共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
P. A. Borisova S. S. Agafonov M. S. Blanter V. A. Somenkov 《Physics of the Solid State》2014,56(1):199-202
The amorphous fullerite C60 has been prepared by mechanical activation (grinding in a ball mill), and its interaction with iron during sintering of powders with 0–95 at % Fe has been studied. After sintering in the range 800–1200°C under a pressure of 70 MPa, the samples have nonequilibrium structures different from the structures of both annealed and quenched steels. In this case, the carbon phase, i.e., amorphous fullerite, undergoes a polyamorphous transition to amorphous graphite. It has also been shown that the interaction of amorphous fullerite with iron is weaker compared to crystalline fullerite or crystalline graphite. 相似文献
3.
V. V. Brazhkin A. G. Lyapin R. N. Voloshin S. V. Popova Yu. A. Klyuev A. M. Naletov S. C. Bayliss A. V. Sapelkin 《JETP Letters》1999,69(11):869-875
The results of an investigation of the transformation of C60 fullerite to diamond under pressure through intermediate three-dimensionally polymerized and amorphous phases are reported.
It is found that treatment of fullerite C60 at pressures 12–14 GPa and temperatures ∼1400°C produces a nanocrystalline graphite-diamond composite with a concentration
of the diamond component exceeding 50%. At lower temperatures (700–1200°C) nanocomposites consisting of diamondlike (sp
3) and graphitic (sp
2) amorphous phases are formed. The nanocomposites obtained have extremely high mechanical characteristics: hardness comparable
to that of best diamond single crystals and fracture resistance two times greater than that of diamond. Mechanisms leading
to the transformation of C60 fullerite into diamond-based nanocomposites and the reasons for the high mechanical characteristics of these nanocomposites
are discussed.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 11, 822–827 (10 June 1999) 相似文献
4.
First phase transformations of amorphous fullerite C60 at high temperatures (up to 1800 K) and high pressures (up to 8 GPa) have been investigated and compared with the previous studies on the crystalline fullerite. The study was conducted using neutron diffraction and Raman spectroscopy. The amorphous fullerite was obtained by ball-milling. We have shown that under thermobaric treatment no crystallization of amorphous fullerite into С60 molecular modification is observed, and it transforms into amorphous-like or crystalline graphite. A kinetic diagram of phase transformation of amorphous fullerite in temperature–pressure coordinates was constructed for the first time. Unlike in crystalline fullerite, no crystalline polymerized phases were formed under thermobaric treatment on amorphous fullerite. We found that amorphous fullerite turned out to be less resistant to thermobaric treatment, and amorphous-like or crystalline graphite were formed at lower temperatures than in crystalline fullerite. 相似文献
5.
A series of polycrystalline phases corresponding to different stages of three-dimensional polymerization and destruction of
C60 molecules has been synthesized by heating fullerite C60 under a pressure P=12.5 GPa. The structure of the phases can be identified as fcc, and the lattice period decreases with increasing heating
temperature. A model of three-dimensional polymerization in which the lattice parameter is a continuous function of the fraction
of covalently bonded molecules is proposed. The model makes it possible to estimate the number of atoms in the sp
3 state. The hardness of the polymerized fcc phases is studied on the basis of percolation of rigidity. It is shown experimentally
that the period a≈13.8 Å is the threshold for the formation of a three-dimensionally rigid C60 polymer. It is found that the thermal stability of the strongly and weakly polymerized phases is qualitatively different.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 755–759 (10 December 1996) 相似文献
6.
A. M. Molodets V. V. Avdonin A. N. Zhukov V. V. Kim A. YU. Osip’yan N. S. Sidorov 《高压研究》2013,33(2):279-290
A study of electrophysical and thermodynamic properties of C60 single crystals under step shock loading has been carried out. The increase and the following reduction in specific electroconductivity of C60 fullerite single crystals at step shock compression up to pressure 30 GPa have been measured. The equations of state for face centred cubic (fcc) C60 fullerite as well as for two-dimensional polymer C60 and for three-dimensional polymer C60 (3D-C60) were constructed. The pressure–temperature states of C60 fullerite were calculated at step shock compression up to pressure 30 GPa and temperature 550 K. The X-ray diffraction studies of shock-recovered samples reveal a mixture of fcc C60 and a X-ray amorphous component of fullerite C60. The start of the formation of the X-ray amorphous component occurs at a pressure P m≈ 19.8 GPa and a temperature T m≈ 520 K. At pressures exceeding P m and temperatures exceeding T m, the shock compressed fullerite consist of a two-phase mixture of fcc C60 fullerite and an X-ray amorphous component presumably consisting of the nucleators of polymer 3D-C60 fullerite. The decrease in electroconductivity of fullerite can be explained by the percolation effect caused by the change of pressure, size and number of polymeric phase nuclei. 相似文献
7.
É. A. Petrakovskaya V. G. Isakova O. A. Bayukov D. A. Velikanov 《Technical Physics》2005,50(6):790-793
A new magnetic material, C60 fullerite powder doped by magnetite (Fe3O4) nanoparticles, is obtained by heating a mixture of fullerite and iron(III) acetylacetonate. It is shown that the material
offers superparamagnetic properties. Surface bonding between the nanoparticles and the fullerite is established. 相似文献
8.
《Physics letters. A》2020,384(1):126035
Lightweight carbon materials with excellent thermal and mechanical properties have important applications in aerospace industry. In this study, the stability, mechanical properties, lattice thermal conductivity, electronic structure, infrared and Raman spectrum of sp3 hybridized low-density fullerite C24 were investigated according to density functional theory (DFT) calculations. It was found that the fullerite C24 was both thermodynamic and dynamic stable. Quasi-harmonic approximation and Grüneisen parameter calculations clarified why the fullerite C24 had a positive thermal expansion coefficient at low temperature. The fullerite C24 also exhibited excellent mechanical properties. Interestingly, the Vickers hardness of carbon allotropes was found to almost be linear proportional to the density of a carbon material. HSE06 electronic structure calculations showed that it was a semiconductor with direct bandgap of 2.56 eV. Anharmonic lattice dynamic calculations showed that its thermal conductivity was higher than semiconductor silicon. Besides, Raman and infrared active modes as well as the corresponding spectra were presented. 相似文献
9.
The great advantage of the C60 molecule is its potential for polymerization, due to which the molecule can be the building block of new all carbon materials. In addition, it contains, both sp 2 and sp 3 hybridized carbon atoms, which allows synthesizing new carbon materials with desired physicochemical properties using both types of carbon bonding. The one- and two-dimensional polymeric phases of C60 are prototype materials of this sort. Their properties, especially polymerization under pressure and room temperature via covalent bonding between molecules belonging to adjacent polymeric chains or polymeric layers, can be used for further development of new materials. The present review focuses on the study of the pressure-induced polymerization and thermodynamic stability of these materials and their recovered new phases by in-situ high-pressure Raman and X-ray diffraction studies. The phonon spectra show that the fullerene molecular cage in the high-pressure phases is preserved, while these polymers decompose under heat treatment into the initial fullerene C60 monomer. 相似文献
10.
The energy band structure, equation of state, density of states, and elastic moduli of a new allotropic carbon modification, namely, fullerite C24 with a simple cubic lattice (known previously as cubic graphite), are calculated by the full-potential linearized augmented-plane-wave (FLAPW) method with geometry optimization for the first time. The dependence of the total energy on the lattice constant exhibits a minimum for a 0 = 0.60546 nm. In this case, the lengths of the C-C bonds between fullerene molecules, the lengths of the 6,6-bonds shared by hexagons, and the lengths of the 4,6-bonds shared by a square and a hexagon are equal to 0.1614, 0.1503, and 0.1637 nm, respectively. An analysis of the energy band structure and the density of states demonstrates that the simple cubic fullerite C24 is a direct-band-gap insulator or a semiconductor with a band gap of 1.6 eV. The calculated bulk modulus B 0 = 196 GPa and the elastic moduli C 11 = 338 GPa, C 12 = 139 GPa, and C 44 = 30 GPa indicate that the fullerite under investigation is a mechanically stable material. The inference is made that the simple cubic fullerite C24 is a new diamond-like molecular zeolite with a unique combination of properties, such as the porosity and nonpolarizability, on the one hand, and the mechanical strength, chemical inertness, and high thermal conductivity, on the other hand. The simple cubic fullerite C24 can be considered a promising low-dielectric-constant (low-k) material (?0 < 5.7) for use in fabricating interconnections and substrates intended for integrated circuits and nanoelectronics. 相似文献
11.
S. Behler H. P. Lang S. H. Pan V. Thommen-Geiser H. -J. Güntherodt 《Zeitschrift für Physik B Condensed Matter》1993,91(1):1-2
Intramolecular contrast of C60 molecules has been observed by scanning tunneling microscopy at 4.5 K on a C60 fullerite thin film sample. This result provides strong evidence for the freezing of the rotational motion of C60 molecules at low temperature as recently proposed by refinement analysis of neutron diffraction data. Different intramolecular patterns are observed. Interpretation of these patterns is suggested by assigning them to carbon ring structures of the C60 molecules in various orientations. 相似文献
12.
V. A. Davydov L. S. Kashevarova A. V. Rakhmanina V. M. Senyavin O. P. Pronina N. N. Oleinikov V. Agafonov H. Szwarc 《JETP Letters》2000,72(11):557-560
Dimerization kinetics was studied for fullerene C60 by IR spectroscopy at a pressure of 1.5 GPa in the temperature range 373–473 K. The kinetic curves for the formation of a dimer (C60)2 were obtained using its analytical IR band at 796 cm?1. Under the assumption that pressure-induced C60 dimerization is a second-order irreversible reaction, the reaction rate constants were determined at different temperatures. The corresponding activation energy and preexponential factor were found to be 134±6 kJ/mol and (1.74± 0.24)×1014 s?1, respectively. The specific features of the solid-phase C60 dimerization in simple cubic and face-centered cubic fullerite phases are discussed. 相似文献
13.
Yu. I. Golovin A. A. Dmitrievskii R. K. Nikolaev I. A. Pushnin 《Physics of the Solid State》2003,45(1):197-200
The suppression of plasticity sensitivity of a C60 fullerite to the action of a magnetic field is revealed. It is found that the C60 fullerite undergoes temporary softening due to irradiation with ultralow (<0.1 cGy) doses of β and γ radiation. 相似文献
14.
A.S. Berdinsky D. Fink J.B. Yoo H.G. Chun L.T. Chadderton A.V. Petrov 《Applied Physics A: Materials Science & Processing》2005,80(8):1711-1715
Au/C60/p-Si sandwich structures can be easily obtained by evaporation of a thin fullerite (C60) film on a silicon substrate and a thin Au film on top of the C60 film. In this case a C60/p-Si p–n heterojunction appears. Both the dark and photoconductivities of the planar pristine and irradiated Au/C60/p-Si structures were measured as a function of the irradiation fluence. Furthermore, the pressure dependence of these structures was determined. A strong dependence on the irradiation damage was found. PACS 81.05.Tp; 72.80.-r; 72.80.Rj; 72.40.+w; 61.82.Rx 相似文献
15.
V. D. Blank K. V. Gogolinsky V. N. Denisov V. A. Ivdenko B. N. Mavrin N. R. Serebryanaya S. N. Sulyanov 《Technical Physics》2002,47(12):1533-1537
X-ray diffraction patterns, Raman spectra, and the hardness of C70 fullerite subjected to a high pressure with shear are investigated. It is shown that these conditions favor the phase transformation of molecular fullerite into the hard amorphous phase. The hardness of a specimen removed from a diamond anvil cell loaded up to 26 GPa under shear deformation applied is found to be equal to 30 GPa. 相似文献
16.
M.E. Kozlov M. Tokumoto K. Yakushi 《Applied Physics A: Materials Science & Processing》1997,64(3):241-245
60 are reported. The material associated with the mixture of rhombohedral and tetragonal phases was synthesized under pressure
of when treatment temperature was only a little lower than the high-temperature limit of C60 stability. The substance exhibits very rich infrared and Raman spectra as well as luminescence spectra of an unusual shape.
They show that vibrational transitions in the prepared carbon architecture substantially deviate from icosahedral symmetry
of buckyballs and exhibit a similarity with lattice phonons in graphite. It may originate from mixing of C60 modes and vibrations of a layer structure on deformed and weakly bound fullerene molecules. The luminescence spectra reveal
three distinct electronic states located below . One of them responsible for the emission peak at is very characteristic for the pressure modified fullerene. The data should be useful for the accurate determination of structural
changes in C60 induced by pressure.
Received: 6 September 1996/Accepted: 10 October 1996 相似文献
17.
Correlations between the density, elastic properties, and hardness of the carbon phases prepared from C60 at a high pressure are studied. By varying the high pressure and temperature properly, one can obtain from C60 a broad class of ordered polymerized and disordered phases, for which the fraction of the sp2 and sp3 states, the characteristic dimensionality of the structure, the degree of covalent bonding, etc. can be varied successfully. 3D-bonded carbon structures are shown to exhibit a clearly pronounced correlation between the hardness or bulk modulus and the density, with these correlations also apparently applying to the carbon phases in a general case. At the same time, the mechanical characteristics of structures with a lower dimension covalent bonding are worse than those of 3D-bonded phases with similar values of the density. 相似文献
18.
V. A. Davydov L. S. Kashevarova A. V. Rakhmanina V. N. Agafonov R. Ceolin H. Szwarc 《JETP Letters》1996,63(10):818-824
Modifications of carbon which are formed from C60 fullerite at pressures up to 10.0 GPa and temperatures up to 1900 K are studied by x-ray diffraction, Raman spectroscopy,
and atomic force microscopy methods. The pressures p and temperatures T at which atomic, molecular, and polymolecular structures form under conditions of quasihydrostatic compression are determined.
It is shown that, together with polymerization, another type of chemical interaction of the molecules, called polycondensation,
which leads to the formation of polymolecular structures with a shortest intermolecular distance of 0.65 nm, is possible in
the system. Three-dimensional polycondensation of C60 fullerene is explained by the special properties of the new carbon states.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 778–783 (25 May 1996)
The spelling of the authors names are presented here in English as requested by the Russian Editorial office. 相似文献
19.
Optical properties in the spectral range from 0.06 to 5.5 eV of fullerite films on different substrates, C60 powder, and dissolved fullerene material are investigated by spectroscopic ellipsometry and optical transmission and reflection measurements. Depolarization effects are taken into account during determination of the dielectric function of fullerite films by ellipsometry. The optical gap for C60 films is found to be 1.63 eV. Three optical absorption bands are observed at 2.69, 3.53, and 4.49 eV.The dielectric function in the infrared shows the four characteristic infrared vibrational modes. The interference pattern seen in UV/VIS reflection measurements are used for high-precision thickness determination of the films. The Clausius-Mossotti formula is successfully applied to reproduce the experimental optical data measured in C60/dichlormethane solutions. Deviations between theory and experiments provide interesting information about the intermolecular interaction of the C60 molecules. A tentative interpretation of the measured absorption bands is presented. 相似文献
20.
A. G. Melent’ev N. V. Klassen N. P. Kobelev R. K. Nikolaev Yu. A. Osip’yan 《Physics of the Solid State》1999,41(6):1021-1024
The mechanical properties of single-crystal fcc C60 fullerite are investigated by sclerometry and precision contact profilometry. Quantitative estimates are obtained for the
microhardness anisotropy on the (100) and (111) planes. Polarity of the mechanical properties is observed in the (111) plane.
The mechanisms considered for the orientational deformation of C60 single crystals by a moving indentor confirm existing data showing that plastic deformation in solid C60 occurs along the [011] (111) systems.
Fiz. Tverd. Tela (St. Petersburg) 41, 1119–1123 (June 1999) 相似文献