Unraveling the structural complexity of and the effect of calcination temperature on calcium phosphates derived from Oreochromis niloticus bones

In this study, the interplay between the structural complexity, microstructure, and mechanical properties of calcium phosphates (CaPs) derived from fish bones, prepared at various calcination temperatures, and their corresponding sintered ceramics was explored. Fourier-transform infrared analysis revealed that the calcined powders primarily consisted of hydroxyapatite (HAp) and carbonated calcium hydroxyapatite, with an increasing concentration of Mg-substituted β-tricalcium phosphate (β-TCP) as the calcination temperature was increased. X-ray diffraction patterns showed enhanced sharpness of the peaks at higher temperatures, indicating a larger crystallite size and improved crystallinity. The ceramics exhibited a significantly larger crystallite size and an increased concentration of the β-TCP phase. Rietveld analysis revealed a larger volume of the β-TCP phase in the ceramics than in their calcined powders; this could be attributed to a newly formed β-TCP phase due to the decomposition of HAp. Extended X-ray absorption fine structure analysis revealed the incorporation of Mg in the Ca2 site of HAp, Ca2 site of β-TCP, and Ca5 site of β-TCP, with a higher substitution of Mg in the Ca5 site of β-TCP at elevated temperatures. The mechanical properties of HAp ceramics can be improved by increasing the calcination temperature because of their improved relative density and dense porous structure at elevated temperatures. This comprehensive investigation sheds light on the phase evolution, microstructural changes, and consequential impact on the mechanical properties of CaPs derived from fish bones, thereby facilitating the development of tailored CaP ceramics for biomedical applications.

Mechanical and self-healing properties of cement paste containing incinerated sugarcane filter cake and Lysinibacillus sp. WH bacteria

Cement is the most widely used construction material due to its strength and affordability, but its production is energy intensive. Thus, the need to replace cement with widely available waste material such as incinerated black filter cake (IBFC) in order to reduce energy consumption and the associated CO2 emissions. However, because IBFC is a newly discovered cement replacement material, several parameters affecting the mechanical properties of IBFC-cement composite have not been thoroughly investigated yet. Thus, this work aims to investigate the impact of IBFC as a cement replacement and the addition of the calcifying bacterium Lysinibacillus sp. WH on the mechanical and self-healing properties of IBFC cement pastes. The properties of the IBFC-cement pastes were assessed by determining compressive strength, permeable void, water absorption, cement hydration product, and self-healing property. Increases in IBFC replacement reduced the durability of the cement pastes. The addition of the strain WH to IBFC cement pastes, resulting in biocement, increased the strength of the IBFC-cement composite. A 20% IBFC cement-replacement was determined to be the ideal ratio for producing biocement in this study, with a lower void percentage and water absorption value. Adding strain WH decreases pore sizes, densifies the matrix in ≤ 20% IBFC biocement, and enhances the formation of calcium silicate hydrate (C-S-H) and AFm ettringite phases. Biogenic CaCO3 and C-S-H significantly increase IBFC composite strength, especially at ≤ 20% IBFC replacement. Moreover, IBFC-cement composites with strain WH exhibit self-healing properties, with bacteria precipitating CaCO3 crystals to bridge cracks within two weeks. Overall, this work provides an approach to produce a "green/sustainable" cement using biologically enabled self-healing characteristics.

Impacts of pre-treatment methods on the morphology, crystal structure, and defects formation of hydroxyapatite extracted from Nile tilapia scales

The comprehensive control of hydroxyapatite (HAp), involving morphological and structural variations, particle sizes, and defect formations, has garnered considerable attention for its versatile functionalities, rendering it applicable in diverse contexts. This work examined the shape, structure and optical characteristics, and defect formation in hydroxyapatite (HAp) extracted from Nile tilapia (Oreochromis niloticus) scales with various pre-treatments through experiments and density functional theory (DFT) calculations. Utilizing scanning electron microscopy, our findings revealed that dried fish scales (FS-D) exhibited a layered pattern of collagen fibers, while boiled fish scales (FS-B) had smoother surfaces and significantly reduced collagen content. After calcination, the FS-D sample produced nanorods with an average length of 150 ± 44 nm, whereas the FS-B samples yielded agglomerated spherical particles whose size increased with the rising calcining temperature. In-depth analysis through X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the presence of biphasic calcium phosphates in the FS-B samples, while the FS-D sample presented a pure HAp phase. The boiled fish scale calcined at 800 °C (FS-B800) exhibited an optical band gap (Eg) of 5.50 eV, whereas the dried fish scale calcined at 800 °C (FS-D800) showed two Eg values of 2.87 and 3.97 eV, as determined by UV-visible spectroscopy. DFT calculations revealed that the band gap of 3.97 eV correlated with OH- vacancies, while that of 2.87 eV indicated Mn-substituted HAp, explaining the blue powder. The Eg value for the white powder resembled pure HAp, S- and Cl- substituted OH- vacancies, and various cations substituting Ca sites of HAp. Different pre-treatment procedures influence the characteristics of HAp, offering opportunities for applications in bone replacement and scaffolds for bone tissue engineering.