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Submitted on 1 Jan 1978
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THERMAL EXPANSION OF METHANES AND
CONVERSION PROCESSES
V. Manzhelii, A. Tolkachev, A. Aleksandrovskii, V. Kokshenev, V. Kuchnev
To cite this version:
JOURNAL DE PHYSIQUE Colloque C6, supplément au n" 8, Tome 39, août 1978, page C6-1021
THERMAL EXPANSION OF METHANES AND CONVERSION PROCESSES
V.G. Manzhelii, A.M. Tolkachev, A.N. Aleksandrovskii, V.B. Kokshenev and V.I. Kuchnev
Physico-Technical Institute of Low Temperatures, UkrSSR, Academy of Sciences, 47, Lenin Prospect,
Kharkov, 310164, USSR
Résumé.- On a étudié la dilatation thermique du méthane solide, contenant de l'oxygène et de l'azote comme impuretés, dans la gamme de température entre 2 et 14 K.
Abstract.- The thermal expansion of solid methane, containing O2 and N2 impurities, was studied in the temperature range from 2 K to 14 K.
The thermal expansion coefficient of methane was obtained for samples in spin equilibrium. Expe-rimentally a relation between the negative thermal expansion coefficient/1-2/ and the spin conversion process was found. Qualitatively our results agree with the measured low energy states in methane/3/ and the theoretical conclusions of Yamamoto's group /4-5/.
From the analysis of the time dependence des-cribing the volume variation of pure methane samples with temperature the typical conversion times and
their temperature dependence were derived, which are shown in figure 1.
Fig. 1 : Temperature dependence of characteristic conversion time.
The presence of O2 and N2 impurities were found to effect significantly the thermal expansion of me-thane equilibrium in the spin modification
composi-Fig. 2 : Temperature dependences of relative elon-gation of methane containing O2 and N2 impurities.
tion (figure 2 ) . The orientationally disordered sub-lattices appeared to be more sensitive to the rity effect. An explanation of the effect of impu-rities with a quadrupole molecular interaction on methane thermal expansion has been proposed.
The studies on solid deuteromethane and methane-deuteromethane solution permitted the
speci-fic features of thermal expansion of orientationally ordered phases of CH^ and CDj, to be found.
References
/ I /
Aleksandrovskii,A.N., Kuchnev,V.I., Manzhelii,V.G.
and Tolkachev,A.M., Phys. Status Solidi (b)
73
(1976) KIII
/2/ Heberlein,D. and Adams,E.D.,
J. Low Temp. Phys.
3 (1970) 115
