Field-assisted Ion Exchange Research Articles

Simulation of field-assisted ion exchange in glass regarding the space-charge density and pseudo-mixed-alkali effect: erratum.

This erratum reports corrections for the original publication, Appl. Opt.60, 6632 (2021)APOPAI0003-693510.1364/AO.427171.

Electric-field assisted ion-exchange of innovative float glass

Electric field-assisted ion exchange process was carried out on an innovative soda magnesia silicate float glass by using a specifically realized equipment which allows to change the applied voltage and the polarity and to measure the flowing current.Parameters such as surface K/Na exchange rate, potassium penetration, inter-diffusion coefficient, residual stress and case depth were measured and correlated with the processing conditions. The results revealed a high propensity of the considered glass to be chemically strengthened and a beneficial effect of the applied electric field in terms of time and temperature. For treatment carried out at 410 °C potassium penetration depth in excess to 10 μm can be achieved in less than 5 min. By alternating the polarity, both sides can be homogeneously reinforced. When the duration of each single cycle at a certain polarity is increased, the potassium penetration depth increases although cycles longer than 10 min can be detrimental.

Asymmetric optical multimode splitters by field-assisted ion exchange using patterned mask openings.

Asymmetric optical multimode splitters based on optical waveguides were fabricated in glass substrates using a field-assisted ion exchange process. Accompanying simulations, conducted to study the light propagation, revealed the possibility to realize asymmetric splitters based on waveguides with different width. In the exchange process, broad mask openings in the blocking layer are compared to those consisting of closely spaced parallel lines with various widths. The waveguide profiles of the resulting splitters were recorded and the optical losses and splitting ratios were determined for a wavelength of 850 nm. Additionally data transmission tests were conducted and showed the suitability of the splitters for a bandwidth of 28 GBit/s.

Solid-state field-assisted ion exchange of Ag in lithium aluminum silicate glass-ceramics: A superfast processing route toward stronger materials with antimicrobial properties

Lithium-aluminum-silicate glass-ceramics (LAS) are of pivotal relevance in various applications as they combine excellent mechanical and functional properties. Due to their use in medical devices and cooking articles, antimicrobial properties are obviously of interest.Herein, we report the solid-state field-assisted (Ag→Li,Na) ion exchange in LAS glass-ceramics containing β-quartz and β-spodumene solid solutions. The ion-exchange is extremely rapid and deep silver penetration (>100 μm) can be achieved within a few minutes (<5 min), this being proportional to the treating time and applied current. The elemental profiles are characterized by a relatively complex shape which reflects the different alkali mobility in the different phases. The ion exchange initiates structural modifications involving: (i) β→α transition in spodumene; (ii) formation of lattice microstrain and quartz cell expansion; (iii) substantial changes in the IR absorption spectra. The obtained materials possess improved resistance to crack formation and antimicrobial activity against Staphylococcus aureus.

Simulation of field-assisted ion exchange in glass regarding the space-charge density and pseudo-mixed-alkali effect.

A model is proposed to describe the field-assisted molten salt ion exchange of Na+ with Ag+ in glass. It accounts for the buildup of space-charge zones and for the pseudo-mixed-alkali effect. Simulations in 1D proved to be consistent with experimental results. The 1D model has been expanded to 2D, making it suitable for simulating the fabrication of channel waveguides. Using a first-order approximation, a good agreement between the simulations and the experimental data can be achieved.

Conventional and electric field-assisted ion exchange on glass-ceramics for dental applications

Ion exchange can be used to mechanically reinforce dental glass-ceramics to reduce the problems associated to the flaws created upon various processing steps and handling. This work introduces a novel ion exchange method to the field of dental glass-ceramic to increase the possibilities of preparing highly reliable glass-ceramic restorations. The aim of the study was to compare Electric Field-Assisted Ion Exchange with conventional method, for newly developed nepheline based dental glass-ceramic. Multicomponent glass system was synthesized using melt-quench method and then prepared into glass-ceramic specimens via powder sinter-crystallisation route. The prepared glass-ceramic specimens were tested for bi-axial flexural strength before and after ion exchange according to the dental ceramics ISO 6872:2015. Ion exchange process was carried out in molten potassium nitride and the potassium penetration depth determined by EDXS was found greater and occurring in a matter of minutes within the nepheline crystal structure during electrical field assisted ion exchange compared with several hours of conventional treatment. The newly developed nepheline glass-ceramic system and the results achieved by electrical field assisted ion exchange may renew the ion exchange concept for dental application.

Solid state field-assisted silver ion exchange in porcelain stoneware: A new route toward antimicrobial tiles?

The development of tiles possessing antimicrobial activity is of great technological and scientific interest to improve the functionality of a very widely used article. Also the current SARS-CoV-2 pandemic is drawing the attention towards materials or compounds able to inactivate the virus, silver being among all the most promising one.In the present work, field-assisted ion exchange process was used to functionalize porcelain stoneware by introducing silver into the material surface using a solid silver electrode. The application of a small direct electric current (10 mA cm−2) at 380 °C allowed to fasten silver diffusion. The penetration of silver into stoneware appears homogeneous and primarily involves an exchange between silver and sodium ions under the effect of the external electric current. Penetration depths approaching 120 μm can be obtained in only 5 min. Preliminary characterization revealed that the Ag-exchanged stoneware possesses a strong biocidal action against Staphylococcus aureus.

Sodium-caesium electric field assisted ion exchange in a mixed-alkali (Na, K) lime silicate glass

In this study, sodium exchange for caesium in a mixed alkali lime silicate glass was carried out using electric field-assisted ion exchange (EF-IE). Na/Cs exchange was realised by applying electric fields up to 2000 V cm−1 for 5 min on glass tubes immersed in molten CsNO3 at 460 °C. The chemical concentration profiles measured near the glass surface showed a bilayer concentration profile which comprises caesium and potassium-rich layers, the formation of the potassium-rich layer being associated with the different mobility of alkali ions. Nanoindentation analysis outlined that surface layer produced by Na/Cs ion-exchange is characterised by poorer mechanical properties than Na/K ion-exchanged layer. Raman spectroscopy investigation revealed that the Na/Cs ion-exchanged layer has a denser structure with respect to raw glass, this being responsible for the different mechanical properties.

Electric field assisted ion exchange of silver in soda-lime glass: A study of ion depletion layers and interactions with potassium

The introduction of silver ions into glass by diffusion from an external source is of interest in modifying the optical and electrical properties of glass for device applications. Silver is introduced to fabricate in-glass waveguides, while potassium ions are introduced to pattern the silver diffusion by locally impeding the diffusion. Electric fields assist the silver diffusion, leading to faster diffusion rates of ions and allowing greater concentrations of silver without a metallic cluster formation. However, ion depletion layers are formed in the glass as a result of the application of electric field. Here, we study the nature of these depletion layers using depth profiles of composition after electric field diffusion, using cross-sectional energy dispersive x-ray spectroscopy analysis and infrared spectroscopy (Fourier transform infrared attenuated total reflection spectroscopy). We confirm the accelerated diffusion of silver by an electric field and show that potassium impedes the diffusion of silver even when a field is present. We find that an ion depletion layer is formed below the glass surface by the applied electric field which leads to a thermal relaxation and depolarization process when the samples are reheated. Observation of this process enables activation energies and threshold temperatures for the diffusion of Ag, K, and Na to be evaluated and compared with values obtained by composition profiles. Potassium was found to increase the initially low temperature threshold for silver diffusion, increase the activation energy, and also impede sodium diffusion.

Influence of electrode shape/location on silver doping phenomena during field-assisted solid-state ion exchange

Influence of electrode shape/location on silver doping phenomena during field-assisted solid-state ion exchange

Dendritic growth of silver nanowires in borosilicate glass formed by field-assisted solid-state ion exchange

The additive voltage application provides silver nanowires in silver-doped glass prepared by electric field-assisted solid-state ion exchange. We experimentally investigate the growth behavior of silver nanowires in a glass substrate. It was found that silver nucleation was initiated at the silver-doped surface contacted with the cathode, and the precipitates dendritically developed toward the doped/un-doped interface as the time of voltage application was increased. After the precipitates reached the interface, the growth direction changed and extended along the interface. Transmission electron microscopy (TEM) observation suggested that the precipitation did not arise from the aggregation or growth of nanoparticles formed in the silver doping process. The experimental results, where the precipitation occurred just below the contacted cathode and was independent of cathode material, indicated that the precipitation resulted from the electrochemical interaction between doped silver ions and supplied electrons. From these findings, we are able to control the silver nucleation area by the arrangement of the cathode configuration.

Formation of Multilayered Conductive Paths in the Borosilicate Glass by Electric Field-Assisted Solid-State Ion Exchange

Formation of Multilayered Conductive Paths in the Borosilicate Glass by Electric Field-Assisted Solid-State Ion Exchange

Transmittance properties and TEM observation of metal doped glass by field-assisted ion exchange

Metal (silver or copper) ions were doped into borosilicate glass using an electric field- assisted ion exchange method. The optical transmittance of the metal doped glass was measured to determine why the doped glass exhibited an excellent laser micro-machinability. The doped metal ions were found to have enhanced the optical absorption of the glass, especially in the ultraviolet range. This in turn facilitated the efficient absorption of incident laser irradiation, and hence improved laser machinability of the glass. The metal doped glass also exhibited some absorption in the visible range, leading to a slight yellow-brown coloration. Transmission electron microscope (TEM) observations indicated that the metal ions had penetrated the glass and therein formed nanometer-sized (~6 nm) fine particles. In an attempt to control the optical characteristics in the ultraviolet-visible range, metal doped glass was heat-treated following the ion exchange doping step. In the case of silver-doped glass with heat treatment at 723 K, silver nanoparticles aggregated locally yielding an inhomogeneous structure. The heat-treated samples had a high optical absorption in the ultraviolet range.

Generation of silver nanoparticles with controlled size and spatial distribution by pulsed laser irradiation of silver ion-doped glass

Silver ions were driven into glass by a direct current electric field-assisted ion exchange technique. The silver ion exchanged glass was then irradiated by laser pulses of 10 ns and 10 ps in length at 355 nm for comparison purposes. In both cases, laser irradiation led to the formation of a metallic-like film at the surface of the ion exchange glass. Scanning electron microscopy showed that the films consist of a very dense single layer of silver nanoparticles with similar particle sizes and separation. Irradiation with different laser parameters shows no significant difference in transmission spectra and modification width between ps- and ns-pulsed lasers. Particle sizes and separation at the surface are increasing with increasing laser power, and are larger for picosecond pulsed laser irradiation. It is also shown that the film formation is a thermal process.

固体イオン交換法によるレーザ加工用ガラスの開発

固体イオン交換法によるレーザ加工用ガラスの開発

Glass structure modifications induced by diffusion of chromium ions into silicate glasses: An investigation by in-depth profiling Raman micro-spectroscopy

The diffusion of chromium from thin metallic films into soda-lime and borosilicate glass matrices is investigated by micro-Raman spectroscopy. The process is attained by simple thermal heating of the samples or by field-assisted solid state ion-exchange (FASSIE) at temperatures ranging from 400 to 500°C. In-depth analyses are performed by means of micro-Raman spectroscopy on sample cross sections. Glass microstructure and network connectivity are studied from the intensity and the positions of the features related to the bending and stretching vibrational modes of the structural units of silica and from the position of the boson peak.

Optical analyses of the formation of a silver nanoparticle-containing layer in glass

We present results of our observations on the formation of a silver nanoparticle-containing layer in glass over time. First, silver ions are driven into the glass by field-assisted ion exchange at 300 °C. A following annealing step at 550 °C resulted in the formation of silver nanoparticles (< 4 nm in diameter). This annealing was performed for five different durations (1h, 2h, 4h, 8h, 48h), and thin slices of the cross sections of the glasses have been prepared. The sequence of slices showed the growth of the nanoparticle-containing layer over time. Transmission spectra of the slices have been measured with a spatial resolution of 1.5 µm. Simulating spectra using the Maxwell-Garnett theory allowed us to determine the volume filling factor distribution of the nanoparticles across the layers. A first attempt to simulate the diffusion of silver is performed.

907 金属添加ガラス中の金属微粒子の存在形態に関する研究

907 金属添加ガラス中の金属微粒子の存在形態に関する研究

Homogenous silver-doped nanocomposite glass

Silver nanoparticles are generated in glass by a dry process. First silver ions are driven into the glass by electric field-assisted ion exchange. Subsequent annealing in air led to the formation of silver nanoparticles beneath the surface of the glass. A thin slice of the cross section of the sample was prepared. This visualization of the depth profile facilitated optical analysis of the embedded layer containing silver nanoparticles to be preformed. We observed that there were narrower plasmon bands close to the sample surface and wider plasmon bands in lower layers. It is attributed to the formation of larger nanoparticles with lower number density close to the surface and slightly smaller nanoparticles with higher number density in the depth of the sample.

Chromium doping of silicate glasses by field-assisted solid-state ion exchange

Field-assisted solid-state ion exchange (FASSIE) is a suitable way to dope glasses with metallic ions. This approach is a promising technique for the production of glass waveguides containing either bivalent or trivalent ions, allowing the doping of glass surfaces with multivalent ions which could not diffuse into the glass matrix by means of the usual thermal ion-exchange process in molten salt baths. In this paper, results on the diffusion of chromium in silicate glasses are presented. A metallic chromium film deposited on the top of the glass substrates was used as the metal ions supplier. The doped layers were investigated by secondary ion mass and Rutherford backscattering spectrometries, as well as by micro-Raman spectroscopy. Chromium entered the glass matrices for some hundreds of nanometers, depending on the process temperature and the applied electric field. Strong compositional modification of the treated glasses was detected, related to alkali and alkali-earth elements distribution. For field-assisted solid-state diffusion, borosilicate glasses seem to be more stable matrices than the soda-lime silicate ones.