Browsing by Author "Kaiser, Patricia"

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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.
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SPP 2419: 3D printing of alumina components via Fused Granulate Fabrication technology and solvent-free debinding of highly filled feedstocks comprising (LD)-polyethylene and cellulose
(Technische Universität Bergakademie Freiberg, 2026-03-30) Brachhold, Nora; Heuer, Claudia; Bock-Seefeld, Benjamin; Kaiser, Patricia; Weigelt, Christian; Malczyk, Piotr; Trimis, Dimosthenis; Aneziris, Christos G.
This study focuses on the development of components in gyroid structure based on alumina as integral part of the novel burner designed for the non-premixed combustion of ammonia. During application, the component has to withstand repeated thermal shocks of approx. 600 K or more. Due to the high geometric complexity of the gyroid structure and the need for lightweight design with both macroporous regions and microporous features only the 3D printing was suitable as manufacturing technology; in the present work Fused Granulate Fabrication was used. The manufacturing routine for the employed granules with special regard to the binder system is developed. A customized thermal debinding regime without wick or solvent debinding is presented. Challenges such as the formation of bubbles and the swelling of the samples during thermal debinding were met by adjusting the printing parameters to create porosity and cavities between the deposited strands during 3D printing. Sintered bars fabricated using optimized printing parameters had a shrinkage of 13 %, an open porosity of 41 % and a flexural strength of 50 MPa, respectively. These values are sufficient for the application of the components in the novel burners. As last part of this work sheet-gyroid structures were prepared using a 1.0 mm and 0.4 mm nozzles. These structures successfully survived 5 thermal shock cycles, each involving heating to 1100 ◦C followed by air quenching, which is an excellent result in terms of thermal shock performance.