A thermodynamic approach to surface modification of calcium phosphate implants by phosphate evaporation and condensation. Issue 15 (December 2020)

• Record Type: Journal Article
• Authors: Döbelin, Nicola; Maazouz, Yassine; Heuberger, Roman; Bohner, Marc; Armstrong, Ashley A.; Wagoner Johnson, Amy J.; Wanner, Christoph
• Is Part Of: Journal of the European Ceramic Society. Volume 40:Issue 15(2020)
• Page Start: 6095
• Page End: 6106
• Publication Date: 2020-12
• Subjects: Calcium phosphate -- Evaporation -- Surface modification -- Bioceramics; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2020.07.028
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: It has been reported in the literature that thermal treatment of calcium phosphate ceramics chemically alters the surface composition by phosphate evaporation. To predict the compositional changes, we have developed a thermodynamic model for the evaporation of phosphorous species from CPP, TCP, HA, and TetCP. In an open atmosphere, the model predicts the formation of a surface layer consisting of a sequence of increasingly phosphate-depleted phases. In a closed system, the atmosphere reaches equilibrium with a single-phase surface layer. To verify our model, we performed a series of experiments which confirmed the predicted formation of phosphate-depleted surface layers. These experiments further demonstrated that controlled supersaturation of the atmosphere led to formation of a phosphate-enriched surface layer as a result of phosphate condensation. In conclusion, our thermodynamic model is capable of predicting the surface modification by phosphate evaporation and condensation of calcium phosphate phases during high-temperature processing in different environments.