Degradation of ion-exchange strengthened glasses due to surface stress relaxation

Seaman, Jared H.; Lezzi, Peter J.; Blanchet, Thierry A.; Tomozawa, M.

doi:10.1016/j.jnoncrysol.2014.07.016

Cited by 37 publications

(47 citation statements)

References 21 publications

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“…Such stress relaxation measurements have some importance in field of ion exchange glasses (e.g. sodium borosilicates) because of the strengthening of the glass surface that is steadily improved [100,101], while it has also been considered for soda-lime [102,103,104] or borosilicate glasses [105]. For the latter [105], a long-time study has permitted the first detectable signatures of glass relaxation far below T g (T /T g ≃0.3), and the measure of strain with time, in other words, the relaxation of the glass, follows a stretched exponent with a Kohlrausch exponent β=0.43 that has been predicted from dimensional arguments [106].…”

Section: Stress Relaxationmentioning

confidence: 99%

Relaxation and physical aging in network glasses: a review

Micoulaut

2016

Rep. Prog. Phys.

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Abstract. Recent progresses in the description of glassy relaxation and ageing are reviewed for the wide class of network-forming materials such as GeO 2 , Ge x Se 1−x , silicates (SiO 2 -Na 2 O) or borates (B 2 O 3 -Li 2 O), all of them having an important usefulness in domestic, geological or optoelectronic applications. A brief introduction of the glass transition phenomenology is given, together with the salient features that are revealed both from theory and experiments. Standard experimental methods used for the characterization of the slowing down of the dynamics are reviewed. We then discuss the important role played by aspect of network topology and rigidity for the understanding of the relaxation of the glass transition, while also permitting analytical predictions of glass properties from simple and insightful models based on the network structure. We also emphasize the great utility of computer simulations which probe the dynamics at the molecular level, and permit to calculate various structure-related functions in connection with glassy relaxation and the physics of ageing which reveals the off-equilibrium nature of glasses. We discuss the notion of spatial variations of structure which leads to the picture of "dynamic heterogeneities", and recent results of this important topic for network glasses are also reviewed.PACS numbers: 61.43. Fs, 64.70.kj Relaxation and physical ageing in network glasses 2 Figure 1. Typical network-forming glasses: a) A stoichiometric glass former (SiO 2 , B 2 S 3 ) whose structure and network connectivity can be altered by the addition (b) of 2-fold coordinated atoms (usually chalcogens, S, Se) that lead to cross-linked chains. The structure can also be depolymerized (c) by the addition of a network modifier (alkali oxides or chalcogenides, Na 2 O, Li 2 S, etc.). Glassy dynamics depends strongly on the network topology, i.e. the way bonds and angles arrange to lead to a connected atomic network. Note that only chalcogenides can produce a mixture of these three kinds of basic networks, e.g. (1-x)Ge y Se 1−y -xAg 2 Se [2], and for the latter system x=0 corresponds to case (b), y=33% corresponds to case (c), and both conditions together (x=0,y=33 %) to case (a).

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Section: Stress Relaxationmentioning

confidence: 99%

Relaxation and physical aging in network glasses: a review

Micoulaut

2016

Rep. Prog. Phys.

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“…For method I, the values of

τ_{1}

appeared to decrease nearly linearly with K 2 O concentration. For Seaman et al’s model,

C_{(s_{0})}^{*} = 2.3, D_{s} = 8.3 \times 10^{- 12} {cm}^{2} / s

, and

D = 1.3 \times 10^{- 11} {cm}^{2} / s

at T = 450°C (based on Equation()), and

\frac{τ_{i}}{τ_{0, i}} = \exp \{- 2.3 e r f c (1.2 α)\}

according to Equation(). Figure shows the dilation coefficient, B vs K 2 O concentration at 450°C estimated by method I and by method II.…”

Section: Resultsmentioning

confidence: 99%

“…In chemically strengthened glasses, residual compressive stresses are introduced near the surface during the ion‐exchange process. In the course of the exchange process, the glasses are heat‐treated below the glass transition temperature, T g , in molten salt baths containing alkali ions larger than the ones originally present . Although the molten salt bath's high temperature promotes ions diffusion and produces deeper exchanged layers, it could also affect negatively the strength of glasses by facilitating stress relaxation …”

Section: Introductionmentioning

confidence: 99%

“…Seaman et al computed the residual stress profiles in ion‐exchanged SLG by assuming that the dilation coefficient, B , was constant and that the stress relaxation was a diffusion‐controlled process aided by water vapor. Seaman et al analyzed Sane and Cooper's set of 27 residual stress profiles obtained from direct, photoelastic measurements.…”

Section: Introductionmentioning

confidence: 99%

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A study on ion‐exchanged, soda‐lime glass’s residual stress relationship with K⁺/Na⁺concentration

Sun

Dugnani

2019

Int J of Appl Glass Sci

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In the past, studies have shown that the chemical composition within the exchanged layer could influence both the stress build‐up magnitude and the stress relaxation rate. In this work, a novel approach was proposed to estimate the relationship between the stress relaxation parameters, the dilation coefficient, and the relative K+/Na+ concentration. The proposed method required knowledge of the residual stress profiles, the molten salt bath's temperature and soaking time, and the bath's composition. Based on the analyses performed on various residual stress profiles in ion‐exchanged soda‐lime glass, both the dilation coefficient and the magnitudes of the relaxation time constants were found to consistently decrease with K2O concentration.

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“…When the surface stress completely relaxes, the resulting surface compressive stress is nearly identical in magnitude to the previously applied tensile stress. 26 More recently, the surface stress relaxation mechanism was combined with a simple fracture mechanics based model to explain the apparent strengthening (or increasing delay time to repropagate a crack under a high stress intensity) for glass aged at subcritical stress intensity factors. Further, surface stress relaxation has been shown to occur for all oxide glass types and is not limited to glasses containing mobile alkali ions.…”

Section: Introductionmentioning

confidence: 99%

Origin of the Static Fatigue Limit in Oxide Glasses

2016

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Oxide glasses exhibit slow crack growth under stress intensities below the fracture toughness in the presence of water vapor or liquid water. The log of crack velocity decreases linearly with decreasing stress intensity factor in Region I. For some glasses, at a lower stress intensity, Ko, log v asymptotically diminishes where there is no measurable crack growth. The same glasses exhibit static fatigue, or a decreasing strength for increasing static loading times, as cracks grow and stress intensity eventually reaches the fracture toughness. In this case, some glasses exhibit a low stress below which no fatigue/failure is observed. The absence of slow crack growth under a low stress intensity factor is called the fatigue limit. Currently, no satisfactory explanation exists for the origin of the fatigue limit. We show that the surface stress relaxation mechanism, which is promoted by molecular water diffusion near the glass surface, may be the origin of the fatigue limit. First, we hypothesize that the slowing down of slow crack growth takes place due to surface stress relaxation during slow crack growth near the static fatigue limit. The applied stress intensity becomes diminished by a shielding stress intensity due to relaxation of crack tip stresses, thus resulting in a reduced crack velocity. This diminishing stress intensity factor should result in a crack growth rate near the static fatigue limit that decreases in time. By performing Double Cantilever Beam crack growth measurements of a soda‐lime silicate glass, a decreasing crack growth rate was measured. These experimental observations indicate that surface stress relaxation is causing crack velocities to asymptotically become immeasurably small at the static fatigue limit. Since the surface stress relaxation was shown to take place for various oxide glasses, the mechanism for fatigue limit explained here should be applicable to various oxide glasses.

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Degradation of ion-exchange strengthened glasses due to surface stress relaxation

Cited by 37 publications

References 21 publications

Relaxation and physical aging in network glasses: a review

Relaxation and physical aging in network glasses: a review

A study on ion‐exchanged, soda‐lime glass’s residual stress relationship with K⁺/Na⁺concentration

Origin of the Static Fatigue Limit in Oxide Glasses

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Degradation of ion-exchange strengthened glasses due to surface stress relaxation

Cited by 37 publications

References 21 publications

Relaxation and physical aging in network glasses: a review

Relaxation and physical aging in network glasses: a review

A study on ion‐exchanged, soda‐lime glass’s residual stress relationship with K+/Na+ concentration

Origin of the Static Fatigue Limit in Oxide Glasses

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Product

Resources

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A study on ion‐exchanged, soda‐lime glass’s residual stress relationship with K⁺/Na⁺concentration