Montanuniversität Leoben
Recent publications
The European Organization for Nuclear Research (CERN) is currently undertaking a feasibility study to build the next-generation particle accelerator, named the Future Circular Collider (FCC), hosted in a 90–100 km subsurface infrastructure in the Geneva Basin, extending across western Switzerland and adjacent France. This article represents a preliminary, basin-scale stratigraphic and lithotype analysis using state-of-the-art Swiss and French stratigraphic terminology, set in context with the FCC. Existing stratigraphic information, rock cores and well reports, laboratory analyses and geophysical well-logs from 661 wells representative for the construction area have been integrated to pave the way for a multidisciplinary approach across several geoscientific and engineering domains to guide the FCC’s upcoming technical design phase. Comparisons with well-log data allowed the identification of rock formations and lithotypes, as well as to formulate a preliminary assessment of potential geological hazards. Regional stratigraphic evaluation revealed the FCC’s intersection of 13 geological formations comprising 25 different lithotypes across the Geneva Basin. A lack of data remains for the western to south-western subsurface region of the FCC construction area shown by well-density coverage modelling. The main geological hazards are represented by karstic intervals in the Grand Essert Formation’s Neuchâtel Member, Vallorbe and Vuache formations, associated to fractured limestone lithotypes, and Cenozoic formations represented by the pure to clayey sandstone-bearing Transition zone and Siderolithic Formation. Potential swelling hazard is associated to the presence of anhydrite, and claystone lithotypes of the Molasse Rouge and Grès et Marnes Gris à gypse formations, yielding up to 17.2% of smectite in the Molasse Rouge formation. Hydrocarbon indices in both gaseous and bituminous forms are encountered in the majority of investigated wells, and bear a potential environmental hazard associated with the Molasse Rouge deposits and fractured limestones of the Mesozoic Jura formations.
Despite their high hardness and indentation modulus, nanostructured crystalline ceramic thin films produced by physical vapour deposition usually lack sufficient fracture strength and toughness. This brittleness is often caused by underdense columnar grain boundaries of low cohesive energy, which serve as preferential paths for crack propagation. In this study, mechanical and structural properties of arc-evaporated Al0.9Cr0.1N thin films were analysed using micromechanical tests, electron microscopy, atom probe tomography and in situ high-energy high-temperature grazing incidence transmission X-ray diffraction. Vacuum annealing at 1100°C resulted in the formation of regularly-distributed globular cubic Cr(Al)N and elongated cubic CrN precipitates at intracrystalline Cr-enriched sublayers and at columnar grain boundaries with sizes of ∼5 and ∼30 nm, respectively. Consequently, in situ micromechanical testing before and after the heat treatment revealed simultaneous enhancement of Young's modulus, fracture stress and fracture toughness by ∼35, 60 and 10%, respectively. The annealing-induced concomitant improvement of toughness and strength was inferred to precipitations observed within grains as well as at grain boundaries enhancing the cohesive energy of the grain boundaries and thereby altering the crack propagation pathway from inter- to trans-crystalline. The here reported experimental data unveil the hitherto untapped potential of precipitation-based grain boundary design for the improvement of mechanical properties of transition metal nitride thin films.
The current paper presents a new computational approach to detect wear and damage to milling tools' cutting edges. The proposed approach is independent from exact information on tool-workpiece interaction conditions and only requires that they remain constant for compared milling operations. Additionally, the approach was thoroughly tested on time-series data obtained from an industrial-scale milling process, instrumented by commercially available instrumentation equipment, during which 18 identical parts were milled. The time-series data contains the bending moments in the x and y directions as well as the torque and tension acting on the milling tool. Some measures used are systematic in nature, based on shape, rotation and work needed for milling, whereas others are statistical in nature, describing the change in the distribution of the data. All of the measures proposed in the current work are relative and mutually invariant, meaning they address different information content of the data independently. A comparison of the mentioned measures with the real-world damage evolution of the milling tool's cutting edges for multiple produced parts yielded consistent results and suggests a high potential for practical tool damage detection in industrial production.
  • Bernhard MitasBernhard Mitas
  • Ville-Valtteri VisuriVille-Valtteri Visuri
  • Johannes SchenkJohannes Schenk
The controlled splashing of metal droplets plays a decisive role in the kinetics of the basic oxygen furnace (BOF) process. In this work, a mathematical model was developed for predicting the size distribution of spherical droplets ejected at an impingement zone. Harmonic oscillators are used to describe the ejection sites, and the upper limit for the droplet population is calculated through a force balance. The model was validated against literature data from high-temperature crucible experiments involving different supply pressures and lance heights as well as both single-hole and multihole lances. The predicted size distribution of the metal droplets was found to be in good agreement with the droplet size distributions measured from outside the crucible. The model was also applied for predicting the size distribution parameters of the Rosin–Rammler–Sperling (RRS) size distribution function. The model developed is computationally light and is suitable to be used as a part of offline and online simulation tools for the BOF process.
Aging of lithium-ion batteries is especially important for applications such as battery electric vehicles, where they constitute a major part of the total cost and practically determine product lifetime. One of the main problems during cycle aging is the swelling of the electrode stack, as this results in increased mechanical stresses inside batteries and can further accelerate aging. Earlier studies have used X-ray tomography to address this issue and were focused on the role of large aberrations in electrode geometry in rapid capacity fade. In this study, however, we focus on batteries not exhibiting such a rapid deterioration, where only small changes to electrode geometry can be expected. Helical trajectory micro-computed X-ray tomography and virtual unrolling were used to reveal axially and radially inhomogeneous swelling of the jelly-roll electrode windings inside commercial 18650 batteries. The results supported by mathematical-physical simulations demonstrate the efficacy of the employed methods in the analysis of minute volumetric changes and show that regions inside the batteries that are comparatively unconstrained mechanically experience accelerated swelling. In particular, the top and bottom of the jelly-roll showed an elevated thickness increase, especially within the innermost windings.
Coffee, as one of the most traded resources, generates a vast amount of biogenic by-products. Coffee silver skins (CSS), a side stream from the roasting process, account for about 4 wt.%. Despite the abundancy of CSS, possible routes to generate added value for broad applications are limited. Herein, we present an approach to use CSS as a precursor material for supercapacitor electrodes. KOH activated carbon (AC) was produced from CSS. The resulting AC—CSS was characterized by X-ray diffraction, gas sorption analysis, scanning electron microscopy, and Raman spectroscopy. The highly porous AC—CSS exposes a specific surface area of more than 2500 m2 g−1. Electrodes formed with AC—CSS were electrochemically characterized by performing cyclic voltammetry and galvanostatic cycling. The electrodes were further assembled into a supercapacitor device and operated using 1 M sulfuric acid as electrolyte. In addition, various quinones were added to the electrolyte and their impact on the capacitance of AC—CSS electrodes was analyzed. In this work, we were able to show that CSS are a valuable source for supercapacitor applications and that coffee-waste-derived quinones can act as capacitance enhancers. Thus, the findings of this research show a valuable path towards sustainable and green energy storage solutions.
High‐temperature corrosion mechanisms in reducing atmospheres containing HCl (3.8 vol%) and a varying amount of H2S (0.02 –2 vol%) were developed for several alloys between 420°C and 680°C. These mechanisms are mainly based on practical observations and kinetic considerations—and less on thermodynamic data. This is due to the complexity of these mixed gas atmospheres, volatile corrosion products, and the ever‐changing conditions within the corrosion layer, which made it not possible to predict and calculate the actual conditions in the corrosion zone. In this article, a detailed thermodynamic analysis of previously achieved corrosion mechanisms and experimental observations is presented. Correlations and deviations between thermodynamic calculations and practical findings are stated and discussed. The corrosion behavior of ferritic K90941, which performs worse than corrosion‐resistant austenitic alloys, except for one test condition at 580°C in the atmosphere with 0.2 vol% H2S, is explained and supported by thermodynamic data. By combining experiments with thermodynamics, corrosion mechanisms in reducing HCl and H2S‐containing atmospheres are explained. High‐temperature corrosion in reducing HCl and H2S‐containing atmospheres is challenging for commercially used alloys as several corrosive agents in the atmosphere show various different reactivities with the numerous alloying elements at different temperatures. Thus, the prediction of corrosion mechanisms in such environments is challenging. By means of thermodynamic data and experimental achieved findings, it is possible to assess such corrosion mechanisms.
The mechanical fracture compliance is of interest in a number of geoscientific applications. Seismic borehole methods, especially full‐waveform sonic (FWS) data, have indicated their potential to infer the compliance of macroscopic fractures under in situ conditions. These approaches rely on the assumption of a homogeneous background embedding the fractures and, as of yet, compliance estimates for individual fractures are limited to static FWS measurements. In this work, we assess the potential of inferring the compliance of individual fractures from standard, production‐type FWS data in the presence of background heterogeneity. We first perform a comparative test on synthetic data to evaluate three approaches known as the transmission, phase, and group time delay methods. The results indicate that the former two produce adequate compliance estimates for scenarios with a strongly heterogeneous background or a damage zone around the fracture. These two methods are then applied to two FWS data sets acquired before and after a hydraulic stimulation campaign in a crystalline rock, which allows to test them on natural and man‐made fractures. The transmission method turned out to be unsuitable for the considered data due to its reliance on amplitudes. Conversely, the travel time behavior remained stable and the phase time delay method produced robust and consistent estimates. The results for a newly created hydro‐fracture imply the capability of resolving remarkably small compliance values of the order of 10⁻¹⁴ m/Pa. This estimate is one order‐of‐magnitude smaller than that for the natural fracture, which may help to distinguish between these two fracture types.
Considerable work has been done on method standardization for experimental characterization of column packings used in absorption processes. A detailed framework for determination of packing hydraulics as well as gas- and liquid-side volumetric mass transfer coefficients (kGa and kLa) has been established. Packing characterization experiments in large diameter columns result in high equipment and operating costs. Accurate extrapolation of packing properties from experiments in smaller diameter columns would therefore be highly desirable. However, diameter influence is currently not completely understood, making further work necessary. In this work, experiments for the determination of kGa and kLa values were carried out and evaluated independently in two plants (inner diameters 422 and 150 mm). Results from measurements conducted with three metal packings RSP 250Y, RMP N 250X and RMP N 250Y are in good agreement with existing literature data. kGa was found to be dependent on column diameter with larger diameters leading to increased kGa values. The overall effect (approx. 15 %) is consistent with previous works, suggesting the possibility of deriving appropriate scaling factors once the findings are validated by a larger sample size. No clear dependence of kLa values on diameter was found with deviations significantly smaller than for kGa measurements.
This research examines the compression, as well as short- and long-term relaxation behaviour of bindered textiles at elevated temperature levels. Experiments were conducted on a carbon fibre non-crimp fabric with epoxy resin binder in a specifically designed compressibility test rig. Expanding past research activities at room temperature [1, 2] it was found in series of loading-relaxation-unloading tests, that the test temperature level significantly influences the maximum compaction pressure during the loading stage as well as the pressure characteristics during the relaxation stage [3]. Furthermore, a significant change in the compression behaviour, well below the specified processing temperature of the binder, was found. Also, a proof-of-concept demonstrates the “in-situ”-injection capability of a novel test-rig, reproducing RTM-like conditions in a controlled laboratory environment. The findings of this work are intended to support optimizing preforming and preform handling steps for liquid composite moulding processes.
Cellulose (rayon) filaments were exposed to various concentrations of hydrochloric acid under aqueous and non-aqueous conditions in order to study differences in degradation. Two sources of polymeric diphenylmethane diisocyanate (pMDI) were used as non-aqueous media. As a consequence of the production process, pMDI was found to contain residual hydrochloric acid. Filament yarns were immersed for either 7h or 7d and purified to obtain pure filaments for further analysis. Single-filament tensile tests and molar mass measurements confirmed a significant degradation of the filament structure under non-aqueous conditions. Samples with the same amount of hydrochloric acid immersed in water, however, were rarely affected. Complementary X-ray diffraction indicated that the removal of the amorphous cellulose resulted in an increase in the cellulose crystallinity, which was manifested by a decrease in the width of the diffraction peaks. With this remarkable difference between aqueous and non-aqueous treatments, a quantitative proof to a new aspect about the processability of regenerated cellulose was presented. Amongst other fields of technical applications, these findings will have to be considered in composite engineering dealing with cellulosic fibre reinforcements. An effective way to avoid acidic hydrolysis was presented based on calcium carbonate as matrix filler.
Zusammenfassung Im Zuge eines EU-Projektes arbeitet CEMTEC Cement and Mining Technology GmbH gemeinsam mit dem LCM Linz Center of Mechatronics GmbH an neuwertigen und innovativen Regelungsansätzen für Granulierprozesse mittels Pelletierteller. Es werden hierbei sowohl physikalisch basierte als auch datenbasierte Modelle in Form eines hybriden Systems kombiniert. Ziel des Projektes ist es, ein Regelsystem zu schaffen, das die jeweiligen Stärken der physikalischen und datenbasierten Modelle erkennt und situativ den optimalen Lösungsweg mit der maximal erzielbaren Anlagenenergieeffizienz wählt.
The challenge of attracting young people to the field of mineral processing as well as the ever-growing worldwide demand for minerals and metals together with lower-grade deposits and shortages of energy and water triggered the establishment of the new Erasmus Mundus Joint Master Program PROMISE. The consortium of four mining universities in Europe and Chile aims at master level education on engineering and sustainability issues in mineral processing. The first academic year of PROMISE will start in September 2022.
Liquid composite molding (LCM) is a widely used group of various different processing techniques allowing to produce small, medium or even very big sized components from prototype level up to series production. During the infiltration it is necessary to run the process in a way preventing void formation. The typically used textile reinforcing structure results in a dual-scale impregnation consisting of micro impregnation within the constituent yarns of the textile structure and a macro impregnation between the yarns. Capillary rise experiments on flat textile samples are used and the well-known Lucas-Washburn equation has been extended to cover the special configuration. A porous capillary wall is assumed to better represent the three-dimensional nature of capillary networks within reinforcing textiles. An according test rig is presented. Accurate experimental results are gained and capillary radii are computed simple and fast via curve regression.
The development of a carbon lean steel production process following the concept of direct carbon avoidance is one of the most challenging tasks the iron and steel industry must tackle in just a few decades. The necessary drastic reduction of 80% of the process’s inherent emissions by 2050 is only possible if a new process concept that uses hydrogen as the primary reductant is developed. The Hydrogen Plasma Smelting Reduction (HPSR) of ultra-fine iron ores is one of those promising concepts. The principle was already proven at a lab scale. The erection of a bench-scale facility followed this, and further scaled-ups are already planned for the upcoming years. For this scale-up, a better understanding of the fundamentals of the process is needed. In particular, knowledge of the kinetics of the process is essential for future economically feasible operations. This investigation shows the principles for evaluating and comparing the process kinetics under varying test setups by defining a representative kinetic parameter. Aside from the fundamentals for this definition, the conducted trials for the first evaluation are shown and explained. Several differences in the reduction behavior of the material at varying parameters of the process have already be shown. However, this investigation focuses on the description and definition of the method. An overall series of trials for detailed investigations will be conducted as a follow-up.
More than half of all recoverable oil reserves are found in carbonate rocks. Most of these fields are highly fractured and develop different zonations during primary and secondary recovery stages; therefore, they require a different developmental approach than conventional reservoirs. Experimental results for water-alternating gas injection [WAG] and foam-assisted water-alternating gas [FAWAG] injection under secondary and tertiary recovery conditions were used to investigate these enhanced oil recovery [EOR] methods in gas-invaded reservoirs. The relative permeability curves of the cores and the fitting foam parameters were derived from these experiments through history matching. These findings were then used in a quarter five-spot, cross-sectional, and a sector model of a carbonate reservoir where a double five-spot setup was implemented. The fracture and matrix properties’ impact on the recovery was illustrated through the cross-sectional model. The gas mobility reduction effect of the FAWAG was more noticeable than that of WAG. The apparent viscosity of the gas was increased due to the foam presence, which caused a diversion of the gas from the fractures into the matrix blocks. This greatly enhanced the sweep efficiency and led to higher oil recovery. The gas front was much sharper, and gravity overrides by the gas were much less of a concern. The properties of the fracture network also had a significant effect on the recovery. Oil recovery was found to be most sensitive to fracture permeability. At the same time, sweep efficiency increased substantially, improving the recovery rate in the early injection stages, and differed slightly at the ultimate recovery. However, a lower fracture permeability facilitated gas entry into the matrix blocks. The results of the reservoir sector model were similar to the core and pilot. However, the WAG injection recovered more of the uppermost layers, whereas significant portions of the lowest layer were not effectively recovered. In contrast, FAWAG was more effective in the lowest layer of the reservoir. The FAWAG was a beneficial aid in the recovery of gas-invaded fractured reservoirs, increasing the oil recovery factor with respect to WAG.
Ultrasonic cavitation radiates huge power in a small solidifying bulk, leading to significant grain refinement, purification and homogenization of the final alloys. Ultrasound vibration has mostly been used for treating the solidification of light metals, but it is difficult to directly introduce ultrasonic vibration into copper alloy due to the lack of proper sonotrode. In this work, we have used a Sialon ceramic sonotrode to propagate acoustic waves in a Cu–Cr alloy melt. Significant grain refinement and modification of primary Cr have been obtained. With the ultrasound vibration treatment, the mechanical properties of the as-cast Cu–Cr alloy have been improved. The wear resistance of the Cu–Cr alloy has also shown enhancement with respect to the untreated alloy. © 2022, The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature.
This study investigates the effect of a high volume fraction of Fe-rich intermetallic phases on microstructure evolution and mechanical properties in a cold rolled Al-Mg-Si wrought alloy. A conventional Al-Mg-Si alloy was modified by significantly increasing its Fe and Mn content, while the Si content was adjusted to keep the matrix composition comparable. Subsequent fast solidification and thermomechanical processing generated a dense distribution of fine intermetallic phases, which culminated in significant grain-refinement and uniform texture. The resulting alloy, with almost 10 vol-% Fe-rich intermetallic phase, features an unusually attractive combination of strength and ductility in addition to the substantially increased strain hardening typical of heterostructured materials, and can facilitate a higher usage of scrap input.
The fragmentation of 12 full-scale one-row blasts has been measured by sieving a large portion of the muckpiles. The procedure followed, the difficulties encountered and the solutions adopted to construct the fragment size distribution curves are described in detail; 11 curves were finally constructed as production constraints prevented the required measurements on one of the blasts. The blasts covered a powder factor range between 0.42 and 0.88 kg/m ³ , and were initiated with two significantly different delays, 4 and 23 ms between holes, to assess the influence of both powder factor and delay on fragmentation. The size distributions are well represented by the Swebrec function, which strongly suggests that the dependence of fragmentation with the powder factor can be analyzed by the fragmentation-energy fan. The result is excellent, and the frag-energy fan model in its simplest form (a four-parameter function) is able to predict sizes between percentage passings 92 to 8% with a mean error of 14.4% and a determination coefficient R ² as high as 0.976. The powder factor above grade has been used, in its energy form obtained as the product of the mass powder factor by the explosive energy per unit mass. The incorporation of six more fragment size distributions, also obtained by sieving in a previous blasting project in the same rock mass, but with different layouts, explosives, delay and blast direction, only reduces R ² to 0.968 and increases the mean error to 15.3%. A strength dependence with the size of the blasted block (burden, bench height, etc.) has been tested for inclusion in the fan formulation, with minor improvement compared with the powder factor alone, as the variation in size of the blasts was very limited. Some size descriptors as in-situ block size and fracture intensity have also been tested, though variations were also limited as all blasts were carried out in the same quarry site, not improving the prediction errors when other blast dimensions (e.g., burden) are used. Incorporating the effect of delay in the fragmentation-energy fan model has been attempted with a cooperation function modifying the powder factor, increasing from instantaneous to an optimum delay value, then decreasing as the delay further increases. The effect of such a function is noticeable in terms of improved prediction; the data analyzed, however, do not allow for a definitive statement on an optimum delay value as calculations with different fan characteristics and data result in different optimum values. The effect of the delay on the fragment size varies with the percentile, from about 10–15% for the high percentiles to somewhat more than 30% for the lower percentiles.
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1,660 members
Daniel Kiener
  • Chair of Materials Physics
Florian Bleibinhaus
  • Chair of Applied Geophysics
Stefan Steinlechner
  • Chair of Nonferrous Metallurgy
Holger Ott
  • Chair of Reservoir Engineering
David Holec
  • Chair of Physical Metallurgy and Metallic Materials
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