Gas solubility in glasses – principles and structural implications

Interstitial voids in silica melts and implication for argon solubility under high pressures

“…These experiments reveal that the solubility of Ar increases linearly with increasing pressure up to $5 GPa, where it reaches a maximum value (ChamorroPerez et al, 1996(ChamorroPerez et al, , 1998 or a plateau (Schmidt and Keppler, 2002), and then drops significantly at higher pressure (Bouhifd and Jephcoat, 2006;Bouhifd et al, 2008;Chamorro-Perez et al, 1996, 1998. This unusual behavior is incompatible with most previous models.…”

“…Because the interactions between noble gases and silicate melts are mainly of van der Waals type, the dissolution behavior of noble gases in silicate melts is often treated as so called "physical solubility" (Paonita, 2003;Shackelford, 1998) where the force between noble gases atoms and the silicate network is much weaker than normal chemical bonds. This is confirmed by X-ray absorption measurements in silica that the krypton atoms take the site of void surrounded by nearest oxygen atoms (Wulf et al, 1999).…”

“…The solubilities of noble gases in silicate melts under lower pressures are reported to be roughly correlated with the properties of melts such as density (Lux, 1987), ionic porosity (Carroll and Stolper, 1993;Marrocchi and Toplis, 2005) or the number of non-bridged oxygen per silicon (NBO/Si) (Shibata et al, 1998), but the relevancies between the experimental solubility and these prosperities are still controversial since the results from different composition are inconsistent (Marrocchi and Toplis, 2005;Shibata et al, 1998). Shackelford and his coworkers (Shackelford, 1998;Shackelford and Masaryk, 1978;Wortman and Shackel- ford, 1990) studied the microscopic mechanism of gas dissolution and reported that the solubility of noble gases depends on the number of available interstitial voids or "holes" larger than the size of noble gases atom in the structure of silica melts. Based on the solubility data of He, Ne and Ar, they propose that the size of voids in vitreous silica follows a log-normal distribution.…”

“…Recently, the solubility of Ar under high pressure has attracted renewed attention and extensive experimental work has been carried out (Bouhifd and Jephcoat, 2006;Bouhifd et al, 2008;Chamorro-Perez et al, 1996, 1998Schmidt and Keppler, 2002). These experiments reveal that the solubility of Ar increases linearly with increasing pressure up to $5 GPa, where it reaches a maximum value (ChamorroPerez et al, 1996(ChamorroPerez et al, , 1998 or a plateau (Schmidt and Keppler, 2002), and then drops significantly at higher pressure (Bouhifd and Jephcoat, 2006;Bouhifd et al, 2008;Chamorro-Perez et al, 1996, 1998.…”

Vacuum packaging technology using localized aluminum/silicon-to-glass bonding

“…Since the glass cap is heated up during the bonding process, out-diffusion of gases from glass will occur and becomes the major factor affecting the vacuum level of the sealed cavity. For example, the solubility of helium in glass is about 6 10 atoms/cm at 1 atm, 300 K and will decrease to 2 10 atoms/cm when the temperature rises to 1000 K [26], which is about the aluminum-to-glass bonding temperature. The mean diffusion length of helium atom ( , where is the diffusion coefficient of helium in glass, 1000 m s at 1000 K, is the bonding time) in Pyrex glass is about 760 m for 10 min at 1000 K [27], which is about the thickness of the Pyrex glass cap.…”