Conference Agenda

Coupled dissolution and precipitation occurring at solid-fluid interfaces plays a crucial role in a multitude of geochemical processes and are essential for the cycling of elements within the Earth. Fluid-cell Raman spectroscopy (FCRS) enables the real-time and space-resolved (operando) study of reaction mechanisms, kinetics, and transport processes at solid-fluid interfaces at the micrometer scale and at elevated temperatures. The ability to monitor reaction and transport of solutes without interrupting the ongoing corrosion of silicate glasses, and other transparent materials, represents a unique strength of this technique, circumventing the limitations of conventional multi-step batch experiments that entail quenching and drying of the sample for post mortem analysis. This, however, is critical as it can change the structural and chemical properties of the surface alteration layer (SAL), due to, e.g., precipitation of minerals during drying, condensation, and polymerization reactions. Present FCRS experiments focus on the aqueous corrosion of borosilicate glasses at ~ 85 °C, providing further insights into the still-debated glass corrosion model. Furthermore, FCRS was applied to study mineral-fluid interactions, including the replacement reaction of celestine by strontianite and silica-based SAL-formation during olivine dissolution under acidic solution conditions. In combination with isotopic tracers, transport processes can be traced across the evolving interfaces of the pristine solid phase and secondary precipitates. Identifying key reaction and transport processes is fundamental to improving the predictive capability of (reactive transport) models, which are used to assess the long-term performance of, e.g., high-level radioactive waste glasses, and minerals used for carbon dioxide removal strategies.

Concentrated solar power (CSP) plants are among the most important technologies for the future development of renewable energy, particularly in the context of climate change. For the next generation of power plants, the aim is to operate at higher temperatures (>700 °C) in order to increase thermal efficiency and economic competitiveness. Chloride melts are to be used as new heat transfer and storage media; whilst these offer numerous advantages, they exhibit highly corrosive behaviour towards metallic materials. The corrosion products are chemically and structurally very heterogenous, but the precise identification of reaction products is crucial for the prediction of long-term performance of the materials. Here, a multi-analytical approach is applied to gain insights into material degradation from different perspectives.

This study investigates material degradation phenomena of austenitic materials after exposure to chloride salt (NaCl/KCl). The samples are exposed to various conditions, including different temperatures (>500 °C) and atmospheres (air and argon). Particular focus is placed on the influence of targeted pre-oxidation and its effect on early reaction kinetics and the formation of corrosion products.

Subsequent the exposure experiments, material changes were analysed across scales using light microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Finally, the different experimental set-ups and the results obtained are compared.

Slags are by-product materials resulting from the smelting and refining of metals. Due to their potential residual environmental toxic compounds, they pose an environmental threat. However, some of the metals in the slags can be recovered, and metals and slags can be utilized by the industry. One technique for recovering these metals is smelting. This process depends on achieving the correct mixture of slag-forming species and flux materials to obtain the suitable viscosity for separating metal from slag, while keeping the process energy efficient. To determine the mixtures that generate the highest metal yield and best phase separation, simulation studies are carried out, followed by lab-scale experiments, and then the optimal mixture is scaled up to pilot-plant experiments.

X-ray micro computed tomography (µXCT) is an invaluable tool for visualization and quantitative evaluation of the results of smelting experiments. Using devices with different energy capabilities, it is possible to screen and evaluate the results of pyrometallurgical products from lab to pilot plant-scale. Combining these capabilities, characteristics such as metal droplets shapes, sizes and distribution within the slag as well as gas bubbles formation in slags and metals can be accessed without needing sample preparation. Additionally, quantifying the sizes of the metal nuggets can be used to determine metal density and total volume recovered. Examples of pyrometallurgical experiments evaluated with µXCT will be presented.

Systematically using this method opens up new possibilities for quickly visualizing and quantifying the results of pyrometallurgical experiments with minimal preparation effort while leaving further analytical possibilities open.

The production of many metals from their natural ores or metal oxides is an energy-intensive process that typically requires high temperatures and significant amounts of reducing agents. Ball-milling is a versatile mechanochemical technique capable of transforming metal oxides directly into metals, which can then be utilized as catalysts, components in battery materials, or as supported nanomaterials. A key advantage of mechanochemical methods is their operation under ambient conditions and the absence of solvents. In this study, we systematically investigate the reduction of various transition metal oxides such as Co₃O₄, ZnO, and Fe₂O₃ using different solid reducing agents (Al, Mg, C) during ball-milling. The process is examined using a combination of ex situ and in situ characterization techniques to elucidate the role of each reducing agent in the transformation mechanism.

Our study integrates a multi-technique analytical approach to decode the complex dynamics of mechanochemical reduction. Ex situ X-ray powder diffraction (XRD) was used to monitor detailed phase evolution, while X-ray photoelectron spectroscopy (XPS) was employed to probe surface chemical states and oxidation levels of transition metals. Complementary SEM/EDS mapping reveals microstructural changes and elemental distribution. Gas evolution analysis (mass spectroscopy and gas chromatography) tracks CO₂ release during carbon-mediated reduction, enabling kinetic assessment.

We further demonstrate that milling parameters profoundly influence reaction kinetics and product phase.

From bulk crystallography to real-time gas monitoring, the techniques used in this work advances the mechanistic understanding of solid-mediated reduction in mechanochemistry and demonstrates how in situ multi-scale analytics is essential for decoding complex solid-state reactions.

To recover lithium from a lithium-ion battery (LIB) recycling slag, one approach is the accumulation of lithium in “engineered artificial minerals” (EnAM).^[1] β-eucryptite (LiAlSiO₄) is a prime candidate as a lithium EnAM, as it has a high lithium content (5.51 mass-% Li) and is chemically similar and structurally identical to the leachable hight temperature γ-modification of the most common lithium ore, spodumene.^[2]

To assess the recycling potential of a solidified slag, multiple parameters, e.g., microstructure, mineral chemistry, and bulk composition, need to be quantified in an exact and meaningful manner. To achieve this goal, image analysis based on scanning electron microscopy (SEM) backscattered electron (BSE) images, electron probe microanalysis (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and X-ray diffraction (XRD)-based Rietveld quantification were applied.

An industrial pyrometallurgical slag from the recycling of LIBs from a standard batch process was investigated. Additionally, a second thermochemically conditioned slag was characterized. It was demonstrated that the quantitative assessment of the microstructure yields valuable data on properties relevant for recycling, such as grain shape relevant for liberation and grain size distribution before and after comminution, which is critical for flotation. Furthermore, it could be demonstrated that XRD-based Rietveld results show a high reproducibility in this system. However, the Rietveld results are strongly affected by microabsorption as the lithium-bearing phases are overquantified due to their mass absorption coefficients (MAC) being much lower than the MAC of the non-lithium-bearing minerals.

[1] Hampel, et al., ACS omega, 2024.

[2] Gantz, et al., Adv Sci, 2026.