Sci. CR, v.v.i. Dolejškova 3, 182 23 Prague 8 (Czech Republic); Luxbacher, Thomas [Anton Paar GmbH, Anton Paar Str. 20, 8054 Graz (Austria); Bačáková, Lucie [Institute of Physiology, Acad. Sci. CR, v.v.i., Vídeňská 1083, Prague 4 (Czech Republic); Starý, Vladimír [Faculty of Mechanical Engineering, Czech Technical University in Prague, Institute of Materials Engineering, Karlovo nám. 13, Prague 2 (Czech Republic)

2013-04-01

β-Stabilized titanium (Ti) alloys containing non-toxic elements, particularly niobium (Nb), are promising materials for the construction of bone implants. Their biocompatibility can be further increased by oxidation of their surface. Therefore, in this study, the adhesion, growth and viability of human osteoblast-like MG 63 cells in cultures on oxidized surfaces of a β-TiNb alloy were investigated and compared with the cell behavior on thermally oxidized Ti, i.e. a metal commonly used for constructing bone implants. Four experimental groups of samples were prepared: Ti or TiNb samples annealed to 600 °C for 60 min in a stream of dry air, and Ti and TiNb samples treated in Piranha solution prior to annealing. We found that on all TiNb-based samples, the cell population densities on days 1, 3 and 7 after seeding were higher than on the corresponding Ti-based samples. As revealed by XPS and Raman spectroscopy, and also by isoelectric point measurements, these results can be attributed to the presence of T-Nb{sub 2}O{sub 5} oxide phase in the surface of the alloy sample, which decreased its negative zeta (ζ)-potential in comparison with zeta (ζ)-potential of the Ti sample at physiological pH. This effect was tentatively explained by the presence of positively charged defects acting as Lewis sites of the surface Nb{sub 2}O{sub 5} phase. Piranha treatment slightly decreases the biocompatibility of the samples, which for the alloy samples may be explained by a decrease in the number of defective sites with this treatment. Thus, the presence of Nb and thermal oxidation of β-stabilized Ti alloys play a significant role in the increased biocompatibility of TiNb alloys. - Highlights: ► T-Nb{sub 2}O{sub 5} and rutile are the main components of the oxidized β-TiNb alloy surface. ► Negative value of ζ potential is reduced by presence of Nb in the alloy surface. ► Less negative ζ potential is beneficial for interaction of the alloy with cells. ► The β-TiNb alloy

Mechanical properties of high-current multifilamentary Nb3Sn conductors

International Nuclear Information System (INIS)

Scanlan, R.M.; Hoard, R.W.; Cornish, D.N.; Zbasnik, J.P.

1980-01-01

Nb 3 Sn is a strain-sensitive superconductor which exhibits large changes in properties for strains of less than 1 percent. The critical current density at 12 T undergoes a reversible degradation of a factor of two for compressive strains of about 1 percent and undergoes an irreversible degradation for tensile strains on the Nb 3 Sn greater than 0.2 percent. Consequently, the successful application of Nb 3 Sn in large high-field magnets requires a complete understanding of the mechanical properties of the conductor. One conductor which is being used for many applications consists of filaments of Nb 3 Sn in a bronze matrix, and much progress has been made in understanding the mechanical behavior of this composite. The Nb 3 Sn filaments are placed in compression due to the differential thermal contraction between Nb 3 Sn and bronze which occurs when the composite is cooled from the Nb 3 Sn formation temperature (typically 700 0 C) to the 4.2 0 K operating temperature. The general behavior of the critical current when this conductor is subjected to a tensile stress is an increase to a maximum when the compressive strain on the Nb 3 Sn is relieved, followed by a decrease as the Nb 3 Sn filemants are placed in tension. The degree of precompression is controlled largely by the ratio of bronze to Nb 3 Sn in the conductor

Synthesis and phase transformation mechanism of Nb{sub 2}C carbide phases

Energy Technology Data Exchange (ETDEWEB)

Vishwanadh, B., E-mail: visubathula@gmail.com [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Murthy, T.S.R.Ch. [Materials Processing Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India); Arya, A.; Tewari, R.; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 094 (India)

2016-06-25

In the present work, Niobium carbide samples were prepared through powder metallurgy route using spark plasma sintering technique. Some of these samples were heat treated at 900 °C up to 7 days. In order to investigate the phase transformation in Nb{sub 2}C carbide, the as-prepared and heat treated samples were characterized by X-ray diffraction, scanning electron microscopy and electron back scattered diffraction (EBSD) and transmission electron microscopy techniques. EBSD could index the same area of the sample in terms of any of the three allotropes of Nb{sub 2}C carbide phases (γ-Nb{sub 2}C, β-Nb{sub 2}C and α-Nb{sub 2}C) with good confidence index. From the EBSD patterns orientation relationships (OR) among γ, β and α-Nb{sub 2}C have been determined. Based on this OR when crystals of the three allotropes were superimposed, it has revealed that the basic Nb metal atom lattice (hcp lattice) in all the Nb{sub 2}C phases is same. The only difference exists in the carbides is the ordering of carbon atoms and vacancies in the octahedral positions of the hcp Nb metal atom lattice. Crystallographic analysis showed that for the transformation of γ-Nb{sub 2}C → β-Nb{sub 2}C → α-Nb{sub 2}C, large movement of Nb atoms is not required; but only by ordering of carbon atoms ensues the phase transformation. Literature shows that in the Nb–C system formation of the α-Nb{sub 2}C is not well established. Therefore, first principle calculations were carried out on these carbides. It revealed that the formation energy for α-Nb{sub 2}C is lower than the β and γ-Nb{sub 2}C carbides which indicate that the formation of α-Nb{sub 2}C is thermodynamically feasible. - Highlights: • Nb{sub 2}C carbide was produced by Spark Plasma Sintering in a single process. • Phase transformation mechanism of different Nb{sub 2}C carbide phases is studied. • In all the three Nb{sub 2}C carbides (γ, β, α), the base Nb lattice remains same. • Among γ, β and α-Nb{sub 2}C

Highly smooth Nb surfaces fabricated by buffered electropolishing

International Nuclear Information System (INIS)

Wu, Andy T; John Mammossor; Phillips, H.; Jean Delayen; Charles Reece; Amy Wilkerson; David Smith; Robert Ike

2005-01-01

It is demonstrated that highly smooth Nb surfaces can be obtained through Buffered ElectroPolishing (BEP) employing an electrolyte consisting of lactic, sulfuric, and hydrofluoric acids. Parameters that control the polishing process are optimized to achieve the smoothest surface finish with the help of surface observations using a scanning electron microscope and a Metallographic Optical Microscope (MOM). The polishing rate of BEP is determined to be 0.646 (micro)m/min that is much higher than 0.381 (micro)m/min achieved by the conventional ElectroPolishing (EP) process widely used in the Superconducting Radio Frequency (SRF) community. A high precision and large scan area 3-D profilometer is used to view morphology of the treated Nb surfaces. Statistical data, such as, rms, total indicator runout, and arithmetic mean deviation of the Nb surfaces are extracted from the profilometer images. It is found that Nb surfaces treated by BEP are an order of magnitude smoother than those treated by the optimized EP process. The chemical composition of the Nb surfaces after BEP is analyzed by static and dynamic Secondary Ion Mass Spectrometer (SIMS) systems. Cracking patterns of the Nb surfaces under different primary ion sources of Ga + , Au + , and Ar + are reported. The depth profile of the surface niobium oxides is studied through continuously monitoring niobium and its relevant oxides' peaks as a function of time. Dynamic SIMS results imply that the surface oxide structure of Nb may be more complicated than what usually believed and can be inhomogeneous. Preliminary results of BEP on Nb SRF single cell cavities and half-cells are reported. It is shown that smooth and bright surfaces can be obtained in 30 minutes when the electric field inside a SRF cavity is uniform during a BEP process. This study reveals that BEP is a highly promising technique for surface treatment on Nb SRF cavities to be used in particle accelerators

Refining U-Zr-Nb alloys by remelting

Energy Technology Data Exchange (ETDEWEB)

Aguiar, B.M.; Kniess, C.T.; Riella, H.G., E-mail: bmaguiar@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ferraz, W.B. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2011-07-01

The high density U-Zr-Nb and U-Nb uranium-based alloys can be employed as nuclear fuel in a PWR reactor due to their high density and nuclear properties. These alloys can stabilize the gamma phase, however, according to TTT diagrams, at the working temperature of a PWR reactor, all gamma phase transforms to {alpha}'' phase in a few hours. To avoid this kind of transformation during the nuclear reactor operation, the U-Zr-Nb alloy and U-Nn are used in {alpha}'' phase. The stability of {alpha}'' phase depends on the alloy composition and cooling rate. The alloy homogenization has to be very effective to eliminate precipitates rich in Zr and Nb to avoid changes in the alloying elements contents in the matrix. The homogenization was obtained by remelting the alloy and keeping it in the liquid state for enough time to promote floating of the precipitates (usually carbides, less dense) and leaving the matrix free of precipitates. However, this floating by density difference may result in segregation between the alloying elements (Nb and Zr, at the top) and uranium (at the bottom). The homogenized alloys were characterized in terms of metallographic techniques, optical microscopy, scanning electronic microscopy, EDS and X-ray diffraction. In this paper, it is shown that the contents of Zr and Nb at the bottom and at the top of the matrix are constant. (author)

Stabilization of a Nb3Sn persistent current switch

International Nuclear Information System (INIS)

Urata, M.; Maeda, H.; Nakayama, S.; Yoneda, E.; Oda, Y.; Kumano, T.; Aoki, N.; Tomisaki, T.; Kabashima, S.

1993-01-01

A 2000 A class Nb 3 Sn persistent current switch has been successfully fabricated in the Toshiba R and D Center. The Nb tube processed conductor with Cu-10 wt.% Ni matrix has been developed for the switch in the Showa Electric Wire and Cable Co. Ltd. The magnetic instability which was observed in the previous 35 Ω Nb 3 Sn persistent current switch was improved in the present switch. The problem of quench current degradation and flux jump on magnetization, emerged in the previous switch, were confirmed to be solved. In the fast ramp, however, the switch degrades from the calculated results assuming the self field ac loss. In the Nb 3 Sn reaction process, Sn in the bronze diffuses into the Nb tube, which decreases the switch resistance. It was observed by a computer aided micro analysis (CMA) that Ni in the CuNi matrix precipitated on the Nb tube, which slightly reduced the switch resistance. (orig.)

Microstructure, mechanical properties and oxidation behaviors of magnetron sputtered NbN_x coatings

International Nuclear Information System (INIS)

Qi, Zhengbing; Wu, Zhengtao; Zhang, Dongfang; Zuo, Juan; Wang, Zhoucheng

2016-01-01

Mechanical properties and oxidation resistance are of importance for the NbN_x coatings as used in cutting and forming tools. In this study, the NbN_x coatings were deposited by magnetron sputtering at nitrogen partial pressure ranging from 0 to 40%. The chemical and phase compositions, morphologies, mechanical properties and oxidation behaviors of the NbN_x coatings were investigated by electron probe microanalysis, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, scanning and transmission electron microscopy, and nanoindentation measurements. The results reveal the composition evolution of the NbN_x coatings as α-Nb (0%), β-Nb_2N (5%), a mixture of β-Nb_2N and δ-NbN (10%), and δ-NbN (20–40%). The single phase coatings exhibit columnar structure while the mixed phases coating shows nano-composite structure. Compared with the single phase δ-NbN coatings (21.6 ± 0.8–28.0 ± 1.2 GPa), higher hardness of the single phase β-Nb_2N coating (30.9 ± 1.0 GPa) is due to the higher covalent character and much finer grains. The maximum hardness reaches 33.3 ± 1.5 GPa for the nano-composite coating with mixed phases of β-Nb_2N and δ-NbN. The oxidation results demonstrate that the activation energies are 219.3 and 192.3 kJ/mol for the Nb_2N and NbN coatings respectively. Non-protective Nb_2O_5 scales with cracks and pores result in poorer oxidation resistance of the NbN coating in comparison to the Nb_2N coating. - Highlights: • Chemical and phase compositions and microstructure of NbN_x coatings were investigated. • Maximum hardness is obtained for nano-composite coating with mixed Nb_2N and NbN phases. • Activation energies are 219.3 and 192.3 kJ/mol for oxidation of Nb_2N and NbN coatings. • Non-protective Nb_2O_5 scales with cracks and pores lower oxidation resistance of NbN coating.

Effect of thermo-mechanical processing on microstructure and mechanical properties of U - Nb - Zr alloys: Part 2 - U - 3 wt % Nb - 9 wt % Zr and U - 9 wt% Nb - 3 wt% Zr

Science.gov (United States)

Morais, Nathanael Wagner Sales; Lopes, Denise Adorno; Schön, Cláudio Geraldo

2018-04-01

The present work is the second and final part of an extended investigation on Usbnd Nb - Zr alloys. It investigates the effect of mechanical processing routes on microstructure of alloys U - 3 wt % Nb - 9 wt % Zr and U - 9 wt% Nb - 3 wt% Zr, through X-ray diffraction and scanning electron microscopy, completing the investigation, which started with alloy U - 6 wt% Nb - 6 wt% Zr in part 1. Mechanical properties are determined using microhardness and bending tests and correlated with the developed microstructures. The results show that processing sequence, in particular the inclusion of a 1000 °C heat treatment step, affects significantly the microstructure and mechanical properties of these alloys alloy in different ways. Microstructural characterization shows that both alloys present significant volume fraction of precipitates of a body-centered cubic (BCC) γ-Nb-Zr rich phase in addition the uranium-rich matrix. Bending tests show that sample ductility does not correlate necessarily with hardness and that the key factor appears to be the amount of the γ-Nb-Zr precipitates, which controls the matrix microstructure. Samples with a monoclinic α″ cellular microstructure and/or with the tetragonally-distorted BCC phase (γ0), although not strictly ductile, showed the largest allowed strains-before-break and complete elastic recovery of the broken pieces, pointing out to the macroscopic observation of superelasticity.

Direct measurements of inter-filament resistance in various multi-filamentary superconducting NbTi and Nb3Sn strands

NARCIS (Netherlands)

Zhou, Chao; Miyoshi, Y.; van Lanen, E.P.A.; Dhalle, Marc M.J.; Nijhuis, Arend

2012-01-01

For a proper characterization of multi-filamentary NbTi and Nb3Sn strands and a better understanding of their performance in short sample tests, as well as for increased understanding of inter-strand current redistribution in cabled conductors, a quantitative knowledge of the inter-filament

Directional solidification and characterization of the Al Nb2 - Al3 Nb eutectic system

International Nuclear Information System (INIS)

Trevisan, Eduardo A.O.; Andreotti, Fabio; Caram, Rubens

1996-01-01

The manufacturing of components to operate at high temperatures requires the use of metallic materials which can keep satisfactory mechanical and chemical properties, even at temperatures beyond 1000 deg C. An interesting alternative is the use of directionally solidified eutectic alloys. The eutectic alloy solidification makes possible the production of 'in situ' composite. A potentially useful system for manufacturing structural materials is the Al-Nb eutectic system. The aim of this work is to present the directional solidification of the Al-Nb eutectic alloy. (author)

NbCN Josephson junctions with AlN barriers

International Nuclear Information System (INIS)

Thomasson, S.L.; Murduck, J.M.; Chan, H.

1991-01-01

This paper reports on niobium carbonitride (NbCN) Josephson circuits which operate over a wider temperature range than either niobium or niobium nitride circuits. Higher operating temperature places NbCN technology more comfortably within the range of closed cycle refrigerators, a key factor in aerospace applications. We have fabricated tunnel junctions from NbCN films with transition temperatures up to 18 Kelvin. High quality NbCN tunnel junction fabrication generally requires low stress films with roughness less than the barrier thickness (∼20 Angstrom). We have developed scanning tunneling microscopy as a tool for measuring and optimizing film smoothness. Junctions formed in situ with AIN tunneling barriers show reproducible I-V characteristics

A review and prospects for Nb3Sn superconductor development

Science.gov (United States)

Xu, Xingchen

2017-09-01

Nb3Sn superconductors have significant applications in constructing high-field (>10 T) magnets. This article briefly reviews development of Nb3Sn superconductor and proposes prospects for further improvement. It is shown that significant improvement of critical current density (J c) is needed for future accelerator magnets. After a brief review of the development of Nb3Sn superconductors, the factors controlling J c are summarized and correlated with their microstructure and chemistry. The non-matrix J c of Nb3Sn conductors is mainly determined by three factors: the fraction of current-carrying Nb3Sn phase in the non-matrix area, the upper critical field B c2, and the flux line pinning capacity. Then prospects to improve the three factors are discussed respectively. An analytic model was developed to show how the ratios of precursors determine the phase fractions after heat treatment, based on which it is predicted that the limit of current-carrying Nb3Sn fraction in subelements is ∼65%. Then, since B c2 is largely determined by the Nb3Sn stoichiometry, a thermodynamic/kinetic theory is presented to show what essentially determines the Sn content of Nb3Sn conductors. This theory explains the influences of Sn sources and Ti addition on stoichiometry and growth rate of Nb3Sn layers. Next, to improve flux pinning, previous efforts in this community to introduce additional pinning centers to Nb3Sn wires are reviewed, and an internal oxidation technique is described. Finally, prospects for further improvement of non-matrix J c of Nb3Sn conductors are discussed, and it is seen that the only opportunity for further significantly improving J c lies in improving flux pinning.

Microstructure and mechanical properties of as-cast Zr-Nb alloys.

Science.gov (United States)

Kondo, Ryota; Nomura, Naoyuki; Suyalatu; Tsutsumi, Yusuke; Doi, Hisashi; Hanawa, Takao

2011-12-01

On the basis of the microstructures and mechanical properties of as-cast Zr-(0-24)Nb alloys the effects of phase constitution on the mechanical properties and magnetic susceptibility are discussed in order to develop Zr alloys for use in magnetic resonance imaging (MRI). The microstructures were evaluated using an X-ray diffractometer, an optical microscope, and a transmission electron microscope; the mechanical properties were evaluated by a tensile test. The α' phase was dominantly formed with less than 6 mass% Nb content. The ω phase was formed in Zr-(6-20)Nb alloys, but disappeared from Zr-22Nb. The β phase dominantly existed in Zr-(9-24)Nb alloys. The mechanical properties as well as the magnetic susceptibility of the Zr-Nb alloys varied depending on the phase constitution. The Zr-Nb alloys consisting of mainly α' phase showed high strength, moderate ductility, and a high Young's modulus, retaining low magnetic susceptibility. Zr-Nb alloys containing a larger volume of ω phase were found to be brittle and, thus, should be avoided, despite their low magnetic susceptibility. When the Zr-Nb alloys consisted primarily of β phase the effect of ω phase weakened the mechanical properties, thereby leading to an increase in ductility, even with an increase in magnetic susceptibility. The minimum value of Young's modulus was obtained for Zr-20Nb, because this composition was the phase boundary between the β and ω phases. However, the magnetic susceptibility of the alloy was half that of Ti-6Al-4V alloys. Zr-Nb alloys consisting of α' or β phase have excellent mechanical properties with low magnetic susceptibility and, thus, these alloys could be useful for medical devices used in MRI. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fabrication and microstructure of CNTs activated sintered W–Nb alloys

International Nuclear Information System (INIS)

Sha, J.J.; Hao, X.N.; Li, J.; Wang, Z.

2014-01-01

Highlights: • Fabrication and microstructure of CNTs activated sintered W-Nb alloys were investigated. • CNTs could significantly enhance the sintering ability of W-Nb alloys at a low temperature. • The improved sintering was due to the enhanced diffusion of W atoms along the GBs induced by CNTs. • The grain size in CNTs activated sintered W-Nb alloys decreased with increasing the Nb content. -- Abstract: In order to fabricate highly dense W-based alloys at low temperature, in the present work, high-energy ball milling and hot pressing were applied to fabricate W–Nb alloys (mass fraction of Nb varied from 0.5% to 5%), where CNTs were used as the activated sintering additives. The phase composition and microstructure were characterized by XRD and SEM equipped with EDS, respectively. The study found coupled effects of CNTs activated sintering and Nb addition on the enhanced sintering ability and refined microstructure of W at 1500 °C. The main results are: (i) XRD characterization revealed that the high-energy ball milling could significantly reduce the crystallite size of W particles and increase lattice distortion, which would enhance the sintering behavior of W alloys. (ii) The addition of CNTs to W (W–0.1CNTs) led to the formation of nanoscale interfacial layer between W grains during hot pressing, resulting in considerable densification and grain growth. Based on this result, it suggested that the activated sintering of W in the present work is due to an enhanced diffusion of W atoms along the GBs induced by CNTs. (iii) With the addition of CNTs to W–Nb alloys, the densification was improved again, but was not so obvious. The optimal densification was obtained for the W–0.1CNTs–1Nb specimen. Moreover, the microstructure characterization in CNTs activated sintered W–Nb alloys indicated that the distribution of sphere-like W(Nb) solid solution particles and decreased W grain sizes with increasing Nb content are the main microstructure features

Nb3Sn for Radio Frequency Cavities

International Nuclear Information System (INIS)

Godeke, A.

2006-01-01

In this article, the suitability of Nb3Sn to improve the performance of superconducting Radio-Frequency (RF) cavities is discussed. The use of Nb3Sn in RF cavities is recognized as an enabling technology to retain a very high cavity quality factor (Q0) at 4.2 K and to significantly improve the cavity accelerating efficiency per unit length (Eacc). This potential arises through the fundamental properties of Nb3Sn. The properties that are extensively characterized in the literature are, however, mainly related to improvements in current carrying capacity (Jc) in the vortex state. Much less is available for the Meissner state, which is of key importance to cavities. Relevant data, available for the Meissner state is summarized, and it is shown how this already validates the use of Nb3Sn. In addition, missing knowledge is highlighted and suggestions are given for further Meissner state specific research

Long-term side effects of radiotherapy for pediatric localized neuroblastoma. Results from clinical trials NB90 and NB94

Energy Technology Data Exchange (ETDEWEB)

Ducassou, Anne [Institut Claudius Regaud, Departement de Radiotherapie, Toulouse (France); Gambart, Marion; Munzer, Caroline; Rubie, Herve [Hopital des Enfants, Departement d' Onco-Hematologie Pediatrique, Toulouse (France); Padovani, Laetitia [Centre Hospitalier et Universitaire, Departement de Radiotherapie, Marseille (France); Carrie, Christian; Claude, Line [Centre Leon Berard, IHOP, Departement de Radiotherapie, Lyon (France); Haas-Kogan, Daphne [University of California, Department of Radiation Oncology, San Francisco (United States); Bernier-Chastagner, Valerie [Centre Alexis Vautrin, Departement de Radiotherapie, Nancy (France); Demoor, Charlotte [Centre Rene Gauducheau, Departement de Radiotherapie, Nantes (France); Helfre, Sylvie [Institut Curie, Departement de Radiotherapie, Paris (France); Bolle, Stephanie [Institut Gustave Roussy, Departement de Radiotherapie, Villejuif (France); Leseur, Julie [Centre Eugene Marquis, Departement de Radiotherapie, Rennes (France); Huchet, Aymeri [Centre Hospitalier et Universitaire, Departement de Radiotherapie, Bordeaux (France); Valteau-Couanet, Dominique [Institut Gustave Roussy, Departement d' Onco-Hematologie Pediatrique, Villejuif (France); Schleiermacher, Gudrun [Institut Curie, Departement d' Onco-Hematologie Pediatrique, Paris (France); Coze, Carole [Aix-Marseille Univ et APHM, Hopital d' Enfants de la Timone, Departement d' hemato-Oncologie Pediatrique, Marseille (France); Defachelles, Anne-Sophie [Centre Oscar Lambret, Departement d' Onco-Hematologie Pediatrique, Lille (France); Marabelle, Aurelien [IHOP, Departement d' Onco-Hematologie Pediatrique, Lyon (France); Ducassou, Stephane [Hopital des Enfants, Departement d' Onco-Hematologie Pediatrique, Bordeaux (France); Devalck, Christine [Hopital des enfants Reine Fabiola, Departement d' Onco-hematologie Pediatrique, Bruxelles (Belgium); Gandemer, Virginie [Centre hospitalier, Departement d' Onco-Hematologie Pediatrique, Rennes (France); Munzer, Martine [Centre hospitalier, Departement d' Onco-hematologie Pediatrique, Reims (France); Laprie, Anne [Institut Claudius Regaud, Departement de Radiotherapie, Toulouse (France); Universite Toulouse III Paul Sabatier, Toulouse (France); INSERM, Toulouse (France); Collaboration: Neuroblastoma study group and radiotherapy group of the French Society of Children with Cancer (SFCE)

2015-07-15

Neuroblastoma (NB) is the most frequent indication for extracranial pediatric radiotherapy. As long-term survival of high-risk localized NB has greatly improved, we reviewed treatment-related late toxicities in pediatric patients who received postoperative radiotherapy (RT) for localized NB within two French prospective clinical trials: NB90 and NB94. From 1990-2000, 610 children were enrolled. Among these, 35 were treated with induction chemotherapy, surgery, and RT. The recommended RT dose was 24 Gy at ≤ 2 years, 34 Gy at > 2 years, ± a 5 Gy boost in both age groups. The 22 patients still alive after 5 years were analyzed. The median follow-up time was 14 years (range 5-21 years). Late effects after therapy occurred in 73 % of patients (16/22), within the RT field for 50 % (11/22). The most frequent in-field effects were musculoskeletal abnormalities (n = 7) that occurred only with doses > 31 Gy/1.5 Gy fraction (p = 0.037). Other effects were endocrine in 3 patients and second malignancies in 2 patients. Four patients presented with multiple in-field late effects only with doses > 31 Gy. After a median follow-up of 14 years, late effects with multimodality treatment were frequent. The most frequent effects were musculoskeletal abnormalities and the threshold for their occurrence was 31 Gy. (orig.) [German] Das Neuroblastom (NB) ist die haeufigste Indikation fuer eine extrakranielle paediatrische Strahlentherapie. Da sich beim lokalisierten Hochrisiko-NB das langfristige Ueberleben stark verbessert hat, ueberprueften wir die behandlungsbedingte spaete Toxizitaet bei paediatrischen Patienten, die im Rahmen zweier prospektiver klinischer Studien in Frankreich (NB90 und NB94) eine postoperative Strahlentherapie (RT) bei lokalisiertem NB erhalten hatten. Von 1990-2000 wurden 610 Kinder eingeschlossen. Von diesen wurden 35 mit Chemotherapie, Chirurgie und RT behandelt. Die empfohlene Bestrahlungsdosis war 24 Gy bei ≤ 2 Jahren, 34 Gy bei > 2 Jahren, ± 5-Gy

Evaluation of the 93Nb (n,n')93mNb reaction cross section from the threshold up to 20 MeV

International Nuclear Information System (INIS)

Badikov, S.A.; Zolotarev, K.I.; Pashchenko, A.B.

1992-01-01

The data base comprising the results of the 93 Nb(n,n') 93m Nb reactions cross section measurements up to 1991 has been compiled. The experimental data have been renormalized to new values of standard cross-sections from the ENDF/B-6 and the IRDF-90 libraries. The evaluation of excitation function for the 93 Nb(n,n') 93m Nb reaction was carried out on the basis of procedure taking the correlation of experimental data into account. The files of evaluated cross-sections and covariance were prepared in the ENDF/B-6 format. The cross-section evaluations from present work and the IRDF-90 library are compared. 37 refs.; 3 figs.; 6 tabs

Comparative Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP

International Nuclear Information System (INIS)

Liu, H W; Richard, P; Zhao, L X; Chen, G-F; Ding, H

2016-01-01

We report a comparative polarized Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP. The evolution of the phonon frequencies with the sample composition allows us to determine experimentally which atoms are mainly involved for each vibration mode. Our results confirm previous first-principles calculations indicating that the A 1 , B 1 (2), E(2) and E(3) modes involve mainly the As(P) atoms, the B 1 (1) mode is mainly related to Ta(Nb) atoms, and the E(1) mode involves both kinds of atoms. By comparing the energy of the different modes, we establish that the B 1 (1), B 1 (2), E(2) and E(3) become harder with increasing chemical pressure. This behaviour differs from our observation on the A 1 mode, which decreases in energy, in contrast to its behaviour under external pressure. (paper)

The use of Nb in rapid solidified Al alloys and composites

Energy Technology Data Exchange (ETDEWEB)

Audebert, F., E-mail: metal@fi.uba.ar [Advanced Materials Group, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, Ciudad de Buenos Aires 1063 (Argentina); Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Department of Mechanical Engineering and Mathematical Sciences, Oxford Brookes University, Wheatley Campus, OX33 1HX Oxford (United Kingdom); Galano, M. [Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Saporiti, F. [Advanced Materials Group, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, Ciudad de Buenos Aires 1063 (Argentina)

2014-12-05

Highlights: • The use of Nb in RS Al alloys and composites has been reviewed. • Nb was found to improve the GFA of rapid solidified Al–Fe and Al–Ni alloys. • Nb has higher effect in increasing the corrosion resistance than RE in Al–Fe alloys. • Nb improves the stability of the Al–Fe–Cr icosahedral phase. • Nb improves strength, ductility and toughness of nanoquasicrystalline Al matrix composites. - Abstract: The worldwide requirements for reducing the energy consumption and pollution have increased the demand of new and high performance lightweight materials. The development of nanostructured Al-based alloys and composites is a key direction towards solving this demand. High energy prices and decreased availability of some alloying elements open up the opportunity to use non-conventional elements in Al alloys and composites. In this work the application of Nb in rapid solidified Al-based alloys and Al alloys matrix composites is reviewed. New results that clarify the effect of Nb on rapid solidified Al alloys and composites are also presented. It is observed that Nb stabilises the icosahedral Al–Fe/Cr clusters, enhances the glass forming ability and shifts the icosahedral phase decomposition towards higher temperatures. Nb provides higher corrosion resistance with respect to the pure Al and Al–Fe–RE (RE: rare earth) alloys in the amorphous and crystalline states. The use of Nb as a reinforcement to produce new Al alloy matrix composites is explored. It is observed that Nb provides higher strength, ductility and toughness to the nanoquasicrystalline matrix composite. Nb appears as a new key element that can improve several properties in rapid solidified Al alloys and composites.

Properties of idealized designs of NB3SN composites

International Nuclear Information System (INIS)

Smathers, D.B.; Larbalestier, D.C.; Lee, P.J.; Marken, K.R.; McDonald, W.K.; O'Larey, P.M.

1985-01-01

A series of seven idealized bronze-Nb 3 Sn composites were manufactured by the MJR process with varying matrix to filament ratios and pure Nb and Nb 0.8 wt.% Ti cores. The central core of each composite was sealed by a diffusion barrier which results in each filament having an identical source of tin. Initial evaluations of the composites from critical current and transmission electron microscopy measurements are presented and their properties compared to standard MJR composites. The Nb 3 Sn current density does not appear to be a strong function of bronze to Nb ratio over the range 2.4 to 3.2:1. The standard MJR composites have higher critical current densities than the idealized composites. It is proposed that the major reason for the increased current density of the normal MJR conductors is the intrinsically higher quality of the filaments close to the central tin core. It is postulated that the high Sn content of the bronze surrounding these filaments leads to an intrinsically higher Nb 3 Sn filament current density

Solubilization and precipitation of {omega} and {alpha} phases in Ti-30 Nb and Ti-35 Nb alloys; Solubilizacao e precipitacao de fases {omega} e {alpha} nas ligas Ti-30Nb e Ti-35Nb

Energy Technology Data Exchange (ETDEWEB)

Hayama, A.O.F.; Lopes, J.F.S.C.; Caram, R., E-mail: alexandrah@fem.unicamp.b [Universidade Estadual de Campinas (DEMa/FEM/UNICAMP), SP (Brazil). Fac. de Engenharia Mecanica. Dept. de Engenharia de Materiais

2010-07-01

This work presents the main results of the characterization of Ti-30Nb and Ti-35Nb alloys (wt%) submitted to the solutioning heat treatment following by aging. Samples were obtained by electric arc melting, followed by solution heat treatment at 1000 deg C during 8 hours and cooling in water, the microstructure obtained is formed by {beta} and {alpha} phases. Samples were aged at 260 and 400 deg C during periods of time varying from 1 to 240 min. Characterization was performed using light optical microscopy, X-ray diffraction, Young's modulus measurements by acoustic emission and Vickers hardness. The results show the presence of {beta} and {alpha}{sup '}' phases in samples of the Ti-30Nb alloy aged at 260 deg C. In samples aged at 400 deg C, precipitation of {omega} and {alpha}{sup '}' phases took place, and due to this fact, an increase in Young's modulus and in hardness occurred. (author)

Amorphization of Fe-Nb by mechanical alloying

International Nuclear Information System (INIS)

Yang, J.Y.; Zhang, T.J.; Cui, K.; Li, X.G.; Zhang, J.

1996-01-01

Elemental powder mixtures of Fe x Nb 1-x were mechanically alloyed in a planetary ball mill. Powders milled for different times were characterized by X-ray diffraction, transmission and scanning electron microscopy, differential thermal analysis and microhardness measurement. The results show that powders with 0.30≤x≤0.70 could be amorphized after 30 h milling; the maximum hardness (Hv) of milled Fe 50 Nb 50 powders attained was 1490. Based on a thermodynamical analysis, the glass forming range of the Fe-Nb system was calculated, and found to agree with the experimental result very well. (orig.)

Thermomechanical processing of In-containing β-type Ti-Nb alloys.

Science.gov (United States)

Pilz, Stefan; Geissler, David; Calin, Mariana; Eckert, Jürgen; Zimmermann, Martina; Freudenberger, Jens; Gebert, Annett

2018-03-01

In this study, the effect of thermomechanical processing on microstructure evolution of the indium-containing β-type Ti alloys (Ti-40Nb)-3.5In and (Ti-36Nb)-3.5In was examined. Both alloys show an increased β-phase stability compared to binary alloys due to In additions. This leads to a reduced α''-phase fraction in the solution treated and recrystallized state in the case of (Ti-36Nb)-3.5In and to the suppression of stress-induced α'' formation and deformation twinning for (Ti-40Nb)-3.5In. The mechanical properties of the alloys were subsequently studied by quasistatic tensile tests in the recrystallized state, revealing reduced Young's modulus values of 58GPa ((Ti-40Nb)-3.5In) and 56GPa ((Ti-36Nb)-3.5In) compared to 60GPa as determined for Ti-40Nb. For both In-containing alloys the ultimate tensile strength is in the range of 560MPa. Due to the suppressed α'' formation, (Ti-40Nb)-3.5In exhibits a linear elastic deformation behavior during tensile loading together with a low Young's modulus and is therefore promising for load-bearing implants. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structure modification of Mg-Nb films under hydrogen sorption cycles

Energy Technology Data Exchange (ETDEWEB)

Mengucci, P., E-mail: p.mengucci@univpm.it [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Barucca, G.; Majni, G. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Bazzanella, N.; Checchetto, R.; Miotello, A. [Dipartimento di Fisica, Universita di Trento, Via Sommarive, I-38123 Povo (Italy)

2011-09-15

Research highlights: > Influence of Nb additions on the hydrogen kinetics of Mg layers. > Structure modification of the Mg matrix during hydrogen cycling. > Lattice strains induced by Nb tends to decrease during hydrogen cycling. > Nb nanoparticles form during hydrogen cycling. > Nb enhances the porous structure of the Mg layer formed during hydrogen cycling. - Abstract: In the present work we focus our attention on the structural modifications induced by repeated absorption/desorption cycles on Mg-Nb layers. Samples consisting of a 30 {mu}m thick pure Mg or Mg-5 at.% Nb doped films, coated with a 20 nm thick Pd layer were submitted to repeated H{sub 2} sorption cycles in a volumetric apparatus. Isothermal desorption analysis at 350 deg. C was performed to evaluate the amount of absorbed hydrogen. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and electron microscopy techniques (SEM and TEM) were used for the structural characterisation of the samples. Analyses show a deep modification of the material upon cycling. The presence of Nb enhances the structural modifications and induces an initial lattice contraction of the Mg matrix that tends to decrease on cycling via the formation of Nb nanoparticles (with average size of {approx}10 nm). SEM and TEM observations performed in cross section evidenced the formation of a porous structure.

Some new experimental results on the Zr-Nb-Fe system

Energy Technology Data Exchange (ETDEWEB)

Ramos, C. [Departamento de Fisica - CAC - Comision Nacional de Energia Atomica, Av. Gral Paz 1499, (1650) San Martin, Buenos Aires (Argentina)]. E-mail: ciramos@cnea.gov.ar; Saragovi, C. [Departamento de Fisica - CAC - Comision Nacional de Energia Atomica, Av. Gral Paz 1499, (1650) San Martin, Buenos Aires (Argentina); Granovsky, M.S. [Departamento de Materiales - CAC - Comision Nacional de Energia Atomica, Av. Gral Paz 1499, (1650) San Martin, Buenos Aires (Argentina)

2007-06-30

The scope of this study is the identification and characterization of intermetallic phases and their binary and ternary fields in the Zr-Nb-Fe phase diagram. A construction of the central region of the phase diagram at 900 {sup o}C was proposed using new experimental results obtained by optical and scanning electron microscopies, X-ray diffraction and microprobe analysis. In addition to the well-known Laves C15-type (ZrNb)Fe{sub 2} phase (the polytypic C14 and C36 structures were not detected in the studied compositions), another Laves C14-type phase was found (Zr(NbFe){sub 2}). Watson and Bennett maps helped to predict the occurrence of both of these phases. Moreover, the validity of the Pettifor prediction model for Laves phases in pseudobinary systems with transition elements was checked, verifying the obtained experimental results in the Zr-Nb-Fe system. On the other hand it was determined that the Zr-Nb-Fe ternary system at 900 {sup o}C, as it happens in the binary Zr-Nb system, would have a miscibility gap ({beta}-Zr + {beta}-Nb) in the 25-70 at.% Nb composition range, accepting up to 3 at.% Fe approximately.

Rietveld refinement and dielectric relaxation of a new rare earth based double perovskite oxide: BaPrCoNbO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Bharti, Chandrahas, E-mail: bharti.chandrahas@gmail.com [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Das, Mrinmoy K.; Sen, A. [Sensor and Actuator Division, CSIR-Central Glass and Ceramic Research Institute, 196, Raja SC Mullick Road, Kolkata 700032 (India); Chanda, Sadhan; Sinha, T.P. [Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata-700009 (India)

2014-02-15

A new rare earth based double perovskite oxide barium praseodymium cobalt niobate, BaPrCoNbO{sub 6} (BPCN) is synthesized by solid-state reaction technique. Rietveld analysis of X-ray diffraction (XRD) data shows that the compound crystallizes in a perovskite like tetragonal structure which belongs to the I4/mmm space group with lattice parameters a=b=5.6828(9) Å, c=8.063(2) Å. Structural analysis reveals 1:1 ordered arrangement for the Co{sup 2+} and Nb{sup 5+} cations over the six-coordinate B-sites of BPCN. The superlattice line (1 0 1) at 2θ=19.10° arising from the alternate ordering of Co{sup 2+} and Nb{sup 5+} sites is observed in the XRD pattern which confirms the presence of cation ordering in BPCN. Fourier transform infrared spectrum shows two phonon modes of the sample due to the antisymmetric NbO{sub 6} stretching vibration. The relaxation dynamics of the conductive process in BPCN is investigated in the temperature range 303 to 503 K and in the frequency range 100 Hz to 1 MHz using impedance spectroscopy. The relaxation mechanism of the sample in the framework of electric modulus formalism is modeled by Davidson–Cole model (DCM). The values of α (distribution of relaxation time) for the DCM varies from 0.1 to 0.3 which suggests the asymmetric distribution of relaxation time for BPCN. The activation energy of the sample, calculated from both conductivity and modulus spectra, are found to be almost the same ∼0.4 eV, which indicates that the conduction mechanism for BPCN is polaron hopping. The scaling behaviour of the imaginary part of electric modulus suggests that the relaxation follows the same mechanism at various temperatures. - Graphical abstract: Rietveld refinement plot for BPCN. Inset shows the schematic presentation of the BPCN tetragonal unit cell. The Co{sup 2+} atoms are located at the centers of the CoO{sub 6} (blue) octahedra. The Nb{sup 5+} atoms are located at the centers of the NbO{sub 6} (green) octahedra. Display Omitted

Influence of microstructure on the accelerated corrosion in Zr-Nb alloys

International Nuclear Information System (INIS)

Muller, S; Lanzani, L

2012-01-01

The influence of microstructure on the accelerated corrosion of Zr-1%Nb and Zr-2.5%Nb (CANDU's pressure tube material) has been studied. The behavior of Zircaloy-4 was also studied in order to compare the Zr-Nb alloys with an alloy that does not have niobium as an alloying element. The corrosion tests were carried out in LiOH 0.1M at 340 o C, in LiOH 1M at the same temperature and in steam at 400 o C. The results showed that the behavior of Zr-Nb alloys in steam at 400 o C is similar to that of Zircaloy-4 in this medium. However, Zr-Nb alloys are more sensitive than Zircaloy-4 to the presence of LiOH. The results suggest that the niobium concentration in the matrix is the parameter that defines the oxidation rate in Zr-Nb alloys, while the presence of second phases in these alloys (β--Zr/β-Nb/Zr-Nb-Fe) could be related with the growth of non-protective oxides in LiOH solutions. In LiOH 1M, the corrosion resistance of Zr-Nb alloys is similar to that of Zircaloy-4, except for the Zr-1Nb martensitic material which showed a sharp increase in the oxidation rate in this medium (author)

Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

Science.gov (United States)

Li, Kun; Li, Yan; Huang, Xu; Gibson, Des; Zheng, Yang; Liu, Jiao; Sun, Lu; Fu, Yong Qing

2017-08-01

Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb2O5. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (Ecorr) and lower corrosion current densities (icorr) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of Ecorr and icorr was found among the Ni-Ti-Nb films.

Reguladores vegetais influenciando número e tamanho de células das bagas da uva 'Niagara Rosada' Plant regulators influencing number and size of berry cells of 'Niagara Rosada' grapes

Directory of Open Access Journals (Sweden)

Cássia Regina Yuriko Ide Vieira

2008-03-01

Full Text Available O objetivo do trabalho foi avaliar o efeito do ácido giberélico, thidiazuron e quinmerac na anatomia das bagas de uvas cultivar 'Niagara Rosada', provenientes de vinhedo localizado em Dourados - MS. Realizaram-se três experimentos. No primeiro ensaio, utilizaram-se soluções aquosas de ácido giberélico (AG3 0; 15; 30; 45; 60; 75 e 90 mg.l-1, aplicadas no florescimento e repetidas aos 14 dias após (E1E2 e, no outro tratamento, o mesmo composto e doses aplicados uma única vez aos 14 dias após o florescimento (E2; no segundo experimento, thidiazuron (TDZ 0; 5; 10; 15; 20; 25 e 30 mg.l-1, aplicados quatro dias antes da antese e repetidos aos seis dias após o florescimento (E1E2; e no outro tratamento, o mesmo composto e doses aplicados uma única vez aos seis dias após o florescimento (E2; e, no terceiro, quinmerac 0; 10; 20; 30; 40; 50 e 60 mg.l-1, aplicados no florescimento e repetidos aos 14 dias após (E1E2, e, no outro tratamento, o mesmo composto e doses aplicados uma única vez, 14 dias após o florescimento (E2. As variáveis avaliadas foram: número e dimensões das células das bagas. Pelos resultados obtidos, verificou-se que duas aplicações de ácido giberélico, thidiazuron e quinmerac promoveram a divisão celular, enquanto a expansão celular foi observada com uma única aplicação de thidiazuron e quinmerac.The objective of this investigation was to evaluate the effect of the gibberellic acid, thidiazuron and quinmerac on grape berries anatomy of grapevine 'Niagara Rosada', in a vineyard located in Dourados - MS. Three trials were carried out. In the first trial, it was used gibberellic acid (AG3 0, 15, 30, 45, 60, 75 and 90 mg.l-1, applied in the bloom and repeated 14 days later (E1E2 and in the other treatment, the same compound and doses applied only once, 14 days after the bloom (E2; in the second experiment, thidiazuron (TDZ 0, 5, 10, 15, 20, 25 and 30 mg.l-1, applied four days before antesis and repeated six days

Phase characterization of Re-based diffusion barrier layer on Nb substrate

International Nuclear Information System (INIS)

Sugiarti, Eni; Wang, Youngmin; Hashimoto, Naoyuki; Ohnuki, Somei; Narita, Toshio

2011-01-01

An electron microscopy phase characterization was carried out for a Re-based diffusion barrier layer, which was deposited on the Nb substrate used as an ultra high temperature material. The coating process produced three layers; an outer Cr(Re) layer, an intermediate Cr-Nb-Re layer, and an inner Nb(Re) layer. The Cr-Nb-Re layer is considered to act as a diffusion barrier layer between the substrate and the outer Cr(Re) reservoir layer. The Cr(Re) and Nb(Re) layers are in single phase with a similar bcc structures, but they are different in structure from the intermediate layer, which is composed of a dual phase of Re 63 Cr 20 Nb 17 with a cubic structure and Nb 42 Re 33 Cr 25 with a hexagonal structure determined by transmission electron microscopy (TEM) in this study. (author)

Study of microstructure and superconducting properties of Nb3Al-tapes, obtained by heat treatment of three-layer and multilayer composites Nb/AlCu

International Nuclear Information System (INIS)

Korzhov, Valeriy P.

2012-01-01

The structure and superconductivity of three- and multilayer composite tapes of Nb/AlCu after high- temperature heating at 1750-1850 0 C for 1-3 seconds were investigated. Three-layer composites of Nb/AlCu/Nb with thickness of 50 microns were obtained by applying a vacuum rolling at 400-450 0 C and subsequent rolling at room temperature. Multilayer lengthy composites of Nb/AlCu obtained by extrusion with subsequent flattening by rolling of complex blank, collected in a special way. The effect of copper on the structure and properties of three-layer tapes was investigated. Copper increased the critical current of the superconductor. The critical current density in multilayered Nb 3 Al-tape reaches the value 8.10 4 A/cm 2 in magnetic field 14 T. The critical bending radius of the tape is 7 mm. Key words: multilayer composite tape, extrusion, rolling, superconducting Nb 3 Al-tape, high- temperature heat treatment, critical current density

Progress of Bep Treatments on Nb at JLAB

International Nuclear Information System (INIS)

Wu, A.T.; Jin, S.; Rimmer, R.A.; Lu, X.Y.; Zhao, K.

2010-01-01

Recent experimental results have indicated that Buffered Electropolishing (BEP) is a promising candidate for the next generation of surface treatment technique for Nb superconducting radio frequency (SRF) cavities to be used in particle accelerators. In order to lay the foundation for using BEP as the next generation surface treatment technique for Nb SRF cavities, some fundamental aspects of BEP treatments for Nb have to be investigated. In this report, recent progress on BEP study at JLab is shown. Improvements on the existing vertical BEP are made to allow water cooling from outside of a Nb single cell cavity in addition to cooling provided by acid circulation so that the temperature of the cavity can be stable during processing. Some investigation on the electrolyte mixture was performed to check the aging effect of the electrolyte. It is shown that good polishing results can still be obtained on Nb at a current density of 171 mA/cm when the BEP electrolyte was at the stationary condition and was more than 1.5 years old.

NbN thin films for superconducting radio frequency cavities

Science.gov (United States)

Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

2012-12-01

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.

NbN thin films for superconducting radio frequency cavities

International Nuclear Information System (INIS)

Roach, W M; Clavero, C; Lukaszew, R A; Skuza, J R; Beringer, D B; Li, Z

2012-01-01

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m −1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed. (paper)

Synthesis of Nb doped TiO2 nanotube/reduced graphene oxide heterostructure photocatalyst with high visible light photocatalytic activity

Science.gov (United States)

Niu, Xiaoyou; Yan, Weijing; Zhao, Hongli; Yang, Jingkai

2018-05-01

Limited by the narrowed photoresponse range and unsatisfactory recombination of photoinduced electron-hole pairs, the photocatalytic efficiency of TiO2 is still far below what is expected. Here, we initially doped TiO2 nanotubes (TNTS) by transition metal ion Nb, then it is coupled with reduced graphene oxide (rGO) to construct a heterostructure photocatalyst. The defect state presented in TiO2 leading to the formation of localized midgap states (MS) in the bandgap, which regulating the band structure of TiO2 and extending the optical absorption to visible light region. The internal charge transport and transfer behavior analyzed by electrochemical impedance spectroscopy (EIS) reveal that the coupling of rGO with TNTS results in the formation of electron transport channel in the heterostructure, which makes a great contribution to the photoinduced charge separation. As expected, the Nb-TNTS/rGO exhibits a stable and remarkably enhanced photocatalytic activity in the visible-light irradiation degradation of methylene blue (MB), up to ∼5 times with respect to TNTS, which is attributed to the effective inhibition of charge recombination, the reduction of bandgap and higher redox potential, as well as the great adsorptivity.

Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

Energy Technology Data Exchange (ETDEWEB)

Li, Kun [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Huang, Xu [Memry Corporation, Bethel, CT 06801 (United States); Gibson, Des [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of the West of Scotland, Paisley PA1 2BE (United Kingdom); Zheng, Yang; Liu, Jiao; Sun, Lu [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Fu, Yong Qing, E-mail: richard.fu@northumbria.ac.uk [Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom)

2017-08-31

Highlights: • The corrosion resistance of Ni-Ti-Nb shape memory thin films is investigated. • Modified surface oxide layers improve the corrosion resistance of Ni-Ti-Nb films. • Further Nb additions reduce the potential corrosion tendency of the films. - Abstract: Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb{sub 2}O{sub 5}. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (E{sub corr}) and lower corrosion current densities (i{sub corr}) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of E{sub corr} and i{sub corr} was found among the Ni-Ti-Nb films.

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.

Synthesis and crystal structure of Mg{sub 0.5}NbO{sub 2}: An ion-exchange reaction with Mg{sup 2+} between trigonal [NbO{sub 2}]{sup -} layers

Energy Technology Data Exchange (ETDEWEB)

Miura, Akira, E-mail: amiura@yamanashi.ac.jp [Center for Crystal Science and Technology, University of Yamanashi (Japan); Takei, Takahiro; Kumada, Nobuhiro [Center for Crystal Science and Technology, University of Yamanashi (Japan)

2013-01-15

A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO{sub 2}]{sup -} layers. It is proposed to be isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc) with lattice parameters of a=2.9052(6) A, c=10.625(15) A. The lattice parameters and formation energy of Mg{sub 0.5}NbO{sub 2} crystallized in LiNbO{sub 2} form and other layered CaNb{sub 2}O{sub 4} one were calculated by density functional theory. - Graphical abstract: A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. It is isostructural with LiNbO{sub 2} with lattice parameters of a=2.9052(6) A, c=10.625(15) A. Mg{sup 2+} are described in spheres located between [NbO{sub 2}]{sup -} trigonal layers and its occupancy is 0.5. Highlights: Black-Right-Pointing-Pointer A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2}. Black-Right-Pointing-Pointer Cation-exchange reaction converted two monovalent Li{sup +} into one divalent Mg{sup 2+} at 450-550 Degree-Sign C. Black-Right-Pointing-Pointer Mg{sub 0.5}NbO{sub 2} was isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc). Black-Right-Pointing-Pointer Its lattice parameters were a=2.9052(6) A and c=10.625(15) A. Black-Right-Pointing-Pointer Synthesized Mg{sub 0.5}NbO{sub 2} was calculated to be thermodynamically more favorable.

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)

Dehydration of Glucose to 5-Hydroxymethylfurfural Using Nb-doped Tungstite

KAUST Repository

Yue, Chaochao; Li, Guanna; Pidko, Evgeny A.; Wiesfeld, Jan J.; Rigutto, Marcello; Hensen, Emiel J. M.

2016-01-01

Dehydration of glucose to 5-hydroxymethylfurfural (HMF) remains a significant problem in the context of the valorization of lignocellulosic biomass. Hydrolysis of WCl6 and NbCl5 leads to precipitation of Nb-containing tungstite (WO3H2O) at low Nb

High-luminosity blue and blue-green gallium nitride light-emitting diodes.

Science.gov (United States)

Morkoç, H; Mohammad, S N

1995-01-06

Compact and efficient sources of blue light for full color display applications and lighting eluded and tantalized researchers for many years. Semiconductor light sources are attractive owing to their reliability and amenability to mass manufacture. However, large band gaps are required to achieve blue color. A class of compound semiconductors formed by metal nitrides, GaN and its allied compounds AIGaN and InGaN, exhibits properties well suited for not only blue and blue-green emitters, but also for ultraviolet emitters and detectors. What thwarted engineers and scientists from fabricating useful devices from these materials in the past was the poor quality of material and lack of p-type doping. Both of these obstacles have recently been overcome to the point where highluminosity blue and blue-green light-emitting diodes are now available in the marketplace.

Microstructure, mechanical properties and oxidation behaviors of magnetron sputtered NbN{sub x} coatings

Energy Technology Data Exchange (ETDEWEB)

Qi, Zhengbing, E-mail: zbqi@xmut.edu.cn [College of Materials Science and Engineering, Xiamen University of Technology, Xiamen (China); Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen (China); Wu, Zhengtao; Zhang, Dongfang [Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen (China); Zuo, Juan [College of Materials Science and Engineering, Xiamen University of Technology, Xiamen (China); Wang, Zhoucheng, E-mail: zcwang@xmu.edu.cn [Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen (China)

2016-08-05

Mechanical properties and oxidation resistance are of importance for the NbN{sub x} coatings as used in cutting and forming tools. In this study, the NbN{sub x} coatings were deposited by magnetron sputtering at nitrogen partial pressure ranging from 0 to 40%. The chemical and phase compositions, morphologies, mechanical properties and oxidation behaviors of the NbN{sub x} coatings were investigated by electron probe microanalysis, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, scanning and transmission electron microscopy, and nanoindentation measurements. The results reveal the composition evolution of the NbN{sub x} coatings as α-Nb (0%), β-Nb{sub 2}N (5%), a mixture of β-Nb{sub 2}N and δ-NbN (10%), and δ-NbN (20–40%). The single phase coatings exhibit columnar structure while the mixed phases coating shows nano-composite structure. Compared with the single phase δ-NbN coatings (21.6 ± 0.8–28.0 ± 1.2 GPa), higher hardness of the single phase β-Nb{sub 2}N coating (30.9 ± 1.0 GPa) is due to the higher covalent character and much finer grains. The maximum hardness reaches 33.3 ± 1.5 GPa for the nano-composite coating with mixed phases of β-Nb{sub 2}N and δ-NbN. The oxidation results demonstrate that the activation energies are 219.3 and 192.3 kJ/mol for the Nb{sub 2}N and NbN coatings respectively. Non-protective Nb{sub 2}O{sub 5} scales with cracks and pores result in poorer oxidation resistance of the NbN coating in comparison to the Nb{sub 2}N coating. - Highlights: • Chemical and phase compositions and microstructure of NbN{sub x} coatings were investigated. • Maximum hardness is obtained for nano-composite coating with mixed Nb{sub 2}N and NbN phases. • Activation energies are 219.3 and 192.3 kJ/mol for oxidation of Nb{sub 2}N and NbN coatings. • Non-protective Nb{sub 2}O{sub 5} scales with cracks and pores lower oxidation resistance of NbN coating.

An evaluation of the Nb-93(n,n')Nb-93m dosimeter reaction for ENDF/B-VI

International Nuclear Information System (INIS)

Smith, D.L.; Geraldo, L.P.

1990-01-01

The Nb-93(n,n')Nb-93m reaction plays an important role in nuclear energy applications. Because of its low threshold energy and relatively long half-life, it is a desirable reaction for long-term neutron fluence dosimetry in nuclear fission reactors. An evaluation of the differential cross section for this reaction was completed in 1985 by this laboratory as part of a comprehensive effort involving all neutron cross sections for niobium. The objective was to provide input for ENDF/B-VI. It was difficult to produce a reliable evaluation for this reaction in 1985 because the information available then was sparse and quite uncertain. In fact, that evaluation was based entirely on nuclear model calculations. The evaluated cross sections below 0.7 MeV were derived from calculations carried out in this laboratory, while the higher energy values were obtained from the work of Strohmaier and co-workers. In 1985 there was only one published experimental differential cross section value to consider for this reaction. Even the half-life of Nb-93m was in serious doubt. During the five years between the completion of the earlier evaluation and the finalization of ENDF/B-VI there have been some significant improvements and additions to the experimental database for this reaction. Also, new model calculations have been performed. Therefore, it was considered worthwhile to produce a new evaluation of Nb-93(n,n')Nb-93m for ENDF/B-VI which would supplant the one that had been completed in 1985

Superconducting Nb{sub 3}Sn intermetallics made by electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} oxides

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B A; Fray, D J; Yan, X-Y; Chen, G

2003-05-01

The article is focused on low temperature superconducting Nb{sub 3}Sn material manufactured by novel electrodeoxidizing method developed in Cambridge whereby the range of alloys and intermetallics are produced cheaply making potential superconducting wires more cost effective. The process of direct electrochemical reduction of Nb{sub 2}O{sub 5}-SnO{sub 2} mixtures and in situ formation of the Nb{sub 3}Sn is discussed in details.

Identification of new phases in the Zr-Nb-Fe system

International Nuclear Information System (INIS)

Granovsky, Marta S.; Arias, Delia E.; Lena, Esteban M.

1999-01-01

Intermediate phases in the Zr - rich region of the Zr - Nb - Fe system have been investigated by X-ray diffraction, optical and electron microscopy and electron microanalysis. The chemical composition ranges of the alloys here studied were (52 - 97) at. % Zr, (14 - 0.9) at. % Nb and (38 - 0.6) at. % Fe. The phases found in this region were the solid solutions α(Zr) and β(Zr), the intermetallic Zr 3 Fe with less than 0.2 at. % Nb in solution, and two new ternary phases: (Zr + Nb) 2 Fe, identified as a cubic Ti 2 Ni - type structure and another compound with composition close to Zr - 12 at. % Nb - 50 at. % Fe. (author)

Experimental investigation of phase equilibria in the Ni-Nb-V ternary system

Energy Technology Data Exchange (ETDEWEB)

Liu, Xingjun; Yang, Shuiyuan; Wang, Cuiping [Xiamen Univ. (China). Dept. of Materials Science and Engineering; Xiamen Univ. (China). Fujian Provincial Key Lab. of Materials Genome; Zhang, Xianjie; Jiang, Hengxing; Shi, Zhan [Xiamen Univ. (China). Dept. of Materials Science and Engineering

2017-09-15

The phase equilibria of the Ni-Nb-V ternary system at 1000 C and 1200 C were established using electron probe microanalysis, X-ray diffraction and differential scanning calorimetry. The results of the investigation revealed that: (1) The Nb solubility in (Ni) and σ{sup '} phases was less than 10 at.%; (2) A ternary compound τ (NiNbV) was confirmed, in which V had a large solubility; (3) A new liquid region was evident at 1200 C, but was absent at 1000 C; (4) The lattice constants of Ni{sub 3}Nb and Ni{sub 6}Nb{sub 7} phase decreased with increase in V content in the Ni{sub 3}Nb and Ni{sub 6}Nb{sub 7}. The phase equilibria of the Ni-Nb-V ternary system will contribute to its thermodynamic assessment.

Dehydration of Glucose to 5-Hydroxymethylfurfural Using Nb-doped Tungstite

KAUST Repository

Yue, Chaochao

2016-08-05

Dehydration of glucose to 5-hydroxymethylfurfural (HMF) remains a significant problem in the context of the valorization of lignocellulosic biomass. Hydrolysis of WCl6 and NbCl5 leads to precipitation of Nb-containing tungstite (WO3H2O) at low Nb content and mixtures of tungstite and niobic acid at higher Nb content. Tungstite is a promising catalyst for the dehydration of glucose to HMF. Compared with Nb2O5, fewer by-products are formed because of the low BrOnsted acidity of the (mixed) oxides. In water, an optimum yield of HMF was obtained for Nb-W oxides with low Nb content owing to balanced Lewis and BrOnsted acidity. In THF/water, the strong Lewis acidity and weak BrOnsted acidity caused the reaction to proceed through isomerization to fructose and dehydration of fructose to a partially dehydrated intermediate, which was identified by LC-ESI-MS. The addition of HCl to the reaction mixture resulted in rapid dehydration of this intermediate to HMF. The HMF yield obtained in this way was approximately 56% for all tungstite catalysts. Density functional theory calculations show that the Lewis acid centers on the tungstite surface can isomerize glucose into fructose. Substitution of W by Nb lowers the overall activation barrier for glucose isomerization by stabilizing the deprotonated glucose adsorbate.

Method for preparing high transition temperature Nb.sub.3 Ge superconductors

Science.gov (United States)

Newkirk, Lawrence R.; Valencia, Flavio A.

1977-01-01

Bulk coatings of Nb.sub.3 Ge superconductors having transition temperatures in excess of 20 K are readily formed by a chemical vapor deposition technique involving the coreduction of NbCl.sub.5 and GeCl.sub.4 in the presence of hydrogen. The NbCl.sub.5 vapor may advantageously be formed quantitatively in the temperature range of about 250.degree. to 260.degree. C by the chlorination of Nb metal provided the partial pressure of the product NbCl.sub.5 vapor is maintained at or below about 0.1 atm.

Inter-filament resistance, effective transverse resistivity and coupling loss in superconducting multifilamentary NbTi and Nb3Sn strands

NARCIS (Netherlands)

Zhou, Chao; Dhalle, Marc M.J.; Nijhuis, Arend

2012-01-01

The effective transverse resistivity of a range of multi-filamentary Nb3Sn and NbTi strands is measured with a direct four-probe method and the data are compared to the transverse resistivity values obtained from AC coupling loss experiments. Correspondence between both is satisfactory provided that

Nb3Sn accelerator magnet development around the world

Energy Technology Data Exchange (ETDEWEB)

Michael J. Lamm

2003-06-23

During the past 30 years superconducting magnet systems have enabled accelerators to achieve energies and luminosities that would have been impractical if not impossible with resistive magnets. By far, NbTi has been the preferred conductor for this application because of its ductility and insensitivity of Jc to mechanical strain. This is despite the fact that Nb{sub 3}Sn has a more favorable Jc vs. B dependence and can operate at much higher temperatures. Unfortunately, NbTi conductor is reaching the limit of it usefulness for high field applications. Despite incremental increases in Jc and operation at superfluid temperatures, magnets are limited to approximately a 10 T field. Improvements in conductor performance combined with future requirements for accelerator magnets to have bore fields greater than 10 T or operate in areas of large beam-induced heat loads now make Nb{sub 3}Sn look attractive. Thus, laboratories in several countries are actively engaged in programs to develop Nb{sub 3}Sn accelerator magnets for future accelerator applications. A summary of this important research activity is presented along with a brief history of Nb{sub 3}Sn accelerator magnet development and a discussion of requirements for future accelerator magnets.

Hydrogen solubility and permeability of Nb-W-Mo alloy membrane

International Nuclear Information System (INIS)

Awakura, Y.; Nambu, T.; Matsumoto, Y.; Yukawa, H.

2011-01-01

Research highlights: → The concept for alloy design of Nb-based hydrogen permeable membrane has been applied to Nb-W-Mo ternary alloy in order to improve further the resistance to hydrogen embrittlement and hydrogen permeability. → The alloying effects of Mo on the hydriding properties of Nb-W alloy have been elucidated. → The addition of Mo and/or W into niobium improves the resistance to hydrogen embrittlement by reducing the dissolved hydrogen concentration in the alloy. → Nb-W-Mo alloy possesses excellent hydrogen permeability together with strong resistance to hydrogen embrittlement. - Abstract: The alloying effects of molybdenum on the hydrogen solubility, the resistance to hydrogen embrittlement and the hydrogen permeability are investigated for Nb-W-Mo system. It is found that the hydrogen solubility decreases by the addition of molybdenum into Nb-W alloy. As a result, the resistance to hydrogen embrittlement improves by reducing the hydrogen concentration in the alloy. It is demonstrated that Nb-5 mol%W-5 mol%Mo alloy possesses excellent hydrogen permeability without showing any hydrogen embrittlement when used under appropriate hydrogen permeation conditions, i.e., temperature and hydrogen pressures.

Quench tests of Nb3Al small racetrack magnets

International Nuclear Information System (INIS)

Yamada, R.; Kikuchi, A.; Tartaglia, Michael Albert; Ambrosio, G.; Andreev, N.; Barzi, E.; Carcagno, R.; Feher, S.; Kashikhin, V.V.; Kotelnikov, S.; Lamm, Michael J.; Fermilab; NIMC, Tsukuba; KEK, Tsukuba

2007-01-01

Two Cu stabilized Nb3Al strands, F1 (Nb matrixed) and F3 (Ta matrixed), have been made at NIMS and their Rutherford cables were made at Fermilab in collaboration with NIMS. A Small Race-track magnet using F1 Rutherford cable, the first Nb3Al dipole magnet in the world, was constructed and tested to full current at Fermilab. This magnet was tested extensively to full short sample data and its quench characteristics were studied and reported. The 3-D magnetic field calculation was done with ANSYS to find the peak field. The quench characteristics of the magnet are explained with the characteristics of the Nb3Al strand and Rutherford cable. The other Small Race-track magnet using Ta matrixed F3 strand was constructed and will be tested in the near future. The advantages and disadvantages of these Nb3Al cables are discussed

Quench tests of Nb3Al small racetrack magnets

Energy Technology Data Exchange (ETDEWEB)

Yamada, R.; Kikuchi, A.; Tartaglia, Michael Albert; Ambrosio, G.; Andreev, N.; Barzi, E.; Carcagno, R.; Feher, S.; Kashikhin, V.V.; Kotelnikov, S.; Lamm, Michael J.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2007-08-01

Two Cu stabilized Nb3Al strands, F1 (Nb matrixed) and F3 (Ta matrixed), have been made at NIMS and their Rutherford cables were made at Fermilab in collaboration with NIMS. A Small Race-track magnet using F1 Rutherford cable, the first Nb3Al dipole magnet in the world, was constructed and tested to full current at Fermilab. This magnet was tested extensively to full short sample data and its quench characteristics were studied and reported. The 3-D magnetic field calculation was done with ANSYS to find the peak field. The quench characteristics of the magnet are explained with the characteristics of the Nb3Al strand and Rutherford cable. The other Small Race-track magnet using Ta matrixed F3 strand was constructed and will be tested in the near future. The advantages and disadvantages of these Nb3Al cables are discussed.

Advances in Nb3Sn Performance

International Nuclear Information System (INIS)

Godeke, Arno

2008-01-01

Nb 3 Sn wires with non-Cu critical current densities (J c ) that surpass 3 kAmm -2 at 12 T and 4.2 K are commercially available in piece lengths longer than 10 km. Accelerator-type magnets that utilize these conductors have achieved record magnetic fields. This article summarizes key developments in the last decade that have led to these significant improvements in the performance of Nb 3 Sn wires.

Multifilamentary Cu-Nb3Sn superconductor wires

International Nuclear Information System (INIS)

Rodrigues, D.; Pinatti, D.G.

1990-01-01

This paper reports on one of the main technological problems concerning Nb 3 Sn superconducting wires production which is the optimization of heat treatments for the formation of the A-15 intermetallic compound. At the present work, Nb 3 Sn superconducting wire is produced by solid-liquid diffusion method which increases considerably the critical current values of the superconductor. Through this method, niobium, copper and Sn 7% wt Cu alloy are kept in the pure state. Thus, the method dispenses intermediate heat treatments of recrystallization during the manufacturing process of the wire. After the wire was ready, optimization work of heat treatments was accomplished aiming to obtain its best superconducting characteristics, Measurement of critical temperature, critical current versus magnetic field, normal and at room temperature resistivity were performed, as well as scanning electron microscopy for determination of Nb 3 Sn layers and transmission electron microscopy measurements of redetermining the grain sizes in Nb 3 Sn formed in each treatment. It was obtained critical current densities of 1.8 x 10 6 A/cm 2 in the Nb 3 Sn layer, at 10 Teslas and 4.2 K. The samples were analyzed by employing the superconducting collective flux pinning theories and a satisfactory agreement between the experimental and theoretical data was attained. The production process and the small size of the filaments used made a successful optimization of the wire possible

Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

KAUST Repository

Ozdogan, K.

2012-03-08

We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

Influence of stresses on superconducting properties of Nb3Sn conductors

International Nuclear Information System (INIS)

Suenaga, M.; Luhman, T.S.; Sampson, W.B.; Onishi, T.; Klamut, C.J.

1978-01-01

This investigation of the degradation in the superconducting properties of Nb 3 Sn conductors when subjected to mechanical strain can be divided into the following areas: (I) monofilamentary Nb 3 Sn wires, (II) multifilamentary Nb 3 Sn conductors and wires, (III) effects of additives to Nb 3 Sn, (IV) mechanisms for degradation, and (V) construction of test facilities. Efforts to the present time have been concentrated in the investigation of T/sub c/, J/sub c/, and H/sub c2/ variations in monofilamentary wires. The most important finding in this study is that a Nb 3 Sn composite wire can sustain an effective mechanical strain well beyond ''1%'' if a proper ratio of the matrix to the Nb core has been chosen

Enhanced carrier density in Nb-doped SrTiO3 thermoelectrics

KAUST Repository

Ozdogan, K.; Upadhyay Kahaly, M.; Sarath Kumar, S. R.; Alshareef, Husam N.; Schwingenschlö gl, Udo

2012-01-01

We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-x Nb x O3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

Tunneling spectroscopy on superconducting Nb3Sn with artioficial barriers

International Nuclear Information System (INIS)

Schneider, U.

1984-03-01

Tunneling diodes on Nb 3 Sn were prepared by magnetron sputtering. The superconducting transition temperatures of the Nb 3 Sn films were in the range of 5 to 18 K. An energetically low-lying structure in the tunneling density of states has been localized by detailed studies of the second derivative of the current-voltage characteristics of the diodes. This structure was found near 5.5 meV for stoichiometric Nb 3 Sn (Tsub(c) approx.= 18 K) and at 6.7 meV for understoichiometric Nb 3 Sn (Tsub(c) approx.= 5 K). The minimum in the conductance at zero energy found in the normal state could be identified to be mainly due to inelastic phonon processes of barrier phonons and Nb 3 Sn phonons. Deformations were found in the tunneling density of states of stoichiometric Nb 3 Sn diodes which lead to contradiction when explained by proximity effects. (orig./GSCH)

Photoluminescence properties of aeschynite-type LaNbTiO6:RE3+ (RE = Tb, Dy, Ho) down-converting phosphors.

Science.gov (United States)

Ma, Qian; Lu, Mengkai; Yang, Ping; Zhang, Aiyu; Cao, Yongqiang

2014-06-01

In this study, a series of LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) down-converting phosphors were synthesized using a modified sol-gel combustion method, and their photoluminescence (PL) properties were investigated as a function of activator concentration and annealing temperature. The resultant particles were characterized using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, UV/Vis diffuse reflectance spectroscopy and PL spectra. The highly crystalline LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) phosphors with an average size of 200-300 nm obtained at 1100°C have an orthorhombic aeschynite-type structure and exhibit the highest luminescent intensity in our study range. The emission spectra of LaNbTiO6:RE(3+) (RE = Tb, Dy, Ho) phosphors under excitations at UV/blue sources are mainly composed of characteristic peaks arising from the f-f transitions of RE(3+), including 489 nm ((5) D4 → (7) F6) and 545 nm ((5) D4 → (7) F5) for Tb(3+), 476 and 482 nm ((4) F9/2 → (6) H15/2) and 571 nm ((4) F9/2 → (6) H13/2) for Dy(3+), and 545 nm ((5) F4 + (5) S2 → (5) I8) for Ho(3+), respectively. The luminescent mechanisms were further investigated. It can be expected that these phosphors are of intense interest and potential importance for many optical applications. Copyright © 2013 John Wiley & Sons, Ltd.

A nano lamella NbTi–NiTi composite with high strength

Energy Technology Data Exchange (ETDEWEB)

Jiang, Jiang [Jiangxi Key Laboratory of Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); Institute of Applied Physics of Jiangxi Academy of Sciences, Nanchang 330029 (China); State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); Jiang, Daqiang [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); School of Mechanical and Chemical Engineering, The University of Western Australia, WA 6009 (Australia); Hao, Shijie; Yu, Cun; Zhang, Junsong [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); Ren, Yang [X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Lu, Deping; Xie, Shifang [Jiangxi Key Laboratory of Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); Institute of Applied Physics of Jiangxi Academy of Sciences, Nanchang 330029 (China); Cui, Lishan, E-mail: lishancui63@126.com [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China)

2015-05-01

A hypereutectic Nb{sub 60}Ti{sub 24}Ni{sub 16} (at%) alloy was prepared by vacuum induction melting, and a nano lamellae NbTi–NiTi composite was obtained by hot-forging and wire-drawing of the ingot. Microscopic analysis showed that NbTi and NiTi nano lamellae distributed alternatively in the composite, and aligned along the wire axial direction, with a high volume fraction (~70%) of NbTi nano lamellae. In situ synchrotron X-ray diffraction analysis revealed that stress induced martensitic transformation occurred upon loading, which would effectively weaken the stress concentration at the interface and avoid the introduction of defects into the nano reinforced phase. Then the embedded NbTi nano lamellae exhibited a high elastic strain up to 2.72%, 1.5 times as high as that of the Nb nanowires embedded in a conventional plastic matrix, and the corresponding stress carried by NbTi was evaluated as 2.53 GPa. The high volume fraction of NbTi nano lamellae improved the translation of high strength from the nano reinforced phase into bulk properties of the composite, with a platform stress of ~1.7 GPa and a fracture strength of ~1.9 GPa.

RHQT Nb3Al 15-Tesla magnet design study

Energy Technology Data Exchange (ETDEWEB)

Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2005-09-01

Feasibility study of 15-Tesla dipole magnets wound with a new copper stabilized RHQT Nb{sub 3}Al Rutherford cable is presented. A new practical long copper stabilized RHQT Nb{sub 3}Al strand is presented, which is being developed and manufactured at the National Institute of Material Science (NIMS) in Japan. It has achieved a non-copper J{sub c} of 1000A/mm{sup 2} at 15 Tesla at 4.2K, with a copper over non-copper ratio of 1.04, and a filament size less than 50 microns. For this design study a short Rutherford cable with 28 Nb{sub 3}Al strands of 1 mm diameter will be fabricated late this year. The cosine theta magnet cross section is designed using ROXIE, and the stress and strain in the coil is estimated and studied with the characteristics of the Nb{sub 3}Al strand. The advantages and disadvantages of the Nb{sub 3}Al cable are compared with the prevailing Nb{sub 3}Sn cable from the point of view of stress-strain, J{sub c}, and possible degradation of stabilizer due to cabling. The Nb{sub 3}Al coil of the magnet, which will be made by wind and react method, has to be heat treated at 800 degree C for 10 hours. As preparation for the 15 Tesla magnet, a series of tests on strand and Rutherford cables are considered.

X-ray diffraction pattern and morphology of superconducting Nb/sub 3/Sn layer grown on a polycrystalline Nb substrate of (111) main texture

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B [Politechnika Wroclawska (Poland)

1983-01-16

A study is presented on structure and crystallographic orientation of Nb/sub 3/Sn layers formed in the process of interaction of polycrystalline Nb substrate with Cu/sub 0.2/Sn/sub 0.8/ solution at 980 /sup 0/C. Grain structure characterization of Nb/sub 3/Sn layers has been carried out with scanning electron microscopy and TV automatic image analysis. The superconducting layer is divided into a fine-grained FG and coarse-grained CG zone. The X-ray patterns of FG and CG zones did not differ from one another and were the same as in randomly oriented Nb/sub 3/Sn polycrystalline powder.

Blue ocean strategy.

Science.gov (United States)

Kim, W Chan; Mauborgne, Renée

2004-10-01

Despite a long-term decline in the circus industry, Cirque du Soleil profitably increased revenue 22-fold over the last ten years by reinventing the circus. Rather than competing within the confines of the existing industry or trying to steal customers from rivals, Cirque developed uncontested market space that made the competition irrelevant. Cirque created what the authors call a blue ocean, a previously unknown market space. In blue oceans, demand is created rather than fought over. There is ample opportunity for growth that is both profitable and rapid. In red oceans--that is, in all the industries already existing--companies compete by grabbing for a greater share of limited demand. As the market space gets more crowded, prospects for profits and growth decline. Products turn into commodities, and increasing competition turns the water bloody. There are two ways to create blue oceans. One is to launch completely new industries, as eBay did with online auctions. But it's much more common for a blue ocean to be created from within a red ocean when a company expands the boundaries of an existing industry. In studying more than 150 blue ocean creations in over 30 industries, the authors observed that the traditional units of strategic analysis--company and industry--are of limited use in explaining how and why blue oceans are created. The most appropriate unit of analysis is the strategic move, the set of managerial actions and decisions involved in making a major market-creating business offering. Creating blue oceans builds brands. So powerful is blue ocean strategy, in fact, that a blue ocean strategic move can create brand equity that lasts for decades.

Electronic properties of blue phosphorene/graphene and blue phosphorene/graphene-like gallium nitride heterostructures.

Science.gov (United States)

Sun, Minglei; Chou, Jyh-Pin; Yu, Jin; Tang, Wencheng

2017-07-05

Blue phosphorene (BlueP) is a graphene-like phosphorus nanosheet which was synthesized very recently for the first time [Nano Lett., 2016, 16, 4903-4908]. The combination of electronic properties of two different two-dimensional materials in an ultrathin van der Waals (vdW) vertical heterostructure has been proved to be an effective approach to the design of novel electronic and optoelectronic devices. Therefore, we used density functional theory to investigate the structural and electronic properties of two BlueP-based heterostructures - BlueP/graphene (BlueP/G) and BlueP/graphene-like gallium nitride (BlueP/g-GaN). Our results showed that the semiconducting nature of BlueP and the Dirac cone of G are well preserved in the BlueP/G vdW heterostructure. Moreover, by applying a perpendicular electric field, it is possible to tune the position of the Dirac cone of G with respect to the band edge of BlueP, resulting in the ability to control the Schottky barrier height. For the BlueP/g-GaN vdW heterostructure, BlueP forms an interface with g-GaN with a type-II band alignment, which is a promising feature for unipolar electronic device applications. Furthermore, we discovered that both G and g-GaN can be used as an active layer for BlueP to facilitate charge injection and enhance the device performance.

Cr3+ and Nb5+ co-doped Ti2Nb10O29 materials for high-performance lithium-ion storage

Science.gov (United States)

Yang, Chao; Yu, Shu; Ma, Yu; Lin, Chunfu; Xu, Zhihao; Zhao, Hua; Wu, Shunqing; Zheng, Peng; Zhu, Zi-Zhong; Li, Jianbao; Wang, Ning

2017-08-01

Ti2Nb10O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate capability. To tackle this issue, a Cr3+-Nb5+ co-doping is employed, and a series of CrxTi2-2xNb10+xO29 compounds are prepared. The co-doping does not change the Wadsley-Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li+-ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr0.6Ti0.8Nb10.6O29 sample delivers a large reversible capacity of 322 mAh g-1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g-1, while that of Ti2Nb10O29 is only 80 mAh g-1. Furthermore, Cr0.6Ti0.8Nb10.6O29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.

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)

High-strength high-conductivity Cu-Nb microcomposite sheet fabricated via multiple roll bonding

International Nuclear Information System (INIS)

Jha, S.C.; Delagi, R.G.; Forster, J.A.; Krotz, P.D.

1993-01-01

Copper-niobium microcomposites are a new class of high-strength high-conductivity materials that have attractive properties for room- and elevated-temperature applications. Since Nb has little solid solubility in Cu, addition of Nb to Cu does not affect its conductivity. Copper-niobium microcomposites are melted and cast so that the microstructure of cast Cu-Nb ingots consists of 1- to 10 μm Nb dendrites uniformly distributed within the copper matrix. Extensive wire drawing with a true processing strain (η> 12) of Cu-Nb alloy leads to refinement and elongation of Nb dendrites into 1- to 10 nm-thick filaments. The presence of such fine Nb filaments causes a significant increase in the strength of Cu-Nb wires. The tensile strength of heavily drawn Cu-Nb wires was determined to be significantly higher than the values predicted by the rule of mixtures. This article reports the fabrication of high-strength Cu-Nb microcomposite sheet by multiple roll bonding. It is difficult and impractical to attain high processing strains (η>3) by simple cold rolling. In most practical cold-rolling operation, the thickness reduction does not exceed 90 pct (η ≅2). Therefore, innovative processing is required to generate high strength in Cu-Nb microcomposite sheet. Multiple roll bonding of Cu-Nb has been utilized to store high processing strain ( η>10) in the material and refine the Nb particle size within the copper matrix. This article describes the microstructure, mechanical properties, and thermal stability of roll-bonded Cu-Nb microcomposite sheet

Thermo-magnetic instabilities in Nb3Sn Superconducting Accelerator Magnets

International Nuclear Information System (INIS)

Bordini, Bernardo; Pisa U.

2006-01-01

The advance of High Energy Physics research using circulating accelerators strongly depends on increasing the magnetic bending field which accelerator magnets provide. To achieve high fields, the most powerful present-day accelerator magnets employ NbTi superconducting technology; however, with the start up of Large Hadron Collider (LHC) in 2007, NbTi magnets will have reached the maximum field allowed by the intrinsic properties of this superconductor. A further increase of the field strength necessarily requires a change in superconductor material; the best candidate is Nb 3 Sn. Several laboratories in the US and Europe are currently working on developing Nb 3 Sn accelerator magnets, and although these magnets have great potential, it is suspected that their performance may be fundamentally limited by conductor thermo-magnetic instabilities: an idea first proposed by the Fermilab High Field Magnet group early in 2003. This thesis presents a study of thermo-magnetic instability in high field Nb 3 Sn accelerator magnets. In this chapter the following topics are described: the role of superconducting magnets in High Energy Physics; the main characteristics of superconductors for accelerator magnets; typical measurements of current capability in superconducting strands; the properties of Nb 3 Sn; a description of the manufacturing process of Nb 3 Sn strands; superconducting cables; a typical layout of superconducting accelerator magnets; the current state of the art of Nb 3 Sn accelerator magnets; the High Field Magnet program at Fermilab; and the scope of the thesis

Influência da cobertura vegetal do solo na qualidade dos frutos de videira 'Niagara Rosada' Influence of soil cover with grass and leguminous plants on fruit characteristics of table grape variety Niagara Rosada

Directory of Open Access Journals (Sweden)

Elaine Bahia Wutke

2005-12-01

Full Text Available Devido ao aumento no custo de produção com a utilização de cobertura morta com capim nas ruas da videira 'Niagara Rosada' e à dificuldade para sua aquisição, objetivou-se a possibilidade de substituí-la por plantas de cobertura intercalares. Em experimentos realizados em Indaiatuba e Jundiaí-SP, de 1999-2000 a 2003-2004, instalaram-se seis tratamentos nas entrelinhas, em blocos ao acaso e quatro repetições, constando de área no limpo; vegetação espontânea roçada; cobertura com capim seco de Brachiaria decumbens; cobertura verde de aveia preta (Avena strigosa; cobertura verde de chícharo (Lathyrus sativus; cobertura verde de tremoço (Lupinus albus, de março a outubro, seguidas de cobertura verde de mucuna anã (Mucuna deeringiana de outubro a março. Determinaram-se massa, comprimento e largura do cacho, engaço e bagas, número total de bagas por cacho e diâmetro do pedicelo de bagas, comparando-se os valores médios pelo teste de Duncan ao nível de 5%. Na média dos anos, os resultados com a cobertura verde foram similares ou mais favoráveis que os da cobertura com braquiária seca, podendo-se substituí-la por coberturas vegetais intercalares com gramínea e leguminosas, o ano todo, sem interferência negativa na qualidade comercial dos frutos.Grape vineyard in Southern Brazil utilize a large amount of mulch during autumn-winter season demanding extra efforts and costs, being its acquisition very difficult nowadays. In order to evaluate the possibility of replacing the tradicionally mulch by green cover species in the inter-row strip, two experiments were carried out in Indaiatuba and Jundiaí, SP, Brazil, from 1999/00 to 2003/04, with the table variety Niagara Rosada. The experimental design was a randomized block with four replications and six treatments: 1 no weeded area; 2 cut spontaneous local vegetation; 3 mulch of Brachiaria decumbens; 4 green cover of Avena strigosa from March to October followed by green cover of

Thermodynamic assessment of the Nb-W-C system

International Nuclear Information System (INIS)

Huang Weiming; Selleby, M.

1997-01-01

The phase equilibrium and thermodynamic information of the Nb-W-C system was reviewed and assessed by using thermodynamic models for the Gibbs energy of individual phases. The assessment was based on the recent evaluations of the W-C, Nb-W and Nb-C, which was revised in the present work taking ternary information into account. The model parameters were evaluated by fitting the selected experimental data by means of a computer program. A consistent set of parameters was obtained, which satisfactorily describes most of the experimental information. (orig.)

Wide-band operation of quasi-optical distributed superconductor/insulator/superconductor mixers with epitaxial NbN/AlN/NbN junctions

International Nuclear Information System (INIS)

Kohjiro, S; Shitov, S V; Wang, Z; Uzawa, Y; Miki, S; Kawakami, A; Shoji, A

2004-01-01

For the optimum design of integrated receivers operating above the gap frequency of Nb, we have designed, fabricated and tested NbN-based quasi-optical superconductor/insulator/superconductor (SIS) mixers. The mixer chip incorporates a resonant half-wavelength epitaxial NbN/AlN/NbN junction, a twin-slot antenna and their coupling circuits. We adopted two kinds of coupling circuit between the antenna and the SIS junction: one is an in-phase feed with a length of 95 μm and the other is an anti-phase feed of 30 μm length. It was found that the anti-phase mixer reveals a 3 dB bandwidth of 43% of the centre frequency; the uncorrected double-sideband receiver noise temperature T RX = 691 K at 0.91 THz and T RX = 844 K at 0.80 THz, while 17% and T RX = 1250 K at 0.79 THz for the in-phase version. Possible reasons for this difference are discussed, which could be transmission loss and its robustness with respect to the variation of junction parameters. These experimental results suggest the NbN-based distributed mixer with the anti-phase feed is a better candidate for wide-band integrated receivers operating above 0.7 THz

Dispersion of complex dielectric constant and electronic characteristics of the compounds Nb-Al and Nb-Ge with A15 structure

International Nuclear Information System (INIS)

Kuzmichev, N.D.; Levchenko, I.S.; Motulevich, G.P.

1989-01-01

This paper reports that the dispersions of complex dielectric constant of the compounds Nb-Al and Nb-Ge with A15 structure, used for determination of electronic characteristics and their variations with temperature, are measured in the 0.177-3.1 eV spectral interval at 295 and 670 K. The squares of the plasma frequencies ω 2 p of conduction electrons are obtained. In both compounds ω 2 p ∼ 19 eV 2 , which is 3.2 times less than for niobium. In this spectral interval, Nb-Al has four interband transition zones at 0.2, 0.35, 1.45, and 3.1 eV, while Nb-Ge has five such bands: 0.21, 0.32, 0.48, 0.95 and 2.0 eV. As the temperature increases ω 2 p of conduction electrons increases somewhat more than for usual metals (in both compounds), and the decrease in the analogous characteristic in the long-wave band for Nb-Ge is unusually great, preserving the sum of the changes, and there is also a significant decrease in the width of the long-wave band. These anomalies can be explained by thermal transfer of electrons from the base state of the long-wave band to the conduction band

Neutron irradiation of sputtered NbN films

International Nuclear Information System (INIS)

Weber, H.W.; Gregshammer, P.; Gray, K.E.; Kampwirth, R.T.

1989-01-01

In addition to the excellent high-field superconducting properties of NbN, it is the strain and radiation tolerance, measured in bulk NbN, which makes the material so attractive for large high-field magnets, especially for fusion applications. The authors report neutron irradiation experiments on sputtered NbN films, up to a fluence of 10/sup 23/ m/sup -2/ (E > 0.1 MeV), which prove that NbN films are also extremely radiation-hard high-field superconductors. Both the transition temperatures, T/sub c/, and the normal state resistivities show only small changes with neutron fluence. Concerning the critical current densities, j/sub c/, degradations by as much as 30% are observed at low fields, whereas in an intermediate field range (11-15 T) virtually no change of j/sub c/ and at high fields near 20 T even an increase of j/sub c/ are found. The latter observation is ascribed to a radiation-induced increase of the upper critical field, B/sub c2/, and to the occurence of peak effects near B/sub c2/

Role of Nb content in nanocrystals

International Nuclear Information System (INIS)

Sitek, J.; Lipka, J.; Miglierini, M.; Toth, I.

1995-01-01

The influence of Nb content on the formation of nanocrystalline phase in the Fe 73.5-x Cu 1 Nb 3+x Si 13.5 B 9 system was studied by Moessbauer spectroscopy. The kinetics of crystallization was observed by isothermal heating at temperature 550 C during annealing time up to 16 h. The samples containing 3 and 4.5 at% were compared. Nanocrystalline phase formation was explained on the basis of cluster model. ((orig.))

Diffusion of Nb in Fe and in some Fe alloys

International Nuclear Information System (INIS)

Kurokawa, S.; Ruzzante, J.E.; Hey, A.M.; Dyment, F.

1981-01-01

Diffusion data of microalloying elements such as Nb, V, Ti, are required when analysing the transformation and recrystallization behaviour of HSLA steels in order to optimize grain refinement and precipitation hardening. The diffusion behaviour of Nb in pure Fe, Fe 1.5 Mn, Fe 0.6 Si and Fe 1.5 Mn 0.6 Si has been measured between 1080 and 1200 0 C. Results indicate that Si increases Nb diffusivity while Mn decreases it. The sequence of diffusion coeficients values is: D sup(Nb) sub(Fe 1.5 Mn) [pt

Nb$_{3}$Sn quadrupole magnets for the LHC IR

CERN Document Server

Sabbi, G L; Chiesa, L; Coccoli, M; Dietderich, D R; Ferracin, P; Gourlay, S A; Hafalia, R R; Lietzke, A F; McInturff, A D; Scanlan, R M

2003-01-01

The development of insertion quadrupoles with 205 T/m gradient and 90 mm bore represents a promising strategy to achieve the ultimate luminosity goal of 2.5 * 10/sup 34/ cm/sup -2/s/sup -1/ at the Large Hadron Collider (LHC). At present, Nb/sub 3/Sn is the only practical conductor which can meet these requirements. Since Nb/sub 3/Sn is brittle, and considerably more strain sensitive than NbTi, the design concepts and fabrication techniques developed for NbTi magnets need to be modified appropriately. In addition, IR magnets must provide high field quality and operate reliably under severe radiation loads. The results of conceptual design studies addressing these issues are presented. (25 refs).

Nb3Sn Quadrupole Magnets for the LHC IR

International Nuclear Information System (INIS)

Sabbi, G.; Caspi, S.; Chiesa, L.; Coccoli, M.; Dietderich, D.R.; Ferracin, P.; Gourlay, S.A.; Hafalia, R.R.; Lietzke, A.F.; McInturff, A.D.; Scanlan, R.M.

2001-01-01

The development of insertion quadrupoles with 205 T/m gradient and 90 mm bore represents a promising strategy to achieve the ultimate luminosity goal of 2.5 x 10 34 cm -2 s -1 at the Large Hadron Collider (LHC). At present, Nb 3 Sn is the only practical conductor which can meet these requirements. Since Nb 3 Sn is brittle, and considerably more strain sensitive than NbTi, the design concepts and fabrication techniques developed for NbTi magnets need to be modified appropriately. In addition, IR magnets must provide high field quality and operate reliably under severe radiation loads. The results of conceptual design studies addressing these issues are presented.

Vaporization study on nonstoichiometric NbOsub(2+-x) by mass-spectrometric method

International Nuclear Information System (INIS)

Matsui, T.; Naito, K.

1981-01-01

The vapor pressures over nonstoichiometric NbOsub(2+-x)(s) (1.972 2 (g) and NbO(g) over nonstoichiometric NbOsub(2+-x), from which the partial molar enthalpies and entropies of oxygen were calculated as a function of O/Nb composition. The composition dependence of the partial molar enthalpy and entropy obtained suggested the existence of some kind of short-range ordering in the nonstoichiometric Nbsub(2+-x) (s) phase. The enthalpies of formation of nonstoichiometric NbOsub(2+-x) (s) were also determined as a function of composition by combining the partial molar enthalpies of oxygen with the enthalpy of formation of stoichiometric NbOsub(2.000) (s). The phase diagram around NbOsub(2+-x) at high temperatures was determined from the vaporization study. (orig.)

Distinct atomic structures of the Ni-Nb metallic glasses formed by ion beam mixing

International Nuclear Information System (INIS)

Tai, K. P.; Wang, L. T.; Liu, B. X.

2007-01-01

Four Ni-Nb metallic glasses are obtained by ion beam mixing and their compositions are measured to be Ni 77 Nb 23 , Ni 55 Nb 45 , Ni 31 Nb 69 , and Ni 15 Nb 85 , respectively, suggesting that a composition range of 23-85 at. % of Nb is favored for metallic glass formation in the Ni-Nb system. Interestingly, diffraction analyses show that the structure of the Nb-based Ni 31 Nb 69 metallic glass is distinctly different from the structure of the Nb-based Ni 15 Nb 85 metallic glass, as the respective amorphous halos are located at 2θ≅38 and 39 deg. To explore an atomic scale description of the Ni-Nb metallic glasses, an n-body Ni-Nb potential is first constructed with an aid of the ab initio calculations and then applied to perform the molecular dynamics simulation. Simulation results determine not only the intrinsic glass forming range of the Ni-Nb system to be within 20-85 at. % of Nb, but also the exact atomic positions in the Ni-Nb metallic glasses. Through a statistical analysis of the determined atomic positions, a new dominant local packing unit is found in the Ni 15 Nb 85 metallic glass, i.e., an icositetrahedron with a coordination number to be around 14, while in Ni 31 Nb 69 metallic glasses, the dominant local packing unit is an icosahedron with a coordination number to be around 12, which has been reported for the other metallic glasses. In fact, with increasing the irradiation dose, the Ni 31 Nb 69 metallic glasses are formed through an intermediate state of face-centered-cubic-solid solution, whereas the Ni 15 Nb 85 metallic glass is through an intermediate state of body-centered-cubic-solid solution, suggesting that the structures of the constituent metals play an important role in governing the structural characteristics of the resultant metallic glasses

Preparation of Nb-Si phases by cathode sputtering, in particulat the superconducting phase of epitactically grown A15-Nb3Si

International Nuclear Information System (INIS)

Siefken, U.

1979-01-01

The search for new superconducting materials with high transition temperatures is concentrated on alloys with a cubic A15 structure (Cr 3 Si structure). In this paper we present the preparation of metastable A15-Nb 3 Si which is expected to have a very high transition temperature Tsub(c). The properties of the A15 structure which are relevant for superconductivity are described, in particular the orthogonal chains as the most important structural characteristic, metastability, and the relation between lattice defects and transition temperature. For target compositions of 75% Nb / 25% Si and 80% Nb / 20% Si A15-Nb 3 Si transition temperatures of Tsub(c) = 5.3 K and Tsub(c) = 7.5 K have been measured respectively, with lattice constants asub(o) = 5.19 A and asub(o) = 5.18 A. (orig.) [de

Thermal stability and phase transformations of martensitic Ti–Nb alloys

Directory of Open Access Journals (Sweden)

Matthias Bönisch, Mariana Calin, Thomas Waitz, Ajit Panigrahi, Michael Zehetbauer, Annett Gebert, Werner Skrotzki and Jürgen Eckert

2013-01-01

Full Text Available Aiming at understanding the governing microstructural phenomena during heat treatments of Ni-free Ti-based shape memory materials for biomedical applications, a series of Ti–Nb alloys with Nb concentrations up to 29 wt% was produced by cold-crucible casting, followed by homogenization treatment and water quenching. Despite the large amount of literature available concerning the thermal stability and ageing behavior of Ti–Nb alloys, only few studies were performed dealing with the isochronal transformation behavior of initially martensitic Ti–Nb alloys. In this work, the formation of martensites (α' and α'' and their stability under different thermal processing conditions were investigated by a combination of x-ray diffraction, differential scanning calorimetry, dilatometry and electron microscopy. The effect of Nb additions on the structural competition in correlation with stable and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α'' martensitically reverts back to β0, which is highly unstable against chemical demixing by formation of isothermal ωiso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α'' martensite form.

Nb 3d and O 1s core levels and chemical bonding in niobates

International Nuclear Information System (INIS)

Atuchin, V.V.; Kalabin, I.E.; Kesler, V.G.; Pervukhina, N.V.

2005-01-01

A set of available experimental data on binding energies of Nb 3d 5/2 and O 1s core levels in niobates has been observed with using energy difference (O 1s-Nb 3d 5/2 ) as a robust parameter for compound characterization. An empirical relationship between (O 1s-Nb 3d 5/2 ) values measured with XPS for Nb 5+ -niobates and mean chemical bond length L(Nb-O) has been discussed. A range of (O 1s-Nb 3d 5/2 ) values possible in Nb 5+ -niobates has been defined. An energy gap ∼1.4-1.8 eV is found between (O 1s-Nb 3d 5/2 ) values reasonable for Nb 5+ and Nb 4+ states in niobates

HIGH-RESOLUTION FOURIER TRANSFORM SPECTROSCOPY OF Nb i IN THE NEAR-INFRARED

Energy Technology Data Exchange (ETDEWEB)

Er, A.; Güzelçimen, F.; Başar, Gö.; Öztürk, I. K. [Faculty of Science, Physics Department, Istanbul University, TR-34134 Vezneciler, Istanbul (Turkey); Tamanis, M.; Ferber, R. [Laser Centre, The University of Latvia, Rainis Boulevard 19, LV-1586 Riga (Latvia); Kröger, S., E-mail: gbasar@istanbul.edu.tr, E-mail: sophie.kroeger@htw-berlin.de [Hochschule für Technik und Wirtschaft Berlin, Wilhelminenhofstrasse 75A, D-12459 Berlin (Germany)

2015-11-15

In this study, a Fourier Transform spectrum of Niobium (Nb) is investigated in the near-infrared spectral range from 6000 to 12,000 cm{sup −1} (830–1660 nm). The Nb spectrum is produced using a hollow cathode discharge lamp in an argon atmosphere. Both Nb and Ar spectral lines are visible in the spectrum. A total of 110 spectral lines are assigned to the element Nb. Of these lines, 90 could be classified as transitions between known levels of atomic Nb. From these classified Nb i transitions, 27 have not been listed in literature previously. Additionally, 8 lines are classified for the first time.

Ceramic insulation for superconducting Nb{sub 3}Sn cables; Isolation ceramique pour cables supraconducteurs en Nb{sub 3}Sn

Energy Technology Data Exchange (ETDEWEB)

Puigsegur, A

2005-01-15

Nb{sub 3}Sn is the best superconductor candidate for the realization of high field magnets (>11 Tesla), its implementation remains delicate because of the great brittleness of material after the heat treatment necessary to the formation of Nb{sub 3}Sn compounds. The conventional insulation for Nb{sub 3}Sn requires to perform, after the heat treatment, a vacuum resin impregnation, which adds to the cost and raises failure risk. We have proposed an innovating ceramic insulation deposited directly on the unreacted conducting cable. After the heat treatment of the niobium tin, we obtain a coil having a mechanical cohesion, while maintaining a proper conductor positioning and a suitable electric insulation. After a rheological study, to characterize the impregnated suspension, we have shown that using this insulation in a coil manufacture process does not affect the electrical properties of the Nb{sub 3}Sn wires. A solenoid of small dimensions was tested with success in high external magnetic fields and has produced a magnetic field of 3.8 T under 740 A. (author)

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

Magnetization measurements on multifilamentary Nb3Sn and NbTi conductors

International Nuclear Information System (INIS)

Ghosh, A.K.; Robins, K.E.; Sampson, W.B.

1984-01-01

The effective filament size has been determined for a number of high current Nb 3 Sn multifilamentary composites. In most cases it is much larger than the nominal filament size. For the smallest filaments (approx. 1 micron) the effective size can be as much as a factor of forty times the nominal size. Samples made by the internal tin, bronze route, and jelly roll methods have been examined with filaments in the range one to ten microns. Rate dependent magnetization and flux jumping have been observed in some cases. NbTi composites ranging in filament size from nine to two hundred microns and with copper to super-conductor ratios between 1.6:1 and 7:1 have been examined in the same apparatus. Low field flux jumping was only observed in conductors with very large filaments and relatively little stabilizing copper. 9 references, 6 figures, 3 tables

Analysis of Nb$_{3}$Sn Rutherford cable production and strand deformations

CERN Document Server

Peggiani, Sonia; Beghi, Marco

The development of cutting-edge 11-12 T superconducting magnets made from Nb$_{3}$Sn technology is one of the major milestones for the upgrade of the Large Hadron Collider at CERN. The upgrade, called High Luminosity LHC Project, was planned in order to reach higher luminosity and discover new particles. Replacing the NbTi superconductor with the Nb$_{3}$Sn makes it possible to reach a practical operating magnetic field limit of up to 16 T. The superconducting coils are formed by Nb$_{3}$Sn Rutherford cables with a trapezoidal cross section and composed of 40 strands. Since the superconducting phase of Nb$_{3}$Sn is very brittle and it is reached after a thermal cycle, the Nb$_{3}$Sn Rutherford cable needs to be wound in a coil before the thermal treatment. The cabling process is a delicate step in the production of high performing cables that need different systems to control their quality. This work aims to provide practical tools to analyze the Nb$_{3}$Sn Rutherford cable production and the strands defo...

Oxygen ordering in Nb(1 1 0) films

International Nuclear Information System (INIS)

Hellwig, O.; Zabel, H.

2003-01-01

Synchrotron X-ray diffraction (XRD) during the atmospheric oxidation of epitaxial Nb(1 1 0) films at elevated temperature reveals the formation of highly ordered oxygen phases within the Nb lattice. The oxygen is stored on interstitial lattice sites without destroying the basic BCC structure of the Nb host lattice. However the lattice exhibits an out-of-plane lattice expansion of up to 4.3%. During oxidation we observe the formation of a non-ordered lattice gas phase succeeded by a well-defined sequence of oxygen superstructures until finally the whole film is consumed by the formation of amorphous Nb 2 O 5 . We show that XRD is an excellent tool to monitor the exact evolution of the different oxygen phases. In addition we demonstrate that UHV post-annealing of partially oxidized films can be used to rearrange the oxygen within the sample while keeping the overall amount of oxygen constant

Nb 3d and O 1s core levels and chemical bonding in niobates

Energy Technology Data Exchange (ETDEWEB)

Atuchin, V.V. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation)]. E-mail: atuchin@thermo.isp.nsc.ru; Kalabin, I.E. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Kesler, V.G. [Technical Center, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Pervukhina, N.V. [Laboratory of Crystal Chemistry, Institute of Inorganic Chemistry, SB RAS, Novosibirsk 630090 (Russian Federation)

2005-02-01

A set of available experimental data on binding energies of Nb 3d{sub 5/2} and O 1s core levels in niobates has been observed with using energy difference (O 1s-Nb 3d{sub 5/2}) as a robust parameter for compound characterization. An empirical relationship between (O 1s-Nb 3d{sub 5/2}) values measured with XPS for Nb{sup 5+}-niobates and mean chemical bond length L(Nb-O) has been discussed. A range of (O 1s-Nb 3d{sub 5/2}) values possible in Nb{sup 5+}-niobates has been defined. An energy gap {approx}1.4-1.8 eV is found between (O 1s-Nb 3d{sub 5/2}) values reasonable for Nb{sup 5+} and Nb{sup 4+} states in niobates.

Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

Science.gov (United States)

Becker, Chaoyue; Posen, Sam; Groll, Nickolas; Cook, Russell; Schlepütz, Christian M.; Hall, Daniel Leslie; Liepe, Matthias; Pellin, Michael; Zasadzinski, John; Proslier, Thomas

2015-02-01

We present an analysis of Nb3Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (Tc) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ˜2 μm thick Nb3Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb3Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

International Nuclear Information System (INIS)

Becker, Chaoyue; Posen, Sam; Hall, Daniel Leslie; Groll, Nickolas; Proslier, Thomas; Cook, Russell; Schlepütz, Christian M.; Liepe, Matthias; Pellin, Michael; Zasadzinski, John

2015-01-01

We present an analysis of Nb 3 Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb 3 Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T c ) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb 3 Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb 3 Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T c regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb 3 Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators

Design study of 15-Tesla RHQT Nb3Al block type dipole magnet

Energy Technology Data Exchange (ETDEWEB)

Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2005-09-01

The design study of the block type 15-Tesla RHQT Nb{sub 3}Al dipole magnet, and its merits over Nb{sub 3}Sn magnets are presented. The copper stabilized RHQT Nb{sub 3}Al strand is now becoming commercially available for the application to the accelerator magnets. A 1 mm diameter RHQT Nb{sub 3}Al strand with filament size about 50 {mu}, non-copper Jc about 1000 A/mm{sup 2} at 15 Tesla at 4.2K, copper ratio of 50%, can now be produced over several hundred meters. The stress and strain characteristics of the Nb{sub 3}Al strand are superior to the Nb{sub 3}Sn strand. Another advantage is that it can tolerate a longitudinal strain up to 0.55%. The RHQT Nb{sub 3}Al Rutherford cable will have less chance of contamination of the stabilizer, compared to Nb{sub 3}Sn cable. These characteristics of the RHQT Nb{sub 3}Al will be beneficial for designing and producing 15-Tesla dipole magnets. An example 15-Tesla magnet cross section, utilizing the RHQT Nb{sub 3}Sn strand is presented. A systematic investigation on RHQT Nb{sub 3}Al strands, its Rutherford cables, and building a small racetrack magnet for cable testing are proposed.

Carbide precipitation kinetics in austenite of a Nb-Ti-V microalloyed steel

International Nuclear Information System (INIS)

Jung, Jae-Gil; Park, June-Soo; Kim, Jiyoung; Lee, Young-Kook

2011-01-01

Highlights: → Carbide precipitation kinetic was fastest at 950 deg. C and accelerated by strain. → Nucleation sites for (Nb,Ti)C above 950 deg. C were mainly undissolved (Ti,Nb)(C,N). → Strain enabled (Nb,Ti)C to nucleate on all sides of (Ti,Nb)(C,N) above 950 deg. C. → Strain changed nucleation sites from (Ti,Nb)(C,N) to dislocations below 900 deg. C. → Strain also accelerated the change in particle composition to equilibrium one. - Abstract: The isothermal precipitation kinetics of carbides in both strain-free and strained austenite (γ) of a microalloyed steel were quantitatively investigated through the electrical resistivity and transmission electron microscopy. The (Nb,Ti)C carbides at the interfaces of the undissolved (Ti,Nb)(C,N) carbonitrides were observed at all temperatures in strain-free γ. However, for strain-induced precipitation, above 950 deg. C, the precipitation of (Nb,Ti)C carbides near the undissolved (Ti,Nb)(C,N) carbonitrides was predominant due to the recrystallization of strained γ. Meanwhile, the fine (Nb,Ti,V)C carbides were homogeneously precipitated in non-recrystallized γ at 850 deg. C and 900 deg. C, as well as near the undissolved (Ti,Nb)(C,N) particles. The electrical resistivity method was successfully used to quantitatively measure the isothermal precipitation kinetics of carbides in both strain-free and strained γ. The precipitation-time-temperature diagrams of the carbide in strain-free and strained γ, with nose temperatures of 950 deg. C, were generated and the precipitation kinetics were greatly accelerated by the applied strain.

Z-contrast imaging of ordered structures in Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3

International Nuclear Information System (INIS)

Yan, Y.; Pennycook, S.J.; Xu, Z.; Viehland, D.

1998-02-01

Lead-based cubic perovskites such as Pb(B 1/3 2+ B 2/3 5+ )O 3 (B 2+ Mg, Co, Ni, Zn; B 5+ = Nb, Ta) are relaxor ferroelectrics. Localized order and disorder often occur in materials of this type. In the Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) family, previous studies have proposed two models, space-charge and charge-balance models. In the first model, the ordered regions carry a net negative charge [Pb(Mg 1/2 Nb 1/2 )O 3 ], while in the second model it does not carry a net charge [Pb((Mg 2/3 Nb 1/3 ) 1/2 Nb 1/2 )O 3 ]. However, no direct evidence for these two models has appeared in the literature yet. In this paper the authors report the first direct observations of local ordering in undoped and La-doped Pb(Mg 1/3 Nb 2/3 )O 3 , using high-resolution Z-contrast imaging. Because the ordered structure in Ba(Mg 1/3 Nb 2/3 )O 3 is well known, the Z-contrast image from an ordered domain is used as a reference for this study

Structure and tensile properties of Fe-Cr model alloy strengthened by nano-scale NbC particles derived from controlled crystallization of Nb-rich clusters

Energy Technology Data Exchange (ETDEWEB)

Dai, Lei [College of Materials and Chemical Engineering, Three Gorges University, Yichang 443002 (China); Guo, Qianying [State Key Lab of Hydraulic Engineering Simulation and Safety, School of Material Science and Engineering, Tianjin University, Tianjin 300354 (China); Liu, Yongchang, E-mail: licmtju@163.com [State Key Lab of Hydraulic Engineering Simulation and Safety, School of Material Science and Engineering, Tianjin University, Tianjin 300354 (China); Yu, Liming; Li, Huijun [State Key Lab of Hydraulic Engineering Simulation and Safety, School of Material Science and Engineering, Tianjin University, Tianjin 300354 (China)

2016-09-30

This article describes the microstructural evolution and tensile properties of Fe-Cr model alloy strengthened by nano-scale NbC particles. According to the results obtained from X-ray diffraction and transmission electron microscope with Energy Dispersive Spectrometer, the bcc ultrafine grains and the disordered phase of Nb-rich nano-clusters were observed in the milled powders. The hot pressing (HP) resulted in a nearly equiaxed ferritic grains and dispersed nano-scale NbC (~8 nm) particles. The microstructure studies reveal that the formation of NbC nanoparticles is composed of nucleation and growth of the Nb-rich nano-clusters involving diffusion of their component. At room temperature the material exhibits an ultimate tensile strength of 700 MPa, yield strength of 650 MPa, and total elongation of 11.7 pct. The fracture surface studies reveal that a typical ductile fracture mode has occurred during tensile test.

Utilization of the {sup 93}Nb(n,n'){sup 93}Nb{sup m} Reaction for for Reactor Neutron Dosimetry

Energy Technology Data Exchange (ETDEWEB)

Czock, K. H.; Houtermans, H. [International Atomic Energy Agency, Division of Research and Laboratories, Vienna (Austria)

1974-09-15

For the measurement of large ({Phi}>10{sup 18}n/cm{sup 2}) fast neutron fluences in research reactors, the reaction {sup 93}Nb(n,n'){sup 93}Nb{sup m} is fairly seldom used (Lloret, Hegedus). The reason is that the excitation function for the production of the {sup 93}Nb isomeric state (half-life{approx_equal}11.4 years) by inelastic neutron scattering is nearly unknown. Also the determination of the absolute {sup 93}Nb{sup m} activity is difficult, e.g. due to the bad knowledge of the conversion coefficients {alpha}{sub tot} and {alpha}{sub K}. But for neutron dosimetry purposes one does not necessarily need absolute activity values, if one irradiated niobium foil (e.g. 10 mm empty and 0.1 mm thick) is accepted to be a reference source to other irradiated niobium foils (of the same original material). If the cross section measurements and the fluence determinations are both based on the same reference source {sup 93}Nb{sup m} as an arbitrary activity standard, the possible inaccuracy of this activity value would not matter. Such an accepted reference source could be deposited at one central institution. Once the reference source activity is defined (at present within 30% of the true absolute activity value) niobium sources with activities determined relative to this reference source could be supplied together with non-irradiated niobium foils to interested laboratories. (author)

Method of mechanochemical synthesis for the production of nanocrystalline Nb-Al alloys

International Nuclear Information System (INIS)

Portnoj, V.K.; Tret'yakov, K.V.; Logacheva, A.I.; Logunov, A.V.; Razumovskij, I.M.

2004-01-01

Using X-ray diffraction and DS analyses the process of solid phase synthesis on cooperative comminution of components (Nb, Al, Cr) in a planetary ball mill is investigated. Powder nanocrystalline Nb 3 Al base alloys of various compositions with simultaneous introduction of chromium are synthesized. High power milling results in block size of ∼ 20 nm. It is shown that final chromium dissolution and partial decomposition of Nb(Al) supersaturated solid solutions proceed after heating up to 1100 deg C only. With the help of doping with niobium by the method of mechanical alloying, a two-phase alloy Nb 3 Al + Nb 2 Al having been produced by arc melting, is corrected by composition and transferred to the two-phase region of Nb 3 Al + Nb(Al). It is revealed that the process of niobium aluminide phase formation during mechanochemical synthesis and the process of mechanical activation of Nb-Al system intermetallics enriched with niobium always proceed through formation of supersaturated solid solutions. The mechanism of the process is probably associated with stacking faults formation due to deformation [ru

Stress effects on multifilamentary Nb3Sn wire

International Nuclear Information System (INIS)

Bartlett, R.J.; Taylor, R.D.; Thompson, J.D.

1979-01-01

Critical current I/sub c/ measurements were obtained on highly stabilized mf Nb 3 Sn wires as a function of heat treatment, stress, temperature, and applied magnetic field. The ratio of the area of the copper to bronze core-niobium tube is about 8, and the filaments are concentrated in the inner 30% of the wire cross section. Values of I/sub c/ and T/sub c/ were determined for samples subjected to a wide range of heat treatments. Diffusion reaction times and temperatures in the ranges 16 to 128 hr and 700 to 750 0 C provided a number of mf Nb 3 Sn wires having similar I/sub c/ characteristics. To some extent the residual compressive loading on the Nb 3 Sn wires varied with the particular heat treatment. This loading arises primarily from the differential contraction of the remaining bronze and the Nb 3 Sn layer when cooled from the reaction temperature to the operating temperature. It was found that, by controlled bending or stretching of the wires, whereby some of the strain in the Nb 3 Sn is relieved, the I/sub c/ at 14 K is increased by as much as 30% and the critical temperature is increased by up to 1 K

THz spectroscopy on superconducting NbN thin films

Energy Technology Data Exchange (ETDEWEB)

Daschke, Lena; Pracht, Uwe S.; Dressel, Martin; Scheffler, Marc [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Ilin, Konstantin S.; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruher Institut fuer Technologie (Germany)

2015-07-01

Epitaxial thin-film niobium nitride (NbN) is a conventional BCS superconductor. In presence of strong disorder, however, electronic inhomogeneities appear, which is not fully understood yet. To obtain a better insight into the physics of such disordered materials, studies on model systems such as structurally tailored films might be useful. Furthermore, disordered NbN films are used for single-photon detection devices, whose proper performance depends on a profound understanding of the superconducting properties. The studied NbN films have a T{sub c} ranging from 10 to 15 K and the superconducting energy gap is easily accessible with THz spectroscopy (0.4 - 5.6 meV). We investigate thin films of NbN sputtered on a sapphire substrate. With a Mach-Zehnder interferometer we measure the amplitude and phase shift of radiation transmitted through the thin-film sample. From there we can determine the real and imaginary parts of the optical conductivity. These results give information about the energy gap, Cooper pair density, and quasiparticle dynamics, including the temperature evolution of these quantities. We found that a film with 10 nm thickness roughly follows the BCS behavior, as expected. We will present results of our measurements on several different NbN samples.

The Niagara Falls Storage Site Remedial Action Project. Status update and summary of special features

International Nuclear Information System (INIS)

Campbell, L.F.; Coxon, G.D.

1986-01-01

The U.S. Department of Energy (DOE) and its Project Management Contractor, Bechtel National, Inc., are conducting remedial action at the Niagara Falls Storage Site (NFSS) near Lewiston, New York to stabilize low-level radioactive wastes stored at the site and to decontaminate over two dozen contaminated vicinity properties. Over the past 4 years a 10-acre interim waste containment facility has been developed at the site to hold the approximately 250,000 yd/sup 3/ of contaminated soil and rubble from the cleanup operations. Several existing buildings were demolished or modified for burial inside the containment area. In addition, residues inside a 165-ft-high concrete tower were transferred to one of the buildings inside the containment area using hydraulic mining techniques. The residues were dewatered and covered with clay to minimize radom emanation; the tower was demolished and the rubble disposed of in the containment area. Environmental monitoring will continue throughout the interim storage period. In addition, the surface and subsurface condition of the containment structure will be monitored to ensure that undesirable trends are detected in time for corrective action to be taken. The DOE Record of Decision on the long-term disposition of the NFSS is expected to be made by the end of April, 1986

Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys: Phase stability in Nb-Cr-Ni ternary system

Energy Technology Data Exchange (ETDEWEB)

Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1997-12-01

Phase stability in a ternary Nb-Cr-Ni Laves phase system was studied in this paper. Their previous study in NbCr{sub 2}-based transition-metal Laves phases has shown that the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based Laves phases when the atomic size ratios are kept identical. Since Ni has ten out-shell electrons, the substitution of Ni for Cr in NbCr{sub 2} will increase the average electron concentration of the alloy, thus leading to the change of the crystal structures from C15 to C14. In this paper, a number of pseudo-binary Nb(Cr,Ni){sub 2} alloys were prepared, and the crystal structures of the alloys after a long heat-treatment at 1000 C as a function of the Ni content were determined by the X-ray diffraction technique. The boundaries of the C15/C14 transition were determined and compared to their previous predictions. It was found that the electron concentration and phase stability correlation is obeyed in the Nb-Cr-Ni system. However, the e/a ratio corresponding to the C15/C14 phase transition was found to move to a higher value than the predicted one. The changes in the lattice constant, Vickers hardness and fracture toughness were also determined as a function of the Ni content, which were discussed in light of the phase stability difference of the alloys.

Me-Si-C (Me= Nb, Ti or Zr) : Nanocomposite and Amorphous Thin Films

OpenAIRE

Tengstrand, Olof

2012-01-01

This thesis investigates thin films of the transition metal carbide systems Ti-Si-C, Nb-Si-C, and Zr-Si-C, deposited at a low substrate temperature (350 °C) with dc magnetron sputtering in an Ar discharge. Both the electrical and mechanical properties of these systems are highly affected by their structure. For Nb-Si-C, both the ternary Nb-Si-C and the binary Nb-C are studied. I show pure NbC films to consist of crystalline NbC grains embedded in a matrix of amorphous carbon. The best combina...

Densification and Mechanical Properties of ZrN-Nb Composites

Directory of Open Access Journals (Sweden)

ZHANG Yan

2018-02-01

Full Text Available Densification of zirconium nitride (ZrN ceramics was investigated by vacuum hot pressing at temperatures range from 1500℃to 2000℃with Nb as sintering additive. Densification was enhanced with Nb addition. ZrN with 5mol% Nb addition achieved a relative density of 98.5% at 1600℃.XRD and lattice parameter measurements indicated that there were structural differences between samples sintered in different temperatures. It was likely that due to the presence of point defects by changes in stoichiometry, the kinetics of mass transport enhanced. As a result, the relative density of the zirconium nitride (ZrN ceramics have been improved, thus the fully densed ZrN ceramics can be prepared in a relative low temperature. The density, the room-temperature mechanical properties of ZrN ceramics are increased after the addition of Nb. Zirconium nitride (ZrNdoped with Nb sintered at 1600℃ are measured and obtained elasticity modulus of 238 GPa, flexural strength of 463.3 MPa, fracture toughness of 7.0 MPa·m1/2 and hardness of 10.7 GPa.

Heat capacity measurement of CeNbO4(s)

International Nuclear Information System (INIS)

Bhojane, S.M.; Kulkarni, Jayanthi; Kulkarni, S.G.

2012-01-01

Molar heat capacity of CeNbO 4 (s) was determined using differential scanning calorimeter in the temperature range of 550 to 900 K. The molar heat capacity values were least squares analysed and the dependence of molar heat capacity with temperature for CeNbO 4 (s) can be given as, J K -1 mol -1 = 94.7320 + 0.0852T-1.6073 x 10 6 T -2 (550≤T(K)≤900) Cerium is commonly used as an inactive analogue to plutonium; also it is an important fission product with moderate yield. Various Nb alloys are used as cladding material in nuclear industry. Hosts of thermodynamic data are needed to understand the various phenomena that occur in a nuclear reactor. In the present study, the molar heat capacity of CeNbO 4 (s) has been determined using high temperature differential scanning calorimeter in temperature range 550 to 900 K. This is one of the important compounds in the ternary system of Ce-Nb-O

Metallurgy, fabrication, and superconducting properties of multifilamentary Nb3Al composites

International Nuclear Information System (INIS)

Hafstrom, J.W.

1976-01-01

The control of metallurgical structure during fabrication that will improve the superconducting properties of multifilamentary, aluminium-stabilized, Nb 3 Al composites is described. Composites are fabricated by placing niobium rods in an aluminum matrix, and then drawing to wire. Nb 3 Al is formed at temperatures exceeding 1800 0 C for about 5 s and ordered at 750 0 C for 48 h. A critical current, J/sub c/(H), in excess of 10 5 A/cm 2 (F/sub p/ approximately equal to 7 x 10 8 dynes/cm 3 ) at 7 T and a T/sub c/ to 18.2 K are obtained. Attempts to improve J/sub c/(H) by controlling the grain size in the Nb 3 Al diffused layer are discussed. Precipitates, arising from the addition of carbon during Nb 3 Al layer growth, do not appear to be effective as grain-boundary or flux pinners. When 1 percent Zr is added to the Nb, the growth of the Nb 3 Al layer is accelerated, T/sub c/ is lowered and J/sub c/(H) is not significantly improved. J/sub c/(H) rapidly decreases with an increase in Nb 3 Al or (Nb-Zr) 3 Al layer thickness, d. J/sub c/(H) is independent of d in composites with d greater than or approximately equal to 1.5 μm. In general, the Nb 3 Al grain size appears comparable to d for d less than or equal to 1 μm. Significant improvement of J/sub c/(H) for Nb 3 Al superconducting composites reacted at temperatures above 1800 0 C (to achieve T/sub c/ greater than 17 K) is achieved only by maintaining the layer thickness well below d approximately equal to 1.0 μm

Evaluation the homogenisation behaviour of Sm-Fe-Nb materials by Moessbauer spectroscopy

International Nuclear Information System (INIS)

Sinan, S. A.; Muryaed, Y.; Alhweg, F. A.

2004-01-01

The microstructure of cast and annealed Sm-Fe-Nb materials were investigated by Moessbauer spectroscopy. The aim of the present work is to study the effect of Nb additions upon the microstructure of Sm 2 Fe 17 material and evaluation the homogenisation behaviour of different Sm-Fe-Nb materials. The niobium free cast material consisting of the Sm 2 Fe 17 phase and significant amounts of the free iron (α -Fe). Therefore, the homogenisation process is necessary to eliminate the free iron and produce a single Sm 2 Fe 17 phase material. This process takes long annealing time, up to seven days. The Sm 9 .5 Fe 8 7.5 Nb 3 alloy contains the lowest amount of α-Fe among, the Sm-Fe-Nb materials. Thus the homogenisation step was carried out with treatment time (12 hours) smaller than the reported annealing time of Nb-free material (Sm 2 Fe 17 ). Therefore, the addition of at 3% Nb reduces the manufacturing cost of the Sm 2 Fe 17 and makes this based material for permanent magnets, more industrially desirable, due to elimination the free iron with lowest treatment time. Also it was found that the existence of the paramagnetic NbFe 2 phase becomes higher after the homogenisation process, which can be explained due to the diffusion of Nb from Sm 2 Fe 17 phase to paramagnetic NbFe 2 phase, during the annealing process. (authors)

Dermatoscopy of blue vitiligo.

Science.gov (United States)

Chandrashekar, L

2009-07-01

Blue vitiligo is a distinct variant of vitiligo characterized by a blue-grey appearance of the skin, which corresponds histologically with absence of epidermal melanocytes and presence of numerous dermal melanophages. A 23-year-old woman of Indian origin with Fitzpatrick skin type V presented with a 1-month history of normoaesthetic depigmented macules over the right forearm, dorsa of the hands and right areola. The macule over the right forearm had a bluish tinge. A clinical diagnosis of vitiligo vulgaris with blue vitiligo was made. Dermatoscopy of the interface between the blue macule and the hypopigmented macule revealed a linear depigmented macule in the centre with multiple blue dots and absence of epidermal melanin on the side of the blue macule, and reticular pigmentation with a few depigmented macules and scattered blue dots over the side of the hypopigmented macule. Blue vitiligo was described previously in a patient seropositive for human immunodeficiency virus, and believed to represent postinflammatory hyperpigmentation in areas bordering the vitiliginous patches as a result of psoralen ultraviolet A treatment. This case is unusual because of its rarity and the description of the associated dermatoscopical findings.

Electrochemical deposition of Cu and Nb from pyrrolidinium based ionic liquid

Energy Technology Data Exchange (ETDEWEB)

Mascia, Michele, E-mail: michele.mascia@unica.it [Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari (Italy); Vacca, Annalisa; Mais, Laura; Palmas, Simonetta [Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari (Italy); Musu, Elodia [Laboratorio Telemicroscopia Industriale, Sardegna Ricerche, Polaris, Parco Tecnologico della Sardegna, Edificio 3, Loc. Piscinamanna, 09010 Pula, CA (Italy); Delogu, Francesco [Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari (Italy)

2014-11-28

A study on the electrochemical deposition of Cu/Nb composites is presented in this work. The electrodeposition tests were performed using 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulphonyl) imide as solvent. The electrochemical behaviour of copper and niobium ions was investigated by cyclic and linear sweep voltammetries, allowing to obtain information on potentials and mechanisms of deposition. Firstly, the electrodeposition of Nb on Cu substrate and of Cu on Nb substrate was investigated; then, the deposition of Cu and Nb in dual bath mode was considered. All the experimental tests were carried out at 125 °C under inert atmosphere, in order to avoid interference of water and oxygen. According to the electrochemistry of the metals considered and based on the experimental results, the possible reaction path for the oxidation/reduction was proposed. Deposition tests were carried out at different potentials and the related samples were analysed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Structural and chemical analyses indicate that the obtained deposits cover uniformly the electrode surface and exhibit individual layers with a characteristic size ranging between 50 and 100 nm. - Highlights: • Cu/Nb composites were obtained by electro-deposition from ionic liquid. • The electrochemical behaviour was studied by cyclic and linear sweep voltammetries. • Anodic dissolution of Cu and cathodic deposition of Cu, Nb and Cu/Nb were studied. • The Cu, Nb and Cu/Nb deposits were characterised through SEM and EDX analyses. • The characteristic length of the deposits ranges between 50 and 100 nm.

In vitro Cytotoxicity, Pharmacokinetics, Tissue Distribution, and Metabolism of Small-Molecule Protein Kinase D Inhibitors, kb-NB142-70 and kb-NB165-09, in Mice bearing Human Cancer Xenografts

Science.gov (United States)

Guo, Jianxia; Clausen, Dana M.; Beumer, Jan H.; Parise, Robert A.; Egorin, Merrill J.; Bravo-Altamirano, Karla; Wipf, Peter; Sharlow, Elizabeth R.; Wang, Qiming Jane; Eiseman, Julie L.

2012-01-01

Purpose Protein kinase D (PKD) mediates diverse biological responses including cell growth and survival. Therefore, PKD inhibitors may have therapeutic potential. We evaluated the in vitro cytotoxicity of two PKD inhibitors, kb-NB142-70 and its methoxy analog, kb-NB165-09, and examined their in vivo efficacy and pharmacokinetics. Methods The in vitro cytotoxicities of kb-NB142-70 and kb-NB165-09 were evaluated by MTT assay against PC-3, androgen independent prostate cancer cells, and CFPAC-1 and PANC-1, pancreatic cancer cells. Efficacy studies were conducted in mice bearing either PC-3 or CPFAC-1 xenografts. Tumor-bearing mice were euthanized between 5 and 1440 min after iv dosing, and plasma and tissue concentrations were measured by HPLC-UV. Metabolites were characterized by LC-MS/MS. Results kb-NB142-70 and kb-NB165-09 inhibited cellular growth in the low-mid μM range. The compounds were inactive when administered to tumor-bearing mice. In mice treated with kb-NB142-70, the plasma Cmax was 36.9 nmol/mL and the PC-3 tumor Cmax was 11.8 nmol/g. In mice dosed with kb-NB165-09, the plasma Cmax was 61.9 nmol/mL while the PANC-1 tumor Cmax was 8.0 nmol/g. The plasma half-lives of kb-NB142-70 and kb-NB165-09 were 6 and 14 min, respectively. Both compounds underwent oxidation and glucuronidation. Conclusions kb-NB142-70 and kb-NB165-09 were rapidly metabolized, and concentrations in tumor were lower than those required for in vitro cytotoxicity. Replacement of the phenolic hydroxyl group with a methoxy group increased the plasma half-life of kb-NB165-09 2.3-fold over that of kb-NB142-70. Rapid metabolism in mice suggests that next-generation compounds will require further structural modifications to increase potency and/or metabolic stability. PMID:23108699

Role of Nb content in nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Sitek, J. [Department of Nuclear Physics and Technology, Slovak Technical University, Ilkovicova 3, 812 19, Bratislava (Slovakia); Lipka, J. [Department of Nuclear Physics and Technology, Slovak Technical University, Ilkovicova 3, 812 19, Bratislava (Slovakia); Miglierini, M. [Department of Nuclear Physics and Technology, Slovak Technical University, Ilkovicova 3, 812 19, Bratislava (Slovakia); Toth, I. [Department of Nuclear Physics and Technology, Slovak Technical University, Ilkovicova 3, 812 19, Bratislava (Slovakia)

1995-02-09

The influence of Nb content on the formation of nanocrystalline phase in the Fe{sub 73.5-x}Cu{sub 1}Nb{sub 3+x}Si{sub 13.5}B{sub 9} system was studied by Moessbauer spectroscopy. The kinetics of crystallization was observed by isothermal heating at temperature 550 C during annealing time up to 16 h. The samples containing 3 and 4.5 at% were compared. Nanocrystalline phase formation was explained on the basis of cluster model. ((orig.)).

Collective flow in central Ca + Ca and Nb + Nb collisions

International Nuclear Information System (INIS)

Fai, G.; Csernai, L.P.; Kapusta, J.I.

1986-01-01

Questions related to the entropy, equation of state and collective flow of nuclear matter are important to the authors understanding of high energy nuclear collisions. Completion of the analysis of exclusive measurements on central Ca + Ca and Nb + Nb collisions triggered renewed interest in these problems. In order to address the results of exclusive measurements, however, the complex multifragment final states of high energy nuclear collisions need to be incorporated in a theoretical description. The microcanonical event generator model provides statistically generated complete events that can be compared to the exclusive data on an event-by-event basis. To describe the disassembly of hot nuclear matter the model uses an approximate scheme in which the available final states are populated according to their microcanonical weight in phase space. This statistical description is front-ended with simple geometric ideas to divide the collision system into subsystems and with a prescription to share energy and momentum among the subsystems. Any physical quantity of interest is in principle calculable in the model if sufficient statistics is accumulated

Energy for the interface system of (Nb, Mo)C/γ-Fe

Energy Technology Data Exchange (ETDEWEB)

Zhou, Yanyuan; Wang, Zhenqiang; Zhao, Jiaying; Niu, Zhongyi; Guo, Chunhuan; Jiang, Fengchun [Harbin Engineering University, Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Material Science and Chemical Engineering, Harbin (China); Leng, Zhe [Harbin Engineering University, Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Material Science and Chemical Engineering, Harbin (China); Zhejiang Ocean University, Innovation and Application Institute, Zhoushan (China); Zhang, Zhengyan; Yao, Chunfa [Central Iron and Steel Research Institute, Department of Structural Steels, Beijing (China); Yang, Zhigang [Tsinghua University, Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Beijing (China)

2017-08-15

The interfacial energies of MC/γ-Fe and formation energies of MC carbides have been investigated using first-principles calculations based on density functional theory (DFT). Results show that the replacement of Nb by Mo in the NbC lattice is unfavorable with respect to the formation energy. However, it reduces the lattice parameter of MC and decreases the σ{sub chemical} (interfacial chemical energy) of MC/γ-Fe, thus favoring the formation of complex (Nb, Mo)C carbide. The substitution of Nb by Mo at the interface of MC/γ-Fe system promotes the hybridizations of Mo-1NNFe and C-1NNFe (or 2NNFe) (the first or second nearest neighboring Fe atoms), which leads to a decrease in σ{sub chemical}. The influence of bond energy is estimated using the discrete lattice plane/nearest neighbor broken bond (DLP/NNBB) model. It is found that the reduced is attributed to the much smaller value of e{sub Fe-C}-e{sub Mo-C} (the difference between Fe-C and Nb-C interactions). The results obtained from the analysis of the precipitates in Nb- and Nb-Mo-bearing steels are in a good agreement with the calculations. (orig.)

Exfoliation and thermal transformations of Nb-substituted layered titanates

DEFF Research Database (Denmark)

Song, H.; Sjåstad, Anja O.; Fjellvåg, Helmer

2011-01-01

Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating...... factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates...

Direction-dependent RBS channelling studies in ion implanted LiNbO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Wendler, E., E-mail: elke.wendler@uni-jena.de; Becker, G.; Rensberg, J.; Schmidt, E.; Wolf, S.; Wesch, W.

2016-07-15

Damage formation in ion implanted LiNbO{sub 3} was studied by Rutherford backscattering spectrometry (RBS) along various directions of the LiNbO{sub 3} crystal. From the results obtained it can be unambiguously concluded that Nb atoms being displaced during ion implantation preferably occupy the free octahedron sites of the LiNbO{sub 3} lattice structure and most likely also form Nb{sub Li} antisite defects.

{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.

Atomic Defects and Doping of Monolayer NbSe2.

Science.gov (United States)

Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

2017-03-28

We have investigated the structure of atomic defects within monolayer NbSe 2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe 2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

Mechanical properties and grindability of dental cast Ti-Nb alloys.

Science.gov (United States)

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2003-09-01

Aiming at developing a dental titanium alloy with better mechanical properties and machinability than unalloyed titanium, a series of Ti-Nb alloys with Nb concentrations up to 30% was made. They were cast into magnesia-based molds using a dental casting machine and the mechanical properties and grindability of the castings were examined. The hardness of the alloys with Nb concentrations of 5% and above was significantly higher than that of titanium. The yield strength and tensile strength of the alloys with Nb concentrations of 10% and above were significantly higher than those of titanium, while the elongation was significantly lower. A small addition of niobium to titanium did not contribute to improving the grindability of titanium. The Ti-30% Nb alloy exhibited significantly better grindability at low grinding speed with higher hardness, strength, and Young's modulus than titanium, presumably due to precipitation of the omega phase in the beta matrix.

Local magnetic moments in dilute Cr-Nb alloys: the effects of applied magnetic field and Nb concentration

International Nuclear Information System (INIS)

Souza, P E N de; Oliveira, L M de; Ortiz, W A; Camargo, P C de; Oliveira, A J A de

2005-01-01

In this work we present magnetic susceptibility results for Cr-x at.% Nb alloys (x = 0.2, 0.6, 0.7, 1.4, and 2.0), showing that a local short-range order spin-density wave (L-SDW) appears at a characteristic temperature (T loc ) above the Neel temperature. The evidence for L-SDW is based on a Curie-Weiss-like behaviour, which is suppressed when large magnetic fields are applied or for alloys with Nb concentration above x = 2.0 at.%

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)

Structural and superconducting properties of as-cast Nb3Al

International Nuclear Information System (INIS)

Mondal, Puspen; Manekar, Meghmalhar; Roy, S.B.; Kumar, Ravi; Ganguli, Tapas

2007-01-01

We present the results of x-ray diffraction and magnetization measurements on the as-cast compound Nb 3 Al. X-ray diffraction shows the presence of the Al 5 Nb 3 Al phase along with a bcc Nb-Al solid solution. The average grain size of Nb 3 Al estimated from the line broadening is about 35 nm. Magnetization measurements show a superconducting transition temperature of about 16.8 K which is amongst the highest known T c for the as-cast sample. In the superconducting state, the sample shows interesting thermo-magnetic history effects in the temperature and field variation of magnetization. (author)

Recent status of studies on the neutron irradiation effect focusing on Nb3Sn and Nb3Al strands

International Nuclear Information System (INIS)

Nishimura, Arata

2011-01-01

A fusion reactor generates a lot of 14 MeV neutrons, some of which penetrate shielding blankets, stream out of ports and reach superconducting magnets. Some important studies were performed in the 1970s and a basic understanding of the mechanisms of neutron irradiation effect was established. Advances in the design concept of nuclear fusion reactors led to the need for consistent studies on the neutron irradiation effect of A-15 strands such as Nb 3 Sn and Nb 3 Al, which are strong candidates for fusion reactors. In the early 2000s, a progressive attempt to organize the collaborative research of universities and national institutes was started using a 14 MeV neutron source at Japan Atomic Energy Agency. This paper outlines the neutron irradiation issues related to superconducting magnets for fusion, and a brief history of research on the neutron irradiation effect is provided. In addition, experimental results regarding changes in the superconducting properties of Nb 3 Sn and Nb 3 Al strands by neutron irradiation obtained in the newly established collaborative framework are presented, and general mechanisms for the property changes are introduced. (author)

Single-Crystal X-Ray Diffraction Studies of Homologues in the Series nBa(Nb,Zr)O 3+3 mNbO with n=2, 3, 4, 5 and m=1

Science.gov (United States)

Nilsson, G.; Svensson, G.

2001-01-01

Single crystals of four homologues in the series nBa(Nb,Zr)O3+3mNbO, with n:m=2:1, 3:1, 4:1, and 5:1, were found in the reduced Ba-Nb-Zr-O system. Single-crystal X-ray diffraction data were collected for all the crystals. For all homologues the space group was found to be P4/mmm. The structures can be described as intergrowths of Ba(Nb,Zr)O3 perovskite and NbO slabs. The refined cell parameters and compositions of the 2:1, 3:1, and 4:1 homologues are a=4.1768(5) Å and c=12.269(2) Å for Ba2Nb4.5(1)Zr0.5(1)O9, a=4.1769(5) Å and c=16.493(3) Å for Ba3+δNb4.8(2)-δ Zr1.2(2)O12-δ (δ=0.098(4)), and a=4.1747(6) Å and c= 20.619(4) Å for Ba4+δNb5.1(4)-δZr1.9(4)O15-δ (δ=0.270(9)). The refined cell parameters of the 5:1 homologue are a=4.1727(3) Å and c=24.804(3) Å. Zr replaces Nb only in the NbO6 octahedra found in the perovskite slabs.

Effects of phase constitution of Zr-Nb alloys on their magnetic susceptibilities

International Nuclear Information System (INIS)

Nomura, Naoyuki; Tanaka, Yuko; Suyalatu; Kondo, Ryota; Doi, Hisashi; Tsutsumi, Yusuke; Hanawa, Takao

2009-01-01

The magnetic susceptibilities and microstructures of Zr-Nb binary alloys were investigated to develop a new metallic biomaterial with a low magnetic susceptibility for magnetic resonance imaging (MRI). The magnetic susceptibility was measured with a magnetic susceptibility balance, and the microstructure was evaluated with an X-ray diffractometer (XRD), an optical microscope (OM), and a transmission electron microscope (TEM). Zr-Nb alloys as-cast showed a minimum value of magnetic susceptibility between 3 and 9 mass% Nb, and the value abruptly increased up to 20 mass% Nb, followed by a gradual increase with the increase of the Nb content. XRD, OM, and TEM revealed that the minimum value of the susceptibility was closely related to the appearance of the athermal ω phase in the β phase. Since the magnetic susceptibility of Zr-3Nb alloy consisting of an α' phase was as low as that of Zr-9Nb alloy consisting of the β and ω phases, that of the ω phase was lower than that of the α' and β phases. When Zr-16Nb alloy was heat-treated, the isothermal ω phase appeared, and, simultaneously, the magnetic susceptibility decreased. Therefore, the ω phase contributes to the decrease of the magnetic susceptibility, independently of the formation process of the ω phase. The magnetic susceptibility of the Zr-3Nb alloy as-cast was almost one-third that of Ti-6Al-4V alloy, which is commonly used for medical implant devices. Zr-Nb alloys are useful for medical devices used under MRI. (author)

Terahertz Mixing Characteristics of NbN Superconducting Tunnel Junctions and Related Astronomical Observations

Science.gov (United States)

Li, J.

2010-01-01

High-sensitivity superconducting SIS (superconductor-insulator-superconductor) mixers are playing an increasingly important role in the terahertz (THz) astronomical observation, which is an emerging research frontier in modern astrophysics. Superconducting SIS mixers with niobium (Nb) tunnel junctions have reached a sensitivity close to the quantum limit, but have a frequency limit about 0.7 THz (i.e., gap frequency of Nb tunnel junctions). Beyond this frequency Nb superconducting films will absorb energetic photons (i.e., energy loss) to break Cooper pairs, thereby resulting in significant degradation of the mixer performance. Therefore, it is of particular interest to develop THz superconducting SIS mixers incorporating tunnel junctions with a larger energy gap. Niobium-nitride (NbN) superconducting tunnel junctions have been long known for their large energy gap, almost double that of Nb ones. With the introduction of epitaxially grown NbN films, the fabrication technology of NbN superconducting tunnel junctions has been considerably improved in the recent years. Nevertheless, their performances are still not as good as Nb ones, and furthermore they are not yet demonstrated in real astronomical applications. Given the facts mentioned above, in this paper we systematically study the quantum mixing behaviors of NbN superconducting tunnel junctions in the THz regime and demonstrate an astronomical testing observation with a 0.5 THz superconducting SIS mixer developed with NbN tunnel junctions. The main results of this study include: (1) successful design and fabrication of a 0.4˜0.6 THz waveguide mixing circuit with the high-dielectric-constant MgO substrate; (2) successful fabrication of NbN superconducting tunnel junctions with the gap voltage reaching 5.6 mV and the quality factor as high as 15; (3) demonstration of a 0.5 THz waveguide NbN superconducting SIS mixer with a measured receiver noise temperature (no correction) as low as five times the quantum limit

Shape-memory effect in Ti-Nb alloys

International Nuclear Information System (INIS)

Peradze, T.; Berikashvili, T.; Chelidze, T.; Gorgadze, K.; Bochorishvili, M.; Taktakishvili, M.

2009-01-01

The work deals with the investigation of the binary alloy of titanium with niobium and is aimed at demonstrating the functional-mechanical possibilities of Ti-Nb alloys from the viewpoint of their potential application in practice. The shape-memory effect, super elasticity and reactive stress in alloys of Ti-Nb system were studied. It turned out that the work carried out expanded the interval of Nb content in the investigated alloys from 25.9 to 33.1 wt%. The shape recovery made up not less than 90% at the deformation of 6-8%. The reactive stress reached 350-450 MPa. In the alloys under study another (high-temperature) shape-memory effect was found, and the influence of hydrogen and oxygen on the inelastic properties of alloys was studied. (author)

Solubilization and precipitation of ω and α phases in Ti-30 Nb and Ti-35 Nb alloys

International Nuclear Information System (INIS)

Hayama, A.O.F.; Lopes, J.F.S.C.; Caram, R.

2010-01-01

This work presents the main results of the characterization of Ti-30Nb and Ti-35Nb alloys (wt%) submitted to the solutioning heat treatment following by aging. Samples were obtained by electric arc melting, followed by solution heat treatment at 1000 deg C during 8 hours and cooling in water, the microstructure obtained is formed by β and α phases. Samples were aged at 260 and 400 deg C during periods of time varying from 1 to 240 min. Characterization was performed using light optical microscopy, X-ray diffraction, Young's modulus measurements by acoustic emission and Vickers hardness. The results show the presence of β and α ' ' phases in samples of the Ti-30Nb alloy aged at 260 deg C. In samples aged at 400 deg C, precipitation of ω and α ' ' phases took place, and due to this fact, an increase in Young's modulus and in hardness occurred. (author)

Topotactic dehydration of the lamellar oxide HK2Ti5NbO14 x H2O: the oxide K4Ti10Nb2O27

International Nuclear Information System (INIS)

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

1987-01-01

The lamellar oxide HK 2 Ti 5 NbO 14 x H 2 O can be topotactically dehydrated to K 4 Ti 10 Nb 2 O 27 . Electron diffraction and X-ray diffraction studies of this phase lead to a monoclinic cell with the parameters a = 17.005, b = 3.78, c = 9.01 A and β 92.14 0 . Diffusion streaks on the electron diffraction patterns indicate disorder whereas the existence of two sets of lattices on the same crystal give evidence of the topotactic character of the reaction. A structural model is proposed for K 4 Ti 10 Nb 2 O 27 , which corresponds to the intergrowth of K 3 TiNbO 14 layers with the K 2 Ti 6 O 13 tunnel structure. The possibility of formation of various intergrowths such as (KTi 5 NbO 13 )/sub n/ (HK 2 Ti 5 NbO 14 )/sub n/' is suggested

Preparação de LiNbO3 e LiNbO3:Eu3+ pelo método dos precursores poliméricos

Directory of Open Access Journals (Sweden)

Souza Luciana A.

2002-01-01

Full Text Available The ferroelectric compound LiNbO3 was prepared by the polymeric precursors method in the polycrystalline form containing different concentrations of Eu3+. The compounds were characterized by X-ray diffraction, vibrational and electronic spectroscopy. Electronic spectroscopy was shown to be sensitive to small concentrations of contaminating phases allowing a good control of the compound purity. The presence of Eu3+ ions leads to the formation of the LiNb3O8 phase in the range of 500 to 800 degreesC. Above this temperature range LiNbO3 and tetragonal (T' EuNbO4 were obtained.

Thermally-activated internal friction peaks in amorphous films of Nb3Ge and Nb3Si

International Nuclear Information System (INIS)

Berry, B.S.; Pritchet, W.C.

1978-01-01

A large number of the thermally-activated internal friction peaks observed in crystalline solids are associated with the general mechanism of stress-induced directional short-range ordering. These peaks are an indirect but nevertheless valuable structural probe, and provide an important means of obtaining quantitative information on the kinetics of local atomic movements. This paper deals with what are thought to be the first-known examples of such peaks in the field of metallic glasses. The peaks have been observed in amorphous films of Nb 3 Ge and Nb 3 Si which are both superconductors with transition temperatures Tsub(c) near 3.6K. Although Tsub(c) is thus well below the record values of approximately equal to 23K reported for crystalline films of Nb 3 Ge, Tsuei has found the amorphous films to be much superior mechanically to their crystalline counterparts. Consequently, the amorphous films have technological interest as an easily-handled source from which the brittle high-Tsub(c) phase may be obtained by a final in-situ anneal. (author)

Electric resistivity and thermoelectricity of Ni-Nb-Zr and Ni-Nb-Zr-H glassy alloys

Science.gov (United States)

Fukuhara, Mikio; Inoue, Akihisa

2010-09-01

Electric resistivity ρ and thermoelectric power S of Ni 36Nb 24Zr 40 and (Ni 0.36Nb 0.24Zr 0.4) 90H 10 glassy alloys were investigated in temperature region between 1.5 and 300 K. After resistivity curves of both alloys increase gradually with decreasing temperature down to around 6 K, they dropped suddenly and then reached zero resistivity at 2.1 K, leading to superconductivity. Linear curve with negative TCR of ρ vs T2 and slight increase of S/ T in temperature region down to around 6 K clearly reveal Fermi-liquid phenomenon in electronic state for both alloys independent of hydrogen content.

Electric resistivity and thermoelectricity of Ni-Nb-Zr and Ni-Nb-Zr-H glassy alloys

International Nuclear Information System (INIS)

Fukuhara, Mikio; Inoue, Akihisa

2010-01-01

Electric resistivity ρ and thermoelectric power S of Ni 36 Nb 24 Zr 40 and (Ni 0.36 Nb 0.24 Zr 0.4 ) 90 H 10 glassy alloys were investigated in temperature region between 1.5 and 300 K. After resistivity curves of both alloys increase gradually with decreasing temperature down to around 6 K, they dropped suddenly and then reached zero resistivity at 2.1 K, leading to superconductivity. Linear curve with negative TCR of ρ vs T 2 and slight increase of S/T in temperature region down to around 6 K clearly reveal Fermi-liquid phenomenon in electronic state for both alloys independent of hydrogen content.

Microstructural evolution and structure property correlation in Zr-1Nb and Zr-1Nb-1Sn-0.1Fe alloys

International Nuclear Information System (INIS)

Neogy, S.; Srivastava, D.; Chakravartty, J.K.; Dey, G.K.

2005-01-01

This study summarizes the evolution of microstructure and precipitation behavior in binary Zr-1Nb and quaternary Zr-1Nb-1Sn-0.1Fe alloys after different thermo mechanical processing. The processed microstructure and morphology of constituent phases and precipitates have been studied in detail using transmission electron microscopy (TEM). Microstructural studies have revealed the shape, size, size distribution and the nature of precipitate phases. Martensite formation and its tempering behavior have been studied in detail in both the alloys. Recrystallization studies on these alloys have been carried out with a view to understand the recrystallization mechanism. In case of the binary alloy the second phase recipitates were of the β type having composition varying from β I (20 wt% Nb) to β II (85 wt% Nb) depending on the heat treatment temperature and time. The second phase precipitates in the quaternary alloy were intermetallic Zr-Nb-Fe type and also β type rich in Zr. The orientation relationship existing between the precipitating phases and the a matrix were established in case of both the alloys. High resolution electron microscopy (HREM) of the martensitic microstructure and the recrystallized microstructure has revealed the internal structure and the interface structure of the martensite and the precipitating phases respectively. Structure-property correlation studies have been carried out on the heat-treated samples to evaluate the effect of the thermo mechanical processing on the microstructures and hence mechanical properties. (author)

Origin of colour stability in blue/orange/blue stacked phosphorescent white organic light-emitting diodes

International Nuclear Information System (INIS)

Kim, Sung Hyun; Jang, Jyongsik; Yook, Kyoung Soo; Lee, Jun Yeob

2009-01-01

The origin of colour stability in phosphorescent white organic light-emitting diodes (PHWOLEDs) with a blue/orange/blue stacked emitting structure was studied by monitoring the change in a recombination zone. A balanced recombination zone shift between the blue and the orange light-emitting layers was found to be responsible for the colour stability in the blue/orange/blue stacked PHWOLEDs.

Alternating field losses in Nb3Sn multifilamentary superconductor

International Nuclear Information System (INIS)

Murphy, J.H.; Deis, D.W.; Shaw, B.J.; Walker, M.S.

1975-01-01

Transverse alternating field losses at 4.2K have been measured from 0.5 Hz to 10 kHz in a Nb 3 Sn multifilamentary superconductor in bias fields to 5 Tesla. The 0.020 inch diameter sample was prepared by heat treating a Cu, Nb-1 wt percent Zr, CuSn composite at 700 0 C for 20 hours to form Nb 3 Sn on the inside surface of the annular filaments. Metallurgical studies have been made to determine the Sn distribution and to estimate the thickness of the Nb 3 Sn layer. The I/sub c/-H curve and resistive and inductive transition curves are presented. The losses are analyzed with respect to the present loss theories using the conductor characteristics measured and excellent agreement between experiment and theory is achieved. 1 table, 6 figures

Efeito do ethephon sobre a brotação e vigor dos ramos da videira 'Niagara Rosada' (Vitis labrusca L. Effect of ethephon on sprout and vigor of branch of 'Niagara Rosada' (Vitis labrusca L.

Directory of Open Access Journals (Sweden)

Antonio Augusto Fracaro

2004-12-01

Full Text Available A produção da videira 'Niagara Rosada' em regiões tropicais e subtropicais do Brasil tem sido freqüentemente prejudicada, principalmente devido à dificuldade de emissão e desenvolvimento das brotações após a poda de produção, realizada nos meses de ocorrência de temperaturas mais baixas, o que tem causado redução nas produções e desestímulo aos viticultores. Para solucionar esse problema, foram conduzidos três experimentos, em pomares comerciais localizados na região Noroeste do Estado de São Paulo, com o objetivo de estudar o efeito do Ethephon, aplicado antes da poda de produção, na emissão e desenvolvimento das novas brotações e na duração do período da poda até a floração. Foram testadas quatro doses de ethephon (0 mg.L-1; 720 mg.L-1; 1.440 mg.L-1; 2.160 mg.L-1 aplicadas via foliar antes da poda de produção, nos meses de junho e julho de 2002. Observou-se que a aplicação de Ethephon proporcionou maior número de gemas brotadas, maior comprimento e diâmetro do ramo e não alterou o período da poda à floração. Especialmente quando da ocorrência de condições climáticas desfavoráveis e quando as plantas apresentaram satisfatório grau de enfolhamento, a aplicação de ethephon, na dose de 2.160 mg.L-1, foi a mais efetiva.The production of ' Niagara Rosada ' in tropical and subtropical regions of Brazil has been frequentmently reduced, mainly due to difficulty of emission and development of sprout after the yield prune carried out in the months of occurrence of lower temperatures, what caused reduction in yields and discourage of farmers. Three experiments was carried out to solve this problem, in commercial areas located in northwest region of São Paulo State, with the objective to verify the effect of Ethephon, applied before the yield prune, in emission and development of sprout and in duration of the period of pruning until the flowering. Four levels of Ethephon (0 mg.L-1; 720 mg.L-1; 1,440 mg.L-1

Aluminium stabilized Nb$-3$/Sn superconductors

International Nuclear Information System (INIS)

Thoener, M.; Krauth, H.; Rudolph, J.; Szulczyk, A.

1988-01-01

Composite superconductors made of reacted Nb 3 Sn stabilized with high purity Al were produced. Two methods were tested. The first involved soft soldering a Cu clad aluminum tape to the Nb 3 Sn conductor. In the second method the conductor, cable or monolith, was coextruded with the aluminum. Results obtained from using both methods indicated that mechanically reinforcing materials can be easily introduced into superconductors. Tests were conducted to determine magnetoresistance, electric contact resistance, yield strength, Young modulus, critical current, and other properties of the composites. Strengthening with Duratherm during coextrusion was also evaluated

Role of Nb in low interstitial 13Cr super martensitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ma, X.P.; Wang, L.J. [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Liu, C.M., E-mail: cmliu@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton, L8S-4L7 (Canada)

2011-08-25

Highlights: {yields} Nb retards the kinetics of reversed austenite formation. {yields} Nb suppresses the occurrence of Cr rich precipitates. {yields} Nano-scale precipitates contribute to the significant increase in strength. - Abstract: The effect of adding 0.1 wt% Nb to low interstitial (N 0.01 wt%, C 0.01 wt%) 13Cr super martensitic stainless steel (SMSS) on solid phase transformation and microstructures achieved by normalizing and tempering was investigated using dilatometer, electron backscattered diffraction (EBSD), transmission electron microscope (TEM), X-ray diffraction (XRD), and its consequence on mechanical properties was examined to clarify the role of Nb in low interstitial martensitic stainless steel. Nb was found to retard kinetics of reversed austenite formation during tempering and to suppress the occurrence of Cr rich precipitates. The measurement of mechanical properties shows that while the strength properties were significantly increased by nano-scale precipitates enriched in Nb in the steel with 0.10 wt% Nb, the ductility and toughness properties were restored by optimum volume fraction of retained austenite. Excellent strength and adequate toughness properties were obtained by tempering the steel with 0.10 wt% Nb and low interstitial (N 0.01 wt%, C 0.01 wt%) steel at 600 deg. C.

Quantitative Auger analysis of Nb-Ge superconducting alloys

International Nuclear Information System (INIS)

Buitrago, R.H.

1980-01-01

The feasibility of using Auger electron analysis for quantitative analysis was investigated by studying Nb 3 Ge thin-film Auger data with different approaches. A method base on elemental standards gave consistent quantitative values with reported Nb-Ge data. Alloy sputter yields were also calculated and results were consistent with those for pure elements

Effects of Nb Modification and Cooling Rate on the Microstructure in an Ultrahigh Carbon Steel

Science.gov (United States)

Hecht, Matthew D.; Webler, Bryan A.; Picard, Yoosuf N.

2018-06-01

In this study, two different melting methods were used to investigate effects of Nb modification on microstructure in ultrahigh carbon steel (UHCS). Nb-free and Nb-modified UHCS samples were produced by melting and resolidifying an industrially produced base UHCS with and without addition of Nb powder. Microstructure was characterized using scanning electron microscopy, X-ray diffraction, and electron dispersive spectroscopy. Equilibrium computations of phase fractions and compositions were utilized to help describe microstructural changes caused by the Nb additions. Nb combined with C to form NbC structures before and during austenite solidification, reducing the effective amount of carbon available for the other phases. Cementite network spacing in the Nb-free samples was controlled by the cooling rate during solidification (faster cooling led to a more refined network). Network spacing in the Nb-modified UHCS could be enlarged by NbC structures that formed cooperatively with austenite.

Microstructural and mechanical characterization of biomedical Ti-Nb-Zr(-Ta) alloys

International Nuclear Information System (INIS)

Elias, L.M.; Schneider, S.G.; Schneider, S.; Silva, H.M.; Malvisi, F.

2006-01-01

In recent years there has been a significant development of novel implant alloys based on β-Ti such as Ti-Nb-Zr and Ti-Nb-Zr-Ta alloys systems. The purpose of this work is to provide characterization of Ti-35.3Nb-5.1Ta-7.1Zr and Ti-41.1Nb-7.1Zr alloys, in which Nb will substitute the atomic amount of Ta, with emphasis in the property-microstructure-composition relationships. These alloys are produced from commercially pure materials (Ti, Nb, Zr and Ta) by an arc melting method. All ingots were submitted to sequences of heat treatment (1000 deg. C/2 h - WQ), cold working by swaging procedures and other heat treatment (1000 deg. C/2 h - WQ). Specimens, in as cast and heat-treated condition, were examined by light and scanning electron microscopy (SEM). These results suggested the presence of β- and ω-phases. Mechanical properties were based on tensile and hardness tests. These alloys exhibit a lower modulus than that of conventional Ti alloys and the other mechanical properties are suitable for biomedical applications

Nb effect in the nickel oxide-catalyzed low-temperature oxidative dehydrogenation of ethane

KAUST Repository

Zhu, Haibo

2012-01-01

A method for the preparation of NiO and Nb-NiO nanocomposites is developed, based on the slow oxidation of a nickel-rich Nb-Ni gel obtained in citric acid. The resulting materials have higher surface areas than those obtained by the classical evaporation method from nickel nitrate and ammonium niobium oxalate. These consist in NiO nanocrystallites (7-13 nm) associated, at Nb contents >3 at.%., with an amorphous thin layer (1-2 nm) of a niobium-rich mixed oxide with a structure similar to that of NiNb 2O 6. Unlike bulk nickel oxides, the activity of these nanooxides for low-temperature ethane oxidative dehydrogenation (ODH) has been related to their redox properties. In addition to limiting the size of NiO crystallites, the presence of the Nb-rich phase also inhibits NiO reducibility. At Nb content >5 at.%, Nb-NiO composites are thus less active for ethane ODH but more selective, indicating that the Nb-rich phase probably covers part of the unselective, non-stoichiometric, active oxygen species of NiO. This geometric effect is supported by high-resolution transmission electron microscopy observations. The close interaction between NiO and the thin Nb-rich mixed oxide layer, combined with possible restructuration of the nanocomposite under ODH conditions, leads to significant catalyst deactivation at high Nb loadings. Hence, the most efficient ODH catalysts obtained by this method are those containing 3-4 at.% Nb, which combine high activity, selectivity, and stability. The impact of the preparation method on the structural and catalytic properties of Nb-NiO nanocomposites suggests that further improvement in NiO-catalyzed ethane ODH can be expected upon optimization of the catalyst. © 2011 Elsevier Inc. All rights reserved.

Corneal edema and permanent blue discoloration of a silicone intraocular lens by methylene blue.

Science.gov (United States)

Stevens, Scott; Werner, Liliana; Mamalis, Nick

2007-01-01

To report a silicone intraocular lens (IOL) stained blue by inadvertent intraoperative use of methylene blue instead of trypan blue and the results of experimental staining of various lens materials with different concentrations of the same dye. A "blue dye" was used to enhance visualization during capsulorhexis in a patient undergoing phacoemulsification with implantation of a three-piece silicone lens. Postoperatively, the patient presented with corneal edema and a discolored IOL. Various IOL materials were experimentally stained using methylene blue. Sixteen lenses (4 silicone, 4 hydrophobic acrylic, 4 hydrophilic acrylic, and 4 polymethylmethacrylate) were immersed in 0.5 mL of methylene blue at concentrations of 1%, 0.1%, 0.01%, and 0.001%. These lenses were grossly and microscopically evaluated for discoloration 6 and 24 hours after immersion. The corneal edema resolved within 1 month after the initial surgical procedure. After explantation, gross and microscopic analyses of the explanted silicone lens revealed that its surface and internal substance had been permanently stained blue. In the experimental study, all of the lenses except the polymethylmethacrylate lenses were permanently stained by methylene blue. The hydrophilic acrylic lenses showed the most intense blue staining in all dye concentrations. This is the first clinicopathological report of IOL discoloration due to intraocular use of methylene blue. This and other tissue dyes may be commonly found among surgical supplies in the operating room and due diligence is necessary to avoid mistaking these dyes for those commonly used during ocular surgery.

Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions

Science.gov (United States)

Komar Varela, C. L.; Gribaudo, L. M.; González, R. O.; Aricó, S. F.

2014-10-01

The selected alloy for designing a high-density monolithic-type nuclear fuel with U-Zr-Nb alloy as meat and Zry-4 as cladding, has to remain in the γU(Zr,Nb) phase during the whole fabrication process. Therefore, it is necessary to define a range of concentrations in which the γU(Zr,Nb) phase does not decompose under the process conditions. In this work, several U alloys with concentrations between 28.2-66.9 at.% Zr and 0-13.3 at.% Nb were fabricated to study the possible transformations of the γU(Zr,Nb) phase under different continuous cooling conditions. The results of the electrical resistivity vs temperature experiments are presented. For a cooling rate of 4 °C/min a linear regression was determined by fitting the starting decomposition temperature as a function of Nb concentration. Under these conditions, a concentration of 45.3 at.% Nb would be enough to avoid any transformation of the γU(Zr,Nb) phase. In experiments that involve higher cooling conditions, it has been determined that this concentration can be halved.

Electromagnetic and optical characteristics of Nb5+-doped double-crossover and salmon DNA thin films

Science.gov (United States)

Babu Mitta, Sekhar; Reddy Dugasani, Sreekantha; Jung, Soon-Gil; Vellampatti, Srivithya; Park, Tuson; Park, Sung Ha

2017-10-01

We report the fabrication and physical characteristics of niobium ion (Nb5+)-doped double-crossover DNA (DX-DNA) and salmon DNA (SDNA) thin films. Different concentrations of Nb5+ ([Nb5+]) are coordinated into the DNA molecules, and the thin films are fabricated via substrate-assisted growth (DX-DNA) and drop-casting (SDNA) on oxygen plasma treated substrates. We conducted atomic force microscopy to estimate the optimum concentration of Nb5+ ([Nb5+]O = 0.08 mM) in Nb5+-doped DX-DNA thin films, up to which the DX-DNA lattices maintain their structures without deformation. X-ray photoelectron spectroscopy (XPS) was performed to probe the chemical nature of the intercalated Nb5+ in the SDNA thin films. The change in peak intensities and the shift in binding energy were witnessed in XPS spectra to explicate the binding and charge transfer mechanisms between Nb5+ and SDNA molecules. UV-visible, Raman, and photoluminescence (PL) spectra were measured to determine the optical properties and thus investigate the binding modes, Nb5+ coordination sites in Nb5+-doped SDNA thin films, and energy transfer mechanisms, respectively. As [Nb5+] increases, the absorbance peak intensities monotonically increase until ˜[Nb5+]O and then decrease. However, from the Raman measurements, the peak intensities gradually decrease with an increase in [Nb5+] to reveal the binding mechanism and binding sites of metal ions in the SDNA molecules. From the PL, we observe the emission intensities to reduce them at up to ˜[Nb5+]O and then increase after that, expecting the energy transfer between the Nb5+ and SDNA molecules. The current-voltage measurement shows a significant increase in the current observed as [Nb5+] increases in the SDNA thin films when compared to that of pristine SDNA thin films. Finally, we investigate the temperature dependent magnetization in which the Nb5+-doped SDNA thin films reveal weak ferromagnetism due to the existence of tiny magnetic dipoles in the Nb5+-doped SDNA

Magnetocapacitance effect in ferromagnetic LiNbO{sub 3} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Díaz-Moreno, Carlos; Lopez, Jorge [Department of Physics of University of Texas at El Paso, 500W. University Ave, El Paso, TX 79968 (United States); González-Hernández, Jesus [Centro de Ingeniería y Desarrollo Industrial, Santiago de Querétaro, 76130 Qro., México (Mexico); Escudero, Roberto [Universidad Nacional Autónoma de México, Departamento de Materia Condensada y Criogenia, Av. Universidad 3000, Coyoacán, México D. F. 04510, México (Mexico); Heiras, Jesus L. [Universidad Nacional Autónoma de México, Centro de Nanociencias y nanotecnología, Km 107 Carretera Tijuana-Ensenada, Ensenada, B.C. 22860, México (Mexico); Yacamán, Miguel J. [Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Mendez-Nonell, Juan; Hurtado-Macias, Abel [Centro de Investigación en Materiales Avanzados S.C., Laboratorio Nacional de Nanotecnología, Miguel de Cervantes 120, Complejo Industrial, Chihuahua, Chihuahua Apdo. Postal 31109 México (Mexico)

2016-06-01

Magnetocapacitance and magnetization behavior as a function of reduction heat treatment at 650 °C and 900 °C in a 5%H{sub 2}–Ar atmosphere on LiNbO{sub 3} nanocrystalline are reported. There is a change of intrinsic dielectric constant (κ) from 822 to 860 produced by spin polarization using an external magnetic field. The Raman, X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy, indicate vibration mode changes localized at Nb–O bonds in the octahedron NbO{sub 6}, shifts in the binding energy of the electronic structure of ions of niobium (3d) and the oxygen (1s). It is due to the oxygen vacancies caused by reduction heat treatment process. Moreover there is ions redistribution of Nb{sup +3}, Nb{sup +4}and Nb{sup +5} at the surface of the nanoparticles. - Highlights: • Magnetocapacitance and magnetization behavior as a function of reduction heat treatment on LiNbO{sub 3} nanocrystalline. • There is a change of intrinsic dielectric constant (¯) from 822 to 860 produced by spin polarization using an external magnetic field. • The Raman and X-ray photoelectron spectroscopy, indicate vibration mode changes localized at Nb–O bonds in the octahedron NbO6. • Magnetization curves measured at external field 9 T at 300 K for two different reduction heat treatment samples 650 °;C and 900 °;C in comparison without RHT. • Measurements are made at room temperature and at nine different frequencies ranging from 50 Hz to 1 MHz.

Structural characterizations and optical properties of new Li–Sr–Nb-phosphate glasses

Energy Technology Data Exchange (ETDEWEB)

Lee, Yi-Mu [Department of Electronic Engineering, National United University, Miao-Li 36003, Taiwan, ROC (China); Hsu, S.M. [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 11221, Taiwan, ROC (China); Yung, S.W., E-mail: hwyang@nuu.edu.tw [Department of Material Science and Engineering, National United University, Miao-Li 36003, Taiwan, ROC (China); Zhang, T. [Institute for Materials Research, Fuzhou University, Fujian (China); Huang, Y.S.; Wu, J.J. [Department of Material Science and Engineering, National United University, Miao-Li 36003, Taiwan, ROC (China); Hsu, C.H. [Department of Electrical Engineering, National United University, Miao-Li 36003, Taiwan, ROC (China); Chin, T.S. [Department of Materials Science and Engineering, Feng Chia University, Taichung, Taiwan, ROC (China)

2014-04-01

A new Li{sub 2}O–SrO–Nb{sub 2}O{sub 5}–P{sub 2}O{sub 5} glass system was prepared by a high-temperature alumina crucible, and structural characterization and optical properties were investigated. Proper content of Li{sub 2}O and Nb{sub 2}O{sub 5} was employed to replace partial SrO and P{sub 2}O{sub 5} to improve the optical properties. It was observed that the enhancement of the refractive index from 1.75 to 1.85 is mainly due to the Nb{sub 2}O{sub 5} content. An addition of Li{sub 2}O significantly increases the optical transmittance; optical transparency can be enhanced from 60% to higher than 85% in the UV–visible region with addition of 20–40 mol% Li{sub 2}O species. However, optical transmittance is monotonically decreased from about 90% to 80% under 10–30 mol% Nb{sub 2}O{sub 5} addition. The 40P{sub 2}O{sub 5}–20Nb{sub 2}O{sub 5}–20SrO–20Li{sub 2}O glasses demonstrate the optimum refractive index (n > 1.75) and high optical transparency (>80%) in the UV–visible region. Furthermore, the effect of Nb{sub 2}O{sub 5} on the structural transition was focused on the (60 − y)P{sub 2}O{sub 5}–yNb{sub 2}O{sub 5}–20SrO–20Li{sub 2}O vitreous system since the transition of FTIR spectra reveals that the Nb{sub 2}O{sub 5} has more pronounced effect than Li{sub 2}O in the glass network due to the higher covalent extent and electronegativity. Addition of Nb{sub 2}O{sub 5} generates Nb–O bonds by dissociating P–O chains and results in the decrease in the intensity of the (PO{sub 2}), (POP), and (PO{sub 3}) absorption bands. The O1s-XPS analysis shows that Nb{sub 2}O{sub 5} addition dissociates symmetric bridging oxygens in P–O–P bonding and forms asymmetric bridging oxygens in P–O–Nb and non-bridging Nb–O{sup -} bonds, in which octahedral [NbO{sub 6}] unit is eventually substituted by [NbO{sub 4}] tetrahedral unit in the Li–Sr–Nb phosphate glasses. - Highlights: • The prepared glasses demonstrate great optical properties

Effect of Nb on magnetic and mechanical properties of TbDyFe alloys

Science.gov (United States)

Wang, Naijuan; Liu, Yuan; Zhang, Huawei; Chen, Xiang; Li, Yanxiang

2018-03-01

The intrinsic brittleness in giant magnetostrictive material TbDyFe alloy has devastating influence on the machinability and properties of the alloy, thus affecting its applications. The purpose of this paper is to study the mechanical properties of the TbDyFe alloy by alloying with Nb element. The samples (Tb0.3Dy0.7)xFe2xNby (y = 0, 0.01, 0.04, 0.07, 0.1; 3x + y = 1) were melted in an arc melting furnace under high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance of the alloys were studied systematically. The results showed that NbFe2 phases were observed in the alloys with the addition of Nb. Moreover, both the NbFe2 phases and rare earth (RE)-rich phases were increased with the increasing of Nb element. The mechanical properties results revealed that the fracture toughness of the alloy with the addition of Nb enhanced 1.5-5 times of the Nb-free alloy. Both the NbFe2 phase and the RE-rich phase had the ability to prevent crack propagation, so that they can strengthen the REFe2 body. However, NbFe2 phase is a paramagnetic phase, which can reduce the magnetostrictive properties of the alloy by excessive precipitation.

Dimerization of A-[alpha]-[SiNb3W9O40]7- by pH-controlled formation of individual Nb−µ-O−Nb linkages

Science.gov (United States)

Gyu-Shik Kim; Huadong Zeng; Wade A. Neiwert; Jennifer J. Cowan; Donald VanDerveer; Craig L. Hill; Ira A. Weinstock

2003-01-01

The reversible, stepwise formation of individual Nb−µ-O−Nb linkages during acid condensation of 2 equiv of A-[alpha]-[SiNb3W9O40]7- (1) to the tri-µ-oxo-bridged structure A-[alpha]-[Si2Nb6W18O77]8- (4) is demonstrated by a combination of X-ray crystallography and variable-pD solution 183W and 29Si NMR spectroscopy. Addition of DCl to a pD 8.4...

Plasma-assisted MOCVD growth of superconducting NbN thin films using Nb dialkylamide and Nb alkylimide precursors

International Nuclear Information System (INIS)

Liu Xiang; Ott, A.W.; Chang, R.P.H.; Babcok, J.R.; Belot, J.A.; Metz, M.V.; Marks, T.J.; Lane, M.A.; Kannewurf, C.R.

2001-01-01

The first example of the use of metal-organic precursors for depositing NbN superconducting thin films is described. The study, which employed niobium(IV) and niobium(V) pulsed source precursors and hydrazine plasma as the nitrogen source, indicates that T c is highly dependent on the lattice parameters and level of oxygen impurities, which are in turn governed by growth and post-deposition annealing temperatures. (orig.)

Analysis of Nb{sub 3}Sn surface layers for superconducting radio frequency cavity applications

Energy Technology Data Exchange (ETDEWEB)

Becker, Chaoyue [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Posen, Sam; Hall, Daniel Leslie [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Groll, Nickolas; Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Cook, Russell [Nanoscience and Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Schlepütz, Christian M. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liepe, Matthias [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Pellin, Michael [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Zasadzinski, John [Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

2015-02-23

We present an analysis of Nb{sub 3}Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb{sub 3}Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T{sub c}) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb{sub 3}Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb{sub 3}Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T{sub c} regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb{sub 3}Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

ADHESION OF BIOCOMPATIBLE TiNb COATING

Directory of Open Access Journals (Sweden)

Tomas Kolegar

2017-06-01

Full Text Available Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering. Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.

Blue-Green Algae

Science.gov (United States)

... that taking a specific blue-green algae product (Super Blue-Green Algae, Cell Tech, Klamath Falls, OR) ... system. Premenstrual syndrome (PMS). Depression. Digestion. Heart disease. Memory. Wound healing. Other conditions. More evidence is needed ...

Effects of Nb content on the Zr2Fe intermetallic stability

International Nuclear Information System (INIS)

Ramos, C.; Saragovi, C.; Granovsky, M.; Arias, D.

2003-01-01

With the aim of studying the stability range of the Zr 2 Fe intermetallic when adding Nb, the range of existence of the cubic ternary phase (λ 1 ) and the corresponding two-phase field between them, four samples were analyzed, each one containing 35 at.% Fe and different at.% Nb: 0.5, 4 10 and 15. Optical and scanning electron metallographies, X-ray diffraction, microprobe analysis and Moessbauer spectroscopy were performed to determine and characterize the phases present in the samples. Results show that the Zr 2 Fe compound accepts up to nearly 0.5 at.% Nb in solution, since the Zr 2 Fe+λ 1 region is stable in the (0.5-3.5) at.% Nb range. To summarize these results an 800 deg. C section of the ternary Zr-Nb-Fe diagram, in the studied zone, was proposed

Development of Nb3Sn AC superconducting wire. Pt. 2

International Nuclear Information System (INIS)

Kasahara, Hobun; Torii, Shinji; Akita, Shirabe; Ueda, Kiyotaka; Kubota, Yoji; Yasohama, Kazuhiko; Kobayashi, Hisayasu; Ogasawara, Takeshi.

1993-01-01

For the realization of superconducting power apparatus, it is important that the development of highly stable superconducting cables. Nb 3 Sn wire has higher critical temperature than NbTi wire. Therefore, it is possible to make highly stable superconducting wires. In this report, we examine a manufacturing process of Ac Nb 3 Sn wire. This manufacturing process has four times higher critical current density than conventional processes. We have made a 400 kVA class AC coil with React and Wind method. The loss density of this coil was 20MW/m 3 at just before the quench. In this case, the temperature of cable increased about 3.8 K. This means that the Nb 3 Sn coil has a very high stability. (author)

Beta decomposition processes in Hf-rich Hf--Nb alloys

International Nuclear Information System (INIS)

Jones, W.B.; Taggart, R.; Polonis, D.H.

1978-01-01

The decomposition of the bcc β-phase by both athermal and isothermal processes has been investigated in Hf-rich Hf--Nb alloys. An all β-phase structure is retained in chill-cast alloys containing 30 to 50 at.% Nb (Cb), although electron diffraction streaking effects and the behavior of the temperature coefficient of electrical resistivity indicate the presence of a bcc lattice instability similar to that reported in solute lean Ti and Zr alloys. Aging a Hf 0 . 65 Nb 0 . 35 alloy at 400 and 600 0 C resulted in the direct precipitation of a fine dispersion of α-phase needles; this morphology differs from the discs of transition α (α/sub t/) which Carpenter et al observed in Nb-rich Nb 0 . 68 Hf 0 . 32 . During continued aging, the needles grow selectively to form colonies or groups of needles in which both the individual needles and the groups of needles have major axes aligned along (110)/sub β/ type directions. The initial α-phase particles exhibit the Burgers orientation relationship with the parent matrix; continued aging changes the electron diffraction patterns in a way that is similar to that observed in aged Ti--Mo and Ti--Mo--Al alloys where they were attributed to the α-phase having a different crystallographic relationship to the β-phase (Type 2 α-phase). The observed changes in the electron diffraction patterns of aged Hf 0 . 65 Nb 0 . 35 cannot be described as resulting from strained Burgers α-phase

Blue gods, blue oil, and blue people.

Science.gov (United States)

Fairbanks, V F

1994-09-01

Studies of the composition of coal tar, which began in Prussia in 1834, profoundly affected the economies of Germany, Great Britain, India, and the rest of the world, as well as medicine and surgery. Such effects include the collapse of the profits of the British indigo monopoly, the growth in economic power of Germany based on coal tar chemistry, and an economic crisis in India that led to more humane tax laws and, ultimately, the independence of India and the end of the British Empire. Additional consequences were the development of antiseptic surgery and the synthesis of a wide variety of useful drugs that have eradicated infections and alleviated pain. Many of these drugs, particularly the commonly used analgesics, sulfonamides, sulfones, and local anesthetics, are derivatives of aniline, originally called "blue oil" or "kyanol." Some of these aniline derivatives, however, have also caused aplastic anemia, agranulocytosis, and methemoglobinemia (that is, "blue people"). Exposure to aniline drugs, particularly when two or three aniline drugs are taken concurrently, seems to be the commonest cause of methemoglobinemia today.

High-field superconductivity in the Nb-Ti-Zr ternary system

International Nuclear Information System (INIS)

Ralls, K.M.; Rose, R.M.; Wulff, J.

1980-01-01

Resistive critical current densities, critical fields, and normal-state electrical resistivities were obtained at 4.2 0 K for 55 alloys in the Nb-Ti-Zr ternary alloy system, excepting Ti-Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb-Ti and Nb-Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys

High-field superconductivity in the Nb-Ti-Zr ternary system

Science.gov (United States)

Ralls, K. M.; Rose, R. M.; Wulff, J.

1980-06-01

Resistive critical current densities, critical fields, and normal-state electrical resistivities were obtained at 4.2 °K for 55 alloys in the Nb-Ti-Zr ternary alloy system, excepting Ti-Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb-Ti and Nb-Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys.

Thin NbN film structures on SOI for SNSPD

Energy Technology Data Exchange (ETDEWEB)

Il' in, Konstantin; Kurz, Stephan; Henrich, Dagmar; Hofherr, Matthias; Siegel, Michael [IMS, KIT, Karlsruhe (Germany); Semenov, Alexei; Huebers, Heinz-Wilhelm [DLR, Berlin (Germany)

2012-07-01

Superconducting Nanowire Single-Photon Detectors (SNSPD) made from ultra-thin NbN films on sapphire demonstrate almost 100% intrinsic detection efficiency (DE). However the system DE values is less than 10% mostly limited by a very low absorptance of NbN films thinner than 5 nm. Integration of SNSPD in Si photonic circuit is a promising way to overcome this problem. We present results on optimization of technology of thin NbN film nanostructures on SOI (Silicon on Insulator) substrate used in Si photonics technology. Superconducting and normal state properties of these structures important for SNSPD development are presented and discussed.

[Acute blue urticaria following subcutaneous injection of patent blue dye].

Science.gov (United States)

Hamelin, A; Vial-Dupuy, A; Lebrun-Vignes, B; Francès, C; Soria, A; Barete, S

2015-11-01

Patent blue (PB) is a lymphatic vessel dye commonly used in France for sentinel lymph node detection in breast cancer, and less frequently in melanoma, and which may induce hypersensitivity reactions. We report a case of acute blue urticaria occurring within minutes of PB injection. Ten minutes after PB injection for sentinel lymph node detection during breast cancer surgery, a 49-year-old woman developed generalised acute blue urticaria and eyelid angioedema without bronchospasm or haemodynamic disturbance, but requiring discontinuation of surgery. Skin testing using PB and the anaesthetics given were run 6 weeks after the episode and confirmed PB allergy. PB was formally contra-indicated. Immediate hypersensitivity reactions to PB have been reported for between 0.24 and 2.2% of procedures. Such reactions are on occasion severe, chiefly involving anaphylactic shock. Two mechanisms are probably associated: non-specific histamine release and/or an IgE-mediated mechanism. Skin tests are helpful in confirming the diagnosis of PB allergy. Blue acute urticaria is one of the clinical manifestations of immediate hypersensitivity reactions to patent blue dye. Skin tests must be performed 6 weeks after the reaction in order to confirm the diagnosis and formally contra-indicate this substance. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Temperature-dependent performance of all-NbN DC-SQUID magnetometers

Science.gov (United States)

Liu, Quansheng; Wang, Huiwu; Zhang, Qiyu; Wang, Hai; Peng, Wei; Wang, Zhen

2017-05-01

Integrated NbN direct current superconducting quantum interference device (DC-SQUID) magnetometers were developed based on high-quality epitaxial NbN/AlN/NbN Josephson junctions for SQUID applications operating at high temperatures. We report the current-voltage and voltage-flux characteristics and the noise performance of the NbN DC-SQUIDs for temperatures ranging from 4.2 to 9 K. The critical current and voltage swing of the DC-SQUIDs decreased by 15% and 25%, respectively, as the temperature was increased from 4.2 to 9 K. The white flux noise of the DC-SQUID magnetometer at 1 kHz increased from 3.9 μΦ0/Hz1/2 at 4.2 K to 4.8 μΦ0/Hz1/2 at 9 K with 23% increase, corresponding to the magnetic field noise of 6.6 and 8.1 fT/Hz1/2, respectively. The results show that NbN DC-SQUIDs improve the tolerance of the operating temperatures and temperature fluctuations in SQUID applications.

Effect of increasing disorder on superconductivity of Mo/Nb superlattices

International Nuclear Information System (INIS)

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

2015-01-01

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 T c of Mo remains below the Nb T c . 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. (paper)

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.

Analysis of A-15 phase in the system Nb-Au

International Nuclear Information System (INIS)

Silveira, M.F. da.

1982-01-01

The Nb-Au system contains a A-15 structure with a superconducting critical temperature of the order of 11 K. According to the actually available phase diagrams there is some incertainty, whether the stoichiometric composition Nb 3 Au (75% at. Nb and 25% at. Au) occurs within the limits of stability. In the present work the samples (alloys of Nb and Au) are produced using a technique of melting by condenser discharge. The advantage of this technique consists in the possibility to obtain samples with compositions exceeding the limits of stability, as shown by lattice parameter analyses of the phase A-2 (Nb - solid solution) samples. The A-15 phase is obtained by heat treatments of samples crystallized originally in the A-2 structure. The inductively determined critical temperatures are close to the highest reported in the literature for this compound (11,5 K). Further we show by lattice parameter analyses that we are able to obtain the A-15 phase also with metastable compositions, very probably inclusively with the stoichiometric composition. (author) [pt

Precipitation and mechanical properties of Nb-modified ferritic stainless steel during isothermal aging

International Nuclear Information System (INIS)

Yan Haitao; Bi Hongyun; Li Xin; Xu Zhou

2009-01-01

The influence of isothermal aging on precipitation behavior and mechanical properties of Nb-modified ferritic stainless steel was investigated using Thermo-calc software, scanning electron microscopy and transmission electron microscopy. It was observed that TiN, NbC and Fe 2 Nb formed in the investigated steel and the experimental results agreed well with the results calculated by Thermo-calc software. During isothermal aging at 800 deg. C, the coarsening rate of Fe 2 Nb is greater than that of NbC, and the calculated average sizes of NbC and Fe 2 Nb of the aged specimen agreed with the experimental results. In addition, the tensile strength and micro-hardness of the ferritic stainless steel increased with increased aging time from 24 h to 48 h. But aging at 800 deg. C for 96 h caused the coarsening of the precipitation, which led to a decrease of tensile strength and micro-hardness

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

Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions

Energy Technology Data Exchange (ETDEWEB)

Komar Varela, C.L., E-mail: cavarela@cnea.gov.ar [Instituto Sabato, UNSAM-CNEA, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gerencia de Ciclo del Combustible Nuclear, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gribaudo, L.M. [Gerencia de Materiales, GAEN, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); González, R.O.; Aricó, S.F. [Instituto Sabato, UNSAM-CNEA, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina); Gerencia de Materiales, GAEN, Comisión Nacional de Energía Atómica, Avenida General Paz 1499, B1650KNA San Martín, Buenos Aires (Argentina)

2014-10-15

The selected alloy for designing a high-density monolithic-type nuclear fuel with U–Zr–Nb alloy as meat and Zry-4 as cladding, has to remain in the γU(Zr,Nb) phase during the whole fabrication process. Therefore, it is necessary to define a range of concentrations in which the γU(Zr,Nb) phase does not decompose under the process conditions. In this work, several U alloys with concentrations between 28.2–66.9 at.% Zr and 0–13.3 at.% Nb were fabricated to study the possible transformations of the γU(Zr,Nb) phase under different continuous cooling conditions. The results of the electrical resistivity vs temperature experiments are presented. For a cooling rate of 4 °C/min a linear regression was determined by fitting the starting decomposition temperature as a function of Nb concentration. Under these conditions, a concentration of 45.3 at.% Nb would be enough to avoid any transformation of the γU(Zr,Nb) phase. In experiments that involve higher cooling conditions, it has been determined that this concentration can be halved.

Transformation behavior of the γU(Zr,Nb) phase under continuous cooling conditions

International Nuclear Information System (INIS)

Komar Varela, C.L.; Gribaudo, L.M.; González, R.O.; Aricó, S.F.

2014-01-01

The selected alloy for designing a high-density monolithic-type nuclear fuel with U–Zr–Nb alloy as meat and Zry-4 as cladding, has to remain in the γU(Zr,Nb) phase during the whole fabrication process. Therefore, it is necessary to define a range of concentrations in which the γU(Zr,Nb) phase does not decompose under the process conditions. In this work, several U alloys with concentrations between 28.2–66.9 at.% Zr and 0–13.3 at.% Nb were fabricated to study the possible transformations of the γU(Zr,Nb) phase under different continuous cooling conditions. The results of the electrical resistivity vs temperature experiments are presented. For a cooling rate of 4 °C/min a linear regression was determined by fitting the starting decomposition temperature as a function of Nb concentration. Under these conditions, a concentration of 45.3 at.% Nb would be enough to avoid any transformation of the γU(Zr,Nb) phase. In experiments that involve higher cooling conditions, it has been determined that this concentration can be halved

Neutron radiation damage in NbO single crystals

International Nuclear Information System (INIS)

Onozuka, T.; Koiwa, M.; Ishikawa, Y.; Yamaguchi, S.; Hirabayashi, M.

1977-01-01

The effect of neutron irradiation and subsequent recovery has been studied for Nb0 single crystals of a defective NaCl structure containing 25% vacancies of niobium and oxygen. A very large increase (about 1%) in the lattice constant is observed after irradiation of 1.5 x 10 19 and 1 x 10 20 nvt (> 1 MeV). From the intensity measurements of x-ray and neutron diffraction, it is revealed that the knock-on atoms fill preferentially their respective vacant sites; Nb atoms occupy Nb-vacancies, and 0 atoms occupy 0-vacancies with nearly the same probabilities; 0.53 for 1.5 x 10 19 nvt. The mean threshold energy for displacement is estimated to be about 3 eV. (author)

Electron microscopy study of Nb-rich nanoprecipitates in Ni–Ti–Nb and their influence on the martensitic transformation

International Nuclear Information System (INIS)

Shi, H.; Pourbabak, S.; Van Humbeeck, J.; Schryvers, D.

2012-01-01

Graphical abstract: -- Nb-rich nanoprecipitates in the matrix of an annealed commercial Ni–Ti–Nb alloy are investigated by scanning and transmission electron microscopy, including slice-and-view and chemical analysis. The precipitates have a diameter of around 100 nm, are faceted and have a cube-on-cube relation with the B2 matrix. In situ TEM cooling shows that the martensitic transformation is hampered by the presence of these precipitates. The latter could explain the increase in hysteresis when compared with the binary system.

Metallurgical study and phase diagram calculations of the Zr-Nb-Fe-(Sn,O) system

International Nuclear Information System (INIS)

Toffolon, C.

2000-01-01

The Framatome M5 TM Zr-Nb-O alloy with small amounts of Fe is of interest for nuclear applications (PWR fuel cladding).The behaviour of this kind of alloy for in-service conditions strongly depends on the microstructure. Therefore, a metallurgical study of alloys of the Zr-Nb-Fe-(O-Sn) system has been developed in order to study the influence of chemical composition variabilities of Nb, Fe and O and thermal treatments on the resultant microstructure. In order to get some insight on the physical metallurgy of Zr-Nb-Fe-(Sn,O) alloys and to minimize the experiments, it is useful to build a thermodynamic database. With this object, it was necessary to re-optimize and to calculate the low order binary systems such as Fe-Nb and Nb-Sn in order to assess the Zr-Nb-Fe-(Sn,O) system. Then, the experimental studies concerned: the influence of small variations in Nb and O contents on the α/β transus temperatures. A comparison between experimental results and thermodynamic predictions showed a good agreement; the precipitation kinetics of βNb and intermetallic phases in the α phase domain. These experiments showed that the kinetics depends on the initial metallurgical conditions; the determination of the crystallographic structure and the stoichiometry of the ternary Zr-Nb-Fe intermetallic compounds as a function of the temperature. Finally, these experimental data were used to propose a first assessment of the Zr-Nb-Fe(O∼1200 ppm) system. (author)

Synchrotron radiation techniques for the characterization of Nb$_{3}$Sn superconductors

CERN Document Server

Scheuerlein, C; Buta, F

2009-01-01

The high flux of high energy x-rays that can be provided through state-of-the-art high energy synchrotron beam lines has enabled a variety of new experiments with the highly absorbing Nb$_{3}$Sn superconductors. We report different experiments with Nb$_{3}$Sn strands that have been conducted at the ID15 High Energy Scattering beam line of the European Synchrotron Radiation Facility (ESRF). Synchrotron x-ray diffraction has been used in order to monitor phase transformations during in-situ reaction heat treatments prior to Nb$_{3}$Sn formation, and to monitor Nb$_{3}$Sn growth. Fast synchrotron micro-tomography was applied to study void growth during the reaction heat treatment of Internal Tin strands. The elastic strain in the different phases of fully reacted Nb$_{3}$Sn composite conductors can be measured by high resolution x-ray diffraction during in-situ tensile tests.

Structure and mechanical properties of as-cast Ti-5Nb-xFe alloys

International Nuclear Information System (INIS)

Hsu, Hsueh-Chuan; Hsu, Shih-Kuang; Wu, Shih-Ching; Lee, Chih-Jhan; Ho, Wen-Fu

2010-01-01

In this study, as-cast Ti-5Nb and a series of Ti-5Nb-xFe alloys were investigated and compared with commercially pure titanium (c.p. Ti) in order to determine their structure and mechanical properties. The series of Ti-5Nb-xFe alloys contained an iron content ranging from 1 to 5 mass% and were prepared by using a commercial arc-melting vacuum-pressure casting system. Additionally, X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer, and three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys possessed a range of different structures and mechanical properties dependent upon the various additions of Fe. With an addition of 1 mass% Fe, retention of the metastable β phase began. However, when 4 mass% Fe or greater was added, the β phase was entirely retained with a bcc crystal structure. Moreover, the ω phase was only detected in the Ti-5Nb-2Fe, Ti-5Nb-3Fe and Ti-5Nb-4Fe alloys. The largest quantity of ω phase and the highest bending modulus were found in the Ti-5Nb-3Fe alloy. The Ti-5Nb-2Fe alloy had the lowest bending modulus, which was lower than that of c.p. Ti by 20%. This alloy exhibited the highest bending strength/modulus ratio of 26.7, which was higher than that of c.p. Ti by 214%, and of the Ti-5Nb alloy (14.4 ) by 85%. Additionally, the elastically recoverable angles of the ductile Ti-5Nb-1Fe (19.9 o ) and Ti-5Nb-5Fe (29.5 o ) alloys were greater than that of c.p. Ti (2.7 o ) by as much as 637% and 993%, respectively. Furthermore, the preliminary cell culturing results revealed that the Ti-5Nb-xFe alloys were not only biocompatible, but also supported cell attachment.

Structure and mechanical properties of as-cast Ti-5Nb-xFe alloys

Energy Technology Data Exchange (ETDEWEB)

Hsu, Hsueh-Chuan; Hsu, Shih-Kuang; Wu, Shih-Ching [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taichung 40605, Taiwan (China); Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Changhua 51591, Taiwan (China); Lee, Chih-Jhan [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Ho, Wen-Fu, E-mail: fujii@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China)

2010-09-15

In this study, as-cast Ti-5Nb and a series of Ti-5Nb-xFe alloys were investigated and compared with commercially pure titanium (c.p. Ti) in order to determine their structure and mechanical properties. The series of Ti-5Nb-xFe alloys contained an iron content ranging from 1 to 5 mass% and were prepared by using a commercial arc-melting vacuum-pressure casting system. Additionally, X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer, and three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys possessed a range of different structures and mechanical properties dependent upon the various additions of Fe. With an addition of 1 mass% Fe, retention of the metastable {beta} phase began. However, when 4 mass% Fe or greater was added, the {beta} phase was entirely retained with a bcc crystal structure. Moreover, the {omega} phase was only detected in the Ti-5Nb-2Fe, Ti-5Nb-3Fe and Ti-5Nb-4Fe alloys. The largest quantity of {omega} phase and the highest bending modulus were found in the Ti-5Nb-3Fe alloy. The Ti-5Nb-2Fe alloy had the lowest bending modulus, which was lower than that of c.p. Ti by 20%. This alloy exhibited the highest bending strength/modulus ratio of 26.7, which was higher than that of c.p. Ti by 214%, and of the Ti-5Nb alloy (14.4 ) by 85%. Additionally, the elastically recoverable angles of the ductile Ti-5Nb-1Fe (19.9{sup o}) and Ti-5Nb-5Fe (29.5{sup o}) alloys were greater than that of c.p. Ti (2.7{sup o}) by as much as 637% and 993%, respectively. Furthermore, the preliminary cell culturing results revealed that the Ti-5Nb-xFe alloys were not only biocompatible, but also supported cell attachment.

Jagua blue derived from Genipa americana L. fruit: A natural alternative to commonly used blue food colorants?

Science.gov (United States)

Brauch, J E; Zapata-Porras, S P; Buchweitz, M; Aschoff, J K; Carle, R

2016-11-01

Due to consumers' increasing health awareness, food industry aims at replacing synthetic dyes by natural counterparts. The substitution of blue synthetic dyes is particularly challenging since current natural alternatives such as phycocyanin (Spirulina) suffer from poor stability. Jagua blue (produced from Genipa americana L. fruit) might represent a potential novel blue pigment source. However, only little is known about its color properties, and application in food systems. Therefore, the blue color and the stability of Jagua blue were assessed for the first time and compared to commonly used colorants, namely, Spirulina, brilliant blue FCF (Blue no. 1), and indigo carmine (Blue no. 2). The reaction rate of Jagua blue was independent of its concentration, confirming thermal degradation to follow first-order kinetics. Between pH 3.6 and 5.0, the color hue of Jagua blue solutions was similar to that of Blue no. 2. However, Jagua blue revealed markedly higher storage stabilities (t 1/2 =86-105days) than Blue no. 2 (t 1 /2 ≤9days) and was less susceptible to acidic pH of 3.6 (t 1 /2 =86days) than Spirulina (t 1 /2 =70days). High negative b* values (blueness) of colored gelatin gels were only obtained for Jagua blue and Spirulina, and the former exhibited higher light stabilities (t 1 /2 =15days) than Spirulina gels (t 1 /2 =4days). Our findings indicate Jagua blue to be a most promising alternative to synthetic dyes, providing relevant information regarding potential food applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

No solid solution compounds in between the binaries. Syntheses and crystal structures of Nb(Br{sub 0.62(4)}Cl{sub 0.38(4)}){sub 2}Cl{sub 2} and NbI{sub 2}Cl{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Reckeweg, Olaf; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

2018-04-01

The anion-mixed niobium tetrahalides Nb(Br{sub 0.62(4)}Cl{sub 0.38(4)}){sub 2}Cl{sub 2} and NbI{sub 2}Cl{sub 2} were obtained by heating NbBr{sub 5} with NbCl{sub 5} and NbI{sub 5} with NbCl{sub 5}, respectively, in equimolar ratios with niobium metal in evacuated, torch-sealed silica ampoules at 720 K for 3 days. The orthorhombic title compounds form as very brittle black needles and were characterized by single-crystal X-ray diffraction [space group: Immm, Z=4; a=704.27(6), b=824.13(7), c=929.64(8) pm for Nb(Br{sub 0.62(4)}Cl{sub 0.38(4)}){sub 2}Cl{sub 2} and a=753.76(6), b=829.38(7) and c=983.41(8) pm for NbI{sub 2}Cl{sub 2}]. Surprisingly enough, these mixed-anionic halides are not isostructural with either NbCl{sub 4}, NbBr{sub 4} or NbI{sub 4}, but crystallize isotypically with TaI{sub 2}Cl{sub 2}, thus being examples for differential site occupancy stabilized materials. Structural features of other niobium(IV) halides are compiled and compared to those of Nb(Br{sub 0.62(4)}Cl{sub 0.38(4)}){sub 2}Cl{sub 2} and NbI{sub 2}Cl{sub 2}. Except for NbF{sub 4}, they all exhibit chains of trans-edge connected [NbX{sub 6}]{sup 2-} octahedra, which allow Peierls distortions to form Nb-Nb single bonds. The packing of these chains differ, however, depending on the actual halide or mixed-halide combination.

Precipitation in Zr-2.5Nb enhanced by proton irradiation

Energy Technology Data Exchange (ETDEWEB)

Cann, C. D.; So, C. B.; Styles, R. C.; Coleman, C. E.

1993-08-15

A 3.6 MeV proton irradiation of annealed Zr-2.5Nb has been performed to determine whether proton irradiation will enhance the precipitation of Nb-rich {beta}-phase precipitates within the {alpha}-grains. a transmission electron microscope examination of a foil after irradiation at 770 K for 18 h and at 720 K for 264.5 h to a total damage of 0.94 dpa revealed a fine dispersion of precipitates within the {alpha}-grains. Electron diffraction analysis of the precipitates found they have lattice plane spacings consistent with the Nb-rich {beta}-phase. This result is in agreement with the {beta}phase precipitation observed following neutron irradiation, and thus it supports the use of proton irradiation to simulate neutron-irradiation effects in Zr-2.5Nb.

Precipitation in Zr-2.5Nb enhanced by proton irradiation

International Nuclear Information System (INIS)

Cann, C.D.; So, C.B.; Styles, R.C.; Coleman, C.E.

1993-08-01

A 3.6 MeV proton irradiation of annealed Zr-2.5Nb has been performed to determine whether proton irradiation will enhance the precipitation of Nb-rich β-phase precipitates within the α-grains. a transmission electron microscope examination of a foil after irradiation at 770 K for 18 h and at 720 K for 264.5 h to a total damage of 0.94 dpa revealed a fine dispersion of precipitates within the α-grains. Electron diffraction analysis of the precipitates found they have lattice plane spacings consistent with the Nb-rich β-phase. This result is in agreement with the βphase precipitation observed following neutron irradiation, and thus it supports the use of proton irradiation to simulate neutron-irradiation effects in Zr-2.5Nb

Supporting data for senary refractory high-entropy alloy CrxMoNbTaVW

Directory of Open Access Journals (Sweden)

B. Zhang

2015-12-01

Full Text Available This data article is related to the research paper entitled “senary refractory high-entropy alloy CrxMoNbTaVW [1]”. In this data article, the pseudo-binary Cr-MoNbTaVW phase diagram is presented to show the impact of Cr content to the senary Cr-MoNbTaVW alloy system; the sub-lattice site fractions are presented to show the disordered property of the Cr-MoNbTaVW BCC structures; the equilibrium and Scheil solidification results with the actual sample elemental compositions are presented to show the thermodynamic information of the melted/solidified CrxMoNbTaVW samples; and the raw EDS scan data of the arc-melted CrxMoNbTaVW samples are also provided.

In situ synthesis of NiAl–NbB2 composite powder through combustion synthesis

International Nuclear Information System (INIS)

Shokati, Ali Akbar; Parvin, Nader; Sabzianpour, Naser; Shokati, Mohammad; Hemmati, Ali

2013-01-01

Highlights: ► A Novel NiAl matrix composite powder with 0–40 wt.% NbB 2 was synthesized. ► Composite powders were synthesized by thermal explosion reaction of Ni–Al–Nb–B system. ► Microhardness of NiAl considerably increased with raising NbB 2 content. ► Synthesized composite powders is a good candidate as precursor for thermal barrier application. - Abstract: Synthesis of a novel NiAl matrix composite powder reinforced with 0–40 wt.% NbB 2 by combustion synthesis in thermal explosion mode was investigated. The elemental powders of Ni, Al, Nb, and amorphous boron were used as starting material. For all compositions final products consisted of only the NiAl and NbB 2 phases. Coarser NbB 2 with a relatively uniform distribution in NiAl matrix was formed with rising NbB 2 content. Microhardness of NiAl considerably increased from 377 ± 13 HV 0.05 to 866 ± 81 HV 0.05 for NiAl with 40 wt.% NbB 2 . High microhardness, proper size and distribution of NbB 2 in NiAl matrix make it a good candidate as precursor for thermal spray application.

Structural properties, deformation behavior and thermal stability of martensitic Ti-Nb alloys

Energy Technology Data Exchange (ETDEWEB)

Boenisch, Matthias

2016-06-10

Ti-Nb alloys are characterized by a diverse metallurgy which allows obtaining a wide palette of microstructural configurations and physical properties via careful selection of chemical composition, heat treatment and mechanical processing routes. The present work aims to expand the current state of knowledge about martensite forming Ti-Nb alloys by studying 15 binary Ti-c{sub Nb}Nb (9 wt.% ≤ c{sub Nb} ≤ 44.5 wt.%) alloy formulations in terms of their structural and mechanical properties, as well as their thermal stability. The crystal structures of the martensitic phases, α{sup '} and α'', and the influence of the Nb content on the lattice (Bain) strain and on the volume change related to the β → α{sup '}/α'' martensitic transformations are analyzed on the basis of Rietveld-refinements. The magnitude of the shuffle component of the β → α{sup '}/α'' martensitic transformations is quantified in relation to the chemical composition. The largest transformation lattice strains are operative in Nb-lean alloys. Depending on the composition, both a volume dilatation and contraction are encountered and the volume change may influence whether hexagonal martensite α{sup '} or orthorhombic martensite α'' forms from β upon quenching. The mechanical properties and the deformation behavior of martensitic Ti-Nb alloys are studied by complementary methods including monotonic and cyclic uniaxial compression, nanoindentation, microhardness and impulse excitation technique. The results show that the Nb content strongly influences the mechanical properties of martensitic Ti-Nb alloys. The elastic moduli, hardness and strength are minimal in the vicinity of the limiting compositions bounding the interval in which orthorhombic martensite α'' forms by quenching. Uniaxial cyclic compressive testing demonstrates that the elastic properties of strained samples are different than those of unstrained ones

The Fictional Black Blues Figure: Blues Music and the Art of Narrative Self-Invention

OpenAIRE

Mack, Kimberly

2015-01-01

The Fictional Black Blues Figure: Blues Music and the Art of Narrative Self-Invention, Kimberly MackMy dissertation examines representations of black American blues musicians in contemporary American fiction, drama, and popular music, and it argues that blues music can be examined as a narrative art rooted in the tradition of fictionalized autobiographical self-fashioning. I contend that the contemporary, multi-racial, literary and musical characters in my project who participate in so-called...

On the hardenability of Nb-modified metastable beta Ti-5553 alloy

Energy Technology Data Exchange (ETDEWEB)

Campo, K.N.; Andrade, D.R.; Opini, V.C.; Mello, M.G.; Lopes, E.S.N.; Caram, R., E-mail: caram@fem.unicamp.br

2016-05-15

Among the commercially available titanium alloys, the metastable β Ti-5553 alloy (Ti–5Al–5V–5Mo–3Cr–0.5Fe wt.%) is an object of great interest because it is employed in aerospace structural applications, primarily in the replacement of steel components. One of the primary advantages of this alloy is its high hardenability, which allows it to retain the β phase at room temperature, even at low cooling rates, thereby allowing the thermoprocessing of thick parts. The aim of this investigation was to evaluate the effect of the replacement of V with Nb on the hardenability of Ti-5553. Based on the molybdenum equivalent criterion, the Nb-modified Ti-5553 alloy was designed to present 12 wt.% of Nb instead of 5 wt.% of V. Samples of both alloys were prepared by melting them in an arc furnace under an inert atmosphere, heat-treated at high temperatures for 12 h and plastic deformed using swage forging. Finally, these samples were solution heat-treated at temperatures above the β-transus followed by cooling at different rates using water quenching, furnace cooling and a modified Jominy end quench test. Characterization was performed by measuring Vickers hardness, X-ray diffraction, and light optical, scanning electron and transmission electron microscopy. The results obtained indicate that metastable β phase can be retained when the cooling rate is higher than 21 °C/s for both alloys. At lower cooling rates, α phase precipitation was observed, but it appeared to be less evident in the Nb-modified Ti-5553, suggesting that the replacement of V with Nb increased the hardenability of the alloy. - Highlights: • Hardenability of Ti alloys are assessed using a modified Jominy end quench test. • Ti-5553 and Nb-modified Ti-5553 are subjected to continuous cooling experiments. • β phase decomposition kinetics is reduced by replacing V with Nb in Ti-5553. • Nb-modified Ti-5553 features improved hardenability. • Replacement of V with Nb causes the �

Isolation and structures of sulfonium salts derived from thioethers: [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)].

Science.gov (United States)

Jura, Marek; Levason, William; Reid, Gillian; Webster, Michael

2009-10-07

Two very unusual sulfonium salts, [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)], obtained from reaction of the thioethers with NbF(5) in CH(2)Cl(2) solution, are reported and their structures described; the eight-coordinate tetrafluoro Nb(v) cation of the dithioether is obtained from the same reaction.

Photocatalytic hydrogen generation with Ag-loaded LiNbO3

Indian Academy of Sciences (India)

Administrator

rhodamine B decomposition under solar illumination was also reported (Stock ... photocatalytic hydrogen production. ... lytic hydrogen production from a methanol aqueous solu- .... estimated bandgap energy of Nb2O5 and LiNbO3 samples.

Mutual Effects of Hydrogenation and Deformation in Ti-Nb Alloys

National Research Council Canada - National Science Library

Zander, D

2002-01-01

...), transmission electron microscopy (TEM), thermal desorption spectroscopy (TDS), and microhardness tests, the influence of hydrogen at high fugacities on the phase stability, desorption behavior, and microhardness in Ti-Nb (20 to 45 wt pct Nb...

Coomassie Brilliant Blue G is a more potent antagonist of P2 purinergic responses than Reactive Blue 2 (Cibacron Blue 3GA) in rat parotid acinar cells

International Nuclear Information System (INIS)

Soltoff, S.P.; McMillian, M.K.; Talamo, B.R.

1989-01-01

The ability of Brilliant Blue G (Coomassie Brilliant Blue G) and Reactive Blue 2 (Cibacron Blue 3GA) to block the effects of extracellular ATP on rat parotid acinar cells was examined by evaluating their effects on ATP-stimulated 45Ca 2+ entry and the elevation of [Ca 2+ ]i (Fura 2 fluorescence). ATP (300 microM) increased the rate of Ca 2+ entry to more than 25-times the basal rate and elevated [Ca 2+ ]i to levels more than three times the basal value. Brilliant Blue G and Reactive Blue 2 greatly reduced the entry of 45 Ca 2+ into parotid cells, but the potency of Brilliant Blue G (IC50 approximately 0.4 microM) was about 100-times that of Reactive Blue 2. Fura 2 studies demonstrated that inhibitory concentrations of these compounds did not block the cholinergic response of these cells, thus demonstrating the selectivity of the dye compounds for purinergic receptors. Unlike Reactive Blue 2, effective concentrations of Brilliant Blue G did not substantially quench Fura 2 fluorescence. The greater potency of Brilliant Blue G suggests that it may be very useful in identifying P2-type purinergic receptors, especially in studies which utilize fluorescent probes

Measuring Blue Space Visibility and 'Blue Recreation' in the Everyday Lives of Children in a Capital City.

Science.gov (United States)

Pearson, Amber L; Bottomley, Ross; Chambers, Tim; Thornton, Lukar; Stanley, James; Smith, Moira; Barr, Michelle; Signal, Louise

2017-05-26

Blue spaces (water bodies) may promote positive mental and physical health through opportunities for relaxation, recreation, and social connections. However, we know little about the nature and extent of everyday exposure to blue spaces, particularly in settings outside the home or among children, nor whether exposure varies by individual or household characteristics. Wearable cameras offer a novel, reliable method for blue space exposure measurement. In this study, we used images from cameras worn over two days by 166 children in Wellington, New Zealand, and conducted content and blue space quantification analysis on each image ( n = 749,389). Blue space was identified in 24,721 images (3.6%), with a total of 23 blue recreation events. Visual exposure and participation in blue recreation did not differ by ethnicity, weight status, household deprivation, or residential proximity to the coastline. Significant differences in both visual exposure to blue space and participation in blue recreation were observed, whereby children from the most deprived schools had significantly higher rates of blue space exposure than children from low deprivation schools. Schools may be important settings to promote equitable blue space exposures. Childhood exposures to blue space may not follow the expected income inequality trends observed among adults.

Holographic recording in a doubly doped lithium niobate crystal with two wavelengths: a blue laser diode and a green laser

Science.gov (United States)

Komori, Yuichi; Ishii, Yukihiro

2010-08-01

A doubly-doped LiNbO3 (LN) crystal has been well used as a nonvolatile two-wavelength recording material. By using two levels of the crystal, two-kind holograms can be recorded on one crystal; a hologram is recorded with a 405-nm blue laser diode (LD) for a deep Mn level, and another hologram is with a 532-nm green laser for a shallow Fe level. The recording capacity doubles. A 780-nm LD is non-volatile reconstructing source since the LD line is insensitive to both levels. Multiplexed reconstructed images are demonstrated by using a sharp angular selectivity of a volume LN crystal keeping Bragg condition with spherical reconstructions.

Structure and thermal expansion of NbC complex carbides

International Nuclear Information System (INIS)

Khatsinskaya, I.M.; Chaporova, I.N.; Cheburaeva, R.F.; Samojlov, A.I.; Logunov, A.V.; Ignatova, I.A.; Dodonova, L.P.

1983-01-01

Alloying dependences of the crystal lattice parameters at indoor temperature and coefficient of thermal linear exspansion within a 373-1273 K range are determined for complex NbC-base carbides by the method of mathematical expemental design. It is shown that temperature changes in the linear expansion coefficient of certain complex carbides as distinct from NbC have an anomaly (minimum) within 773-973 K caused by occurring reversible phase transformations. An increase in the coefficient of thermal linear expansion and a decrease in hardness of NbC-base tungsten-, molybdenum-, vanadium- and hafnium-alloyed carbides show a weakening of a total chemical bond in the complex carbides during alloying

Spherical Nb single crystals containerlessly grown by electrostatic levitation

International Nuclear Information System (INIS)

Sung, Y.S.; Takeya, H.; Hirata, K.; Togano, K.

2003-01-01

Spherical Nb (T m =2750 K) single crystals were grown via containerless electrostatic levitation (ESL). Samples became spherical at melting in levitation and undercooled typically 300-450 K prior to nucleation. As-processed samples were still spherical without any macroscopic shape change by solidification showing a uniform dendritic surface morphology. Crystallographic {111} planes exposed in equilateral triangular shapes on the surface by preferential macroetching and spotty back-reflection Laue patterns confirm the single crystal nature of the ESL-processed Nb samples. No hysteresis in magnetization between zero field and field cooling also implies a clean defect-free condition of the spherical Nb single crystals

Tritium diffusion in V, Nb and Ta

International Nuclear Information System (INIS)

Qi, Z.; Voelkl, J.; Laesser, R.; Wenzl, H.

1983-01-01

Gorsky-effect measurements of the diffusion coefficient of tritium (T) in V, Nb and Ta are reported. The measurements were performed at small T concentrations (less than about 1.4 at%), and in the temperature range from -140 0 C to 100 0 C. Comparison with results obtained for H and D shows an increase of the activation energy with increasing isotopic mass. For Nb and Ta, the pre-exponential factors are identical for all the isotopes, whereas for V this factor is appreciably larger for T than for H and D. The reduction of the relaxation strength in the presence of precipitation allows a rough determination of the solubility limit, which is found to be isotope independent for Nb and Ta. In V, the solubility limit for T is shifted slightly to lower temperatures. The H, D or T induced lattice expansion calculated from the relaxation strength shows no dependence on isotopic mass. (author)

A Nb3Sn high field dipole

International Nuclear Information System (INIS)

McClusky, R.; Robins, K.E.; Sampson, W.B.

1990-01-01

A dipole magnet approximately 1 meter long with an 8 cm bore has been fabricated from cable made from Nb 3 Sn multifilamentary strands. The coil consists of four layers of conductor wound in pairs to eliminate internal joints. Each set of layers is separately constrained with Kevlar-epoxy bands and the complete assembly clamped in a split laminated iron yoke. The inner coil pairs were wound before heat treating while the outer coils were formed from pre-reacted cable using conventional insulation. A NbTi version of the magnet was fabricated using SSC version of the magnet was fabricated using SSC conductor to test the construction techniques. This magnet reached a maximum central field of 7.6 Tesla, at 4.4K which is very close to the limit estimated from conductor measurements. The Nb 3 Sn magnet, however, only reached a maximum field at 8.1T considerably short of the field expected from measurements on the inner cable. 7 refs., 5 figs

Microstructure and tri biological properties of sputtered NbTex thin films

International Nuclear Information System (INIS)

Kassem, M.; Langlade, C.; Fayeulle, S.; Mathy, Y.; Pailharey, D.

1997-01-01

Thin NbTex films were deposited on steel by sputtering. Annealing was performed at several temperatures. Phase transition phenomena were analysed by X-ray diffraction (0-20 and grazing incidence). Depending on the conditions (Sputtering and annealing) the structure of the films changed from the NbTe2 (Two-dimensional) to the Nb3Te4 (Three-dimensional with linear channels) structural type and the intercalation of Te of Nb atoms within the parent structures was suggested. Films were evaluated under fretting conditions at 1 Hz in a dry environment. The displacement was ± 50 μ m and the contact pressure was 300 MPa. Friction coefficients were low, ranging from 0.08 to 0.18 depending on the film structure. The classical dependence of friction coefficient on pressure, well known for solid lubricants, was observed for NbTe2. Thickness and annealing temperature were shown to have a major effect of endurance. (author). 21 Refs., 7 Figs

Magnetization, Low Field Instability and Quench of RHQT Nb(3)Al Strands

Energy Technology Data Exchange (ETDEWEB)

Yamada, R.; Wake, M.; Kikuchi, A.; Velev, V.; /Fermilab

2009-01-01

Since 2005, we made and tested three RHQT Nb{sub 3}Al strands, one with Nb matrix and two with Ta matrix, which are fully stabilized with Cu electroplating. We observed anomalously large magnetization curves extending beyond 1 to 1.5 Tesla with the F1 Nb matrix strand at 4.2 K, when we measured its magnetization with a balanced coil magnetometer. This problem was eliminated with the Ta matrix strands operating at 4.2 K. But with these strands a similar but smaller anomalous magnetization was observed at 1.9 K. We studied these phenomena with FEM. With the F1 Nb matrix strand, it is explained that at low external field, inter-filamentary coupling currents in the outer layers of sub-elements create a shielding effect. It reduces the inside field, keeps the inside Nb matrix superconductive, and stands against a higher outside field beyond the Hc of Nb. At an even higher external field, the superconductivity of the whole Nb matrix collapses and releases a large amount of energy, which may cause a big quench. Depending on the size of the energy in the strand or the cable, a magnet could quench, causing the low field instability. Some attempt to analyze the anomaly with FEM is presented.

Comportamento produtivo da videira 'Niagara Rosada' em diferentes sistemas de condução, com e sem cobertura plástica, durante as safras de inverno e de verão

Directory of Open Access Journals (Sweden)

José Luiz Hernandes

2013-03-01

Full Text Available Na região de Jundiaí (SP, os produtores de uva de mesa utilizam principalmente a cultivar Niagara Rosada. Atualmente, para aumentar a renda, o viticultor usa algumas alternativas tecnológicas que têm sido preconizadas, como o cultivo em manjedoura na forma de Y, em substituição ao sistema de condução em espaldeira; a poda extemporânea que permite duas safras por ano (de verão e de inverno e o uso de cobertura plástica para a proteção dos cachos contra intempéries e doenças. Portanto, foi desenvolvido um experimento visando a caracterizar a influência do sistema de condução, do uso de cobertura plástica e da poda extemporânea na produção e no tamanho dos cachos de 'Niagara Rosada'. Os resultados obtidos durante as safras de verão (2008 e 2009 e de inverno (2009 e 2010 permitiram verificar que, no sistema de condução em Y, foram obtidas maiores produções e tamanho de cacho em relação ao espaldeira. O uso de cobertura plástica no sistema em Y propiciou aumento de produção devido ao incremento em número e massa dos cachos. Também foi verificado que tanto a produção quanto a massa do cacho foram superiores na safra de verão em comparação à de inverno.

75 FR 65525 - Anthem Blue Cross Blue Shield, Claim Management Services, Inc. Operations, a Division of...

Science.gov (United States)

2010-10-25

... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-74,327] Anthem Blue Cross Blue Shield, Claim Management Services, Inc. Operations, a Division of Wellpoint, Inc., Green Bay, WI; Notice... former workers of Anthem Blue Cross Blue Shield, Claim Management Services, Inc. Operations, a Division...

Dyes adsorption blue vegetable and blue watercolor by natural zeolites modified with surfactants

International Nuclear Information System (INIS)

Jardon S, C. C.; Olguin G, M. T.; Diaz N, M. C.

2009-01-01

In this work was carried out the dyes removal blue vegetable and blue watercolor of aqueous solutions, to 20 C, at different times and using a zeolite mineral of Parral (Chihuahua, Mexico) modified with hexadecyl trimethyl ammonium bromide or dodecyl trimethyl ammonium bromide. The zeolite was characterized before and after of its adaptation with NaCl and later with HDTMABr and DTMABr. For the materials characterization were used the scanning electron microscopy of high vacuum; elementary microanalysis by X-ray spectroscopy of dispersed energy and X-ray diffraction techniques. It was found that the surfactant type absorbed in the zeolite material influences on the adsorption process of the blue dye. Likewise, the chemical structure between the vegetable blue dye and the blue watercolor, determines the efficiency of the color removal of the water, by the zeolites modified with the surfactants. (Author)

Experimental investigation of phase equilibria in the Nb-Si-Ta ternary system

Energy Technology Data Exchange (ETDEWEB)

Li, Jian; Wang, Cuiping; Yao, Jun; Yang, Shuiyuan; Zhan Shi; Liu, Xingjun [Xiamen Univ. (China). Dept. of Materials Science and Engineering; Xiamen Univ. (China). Fujian Provincial Key Laboratory of Materials Genome; Kang, Yongwang [Beijing Institute of Aeronautical Materials (China). Science and Technology on Advanced High Temperature Structural Materials Lab.

2016-12-15

The phase equilibria in the Nb-Si-Ta ternary system at 1 373 K, 1 473 K and 1 573 K were investigated by means of back-scattered electron imaging, electron probe microanalysis and X-ray diffraction. The isothermal sections at 1 373 K, 1 473 K and 1 573 K consist of two three-phase regions and seven two-phase regions, without any ternary compounds. The compounds of NbSi{sub 2} and TaSi{sub 2}, αNb{sub 5}Si{sub 3} and αTa{sub 5}Si{sub 3} form continuous solid solutions, respectively. The solubilities of Nb in Ta{sub 3}Si and Ta{sub 2}Si phases are extremely large, whereas the solubility of Si in the β(Nb, Ta) phase is relatively small.

Metallurgical study and phase diagram calculations of the Zr-Nb-Fe-(Sn,O) system; Etude metallurgique et calculs des diagrammes de phases des alliages base zirconium du systeme: Zr-Nb-Fe-(O,Sn)

Energy Technology Data Exchange (ETDEWEB)

Toffolon, C. [CEA/Saclay, Dept. d' Etudes du Comportement des Materiaux (DECM), 91 - Gif-sur-Yvette (France)]|[Paris-6 Univ., 75 (France)

2000-07-01

The Framatome M5{sup TM} Zr-Nb-O alloy with small amounts of Fe is of interest for nuclear applications (PWR fuel cladding).The behaviour of this kind of alloy for in-service conditions strongly depends on the microstructure. Therefore, a metallurgical study of alloys of the Zr-Nb-Fe-(O-Sn) system has been developed in order to study the influence of chemical composition variabilities of Nb, Fe and O and thermal treatments on the resultant microstructure. In order to get some insight on the physical metallurgy of Zr-Nb-Fe-(Sn,O) alloys and to minimize the experiments, it is useful to build a thermodynamic database. With this object, it was necessary to re-optimize and to calculate the low order binary systems such as Fe-Nb and Nb-Sn in order to assess the Zr-Nb-Fe-(Sn,O) system. Then, the experimental studies concerned: the influence of small variations in Nb and O contents on the {alpha}/{beta} transus temperatures. A comparison between experimental results and thermodynamic predictions showed a good agreement; the precipitation kinetics of {beta}Nb and intermetallic phases in the {alpha} phase domain. These experiments showed that the kinetics depends on the initial metallurgical conditions; the determination of the crystallographic structure and the stoichiometry of the ternary Zr-Nb-Fe intermetallic compounds as a function of the temperature. Finally, these experimental data were used to propose a first assessment of the Zr-Nb-Fe(O{approx}1200 ppm) system. (author)