Pore size influence in fabricating DCPD-Coated Porous -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 beta-tricalcium phosphate (beta-TCP) granules. This study produced 300-600 mu m granular sizes of porous beta-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 beta-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 beta-TCP granules' pore size. Furthermore, The formation of DCPD on and inside the porous beta-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 mu m pore sizes. The major XRD peaks of the DCPD and beta-TCP phases with 2.8, 4.9, and 6.91 mu m pores were also slightly shifted to the right, while granules with 7.53 mu m pores demonstrated DCPD and beta-TCP peaks aligned with pure beta-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 beta-TCP granules.