Synthesis of Submicron Са3–хNa2х(PO4)2 Substituted Calcium Phosphate Powders in a Nonaqueous Medium for Stereolithographic Fabrication of Bioceramics

• Published in: Inorganic materials Vol. 57; no. 9; pp. 958 - 966
• Main Authors: Larionov, D. S., Evdokimov, P. V., Garshev, A. V., Kozlov, D. A., Putlyaev, V. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-09-2021; Springer Nature B.V
• Subjects: Bioceramics; Biomedical materials; Calcium phosphates; Chemical precipitation; Chemistry; Chemistry and Materials Science; Citric acid; Ethylene glycol; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Materials Science; Particle size; Phase composition; Sinterability; Sodium; Sodium phosphate; Sol-gel processes; Solid solutions; Solvolysis; Substitutes; Synthesis; Three dimensional printing; nonaqueous solvents; bioceramics; precipitation; calcium sodium phosphates; tricalcium phosphate; rhenanite; ethylene glycol; sol–gel synthesis; 3D printing
• ISSN: 0020-1685; 1608-3172
• DOI: 10.1134/S0020168521090107

—
This paper compares the synthesis of tricalcium phosphate (TCP) (β-Са
3
(РО
4
)
2
) and Са
3–
х
Na
2
х
(PO
4
)
2
substituted calcium phosphates (
x
= 0.5 and 1: solid solution
A
and β-CaNaPO
4
sodium rhenanite, respectively) via precipitation and by a sol–gel process in ethylene glycol (EG). We have determined the phase composition of the synthesized phosphate powders and studied their micromorphology. Slow addition of ammonium (di)hydrogen phosphate to calcium ethylene glycolate at temperatures above 110°C leads to precipitation of crystalline β-TCP (with an average particle size under 200 nm) from the solution. In the synthesis of sodium calcium substituted phosphates, solvolysis of the sodium phosphates prevents congruent precipitation and requires correction of solution composition. The powder precipitated from a solution of sodium ethylate and calcium ethylene glycolate in EG (molar ratio above 2) crystallizes at 800°C in the rhenanite structure (particle size under 500 nm). In sol–gel synthesis, triethyl phosphate (TEP) was used as a phosphate component. For gelation, we used TEP solvolysis in EG and the formation of ester polymers as a result of reaction between citric acid and EG (Pechini process). The gel thermolysis products obtained between 600 and 800°C contained considerable amounts of residual carbon. The particle size characteristics and sinterability of the calcium phosphate powders precipitated from solutions in EG allow them to be used for filling photosuspensions that are employed in the fabrication of osteoconductive bioceramics with the use of stereolithographic 3D printing.