Investigating the mechanical behavior of hydroxyapatite-reduced graphene oxide nanocomposite under different loading rates

Photocatalytic and photo-electrochemical ammonia synthesis over dimensional oriented cobalt titanate/nitrogen-doped reduced graphene oxide junction interface catalyst

Nitrogen reduction to ammonia is vital for chemical industries and renewable clean energy. Denying the harsh reaction conditions adopted in the Haber-Bosch process and stimulation research for ammonia production through sustainable technologies is a smart approach. Hitherto, photocatalyst acquiring the potential to attain high nitrogen reduction reaction (NRR) efficiency is a challenging task. Here, this study demonstrated cobalt titanate (CoTiO₃) rods (p-type) straddled with two-dimensional (2D) sheets of nitrogen-doped reduced graphene oxide (N-rGO, n-type) via, reflux method; realizing the advantages of dissimilar dimensionalities and strong interfacial junction coupling for efficient NRR under visible light irradiation. The successful interface junction establishment between CoTiO₃ and N-rGO has been witnessed from Raman, x-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. Moreover, a well-defined type-II band structure is capable to curl the charge anti-recombination process; reflected in upgraded photo-catalytic/electrocatalytic upshots. The CoTiO₃ modified with an optimized concentration of N-rGO exhibits high stability with an improved photocatalytic (1722.22 μmolL^-1h^-1) and photo-electrocatalytic (16.8 µg cm^-1h^-1) nitrogen reduction to ammonia production; multiple times higher than counterparts. This improved photo-activity of CoTiO₃/N-rGO junction hybrid stems from the built-in electric field existing across the dissimilar junction interface, triggering charge transfer channels for reduction reaction in mild reaction conditions. The result of these materials might strategies the way for future development of new functionalities bearing highly active catalyst materials for sustainable energy-related conversion.

Improved Mechanical Properties of Ultra-High Shear Force Mixed Reduced Graphene Oxide/Hydroxyapatite Nanocomposite Produced Using Spark Plasma Sintering

The addition of nanomaterials, such as graphene and graphene oxide, can improve the mechanical properties of hydroxyapatite (HA) nanocomposites (NCPs). However, both the dispersive state of the starting materials and the sintering process play central roles in improving the mechanical properties of the final HA NCPs. Herein, we studied the mechanical properties of a reduced graphene oxide (r-GO)/HA NCP, for which an ultra-high shear force was used to achieve a nano-sized mixture through the dispersion of r-GO. A low-temperature, short-duration spark plasma sintering (SPS) process was used to realize high-density, non-decomposing r-GO/HA NCPs with an improved fracture toughness of 97.8% via the addition of 0.5 wt.% r-GO. Greater quantities of r-GO improve the hardness and the fracture strength. The improved mechanical properties of r-GO/HA NCPs suggest their future applicability in biomedical engineering, including use as sintered bodies in dentistry, plasma spray-coatings for metal surfaces, and materials for 3D printing in orthopedics.

Comparison of the effect of argon, hydrogen, and nitrogen gases on the reduced graphene oxide-hydroxyapatite nanocomposites characteristics

In this study, the effect of the argon, nitrogen, and hydrogen gases on the final properties of the reduced graphene oxide- hydroxyapatite nanocomposites synthesized by gas injected hydrothermal method was investigated. Four samples were synthesized, which in the first sample the pressure was controlled by volume change at a constant concentration. In subsequent samples, the pressure inside the autoclave was adjusted by the injecting gases. The initial pressure of the injected gases was 10 bar and the final pressure considered was 25 bar. The synthesized powders were consolidated at 950 °C and 2 MPa by spark plasma sintering method. The final samples were subjected to Vickers indentation analysis. The findings of this study indicate that the injection of argon, hydrogen, and nitrogen gases improved the mechanical properties of the nanocomposites. Injection of gases increased the crystallinity and particle size of hydroxyapatite, and this increase was greater for nitrogen gas than for others. Injection of these gases increased the rate of graphene oxide reduction and in this case the effect of nitrogen gas was greater than the others.