Abstract
The fabrication of novel oxide glass is a challenging topic in glass science. Alumina (Al2O3) glass cannot be fabricated by a conventional melt–quenching method, since Al2O3 is not a glass former. We found that amorphous Al2O3 synthesized by the electrochemical anodization of aluminum metal shows a glass transition. The neutron diffraction pattern of the glass exhibits an extremely sharp diffraction peak owing to the significantly dense packing of oxygen atoms. Structural modeling based on X-ray/neutron diffraction and NMR data suggests that the average Al–O coordination number is 4.66 and confirms the formation of OAl3 triclusters associated with the large contribution of edge-sharing Al–O polyhedra. The formation of edge-sharing AlO5 and AlO6 polyhedra is completely outside of the corner-sharing tetrahedra motif in Zachariasen’s conventional glass formation concept. We show that the electrochemical anodization method leads to a new path for fabricating novel single-component oxide glasses.
Highlights
The fabrication of novel oxide glass is a challenging topic in glass science
Sun classified single-component oxides into glass formers, glass modifiers, and intermediates3. SiO2, B2O3, P2O5, and A s2O3 are typical glass formers, in which the cation–oxygen coordination number is 3 or 4 and the glass network is formed by cornersharing oxygen atoms
Shi et al have recently reported the comparison between amorphous Al2O3 and liquid Al2O3, and they concluded on the basis of molecular dynamics (MD) and empirical potential structure refinement (EPSR)[14] simulations based on diffraction data[15] that the are 36.82 Å3kj1/2mol−1/2 (Al)–O coordination number is increased in amorphous Al2O3
Summary
The fabrication of novel oxide glass is a challenging topic in glass science. Alumina (Al2O3) glass cannot be fabricated by a conventional melt–quenching method, since Al2O3 is not a glass former. The first sharp diffraction peak (FSDP)[34], which is from p seudo35 (quasi36) Bragg planes (successive small c ages37) created along a void, is observed at Q = 1.52 Å−1 for g-SiO2, a typical glass forming oxide, whereas the FSDP observed at Q ~ 2 Å−1 is not prominent in g-Al2O3, suggesting the formation of a densely packed structure with a small void volume.
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