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Abstract HCl and CO 2 are active participant molecules in the re-modeling phase of bone materials of vertebrates, wherein old bone is dissolved (resorbed) by osteoclast cells (HCl acid and collagenase secreting cells) and new bone becomes deposited (mineralized) by osteoblast cells. The mineralization process results in the deposition of mature (i.e., non-carbonated) or immature (i.e., partially carbonated) hydroxyapatite (HAP), which may involve CO 2 -carbonation, depending on the function of the perceived bone (e.g., non-dissolvable tooth enamel bone or dissolvable skeletal bone). The present investigation adopted a surface chemical approach to examine impacts of interfacial interactions of wet HCl vapor (at 673 K) and CO 2 gas molecules (at 298 K) on the chemical composition and particle morphology of synthetic and biological apatite (AP) materials of varied contents of mature HAP. Studies employing X-ray powder diffractometry, Fourier-transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray micro-probing were carried out. Accordingly, high relative crystallinity, extent of hydroxylation and Ca/P atomic ratio were found to discern synthetic from biological APs. Furthermore, results obtained helped revealing that (i) compositional (atomic ratios, and extents of hydroxylation and carbonation) and morphological (particle shape and agglomeration) parameters are more diagnostic to the HAP maturity than the geometric structural (crystallization and crystallinity) parameters, (ii) the higher the maturity of the contained HAP, the higher is the resistance of chemical integrity and morphology of the AP material particles to the HCl-acidification, and (iii) a preceding CO 2 -carbonation lessens HAP-maturity of the AP materials thus rendering them more vulnerable to retrogressive chemical and morphological consequences of the acidification. Highlights • Hydroxyapatite maturity is diagnosed by compositional parameters of apatite. • Synthetic apatites are richer in mature hydroxyapatite than biological ones. • Hence, chemical integrity of biological apatites is retrogressed via HCl treatment. • HCl retrogressive consequences are deepened after pre-carbonation of apatites. • Carbonation enables apatite nano-particle coalescence into micro-agglomerates. [ABSTRACT FROM AUTHOR]

Abstract: Two samples (S1 and S2) of magnetite were synthesized, using two different methods, and characterized by means of X-ray powder diffractometry, infrared and Mössbauer spectroscopy, N2 sorptiometry and electron microscopy. Particles of sample-S1 were found to be loosely agglomerated, micro-sized spheroids (200–350nm) composed almost solely of highly aggregated (fused) crystallites (size averaged at 35nm) of cubic-Fe3O4. In contrast, particles of sample-S2 were strongly agglomerated, nano-sized spheroids (25–30nm) composed of slightly aggregated crystallites (size averaged at 11nm) of cubic-Fe3O4 and noncrystalline domains made-up of FeO(OH) species. Temperature-programed reduction (TPR) profiles obtained for the two samples were similar in monitoring two peaks at >450°C assignable to a two-step reduction of Fe3O4 (→FeO→Fe), but different in monitoring a peak at<450°C only for the reduction of FeO(OH) (→Fe3O4) contained in sample-S2. However, curve fitting analysis of the TPR profiles and molecular stoichiometry calculations based on amounts of hydrogen consumed revealed that the two-step reduction of Fe3O4 is not straightforward. That is by resolving two consecutive pathways for each step and, hence, nonstoichiometric intermediate products whose composition was found to be critically controlled by the composition of the reducing gas atmosphere (5 or 80% H2/N2) and characteristics of the starting sample particles (chemical and phase composition, and, but to lesser extents, the agglomeration and average size). [Copyright &y& Elsevier]

Abstract: Pure, phosphated, and phosphonated CaO samples were prepared and characterized by X-ray powder diffractometry, FTIR spectroscopy, scanning electron microscopy, and energy-dispersive X-ray microprobing. Surface acid–base properties were probed by in situ FTIR spectroscopy of adsorbed CO (at 85 K), CDCl3 (at RT), CO2 (at RT), and methyl butynol decomposition reactions (at 473 K). Results obtained have shown phosphate and, to a larger extent, phosphonate additives to enhance the strength of Lewis acid sites exposed on CaO surfaces, at the expense of the Lewis base site strength. The phosphonation has been found, moreover, to make CaO particles grow in a preferential direction and be less susceptible to rehydration. These findings may establish surface chemical attributes for the application of the methylene bisphosphonate (MBP) class of drugs to hamper acid-induced resorption of bone materials (osteoporosis). [Copyright &y& Elsevier]

Abstract: A surfactant-stabilized microemulsion method was used to prepare nano-sized particles (<10 nm) of cubic-CeO2 exposing surfaces of not only highest specific areas (142–201 m2/g) ever reported for polycrystalline ceria, but also high thermal stability at 800 °C. Three different surfactants, a non-ionic, an anionic and a cationic, were used to form the microemulsions. Then, N2 sorptiometry and pore volume distribution calculations, were used to reveal microporous and mesoporous structures of these cerias as a function of surfactant type. Transmission electron microscopy was used to visualize consequent particle behaviors. Suggestions have been made as to the textural attributes of the high surface area and thermal stability. Accordingly, cationic surfactants, in the presence or absence of added non-ionic surfactant, are seen to assist in producing cerias of promising surface textural properties for the chemical makeup of combustion catalysts. [Copyright &y& Elsevier]