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Träfflista för sökning "WFRF:(Sundqvist Bertil) srt2:(1995-1999)"

Sökning: WFRF:(Sundqvist Bertil) > (1995-1999)

  • Resultat 1-10 av 71
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1.
  • Aksenova, N.A., et al. (författare)
  • Structural studies of C60 polymerized at high pressure
  • 1997
  • Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771927
  • Konferensbidrag (refereegranskat)
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2.
  • Aksenova, N.A., et al. (författare)
  • Structure studies of C60 polymerized at low pressures
  • 1997
  • Ingår i: Fullerenes. - Pennington, NJ : The Electrochemical Society. - 1566771927 ; , s. 687-694
  • Konferensbidrag (refereegranskat)abstract
    • The structure and lattice properties of a polymerized C60 sample were investigated by X-ray powder diffraction over the range from liquid-nitrogen to room temperature. The aim of these studies was to establish the effect of low-pressure compression (up to 1.1 GPa) on the phase composition of the sample, to determine the structure of the phases involved, to obtain the variation of the lattice parameters with temperature, to observe eventual phase transformation in polymerized C60, and to elucidate the evolution of the orientational order with varying temperature. Analysis of the room-temperature diffraction patterns indicates that the sample contained at least two major phases, namely rhombohedral and and tetragonal with the polymerization array close to two-dimensional. Our data obtained on samples annealed at 300 C in the air allow us to conclude that polymerized C60 converts to a mixture of the fcc structure plus a new phase, presumably C60O.
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3.
  • Aleksandrovskii, A. N., et al. (författare)
  • Negative thermal expansion of fullerite C60 at helium temperatures
  • 1997
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 23:11, s. 943-946
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermal expansion of fullerite C60 has been measured in the temperature range 2–9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ~ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed
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4.
  • Andersson, Odd E., et al. (författare)
  • A study of temperature and pressure induced structural and electronic changes in SbCl5 intercalated graphite : Part IV: Basal plane resistivity
  • 1995
  • Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 10:7, s. 1653-1660
  • Tidskriftsartikel (refereegranskat)abstract
    • Using an inductive technique, we have measured the in-plane resistivity rhoa of stages 2, 4, 5, and 8 SbCl5-GIC's versus temperature T and pressure p in the ranges 130–300 K and 0–0.85 GPa. The room temperature values of rhoa range from 4.0 µOcm for the stages 5 sample to 7.7 µOcm for the stage 8 sample. At all pressures, rhoa shows a metallic temperature dependence rhoa ~ Ta, with 1 < a < 2, but in contrast to the c-axis resistivity rhoc, it depends only very weakly on pressure and/or intercalate structural order. We show that the behavior observed is consistent with a band conduction model.
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5.
  • Andersson, Odd E., et al. (författare)
  • Low temperature calibration of Manganin pressure gauges
  • 1997
  • Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 68:2, s. 1344-1345
  • Tidskriftsartikel (refereegranskat)abstract
    • High pressures are often measured using the resistance of Manganin wires. However, the pressure coefficient of resistance is known to depend on temperature. We have measured this temperature dependence by comparing the output from a Manganin gauge with that of a well calibrated Zeranin gauge and determined a correction factor which enables us to measure the pressure at any temperature between 150 and 300 K with a temperature dependent error well below 0.5%.
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6.
  • Andersson, Odd E., et al. (författare)
  • The c-axis resistivity for two HOPG-based, first stage CuAl2Cl8 and second stage CuCl2 - graphite intercalation compounds as a function of both pressure and temperature
  • 1996
  • Ingår i: Journal of Physics and Chemistry of Solids, volume 57, issues 6-8. - : Elsevier Ltd.. ; , s. 719-723
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present data for the c-axis resistivity of first stage CuAl2Cl8 GIC and second stage CuCl2 GIC as functions of pressure, p, (0.0 < p < 1.5 GPa) and of temperature, T, (4 < T < 300 K). We show evidence of a possible new high-pressure phase above 1.0 GPa for the CuAl2Cl8 GIC and we show that the CuCl2 GIC is very stable at all pressures and temperature investigated. We make a comparison with previous results on SbCl5 GICs and other chloride intercalation compounds and with theories treating the temperature and pressure coefficients of transport parameters in layered solids.
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7.
  • Andersson, Ove, et al. (författare)
  • Reorientational relaxation in C60 following a pressure induced change in the pentagon/hexagon equilibrium ratio
  • 1995
  • Ingår i: Physics Letters A. - : Elsevier Science B.V.. - 0375-9601 .- 1873-2429. ; 206:3-4, s. 260-264
  • Tidskriftsartikel (refereegranskat)abstract
    • The orientational structure of C60 depends on pressure and temperature. Pressurization below the glass transition temperature Tg can freeze in non-equilibrium orientational structures. The relaxation of such structures on heating through Tg has been studied through thermal conductivity measurements and the effects observed are explained in a simple model.
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8.
  • Andersson, Ove, et al. (författare)
  • Thermal conductivity of C60 at pressures up to 1 GPa and temperatures in the range 50-300 K
  • 1996
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 54:5, s. 3093-3100
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermal conductivity λ of C60 shows anomalies near 260 K and 90 K which are associated with the well-established phase transition and glass transition, respectively. Both transition temperatures increase with pressure, at the rates 120 K GPa-1 and 62 K GPa-1, respectively. With increasing temperature, λ of the simple cubic (sc) phase increased below 170 K (glasslike behavior) but decreased above. The glasslike behavior of λ is probably due to a substantial amount of lattice defects. Possible reasons for the change of sign of dλ/dT near 170 K are discussed. In the face centered cubic (fcc) phase (T≳260 K at atmospheric pressure) λ was almost independent of temperature, a behavior which is far from that of an ordered crystal (λ∝T-1 for T≳Debye temperature). This result can be attributed to the molecular orientational disorder of the fcc phase. The relaxation behavior associated with the glassy state and its unusually strong dependence on thermal history are discussed briefly, and data which support a previously reported relaxation model are presented. At room temperature, the density dependencies of λ, (∂ lnλ/∂ lnρ)T, were 5.5 and 9.5 for the fcc and sc phases, which are values typical for an orientationally disordered phase and a normal crystal phase, respectively.
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9.
  • Andersson, Ove, et al. (författare)
  • Thermal conductivity of C60 under high pressure
  • 1995
  • Ingår i: Science and Technology of Fullerene Materials. - Pittsburgh, PA : Materials Research Society. - 155899260X ; , s. 549-554
  • Konferensbidrag (refereegranskat)abstract
    • We have measured the thermal conductivity lambda of highly pure polycrystalline C60 in the range 50 to 300 K under pressures up to 1 GPa. The results are discussed in terms of the lattice structure and dynamics. In particular, we discuss the phase diagram as delineated by anomalies observed in lambda and cp at the f.c.c.-to-s.c. transition at 260 K and the glass transition at Tg = 90 K, and also the effect on lambda of the orientational motion in the s.c. phase. The results are found to be compatible with a p/T phase diagram recently suggested by us.
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10.
  • Blank, Vladimir D., et al. (författare)
  • Electric resistivity and  magnetoresistance of some superhard and ultrahard fullerites in the range 300-2K
  • 1999
  • Ingår i: AIP Conference Proceedings vol. 486. - Melville, NY : American Institute of Physics (AIP). - 1563969009 ; , s. 416-420
  • Konferensbidrag (refereegranskat)abstract
    • Electric resistivity and magnetoresistance were measured on samples with disordered structure synthesized from pure C60 and C70 at pressures in the range 8 - 12.5 GPa and temperature 900 - 1500 K. Different type of behaviour were observed: semimetallic and semiconducting, depending on the particular short-range order of the structure.
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  • Resultat 1-10 av 71

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