High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study
The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf<sub>0.2</sub>Mo<sub>0.2</sub>...
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2024-02-01
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| Online Access: | https://www.mdpi.com/1996-1944/17/3/718 |
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| author | Ekaterina Pakhomova Giacomo Cao Roberto Orrù Sebastiano Garroni Paolo Ferro Roberta Licheri |
| author_facet | Ekaterina Pakhomova Giacomo Cao Roberto Orrù Sebastiano Garroni Paolo Ferro Roberta Licheri |
| author_sort | Ekaterina Pakhomova |
| collection | DOAJ |
| description | The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf<sub>0.2</sub>Mo<sub>0.2</sub>Ti<sub>0.2</sub>Ta<sub>0.2</sub>Nb<sub>0.2</sub>)B<sub>2</sub>–SiC and (Hf<sub>0.2</sub>Mo<sub>0.2</sub>Ti<sub>0.2</sub>Ta<sub>0.2</sub>Zr<sub>0.2</sub>)B<sub>2</sub>–SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B<sub>4</sub>C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m<sup>1/2</sup>) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO<sub>3</sub> formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS–SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed. |
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| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-08T03:52:37Z |
| publishDate | 2024-02-01 |
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| spelling | doaj.art-506685806cb64c4ab5f05f4a4565269a2024-02-09T15:17:51ZengMDPI AGMaterials1996-19442024-02-0117371810.3390/ma17030718High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative StudyEkaterina Pakhomova0Giacomo Cao1Roberto Orrù2Sebastiano Garroni3Paolo Ferro4Roberta Licheri5Unità di Ricerca del Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, ItalyUnità di Ricerca del Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, ItalyUnità di Ricerca del Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, ItalyDipartimento di Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, 07100 Sassari, ItalyDipartimento di Tecnica e Gestione dei Sistemi Industriali, Università di Padova, Stradella S. Nicola 3, 36100 Vicenza, ItalyUnità di Ricerca del Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, ItalyThe reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf<sub>0.2</sub>Mo<sub>0.2</sub>Ti<sub>0.2</sub>Ta<sub>0.2</sub>Nb<sub>0.2</sub>)B<sub>2</sub>–SiC and (Hf<sub>0.2</sub>Mo<sub>0.2</sub>Ti<sub>0.2</sub>Ta<sub>0.2</sub>Zr<sub>0.2</sub>)B<sub>2</sub>–SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B<sub>4</sub>C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m<sup>1/2</sup>) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO<sub>3</sub> formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS–SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed.https://www.mdpi.com/1996-1944/17/3/718high-entropy boridessilicon carbidespark plasma sinteringself-propagating high-temperature synthesisresistance to oxidationfracture toughness |
| spellingShingle | Ekaterina Pakhomova Giacomo Cao Roberto Orrù Sebastiano Garroni Paolo Ferro Roberta Licheri High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study Materials high-entropy borides silicon carbide spark plasma sintering self-propagating high-temperature synthesis resistance to oxidation fracture toughness |
| title | High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study |
| title_full | High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study |
| title_fullStr | High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study |
| title_full_unstemmed | High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study |
| title_short | High-Entropy Diborides—Silicon Carbide Composites by Reactive and Non-Reactive Spark Plasma Sintering: A Comparative Study |
| title_sort | high entropy diborides silicon carbide composites by reactive and non reactive spark plasma sintering a comparative study |
| topic | high-entropy borides silicon carbide spark plasma sintering self-propagating high-temperature synthesis resistance to oxidation fracture toughness |
| url | https://www.mdpi.com/1996-1944/17/3/718 |
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