Polymeric precursors to refractory metal borides

Formation of zirconium diboride (ZrB2) by room temperature mechanochemical reaction between ZrO2, B2O3 and Mg

“…However, the use of elemental Zr and B is much more expensive than using the oxides due to the high cost of extracting metals from the minerals. A similar argument regarding costs can be made for recent processes which use complex polymeric metal alkoxides or air and moisture sensitive materials, such as borazine, as the precursors [9,10]. These preparations also require pyrolysis before the required phases are formed.…”

Refractory Diborides of Zirconium and Hafnium

“…Similar processes should also work for nano‐crystalline diborides, but, to date, only conventional micro‐sized oxides have been converted to diborides 82 . A pre‐ceramic polymer has been directly converted to a refractory diboride, 83 but the polymer was used as a binder for commercial ZrB 2 powder, not to produce a stand‐alone coating or a monolithic ceramic. Finally, diboride‐based composites have been prepared by combining conventional diboride powders with SiC‐bearing pre‐ceramic polymers such as polycarbosilane 84,85 .…”

Effects of TaB2 and TiB2 on the grain growth behavior and kinetics of HfB2 ceramics during pressureless sintering

“…Hafnium diboride powders could be mainly prepared by the following routes: (a) self‐propagating high‐temperature synthesis; (b) polymer‐precursor route; (c) the sol‐gel process; (d) borothermal and boro/carbothermal reduction . Refinement of the starting HfB 2 powders could enhance the surface energy, thereby increasing the driving force of sintering and improving the mechanical properties.…”

“…Reaping benefits from excellent mechanical properties and oxidation resistance versus adverse conditions, hafnium diboride (HfB 2 ) is critically regarded as one of the most promising candidates to be applied in extreme conditions, such as supersonic aircraft tip, reusable trans-atmosphere aircraft, etc. [1][2][3][4] Hafnium diboride powders could be mainly prepared by the following routes: (a) self-propagating high-temperature synthesis; 5,6 (b) polymer-precursor route; 7,8 (c) the sol-gel process; 9,10 (d) borothermal and boro/carbothermal reduction. 11,12 Refinement of the starting HfB 2 powders could enhance the surface energy, thereby increasing the driving force of sintering and improving the mechanical properties.…”