Ján Dusza

Ján Dusza

PROMATECH Institute of Materials Research of SAS, Slovakia

duszajyahoo [dot] com

Ján Dusza is professor of materials science and technology and advanced ceramics at the Institute of materials research, SAS, Kosice, Slovak Republic since 1997. He finished at the ELTE University in Budapest, Hungary as a physicist in 1976 and received his PhD and DrSc degree at Technical University of Kosice, Slovak Republic in 1983 and 1994, respectively. He is a professor at the Technical University of Kosice, Slovak Republic and at the Obuda University, Budapest in Hungary. J. Dusza is working at the IMR SAS since 1976 up to now, as a PhD student, scientist, senior scientist, head of the structural ceramics department and vice-director for science. He has over 250 scientific publications/over 2800 citations in Scopus, 60 invited lectures, 3 patents and he edited/co-edited many International conference proceedings, e.g. he is the founding chair of the International Conference on Fractography of Advanced Ceramics. J. Dusza has received many awards, including the Award of the SAS – For excellent research results, Bratislava; Award of the SAS – For infrastructure building, Bratislava; Dennis Gabor Award, Budapest. He is an Academician of the World Academy of Ceramics and Hungarian Academy of Sciences, a fellow of the European Ceramic Society, member of the Learn Society of SAS. He is an honorary citizen of the city TornaÄža in the Slovak Republic.

Development and Characterization of High - Entropy Carbides

Abstract

A High Entropy (Hf-Ta-Zr-Nb)C Ultra-High Temperature Ceramic (UHTC) was processed by ball milling and Spark Plasma Sintering (SPS) with a density of 99%. It was found that the lattice parameter mismatch of the component monocarbides is a key factor for predicting single phase solid solution formation. According to the results the grain size ranged from approximately 5μmto 25μm with average grain size of 12μm. Chemical analyses proved that all grains had the same chemical composition at the micro as well as on the nano/atomic level without any detectable segregation. The approximately 1.5 nm thin amorphous grain boundary phase contained impurities that came from the starting powders and the ball milling process. The system was subjected to nanoindentation testing and directly compared to the constituent mono/binary carbides, revealing a significantly enhanced hardness (36.1 ± 1.6 GPa,) compared to the hardest monocarbide (HfC, 31.5 ± 1.3 GPa) and the binary (Hf-Ta)C (32.9 ± 1.8 GPa). The measured steady-state creep rates investigated at temperatures between1400 and 1600 °C in vacuum under compressive stresses from 150 to 300 MPa. ranged from 2 × 10−9/s to 8 × 10-8/s, which are approximately 10 times lower than the published creep rates of the corresponding monocarbides. The stress exponent n is in the range of 2.34∼2.89 and the averageactivation energy is 212 kJ/mol. The creep mechanisms involve dislocation glide/climb and the formation ofvoids and cracks. The micro pillar compression test revealed that (Hf-Ta-Zr-Nb)C had a significantly enhanced yield and failure strength compared to the corresponding base monocarbides, while maintaining a similar ductility to the least brittle monocarbide (TaC) during the operation of {110} 110 slip systems. Additionally, it was concluded that the crystal orientation and stress conditions determine the operation of slip systems in mono- and high-entropy carbides at room temperature.