Browsing by Author "Yaroshevskyi, Serhii"

Filter results by typing the first few letters
Now showing 1 - 8 of 8
  • ItemOpen Access
    Corrosion and Process Analysis of a Preoxidized MgO Recyclate-based Cermet Anode in Laboratory-Scale Na-Cryolite Molten Salt Electrolysis of Aluminum at 1000 °C
    (Technische Universität Bergakademie Freiberg, 2026-07-14) Adamczyk, Alexander; Hossain, Farhan; Garcia Paz, Felipe A.; Yaroshevskyi, Serhii; Vogt, Daniel; Aneziris, Christos G.; Charitos, Alexandros
    The development of inert anodes for aluminum electrolysis remains challenging due to the high corrosivity of cryolite-based melts at 950°C–1000°C. This study investigates the corrosion and process behavior of a carbon-free MgO–steel cermet anode derived from refractory recycling during laboratory-scale Na-cryolite electrolysis at 1000°C, focusing on the effect of a pre-oxidation treatment on its corrosion behavior. In the as-sintered state, MgO grains are mechanically bonded to a 316L steel matrix with interfacial porosity that limits corrosion resistance. Pre-oxidation at 900°C for 24 h forms a dense Mg–M–O (M=Fe, Cr) oxide-rich surface layer, sealing pores and improving resistance to cryolite infiltration, albeit at the cost of reduced electrical conductivity, which translated into an overall higher cell voltage compared to the as-sintered state. During electrolysis, this layer degrades under anodic polarization, O2 evolution, and fluorination. The surface transforms into a Fe–O-rich magnetite layer (Fe3O4), while a Cr-containing oxide and an in situ Mg–Fe–O transition zone form beneath, maintaining partial protection. Overall, pre-oxidation effectively delays electrolyte penetration by converting MgO into new oxide phases but introduces conductivity losses and surface instability. The results highlight both the potential and limitations of MgO-based cermet anodes for sustainable aluminum production.
  • ItemPublic Metadata
    GRK 2802: Anodes Based On MgO-C Recyclates And 316L Steel For Prospective Aluminium Fused-Salt Electrolysis Application
    (Technische Universität Bergakademie Freiberg, 2026-06-25) Yaroshevskyi, Serhii; Gehre, Patrick; Kaiser, Patricia; Brachhold, Nora; Hubálková, Jana; Aneziris, Christos G.
    Every year, approx. 28 million tons of used refractories accumulate worldwide. The majority of them are used as aggregates for road construction (downcycling) or are deposited in landfills. For ecological and economic reasons, an increased research potential was identified in recent years, dedicated to increasing the recycling rate and finding new markets and application fields with a higher value of the refractory recyclates. The study presents the current findings of the development of inert electrodes for the aluminum fused-salt electrolysis composed of steel and MgO gained from MgO-C recyclates. To withstand the chemical attack of molten aluminum and cryolitic melts, the metal-ceramic composites were preoxidized (PO) at 800 °C, 900 °C, and 1000 °C. The microstructure after each PO thermal treatment was analyzed. After PO at 800 °C, a (Cr,Fe)3O4 spinel-like phase and Fe-O Mg-O solid solution form. After PO at 900 °C, a larger amount of the Fe-O Mg-O solid solution and a (Cr,Fe)2O3 solid solution around the steel grains was identified. Furthermore, the electrical conductivity of the metal-ceramic-composites preoxidized at 900 °C amounts to 1.49·10^2 S/cm and hence is in the range of carbon, which exhibits a value of 1.54·10^2 S/cm. Additionally, the impact of different preoxidation treatments at 900 °C by applying furnaces equipped with electrical heating, natural gas burner, and microwave plasma burner on the microstructure was investigated.
  • ItemPublic Metadata
    GRK 2802: Characterization of a recyclate-based MgO-steel as-sintered inert anode candidate after exposure to cryolite electrolysis
    (Technische Universität Bergakademie Freiberg, 2026-02-12) Yaroshevskyi, Serhii; Adamczyk, Alexander; Brachhold, Nora; Schmidt, Gert; Hubalkova, Jana; Gumeniuk, Roman; Charitos, Alexandros; Aneziris, Christos
    The replacement of consumable carbon anodes with oxygen-evolving inert, carbon free anodes is a key technological challenge for decarbonizing primary aluminum production. While metallic, ceramic, and cermet anodes have been extensively studied, the use of recycled raw materials remains largely unexplored. In this work, composite cermet anodes consisting of 60 vol% AISI 316L stainless steel and 40 vol% recycled MgO from spent refractories were developed and tested under galvanostatic Hall-Héroult electrolysis conditions in cryolite at 1000 °C. The as-sintered composites exhibited stable cell voltage (3.2-3.3 V) over 2 h of operation. Post-mortem SEM/EDS/EBSD analyses revealed a multilayered structure with protective Fe-oxide, Al/Cr spinel formation, corroded Mg-F-rich phases, and cryolite infiltration extending beyond 2 mm depth. While the 316L steel matrix showed relative stability, the recycled MgO fraction proved chemically reactive, generating porosity and acting as the primary pathway for melt intrusion and secondary Al2O3 precipitation. Complementary static contact corrosion tests confirmed rapid fluoridation of MgO, whereas steel grains remained intact.
  • ItemPublic Metadata
    GRK 2802: Investigations on the corrosion of 316L steel composite materials with MgO/TiO2 ceramic immersed in molten cryolite
    (Technische Universität Bergakademie Freiberg, 2026-06-25) Yaroshevskyi, Serhii; Weigelt, Christian; Kerber, Florian; Brachhold, Nora; Zienert, Tilo; Adamczyk, Alexander; Vogt, Daniel; Charitos, Alexandros; Aneziris, Christos G.
    Composites based on a steel with 40 vol% magnesia or titania were produced with the ceramics-derived extrusion and pressureless sintering. The materials were tested in a laboratory-scale fused-salt electrolysis cell with a synthetic cryolite in order to identify their potential use as electrode material in the Hall-Heroult process. The highly corrosive atmosphere and salt melt initiated certain corrosion effects in both material variants. The corrosion depth was determined with 1160 μm for magnesia and 463 μm for titania, respectively, after 8 h corrosion test. The initial corrosion includes the complete penetration of the specimens with cryolite and the dissolution of the ceramic component. A pre-oxidation of the specimens containing magnesia depressed the corrosion depth by 75% due to the formation of an aluminium oxide layer in the composite material during corrosion tests. The reduction in corrosion depth by pre-oxidation was less ronounced for the TiO2 composite materials (- 15%).
  • ItemPublic Metadata
    GRK 2802: Pre‐oxidized Recycled MgO–Steel Composite Material for Possible Application in Cryolitic Melts
    (Technische Universität Bergakademie Freiberg, 2026-02-16) Yaroshevskyi, Serhii; Brachhold, Nora; Malczyk, Piotr; Gehre, Patrick; Aneziris, Christos
    Recycled MgO–C lining bricks and 316L stainless steel are used to manufacture composite material for inert anode samples for aluminum electrolysis cell. The microstructure of the composite material is characterized after preoxidation thermal treatments at 800, 900, and 1000 °C as well as in its sintered state. Preoxidation (PO) process is designed to enhance the material's corrosion resistance in molten cryolite environments by developing robust Fe–Mg–O, Fe–Cr–O- containing phases. Analytical techniques including scanning electron microscopy, electron backscatter diffraction, and energy dispersive X-ray spectrometry are applied to characterize the phase formation, revealing the potential of these composites for use as inert anodes in aluminum electrolysis cells. PO at 800 °C is not sufficient to form adequate protective oxide layers. Whereas, PO at 900 and 1000 °C leads to the formation of protective oxide layers containing Mg–O Fe–O halite-like solid solutions and (Cr,Fe)3O4 spinel phase. Sample, preoxidized at 1000 °C is sealed in Mg–Fe–O spinel phase.
  • ItemPublic Metadata
    GRK 2802: Raman Spectroscopic Identi cation of Oxide Phases in a Cor- roded MgO-Steel Composite Anode Used in Aluminum Molten Salt Electrolysis
    (Technische Universität Bergakademie Freiberg, 2026-03-04) Drechsler, Felix; Yaroshevskyi, Serhii; Adamczyk, Alexander; Mehdizadehlima, Mahnaz; Richter, Julia; Himcinschi, Cameliu; Rafaja, David; Charitos, Alexandros; Aneziris, Christos G.; Kortus, Jens
    This study presents the post-mortem phase characterization of a metal ceramic composite anode composed of 316L stainless steel and recycled MgO, sourced from spent refractory lining bricks, employed in aluminium molten salt electrolysis. The analysis focused on the immersed section of the anode, where direct exposure to the molten Na-cryolite melt promotes the formation of corrosion products. Raman spectroscopy was applied as a structural characterization technique, providing phase information that complements the morphological and elemental analyses obtained from SEM EDX measurements. Due to its high spatial resolution, micro-Raman spectroscopy enabled the identi cation of local phases within the corrosion layer and the determination of their depth-dependent distribution. The local chemical analysis revealed an outer Fe O-rich layer penetrating several tens of micrometers into the material, followed by a Fe Al O-containing zone. Raman spectroscopy identi ed the Fe O layer as magnetite (Fe3O4) and the inner layer as hercynite (FeAl2O4), with a transition region consisting of Al-doped Fe3O4. The results demonstrate the applicability of Raman spectroscopy for identifying corrosion products to provide contributions to the corrosion mechanisms of MgO-steel anodes under electrolytic conditions.
  • ItemPublic Metadata
    GRK 2802: Recycled magnesia particles in steel-based composites: Impact on thermo-mechanical behaviour
    (Technische Universität Bergakademie Freiberg, 2026-02-02) Müller, Moritz; Mehdizadehlima, Mahnaz; Yaroshevskyi, Serhii; Aneziris, Christos G.; Biermann, Horst; Weidner, Anja
    This study investigates the thermo-mechanical behaviour of steel-ceramic composites based on a matrix of austenitic stainless steel and coarse-grained magnesia particles. Composites reinforced with fresh-fused magnesia particles were compared to those reinforced with recycled magnesia sourced from spent MgO-C refractory lining bricks. The volume fraction of recycled magnesia varied from 20 vol% to 40 vol%. Quasi-static compression tests were performed at room temperature and within a temperature range of 800 ◦C–1100 ◦C. Results showed that incorporating coarse-grained ceramic reinforcements into the steel matrix increased the compressive strength at all temperatures. The composite reinforced with recycled magnesia demonstrated superior mechanical properties over the variant with fresh-fused magnesia due to a smaller and more uniform particle size distribution resulting from crushing steps in the recycling process. Although non-metallic inclusions from contaminated zones of the refractory bricks were present in the recycled powder, they did not affect the overall damage mechanisms.
  • ItemPublic Metadata
    GRK 2802: Steel ceramic composite anodes based on recycled MgO–C lining bricks for applications in cryolite/aluminum melts
    (Technische Universität Bergakademie Freiberg, 2026-02-16) Yaroshevskyi, Serhii; Weigelt, Christian; Malczyk, Piotr; Roungos, Vasileios; Hubalkova, Jana; Zienert, Tilo; Kraft, Bastian; Wagner, Stefan; Aneziris, Christos
    Novel manufacturing route for composite inert anodes containing 60:40 of 316 L stainless steel and MgO powder obtained from recycled MgO-C brick material has been developed and evaluated. After burnout of residual carbon from the recycled MgO-C powder, MgO and steel were granulated and pre-sintered in order to generate agglomerates of composite material acting as coarse grains within the composite material, and thus lowering the sintering-related shrinkage. The pre-sintered granules were mixed with raw steel and MgO powder in order to achieve a high particle packing and subsequently cold isostatically pressed in the form of electrodes. All manufactured anode samples were subjected to sintering at 1350 ◦C and pre-oxidation at different temperatures – 800 °C, 900 °C, and 1000 °C. Afterwards, mechanical and electrical properties of the manufactured electrodes were characterized. The results show that upcycling of the MgO-C material enables manufacturing of sophisticated electrode products, which can be applied in the aluminum industry.