Abstract
In orthopedic surgery, infection after implantation is a serious complication. Silver (Ag) exhibits antibacterial activity and a broad antibacterial spectrum and is considered to exhibit low toxicity in the human body. In our previous work, we developed an Ag-containing hydroxyapatite (Ag–HA) coating process in which the coatings were applied to substrates using a thermal spraying system and subsequently evaluated the antibacterial properties of the coatings. In this study, we investigated the structure of Ag–HA coatings, especially the microstructure of Ag. Hydroxyapatite powder containing silver oxide (Ag2O) was used as a thermal spraying powder. The coatings were applied onto pure titanium disks by the thermal spraying method, followed by a vacuum heat treatment to crystallize the hydroxyapatite phase of the coatings. X-ray diffraction (XRD) patterns indicated that the Ag–HA coatings consisted primarily of hydroxyapatite and a small amount of Ag metal and that the amount of Ag metal increased with increasing amount of Ag2O in the thermal spraying powder. XANES spectra of the coatings were compared with the spectrum of Ag metal as a reference material, and the peaks associated with the Ag–HA coatings were similar to those of Ag metal; however, the edge peaks shifted to the low-energy side. These results suggested that the Ag in the Ag–HA coatings existed primarily as Ag metal.
