Thermodynamic modelling and production of manganese boride compounds via self-propagating high temperature synthesis

Transition metal borides are advanced materials with superior mechanical and thermal properties. Manganese borides combine high hardness with thermal stability and wear resistance, making them suitable for energy-storage parts, magnetic devices, and high-temperature service. In this study, Mn-B compounds were synthesised via self-propagating high-temperature synthesis (SHS) for the first time. The MnO-B2O3-Mg system was thermodynamically modelled in FactSage 7.1 to define the reaction conditions. Experiments were conducted using magnesium as the reductant at stoichiometries ranging from 100% to 115%. XRD showed MgO as the dominant phase at all levels; MgB2 appeared at 100% Mg, and MnB with Mn3B2O6 was present in every composition. Mg-based by-products appeared in all stoichiometries and were removed by acid leaching with 6 M HCl. After leaching, the primary phases were Mn2B, MnB, and MnB2, while boron-related peaks appeared only at 100% stoichiometry. Accordingly, the formation of manganese - boron compounds requires at least 105% Mg stoichiometry. SEM/EDS analysis of the leached sample confirmed the removal of Mg- and O-containing impurities. Since 110-115% offered no advantage but raised magnesium use, 105% was identified as the optimum stoichiometry. These findings confirm SHS as a viable route for producing manganese boride ceramics for advanced applications. Les borures de m & eacute;taux de transition sont des mat & eacute;riaux avanc & eacute;s aux propri & eacute;t & eacute;s m & eacute;caniques et thermiques sup & eacute;rieures. Les borures de mangan & egrave;se combinent une duret & eacute; & eacute;lev & eacute;e & agrave; une stabilit & eacute; thermique et une r & eacute;sistance & agrave; l'usure, ce qui les rend adapt & eacute;s aux pi & egrave;ces de stockage d'& eacute;nergie, aux dispositifs magn & eacute;tiques et aux applications & agrave; haute temp & eacute;rature. Dans cette & eacute;tude, on a synth & eacute;tis & eacute; des compos & eacute;s Mn-B par synth & egrave;se autopropag & eacute;e & agrave; haute temp & eacute;rature (SHS) pour la premi & egrave;re fois. On a mod & eacute;lis & eacute; thermodynamiquement le syst & egrave;me MnO-B2O3-Mg dans FactSage 7.1 afin de d & eacute;finir les conditions de r & eacute;action. On a effectu & eacute; des exp & eacute;riences en utilisant le magn & eacute;sium comme agent r & eacute;ducteur & agrave; des st oe chiom & eacute;tries allant de 100% & agrave; 115%. La DRX a montr & eacute; le MgO comme phase dominante & agrave; tous les niveaux; MgB2 apparaissait & agrave; 100% de Mg, et MnB avec Mn3B2O6 & eacute;tait pr & eacute;sent dans toutes les compositions. Des sous-produits & agrave; base de Mg apparaissaient dans toutes les st oe chiom & eacute;tries et & eacute;taient & eacute;limin & eacute;s par lixiviation acide avec du HCl 6 M. Apr & egrave;s lixiviation, les phases principales comprenaient Mn2B, MnB et MnB2, tandis que les pics associ & eacute;s au bore n'apparaissaient qu'& agrave; 100% de st oe chiom & eacute;trie. Par cons & eacute;quent, la formation de compos & eacute;s de mangan & egrave;se-bore n & eacute;cessite une st oe chiom & eacute;trie en Mg d'au moins 105%. L'analyse MEB/EDS de l'& eacute;chantillon lixivi & eacute; a confirm & eacute; l'& eacute;limination des impuret & eacute;s contenant Mg et O. Puisque 110 & agrave; 115% n'offraient aucun avantage mais & eacute;levaient la consommation de magn & eacute;sium, on a identifi & eacute; la st oe chiom & eacute;trie optimale & agrave; 105%. Ces r & eacute;sultats confirment la SHS comme une voie viable pour la production de c & eacute;ramiques de borure de mangan & egrave;se pour des applications avanc & eacute;es.