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Träfflista för sökning "L773:1063 777X srt2:(1997-1999)"

Sökning: L773:1063 777X > (1997-1999)

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1.
  • 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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2.
  • Isakina, A.P., et al. (författare)
  • Structure and microhardness of low pressure polymerized fullerite C60
  • 1998
  • Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 24:12, s. 896-903
  • Tidskriftsartikel (refereegranskat)abstract
    • We have carried out low-temperature x-ray diffraction studies on C60 fullerite polymerized by low quasi-hydrostatic pressure of 1.1 GPa at T = 563 K. It is established that at room temperature in freshly prepared samples three phases mainly coexist, viz. a compressed cubic phase with the lattice parameter a = 13.94 Å, an orthorhombic O' phase with the lattice parameters a = 9.12 Å, b = 9.82 Å, c = 14.60 Å, and a rhombohedral phase of symmetry R3m with the parameters a = 9.20 Å and c = 24.27 Å. Mechanical grinding or annealing at 573 K entails depolymerization of sintered samples and restoration of the fcc structure of pristine C60. During annealing in air, intercalation of fullerite lattice by oxygen molecules occurs as well as a substantial amount of some new phase is formed, most probably with tetragonal symmetry, the chemical composition and structure of which have not been determined. The microhardness of polymerized C60 is higher than that of single crystal samples roughly four-fold at room temperature and by a factor of 2.6 at liquid nitrogen temperature. Analysis shows that polymerization and grain boundaries give contributions to the microhardness of sintered samples but we did not succeed in separating these two contributions. The temperature dependence of the microhardness of polymerized samples exhibits a jump in the vicinity of 260 K, where pristine C60 fullerite undergoes the fcc-sc phase transition. We think that this jump is due to a partial destruction of the polymerized state under indentor as a result of shear straining in inhomogeneous stress fields. Annealing of polymerized C60 at a temperature of 573 K, which restores the fcc phase, leads to a considerable decrease in microhardness, the hardness "jump" near the fcc-sc transition extends in temperature and shifts to lower temperatures
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3.
  • Pluzhnikov, VB, et al. (författare)
  • Effect of pressure on the Fermi surface and electronic structure of ErGa3
  • 1999
  • Ingår i: LOW TEMPERATURE PHYSICS. - : AMER INST PHYSICS. - 1063-777X. ; 25:8-9, s. 670-676
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The Fermi surface and cyclotron masses of the ErGa3 compound are studied by means of the de Haas-van Alphen technique under pressure. Concurrently, the electronic structure is calculated ab initio for the ferromagnetic phase of ErGa3. The experimental dat
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