No abstract

Apatitic calcium phosphates powders with Ca/P molar ratio of 1.5 to 1.8 were synthesized at 25°C using the neutralization method. These powders, differing by stoichiometry and particle morphology, were compacted in similar conditions. For a similar morphology of particles, compacts of the non-stoichiometric powders have better cohesion than those of the stoichiometric hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2 : Ca/P = 1.67). The lacunar structure, with deficiency of calcium (Ca 10 − x (HPO 4) x (PO 4) 6 − x (OH) 2 − x : 1.5 b Ca/P b 1.67), seems to favour the densification process and cohesion between particles during the compaction. The better tensile strength (0.79 MPa) was obtained for the powder with the lowest atomic ratio (Ca/P = 1.5, x = 1). The apatite powder (Ca/P = 1.78), which has a smooth and porous structure, presented the best transmission load ratio (95.5%), the lowest die-wall friction (μ = 0.1) and the highest strength (3.12 MPa). These results show the importance of chemical composition and morphological properties of synthesized particles in the development of better hydroxyapatite powders for the compaction process.

In this work, we characterize tricalcium phosphate powders Ca9(HPO4)(PO4)5(OH) resulting from a reaction between calcium hydroxide and orthophosphoric acid at room temperature, without pH adjustment and in absence of ionic impurities. The prepared powder has an atomic ratio Ca/P of 1.512 ± 0.005. The real density is 2.68 ± 0.02 g/cm3 and the specific surface area is 80 ± 02 m2 /g. During compression, the microstructure of Cadeficient apatite powder with the presence of HPO4 groups seems to support the cohesion between particles. The transmission ratio is 90%, the transfer ratio is 41.8 and the ratio of the die-wall friction is 0.22. These results show that apatitic tricalcium powder gives a good aptitude to the compaction which leads to a good tensile strength (0.79 MPa). The heat treatment of the prepared powder shows the precise temperature for the formation of pyrophosphate, β-TCP and α-TCPa phases. The purity and aptitude to compaction of the prepared powders are very promising for pharmaceutical and medical applications.

No abstract

Abstract:The aim of this work is to study the effect of trace ions as Mg showed that the dissolution of calcium ions is more important in the presence of ions trace while the phosphor ions were not affected. The dissolution and dissolution-reprecipitation observed of various ions trace can modify the surface properties of calcium phosphate bioceramics and therefore the properties of biological products, such as resorbtion and reactivity can be affected.