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Publications (10 of 12) Show all publications
Tahira, A., Ibupoto, Z., Mazzaro, R., You, S., Morandi, V., Natile, M. M., . . . Vomiero, A. (2019). Advanced Electrocatalysts for Hydrogen Evolution Reaction Based on Core–Shell MoS2/TiO2 Nanostructures in Acidic and Alkaline Media. ACS APPLIED ENERGY MATERIALS, 2(3), 2053-2062
Open this publication in new window or tab >>Advanced Electrocatalysts for Hydrogen Evolution Reaction Based on Core–Shell MoS2/TiO2 Nanostructures in Acidic and Alkaline Media
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2019 (English)In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 3, p. 2053-2062Article in journal (Refereed) Published
Abstract [en]

Hydrogen production as alternative energy source is still a challenge due to the lack of efficient and inexpensive catalysts, alternative to platinum. Thus, stable, earth abundant, and inexpensive catalysts are of prime need for hydrogen production via hydrogen evolution reaction (HER). Herein, we present an efficient and stable electrocatalyst composed of earth abundant TiO2 nanorods decorated with molybdenum disulfide thin nanosheets, a few nanometers thick. We grew rutile TiO2 nanorods via the hydrothermal method on conducting glass substrate, and then we nucleated the molybdenum disulfide nanosheets as the top layer. This composite possesses excellent hydrogen evolution activity in both acidic and alkaline media at considerably low overpotentials (350 mV and 700 mV in acidic and alkaline media, respectively) and small Tafel slopes (48 and 60 mV/dec in acidic and alkaline conditions, respectively), which are better than several transition metal dichalcogenides, such as pure molybdenum disulfide and cobalt diselenide. A good stability in acidic and alkaline media is reported here for the new MoS2/TiO2 electrocatalyst. These results demonstrate the potential of composite electrocatalysts for HER based on earth abundant, cost-effective, and environmentally friendly materials, which can also be of interest for a broader range of scalable applications in renewable energies, such as lithium sulfur batteries, solar cells, and fuel cells.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
acidic, alkaline, catalyst, hydrogen evolution reaction, MoS2, TiO2
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-73610 (URN)10.1021/acsaem.8b02119 (DOI)000462944700053 ()2-s2.0-85064810223 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-04-12 (oliekm)

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-06-24Bibliographically approved
Solomon, G., Mazzaro, R., You, S., Natile, M. M., Morandi, V., Concina, I. & Vomiero, A. (2019). Ag2S/MoS2 Nanocomposites Anchored on Reduced Graphene Oxide: Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction. ACS Applied Materials and Interfaces, 11(25), 22380-22389
Open this publication in new window or tab >>Ag2S/MoS2 Nanocomposites Anchored on Reduced Graphene Oxide: Fast Interfacial Charge Transfer for Hydrogen Evolution Reaction
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2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 25, p. 22380-22389Article in journal (Refereed) Published
Abstract [en]

Hydrogen evolution reaction through electrolysis holds great potential as a clean, renewable, and sustainable energy source. Platinum-based catalysts are the most efficient to catalyze and convert water into molecular hydrogen; however, their large-scale application is prevented by scarcity and cost of Pt. In this work, we propose a new ternary composite of Ag2S, MoS2, and reduced graphene oxide (RGO) flakes via a one-pot synthesis. The RGO support assists the growth of two-dimensional MoS2 nanosheets partially covered by silver sulfides as revealed by high-resolution transmission electron microscopy. Compared with the bare MoS2 and MoS2/RGO, the Ag2S/MoS2 anchored on the RGO surface (the ternary system Ag2S/MoS2/RGO) demonstrated a high catalytic activity toward hydrogen evolution reaction (HER). Its superior electrochemical activity toward HER is evidenced by the positively shifted (−190 mV vs reversible hydrogen electrode (RHE)) overpotential at a current density of −10 mA/cm2 and a small Tafel slope (56 mV/dec) compared with a bare and binary system. The Ag2S/MoS2/RGO ternary catalyst at an overpotential of −200 mV demonstrated a turnover frequency equal to 0.38 s–1. Electrochemical impedance spectroscopy was applied to understand the charge-transfer resistance; the ternary sample shows a very small charge-transfer resistance (98 Ω) at −155 mV vs RHE. Such a large improvement can be attributed to the synergistic effect resulting from the enhanced active site density of both sulfides and to the improved electrical conductivity at the interfaces between MoS2 and Ag2S. This ternary catalyst opens up further optimization strategies to design a stable and cheap catalyst for hydrogen evolution reaction, which holds great promise for the development of a clean energy landscape.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
electrocatalyst, hydrogen evolution, silver sulfide, molybdenum sulfide, reduced graphene oxide
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-75551 (URN)10.1021/acsami.9b05086 (DOI)000473251100036 ()2-s2.0-85068008830 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-16 (johcin)

Available from: 2019-08-16 Created: 2019-08-16 Last updated: 2019-08-16Bibliographically approved
Leduc, J., Goenuellue, Y., Ghamgosar, P., You, S., Mouzon, J., Choi, H., . . . Mathur, S. (2019). Electronically-Coupled Phase Boundaries in α‑Fe2O3/Fe3O4 Nanocomposite Photoanodes for Enhanced Water Oxidation. ACS APPLIED NANO MATERIALS, 2(1), 334-342
Open this publication in new window or tab >>Electronically-Coupled Phase Boundaries in α‑Fe2O3/Fe3O4 Nanocomposite Photoanodes for Enhanced Water Oxidation
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2019 (English)In: ACS APPLIED NANO MATERIALS, E-ISSN 2574-0970, Vol. 2, no 1, p. 334-342Article in journal (Refereed) Published
Abstract [en]

Photoelectrochemical (PEC) water splittingreactions are promising for sustainable hydrogen productionfrom renewable sources. We report here, the preparation of α-Fe2O3/Fe3O4 composite films via a single-step chemical vapordeposition of [Fe(OtBu)3]2 and their use as efficient photoanode materials in PEC setups. Film thickness and phase segregation was controlled by varying the deposition time and corroborated through cross-section Raman spectroscopy and scanning electron microscopy. The highest water oxidationactivity (0.48 mA/cm2 at 1.23 V vs RHE) using intermittent AM 1.5 G (100 mW/cm2) standard illumination was found forhybrid films with a thickness of 11 μm. This phenomenon is attributed to an improved electron transport resulting from ahigher magnetite content toward the substrate interface and an increased light absorption due to the hematite layer mainly located at the top surface of the film. The observed high efficiency of α-Fe2O3/Fe3O4 nanocomposite photoanodes is attributed to the close proximity and establishment of 3D interfaces between the weakly ferro- (Fe2O3) and ferrimagnetic (Fe3O4) oxides, which in view of their differential chemical constitution andvalence states of Fe ions (Fe2+/Fe3+) can enhance the charge separation and thus the overall electrical conductivity of the layer.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
solar water splitting, valence dynamics, magnetite, Raman, single-source CVD, heterostructures
National Category
Composite Science and Engineering Chemical Process Engineering
Research subject
Experimental Physics; Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-73139 (URN)10.1021/acsanm.8b01936 (DOI)000464491500036 ()
Note

Validerad;2019;Nivå 2;2019-03-13 (oliekm)

Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-05-02Bibliographically approved
Ghamgosar, P., Rigoni, F., Gilzad Kohan, M., You, S., Morales, E. A., Mazzaro, R. & Morandi, V. (2019). Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions. ACS Applied Materials and Interfaces, 11(26), 23454-23462
Open this publication in new window or tab >>Self-Powered Photodetectors Based on Core-Shell ZnO-Co3O4 Nanowire Heterojunctions
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2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 26, p. 23454-23462Article in journal (Refereed) Published
Abstract [en]

Self-powered photodetectors operating in the UV–visible–NIR window made of environmentally friendly, earth abundant, and cheap materials are appealing systems to exploit natural solar radiation without external power sources. In this study, we propose a new p–n junction nanostructure, based on a ZnO–Co3O4 core–shell nanowire (NW) system, with a suitable electronic band structure and improved light absorption, charge transport, and charge collection, to build an efficient UV–visible–NIR p–n heterojunction photodetector. Ultrathin Co3O4 films (in the range 1–15 nm) were sputter-deposited on hydrothermally grown ZnO NW arrays. The effect of a thin layer of the Al2O3 buffer layer between ZnO and Co3O4 was investigated, which may inhibit charge recombination, boosting device performance. The photoresponse of the ZnO–Al2O3–Co3O4 system at zero bias is 6 times higher compared to that of ZnO–Co3O4. The responsivity (R) and specific detectivity (D*) of the best device were 21.80 mA W–1and 4.12 × 1012 Jones, respectively. These results suggest a novel p–n junction structure to develop all-oxide UV–vis photodetectors based on stable, nontoxic, low-cost materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
ZnO−CoO core−shell, all-oxide p−n heterojunction, nanowire geometry, photovoltaic photodetector, self-powered photodetector
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-75216 (URN)10.1021/acsami.9b04838 (DOI)000474670100061 ()31252456 (PubMedID)
Note

Validerad;2019;Nivå 2;2019-07-04 (svasva)

Available from: 2019-07-04 Created: 2019-07-04 Last updated: 2019-08-16Bibliographically approved
Enrichi, F., Belmokhtar, S., Benedetti, A., Bouajaj, A., Cattaruzza, E., Coccetti, F., . . . Zur, L. Z. (2018). Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics. Optical materials (Amsterdam), 84, 668-674
Open this publication in new window or tab >>Ag nanoaggregates as efficient broadband sensitizers for Tb3+ ions in silica-zirconia ion-exchanged sol-gel glasses and glass-ceramics
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2018 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 84, p. 668-674Article in journal (Refereed) Published
Abstract [en]

In this paper we report the study of down-shifting silica-zirconia glass and glass-ceramic films doped by Tb3+ ions and Ag nanoaggregates, which combine the typical spectral properties of the rare-earth-ions with the broadband sensitizing effect of the metal nanostructures. Na-Tb co-doped silica-zirconia samples were obtained by a modified sol-gel route. Dip-coating deposition followed by annealing for solvent evaporation and matrix densification were repeated several times, obtaining a homogeneous crack-free film. A final treatment at 700 °C or 1000 °C was performed to control the nanoscale structural properties of the samples, resulting respectively in a glass (G) or a glass-ceramic (GC), where tetragonal zirconia nanocrystals are surrounded by an amorphous silica matrix. Ag introduction was then achieved by ion-exchange in a molten salt bath, followed by annealing in air to control the migration and aggregation of the metal ions. The comparison of the structural, compositional and optical properties are presented for G and GC samples, providing evidence of highly efficient photoluminescence enhancement in both systems, slightly better in G than in GC samples, with a remarkable increase of the green Tb3+ PL emission at 330 nm excitation: 12 times for G and 8 times for GC samples. Furthermore, after Ag-exchange, the shape of Tb3+ excitation resembles the one of Ag ions/nanoaggregates, with a broad significant absorption in the whole UV-blue spectral region. This broadband enhanced downshifting could find potential applications in lighting devices and in PV solar cells.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-70344 (URN)10.1016/j.optmat.2018.07.074 (DOI)000446145200099 ()2-s2.0-85050857389 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-13 (andbra)

Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2018-10-22Bibliographically approved
Yusupov, K., Stumpf, S., You, S., Bogach, A., Martinez, P. M., Zakhidov, A., . . . Vomiero, A. (2018). Flexible Thermoelectric Polymer Composites Based on a Carbon Nanotubes Forest. Advanced Functional Materials, 28(40), Article ID 1801246.
Open this publication in new window or tab >>Flexible Thermoelectric Polymer Composites Based on a Carbon Nanotubes Forest
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2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 40, article id 1801246Article in journal (Refereed) Published
Abstract [en]

Polymer-based composites are of high interest in the field of thermoelectric (TE) materials because of their properties: abundance, low thermal conductivity, and nontoxicity. In applications, like TE for wearable energy harvesting, where low operating temperatures are required, polymer composites demonstrate compatible with the targeted specifications. The main challenge is reaching high TE efficiency. Fillers and chemical treatments can be used to enhance TE performance of the polymer matrix. The combined application of vertically aligned carbon nanotubes forest (VA-CNTF) is demonstrated as fillers and chemical post-treatment to obtain high-efficiency TE composites, by dispersing VA-CNTF into a poly (3,4-ethylenedioxythiophene) polystyrene sulfonate matrix. The VA-CNTF keeps the functional properties even in flexible substrates. The morphology, structure, composition, and functional features of the composites are thoroughly investigated. A dramatic increase of power factor is observed at the lowest operating temperature difference ever reported. The highest Seebeck coefficient and electrical conductivity are 58.7 μV K-1 and 1131 S cm-1, respectively. The highest power factor after treatment is twice as high in untreated samples. The results demonstrate the potential for the combined application of VA-CNTF and chemical post-treatment, in boosting the TE properties of composite polymers toward the development of high efficiency, low-temperature, flexible TEs.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-70421 (URN)10.1002/adfm.201801246 (DOI)000446155700001 ()2-s2.0-85051061872 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-03 (johcin)

Available from: 2018-08-15 Created: 2018-08-15 Last updated: 2018-10-22Bibliographically approved
Ghamgosar, P., Rigoni, F., You, S., Dobryden, I., Gilzad Kohan, M., Pellegrino, A. L., . . . Vomiero, A. (2018). ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors. Nano Energy, 51, 308-316
Open this publication in new window or tab >>ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 51, p. 308-316Article in journal (Refereed) Published
Abstract [en]

In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap Eg=3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 °C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 °C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0 V bias voltage up to 7.7 µA/W and time response ≤0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-69838 (URN)10.1016/j.nanoen.2018.06.058 (DOI)000440682100034 ()2-s2.0-85049324019 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-02 (rokbeg)

Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2019-04-19Bibliographically approved
Prikhna, T., Noudem, J., Gawalek, W., Mamalis, A. G., Soldatov, A., Savchuk, Y., . . . Kuznietsov, R. (2012). Spark plasma synthesis and sintering of superconducting MgB 2-based materials (ed.). In: (Ed.), A.G. Mamalis; A. Kaladas; M. Enokizono (Ed.), Applied Electromagnetic Engineering for Magnetic, Superconducting and Nano Materials: Selected Peer Reviewed Papers from the Selected Peer-reviewed Papers from the Seventh Japanese-mediterranean and Central European Workshop. Paper presented at Japanese-Mediterranean and Central European Workshop on Applied Electromagnetic Engineering for Magnetic, Superconducting and Nano Materials : 06/07/2011 - 09/07/2011 (pp. 42437). : Trans Tech Publications Inc.
Open this publication in new window or tab >>Spark plasma synthesis and sintering of superconducting MgB 2-based materials
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2012 (English)In: Applied Electromagnetic Engineering for Magnetic, Superconducting and Nano Materials: Selected Peer Reviewed Papers from the Selected Peer-reviewed Papers from the Seventh Japanese-mediterranean and Central European Workshop / [ed] A.G. Mamalis; A. Kaladas; M. Enokizono, Trans Tech Publications Inc., 2012, p. 42437-Conference paper, Published paper (Refereed)
Abstract [en]

Superconducting (SC) and mechanical properties of spark plasma (or SPS) produced MgB 2 -based materials allow their efficient applications in fault current limiters, superconducting electromotors, pumps, generators, magnetic bearings, etc. The synthesized from Mg and B at 50 MPa, 1050 °C for 30 min material has a density of 2.52 g/cm 3, critical current density, j c = 7.1·10 5 A/cm 2 at 10 K , 5.4·10 5 A/cm 2 at 20 K, and 9·10 4 A/cm 2 at 35 K in zero magnetic field; at 20 K its field of irreversibility B irr(20)=7 T and upper critical field B c2(20)=11 T; microhardness H V=10.5 GPa and fracture toughness K 1C =1.7 MPa·m 1/2 at 4.9 N-load. SPS-manufactured in- situ MgB 2- based materials usually have somewhat higher j c than sintered ex-situ. The pressure variations from 16 to 96 MPa during the SPS-process did not affect material SC characteristics significantly; the j c at 10-20 K was slightly higher and the material density was higher by 11%, when pressures of 50-96 MPa were used. The structure of SPS-produced MgB 2 material contains Mg-B-O inclusions and inclusions of higher borides (of compositions near MgB 4, MgB 7, MgB 12, MgB 17, MgB 20), which can be pinning centers. The presence of higher borides in the MgB 2 structure can be revealed by the SEM and Raman spectroscopy.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2012
Series
Materials Science Forum, ISSN 0255-5476 ; 721
National Category
Other Physics Topics
Research subject
Experimental physics
Identifiers
urn:nbn:se:ltu:diva-30249 (URN)10.4028/www.scientific.net/MSF.721.3 (DOI)000309323300001 ()2-s2.0-84864248198 (Scopus ID)4044ba8a-48fd-447e-a4c3-83c1f454d55d (Local ID)978-3-03785-420-4 (ISBN)4044ba8a-48fd-447e-a4c3-83c1f454d55d (Archive number)4044ba8a-48fd-447e-a4c3-83c1f454d55d (OAI)
Conference
Japanese-Mediterranean and Central European Workshop on Applied Electromagnetic Engineering for Magnetic, Superconducting and Nano Materials : 06/07/2011 - 09/07/2011
Note
Validerad; 2012; 20120807 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-07-10Bibliographically approved
Prikhna,, T., Gawalek, W., Savchuk, Y., Soldatov, A., Sokolovsky, V., Eisterer,, M., . . . Sverdun, V. (2011). Effects of high pressure on the physical properties of MgB2 (ed.). Journal of Superconductivity and Novel Magnetism, 24(5), 137-150
Open this publication in new window or tab >>Effects of high pressure on the physical properties of MgB2
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2011 (English)In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 24, no 5, p. 137-150Article in journal (Refereed) Published
Abstract [en]

The synthesis of MgB2-based materials under high pressure gave the possibility to suppress the evaporation of magnesium and to obtain near theoretically dense nanograined structures with high superconducting, thermal conducting, and mechanical characteristics: critical current densities of 1.8-1.0×106 A/cm2 in the self-field and 103 A/cm2 in a magnetic field of 8 T at 20 K, 5-3×105 A/cm2 in self-field at 30 K, the corresponding critical fields being Hc2=15 T at 22 K and irreversible fields Hirr=13 T at 20 K, and Hirr=3.5 T at 30 K, thermal conduction of 53±2 W/(m{dot operator}K), the Vickers hardness HV=10.12±0.2 GPa under a load of 148.8 N and the fracture toughness K1 C=7.6±2.0 MPa{dot operator}m0.5 under the same load, the Young modulus E=213 GPa. Estimation of quenching current and AC losses allowed the conclusion that high-pressure-prepared materials are promising for application in transformer-type fault current limiters working at 20-30 K.

National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-2417 (URN)10.1007/s10948-010-0909-3 (DOI)000289855700020 ()2-s2.0-80052153798 (Scopus ID)0098fe20-d77b-11df-8b36-000ea68e967b (Local ID)0098fe20-d77b-11df-8b36-000ea68e967b (Archive number)0098fe20-d77b-11df-8b36-000ea68e967b (OAI)
Note

Validerad; 2011; 20101014 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Prikhna, T. A., Gawalek, W. ., Goldacker, W., Savchuk, Y. M. ., Noudem, J., Soldatov, A., . . . Sverdun, V. (2011). High-pressure synthesized nanostructural MgB2 materials with high performance of superconductivity, suitable for fault current limitation and other applications (ed.). Paper presented at . IEEE transactions on applied superconductivity (Print), 21(3), 2694-2697
Open this publication in new window or tab >>High-pressure synthesized nanostructural MgB2 materials with high performance of superconductivity, suitable for fault current limitation and other applications
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2011 (English)In: IEEE transactions on applied superconductivity (Print), ISSN 1051-8223, E-ISSN 1558-2515, Vol. 21, no 3, p. 2694-2697Article in journal (Refereed) Published
Abstract [en]

A variety of samples made via different routes were investigated. Samples are nanostructured (average grain sizes are about 20 nm). The advantage of high-pressure (HP)-manufactured (2 GPa, 800-1050 degrees C, 1 h) MgB2 bulk is the possibility to get almost theoretically dense (1-2% porosity) material with very high critical current densities reaching at 20 K, in 0-1 T j(c) = 1.2 - 1.0 . 10(6) A/cm(2) (with 10% SiC doping) and j(c) = 9.2 - 7.3 10(5) A/cm(2) (without doping). Mechanical properties are also very high: fracture toughness up to 4.4 +/- 0.04 MPa . m(0.5) and 7.6 +/- 2.0 MPa . m(0.5) at 148.8 N load for MgB2 undoped and doped with 10% Ta, respectively. The HP-synthesized material at moderate temperature (2 GPa, 600 degrees C, 1 h) from B with high amount of impurity C (3.15%) and H (0.87%) has j(c) = 10(3) A/cm(2) in 8 T field at 20 K, highest irreversibility fields (at 18.4 K H-irr = 15 T) and upper critical fields (at 22 K H-C2 = 15 T) but 17% porosity. HP materials with stoichiometry near MgB12 can have T-c = 37 K and j(c) = 6 . 10(4) A/cm(2) at 0 T and H-irr = 5 T at 20 K. The spark plasma synthesized (SPS) material (50 MPa, 600-1050 degrees C 1.3 h, without additions), demonstrated at 20 K, in 0-1 T j(c) = 4.5 - 4 10(5) A/cm(2). Dispersed inclusions of higher magnesium borides, which are usually present in MgB2 structure and obviously create new pinning centers can be revealed by Raman spectroscopy (for the first time a spectrum of MgB7 was obtained). Tests of quench behavior, losses on MgB2 rings and material thermal conductivity show promising properties for fault current limiters. Due to high critical fields, the material can be used for magnets

National Category
Other Physics Topics
Research subject
Fysik
Identifiers
urn:nbn:se:ltu:diva-7563 (URN)10.1109/TASC.2010.2096494 (DOI)000291068200047 ()2-s2.0-79957965073 (Scopus ID)5f27208c-afa6-447f-b6a3-7849731ee23c (Local ID)5f27208c-afa6-447f-b6a3-7849731ee23c (Archive number)5f27208c-afa6-447f-b6a3-7849731ee23c (OAI)
Note
Validerad; 2011; 20110617 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7475-6394

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