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This work deals with oxygenated apatite synthesis from calcium chloride and phosphoric acid using a wet precipitation method. An experimental design is applied to precise the influence of the synthesis parameters (pH of the reaction medium, atomic ratio Ca/P of the reagents, concentration of the calcium solution (Ca2+), temperature of the reaction medium (T), and duration of the reaction (D)) on the chemical composition (Ca/P molar ratio, % O2, and % O 2 2 − ). An empirical model was developed and validated by applying the ANOVA analysis incorporating the interaction effects of all parameters and optimized using the response surface methodology. A reproducible synthesis of more oxygenated apatite with speed of dissolution adaptable to that of the osseous neoformation and allowing a progressive diffusion of oxygenated species (Ca/P = 1.575) is attained. [ABSTRACT FROM AUTHOR]

Geopolymers are considered as an alternative solution of portland cement. The setting of these materials depends on the gelling reaction of sodium silicate, which can lead to the formation of three types of gels; irreversible gel that has interest and no interest gels (reversible and a non-gelling solution). Obtaining an irreversible gel depends on several parameters. In order to control the influence of these parameters on the development of irreversible gel, a central composite design with 23 experiments is employed to improve the irreversibility (Irr) and the variation of the gelling time according to the following parameters (concentration of sodium silicate, concentration of hydrochloric acid and the volume of hydrochloric acid added), while considering their square and rectangular interactions. Optimization of the model by reports to the factors shows that in order to obtain an irreversible gel, the optimal gelling time should be between 10 and 45 min with an acid concentration varying between 1.20 and 1.40 mol/L and a concentration of sodium silicate between 1.70 and 1.80 mol/L with addition of 12.5 mL of hydrochloric acid to the alkaline solution. [ABSTRACT FROM AUTHOR]