Vidar Folke Hansen

• Adasooriya, Mudiyan Nirosha Damayanthi; Tucho, Wakshum Mekonnen; Holm, Erlend; Årthun, Terje; Hansen, Vidar; Solheim, Karl Gunnar & Hemmingsen, Tor (2020). Effect of hydrogen on mechanical properties and fracture of martensitic carbon steel under quenched and tempered conditions. Materials Science & Engineering: A.  ISSN 0921-5093.  803 . doi: 10.1016/j.msea.2020.140495
• Belsvik, Marius Aga; Tucho, Wakshum Mekonnen & Hansen, Vidar (2020). Microstructural studies of direct‑laser‑deposited stainless steel 316L‑Si on 316L base material. SN Applied Sciences.  ISSN 2523-3963.  2 . doi: 10.1007/s42452-020-03530-3
• Hansen, Vidar; Kosinskiy, Andrey & Taftø, Johan (2020). Distinguishing space groups by electron channelling: centrosymmetric full-Heusler or non-centrosymmetric half-Heusler?. Acta Crystallographica Section A: Foundations and Advances.  ISSN 2053-2733.  A76, s 211- 213 . doi: 10.1107/S2053273319016942 Full text in Research Archive.
• Delimitis, Andreas; Hansen, Vidar & Gjønnes, Jon (2019). Geometry determination and refinement in the rotation electron diffraction technique. Ultramicroscopy.  ISSN 0304-3991.  201, s 68- 76 . doi: 10.1016/j.ultramic.2019.02.011 Full text in Research Archive. Show summary

  The necessary parameters (rotation axis, incident electron beam direction and beam tilt path) in order to describe the diffraction geometry in the Rotation Electron Diffraction (RED) method during data collection are determined and refined. These parameters are prerequisites for the subsequent calculations of excitation errors, sg, for zero (ZOLZ) or higher order Laue zones (HOLZ) reflections. Comparison with simulated results, for a CoP3 thermoelectric crystal, shows excellent agreement between the two approaches -calculated and simulated. In addition to their determination, a thorough refinement methodology for the incident electron beam direction and beam tilt path has been applied, too, based on Kikuchi lines of HOLZ reflections. Incorporation of the refined excitation error values can be considered both in theoretical calculations for diffracted beam intensities, based on the Bloch wave method, as well as in deducing integrated intensities from experimental rocking curves. The methodology described in this study is quite indispensable, as it forms an essential step for performing dynamical calculations in RED, enabling thus enhanced accuracy in structural parameter clarification. The latter is especially important in the case of thermal factors refinement for e.g. thermoelectrics, which are imperative for material properties’ evaluation.

• Guo, Kun; Hansen, Vidar; Li, Hailong & Yu, Zhixin (2018). Monodispersed nickel and cobalt nanoparticles in desulfurization of thiophene for in-situ upgrading of heavy crude oil. Fuel.  ISSN 0016-2361.  211, s 697- 703 . doi: 10.1016/j.fuel.2017.09.097 Show summary

  Monodispersed nickel (Ni) and cobalt (Co) nanoparticles (NPs) with different sizes are synthesized via the thermal decomposition of organometallic precursors by controlling the reaction temperature and surfactant amount. X-ray diffraction analysis of the as-prepared NP samples shows the formation of cubic Ni metal phases with good crystallinity, while the cubic Co metal samples are semi-amorphous. Transmission electron microscopy characterization further confirms that two Ni NP samples with average sizes of 9 and 27 nm, and Co NPs with an average size of 6 nm are successfully prepared with a narrow size distribution. Furthermore, catalytic performance of these monodispersed NPs towards the hydrodesulfurization (HDS) reaction, which plays a pivotal role in the upgrading of heavy crude oil, is evaluated under reservoir-relevant conditions using thiophene as a sulfur-containing model compound. Different parameters including particle size, catalyst dosage, hydrogen donor ratio, temperature, and reaction duration are systematically studied to optimize the catalytic HDS performance. The morphology and size of the spent NP catalysts after the reaction are also analyzed. The results show that the 9 nm Ni NPs exhibit the best HDS activity and stability compared with other catalysts, which suggests that such well-dispersed Ni NPs are promising candidates for the in-situ upgrading and recovery of heavy crude oil from underground reservoirs.

• Hansen, Vidar; Echevarria-Bonet, Cristina; Minde, Mona Wetrhus & Taftø, Johan (2018). Determination of atomic positions and polar direction in half-Heusler material Sb1- xSnxTi1-y-zHfyZrzCo using electron channeling. AIP Advances.  ISSN 2158-3226.  8(12), s 1- 9 . doi: 10.1063/1.5042816 Full text in Research Archive.
• Hjuler, M.Leth; Hansen, Vidar & Fabricius, Ida Lykke (2018). Interpretational challenges related to studies of chalk particle surfaces in scanning and transmission electron microscopy. Bulletin of the Geological Society of Denmark.  ISSN 0011-6297.  66, s 151- 165
• Tucho, Wakshum Mekonnen & Hansen, Vidar (2018). Characterization of SLM-fabricated Inconel 718 after solid solution and precipitation hardening heat treatments. Journal of Materials Science.  ISSN 0022-2461.  54(1), s 823- 839 . doi: 10.1007/s10853-018-2851-x
• Tucho, Wakshum Mekonnen; Lysne, Vidar Hellandsjø; Austbø, Jon Håkon; Sjølyst-Kverneland, Atle & Hansen, Vidar (2018). Investigation of effects of process parameters on microstructure and hardness of SLM manufactured SS316L. Journal of Alloys and Compounds.  ISSN 0925-8388.  740, s 910- 925 . doi: 10.1016/j.jallcom.2018.01.098
• Buxhuku, Mika; Hansen, Vidar & Gjønnes, Jon (2017). The measurement of intensities in the Rotation Electron Diffraction Technique. Micron.  ISSN 0968-4328.  101, s 103- 107 . doi: 10.1016/j.micron.2017.06.006
• Tucho, Wakshum Mekonnen; Cuvillier, Priscille; Sjølyst-Kverneland, Atle & Hansen, Vidar (2017). Microstructure and hardness studies of Inconel 718 manufactured by selective laser melting before and after solution heat treatment. Materials Science & Engineering: A.  ISSN 0921-5093.  689, s 220- 232 . doi: 10.1016/j.msea.2017.02.062
• Buxhuku, Mika; Hansen, Vidar; Oleynikov, Peter & Gjønnes, Jon (2013). The determination of rotation axis in the Rotation Electron Diffraction Technique. Microscopy and Microanalysis.  ISSN 1431-9276.  19(5), s 1276- 1280 . doi: 10.1017/S1431927613012749
• Sjølyst-Kverneland, Atle; Hansen, Vidar; Thorkildsen, Gunnar; Larsen, Helge Bøvik; Pattison, P; Li, X.Z. & Gjønnes, Jon (2011). Transformations and structures in the Al-Zn-Mg alloy system: A diffraction study using synchrotron radiation and electron precession. Materials Science & Engineering: A.  ISSN 0921-5093.  528(3), s 880- 887 . doi: 10.1016/j.msea.2010.10.001
• Sjølyst-Kverneland, Atle; Hansen, Vidar; Thorkildsen, Gunnar; Larsen, Helge Bøvik; Pattison, Philip; Li, XZ & Gjønnes, Jon (2010). Transformations and structures in the Al?Zn?Mg alloy system: A diffraction study using synchrotron radiation and electron precession. Materials Science & Engineering: A.  ISSN 0921-5093. . doi: 10.1016/j.msea.2010.10.001 Show summary

  The structure of the hardening ??-phase precipitates in Al?Zn?Mg alloys has been investigated by using precession electron diffraction and X-ray synchrotron radiation diffraction. The latter was recorded as a three-dimensional, continuous intensity distribution from a single alloy grain, from which patterns of remarkable sharpness from the precipitate particles could be extracted. High resolution electron microscopy revealed extensive structural variations with prolific faults in the ?? precipitates. The ??-structures are described in terms of two structure models based on two icosahedral elements that are inherent in the equilibrium ?-MgZn2 structure. The role of these icosahedra in the transformations of the alloy system is discussed.

• Haakenaasen, Randi; Selvig, Espen; Hadzialic, S; Skauli, Torbjørn; Hansen, Vidar; Tibballs, J.E.; Steen, Harald; Foss, S.; Trosdahl-Iversen, Laila; Tafto, Johan; Halsall, M. & Orr, John (2008). Nanowires in the CdHgTe material system. Journal of Electronic Materials.  ISSN 0361-5235.  37(9), s 1311- 1317 Show summary

  HgTe nanowires have been grown by molecular beam epitaxy (MBE). They are nucleated at Au particles on Si or GaAs substrates and subsequently self-organize and grow laterally on the surface into 20-50 nm wide, 0.5-1 mu m long twisted, but single-crystal, wires. Further growth gives longer, wider, and straighter polycrystalline wires. When unimpeded by Au particles on the surface, the wires become straight and consist of segments of cubic < 111 > HgTe and hexagonal < 001 > Te parallel to the wire. Te nanowires and Au nanowires have also occasionally been formed. All attempts to grow CdHgTe on Si substrates with or without Au particles have resulted in polycrystalline layers. The phase diagrams and diffusion coefficients imply that CdHgTe or HgTe nanowires will not grow by the vapor-liquid-solid technique at the low MBE growth temperatures. SiO2 functions as a mask for selective growth of HgTe, but not for CdHgTe.

• Selvig, Espen; Hadzialic, S; Skauli, Torbjørn; Steen, Harald; Hansen, Vidar; Trosdahl-Iversen, L; van Rheenen, Arthur D.; Lorentzen, T & Haakenaasen, Randi (2006). Growth of HgTe nanowires. Physica scripta. Topical Issues.  ISSN 0281-1847.  126, s 115- 120
• Hansen, Vidar; Vevecka-Priftaj, A; Fjerdingen, J; Langsrud, Y & Gjønnes, Jon (2006). The influence of silicon on age hardening kinetics and phase precipitations in Al-Mg-Zn alloys. Materials Science Forum.  ISSN 0255-5476.  519-521, s 579- 584
• Kverneland, A.; Hansen, Vidar; Vincent, R.; Gjønnes, Kjersti & Gjønnes, Jon (2006). Structure analysis of embedded nano-sized particles by precession electron diffraction. eta '-precipitate in an Al-Zn-Mg alloy as example. Ultramicroscopy.  ISSN 0304-3991.  106(106), s 492- 502
• Gjonnes, J.; Hansen, Vidar & Kverneland, Atle (2004). The precession technique in electron diffraction and its application to structure determination of nano-size precipitates in alloys. Microscopy and Microanalysis.  ISSN 1431-9276.  10, s 16- 20
• Gjønnes, Jon; Hansen, Vidar & Kverneland, Atle (2004). The precession technique in electron diffraction and its application to structure determination of nano-size precipitates in alloys. Microscopy and Microanalysis.  ISSN 1431-9276.  10, s 16- 20
• Hansen, Vidar; Karlsen, Ole Bjørn; Langsrud, Yngve & Gjønnes, Jon (2004). Precipitates, zones and transitions during ageing of Al-Zn-Mg-Zr 7000 series alloy. Materials Science and Technology.  ISSN 0267-0836.  (20), s 185- 193
• Hansen, Vidar; Karlsen, Ole Bjørn; Langsrud, Yngve & Gjønnes, Jon (2004). Precipitates, zones and transitions during aging of Al-Zn-Mg-Zr7000series alloy. Materials Science and Technology.  ISSN 0267-0836.  20, s 185- 193
• Gjønnes, Jon; Hansen, Vidar; Andersen, S.J.; Marioara, C.D. & Li, XZ (2003). Electron crystallography of aluminium alloy phases. ?.  218, s 293- 307
• Berg, Line; Gjønnes, Jon; Hansen, Vidar; Li, X.Z; Knutson-Wedel, Maria; Waterloo, Grethe; Schryvers, D & Wallenberg, L.R. (2001). GP-Zones in Al-Zn-Mg Alloys and Their Role in Artificial Aging. Acta Materialia.  ISSN 1359-6454.  49(17), s 3443- 3451
• Burchardt, Trygve; Hansen, Vidar & Våland, Torstein (2001). Microstructure and catalytic activity towards the hydrogen evolution reaction of electrodeposited NiPx alloys. Electrochimica Acta.  ISSN 0013-4686.  46(18), s 2761- 2766
• Jiang, X.J.; Noble, B.; Hansen, Vidar & Tafto, Johan (2001). Influence of Zirconium and Copper on the Early Stages of Aging in Al-Zn-Mg Alloys. ?.  32A, s 1063- 1073
• Waterloo, Grethe; Hansen, Vidar; Gjønnes, Jon & Skjervold, Svein Roger (2001). Effect of predeformation and preaging at room temperature in Al-Zn-Mg-(Cu,Zr) alloys. Materials Science and Engineering.  ISSN 0025-5416.  (A303), s 226- 233
• Wulff-Pedersen, Erik; Neumann, Else-Ragnhild; Burke, Ernst A. J.; Vannucci, Riccardo; Gjønnes, Jon & Hansen, Vidar (2000). Origin and structural character of Hauyne in spinel dunite xenoliths from La Palma, Canary Island. American Mineralogist.  ISSN 0003-004X.  85, s 1397- 1405

View all works in Cristin

• Delimitis, Andreas; Gjønnes, Jon & Hansen, Vidar Folke (2019). Refinement Approaches in the Diffraction Geometry of the Rotation Electron Diffraction Method. Show summary

  Rotation Electron Diffraction (RED) has been established as a quite powerful method for structure analysis and refinement. Although its capability is based, among others, on eliminating dynamical diffraction effects, some residual ones may still exist, which limit method accuracy. A way of improving RED correctness is to account for these dynamical interactions, by employing Bloch wave calculations to theoretically deduce diffracted beam intensities and estimate structural data. As a first step, the diffraction geometry in RED experiments needs to be precisely determined and refined. In this study, we aim on determining the rotation axis and deriving analytical calculations and refinement of the incident electron beam direction and beam tilt path. This is accomplished by a combination of Kikuchi line pattern analysis and simulation, from zero order and higher order Laue zones (ZOLZ and HOLZ) reflections. Employing Kikuchi lines, especially of HOLZ reflections, is highly suitable as they are extremely sensitive to tilting experiments in RED, thus enabling calculations with increased precision. Subsequent expressions of excitation errors, sg, for ZOLZ and HOLZ reflections will be also deduced. The importance of this methodology for subsequent dynamical calculations of diffracted electron beam intensities by the Bloch wave formalism will be demonstrated. Results of the refinement strategy from RED experiments on thermoelectric materials will be analysed and evaluated.

• Delimitis, Andreas; Gjønnes, Jon & Hansen, Vidar Folke (2019). Rotation Electron Diffraction for Structure Determination and Refinement: Applications in Nanocrystalline Thermoelectrics. Show summary

  Their unparalleled spatial resolution and strong interaction with matter render high energy electrons ideal for structure determination by diffraction methods, some of which date back since the 1950’s. However, it was soon realised that the complex dynamical interactions between electron beams impose a significant drawback towards enhancing data accuracy. A major breakthrough in overcoming this was accomplished initially by Precession Electron Diffraction (PED) and, more recently, by Rotation Electron Diffraction (RED), where the beam intensities can be treated, to a certain extent, kinematically. In addition, RED further enabled the acquisition of complete three dimensional (3D) electron diffraction data, without the need for additional hardware attachments in the transmission electron microscope. Nonetheless, RED experimental outcomes must account for remaining dynamical effects that limit accuracy and precise determination of fine structural parameters, such as thermal ones, i.e. Debye-Waller factors. Incorporating such dynamical effects is accomplished by Bloch wave calculations of diffracted beam intensities, which require a priori determination of excitation errors sg and refinement of diffraction geometry in RED. In this contribution, the methodology to incorporate these dynamical interactions in RED will be presented, focusing on refinement of diffraction geometry and subsequent sg calculations. RED investigations have been predominately applied in materials for renewable technologies and energy harvesting, such as thermoelectrics. Synthesis of thermoelectrics in nanocrystal morphologies is widely exploited with a scope to improve their properties and performance; consequently structure determination by RED, down to refinement of thermal parameters is highly essential.

• Delimitis, Andreas; Hansen, Vidar Folke; Symeou, Elli; Kyratsi, Theodora; Minde, Mona Wetrhus & Taftø, Johan (2019). DETERMINATION OF HOST AND DOPANT ION DISTRIBUTION IN MG2SI1-XSNX THERMOELECTRIC MATERIALS BY ELECTRON CHANNELING. Acta Crystallographica Section A: Foundations and Advances.  ISSN 2053-2733.  75, s e321 . doi: 10.1107/S2053273319092350 Show summary

  Detailed structure studies by electron microscopy methods have been widely exploited due to the unique capabilities electrons provide. Precise identification of atomic positions is feasible by employing spectroscopy techniques in an analytical transmission electron microscope. In this aspect, methods such as energy dispersive Xray spectroscopy (EDS) are utilised, under strong channelling conditions, where the yield of element characteristic X-ray emission can be modified and manipulated, dependent upon crystallographic directions of the incident beam. These channelling effects are powerful in determining atomic site locations in crystals and techniques such as ALCHMI (Atom Location by Channeling Enhanced MIcroanalysis) have been developed and evaluated. Structural analyses employing electron channelling have a recent focus in systems for renewable technologies and energy harvesting, such as thermoelectric (TE) materials. TEs based on Mg2Si1-xSnx have gained increased interest, due to inexpensive production costs, abundancy and a toxic nature of raw materials, especially for power generation applications within the intermediate temperature range (500–900 K). Synthesis of Mg2Si1-xSnx in nanocrystal morphologies, often coupled by incorporation of dopants in their host matrix is exploited, with a scope to efficiently reduce thermal conductivity, particularly for Sn-rich or Bi doped Si-rich compounds. Previous studies confirmed the multiplicity of phases in this system, however, the precise distribution of host and dopant ions location is still controversial. Application of the electron channelling technique is therefore more than essential in order to accurately determine and refine their structural characteristics. Experimental outcomes will be demonstrated and discussed.

• Delimitis, Andreas; Hansen, Vidar Folke; Symeou, Elli; Kyratsi, Theodora; Minde, Mona Wetrhus & Taftø, Johan (2019). Determination of host and dopant ion distribution in Mg2Si1-xSnx thermoelectric materials by electron channeling. Show summary

  Detailed structure studies by electron microscopy methods have been widely exploited due to the unique capabilities electrons provide. Precise identification of atomic positions is feasible by employing spectroscopy techniques in an analytical transmission electron microscope. In this aspect, methods such as energy dispersive X-ray spectroscopy (EDS) are utilised, under strong channeling conditions, where the yield of element characteristic X-ray emission can be modified and manipulated, dependent upon crystallographic directions of the incident beam. These channeling effects are powerful in determining atomic site locations in crystals and techniques such as ALCHEMI (Atom Location by CHanneling Enhanced MIcroanalysis) have been developed and evaluated. Structural analyses employing electron channeling have a recent focus in systems for renewable technologies and energy harvesting, such as thermoelectric (TE) materials. TEs based on Mg2Si1-xSnx have gained increased interest, due to inexpensive production costs, abundancy and atoxic nature of raw materials, especially for power generation applications within the intermediate temperature range (500–900 K). Synthesis of Mg2Si1-xSnx in nanocrystal morphologies, often coupled by incorporation of dopants in their host matrix is exploited, with a scope to efficiently reduce thermal conductivity, particularly for Sn-rich or Bi doped Si-rich compounds. Previous studies confirmed the multiplicity of phases in this system, however, the precise distribution of host and dopant ions location is still controversial. Application of the electron channeling technique is therefore more than essential in order to accurately determine and refine their structural characteristics. Experimental outcomes will be demonstrated and discussed.

• Tofan, Raluca; Echevarria-Bonet, Cristina; Berland, Kristian; Schrade, Matthias; Sørby, Magnus Helgerud; Hauback, Bjørn Christian; Persson, Clas; Prytz, Øystein; Hansen, Vidar & Gunnæs, Anette Eleonora (2016). Microstructural characterization of spark plasma sintered (X,X’)NiSn half‐Heusler alloys.
• Tofan, Raluca; Echevarria-Bonet, Cristina; Berland, Kristian; Schrade, Matthias; Sørby, Magnus Helgerud; Hauback, Bjørn Christian; Persson, Clas; Prytz, Øystein; Hansen, Vidar & Gunnæs, Anette Eleonora (2016). The effect of spark plasma sintering on structure and phase stability in half-Heusler thermoelectric alloys.
• Song, Xin; Persson, Clas; Norby, Truls; Flage-Larsen, Espen; Karlsen, Ole Bjørn; Hansen, Vidar; Gunnæs, Anette Eleonora; Prytz, Øystein; Løvvik, Ole Martin; Finstad, Terje; Valset, Kjetil; Cui, Xuemei; Taftø, Johan; Fjeld, Harald; Hauback, Bjørn & Schrade, Matthias (2014). Conversion of Heat and Energy: Thermoelectrics.
• Buxhuku, Mika; Hansen, Vidar & Gjønnes, Jon (2012). The geometry and measurement of integrated intensities in Rotation Electron Diffraction method.
• Buxhuku, Mika; Hansen, Vidar & Magnus, Sørby (2012). Electron and powder diffraction techniques for accurate structure factors.
• Buxhuku, Mika; Hansen, Vidar; Oleynikov, P. & Gjønnes, Jon (2012). Determination of crystallographic tilt axis in Rotation Electron Diffraction.
• Løvvik, Ole Martin; Valset, Kjetil; Rauwel, Protima; Prytz, Øystein; Flage-Larsen, Espen; Song, Xin; Karlsen, Ole Bjørn; Bording, Jan Kåre; Hansen, Vidar; Norby, Truls; Finstad, Terje & Taftø, Johan (2012). Thermoelectricity in Oslo.
• Qureishy, Thomas; Hansen, Vidar; Karlsen, Ole Bjørn; Gunnæs, Anette Eleonora & Taftø, Johan (2012). Superstructures in Mg2Si1-xSnx.
• Valset, Kjetil; Prytz, Øystein; Hansen, Vidar & Taftø, Johan (2012). Quantitative study of structure factors at large reciprocal vectors using convergent beam electron diffraction: Application to anharmonicity of the thermal motion in Mg2Si.
• Bording, Jan Kåre & Hansen, Vidar (2011, 05. mai). A Totally New Take On Heat Pumps. [Internett].  Efie.net.
• Bording, Jan Kåre & Hansen, Vidar (2011, 30. april). Forskere fra Universitetet i Stavanger Arbeidet med en varmepumpe som varer evig. [Internett].  Azocleantech.
• Bording, Jan Kåre & Hansen, Vidar (2011, 27. april). New heat pump could last 10,000 years, experts say. [Internett].  Environment news blog.
• Bording, Jan Kåre & Hansen, Vidar (2011, 01. mai). Researchers Develop a Heat Pump That Can Last 10,000 Years. [Internett].  Zeitnews. Show summary

  Researchers now are testing an entirely new heat pump. While those we use today last ten to twenty years, the new one will last almost forever.

• Bording, Jan Kåre & Hansen, Vidar (2011, 29. april). Researchers claim that new heat pump can last almost forever?. [Internett].  Engineers Edge.
• Bording, Jan Kåre & Hansen, Vidar (2011, 30. april). Researchers from University of Stavanger Work on a Heat Pump that Lasts Forever. [Internett].  Azocleantech.
• Bording, Jan Kåre & Hansen, Vidar (2011, 05. mai). This heat pump can last 10 000 years. [Internett].  Scientific Computing.
• Bording, Jan Kåre & Hansen, Vidar (2011, 29. april). This heat pump can last 10 000 years. [Internett].  Abovetopsecret.
• Bording, Jan Kåre & Hansen, Vidar (2011, 03. mai). This heat pump can last 10000 years.... [Internett].  Fluid World.
• Bording, Jan Kåre & Hansen, Vidar (2011, 27. april). Wärmepumpen: Kältemittel bald überflüssig. [Internett].  Innovations Report.
• Buxhuku, Mika; Karlsen, Ole Bjorn; Gjønnes, Jon; Gjønnes, Kjesti & Hansen, Vidar (2011). Accurate structure factors of skutterudites:Electron Diffraction Techniques. Acta Crystallographica Section A: Foundations of Crystallography.  ISSN 0108-7673.  67, s 696- 697
• Bording, Jan Kåre & Hansen, Vidar (2010, 23. desember). Denne varmepumpa kan vare i 10 000 år. [Internett].  forskning.no. Show summary

  Forskarar prøver no ut ei heilt ny varmepumpe. Medan dei vi brukar i dag ryk etter ti til tjue år, vil den nye vare nesten evig.

• Bording, Jan Kåre & Hansen, Vidar (2010). Denne varmepumpa kan vare i 10000 år. UniverS : magasin for Universitetet i Stavanger.  4
• Bording, Jan Kåre & Hansen, Vidar (2010, 15. desember). Denne varmepumpa kan vare i 10000 år. Show summary

  Forskarar prøver no ut ei heilt ny varmepumpe. Medan dei vi brukar i dag ryk etter ti til tjue år, vil den nye vare nesten evig.

• Bording, Jan Kåre & Hansen, Vidar (2010). Termoelektrisitet - en "ny type" varmepumpe. Show summary

  Hvordan virker en konvensjonell varmepumpe og hvor effektiv er den. Hva er termoelektrisitet, hvordan kan dette brukes til å varme hus og hva er dets gode og mindre gode egenskaper.

• Bording, Jan Kåre & Hansen, Vidar (2010). Varmepumpe for evigheten. Aftenposten (morgenutg. : trykt utg.).  ISSN 0804-3116.  s 7- 8
• Bording, Jan Kåre & Hansen, Vidar (2010, 18. desember). Varmepumpe for evigheten Form og størrelse kan tilpasses etter behov. Show summary

  Forskere ved Universitetet i Stavanger er i ferd med å utvikle en ny termoelektrisk varmepumpe som vil kunne vare nesten evig.

• Bording, Jan Kåre & Hansen, Vidar (2009). Improved thermoelectric materials through nanostructuring: implications for energy savings. Show summary

  In a small scale test of thermoelectric heat-pumps we have achieved an energy efficiency of 2.65 at a temperature difference of 10 degrees. In the test we used commercial Peltier elements with Bi2Te3 based thermoelectric materials. Thermoelectric materials have a dimensionless figure of merit, ZT, given by where is the absolute temperature, the thermal conductivity, the electrical conductivity and the Seebeck coefficient of the thermoelectric material. is defined by which means that a voltage difference of is set up across the material at a temperature difference . An energy efficient Peltier element needs both a p-type and an n-type thermoelectric material with high ZT, and the efficiency of the Peltier element is somewhat reduced due to parasitic effects. According to general predictions based on thermodynamics the upper limit for the energy efficiency of a heat-pump with Peltier elements having ZT = 1 is 3 at a difference of 20 degrees between indoor and outdoor temperature [1]. A strategy for improving the dimensionless figure of merit is to modify the material at the nanoscale, thereby reducing the phonon contribution to the thermal conductivity. Recently, a dimensionless figure of merit above 1.5 has been achieved in bulk p-type Bi2Te3 based materials fabricated by melt spinning [2,3]. With a dimensionless figure of merit of 1.5 for the Peltier element, the upper limit for the energy efficiency of the heat-pump would rise from 3 to 4. This improvement would reduce the electricity consumption to 25 % compared with the use conventional electrical heating. Advantages of thermoelectric heat-pumps compared to traditional ones would be the elimination of compressors and unwanted climate gases. In a recently started project we will perform large scale tests of thermoelectric heat pumps to assess their feasibility for large scale heating. Thermoelectric heat pumps require a design different from conventional heat pumps, so effort will be put on optimizing this design.

• Bording, Jan Kåre; Prytz, Øystein; Hansen, Vidar & Taftø, Johan (2009). Improved thermoelectric materials through nanostructuring: implications for energy savings.
• Böttger, Paul Heinrich Michael; Valset, Kjetil; Flage-Larsen, Espen; Prytz, Øystein; Bording, Jan Kåre; Karlsen, Ole Bjørn; Løvvik, Ole Martin; Hansen, Vidar; Finstad, Terje & Taftø, Johan (2009). An overview of our basic and applied thermoelectric research activity.
• Hansen, Vidar; Oddsen, Ingunn Cecilie; Kverneland, Atle; Larsen, Helge Bøvik; Pattison, Philip; Thorkildsen, Gunnar & Gjønnes, Jon (2009). Diffuse scattering from zones and particles in the Al-Zn-Mg alloy system.
• Hansen, Vidar; Kverneland, Atle; Li, X.Z.; Thorkildsen, Gunnar; Larsen, Helge Bøvik & Gjønnes, Jon (2008). Elektronmikroskopi og synkrotronrøntgen diffraksjonsstudier av transformasjoner og strukturer i 7xxx-legeringer.
• Oddsen, Ingunn Cecilie; Hansen, Vidar; Kverneland, Atle & Gjønnes, Jon (2008). Phase transition in age-hardening Al-Zn-Mg alloys. Show summary

  HREM images of precipitates embedded in Al matrix has been analysed and compared to the known lattice parameters of the metastable _h¿- phas and the equilibrium _h ¿ phase. The local variation in the stacking o the icosahedrons suggests that the particles may consist of both phases, with a gradually continuous transition starting near the edges of the particle.

• Hansen, Vidar; Kverneland, Atle; Thorkildsen, Gunnar; Larsen, Helge Bøvik; Vincent, Roger & Gjønnes, Jon (2007). Structure analysis of the n'-precipitate in Al-Zn-Mg alloys by the precession technique in electron diffraction and synchrotron radiation.
• Hansen, Vidar; Kverneland, Atle; Thorkildsen, Gunnar; Larsen, Helge Bøvik; Pattison, Philip; Gilmore, Cristopher; Vincent, Roger & Gjønnes, Jon (2006). Structure determination of nanosized semi-coherent Al-Mg-Zn precipitates by precession electron diffraction and synchrotron X-ray diffraction.
• Hansen, Vidar; Kverneland, Atle; Larsen, Helge Bøvik; Pattison, Philip; Vincent, Roger & Gjønnes, Jon (2005). Structure Determination of Embedded Precipitates by Precession Electron Diffraction and Synchrotron Radiation: A Comparison.
• Hjuler, Morten Leth & Hansen, Vidar (2005). Characterization and distribution of different silica and clay phases in outcrop chalk.
• Hansen, Vidar (2004). Elektronmikroskopi ved HIS; Utrustning og aktiviteter.
• Hansen, Vidar; Kverneland, Atle; Vincent, Roger; Li, X.Z.; Stiller, Krystyna & Gjønnes, Jon (2004). Precession electron diffraction, high-resolution microscopy and atom probe analysis of nano-sized precipitates in Al-Zn-Mg industrial alloys.
• Kverneland, Atle; Hansen, Vidar; Vincent, Roger & Gjønnes, Jon (2004). Strukturmodeller for herdefasen etta merket-MgZn i 7xxx legeringer.
• Hansen, Vidar (2003). Fast stoff reaksjoner i aluminium, en norsk gullgruve.
• Hansen, Vidar; Kverneland, Atle; Li, X.Z; Stiller, Krystyna; Vincent, Roger; Gjønnes, Kjersti & Gjønnes, Jon (2003). Crystal structures along the transformation path during age hardening in Al-Zn-Mg alloys by high resolution electron microscopy, precession electron diffraction and atom probe analysis.
• Knutsen, Turid; Hansen, Vidar; Håkansson, B; Gunnæs, Anette; Jørgensen, Sissel; Våland, Torstein & Taftø, Johan (2003). A Study of Amorphous and Crystalline Ni78Si8B14.
• Kverneland, Atle; Gjønnes, Jon; Hansen, Vidar & Vincent, Roger (2003). Structure solution of the hardening n'-precipitate in Al-Mg-Zn alloys by the precession technique in electron diffraction.
• Kverneland, Atle; Hansen, Vidar; Gjønnes, Jon & Vincent, Roger (2003). Structure solution of the hardening etta prime precipitate in Al-Zn-Mg alloys by the precession technique in electron diffraction.
• Gao, Robert Qiang; Stiller, Krystyna; Hansen, Vidar; Oskarsson, Anders & Danoix, Frederic (2002). Influence of Aging Conditions on the Microstructure and Tensile Strenght of Aluminium Alloy 6063.
• Gjønnes, Jon; Hansen, Vidar & Li, X.Z (2002). The collection of electron intensity data and its use in structure determination.
• Hansen, Vidar (2002). Tid-temperatur transformasjoner i 7xxx-aluminiumslegeringer.
• Hansen, Vidar & Larsen, Helge Bøvik (2002). Metallenes indre liv.
• Hansen, Vidar; Stiller, Krystyna; Waterloo, Grethe & Gjønnes, Jon (2002). Structures and Transformations During Artificial Aging of an Industrial 7xxx-Series Al-Zn-Mg-Zr Alloy.
• Sørbrøden, Erik; Hansen, Vidar; Olsen, Arne; Holme, Børge & Taftø, Johan (2002). Imaging of hardening particles in an Al-Mg-Zn alloy using plasmon electron energy losses.
• Gjønnes, Jon; Hansen, Vidar & Waterloo, Grethe (2001). Nucleation and growth of hardening precipitates in 7xxx-alloys.
• Hansen, Vidar (2001). Strukturer og fasetransformasjoner i utherdbare industrilegeringer.
• Hansen, Vidar (2001). Zones and Age Hardening Particles in the 7xxx-Alloy System.
• Hansen, Vidar; Karlsen, Ole Bjørn & Gjønnes, Jon (2001). Utbredelse av soner og herdepartikler i 7108.70; transmisjonselektronmikroskopi og differensiell skanning kalorimetri.
• Solberg, Jan Ketil & Hansen, Vidar (2001). Innføring i transmisjon elektronmikroskopi.

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