Ceramics have long occupied a central position in dentistry, orthopedics, and tissue repair because of their chemical stability, wear resistance, mechanical strength, and compatibility with mineralized tissues [...]
Fabrication of biomaterials that closely mimic the architecture of native biological tissues is one of the main goals of tissue engineering. In this regard, hydrogels featuring high-water content and porous networks may closely resemble the extracellular matrix of living tissue. The aim of this work was to obtain and to provide structural characterization along with preliminary biological assessment of the hydrogel assemblies composed of bioactive glass (BG), chitosan (Ch), and monoammonium salt of glycyrrhizic acid (MSGA). The structural characterization of reactants and products performed by means of Fourier transform infrared and scanning electron microscopy revealed the complex relationships through the formation of hydrogen bonds and interaction of the chitosan’s amino and hydroxyl groups with the structural units of BG. Finally, new assemblies were introduced to a culture of the human osteoblast cell line (hFOB) in order to assess cytocompatibility, as well as their influence on proliferation and osteogenic differentiation. According to indirect MTS analysis, experimental compositions demonstrated about 100% or high cell viability after incubation in a culture of the human osteoblast cell line for 96 h. These promising results support the feasibility of further investigations involving osteogenic marker expression and in vivo implantation studies to evaluate the tissue regeneration potential of the developed materials
Simultaneously realizing high room temperature permittivity and X8R temperature stability (−55 °C to 150 °C, ΔC/C25 °C ≤ ±15%) remains a significant obstacle for lead-free BaTiO3-based dielectrics. Herein, a synergistic strategy combining Curie-point shifting and weak relaxor engineering is demonstrated. A single composition, 0.95BaTi0.8Hf0.2O3-0.05Bi(Zn0.5Ti0.5)O3 is prepared via solid-state reaction. The ceramic possesses a pure perovskite structure and a dense and chemically homogeneous microstructure. At 1 kHz and room temperature, it delivers a high dielectric constant exceeding 1000 and a low loss below 0.02, while the capacitance variation remains within ±15% from −100 °C to 313 °C, fully satisfying the X8R specification. Moreover, an ultrafast discharge time of 39 ns, a power density of 315 MW/cm3, and a discharge energy density of 3.3 J/cm3 are achieved at 300 kV/cm. The synergy between Hf-driven peak shifting and minimal relaxor incorporation yields a composition that balances high polarization, thermal stability, and rapid energy release, offering a promising route for high-performance temperature-stable and pulsed-power capacitors.
Sr2TiSi2O8 (STS) polar glass-ceramics are promising piezoelectric materials for high-temperature surface acoustic wave (SAW) devices, provided that the orientation of the STS polar axis and the thermomechanical stability of the substrate can be controlled. In this work, the effect of the residual glass fraction on the crystallization behavior, microstructure, and thermomechanical properties of glass-ceramics synthesized from parent glasses belonging to the Sr–Ti–Si–K–Al–O system was investigated. Dilatometry, differential scanning calorimetry, and controlled heat treatments performed on the parent glasses showed that increasing the residual-glass-forming fraction slows the crystallization kinetics of STS. All investigated compositions exhibited a surface-crystallization mechanism, and the growth rate of the crystallized layer at 900 °C decreased with increasing residual glass content, thereby affecting the preferential orientation of STS crystals. The thermomechanical behavior of the resulting glass-ceramics was investigated by dilatometry and by measuring the temperature dependence of Young’s modulus using the impulse excitation technique (IET). The results were analyzed with reference to the behavior of both the residual glass and pure STS. Increasing the residual glass fraction only slightly affected the coefficient of thermal expansion (CTE) below the glass transition temperature (Tg) of the residual glass but led to a significant increase in CTE at higher temperatures. Nonlinear thermal-expansion behavior, attributed to the commensurate–incommensurate (C–I) phase transition of STS, was observed in the temperature range 100–200 °C. This phase transition also affected the evolution of Young’s modulus with temperature. Furthermore, the combined dilatometry and IET results suggest that residual stresses generated during crystallization contribute to a downward shift in the apparent commensurate–incommensurate (C–I) transition temperature of STS.
In this work, zirconia ceramic structures were fabricated by Direct Ink Writing (DIW) using water-based, yttria-stabilized nano-zirconia pastes. The pastes were prepared from 3 mol% yttria-stabilized zirconia nanopowders synthesized by sol–gel and co-precipitation routes. The effects of dispersant concentration and organic additives on paste preparation and printability were investigated, and the rheological behavior of the printable formulations was evaluated. The microstructure of the sintered 3D-printed specimens was examined by scanning electron microscopy (SEM), while apparent porosity, density, and compressive strength were determined. All printable pastes exhibited shear-thinning behavior. After sintering at 1500 °C, the printed specimens showed submicron grain sizes and apparent porosities as low as 3%. The formulation prepared without acrylamide and crosslinking agent (O12X) exhibited an apparent porosity of 3% and a compressive strength of 350 ± 25 MPa. The co-precipitated-powder formulation (2N) reached compressive-strength values of up to 360 ± 25 MPa. These results demonstrate the feasibility of using high-solids, water-based nano-zirconia pastes for DIW fabrication of dense zirconia structures and support further investigation of this approach for dental applications.
