Composition of Coexisting Phases in Sodium Borosilicate Glasses Exhibiting Phase Separation

Nuclear magnetic resonance and acoustic investigations of the melting - freezing phase transition of gallium in a porous glass

“…Assuming the validity of the relationship (2) for gallium in fine pores, one can estimate the width of the fine-pore diameter distribution from the NMR data as 1 nm. This estimation coincides with the fact that the distribution of fine pore sizes usually is rather narrow [23]. Nearly the same estimation (of 1.2 nm) can be evaluated from the melting data.…”

“…From comparison of figures 1 and 2 one can see that the rather small change in NMR intensity corresponds to the maximal alteration in acoustical velocity and attenuation. A further change in the NMR signal intensity near 240 K can be ascribed to freezing within coarse pores with smaller diameters than 200 nm, which could be formed during incomplete leaching [23]. The step in the temperature dependence of the amount of liquid gallium near 210 K arises obviously due to freezing gallium within fine pores.…”

“…The reason for this behaviour is not quite clear. A probable explanation for the non-monotonic temperature shift of melting with changing pore size consists in different forms of pore of distinct sizes [23], fine pores having a quasi-spherical form and coarse pores being quasi-cylindrical. Since the Gibbs-Thompson equation has been written for spherical particles, the alterations in pore form and form of gallium nanoparticles within pores can affect the size dependence of T m .…”

“…The sample under study was prepared from a phase-separated soda borosilicate glass whose pore structure was produced by acid leaching [23]. After acid leaching, the sample exhibits a well defined bimodal pore size distribution, with diameters around about 200 nm and near 7 nm for the coarse and the fine pores, respectively, as determined by mercury intrusion porosimetry and by electron microscopy.…”