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  • 1. Blank, Vladimir D.
    et al.
    Buga, Sergey G.
    Dubitsky, Gennadii A.
    Serebryanaya, Nadejda R.
    Popov, M. Yu.
    Kulnitskiy, B.A.
    Prokhorov, V.M.
    Levin, V.M.
    Zhu, Xiaomei
    Nyeanchi, Emmanuel
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    High-pressure synthesis, structure and properties of superhard and ultrahard fullerites2000Inngår i: High Pressure - 2000: Proceedings of the VI International Conference on High Pressure, Donetsk, Ukraina: Donetsk Intitute for Physics and Engineering , 2000, s. 127-132Konferansepaper (Fagfellevurdert)
  • 2. Buga, Sergei
    et al.
    Blank, Vladimir
    Bagramov, Rustem
    Dubitsky, Gennadii
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Serebryanaya, Nadejda
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Thermal stability of superhard and ultrahard fullerites2000Inngår i: Proceedings of International Conference on Engineering and Technological Sciences 2000 (ICETS-2000), vol. 1, Beijng: Chinese Academy of Engineering: New World Press , 2000, s. 505-511Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The thermal stability of superhard and ultrahard carbon phases synthesized from C60 and C70 fullerenes under pressure in the range 9.5-13 GPa and temperature between 670 and 1850 K was investigated by DSC in the range 260-640 K and TGA up to 1200 K. Endothermal heat effects were observed with a peak maximum just below 540 K, a temperature characteristic for breakdown of (2+2) intermolecular links in dimers, 1D and 2D polymers. Exothermal effects, starting from 380 K, were observed for the first time in polymeric fullerenes. These effects are attributed to relaxation processes and to breakdown of other types of intermolecular bonds.

  • 3. Buga, Sergei G.
    et al.
    Blank, Vladimir D.
    Dubitsky, Gennadii A.
    Serebryanaya, Nadejda R.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Synthesis of superhard 3D-polymeric C60 fullerites from rhombohedral 2D-polymer by high-pressure-high-temperature treatment.2003Inngår i: High Pressure Research vol. 23, issue 3: Proceedings of the 40th European High Pressure Research Group Meeting on Advances in High Pressure Research (EHPRG'40), London: Taylor & Francis , 2003, s. 259-264Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Rhombohedral C60 polymer was subjected to high-pressure-high-temperature treatment at P =13 GPa, T =620-1620 K. After quenching, crystalline and disordered structures with densities in the range of 2.1-2.9 g cm-1 were obtained. The structures of the samples have been investigated by powder X-ray diffraction and Raman scattering. DSC analysis showed a transformation of the polymeric structure into monomeric on annealing in the range 400-640 K. The temperature dependence of the electrical resistance of samples with disordered structure was measured in the range 2.5-300K. For different samples, the conductivity was proportional to T1/2, T3/2, T4 and exp(-1/T1/4).

  • 4. Buga, Sergei G.
    et al.
    Blank, Vladimir D.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Serebryanaya, Nadejda R.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    DSC study of annealing and phase transformations of C60 and C70 polymerized under pressures in the range 9.5 - 13 GPa.2002Inngår i: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 63, nr 2, s. 331-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    C60 and C70 fullerenes polymerized under pressures between 9.5 and 13 GPa and temperatures between 670 and 1850 K were investigated by differential scanning calorimetry (DSC) in the range 240–640 K. Endothermal heat effects were observed with a peak maximum just below 540 K, a temperature characteristic for breakdown of (2+2) intermolecular links in dimers, 1D and 2D polymers. Exothermal effects, starting from 380 K, were observed for the first time in polymeric fullerenes. These effects are attributed to relaxation processes and to breakdown of other types of intermolecular bonds such as common four-sided rings and (3+3) interlinks.

  • 5. Buga, Sergei G.
    et al.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Serebryanaya, Nadejda R.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Blank, Vladimir D.
    Dubitsky, Gennadii A.
    Dissociation energy of 3D-polymeric C60: Calorimetric study and structural analysis2001Inngår i: Electronic Properties of Novel Materials - Science and Technology of Molecular Nanostructures: Proceedings of the XV International Winter School on Electronic Properties of Novel Materials, Kirchberg 2001, Melville, NY: American Institute of Physics , 2001, s. 49-53Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Annealing of 2D- and 3D-polymeric C[sub60] fullerene obtained under pressures of 9.5 and 12.5 GPa and temperatures of 670 and 770 K has been investigated by DSC in the range 240–640 K. An endothermal heat effect was observed with a peak maximum just below 540 K, a temperature characteristic for breakdown of (2+2) intermolecular links in dimers, 1D and 2D polymers. Exothermal effects, starting from 380 K, were observed for the first time in polymeric fullerenes. These effects are attributed to relaxation processes and to breakdown of other types of intermolecular bonds such as common four-sided rings and (3+3) interlinks.

  • 6.
    Fransson, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bäckström, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Automated differential scanning calorimetry at low temperatures1985Inngår i: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 6, nr 2, s. 165-175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Perkin-Elmer DSC-2 scanning calorimeter was operated by means of a PDP-11/34 computer with time-shared scanner and voltmeter. Special attention was paid to the problems of measurement below room temperature down to the low-temperature limit. It was found that Ne, rather than He, should be used as a purge gas, that scans should always be started at a standardized liquid nitrogen level, and that gas flow to the dry box should be stopped during measurements. Results on benzoic acid were then accurate to 0.6 % from 120 to 300 K. The specific heat of antimony was measured in the temperature interval 120–720 K.

  • 7.
    Fransson, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bäckström, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Isothermal enthalpy relaxation of glassy 1,2,6-hexanetriol1987Inngår i: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 61, nr 1, s. 131-141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The isothermal enthalpy relaxation of glassy 1,2,6-hexanetriol has been measured at six temperatures. The relaxation time and the distribution parameters extracted from fits of the Williams-Watts relaxation function are compared with parameters obtained by other techniques and on other substances. A detailed comparison of the Williams-Watts and the Davidson-Cole relaxation functions is presented.

  • 8.
    Fransson, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bäckström, Gunnar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Isothermal enthalpy relaxation of glycerol1987Inngår i: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 8, nr 3, s. 351-362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The isothermal enthalpy relaxation of glycerol has been measured at 13 different annealing times at temperatures of 170, 175, 180, and 185 K. The glasses were formed by linear cooling at 0.667 and 0.083 K·s−1 in a differential scanning calorimeter (DSC). The Williams-Watts relaxation function was fitted to data of enthalpy versus time. A strong temperature dependence was found for the relaxation time. The distribution parameter, β, showed an increase from 0.49 at 170 K to 0.65 at 185 K. We also found indications of an enthalpy dependence in β. Comparison with a theory of volume relaxation showed differences between rates of volume and enthalpy relaxation.

  • 9.
    Fransson, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ross, Russel G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Thermal conductivity, heat capacity and phase stability of solid sodium chlorate (NaClO3) under pressure1983Inngår i: Journal of Physics C: Solid State Physics, ISSN 0022-3719, Vol. 16, nr 15, s. 2861-2869Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal conductivity, lambda, and the specific heat capacity at constant pressure, cp, have been measured for solid sodium chlorate (NaClO3) in the temperature range 100-300K. Differential scanning calorimetry (DSC) was used to measure cp at atmospheric pressure, whilst the transient hot-wire method was used to measure simultaneously both lambda and the heat capacity per unit volume, rho cp, up to a pressure of 2 GPa. We found that our measured DSC values of cp exceeded those previously predicted from a lattice dynamical model, consistent with a previous prediction of disorder in Cl atom positions at high temperatures. However, such disorder, if it exists, did not affect the transport of heat, since we found that lambda (T) under isochoric conditions appeared to be determined entirely by three-phonon umklapp interactions. We found no evidence for a phase transition in NaClO3 up to 2 GPa at 300K, contrary to some previous results. However, we did observe an explosive chemical instability to occur at about 1 GPa and 130K. 

  • 10. Inaba, Akira
    et al.
    Matsuo, Takasuke
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Lattice vibrations and thermodynamic stability of polymerized C60 deduced from heat capacities1999Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 110, nr 24, s. 12226-12232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heat capacities of 1D and 2D pressure polymerized C60 as well as the thermally depolymerized C60 have been measured at temperatures between 4 and 350 K and the results analyzed for the lattice vibrations and the thermodynamic stability. It was found from the low-temperature heat capacity (T < 100 K) that on polymerization (1) the lattice vibrations, both translational and rotational, stiffen substantially, (2) an anisotropic nature emerges in response to the lower dimensionality, and (3) an anharmonicity still remains as in pristine C60. The normal C60 has an excess entropy of 67.8 and 99.4 J K – 1 mol – 1 at 300 K relative to the 1D and 2D polymerized C60, respectively. The thermodynamic stability is considered with two possible phase diagrams.

  • 11.
    Jonsson, Ulf G
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Andersson, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Investigations of the temperature gradients affecting the temperature scale of a 3ω-heat capacity spectrometer2000Inngår i: Thermochimica Acta, ISSN 0040-6031, E-ISSN 1872-762X, Vol. 347, nr 1-2, s. 45-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The temperature gradients affecting the temperature scale of a dynamic heat capacity spectrometer based on the 3ω-method are investigated using the SmecticA-Nematic (SmA/N) transition in the liquid crystal octyloxycyanobiphenyl (80CB). The heater (sample) temperature was obtained from a thermocouple by superimposing the temperature increase of the heater, where the increase was calculated from the heater power. The calibration using the SmA/N transition yields a linear relation between the temperature rise of the heater ΔTh and the heater power P:ΔTh = 55.2 P. An estimation of the maximum temperature gradient in the 80CB sample shows that the correction of the sample temperature due to the gradient is small compared to ΔTh (<-0.01 K for ω=3.98.2π rads-1 and -0.14 K for ω=0.01. 2π rads-1). For high heating powers there is a significant temperature gradient in the heater, which causes a broadening of the SmA/N peakwidth from 0.5 K for P=7.7 mW to 2 K for P=29.4 mW. 

  • 12.
    Lundin, Anders
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Skoglund, Peter
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Pettersson, Sune
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Compressibility, specific heat capacity, and Grüneisen parameter for C60/C701992Inngår i: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 84, nr 9, s. 879-883Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have measured the specific heat capacity cp of C60/C70 between 110 and 310 K and its compressibility κ up to 1.1 GPa (11 kbar) at 293 K, a range in t and p which overlaps reported ranges of stability of both the rotationally disordered high T, low p fcc phase and the low T high p orientationally ordered sc phase. No sharp anomaly is observed in cp at the transition. The bulk modulus B near p = 0 was 8.4 GPa, rapidly increasing to about 16 GPa near 1 GPa. For our data, the intermolecular forces could be modeled by either a Lennard-Jones or a Born-Mayer potential, but this was not the case if literature data for compression vs. p were used.

  • 13.
    Nair, Gireesh
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Perspectives of building professionals on the use of LCA tools in Swedish climate declaration2021Inngår i: E3S Web of Conferences / [ed] J. Kurnitski and M. Thalfeldt, EDP Sciences, 2021, artikkel-id 13004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    From 1st January 2022, Swedish government plan to introduce the climate declarations as a legal requirement for new buildings. LCA is a method that could be used to quantify buildings' climate impact. The climate declaration in the Swedish building code expects to create interest in LCA among stakeholders. This study aims to identify and understand the challenges and opportunities of using LCA by stakeholders during the early stage of construction process. The study is based on responses from six building professionals to a questionnaire. The policy implications of the study findings are discussed.

    Fulltekst (pdf)
    fulltext
  • 14.
    Ohlsson, K.E. Anders
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Social wasp nests as source of bioinspired design of building skins: 1-2 October 2018, Bern, Switzerland2018Inngår i: Advanced Building Skins, Advanced Building Skins GmbH , 2018Konferansepaper (Fagfellevurdert)
  • 15.
    Olofsson, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nair, Gireesh
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    State of knowledge in Sweden during the Corona pandemic2020Inngår i: REHVA Journal, ISSN 1307-3729, nr 5, s. 69-71Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    During the ongoing Corona pandemic, a survey of Swedish authorities, industry associations, and consultancy and real estate companies summarize the need to increase competence on HVAC and indoor environment. The knowledge improvement span the entire area: from the choice of technical components to the design, operation and maintenance. A topic emphasized is the requirement of an interdisciplinary perspective related to establishing knowledge.

  • 16.
    Olofsson, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nair, Gireesh
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Så påverkar pandemin inomhusmiljön2020Inngår i: Energi & miljö, ISSN 1101-0568, nr 10, s. 50-51Artikkel, forskningsoversikt (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
    fulltext
  • 17.
    Persson, Per-Axel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edlund, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Inaba, Akira
    Jacobsson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johnels, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Meingast, Christoph
    Soldatov, Alexander
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Physical properties of pressure polymerized C601996Inngår i: High Pressure Science and Technology: Proceedings of the Joint XV AIRAPT and XXXIII EHPRG International Conference, Warsaw 1995, Singapore: World Scientific , 1996, s. 716-718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The properties of C60 have been studied after treatment at high temperature and high pressure (1.1 GPa and 565 K for 2 h). The treated material is insoluble in organic solvents. We present results obtained in NMR and Raman studies and measured data for the specific heat and the thermal expansion. Our results show clearly that there are no covalent bonds and no molecular rotation, but suggest that the molecules are slightly deformed and held together by weak pi-type bonds.

  • 18.
    Shin, Joon-Ho
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Dzwilewski, Andrzej
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Iwasiewicz, Agnieszka
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Xiao, Steven
    Fransson, Åke
    Tillämpad fysik och elektronik.
    Ankah, Genesis Ngwa
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Light emission at 5 V from a polymer device with a millimeter-sized interelectrode gap2006Inngår i: Applied Physics Letters, Vol. 89, s. 013509-Artikkel i tidsskrift (Fagfellevurdert)
  • 19.
    Shin, Joon-Ho
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Xiao, Steven
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Polymer light-emitting electrochemical cells: frozen-junction operation of an “ionic liquid” device2005Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, nr 4, artikkel-id 043506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report frozen-junction operation of a polymer light-emitting electrochemical cell containing a mixture of poly[2-methoxy-5-(2(')-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and the ionic liquid tetra-n-butylammonium trifluoromethanesulfonate (TBA-TF) as the active material. We find fast turn-on time, unipolar light emission, and significant operational lifetime up to T=200 K for planar Au/(TBA-TF+MEH-PPV)/Au surface cells, which had been charged (i.e., electrochemically p- and n-type doped in situ) at T=393 K and V=4 V and then cooled to 80 K at V=4 V. We employed differential scanning calorimetry to demonstrate that (TBA-TF+MEH-PPV) exhibits two melting transitions of TBA-TF crystalline phases located at T(m,1)approximate to 280 K and T(m,2)approximate to 380 K, respectively. The lower T-m,T-1 sets the upper limit for frozen-junction operation (with zero-ionic conductivity), while the larger T-m,T-2 correlates to the lower limit for the charging regime (with high ionic conductivity).

  • 20.
    Sundqvist, Bertil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edlund, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Inaba, Akira
    Jacobsson, Per
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johnels, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Launois, Pascale
    Meingast, Christoph
    Moret, Roger
    Moritz, Thomas
    Persson, Per-Axel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soldatov, Alexander
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Physical properties of pressure polymerized C601996Inngår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, volume 3: Proceedings of the 189th ECS Meeting, Symposium Fullerenes: Chemistry, Physics, and New Directions VIII, Los Angeles 1996, Pennington, NJ: The Electrochemical Society , 1996, s. 1014-1028Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present in this paper an overview of the physical properties of the high pressure polymerized C60 phase commonly known as "soft fcc". This phase has been studied by several methods over wide ranges in temperature T and/or pressure, p. We present here experimental information about the specific heat capacity, the thermal expansion coefficient, the lattice structure, and the thermal conductivity, and we also show results obtained by NMR and Raman spectroscopy. All data presented agree with the accepted model that the individual molecules in this phase are covalently bound to form linear molecular chains. In particular, the NMR data show clearly the presence of covalent bonds, and the Raman data exhibit several new lines at very low energies connected with chain vibrations. Thermal conductivity data obtained during polymerization show both the time dependence of the process and that polymerization occurs at lower p and T than observed previously for this phase.

  • 21.
    Sundqvist, Bertil
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Inaba, Akira
    Meingast, Christoph
    Nagel, Peter
    Pasler, Volker
    Renker, Burkhard
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Physical properties of two-dimensionally polymerized C601998Inngår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 6: Proceedings of the 193rd Meeting of the Electrochemical Society, Symposium Fullerenes: Chemistry, Physics, and New Directions XI, San Diego 1998, Pennington, NJ: The Electrochemical Society , 1998, s. 705-716Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Preliminary data are reported for the thermal expansion, compressibility, and specific heat of two-dimensionally polymerized C60 obtained by treating fullerene samples at temperatures above 800 K under a pressure of 2 GPa. The samples have also been characterized by Raman spectroscopy and inelastic neutron scattering. The measured data for the thermophysical properties are strongly modified by the creation of strong covalent intermolecular bonds and we show that the results are compatible with the predictions of simple theories.

  • 22.
    Zhou, Hongxia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    An explicit finite element method for thermal simulations of buildings with phase change materials2021Inngår i: Energies, E-ISSN 1996-1073, Vol. 14, nr 19, artikkel-id 6194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The thermal performance of building envelopes is essential for building thermal comfort and the reduction of building energy requirements. Phase change materials (PCMs) implemented in building envelopes can improve thermal performance. An explicit finite element method (ex-FEM) has been developed based on a previous study to investigate the heat transfer performance through building walls with installed PCMs. For verification, we introduce an electrical circuit analogy (ECA) method. For model validation, at first, COMSOL is used. For comparison, data were collected from experiments using a small hotbox, part of the sides are covered by PCMs with different configurations. This work shows how the ex-FEM model can predict the wall's temperature profile with and without incorporated PCM. With the implementation of PCMs, the work problematizes unpredictable influences for modeling. In addition, the study introduces results from simulations of sequencing of PCM layers in wall construction.

    Fulltekst (pdf)
    fulltext
  • 23.
    Zhou, Hongxia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Influence of Phase Change Materials (PCMs) on the thermal performance of building envelopes2020Inngår i: 12th Nordic Symposium on Building Physics (NSB 2020) / [ed] Kurnitski, J Kalamees, T, EDP Sciences, 2020, artikkel-id 21002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To understand the influence of PCM wall configurations on the thermal performance of building envelopes, an explicit finite element model of heat transfer from indoor to outdoor (or vice versa) is developed. The accuracy of this model is first validated against the electrical circuit analogy model, and then compared with the experimental data measured in a Hot-Box device. A good agreement between the simulation results and experimental results is obtained. The results of this study show that the PCM configuration layer sequence significantly will affect the thermal performance of building envelopes and that the FEM model developed is a promising tool, which after some more development may be used for optimising PCM wall configurations.

    Fulltekst (pdf)
    fulltext
  • 24.
    Zhou, Hongxia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Investigation of phase change materials (PCMs) on the heat transfer performance of building systems2021Inngår i: Journal of Physics: Conference Series, Institute of Physics (IOP), 2021, Vol. 2069, artikkel-id 012020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The energy use of building systems contributes to a large percentage of total energy consumption, which requires consideration. Solutions of improvement to save energy are crucial. Phase change materials have been proved to be good candidates to be used in building envelopes for energy save. In this paper, an extended Explicit Finite Element Method (ex-FEM), which has been previously introduced and improved, is taken for simulation of temperatures and heat transfer in simplified multilayer wall constructions, consisting of PCM and insulation. The method has been validated against experimental data measured in a so-called Hot-Box. Temperature data are measured at different positions in a number of simplified multilayer walls. Our results show a reasonable good agreement between the simulations and the experiments, at both heating and cooling considering the temperature hysteresis effect in the PCM. The temperature stabilization ability of the PCM is clear, in both the simulations and the experiments, and particularly in the data when the transition range of the PCM is fully activated and matching the temperature variation in the wall at that particular PCM position. Our ex-FEM tool has here been proved to be able to predict the thermal performance of simplified wall constructions of multiple layers with PCMs incorporated.

    Fulltekst (pdf)
    fulltext
  • 25.
    Olofsson, Thomas ()
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Fransson, Åke ()
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nair, Gireesh ()
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Mattson, Moa ()
    Energirelaterade konsekvenser i bebyggelsen orsakad av Coronapandemin2020Annet (Annet vitenskapelig)
    Abstract [sv]

    Coronapandemi som kom i början på året 2020 har på många sätt förändrat användningen av den bebyggda miljön. En kunskapskartläggning har genomförts med syfte att synliggöra det specifika kunskapsläget om ventilation, uppvärmning och kyla av inomhusmiljön och behovet av den nya kunskap som aktualiseras av Coronapandemin. Informationsinsamlingen utgjordes av en litteraturstudie och intervjuer med experter på inomhusmiljö, ventilation, uppvärmning och kyla som verkar i olika sektorer i samhället. Därtill har en referensgrupp deltagit.

    När det gäller att minska spridningen av COVID-19 i inomhusluften så är det nödvändigt att förhålla sig till diskussionen om evidensen för att människor kan smittas genom överföring av SARS-CoV-2 med luften. Experimentella och epidemiologiska data talar för att smittspridning förekommer på flera meters avstånd och att ventilationens beskaffenhet påverkar smittrisken. Det råder osäkerhet om smitta förs mellan rum med ventilationsluft. Föreliggande undersökning utgår från försiktighetsprincipen, som förespråkar att med brist på bevis för motsatsen så kan inte heller det värre scenariot förkastas.

    Undersökningen har identifierat behov av kunskapsförstärkning med både allmän kompetens och expertkompetens i det luftbehandlingstekniska området. Exempel på behov av ny kunskap avser hur smittan sprids, hur spridningen beror av ventilerade luftflöden, möjligheter att filtrera för att minska spridning av virus, behov av luftmängder för att förhindra virusspridning, mer kunskap om renrumsteknik, undersökningar av smittspridning och ventilation i sjukhusmiljöer och äldreboenden, fuktens betydelse för smittspridning och mottagligheten av sjukdom. Andra kunskapsområden som identifierats är trångboddhetens betydelse för smitta och städningens betydelse för att minska sjukdomsspridning.

    Kunskapsområdet är tvärvetenskapligt och omfattar medicin, teknik och naturvetenskap. Det tvärvetenskapliga perspektivet är angeläget att beakta när strategier ska formuleras för kunskapsförstärkning. Under den pågående pandemin är det svenska regelverket för ventilation inte aktuellt för revidering, medan vissa internationella organisationers regelverk har uppdateras, exempelvis REHVA. Det framgick av intervjuerna att det följs av vissa med stort intresse, men det är okänt vad det får för konsekvenser De intervjuande personerna uttrycker en stor tillit för den information som förmedlas från Folkhälsomyndigheten. Vissa aktörer avvaktar med att göra driftåtgärder i byggnadernas tekniska system i väntan på att Folkhälsomyndigheten ska ge direktiv, vilket kan skapa handlingsförlamning. Detta påkallar fortsatta undersökningar.

    Hyresgäster uttrycker liten oro för att ventilationssystemet bidrar till överföring av virus, men i vissa fall finns stor oro för besök av driftpersonal vid OVK och filterbyten, vilket resulterar i att de inte genomförs. Det konstateras att förvaltarna i allmänhet inte ändrat luftflöden. Däremot justerar VAV-systemen automatiskt ner flödet då persontätheten minskar. För vårdlokaler konstateras det att flöden och tryckskillnader justerats i vissa fall för att minska spridningen av virus. Omfattningen och konsekvenserna av dessa förhållanden kan vara värda att undersöka vidare.

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