Method for producing particles, particles, and sintered body
View Patent ↗Disclosed herein are a particle production method whereby spherical fine particles of a crystalline calcium phosphate-based compound can be efficiently produced at low cost, fine particles (especially, spherical particles) with good flowability produced by the particle production method, and a high-quality sintered body obtained by sintering a molded body of the particles. The particle production method comprises a first step of mixing a first substance containing phosphorus and a second substance containing calcium so that the phosphorus and the calcium are present in a predetermined mole ratio and feeding, into a heated atmosphere, droplets of a slurry containing an amorphous reaction product, obtained by the reaction between the first substance and the second substance, to bring the reaction product into a gaseous state; and a second step of crystallizing the reaction product in the gaseous state to obtain particles mainly composed of a calcium phosphate-based compound containing phosphorus and calcium in the predetermined mole ratio. The heated atmosphere preferably contains plasma produced by ionization of an ambient gas.
1. A method for producing particles, comprising:
mixing a first substance containing at least either one phosphorus oxide selected from the group consisting of phosphorus suboxide, diphosphorus trioxide, diphosphorus tetroxide, and diphosphorus pentoxide, or triethyl phosphate and a second substance containing calcium in a solvent to react the first substance with the second substance to thereby obtain a slurry in a gelled liquid state;
feeding droplets of the slurry containing an amorphous reaction product obtained from a reaction between the first substance and the second substance in a heated atmosphere to bring the amorphous reaction product into a gaseous state; and
crystallizing the amorphous reaction product in the gaseous state to obtain particles mainly composed of a calcium phosphate-based compound.
2. The method for producing particles as claimed in claim 1 , wherein the second substance contains as a main ingredient, at least either calcium alkoxide or calcium salt.
3. The method for producing particles as claimed in claim 1 , wherein the amount of impurities contained in the calcium phosphate-based compound is 5 wt % or less.
4. The method for producing particles as claimed in claim 3 , wherein the impurities mainly contain at least either a by-product other than the reaction product or a decomposition product of the calcium phosphate-based compound.
5. The method for producing particles as claimed in claim 1 , wherein the heated atmosphere contains plasma produced by ionization of an ambient gas.
6. The method for producing particles as claimed in claim 5 , wherein the temperature of the plasma is in the range of 2,000 to 15,000° C.
7. The method for producing particles as claimed in claim 1 , wherein the crystallizing step further comprises the step of forcibly cooling the reaction product in the gaseous state.
8. The method for producing particles as claimed in claim 1 , wherein the particles are substantially spherical in shape.
9. The method for producing particles as claimed in claim 8 , wherein the average particle diameter of the spherical particles is in the range of 5 to 300 nm.
10. The method for producing particles as claimed in claim 1 , wherein the calcium phosphate-based compound is hydroxyapatite or tricalcium phosphate.
11. Particles produced by the method for producing particles as claimed in claim 1 .
12. The particles as claimed in claim 11 , which contain hollow particles in the proportion of 5 to 40%.
13. A sintered body obtained by sintering a molded body of the particles as claimed in claim 11 .
14. The method according to claim 1 , wherein the second substance contains calcium nitrate tetrahydrate.
15. The method according to claim 1 , wherein the solvent contains at least one alcohol selected from the group consisting of methanol, ethanol, propanol, and butanol.