Mesoporous bioactive glasses have been widely investigated for applications in bone tissue regeneration and, more recently, in soft tissue repair and wound healing. In this study we produced mesoporous bioactive glass nanoparticles (MBGNs) based on the SiO2–CaO system. With the intention of adding subsidiary biological function, MBGNs were doped with Zn2+ ions. Zn-MBGNs with 8 mol% ZnO content were synthesized via microemulsion assisted sol-gel method. The synthesized particles were homogeneous in shape and size. They exhibited spherical shape, good dispersity, and a size of 130 ± 10 nm. The addition of zinc precursors did not affect the morphology of particles, while their specific surface area increased in comparison to MBGNs. The presence of Zn2+ ions inhibited the formation of hydroxycarbonate apatite (HCAp) on the particles after immersion in simulated body fluid (SBF). No formation of HCAp crystals on the surface of Zn-MBGNs could be observed after 14 days of immersion. Interestingly, powders containing relatively high amount of zinc released Zn2+ ions in low concentration (0.6–1.2 mg L−1) but in a sustained manner. This releasing feature enables Zn-MBGNs to avoid potentially toxic levels of Zn2+ ions, indeed Zn-MBGNs were seen to improve the differentiation of osteoblast-like cells (MG-63). Additionally, Zn-MBGNs showed higher ability to adsorb proteins in comparison to MBGNs, which could indicate a favourable later attachment of cells. Due to their advantageous morphological and physiochemical properties, Zn-MBGNs show great potential as bioactive fillers or drug delivery systems in a variety of applications including bone regeneration and wound healing.

Silicon oxycarbide-based ceramic nanocomposites (SiOC, SiZrOC and SiHfOC) were prepared by means of hot pressing techniques and their behavior upon hydrothermal corrosion at moderate temperatures (up to 250°C) was investigated. The results indicated linear corrosion behavior for all samples. The corrosion rates of the SiOC ceramic materials were found to be remarkably lower than those of silicon carbide and comparable to values reported for silicon nitride. Furthermore, SiZrOC and SiHfOC were found to show improved resistance with respect to the non-modified SiOC, due to a unique synergistic effect: whereas zirconia/hafnia act as “reinforcing” phases with respect to hydrothermal corrosion (due to their extremely low solubility in water under the testing conditions), the silicon oxycarbide matrix protects the MO2 phase from a corrosion-induced t-MO2 → m-MO2 phase transformation. Consequently, the prepared silicon oxycarbide-based materials exhibit high potential for applications which require high resistance in corrosive media at moderate temperatures.

The results presented in this paper compare the behavior of silicon nitride prepared with the addition of yttria as sintering additive, and of a sialon ceramic in contact with an aqueous solution of sodium chloride (NaCl) at T≤290°C. Both studied ceramics dissolved by preferential attack of Si–N bonds in the matrix accompanied by the release of ammonia and formation of protective, mostly oxide layer of corrosion products at the surface. Increase of dissolution rate of sialon in aqueous NaCl solution at 290°C was observed in comparison to dissolution in deionized water, achieving the value 27 mmol·(m2·h)−1. Penetration of chloride anions through protective layer of corrosion products is proposed to contribute to destruction of the passivation layer and renewal of the exposure of vulnerable material surface to corrosion medium.

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