REES RAWLINGS FESTSCHRIFT Polymer-derived microcellular SiOC foams with magnetic functionality Lisa Biasetto Æ Adel Francis Æ Petru Palade Æ Giovanni Principi Æ Paolo Colombo Received: 12 June 2007 / Accepted: 10 October 2007 / Published online: 3 April 2008 Ó Springer Science+Business Media, LLC 2008 Abstract SiOC microcellular ceramic foams possessing soft-ferromagnetic properties were produced from a pre- ceramic polymer, poly-methyl-methacrylate microbeads (PMMA) (used as sacrificial pore formers) and iron silicide micro-powders (as functional filler). The interactions between the matrix and the filler were studied as a function of the amount of powders introduced and the pyrolysis temperature. Magnetic and mechanical properties were also investigated. Introduction Si-based pre-ceramic polymers (polysilane, polysiloxanes, polycarbosilane, polysilazanes) have gained increasing interest as precursors for ceramic materials possessing improved and novel properties compared to conventional ceramics. These include resistance to very harsh environ- ments [1], absence of steady state creep, viscoelasticity at very high temperature, [2–4] resistance to crystallization and oxidation [5]. The advantages in using these polymers as ceramic precursors concern both processing (easy shaping, low firing temperatures) and the final material composition and properties. By varying the polymer composition and architecture it is possible to obtain, after crosslinking and pyrolysis (800–1,200 °C, Nitrogen or Argon atmosphere), various ceramic compositions (SiC, SiOC, Si 3 N 4 , SiCN, SiEOC, SiECN, where E = Al, B, Ti, …) possessing different structures at the nano- and microme- ter-range. On the other hand, since such ceramics derive from the pyrolysis of a polymer containing organic func- tional groups (–CH 3 , –C 6 H 5 , –CH = CH 2 , etc.), their elimination during the polymer-to-ceramic conversion leads to components containing pores and cracks, with a volume shrinkage as high as 70%. Manufacturing of bulk components from pre-ceramic polymers, however, is facilitated when the polymer is loaded with a filler powder. Inert filler powders such as Al 2 O 3 , SiC, B 4 C, Si 3 N 4 , etc., as well as reactive fillers like Ti, Cr, Mo, B, MoSi 2 , etc., which may react with the solid and gaseous decomposition products of the polymer precursor (and with the heating atmosphere) to form carbides, nitrides, oxides, etc., were successfully used to reduce the polymer-to-ceramic shrinkage and to improve the mechanical properties of non- oxide as well as oxide based polymer-derived ceramics [6–8]. Pyrolysis temperature and atmosphere affect the composition of the resulting filler-loaded ceramics [9]. One further advantage of using fillers in conjunction with pre-ceramic polymers is the possibility to tailor functional properties of the final ceramic materials. For instance, adding filler materials with a high electrical conductivity such as metals or intermetallics offers the possibility of creating polymer-derived ceramic composite materials with low resistivity. Polysiloxanes loaded with 40–50 vol. % of MoSi 2 filler powder have been shown to possess an electrical resistivity lower than 10 -2 XÁm after pyrolysis at temperatures above 1,000 °C[10, 11]. Saha L. Biasetto (&) Á P. Palade Á G. Principi Á P. Colombo Dipartimento di Ingegneria Meccanica-Settore Materiali, Universita ` di Padova, Via Marzolo 9, 35131 Padova, Italy e-mail: lisa.biasetto@lnl.infn.it A. Francis Central Metallurgical Research and Development Institute, CMRDI, Helwan, 87, Cairo, Egypt P. Colombo Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA 123 J Mater Sci (2008) 43:4119–4126 DOI 10.1007/s10853-007-2224-3