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Laser dielectric breakdown as a novel method for producing molybdenum borides

  • Superhard materials with a Vickers hardness in the range of 30-40 GPa are of great interest, both from a fundamental and a practical viewpoints, since they have outstanding mechanical, thermal and chemical properties. Molybdenum borides belong to this group of materials. A review of publications on synthesis of molybdenum boride indicates a) great interest in this superhard material and b) the need for new effective methods of its synthesis, especially in a nanocrystalline form. Very promising are the plasma-chemical methods based on laser induced breakdown. The breakdown can be created either in reactive gases containing volatile compounds of boron and molybdenum or on solid samples. For gas breakdown, molybdenum hexafluoride MoF6 and boron trifluoride BF3 were used in the mixture with hydrogen and argon; for solid breakdown, the pure molybdenum sample was ablated into the mixture of H2 and BF3. The plasma-chemical synthesis of MoxBy structures was carried out in the reactor shownSuperhard materials with a Vickers hardness in the range of 30-40 GPa are of great interest, both from a fundamental and a practical viewpoints, since they have outstanding mechanical, thermal and chemical properties. Molybdenum borides belong to this group of materials. A review of publications on synthesis of molybdenum boride indicates a) great interest in this superhard material and b) the need for new effective methods of its synthesis, especially in a nanocrystalline form. Very promising are the plasma-chemical methods based on laser induced breakdown. The breakdown can be created either in reactive gases containing volatile compounds of boron and molybdenum or on solid samples. For gas breakdown, molybdenum hexafluoride MoF6 and boron trifluoride BF3 were used in the mixture with hydrogen and argon; for solid breakdown, the pure molybdenum sample was ablated into the mixture of H2 and BF3. The plasma-chemical synthesis of MoxBy structures was carried out in the reactor shown in Figure. Laser breakdown was created by a pulsed Nd: YAG laser operating at 1064 nm with a 15 ns pulse duration, 5 Hz repetition rate, and 800 mJ pulse energy. The laser was focused by a 5 cm focal length lens to produce 26 J/cm3 energy density in the focal point. The ratios H2:BF3: MoF6 = 5:2:1 and H2:BF3 = 3:1 were used in a pressure range 30 - 760 Torr. After ablation in the mixture H2 + BF3 + MoF6, the deposit contained an amorphous phase with a small impurity of crystalline molybdenum and no boride phase. After ablation of metallic Mo into H2 + BF3, the main phase was MoB2 in the form of nano dispersed powder with an average grain size of 100 nm. The degree of conversion of boron trifluoride and the yield of molybdenum boride were studied as a function of pressure. It was established that 30 Torr is optimal for the formation of MoB2. This work was supported by the Russian Science Foundation grant No. 20-13-00035.zeige mehrzeige weniger

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Metadaten
Autor*innen:Igor B. GornushkinORCiD
Koautor*innen:Roman Kornev, A. R. Kornev, A. A. Ermakov
Dokumenttyp:Posterpräsentation
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2021
Organisationseinheit der BAM:1 Analytische Chemie; Referenzmaterialien
1 Analytische Chemie; Referenzmaterialien / 1.3 Instrumentelle Analytik
DDC-Klassifikation:Naturwissenschaften und Mathematik / Chemie / Analytische Chemie
Freie Schlagwörter:Laser induced plasma; Molybdenum boride; Plasma chemistry; Plasma enhanced chemical deposition
Themenfelder/Aktivitätsfelder der BAM:Chemie und Prozesstechnik
Veranstaltung:Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy
Veranstaltungsort:Online meeting
Beginndatum der Veranstaltung:29.11.2021
Enddatum der Veranstaltung:02.12.2021
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:06.12.2021
Referierte Publikation:Nein
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