Diana Filipa Guimarães

Abstract
Laser-induced breakdown spectroscopy is a spectroscopic technique that allows for fast elemental mapping of heterogeneous samples. Yet, detailed maps need high-resolution sampling grids, which can turn the task into a time-consuming process and can increase sample damage. In this work, we present the implementation of an imaged-based intelligent mesh algorithm that makes use of superpixel segmentation to optimize elemental mapping processes. Our results show that the approach can increase the elemental mapping resolution and decrease acquisition times, fostering opportunities for applications that benefit from minimal sample damage such as heritage analysis, or timely analysis such as industrial applications. © 2022 The Author(s)

Abstract
Imaging the spatial distribution of chemical elements at a sample surface is a common application of laserinduced breakdown spectroscopy with vast scientific and technological applications. Yet, typical imaging solutions only explore the creation of two-dimensional maps, which can limit the interpretability of the results and further diagnostics in three-dimensional settings. Within this context, this work explores the combination of spectral imaging techniques and photogrammetry to deploy a versatile solution for the creation of threedimensional spectral imaging models. First, by making use of a numerical algorithm that is able to match features in the spectral image with those of the three-dimensional model, we show how to match the mesh from distinct sensor modalities. Then, we describe a possible visualization workflow, making use of dedicated photogrammetry and visualization software to easily deploy interactive models. Overall, the results demonstrate the versatility of our approach and pave for the development of novel spectral imaging diagnostic strategies that are able to deliver better qualitative analysis and insight in the three-dimensional space.

Abstract
Anode-less batteries are a promising innovation in energy storage technology, eliminating the need for traditional anodes and offering potential improvements in efficiency and capacity. Here, we have fabricated and tested two types of anode-less pouch cells, the first using solely a copper negative current collector and the other the same current collector but coated with a nucleation seed ZnO layer. Both types of cells used the same all-solid-state electrolyte, Li2.99Ba0.005ClO composite, in a cellulose matrix and a LiFePO4 cathode. Direct and indirect methods confirmed Li metal anode plating after charging the cells. The direct methods are X-ray photoelectron spectroscopy (XPS) and laser-induced breakdown spectroscopy (LIBS), a technique not divulged in the battery world but friendly to study the surface of the negative current collector, as it detects lithium. The indirect methods used were electrochemical cycling and impedance and scanning electron microscopy (SEM). It became evident the presence of plated Li on the surface of the current collector in contact with the electrolyte upon charging, both directly and indirectly. A maximum average lithium plating thickness of 2.9 µm was charged, and 0.13 µm was discharged. The discharge initiates from a maximum potential of 3.2 V, solely possible if an anode-like high chemical potential phase, such as Li, would form while plating. Although the ratings and energy densities are minor in this study, it was concluded that a layer of ZnO, even at 25 °C, allows for higher discharge power for more hours than plain Cu. It was observed that where Li plates on ZnO, Zn is not detected or barely detected by XPS. The present anode-less cells discharge quickly initially at higher potentials but may hold a discharge potential for many hours, likely due to the ferroelectric character of the electrolyte.

Abstract
Laser-induced breakdown spectroscopy (LIBS) is a technique that leverages atomic emission towards element identification and quantification. While the potential of the technology is vast, it still struggles with obstacles such as the variability of the technique. In recent years, several methods have exploited modifications to the standard implementation to work around this problem, mostly focused on the laser side to increase the signal-to-noise ratio of the emission. In this paper, we explore the effect of pulse duration on the detected signal intensity using a tunable LIBS system that consists of a versatile fiber laser, capable of emitting square-shaped pulses with a duration ranging from 10 to 100 ns. Our results show that, by tuning the duration of the pulse, it is possible to increase the signal-to-noise ratio of relevant elemental emission lines, an effect that we relate with the computed plasma temperature and associated density for the ion species. Despite the limitations of the work due to the low-resolution and small range of the spectrometer used, the preliminary results pave an interesting path towards the design of controllable LIBS systems that can be tailored to increase the signal-to-noise ratio and thus be useful for the deployment of more sensitive instruments both for qualitative and quantitative purposes. © 2022, Universidade do Porto - Faculdade de Engenharia. All rights reserved.

Abstract