Calcium phosphates (CaPs) are major chemical constituents of mammalian bone.
Their osteoconductivity in vitro and in vivo has encouraged their use in
biomaterial applications such as implant materials and drug delivery. High
aspect ratio nanoparticles are attractive for many biomedical applications;
however, precise control of the phase and morphology is challenging. The impact
of fuel-to-oxidant ratio, pH, and cation chemistry on morphology and phase was
studied for CaP-based compositions by microwave-assisted solution combustion
synthesis (MASCS) in a urea–nitrate (fuel–oxidant) system.
An initial calcium to phosphate ratio of 1.5 was used. Highly crystalline
hydroxyapatite (HA) and biphasic CaP nanoparticle compositions were produced as
confirmed by x-ray diffraction, scanning electron microscopy, and transmission
electron microscopy. MASCS was capable of synthesizing high aspect ratio
(∼5 to 20) single and biphasic CaP nanoparticles with diameters
ranging from 250 to 500 nm and lengths between 2 and 10 μm.