Structural, Mechanical, Imaging and in Vitro Evaluation of the Combined Effect of Gd3+ and Dy3+ in the ZrO2-SiO2 Binary System.

Mechanical strength and biocompatibility are considered the main prerequisites for materials in total hip replacement or joint prosthesis. Noninvasive surgical procedures are necessary to monitor the performance of a medical device in vivo after implantation. To this aim, simultaneous Gd3+ and Dy3+ additions to the ZrO2-SiO2 binary system were investigated. The results demonstrate the effective role of Gd3+ and Dy3+ to maintain the structural and mechanical stability of cubic zirconia ( c-ZrO2) up to 1400 °C, through their occupancy of ZrO2 lattice sites. A gradual tetragonal to cubic zirconia ( t-ZrO2 → c-ZrO2) phase transition is also observed that is dependent on the Gd3+ and Dy3+ content in the ZrO2-SiO2. The crystallization of either ZrSiO4 or SiO2 at elevated temperatures is delayed by the enhanced thermal energy consumed by the excess inclusion of Gd3+ and Dy3+ at c-ZrO2 lattice. The addition of Gd3+ and Dy3+ leads to an increase in the density, elastic modulus, hardness, and toughness above that of unmodified ZrO2-SiO2. The multimodal imaging contrast enhancement of the Gd3+ and Dy3+ combinations were revealed through magnetic resonance imaging and computed tomography contrast imaging tests. Biocompatibility of the Gd3+ and Dy3+ dual-doped ZrO2-SiO2 systems was verified through in vitro biological studies.

Structural and bio-mineralization features of alumina zirconia composite influenced by the combined Ca2+ and PO43- additions.

The structural and bioactivity features of alumina zirconia composite (AZC) due to Ca2+ and PO43- additions are demonstrated. An in situ synthetic approach, starting from the solution precursors is devised for the powder synthesis in which the assorted range of Ca2+ and PO43- additions were done to the equimolar concentrations of Al3+ and Zr4+ precursors. The results witnessed the unique crystallization of tetragonal zirconia (t-ZrO2) at 1100 °C while Ca2+, PO43- and Al2O3 remained in their amorphous state in the system. On further heat treatment, α-Al2O3 crystallized at 1200 °C, which enforced t- → m-ZrO2 transformation while Ca2+ and PO43- still retained their amorphous state. The immersion tests in simulated body fluid (SBF) solution validated the enhanced bio-mineralization activity of AZC due to Ca2+ and PO43- additions. The results from the indentation tests demonstrated good uniformity in the elastic modulus and hardness data of the investigated specimens. Further, in vitro cell culture tests ascertained the bioactivity of all the AZC compositions.

Tuning the structural and mechanical properties in ZrO2-SiO2 binary system through Y3+ inclusions.

The present investigation explores the influence of yttrium (Y3+) inclusions in ZrO2-SiO2 binary system (YSZ) on its structural and mechanical features. The powders were synthesized through sol-gel technique and an exclusive characterization were undertaken to investigate the structural and mechanical features influenced by Y3+ additions. Characterization techniques affirmed the crucial role of Y3+ on the resultant structural and thermal stability of the YZS system. Instrumented indentation inferred the enhanced mechanical properties demonstrated by YZS system in comparison with pure ZrO2-SiO2 binary system (ZS).

Stabilization of a t-ZrO2 polymorph in a glassy SiO2 matrix at elevated temperatures accomplished by ceria additions.

Glass-ceramic composites are considered important candidates for load bearing orthopaedic applications owing to their combined salient features of bioactivity and mechanical strength. Herein, we report the impact of ceria (CeO2) additions on the structural and mechanical behaviour of ZrO2-SiO2 binary oxides as a glass-ceramic composite for hard tissue replacements. A wide range of ceria additions to the ZrO2-SiO2 system have been performed via sol-gel synthesis. The structural behaviour of the synthesized compositions is investigated at elevated temperatures using a combination of XRD, Raman spectroscopy, TEM and SEM. The stabilization of tetragonal zirconia (t-ZrO2) and CeO2 in the presence of an amorphous SiO2 matrix under heat treatment up to 1300 °C was confirmed. The t-ZrO2 phase is stabilised through Ce4+ substitution up to 20 wt% CeO2 additions, and above this CeO2 crystallization occurs in the amorphous matrix. The morphological and mechanical behaviour of the ceramic reinforced glass matrix is presented with the CeO2 stabilised system showing mechanical properties comparable with commercial biomaterial systems.