Effect of aluminum oxide on the structure and conduction behaviors of silver borate glasses

Abstract

ABSTRACT. The current study focuses on glass preparation and characterization in the glass system of chemical formula xAl2O3 (35-x) Ag2O.65B2O3 (0≤x≤35 mol%), where Ag2O is replaced with Al2O3. To examine a wide range of both structure and morphology of the prepared glasses, nuclear magnetic resonance (NMR) of 27Al nuclei, X-ray diffraction (XRD) spectroscopy, and transmission electron microscopy (TEM) are used. In Al2O3-rich glass, the well-formed AlO6, AlO5, and AlO4 structural groups are the well-formed units. In samples of (20 and 30 mol % Al2O3), tetrahedral AlO4 and traces from AlO6 units could be detected. At lower concentrations of Al2O3 (10 mol%), the dominant forming unit is only AlO4 groups containing non-bridging oxygen bonds (NBO). The XRD spectra confirm the amorphous nature of the glasses of Al2O3 ˂20 mol% while glasses of higher Al2O3 concentrations contain crystalline Ag2Al2B2O7 formed due to the higher oxygen packaging of the mixed AlO5 and AlO4 compared with that of glasses containing only AlO4 species only. The morphology of crystalline units is confirmed from TEM to differ from that of an amorphous composition. The increase of activation energy and the hardness number of the glasses led to an increase in the durability of the investigated glasses.
 
 KEY WORDS: Aluminum borate glass, NMR, Coordination of aluminum atom, Conductivity, Crystallization process
 Bull. Chem. Soc. Ethiop. 2022, 36(3), 597-606. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i3.9

A review on borate bioactive glasses (BBG): effect of doping elements, degradation, and applications

“…Additionally, incorporating Al 2 O 3 into BG functions as a network former, producing more oxygen atoms that bridge with BO 3 units, thereby enhancing the material's long-term resilience, crack resistance, and chemical durability. [125][126][127] Even though adding a varying proportion of Al mol% in the BG composition can result in delayed HAP generation and other structural and chemical modifications, up to roughly 1.5 mol% Al 2 O 3 can be introduced into the glass composition without significantly reducing bioactivity. 128 Besides this, an experimental investigation by Mohini et al demonstrates that the HAP occurrence of post-soaked Al-doped BBG sample gradually declines with an increase in Al 2 O 3 content up to 1.9 mol%, indicating a decrease in the glass's bioactivity.…”

“…123 Meanwhile, numerous investigations on the impact of Al-doped BBGs on their physicochemical and mechanical properties have been conducted. 121,[123][124][125][127][128][129][130][131][132][133] Besides, a great deal of research has been done on the biological effects of aluminium, which is used in glass ionomers for dental cement and is known to be potentially toxic and to negatively influence biomineralization. [134][135][136][137][138] However, a thorough review of the literature reveals that studies on Al-doped BBGs, particularly their effect on critical osteogenic biomarkers and cell differentiation for bone regeneration, are still lacking.…”