WorldWideScience

Sample records for random nb send

  1. RADB: Random Access with Differentiated Barring for Latency-Constrained Applications in NB-IoT Network

    OpenAIRE

    Miao, Yiming; Tian, Yuanwen; Cheng, Jingjing; Hossain, M. Shamim; Ghoneim, Ahmed

    2018-01-01

    With the development of LPWA (Low Power Wide Area) technology, the emerging NB-IoT (Narrowband Internet of Things) technology is becoming popular with wide area and low-data-rate services. In order to achieve objectives such as huge amount of connection and wide area coverage within NB-IoT, the problem of network congestion generated by random access of numerous devices should be solved. In this paper, we first introduce the background of NB-IoT and investigate the research on random access o...

  2. Impact of sending email reminders of the legal requirement for posting results on ClinicalTrials.gov: cohort embedded pragmatic randomized controlled trial.

    Science.gov (United States)

    Maruani, Annabel; Boutron, Isabelle; Baron, Gabriel; Ravaud, Philippe

    2014-09-19

    To evaluate the impact of sending an email to responsible parties of completed trials that do not comply with the Food and Drug Administration Amendments Act 801 legislation, to remind them of the legal requirement to post results. Cohort embedded pragmatic randomized controlled trial. Trials registered on ClinicalTrials.gov. 190 out of 379 trials randomly selected by computer generated randomization list to receive the intervention (personalized emails structured as a survey and sent by one of us to responsible parties of the trials, indirectly reminding them of the legal requirement and potential penalties for non-compliance). The primary outcome was the proportion of results posted on ClinicalTrials.gov at three months. The secondary outcome was the proportion posted at six months. In a second step, two assessors blinded to the intervention group collected the date of the first results being received on ClinicalTrials.gov. A post hoc sensitivity analysis excluding trials wrongly included was performed. Among 379 trials included, 190 were randomized to receive the email intervention. The rate of posting of results did not differ at three months between trials with or without the intervention: 36/190 (19%) v 24/189 (13%), respectively (relative risk 1.5, 95% confidence interval 0.9 to 2.4, P=0.096) but did at six months: 46/190 (24%) v 27/189 (14%), 1.7, 1.1 to 2.6, P=0.014. In the sensitivity analysis, which excluded 48/379 trials (13%), 26/190 (14%) and 22/189 (12%), respectively, results were significant at three months (relative risk 5.1, 1.1 to 22.9, P=0.02) and at six months (4.1, 1.3 to 10.6, P=0.001). Sending email reminders about the FDA's legal requirement to post results at ClinicalTrials.gov improved significantly the posting rate at six months but not at three months.Trial registration ClinicalTrials.gov NCT01658254. © Maruani et al 2014.

  3. Sending Money Like Sending E-mails: Cryptoaddresses, The Universal Decentralised Identities

    Directory of Open Access Journals (Sweden)

    Michal Zima

    2016-12-01

    Full Text Available Sending money in cryptocurrencies is majorly based on public keys or their hashed forms—"addresses." These long random-looking strings are user unfriendly for transferring by other means than via copy-and-paste or QR codes. Replacing such strings with identifiers chosen by users themselves would significantly improve usability of cryptocurrencies. Such identifiers could be memorable, easier to write on paper or to dictate over phone. Main challenge lies in designing a practically usable decentralised system for providing these identifiers. Former solutions have been built as centralised systems or come with nonnegligible limitations. Our solution is reminiscent of a prevalent e-mail system, which is an already user friendly and desirably decentralised system. It is shown that our approach is directly applicable also to other systems that use long cryptographic identifiers.

  4. Resistive switching and electrical control of ferromagnetism in a Ag/HfO₂/Nb:SrTiO₃/Ag resistive random access memory (RRAM) device at room temperature.

    Science.gov (United States)

    Ren, Shaoqing; Zhu, Gengchang; Xie, Jihao; Bu, Jianpei; Qin, Hongwei; Hu, Jifan

    2016-02-10

    Electrically induced resistive switching and modulated ferromagnetism are simultaneously found in a Ag/HfO2/Nb:SrTiO3/Ag resistive random access memory device at room temperature. The bipolar resistive switching (RS) can be controlled by the modification of a Schottky-like barrier with an electron injection-trapped/detrapped process at the interface of HfO2-Nb:SrTiO3. The multilevel RS transition can be observed in the reset process with larger negative voltage sweepings, which is connected to the different degree of electron detrapping in the interfacial depletion region of the HfO2 layer during the reset process. The origin of the electrical control of room-temperature ferromagnetism may be connected to the change of density of oxygen vacancies in the HfO2 film. The multilevel resistance states and the electric field controlled ferromagnetism have potential for applications in ultrahigh-density storage and magnetic logic device.

  5. Sending Scholarship Students Abroad in Ottoman Empire

    Science.gov (United States)

    Kulaç, Onur; Özgür, Hüseyin

    2017-01-01

    The implementation of sending scholarship students abroad that started in the 19th century by Sultan Selim III in Ottoman Empire continued during the period of other Sultans became a significant reference point for the abroad scholarship policy of Turkey. The students that were firstly sent abroad especially for military training, were sent to…

  6. Hochauflösende CT-Densitometrie

    Directory of Open Access Journals (Sweden)

    Patsch J

    2013-01-01

    Full Text Available Die hochauflösende periphere quantitative Computertomographie (HR-pQCT ist eine nicht-invasive Bildgebungstechnik, die in der klinischen und translationellen Knochenforschung zum Einsatz kommt. Neben der getrennten Quantifizierung von kortikaler und trabekulärer Knochenmineraldichte können auch Mikrostrukturparameter und Knochengeometrie volumetrisch erfasst werden. Dichtemessungen erscheinen stabiler gegenüber leichten Bewegungsartefakten als Strukturbestimmungen, was für die Planung von longitudinalen Studien wichtig sein kann.

  7. Special Quasirandom Structures to Study the (K0.5Na0.5)NbO3 Random Alloy

    Science.gov (United States)

    2014-07-31

    and Na on the perovskite A-site. Using these structures, local variations in Na-O interactions are suggested to be the driving force behind the R3c to...structure patterns derived from the random distribution of K and Na on the perovskite A-site. Using these structures, local variations in Na-O...representing the physical properties of the ABO3 perovskite compounds PZT [14] and BaTiO3-SrTiO3 [15,16]. Unfortunately, these approaches require extensive

  8. Sending Nudes: Sex, Self-Rated Mate Value, and Trait Machiavellianism Predict Sending Unsolicited Explicit Images

    Directory of Open Access Journals (Sweden)

    Evita March

    2017-12-01

    Full Text Available Modern dating platforms have given rise to new dating and sexual behaviors. In the current study, we examine predictors of sending unsolicited explicit images, a particularly underexplored online sexual behavior. The aim of the current study was to explore the utility of dark personality traits (i.e., narcissism, Machiavellianism, psychopathy, and sadism and self-rated mate value in predicting attitudes toward and behavior of sending unsolicited explicit images. Two hundred and forty participants (72% female; Mage = 25.96, SD = 9.79 completed an online questionnaire which included a measure of self-rated mate value, a measure of dark personality traits, and questions regarding sending unsolicited explicit images (operationalized as the explicit image scale. Men, compared to women, were found to have higher explicit image scale scores, and both self-rated mate value and trait Machiavellianism were positive predictors of explicit image scale scores. Interestingly, there were no significant interactions between sex and these variables. Further, Machiavellianism mediated all relationships between other dark traits and explicit image scale scores, indicating this behavior is best explained by the personality trait associated with behavioral strategies. In sum, these results provide support for the premise that sending unsolicited explicit images may be a tactic of a short-term mating strategy; however, future research should further explore this claim.

  9. How far can one send a photon?

    Science.gov (United States)

    Gisin, Nicolas

    2015-10-01

    The answer to the question How far can one send a photon? depends heavily on what one means by a photon and on what one intends to do with that photon. For direct quantum communication, the limit is approximately 500 km. For terrestrial quantum communication, near-future technologies based on quantum teleportation and quantum memories will soon enable quantum repeaters that will turn the development of a world-wide-quantum-web (WWQW) into a highly non-trivial engineering problem. For Device-Independent Quantum Information Processing, near-future qubit amplifiers (i.e., probabilistic heralded amplification of the probability amplitude of the presence of photonic qubits) will soon allow demonstrations over a few tens of kilometers.

  10. Random mutagenesis of the nucleotide-binding domain of NRC1 (NB-LRR Required for Hypersensitive Response-Associated Cell Death-1), a downstream signalling nucleotide-binding, leucine-rich repeat (NB-LRR) protein, identifies gain-of-function mutations in the nucleotide-binding pocket

    NARCIS (Netherlands)

    Sueldo, D.J.; Shimels, M.Z.; Spiridon, L.N.; Caldararu, O.; Petrescu, A.J.; Joosten, M.H.A.J.; Tameling, W.I.L.

    2015-01-01

    •Plant nucleotide-binding, leucine-rich repeat (NB-LRR) proteins confer immunity to pathogens possessing the corresponding avirulence proteins. Activation of NB-LRR proteins is often associated with induction of the hypersensitive response (HR), a form of programmed cell death. •NRC1 (NB-LRR

  11. Sensing the sending of SMS messages: an automated test.

    Science.gov (United States)

    Sheldrake, Rupert; Avraamides, Leonidas; Novák, Matous

    2009-01-01

    The aim of this study was to carry out automated experiments to test for telepathy in connection with text messages. Subjects, aged from 11 to 72, registered online with the names and mobile telephone numbers of three senders. A computer selected a sender at random and asked him/her to send a short message service (SMS) message to the subject via the computer. The computer then asked the subject to guess the sender's name and delivered the message after receiving the guess. A test consisted of nine trials. The effects of subjects' sex and age and the effects of delay on guesses were evaluated. The main outcome measure was the proportion of correct guesses of the sender's name, compared with the 33.3% mean chance expectation. In 886 trials, there were 336 hits (37.9%), significantly above the 33.3% chance level (P = .001). The hit rate in incomplete tests was 38.4% (P = .03), showing that optional stopping could not explain the positive results. Most tests were unsupervised, which left open the possibility of cheating, but high-scoring subjects were retested under filmed conditions, where no cheating was detected, with 19 hits in 43 trials (44.2%; P = 0.09).

  12. Die posisie van die Helper in die sending

    Directory of Open Access Journals (Sweden)

    I. J. van der Walt

    1972-06-01

    Full Text Available Gedurende die aanvangsjare van die sending het die helper ’n onmisbare funksie vervul. Hulle het die onherbergsame binnelande geken, waardevolle kontakpunte vir die sendelinge geopen en hulle mense geestelik help voorlig en voorberei.

  13. DIE EINDE VAN SENDING Fases in die Sendingbedryf

    African Journals Online (AJOL)

    questions are focused on the situation in the mission work of the Dutch ..... opmerkings gemaak wat relevant is vir ons argument. ... onafhanklik sou funksioneer (“self support”), en self met die verdere sending ... (“the euthanasia of mission”).

  14. Die posisie van die Helper in die sending

    Directory of Open Access Journals (Sweden)

    I. J. van der Walt

    1972-05-01

    Full Text Available Gedurende die aanvangsjare van die sending het die helper ’n onmisbare funksie vervul. Hulle het die onherbergsame binnelande geken, waardevolle kontakpunte vir die sendelinge geopen en hulle mense geestelik help voorlig en voorberei.

  15. The Role of Altruism in Sending and Spending Remittances

    Directory of Open Access Journals (Sweden)

    Akira Shimada

    2011-06-01

    Full Text Available We investigate the effects of altruism on migrants' decisions to send money home and on their households' decisions to invest or to consume those remittances. Previous studies have devoted extensive attention to migrants' altruism toward recipients and little to recipients'altruism toward migrants. We find that the migrant sends larger remittances home when he feels more altruistic toward other household members, while he may send nothing if he feels less altruistic. We also find that other household members in the home country likely consume rather than invest remittances if they are highly altruistic toward the migrant. Our results may partially explain why countries receiving large remittances do not always make large investments, and suggest that altruism among household members does not necessarily enhance a country's development and growth through remittances.

  16. Total Ionizing Dose Effects of Gamma-Ray Radiation on NbOx-Based Selector Devices for Crossbar Array Memory

    Science.gov (United States)

    Gao, Ligang; Holbert, Keith E.; Yu, Shimeng

    2017-06-01

    The transition metal oxide NbO2 is regarded as a promising selector device to be integrated with resistive random access memory for the high-density crossbar array architecture. Understanding its total ionizing dose (TID) response would help assess the reliability of using this selector device in radiation environments. In this paper, we investigate the TID effect of gamma-ray (γ-ray) radiation on a Pt/NbOx/Pt selector device using electrical characterization and an X-ray photoelectron spectroscopy (XPS). The NbOx devices were irradiated with 60Co γ-rays to a maximum dose of 5 Mrad (NbO2). The experimental results show that the threshold switching behavior can withstand the 5 Mrad (NbO2) without significant change in the switching parameters. The XPS results reveal that there are mixed NbO2 and Nb2O5 phases in the NbOx thin film. After 5 Mrad (NbO2) γ-ray irradiation, the peak intensity of NbO2 increases and the peak intensity of Nb2O5 decreases in the XPS spectra, probably due to the reduction of Nb2O5 under radiation. Nevertheless, the electrical properties of the NbOx-based selector have remained after 5 Mrad (NbO2) γ-ray irradiation, indicating the potential use of the NbOx-based selector device in aerospace applications.

  17. [The labor migration sending regions in the state of Zacatecas].

    Science.gov (United States)

    Tamayo, J; Lozano Ascencio, F

    1991-01-01

    "In a preliminary survey in the state of Zacatecas, [Mexico,] we identified those municipalities which contribute most to the migration of Mexican workers to the United States; later, we corroborated our findings in situ and drew up an approximation of the geographic and economic characteristics of those municipalities, which make up 'migration sending zones or regions' in the state." (SUMMARY IN ENG) excerpt

  18. Fabrication and microstructures of functional gradient SiBCN–Nb composite by hot pressing

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Min, E-mail: lcxsunmin@163.com [Beijing Institute of Control Engineering, Beijing 100190 (China); Fu, Ruoyu; Chen, Jun; Mao, Xiaofang; Zhang, Jie [Beijing Institute of Control Engineering, Beijing 100190 (China); Yang, Zhihua; Liang, Bin [Institute for Advanced Ceramics, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150080 (China)

    2016-04-15

    A functional gradient material with five layers composed of SiBCN ceramic and niobium (Nb) was prepared successfully by hot pressing. The phase composition, morphology features and microstructures were investigated in each layer of the gradient material. The Nb-containing compounds involving NbC, Nb{sub 6}C{sub 5}, Nb{sub 4}C{sub 3}, Nb{sub 5}Si{sub 3} and NbN increase with the volume fraction of Nb increasing in the sub-layer. They are randomly scattered (≤ 25 vol.% Nb), then strip-like, and finally distribute continuously (≥ 75 vol.% Nb). The size of BN(C) and SiC grains in Nb-containing layers is larger than in 100% SiBCN layer due to the loss of the capsule-like structures. No distinct interfaces form in the transition regions indicating the gradual changes in phase composition and microstructures. - Highlights: • A functional gradient SiBCN–Nb material was prepared successfully by hot pressing. • Phase composition, morphology features and microstructures were investigated. • Thermodynamic calculation was used to aid in the phase analysis. • No distinct interfaces form typical of the functional gradient material.

  19. Cloud Instrument Powered by Solar Cell Sends Data to Pachube

    OpenAIRE

    Doru Ursutiu; Silviu Folea; Marius Ghercioiu

    2010-01-01

    Despite the economic downturn, there have been quite a few new developments in the world of remote measurements lately. Tag4M (www.tag4m.com) introduced the concept of cloud instrument where sensors connected to WiFi tags send data to off-the-shelf Access Points which are part of the WiFi infrastructure that exists in enterprises, retail outlets, factories, and warehouses. Access Points route the data to the Internet where specialized web applications receive the information for processing an...

  20. Hospitals will send an integrated nurse home with each discharge.

    Science.gov (United States)

    Morrow, Thomas

    2015-01-01

    Hospitals must adapt to the rapidly changing environment of risk by changing the health behavior of their population. There is only one way to do this efficiently and at scale; send a nurse home with every patient at the time of discharge. That nurse can ensure adherence to medication and slowly, over time, transform personal behavior to evidence based levels ... basically taking their medication as prescribed, changing eating habits, increasing exercise, getting people to throw away their cigarettes, teaching them how to cope, improving their sleep and reducing their stress. But, this approach will require a nurse to basically "live" with the patient for prolonged periods of time, as bad health behaviors are quick to start but slow to change or end. The rapid developments in artificial intelligence and natural language understanding paired with cloud based computing and integrated with a variety of data sources has led to a new marketplace comprised of cognitive technologies that can emulate even the most creative, knowledgeable and effective nurse. Termed the Virtual Health Assistant, your patients can literally talk to these agents using normal conversational language. The possibility to send a nurse home with each patient to maintain adherence and prevent readmissions has arrived. The technology is available. Who will step forward to reap the rewards first?

  1. Send and Receive fax documents using electronic mail

    CERN Multimedia

    2005-01-01

    Any CERN Staff Member can now send and receive faxes directly through email using the new fax service. To do so, you need to register and obtain your “personal” fax number using the page http://cern.ch/fax. Once you have your fax number, you can fax someone by sending an email message to the address of the form name@number.mail2fax.cern.ch, for example: Joe.Bloggs@000441719999999.mail2fax.cern.ch In the example, “000441719999999” is the fax number to call, as seen from inside CERN, in this case, in London. “Joe.Bloggs” is the name of your correspondent and it will appear on the cover page along with your name, email address, your “personal” fax number, and the subject of the email. Documentation and additional examples of fax addresses are on http://cern.ch/fax The eventual text of your email will be transmitted in the fax, followed by the optional attachments, as extra pages. Attachments can be in Acrobat (.pdf), Text (.txt), Word (.doc) , Excel (.xls) or Powerpoint (.ppt) formats. Once ...

  2. Send and Receive fax documents using electronic mail

    CERN Multimedia

    2005-01-01

    Any CERN Staff Member can now send and receive faxes directly through email using the new fax service. To do so, you need to register and obtain your “personal” fax number using the page http://cern.ch/fax. Once you have your fax number, you can fax someone by sending an email message to the address of the form name@number.mail2fax.cern.ch, for example: Joe.Bloggs@000441719999999.mail2fax.cern.ch In the example, “000441719999999” is the fax number to call, as seen from inside CERN, in this case, in London. “Joe.Bloggs” is the name of your correspondent and it will appear on the cover page along with your name, email address, your “personal” fax number, and the subject of the email. Documentation and additional examples of fax addresses are on http://cern.ch/fax The eventual text of your email will be transmitted in the fax, followed by the optional attachments, as extra pages. Attachments can be in Acrobat (.pdf), Text (.txt), Word (.doc) , Excel (.xls) or Powerpoint (.ppt) formats. Once the ...

  3. Theoretical study of the electronic states of Nb4, Nb5 clusters and their anions (Nb4?, Nb5?)

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, K; Majumdar, D

    2004-05-06

    Geometries and energy separations of the various low-lying electronic states of Nb{sub n} and Nb{sub n}{sup -} (n = 4, 5) clusters with various structural arrangements have been investigated. The complete active space multi-configuration self-consistent field (CASMCSCF) method followed by multi-reference singles and doubles configuration interaction (MRSDCI) calculations that included up to 52 million configuration spin functions have been used to compute several electronic states of these clusters. The ground states of both Nb{sub 4} ({sup 1}A', pyramidal) and Nb{sub 4}{sup -} ({sup 2}B{sub 3g}, rhombus) are low-spin states at the MRSDCI level. The ground state of Nb{sub 5} cluster is a doublet with a distorted trigonal bipyramid (DTB) structure. The anionic cluster of Nb{sub 5} has two competitive ground states with singlet and triplet multiplicities (DTB). The low-lying electronic states of these clusters have been found to be distorted due to Jahn-Teller effect. On the basis of the energy separations of our computed electronic states of Nb{sub 4} and Nb{sub 5}, we have assigned the observed photoelectron spectrum of Nb{sub n}{sup -}(n = 4, 5) clusters. We have also compared our MRSDCI results with density functional calculations. The electron affinity, ionization potential, dissociation and atomization energies of Nb{sub 4} and Nb{sub 5} have been calculated and the results have been found to be in excellent agreement with the experiment.

  4. Ideologies of nationhood in sending-state transnationalism: comparing Surinam and Turkey

    NARCIS (Netherlands)

    Mügge, L.

    2013-01-01

    Why do some sending states encourage continued emigrant involvement whereas others do not? And to what extent does sending-state transnationalism lead to a redefinition of borders? Although research on sending-state transnationalism is flourishing, so far it only covers the positive cases and

  5. Send your data into the cloud and make it… vaporize

    CERN Multimedia

    Computer Security Team

    2011-01-01

    “Cloud computing” --- the term is as nebulous as real clouds.   Basically, it means storing data somewhere on the Internet. This certainly has advantages, since this data will be available anytime from anywhere. For example, the Google mailbox is available from everywhere; “Dropbox” provides a central storage for any type of files; “ZAPR” and “TeamViewer”, once installed, allow you to share your local files by just sending around links, or give third parties full remote access to your PC, respectively. In addition, there is a growing number of cloud synchronisation services (e.g. “iCloud”/”MobileMe”, “Firefox Sync”, “Dropbox”) which provide (semi-)automatic back-ups of all local files of a laptop, PC or mobile phone. But hold on. What actually is transferred into the cloud? Personal files like bank statements? Passwords, especially CE...

  6. Sending Safety Video over WiMAX in Vehicle Communications

    Directory of Open Access Journals (Sweden)

    Jun Steed Huang

    2013-10-01

    Full Text Available This paper reports on the design of an OPNET simulation platform to test the performance of sending real-time safety video over VANET (Vehicular Adhoc NETwork using the WiMAX technology. To provide a more realistic environment for streaming real-time video, a video model was created based on the study of video traffic traces captured from a realistic vehicular camera, and different design considerations were taken into account. A practical controller over real-time streaming protocol is implemented to control data traffic congestion for future road safety development. Our driving video model was then integrated with the WiMAX OPNET model along with a mobility model based on real road maps. Using this simulation platform, different mobility cases have been studied and the performance evaluated in terms of end-to-end delay, jitter and visual experience.

  7. Generic Model to Send Secure Alerts for Utility Companies

    Directory of Open Access Journals (Sweden)

    Perez–Díaz J.A.

    2010-04-01

    Full Text Available In some industries such as logistics services, bank services, and others, the use of automated systems that deliver critical business information anytime and anywhere play an important role in the decision making process. This paper introduces a "Generic model to send secure alerts and notifications", which operates as a middleware between enterprise data sources and its mobile users. This model uses Short Message Service (SMS as its main mobile messaging technology, however is open to use new types of messaging technologies. Our model is interoperable with existing information systems, it can store any kind of information about alerts or notifications at different levels of granularity, it offers different types of notifications (as analert when critical business problems occur,asanotificationina periodical basis or as 2 way query. Notification rules can be customized by final users according to their preferences. The model provides a security framework in the cases where information requires confidentiality, it is extensible to existing and new messaging technologies (like e–mail, MMS, etc. It is a platform, mobile operator and hardware independent. Currently, our solution is being used at the Comisión Federal de Electricidad (Mexico's utility company to deliver secure alerts related to critical events registered in the main power generation plants of our country.

  8. Independent Validation of the SEND-PD and Correlation with the MDS-UPDRS Part IA

    OpenAIRE

    Mayela Rodríguez-Violante; Amin Cervantes-Arriaga; Salvador Velázquez-Osuna; Rodrigo Llorens-Arenas; Humberto Calderón-Fajardo; Dan Piña-Fuentes; Pablo Martinez-Martin

    2014-01-01

    Introduction. Neuropsychiatric symptoms in Parkinson's disease can be assessed by the MDS-UPDRS part IA. The Scale for Evaluation of Neuropsychiatric Disorders in Parkinson's disease (SEND-PD) has been recently developed to assess the severity of some neuropsychiatric symptoms. The objective of this study is to compare the performance of the SEND-PD with the corresponding items of the MDS-UPDRS part IA. Methods. Patients with Parkinson's disease were evaluated using the MDS-UPDRS and the SEND...

  9. EXPECTATIONS OF PARENTS WHO ARE SENDING THEIR CHILDREN TO SWIMMING SPORTS

    OpenAIRE

    Hüseyin Öztürk; Ahmet Yılgın; Fatih Armutcu

    2017-01-01

    This study was designed to investigate the causes of families' sending their children to swimming summer schools. The working group constitutes the parents who send their children to the summer school swimming schools in Kahramanmaras. A total of 203 people, 155 female and 48 male, participated in the research. In order to determine the reasons for sending the children to the swimming schools, the scale developed by Meral (2010) was utilized. While the findings obtained in the study were eval...

  10. 29 CFR 4000.28 - What if I send a computer disk?

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false What if I send a computer disk? 4000.28 Section 4000.28... I send a computer disk? (a) In general. We determine your filing or issuance date for a computer... paragraph (b) of this section. (1) Filings. For computer-disk filings, we may treat your submission as...

  11. Sending family history questionnaires to patients before a colonoscopy improves genetic counseling for hereditary colorectal cancer

    NARCIS (Netherlands)

    Kessels, K.; Eisinger, J.D.; Letteboer, T.G.; Offerhaus, G.J.; Siersema, P.D.; Moons, L.M.

    2017-01-01

    OBJECTIVES: To investigate whether sending a family history questionnaire to patients prior to undergoing colonoscopy results in an increased availability of family history and better genetic counseling. METHODS: A questionnaire was mailed to patients before they underwent outpatient colonoscopy at

  12. Sending family history questionnaires to patients before a colonoscopy improves genetic counseling for hereditary colorectal cancer

    NARCIS (Netherlands)

    Kessels, Koen; Eisinger, Joey D; Letteboer, Tom G|info:eu-repo/dai/nl/304815837; Offerhaus, G Johan A; Siersema, Peter D|info:eu-repo/dai/nl/110603826; Moons, Leon M G

    OBJECTIVES: To investigate whether sending a family history questionnaire to patients prior to undergoing colonoscopy results in an increased availability of family history and better genetic counseling. METHODS: A questionnaire was mailed to patients before they underwent outpatient colonoscopy at

  13. Materials Analysis of CED Nb Films Being Coated on Bulk Nb Single Cell SRF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin; Reece, Charles; Palczewski, Ari; Ciovati, Gianluigi; Krishnan, Mahadevan; James, Colt; Irfan, Irfan

    2013-09-01

    This study is an on-going research on depositing a Nb film on the internal wall of bulk Nb single cell SRF cavities, via a cathodic arc Nb plasma ions source, an coaxial energetic condensation (CED) facility at AASC company. The motivation is to firstly create a homoepitaxy-like Nb/Nb film in a scale of a ~1.5GHz RF single cell cavity. Next, through SRF measurement and materials analysis, it might reveal the baseline properties of the CED-type homoepitaxy Nb films. Literally, a top-surface layer of Nb films which sustains SRF function, always grows up in homo-epitaxy mode, on top of a Nb nucleation layer. Homo-epitaxy growth of Nb must be the final stage (a crystal thickening process) of any coatings of Nb film on alternative cavity structure materials. Such knowledge of Nb-Nb homo-epitaxy is useful to create future realistic SRF cavity film coatings, such as hetero-epitaxy Nb/Cu Films, or template-layer-mitigated Nb films. One large-grain, and three fine grain bulk Nb cavities were coated. They went through cryogenic RF measurement. Preliminary results show that the Q0 of a Nb film could be as same as the pre-coated bulk Nb surface (which received a chemically-buffered polishing plus a light electro-polishing); but quality factor of two tested cavities dropped quickly. We are investigating if the severe Q-slope is caused by hydrogen incorporation before deposition, or is determined by some structural defects during Nb film growth.

  14. Independent Validation of the SEND-PD and Correlation with the MDS-UPDRS Part IA

    Directory of Open Access Journals (Sweden)

    Mayela Rodríguez-Violante

    2014-01-01

    Full Text Available Introduction. Neuropsychiatric symptoms in Parkinson’s disease can be assessed by the MDS-UPDRS part IA. The Scale for Evaluation of Neuropsychiatric Disorders in Parkinson’s disease (SEND-PD has been recently developed to assess the severity of some neuropsychiatric symptoms. The objective of this study is to compare the performance of the SEND-PD with the corresponding items of the MDS-UPDRS part IA. Methods. Patients with Parkinson’s disease were evaluated using the MDS-UPDRS and the SEND-PD by independent raters. Partial SEND-PD and neuropsychiatric MDS-UPDRS part IA were constructed with equivalent items for comparison. Results. A total of 260 consecutive patients were included. Overall, 61.2% of the patients did not report any psychotic symptom and 83.5% did not report any ICD symptom. On the other hand, 78.5% of the patients did report at least one symptom related to apathy, depression, or anxiety. The partial SEND-PD score was 2.9±3.1 (range from 0 to 16. The neuropsychiatric MDS-UPDRS part IA score was 2.9±3 (range from 0 to 14. The correlation coefficient between corresponding items ranged from 0.67 to 0.98 and between both summary indexes was rs=0.93 (all, P<0.001. Conclusion. A high association between equivalent items of the SEND-PD and the MDS-UPDRS was found.

  15. Characteristics and Preparation Technologies of Nb/Nb5Si3 Microlaminate

    Directory of Open Access Journals (Sweden)

    MU Rende

    2016-06-01

    Full Text Available Nb/Nb5Si3 superalloy has the most potential in the application of future high temperature structures. Realization of microstructure lamination for this material is a new material design and preparation method. Characteristics and prevailing preparation technologies of Nb/Nb5Si3 microlaminate, including hot pressing, plasma spaying, magnetic sputtering and electron beam physical vapor deposition (EB-PVD are reviewed. It is pointed out that EB-PVD is a promising technology for producing Nb/Nb5Si3 microlaminate from the engineering application point of view. Structure and function compound, nano-laminating and toughening are the developing directions in the future electron beam physical vapor deposited Nb/Nb5Si3 microlaminate field.

  16. On Mossbauer dynamics in Nb3Sn

    Indian Academy of Sciences (India)

    Before the advent of high temperature oxide superconductivity, several intermetallic com- pounds possessing A15 crystal structure [1] have been known to be good superconductors; namely V3Si (Мc=17.1 K), V3Ga (Мc=16.8 K), Nb3Sn (Мc=18 K), Nb3Al (Мc=18.5 K) and Nb3Alo75 Geo75 (Мc=20 K). A15 group of ...

  17. Making sense of SEND; the Standard for Exchange of Nonclinical Data.

    Science.gov (United States)

    Briggs, Katharine

    2017-12-01

    The Standard for Exchange of Nonclinical Data (SEND) is currently the preferred submission format for nonclinical animal data by the US FDA and became a requirement on the 18th December 2016. Application of these data standards is the first step to being able to perform cross-study querying and is expected to open up opportunities for data mining and meta-analysis by the pharmaceutical industry. This paper reports on our experiences in developing a tool to allow recent SEND formatted studies to be explored alongside historical nonclinical data already gathered as part of the eTOX project. Combining SEND data with historical data will positively impact the power of any analysis performed and increase the likelihood of being able to detect rare effects. It describes the use of KNIME in generating dose group averages and incidences from individual animal level data captured in SEND. There are a number of options for opening and reading SEND files but the benefits of using KNIME are that it is a free, open source data mining framework which allows the data to be viewed in a holistic manner rather than one domain at a time. Additionally it incorporates several nodes useful for aggregating and visualising the data to more easily identify patterns and trends. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Preparation of superconducting Nb-Zr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Drapala, J.; Kuchar, L. (Vysoka Skola Banska, Ostrava (Czechoslovakia). Katedra Nezeleznych Kovu a Jaderne Metalurgie)

    1983-01-01

    Superconducting Nb-Zr alloy with a zirconium content of up to 3 wt.% was prepared by a combination of arc and electron zone melting. First, the Nb-Zr master alloy with 1 wt.% Zr was prepared in a horizontal arc furnace under an argon atmosphere. This master alloy was remelted several times to achieve the highest possible homogeneity of samples. The Nb-Zr ingot was then remelted through two zone passes on equipment for high-vacuum electron zone melting. Samples were taken of the Nb-Zr alloy and a metallographic analysis was made.

  19. Experimentally Determining β-Decay Intensities for 103,104Nb to Improve R-process Calculations

    Science.gov (United States)

    Gombas, J.; Deyoung, P. D.; Spyrou, A.; Dombos, A. C.; Lyons, S.; The SuN Collaboration

    2017-09-01

    The rapid neutron capture process (r-process) is responsible for the formation of nuclei heavier than iron. This process is theorized to occur in supernovas and/or neutron star mergers. R-process calculations require the accurate knowledge of a significant amount of nuclear properties, the majority of which are not known experimentally. Nuclear masses, β-decay properties and neutron-capture reactions are all input ingredients into r-process models. This present study focuses on the β decay of 103Nb and 104Nb. The β decay of 103Nb and 104Nb, two nuclei found in the r-process, were observed at the NSCL using the Summing NaI (SuN) detector. An unstable beam implanted inside SuN. The γ rays were measured in coincidence with the emitted electrons. The β-decay intensity function was then extracted. The experimentally determined functions for 103Nb and 104Nb will be compared to predictions made by the Quasi Random Phase Approximation (QRPA) model. These theoretical calculations are used in astrophysical models of the r-process. This comparison will lead to a better understanding of the nuclear structure for 103Nb and 104Nb. A more dependable prediction of the formation of heavier nuclei birthed from supernovas or neutron star mergers can then be made. This material is based upon work supported by the National Science Foundation under Grant No. PHY-1613188 and PHY-1306074, and by the Hope College Department of Physics Guess Research Fund.

  20. In vitro cytotoxicity and hemocompatibility studies of Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B L; Li, L; Zheng, Y F, E-mail: blwang@hrbeu.edu.c, E-mail: lili_heu@hrbeu.edu.c, E-mail: yfzheng@pku.edu.c [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China)

    2010-08-01

    The in vitro cytotoxicity and hemocompatibility of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf biomedical shape memory alloys (SMAs) were investigated by cell culture (L-929 fibroblast cell), hemolytic test and platelet adhesion test, with CP Ti as a reference material. The cytotoxicity test indicates that all the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs show over 94% cell viability for different incubation times (2, 4 and 7 days) in comparison with a negative control and CP Ti. The cell morphology observation shows good polygon-like adherent growth and proliferation of L-929 in the extracts of all the test samples and CP Ti. These results suggest excellent cytocompatibility for the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs. The hemolytic test reveals that the hemolysis ratios of the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf alloys are far less than 5%, so they cannot give rise to acute hemolysis. The platelet morphology observation shows almost the same adhered platelet morphology and activation ratio for the test samples in comparison with CP Ti, except the Ti-22Nb-6Hf alloy, which shows a lower activation ratio of platelets, indicating excellent blood compatibility. Therefore, it is proposed that the Ti-Nb, Ti-Nb-Zr and Ti-Nb-Hf SMAs will be candidates to replace Ti-Ni for biomedical applications.

  1. Enhancement web proxy cache performance using Wrapper Feature Selection methods with NB and J48

    Science.gov (United States)

    Mahmoud Al-Qudah, Dua’a.; Funke Olanrewaju, Rashidah; Wong Azman, Amelia

    2017-11-01

    Web proxy cache technique reduces response time by storing a copy of pages between client and server sides. If requested pages are cached in the proxy, there is no need to access the server. Due to the limited size and excessive cost of cache compared to the other storages, cache replacement algorithm is used to determine evict page when the cache is full. On the other hand, the conventional algorithms for replacement such as Least Recently Use (LRU), First in First Out (FIFO), Least Frequently Use (LFU), Randomized Policy etc. may discard important pages just before use. Furthermore, using conventional algorithm cannot be well optimized since it requires some decision to intelligently evict a page before replacement. Hence, most researchers propose an integration among intelligent classifiers and replacement algorithm to improves replacement algorithms performance. This research proposes using automated wrapper feature selection methods to choose the best subset of features that are relevant and influence classifiers prediction accuracy. The result present that using wrapper feature selection methods namely: Best First (BFS), Incremental Wrapper subset selection(IWSS)embedded NB and particle swarm optimization(PSO)reduce number of features and have a good impact on reducing computation time. Using PSO enhance NB classifier accuracy by 1.1%, 0.43% and 0.22% over using NB with all features, using BFS and using IWSS embedded NB respectively. PSO rises J48 accuracy by 0.03%, 1.91 and 0.04% over using J48 classifier with all features, using IWSS-embedded NB and using BFS respectively. While using IWSS embedded NB fastest NB and J48 classifiers much more than BFS and PSO. However, it reduces computation time of NB by 0.1383 and reduce computation time of J48 by 2.998.

  2. SENDS criteria from the diversification of MAST procedures. Implementation of preoperative simulation; SENDS-Kriterien als Entwicklungstheorem der MAST-Prozeduren. Einfuehrung praeoperativer Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rieger, B. [Universitaetsklinikum Carl Gustav Carus, Klinik und Poliklinik fuer Neurochirurgie, Dresden (Germany)

    2015-10-15

    Minimal access spinal technologies (MAST) lead to a diversification of surgical procedures, which requires careful selection of the procedure and outcome monitoring. For a rational selection of the procedure simulation, endoscopy, navigation, decompression and stabilization (SENDS) criteria can be derived from the development of the MAST procedures. Preoperative simulation has diagnostic and therapeutic values. The SENDS criteria can be verified indirectly via outcome control. Biomechanically meaningful diagnostic x-rays of the spinal segment to be surgically treated are currently carried out with the patient in inclination and reclination. Software-related preoperative simulation based on these x-ray images facilitates the selection and implementation of the MAST procedure. For preoperative simulation motion shots are needed in inclination, neutral position and reclination and the dimensions can be obtained using an x-ray ball or a computed tomography (CT) scan. The SENDS criteria are useful because established procedures based on these criteria reach a comparable outcome. Preoperative simulation appears to be a useful selection criterion. Preoperatively it is necessary to collate patient and segment information in order to provide each patient with individualized treatment. So far there is no evidence for a better outcome after preoperative simulation but a reduction of surgery time and intraoperative radiation exposure could already be demonstrated. Minimally invasive methods should be preferred if there is a comparable outcome. The establishment of new procedures has to be accompanied by the maintenance of a spine register. Minimally invasive surgical procedures should be individualized for each patient and segment. Mobility X-ray images should be prepared for use with the preoperative simulation as the information content significantly increases with respect to the MAST procedure. (orig.) [German] Die Minimal Access Spine Technology (MAST) fuehrt zur

  3. 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.

  4. All NbN tunnel junction fabrication

    Science.gov (United States)

    Leduc, H. G.; Khanna, S. K.; Stern, J. A.

    1987-01-01

    The development of SIS tunnel junctions based on NbN for mixer applications in the submillimeter range is reported. The unique technological challenges inherent in the development of all refractory-compound superconductor-based tunnel junctions are highlighted. Current deposition and fabrication techniques are discussed, and the current status of all-NbN tunnel junctions is reported.

  5. Formation and characterization of Al–Ti–Nb alloys by electron-beam surface alloying

    Energy Technology Data Exchange (ETDEWEB)

    Valkov, S., E-mail: stsvalkov@gmail.com [Institute of Electronics, Bulgarian Academy of Science, 72 Tzarigradsko Chaussee blvd., 1784 Sofia (Bulgaria); Petrov, P. [Institute of Electronics, Bulgarian Academy of Science, 72 Tzarigradsko Chaussee blvd., 1784 Sofia (Bulgaria); Lazarova, R. [Institute of Metal Science, Equipment and Technologies with Hydro and Aerodynamics Center, Bulgarian Academy of Science, 67 Shipchenski Prohod blvd., 1574 Sofia (Bulgaria); Bezdushnyi, R. [Department of Solid State Physics and Microelectronics, Faculty of Physics, Sofia University “St. Kliment Ohridsky”, 1164 Sofia (Bulgaria); Dechev, D. [Institute of Electronics, Bulgarian Academy of Science, 72 Tzarigradsko Chaussee blvd., 1784 Sofia (Bulgaria)

    2016-12-15

    Highlights: • Al–Ti–Nb surface alloys have been successfully obtained by electron-beam surface alloying technology. • The alloys consist of (Ti,Nb)Al{sub 3} fractions, distributed in the biphasic structure of (Ti,Nb)Al{sub 3} particles dispersed in α-Al. • The alloying speed does not affect the lattice parameters of (Ti,Nb)Al{sub 3} and, does not form additional stresses, strains etc. • It was found that lower velocity of the specimen motion during the alloying process develops more homogeneous structures. • The measured hardness of (Ti,Nb)Al{sub 3} compound reaches 775 HV[kg/cm{sup 2}] which is much greater than the values of NbAl{sub 3}. - Abstract: The combination of attractive mechanical properties, light weight and resistance to corrosion makes Ti-Al based alloys applicable in many industrial branches, like aircraft and automotive industries etc. It is known that the incorporation of Nb improves the high temperature performance and mechanical properties. In the present study on Al substrate Ti and Nb layers were deposited by DC (Direct Current) magnetron sputtering, followed by electron-beam alloying with scanning electron beam. It was chosen two speeds of the specimen motion during the alloying process: V{sub 1} = 0.5 cm/s and V{sub 2} = 1 cm/s. The alloying process was realized in circular sweep mode in order to maintain the melt pool further. The obtained results demonstrate a formation of (Ti,Nb)Al{sub 3} fractions randomly distributed in biphasic structure of intermetallic (Ti,Nb)Al{sub 3} particles, dispersed in α-Al solid solution. The evaluated (Ti,Nb)Al{sub 3} lattice parameters are independent of the speed of the specimen motion and therefore the alloying speed does not affect the lattice parameters and thus, does not form additional residual stresses, strains etc. It was found that lower velocity of the specimen motion during the alloying process develops more homogeneous structures. The metallographic analyses demonstrate a

  6. 'It sends a message': Liberian opinion leaders' responses to the trial of Charles Taylor

    NARCIS (Netherlands)

    Glasius, M.

    2015-01-01

    This article investigates the potential impact of an international criminal trial on a post-conflict society. It assesses the claims of legal expressivism, which conceptualizes criminal justice as a message sending mechanism that can enunciate societal condemnation of atrocities, establish an

  7. Students with Self-Identified Special Educational Needs and Disabilities (Si-SEND): Flourishing or Languishing!

    Science.gov (United States)

    Skrzypiec, Grace; Askell-Williams, Helen; Slee, Phillip; Rudzinski, Adrian

    2016-01-01

    Students' wellbeing is an essential component of their ability to function well, not only at school but also in all life domains. Many studies have investigated student wellbeing. However, empirical studies about the wellbeing of students with special educational needs and disabilities (SEND) are scarce. Furthermore, many studies have adopted a…

  8. LCD plus NB-UVB reduces time to improvement of psoriasis vs. NB-UVB alone.

    Science.gov (United States)

    Bagel, Jerry

    2009-04-01

    Use of coal tar with narrowband (NB) ultraviolet B (UVB) light (the Goeckerman regimen) is an effective treatment for plaque psoriasis that has become impractical in outpatient care mainly due to the inconvenience and aesthetic concerns of coal tar. This study evaluated the safety, efficacy, and convenience of adding a novel LCD (coal tar) solution to standard NB-UVB phototherapy in adults with chronic plaque psoriasis. Patients applied LCD solution to half-body twice daily at home and received outpatient full-body NB-UVB light therapy 3 times a week for up to 12 weeks. A blinded investigator graded psoriasis severity of body halves and bilateral target lesions and monitored adverse reactions. Patients rated their psoriasis symptoms and LCD solution aesthetics. NB-UVB + LCD therapy reduced the median time to clearance or minimal disease in at least 50% of the population by 3 weeks (4 weeks with NB-UVB + LCD versus 7 weeks with NB-UVB alone). A statistically superior clinical response was observed by the end of week 4 with NB-UVB + LCD versus NB-UVB alone (P LCD solution into outpatient NB-UVB light therapy is safe, convenient, effective, and can improve psoriasis more quickly than NB-UVB light therapy alone.

  9. Phase Evolution in and Creep Properties of Nb-Rich Nb-Si-Cr Eutectics

    Science.gov (United States)

    Gang, Florian; Kauffmann, Alexander; Heilmaier, Martin

    2017-10-01

    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.

  10. 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.

  11. Subduction related fluids fractionate Nb/Ta

    Science.gov (United States)

    Salters, V. J.; Bizimis, M.; Sachi-Kocher, A.; Taylor, R.; Savov, I. P.; Stern, C. R.

    2009-12-01

    Key differences between the chemical composition of terrestrial materials and those of meteorites have led to the suggestion that a `hidden’ high Nb/Ta reservoir exists in the Earth’s mantle. In order to test this hypothesis we must identify the processes that can create such a reservoir. It has been suggested that during subduction Nb is more refractory then Ta resulting in low Nb/Ta in the subducted slab, which then serves as a reservoir for the high Nb/Ta. Here we report high precision HFSE data on products of the subduction processes thought to fractionate Nb from Ta: boninites (hydrous melting), adakites (slab melting), oceanic island arc basalts and supra subduction zone peridotites. We developed a new method for the high precision determination of Nb, Ta, Zr, Hf concentrations based on a modified version of standard addition. All analyses were performed on a single collector ICPMS (ELEMENT 1), using Y and Yb as internal standards to correct for instrumental drift during the unspiked -spiked sample sequence. Concentrations are calculated using a York- type regression that accounts for all measured and propagated errors. Long-term reproducibility (multiple dissolutions and multiple spike solutions) for the standards BHVO-1, BIR-1 AGV-1 and BCR-1 are better than 0.8% (1s) for Nb/Ta and Zr/Hf ratios. The advantages of this method compared to previous methods are fast throughput, no column chemistry and low blanks. While the Zr/Hf ratios in subduction-related volcanics and ocean island basalts vary by less than a factor of two, the Nb/Ta ratio varies by a factor of four. Most of the Nb/Ta variation is observed in subduction related rocks. Samples with the highest Nb/Ta ratio (up to 19.5) are adakites from the Austral Volcanic Zone (Andes) which are thought to represent eclogitic melts from subducted oceanic crust which was most likely dehydrated. The lowest Nb/Ta (5) was found in boninites from Chichi-Jima, Bonin Island. Samples from Chichi-Jima and from the

  12. 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.

  13. Binary Ni-Nb bulk metallic glasses

    Science.gov (United States)

    Xia, L.; Li, W. H.; Fang, S. S.; Wei, B. C.; Dong, Y. D.

    2006-01-01

    We studied the glass forming ability of Ni-Nb binary alloys and found that some of the alloys can be prepared into bulk metallic glasses by a conventional Cu-mold casting. The best glass former within the compositional range studied is off-eutectic Ni62Nb38 alloy, which is markedly different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism for binary Ni-Nb alloys was studied from the thermodynamic point of view and a parameter γ* was proposed to approach the ability of glass formation against crystallization.

  14. Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

    Science.gov (United States)

    Stein, Frank; Philips, Noah

    2017-09-01

    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).

  15. Studies on superconducting NbN thin films and NbN microbridges

    Energy Technology Data Exchange (ETDEWEB)

    Xiuwen, W.; Jiazhang, L.; Taiping, Z.; Weixin, G.; Guangji, C.

    1984-06-01

    RF reactively of sputtred NbN films were fabricated by changing the ratio of argon to nittogen and using a range of substrate temperatures. The transition temperature T/sub c/, electrical resistivity and resistivity ratio of NbN films were measured. T/sub c/ was usually between 13K and 15K, and sometimes up to 15.2K. X-ray analysis and XPS studies on NbN films were made and superconducting microbridges and VTBS of NbN were fabricated.

  16. 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.

  17. Magnetron Sputtered NbN Films with Nb Interlayer on Mild Steel

    Directory of Open Access Journals (Sweden)

    Kulwant Singh

    2011-01-01

    Full Text Available The aim of the study is to extend the NbN coating on MS with Nb interlayer to explore the benefits of hard nitride coatings on low-cost structural material and to compare the coating with NbN monolithic coating on SS. NbN on MS and SS was deposited by reactive d.c. magnetron sputtering at various N2/Ar flow ratios and substrate bias. Deposition rate decreased from 20 to 10 nm/min (without biasing and from 16 to 8 nm/min (−50 V biasing when N2/Ar ratio was varied from zero to 70%. Deposition rate decreased with the increase in bias voltage. Coatings showed hexagonal β Nb2N, cubic δ NbN, and hexagonal δ′ NbN as major phases with the increasing N2 flow. Surface hardness reached a maximum of 2040 HK25 at a N2/Ar of 20%. Critical loads, for cohesive and adhesive failure for coating on MS, were between 6–8 N and 9–12 N respectively; for coating on SS, the values were between 7–15 N and 12–25 N respectively. Duplex coatings were studied for hardness by Knoop microindentation, adhesion by scratch tester, and corrosion by potentiodynamic polarization technique. Hardness, adhesion, and corrosion resistance all improved when NbN coating was incorporated with Nb interlayer on MS.

  18. Explaining Labour Market Inactivity in Migrant-Sending Families: Housework, Hammock, or Higher Education

    OpenAIRE

    Görlich, Dennis; Omar Mahmoud, Toman; Trebesch, Christoph

    2007-01-01

    This article presents a new perspective on the impact of migration and remittances on labour market participation and time allocation in migrant-sending families. Departing from the common finding that labour market participation is lower in migrant households, we investigate whether the reasons for inactivity, i.e. leisure consumption, home production and higher education are affected by migration. Based on household survey data from Moldova, our results challenge the assertion that those wh...

  19. When Germany sends troops abroad: the case for a limited reform of the Parliamentary Participation Act

    OpenAIRE

    Brose, Ekkehard

    2013-01-01

    "The Parliamentary Participation Act has proved to be a valuable tool for ensuring the democratic legitimacy of any decision to send Bundeswehr troops abroad. Since it came into force in 2005, the German Bundestag has given its assent to more than 70 requests of the Federal Government for the deployment of German troops abroad, or the extension of such mandates, and has not rejected a single application. Nevertheless, there is a problem: Germany's partners see participation with military pers...

  20. 13 CFR 134.614 - What deadlines apply to my application for an award and where do I send it?

    Science.gov (United States)

    2010-01-01

    ... application for an award and where do I send it? 134.614 Section 134.614 Business Credit and Assistance SMALL... and where do I send it? After you have prevailed in an administrative proceeding or in a discrete... award for fees and expenses may still be filed, but it will not be considered by the ALJ until a final...

  1. 41 CFR 102-118.195 - What documents must a transportation service provider (TSP) send to receive payment for a...

    Science.gov (United States)

    2010-07-01

    ... transportation service provider (TSP) send to receive payment for a transportation billing? 102-118.195 Section... must a transportation service provider (TSP) send to receive payment for a transportation billing? For shipments bought on a TD, the TSP must submit an original properly certified GBL, PPGBL, or bill of lading...

  2. Rapid solidification of Nb-base alloys

    Science.gov (United States)

    Gokhale, A. B.; Javed, K. R.; Abbaschian, G. J.; Lewis, R. E.

    1988-01-01

    New Nb-base alloys are of interest for aerospace structural applications at high temperatures, viz, 800 to 1650 C. Fundamental information regarding the effects of rapid solidification in achieving greatly refined microstructures, extended solid solubility, suppression of embrittling equilibrium phases, and formation of new phases is desired in a number of Nb-X alloys. The microstructures and selected properties of Nb-Si and other Nb-base alloys are presented for materials both rapidly quenched from the equilibrium liquidus and rapidly solidified following deep supercooling. Electromagnetic levitation was used to achieve melting and supercooling in a containerless inert gas environment. A variety of solidification conditions were employed including splatting or drop casting of supercooled samples. The morphology and composition of phases formed are discussed in terms of both solidification history and bulk composition.

  3. Surface Treatments of Nb by Buffered Electropolishing

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Andy T. [JLAB; Rimmer, Robert A. [JLAB; Ciovati, Gianluigi [JLAB; Manus, Robert L. [JLAb; Reece, Charles E. [JLAB; Williams, J. S. [JLAB; Eozénou, F. [CEA, Gif-sur-Yvette; Jin, S. [PKU/IHIP, Beijing; Lin, L. [PKU/IHIP, Beijing; Lu, X.Y. [PKU/IHIP, Beijing; Mammosser, John D. [JLAB; Wang, E. [BNL

    2009-11-01

    Buffered electropolishing (BEP) is a Nb surface treatment technique developed at Jefferson Lab1. Experimental results obtained from flat Nb samples show2-4 that BEP can produce a surface finish much smoother than that produced by the conventional electropolishing (EP), while Nb removal rate can be as high as 4.67 μm/min. This new technique has been applied to the treatments of Nb SRF single cell cavity employing a vertical polishing system5 constructed at JLab as well as a horizontal polishing system at CEA Saclay. Preliminary results show that the accelerating gradient can reach 32 MV/m for a large grain cavity and 26.7 MV/m for a regular grain cavity. In this presentation, the latest progresses from the international collaboration between Peking University, CEA Saclay, and JLab on BEP will be summarized.

  4. Sexting among singles in the USA: prevalence of sending, receiving, and sharing sexual messages and images.

    Science.gov (United States)

    Garcia, Justin R; Gesselman, Amanda N; Siliman, Shadia A; Perry, Brea L; Coe, Kathryn; Fisher, Helen E

    2016-07-29

    Background: The transmission of sexual images and messages via mobile phone or other electronic media (sexting) has been associated with a variety of mostly negative social and behavioural consequences. Research on sexting has focussed on youth, with limited data across demographics and with little known about the sharing of private sexual images and messages with third parties. Methods: The present study examines sexting attitudes and behaviours, including sending, receiving, and sharing of sexual messages and images, across gender, age, and sexual orientation. A total of 5805 single adults were included in the study (2830 women; 2975 men), ranging in age from 21 to 75+ years. Results: Overall, 21% of participants reported sending and 28% reported receiving sexually explicit text messages; both sending and receiving 'sexts' was most common among younger respondents. Although 73.2% of participants reported discomfort with unauthorised sharing of sexts beyond the intended recipient, of those who had received sext images, 22.9% reported sharing them with others (on average with 3.17 friends). Participants also reported concern about the potential consequences of sexting on their social lives, careers, and psychosocial wellbeing. Conclusion: Views on the impact of sexting on reputation suggest a contemporary struggle to reconcile digital eroticism with real-world consequences. These findings suggest a need for future research into negotiations of sexting motivations, risks, and rewards.

  5. Nanostructured Nb2O5 catalysts

    OpenAIRE

    Tsang, Edman; Zhou, Xiwen; Ye, Lin; Edman Tsang, Shik Chi

    2012-01-01

    Niobium pentoxide (Nb2O5) has long been known to catalyze unique acid induced reactions, redox reductions and photo-catalytic reactions, etc. Recently, there have been significant advancements in tailoring the oxide materials with controlled structures and morphologies using nano-chemical synthesis by the help of surfactant or stabilizer for optimal catalytic performance. In this short review, we will particularly highlight these synthetic methods for preparation of Nb2O5 nanostructures, thei...

  6. Syntesis and Crystal Structure of Cs 2Nb 6Br 5F 12: A Nb 6 Cluster Compound with a One-Dimensional Nb 6Br i5F i7F a6 Unit Connection

    Science.gov (United States)

    Cordier, S.; Hernandez, O.; Perrin, C.

    2002-01-01

    The synthesis and the crystal structure of Cs2Nb6Br5F12 containing octahedral niobium clusters are presented in this work. This bromofluoride is based on a Nb6Li12Fa6 (L=Br and F) unit and crystallizes in the orthorhombic system (space group, Cccm; Z=4; a=9.2446(2) Å, b=13.6256(3) Å, and c=17.1665(4) Å; R=0.0241). Fluorine and bromine are randomly distributed on the inner ligand positions, Li, that edge-bridge the Nb6 cluster whereas fluorine fully occupies the apical positions (La). The units are linked to each other by apical ligands leading to an original one-dimensional unit connection. The cesium atoms are statistically distributed on several sites that describe parallel channels along the [1 0 0] direction. The influence of fluorine ligands upon the stabilization of this structure type as well as the structural relationships with Ba2Zr6Cl17(B), Nb6F15, and NaMo6Cl13 will be evidenced and discussed.

  7. SUBMM heterodyne mixing using NbCN/Nb SIS tunnel junctions.

    NARCIS (Netherlands)

    vandeStadt, H; Mees, J; Barber, Z; Blamire, M; Dieleman, P; deGraauw, T

    We describe heterodyne mixing experiments with NbCN/Nb quasi-particle tunnel junctions at submillimeter wavelengths. In this wavelength range junctions with niobium nitride as superconducting material are promising because of the high gap voltage, about 5.7 mV, as compared to 3 mV for the more

  8. NbN/MgO/NbN SIS tunnel junctions for submm wave mixers

    Science.gov (United States)

    Stern, J. A.; Hunt, B. D.; Leduc, H. G.; Judas, A.; Mcgrath, W. R.; Cypher, S. R.; Khanna, S. K.

    1989-01-01

    The authors report on the fabrication and testing of all-refractory NbN/MgO/NbN SIS (superconductor-insulator-superconductor) tunnel junctions for use as high-frequency mixers. Progress in the development of techniques for the fabrication of submicron-area tunnel junctions is described. Junction structures which have been investigated include mesa, crossline, and edge geometries. Using reactive sputtering techniques, NbN tunnel junctions with critical currents in excess of 104 A/sq cm have been fabricated with Vm values as high as 65 mV and areas down to 0.1 sq micron. Specific capacitance measurements on NbN/MgO/NbN mesa-type tunnel junctions give values in the range 60-90 fF/sq micron. These SIS tunnel junctions have been integrated with antennas and coupling structures for mixer tests in a waveguide receiver at 207 GHz. Preliminary mixer results are reported.

  9. Determination of Activities of Niobium in Cu-Nb Melts Containing Dilute Nb

    Science.gov (United States)

    Wang, Daya; Yan, Baijun; Sichen, Du

    2015-04-01

    The activity coefficients of niobium in Cu-Nb melts were measured by equilibrating solid NbO2 with liquid copper under controlled oxygen potentials in the temperature range of 1773 K to 1898 K (1500 °C to 1625 °C). Either CO-CO2 gas mixture or H2-CO2 gas mixture was employed to obtain the desired oxygen partial pressures. Cu-Nb system was found to follow Henry's law in the composition range studied. The temperature dependence of Henry's constant in the Cu-Nb melts could be expressed as follows: The partial molar excess Gibbs energy change of niobium in Cu-Nb melts can be expressed as follows:

  10. Nb/Ta - Zr/Hf Fractionations during Subduction: Implications for the'Missing' Nb.

    Science.gov (United States)

    Zateslo, T.; Bizimis, M.; Salters, V. J.; Stern, C.; Taylor, R. N.

    2008-12-01

    Key differences between the chemical composition of terrestrial materials and those of meteorites have led to the suggestion that a 'hidden' high Nb/Ta reservoir exists in the Earth's mantle. In order to test this hypothesis we must identify the processes that can create such a reservoir. Here we report the first high precision HFSE data on products of the subduction processes thought to fractionate Nb from Ta: boninites (hydrous melting), adakites (slab melting), OIBs (Koolau, Walvis: plume with recycled oceanic crust), as well as kimberlites and lamproites. We developed a new method for the high precision determination of Nb, Ta, Zr, Hf concentrations based on a modified version of standard addition. All analyses were performed on a single collector ICPMS (ELEMENT 1), using Y and Yb as internal standards to correct for instrumental drift during the unspiked -spiked sample sequence. Concentrations are calculated using a York- type regression that accounts for all measured and propagated errors. Long-term reproducibility (multiple dissolutions and multiple spike solutions) for the standards BHVO-1, BIR-1 AGV-1 and BCR-1 are better than 0.8% (1s) for Nb/Ta and Zr/Hf ratios. The advantages of this method compared to previous methods are fast throughput, no column chemistry and low blanks. The Koolau and Walvis Ridge lavas have subchondritic Nb/Ta for a given Zr/Hf, overlapping other OIB suites and show no evidence for a recycled, high Nb/Ta reservoir in their source. OIB, considered as a group, have relatively constant Nb/Ta (15-16) but more variable Zr/Hf (35-50). In contrast, boninites (Chichi Jima) have significantly subchondritic Nb/Ta (4-12) at near constant Zr/Hf (35), while adakites (South Andes) extend to near chondritic Nb/Ta (13-19) at more variable Zr/Hf (30-40). The adakites showing the least evidence for crustal contamination have the highest Nb/Ta. The arc lavas cross the OIB trend at near right angle on a Nb/Ta vs. Zr/Hf plot having larger Nb

  11. Journal Club: Voice recognition dictation: analysis of report volume and use of the send-to-editor function.

    Science.gov (United States)

    Williams, Dennis R; Kori, Sheila K; Williams, Brenda; Sackrison, Sandra J; Kowalski, Henryk M; McLaughlin, Michael G; Kuszyk, Brian S

    2013-11-01

    The purpose of this study was to evaluate use of the send-to-editor function of a radiology voice recognition dictation system and compare study volumes of radiologists who self-edit with those of radiologists who send reports to the editor. Use of voice recognition shortcuts was also evaluated. Voice recognition dictation systems were installed in a six-hospital system, including an 800-bed tertiary care center and five community hospitals, in 2002. This became the only means of radiologist dictation in July 2005. Report volumes, use of the send-to-editor function, and use of shortcuts were tracked from October 2005 through October 2008. A subspecialty private radiology group, ranging from 37 radiologists in July 2005 to 50 radiologists in October 2008, interpreted the imaging studies. Radiologists had no financial incentives to self-edit. The percentage of radiologists using the send-to-editor function remained relatively constant at 46%, resulting in 21% of total reports sent to the editor. Radiologists who used the send-to-editor function dictated approximately 41% more reports than those who self-edited. The volume of reports generated by general radiologists reading large volumes of computed radiography cases and sending to the editor was greater than that of radiologists who self-edited (p reports than radiologists who did not, suggesting that the send-to-editor function may be useful for improving productivity among radiologists reading large volumes of computed radiography cases.

  12. The Gatekeeper Disparity: Why Do Some Medical Schools Send More Medical Students into Urology?

    Science.gov (United States)

    Kutikov, Alexander; Bonslaver, Jason; Casey, Jessica T.; Degrado, Justin; Dusseault, Beau N.; Fox, Janelle A.; Lashley-Rogers, Desri; Richardson, Ingride; Smaldone, Marc C.; Steinberg, Peter L.; Trivedi, Deep B.; Routh, Jonathan C.

    2010-01-01

    Introduction Urology continues to be a highly desirable specialty, despite decreasing exposure of students to Urology in U.S. medical schools. In this study, we set out to assess how U.S. medical schools compare to one another with regard to the number of students that each sends into Urological training and to evaluate the reasons why some medical schools consistently send more students into urology than others. Materials and Methods The authors obtained AUA Match data for the 5 Match seasons from 2005–2009. A survey of all successful participants was then performed. The survey instrument was designed to determine what aspects of the medical school experience influenced students to choose to specialize in Urology. A bivariate and multivariate analysis was then performed to assess which factors correlated with more students entering Urology from a particular medical school. Results Between 2005 and 2009, 1,149 medical students from 130 medical schools successfully participated in the Urology match. Of the 132 allopathic medical schools, 128 sent at least 1 student into Urology (mean 8.9, median 8, SD 6.5). A handful of medical schools were remarkable outliers, sending significantly more students into Urology than other institutions. Multivariate analysis revealed that a number of medical-school related variables including strong mentorship, medical school ranking, and medical school size correlated with more medical students entering Urology. Conclusion Some medical schools launch more Urologic careers than others. Although reasons for these findings are multifactorial, recruitment of Urologic talent pivots on these realities. PMID:21168862

  13. Nb 3Sn material development in Russia

    Science.gov (United States)

    Pantsyrny, V.; Shikov, A.; Vorobieva, A.

    2008-07-01

    In the USSR and later in Russia, the main activities in technical superconductivity were concentrated in the institutes that belonged to the Ministry of Atomic Energy (Minatom). The development of new technologies shortly transferred to the large-scale industrial production of NbTi and Nb 3Sn superconductors in early 1970s. Two main technologies for multifilamentary Nb 3Sn strands were under investigation during that time - bronze-process and internal tin method. More than 25 ton of Nb 3Sn bronze-processed strands were produced for the fabrication of 90 ton of conductors for application in the magnet system of first in the world fusion facility (tokamak T-15) with magnet system based on the intermetallic compound. The characteristics of these strands and conductors have been briefly described. The requirements for the Nb 3Sn strands constantly increased and the main R&D on the enhancement of critical current density have been reviewed. For bronze-processed strands the increase of the tin content in large ingots was the crucial factor. The artificial doping of niobium filaments by niobium-titanium alloy was invented, which enabled to improve the workability of Nb 3Sn strands, with enhanced critical current density in high fields. For internal tin Nb 3Sn strands the main R&D were concentrated on the optimization of the layouts of the strand and on the multistage heat treatment because of the inevitable liquid phase formation which could result in severe distortion of the geometrical arrangement of the filaments and even in destruction of the whole strand. The main results of these investigations have been presented. The corresponding impact of these R&D on the design of bronze-processed and internal tin strands has been analyzed. The quantitative estimations of the grain size were made for bronze-processed and internal tin strands. It was shown that in bronze-processed and internal tin strands subjected to the standard ITER heat treatment characterized by two stages

  14. 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.

  15. Predictors of discontinuation of benzodiazepine prescription after sending a letter to long-term benzodiazepine users in family practice.

    NARCIS (Netherlands)

    Gorgels, W.J.M.J.; Oude Voshaar, R.C.; Mol, A.J.J.; Lisdonk, E.H. van de; Balkom, A.J.L.M. van; Breteler, M.H.M.; Hoogen, H.J.M. van den; Mulder, J.; Zitman, F.G.

    2006-01-01

    BACKGROUND: Predictors of benzodiazepine discontinuation after sending a discontinuation letter by the family practitioner have not been established sufficiently. OBJECTIVE: To identify predictors of short- and long-term discontinuation of benzodiazepine use and relapse in use after a minimal

  16. The research and application of the NDP protocol vulnerability attack and the defense technology based on SEND

    Science.gov (United States)

    Xi, Huixing

    2017-05-01

    Neighbor discovery protocol (NDP) is the underlying protocol in the IPv6 protocol, which is mainly used to solve the problem of interconnection between nodes on the same link. But with wide use of IPV6, NDP becomes the main objects of a variety of attacks due to a lack of security mechanism. The paper introduces the working principle of the NDP and methods of how the SEND protocol to enhance NDP security defense. It also analyzes and summarizes the security threats caused by the defects of the protocol itself. On the basis of the SEND protocol, the NDP data packet structure is modified to enhance the security of the SEND. An improved NDP cheating defense technology is put forward to make up the defects of the SEND protocol which can't verify the correctness of the public key and cannot bind the MAC address.

  17. Creep behavior of Zr-Nb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Yong Chan; Kim, Young Suk; Cheong, Yong Mu; Kwon, Sang Chul; Kim, Sung Soo; Choo, Ki Nam [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-01-01

    The creep characteristics of Zirconium alloy is affected by several parameters. Out-reactor creep increases both with an increasing amount of Nb, Sn and S contained in alpha-Zr and decreases with the increasing volume of alpha-Zr. Especially, the creep of Zr-2.5Nb alloy depends on the solubility of Nb in alpha-Zr, which is associated with the decomposition of beta-Zr. Since Zr of the hcp structure is strongly anisotropic, it shows the characteristics of texture and results in the anisotropy of creep. Due to the circumferential texture of Zr-2.5%Nb alloy (CANDU Pressure tube), the longitudinal slip is easier than the circumferential one, resulting in the high creep rate. The irradiation creep also increases with increasing neutron fluence. The neutron irradiation increases the strength of the zirconium alloys but decreases their creep strength. In contrast to the out-reactor creep, the irradiation creep is little sensitive to temperature, resulting in the lower activation energy. The most important factor to affect the in-reactor and out-reactor creep of niobium containing alloys seems to be the solution hardening by Nb or Sn which is soluble in alpha-zirconium and the texture as well. Irradiation growth is the mechanism which is caused only by the irradiation. It becomes saturated at lower fluence than the critical fluence but beyond it, shows the break-away growth. The onset of accelerated irradiation growth corresponds with the c-dislocation loop formation, though its mechanism needs better understanding. Generally, the irradiation growth of Zr-Nb alloys increases with an increase in fluence, cold working, dislocation, density and temperature, and with a decrease in the grain size. 141 refs., 59 figs., 10 tabs. (Author)

  18. Low-field Instabilities in Nb3Sn 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 Nb3Sn 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.

  19. Nanostructured Nb2O5 catalysts

    Directory of Open Access Journals (Sweden)

    Yun Zhao

    2012-08-01

    Full Text Available Niobium pentoxide (Nb2O5 has long been known to catalyze unique acid induced reactions, redox reductions and photo-catalytic reactions, etc. Recently, there have been significant advancements in tailoring the oxide materials with controlled structures and morphologies using nano-chemical synthesis by the help of surfactant or stabilizer for optimal catalytic performance. In this short review, we will particularly highlight these synthetic methods for preparation of Nb2O5 nanostructures, their potential applications in catalysis and their structure-activity relationships.

  20. Aluminum-stabilized NB3SN superconductor

    Science.gov (United States)

    Scanlan, Ronald M.

    1988-01-01

    An aluminum-stabilized Nb.sub.3 Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb.sub.3 Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  1. Mechanical Properties of Ingot Nb Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  2. What determines the interfacial configuration of Nb/Al2O3 and Nb/MgO interface

    Science.gov (United States)

    Du, J. L.; Fang, Y.; Fu, E. G.; Ding, X.; Yu, K. Y.; Wang, Y. G.; Wang, Y. Q.; Baldwin, J. K.; Wang, P. P.; Bai, Q.

    2016-01-01

    Nb films are deposited on single crystal Al2O3 (110) and MgO(111) substrates by e-beam evaporation technique. Structure of Nb films and orientation relationships (ORs) of Nb/Al2O3 and Nb/MgO interface are studied and compared by the combination of experiments and simulations. The experiments show that the Nb films obtain strong (110) texture, and the Nb film on Al2O3(110) substrate shows a higher crystalline quality than that on MgO(111) substrate. First principle calculations show that both the lattice mismatch and the strength of interface bonding play major roles in determining the crystalline perfection of Nb films and ORs between Nb films and single crystal ceramic substrates. The fundamental mechanisms for forming the interfacial configuration in terms of the lattice mismatch and the strength of interface bonding are discussed. PMID:27698458

  3. Effects of pre-strain and Nb content on transformation temperatures in Ti-Ni-Nb shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, T. [Central Research Inst. of Electric Power Industry, Komae (Japan); Mihara, Y. [Graduate School, Univ. of Electro-Communications, Chofu (Japan); Ochi, Y. [Univ. of Electro-Communications, Chofu (Japan); Ozawa, M. [NEC Tokin, Co., Sendai (Japan); Okita, K. [Graduate School, Ehime Univ., Matsuyama (Japan); Okabe, N. [Ehime Univ., Matsuyama (Japan)

    2005-07-01

    Ti-Ni-Nb shape memory alloy has a wide transformation hysteresis, and has been used as coupling devices and so on. However systematic researches of the influence of the amount of Nb addition on transformation temperatures are few. The purpose of this work is to clarify the influences of pre-strain and Nb content on transformation temperatures in Ti-Ni-Nb shape memory alloys. The specimens were Ti-Ni-Nb alloys (Ni/Ti=1.0, Nb=0-15at%), annealed at 1223 K for 0.3 ks. The variation of transformation temperatures with pre-strain and Nb content were investigated experimentally. The variation of A{sub s}, M{sub s} and transformation temperature hysteresis with pre-strain and Nb content will be discussed in relation to the elastic strain energy and the volume fraction of slip-deformed martensite. (orig.)

  4. A Study of Relationship between "Effective Listening" and "Understanding and Sending Messages" with Conflict Management among Managers in Ardabil Elementary Schools

    Directory of Open Access Journals (Sweden)

    Shahin Taghavinejad-Namin

    2015-08-01

    Full Text Available Background and objectives : This study has been accomplished with the aim of investigating the relationship between managers' communication skills and conflict management in elementary schools in the city of Ardabil. Material and Methods: This is a cross-sectional study. The statistical population consisted of 150 elementary school principals in Ardabil. 106 participants were selected by using Krejcie-Morgan table randomly and through stratified sampling method. Data were collected through Jerabek communication skills questionnaire and Robbins conflict management questionnaire. Questionnaire’s face validity was reviewed and confirmed by the experts. Their reliability coefficient was (0.82 for communication skills and (0.95 for conflict management by using Cronbach's alpha. Data were analyzed using analytical and descriptive statistical methods (Pearson correlation coefficient test, single-sample t-test, and multiple regression. Results: Results showed that there are positive and significant relationship between communication skills (effective listening, understanding and sending messages, regulating emotions, insight into learning process, and decisiveness in communication and conflict management strategies(denial of opposition, control, solution orientation. Conclusion: Communication skills such as effective listening can be a good predictor for solving conflicts in conflict management but understanding and sending messages cannot predict conflict management abilities of managers. ​

  5. Niobium thiobromide, Nb{sub 3}SBr{sub 7}, with triangle Nb{sub 3} cluster: Structure and bonding

    Energy Technology Data Exchange (ETDEWEB)

    Khvorykh, G.V.; Shevelkov, A.V.; Dolgikh, V.A.; Popovkin, B.A. [Moscow State Univ., Moscow (Russian Federation)

    1995-12-01

    The reaction of Nb, S, and Br{sub 2} in a sealed quartz ampoule at 550{degrees}C yielded Nb{sub 3}SBr{sub 7}. The structure of Nb{sub 3}SBr{sub 7} determined by the single-crystal X-ray diffraction method (P3m1, a=7.1012(6){angstrom}, c=6.3040(9){angstrom}, V=275.30(9){angstrom}{sup 3}, Z=1, d{sub calc}=5.248(2) g.cm{sup 3}, R=0.0395, R{sub w}=0.0392) consists of one-layer packing of ([Nb{sub 3}SBr{sub 3}]Br{sub 6/2}Br{sub 3/3}){sup 2}{infinity} layers. The molecular orbitals of the model anions [Nb{sub 3}Br{sub 13}]{sup 5-} and [Nb{sub 3}SBr{sub 12}]{sup {minus}5-}, which involve the triangle Nb{sub 3} cluster with the nearest ligand environment in the structures of Nb{sub 3}Br{sub 8} and Nb{sup 3}SBr{sub 7} respectively, were calculated by applying the extended Huckel method. The HOMO in [Nb{sub 3}Br{sub 13}]{sup 5-} has slightly metal-metal bonding character which is consistent with an Nb-Nb bond length increase from 2.88 {angstrom} in a seven-electron Nb{sub 3}Br{sub 8} to 2.896(1) {angstrom} in a six-electron Nb{sub 3}SBr{sub 7}. The bonding schemes are in accordance with magnetic properties of Nb{sub 3}Br{sub 8}, which is a paramagnetic, and Nb{sub 3}SBr{sub 7}, which is diamagnetic.

  6. NbN/MgO/NbN edge-geometry tunnel junctions

    Science.gov (United States)

    Hunt, B. D.; Leduc, H. G.; Cypher, S. R.; Stern, J. A.; Judas, A.

    1989-01-01

    The fabrication and low-frequency testing of the first edge-geometry NbN/MgO/NbN superconducting tunnel junctions are reported. The use of an edge geometry allows very small junction areas to be obtained, while the all-NbN electrodes permit operation at 8-10 K with a potential maximum operating frequency above 1 THz. Edge definition in the base NbN film was accomplished utilizing Ar ion milling with an Al2O3 milling mask, followed by a lower energy ion cleaning step. This process has produced all-refractory-material tunnel junctions with areas as small as 0.1 sq micron, resistance-area products less than 21 ohm sq micron, and subgap to normal state resistance ratios larger than 18.

  7. Effect of Nb on the Microstructure, Mechanical Properties, Corrosion Behavior, and Cytotoxicity of Ti-Nb Alloys

    Directory of Open Access Journals (Sweden)

    Mi-Kyung Han

    2015-09-01

    Full Text Available 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.

  8. Migration and Sexuality: A Comparison of Mexicans in Sending and Receiving Communities.

    Science.gov (United States)

    Parrado, Emilio A; Flippen, Chenoa A

    2010-03-01

    The reconstruction of sexuality after migration is a central dimension of immigrant health and an integral part of the process of adaptation and incorporation. Despite its significance there is little quantitative information measuring the changes in sexual behavior accompanying migration. This paper contributes to the literature connecting immigrant adaptation and health risks by comparing sexual practices and attitudes among Mexicans in Durham, NC and Mexican sending communities. Consistent with a social constructivist approach to sexuality we show that compared to non-migrants, Mexicans residing in the U.S. exhibit heightened exposure to risk, including casual and, among men, commercial partners. The enhanced risks associated with migration vary systematically by gender and marital status and are accompanied by variation in attitudes towards sexuality, with the U.S. context associated with higher tolerance for infidelity and biological explanations of sexuality. We discuss the implications for immigrant adaptation and health policies in the U.S. and abroad.

  9. Limits of Nb3Sn Accelerator Magnets

    CERN Document Server

    Caspi, Shlomo

    2005-01-01

    Pushing accelerator magnets beyond 10T holds a promise of future upgrades to machines like the Tevatron at FermiLab and the LHC at CERN. Exhausting the current density limits of NbTi, superconductor, Nb3Sn is at the present time the only practical superconductor capable of generating fields beyond 10T. Several Nb3Sn pilot magnets, with fields as high as 16T, have been built and tested, paving the way for future attempts at fields approaching 20T. The combination of high current density and the required high magnetic fields has resulted in reduced conductor volume and significantly increased the accumulated Lorentz forces. Future coil and structure designs will be required to deal with stresses of several 100’s of MPa and forces of 10’s of MN/m. The combined engineering requirements on size and cost of accelerator magnets will require a magnet technology that diverges from the one currently used with NbTi conductor. How far can the engineering of high field magnets be pushed, what are the i...

  10. 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.

  11. Energetic condensation growth of Nb thin films

    Directory of Open Access Journals (Sweden)

    M. Krishnan

    2012-03-01

    Full Text Available This paper describes energetic condensation growth of Nb films using a cathodic arc plasma, whose 60–120 eV ions penetrate a few monolayers into the substrate and enable sufficient surface mobility to ensure that the lowest energy state (crystalline structure with minimal defects is accessible to the film. Heteroepitaxial films of Nb were grown on a-plane sapphire and MgO crystals with good superconducting properties and crystal size (10  mm×20  mm limited only by substrate size. The substrates were heated to temperatures of up to 700°C and coated at 125°C, 300°C, 500°C, and 700°C. Film thickness was varied from ∼0.25  μm to >3  μm. Residual resistivity ratio (⟨RRR⟩ values (up to a record ⟨RRR⟩=587 on MgO and ⟨RRR⟩=328 on a-sapphire depend strongly on substrate annealing and deposition temperatures. X-ray diffraction spectra and pole figures reveal that RRR increases as the crystal structure of the Nb film becomes more ordered, consistent with fewer defects and, hence, longer electron mean-free path. A transition from Nb(110 to Nb(100 orientation on the MgO(100 lattice occurs at higher temperatures. This transition is discussed in light of substrate heating and energetic condensation physics. Electron backscattered diffraction and scanning electron microscope images complement the XRD data.

  12. Single-crystalline nanoporous Nb2O5 nanotubes

    Directory of Open Access Journals (Sweden)

    Liu Jun

    2011-01-01

    Full Text Available Abstract Single-crystalline nanoporous Nb2O5 nanotubes were fabricated by a two-step solution route, the growth of uniform single-crystalline Nb2O5 nanorods and the following ion-assisted selective dissolution along the [001] direction. Nb2O5 tubular structure was created by preferentially etching (001 crystallographic planes, which has a nearly homogeneous diameter and length. Dense nanopores with the diameters of several nanometers were created on the shell of Nb2O5 tubular structures, which can also retain the crystallographic orientation of Nb2O5 precursor nanorods. The present chemical etching strategy is versatile and can be extended to different-sized nanorod precursors. Furthermore, these as-obtained nanorod precursors and nanotube products can also be used as template for the fabrication of 1 D nanostructured niobates, such as LiNbO3, NaNbO3, and KNbO3.

  13. KARAKTERISTIK INGOT PADUAN U-Zr-Nb PASCA PROSES QUENCHING

    Directory of Open Access Journals (Sweden)

    Masrukan Masrukan

    2017-08-01

    Full Text Available Telah dilakukan percobaan perlakuan panas (quenching paduan U-Zr-Nb yang bervariasi komposisi Nb. Ingot paduan U-Zr-Nb dengan komposisi Nb yang bervariasi yakni 1%, 4% dan 7% dan komposisi Zr tetap 10% dibuat melalui peleburan logam U, Zr dan Nb di dalam tungku busur listrik. Percobaan perlakuan panas (quenching dimaksudkan untuk mengubah fasa άU yang tidak stabil menjadi fasa gU yang stabil.  Pada percobaan quenching, ingot paduan U-10Zr-1Nb, U-10Zr-4Nb, U-10Zr-7Nb  dimasukkan ke dalam ampul  yang terbuat dari pelat baja  kemudian dimasukkan ke dalam tungku pemanasan dan dipanaskan pada temperatur  900 oC  serta ditahan selama 2 jam untuk selanjutnya didinginkan dengan cepat di dalam air. Setelah diquenching dikenai pengujian fasa dan pemeriksaan mikrostruktur. Pengujian fasa dilakukan menggunakan difrkasi sinar X (XRD  yang datanya diolah menggunakan software High Score, sedangkan pemeriksaan mikrostrutur menggunakan mikroskop optik. Hasil pengujian dengan XRD menunjukkan bahwa paduan  U-10Zr-1Nb sebelum diquenching terdiri dari fasa αU, paduan U-10Zr-4Nb terdiri dari fasa αU  sebesar 23,1504 % dan fasa γU sebesar 76,8495 %, sedangkan pada U-10Zr-7Nb  terdiri dari fasa αU sebesar 34,1873 %  dan fasa γU sebesar  65,8127 %. Untuk paduan U-10Zr-1Nb setelah  diquenching  terdiri fasa  αU,  paduan U-10Zr-4Nb terdiri dari fasa αU  sebesar  44.6711 % dan fasa γU sebesar  55.3289 %, paduan U-10Zr-7Nb  terdiri dari fasa αU sebesar 17.9918 % dan fasa γU sebesar 82.0082 %.  Hasil analisis densitas teoritis terhadap fasa yang terbentuk pada paduan U-10Zr-1Nb, U-10Zr-4Nb, U-10Zr-7Nb  baik sebelum maupun setelah diquenching diperoleh bahwa  ingot paduan U-10Zr-1Nb, U-10Zr-4Nb, U-10Zr-7Nb  menunjukkan bahwa densitas fasa αU dan fasa γU mengalami penurunan sedikit apabila kandungan Nb semakin rendah. Sementara itu, hasil pemeriksaan mikrostruktur menunjukkan bahwa pada kandungan Zr yang semakin tinggi (7% Nb terbentuk

  14. Microstructure and electrical properties of Aurivillius phase (CaBi2Nb2O9)1-x(BaBi2Nb2O9)x solid solution

    Science.gov (United States)

    Zhang, Hongtao; Yan, Haixue; Reece, Michael J.

    2010-07-01

    The microstructures and electrical properties of Aurivillius phase ferroelectric solid solutions of (CaBi2Nb2O9)1-x(BaBi2Nb2O9)x (0≤x≤1) have been studied. X-ray diffraction analyses revealed a bismuth layered structure for all compositions. Scanning electron microscope images showed randomly oriented and platelike grain morphology. The Curie point Tc or the maximum permittivity temperature Tm decreased with increasing x. The (CaBi2Nb2O9)1-x(BaBi2Nb2O9)x ceramics exhibited a ferroelectric-paraelectric phase transition at small x values (x ≤0.5), whereas a relaxor behavior was observed at high x values (x ≥0.8). The d33 value of CaBi2Nb2O9 ceramics was enhanced by Ba2+ doping on the A-sites (x ≤0.3). A combination of high d33 values and high Tc points (>700 °C) suggests that compositions with x ≤0.3 could be good candidates for high-temperature piezoelectric applications. The composition with x =0.8 is a relaxor ferroelectric with Tm around 320 °C at 1 MHz.

  15. Critical current of Nb-(Nb/Pd{sub 0.95}Fe{sub 0.05})-Nb Josephson junctions

    Energy Technology Data Exchange (ETDEWEB)

    Vavra, O.; Meindl, W.; Strunk, C.

    2008-07-01

    The antagonism of superconductivity and magnetism is investigated by fabricating Nb based Josephson Junction with lateral weak links consisting of Nb-Pd{sub 0.95}Fe{sub 0.05} bi-layers with lengths between 200 and 500 nm. The critical current (I{sub C}) of the Nb-Pd{sub 0.95}Fe{sub 0.05} bi-layer is found to be significantly reduced by the weak ferromagnetism in the Pd{sub 0.95}eFe{sub 0.05} alloy. We have studied the temperature and magnetic field (B) dependencies of the critical current. In magnetic field an irregular supercurrent interference pattern I{sub C}(B) is observed. The shape of the I{sub C}(B) oscillations is similar to that observed for grain boundary junctions between cuprate superconductors. We also investigate the dependence of I{sub C}(B) oscillations on the orientation of the magnetic field.

  16. Domestic horses send signals to humans when they face with an unsolvable task.

    Science.gov (United States)

    Ringhofer, Monamie; Yamamoto, Shinya

    2017-05-01

    Some domestic animals are thought to be skilled at social communication with humans due to the process of domestication. Horses, being in close relationship with humans, similar to dogs, might be skilled at communication with humans. Previous studies have indicated that they are sensitive to bodily signals and the attentional state of humans; however, there are few studies that investigate communication with humans and responses to the knowledge state of humans. Our first question was whether and how horses send signals to their potentially helpful but ignorant caretakers in a problem-solving situation where a food item was hidden in a bucket that was accessible only to the caretakers. We then examined whether horses alter their behaviours on the basis of the caretakers' knowledge of where the food was hidden. We found that horses communicated to their caretakers using visual and tactile signals. The signalling behaviour of the horses significantly increased in conditions where the caretakers had not seen the hiding of the food. These results suggest that horses alter their communicative behaviour towards humans in accordance with humans' knowledge state.

  17. Discovery Monday - 'The hunt for the phantom particles: sending neutrinos through the Alps'

    CERN Multimedia

    2004-01-01

    Work on the decay tube for the CERN Neutrinos to Gran Sasso (CNGS) Project. Each second, billions of neutrinos bombard every square centimetre of the Earth's surface and therefore pass through our bodies, without us realising it. These phantom particles only rarely interact with matter. They provide physicists with much food for thought, as they are difficult to 'catch' in detectors. Neutrinos are all the more elusive as they are capable of metamorphosis. There are in fact three types of neutrino, the electron neutrino, the muon neutrino and the tau neutrino, and each can mutate into the other. In 2006 CERN will send a beam of muon neutrinos through the Earth's crust to the Gran Sasso National Laboratory (Italy) some 730 kilometres away, in order to better understand the metamorphoses which the neutrino undergoes. At the next Discovery Monday, light will be shed on the path that these intriguing particles will take to Gran Sasso. You will also learn about the methods physicists use to try and catch them in or...

  18. "Fine grain Nb tube for SRF cavities"

    Energy Technology Data Exchange (ETDEWEB)

    Robert E. Barber

    2012-07-08

    Superconducting radio frequency (SRF) cavities used in charged particle linear accelerators, are currently fabricated by deep drawing niobium sheets and welding the drawn dishes together. The Nb sheet has a non-uniform microstructure, which leads to unpredictable cavity shape and surface roughness, and inconsistent "spring-back" during forming. In addition, weld zones cause hot spots during cavity operation. These factors limit linear accelerator performance and increase cavity manufacturing cost. Equal channel angular extrusion (ECAE) can be used to refine and homogenize the microstructure of Nb tube for subsequent hydroforming into SRF cavities. Careful selection of deformation and heat treatment conditions during the processing steps can give a uniform and consistent microstructure in the tube, leading to improved deformability and lower manufacturing costs. Favorable microstructures were achieved in short test samples of RRR Nb tube, which may be particularly suitable for hydroforming into SRF cavity strings. The approach demonstrated could be applicable to microstructure engineering of other tube materials including tantalum, titanium, and zirconium.

  19. 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.

  20. 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.

  1. Electronic signature of the vacancy ordering in NbO (Nb3O3)

    Science.gov (United States)

    Efimenko, A. K.; Hollmann, N.; Hoefer, K.; Weinen, J.; Takegami, D.; Wolff, K. K.; Altendorf, S. G.; Hu, Z.; Rata, A. D.; Komarek, A. C.; Nugroho, A. A.; Liao, Y. F.; Tsuei, K.-D.; Hsieh, H. H.; Lin, H.-J.; Chen, C. T.; Tjeng, L. H.; Kasinathan, D.

    2017-11-01

    We investigated the electronic structure of the vacancy-ordered 4 d -transition-metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray photoelectron spectroscopies as well as ultraviolet angle-resolved photoelectron spectroscopy. We found that density-functional-based band-structure calculations can describe the spectral features accurately provided that self-interaction effects are taken into account. In the angle-resolved spectra we were able to identify the so-called `vacancy' band that characterizes the ordering of the vacancies. This together with the band-structure results indicate the important role of the very large inter-Nb-4 d hybridization for the formation of the ordered vacancies and the high thermal stability of the ordered structure of niobium monoxide.

  2. 40 CFR 1054.250 - What records must I keep and what reports must I send to EPA?

    Science.gov (United States)

    2010-07-01

    ... ENGINES AND EQUIPMENT Certifying Emission Families § 1054.250 What records must I keep and what reports... model year, you must send us a report describing information about engines you produced during the model year as follows: (1) State the total production volume for each engine family that is not subject to...

  3. 41 CFR 102-118.260 - Must my agency send all quotations, tenders, or contracts with a TSP to GSA?

    Science.gov (United States)

    2010-07-01

    ... quotations, tenders, or contracts with a TSP to GSA? 102-118.260 Section 102-118.260 Public Contracts and..., Tenders Or Contracts § 102-118.260 Must my agency send all quotations, tenders, or contracts with a TSP to... submitted with the tender: (1) Issuing TSP, Bureau, Agency or Conference. (2) Tender number. (3) Standard...

  4. Channeling irradiation of LiNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Steinbach, Tobias; Schrempel, Frank; Gischkat, Thomas; Wesch, Werner [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena (Germany)

    2008-07-01

    The influence of the crystal orientation on the damage formation of x- and z-cut LiNbO{sub 3} single crystals irradiated with 550 and 750 keV Si-ions was investigated. The irradiation was carried out along the corresponding axial channel as well as at different tilt angles. The damage accumulation was investigated by means of Rutherford Backscattering Spectrometry (RBS/C). Because the channelled ions are prevented from close collisions with the target atoms, the projected range of the ions is increased and the number of defects created by channelled ions at a certain ion fluence is less compared to a random irradiation. As a consequence the damage distribution is shifted to larger depths if the irradiation is performed along low index crystallographic directions. Selected samples were etched at 40 {sup circle} C in a HF-solution of 3.7% and 40%, respectively. Compared to the random irradiation with 550 keV Si-ions, the etched depth increases by a factor of 1.4 and 1.2 if the irradiation is carried out along the x- and the z-axis, respectively. From the dependence of the shift of the damage peak on the tilt angle a critical angle to avoid channeling of about 1.35 {sup circle} was determined for 750 keV Si-ions.

  5. Elastic anisotropy in multifilament Nb$_3$Sn superconducting wires

    CERN Document Server

    Scheuerlein, C; Alknes, P; Arnau, G; Bjoerstad, R; Bordini, B

    2015-01-01

    The elastic anisotropy caused by the texture in the Nb3Sn filaments of PIT and RRP wires has been calculated by averaging the estimates of Voigt and Reuss, using published Nb3Sn single crystal elastic constants and the Nb3Sn grain orientation distribution determined in both wire types by Electron Backscatter Diffraction. At ambient temperature the calculated Nb3Sn E-moduli in axial direction in the PIT and the RRP wire are 130 GPa and 140 GPa, respectively. The calculated E-moduli are compared with tensile test results obtained for the corresponding wires and extracted filament bundles.

  6. Synthesis of a Mo/Nb mixed carbide

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira da Silva, V.L. [NUCAT/PEQ/COPPE/Universidade Federal do Rio de Janeiro, Caixa Postal 68502, Rio de Janeiro, RJ-21945-970 (Brazil)]|[Environmental Catalysis and Materials Laboratory, Department of Chemical Engineering, Virginia Polytechnic Institute State University, Blacksburg, Virginia 24061 (United States); Schmal, M. [NUCAT/PEQ/COPPE/Universidade Federal do Rio de Janeiro, Caixa Postal 68502, Rio de Janeiro, RJ-21945-970 (Brazil); Schwartz, V.; Oyama, S.T. [Environmental Catalysis and Materials Laboratory, Department of Chemical Engineering, Virginia Polytechnic Institute State University, Blacksburg, Virginia 24061 (United States)

    1998-07-01

    Molybdenum and niobium carbides ({beta}{endash}Mo{sub 2}C, NbC), as well as mixed carbides of molybdenum and niobium, were synthesized by the temperature-programmed carburization method (TPC) using a 20 vol.thinsp{percent} CH{sub 4}/H{sub 2} gas mixture. The starting materials were MoO{sub 3}, B-Nb{sub 2}O{sub 5}, and physical mixtures of B-Nb{sub 2}O{sub 5}/MoO{sub 3} with Nb/(Nb+Mo) atomic ratios varying from 0.2 to 0.8, respectively. Results from catalytic and temperature-programmed oxidation (TPO) measurements indicate that during the carburization of the Nb{sub 2}O{sub 5}/MoO{sub 3} physical mixture with Nb/(Nb+Mo)=0.8 there is, besides {beta}{endash}Mo{sub 2}C and NbC formation, the appearance of a carbidic phase not detectable by x-ray diffraction (XRD). This phase appears to be highly active and selective for the dibenzothiophene hydrodesulfurization (HDS) reaction. {copyright} {ital 1998 Materials Research Society.}

  7. Local structure analysis of NaNbO3 and AgNbO3 modified by Li substitution

    Science.gov (United States)

    Yoneda, Yasuhiro; Aoyagi, Rintaro; Fu, Desheng

    2016-10-01

    We analyzed the local structures of NaNbO3 and AgNbO3 by combining the X-ray absorption fine structure (XAFS) and atomic pair-distribution function (PDF) techniques. NaNbO3 is known to be an antiferroelectric material at room temperature. It also undergoes a diffuse phase transition, in which orthorhombic and rhombohedral phases coexist over a wide temperature range. We found a disordered feature in the nearest-neighbor bond distance corresponding to the Nb-O bonds. The disordered bond distribution disappeared when Li was substituted for Na. A similar disorder feature was found in AgNbO3. The disordered site can be specified by combining XAFS and PDF techniques. The sequences of disordered and complex phase transitions are attributable to the competition between the tolerance of the AO12 cage and the tilt of NbO6 octahedra.

  8. Conductance studies on different types of Nb/Al, AlO x,(/A1)/Nb Josephson tunnel junctions

    Science.gov (United States)

    Adelerhof, D. J.; Houwman, E. P.; Veldhuis, D.; Flokstra, J.; Rogalla, H.

    1990-08-01

    The conductance-voltage characteristics of different types of Josephson tunnel junctions have been measured at 4.2 K: symmetric Nb/Al, AlO x/Al/Nb, asymmetric Nb/Al, AlO x/Nb and Nb/Al/AlO x-/AlO x/Nb, containing a double oxidation layer. The symmetric junctions can be described very well by a trapezoidal potential barrier model. The asymmetric junctions show less agreement with theory. In these junctions resistance switching occurs, possibly due to charge trapping. The resistance is lower than in symmetric junctions. The conductance measurements on double oxidation layer junctions show, that this type of junction has an inhomogeneous oxide layer.

  9. The importance of role sending in the sensemaking of change agent roles.

    Science.gov (United States)

    Tucker, Danielle A; Hendy, Jane; Barlow, James

    2015-01-01

    The purpose of this paper is to investigate what happens when a lack of role-sending results in ambiguous change agent roles during a large scale organisational reconfiguration. The authors consider the role of sensemaking in resolving role ambiguity of middle manager change agents and the consequences of this for organisational restructuring. Data were collected from a case study analysis of significant organisational reconfiguration across a local National Health Service Trust in the UK. Data consists of 82 interviews, complemented by analysis of over 100 documents and field notes from 51 hours of observations collected over five phases covering a three year period before, during and after the reconfiguration. An inductive qualitative analysis revealed the sensemaking processes by which ambiguity in role definition was resolved. The data explains how change agents collectively make sense of a role in their own way, drawing on their own experiences and views as well as cues from other organisational members. The authors also identified the organisational outcomes which resulted from this freedom in sensemaking. This study demonstrates that by leaving too much flexibility in the definition of the role, agents developed their own sensemaking which was subsequently very difficult to manipulate. In creating new roles, management first needs to have a realistic vision of the task and roles that their agents will perform, and second, to communicate these expectations to both those responsible for recruiting these roles and to the agents themselves. Much of the focus in sensemaking research has been on the importance of change agents' sensemaking of the change but there has been little focus on how change agents sensemake their own role in the change.

  10. 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.

  11. 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.

  12. X-ray photoelectron spectroscopy studies of the electronic structure of superconducting Nb{sub 2}SnC and Nb{sub 2}SC

    Energy Technology Data Exchange (ETDEWEB)

    Romero, M.; Huerta, L.; Akachi, T. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México D.F. 04510 (Mexico); Llamazares, J.L. Sánchez [Instituto Potosino de Investigación Científica y Tecnológica, Camino a la Presa San José 2055, Col. Lomas 4a, San Luis Potosí, S.L.P. 78216 (Mexico); Escamilla, R., E-mail: rauleg@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México D.F. 04510 (Mexico)

    2013-12-05

    Highlights: •XPS was used to investigate chemical shift in the Nb{sub 2}SnC and Nb{sub 2}SC compounds. •Valence band of the Nb{sub 2}SnC and Nb{sub 2}SC compounds was studied by XPS. •Positive and negative chemical shift are observed in the Nb{sub 2}SnC and Nb{sub 2}SC. •The charge transfer model can be applicable to the Nb{sub 2}SnC and Nb{sub 2}SC compounds. •The decrease of the N(E{sub F}) of Nb{sub 2}SC respect to Nb{sub 2}SnC explain the decrease of T{sub c}. -- Abstract: X-ray photoelectron spectroscopy (XPS) was used to investigate the binding energies and valence band of the Nb{sub 2}SnC and Nb{sub 2}SC compounds. The Nb 3d{sub 5/2}, Sn 3d{sub 5/2}, S 2p{sub 3/2} and C 1s core levels associated with the chemical states of Nb{sub 2}SnC and Nb{sub 2}SC were identified. The spectra for Nb{sub 2}SnC revealed Nb and Sn oxides on the surface of the sample, mainly Nb{sub 2}O{sub 5} and SnO{sub 2}, while the Nb{sub 2}SC only Nb{sub 2}O{sub 5} oxide. After Ar{sup +} ion etching the intensity of the oxides decreased in both samples. Comparing the Nb 3d, Sn 3d, S 2p and C 1s core levels with metallic Nb, Sn, S and C reference materials, we observed a positive chemical shift for Nb 3d{sub 5/2} and a negative chemical shift for C 1s in both samples. These results suggest that the charge transfer model can be applicable to the Nb{sub 2}SnC and Nb{sub 2}SC compounds. Finally, the decrease in the T{sub c} in the Nb{sub 2}SC compound respect to Nb{sub 2}SnC might be associated to decrease in the density of states N(E{sub F})

  13. Effects of Nb doping on the microstructure, ferroelectric and ...

    Indian Academy of Sciences (India)

    ... by a conventional oxide-mixed method and the effects of Nb-doping on microstructure, piezoelectric and ferroelectricproperties of the ceramics were investigated. All the ceramics exhibit a pure perovskite structure with rhombohedral symmetry. The grain growth of the ceramics is inhibited after the addition of Nb doping.

  14. 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.

  15. Cemented NbC-Co for geothermal drilling applications

    Energy Technology Data Exchange (ETDEWEB)

    Rowcliffe, D.J. (SRI International, Menlo Park, CA (USA). Materials Research Lab.)

    1989-06-01

    Sintering and hot isostatic pressing were explored to produce a range of NbC-Co materials. Stoichiometric NbC-10Co and NbC-20Co were sintered close to the theoretical density relatively easily. Cemented NbC{sub 0.83}-10Co and NbC{sub 0.83}-20Co were more difficult to process. Some dense materials were prepared by a combination of sintering and hot isostatic pressing at 1420{degrees} to 1450{degrees}C. The carbide in these samples appeared to have the composition NbC{sub 0.9}. Hardness, toughness,and wear tests showed that the properties of these NbC{sub 0.9}-10Co samples were inferior to those of NbC{sub 0.83}-10Co materials produced previously by hot pressing. We concluded that contamination from WC milling balls and excessive processing times were the main causes of the difficulty in controlling the composition and properties of substoichiometric cemented niobium carbide. 3 figs., 7 tabs.

  16. Discovery of Superconductivity in Hard Hexagonal ε-NbN.

    Science.gov (United States)

    Zou, Yongtao; Qi, Xintong; Zhang, Cheng; Ma, Shuailing; Zhang, Wei; Li, Ying; Chen, Ting; Wang, Xuebing; Chen, Zhiqiang; Welch, David; Zhu, Pinwen; Liu, Bingbing; Li, Qiang; Cui, Tian; Li, Baosheng

    2016-02-29

    Since the discovery of superconductivity in boron-doped diamond with a critical temperature (TC) near 4 K, great interest has been attracted in hard superconductors such as transition-metal nitrides and carbides. Here we report the new discovery of superconductivity in polycrystalline hexagonal ε-NbN synthesized at high pressure and high temperature. Direct magnetization and electrical resistivity measurements demonstrate that the superconductivity in bulk polycrystalline hexagonal ε-NbN is below ∼11.6 K, which is significantly higher than that for boron-doped diamond. The nature of superconductivity in hexagonal ε-NbN and the physical mechanism for the relatively lower TC have been addressed by the weaker bonding in the Nb-N network, the co-planarity of Nb-N layer as well as its relatively weaker electron-phonon coupling, as compared with the cubic δ-NbN counterpart. Moreover, the newly discovered ε-NbN superconductor remains stable at pressures up to ∼20 GPa and is significantly harder than cubic δ-NbN; it is as hard as sapphire, ultra-incompressible and has a high shear rigidity of 201 GPa to rival hard/superhard material γ-B (∼227 GPa). This exploration opens a new class of highly desirable materials combining the outstanding mechanical/elastic properties with superconductivity, which may be particularly attractive for its technological and engineering applications in extreme environments.

  17. Prediction-Based Energy Saving Mechanism in 3GPP NB-IoT Networks.

    Science.gov (United States)

    Lee, Jinseong; Lee, Jaiyong

    2017-09-01

    The current expansion of the Internet of things (IoT) demands improved communication platforms that support a wide area with low energy consumption. The 3rd Generation Partnership Project introduced narrowband IoT (NB-IoT) as IoT communication solutions. NB-IoT devices should be available for over 10 years without requiring a battery replacement. Thus, a low energy consumption is essential for the successful deployment of this technology. Given that a high amount of energy is consumed for radio transmission by the power amplifier, reducing the uplink transmission time is key to ensure a long lifespan of an IoT device. In this paper, we propose a prediction-based energy saving mechanism (PBESM) that is focused on enhanced uplink transmission. The mechanism consists of two parts: first, the network architecture that predicts the uplink packet occurrence through a deep packet inspection; second, an algorithm that predicts the processing delay and pre-assigns radio resources to enhance the scheduling request procedure. In this way, our mechanism reduces the number of random accesses and the energy consumed by radio transmission. Simulation results showed that the energy consumption using the proposed PBESM is reduced by up to 34% in comparison with that in the conventional NB-IoT method.

  18. 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.)

  19. Childbearing among first- and second-generation Russians in Estonia against the background of the sending and host countries

    Directory of Open Access Journals (Sweden)

    Allan Puur

    2017-04-01

    Full Text Available Background: An expanding literature documents the childbearing patterns of migrants and their descendants in contemporary Europe. The existing evidence pertains mainly to the northern, western, and southern regions of the continent, while less is known about the fertility of migrants who have moved between the countries of Eastern Europe. Objective: The aim of this study is to examine the fertility patterns of first- and second-generation Russians in Estonia, relative to the sending and host populations. Methods: The study draws on the Estonian and Russian Generations and Gender Surveys. Proportional hazards models are estimated for the transitions to first, second, and third births. Results: Russian migrants in Estonia exhibit greater similarity to the sending population, with a lower propensity for having a second and third birth than the host population. This pattern extends to the descendants of migrants. However, mixed Estonian-Russian parentage, enrolment in Estonian-language schools, and residence among the host population are associated with the convergence of Russians' childbearing behaviour with the host-country patterns. The findings support the cultural maintenance and adaptation perspectives; selectivity was found to be less important. Contribution: The study focuses on a previously under-researched context and underscores the importance of contextual factors in shaping migrants' fertility patterns. It raises the possibility that, depending on the childbearing trends and levels among the sending and receiving populations, large-scale migration may reduce rather than increase aggregate fertility in the host country. With the advancement of the fertility transition in sending countries, this situation may become more common in Europe in the future.

  20. 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.

  1. 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.

  2. Th-REE- and Nb-Ta-accessory minerals in post-collisional Ediacaran felsic rocks from the Katerina Ring Complex (S. Sinai, Egypt): An assessment for the fractionation of Y/Nb, Th/Nb, La/Nb and Ce/Pb in highly evolved A-type granites

    Science.gov (United States)

    Moreno, J. A.; Molina, J. F.; Bea, F.; Abu Anbar, M.; Montero, P.

    2016-08-01

    The relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios in A-type felsic rocks from the Ediacaran Katerina Ring Complex, northernmost Arabian-Nubian Shield (ANS; S. Sinai, Egypt), are investigated in this work to understand their behavior during generation of highly evolved granitic magmas and to explore the nature of magma sources. Textural and compositional relationships of cognate Th-REE- and Nb-Ta-accessory minerals in Katerina felsic rocks show that chevkinite-group minerals (CGM), monazite, thorite, allanite and xenotime formed from residual liquids in quartz syenite porphyries, quartz monzonites and peralkaline granites, whereas in aluminous granites, allanite and monazite crystallized early, and thorite and columbite formed from residual liquids. Relationships of Y/Nb, Th/Nb, La/Nb and Ce/Pb ratios with Zr/Hf ratios in the aluminous granites and with Be abundances in the peralkaline granites suggest a decrease in La/Nb and Ce/Pb ratios in the former, and in Y/Nb and La/Nb ratios in the latter with crystallization progress. This contrasts with absence of systematic variations of Th/Nb and Ce/Pb ratios in the peralkaline compositions and of Y/Nb ratio in the aluminous ones. In this latter, Th/Nb ratio can present a significant decrease only in highly evolved compositions. An analysis of Y/Nb, Th/Nb, La/Nb and Ce/Pb relationships in worldwide OIB and subduction-related magmatic suites reveals that A-type felsic rocks with (Th/Nb)N 1 may have A1-type affinity, and those with (Th/Nb)N > 2, (La/Nb)N > 2, and (Ce/Pb)N 0.18, (Th/Nb)N > 2, (La/Nb)N > 2, (Ce/Pb)N < 1, and crustal-like Nb/Ta ratios may point to a significant contribution of crustal sources.

  3. Executing scatter operation to parallel computer nodes by repeatedly broadcasting content of send buffer partition corresponding to each node upon bitwise OR operation

    Science.gov (United States)

    Archer, Charles J [Rochester, MN; Ratterman, Joseph D [Rochester, MN

    2009-11-06

    Executing a scatter operation on a parallel computer includes: configuring a send buffer on a logical root, the send buffer having positions, each position corresponding to a ranked node in an operational group of compute nodes and for storing contents scattered to that ranked node; and repeatedly for each position in the send buffer: broadcasting, by the logical root to each of the other compute nodes on a global combining network, the contents of the current position of the send buffer using a bitwise OR operation, determining, by each compute node, whether the current position in the send buffer corresponds with the rank of that compute node, if the current position corresponds with the rank, receiving the contents and storing the contents in a reception buffer of that compute node, and if the current position does not correspond with the rank, discarding the contents.

  4. Measurements of tunneling barrier thicknesses for Nb/Al–AlO{sub x}/Nb tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Xinjie [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); Ying, Liliang [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, Hai [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); Zhang, Guofeng; Peng, Wei; Kong, Xiangyan; Xie, Xiaoming [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)

    2014-08-15

    Highlights: • We estimate the average barrier height (Φ) of Nb/Al–AlO{sub x}/Nb tunnel junctions. • Dependence of the AlOx thickness (dAlOx) on O{sub 2} exposure was described. • The thicknesses of AlOx barriers were measured using transmission electron microscopy (TEM). • X-ray Reflection (XRR) measurements and simulations were used to verify the AlOx thickness. - Abstract: The tunnel barrier thicknesses of Nb/Al–AlO{sub x}/Nb tunnel junctions were measured using transmission electron microscopy (TEM) and X-ray Reflection (XRR). By investigating the barrier thickness dependence of current density J{sub c}, the barrier height for Nb/Al–AlO{sub x}/Nb junctions was calculated. Nb/Al–AlO{sub x}/Nb junctions with different J{sub c} were fabricated by controlling the O{sub 2} exposure in Al oxidation. The junctions show good tunneling properties with subgap leakage factor V{sub m} larger than 30 mV in the range of J{sub c} from tens of A/cm{sup 2} to several kA/cm{sup 2}. TEM images showed clear interface and indicated the AlO{sub x} thicknesses ranging from 0.8 nm to 1.9 nm, and the average barrier height was estimated to be 0.17 eV for Nb/Al–AlO{sub x}/Nb tunnel junctions.

  5. Magnetization measurements on multifilamentary Nb/sub 3/Sn and NbTi conductors

    Energy Technology Data Exchange (ETDEWEB)

    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/sub 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.

  6. 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.

  7. 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.

  8. 47 CFR 80.1159 - Narrow-band direct-printing (NB-DP).

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Narrow-band direct-printing (NB-DP). 80.1159... Narrow-band direct-printing (NB-DP). NB-DP is a form of telegraphy for the transmission and receipt of direct printing public correspondence. Ships must use NB-DP techniques only with authorized public coast...

  9. Highly smooth Nb surfaces fabricated by buffered electropolishing

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-05-01

    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{sup +}, Au{sup +}, and Ar{sup +} 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.

  10. A new approach to fabricate superconducting NbTi alloys

    Science.gov (United States)

    Mousavi, Tayebeh; Hong, Zuliang; Morrison, Alasdair; London, Andrew; Grant, Patrick S.; Grovenor, Chris; Speller, Susannah C.

    2017-09-01

    Superconducting NbTi alloys have been successfully fabricated by a simple powder processing route involving ball-milling, pressing and annealing. The microstructure and superconducting properties of the NbTi alloys after each processing step have been characterised and compared to the microstructure and performance of NbTi wire manufactured by a conventional thermomechanical process. At the early stages of milling, a lamellar structure of pure Nb and Ti regions is formed, which is gradually refined by further milling leading to the introduction of a high density of microstructural defects. After 20 h milling, diffusion of Ti into the Nb generates a matrix of β-Nb-50 wt%Ti alloy, with a small grain size (50 nm) and high strain (1.8%), containing an even distribution of thin Ti flakes (10-40 nm). In some regions, these Ti flakes contain a supersaturation of Nb as a result of the energetic ball-milling process. The T c (8.1 K) and B c2 (9.8 T at 4.2 K) values of this as-milled material are slightly lower than those reported for Nb-47 wt%Ti due to the impurity content and lattice disorder. Sintering at 400 ^\\circ C leads to well consolidated, high density bulk samples, but annealing at temperatures above 600 ^\\circ C decreases J c values due to excessive grain growth and strain release. Annealing at lower temperatures results in higher J c values, a shift of the pinning force density peak towards higher fields and the presence of thermodynamically stable α-Ti precipitates which are effective pinning sites leading to critical current density values comparable with those of commercial NbTi wires.

  11. Electrical and magnetic properties of Nb2O5-γ crystallographic shear structures

    DEFF Research Database (Denmark)

    Cava, R.J.; Batlogg, B.; Krajewski, J.J.

    1991-01-01

    The reduced niobium oxides Nb25O62, Nb47O116, Nb22O54, and Nb12O29 have been prepared in pure polycrystalline form by a niobium-metal gettering technique. They are related to the high niobia parent structure through the action of cystallographic shear to accommodate oxygen deficiency in Nb2O5-del....... Electrical conductivities increase with increasing reduction: Nb12O29 is a metallic conductor down to 0.3 K. All show, surprisingly, Curie-Weiss behavior in the chi-vs-T curves, with Nb12O29 ordering antiferromagnetically at 12 K....

  12. Josephson junctions and dc SQUIDs based on Nb/Al technology

    OpenAIRE

    Flokstra, Jakob; Adelerhof, Derk Jan; Adelerhof, D.J.; Houwman, Evert Pieter; Veldhuis, Dick; Rogalla, Horst

    1991-01-01

    A process for fabricating high-quality Josephson junctions and DC SQUIDS on basis of Nb/Al technology has been developed. DC magnetron sputtering is used for the deposition of the metal layers and the barrier is formed by thermal oxidation of the Al-layer. The junction area of 5 µm × 5 5 µm is obtained using anodisation. Three types of Josephson tunnel junctions have been prepared: standard Nb/Al, AlOx/Nb, symmetric Nb/Al, AlOx, Al/Nb and Nb/Al, AlOx/AlOx/Nb, the latter having a double oxide ...

  13. 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...

  14. Did send-down experience benefit youth? A reevaluation of the social consequences of forced urban-rural migration during China's Cultural Revolution.

    Science.gov (United States)

    Xie, Yu; Jiang, Yang; Greenman, Emily

    2008-06-01

    During China's Cultural Revolution, a large proportion of urban youth were forced to go to the countryside as a result of the state's "send-down" policy. Past research has been ambivalent about the long-term social consequences for the Chinese youth who experienced send-down. Some scholars have suggested that the send-down experience may have yielded beneficial effects. To test this claim, we analyze data from the Survey of Family Life in Urban China, which we conducted in three large cities in 1999. Questions available in this data set allow us to ascertain the send-down experience of both the respondent and a sibling and educational attainment at the times of send-down and return. Our analyses of the new data show that the send-down experience does not seem to have benefited the affected Chinese youth. Differences in social outcomes between those who experienced send-down and those who did not are either non-existent or spurious due to other social processes.

  15. A Facile Approach for the Synthesis of Porous KTiNbO5 Catalyst ...

    Indian Academy of Sciences (India)

    49

    synthesized KTiNbO5, porous KTiNbO5 and Au-MnO2-KTiNbO5 composites; N2 adsorption and desorption isotherms of the MnO2-pillared KTiNbO5 composites; the recycle effect of the as-synthesized. Au-MnO2-KTiNbO5 composites on the catalytic ...

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

    Directory of Open Access Journals (Sweden)

    Gorka Larzabal

    2017-02-01

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

  17. Chiral magnetoresistance in the Weyl semimetal NbP

    Science.gov (United States)

    Niemann, Anna Corinna; Gooth, Johannes; Wu, Shu-Chun; Bäßler, Svenja; Sergelius, Philip; Hühne, Ruben; Rellinghaus, Bernd; Shekhar, Chandra; Süß, Vicky; Schmidt, Marcus; Felser, Claudia; Yan, Binghai; Nielsch, Kornelius

    2017-03-01

    NbP is a recently realized Weyl semimetal (WSM), hosting Weyl points through which conduction and valence bands cross linearly in the bulk and exotic Fermi arcs appear. The most intriguing transport phenomenon of a WSM is the chiral anomaly-induced negative magnetoresistance (NMR) in parallel electric and magnetic fields. In intrinsic NbP the Weyl points lie far from the Fermi energy, making chiral magneto-transport elusive. Here, we use Ga-doping to relocate the Fermi energy in NbP sufficiently close to the W2 Weyl points, for which the different Fermi surfaces are verified by resultant quantum oscillations. Consequently, we observe a NMR for parallel electric and magnetic fields, which is considered as a signature of the chiral anomaly in condensed-matter physics. The NMR survives up to room temperature, making NbP a versatile material platform for the development of Weyltronic applications.

  18. Resistive Switching Characteristics of 10-nm-Thick Amorphous HoScO x Films Doped with Nb and Zn

    Science.gov (United States)

    Wang, Sea-Fue; Hsu, Chia-Chun; Chu, Jinn P.; Liu, Yi-Xin; Chen, Liang-Wei

    2017-03-01

    In this study, 10-nm rare-earth metal-oxide (REMO) films, namely, pure HoScO x (HSO) and HoScO x doped with Nb (HSO-Nb) and Zn (HSO-Zn), were deposited to build resistive random access memory (RRAM) devices with a Pt/REMO/Pt structure using radio frequency magnetron sputtering. The results of x-ray diffraction and transmission electron microscopy showed that all as-deposited REMO films are featureless microstructures lacking long-range order. In all RRAM devices, layer structures were well adhered to each other with relatively smooth interfaces and no cracks or holes were observed. Hall measurements demonstrated n-type conduction in the as-deposited films. The addition of Nb and Zn increased carrier concentration and mobility of the HSO films and reduced electrical resistivity. The former was possibly caused by the electronic compensation of NbSc ··, thereby triggering the formation of polarons, and the latter was probably due to the increase in concentration of oxygen vacancies associated with acceptor doping. The RRAM devices revealed unipolar switching behavior characterized by a resistance ratio of more than three orders of magnitude, good endurance, and a long retention time. The switching behavior of the RRAM with amorphous HSO films was altered by the doping species. Doping with Nb and Zn decreased the forming voltage, facilitated the use of a smaller switching voltage, and increased the resistance ratio of high- and low-resistance states. The conduction mechanisms for the low resistive state and high resistive state were dominated by Ohmic conduction and trap-controlled space-charge-limited current mechanisms, respectively.

  19. Effects of Nb doping on the microstructure, ferroelectric and ...

    Indian Academy of Sciences (India)

    Abstract. Donor-doped lead-free Bi0.7Ba0.3(Fe0.7Ti0.3)1−xNb0.66xO3 + 1 mol% MnO2 ceramics were prepared by a conventional oxide-mixed method and the effects of Nb-doping on microstructure, piezoelectric and ferroelec- tric properties of the ceramics were investigated. All the ceramics exhibit a pure perovskite ...

  20. Analgesic effects of NB001 on mouse models of arthralgia

    OpenAIRE

    Tian, Zhen; Wang, Dong-sheng; Wang, Xin-shang; Tian, Jiao; Han, Jing; Guo, Yan-yan; Feng, Bin; Zhang, Nan; Zhao, Ming-gao; Liu, Shui-bing

    2015-01-01

    Our previous studies have demonstrated the critical roles of calcium-stimulated adenylyl cyclase 1 (AC1) in the central nervous system in chronic pain. In the present study, we examined the analgesic effects of NB001, a selective inhibitor of AC1, on animal models of ankle joint arthritis and knee joint arthritis induced by complete Freund’s adjuvant injection. NB001 treatment had no effect on joint edema, stiffness, and joint destruction. Furthermore, the treatment failed to attenuate the di...

  1. Hydrothermal Conversion of Layered Niobate K4Nb6O17·3H2O to Rare Microporous Niobate K6Nb10.8O30.

    Science.gov (United States)

    Ide, Yusuke; Shirae, Wataru

    2017-09-18

    We report a new facile route to synthesizing K6Nb10.8O30, a rare microporous niobate. When hydrothermally treated under alkali conditions, a layered niobate, K4Nb6O17·3H2O, was converted to K6Nb10.8O30. This product had a much smaller particle size than K6Nb10.8O30, prepared by a conventional solid-state reaction, and showed enhanced adsorption properties.

  2. Diffusion between Nb and Ti related to superconductor wire processing

    CERN Document Server

    Bormio-Nunes, C; Porto, F S A; Souza, V S D; Tirelli, M A; Edwards, E R

    2003-01-01

    Quantitative data on the diffusion between Nb and Ti are important for the processing of Nb-Ti superconductor wires through the 'artificial pinning centre-diffusion process'. In the literature, most of the Nb-Ti diffusion studies are focused on the 1173-1973 K temperature range which is inappropriate for this application. The objective of this study was to evaluate the diffusion between Nb and Ti at 1023 K and 1073 K, from a Nb-Ti cylindrical composite that has been mechanically deformed by swaging. It has been found that at both temperatures most of the diffusion layer is formed through the diffusion of Nb into Ti. A plot of diffusion layer thickness versus t sup 1 sup / sup 2 (t is the time) showed a linear behaviour for both temperatures with angular coefficients of 0.0867 mu m s sup - sup 1 sup / sup 2 (1023 K) and 0.253 mu m s sup - sup 1 sup / sup 2 (1073 K). Longer heat treatment and higher temperature leads to a Ti-rich diffusion layer, which is not interesting in terms of superconducting properties. ...

  3. EFFECT OF Nb ELEMENT CONTENT IN U-Zr ALLOY ON HARDNESS, MICROSTRUCTURE AND PHASE FORMATION

    Directory of Open Access Journals (Sweden)

    Masrukan Masrukan

    2015-07-01

    Full Text Available EFFECT OF Nb ELEMENT CONTENT IN U-Zr-Nb ALLOY ON HARDNESS, MICROSTRUCTURE AND PHASE FORMATION. 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,Nbat 2% Nb to be αU, γU (Zr,Nb and δ1 (UZr2 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.   PENGARUH KADAR UNSUR Nb PADA PADUAN U-Zr-Nb TERHADAP SIFAT MEKANIK, MIKROSTRUKTUR DAN PEMBENTUKAN FASA. Percobaan untuk mengtahui pengaruh kadar Nb pada paduan U-Zr-Nb terhadap sifat mekanik, mikrostruktur dan pembentukan fasa telah dilakukan. Penambahan unsur Nb diduga akan mempengaruhi sifat mekanik, mikrosruktur, ketahanan korosi dan fasa yang terbentuk. Penambahan unsur Nb ke dalam paduan U-Zr dimaksudkan untuk memperluas daerah fasa gamma

  4. First principles theoretical investigations of low Young's modulus beta Ti-Nb and Ti-Nb-Zr alloys compositions for biomedical applications.

    Science.gov (United States)

    Karre, Rajamallu; Niranjan, Manish K; Dey, Suhash R

    2015-05-01

    High alloyed β-phase stabilized titanium alloys are known to provide comparable Young's modulus as that to the human bones (~30 GPa) but is marred by its high density. In the present study the low titanium alloyed compositions of binary Ti-Nb and ternary Ti-Nb-Zr alloy systems, having stable β-phase with low Young's modulus are identified using first principles density functional framework. The theoretical results suggest that the addition of Nb in Ti and Zr in Ti-Nb increases the stability of the β-phase. The β-phase in binary Ti-Nb alloys is found to be fully stabilized from 22 at.% of Nb onwards. The calculated Young's moduli of binary β-Ti-Nb alloy system are found to be lower than that of pure titanium (116 GPa). For Ti-25(at.%)Nb composition the calculated Young's modulus comes out to be ~80 GPa. In ternary Ti-Nb-Zr alloy system, the Young's modulus of Ti-25(at.%)Nb-6.25(at.%)Zr composition is calculated to be ~50 GPa. Furthermore, the directional Young's moduli of these two selected binary (Ti-25(at.%)Nb) and ternary alloy (Ti-25(at.%)Nb-6.25(at.%)Zr) compositions are found to be nearly isotropic in all crystallographic directions. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Ferroelectric domain structures of epitaxial CaBi2Nb2O9 thin films on single crystalline Nb doped (1 0 0) SrTiO3 substrates

    Science.gov (United States)

    Ahn, Yoonho; Seo, Jeong Dae; Son, Jong Yeog

    2015-07-01

    Epitaxial CaBi2Nb2O9 (CBNO) thin films were deposited on Nb-doped SrTiO3 substrates. The CBNO thin films as a lead-free ferroelectric material exhibit a good ferroelectric property with the remanent polarization of 10.6 μC/cm2. In the fatigue resistance test, the CBNO thin films have no degradation in polarization up to 1×1012 switching cycles, which is applicable for non-volatile ferroelectric random access memories (FeRAMs). Furthermore, piezoresponse force microscopy study (PFM) reveals that the CBNO thin films have larger ferroelectric domain structures than those of PbTiO3 thin films. From the Landau, Lifshiftz, and Kittel's scaling law, it is inferred that the domain wall energy of CBNO thin films is probably very similar to that of the PbTiO3 thin films.

  6. 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

  7. Hand preference for sending mobile-phone text messages: associations with sex, writing hand, and throwing hand.

    Science.gov (United States)

    Lambert, Anthony; Hallett, Charlene

    2009-07-01

    Hand preference for sending mobile-phone text messages ("texting") and its relationship with hand preference for other activities were investigated in a questionnaire study with 886 participants. Overall rates of both sinistrality and dextrality were reduced for texting, in comparison with other activities, due to the substantial number of individuals who use both hands simultaneously when performing this activity. Because they both involve verbal expression, it was hypothesised that the association between hand preferences for texting and writing might be stronger than the association between either of these tasks and more spatial activities, such as throwing. This prediction was not confirmed, either in the sample as a whole or in a sub-group of individuals who reported writing and throwing with opposite hands. Females were less likely than males to use their left hand when sending text messages. Implications of these findings are discussed, in relation to theoretical views of handedness and in relation to practical aspects of mobile-phone design.

  8. Accuracy of send-out test ordering: a College of American Pathologists Q-Probes study of ordering accuracy in 97 clinical laboratories

    National Research Council Canada - National Science Library

    Valenstein, Paul N; Walsh, Molly K; Stankovic, Ana K

    2008-01-01

    .... Representatives from 97 clinical laboratories provided information about the processes they use to send tests to reference facilities and their order entry and specimen routing error rates. In aggregate, 98...

  9. Two nanoscale Nb containing polyoxometalates based on {P2W15Nb3O62} clusters and chromium cations.

    Science.gov (United States)

    Huang, Peng; Wang, Xin-Long; He, De-Qing; Wu, Hai-Yang; Qin, Chao; Du, Meng; Lai, Chao; Su, Zhong-Min

    2017-10-10

    Two novel mixed-addenda Nb/W polyoxometalates are successfully fabricated, and investigated as anode materials for lithium-ion batteries. For the Cs5K4{Cr3(H2O)12[P2W15Nb3O62]2}·60H2O sample, a reversible capacity (466.6 mA h g(-1)) and stable cycle performance are obtained.

  10. Fabrication and properties of Nb/Al, Alox/Nb Josephson tunnel junctions with a double-oxide barrier

    Science.gov (United States)

    Houwman, E. P.; Veldhuis, D.; Flokstra, J.; Rogalla, H.

    1990-02-01

    High-quality Nb/Al, Alox/Nb Josephson tunnel junctions using double-oxide layers as barriers have been fabricated. The critical current density is controlled by the thickness of the second Al layer. This layer has to be oxidized completely through in order to obtain high-quality junctions. Typically, gap voltages of 2.8-3.0 mV and Vm up to 70 mV at 4.2 K were obtained.

  11. AC susceptibility in NbTi multifilamentary wires; NbTi gokusai tashinsen no koryu taijiritsu

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, R.; Muranaka, T.; Akune, T.; Sakamoto, N. [Kyushu Sangyo Univ., Fukuoka (Japan). Dept. of Electrical Engineering

    1999-06-07

    In the superfine polycore line, the matrix shows the weakness superconductivity by affection broth of the electron pair from the NbTi filament. The filament of the polycore line is made to combine by this, and we cause magnetization and ac losses, increase in magnetic flux creep, etc.. It is possible to obtain superconductive critical current density J{sub cp} of the matrix by the proximity effect from twist pitch l{sub p} dependence of magnetization M. Here, the relation with the peak in the imaginary part of ac magnetic susceptibility is reported on evaluation and result of examining. (NEDO)

  12. Synthesis and characterization of Nb2O5@C core-shell nanorods and Nb2O5nanorods by reacting Nb(OEt5via RAPET (reaction under autogenic pressure at elevated temperatures technique

    Directory of Open Access Journals (Sweden)

    George PP

    2006-01-01

    Full Text Available AbstractThe reaction of pentaethoxy niobate, Nb(OEt5, at elevated temperature (800 °C under autogenic pressure provides a chemical route to niobium oxide nanorods coated with amorphous carbon. This synthetic approach yielded nanocrystalline particles of Nb2O5@C. As prepared Nb2O5@C core-shell nanorods is annealed under air at 500 °C for 3 h (removing the carbon coating results in neat Nb2O5nanorods. According to the TEM measurements, the Nb2O5crystals exhibit particle sizes between 25 nm and 100 nm, and the Nb2O5crystals display rod-like shapes without any indication of an amorphous character. The optical band gap of the Nb2O5nanorods was determined by diffuse reflectance spectroscopy (DRS and was found to be 3.8 eV.

  13. 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.

  14. Influence of Nb Doping Concentration on Bolometric Properties of RF Magnetron Sputtered Nb:TiO2- x Films

    Science.gov (United States)

    Reddy, Y. Ashok Kumar; Shin, Young Bong; Kang, In-Ku; Lee, Hee Chul

    2018-03-01

    The present study directly addresses the improved bolometric properties by means of different Nb doping concentrations into TiO2- x films. The x-ray diffraction patterns do not display any obvious diffraction peaks, suggesting that all the films deposited at room temperature had an amorphous structure. A small binding energy shift was observed in x-ray photo electron spectroscopy due to the change of chemical composition with Nb doping concentration. All the device samples exhibit linear I- V characteristics, which attests to the formation of good ohmic contact with low contact resistance between the Nb:TiO2- x (TNO) film and the electrode (Ti) material. The performance of the bolometric material can be evaluated through the temperature coefficient of resistance (TCR), and the absolute value of TCR was found to be increased from 2.54% to 2.78% with increasing the Nb doping concentration. The voltage spectral density of 1/ f noise was measured in the frequency range of 1-60 Hz and found to be decreased with increase of Nb doping concentration. As a result, for 1 at.% Nb-doped TNO sample exhibits improved bolometric properties towards the good infrared image sensor device.

  15. Nitridation of Ti/Nb alloys and solid-state properties of {delta}-(Ti,Nb)N

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, W.; Lengauer, W. [Technische Univ., Vienna (Austria). Inst. fuer Chemische Technologie Anorganischer Stoffe; Buscaglia, V. [Istituto di Chimica Fisica Applicata dei Materiali, Consiglio Nazionale delle Ricerche, via de Marini 6, I-16149, Genoa (Italy); Bauer, J. [Laboratoire du Chimie Solide et Inorganique Moleculaire, Universite de Rennes I, Avenue General Leclerc, F-35042, Rennes (France); Bohn, M. [IFREMER, Centre de la Microsonde de l`Ouest, CNRS-UNR 6538, F-29280, Plouzane/Brest (France); Fialin, M. [Centre d`Analyses par Microsonde CAMPARIS, Universite P. et M. Curie, Tour 26 et 3, 4, Place Jussieu, F-75252, Paris Cedex 05 (France)

    1997-11-14

    The formation of microstructures and diffusion layers in the Ti-Nb-N system was investigated by annealing compact Ti/Nb alloys (0-100 at% Ti) in a high-purity nitrogen atmosphere (3 and 30 bar N{sub 2}) in the temperature range 1300-1600 C. The alloy starting material was in the form of wedge-type samples as well as in the form of plane sheets. After nitridation all samples showed a yellow colour which is characteristic for the fcc {delta}-(Ti,Nb)N phase, the layer growth rate of which was a minimum at 75 at% Ti. The nitride layer as well as the precipitates were rich in Ti whereas in the {beta} alloy an Nb increase was observed. During nitridation needles with different length and width grew from the inner layer boundary into the original alloy. Electron probe microanalysis (EPMA) was performed to gain insight into the time evolution of the diffusion profiles of Ti, Nb and N. Homogeneous plane-sheet samples were used for measurements of the microhardness, the superconducting transition temperature and the lattice parameter of {delta}-(Ti,Nb)N. (orig.) 14 refs.

  16. Influence of Nb Doping Concentration on Bolometric Properties of RF Magnetron Sputtered Nb:TiO2-x Films

    Science.gov (United States)

    Reddy, Y. Ashok Kumar; Shin, Young Bong; Kang, In-Ku; Lee, Hee Chul

    2017-12-01

    The present study directly addresses the improved bolometric properties by means of different Nb doping concentrations into TiO2-x films. The x-ray diffraction patterns do not display any obvious diffraction peaks, suggesting that all the films deposited at room temperature had an amorphous structure. A small binding energy shift was observed in x-ray photo electron spectroscopy due to the change of chemical composition with Nb doping concentration. All the device samples exhibit linear I-V characteristics, which attests to the formation of good ohmic contact with low contact resistance between the Nb:TiO2-x (TNO) film and the electrode (Ti) material. The performance of the bolometric material can be evaluated through the temperature coefficient of resistance (TCR), and the absolute value of TCR was found to be increased from 2.54% to 2.78% with increasing the Nb doping concentration. The voltage spectral density of 1/f noise was measured in the frequency range of 1-60 Hz and found to be decreased with increase of Nb doping concentration. As a result, for 1 at.% Nb-doped TNO sample exhibits improved bolometric properties towards the good infrared image sensor device.

  17. 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.

  18. INSTABILITES IN NB3SN WIRES.

    Energy Technology Data Exchange (ETDEWEB)

    COOLEY, L.; GHOSH, A.

    2006-04-03

    High current-density Nb{sub 3}Sn strands made by internal-tin routes are not stable against flux jumps at low fields. Since flux jumps release heat, they can initiate quenching if thermal conductivity to the liquid helium is poor. To make matters worse, tin is a potent contaminant of copper, and reaction of strands to maximize performance leads to the loss of thermal conductivity. We discuss how the root of a solution of this problem lies in optimizing two parameters, RRR and J{sub c}, instead of J{sub c} alone. An important workaround for magnet designers is controlling the balance between performance and stability by reducing the temperature or time of the final heat treatment step. This provides ample J{sub c} while also keeping RRR high. Under these conditions, the instability current density threshold J{sub s} is higher than J{sub c}. Additional factors are also available to improve the management of instabilities, including new strand designs with smaller subelements or divided subelements.

  19. Nb-benzoyltryptamine derivatives with relaxant activity in guinea-pig ileum.

    Science.gov (United States)

    Gutierrez, Stanley Juan C; de S Claudino, Fladmir; Da Silva, Bagnólia A; Câmara, Celso A; de Almeida, Reinaldo N; de Fátima V de Souza, Maria; Da Silva, Marcelo S; Da-Cunha, Emídio V L; Barbosa-Filho, José Maria

    2005-01-01

    A series of derivatives analogous to Nb-benzoyltryptamine were synthesized by the Schotten-Bauman procedure. The products obtained were: Nb-4-methoxy-benzoyltryptamine, Nb-2,4-dimethoxy-benzoyltryptamine, Nb-3,4-dimethoxy-benzoyltryptamine, Nb-3,4-methylenedioxy-benzoyltryptamine and Nb-3,4,5-trimethoxy-benzoyltryptamine. They were characterized through the usual spectrometric methods (UV, IR, 1H and 13C NMR) and showed non-selective relaxant activity in guinea-pig ileum pre-contracted with acetylcholine, histamine and KCl.

  20. 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.

  1. Coherent quantum transport in hybrid Nb-InGaAs-Nb Josephson junctions

    Science.gov (United States)

    Delfanazari, Kaveh; Puddy, R.; Ma, P.; Cao, M.; Yi, T.; Gul, Y.; Farrer, I.; Ritchie, D.; Joyce, H.; Kelly, M.; Smith, C.

    Because of the recently reported detection of Majorana fermions states at the superconductor-semiconductor (S-Sm) interface in InAs nanowire devices, the study of hybrid structures has received renewed interest. In this paper we present experimental results on proximity induced superconductivity in a high-mobility two-dimensional electron gas in InGaAs heterostructures. Eight symmetric S-Sm-S Josephson junctions were fabricated on a single InGaAs chip and each junction was measured individually using a lock-in measurement technique. The superconducting electrodes were made of Niobium (Nb). The measurements were carried out in a dilution fridge with a base temperature of 40 mK, and the quantum transport of junctions were measured below 800 mK. Owing to Andreev reflections at the S-Sm interfaces, the differential resistance (dV/dI) versus V curve shows the well-known subharmonic energy gap structure (SGS) at V = 2ΔNb/ne. The SGS features suppressed significantly with increasing temperature and magnetic field, leading to a shift of the SGSs toward zero bias. Our result paves the way for development of highly transparent hybrid S-Sm-S junctions and coherent circuits for quantum devices capable of performing quantum logic and processing functions.

  2. Proximity effect in Nb/Al, AlOxide, Al/Nb Josephson tunnel junctions

    Science.gov (United States)

    Houwman, E. P.; Gijsbertsen, J. G.; Flokstra, J.; Rogalla, H.; Le Grand, J. B.; de Korte, P. A. J.; Golubov, A. A.

    1993-03-01

    Regions with reduced energy gap induced by the proximity effect give rise to quasi-particle loss in Josephson-junction X-ray detectors, but may also be used advantageously for quasi-particle collection. The influence of the thickness of the Al proximity layers in Nb/Al1,AlO(x),Al2/Nb Josephson tunnel junctions on the electrical characteristics has been investigated theoretically and experimentally. Theoretically it is found that the strength of the proximity effect is mainly determined by the proximity parameters gammaM1 (gammaM2) of the electrodes. Good fits of the measured I-V curves with theory were obtained for junctions with thicknesses dA11 ranging from 4 to 25 nm and dA12 = 3 nm, with gammaM2 about 0.12 and gammaM1/gammaM2 = dA11/dA12. For all junctions the proximity knee remains more pronounced than predicted.

  3. 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.

  4. Dopant occupancy and exposure energy in Hf:Nd:LiNbO3 crystal as a function of [Li]/[Nb] ratios

    Science.gov (United States)

    Dai, Li; Liu, Chunrui; Han, Xianbo; Yan, Zhehua; Tan, Chao; Wang, Luping; Xu, Yuheng

    2017-09-01

    A series of Hf: Nd: LiNbO3 crystals with various [Li]/[Nb] ratios ([Li]/[Nb] = 0.94, 1.05, 1.20, 1.38) in the melt were grown by conventional Czochralski technique. The distribution coefficients of Hf4+ and Nd3+ ions were recorded by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The effective distribution coefficient of Hf4+ is reduced and that of Nd3+ is increased with the increase of [Li]/[Nb] ratio in the melts. In all cases, the effective distribution coefficients is less than 1. The IR transmission spectroscopy of the Hf: Nd: LiNbO3 crystals were measured, getting the results that Hf: Yb: Ho: LiNbO3 crystals with 1.05 [Li]/[Nb] ratios was the stoichiometric. The optical damage resistance ability of Hf:Nd:LiNbO3 crystals were studied by light-induced scattering exposure energy flux threshold method and it increases with the increasing of [Li]/[Nb] ratios. When the [Li]/[Nb] ratio is 1.38 in the melt (the sample 4#), the exposure energy achieves 687.35 J/cm2, approximately 441 folds than that of the sample 1# ([Li]/[Nb] = 0.94) in magnitude.

  5. Fabrication of a strain-induced high performance NbN ultrathin film by a Nb5N6 buffer layer on Si substrate

    Science.gov (United States)

    Jia, X. Q.; Kang, L.; Gu, M.; Yang, X. Z.; Chen, C.; Tu, X. C.; Jin, B. B.; Xu, W. W.; Chen, J.; Wu, P. H.

    2014-03-01

    Lattice mismatch between NbN and silicon (Si) reduces the superconducting properties of NbN film on Si substrate, and this in turn affects the performance of devices such as the hot electron bolometer (HEB) and superconducting nanowire single photon detector (SNSPD). We have found that the superconducting properties of NbN film on Si will be significantly improved by a Nb5N6 buffer layer. The strain of the NbN film was optimized by varying the thickness of the buffer layer. With 30 nm thick Nb5N6, the zero resistance superconducting transition temperature (TC0) of a 6 nm thick NbN film on Si is up to 13.5 K and the critical current density (JC) of the film is more than 107 A cm-2. All the details of preparation, improvement and characteristics of this film are also presented.

  6. Impact of UVA on pruritus during UVA/B phototherapy of inflammatory skin diseases: a randomized double-blind study.

    Science.gov (United States)

    Maul, J-T; Kretschmer, L; Anzengruber, F; Pink, A; Murer, C; French, L E; Hofbauer, G F; Navarini, A A

    2017-07-01

    Narrowband (TL-01) UVB phototherapy (UVB nb) is effective in treating inflammatory skin disease. The addition of UVA is traditionally advocated to reduce pruritus, but lacks evidence for this recommendation. The aim of this study was to assess the effect of UVB nb and UVA phototherapy in combination compared against UVB nb monotherapy on pruritus, disease activity and quality of life. In this double-blind randomized clinical trial, 53 patients suffering from inflammatory skin diseases with pronounced itching (Visual Analogue Scale (VAS) for pruritus ≥5) were randomized into two treatment groups. One group received UVB nb (311 nm) phototherapy alone and another group received a combination of UVB nb and UVA (320-400 nm) phototherapy. UV therapy was performed three times per week over 16 weeks. Pruritus (VAS and 5-D itch score), disease activity and quality of life (Dermatology Life Quality Index, DLQI) were assessed at baseline and weeks 4, 8, 12 and 16. In both treatment groups, there was a reduction in pruritus scores, disease activity and DLQI. No difference in pruritus score, disease activity and quality of life could be detected between the group receiving UVB nb alone and those receiving UVB nb combined with UVA. Phototherapy with UVB nb alone, and UVB nb combined with UVA are equally effective in treating inflammatory skin disease and indifferent in reducing disease-associated pruritus. Given this non-inferiority for UVB nb monotherapy, the recommendation of adding UVA to UVB nb phototherapy for pruritic inflammatory skin disease should be abandoned. © 2016 European Academy of Dermatology and Venereology.

  7. Sending-country violence and receiving-country discrimination: effects on the health of Colombian refugees in Ecuador.

    Science.gov (United States)

    Shedlin, Michele G; Decena, Carlos U; Noboa, Hugo; Betancourt, Óscar

    2014-02-01

    This study explored factors affecting the health and well being of recent refugees from Colombia in Ecuador. Data collection focused on how sending-country violence and structural violence in a new environment affect immigrant health vulnerability and risk behaviors. A qualitative approach included ethnographic observation, media content analysis, focus groups, and individual interviews with refugees (N = 137). The focus groups (5) provided perspectives on the research domains by sex workers; drug users; male and female refugees; and service providers. Social and economic marginalization are impacting the health and well being of this growing refugee population. Data illustrate how stigma and discrimination affect food and housing security, employment and health services, and shape vulnerabilities and health risks in a new receiving environment. Widespread discrimination in Ecuador reflects fears, misunderstanding, and stereotypes about Colombian refugees. For this displaced population, the sequelae of violence, combined with survival needs and lack of support and protections, shape new risks to health and well-being.

  8. Throughput Improvement for TCP with a Performance Enhancing Proxy Using a UDP-Like Packet Sending Policy

    Science.gov (United States)

    Wang, Hui; Nishida, Yuichi; Fukushima, Yukinobu; Yokohira, Tokumi; Wu, Zhen

    To improve TCP throughput even if the maximum receiving window size is small, a TCP performance enhancing proxy (PEP) using a UDP-like packet sending policy with error control has been proposed. The PEP operates on a router along a TCP connection. When the PEP receives a data packet from the source host, it transmits the packet to the destination host, copies the packet into the local buffer (PEP buffer) in case the packets need to be transmitted and sends a premature ACK acknowledging receipt of the packet to the source host. In the PEP, the number of prematurely acknowledged packets in the PEP buffer is limited to a fixed threshold (watermark) value to avoid network congestion. Although the watermark value should be adjusted to changes in the network conditions, watermark adjusting algorithms have not been investigated. In this paper, we propose a watermark adjusting algorithm the goal of which is to maximize the throughput of each connection as much as possible without excessively suppressing the throughputs of the other connections. In our proposed algorithm, a newly established connection uses the initial watermark value of zero to avoid drastic network congestion and increases the value as long as its throughput increases. In addition, when a new connection is established, every already-established connection halves its watermark value to allow the newly established connection to use some portion of the bandwidth and increases again as long as its throughput increases. We compare the proposed algorithm (CW method) with other methods: the FW method that uses a fixed large watermark value and the NP method that does not use the PEP. Numerical results with respect to throughput and fairness showed that the CW method is generally superior to the other two methods.

  9. Selective dissolution in AlFeNb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Drensler, Stefanie; Mardare, Cezarina Cela; Hassel, Achim Walter [Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Linz (Austria); Milenkovic, Srdjan [IMDEA Materials, Parque Cientifico de la Universidad Carlos III de Madrid, Avda. del mar Mediterraneo 22, 28918 Leganes (Spain)

    2012-05-15

    Three different AlFeNb alloys of various compositions were prepared by arc melting. X-ray diffraction (XRD) investigation of the melted samples proved the presence of two phases identified as a bcc {alpha}(Fe,Al) solid solution and a hexagonal C14 (Fe,Al){sub 2}Nb Laves phase. Subsequent electrochemical treatment allowed for a selective dealloying of the {alpha}(Fe,Al) or respective FeAl phase and resulted in releasing differently microstructured surfaces. These structures ranged from regular lamellar structures towards branched, fibrous structures. Scanning electron microscope (SEM) characterisation along with a local energy dispersive X-ray spectroscopic (EDX) analysis of the samples and atomic absorption spectrometry (AAS) analysis of the electrolyte revealed a preferential Fe dissolution and the passive nature of the Nb. The results demonstrate that the phases present in the alloys strongly depend on the production and heat treatment history of the sample. SEM micrograph of (A) Fe-15Al-10Nb and (B) Fe-26Al-4Nb after anodisation in 0.4 M borate buffer. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. 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.

  11. 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.

  12. Electronic parameters of Sr2Nb2O7 and chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, V.V.; Grivel, Jean-Claude; Korotkov, A.S.

    2008-01-01

    /2)) and Delta(O-Sr) = BE(O 1s)-BE(Sr 3d(5/2)), were used to characterize the valence electron transfer on the formation of the Nb-O and Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and earlier published structural and XPS data for other Sr- or Nb......-containing oxide compounds. The new data point for Sr2Nb2O7 is consistent with the previously derived relationship for a set of Nb5+ -niobates that Delta (O-Nb) increases with increasing mean Nb-O bond distance, L(Nb-O). A new empirical relationship between Delta(O-Sr) and L(Sr-O) was also obtained. Interestingly...

  13. Superconductivity in quasi-one-dimensional BaNbS3

    Science.gov (United States)

    Neumeier, J. J.; Smith, M. G.

    2017-11-01

    BaNbS3 is a quasi-one-dimensional metal possessing Nb-Nb chains. Superconductivity was observed at the transition temperature Tc = 0.89 K. Specific heat measurements reveal the bulk nature of the superconductivity, and an energy gap Eg = 0.245(3) meV, which agrees well with BCS theory. The upper critical magnetic field was used to estimate the coherence lengths parallel (ξ∥ = 987(17) Å) and perpendicular (ξ⊥ = 204(12) Å) to the Nb-Nb chains. Despite the anisotropy evident through ξ∥/ξ⊥, the large magnitudes of each reveal that coherence extends over a large enough volume that superconductivity in BaNbS3 can be viewed as isotropic on the scale of tens of Nb-Nb distances.

  14. Electron-microscopy study of the A15 Nb/sub 3/Ge substrate interface

    Energy Technology Data Exchange (ETDEWEB)

    Antonovsky, A.; Toth, L.E.; Bradford, B.; Goldman, A.M.

    1980-02-01

    Electron microscopy has been used to study very thin Nb-Ge films sputtered-deposited onto copper substrates. Micrographs and selected-area electron-diffraction patterns reveal an interface region between the substrate and the first A15 Nb/sub 3/Ge to form. This interface consists of microcrystalline Nb-N-O and a two-phase region consisting of Nb-N-O grains and an unidentifiable tetragonal Nb-Ge phase. The A15 Nb/sub 3/Ge grains which form later in the growth of the film exhibit the same grain size and shape as the Nb-N-O grains. From the results a model for the role of the interface in the initial formation of A15 Nb/sub 3/Ge is proposed.

  15. 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 Nb3Sn 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 Nb3Sn technologies by taking into account their specific operating...

  16. Cost of high-field Nb/sub 3/Sn and NbTi accelerator dipole magnets

    Energy Technology Data Exchange (ETDEWEB)

    Hassenzahl, W.V.

    1982-11-01

    Future high-energy proton accelerators will likely require very high magnetic fields if the size of the accelerator and associated experimental areas are to be limited to dimensions that can be accomodated by the terrain at convenient sites. Two commercially available superconductors can be used to produce magnetic fields of 10T or more. The first is Nb/sub 3/Sn, which can operate in pool boiling helium at 4.4 K. The second is NbTi, which must be cooled to about 1.9 K in superfluid helium. In this paper the costs of 5-cm-bore, 6-m-long magnets made of these materials and operating at fields from 5 to 11 T are compared. At 10 T the capital cost of a NbTi coil operating in superfluid helium is 35% less than the cost of a Nb/sub 3/Sn coil. The cost of the NbTi coil is still 10% less after the differential operating costs that will be incurred over the life of the accelerator are included. The results presented here are a summary of a detailed analysis of these costs given in a separate report.

  17. Preparation and characterization of biocompatible Nb-C coatings

    Energy Technology Data Exchange (ETDEWEB)

    Braic, M.; Braic, V.; Balaceanu, M. [National Institute for Optoelectronics, 409 Atomistilor, Magurele (Romania); Vladescu, A., E-mail: alinava@inoe.r [National Institute for Optoelectronics, 409 Atomistilor, Magurele (Romania); Zoita, C.N. [National Institute for Optoelectronics, 409 Atomistilor, Magurele (Romania); Titorencu, I. [Petru Poni Institute of Macromolecular Chemistry, 41A, Aleea G.G.Voda, Iasi (Romania); Institute of Cellular Biology and Pathology ' Nicolae Simionescu' , 8 B.P. Hasdeu, Bucharest (Romania); Jinga, V. [Petru Poni Institute of Macromolecular Chemistry, 41A, Aleea G.G.Voda, Iasi (Romania); Miculescu, F. [University Politehnica of Bucharest, 313 Sp. Independentei, Bucharest (Romania)

    2011-04-01

    Nb-C composite films, obtained by DC magnetron sputtering method, were investigated as possible candidates for the protective layers used in medical implants. Coatings of different carbon/niobium ratios were prepared and analyzed for elemental and phase composition, crystallographic structure, texture, corrosion behavior, and cell viability. The coating with the highest C/Nb ratio ({approx} 1.9) was found to have a nanocomposite structure, in which NbC nanocrystalline phase coexists with an amorphous a-C one. The coated samples exhibited an improved corrosion resistance as compared with the Ti alloy. Cell viability measurements proved that human osteosarcoma cells are adherent to the coating surfaces, the highest viability being found for the film with the highest carbon content.

  18. Advanced alumina composites reinforced with Nb-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, R.; Klassen, T.; Bormann, R. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung; Dickau, B.; Bartels, A.; Bormann, R. [Dept. of Material Science and Technology, Technical Univ. Hamburg-Harburg, Hamburg (Germany); Gaertner, F. [Inst. of Mechanical Engineering, Univ. of the Federal Armed Forces, Hamburg (Germany)

    2002-03-01

    New (inter)metallic-ceramic composites for high-temperature structural and functional applications are prepared via high-energy ball milling of Nb, Al and Al{sub 2}O{sub 3}. During compaction by pressureless sintering, dense alumina aluminide alloys are formed that consist of interconnected networks of the ceramic and the (inter)metallic phases. Mechanical properties, wear resistance and resistivity measurements of the system Nb-Nb{sub 3}Al/Al{sub 2}O{sub 3} show that these composites have superior damage tolerance, i.e. high fracture toughnesses and bending strengths of about a factor 4 over monolithic Al{sub 2}O{sub 3}. The wear resistance has been determined to be in the range of galvanic Cr-coatings. Owing to the good wear resistance and the high damage tolerance, these composites are promising for automotive applications, such as valves or brake discs. (orig.)

  19. Abnormal phase transition in BiNbO{sub 4} powders prepared by a citrate method

    Energy Technology Data Exchange (ETDEWEB)

    Zhai Haifa; Qian Xu; Kong Jizhou [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Li Aidong, E-mail: adli@nju.edu.cn [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Gong Youpin [Nano Device and Material Division, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123 (China); Li Hui; Wu Di [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2011-10-20

    Highlights: > Pure BiNbO{sub 4} powders were successfully prepared by a citrate method using home-made Nb-citrate (Nb-CA) aqueous solution. > Abnormal phase transition from {beta}-BiNbO{sub 4} to {alpha}-BiNbO{sub 4} was first observed in BiNbO{sub 4} system. > The synthesis of Low-{beta} can be attributed to the formation of the intermediated phase Bi{sub 5}Nb{sub 3}O{sub 15} and the mechanism of the phase transition from {beta}-BiNbO{sub 4} to {alpha}-BiNbO{sub 4} was proposed. > We identified that the stress in pellet format can accelerate the phase transition compared with powder samples. - Abstract: Triclinic {beta}-BiNbO{sub 4} prepared below 750 deg. C and above 1040 deg. C (denoted as Low-{beta} and High-{beta}, respectively) and pure orthorhombic {alpha}-BiNbO{sub 4} at 900 deg. C were successfully derived from a citrate method and the phase transition from {beta}-BiNbO{sub 4} to {alpha}-BiNbO{sub 4} was first observed in BiNbO{sub 4} powders. This phenomenon proves that the abnormal phase transition from {beta}-BiNbO{sub 4} to {alpha}-BiNbO{sub 4} exists in BiNbO{sub 4} powder system. The synthesis of Low-{beta} powders can be attributed to the formation of the intermediate phase of Bi{sub 5}Nb{sub 3}O{sub 15} by the citrate method. With increasing temperature, the Low-{beta} phase gradually turns into {alpha}-BiNbO{sub 4} due to the thermodynamically metastable state of Low-{beta}. We also identified that the stress in pellet format can accelerate the phase transition from Low-{beta} to {alpha} phase of BiNbO{sub 4} in comparison with powder samples. It brings us new understanding of the BiNbO{sub 4} system and also provides a simple way to obtain BiNbO{sub 4} for microwave and photocatalytic applications.

  20. Assessment on the structural, elastic and electronic properties of Nb3Ir and Nb3Pt: A first-principles study

    Directory of Open Access Journals (Sweden)

    Xianfeng Li

    2017-06-01

    Full Text Available The pressure dependent behaviors on the structural, elastic and electronic properties of the A15 structure Nb3Ir and Nb3Pt were studied using first-principles calculations based on the density functional theory within generalized gradient approximation and local density approximation methods. Initially, the optimized lattice constants of Nb3Ir and Nb3Pt are consistent with the available experimental and theoretical results. Furthermore, Nb3Ir is found to be more thermodynamically stable than Nb3Pt due to its lower formation enthalpy and higher melting temperature. In addition, the elastic constants of Nb3Ir and Nb3Pt show an increasing tendency, and keep mechanically stable structures under pressures to 40 GPa. Besides, the increasing Cauchy pressures and B/G values have indicated that higher pressures can improve their ductility in both Nb3Ir and Nb3Pt. Finally, the pressure-dependent behaviors on the density of states, Mulliken charges and bond lengths are discussed for both compounds.

  1. Contrasting ion-association behaviour of Ta and Nb polyoxometalates.

    Science.gov (United States)

    Fullmer, Lauren B; Molina, Pedro I; Antonio, Mark R; Nyman, May

    2014-11-07

    Small-angle X-ray scattering (SAXS) studies of aqueous [Ta6O19](8-) compared to prior studies of aqueous [Nb6O19](8-) reveals key differences in behaviour, which is likely at the root of the difficultly in developing polyoxotantalate chemistry. Specifically, where contact ion-pairing dominates between [Nb6O19](8-) and its counterions, solvent-separated ion-pairing between [Ta6O19](8-) and its counterions has been unveiled in the current study.

  2. Selective Laser Melting of Ti-45Nb Alloy

    Directory of Open Access Journals (Sweden)

    Holger Schwab

    2015-04-01

    Full Text Available Ti-45Nb is one of the potential alloys that can be applied for biomedical applications as implants due to its low Young’s modulus. Ti-45Nb (wt.% gas atomized powders were used to produce bulk samples by selective laser melting with three different parameter sets (energy inputs. A β-phase microstructure consisting of elliptical grains with an enriched edge of titanium was observed by scanning electron microscopy and X-ray diffraction studies. The mechanical properties of these samples were evaluated using hardness and compression tests, which suggested that the strength of the samples increases with increasing energy input within the range considered.

  3. Metastable bcc phase formation in the Nb-Cr system

    Energy Technology Data Exchange (ETDEWEB)

    Thoma, D.J.; Schwarz, R.B. [Los Alamos National Lab., NM (United States); Perepezko, J.H. [Wisconsin Univ., Madison, WI (United States). Dept. of Materials Science and Engineering; Plantz, D.H. [Coast Guard Academy, New London, CT (United States). Dept. of Engineering

    1993-08-01

    Extended metastable bcc solid solutions of Nb-Xat.%Cr (X = 35, 50, 57, 77, 82, and 94) were synthesized by two-anvil splat-quenching. In addition, bcc (Nb-67at.%Cr) was prepared by mechanically alloying mixtures of niobium and chromium powders. The lattice parameters were measured by X-ray diffraction and the Young`s moduli were measured by low-load microindentation. The composition dependence of the lattice parameters and elastic moduli show a positive deviation with respect to a rule of mixtures. During continuous heating at 15C/min., the metastable precursor bcc phases decomposed at temperatures above 750C to uniformly refined microstructures.

  4. Nb-based MXenes for Li-ion battery applications

    KAUST Repository

    Zhu, Jiajie

    2015-11-16

    Li-ion batteries depend critically on the stability and capacity of the electrodes. In this respect the recently synthesized two-dimensional MXenes are promising materials, as they combine an excellent Li-ion capacity with very high charging rates. We employ density functional theory to investigate the impact of Li adsorption on the structural and electronic properties of monolayer Nb2C and Nb2CX2. The Li ions are predicted to migrate easily on the pristine MXene due to a diffusion barrier of only 36 meV, whereas larger diffusion barriers are obtained for the functionalized MXenes.

  5. Strand critical current degradation in $Nb_{3}$ Sn Rutherford cables

    CERN Document Server

    Barzi, E; Higley, H C; Scanlan, R M; Yamada, R; Zlobin, A V

    2001-01-01

    Fermilab is developing 11 Tesla superconducting accelerator magnets based on Nb/sub 3/Sn superconductor. Multifilamentary Nb/sub 3/Sn strands produced using the modified jelly roll, internal tin, and powder-in-tube technologies were used for the development and test of the prototype cable. To optimize the cable geometry with respect to the critical current, short samples of Rutherford cable with packing factors in the 85 to 95% range were fabricated and studied. In this paper, the results of measurements of critical current, n-value and RRR made on the round virgin strands and on the strands extracted from the cable samples are presented. (5 refs).

  6. Aluminum-stabilized Nb/sub 3/Sn superconductor

    Science.gov (United States)

    Scanlan, R.M.

    1984-02-10

    This patent discloses an aluminum-stabilized Nb/sub 3/Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb/sub 3/Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials.

  7. Aluminum-stabilized Nb[sub 3]Sn superconductor

    Science.gov (United States)

    Scanlan, R.M.

    1988-05-10

    Disclosed are an aluminum-stabilized Nb[sub 3]Sn superconductor and process for producing same, utilizing ultrapure aluminum. Ductile components are co-drawn with aluminum to produce a conductor suitable for winding magnets. After winding, the conductor is heated to convert it to the brittle Nb[sub 3]Sn superconductor phase, using a temperature high enough to perform the transformation but still below the melting point of the aluminum. This results in reaction of substantially all of the niobium, while providing stabilization and react-in-place features which are beneficial in the fabrication of magnets utilizing superconducting materials. 4 figs.

  8. Defect and electrical transport properties of Nb-doped SrTiO3

    DEFF Research Database (Denmark)

    Blennow Tullmar, Peter; Hagen, Anke; Kammer Hansen, Kent

    2008-01-01

    species that is reduced to a lower oxidation state (from Ti4+ to Ti3+). The pre-edge fine structure (PEFS) from the XANES results indicated that Nb improved the overlap of the Ti atomic orbitals and thereby provided one more explanation for the positive effect of Nb on the electronic conductivity of Nb...

  9. Tensile Properties of the Individual Phases in Unreacted Multifilament Nb3Sn Wires

    CERN Document Server

    Scheuerlein, C; Fedelich, B; Finn, M; Griepentrog, M; El-Kallassi, P; Lecouturier, F; Oberli, L; Rehmer, B; Sgobba, Stefano; Thilly, L; Vidal, V

    2007-01-01

    The room temperature elastic and plastic properties under uniaxial tensile loading of the different phases of an un-reacted, internal-tin process, Nb3Sn wire have been determined by tensile tests of whole wires and of extracted Ta, Nb and Nb alloy filaments, as well as by indentation hardness measurements in metallographic wire cross sections.

  10. Sending servers to Morocco

    CERN Multimedia

    Joannah Caborn Wengler

    2012-01-01

    Did you know that computer centres are like people? They breathe air in and out like a person, they have to be kept at the right temperature, and they can even be organ donors. As part of a regular cycle of equipment renewal, the CERN Computer Centre has just donated 161 retired servers to universities in Morocco.   Prof. Abdeslam Hoummada and CERN DG Rolf Heuer seeing off the servers on the beginning of their journey to Morocco. “Many people don’t realise, but the Computer Centre is like a living thing. You don’t just install equipment and it runs forever. We’re continually replacing machines, broken parts and improving things like the cooling.” Wayne Salter, Leader of the IT Computing Facilities Group, watches over the Computer Centre a bit like a nurse monitoring a patient’s temperature, especially since new international recommendations for computer centre environmental conditions were released. “A new international s...

  11. Send flere bureaukrater

    DEFF Research Database (Denmark)

    Veicherts, Nicolas Teodors

    2007-01-01

    Afghanistan. Det er ikke kun Taleban, der er fjenden. Fraværet af en markant og effektiv civil indsats for genopbygning og socioøkonomisk fremgang kan medføre, at den militære indsats viser sig Forgæves....

  12. Chalcogenoether complexes of Nb(v) thio- and seleno-halides as single source precursors for low pressure chemical vapour deposition of NbS2 and NbSe2 thin films.

    Science.gov (United States)

    Chang, Yao-Pang; Hector, Andrew L; Levason, William; Reid, Gillian

    2017-08-14

    NbSCl3 was obtained via reaction of NbCl5 with S(SiMe3)2 in anhydrous CH2Cl2, whilst in MeCN solution the same reaction gives [NbSCl3(MeCN)2]. [NbSeCl3(MeCN)2] was obtained similarly from NbCl5 with Se(SiMe3)2. The chalcogenoether complexes, [NbSCl3(ER2)] (E = S: R = Me, nBu; E = Se: R = nBu), were obtained from reaction of NbCl5, ER2 and S(SiMe3)2 in CH2Cl2. The structure of the [Nb2S2Cl6(SMe2)2] reveals a Cl-bridged dimer with the SMe2 ligands disposed syn. The Cl bridges are highly asymmetric, with the long Nb-Cl bond trans Nb[double bond, length as m-dash]S. The complexes, [NbSCl3(L-L)] (L-L = MeSCH2CH2SMe, MeS(CH2)3SMe, iPrSCH2CH2SiPr, MeSe(CH2)3SeMe and nBuS(CH2)3SnBu), were obtained from reaction of L-L with preformed [NbSCl3(MeCN)2]. The structures of the Me-substituted complexes reveal distorted octahedral monomers with the neutral ligands trans to S/Cl. Solution 1H and 77Se{1H} NMR data showed that the neutral ligands are partially dissociated and undergoing fast exchange at ambient temperatures in CH2Cl2 solution, consistent with weak Lewis acidity for NbSCl3. The complexes containing nBu-substituted ligands have been used as single source precursors for low pressure chemical vapour deposition (CVD) of 3R-NbS2 thin films. 2H-NbSe2 thin films were also obtained via low pressure CVD using [NbSe2Cl3(SenBu2)]. The thin films were characterised by grazing incidence and in-plane XRD, pole figure analysis, scanning electron microscopy and energy dispersive X-ray analysis.

  13. Afamelanotide and narrowband UV-B phototherapy for the treatment of vitiligo: a randomized multicenter trial.

    Science.gov (United States)

    Lim, Henry W; Grimes, Pearl E; Agbai, Oma; Hamzavi, Iltefat; Henderson, Marsha; Haddican, Madelaine; Linkner, Rita V; Lebwohl, Mark

    2015-01-01

    Narrowband UV-B (NB-UV-B) phototherapy is used extensively to treat vitiligo. Afamelanotide, an analogue of α-melanocyte-stimulating hormone, is known to induce tanning of the skin. To evaluate the efficacy and safety of combination therapy for generalized vitiligo consisting of afamelanotide implant and NB-UV-B phototherapy. This study was performed in 2 academic outpatient dermatology centers and 1 private dermatology practice. We enrolled men and women 18 years or older with Fitzpatrick skin phototypes (SPTs) III to VI and a confirmed diagnosis of nonsegmental vitiligo that involved 15% to 50% of total body surface area. Vitiligo was stable or slowly progressive for 3 months. Patients were randomized to combination therapy (n = 28) vs NB-UV-B monotherapy (n = 27). After 1 month of NB-UV-B phototherapy, 16 mg of afamelanotide was administered subcutaneously to the combination therapy group monthly for 4 months while NB-UV-B phototherapy continued; the other group continued to receive NB-UV-B monotherapy. Narrowband UV-B monotherapy vs combined NB-UV-B phototherapy and afamelanotide. Response on the Vitiligo Area Scoring Index and Vitiligo European Task Force scoring system. Response in the combination therapy group was superior to that in the NB-UV-B monotherapy group (P afamelanotide implant and NB-UV-B phototherapy resulted in clinically apparent, statistically significant superior and faster repigmentation compared with NB-UV-B monotherapy. The response was more noticeable in patients with SPTs IV to VI. clinicaltrials.gov Identifier: NCT01430195.

  14. A self-aligned nano-fabrication process for vertical NbN-MgO-NbN Josephson junctions

    Science.gov (United States)

    Grimm, A.; Jebari, S.; Hazra, D.; Blanchet, F.; Gustavo, F.; Thomassin, J.-L.; Hofheinz, M.

    2017-10-01

    We present a new process for fabricating vertical NbN-MgO-NbN Josephson junctions using self-aligned silicon nitride spacers. It allows for a wide range of junction areas from 0.02 to several 100 μm2. At the same time, it is suited for the implementation of complex microwave circuits with transmission line impedances ranging from 1 {{k}}{{Ω }}. The constituent thin films and the finished junctions are characterized. The latter are shown to have high gap voltages (> 4 {mV}) and low sub-gap leakage currents.

  15. Giant polyniobate clusters based on [Nb7O22]9- units derived from a Nb6O19 precursor.

    Science.gov (United States)

    Niu, Jingyang; Ma, Pengtao; Niu, Hongyu; Li, Jie; Zhao, Junwei; Song, You; Wang, Jingping

    2007-01-01

    Rational self-assembly of hexaniobate Lindqvist-type precursor [HNb6O19]7- with soluble Cu2+ salts utilizing different strategies produces a series of giant polyniobate clusters, namely, (H2en)1.25[Cu(en)2(H2O)]2Cl4[Nb24O72H21.5]7 H2O (1; en: ethylenediamine), [Cu(en)2]3[Cu(en)2(H2O)]9[{H2Nb6O19} subset{[({KNb24O72H10.25}{Cu(en)2})2{Cu3(en)3(H2O)3}{Na1.5Cu1.5(H2O)8}{Cu(en)2}4]6}]144 H2O (2), K12Na4[H23NaO8Cu24(Nb7O22)8]106 H2O (3), and K16Na12[H9Cu25.5O8(Nb7O22)8] 73.5 H2O (4). Their structures were determined and further characterized by single-crystal X-ray diffraction analysis, IR and Raman spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Structural analyses reveal that compound 2 comprises a giant capsule anion based on a wheel-shaped cluster encapsulating a Lindqvist diprotonated cluster [H2Nb6O19]6- unit, and forms a honeycomb-like structure with the inclusion of Lindqvist-type anions [H2Nb6O19]6- in the holes, whereas 3 and 4 represent an unprecedented giant cube-shaped framework. All the compounds are built from [Nb7O22]9- fundamental building blocks. Solution Raman spectroscopy studies of 2 and 3 reveal that the solid-state structures of these polyniobate cluster anions disassemble and exist in the form of the [Nb6O19]8- unit in solution. Magnetic susceptibility measurement of 3 shows antiferromagnetic coupling interactions between CuII ions with the spin-canting phenomenon.

  16. Fabrication and properties of Nb/Al, Al sub ox /Nb Josephson tunnel junctions with a double-oxide barrier

    Energy Technology Data Exchange (ETDEWEB)

    Houwman, E.P.; Veldhuis, D.; Flokstra, J.; Rogalla, H. (University of Twente, Faculty of Applied Physics, P.O.B. 217, 7500 AE Enschede, The Netherlands (NL))

    1990-02-15

    High-quality Nb/Al, Al{sub ox}/Nb Josephson tunnel junctions using double-oxide layers as barriers have been fabricated. The critical current density is controlled by the thickness of the second Al layer. This layer has to be oxidized completely through in order to obtain high-quality junctions. Typically, gap voltages of 2.8--3.0 mV and {ital V}{sub {ital m}} up to 70 mV at 4.2 K were obtained.

  17. ASSESSMENT OF RIP-V1 AND OSPF-V2 PROTOCOL WITH CONSIDERATION OF CONVERGENCE CRITERIA AND SENDING PROTOCOLS TRAFFIC

    Directory of Open Access Journals (Sweden)

    Hamed Jelodar

    2014-03-01

    Full Text Available Routing Protocols are underlying principles in networks like internet, transport and mobile. Routing Protocols include a series of rules and algorithms that consider routing metric and select the best way for sending healthy data packets from origin to destination. Dynamic routing protocol compatible to topology has a changeable state. RIP and OSPF are dynamic routing protocol that we consider criteria like convergence and sending protocols traffic assessment RIP first version and OSPF second version. By the test we have done on OPNET stimulation we understood that the OSPF protocol was more efficient than RIP protocol.

  18. 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.

  19. Predictors of discontinuation of benzodiazepine prescription after sending a letter to long-term benzodiazepine users in family practice.

    Science.gov (United States)

    Gorgels, W J M J; Oude Voshaar, R C; Mol, A J J; van de Lisdonk, E H; van Balkom, A J L M; Breteler, M H M; van den Hoogen, H J M; Mulder, J; Zitman, F G

    2006-02-01

    Predictors of benzodiazepine discontinuation after sending a discontinuation letter by the family practitioner have not been established sufficiently. To identify predictors of short- and long-term discontinuation of benzodiazepine use and relapse in use after a minimal intervention with a discontinuation letter followed by an offer for an evaluation consultation. Predictors of benzodiazepine discontinuation and relapse in use were studied by logistic regression analysis and survival analysis within a family practice population of long-term benzodiazepine users (n = 1707) addressed by a discontinuation letter and followed for 21 months. A lower baseline prescription, a shorter duration of use, male gender and use of an agent with a half-life time discontinuation in the short (6 months) and long term (21 months). Multiple agent use at baseline, use of antidepressants at 6 months and benzodiazepine type (anxiolytic/hypnotic) at baseline predicted relapse. Attendance at an evaluation consultation 3 months after the letter was sent was not predictive of discontinuation or relapse. Amount of baseline use and duration of use are the main determinative characteristics of successful discontinuation. The discontinuation letter intervention is suitable for use with a broad group of long-term benzodiazepine users in family practice and can be used as a first step within a stepped care approach to decrease long-term benzodiazepine use.

  20. TOD-Tree: Task-Overlapped Direct Send Tree Image Compositing for Hybrid MPI Parallelism and GPUs.

    Science.gov (United States)

    Grosset, A V Pascal; Prasad, Manasa; Christensen, Cameron; Knoll, Aaron; Hansen, Charles

    2017-06-01

    Modern supercomputers have thousands of nodes, each with CPUs and/or GPUs capable of several teraflops. However, the network connecting these nodes is relatively slow, on the order of gigabits per second. For time-critical workloads such as interactive visualization, the bottleneck is no longer computation but communication. In this paper, we present an image compositing algorithm that works on both CPU-only and GPU-accelerated supercomputers and focuses on communication avoidance and overlapping communication with computation at the expense of evenly balancing the workload. The algorithm has three stages: a parallel direct send stage, followed by a tree compositing stage and a gather stage. We compare our algorithm with radix-k and binary-swap from the IceT library in a hybrid OpenMP/MPI setting on the Stampede and Edison supercomputers, show strong scaling results and explain how we generally achieve better performance than these two algorithms. We developed a GPU-based image compositing algorithm where we use CUDA kernels for computation and GPU Direct RDMA for inter-node GPU communication. We tested the algorithm on the Piz Daint GPU-accelerated supercomputer and show that we achieve performance on par with CPUs. Last, we introduce a workflow in which both rendering and compositing are done on the GPU.

  1. Sending and Receiving Text Messages with Sexual Content: Relations with Early Sexual Activity and Borderline Personality Features in Late Adolescence.

    Science.gov (United States)

    Brinkley, Dawn Y; Ackerman, Robert A; Ehrenreich, Samuel E; Underwood, Marion K

    2017-05-01

    This research examined adolescents' written text messages with sexual content to investigate how sexting relates to sexual activity and borderline personality features. Participants (N = 181, 85 girls) completed a measure of borderline personality features prior to 10th grade and were subsequently given smartphones configured to capture the content of their text messages. Four days of text messaging were micro-coded for content related to sex. Following 12th grade, participants reported on their sexual activity and again completed a measure of borderline personality features. Results showed that engaging in sexting at age 16 was associated with reporting an early sexual debut, having sexual intercourse experience, having multiple sex partners, and engaging in drug use in combination with sexual activity two years later. Girls engaging in sex talk were more likely to have had sexual intercourse by age 18. Text messaging about hypothetical sex in grade 10 also predicted borderline personality features at age 18. These findings suggest that sending text messages with sexual content poses risks for adolescents. Programs to prevent risky sexual activity and to promote psychological health could be enhanced by teaching adolescents to use digital communication responsibly.

  2. D-SEND#2搭載カメラの検討と試験結果

    OpenAIRE

    高戸谷, 健; 平野, 義鎭; Takatoya, Takeshi; Hirano, Yoshiyasu

    2016-01-01

    ソニックブームを半減させる技術の獲得に向けて小型の無人機供試体を用いた低ソニックブーム設計概念実証プロジェクトを進め,第二回飛行試験を2015年7月24日に実施した.D-SEND#2 供試体に搭載した搭載カメラについて仕様を定め,候補を選定し,確認試験を行い搭載カメラの構成を決定した.同時に供試体のプライムメーカのFHIやJAXA内との調整を実施して,搭載カメラを載せる位置やカメラカバーの形状,作業手順などを順次決めていった.第二回飛行試験においては,放球から着地までの映像を取得することができた成果について報告する....

  3. Sending-Country Violence & Receiving-Country Discrimination: Effects on the Health of Colombian Refugees in Ecuador

    Science.gov (United States)

    Shedlin, Michele G.; Decena, Carlos U.; Noboa, Hugo; Betancourt, Óscar

    2013-01-01

    BACKGROUND This study explored factors affecting the health and well being of recent refugees from Colombia in Ecuador. Data collection focused on how sending-country violence and structural violence in a new environment affect immigrant health vulnerability and risk behaviors. METHODS A qualitative approach included ethnographic observation, media content analysis, focus groups, and individual interviews with refugees (N=137). The focus groups (5) provided perspectives on the research domains by sex workers; drug users; male and female refugees; and service providers. RESULTS Social and economic marginalization are impacting the health and well being of this growing refugee population. Data illustrate how stigma and discrimination affect food and housing security, employment and health services, and shape vulnerabilities and health risks in a new receiving environment. DISCUSSION Widespread discrimination in Ecuador reflects fears, misunderstanding, and stereotypes about Colombian refugees. For this displaced population, the sequelae of violence, combined with survival needs and lack of support and protections, shape new risks to health and well-being. PMID:23377565

  4. Circular Migration by Mexican Female Sex Workers Who are Injection Drug Users: Implications for HIV in Mexican Sending Communities

    Science.gov (United States)

    Ojeda, Victoria D.; Burgos, José Luis; Hiller, Sarah P.; Lozada, Remedios; Rangel, Gudelia; Vera, Alicia; Artamonova, Irina; Rodriguez, Carlos Magis

    2013-01-01

    Background Circular migration and injection drug use increase the risk of HIV transmission in sending communities. We describe female sex workers who are injection drug users’ (FSW-IDUs) circular migration and drug use behaviors. Methods Between 2008-2010, 258 migrant FSW-IDUs residing in Tijuana and Ciudad Juarez, Mexico responded to questionnaires. Results 24% of FSW-IDUs were circular migrants. HIV prevalence was 3.3% in circular migrants and 6.1% in non-circular migrants; 50% of circular and 82% of non-circular migrants were unaware of their HIV infection. Among circular migrants, 44% (n=27) consumed illicit drugs in their birthplace; 70% of these (n=20) injected drugs and one-half of injectors shared injection equipment in their birthplace. Women reporting active social relationships were significantly more likely to return home. Discussion Circular migrant FSW-IDUs exhibit multiple HIV risks and opportunities for bridging populations. Regular HIV testing and treatment and access to substance use services is critical for FSW-IDUs and their sexual/drug-using contacts. PMID:21833727

  5. "NB festivali" mõistavad kõik / Katrin Nielsen

    Index Scriptorium Estoniae

    Nielsen, Katrin

    2005-01-01

    15. okt. algab Pärnus Assitej Eesti Keskuse korraldatud rahvusvaheline teatrifestival "NB festival 2005", kus professionaalsed teatritrupid üheksast riigist annavad kokku 17 etendust lastele ja lapsemeelsetele. Ära toodud festivali kava ja lühike tutvustus iga etenduse kohta

  6. Dendritic flux avalanches in superconducting Nb3Sn films

    NARCIS (Netherlands)

    Rudnev, IA; Antonenko, SV; Shantsev, DV; Johansen, TH; Primenko, AE

    2003-01-01

    The penetration of magnetic flux into a thin superconducting film of Nb3Sn with critical temperature 17.8 K and critical current density 6 MA/cm(2) was visualized using magneto-optical imaging. Below 8 K an avalanche-like flux penetration in form of big and branching dendritic structures was

  7. Elasto-plastic properties of Cu-Nb nanolaminate

    Science.gov (United States)

    Betekhtin, V. I.; Kolobov, Yu. R.; Kardashev, B. K.; Golosov, E. V.; Narykova, M. V.; Kadomtsev, A. G.; Klimenko, D. N.; Karpov, M. I.

    2012-02-01

    The Young's modulus, internal friction, and microplastic flow stress in Cu-Nb nanolaminate has been determined by an acoustic technique. The influence of high hydrostatic compression (1 GPa) on these elasto-plastic properties of the nanolaminate has been studied.

  8. Experimental adiabatic vortex ratchet effect in Nb films with ...

    Indian Academy of Sciences (India)

    Nb films grown on top of an array of asymmetric pinning centers show a vortex ratchet effect. A net flow of vortices is induced when the vortex lattice is driven by fluctuating forces on an array of pinning centers without reflection symmetry. This effect occurs in the adiabatic regime and it could be mimiced only by reversible DC ...

  9. Electrochemical stability of binary TiNb for biomedical applications

    Science.gov (United States)

    Reyes, K. M.; Kuromoto, N. K.; Alves Claro, A. P. R.; Marino, C. E. B.

    2017-07-01

    The Ti-Nb alloy binary system has been widely studied with regard to biomedical applications due to the high biocompatibility and excellent mechanical properties of the alloys. Regarding physical-chemical stability, Ti-Nb alloys maintain the properties of Ti metal, which is highly resistant to corrosion in aggressive media due to a spontaneous stable oxide layer (TiO2) formed on its surface. The objective of this study was to evaluate the corrosion resistance of the Ti-40Nb alloy in artificial blood. The thermodynamic stability was studied using the open circuit potential technique and the corrosion resistance was assessed by potentiodynamic measurements and electrochemical impedance spectroscopy. The electrochemical results indicated that the Ti-40Nb alloy has high corrosion resistance and good thermodynamic stability, with an OCP of around  -485 mV, and the alloy remained electrochemically stable in potentiodynamic conditions with initial and final potentials of  -1.0 V to  +2.0 Vsce, respectively, in low current densities (~µA cm-2) with an absence of hysteresis, aspure Ti. The results obtained showed that this specific alloy has the potential to be used in biomedical applications.

  10. Poling piezoelectric (K,Na,Li)NbO

    NARCIS (Netherlands)

    Deutz, D.B.; Mascarenhas, N.T.; van der Zwaag, S.; Groen, W.A.

    2017-01-01

    Composites of aligned (K,Na,Li)NbO3 (KNLN) piezoceramic particles in a PDMS polymer matrix are presented as promising materials for flexible sensors and energy harvesters. Their ease of processing is matched with a relatively high damage tolerance and piezoelectric performance at low

  11. Directed motion of vortices in faceted Nb films

    CERN Document Server

    Soroka, A K

    2002-01-01

    Guided motion of vortices in the Nb films on a faceted Al sub 2 O sub 3 substrate is observed. Even and odd components of longitudinal and transverse magnetoresistivities of the samples with different orientation of transport current to the facet ridges are measured. The field inversion was used to separate the even and odd components of the measured magnetoresistivities.

  12. Simultaneous improvement and worsening of vitiligo lesions during the course of NB-UVB phototherapy; vitiligo may not act as one unit.

    Science.gov (United States)

    Anbar, Tag; Abdel-Rahman, Amal; Hegazy, Rehab; El-Khayyat, Mohamed; Ragaie, Maha

    2017-01-01

    Re-pigmentation and stabilization are the two ultimate goals of any re-pigmenting plan designed for vitiligo management. Furthermore, whether the improvement of some vitiligo lesions could be considered a guarantee for a similar response and/or stabilization of the rest of the lesions or not, remains to be clarified. To evaluate the behavior of non-segmental vitiligo (NSV), while on narrow band-ultraviolet B (NB-UVB) phototherapy. 25 patients with stable generalized NSV were included and received NB-UVB twice weekly. For the sake of ensuring accuracy of follow up, up to four lesions were randomly chosen in each patient and regularly measured using the point counting technique. The over-all point counting technique of all included patients showed a significant reduction (18.5 ± 8.4 cm2 to 8.2± 3.1 cm2 ) after 6 months of therapy (p vitiligo during NB-UVB and any of the demographic or clinical data of the patients. NB-UVB is a pillar in the management of vitiligo, however close follow-up of the patient as a whole and his lesions, by both subjective and objective measures are mandatory to detect activity as early as possible, as vitiligo at many times may not act as one unit. This early detection of activity and the subsequent change in the treatment policy may ultimately change the final outcome of treatment. © 2016 Wiley Periodicals, Inc.

  13. 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.

  14. Microstructures and mechanical properties of Ti3Al/Ni-based superalloy joints arc welded with Ti–Nb and Ti–Ni–Nb filler alloys

    Directory of Open Access Journals (Sweden)

    Bingqing Chen

    2014-08-01

    Full Text Available Dissimilar joining of Ti3Al-based alloy to Ni-based superalloy has been carried out using gas tungsten arc (GTA welding technology with Ti–Nb and Ti–Ni–Nb filler alloys. The joint welded with the Ti–Nb filler alloy contained much less interfacial brittle phases than the one using the Ti–Ni–Nb filler alloy. The average room-temperature tensile strength of the joint welded with Ti–Nb was 202 MPa and the strength value of the one welded with Ti–Ni–Nb was 128 MPa. For both fillers, the weak links of the dissimilar joints were the weld/In718 interfaces. The presence of TiNi, TiNi3 and Ni3Nb intermetallic compounds in the joint welded with Ti–Ni–Nb induced microcracks at the weld/In718 interface and deteriorated the mechanical properties of the joint. And the adoption of the Ti–Nb filler alloy decreased the formation tendency of interfacial brittle phases to some extent and thus enhanced the tensile strength of the joint.

  15. Nitridation of Nb surface by nanosecond and femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Ashraf Hassan [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States); Department of Physics, Faculty of Science, Ain Shams University, Cairo 11566 (Egypt); Ozkendir, Osman Murat [Tarsus Technology Faculty, Mersin University, Tarsus 33480 (Turkey); Koroglu, Ulas; Ufuktepe, Yüksel [Department of Physics, Cukurova University, Adana 01330 (Turkey); Elsayed-Ali, Hani E., E-mail: helsayed@odu.edu [Department of Electrical and Computer Engineering and the Applied Research Center, Old Dominion University, Norfolk, VA 23529 (United States)

    2015-01-05

    Highlights: • Laser nitridation of niobium is performed with nanosecond and femtosecond pulses. • Formation of NbN{sub x} with mixed α, β and δ phases was observed. • For femtosecond laser processed samples, laser induced ripple patterns oriented parallel to the beam polarization were formed. • X-ray absorption near edge structure show formation of Nb{sub 2}O{sub 5} on the surface of the samples. - Abstract: Niobium nitride samples were prepared by laser nitridation in a reactive nitrogen gas environment at room temperature using a Q-switched Nd:YAG nanosecond laser and a Ti:sapphire femtosecond laser. The effects of laser fluence on the formed phase, surface morphology, and electronic properties of the NbN{sub x} were investigated. The samples were prepared at different nanosecond laser fluences up to 5.0 ± 0.8 J/cm{sup 2} at fixed nitrogen pressure of ∼2.7 × 10{sup 4} Pa formed NbN{sub x} with mainly the cubic δ-NbN phase. Femtosecond laser nitrided samples were prepared using laser fluences up to 1.3 ± 0.3 mJ/cm{sup 2} at ∼4.0 × 10{sup 4} Pa nitrogen pressure. Laser induced ripple patterns oriented parallel to the beam polarization were formed with spacing that increases with the laser fluence. To achieve a laser-nitrided surface with desired crystal orientation the laser fulence is an important parameter that needs to be properly adjusted.

  16. Investigation on microstructural evolution and hardening mechanism in dilute Zr–Nb binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yang, H.L., E-mail: yanghuilong@tokai.t.u-tokyo.ac.jp [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Matsukawa, Y. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Kano, S. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Duan, Z.G. [Graduate School of Engineering, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Murakami, K. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Abe, H. [Department of Nuclear Engineering, Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Ibaraki 319-1188 (Japan); Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)

    2016-12-01

    In this study, the microstructural changes induced by doping of Nb in Zr were investigated by the combined utilization of electron backscatter diffraction and electron transmission microscopy techniques, followed by the correlated hardening mechanism being elucidated based on the obtained microstructural parameters. Microstructural characterization results revealed that microstructural changes caused by doping of Nb in Zr were mainly embodied via two aspects: reducing the matrix α-Zr grain size and increasing the amount of β-Nb particles. β-phase stabilizing effect, dragging effect and pinning effect introduced and enhanced by Nb addition, worked together to significantly reduce the grain size in Zr–Nb alloys. β-Nb particles were firstly observed in Zr0.5Nb specimen with the fairly low number density of ∼2.0 × 10{sup 18}/m{sup 3}, then this value explosively increased to ∼3.3 × 10{sup 20}/m{sup 3} for Zr2Nb specimen. In addition, hardness was increased with an increase in the Nb content. The hardening contributions from solid solution hardening, grain boundary hardening and precipitation hardening were quantitatively estimated as per the obtained microstructural parameters. Results inferred that solid solution hardening contributed the majority when the Nb atoms were solid dissolved (≤0.5 wt%), whereas the precipitation hardening surpassed any other factors when the β-Nb particles were steadily precipitated (≥1 wt%).

  17. Characterization of different types of Nb-AlO sub x based Josephson tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Adelerhof, D.J.; Houwman, E.P.; Fransen, P.B.M.; Veldhuis, D.; Flokstra, J.; Rogalla, H. (Univ. of Twente, Faculty of Applied Physics, P.O. Box 217, 7500 AE Enschede (NL))

    1991-03-01

    This paper reports on three types of Josephson tunnel junctions, standard Nb/Al,AlO{sub x}/Nb, symmetric Nb/Al,AlO{sub x}/Al/Nb, and Nb/Al,AlO{sub x}/AlO{sub x}/Nb containing a double oxide layer investigated by means of temperature dependent I-V measurements, conductance-voltage measurements, noise analysis, and Auger Electron Spectroscopy scanning across the edge of a sputtered crater profile. In standard junctions frequently small leakage currents have been observed as well as resistance fluctuations, leading to telegraph noise. Both effects can be related to the direct contact between the AlO{sub x} and the Nb counter electrode. In none of the symmetric junctions leakage currents larger than 0.01% of the theoretical maximum critical current have been observed.

  18. Strong Proximity Josephson Coupling in Vertically Stacked NbSe2-Graphene-NbSe2van der Waals Junctions.

    Science.gov (United States)

    Kim, Minsoo; Park, Geon-Hyoung; Lee, Jongyun; Lee, Jae Hyeong; Park, Jinho; Lee, Hyunwoo; Lee, Gil-Ho; Lee, Hu-Jong

    2017-10-11

    A layered two-dimensional superconducting material 2H-NbSe 2 is used to build a van der Waals heterostructure, where a proximity-coupled superconducting order can be induced in the interfacing materials. Vertically stacked NbSe 2 -graphene-NbSe 2 is fabricated using van der Waals interlayer coupling, producing defect-free contacts with a high interfacial transparency. The atomically thin graphene layer allows the formation of a highly coherent proximity Josephson coupling between the two NbSe 2 flakes. The temperature dependence of the junction critical current (I c ) reveals short and ballistic Josephson coupling characteristics that agree with theoretical prediction. The strong Josephson coupling is confirmed by a large junction critical current density of 1.6 × 10 4 A/cm 2 , multiple Andreev reflections in the subgap structure of the differential conductance, and a magnetic-field modulation of I c . This is the first demonstration of strongly proximity-coupled Josephson junctions with extremely clean interfaces in a dry-transfer-stacked van der Waals heterostructure.

  19. Two-Dimensional Haeckelite NbS2 : A Diamagnetic High-Mobility Semiconductor with Nb(4+) Ions.

    Science.gov (United States)

    Ma, Yandong; Kuc, Agnieszka; Jing, Yu; Philipsen, Pier; Heine, Thomas

    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-NbX2 (X=S, Se, Te) are diamagnetic direct-band-gap semiconductors even though the Nb atoms are in the 4+ oxidation state. In contrast, 1S-VX2 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-NbX2 MLs are excellent candidates for optoelectronic applications owing to their small band gaps (between 0.5 and 1 eV). Moreover, 1S-NbS2 shows a particularly high hole mobility of 2.68×10(3)  cm(2)  V(-1)  s(-1) , which is significantly higher than that of MoS2 and comparable to that of WSe2 . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Host-Guest Interactions between Calixarenes and Cp(2)NbCl(2).

    Science.gov (United States)

    Morales, Alexis; Santana, Alberto; Althoff, Gerhard; Melendez, Enrique

    2011-07-01

    The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, (1)H NMR solution and solid state (13)C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp(2)NbCl(2). Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp(2)NbCl(2), a band between 500-850 cm(-1) characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp(2)NbCl(2)) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp(2)NbCl(2)(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp(2)NbCl(2)(OH). Solid State (13)C CP MAS NMR and solution (1)H NMR spectroscopies together with ab-initio results showed that Cp(2)NbCl(2) is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution (1)H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp(2)NbCl(2) in CDCl(3) solution. Cp(2)NbCl(2) is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp(2)NbCl(2) into the cavity.

  1. 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

  2. The influence of oxide on the electrochemical processes in K2NbF7-NaCl-KCl melts

    DEFF Research Database (Denmark)

    Lantelme, F.; Berghoute, Y.; Barner, Jens H. Von

    1995-01-01

    Transient electrochemical techniques showed that in NaCl-KCl melts the reduction of K2NbF7 occurs through atwo-step reaction Nb(V) --> Nb(IV) --> Nb. When oxide ions were introduced, cyclic voltammetry indicated that the wavescorresponding to reduction of the complex NbF72- progressively disappea......Transient electrochemical techniques showed that in NaCl-KCl melts the reduction of K2NbF7 occurs through atwo-step reaction Nb(V) --> Nb(IV) --> Nb. When oxide ions were introduced, cyclic voltammetry indicated that the wavescorresponding to reduction of the complex NbF72- progressively......, appeared at the electrode surface. The present study confirms the high oxygen affinity of niobiumand shows that a careful purification of the electrolyte and feeding materials is required for producing niobium with a lowoxygen content....

  3. 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.

  4. Characterization of Nb hydrides synthesized in high-pressure supercritical water by micro-beam hard X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Soda, Kazuo, E-mail: j45880a@nucc.cc.nagoya-u.ac.jp [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kondo, Hiroki; Kato, Masahiko [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Shiraki, Tatsuhito [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Niwa, Ken; Kusaba, Keiji; Hasegawa, Masashi [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2013-02-15

    Highlights: •Nb hydride specimens were synthesized in high-pressure supercritical water. •Synthesized specimens were characterized by hard X-ray photoelectron spectroscopy. •The synthesized Nb hydrides are covered with several 10 nm thick Nb oxides. •Nb hydrides are formed deep inside the specimens. -- Abstract: We have characterized Nb hydrides synthesized in high-pressure supercritical water by hard X-ray photoelectron spectroscopy. Comparison is made, in particular, of the Nb 2p core level spectra and valence band ones for the Nb hydride specimens in different stages of hydrogenation with those for Nb oxide and metallic references. The Nb 2p core level spectra of the Nb hydride specimens synthesized at relatively low temperature show an intense Nb{sub 2}O{sub 5} component and a shoulder structure, which is attributed to Nb hydrides, at the high binding energy side of a metallic component of the Nb metal. The valence band spectra of the Nb hydride specimens also show a broad band at the binding energy E{sub B} between 5 and 9 eV, which is ascribed mainly to Nb oxides. The present results indicate that the surface of the synthesized Nb hydrides is covered with several 10 nm thick Nb oxides and suggest that the Nb hydrides are formed deep inside the specimens. The Nb 2p chemical shift implies the Nb valence of +1.4 for the synthesized hydride NbH{sub x}.

  5. 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

  6. Difference in charge transport properties of Ni-Nb thin films with native and artificial oxide

    Energy Technology Data Exchange (ETDEWEB)

    Trifonov, A. S., E-mail: trifonov.artem@phys.msu.ru [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 1(2), Leninskie Gory, GSP-1, Moscow 119991 (Russian Federation); Physics Faculty, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Lubenchenko, A. V. [Department of General Physics and Nuclear Fusion, National Research University ' Moscow Power Engineering Institute,' Moscow 111250 (Russian Federation); Polkin, V. I. [National University of Science and Technology “MISiS,” Moscow 119049 (Russian Federation); Pavolotsky, A. B. [Chalmers University of Technology, Göteborg 41296 (Sweden); Ketov, S. V.; Louzguine-Luzgin, D. V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2015-03-28

    Here, we report on the properties of native and artificial oxide amorphous thin film on a surface of an amorphous Ni-Nb sample. Careful measurements of local current-voltage characteristics of the system Ni-Nb / NiNb oxide/Pt, were carried out in contact mode of an atomic force microscope. Native oxide showed n-type conductivity, while in the artificial one exhibited p-type one. The shape of current-voltage characteristic curves is unique in both cases and no analogical behavior is found in the literature. X-ray photoelectron spectroscopy (XPS) measurements were used to detect chemical composition of the oxide films and the oxidation state of the alloy components. Detailed analysis of the XPS data revealed that the structure of natural Ni-Nb oxide film consists of Ni-NbO{sub x} top layer and nickel enriched bottom layer which provides n-type conductivity. In contrast, in the artificial oxide film Nb is oxidized completely to Nb{sub 2}O{sub 5}, Ni atoms migrate into bulk Ni-Nb matrix. Electron depletion layer is formed at the Ni-Nb/Nb{sub 2}O{sub 5} interface providing p-type conductivity.

  7. 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.

  8. Highly Ordered Single Crystalline Nanowire Array Assembled Three-Dimensional Nb3O7(OH) and Nb2O5 Superstructures for Energy Storage and Conversion Applications.

    Science.gov (United States)

    Zhang, Haimin; Wang, Yun; Liu, Porun; Chou, Shu Lei; Wang, Jia Zhao; Liu, Hongwei; Wang, Guozhong; Zhao, Huijun

    2016-01-26

    Three-dimensional (3D) metal oxide superstructures have demonstrated great potentials for structure-dependent energy storage and conversion applications. Here, we reported a facile hydrothermal method for direct growth of highly ordered single crystalline nanowire array assembled 3D orthorhombic Nb3O7(OH) superstructures and their subsequent thermal transformation into monoclinic Nb2O5 with well preserved 3D nanowire superstructures. The performance of resultant 3D Nb3O7(OH) and Nb2O5 superstructures differed remarkably when used for energy conversion and storage applications. The thermally converted Nb2O5 superstructures as anode material of lithium-ion batteries (LiBs) showed higher capacity and excellent cycling stability compared to the Nb3O7(OH) superstructures, while directly hydrothermal grown Nb3O7(OH) nanowire superstructure film on FTO substrate as photoanode of dye-sensitized solar cells (DSSCs) without the need for further calcination exhibited an overall light conversion efficiency of 6.38%, higher than that (5.87%) of DSSCs made from the thermally converted Nb2O5 film. The high energy application performance of the niobium-based nanowire superstructures with different chemical compositions can be attributed to their large surface area, superior electron transport property, and high light utilization efficiency resulting from a 3D superstructure, high crystallinity, and large sizes. The formation process of 3D nanowire superstructures before and after thermal treatment was investigated and discussed based on our theoretical and experimental results.

  9. Zurek-Kibble mechanism for the spontaneous vortex formation in Nb-Al/Al-ox/Nb Josephson tunnel junctions: New theory and experiment

    DEFF Research Database (Denmark)

    Monaco, R.; Mygind, Jesper; Aarøe, Morten

    2006-01-01

    New scaling behavior has been both predicted and observed in the spontaneous production of fluxons in quenched Nb-Al/Al-ox/Nb annular Josephson tunnel junctions (JTJs) as a function of the quench time, tau(Q). The probability f(1) to trap a single defect during the normal-metal-superconductor pha...

  10. 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 Nb3Sn 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 (Nb0.75Cu0....

  11. Nb2©Au6: a molecular wheel with a short Nb 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 Nb triple bond coordinated by an Au6ring and reinforced by σ aromaticity.

    Science.gov (United States)

    Jian, Tian; Cheung, Ling Fung; Czekner, Joseph; Chen, Teng-Teng; Lopez, Gary V; Li, Wei-Li; Wang, Lai-Sheng

    2017-11-01

    We report a photoelectron spectroscopy and high-resolution photoelectron imaging study of a bimetallic Nb 2 Au 6 - cluster. Theoretical calculations, in conjunction with the experimental data, reveal that Nb 2 Au 6 -/0 possess high-symmetry D 6h structures featuring a Nb-Nb axis coordinated equatorially by an Au 6 ring. Chemical bonding analyses show that there are two π bonds and one σ bond in the Nb 2 moiety in Nb 2 ©Au 6 , as well as five totally delocalized σ bonds. The Nb 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 Nb triple bond is strengthened significantly by the delocalized σ bonds, resulting in an extremely short Nb-Nb bond length comparable to the quintuple bond in gaseous Nb 2 . The totally delocalized σ bonding in Nb 2 ©Au 6 is reminiscent of σ aromaticity, representing a new bonding mode in metal-ligand systems. The

  12. Thermite welding of Cu-Nb microcomposite wires

    Energy Technology Data Exchange (ETDEWEB)

    Visniakov, Nikolaj; Mikalauskas, Gediminas; Lukauskaite, Raimonda; Cernasejus, Olegas; Rudzinskas, Vitalijus [Vilnius Gediminas Technical Univ. (Lithuania). Faculty of Mechanics; Skamat, Jelena; Boris, Renata [Vilnius Gediminas Technical Univ. (Lithuania). Inst. of Thermal Insulation

    2017-10-15

    Thermite welding of Cu-Nb microcomposite wires was investigated. Suitable compositions of thermite material and slag were determined from the equation of the exothermic combustion synthesis reaction. The phase compositions of the thermite mixture and slag determined by X-ray diffraction analysis correspond to those assessed from the equation. According to non-destructive radiographic testing, the joint structure does not have welding defects. Microstructural examination of the joint cross-section with scanning electron microscopy showed that the Cu-Nb wire retained its shape and microstructure and only a thin surface layer of wire was melted during welding. The difference in electrical resistances of the conductor and welded joint was below 20 %. The thermite joint can withstand a maximum load equal to 62.5 % of the load-bearing capacity of microcomposite conductor.

  13. Superconductivity and ferromagnetism in nanomaterial NbSe2

    Science.gov (United States)

    Gill, Raminder

    2017-07-01

    Finding of superconductivity (SC) in ultra thin layer of Niobium diselenide (NbSe2) caught the attention of each condensed matter physicist in the era of nanotechnology. The coexistence of SC and magnetism have been a topic of interesting research in solid-state physics since the discovery of superconductivity. Ferromagnetism induced in any compound could destroy superconductivity by disturbing the cooper pairing of electrons of the atoms. The interplay between ferromagnetism (FM) and SC in nanomaterial NBSe2 impressed to study and to know the exact mechanism behind this coexistence which can lead to a very interesting research: superconductivity at room temperature. In this paper, I have theoretically studied the coexistence of SC and FM in NbSe2 and how this material could be useful in finding many high Tc nanomaterials.

  14. Microstructure and Flow Stress of Nanoscale Cu/Nb Multilayers

    Directory of Open Access Journals (Sweden)

    F. Wang

    2013-01-01

    Full Text Available Nanoscale Cu/Nb multilayers with individual layer thicknesses of 2, 5, and 15 nm were prepared by d.c. magnetron sputtering. The cross-sectional morphologies of the multilayers were examined under transmission electron microscopy (TEM as well as high resolution TEM, whilst the flow stresses were measured with nanoindentation. A unique cross-sectional microstructure comprising well-modulated and mixed regions was observed, causing length-scale-independent flow stresses not found in existing studies, and shear bands were absent upon plastic deformation. Built upon this unique microstructure, possible mechanisms underlying the high plastic stability and length-scale-independent flow stresses of Cu/Nb multilayers were discussed in terms of amorphous-crystalline interface and its interaction with both mixed and well-modulated regions.

  15. NbB{sub 2}: a density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Islam, A.K.M.A. [International Islamic University Chittagong, 154/A College Road, Chittagong-4203 (Bangladesh)]. E-mail: azislam46@yahoo.com; Sikder, A.S. [Department of Physics, Rajshahi University, Rajshahi-6205 (Bangladesh); Islam, F.N. [Department of Physics, Rajshahi University, Rajshahi-6205 (Bangladesh)

    2006-02-06

    The ground state properties and electronic structure of NbB{sub 2} are studied by an ab initio density functional method using the gradient-corrected approximation. The structural and bonding properties and pressure effects are discussed and the results compared with other calculations and experiments where available. The five independent elastic constants have been calculated for the first time for NbB{sub 2}. In the absence of experimental data, the results are compared with those of other related diborides. The pressure dependence of T{sub c} is also discussed. The band structure is presented and the bonding nature is analysed using the charge density plot and density of state histogram.

  16. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A. [Oak Ridge National Lab., TN (United States)] [and others

    1996-08-01

    Alloys of Cr-Cr{sub 2}Nb with exceptionally high strength at 1200{degrees}C have been developed. However, these compositions suffer from limited ductility and toughness at room temperature. Despite improvements from processing modifications, as-fabricated defects still limit room temperature mechanical behavior. In contrast, an alloy system with only a small mismatch of the coefficients of thermal expansion of the two phases, Cr-Cr{sub 2}Zr, showed good fabricability. However, these alloys are weaker than Cr-Cr{sub 2}Nb compositions at high temperatures and have poor oxidation resistance. Silicide coatings can provide high-temperature oxidation and sulfidation protection of these alloys. Improvements in room temperature mechanical properties of Laves-phase-strengthened alloys will rely on further development based on increasing the ductility of the matrix phase by impurity control and compositional modifications.

  17. Valence shell charge concentrations at pentacoordinate d0 transition-metal centers: non-VSEPR structures of Me2NbCl3 and Me3NbCl2.

    Science.gov (United States)

    McGrady, G Sean; Haaland, Arne; Verne, Hans Peter; Volden, Hans Vidar; Downs, Anthony J; Shorokhov, Dmitry; Eickerling, Georg; Scherer, Wolfgang

    2005-08-19

    The molecular structures of the monomeric, pentacoordinated methylchloroniobium(IV) compounds Me3NbCl2 and Me2NbCl3 have been determined by gas electron diffraction (GED) and density functional theory (DFT) calculations, and, for Me3NbCl2, by single crystal X-ray diffraction. Each of the molecules is found to have a heavy-atom skeleton in the form of a trigonal bipyramid (TBP) with Cl atoms in the axial positions, in accord with their vibrational spectra. The TBP is somewhat distorted in the case of Me2NbCl3 with the two axial Nb--Cl bonds bent away from the equatorial, slightly shorter Nb--Cl bond. In the case of Me3NbCl2, moreover, the X-ray model suggests structural distortions away from the idealized C3h geometry, in line with the results of quantum chemical calculations. Structure optimizations by DFT calculations and least-squares refinement to the GED data yield the following structural parameters (calcd/exptl; eq=equatorial; ax=axial; distances in A, angles in degrees; average values in brackets): Me3NbCl2, in C(3v) symmetry, Nb--Cl 2.370/2.319(3), Nb--C 2.173/2.152(4), C--H 1.096/1.124(5), angle-spherical NbCH 109.3/105.2(8), angle-spherical ClNbC 92.2/93.3(2), angle-spherical CNbC 119.9/119.7(1); Me2NbCl3, in C(2v) symmetry, Nb--Cl(ax) 2.361/2.304(5), Nb--Cl(eq) 2.321/2.288(9), Nb--C 2.180/2.135(9), C--H 1.094/1.12(1), angle-spherical Cl(ax)NbCl(eq) 98.5/96.5(6), angle-spherical CNbC 121.0/114(2), angle-spherical NbCH 108.9/109(2). The electronic structures of Me2NbCl3 and Me3NbC(2 have been explored by rigorous analysis of both the wavefunction and the topology of the electron density, employing DFT calculations. Hence the structures of these compounds are shown to reflect repulsion between the Nb--C and Nb--Cl bonding electron density and charge concentrations induced by the methyl ligands in the valence shell of the Nb atom and arising mainly from use of Nb(4d) functions in the Nb--C bonds.

  18. Effects of Defects on Hydrogen Diffusion in NbC

    Energy Technology Data Exchange (ETDEWEB)

    Salehinia, Iman, E-mail: isalehinia@niu.edu [Department of Mechanical Engineering, Northern Illinois University, DeKalb, IL 60115 (United States); Mastorakos, Ioannis [Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY 13699 (United States); Zbib, Hussein M. [School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States)

    2017-04-15

    Highlights: • MD simulations are used to study the effects of defects on the H diffusion in NbC. • Buckingham potential is more accurate for diffusion of H atoms than LJ potential. • H diffusion coefficient (D) increases with carbon vacancy concentration. • H diffusion coefficient for 6 Å pore (radius = 6 Å) is as high as that for 20 Å pore. • For small pores, H diffusion coefficient drops notably at elevated temperatures. - Abstract: Exceptional mechanical and physical properties of transition metal carbides and nitrides make them good coating-material candidates for extreme corrosive environments such as oil and natural gas wells. However, existence of small pores, pinholes and columnar structures of these ceramics significantly affect their resistance to corrosion, as pore sites would accelerate the diffusion of corrosive media into the substrate. In this research, molecular dynamics atomistic simulations are employed to investigate the effects of the isolated vacancies and the columnar structure on the diffusion rate of H atoms in NbC single crystal at various temperatures. Diffusion coefficient (D) of H atoms in NbC increased with C vacancy concentration. At elevated temperatures, the trapping effect of Nb vacancies is less effective when C vacancies are also present, as H atoms gain enough energy to jump back and forth between the C vacancies. Atomistic simulations also showed a jump in diffusion coefficient for cylindrical pore size of larger than 3 Å radius. Furthermore, D increased monotonically with temperature up to 1000 K in the presence of cylindrical pores. Further increase in temperature resulted in a drop in the diffusion coefficient for small pores while the large pores only showed a lower increasing trend in diffusion coefficient with the temperature.

  19. Effects of Defects on Hydrogen Diffusion in NbC

    Science.gov (United States)

    Salehinia, Iman; Mastorakos, Ioannis; Zbib, Hussein M.

    2017-04-01

    Exceptional mechanical and physical properties of transition metal carbides and nitrides make them good coating-material candidates for extreme corrosive environments such as oil and natural gas wells. However, existence of small pores, pinholes and columnar structures of these ceramics significantly affect their resistance to corrosion, as pore sites would accelerate the diffusion of corrosive media into the substrate. In this research, molecular dynamics atomistic simulations are employed to investigate the effects of the isolated vacancies and the columnar structure on the diffusion rate of H atoms in NbC single crystal at various temperatures. Diffusion coefficient (D) of H atoms in NbC increased with C vacancy concentration. At elevated temperatures, the trapping effect of Nb vacancies is less effective when C vacancies are also present, as H atoms gain enough energy to jump back and forth between the C vacancies. Atomistic simulations also showed a jump in diffusion coefficient for cylindrical pore size of larger than 3 Å radius. Furthermore, D increased monotonically with temperature up to 1000 K in the presence of cylindrical pores. Further increase in temperature resulted in a drop in the diffusion coefficient for small pores while the large pores only showed a lower increasing trend in diffusion coefficient with the temperature.

  20. Temperature Induced Degradation of Nb Ti/Cu Composite Superconductors

    CERN Document Server

    Scheuerlein, C; Senatore, C; Di Michiel, M; Thilly, L; Gerardin, A; Reluner, B; Oberli, L; Willering, G; Bottura, L

    2009-01-01

    The degradation mechanisms of state-of-the-art Nb-Ti/Cu superconductors are described, based on in-situ synchrotron X-ray diffraction measurements during heat treatment. A quantitative description of the Nb-Ti/Cu degradation in terms of critical current density, Cu stabiliser resistivity and mechanical composite strength is presented. In an applied magnetic field a significant critical current degradation is already observed after a 5-minute 400 °C heat treatment, due to variations of a-Ti precipitate size and distribution within the Nb-Ti alloy filaments. A strong degradation of the strand mechanical properties is observed after several minutes heating above 550 °C, which is also the temperature at which the formation of Cu Ti intermetallic phases is detected. Several minutes heating at 250 °C are sufficient to increase the RRR of the strongly cold work strands inside a Rutherford type cable from about 80 to about 240. Heating for several minutes at 400 °C does not cause a significant conductor degradati...

  1. Design of Nb3Sn Coils for LARP Long Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ferracin, Paolo; Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Ferracin, P.; Caspi, S.; Lietzke, A. F.

    2007-06-01

    The LHC Accelerator Research Program (LARP) has a primary goal to develop, assemble, and test full size Nb{sub 3}Sn quadrupole magnet models for a luminosity upgrade of the Large Hadron Collider (LHC). A major milestone in this development is to assemble and test, by the end of 2009, two 4 m-long quadrupole cold masses, which will be the first Nb{sub 3}Sn accelerator magnet models approaching the length of real accelerator magnets. The design is based on the LARP Technological Quadrupoles (TQ), under development at FNAL and LBNL, with gradient higher than 200 T/m and aperture of 90 mm. The mechanical design will be chosen between two designs presently explored for the TQs: traditional collars and Al-shell based design (preloaded by bladders and keys). The fabrication of the first long quadrupole model is expected to start in the last quarter of 2007. Meanwhile the fabrication of 4 m-long racetrack coils started this year at BNL. These coils will be tested in an Al-shell based supporting structure developed at LBNL. Several challenges have to be addressed for the successful fabrication of long Nb{sub 3}Sn coils. This paper presents these challenges with comments and solutions adopted or under study for these magnets. The coil design of these magnets, including conductor and insulation features, and quench protection studies are also presented.

  2. Design of Nb3Sn coils for LARP long magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, G.; Andreev, N.; Anerella, M.; Barzi, E.; Bossert, R.; Dietderich, D.; Feher, S.; Ferracin, P.; Ghosh, A.; Gourlay, S.; Kashikhin, V.V.; /Fermilab /Brookhaven /LBL, Berkeley /Texas A-M

    2006-08-01

    The LHC Accelerator Research Program (LARP) has a primary goal to develop, assemble, and test full size Nb{sub 3}Sn quadrupole magnet models for a luminosity upgrade of the Large Hadron Collider (LHC). A major milestone in this development is to assemble and test, by the end of 2009, two 4m-long quadrupole cold masses, which will be the first Nb3Sn accelerator magnet models approaching the length of real accelerator magnets. The design is based on the LARP Technological Quadrupoles (TQ), under development at FNAL and LBNL, with gradient higher than 200 T/m and aperture of 90 mm. The mechanical design will be chosen between two designs presently explored for the TQs: traditional collars and Al-shell based design (preloaded by bladders and keys). The fabrication of the first long quadrupole model is expected to start in the last quarter of 2007. Meanwhile the fabrication of 4m-long racetrack coils started this year at BNL. These coils will be tested in an Al-shell based supporting structure developed at LBNL. Several challenges have to be addressed for the successful fabrication of long Nb{sub 3}Sn coils. This paper presents these challenges with comments and solutions adopted or under study for these magnets. The coil design of these magnets, including conductor and insulation features, and quench protection studies are also presented.

  3. Influence of Nb+5 doping in Mn–Zn nanoferrites

    Science.gov (United States)

    Sridhar, Ch S. L. N.; Lakshmi, Ch S.; Maha Laxmi, K. S.; Manorama, Sunkara V.; Govindraj, G.; Bangarraju, S.; Potukuchi, D. M.

    2017-11-01

    Structure and morphology by x-ray diffraction and scanning electron microscopy in Mn0.5‑x/2Zn0.5‑x/2Nb x Fe2O4 nano-ferrites, for x, i.e. Nb+5 ranging from 0–0.3 infer cubic and hematite phase structures. Dopant cation complementarily occupy tetrahedral and octahedral sites. Lower x initiates grain formation and further promotes its growth. X-rays and Fourier transform infra-red spectroscopy confirm nanophased structure. Dielectric constant (ε r) and loss decreases, while ac resistivity (ρ) increases with x. Lower loss (Tanδ ~ 10‑3 to 10‑4) and high resistivity (~108 to 109 Ω cm) at 1 MHz ac field indicate preferred utility in high-frequency applications. The influence of grain size is identified by correlative study. Magnetization decreases with doping due to spin canting triggered by diamagnetic dopant. Enhanced field response is attributed to the synthetic route, nanoform, grain size D, spin canting and sintering temperatures. Comparative analysis emphasized the impact of D. Reduced saturation magnetization with x is explained by Yaffet–Kittel angles. Enhanced resistivity by 1–2 orders and less loss vouch for high-frequency applications of Nb+5-doped Mn–Zn nanoferrites as the materials of choice.

  4. 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)

  5. Development of a $Nb_{3}$Sn quadrupole magnet model

    CERN Document Server

    Devred, Arnaud; Gourdin, C; Juster, F P; Peyrot, M; Rey, J M; Rifflet, J M; Streiff, J M; Védrine, P

    2001-01-01

    One possible application of Nb/sub 3/Sn, whose superconducting properties far exceed those of NbTi, is the fabrication of short and powerful quadrupole magnets for the crowded interaction regions of large particle accelerators. To learn about Nb/sub 3/Sn technology and to evaluate fabrication techniques, DAPNIA/STCM at CEA/Saclay has undertaken an R&D program aimed at designing and building a 1 m-long, 56 mm single-aperture quadrupole magnet model. The model relies on the same coil geometry as the LHC arc quadrupole magnets, but has no iron yoke. It is expected to produce a nominal field gradient of 211 T/m at 11870 A. The coils are wound from Rutherford-type cables insulated with quartz fiber tapes, before being heat-treated and vacuum-impregnated with epoxy resin. Laminated, austenitic collars, locked around the coil assembly by means of keys restrain the Lorentz forces. After reviewing the conceptual design of the magnet model, we report on the cable and cable insulation development programs and we pre...

  6. Polaron-mediated low-frequency dielectric anomaly in reduced LiNbO3:Ti

    Science.gov (United States)

    Granzow, Torsten

    2017-07-01

    Measurements of the real and imaginary parts of the dielectric permittivity of reduced Ti-doped lithium niobate reveal a low-frequency dielectric relaxation as well as a strong increase in the conductivity compared to undoped samples. The low-frequency permittivity is increased by about an order of magnitude due to the relaxation. The analysis of the temperature-dependence of the relaxation frequency reveals a thermally activated behavior with an activation energy of Ea = 0.65 eV, which is in agreement with a transition between NbLi4 + small bound polarons and NbNb4 + free polarons. Both low-field ac conductivity and high-field dc conductivity indicate a Poole-Frenkel-type electron hopping mechanism between NbLi4 + sites at low temperature, turning into similar hopping between NbNb4 + at high temperatures.

  7. Growth of ordered lamellar precipitates during nitridation of Nb-10 at.% Ti at 1300 C

    Energy Technology Data Exchange (ETDEWEB)

    Buscaglia, V.; Martinelli, A.; Bottino, C. [Nat. Res. Council, Genoa (Italy). Inst. of Phys. Chem. of Mater.; Musenich, R. [National Institute of Nuclear Physics, via Dodecaneso 33, I-16146 Genoa (Italy)

    1999-02-01

    Growth of three morphologically distinct layers occurs during the parabolic nitridation of Nb-10 at.% Ti at 1300 C under 0.3 bar nitrogen atmosphere. The outermost layer is composed of {delta}-(Nb,Ti)N, the intermediate layer of {beta}-(Nb,Ti){sub 2}N and the innermost layer corresponds to an internal precipitation zone with ordered lamellar precipitates of {beta}-(Nb,Ti){sub 2}N+{beta}-(Nb,Ti). The internal precipitation front advances with parabolic kinetics and the three layers grow by nitrogen inward diffusion. The interlamellar spacing at the precipitation front increases as the reaction time increases. The formation of the lamellar microstructure can be described as a discontinuous precipitation process and the interlamellar spacing can be considered as a measure of the distance over which lateral Nb-Ti interdiffusion occurs in the alloy. (orig.) 25 refs.

  8. 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.

  9. 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.

  10. Effect of trace Ce and B additions on the microstructure of Nb-3Si-22Ti alloys

    Directory of Open Access Journals (Sweden)

    Meiling Wu

    2017-06-01

    Full Text Available The effects of trace Ce and B additions on the microstructure Nb-22Ti-3Si alloys were studied. The microstructure of the alloys was observed by scanning electron microscope (SEM, and their phase compositions were analyzed with X-ray diffraction (XRD and Electro-Probe micro-analyzer (EPMA. The distributions of the elements were detected by Spectrum analyzer. The interface of the phases in the alloys was investigated by transmission electron microscopy (TEM. The results indicated that two phases of Nbss and Nb3Si presented in Nb-22Ti-3Si, Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys. The segregation of Ti at the interface between Nbss and Nb3Si was promoted and the volume fraction of silicides in the alloy increased with the trace B and Ce addition to the Nb-22Ti-3Si alloy respectively. And there was no single and definite orientation relationship between Nb3Si and Nbss in Nb-22Ti-3Si, Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys. Compared with the Nb-22Ti-3Si alloy, the Nbss superlattice structure was found in Nb-22Ti-3Si-0.2Ce and Nb-22Ti-3Si-0.2B alloys.

  11. Planar Metal-Insulator-Metal Diodes Based on the Nb/Nb2O5/X Material System

    Science.gov (United States)

    2013-10-01

    performance of various planar metal–insulator–metal (MIM) tunneling diodes, which are being investigated for use in rectenna devices for energy...which are being investigated for use in rectenna devices for energy harvesting applications. Six cathode materials (M2): Nb, Ag, Cu, Ni, Au, and Pt...insulator–metal (MIM) tunneling diodes, which are being investigated for use in rectenna devices for energy harvesting applications. Six cathode

  12. Bias sputtered NbN and superconducting nanowire devices

    Science.gov (United States)

    Dane, Andrew E.; McCaughan, Adam N.; Zhu, Di; Zhao, Qingyuan; Kim, Chung-Soo; Calandri, Niccolo; Agarwal, Akshay; Bellei, Francesco; Berggren, Karl K.

    2017-09-01

    Superconducting nanowire single photon detectors (SNSPDs) promise to combine near-unity quantum efficiency with >100 megacounts per second rates, picosecond timing jitter, and sensitivity ranging from x-ray to mid-infrared wavelengths. However, this promise is not yet fulfilled, as superior performance in all metrics is yet to be combined into one device. The highest single-pixel detection efficiency and the widest bias windows for saturated quantum efficiency have been achieved in SNSPDs based on amorphous materials, while the lowest timing jitter and highest counting rates were demonstrated in devices made from polycrystalline materials. Broadly speaking, the amorphous superconductors that have been used to make SNSPDs have higher resistivities and lower critical temperature (Tc) values than typical polycrystalline materials. Here, we demonstrate a method of preparing niobium nitride (NbN) that has lower-than-typical superconducting transition temperature and higher-than-typical resistivity. As we will show, NbN deposited onto unheated SiO2 has a low Tc and high resistivity but is too rough for fabricating unconstricted nanowires, and Tc is too low to yield SNSPDs that can operate well at liquid helium temperatures. By adding a 50 W RF bias to the substrate holder during sputtering, the Tc of the unheated NbN films was increased by up to 73%, and the roughness was substantially reduced. After optimizing the deposition for nitrogen flow rates, we obtained 5 nm thick NbN films with a Tc of 7.8 K and a resistivity of 253 μΩ cm. We used this bias sputtered room temperature NbN to fabricate SNSPDs. Measurements were performed at 2.5 K using 1550 nm light. Photon count rates appeared to saturate at bias currents approaching the critical current, indicating that the device's quantum efficiency was approaching unity. We measured a single-ended timing jitter of 38 ps. The optical coupling to these devices was not optimized; however, integration with front-side optical

  13. 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.

  14. 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.

  15. Fabrication techniques and properties of multifilamentary Nb/sub 3/Sn conductors

    Energy Technology Data Exchange (ETDEWEB)

    Suenaga, M; Sampson, W B; Luhman, T S

    1980-01-01

    Various processing techniques for multifilamentary Nb/sub 3/Sn and V/sub 3/Ga are reviewed. The critical current of commercially produced Nb/sub 3/Sn wires manufactured by both the bronze and external diffusion techniques are compared. Critical currents for in situ and powder processed Nb/sub 3/Sn are also included. New developments which promise improvements in J/sub c/ are discussed.

  16. Performance of Nb3Sn quadrupole magnets under localized thermal load

    Energy Technology Data Exchange (ETDEWEB)

    Kashikhin, V.V.; Bossert, r.; Chlachidze, G.; Lamm, M.; Mokhov, N.V.; Novitski, I.; Zlobin, A.V.; /Fermilab

    2009-06-01

    This paper describes the results of design and analyses performed on 120-mm Nb{sub 3}Sn and NbTi quadrupole magnets with parameters relevant for the LHC IR upgrade. A realistic radiation heat load is evaluated in a wide luminosity range and translated into the magnet quench performance. The simulation results are supported by thermal measurements on a 90-mm Nb{sub 3}Sn quadrupole coil.

  17. Current oscillations in ultra-small superconducting Nb-Nb junctions formed by STM at mK temperatures

    Science.gov (United States)

    Dreyer, Michael; Roychowdhury, Anita; Dana, Rami

    2014-03-01

    Using etched Nb STM tips we formed ultra-small tunnel junctions on a Nb crystal at an effective temperature of ~ 200 mK using an Oxford dilution refrigerator. The Nb crystal was prepared in UHV and then transferred into the mK STM. The resulting superconductor-insulator-superconductor (SIS) junction displayed several sub-gap features from multiple Andreev reflections to a zero bias conductance peak. The latter showed features of a Josephson junction in the phase diffusion limit with side structures due to the electrical environment. Upon microwave irradiation the peak split into multiple peaks in accordance with theory, verifying Josephson tunneling. In addition we observed bias dependent oscillations of the tunneling current. The oscillations where recorded at a rate of 10 kS/s while acquiring conventional dI/dV or I(V) spectroscopic curves. Histograms of the current for each bias voltage step then reveal the nature of the oscillation. It ranges from multiple states in certain bias regions through pure oscillations to supercurrent-normal switching. Fourier transform of the current show in some cases a bias dependence of the main frequencies. Possible causes will be discussed.

  18. Randomization tests

    CERN Document Server

    Edgington, Eugene

    2007-01-01

    Statistical Tests That Do Not Require Random Sampling Randomization Tests Numerical Examples Randomization Tests and Nonrandom Samples The Prevalence of Nonrandom Samples in Experiments The Irrelevance of Random Samples for the Typical Experiment Generalizing from Nonrandom Samples Intelligibility Respect for the Validity of Randomization Tests Versatility Practicality Precursors of Randomization Tests Other Applications of Permutation Tests Questions and Exercises Notes References Randomized Experiments Unique Benefits of Experiments Experimentation without Mani

  19. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    Science.gov (United States)

    Stem, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire singlephoton detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize NbxTi1 xN in the high-superconducting-transitiontemperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  20. Dependence of superconducting properties of NbN thin films on sputtering parameters

    Science.gov (United States)

    Khaire, Trupti; Carter, Faustin; Ding, Junjia; Posada, Chrystian; Bender, Amy; Wang, Gensheng; Yefremenko, Volodymyr; Pearson, John; Padin, Steve; Chang, Clarence; Hoffmann, Axel; Novosad, Valentyn; SPT3G Collaboration

    Recently, there has been growing interest in utilizing NbN, TiN, NbTiN thin films in superconducting device applications (e.g. detectors for CMB, mm and sub-mm astronomy). In this work, we have fabricated NbN superconducting thin films by DC reactive magnetron sputtering of Nb in the presence of argon and nitrogen gases. We found that the critical temperature of NbN films is sensitive to various deposition parameters like nitrogen flow rate, target voltage, base pressure, RF substrate bias, and the substrate temperature. By studying each of these factors we have been able to create highly reproducible NbN thin films. We obtained a Tc of 15.25 +/-0.25 K for 300 nm thick NbN film grown on silicon substrate at modest temperature of 250 C in the presence of RF substrate bias. We are also investigating the microwave properties of these NbN films at temperatures well below 50 mK by fabricating quarter wavelength CPW resonators out of NbN and characterizing their frequency shifts and quality factors as functions of temperature and power. In this work we present the results of these analyses. This work was supported by BES-DOE Grant DE-AC02-06CH11357.

  1. Containerless processing and rapid solidification of Nb-Si alloys of hypereutectic composition

    Science.gov (United States)

    Hofmeister, W. H.; Bayuzick, R. J.; Robinson, M. B.; Bertero, G. A.

    1991-01-01

    A combination of bulk undercooling in an electromagnetic levitation apparatus and splat quenching between two copper plates is used to process Nb-Si alloys in order to maximize rapid solidification conditions and minimize the effects of recalescence, with emphasis on the solidification of characteristics of alloys in the 21 to 27 at. pct Si range of composition. SEM and TEM as well as X-ray diffraction are used to characterize the microstructures of the processed samples. In the range of compositions studied, the splat-quenched drops always formed the tetragonal Nb3Si phase directly from the liquid. Drops solidified in the coil were characterized by the presence of the primary intermetallic Nb5Si3 and the absence of both peritectic Nb3Si and the equilibrium eutectic. In these cases, a metastable alpha-Nb + beta-Nb5Si3 eutectic formed. The results are discussed in terms of possible metastable configurations of the Nb-Si phase diagram as well as concepts of nucleation and growth kinetics applied to the Nb3Si and Nb5Si3 intermetallics.

  2. Recent Progress in Application of Internal Oxidation Technique in Nb3Sn Strands

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xingchen [Fermilab; Peng, Xuan [Hyper Tech Research Inc.; Sumption, Michael [Ohio State U.; Collings, E. W. [Ohio State U.

    2016-10-13

    The internal oxidation technique can generate ZrO2 nano particles in Nb3Sn strands, which markedly refine the Nb3Sn grain size and boost the high-field critical current density (Jc). This article summarizes recent efforts on implementing this technique in practical Nb3Sn wires and adding Ti as a dopant. It is demonstrated that this technique can be readily incorporated into the present Nb3Sn conductor manufacturing technology. Powder-in-tube (PIT) strands with fine subelements (~25 µm) based on this technique were successfully fabricated, and proper heat treatments for oxygen transfer were explored. Future work for producing strands ready for applications is proposed.

  3. Phase transformation during aging and resulting mechanical properties of two Ti-Nb-Ta-Zr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Li, S.J.; Yang, R.; Niinomi, M.; Hao, Y.L.; Cui, Y.Y.; Guo, Z.X.

    2005-06-15

    Phase transformations and mechanical properties of both Ti-29Nb-13Ta-4.6Zr and Ti-39Nb-13Ta-4.6Zr (wt-%) alloys were investigated. The microstructure of the 29Nb alloy is sensitive to solution and aging treatment. Ice water quenching from the solution treatment temperature resulted in ({beta}+{alpha}'') microstructure but air or furnace cooling led to a mixture of ({beta}+{omega}). The formation of the orthorhombic {alpha}'' martensite thus suppresses {omega} formation in the ice water quenched 29Nb alloy. Cooling rate from the solution treatment temperature also has a significant effect on the formation of {alpha} and {omega} phases during subsequent isothermal aging below the {omega} start temperature: slow cooling enhances {omega} but depresses {alpha} formation. This cooling rate dependence of aged microstructure was attributed to {alpha}'' martensite acting as precursor of the {alpha} phase, thus providing a low energy path to the precipitation of {alpha} at the expense of {omega}. Phase transformation in the 39Nb alloy is more sluggish than that in the 29Nb alloy, owing to the presence of the higher content of {beta} stabiliser Nb. For the 29Nb alloy, Young's modulus and mechanical properties are sensitive to the fraction of phases, and change significantly during aging, in contrast with the 39Nb alloy. (author)

  4. Deformation Twinning in Nb-Microalloyed Fe-Mn-C-Al Twinning-Induced Plasticity Steel

    Science.gov (United States)

    Kwon, Eui Pyo; Kim, Dae Young; Park, Hyun Kyeong

    2017-09-01

    Work hardening and deformation twinning in microalloyed Fe-Mn-C-Al twinning-induced plasticity (TWIP) steel with Nb were investigated in this study, and it was found that the addition of Nb affected the work-hardening behavior of TWIP steel. Moreover, the quantitative characterization of twinning was performed on the deformed microstructure by electron backscattering diffraction analysis, and the results indicate that the addition of Nb causes a reduction in twinning kinetics. The decrease in deformation twinning in TWIP steel with added Nb can be attributed to the effect of fine grain, dislocations in non-recrystallized grains, and the formation of twins on a particular grain orientation.

  5. In situ Precursor-Template Route to Semi-Ordered NaNbO3 Nanobelt Arrays.

    Science.gov (United States)

    Wu, Junshu; Xue, Dongfeng

    2011-12-01

    We exploited a precursor-template route to chemically synthesize NaNbO3 nanobelt arrays. Na7(H3O)Nb6O19·14H2O nanobelt precursor was firstly prepared via a hydrothermal synthetic route using Nb foil. The aspect ratio of the precursor is controllable facilely depending on the concentration of NaOH aqueous solution. The precursor was calcined in air to yield single-crystalline monoclinic NaNbO3 nanobelt arrays. The proposed scheme for NaNbO3 nanobelt formation starting from Nb metal may be extended to the chemical fabrication of more niobate arrays.

  6. 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)

  7. Microstructural and mechanical characterization of Nb-based in situ composites from Nb-Si-Ti ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z. [Department of Mechanics and Mechanical Engineering, CAS Key Laboratory for Mechanical Behavior and Design of Materials, School of Engineering Science, University of Science and Technology of China, Hefei 230026, Anhui (China); Peng, L.M. [Department of Mechanics and Mechanical Engineering, CAS Key Laboratory for Mechanical Behavior and Design of Materials, School of Engineering Science, University of Science and Technology of China, Hefei 230026, Anhui (China)], E-mail: penglm@ustc.edu.cn

    2007-11-15

    This study deals with the Nb-niobium silicide-based composites developed by the hot-pressing of Nb-Si-Ti ternary powder mixtures with a fixed Ti addition (6 at.%) and Si content ranging from hypereutectic (11 at.%) to near-eutectic compositions (18 at.%). The effects of Si content, Ti addition and strain rates on the sample microstructural characterization, flexural strength, fracture toughness, quasi-static compressive deformation and failure processes were investigated. It was revealed that the volume fraction of silicides increased with increasing Si content, and most of the Ti atoms dissolved into the niobium silicides to form (Nb,Ti){sub 5}Si{sub 3} solid solutions instead of binary titanium silicides. The experimental evidence showed that a moderate improvement in the flexural strength, fracture toughness and compressive yield stress of the composites was achieved by the addition of Ti. Higher Si additions produced a much more remarkable enhancement in the compressive yield stress and bulk hardness, whereas both the flexural strength and fracture toughness decreased with increasing Si content owing to the existence of residual porosities in the samples. The composites showed remarkable superiority to the arc-melted Nb-Si alloys and monolithic niobium silicides in fracture toughness (8.3-13.0MPa{radical}(m) vs. 4.5MPa{radical}(m)), where the toughening effect was attributed mainly to crack bridging and crack deflection by the remaining ductile Nb phase. Moreover, quasi-static uniaxial compression tests at strain rates between 10{sup -5} and 10{sup -3} s{sup -1} indicated that the deformation behavior and failure processes were significantly affected by Si content and strain rates. The strain-rate-hardening behavior for all the strain rates was observed in the composite materials and the strain-rate sensitivity decreased with increasing Si content. At a lower strain rate, the composite materials with a hypoeutectic Si composition failed with a pseudoplastic

  8. 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%.

  9. 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...

  10. {sup 90}Nb - a potential PET nuclide. Production and labeling of monoclonal antibodies

    Energy Technology Data Exchange (ETDEWEB)

    Radchenko, V.; Roesch, F. [Mainz Univ. (Germany). Inst. of Nuclear Chemistry; Hauser, H.; Eisenhut, M. [German Cancer Research Center, Heidelberg (Germany). Radiopharmaceutical Chemistry; Vugts, D.J.; Dongen, G.A.M.S. van [VU University Medical Center, Amsterdam (Netherlands). Dept. of Nuclear Medicine and PET Research; VU University Medical Center, Amsterdam (Netherlands). Dept. of Otolaryngology/Head and Neck Surgery

    2012-07-01

    Fast progressing immuno-PET gives reasons to develop new potential medium-long and long-lived radioisotopes. One of the promising candidates is {sup 90}Nb. It has a half-life of 14.6 h, which allows visualizing and quantifying processes with medium and slow kinetics, such as tumor accumulation of antibodies and antibodies fragments or polymers and other nanoparticles. {sup 90}Nb exhibits a high positron branching of 53% and an optimal energy of {beta}{sup +} emission of E{sub mean} = 0.35 MeV only. Consequently, efficient radionuclide production routes and Nb{sup V} labeling techniques are required. {sup 90}Nb was produced by the {sup 90}Zr(p,n){sup 90}Nb nuclear reaction on natural zirconium targets. No-carrier-added (n.c.a.) {sup 90}Nb was separated from the zirconium target via a multi-step separation procedure including extraction steps and ion-exchange chromatography. Protein labeling was exemplified using the bifunctional chelator desferrioxamine attached to the monoclonal antibody rituximab. Desferrioxamine was coupled to rituximab via two different routes, by the use of N-succinyl-desferrioxamine (N-suc-Df) and by means of the bifunctional derivative p-isothiocyanatobenzyl-desferrioxamine B (Df-Bz-NCS), respectively. Following antibody modification, labeling with {sup 90}Nb was performed in HEPES buffer at pH 7 at room temperature. In vitro stability of the radiolabeled conjugates was tested in saline buffer at room temperature and in fetal calf serum (FCS) at 37 C. The selected production route led to a high yield of 145 {+-} 10 MBq/{mu}A h of {sup 90}Nb with high radioisotopic purity of > 97%. This yield may allow for large scale production of about 10 GBq {sup 90}Nb. The separation procedure resulted in 76-81% yield. The Zr/{sup 90}Nb decontamination factor reaches 10{sup 7}. Subsequent radiolabeling of the two different conjugates with {sup 90}Nb gave high yields; after one hour incubation at room temperature, more than 90% of {sup 90}Nb-Df-mAb was

  11. LiNbO3 surfaces from a microscopic perspective

    Science.gov (United States)

    Sanna, Simone; Gero Schmidt, Wolf

    2017-10-01

    A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts. Lithium niobate (LiNbO3) is a ferroelectric with a high spontaneous polarization, whose surfaces have a huge and largely unexplored potential. Owing to recent advances in experimental techniques and sample preparation, peculiar and exclusive properties of LiNbO3 surfaces could be demonstrated. For example, water films freeze at different temperatures on differently polarized surfaces, and the chemical etching properties of surfaces with opposite polarization are strongly different. More important, the ferroelectric domain orientation affects temperature dependent surface stabilization mechanisms and molecular adsorption phenomena. Various ab initio theoretical investigations have been performed in order to understand the outcome of these experiments and the origin of the exotic behavior of the lithium niobate surfaces. Thanks to these studies, many aspects of their surface physics and chemistry could be clarified. Yet other puzzling features are still not understood. This review gives a résumé on the present knowledge of lithium niobate surfaces, with a particular view on their microscopic properties, explored in recent years by means of ab initio calculations. Relevant aspects and properties of the surfaces that need further investigation are briefly discussed. The review is concluded with an outlook of challenges and potential payoff

  12. Nb$_{3}$Sn quadrupoles designs for the LHC upgrades

    CERN Document Server

    Felice, H

    2009-01-01

    In preparation for the LHC luminosity upgrades, high field and large aperture Nb3Sn quadrupoles are being studied. This development has to incorporate all the relevant features for an accelerator magnet like alignment and cooling channels. The LARP HQ model is a high field and large bore quadrupole that will meet these requirements. The 2-layer coils are surrounded by a structure based on key and bladder technology with supporting iron yoke and aluminum shell. This structure is aimed at pre-stress control, alignment and field quality. We present here the magnetic and mechanical design of HQ, along with recent progress on the development of the first 1-meter model.

  13. Effect of solute interactions in columbium /Nb/ on creep strength

    Science.gov (United States)

    Klein, M. J.; Metcalfe, A. G.

    1973-01-01

    The creep strength of 17 ternary columbium (Nb)-base alloys was determined using an abbreviated measuring technique, and the results were analyzed to identify the contributions of solute interactions to creep strength. Isostrength creep diagrams and an interaction strengthening parameter, ST, were used to present and analyze data. It was shown that the isostrength creep diagram can be used to estimate the creep strength of untested alloys and to identify compositions with the most economical use of alloy elements. Positive values of ST were found for most alloys, showing that interaction strengthening makes an important contribution to the creep strength of these ternary alloys.

  14. Polar behavior of double perovskite (Bi,Pb)ZnNbO6 and (Bi,Sr)ZnNbO6: Density functional calculations

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Shigeyuki M [ORNL; Subedi, Alaska P [ORNL; Singh, David J [ORNL; Cooper, Valentino R [ORNL

    2010-01-01

    The polar behavior of double perovskite (Bi,Pb)ZnNbO{sub 6} and (Bi,Sr)ZnNbO{sub 6} was investigated using first principles density functional calculations within the local density approximation. These materials have both A-site size disorder and ions with sterochemical activity. We found a strong ferroelectric distortion in both materials. The polarization of the Pb material is >80 muCcm{sup 2} along the rhombohedral direction and the Sr based material is only slightly inferior. The high polarization results mainly from a large off-centering of Bi and the large Born effective charge of Nb, which yields a large contribution polarization although the Nb off-centers by a smaller amount. Neither of these materials favors a tetragonal state, and therefore solid solutions with PbTiO{sub 3} may show morphotoropic phase boundaries.

  15. An Experimental 11.5 T Nb3Sn LHC Type of Dipole Magnet

    NARCIS (Netherlands)

    den Ouden, A.; Wessel, Wilhelm A.J.; Krooshoop, Hendrikus J.G.; Dubbeldam, R.; ten Kate, Herman H.J.

    1994-01-01

    As part of the magnet development program for the LHC an experimental 1 m long 11.5 T single aperture Nb3Sn dipole magnet has been designed and is now under construction. The design is focused on full utilisation of the high current density in the powder tube Nb3Sn. A new field optimisation has led

  16. 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.

  17. 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.

  18. 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.

  19. Microstructural study of brass matrix internal tin multifilamentary Nb3Sn superconductors

    Science.gov (United States)

    Banno, Nobuya; Miyamoto, Yasuo; Tachikawa, Kyoji

    2018-03-01

    Zn addition to the Cu matrix in internal-tin-processed Nb3Sn superconductors is attractive in terms of the growth kinetics of the Nb3Sn layers. Sn activity is enhanced in the Cu-Zn (brass) matrix, which accelerates Nb3Sn layer formation. Here, we prepared multifilamentary wires using a brass matrix with a Nb core diameter of less than 10 μm and investigated the potential for further Jc improvement through microstructural and microchemical studies. Ti was added into the Sn cores in the precursor wire. Microchemical analysis showed that Ti accumulates between subelements consisting of Nb cores, which blocks Sn diffusion through this region when the spacing between the subelements in the precursor wire is a few microns. The average grain size was found to be about 230 nm through image analysis. To date, matrix Jc values of 1470 and 640 A/mm-2 have been obtained at 12 and 16 T, respectively. The area fraction of Nb cores in the filamentary region of the precursor wire was about 36.3%. There was still some unreacted Nb core area after heat treatment. Insufficient Ti diffusion into the Nb3Sn layers was identified in the outer subelements. These findings suggest that there is still room for improvement in Jc.

  20. Field dependence of Fiske resonances in Nb-AlOx based Josephson junctions

    NARCIS (Netherlands)

    Gijsbertsen, Hans; Gijsbertsen, J.G.; Houwman, Evert Pieter; Flokstra, Jakob; Rogalla, Horst; Le grand, J.B.; de Korte, P.A.J.

    1993-01-01

    Fiske resonances have been measured in a rectangular Nb-Al, AlO x, Al-Nb Josephson junction as a function of the magnetic field applied parallel to a junction side. Due to the high quality factor of the junction, many resonant modes could be measured, using a special measuring technique. Each mode

  1. Photocatalytic hydrogen generation with Ag-loaded LiNbO3

    Indian Academy of Sciences (India)

    Administrator

    Abstract. In this contribiution LiNbO3 and Ag-loaded LiNbO3 photocatalysts were tested in the reaction of hydrogen evolution. The silver modified samples contained different loading of co-catalyst in the range of. 0∙5–4 wt%. It was essential to optimize the sample composition to achieve an efficient hydrogen evolution. The.

  2. Short-range Ferromagnetism in Alloy Ribbons of Fe-Cr-Si-Nb-(Ag, Cu)

    DEFF Research Database (Denmark)

    Thanh, P. Q.; Hoa, N. Q.; Chau, N.

    2014-01-01

    We have studied the magnetic properties of two amorphous alloy ribbons Fe72Cr6Si4Nb5B12Ag1 (FCSNB-Ag) and Fe72Cr6Si4Nb5B12Cu1 (FCSNB-Cu), prepared by using a melt-spinning technique. Magnetization (M) measurements for various temperatures (T) and magnetic fields (H) indicate that ferromagnetic...

  3. Critical current degradation in Nb3Sn superconductors in accelerator magnets

    NARCIS (Netherlands)

    van Oort, H.; van Oort, Johannes Martinus

    2000-01-01

    This thesis deals with various aspects in the construction of a 13 T Nb3Sn model accelerator dipole magnet. The basis for the successful construction of such a magnet is a thorough understanding of the sensitivity of the Nb3Sn conductor to stress and strain, and a detailed measurement of the stress

  4. Long-ranged interactions in bcc NbMoTaW high-entropy alloys

    NARCIS (Netherlands)

    Kormann, F.H.W.; Ruban, A.V.; Sluiter, M.H.F.

    2017-01-01

    We reveal that in a prototypical bcc high-entropy alloy NbMoTaW chemical interactions are long ranged and highly frustrated. We show that this is the reason that bcc solid solutions in NbMoTaW can persist to low temperatures. The ab initio-computed long-ranged interactions strongly impact

  5. Josephson junctions and DC SQUIDS based on Nb/Al technology.

    Science.gov (United States)

    Flokstra, J; Adelerhof, D J; Houwman, E P; Veldhuis, D; Rogalla, H

    1991-01-01

    A process for fabricating high-quality Josephson junctions and DC SQUIDs on basis of Nb/Al technology has been developed. DC magnetron sputtering is used for the deposition of the metal layers and the barrier is formed by thermal oxidation of the Al-layer. The junction area of 5 microns x 5 microns is obtained using anodisation. Three types of Josephson tunnel junctions have been prepared: standard Nb/Al, AlO kappa/Nb, symmetric Nb/Al, AlO kappa, Al/Nb and Nb/Al, AlO kappa/AlO kappa/Nb, the latter having a double oxide layer. We performed current-voltage and conductance-voltage measurements at different temperatures and special attention was paid to the noise behaviour. Gap and sub-gap parameters as well as barrier parameters are presented. Three different DC SQUID configurations were developed on basis of the Nb/Al Josephson junctions. The measured characteristics of the standard Tesche-Clarke DC SQUID, the resistively shunted SQUID and the inductively shunted SQUID are compared with special attention being paid to the noise properties. A 19-channel DC SQUID magnetometer with standard and/or resistively-shunted DC SQUIDs is under construction.

  6. Development of high resolution resonance ionization mass spectrometry for trace analysis of {sup 93m}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Takatsuka, Takaaki; Tomita, Hideki, E-mail: tomita@nagoya-u.jp [Nagoya University (Japan); Sonoda, Tetsu [RIKEN Nishina Center (Japan); Sonnenschein, Volker [Johannes Gutenberg University (Germany); Sakamoto, Chika [Nagoya University (Japan); Mita, Hiroki [University of Tsukuba, Institute of Physics (Japan); Noto, Takuma [Nagoya University (Japan); Ito, Chikara; Maeda, Shigetaka [Japan Atomic Energy Agency, Oarai Research and Development Center (Japan); Iguchi, Tetsuo [Nagoya University (Japan); Wada, Michiharu [RIKEN Nishina Center (Japan); Wendt, Klaus [Johannes Gutenberg University (Germany); Moore, Iain [University of Jyvaeskylae, Department of Physics (Finland)

    2013-04-15

    {sup 93}Nb(n, n Prime ){sup 93m}Nb reaction allows retrospective estimation of integrated fast neutron dose in nuclear reactor. We proposed isomer-selective trace analysis of {sup 93m}Nb by Resonance Ionization Mass Spectrometry (RIMS) combined with a gas-jet atomic source and an injection locked Ti:Sapphire laser system operated at several kHz. Resonant ionization spectroscopy of Nb in gas-jet using Ti:Sapphire laser was demonstrated.

  7. Triple-combination treatment with oral α-lipoic acid, betamethasone injection, and NB-UVB for non-segmental progressive vitiligo.

    Science.gov (United States)

    Li, Li; Li, Lu; Wu, Yan; Gao, Xing-Hua; Chen, Hong-Duo

    2016-06-01

    Vitiligo is an acquired depigmenting disease with uncertain etiopathogenesis and the treatment modalities need to be consistently updated. To evaluate a triple-combination treatment with oral α-lipoic acid (ALA), betamethasone injection, and narrowband ultraviolet B (NB-UVB) on vitiligo. Patients with non-segmental and progressive vitiligo lesions were randomly assigned to two groups. The treatment group and the control group were respectively treated with oral ALA and placebo, in combination with betamethasone injection and NB-UVB. The effectiveness and adverse events were evaluated by investigators and patients before and after treatment. Fifty non-segmental progressive vitiligo patients were enrolled in the study. The treatment period was 6 months. In treatment group, over 40% patients achieved > 50% improvement and ≥ 5 satisfaction score by 3-month therapy (M3). This percentage increased to 90% at M6. Treatment group achieved better efficacy than control group at M3, while no difference was seen at M6. The combined treatment with oral ALA, betamethasone injection, and NB-UVB was effective and safe on non-segmental progressive vitiligo. ALA could accelerate the initial response of repigmentation.

  8. Superconducting thermomagnetic instabilities tuned through electric-field-controlled strain in Nb/PMN-PT/Nb hybrids

    Science.gov (United States)

    Zeibekis, M.; Zhang, S. J.; Stamopoulos, D.

    2018-01-01

    Electric-field-controlled piezoelectric strain has been used, recently, to modify the superconducting properties in a new class of piezoelectric/superconducting (PE/SC) hybrids. Here, we investigate the appearance of thermomagnetic instabilities (TMIs) and the respective modification of the critical current density (JC) through the application of electric field (Eex) in PE/SC hybrids. Specifically, the SC nanolayers are Nb (thickness, dSC= 20 nm) deposited on both surfaces of PE macroscopic crystals of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) with optimum composition x = 0.31 (thickness, dPE= 0.5-0.8 mm). The appearance of TMIs and the modification of JC by Eex is studied for two PMN-PT crystals of drastically different surface roughness (Sa). In the case of the PMN-PT crystal with low Sa (on the order of a few tenths of nm) TMIs are absent so that JC does not change under the variation of Eex. On the contrary, in the case of the PMN-PT crystal with high Sa (on the order of a few hundreds of nm) Eex induces TMIs in the Nb nanolayers. Specifically, the number of TMIs exhibits a non-monotonic increase on Eex, thus causing a non-monotonic degradation of JC. These experimental data are interpreted in terms of the variation of both volume strain and surface roughness on Eex. This work highlights practical means to control the current-carrying capability of SC nanolayers through strain provided by PE substrates.

  9. Structural evolution in Ni-Nb and Ni-Nb-Ta liquids and glasses - A measure of liquid fragility?

    Energy Technology Data Exchange (ETDEWEB)

    Mauro, N. A.; Johnson, M. L.; Bendert, J. C.; Kelton, K. F. [WU

    2013-01-07

    The structures of Ni59.5Nb40.5, Ni62Nb38, and Ni60Nb30Ta10 liquids and glasses were studied using synchrotron high-energy X-ray diffraction. To avoid reactions between the liquids and their containers and to deeply supercool them below their equilibrium liquidus temperatures, the liquids were processed without a container using the beamline electrostatic levitation (BESL) technique. The total static structure factor, S(q), and the total pair-correlation function, g(r), were obtained for all liquid compositions over a temperature range of approximately 250 °C; S(q) and g(r) were measured for the corresponding glasses at room temperature. All of the S(q)s have a shoulder on the high-q side of the second peak; this becomes more pronounced as the liquid is supercooled, and is most prominent in the glass. Based on a Honeycutt–Andersen analysis of the atomic configurations obtained from Reverse Monte Carlo fits to the total structure factors obtained from the scattering data, icosahedral short-range order (ISRO) is dominant in all liquids and becomes particularly pronounced in the glasses. No correlation is noted, however, between the amount of ISRO and easy glass formability. Structural features show evidence for an acceleration of ordering in the supercooled liquid above the glass transition temperature, consistent with the behavior expected for fragile liquids. This suggests that scattering data can provide a new method to assess liquid fragility, which is typically obtained from the temperature behavior of the viscosity near the glass transition temperature.

  10. High-temperature nitridation of Nb-Ti alloys in nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Buscaglia, V.; Martinelli, A. [Nat. Res. Council, Genoa (Italy). Inst. of Phys. Chem. of Mater.; Musenich, R. [National Institute of Nuclear Physics, via Dodecaneso 33, I-16146 Genoa (Italy); Mayr, W.; Lengauer, W. [Institute for Chemical Technology of Inorganic Materials, Vienna University of Technology, Getreidemarkt 9/161, A-1060 Vienna (Austria)

    1999-02-01

    Microstructure evolution, phase composition, weight gain and layer growth kinetics of Nb-Ti alloys (10, 47, 63 and 90 at.% Ti) annealed in high-purity nitrogen atmosphere (0.3, 3 and 30 bar) were studied in the temperature range 1300-1600 C. After nitridation, the formation of an external compact nitride layer as well as extensive internal nitride precipitation was observed. The overall nitridation kinetics (weight gain) is invariably parabolic; a deviation from the initial rate law is observed at 1450 and 1600 C for the longer reaction times when the alloy core approaches nitrogen saturation and internal precipitation slows down. The parabolic rate constant is strongly affected by the Nb content in the alloy. The phases detected in the reacted samples are isostructural with those of the Nb-Ti, Nb-N and Ti-N systems. The surface nitride was {delta}-(Ti,Nb)N in any case. The morphology of the internal nitridation zone corresponds to the growth of large, oriented, nitride needles for the three alloys richer in titanium. The needles are composed of {alpha}-(Ti,Nb)(N) in the case of Ti{sub 90}Nb{sub 10} alloy and of {delta}-(Ti,Nb)N{sub 1-x} in the case of Ti{sub 63}Nb{sub 37} and Ti{sub 47}Nb{sub 53}. Such a microstructure is evidence for nucleation difficulty; coarsening of the existing particles is favoured in comparison to the formation of new precipitates. Homogeneous nucleation is hindered by the small chemical Gibbs free energy available and the elastic strain energy related to volume misfit. After initial reaction, microstructure evolution is mainly determined by the fast inward diffusion of nitrogen and the slow Nb-Ti interdiffusion in the {beta}-(Ti,Nb) alloy. Internal nitridation of Ti{sub 10}Nb{sub 90} at 1450 and 1600 C leads to the formation of fine and numerous precipitates of {beta}-(Nb,Ti){sub 2}N. (orig.) 58 refs.

  11. The 2D-3D crossover and anisotropy of upper critical fields in Nb and NbN superconducting thin films

    Science.gov (United States)

    Joshi, Lalit M.; Verma, Apoorva; Rout, P. K.; Kaur, Mandeep; Gupta, Anurag; Budhani, R. C.

    2017-11-01

    The upper critical field (Bc2) of superconducting thin films of Nb (film thickness d = 40 nm) and NbN (d = 10, 50 and 100 nm) have been measured and analyzed as a function of temperature (T = 1.8-15 K) in both parallel and perpendicular magnetic field (B = 0-7 T) directions with respect to the film plane. Dimensional crossover from 2D to 3D is observed for all the thin films except for the 10 nm thick NbN film which exhibits only 2D behavior in the measured T and B range. Further, the upper critical fields were found to be anisotropic in case of both Nb and NbN films. However, the anisotropy shows different behavior in all the four samples. In case of Nb, below the 2D-3D crossover temperature, the Bc2∥(T) is higher than Bc2⊥(T) and both curves branch away further from each other. On the other hand, in case of NbN (50 and 100 nm), there is a reversal of anisotropy, i.e., in the 2D region Bc2∥(T) > Bc2⊥(T) and in the 3D region at some temperature Bc2⊥(T) > Bc2∥(T) . In the NbN films with increasing thickness, the 2D region shrinks and 3D region expands, and the 2D-3D crossover and anisotropy reversal characteristic temperatures shift toward Tc. These observations are quantitatively explained using the Ginzburg-Landau theoretical approach after Schneider and Locquet (Physica C, 179 (1991) 125).

  12. 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.

  13. Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.; DeVan, J.H.

    1994-09-01

    Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb were examined on the basis of isothermal exposures to air at 950 C. Additions of either Re and Al or Fe, Ni, and Al had relatively little effect on weight gains relative to the Cr-6% Nb binary alloy. One alloying element that improved the mechanical behavior of Cr-Cr{sub 2}Nb alloys substantially increased the oxidation rates and spallation susceptibilities of Cr-6 and -12% Nb alloys. However, the addition of another element completely offset these deleterious effects. The presence of this latter element resulted in the best overall oxidation behavior (in terms of both weight gains and spallation tendencies) of all Cr-Cr{sub 2}Nb compositions. Its beneficial effect can be attributed to improvement in the oxidation resistance of the Cr-rich phase.

  14. Topology and electronic structure of flexible (Nb,Ru)O2 thermoelectrics

    Science.gov (United States)

    Music, Denis; Schnabel, Volker; Bednarcik, Jozef

    2017-03-01

    Using combinatorial reactive sputtering, we have synthesised Nb-Ru-O thin films on Kapton (polyimide) with the Ru/Nb ratio from 0.5 to 1.1 in a dioxide type of environment. Based on correlative analysis, including synchrotron diffraction experiments and density functional theory, the topology of these amorphous samples is characterised by short metal-oxygen bonds and very pronounced metal-metal interactions within the second coordination shell. We suggest that the role of Nb is within bond length reduction and promotion of quantum confinement, giving rise to an increase in the Seebeck coefficient. Furthermore, these Nb-Ru-O thin films are mechanically flexible as there are no crack formation and delamination upon bending or rolling. This may be rationalised as follows. Nb-Ru-O appears ductile due to low topological connectivity and forms strong bonds with Kapton.

  15. Deformation of a super-elastic NiTiNb alloy with controllable stress hysteresis

    Energy Technology Data Exchange (ETDEWEB)

    Cai, S.; Schaffer, J. E. [Fort Wayne Metals Research Products Corporation, 9609 Ardmore Ave., Fort Wayne, Indiana 46809 (United States); Ren, Y. [Adanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Wang, L. [Beijing Institute of Technology, 5 South Zhongguancun St., Haidian District, Beijing 100081 (China)

    2016-06-27

    Room temperature deformation of a Ni{sub 46.7}Ti{sub 42.8}Nb{sub 10.5} alloy was studied by in-situ synchrotron X-ray diffraction. Compared to binary NiTi alloy, the Nb dissolved in the matrix significantly increased the onset stress for Stress-Induced Martensite Transformation (SIMT). The secondary phase, effectively a Nb-nanowire dispersion in a NiTi-Nb matrix, increased the elastic stiffness of the bulk material, reduced the strain anisotropy in austenite families by load sharing during SIMT, and increased the stress hysteresis by resisting reverse phase transformation during unloading. The stress hysteresis can be controlled over a wide range by heat treatment through its influences on the residual stress of the Nb-nanowire dispersion and the stability of the austenite.

  16. Deformation of a super-elastic NiTiNb alloy with controllable stress hysteresis

    Energy Technology Data Exchange (ETDEWEB)

    Cai, S.; Schaffer, J. E.; Ren, Y.; Wang, L.

    2016-06-27

    Room temperature deformation of a Ni46.7Ti42.8Nb10.5 alloy was studied by in-situ synchrotron X-ray diffraction. Compared to binary NiTi alloy, the Nb dissolved in the matrix significantly increased the onset stress for Stress-Induced Martensite Transformation (SIMT). The secondary phase, effectively a Nb-nanowire dispersion in a NiTi-Nb matrix, increased the elastic stiffness of the bulk material, reduced the strain anisotropy in austenite families by loading sharing during SIMT, and increased the stress hysteresis by resisting reverse phase transformation during unloading. The stress hysteresis can be controlled over a wide range by changing the heat treatment temperature through its influences on the residual stress-strain state of the Nb-nanowire dispersion.

  17. Nb3Sn accelerator magnet technology scale up based on cos-theta coils

    Energy Technology Data Exchange (ETDEWEB)

    Nobrega, F.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; Carcagno, R.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Novitski, I.; Pischalnikov, Yu.; Sylvester, C.; Tartaglia, M.; Turrioni, D.; Yamada, R.; Zlobin, A.V.; /Fermilab

    2006-08-01

    After successful testing of a 1 m long dipole mirror magnet and three dipole models based on two-layer Nb{sub 3}Sn coils, Fermilab has started a Nb{sub 3}Sn technology scale-up program using the dipole mirror design and the developed Nb{sub 3}Sn coil fabrication technology based on the wind-and-react method. The scale-up will be performed in several steps starting from a 2 m long coil made of Powder-in-Tube (PIT) strand. This will be followed by 4 m long Nb{sub 3}Sn coils made of PIT and RRP strands that will be fabricated into dipole mirror magnets and tested. This paper presents a summary of Fermilab's wind-and-react short model program. It includes details on the 2 m and 4 m long, 2 layer Nb{sub 3}Sn dipole mirror magnet design, mechanical structure, and fabrication infrastructure.

  18. Nb2O5 as a new electron transport layer for double junction polymer solar cells.

    Science.gov (United States)

    Siddiki, Mahbube K; Venkatesan, Swaminathan; Qiao, Qiquan

    2012-04-14

    Nb(2)O(5) as a new electron transport layer (ETL) was used for double junction polymer solar cells. The Nb(2)O(5) ETL was prepared by spin coating a Nb(2)O(5) sol-gel solution onto the active layer of the optical front subcell. The double junction devices using Nb(2)O(5) ETL exhibit an open circuit voltage (V(oc)) of 1.30 V, which is close to the sum of the s of the individual subcells. The current density-voltage (J-V) simulation showed that the double junction device performance using Nb(2)O(5) as ETL could be significantly increased by reducing the series resistance (R(se)) and matching the current densities of the individual subcells.

  19. Evaluation of Nb-base alloys for the divertor structure in fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Purdy, I.M. [Argonne National Laboratory, Upton, IL (United States)

    1996-04-01

    Niobium-base alloys are candidate materials for the divertor structure in fusion reactors. For this application, an alloy should resist aqueous corrosion, hydrogen embrittlement, and radiation damage and should have high thermal conductivity and low thermal expansion. Results of corrosion and embrittlement screening tests of several binary and ternary Nb alloys in high-temperature water indicated the Mb-1Zr, Nb-5MO-1Zr, and Nb-5V-1Z4 (wt %) showed sufficient promise for further investigation. These alloys, together with pure Nb and Zircaloy-4 have been exposed to high purity water containing a low concentration of dissolved oxygen (<12 ppb) at 170, 230, and 300{degrees}C for up to {approx}3200 h. Weight-change data, microstructural observations, and qualitative mechanical-property evaluation reveal that Nb-5V-1Zr is the most promising alloy at higher temperatures. Below {approx}200{degrees}C, the alloys exhibit similiar corrosion behavior.

  20. 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.

  1. Development of Fast NbN RSFQ Logic Gates in Sigma-Delta Converters for Space Telecommunications

    National Research Council Canada - National Science Library

    Baggaetta, Emanuele; Maignan, Michel; Villegier, Jean-Claude

    2005-01-01

    ... (NbN) presently developed at CEA-G involves NbN/Ta(sub X)N/NbN internally shunted Josephson junctions with high critical current density and high maximum switching frequency close to 1THz, as required by ultra-fast RSFQ electronics...

  2. Full Article: Stoichiometry, Vibrational Modes and Structure of Molten Nb2O5-K2S2O7 Mixtures

    DEFF Research Database (Denmark)

    Boghosian, S.; Borup, F.; Berg, Rolf W.

    1998-01-01

    The dissolution reaction of Nb205 in pure molten K2S207 has been studied and high temperature Raman spectroscopy has been used for determining the vibrational and structural properties of the Nb(V) complex(es) formed according to the reaction Nb205 + n S207(2-) -> complex. By means of a recently ...

  3. Charge density wave and superconductivity in 2H-and 4H-NbSe2: A ...

    Indian Academy of Sciences (India)

    Good-quality hexagonal NbSe2 single crystals were prepared. In 2H-NbSe2, superconducting and charge density wave (CDW) transitions were found at = 7.4 K and = 35 K respectively as reported previously. We have noticed that these two transitions are changed to = 42 K and = 6.5 K, in 4H-NbSe2.

  4. 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...

  5. Nb nanoSQUIDs for detection of small spin systems

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

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

  6. SLPX: superconducting long-pulse tokamak experiment. [NbTi

    Energy Technology Data Exchange (ETDEWEB)

    Jassby, D.L.; File, J.; Bronner, G.

    1978-09-25

    The principal objectives of the SLPX (Superconducting Long-Pulse Experiment) are: (1) to demonstrate quasi-steady operation of 3 to 5 MA hydrogen and deuterium tokamak plasmas at high temperature and high thermal wall loading, and (2) to develop reliable operation of prototypical tokamak reactor magnetics systems featuring a toroidal assembly of high-field niobium-tin coils, and a system of pulsed niobium-titanium superconducting poloidal-field coils. This paper describes the status of the engineering design features of the SLPX, with emphasis on the magnetics systems. The toroidal-field coils have an aperture of 3.1 x 4.8 m and can operate with a maximum field at the conductor of 12 T. The superconducting poloidal field magnetics system consists of a pulsed NbTi central solenoid and a set of dc NbTi equilibrium-field coils. The entire machine is enclosed in an outer vacuum container equipped with re-entrant ports that provide ambient access to the room-temperature plasma vessel.

  7. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.; Easton, D.S.; Heatherly, L.

    1996-06-01

    The objective of this work is to develop a new generation of structural materials based on intermetallic alloys for use at high temperatures in advanced fossil energy conversion systems. Target applications of such ultrahigh strength alloys include hot components (for example, air heat exchangers) in advanced energy conversion systems and heat engines. However, these materials may also find use as wear-resistant parts in coal handling systems (for example, nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. One potential class of such alloys is that based on Cr-Cr{sub 2}Nb alloys. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for initial development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), and excellent high-temperature strength (at 1000 to 1250{degrees}C). This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions.

  8. Low-energy deuteron-induced reactions on 93Nb

    Science.gov (United States)

    Avrigeanu, M.; Avrigeanu, V.; Bém, P.; Fischer, U.; Honusek, M.; Koning, A. J.; Mrázek, J.; Šimečková, E.; Štefánik, M.; Závorka, L.

    2013-07-01

    The activation cross sections of (d,p), (d,2n), (d,2np+nd+t), (d,2nα), and (d,pα) reactions on 93Nb were measured in the energy range from 1 to 20 MeV using the stacked-foil technique. Then, within a simultaneous analysis of elastic scattering and reaction data, the available elastic-scattering data analysis was carried out in order to obtain the optical potential for reaction cross-section calculations. Particular attention was paid to the description of the breakup mechanism and direct reaction stripping and pick-up, followed by pre-equilibrium and compound-nucleus calculations. The measured cross sections as well as all available deuteron activation data of 93Nb were compared with results of local model calculations carried out using the codes fresco and stapre-h and both default and particular predictions of the code talys-1.4 and tendl-2012-evaluated data.

  9. Hydrogen ingress into oxidized Zr-2.5Nb

    Science.gov (United States)

    Laursen, T.; Palmer, G. R.; Haysom, J. E.; Nolan, J.; Tapping, R. L.

    1994-03-01

    Deuterium (D) distributions in D 2O-corroded Zr-2.5 wt% Nb samples have been measured for three different corrosion temperatures: 763, 673 and 573 K. The oxide thickness and details in the D profile for 763 K show considerable variation due to changes in surface preparation. Nevertheless, the D concentration in the central part of the oxide is within 0.002-0.005 {D}/{Zr} atomic ratio. At lower temperatures - 673 K and below — the D concentration is somewhat higher: ˜ 0.01 {D}/{Zr}. These concentrations are less than the 2-5% level observed with Zircaloy-2 after corrosion at 763 K. D distributions in O 2-oxidized Zr-2.5 wt% Nb have been measured following a subsequent exposure to either D 2 or D 2O exposure at 573 K. D ingress into the metal is enhanced with D 2 compared to D 2O, supporting the expectation that reducing conditions (D 2) may lead to a degradation of the protective oxide. Evidence is presented that two different diffusing species are responsible for the different D distributions measured in the oxide for the two types of exposure.

  10. Why and How Do Parents Decide to Send Their Children to the Interdistrict School Choice Program at the Magnet Program for Math and Science

    Science.gov (United States)

    Doyle, Kevin S.

    The New Jersey Interdistrict School Choice Program allows parents to send their students to schools outside of their local school district. Determining why parents send their students to choice schools is important to school leaders who are trying to attract new students, as well as those who are trying to retain their current students. This study examined the reasons why parents decided to send their students to the Magnet Program for Math and Science (MP4M&S), a school choice program in a suburban school district in northwest New Jersey, during the 2015- 2016 school year. A large volume of research has focused on school choice programs in urban and poor communities. This study addressed the gap in the research by focusing on an affluent suburban school district. This mixed methods study focused on three areas, why parents choose to send their students to the MP4M&S, what criteria they used to make their decision, and where they got their information. Research shows that these three areas of focus can be influenced by parental level of education, socioeconomic status, geographic location, academic rigor, school quality, and school environment. Parents from different groups, based upon their out-of-district status, were interviewed. The information from the interviews was used to focus a survey that was given to the families of all 137 students in the MP4M&S during the 2015-2016 school year. The results of this study show that parents found the academic focus, academic rigor, the school environment, the original research project, the activity offerings, and the economics involved in attending the program to be important attractors. The study also found that the Information Nights, the school website, and interactions with members of the MP4M&S community to be important sources of information. Finally, the study found that there were few differences between in and out-of-district parents when assigning importance to both the attractors and the sources in the study

  11. Study of the influence of Nb buffer layer on the exchange coupling induced at the Co/IrMn interface

    Energy Technology Data Exchange (ETDEWEB)

    Merino, I.L.C., E-mail: isabel5cas@gmail.com [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Figueiredo, L.C. [Instituto de Física, Universidade de Brasília, Brasília 70910-900 (Brazil); Passamani, E.C.; Nascimento, V.P. [Departamento de Física, Universidade Federal do Espírito Santo, Vitória 29075-910 (Brazil); Pelegrini, F. [Instituto de Física, Universidade Federal de Goiás, Goiânia 74560-900 (Brazil); Baggio Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil)

    2017-06-15

    Highlights: • Nb buffer layer favors smooth/rough Co/IrMn interfaces, depending on its thickness. • Double and single-like hysteresis loop features depend on the Nb thickness. • Co uniaxial anisotropy induced exchange-bias in as-deposited sample. • Uniaxial and exchange-bias anisotropy directions depend on the Nb thickness. • Thicker Nb favors non-collinear anisotropies, while thinner Nb favors collinear. - Abstract: Hybrid Nb(t{sub Nb})/Co(10 nm)/IrMn(15 nm)/Nb(10 nm) heterostructured materials were prepared by DC Magnetron Sputtering and systematically studied by X-ray, magnetization and ferromagnetic resonance techniques. For thinner Nb buffer layer (≤10 nm), it was found that there is an inter-diffusion at Co/IrMn interface, which favors double-like hysteresis loop. For thicker Nb layers, however, a gradual transition from double to single-like hysteresis loops is observed and it is associated with the reduction of the Nb roughness, which also enhances the exchange coupling at the Co/IrMn interface. Nb grown on IrMn layer induces the formation of an NbIrMn alloy layer, while no evidence of inter-diffusion at the Co/Nb interface is observed. For rougher Nb buffer layers (t{sub Nb} < 50 nm), exchange bias and Co uniaxial anisotropies are pointing at the same direction (β∼zero), but for smoother Nb buffer layer (t{sub Nb} = 50 nm) a β angle of 150{sup o} is found. Exchange bias effect was measured in as-prepared and in field-cooled samples; being its presence, in as-prepared sample, attributed to the unidirectional anisotropy of the Co layer (its intensity is modified in case of sample with a CoIrMn alloy layer). Considering that the Si/Nb/Co/IrMn interfaces have different β values (t{sub Nb} = 35 and 50 nm), a study of the influence of magnetization direction, governed by exchange-biased layers, on superconducting properties of Nb films can be successfully done in this hybrid system.

  12. Desgn of a 20-MJ superconducting ohmic-heating coil. [NbTi and Nb/sub 3/Sn

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.K.; Murphy, J.H.; Janocko, M.A.; Haller, H.E.; Litz, D.C.; Eckels, P.W.; Rogers, J.D.; Thullen, P.

    1979-01-01

    Conceptual designs of 20-MJ superconducting coils which were developed to demonstrate the feasibility of an ohmic-heating system were discussed. The superconductor materials were NbTi and Nb/sub 3/Sn for the pool boil and forced-flow cooling, respectively. The coils were designed to be cryostable for bipolar operation from +7 to -7 tesla maximum field within one second. The structural design addresses the distribution of structure and structural materials used in the pulsed field environment. The cyclic stresses anticipated and the fatigue limits of the structural materials were examined in view of the operating life of the coil. The coils were designed to generate the flux swings while simultaneously meeting the limitations imposed by cooling, insulation, current density and the stresses in the materials. Both the pool and forced cooled conductors have the same criterion for cryostability, i.e., the conductor must return to the superconducting state from an initial temperature of 20/sup 0/K while the full transport current is flowing through the conductor.

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

    Science.gov (United States)

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

    2017-05-01

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

  14. Effect of electron count and chemical complexity in the Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor.

    Science.gov (United States)

    von Rohr, Fabian; Winiarski, Michał J; Tao, Jing; Klimczuk, Tomasz; Cava, Robert Joseph

    2016-11-15

    High-entropy alloys are made from random mixtures of principal elements on simple lattices, stabilized by a high mixing entropy. The recently discovered body-centered cubic (BCC) Ta-Nb-Hf-Zr-Ti high-entropy alloy superconductor appears to display properties of both simple crystalline intermetallics and amorphous materials; e.g., it has a well-defined superconducting transition along with an exceptional robustness against disorder. Here we show that the valence electron count dependence of the superconducting transition temperature in the high-entropy alloy falls between those of analogous simple solid solutions and amorphous materials and test the effect of alloy complexity on the superconductivity. We propose high-entropy alloys as excellent intermediate systems for studying superconductivity as it evolves between crystalline and amorphous materials.

  15. Synthesis and structure of nanomaterials in the system K2O-Nb2O5-SiO2

    Directory of Open Access Journals (Sweden)

    Georgi Chernev

    2009-06-01

    Full Text Available The aim of the present work is synthesis of ferroelectric nanomaterials, in the K2O-Nb2O5-SiO2 system via solgel method and studying the processes of formation and structure of the synthesized ferroelectric nanomaterials. The structure of synthesized materials has been studied by means of the following methods: EDS, XRD, FT-IR, SEM and AFM. The results obtained showed that the structure of the investigated compositions does not depend on the niobium content and all the samples keep their amorphous nature at room temperature. The surface structure shows random distribution of different kinds of aggregates with dimensions about 200–500 nm. The presence of a hybrid nanostructure with well-defi ned nanounits having special geometry is clearly observed.

  16. Processing and properties of Pb(Mg(1/3)Nb(2/3))O3--PbTiO3 thin films by pulsed laser deposition

    Science.gov (United States)

    Tantigate, C.; Lee, J.; Safari, A.

    1995-03-01

    The objectives of this study were to prepare in situ Pb(Mg(1/3)Nb(2/3))O3 (PMN) and PMN-PT thin films by pulsed laser deposition and to investigate the electrical features of thin films for possible dynamic random access memory (DRAM) and microactuator applications. The impact of processing parameters such compositions, substrate temperature, and oxygen pressure on perovskite phase formation and dielectric characteristics were reported. It was found that the highest dielectric constant, measured at room temperature and 10 kHz, was attained from the PMN with 99% perovskite.

  17. Avaliação da atividade fotocatalítica de Nb2O5 = Evaluation of the photocatalytic activity of Nb2O5

    Directory of Open Access Journals (Sweden)

    Veronice Slusarski Santana

    2010-01-01

    Full Text Available Como a fotocatálise heterogênea é um dos métodos de tratamento de efluentes mais promissores, o estudo da atividade fotocatalítica de novos catalisadores é de primordial interesse. Assim, testes de degradação de solução de sacarose parcialmente caramelizada foram realizados empregando 2 g de Nb2O5 e TiO2 mássicos e Nb2O5 impregnado em microesferas de vidro (5,0, 10 e 15%Nb2O5 vidro-1 sob radiação UV durante 168h. TiO2 e Nb2O5 foram submetidos a processo de aglomeração (tamanho de partícula: 0,210 e 0,297 mm e calcinados a 500ºC por 5h. Nb2O5 foi solubilizado em ácido oxálico (0,5 mol L-1 a 70ºC por 8h, misturado com as microesferas de vidro, seco a 110ºC por 12h e calcinado a 500ºC por 5h. A eficiência do processo fotocatalítico foi avaliada por espectrofotometria UV-VIS e método DNS. Os resultados mostraram que catalisadores de Nb2O5 são promissores para aplicação em fotocatálise, principalmente o 15% Nb2O5 vidro-1, o qual apresentou resultados semelhantes ao do TiO2.As heterogeneous photocatalysis has proved to be one of the most promising methods for the treatment of effluents, the study of photocatalytic activity of new catalysts is of great interest. Thus,degradation tests of burnt sugar solution were conducted through using 2 g of Nb2O5 and TiO2, massic, and Nb2O5 impregnated in glass beads (5.0, 10 and 15% Nb2O5 glass-1 under UV radiation for 168 hours. TiO2 and Nb2O5 were submitted to the agglomeration process(particle size: 0.210 and 0.297 mm and calcined at 500ºC for 5h. Nb2O5 was solubilized in oxalic acid (0.5 mol L-1 at 70ºC for 8h, mixed with the glass beads, dried at 110ºC for 12h and calcined at 500ºC for 5h. The efficiency of the photocatalytic process was evaluated by UV-VIS spectrophotometry and DNS method. The results showed that catalysts of Nb2O5 are promising for application in photocatalysis, mainly 15% Nb2O5 glass-1, which presented similar results to TiO2.

  18. A statistical model for the study of U-Nb aging (u)

    Energy Technology Data Exchange (ETDEWEB)

    Hemphill, Geralyn M [Los Alamos National Laboratory; Hackenberg, Robert E [Los Alamos National Laboratory

    2009-01-01

    This study was undertaken to model the aging response of U-Nb alloys in order to quantify property and lifetime predictions and uncertainties, in response to concerns that aging during long-term stockpile storage may change the microstructure and properties of U-6 wt%Nb alloy components in ways adversely affecting performance. U-6Nb has many desirable properties, but is a complex material because of its gross compositional inhomogeneity (its chemical banding spans 4-8 wt%), its metastable starting microstructure, and the fact that a variety of external factors such as temperature, stress, and gaseous species can cause aging through multiple mechanisms. The most significant aging mechanism identified in earlier studies [2007hac2] is age hardening, phenomenologically defined as increasing hardness and strength and decreasing ductility observed as a function of increasing aging time-at-temperature. The scientific fundamentals of age hardening at temperatures relevant to U-6Nb material processing ({le}200 C) and stockpile storage ({le}60 C) remain unresolved in spite of significant experimental efforts [2007hac2, 2009cla]. Equally problematic is the lack of a well-established U-6Nb component failure criterion. These limitations make the most desirable approach of property response and lifetime prediction - that based on fundamental physics - unattainable at the present time. Therefore, a semi-empirical approach was taken to model the phenomenological property evolution during aging. This enabled lifetime estimates to be made from an assumed failure criterion (derived from a manufacturing acceptance criterion) couched in terms of an age-sensitive property, namely quasi-static tensile elongation to failure. The predictions of this and other age-sensitive properties are also useful for U-6Nb component surveillance studies. Drawing upon a large body of artificial aging data obtained from nonbanded (chemically homogeneous) U-5.6Nb and U-7.7Nb material [2007hacJ ] over 100

  19. Synthesis and Characterization of [(OH)TeNb5O18](6-) in Water Solution, Comparison with [Nb6O19](8-).

    Science.gov (United States)

    Abramov, Pavel A; Zemerova, Tatiana P; Moroz, Nikolay K; Kompankov, Nikolay B; Zhdanov, Artem A; Tsygankova, Alfiya R; Vicent, Cristian; Sokolov, Maxim N

    2016-02-15

    Reaction of [Nb6O19](8-) with H6TeO6 in water gives telluropentaniobate [(OH)TeNb5O18](6-) (1) as single product, which was isolated as Na(+) and mixed Na(+)/K(+) salts. Crystal structures were determined for Na6[(OH)TeNb5O18]·15H2O (Na6-1) and K6Na[Nb(5.5){Te(OH)}(0.5)O(18.5)]·26H2O (K6Na-1). Formation of 1 was monitored with electrospray ionization mass spectrometry (ESI-MS) and (125)Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)TeNb5O18](6-) and [Nb6O19](8-) in borate buffer. No condensation or degradation products were detected. Reactions of 1 with {Cp*Rh}(2+) sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by (125)Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}(2+) to different {M3O3} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na3[{Cp*Rh}2TeNb5O19]·24H2O (Cp*2Rh2-1) with two {Cp*Rh}(2+) fragments capping the opposing faces of the Lindqvist anion.

  20. Effect of microstructural evolution on in-reactor creep of Zr-2.5Nb tubes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, YoungSuk [Korea Atomic Energy Research Institute, Zirconium Group, P.O. Box 105, Yusong, Daejon 305-353 (Korea, Republic of)]. E-mail: yskim1@kaeri.re.kr; Im, KyungSoo [Korea Atomic Energy Research Institute, Zirconium Group, P.O. Box 105, Yusong, Daejon 305-353 (Korea, Republic of); Cheong, YongMoo [Korea Atomic Energy Research Institute, Zirconium Group, P.O. Box 105, Yusong, Daejon 305-353 (Korea, Republic of); Ahn, SangBok [Korea Atomic Energy Research Institute, Zirconium Group, P.O. Box 105, Yusong, Daejon 305-353 (Korea, Republic of)

    2005-11-15

    Dislocation density, decomposition of the {beta}-Zr phase and diametral creep were examined as a function of the location of the Zr-2.5Nb tube irradiated in the Wolsong Unit 1 for 9.3 effective full power years (EFPYs). The maximum a-dislocation density occurred at the inlet part of the irradiated Zr-2.5Nb tube exposed to the lowest temperature while the outlet part of the tube exposed to the higher temperature had the higher extent of decomposition of the {beta}-Zr phase and the maximum diametral creep. Thus, it is concluded that in-reactor creep of the Zr-2.5Nb tube is not related to the dislocation density but governed by the Nb concentration of the {alpha}-Zr grains caused by thermal decomposition of the {beta}-Zr phase. Supplementary creep tests on the Zr-2.5Nb sheets with different Nb contents in the {beta}-Zr phase provide supportive evidence to this conclusion. The acceleration of the in-reactor creep of the Zr-2.5Nb tubes is suggested after a long-term operation.

  1. Electrically tuned photoelectrochemical properties of ferroelectric nanostructure NaNbO3 films

    Science.gov (United States)

    Singh, Simrjit; Khare, Neeraj

    2017-04-01

    Photoelectrochemical (PEC) properties of NaNbO3 nanostructure ferroelectric films are investigated, and it is demonstrated that the efficiency of PEC water splitting can be tuned (7%-23%) by electrical polarization of the NaNbO3 films. The NaNbO3 photoelectrode is fabricated using hydrothermally synthesized NaNbO3 nanoparticles. Compared to the as-prepared photoanode, photocurrent is enhanced from 0.31 to 0.51 mA/cm2 (at 1 V vs. Ag/AgCl) for the negatively polarized NaNbO3 film, whereas the photocurrent is found to decrease from 0.31 to 0.09 mA/cm2 for the positively polarized NaNbO3 film. The change in the photoelectrochemical activity after the polarization of NaNbO3 films has been attributed to the change in the conduction/valence band bending at the semiconductor/electrolyte interface, leading to a change in the efficiency of charge transfer at the interface. Mott-Schottky studies confirmed the change in band bending after polarization, and electrochemical impedance spectroscopy studies confirmed the modulation in the charge transfer process after polarization.

  2. Electron beam refining of Nb-Zr alloy prepared by aluminothermic reduction. 2nd Report. ; Production of Nb-Zr alloy by aluminothermic reduction-electron beam refining. Aluminium thermit kangen Nb-Zr gokin no denshi beam yokai. 2. ; Aluminium thermit kangen-denshi beam yokai seirenho ni yoru Nb-Zr kei gokin no seizo

    Energy Technology Data Exchange (ETDEWEB)

    Uejo, S.; Numa, K. (Nippon Mining Co. Ltd., Tokyo (Japan))

    1991-11-25

    Aluminothermic reduction of Nb{sub 2}O{sub 5}-ZrO{sub 2} mixture and subsequent electron beam refining of Nb-Zr-Al alloys were reported. In 2 kg batch aluminothermic reduction tests, the Nb-Zr-Al alloys containing 1-10% Zr and 14-25% Al were obtained as the Nb{sub 2}O{sub 5}-ZrO{sub 2} mixture containing amounts of ZrO{sub 2} equivalent to 20-40% Zr was reduced by Al of 15-56% in excess of stoichiometric requirement. In electron beam refining tests, the Nb-Zr-Al alloys containing 0.1-8% Zr and 7-28% Al were used as specimens. The Al content in the Nb-Zr-Al alloy was easily reduced to 50 ppm or less by refining in a short time, and the Zr content was also evaporated decreasing its concentration. Even the Nb-l%Zr alloy could be produced by adjusting mixing conditions in aluminothermic reduction and beam conditions during refining. 6 refs., 6 figs., 6 tabs.

  3. Identification and localisation of the NB-LRR gene family within the potato genome

    Directory of Open Access Journals (Sweden)

    Jupe Florian

    2012-02-01

    Full Text Available Abstract Background The potato genome sequence derived from the Solanum tuberosum Group Phureja clone DM1-3 516 R44 provides unparalleled insight into the genome composition and organisation of this important crop. A key class of genes that comprises the vast majority of plant resistance (R genes contains a nucleotide-binding and leucine-rich repeat domain, and is collectively known as NB-LRRs. Results As part of an effort to accelerate the process of functional R gene isolation, we performed an amino acid motif based search of the annotated potato genome and identified 438 NB-LRR type genes among the ~39,000 potato gene models. Of the predicted genes, 77 contain an N-terminal toll/interleukin 1 receptor (TIR-like domain, and 107 of the remaining 361 non-TIR genes contain an N-terminal coiled-coil (CC domain. Physical map positions were established for 370 predicted NB-LRR genes across all 12 potato chromosomes. The majority of NB-LRRs are physically organised within 63 identified clusters, of which 50 are homogeneous in that they contain NB-LRRs derived from a recent common ancestor. Conclusions By establishing the phylogenetic and positional relationship of potato NB-LRRs, our analysis offers significant insight into the evolution of potato R genes. Furthermore, the data provide a blueprint for future efforts to identify and more rapidly clone functional NB-LRR genes from Solanum species.

  4. Analysis of Nb3Sn 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 Nb3Sn 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 Nb3Sn makes it possible to reach a practical operating magnetic field limit of up to 16 T. The superconducting coils are formed by Nb3Sn Rutherford cables with a trapezoidal cross section and composed of 40 strands. Since the superconducting phase of Nb3Sn is very brittle and it is reached after a thermal cycle, the Nb3Sn 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 Nb3Sn Rutherford cable production and the strands deformations due to the high aspec...

  5. Effect of Nb Doping on High Temperature Oxidation Resistance of Ti-Al Alloyed Coatings

    Directory of Open Access Journals (Sweden)

    DAI Jing-jie

    2017-02-01

    Full Text Available Ti-Al alloyed coatings with different Nb doping contents were fabricated on TC4 titanium alloy by laser surface alloying to improve high temperature oxidation resistance of the alloy. Structures and high temperature oxidation behaviors of the alloyed coatings were analyzed and tested by X-ray diffraction (XRD, scanning electron microscope (SEM, energy dispersive spectrometer (EDS and box-type resistance furnace. The results show that the alloyed coatings consist of TiAl and Ti3Al, and no niobium compound are formed in Ti-Al-Nb alloyed coatings. The alloyed coatings are uniform and exhibit excellent metallurgical bonding with the substrates. A large amount of surface cracks and a few penetrating cracks are formed in Ti-Al alloyed coating without Nb doping, while no obvious cracks are formed in Ti-Al alloyed coating with Nb doping. The oxidation mass gains of all the alloyed coatings were significantly lower than those of the substrate. The alloyed coatings with Nb doping exhibit more excellent high temperature oxidation resistance due to the beneficial machanism of Nb doping. The mechanism of Nb doping on improving high temperature oxidation resistance of Ti-Al alloyed coatings includes reducing the defect concentration of TiO2, refining oxide grains and promoting the formation of Al2O3.

  6. 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.)

  7. Transformation Heat Treatment of Rapidly Quenched Nb3A1 Precursor Monitored in situ by High Energy Synchrotron Diffraction

    CERN Document Server

    Scheuerlein, C; Di Michiel, M; Jin, X; Takeuchi, T; Kikuchi, A; Tsuchiya, K; Nakagawa, K; Nakamoto, T

    2013-01-01

    Nb3Al superconductors are studied for use in high field magnets. Fine grained Nb3Al with nearly stoichiometric Al content is obtained by a Rapid Heating Quenching and Transformation (RHQT) process. We describe a non destructive in situ study of the transformation process step of a RHQ Nb3Al precursor wire with ramp rates of either 120 °C/h or 800 °C/h. High energy synchrotron x-ray diffraction measurements show the transformation from a Nb(Al)SS supersaturated solid solution into Nb3Al. When heating with a ramp rate of 120 °C/h a strong reduction of the Nb(Al)SS (110) diffraction peak component is observed when the temperature exceeds 660 °C. Additional diffraction peaks are detectable in the approximate temperature interval 610 °C - 750 °C and significant Nb3Al growth is observed above 730 °C.

  8. Combustion synthesis in the Ni-Al-Nb ternary system: A Time-Resolved X-ray Diffraction study

    Science.gov (United States)

    Sytschev, Alexander E.; Kovalev, Dmitry Yu.; Vrel, Dominique; Vadchenko, Sergey G.

    Combustion synthesis of intermetallics, using the thermal explosion mode, in the Ni-Al-Nb ternary system is presented, with a 40:40:20 atomic ratio. The kinetic pathway is determined using Time-Resolved X-ray Diffraction, with a time-step resolution of 1 s and demonstrated a first formation of the B2 NiAl structure followed by progressive dissolution of Nb to yield NiAlNb intermetallic Laves phase, representing 35 w% of the final product. SEM observations show a double dendritic (coarse and fine) microstructure, resulting from eutectic crystallization. Due to a high cooling rate, Nb dissolution is not complete at the surface, and yields slightly more complex microstructure, including the Ni2AlNb Geissler phase, the (Ni,Al)2Nb Laves phase, and (Ni, Al)7Nb6.

  9. Processing and characterization of Al-Al3Nb prepared by mechanical alloying and equal channel angular pressing

    Science.gov (United States)

    Chandran, P.; Zafari, A.; Lui, E. W.; Xia, K.

    2017-05-01

    Mechanically alloyed Al with immiscible elements such as Nb can lead to a uniform distribution of nanoscaled precipitates which are highly stable compared to conventional alloying and with excellent interface, resulting in significant increase in strength without problems associated with nano ceramic particles in metal matrix composites. Although immiscible, Nb can be alloyed with Al through mechanical milling, forming trialuminide (Al3Nb), either directly or upon subsequent precipitation, which possesses high strength, stiffness and stability at elevated temperatures. In the present study, Al-5 at.% Nb supersaturated solid solution was achieved after prolonged ball milling and nano Al3Nb precipitates were formed during subsequent ageing at 530°C. The Al-Al3Nb powder was consolidated by equal channel angular pressing (ECAP) at 400°C, resulting in a fully dense material with a uniform distribution of nanoscaled Al3Nb precipitates in the Al matrix.

  10. 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.

  11. Electron concentration and phase stability in NbCr2-based Laves phase alloys

    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.

    1997-05-12

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases was studied, based on the data reported for binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor, e/a, is the dominating factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves polytypes were determined as followed: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88--7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure is stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of Mg-based Laves phases and transition-metal A{sub 3}B intermetallic compounds is also reviewed and compared with the present observations in transition-metal Laves phases. In order to verify the e/a/phase stability relationship experimentally, additions of Cu (with e/a = 11) were selected to replace Cr in the NbCr{sub 2} Laves phase. Experimental results for the ternary Nb-Cr-Cu system are reported and discussed in terms of the correlation between the e/a ratio and phase stability in NbCr{sub 2}-based Laves phases. A new phase was found, which has an average composition of Nb-47Cr-3Cu. Within the solubility limit, the electron concentration and phase stability relationship is obeyed in the Nb-Cr-Cu system.

  12. Investigation on hydrogenation performance of Mg{sub 2}Ni+10 wt.% NbN composite

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin; Han, Shumin [Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhu, Yi [Inner Mongolia Rare Earth Ovonic Metal Hydride Co. Ltd., Baotou 014030 (China); Chen, Xiaocui; Ke, Dandan; Wang, Zhibin; Liu, Ting; Ma, Yufei [Hebei Key Laboratory of Applied Chemistry, College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2015-01-15

    The Mg{sub 2}Ni+10 wt.% NbN composite was prepared by mechanical milling and its hydrogen absorption/desorption properties and microstructure were systematically investigated. XRD results indicated that NbN was stable during ball milling process while partly decomposed into NbN{sub 0.95} and NbH during hydriding/dehydriding cycles irreversibly. The composite exhibited excellent hydrogenation/dehydrogenation kinetics performance with 2.71 wt.% hydrogen absorbed in 60 s at 423 K and 0.81 wt.% hydrogen released in 2 h at 523 K, respectively. The H diffusion constant of the composite reached 14.98×10{sup −5} s{sup −1} which was more than twice increased than that of pure Mg{sub 2}Ni powder. The superior hydrogen storage properties of the composite were ascribed to the refined grain size and abundant N-defect points provided by NbN and NbN{sub 0.95} in the composite. - Graphical abstract: The Mg{sub 2}Ni+10 wt.% NbN composite displays improvements on particle size distribution as well as hydrogen storage properties compared with that of pure Mg{sub 2}Ni. - Highlights: • NbN is introduced into Mg{sub 2}Ni hydride by Ar protected ball-milling. • Surfaces of the additive NbN particle are reduced by Mg{sub 2}NiH{sub 4}. • Hydrogenation kinetic property at 423 K is double improved. • Dehydrogenation capacity at 523 K of composites is beyond double improved.

  13. Efficient ultraviolet photorefraction in LiNbO3

    Science.gov (United States)

    Jungen, R.; Angelow, G.; Laeri, F.; Grabmaier, C.

    1992-07-01

    A nominally undoped LiNbO3 crystal with a slightly broadened absorption edge is used to study beam coupling effects in the UV at 351 nm. At this wavelength the crystal exhibits a diffusion-dominated charge transport mechanism, which allows steady state beam amplification of up to 700 times, comparable to BaTiO3 in the visible. The used crystal material was characterized by an absorption coefficient α=2.68 cm-1 at 351 nm and a maximal gain coefficient Г=13.94 cm-1. This high gain value in the UV can be attributed to a hole diffusion-dominated charge transport mechanism together with a low bulk photovoltaic effect. We measured photovoltaic fields of the order of 550 V/cm.

  14. Excitation function calculations for α + {sup 93}Nb nuclear reactions

    Energy Technology Data Exchange (ETDEWEB)

    Yiğit, M., E-mail: mustafayigit@aksaray.edu.tr [Aksaray University, Physics Dept., Aksaray (Turkey); Tel, E. [Osmaniye Korkut Ata University, Physics Dept., Osmaniye (Turkey); Sarpün, İ.H. [Afyon Kocatepe University, Physics Dept., Afyonkarahisar (Turkey)

    2016-10-15

    In this study, the excitation functions of alpha-induced reactions on the {sup 93}Nb target nucleus were calculated by using ALICE-ASH code. The hybrid model, Weisskopf-Ewing model and geometry dependent hybrid model in this code were used to understand the alpha-niobium interaction. The contribution on the nuclear interaction of compound and pre-compound processes, with variation of the incident alpha particle energy, was presented. Furthermore, the reaction cross sections were calculated by using different level density models such as Superfluid nuclear model, Fermi gas model and Kataria-Ramamurthy Fermi gas model. Obtaining a good agreement between the calculated and the measured cross sections, the exciton numbers and the nuclear level density models were varied. Finally, the proper choice of the exciton numbers and the nuclear level density models was found to be quite important in order to obtain the more realistic cross section values.

  15. High Gradient $Nb_3Sn$ Quadrupole Demonstrator MKQXF Engineering Design

    CERN Document Server

    Kokkinos, C; Karppinen, Mikko; CERN. Geneva. ATS Department

    2016-01-01

    A new mechanical design concept for the $Nb_3Sn$ quadrupoles has been developed with a goal of an accelerator quality magnet that can be industrially produced in large series. This concept can easily be extended to any length and applied on both 1-in-1 and 2-in-1 configurations. It is based on the pole-loading concept and collared coils using dipole-type collars. Detailed design optimisation of a demonstrator magnet based on present base-line HL-LHC IR quadrupole QXF coil geometry has been carried out including the end regions. This report describes the design concept and the fully parametric multi-physics finite element (FE) models that were used to determine the optimal assembly parameters including the effects of the manufacturing tolerances.

  16. Dielectric Properties of Rhombohedral PbNb2O6

    Directory of Open Access Journals (Sweden)

    Kriti Ranjan Sahu

    2013-01-01

    Full Text Available Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. PbNb2O6 (PN is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS up to ~700∘C and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (τ, AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data.

  17. Nb3Sn Dipole Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Sampson, W. B.; Kiss, S.; Robins, K. E.; McInturff, A. D.

    1978-09-01

    Multifilamentary Nb3Sn conductors suitable for use in accelerator magnets have been under development at BNL for a number of years. To date three one meter long dipole magnets have been constructed from braided conductor which had been reacted prior to winding. The first of these dipoles and the method of construction has been described in an earlier paper. The most recent magnet in this series was tested over the temperature range 4.2 K to 15 K using high pressure gas cooling. The maximum field 4.8 T, was achieved at 4.2 K. At higher temperatures the field decreased approximately linearly with temperature passing through 4.0 T at just under 8 K.

  18. Enhanced thermoelectric performance of amorphous Nb based oxynitrides

    Energy Technology Data Exchange (ETDEWEB)

    Music, Denis, E-mail: music@mch.rwth-aachen.de; Geyer, Richard W.; Hans, Marcus

    2015-12-15

    Using density functional theory, amorphous Nb{sub 0.27}Ru{sub 0.06}O{sub 0.56}N{sub 0.10} was designed to facilitate a combination of an enhanced Seebeck coefficient and low electrical resistivity. Based on a positive Cauchy pressure, ductile behavior is expected. To verify these predictions, the transport and mechanical properties of amorphous thin films were evaluated. Metallic electrical resistivity and the Seebeck coefficient of −94 µV K{sup −1} are obtained, which is consistent with our predictions. As there is no crack formation, these samples can be perceived as ductile. We demonstrate that the power factor can be increased by an order of magnitude, while keeping the thermal fatigue low.

  19. Effect of Nb on barium titanate prepared from citrate solutions

    Directory of Open Access Journals (Sweden)

    Stojanović Biljana D.

    2002-01-01

    Full Text Available The influence of the addition of dopants on the microstructure development and electrical properties of BaTiO3 doped with 0.2, 0.4, 0.6, 0.8 mol% of Nb and 0.01 mol% of Mn based compounds was studied. Doped barium titanate was prepared using the polymeric precursor method from citrate solutions. The powders calcined at 700°C for 4 hours were analysed by infrared (IR spectroscopy to verify the presence of carbonates, and by X-ray diffraction (XRD for phase formation. The phase composition, microstructure and dielectric properties show a strong dependence on the amount of added niobium.

  20. Austenite grain growth calculation of 0.028% Nb steel

    Directory of Open Access Journals (Sweden)

    Priadi D.

    2011-01-01

    Full Text Available Modeling of microstructural evolution has become a powerful tool for materials and process design by providing quantitative relationships for microstructure, composition and processing. Insufficient attention has been paid to predicting the austenite grain growth of microalloyed steel and the effect of undissolved microalloys. In this research, we attempted to calculate a mathematical model for austenite grain growth of 0.028% Nb steel, which can account for abnormal grain growth. The quantitative calculation of austenite grain growth generated from this model fit well with the experimental grain growth data obtained during reheating of niobium steels. The results of this study showed that increasing the temperature increases the austenite grain size, with a sharp gradient observed at higher temperatures.

  1. NB Coating Developments with HIPIMS for SRF Applications

    CERN Document Server

    Terenziani, G; Junginger, T; Santillana, I A; Ehiasarian, A P

    2013-01-01

    In the last few years the interest of the thin film science and technology community on High Impulse Power Magnetron Sputtering (HIPIMS) coatings has steadily increased. HIPIMS literature shows that better thin film morphology, denser and smoother films can be achieved when compared with standard dc Magnetron Sputtering (dcMS) coating technology [1]. Furthermore the capability of HIPIMS to produce a high quantity of ionized species [2,3] can allow conformal coatings also for complex geometries. A study is under way at CERN to apply this technology for the Nb coating of SRF 1.3-1.5 GHz Cu cavities, and in parallel at SHU the plasma physics and its correlation with film morphology are being investigated [2]. Recent results achieved with this technique are presented in the paper.

  2. New Mechanical Concept for Nb$_{3}$Sn Quadrupole

    CERN Document Server

    AUTHOR|(CDS)2051169

    2014-01-01

    A new mechanical design concept for the Nb3Sn quadrupoles has been developed with a goal of an accelerator quality magnet that can be industrially produced in large series. This concept can easily be extended to any length and applied on both 1-in-1 and 2-in-1 configurations. It is based on the pole-loading concept and collared coils using dipole-type collars. First conceptual design study using finite element analysis has been carried out using the present base-line HL-LHC IR quadrupole QXF coil geometry for direct comparison with the bladder-and-key structure. The main features of the new design concept are described and the main results of the structural analysis discussed.

  3. Guided vortex motion in Nb films on facetted substrate surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Soroka, Oleksiy K.; Huth, Michael; Shklovskij, Valerij A.; Oster, Jens; Adrian, Hermann

    2003-05-15

    Anisotropy of the pinning force in a superconductor can cause a guiding effect on the vortices, which leads to the appearance of new components in the galvanomagnetic quantities of the sample. In this case one can observe an additional odd magnetoresistive component with respect to magnetic field reversal. Furthermore, an even contribution to the Hall voltage is observed. Guided motion of vortices in Nb films on facetted {alpha}-Al{sub 2}O{sub 3} (1 0 1-bar 0) was found by measuring the longitudinal and transversal resistivities of three films with transport current directed parallel, perpendicular and at an angle of 45 deg. with respect to the facet ridges. Field inversion was used to separate the even and odd components of the measured magnetoresistivities and thus to obtain the contributions caused by the guided vortex motion.

  4. Developing a bone mineral density test result letter to send to patients: a mixed-methods study

    Directory of Open Access Journals (Sweden)

    Edmonds SW

    2014-06-01

    Full Text Available Stephanie W Edmonds,1,2 Samantha L Solimeo,3 Xin Lu,1 Douglas W Roblin,4,8 Kenneth G Saag,5 Peter Cram6,7 1Department of Internal Medicine, 2College of Nursing, University of Iowa, Iowa City, IA, USA; 3Center for Comprehensive Access and Delivery Research and Evaluation, Iowa City Veterans Affairs Health Care System, Iowa City, IA, USA; 4Kaiser Permanente of Atlanta, Atlanta, GA, USA; 5Department of Rheumatology, University of Alabama at Birmingham, Birmingham, AL, USA; 6Faculty of Medicine, University of Toronto, Toronto, ON, Canada; 7University Health Network and Mount Sinai Hospital, Toronto, ON, Canada; 8School of Public Health, Georgia State University, Atlanta, GA, USA Purpose: To use a mixed-methods approach to develop a letter that can be used to notify patients of their bone mineral density (BMD results by mail that may activate patients in their bone-related health care. Patients and methods: A multidisciplinary team developed three versions of a letter for reporting BMD results to patients. Trained interviewers presented these letters in a random order to a convenience sample of adults, aged 50 years and older, at two different health care systems. We conducted structured interviews to examine the respondents’ preferences and comprehension among the various letters. Results: A total of 142 participants completed the interview. A majority of the participants were female (64.1% and white (76.1%. A plurality of the participants identified a specific version of the three letters as both their preferred version (45.2%; P<0.001 and as the easiest to understand (44.6%; P<0.01. A majority of participants preferred that the letters include specific next steps for improving their bone health. Conclusion: Using a mixed-methods approach, we were able to develop and optimize a printed letter for communicating a complex test result (BMD to patients. Our results may offer guidance to clinicians, administrators, and researchers who are

  5. Reentrant metallic behavior in the Weyl semimetal NbP

    Science.gov (United States)

    Xu, J.; Bugaris, D. E.; Xiao, Z. L.; Wang, Y. L.; Chung, D. Y.; Kanatzidis, M. G.; Kwok, W. K.

    2017-09-01

    We report the occurrence of reentrant metallic behavior in the Weyl semimetal NbP. When the applied magnetic field H is above a critical value Hc, a reentrance appears as a peak in the temperature-dependent resistivity ρx x(T ) at T =Tp , similar to that observed in graphite where it was attributed to local superconductivity. The Tp(H ) relationship follows a power-law dependence Tp˜(H-Hc) 1 /ν where ν can be derived from the temperature dependence of the zero-field resistivity ρ0(T ) ˜Tν . From concurrent measurements of the transverse ρx x(T ) and Hall ρx y(T ) magnetoresistivities, we reveal a clear correlation between the rapidly increasing ρx y(T ) and the occurrence of a peak in the ρx x(T ) curve. Quantitative analysis indicates that the reentrant metallic behavior arises from the competition of the magnetoconductivity σx x(T ) with an additional component Δ σx x(T ) =κHσx x(T ) where κH=[ρxy(T ) /ρx x(T ) ] 2 is the Hall factor. We find that the Hall factor (κH≈0.4 ) at peak temperature Tp is nearly field independent, leading to the observed Tp(H ) relationship. Furthermore, the reentrant metallic behavior in ρx x(T ) also is reflected in the behavior of ρx x(H ) that ranges from nonsaturating at T >70 K to saturation at liquid-helium temperatures. The latter can be explained with the magnetic field dependence of the Hall factor κH(H ) . Our paper demonstrates that a semiclassical theory can account for the "anomalies" in the magnetotransport phenomena of NbP without invoking an exotic mechanism.

  6. Reentrant metallic behavior in the Weyl semimetal NbP

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.; Bugaris, D. E.; Xiao, Z. L.; Wang, Y. L.; Chung, D. Y.; Kanatzidis, M. G.; Kwok, W. K.

    2017-09-01

    We report the occurrence of reentrantmetallic behavior in theWeyl semimetal NbP. When the appliedmagnetic field H is above a critical value H-c, a reentrance appears as a peak in the temperature-dependent resistivity rho(xx) (T) at T = T-p, similar to that observed in graphite where it was attributed to local superconductivity. The Tp(H) relationship follows a power-law dependence T-p similar to (H-H-c)(1/nu) where. can be derived from the temperature dependence of the zero-field resistivity rho(0)(T) similar to T-nu. From concurrent measurements of the transverse rho(xx) (T) and Hall rho(xy)(T) magnetoresistivities, we reveal a clear correlation between the rapidly increasing rho(xy) (T) and the occurrence of a peak in the rho(xx) (T) curve. Quantitative analysis indicates that the reentrantmetallic behavior arises from the competition of the magnetoconductivity sigma(xx) (T) with an additional component Delta sigma(xx) (T) = kappa(H)sigma(xx)(T) where kappa(H) = [rho(xy)(T)/rho(xx)(T)](2) is the Hall factor. We find that the Hall factor (kappa(H) approximate to 0.4) at peak temperature T-p is nearly field independent, leading to the observed T-p (H) relationship. Furthermore, the reentrant metallic behavior in rho(xx) (T) also is reflected in the behavior of rho(xx) (H) that ranges from nonsaturating at T > 70K to saturation at liquid-helium temperatures. The latter can be explained with the magnetic field dependence of the Hall factor kappa(H) (H). Our paper demonstrates that a semiclassical theory can account for the "anomalies" in the magnetotransport phenomena of NbP without invoking an exotic mechanism.

  7. The {Ni10Nb32} aggregate: a perspective on isopolyniobates as ligands.

    Science.gov (United States)

    Liang, Zhijie; Zhang, Dongdi; Wang, Haiying; Ma, Pengtao; Yang, Zongfei; Niu, Jingyang; Wang, Jingping

    2016-10-18

    [H4Ni10(H2O)8Nb32O102]20-, representing the first high-nuclear nickel-cation-bridged polyoxoniobate, has been synthesized. It incorporates two [{Ni2O4}(H2O)2(Nb6O19)]12- and two [Ni3(H2O)2Nb10O34]12- subunits exhibiting a rhombus-like architecture. Furthermore, the solution behaviour was examined by electrospray ionization mass spectrometry and the magnetic properties in the low temperature range indicate the presence of ferromagnetic interactions.

  8. A Primer on 3GPP Narrowband Internet of Things (NB-IoT)

    OpenAIRE

    Wang, Y. -P. Eric; Lin, Xingqin; Adhikary, Ansuman; Grövlen, Asbjörn; Sui, Yutao; Blankenship, Yufei; Bergman, Johan; Razaghi, Hazhir S.

    2016-01-01

    Narrowband Internet of Things (NB-IoT) is a new cellular technology introduced in 3GPP Release 13 for providing wide-area coverage for the Internet of Things (IoT). This article provides an overview of the air interface of NB-IoT. We describe how NB-IoT addresses key IoT requirements such as deployment flexibility, low device complexity, long battery life time, support of massive number of devices in a cell, and significant coverage extension beyond existing cellular technologies. We also sha...

  9. Piezoelectric, Mechanical and Acoustic Properties of KNaNbOF5 from First-Principles Calculations

    Directory of Open Access Journals (Sweden)

    Han Han

    2015-12-01

    Full Text Available Recently, a noncentrosymmetric crystal, KNaNbOF5, has attracted attention due to its potential to present piezoelectric properties. Although α- and β-KNaNbOF5 are similar in their stoichiometries, their structural frameworks, and their synthetic routes, the two phases exhibit very different properties. This paper presents, from first-principles calculations, comparative studies of the structural, electronic, piezoelectric, and elastic properties of the α and the β phase of the material. Based on the Christoffel equation, the slowness surface of the acoustic waves is obtained to describe its acoustic prosperities. These results may benefit further applications of KNaNbOF5.

  10. Effects of Nb impurity on orthorhombic PbZrO{sub 3} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Rivera, Richard; Stashans, Arvids [Grupo de FisicoquImica de Materiales, Instituto de Quimica Aplicada, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)], E-mail: arvids@utpl.edu.ec

    2008-10-15

    A study of Nb doping in lead zirconate (PbZrO{sub 3}) has been carried out by using a quantum-chemical method developed for crystals and a periodic supercell model. One of the Zr atoms was replaced by an Nb atom in the supercell consisting of 80 atoms. The obtained geometry optimization for the defective region points to defect-outward atomic movements, which are accompanied by some reduction of atomic charges. It is observed that an extra electron imposed by the Nb impurity is transferred to the conduction band of the material and contributes to the n-type electrical conductivity, explaining indirectly some of the experimental observations.

  11. Formation of amorphous alloys through the multilayer method in an immiscible Y-Nb system

    CERN Document Server

    Chen, Y G; Zhang, Q

    1997-01-01

    Amorphization was achieved by room-temperature 190 keV xenon ion mixing of multilayered films in the Y-Nb system, which has a positive enthalpy of formation exceeding +44 kJ mol sup - sup 1. To give further insight into the singularity of the amorphization behaviour of the system, a Gibbs free-energy diagram of the system was constructed by calculating the free energies of the amorphous phase and those of the as-deposited Y-Nb multilayers, in which the interfacial free energy was estimated and added. The established diagram can explain the irradiation-induced amorphization behaviour in the Y-Nb system well. (author)

  12. On the role of Nb in Z-phase formation in a 12% Cr steel

    DEFF Research Database (Denmark)

    Cipolla, L.; Danielsen, Hilmar Kjartansson; Di Nunzio, P.E.

    2010-01-01

    Z-phase precipitation in two model alloys, 12CrVNbN and 12CrVN, has been investigated. The alloys were aged up to 104 h and their precipitate evolution was followed by X-ray diffraction and transmission electron microscopy. The formation rate of Z-phase from vanadium-based nitrides, (V......,Nb)N, in the Nb-containing alloy was observed to proceed considerably faster than in the Nb-free alloy. A hypothesis is put forward that explains the enhanced stability of VN in terms of changes in the interfacial energy of VN with the ferrite matrix....

  13. Microstructure and tribological properties of NbN-Ag composite films by reactive magnetron sputtering

    Science.gov (United States)

    Ju, Hongbo; Xu, Junhua

    2015-11-01

    Recently, the chameleon thin films were developed with the purpose of adjusting their chemistry at self-mating interfaces in response to environmental changes at a wide temperature range. However, very few studies have focused on what state the lubricious noble metal exists in the films and the tribological properties at room temperature (RT). Composite NbN-Ag films with various Ag content (Ag/(Nb + Ag)) were deposited using reactive magnetron sputtering to investigate the crystal structure, mechanical and tribological properties. A combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analyses showed that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc silver coexisted in NbN-Ag films. The incorporation of soft Ag into NbN matrix led to the hardness decrease from 29.6 GPa at 0 at.% Ag to 11.3 GPa at 19.9 at.% Ag. Tribological properties of NbN-Ag films performed using dry pin-on-disc wear tests against Al2O3 depended on Ag content to a large extent. The average friction coefficient and wear rate of NbN-Ag films decreased as Ag content increased from 4.0 to 9.2 at.%. With a further increase of Ag content, the average friction coefficient further decreased, while the wear rate increased gradually. The optimal Ag content was found to be 9.2-13.5 at.%, which showed low average friction coefficient values of 0.46-0.40 and wear rate values of 1.1 × 10-8 to 1.7 × 10-8 mm3/(mm N). 3D Profiler and Raman spectroscopy measurements revealed that the lubricant tribo-film AgNbO3 detected on the surface of the wear tracks could lead to the friction coefficient curve stay constant and decrease the average friction coefficients. The decrease of wear rate was mainly attributed to the lubricant tribo-film AgNbO3 as Ag content increased from 4.0 to 9.2 at.%; with a further increase in Ag content, the wear rate increased with increasing Ag content in NbN-Ag films because a

  14. Synthesis of cubic LiNbO{sub 3} nanoparticles and their application in vitro bioimaging

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.; Chen, Z.; Cai, B.; Ye, Z.Z.; Huang, J.Y. [Zhejiang University, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Room 332, Hangzhou (China); Zhou, X.Y.; Gao, C.Y. [Zhejiang University, Department of Polymer Science and Engineering, Hangzhou (China)

    2014-12-15

    Stoichiometric LiNbO{sub 3} nanoparticles with regular rhombohedral morphology and high crystallinity were synthesized through a molten salt approach. The as-synthesized cubic LiNbO{sub 3} nanoparticles as nanoprobes for long-term imaging in vitro were investigated. The as-synthesized nanoprobes exhibit unique properties of long-term observation without photobleaching, flexibility in excitation wavelength, and excellent photostability. The biocompatibility of LiNbO{sub 3} nanoprobes was determined by in vitro assay of cytotoxicity. All the tested samples presented no obvious toxicity. (orig.)

  15. Hydrogen trapping by solute atoms in Nb-Mo alloys as observed by the channelling method

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, Eiichi; Nakamura, Shiho; Kano, Fumihisa; Kobayashi, Takane (Institute of Physical and Chemical Research, Wako, Saitama (Japan)); Watanabe, Kenyi; Fukai, Yuh (Chuo Univ., Tokyo (Japan). Dept. of Physics); Matsumoto, Takehiko (National Research Inst. for Metals, Tokyo (Japan))

    1989-01-01

    The enhancement of the terminal solubility for hydrogen (TSH) in group Va metals (V, Nb and Ta) on alloying with metal solute atoms has been reported for various alloying elements. To elucidate the mechanism of this enhancement, in the present study the lattice location of hydrogen was investigated by the channeling method using a nuclear reaction {sup 1}H({sup 11}B,{alpha}){alpha}{alpha} on the Nb alloys containing undersized Mo atoms (Nb-3at%Mo alloys). (orig./MM).

  16. PERSISTENT CURRENT EFFECT IN 15-16 T NB3SN ACCELERATOR DIPOLES AND ITS CORRECTION

    Energy Technology Data Exchange (ETDEWEB)

    Kashikhin, V. V. [Fermilab; Zlobin, A. V. [Fermilab

    2016-11-08

    Nb3Sn magnets with operating fields of 15-16 T are considered for the LHC Energy Doubler and a future Very High Energy pp Collider. Due to large coil volume, high critical current density and large superconducting (SC) filament size the persistent current effect is very large in Nb3Sn dipoles al low fields. This paper presents the results of analysis of the persistent current effect in the 15 T Nb3Sn dipole demonstrator being developed at FNAL, and describes different possibilities of its correction including passive SC wires, iron shims and coil geometry.

  17. Room-Temperature Processed Nb2O5as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells.

    Science.gov (United States)

    Ling, Xufeng; Yuan, Jianyu; Liu, Dongyang; Wang, Yongjie; Zhang, Yannan; Chen, Si; Wu, Haihua; Jin, Feng; Wu, Fupeng; Shi, Guozheng; Tang, Xun; Zheng, Jiawei; Liu, Shengzhong Frank; Liu, Zhike; Ma, Wanli

    2017-07-12

    In this work, we demonstrate high-efficiency planar perovskite solar cells (PSCs), using room-temperature sputtered niobium oxide (Nb 2 O 5 ) as the electron-transporting layer (ETL). Widely spread ETL-like TiO 2 often requires high-temperature (>450 °C) sintering, which is not desired for the fabrication of flexible devices. The amorphous Nb 2 O 5 (labeled as a-Nb 2 O 5 ) ETL, without any heat treatment, can give a best power conversion efficiency (PCE) of 17.1% for planar PSCs. Interestingly, the crystalline Nb 2 O 5 (labeled as c-Nb 2 O 5 ), with high-temperature (500 °C) annealing, results in a very similar PCE of 17.2%, indicating the great advantage of a-Nb 2 O 5 in energy saving. We thus carried out a systematical investigation on the properties of the a-Nb 2 O 5 film. The Hall effect measurements indicate both high mobility and conductivity of the a-Nb 2 O 5 film. Kelvin probe force microscopy measurements define the Fermi levels of a-Nb 2 O 5 and c-Nb 2 O 5 as -4.31 and -4.02 eV, respectively, which allow efficient electron extraction at the Nb 2 O 5 /perovskite interface, regardless of the additional heat treatment on Nb 2 O 5 film. Benefitting from the low-temperature process, we further demonstrated flexible PSCs based on a-Nb 2 O 5 , with a considerable PCE of 12.1%. The room-temperature processing and relatively high device performance of a-Nb 2 O 5 suggest a great potential for its application in optoelectrical devices.

  18. Private randomness expansion with untrusted devices

    Energy Technology Data Exchange (ETDEWEB)

    Colbeck, Roger; Kent, Adrian, E-mail: rcolbeck@perimeterinstitute.ca, E-mail: a.p.a.kent@damtp.cam.ac.uk [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5 (Canada)

    2011-03-04

    Randomness is an important resource for many applications, from gambling to secure communication. However, guaranteeing that the output from a candidate random source could not have been predicted by an outside party is a challenging task, and many supposedly random sources used today provide no such guarantee. Quantum solutions to this problem exist, for example a device which internally sends a photon through a beamsplitter and observes on which side it emerges, but, presently, such solutions require the user to trust the internal workings of the device. Here, we seek to go beyond this limitation by asking whether randomness can be generated using untrusted devices-even ones created by an adversarial agent-while providing a guarantee that no outside party (including the agent) can predict it. Since this is easily seen to be impossible unless the user has an initially private random string, the task we investigate here is private randomness expansion. We introduce a protocol for private randomness expansion with untrusted devices which is designed to take as input an initially private random string and produce as output a longer private random string. We point out that private randomness expansion protocols are generally vulnerable to attacks that can render the initial string partially insecure, even though that string is used only inside a secure laboratory; our protocol is designed to remove this previously unconsidered vulnerability by privacy amplification. We also discuss extensions of our protocol designed to generate an arbitrarily long random string from a finite initially private random string. The security of these protocols against the most general attacks is left as an open question.

  19. Mechanical Properties, Quantum Mechanical Calculations, and Crystallographic/Spectroscopic Characterization of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4.

    Science.gov (United States)

    Perfler, Lukas; Kahlenberg, Volker; Többens, Daniel; Schaur, Andreas; Tribus, Martina; Orlova, Maria; Kaindl, Reinhard

    2016-06-06

    Single crystals as well as polycrystalline samples of GaNbO4, Ga(Ta,Nb)O4, and GaTaO4 were grown from the melt and by solid-state reactions, respectively, at various temperatures between 1698 and 1983 K. The chemical composition of the crystals was confirmed by wavelength-dispersive electron microprobe analysis, and the crystal structures were determined by single-crystal X-ray diffraction. In addition, a high-P-T synthesis of GaNbO4 was performed at a pressure of 2 GPa and a temperature of 1273 K. Raman spectroscopy of all compounds as well as Rietveld refinement analysis of the powder X-ray diffraction pattern of GaNbO4 were carried out to complement the structural investigations. Density functional theory (DFT) calculations enabled the assignment of the Raman bands to specific vibrational modes within the structure of GaNbO4. To determine the hardness (H) and elastic moduli (E) of the compounds, nanoindentation experiments have been performed with a Berkovich diamond indenter tip. Analyses of the load-displacement curves resulted in a high hardness of H = 11.9 ± 0.6 GPa and a reduced elastic modulus of Er = 202 ± 9 GPa for GaTaO4. GaNbO4 showed a lower hardness of H = 9.6 ± 0.5 GPa and a reduced elastic modulus of Er = 168 ± 5 GPa. Spectroscopic ellipsometry of the polished GaTa0.5Nb0.5O4 ceramic sample was employed for the determination of the optical constants n and k. GaTa0.5Nb0.5O4 exhibits a high average refractive index of nD = 2.20, at λ = 589 nm. Furthermore, in situ high-temperature powder X-ray diffraction experiments enabled the study of the thermal expansion tensors of GaTaO4 and GaNbO4, as well as the ability to relate them with structural features.

  20. Microstructure and tribological properties of NbN-Ag composite films by reactive magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Hongbo; Xu, Junhua, E-mail: jhxu@just.edu.cn

    2015-11-15

    Highlights: • NbN-Ag films were deposited by reactive magnetron sputtering. • The fcc-NbN, hcp-NbN and fcc-Ag coexisted in NbN-Ag films. • The incorporation of Ag into NbN matrix led to the decrease of hardness. • The films (9.2–13.5 at.% Ag) were found to be optimized for wear resistance tools. - Abstract: Recently, the chameleon thin films were developed with the purpose of adjusting their chemistry at self-mating interfaces in response to environmental changes at a wide temperature range. However, very few studies have focused on what state the lubricious noble metal exists in the films and the tribological properties at room temperature (RT). Composite NbN-Ag films with various Ag content (Ag/(Nb + Ag)) were deposited using reactive magnetron sputtering to investigate the crystal structure, mechanical and tribological properties. A combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analyses showed that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc silver coexisted in NbN-Ag films. The incorporation of soft Ag into NbN matrix led to the hardness decrease from 29.6 GPa at 0 at.% Ag to 11.3 GPa at 19.9 at.% Ag. Tribological properties of NbN-Ag films performed using dry pin-on-disc wear tests against Al{sub 2}O{sub 3} depended on Ag content to a large extent. The average friction coefficient and wear rate of NbN-Ag films decreased as Ag content increased from 4.0 to 9.2 at.%. With a further increase of Ag content, the average friction coefficient further decreased, while the wear rate increased gradually. The optimal Ag content was found to be 9.2–13.5 at.%, which showed low average friction coefficient values of 0.46–0.40 and wear rate values of 1.1 × 10{sup −8} to 1.7 × 10{sup −8} mm{sup 3}/(mm N). 3D Profiler and Raman spectroscopy measurements revealed that the lubricant tribo-film AgNbO{sub 3} detected on the surface of the

  1. Giant increase in piezoelectric coefficient of AlN by Mg-Nb simultaneous addition and multiple chemical states of Nb

    Science.gov (United States)

    Uehara, Masato; Shigemoto, Hokuto; Fujio, Yuki; Nagase, Toshimi; Aida, Yasuhiro; Umeda, Keiichi; Akiyama, Morito

    2017-09-01

    Aluminum nitride (AlN) is one of piezoelectric materials, which are eagerly anticipated for use in microelectromechanical systems (MEMS) applications such as communication resonators, sensors, and energy harvesters. AlN is particularly excellent in generated voltage characteristics for the MEMS rather than oxide piezoelectric materials such as lead zirconium titanate Pb(Zr, Ti)O3. However, it is necessary to improve the piezoelectric properties of AlN in order to advance the performance of the MEMS. We dramatically increased the piezoelectric coefficient d33 of AlN films by simultaneously adding magnesium (Mg) and niobium (Nb). The d33 of Mg39.3Nb25.0Al35.7N is 22 pC/N, which is about four times that of AlN. The d33 is increased by Mg and Nb simultaneous addition, and is not increased by Mg or Nb single addition. Interestingly, the Nb has multiple chemical states, and which are influenced by the Mg concentration.

  2. A NOVEL OCTAHEDRAL NIOBIUM OXYCHLORIDE CLUSTER BUILT FROM INTERCONNECTED Nb6Cl12O4 UNITS: Cs2Sc3Nb1227O8

    Directory of Open Access Journals (Sweden)

    Fakhili Gulo

    2011-11-01

    Full Text Available A novel octahedral niobium cluster oxychloride compound, Cs2Sc3Nb12Cl27O8 was synthesized by solid-state route techniques from stoichiometric mixture of CsCl, Sc2O3, Nb, NbCl5, and Nb2O5, heated at 700 °C for two days. The crystal structure was determined by single crystal X-ray diffraction method. It crystallizes in orthorhombic system with space group of Pnma, a = 17.5206(1 Å, b = 29.6899(3 Å, c = 9.2114(1 Å, and V = 4791.63(8 Å3. The structure is based on  unit in which four oxygen ligands selectively occupy inner positions arranged in sets of three and one on opposite side of the Nb6 octahedron. Each cluster shares three apical-chlorine ligands with three adjacent clusters to form layers with topology similar to that of graphite. The cluster units are also connected to each other by both cesium and scandium atoms to form a three-dimensional framework. This compound exhibits 14 valence electrons per cluster.

  3. Measurement of Meissner effect in micro-sized Nb and FeSe crystals using an NbN nano-SQUID

    Science.gov (United States)

    Wu, Long; Chen, Lei; Wang, Hao; Wang, Qisi; Wo, Hongliang; Zhao, Jun; Liu, Xiaoyu; Wu, Xiaolei; Wang, Zhen

    2017-07-01

    The nano-superconducting quantum interference device (SQUID) is considered one of the most sensitive magnetic sensors for the characterization of mesoscopic and microscopic magnetic moments. Therefore, it is suitable for measuring the Meissner effect in small superconductors that cannot generate large enough signals for commercial magnetometers. To achieve an optimized coupling, the sample is usually placed directly on a SQUID chip and as close to the SQUID washer as possible. Therefore, a large working temperature range of the nano-SQUID is desirable to measure a wider range of samples. Here, we achieved the measurement of the Meissner effect in a 25 μm-sized Nb and a 40 μm × 120 μm-sized FeSe crystals using a niobium nitride (NbN) nano-SQUID. This nano-SQUID has a usable magnetic flux modulation for temperatures up to 9.5 K. The flux noise is around 50-60 μΦ0 Hz-1/2 for the entire measurement system. The diamagnetic branches induced by the Meissner effect below the lower critical field were observed for both Nb and FeSe crystals with the NbN nano-SQUID device. In addition, at various temperatures, strong magnetic hysteresis arising from vortices pinning was also observed and analyzed for both Nb and FeSe crystals.

  4. Role of vein-phases in nanoscale sequestration of U, Nb, Ti, and Pb during the alteration of pyrochlore

    Science.gov (United States)

    Deditius, Artur P.; Smith, Frances N. (Skomurski); Utsunomiya, Satoshi; Ewing, Rodney C.

    2015-02-01

    Grains of pyrochlore and secondary phases from tailings of Silver Crater Mine in Bancroft, Ontario (Canada) have been studied to understand the alteration processes, redox conditions, and retention of pyrochlore-derived species (U, Ti, Nb, Pb, Ta, REE) in near-field environments. Alteration processes are documented by the formation of two types of co-existing secondary veins associated with primary apatite and calcite: (i) amorphous Fe-rich veins, 46-75 wt.% of FeO, and ∼500 ppm of UO2, and (ii) crystalline calcite-rich veins, found in fractures and penetrating the pyrochlore. Based on electron microprobe analysis (EMPA), the chemical composition of the pyrochlore is: (Ca0.84U0.35Fe0.20Na0.09Pb0.04Ln0.04Mn0.03Sr0.01Th0.01Mg0.01)1.62 (Nb1.00Ti0.87Ta0.10Si0.02)2.0O6.5F0.14. Elemental mapping revealed that migration of liberated U, Pb, Nb, Ta, Ti, and REE, is confined to the secondary veins of Fe-rich and calcite-rich compositions. Transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) results showed that pyrochlore contains nanoparticulate inclusions of uraninite, galena, and magnetite, while secondary veins host betafite, magnetite, Pb0, cerusite, and 10 Å mica nanoparticles (NPs). Randomly oriented uraninite NPs, 15 nm in size, concentrate around pores, 50-100 nm in size, in the pyrochlore. In the Fe-rich veins, HAADF-STEM images revealed that U, Pb, Nb, and Ti were sequestered in the form of spherical betafite NPs, <800 nm in size, with composition: (Ca1.1Fe0.35Pb0.28U0.09)1.83(Ti1.56Nb0.44)2.0O6.1. The association of betafite NPs, magnetite, and Pb0 NPs in Fe-rich and calcite-rich veins indicates reducing conditions during alteration of pyrochlore and immobilization of pyrochlore derived elements. This observation combined with identification of nanoscale galena and magnetite in pyrochlore, and the association of Pb0 and Fe3O4 in veins

  5. Direct Measurement of Inter-Filament Resistance in Superconducting Multifilamentary NbTi and Nb(3)Sn Strands

    CERN Document Server

    Zhou, C; Veldhuis, D; van Lanen, E P A; ten Kate, H H J; Dhalle, M

    2011-01-01

    A quantitative knowledge of inter-filament transverse resistance will allow us to describe current redistribution processes inside strands more accurately. This is particularly important for the analysis of the influence of strain and crack distribution patterns in Nb(3)Sn filaments on the shape of the voltage-current curves. Several indirect methods are commonly used to assess inter-filament resistance. Here we use a direct method to measure transverse inter-filament resistance and filament-to-matrix contact resistance. Two four-probe voltage-current methods are developed for measurements below 10 K at various background magnetic fields. In addition to FEM (Finite Element Method) simulation, also a new 3D strand model is developed to simulate the current-and voltage distributions. The experimental methods, first results as well as the simulations using the FEM method and new 3D strand model are described.

  6. Added value of sending photograph in diagnosing a medical disease declared at sea: experience of the French Tele-Medical Assistance Service.

    Science.gov (United States)

    Dehours, Emilie; Saccavini, Alexandre; Roucolle, Pierre; Roux, Patrick; Bounes, Vincent

    2017-01-01

    The maritime medical tele-consultation carried out by a doctor from the Toulouse Tele-Medical Assistance Service is currently based on tele-consultation using radiotelegraphy and the complementary transmission of data (photographs, electrocardiogram) via the Internet. In a previous article, we presented the benefits of photograph transmission for trauma management in isolated areas. Through this new series of cases, we wanted to expose the aspect of the medical pathologies and the contribution of sending photographs in their management. Case 1. Myocardial infarction. Case 2. Toxic epidermal necrolysis. Case 3. Tooth abscess. Case 4. Shingles. Case 5. Junctional tachycardia. The tele-transmission of photographs provides a real diagnostic and follow-up tool for patients suffering from medical pathologies. The constant increase in the number of tele-consultations with the exchange of photographs shows its necessity and the interest of the participants in the development of these technologies.

  7. The impact of outmigration of men on fertility and marriage in the migrant-sending states of Mexico, 1995-2000.

    Science.gov (United States)

    White, Kari; Potter, Joseph E

    2013-01-01

    Using the 2000 Mexican Census, we examined whether the level of migration was associated with total fertility and the proportion of women married in 314 municipalities from seven traditional sending states. Across these municipalities, we observe lower fertility in higher-migration areas. Municipalities in the quartile with the highest levels of migration have total fertility more than half a child lower than municipalities in the lowest migration quartile. However, there are no differences in marital fertility by level of migration, indicating that lower proportions of women married account for lower total fertility in high-migration municipalities. In municipal-level regression models, lower sex ratios are associated with a lower proportion of women married, while there is an inverse association between education and marriage. The level of migration also has an independent association with marriage, suggesting that there may be changing ideas surrounding family formation in high-migration areas.

  8. Dendritic solidification and thermal expansion of refractory Nb-Zr alloys investigated by electrostatic levitation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.J.; Hu, L.; Wang, L.; Wei, B. [Northwestern Polytechnical University, Department of Applied Physics, Xi' an (China)

    2017-05-15

    The dendritic growth and thermal expansion of isomorphous refractory Nb-5%Zr, Nb-10%Zr, and Nb-15%Zr alloys were studied by electrostatic levitation technique. The obtained maximum undercoolings for the three alloys were 534 (0.2T{sub L}), 498 (0.19T{sub L}), and 483 K (0.18T{sub L}), respectively. Within these undercooling ranges, the dendritic growth velocities of the three alloys all exhibited power laws, and achieved 38.5, 34.0, and 27.1 m s{sup -1} at each maximum undercooling. The microstructures were characterized by coarse dendrites at small undercooling, while they transformed into refined dendrites under large undercooling condition. In addition, the measured thermal expansion coefficients of solid Nb-Zr alloys increased linearly with temperature. The values at liquid state were more than double of those at solid state, which also displayed linear dependence on temperature. (orig.)

  9. Nanotubular Structure on the Ti-29Nb-5Zr Alloy by Scanning Transmission Electron Microscope.

    Science.gov (United States)

    Kim, Eun-Ju; Jeong, Yong-Hoon; Kang, Bo-An; Choe, Han-Cheol

    2015-01-01

    In this study, we reported the observation of highly ordered nanotubular structure on the Ti-29Nb-5Zr alloy in various potentials and electrolytes by field emission scanning electron microscopy and scanning transmission electron microscope. From the X-ray diffraction results and microstructure analysis, Ti-29Nb-5Zr alloy had β phase. The nanotube morphologies of Ti-29Nb-5Zr alloy were transformed from nano-porous structure to nanotube structure as NaF concentration and voltage increased. Nanotube diameter and layer changed with different concentration of NaF in 1 M H3PO4 at the same voltage. From the X-ray photoelectron spectroscopy results, nanotube was formed by Nb, Zr, and Ti oxide. Also, barrier layer of large tube was about 50 nm thickness, small one was 60 nm thickness. The nanotube size and crystallinity on the β Ti alloy was controlled by fluoride concentration, applied potential, anodization time, and tube layer.

  10. Structure of TeO2 - LiNbO3 glasses

    Science.gov (United States)

    Shinde, A. B.; Krishna, P. S. R.; Rao, Rekha

    2017-05-01

    Tellurite based lithium niobate glasses with composition (100-x)TeO2-xLiNbO3 (x=0.1,0.2 & 0.3) were prepared by conventional melt quenching method. The microscopic structural investigation of these glasses is carried out by means of neutron diffraction and Raman scattering measurements. It is found that the basic structural units in these glasses are TeO4 trigonal bipyramids(TBP), TeO3 trigonal pyramids(TP) and NbO6 Octahedra depending on the composition. It is evident from Raman studies that TBPs decreases, TPs increases and NbO6 Octahedra increases with increasing x. From Neutron diffraction studies it is found that network is comprised of TBPs and TPs along with TeO3+1 structural units. Distorted NbO6 octahedral units are present and also increase with the increase in x.

  11. Several Issues in the Development of Ti-Nb-Based Shape Memory Alloys

    Science.gov (United States)

    Kim, Hee Young; Miyazaki, Shuichi

    2016-12-01

    Ni-free Ti-based shape memory alloys, particularly Ti-Nb-based alloys, have attracted increasing attraction since the early 2000s due to their wide application potentials in biomedical fields. Recently, there has been significant progress in understanding the martensitic transformation behavior of Ti-Nb-based alloys and many novel superelastic alloys have been developed. The superelastic properties of Ti-Nb-based alloys have been remarkably improved through the optimization of alloying elements and microstructure control. In this paper, in order to explore and establish the alloy design strategy, several important issues in the development of Ti-Nb-based shape memory alloys are reviewed. Particularly, the effects of alloying elements on the martensitic transformation temperature and the transformation strain are analyzed. The effects of omega phase and texture on the superelastic properties are also discussed.

  12. Ni/sub 3/Nb alloy species in oxide surfaces of INCONEL 718

    Energy Technology Data Exchange (ETDEWEB)

    Moddeman, W.E.; Craven, S.M.; Kramer, D.P.

    1986-02-01

    INCONEL 718 has been studied by Auger and X-ray photoelectron spectroscopy to determine the effect on the surface stoichiometry caused by heat treating in argon to 1000 C. Two surface regions are produced, the one closest to the argon-metal oxide interface being rich in O, Ti, Al, and Cr, and the one closest to the alloy being rich in O, Al, and Nb. Profiles show a gradual increase in the Ni and Nb signals as the profiling time increases. It is noted that during the profile, Al remains an oxide, and that the Ni and Nb signals have metal-like character even in the aluminum oxide phase, suggesting that N/sub 3/Nb exists with oxide at the surface. 6 references.

  13. Quench Protection Studies of the 11-T $Nb_3Sn$ Dipole for LHC Upgrades

    CERN Document Server

    Izquierdo Bermudez, Susana; BAJAS, Hugues; Bajko, Marta; Bordini, Bernardo; Bottura, Luca; Chlachidze, Guram; Karppinen, Mikko; Rysti, Juho; Savary, Frederic; Willering, Gerard; Zlobin, Alexander

    2016-01-01

    The planned upgrade of the LHC collimation system foresees additional collimators to be installed in the dispersion suppressor areas. Fermilab and CERN are developing an 11 T Nb3Sn dipole to replace some 8.33 T-15-m-long Nb-Ti LHC main dipoles providing longitudinal space for the collimators. In case of a quench, the large stored energy and the low copper stabilizer fraction make the protection of the 11 T Nb3Sn dipoles challenging. This paper presents the results of quench protection analysis, including quench protection heater design and efficiency, quench propagation and coil heating. The numerical results are compared with the experimental data from the 2-m-long Nb3Sn dipole models. The validated model is used to predict the current decay and hot spot temperature under operating conditions in the LHC and the presently foreseen magnet protection scheme is discussed.

  14. Examining metallic glass formation in LaCe:Nb by ion implantation

    Directory of Open Access Journals (Sweden)

    Sisson Richard

    2017-01-01

    Full Text Available In order to combine niobium (Nb with lanthanum (La and cerium (Ce, Nb ions were deposited within a thin film of these two elements. According to the Hume-Rothery rules, these elements cannot be combined into a traditional crystalline metallic solid. The creation of an amorphous metallic glass consisting of Nb, La, and Ce is then investigated. Amorphous metallic glasses are traditionally made using fast cooling of a solution of molten metals. In this paper, we show the results of an experiment carried out to form a metallic glass by implanting 9 MeV Nb 3+ atoms into a thin film of La and Ce. Prior to implantation, the ion volume distribution is calculated by Monte Carlo simulation using the SRIM tool suite. Using multiple methods of electron microscopy and material characterization, small quantities of amorphous metallic glass are indeed identified.

  15. Development of Nb{sub 3}Sn Cavity Vapor Diffusion Deposition System

    Energy Technology Data Exchange (ETDEWEB)

    Eremeev, Grigory V.; Macha, Kurt M.; Clemens, William A.; Park, HyeKyoung; Williams, R. Scott

    2014-02-01

    Nb{sub 3}Sn is a BCS superconductors with the superconducting critical temperature higher than that of niobium, so theoretically it surpasses the limitations of niobium in RF fields. The feasibility of technology has been demonstrated at 1.5 GHz with Nb{sub 3}Sn vapor deposition technique at Wuppertal University. The benefit at these frequencies is more pronounced at 4.2 K, where Nb{sub 3}Sn coated cavities show RF resistances an order of magnitude lower than that of niobium. At Jefferson Lab we started the development of Nb{sub 3}Sn vapor diffusion deposition system within an R\\&D development program towards compact light sources. Here we present the current progress of the system development.

  16. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    Science.gov (United States)

    Ellis, D. L.; Michal, G. M.; Dreshfield, R. L.

    1995-01-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

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

    Science.gov (United States)

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

    2018-01-01

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

  18. Texture in state-of-the-art Nb3Sn multifilamentary superconducting wires

    CERN Document Server

    Scheuerlein, C; Alknes, P; Jimenez, N; Bordini, B; Ballarino, A; Di Michiel, M; Thilly, L; Besara, T; Siegrist, T

    2014-01-01

    The texture of Nb3Sn in recent multifilamentary composite wires has been studied by neutron diffraction, synchrotron x-ray diffraction and electron backscatter diffraction. In powder-in-tube (PIT) type superconductors the Nb precursor filaments exhibit a strong 〈110〉 fiber texture as a consequence of the severe cold drawing process, and a 〈110〉 texture is also observed in the Nb3Sn. In the Nb–Ta precursor of the restacked rod process (RRP) strand there is an additional texture component, and in both Ta-alloyed and Ti-alloyed RRP type conductors the Nb3Sn grains grow with a preferential 〈100〉 orientation.

  19. A multiple-field coupled resistive transition model for superconducting Nb3Sn

    Science.gov (United States)

    Yang, Lin; Ding, He; Zhang, Xin; Qiao, Li

    2016-12-01

    A study on the superconducting transition width as functions of the applied magnetic field and strain is performed in superconducting Nb3Sn. A quantitative, yet universal phenomenological resistivity model is proposed. The numerical simulation by the proposed model shows predicted resistive transition characteristics under variable magnetic fields and strain, which in good agreement with the experimental observations. Furthermore, a temperature-modulated magnetoresistance transition behavior in filamentary Nb3Sn conductors can also be well described by the given model. The multiple-field coupled resistive transition model is helpful for making objective determinations of the high-dimensional critical surface of Nb3Sn in the multi-parameter space, offering some preliminary information about the basic vortex-pinning mechanisms, and guiding the design of the quench protection system of Nb3Sn superconducting magnets.

  20. A multiple-field coupled resistive transition model for superconducting Nb3Sn

    Directory of Open Access Journals (Sweden)

    Lin Yang

    2016-12-01

    Full Text Available A study on the superconducting transition width as functions of the applied magnetic field and strain is performed in superconducting Nb3Sn. A quantitative, yet universal phenomenological resistivity model is proposed. The numerical simulation by the proposed model shows predicted resistive transition characteristics under variable magnetic fields and strain, which in good agreement with the experimental observations. Furthermore, a temperature-modulated magnetoresistance transition behavior in filamentary Nb3Sn conductors can also be well described by the given model. The multiple-field coupled resistive transition model is helpful for making objective determinations of the high-dimensional critical surface of Nb3Sn in the multi-parameter space, offering some preliminary information about the basic vortex-pinning mechanisms, and guiding the design of the quench protection system of Nb3Sn superconducting magnets.

  1. Small-polaron based holograms in LiNbO₃ in the visible spectrum.

    Science.gov (United States)

    Brüning, H; Dieckmann, V; Schoke, B; Voit, K-M; Imlau, M; Corradi, G; Merschjann, C

    2012-06-04

    Diffraction efficiency, relaxation behavior and dependence on pump-beam intensity of small-polaron based holograms are studied in thermally reduced, nominally undoped lithium niobate in the visible spectrum (λ = 488 nm). The pronounced phase gratings with diffraction efficiency up to η = (10.8 ± 1.0)% appeared upon irradiation by single ns-laser pulses (λ = 532 nm) and are comprehensively assigned to the optical formation of spatially modulated densities of small bound NbLi4+ electron polarons, NbLi4+:NbNb4+ electron bipolarons, and O⁻ hole polarons. A remarkable quadratic dependence on the pump-beam intensity is discovered for the recording configuration K || c-axis and can be explained by the electro-optic contribution of the optically generated small bound polarons. We discuss the build-up of local space-charge fields via small-polaron based bulk photovoltaic currents.

  2. Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

    KAUST Repository

    Zhu, Haibo

    2015-03-05

    The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH) of ethane to ethylene at a relatively low temperature (T<300°C). These catalysts appear to be much more stable than the corresponding composites prepared by other chemical methods; more than 90% of their original intrinsic activity was retained after 50h with time on-stream. Furthermore, the stability was much less affected by the Nb content than in composites prepared by classical "wet" syntheses. These materials, obtained in a solvent-free way, are thus promising green and sustainable alternatives to the current Ni-Nb candidates for the low-temperature ODH of ethane.

  3. Electrochemical studies of the molten system K2NbF7-Na2O-Nb-(LiF-NaF-KF)(eut) at 700 degrees C

    DEFF Research Database (Denmark)

    Rosenkilde, C.; Vik, A.; Østvold, T.

    2000-01-01

    Various voltammetric methods have been used to study FLINAK (LiF-NaF-KF eutectic melt 46.5-11.5-42 mol %) melts containing about 1 mol % niobium-fluoro and -oxofluoro complexes with Nh in oxidation states (V) and (IV) at 700 degrees C and varying amounts of Na2O in the range 0 ... indications of the coexistence of the oxygen rich Nb(V)OF complexes and O-2(-) ions in FLINAK at n(O)(0)/n(Nb)(0) > 4 have been found. An equilibrium/sampling/analysis technique was also used to study this system without Nb metal added. The results mainly agree with the results of the voltammetric studies...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

  5. Measurement of quality factor and losses in superconducting microwave resonator integrated with NbN/AlN/NbN qubit circuit

    Science.gov (United States)

    Qiu, W.; Makise, K.; Terai, H.; Nakamura, Y.; Wang, Z.

    2014-05-01

    Dielectric loss from two-level systems (TLSs) formed by local defects have shown a significant impact on the qubit coherence time. These defects can originate in the insulation material for superconducting wires isolation or in the Josephson junction tunnel barrier material. Due to the complexity of the qubit circuit fabrication process, identifying the contribution from each decoherence source is challenging. In an effort to address this issue, we have developed superconducting qubit that consists of full epitaxially-grown NbN/AlN/NbN Josephson junctions in NbN coplanar waveguide (CPW) resonator circuit. The dielectric loss introduced from TLFs in tunnel junction barrier has been largely reduced due to the unique epitaxial feature of the tunnel junction. The quality factor Qi of the CPW resonator was measured and the dielectric loss tanδ is 3×10-4. The relaxation time inferred from the measured resonator quality factor was comparable to the qubit relaxation time.

  6. Rapid catalyst-free flame synthesis of α-Nb{sub 2}O{sub 5} micro/nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Merchan-Merchan, Wilson; Farmahini Farahani, Moien, E-mail: wmerchan-merchan@ou.edu

    2013-07-15

    We report the ultra-rapid synthesis of Nb oxide nano/micron sized rods using a flame method; the single-step process is achieved in less than a few minutes. The synthesis is performed using 1-mm diameter Nb probes (metal source) inserted in the oxygen-rich part of an counter-flow methane/acetylene oxy-flame. The niobium oxide structures can grow nearly instantaneously in a white layer of material surrounding the surface of the Nb probe. The Nb oxide layer is composed of individual and coalesced micro/nanorods that are rapidly formed on the surface of the Nb wire. The grown crystals forming the metal oxide layer grow through a basal growth mechanism due to the constant flow of oxygen and oxygen radicals from the flame onto the surface of the niobium probe. The morphology of the grown Nb oxide structures strongly depends on the flame position (temperature and chemical species). X-Ray Diffraction analysis reveals that the micro/nanorods forming the layer are composed of monoclinic α-Nb{sub 2}O{sub 5}. - Graphical abstract: Display Omitted - Highlights: • Niobium oxide crystals were grown on the surface of Nb probes using the flame method. • We report the flame as an ultra-rapid process for the growth of Nb oxide structures. • In the flame method the growth of Nb{sub 2}O{sub 5} structures is achieved in only a few minutes.

  7. Thermo-magnetic instabilities in Nb3Sn superconducting accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Bordini, Bernardo [Univ. of Pisa (Italy)

    2006-09-01

    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 Nb3Sn. Several laboratories in the US and Europe are currently working on developing Nb3Sn 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 Nb3Sn 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 Nb3Sn; a description of the manufacturing process of Nb3Sn strands; superconducting cables; a typical layout of superconducting accelerator magnets; the current state of the art of Nb3Sn accelerator magnets; the High Field Magnet program at Fermilab; and the scope of the thesis.

  8. The in vitro study of apoptosis in NB4 cell induced by citral

    OpenAIRE

    Xia, Hailong; Liang, Wei; Song, Qin; Chen, Xiaowen; Chen, Xin; Hong, Jian

    2012-01-01

    Citral, 3,7-dimethyl-2,6-octadienal, is a key component of the essential oils extracted from several lemon-scented herbal plants. Besides its antifungal activity, the anticancer effect of citral was studied in recent years. In this study, we investigated the effect of citral on the acute promyelocytic leukemia cell line NB4. Citral treatment had an antiproliferative effect in NB4 cells via the induction of apoptosis assessed by morphology, proliferation assay, DNA electrophoresis, Annexin V-F...

  9. Calculations for nuclear data evaluation for Nb, Zr and W in the high energy region

    Energy Technology Data Exchange (ETDEWEB)

    Kitsuki, Hirohiko; Maruyama, Shin-ichi; Ishibashi, Kenji [Kyushu Univ., Fukuoka (Japan)

    1998-03-01

    Neutron total cross sections on Nb, Zr and W were calculated in the high energy region. In this calculation, we used the neutron optical-model potentials derived from those for proton incidence with introducing the symmetry term. Proton-induced activation yields for Nb and Zr was calculated by means of HETC/KFA2 and QMD plus SDM at incident energies up to 5 GeV. (author)

  10. Microcosmic mechanism of carbon influencing on NiTiNb{sub 9} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, G.F., E-mail: lgf_918@yahoo.cn [School of Material Science and Engineering, Nanchang Hangkong University, Jiangxi 330063 (China); School of Materials Science and Engineering, Hunan University, Hunan 410082 (China); Lu, S.Q.; Dong, X.J. [School of Material Science and Engineering, Nanchang Hangkong University, Jiangxi 330063 (China); Peng, P. [School of Materials Science and Engineering, Hunan University, Hunan 410082 (China)

    2012-11-25

    Highlights: Black-Right-Pointing-Pointer An obvious NbTiC carbonization 'cluster' is detected in NiTi matrix phase. Black-Right-Pointing-Pointer The Nb element can enhances the influence of the C element on NiTiNb shape memory alloy. Black-Right-Pointing-Pointer The interaction between Nb and C can decrease mechanics performance of NiTiNb alloy. Black-Right-Pointing-Pointer This method is helpful for alloying shape memory alloy. - Abstract: The microcosmic mechanism, by which the C impurity decreases the M{sub s} and fracture toughness, remains mysterious at present. Using first-principles pseudo-potential plane wave method, the formation enthalpy {Delta}H, binding energy {Delta}E, electronic structure and diffusivity of the C element in NiTiNb{sub 9} shape memory alloy have been systematically calculated and analyzed in the thermodynamic and kinetic processes. The results show that the addition of C trends to compose carbonization 'cluster' in NiTi matrix phase, which not only can decrease the M{sub s} of alloy by enhancing the ratio Ni/Ti, but also it can slack down the ductility by its special 'jujube nut ' system. Otherwise, because of the unfilled s orbits, the Nb element can enhance the formation ability and diffusivity of carbonization 'cluster' structure, and promote the impact of the C element to the shape memory effect and mechanics performance in NiTiNb alloy. Thus, our findings open an avenue for detailed and comprehensive studies of alloying shape memory alloy.

  11. NbCl5 and CrCl3 catalysts effect on synthesis and hydrogen storage ...

    Indian Academy of Sciences (India)

    The hydriding–dehydriding kinetics performance of the CrCl3-doped sample did not improve, but it did exhibit a lower onset desorption temperature of 543 K under 0.1 MPa, which was 20 K lower than that of the no-halide doped sample. NbO, NiO and NbH2 played important roles in improving absorption and desorption ...

  12. Charge density wave and superconductivity in 2H- and 4H-NbSe2 ...

    Indian Academy of Sciences (India)

    ρ300/ρTs , where ρTs is the resistivity at superconducting transition temperature Ts and we have calculated ∼66.7 for 2H-NbSe2. 2H-NbSe2 exhibits superconductor and CDW tran- sitions at 7.4 and 35 K respectively and the values are the same as in the previous result. We have found its room temperature resistivity to be ...

  13. First principles total energy study of NbCr{sub 2} + V Laves phase ternary system

    Energy Technology Data Exchange (ETDEWEB)

    Ormeci, A. [Koc Univ., Istanbul (Turkey); Chen, S.P.; Wills, J.M.; Albers, R.C. [Los Alamos National Lab., NM (United States)

    1999-04-01

    The C15 NbCr{sub 2} + V Laves phase ternary system is studied by using a first-principles, self-consistent, full-potential total energy method. Equilibrium lattice parameters, cohesive energies, density of states and formation energies of substitutional defects are calculated. Results of all these calculations show that in the C15 NbCr{sub 2} + V compounds, V atoms substitute Cr atoms only.

  14. X-ray attenuation around K-edge of Zr, Nb, Mo and Pd: A ...

    Indian Academy of Sciences (India)

    Abstract. Mass attenuation coefficients (µ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd, Cd and Sn foils. The measurements were carried out at the Kα and Kβ energy values of the target elements ...

  15. Strain induced precipitation of complex carbonitrides in Nb-V and Ti-V microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Pandit, Ashwin [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India); Murugaiyan, A. [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India); Podder, A. Saha [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India); Haldar, A. [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India); Bhattacharjee, D. [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India)]. E-mail: dbhattac@lot.tatasteel.com; Chandra, S. [R and D and Scientific Services Division, Tata Steel, Jamshedpur 831001 (India); Ray, R.K. [Department of Materials and Metallurgical Engineering, IIT Kanpur 208016 (India)

    2005-12-15

    Strain induced precipitation of complex carbonitrides in two microalloyed steels (Nb-V and Ti-V) has been studied using a stress relaxation technique. The results confirm the faster kinetics of precipitation in the case of Nb-V steel. The thermodynamic software Thermo-calc{sup T}M has been used to determine the composition gradient of equilibrium precipitates for the two steels.

  16. Photocatalytic hydrogen generation with Ag-loaded LiNbO3

    Indian Academy of Sciences (India)

    In this contribiution LiNbO3 and Ag-loaded LiNbO3 photocatalysts were tested in the reaction of hydrogen evolution. The silver modified samples contained different loading of co-catalyst in the range of 0.5–4 wt%. It was essential to optimize the sample composition to achieve an efficient hydrogen evolution. The optimal ...

  17. Ba2ErNbO6: A new perovskite ceramic substrate for Bi (2223 ...

    Indian Academy of Sciences (India)

    Barium erbium niobate (Ba2ErNbO6) has been developed as a new substrate for (Bi,Pb)2Sr2Ca2Cu3O [Bi(2223)] superconductor film. Ba2ErNbO6 (BENO) has a cubic perovskite structure with lattice constant, = 8.318 Å. The Bi(2223) superconductor does not show any detectable chemical reaction with BENO even ...

  18. A low elastic modulus Ti-Nb-Hf alloy bioactivated with an elastin-like

    OpenAIRE

    González, Marta; Salvagni, Emiliano; Rodríguez Cabello, J.C.; Rupérez de Gracia, Elisa; Gil Mur, Francisco Javier; Manero Planella, José María; Peña, Javier

    2012-01-01

    b-type titanium alloys with low Young’s modulus are desirable to reduce stress shielding effect and enhance bone remodeling for implants used to substitute failed hard tissue. For biomaterials application, the surface bioactivity is necessary to achieve optimal osseointegration. In the previous work, the low elastic modulus (43 GPa) Ti-25Nb-16Hf (wt %) alloy was mechanically and microstructurally characterized. In the present work, the biological behavior of Ti-25Nb- 1...

  19. Creation of domains by direct electron beam writing in magnesium-doped LiNbO{sub 3} and LiNbO{sub 3}:Fe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palatnikov, M.N. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Kokhanchik, L.S.; Emelin, E.V. [Institute of Microelectronics Technology and High Purity Materials of Russian Academy of Sciences, 6 Academician Ossipyan st, Chernogolovka, Moscow 142432 (Russian Federation); Sidorov, N.V. [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation); Manukovskaya, D.V., E-mail: deenka@yandex.ru [Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, 26a Akademgorodok, Apatity, Murmansk 184209 (Russian Federation)

    2016-03-01

    Highlights: • The periodic domains are created in crystal LiNbO{sub 3}:Mg by direct electron beam writing. • Periodic domains appear only at equilibrium between switching and screening times. • Equilibrium exists in crystal co-doped by Fe. • Shape and appearance of domains depend on the conductivity type. - Abstract: Domain structures in the Z-cut of highly doped LiNbO{sub 3}:Mg and LiNbO{sub 3}:Mg,Fe single crystals were created by direct electron beam writing (DEBW). It was found that the value and type of electron conductivity influence the shape and number of domains thus created. Controlled electron beam regular domains were created only in samples of the crystal LiNbO{sub 3}:Mg,Fe [MgO] = 5.16 mol.%, [Fe] = 0.007 mol.%. In highly doped LiNbO{sub 3}:Mg ([MgO] = 5.19 mol.%) crystal, the domains were formed chaotically and controlled creation of domains did not occur. The domain shapes were analyzed in the framework of the theory of screening of domain nuclei depolarizing electric fields and the influence of screening on the final shape of domains. It was found that screening of intrinsic electric fields is faster in the LiNbO{sub 3}:Mg,Fe crystal. This crystal has a high electronic conductivity of hopping type with a high mobility of charge carriers. Thus, a small amount of Fe provides equilibrium between the ferroelectric switching velocity and screening of the depolarizing electric field velocity. The results are discussed considering differences in the electron conductivity mechanisms, which control the screening of depolarizing electric field velocity and spatial charge area formed under an electron beam.

  20. 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.

  1. Strong anisotropy of electric field effects on uniaxial relaxor ferroelectric Sr0.75Ba0.25Nb2O6 crystals proved by acoustic emission

    Science.gov (United States)

    Dul'kin, E.; Kojima, S.; Roth, M.

    2018-01-01

    [001] oriented Sr0.75Ba0.25Nb2O6 uniaxial relaxor ferroelectric crystals have been studied by acoustic emission in the temperature range of 20÷200 °C and under an external electric field up to 1 kV/cm. Under the application of an electric field the temperature of a dielectric maximum exhibits a nontrivial behavior: it remains constant at first, secondly steep decreases down to some threshold field, and thirdly starts to increase as a field enhances, whereas the same temperature of a dielectric maximum under a bias electric field to [100] oriented Sr0.75Ba0.25Nb2O6 crystals exhibits a smoothed minimum before the start to increase as a field enhances (E. Dul'kin et al., J. Appl. Phys. 110, 044106 (2011)). Such a difference of electric field effects in c- and a-cut crystals is discussed from the viewpoint of random-bond-random-field model of relaxor ferroelectrics. By the comparison between experimental and theoretical data, a dipole moment of the PNR was estimated to be 0.1 (C cm).

  2. Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys

    Science.gov (United States)

    Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

    2014-04-01

    In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

  3. Nb-doped rutile TiO₂: a potential anode material for Na-ion battery.

    Science.gov (United States)

    Usui, Hiroyuki; Yoshioka, Sho; Wasada, Kuniaki; Shimizu, Masahiro; Sakaguchi, Hiroki

    2015-04-01

    The electrochemical properties of the rutile-type TiO2 and Nb-doped TiO2 were investigated for the first time as Na-ion battery anodes. Ti(1-x)Nb(x)O2 thick-film electrodes without a binder and a conductive additive were prepared using a sol-gel method followed by a gas-deposition method. The TiO2 electrode showed reversible reactions of Na insertion/extraction accompanied by expansion/contraction of the TiO2 lattice. Among the Ti(1-x)Nb(x)O2 electrodes with x = 0-0.18, the Ti(0.94)Nb(0.06)O2 electrode exhibited the best cycling performance, with a reversible capacity of 160 mA h g(-1) at the 50th cycle. As the Li-ion battery anode, this electrode also attained an excellent rate capability, with a capacity of 120 mA h g(-1) even at the high current density of 16.75 A g(-1) (50C). The improvements in the performances are attributed to a 3 orders of magnitude higher electronic conductivity of Ti(0.94)Nb(0.06)O2 compared to that of TiO2. This offers the possibility of Nb-doped rutile TiO2 as a Na-ion battery anode as well as a Li-ion battery anode.

  4. Nanomechanical properties of NbN films prepared by pulsed laser deposition using nanoindendation

    Science.gov (United States)

    Mamun, M. A.; Farha, A. H.; Er, A. O.; Ufuktepe, Y.; Gu, D.; Elsayed-Ali, H. E.; Elmustafa, A. A.

    2012-03-01

    Structural and mechanical properties of niobium nitride thin films deposited by pulsed laser deposition were investigated using X-ray diffraction, atomic force microscopy, and nanoindentation. Niobium nitride was deposited on Si(1 0 0) by pulsed laser deposition (PLD) of Nb in nitrogen background. A Nanoindenter XP equipped with a dynamic contact module (DCM II) head was used in conjunction with the continuous stiffness method (CSM) in depth and load control modes to measure the hardness and modulus of the NbN thin films. NbN film reveals simple cubic δ-NbN structure with the corresponding reflections of (1 1 1), (2 0 0), and (2 2 0) planes. Highly textured NbN film shows a strong (1 1 1) preferred orientation. The NbN thin films depict polycrystalline structure, with a wide range of grain sizes that range from 15 to 40 nm with an average surface roughness of 6 nm. The average modulus of the film is 420 ± 60 GPa, whereas for the substrate the average modulus is 180 GPa, which is considered higher than the average modulus for Si reported in the literature due to pile-up. The hardness of the film increases monotonically from an average of 12 GPa for deep indents (Si substrate) measured using XP CSM and load control (LC) modes to an average of 25 GPa measured using the DCM II head in CSM and LC modules. The average hardness of the Si substrate is 12 GPa.

  5. {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.

  6. X-ray determination of the atomic displacements in NbC/sub 0. 72/

    Energy Technology Data Exchange (ETDEWEB)

    Morinaga, M.; Ohshima, K.; Harada, J.; Otani, S.

    1986-12-01

    Integrated X-ray intensities of Bragg peaks have been measured with an NbC/sub 0.72/ single crystal which contains a large number of non-stoichiometric carbon vacancies. By standard structural analysis the mean-square displacements were determined to be Nb/> = 0.0041(7) A/sup 2/ for Nb atoms and Nb/> is comparable to the value of 0.0045 A/sup 2/, extrapolatd from the compositional dependence of Nb/> proposed by Metzger, Peisl and Kaufmann. It was confirmed that the existence of carbon vacancies induces larger static displacements of neighbouring niobium atoms, and the contribution of thermal displacements to the observed Nb/> appears to be rather small in a non-stoichiometric niobium monocarbide.

  7. Effect of Nb on hydrogen-induced delayed fracture in high strength hot stamping steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shiqi [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); College of Mechanical Engineering, Yangtze University, Jingzhou 434023 (China); Huang, Yunhua, E-mail: huangyh@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Sun, Bintang, E-mail: bingtangsun@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liao, Qingliang [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lu, Hongzhou [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); The School of Resources and Environmental Engineering, East China University of Science and Technology, Meilong road 130, Xujiahui District, Shanghai 200237 (China); Jian, Bian [Niobium Tech Asia, 068898 Singapore (Singapore); Mohrbacher, Hardy [NiobelCon bvba, 2970 Schilde (Belgium); Zhang, Wei; Guo, Aimin [CITIC Metal Co. Ltd., Room 1901, Capital Mansion 6, Xin Yuan Nanlu, Chaoyang District, Beijing 100004 (China); Zhang, Yue [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); The State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-02-25

    The effect of Nb addition (0.022, 0.053, 0.078 wt%) on the hydrogen-induced delayed fracture resistance of 22MnB5 was studied by constant load test and electrochemical hydrogen permeation method. It is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of tested steel, especially when the steel contains high concentration of hydrogen, and the maximum delayed fracture resistance is obtained at a Nb content of 0.053%.The result of hydrogen permeation test shows that the diffusion coefficient of hydrogen in the steel containing niobium is lower than that in steel without niobium, which indicates that it is harder for hydrogen in the steels containing niobium to diffuse and aggregate. In addition, the reason for Nb improving the delayed fracture resistance of steels is discussed from two aspects: hydrogen trap effect and grain refinement effect. The analysis shows that the main reason leading to the improvement of the delayed fracture resistance is the hydrogen trapping effect of NbC while the grain refinement effect of Nb(C,N) secondary.

  8. The dissociation and ionization of LiNbO 3 melts

    Science.gov (United States)

    Uda, Satoshi; Tiller, William A.

    1992-06-01

    The thermodynamic and kinetic behavior of LiNbO 3 melts has been studied experimentally by differential thermal analysis (DTA). Theoretical modeling has been carried out for three cases and the predicted results matched to the experimental data: (1) the melt contains only one species and no chemical reactions are present during heating and cooling, (2) the melt contains three species and a dissociation/recombination reaction occurs between LiNbO 3 and Li 2O+Nb 2O 5 and (3) the melt contains seven species with both dissociation and ionization reactions occuring to form the additional species Li +, LiO -, Nb 2O 4V 2+O, and O 2-. The best fit, using the linear programming technique LINDO, was for case 3 with seven active species in the melt. Δ G - values, Δ H - values and reaction rate constants (β - values) were found for the dissociation/recombination reaction as well as for the two ionization reactions. These values allowed the species populations to be calculated for both the congruent liquid (mole ratio of Li 2O to Nb 2O 5 = k = 0.942) and the Nb - rich ( k = 0.724) and Li - rich ( k = 1.222) liquid cases studied experimentally by DTA at 1275°C.

  9. Coprecipitation synthesis and negative thermal expansion of NbVO5.

    Science.gov (United States)

    Wang, Jinrui; Deng, Jinxia; Yu, Ranbo; Chen, Jun; Xing, Xianran

    2011-04-07

    We develop a coprecipitation synthesis route to prepare NbVO(5) with simple oxide Nb(2)O(5) and NH(4)VO(3) as starting materials. No metal alkoxide or organometallic substance was used in the process. Nano-crystal NbVO(5) was obtained by calcination of the coprecipitates at 550 °C for 2 h. DSC/TG and XRD investigations indicate that the target compound NbVO(5) is completely formed up to 504.5 °C and is thermally stable below 658 °C. Rietveld XRD refinements give an orthorhombic structure with space group Pnma and lattice parameters, a=11.8453(2), b=5.5126(3) and c=6.9212(2) Å, respectively. In particular, HTXRD determinations show a negative thermal expansion in NbVO(5) with a TEC of -6.63 × 10(-6) °C(-1) in the temperature range of RT-600 °C. This fact is ascribed to the tilting of NbO(6) octahedra and VO(4) tetrahedra in the flexible framework structure. The present synthesis route is facile and easy to be extended to prepare analogues such as TaVO(5), etc. © The Royal Society of Chemistry 2011

  10. Thick CrN/NbN multilayer coating deposited by cathodic arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Juliano Avelar; Tschiptschin, Andre Paulo; Souza, Roberto Martins, E-mail: antschip@usp.br [Universidade de Sao Paulo (USP), SP (Brazil); Lima, Nelson Batista de [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-01-15

    The production of tribological nanoscale multilayer CrN/NbN coatings up to 6 μm thick by Sputtering/HIPIMS has been reported in literature. However, high demanding applications, such as internal combustion engine parts, need thicker coatings (>30 μm). The production of such parts by sputtering would be economically restrictive due to low deposition rates. In this work, nanoscale multilayer CrN/NbN coatings were produced in a high-deposition rate, industrial-size, Cathodic Arc Physical Vapor Deposition (ARC-PVD) chamber, containing three cathodes in alternate positions (Cr/ Nb/Cr). Four 30 μm thick NbN/CrN multilayer coatings with different periodicities (20, 10, 7.5 and 4 nm) were produced. The coatings were characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The multilayer coating system was composed of alternate cubic rock salt CrN and NbN layers, coherently strained due to lattice mismatch. The film grew with columnar morphology through the entire stratified structure. The periodicities adopted were maintained throughout the entire coating. The 20 nm periodicity coating showed separate NbN and CrN peaks in the XRD patterns, while for the lower periodicity (≤10nm) coatings, just one intermediate lattice (d-spacing) was detected. An almost linear increase of hardness with decreasing bilayer period indicates that interfacial effects can dominate the hardening mechanisms. (author)

  11. Propriedade Microestrutural do Refinamento da Liga Amorfa Al54Nb45B7

    Directory of Open Access Journals (Sweden)

    Luciano Nascimento

    2016-07-01

    Full Text Available The presence of niobium in the alloy creates regions of intermetallic phases contained in Al54Nb45B7 amorphous alloy which becomes a potent heterogeneous nucleation on the substrate for nucleation with dendritic presence of aluminum oxides due to diffusive processes on the surface of the amorphous alloy Al54Nb45B7. This alloy is extremely low cost, but with applications in many sectors of the chemical and petrochemical industry in emphasis because its mechanical deformation is high due to the presence of (Nb or B in the aluminum acting mainly as grain refiners to improve their mechanical and thermal properties by using the mechanical alloying. The combined use of Niobium and Boron (intermetallic phases are formed by adding powder of Al and Nb, instead of Niobium or Boron, individually, is a highly effective way to refine the grain size of alloy Al Nb-B in their microstructure without causing inconvenience in your network for unwanted deformations. To that end the present study compared the effect of grain refining promoted by the addition of niobium and the addition of Boron in Al54Nb45B5 obtained by high energy mill under argon atmosphere and analyzed by diffraction of X rays (XRD, scanning electron microscopy and Energy Dispersive (SEM / EDS. DOI: http://dx.doi.org/10.17807/orbital.v8i3.808

  12. Binomial mitotic segregation of MYCN-carrying double minutes in neuroblastoma illustrates the role of randomness in oncogene amplification.

    Directory of Open Access Journals (Sweden)

    Gisela Lundberg

    2008-08-01

    Full Text Available Amplification of the oncogene MYCN in double minutes (DMs is a common finding in neuroblastoma (NB. Because DMs lack centromeric sequences it has been unclear how NB cells retain and amplify extrachromosomal MYCN copies during tumour development.We show that MYCN-carrying DMs in NB cells translocate from the nuclear interior to the periphery of the condensing chromatin at transition from interphase to prophase and are preferentially located adjacent to the telomere repeat sequences of the chromosomes throughout cell division. However, DM segregation was not affected by disruption of the telosome nucleoprotein complex and DMs readily migrated from human to murine chromatin in human/mouse cell hybrids, indicating that they do not bind to specific positional elements in human chromosomes. Scoring DM copy-numbers in ana/telophase cells revealed that DM segregation could be closely approximated by a binomial random distribution. Colony-forming assay demonstrated a strong growth-advantage for NB cells with high DM (MYCN copy-numbers, compared to NB cells with lower copy-numbers. In fact, the overall distribution of DMs in growing NB cell populations could be readily reproduced by a mathematical model assuming binomial segregation at cell division combined with a proliferative advantage for cells with high DM copy-numbers.Binomial segregation at cell division explains the high degree of MYCN copy-number variability in NB. Our findings also provide a proof-of-principle for oncogene amplification through creation of genetic diversity by random events followed by Darwinian selection.

  13. Chaotic dynamics in nanoscale NbO2 Mott memristors for analogue computing

    Science.gov (United States)

    Kumar, Suhas; Strachan, John Paul; Williams, R. Stanley

    2017-08-01

    At present, machine learning systems use simplified neuron models that lack the rich nonlinear phenomena observed in biological systems, which display spatio-temporal cooperative dynamics. There is evidence that neurons operate in a regime called the edge of chaos that may be central to complexity, learning efficiency, adaptability and analogue (non-Boolean) computation in brains. Neural networks have exhibited enhanced computational complexity when operated at the edge of chaos, and networks of chaotic elements have been proposed for solving combinatorial or global optimization problems. Thus, a source of controllable chaotic behaviour that can be incorporated into a neural-inspired circuit may be an essential component of future computational systems. Such chaotic elements have been simulated using elaborate transistor circuits that simulate known equations of chaos, but an experimental realization of chaotic dynamics from a single scalable electronic device has been lacking. Here we describe niobium dioxide (NbO2) Mott memristors each less than 100 nanometres across that exhibit both a nonlinear-transport-driven current-controlled negative differential resistance and a Mott-transition-driven temperature-controlled negative differential resistance. Mott materials have a temperature-dependent metal-insulator transition that acts as an electronic switch, which introduces a history-dependent resistance into the device. We incorporate these memristors into a relaxation oscillator and observe a tunable range of periodic and chaotic self-oscillations. We show that the nonlinear current transport coupled with thermal fluctuations at the nanoscale generates chaotic oscillations. Such memristors could be useful in certain types of neural-inspired computation by introducing a pseudo-random signal that prevents global synchronization and could also assist in finding a global minimum during a constrained search. We specifically demonstrate that incorporating such

  14. 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.

  15. 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.

  16. Atom-Driven Permeation of Deuterium Through Nb

    Science.gov (United States)

    Ohkoshi, K.; Tohda, S.; Shimura, K.; Yamaguchi, K.; Terai, T.; Yamawaki, M.

    In order to investigate the difference of the hydrogen transport behavior of IDP (ion-driven permeation, i.e. permeation under impingement of the energetic hydrogen ion beam) and ADP (atom-driven permeation, i.e. permeation under exposure of thermal atom beam), an ADP experiment through Nb (niobium) was performed. The dependence of the ADP flux on the specimen temperature turned out to be different from the IDP, where the maximum was observed in the temperature range of 500--1000 K. Such a case has not been seen in the IDP or GDP (gas-driven permeation) case. The deuterium concentration at the downstream-side end bulk volume was estimated employing the phenomenological recombination rate coefficient. Computer calculation showed that the profile of the deuterium concentration becomes almost “flat” under the experimental conditions. Though the experiment'was performed under UHV conditions, the assumption of Sieverts' law-like relation between P*U (virtual pressure of atomic gas, or pressure equivalent to “atomic flow” in the upstream-side vacuum in terms of the molecular flow theory), bulk concentration and PD (pressure of permeated molecules) explains well the strange temperature dependence of the permeation plot.

  17. Magnetization Measurements of High-Jc Nb3Sn strands

    CERN Document Server

    Bordini, B; Alknes, P; Ballarino, A; Bottura, L; Oberli, L

    2013-01-01

    High critical current density Nb3Sn wires (Jc > 2500 A/mm2 at 4.2 K and 12 T) are the conductors considered for next generation accelerator magnets. At present, the large magnetization of these strands is a concern within the scientific community because of the impact it might have on the magnet field quality. In order to characterize the magnetic behavior of these wires, an extensive campaign of magnetization measurements was launched at CERN. Powder In Tube (PIT) strands by Bruker-EAS and Restacked Rod Process (RRP®) strands by Oxford Superconducting Technology (OST) were measured between 0 T and 10.5 T at different temperatures (ranging from 1.9 K to 14.5 K). The samples, based on strands with different sub-elements dimensions (35 to 80 μm), were measured with a Vibrating Sample Magnetometer (VSM). The experimental data were analyzed to: 1) calculate the effective filament size and the optimal parameters for the pinning force scaling law; 2) define the field-temperature region where there are flux...

  18. Corrosion behavior of Ti-39Nb alloy for dentistry.

    Science.gov (United States)

    Fojt, Jaroslav; Joska, Ludek; Malek, Jaroslav; Sefl, Vaclav

    2015-11-01

    To increase an orthopedic implant's lifetime, researchers are now concerned on the development of new titanium alloys with suitable mechanical properties (low elastic modulus-high fatigue strength), corrosion resistance and good workability. Corrosion resistance of the newly developed titanium alloys should be comparable with that of pure titanium. The effect of medical preparations containing fluoride ions represents a specific problem related to the use of titanium based materials in dentistry. The aim of this study was to determine the corrosion behavior of β titanium alloy Ti-39Nb in physiological saline solution and in physiological solution containing fluoride ions. Corrosion behavior was studied using standard electrochemical techniques and X-ray photoelectron spectroscopy. It was found that corrosion properties of the studied alloy were comparable with the properties of titanium grade 2. The passive layer was based on the oxides of titanium and niobium in several oxidation states. Alloying with niobium, which was the important part of the alloy passive layer, resulted in no significant changes of corrosion behavior. In the presence of fluoride ions, the corrosion resistance was higher than the resistance of titanium. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Biocompatibility of new Ti-Nb-Ta base alloys.

    Science.gov (United States)

    Hussein, Abdelrahman H; Gepreel, Mohamed A-H; Gouda, Mohamed K; Hefnawy, Ahmad M; Kandil, Sherif H

    2016-04-01

    β-type titanium alloys are promising materials in the field of medical implants. The effect of β-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed β-type (Ti77Nb17Ta6) biocompatible alloys are studied. The β-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the β-phase in the treated solution condition. The strength and hardness have increased with the increase in β-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti-6Al-4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Measurement of a Conduction Cooled Nb3Sn Racetrack Coil

    Science.gov (United States)

    Kim, HS; Kovacs, C.; Rochester, J.; Sumption, MD; Tomsic, M.; Peng, X.; Doll, D.

    2017-12-01

    Use of superconducting coils for wind turbines and electric aircraft is of interest because of the potential for high power density and weight reduction. Here we test a racetrack coil developed as a proof-of-concept for cryogen-free superconducting motors and generators. The coil was wound with 1209 m of 0.7-mm-diameter insulated tube-type Nb3Sn wire. The coil was epoxy-impregnated, instrumented, covered with numerous layers of aluminized mylar insulation, and inserted vertically into a dewar. The system was cooled to 4.2 K, and a few inches of liquid helium was allowed to collect at the bottom of the dewar but below the coil. The coil was cooled by conduction via copper cooling bars were attached to the coil but also were immersed in the liquid helium at their lower ends. Several current tests were performed on the coil, initially in voltage mode, and one run in current mode. The maximum coil Ic at 4.2 K was 480 A, generating 3.06 T at the surface of the coil. The coil met the design targets with a noticeable margin.

  1. Superconducting transport in single and parallel double InAs quantum dot Josephson junctions with Nb-based superconducting electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shoji, E-mail: baba@meso.t.u-tokyo.ac.jp; Sailer, Juergen [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Deacon, Russell S. [Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); RIKEN Advanced Science Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oiwa, Akira [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Shibata, Kenji [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai 982-8577 (Japan); Hirakawa, Kazuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); JST CREST, 4-1-8 Hon-cho, Kawaguchi-shi, Saitama 332-0012 (Japan); Tarucha, Seigo [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); INQIE, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); QPEC, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656 (Japan)

    2015-11-30

    We report conductance and supercurrent measurements for InAs single and parallel double quantum dot Josephson junctions contacted with Nb or NbTiN superconducting electrodes. Large superconducting gap energy, high critical field, and large switching current are observed, all reflecting the features of Nb-based electrodes. For the parallel double dots, we observe an enhanced supercurrent when both dots are on resonance, which may reflect split Cooper pair tunneling.

  2. Fabrication and characterization of perovskite-type solar cells with Nb-doped TiO{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Jo; Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Suzuki, Atsushi; Akiyama, Tsuyoshi [The University of Shiga Prefecture, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    Organic-inorganic hybrid heterojunction solar cells containing perovskite CH{sub 3}NH{sub 3}PbI{sub 3} using Nb-doped TiO{sub 2} as an electron-transporting layer were fabricated and characterized. Nb-doped TiO{sub 2} layer showed an improvement of the short-circuit current density and power conversion efficiency using Ti{sub 0.95}Nb{sub 0.05}O{sub 2}.

  3. NMR study of intrinsic defects in congruent LiNbO 3. 1. “Unoverlapping” defects

    Science.gov (United States)

    Yatsenko, A. V.; Ivanova, E. N.; Sergeev, N. A.

    1997-10-01

    The simulations of NMR spectra of 7Li and 93Nb nuclei for different models of intrinsic defects in single crystal of congruent lithium niobate have been performed. It has been shown that the most probable defects in LiNbO 3 are complex (Nb Li + 3V Li) and isolated V Li. The NMR spectra of 7Li have been simulated assuming that the potential surface of Li ion in distorted LiO 6 octahedron has four minima.

  4. Synthesis and reactivity of {Ru(p-cymene)}2+ derivatives of [Nb6O19]8-: a rational approach towards fluxional organometallic derivatives of polyoxometalates.

    Science.gov (United States)

    Laurencin, Danielle; Thouvenot, René; Boubekeur, Kamal; Proust, Anna

    2007-04-07

    Three {Ru(p-cym)}(2+) (p-cym = p-cymene) derivatives of [Nb(6)O(19)](8-)-[Nb(6)O(19){Ru(p-cym)}](6-) (Nb(6)Ru(1)), trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) (t-Nb6Ru2), and [Nb(6)O(19){Ru(p-cym)}(4)] (Nb(6)Ru(4))--have been synthesized in water by reaction between [Ru(p-cym)Cl(2)](2) and the hexaniobate. In the solid state, Nb(6)Ru(1) and Nb(6)Ru(4) have been characterized by IR and EDX spectroscopies, whereas t-Nb(6)Ru(2) has been characterized by IR spectroscopy and single-crystal X-ray diffraction (crystal data for K(4)-trans-[Nb(6)O(19){Ru(p-cym)}(2)].14H(2)O (K(4)-t-Nb(6)Ru(2).14H(2)O). In solution, all compounds were characterized by (1)H NMR and ESI mass spectrometry analyses, and Nb(6)Ru(1) was also analyzed by (17)O NMR. These studies allowed a comparison of the differences in behaviour of the three complexes in water: Nb(6)Ru(1) is particularly stable, Nb(6)Ru(4) decomposes by loss of {Ru(p-cym)}(2+) fragments, and trans-[Nb(6)O(19){Ru(p-cym)}(2)](4-) isomerizes into cis-[Nb(6)O(19){Ru(p-cym)}(2)](4-). A rational mechanism for the isomerisation of t-Nb(6)Ru(2) is proposed on the basis of a kinetic study.

  5. 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)

  6. Ba(Mg1/3Nb2/3)O3−xBa(Mg1/8Nb3/4)

    Indian Academy of Sciences (India)

    2017-09-05

    Sep 5, 2017 ... which have application in wireless communications. Their high permittivity (εr), high quality ... ture disorders. High-temperature treatment also results into secondary phases that deteriorate dielectric properties. Kolo- diazhnyi et al [7] reported ordering for BMN ceramics at. 1620. ◦. C, along with Ba3Nb5O15 ...

  7. 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)

  8. Study of fatigue and fracture behavior of NbCr{sub 2}-based alloys and intermetallic materials: Phase stability in NbCr{sub 2} Laves phase alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.H.; Liaw, P.K. [Univ. of Tennessee, Knoxville, TN (United States); Liu, C.T. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    Phase stability in NbCr{sub 2}-based transition-metal Laves phases is studied in this paper, using data from binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor (e/a = the average number of electrons per atom outside the closed shells of the component atoms) is the determinate factor in controlling the phase stability of NbCr{sub 2}-based transition-metal Laves phases. The e/a ratios for different Laves phase structures were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an e/a range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure was stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. The electron concentration effect on the phase stability of transition-metal A{sub 3}B intermetallic compounds and Mg-based Laves phases is also reviewed and compared with the present observations in transition-metal Laves phases.

  9. On the substitution site of Cr and Fe in LiNbO3: an exafs study

    Science.gov (United States)

    Corradi, G.; Chadwick, A. V.; West, A. R.; Cruickshankand, K.; Paul, M.

    1995-12-01

    K-edge EXAFS spectra of 5 molar% Cr or Fe have been observed in LiNbO3 and also in Mg co-doped samples. The results in congruent LiNbO3 can be interpreted in terms of a relaxed Li substitution model, however, in the case of Cr, the formation of pairs occupying Li and Nb sites seems also to be important. In stoichiometric or Mg-containing samples Fe is partly displaced to the Nb site while for Cr the dominating process seems to be the formation of aggregates with the participation of Mg.

  10. Structure and properties of the Mo3Nb2O14 oxide.

    Science.gov (United States)

    Afanasiev, Pavel

    2005-10-06

    Mixed Nb-Mo oxides were prepared by solid-state reaction of Nb(V) and Mo(VI) oxides at 973-1123 K. Optimal conditions were determined for the formation of the Mo3Nb2O14 compound. As established by Rietveld refinement of the powder X-ray diffraction patterns, the Mo3Nb2O14 oxide has the tetragonal cell with a = 23.150(6) A and c = 3.998(4) A and a tunnel structure similar to that of the Mo5O14 oxide. The solids were characterized by several physical techniques, including scanning and transmission electron microscopy, FT-IR, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and electron spin resonance spectroscopy. It has been shown that the Mo3Nb2O14 solid prepared in air at 973-1073 K after cooling to room temperature contains high amounts of Mo(V) species (ca. 1% of total molybdenum). The presence of paramagnetic species correlates with the intense green color of the solids and the strong d-d transition band in the UV-visible spectra, typical for the d1 species. The amount of paramagnetic species does not depend on the solid annealing and/or on the small variations of its composition. Neither is it related to the oxygen release upon the solid heating, being therefore an intrinsic property of the Mo3Nb2O14 oxide. The unusual stabilization of reduced Mo species in the highly oxidizing conditions was explained by the substitution disorder between Nb and Mo atoms. It is supposed that a configuration containing mu3 oxygen bonded to three Mo(VI) atoms is unstable and decomposes, leading to a Mo(V) center and a hole in the valence band.

  11. 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.

  12. Effect of microstructure on the nanotube growth by anodic oxidation on Ti-10Nb alloy

    Science.gov (United States)

    Luz, A. R.; Lepienski, C. M.; Henke, S. L.; Grandini, C. R.; Kuromoto, N. K.

    2017-07-01

    Several papers have reported the grown self-organized nanotube arrays on pure Ti and its alloys to improve the surface of these materials for biomedical applications. The growth of nanotubes can be influenced by microstructure of material; however, few papers concerning this topic have been published. The aim of this work was to investigate the morphology, the cross-section view and the oxides in nanotube arrays in relationship to the microstructure of the Ti-10Nb alloy. The growth of nanotubes on the Ti-10Nb alloy obtained by anodic oxidation (AO). The Ti-10Nb alloy is composed by alfa and beta phases that were investigated by metallographic analysis, patterns of x-ray diffraction and EDS analysis. SEM images and EDS analysis revealed the morphology was composed by self-organized nanotube arrays on the alpha phase and walls with transversal holes on beta phase. X-ray patterns show crystalline oxides formation. Raman spectrum confirms the presence of anatase and Nb2O5 oxides. A significant contribution of the Nb2O5 was observed by bi-dimensional (x, y) Raman mapping, which also showed that the all oxide film was homogeneous oxide distributed on Ti-10Nb alloy. The nanostructured films have higher thickness in the beta than in the alpha phase, and have a small different in structure and oxide composition; as observed by SEM and Raman mapping. The results indicate that the microstructure of the Ti-10Nb affects the nanotubes morphology and the cross-section view, but the oxide formation was similar for all regions analyzed.

  13. Structure and stability of phases within the NbN-AlN system

    Energy Technology Data Exchange (ETDEWEB)

    Holec, David; Mayrhofer, Paul H [Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Franz, Robert; Mitterer, Christian, E-mail: david.holec@unileoben.ac.a [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria)

    2010-04-14

    The outstanding electronic and physical properties of NbN and the continuous need for advanced materials, e.g. in the field of hard coatings, motivated us to investigate the Nb{sub 1-x}Al{sub x}N pseudo-binary alloy by means of first principles calculations and experimental studies. The experimentally reported phases for NbN and AlN, cubic B1, hexagonal B{sub k}, B8{sub 1} ({delta}'-NbN) and B{sub i} ({epsilon}-NbN) and wurtzite B4 were considered for the calculations. The phase stability analysis based on the comparison of formation energies of various phases yields that the Nb-rich alloys favour the hexagonal B8{sub 1}-like structure (up to an AlN fraction of x {approx} 0.14), the Al-rich side favours the wurtzite B4 structure (for x {approx}> 0.7) and the intermediate compositions favour the cubic B1 phase. The available hybridization schemes together with the analysis of the density of states and the (difference) charge density maps provide reasoning for the obtained results. Experimental investigations confirm preferred B1 structure for Nb{sub 1-x}Al{sub x}N coatings with x below 0.45, a mixed B1, B{sub k} and B4 structure for x in the range 0.45-0.71 and a preferred B4 structure for x above 0.71.

  14. Microstructure of rapidly solidified Nb-based pre-alloyed powders for additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yueling; Jia, Lina, E-mail: jialina@buaa.edu.cn; Kong, Bin; Zhang, Shengnan; Zhang, Fengxiang; Zhang, Hu

    2017-07-01

    Highlights: • Sphere shaped Nb-37Ti-13Cr-2Al-1Si pre-alloyed powders were prepared by PREP. • An oxide layer with a thickness of 9.39 nm was generated on the powder surface. • The main phases of the pre-alloyed powders were Nbss and Cr{sub 2}Nb. • SDAS increased and microhardness decreased with the increase of powder size. • Microstructure of powders evolved into large grains from dendrite structures after HT. - Abstract: For powder-based additive manufacturing, sphere-shaped Nb-37Ti-13Cr-2Al-1Si pre-alloyed powders were prepared by plasma rotating electrode processing (PREP). The microstructure, surface oxidation and microhardness of the pre-alloyed powders were systematically investigated. Results showed that the main phases were Nb solid solution (Nbss) and Cr{sub 2}Nb. The Cr{sub 2}Nb phases were further determined using transmission electron microscopy (TEM). Fine dendrite structures were observed in the as-fabricated pre-alloyed powders, which transformed to large grains after heat treatment (HT) at 1450 °C for 3 h. With the increase of powder size, the secondary dendrite arm spacing (SDAS) increased and the microhardness (HV) decreased. A clean powder surface free of oxide particles was obtained by PREP and an oxide layer with 9.39 nm in thickness was generated on the powder surface. Compared with Cr- and Nb-oxides, more Ti-oxides were formed on outmost powder surface with a higher content of Ti (up to 47.86 at.%). The differences upon the microstructure and microhardness of the pre-alloyed powders with different sizes were discussed.

  15. Microstructural evolution of Ti-10Nb and Ti-15Nb alloys produced by the blended elemental technique

    Energy Technology Data Exchange (ETDEWEB)

    Martins, G.V.; Souza, J.V.C.; Machado, J.P.B., E-mail: givmartins@yahoo.com.br, E-mail: vitor@las.inpe.br, E-mail: joaopaulo@las.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Silva, C.R.M. [Universidade de Brasilia (UnB), Brasilia, DF (Brazil); Henriques, V.A.R., E-mail: vinicius@iae.cta.br [Instituto de Aeronautica e Espaco (DCTA/IAE/AMR), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial; Borges Junior, L.A., E-mail: borges.jr@itelefonica.com.br [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil)

    2009-07-01

    Alfa/beta titanium alloys have been intensely used for aerospace and biomedical applications. Production of powder metallurgy titanium alloys components may lead to a reduction in the cost of parts, compared to those produced by conventional cast and wrought (ingot metallurgy) processes, because additional working operations (machining, turning, milling, etc.) and material waste can be avoided. In this work, samples of Ti- 10, 15Nb (weight%) alloys were obtained by the blended elemental technique using hydride-de hydride (HDH) powders as raw material, followed by uniaxial and cold isostatic pressing with subsequent densification by sintering carried out in the range 900-1500 deg C. These alloys were characterized by X-ray diffractometry for phase composition, scanning electron microscopy for microstructure, Vickers indentation for hardness, Archimedes method for specific mass and resonance ultrasound device for elastic modulus. For the samples sintered at 1500 deg C it was identified α and β phases. It was observed the influence of the sintering temperatures on the final microstructure. With increasing sintering temperature, microstructure homogenization of the alloy takes place and at 1500 deg C this process is complete. The same behavior is observed for densification. Comparing to the Ti6Al4V alloy properties, these alloys hardness (sintered at 1500 deg C) are near and elastic modulus are 18% less. (author)

  16. 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)

  17. Random thoughts

    Science.gov (United States)

    ajansen; kwhitefoot; panteltje1; edprochak; sudhakar, the

    2014-07-01

    In reply to the physicsworld.com news story “How to make a quantum random-number generator from a mobile phone” (16 May, http://ow.ly/xFiYc, see also p5), which describes a way of delivering random numbers by counting the number of photons that impinge on each of the individual pixels in the camera of a Nokia N9 smartphone.

  18. Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

    Science.gov (United States)

    1995-01-01

    A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu

  19. 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

  20. 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

  1. 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

  2. XYO{sub 3} (X = K, Na; Y = Nb, Ta) based superlattices for photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guang-Zhao; Chen, Xiao-Rui; Yuan, Hong-Kuan; Kuang, An-Long [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Chen, Hong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Key Laboratory of Luminescent and Real-Time Analytical Chemistry, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2017-05-15

    The photocatalytic activities of XYO{sub 3} (X = K, Na; Y = Ta, Nb) and XYO{sub 3}/X1Y1O{sub 3} (X, X1 = K, Na; Y, Y1 = Ta, Nb) systems are investigated by using hybrid density functional. All the XYO{sub 3} and XYO{sub 3}/X1Y1O{sub 3} systems are indirect band gap semiconductors, and the band gap of KNbO{sub 3}/KTaO{sub 3} is smaller than those of KNbO{sub 3} and KTaO{sub 3}, while the band gaps of KNbO{sub 3}/NaNbO{sub 3}, KNbO{sub 3}/NaTaO{sub 3}, KTaO{sub 3}/NaNbO{sub 3}, KTaO{sub 3}/NaTaO{sub 3}, and NaNbO{sub 3}/NaTaO{sub 3} are respectively between the band gaps of these two crystals which make up these superlattices. The electronic structure of KNbO{sub 3}/NaTaO{sub 3} is the same as that of KTaO{sub 3}/NaNbO{sub 3} since both have the same component and similar crystal structure. The band edges of all the considered superlattices are thermodynamically allowed for the water reduction and oxidation processes, and therefore, they could be used for photocatalytic water splitting. Band structures for (i) KNbO{sub 3}/KTaO{sub 3}, (ii) KNbO{sub 3}/NaNbO{sub 3}, (iii) KNbO{sub 3}/NaTaO{sub 3}, (iv) KTaO{sub 3}/NaNbO{sub 3}, (v) KTaO{sub 3}/NaTaO{sub 3}, and (vi) NaNbO{sub 3}/NaTaO{sub 3} superlattices. The horizontal dashed lines represent the Fermi levels. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Modified ring stretch tensile testing of Zr-1Nb cladding

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, A.B.; Majumdar, S.; Ruther, W.E.; Billone, M.C.; Chung, H.M.; Neimark, L.A. [Argonne National Lab., IL (United States)

    1998-03-01

    In a round robin effort between the US Nuclear Regulatory Commission, Institut de Protection et de Surete Nucleaire in France, and the Russian Research Centre-Kurchatov Institute, Argonne National Laboratory conducted 16 modified ring stretch tensile tests on unirradiated samples of zr-1Nb cladding, which is used in Russian VVER reactors. Test were conducted at two temperatures (25 and 400 C) and two strain rates (0.001 and 1 s{sup {minus}1}). At 25 C and 0.001 s{sup {minus}1}, the yield strength (YS), ultimate tensile strength (UTS), uniform elongation (UE), and total elongation (TE) were 201 MPa, 331 MPa, 18.2%, and 57.6%, respectively. At 400 C and 0.001 s{sup {minus}1}, the YS, UTS, UE, and TE were 109 MPa, 185 MPa, 15.4%, and 67.7%, respectively. Finally, at 400 C and 1 s{sup {minus}1}, the YS, UTS, UE, and TE were 134 MPa, 189 MPa, 18.9%, and 53.4%, respectively. The high strain rate tests at room temperature were not successful. Test results proved to be very sensitive to the amount of lubrication used on the inserts; because of the large contact area between the inserts and specimen, too little lubrication leads to significantly higher strengths and lower elongations being reported. It is also important to note that only 70 to 80% of the elongation takes place in the gauge section, depending on specimen geometry. The appropriate percentage can be estimated from a simple model or can be calculated from finite-element analysis.

  4. Influence of atomic ordering on the Fe{sub 2}Nb antiferromagnetic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Vélez, G.Y., E-mail: g.y.velezcastillo@gmail.com; Alcázar, G.A. Pérez; Zamora, Ligia E.

    2014-03-15

    Fe{sub 2}Nb samples were obtained by arc melting, ordered by heat treatment, and finally disordered by means of mechanical alloying with milling times of 0.5, 1, 2 and 4 h. The ordered alloy shows only the hcp-Fe{sub 2}Nb structure which is paramagnetic at room temperature, and at low temperatures exhibits spin glass and antiferromagnetic behaviours. Mechanical alloying destroys the ordered structure and permits the formation of bcc iron-rich grains. Atomic disorder maintains the antiferromagnetic behaviour of the alloy, but increases its freezing temperature. The Néel temperature of the hcp grains is increased by the apparition of bcc grains. - Highlights: • By means of arc-melting the ordered Fe{sub 2}Nb alloy was obtained. • The ordered Fe{sub 2}Nb alloy exhibits antiferromagnetic behaviour. • Atomic disorder does not affect the antiferromagnetic phase of the alloy. • Néel temperature increases only due to the formation of the bcc Fe–Nb grains that appear during mechanical alloying.

  5. [Effect of Silencing SET Gene on Acute Promyelocytic Leukemia NB4-R1 Cells].

    Science.gov (United States)

    Wang, Yuan; Zhang, Mei; He, Peng-Cheng; Qi, Jun; Liu, Yan-Feng; Zhu, Hua-Chao

    2016-02-01

    To investigate the effect of silencing SET gene on the biological characteristics of acute promyelocytic leukemia NB4-R1 cells. The expression vector of pGCSIL containing SET-shRNA were transfected into 293T cells by using other packaging plasmids. The supernatant of the 293T cells was harvested for lentivirus. The SET-shRNA lentiviral vector was transfected into acute promyelocytic leukemia NB4-R1 cells and a stably transfected cell line was established. Real-time quantitative PCR and Western blot were used to assay the silencing efficiency on SET gene and the expression of PP2A. The cell cycle distribution was tested by flow cytometry. The expression of SET in experimental group statistically decreased as compared with that of the control group. The expression of PP2A was obviously raised at the level of mRNA and protein. The percentage of NB4-R1 cells in G0/G1 phase significantly increased, while the percentage of cells in S phase significantly decreased. The silencing gene in acute promyelocytic leukemia NB4-R1 cells using SET-shRNA lentiviral vector can increase the expression of PP2A and interfere of the cell cycle in NB4-R1 cells. This study has laid a experimental base for targed therapy of patients with acute promyelocytic leukemia.

  6. RbNb6Cl12O2: CRYSTAL STRUCTURE AND MAGNETIC PROPERTIES

    Directory of Open Access Journals (Sweden)

    Fakhili Gulo

    2010-06-01

    Full Text Available A novel niobium oxychloride cluster compound, RbNb6Cl12O2 was obtained by solid state synthesis from stoichiometric mixture of RbCl, Nb2O5, NbCl5 and Nb powder, heated at 675 °C. Its structure was determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic system (a = 6.8097(4 Å, b = 11.6700(9 Å, c = 12.5090(9 Å, ß = 101.337(4 °, V = 974.68(12 Å3, and Z = 2 with the space group of P21/c. The cluster framework of this compound is based on  units connected via oxide ligands in the a-direction with two Nb-O linkages between adjacent clusters, which resembles intercluster bonding in Chevrel-Sergent phases. In the other two directions, the linkages occur through single Cla-a bridges. The framework generates channels where the cations Rb+ are located. This compound contains valence electron concentration (VEC of 15 per cluster unit and therefore exhibits the paramagnetic behavior.   Keywords: niobium oxychloride cluster, solid state, VEC, paramagnetic

  7. Processing and microstructure of Nb-1%Zr-0.1%C alloy sheet

    Energy Technology Data Exchange (ETDEWEB)

    Uz, M. [Lafayette College, Easton, PA (United States); Titran, R.H. [Lewis Research Center, Cleveland, OH (United States)

    1994-09-01

    A systematic study was carried out to evaluate the effects of processing on the microstructure of a Nb-1wt.%Zr-0.1wt.%C alloy sheet. The samples were fabricated by cold rolling different sheet bars that were single-, double- or triple-extruded at 1900 K. Heat treatment consisted of one- or two-step annealing of different samples at temperatures ranging from 1350 K to 1850 K. The assessment of the effects of processing on microstructure involved characterization of the precipitates including the type, crystal structure, chemistry and distribution within the material as well as an examination of the grain structure. A combination of various analytical and metallographic techniques were used on both the sheet samples and the residue extracted from them. The results show that the relatively coarse orthorhombic Nb{sub 2}C carbides in the as-rolled samples transformed to rather fine cubic monocarbides of Nb and Zr with varying Zr/Nb ratios upon subsequent heat treatment. The relative amount of the cubic carbides and the Zr/Nb ratio increased with increasing number of extrusions prior to cold rolling. Furthermore, the size and the aspect ratio of the grains appear to be strong functions of the processing history of the material. These and other results obtained will be presented with the emphasis on a possible relationship between processing and microstructure.

  8. Processing and microstructure of Nb-1% Zr-0. 1% C alloy sheet

    Energy Technology Data Exchange (ETDEWEB)

    Uz, M. (Lafayette College, Easton, Pennsylvania 18042 (United States)); Titran, R.H. (NASA Lewis Research Center, Cleveland, Ohio 44135 (United States))

    1993-01-10

    A systematic study was carried out to evaluate the effects of processing on the microstructure of a Nb-1 wt. % Zr-0.1 wt. % C alloy sheet. The samples were fabricated by cold rolling different sheet bars that were single-, double- or triple-extruded at 1900 K. Heat treatment consisted of one- or two-step annealing of different samples at temperatures ranging from 1350 K to 1850 K. The assessment of the effects of processing on microstructure involved characterization of the precipitates including the type, crystal structure, chemistry and distribution within the material as well as an examination of the grain structure. A combination of various analytical and metallographic techniques were used on both the sheet samples and the residue extracted from them. The results show that the relatively coarse orthorhombic Nb[sub 2]C carbides in the as-rolled samples transformed to rather fine cubic monocarbides of Nb and Zr with varying Zr/Nb ratios upon subsequent heat treatment. The relative amount of the cubic carbides and the Zr/Nb ratio increased with increasing number of extrusions prior to cold rolling. Furthermore, the size and the aspect ratio of the grains appear to be strong functions of the processing history of the material. These and other results obtained will be presented with the emphasis on a possible relationship between processing and microstructure.

  9. The quinternary thiophosphate Cs0.5Ag0.5Nb2PS10

    Directory of Open Access Journals (Sweden)

    Sojeong Park

    2010-07-01

    Full Text Available The quinternary thiophosphate Cs0.5Ag0.5Nb2PS10, cesium silver tris(disulfido[tetrathiophosphato(V]diniobate(IV, has been prepared from the elements using a CsCl flux. The crystal structure is made up of ∞1[Nb2PS10] chains expanding along [010]. These chains are built up from bicapped trigonal-prismatic [Nb2S12] units and tetrahedral [PS4] groups and are linked through a linear S—Ag—S bridge, forming a two-dimensional layer. These layers then stack on top of each other, completing the three-dimensional structure with an undulating van der Waals gap. The disordered Cs+ ions reside on sites with half-occupation in the voids of this arrangement. Short [2.8843 (5 Å] and long [3.7316 (4 Å] Nb—Nb distances alternate along the chains, and anionic S22− and S2− species are observed. The charge balance of the compound can be represented by the formula [Cs+]0.5[Ag+]0.5[Nb4+]2[PS43−][S22−]3.

  10. Photocathode quantum efficiency of ultrathin Cs2Te layers on Nb substrates

    Science.gov (United States)

    Yusof, Zikri; Denchfield, Adam; Warren, Mark; Cardenas, Javier; Samuelson, Noah; Spentzouris, Linda; Power, John; Zasadzinski, John

    2017-12-01

    The quantum efficiencies (QE) of photocathodes consisting of bulk Nb substrates coated with thin films of Cs2Te are reported. Using the standard recipe for Cs2Te deposition developed for Mo substrates (220 Å Te thickness), a QE ˜11 % - 13 % at light wavelength of 248 nm is achieved for the Nb substrates, consistent with that found on Mo. Systematic reduction of the Te thickness for both Mo and Nb substrates reveals a surprisingly high residual QE ˜6 % for a Te layer as thin as 15 Å. A phenomenological model based on the Spicer three-step model along with a solution of the Fresnel equations for reflectance, R , leads to a reasonable fit of the thickness dependence of QE and suggests that layers thinner than 15 Å may still have a relatively high QE. Preliminary investigation suggests an increased operational lifetime as well. Such an ultrathin, semiconducting Cs2Te layer may be expected to produce minimal Ohmic losses for rf frequencies ˜1 GHz . The result thus opens the door to the potential development of a Nb (or Nb3Sn ) superconducting photocathode with relatively high QE and minimal rf impedance to be used in a superconducting radiofrequency (SRF) photoinjector.

  11. Structural properties of nanometric and micrometric TiCN/TiNbCN supperlattices

    Science.gov (United States)

    Caicedo, Julio; Yate, Luis; Ramírez, Juan; Gómez, Maria Elena; Lousa, Arturo; Esteve, Joan; Prieto, Pedro

    2010-03-01

    TiCN and TiNbCN systems have broadly been used as protective hard and anticorrosive coatings. [TiCN/TiNbCN]n multilayers were deposited on silicon substrates by two-target-r.f. magnetron sputtering with alternatively changing the sputtering plasma composition between pure Ti+C and Nb elements under a reactive mixture Ar/N2. TiCN/TiNbCN bilayer period varied from nanometric range (15 nm) to higher micrometric range (1.5 μm) values. Structural, morphological and stoichiometric of the coatings were analyzed by high-angle- and low-angle X-ray diffraction, X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and cross-sectional transmission electron microscopy (TEM). We determined multilayer period, λ, and individual layer thicknesses. We found a cube-on-cube epitaxial growth structure and with epitaxial relationship between layers inside each columnar crystallite given by (111)[110]TiCN//(111)[110]TiNbCN.

  12. Functionalized NbS2 as cathode for Li- and Na-ion batteries

    KAUST Repository

    Zhu, Jiajie

    2017-07-27

    Cathodes of Li- and Na-ion batteries usually have capacities <200 mAh/g, significantly less than the anodes. Two-dimensional materials can overcome this limitation but suffer from low voltages. In this context, we investigate NbS2 functionalized by O, F, and Cl as a cathode material by first-principles calculations, considering both the conversion and intercalation mechanisms. NbS2O2 shows a higher voltage than NbS2 for both Li and Na, but the voltage decreases drastically for increasing ion coverage. Even higher voltages and favorable dependences on the ion coverage are achieved by F and Cl functionalization. We obtain NbS2F2 and NbS2Cl2 energy densities of 1223 mW h/g and 823 mW h/g for lithiation and 1086 mW h/g and 835 mW h/g for sodiation, respectively. These values are higher than those for most state-of-the-art cathode materials (∼600 mW h/g). In addition, low diffusion barriers enable high cycling rates.

  13. Microstructure of rapidly solidified Nb-based pre-alloyed powders for additive manufacturing

    Science.gov (United States)

    Guo, Yueling; Jia, Lina; Kong, Bin; Zhang, Shengnan; Zhang, Fengxiang; Zhang, Hu

    2017-07-01

    For powder-based additive manufacturing, sphere-shaped Nb-37Ti-13Cr-2Al-1Si pre-alloyed powders were prepared by plasma rotating electrode processing (PREP). The microstructure, surface oxidation and microhardness of the pre-alloyed powders were systematically investigated. Results showed that the main phases were Nb solid solution (Nbss) and Cr2Nb. The Cr2Nb phases were further determined using transmission electron microscopy (TEM). Fine dendrite structures were observed in the as-fabricated pre-alloyed powders, which transformed to large grains after heat treatment (HT) at 1450 °C for 3 h. With the increase of powder size, the secondary dendrite arm spacing (SDAS) increased and the microhardness (HV) decreased. A clean powder surface free of oxide particles was obtained by PREP and an oxide layer with 9.39 nm in thickness was generated on the powder surface. Compared with Cr- and Nb-oxides, more Ti-oxides were formed on outmost powder surface with a higher content of Ti (up to 47.86 at.%). The differences upon the microstructure and microhardness of the pre-alloyed powders with different sizes were discussed.

  14. Mesoporous nanostructured Nb-doped titanium dioxide microsphere catalyst supports for PEM fuel cell electrodes.

    Science.gov (United States)

    Chevallier, Laure; Bauer, Alexander; Cavaliere, Sara; Hui, Rob; Rozière, Jacques; Jones, Deborah J

    2012-03-01

    Crystalline microspheres of Nb-doped TiO(2) with a high specific surface area were synthesized using a templating method exploiting ionic interactions between nascent inorganic components and an ionomer template. The microspheres exhibit a porosity gradient, with a meso-macroporous kernel, and a mesoporous shell. The material has been investigated as cathode electrocatalyst support for polymer electrolyte membrane (PEM) fuel cells. A uniform dispersion of Pt particles on the Nb-doped TiO(2) support was obtained using a microwave method, and the electrochemical properties assessed by cyclic voltammetry. Nb-TiO(2) supported Pt demonstrated very high stability, as after 1000 voltammetric cycles, 85% of the electroactive Pt area remained compared to 47% in the case of commercial Pt on carbon. For the oxygen reduction reaction (ORR), which takes place at the cathode, the highest stability was again obtained with the Nb-doped titania-based material even though the mass activity calculated at 0.9 V vs RHE was slightly lower. The microspherical structured and mesoporous Nb-doped TiO(2) is an alternative support to carbon for PEM fuel cells. © 2012 American Chemical Society

  15. Photocathode quantum efficiency of ultrathin Cs_{2}Te layers on Nb substrates

    Directory of Open Access Journals (Sweden)

    Zikri Yusof

    2017-12-01

    Full Text Available The quantum efficiencies (QE of photocathodes consisting of bulk Nb substrates coated with thin films of Cs_{2}Te are reported. Using the standard recipe for Cs_{2}Te deposition developed for Mo substrates (220 Å Te thickness, a QE∼11%–13% at light wavelength of 248 nm is achieved for the Nb substrates, consistent with that found on Mo. Systematic reduction of the Te thickness for both Mo and Nb substrates reveals a surprisingly high residual QE∼6% for a Te layer as thin as 15 Å. A phenomenological model based on the Spicer three-step model along with a solution of the Fresnel equations for reflectance, R, leads to a reasonable fit of the thickness dependence of QE and suggests that layers thinner than 15 Å may still have a relatively high QE. Preliminary investigation suggests an increased operational lifetime as well. Such an ultrathin, semiconducting Cs_{2}Te layer may be expected to produce minimal Ohmic losses for rf frequencies ∼1  GHz. The result thus opens the door to the potential development of a Nb (or Nb_{3}Sn superconducting photocathode with relatively high QE and minimal rf impedance to be used in a superconducting radiofrequency (SRF photoinjector.

  16. Study of the non-linear stress-strain behavior in Ti-Nb-Zr alloys

    Directory of Open Access Journals (Sweden)

    Sergio Schneider

    2005-12-01

    Full Text Available The aim of this work is to study the elastic behavior of some Ti-Nb-Zr alloys (Ti-8Nb-13Zr, Ti-13Nb-13Zr, Ti-18Nb-13Zr and Ti-41.1Nb-7.1Zr developed to biomedical applications. These alloys were produced by arc melting under argon atmosphere. Uniaxial tensile tests, carried out in a MST servo-hydraulic machine, were employed in their mechanical characterization. The occurrence of non-linear stress-strain behavior in the conventional elastic region (total strain values up to 0.2% lead to the Ramberg-Osgood relationship, modified by Hill, in order to analyze that portion of the obtained curves. The present study involves the following properties: initial elastic modulus, tangent modulus, secant modulus, proof stress and the Ramberg-Osgood parameter (n. The results demonstrate that these alloys are not similar with respect to the mechanical behavior. Furthermore, it is shown that the degree of non-linearity in the stress-strain behavior is quantified by the parameter (n.

  17. Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy

    Science.gov (United States)

    Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

    2014-09-01

    Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

  18. The role of Nb in intensity increase of Er ion upconversion luminescence in zirconia

    Science.gov (United States)

    Smits, K.; Sarakovskis, A.; Grigorjeva, L.; Millers, D.; Grabis, J.

    2014-06-01

    It is found that Nb co-doping increases the luminescence and upconversion luminescence intensity in rare earth doped zirconia. Er and Yb-doped nanocrystalline samples with or without Nb co-doping were prepared by sol-gel method and thermally annealed to check for the impact of phase transition on luminescence properties. Phase composition and grain sizes were examined by X-ray diffraction; the morphology was checked by scanning- and high-resolution transmission electron microscopes. Both steady-state and time-resolved luminescence were studied. Comparison of samples with different oxygen vacancy concentrations and different Nb concentrations confirmed the known assumption that oxygen vacancies are the main agents for tetragonal or cubic phase stabilization. The oxygen vacancies quench the upconversion luminescence; however, they also prevent agglomeration of rare-earth ions and/or displacement of rare-earth ions to grain surfaces. It is found that co-doping with Nb ions significantly (>20 times) increases upconversion luminescence intensity. Hence, ZrO2:Er:Yb:Nb nanocrystals may show promise for upconversion applications.

  19. Surface activation of MnNb2O6 nanosheets by oxalic acid for enhanced photocatalysis

    Science.gov (United States)

    Wu, Junshu; Wang, Jinshu; Li, Hongyi; Li, Yongli; Du, Yucheng; Yang, Yilong; Jia, Xinjian

    2017-05-01

    MnNb2O6 nanosheets (P-MNOs) is selectively crystallized by using surface capping ligand with functional sulfonate group (sodium dodecyl benzene sulphonate), which binds to the (131) surface of MnNb2O6 inducing the morphology-controlled crystallization of MnNb2O6 materials. Surface modification of photoactive P-MNOs with electron-rich oxalic acid ligands establishes an excited surface complex layer on phase-pure P-MNO as evidenced by spectroscopic analyses (FT-IR, UV-vis, Raman, PL, etc.), and thus more efficiently photocatalyzes the reduction of Cr(VI) into Cr(III) than solely P-MNOs or oxalic acid under visible light (λ > 420 nm) via a ligand-to-metal interfacial electron transfer pathway. However, the interaction between oxalic acid and MnNb2O6 is highly dependent upon the morphology of solid MnNb2O6 substrate due to the higher surface-area-to-volume ratio and higher surface activity of (131) planes in the sheet-like morphology. This study could assist the construction of stable niobate material systems to allow a versatile solid surface activation for establishing more energy efficient and robust catalysis process under visible light.

  20. Hydrothermal crystal growth, piezoelectricity, and triboluminescence of KNaNbOF{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Kelvin B. [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States); Edwards, Bryce W. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Frazer, Laszlo; Lenferink, Erik J.; Stanev, Teodor K.; Stern, Nathaniel P. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Nino, Juan C. [Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States); Poeppelmeier, Kenneth R., E-mail: krp@northwestern.edu [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States)

    2016-04-15

    Single crystals of the noncentrosymmetric KNaNbOF{sub 5} polymorph were grown for piezoelectric and triboluminescent measurements. Piezoelectric measurements yielded a d{sub 33} value of ±6.3 pCN{sup −1} and an effective electromechanical coupling coefficient of up to 0.1565 in the frequency range 1960–2080 kHz. Crystals of KNaNbOF{sub 5} were found to exhibit a strong triboluminscence effect visible to the naked eye as blue sparks when crystals are crushed. This triboluminescence effect is uncommon in that it is likely independent from both the piezoelectric effect and atmospheric electrical discharge. Instead, triboluminescence may originate from crystal defects or be related to an electroluminescence effect. - Graphical abstract: An optical emission visible to the naked eye as blue sparks is observed when KNaNbOF{sub 5} single crystals are fractured. - Highlights: • Single crystals of KNaNbOF{sub 5} were grown under hydrothermal conditions. • Piezoelectric and triboluminescent properties were characterized. • Piezoelectric measurements yielded a d{sub 33} value of ±pCN{sup −1}. • KNaNbOF{sub 5} exhibits strong triboluminscence visible to the naked eye as blue sparks.

  1. Angle-dependent hard X-ray photoemission study of Nb hydride formation in high-pressure supercritical water

    Energy Technology Data Exchange (ETDEWEB)

    Soda, Kazuo, E-mail: j45880a@cc.nagoya-u.ac.jp [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kondo, Hiroki; Yamaguchi, Kanta; Kato, Masahiko [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Shiraki, Tatsuhito; Niwa, Ken; Kusaba, Keiji; Hasegawa, Masashi [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Xeniya, Kozina; Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

    2015-09-15

    Highlights: • Nb hydrides in 10-GPa supercritical water are studied by photoelectron spectroscopy. • The hydride components of the Nb 3d core-level spectra are increased with the depth. • The bulk valence-band spectrum shows a split band due to the Nb–H bond formation. • The hydrides are formed in the bulk and their surfaces are covered with Nb oxides. - Abstract: Nb hydrides formation in 10-GPa supercritical water has been investigated by angle-dependent micro-beam hard X-ray photoemission spectroscopy. In the Nb 3d core-level spectra, Nb hydride components are found in the slightly high binding energy side of the metallic components, and the oxide ones are observed even though little oxides are recognized in X-ray diffraction patterns. Obtained emission-angle dependence of the Nb 3d core-level spectra of Nb hydride specimens shows that the Nb hydride components increase with the emission angle decreased i.e. the sampling depth increased, while the oxide ones decrease. The bulk valence-band spectrum is obtained by decomposing the measured valence-band spectra into a bulk and surface components with use of the emission-angle dependence of the core-level and valence-band spectra; it consists of two bands. This implies the Nb–H chemical bond formation and Nb in an oxidation state, consistent with reported band structure calculations and the observed core-level chemical shifts. Thus it is confirmed by valence-band and core-level photoelectron spectroscopy that the Nb hydrides are formed inside the specimen, irrespective to the well-known high oxidation ability of supercritical water.

  2. Superconducting properties of internally stabilized Nb{sub 3}Al wires fabricated by rapid-quenched and transformed process; Naibu anteika kyunetsu kyurei{center_dot}hentai ho Nb{sub 3}Al senzai no chodendo tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Tagawa, K. [Hitachi Cable, Ltd., Tokyo (Japan); National Research Institute for Metals, Tokyo (Japan); Japan Science and Technology Corp., Saitama (Japan); Nakagawa, K. [Hitachi Cable, Ltd., Tokyo (Japan); Takeuchi, T.; Banno, N.; Kiyoshi, T.; Ito, K.; Wada, H. [National Research Institute for Metals, Tokyo (Japan); Yuyama, M.; Kosuge, M. [National Research Institute for Metals, Tokyo (Japan)

    2000-05-29

    Nb{sub 3}AL wire using Ag coated by Nb as stabilizer was manufactured as trial and the critical current density Jc was examined. Compared Ag with Nb as fill-in core bar, Jc of wire using silver filament core bar was higher than one using Nb filament core. It was considered that uniform current in Ag caused to produce homogeneous solid solution. Jc also increased by about 45% following processing of decreasing area after rapid heating and quench. N value also showed at least a value above and equal to 25 at the 21 T magnetic field. (NEDO)Nb{sub 3}AL wire using Ag coated by Nb as stabilizer was manufactured as trial and the critical current density Jc was examined. Compared Ag with Nb as fill-in core bar, Jc of wire using silver filament core bar was higher than one using Nb filament core. It was considered that uniform current in Ag caused to produce homogeneous solid solution. Jc also increased by about 45% following processing of decreasing area after rapid heating and quench. N value also showed at least a value above and equal to 25 at the 21 T magnetic field. (NEDO)

  3. 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.%.

  4. Sc and Nb Dopants in SrCoO3 Modulate Electronic and Vacancy Structures for Improved Water Splitting and SOFC Cathodes

    KAUST Repository

    Tahini, Hassan A.

    2017-01-12

    SrCoO3 is a promising material in the field of electrocatalysis. Difficulties in synthesising the material in its cubic phase have been overcome by doping it with Sc and Nb ions [Mater. Horiz.2015, 2, 495–501]. Using ab initio calculations and special quasi random structures we undertake a systematic study of these dopants in order to elucidate the effect of doping on electronic structure of the SrCoO3 host and the formation of oxygen vacancies. We find that while the overall electronic structure of SrCoO3 is preserved, increasing the Sc fraction leads to a decrease of electrical conductivity, in agreement with earlier experimental work. For low Sc and Nb doping fractions we find that the oxygen vacancy formation increases relative to undoped SrCoO3. However, as the dopants concentration is increased the vacancy formation energy drops significantly, indicating a strong tendency to accommodate high concentration of oxygen vacancies and hence non-stoichiometry. This is explained based on the electronic instabilities caused by the presence of Sc ions which weakens the B-O interactions as well as the increased degree of electron delocalization on the oxygen sublattice. Sc dopants also shift the p-band centre closer to the Fermi level, which can be associated with experimentally reported improvements in oxygen evolution reactions. These findings provide crucial baseline information for the design of better electrocatalysts for oxygen evolution reactions as well as fuel-cell cathode materials.

  5. 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.

  6. Heat treatment study of $Nb_{3}Sn$ strands for the Fermilab's high field dipole model

    CERN Document Server

    Barzi, E; Limon, P J; Ozelis, J P; Yamada, R; Zlobin, A V; Gregory, E; Pyon, T; Wake, M

    2000-01-01

    Fermilab is developing high field superconducting dipole magnets based on Nb/sub 3/Sn for a post-LHC very large hadron collider (VLHC) . The first prototype is a 1 meter long two-layer shell-type (cos- theta) coil with a nominal field of 11 T. A keystoned Rutherford-type cable made of 28 Nb/sub 3/Sn strands of 1 mm in diameter is used. The development of high J/sub c/ multifilamentary Nb/sub 3/Sn strands with low magnetization is an important step of this program. To achieve this goal, strand R&D is actively pursued by Fermilab and IGC using the internal tin process. Conductor designs, heat treatment studies, and results of measurements, including I/sub c/, n-value, RRR, magnetization, and chemical analyses, are presented. (4 refs).

  7. Direct Cast U-6Nb – 2017 Progress on Cylindrical Castings

    Energy Technology Data Exchange (ETDEWEB)

    Aikin, Jr., Robert M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-04

    This report describes work to further develop a sound technical basis and best practices for mold design and process parameters for the Direct Casting of U-6wt%Nb components. One major challenge to the production of U-6Nb components is the propensity for niobium segregation during casting and solidification. This is especially true for cylindrical castings where the vertical side walls allow flotation of Nb resulting in severe inverse macrosegregation. In this work, a small (120 mm diameter by 180 mm tall) and large cylinder (250 mm diameter by 310 mm tall) are examined with a focus on reducing, or eliminating, niobium segregation. It is demonstrated that counter gravity casting (top-to-bottom solidification) can be used to minimize segregation in the small cylinder. Attempts to counter gravity cast the large cylinder were unsuccessful, in large part due to size limitations of the current furnace. A path forward for casting of the large cylinders is discussed.

  8. Crystal structure and ion conducting properties of La5NbMo2O16

    KAUST Repository

    Vu, T.D.

    2016-01-29

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

  9. Synthesis and crystal structure of the first Sc-Nb-O-N phases

    Energy Technology Data Exchange (ETDEWEB)

    Orthmann, Steven; Lerch, Martin [Institut fuer Chemie, Technische Universitaet Berlin (Germany)

    2017-11-17

    Synthesis of phase-pure materials in the system Sc-Nb-O-N is challenging. In this contribution we report on the preparation of the first scandium niobium oxide nitrides via reaction of water-saturated gaseous ammonia or an ammonia-oxygen mixture with amorphous scandium niobium oxides. Two new phases were obtained: rutile-type ScNb{sub 4}O{sub 7}N{sub 3}, which crystallizes in space group P4{sub 2}/mnm, and an anion-deficient fluorite-type Sc{sub 2}Nb(O,N,⬜){sub 6} phase crystallizing in space group Fm anti 3m. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Magnetic and ferroelectric studies of double perovskite (KBi)(FeNb)O{sub 6} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, B. K.; Singh, S. N. [University Department of Physics, Ranchi University, Jharkhand, 834 001 (India); Himanshu, A. K.; Bandyopadhayay, S. K.; Sen, Pintu [Nanostructrured and Advanced Materials Laboratory,VECC, 1/AF Bidhannagar, Kolkata-700 064 (India); Kumar, Uday [Department of Physical Sciences, IISER, Mohanpur Campus, Mohanpur-741252, West Bengal (India); Sinha, T. P. [Department of Physics, Bose Institute, 93/1, A.P.C. Road, Kolkata 700 009 (India)

    2013-02-05

    This work describe the synthesis and characterization of the (KBi)(FeNb)O{sub 6} (KBFN) complex Perovskite. This compound has been structurally characterized by powder X-ray diffraction. The magnetic property of KBFN has been measured. The magnetic properties of (KBi)(FeNb)O{sub 6} is found to be a antiferromagnetically at temperature ranging from {approx}26K. The experimental results indicates that the magnetic moments of Fe{sup 3+} ion in (KBi)(FeNb)O{sub 6} order antiferromagnetically with a slight ferromagnetic moment below ca .26K and weak ferromagnetic moments disappears above ca. 26 K. The ferroelectric behaviour of polarization vs. applied electric field measurements were taken for the KBFN pellet. The shape of the curve are neither consistent with ferroelectric behaviour but rather indicative of conduction.

  11. Magnetic and ferroelectric studies of double perovskite (KBi)(FeNb)O6 ceramics

    Science.gov (United States)

    Choudhary, B. K.; Himanshu, A. K.; Kumar, Uday; Bandyopadhayay, S. K.; Sen, Pintu; Singh, S. N.; Sinha, T. P.

    2013-02-01

    This work describe the synthesis and characterization of the (KBi)(FeNb)O6 (KBFN) complex Perovskite. This compound has been structurally characterized by powder X-ray diffraction. The magnetic property of KBFN has been measured. The magnetic properties of (KBi)(FeNb)O6 is found to be a antiferromagnetically at temperature ranging from ˜26K. The experimental results indicates that the magnetic moments of Fe3+ ion in (KBi)(FeNb)O6 order antiferromagnetically with a slight ferromagnetic moment below ca .26K and weak ferromagnetic moments disappears above ca. 26 K. The ferroelectric behaviour of polarization vs. applied electric field measurements were taken for the KBFN pellet. The shape of the curve are neither consistent with ferroelectric behaviour but rather indicative of conduction.

  12. The Impact of Standard Semiconductor Fabrication Processes on Polycrystalline Nb Thin Film Surfaces

    Science.gov (United States)

    Brown, Ari David; Barrentine, Emily; Moseley, S. Harvey; Noroozian, Omid; Stevenson, Thomas

    2016-01-01

    Polycrystalline Nb thin films are extensively used for microwave kinetic inductance detectors (MKIDs) and superconducting transmission line applications. The microwave and mm-wave loss in these films is impacted, in part, by the presence of surface nitrides and oxides. In this study, glancing incidence x-ray diffraction was used to identify the presence of niobium nitride and niobium monoxide surface layers on Nb thin films which had been exposed to chemicals used in standard photolithographic processing. A method of mitigating the presence of ordered niobium monoxide surface layers is presented. Furthermore, we discuss the possibility of using glancing incidence x-ray diffraction as a non-destructive diagnostic tool for evaluating the quality of Nb thin films used in MKIDs and transmission lines. For a given fabrication process, we have both the X-ray diffraction data of the surface chemistry and a measure of the mm-wave and microwave loss, the latter being made in superconducting resonators.

  13. Dimensional Changes of Nb3Sn Rutherford Cables During Heat Treatment

    CERN Document Server

    Rochepault, E; Ambrosio, G; Anerella, M; Ballarino, A; Bonasia, A; Bordini, B; Cheng, D; Dietderich, D R; Felice, H; Garcia Fajardo, L; Ghosh, A; Holik, E F; Izquierdo Bermudez, S; Perez, J C; Pong, I; Schmalzle, J; Yu, M

    2016-01-01

    In high field magnet applications, Nb3Sn coils undergo a heat treatment step after winding. During this stage, coils radially expand and longitudinally contract due to the Nb3Sn phase change. In order to prevent residual strain from altering superconducting performances, the tooling must provide the adequate space for these dimensional changes. The aim of this paper is to understand the behavior of cable dimensions during heat treatment and to provide estimates of the space to be accommodated in the tooling for coil expansion and contraction. This paper summarizes measurements of dimensional changes on strands, single Rutherford cables, cable stacks, and coils performed between 2013 and 2015. These samples and coils have been performed within a collaboration between CERN and the U.S. LHC Accelerator Research Program to develop Nb3Sn quadrupole magnets for the HiLumi LHC. The results are also compared with other high field magnet projects.

  14. Highly oriented, free-standing, superconducting NbN films growth on chemical vapor deposited graphene

    Directory of Open Access Journals (Sweden)

    Garima Saraswat

    2014-05-01

    Full Text Available NbN films are grown on chemical vapor deposited graphene using dc magnetron sputtering. The orientation and transition temperature of the deposited films is studied as a function of substrate temperature. A superconducting transition temperature of 14 K is obtained for highly oriented (111 films grown at substrate temperature of 150 °C, which is comparable to epitaxial films grown on MgO and sapphire substrates. These films show a considerably high upper critical field of ∼33 T. In addition, we demonstrate a process for obtaining flexible, free-standing NbN films by delaminating graphene from the substrate using a simple wet etching technique. These free-standing NbN layers can be transferred to any substrate, potentially enabling a range of novel superconducting thin-film applications.

  15. High field matching effects in superconducting Nb porous arrays catalyzed from anodic alumina templates

    DEFF Research Database (Denmark)

    Vinckx, W.; Vanacken, J.; Moshchalkov, V.V.

    2007-01-01

    Vortex pinning in a superconducting Nb thin film deposited on an anodically grown alumina template is investigated. Anodic oxidation of aluminium layers permits under specific conditions the formation of highly ordered porous alumina, a membrane-like structure consisting of triangular arrays...... of parallel pores. Its pore diameter and interpore distance are set by careful tuning of the anodization parameters. A superconducting Nb thin film is deposited directly onto the alumina film. The porous alumina acts as a template and it allows Nb to form a periodic pinning array during its growth. Pinning...... force vs. field measurements derived from magnetization measurements, show matching effects in fields up to 1 T. We demonstrate that the anodic alumina template with 50 nm interpore spacing provides enhanced vortex pinning in a large field and temperature range....

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-01

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

  17. Pinning Properties of Commercial Nb-Ti Wires Described by a 2-Components Model

    CERN Document Server

    Muzzi, L; Zignani, Chiarasole Fiamozzi; De Marzi, Gianluca; Muzzi, Luigi; Dominguez, Cesar Octavio; Bottura, Luca; Napolitano, Mathieu; Viola, Rosario; Affinito, Luigi; della Corte, Antonio; Le Naour, Sandrine

    2010-01-01

    We report on the magnetic and transport characterization of different NbTi commercial strands, carried out at variable temperature and magnetic field. From the critical current densities extracted from transport measurements and magnetization cycles we were able to calculate the normalized bulk pinning forces. The curves show good temperature scaling throughout the explored temperature range, and the reduced pinning force can be described by a simple two-components model system. The extension of the 2-components description of the pinning force to an expression for the critical current density gives a very good agreement with experimental measurements over the whole explored B, T range. The model works for all investigated samples, which are different in size, Cu:nonCu ratios, filament diameters and layouts. These results suggest that pinning mechanisms in conventional NbTi strands should be revised, since Nb-Ti composition gradients and grain boundaries seems to play a not negligible role.

  18. Distortion-induced scattering due to vacancies in NbC/sub 0. 72/

    Energy Technology Data Exchange (ETDEWEB)

    Ohshima, K.; Harada, J.; Morinaga, M.; Georgopoulos, P.; Cohen, J.B.

    1988-03-01

    The diffuse X-ray (and electron) scattering from NbC/sub 0.72/, previously thought to be due to vacancy octahedra, is shown to be dominated by the scattering due to mean-square atomic displacements with wave vectors near the Brillouin-zone boundary. The atomic displacements are similar to those produced by an optical phonon. On the basis of the sign and amplitude of the displacement parameters a model for the environment around a carbon vacancy is proposed. The Nb nearest neighbors to a vacancy move away from it, whereas the C neighbors move toward it, and this appears to be due to an enhancement of the strength of the Nb-C bond arising from the presence of vacancies on the C sublattice. There is evidence that these vacancies tend to be correlated along 211 vectors.

  19. Computational studies of physical properties of Nb-Si based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ouyang, Lizhi [Middle Tennessee State Univ., Murfreesboro, TN (United States)

    2015-04-16

    The overall goal is to provide physical properties data supplementing experiments for thermodynamic modeling and other simulations such as phase filed simulation for microstructure and continuum simulations for mechanical properties. These predictive computational modeling and simulations may yield insights that can be used to guide materials design, processing, and manufacture. Ultimately, they may lead to usable Nb-Si based alloy which could play an important role in current plight towards greener energy. The main objectives of the proposed projects are: (1) developing a first principles method based supercell approach for calculating thermodynamic and mechanic properties of ordered crystals and disordered lattices including solid solution; (2) application of the supercell approach to Nb-Si base alloy to compute physical properties data that can be used for thermodynamic modeling and other simulations to guide the optimal design of Nb-Si based alloy.

  20. PLD prepared bioactive BaTiO3 films on TiNb implants.

    Science.gov (United States)

    Jelínek, Miroslav; Vaněk, Přemysl; Tolde, Zdeněk; Buixaderas, Elena; Kocourek, Tomáš; Studnička, Václav; Drahokoupil, Jan; Petzelt, Jan; Remsa, Jan; Tyunina, Marina

    2017-01-01

    BaTiO3 (BTO) layers were deposited by pulsed laser deposition (PLD) on TiNb, Pt/TiNb, Si (100), and fused silica substrates using various deposition conditions. Polycrystalline BTO with sizes of crystallites in the range from 90nm to 160nm was obtained at elevated substrate temperatures of (600°C-700°C). With increasing deposition temperature above 700°C the formation of unwanted rutile phase prevented the growth of perovskite ferroelectric BTO. Concurrently, with decreasing substrate temperature below 500°C, amorphous films were formed. Post-deposition annealing of the amorphous deposits allowed obtaining perovskite BTO. Using a very thin Pt interlayer between the BTO films and TiNb substrate enabled high-temperature growth of preferentially oriented BTO. Raman spectroscopy and electrical characterization indicated polar ferroelectric behaviour of the BTO films. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Development of an experimental 10 T Nb sub 3 Sn dipole magnet for the CERN LHC

    Energy Technology Data Exchange (ETDEWEB)

    ten Kate, H.H.J.; den Ouden, A.; ter Avest, D.; Wessel, S. (Univ. of Twente, Applied Superconductivity Centre, P.O. Box 217, 7500 AE Enschede (NL)); Dubbeldam, R. (HOLEC, Ridderkerk (NL)); van Emden, W.; Daum, C. (NIKHEF-H, Amsterdam (NL)); Bona, M.; Perin, R. (CERN, Geneva (CH))

    1991-03-01

    This paper reports on an experimental 1 meter long twin aperture dipole magnet developed using a high current density Nb{sub 3}Sn conductor in order to attain a magnetic field well beyond 10 T at 4.2 K. The emphasis in this Nb{sub 3}Sn project is on the highest possible field within the known LHC twin aperture configuration. A design target of 11.5 tesla was chosen, a value which can be achieved with the presently available Nb{sub 3}Sn. Though the basic properties of this experimental magnet are the same as those of the reference design, a few new solutions are implemented. The arrangement of the conductors in the magnet cross section has been optimized in a different way also leading to new dimensions of the conductors.

  2. Tests results of Nb$_{3}$Sn quadrupole magnets using a shell-based support structure

    CERN Document Server

    Caspi, S

    2009-01-01

    In support of the development of a 90 mm aperture Nb3Sn superconducting quadrupole for the US LHC Accelerator Research Program (LARP), test results of five quadrupole magnets are compared. All five assemblies used key and bladder technology to compress and support the coils within an iron yoke and an aluminium shell. The first three models (TQS01a, b, c) used Nb3Sn MJR conductor and segmented bronze poles. The last two models (TQS02a, b) used Nb3Sn RRP conductor, and segmented titanium alloy (TiAl6V4) poles, with no axial gaps during reaction. This presentation summarizes the magnets performance during assembly, cool-down and excitation and compares measurements with design expectations.

  3. Study of magnetic defects in Nb{sub 2}VSbO{sub 10}

    Energy Technology Data Exchange (ETDEWEB)

    Typek, J., E-mail: typjan@zut.edu.pl [Institute of Physics, West Pomeranian University of Technology, Szczecin, Al. Piastow 48, 70-311 Szczecin (Poland); Cyran, A.; Zolnierkiewicz, G.; Bobrowska, M. [Institute of Physics, West Pomeranian University of Technology, Szczecin, Al. Piastow 48, 70-311 Szczecin (Poland); Filipek, E.; Piz, M. [Department of Inorganic and Analytical Chemistry, West Pomeranian University of Technology, Szczecin, Al. Piastow 42, 71-065 Szczecin (Poland)

    2017-02-15

    Magnetic properties of Nb{sub 2}VSbO{sub 10}, the compound formed in V–Sb–Nb oxide system, were investigated by dc magnetisation measurements using an MPMS-7 SQUID magnetometer and EPR conventional X–band Bruker E 500 spectrometer. Although the nominal valences of the constituting metal ions indicated a diamagnetic material, Nb{sub 2}VSbO{sub 10} displayed rich and interesting magnetic behaviour due to the existence of numerous defects related to oxygen vacancies. Isothermal magnetisation has revealed the presence of three spin subsystems – two different paramagnetic systems and antiferromagnetic spin clusters. EPR spectra showed the presence of three components, involving isolated and interacting V{sup 4+} ions as well as antiferromagnetic spin clusters. All these magnetic defects are the result of valence changes of metal ions due to charge compensation in the neighborhood of oxygen vacancies, most probably located on grains boundaries.

  4. Cable Insulation Scheme to Improve Heat Transfer to Superfluid Helium in Nb-Ti Accelerator Magnets

    CERN Document Server

    La China, M

    2008-01-01

    In superconducting magnets operating at high heat loads as the ones for interaction region of particle colliders or for fast cycling synchrotrons, the limited heat transfer capability of state-of-the-art electrical insulation may constitute a heavy limitation to performance. In the LHC main magnets, Nb-Ti epoxy-free insulation, composed of polyimide tapes, has proved to be permeable to superfluid helium, however the heat flux is rather limited. After a review of the standard insulation scheme for Nb-Ti and of the associated heat transfer mechanisms, we show the existence of a large margin available to improve insulation permeability.We propose a possible way to profit of such a margin in order to increase significantly the maximum heat flux drainable from an all polyimide insulated Nb-Ti coil, as it is used in modern accelerator magnets.

  5. Luminescence processes in A3IILaNb3O12 (AII = Ba, Sr) layered perovskites

    Science.gov (United States)

    Chukova, Oksana; Gomenyuk, Olga; Nedilko, Sergiy; Polubinskii, Vitaliy; Scherbatsky, Vasyl; Sheludko, Vadim; Titov, Yuriy

    2014-08-01

    The A3IILaNb3O12 (AII = Sr, Ba) layered perovskites were synthesized by co-precipitation method. Luminescence properties of these compositions have been investigated for the first time. Emission spectra consist of wide bands with maxima located near 430 and 500 nm. Luminescence processes are discussed in connection with features of cation compositions, crystal structure and distortions of the NbO67- groups’ symmetry. Possible scheme of electron states and the lowest allowed electron transitions has been built for the niobate groups of Oh and C3v symmetry. In this scheme, the 430 and 500 nm emission bands were assigned to T1 → A1 and E → A1 electron transitions in the perfect and distorted NbO67- oxyanions, respectively.

  6. Metallographic investigation of fracture behavior in ITER-style Nb$_{3}$Sn superconducting strands

    CERN Document Server

    Jewell, M C; Larbalestier, D C; Nijhuis, A

    2009-01-01

    In this work we specify the extent to which fracture in two ITER-style Nb3Sn composite strands occurs in a collective or individual manner, under mechanical tension and bending from the TARSIS apparatus at the University of Twente. A bronze-route strand from European Advanced Superconductors (EAS), which has very uniform, well-spaced filaments, has a widely distributed (200 μm) fracture field and exhibits a composite of individual and collective cracks. An internal tin strand from Oxford Instruments – Superconducting Technology (OST) demonstrates much more localized, collective fracture behavior. The filaments in this strand are about four times larger (in area) than the filaments in the EAS strand, and also agglomerate significantly during heat treatment upon conversion of the Nb to Nb3Sn. These results demonstrate that the architecture of the strand can play a significant role in determining the mechanical toughness of the composite, and that strand design should incorporate mechanical considerations in ...

  7. Measurements of Dynamic Effects in FNAL 11 T $Nb_3Sn$ Dipole Models

    Energy Technology Data Exchange (ETDEWEB)

    Velev, G. [Fermilab; Strauss, T. [Fermilab; Barzi, E. [Fermilab; Chlachidze, G. [Fermilab; Di Marco, J. [Fermilab; Nobrega, F. [Fermilab; Novitshi, I. [Fermilab; Stoynev, S. [Fermilab; Turrioni, D. [Fermilab; Zlobin, A. V. [Fermilab

    2017-01-01

    Fermilab, in collaboration with CERN, has developed a twin-aperture 11 T $Nb_3Sn$ dipole suitable for the high-luminosity LHC upgrade. During 2012-2014, a 2-m long single-aperture dipole demonstrator and three 1-m long single-aperture dipole models were fabricated by FNAL and tested at its Vertical Magnet Test Facility. Collared coils from two of the 1-m long models were then used to assemble the first twin-aperture dipole demonstrator. This magnet had extensive testing in 2015-2016, including quench performance, quench protection, and field quality studies. This paper reports the results of measurements of persistent current effects in the single-aperture and twin-aperture 11 T $Nb_3Sn$ dipoles and compares them with similar measurements in previous NbTi magnets

  8. Corrosion Characteristics of Ti-29Nb-xHf Ternary Alloy for Biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Pak, Sun Young; Choi, Han Chul [Chosun Univ., Kwangju (Korea, Republic of)

    2015-12-15

    The Cp-Ti and Ti-6Al-4V alloys were widely used for dental materials due to their mechanical properties and good corrosion resistance. However, Cp-Ti was known as bio-inert materials, Ti-6Al-4V alloy has a problem such as high Young modulus, potential loss of the surrounding bone, and to the release of potentially toxic ions from the alloy. To overcome this problem, Ti alloys containing Nb and Hf elements have been used for biomaterials due to low toxicity and high corrosion resistance. Especially, alloying element of Nb was known as β phase stabilizer. The β phase alloy was widely used to replace currently used implant materials. The corrosion resistances of Ti-29Nb-xHf ternary alloys were dependent on Hf content in oral environment solution.

  9. Nb-doped TiO2 air-electrode for advanced Li-air batteries

    Directory of Open Access Journals (Sweden)

    Hee-Dae Lim

    2015-03-01

    Full Text Available As new substrate materials to replace a conventional carbon substrate, TiO2 and Nb-doped TiO2 air-electrodes for Li-air batteries were investigated. Through a simple two-step process, we successfully synthesized anatase Nb-doped TiO2 nanoparticles and demonstrated the potential applicability of TiO2-based materials for use in Li-air battery electrode. An air-electrode with Nb-doped TiO2 nanoparticles could deliver a higher discharge capacity than a bare TiO2 electrode due to the enhanced conductivity, which implies the importance of facile electron transport during the discharge process.

  10. submitter Optimization of Nb$_{3}$Sn Rutherford Cables Geometry for the High Luminosity LHC

    CERN Document Server

    Fleiter, Jerome; Bonasia, Angelo; Bordini, Bernardo; Richter, David

    2017-01-01

    The quadrupole and dipole magnets for the LHC High Luminosity (HL-LHC) upgrade will be based on Nb3Sn Rutherford cables that operate at 1.9 K and experience magnetic fields of up to about 12 T. An important step in the design of these magnets is the development of the high aspect ratio Nb3Sn cables to achieve the nominal field with sufficient margin. The strong plastic deformation of unreacted $Nb_3Sn$ strands during the Rutherford cabling process may induce non negligible $I_c$ and RRR degradation. In this paper, the cabling degradation is investigated as a function of the cable geometry for both PIT and RRP conductors. Based on this analysis, new baseline geometries for both 11 T and QXF magnets of HL-LHC are proposed.

  11. A survey on LPWA technology: LoRa and NB-IoT

    Directory of Open Access Journals (Sweden)

    Rashmi Sharan Sinha

    2017-03-01

    Full Text Available By 2020, more than twenty five billion devices would be connected through wireless communications. In accordance with the rapid growth of the internet of things (IoT market, low power wide area (LPWA technologies have become popular. In various LPWA technologies, narrowband (NB-IoT and long range (LoRa are two leading technologies. In this paper, we provide a comprehensive survey on NB-IoT and LoRa as efficient solutions connecting the devices. It is shown that unlicensed LoRa has advantages in terms of battery lifetime, capacity, and cost. Meanwhile, licensed NB-IoT offers benefits in terms of QoS, latency, reliability, and range.

  12. Mirror Protected Dirac Fermions on a Weyl Semimetal NbP Surface

    Science.gov (United States)

    Zheng, Hao; Chang, Guoqing; Huang, Shin-Ming; Guo, Cheng; Zhang, Xiao; Zhang, Songtian; Yin, Jiaxin; Xu, Su-Yang; Belopolski, Ilya; Alidoust, Nasser; Sanchez, Daniel S.; Bian, Guang; Chang, Tay-Rong; Neupert, Titus; Jeng, Horng-Tay; Jia, Shuang; Lin, Hsin; Hasan, M. Zahid

    2017-11-01

    The first Weyl semimetal was recently discovered in the NbP class of compounds. Although the topology of these novel materials has been identified, the surface properties are not yet fully understood. By means of scanning tunneling spectroscopy, we find that NbP's (001) surface hosts a pair of Dirac cones protected by mirror symmetry. Through our high-resolution spectroscopic measurements, we resolve the quantum interference patterns arising from these novel Dirac fermions and reveal their electronic structure, including the linear dispersions. Our data, in agreement with our theoretical calculations, uncover further interesting features of the Weyl semimetal NbP's already exotic surface. Moreover, we discuss the similarities and distinctions between the Dirac fermions here and those in topological crystalline insulators in terms of symmetry protection and topology.

  13. Characterization of La0.995Ca0.005NbO4/Ni anode functional layer by electrophoretic deposition in a La0.995Ca0.005NbO4 electrolyte based PCFC

    DEFF Research Database (Denmark)

    Bozza, Francesco; Schafbauer, W.; Meulenberg, W.A.

    2012-01-01

    The Electrophoretic Deposition (EPD) technique has been applied to the preparation of a porous La0.995Ca0.005NbO4/Ni composite anode layer, deposited on a porous pre-sintered La0.995Ca0.005NbO4/Ni support. Powders of La0.995Ca0.005NbO4 and NiO were suspended in a solution of acetylacetone, iodine...... and water. Selectivity in the composition of the deposited layer was analyzed as a function of the suspension compositions and deposition conditions. A quasi-symmetrical cell was produced by depositing La0.995Ca0.005NbO4 electrolyte layer on the anode layer by EPD, and by applying a porous La0.995Ca0.005Nb...

  14. Universal randomness

    Energy Technology Data Exchange (ETDEWEB)

    Dotsenko, Viktor S [Landau Institute for Theoretical Physics, Russian Academy of Sciences, Moscow (Russian Federation)

    2011-03-31

    In the last two decades, it has been established that a single universal probability distribution function, known as the Tracy-Widom (TW) distribution, in many cases provides a macroscopic-level description of the statistical properties of microscopically different systems, including both purely mathematical ones, such as increasing subsequences in random permutations, and quite physical ones, such as directed polymers in random media or polynuclear crystal growth. In the first part of this review, we use a number of models to examine this phenomenon at a simple qualitative level and then consider the exact solution for one-dimensional directed polymers in a random environment, showing that free energy fluctuations in such a system are described by the universal TW distribution. The second part provides detailed appendix material containing the necessary mathematical background for the first part. (reviews of topical problems)

  15. High-RRR thin-films of NB produced using energetic condensation from a coaxial, rotating vacuum ARC plasma (CEDTM)

    Science.gov (United States)

    Valderrama, Enrique Francisco; James, Colt; Krishnan, Mahadevan; Zhao, Xin; Phillips, Larry; Reece, Charles; Seo, Kang

    2012-06-01

    We have recently demonstrated unprecedentedly high values of RRR (up to 542) in thin-films of pure Nb deposited on a-plane sapphire and MgO crystal substrates. The Nb films were grown using a vacuum arc discharge struck between a reactor grade Nb cathode rod (RRR 30) and a coaxial, semi-transparent Mo mesh anode, with a heated substrate placed just outside it. The substrates were pre-heated for several hours prior to deposition at different temperatures. Low pre-heat temperatures (600°C) is correlated with better epitaxial crystal structure in both a-sapphire and MgO substrate grown films. However, the SIMS data reveal that the most important requirement for high-RRR Nb films on either substrate is the reduction of impurities in the film, especially hydrogen. The hydrogen content in the MgO grown films is 1000 times lower than in bulk Nb tested as a reference from SRF cavity grade Nb. This result has potential implications for SRF accelerators. Coating bulk Nb cavities with an MgO layer followed by our CEDTM deposited Nb films, might create superior SRF cavities that would avoid Q-slope and operate at higher peak fields. This research was supported by Department of Energy grants DE-SC0004994 and DE-FG02-08ER85162.

  16. Facile preparation of C, N co-modified Nb2O5 nanoneedles with enhanced visible light photocatalytic activity

    KAUST Repository

    Xue, Jiao

    2016-09-28

    C, N co-modified niobium pentoxide (Nb2O5) nanoneedles have been successfully synthesized via a facile hydrothermal method with Niobium Chloride (NbCl5) as a precursor and triethylamine as both the carbon and nitrogen source. The formation process of Nb2O5 nanoneedles has been presented in detail by investigating the effect of the crystallization temperature, the amount of triethylamine and the calcination temperature. The as-prepared Nb2O5 nanoneedles exhibit more efficient photocatalytic activity than commercial Degussa P25 and commercial Nb2O5 towards photodegradation of Rhodamine B (RhB) at a concentration of 10 mg L−1 under visible light. Special chemical species, such as carbonate species and NOX species, that exist on the surface of the as-prepared catalyst could extend the absorption into the visible region and thus enhance the photocatalytic activity of the Nb2O5 nanoneedles. At the same time, the obtained Nb2O5 nanoneedles exhibit excellent stability even after three successive cycles. A possible photodegradation mechanism was proposed and the corresponding photodecomposition process of RhB over the Nb2O5 nanoneedles was elucidated by a reactive species trapping experiment, suggesting that h+ and O2˙− play a major role in the photodegradation of RhB in aqueous solution.

  17. Design Concept and Parameters of a 15 T $Nb_{3}Sn$ Dipole Demonstrator for a 100 TEV Hadron Collider

    Energy Technology Data Exchange (ETDEWEB)

    Zlobin, A. V. [Fermilab; Andreev, N. [Fermilab; Barzi, E. [Fermilab; Kashikhin, V. V. [Fermilab; Novitski, I. [Fermilab

    2015-06-01

    FNAL has started the development of a 15 T $Nb_{3}Sn$ dipole demonstrator for a 100 TeV scale hadron collider. This paper describes the design concept and parameters of the 15 T $Nb_{3}Sn$ dipole demonstrator. The dipole magnetic, mechanical and quench protection concept and parameters are presented and discussed.

  18. Fabrication and characterization of Ti-Nb-HA alloy by mechanical alloying and spark plasma sintering for hard tissue replacements

    Science.gov (United States)

    Singh, Ramandeep; Pal Singh, Bhupinder; Gupta, Anjali; Prakash, Chander

    2017-08-01

    In the present research work, a β-type Ti-35Nb-10HA alloy was successfully fabricated by mechanical alloying of titanium (Ti), niobium (Nb), and hydroxyaptite (HA) powders followed by consolidation using Spark Plasma Sintering technique. The effect of HA on the microstructure and mechanical properties were studied. The microstructure, surface topography, and element composition of the Ti-Nb-HA alloy was investigated using optical microscope, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The micro-hardness of the specimens was measured on a Vickers hardness tester. The microstructure examination of the compact revealed that the alloy distinctly shows the primary grain boundaries along with secondary grain boundary. It was observed that complex reactions between HA and alloy elements occurred during the sintering process of Ti-35Nb-10HA alloy and biocompatible phases [Ca3(PO4)2, CaTiO3, Nb8P5, CaO, TiP, Nb4O5, and TiO2] were generated in the compact, which is beneficial to form apatite and improved the bioactivity of the alloy for osseiointegartion. The fabricated Ti-35Nb-15HA alloy exhibits maximum micro-hardness (∼786 HV), which is very high value as compared to the alloys reported in literature. Based on these above observations, it is expected that the as-fabricated Ti-35Nb-10HA alloy is suggested for dental and orthopaedic applications.

  19. Nanoscale analysis of structural and chemical changes in aged hybrid Pt/NbOx/C fuel cell catalysts

    Science.gov (United States)

    Chinchilla, Lidia; Rossouw, David; Trefz, Tyler; Susac, Darija; Kremliakova, Natalia; Botton, Gianluigi A.

    2017-07-01

    We characterize the structural and chemical changes that take place in an electrochemically tested proton-exchange fuel cell cathode material composed of platinum nanoparticles on a niobium oxide-carbon black hybrid support. Two hybrid catalysts with different niobium oxide content (5 wt% and 12 wt%) are compared at the beginning and end of potential cycling. We observe an overall increase in the particle size of the hybrid catalysts after potential cycling, mediated by Ostwald ripening process. The general nanostructure of the catalysts was composed of small Pt-rich particles that were linked to niobium oxide particles. Nanoscale and microscale spectroscopy of the pristine materials reveals several co-existing oxidized forms of niobium (5+, 4+, 2+) in the systems; the most predominant being Nb(V). The study of the energy loss near-edge structure of the Niobium L2,3 edge of catalysts after being subjected to accelerated stress test (AST) potential cycles provides clues on the evolution of niobium oxides (NbOx), in which the relative distribution of Nb(V) decreases, while the number of Nb particles in lower oxidation states slightly increases. Furthermore, energy-dispersive spectroscopy reveals that the content of Nb decreased after cycling, implying that the loss of NbOx eventually altered the fraction of linked Pt-NbOx sites. The observed nanoscale catalyst changes and the presence of the NbOx may have important implications for developing an alternative design for improved hybrid catalyst materials.

  20. Steps in growth of Nb-doped layered titanates with very high surface area suitable for water purification

    Energy Technology Data Exchange (ETDEWEB)

    Milanović, Marija, E-mail: majam@uns.ac.rs [Department of Materials Engineering, Faculty of Technology Novi Sad, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad (Serbia); Nikolić, Ljubica M., E-mail: ljunik@uns.ac.rs [Department of Materials Engineering, Faculty of Technology Novi Sad, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad (Serbia); Stijepović, Ivan, E-mail: ivan.stijepovic@gmail.com [Department of Materials Engineering, Faculty of Technology Novi Sad, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad (Serbia); Kontos, Athanassios G., E-mail: akontos@chem.demokritos.gr [Institute for Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, NCSR “Demokritos”, Agia Paraskevi, 15310 Athens (Greece); Giannakopoulos, Konstantinos P., E-mail: kyann@imel.demokritos.gr [Institute for Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, NCSR “Demokritos”, Agia Paraskevi, 15310 Athens (Greece)

    2014-12-15

    Nb-doped layered titanates, as highly efficient adsorbents, have been synthesized by hydrothermal reaction for variable duration and at 150 °C in a highly alkaline solution with NbCl{sub 5} as the Nb source. The results have shown the formation of nanosheets already after 1 h of hydrothermal processing, but morphology and phase composition change as the reaction proceeds. The prepared layered titanates have been structurally investigated via scanning and transmission electron microscopy, X-ray diffraction, as well as Raman and Fourier transform infrared spectroscopies. The steps of layered titanate growth have been followed and an intermediate layered anatase phase is identified. Thus optimized growth of mesoporous titanate materials with 10% Nb atomic content present very high specific surface area of 345.3 m{sup 2} g{sup −1}, and perform as very efficient adsorbents for wastewater treatment applications. - Highlights: • Nb-doped layered titanates have been prepared by a hydrothermal procedure. • Introduction of Nb to precursor lowers the rate of layered titanate formation. • Steps in growth of Nb-doped layered titanates are considered. • Nb-doped layered titanates show high/fast MB adsorption from concentrated solution.