Pore REconstruction and Segmentation (PORES) method for improved porosity quantification of nanoporous materials

Electron tomography is currently a versatile tool to investigate the connection between the structure and properties of nanomaterials. However, a quantitative interpretation of electron tomography results is still far from straightforward. Especially accurate quantification of pore-space is hampered by artifacts introduced in all steps of the processing chain, i.e., acquisition, reconstruction, segmentation and quantification. Furthermore, most common approaches require subjective manual user input. In this paper, the PORES algorithm “POre REconstruction and Segmentation” is introduced; it is a tailor-made, integral approach, for the reconstruction, segmentation, and quantification of porous nanomaterials. The PORES processing chain starts by calculating a reconstruction with a nanoporous-specific reconstruction algorithm: the Simultaneous Update of Pore Pixels by iterative REconstruction and Simple Segmentation algorithm (SUPPRESS). It classifies the interior region to the pores during reconstruction, while reconstructing the remaining region by reducing the error with respect to the acquired electron microscopy data. The SUPPRESS reconstruction can be directly plugged into the remaining processing chain of the PORES algorithm, resulting in accurate individual pore quantification and full sample pore statistics. The proposed approach was extensively validated on both simulated and experimental data, indicating its ability to generate accurate statistics of nanoporous materials

Automated discrete electron tomography – Towards routine high-fidelity reconstruction of nanomaterials

Electron tomography is an essential imaging technique for the investigation of morphology and 3D structure of nanomaterials. This method, however, suffers from well-known missing wedge artifacts due to a restricted tilt range, which limits the objectiveness, repeatability and efficiency of quantitative structural analysis. Discrete tomography represents one of the promising reconstruction techniques for materials science, potentially capable of delivering higher fidelity reconstructions by exploiting the prior knowledge of the limited number of material compositions in a specimen. However, the application of discrete tomography to practical datasets remains a difficult task due to the underlying challenging mathematical problem. In practice, it is often hard to obtain consistent reconstructions from experimental datasets. In addition, numerous parameters need to be tuned manually, which can lead to bias and non-repeatability. In this paper, we present the application of a new iterative reconstruction technique, named TVR-DART, for discrete electron tomography. The technique is capable of consistently delivering reconstructions with significantly reduced missing wedge artifacts for a variety of challenging data and imaging conditions, and can automatically estimate its key parameters. We describe the principles of the technique and apply it to datasets from three different types of samples acquired under diverse imaging modes. By further reducing the available tilt range and number of projections, we show that the proposed technique can still produce consistent reconstructions with minimized missing wedge artifacts. This new development promises to provide the electron microscopy community with an easy-to-use and robust tool for high-fidelity 3D characterization of nanomaterials

Insights into CO2-mineralization using non-ferrous metallurgy slags:CO2(g)-induced dissolution behavior of copper and lead slags

Abstract The possibility of utilizing non-ferrous slags for CO₂-mineralization is explored in this study by investigating their dissolution behaviors in CO₂-environments, since dissolution is usually considered as a major rate-limiting step during CO₂-mineralization. Dissolution of two copper slags and a lead slag are studied at the liquid to solid ratio (w/w) of 1000 at combinations of two temperatures (30 and 60 °C) and two CO₂-pressures (1 and 10 barg) with time (30, 60, 120, and 240 min). Among the systems in which the slags are dissolved in CO₂-environments, the lead slag exhibits Fe-dissolution of up to 10%, and the copper slags up to 5–6% within four hours. The solution-pH were between 4 and 5 in almost all the observations. The dissolution rates of the slags are found to be in the range of 10−7-10−9 mol/m²/s which are comparable with the dissolution of natural fayalite in (in)organic acids. Following the dissolution during the initial 30–60 min, the systems at a higher temperature (at constant CO₂-pressure) and higher CO₂-pressure (at constant temperature) exhibit higher (or comparable) [Ca], [Fe], [Si], and solution-pH. Moreover, even though the systems at higher temperature and CO₂-pressure exhibit higher solution-pH following the initial 30–60 min of dissolution, they continue to exhibit higher dissolution rates throughout the study. Since the residues like non-ferrous copper and lead slags are readily available compared to the analogous natural minerals (like olivines) that usually need to be pre-processed before carbonation, they are proposed as promising sources for CO₂-mineralization

Accelerated carbonation of ferrous and non-ferrous slags to produce clinker-free carbonate-bonded blocks:synergetic reduction in environmental leaching

Abstract Clinker-free, carbonate-bonded monoliths are prepared by accelerated carbonation for immobilization of hazardous elements present in: a stainless-steel slag, two copper slags, and one lead slag. In addition to the studies on individual slags, mixes of copper slags and lead slags with 33 % and 66 % replacements of stainless-steel slag are also studied. Combinations of two temperatures (30 and 60 °C) and three CO2-pressures (1, 5, and 10 barg) are studied. Among the non-ferrous slags carbonated individually, lead slag carbonated at 10 barg exhibited carbonate-cementation. The carbonate-bonded monoliths containing stainless-steel slag exhibited high compressive strengths, individually or as in its mixes with other slags. In stainless-steel slag, while its individual carbonation also showed a decrease in Cr-leaching, the Cr-leaching from its mixes with non-ferrous slags are disproportionately lower: possible chemical synergy of stainless-steel slag with sulfidic non-ferrous slags is discussed. For lead slag individually, carbonation significantly decreases Pb-leaching; while Co, Zn, and Mn leaching first increase and then decrease with an increase in CO2-pressure. In mixes of lead slag with stainless-steel slag, Pb, Co, Zn, and Mn leaching are significantly decreased. Temperature does not have a significant influence on the product properties. Copper slag remained relatively insensitive towards carbonation. Comparisons are made with the Flemish legislative limits