M. Suszynska

Optical studies in gamma-irradiated commercial soda–lime silicate glasses

Optical absorption measurements of gamma-irradiated (60Co) commercial soda–lime silicate (SLS) glasses were performed at room temperature (RT) to detect and characterize the induced radiation damage in these materials. Isothermal bleaching (RT–723K) of the radiation-induced defects, followed the irradiation of samples. In glasses containing different amount of the glass-network modifiers (Na2O,K2O) and some multivalent transition metal cations (Fe2+/Fe3+,Ni2+ and/or Mn2+) three absorption bands have been distinguished in the wavelength region extending from 250 to 1800 nm. In contrast to the electron-type color centers, detected at low temperatures for X-irradiated nominally pure sodium silicates [1], we propose that the absorption bands found for gamma-irradiated SLS glasses are induced by some hole-type color centers related with nonbridging oxygen ions (NBO−) located in different surroundings. The radiation-induced enhancement of diffusivity of ions together with bond breaking and defect creation in the glass-network could give materials with well-defined nonlinear optical properties.

Microstructure and silver nanoparticles in ion-exchanged and deformed soda-lime silicate glasses

Abstract Optical absorption, microspectrophotometry, thermally stimulated depolarization current, and transmission electron microscopy were applied to a commercial multicomponent soda-lime silicate glass subjected to the Na + ⇔Ag + ion-exchange, annealing in air or hydrogen, and to mechanical stretching. The treatments affect both the matrix microstructure and the morphology of the silver particles. Mechanical stretching of the exchanged specimens annealed in hydrogen induces the most interesting effects. Secondary phase separation occurs within the glassy matrix, and causes drastic changes of the thermocurrent data, which are interpreted in terms of the Maxwell–Wagner interfacial polarization. Elongation of the spherical silver nanoparticles produces a remarkable dichroism of the optical absorption, which could be exploited for new applications. The sample stretching affects only particles with a diameter larger than 5 nm interpreted as a threshold size, at least at the stresses used in the present work.

Some effects of γ-irradiation in soda-lime silicate glasses

Abstract Nanosized metallic silver particles have been formed in multicomponent commercial soda-lime silicate glasses partly substituted with ionic silver and irradiated at room temperature by γ-rays from a 60Co-source (1.33 MeV). To characterize the obtained composites, combined measurements of thermally stimulated depolarization current and optical absorption, accompanied by microspectrophotometric analysis and electron microscopy observations have been used. It has been shown that γ-irradiation might be an effective means to modify and control the concentration, size and spatial distribution of the dopant within the near-surface layer of the glass-matrix. This procedure also allows the conversion of some glassy areas in this region into a partially crystalline material with improved mechanical characteristics.

FORMATION OF SILVER COLLOIDS ON ION EXCHANGED SODA LIME SILICATE GLASSES BY IRRADIATION

Abstract The effect of ionizing radiation (gamma rays, X-rays and electrons) on soda lime silicate glasses, in which part of the Na+ was substituted by Ag+ by means of an ionic exchange process, was studied. The techniques of thermally stimulated depolarization current (TSDC) and transmission electron microscopy (TEM) were employed to follow the formation of silver colloids by irradiation. Also the thermoluminescence (TL) of the samples was measured and three peaks between room temperature and 450°C were observed. The TEM and TSDC results agree that, as expected, ionizing radiation promotes the formation of silver colloids on the ion exchanged surface of soda lime glasses. Soft X-rays are much more efficient in the process than gamma rays and electrons. The correlation with thermoluminescence glow curves indicates that the intensity of a TL peak at 230°C can provide a rapid means of evaluating the presence of silver colloids. TL sensitivities, measured as area under the glow curve per unit mass and unit dose, are very similar for ion exchanged and not exchanged samples submitted to X-ray irradiation, although the peak temperatures differ in about 40°C in the two cases. For both electron and gamma irradiated samples, the TL sensitivity drops about an order of magnitude when compared to the X-ray irradiated ones.

Mechanical characteristics of mixed soda-lime silicate glasses

Abstract The Vickers hardness number and the crack-formation resistance were determined for soda-lime silicate glasses (SLS) subjected to chemical treatment either in AgNO 3 +NaNO 3 or in a KNO 3 bath. The effectiveness of the Na + ⇄Ag + ion exchange process was modified by thermal treatment of the samples. It was found that partial substitution of the mobile Na + ions either by Ag + or K + ions results in a strengthening of the SLS glasses, while the effect of potassium is larger than that induced by silver, although the radius of both ions is nearly the same.

Preparation and optical properties of soda-lime silicate glasses partially substituted by copper

The ion-exchange process was used to introduce copper ions into soda lime silicate glasses (SLS), the composition of which corresponds to the miscibility gape in the Na 2 O-SiO 2 system. The samples have been immersed either in a molten Cu 2 Cl 2 or CuCl 2 at various temperatures from the range 720-940 v K for different time. The observed green colour of glass is related with the 790-nm absorption band related to the cupric ions. The annealing either in air or in the hydrogen atmosphere was used for the reduction of copper. The effectiveness of these procedures was analysed on a basis of the penetration profiles monitored by roentgenographic methods (diffraction and EDAX). Transmission electron microscopy (TEM) observations of the replicated surface and common optical absorption measurements have been used to study the morphology of the dopant ions.

Sodium motion in phase-separated and silver-exchanged soda-lime silicate glasses

Abstract Thermally stimulated depolarization currents, absorption microspectrophotometry and electron microscopy were used to characterize soda-lime silicate glasses with droplets of the Na2O-rich phase distributed within the SiO2-rich matrix and with nanosized particles of elemental silver. It has been shown that the detected polarizations are mainly of interfacial type related with different modes of the Na+ motion affected by the dopant as well as thermal and mechanical treatments of samples.

Radiation-induced effects in soda-lime silicate glasses of different origin

Abstract Correlated measurements of optical absorption and thermoluminescence of γ-irradiated soda-lime silicate (SLS) glasses were performed to detect and characterize the induced radiation damage in these materials. Three kinds of hole-type defect centers have been distinguished in glasses which differ with respect to the content of the glass-network modifiers and some multivalent transient metal cations. The main features of the related absorption bands are compared and discussed in terms of the purity and pre-irradiation history of samples.

Optical and electrical characterization of silver nanoparticles in soda lime silicate glasses

Optical absorption microspectrophotometry, thermally stimulated depolarization currents, and transmission electron microscopy were applied to characterize soda lime silicate glasses, in which Na was partially substituted by Ag, by means of an ion exchange process. The role of the exchange parameters (bath composition, time and temperature) and of annealing on the penetration depth and size-distribution of the silver nanoparticles was analysed. The TSDC spectra show up to three peaks in the range 200-450 K: the two main ones are in the ranges 280-290 K and 310-370 K, respectively. The latter is very sensitive to silver concentration, thermal annealing, and poling procedure and could be related to interfacial polarization effects.

The colouration by 60 Co-gamma rays of NaCl and KCl crystals doped with europium ions

Pure and europium doped NaCl and KCl crystals have been irradiated with 60 Co gamma rays and with ultraviolet light. The dose was 10 v kGy and temperatures during irradiation were ambient and liquid nitrogen. The effects of irradiation are determined using optical absorption and thermoluminescence. The role of the europium dopant is compared for the two materials. Factors investigated include the temperature of irradiation, the concentration of the dopant and the state of impurity aggregation and precipitation. A link is indicated between impurity precipitates and UV stimulated thermoluminescence.