Synthesis of hydroxyapatite without additives was carried out via precipitation from solution according to the procedure described in [67 ,68 (link)]. The scheme of the synthesis of hydroxyapatite and hydroxyapatite with additives is shown in Figure 11 .
To obtain the hydroxyapatite (hereafter referred to as HAp), a stoichiometrically required amount of calcium (II) nitrate was dissolved in a specific volume of calcium nitrate solution according to out calculations. The stoichiometric Ca/P elemental ratio should be 1.67, which corresponds to the element ratio in biogenic hydroxyapatite [69 ]. Next, under intensive stirring, an ammonium hydrogen phosphate solution was added, and the pH of the reagents was then adjusted to 10 using a concentrated ammonia solution (ρ = 0.903 g/mL). The solution was stirred using a magnetic stirrer for 2 h while monitoring the pH and temperature; then, the solution was left to stand for 44 h. The equation of the reaction is shown in (3):
Then, the precipitate was filtered using a Buchner funnel, washed with hot distilled water on the filter, and dried at 100 °C for 2 h and at 250 °C for 1 h. HAp was selected for analysis during the drying stage at 100 °C. After drying, the obtained sample was annealed in a muffle furnace at 900 °C for 2 h. A modified synthesis method was also used to obtain CPs. PVP polymer was added to vary the phase composition of the material.
To obtain the hydroxyapatite (hereafter referred to as HAp), a stoichiometrically required amount of calcium (II) nitrate was dissolved in a specific volume of calcium nitrate solution according to out calculations. The stoichiometric Ca/P elemental ratio should be 1.67, which corresponds to the element ratio in biogenic hydroxyapatite [69 ]. Next, under intensive stirring, an ammonium hydrogen phosphate solution was added, and the pH of the reagents was then adjusted to 10 using a concentrated ammonia solution (ρ = 0.903 g/mL). The solution was stirred using a magnetic stirrer for 2 h while monitoring the pH and temperature; then, the solution was left to stand for 44 h. The equation of the reaction is shown in (3):
Then, the precipitate was filtered using a Buchner funnel, washed with hot distilled water on the filter, and dried at 100 °C for 2 h and at 250 °C for 1 h. HAp was selected for analysis during the drying stage at 100 °C. After drying, the obtained sample was annealed in a muffle furnace at 900 °C for 2 h. A modified synthesis method was also used to obtain CPs. PVP polymer was added to vary the phase composition of the material.
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