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Polymer‐to‐ceramic transformation is a suitable technology to produce a broad spectrum of ceramic‐based composite materials with adjusted chemical, mechanical, and physical properties. Their properties depend on the chemical structure of preceramic polymers, the carbon content of the ceramic, the conditions used for pyrolysis (eg, temperature, atmosphere) as well as the use of additional active or passive fillers. The intimate relationship between the molecular architecture of the precursor and the nano/microstructure as well as the functional and structural properties of the resulting ceramics is one of the most important features of this class of ceramics. Chemical design of precursors, such as polysilanes, polycarbosilanes, polysiloxanes, polysilazanes, and polysilylcarbodiimides, enables the production of nanostructured SiC, SiOC, and SiCN ceramics via thermal conversion in an inert or active atmosphere. A key aspect of a polymer‐derived ceramics (PDCs) route is the possibility to “dissolve” carbon in phases such as Si 3 N 4 and SiO 2 and to create ternary phase ceramics such as SiOC and SiCN, which is only realizable by using single‐source‐precursors techniques. Synthetic routes for silicon‐based polymers as well as their transformation steps to ceramics (namely cross‐linking and pyrolysis) will be presented in this review. A short overview on PDCs as a unique class of ceramics is provided as well. Preceramic polymers, which are used for the synthesis of multinary PDCs such as SiBCN and SiMOCN (M = metal), are also described.

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The bioactivity of Ca and/or B modified silicon oxycarbides has been assessed in vitro upon immersion in SBF (simulated body fluid). In the context of the present work, bioactivity refers to the likeliness of hydroxyapatite crystallization (biomineralization) on the surface of a material when in contact with physiological fluids. The incorporation of Ca and B into the silicon oxycarbide glass network is found to increase its bioactivity, which seems to scale with the content of Ca; thus, SiOC glass with a relatively large Ca/Si molar ratio (i.e., 0.12) is shown to exhibit bioactive characteristics similar to those of the benchmark silicate bioactive glass of 45S5 composition. The release kinetics of the SiOC glasses modified with Ca and/or B during the SBF test was studied by inductively coupled plasma-optical emission spectroscopy. It has been observed that the Si release kinetics can be correlated with the Ca content in the SiOC glasses: SiOC based glasses modified with Ca exhibited low Si release activation energies (i.e., 0.07 eV), being comparable to that of 45S5 bioactive glass (i.e., 0.04 eV); whereas silicon oxycarbides without Ca modification showed higher activation energies for Si release (i.e., 0.27 eV).

The atomic structure of the Si–O–C tetrahedral network of an amorphous silicon oxycarbide polymer-derived ceramic (PDC) of the composition SiO0.94±0.11C1.13±0.08 was studied at both the short range and the intermediate range using 1D and 2D 29Si nuclear magnetic resonance (NMR) spectroscopic techniques, respectively . The 1D 29Si magic angle-spinning NMR spectrum of the PDC indicates that the Si–O–C network consists of SiO4, SiO3C, SiO2C2, and SiC4 units with relative abundances of approximately 26, 25, 20, and 29%, respectively. The 2D 29Si extended CSA amplification spectrum of this PDC shows that the chemical shift anisotropy (Δ) of the mixed-bond SiO x C4–x units is significantly higher than that of the SiO4 units. On the other hand, the unusually high Δ-value for the SiC4 units was interpreted to be indicative of its role as the connecting element between the Si–O–C network and the free-carbon nanodomains. The 2D 29Si double-quantum correlation NMR spectrum of this PDC indicates that there is extensive direct linking between SiO4 and SiO3C units in the Si–O–C network besides the connectivity between like SiO x C4–x units, while the SiO4 and SiO2C2 units are only linked via a SiO3C unit. In contrast, the SiO3C units show no restriction in linking with the other SiO x C4–x units in the network. Finally, the SiC4 units show significant clustering, which is consistent with their spatial localization at the interface between the Si–O–C network and the sp2 C nanodomains. Such a spatial distribution of the SiO x C4–x units is argued to be consistent with their mass-fractal dimensions measured in previous studies.

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