title: Micro-Raman spectroscopy shows how the coating process affects the characteristics of hydroxylapatite.
abstract: The diversity in the structural and chemical state of apatites allows implant manufacturers to fine-tune implant properties. This requires suitable manufacturing processes and characterization tools to adjust the amorphous phase and hydroxyl content from the source hydroxylapatite. Hydroxylapatite was processed by high-velocity oxy-fuel spraying, plasma spraying and flame spraying, and primarily analyzed by Raman spectroscopy. Investigation of rounded splats, the building blocks of thermal spray coatings, allowed correlation between the visual identity of the splat surface and the Raman spectra. Splats were heat-treated to crystallize any remaining amorphous phase. The ν1 PO4 stretching peak at 950-970 cm(-1) displayed the crystalline order, but the hydroxyl peak at 3572 cm(-1) followed the degree of dehydroxylation. Hydroxyl loss was greatest for flame-sprayed particles, which create the longest residence time for the melted particle. Higher-frequency hydroxyl peaks in flame- and plasma-sprayed splats indicated a lower structural order for the recrystallized hydroxylapatite within the splats. Crystallization at 700 °C has shown potential for revealing hydroxyl ions previously trapped in amorphous calcium phosphate. This work compares Fourier transform infrared and Raman spectroscopy to measure the hydroxyl content in rapidly solidified apatites and shows that Raman spectroscopy is more suitable.
authors: New Technologies Research Centre, Amirkabir University of Technology, PO Box 1591633311, Tehran, Iran. Electronic address: saeedss@aut.ac.ir.
authors: Saeed
authors: S
authors: Saber-Samandari
authors: Kadhim
authors: K
authors: Alamara
authors: Samaneh
authors: S
authors: Saber-Samandari
authors: Karlis A
authors: KA
authors: Gross
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D010710:Phosphates / Q000032:analysis; D058626:Plasma Gases / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D020099:Coated Materials, Biocompatible; D010710:Phosphates; D058626:Plasma Gases; D017886:Durapatite
keywords: Biomedical implants; Calcium phosphate; Hydroxylapatite; Hydroxylation; Raman spectroscopy; Thermal spraying