Porous glasses are produced by thermally induced phase separation and chemical leaching of glasses with suitable compositions. Prominent examples for phase separation are sodium borosilicate (NBS) glasses, one of the best investigated phase separating glass systems.
The introduction of Al2O3 into such (NBS) glasses allows a better control of the phase separation process [1] and the incorporated [AlOx]-groups can act as acid centers in catalytic processes [2]. By this, various applications are conceivable for such materials, e.g. as continuous flow micro reactors. Several investigations on the influence of heat treatment on phase separation are published, but only few with systematically added Al2O3.
To analyze the effect of Al2O3 on the properties of phase separated sodium borosilicate glass, a series of glasses with 66 SiO2 : 26 B2O3 : 8 Na2O + x Al2O3 with x = 0 to 6 mol % were synthesized and heat-treated for phase separation. Treatment times up to 120 h and temperatures between 630 and 760° C were applied. The initial glasses before and after phase separation were characterized (XRF, XRD, pycnometry, dilatometry, DSC, 11B/27Al NMR) as well as leached with acids and alkaline solutions, subsequently. The obtained porous materials were analyzed by ICP-OES, electron microscopy and mercury intrusion porosimetry. Since in literature no information on chemical durability of such material is known, the leaching stability against boiling water and alkaline solutions were tested.
References:
[1] F. Janowski, D. Enke, “Porous glasses” in: J. Weitkamp, K.S.W. Sing, F. Schüth (2002) Handbook of porous solids. (1stedn) Wiley-VCH, Weinheim.
[2] W.-F. Du et al., Journal of Materials Science 35 (2000) 4865 - 4871.
| Subject : | : | Oral |
| Topics | : | Session 6 - Glass-ceramic / Crystallization / Nano and microtexturation |
| Keywords | : | phase separation ; microstructure ; porous glasses ; chemical durability |
| PDF version | : |  PDF version |
