Effects of Fe2O3-[BOx] reaction on sodium borosilicate glass structure doping with nano to macro sized α-Fe2O3 particles

Abstract

Fe3+ is readily reacted with structural units to modify various properties of the borosilicate glasses and glass ceramics. However, there exists some controversies on Fe2O3 containing borosilicate glasses: (1) whether the Fe2O3 turned into the nanometer-sized polycrystalline structure or reacted with the glass matrix to form a new substance and (2) whether the role of Fe2O3 was depended on its concentration in the network of glass. Theoretical extinction spectra of α-Fe2O3 particles ranging from 1 to 180 nm in borosilicate glass align with UV–vis absorption spectra. Based on the Na2O-B2O3-Fe2O3 phase diagram, xFe2O3·(100-x) [41.6B2O3–20.7Na2O-19.2CaO-9.7Al2O3–7.0SiO2–0.6ZnO] (x=1.20∼1.95 mol%) were prepared for this study, analyzing from exterior characteristics to interior structure. Molecular vibrational spectroscopy and component structure measurement were applied to study the effect of doping α-Fe2O3 powders (particle sizes of 30 nm, 1 μm, 75 μm) on the sodium borosilicate glasses. Combination of experimental characterization and numerical simulation were also utilized to investigate the effects of iron oxide particle size on the color of dispersion systems. We discovered that (i) doping with either nanometer-sized or micron-sized particles of α-Fe2O3 can result in both the substitution for B3+ in tetra-coordination [BO4] and the bonding with [BO3] units within the amorphous network of sodium borosilicate glasses; (ii) Even at lower concentrations, α-Fe2O3 can still act as a network intermediate, combining both its former role and modifying properties. Based on these outcomes, for the reactive process, we formulated a constitutive model which offers valuable insights into understanding the behavior of iron oxide in sodium borosilicate glass. These findings are crucial for comprehending the processes involved in matrix preparation and are pivotal for progressing to the subsequent stage where designing and fabricating nanocomposite materials based on these matrices with spatial separation.