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Magnetoceramics from the Bulk Pyrolysis of Polysilazane Cross-Linked by Polyferrocenylcarbosilanes with Hyperbranched Topology

Kong, Jie, Kong, Minmin, Zhang, Xiaofei, Chen, Lixin, An, Linan
ACS Applied Materials & Interfaces 2013 v.5 no.20 pp. 10367-10375
ammonia, annealing, ceramics, crosslinking, crystals, hydrocarbons, hysteresis, iron, magnetism, pyrolysis, silicon carbide, topology
In this contribution, we report a novel strategy for the synthesis of nanocrystal-containing magnetoceramics with an ultralow hysteresis loss by the pyrolysis of commercial polysilazane cross-linked with a functional metallopolymer possessing hyperbranched topology. The usage of hyperbranched polyferrocenylcarbosilane offers either enhanced ceramic yield or magnetic functionality of pyrolyzed ceramics. The ceramic yield was enhanced accompanied by a decreased evolution of hydrocarbons and NH₃ because of the cross-linking of precursors and the hyperbranched cross-linker. The nucleation of Fe₅Si₃ from the reaction of iron atoms with Si–C–N amorphous phase promoted the formation of α-Si₃N₄ and SiC crystals. After annealing at 1300 °C, stable Fe₃Si crystals were generated from the transformation of the metastable Fe₅Si₃ phase. The nanocrystal-containing ceramics showed good ferromagnetism with an ultralow (close to 0) hysteresis loss. This method is convenient for the generation of tunable functional ceramics using a commercial polymeric precursor cross-linked by a metallopolymer with a designed topology.