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Abstract Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na2O concentration of 12.7 mol%. We used these glasses to investigate the influence ofR = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm asRincreases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na+, Ca2+, and Mg2+) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless ofRand the leaching of modifier cations resulted in a silica‐rich layer in the surface. The leaching of Ca2+and Mg2+ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function ofR. The leaching of Na+ions varied monotonically; the thickness of the Na+depletion layer increased from ~100 nm atR = 0 to ~200 nm atR = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re‐arrangement or re‐polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.
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Mixed modifier effects on structural, mechanical, chemical, and mechanochemical properties of sodium calcium aluminosilicate glass
Abstract Glass properties are governed by the interplay between network formers and network modifiers; for a given composition of network formers, the ratio of different cationic modifiers compensating the anionic species in the network has a profound effect, which is often nonlinear, called a mixed modifier effect (MME). We have investigated the MME of sodium (Na) and calcium (Ca) in an aluminosilicate (NCAS) glass series following the formula [Na2O]30−x[CaO]x[Al2O3]10[SiO2]60, wherex = 0, 7.5, 15, 22.5, and 30. A nonadditive trend was observed in hardness and indentation toughness, with aqueous corrosion resistance exhibiting a shift from incongruent to congruent corrosion, whereas the network structure determined by molecular dynamics simulations revealed no significant trend with composition. Additionally, the NCAS glass containing both [Na2O] and [CaO] within an intermediate range exhibited superior resistance to wear at high humidity, a clear MME phenomenon previously only observed in soda–lime silica.
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- Award ID(s):
- 2011410
- PAR ID:
- 10433619
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 106
- Issue:
- 11
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 6541-6554
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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