wizyta

od 2020-09-20

Title: The aluminum effect on the structure of silico-phosphate glasses studied by NMR and FTIR

Source: Journal of Molecular Structure

Year : 2009

Abstract:

Silico-phosphate glasses of NaCaPO(4)-SiO(2) and NaCaPO(4)-AlPO(4)-SiO(2) system have been the subject of the presented investigations. Classes of these systems are the basis for the preparation of glassy-crystalline biomaterials [R.D. Rawlings, Clin. Mater. 14 (1993) 155]. Detailed knowledge of the precursor glass structure is necessary for proper design of the glassy-crystalline biomaterials preparation procedure. Since there is no long-range ordering in glasses, spectroscopic methods which make it possible to study the short range ordering should be applied. MIR studies carried out in the work have allowed to establish that the glasses of the systems studied show domain composition [L.L. Hench, RJ. Splinter, T.K. Greenlee, W.C. Allen, J. Biol. Res. Symp. 2 (1971) 117: L.L. Hench, RJ. Splinter, W.C. Allen, T.K. Greenlee, J. Biol. Res. 5 (1972) 117]. Domain structure is close to that of the corresponding crystalline phases. It has been shown that even small amount of aluminium in the glass (5 mol.% of AlPO(4)) significantly influences both, its texture (microscopic and EDX studies) and its structure (spectroscopic studies). (27)Al NMR investigations have made it possible to establish unequivocally that aluminium occurs exclusively in tetrahedral coordination, i.e. it is involved in the formation of glass framework. Presence of aluminium results in significant changes in the [SiO(4)](4-) and [PO(4)](3-) tetrahedra environment which is reflected in (23)Na, (31)P and (29)Si NMR spectra. Changes in the shapes and positions of the bands in the NMR spectra of glasses belonging to the NaCaPO(4)-AlPO(4)-SiO(2) system confirm great influence of aluminium on silico-phosphate glasses structure.
(C) 2008 Elsevier B.V. All rights reserved.

DOI: 10.1016/j.molstruc.2008.10.043   (Pobrane:  2020-10-23)