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Varshneya A.K.,Saxon Glass Technologies Inc. | Varshneya A.K.,Alfred University
Journal of Non-Crystalline Solids | Year: 2010

Glasses strengthen during an ion exchange experiment as a result of the high surface compression that develops from the stuffing of the invading alkali ion into the smaller host alkali ion site and the non-relaxation of this compression. The kinetics are described in terms of a Nernst-Planck interdiffusion coefficient of the exchanging ions in a stack of mixed-alkali glass layers with varying ratios of the alkali. The interdiffusion coefficient is suppressed by compression and enhanced by tension. However, the measured surface compression is usually 2-4 times lower than that calculated using thermal stress analogy incorporating an elastic suppression of the molar volume difference of the as-melted mixed-alkali glasses. A new view of the physics of deformations and failure of stress to continue to buildup is presented in an effort to seek technology improvements. Reduced stresses are ascribed to network yield in two separate modes: yielding of the shape-conserving hydrostatic stress component which prevents elastic expansion of molar volume and yielding of the volume-conserving deviatoric (pure shear) stress which leads to measurable shape change. An anomalous subsurface tension is also explained in this view. By drawing analogy to microindentation, it is concluded that optimum network topology glasses should undergo the least plastic deformation and, hence, develop a higher surface compression. © 2010 Elsevier B.V. All rights reserved.


Varshneya A.K.,Saxon Glass Technologies Inc. | Varshneya A.K.,Alfred University
International Journal of Applied Glass Science | Year: 2010

This paper reviews the progress that has been made in our understanding of the chemical strengthening of glass by ion exchange over its nearly five decades of history. Lessons learned are briefly discussed; more importantly, those which are yet to be learned are highlighted. It is recognized that, except for detailed compositional effects, the kinetics of ion interdiffusion process and the chemical strengthening technology are reasonably well understood. However, the science of stress generation and its concurrent relaxation is far from being clear despite the elegant analogy to thermal stresses invoked by Cooper. The need to understand plasticity of glass network during accommodation of a larger invading ion is emphasized. In turn, the influence of network topology on its yield strength in shear as well as hydrostatic modes is recognized. For expanded applications under extreme conditions of loading, damage evolution in chemically strengthened glass needs to be studied. Such a study is linked to our understanding of the terms "strength,""hardness,""toughness," and "brittleness" of glass. © 2010 Saxon Glass Technologies Inc. Journal compilation © 2010 The American Ceramic Society and Wiley Periodicals, Inc.


Patent
Saxon Glass Technologies Inc. | Date: 2013-10-05

Chemically strengthened glass and a method for making utilizing differential time are provided. The method includes providing a substrate. The substrate includes a glass chemical structure. Host alkali ions are situated in the chemical structure. The substrate has a treatment-rich volume and a treatment-poor volume located as opposed to each other in the substrate. The method also includes providing an exchange medium including invading alkali ions having an average ionic radius that is larger than an average ionic radius of the host alkali ions. The method also includes applying the exchange medium to a surface of the treatment-rich volume for a period of time and applying the exchange medium to a surface of the treatment-poor volume for a modified period of time. The method also includes conducting ion exchange while applying the exchange medium to produce the strengthened substrate.


Patent
Saxon Glass Technologies Inc. | Date: 2013-10-05

Chemically strengthened glass and a method for making utilizing differential areal density are provided. The method includes providing a substrate having a glass chemical structure. Host alkali ions are situated in the chemical structure. The substrate has a treatment-rich volume and a treatment-poor volume located as opposed to each other in the substrate. The method also includes providing an exchange medium characterized by having an areal density, associated with an ion exchange rate, of invading alkali ions having an average ionic radius that is larger than an average ionic radius of the host alkali ions. The method also includes providing a modified exchange medium characterized by having a modified areal density, associated with a modified ion exchange rate, of the invading alkali ions. The method also includes applying the exchange mediums and conducting ion exchange to produce the strengthened substrate.


Patent
Saxon Glass Technologies Inc. | Date: 2013-10-05

Chemically strengthened glass and a method for making utilizing differential chemistry are provided. The method includes providing a substrate having a glass chemical structure. Host alkali ions are situated in the chemical structure. The substrate has a treatment-rich volume and a treatment-poor volume located as opposed to each other in the substrate. The method also includes providing an exchange medium characterized by including a composition associated with an ion exchange rate of invading alkali ions having an average ionic radius that is larger than an average ionic radius of the host alkali ions. The method also includes providing a modified exchange medium including a modified composition associated with a modified ion exchange rate of the invading alkali ions. The method also includes applying the exchange mediums and conducting ion exchange to produce the strengthened substrate.

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