Место издания:AKCongress Akadémiai Kiadó, Budapest, Венгрия
Первая страница:74
Последняя страница:75
Аннотация:The topical issues of modern biomaterials science include the manufacture of nanosized bioceramics
for bone tissue replacement. The latest developments are related to regenerative
approach, which requires the investigation of calcium phosphate based materials with Ca/P
ratio < 1.5. The usage of non-aqueous media is a promising way to eliminate water influence,
avoid the impurities and gain strong control over the material. Another advantage of
non-aqueous media is the ability to explore low-temperature synthesis and thus to liquidate
calcination stage.
The key objects of the research were tricalcium orthophosphate (Ca3(PO4)2, TCP) and
several condensed calcium phosphates (e.g. Ca2P2O7, CPP). The main requirement was the
usage of liquids with high boiling point and fusible salts.
Ethylene glycol was chosen due to its solvent abilities and the fact that the only coproduct
of the reaction should be the solvent itself. The precursors, such as calcium glycolate, crystal
orthophosphoric acid, ammonium pyrophosphate were obtained previously. TCP was obtained
by adding orthophosphoric acid or commercial ammonium hydrophosphate solutions
in ethylene glycol to calcium glycolate solution. CPP was obtained in ethylene glycol using
the same technique: ammonium pyrophosphate solution was added to calcium glycolate solution.
The syntheses were carried out in the range from 30 to 150 °C.
The usage of ionic liquids is the key idea of the second approach. Temperature range
from 150 to 350 °C was chosen for the calcium phosphates synthesis according to the
KNO3-NaNO3 phase diagram. Calcium phosphates were obtained by mixing Ca(NO3)2-
NaNO3-KNO3 melt with suspension of corresponding sodium phosphate in molten KNO3-
NaNO3. By-products were washed out with alcohol.
The main aspects of the samples sintering, as well as the microstructure and qualities,
were analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission
electron microscopy (TEM) and dynamic light scattering (DLS).
We have developed a unique method of microcrystalline calcium ortho- and pyrophosphate
powder synthesis in non-aqueous media. Also we have investigated low-temperature
range for calcium phosphate synthesis.
Development of the novel phosphate synthesis method makes possible obtainment of pure
calcium phosphate phases without impurities of hydrophosphates. XRD data have confirmed
the obtainment of pure crystalline TCP and CPP phases. DLS, SEM and TEM have demonstrated
that phosphate particle size from 100 to 200 nm can be obtained.
