WorldWideScience

Sample records for magnesium diboride mgb2

  1. Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

    Science.gov (United States)

    Tan, Teng

    The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates

  2. Development of magnesium diboride (MgB 2) wires and magnets using in situ strand fabrication method

    Science.gov (United States)

    Tomsic, Michael; Rindfleisch, Matthew; Yue, Jinji; McFadden, Kevin; Doll, David; Phillips, John; Sumption, Mike D.; Bhatia, Mohit; Bohnenstiehl, Scot; Collings, E. W.

    2007-06-01

    Since 2001 when magnesium diboride (MgB 2) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in magnets and coils. Work has started on demonstrating MgB 2 wire in superconducting devices now that the wire is available commercially. MgB 2 superconductors and coils have the potential to be integrated in a variety of commercial applications such as magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, energy storage, and high energy physics applications. This paper discusses the progress on MgB 2 conductor and coil development in the last several years at Hyper Tech Research, Inc.

  3. Development of magnesium diboride (MgB2) wires and magnets using in situ strand fabrication method

    International Nuclear Information System (INIS)

    Tomsic, Michael; Rindfleisch, Matthew; Yue, Jinji; McFadden, Kevin; Doll, David; Phillips, John; Sumption, Mike D.; Bhatia, Mohit; Bohnenstiehl, Scot; Collings, E.W.

    2007-01-01

    Since 2001 when magnesium diboride (MgB 2 ) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in magnets and coils. Work has started on demonstrating MgB 2 wire in superconducting devices now that the wire is available commercially. MgB 2 superconductors and coils have the potential to be integrated in a variety of commercial applications such as magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, energy storage, and high energy physics applications. This paper discusses the progress on MgB 2 conductor and coil development in the last several years at Hyper Tech Research, Inc

  4. Magnesium Diboride Current Leads

    Science.gov (United States)

    Panek, John

    2010-01-01

    A recently discovered superconductor, magnesium diboride (MgB2), can be used to fabricate conducting leads used in cryogenic applications. Dis covered to be superconducting in 2001, MgB2 has the advantage of remaining superconducting at higher temperatures than the previously used material, NbTi. The purpose of these leads is to provide 2 A of electricity to motors located in a 1.3 K environment. The providing environment is a relatively warm 17 K. Requirements for these leads are to survive temperature fluctuations in the 5 K and 11 K heat sinks, and not conduct excessive heat into the 1.3 K environment. Test data showed that each lead in the assembly could conduct 5 A at 4 K, which, when scaled to 17 K, still provided more than the required 2 A. The lead assembly consists of 12 steelclad MgB2 wires, a tensioned Kevlar support, a thermal heat sink interface at 4 K, and base plates. The wires are soldered to heavy copper leads at the 17 K end, and to thin copper-clad NbTi leads at the 1.3 K end. The leads were designed, fabricated, and tested at the Forschungszentrum Karlsruhe - Institut foer Technische Physik before inclusion in Goddard's XRS (X-Ray Spectrometer) instrument onboard the Astro-E2 spacecraft. A key factor is that MgB2 remains superconducting up to 30 K, which means that it does not introduce joule heating as a resistive wire would. Because the required temperature ranges are 1.3-17 K, this provides a large margin of safety. Previous designs lost superconductivity at around 8 K. The disadvantage to MgB2 is that it is a brittle ceramic, and making thin wires from it is challenging. The solution was to encase the leads in thin steel tubes for strength. Previous designs were so brittle as to risk instrument survival. MgB2 leads can be used in any cryogenic application where small currents need to be conducted at below 30 K. Because previous designs would superconduct only at up to 8 K, this new design would be ideal for the 8-30 K range.

  5. Synthesis of Bulk Superconducting Magnesium Diboride

    Directory of Open Access Journals (Sweden)

    Margie Olbinado

    2002-06-01

    Full Text Available Bulk polycrystalline superconducting magnesium diboride, MgB2, samples were successfully prepared via a one-step sintering program at 750°C, in pre Argon with a pressure of 1atm. Both electrical resistivity and magnetic susceptibility measurements confirmed the superconductivity of the material at 39K, with a transition width of 5K. The polycrystalline nature, granular morphology, and composition of the sintered bulk material were confirmed using X-ray diffractometry (XRD, scanning electron microscopy (SEM, and energy dispersive X-ray analysis (EDX.

  6. Interaction of magnesium diboride with HΛ2O, HΛ2OΛ2 and with acids

    International Nuclear Information System (INIS)

    Lyashenko, V.I.; Kosolapova, T.Ya.; Serebryakova, T.I.

    1985-01-01

    Chemical stability of magnesium diboride in some agressive media is investigated. It is shown that magnesium diboride possesses high chemical activity in relation to acids (nitric, phosphoric, hydrochloric, sulphuric). The fluohydric acid and hydrogen peroxide completely decompose magnesium boride. The kinetics of MgB 2 decomposition in aqueous solutions of acids (hydrochloric, sulphuric, nitric) and in water is studied. Activation energies and solubility rate constants are calculated

  7. Magnesium diboride on inner wall of copper tube: A test case for superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Wenura K. Withanage

    2017-10-01

    Full Text Available Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB_{2} coating on the inner wall of a copper cavity will allow operation at higher temperatures (20–25 K than Nb cavities due to the high transition temperature of MgB_{2} (39 K and the high thermal conductivity of Cu. In this paper, we present results of MgB_{2} coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB_{2} layer on the inner wall of the Cu tubes with T_{c} as high as 37 K.

  8. Magnesium diboride on inner wall of copper tube: A test case for superconducting radio frequency cavities

    Science.gov (United States)

    Withanage, Wenura K.; Lee, N. H.; Penmatsa, Sashank V.; Wolak, M. A.; Nassiri, A.; Xi, X. X.

    2017-10-01

    Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB2 coating on the inner wall of a copper cavity will allow operation at higher temperatures (20-25 K) than Nb cavities due to the high transition temperature of MgB2 (39 K) and the high thermal conductivity of Cu. In this paper, we present results of MgB2 coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB2 layer on the inner wall of the Cu tubes with Tc as high as 37 K.

  9. The road to magnesium diboride thin films, Josephson junctions and SQUIDs

    International Nuclear Information System (INIS)

    Brinkman, Alexander; Mijatovic, Dragana; Hilgenkamp, Hans; Rijnders, Guus; Oomen, Ingrid; Veldhuis, Dick; Roesthuis, Frank; Rogalla, Horst; Blank, Dave H A

    2003-01-01

    The remarkably high critical temperature at which magnesium diboride (MgB 2 ) undergoes transition to the superconducting state, T c ∼ 40 K, has aroused great interest and has encouraged many groups to explore the properties and application potential of this novel superconductor. For many electronic applications and further basic studies, the availability of superconducting thin films is of great importance. Several groups have succeeded in fabricating superconducting MgB 2 films. An overview of the deposition techniques for MgB 2 thin film growth will be given, with a special focus on the in situ two-step process. Although, meanwhile, many problems to obtain suitable films have been solved, such as oxygen impurities and magnesium volatility, the question of how single-phase epitaxial films can be grown still remains. The possibility of growing single-crystalline epitaxial films will be discussed from the deposition conditions' point of view as well as substrate choice. Necessary conditions are discussed and possible routes are reviewed. The applicability of MgB 2 in superconducting electronic devices depends on the possibility of making well-controlled, i.e., reproducible and stable, Josephson junctions. The first attempts to make MgB 2 -MgO-MgB 2 ramp-type junctions and SQUIDs from MgB 2 nanobridges are discussed

  10. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

    2014-01-01

    We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.

  11. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    M. A. Wolak

    2014-01-01

    Full Text Available We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD. To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.

  12. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    Energy Technology Data Exchange (ETDEWEB)

    Marzik, James, V.

    2005-10-13

    Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated with liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing

  13. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    International Nuclear Information System (INIS)

    Marzik, James V.

    2005-01-01

    Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated with liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing

  14. Magnesium diboride: one year on

    International Nuclear Information System (INIS)

    Canfield, Paul; Bud'ko, Sergey L.

    2002-01-01

    Last January physicists discovered that an innocuous compound that had been sitting on the shelf for decades was, in fact, a record-breaking intermetallic superconductor. At the end of 2000 superconductivity in metal alloys and compounds appeared to remain trapped by a glass ceiling. Over the previous 10 years the temperature at which certain oxide-based compounds - such as bismuth strontium calcium copper oxide and mercury barium calcium copper oxide - lost their resistance to electric current had soared to well over 100 K. Meanwhile, the transition temperature, Tc, for carbon-based materials, including alkali-doped carbon-60 compounds, had risen close to the boiling point of liquid nitrogen (77 K). During the same period, however, the superconducting transition temperature of intermetallic compounds (materials made solely of metals and metal-like elements) remained close to 20 K - as it had been since the mid-1960s. By February 2001 everything had totally changed. It was as if a firecracker had gone off in the tidy little ant hill of superconductivity research. For the first few months of 2001, groups all over the world raced to understand the properties of a new intermetallic superconductor. The substance that everyone was scrambling to buy or make, the substance that was causing this grand commotion, was magnesium diboride (Mg B 2 ). This seemingly innocuous binary compound, which had been present in many labs for over half a century, had been discovered to superconduct just below 40 K. Even though we already know an amazing amount about Mg B 2 , our knowledge of superconductivity in this compound is only one year old. There is therefore the very real potential to improve its critical properties. In a similar vein, it is almost certain that our understanding of this extreme example of intermetallic superconductivity will greatly improve over the next few years and may even reveal other extreme superconductors. (U.K.)

  15. Hybrid Physical Chemical Vapor Deposition of Superconducting Magnesium Diboride Coatings for Large Scale Radio Frequency Cavities

    Science.gov (United States)

    Lee, Namhoon; Withanage, Wenura; Tan, Teng; Wolak, Matthaeus; Xi, Xiaoxing

    2016-03-01

    Magnesium diboride (MgB2) is considered to be a great candidate for next generation superconducting radio frequency (SRF) cavities due to its higher critical temperature Tc (40 K) and increased thermodynamic critical field Hc compared to other conventional superconductors. These properties significantly reduce the BCS surface resistance (RsBCS)and residual resistance (Rres) according to theoretical studies and suggest the possibility of an enhanced accelerating field (Eacc) . We have investigated the possibility of coating the inner surface of a 3 GHz SRF cavity with MgB2 by using a hybrid physical-vapor deposition (HPCVD) system which was modified for this purpose. To simulate a real 3 GHz SRF cavity, a stainless steel mock cavity has been employed for the study. The film quality was characterized on small substrates that were placed at selected locations within the cavity. MgB2 films on stainless steel foils, niobium pieces and SiC substrates showed transition temperatures of above 36 K. Dielectric resonance measurements resulted in promising Q values as obtained for the MgB2 films grown on the various substrates. By employing the HPCVD technique, a uniform film was achieved across the cavity interior, demonstrating the feasibility of HPCVD for MgB2 coatings for SRF cavities.

  16. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-02-16

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  17. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-04-01

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20-25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical-chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg-Cu alloy layer with occasional intrusion of Mg-Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  18. Distinction between magnesium diboride and tetraboride by kelvin probe force microscopy

    International Nuclear Information System (INIS)

    Kim, Du-Na; Caron, Arnaud; Park, Hai Woong

    2016-01-01

    We analyze mixtures of magnesium diboride and tetraboride synthesized with magnesium powders of different shapes. To distinguish between magnesium diboride and tetraboride we use the contrast of kelvin probe force microscopy. The microstructural morphology strongly depends on the shape of the magnesium powders used in the reaction between magnesium and magnesium tetraboride to form magnesium diboride. With spherical magnesium powder an equiaxed microstructure of magnesium diboride is formed with residual magnesium tetraboride at the grain boundaries. With plate-like magnesium powders elongated magnesium diboride grains are formed. In this case, residual magnesium tetraboride is found to agglomerate.

  19. Al-doped MgB_2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan

    2016-01-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB_2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB_2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB_2. Above a certain level of Al doping, enhanced conductive properties of MgB_2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  20. Electronic structure of magnesium diboride and related compounds

    International Nuclear Information System (INIS)

    Paduani, C.

    2003-01-01

    The electronic structure of AlB 2 -type diborides and related compounds has been investigated in first-principles calculations with the molecular cluster discrete variational method. For MgB 2 was studied the effect of the lattice relaxation on the total density of states at the Fermi energy (N(ε F )). The results indicated that a contraction of about 2% in the lattice spacings a and c can lead to a slight increase of N(ε F ) for boron. In the MB 2 diborides, M=Al, Ti, V, Cr, Zr, Nb, Mo and Ta, the largest contributions to N(ε F ) is observed for Cr, Mo and Nb. TiB 2 possess the highest chemical stability in the series. The electronic specific heat coefficient γ also is calculated for the diborides. The method is employed to obtain the partial B2p contribution to the total DOS at the Fermi level with the introduction of a monolayer of solute atoms as a substitution for Mg atoms of Na, Al, Ca, Ti, V, Cr, Zr, Nb, Mo and Ta in layered superstructures.. /M/B 2 /Mg/B 2 /.. A stronger covalent bonding between boron atoms is identified in these cases. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Magnesium diboride coated bulk niobium: a new approach to higher acceleration gradient

    Science.gov (United States)

    Civale, Leonardo; Tan, Teng; Wolak, M.; Xi, Xiaoxing; Tajima, Tsuyoshi

    Bulk niobium Superconducting Radio-Frequency cavities are a leading accelerator technology. Their performance is limited by the cavity loss and maximum acceleration gradient, which are negatively affected by vortex penetration into the superconductor when the peak magnetic field at the cavity wall surface exceeds the vortex penetration field (Hvp). It has been proposed that coating the inner wall of an SRF cavity with superconducting thin films increases Hvp. In this work, we utilized Nb ellipsoids to simulate an inverse SRF cavity and investigate the effect of coating it with magnesium diboride layer on the vortex penetration field. A significant enhancement of Hvp was observed. At 2.8 K, Hvp increased from 2100 Oe for an uncoated Nb ellipsoid to 2700 Oe for a Nb ellipsoid coated with 200 nm thick MgB2 thin film. This finding creates a new route towards achieving higher acceleration gradient in SRF cavity accelerator beyond the theoretical limit of bulk Nb.

  2. Distinction between magnesium diboride and tetraboride by kelvin probe force microscopy; Unterscheidung von Magnesiumdiborid und Magnesiumtetraborid durch Kelvinsondenkraftmikroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Du-Na; Caron, Arnaud; Park, Hai Woong [KoreaTech - Korea Univ. of Technology and Education, Chungnam (Korea, Republic of). School of Energy, Materials and Chemical Engineering

    2016-08-15

    We analyze mixtures of magnesium diboride and tetraboride synthesized with magnesium powders of different shapes. To distinguish between magnesium diboride and tetraboride we use the contrast of kelvin probe force microscopy. The microstructural morphology strongly depends on the shape of the magnesium powders used in the reaction between magnesium and magnesium tetraboride to form magnesium diboride. With spherical magnesium powder an equiaxed microstructure of magnesium diboride is formed with residual magnesium tetraboride at the grain boundaries. With plate-like magnesium powders elongated magnesium diboride grains are formed. In this case, residual magnesium tetraboride is found to agglomerate.

  3. Two-band superconductor magnesium diboride

    International Nuclear Information System (INIS)

    Xi, X X

    2008-01-01

    This review focuses on the most important features of the 40 K superconductor MgB 2 -the weakly interacting multiple bands (the σ and π bands) and the distinct multiple superconducting energy gaps (the σ and π gaps). Even though the pairing mechanism of superconductor MgB 2 is the conventional electron-phonon coupling, the prominent influence of the two bands and two gaps on its properties sets it apart from other superconductors. It leads to markedly different behaviors in upper critical field, vortex structure, magnetoresistance and many other superconducting and normal-state properties in MgB 2 from single-band superconductors. Further, it gives rise to new physics that does not exist in single-band superconductors, such as the internal Josephson effects between the two order parameters. These unique phenomena depend sensitively on scattering inside and between the two bands, and the intraband and interband scattering can be modified by chemical substitution and irradiation. MgB 2 has brought unprecedented attention to two-band superconductivity, which has been found to exist in other old and new superconductors. The legacy of MgB 2 will be long lasting because of this, as well as the lessons it teaches in terms of the search for new phonon-mediated higher T c superconductors

  4. Towards a Cryogen-Free MgB2-Based Superconducting Radio Frequency Accelerating Cavities

    Science.gov (United States)

    Nassiri, Alireza

    Studies on the application of Magnesium diboride (MgB2) superconducting films have shown promise for use with the radio-frequency (SRF) accelerating cavities. MgB2\\ coating is a potential candidate to replace bulk niobium (Nb) SRF cavities. The ultimate goal of our research is to demonstrate MgB2 coating on copper cavities to allow operation at about 20 K or so as a result of the high transition temperature (Tc) of MgB2 and taking advantage of the excellent thermal conductivity of copper. Here, we will report on our recent experimental results of applying hybrid physical-chemical vapor deposition (HPCVD) to grow MgB2 films on 2-inch diameter copper discs as well as on a 2.8 GHz resonator cavity *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.

  5. MgB2 superconducting wires basics and applications

    CERN Document Server

    2016-01-01

    The compendium gives a complete overview of the properties of MgB2 (Magnesium Diboride), a superconducting compound with a transition temperature of Tc = 39K, from the fundamental properties to the fabrication of multifilamentary wires and to the presentation of various applications. Written by eminent researchers in the field, this indispensable volume not only discusses superconducting properties of MgB2 compounds, but also describes known preparation methods of thin films and of bulk samples obtained under high pressure methods. A unique selling point of the book is the detailed coverage of various applications based on MgB2, starting with MRI magnets and high current cables, cooled by Helium (He) vapor. High current cables cooled by liquid hydrogen are also highlighted as an interesting alternative due to the shrinking He reserves on earth. Other pertinent subjects comprise permanent magnets, ultrafine wires for space applications and wind generator projects.

  6. Magnesium Diboride Superconducting Coils for Electric Propulsion Systems for Large Aircraft, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The recent development of magnesium diboride superconducting wires makes possible the potential to have much lighter weight superconducting coils for heavy aircraft...

  7. Low-temperature synthesis of superconducting nanocrystalline MgB2

    International Nuclear Information System (INIS)

    Lu, J.; Xiao, Z.; Lin, Q.; Claus, H.; Fang, Z.Z.

    2010-01-01

    Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

  8. Active Protection of an MgB2 Test Coil

    Science.gov (United States)

    Park, Dong Keun; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu

    2011-01-01

    This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with ~500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a “hot spot” of a length ~10 cm, induced by a “quench heater,” a “protection heater” (PH) of ~600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil’s entire initial stored energy and still keeps the peak temperature within the winding below ~260 K. PMID:22081754

  9. Fabrication and radio frequency test of large-area MgB2 films on niobium substrates

    Science.gov (United States)

    Ni, Zhimao; Guo, Xin; Welander, Paul B.; Yang, Can; Franzi, Matthew; Tantawi, Sami; Feng, Qingrong; Liu, Kexin

    2017-04-01

    Magnesium diboride (MgB2) is a promising candidate material for superconducting radio frequency (RF) cavities because of its higher transition temperature and critical field compared with niobium. To meet the demand of RF test devices, the fabrication of large-area MgB2 films on metal substrates is needed. In this work, high quality MgB2 films with 50 mm diameter were fabricated on niobium by using an improved HPCVD system at Peking University, and RF tests were carried out at SLAC National Accelerator Laboratory. The transition temperature is approximately 39.6 K and the RF surface resistance is about 120 μΩ at 4 K and 11.4 GHz. The fabrication processes, surface morphology, DC superconducting properties and RF tests of these large-area MgB2 films are presented.

  10. Molecular-Beam Epitaxially Grown MgB2 Thin Films and Superconducting Tunnel Junctions

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Laloë

    2011-01-01

    Full Text Available Since the discovery of its superconducting properties in 2001, magnesium diboride has generated terrific scientific and engineering research interest around the world. With a of 39 K and two superconducting gaps, MgB2 has great promise from the fundamental point of view, as well as immediate applications. Several techniques for thin film deposition and heterojunction formation have been established, each with its own advantages and drawbacks. Here, we will present a brief overview of research based on MgB2 thin films grown by molecular beam epitaxy coevaporation of Mg and B. The films are smooth and highly crystalline, and the technique allows for virtually any heterostructure to be formed, including all-MgB2 tunnel junctions. Such devices have been characterized, with both quasiparticle and Josephson tunneling reported. MgB2 remains a material of great potential for a multitude of further characterization and exploration research projects and applications.

  11. Effect of Platinum Group Metal Doping in Magnesium Diboride Wires

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Alexiou, Aikaterini; Namazkar, Shahla

    2016-01-01

    The effect of some platinum group metals(PGM = Rh, Pd, and Pt) on the microstructure and critical current density of Cu/Nb-sheathed MgB2 wires has been studied using Mg1-x PGMxB2 powders with low doping levels. It was found that Pt and Pd do not enter the MgB2 lattice and have only limited influe...

  12. Formation of polycrystalline MgB2 synthesized by powder in sealed tube method with different initial boron phase

    Science.gov (United States)

    Yudanto, Sigit Dwi; Imaduddin, Agung; Kurniawan, Budhy; Manaf, Azwar

    2018-04-01

    Magnesium diboride, MgB2 is a new high critical temperature superconductor that discovered in the beginning of the 21st century. The MgB2 has a simple crystal structure and a high critical temperature, which can be manufactured in several forms like thin films, tapes, wires including bulk in the large scale. For that reason, the MgB2 has good prospects for various applications in the field of electronic devices. In the current work, we have explored the synthesis of MgB2 polycrystalline using powder in a sealed tube method. Different initial boron phase for the synthesized of MgB2 polycrystalline were used. These were, in addition to magnesium powders, crystalline boron, amorphous boron and combination both of them were respectively fitted in the synthesis. The raw materials were mixed in a stoichiometric ratio of Mg: B=1:2, ground using agate mortar, packed into stainless steel SS304. The pack was then sintered at temperature of 800°C for 2 hours in air atmosphere. Phase formation of MgB2 polycrystalline in difference of initial boron phase was characterized using XRD and SEM. Referring to the diffraction pattern and microstructure observation, MgB2 polycrystalline was formed, and the formation was effective when using the crystalline Mg and fully amorphous B as the raw materials. The critical temperature of the specimen was evaluated by the cryogenic magnet. The transition temperature of the MgB2 specimen synthesized using crystalline magnesium and full amorphous boron is 42.678 K (ΔTc = 0.877 K).

  13. Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique

    Science.gov (United States)

    Portesi, C.; Borini, S.; Amato, G.; Monticone, E.

    2006-03-01

    In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.

  14. The inclusions of Mg-B (MgB12?) as potential pinning centres in high-pressure-high-temperature-synthesized or sintered magnesium diboride

    International Nuclear Information System (INIS)

    Prikhna, T A; Gawalek, W; Savchuk, Ya M; Habisreuther, T; Wendt, M; Sergienko, N V; Moshchil, V E; Nagorny, P; Schmidt, Ch; Dellith, J; Dittrich, U; Litzkendorf, D; Melnikov, V S; Sverdun, V B

    2007-01-01

    A systematic study of the structure and superconductive characteristics of high-pressure-high-temperature (2 GPa, 700-1000 deg. C )-synthesized and sintered MgB 2 without additions from different initial powders was performed. Among various secondary phases Mg-B inclusions with a stoichiometry close to MgB 12 were identified. With an increasing amount of these inclusions the critical current density increased. So these inclusions can be feasible pinning centres in MgB 2 . The highest j c values in zero field were 1300 kA cm -2 at 10 K, 780 kA cm -2 at 20 K and 62 kA cm -2 at 35 K and in 1 T field were 1200 kA cm -2 at 10 K, 515 kA cm -2 at 20 K and 0.1 kA cm -2 at 35 K for high-pressure-synthesized magnesium diboride and the field of irreversibility at 20 K reached 8 T. The average grain sizes calculated from x-ray examinations in materials having high j c were 15-37 nm

  15. Study of transport and micro-structural properties of magnesium di-boride strand under react and bend mode and bend and react mode

    International Nuclear Information System (INIS)

    Kundu, Ananya; Das, Subrat Kumar; Bano, Anees; Pradhan, Subrata

    2015-01-01

    I-V characterization of commercial multi-filamentary Magnesium Di-Boride (MgB 2 ) wire of diameter 0.83 mm were studied in cryocooler based self-field characterization system under both react and bent mode and bent and react mode for a range of temperature 6 K - 25 K. This study is of practical technical relevance where the heat treatment of the superconducting wire makes the sample less flexible for winding in magnet and in other applications. There are limited reported data, available on degradation of MgB 2 wire with bending induced strain in react and wind and wind and react method. In the present work the bending diameter were varied from 80 mm to 20 mm in the interval of 10 mm change of bending diameter and for each case critical current (Ic) of the strand is measured for the above range of temperature. An ETP copper made customized sample holder for mounting the MgB 2 strand was fabricated and is thermally anchored to the cooling stage of the cryocooler. It is seen from the experimental data that in react and bent mode the critical current degrades from 105 A to 87 A corresponding to bending diameter of 80 mm and 20 mm respectively. The corresponding bending strain was analytically estimated and compared with the simulation result. It is also observed that in react and bent mode, the degradation of the transport property of the strand is less as compared to react and bent mode. For bent and react mode in the same sample, the critical current (Ic) was measured to be ∼145 A at 15 K for bending diameter of 20 mm. Apart from studying the bending induced strain on MgB 2 strand, the tensile test of the strand at RT was carried out. The electrical characterizations of the samples were accompanied by the microstructure analyses of the bent strand to examine the bending induced degradation in the grain structure of the strand. All these experimental findings are expected to be used as input to fabricate prototype MgB 2 based magnet. (author)

  16. Superconducting properties of MgB2 particle impregnated with Mg-based alloys

    International Nuclear Information System (INIS)

    Shimizu, Yusuke; Matsuda, Kenji; Mizutani, Manabu; Nishimura, Katsuhiko; Kawabata, Tokimasa; Ikeno, Susumu; Hishinuma, Yoshimitsu; Aoyama, Shigeki

    2011-01-01

    The three-dimensional penetration method combined with semi-solid casting (SS-3DPC) was utilized to prepare magnesium diboride (MgB 2 ) powder composite materials with various host materials of Mg, Mg-3%Al, Mg-3%Al-1%Zn, Mg-9%Al, and Mg-9%Al-1%Zn. X-ray diffraction measurements indicated predominant peak patterns of MgB 2 and a host alloy, implying that the host material tightly bonded MgB 2 grains without melting the MgB 2 powder. This was confirmed by SEM images. Measured electrical resistivity and magnetization versus temperature showed clear signals of superconducting transition temperature of 27-38 K for all the samples cut out from the billets. Magnetic hysteresis loop observed at 5 K enabled us to estimate a critical current density (J c ) based on the extended Bean model. Additions of aluminum and zinc elements to magnesium host-matrix were found to enhance J c and increase residual resistivity (ρ 0 ) suggesting that aluminum and zinc have an effect on pinning magnetic flux flow for J c enhancement, and scattering conduction electrons for increase of ρ 0 . (author)

  17. Raman study of electronic excitations in MgB2 with application of high magnetic field

    International Nuclear Information System (INIS)

    Machtoub, L.; Takano, Y.; Kito, H.

    2006-01-01

    We present the first results of Raman scattering with application of magnetic field on magnesium diboride (MgB 2 ). In this work, we have investigated the magnetic field dependence of the 72 meV (E 2g mode) and the pair-breaking peak around 100 cm -1 which corresponds to σ-band gap. Intensity enhancement of Raman features around 800 cm -1 accompanied with broadening in the line shape of E 2g mode has been observed in some polycrystalline samples at 0 GPa. Results are compared with previous Raman study under hydrostatic pressure

  18. Effects of disorder on the microwave properties of MgB2 polycrystalline films

    International Nuclear Information System (INIS)

    Ghigo, G.; Gerbaldo, R.; Gozzelino, L.; Laviano, F.; Mezzetti, E.; Ummarino, G. A.

    2006-01-01

    The role of disorder in superconducting magnesium diboride (MgB 2 ) policrystalline films is investigated in the high frequency range by a coplanar microwave resonator technique. Two sources of disorder are considered, heavy-ion irradiation damage and sample ageing. Microwave measurements are analyzed in the framework of the two-gap model with strong interband scattering contribution. It turns out that disorder enhancement increases the interband scattering rate, resulting in a reduction of the surface resistance at low temperatures, due to a slight increase of the π gap. Moreover, increasing disorder at grain boundaries induces a nonmonotonic residual surface resistance, showing the features of a resistive behavior for the highest disorder level. Finally, the effects of the different kinds of disorder on the intrinsic and on the grain-boundary properties of the MgB 2 films are compared and discussed

  19. The MgB2 superconducting energy gaps measured by Raman spectroscopy

    International Nuclear Information System (INIS)

    Quilty, James William

    2003-01-01

    Understanding the nature of the superconducting energy gap in magnesium diboride is an essential part of understanding this unusual superconductor, and Raman scattering is a convenient and powerful technique which is able to directly measure the key physical properties of the gap. The Raman spectra of MgB 2 show clear superconductivity induced renormalisations and evidence is found for two superconducting gaps residing on the σ and π Fermi surfaces with maximum magnitudes of around 110 and 30 cm -1 . The larger gap appears as a sharp peak in the electronic Raman scattering continuum while the smaller gap manifests itself as a threshold in the low-frequency spectral intensity, indicating that the gaps form in different electronic environments. The physical properties of the gaps favour explanations of the extraordinarily high T c in MgB 2 within strong coupling theory

  20. Electronic structure of magnesium diboride and related compounds

    Energy Technology Data Exchange (ETDEWEB)

    Paduani, C. [Departamento de Fisica, Universidade Federal de Santa Catarina, UFSC, Florianopolis, CEP 88040-900, SC (Brazil)

    2003-11-01

    The electronic structure of AlB{sub 2}-type diborides and related compounds has been investigated in first-principles calculations with the molecular cluster discrete variational method. For MgB{sub 2} was studied the effect of the lattice relaxation on the total density of states at the Fermi energy (N({epsilon}{sub F})). The results indicated that a contraction of about 2% in the lattice spacings a and c can lead to a slight increase of N({epsilon}{sub F}) for boron. In the MB{sub 2} diborides, M=Al, Ti, V, Cr, Zr, Nb, Mo and Ta, the largest contributions to N({epsilon}{sub F}) is observed for Cr, Mo and Nb. TiB{sub 2} possess the highest chemical stability in the series. The electronic specific heat coefficient {gamma} also is calculated for the diborides. The method is employed to obtain the partial B2p contribution to the total DOS at the Fermi level with the introduction of a monolayer of solute atoms as a substitution for Mg atoms of Na, Al, Ca, Ti, V, Cr, Zr, Nb, Mo and Ta in layered superstructures.. /M/B{sub 2}/Mg/B{sub 2}/.. A stronger covalent bonding between boron atoms is identified in these cases. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Magnesium diboride(MgB2) wires for applications

    International Nuclear Information System (INIS)

    Patel, Dipak; Kim, Jung Ho

    2016-01-01

    Field and temperature dependence of the critical current density, Jc, were measured for both un-doped and carbon doped MgB 2 /Nb/Monel wires manufactured by Hyper Tech Research, Inc. In particular, carbon incorporation into the MgB 2 structure using malic acid additive and a chemical solution method can be advantageous because of the highly uniform mixing between the carbon and boron powders. At 4.2 K and 10 T, Jc was estimated to be 25,000 - 25,300 Acm -2 for the wire sintered at 600 degrees C for 4 hours. The irreversibility field, Birr, of the malic acid doped wire was approximately 21.0 - 21.8 T, as obtained from a linear extrapolation of the J-B characteristic. Interestingly enough, the Jc of the malic acid doped sample exceeds 10 5 Acm -2 at 6 T and 4.2 K, which is comparable to that of commercial Nb-Ti wires

  2. Hybrid type I-type II superconducting behavior in magnesium diboride

    International Nuclear Information System (INIS)

    Kunchur, M.N.; Saracila, G.; Arcos, D.A.; Cui, Y.; Pogrebnyakov, A.; Orgiani, P.; Xi, X.X.

    2006-01-01

    In traditional type-II superconductors, an applied magnetic field depresses the transition temperature and introduces magnetic flux vortices that cause resistive losses accompanied by a broadening of the transition. High-field high-pulsed-current measurements have revealed a new hybrid behavior in disordered magnesium diboride films: The superconductivity survives high magnetic fields by entering a mixed state with vortices (like a type II superconductor) but holds its vortices nearly motionless and avoids dissipation (like a type I superconductor). A study of this phenomenon in magnesium diboride films with varying degrees of scattering indicate that the hybrid type I-type II behavior arises from the two-band nature of the superconductivity and the different degrees of influence that disorder exerts on its different bands. (author)

  3. Ex-situ manufacturing of SiC-doped MgB2 used for superconducting wire in medical device applications

    Science.gov (United States)

    Herbirowo, Satrio; Imaduddin, Agung; Sofyan, Nofrijon; Yuwono, Akhmad Herman

    2017-02-01

    Magnesium diboride (MgB2) is a superconductor material with a relatively high critical temperature. Due to its relatively high critical temperature, this material is promising and has the potential to replace Nb3Sn for wire superconducting used in many medical devices. In this work, nanoparticle SiC-doped MgB2 superconducting material has been fabricated through an ex-situ method. The doping of nanoparticle SiC by 10 and 15 wt% was conducted to analyze its effect on specific resistivity of MgB2. The experiment was started by weighing a stoichiometric amount of MgB2 and nanoparticles SiC. Both materials were mixed and grounded for 30 minutes by using an agate mortar. The specimens were then pressed into a 6 mm diameter stainless steel tube, which was then reduced until 3 mm through a wire drawing method. X-ray diffraction analysis was conducted to confirm the phase, whereas the superconductivity of the specimens was analyzed by using resistivity measurement under cryogenic magnetic system. The results indicated that the commercial MgB2 showed a critical temperature of 37.5 K whereas the SiC doped MgB2 has critical temperature of 38.3 K.

  4. Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB2 superconductor nanomaterials

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan; Acar, Selcuk; Kokal, Ilkin; Häßler, Wolfgang

    2015-01-01

    Undoped and carbon-doped magnesium diboride (MgB 2 ) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB 2 samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp 3 -hybridized carbon radicals were detected. A strong reduction in the critical temperature T c was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra

  5. Study of Transport and Micro-structural properties of Magnesium Di-Boride Strand under react and bend mode and bend and react mode

    International Nuclear Information System (INIS)

    Kundu, Ananya; Kumar Das, Subrat; Bano, Anees; Pradhan, Subrata

    2017-01-01

    I-V characterization of commercial multi-filamentary Magnesium Di-Boride (MgB 2 ) wire of diameter 0.83 mm were studied in Cryocooler at self-field I-V characterization system under both react and bend mode and bend and react mode for a range of temperature 6 K - 25 K. This study is of practical technical relevance where the heat treatment of the superconducting wire makes the wire less flexible for winding in magnet and in other applications. In the present work the bending diameter was varied from 40 mm to 20 mm and for each case critical current (I c ) of the strand is measured for above range of temperature. A customized sample holder is fabricated and thermally anchored with the 2 nd cold stage of Cryocooler. It is observed from the measurement that the strand is more susceptible to degradation for react and bend cases. The transport measurement of the strand was accompanied by SEM analyses of bend samples. Also the tensile strength of the raw strands and the heat treated strands were carried out at room temperature in Universal Testing Machine (UTM) to have an estimate about the limiting winding tension value during magnet fabrication. (paper)

  6. Automatic development of normal zone in composite MgB2/CuNi wires with different diameters

    Science.gov (United States)

    Jokinen, A.; Kajikawa, K.; Takahashi, M.; Okada, M.

    2010-06-01

    One of the promising applications with superconducting technology for hydrogen utilization is a sensor with a magnesium-diboride (MgB2) superconductor to detect the position of boundary between the liquid hydrogen and the evaporated gas stored in a Dewar vessel. In our previous experiment for the level sensor, the normal zone has been automatically developed and therefore any energy input with the heater has not been required for normal operation. Although the physical mechanism for such a property of the MgB2 wire has not been clarified yet, the deliberate application might lead to the realization of a simpler superconducting level sensor without heater system. In the present study, the automatic development of normal zone with increasing a transport current is evaluated for samples consisting of three kinds of MgB2 wires with CuNi sheath and different diameters immersed in liquid helium. The influences of the repeats of current excitation and heat cycle on the normal zone development are discussed experimentally. The aim of this paper is to confirm the suitability of MgB2 wire in a heater free level sensor application. This could lead to even more optimized design of the liquid hydrogen level sensor and the removal of extra heater input.

  7. World-record current in the MgB2 superconductor

    CERN Multimedia

    Antonella Del Rosso

    2014-01-01

    In the framework of the High-Luminosity LHC project, experts from the CERN Superconductors team recently obtained a world-record current of 20 kA at 24 K in an electrical transmission line consisting of two 20-metre long cables made of Magnesium Diboride (MgB2) superconductor. This result makes the use of such technology a viable solution for long-distance power transportation.   The 20-metre long electrical transmission line containing the two 20 kA MgB2 cables. “The test is an important step in the development of cold electrical power transmission systems based on the use of MgB2,” says Amalia Ballarino, head of the Superconductors and Superconducting Devices section in the Magnet, Superconductors and Cryostat group of the Technology Department, and initiator of this project. “The cables and associated technologies were designed, developed and tested at CERN. The superconducting wire is the result of a long R&D effort that started ...

  8. The effect of copper additions in the synthesis of in situ MgB2 Cu-sheathed wires

    International Nuclear Information System (INIS)

    Woźniak, M.; Hopkins, S.C.; Gajda, D.; Glowacki, B.A.

    2012-01-01

    The powder-in-tube (PIT) technique has been used to fabricate copper-sheathed magnesium diboride (MgB 2 ) wires using an insitu reaction method. The effect of copper powder additions, magnesium-boron molar ratio and heat treatment is studied by SEM, XRD, transport critical current I c (B) and resistivity ρ(T, B) measurements. The results show that addition of copper powder to the core of the wire accelerates the formation of MgB 2 and hence increases its amount and greatly decreases the amount of Mg-Cu intermetallic phases present in the core of the wire after heat treatment. Excess magnesium proved to be effective in compensating for Mg loss due to interdiffusion with the Cu of the wire sheath and resulted in less unreacted boron in the core for wires without added Cu, but seems to oppose the accelerated formation of MgB 2 in Cu added wires. The highest critical current density, 2.8 × 10 4 A cm -2 at 3 T and 4.2 K, was achieved for a wire with a stoichiometric Mg:B ratio and 3 at.% added copper powder heat treated at 700 °C for 5 min.

  9. Tests on MgB2 for Application to SRF Cavities

    International Nuclear Information System (INIS)

    Tajima, T.; Canabal, A.; Los Alamos; Zhao, Y.; Wollongong U.; Romanenko, A.; Cornell U., LNS; Nantista, C.; Tantawi, S.; SLAC; Phillips, L.; Jefferson Lab; Iwashita, Y.; Kyoto U., Inst. Chem. Res.; Campisi, I.; Oak Ridge; Moeckly, B.; Superconductor Tech., Santa Barbara

    2006-01-01

    Magnesium diboride (MgB 2 ) has a transition temperature (T c ) of ∼40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (R s ) than Nb at 4 K and seems to have much less power dependence than high-T c materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in R s with higher surface magnetic fields compared to the film deposited with reactive evaporation method

  10. MgB2 magnetometer with a directly coupled pick-up loop

    Science.gov (United States)

    Portesi, C.; Mijatovic, D.; Veldhuis, D.; Brinkman, A.; Monticone, E.; Gonnelli, R. S.

    2006-05-01

    In this work, we show the results obtained in the fabrication and characterization of an MgB2 magnetometer with a directly coupled pick-up loop. We used an all in situ technique for fabricating magnesium diboride films, which consists of the co-evaporation of B and Mg by means of an e-gun and a resistive heater respectively. Consequently, we realized the superconducting device, which incorporates two nanobridges as weak links in a superconducting loop. The nanobridges were realized by focused ion beam milling; they were 240 nm wide and had a critical current density of 107 A cm-2. The magnetometer was characterized at different temperatures and also measurements of the noise levels have been performed. The device shows Josephson quantum interference up to 20 K and the calculated effective area at low temperatures was 0.24 mm2. The transport properties of the magnetometer allow determining fundamental materials properties of the MgB2 thin films, such as the penetration depth.

  11. MgB2 for Application to RF Cavities for Accelerators

    International Nuclear Information System (INIS)

    Tajima, T.; Canabal, A.; Zhao, Y.; Romanenko, A.; Moeckly, B.H.; Nantista, C.D.; Tantawi, S.; Phillips, L.; Iwashita, Y.; Campisi, I.E.

    2007-01-01

    Magnesium diboride (MgB 2 ) has a transition temperature (T c ) of ∼40 K, i.e., about 4 times as high as that of niobium (Nb).We have been evaluating MgB 2 as a candidate material for radio-frequency (RF) cavities for future particle accelerators. Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb at 4 K. A power dependence test using a 6 GHz TE011 mode cavity has shown little power dependence up to ∼12 mT (120 Oe), limited by available power, compared to other high-Tc materials such as YBCO. A recent study showed, however, that the power dependence of Rs is dependent on the coating method. A film made with on-axis pulsed laser deposition (PLD) has showed rapid increase in Rs compared to the film deposited by reactive evaporation method. This paper shows these results as well as future plans

  12. Properties of boride-added powder metallurgy magnesium alloys

    Science.gov (United States)

    Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

    2009-06-01

    Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.

  13. Properties of boride-added powder metallurgy magnesium alloys

    International Nuclear Information System (INIS)

    Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi

    2009-01-01

    Magnesium alloys with metallic borides, magnesium diboride (MgB 2 ) or aluminum diboride (AlB 2 ), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB 2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB 2 , did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg 17 Al 12 , formed in the alloy with AlB 2 , which was consistent with its higher hardness.

  14. Experimental testing and modelling of a resistive type superconducting fault current limiter using MgB2 wire

    International Nuclear Information System (INIS)

    Smith, A C; Pei, X; Oliver, A; Husband, M; Rindfleisch, M

    2012-01-01

    A prototype resistive superconducting fault current limiter (SFCL) was developed using single-strand round magnesium diboride (MgB 2 ) wire. The MgB 2 wire was wound with an interleaved arrangement to minimize coil inductance and provide adequate inter-turn voltage withstand capability. The temperature profile from 30 to 40 K and frequency profile from 10 to 100 Hz at 25 K were tested and reported. The quench properties of the prototype coil were tested using a high current test circuit. The fault current was limited by the prototype coil within the first quarter-cycle. The prototype coil demonstrated reliable and repeatable current limiting properties and was able to withstand a potential peak current of 372 A for one second without any degradation of performance. A three-strand SFCL coil was investigated and demonstrated scaled-up current capacity. An analytical model to predict the behaviour of the prototype single-strand SFCL coil was developed using an adiabatic boundary condition on the outer surface of the wire. The predicted fault current using the analytical model showed very good correlation with the experimental test results. The analytical model and a finite element thermal model were used to predict the temperature rise of the wire during a fault. (paper)

  15. MgB2 thin films by hybrid physical-chemical vapor deposition

    International Nuclear Information System (INIS)

    Xi, X.X.; Pogrebnyakov, A.V.; Xu, S.Y.; Chen, K.; Cui, Y.; Maertz, E.C.; Zhuang, C.G.; Li, Qi; Lamborn, D.R.; Redwing, J.M.; Liu, Z.K.; Soukiassian, A.; Schlom, D.G.; Weng, X.J.; Dickey, E.C.; Chen, Y.B.; Tian, W.; Pan, X.Q.; Cybart, S.A.; Dynes, R.C.

    2007-01-01

    Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB 2 thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB 2 films. The epitaxial pure MgB 2 films grown by HPCVD show higher-than-bulk T c due to tensile strain in the films. The HPCVD films are the cleanest MgB 2 materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB 2 . The carbon-alloyed HPCVD films demonstrate record-high H c2 values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB 2 Josephson junctions

  16. Why is magnesium diboride's superconducting temperature increased by the hydrogenation process?

    International Nuclear Information System (INIS)

    Flaumbaum, V.V.; Russell, G.J.; Stewart, G.A.

    2002-01-01

    Full text: This work demonstrates that the superconducting transition temperature for MgB 2 can be increased significantly by the hydrogenation process. A preliminary electronic report has already been placed on the archival web site http://au.arXiv.org/with reference number cond-mat/0112301. Given that there appears not to be a large enough interstitial site to accommodate the hydrogen, it is not yet clear what mechanism is involved. The justification for attempting hydrogenation was that metallic Pd becomes a superconductor when it is hydrogenated. We exposed MgB 2 powder to pure hydrogen gas in a stainless steel chamber and heated it. Before removing the specimen, the chamber was cooled in liquid N 2 and opened to air. This was an attempt to 'poison' the specimen's surface. The T c , determined using ac susceptibility, was found to increased for all hydrogenated specimens. The largest increase achieved so far is AT C ∼1.25 K for a specimen hydrogenated under 10 atm H 2 at 600 deg C for 2 hours (H/MgB 2 ∼ 0.03). However, the optimum conditions are yet to be determined. A further complication is that a similar effect (albeit smaller) is obtained by subjecting the MgB 2 to the same process but with helium or argon gas instead of hydrogen

  17. Development of magnesium diboride (MgB{sub 2}) wires and magnets using in situ strand fabrication method

    Energy Technology Data Exchange (ETDEWEB)

    Tomsic, Michael [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States); Rindfleisch, Matthew [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States)]. E-mail: mrindfleisch@hypertechresearch.com; Yue, Jinji [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States); McFadden, Kevin [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States); Doll, David [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States); Phillips, John [Hyper Tech Research, Inc., 1275 Kinnear Road, Columbus, OH 43212 (United States); Sumption, Mike D. [LASM, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, 43210 (United States); Bhatia, Mohit [LASM, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, 43210 (United States); Bohnenstiehl, Scot [LASM, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, 43210 (United States); Collings, E.W. [LASM, Department of Materials Science and Engineering, Ohio State University, Columbus, OH, 43210 (United States)

    2007-06-01

    Since 2001 when magnesium diboride (MgB{sub 2}) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB{sub 2} superconductor wire in kilometer-long piece-lengths has been demonstrated in magnets and coils. Work has started on demonstrating MgB{sub 2} wire in superconducting devices now that the wire is available commercially. MgB{sub 2} superconductors and coils have the potential to be integrated in a variety of commercial applications such as magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, energy storage, and high energy physics applications. This paper discusses the progress on MgB{sub 2} conductor and coil development in the last several years at Hyper Tech Research, Inc.

  18. Development of ex situ processed MgB2 wires and their applications to magnets

    International Nuclear Information System (INIS)

    Braccini, Valeria; Nardelli, Davide; Penco, Roberto; Grasso, Giovanni

    2007-01-01

    In spite of the relatively short time dedicated to the development of magnesium diboride conductors since its discovery in early 2001, a substantial improvement was soon achieved in their manufacture and use. Unlike many others HTS and LTS materials, the MgB 2 conductor processing is more open to a number of improvements and modifications that help in making it more attractive for several DC and AC applications. Many kilometres of conductors were already produced throughout the world and it is now possible to start seriously thinking about a systematic industrial production of this material, as it is already possible to purchase it in reasonable lengths on the free market. These remarkable lengths of conductor were also wound in coils and their performance continuously improved in the past years. Here we will present a review of the recent results and a perspective for the future development of this 'new' superconductor, starting from the optimisation of the precursor powders needed to improve the magnetic field behaviour of the tapes, to the conductor development, i.e. the production of multifilamentary Cu-stabilized tapes in lengths up to 1.78 km, to the realization of the first large-scale application devices such as MRI magnets and fault current limiters

  19. Effects of sintering conditions on critical current properties and microstructures of MgB2 bulks

    International Nuclear Information System (INIS)

    Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Ueda, Shinya; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

    2005-01-01

    The effects of heating conditions on critical current properties and microstructures of undoped MgB 2 bulks were systematically studied. Strong correlation was observed between J c and microstructures. The network structure with an excellent inter-grain connectivity of MgB 2 grains contributed to high-J c under low magnetic fields, and small grain size of MgB 2 enhanced the grain boundary flux pinning. Long time heating at low temperatures below the melting point of magnesium was discovered to be most effective for synthesis of MgB 2 bulks having strongly connected MgB 2 network structure with small grains. The sample heated at 550 deg. C for 1200 h recorded a high-J c of 4.02 x 10 5 A cm -2 at 20 K in self-field, while high-temperature and long time heating brought a significant grain growth which resulted in low J c

  20. Ultrashort Pulsed Laser Ablation of Magnesium Diboride: Plasma Characterization and Thin Films Deposition

    Directory of Open Access Journals (Sweden)

    Angela De Bonis

    2015-01-01

    Full Text Available A MgB2 target has been ablated by Nd:glass laser with a pulse duration of 250 fs. The plasma produced by the laser-target interaction, showing two temporal separated emissions, has been characterized by time and space resolved optical emission spectroscopy and ICCD fast imaging. The films, deposited on silicon substrates and formed by the coalescence of particles with nanometric size, have been analyzed by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The first steps of the films growth have been studied by Transmission Electron Microscopy. The films deposition has been studied by varying the substrate temperature from 25 to 500°C and the best results have been obtained at room temperature.

  1. Development of Ti-sheathed MgB2 wires with high critical current density

    International Nuclear Information System (INIS)

    Liang, G; Fang, H; Hanna, M; Yen, F; Lv, B; Alessandrini, M; Keith, S; Hoyt, C; Tang, Z; Salama, K

    2006-01-01

    Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB 2 wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB 2 wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, J c , measured in magnetic fields of 0, 5, and 8 T are about 4.2 x 10 5 , 3.6 x 10 4 , and 1.4 x 10 4 A cm -2 , respectively. At 20 K and 0 T, the magnetic J c is about 2.4 x 10 5 A cm -2 . These results show that at zero and low fields, the values of the magnetic J c for Ti-sheathed MgB 2 wires are comparable with the best results available for the Fe-sheathed MgB 2 wires. At high fields, however, the J c for Ti-sheathed MgB 2 wires appears higher than that for the Fe-sheathed MgB 2 wires

  2. Electronic structure of MgB2

    Indian Academy of Sciences (India)

    Abstract. Results of ab initio electronic structure calculations on the compound MgB2 using the. FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, c/a ratio and the bulk modulus, all of which are in excellent ...

  3. Electronic structure of MgB 2

    Indian Academy of Sciences (India)

    Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...

  4. MgB2 magnetometer with directly coupled pick-up loop

    NARCIS (Netherlands)

    Portesi, C.; Mijatovic, D.; Veldhuis, Dick; Brinkman, Alexander; Monticone, E.; Gonnelli, R.S.

    2006-01-01

    magnetometer with a directly coupled pick-up loop. We used an all in situ technique for fabricating magnesium diboride films, which consists of the co-evaporation of B and Mg by means of an e-gun and a resistive heater respectively. Consequently, we realized the superconducting device, which

  5. Mechanically activated self-propagated high-temperature synthesis of nanometer-structured MgB2

    International Nuclear Information System (INIS)

    Radev, D.D.; Marinov, M.; Tumbalev, V.; Radev, I.; Konstantinov, L.

    2005-01-01

    Nanometer-sized MgB 2 was prepared via a two-step modification of the mechanically activated self-propagated high-temperature synthesis. The experimental conditions and some structural and phase characteristics of the synthesized product are reported. It is shown that a single-phase material can be prepared after 2 h of intense mechanical treatment of the starting magnesium and boron powders and a synthesis induced at a current-pulse density of 30 A cm -2 . The average size of MgB 2 particles synthesized in this way is 70-80 nm. It is also shown that using the same reagents and the 'classic' high-temperature interaction at 850 deg C with a protective atmosphere of pure Ar, mean particle size of the MgB 2 obtained is 50 μm

  6. Multiband model for tunneling in MgB2 junctions

    NARCIS (Netherlands)

    Brinkman, Alexander; Golubov, Alexandre Avraamovitch; Rogalla, Horst; Dolgov, O.V.; Kortus, J.; Kong, Y.; Jepsen, O.; Andersen, O.K.

    2002-01-01

    A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results of band structure calculations. The

  7. Defect structure of ultrafine MgB2 nanoparticles

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Repp, Sergej; Erdem, Emre; Thomann, Ralf; Acar, Selçuk

    2014-01-01

    Defect structure of MgB 2 bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB 2 , namely, boron 95 (purity 95%–97%, <1.5 μm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB 2 , respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB 2 in comparison with bulk MgB 2 . Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB 2 can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB 2 material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications

  8. The effects of Fe2O3 nanoparticles on MgB2 superconducting thin films

    International Nuclear Information System (INIS)

    Koparan, E.T.; Sidorenko, A.; Yanmaz, E.

    2013-01-01

    Full text: Since the discovery of superconductivity in binary MgB 2 compounds, extensive studies have been carried out because of its excellent properties for technological applications, such as high transition temperature (T c = 39 K), high upper critical field (H c2 ), high critical current density (J c ). Thin films are important for fundamental research as well as technological applications of any functional materials. Technological applications primarily depend on critical current density. The strong field dependence of J c for MgB 2 necessitates an enhancement in flux pinning performance in order to improve values in high magnetic fields. An effective way to improve the flux pinning is to introduce flux pinning centers into MgB 2 through a dopant having size comparable to the coherence length of MgB 2 . In this study, MgB 2 film with a thickness of about 600 nm was deposited on the MgO (100) single crystal substrate using a 'two-step' synthesis technique. Firstly, deposition of boron thin film was carried out by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850 degrees Celsius in magnesium vapour. In order to investigate the effect of Fe 2 O 3 nanoparticles on the structural and magnetic properties of films, MgB 2 films were coated with different concentrations of Fe 2 O 3 nanoparticles by a spin coating process. The effects of different concentrations of ferromagnetic Fe 2 O 3 nanoparticles on superconducting properties of obtained films were carried out by using structural (XRD, SEM, AFM), electrical (R-T) and magnetization (M-H, M-T and AC Susceptibility) measurements. It was calculated that anisotropic coefficient was about γ = 1.2 and coherence length of 5 nm for the uncoated film. As a result of coherence length, the appropriate diameters of Fe 2 O 3 nanoparticles were found to be 10 nm, indicating that these nanoparticles served as the pinning centers. Based on the data obtained from this study, it can be

  9. Flux pinning properties of impurity doped MgB2 bulks synthesized by diffusion method

    International Nuclear Information System (INIS)

    Ueda, Shinya; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

    2005-01-01

    Doping effects of carbon-containing impurities on the critical current properties and microstructure were systematically studied for highly dense MgB 2 bulks prepared by the diffusion method starting from magnesium and boron which are separately packed in sealed stainless tubes. Obtained samples exhibited improved critical current density, J c , simply by an increase of effective current pass. A non-doped MgB 2 recorded almost double high J c at 20 K compared with those of the conventional porous MgB 2 bulks having ∼50% of the theoretical density, while irreversibility field, H irr , did not largely change. J c under high magnetic fields were enhanced by doping of carbon-containing impurities, such as SiC and B 4 C. Optimal doping levels of SiC and B 4 C for high critical current properties at 20 K are found to be ∼2% and 5%, respectively, as nominal carbon concentration at boron site. Difference in the optimal doping levels is originated from the difference in their reactivity

  10. Pulse laser irradiation into superconducting MgB2 detector

    International Nuclear Information System (INIS)

    Fujiwara, Daisuke; Miki, Shigehito; Satoh, Kazuo; Yotsuya, Tsutomu; Shimakage, Hisashi; Wang, Zhen; Okayasu, Satoru; Katagiri, Masaki; Machida, Masahiko; Kato, Masaru; Ishida, Takekazu

    2005-01-01

    We performed 20-ps pulse laser irradiation experiments on a MgB 2 neutron detector to know a thermal-relaxation process for designing a MgB 2 neutron detector. The membrane-type structured MgB 2 device was fabricated to minimize the heat capacity of sensing part of a detector as well as to enhance its sensitivity. We successfully observed a thermal-relaxation signal resulting from pulse laser irradiation by developing a detection circuit. The response time was faster than 1 μs, meaning that the detector would be capable of counting neutrons at a rate of more than 10 6 events per second

  11. Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors

    International Nuclear Information System (INIS)

    Taylan Koparan, E.; Savaskan, B.; Guner, S.B.; Celik, S.

    2016-01-01

    We present a detailed investigation of the effects of Bi 2 Sr 2 Ca 1 Cu 2 O 8+κ (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB 2 obtained by hot press method. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 10 wt%) of the total MgB 2 . Moreover, we present MgB 2 bulk samples fabricated by using different production methods including hot pressing method to our knowledge. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano-boron (B) powder and Bi-2212 powder which are produced by hot press method. As a result of hot press process, compact pellet samples were manufactured. The vertical and lateral levitation force measurements were executed at the temperatures of 20, 24 and 28 K under zero-field-cooled (ZFC) and field-cooled (FC) regimes for samples with various adding levels. At 24 K and 28 K under ZFC regime, the 2 wt% Bi-2212 added sample exhibits a higher vertical levitation force than the pure sample. Bi-2212 added MgB 2 samples compared to the pure sample have lower attractive force values in FC regime. The magnetic field dependence of the critical current density J c was calculated from the M-H loops for Bi-2212 added MgB 2 samples. The 2 wt% Bi-2212 added sample has the best levitation and critical current density performance compared to other samples. The critical temperature (T c ) has slightly dropped from 37.8 K for the pure MgB 2 sample to 36.7 K for the 10 wt% of Bi-2212 added sample. The transition temperature slightly decreases when Bi-2212 adding level is increased. (orig.)

  12. Pseudopotential approach to superconductivity in MgB2

    International Nuclear Information System (INIS)

    Sharma, K.S.; Bhargava, Nidhi; Jain, Ritu; Goyal, Varsha; Sharma, Ritu; Sharma, Smita

    2010-01-01

    Superconductivity in MgB 2 has been re-examined in BCS-Eliashberg framework by employing Mc-Millan's T c -equation and form factors of MgB 2 computed from the form factors of component metals (Model-I). The empty core model pseudopotential due to Ashcroft and random phase approximation form of dielectric screening due to Gellmann and Brueckner are used in the present work. An excellent agreement between the present values and other theoretically computed values of T c and with the relevant experimental data for MgB 2 confirms the validity of the present approach. The explicit dependence of λ and T c on the isotopic masses of Mg and B, as revealed from the present work, confirms the role of lattice vibrations in the superconducting behaviour of MgB 2 and the high value of T c in it may be attributed to the phonon mediated e-e interaction coupled with higher values of phonon frequencies due to light mass of B atoms. It has also been observed that the pseudo-atom model (Model-II) with appropriate choice of the potential parameter r c successfully explains high value of T c and isotope effect in MgB 2 , confirming the prominent role played by electron-phonon interaction in the high-T c superconductivity observed in MgB 2 . The isotope effect exponent α-values obtained from the two models are in complete agreement with each other and the present value α = 0.46 is also much closer to the BCS value of 0.5. Interaction strength N 0 V values obtained from the two models are also in perfect agreement with each other and the present value N 0 V = 0.48 suggests that MgB 2 is a strong coupling superconductor. (author)

  13. Dry cryomagnetic system with MgB2 coil

    Science.gov (United States)

    Abin, D. A.; Mineev, N. A.; Osipov, M. A.; Pokrovskii, S. V.; Rudnev, I. A.

    2017-12-01

    MgB2 may be the future superconducting wire material for industrial magnets due to it’s higher operation temperature and potentially lower cost than low temperature superconductors (LTS) have. We designed a compact cryomagnetic system with the use of MgB2. The possibility of creating a magnet with a central field of 5 T from a commercial MgB2 wire by the “react and wound” method was investigated. The magnetic system is cooled by a cryocooler through a copper bus. The magnet has a warm bore diameter of 4 cm. The design of a magnet consisting of three concentric solenoids is proposed: an internal one of high-temperature superconductor (HTS), an average of MgB2, and an external of NbTi. The operating current of the system is 100 A. Two pairs of current leads are used. A separate pair of current leads for power supplying NbTi coil allows testing of MgB2 and HTS coils in an external field. The load curves for each of the magnets are calculated.

  14. MgB2 and Mg1-xAlxB2 single crystals: high pressure growth and physical properties

    International Nuclear Information System (INIS)

    Karpinski, J.; Kazakov, S.M.; Jun, J.; Zhigadlo, N.D.; Angst, M.; Puzniak, R.; Wisniewski, A.

    2004-01-01

    Single crystals of MgB 2 have been grown with a high pressure cubic anvil technique. They grow via the peritectic decomposition of the MgNB 9 ternary nitride. The crystals are of a size up to 2 x 1 x 0.1 mm 3 with a weight up to 230 μg. Typically they have transition temperatures between 38 and 38.6 K with a width of 0.3-0.5 K. Investigations of the P-T phase diagram prove that the MgB 2 phase is stable at least up to 2190 deg. C at high hydrostatic pressure in the presence of Mg vapor under high pressure. Substitution of aluminum for magnesium in single crystals leads to stepwise decrease of T c . This indicates a possible appearance of superstructures or phases with different T c 's. The upper critical field decreases with Al doping

  15. Microwave absorption studies of MgB2 superconductor

    Indian Academy of Sciences (India)

    band (9–. 10 GHz) spectrometer. Both polycrystalline pellet and single-grain MgB2, having nearly the same Tc (∼ 39 K) and same size (3×2×1 mm3), were used in the present investigations. Low field modulated microwave absorption signals ...

  16. Electronic structure and superconductivity of MgB 2

    Indian Academy of Sciences (India)

    Results of ab initio electronic structure calculations on the compound, MgB2, using the FPLAPW method employing GGA for the exchange–correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...

  17. Preparation and characterization of MgB2 superconductor

    Indian Academy of Sciences (India)

    2Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. Abstract. The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been ...

  18. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10m) samples suggested the absence of weak-link character. The field dependent direct microwave ...

  19. Nanostructure characterization of Ni and B layers as artificial pinning centers in multilayered MgB2/Ni and MgB2/B superconducting thin films

    International Nuclear Information System (INIS)

    Sosiati, H.; Hata, S.; Doi, T.; Matsumoto, A.; Kitaguchi, H.; Nakashima, H.

    2013-01-01

    Highlights: ► Nanostructure characterization of Ni and B layers as artificial pinning centers (APCs). ► Relationship between nanostructure and J c property. ► Enhanced J c in parallel field by parallel APCs within the MgB 2 film. -- Abstract: Research on the MgB 2 /Ni and MgB 2 /B multilayer films fabricated by an electron beam (EB) evaporation technique have been extensively carried out. The critical current density, J c of MgB 2 /Ni and MgB 2 /B multilayer films in parallel fields has been suggested to be higher than that of monolayer MgB 2 film due to introducing the artificial pinning centers of nano-sized Ni and B layers. Nanostructure characterization of the artificial pinning centers in the multilayer films were examined by transmission electron microscopy (TEM) and scanning TEM (STEM-energy dispersive X-ray spectroscopy (STEM-EDS))–EDS to understand the mechanism of flux pinning. The growth of columnar MgB 2 grains along the film-thickness direction was recognized in the MgB 2 /Ni multilayer film, but not in the MgB 2 /B multilayer film. Nano-sized Ni layers were present as crystalline epitaxial layers which is interpreted that Ni atoms might be incorporated into the MgB 2 lattice to form (Mg,Ni)B 2 phase. On the other hand, nano-sized B layers were amorphous layers. Crystalline (Mg,Ni)B 2 layers worked more effectively than amorphous B-layers, providing higher flux-pinning force that resulted in higher J c of the MgB 2 /Ni multilayer film than the MgB 2 /B multilayer film

  20. A new approach to MgB2 superconducting magnet fabrication

    International Nuclear Information System (INIS)

    Miyazoe, A; Ando, T; Wada, H; Abe, H; Hirota, N; Sekino, M

    2008-01-01

    Fabrication of MgB 2 -based superconducting magnets has been attempted by a new approach using film coated on symmetric tubes. Superconducting MgB 2 films have been prepared on iron substrates by electroplating in molten electrolytes. The critical current (I c ) of the MgB 2 electroplating films at 4.2 K and at self-field was 15 A on the basis of 1 μV/cm of I c criterion. A model calculation has shown that MgB 2 -based superconducting magnets based on MgB 2 electroplating films have the potential to generate magnetic fields over 0.5 T

  1. Electromagnetic densification of MgB2/Cu wires

    International Nuclear Information System (INIS)

    Woźniak, M; Glowacki, B A

    2014-01-01

    Electromagnetic compaction of in situ MgB 2 /Cu wire has been achieved using a custom-built 200 J device. The monofilament core packing density was increased by 8% and up to 31% for unreacted and reacted wires respectively. The higher density of the MgB 2 core resulted in a critical current density increase of up to 75% in comparison to that for cold-drawn-only wire. Applying this treatment to a wire with Cu powder additions to the core and with an optimized heat treatment resulted in one of the highest ever reported values of J c for MgB 2 /Cu wires of 6.83 × 10 3  A cm −2 at 4.2 K and 6 T. (paper)

  2. Observation of pseudogap in MgB2

    Science.gov (United States)

    Patil, S.; Medicherla, V. R. R.; Ali, Khadiza; Singh, R. S.; Manfrinetti, P.; Wrubl, F.; Dhar, S. K.; Maiti, Kalobaran

    2017-11-01

    We investigate the electronic structure of a specially prepared highly dense conventional high temperature superconductor, MgB2, employing high resolution photoemission spectroscopy. The spectral evolution close to the Fermi energy is commensurate to BCS descriptions as expected. However, the spectra in the wider energy range reveal the emergence of a pseudogap much above the superconducting transition temperature indicating an apparent departure from the BCS scenario. The energy scale of the pseudogap is comparable to the energy of the E2g phonon mode responsible for superconductivity in MgB2 and the pseudogap can be attributed to the effect of electron-phonon coupling on the electronic structure. These results reveal a scenario of the emergence of the superconducting gap within an electron-phonon coupling induced pseudogap and have significant implications in the study of high temperature superconductors.

  3. Investigation of pinning in MgB2 superconductors

    International Nuclear Information System (INIS)

    Mohammad, S.; Reissner, M.; Steiner, W.; Bauer, E.; Giovannini, M.

    2006-01-01

    Full text: The pinning behaviour of bulk MgB 2 superconductors is peculiar in many respects. Pinning seems to be stronger than in classical high T C materials and there seems to be no weak link problem in these compounds, giving hope to produce bulk samples and wires with current densities appropriate for technical applications. But, although many studies concerning the pinning behaviour in this compound appeared in recent years, the results are still contradictory. In the present work we present results of an investigation of the pinning behaviour by magnetic relaxation measurements of three MgB 2 samples: a pure one, a sample with 8 at% Al substitution and a sample with 10 wt% of SiC admixture. A comparison of different analyses methods is given. (author)

  4. Insulator layer formation in MgB2 SIS junctions

    International Nuclear Information System (INIS)

    Shimakage, H.; Tsujimoto, K.; Wang, Z.; Tonouchi, M.

    2005-01-01

    The dependence of current-voltage characteristics on thin film deposition conditions was investigated using MgB 2 /AlN/NbN SIS junctions. By increasing the substrate temperature in AlN insulator deposition, the current density decreased and the normal resistance increased. The results indicated that an additional insulator layer between the MgB 2 and AlN formed, either before or during the AlN deposition. The thickness of the additional insulator layer was increased with an increase in the AlN deposition temperature. From the dependence of current density on the thickness of AlN in low temperature depositions, the thickness of the additional insulator layer was estimated to be 1-1.5 nm when the AlN insulator was deposited from 0.14 to 0.7 nm. Moreover, with the current density of MgB 2 /AlN/MgB 2 SIS junctions, further insulator layer formation was confirmed

  5. Ball-milling and AlB2 addition effects on the hydrogen sorption properties of the CaH2 + MgB2 system

    International Nuclear Information System (INIS)

    Schiavo, B.; Girella, A.; Agresti, F.; Capurso, G.; Milanese, C.

    2011-01-01

    Research highlights: → Calcium hydride + magnesium-aluminum borides as candidates for hydrogen storage. → Long time ball milling improves hydrogen sorption kinetics of the CaH 2 +MgB 2 system. → Coexistence of MgB 2 and AlB 2 does not improve hydrogen sorption performances. → Total substitution of MgB 2 with AlB 2 improves the system kinetics and reversibility. → Below 400 deg. C almost the full hydrogen capacity of the CaH 2 + AlB 2 system is reached. - Abstract: Among the borohydrides proposed for solid state hydrogen storage, Ca(BH 4 ) 2 is particularly interesting because of its favourable thermodynamics and relatively cheap price. Composite systems, where other species are present in addition to the borohydride, show some advantages in hydrogen sorption properties with respect to the borohydrides alone, despite a reduction of the theoretical storage capacity. We have investigated the milling time influence on the sorption properties of the CaH 2 + MgB 2 system from which Ca(BH 4 ) 2 and MgH 2 can be synthesized by hydrogen absorption process. Manometric and calorimetric measurements showed better kinetics for long time milled samples. We found that the total substitution of MgB 2 with AlB 2 in the starting material can improve the sorption properties significantly, while the co-existence of both magnesium and aluminum borides in the starting mixture did not cause any improvement. Rietveld refinements of the X-ray powder diffraction spectra were used to confirm the hypothesized reactions.

  6. Properties of hot pressed MgB2/Ti tapes

    International Nuclear Information System (INIS)

    Kovac, P.; Husek, I.; Melisek, T.; Fedor, J.; Cambel, V.; Morawski, A.; Kario, A.

    2009-01-01

    Hot axial and hot isostatic pressing was applied for single-core MgB 2 /Ti tapes. Differences in transport current density, n-exponents and critical current anisotropy are discussed and related to the grain connectivity influenced by pressing. The magnetic Hall probe scanning measurements allowed observing the isolated regions for axially hot pressed sample attributed to the longitudinally oriented cracks introduced by pressing. The highest current densities were measured for the tape subjected to hot isostatic pressing due to improved connectivity.

  7. Specific heat of MgB_2 after irradiation

    OpenAIRE

    Wang, Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W.; Hinderer, Joerg; Junod, Alain

    2002-01-01

    We studied the effect of disorder on the superconducting properties of polycrystalline MgB_2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2 Delta 0 / k_B T_c = 1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T_c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutr...

  8. MgB2-based superconductors for fault current limiters

    Science.gov (United States)

    Sokolovsky, V.; Prikhna, T.; Meerovich, V.; Eisterer, M.; Goldacker, W.; Kozyrev, A.; Weber, H. W.; Shapovalov, A.; Sverdun, V.; Moshchil, V.

    2017-02-01

    A promising solution of the fault current problem in power systems is the application of fast-operating nonlinear superconducting fault current limiters (SFCLs) with the capability of rapidly increasing their impedance, and thus limiting high fault currents. We report the results of experiments with models of inductive (transformer type) SFCLs based on the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa). It was shown that the SFCLs meet the main requirements to fault current limiters: they possess low impedance in the nominal regime of the protected circuit and can fast increase their impedance limiting both the transient and the steady-state fault currents. The study of quenching currents of MgB2 rings (SFCL activation current) and AC losses in the rings shows that the quenching current density and critical current density determined from AC losses can be 10-20 times less than the critical current determined from the magnetization experiments.

  9. Note: Progress on the use of MgB2 superconducting joint technique for the development of MgB2 magnets for magnetic resonance imaging (MRI).

    Science.gov (United States)

    Kim, Y G; Song, J B; Kim, J C; Kim, J M; Yoo, B H; Yun, S B; Hwang, D Y; Lee, H G

    2017-08-01

    This note presents a superconducting joint technique for the development of MgB 2 magnetic resonance imaging (MRI) magnets. The MgB 2 superconducting joint was fabricated by a powder processing method using Mg and B powders to establish a wire-bulk-wire connection. The joint resistance measured using a field-decay method was magnets operating in the persistent current mode.

  10. Formation of MgB2 at ambient temperature with an electrochemical process: a plausible mechanism

    International Nuclear Information System (INIS)

    Jadhav, A B; Subhedar, K M; Hyam, R S; Talaptra, A; Sen, Pintu; Bandyopadhyay, S K; Pawar, S H

    2005-01-01

    The binary intermetallic MgB 2 superconductor has been synthesized by many research groups. However, the mechanism of its formation is not clearly understood. In this communication, a comprehensive mechanism of the formation of MgB 2 from Le Chatelier's principle of equilibrium reaction has been explained both for solid-state reaction and electrodeposition methods. (rapid communication)

  11. Measurement of the anisotropy ratios in MgB2 single crystals

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Kang, Byeongwon; Lee, Hyun-Sook; Lee, Sung-Ik

    2006-01-01

    We present our recent measurements on the anisotropy ratios of MgB 2 single crystals. Our measurements indicate that the anisotropy ratios of the penetration depth and of the upper critical field have different magnitudes and temperature dependences, as predicted by theoretical calculations. These results imply that the two-gap nature can strongly influence the superconducting properties of MgB 2

  12. Directional scanning tunneling spectroscopy in MgB2

    International Nuclear Information System (INIS)

    Iavarone, M.; Karapetrov, G.; Koshelev, A.E.; Kwok, W.K.; Crabtree, G.W.; Hinks, D.G.; Cook, R.; Kang, W.N.; Choi, E.M.; Kim, H.J.; Lee, S.I.

    2003-01-01

    The superconductivity in MgB 2 has a two-band character with the dominating band having a 2D character and the second band being isotropic in the three dimensions. We use tunneling microscopy and spectroscopy to reveal the two distinct energy gaps at Δ 1 =2.3 meV and Δ 2 =7.1 meV. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multi-band system. The results are consistent with the existence of two-band superconductivity in the presence of strong interband superconducting pair interaction and quasiparticle scattering. The temperature evolution of the tunneling spectra shows both gaps vanishing at the bulk T c

  13. Specific heat of MgB2 after irradiation

    International Nuclear Information System (INIS)

    Wang Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W; Hinderer, Joerg; Junod, Alain

    2003-01-01

    We studied the effect of disorder on the superconducting properties of polycrystalline MgB 2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2Δ 0 /k B T c =1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutrons, a substantial bulk increase of dH c2 /dT at T c can be obtained without sacrificing more than a few degrees in T c . The upper critical field of the sample after irradiation exceeds 28 T at T→0

  14. On heavy carbon doping of MgB2

    International Nuclear Information System (INIS)

    Kasinathan, Deepa; Lee, K.-W.; Pickett, W.E.

    2005-01-01

    Heavy carbon doping of MgB 2 is studied by first principles electronic structure studies of two types, an ordered supercell (Mg(B 1-x C x ) 2 , x 0.0833) and also the coherent potential approximation method that incorporates effects of B-C disorder. For the ordered model, the twofold degenerate σ-bands that are the basis of the high temperature superconductivity are split by 60 meV (i.e. 7 meV/% C) and the σ Fermi cylinders contain 0.070 holes/cell, compared to 0.11 for MgB 2 . A virtual crystal treatment tends to overestimate the rate at which σ holes are filled by substitutional carbon. The coherent potential approximation (CPA) calculations give the same rate of band filling as the supercell method. The occupied local density of states of C is almost identical to that of B in the upper 2 eV of the valence bands, but in the range -8 eV to -2 eV, C has a considerably larger density of states. The calculations indicate that the σ Fermi surface cylinders pinch off at the zone center only above the maximum C concentration x ∼ 0.10. These results indicate that Mg(B 1-x C x ) 2 as well as Mg 1-x Al x B 2 is a good system in which to study the evolution of the unusual electron-phonon coupling character and strength as the crucial σ hole states are filled

  15. MgB2 thick films on three-dimensional structures fabricated by HPCVD

    Science.gov (United States)

    Guo, Zhengshan; Cai, Xingwei; Liao, Xuebin; Chen, Yiling; Yang, Can; Niu, Ruirui; Luo, Wenhao; Huang, Zigeng; Feng, Qingrong; Gan, Zizhao

    2018-06-01

    Magnetic shielding has been a key factor in the measurement of ultra-weak magnetic fields, especially for shielding from low frequency electromagnetic noise. With the recent development of superconducting quantum interference devices, superconducting magnetic shielding has become an important area of research. MgB2 has shown great potential in magnetic shielding for its remarkable superconducting properties, the feasibility of its use in this capacity having been demonstrated by MgB2 bulk samples. However, the potential for application of such bulk samples is limited. In this work, we have investigated the possibility of the fabrication of MgB2 films on three-dimensional (3D) structures using a hybrid physical‑chemical vapor deposition system. MgB2 films 10 μm thick have been fabricated on the outer surface of a polycrystalline Al2O3 cylinder. The deposited film showed a transition temperature (TC) of 39 K and J C of 5.1 × 105 A · cm‑2, which are comparable to those of planar MgB2 films. This work shows the feasibility of depositing MgB2 films onto a 3D structure, and sheds light on the potential use of MgB2 films in superconducting magnetic shielding.

  16. Growth of high quality large area MgB2 thin films by reactive evaporation

    OpenAIRE

    Moeckly, Brian H.; Ruby, Ward S.

    2006-01-01

    We report a new in-situ reactive deposition thin film growth technique for the production of MgB2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB2 films for real-world applications. We have used this growth method, which incorporates a rotating pocket heater, to deposit MgB2 films on a variety of substrates, including single-crystalline, polycrystalline, metallic, and semiconductor materials u...

  17. Improving magnetic properties of MgB_2 bulk superconductors by synthetic engine oil treatment

    International Nuclear Information System (INIS)

    Taylan Koparan, E.; Savaskan, B.; Yanmaz, E.

    2016-01-01

    Highlights: • The effects of synthetic engine oil treatment on magnetic properties of bulk MgB_2 superconductors has been first time investigated and reported. • Synthetic engine oil used as a product which is cheap and a rich carbon source obviously has improved the superconducting magnetic properties of MgB_2. • The critical current density of all of MgB_2 samples immersed at different standby time in engine oil in whole field range has been better than that of the pure MgB_2 sample. • The MgB_2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. - Abstract: The present study focuses on the effects of standby time of the MgB_2 samples immersed in synthetic engine oil on the critical current density ( J_c(H)), magnetic field dependence of the pinning force density f_p(b) and T_c performances of MgB_2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB_2 pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB_2 samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB_2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB_2 sample because of the number of the pinning centers. The MgB_2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The J_c value for the pure sample is 2.0 × 10"3 A/cm"2, whereas for the MgB_2 sample immersed at 300 min standby time in engine oil the J_c is enhanced to 4.8 × 10"3 A/cm"2 at 5 K and 3 T. The superconducting transition temperature (T_c) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was obtained from the sample which kept in synthetic engine oil for 300 min. Synthetic engine oil treatment results in remarkable improvement of the critical current density and pinning force performances of MgB_2 superconductors. It was found that all MgB_2 samples have a different pinning property at different measuring temperatures. Using synthetic engine oil as a product which is cheap and a rich carbon source in MgB_2 bulk superconductors makes MgB_2 samples immersed in synthetic engine oil a good candidate for industrial applications.

  18. Lightweight MgB2 superconducting 10 MW wind generator

    Science.gov (United States)

    Marino, I.; Pujana, A.; Sarmiento, G.; Sanz, S.; Merino, J. M.; Tropeano, M.; Sun, J.; Canosa, T.

    2016-02-01

    The offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator's main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator.

  19. Lightweight MgB2 superconducting 10 MW wind generator

    International Nuclear Information System (INIS)

    Marino, I; Pujana, A; Sarmiento, G; Sanz, S; Merino, J M; Tropeano, M; Sun, J; Canosa, T

    2016-01-01

    The offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB 2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator’s main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator. (paper)

  20. Phthalocyanine doping to improve critical current densities in MgB2 tapes

    International Nuclear Information System (INIS)

    Zhang Xianping; Ma Yanwei; Wang Dongliang; Gao Zhaoshun; Wang Lei; Qi Yanpeng; Awaji, Satoshi; Watanabe, Kazuo; Mossang, Eric

    2009-01-01

    Phthalocyanine-doped MgB 2 tapes were prepared by the in situ powder-in-tube method. The relationships between the critical current properties, crystallinity and microstructure were studied as a function of the phthalocyanine doping level. It is found that both H irr and H c2 were improved when MgB 2 samples were doped with phthalocyanine, which are mainly attributed to the effective carbon substitution and enhanced flux pinning strength caused by very fine grain sizes. Furthermore, compared to pure samples, the MgO content remained almost unchanged in all doped tapes, which is very beneficial to having better grain connectivity in MgB 2 . Significantly improved J c was obtained in the phthalocyanine-doped MgB 2 tapes, especially under high magnetic fields.

  1. Progress in the deposition of MgB2 thin films

    International Nuclear Information System (INIS)

    Xi, X X; Pogrebnyakov, A V; Zeng, X H; Redwing, J M; Xu, S Y; Li, Qi; Liu, Zi-Kui; Lettieri, J; Vaithyanathan, V; Schlom, D G; Christen, H M; Zhai, H Y; Goyal, A

    2004-01-01

    An MgB 2 thin film deposition technology is the first critical step in the development of superconducting electronics utilizing the 39 K superconductor. It turned out to be a challenging task due to the volatility of Mg and phase stability of MgB 2 , the low sticking coefficients of Mg at elevated temperatures, and the reactivity of Mg with oxygen. A brief overview of current deposition techniques is provided here from a thermodynamic perspective, with an emphasis on a very successful technique for high quality in situ epitaxial MgB 2 films, the hybrid physical-chemical vapour deposition. Examples of heterostructures of MgB 2 with other materials are also presented

  2. Development of MgB2 superconductor wire with high critical current

    International Nuclear Information System (INIS)

    Kim, Chan Joong; Jun, Byung Hyuk; Park, Soon Dong; Kim, Nam Kyu; Kim, Yi Jeong; Yi, Ji Hye; Lee, Ji Hyun; Tan, Kai Sin

    2009-07-01

    The MgB 2 superconductor with smaller grain size could improve its critical properties by providing flux pinning centers with high grain boundary density. The effects of C doping such as charcoal, paper ash and glycerin on the superconducting properties was investigated for in situ processed MgB 2 samples using low purity semi-crystalline B powder. The results show a decrease in Tc and an enhancement of Jc at high fields for the C-doped samples as compared to the un-doped samples. A combined process of a mechanical ball milling and liquid glycerin (C 3 H 8 O 3 ) treatment of B powder has been conducted to enhance the superconducting properties of MgB 2 . The mechanical ball milling was effective for grain refinement, and a lattice disorder was easily achieved by glycerin addition. With the combined process, the critical properties was further increased due to a higher grain boundary density and a greater C substitution. To get fine grain structure of MgB 2 with high critical current properties, mechanical milling for as-received B powder and low temperature solid-state reaction of 550 or 600 .deg. C were attempted to in situ powder-in-tube processed MgB 2 /Fe wires. The critical current properties of the MgB 2 wires using the milled B powder were enhanced due to a smaller grain size and an increased volume of the superconducting phase. The solid-state reaction of a low temperature process for the samples using the milled B powder resulted in a poorer crystallinity with a smaller grain size, which improved superconducting properties. We established the system to measure the transport current properties of the MgB 2 wires. The field dependence of the transport Jc was evaluated for the MgB 2 wires heat-treated at different heat treatment conditions using ball-milled and glycerin-treated B powder. The MgB 2 magnet was developed and the AC loss of MgB 2 wire was also investigated. A conduction cooling device to cool the MgB 2 coil down to 4 K has been fabricated and the coil was tested up to 100 A

  3. Preparation of high quality superconducting thin MgB2 films for electronics

    International Nuclear Information System (INIS)

    Surdu, Andrei; Zdravkov, Vladimir; Sidorenko, Anatolie; Rossolenko, Anna; Ryazanov, Valerii; Bdikin, Igor; Kroemer, Oliver; Nold, Eberhard; Koch, Thomas; Schimmel, Thomas

    2007-01-01

    In this work we report the growth of high-Tc MgB 2 smooth films which are prepared in a two-step process: 1) deposition of the precursor films and 2) their annealing in Mg vapor with a specially designed, reusable reactor. Our method opens perspectives for the use of MgB 2 films in microelectronics, especially for high-frequency applications. (authors)

  4. Design of MgB2 Superconducting coils for the Ignitor Experiment*

    Science.gov (United States)

    Grasso, G.; Penco, R.; Berta, S.; Coppi, B.; Giunchi, G.

    2009-11-01

    A feasibility study for the adoption of MgB2 superconducting cables for the largest (about 5 m in diameter) of the poloidal field coils of the Ignitor machine is being carried out. This initiative was prompted by the progress made in the fabrication of MgB2 long cables, and related superconducting magnets of relatively large dimensions. These magnets will be cryocooled at the operating temperature of 10-15 K that is compatible with the He-gas cryogenic cooling system of Ignitor as well as with the projected superconducting current density of the MgB2 material, at the magnetic field values (˜4-5 T) in which these coils are designed to operate. The optimal cable configuration has been identified that can provide an efficient cooling of the MgB2 conductors over times compatible with the machine duty cycles. MgB2 superconductors hold the promise of becoming suitable for high field magnets by appropriate doping of the material and of replacing gradually the normal conducting coils adopted, by necessity, in high field experiments. Therefore, an appropriate R&D program on the development of improved MgB2 material and related superconducting cabling options has been undertaken, involving different institutions.

  5. Flux pinning behaviors of Ti and C co-doped MgB2 superconductors

    International Nuclear Information System (INIS)

    Yang, Y.; Zhao, D.; Shen, T.M.; Li, G.; Zhang, Y.; Feng, Y.; Cheng, C.H.; Zhang, Y.P.; Zhao, Y.

    2008-01-01

    Flux pinning behavior of carbon and titanium concurrently doped MgB 2 alloys has been studied by ac susceptibility and dc magnetization measurements. It is found that critical current density and irreversibility field of MgB 2 have been significantly improved by doping C and Ti concurrently, sharply contrasted to the situation of C-only-doped or Ti-only-doped MgB 2 samples. AC susceptibility measurement reveals that the dependence of the pinning potential on the dc applied field of Mg 0.95 Ti 0.05 B 1.95 C 0.05 has been determined to be U(B dc )∝B dc -1 compared to that of MgB 2 U(B dc )∝B dc -1.5 . As to the U(J) behavior, a relationship of U(J) ∝ J -0.17 is found fitting well for Mg 0.95 Ti 0.05 B 1.95 C 0.05 with respect to U(J) ∝ J -0.21 for MgB 2 . All the results reveal a strong enhancement of the high field pinning potential in C and Ti co-doped MgB 2

  6. Microwave surface impedance of MgB2 thin film

    International Nuclear Information System (INIS)

    Jin, B B; Klein, N; Kang, W N; Kim, Hyeong-Jin; Choi, Eun-Mi; Lee, Sung-I K; Dahm, T; Maki, K

    2003-01-01

    The microwave surface impedance Z s = R s + jωμ 0 λ was measured with dielectric resonator techniques for two c-axis-oriented MgB 2 thin films. The temperature dependence of the penetration depth λ measured with a sapphire resonator at 17.93 GHz can be well fitted from 5 K close to T c by the standard BCS integral expression assuming the reduced energy gap Δ(0)/kT c to be as low as 1.13 and 1.03 for the two samples. From these fits the penetration depth at zero temperatures was determined to be 102 nm and 107 nm, respectively. The results clearly indicate the s-wave nature of the order parameter. The temperature dependence of surface resistance R s , measured with a rutile dielectric resonator, shows an exponential behaviour below about T c /2 with a reduced energy gap being consistent with the one determined from the λ data. The R s value at 4.2 K was found to be as low as 19 μΩ at 7.2 GHz, which is comparable with that of a high-quality high-temperature thin film of YBa 2 Cu 3 O 7 . A higher-order mode at 17.9 GHz was employed to determine the frequency f dependence of R s ∝ f n(T) . Our results revealed a decrease of n with increasing temperature ranging from n = 2 below 8 K to n 1 from 13 to 34 K

  7. Aluminum and carbon substitution in MgB2. Electron doping and scattering effects

    International Nuclear Information System (INIS)

    Samuely, P.; Szabo, P.; Pribulova, Z.; Angst, M.; Bud'ko, S.L.; Canfield, P.C.; Klein, T.; Lyard, L.; Marcus, J.; Marcenat, C.; Kang, B.W.; Kim, H.-J.; Lee, H.-S.; Lee, H.-K.; Lee, S.I.

    2007-01-01

    The point-contact spectroscopy is used to address the evolution of two superconducting energy gaps in the Al- and C-doped magnesium diboride polycrystals and single crystals with T c 's from 39 to 22 K prepared by different techniques. The obtained evolution of two gaps does not show any anomalous behavior but can be consistently described by the combination of the (prevailing) band filling effect and a (minor) increased interband scattering as proposed by Kortus et al. [Kortus et al., Phys. Rev. Lett. 94 (2005) 027002]. The approaching of two gaps is stronger in the Al-doped systems but interband scattering is still not large enough to merge two gaps. The full merging can expected only for higher dopings with T c 's below 10-15 K. In-magnetic-field measurements are used to analyze the intraband scatterings introduced by these two substitutions. It is shown that the carbon doping introduces significant disorder mainly by decreasing the diffusion coefficient in the π band while the Al substitution leaves the samples in the clean limit

  8. Tuning the Superconducting Properties of Magnesium Diboride

    Energy Technology Data Exchange (ETDEWEB)

    Theoderich Wilke, Rudeger Heinrich [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    This work is presented in the following order: A review of the relevant physics and discussion of theoretical predictions for a two gap superconducting compound is given in chapter 2. Chapter 3 provides a review of the basic properties of MgB2. Details of sample synthesis and characterization are given in chapter 4. Chapter 5 presents normal state and superconducting properties of Mg(B1-xCx)2 wires. Attempts to increase critical current densities in filaments via titanium additions are discussed in chapter 6. In chapters 7 and 8 alternative methods for synthesizing doped MgB2 powders are explored. In chapter 7 we synthesize Mg(B1-xCx)2 up to x=0.069 using a mixture of Mg, B, and the binary compound B4C. Chapter 8 explores an alternative method, plasma spray synthesis, to produce nanometer sized doped boron powders for powder-in-tube applications. The effects of neutron irradiation on pure MgB2 wires is discussed in chapter 9. This is followed by a study of the effects of neutron irradiation on Mg(B.962C.038)2 wires, presented in chapter 10. I will summarize the results of all of these studies in chapter 11 and discuss future directions for research in understanding the physics behind this novel material as well as its development for practical applications. In this thesis I have presented the results of investigations into the changes in the superconducting properties of MgB2 as a function of carbon doping and neutron irradiation. The goal has been to understand the physics underlying this unique two-gap superconductor as different types of perturbations are made to the system. Such knowledge not only contributes to our understanding of two-gap superconductivity, but could potentially lead to the development of superconducting MgB2 wires for the use in power applications near 20 K.

  9. Assessment of liquid hydrogen cooled MgB2 conductors for magnetically confined fusion

    International Nuclear Information System (INIS)

    Glowacki, B A; Nuttall, W J

    2008-01-01

    Importantly environmental factors are not the only policy-driver for the hydrogen economy. Over the timescale of the development of fusion energy systems, energy security issues are likely to motivate a shift towards both hydrogen production and fusion as an energy source. These technologies combine local control of the system with the collaborative research interests of the major energy users in the global economy. A concept Fusion Island Reactor that might be used to generate H 2 (rather than electricity) is presented. Exploitation of produced hydrogen as a coolant and as a fuel is proposed in conjunction with MgB 2 conductors for the tokomak magnets windings, and electrotechnical devices for Fusion Island's infrastructure. The benefits of using MgB 2 over the Nb-based conductors during construction, operation and decommissioning of the Fusion Island Reactor are presented. The comparison of Nb 3 Sn strands for ITER fusion magnet with newly developed high field composite MgB 2 PIT conductors has shown that at 14 Tesla MgB 2 possesses better properties than any of the Nb 3 Sn conductors produced. In this paper the potential of MgB 2 conductors is examined for tokamaks of both the conventional ITER type and a Spherical Tokamak geometry. In each case MgB 2 is considered as a conductor for a range of field coil applications and the potential for operation at both liquid helium and liquid hydrogen temperatures is considered. Further research plans concerning the application of MgB 2 conductors for Fusion Island are also considered

  10. Enhancing the superconducting temperature of MgB2 by SWCNT dilution

    Science.gov (United States)

    Ma, Danhao; Jayasingha, Ruwantha; Hess, Dustin T.; Adu, Kofi W.; Sumanasekera, Gamini U.; Terrones, Mauricio

    2014-02-01

    We report, for the first time, an increase in the superconducting critical temperature, TC of commercial “dirty” MgB2 by a nonsubstitutional hole-doping of the MgB2 structure using minute, single-wall carbon nanotube (SWCNT) inclusions. We varied the SWCNTs concentration from 0.05 wt% to 5 wt% and investigated the temperature-dependent resistivity from 10 K to 300 K. We used micro-Raman spectroscopy, field-emission scanning electron microscopy, and X-ray diffraction to analyze the interfacial interactions between the SWCNTs and the MgB2 grains. We obtained an increase in TC from 33.0 to 37.8 K (ΔTC+=4.8 K), which is attributed to charge transfer from the MgB2 structure to the SWCNT structure. The charge transfer phenomenon is confirmed by micro-Raman analysis of the phonon states of the SWCNT tangential band frequency in the composites. We determined the charge transfer per carbon atom to be 0.0023/C, 0.0018/C and 0.0008/C for 0.05 wt%, 0.5 wt% and 5 wt% SWCNT inclusions, respectively, taking into account the contributions from the softening of the lattice constant and the nonadiabatic (dynamic) effects at the Fermi level. This report provides an experimental, alternative pathway to hole-doping of MgB2 without appealing to chemical substitution.

  11. MgB_{2} nonlinear properties investigated under localized high rf magnetic field excitation

    Directory of Open Access Journals (Sweden)

    Tamin Tai

    2012-12-01

    Full Text Available The high transition temperature and low surface resistance of MgB_{2} attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB_{2} at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the π band, the nonlinear response of MgB_{2} at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB_{2}, as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615 (2011ITASE91051-822310.1109/TASC.2010.2096531]. MgB_{2} films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.

  12. Evaluations of MgB2 Coatings on 2'' Copper Discs for Superconducting Radio Frequency Applications

    Science.gov (United States)

    Withanage, Wenura; Tan, Teng; Lee, Namhoon; Banjade, Huta; Eremeev, Grigory; Welander, Paul; Valente-Feliciano, Anne-Marie; Kustom, Robert; Wolak, Matthäus; Nassiri, Alireza; Xi, Xiaoxing

    We propose that coating the inner walls of copper RF cavities with superconducting MgB2 (Tc = 39 K) can result in a viable alternative to the already established niobium-based SRF technology. This approach improves the thermal conductivity, allows for operation at higher temperatures, and reduces the need for large helium refrigeration, thereby resulting in lower operational costs. For our studies, we grew MgB2 films via hybrid physical chemical vapor deposition (HPCVD) on 2'' Cu substrates. Since Mg and Cu readily form an alloy at higher temperatures, the HPCVD setup was modified in order to achieve lower deposition temperatures, minimize alloy formation, and provide high quality MgB2 films. This method yielded MgB2 coatings on 2'' Cu discs with transition temperatures around 38 K. The samples were characterized with regards to their RF attributes and showed similar performance in comparison to Nb reference samples. The presented results show that MgB2 coated copper can be a suitable alternative for use in SRF cavities.

  13. Energy gap in MgB2 superconductor: Andreev reflection studies

    International Nuclear Information System (INIS)

    Aswal, D.K.

    2003-01-01

    To investigate the nature of energy gap in MgB 2 superconductor, we have performed Andreev-reflection studies on MgB 2 / Ag planar junctions. The differential resistance (dV/dI) versus voltage (V) characteristics were recorded as a function of temperature, magnetic field and junction-type. The dV/dI vs V characteristic recorded at low temperature and zero-field for a clean MgB 2 / Ag planar junction exhibited several interesting features, such as, zero bias anomaly, a distinct double-minima, sharp resonance peaks near the energy gap etc. The data, however, could not be explained using Blonder-Tinkham-Klapwijk theory of isotropic superconductor, which indicated that energy gap in MgB 2 is not consistent with the weak-coupling BCS theory. This is further supported by unusual temperature and magnetic field dependence of the tunneling characteristics. The results indicate several possibilities for the energy gap in MgB 2 , such as, an anisotropic energy gap, two-energy or an unconventional gap scenario. (author)

  14. Design of MgB2 superconducting dipole magnet for particle beam transport in accelerators

    DEFF Research Database (Denmark)

    Abrahamsen, A.B.; Zangenberg, N.; Baurichter, A.

    2006-01-01

    for the collaborating company Danfysik A/S, which has a strongtradition in building resistive magnets for particle accelerators[4]. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European...... in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the criticalcurrent density of primarily MgB2 will be compared with current density determined by specifications similar to the Tevatron...... accelerator, B = 4:4 Tesla and coil aperture D = 76 mm [6], which has been identified by Danfysik A/S as interesting. It isconcluded that MgB2 is useful for the dipole application and construction of a small test coil of one half of the magnet is planned in 2007....

  15. Microstructure and pinning properties of hexagonal-disc shaped single crystalline MgB2

    Science.gov (United States)

    Jung, C. U.; Kim, J. Y.; Chowdhury, P.; Kim, Kijoon H.; Lee, Sung-Ik; Koh, D. S.; Tamura, N.; Caldwell, W. A.; Patel, J. R.

    2002-11-01

    We synthesized hexagonal-disc-shaped MgB2 single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from x-ray micro-diffraction showed the crystal symmetry of MgB2. A thorough crystallographic mapping within a single crystal showed that the edge and c axis of hexagonal-disc shape exactly matched the [101¯0] and the [0001] directions of the MgB2 phase. Thus, these well-shaped single crystals may be the best candidates for studying the direction dependences of the physical properties. The magnetization curve and the magnetic hysteresis curve for these single crystals showed the existence of a wide reversible region and weak pinning properties, which supported our single crystals being very clean.

  16. Possible superlattice formation in high-temperature treated carbonaceous MgB2 at elevated pressure

    International Nuclear Information System (INIS)

    Tschauner, Oliver; Errandonea, Daniel; Serghiou, George

    2006-01-01

    We report indications of a phase transition in carbonaceous MgB 2 above 9 GPa at 300 K after stress relaxation by laser heating. The transition was detected using Raman spectroscopy and X-ray diffraction. The observed changes are consistent with a second-order structural transition involving a doubling of the unit cell along c and a reduction of the boron site symmetry. Moreover, the Raman spectra suggest a reduction in electron-phonon coupling in the slightly modified MgB 2 structure consistent with the previously proposed topological transition in MgB 2 . However, further attributes including deviatoric stress, lattice defects, and compositional variation may play an important role in the observed phenomena

  17. Crystallinity and flux pinning properties of MgB2 bulks

    International Nuclear Information System (INIS)

    Yamamoto, A.; Shimoyama, J.; Ueda, S.; Katsura, Y.; Iwayama, I.; Horii, S.; Kishio, K.

    2006-01-01

    The relationship between flux pinning properties and crystallinity of MgB 2 bulks was systematically studied. Improved flux pinning properties under high fields were observed for samples with low crystallinity. Increased impurity scattering due to strain and defects in lattice corresponding to the degraded crystallinity was considered to enhance flux pinning strength at grain boundaries. Low-temperature synthesis and carbon substitution were confirmed to be effective for degrading crystallinity of MgB 2 bulks, resulting in high critical current properties under high fields

  18. Properties of stabilized MgB2 composite wire with Ti barrier

    International Nuclear Information System (INIS)

    Kovac, P; Husek, I; Melisek, T; Holubek, T

    2007-01-01

    Stabilized four-filament in situ MgB 2 /Ti/Cu/Monel composite wire was produced by the rectangular wire-in-tube (RWIT) technique. 10 wt% of nanosize SiC was added into the Mg-B powder mixture, which was packed into the Ti/Cu and Monel tubes, respectively. The assembled composite was two-axially rolled into wire and/or tape form and sintered at temperatures of 650-850 deg. C/0.5 h. Stabilized MgB 2 wire with Ti barrier is studied in terms of field-dependent transport critical current density, effects of filament size reduction and thermal stability

  19. Laser-induced thermoelectric voltage in normal state MgB2 thin films

    International Nuclear Information System (INIS)

    Zhao Songqing; Zhou Yueliang; Zhao Kun; Wang Shufang; Chen Zhenghao; Jin Kuijuan; Lue Huibin; Cheng Bolin; Yang Guozhen

    2006-01-01

    Laser-induced voltage has been observed in c-axis oriented MgB 2 thin film at room temperature. The amplitude of the signal is approximately proportional to the film thickness. For the film with the thickness of 150 nm, a very fast response has been detected when the film was irradiated by a 308 nm pulsed laser of 20 ns duration. The rise time and full width at half-maximum of the signal are about 3 and 25 ns, respectively. The physical origin of the laser-induced voltage can be attributed to a transverse thermoelectricity due to the anisotropic thermopower in MgB 2

  20. MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

    Directory of Open Access Journals (Sweden)

    Narendra Acharya

    2016-08-01

    Full Text Available In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc and high critical current density (Jc. The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

  1. Preparation of MgB2 superconducting microbridges by focused ion beam direct milling

    Science.gov (United States)

    Zhang, Xuena; Li, Yanli; Xu, Zhuang; Kong, Xiangdong; Han, Li

    2017-01-01

    MgB2 superconducting microbridges were prepared by focused ion beam (FIB) direct milling on MgB2 films. The surface topography of the microbridges were observed using SEM and AFM and the superconductivity was measured in this paper. Lots of cracks and holes were found near the milled area. And the superconducting transition temperature was decreased a lot and the bridges prepared were not superconducting due to ion damage after milled with large dose. Through these works, we explored the effect regular of FIB milling and experimental parameters on the performance of microbridges.

  2. Superconducting and normal state properties of carbon doped and neutron irradiated MgB2

    International Nuclear Information System (INIS)

    Wilke, R.H.T.; Samuely, P.; Szabo, P.; Holanova, Z.; Bud'ko, S.L.; Canfield, P.C.; Finnemore, D.K.

    2007-01-01

    Current research in MgB 2 focuses on the effects various types of perturbations have on the superconducting properties of this novel two-gap superconductor. In this article we summarize the effects of carbon doping and neutron irradiation in bulk MgB 2 . Low levels of carbon doping and light neutron irradiation result in significant enhancements in H c2 . At high fluences, where superconductivity is nearly fully suppressed, superconductivity can be restored through post exposure annealing. However, this results in a change in the interdependencies of the normal state and superconducting properties (ρ 0 , T c , H c2 ), with little or no enhancement in H c2

  3. The preliminary study of the quench protection of an MgB2

    Science.gov (United States)

    Juster, F. P.; Berriaud, C.; Bonelli, A.; Pasquet, R.; Przybilski, H.; Schild, T.; Scola, L.

    2014-01-01

    In the framework of general studies currently carried out at CEA/Saclay in collaboration with Sigmaphi Company on dry MgB2 magnet operating at 10 K and medium range field, 1 T up to 4 T., we plan to build a prototype-coil with a commercial MgB2 wire. This coil, the nominal axial magnetic field of which is 1 tesla, will be placed in a 3 teslas background field generated by a classical NbTi coil. This paper deals with the preliminary quench protection studies including stability and quench propagation modeling.

  4. Evaluation of carbon incorporation and strain of doped MgB2 superconductor by Raman spectroscopy

    International Nuclear Information System (INIS)

    Yeoh, W.K.; Zheng, R.K.; Ringer, S.P.; Li, W.X.; Xu, X.; Dou, S.X.; Chen, S.K.; MacManus-Driscoll, J.L.

    2011-01-01

    Raman spectroscopy is employed to study both the strain and the carbon substitution level in SiC-doped MgB 2 bulk samples. Raman spectroscopy was demonstrated to be a better method to distinguish the individual influences of strain and carbon than standard X-ray diffraction. It is found that the lattice parameter correlation method for C content determination is invalid for highly strained samples. Our result also provides an alternative explanation for lattice variation in non-carbon-doped MgB 2 , which is basically due to lattice strain.

  5. Defect structures in MgB2 wires introduced by hot isostatic pressing

    International Nuclear Information System (INIS)

    Liao, X Z; Serquis, A; Zhu, Y T; Civale, L; Hammon, D L; Peterson, D E; Mueller, F M; Nesterenko, V F; Gu, Y

    2003-01-01

    The microstructures of MgB 2 wires prepared by the powder-in-tube technique and subsequent hot isostatic pressing were investigated using transmission electron microscopy. A large amount of crystalline defects including small-angle twisting, tilting and bending boundaries, in which high densities of dislocations reside, was found forming sub-grains within MgB 2 grains. It is believed that these defects resulted from particle deformation during the hot isostatic pressing process and are effective flux pinning centres that contribute to the high critical current densities of the wires at high temperatures and at high fields

  6. Quantitative electron microscopy and spectroscopy of MgB2 wires and tapes

    International Nuclear Information System (INIS)

    Birajdar, B; Peranio, N; Eibl, O

    2008-01-01

    In MgB 2 the correlation of microstructure with superconducting properties, in particular the critical current density, requires powerful analytical tools. Critical current densities and electrical resistivities of different MgB 2 superconductors differ by orders of magnitudes and the current limiting mechanisms have not been fully understood. Granularity of MgB 2 is one significant reason for reduced critical current densities and is introduced intrinsically by the anisotropy of B c2 but also extrinsically by the microstructure of the material. B c2 enhancement by doping is another important challenge for chemical analysis and, at present, doping levels are not well controlled on the sub-μm scale. In this paper the quantitative electron microscopy and spectroscopy methods essential for the microstructural analysis of MgB 2 are described. By quantitative electron microscopy and spectroscopy we mean a combined SEM and TEM analysis that covers various length scales from μm to nm. Contamination-free sample preparation, chemical mapping including B, and advanced chemical quantification using x-ray microanalysis were essential elements of the applied methodology. The methodology was applied to in situ and ex situ MgB 2 wires and tapes with and without SiC additives. Quantitative B analysis by EDX spectroscopy was applied quantitatively in the SEM and TEM, which is a major achievement. Although MgB 2 is a binary system, the thermodynamics of phase formation is complex, and the complexity is dramatically increased if additives like SiC are used. The small, sub-μm grain sizes of the matrix and secondary phases require TEM methods. However, granularity on the μm scale was also identified and underlines the importance of the combined SEM and TEM studies. Significant differences in the microstructure were observed for in situ and ex situ samples. This holds particularly if SiC was added and yielded Mg 2 Si for in situ samples annealed at 600-650 deg. C and Mg-Si-O phases for ex situ samples annealed between 900-1050 deg. C. Only with such a systematic approach combining a large number of microscopy and spectroscopy methods, could a microstructure critical current density model be established that will be presented in another paper. Four microstructural parameters were identified as relevant for the critical current density of wires and tapes and these were: (1) MgB 2 grain size, (2) colony size (a colony is a dense arrangement of MgB 2 grains), (3) oxygen content and (4) volume fraction of B-rich secondary phases. MgB 2 grain size can only be determined by TEM, while colony size, oxygen content and volume fraction of B-rich secondary phases were determined by SEM methods. The formation of oxides was also studied in detail by TEM methods. The importance of electron microscopy methods in the understanding of the thermodynamics of phase formation in MgB 2 as well as in improving the synthesis technology and the superconducting properties of MgB 2 wires and tapes is described. (topical review)

  7. RAPID COMMUNICATION: Formation of MgB2 at ambient temperature with an electrochemical process: a plausible mechanism

    Science.gov (United States)

    Jadhav, A. B.; Subhedar, K. M.; Hyam, R. S.; Talaptra, A.; Sen, Pintu; Bandyopadhyay, S. K.; Pawar, S. H.

    2005-06-01

    The binary intermetallic MgB2 superconductor has been synthesized by many research groups. However, the mechanism of its formation is not clearly understood. In this communication, a comprehensive mechanism of the formation of MgB2 from Le Chatelier's principle of equilibrium reaction has been explained both for solid-state reaction and electrodeposition methods.

  8. An innovative technique to synthesize C-doped MgB2 by using chitosan as the carbon source

    International Nuclear Information System (INIS)

    Bovone, G; Kawale, S; Siri, A S; Vignolo, M; Bernini, C

    2014-01-01

    Here, we report a new technique to synthesize carbon-doped MgB 2 powder. Chitosan was innovatively used as the carbon source during the synthesis of boron from boron oxide. This allowed the introduction of local defects, which later on served as pinning centers in MgB 2 , in the boron lattice itself, avoiding the traditional and time consuming ways of ex situ MgB 2 doping (e.g. ball milling). Two volume percentages of C-doping have been tried and its effect on the superconducting properties, evaluated by magnetic and transport measurements, are discussed here. Morphological analysis by scanning electron microscopy revealed nano-metric grains’ distribution in the boron and MgB 2 powder. Mono-filamentary MgB 2 wires have been fabricated by an ex situ powder-in-tube technique by using the thus prepared carbon-doped MgB 2 and pure MgB 2 powders. Transport property measurements on these wires were made and compared with MgB 2 wire produced using commercial boron. (fast track communication)

  9. Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB2

    International Nuclear Information System (INIS)

    Zhao, Y.; Ke, C.; Cheng, C.H.; Feng, Y.; Yang, Y.; Munroe, P.

    2010-01-01

    Nano-diamond and titanium concurrently doped MgB 2 nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on J c -H behavior and pinning force scaling features of MgB 2 have been investigated. Although T c was slightly depressed, J c of MgB 2 have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the J c value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB 2 , a unique nanocomposite in which TiB 2 forms a thin layer surrounding MgB 2 grains whereas nano-diamond particles were wrapped inside the MgB 2 grains. Besides, nano-diamond doping results in a high density stress field in the MgB 2 samples, which may take responsibility for the Δκ pinning behavior in the carbon-doped MgB 2 system.

  10. Feasibility study on partial insulation winding technique for the development of self-protective MgB2 magnet

    Science.gov (United States)

    Kim, Y. G.; Kim, J. C.; Kim, J. M.; Yoo, B. H.; Hwang, D. Y.; Lee, H. G.

    2018-06-01

    This study investigates the feasibility of using the partial insulation winding technique for the development of a self-protective MgB2 MRI magnet with a fast charge-discharge rate. Charge-discharge and quench tests for a prototype PI MgB2 magnet confirmed that the magnet was successfully operated at full-field performance and exhibited self-protecting behavior in the event of a quench. Nonetheless, the required time to charge the 0.5-T/300-mm PI MgB2 magnet was almost five days, implying that the charge-discharge delay of the PI MgB2 magnet still needs to be ameliorated further to develop a real-scale MgB2 MRI magnet with a fast charge-discharge rate.

  11. Composite superconducting MgB2 wires made by continuous process

    NARCIS (Netherlands)

    Kutukcu, Mehmet; Atamert, Serdar; Scandella, Jean Louis; Hopstock, Ron; Blackwood, Alexander C.; Dhulst, Chris; Mestdagh, Jan; Nijhuis, Arend; Glowacki, Bartek A.

    Previously developed manufacturing technology of a low-cost composite single core MgB2 superconductive wires has been investigated in details using monel sheath and titanium diffusion barrier. In this process Mg and nano-sized B as well as SiC dopant powders were fed continuously to a "U" shaped

  12. Critical current and cryogenic stability modelling of filamentary MgB2 conductors

    DEFF Research Database (Denmark)

    Glowacki, B.A.; Majoros, M.; Tanaka, K.

    2006-01-01

    The modelling of a single filament, 6 filaments and 19 filaments MgB(2) conductors was performed for two limiting cases: a) isothermal conditions considering J(c)(B) dependence, b) considering heating effects but with J(c) magnetic field independent. As a starting point of the modelling in case a...

  13. Scanning tunneling spectroscopy on neutron irradiated MgB2 thin films

    International Nuclear Information System (INIS)

    Di Capua, Roberto; Salluzzo, Marco; Vaglio, Ruggero; Ferdeghini, Carlo; Ferrando, Valeria; Putti, Marina; Xi Xiaoxing; Aebersold, Hans U.

    2007-01-01

    Neutron irradiation was performed on MgB 2 thin films grown by hybrid physical chemical vapor deposition. Samples irradiated with different neutron fluences, having different critical temperatures, were studied by scanning tunneling spectroscopy in order to investigate the effect of the introduced disorder on the superconducting and spectroscopic properties. A monotonic increase of the π gap with increasing disorder was found

  14. Composite superconducting MgB2 wires made by continuous process

    NARCIS (Netherlands)

    Kutukcu, Mehmet; Atamert, Serdar; Scandella, Jean Louis; Hopstock, Ron; Blackwood, Alexander C.; Dhulst, Chris; Mestdagh, Jan; Nijhuis, Arend; Glowacki, Bartek A.

    2018-01-01

    Previously developed manufacturing technology of a low-cost composite single core MgB2 superconductive wires has been investigated in details using monel sheath and titanium diffusion barrier. In this process Mg and nano-sized B as well as SiC dopant powders were fed continuously to a "U" shaped

  15. Two ways to model voltage-current curves of adiabatic MgB2 wires

    International Nuclear Information System (INIS)

    Stenvall, A; Korpela, A; Lehtonen, J; Mikkonen, R

    2007-01-01

    Usually overheating of the sample destroys attempts to measure voltage-current curves of conduction cooled high critical current MgB 2 wires at low temperatures. Typically, when a quench occurs a wire burns out due to massive heat generation and negligible cooling. It has also been suggested that high n values measured with MgB 2 wires and coils are not an intrinsic property of the material but arise due to heating during the voltage-current measurement. In addition, quite recently low n values for MgB 2 wires have been reported. In order to find out the real properties of MgB 2 an efficient computational model is required to simulate the voltage-current measurement. In this paper we go back to basics and consider two models to couple electromagnetic and thermal phenomena. In the first model the magnetization losses are computed according to the critical state model and the flux creep losses are considered separately. In the second model the superconductor resistivity is described by the widely used power law. Then the coupled current diffusion and heat conduction equations are solved with the finite element method. In order to compare the models, example runs are carried out with an adiabatic slab. Both models produce a similar significant temperature rise near the critical current which leads to fictitiously high n values

  16. The Raman spectrum and lattice parameters of MgB2 as a function of temperature

    International Nuclear Information System (INIS)

    Shi Lei; Zhang Huarong; Chen Lin; Feng Yong

    2004-01-01

    The temperature dependences of the Raman spectrum and lattice parameters of polycrystalline MgB 2 have been investigated by means of Raman spectroscopy and x-ray diffraction. It is found that the lattice parameters show an approximately linear change with the temperature decrease, giving different thermal expansions along the a- and c-axes, which is caused by the comparatively weak metal-boron bonding in MgB 2 . The grain size of MgB 2 determined by means of x-ray diffraction is around 45 nm for both [100] and [001] directions. There is no evidence for any structural transition while the temperature changes from 300 K down to 12 K. An anomalous Raman band at 603 cm -1 is observed, which is consistent with the theoretical prediction for the E 2g in-plane boron stretching mode. The Raman frequency increases and the linewidth decreases as the temperature decreases. A possible origin of the temperature dependences of the Raman frequency and the linewidth is discussed. It is suggested that the grain size effect of MgB 2 on the nanometric scale will have a clear influence on the frequency and the linewidth of the Raman spectrum

  17. Design of an MgB2 race track coil for a wind generator pole demonstration

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Jensen, Bogi Bech

    2014-01-01

    An MgB2 race track coil intended for demonstrating a down scaled pole of a 10 MW direct drive wind turbine generator has been designed. The coil consists of 10 double pancake coils stacked into a race track coil with a cross section of 84 mm × 80 mm. The length of the straight section is 0.5 m...

  18. Electrical, Structural and Mechanical Properties of Superconducting MGB2/MG Composites

    International Nuclear Information System (INIS)

    Ulucan, S.

    2004-01-01

    The brittle nature of MgB 2 does not allow this material to be used as a stand-alone material for large scale applications based on wire production. MgB 2 /Mg composites were prepared using metal matrix composite fabrication technique. To obtain composites MgB 2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical dye under the pressure of 0.5 GPa and 1.0 GPa for two hours at various temperatures. XRD, SEM and EDX techniques were used for phase identification and microstructural studies. Resistivities of the composites were measured between 20 K and room temperature. The effect of temperature on the mechanical properties of MgB 2 /Mg composites was investigated. For this purpose, compressive mechanical testing was performed to measure elastic modulus and strain at failure values of the composites. It was found that the relative weight fraction of the powders and the temperature have same considerable effect on the electrical, microstructural and the mechanical properties of the composites

  19. Microwave Synthesis and Magnetic Properties of High Tc Superconductor MGB2

    International Nuclear Information System (INIS)

    Koeseoglu, Y.

    2004-01-01

    Polycrystalline powders of MgB 2 have been synthesized by microwave synthesis technique. Crystallographic information of the sample was investigated by powder X-ray diffraction (XRD). The main phase was determined as MgB2, and secondary phases as MgB4 and MgO. The temperature dependence of magnetic properties of polycrystalline MgB2, synthesized by using microwave heating of the constituents have been characterized by SQUID magnetometer and X-band EPR spectrometer. The transition temperature to the superconducting phase is observed as 39K for both measurements. An isotropic, strong and very narrow EPR signal corresponding to free electron g-value (ge=2.0023) is observed. The observed line broadening with decreasing temperature might arise from the dipolar interactions between the superparamagnetic nanoparticles. Normally, the internal magnetic field originating from magnetic entities is expected to be more uniform as a result of highly ordered magnetic moments at low temperatures; giving narrower ESR line in contrary in our case. While the ESR line is broadened, the signal intensity is drastically decreased just below T c =39 K corresponding to a transition temperature from normal to superconducting state. Some minor changes in both intensity and line width curves might be taken as signs for changes of local crystalline field symmetry around weakly localized conduction electrons or holes, which are the sources of ESR signal in MgB 2 compound

  20. Texture gradients in Fe-sheathed ex situ produced MgB2 tapes

    International Nuclear Information System (INIS)

    Lezza, P; Gladyshevskii, R; Abaecherli, V; Fluekiger, R

    2006-01-01

    Superconducting Fe-sheathed MgB 2 monofilamentary tapes have been fabricated by the powder-in-tube technique, varying the particle size of the starting MgB 2 powder and applying either cold or hot rolling during the last deformation process. Measurements of the critical current density J c with the magnetic field applied parallel or perpendicular to the tape surface revealed a pronounced anisotropy for the cold rolled tapes, which was found to increase with increasing particle size and magnetic field strength. The microstructural origin of the J c anisotropy was confirmed by means of x-ray diffraction performed on the filaments after mechanical removal of the sheath. The local texture was studied in a series of diffraction patterns collected at different distances from the filament centre, removing each time some 25 μm of the filament thickness. In the cold rolled tapes, the average orientation of the MgB 2 grains was found to approach a preferred orientation with the crystallographic c-axis perpendicular to the tape surface, near the interface with the sheath; however, the misalignment angle increased towards the centre of the tape. In the hot rolled tapes, for which no J c anisotropy was observed, the grains were found to be approximately randomly oriented. Roughness measurements performed on the side of the Fe sheath in contact with the MgB 2 filament are in agreement with the difference in texture observed for cold and hot rolled tapes

  1. Pinning enhancement in MgB2 superconducting thin films by ...

    Indian Academy of Sciences (India)

    The magnetic field dependence of the critical current density Jc was calculated from the M–H loops and magnetic field dependence of ... MgB2 thin film; Fe2O3 nanoparticles; critical current density; r-plane Al2O3 substrate. 1. Introduction. The discovery of ... It was thought that from these cal- culations, one can choose an ...

  2. Low-temperature dependence of the optical conductivity in superconductor MgB2

    International Nuclear Information System (INIS)

    Shahzamanian, M.A.; Yavary, H.; Moarrefi, M.

    2005-01-01

    The real part of the optical conductivity is calculated by using the Kubo formula approach, and in the framework of the two-bands model. It is shown that a single-gap model is insufficient to describe the optical behavior of superconductor MgB 2 film, but the two-gap model with different symmetries is sufficient to explain the experimental results

  3. Doping effects of carbon and titanium on the critical current density of MgB2

    International Nuclear Information System (INIS)

    Shen, T M; Li, G; Cheng, C H; Zhao, Y

    2006-01-01

    MgB 2 bulks doped with Ti or/and C were prepared by an in situ solid state reaction method to determine the combined effect of C and Ti doping and to probe the detailed mechanism. The magnetization measurement shows that Mg 0.95 Ti 0.05 B 1.95 C 0.05 sample has significantly improved flux pinning compared to the MgB 1.95 C 0.05 sample at 20 K, indicating that C and Ti are largely cooperative in improving the J c (H) behaviour. No TiC phase was detected in the x-ray diffraction (XRD) patterns. Moreover, the overlap of the (100) peaks of MgB 1.95 C 0.05 and Mg 0.95 Ti 0.05 B 1.95 C 0.05 showed that Ti doping does not reduce the amount of C in MgB 2 . Microstructural analyses revealed that the addition of Ti eliminated the porosity present in the carbon-doped MgB 2 pellet, resulting in an improved intergrain connectivity and an increase of effective current pass. Further, MgB 2 doped with C and Ti, which mainly consists of spherical grains about 200-300 nm in size, shows an higher grain homogeneity than the C-doped sample, suggesting that the Ti doping in MgB 1-x C x has played an important role in obtaining uniform grains

  4. Low AC-Loss Superconducting Cable Technology for Electric Aircraft Propulsion, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The availability of low AC loss magnesium diboride (MgB2) superconducting wires enables much lighter weight superconducting stator coils than with any other metal or...

  5. Thickness dependence of J_c (0) in MgB_2 films

    International Nuclear Information System (INIS)

    Chen, Yiling; Yang, Can; Jia, Chunyan; Feng, Qingrong; Gan, Zizhao

    2016-01-01

    Highlights: • A serial of MgB_2 superconducting films from 10 nm to 8 µm have been prepared. • T_c and J_c (5 K, 0 T) of films are high. • J_c (5 K, 0 T) reaches its maximum 2.3 × 10"8 A cm"−"2 for 100 nm films. • The relationship between thickness and J_c has been discussed in detail. - Abstract: MgB_2 superconducting films, whose thicknesses range from 10 nm to 8 µm, have been fabricated on SiC substrates by hybrid physical–chemical vapor deposition (HPCVD) method. It is the first time that the T_c and the J_c of MgB_2 films are studied on such a large scale. It is found that with the increasing of thickness, T_c elevates first and then keeps roughly stable except for some slight fluctuations, while J_c (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum J_c (5 K, 0 T) = 2.3 × 10"8 A cm"−"2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB_2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB_2 films.

  6. Multiple superconducting gaps in MgB2 single crystals from magnetic torque

    International Nuclear Information System (INIS)

    Atsumi, Toshiyuki; Xu, Mingxiang; Kitazawa, Hideaki; Ishida, Takekazu

    2004-01-01

    We have measured the magnetic torque of an MgB 2 single crystal in the various different fields below 10 kG by using a torque magnetometer and a 4 K closed cycle refrigerator. The MgB 2 single crystal was synthesized by the vapor transport method. The torque can be measured as an off-balance signal of the Wheatstone bridge of the four piezoresistors on a Si cantilever. The torque curves are analyzed by the Kogan model. The superconducting anisotropy γ is rather independent of temperature in 5 and 10 kG, but is dependent on field up to 60 kG. We consider that the field dependence of γ comes from the nature of the multiple superconducting gaps. The experimental results show that the π-band superconducting gaps have been deteriorated gradually up to a crossover field H * (π) ∼ 20 kG at 10 K when the magnetic field increases

  7. Influence of iridium doping in MgB2 superconducting wires

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2018-01-01

    MgB2 wires with iridium doping were manufactured using the in-situ technique in a composite Cu-Nb sheath. Reaction was performed at 700°C, 800°C or 900°C for 1h in argon atmosphere. A maximum of about 1.5 at.% Ir replaces Mg in MgB2. The superconducting transition temperature is slightly lowered...... by Ir doping. The formation of IrMg3 and IrMg4 secondary phase particles is evidenced, especially for a nominal stoichiometry with 2.0 at.% Ir doping. The critical current density and accommodation field of the wires are strongly dependent on the Ir content and are generally weakened in the presence...

  8. Mixed-state flux dynamics in bulk MgB2

    International Nuclear Information System (INIS)

    Li Shi; Taylor, B.J.; Frederick, N.A.; Maple, M.B.; Nesterenko, V.F.; Indrakanti, S.S.

    2002-01-01

    Electric field vs. current density (E-J) isotherms in the mixed-state of a bulk sample of the high-temperature superconductor MgB 2 (T c =38.5 K), synthesized under 200 MPa pressure by hot isostatic pressing (HIPing), have been measured and analyzed in terms of the critical scaling model. Magnetization data reveal distinctly different critical current density (J c ) behaviors in high and low magnetic field critical scaling regions. E-J isotherm sets at fields ranging from 2 to 90 kOe conform to the vortex-glass (VG) scaling anzatz. Scaling analysis, resistivity data and J c data suggest that a Bragg-glass state may exist for H c2 (T), the VG transition line H g (T), and the magnetic irreversibility line H irr (T) has been established for bulk MgB 2

  9. MgB2 thin films on silicon nitride substrates prepared by an in situ method

    International Nuclear Information System (INIS)

    Monticone, Eugenio; Gandini, Claudio; Portesi, Chiara; Rajteri, Mauro; Bodoardo, Silvia; Penazzi, Nerino; Dellarocca, Valeria; Gonnelli, Renato S

    2004-01-01

    Large-area MgB 2 thin films were deposited on silicon nitride and sapphire substrates by co-deposition of Mg and B. After a post-annealing in Ar atmosphere at temperatures between 773 and 1173 K depending on the substrate, the films showed a critical temperature higher than 35 K with a transition width less than 0.5 K. The x-ray diffraction pattern suggested a c-axis preferential orientation in films deposited on amorphous substrate. The smooth surface and the good structural properties of these MgB 2 films allowed their reproducible patterning by a standard photolithographic process down to dimensions of the order of 10 μm and without a considerable degradation of the superconducting properties

  10. MgB2 energy gap determination by scanning tunnelling spectroscopy

    International Nuclear Information System (INIS)

    Heitmann, T W; Bu, S D; Kim, D M; Choi, J H; Giencke, J; Eom, C B; Regan, K A; Rogado, N; Hayward, M A; He, T; Slusky, J S; Khalifah, P; Haas, M; Cava, R J; Larbalestier, D C; Rzchowski, M S

    2004-01-01

    We report scanning tunnelling spectroscopy (STS) measurements of the gap properties of both ceramic MgB 2 and c-axis oriented epitaxial MgB 2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunnelling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap δ = 2.2-2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, δ 7.2 meV, consistent with a proposed two-band model

  11. Effect of sheath material on critical current characteristics of MgB2 at high temperatures

    International Nuclear Information System (INIS)

    Kiuchi, M.; Yamauchi, K.; Kurokawa, T.; Otabe, E.S.; Matsushita, T.; Okada, M.; Tanaka, K.; Kumakura, H.; Kitaguchi, H.

    2004-01-01

    Critical current density and irreversibility field were measured at various temperatures and magnetic fields for MgB 2 PIT tape specimens with different sheaths materials. The experimental results were compared with theoretical estimations using the flux creep-flow model. It is found that the hardness of sheath material indirectly affects the pinning property only through the packing density of MgB 2 . It is considered that the critical current density is mainly determined by a low value of distributed local critical current density determined by grain connectivity. On the other hand, the irreversibility field which is approximately the same among the three tapes is mainly determined by the average pinning strength

  12. MgB2 superconducting particles in a strong electric field

    International Nuclear Information System (INIS)

    Tao, R.; Xu, X.; Amr, E.

    2003-01-01

    The electric-field induced ball formation has been observed with MgB 2 powder in a strong static or quasi-static electric field. The effect of temperature and magnetic field on the ball formation shows surprising features. For quite a wide range of temperature from T c =39 K and below, the ball size is proportional to (1-T/T c ). As the temperature further goes below 20 K, the ball size becomes almost a constant. If MgB 2 particles are in a strong electric field and a moderate magnetic field, the electric-field induced balls align in the magnetic-field direction to form ball chains

  13. Raman spectra of MgB2 at high pressure and topological electronic transition

    International Nuclear Information System (INIS)

    Meletov, K.P.; Kulakov, M.P.; Kolesnikov, N.N.; Arvanitidis, J.; Kourouklis, G.A.

    2002-01-01

    Raman spectra of the MgB 2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ∼ 590 cm -1 related to the E 2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 18 GPa, whereas beyond this region the slope of the pressure-induced frequency shift is reduced by about a factor of two. The pressure dependence of the phonon mode up to ∼ 5 GPa exhibits a change in the slope as well as a hysteresis effect in the frequency vs. pressure behavior. These singularities in the E 2g mode behavior under pressure support the suggestion that MgB 2 may undergo a pressure-induced topological electronic transition [ru

  14. Scaling behavior of mixed-state hall effect in MgB2 thin films

    International Nuclear Information System (INIS)

    Jung, Soon-Gil; Seong, W.K.; Kang, W.N.; Choi, Eun-Mi; Kim, Heon-Jung; Lee, Sung-Ik; Kim, Hyeong-Jin; Kim, H.C.

    2006-01-01

    The Hall resistivity (ρ xy ) and the longitudinal resistivity (ρ xx ) in c-axis-oriented superconducting MgB 2 thin films have been investigated in extended fields up to 18T. We have observed a scaling behavior between the Hall resistivity and the longitudinal resistivity, ρ xy =Aρ xx β , where the exponent (β) is observed to be independent of the temperatures and the magnetic fields. For a wide magnetic field region from 1 to 18T and a wide temperature region from 10 to 28K, a universal power law with β=2.0+/-0.1 was observed in c-axis-oriented MgB 2 thin films. These results can be well interpreted by using recent models

  15. Quench Property of Twisted-Pair MgB$_2$ Superconducting Cables in Helium Gas

    CERN Document Server

    Spurrell, J; Falorio, I; Pelegrin, J; Ballarino, A; Yang, Y

    2015-01-01

    CERN's twisted-pair superconducting cable is a novel design which offers filament transposition, low cable inductance and is particularly suited for tape conductors such as 2G YBCO coated conductors, Ag-sheathed Bi2223 tapes and Ni/Monel-sheathed MgB2 tapes. A typical design of such twistedpair cables consists of multiple superconducting tapes intercalated with thin copper tapes as additional stabilizers. The copper tapes are typically not soldered to the superconducting tapes so that sufficient flexibility is retained for the twisting of the tape assembly. The electrical and thermal contacts between the copper and superconducting tapes are an important parameter for current sharing, cryogenic stability and quench propagation. Using an MgB2 twisted-pair cable assembly manufactured at CERN, we have carried out minimum quench energy (MQE) and propagation velocity (vp) measurements with point-like heat deposition localized within a tape. Furthermore, different contacts between the copper and superconductor aroun...

  16. Low-field vortex pinning model for undoped sintered MgB2 powders

    International Nuclear Information System (INIS)

    Agassi, Y D

    2011-01-01

    Sintered MgB 2 powders constitute a porous ensemble of irregularly shaped agglomerates of tightly packed grains. The low-field critical current density in such powders was experimentally observed to scale with the inverse of the average agglomerate size. Motivated by this observation we consider a flux pinning model which accounts for the MgB 2 powder porosity by focusing on a single finite-size agglomerate size. According to the model the observed critical current density dependence on the agglomerate size reflects the outward pull exerted on a vortex that is pinned in proximity to the agglomerate edges. The calculated critical current density replicates the observed scaling within agglomerate-size bounds. Implications of the model are discussed.

  17. Small Fermi energy, strong electron-phonon effects and anharmonicity in MgB2

    International Nuclear Information System (INIS)

    Cappelluti, E.; Pietronero, L.

    2007-01-01

    The investigation of the electron-phonon properties in MgB 2 has attracted a huge interest after the discovery of superconductivity with T c 39 K in this compound. Although superconductivity is often described in terms of the conventional Eliashberg theory, properly generalized in the multiband/multigap scenario, important features distinguish MgB 2 from other conventional strong-coupling superconductors. Most important it is the fact that a large part of the total electron-phonon strength seems to be concentrated here in only one phonon mode, the boron-boron E 2g stretching mode. Another interesting property is the small Fermi energy of the σ bands, which are strongly coupled with the E 2g mode. In this contribution, we discuss how the coexistence of both these features give rise to an unconventional phenomenology of the electron-phonon properties

  18. Direct observation of superconducting gaps in MgB 2 by angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J. C.; Sasaki, S.; Kadowaki, K.

    2004-08-01

    High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2. We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2.

  19. Direct observation of superconducting gaps in MgB2 by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Souma, S.; Machida, Y.; Sato, T.; Takahashi, T.; Matsui, H.; Wang, S.-C.; Ding, H.; Kaminski, A.; Campuzano, J.C.; Sasaki, S.; Kadowaki, K.

    2004-01-01

    High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2 . We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2

  20. Transport properties and Raman spectra of impurity substituted MgB2

    International Nuclear Information System (INIS)

    Masui, T.

    2007-01-01

    Recent advances in the study of MgB 2 are reviewed, with focus on the transport properties and Raman scattering measurements for impurity substituted crystals. Carbon and Aluminium substitution change band filling, introduce intraband and interband scattering. These effects are seen in the temperature dependence of resistivity, Hall coefficients, and phonon peak of Raman spectra. Manganese substitution introduces magnetic scattering, that increases resistivity but gives little change in Raman spectra. The effect of disorder in neutron irradiated samples is also discussed

  1. Surface barrier and bulk pinning in MgB$_2$ superconductor

    OpenAIRE

    Pissas, M.; Moraitakis, E.; Stamopoulos, D.; Papavassiliou, G.; Psycharis, V.; Koutandos, S.

    2001-01-01

    We present a modified method of preparation of the new superconductor MgB$_2$. The polycrystalline samples were characterized using x-ray and magnetic measurements. The surface barriers control the isothermal magnetization loops in powder samples. In bulk as prepared samples we always observed symmetric magnetization loops indicative of the presence of a bulk pinning mechanism. Magnetic relaxation measurements in the bulk sample reveal a crossover of surface barrier to bulk pinning.

  2. Design study of a 10 MW MgB2 superconductor direct drive wind turbine generator

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Liu, Dong

    2014-01-01

    A design study of a 10 MW direct drive wind turbine generator based on MgB2 superconducting wires is presented and the cost of the active materials of the generator is estimated to be between 226 €/kW and 84 €/kw, which is lower than the threshold values of 300 €/kW of the INNWIND.EU project. A n...

  3. Tunneling Spectroscopy of the Energy Gap in MgB2 Under Magnetic Fields

    International Nuclear Information System (INIS)

    Ekino, T.; Takasaki, T.; Fujii, H.; Muranaka, T.; Akimitsu, J.

    2003-01-01

    Effects of magnetic field on the multiple-gap structure in the superconductor MgB 2 have been studied by break junctions. With increasing the field, the gap value decreases with filling up of the states inside of the gap. The gap-closing field B c correlates with the gap size. The extrapolated B c value for the larger gap is almost consistent with the upper critical field of this compound. (author)

  4. Enhancement of Jc of MgB2 thin films by introduction of oxygen during deposition

    International Nuclear Information System (INIS)

    Mori, Zon; Doi, Toshiya; Hakuraku, Yoshinori; Kitaguchi, Hitoshi

    2006-01-01

    The introduction of various pinning center are examined as the effective means for improvement of J c of MgB 2 thin films. We have investigated the effects of introduction of oxygen during deposition on the superconducting properties of MgB 2 thin films. MgB 2 thin films were prepared on polished sapphire C(0001) single crystal substrates by using electron beam evaporation technique (EB) without any post-annealing. The background pressure was less than 1.3x10 -6 Pa. The evaporation flux ratio of Mg was set at 30 times as high as that of B, and the growth rate of MgB 2 film was 1nm/s. The film thickness was typically 300nm at 5min deposition. The substrate temperature was 245 deg. C. Under these conditions, we controlled the oxygen partial pressure (P O 2 ) within the range from 1.3x10 -6 to 1.3x10 -3 Pa by using a quadrapole mass spectrometer. Although T c of deposited thin film decreased in order of P O 2 , ΔM in the magnetization hysteresis loops measured from 0 to 6T at 4.2K increased up to 1.3x10 -5 . On the other hand, thin film prepared under P O 2 of 1.3x10 -3 Pa does not show superconducting transition. Between these films, there is no difference in the crystal structure from X-ray diffraction (XRD). These results suggest that the pinning center in the thin films increased by introduction of oxygen. Extremely small amount of oxygen introduction has enabled the control of growth of oxide

  5. Intraband scattering studies in carbon- and aluminium-doped MgB2

    International Nuclear Information System (INIS)

    Samuely, P.; Szabo, P.; Hol'anova, Z.; Bud'ko, S.; Canfield, P.

    2006-01-01

    Magnetic field effect on the point-contact spectra of the Al- and C-substituted MgB 2 is presented. It is shown that suppression of the π-band contribution to the spectrum is different in the aluminium- and carbon-doped samples. The carbon substitution leads to a stronger enhancement of the π-band scattering while the Al-doping does not change the ratio between the π and σ scatterings

  6. The mechanism of Tc performance for Zn doped MgB2 sintered in magnetic field

    International Nuclear Information System (INIS)

    Li, W.X.; Li, Y.; Chen, R.H.; Zeng, R.; Dou, S.X.

    2010-01-01

    The mechanism of magnetic field sintering on the critical transition temperature, T c , for the Zn doped MgB 2 superconductor was investigated with the observation of Raman scattering measurement and the Raman spectra fit analysis. The broadened E 2g mode in Raman spectra shows the strengthening of the electron-phonon coupling (EPC) for the sample sintered in magnetic field. A synchronous fluctuation is observed between the Raman characters of the E 2g mode and the T c .

  7. Comparison between nano-diamond and carbon nanotube doping effects on critical current density and flux pinning in MgB2

    International Nuclear Information System (INIS)

    Cheng, C H; Yang, Y; Munroe, P; Zhao, Y

    2007-01-01

    Doping effects of nano-diamond and carbon nanotubes (CNTs) on critical current density of bulk MgB 2 have been studied. CNTs are found prone to be doped into the MgB 2 lattice whereas nano-diamond tends to form second-phase inclusions in the MgB 2 matrix, leading to a more significant improvement of J c (H) by doping by nano-diamond than by CNTs in MgB 2 . TEM reveals tightly packed MgB 2 nanograins (50-100 nm) with a dense distribution of diamond nanoparticles (10-20 nm) inside MgB 2 grains in nano-diamond-doped samples. Such a unique microstructure leads to a flux pinning behaviour different from that in CNTs-doped MgB 2

  8. Stabilization of the dissipation-free current transport in inhomogeneous MgB2 thin films

    International Nuclear Information System (INIS)

    Treiber, S.; Stahl, C.; Schütz, G.; Soltan, S.; Albrecht, J.

    2014-01-01

    Highlights: • We investigate transport properties of inhomogeneous MgB 2 films. • An inhomogeneous microstructure stabilizes supercurrents. • Vortex pinning forces and energies have been analyzed experimentally. • In inhomogeneous films the increase of the pinning energy is responsible for stable supercurrents. - Abstract: In type-II superconductors at T = 0 the critical current density is determined by the pinning of flux lines. Considering an arbitrarily shaped energy landscape the pinning force at each pinning site is given by the derivative of the flux line energy with respect to the considered direction. At finite temperatures, in addition, thermal activation can lead to a depinning of flux lines. The governing property in this case is the depth of the corresponding pinning potential, i.e. the pinning energy. We show a detailed analysis of both pinning forces and pinning energies of MgB 2 films with inhomogeneous microstructure. We show that a pronounced increase of the pinning energy is responsible for the significantly enhanced stability of the dissipation-free current transport in thin inhomogeneous MgB 2 films. This is found even if the corresponding pinning forces are small

  9. Peak effect and vortex dynamics in superconducting MgB2 single crystals

    International Nuclear Information System (INIS)

    Lee, Hyun-Sook; Jang, Dong-Jin; Kim, Heon-Jung; Kang, Byeongwon; Lee, Sung-Ik

    2007-01-01

    The dynamic nature of the vortex state of MgB 2 single crystals near the peak effect (PE) region, which is very different either from that of conventional low-temperature superconductors or from that of high-temperature cuprate superconductors, is introduced in this article. Relaxation from a disordered, metastable field-cooled (FC) state to an ordered, stable zero-field-cooled (ZFC) state of the MgB 2 single crystals under an applied magnetic field and current is investigated. From an analysis of the noise properties in the ZFC state, a dynamic vortex phase diagram of the MgB 2 is obtained near the PE region. Between the onset and the peak region in the critical current vs. magnetic field diagram, crossovers from a high-noise state to a noise-free state are observed with increasing current. Above the peak, however, an opposite phenomenon, crossovers from a noise-free to a high-noise state, is observed which has not been observed in any other superconductors. The hysteresis in the I-V curves and the two-level random telegraph noise in the time evolution of the voltage response under an constant applied current at the ZFC state are also studied in detail

  10. Influence of Ni and Cu contamination on the superconducting properties of MgB2 filaments

    International Nuclear Information System (INIS)

    Jung, A; Schlachter, S I; Runtsch, B; Ringsdorf, B; Fillinger, H; Orschulko, H; Drechsler, A; Goldacker, W

    2010-01-01

    Technical MgB 2 wires usually have a sheath composite consisting of different metals. For the inner sheath with direct contact to the superconducting filament, chemically inert Nb may be used as a reaction barrier and thermal stabilization is provided by a highly conductive metal like Cu. A mechanical reinforcement can be achieved by the addition of stainless steel. In order to illuminate the influence of defects in the reaction barrier, monofilament in situ wires with direct contact between the MgB 2 filament and frequently applied reactive sheath metals like Cu, Ni or Monel are studied. Reactions of Mg and B with a Cu-containing sheath lead to Cu-based by-products penetrating the whole filament. Reactions with Ni-containing sheaths lead to Ni-based by-products which tend to remain at the filament-sheath interface. Cu and/or Ni contamination of the filament lowers the MgB 2 -forming temperature due to the eutectic reaction between Mg, Ni and Cu. Thus, for the samples heat-treated at low temperatures J C and (partly) T C are increased compared to stainless-steel-sheathed wires. At high heat treatment temperatures uncontaminated filaments lead to the highest J C values. From the point of view of broken reaction barriers in real wires, the contamination of the filament with Cu and/or Ni does not necessarily constrain the superconductivity; it may even improve the properties of the wire, depending on the desired application.

  11. Intrinsic flux pinning mechanisms in different thickness MgB2 films

    Directory of Open Access Journals (Sweden)

    C. Yang

    2017-03-01

    Full Text Available MgB2 films in four thickness (60 nm, 200nm, 600nm and 1μm have been fabricated by hybrid physical–chemical vapor deposition technique (HPCVD. By measuring the magnetization hysteresis loops and the resistivity, we have obtained the transport and magnetic properties of the four films. After that, the pinning mechanisms in them were discussed. Comparing the pinning behaviors in these ultrathin films, thin films and thick films, it was found that there exist different pinning types in MgB2 films of different thickness. In combination with the study of the surface morphology, cross-section and XRD results, we concluded that MgB2 films had different growth modes in different growth stages. For thin films, films grew along c axis, and grain boundaries acted as surface pinning. While for thick films, films grew along c axis at first, and then changed to a-b axis growth. As a result, the a-b axis grains acted as strong volume pinning.

  12. A trapped field of >3 T in bulk MgB2 fabricated by uniaxial hot pressing

    International Nuclear Information System (INIS)

    Durrell, J H; Dennis, A; Shi, Y; Xu, Z; Campbell, A M; Babu, N Hari; Cardwell, D A; Dancer, C E J; Todd, R I; Grovenor, C R M

    2012-01-01

    A trapped field of over 3 T has been measured at 17.5 K in a magnetized stack of two disc-shaped bulk MgB 2 superconductors of diameter 25 mm and thickness 5.4 mm. The bulk MgB 2 samples were fabricated by uniaxial hot pressing, which is a readily scalable, industrial technique, to 91% of their maximum theoretical density. The macroscopic critical current density derived from the trapped field data using the Biot–Savart law is consistent with the measured local critical current density. From this we conclude that critical current density, and therefore trapped field performance, is limited by the flux pinning available in MgB 2 , rather than by lack of connectivity. This suggests strongly that both increasing sample size and enhancing pinning through doping will allow further increases in trapped field performance of bulk MgB 2 . (rapid communication)

  13. Improved flux pinning behaviour in bulk MgB2 achieved by nano-SiO2 addition

    International Nuclear Information System (INIS)

    Rui, X F; Zhao, Y; Xu, Y Y; Zhang, L; Sun, X F; Wang, Y Z; Zhang, H

    2004-01-01

    Bulk MgB 2 with SiO 2 nanoparticles added has been synthesized using a simple solid-state reaction route. The lattice constant in the c direction increases with additive content due to a small amount of Si being doped into the lattice of the MgB 2 ; however, T c is almost fixed at 37.2 K. The addition of SiO 2 nanoparticles also improves the J c -H and H irr -T characteristics of MgB 2 when the additive content is lower than 7%. At 20 K and 1 T, J c for the sample with 7% additive content reaches 2.5 x 10 5 A cm -2 . Microstructural analysis reveals that a high density of MgSi 2 nanoparticles (10-50 nm) exists inside the MgB 2 grains, leading to the formation of a nanocomposite superconductor

  14. Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density

    Science.gov (United States)

    Shahabuddin, Mohammed; Alzayed, Nasser S.; Oh, Sangjun; Choi, Seyong; Maeda, Minoru; Hata, Satoshi; Shimada, Yusuke; Hossain, Md Shahriar Al; Kim, Jung Ho

    2014-01-01

    A comprehensive study of the effects of structural imperfections in MgB2 superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths.

  15. The effect of citric and oxalic acid doping on the superconducting properties of MgB2

    International Nuclear Information System (INIS)

    Ojha, N; Singla, Rashmi; Varma, G D; Malik, V K; Bernhard, C

    2009-01-01

    In this paper we report the effect of carbon doping on the structural and superconducting properties of MgB 2 using citric and oxalic acids as carbon sources. The bulk polycrystalline samples have been synthesized via a standard solid state reaction route with composition MgB 2 +x wt% of citric and oxalic acids (x = 0, 5 and 10). The x-ray diffraction results reveal the formation of dominantly MgB 2 with only a small amount of impurity phase MgO and substitution of C at the B site of MgB 2 for both dopants. Improvements in the upper critical field (H C2 ), irreversibility field (H irr ) and high field (>2.5 T) critical current density (J C ) have been observed on C doping in the samples. The correlations between superconducting properties and structural characteristics of the samples are described and discussed in this paper.

  16. Thermal analysis, phase equilibria, and superconducting properties in magnesium boride and carbon doped magnesium boride

    Science.gov (United States)

    Bohnenstiehl, Scot David

    In this work, the low temperature synthesis of MgB2 from Mg/B and MgH2/B powder mixtures was studied using Differential Scanning Calorimetry (DSC). For the Mg/B powder mixture, two exothermic reaction events were observed and the first reaction event was initiated by the decomposition of Mg(OH)2 on the surface of the magnesium powder. For the MgH 2/B powder mixture, there was an endothermic event at ˜375 °C (the decomposition of MgH2 into H2 and Mg) and an exothermic event ˜600 °C (the reaction of Mg and B). The Kissinger analysis method was used to estimate the apparent activation energy of the Mg and B reaction using DSC data with different furnace ramp rates. The limitations of MgB2 low temperature synthesis led to the development of a high pressure induction furnace that was constructed using a pressure vessel and an induction heating power supply. The purpose was to not only synthesize more homogeneous MgB2 samples, but also to determine whether MgB2 melts congruently or incongruently. A custom implementation of the Smith Thermal Analysis method was developed and tested on aluminum and AlB2, the closest analogue to MgB2. Measurements on MgB2 powder and a high purity Mg/B elemental mixture confirmed that MgB2 melts incongruently and decomposes into a liquid and MgB4 at ˜1445 °C at 10 MPa via peritectic decomposition. Another measurement using a Mg/B elemental mixture with impure boron suggested that ˜0.7 wt% carbon impurity in the boron raised the incongruent melting temperature to ˜1490-1500 °C. Lastly, the solubility limit for carbon in MgB2 was studied by making samples from B4C and Mg at 1530 °C, 1600 °C and 1700 °C in the high pressure furnace. All three samples had three phases: Mg, MgB2C2, and carbon doped MgB2. The MgB 2C2 and carbon doped MgB2 grain size increased with temperature and the 1700 °C sample had needle-like grains for both phases. The presence of the ternary phase, MgB2C2, suggested that the maximum doping limit for carbon in

  17. Numerical investigations on the characteristics of thermomagnetic instability in MgB2 bulks

    Science.gov (United States)

    Xia, Jing; Li, Maosheng; Zhou, Youhe

    2017-07-01

    This paper presents the characteristics of thermomagnetic instability in MgB2 bulks by numerically solving the macroscopic dynamics of thermomagnetic interaction governed by the coupled magnetic and heat diffusion equations in association with a modified E-J power-law relationship. The finite element method is used to discretize the system of partial differential equations. The calculated magnetization loops with flux jumps are consistent with the experimental results for MgB2 slabs bathed in a wide range of ambient temperatures. We reveal the evolution process of the thermomagnetic instability and present the distributions of the magnetic field, temperature, and current density before and after flux jumps. A 2D axisymmetric model is used to study the thermomagnetic instability in cylindrical MgB2 bulks. It is found that the number of flux jumps monotonously reduces as the ambient temperature rises and no flux jump appears when the ambient temperature exceeds a certain value. Moreover, the flux-jump phenomenon exists in a wide range of the ramp rate of the applied external field, i.e. 10-2-102 T s-1. Furthermore, the dependences of the first flux-jump field on the ambient temperature, ramp rate, and bulk thickness are investigated. The critical bulk thicknesses for stability are obtained for different ambient temperatures and sample radii. In addition, the influence of the capability of the interfacial heat transfer on the temporal response of the bulk temperature is discussed. We also find that the prediction of thermomagnetic instability is sensitive to the employment of the flux creep exponent in the simulations.

  18. Stress-strain effects on powder-in-tube MgB2 tapes and wires

    International Nuclear Information System (INIS)

    Katagiri, Kazumune; Takaya, Ryuya; Kasaba, Koichi; Tachikawa, Kyoji; Yamada, Yutaka; Shimura, Satoshi; Koshizuka, Naoki; Watanabe, Kazuo

    2005-01-01

    The effects of stress-strain on the critical current, I c , of ex situ powder-in-tube (PIT)-processed Ni-sheathed MgB 2 tapes and round wires as well as in situ PIT-processed Cu-sheathed wires at 4.2 K in a magnetic field up to 5 T have been studied. The effect of In powder addition on the Ni-sheathed MgB 2 wire was not so clear compared with that in the tape, in which the irreversible strain, ε irr , for the I c degradation onset increases significantly by the addition. This is attributed to the difference in the microstructure of the core associated with cold workings. A peak and gradual degradation behaviour of I c with strain beyond ε irr was found in the wire, whereas no evident peak and a steep degradation behaviour was found in the tape. As a possible reason, the difference in the triaxial residual stress state at 4.2 K due to the difference in geometry of the cross-section is suspected. The transverse compression tests revealed that I c of the wire did not degrade up to 270 MPa. Again, the effect of In addition was minimal. The Young's modulus of MgB 2 , 31-41 GPa, at room temperature was estimated by a tensile test of Cu sheath wire using a high-accuracy extensometer and the law of mixtures. The tensile strain dependence of I c in the Cu sheath wire was similar to that in the Ni-sheathed wire, ε irr being 0.4%. However, the stress corresponding to ε irr , 50 MPa, was about 1/10 of that for the Ni-sheath wire and the irreversible transverse compressive stress, 150 MPa, was also lower. The effect of bending strain on the I c in Cu-sheathed wire was compared with that of the tensile strain

  19. Contribution to the development of dry R and W MgB2 superconducting magnets

    International Nuclear Information System (INIS)

    Pasquet, Raphael

    2015-01-01

    Currently, the majority of superconducting magnets, including MRI, are cooled by a bath of liquid helium at atmospheric pressure. Nevertheless, this type of cooling is expensive and imposes significant security constraints for large volumes. For these reasons, the cooling of superconducting magnets is desirable without liquid helium. Cryo-cooler provides dry cooling to 4 K without any liquid helium. However, the power available is low and dry cooling is difficult. In these conditions, it is complicate to use NbTi with dry cooling. But if we increase the operating temperature to 10 K, the power of cryo-cooler increases by a factor of ten. Nevertheless in this case, it is necessary to use of a high critical temperature superconductor. We choose to use MgB 2 R and W conductors because it is relatively low cost but it has the handicap to be sensible at mechanical stress. It is therefore necessary to be careful during their winding to not degrade their superconducting performance. As part of this thesis, we have developed a dry test facility to measure the critical current of MgB 2 R and W conductors as well as mock-ups. To do this, a new type of thermal contact based on aluminum nitride has been developed. In addition to this development, we designed two MgB 2 R and W magnet mock-ups: a solenoid and a double pancake. The double pancake was manufactured (with a new patented winding method) and it has been successfully tested. (author) [fr

  20. Vibrational spectroscopy of superconducting MgB2 by neutron inelastic scattering

    International Nuclear Information System (INIS)

    Muranaka, Takahiro

    2001-01-01

    Neutron inelastic scattering measurements have been performed on superconducting MgB 2 above and below T c . The temperature dependence of the generalized phonon density-of-states showed clear anomalous behaviour near 24 meV in the acoustic phonon region, which may be interpreted as evidence of a substantial contribution to the total electron-phonon coupling strength deriving from these phonons. Weaker evidence for a corresponding response in the high-energy B bond stretching phonons was also encountered. (author)

  1. Recent developments in melt processed Gd-123 and MgB2 materials at RTRI

    International Nuclear Information System (INIS)

    Muralidhar, M.; Fukumoto, Y.; Ishihara, A.; Suzuki, K.; Tomita, M.; Koblischka, M.R.; Yamamoto, A.; Kishio, K.

    2014-01-01

    Highlights: •Large size Gd-123 bulk material grown in air, using novel thin film Nd-123 seeds grown on MgO crystals. •Quality and uniformity of the Gd-123 materials are excellent. •Batch processed Gd-123 material was used for construction of chilled Maglev vehicle. •MgB 2 bulks can be utilized around 20 K similarly to the Gd-123 material at 77 K. -- Abstract: In this contribution we will report on the current status, recent developments in GdBa 2 Cu 3 O y “Gd-123” and MgB 2 material processing, characterization, and applications at the Railway Technical Research Institute (RTRI). Batch-processing of Gd-123 bulk material grown in air was performed using novel thin film Nd-123 seeds grown on MgO crystals. In this way, we are able to fabricate materials with good quality, and uniform performance. We examined the technology of the uniform performance of the large 45 mm diameter, single grain Gd-123 bulks for use in application of NMR. For this purpose, four 5 mm thick pieces are cut vertically from a single grain Gd-123 material and the magnetic field distribution is measured using a scanning hall sensor. We found that all four pieces are single domain and exhibit a quite uniform field distribution. Furthermore, the batch-processed bulk materials are used for the construction of a chilled Maglev vehicle. On the other hand, to optimize the trapped field performance of bulk MgB 2 material, several samples were prepared by solid state reaction at different temperatures ranging from 750 to 950 °C in pure argon atmosphere. X-ray diffraction results indicated that single phase and homogenous MgB 2 bulks are produced when sintering them around 775 °C. Further, atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicated that an uniform grain size results by controlling the processing temperature. So, higher trapped fields can be achieved in sintered MgB 2 material

  2. Correlated vortex pinning in Si-nanoparticle doped MgB2

    OpenAIRE

    Kusevic, I.; Babic, E.; Husnjak, O.; Soltanian, S.; Wang, X. L.; Dou, S. X.

    2003-01-01

    The magnetoresistivity and critical current density of well characterized Si-nanoparticle doped and undoped Cu-sheathed MgB$_{2}$ tapes have been measured at temperatures $T\\geq 28$ K in magnetic fields $B\\leq 0.9$ T. The irreversibility line $B_{irr}(T)$ for doped tape shows a stepwise variation with a kink around 0.3 T. Such $B_{irr}(T)$ variation is typical for high-temperature superconductors with columnar defects (a kink occurs near the matching field $% B_{\\phi}$) and is very different ...

  3. Enhanced superconducting properties of MgB2 by carbon substitution using carbon containing nano additives

    International Nuclear Information System (INIS)

    Devadas, K.M.; Varghese, Neson; Vinod, K.; Rahul, S.; Thomas, Syju; Anooja, J.B.; Syamaprasad, U.; Sundaresan, A.; Roy, S.B.

    2010-01-01

    A comparative study on the effect of doping of nano carbon, nano diamond and nano SiC in MgB 2 is carried out. The J c (H) is significantly enhanced for all doped samples compared to the pure sample among which MgB 1.9 C 0.1 (nano C) exhibits the best J c (H) performance. The enhanced performance is due to the effective substitution of C at B site which is confirmed by the systematic decrease in both α axis and T c . (author)

  4. The microwave surface impedance of MgB2 thin films

    International Nuclear Information System (INIS)

    Purnell, A J; Zhukov, A A; Nurgaliev, T; Lamura, G; Bugoslavsky, Y; Lockman, Z; MacManus-Driscoll, J L; Zhai, H Y; Christen, H M; Paranthaman, M P; Lowndes, D H; Jo, M H; Blamire, M G; Hao, Ling; Gallop, J C; Cohen, L F

    2003-01-01

    In this paper we present the results of measurements of the microwave surface impedance of a powder sample and two films of MgB 2 . The powder sample has a T c = 39 K and the films have T c = 29 K and 38 K. These samples show different temperature dependences of the field penetration depth. Over a period of six months, the film with T c = 38 K degraded to a T c of 35 K. We compare the results on all samples with data obtained elsewhere and discuss the implications as far as is possible at this stage

  5. Plasma Synthesized Doped Boron Nanopowder for MgB2 Superconductors

    International Nuclear Information System (INIS)

    Marzik, James V.

    2012-01-01

    Under this program, a process to synthesize nano-sized doped boron powder by a plasma synthesis process was developed and scaled up from 20 gram batches at program start to over 200 grams by program end. Over 75 batches of boron nanopowder were made by RF plasma synthesis. Particle sizes were typically in the 20-200 nm range. The powder was synthesized by the reductive pyrolysis of BCl 3 in hydrogen in an RF plasma. A wide range of process parameters were investigated including plasma power, torch geometry, gas flow rates, and process pressure. The powder-in-tube technique was used to make monofilament and multifilament superconducting wires. MgB 2 wire made with Specialty Materials plasma synthesized boron nanopowder exhibited superconducting properties that significantly exceeded the program goals. Superconducting critical currents, J c , in excess of 10 5 A cm -2 at magnetic fields of 8 tesla were reproducibly achieved. The upper critical magnetic field in wires fabricated with program boron powder were H c2 (0) = 37 tesla, demonstrating the potential of these materials for high field magnet applications. T c in carbon-doped MgB 2 powder showed a systematic decrease with increasing carbon precursor gas flows, indicating the plasma synthesis process can give precise control over dopant concentrations. Synthesis rates increased by a factor of 400% over the course of the program, demonstrating the scalability of the powder synthesis process. The plasma synthesis equipment at Specialty Materials has successfully and reproducibly made high quality boron nanopowder for MgB 2 superconductors. Research and development from this program enabled Specialty Materials to successfully scale up the powder synthesis process by a factor of ten and to double the size of its powder pilot plant. Thus far the program has been a technical success. It is anticipated that continued systematic development of plasma processing parameters, dopant chemistry and concentration, wire processing technology, and collection technology will lead to the commercialization of boron nanopowder as a precursor for MgB 2 superconductors. Potential commercial applications include magnets for magnetic resonance imaging (MRI), fault current limiters, wind turbine generators.

  6. Multifilamentary MgB2 wires fracture behavior during the drawing process

    International Nuclear Information System (INIS)

    Shan, D.; Yan, G.; Zhou, L.; Li, J.S.; Li, C.S.; Wang, Q.Y.; Xiong, X.M.; Jiao, G.F.

    2012-01-01

    The fracture behavior of 6 + 1 filamentary MgB 2 superconductive wires is presented here. The composite wires were fabricated by in situ Powder-in-Tube method using Nb as a barrier and copper as a stabilizer. The microstructure of the material has a great influence on its fracture behavior. The microstructural aspects of crack nucleation and propagation are discussed. It shows that there are complicated correlations between fracture behavior and the main influencing parameters, which contain specific drawing conditions (drawing velocity, reduction in area per pass), materials properties (strength, yield stress, microstructure) as well as the extent of bonding between the metal sheaths at their interface.

  7. Temperature dependence of the optical conductivity and penetration depth in superconductor MgB2 film

    International Nuclear Information System (INIS)

    Moarrefi, M.; Yavari, H.; Elahi, M.

    2010-01-01

    By using Green's function method the temperature dependence of the optical conductivity and penetration depth of high-quality MgB 2 film are calculated in the framework of the two-band model. We compare our results with experimental data and we argue that the single gap model is insufficient to describe the optical and penetration depth behavior, but the two-band model with different symmetries describes the data rather well. In the two gap model we consider that the both components of optical conductivity are a weighted sum of the contribution from σ and π bonds and hybridization between them is negligible.

  8. Design of MgB2 superconducting dipole magnet for particle beam transport in accelerators

    International Nuclear Information System (INIS)

    Abrahamsen, A.B.; Givel, J.C.; Andersen, N.H.; Zangenberg, N.; Baurichter, A.

    2006-11-01

    A comprehensive analysis of the innovation potential of superconductivity at Risoe was performed in February 2004 by the main author of this report. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risoe. The existing markets of superconducting technology is within highly specialized scientific areas such as magnetic confinement in fusion energy, sample environment in neutron scattering and large scale accelerators such as the Large Hadron Collider(LHC) at Cern, or in the nuclear magnetic resonance (NMR) community using MR-imaging scanners in medicine and phase identification in organic chemistry. Only the NMR applications can be categorized as a highly profitable and commercial market today. The superconductivity group of Risoe formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept, but further initiatives were stopped due to unclear patent possibilities. The experience of the innovation review was used in the STVF framework program 'New superconductors: mechanisms, processes and products' to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition in building resistive magnets for particle accelerators. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European Framework Program 6 project HIPERMAG. It was presented at the Risoe innovation seminar January 2006, and recently a collaboration between Risoe and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB 2 superconductors in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the critical current density of primarily MgB 2 will be compared with current density determined by specifications similar to the Tevatron accelerator, B = 4:4 Tesla and coil aperture D = 76 mm, which has been identified by Danfysik A/S as interesting. It is concluded that MgB 2 is useful for the dipole application and construction of a small test coil of one half of the magnet is planned in 2007. (au)

  9. Characterisation of nano-grains in MgB2 superconductors by transmission Kikuchi diffraction

    International Nuclear Information System (INIS)

    Wong, D.C.K.; Yeoh, W.K.; Trimby, P.W.; De Silva, K.S.B.; Bao, P.; Li, W.X.; Xu, X.; Dou, S.X.; Ringer, S.P.; Zheng, R.K.

    2015-01-01

    We report the first application of the emerging transmission Kikuchi diffraction technique in the scanning electron microscope to investigate nano-grain structures in polycrystalline MgB 2 superconductors. Two sintering conditions were considered, and the resulting differences in superconducting properties are correlated to differences in grain structure. A brief comparison to X-ray diffraction results is presented and discussed. This work focusses more on the application of this technique to reveal grain structure, rather than on the detailed differences between the two sintering temperatures

  10. Using Fast Hot Shock Wave Consolidation Technology to Produce Superconducting MgB2

    Directory of Open Access Journals (Sweden)

    T. Gegechkori

    2018-02-01

    Full Text Available The original hot shock wave assisted consolidation method combining high temperature was applied with the two-stage explosive process without any further sintering to produce superconducting materials with high density and integrity. The consolidation of MgB2 billets was performed at temperatures above the Mg melting point and up to 1000oC in partially liquid condition of Mg-2B blend powders. The influence of the type of boron (B isotope in the composition on critical temperature and superconductive properties was evaluated. An example of a hybrid Cu-MgB2–Cu superconducting tube is demonstrated and conclusions are discussed.

  11. Characterization of Mechanical Properties of MgB$_2$ Conductor for the Superconducting Link Project at CERN

    CERN Document Server

    Sugano, M; Bartova, B; Bjoerstad, R; Scheuerlein, C; Grasso, G

    2015-01-01

    In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young's modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB2, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young's modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young's modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such diff...

  12. S-I-N tunneling spectroscopy of MgB2 superconductor: evidence of two superconducting energy gaps

    International Nuclear Information System (INIS)

    Sen, Shashwati; Aswal, D.K.; Singh, Ajay; Gadkari, S.C.; Shah, K.; Gupta, S.K.; Sahni, V.C.

    2002-01-01

    The tunneling spectra of polycrystalline MgB 2 , have been recorded, at different temperatures between 29 K and T c , using planar superconductor- insulating-normal (S-I-N) tunneling spectroscopy. The planar S-I-N tunnel junctions have been fabricated by thermally evaporating Ag electrodes on MgB 2 surface. The naive layer, which forms at the surface of MgB 2 , due to atmospheric degradation, was employed as an insulating layer between Ag electrodes and MgB 2 . We have found presence of two clear superconducting energy gaps in MgB 2 . The magnitudes of these gaps at 29.5 K are 1.8 and 5.9 MeV, respectively. In the vicinity of T c , while larger energy gap obeyed BCS temperature dependence, the smaller energy gap deviated from BCS dependence. All the spectra exhibited zero-bias conductance, which decreased linearly with temperature and vanished at T c . (author)

  13. Magnetic microscopy for characterization of local critical current in iron-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Higashikawa, K.; Yamamoto, A.; Kiss, T.; Ye, S.; Matsumoto, A.; Kumakura, H.

    2014-01-01

    Highlights: • We developed a characterization method of local critical current in MgB 2 wires. • Local homogeneity was visualized by the scanning Hall-probe microscopy (SHPM). • Local critical current value was quantified with the aid of the finite element method (FEM). • MgB 2 wire still has inhomogeneous distribution in local critical current. • Higher potential than that estimated by the four-probe transport method was suggested. - Abstract: We have developed a characterization method of local critical current in iron-sheathed MgB 2 wires. Local homogeneity was visualized by the scanning Hall-probe microscopy (SHPM). The value of local critical current was quantified with the aid of the finite element method (FEM) considering the ferromagnetic properties of the iron sheath. The results suggested that MgB 2 wires fabricated by internal Mg diffusion processes still have large longitudinal inhomogeneity and much higher potential than that estimated by the four-probe transport method. This will be very important information for making a correct strategy for further development of MgB 2 wires

  14. Vapor annealing synthesis of non-epitaxial MgB2 films on glassy carbon

    Science.gov (United States)

    Baker, A. A.; Bayu Aji, L. B.; Bae, J. H.; Stavrou, E.; Steich, D. J.; McCall, S. K.; Kucheyev, S. O.

    2018-05-01

    We describe the fabrication and characterization of 25–800 nm thick MgB2 films on glassy carbon substrates by Mg vapor annealing of sputter-deposited amorphous B films. Results demonstrate a critical role of both the initial B film thickness and the temperature–time profile on the microstructure, elemental composition, and superconducting properties of the resultant MgB2 films. Films with thicknesses of 55 nm and below exhibit a smooth surface, with a roughness of 1.1 nm, while thicker films have surface morphology consisting of elongated nano-crystallites. The suppression of the superconducting transition temperature for thin films scales linearly with the oxygen impurity concentration and also correlates with the amount of lattice disorder probed by Raman scattering. The best results are obtained by a rapid (12 min) anneal at 850 °C with large temperature ramp and cooling rates of ∼540 °C min‑1. Such fast processing suppresses the deleterious oxygen uptake.

  15. Flux pinning and inhomogeneity in magnetic nanoparticle doped MgB2/Fe wires

    Science.gov (United States)

    Novosel, Nikolina; Pajić, Damir; Mustapić, Mislav; Babić, Emil; Shcherbakov, Andrey; Horvat, Joseph; Skoko, Željko; Zadro, Krešo

    2010-06-01

    The effects of magnetic nanoparticle doping on superconductivity of MgB2/Fe wires have been investigated. Fe2B and SiO2-coated Fe2B particles with average diameters 80 and 150 nm, respectively, were used as dopands. MgB2 wires with different nanoparticle contents (0, 3, 7.5, 12 wt.%) were sintered at temperature 750°C. The magnetoresistivity and critical current density Jc of wires were measured in the temperature range 2-40 K in magnetic field B doped wires decreases quite rapidly with doping level (~ 0.5 K per wt.%). This results in the reduction of the irreversibility fields Birr(T) and critical current densities Jc(B,T) in doped samples (both at low (5 K) and high temperatures (20 K)). Common scaling of Jc(B,T) curves for doped and undoped wires indicates that the main mechanism of flux pinning is the same in both types of samples. Rather curved Kramer's plots for Jc of doped wires imply considerable inhomogeneity.

  16. Effect of malic acid doping on the structural and superconducting properties of MgB2

    International Nuclear Information System (INIS)

    Ojha, N.; Sudesh; Stuti Rani; Varma, G.D.

    2010-01-01

    The samples have been prepared via standard solid state reaction route with nominal compositions MgB 2 + x wt% malic acid (x = 0, 5 and 10) by sintering at two different temperatures: 800 and 850 deg C in argon atmosphere. Improvement in upper critical fields (H c2 ) and irreversibility field (H irr ) of doped samples as compared to undoped samples have been observed. At 10 K, critical current densities (J c ) of the 5 and 10 wt% malic acid doped MgB 2 samples sintered at 850 deg C have higher values as compared to undoped sample sintered at the same temperature in the fields greater than 3 T. However, J c values of 5 wt% malic acid doped sample are higher than 10 wt% doped sample in the entire applied field region (0 - 7 T). In case of the samples sintered at 800 deg C improvement in J c values of 5 wt% doped sample have been found in entire field region as compared to undoped sample. On the other hand we see deterioration in J c values of 10 wt% doped samples sintered at 800 deg C as compared to undoped samples sintered at same temperature. The correlations between structural and superconducting properties will be described and discussed in this paper. (author)

  17. Growth of high-quality large-area MgB2 thin films by reactive evaporation

    International Nuclear Information System (INIS)

    Moeckly, B H; Ruby, W S

    2006-01-01

    We report a new in situ reactive deposition thin film growth technique for the production of MgB 2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB 2 films for real-world applications. We have used this growth method, which incorporates a rotating pocket heater, to deposit MgB 2 films on a variety of substrates, including single-crystalline, polycrystalline, metallic, and semiconductor materials up to 4 inch in diameter. This technique allows growth of double-sided, large-area films in the intermediate temperature range of 400-600 deg. C. These films are clean, well-connected, and consistently display T c values of 38-39 K with low resistivity and residual resistivity values. They are also robust and uncommonly stable upon exposure to atmosphere and water. (rapid communication)

  18. Effects of TiC doping on the upper critical field of MgB2 superconductors

    International Nuclear Information System (INIS)

    Yan, S.C.; Zhou, L.; Yan, G.; Lu, Y.F.

    2008-01-01

    TiC doped MgB 2 bulks were fabricated by two-step reaction method. The sample with a nominal compositions of Mg(B 0.95 (TiC) 0.05 ) 4 was first sintered at 1000 deg. C for 0.5 h. An appropriate amount of Mg was added to reach the stoichiometry of Mg(B 0.95 (TiC) 0.05 ) 2 , which was sintered at 750 deg. C for 2 h. The H c2 for the micro-TiC doped MgB 2 reached 12 T at 20 K. And J c is 5.3 x 10 4 A/cm 2 at 20 K and 1 T. The results indicate that the two-step reaction method could effectively introduce the carbon in TiC into the MgB 2 crystalline lattice, and therefore improve the upper critical field

  19. NMR relaxation rates and Knight shifts in MgB2 and AlB2: theory versus experiments

    International Nuclear Information System (INIS)

    Pavarini, E; Baek, S H; Suh, B J; Borsa, F; Bud'ko, S L; Canfield, P C

    2003-01-01

    We have performed 11 B NMR measurements in 11 B enriched MgB 2 powder sample in the normal phase. The Knight shift was accurately determined by using the magic angle spinning technique. Results for 11 B and 27 Al Knight shifts (K) and relaxation rates (1/T 1 ) are also reported for AlB 2 . The data show a dramatic decrease of both K and 1/T 1 for 11 B in AlB 2 with respect to MgB 2 . We compare experimental results with ab initio calculated NMR relaxation rates and Knight shifts. The experimental values for 1/T 1 and K are in most cases in good agreement with the theoretical results. We show that the decrease of K and 1/T 1 for 11 B is consistent with a drastic drop of the density of states at the boron site in AlB 2 with respect to MgB 2

  20. Electro-mechanical characterization of MgB2 wires for the Superconducting Link Project at CERN

    Science.gov (United States)

    Konstantopoulou, K.; Ballarino, A.; Gharib, A.; Stimac, A.; Garcia Gonzalez, M.; Perez Fontenla, A. T.; Sugano, M.

    2016-08-01

    In previous years, the R & D program between CERN and Columbus Superconductors SpA led to the development of several configurations of MgB2 wires. The aim was to achieve excellent superconducting properties in high-current MgB2 cables for the HL-LHC upgrade. In addition to good electrical performance, the superconductor shall have good mechanical strength in view of the stresses during operation (Lorenz forces and thermal contraction) and handling (tension and bending) during cabling and installation at room temperature. Thus, the study of the mechanical properties of MgB2 wires is crucial for the cable design and its functional use. In the present work we report on the electro-mechanical characterization of ex situ processed composite MgB2 wires. Tensile tests (critical current versus strain) were carried out at 4.2 K and in a 3 T external field by means of a purpose-built bespoke device to determine the irreversible strain limit of the wire. The minimum bending radius of the wire was calculated taking into account the dependence of the critical current with the strain and it was then used to obtain the minimum twist pitch of MgB2 wires in the cable. Strands extracted from cables having different configurations were tested to quantify the critical current degradation. The Young’s modulus of the composite wire was measured at room temperature. Finally, all measured mechanical parameters will be used to optimize an 18-strand MgB2 cable configuration.

  1. Microscopic unravelling of nano-carbon doping in MgB2 superconductors fabricated by diffusion method

    International Nuclear Information System (INIS)

    Wong, D.C.K.; Yeoh, W.K.; De Silva, K.S.B.; Kondyurin, A.; Bao, P.; Li, W.X.; Xu, X.; Peleckis, G.; Dou, S.X.; Ringer, S.P.; Zheng, R.K.

    2015-01-01

    Highlights: • First report on nano-carbon doped MgB 2 superconductors synthesized by diffusion method. • Microstructure and superconducting properties of the superconductors are discussed. • B 4 C region blocks the Mg from reacting with B in the 10% nano-carbon doped sample. • MgB 2 with 2.5% nano-carbon doped showed the highest J c , ≈10 4 A/cm 2 for 20 K at 4 T. - Abstract: We investigated the effects of nano-carbon doping as the intrinsic (B-site nano-carbon substitution) and extrinsic (nano-carbon derivatives) pinning by diffusion method. The contraction of the in-plane lattice confirmed the presence of disorder in boron sublattice caused by carbon substitution. The increasing value in full width half maximum (FWHM) in the X-ray diffraction (XRD) patterns with each increment in the doping level reveal smaller grains and imperfect MgB 2 crystalline. The strain increased across the doping level due to the carbon substitution in the MgB 2 matrix. The broadening of the T c curves from low to high doping showed suppression of the connectivity of the bulk samples with progressive dirtying. At high doping, the presence of B 4 C region blocked the Mg from reacting with crystalline B thus hampering the formation of MgB 2 . Furthermore, the unreacted Mg acted as a current blocking phase in lowering down the grain connectivity hence depressing the J c of the 10% nano-carbon doped MgB 2 bulk superconductor

  2. Sugar as an optimal carbon source for the enhanced performance of MgB2 superconductors at high magnetic fields

    Science.gov (United States)

    Shcherbakova, O. V.; Pan, A. V.; Wang, J. L.; Shcherbakov, A. V.; Dou, S. X.; Wexler, D.; Babić, E.; Jerčinović, M.; Husnjak, O.

    2008-01-01

    In this paper we report the results of an extended study of the effect of sugar doping on the structural and electromagnetic properties of MgB2 superconductors. High values of the upper critical field (Bc2) of 36 T and the irreversibility field (Birr) of 27 T have been estimated at the temperature of 5 K in a bulk MgB2 sample with the addition of 10 wt% of sugar. The critical current density (Jc(Ba)) of sugar-doped samples has been significantly improved in the high field region. The value of transport Jc has reached as high as 108 A m-2 at 10 T and 5 K for Fe-sheathed sugar-doped MgB2 wire. The analysis of the pinning mechanism in the samples investigated indicated that dominant vortex pinning occurs on the surface type of pinning defects, such as grain boundaries, dislocations, stacking faults etc, for both pure and doped MgB2. In sugar-doped samples, pinning is governed by numerous crystal lattice defects, which appear in MgB2 grains as a result of crystal lattice distortion caused by carbon substitution for boron and nano-inclusions. The drastically improved superconducting properties of sugar-doped samples are also attributed to the highly homogeneous distribution and enhanced reactivity of this dopant with host Mg and B powders. The results of this work suggest that sugar is the optimal source of carbon for doping MgB2 superconductor, especially for application at high magnetic fields.

  3. Physical properties in flux line lattice state in MgB2 probed by μSR

    International Nuclear Information System (INIS)

    Ohishi, Kazuki; Muranaka, Takahiro; Akimitsu, Jun; Koda, Akihiro; Higemoto, Wataru; Kadono, Ryosuke

    2002-01-01

    We have performed muon spin rotation (μSR) measurements to deduce the magnetic penetration depth λ in the flux line lattice state of MgB 2 microscopically. It is observed that λ shows a quadratic temperature dependence which is predicted for the case of superconducting gap with line nodes. Furthermore, it clearly exhibits a strong field dependence, where λ increases almost linearly with H. These results strongly suggest that the superconducting order parameter in MgB 2 is highly anisotropic. (author)

  4. Design, manufacturing and tests of first cryogen-free MgB2 prototype coils for offshore wind generators

    International Nuclear Information System (INIS)

    Sarmiento, G; Sanz, S; Pujana, A; Merino, J M; Apiñaniz, S; Marino, I; Iturbe, R; Nardelli, D

    2014-01-01

    Although renewable sector has started to take advantage of the offshore wind energy recently, the development is very intense. Turbines reliability, size, and cost are key aspects for the wind industry, especially in marine locations. A superconducting generator will allow a significant reduction in terms of weight and size, but cost and reliability are two aspects to deal with. MgB 2 wire is presented as one promising option to be used in superconducting coils for wind generators. This work shows the experimental results in first cryogen-free MgB 2 prototype coils, designed according to specific requirements of TECNALIA's wind generator concept.

  5. Enthalpy of formation of titanium diboride

    International Nuclear Information System (INIS)

    Akhachinskij, V.V.; Chirin, N.A.

    1975-01-01

    The values given in the literature for the enthalpy of the formation of titanium diboride, as obtained experimentally and by theoretical estimation, range between -32 and -74.4 kcal/mol. In this paper the authors use the method of direct synthesis from elements in a Calvet calorimeter to determine the enthalpy of formation, ΔHsub(f) 0 , sub(298), of titanium diboride with the composition Tisub(1.000+-0.002)Bsub(2.056+-0.006)Csub(0.009)Nsub(0.003), which was found to be -76.78+-0.83 kcal/mol. They calculate that ΔHsub(f,298) (TiBsub(2.056)=-76.14+-0.85 kcal/mol. The procedure employed makes it possible to carry out the titanium diboride synthesis reaction with the calorimeter at room temperature

  6. Phase 1 Final Technical Report - MgB2 Synthesis: Pushing to High Field Performance

    International Nuclear Information System (INIS)

    Bhatia, Mohit; McIntyre, Peter

    2009-01-01

    Accelerator Technology Corp. (ATC) has successfully completed its Phase 1 effort to develop rf plasma torch synthesis of MgB2 superconducting powder. The overall objective is to de-velop a way to introduce homogeneous alloying of C and SiC impurities into phase-pure MgB2. Several groups have attained remarkable benefits from such alloying in raising the upper critical field Hc2 from ∼14 T to ∼30 T (bulk) and ∼50 T (thin films). But no one has succeeded in pro-ducing that benefit homogeneously, so that current transport in a practical powder-in-tube (PIT) conductor is largely the same as without the alloying. ATC has conceived the possibility of attaining such homogeneity by passing aerosol suspen-sions of reactant powders through an rf plasma torch, with each reactant transported on a stream-line that heats it to an optimum temperature for the synthesis reaction. This procedure would uniquely access non-equilibrium kinetics for the synthesis reaction, and would provide the possi-bility to separately control the temperature and stoichiometry of each reactant as it enters the mixing region where synthesis occurs. It also facilitates the introduction of seed particles (e.g. nanoscale SiC) to dramatically enhance the rate of the synthesis reaction compared to gas-phase synthesis in rf plasma reported by Canfield and others. During the Phase 1 effort ATC commissioned its 60 kW 5 MHz rf source for a manufactur-ing-scale rf plasma torch. This effort required repair of numerous elements, integration of cooling and input circuits, and tuning of the load characteristics. The effort was successful, and the source has now been tested to ∼full power. Also in the Phase 1 effort we encountered a subsidiary but very important problem: the world is running out of the only present supply of phase-pure amorphous boron. The starting boron powder must be in the amorphous phase in order for the synthesis reaction to produce phase-pure MgB2. Even small contamination with crystalline boron results in the formation of parasitic phases such as MgB4, MgB7, etc. Such parasitic phases are a primary element of the connectivity problem, in which even though a sample powder may contain grains of high-quality MgB2, adjacent grains are surrounded by intergrowths of parasitic phases so that current trans-port is badly degraded. The best results to date have been obtained using boron powder produced long ago for a rocket propellant development project. The synthesis process was complex and is now largely lost, and the manufacturing equipment has long since been scrapped. The last batch of the powder has been used during recent years to support MgB2 R and D at several labs, but supplies are dwindling. ATC has identified a first application of its plasma torch to synthesize phase-pure amorphous boron flake using a rapid-quench splat technique. Inexpensive technical-grade boron would be purified of contaminants, then dispersed as an aerosol in inert gas and passed through the plasma torch to melt it into a spray. The spray would be splat-condensed on a rotating drum to form pure amorphous flake. The process would begin with technical-grade boron powder, having good stoichiometric purity, nanoscale particles, but significant contamination of MgO and crystalline boron. We used wet chemistry to remove B2O3 completely and reduced the MgO impurity, and analyzed the particle size distribution using a Coulter counter and the phase composition using X-ray diffrac-tion (XRD). The next step will be to build an rf plasma torch with a recirculating single-component aerosol feed and the cooled splat drum and collector, and undertake process devel-opment for amorphous boron powder. This revised goal has two benefits. First, it is an easier technology than our ultimate goal of a multi-component laminar flow torch. We have been counseled by those experienced in plasma torch technology that our ultimate goal will require a torch that should be feasible but has never been attempted. It may require an extended period of R and D for both the torch itself and the gas dynamics in the reaction region. Second, this simpler single-component process will yield a product powder that is important today for the many groups undertaking powder-metallurgy routes to MgB2. The above success and learning curve has brought us to a significant shift of strategy from what was originally set out in the Phase 1 plan. But this shift has brought us to within sight of a powder product that will itself be an enabling boost for the community of MgB2 developers.

  7. Structural and critical current properties in Al-doped MgB2

    International Nuclear Information System (INIS)

    Zheng, D.N.; Xiang, J.Y.; Lang, P.L.; Li, J.Q.; Che, G.C.; Zhao, Z.W.; Wen, H.H.; Tian, H.Y.; Ni, Y.M.; Zhao, Z.X.

    2004-01-01

    A series of Al-doped Mg 1-x Al x B 2 samples have been fabricated and systematic study on structure and superconducting properties have been carried out for the samples. In addition to a structural transition observed by XRD, TEM micrographs showed the existence of a superstructure of double c-axis lattice constant along the direction perpendicular to the boron honeycomb sheet. In order to investigate the effect of Al doping on flux pinning and critical current properties in MgB 2 , measurements on the superconducting transition temperature T c , irreversible field B irr and critical current density J c were performed too, for the samples with the doping levels lower than 0.15 in particular. These experimental observations were discussed in terms of Al doping induced changes in carrier concentration

  8. Structural and critical current properties in Al-doped MgB 2

    Science.gov (United States)

    Zheng, D. N.; Xiang, J. Y.; Lang, P. L.; Li, J. Q.; Che, G. C.; Zhao, Z. W.; Wen, H. H.; Tian, H. Y.; Ni, Y. M.; Zhao, Z. X.

    2004-08-01

    A series of Al-doped Mg 1- xAl xB 2 samples have been fabricated and systematic study on structure and superconducting properties have been carried out for the samples. In addition to a structural transition observed by XRD, TEM micrographs showed the existence of a superstructure of double c-axis lattice constant along the direction perpendicular to the boron honeycomb sheet. In order to investigate the effect of Al doping on flux pinning and critical current properties in MgB 2, measurements on the superconducting transition temperature Tc, irreversible field Birr and critical current density Jc were performed too, for the samples with the doping levels lower than 0.15 in particular. These experimental observations were discussed in terms of Al doping induced changes in carrier concentration.

  9. Interplay of dendritic avalanches and gradual flux penetration in superconducting MgB2 films

    International Nuclear Information System (INIS)

    Shantsev, D V; Goa, P E; Barkov, F L; Johansen, T H; Kang, W N; Lee, S I

    2003-01-01

    Magneto-optical imaging was used to study a zero-field-cooled MgB 2 film at 9.6 K where in a slowly increasing field the flux penetrates by an abrupt formation of large dendritic structures. Simultaneously, a gradual flux penetration takes place, eventually covering the dendrites, and a detailed analysis of this process is reported. We find an anomalously high gradient of the flux density across a dendrite branch, and a peak value that decreases as the applied field increases. This unexpected behaviour is reproduced by flux creep simulations based on the non-local field-current relation in the perpendicular geometry. The simulations also provide indirect evidence that flux dendrites are formed at an elevated local temperature, consistent with a thermo-magnetic mechanism of the instability

  10. Microwave second-harmonic response of ceramic MgB2 samples

    International Nuclear Information System (INIS)

    Agliolo Gallitto, A.; Bonsignore, G.; Li Vigni, M.

    2005-01-01

    Nonlinear microwave response of different ceramic MgB 2 samples has been investigated by the technique of second-harmonic emission. The second-harmonic signal has been investigated as a function of temperature, DC magnetic field and input microwave power. The attention has mainly been devoted to the response at low magnetic fields, where nonlinear processes arising from motion of Abrikosov fluxons are ineffective. The results show that different mechanisms are responsible for the nonlinear response in the different ranges of temperature. At low temperatures, the nonlinear response is due to processes involving weak links. At temperatures close to T c , a further contribution to the harmonic emission is present; it can be ascribed to modulation of the order parameter by the microwave field and gives rise to a peak in the temperature dependence of the harmonic signal

  11. Progress in electrical and mechanical properties of rectangular MgB2 wires

    International Nuclear Information System (INIS)

    Kovac, P; Melisek, T; Kopera, L; Husek, I; Polak, M; Kulich, M

    2009-01-01

    Critical current densities and mechanical resistance of MgB 2 wires made by the rectangular wire-in-tube technique (RWIT) have been studied. Wires prepared from different precursor powders and variable sheath materials are compared. The best electrical performance (10 4 A cm -2 at 11.3 T) was measured for the wire with mechanically alloyed powder doped by SiC. While the critical current densities, J c , at 4.2 K are considerably influenced by the powder used, the differences at 20 K are much smaller. Flattened wires show different levels of critical current anisotropy influenced by the precursor powder used. Stress-strain characteristics and critical current degradation are strongly affected by the applied metallic materials and also by the filament's strength. The highest irreversible strain ε irr = 0.55% was measured for Ti/Cu/Monel sheathed wire with filaments from mechanically alloyed powder.

  12. The superconducting properties of co-doped polycrystalline MgB2

    International Nuclear Information System (INIS)

    Moore, J D; Perkins, G K; Branford, W; Yates, K A; Caplin, A D; Cohen, L F; Chen, Soo Kien; Rutter, N A; MacManus-Driscoll, Judith L

    2007-01-01

    In this study we compare the critical current density, the irreversibility line and the upper critical field of four MgB 2 polycrystalline samples, which are either undoped or have 5% carbon or 5% carbon plus either 1% aluminium or 2% zirconium. We discuss how care must be taken for the extraction of the irreversibility line in such samples. We also show how ac susceptibility and Hall probe imaging can be used to examine whether the samples remain fully connected to the highest available fields. Compared to simple 5% carbon doping we find that co-doping provides modest improvement in the pinning properties at intermediate fields in the carbon plus zirconium doped sample

  13. Hall conductivity and the vortex phase in MgB2 thin films

    International Nuclear Information System (INIS)

    Jung, Soon-Gil; Seong, W K; Huh, Ji Young; Lee, T G; Kang, W N; Choi, Eun-Mi; Kim, Heon-Jung; Lee, Sung-Ik

    2007-01-01

    In a MgB 2 thin film superconductor, we have found that Hall conductivity (σ xy ) is described by the sum of two terms, σ xy = C 1 /H+C 3 H, where C 1 and C 3 are independent of the magnetic fields and have positive values. C 1 is observed to be proportional to (1-t) n with n = 4.2, where t is the reduced temperature (T/T c ), and C 3 is weakly dependent on the temperature. These results are consistent with those of the overdoped La 2-x Sr x CuO 4 superconductors. Based on Hall angle data, we obtained a vortex phase diagram with three regions, vortex-solid, crossover, and vortex-liquid regions in the H-T plane

  14. Critical current density of MgB2 thin films and the effect of interface pinning

    International Nuclear Information System (INIS)

    Choi, Eun-Mi; Gupta, S K; Sen, Shashwati; Lee, Hyun-Sook; Kim, Hyun-Jung; Lee, Sung-Ik

    2004-01-01

    Preferentially oriented MgB 2 thin films with c-axis normal to the surface have been prepared and characterized for microstructure and transport properties. The magnetic field dependence of superconducting critical current density J c has been determined from the magnetization hysteresis (M-H) loops at various temperatures using the Bean's critical state model. High J c of these films show their potential for applications. We have also measured the angular dependences of J c . The angular dependence is seen to be in agreement with the anisotropic Ginzburg-Landau model except that at angles close to the ab plane, increased pinning due to film-substrate interaction is observed. The angular range where interface pinning is effective has been determined by measurement of asymmetry in dissipation on reversal of current for fields applied at angles close to the ab plane

  15. Comparative study of neutron irradiation and carbon doping in MgB2 single crystals

    International Nuclear Information System (INIS)

    Krutzler, C.; Zehetmayer, M.; Eisterer, M.; Weber, H. W.; Zhigadlo, N. D.; Karpinski, J.

    2007-01-01

    We compare the reversible and irreversible magnetic properties of superconducting carbon doped and undoped MgB 2 single crystals before and after neutron irradiation. A large number of samples with transition temperatures between 38.3 and 22.8 K allows us to study the effects of disorder systematically. Striking similarities are found in the modification of the reversible parameters by irradiation and doping, which are discussed in terms of impurity scattering and changes of the Fermi surface. The irreversible properties are influenced by two counteracting mechanisms: they are enhanced by the newly introduced pinning centers but degraded by changes in the thermodynamic properties. Accordingly, the large neutron induced defects and the small defects from carbon doping lead to significantly different effects on the irreversible properties. Finally, the fishtail effect caused by all kinds of disorder is discussed in terms of an order-disorder transition of the flux-line lattice

  16. Using specific heat to scan gaps and anisotropy of MgB2

    International Nuclear Information System (INIS)

    Bouquet, F.; Wang, Y.; Toulemonde, P.; Guritanu, V.; Junod, A.; Eisterer, M.; Weber, H.W.; Lee, S.; Tajima, S.

    2004-01-01

    We performed specific heat measurements to study the superconducting properties of the ∼40 K superconductor MgB 2 , up to 16 T, using polycrystal and single crystal samples. Our results establish the validity of the two-gap model. We tested the effect of disorder by irradiating our sample. This procedure decreased T c down to ∼26 K, but did not suppress completely the smaller gap, at variance with theoretical expectations. A positive effect of the irradiation was the increase of H c2 up to almost 30 T. Our results on the single crystal allow the anisotropy of each band to be determined independently, and show the existence of a cross-over field well below H c2 characterizing the physics of the small-gapped band. We also present preliminary results on Nb 3 Sn, showing similar, but weaker effects

  17. Phase dynamics of single long Josephson junction in MgB2 superconductor

    Science.gov (United States)

    Chimouriya, Shanker Pd.; Ghimire, Bal Ram; Kim, Ju H.

    2018-05-01

    A system of perturbed sine Gordon equations is derived to a superconductor-insulator-superconductor (SIS) long Joseph-son junction as an extension of the Ambegaokar-Baratoff relation, following the long route of path integral formalism. A computer simulation is performed by discretizing the equations using finite difference approximation and applied to the MgB2 superconductor with SiO2 as the junction material. The solution of unperturbed sG equation is taken as the initial profile for the simulation and observed how the perturbation terms play the role to modify it. It is found initial profile deformed as time goes on. The variation of total Josephson current has also been observed. It is found that, the perturbation terms play the role for phase frustration. The phase frustration achieves quicker for high tunneling current.

  18. The increase in Tc for MgB2 superconductor under high pressure

    International Nuclear Information System (INIS)

    Liu, Z-X; Jin, C-Q; You, J-Y; Li, S-C; Zhu, J-L; Yu, R-C; Li, F-Y; Su, S-K

    2002-01-01

    We report in situ high-pressure studies up to 1.0 GPa on MgB 2 superconductor which had been synthesized at high pressure. The as-prepared sample is of high quality as regards having a sharp superconducting transition (T c ) at 39 K. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with a mixed oil as the pressure-transmitting medium, which provides a quasi-hydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that T c increases with pressure in the initial pressure range, leading to a parabolic-like T c -P evolution

  19. Process for making a titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition

    Science.gov (United States)

    Holcombe, C.E.; Dykes, N.L.

    1992-04-28

    A ceramic composition is described. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1--A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2--The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3--The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness. No Drawings

  20. A possibility of enhancing Jc in MgB2 film grown on metallic hastelloy tape with the use of SiC buffer layer

    International Nuclear Information System (INIS)

    Putri, W. B. K.; Kang, B.; Ranot, M.; Lee, J. H.; Kang, W. N.

    2014-01-01

    We have grown MgB 2 on SiC buffer layer by using metallic Hastelloy tape as the substrate. Hastelloy tape was chosen for its potential practical applications, mainly in the power cable industry. SiC buffer layers were deposited on Hastelloy tapes at 400, 500, and 600 degrees C by using a pulsed laser deposition method, and then by using a hybrid physical-chemical vapor deposition technique, MgB 2 films were grown on the three different SiC buffer layers. An enhancement of critical current density values were noticed in the MgB 2 films on SiC/Hastelloy deposited at 500 and 600 degrees C. From the surface analysis, smaller and denser grains of MgB 2 tapes are likely to cause this enhancement. This result infers that the addition of SiC buffer layers may contribute to the improvement of superconducting properties of MgB 2 tapes.

  1. EDX and ion beam treatment studies of filamentary in situ MgB2 wires with Ti barrier

    International Nuclear Information System (INIS)

    Rosova, A.; Kovac, P.; Husek, I.; Kopera, L.

    2011-01-01

    Highlights: → SiC-doped MgB 2 wires with Ti barrier showed good Jc in magnetic field. → Explanation why the Ti barrier fits to SiC-doped MgB 2 filaments. → Ti barrier getters Si from SiC-doped filaments and improve their properties. → Si accumulated in an inner layer of Ti barrier protects filaments from Cu diffusion. → Ion beam treatment helps to discover microstructure of complicated systems. - Abstract: In situ SiC-doped filamentary MgB 2 wires (with the diameter of 0.860 and 0.375 mm) with Cu stabilization separated by Ti barrier layers supported by outer SS sheath and annealed at 800 deg. C/0.5 h have been studied by combination of EDX analysis and ion beam selective etching. It was found that several Ti-Cu inter-metallic compounds were created by Cu-Ti interdiffusion and thus the barrier protection against Cu penetration into the superconducting filaments is limited. We showed an advantage of Ti use as the barrier material in our wires. Ti getters silicon out from the superconducting filament, what purges superconducting MgB 2 from Si and creates an additional Si-rich layer in inner part of Ti barrier which prevents Cu diffusion more effectively.

  2. Magnetic properties and critical current density of bulk MgB2 polycrystalline with Bi-2212 addition

    International Nuclear Information System (INIS)

    Shen, T M; Li, G; Zhu, X T; Cheng, C H; Zhao, Y

    2005-01-01

    Bulk samples of MgB 2 were prepared with 0, 3, 5, and 10 wt% Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) particles, added using a simple solid-state reaction route in order to investigate the effect of inclusions of a material with higher T c than the superconducting matrix. The density, diamagnetic signal, and critical current density, J c , of the samples change significantly with the doping level. It is found that J c is significantly enhanced by the Bi-2212 addition. Microstructural analysis indicates that a small amount of Bi-2212 is decomposed into Cu 2 O and other impurity phases while a significant amount of unreacted Bi-2212 particles remains in MgB 2 matrix, and these act as effective pinning centres for vortices. The enhanced pinning force is mainly attributable to these highly dispersed inclusions inserted in the MgB 2 grains. Despite the effectiveness of the high-T c inclusions in increasing superconducting critical currents in our experiment, our results seem to demonstrate the superiority of attractive centres over repulsive ones. A pinning mechanism is proposed to account for the contribution of this type of pinning centre in MgB 2 superconductors. (rapid communication)

  3. Fabrication of extruded wire of MgB2/Al composite material and its superconducting property and microstructure

    Czech Academy of Sciences Publication Activity Database

    Matsuda, K.; Nishimura, K.; Ikeno, S.; Mori, K.; Aoyama, S.; Yabumoto, Y.; Hishinuma, Y.; Müllerová, Ilona; Frank, Luděk; Yurchenko, V. V.; Johansen, T. H.

    2008-01-01

    Roč. 97, - (2008), 012230:1-6 E-ISSN 1742-6596. [European Conference on Applied Superconductivity /8./ - EUCAS 2007. Brussels, 16.09.2007-20.09.2007] Institutional research plan: CEZ:AV0Z20650511 Keywords : MgB2/Al composite * superconductors * electron microscopy Subject RIV: JI - Composite Materials

  4. Crystallinity and superconductivity of as-grown MgB2 thin films with AlN buffer layers

    International Nuclear Information System (INIS)

    Tsujimoto, K.; Shimakage, H.; Wang, Z.; Kaya, N.

    2005-01-01

    The effects of aluminum nitride (AlN) buffer layers on the superconducting properties of MgB 2 thin film were investigated. The AlN buffer layers and as-grown MgB 2 thin films were deposited in situ using the multiple-target sputtering system. The best depositing condition for the AlN/MgB 2 bi-layer occurred when the AlN was deposited on c-cut sapphire substrates at 290 deg. C. The crystallinity of the AlN/MgB 2 bi-layer was studied using the XRD φ-scan and it showed that AlN and MgB 2 had the same in-plane alignment rotated at an angle of 30 deg. as compared to c-cut sapphire. The critical temperature of the MgB 2 film was 29.8 K and the resistivity was 50.0 μΩ cm at 40 K

  5. Effects of graphite doping on critical current density and microstructure of MgB2 bulks by an improved Mg-diffusion method

    International Nuclear Information System (INIS)

    Pan, X.F.; Zhao, Y.; Feng, Y.; Yang, Y.; Cheng, C.H.

    2008-01-01

    abstract: A series of graphite-doped MgB 2 bulks with high density have been successfully prepared by an improved Mg-diffusion method in ambient pressure. The effects of graphite doping on lattice parameters, T c , J c and microstructure of MgB 2 have been investigated. The results show that compared to the nano-C-doped or CNTs-doped MgB 2 , C is not easy to substitute B in graphite-doped MgB 2 . However, at the same C content, the graphite-doped MgB 2 has a higher J c . At 10 K and self-field, the J c for MgB 1.985 C 0.015 reaches 0.58 MA/cm 2 . For the MgB 1.945 C 0.055 , at 5 K, 7 T and 10 K, 6 T the J c achieves 10,000 A/cm 2 which is two orders of magnitude higher than that for the undoped sample. In addition to improving electron scattering and intergranular connectivity, the unreacted graphite in the graphite-doped MgB 2 is proposed to be responsible to the excellent J c properties of MgB 2 in high fields, due to depressed grain growth and enhanced grain boundary flux pinning

  6. Effect of process variables on synthesis of MgB2 by a high energy ball mill

    Directory of Open Access Journals (Sweden)

    Kurama Haldun

    2016-01-01

    Full Text Available The discovery of superconductivity of MgB2 in 2001, with a critical temperature of 39 K, offered the promise of important large-scale applications at around 20 K. Except than the other featured synthesis methods, mechanical activation performed by high energy ball mills, as bulk form synthesis or as a first step of wire and thin film productions, has considered as an effective alternative production route in recent years. The process of mechanical activation (MA starts with mixing the powders in the right proportion and loading the powder mixture into the mill with the grinding media. The milled powder is then consolidated into a bulk shape and heat-treated to obtain desired microstructure and properties. Thus, the important components of the MA process are the raw materials, mill type and process variables. During the MA process, heavy deformation of particles occure. This is manifested by the presence of a variety of crystal defects such as dislocations, vacancies, stacking faults and increased number of particle boundaries. The presence of this defect structure enhances the diffusivity of solute hence the critical currents and magnetic flux pinning ability of MgB2 are improved. The aim of the present study is to determine the effects of process variables such as ball-to-powder mass ratio, size of balls, milling time, annealing temperature and contribution of process control agent (toluene on the product size, morphology and conversion level of precursor powders to MgB2 after subsequent heat treatment. The morphological analyses of the samples were performed by a high vacuum electron microscope ZEISS SUPRA VP 50. The phase compositions of the samples were performed with an Rigaku-Rint 2200 diffractometer, with nickel filtered Cu Kα radiation and conversion level. The MgB2 phase wt % was calculated by the Rietveld refinement method. The obtained results were discussed according to the process variables to find out their affect on the structure of MgB2 and to determine the optimum synthesis condition. It was found that the ball-to-powder mass ratio of precursors mixed and the milling time remarkably affect the MgB2 phase wt % and product size.

  7. Multi-gap superconductivity in MgB2: Magneto-Raman spectroscopy

    International Nuclear Information System (INIS)

    Blumberg, G.; Mialitsin, A.; Dennis, B.S.; Zhigadlo, N.D.; Karpinski, J.

    2007-01-01

    Electronic Raman scattering studies on MgB 2 single crystals as a function of excitation and polarization have revealed three distinct superconducting features: a clean gap below 37 cm -1 and two coherence peaks at 109 and 78 cm -1 which we identify as the superconducting gaps in π- and σ-bands and as the Leggett's collective mode arising from the fluctuation in the relative phase between two superconducting condensates residing on corresponding bands. The temperature and field dependencies of the superconducting features have been established. A phononic Raman scattering study of the E 2g boron stretching mode anharmonicity and of superconductivity induced self-energy effects is presented. We show that anharmonic two phonon decay is mainly responsible for the unusually large linewidth of the E 2g mode. We observe ∼2.5% hardening of the E 2g phonon frequency upon cooling into the superconducting state and estimate the electron-phonon coupling strength associated with this renormalization

  8. Transport relaxation measurements and glassy state effects in superconducting MgB2

    International Nuclear Information System (INIS)

    Olutas, M.; Yetis, H.; Altinkok, A.; Kilic, A.; Kilic, K.

    2008-01-01

    Time dependent effects in superconducting MgB 2 have been studied systematically for the first time by transport relaxation measurements (V-t curves) as a function of transport current (I), temperature (T) and external magnetic field (H). At very low dissipation levels (below ∼1 μV), it was observed that the sample voltage grows up smoothly in time by exhibiting the details of initial stage of relaxation process. At high dissipation levels, steady state corresponding to constant flow rate is maintained within a very short time and monitoring of details of flux dynamic evolving along sample becomes difficult on long time scales. Another interesting behavior is the appearance of voltage peak when the transport current was reduced to a finite value. After peak, it was observed that the sample voltage relaxes smoothly by leveling off within a very short time. The evolution of V-t curves suggests that formation of resistive flow channels along sample develops easily, which is quite similar to that of obtained for the superconducting ceramic samples whose grain boundaries are improved. Time dependent effects were also observed in magnetovoltage measurements (V-H curves) as the field sweep rate (dH/dt) varies. The observations were interpreted mainly in terms of flux trapping in grains

  9. Investigation of the resistive transition of MgB2 thin film through current noise

    International Nuclear Information System (INIS)

    Gandini, C; Rajteri, M; Portesi, C; Monticone, E; Masoero, A; Mazzetti, P

    2006-01-01

    In this paper we present measurements concerning the current noise produced during the resistive transition in a MgB 2 polycrystalline thin film. The power spectrum of the current noise, observed when the temperature is slowly changed across its critical value, presents a large electrical noise of the 1/f n type (n ≅ 3) over a quite wide range of frequencies. This noise may be considered as generated by the abrupt creation of resistive strips across the specimen constituted by grains which have undergone the resistive transition. A computer model that takes into account fluctations of the grain critical currents and of the number of grain per strips, has been developed to simulate the resistive transition and to evaluate the noise power spectrum. When the temperature is incresed and reaches its critical value, resistive strips are formed according to a percolative process, giving rise to resistance steps which are at the origin of the noise. The theoretical results obtained by this model are in good agreement, concerning both the shape and intensity of the noise power spectrum, with the experimental data directly measured on the specimen

  10. Development and fundamental study on a superconducting induction/synchronous motor incorporated with MgB2 cage windings

    International Nuclear Information System (INIS)

    Nakamura, T; Yamada, Y; Nishio, H; Sugano, M; Amemiya, N; Kajikawa, K; Wakuda, T; Takahashi, M; Okada, M

    2012-01-01

    In this paper, a fundamental study of the rotating characteristics of a induction/synchronous motor by use of superconducting MgB 2 cage windings is carried out based on analysis and experiment. Current transport properties of the produced monofilamentary MgB 2 wires are firstly characterized, and then utilized for the determination of the current carrying capacity of the rotor bars. Then, the motor model is designed and fabricated with the aid of conventional (copper) stator windings. We successfully observe the synchronous rotation of the fabricated motor at a rotation speed range from 300 to 1800 rpm. We can also realize an almost constant torque versus speed curve, and this characteristic is explained from the steep take-off of the electric field versus the current density curve, based on the nonlinear electrical equivalent circuit. These results are promising for the practical applications of a high efficiency motor for a liquid hydrogen circulation pump.

  11. Mechanical properties and bending strain effect on Cu-Ni sheathed MgB2 superconducting tape

    International Nuclear Information System (INIS)

    Fu, Minyi; Chen, Jiangxing; Jiao, Zhengkuan; Kumakura, H.; Togano, K.; Ding, Liren; Zhang, Yong; Chen, Zhiyou; Han, Hanmin; Chen, Jinglin

    2004-01-01

    The Young's modulus (E) of Cu-Ni sheathed MgB 2 monofilament tape was measured using electric method. It is about 8.05 x 10 10 Pa, the same order of Cu and its alloys. We found that the lower E value of the MgB 2 component seemed to relate to the lower filament density. The benefits of pre-compression in filaments were discussed in terms of improving stress distribution in the wires and tapes during winding and operation of superconducting magnets. The magnetic field dependence of J c was investigated on the sample subjected to various strain levels through bending with different radii at 4.2 K

  12. Critical current density improvements in MgB2 superconducting bulk samples by K2CO3 additions  

    DEFF Research Database (Denmark)

    Grivel, J.-C.

    2018-01-01

    MgB2 bulk samples with potassium carbonate doping were made by means of reaction of elemental Mg and B powders mixed with various amounts of K2CO3. The Tc of the superconducting phase as well as its a-axis parameter were decreased as a result of carbon doping. Potassium escaped the samples during...... reaction. The critical current density of MgB2 was improved both in self field and under applied magnetic field for T ≤ 30 K, with optimum results for 1 mol% K2CO3 addition. The normalized flux pinning force (f(b)) shows that the flux pinning mechanism at low field is similar for all samples, following...

  13. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-06

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  14. Effects of α-particle beam irradiation on superconducting properties of thin film MgB2 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Bum; Duong, Pham van; Ha, Dong Hyup; Oh, Young Hoon; Kang, Won Nam; Chai, Jong Seo [Sungkunkwan Univeversity, Suwon (Korea, Republic of); Hong, Seung Pyo; Kim, Ran Young [Kore Institute of Radiological and Medical Science, Seoul (Korea, Republic of)

    2016-06-15

    Superconducting properties of thin film MgB2 superconductors irradiated with 45 MeV α-particle beam were studied. After the irradiation, enhancement of the critical current density and pinning force was observed, scaling close to strong pinning formula. Double logarithmic plots of the maximum pinning force density with irreversible magnetic field show a power law behavior close to carbon-doped MgB2 film or polycrystals. Variation of normalized pinning force density in the reduced magnetic field suggests scaling formulas for strong pinning mechanism like planar defects. We also observed a rapid decay of critical current density as the vortex lattice constant decreases, due to the strong interaction between vortices and increasing magnetic field.

  15. Measurement of the penetration depth and coherence length of MgB2 in all directions using transmission electron microscopy

    DEFF Research Database (Denmark)

    Loudon, J. C.; Yazdi, Sadegh; Kasama, Takeshi

    2015-01-01

    We demonstrate that images of flux vortices in a superconductor taken with a transmission electron microscope can be used to measure the penetration depth and coherence length in all directions at the same temperature and magnetic field. This is particularly useful for MgB2, where these quantities...... vary with the applied magnetic field and values are difficult to obtain at low field or in the c direction. We obtained images of flux vortices from a MgB2 single crystal cut in the ac plane by focused ion beam milling and tilted to 45 degrees. with respect to the electron beam about...... the crystallographic a axis. A new method was developed to simulate these images that accounted for vortices with a nonzero core in a thin, anisotropic superconductor and a simplex algorithm was used to make a quantitative comparison between the images and simulations to measure the penetration depths and coherence...

  16. First-principles study of the (0001)-MgB2 surface finished in Mg and B

    International Nuclear Information System (INIS)

    Segura, Sully; Martínez, Jairo Arbey Rodríguez; Moreno-Armenta, María Guadalupe

    2014-01-01

    We present a study based on Density Functional Theory (DFT) of the volume and two surfaces (0001) of MgB 2 , one of them terminated in Mg and the other one terminated in B. Each one of the surface was relaxed and their electronic properties were determined. From calculation of the enthalpy of formation we found that the Mg-terminated surface is energetically favored. The bands seem to present a formation similar to the Dirac's cone as that are presented in graphene, but in MgB 2 is above of the Fermi level. In the three cases, volume and the two surfaces, the behaviour is boron-metallic, because there are strong presence of B orbital's in the neighborhood of the Ferm level

  17. Nanoparticles of the superconductor MgB2: structural characterization and in situ study of synthesis kinetics

    International Nuclear Information System (INIS)

    Cui Chunxiang; Liu Debao; Shen Yutian; Sun Jinbin; Meng Fanbin; Wang Ru; Liu Shuangjin; Greer, A.L.; Chen, S.K.; Glowacki, B.A.

    2004-01-01

    Single-crystal MgB 2 nanoparticles, with diameters in the range 20-100 nm, have been synthesized in situ in the sample chamber of an X-ray diffractometer. The reaction kinetics are analyzed and related to the atomic-level structure of the particles as observed by high-resolution electron microscopy. Synthesis conditions may have a significant influence on microstructure and superconducting properties

  18. Dynamic vortex-phase diagram of MgB2 single crystals near the peak-effect region

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Lee, Hyun-Sook; Kang, Byeongwon; Chowdhury, P.; Kim, Kyung-Hee; Park, Min-Seok; Lee, Sung-Ik

    2006-01-01

    The dynamic vortex-phase diagram of MgB 2 single crystals has been constructed by using voltage noise characteristics. Between the onset (H on ) and the peak (H p ) magnetic fields, crossovers from a state with large noises to a noise-free state were observed with increasing current while above H p , a reverse behavior was found. We will discuss the dynamic vortex phase diagram and the possible origins of the crossovers

  19. In-situ synchrotron x-ray study of MgB2 formation when doped by SiC

    Science.gov (United States)

    Abrahamsen, A. B.; Grivel, J.-C.; Andersen, N. H.; Herrmann, M.; Häßler, W.; Birajdar, B.; Eibl, O.; Saksl, K.

    2008-02-01

    We have studied the evolution of the reaction xMg + 2B + ySiC → zMg1-p(B1-qCq)2 + yMg2Si in samples of 1, 2, 5 and 10 wt% SiC doping. We found a coincident formation of MgB2 and Mg2Si, whereas the crystalline part of the SiC nano particles is not reacting at all. Evidence for incorporation of carbon into the MgB2 phase was established from the decrease of the a-axis lattice parameter upon increasing SiC doping. An estimate of the MgB2 lower limit grain size was found to decrease from L100 = 795 Å and L002 = 337 Å at 1 wt% SiC to L100 = 227 Å and L002= 60 Å at 10 wt% SiC. Thus superconductivity might be suppressed at 10 wt% SiC doping due to the grain size approaching the coherence length.

  20. Fabrication and properties of multifilamentary MgB 2 wires by in-situ powder-in-tube process

    Science.gov (United States)

    Wang, Q. Y.; Jiao, G. F.; Liu, G. Q.; Xiong, X. M.; Yan, S. C.; Zhang, P. X.; Sulpice, A.; Mossang, E.; Feng, Y.; Yan, G.

    2010-11-01

    We have fabricated the long TiC-doped MgB2 wires with 6 filaments by in-situ powder-in-tube method using Nb as the barrier and copper as the stabilizer. To improve the strength of wires, the Nb-core was used as the central filament. The transport engineering critical current density (Jce) of the samples sintered at different temperature were measured, which reaches 2.5 × 104 A/cm2 at 4.2 K, 5 T. 100 m MgB2 wires with different diameter were wound into coils and the transport critical current (Ic) of the coil were measured at 30 K in self-field. The Jce value 100 m coil achieves 1.1 × 104 A/cm2 in 1.2 mm wire. The reasons leading to the enhancement of high field Jce were discussed. The results show a good potential to fabricate high performance MgB2 wires and tapes at ambient pressure on an industrial scale.

  1. The Influence of CuFe2O4 Nanoparticles on Superconductivity of MgB2

    Science.gov (United States)

    Novosel, Nikolina; Pajić, Damir; Skoko, Željko; Mustapić, Mislav; Babić, Emil; Zadro, Krešo; Horvat, Joseph

    The influence of CuFe2O4 nanoparticle doping on superconducting properties of Fe-sheated MgB2 wires has been studied. The wires containing 0, 3 and 7.5 wt.% of monodisperse superparamagnetic nanoparticles (˜7 nm) were sintered at 650°C or 750°C for 1 hour in the pure argon atmosphere. X-ray diffraction patterns of doped samples showed very small maxima corresponding to iron boride and an increase in the fraction of MgO phase indicating some interaction of nanoparticles with Mg and B. Both magnetic and transport measurements (performed in the temperature range 2-42 K and magnetic field up to 16 T) showed strong deterioration of the superconducting properties upon doping with CuFe2O4. The transition temperatures, Tc, of doped samples decreased for about 1.4 K per wt.% of CuFe2O4. Also, the irreversibility fields Birr(T) decreased progressively with increasing doping. Accordingly, also the suppression of Jc with magnetic field became stronger. The observed strong deterioration of superconducting properties of MgB2 wires is at variance with reported enhancement of critical currents at higher temperatures (determined from magnetization) in bulk MgB2 samples doped with Fe3O4 nanoparticles. The probable reason for this discrepancy is briefly discussed

  2. Behaviour of filamentary MgB2 wires subjected to tensile stress at 4.2 K

    International Nuclear Information System (INIS)

    Kováč, P; Kopera, L; Melišek, T; Hušek, I; Rindfleisch, M; Haessler, W

    2013-01-01

    Different filamentary MgB 2 wires have been subjected to tensile stress at 4.2 K. Stress–strain and critical current versus stress and strain characteristics of wires differing by filament architecture, sheath materials, deformation and heat treatment were measured and compared. It was found that the linear increase of critical current due to the pre-compression effect (ranging from 5% up to ≈20%) is affected by thermal expansion and the strength of used metallic sheaths. The values of irreversible strain ε irr and stress σ irr depend dominantly on the applied outer sheath and its final heat treatment conditions. Consequently, the strain-tolerance of MgB 2 wires is influenced by several parameters and it is difficult to see a clear relation between I c (ε) and σ(ε) characteristics. The lowest ε irr was measured for Monel sheathed wires (0.3–0.6%), medium for GlidCop ® sheath (0.48–0.6%), and the highest ε irr = 0.6–0.9% were obtained for MgB 2 wires reinforced by the stainless steel 316L annealed at temperature between 600 and 800 ° C. The highest ε irr = 0.9% and σ irr = 900 MPa were measured for the work-hardened steel, which is not considerably softened by the heat treatment at 600 ° C/2.5 h. (paper)

  3. Refinement of Crystalline Boron and the Superconducting Properties of MgB2 by Attrition Ball Milling

    International Nuclear Information System (INIS)

    Lee, J. H.; Shin, S. Y.; Park, H. W.; Jun, B. H.; Kim, C. J.

    2008-01-01

    We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the MgB 2 pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the MgB 2 that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the B 2 O 3 peak became stronger in the powders, resulting in an increase in the amount of MgO within the MgB 2 volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density (J c ), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

  4. Superconductivity and thermal property of MgB2/aluminum matrix composite materials fabricated by 3-dimensional penetration casting method

    International Nuclear Information System (INIS)

    Matsuda, Kenji; Saeki, Tomoaki; Nishimura, Katsuhiko; Ikeno, Susumu; Mori, Katsunori; Yabumoto, Yukinobu

    2006-01-01

    Superconductive MgB 2 /Al composite material with low and high volume fractions of particles were fabricated by our special pre-packing technique and 3-dimensional penetration casting method. The composite material showed homogeneous distribution of MgB 2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (T C ) was determined by electrical resistivity and magnetization to be about 37-39 K. Specific heat measurements further supported these T C findings. The Meissner effect was also verified in the liquid He, in which a piece of the composite floated above a permanent magnet. The thermal conductivity of the MgB 2 /Al composite material was about 25 W/K·m at 30K, a value much higher than those found for NbTi or Nb 3 Sn superconducting wires normally used in practice, which are 0.5 and 0.2 W/K·m at 10 K, respectively. A billet of the superconducting material was successfully hot-extruded, forming a rod. The same as the billet sample, the rod showed an onset T C of electrical resistivity of 39 K. (author)

  5. Magnesium doping of boron nitride nanotubes

    Science.gov (United States)

    Legg, Robert; Jordan, Kevin

    2015-06-16

    A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

  6. Magnesium diboride(MgB{sub 2}) wires for applications

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Dipak; Kim, Jung Ho [Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, North Wollongong (Australia)

    2016-03-15

    Field and temperature dependence of the critical current density, Jc, were measured for both un-doped and carbon doped MgB{sub 2}/Nb/Monel wires manufactured by Hyper Tech Research, Inc. In particular, carbon incorporation into the MgB{sub 2} structure using malic acid additive and a chemical solution method can be advantageous because of the highly uniform mixing between the carbon and boron powders. At 4.2 K and 10 T, Jc was estimated to be 25,000 - 25,300 Acm{sup -2} for the wire sintered at 600 degrees C for 4 hours. The irreversibility field, Birr, of the malic acid doped wire was approximately 21.0 - 21.8 T, as obtained from a linear extrapolation of the J-B characteristic. Interestingly enough, the Jc of the malic acid doped sample exceeds 10{sup 5} Acm{sup -2} at 6 T and 4.2 K, which is comparable to that of commercial Nb-Ti wires.

  7. Magnesium Diboride thin Films, multilayers, and coatings for SRF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Xiaoxing [Temple Univ., Philadelphia, PA (United States)

    2017-08-17

    Superconducting radio frequency (SRF) cavities currently use low-temperature superconductor niobium, and the Nb SRF cavities have approached the performance levels predicted theoretically. Compared to Nb, MgB2 becomes superconducting at a much higher temperature and promises a better RF performance in terms of higher quality factor Q and higher acceleration capability. An MgB2 SRF technology can significantly reduce the operating costs of particle accelerators when these potentials are realized. This project aimed to advance the development of an MgB2 SRF technology. It had two main objectives: (1) materials issues of MgB2 thin films and multilayers related to their applications in SRF cavities; and (2) coating single-cell cavities for testing at RF frequencies. The key technical thrust of the project is the deposition of high quality clean MgB2 films and coatings by the hybrid physical-chemical vapor deposition (HPCVD) technique, which was developed in my group. We have achieved technical progress in each of the two areas. For the first objective, we have confirmed that MgB2 thin film coatings can be used to effectively enhance the vortex penetration field of an SRF cavity. A vortex is a normal region in the shape of spaghetti that threads through a superconductor. Its existence is due to an applied magnetic field that is greater than a so-called lower critical field, Hc1. Once a vortex enters the superconductor, its movement leads to loss. This has been shown to be the reason for an SRF cavity to break down. Thus, enhancing the magnetic field for a vortex to enter the superconductor that forms the SRF cavity has be a goal of intense research. To this end, Gurevich proposed that a coating of thin superconductor layer can impede the vortex entrance. In this project, we have done two important experiment to test this concept. One, we showed that the enhancement of Hc1 can be achieved by using in both epitaxial and polycrystalline MgB2 films. Although Hc1 is low for bulk MgB2 samples, about 600 Oe at 5 K, it increases with decreasing film thickness, reaching 1880 Oe when the film thickness is 100 nm. Two, we coated Nb ellipsoids with MgB2 films to achieve an “inverse cavity” configuration, mimicking the coating of an actual RF cavity. Our results demonstrate that it is indeed possible to increase the vortex penetration field of a cavity by a substantial amount (~600 Oe) by coating it with a thin MgB2 film. For the second objective, we modified the existing HPCVD system to be able to coat a 3.9 GHz SRF cavity, and using a stainless steel mock cavity showed that a uniform film with good superconducting property can be grown across the cavity interior. Further, we successfully deposited MgB2 on Cu disc. The two results combined demonstrate that it is possible to coat Cu cavities with high quality MgB2 films using HPCVD. MgB2 coated Cu could open up a possibility of using SRF cavities at 20–25 K with cryocoolers.

  8. Evaluation of Young’s modulus of MgB2 filaments in composite wires for the superconducting links for the high-luminosity LHC upgrade

    Science.gov (United States)

    Sugano, Michinaka; Ballarino, Amalia; Bartova, Barbora; Bjoerstad, Roger; Gerardin, Alexandre; Scheuerlein, Christian

    2016-02-01

    MgB2 wire is a promising superconductor for the superconducting links for the high-luminosity upgrade of the large Hadron collider at CERN. The mechanical properties of MgB2 must be fully quantified for the cable design, and in this study, we evaluate the Young’s modulus of MgB2 filaments in wires with a practical level of critical current. The Young’s moduli of MgB2 filaments by two different processes, in situ and ex situ, were compared. Two different evaluation methods were applied to an in situ MgB2 wire, a single-fiber tensile test and a tensile test after removing Monel. In addition, the Young’s modulus of the few-micron-thick Nb-Ni reaction layer in an ex situ processed wire was evaluated using a nanoindentation testing technique to improve the accuracy of analysis based on the rule of mixtures. The Young’s moduli of the in situ and ex situ MgB2 wires were in the range of 76-97 GPa and no distinct difference depending on the fabrication process was found.

  9. submitter Evaluation of Young’s modulus of MgB2 filaments in composite wires for the superconducting links for the high-luminosity LHC upgrade

    CERN Document Server

    Sugano, Michinaka; Bartova, Barbora; Bjoerstad, Roger; Gerardin, Alexandre; Scheuerlein, Christian

    2015-01-01

    MgB2 wire is a promising superconductor for the superconducting links for the high-luminosity upgrade of the large Hadron collider at CERN. The mechanical properties of MgB2 must be fully quantified for the cable design, and in this study, we evaluate the Young's modulus of MgB2 filaments in wires with a practical level of critical current. The Young's moduli of MgB2 filaments by two different processes, in situ and ex situ, were compared. Two different evaluation methods were applied to an in situ MgB2 wire, a single-fiber tensile test and a tensile test after removing Monel. In addition, the Young's modulus of the few-micron-thick Nb–Ni reaction layer in an ex situ processed wire was evaluated using a nanoindentation testing technique to improve the accuracy of analysis based on the rule of mixtures. The Young's moduli of the in situ and ex situ MgB2 wires were in the range of 76–97 GPa and no distinct difference depending on the fabrication process was found.

  10. Superior critical current density obtained in MgB_2 bulks via employing carbon-coated boron and minor Cu addition

    International Nuclear Information System (INIS)

    Peng, Junming; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M.; Xin, Ying; Jin, Jianxun

    2016-01-01

    Highlights: • Usage of carbon-coated boron leads to high level of homogeneous carbon doping. • Cu addition improves MgB_2 grain connectivity, leading to higher J_c at low fields. • Cu addition reduces MgO impurity, also contributing to the improvement of J_c. - Abstract: High performance Cu doped MgB_2 bulks were prepared by an in-situ method with carbon-coated amorphous boron as precursor. It was found that the usage of carbon-coated boron in present work leads to the formation of uniformly refined MgB_2 grains, as well as a high level of homogeneous carbon doping in the MgB_2 samples, which significantly enhance the J_c in both Cu doped and undoped bulks compared to MgB_2 bulks with normal amorphous boron precursor. Moreover, minor Cu can service as activator, and thus facilitates the growth of MgB_2 grains and improves crystallinity and grain connectivity, which can bring about the excellent critical current density (J_c) at self fields and low fields (the best values are 7 × 10"5 A/cm"2 at self fields, and 1 × 10"5 A/cm"2 at 2 T, 20 K, respectively). Simultaneously, minor Cu addition can reduce the amount of MgO impurity significantly, also contributing to the improvement of J_c at low fields. Our work suggests that Cu-activated sintering combined with employment of carbon-coated amorphous boron as precursor could be a promising technique to produce practical MgB_2 bulks or wires with excellent J_c on an industrial scale.

  11. Co-current Doping Effect of Nanoscale Carbon and Aluminum Nitride on Critical Current Density and Flux Pinning Properties of Bulk MgB2 Superconductors

    Science.gov (United States)

    Tripathi, D.; Dey, T. K.

    2018-05-01

    The effect of nanoscale aluminum nitride (n-AlN) and carbon (n-C) co-doping on superconducting properties of polycrystalline bulk MgB2 superconductor has been investigated. Polycrystalline pellets of MgB2, MgB2 + 0.5 wt% AlN (nano), MgB_{1.99}C_{0.01} and MgB_{1.99}C_{0.01} + 0.5 wt% AlN (nano) have been synthesized by a solid reaction process under inert atmosphere. The transition temperature (TC) estimated from resistivity measurement indicates only a small decrease for C (nano) and co-doped MgB2 samples. The magnetic field response of investigated samples has been measured at 4, 10, and 20 K in the field range ± 6 T. MgB2 pellets co-doped with 0.5 wt% n-AlN and 1 wt% n-C display appreciable enhancement in critical current density (J_C) of MgB2 in both low (≥ 3 times), as well as, high-field region (≥ 15 times). J_C versus H behavior of both pristine and doped MgB2 pellets is well explained in the light of the collective pinning model. Further, the normalized pinning force density f_p(= F_p/F_{pmax}) displays a fair correspondence with the scaling procedure proposed by Eisterer et al. Moreover, the scaled data of the pinning force density (i.e., f_p{-}h data) of the investigated pellets at different temperature are well interpreted by a modified Dew-Hughes expression reported by Sandu and Chee.

  12. Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering

    International Nuclear Information System (INIS)

    Gurevich, A; Patnaik, S; Braccini, V; Kim, K H; Mielke, C; Song, X; Cooley, L D; Bu, S D; Kim, D M; Choi, J H; Belenky, L J; Giencke, J; Lee, M K; Tian, W; Pan, X Q; Siri, A; Hellstrom, E E; Eom, C B; Larbalestier, D C

    2004-01-01

    We report a significant enhancement of the upper critical field H c2 of different MgB 2 samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities ρ, we show a clear trend of an increase in H c2 as ρ increases. One particular high resistivity film had a zero-temperature H c2 (0) well above the H c2 values of competing non-cuprate superconductors such as Nb 3 Sn and Nb-Ti. Our high-field transport measurements give record values H c2 perp (0) ∼ 34 T and H c2 par (0) ∼ 49 T for high resistivity films and H c2 (0) ∼ 29 T for untextured bulk polycrystals. The highest H c2 film also exhibits a significant upward curvature of H c2 (T) and a temperature dependence of the anisotropy parameter γ(T)=H c2 par / H c2 opposite to that of single crystals: γ(T) decreases as the temperature decreases, from γ(T c ) ∼ 2 γ(0) ∼ 1.5. This remarkable H c2 enhancement and its anomalous temperature dependence are a consequence of the two-gap superconductivity in MgB 2 , which offers special opportunities for further H c2 increases by tuning of the impurity scattering by selective alloying on Mg and B sites. Our experimental results can be explained by a theory of two-gap superconductivity in the dirty limit. The very high values of H c2 (T) observed suggest that MgB 2 can be made into a versatile, competitive high-field superconductor

  13. Effect of nano-carbon particle doping on the flux pinning properties of MgB2 superconductor

    OpenAIRE

    Soltanian, S.; Horvat, J.; Wang, X. L.; Munroe, P.; Dou, S. X.

    2003-01-01

    Polycrystalline MgB2-xCx samples with x=0.05, 0.1, 0.2, 0.3, 0.4 nano-particle carbon powder were prepared using an in-situ reaction method under well controlled conditions to limit the extent of C substitution. The phases, lattice parameters, microstructures, superconductivity and flux pinning were characterized by XRD, TEM, and magnetic measurements. It was found that both the a-axis lattice parameter and the Tc decreased monotonically with increasing doping level. For the sample doped with...

  14. Mapping flux avalanches in MgB2 films-equivalence between magneto-optical imaging and magnetic measurements

    International Nuclear Information System (INIS)

    Colauto, F; Choi, E M; Lee, J Y; Lee, S I; Yurchenko, V V; Johansen, T H; Ortiz, W A

    2007-01-01

    Vortex avalanches are known to occur in MgB 2 films within a certain range of temperatures and magnetic fields. These events, resulting from a thermomagnetic instability, were first revealed by real-time magneto-optical imaging, which exposed dendritic paths of abrupt flux propagation. This very powerful technique has, however, a practical limitation, since sensors that are currently available cannot be used at high magnetic fields. This letter shows that results obtained using dc magnetometry are in good correspondence with those furnished by magneto-optical imaging, demonstrating that the two techniques can be efficiently used as complementary tools to map vortex avalanches in superconducting films. (rapid communication)

  15. Multi-band description of the specific heat and thermodynamic critical field in MgB2 superconductor

    Science.gov (United States)

    Szcześniak, R.; Jarosik, M. W.; Tarasewicz, P.; Durajski, A. P.

    2018-05-01

    The thermodynamic properties of MgB2 superconductor can be explained using the multi-band models. In the present paper we have examined the experimental data available in literature and we have found out that it is possible to reproduce the measured values of the superconducting energy gaps, the thermodynamic critical magnetic field and specific heat jump within the framework of two-band Eliashberg formalism and appropriate defined free energy difference between superconducting and normal state. Moreover, we found that the obtained results differ significantly from the predictions of the conventional Bardeen-Cooper-Schrieffer theory.

  16. Superhard Rhenium/Tungsten Diboride Solid Solutions.

    Science.gov (United States)

    Lech, Andrew T; Turner, Christopher L; Lei, Jialin; Mohammadi, Reza; Tolbert, Sarah H; Kaner, Richard B

    2016-11-02

    Rhenium diboride (ReB 2 ), containing corrugated layers of covalently bonded boron, is a superhard metallic compound with a microhardness reaching as high as 40.5 GPa (under an applied load of 0.49 N). Tungsten diboride (WB 2 ), which takes a structural hybrid between that of ReB 2 and AlB 2 , where half of the boron layers are planar (as in AlB 2 ) and half are corrugated (as in ReB 2 ), has been shown not to be superhard. Here, we demonstrate that the ReB 2 -type structure can be maintained for solid solutions of tungsten in ReB 2 with tungsten content up to a surprisingly large limit of nearly 50 atom %. The lattice parameters for the solid solutions linearly increase along both the a- and c-axes with increasing tungsten content, as evaluated by powder X-ray and neutron diffraction. From micro- and nanoindentation hardness testing, all of the compositions within the range of 0-48 atom % W are superhard, and the bulk modulus of the 48 atom % solid solution is nearly identical to that of pure ReB 2 . These results further indicate that ReB 2 -structured compounds are superhard, as has been predicted from first-principles calculations, and may warrant further studies into additional solid solutions or ternary compounds taking this structure type.

  17. Preparation of titanium diboride powders from titanium alkoxide and ...

    Indian Academy of Sciences (India)

    Administrator

    Department of Materials and Manufacturing Process, Malek Ashtar University of Technology, Tehran. 15875-1744, Iran ... Titanium diboride is a hard refractory material with a high melting point ... (λ = 1⋅540598 Å) radiation. Morphology of the ...

  18. Optimization of the copper addition to the core of in situ Cu-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Woźniak, M; Juda, K L; Hopkins, S C; Glowacki, B A; Gajda, D

    2013-01-01

    Recent results on powder-in-tube in situ Cu-sheathed MgB 2 wires have shown that copper powder additions to the core can accelerate the formation of MgB 2 , increasing its volume fraction and greatly decreasing the amount of Mg–Cu intermetallic phases present in the core after heat treatment. The amount of added copper and heat treatment conditions strongly affect the critical current of the wire and require optimization. To identify the optimum parameters, eight wires with starting core compositions of Mg+2B+xCu with x = 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.12 and 0.15 were prepared with two heating ramp rates and their properties were investigated by SEM, XRD and J c and n-value measurements. The highest J c was found to be for x = 0.09, whereas x = 0.03 resulted in the highest n-value. The results are relatively independent of the heating ramp rate used for heat treatment. (paper)

  19. Large-scale high-resolution scanning Hall probe microscope used for MgB2 filament characterization

    International Nuclear Information System (INIS)

    Cambel, V; Fedor, J; Gregusova, D; Kovac, P; Husek, I

    2005-01-01

    The scanning Hall probe microscope (SHPM) is an important imaging tool used for detailed studies of superconductors in basic science as well as in the industrial sector. It can be used for the studies of losses, current distribution, and effects at grain boundaries. However, only a few SHPMs for magnetic field imaging at temperatures below 77 K have been proposed up to now, most of them designed for small-area (∼10x10 μm 2 ) scanning. We present a large-scale low-temperature SHPM developed for imaging the entire magnetic field in close proximity to magnetic and superconducting samples at 4.2-300 K. The microscope combines a large scanned area and high spatial and magnetic field resolution. The instrument is designed as an insert of standard helium flowing cryostats. The Hall sensor scans an area up to 7 x 25 mm 2 in the whole temperature interval with a spatial resolution better than 5 μm. The presented system is used for the study of ex situ prepared MgB 2 filament. We show that external magnetic field induces local supercurrents in the MgB 2 , from which the critical current can be estimated. Moreover, it indicates the microstructure and space homogeneity of the superconductor

  20. Field cooling of a MgB2 cylinder around a permanent magnet stack: prototype for superconductive magnetic bearing

    International Nuclear Information System (INIS)

    Perini, E; Giunchi, G

    2009-01-01

    The behaviour of bulk superconductors as levitators of permanent magnets (PMs) has been extensively studied for the textured YBCO high-temperature superconductor material, in the temperature range lower than 77 K, obtaining extremely high trapped fields but also experiencing limitations on the mechanical characteristics of the material and on the possibility to produce large objects. Alternatively, bulk MgB 2 , even if it is superconducting at lower temperatures, has fewer mechanical problems, when fully densified, and presents stable magnetization in the temperature range between 10 and 30 K. With the reactive Mg-liquid infiltration technique we have produced dense MgB 2 bulk cylinders of up to 65 mm diameter and 100 mm height. This kind of cylinder can be consider as a prototype of a passive magnetic bearing for flywheels or other rotating electrical machines. We have conductively cooled one of these superconducting cylinders inside a specially constructed cryostat, and the levitation forces and stiffness, with respect to axial movements of various arrangements of the PM, have been measured as a function of the temperature below T c . We verified the very stable characteristics of the induced magnetization after several cycles of relative movements of the PM and the superconducting cylinder.

  1. Effects of carbon concentration and filament number on advanced internal Mg infiltration-processed MgB2 strands

    International Nuclear Information System (INIS)

    Li, G Z; Sumption, M D; Zwayer, J B; Susner, M A; Collings, E W; Rindfleisch, M A; Thong, C J; Tomsic, M J

    2013-01-01

    In this paper we show that an advanced internal Mg infiltration method (AIMI) is effective in producing superconducting wires containing dense MgB 2 layers with high critical current densities. The in-field critical current densities of a series of AIMI-fabricated MgB 2 strands were investigated in terms of C doping levels, heat treatment (HT) time and filament numbers. The highest layer J c for our monofilamentary AIMI strands was 1.5 × 10 5 A cm −2 at 10 T, 4.2 K, when the C concentration was 3 mol% and the strand was heat-treated at 675 ° C for 4 h. Transport critical currents were also measured at 4.2 K on short samples and 1 m segments of 18-filament C doped AIMI strands. The layer J c s reached 4.3 × 10 5 A cm −2 at 5 T and 7.1 × 10 4 A cm −2 at 10 T, twice as high as those of the best powder-in-tube strands. The analysis of these results indicates that the AIMI strands, possessing both high layer J c s and engineering J e s after further optimization, have strong potential for commercial applications. (paper)

  2. Critical Current and Stability of MgB$_2$ Twisted-Pair DC Cable Assembly Cooled by Helium Gas

    CERN Document Server

    AUTHOR|(CDS)2069632; Ballarino, Amalia; Yang, Yifeng; Young, Edward Andrew; Bailey, Wendell; Beduz, Carlo

    2013-01-01

    Long length superconducting cables/bus-bars cooled by cryogenic gases such as helium operating over a wider temperature range are a challenging but exciting technical development prospects, with applications ranging from super-grid transmission to future accelerator systems. With limited existing knowledge and previous experiences, the cryogenic stability and quench protection of such cables are crucial research areas because the heat transfer is reduced and temperature gradient increased compared to liquid cryogen cooled cables. V-I measurements on gas-cooled cables over a significant length are an essential step towards a fully cryogenic stabilized cable with adequate quench protection. Prototype twisted-pair cables using high-temperature superconductor and MgB2 tapes have been under development at CERN within the FP7 EuCARD project. Experimental studies have been carried out on a 5-m-long multiple MgB$_2$ cable assembly at different temperatures between 20 and 30 K. The subcables of the assembly showed sim...

  3. The elastic properties, generalized stacking fault energy and dissociated dislocations in MgB2 under different pressure

    KAUST Repository

    Feng, Huifang

    2013-05-31

    The 〈112̄0〉 perfect dislocation in MgB2 is suggested to dissociate into two partial dislocations in an energy favorable way 〈112̄0〉 → 1/2 〈112̄0〉 + SF + 1/2 〈112̄0〉. This dissociation style is a correction of the previous dissociation 〈1000〉 → 1/3 〈11̄00〉 SF + 1/3 〈 2100〉proposed by Zhu et al. to model the partial dislocations and stacking fault observed by transmission electron microscopy. The latter dissociation results in a maximal stacking fault energy rather than a minimal one according to the generalized stacking fault energy calculated from first-principles methods. Furthermore, the elastic constants and anisotropy of MgB2 under different pressure are investigated. The core structures and mobilities of the 〈112̄0〉 dissociated dislocations are studied within the modified Peierls-Nabarro (P-N) dislocation theory. The variational method is used to solve the modified P-N dislocation equation and the Peierls stress is also determined under different pressure. High pressure effects on elastic anisotropy, core structure and Peierls stress are also presented. © 2013 Springer Science+Business Media New York.

  4. Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0T full body MRI systems

    Science.gov (United States)

    Baig, Tanvir; Al Amin, Abdullah; Deissler, Robert J; Sabri, Laith; Poole, Charles; Brown, Robert W; Tomsic, Michael; Doll, David; Rindfleisch, Matthew; Peng, Xuan; Mendris, Robert; Akkus, Ozan; Sumption, Michael; Martens, Michael

    2017-01-01

    Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB2. A new ‘active’ protection scheme for medium Tc based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB2 magnet designs. PMID:29170604

  5. Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping

    Science.gov (United States)

    Dou, S. X.; Soltanian, S.; Horvat, J.; Wang, X. L.; Zhou, S. H.; Ionescu, M.; Liu, H. K.; Munroe, P.; Tomsic, M.

    2002-10-01

    Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2-x)(SiCx/2 with x=0, 0.2, and 0.3 and for 10 wt % nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing Jc and Hirr. Compared to the undoped sample, Jc for the 10 wt % doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, and 14 at 30 K and 2 T. At 20 K and 2 T, the Jc for the doped sample was 2.4 x105 A/cm2, which is comparable to Jc values for the best Ag/Bi-2223 tapes. At 20 K and 4 T, Jc was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. The magnetic Jc is consistent with the transport Jc which remains at 20 000 A/cm2 even at 10 T and 5 K for the doped sample, an order of magnitude higher than the undoped one. Because of such high performance, it is anticipated that the future MgB2 conductors will be made using a formula of MgBxSiyCz instead of pure MgB2.

  6. MgB2 thin-film bolometer for applications in far-infrared instruments on future planetary missions

    International Nuclear Information System (INIS)

    Lakew, B.; Aslam, S.; Brasunas, J.; Cao, N.; Costen, N.; La, A.; Nguyen, L.; Stevenson, T.; Waczynski, A.

    2012-01-01

    A SiN membrane based MgB 2 thin-film bolometer, with a non-optimized absorber, has been fabricated that shows an electrical noise equivalent power of 2.56 × 10 -13 W/√Hz operating at 30 Hz and a responsivity of 702 kV/W. It is predicted that with the inclusion of a gold black absorber that an optical specific detectivity of 8.3 × 10 10 cm/√Hz/W at an operational frequency of 10 Hz, can be realized for integration into future planetary exploration instrumentation where high sensitivity is required in the 17-250 μm spectral wavelength range.

  7. Effect of sorbic acid doping on flux pinning in bulk MgB2 with the percolation model

    International Nuclear Information System (INIS)

    Yang, Y.; Cheng, C.H.; Wang, L.; Sun, H.H.; Zhao, Y.

    2010-01-01

    In this paper, we study the doping effect of sorbic acid (C 6 H 8 O 2 ), from 0 to 20 wt.% of the total MgB 2 , on critical temperature (T c ), critical current density (J c ), irreversibility field (H irr ) and crystalline structure. The XRD patterns of samples show a slightly decrease in a-axis lattice parameter for doped samples, due to the partial substitution of carbon at boron site. On the other hand, we investigate the influence of doping on the behavior of flux pinning and J c (B) in the framework of percolation theory and it is found that the J c (B) behavior could be well fitted in high field region. The two key parameters, anisotropy and percolation threshold, play very important roles. It is believed that the enhancement of J c is due to the reduction of anisotropy in high field region.

  8. Ripple Field AC Losses in 10-MW Wind Turbine Generators With a MgB2 Superconducting Field Winding

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Magnusson, Niklas

    2016-01-01

    Superconducting (SC) synchronous generators are proposed as a promising candidate for 10-20-MW direct-drive wind turbines because they can have low weights and small sizes. A common way of designing an SC machine is to use SC wires with high current-carrying capability in the dc field winding...... and the ac armature winding is made with copper conductors. In such generators, the dc field winding is exposed to ac magnetic field ripples due to space harmonics from the armature. In generator design phases, the ac loss caused by these ripple fields needs to be evaluated to avoid local overheating...... and an excessive cooling budget. To determine the applicability of different design solutions in terms of ac losses, this paper estimates the ac loss level of 10-MW wind generator designs employing a MgB2 SC field winding. The effects on ac losses are compared between nonmagnetic and ferromagnetic teeth...

  9. Enhancement of the irreversibility field in bulk MgB2 by TiO2 nanoparticle addition

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2004-01-01

    MgB2 samples doped with TiO2 nanoparticles were prepared and the effect of TiO2 addition on the superconducting transition temperature (T-c), irreversibility field (H-irr) and critical current density (J(c)) were investigated. It is found that the hexagonal lattice parameters a and c decrease...... with TiO2 doping. Tc decreases gradually from 38.2 to 37.8 K as the TiO2 content increases from 0 to 15 wt%. The H-irr increases at 20 K from 4.3 to 4.9 T as the TiO2 content increases from 0 to 10 wt%, and at the same temperature J(c) increases from 450 to 4250 A/cm(2) at 4.2 T. (C) 2004 Published...

  10. Magnetic anisotropy of thin sputtered MgB2 films on MgO substrates in high magnetic fields

    Directory of Open Access Journals (Sweden)

    Savio Fabretti

    2014-03-01

    Full Text Available We investigated the magnetic anisotropy ratio of thin sputtered polycrystalline MgB2 films on MgO substrates. Using high magnetic field measurements, we estimated an anisotropy ratio of 1.35 for T = 0 K with an upper critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear behavior, confirmed by a linear fit for magnetic fields perpendicular to the film plane. Furthermore, we observed a change of up to 12% of the anisotropy ratio in dependence of the film thickness.

  11. Stress/strain characteristics of Cu alloy sheath in situ processed MgB2 superconducting wires

    International Nuclear Information System (INIS)

    Katagiri, Kazumune; Kasaba, Koichi; Shoji, Yoshitaka

    2005-01-01

    The mechanical properties of copper and copper alloy (Cu-Zr, Cu-Be and Cu-Cr) sheath in situ PIT-processed MgB 2 superconducting wires were studied at room temperature (RT) and 4.2 K. The effects of stress-strain on the critical current (I c ) of the wires have also been studied at 4.2 K and in magnetic fields up to 5 T. It has been clarified that alloying the Cu sheath significantly increases the yield and flow stresses of the wires at both RT and 4.2 K. The 0.5% flow stresses of the Cu alloy sheath wire were 147-237 MPa, whereas that of Cu was 55 MPa. At RT, serration corresponding to multiple cracking was observed around a strain of 0.4% and the stress-strain curves saturated beyond that point. The strain dependence of I c prior to the critical strain (ε irr ) was different depending on the magnetic field; being almost constant at 2 T and increasing with strain at 5 T. The I c decreased beyond ε irr , which is much larger for Cu alloy sheath wires as compared to Cu sheath wire. This is due to the difference in the residual compressive strain in the MgB 2 core during cooling from the heat-treatment temperature to 4.2 K, which is determined through relaxation by yielding in the sheath materials. The transverse compression tests revealed that the I c of the Cu alloy sheath wire did not degrade up to 314 MPa, which is also higher than that of Cu sheath wire. (author)

  12. Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator

    International Nuclear Information System (INIS)

    Vargas-Llanos, Carlos Roberto; Zermeño, Víctor M R; Grilli, Francesco; Sanz, Santiago; Trillaud, Frederic

    2016-01-01

    Hysteretic losses in the MgB 2 wound superconducting coils of a 550 kW synchronous hybrid scaled generator were estimated as part of the European project SUPRAPOWER led by the Spanish Fundación Tecnalia Research and Innovation. Particular interest was given to the losses caused by the magnetic flux ripples in the rotor coils originating from the conventional stator during nominal operation. To compute these losses, a 2D finite element analysis was conducted and Maxwell’s equations written in the H-formulation were solved considering the nonlinear material properties of the conductor materials. The modeled tapes are made of multiple MgB 2 filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity were studied: (1) the first model reproduced closely the actual cross section obtained from tape micrographs. (2) The second model was obtained from the computed elasto-plastic deformation of a round Ni wire. (3) The third model was based on a simplified cross section with the superconducting filaments bundled in a single elliptical bulky structure. The last geometry allowed the validation of the modeling technique by comparing numerical losses with results from well-established analytical expressions. Additionally, the following cases of filament transpositions of the multi-filamentary tape were studied: no transposition, partial and full transposition; thereby improving understanding of the relevance of the tape fabrication process on the magnitude of the determination of ac losses. Finally, choosing the right level of geometrical detail, the following operational regimes of the machine and its impact on individual superconducting tape losses in the rotor were studied: bias-dc current, ramping current under ramping background field and magnetic flux ripples under dc background current and field. (paper)

  13. Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator

    Science.gov (United States)

    Vargas-Llanos, Carlos Roberto; Zermeño, Víctor M. R.; Sanz, Santiago; Trillaud, Frederic; Grilli, Francesco

    2016-03-01

    Hysteretic losses in the MgB2 wound superconducting coils of a 550 kW synchronous hybrid scaled generator were estimated as part of the European project SUPRAPOWER led by the Spanish Fundación Tecnalia Research & Innovation. Particular interest was given to the losses caused by the magnetic flux ripples in the rotor coils originating from the conventional stator during nominal operation. To compute these losses, a 2D finite element analysis was conducted and Maxwell’s equations written in the H-formulation were solved considering the nonlinear material properties of the conductor materials. The modeled tapes are made of multiple MgB2 filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity were studied: (1) the first model reproduced closely the actual cross section obtained from tape micrographs. (2) The second model was obtained from the computed elasto-plastic deformation of a round Ni wire. (3) The third model was based on a simplified cross section with the superconducting filaments bundled in a single elliptical bulky structure. The last geometry allowed the validation of the modeling technique by comparing numerical losses with results from well-established analytical expressions. Additionally, the following cases of filament transpositions of the multi-filamentary tape were studied: no transposition, partial and full transposition; thereby improving understanding of the relevance of the tape fabrication process on the magnitude of the determination of ac losses. Finally, choosing the right level of geometrical detail, the following operational regimes of the machine and its impact on individual superconducting tape losses in the rotor were studied: bias-dc current, ramping current under ramping background field and magnetic flux ripples under dc background current and field.

  14. Influence of the cooling rate on the main factors affecting current-carrying ability in pure and SiC-doped MgB2 superconductors

    International Nuclear Information System (INIS)

    Shcherbakova, O V; Pan, A V; Soltanian, S; Dou, S X; Wexler, D

    2007-01-01

    We have systematically studied and compared the effect of cooling rate on microstructure, critical current density, upper critical field and irreversibility field in pure and 10 wt% SiC-added MgB 2 superconductors. The sintering process was carried out on the samples at a temperature of 750 deg. C for 1 h followed by quenching or cooling to room temperature in 0.3 h (2433 deg. C h -1 ), 14 h (52 deg. C h -1 ) and 25 h (30 deg. C h -1 ). Changes in the microstructure due to variations in cooling rate have been studied with the help of scanning and transmission electron microscopy. Correlations between microstructure and superconducting properties have been observed, identified and explained for both pure and SiC-added MgB 2 samples. Modifications to the pinning environment and grain boundary transparency are considered to be responsible for variations in the current-carrying ability. The dominant pinning on grain boundaries in the pure MgB 2 samples and on nano-inclusions (inducing accompanying defects) in the SiC-doped samples is clearly distinguished. On the basis of our experimental results, we have concluded that the cooling rate can be an important parameter influencing the superconducting properties of MgB 2 samples

  15. Numerical simulation of quench protection for a 1.5 T persistent mode MgB2 conduction-cooled MRI magnet

    Science.gov (United States)

    Deissler, Robert J.; Baig, Tanvir; Poole, Charles; Amin, Abdullah; Doll, David; Tomsic, Michael; Martens, Michael

    2017-02-01

    The active quench protection of a 1.5 T MgB2 conduction-cooled MRI magnet operating in persistent current mode is considered. An active quench protection system relies on the detection of the resistive voltage developed in the magnet, which is used to trigger the external energizing of quench heaters located on the surfaces of all ten coil bundles. A numerical integration of the heat equation is used to determine the development of the temperature profile and the maximum temperature in the coil at the origin, or ‘hot spot’, of the quench. Both n-value of the superconductor and magnetoresistance of the wire are included in the simulations. An MgB2 wire manufactured by Hyper Tech Research, Inc. was used as the basis to model the wire for the simulations. With the proposed active quench protection system, the maximum temperature was limited to 200 K or less, which is considered low enough to prevent damage to the magnet. By substituting Glidcop for the Monel in the wire sheath or by increasing the thermal conductivity of the insulation, the margin for safe operation was further increased, the maximum temperature decreasing by more than 40 K. The strain on the MgB2 filaments is calculated using ANSYS, verifying that the stress and strain limits in the MgB2 superconductor and epoxy insulation are not exceeded.

  16. Transport properties and exponential n-values of Fe/MgB2 tapes with various MgB2 particle sizes

    International Nuclear Information System (INIS)

    Lezza, P.; Abaecherli, V.; Clayton, N.; Senatore, C.; Uglietti, D.; Suo, H.L.; Fluekiger, R.

    2004-01-01

    Fe/MgB 2 tapes have been prepared starting with pre-reacted binary MgB 2 powders. As shown by resistive and inductive measurements, the reduction of particle size to a few microns by ball milling has little influence on B c2 , while the superconducting properties of the individual MgB 2 grains are essentially unchanged. Reducing the particle size causes an enhancement of B irr from 14 to 16 T, while J c has considerably increased at high fields, its slope J c (B) being reduced. At 4.2 K, values of 5.3 x 10 4 and 1.2 x 10 3 A/cm 2 were measured at 3.5 and 10 T, respectively, suggesting a dominant role of the conditions at the grain interfaces. A systematic variation of these conditions at the interfaces is undertaken in order to determine the limit of transport properties for Fe/MgB 2 tapes. The addition of 5% Mg to MgB 2 powder was found to affect neither J c nor B c2 . For the tapes with the highest J c values, very high exponential n factors were measured: n=148, 89 and 17 at 3.5, 5 and 10 T, respectively and measurements of critical current versus applied strain have been performed. The mechanism leading to high transport critical current densities of filamentary Fe/MgB 2 tapes based on MgB 2 particles is discussed

  17. Synthesis, thermal and magnetic properties of RE-diborides

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, V.V., E-mail: vvnovikov@mail.ru [Training-Research Center ' Bryansk Physical Laboratory' , Petrovsky Bryansk State University, 14, Bezhitskaya St, 241036 Bryansk (Russian Federation); Matovnikov, A.V. [Training-Research Center ' Bryansk Physical Laboratory' , Petrovsky Bryansk State University, 14, Bezhitskaya St, 241036 Bryansk (Russian Federation); Volkova, O.S. [Lomonosov Moscow State University, GSP-1, Leninskie Gory, 119991 Moscow (Russian Federation); Vasil' ev, A.N., E-mail: vasil@mig.phys.msu.ru [Lomonosov Moscow State University, GSP-1, Leninskie Gory, 119991 Moscow (Russian Federation)

    2017-04-15

    Techniques of synthesis of RE diborides (RB{sub 2}) are developed (R=Tb, Dy, Ho, Er, Lu). Temperature dependence of magnetisation, a heat capacity, a lattice parameters of diborides in the range of 2–300 K are measured. According to joint calorimetric and X-ray research the analysis of a phonon component of a heat capacity and thermal expansion of RE-diborides is carried out by Debye-Einstein's models, the parameters of the model are determined. The change of magnetisation of the ferromagnetic RB{sub 2} compounds with growth of temperature caused by violation of ordering in the system of the atomic magnetic moments is compared with the change of entropy of a magnetic subsystem calculated from calorimetric data. Analytical expansion for calculation of a magnetic component of a heat capacity by RB{sub 2} magnetisation data at the temperatures of 2–300 K is obtained. - Highlights: • 1 Techniques of synthesis of RE diborides (RB{sub 2}) are developed (R=Tb, Dy, Ho, Er, Lu). • 2 Temperature dependence of magnetisation of diborides at 2–300 K is determined. • 3 Calculation method of RB{sub 2} magnetic heat capacity from magnetic data is obtained.

  18. A study on the role of diboride in the heterogeneous nucleation of aluminium

    International Nuclear Information System (INIS)

    Suarez, O. M.

    2004-01-01

    The intangible role of titanium and aluminium diboride in the nucleation of aluminium was re-examined. Two different techniques, complemented with scanning electron microscopy, allowed determining the stability of the diboride in the presence of titanium tri aluminides and liquid aluminium phases. Through rapid scintillated quenching the high temperature diboride were retained and studied. Then, in a diffusion couple, the reactivity of such diboride was tested in contact with pure titanium tri aluminide. It is proposed that a ternary diboride acts as the main catalytic particle in the crystallization of aluminium alloys with refined grains. (Author) 27 refs

  19. Influence of particle size of Mg powder on the microstructure and critical currents of in situ powder-in-tube processed MgB_2 wires

    International Nuclear Information System (INIS)

    Kumakura, Hiroaki; Ye, Shujun; Matsumoto, Akiyoshi; Nitta, Ryuji

    2016-01-01

    We fabricated in situ powder-in-tube(PIT) MgB_2 wires using three kinds of Mg powders with particle size of ∼45 μm, ∼150 μm and 212∼600 μm. Mg particles were elongated to filamentary structure in the wires during cold drawing process. Especially, long Mg filamentary structure was obtained for large Mg particle size of 212∼600 μm. Critical current density, J_c, increased with increasing Mg particle size for 1 mm diameter wires. This is due to the development of filamentary structure of high density MgB_2 superconducting layer along the wires. This MgB_2 structure is similar to that of the internal Mg diffusion (IMD) processed MgB_2 wires. However, J_c of the wires fabricated with 212∼600 μm Mg particle size decreased and the scattering of J_c increased with decreasing wire diameter, while the J_c of the wires with ∼45 μm Mg particle was almost independent of the wire diameter. The cross sectional area reduction of the Mg particles during the wire drawing is smaller than that of the wire. When using large size Mg particle, the number of Mg filaments in the wire cross section is small. These two facts statistically lead to the larger scattering of Mg areal fraction in the wire cross section with proceeding of wire drawing process, resulting in smaller volume fraction of MgB_2 in the wire and lower J_c with larger scattering along the wire. SiC nano powder addition is effective in increasing J_c for all Mg particle sizes. (author)

  20. Critical current density in MgB2 bulk samples after co-doping with nano-SiC and poly zinc acrylate complexes

    International Nuclear Information System (INIS)

    Zhang, Z.; Suo, H.; Ma, L.; Zhang, T.; Liu, M.; Zhou, M.

    2011-01-01

    SiC and poly zinc acrylate complexes co-doped MgB 2 bulk has been synthesized. Co-doping can cause higher carbon substitutions and the second phase particles. Co-doping can further increase the Jc value of MgB 2 bulk on the base of the SiC doping. The co-doped MgB 2 bulk samples have been synthesized using an in situ reaction processing. The additives is 8 wt.% SiC nano powders and 10 wt.% [(CH 2 CHCOO) 2 Zn] n poly zinc acrylate complexes (PZA). A systematic study was performed on samples doped with SiC or PZA and samples co-doped with both of them. The effects of doping and co-doping on phase formation, microstructure, and the variation of lattice parameters were studied. The amount of substituted carbon, the critical temperature (T c ) and the critical current density (J c ) were determined. The calculated lattice parameters show the decrease of the a-axis, while no obvious change was detected for c-axis parameter in co-doped samples. This indicates that the carbon was substituted by boron in MgB 2 . The amount of substituted carbon for the co-doped sample shows an enhancement compared to that of the both single doped samples. The co-doped samples perform the highest J c values, which reaches 3.3 x 10 4 A/cm 2 at 5 K and 7 T. It is shown that co-doping with SiC and organic compound is an effective way to further improve the superconducting properties of MgB 2 .

  1. Properties of boride-added powder metallurgy magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi [Department of Mechanical Engineering, Tokyo City University 1-28-1 Tamazutsumi, Setagaya, Tokyo 158-8557 (Japan)], E-mail: ktakagi@tcu.ac.jp

    2009-06-01

    Magnesium alloys with metallic borides, magnesium diboride (MgB{sub 2}) or aluminum diboride (AlB{sub 2}), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB{sub 2} exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB{sub 2}, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg{sub 17}Al{sub 12}, formed in the alloy with AlB{sub 2}, which was consistent with its higher hardness.

  2. Theoretical investigation of the vortex state in new superconductors: MgB2 and PrOs4Sb12

    International Nuclear Information System (INIS)

    Dao, V.H.

    2006-01-01

    As illustrated by the present thesis work, gap function anisotropy and crystal anisotropy are combined when influencing superconducting properties under a magnetic field. In order to study the mixed state of the recently discovered multiband superconductor MgB 2 , we first derive the Ginzburg-Landau functional for a two-gap superconductor from a weak coupling BCS model. The interaction between the two condensates is then described by a unique Josephson-type coupling. The two-gap theory then enables to explain the curvature and the anisotropy of the upper critical field, as well as the 30 degrees change of orientation for the vortex lattice which is observed when increasing the strength of the magnetic field applied along the c-tilde axis. Besides, we investigate the vortex lattice geometry in the superconducting heavy fermion PrOs 4 Sb 12 . When taking into account non local corrections for an s-wave T h -tetrahedral superconductor, we can explain the observed deformation of the lattice by the crystal symmetry of the compound. Ab initio results of the band structures confirm quantitatively our analysis. (author)

  3. Carbon-coated boron using low-cost naphthalene for substantial enhancement of Jc in MgB2 superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ranot, Mahipal; Shinde, K. P.; Oh, Y. S.; Kang, S. H.; Jang, S. H.; Hwang, D. Y.; Chung, K. C. [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2017-09-15

    Carbon coating approach is used to prepare carbon-doped MgB{sub 2} bulk samples using low-cost naphthalene (C{sub 10}H{sub 8}) as a carbon source. The coating of carbon (C) on boron (B) powders was achieved by direct pyrolysis of naphthalene at 120 degrees C and then the C-coated B powders were mixed well with appropriate amount of Mg by solid state reaction method. X-ray diffraction analysis revealed that there is a noticeable shift in (100) and (110) Bragg reflections towards higher angles, while no shift was observed in (002) reflections for MgB2 doped with carbon. As compared to un-doped MgB{sub 2}, a systematic enhancement in Jc(H) properties with increasing carbon doping level was observed for naphthalene-derived C-doped MgB{sub 2} samples. The substantial enhancement in Jc is most likely due to the incorporation of C into MgB{sub 2} lattice and the reduction in crystallite size, as evidenced by the increase in the FWHM values for doped samples.

  4. MgB2-Based Bolometer Array for Far Infra-Red Thermal Imaging and Fourier Transform Spectroscopy Applications

    Science.gov (United States)

    Lakew, B.; Aslam, S.; Brasunas, J.

    2012-01-01

    The mid-superconducting critical temperature (T(sub c) approximately 39 K) of the simple binary, intermetallic MgB, [1] makes it a very good candidate for the development of the next generation of electrooptical devices (e.g. [2]). In particular, recent advances in thin film deposition teclmiques to attain higb quality polycrystalline thin film MgB, deposited on SiN-Si substrates, with T(sub c) approximately 38K [3] coupled with the low voltage noise performance of the film [4] makes it higbly desirable for the development of moderately cooled bolometer arrays for integration into future space-bourne far infra-red (FIR) spectrometers and thermal mappers for studying the outer planets, their icy moons and other moons of interest in the 17-250 micrometer spectral wavelength range. Presently, commercially available pyroelectric detectors operating at 300 K have specific detectivity, D(*), around 7 x 10(exp 8) to 2 x 10(exp 9) centimeters square root of Hz/W. However, a MgB2 thin film based bolometer using a low-stress (less than 140 MPa) SiN membrane isolated from the substrate by a small thermal conductive link, operating at 38 K, promises to have two orders of magnitude higher specific detectivity [5][6].

  5. Growth of superconducting MgB2 films by pulsed-laser deposition using a Nd-YAG laser

    International Nuclear Information System (INIS)

    Badica, P; Togano, K; Awaji, S; Watanabe, K

    2006-01-01

    Thin films of MgB 2 on r-cut Al 2 O 3 substrates have been grown by pulsed-laser deposition (PLD) using a Nd-YAG laser (fourth harmonic-266 nm) instead of the popular KrF excimer laser. The growth window to obtain superconducting films is laser energy 350-450 mJ and vacuum pressure with Ar-buffer gas of 1-8/10 Pa (initial background vacuum 0.5-1 x 10 -3 Pa). Films were deposited at room temperature and post-annealed in situ and ex situ at temperatures of 500-780 0 C and up to 1 h. Films are randomly oriented with maximum critical temperature (offset of resistive transition) of 27 K. SEM/TEM/EDS investigations show that they are mainly composed of small sphere-like particles (≤20 nm), and contain oxygen and some carbon, uniformly distributed in the flat matrix, but the amount of Mg and/or oxygen is higher in the aggregates-droplets (100-1000 nm) observed on the surface of the film's matrix. Some aspects of the processing control and dependences on film characteristics are discussed. The technique is promising for future development of coated conductors

  6. MgB2 Thin-Film Bolometer for Applications in Far-Infrared Instruments on Future Planetary Missions

    Science.gov (United States)

    Lakew, B.; Aslam, S.; Brasunas, J.; Cao, N.; Costen, N.; La, A.; Stevenson, T.; Waczynski, A.

    2012-01-01

    A SiN membrane based MgB2 thin-film bolometer, with a non-optimized absorber, has been fabricated that shows an electrical noise equivalent power of 256 fW/square root Hz operating at 30 Hz in the 8.5 - 12.35 micron spectral bandpass. This value corresponds to an electrical specific detectivity of 7.6 x 10(exp 10) cm square root Hz/W. The bolometer shows a measured blackbody (optical) specific detectivity of 8.8 x 10(exp 9) cm square root Hz/W, with a responsivity of 701.5 kV/W and a first-order time constant of 5.2 ms. It is predicted that with the inclusion of a gold black absorber that a blackbody specific detectivity of 6.4 x 10(exp 10) cm/square root Hz/W at an operational frequency of 10 Hz, can be realized for integration into future planetary exploration instrumentation where high sensitivity is required in the 17 - 250 micron spectral wavelength range.

  7. Magnesium Gluconate

    Science.gov (United States)

    Magnesium gluconate is used to treat low blood magnesium. Low blood magnesium is caused by gastrointestinal disorders, prolonged vomiting or ... disease, or certain other conditions. Certain drugs lower magnesium levels as well.This medication is sometimes prescribed ...

  8. Critical current density analysis of ex situ MgB2 wire by in-field and temperature Hall probe imaging

    International Nuclear Information System (INIS)

    Bartolome, E; Granados, X; Cambel, V; Fedor, J; Kovac, P; Husek, I

    2005-01-01

    The irreversible magnetic behaviour at different temperatures of an ex situ Fe-alloy/MgB 2 wire, exhibiting a granular compositional distribution, was studied using an in-field, high resolution Hall probe imaging system. Quantitative information about the local current density was obtained by solving the Biot-Savart inversion problem. The flux penetration and current distribution maps obtained can be attributed to a inhomogeneous compositional 'plum-cake-like' system, consisting of large, isolated MgB 2 agglomerations embedded in a matrix of finely distributed MgB 2 +MgO. The critical current densities within the grains and their evolution with the applied magnetic field and temperature have been obtained, and compared to the mean J c (H,T) in the matrix

  9. A Novel Method for Measurements of the Penetration Depth of MgB2 Superconductor Films by Using Sapphire Resonators with Short-Circuited Parallel Plates

    International Nuclear Information System (INIS)

    Jung, Ho Sang; Lee, J. H.; Cho, Y. H.; Lee, Sang Young; Seong, W. K.; Lee, N. H.; Kang, W. N.

    2009-01-01

    We introduce a measurement method that enables to measure the penetration depth(λ) of superconductor films by using a short-ended parallel plate sapphire resonator. Variations in the (λof MgB 2 films could be measured down to the lowest temperature using a sapphire resonator with a YBa 2 Cu 3 O 7-x film at the bottom. A model equation of λλ 0 [1-(T/T c ) τ ] -1/2 for MgB 2 films appeared to describe the observed variations of the resonant frequency of the sapphire resonator with temperature, with λ 0 , τ and T c used as the fitting parameters.

  10. Enhancement of the critical current density in FeO-coated MgB2 thin films at high magnetic fields

    Directory of Open Access Journals (Sweden)

    Andrei E. Surdu

    2011-12-01

    Full Text Available The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB2 thin films on the critical current density was studied in comparison with the case of uncoated MgB2 thin films. We calculated the superconducting critical current densities (Jc from the magnetization hysteresis (M–H curves for both sets of samples and found that the Jc value of FeO-coated films is higher at all fields and temperatures than the Jc value for uncoated films, and that it decreases to ~105 A/cm2 at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.

  11. de Haas-van Alphen effect investigations of the electronic structure of pure and aluminum-doped MgB2

    International Nuclear Information System (INIS)

    Carrington, A.; Yelland, E.A.; Fletcher, J.D.; Cooper, J.R.

    2007-01-01

    Our understanding of the superconducting properties of MgB 2 is strongly linked to our knowledge of its electronic structure. In this paper we review experimental measurements of the Fermi surface parameters of pure and Al-doped MgB 2 using the de Haas-van Alphen (dHvA) effect. In general, the measurements are in excellent agreement with the theoretical predictions of the electronic structure, including the strength of the electron-phonon coupling on each Fermi surface sheet. For the Al doped samples, we are able to measure how the band structure changes with doping. These results are in excellent agreement with calculations based on the virtual crystal approximation. We also review work on the dHvA effect in the superconducting state

  12. Enhancement of Critical Current Density and Flux Pinning in Acetone and La2O3 Codoped MgB2 Tapes

    International Nuclear Information System (INIS)

    Gao Zhao-Shun; Ma Yan-Wei; Wang Dong-Liang; Zhang Xian-Ping; Awaji Satoshi; Watanabe Kazuo

    2010-01-01

    MgB 2 tape samples with simultaneous additions of acetone and La 2 O 3 were prepared by an in-situ processed powder-in-tube method. Compared to the pure and single doped tapes, both transport J c and fluxing pinning are greatly improved by acetone and La 2 O 3 codoping. Acetone supplies carbon into the MgB 2 crystal lattice and increases the upper critical field, while the La 2 O 3 reacts with B to form LaB 6 nanoparticles as effective flux pining centers. The improvement of the superconducting properties in codoped tapes can be attributed to the combined effects of improvement in H c2 and flux pinning. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  13. Enhanced J c property in nano-SiC doped thin MgB2/Fe wires by a modified in situ PIT process

    International Nuclear Information System (INIS)

    Jiang, C.H.; Nakane, T.; Hatakeyama, H.; Kumakura, H.

    2005-01-01

    A modified in situ PIT process, which included a short time pre-annealing and intermediate drawing step in the conventional in situ PIT process, was employed to fabricate thin round MgB 2 /Fe wires from MgH 2 and B powders. The pores and cracks resulted from the MgH 2 decomposition during the pre-annealing were effectively eliminated by the intermediate drawing step, which subsequently increased the core density and J c property of final heat treated wires. A higher reduction rate after the pre-annealing led to a larger enhancement in J c within this study. The reproducibility of our new process on the J c improvement in MgB 2 wires was confirmed in two series of wires doped with 5 mol% or 10 mol% nano-SiC particles separately

  14. Fabrication of a Scaled MgB2 Racetrack Demonstrator Pole for a 10-MW Direct-Drive Wind Turbine Generator

    DEFF Research Database (Denmark)

    Magnusson, Niklas; Eliassen, Jan Christian; Abrahamsen, Asger Bech

    2018-01-01

    Field windings made of MgB2 wires or tapes are considered for their potential to reduce volume, weight, and cost of large offshore wind turbine generators. To gain experience of how to use this relatively new material in full-scale generators, tests of different winding methodologies and techniques...... are needed. In this paper, we describe in detail the steps used to wind a racetrack coil with a length of 1 m and a width of 0.5 m out of 4.5 km of MgB2 superconducting tape. The width corresponds to a full-scale pole of a 10-MW generator, whereas the length of the straight section is shorter than...... the corresponding full-scale pole. The coil was built up of ten double pancake coils. Each double pancake coil was wet wound using a semiautomatic winding process, where Stycast 2850 was applied directly to the MgB2 tape without any other dedicated electrical insulation. The strengths and weaknesses of the winding...

  15. Superconductivity, critical current density, and flux pinning in MgB2-x(SiC)x/2 superconductor after SiC nanoparticle doping

    Science.gov (United States)

    Dou, S. X.; Pan, A. V.; Zhou, S.; Ionescu, M.; Wang, X. L.; Horvat, J.; Liu, H. K.; Munroe, P. R.

    2003-08-01

    We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2-x(SiC)x/2 samples with x=0-1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2-x(SiC)x/2 superconductors.

  16. Effects of MgO impurities and micro-cracks on the critical current density of Ti-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Liang, G.; Alessandrini, M.; Yen, F.; Hanna, M.; Fang, H.; Hoyt, C.; Lv, B.; Zeng, J.; Salama, K.

    2007-01-01

    Ti-sheathed monocore MgB 2 wires with improved magnetic critical current density (J c ) have been fabricated by in situ powder-in-tube (PIT) method and characterized by magnetization, X-ray diffraction, scanning electron microscopy and electrical resistivity measurements. For the best wire, the magnetic J c values at 5 K and fields of 2 T, 5 T, and 8 T are 4.1 x 10 5 A/cm 2 , 7.8 x 10 4 A/cm 2 , and 1.4 x 10 4 A/cm 2 , respectively. At 20 K and fields of 0.5 T and 3 T, the J c values are about 3.6 x 10 5 A/cm 2 and 3.1 x 10 4 A/cm 2 , respectively, which are much higher than those of the Fe-sheathed mono-core MgB 2 wires fabricated with the same in situ PIT process and under the same fabricating conditions. It appears that the overall J c for the average Ti-sheathed wires is comparable to that of the Fe-sheathed wires. Our X-ray diffraction and scanning electron microscopy analysis indicates that J c in the Ti-sheathed MgB 2 wires can be strongly suppressed by MgO impurities and micro-cracks

  17. A Mathematical Model of the Single Aluminium Diboride Particle Ignition

    Directory of Open Access Journals (Sweden)

    D. A. Yagodnikov

    2014-01-01

    Full Text Available The paper presents a developed mathematical model of ignition of the single aluminum diboride particle as an aluminum-boron alloy in the oxidizing environment of a complicated chemical composition containing oxygen, water vapor, and carbon dioxide. The mathematical model is based on the theory of parallel chemical reactions proceeding on the appropriate parts of the particle surface occupied by each element in proportion to their molar share in the alloy. The paper considers a possibility to establish a thermodynamic balance between components over a particle surface in the gas phase. The composition of components is chosen as a result of thermodynamic calculation, namely В g , B2O3 g , BO, B2O2, BO2, Alg , AlO, Al2O, N2. The mathematical model is formed by a system of the differential equations of enthalpy balance, mass of aluminum diboride particle, and of formed oxides, which become isolated by initial and boundary conditions for temperature and size of particles, concentration of an oxidizer, and temperature of gas. The software package “AlB2“ is developed. It is a complete independent module written in Fortran algorithmic language, which together with a package of the subroutines “SPARKS” is used to calculate parameters of burning aluminum diboride particle by the Runge-Kutt method.For stoichiometry of chemical reactions of interaction between aluminum diboride and oxygen, a dynamics of changing temperature of a particle and thickness of an oxide film on its surface is calculated. It was admitted as initial conditions that the aluminum diboride particle radius was 100μ and the reference temperature of environment was 500 K, 1000 K, 2300 K, and 3000 K. Depending on this temperature the aluminum diboride particle temperature was calculated. Changing thickness of the oxide film on the particle surface at various initial gas temperatures characterizes its increase at the initial heating period of ~ 0,01 s and a gradual slowdown of the

  18. Finite Strain Analysis of Shock Compression of Brittle Solids Applied to Titanium Diboride

    Science.gov (United States)

    2014-07-01

    dislocation motion [18,19] may take place at high pressures. Multiple investigations have discovered that tita - nium diboride demonstrates a rather unique...mean stress under shock compression. It has been suggested [5] that pore collapse may be an important source of inelasticity in tita - nium diboride

  19. Recent achievements in MgB 2 physics and applications: A large-area SQUID magnetometer and point-contact spectroscopy measurements

    Science.gov (United States)

    Gonnelli, R. S.; Daghero, D.; Calzolari, A.; Ummarino, G. A.; Tortello, M.; Stepanov, V. A.; Zhigadlo, N. D.; Rogacki, K.; Karpinski, J.; Portesi, C.; Monticone, E.; Mijatovic, D.; Veldhuis, D.; Brinkman, A.

    2006-03-01

    In the first part of the present paper we discuss the fabrication and the characterization of an MgB2-based SQUID magnetometer with a directly coupled large-area pick-up loop, made on an MgB2 film deposited by an all in situ technique. The coarse structure of the SQUID was defined by optical lithography and Ar-ion milling, while the two nanobridges acting as weak links in the superconducting loop were made by focused ion beam (FIB) milling. The device was characterized at different temperatures and showed Josephson quantum interference up to 20 K as well as a noise level already compatible with the recording of an adult magnetocardiogram. In the second part, concerning the fundamental physics of MgB2, we present the results of very recent point-contact measurements on Mg1-xMnxB2 single crystals with 34.1 ⩾ Tc ⩾ 13.3 K (i.e. 0.37% ⩽ x ⩽ 1.5%). The experimental conductance curves were fitted with the generalized two-band BTK model and their behaviour in magnetic fields was studied to check if both the order parameters (OPs) of the σ and π bands were present in the whole doping range. The dependence of the OPs (evaluated through the fit) on the Andreev critical temperature of the junctions is analyzed in the framework of the two-band Eliashberg theory by including the effects of magnetic impurities. The results give an evidence of a dominant effect of the magnetic impurities on the σ-band channel.

  20. Specific heat of MgB2 in a one- and a two-band model from first-principles calculations

    International Nuclear Information System (INIS)

    Golubov, A.A.; Dolgov, O.V.; Jepsen, O.; Kong, Y.; Andersen, O.K.; Gibson, B.J.; Ahn, K.; Kremer, R.K.; Kortus, J.

    2002-01-01

    The heat capacity anomaly at the transition to superconductivity of the layered superconductor MgB 2 is compared to first-principles calculations with the Coulomb repulsion, μ*, as the only parameter which is fixed to give the measured T c . We solve the Eliashberg equations for both an isotropic one-band model and a two-band model with different superconducting gaps on the π-band anσd-band Fermi surfaces. The agreement with experiments is considerably better for the two-band model than for the one-band model. (author)

  1. Specific heat of the 38-K superconductor MgB_2 in the normal and superconducting state: bulk evidence for a double gap

    OpenAIRE

    Junod, Alain; Wang, Yuxing; Bouquet, Frederic; Toulemonde, Pierre

    2001-01-01

    The specific heat of two polycrystalline samples of MgB_2 is presented and analyzed (2 - 300 K, 0 - 16 T), together with magnetic properties. The main characteristics are a low density of states at the Fermi level, high phonon frequencies, and an anomalous temperature- and field- dependence of the specific heat at T < T_c. A two-gap model with a gap ratio of 3:1 fits the specific heat in zero field. The smaller gap is washed out by a field of 0.5 T.

  2. Magnesium, magnesium alloys, and magnesium composites

    National Research Council Canada - National Science Library

    Gupta, M; Sharon, Nai Mui Ling

    2011-01-01

    "Properties of Magnesium Composites for Material Scientists, Engineers and Selectors is the first book-length reference to provide an insight into current and future magnesium-based materials in terms...

  3. The reduction of optimal heat treatment temperature and critical current density enhancement of ex situ processed MgB2 tapes using ball milled filling powder

    Science.gov (United States)

    Fujii, Hiroki; Iwanade, Akio; Kawada, Satoshi; Kitaguchi, Hitoshi

    2018-01-01

    The optimal heat treatment temperature (Topt) at which best performance in the critical current density (Jc) property at 4.2 K is obtained is influenced by the quality or reactivity of the filling powder in ex situ processed MgB2 tapes. Using a controlled fabrication process, the Topt decreases to 705-735 °C, which is lower than previously reported by more than 50 °C. The Topt decrease is effective to suppress both the decomposition of MgB2 and hence the formation of impurities such as MgB4, and the growth of crystallite size which decreases upper critical filed (Hc2). These bring about the Jc improvement and the Jc value at 4.2 K and 10 T reaches 250 A/mm2. The milling process also decreases the critical temperature (Tc) below 30 K. The milled powder is easily contaminated in air and thus, the Jc property of the contaminated tapes degrades severely. The contamination can raise the Topt by more than 50 °C, which is probably due to the increased sintering temperature required against contaminated surface layer around the grains acting as a barrier.

  4. Deposition of MgB2 Thin Films on Alumina-Buffered Si Substrates by using Hybrid Physical-Chemical Vapor Deposition Method

    International Nuclear Information System (INIS)

    Lee, T. G.; Park, S. W.; Seong, W. K.; Huh, J. Y.; Jung, S. G.; Kang, W. N.; Lee, B. K.; An, K. S.

    2008-01-01

    [ MgB 2 ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures 500 - 600 degrees C and under the reactor pressures of 25 - 50 degrees C. There are some interfacial reactions in the as-grown films with impurities of mostly Mg 2 Si, MgAl 2 O 4 , and other phases. The T c 's of MgB 2 films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly Mg 2 Si impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

  5. Titanium diboride ceramic fiber composites for Hall-Heroult cells

    Science.gov (United States)

    Besmann, T.M.; Lowden, R.A.

    1990-05-29

    An improved cathode structure is described for Hall-Heroult cells for the electrolytic production of aluminum metal. This cathode structure is a preform fiber base material that is infiltrated with electrically conductive titanium diboride using chemical vapor infiltration techniques. The structure exhibits good fracture toughness, and is sufficiently resistant to attack by molten aluminum. Typically, the base can be made from a mat of high purity silicon carbide fibers. Other ceramic or carbon fibers that do not degrade at temperatures below about 1000 C can be used.

  6. RBS and XRD analysis of silicon doped titanium diboride films

    International Nuclear Information System (INIS)

    Mollica, S.; Sood, D.K.; Ghantasala, M.K.; Kothari, R.

    1999-01-01

    Titanium diboride is a newly developed material suitable for protective coatings. Its high temperature oxidation resistance at temperatures of 700 deg C and beyond is limited due to its poor oxidative behaviour. This paper presents a novel approach to improving the coatings' oxidative characteristics at temperatures of 700 deg C by doping with silicon. Titanium diboride films were deposited onto Si(100) wafer substrates using a DC magnetron sputtering system. Films were deposited in two different compositions, one at pure TiB 2 and the other with 20 % Si doping. These samples were vacuum annealed at 700 deg C at 1x10 -6 Torr to investigate the anaerobic behaviour of the material at elevated temperatures and to ensure that they were crystalline. Samples were then oxidised in air at 700 deg C to investigate their oxidation resistance. Annealing the films at 700 deg C in air results in the oxidation of the film as titanium and boron form TiO 2 and B 2 O 3 . Annealing is seen to produce only minor changes in the films. There is some silicon diffusion from the substrate at elevated temperatures, which is related to the porous nature of the deposited film and the high temperature heat treatments. However, silicon doped films showed relatively less oxidation characteristics after annealing in air compared with the pure TiB 2 samples

  7. Magnesium Hydroxide

    Science.gov (United States)

    Magnesium hydroxide is used on a short-term basis to treat constipation.This medication is sometimes prescribed ... Magnesium hydroxide come as a tablet and liquid to take by mouth. It usually is taken as ...

  8. Magnesium Oxide

    Science.gov (United States)

    Magnesium is an element your body needs to function normally. Magnesium oxide may be used for different reasons. Some people use it as ... one to four times daily depending on which brand is used and what condition you have. Follow ...

  9. Pressure dependence of the Raman spectrum, lattice parameters and superconducting critical temperature of MgB2: evidence for pressure-driven phonon-assisted electronic topological transition

    International Nuclear Information System (INIS)

    Goncharov, A.F.; Struzhkin, V.V.

    2003-01-01

    We overview recent high-pressure studies of high-temperature superconductor MgB 2 by Raman scattering technique combined with measurements of superconducting critical temperature T c and lattice parameters up to 57 GPa. An anomalously broadened Raman band at 620 cm -1 is observed and assigned to the in-plane boron stretching E 2g mode. It exhibits a large Grueneisen parameter indicating that the vibration is highly anharmonic. The pressure dependencies of the E 2g mode and T c reveal anomalies at 15-22 GPa (isotope dependent). The anharmonic character of the E 2g phonon mode, its anomalous pressure dependence, and also that for T c are interpreted as a result of a phonon-assisted Lifshitz electronic topological transition

  10. Magnesium, magnesium alloys, and magnesium composites

    National Research Council Canada - National Science Library

    Gupta, M; Sharon, Nai Mui Ling

    2011-01-01

    .... With the popularity of magnesium-based materials in the automotive, aerospace, electronics, and sports equipment industries, and its unique role as a lightweight, energy-saving and high-performance...

  11. Magnesium, magnesium alloys, and magnesium composites

    National Research Council Canada - National Science Library

    Gupta, M; Sharon, Nai Mui Ling

    2011-01-01

    ... of science, characteristics, and applications. It emphasizes the properties of magnesium-based composites and the effects of different types of reinforcements, from micron length to nanometer scale, on the properties of the resulting composites...

  12. Thermionic vacuum arc (TVA) technique for magnesium thin film deposition

    Energy Technology Data Exchange (ETDEWEB)

    Balbag, M.Z., E-mail: zbalbag@ogu.edu.t [Eskisehir Osmangazi University, Education Faculty, Primary Education, Meselik Campus, Eskisehir 26480 (Turkey); Pat, S.; Ozkan, M.; Ekem, N. [Eskisehir Osmangazi University, Art and Science Faculty, Physics Department, Eskisehir 26480 (Turkey); Musa, G. [Ovidius University, Physics Department, Constanta (Romania)

    2010-08-15

    In this study, magnesium thin films were deposited on glass substrate by the Thermionic Vacuum Arc (TVA) technique for the first time. We present a different technique for deposition of high-quality magnesium thin films. By means of this technique, the production of films is achieved by condensing the plasma of anode material generated using Thermionic Vacuum Arc (TVA) under high vacuum conditions onto the surface to be coated. The crystal orientation and morphology of the deposited films were investigated by using XRD, EDX, SEM and AFM. The aim of this study is to search the use of TVA technique to coat magnesium thin films and to determine some of the physical properties of the films generated. Furthermore, this study will contribute to the scientific studies which search the thin films of magnesium or the compounds containing magnesium. In future, this study will be preliminary work to entirely produce magnesium diboride (MgB{sub 2}) superconductor thin film with the TVA technique.

  13. Nanostructures of Boron, Carbon and Magnesium Diboride for High Temperature Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa [Yale Univ., New Haven, CT (United States); Fang, Fang [Yale Univ., New Haven, CT (United States); Iyyamperumal, Eswarmoorthi [Yale Univ., New Haven, CT (United States); Keskar, Gayatri [Yale Univ., New Haven, CT (United States)

    2013-12-23

    Direct fabrication of MgxBy nanostructures is achieved by employing metal (Ni,Mg) incorporated MCM-41 in the Hybrid Physical-Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at the reaction temperature of 600oC, with the yield of the nanostructures increasing with increasing reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3-5nm, which do not increase with the reaction temperature consistent with templated synthesis. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with possible contamination of Si and O. NEXAFS and Raman spectroscopy analysis suggested a concentric layer-by-layer MgxBy nanowire/nanotube growth model for our as-synthesized nanostructures. Ni k-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor-Liquid-Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni-Mg clusters. Physical templating by the MCM-41 pores was shown to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized samples.

  14. The influence of the roll diameter in flat rolling of of superconducting in situ and ex situ MgB2 tape

    DEFF Research Database (Denmark)

    Hancock, Michael Halloway; Bay, Niels

    2007-01-01

    , 150 and 210 mm in each step. The investigation has shown that the in situ powder is more readily compacted than the ex situ powder, with an average increase of relative density after mechanical processing of 37% for in situ powder and 19% for ex situ powder. Statistical analysis showed that the choice......Applying the powder in tube (PIT) method, single-filament MgB2/Fe wire and tape has been manufactured applying both the ex situ and the in situ approach. The influence of the roll diameter in three-step flat rolling on the powder density and critical temperature has been examined using rolls of 70...... roll in the first and second reductions followed by the 150 mm or 210 mm roll in the last reduction was the optimum strategy for both powder types. AC susceptibility testing showed that for the in situ tapes there was no correlation between the powder density and the critical temperature. For ex situ...

  15. Negative effects of crystalline-SiC doping on the critical current density in Ti-sheathed MgB2(SiC)y superconducting wires

    International Nuclear Information System (INIS)

    Liang, G; Fang, H; Luo, Z P; Hoyt, C; Yen, F; Guchhait, S; Lv, B; Markert, J T

    2007-01-01

    Ti-sheathed MgB 2 wires doped with nanosize crystalline-SiC up to a concentration of 15 wt% SiC have been fabricated, and the effects of the SiC doping on the critical current density (J c ) and other superconducting properties studied. In contrast with the previously reported results that nano-SiC doping with a doping range below 16 wt% usually enhances J c , particularly at higher fields, our measurements show that SiC doping decreases J c over almost the whole field range from 0 to 7.3 T at all temperatures. Furthermore, it is found that the degradation of J c becomes stronger at higher SiC doping levels, which is also in sharp contrast with the reported results that J c is usually optimized at doping levels near 10 wt% SiC. Our results indicate that these negative effects on J c could be attributed to the absence of significant effective pinning centres (mainly Mg 2 Si) due to the high chemical stability of the crystalline-SiC particles

  16. Fabrication of seven-core multi-filamentary MgB2 wires with high critical current density by an internal Mg diffusion process

    International Nuclear Information System (INIS)

    Togano, K; Hur, J M; Matsumoto, A; Kumakura, H

    2009-01-01

    We found that the reaction between a Mg core and a B powder layer in an internal Mg diffusion (IMD)-processed multi-filamentary wire can proceed rapidly even at a furnace temperature lower than the melting point of Mg (650 deg. C), resulting in the formation of a reacted layer with a fine composite structure and, hence, excellent in-field critical current properties. The multi-filamentary wire is composed of an outermost Cu-Ni sheath and seven filaments with a Ta sheath, a Mg core, and B+SiC powder filled in the space between the Ta sheath and the Mg core. Heat treatment at 645 deg. C for 1 h produced a reacted layer with dense composite structure along the inner wall of the Ta sheath and a hole at the center of each core. This reaction probably initiated from the heat generation at the B/Mg interface, resulting in a temperature rise of the Mg core and the occurrence of liquid Mg infiltration. The J c value at 4.2 K for the reacted layer exceeds 10 5 cm -2 at 9 T, which is the highest reported so far for MgB 2 wire, including powder-in-tube (PIT)-processed wires. These results indicate that the IMD process can compete in terms of practical wire fabrication with the conventional PIT process.

  17. Study of the potential of three different MgB2 tapes for application in cylindrical coils operating at 20 K

    International Nuclear Information System (INIS)

    Pitel, J; Kováč, P; Tropeano, M; Grasso, G

    2015-01-01

    The goal of this theoretical study is to illustrate the potential of three different MgB 2 tapes, developed by Columbus Superconductors, for application in cylindrical coils. First, the distribution of critical currents and electric fields of individual turns is compared when the winding of the model coil is made with tapes having different I c (B) and anisotropy values. Second, the influence of the winding geometry on basic parameters of cylindrical coils which consist of a set of pancake coils, such as critical current I cmin , central magnetic field B 0 and stored energy E, is analysed. The winding geometry of the coils, i.e. the outer winding radius and the coil length, with the same inner winding radius, was changed from a disc shape to a long thin solenoid in such a way that the overall tape length was held constant, and considered as a parameter. Finally, the winding cross-section of the coil is optimized with respect to the constant tape length in order to reach the maximum central field. The results of calculations show that for a given overall tape length and inner winding radius there exists only one winding geometry which generates the maximum central field. The overall tape length, as a parameter, is changed in a broad range from 500 m to 10 km. All calculations were performed using the experimental data measured at 20 K while the effect of the anisotropy in the I c (B) characteristic of the short samples is taken into account. (paper)

  18. Superconducting properties of in situ powder-in-tube-processed MgB2 tapes fabricated with sub-micrometre Mg powder prepared by an arc-plasma method

    International Nuclear Information System (INIS)

    Yamada, H; Uchiyama, N; Matsumoto, A; Kitaguchi, H; Kumakura, H

    2007-01-01

    We fabricated in situ powder-in-tube-processed MgB 2 /Fe tapes using sub-micrometre Mg powder prepared by applying an arc-plasma method. We found that the use of this sub-micrometre Mg powder was very effective in increasing the J c values. The transport J c value of 10 mol% SiC-added tapes fabricated with this sub-micrometre Mg powder reached 275 A mm -2 at 4.2 K and 10 T. This value was about six times that of 5 mol% SiC-added tapes fabricated with commercial Mg powder. Microstructure analyses suggest that this J c enhancement is primarily due to the smaller MgB 2 grain size

  19. Processing, microstructure, and mechanical properties of large-grained zirconium diboride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Neuman, Eric W.; Hilmas, Gregory E., E-mail: ghilmas@mst.edu; Fahrenholtz, William G.

    2016-07-18

    Zirconium diboride ceramics produced using commercial ZrB{sub 2} powders, and milled with zirconium diboride grinding media, were fabricated by hot-pressing at temperatures of 2100–2200 °C with hold times of 30–120 min. This ZrB{sub 2} exhibits no additional impurities typically introduced by milling with grinding media of differing composition. Microstructure analysis revealed grain sizes ranging from ~25 to ~50 µm along with ~3 vol% porosity. Flexure strength ranged from 335 to 400 MPa, elastic modulus from 490 to 510 GPa, fracture toughness from 2.7 to 3.2 MPa m{sup ½}, and hardness from 13.0 to 14.4 GPa. Strength limiting flaws were identified as surface grain pullout induced by machining. Elastic modulus and hardness were found to increase with decreasing porosity. Compared to the fine grained ceramics typically reported, large grain zirconium diboride ceramics exhibit higher than expected room temperature strengths.

  20. Titanium diboride coatings and their interaction with the substrates

    International Nuclear Information System (INIS)

    Pierson, H.O.; Randich, E.

    1978-01-01

    An experimental investigation of the chemical vapor deposition (CVD) of titanium diboride (TiB 2 ) on metallic substrates, using the hydrogen reduction of TiCl 4 and BCl 3 at 1 atmosphere and at temperatures between 850 0 C and 1050 0 C is described. To be coated, the substrate had to meet the following requirements: (1) ability to withstand the deposition temperature without detrimental transformation, (2) chemical inertness to the by-products of the reaction (mostly HCl), (3) reasonable matching of its thermal expansion with that of TiB 2 . The latter requirement may be partially circumvented by using a ductile intermediate coating such as Cu or Ni. Substrates meeting these requirements were W, Ta, Ni, WC, TiC, Kovar and some high chrome steels. Coatings on these substrates were examined by metallographic techniques, scanning electron microscope, x-ray diffraction and electron microprobe. The structures and the degree of interdiffusion were determined. In most cases, intermediate borides of the type M 3 B and M 2 B were formed. The hardness of the coatings was 3330 +- 310 kg/mm 2 (VHN 50 ). Coatings of TiB 2 have already been used successfully on letdown valves in a bench scale coal liquefaction reactor at Sandia Laboratories

  1. Production of magnesium metal

    Science.gov (United States)

    Blencoe, James G [Harriman, TN; Anovitz, Lawrence M [Knoxville, TN; Palmer, Donald A [Oliver Springs, TN; Beard, James S [Martinsville, VA

    2010-02-23

    A process of producing magnesium metal includes providing magnesium carbonate, and reacting the magnesium carbonate to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The carbon dioxide is used as a reactant in a second process. In another embodiment of the process, a magnesium silicate is reacted with a caustic material to produce magnesium hydroxide. The magnesium hydroxide is reacted with a source of carbon dioxide to produce magnesium carbonate. The magnesium carbonate is reacted to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The invention further relates to a process for production of magnesium metal or a magnesium compound where an external source of carbon dioxide is not used in any of the reactions of the process. The invention also relates to the magnesium metal produced by the processes described herein.

  2. The superconducting gaps of C-substituted and Al-substituted MgB2 single crystals by point-contact spectroscopy

    International Nuclear Information System (INIS)

    Daghero, D.; Gonnelli, R.S.; Ummarino, G.A.; Calzolari, A.; Dellarocca, Valeria; Stepanov, V.A.; Zhigadlo, N.; Kazakov, S.M.; Karpinski, J.

    2005-01-01

    We studied the effects of carbon and aluminum substitutions on the gaps of the two-band superconductor MgB 2 by means of point-contact measurements in Mg(B 1-x C x ) 2 and Mg 1-y Al y B 2 single crystals with 0≤x≤0.132 and 0≤y≤0.21. The gap amplitudes, Δ ω and Δ π , were determined by fitting the conductance curves of the point contacts with the standard Blonder-Tinkham-Klapwijk (BTK) model generalized to the two-band case. Whenever possible, their values were confirmed by the independent fit (with a single-band BTK model) of the partial contribution of the two bands to the conductance, separated by means of a suitable magnetic field B*. In C-substituted crystals, the two gaps remain clearly distinct up to x∝0.10, but at x=0.132 we observed for the first time their merging into a single gap Δ≅3 meV with a gap ratio 2Δ=k B T c close to the standard BCS value. In Al-substituted crystals, we found no evidence of this gap merging. Instead, Δ π reaches the value 0.4 meV at y=0.21, where Δ π saturates at about 4 meV. These results are compared with other recent experimental findings in polycrystals and with the predictions of the models for multiband superconductivity. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Thermal properties of zirconium diboride -- transition metal boride solid solutions

    Science.gov (United States)

    McClane, Devon Lee

    This research focuses on the thermal properties of zirconium diboride (ZrB2) based ceramics. The overall goal was to improve the understanding of how different transition metal (TM) additives influence thermal transport in ZrB2. To achieve this, ZrB2 with 0.5 wt% carbon, and 3 mol% of individual transition metal borides, was densified by hot-press sintering. The transition metals that were investigated were: Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, and Re. The room temperature thermal diffusivities of the compositions ranged from 0.331 cm2/s for nominally pure ZrB2 to 0.105 cm2/s for (Zr,Cr)B2 and converged around 0.155cm2/s at higher temperatures for all compositions. Thermal conductivities were calculated from the diffusivities, using temperature-dependent values for density and heat capacity. The electron contribution to thermal conductivity was calculated from measured electrical resistivity according to the Wiedemann-Franz law. The phonon contribution to thermal conductivity was calculated by subtracting the electron contribution from the total thermal conductivity. Rietveld refinement of x-ray diffraction data was used to determine the lattice parameters of the compositions. The decrease in thermal conductivity for individual additives correlated directly to the metallic radius of the additive. Additional strain appeared to exist for additives when the stable TM boride for that metal had different crystal symmetries than ZrB2. This research provided insight into how additives and impurities affect thermal transport in ZrB2. The research potentially offers a basis for future modeling of thermal conductivity in ultra-high temperature ceramics based on the correlation between metallic radius and the decrease in thermal conductivity.

  4. MICROSTRUCTURE OF SUPERCONDUCTING MGB(2).

    Energy Technology Data Exchange (ETDEWEB)

    ZHU,Y.; LI,Q.; WU,L.; VOLKOV,V.; GU,G.; MOODENBAUGH,A.R.

    2001-07-12

    Recently, Akimitsu and co-workers [1] discovered superconductivity at 39 K in the intermetallic compound MgB{sub 2}. This discovery provides a new perspective on the mechanism for superconductivity. More specifically, it opens up possibilities for investigation of structure/properties in a new class of materials. With the exceptions of the cuprate and C{sub 60} families of compounds, MgB{sub 2} possesses the highest superconducting transition temperature T{sub c}. Its superconductivity appears to follow the BCS theory, apparently being mediated by electron-phonon coupling. The coherence length of MgB{sub 2} is reported to be longer than that of the cuprates [2]. In contrast to the cuprates, grain boundaries are strongly coupled and current density is determined by flux pinning [2,3]. Presently, samples of MgB{sub 2} commonly display inhomogeneity and porosity on the nanoscale, and are untextured. In spite of these obstacles, magnetization and transport measurements show that polycrystalline samples may carry large current densities circulating across many grains [3,4]. Very high values of critical current densities and critical fields have been recently observed in thin films [5,6]. These attributes suggest possible large scale and electronic applications. The underlying microstructure can be intriguing, both in terms of basic science and in applied areas. Subsequent to the discovery, many papers were published [1-13], most dealing with synthesis, physical properties, and theory. There have yet been few studies of microstructure and structural defects [11, 14]. A thorough understanding of practical superconducting properties can only be developed after an understanding of microstructure is gained. In this work we review transmission electron microscopy (TEM) studies of sintered MgB{sub 2} pellets [14]. Structural defects, including second phase particles, dislocations, stacking faults, and grain boundaries, are analyzed using electron diffraction, electron-energy loss spectroscopy (EELS), high resolution imaging, and structural modeling.

  5. Magnesium compounds

    Science.gov (United States)

    Kramer, D.A.

    2012-01-01

    Seawater and natural brines accounted for about 57 percent of magnesium compounds produced in the United States in 2011. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties LLC from well brines in Michigan. Caustic-calcined magnesia was recovered from seawater by Premier Magnesia LLC in Florida, from well brines in Michigan by Martin Marietta and from magnesite in Nevada by Premier Magnesia. Intrepid Potash Wendover LLC and Great Salt Lake Minerals Corp. recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from seawater by SPI Pharma Inc. in Delaware and Premier Magnesia in Florida, and by Martin Marietta from its brine operation in Michigan.

  6. Magnesium compounds

    Science.gov (United States)

    Kramer, D.A.

    2007-01-01

    Seawater and natural brines accounted for about 52 percent of U.S. magnesium compounds production in 2006. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from sea-water by Premier Chemicals in Florida; from well brines in Michigan by Martin Marietta and Rohm and Haas; and from magnesite in Nevada by Premier Chemicals. Intrepid Potash-Wendover and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from brucite by Applied Chemical Magnesias in Texas, from seawater by SPI Pharma in Delaware and Premier Chemicals in Florida, and by Martin Marietta and Rohm and Haas from their operations mentioned above. About 59 percent of the magnesium compounds consumed in the United States was used for refractories that are used mainly to line steelmaking furnaces. The remaining 41 percent was consumed in agricultural, chemical, construction, environmental and industrial applications.

  7. Enthalpies of Formation of Transition Metal Diborides: A First Principles Study

    Directory of Open Access Journals (Sweden)

    Catherine Colinet

    2015-11-01

    Full Text Available The enthalpies of formation of transition metals diborides in various structures have been obtained from density functional theory (DFT calculations in order to determine the ground state at T = 0 K and p = 0. The evolution of the enthalpies of formation along the 3D, 4D, and 5D series has been correlated to the considered crystal structures. In the whole, the calculated values of the enthalpies of formation of the diborides in their ground state are in good agreement with the experimental ones when available. The calculated values of the lattice parameters at T = 0 K of the ground state agree well with the experimental values. The total and partial electronic densities of states have been computed. Special features of the transition metal electronic partial density of states have been evidenced and correlated to the local environment of the atoms.

  8. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    Science.gov (United States)

    Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

    2013-01-22

    Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.

  9. Preparation of fiber reinforced titanium diboride and boron carbide composite bodies

    International Nuclear Information System (INIS)

    Newkirk, L.R.; Riley, R.E.; Sheinberg, H.; Valencia, F.A.; Wallace, T.C.

    1979-01-01

    A process is described for uniformly infiltrating woven carbon cloth with either titanium diboride or boron carbide at reduced pressure (15 to 25 torr). The effects of deposition temperature on the uniformity of penetration and on coating rate are described for temperatures from 750 to 1000 0 C and deposit loadings from 20 to 43 vol. %. For the boron carbides, boron composition is discussed and evidence is presented suggesting that propene is the dominant rate controlling reactant

  10. Fracture Mechanisms of Zirconium Diboride Ultra-High Temperature Ceramics under Pulse Loading

    Science.gov (United States)

    Skripnyak, Vladimir V.; Bragov, Anatolii M.; Skripnyak, Vladimir A.; Lomunov, Andrei K.; Skripnyak, Evgeniya G.; Vaganova, Irina K.

    2015-06-01

    Mechanisms of failure in ultra-high temperature ceramics (UHTC) based on zirconium diboride under pulse loading were studied experimentally by the method of SHPB and theoretically using the multiscale simulation method. The obtained experimental and numerical data are evidence of the quasi-brittle fracture character of nanostructured zirconium diboride ceramics under compression and tension at high strain rates and the room temperatures. Damage of nanostructured porous zirconium diboride -based UHTC can be formed under stress pulse amplitude below the Hugoniot elastic limit. Fracture of nanostructured ultra-high temperature ceramics under pulse and shock-wave loadings is provided by fast processes of intercrystalline brittle fracture and relatively slow processes of quasi-brittle failure via growth and coalescence of microcracks. A decrease of the shear strength can be caused by nano-voids clusters in vicinity of triple junctions between ceramic matrix grains and ultrafine-grained ceramics. This research was supported by grants from ``The Tomsk State University Academic D.I. Mendeleev Fund Program'' and also N. I. Lobachevski State University of Nizhny Novgorod (Grant of post graduate mobility).

  11. Low magnesium level

    Science.gov (United States)

    Low magnesium level is a condition in which the amount of magnesium in the blood is lower than normal. The medical ... that convert or use energy ( metabolism ). When the level of magnesium in the body drops below normal, ...

  12. Combined addition of nano diamond and nano SiO2, an effective method to improve the in-field critical current density of MgB2 superconductor

    International Nuclear Information System (INIS)

    Rahul, S.; Varghese, Neson; Vinod, K.; Devadas, K.M.; Thomas, Syju; Anees, P.; Chattopadhyay, M.K.; Roy, S.B.; Syamaprasad, U.

    2011-01-01

    Highlights: → Both nano diamond and nano SiO 2 caused significant modifications in the structural properties of pure MgB 2 sample. → Reduction in T C for the best codoped sample was approximately 2 K. → The best codoped sample yielded a J C , an order of magnitude more than the undoped one at 5 K and 8 T. → The enhanced flux pinning capability provided by the additives is responsible for the improved in-field J C . -- Abstract: MgB 2 bulk samples added with nano SiO 2 and/or nano diamond were prepared by powder-in-sealed-tube (PIST) method and the effects of addition on structural and superconducting properties were studied. X-ray diffraction (XRD) analysis revealed that the addition caused systematic reduction in 'a' lattice parameter due to the substitution of C atoms at B sites and the strain caused by reacted intragrain nano particles of Mg 2 Si as evinced by transmission electron microscope image. Scanning electron microscopy images showed distinct microstructural variations with SiO 2 /diamond addition. It was evident from DC magnetization measurements that the in-field critical current density [J C (H)] of doped samples did not fall drastically like the undoped sample. Among the doped samples the J C (H) of co-doped samples were significantly higher and the best co-doped sample yielded a J C , an order of magnitude more than the undoped one at 5 K and 8 T.

  13. Oxide films on magnesium and magnesium alloys

    International Nuclear Information System (INIS)

    Shih, T.-S.; Liu, J.-B.; Wei, P.-S.

    2007-01-01

    Magnesium alloys are very active and readily ignite during heating and melting. In this study, we discuss the combustion of magnesium and magnesium alloys and propose prospective anti-ignition mechanisms for magnesium alloys during the heating process. When magnesium and magnesium alloys were heated in air, the sample surfaces produced layers of thermally formed oxides. These thermally formed oxides played an important role in affecting the combustion of the magnesium and magnesium alloys. When magnesium was heated in air, brucite that formed in the early stage was then transformed into periclase by dehydroxylation. By extending the heating time, more periclase formed and increased in thickness which was associated with microcracks formation. When magnesium was heated in a protective atmosphere (SF 6 ), a film of MgF 2 formed at the interface between the oxide layer and the Mg substrate. This film generated an anti-ignition behavior which protected the substrate from oxidation. When solution-treated AZ80 alloy was heated, spinel developed at the interface between the thermally formed oxide layer and the Mg substrate, improving the anti-ignition properties of the substrate. In addition, we also explain the effects of beryllium in an AZB91 alloy on the ignition-proofing behavior

  14. Incoherent x-ray emission of titanium diboride at the boron site

    Energy Technology Data Exchange (ETDEWEB)

    Ederer, D.L.; Winarski, R.; Ek, J. van [Tulane Univ., New Orleans, LA (United States)] [and others

    1997-04-01

    This group has made a study of a large number of transition metal diborides and hexaborides. As an example they would like to consider one of them. This class of compounds are of technical interest because they are quite hard, metallic, and chemically stable, and have high melting points. In addition to the technical importance of the borides, the group is interested in compounds of this type because of the very strong 1s {r_arrow} p* resonance that has been observed and associated with the boron atom.

  15. Electron transport in diborides: observation of superconductivity in ZrB sub 2

    CERN Document Server

    Gasparov, V A; Zverkova, I I; Kulakov, M P

    2001-01-01

    Results on syntheses and electron transport properties of polycrystalline samples of diborides (AB sub 2) with different transition metals atoms (A = Zr, Nb, Ta) are reported. The temperature dependences of resistivity and ac susceptibility of these samples reveal superconducting transition of ZrB sub 2 with T sub c = 5.5 K, while NbB sub 2 and TaB sub 2 have been observed nonsuperconducting up to 0.37 K. The upper critical field H sub c sub 2 (T) is linear in temperature below T sub c. At T close to T sub c H sub c sub 2 (T) demonstrates a downward curvature. It is concluded that these diborides as well as MgB sub 2 samples behave like simple metals in the normal state with usual Bloch-Grueneisen temperature dependence of resistivity and with Debye temperatures: 280, 460 and 440 K, for ZrB sub 2 , NbB sub 2 and MgB sub 2 , respectively

  16. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    TECS

    exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution ... Having tremendous load bearing capacity, it can withstand .... retention coefficients for similar concrete compositions.

  17. Calcium and magnesium determination

    International Nuclear Information System (INIS)

    Bhattacharya, S.K.

    1982-01-01

    The roles of calcium and magnesium in human health and disease have been extensively studied. Calcium and magnesium have been determined in biological specimens by atomic absorption spectroscopy using stiochiometric nitrous oxide-acetylene flame

  18. Choline Magnesium Trisalicylate

    Science.gov (United States)

    Choline magnesium trisalicylate is used to relieve the pain, tenderness, inflammation (swelling), and stiffness caused by arthritis and painful ... used to relieve pain and lower fever. Choline magnesium trisalicylate is in a class of nonsteroidal anti- ...

  19. Structure, elastic stiffness, and hardness of Os 1- xRu xB 2 solid solution transition-metal diborides

    KAUST Repository

    Kanoun, Mohammed; Hermet, Patrick; Goumri-Said, Souraya

    2012-01-01

    On the basis of recent experiments, the solid solution transition-metal diborides were proposed to be new ultra-incompressible hard materials. We investigate using density functional theory based methods the structural and mechanical properties, electronic structure, and hardness of Os 1-xRu xB 2 solid solutions. A difference in chemical bonding occurs between OsB 2 and RuB 2 diborides, leading to significantly different elastic properties: a large bulk, shear moduli, and hardness for Os-rich diborides and relatively small bulk, shear moduli, and hardness for Ru-rich diborides. The electronic structure and bonding characterization are also analyzed as a function of Ru-dopant concentration in the OsB 2 lattice. © 2012 American Chemical Society.

  20. Structure, elastic stiffness, and hardness of Os 1- xRu xB 2 solid solution transition-metal diborides

    KAUST Repository

    Kanoun, Mohammed

    2012-05-31

    On the basis of recent experiments, the solid solution transition-metal diborides were proposed to be new ultra-incompressible hard materials. We investigate using density functional theory based methods the structural and mechanical properties, electronic structure, and hardness of Os 1-xRu xB 2 solid solutions. A difference in chemical bonding occurs between OsB 2 and RuB 2 diborides, leading to significantly different elastic properties: a large bulk, shear moduli, and hardness for Os-rich diborides and relatively small bulk, shear moduli, and hardness for Ru-rich diborides. The electronic structure and bonding characterization are also analyzed as a function of Ru-dopant concentration in the OsB 2 lattice. © 2012 American Chemical Society.

  1. Magnesium and Space Flight

    Directory of Open Access Journals (Sweden)

    Scott M. Smith

    2015-12-01

    Full Text Available Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female, 35 ± 7 years old. We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions.

  2. Magnesium and Space Flight

    Science.gov (United States)

    Smith, Scott M.; Zwart, Sara R.

    2015-01-01

    Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD) before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female), 35 ± 7 years old). We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions. PMID:26670248

  3. First-principles study of defects and fission product behavior in uranium diboride

    Science.gov (United States)

    Jossou, Ericmoore; Oladimeji, Dotun; Malakkal, Linu; Middleburgh, Simon; Szpunar, Barbara; Szpunar, Jerzy

    2017-10-01

    A Systematic study of defects and incorporation of xenon (Xe) and zirconium (Zr) fission products in uranium diboride (UB2) has been investigated using density functional theory (DFT) calculations as implemented in Quantum ESPRESSO code. The incorporation and solution energies show that both FPs (Xe and Zr) are most stable in U vacancies with Zr being more stable than Xe. A volume expansion is observed as the concentration of Xe increases in the fuel matrix while Zr incorporation leads to a contraction. Bader charge analysis is used to establish the formation of Zr-B ionic/covalent bond due to large electron transfer observed while there is only a weak electronic interaction between Xe and the UB2 lattice. Finally, using climbing-image nudged elastic band calculation, we found that the energy barrier of U in UB2 is 0.08 eV higher than B migration energy.

  4. Fabrication of Titanium Diboride-Cu Composite by Self-High Temperature Synthesis plus Quick Press

    Institute of Scientific and Technical Information of China (English)

    Jinyong ZHANG; Zhengyi FU; Weimin WANG

    2005-01-01

    Titanium diboride based composites, good candidates for contact materials, have high hardness, Young's modulus,high temperature stability, and excellent electrical, thermal conductivity. However a good interface of TiB2/Cu is very difficult to achieve for oxidation of TiB2. To avoid this oxidation behavior, the in situ combusting synthesis technology, SHS, was used to prepare TiB2/Cu composite. Thecharacters of Ti-B-xCu SHS were studied in detail,such as combustion temperature, products phases and grain size. Based on the experimental results a proper technology way of self-high temperature synthesis plus quick press (SHS/QP) was determined and compact TiB2/Cu composites with relative density over than 97 pct of the theoretical were fabricated by this method. The properties and microstructures of these TiB2 based composites were also investigated.

  5. Magnesium and Osteoporosis

    Directory of Open Access Journals (Sweden)

    Ferda Özdemir

    2004-03-01

    Full Text Available Osteoporosis (OP is a condition of bone fragility resulting from micro-architectural deterioration and decreased bone mass. OP depends on the interaction of genetic, hormonal, environmental and nutritional factors. Chronic low intakes of vitamin D and possibly magnesium, zinc, fluoride and vitamins K, B12, B6 and folic acid may predispose to osteoporosis. Magnesium is a mineral needed by every cell of your body. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, and bones strong. Mg serves as co-factors for enzymes that help build bone matrix. Magnesium deficiency occurs due to excessive loss of magnesium in urine, gastrointestinal system disorders that cause a loss of magnesium or limit magnesium absorption, or a chronic low intake of magnesium. Signs of magnesium deficiency include confusion, disorientation, loss of appetite, depression, muscle contractions and cramps, tingling, numbness, abnormal heart rhythms, coronary spasm, and seizures. Magnesium deficiency alters calcium metabolism and the hormones that regulates calcium. Several studies have suggested that magnesium supplementation may improve bone mineral density and prevent fractures.

  6. Magnesium motorcycle applications

    International Nuclear Information System (INIS)

    Jianyong Cao; Zonghe Zhang; Dongxia Xiang; Jun Wang

    2005-01-01

    Magnesium, the lightest engineering structural metal, has been comprehensively used in castings of aviation and aerospace, communication and transportation, and IT components. This paper introduced the history, advantages and difficulties of magnesium castings for motorcycle application as well as its application state in China. It also indicated the production situation of magnesium motorcycle components in CQMST and difficulties need to overcome for further development. (orig.)

  7. Magnesium in pregnancy.

    Science.gov (United States)

    Dalton, Lynne M; Ní Fhloinn, Deirdre M; Gaydadzhieva, Gergana T; Mazurkiewicz, Ola M; Leeson, Heather; Wright, Ciara P

    2016-09-01

    Magnesium deficiency is prevalent in women of childbearing age in both developing and developed countries. The need for magnesium increases during pregnancy, and the majority of pregnant women likely do not meet this increased need. Magnesium deficiency or insufficiency during pregnancy may pose a health risk for both the mother and the newborn, with implications that may extend into adulthood of the offspring. The measurement of serum magnesium is the most widely used method for determining magnesium levels, but it has significant limitations that have both hindered the assessment of deficiency and affected the reliability of studies in pregnant women. Thus far, limited studies have suggested links between magnesium inadequacy and certain conditions in pregnancy associated with high mortality and morbidity, such as gestational diabetes, preterm labor, preeclampsia, and small for gestational age or intrauterine growth restriction. This review provides recommendations for further study and improved testing using measurement of red cell magnesium. Pregnant women should be counseled to increase their intake of magnesium-rich foods such as nuts, seeds, beans, and leafy greens and/or to supplement with magnesium at a safe level. © The Author(s) 2016. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  8. Magnesium Technology : Preface

    NARCIS (Netherlands)

    Sillekens, W.H.; Agnew, S.R.; Neelameggham, N.R.; Mathaudhu, S.N.

    2011-01-01

    The Magnesium Technology Symposium, which takes place every year at the TMS Annual Meeting & Exhibition, is one of the largest yearly gatherings of magnesium specialists in the world. Papers are presented in all aspects of the field, ranging from primary production to applications to recycling.

  9. Nutrition and magnesium absorption

    NARCIS (Netherlands)

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true

  10. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

    Science.gov (United States)

    Nguyen, Duc; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Girolami, Gregory S.; Lyding, Joseph; Gruebele, Martin

    2014-11-01

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses.

  11. Trends in elasticity and electronic structure of 5d transition metal diborides: first-principles calculations

    International Nuclear Information System (INIS)

    Hao Xianfeng; Wu Zhijian; Xu Yuanhui; Zhou Defeng; Liu Xiaojuan; Meng Jian

    2007-01-01

    We investigate the cohesive energy, heat of formation, elastic constant and electronic band structure of transition metal diborides TMB 2 (TM = Hf, Ta, W, Re, Os and Ir, Pt) in the Pmmn space group using the ab initio pseudopotential total energy method. Our calculations indicate that there is a relationship between elastic constant and valence electron concentration (VEC): the bulk modulus and shear modulus achieve their maximum when the VEC is in the range of 6.8-7.2. In addition, trends in the elastic constant are well explained in terms of electronic band structure analysis, e.g., occupation of valence electrons in states near the Fermi level, which determines the cohesive energy and elastic properties. The maximum in bulk modulus and shear modulus is attributed to the nearly complete filling of TM d-B p bonding states without filling the antibonding states. On the basis of the observed relationship, we predict that alloying W and Re in the orthorhombic structure OsB 2 might be harder than alloying the Ir element. Indeed, the further calculations confirmed this expectation

  12. Trends in elasticity and electronic structure of 5d transition metal diborides: first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Hao Xianfeng [Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wu Zhijian [Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Xu Yuanhui [School of Biological Engineering, Changchun University of Technology, Changchun 130012 (China); Zhou Defeng [School of Biological Engineering, Changchun University of Technology, Changchun 130012 (China); Liu Xiaojuan [Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng Jian [Key Laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2007-05-16

    We investigate the cohesive energy, heat of formation, elastic constant and electronic band structure of transition metal diborides TMB{sub 2} (TM = Hf, Ta, W, Re, Os and Ir, Pt) in the Pmmn space group using the ab initio pseudopotential total energy method. Our calculations indicate that there is a relationship between elastic constant and valence electron concentration (VEC): the bulk modulus and shear modulus achieve their maximum when the VEC is in the range of 6.8-7.2. In addition, trends in the elastic constant are well explained in terms of electronic band structure analysis, e.g., occupation of valence electrons in states near the Fermi level, which determines the cohesive energy and elastic properties. The maximum in bulk modulus and shear modulus is attributed to the nearly complete filling of TM d-B p bonding states without filling the antibonding states. On the basis of the observed relationship, we predict that alloying W and Re in the orthorhombic structure OsB{sub 2} might be harder than alloying the Ir element. Indeed, the further calculations confirmed this expectation.

  13. Magnesium in diet

    Science.gov (United States)

    ... sources of magnesium: Fruits or vegetables (such as bananas, dried apricots, and avocados) Nuts (such as almonds ... deficiency: Low blood calcium level (hypocalcemia) Low blood potassium level (hypokalemia) Recommendations These are the recommended daily ...

  14. Theoretical calculations of hardness and metallicity for multibond hexagonal 5d transition metal diborides with ReB2 structure

    International Nuclear Information System (INIS)

    Yang Jun; Gao Fa-Ming; Liu Yong-Shan

    2017-01-01

    The hardness, electronic, and elastic properties of 5d transition metal diborides with ReB 2 structure are studied theoretically by using the first principles calculations. The calculated results are in good agreement with the previous experimental and theoretical results. Empirical formulas for estimating the hardness and partial number of effective free electrons for each bond in multibond compounds with metallicity are presented. Based on the formulas, IrB 2 has the largest hardness of 21.8 GPa, followed by OsB 2 (21.0 GPa) and ReB 2 (19.7 GPa), indicating that they are good candidates as hard materials. (paper)

  15. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

    International Nuclear Information System (INIS)

    Nguyen, Duc; Girolami, Gregory S.; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Lyding, Joseph; Gruebele, Martin

    2014-01-01

    Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB 2 glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB 2 has a very high bulk glass transition temperature T g , and we observe no three-state hopping or sequential two-state hopping previously seen on lower T g glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how “mixed” features can show up in surface dynamics of glasses

  16. Development of microstructure during sintering and aluminium exposure of titanium diboride ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Gunnar

    1997-12-31

    In the production of aluminium, much less energy need be consumed if an inert, wetted cathode is present in the electrolysis cell. Titanium diboride, TiB{sub 2}, is easily wetted and does not readily dissolve in liquid aluminium, but it degrades, probably because aluminium penetrates into it during electrolysis. This degradation is linked to impurities present in the TiB{sub 2} after sintering. This thesis studies the sintering process and how aluminium penetrates into the material. High-purity, high-density TiB{sub 2} compacts were made by hot pressing at 50 MPa in an argon atmosphere at 1790-1960 {sup o}C. Samples were made with different impurity additions. These samples were exposed to liquid aluminium at 980 {sup o}C for 24 hours. All samples were penetrated, but the amount and appearance depended on the sintering aid used. Unlike the other samples, pure TiB{sub 2} was easily penetrated by metallic aluminium because of the open porosity and microcracks of this material. Grain boundary penetration was common among the samples. Differences in penetration behaviour between grain boundaries are probably due to differences in grain boundary energy. But no relation to segregants or boundary misorientation was found. The orientation of grain boundary planes and de-wetting of thin films upon cooling may explain the observed microstructure development. The samples sintered with Ti addition suffered extensive penetration despite their high densities. The grain boundaries of these samples became faceted and contained thicker films of metallic aluminium, presumably because of increased solubility due to iron segregations. All secondary phases present in the grain junctions after sintering, except from the B{sub 4}C phase, reacted with the penetrated aluminium. This did not cause swelling and cracking, as has been suggested by other authors. 101 refs., 48 figs., 7 tabs.

  17. The stability boundary of group-III transition metal diboride ScB 2 (0 0 0 1) surfaces

    Science.gov (United States)

    Zhao, Hui; Qin, Na

    2012-01-01

    Experimental observations and theoretical investigations exhibit that a group-IV(V) transition metal diboride (0 0 0 1) surface is terminated with a 1 × 1 TM(B) layer. As to a group-III transition metal diboride, we have investigated the stability boundary of ScB2 (0 0 0 1) surfaces using first principles total energy plane-wave pseudopotential method based on density functional theory. The Mulliken charge population analysis shows that Sc atoms in the second layer cannot provide B atoms in the first layer with sufficient electrons to form a complete graphene-like boron layer. We also found that the charge transfer between the first and the second layer for the B-terminated surface is more than that for Sc-terminated surface. It elucidates the reason that the outermost interlayer spacing contract more strongly in the B-terminated surface than in the Sc-terminated surface. The surface energies of both terminated ScB2 (0 0 0 1) surfaces as a function of the chemical potential of B are also calculated to check the relative stability of the two surface structures.

  18. Magnesium Borohydride: From Hydrogen Storage to Magnesium Battery**

    OpenAIRE

    Mohtadi, Rana; Matsui, Masaki; Arthur, Timothy S; Hwang, Son-Jong

    2012-01-01

    Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH_4)_2 electrolyte was utilized in a rechargeable magnesium battery.

  19. INVESTIGATION OF MAGNESIUM ALLOYS MACHINABILITY

    Directory of Open Access Journals (Sweden)

    Berat Barıs BULDUM

    2013-01-01

    Full Text Available Magnesium is the lightest structural metal. Magnesium alloys have a hexagonal lattice structure, which affects the fundamental properties of these alloys. Plastic deformation of the hexagonal lattice is more complicated than in cubic latticed metals like aluminum, copper and steel. Magnesium alloy developments have traditionally been driven by industry requirements for lightweight materials to operate under increasingly demanding conditions. Magnesium alloys have always been attractive to designers due to their low density, only two thirds that of aluminium and its alloys [1]. The element and its alloys take a big part of modern industry needs. Especially nowadays magnesium alloys are used in automotive and mechanical (trains and wagons manufacture, because of its lightness and other features. Magnesium and magnesium alloys are the easiest of all metals to machine, allowing machining operations at extremely high speed. All standard machining operations such as turning, drilling, milling, are commonly performed on magnesium parts.

  20. Aluminum Hydroxide and Magnesium Hydroxide

    Science.gov (United States)

    Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They ... They combine with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription. ...

  1. Magnesium Tube Hydroforming

    International Nuclear Information System (INIS)

    Liewald, M.; Pop, R.; Wagner, S.

    2007-01-01

    Magnesium alloys can be considered as alternative materials towards achieving light weight structures with high material stiffness. The formability of two magnesium alloys, viz. AZ31 and ZM21 has been experimentally tested using the IHP forming process. A new die set up for hot IHP forming has been designed and the process experimentally investigated for temperatures up to 400 deg. C. Both alloys exhibit an increase in formability with increasing forming temperature. The effect of annealing time on materials forming properties shows a fine grained structure for sufficient annealing times as well as deterioration with a large increase at the same time. The IHP process has also been used to demonstrate practicability and feasibility for real parts from manufacture a technology demonstrator part using the magnesium alloy ZM21

  2. Magnesium for Hydrogen Storage

    DEFF Research Database (Denmark)

    Vigeholm, B.; Kjøller, John; Larsen, Bent

    1980-01-01

    The reaction of hydrogen with commercially pure magnesium powder (above 99.7%) was investigated in the temperature range 250–400 °C. Hydrogen is readily sorbed above the dissociation pressure. During the initial exposure the magnesium powder sorbs hydrogen slowly below 400 °C but during the second...... that the particles do not disintegrate is explained by a sintering process at the working temperatures. Exposure to air does not impair the sorption ability; on the contrary, it appears that surface oxidation plays an important role in the reaction. Some handling problems, e.g. the reaction of the hydride with water...

  3. Nanostructure and bonding of zirconium diboride thin films studied by X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, David M., E-mail: david.stewart@maine.edu; Meulenberg, Robert W.; Lad, Robert J., E-mail: rjlad@maine.edu

    2015-12-01

    Zirconium diboride (ZrB{sub 2}) is an important ceramic due to its extremely high melting temperature of 3245 °C and metallic electrical conductivity, properties that make it an ideal candidate thin film electrode material for high temperature electronics. In this report, thin films of varying B:Zr ratio ranging from 3–0.67 have been grown by e-beam evaporation from elemental sources. X-ray absorption spectra at the Zr K-edge were measured before and after annealing in ultra-high vacuum for 9 h at 1000 °C. Films with compositions near ZrB{sub 2} stoichiometry show X-ray absorption fine structure that can be well modeled by crystalline ZrB{sub 2} with a small portion of a coexisting tetragonal zirconia (t-ZrO{sub 2}) phase. Films far from stoichiometry show substantial disorder beyond the nearest-neighbor distances, and after vacuum annealing exhibit high levels of oxidation. Contributions to the X-ray absorption fine structure from a pure Zr phase are very small compared to ZrB{sub 2} and t-ZrO{sub 2} phases. The fact that nearly stoichiometric (3 < B:Zr < 1.6) as-deposited amorphous films form the same crystalline ZrB{sub 2} nanostructure after annealing is particularly encouraging for high temperature thin film electronics applications, because it would allow the production of highly stable electrodes with e-beam evaporation without the need of any high temperature heating during film growth. - Highlights: • Zr–B thin films of different compositions were grown at low substrate temperatures. • EXAFS analysis indicates a ZrB{sub 2} crystal structure after vacuum annealing. • The coexistence of crystalline and amorphous Zr–B phases is also observed. • Films with excess Zr readily form t-ZrO{sub 2} during deposition, which coexists with ZrB{sub 2}. • Low temperature synthesis routes are important for technological applications.

  4. Magnesium fluoride recovery method

    International Nuclear Information System (INIS)

    Gay, R.L.; McKenzie, D.E.

    1989-01-01

    A method of obtaining magnesium fluoride substantially free from radioactive uranium from a slag formed in the production of metallic uranium by the reduction of depleted uranium tetrafluoride with metallic magnesium in a retort wherein the slag contains the free metals magnesium and uranium and also oxides and fluorides of the metals. The slag having a radioactivity level of at least about 7,000 rhoCi/gm. The method comprises the steps of: grinding the slag to a median particle size of about 200 microns; contacting the ground slag in a reaction zone with an acid having a strength of from about 0.5 to 1.5 N for a time of from about 4 to about 20 hours in the presence of a catalytic amount of iron; removing the liquid product; treating the particulate solid product; repeating the last two steps at least one more time to produce a solid residue consisting essentially of magnesium fluoride substantially free of uranium and having a residual radioactivity level of less than about 1000 rhoCi/gm

  5. FOCUS ON MAGNESIUM BASED DRUGS

    Directory of Open Access Journals (Sweden)

    I. I. Esenova

    2011-01-01

    Full Text Available Magnesium deficiency in the organism is one of the most common human deficiency states. The prevalence of magnesium deficiency is about 15%, and suboptimal magnesium level is observed more than in 30% of people in the general population. Clinical signs of hypomagnesaemia are observed in 40% of patients in general care hospitals, in 70% of patients - in intensive care units, and magnesium deficiency occurs in 90% of patients with acute coronary syndrome. Magnesium metabolic disorders in the organism accelerate significantly development of complications of coronary heart disease, hypertension, type 2 diabetes, asthma and a number of neurological and psychiatric diseases. The value of this macro in the body is well studied, and its daily need is identified depending on age and sex. It is known that magnesium intake with the food does not cover an organism need. It is a rationale for preventive and therapeutic use of magnesium based drugs in various diseases. Organic salts of magnesium are recommended for these purposes. Magnesium metabolic disorders, approaches to pharmacotherapeutic correction of magnesium deficiency, advantages of magnesium salts of orotic acid are reviewed.

  6. How does the composition of quasi-stoichiometric titanium diboride affect its wetting by molten Cu and Au?

    International Nuclear Information System (INIS)

    Aizenshtein, M.; Froumin, N.; Barth, P.; Shapiro-Tsoref, E.; Dariel, M.P.; Frage, N.

    2007-01-01

    The poor wetting in non-oxide ceramic/metal (M = Au or Cu) systems is usually attributed to the lack of chemical interaction at the solid/liquid interface. In contrast, sessile drop experiments on two non-stoichiometric titanium diboride substrates (TiB 1.9 and TiB 1.95 ) displayed a surprisingly good wetting. The experimental results are well accounted for by the thermodynamic analysis of the Me-Ti-B systems. According to this analysis, some limited boride dissolution and altering of the substrate composition takes place at the TiB x /Me interface. These changes are more substantial, the stronger the departure from stoichiometry of the initial substrate composition. Minor composition changes are sufficient for improving wetting. Based on the results of the thermodynamic analysis and the wetting experiments, a novel method for the fabrication of Cu infiltrated composites is put forward

  7. Reactive Spark Plasma Sintering and Mechanical Properties of Zirconium Diboride–Titanium Diboride Ultrahigh Temperature Ceramic Solid Solutions

    Directory of Open Access Journals (Sweden)

    Karthiselva N. S.

    2016-09-01

    Full Text Available Ultrahigh temperature ceramics (UHTCs such as diborides of zirconium, hafnium tantalum and their composites are considered to be the candidate materials for thermal protection systems of hypersonic vehicles due to their exceptional combination of physical, chemical and mechanical properties. A composite of ZrB2-TiB2 is expected to have better properties. In this study, an attempt has been made to fabricate ZrB2-TiB2 ceramics using mechanically activated elemental powders followed by reactive spark plasma sintering (RSPS at 1400 °C. Microstructure and phase analysis was carried out using X-ray diffractometer (XRD and electron microscopy to understand microstructure evolution. Fracture toughness and hardness were evaluated using indentation methods. Nanoindentation was used to measure elastic modulus. Compressive strength of the composites has been reported.

  8. Exploring the behavior of molybdenum diboride (MoB2): A high pressure x-ray diffraction study

    International Nuclear Information System (INIS)

    Liu, Pingping; Peng, Fang; Yin, Shuai; Liu, Fangming; Wang, Qiming; Zhu, Xuhui; Wang, Pei; He, Duanwei; Liu, Jing

    2014-01-01

    Investigation of the equation of state of molybdenum diboride (MoB 2 ) has been performed to 24.1 GPa using synchrotron radiation angle-dispersive x-ray diffraction techniques (ADXRD) in a diamond anvil cell (DAC) at room temperature. Rietveld refinement of the X-ray powder diffraction data reveals that the rhombohedral structure MoB 2 is stable up to 24.1 GPa. The ADXRD data yield a bulk modulus K 0  = 314(11) GPa with a pressure derivative K 0 ′  = 6.4(1.5). The experimental data are discussed and compared to the results of first-principles calculations. In addition, the compressibility of the unit cell axes (a and c axes) of MoB 2 demonstrates an anisotropic property with pressure increasing

  9. Phase stability, physical properties of rhenium diboride under high pressure and the effect of metallic bonding on its hardness

    International Nuclear Information System (INIS)

    Zhong, Ming-Min; Kuang, Xiao-Yu; Wang, Zhen-Hua; Shao, Peng; Ding, Li-Ping; Huang, Xiao-Fen

    2013-01-01

    Highlights: •The transition pressure P t between the ReB 2 –ReB 2 and MoB 2 –ReB 2 phases is firstly determinate. •The single-bonded B–B feather remains in ReB 2 compounds. •A semiempirical method to evaluate the hardness of crystals with partial metallic bond is presented. •The large hardness (39.1 GPa) of ReB 2 –ReB 2 indicate that it is a superhard material. •The zigzag interconnected B–Re and B–B covalent bonds underlie the ultraincompressibilities. -- Abstract: Using first-principles calculations, the elastic constants, thermodynamic property and structural phase transition of rhenium diboride under pressure are investigated by means of the pseudopotential plane-waves method, as well as the effect of metallic bond on its hardness. Eight candidate structures of known transition-metal compounds are chosen to probe for rhenium diboride ReB 2 . The calculated lattice parameters are consistent with the experimental and theoretical values. Based on the third order Birch–Murnaghan equation of states, the transition pressure P t between the ReB 2 –ReB 2 and MoB 2 –ReB 2 phases is firstly determinate. Elastic constants, shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature are derived. The single-bonded B–B feather remains in ReB 2 compounds. Furthermore, according to Mulliken overlap population analysis, a semiempirical method to evaluate the hardness of multicomponent crystals with partial metallic bond is presented. Both strong covalency and a zigzag topology of interconnected bonds underlie the ultraincompressibilities. In addition, the superior performance and large hardness (39.1 GPa) of ReB 2 –ReB 2 indicate that it is a superhard material

  10. Magnesium borohydride: from hydrogen storage to magnesium battery.

    Science.gov (United States)

    Mohtadi, Rana; Matsui, Masaki; Arthur, Timothy S; Hwang, Son-Jong

    2012-09-24

    Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH(4))(2) electrolyte was utilized in a rechargeable magnesium battery. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A superconducting shield to protect astronauts

    CERN Document Server

    Antonella Del Rosso

    2015-01-01

    The CERN Superconductors team in the Technology department is involved in the European Space Radiation Superconducting Shield (SR2S) project, which aims to demonstrate the feasibility of using superconducting magnetic shielding technology to protect astronauts from cosmic radiation in the space environment. The material that will be used in the superconductor coils on which the project is working is magnesium diboride (MgB2), the same type of conductor developed in the form of wire for CERN for the LHC High Luminosity Cold Powering project.   Image: K. Anthony/CERN. Back in April 2014, the CERN Superconductors team announced a world-record current in an electrical transmission line using cables made of the MgB2 superconductor. This result proved that the technology could be used in the form of wire and could be a viable solution for both electrical transmission for accelerator technology and long-distance power transportation. Now, the MgB2 superconductor has found another application: it wi...

  12. Magnesium borate radiothermoluminescent detectors

    International Nuclear Information System (INIS)

    Kazanskaya, V.A.; Kuzmin, V.V.; Minaeva, E.E.; Sokolov, A.D.

    1974-01-01

    In the report the technology of obtaining polycrystalline magnesium borate activated by dysprosium is described briefly and the method of preparing the tabletted detectors from it is presented. The dependence of the light sum of the samples on the proportion of the components and on the sintering regime has shown that the most sensitive material is obtained at the proportion of boric anhydride and magnesium oxide 2.2-2.4 and at the dysprosium concentration about 1 milligram-atom per gram molecule of the base. The glow curve of such a material has a simple form with one peak the maximum of which is located at 190-200 0 C. The measurement of the main dosimetric characteristics of the magnesium borate tabletted detectors and the comparison with similar parmaeters of the lithium fluoride tabletted detectors have shown that at practically identical effective number the former detectors have the following substantial advantages: the sensitivity is ten-twenty times as large, they are substantially more technological on synthesis of the radiothermoluminophor and during the production of the tabletted detectors, they have a simple glow curve, they do not require the utilization of the thermocycling during the use. (author)

  13. Function of magnesium aluminate hydrate and magnesium nitrate ...

    Indian Academy of Sciences (India)

    MgO was added both as spinel (MgAl2O4) forming precursor i.e. magnesium aluminate hydrate, and magnesium nitrate. Sintering investigations were conducted in the temperature range 1500–1600°C with 2 h soaking. Structural study of sintered pellets was carried out by extensive XRD analysis. Scanning electron mode ...

  14. Magnesium Hall Thruster

    Science.gov (United States)

    Szabo, James J.

    2015-01-01

    This Phase II project is developing a magnesium (Mg) Hall effect thruster system that would open the door for in situ resource utilization (ISRU)-based solar system exploration. Magnesium is light and easy to ionize. For a Mars- Earth transfer, the propellant mass savings with respect to a xenon Hall effect thruster (HET) system are enormous. Magnesium also can be combusted in a rocket with carbon dioxide (CO2) or water (H2O), enabling a multimode propulsion system with propellant sharing and ISRU. In the near term, CO2 and H2O would be collected in situ on Mars or the moon. In the far term, Mg itself would be collected from Martian and lunar regolith. In Phase I, an integrated, medium-power (1- to 3-kW) Mg HET system was developed and tested. Controlled, steady operation at constant voltage and power was demonstrated. Preliminary measurements indicate a specific impulse (Isp) greater than 4,000 s was achieved at a discharge potential of 400 V. The feasibility of delivering fluidized Mg powder to a medium- or high-power thruster also was demonstrated. Phase II of the project evaluated the performance of an integrated, highpower Mg Hall thruster system in a relevant space environment. Researchers improved the medium power thruster system and characterized it in detail. Researchers also designed and built a high-power (8- to 20-kW) Mg HET. A fluidized powder feed system supporting the high-power thruster was built and delivered to Busek Company, Inc.

  15. Magnesium for Hydrogen Storage

    DEFF Research Database (Denmark)

    Pedersen, Allan Schrøder; Kjøller, John; Larsen, B.

    1983-01-01

    A study of the hydrogenation characteristics of fine magnesium powder during repeated cycling has been performed using a high-pressure microbalance facility. No effect was found from the cycling regarding kinetics and storage capacity. The reaction rate of the absorption process was fast...... at temperatures around 600 K and above, but the reversed reaction showed somewhat slower kinetics around 600 K. At higher temperatures the opposite was found. The enthalpy and entropy change by the hydrogenation, derived from pressure-concentration isotherms, agree fairly well with those reported earlier....

  16. Electrolytes for magnesium electrochemical cells

    Science.gov (United States)

    Burrell, Anthony K.; Sa, Niya; Proffit, Danielle Lee; Lipson, Albert; Liao, Chen; Vaughey, John T.; Ingram, Brian J.

    2017-07-04

    An electrochemical cell includes a high voltage cathode configured to operate at 1.5 volts or greater; an anode including Mg.sup.0; and an electrolyte including an ether solvent and a magnesium salt; wherein: a concentration of the magnesium salt in the ether is 1 M or greater.

  17. Hydrostatic extrusion of magnesium alloys

    NARCIS (Netherlands)

    Sillekens, W.H.; Bohlen, J.

    2012-01-01

    This chapter deals with the capabilities and limitations of the hydrostatic extrusion process for the manufacturing of magnesium alloy sections. Firstly, the process basics for the hydrostatic extrusion of materials in general and of magnesium in particular are introduced. Next, some recent research

  18. Innovative Vacuum Distillation for Magnesium Recycling

    Science.gov (United States)

    Zhu, Tianbai; Li, Naiyi; Mei, Xiaoming; Yu, Alfred; Shang, Shixiang

    Magnesium recycling now becomes a very important subject as magnesium consumption increases fast around the world. All commonly used magnesium die-casting alloys can be recycled and recovered to the primary metal quality. The recycled materials may be comprised of biscuits, sprues, runners, flash, overflows, dross, sludge, scrap parts, and old parts that are returned from service, An innovative magnesium recycle method, vacuum distillation, is developed and proved out to be able to recycle magnesium scraps, especially machining chips, oily magnesium, smelting sludge, dross or the mixture. With this process at a specific temperature and environment condition, magnesium in scraps can be gasified and then solidified to become crystal magnesium crown. This `recycled' magnesium crown is collected and used as the raw material of magnesium alloys. The experimental results show the vacuum distillation is a feasible and plausible method to recycle magnesium. Further, the cost analysis will be addressed in this paper.

  19. Magnesium in Prevention and Therapy

    Science.gov (United States)

    Gröber, Uwe; Schmidt, Joachim; Kisters, Klaus

    2015-01-01

    Magnesium is the fourth most abundant mineral in the body. It has been recognized as a cofactor for more than 300 enzymatic reactions, where it is crucial for adenosine triphosphate (ATP) metabolism. Magnesium is required for DNA and RNA synthesis, reproduction, and protein synthesis. Moreover, magnesium is essential for the regulation of muscular contraction, blood pressure, insulin metabolism, cardiac excitability, vasomotor tone, nerve transmission and neuromuscular conduction. Imbalances in magnesium status—primarily hypomagnesemia as it is seen more common than hypermagnesemia—might result in unwanted neuromuscular, cardiac or nervous disorders. Based on magnesium’s many functions within the human body, it plays an important role in prevention and treatment of many diseases. Low levels of magnesium have been associated with a number of chronic diseases, such as Alzheimer’s disease, insulin resistance and type-2 diabetes mellitus, hypertension, cardiovascular disease (e.g., stroke), migraine headaches, and attention deficit hyperactivity disorder (ADHD). PMID:26404370

  20. Combustion and extinction of magnesium fires

    International Nuclear Information System (INIS)

    Malet, J.C.; Duverger de Cuy, G.

    1988-01-01

    The studies made in France on magnesium combustion and extinguishing means are associated at the nuclear fuel of the graphite-gas reactor. Safety studies are made for ameliorate our knowledge on: - magnesium combustion - magnesium fire propagation - magnesium fire extinguishing [fr

  1. 21 CFR 184.1443 - Magnesium sulfate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium sulfate. 184.1443 Section 184.1443 Food... Specific Substances Affirmed as GRAS § 184.1443 Magnesium sulfate. (a) Magnesium sulfate (MgSO4·7H2O, CAS... magnesium oxide, hydroxide, or carbonate with sulfuric acid and evaporating the solution to crystallization...

  2. Mineral resource of the month: magnesium

    Science.gov (United States)

    Kramer, Deborah A.

    2012-01-01

    Magnesium is the eighthmost abundant element in Earth’s crust, and the second-most abundant metal ion in seawater. Although magnesium is found in more than 60 minerals, only brucite, dolomite, magnesite and carnallite are commercially important for their magnesium content. Magnesium and its compounds also are recovered from seawater, brines found in lakes and wells, and bitterns (salts).

  3. 21 CFR 184.1431 - Magnesium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium oxide. 184.1431 Section 184.1431 Food and... Substances Affirmed as GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No. 1309-48-4... powder (light) or a relatively dense white powder (heavy) by heating magnesium hydroxide or carbonate...

  4. 21 CFR 184.1426 - Magnesium chloride.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium chloride. 184.1426 Section 184.1426 Food... Specific Substances Affirmed as GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS... hydrochloric acid solution and crystallizing out magnesium chloride hexahydrate. (b) The ingredient meets the...

  5. Magnesium deficiency: What is our status

    Science.gov (United States)

    Low magnesium intake has been implicated in a broad range of cardiometabolic conditions, including diabetes, hypertension, and cardiovascular disease. Dietary magnesium and total body magnesium status have a widely-used but imperfect biomarker in serum magnesium. Despite serum magnesium’s limitation...

  6. Importance of Fuel Cell Tests for Stability Assessment—Suitability of Titanium Diboride as an Alternative Support Material

    Directory of Open Access Journals (Sweden)

    Christina Roth

    2014-06-01

    Full Text Available Carbon corrosion is a severe issue limiting the long-term stability of carbon-supported catalysts, in particular in the highly dynamic conditions of automotive applications. (Doped oxides have been discussed as suitable alternatives to replace carbon, but often suffer from poor electron conductivity. That is why non-oxide ceramics, such as tungsten carbide and titanium nitride, have been discussed recently. Titanium diboride has also been proposed, due to its promising activity and stability in an aqueous electrochemical cell. In this work, Pt nanoparticles were deposited onto μm-sized TiB2 particles with improved grain size, manufactured into porous gas diffusion electrodes and tested in a realistic polymer electrolyte membrane (PEM fuel cell environment. In contrast to the model studies in an aqueous electrochemical cell, in the presence of oxygen and high potentials at the cathode side of a real fuel cell, TiB2 becomes rapidly oxidized as indicated by intensely colored regions in the membrane-electrode assembly (MEA. Moreover, already the electrode manufacturing process led to the formation of titanium oxides, as shown by X-ray diffraction measurements. This demonstrates that Cyclic Voltammetry (CV measurements in an aqueous electrochemical cell are not sufficient to prove stability of novel materials for fuel cell applications.

  7. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  8. Magnesium Repair by Cold Spray

    National Research Council Canada - National Science Library

    Champagne, V. K; Leyman, P.F; Helfritch, D. J

    2008-01-01

    .... Army Research Laboratory has developed a cold spray process to reclaim magnesium components that shows significant improvement over existing methods and is in the process of qualification for use on rotorcraft...

  9. Magnesium - distribution and basic metabolism

    African Journals Online (AJOL)

    losses of water, sodium, chloride and potassium are concerned. However, it has ... (calcium and magnesium carbonate), although only 10% of the element in soil is ... DNA transcription, RNA aggregation, protein synthesis and various cell ...

  10. Effect of magnesium deficiency on renal magnesium and calcium transport in the rat.

    OpenAIRE

    Carney, S L; Wong, N L; Quamme, G A; Dirks, J H

    1980-01-01

    Recollection of micropuncture experiments were performed on acutely thyroparathyroidectomized rats rendered magnesium deficient by dietary deprivation. Urinary magnesium excretion fell from a control of 15 to 3% of the filtered load after magnesium restriction. The loop of Henle, presumably the thick ascending limb, was the major modulator for renal magnesium homeostasis. The transport capacity for magnesium, however, was less in deficient rats than control animals. Absolute magnesium reabsor...

  11. Timeline (Bioavailability) of Magnesium Compounds in Hours: Which Magnesium Compound Works Best?

    Science.gov (United States)

    Uysal, Nazan; Kizildag, Servet; Yuce, Zeynep; Guvendi, Guven; Kandis, Sevim; Koc, Basar; Karakilic, Aslı; Camsari, Ulas M; Ates, Mehmet

    2018-04-21

    Magnesium is an element of great importance functioning because of its association with many cellular physiological functions. The magnesium content of foods is gradually decreasing due to food processing, and magnesium supplementation for healthy living has become increasingly popular. However, data is very limited on the bioavailability of various magnesium preparations. The aim of this study is to investigate the bioavailability of five different magnesium compounds (magnesium sulfate, magnesium oxide, magnesium acetyl taurate, magnesium citrate, and magnesium malate) in different tissues. Following a single dose 400 mg/70 kg magnesium administration to Sprague Dawley rats, bioavailability was evaluated by examining time-dependent absorption, tissue penetration, and the effects on the behavior of the animals. Pharmacokinetically, the area under the curve calculation is highest in the magnesium malate. The magnesium acetyl taurate was found to have the second highest area under the curve calculation. Magnesium acetyl taurate was rapidly absorbed, able to pass through to the brain easily, had the highest tissue concentration level in the brain, and was found to be associated with decreased anxiety indicators. Magnesium malate levels remained high for an extended period of time in the serum. The commonly prescribed dietary supplements magnesium oxide and magnesium citrate had the lowest bioavailability when compared to our control group. More research is needed to investigate the bioavailability of magnesium malate and acetyl taurate compounds and their effects in specific tissues and on behavior.

  12. Formation of titanium diboride coatings during the anodic polarization of titanium in a chloride melt with a low boron oxide content

    Science.gov (United States)

    Elshina, L. A.; Malkov, V. B.; Molchanova, N. G.

    2015-02-01

    The corrosion-electrochemical behavior of titanium in a molten eutectic mixture of cesium and sodium chlorides containing up to 1 wt % boron oxide is studied in the temperature range 810-870 K in an argon atmosphere. The potential, the current, and the rate of titanium corrosion are determined. The optimum conditions of forming a dense continuous titanium diboride coating on titanium with high adhesion to the metallic base are found for the anodic activation of titanium in the molten electrolyte under study.

  13. SHMUTZ & PROTON-DIAMANT H + Irradiated/Written-Hyper/Super-conductivity(HC/SC) Precognizance/Early Experiments Connections: Wet-Graphite Room-Tc & Actualized MgB2 High-Tc: Connection to Mechanical Bulk-Moduli/Hardness: Diamond Hydrocarbon-Filaments, Disorder, Nano-Powders:C,Bi,TiB2,TiC

    Science.gov (United States)

    Wunderman, Irwin; Siegel, Edward Carl-Ludwig; Lewis, Thomas; Young, Frederic; Smith, Adolph; Dresschhoff-Zeller, Gieselle

    2013-03-01

    SHMUTZ: ``wet-graphite''Scheike-....[Adv.Mtls.(7/16/12)]hyper/super-SCHMUTZ-conductor(S!!!) = ``wet''(?)-``graphite''(?) = ``graphene''(?) = water(?) = hydrogen(?) =ultra-heavy proton-bands(???) = ...(???) claimed room/high-Tc/high-Jc superconductOR ``p''-``wave''/ BAND(!!!) superconductIVITY and actualized/ instantiated MgB2 high-Tc superconductors and their BCS- superconductivity: Tc Siegel[ICMAO(77);JMMM 7,190(78)] connection to SiegelJ.Nonxline-Sol.40,453(80)] disorder/amorphous-superconductivity in nano-powders mechanical bulk/shear(?)-moduli/hardness: proton-irradiated diamond, powders TiB2, TiC,{Siegel[Semis. & Insuls.5:39,47, 62 (79)])-...``VS''/concommitance with Siegel[Phys.Stat.Sol.(a)11,45(72)]-Dempsey [Phil.Mag. 8,86,285(63)]-Overhauser-(Little!!!)-Seitz-Smith-Zeller-Dreschoff-Antonoff-Young-...proton-``irradiated''/ implanted/ thermalized-in-(optimal: BOTH heat-capacity/heat-sink & insulator/maximal dielectric-constant) diamond: ``VS'' ``hambergite-borate-mineral transformable to Overhauser optimal-high-Tc-LiBD2 in Overhauser-(NW-periodic-table)-Land: CO2/CH4-ETERNAL-sequestration by-product: WATER!!!: physics lessons from

  14. First experiment on liquid hydrogen transportation by ship inside Osaka bay

    Science.gov (United States)

    Maekawa, K.; Takeda, M.; Hamaura, T.; Suzuki, K.; Miyake, Y.; Matsuno, Y.; Fujikawa, S.; Kumakura, H.

    2017-12-01

    A project to import a large amount of liquid hydrogen (LH2) from Australia by a cargo carrier, which is equipped with two 1250 m3 tanks, is underway in Japan. It is important to understand sloshing and boil-off characteristics inside the LH2 tank during marine transportation. However, the LH2 sloshing and boil-off characteristics on the sea have not yet been clarified. First experiment on the LH2 transportation of 20 liter with magnesium diboride (MgB2) level sensors by the training ship “Fukae-maru”, which has 50 m long and 449 ton gross weight, was carried out successfully inside Osaka bay on February 2, 2017. In the experiment, synchronous measurements of liquid level, temperature, pressure, ship motions, and accelerations as well as the rapid depressurization test were done. The increase rate of the temperature and the pressure inside the LH2 tank were discussed under the rolling and the pitching conditions.

  15. 21 CFR 862.1495 - Magnesium test system.

    Science.gov (United States)

    2010-04-01

    ... magnesium levels in serum and plasma. Magnesium measurements are used in the diagnosis and treatment of hypomagnesemia (abnormally low plasma levels of magnesium) and hypermagnesemia (abnormally high plasma levels of magnesium). (b) Classification. Class I. ...

  16. Structural and mechanical properties of titanium and titanium diboride monolayers and Ti/TiB2 multilayers

    International Nuclear Information System (INIS)

    Chu, K.; Lu, Y.H.; Shen, Y.G.

    2008-01-01

    Nano-multilayers represent a new class of engineering materials that are made up of alternating nanometer scale layers of two different components. In the present work a titanium (Ti) monolayer was combined with titanium diboride (TiB 2 ) to form a Ti/TiB 2 nano-multilayer. Designed experimental parameters enabled an evaluation of the effects of direct current bias voltage (U b ) and bilayer thickness (Λ) during multilayer deposition on the mechanical properties of reactively sputtered Ti/TiB 2 multilayer films. Their nanostructures and mechanical properties were characterized and analyzed using X-ray photoelectron spectroscopy (XPS), low-angle and high-angle X-ray diffraction (XRD), plan-view and cross-sectional high-resolution transmission electron microscopy (HRTEM), and microindentation measurements. Under the optimal bias voltage of U b = - 60 V, it was found that Λ (varied from 1.1 to 9.8 nm) was the most important factor which dominated the nanostructure and hardness. The hardness values obtained varied from 12 GPa for Ti and 15 GPa for TiB 2 monolayers, up to 33 GPa for the hardest Ti/TiB 2 multilayer at Λ = 1.9 nm. The observed hardness enhancement correlated to the layer thickness, followed a relation similar to the Hall-Petch strengthening dependence, with a generalized power of ∼ 0.6. In addition, the structural barriers between two materials (hcp Ti/amorphous TiB 2 ) and stress relaxation at interfaces within multilayer films resulted in a reduction of crack propagation and high-hardness

  17. Myth or Reality-Transdermal Magnesium?

    Science.gov (United States)

    Gröber, Uwe; Werner, Tanja; Vormann, Jürgen; Kisters, Klaus

    2017-07-28

    In the following review, we evaluated the current literature and evidence-based data on transdermal magnesium application and show that the propagation of transdermal magnesium is scientifically unsupported. The importance of magnesium and the positive effects of magnesium supplementation are extensively documented in magnesium deficiency, e.g., cardiovascular disease and diabetes mellitus. The effectiveness of oral magnesium supplementation for the treatment of magnesium deficiency has been studied in detail. However, the proven and well-documented oral magnesium supplementation has become questioned in the recent years through intensive marketing for its transdermal application (e.g., magnesium-containing sprays, magnesium flakes, and magnesium salt baths). In both, specialist and lay press as well as on the internet, there are increasing numbers of articles claiming the effectiveness and superiority of transdermal magnesium over an oral application. It is claimed that the transdermal absorption of magnesium in comparison to oral application is more effective due to better absorption and fewer side effects as it bypasses the gastrointestinal tract.

  18. Effect of oxygen on the hydrogenation properties of magnesium films

    DEFF Research Database (Denmark)

    Ostenfeld, Christopher Worsøe; Chorkendorff, Ib

    2006-01-01

    The effect of magnesium oxide on the magnesium and hydrogen desorption properties of magnesium films have been investigated. We find that by capping metallic magnesium films with oxide overlayers the apparent desorption energy of magnesium is increased from 146 kJ/mol to 314 kJ/mol. The results...... are discussed in light of previous investigations of ball-milled magnesium powders....

  19. Alkoxide-based magnesium electrolyte compositions for magnesium batteries

    Science.gov (United States)

    Dai, Sheng; Sun, Xiao-Guang; Liao, Chen; Guo, Bingkun

    2018-01-30

    Alkoxide magnesium halide compounds having the formula: RO--Mg--X (1) wherein R is a saturated or unsaturated hydrocarbon group that is unsubstituted, or alternatively, substituted with one or more heteroatom linkers and/or one or more heteroatom-containing groups comprising at least one heteroatom selected from fluorine, nitrogen, oxygen, sulfur, and silicon; and X is a halide atom. Also described are electrolyte compositions containing a compound of Formula (1) in a suitable polar aprotic or ionic solvent, as well as magnesium batteries in which such electrolytes are incorporated.

  20. System and process for production of magnesium metal and magnesium hydride from magnesium-containing salts and brines

    Science.gov (United States)

    McGrail, Peter B.; Nune, Satish K.; Motkuri, Radha K.; Glezakou, Vassiliki-Alexandra; Koech, Phillip K.; Adint, Tyler T.; Fifield, Leonard S.; Fernandez, Carlos A.; Liu, Jian

    2016-11-22

    A system and process are disclosed for production of consolidated magnesium metal products and alloys with selected densities from magnesium-containing salts and feedstocks. The system and process employ a dialkyl magnesium compound that decomposes to produce the Mg metal product. Energy requirements and production costs are lower than for conventional processing.

  1. Bond deformation paths and electronic instabilities of ultraincompressible transition metal diborides: Case study of OsB2 and IrB2

    Science.gov (United States)

    Zhang, R. F.; Legut, D.; Wen, X. D.; Veprek, S.; Rajan, K.; Lookman, T.; Mao, H. K.; Zhao, Y. S.

    2014-09-01

    The energetically most stable orthorhombic structure of OsB2 and IrB2 is dynamically stable for OsB2 but unstable for IrB2. Both diborides have substantially lower shear strength in their easy slip systems than their metal counterparts. This is attributed to an easy sliding facilitated by out-of-plane weakening of metallic Os-Os bonds in OsB2 and by an in-plane bond splitting instability in IrB2. A much higher shear resistance of Os-B and B-B bonds than Os-Os ones is found, suggesting that the strengthened Os-B and B-B bonds are responsible for hardness enhancement in OsB2. In contrast, an in-plane electronic instability in IrB2 limits its strength. The electronic structure of deformed diborides suggests that the electronic instabilities of 5d orbitals are their origin of different bond deformation paths. Neither IrB2 nor OsB2 can be intrinsically superhard.

  2. Magnesium sulphate for fetal neuroprotection

    DEFF Research Database (Denmark)

    Bickford, Celeste D; Magee, Laura A; Mitton, Craig

    2013-01-01

    of cerebral palsy (CP) averted and quality-adjusted life years (QALYs). RESULTS: From a health system and a societal perspective, respectively, a savings of $2,242 and $112,602 is obtained for each QALY gained and a savings of $30,942 and $1,554,198 is obtained for each case of CP averted when magnesium......BACKGROUND: The aim of this study was to assess the cost-effectiveness of administering magnesium sulphate to patients in whom preterm birth at ... sensitivity analyses were used to compare the administration of magnesium sulphate with the alternative of no treatment. Two separate cost perspectives were utilized in this series of analyses: a health system and a societal perspective. In addition, two separate measures of effectiveness were utilized: cases...

  3. Telomere Homeostasis: Interplay with Magnesium

    Directory of Open Access Journals (Sweden)

    Donogh Maguire

    2018-01-01

    Full Text Available Telomere biology, a key component of the hallmarks of ageing, offers insight into dysregulation of normative ageing processes that accompany age-related diseases such as cancer. Telomere homeostasis is tightly linked to cellular metabolism, and in particular with mitochondrial physiology, which is also diminished during cellular senescence and normative physiological ageing. Inherent in the biochemistry of these processes is the role of magnesium, one of the main cellular ions and an essential cofactor in all reactions that use ATP. Magnesium plays an important role in many of the processes involved in regulating telomere structure, integrity and function. This review explores the mechanisms that maintain telomere structure and function, their influence on circadian rhythms and their impact on health and age-related disease. The pervasive role of magnesium in telomere homeostasis is also highlighted.

  4. Magnesium and related low alloys

    International Nuclear Information System (INIS)

    Bernard, J.; Caillat, R.; Darras, R.

    1959-01-01

    In the first part the authors examine the comparative corrosion of commercial magnesium, of a magnesium-zirconium alloy (0,4 per cent ≤ Zr ≤ 0,7 per cent) of a ternary magnesium-zinc-zirconium alloy (0,8 per cent ≤ Zn ≤ 1,2 per cent) and of english 'Magnox type' alloys, in dry carbon dioxide-free air, in damp carbon dioxide-free air, and in dry and damp carbon dioxide, at temperatures from 300 to 600 deg. C. In the second part the structural stability of these materials is studied after annealings, of 10 to 1000 hours at 300 to 450 deg. C. Variations in grain after these heat treatments and mechanical stretching properties at room temperature are presented. Finally various creep rate and life time diagrams are given for these materials, for temperatures ranging from 300 to 450 deg. C. (author) [fr

  5. Magnesium and related low alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bernard, J; Caillat, R; Darras, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In the first part the authors examine the comparative corrosion of commercial magnesium, of a magnesium-zirconium alloy (0,4 per cent {<=} Zr {<=} 0,7 per cent) of a ternary magnesium-zinc-zirconium alloy (0,8 per cent {<=} Zn {<=} 1,2 per cent) and of english 'Magnox type' alloys, in dry carbon dioxide-free air, in damp carbon dioxide-free air, and in dry and damp carbon dioxide, at temperatures from 300 to 600 deg. C. In the second part the structural stability of these materials is studied after annealings, of 10 to 1000 hours at 300 to 450 deg. C. Variations in grain after these heat treatments and mechanical stretching properties at room temperature are presented. Finally various creep rate and life time diagrams are given for these materials, for temperatures ranging from 300 to 450 deg. C. (author) [French] Dans une premiere partie les auteurs etudient la corrosion comparee du magnesium commercial, d'un alliage magnesium-zirconium (0,4 pour cent {<=} Zr {<=} 0,7 pour cent), d'un alliage ternaire magnesium-zinc-zirconium (0,8 pour cent {<=} Zn {<=} 1,2 pour cent), et d'alliages anglais 'type Magnox', dans l'air sec decarbonate, l'air humide decarbonate, le gaz carbonique sec et humide a des temperatures de 300 a 600 deg. C. Dans une seconde partie, est etudiee la stabilite structurale de ces materiaux apres des recuits de 300 a 450 deg. C, et de 10 a 1000 heures. Sont presentees les variations, apres ces traitements thermiques, de la grosseur du grain, et des caracteristiques mecaniques de traction a la temperature ambiante. Enfin, quelques diagrammes de vitesse de fluage et de durees de vie sont presentes sur ces materiaux pour des temperatures variant entre 300 et 450 deg. C. (auteur)

  6. 21 CFR 582.5431 - Magnesium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium oxide. 582.5431 Section 582.5431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

  7. 21 CFR 582.1431 - Magnesium oxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

  8. EFFECT OF MAGNESIUM SULFATE (A LAXATIVE) ON ...

    African Journals Online (AJOL)

    use with little success . Magnesium sulfate also known as Epsom salt or bitter salt is a hydrate salt with a chemical name of magnesium sulfate heptahydrate . Chemical formula is MgSO. 7HO and trade name is. Andrews liver salt. Dried magnesium sulfate is an osmotic laxative or a saline laxative that acts by increasing the.

  9. 21 CFR 582.5443 - Magnesium sulfate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium sulfate. 582.5443 Section 582.5443 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5443 Magnesium sulfate. (a) Product. Magnesium sulfate. (b) Conditions of use. This...

  10. Research Progress in Plasma arc welding of Magnesium Alloys and Magnesium Matrix Composites

    Science.gov (United States)

    Hui, Li; Yang, Zou; Yongbo, Li; Lei, Jiao; Ruijun, Hou

    2017-11-01

    Magnesium alloys and magnesium matrix composites by means of its excellent performance have wide application prospect in electronics, automotive, biotechnology, aerospace field, and welding technology has become a key of restricting its application. This paper describes the welding characteristics of magnesium, the obvious advantages in the application and the domestic and foreign research advance technology of plasma arc welding of magnesium, and summarizes the existing problems and development trends of plasma arc welding technology of magnesium.

  11. On the effect of interaction of molybdenum trioxide and magnesium oxide in water

    International Nuclear Information System (INIS)

    Bunin, V.M.; Karelin, A.I.; Solov'eva, L.N.

    1992-01-01

    Interaction of molybdenum trioxide and magnesium oxide in water was studied. It is shown that molybdenum trioxide forms consecutively magnesium molybdate, dimolybdate and magnesium polymolybdates with magnesium oxide

  12. A SEARCH FOR MAGNESIUM IN EUROPA'S ATMOSPHERE

    International Nuclear Information System (INIS)

    Hörst, S. M.; Brown, M. E.

    2013-01-01

    Europa's tenuous atmosphere results from sputtering of the surface. The trace element composition of its atmosphere is therefore related to the composition of Europa's surface. Magnesium salts are often invoked to explain Galileo Near Infrared Mapping Spectrometer spectra of Europa's surface, thus magnesium may be present in Europa's atmosphere. We have searched for magnesium emission in the Hubble Space Telescope Faint Object Spectrograph archival spectra of Europa's atmosphere. Magnesium was not detected and we calculate an upper limit on the magnesium column abundance. This upper limit indicates that either Europa's surface is depleted in magnesium relative to sodium and potassium, or magnesium is not sputtered as efficiently resulting in a relative depletion in its atmosphere.

  13. Anticorrosive magnesium hydroxide coating on AZ31 magnesium alloy by hydrothermal method

    International Nuclear Information System (INIS)

    Zhu Yanying; Wu Guangming; Xing Guangjian; Li Donglin; Zhao Qing; Zhang Yunhong

    2009-01-01

    Magnesium alloys are potential biodegradable biomaterials in orthopedic surgery. However, the rapid degradation rate has limited their application in biomedical field. A great deal of studies have been done to improve the resistance of magnesium alloys. In this article, An anticorrosive magnesium hydroxide coating with a thickness of approximately 100μm was formed on an AZ31 magnesium alloy by hydrothermal method. The morphology of the coatings were observed by an optical microscope and SEM. And the samples were soaked in hank's solution (37 deg. C) to investigate the corrosion resistance. Magnesium alloy AZ31 with magnesium hydroxide coatings present superior corrosion resistance than untreated samples.

  14. Magnesium-based implants: a mini-review.

    Science.gov (United States)

    Luthringer, Bérengère J C; Feyerabend, Frank; Willumeit-Römer, Regine

    2014-01-01

    The goal of this review is to bring to the attention of the readership of Magnesium Research another facet of the importance of magnesium, i.e. magnesium-based biomaterials. A concise history of biomaterials and magnesium are thus presented. In addition, historical and current, clinical magnesium-based applications are presented.

  15. Energy Deposition and DPA in the Superconducting Links for the HILUMI LHC Project at the LHC Interaction Points

    CERN Document Server

    AUTHOR|(CDS)2092158; Broggi, Francesco; Santini, C; Ballarino, Amalia; Cerutti, Francesco; Esposito, Luigi Salvatore

    2015-01-01

    In the framework of the upgrade of the LHC machine, the powering of the LHC magnets foresees the removal of the power converters and distribution feedboxes from the tunnel and its location at the surface[1]. The Magnesium Diboride (MgB2) connecting lines in the tunnel will be exposed to the debris from 7+7 TeV p-p interaction. The Superconducting (SC) Links will arrive from the surface to the tunnel near the separation dipole, at about 80 m from the Interaction Point at IP1 and IP5. The Connection Box (where the cables of the SC Links are connected to the NbTi bus bar) will be close to the beam pipe. The debris and its effect on the MgB2 SC links in the connection box (energy deposition and displacement per atom) are presented. The effect of thermal neutrons on the Boron consumption and the contribution of the lithium nucleus and the alpha particle on the DPA are evaluated. The results are normalized to an integrated luminosity of 3000 fb-1, value that represents the LHC High Luminosity lifetime. The dose de...

  16. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  17. Unconventional conventional superconductivity in MgB2

    Science.gov (United States)

    Mazin, Igor

    2002-03-01

    State-of-the-art numerical estimates of the electron-phonon coupling (EPC) constant are of the order of 0.8, which is just a little too low for Tc=39 K. Furthermore, there are indication that this conventional picture faces some problems: (a) specific heat suggests EPC even smaller that the calculatons (b) there is evidence of a gap smaller than 3.5 Tc, and of more than one gap (c) Low-temperature thermodynamics disagrees with the simple BCS picture. There are also theoretical indications of interesting deviations from the standard Eliashberg theory: (1) most of the coupling comes from interaction of just two phonons with two (out of four) bands. (2) The phonons in question are strongly anharmonic (3) Very unusually, nonlinear coupling of these phonons with electrons (i.e., two-phonon exchange) is stronger that the linear coupling. (4) Calculations predict two considerably different order parameters for the two sets of bands. This multigap scenario explains naturally a number of puzzling experiments, but seems to be at odds with the lack of any correlation between the residual resistivity and Tc. One can reconcile these, though, if the defect scattering occurs primarily in the intraband channels. This is supported by chemical arguments and by recent optical experiments. Furthermore, the hypothesis of two qualitatively different scattering rates for the two types of bands is consistent with a number of otherwise hard to explain transport measurements.

  18. Electronic structure and superconductivity of MgB2

    Indian Academy of Sciences (India)

    Unknown

    High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. Abstract. Results ... compared to the experimentally determined values of these quantities. ... that spectroscopies which probe the superconducting gap.

  19. Lightweight Heat Pipes Made from Magnesium

    Science.gov (United States)

    Rosenfeld, John N.; Zarembo, Sergei N.; Eastman, G. Yale

    2010-01-01

    Magnesium has shown promise as a lighter-weight alternative to the aluminum alloys now used to make the main structural components of axially grooved heat pipes that contain ammonia as the working fluid. Magnesium heat-pipe structures can be fabricated by conventional processes that include extrusion, machining, welding, and bending. The thermal performances of magnesium heat pipes are the same as those of equal-sized aluminum heat pipes. However, by virtue of the lower mass density of magnesium, the magnesium heat pipes weigh 35 percent less. Conceived for use aboard spacecraft, magnesium heat pipes could also be attractive as heat-transfer devices in terrestrial applications in which minimization of weight is sought: examples include radio-communication equipment and laptop computers.

  20. Low Temperature Synthesis of Magnesium Aluminate Spinel

    International Nuclear Information System (INIS)

    Lebedovskaya, E.G.; Gabelkov, S.V.; Litvinenko, L.M.; Logvinkov, D.S.; Mironova, A.G.; Odejchuk, M.A.; Poltavtsev, N.S.; Tarasov, R.V.

    2006-01-01

    The low-temperature synthesis of magnesium-aluminum spinel is carried out by a method of thermal decomposition in combined precipitated hydrates. The fine material of magnesium-aluminium spinel with average size of coherent dispersion's area 4...5 nanometers is obtained. Magnesium-aluminum spinel and initial hydrates were investigated by methods of the differential thermal analysis, the x-ray phase analysis and measurements of weight loss during the dehydration and thermal decomposition. It is established that synthesis of magnesium-aluminum spinel occurs at temperature 300 degree C by method of the x-ray phase analysis

  1. Exoelectron emission from magnesium borate glass ceramics

    International Nuclear Information System (INIS)

    Kawamoto, Takamichi; Yanagisawa, Hideo; Nakamichi, Hiroshi; Kikuchi, Riichi; Kawanishi, Masaharu.

    1986-01-01

    Thermally stimulated exoelectron emission (TSEE) of a magnesium borate glass ceramics was investigated for its application to dosemetric use. It has been found that the TSEE glow patterns of the magnesium borate glass ceramics as well as a Li 2 B 4 O 7 glass ceramics depend on the kind of the radiation used and that the heat resistance of the magnesium borate glass ceramics is higher than that of the Li 2 B 4 O 7 glass ceramics. Therefore, the TSEE glow patterns of the magnesium borate glass ceramics indicate a possibility to be used as the dose measurement for each kind of radiation in the mixed radiation field. (author)

  2. Wide Strip Casting Technology of Magnesium Alloys

    Science.gov (United States)

    Park, W.-J.; Kim, J. J.; Kim, I. J.; Choo, D.

    Extensive investigations relating to the production of high performance and low cost magnesium sheet by strip casting have been performed for the application to automotive parts and electronic devices. Research on magnesium sheet production technology started in 2004 by Research Institute of Industrial Science and Technology (RIST) with support of Pohang Iron and Steel Company (POSCO). POSCO has completed the world's first plant to manufacture magnesium coil. Another big project in order to develop wide strip casting technology for the automotive applications of magnesium sheets was started in succession.

  3. Synthesis of Nano-Light Magnesium Hydride for Hydrogen Storage ...

    African Journals Online (AJOL)

    Abstract. Nano-light magnesium hydride that has the capability for hydrogen storage was synthesized from treatment of magnesium ribbon with hydrogen peroxide. The optimum time for complete hydrogenation of the magnesium hydride was 5 hours.

  4. Titanium Diboride Electrodeposited Coatings

    Science.gov (United States)

    1977-06-01

    4 Ti02. This material was deposited in the form of a porous mass or loose particles which must be leached in water and acid to remove adherent...poudres metallique par electrolyse ignee. Revue de Metallurgie, v. 45, 1948, p. 49-59. 7. POWELL, C. F. Borides in High Temperature Materials and... water solution of thallium formate-thallium malonate 50-50 mole percent mixture with a density ranging from about 5 g/cm^ at the bottom to about 2 g/cm

  5. In vitro studies on magnesium uptake by rumen epithelium using magnesium-28

    International Nuclear Information System (INIS)

    Martens, H.; Harmeyer, J.; Breves, G.

    1976-01-01

    Magnesium-28 transfer across the rumen epithelium has been studied using surviving epithelia in an in vitro system. Net absorption of magnesium in the direction from lumen to blood could be observed as the result of two opposite unidirectional fluxes of different magnitude. Net uptake of magnesium occurred against an electrical potential difference, and was associated with the presence of an unaltered transmural potential difference in the mucosal tissue. Both the net transfer of magnesium and the transmural potential difference decreased during two hours of incubation. Unidirectional fluxes of magnesium and net efflux from the lumen were markedly reduced although not completely inhibited by the addition of ouabain (10 -4 mol/l). The findings suggest that the mechanism of magnesium absorption by the rumen epithelium can be considered as an active transport process, and that the rumen is the main area of magnesium absorption in the living animal. (author)

  6. Magnesium stannide as a high-capacity anode for magnesium-ion batteries

    Science.gov (United States)

    Nguyen, Dan-Thien; Song, Seung-Wan

    2017-11-01

    Driven by the limited global resources of lithium, magnesium metal batteries are considered as potential energy storage systems. The battery chemistry of magnesium metal anode, however, limits the selection of electrolytes, cathode materials and working temperature, making the realization of magnesium metal batteries complicated. Herein, we report the development of a new magnesium-insertion anode, magnesium stannide (Mg2Sn), and demonstrate reversible electrochemical Mg2+-extraction and insertion of Mg2Sn anode at 0.2 V versus Mg, delivering discharge capacity of 270 mAhg-1 in a half-cell with the electrolyte of PhMgCl/THF and enabling of room temperature magnesium-ion batteries with Mg2Sn anode combined with Mg-free oxide cathode and conventional-type electrolyte of Mg(TFSI)2/diglyme. The combination of Mg2Sn anode with various cathodes and electrolytes holds great promise for enabling room temperature magnesium-ion batteries.

  7. Magnesium growth in magnesium deuteride thin films during deuterium desorption

    Energy Technology Data Exchange (ETDEWEB)

    Checchetto, R., E-mail: riccardo.checchetto@unitn.it [Dipartimento di Fisica and CNISM, Università di Trento, Via Sommarive 14, I-38123 Trento (Italy); Miotello, A. [Dipartimento di Fisica and CNISM, Università di Trento, Via Sommarive 14, I-38123 Trento (Italy); Mengucci, P.; Barucca, G. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Università Politecnica delle Marche, I-60131 Ancona (Italy)

    2013-12-15

    Highlights: ► Highly oriented Pd-capped magnesium deuteride thin films. ► The MgD{sub 2} dissociation was studied at temperatures not exceeding 100 °C. ► The structure of the film samples was analyzed by XRD and TEM. ► The transformation is controlled by the re-growth velocity of the Mg layers. ► The transformation is thermally activated, activation energy value of 1.3 ± 0.1 eV. -- Abstract: Pd- capped nanocrystalline magnesium thin films having columnar structure were deposited on Si substrate by e-gun deposition and submitted to thermal annealing in D{sub 2} atmosphere to promote the metal to deuteride phase transformation. The kinetics of the reverse deuteride to metal transformation was studied by Thermal Desorption Spectroscopy (TDS) while the structure of the as deposited and transformed samples was analyzed by X-rays diffraction and Transmission Electron Microscopy (TEM). In Pd- capped MgD{sub 2} thin films the deuteride to metal transformation begins at the interface between un-reacted Mg and transformed MgD{sub 2} layers. The D{sub 2} desorption kinetics is controlled by MgD{sub 2}/Mg interface effects, specifically the re-growth velocity of the Mg layers. The Mg re-growth has thermally activated character and shows an activation energy value of 1.3 ± 0.1 eV.

  8. Magnesium Hydride for Load Levelling Energy Storage

    DEFF Research Database (Denmark)

    Vigeholm, B.

    Some of the magnesium properties essential to the applicability of the reaction Mg+H2⇆MgH2 as a hydrogen storage system have been investigated. Three magnesium powders with particle size smaller than 50 μm average diameter were cycled, over 31, 71 and 151 cycles respectively, at 675K (400°C...

  9. Nanostructured magnesium increases bone cell density.

    Science.gov (United States)

    Weng, Lucy; Webster, Thomas J

    2012-12-07

    Magnesium has attracted some attention in orthopedics due to its biodegradability and mechanical properties. Since magnesium is an essential natural mineral for bone growth, it can be expected that as a biomaterial, it would support bone formation. However, upon degradation in the body, magnesium releases OH(-) which results in an alkaline pH that can be detrimental to cell density (for example, osteoblasts or bone forming cells). For this reason, modification of magnesium may be necessary to compensate for such detrimental effects to cells. This study created biologically inspired nanoscale surface features on magnesium by soaking magnesium in various concentrations of NaOH (from 1 to 10 N) and for various periods of time (from 10 to 30 min). The results provided the first evidence of increased roughness, surface energy, and consequently greater osteoblast adhesion, after 4 h as well as density up to 7 days on magnesium treated with any concentration of NaOH for any length of time compared to untreated controls. For these reasons, this study suggests that soaking magnesium in NaOH could be an inexpensive, simple and effective manner to promote osteoblast functions for numerous orthopedic applications and, thus, should be further studied.

  10. Nanostructured magnesium increases bone cell density

    International Nuclear Information System (INIS)

    Weng, Lucy; Webster, Thomas J

    2012-01-01

    Magnesium has attracted some attention in orthopedics due to its biodegradability and mechanical properties. Since magnesium is an essential natural mineral for bone growth, it can be expected that as a biomaterial, it would support bone formation. However, upon degradation in the body, magnesium releases OH − which results in an alkaline pH that can be detrimental to cell density (for example, osteoblasts or bone forming cells). For this reason, modification of magnesium may be necessary to compensate for such detrimental effects to cells. This study created biologically inspired nanoscale surface features on magnesium by soaking magnesium in various concentrations of NaOH (from 1 to 10 N) and for various periods of time (from 10 to 30 min). The results provided the first evidence of increased roughness, surface energy, and consequently greater osteoblast adhesion, after 4 h as well as density up to 7 days on magnesium treated with any concentration of NaOH for any length of time compared to untreated controls. For these reasons, this study suggests that soaking magnesium in NaOH could be an inexpensive, simple and effective manner to promote osteoblast functions for numerous orthopedic applications and, thus, should be further studied. (paper)

  11. Comparison of Serum Calcium and Magnesium Between ...

    African Journals Online (AJOL)

    Background: Evidence suggests the involvement of calcium and magnesium metabolism in the pathophysiology of preeclampsia. However, findings from studies are heterogenous and inconsistent. Aim: The study aimed to compare the total serum calcium and magnesium levels in preeclamptic women with that of ...

  12. The Role of Magnesium in Neurological Disorders

    Directory of Open Access Journals (Sweden)

    Anna E. Kirkland

    2018-06-01

    Full Text Available Magnesium is well known for its diverse actions within the human body. From a neurological standpoint, magnesium plays an essential role in nerve transmission and neuromuscular conduction. It also functions in a protective role against excessive excitation that can lead to neuronal cell death (excitotoxicity, and has been implicated in multiple neurological disorders. Due to these important functions within the nervous system, magnesium is a mineral of intense interest for the potential prevention and treatment of neurological disorders. Current literature is reviewed for migraine, chronic pain, epilepsy, Alzheimer’s, Parkinson’s, and stroke, as well as the commonly comorbid conditions of anxiety and depression. Previous reviews and meta-analyses are used to set the scene for magnesium research across neurological conditions, while current research is reviewed in greater detail to update the literature and demonstrate the progress (or lack thereof in the field. There is strong data to suggest a role for magnesium in migraine and depression, and emerging data to suggest a protective effect of magnesium for chronic pain, anxiety, and stroke. More research is needed on magnesium as an adjunct treatment in epilepsy, and to further clarify its role in Alzheimer’s and Parkinson’s. Overall, the mechanistic attributes of magnesium in neurological diseases connote the macromineral as a potential target for neurological disease prevention and treatment.

  13. Magnesium - distribution and basic metabolism | Olhaberry | South ...

    African Journals Online (AJOL)

    Magnesium is extensively distributed in soil, water and plants. It is essential for ehzymatic reactions requiring adenosine triphosphate, and the recommended dietary allowance in man is 5 - 10 mg/kg/d. About 50% of magnesium in man is stored in bone, where it is regulated by parathyroid hormone'and 1,25(OH)2-D3.

  14. A Shortened versus Standard Matched Postpartum Magnesium ...

    African Journals Online (AJOL)

    Magnesium sulphate is currently the most ideal drug for the treatment of eclampsia but its use in Nigeria is still limited due its cost and clinicians inexperience with the drug. The purpose of this study was to determine whether a shortened postpartum course of magnesium sulphate is as effective as the standard Pritchard ...

  15. Magnesium analysis. Spectrophotometric determination of chromium

    International Nuclear Information System (INIS)

    Anon.

    Chromium determination in magnesium used in uranium fabrication by magnesiothermics, applicable for chromium content between 2 to 10 ppm. Magnesium is dissolved in sulfuric acid, oxidized by potassium permanganate, the excess of permanganate is eliminated by sodium nitride. Spectrophotometry at 540 nm of the chromium (VI)-diphenylcarbazide complex [fr

  16. Magnesium removal in the electrolytic zinc industry

    NARCIS (Netherlands)

    Booster, J.L.

    2003-01-01

    Electrolytic zinc plants need to take measures to control the magnesium content in their process liquors, because the natural magnesium bleed does not balance the input from concentrates. Presently used methods are environmentally unfriendly (due to the production of large amounts of waste gypsum)

  17. Magnesium supplementation in children with attention deficit ...

    African Journals Online (AJOL)

    Background: Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with associated mineral deficiency. Aim: To assess magnesium level in ADHD children and compare it to the normal levels in children. Then, to detect the effect of magnesium supplementation as an add on therapy, ...

  18. Improved cytotoxicity testing of magnesium materials

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Janine [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Proefrock, Daniel [Helmholtz-Zentrum Geesthacht, Institute for Coastal Research, Department for Marine Bioanalytical Chemistry, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Hort, Norbert [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Magnesium Processing, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Willumeit, Regine; Feyerabend, Frank [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany)

    2011-06-25

    Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

  19. Improved cytotoxicity testing of magnesium materials

    International Nuclear Information System (INIS)

    Fischer, Janine; Proefrock, Daniel; Hort, Norbert; Willumeit, Regine; Feyerabend, Frank

    2011-01-01

    Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

  20. Imparting passivity to vapor deposited magnesium alloys

    Science.gov (United States)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning

  1. Irradiation effects in magnesium and aluminium alloys

    International Nuclear Information System (INIS)

    Sturcken, E.F.

    1979-01-01

    Effects of neutron irradiation on microstructure, mechanical properties and swelling of several magnesium and aluminium alloys were studied. The neutron fluences of 2-3 X 10 22 n/cm 2 , >0.2 MeV produced displacement doses of 20 to 45 displacements per atom (dpa). Ductility of the magnesium alloys was severely reduced by irradiation induced recrystallization and precipitation of various forms. Precipitation of transmuted silicon occurred in the aluminium alloys. However, the effect on ductility was much less than for the magnesium alloys. The magnesium and aluminium alloys had excellent resistance to swelling: The best magnesium alloy was Mg/3.0 wt% Al/0.19 wt% Ca; its density decreased by only 0.13%. The best aluminium alloy was 6063, with a density decrease of 0.22%. (Auth.)

  2. Recrystallization of magnesium deformed at low temperatures

    International Nuclear Information System (INIS)

    Fromageau, R.; Pastol, J.L.; Revel, G.

    1978-01-01

    The recrystallization of magnesium was studied after rolling at temperatures ranging between 248 and 373 K. For zone refined magnesium the annealing behaviour as observed by electrical resistivity measurements showed two stages at about 250 K and 400 K due respectively to recrystallization and grain growth. The activation energy associated with the recrystallization stage was 0.75 +- 0.01 eV. In less pure magnesium, with nominal purity 99.99 and 99.9%, the recrystallization stage was decomposed into two substages. Activation energies were determined in relation with deformation temperature and purity. The magnesium of intermediate purity (99.99%) behaved similarly to the lowest purity metal when it was deformed at high temperature and to the purest magnesium when the deformation was made at low temperature. This behaviour was discussed in connection with the theories of Luecke and Cahn. (Auth.)

  3. Porous bioresorbable magnesium as bone substitute

    Energy Technology Data Exchange (ETDEWEB)

    Wen, C.E.; Yamada, Y.; Shimojima, K.; Chino, Y.; Hosokawa, H.; Mabuchi, M. [Inst. for Structural and Engineering Materials, National Inst. of Advanced Industrial Science and Technology, Nagoya (Japan)

    2003-07-01

    Recently magnesium has been recognized as a very promising biomaterial for bone substitutes because of its excellent properties of biocompatibility, biodegradability and bioresorbability. In the present study, magnesium foams were fabricated by using a powder metallurgical process. Scanning electron microscopy equipped with energy dispersive X-ray spectrometer (EDS) and compressive tester were used to characterize the porous magnesium. Results show that the Young's modulus and the peak stress of the porous magnesium increase with decreasing porosity and pore size. This study suggests that the mechanical properties of the porous magnesium with the low porosity of 35% and/or with the small pore size of about 70 {mu}m are close to those of human cancellous bones. (orig.)

  4. On the ionization of interstellar magnesium

    International Nuclear Information System (INIS)

    Gurzadyan, G.A.

    1977-01-01

    It has been shown that two concentric ionization zones of interstellar magnesium must exist around each star: internal, with a radius coinciding with that of the zone of hydrogen ionization Ssub(H); and external, with a radius greater than Ssub(H), by one order. Unlike interstellar hydrogen, interstellar magnesium is ionized throughout the Galaxy. It also transpires that the ionizing radiation of ordinary hot stars cannot provide for the observed high degree of ionization of interstellar magnesium. The discrepance can be eliminated by assuming the existence of circumstellar clouds or additional ionization sources of interstellar magnesium (X-ray background radiation, high-energy particles, etc.). Stars of the B5 and BO class play the main role in the formation of ionization zones of interstellar magnesium; the contribution of O class stars is negligible (<1%). (Auth.)

  5. Benefits of magnesium wheels for consumer cars

    Science.gov (United States)

    Frishfelds, Vilnis; Timuhins, Andrejs; Bethers, Uldis

    2018-05-01

    Advantages and disadvantages of magnesium wheels are considered based on a mechanical model of a car. Magnesium wheels are usually applied to racing cars as they provide slightly better strength/weight ratio than aluminum alloys. Do they provide notable benefits also for the everyday user when the car speeds do not exceed allowed speed limit? Distinct properties of magnesium rims are discussed. Apart from lighter weight of magnesium alloys, they are also good in dissipating the energy of vibrations. The role of energy dissipation in the rim of a wheel is estimated by a quarter car model. Improvements to safety by using the magnesium wheels are considered. Braking distance and responsiveness of the car is studied both with and without using an Anti Blocking System (ABS). Influence of rim weight on various handling parameters of the car is quantitatively tested.

  6. Magnesium deficiency and increased inflammation: current perspectives

    Directory of Open Access Journals (Sweden)

    Nielsen FH

    2018-01-01

    Full Text Available Forrest H Nielsen Research Nutritionist Consultant, Grand Forks, ND, USA Abstract: Animal studies have shown that magnesium deficiency induces an inflammatory response that results in leukocyte and macrophage activation, release of inflammatory cytokines and acute-phase proteins, and excessive production of free radicals. Animal and in vitro studies indicate that the primary mechanism through which magnesium deficiency has this effect is through increasing cellular Ca2+, which is the signal that results in the priming of cells to give the inflammatory response. Primary pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL-1; the messenger cytokine IL-6; cytokine responders E-selectin, intracellular adhesion molecule-1 and vascular cell adhesion molecule-1; and acute-phase reactants C-reactive protein and fibrinogen have been determined to associate magnesium deficiency with chronic low-grade inflammation (inflammatory stress. When magnesium dietary intake, supplementation, and/or serum concentration suggest/s the presence of magnesium deficiency, it often is associated with low-grade inflammation and/or with pathological conditions for which inflammatory stress is considered a risk factor. When magnesium intake, supplementation, and/or serum concentration suggest/s an adequate status, magnesium generally has not been found to significantly affect markers of chronic low-grade inflammation or chronic disease. The consistency of these findings can be modified by other nutritional and metabolic factors that affect inflammatory and oxidative stress. In spite of this, findings to date provide convincing evidence that magnesium deficiency is a significant contributor to chronic low-grade inflammation that is a risk factor for a variety of pathological conditions such as cardiovascular disease, hypertension, and diabetes. Because magnesium deficiency commonly occurs in countries where foods rich in magnesium are not consumed in

  7. Magnesium sulfate reduces formalin-induced orofacial pain in rats with normal magnesium serum levels.

    Science.gov (United States)

    Srebro, Dragana P; Vučković, Sonja M; Dožić, Ivan S; Dožić, Branko S; Savić Vujović, Katarina R; Milovanović, Aleksandar P; Karadžić, Branislav V; Prostran, Milica Š

    2018-02-01

    In humans, orofacial pain has a high prevalence and is often difficult to treat. Magnesium is an essential element in biological a system which controls the activity of many ion channels, neurotransmitters and enzymes. Magnesium produces an antinociceptive effect in neuropathic pain, while in inflammatory pain results are not consistent. We examined the effects of magnesium sulfate using the rat orofacial formalin test, a model of trigeminal pain. Male Wistar rats were injected with 1.5% formalin into the perinasal area, and the total time spent in pain-related behavior (face rubbing) was quantified. We also spectrophotometrically determined the concentration of magnesium and creatine kinase activity in blood serum. Magnesium sulfate administered subcutaneously (0.005-45mg/kg) produced significant antinociception in the second phase of the orofacial formalin test in rats at physiological serum concentration of magnesium. The effect was not dose-dependent. The maximum antinociceptive effect of magnesium sulfate was about 50% and was achieved at doses of 15 and 45mg/kg. Magnesium did not affect increase the levels of serum creatine kinase activity. Preemptive systemic administration of magnesium sulfate as the only drug can be used to prevent inflammatory pain in the orofacial region. Its analgesic effect is not associated with magnesium deficiency. Copyright © 2017 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  8. Magnesium

    Science.gov (United States)

    ... deficiency can cause numbness, tingling, muscle cramps, seizures , personality changes, and an abnormal heart rhythm . The following ... Office of Dietary Supplements Frequently Asked Questions: Which brand(s) of dietary supplements should I purchase? For information ...

  9. Magnesium bicarbonate as an in situ uranium lixiviant

    International Nuclear Information System (INIS)

    Sibert, J.W.

    1984-01-01

    In the subsurface solution mining of mineral values, especially uranium, in situ, magnesium bicarbonate leaching solution is used instead of sodium, potassium and ammonium carbonate and bicarbonates. The magnesium bicarbonate solution is formed by combining carbon dioxide with magnesium oxide and water. The magnesium bicarbonate lixivant has four major advantages over prior art sodium, potassium and ammonium bicarbonates

  10. Urinary and plasma magnesium and risk of ischemic heart disease

    NARCIS (Netherlands)

    Joosten, Michel M.; Gansevoort, Ron T.; Mukamal, Kenneth J.; van der Harst, Pim; Geleijnse, Johanna M.; Feskens, Edith J. M.; Navis, Gerjan; Bakker, Stephan J. L.

    Background: Previous studies on dietary magnesium and risk of ischemic heart disease (IHD) have yielded inconsistent results, in part because of a lack of direct measures of actual magnesium uptake. Urinary excretion of magnesium, an indicator of dietary magnesium uptake, might provide more

  11. Radioactive {sup 210}Po in magnesium supplements

    Energy Technology Data Exchange (ETDEWEB)

    Struminska-Parulska, Dagmara Ida [Gdansk Univ. (Poland). Environmental Chemistry and Radiochemistry Chair

    2016-08-01

    The aim of this pioneer study was to determine polonium {sup 210}Po in the most popular magnesium supplements in Poland and estimate the possible related dose assessment to the consumers. The analyzed magnesium pharmaceutics contained organic or inorganic magnesium compounds; some from natural sources. The objectives of this research were to investigate the naturally occurring {sup 210}Po activity concentrations in magnesium supplements, find the correlations between {sup 210}Po concentration in medicament and magnesium chemical form, and calculate the effective radiation dose connected to analyzed magnesium supplement consumption. The highest {sup 210}Po activity concentrations were determined in mineral tablets made from sedimentary rocks, namely dolomite - 3.84 ± 0.15 mBq g{sup -1} (sample Mg17). The highest annual radiation dose from {sup 210}Po taken with 1 tablet of magnesium supplement per day or with 400 mg of pure Mg daily would come from sample Mg17 (dolomite) - 1.35 ± 0.5 and 8.44 ± 0.33 μSv year{sup -1} respectively.

  12. Computational micromechanics of bioabsorbable magnesium stents.

    Science.gov (United States)

    Grogan, J A; Leen, S B; McHugh, P E

    2014-06-01

    Magnesium alloys are a promising candidate material for an emerging generation of absorbable metal stents. Due to its hexagonal-close-packed lattice structure and tendency to undergo twinning, the deformation behaviour of magnesium is quite different to that of conventional stent materials, such as stainless steel 316L and cobalt chromium L605. In particular, magnesium exhibits asymmetric plastic behaviour (i.e. different yield behaviours in tension and compression) and has lower ductility than these conventional alloys. In the on-going development of absorbable metal stents it is important to assess how the unique behaviour of magnesium affects device performance. The mechanical behaviour of magnesium stent struts is investigated in this study using computational micromechanics, based on finite element analysis and crystal plasticity theory. The plastic deformation in tension and bending of textured and non-textured magnesium stent struts with different numbers of grains through the strut dimension is investigated. It is predicted that, unlike 316L and L605, the failure risk and load bearing capacity of magnesium stent struts during expansion is not strongly affected by the number of grains across the strut dimensions; however texturing, which may be introduced and controlled in the manufacturing process, is predicted to have a significant influence on these measures of strut performance. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Radioactive 210Po in magnesium supplements

    International Nuclear Information System (INIS)

    Struminska-Parulska, Dagmara Ida

    2016-01-01

    The aim of this pioneer study was to determine polonium 210 Po in the most popular magnesium supplements in Poland and estimate the possible related dose assessment to the consumers. The analyzed magnesium pharmaceutics contained organic or inorganic magnesium compounds; some from natural sources. The objectives of this research were to investigate the naturally occurring 210 Po activity concentrations in magnesium supplements, find the correlations between 210 Po concentration in medicament and magnesium chemical form, and calculate the effective radiation dose connected to analyzed magnesium supplement consumption. The highest 210 Po activity concentrations were determined in mineral tablets made from sedimentary rocks, namely dolomite - 3.84 ± 0.15 mBq g -1 (sample Mg17). The highest annual radiation dose from 210 Po taken with 1 tablet of magnesium supplement per day or with 400 mg of pure Mg daily would come from sample Mg17 (dolomite) - 1.35 ± 0.5 and 8.44 ± 0.33 μSv year -1 respectively.

  14. Corrosion of Magnesium in Multimaterial System

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Vineet V.; Agnew, Sean

    2017-08-16

    The TMS Magnesium Committee has been actively involved in presenting cutting-edge research and development and the latest trends related to magnesium and its alloys to industry and academia. Topics including magnesium alloy development, applications, mechanism of deformation and corrosion, thermomechanical processing, modelling, etc. have been captured year after year through the Magnesium Technology symposium and conference proceedings at TMS and through special topics in JOM. Every year, based on the unanimous endorsement from the industry and academia, a topic is selected to address the latest developments within this subject in JOM. In continuation with last year’s coverage of Advances and Achievements in In-Situ Analysis of Corrosions and Structure–Property Relationship in Mg Alloys,[1] this year’s topic focuses on the Corrosion of Magnesium in Multimaterial Systems. Magnesium, the lightest of all the structural materials, has garnered much interest in the transportation, electronics packaging, defense equipments and industries alike and are more commonly being incorporated in multimaterial design concepts.[2-4] However, the application of the same is limited due to its highly corrosive nature, and understanding and mitigating the corrosion of magnesium has been a major research challenge.

  15. Magnesium supplement in pregnancy-induced hypertension. A clinicopathological study

    DEFF Research Database (Denmark)

    Rudnicki, M; Junge, Jette; Frølich, A

    1990-01-01

    as a double-blind randomized controlled study in which 11 women were allocated to magnesium and 7 to placebo treatment. The treatment comprised a 48-hour intravenous magnesium/placebo infusion followed by daily oral magnesium/placebo intake until one day after delivery. Magnesium supplement increased birth....... There was no significant difference when the magnesium group, the placebo group and the control group were compared separately. The present study suggests that magnesium supplement has a beneficial effect on fetal growth in pregnancy-induced hypertension. With regard to the light and electron microscopic changes we were...... unable to demonstrate any significant difference between the magnesium, placebo and control groups....

  16. Corrosion and protection of magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ghali, E. [Laval Univ., Quebec City, PQ (Canada). Dept. of Mining and Metallurgy

    2000-07-01

    The oxide film on magnesium offers considerable surface protection in rural and some industrial environments and the corrosion rate lies between that of aluminum and low carbon steels. Galvanic coupling of magnesium alloys, high impurity content such as Ni, Fe, Cu and surface contamination are detrimental for corrosion resistance of magnesium alloys. Alloying elements can form secondary particles which are noble to the Mg matrix, thereby facilitating corrosion, or enrich the corrosion product thereby possibly inhibiting the corrosion rate. Bimetallic corrosion resistance can be increased by fluxless melt protection, choice of compatible alloys, insulating materials, and new high-purity alloys. Magnesium is relatively insensible to oxygen concentration. Pitting, corrosion in the crevices, filiform corrosion are observed. Granular corrosion of magnesium alloys is possible due to the cathodic grain-boundary constituent. More homogeneous microstructures tend to improve corrosion resistance. Under fatigue loading conditions, microcrack initiation in Mg alloys is related to slip in preferentially oriented grains. Coating that exclude the corrosive environments can provide the primary defense against corrosion fatigue. Magnesium alloys that contain neither aluminum nor zinc are the most SCC resistant. Compressive surface residual stresses as that created by short peening increase SCC resistance. Cathodic polarization or cladding with a SCC resistant sheet alloy are good alternatives. Effective corrosion prevention for magnesium alloy components and assemblies should start at the design stage. Selective surface preparation, chemical treatment and coatings are recommended. Oil application, wax coating, anodizing, electroplating, and painting are possible alternatives. Recently, it is found that a magnesium hydride layer, created on the magnesium surface by cathodic charging in aqueous solution is a good base for painting. (orig.)

  17. A Case of a Magnesium Oxide Bezoar.

    Science.gov (United States)

    Iwamuro, Masaya; Saito, Shunsuke; Yoshioka, Masao; Urata, Haruo; Ueda, Kumiko; Yamamoto, Kazuhide; Okada, Hiroyuki

    2018-06-06

    A 75-year-old Japanese woman presented with nausea and appetite loss. Computed tomography showed a radiopaque substance in the stomach. Esophagogastroduodenoscopy revealed bezoars in the stomach, which were endoscopically retrieved. The bezoars were mainly composed of magnesium and oxide. Although bezoar formation associated with magnesium oxide consumption is infrequently encountered, the present case indicates that pharmacobezoar should be considered among the differential diagnoses in patients who demonstrate a radiopaque mass in the digestive tract and have a history of magnesium oxide use.

  18. The reference range of serum, plasma and erythrocyte magnesium

    Directory of Open Access Journals (Sweden)

    Suzanna Immanuel

    2006-12-01

    Full Text Available The interest in the clinical importance of serum magnesium level has just recently begun with the analysis and findings of abnormal magnesium level in cardiovascular, metabolic and neuromuscular disorder. Although the serum level does not reflect the body magnesium level, but currently, only serum magnesium determination is widely used. Erythrocyte magnesium is considered more sensitive than serum magnesium as it reflects intracellular magnesium status. According to NCCLS (National Committee for Clinical Laboratory Standards every laboratory is recommended to have its own reference range for the tests it performs, including magnesium determination. The reference range obtained is appropriate for the population and affected by the method and technique. This study aimed to find the reference range of serum and plasma magnesium and also intracellular magnesium i.e. erythrocyte magnesium by direct method, and compare the results of serum and plasma magnesium. Blood was taken from 114-blood donor from Unit Transfusi Darah Daerah (UTDD Budhyarto Palang Merah Indonesia (PMI DKI Jakarta, consisted of 57 male and 57 female, aged 17 – 65 years, clinically healthy according to PMI donor criteria. Blood was taken from blood set, collected into 4 ml vacuum tube without anticoagulant for serum magnesium determination and 3 ml vacuum tube with lithium heparin for determination of erythrocyte and plasma magnesium Determination of magnesium level was performed with clinical chemistry auto analyzer Hitachi 912 by Xylidil Blue method colorimetrically. This study showed no significant difference between serum and heparinized plasma extra cellular magnesium. The reference range for serum or plasma magnesium was 1.30 – 2.00 mEq/L and for erythrocyte magnesium was 4.46 - 7.10 mEq/L. (Med J Indones 2006; 15:229-35Keywords: Reference range, extracellular magnesium, intracellular magnesium

  19. A multidisciplinary study on magnesium

    Directory of Open Access Journals (Sweden)

    Radić-Perić Jelena

    2012-01-01

    Full Text Available During plasma electrolytic oxidation of a magnesium alloy (96% Mg, 3% Al, 1% Zn we obtained a luminescence spectrum in the wave number range between 19 950 and 20 400 cm-1. The broad peak with clearly pronounced structure was assigned to the v’-v” = 0 sequence of the B 1Σ+ → X 1Σ+ electronic transition of MgO. Quantum-mechanical perturbative approach was applied to extract the form of the potential energy curves for the electronic states involved in the observed spectrum, from the positions of spectral bands. These potential curves, combined with the results of quantum-chemical calculations of the electric transition moment, were employed in subsequent variational calculations to obtain the Franck-Condon factors and transition moments for the vibrational transitions observed. Comparing the results of these calculations with the measured intensity distribution within the spectrum we derived relative population of the upper electronic state vibration levels. This enabled us to estimate the plasma temperature. Additionally, the temperature was determined by analysis of the recorded A 2Σ+ (v’ = 0 - X 2П (v” = 0 emission spectrum of OH. The composition of plasma containing magnesium, oxygen, and hydrogen under assumption of local thermal equilibrium was calculated in the temperature range up to 12 000 K and for pressures of 105, 106, 107, and 108 Pa, in order to explain the appearance of the observed spectral features and to contribute to elucidation of processes taking place during the electrolytic oxidation of Mg. [Projekat Ministarstva nauke Republike Srbije, br. 172040

  20. Magnesium stearine production via direct reaction of palm stearine and magnesium hydroxide

    Science.gov (United States)

    Pratiwi, M.; Ylitervo, P.; Pettersson, A.; Prakoso, T.; Soerawidjaja, T. H.

    2017-06-01

    The fossil oil production could not compensate with the increase of its consumption, because of this reason the renewable alternative energy source is needed to meet this requirement of this fuel. One of the methods to produce hydrocarbon is by decarboxylation of fatty acids. Vegetable oil and fats are the greatest source of fatty acids, so these can be used as raw material for biohydrocarbon production. From other researchers on their past researchs, by heating base soap from divalent metal, those metal salts will decarboxylate and produce hydrocarbon. This study investigate the process and characterization of magnesium soaps from palm stearine by Blachford method. The metal soaps are synthesized by direct reaction of palm stearine and magnesium hydroxide to produce magnesium stearine and magnesium stearine base soaps at 140-180°C and 6-10 bar for 3-6 hours. The operation process which succeed to gain metal soaps is 180°C, 10 bar, for 3-6 hours. These metal soaps are then compared with commercial magnesium stearate. Based on Thermogravimetry Analysis (TGA) results, the decomposition temperature of all the metal soaps were 250°C. Scanning Electron Microscope with Energy Dispersive X-ray (SEM-EDX) analysis have shown the traces of sodium sulphate for magnesium stearate commercial and magnesium hydroxide for both type of magnesium stearine soaps. The analysis results from Microwave Plasma-Atomic Emission Spectrometry (MP-AES) have shown that the magnesium content of magnesium stearine approximate with magnesium stearate commercial and lower compare with magnesium stearine base soaps. These experiments suggest that the presented saponification process method could produced metal soaps comparable with the commercial metal soaps.

  1. Study of Serum Magnesium in Surgical Stress

    Directory of Open Access Journals (Sweden)

    Sandip D. Lambe

    2016-10-01

    Full Text Available Background: A deficiency of magnesium is of clinical importance in hospitalized patients. The prevalence of hypomagnesaemia is high in critically ill patients. Knowing the important role of magnesium in surgical cases, it is necessary to anticipate and diagnose magnesium deficiency prior to surgery and in the immediate postoperative period to correct it. Aims and Objectives: The aim of this study was to analyse serum magnesium levels in patients undergoing emergency surgical procedures, planned surgical procedures and normal healthy matched controls and to compare the serum magnesium levels in all the three groups. Materials and Methods: The study participants were divided into three groups: i Group I: patients undergoing emergency major surgery ii Group II: patients undergoing planned major surgery iii Group III: normal healthy controls. Serum Magnesium investigation was done by Xylidyl Blue Method using UV-1800/Shimadzu UV-Spectrophotometer. Results: The mean serum Magnesium in control group was found to be 2.16 ± 0.30 mg/dl. In patients undergoing planned surgery, pre-operative serum magnesium was normal (2.16 ± 0.22 mg/dl but decreased significantly on postoperative day 3 (1.63 ± 0.27 mg/dl and day 6 (1.97 ± 0.12 mg/dl and returned to normal level by post-operative day 9 (2.14 ± 0.14 mg/dl compared to controls. In patients undergoing emergency surgery, serum magnesium was decreased pre-operatively (1.90 ± 0.48 mg/dl.Further significant reduction was found at post-operative day 3 (1.38 ± 0.28 mg/dl, day 6 (1.59 ± 0.30 mg/dl and day 9 (1.88 ± 0.46 mg/dl compared to controls. Mean serum Magnesium overall in emergency surgery patients was reduced significantly compared to planned surgery patients. Conclusion: A transient fall in the serum Magnesium as compared to its pre-operative level was seen in every patient undergoing surgical procedure due to surgical stress. In patients undergoing emergency surgical procedure, the decrease was

  2. Nuclear reactor shield including magnesium oxide

    International Nuclear Information System (INIS)

    Rouse, C.A.; Simnad, M.T.

    1981-01-01

    An improvement is described for nuclear reactor shielding of a type used in reactor applications involving significant amounts of fast neutron flux. The reactor shielding includes means providing structural support, neutron moderator material, neutron absorber material and other components, wherein at least a portion of the neutron moderator material is magnesium in the form of magnesium oxide either alone or in combination with other moderator materials such as graphite and iron

  3. Distribution of magnesium in groundwater of Serbia

    OpenAIRE

    Milosavljević Jovana; Andrijašević Jakov; Todorović Maja

    2013-01-01

    Magnesium is chemical element commonly found in the environment and the main constituent of many types of minerals and rocks. This element is also essential to man. Owing to its abundance in nature, magnesium is present in all water resources and generally occur as the dominant cation, with calcium, in those that feature low TDS levels, whose origin is associated with large formations of sedimentary rocks (limestones, dolomites), and to a lesser extent with...

  4. Immunological Response to Biodegradable Magnesium Implants

    Science.gov (United States)

    Pichler, Karin; Fischerauer, Stefan; Ferlic, Peter; Martinelli, Elisabeth; Brezinsek, Hans-Peter; Uggowitzer, Peter J.; Löffler, Jörg F.; Weinberg, Annelie-Martina

    2014-04-01

    The use of biodegradable magnesium implants in pediatric trauma surgery would render surgical interventions for implant removal after tissue healing unnecessary, thereby preventing stress to the children and reducing therapy costs. In this study, we report on the immunological response to biodegradable magnesium implants—as an important aspect in evaluating biocompatibility—tested in a growing rat model. The focus of this study was to investigate the response of the innate immune system to either fast or slow degrading magnesium pins, which were implanted into the femoral bones of 5-week-old rats. The main alloying element of the fast-degrading alloy (ZX50) was Zn, while it was Y in the slow-degrading implant (WZ21). Our results demonstrate that degrading magnesium implants beneficially influence the immune system, especially in the first postoperative weeks but also during tissue healing and early bone remodeling. However, rodents with WZ21 pins showed a slightly decreased phagocytic ability during bone remodeling when the degradation rate reached its maximum. This may be due to the high release rate of the rare earth-element yttrium, which is potentially toxic. From our results we conclude that magnesium implants have a beneficial effect on the innate immune system but that there are some concerns regarding the use of yttrium-alloyed magnesium implants, especially in pediatric patients.

  5. Magnesium-phosphate-glass cements with ceramic-type properties

    Science.gov (United States)

    Sugama, T.; Kukacka, L.E.

    1982-09-23

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate, exhibits rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  6. Magnesium phosphate glass cements with ceramic-type properties

    Science.gov (United States)

    Sugama, Toshifumi; Kukacka, Lawrence E.

    1984-03-13

    Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

  7. The role of magnesium in the electrochemical behaviour of 5XXX aluminium-magnesium alloys

    NARCIS (Netherlands)

    Flores Ramirez, J.R.

    2006-01-01

    An investigation concerning the effects of magnesium on the intergranular corrosion susceptibility of AA5XXX aluminium alloys was carried out. In the present work, magnesium is found to be highly mobile in the bulk metal as well as in the aluminium oxide. This mobility is also found to be dependent

  8. Blood compatibility of magnesium and its alloys.

    Science.gov (United States)

    Feyerabend, Frank; Wendel, Hans-Peter; Mihailova, Boriana; Heidrich, Stefanie; Agha, Nezha Ahmad; Bismayer, Ulrich; Willumeit-Römer, Regine

    2015-10-01

    Blood compatibility analysis in the field of biomaterials is a highly controversial topic. Especially for degradable materials like magnesium and its alloys no established test methods are available. The purpose of this study was to apply advanced test methodology for the analysis of degrading materials to get a mechanistic insight into the corrosion process in contact with human blood and plasma. Pure magnesium and two magnesium alloys were analysed in a modified Chandler-Loop setup. Standard clinical parameters were determined, and a thorough analysis of the resulting implant surface chemistry was performed. The contact of the materials to blood evoked an accelerated inflammatory and cell-induced osteoconductive reaction. Corrosion products formed indicate a more realistic, in vivo like situation. The active regulation of corrosion mechanisms of magnesium alloys by different cell types should be more in the focus of research to bridge the gap between in vitro and in vivo observations and to understand the mechanism of action. This in turn could lead to a better acceptance of these materials for implant applications. The presented study deals with the first mechanistic insights during whole human blood contact and its influence on a degrading magnesium-based biomaterial. The combination of clinical parameters and corrosion layer analysis has been performed for the first time. It could be of interest due to the intended use of magnesium-based stents and for orthopaedic applications for clinical applications. An interest for the readers of Acta Biomaterialia may be given, as one of the first clinically approved magnesium-based devices is a wound-closure device, which is in direct contact with blood. Moreover, for orthopaedic applications also blood contact is of high interest. Although this is not the focus of the manuscript, it could help to rise awareness for potential future applications. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All

  9. Post traumatic tetanus and role magnesium sulphate

    International Nuclear Information System (INIS)

    Sikendr, R.I.; Samad, B.U.; Memon, M.I.

    2009-01-01

    Tetanus is a life threatening disease. Reported mortality for tetanus is 15-39%. Conventional treatment includes heavy sedation and artificial ventilation. Complications resulting from long term heavy sedation and artificial ventilation contribute to 60% of the total mortality caused by tetanus. In this study magnesium sulphate was used to reduce the need for sedation and artificial ventilation. Objectives of this prospective study were to determine the role of magnesium sulphate in post traumatic tetanus. The study was carried out in surgical Intensive Care at Pakistan Institute of Medical Sciences (PIMS), Islamabad from Jan 2004 to Dec 2007. Forty-four patients presented during this period and 33 patients were included in the study. All patients had tracheostomy done within 48 hours. Every patient was started Magnesium Sulphate therapy for control of spasms after sending baseline investigations. Patients were given ventilatory support when needed. All data was entered in well structured proforma. SPSS-10 was used to analyse data. Thirty-three patients were included in the study and all patients were given magnesium sulphate. Out of these, 45.5% cases were grade 4 tetanus, 73.6% and 63.3% cases did not require artificial ventilation and additional sedation respectively, 51.1% patients remained free of complications of tetanus. Overall mortality was 30.3%. Use of Magnesium Sulphate is safe and reduces the need for sedation and artificial ventilation in high grade tetanus thus contributing to survival benefit in adult post-traumatic tetanus cases. (author)

  10. Magnesium and manganese content of halophilic bacteria

    International Nuclear Information System (INIS)

    de Medicis, E.; Paquette, J.; Gauthier, J.J.; Shapcott, D.

    1986-01-01

    Magnesium and manganese contents were measured by atomic absorption spectrophotometry in bacteria of several halophilic levels, in Vibrio costicola, a moderately halophilic eubacterium growing in 1 M NaCl, Halobacterium volcanii, a halophilic archaebacterium growing in 2.5 NaCl, Halobacterium cutirubrum, an extremely halophilic archaebacterium growing in 4 M NaCl, and Escherichia coli, a nonhalophilic eubacterium growing in 0.17 M NaCl. Magnesium and manganese contents varied with the growth phase, being maximal at the early log phase. Magnesium and manganese molalities in cell water were shown to increase with the halophilic character of the logarithmically growing bacteria, from 30 mmol of Mg per kg of cell water and 0.37 mmol of Mn per kg of cell water for E. coli to 102 mmol of Mg per kg of cell water and 1.6 mmol of Mn per kg of cell water for H cutirubrum. The intracellular concentrations of manganese were determined independently by a radioactive tracer technique in V. costicola and H. volcanii. The values obtained by 54 Mn loading represented about 70% of the values obtained by atomic absorption. The increase of magnesium and manganese contents associated with the halophilic character of the bacteria suggests that manganese and magnesium play a role in haloadaptation

  11. The initial oxidation of magnesium

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, M.

    2004-07-01

    Pure Magnesium samples have been oxidised in an UHV chamber under controlled conditions. Pressure range was 10{sup -10} Torr to 10{sup -7} Torr, temperature range was 273 K to 435 K. The samples have then been investigated with XPS, Ellipsometry and HERDA. Additionally, furnace oxidations at 750 Torr and 673 K have been carried out and investigated with XPS. From the XPS measurements data concerning layer thickness, composition, oxidation state and binding state have been gained. The ellipsometrie measurements yielded additional data concerning layer thickness as well as the size of the band gap of the developing oxide. With the HERDA measurements, the oxygen content within the oxide layer has been determined yielding additional information about composition and layer thickness. The layer thickness as a function of time have then been modelled with a kinetic growth model of Fromhold and Cook. For the refinement of the XPS data concerning layer thickness and composition, the pronounced plasmon excitations that occur in magnesium have been determined with two different procedures which have been developed in the methodical part of this work. The layer thickness and composition values have thus been corrected. Results: Two oxidation stages could be identified: a strong increase for the first few Langmuirs (1L = 1s x 10{sup -6} Torr), followed by a saturation'' region which was about 1.2 nm to 1.5 nm in magnitude. XPS and ellipsometry results have thereby been in very good agreement. The composition of the developing oxide showed a clear deviation from stoichiometric MgO, mainly caused by an oxygen deficiency; this deficiency has also been confirmed with the HERDA measurements. The Mg/O ratio as a function of layer thickness showed a continous decay starting from very high values for the thinnest layers (>{proportional_to}2.5) down to a saturation value of about 1.4, even for larger layer thicknesses gained with the furnace oxidations. The determination of

  12. Investigation of magnesium oxychloride cement at the initial hardening stage

    Directory of Open Access Journals (Sweden)

    Averina Galina

    2018-01-01

    Full Text Available The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.

  13. Small for Gestational Age and Magnesium: Intrauterine magnesium deficiency may induce metabolic syndrome in later life

    Directory of Open Access Journals (Sweden)

    Junji Takaya

    2015-12-01

    Full Text Available Magnesium deficiency during pregnancy as a result of insufficient or low intake of magnesium is common in developing and developed countries. Previous reports have shown that intracellular magnesium of cord blood platelets is lower among small for gestational age (SGA groups than that of appropriate for gestational age (AGA groups, suggesting that intrauterine magnesium deficiency may result in SGA. Additionally, the risk of adult-onset diseases such as insulin resistance syndrome is greater among children whose mothers were malnourished during pregnancy, and who consequently had a low birth weight. In a number of animal models, poor nutrition during pregnancy leads to offspring that exhibit pathophysiological changes similar to human diseases. The offspring of pregnant rats fed a magensium restricted diet have developed hypermethylation in the hepatic 11β-hydroxysteroid dehydrogenase-2 promoter. These findings indicate that maternal magnesium deficiencies during pregnancy influence regulation of non-imprinted genes by altering the epigenetic regulation of gene expression, thereby inducing different metabolic phenotypes. Magnesium deficiency during pregnancy may be responsible for not only maternal and fetal nutritional problems, but also lifelong consequences that affect the offspring throughout their life. Epidemiological, clinical, and basic research on the effects of magnesium deficiency now indicates underlying mechanisms, especially epigenetic processes.

  14. Friction welding of AZ31 magnesium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tsujino, R.; Ochi, H. [Osaka Inst. of Tech., Osaka (Japan); Kawai, G. [Osaka Sangyo Univ., Osaka (Japan); Yamaguchi, H.; Ogawa, K. [Osaka Prefecture Univ., Osaka (Japan); Suga, Y. [Keio Univ., Kanagawa (Japan)

    2003-07-01

    In this paper, for an acceleration of utilization of magnesium alloy which is being interested in recent years, friction welding of AZ31 magnesium alloy was carried out, and the joint performance was discussed in relation to the deformation heat input in the upset stage and upset loss as a evaluation factor. Where, the deformation heat input in the upset stage is mechanical work represented by the product of upset speed and axial pressure. As a result, it was made clear that the friction welding of AZ31 magnesium alloy was easy in the atmosphere, and good welded joints without a non- adhesion area at the weld interface could de obtained. Moreover, the evaluation factors discussed were possible to evaluate to joint performance. (orig.)

  15. Magnesium sacrificial anode behavior at elevated temperature

    International Nuclear Information System (INIS)

    Othman, Mohsen Othman

    2006-01-01

    Magnesium sacrificial anode coupled to mild steel was tasted in sodium chloride and tap water environments at elevated temperatures. The anode failed to protect the mild steel specimens in tap water environment at all temperatures specified. This was partly due to low conductivity of this medium. The temperature factor did not help to activate the anode in this medium. In sodium chloride environment the anode demonstrated good protection for steel cathodes. The weight loss was high for magnesium in sodium chloride environment particularly beyond 60 degree centigrade. In tap water environment the weight loss was negligible for the anode. It also suffered localized shallow pitting corrosion. Magnesium anode cannot be utilized where high temperature is involved particularly in high conductivity mediums. Protection of structures containing high resistivity waters is not feasible using sacrificial anode system. (author)

  16. The potential for ionic liquid electrolytes to stabilise the magnesium interface for magnesium/air batteries

    International Nuclear Information System (INIS)

    Khoo, Timothy; Howlett, Patrick C.; Tsagouria, Maureen; MacFarlane, Douglas R.; Forsyth, Maria

    2011-01-01

    Magnesium/air batteries are a possible high-energy density power source that, to date, have not received strong commercial interest due to issues with the corrosion of the magnesium and evaporation of the electrolyte. In this work we report on the use of ionic liquid based electrolytes to stabilise the metal/electrolyte interface and their impact on the electrochemical performance. Galvanostatic measurements indicate that the water content of the ionic liquid electrolyte plays an important role in the cell discharge characteristics. Surface characterisation using EIS, ATR-FTIR and powder diffraction examined the unique properties of the surface film formed on the magnesium anode.

  17. Mechanistic Study of Magnesium Carbonate Semibatch Reactive Crystallization with Magnesium Hydroxide and CO2

    DEFF Research Database (Denmark)

    Han, B.; Qu, H. Y.; Niemi, H.

    2014-01-01

    This work investigates semibatch precipitation of magnesium carbonate at ambient temperature and pressure using Mg(OH)(2) and CO2 as starting materials. A thermal analysis method was developed that reflects the dissolution rate of Mg(OH)(2) and the formation of magnesium carbonate. The method...... the liquid and solid phases. A stirring rate of 650 rpm was found to be the optimum speed as the flow rate of CO2 was 1 L/min. Precipitation rate increased with gas flow rate, which indicates that mass transfer of CO2 plays a critical role in this precipitation case. Magnesium carbonate trihydrate...

  18. Nanostructured magnesium has fewer detrimental effects on osteoblast function

    Directory of Open Access Journals (Sweden)

    Weng L

    2013-05-01

    Full Text Available Lucy Weng, Thomas J Webster School of Engineering and Department of Orthopedics, Brown University, Providence, RI, USA Abstract: Efforts have been made recently to implement nanoscale surface features on magnesium, a biodegradable metal, to increase bone formation. Compared with normal magnesium, nanostructured magnesium has unique characteristics, including increased grain boundary properties, surface to volume ratio, surface roughness, and surface energy, which may influence the initial adsorption of proteins known to promote the function of osteoblasts (bone-forming cells. Previous studies have shown that one way to increase nanosurface roughness on magnesium is to soak the metal in NaOH. However, it has not been determined if degradation of magnesium is altered by creating nanoscale features on its surface to influence osteoblast density. The aim of the present in vitro study was to determine the influence of degradation of nanostructured magnesium, created by soaking in NaOH, on osteoblast density. Our results showed a less detrimental effect of magnesium degradation on osteoblast density when magnesium was treated with NaOH to create nanoscale surface features. The detrimental degradation products of magnesium are of significant concern when considering use of magnesium as an orthopedic implant material, and this study identified a surface treatment, ie, soaking in NaOH to create nanoscale features for magnesium that can improve its use in numerous orthopedic applications. Keywords: nanostructured magnesium, degradation, detrimental effects, osteoblasts

  19. Fatigue Analysis of Magnesium Alloys Components for Car Industry

    Science.gov (United States)

    Marsavina, Liviu; Rusu, Lucian; Șerban, Dan Andrei; Negru, Radu Marcel; Cernescu, Anghel

    2017-12-01

    The use of magnesium alloys in the automotive industry increased in the last decade because of their low weight and relative good mechanical properties. However, the variable loading conditions require a good fatigue behavior. This paper summaries the fatigue properties of magnesium alloys and presents new fatigue curve results for die cast AM50 magnesium alloy.

  20. Serum Magnesium Levels in Non-Pregnant, Pregnant And Pre ...

    African Journals Online (AJOL)

    The objective of this study was to compare the serum magnesium levels in normal pregnancy and pregnancy complicated by pre-eclampsia since magnesium has been implicated in the pathogenesis of vascular dysfunction. We measured serum magnesium levels in patients with pre-eclampsia (n=36), patients with normal ...

  1. Is serum magnesium estimate necessary in patients with Eclampsia ...

    African Journals Online (AJOL)

    The therapeutic index of magnesium is said to be low, hence, there are fears of toxicity when used as anticonvulsant in eclamptic patients. The objective of this study was to determine the serum levels of magnesium in eclamptic patients treated with magnesium sulphate and relate the levels with clinical indicators. It was a ...

  2. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

  3. Higher dietary magnesium intake and higher magnesium status are associated with lower prevalence of coronary heart disease in patients with type 2 diabetes

    NARCIS (Netherlands)

    Gant, C.M.; Soedamah-Muthu, S.S.; Binnenmars, S.H.; Bakker, S.J.L.; Navis, G.; Laverman, G.D.

    2018-01-01

    In type 2 diabetes mellitus (T2D), the handling of magnesium is disturbed. Magnesium deficiency may be associated with a higher risk of coronary heart disease (CHD). We investigated the associations between (1) dietary magnesium intake; (2) 24 h urinary magnesium excretion; and (3) plasma magnesium

  4. On the hydrogenation mechanism in magnesium I

    DEFF Research Database (Denmark)

    Pedersen, A.S.; Kjøller, John; Larsen, Bent

    1985-01-01

    The first time hydriding of spherical magnesium particles covered by a thin oxide layer and sieve-fractionated into narrow size distributions within the range 40–90 μm was followed by microgravimetry. The size distributions of the fractions were determined by semiautomatic image analysis....... The hydridings were run at 402°C and 3 MPa hydrogen pressure after heating in helium. A dependence of the rate of hydriding on the heat treatment prior to reaction was observed and it is proposed that the heat treatment causes oxygen atoms to diffuse into the bulk metal and thereby break up the protective oxide...... generalizing results from the hydriding of magnesium powders....

  5. Ionized magnesium in plasma and erythrocytes for the assessment of low magnesium status in alcohol dependent patients.

    Science.gov (United States)

    Ordak, Michal; Maj-Zurawska, Magdalena; Matsumoto, Halina; Bujalska-Zadrozny, Magdalena; Kieres-Salomonski, Ilona; Nasierowski, Tadeusz; Muszynska, Elzbieta; Wojnar, Marcin

    2017-09-01

    Studies on the homeostasis of magnesium in alcohol-dependent patients have often been characterized by low hypomagnesemia detection rates. This may be due to the fact that the content of magnesium in blood serum constitutes only 1% of the average magnesium level within the human body. However, the concentration of ionized magnesium is more physiologically important and makes up 67% of the total magnesium within a human organism. There are no data concerning the determination of the ionized fraction of magnesium in patients addicted to alcohol and its influence on mental health status. This study included 100 alcohol-dependent patients and 50 healthy subjects. The free magnesium fraction was determined using the potentiometric method by means of using ion-selective electrodes. The total magnesium level was determined by using a biochemical Indiko Plus analyzer. In this study, different psychometric scales were applied. Our results confirm the usefulness of ionized magnesium concentrations in erythrocytes and plasma as a diagnostic parameter of low magnesium status in alcohol-dependent patients. The lower the concentration of ionized magnesium, the worse the quality of life an alcohol-dependent person might experience. In the case of total magnesium, no such correlation was determined. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Magnesium substitution in the structure of orthopedic nanoparticles: A comparison between amorphous magnesium phosphates, calcium magnesium phosphates, and hydroxyapatites

    International Nuclear Information System (INIS)

    Nabiyouni, Maryam; Ren, Yufu; Bhaduri, Sarit B.

    2015-01-01

    As biocompatible materials, magnesium phosphates have received a lot of attention for orthopedic applications. During the last decade multiple studies have shown advantages for magnesium phosphate such as lack of cytotoxicity, biocompatibility, strong mechanical properties, and high biodegradability. The present study investigates the role of Mg +2 and Ca +2 ions in the structure of magnesium phosphate and calcium phosphate nanoparticles. To directly compare the effect of Mg +2 and Ca +2 ions on structure of nanoparticles and their biological behavior, three groups of nanoparticles including amorphous magnesium phosphates (AMPs) which release Mg +2 , calcium magnesium phosphates (CMPs) which release Mg +2 and Ca +2 , and hydroxyapatites (HAs) which release Ca +2 were studied. SEM, TEM, XRD, and FTIR were used to evaluate the morphology, crystallinity, and chemical properties of the particles. AMP particles were homogeneous nanospheres, whereas CMPs were combinations of heterogeneous nanorods and nanospheres, and HAs which contained heterogeneous nanosphere particles. Cell compatibility was monitored in all groups to determine the cytotoxicity effect of particles on studied MC3T3-E1 preosteoblasts. AMPs showed significantly higher attachment rate than the HAs after 1 day and both AMPs and CMPs showed significantly higher proliferation rate when compared to HAs after 7 days. Gene expression level of osteoblastic markers ALP, COL I, OCN, OPN, RUNX2 were monitored and they were normalized to GAPDH housekeeping gene. Beta actin expression level was monitored as the second housekeeping gene to confirm the accuracy of results. In general, AMPs and CMPs showed higher expression level of osteoblastic genes after 7 days which can further confirm the stimulating role of Mg + 2 and Ca +2 ions in increasing the proliferation rate, differentiation, and mineralization of MC3T3-E1 preosteoblasts. - Highlights: • Role of Mg 2+ and Ca 2+ ions in proliferation, and differentiation

  7. Investigation of samarium solubility in the magnesium based solid solution

    International Nuclear Information System (INIS)

    Rokhlin, L.L.; Padezhnova, E.M.; Guzej, L.S.

    1976-01-01

    Electric resistance measurements and microscopic analysis were used to investigate the solubility of samarium in a magnesium-based solid solution. The constitutional diagram Mg-Sm on the magnesium side is of an eutectic type with the temperature of the eutectic transformation of 542 deg C. Samarium is partly soluble in solid magnesium, the less so, the lower is the temperature. The maximum solubility of samarium in magnesium (at the eutectic transformation point) is 5.8 % by mass (0.99 at. %). At 200 deg C, the solubility of samarium in magnesium is 0.4 % by mass (0.063 at. %)

  8. A review on hot tearing of magnesium alloys

    Directory of Open Access Journals (Sweden)

    Jiangfeng Song

    2016-09-01

    Full Text Available Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products. Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood, it is of great importance to investigate the hot tearing behaviour of magnesium alloys. This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades. The hot tearing criteria including recently developed Kou's criterion are summarized and compared. The numeric simulation and assessing methods of hot tearing, factors influencing hot tearing, and hot tearing susceptibility (HTS of magnesium alloys are discussed.

  9. Photoluminescence of magnesium-associated color centers in LiF crystals implanted with magnesium ions

    Science.gov (United States)

    Nebogin, S. A.; Ivanov, N. A.; Bryukvina, L. I.; V. Shipitsin, N.; E. Rzhechitskii, A.; Papernyi, V. L.

    2018-05-01

    In the present paper, the effect of magnesium nanoparticles implanted in a LiF crystal on the optical properties of color centers is studied. The transmittance spectra and AFM images demonstrate effective formation of the color centers and magnesium nanoparticles in an implanted layer of ∼ 60-100 nm in thickness. Under thermal annealing, a periodical structure is formed on the surface of the crystal and in the implanted layer due to self-organization of the magnesium nanoparticles. Upon excitation by argon laser with a wavelength of 488 nm at 5 K, in a LiF crystal, implanted with magnesium ions as well as in heavily γ-irradiated LiF: Mg crystals, luminescence of the color centers at λmax = 640 nm with a zero-phonon line at 601.5 nm is observed. The interaction of magnesium nanoparticles and luminescing color centers in a layer implanted with magnesium ions has been revealed. It is shown that the luminescence intensity of the implanted layer at a wavelength of 640 nm is by more than two thousand times higher than that of a heavily γ-irradiated LiF: Mg crystal. The broadening of the zero-phonon line at 601.5 nm in the spectrum of the implanted layer indicates the interaction of the emitting quantum system with local field of the surface plasmons of magnesium nanoparticles. The focus of this work is to further optimize the processing parameters in a way to result in luminescence great enhancement of color centers by magnesium nanoparticles in LiF.

  10. Friction phenomena in hydrostatic extrusion of magnesium

    NARCIS (Netherlands)

    Moodij, Ellen

    2014-01-01

    When magnesium is hydrostatically extruded an inconsistent and sometimes bad surface quality is encountered. In hydrostatic extrusion the billet is surrounded by a lubricant, usually castor oil. The required pressure to deform the material is applied onto this lubricant and not directly to the

  11. High grade magnesium from waste bittern

    International Nuclear Information System (INIS)

    El-Yamani, I.S.; Farah, M.Y.; Isaac, S.L.

    1979-01-01

    The production of high grade magnesia for nuclear purposes from sea water by use of both aqueous and gaseous ammonia has been described. The effect of precipitating conditions on the settling rate and magnesium recovery, was thoroughly examined. Ammonia gas approach was recommended and justified

  12. 76 FR 69284 - Pure Magnesium From China

    Science.gov (United States)

    2011-11-08

    ... China Determination On the basis of the record \\1\\ developed in the subject five-year review, the United... China would be likely to lead to continuation or recurrence of material injury to an industry in the...), entitled Pure Magnesium from China: Investigation No. 731-TA-696 (Third Review). Issued: November 2, 2011...

  13. Cathodoluminescence study of vickers indentations in magnesium ...

    African Journals Online (AJOL)

    Vickers diamond pyramid indentations made in single crystal of magnesium oxide (MgO) were examined in an environmental scanning electron microscope interfaced with an AVS-2000 spectrophotometer for luminescence. Three distinct zones around the indentations were identified to exhibit cathodoluminescence, which ...

  14. Magnesium hydrides and their phase transitions

    Czech Academy of Sciences Publication Activity Database

    Paidar, Václav

    2016-01-01

    Roč. 41, č. 23 (2016), s. 9769-9773 ISSN 0360-3199 R&D Projects: GA MŠk(CZ) LD13069 Institutional support: RVO:68378271 Keywords : hydrogen * magnesium and transition metal hydrides * crystal structure stability * displacive phase transformations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.582, year: 2016

  15. Precipitation and Hardening in Magnesium Alloys

    Science.gov (United States)

    Nie, Jian-Feng

    2012-11-01

    Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

  16. Short Communication - Blood Magnesium levels in migraineurs ...

    African Journals Online (AJOL)

    Introduction: Some probable mechanisms have been described to the relationship between magnesium (Mg) level and migraine headache attacks. In the study reported here, we sought to determine the total Mg serum status of patients with migraine within and between the headache attacks and compare it with ...

  17. Magnesium supplementation in children with attention deficit ...

    African Journals Online (AJOL)

    Farida El Baza

    2015-07-07

    Jul 7, 2015 ... compared to normal children, in both serum and hair. Then, the effects of .... regards attention, memory loss, fear, restlessness, insomnia, tics, cramps and ..... the effectiveness and safety of magnesium and vitamin B6. Trials ... 143–8. [17] Mousain-Bosc M, Roche M, Polge A, Pradal-Prat D, Rapin J, · Bali JP.

  18. Design Considerations for Developing Biodegradable Magnesium Implants

    Science.gov (United States)

    Brar, Harpreet S.; Keselowsky, Benjamin G.; Sarntinoranont, Malisa; Manuel, Michele V.

    The integration of biodegradable and bioabsorbable magnesium implants into the human body is a complex undertaking that faces major challenges. The complexity arises from the fact that biomaterials must meet both engineering and physiological requirements to ensure the desired properties. Historically, efforts have been focused on the behavior of commercial magnesium alloys in biological environments and their resultant effect on cell-mediated processes. Developing causal relationships between alloy chemistry and micro structure, and its effect on cellular behavior can be a difficult and time intensive process. A systems design approach driven by thermodynamics has the power to provide significant contributions in developing the next generation of magnesium alloy implants with controlled degradability, biocompatibility, and optimized mechanical properties, at reduced time and cost. This approach couples experimental research with theory and mechanistic modeling for the accelerated development of materials. The aim of this article is to enumerate this strategy, design considerations and hurdles for developing new magnesium alloys for use as biodegradable implant materials [1].

  19. Spider silk as a template for obtaining magnesium oxide and magnesium hydroxide fibers

    Directory of Open Access Journals (Sweden)

    Dmitrović Svetlana

    2018-01-01

    Full Text Available Spider silk fibers, collected from Pholcus Phalangioides spider were used as a template for obtaining magnesium oxide (MgO, periclase as well as magnesium hydroxide (Mg(OH2, brucite fibers. Magnesium oxide fibers were obtained in a simple manner by heat induced decomposition of magnesium salt (MgCl2 in the presence of the spider silk fibers, while magnesium hydroxide fibers were synthesized by hydration of MgO fibers at 50, 70 and 90 C, for 48 and 96 h. According to Scanning electron microscopy (SEM, dimensions of spider silk fibers determined the dimension of synthesized MgO fibers, while for Mg(OH2 fibers, the average diameter was increased with prolonging the hydration period. The surface of Mg(OH2 fibers was noticed to be covered with brucite in a form of plates. X-Ray diffraction (XRD analysis showed that MgO fibers were single-phased (the pure magnesium oxide fibers were obtained, while Mg(OH2 fibers were two- or single-phased brucite depending on incubation period, and/or incubation temperature. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 45012

  20. Nanostructured magnesium has fewer detrimental effects on osteoblast function.

    Science.gov (United States)

    Weng, Lucy; Webster, Thomas J

    2013-01-01

    Efforts have been made recently to implement nanoscale surface features on magnesium, a biodegradable metal, to increase bone formation. Compared with normal magnesium, nanostructured magnesium has unique characteristics, including increased grain boundary properties, surface to volume ratio, surface roughness, and surface energy, which may influence the initial adsorption of proteins known to promote the function of osteoblasts (bone-forming cells). Previous studies have shown that one way to increase nanosurface roughness on magnesium is to soak the metal in NaOH. However, it has not been determined if degradation of magnesium is altered by creating nanoscale features on its surface to influence osteoblast density. The aim of the present in vitro study was to determine the influence of degradation of nanostructured magnesium, created by soaking in NaOH, on osteoblast density. Our results showed a less detrimental effect of magnesium degradation on osteoblast density when magnesium was treated with NaOH to create nanoscale surface features. The detrimental degradation products of magnesium are of significant concern when considering use of magnesium as an orthopedic implant material, and this study identified a surface treatment, ie, soaking in NaOH to create nanoscale features for magnesium that can improve its use in numerous orthopedic applications.