Process
Overview [1]:
Generally, the beta-TCP powder can be produced through 3 main methods, which include wet process, dry process and hydrothermal process.
Wet Process is the most common way for beta-TCP processing with the advantage of low cost. It includes 2 specific processes, soluble calcium salt and phosphate reaction process and neutralization reaction process. The final product obtained by wet process is suitable for producing a ceramic block with a porous structure. However, wet process also has a problem of non-uniform particle size.
Dry Process usually requires a high-temperature environment without water. The crystal structure of TCP powder prepared by dry process has no lattice shrinkage and good crystallinity, but the crystal composition of the powder is not uniform and there are often impurities.
Hydrothermal Process is not a common process for beta-TCP. Although the final product has an advantage of complete lattice and larger grain diameter.
Specific preparation process [1]:
1. Wet process
- Soluble Calcium Salt and Phosphate Reaction:
Raw material: Ca (NO3)2 and (NH4)2HPO4
Preparation process: (NH4)2HPO4 solution was added to Ca(NO3)2 solution under stirring condition, and aqueous ammonia was added to adjust the pH value of the solution. The ceramics powder of beta-TCP was prepared by aging, filtering, washing, drying and calcining.
Related chemical reactions are as follows:
(1)2Ca(OH)2+2H3PO4→Ca3(PO4)2+6H2O
(2)3Ca(NO3)2+2(NH4)2HPO4+2NH4OH→Ca3(PO4)2↓+6NH4NO3+6H2O
- Neutralization reaction process:
Raw material: Ca(OH)2 and H3PO4
Preparation process: H3PO4 were dropped into the suspension of Ca(OH)2 and filtered after stationary and precipitation. The precipitate is dried and calcined to obtain the powder of beta-TCP.
2. Dry process
Raw material: CaHPO4·2H2O and CaCO3 or Ca(OH)2
Preparation process: Over 900℃, the beta-TCP powder can be obtained by solid-phase reaction:
2CaHPO4·2H2O+CaCO3→Ca3(PO4)2+CO2↑+5H2O↑
3. Hydrothermal process:
Raw material: CaHPO4 or CaHPO4·2H2O
Preparation process: CaHPO4 or CaHPO4·2H2O will translate into Ca3(PO4)2 under a certain temperature and pressure. beta-TCP powder can be obtained by controlling temperature and pressure.
Reference
[1] Li Chaoyang, Yang Dean, Xu Tingxian. Preparation and application of degradable beta-tricalcium phosphate [J]. Silicate Bulletin, 2002 (03): 30-34.