Glass Reflections
Cambridge 7th to 9th September

Presenting Author:
Michael Ojovan

article posted 24 Feb 2015

Michael Ojovan

Michael I. Ojovan has been Nuclear Engineer at International Atomic Energy Agency, Assistant Professor (Reader) in the Department of Materials Science and Engineering of the University of Sheffield and Visiting Professor in the Department of Materials of Imperial College London. He has been awarded the degrees of Doctor of Science in Physical Chemistry and PhD in Solid State Physics. Michael is Editor of International Journal of Corrosion, Science and Technology of Nuclear Installations, Innovations in Corrosion and Materials Science and Journal of Nuclear Materials.

Michael has authored over 300 peer-reviewed scientific papers, 42 patents, and 12 monographs on nuclear materials including the second edition of "An Introduction to Nuclear Waste Immobilisation" by Elsevier. He has been known for the two-exponential universal viscosity equation, the connectivity-percolation theory of glass transition, condensed excited state of matter (Rydberg matter), glass-composite materials for nuclear waste, and metal matrix immobilisation technology.

Mass spectrometric evidencing on
modified random network microstructure and medium range order

Michael Ojovan
Department of Materials Science and Engineering,
The University of Sheffield

Mass spectrometric analysis of newly formed surface on breaking a sodium borosilicate glass bar revealed its significant enrichment with sodium, slight higher content of boron and depletion in Mg, Ca, Al, Ti and Mo compared the initial glass surface. This conforms to recent low energy ion observation of Almeida, Pantano &Jain [1] and evidences on modified random network (MRN) microstructure and medium range order (fractal in nature) in silicate glasses.

The glass investigated was a borosilicate glass (wt.%) 48.2 SiO2 7.5 B2O3 2.5 Al2O3 1.5 Fe2O3 15.5 CaO 16.1 Na2O 8.7 Misc, which is a simulant of high-sodium nuclear waste glass K-26 [2].

The glass bar after annealing was broken openly in air using a hammer. Laser Ablation System New Wave UP 213 (LAS) coupled with ICP-MS 4500 system was used for analysis of elemental composition of near-surface layers of glass.

The analysis comprised the elements: 95Mo, 11B, 23Na, 24Mg, 27Al, 30Si, 43Ca, and 47Ti. The LAS was taken samples from the freshly formed surface as well as from the initial surface of glass bar. The relative changes of average ICP MS normalised signal intensities on formation of a new glass surface were as follows: 1.14 for 11B, 1.35 for 23Na, 0.8 for 24Mg, 0.83 for 27Al, 0.75 for 43Ca, 0.76 for 47Ti and 0.77 for 95Mo.

These data evidence on MRN model of glass and show that the glass breaks along weaker ionic percolating channels formed by alkalis. The results obtained may be useful for configuron percolation theory (CPT) of glass transition [3], interpretation and controlling glass corrosion, as well as for potential applications in medicine and biology.

[1] R.M. Almeida, C.G. Pantano, H. Jain. Role of composition in the fracture of silicate glasses. Mat. Res. Soc. Symp. Proc., 1757, mrsf14-1757-uu9-04 (2015).

[2] M.I. Ojovan, W.E. Lee, A.S. Barinov, I.V. Startceva, D.H. Bacon, B.P. McGrail, J.D. Vienna. Corrosion of low level vitrified radioactive waste in a loamy soil. Glass Technol., 47 (2), 48-55 (2006).

[3] M.I. Ojovan. Ordering and structural changes at the glass-liquid transition. J. Non-Cryst. Solids, 382, 79-86 (2013).