TU Bergakademie Freiberg

Bake hardening (BH) is a static strain aging phenomenon, where the yield strength of steel increases during industrial paint baking. In this study, the effect of standard BH treatment on the mechanical properties of a quenched and partitioned (Q&P) AISI 420 stainless steel is investigated. The parameters for the Q&P treatment are selected based on numerical simulations, dilatometry, X‐ray diffraction, and tensile tests, and the results are compared to conventional quenching and tempering (Q&T) treatment. It is shown that, in comparison with Q&T, Q&P can slightly increase the strength of the steel without sacrificing elongation. Heat‐treated samples are then subjected to a paint baking treatment with and without prestrain. It is indicated that the mechanical properties of the heat‐treated steel are not affected by paint baking without prestrain, whereas after a 2% prestrain the yield strength is drastically increased up to 1800 MPa, resulting in BH index exceeding 100 MPa. However, this increase in yield strength is instantly followed by necking and reduced post‐uniform elongation. The results suggest that the effect of industrial paint baking is a considerable practical aspect in the design of Q&P components if the steel is subjected to deformation before painting.

A novel class of resource‐efficient, woven‐glass‐grid current collectors (CCs) for Li‐ion batteries is introduced. These CCs are based on ultra‐light multifilament glass threads, woven to a grid and surrounded with a thin metal layer (equivalent to a 1 μm‐thick metal foil) in a roll‐to‐roll physical vapor deposition process. This saves >90 % of the required Cu and Al metals and reduces the mass of the CCs by >80 %. At the same time, the gravimetric capacity of anodes with graphite and cathodes with LiCoO2 active material increases by 48 % and 14 %, respectively, while full cells are characterized by an increase of 26 %. Thus, the specific energy can be improved by 25 %. A complete anode and cathode fabrication process from preparing the CCs and electrodes to cells is described and demonstrated in coin cell format. Coin cells with woven‐glass‐grid CCs achieved 300 cycles with a capacity retention of 93 %, a Coulombic efficiency of >99.9 %, and a higher rate capability until a C‐rate of 3 C. This technology opens up new possibilities for designing ultralight CCs with dedicated surface properties for Li and beyond Li batteries.

Mining and its associated industries contribute to greenhouse gas (GHG) emissions, exacerbating climate change. To address this, our study employed life cycle assessment to assess the carbon footprint of utilizing carbonates made from steel dust from the Golgohar complex in a carbon mineralization process to treat acid mine drainage (AMD) at the Darrezar copper mine. We considered four scenarios and two sensitivity analyses, including the baseline scenario, solar energy utilization, dust variations, limestone purchase, transportation impact, and AMD quantity. The baseline scenario yielded a negative carbon footprint of – 107 kg of CO2eq/100 kg of CO2 from flue gas. Using solar energy prevented most of the GHG emissions. In addition, using a waste with high alkalinity reduced energy consumption throughout the process. Furthermore, the utilization of trucks with high capacity for product transportation and treating a low amount of AMD improved the entire process and kept it in the negative carbon footprint range. Finally, comparing scenarios to the conventional use of purchased limestone for AMD treatment demonstrated environmental viability. The study demonstrates the potential for sustainable practices in mining, promoting a shift towards methods that would mitigate environmental impact and contribute to a more carbon–neutral future.

Phosphorus partition data from Ukrainian integrated steel plants are analyzed, focusing on the influence of parameters such as the basicity (CaO/SiO 2 ), optical basicity, tapping temperature, and the contents of (FeO), (MgO), and (Al 2 O 3 ) in the slag. It is found that the phosphorus partition decreases with increase in tapping temperature and increases with the optical basicity. An increase in the phosphorus partition (P)/[P] followed by a decrease with increase of (CaO/SiO 2 ) are observed. It is found that the optimal value, break point at which phosphorus partition changes its dependence to opposite, has a direct dependence on tapping temperature. At (CaO/SiO 2 ) = 1.9–2.1, (P)/[P] increases linearly with increasing (FeO). However with higher value of (CaO/SiO 2 ) the breaking point when (P)/[P] starts to decrease with increase in (FeO) is noticed. Thereby the optimal value of (FeO) decreases with increasing tapping temperature. In case of (Al 2 O 3 ) there is only decreasing of (P)/[P] with all (CaO/SiO 2 ) and tapping temperatures. Moreover, the effect of (MgO) varies with (CaO/SiO 2 ). These industrial results are supported by thermodynamic simulations using FactSage 8.1 and aligned with existing results from the literature.

The solidification behavior of a novel X1CrCuNiN 18‐9‐6 (concentrations in wt%) stainless steel is studied by thermodynamic calculations and corresponding microstructure investigations. The thermodynamic calculations of the X1CrCuNiN 18‐9‐6 steel predict a metastable austenitic structure, which is verified by microstructural analyses. In the as‐cast state before heat treatment, a few copper precipitates, mostly over 50 μm in size, are visible, which are located exclusively in the interdendritic regions. The electrode inert gas atomization process is applied to produce a steel powder using a pre‐material in as‐cast state with significantly increased Cu content of 9 wt%. After atomization, despite the rapid cooling, micrometer‐sized copper precipitates form again, which are homogeneously distributed in the microstructure, but are mostly less than 10 μm in size and thus much finer than in the initial cast state. The short processing times during field‐assisted sintering technique/spark plasma sintering makes it possible to produce a bulk material with a porosity of less than 1%. Miniature samples produced from the as‐sintered material exhibit uniform elongation values of 30%–40% with a tensile strength of about 640 MPa under tensile loading conditions.

This paper examines the need for innovation in phosphorus fertilizer production. An important area requiring action is the use of sulfuric acid in the wet chemical process (WCP), which is the dominant process in phosphate fertilizer production. About 50 % of the sulfuric acid produced worldwide is used for fertilizers, and ~95 % of the world's fertilizers are based on sulfuric acid. The latter is almost exclusively a by‐product of gas and oil production, so the production of conventional P fertilizer is largely dependent on the availability of oil and gas. In addition to rendering P fertilizer production independent of fossil raw materials, energy consumption, CO2 emissions, phosphogypsum production and water consumption should also be considered. With the example of the PARFORCE process and the Improved Hard Process (IHP), new non‐sulfuric acid‐based alternatives are discussed with respect to overcoming the drawbacks of the classical WCP by being completely independent of fossil sources, working with renewable energies as the sole energy source, and the option of using seawater instead of fresh water. These new processes adhere to the principles of climate neutrality, zero waste production, low CO2 footprint, water conservation, renewable energy use, and energy and resource efficiency. This demonstrates what sustainable innovation can look like from a production perspective. The discussion will focus on whether current incentives are sufficient to realize the sustainability innovations discussed.

The present work focuses on the formation of the γ′-phase and its impact on the functional properties of a Fe-28Ni–17Co–11.5Al–2,5Ti (at.-%) shape memory alloy (SMA) under cyclic loading conditions at different testing temperatures. The effect of aging treatments conducted in a wide range of aging temperatures and times was investigated. While specific heat treatments, namely 600 °C for 4 h, result in excellent superelastic properties with a fully reversible material response in single cycle experiments, interestingly, functional degradation is found to be more pronounced under cyclic loading compared to other derivatives of the Fe–Ni–Co–Al-based SMA systems. In addition to mechanical testing, a detailed microstructural analysis was conducted using transmission electron microscopy. The results of the present study clearly reveal that chemical inhomogeneities have to be carefully considered for the characterization of the functional performance of these iron-based SMAs. Chemical heterogeneities are not only identified as the underlying microstructural mechanism for the pronounced cyclic degradation behavior, but are also supposed to have a significant influence on the precipitation kinetics of the γ′-phase.

Reducing dependence on toxic electrofused magnesia‐chromium aggregates is essential to meet demands for eco‐friendly refractories. Some authors have proposed alternative compositions using lab‐scale electrofusion to produce small specimens (< 0.5 g). However, this size limits the evaluation of key refractory properties, such as thermal expansion. As an alternative, this study explored conventional sintering at 1600°C for 5 h and both methods resulted in equivalent chemical and mineralogical compositions. Despite presenting higher porosity (24 % – 30 %) than the electrofused ones (4 % – 6 %), consistent microstructural parameters supported using the sintering route to produce larger specimens (5 × 5 × 25 mm³), which were assessed for dilatometric profiles up to 1400°C. Combined with thermodynamic calculations, Rietveld's refining of X‐ray diffraction patterns and differential scanning calorimetry, the dilatometric analysis indicated that spinel dissolution in the periclase causes a high expansion during heating, whereas its re‐precipitation results in shrinkage. As this behavior could result in challenges for the refractory lining design, computational thermodynamics was used to find additives capable of increasing this transition temperature. TiO₂ was identified as a promising candidate and its effectiveness was attested.

Yb 5 Rh 6 Sn 18 is a valence fluctuating system with a unique structural arrangement characterized by the enlarged Friauf polyhedra incorporating rattling Sn atoms, which causes additional phonon scattering and thus, reduction of thermal conductivity.

Motivated by the exceptional optoelectronic properties of 2D Janus layers (JLs), we explore the properties of group Va antimony-based JLs SbXY (X=Se/Te, Y=I/Br). From the Bader charges, the elec-tric dipole...

We present a comprehensive theoretical analysis of the structural and electronic properties of a van der Waals heterostructure composed of CdS and α-Te single layers (SLs). The investigation includes an in-depth study of fundamental structural, electronic, and optical properties with a focus on their implications for photocatalytic applications. The findings reveal that the α-Te SL significantly influences the electronic properties of the heterostructure. Specifically, the optical properties of the heterostructure are notably dominated by the contribution of α-Te. The layer-resolved density of states analyses indicate that the valence and conduction bands near the Fermi level are mainly determined by the α-Te SL. Band edge analyses demonstrate a type-I band alignment in the heterostructure, causing charge carriers (electrons and holes) to localize within α-Te. The electronic properties can be further modulated by external strain and electric fields. Remarkably, the CdS-α-Te heterostructure undergoes a transition from type-I to type-II band alignment when subjected to biaxial strain and an external electric field. This may be interesting for the application of the heterostructure for photocatalysis.

Entropy of measure-preserving or continuous actions of amenable discrete groups allows for various equivalent approaches. Among them are those given by the techniques developed by Ollagnier and Pinchon on the one hand and the Ornstein–Weiss lemma on the other. We extend these two approaches to the context of actions of amenable topological groups. In contrast to the discrete setting, our results reveal a remarkable difference between the two concepts of entropy in the realm of non-discrete groups: while the first quantity collapses to 0 in the non-discrete case, the second yields a well-behaved invariant for amenable unimodular groups. Concerning the latter, we moreover study the corresponding notion of topological pressure, prove a Goodwyn-type theorem, and establish the equivalence with the uniform lattice approach (for locally compact groups admitting a uniform lattice). Our study elaborates on a version of the Ornstein–Weiss lemma due to Gromov.

A novel approach was proposed, based on the application of the fuzzy logic (FL) method for the fast analysis of the hot deformation process of 80MnSi8-6 steel. In the first stage, the curves developed from plastometric tests and the results of studies of the microstructure of the deformed samples were used as input data for the analysis. Input and output variables were adopted and a set of rules based on cause-and-effect relationships was defined, defining the interactions between the variables. A fast FL-controller was designed, and the correctness of its operation was verified by comparison with experimental results and the results of finite element method (FEM) analysis, carried out taking into account the evolution of the microstructure. The process of hot compression under isothermal conditions of 80MnSi8-6 steel specimens was simulated on the Warmumformsimulator (WUMSI), assuming such parameters and other conditions as were used in real tests. It was confirmed that the proposed method, based on the analysis of flow curves and prior austenite grain size using a fuzzy controller, gave satisfactory results. Subsequently, a novel FL-controller was developed to analyze the kinetics of dynamic recrystallization (DRX), using data obtained from the author’s model of this phenomenon for its construction and calibration. The correctness of the controller was confirmed by comparing the results of its DRX volume fraction calculations with the distributions of this value determined by the model and the model-based FEM analysis method, respectively. It was shown that FL is applicable also when a model of the analyzed phenomenon is available. Unlike model-based calculations, a properly designed controller allows the indication of deviations from general trends that can be pointed out and interpreted by a human expert, but significantly faster. It can also serve as a component of a system analyzing complex processes, such as hot multi-stage forging. Fuzzy controller can be used in parallel with modeling or replace models in calculations.

Impurity doping at the nanoscale for silicon is becoming less efficient with conventional techniques. Here, an alternative virtual doping method is presented for silicon that can achieve an equivalent carrier density while addressing the primary limitations of traditional doping methods. The doping for silicon is carried out by placing aluminum‐induced acceptor states externally in a silicon dioxide dielectric shell. This technique can be referred to as direct modulation doping. The resistivity, carrier density, and mobility are investigated by Hall effect measurements to characterize the carrier transport using the new doping method. The results thereof are compared with carrier transport analysis of conventionally doped silicon at room‐temperature, demonstrating a 100% increase in carrier mobility at equal carrier density. The sheet density of hole carriers in silicon due to modulation doping remains nearly constant, ≈4.7 × 10¹² cm⁻² over a wide temperature range from 300 down to 2 K, proving that modulation‐doped devices do not undergo carrier freeze‐out at cryogenic temperatures. In addition, a mobility enhancement is demonstrated with an increase from 89 cm² Vs⁻¹ at 300 K to 227 cm² Vs⁻¹ at 10 K, highlighting the benefits of the new method for creating emerging nanoscale electronic devices or peripheral cryo‐electronics to quantum computing.

Here, we report the first discovery of Antarctic fossil resin (commonly referred to as amber) within a ~5 cm-thick lignite layer, which constitutes the top part of a ~3 m-long palynomorph-rich and root-bearing carbonaceous mudstone of mid-Cretaceous age. The sedimentary sequence was recovered by the MARUM-MeBo70 seafloor drill rig at Site PS104_20 (73.57° S, 107.09° W; 946 m water depth) from the mid-shelf section of Pine Island trough in the Amundsen Sea Embayment, West Antarctica, during RV Polarstern Expedition PS104 in early 2017. So far, amber deposits have been described from every continent except Antarctica.

Even though the descriptive definition of orientation is the same in both settings, the explicitnotation of a crystallographic orientation as (3 3) matrix in terms of Euler angles featuredby the popular MATLAB toolbox MTEX differs by an inversion from the quasi-standard notation datedback to the early days of quantitative texture analysis championed by H.-J. Bunge. The origin of thisdiscrepancy is revealed by an enlightening view provided in algebraic terms of a change of basis.Understanding the effect of inversion is instrumental to do proper computations with crystallographicorientations and rotations, e.g. when multiplying with elements of a crystallographic symmetry group,and to compare results of texture analyses accomplished in different settings.

This research introduces a non-enzymatic electrochemical sensor utilizing flower-like nickel oxide/carbon (fl-NiO/C) microspheres for the precise detection of L-glutamic acid (LGA), a crucial neurotransmitter in the field of healthcare and a frequently utilized food additive and flavor enhancer. The fl-NiO/C were synthesized with controllable microstructures using metal–organic frameworks (MOFs) as precursors followed by a simple calcination process. The uniformly synthesized fl-NiO/C microspheres were further characterized using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The fl-NiO/C was utilized as a modifier on the surface of a glassy carbon electrode, and an impedimetric sensor based on electrochemical impedance spectroscopy (EIS) was developed for the detection of LGA. The proposed sensor demonstrated excellent catalytic activity and selectivity towards LGA across a broad concentration range of 10–800 μM with a sensitivity of 486.9 µA.mM−1.cm−2 and a detection limit of 1.28 µM (S/N = 3). The sensor was also employed to identify LGA in blood plasma samples, yielding results that align with those obtained through HPLC. This achievement highlights the potential of fl-NiO/C microspheres in advancing cutting-edge biosensing applications.

Carbon‐bonded alumina filters have been established in the steel industry for decades to increase the quality of cast steel components. The carbon bonding of the filter materials is commonly achieved by using pitches or resins. However, the pyrolysis of both substances results in the release of carcinogenic substances such as free phenols or benzo[a]pyrene. An alternative binder system is provided by lactose and tannin, which is considered to be more environmentally friendly, but they tend to result in insufficient mechanical filter properties.To ensure higher environmental sustainability and good mechanical properties, the effect of the stepwise replacement of the pitch‐binder CarboresP by lactose and tannin is investigated in the present study. Additionally, the impact of semiconductive additives (P‐doped n–Si and SiC) and the filter manufacturing method on the filter properties is analyzed. Based on the most promising filter composition, different lactose/tannin ( L / T ) ratios (5:1, 4:1, 3:1) are applied and the resulting properties evaluated. The results suggested that the pitch binder can be completely replaced by lactose and tannin by using SiC as additive and adjusting the filter manufacturing process. The variation of the L / T ratio shows no significant impact on the filter prope.

This study investigates the functional properties of the expanded austenite layers generated on AISI 316L austenitic stainless steel resulting from active screen plasma nitrocarburizing using different active screen materials, i.e. steel or solid carbon. Treatments were conducted at 460 °C for 5 h in a nitrogen-hydrogen feed gas, whereas for the treatments using a steel active screen, methane was added as a carbon precursor. Additionally, the bias plasma conditions applied at the samples were varied between 0 kW and 1.25 kW. Samples were characterized by complementary microstructural and compositional investigations, surface roughness and hardness measurements, pin-on-disk tribological tests as well as potentiodynamic polarization tests in H2SO4 and NaCl electrolytes. The functional properties of the case are discussed based on the contents of nitrogen and carbon in the expanded austenite and their effective diffusion depths. The results show that the usage of a carbon screen generally produces surfaces with uniform layer thickness, high hardness, improved wear resistance and a delayed tendency to pitting corrosion independent of the bias condition applied to the samples. When applying both screen materials at non-biased condition, the general corrosion resistance is slightly reduced under the conditions used, however, the layers generated using the carbon screen have a wear rate that is 3 times lower. It can be concluded that the carbon screen represents a robust treatment variant for austenitic stainless steels to produce sufficiently thick and wear-resistant surface layers in a short treatment duration, which still have the potential to maintain the corrosion resistance in different environments.