## 3 Results and Discussion
In the case of PR1/24h, which comprises CDHA in conjunction with the Mg-WH phase, the increased intensity of the 1065 cm\({}^{-1}\) band can be attributed to the absence of a notable contribution from CDHA, given that this phase does not exhibit a pronounced absorption at this wavenumber [26]. In contrast, the 1065 cm\({}^{-1}\) band is prominent in the PR2/24h sample and barely noticeable in the PR3/24h sample, where it corresponds to the P-O stretching vibration characteristic of the DCPA phase, resulting in a smaller intensity for this absorption band [27]. Furthermore, the PR1/24h and PR2/24h samples display a relatively  
Figure 4: FTIR spectra of R1–R3 (**a**), PR1/24h–PR3/24h (**b**), and PR1/48h–PR3/48h (**c**) granules synthesized via a dissolution–precipitation reaction. broad absorption band with a maximum at 863 cm\({}^{-1}\), which is attributed to the stretching vibration of the P-O(H) bond. The broadness of this band indicates the coexistence of two distinct crystallographic environments for hydrogen phosphate ions, which are likely the result of the presence of two different calcium phosphate phases in the samples. At lower wavenumbers, the absorption bands at 601 cm\({}^{-1}\), 545 cm\({}^{-1}\), and 465 cm\({}^{-1}\) are primarily associated with the Mg-WH phase and correspond to the bending modes of P-O and O-P-O bonds [5]. In the case of the PR1/24h sample, the peak at 545 cm\({}^{-1}\) displays a slight degree of broadening due to the presence of CDHA, which exhibits an absorption band in the vicinity of 560 cm\({}^{-1}\). The FTIR spectra of PR1/48h-PR3/48h granules (Figure 4c) display a series of absorption bands at 1180 cm\({}^{-1}\), 1065 cm\({}^{-1}\), 1011 cm\({}^{-1}\), 954 cm\({}^{-1}\), 865 cm\({}^{-1}\), and within the 600-460 cm\({}^{-1}\) range. These bands are ascribed to the P-O and P-O(H) stretching and deformation vibrations of the PO\({}_{4}\)\({}^{3-}\) and HPO\({}_{4}\)\({}^{2-}\) groups, which are distinctive of the crystal structure of the Mg-WH phase. Figures 5-7 present the SEM micrographs of the synthesized R1-R3 raw granules, the PR1/24h-PR3/24h granules, and the PR1/48h-PR3/48h granules, respectively. An inspection of the surface of approximately 200-400 \(\upmu\)m rough-edged raw granules (see Figure 5a,d,g; surface views in Figure 5b,e,h) discloses the presence of rod-like crystals, which are indicative of calcium sulfate dihydrate. These crystals are accompanied by randomly oriented plate-shaped crystals, as observed in the higher-magnification images (see Figure 5c,f,i). The surface morphology of the irregularly shaped PR1/24h to PR3/24h granules (Figure 6a,d,g; surface views in Figure 6b,e,h) shows notable variation, influenced by both the type of raw granules used and possible differences in local reaction environments during synthesis. Figure 5: SEM images of raw granules R1 (**a–c**), R2 (**d–f**), and R3 (**g–i**). A thorough inspection of the surface of the PR1/48h-PR3/48h granules (see Figure 7a,d,g; surface views in Figure 7b,e,h) of 200-450 \(\upmu\)m granules reveals that they are composed of interlocked spherical and rod-like particles, which are composed of fine crystals. The higher magnification SEM micrograph provides a detailed analysis of the granules, revealing their composition as a stack of characteristic Mg-WH rhombohedral crystals (see Figure 7c,f) with an average size of approximately 150-200 nm [5]. As illustrated in Figure 7i, the PR3/48h specimen displays a well-developed porous microstructure, which is composed of  
Figure 6: SEM images of PR1/24h (**a–c**), PR2/24h (**d–f**), and PR3/24h (**g–i**) granules synthesized via a dissolution–precipitation reaction. Figure 7: SEM images of PR1/48h (**a–c**), PR2/48h (**d–f**), and PR3/48h (**g–i**) granules synthesized via a dissolution–precipitation reaction. an assembly of plate-like crystals with an approximate diameter of 200 nm.