Atomic mobility in liquid gallium under nanoconfinement

Abstract

Results of NMR studies of nuclear spin-lattice relaxation in liquid metallic gallium confined within random pore networks of two different porous glasses with 16 and 2 nm pore sizes are presented. The measurements were run in the temperature range from 330 K to confined gallium freezing. Relaxation for both gallium isotopes 71 Ga and 69 Ga was found to accelerate remarkably compared to the bulk melt, the dominant mechanism of relaxation changing from magnetic to quadrupolar. The correlation time of electric field gradient fluctuations caused by atomic motion was estimated at various temperatures using data for quadrupolar relaxation contribution and was found to increase drastically compared to bulk, which corresponded to a pronounced slowdown of atomic mobility in confined liquid gallium. The influence of confinement was more effective for smaller pore sizes. The temperature dependence of the correlation time for confined gallium was found to be noticeably stronger than in bulk, an additional slowdown of atomic mobility being observed at low temperatures.

Diffusion slowdown in the nanostructured liquid Ga‐Sn alloy

“…It should be also emphasized that the calculated magnetic relaxation times coincide within experimental accuracy with those found for two gallium isotopes in liquid pure gallium and eutectic gallium indium alloy which shows that the conduction electron density on nuclei is about the same for all those bulk melts. The invariability of the magnetic contribution to relaxation agrees with quite similar magnitudes of the Knight shift which in the Ga‐Sn alloy is less than in pure melted gallium by only 16 ppm .…”

“…To get the line shape the number of scans mounted up to 8192. The repetition time was 0.1 s. The Knight shift for gallium isotopes was referenced to NMR signals from a GaAs single crystal as in . Similar experiments were carried out for bulk Ga‐Sn melt of the same composition to compare the results obtained for bulk and nanostructured alloys.…”

“…In this case the correlation time can be directly calculated from the quadrupole contribution to nuclear spin relaxation while in solids more complicated experiments might be necessary . This method was successfully applied to get data on mobility in small particles and thin films of melted indium, gallium, and their alloy . To extend the knowledge of the influence of size reduction on self‐diffusion in metallic melts we carried out studies of atomic mobility in the nanostructured liquid gallium‐tin alloy.…”

Slowdown of self-diffusion induced by partial freezing in confined liquid indium

“…Note that the remarkable slowdown of self-diffusion was also observed near room temperature in liquid gallium within nanoporous matrices, 11 in thin gallium films, 30 and in isolated gallium particles 31 and at reduced temperatures in liquid gallium embedded into porous glasses. 12 The increase in the correlation time for indium within pores upon decreasing the amount of the unfrozen melt should also influence the quadrupole contribution to transverse spin relaxation. Within the framework of the extreme narrowing approximation, the longitudinal and transverse relaxation times are equal to each other.…”

Динамический сдвиг линий ЯМР в наноструктурированном расплаве Ga-In-Sn

“…Большинство ЯМР-иссле-дований проводников в условиях ограниченной геомет-рии проводилось для легкоплавких металлов, таких как галлий, индий, ртуть и их сплавы (см. [2][3][4] и ссылки в этих работах). Было выявлено существенное влияние размера пор и соответственно размера метал-лических частиц на атомную подвижность, электрон-ную восприимчивость и фазовые переходы плавление-кристаллизация.…”