Ferro, Alberto C.Seixas, TomásGuedes, Mafalda2025-08-182025-08-182024-01-01Ferro, A. C., Seixas, T., & Guedes, M. (2024). Reaction path in the mechanosynthesis of calcium phosphates using a biogenic calcium source. Ceramics International, 50(1), Part: A, 282-292. https://doi.org/10.1016/j.ceramint.2023.10.1020272-8842http://hdl.handle.net/10400.21/22014Calcium phosphates were produced by mechanosynthesis, using eggshell, H3PO4 and 6-83 wt%-H2O. Mixtures were milled at 600 rpm during 0.5-12 h. Resulting calcium phosphates occur within specific milling domains; H2O concentration determines onset and stability of monophasic hydroxyapatite. Within the tested conditions, brushite is the first detected calcium phosphate precipitated from solution. In 6, 40 and 56 wt%-H2O, monetite intermediates brushite's transformation to hydroxyapatite; in 71 and 83 wt%-H2O transformation is direct. Hydroxyapatite formation is favoured at the H2O extremes tested, 6 and 83 wt%. CO2 build-up in the confined jar and nucleation-and-growth events during drying are possible obstacles upon control of morphology and composition of synthesised particles. The potential of chicken eggshell as direct biogenic source and the ability of high-energy milling as corresponding processing route to produce calcium phosphates was demonstrated. This signals a route for reliable production of brushite, monetite and hydroxyapatite. A preliminary milling map was built, allowing to obtain desired final product under specific milling conditions.engHigh energy millingBiogenic raw-materialsCalcium phosphates mechanosynthesisPowder characterizationBiomedical applicationsresearch articlehttps://doi.org/10.1016/j.ceramint.2023.10.1021873-3956