Li, Wei ; Du, Hanzi ; Tian, Chuanmu ; Jiang, Tianshu ; Bernauer, Jan ; Widenmeyer, Marc ; Wiehl, Leonore ; Molina‐Luna, Leopoldo ; Hofmann, Jan Philipp ; Weidenkaff, Anke ; Yu, Zhaoju ; Riedel, Ralf (2022)
Single‐source‐precursor derived bulk Si₃N₄/HfBxN₁‐x ceramic nanocomposites with excellent oxidation resistance.
In: Zeitschrift für anorganische und allgemeine Chemie, 648 (21)
doi: 10.1002/zaac.202200203
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

In the present work, bulk Si₃N₄/HfBxN₁‐x ceramic nanocomposites were successfully fabricated via a polymer-derived ceramic approach. The chemical reaction to form the single-source precursor was confirmed by FT-IR and XPS, in which both Si−H and N−H groups of perhydropolysilazane react with borane dimethyl sulfide complex and tetrakis(dimethylamido) hafnium(IV). The investigation of the polymer-to-ceramic transformation of the synthesized precursors indicates that Hf- and B-modified PHPS exhibits high ceramic yields of up to 100 wt % after pyrolysis at 1000 °C under ammonia. Moreover, XRD and TEM results show that the SiHfBN ceramics with a molar ratio of B : Hf=5 and 10 resist crystallization at temperatures up to 1500 °C and separate after annealing at 1700 °C into nanocomposites comprising of an α-Si₃N₄ matrix with embedded ternary HfBxN1-x phases, solid solutions of rock salt-type HfN and HfB. Based on the investigation, warm-pressing was applied to fabricate bulk SiHfBN specimens, and the oxidation behavior of samples annealed at 1700 °C was recorded at 1500 °C over a range of oxidation times between 1 and 50 h. The weight changes of Si₃N₄/HfBxN₁‐x ceramics with B : Hf molar ratios of 2 : 1, 5 : 1 and 10 : 1 are 4.31 %, 4.37 % and 2.57 %, respectively. The formation of HfSiO₄, B₂O₃ and SiO₂ during oxidation plays a crucial role for the improvement of the oxidation resistance of the Si₃N₄/HfBxN₁‐xceramics.

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