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In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review. [ABSTRACT FROM AUTHOR]

In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review.

Featured Application: The paper describes a method allowing to control the chemical strengthening of glass by the ion exchange method. Process control is very simple; it comes down to current temperature measurements. The proposed method can find applications in industrial processes. The paper presents the results of tests on stresses produced by the K+↔Na+ ion exchange method in BK7 glass. Diffusion ion exchange processes were carried out in glass plates with a surface area of a few cm2. The duration of these processes ranged from several hours to several hundred hours; process temperatures from 370 to 402 degree Celsius were used. The area of the glass in which the ion exchange took place shows refractive changes which are also accompanied by stresses. The planar waveguides produced in this way were tested by optical methods (for wavelength λ = 677 nm) and the refractive index profiles for the Transverse Electric (TE) and Transverse Magnetic (TM) polarization states were determined. On the basis of elasto-optic constants, the resulting stresses were determined. The temperature characteristics of diffusion coefficients of exchanged ions were also determined. Based on them a numerical simulation of real-time diffusion processes was possible, which allowed to predict the stresses arising in the glass. A good agreement between these predictions and the results of measurements was obtained. [ABSTRACT FROM AUTHOR]

Monovalent cations enable efficient ion-exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical, or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda-lime-silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+, and Cs+) by drawing relations to physicochemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion-exchange rate.

The paper presents the results of tests on stresses produced by the K+↔Na+ ion exchange method in BK7 glass. Diffusion ion exchange processes were carried out in glass plates with a surface area of a few cm2. The duration of these processes ranged from several hours to several hundred hours; process temperatures from 370 to 402 degree Celsius were used. The area of the glass in which the ion exchange took place shows refractive changes which are also accompanied by stresses. The planar waveguides produced in this way were tested by optical methods (for wavelength λ = 677 nm) and the refractive index profiles for the Transverse Electric (TE) and (space necessary) Transverse Magnetic (TM) polarization states were determined. On the basis of elasto-optic constants, the resulting stresses were determined. The temperature characteristics of diffusion coefficients of exchanged ions were also determined. Based on them a numerical simulation of real-time diffusion processes was possible, which allowed to predict the stresses arising in the glass. A good agreement between these predictions and the results of measurements was obtained.

This paper presents the technological aspect of application of the ion exchange method in producing gradient refractive index in glass. The possibility of predictable and repeatable producing of the changes in glass refraction with the use of this method has been presented, as well as the method of in situ control of the process of diffusion doping of glass based on the measurement of the temperature. This method is based on simultaneous (to the carried process) solving the nonlinear diffusion equation modeling the spatio-temporal changes in normalized concentration of the admixture ions in glass. For this purpose the knowledge of temperature characteristics of diffusion coefficients of exchanged ions is used. The result of such control of diffusion processes is information on the current (temporary) refractive index profile of the resulting waveguide. The presented method of control has been confirmed by experimental results, which concern modeling and measurements of planar waveguide structures of slab type. The proposed methodology can also be used to control the diffusion processes of producing another type of two- and three-dimensional gradient structures. According to the author's knowledge the method mentioned above has not been described in literature before. [ABSTRACT FROM AUTHOR]