Jiayu He

Silicon nitride is a type of bioceramic with great application potential. However, the brittleness of silicon nitride can be addressed through toughening. In this study, various proportions of TiC were incorporated into the sintering additive system to explore the effects of different amounts of TiC on the mechanical properties, cell compatibility, and antibacterial properties of silicon nitride. Silicon nitride was prepared by gas pressure sintering, with TiC addition amounts of 3%, 5%, 8%, and 13% wt. Among the four types of silicon nitride, the mechanical properties of silicon nitride with 3% and 5% wt TiC addition were improved, with the flexural strength and fracture toughness of the former being 571 MPa and 8.35 MPa·m^1/2, respectively, and the flexural strength and fracture toughness of the latter being 532 MPa and 8.53 MPa·m^1/2, respectively. The surface of all four types of silicon nitride was enriched with Ti as the amount of TiC added increased, and the surface properties of the four silicon nitrides were the same. All four types of silicon nitride could continuously release Si ions in liquid. In vitro cell experiments showed that all four types of silicon nitride could enable normal cell proliferation and adhesion. Silicon nitride with different TiC addition amounts all exhibited good cell compatibility. Compared with the control material, each of the four types of silicon nitride demonstrated robust antibacterial efficacy against Staphylococcus aureus and Escherichia coli, with comparable potency across all types. These findings indicate that the incorporation of titanium carbide (TiC) within the silicon nitride matrix, particularly within the 3–5% weight ratio range, not only enhances mechanical integrity and cellular compatibility, but also confers notable antibacterial attributes. Consequently, these results demonstrate the promising viability of TiC-modified silicon nitride as a prospective material for the fabrication of bone implants.

Nowadays, research on promoting the dissolution of chalcopyrite is important. As a natural symbiotic mineral of chalcopyrite, arsenopyrite will have an impact on the dissolution of chalcopyrite. This paper shows the influence of arsenopyrite on the dissolution of chalcopyrite in an acidic culture medium. The leaching results showed that adding arsenopyrite increased the leaching concentration of copper by 332 mg/L. The residues showed a decrease in sulfur through X-ray diffraction analysis (XRD) and an increase in dissolution degree through scanning electron microscope (SEM). Electrochemical experiments have shown that the rest potential of arsenopyrite is higher than that of chalcopyrite, so there is a galvanic interaction, and the impact on chalcopyrite is greater than that of arsenopyrite. The polarization curve also proves this. Under the interaction of galvanic couples, the reduction of S⁰ production and the enhancement of Cu²⁺ release can promote the dissolution of chalcopyrite. In addition, X-ray photoelectron spectrometer (XPS) analysis under the action of galvanic coupling indicates that more SO₄²⁻ is generated on the surface of chalcopyrite, replacing S_n²⁻/S⁰, and SEM shows a stronger corrosion morphology. All results confirm that the electrochemical effect between arsenopyrite and chalcopyrite promotes the dissolution of chalcopyrite in the acidic culture medium.

Silicon nitride is a bioceramic with great potential, and multiple studies have demonstrated its biocompatibility and antibacterial properties. In this study, silicon nitride was prepared by a microwave sintering technique that was different from common production methods. SEM and pore distribution analysis revealed the microstructure of microwave-sintered silicon nitride with obvious pores. Mechanical performance analysis shows that microwave sintering can improve the mechanical properties of silicon nitride. The CCK-8 method was used to demonstrate that microwave-sintered silicon nitride has no cytotoxicity and good cytocompatibility. From SEM and CLSM observations, it was observed that there was good adhesion and cross-linking of cells during microwave-sintered silicon nitride, and the morphology of the cytoskeleton was good. Microwave-sintered silicon nitride has been proven to be non-cytotoxic. In addition, the antibacterial ability of microwave-sintered silicon nitride against Staphylococcus aureus and Escherichia coli was tested, proving that it has a good antibacterial ability similar to the silicon nitride prepared by commonly used processes. Compared with silicon nitride prepared by gas pressure sintering technology, microwave-sintered silicon nitride has excellent performance in mechanical properties, cell compatibility, and antibacterial properties. This indicates its enormous potential as a substitute material for manufacturing bone implants.