Measurement of Li diffusion in porous carbon by neutron depth profiling

Diffusion of Lithium in Thin Copper Measured by Neutron Depth Profiling

“…Figure 2 shows a typical energy spectrum obtained by the NDP method from the as-prepared Cu/Li/Cu sample. The two peaks on the channels ∼620 and ∼985 are due to the α and t particles, respectively, produced by the reaction of 6 Li(n th , α)t with thermal neutrons in the buried Li slab, which reached the detector after passing through the Cu top layer with the corresponding (residual) energies. To determine the Li depth profile, only α particles were taken into account in the simulation for their better energy and depth resolutions.…”

“…From the extracted data, the thickness of the Cu and Li layers could be estimated: ∼550 nm for each Cu layer and ∼50 nm for a Li slab between the Cu layers. Figure 5 shows the 6 Li depth profiles after 1 h of isochronal annealing at 300 and 500 °C compared to the profile in the as-deposited Cu/Li/Cu multilayer. One can see also that after annealing the depth profiles of 6 Li retain the Gaussian-like shape but expand with increasing annealing temperature.…”

“…The samples were annealed isochronally for 1 h in high vacuum (with a base pressure of 10 −4 mbar) at different temperatures between 100 and 500 °C (with steps of 100 °C/1 h) to induce thermal diffusion of lithium atoms in Cu. After each annealing step, the depth profile of Li was measured by the NDP method using an intense nuclear reaction (n th , α) of thermal neutrons with the 6 Li isotope (7.5 % in natural Li), which can be written as Reaction products, α and t charged particles, passing through the Cu layers, gradually lose their energy. Thus, the original position of the 6 Li atoms can be reconstructed by measuring the energy spectra and comparing them with the simulated data (see below).…”

“…After each annealing step, the depth profile of Li was measured by the NDP method using an intense nuclear reaction (n th , α) of thermal neutrons with the 6 Li isotope (7.5 % in natural Li), which can be written as Reaction products, α and t charged particles, passing through the Cu layers, gradually lose their energy. Thus, the original position of the 6 Li atoms can be reconstructed by measuring the energy spectra and comparing them with the simulated data (see below). The employed neutron beam was provided by the nuclear reactor LWR-15 in Rez (operated by the Research Center Rez, www.cvrez.cz, with a flux of about 10 7 n th /cm 2 /s).…”

“…The experimental data, obtained in this way, are subjected to an error of about 10−15 % due to uncertainties in monitoring the neutron fluence, geometry of detector−sample system, energy spectra simulation, etc. From the recorded energy spectrum, the depth distribution of 6 Li nuclei could be determined using the LIBOR code developed by our team in 2010. 21 The code is based on an algorithm that optimizes the match between the simulated and measured spectra.…”