Pyrolytic conversion of preceramic polymers such as polysilanes, -silazanes, or -siloxanes to ceramics may be significantly influenced by the resence of active filler dispersoids. Based on thermodynamic and microstructural considerations a variety of suitable polymer-filler systems can be found which allow the fabrication of microcrystalline composite materials with low dimensional change upon polymer- ceramic conversion. As an example the active filler controlled reaction pyrolysis of polysiloxane with addition of titanium powder was investigated. A composite material with microcrystalline titanium carbide inclusions embedded in an amorphous (< 1000 °C) or nanocrystalline (>1000 °C) silicon oxycarbide matrix was formed. Property changes with increasing pyrolysis temperature can be attributed to various microstructural transformations. Thus, a variety of potential fillers may be used to tailor the microstructure of polymer-derived ceramic composite materials in order to fabricate bulk materials and components with a broad range of compositions and properties.

Ferrite particle-dispersed carbon composite were synthesized by in-situ pressure pyrolysis of organometallic polymers at temperatures from 500 to 700°C under 125 MPa. Magnetite-dispersed carbon composite could be prepared from 550 to 700°C at 125 MPa. Nickel and nickel zinc ferrite particles were dispersed in carbon matrices at 550°C and 500°C, respectively, under 125 MPa. The morphology of the carbon matrix can be controlled by the pyrolysis conditions and the amount of coexistent supercritical water. Carbon spherulites of several micrometers dispersed with ferrite particles less than 100 nm were successfully synthesized by pressure pyrolysis of organometallic polymers in the presence of supercritical water. The saturation magnetization of magnetite-, nickel ferrite- and nickel zinc ferrite-dispersed carbon were 74, 30 and 65 emu/g, respectively. The coercive force of nickel ferrite-dispersed carbon was about 200 Oe.

Metal powders of the composition 70 at% Cu and 30 at% Fe were produced by high energy mechanical alloying of the elemental powders. The powders were processed in a Spex 8000 mixer/mill for various times to investigate the potential of the mechanical alloying process for producing nano-composite structures with modified magnetic properties. Optical microscopy revealed a layered structure of alternating copper and iron that developed upon milling. The spacing between the layers decreased with milling time, becoming optically unresolvable (< 1 μm) after four hours of milling. A single profile x-ray diffraction profile shape analysis technique was used to determine the average diffracting particle size of the copper and iron phases. The diffracting particle size decreases with alloying time reaching values of 7.5 nm and 2 nm, for copper and iron respectively, after eight hours of alloying. The magnetic coercivity increased with milling time initially, reaching a maximum value above 300 Oe after six hours of milling. These results are discussed and compared to results obtained in Ag/Fe and Cu/Fe nano-composite films.