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Loberg, Bengt
Publications (10 of 29) Show all publications
Larker, R., Wei, L.-Y., Loberg, B., Olsson, M. & Johansson, S. (1994). AEM investigation of ceramic/incology 909 diffusional reactions after joining by HIP (ed.). Paper presented at . Journal of Materials Science, 29(16), 4404-4414
Open this publication in new window or tab >>AEM investigation of ceramic/incology 909 diffusional reactions after joining by HIP
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1994 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 29, no 16, p. 4404-4414Article in journal (Refereed) Published
Abstract [en]

Diffusion bonding by hot isostatic pressing (HIP) was performed between Incoloy 909 and five different ceramics. Two of the ceramics were composites made from powder mixtures of Si3N4 and either 60 vol% TiN or 50 vol% TiB2, while three were monolithic materials, namely Si3N4 with 2.5 wt% Y2O3 as a sintering additive, Si3N4 without additives, and Si2 N2O without additives. A diffusion couple geometry was developed to facilitate the preparation of thin-foil specimens for examination by analytical electron microscopy (AEM). Diffusion bonding was performed by HIP at 927°C (1200K) and 200 MPa for 4 h. The formation of reaction layers was very limited, being less than 1 μm in total layer thickness. Two reaction products were found by AEM; a continuous, very thin, (≤100 nm) layer of fine TiN crystals at the initial ceramic/metal interface, and larger grains extending about 100–500 nm into the superalloy and forming a semi-continuous layer of a G-phase suicide containing mainly nickel, silicon and niobium.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-4144 (URN)10.1007/BF00414229 (DOI)A1994PD44500038 ()2-s2.0-0028482745 (Scopus ID)20903170-f3e6-11db-ac9f-000ea68e967b (Local ID)20903170-f3e6-11db-ac9f-000ea68e967b (Archive number)20903170-f3e6-11db-ac9f-000ea68e967b (OAI)
Note
Godkänd; 1994; 20070426 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Niska, J. & Loberg, B. (1994). Hot isostatic pressing of high temperature superconducting ceramics (ed.). Paper presented at . Materials technology (New York, N.Y.), 9(9-10), 211-215
Open this publication in new window or tab >>Hot isostatic pressing of high temperature superconducting ceramics
1994 (English)In: Materials technology (New York, N.Y.), ISSN 1066-7857, E-ISSN 1753-5557, Vol. 9, no 9-10, p. 211-215Article in journal (Refereed) Published
Abstract [en]

Large specimens of ceramic superconductors are difficult to solid-state sinter to full density, while maintaining superconductivity, without the high temperatures and pressures found in a hot isostatic press (HIP). HIPing can give highly dense, superconducting Bi2Sr2CaCu2O8 (Bi2212) and Bi2Sr2Ca2Cu3O10 (Bi2223) with only slight decomposition. If Y123 is HIPed to full density in a metal capsule, then the nonsuperconducting tetragonal phase forms as a result of decomposition. HIPing of CuO plus YBa2Cu3O7 gives highly dense, superconducting YBa2Cu4O8 (Y124), which is stable at high temperatures and oxygen pressures.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-5281 (URN)35711540-f3e7-11db-ac9f-000ea68e967b (Local ID)35711540-f3e7-11db-ac9f-000ea68e967b (Archive number)35711540-f3e7-11db-ac9f-000ea68e967b (OAI)
Note
Godkänd; 1994; 20070426 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Grishin, A., Niska, J., Loberg, B. & Weber, H. (1994). Straightened voltage effect in high-Tc superconductors (ed.). Paper presented at . Journal of Applied Physics, 76(10), 6947-6949
Open this publication in new window or tab >>Straightened voltage effect in high-Tc superconductors
1994 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 76, no 10, p. 6947-6949Article in journal (Refereed) Published
Abstract [en]

A new effect called ``ac-current straightening'' has been observed in ceramic (Bi,Pb)-2223 slabs carrying ac current Idc+Iac cos(ωt). The current-voltage (I-V) characteristics of the ceramic were measured at 77 K at frequencies ranging from 50 to 20 000 Hz. A spectrum analyzer showed a series of high harmonics in the voltage signal as well as a constant voltage drop. The full set of experimental data has been explained theoretically using the Bean-Kim critical state model with a magnetic field dependent critical current jc(H)=jc(0)/(1+H/H0). A low transport ac current gives a voltage linearly proportional to the frequency and quadratically proportional to the ac-current amplitude Iac. It consists of odd harmonics only. If a bias dc current is switched on, then even harmonics and a dc-voltage drop appear. Their amplitudes are proportional to the small parameter Iac/cH0 and depend on the Idc/Iac ratio.

National Category
Other Materials Engineering Other Physics Topics
Research subject
Engineering Materials; Fysik
Identifiers
urn:nbn:se:ltu:diva-15831 (URN)10.1063/1.358083 (DOI)A1994PT84800305 ()2-s2.0-0009125688 (Scopus ID)f638e3a0-e6c9-11db-8a98-000ea68e967b (Local ID)f638e3a0-e6c9-11db-8a98-000ea68e967b (Archive number)f638e3a0-e6c9-11db-8a98-000ea68e967b (OAI)
Note
Godkänd; 1994; 20070409 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Andersson, B., Sundqvist, B., Niska, J. & Loberg, B. (1994). Thermal conductivity of polycrystalline YBa2Cu4O8 (ed.). Paper presented at . Physical Review B Condensed Matter, 49(6), 4189-4198
Open this publication in new window or tab >>Thermal conductivity of polycrystalline YBa2Cu4O8
1994 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 49, no 6, p. 4189-4198Article in journal (Refereed) Published
Abstract [en]

We have measured the thermal conductivity κ and the thermal diffusivity a of a dense bulk ceramic polycrystalline sample of YBa2Cu4O8 (1:2:4) in the temperature range 30-300 K. We find κ≊10 W m-1 K-1 at 100 K, significantly higher than in ceramic YBa2Cu3O7-δ (1:2:3) and approaching the in-plane value for single-crystal 1:2:3, and decreasing to 7.6 W m-1 K-1 at 300 K. The data for this sample can be described by standard theories for phonon thermal conductivity of crystalline materials with boundary, phonon, and electron scattering. The higher κ in 1:2:4 as compared to 1:2:3 is, in this model, due to the smaller point defect scattering in the former. The fitted parameters for the three scattering mechanisms all agree with independent estimates based on simple models; inserting data for electric resistivity, grain size, carrier density, and lattice properties we can predict κ and its T dependence to within about 20%. We also discuss models for the phonon and electron thermal conductivities in some detail, including some second-order effects such as inelastic electron scattering and a T-dependent carrier density.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-15106 (URN)10.1103/PhysRevB.49.4189 (DOI)A1994MW35100059 ()2-s2.0-24244473445 (Scopus ID)e9185570-13b4-11dd-b7d2-000ea68e967b (Local ID)e9185570-13b4-11dd-b7d2-000ea68e967b (Archive number)e9185570-13b4-11dd-b7d2-000ea68e967b (OAI)
Note
Godkänd; 1994; 20080426 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Niska, J. & Loberg, B. (1993). Evidence for unpinned magnetic flux vortices above the Ic transition in the 2223-phase high-Tc superconductor (ed.). Paper presented at . Journal of Superconductivity, 6(4), 255-259
Open this publication in new window or tab >>Evidence for unpinned magnetic flux vortices above the Ic transition in the 2223-phase high-Tc superconductor
1993 (English)In: Journal of Superconductivity, ISSN 0896-1107, E-ISSN 1572-9605, Vol. 6, no 4, p. 255-259Article in journal (Refereed) Published
Abstract [en]

similarity in the dc voltage-current (V I) curves for both direct and alternating transport currents is used to propose that unpinned flux vortices are generated above the Ic transition for dc transport currents, when Abrikosov flux vortices begin to penetrate the superconductor. Two methods can be used to give a dc voltage drop for an ac transport current: (1) if there is a slight dc voltage in the ac current which favors vortex loop collapse as in a traditional dc Ic test, or (2) if an asymmetric transverse magnetic field is present which favors vortex loop collapse for current in one direction over the reverse direction.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-2897 (URN)10.1007/BF00626266 (DOI)A1993MC60800007 ()2-s2.0-0027646702 (Scopus ID)0a0e1630-f3e4-11db-ac9f-000ea68e967b (Local ID)0a0e1630-f3e4-11db-ac9f-000ea68e967b (Archive number)0a0e1630-f3e4-11db-ac9f-000ea68e967b (OAI)
Note
Godkänd; 1993; 20070426 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Loberg, B., Niska, J., Rubin, P. & Gustafsson, R. (1993). High critical currents in Bi-2223 phase bars (ed.). Paper presented at . Cryogenics (Guildford), 33(5), 475-476
Open this publication in new window or tab >>High critical currents in Bi-2223 phase bars
1993 (English)In: Cryogenics (Guildford), ISSN 0011-2275, E-ISSN 1879-2235, Vol. 33, no 5, p. 475-476Article in journal (Refereed) Published
Abstract [en]

The critical current Ic and the critical current density Jc of Bi-2223 phase bars have been found to depend on the mass density of the bars. Bars densified using a cold isostatic pressing (CIPing) process have been obtained with transport critical currents of gt;150 A with Jc levels up to approximately equals 103 A cm-2 at 77 K in the absence of an applied magnetic field. Bending or kinking of the grains may promote densification during CIPing of a sintered bar.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-13360 (URN)10.1016/0011-2275(93)90237-I (DOI)A1993KZ00300001 ()2-s2.0-0027597216 (Scopus ID)c9328300-f3e6-11db-ac9f-000ea68e967b (Local ID)c9328300-f3e6-11db-ac9f-000ea68e967b (Archive number)c9328300-f3e6-11db-ac9f-000ea68e967b (OAI)
Note
Godkänd; 1993; 20070426 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Niska, J., Babushki, O. & Loberg, B. (1993). High-temperature X-ray diffraction of the PbBi-2223 phase superconductor in different atmospheres (ed.). Paper presented at . Journal of materials science letters, 12(17), 1337-1339
Open this publication in new window or tab >>High-temperature X-ray diffraction of the PbBi-2223 phase superconductor in different atmospheres
1993 (English)In: Journal of materials science letters, ISSN 0261-8028, E-ISSN 1573-4811, Vol. 12, no 17, p. 1337-1339Article in journal (Refereed) Published
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-12330 (URN)10.1007/BF00241700 (DOI)2-s2.0-34250075286 (Scopus ID)b73b1930-e609-11dc-bcb4-000ea68e967b (Local ID)b73b1930-e609-11dc-bcb4-000ea68e967b (Archive number)b73b1930-e609-11dc-bcb4-000ea68e967b (OAI)
Note
Godkänd; 1993; 20080228 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Loberg, B., Niska, J. & Rubin, P. (1993). Measurements of the self-field limitations of the critical current in Bi-2223 superconductive bars (ed.). In: (Ed.), (Ed.), Proceedings of the 3rd international conference and exhibition: World Congress on Superconductivity : 15 - 18 September 1992, Munich, Germany. Paper presented at World Congress on Superconductivity : 15/09/1992 - 18/09/1992 (pp. 1757-1762). Oxford: Pergamon Press
Open this publication in new window or tab >>Measurements of the self-field limitations of the critical current in Bi-2223 superconductive bars
1993 (English)In: Proceedings of the 3rd international conference and exhibition: World Congress on Superconductivity : 15 - 18 September 1992, Munich, Germany, Oxford: Pergamon Press, 1993, p. 1757-1762Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Oxford: Pergamon Press, 1993
Series
Applied Superconductivity, ISSN 0964-1807 ; 10-12 pt 3
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-36925 (URN)27675765 (Scopus ID)ac00af40-fd3d-11db-b816-000ea68e967b (Local ID)ac00af40-fd3d-11db-b816-000ea68e967b (Archive number)ac00af40-fd3d-11db-b816-000ea68e967b (OAI)
Conference
World Congress on Superconductivity : 15/09/1992 - 18/09/1992
Note
Godkänd; 1993; 20070508 (cira)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Larker, R., Wei, L.-Y., Olsson, M. & Loberg, B. (1992). Diffusion bonding of Si3N4/TiN and Si3N4/TiB2 composites to Incoloy 909 (ed.). In: (Ed.), Roger Carlsson; Thomas Johansson; Lars Kahlman (Ed.), 4th International Symposium on Ceramic Materials and Components for Engines: [proceedings ... held at Göteborg, Sweden, 10 - 12 June 1991]. Paper presented at International Symposium on Ceramic Materials and Components for Engines : 10/06/1991 - 10/06/1991 (pp. 340-347). London: Elsevier
Open this publication in new window or tab >>Diffusion bonding of Si3N4/TiN and Si3N4/TiB2 composites to Incoloy 909
1992 (English)In: 4th International Symposium on Ceramic Materials and Components for Engines: [proceedings ... held at Göteborg, Sweden, 10 - 12 June 1991] / [ed] Roger Carlsson; Thomas Johansson; Lars Kahlman, London: Elsevier, 1992, p. 340-347Conference paper, Published paper (Refereed)
Abstract [en]

Hot isostatic pressed (HIPed) mixtures of Si3N4/60%TiN and Si3N4 /50%TiB2 were joined to Incoloy 909 (42%Fe, 38%Ni, 12.9%Cr, 4.7%Nb, 1.5%Ti, 0.4%Si) by hot isostatic pressing at 927 deg.C and 200 MPa. Microstructure (TEM and STEM) and diffusion profiles are reported and discussed. The work is relevant to the use of graded ceramics to reduce thermomechanical stresses in silicon nitride /superalloy joints

Place, publisher, year, edition, pages
London: Elsevier, 1992
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-39525 (URN)e50fc8f0-1d36-11de-aa3f-000ea68e967b (Local ID)1-85166-776-8 (ISBN)e50fc8f0-1d36-11de-aa3f-000ea68e967b (Archive number)e50fc8f0-1d36-11de-aa3f-000ea68e967b (OAI)
Conference
International Symposium on Ceramic Materials and Components for Engines : 10/06/1991 - 10/06/1991
Note
Godkänd; 1992; 20090330 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Larker, R., Nissen, A., Pejryd, L. & Loberg, B. (1992). Diffusion bonding reactions between a SiC/SiC composite and two superalloys during joining by hot isostatic pressing (ed.). Paper presented at . Acta Metallurgica et Materialia, 40(11), 3129-3139
Open this publication in new window or tab >>Diffusion bonding reactions between a SiC/SiC composite and two superalloys during joining by hot isostatic pressing
1992 (English)In: Acta Metallurgica et Materialia, ISSN 0956-7151, Vol. 40, no 11, p. 3129-3139Article in journal (Refereed) Published
Abstract [en]

Diffusion reactions during solid state joining of a ceramic SiC/SiC composite to two superalloys, Hastelloy X and Incoloy 909, by hot isostatic pressing (HIP) have been investigated. The HIP pressure was 200 MPa in all joining cycles, and the temperature/dwell time were either 800°C/15 min, 900°C/1 h or 1000°C/1 h. The reaction zones formed consisted of a thin layer of carbides surrounded by several layers containing silicides and free carbon. The thicknesses of the reaction layers increased with increasing temperature, but were more affected by the composition of the alloy. With more carbide formers in the alloy, the thickness of the reaction layer decreased. The SiC composite was found to be considerably more prone to reactions with these superalloys during HIP as compared to Si3N4 under similar conditions

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-8076 (URN)10.1016/0956-7151(92)90476-U (DOI)A1992JT43100030 ()2-s2.0-0026945878 (Scopus ID)6839bc40-f48a-11db-ac9f-000ea68e967b (Local ID)6839bc40-f48a-11db-ac9f-000ea68e967b (Archive number)6839bc40-f48a-11db-ac9f-000ea68e967b (OAI)
Note
Godkänd; 1992; 20070427 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved

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