Nanocluster-containing mesoporous magnetoceramics from hyperbranched organometallic polymer precursors

Pyrolysis of hyperbranched poly[1,1'-ferrocenylene(methyl)silyne] (5) yield s mesoporous, conductive, and magnetic ceramics (6). Sintering at high temp eratures (1000-1200 degrees C) under nitrogen and argon converts 5 to 6N an d 6A, respectively, in similar to 48-62% yields. The ceramization yields of 5 are higher than that (similar to 36%) of its linear counterpart poly[1,1 '-ferrocenylene(dimethyl)silylene] (1), revealing that the hyperbranched po lymer is superior to the linear one as a ceramic precursor. The ceramic pro ducts 6 are characterized by SEM, XPS, EDX, XRD, and SQUID. It is found tha t the ceramics are electrically conductive and possess a mesoporous archite cture constructed of tortuously interconnected nanoclusters. The iron conte nts of 6 estimated by EDX are 36-43%, much higher than that (11%) of the ce ramic 2 prepared from the linear precursor 1. The nanocrystals in 6N are ma inly alpha-Fe2O3 whereas those in 6A are mainly Fe3Si. When magnetized by a n external field at room temperature, 6A exhibits a high-saturation magneti zation (M-s similar to 49 emu/g) and near-zero remanence and coercivity; th at is, 6A is an excellent soft ferromagnetic material with an extremely low hysteresis loss.