Thermal properties of sodium borosilicate glasses as a function of sulfur content

Abstract

Sulfur trioxide (SO3) additions, up to 3.0 mass%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur‐free composition of 50SiO2–10Al2O3–12B2O3–21Na2O–7CaO (mass%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.2 mass% SO3. It was found that measured sulfur (here as sulfate) additions up to 1.18 mass% increased the glass transition temperature by 3%, thermal diffusivity by 11%, heat capacity by 10%, and thermal conductivity by 20%, and decreased the mass density by 1%. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions up to 3.0 mass%, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non‐bridging oxygen in the silicate network. It is postulated that this increased cross‐linking of the borosilicate backbone led to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

Structural drivers controlling sulfur solubility in alkali aluminoborosilicate glasses

“…However, the mechanisms through which either cationic field strength or degree of network polymerization control the sulfate solubility are still ambiguous. Furthermore, assuming that the majority of sulfur dissolves in the borosilicate glasses as (as has been reported in the literature), 10–23 it will also need to be charge compensated by a non‐framework cation. In this case, does prefer to take away a modifier cation from the silicate units or borate units in the borosilicate glass network?…”

“…Similarly, it has been shown that sulfate solubility is inversely proportional to the ionic field strength of the non-framework cations, or the degree of polymerization in the glass network. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] However, the mechanisms through which either cationic field strength or degree of network polymerization control the sulfate solubility are still ambiguous. Furthermore, assuming that the majority of sulfur dissolves in the borosilicate glasses as SO 2 − 4 (as has been reported in the literature), [10][11][12][13][14][15][16][17][18][19][20][21][22][23] it will also need to be charge compensated by a non-framework cation.…”

“…However, the reason for this behavior is still unclear. Similarly, it has been shown that sulfate solubility is inversely proportional to the ionic field strength of the non‐framework cations, or the degree of polymerization in the glass network 10–23 . However, the mechanisms through which either cationic field strength or degree of network polymerization control the sulfate solubility are still ambiguous.…”

Microparticle Impact Testing at High Precision, Higher Temperatures, and with Lithographically Patterned Projectiles

“…In the new launch pad, the thickness of the employed glass layers is sufficient for thermal shielding before launch. In particular, for borosilicate glass with a thermal diffusivity of D ≈ 4 × 10 −3 cm 2 s −1 [ 20 ] (approximately a factor four higher than that of PU), even in 1 µs the thermal diffusion length is only d ≈ 500 nm (compare with the glass thickness of 100–200 µm). Consistent with this, in previous work on laser‐driven flyer plates, epoxy heat shields 3.5 µm thick have been argued to provide sufficient thermal protection in shock‐assisted launch scenarios.…”

Impacts of temperature on sulfur solubility in low‐activity waste glasses

“…[39][40][41][42] This behavior has been thoroughly investigated and indicates that temperature is an important factor in the fining process of industrial glass melting. 35 On the other hand, previous studies on glass melts saturated with sulfate salt mostly considered the compositional effect 10,14,28,29,[43][44][45] with only a few papers tested temperature as an influencing factor. 46,47 When the glass melt is saturated with sulfate salt, increasing temperature led to no changes of or slightly increased sulfur solubility.…”