The surface microstructures of calcium phosphate ceramics play an essential role in determining bone regeneration. However, it is difficult to produce micro/nano-structures on the surface of the porous hydroxyapatite (HA) scaffolds. In this study, we successfully developed and fabricated various micro/nano-structured surfaces on the HA scaffolds in copper ion (Cu2+)-containing solutions under hydrothermal conditions. The micro/nano-structures on the surface of the HA scaffolds were controlled by modulating the Cu2+ concentrations during the hydrothermal process. With an increase in the Cu2+ concentration, the surface morphology of the HA scaffolds changed significantly from sphere-like to flower-like, before becoming nano-structures. These findings indicated that the Cu2+ concentration affects the morphologies of calcium phosphate coatings that grow on the HA scaffolds. In vitro endothelial cell (EC) cultures showed that the cell proliferation was significantly enhanced when cultured on the flower-like morphology compared with other morphologies. Furthermore, an in vivo test in New Zealand rabbits demonstrated that the HA scaffold with the flower-like surface resulted in more angiogenesis compared with the control scaffold. This copper-assisted hydrothermal deposition process provides a simple and controllable route for engineering a micro/nano-structured surface on the HA scaffolds, which has benefits in terms of angiogenesis and bone regeneration.

This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties.

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