Hydrogen absorption and desorption kinetics in fullerite C 60 single crystals. Low-temperature micromechanical and structural characteristics of the interstitial solid solution C 60 ( H 2 ) x

• Published in: Low temperature physics (Woodbury, N.Y.) N.Y.), 2008-01, Vol.34 (1), p.69-74
• Main Authors: Fomenko, L. S., Lubenets, S. V., Natsik, V. D., Stetsenko, Yu. E., Yagotintsev, K. A., Strzhemechny, M. A., Prokhvatilov, A. I., Osipyan, Yu. A., Izotov, A. N., Sidorov, N. S.
• Format: Article
• Language: English
• ISSN: 1063-777X; 1090-6517
• DOI: 10.1063/1.2832358

The microhardness H V and lattice parameter a of C 60 single crystals are measured at room temperature as functions of the hydrogen saturation time t for several values of the saturation temperature (250, 300, and 350 ° C ) at a fixed hydrogen pressure p = 30 atm . According to the measurements of H V and a , the kinetics of hydrogen absorption is described by a simple exponential law with a single, temperature-dependent characteristic time. In highly saturated samples the microhardness is 4 times greater than for the initial C 60 crystal, while the lattice parameter is 0.2% larger. The temperature dependence of the microhardness H V and lattice parameter a of C 60 ( H 2 ) x crystals is investigated in the temperature interval 77 – 300 K . The introduction of hydrogen lowers the temperature of the fcc–sc phase transition, and the transition becomes strongly broadened in temperature. The dependence of the microhardness of the saturated sample on the hold time in air at room temperature is described by the sum of two exponentials with different characteristic times. Kinetics of this kind is presumably due to two processes: desorption of hydrogen from the sample, which causes a decrease of the microhardness, and a simultaneous penetration of gaseous impurities into the sample from the surrounding air, which is accompanied by hardening. The influence of the H 2 molecules on the characteristic of the intermolecular interaction in fullerite C 60 is discussed and the intercalation-induced processes of dislocation slip and microfracture.