In melting process of lead silicate glasses containing 70 wt% PbO, the bubble size distribution, and the manner of formation and elimination of gas bubbles of glass melt at different temperatures and times were investigated. The lead silicate glass was manufactured by melting, fritting and milling of glass powder for several stages. At first, 50 grams of lead silicate glass powder was poured into each alumina crucible for maintaining the batches separately at temperatures of 900, 950, 1000, 1050 and 1100oC for 15, 30 and 45 minutes, to study the effects of time and temperature on the bubble nucleation, growth and ascension from the lead silicate glass melt. Because of the dissolution of air molecules inside the glass melt and owing to the achievement of super-saturation, gas bubbles were nucleated and grown. Due to the density of the gradient between the gas bubbles and glass melt, the bubbles ascended to the surface of the melt where they ruptured afterwards. The density of alumina crucibles and the glass inside them were measured. The volume and the mean value of the diameter of bubbles were determined by images from the lateral cross section of glass inside crucibles and from the images taken from the surface of the bubbly glassy layer on the surface of the samples.

Background: lead glass has a wide variety of applications in radiation protection. This study aims to investigate some characteristics of lead glass such as the γ-ray energy-dependent mass and linear attenuation coefficients, the half-value layer thickness, and the absorbed dose distribution for specific energy. Materials and Methods: The attenuation parameters of different lead glass types against high-energy photons (0. 2-3 MeV) of gamma rays have been calculated by the Monte Carlo technique and a deterministic method. Besides, the depth dose distribution inside the volume of two cubic lead glass samples was calculated by two Monte Carlo-based computer codes, for gamma rays of 300 keV. In each part of the study, the results of the two methods have been compared. Results: Increasing the Pb concentration (weight in %) by 1% in the lead glass causes a 1. 6%-3% increase in the linear attenuation coefficient, depending on the energy. However, the mass attenuation coefficient does not show significant variation for different types of lead glass, especially for the energies higher than 400 keV. Moreover, almost half of the total dose from 300 keV photons will be absorbed in the first 3. 5 mm of the sample’ s thickness. Conclusion: Results indicate that the Monte Carlo technique is as reliable as the deterministic methods for calculating the attenuation characteristics of the lead glass. The provided data in this investigation can be useful for radiation protection purposes, especially in the case of selecting the lead glass type and dimension based on a specific application.

Cathode ray tube funnel glass is an environmentally problematic relict of old television sets. In particular, landfilling of this material is strongly discouraged because of its high lead content. However, recovery of this toxic lead could prevent its release into the environment and allow its reuse. In this research, lead was separated from the glass matrix by a chloride volatilization process. Melting of the funnel glass together with CaCl2 resulted in the volatilization of 80% of lead at 1,000oC. The use of NaCl as a chlorination agent yielded less volatile lead, while poly (vinyl chloride) and gaseous HCl proved to be ineffective chlorination agents. The differences in the chlorination agent efficiencies could be attributed to differences in the corresponding formation of silicates. Energy-dispersive X-ray spectroscopy showed that diffusion plays an important role in the volatilization of PbCl2.

The aim of this work is to introduce the application of a rotary kiln system to be used in enamel industry for the purpose of melting lead silicate glass. Due to low volume of lead silicate glass produces during a day or a year, and the necessity to spend a large capital investment for using customary glass melting furnaces, it was decided to apply a rotary kiln system for melting lead silicate glass. In order to be assured for the high corrosion and temperature resistance, alumina refractories were used as a refractory for the inner lining of the rotary kiln. The lead silicate glass after melting and mixing inside the kiln and fritting was grinded inside a ball mill with alumina lining and balls to a powder of mesh size finer than 75 micron. The melting, fritting and milling were repeated 5 times. The results showed that there was neither entered any impurity from the refractory particles nor observed any color and composition change due to entrance of aluminum element to the lead silicate glass melt. The homogenization of the glass composition and the removal of the bubble from the glass melt was carried out extremely well.

Introduction of the nanoparticles in the bulk glass received a large interest due to their versatile application. The composition of Er+3-doped Zinc-lead-Phosphate glass samples are prepared by melt-quenching technique. The structural and optical properties of phosphate glass have been examined by x-ray diffraction, field emission scanning electron microscopy, photoluminescence spectroscopy and UV-Vis-NIR scanning spectrophotometer. The x-ray diffraction pattern has confirmed their amorphous nature and the field emission scanning electron microscopy micrograph showed the distribution of nanoparticles in glass. The study indicates that doped SnO2 nanoparticles have an influence on the band gap energy that decreases with the increasing amount of nanoparticles.The photoluminescence spectra showed three peaks at the green-orange region of the visible spectrum and four times enhancement for doped 0.25% SnO2 nanoparticles. The enhancement in the luminescence intensity of the green-orange region is found to be due to the effective local field of nanoparticles. The optical properties motivate to use these glassed as novel luminescent optical materials.

Background and Aims: Micro leakage is a criterion proposed for assessing the success of any restorative material. Complete seal is difficult especially for dentin margins compared to enamel margins. The aim of this study was to assess the micro leakage at the enamel and dentin margins of class V cavities restored by two GIs and two self-etch adhesive systems.Materials and Methods: This study was done on forty third molars. Class V cavities (3´2´2mm) were prepared on the buccal and lingual surfaces of teeth using high speed handpiece with 0.8 mm diamond fissure burr. The occlusal margins of the cavities in the enamel and gingival margins were placed 1 mm below the CEJ. The teeth were divided into 4 groups and the bondings were cured for 20 sec and the teeth were restored. The specimens were kept in distilled water at the temperature of 37°C for 24 hrs. The teeth were thermo cycled and cut in buccolingual direction using diamond disc under water. The dye penetration was evaluated using a stereomicroscope and the leakage was scored. The scores were compared using Kruskal-Wallis test while the paired comparisons were done using Bonferroni correction. P≤0.05 was regarded as significant results.Results: Micro leakage scores were similar at the occlusal and gingival walls of all test groups. At the gingival walls, the least micro leakage scores were observed. “Fuji IX + SE bond” group showed significant differences with the “Fuji IX + G bond” and “Nano glass + G bond” groups (P£0.05). At the occlusal walls, the least scores were observed in the “Fuji IX+SE bond” specimens which were significantly different from the other groups (P£0.05).Conclusion: Self-Cure glass ionomers yielded less micro leakage scores compared to the different types of light-cures due to the less polymerization shrinkage.

Today, the use of lead-containing glasses and heavy transparent shields in various medical applications of radiation, including diagnostic radiology procedures, especially in angiography departments, has become very popular. In such departments, roof shields, transparent shields, and glasses made of lead glass are widely used for the radiation protection of personnel. In this study, the MCNPX Monte Carlo simulation code was used to design transparent and lead-free shields that can be used for radiation protection. For this purpose, two types of phosphate glass containing different percentages of heavy materials were simulated and compared with each other in terms of attenuation coefficients of photons with different energies. After simulating different glass types, the mass attenuation coefficients of each sample were calculated for single-energy photons. After that, by simulating the X-ray spectra used in angiography, the thicknesses of the first and second half-value layers were calculated for each spectrum. The results of this study show that the simulated values of the mass attenuation coefficient of glass types show good agreement with the results of XCOM. According to the results, the designed lead-free glass types have an attenuation comparable to leaded shields, which can be used as a suitable alternative to leaded glass types.