4He Sorption in Graphene Oxide at Low Temperatures

The sorption and subsequent desorption of 4He gas by grapheme oxide (GO) and hydrazine-reduced grapheme oxide (RGO-Hz) powders have been investigated in the temperature interval 2 – 25 K. It is found that the Hz-reduction of GO increases the sorptive capacitance of RGO-Hz by a factor of 3.3 in com-parison with GO. It is assumed that the sorptive capacity of the RGO-Hz sample increases because the O2-containing groups are removed in the process of Hz-reduction of GO, which makes the interlayer space ac-cessible for sorption When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3520

4He Sorption in Graphene Oxide at Low Temperatures

The sorption and subsequent desorption of 4He gas by grapheme oxide (GO) and hydrazine-reduced grapheme oxide (RGO-Hz) powders have been investigated in the temperature interval 2 – 25 K. It is found that the Hz-reduction of GO increases the sorptive capacitance of RGO-Hz by a factor of 3.3 in com-parison with GO. It is assumed that the sorptive capacity of the RGO-Hz sample increases because the O2-containing groups are removed in the process of Hz-reduction of GO, which makes the interlayer space ac-cessible for sorption When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3520

Peculiarities of thermal expansion of quasi-two-dimensional organic conductor κ-(BEDT–TTF)₂Cu[N(CN)₂]Cl

Linear coefficient of thermal expansion α( T) of single crystal (BEDT–TTF)₂Cu[N(CN)₂]Cl was studied along the crystal layers using the method of precise capacitive dilatometry in the temperature range 2–285 K. It is positive in this direction over the entire temperature range. Anomalies of thermal expansion were observed at 29–30 K and 74–80 K. The anomaly near 30 K is, apparently, due to the transition between the paramagnetic phase and the antiferromagnetic insulator state. Peak of α( T) at 78 K corresponds to a phase transition related to orientational disordering of ethylene groups in dimers of BEDT–TTF. A broad maximum of α(T) in the temperature range 40–70 K, is apparently explained by fluctuations of charge within the dimers, and by spin fluctuations, which first increase with increasing temperature, and then decrease in process of thermal disordering of dimers

Theory of Sound Propagation in Superfluid Solutions Filled Porous Media

A theory of the propagation of acoustic waves in a porous medium filled with superfluid solution is developed. The elastic coefficients in the system of equations are expressed in terms of physically measurable quantities. The equations obtained describe all volume modes that can propagate in a porous medium saturated with superfluid solution. Finally, derived equations are applied to the most important particular case when the normal fluid component is locked inside a highly porous media (aerogel) by viscous forces and the velocities of two longitudinal sound modes are calculated.Comment: 13 pages, 0 figure

NEW PHENOMENA RELATED TO PROPAGATION OF WAVE PROCESSES IN He–II FLOW

On étudie les effets d'une perturbation alternative sur les écoulements stationnaires d'He–II dans les films et les capillaires. L'étude de la dépendance en fréquence des effets obtenus permet de donner une estimation des temps caractéristiques associés aux processus dissipatifs présents dans ces écoulements. Les résultats expérimentaux sont en bon accord avec un modèle théorique basé sur une force dissipative non-linéaire en vitesse.Specific features of steady superfluid He–II flow modulated by a wave process have been studied in He II-films and narrow channels. The frequency dependence of the effects permits the characteristic times of the dissipative processes developing in superfluidity to be estimated. The experimental results are in agreement with the theoretical model based on a nonlinear behaviour of the dependence of friction force on superflow velocity

QUANTUM DIFFUSION IN SOLID HELIUM, DETECTION AND INVESTIGATION OF IMPURITON-PHONON MECHANISM OF SCATTERING

On mesure par la méthode des échos de spin en RMN le coefficient de diffusion D de 3He dans 4He solide pour des concentrations x en 3He comprises entre 6 x 10-5 et 1,2 x 10-3. Les résultats obtenus montrent que pour x < 10-3, D augmente brusquement lorsqu'on abaisse la température T suivant la loi D α T-9, ce qui révèle le rôle dominant de la diffusion des phonons par les impuretés. Par diverses méthodes on évalue la largeur de la bande d'impuritons à environ 10-4K.The diffusion coefficient, D, of 3He in solid 4He with the concentration of 6 x 10-5 < X < 1.2 x 10-3 has been measured using the pulse NMR method. The results suggest that for the 3He concentration less than 10-3 there is a sharp increase in D with lowering the temperature by the law D ~ T-9, indicating the dominant role of the processes of lattice phonon scattering of impuritons in solid helium. Estimated by various methods, the energy gap of impuritons is about ~ 10-4K