Pore size influence in fabricating DCPD-Coated Porous β-TCP granules: compositional, morphological, and functional group perspective

This study aims to understand the influence of pore size on the compositional, morphological, and functional group characteristics of dicalcium phosphate dihydrate (DCPD)-coated porous β-tricalcium phosphate (β-TCP) granules. This study produced 300–600 μm granular sizes of porous β-TCP granules with various pore diameters. This was achieved by combining dry powders of DCPD and calcium carbonate (CaCO₃) [Ca/P ratio: 1.5] with varied quantities of 10%, 20%, 30%, and 40% of sodium chloride (NaCl) powders to obtain mixtures composed of weight percentages (wt%) ratios of 90:10, 80:20, 70:30, and 60:40, respectively. Post-sintering, the porous β-TCP granules fabricated were soaked in an acidic calcium phosphate solution for 30 min to coat the surfaces with DCPD crystals formation via a dissolution-precipitation reaction. Subsequently, the specimens were examined with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR). The morphological observations demonstrated that increasing NaCl powder up to 40% with a mixture of CaCO₃ and DCPD enhanced the β-TCP granules' pore size. Furthermore, The formation of DCPD on and inside the porous β-TCP granules has been accelerated due to the presence of large pores. Conversely, dissolution-precipitation reactions were incomplete on granules with 2.8, 4.9, and 6.91 μm pore sizes. The major XRD peaks of the DCPD and β-TCP phases with 2.8, 4.9, and 6.91 μm pores were also slightly shifted to the right, while granules with 7.53 μm pores demonstrated DCPD and β-TCP peaks aligned with pure β-TCP and DCPD phases. This study's findings are expected to offer insight into the role of pore size in influencing the dissolution-precipitation process that affects the morphological, compositional, and functional group characteristics of DCPD-coated β-TCP granules.