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The paper presents post-mortem analysis of commercial LiFePO4 battery cells, which are aged at 55 °C and − 20 °C using dynamic current profiles and different depth of discharges (DOD). Post-mortem analysis focuses on the structure of the electrodes using atomic force microscopy (AFM) and scanning electron microscopy (SEM) and the chemical composition changes using energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS). The results show that ageing at lower DOD results in higher capacity fading compared to higher DOD cycling. The anode surface aged at 55 °C forms a dense cover on the graphite flakes, while at the anode surface aged at − 20 °C lithium plating and LiF crystals are observed. As expected, Fe dissolution from the cathode and deposition on the anode are observed for the ageing performed at 55 °C, while Fe dissolution and deposition are not observed at − 20 °C. Using atomic force microscopy (AFM), the surface conductivity is examined, which shows only minor degradation for the cathodes aged at − 20 °C. The cathodes aged at 55 °C exhibit micrometer size agglomerates of nanometer particles on the cathode surface. The results indicate that cycling at higher SOC ranges is more detrimental and low temperature cycling mainly affects the anode by the formation of plated Li. [ABSTRACT FROM AUTHOR]

The advantages of using the method of laser coloration for investigation of specific features of filamentation in homogeneous transparent dielectrics are described. The results of several experiments conducted with a lithium fluoride crystal by this method are presented. The possibility is shown of obtaining data on the structure of the light field in a filament formed by a single laser pulse and processing them at a substantially later time after the experiment, which is not available by using other methods, allowed observing a plasma-free regime of filamentation, detecting single-cycle light bullets, and demonstrating their robustness. [ABSTRACT FROM AUTHOR]

Abstract Depth profiles of nanohardness and photoluminescence of F 2 and F 3 + centers in LiF crystals irradiated with 12 MeV 12C, 56 MeV 40Ar and 34 MeV 84Kr ions at fluences 1010–1015 ions/cm2 have been studied using laser scanning confocal microscopy, dislocation etching and nanoindentation techniques. The room temperature irradiation experiments were performed at DC-60 cyclotron (Astana, Kazakhstan). It was found that the luminescence intensity profiles of aggregate color centers at low ion fluences correlate with electronic stopping profiles. The maximum intensity of aggregate center luminescence is observed at fluence around 1013 ions/cm2 and rapidly decreases with further increase of fluence. At the highest ion fluences, the luminescence signal is registered in the end-of-range area only. The depth profiles of nanohardness and chemical etching have shown remarkable ion-induced formation of dislocations and increase of hardness which in the major part of the ion range correlate with the depth profile of electronic energy loss. An exception is the end-of-range region where strong contribution of nuclear energy loss to hardening at high fluences is observed. Highlights • Ion-induced formation of complex color centers and dislocation loops is observed. • The depth profiles of ion-induced damage in LiF are studied using photoluminescence, dislocation etching and nanoindentation. • The fluence behavior of photoluminescence has been studied. • The contribution of electronic and nuclear stopping mechanisms to damage is compared. [ABSTRACT FROM AUTHOR]

Influence of the irradiation with 13.5 MeV 3 He and 5 MeV 4 He ions on the micro-structure and mechanical properties of LiF single crystals was studied. The depth profiles of nanoindentation, dislocation mobility, selective chemical etching and photoluminescence served for the characterization of damage. Strong ion-induced increase of hardness and decrease in dislocation mobility at the stage of track overlapping due to accumulation of dislocations and other extended defects was observed. At high fluences (10 15 ions/cm 2 ) the hardness saturates at about 3.5 GPa (twofold increase in comparison to a virgin crystal) thus confirming high efficiency of light projectiles in modifications of structure and properties. The effects of ion-induced increase of hardness and decrease of dislocation mobility are observed also beyond the ion range and possible mechanisms of such damage are discussed. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL), being one of the common luminescence methods, is very sensitive to the presence of any impurities in the material structure and can be used for the detection of impurity distribution in the bulk of the crystal. If in a TL reader a CCD camera is used, a measurement of TL signal would give us an unique two-dimensional (2-D) imaging of TL signal distribution, and thereby the distribution of dopants. The possibility of the application of 2-D TL method for the control of uniformity of the crystal related to dopant distribution in the volume of the bulk crystal was tested on the large area samples of LiF doped and un-doped crystals grown by Czochralski method at the IFJ PAN in Kraków. The special TL reader with a CCD camera was used for analyzing of luminescence emitting during the heating of the irradiated in uniform radiation field slices of crystals cut longitudinal and perpendicular to the growth axis and for analyzing of the shape of TL glow curves for selected crystal areas. Non-uniform distribution of the dopants was demonstrated for doped crystal grown with relatively slow growth rate. [ABSTRACT FROM AUTHOR]

The modifications of the structure and hardness of LiF crystals under high-fluence irradiation with MeV- and GeV-energy Au ions have been studied using nanoindentation and atomic force microscopy. The formation of ion-induced dislocations and bulk nanostructures consisting of grains with nanoscale dimensions (50 nm - 100 nm) has been observed. The structural modifications are accompanied by a strong ion-induced hardening which is related to dislocation impeding by assemblies of defect aggregates, dislocation loops of vacancy and interstitial types and grain boundaries. For MeV ions, the modifications are localized in a thin surface layer (few mm) where much higher density of deposited energy is reached and deeper stage of aggregation of radiation defects is achieved than for GeV ions with the same absorbed energy.http://dx.doi.org/10.5755/j01.ms.17.3.583

The results obtained using methods of total current spectroscopy (TCS) and secondary-ion mass spectroscopy (SIMS) under ion bombardment of LiF crystals are analyzed. It is shown that the majority of the products of crystal sputtering contain point defects. A procedure for determining defects in sputtered clusters of ionic crystals is developed. [ABSTRACT FROM AUTHOR]

Abstract: Luminescence of color centers in the near-infrared region under cathode beam excitation is revealed for the first time in as-grown pure LiF and LiF:Mg,O crystals. Emission efficiency of , and centers is higher for the samples enriched by oxygen and magnesium than for ultrapure crystals. The intensity of the NIR luminescence remains practically constant with the increase of the electron beam density. In contrast, visible emission typical for and F2 centers is suppressed due to the induced absorption bands. It is assumed that the high-density electronic irradiation leads to the strongly pronounced thermal- and radiation-stimulated diffusion in a relatively thin layer. It causes the association of point radiation defects with the formation of various complex centers and aggregates. Results obtained suggest that LiF crystals can be used for in-situ detection of ionizing radiation. [Copyright &y& Elsevier]

The monochromatic soft X-ray femtosecond pulses of the Free Electron Laser (FEL) with wavelengths of 17.2-61.5 nm were applied for measurements of optical features of point defects photoluminescence in LiF crystals. It was observed that peak of photoluminescence spectra appears near 530 nm and is associated with emission of F3+ centers. Our results suggest that a shortening of the applied laser pulses down to pico - or femtosecond duration causes redistribution of photolumi-nescence peak intensity from the red to the green part of the spectra and does not depend on the energy of EUV or X-ray photons. Dependence of peak intensity of photoluminescence spectra on the fluence of FEL radiation was measured. Even for relatively high fluencies a quenching phenomenon was not observed. [ABSTRACT FROM AUTHOR]

The modifications of the structure and hardness of LiF crystals under high-fluence irradiation with MeV- and GeVenergy Au ions have been studied using nanoindentation and atomic force microscopy. The formation of ion-induced dislocations and bulk nanostructures consisting of grains with nanoscale dimensions (50 nm - 100 nm) has been observed. The structural modifications are accompanied by a strong ion-induced hardening which is related to dislocation impeding by assemblies of defect aggregates, dislocation loops of vacancy and interstitial types and grain boundaries. For MeV ions, the modifications are localized in a thin surface layer (few µm) where much higher density of deposited energy is reached and deeper stage of aggregation of radiation defects is achieved than for GeV ions with the same absorbed energy. [ABSTRACT FROM AUTHOR]

This paper describes an overview of our recent discovery – clear demonstration that LiF crystals can be efficiently used as a high-performance neutron imaging detector based on optically stimulated luminescence of color centers generated by neutron irradiation. It is shown that the neutron images we have obtained are almost free from granular noise, have a spatial resolution of ${\sim}5.4~{\rm\mu}\text{m}$ and a linear response with a dynamic range of at least $10^{3}$. The high contrast and good sensitivity of LiF crystals allow us to distinguish two holes with less than 2% transmittance difference. We propose to use such detectors in areas where high spatial resolution with high image gradation resolution is needed, including diagnostics of different plasma sources such as laser and z-pinch produced plasmas. [ABSTRACT FROM AUTHOR]