Wear Resistance Mechanism of Alumina Ceramics Containing Gd₂O₃

pH-Responsive Drug Delivery and Imaging Study of Hybrid Mesoporous Silica Nanoparticles

A system of pH-responsive and imaging nanocarriers was developed using mesoporous silica nanoparticles (MSNs), in which gadolinium (Gd) was doped through in situ doping (Gd₂O₃@MSN). Sodium alginate (SA) was attached to the surfaces of the amino groups of MSNs (NH₂-Gd₂O₃@MSN) through the electrostatic adsorption between the amino groups and the carboxyl groups with the formation of hybrid SA-Gd₂O₃@MSN nanoparticles (NPs). The SA-coated NPs were spherical or near-spherical in shape with an average size of nearly 83.2 ± 8.7 nm. The in vitro drug release experiments of a model rhodamine B (RhB) cargo were performed at different pH values. The result confirmed the pH-responsiveness of the nanocarriers. The results of the cytotoxicity studies indicated that the SA-Gd₂O₃@MSN NPs were not cytotoxic by themselves. The results of the in vivo safety evaluation and the hemolysis assay confirmed that the system is highly biocompatible. It is noteworthy that the T1 contrast of the system was significantly enhanced by the Gd, as indicated by the result of the MR imaging. This study confirms that the synthesized hybrid nanosystem is promising for pH-responsive drug delivery and MR imaging for cancer diagnosis and treatment.

The Effect of TiC Additive on Mechanical and Electrical Properties of Al2O3 Ceramic

In this study the influence of TiC content on the mechanical and electrical properties of Al2O3-TiC composites containing 30 and 40 vol.% TiC were investigated. The Vickers hardness and fracture toughness of the composites increased with the addition of TiC phase. The composite with 40 vol.% TiC showed the highest flexural strength (687 ± 39 MPa), fracture toughness (7.8 ± 0.4 MPa·m1/2) and hardness (22.3 ± 0.3 GPa) with a homogeneous distribution of the second phase within the ceramic matrix. Besides enhanced mechanical properties, it was found that ceramic composites with more than 30 vol.% TiC fabricated by the spark plasma sintering possess sufficient electrical conductivity for electrical discharge machining as well. Therefore, they do not limit the flexibility of the shape, and any intricate parts can be easily made with these composites which can be recommended for the production of cutting inserts in the tools for machining of superhard hardened steels, hard-to-machine materials, composites and other materials used in mechanical engineering.