Development of multiphase bioceramics from a filler-containing preceramic polymer E. Bernardo a, * , E. Tomasella a , P. Colombo a,b a Dipartimento di Ingegneria Meccanica - Settore Materiali, Universita ` di Padova, via Marzolo 9, 35151 Padova, Italy b Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA Received 12 May 2008; received in revised form 23 June 2008; accepted 16 July 2008 Available online 5 August 2008 Abstract Multiphase bioceramics based on wollastonite and wollastonite/hydroxylapatite (W/HAp) have been successfully prepared by the heat treatment of a filler-containing preceramic polymer. CaO-bearing precursors (Ca-carbonate, Ca-acetate, and CaO nano-particles) were dispersed in a solution of silicone resin, subsequently dried and pyrolysed in nitrogen. The reaction between silica, deriving from the oxycarbide (SiOC) residue of the silicone resin, and CaO ‘‘active filler’’ led to the formation of several calcium silicates, mainly consisting of wollastonite (CaSiO 3 ), in both low and high temperature forms. The phase assemblage of the final ceramic varied with the pyrolysis temperature (varying from 1000 to 1200 8C). HAp was additionally inserted, as ‘‘passive filler’’ (i.e. not reacting with SiOC), for the preparation of bioceramics based on W/HAp mixtures. The use of a filler-containing preceramic polymer to obtain bioceramics is favourable, besides for the simplicity of the procedure, for the possibility of achieving complex shapes. In fact, we demonstrated the possibility of fabricating an open-celled microcellular foam, prepared by mixing the filler- containing preceramic polymer with sacrificial PMMA microbeads. The proposed approach, due to the well-known bioactivity of wollastonite, W/ HAp composites, and secondary calcium silicates, could be profitable for manufacturing various ceramic components for medical use. # 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: A. Shaping; B. Nano-composites; B. X-ray methods; E. Biomedical applications 1. Introduction Preceramic polymers are well known for their use in the production of advanced ceramic components (fibers, coatings, micro-components, foams, membranes), especially based on the Si–O–C, Si–C and Si–(B)–N–C systems [1,2]. These ceramics, also known as polymer-derived-ceramics (PDCs), rely on a particular microstructure, generally consisting of nano-crystal- line domains (based on SiC or C) embedded within an amor- phous matrix, which yields unusual properties (such as very low creep, high chemical resistance etc.) [3,4]. A key advantage of PDCs is the possibility of shaping ceramic components by using conventional plastic-forming techniques (spinning, blowing, injection-molding, warm pressing, resin transfer-molding), applied to the precursor polymers. The main drawbacks, however, are the poor control of the shrinkage and the formation of cracks deriving from the gas release occurring during the polymer-to-ceramic conversion upon pyrolysis. The pioneering research carried by Greil [5] showed the possibility of both controlling the shrinkage and obtaining relatively dense and crack-free components by simply adding to preceramic polymers so-called ‘‘active fillers’’. Metal (or intermetallic) particles, upon pyrolysis in inert atmosphere, may react with the gaseous decomposition products coming off the preceramic polymer or with the pyrolysis gas, to yield mainly carbide or nitride ceramics. The volume expansion occurring upon conversion of metal particles into ceramics (e.g. Ti to TiC) limits both the formation of defects and the large shrinkage otherwise occurring upon pyrolysis. As an alternative, inert filler powders (in particular SiC or Si 3 N 4 ), which do not react with the preceramic polymer decomposition products, can be added. In this case, the fillers simply partially reduce the total shrinkage in the component, by diluting the transforming mass [6]. Oxide powders have rarely been added as fillers to produce all-oxide ceramics [7–9], probably due to the fact that typically preceramic polymers are processed in inert atmosphere in order to retain the C atoms which play a key role in the development of the unique microstructure and properties of PDCs [10]. However, some www.elsevier.com/locate/ceramint Available online at www.sciencedirect.com Ceramics International 35 (2009) 1415–1421 * Corresponding author. Tel.: +39 049 8275510; fax: +39 049 8275505. E-mail address: enrico.bernardo@unipd.it (E. Bernardo). 0272-8842/$34.00 # 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2008.07.003