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Foamed glass preparation is a complex combination of reactions, greatly influenced by the composition of the used glass and often hindered by simultaneous crystallization. The crystallization phenomenon is undesirable in foamed glass production since it decreases the quality of the final product. In this work the influence of different types of additives (foaming agents, flux agents, crystallization inhibitors and nucleating agent) on the crystallization of waste container glass and properties of the sintered samples (density and thermal conductivity) was studied. Results of our study confirmed partial crystallization during sintering stage. We found that waste container glass manifests complex crystallization with the formation of four main crystalline phases, which can be inhibited with the addition of fluxing agents (B 2 O 3 and borax). Moreover, here we show that prevention of the crystallization can lead to a significant decrease of the thermal conductivity. [ABSTRACT FROM AUTHOR]

The crystal growth rate of La2SrB10O19 in an undercooled melt of stoichiometric composition was studied. The crystallization of the bulk samples was performed in a single-stage regime under isothermal conditions at the selected temperatures for the different time periods. The surface crystallization was observed and in all crystallized samples, the La2SrB10O19 crystalline phase was identified. Based on the dependence of the crystalline layer thickness on treatment time at selected temperature, crystal growth rate was obtained. The crystal growth rates were from 1.65 × 10−8 to 2.77 × 10−7 m s−1 in the temperature interval (700–780 °C). The experimental values were compared to the calculated values using theoretical model of the crystal growth. The experimental growth rate followed the same trend as the calculated growth rate, but the experimental values were higher than the calculated. [ABSTRACT FROM AUTHOR]

The peculiarities of sinter-crystallization of La 2 O 3 ·SrO·5B 2 O 3 fine glass powder (below 1 μm) are investigated and discussed. The sintering was studied by contactless optical dilatometry and porosity measurements. The crystallization process was evaluated by differential scanning calorimetry (DSC) and the crystalline phase formation was analyzed by X-ray diffraction (XRD). Finally the microstructures of the samples sintered at different temperatures were observed by field emission scanning electron microscope (FESEM). The specific aim of this study was to highlight the influence of sintering temperature and heating rate on the densification process and the final structure of glass-ceramic samples. It was shown that zero water adsorption and minimum closed porosity of ~ 3% were obtained at heating rate of 2 °C/min and at about 1 h holding at 690 °C. The temperature increase accelerated intense foaming process that resulted in formation of total porosity of 35–45%. It was also demonstrated that the foaming depended on the heating rate: the higher the heating rate – the more intensive was the bloating. The observed foaming process was related to intensive crystallization and re-crystallization of La 2 O 3 ·SrO·5B 2 O 3 crystal phase. The phase formation processes entirely completed after 30–60 min at 730–740 °C with the formation of intriguing and unusual crystal structures. [ABSTRACT FROM AUTHOR]

The selected lanthanum-strontium borate glasses were prepared by a conventional melt-quenching technique. The compositions of the investigated glasses were chosen to be: 5.7, 9.5, 14.3, 19.1 mol% for La2O3, 22.9, 19.1, 14.3, 9.5 mol% for SrO and 71.4 mol% for B2O3. The density, molar volume, oxygen molar volume, oxygen packing density, oxygen/boron ratios and structural transformations in the glass network were investigated according to the substitution of SrO by La2O3. The density and the molar volume increased in parallel with La2O3 content increase. Simultaneously, oxygen molar volume values increased while the oxygen packing density values decreased. A hot stage microscope (HSM) and a differential thermal analysis (DTA) were used to determine the characteristic temperatures. By increasing the content of lanthanum, the glass transition temperatures, changed with the same trend as the molar volume. Glass stability parameters were calculated from the temperatures obtained by DTA and HSM. The HSM results were used to obtain the viscosity curves by applying the Vogel-Fulcher-Tamman (VFT) equation. [ABSTRACT FROM AUTHOR]

The aim of this research was to show the way in which media in Serbia show the church and religion. Unprofessional reporting can lead to the most troublesome confli-ct in one country, the region and beyond. Pages of historical significance are full of in-ter-religious conflicts, and because history repeats, similar events are still happening. Problem is that people don 't care a lot. The paper contains few analazyed examples ta-ken from existing media, as well as the conclusion of the research that online media are seeking a greater number of readers, but they do not think enough about the consequen-ces on public opinion. [ABSTRACT FROM AUTHOR]

Abstract: Glasses with a constant B2O3 and an increasing La2O3 content in the system La2O3–SrO–B2O3 were obtained by the usual melt quenching procedure. The crystallization and sinterability of the glasses were investigated by hot stage microscopy (HSM), differential thermal analysis (DTA), X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD analysis of the bulk samples evidenced the formation of the crystalline phases: La2SrB10O19, SrB6O10 and SrLaBO4. XRD and TEM/SAED analyses showed a polymorphic crystallization of the glass sample containing 14.3mol% La2O3 with precipitation of the La2SrB10O19 phase. SEM analysis confirmed the surface crystallization mechanism of this sample. The kinetics of crystallization of the same sample was examined by DTA and the activation energy of crystal growth was calculated by the Kissinger model to be E a=458±63kJmol–1. [Copyright &y& Elsevier]

• Sinter-crystallization of La 2 O 3 •SrO•5B 2 O 3 nano glass powders is studied. • The sintering entirely completes before the crystallization. • During the crystallization, due to gas release, foaming starts. • The formation of two quite different crystal structures is observed. Sintering, crystallization and foaming of nano glass powders with composition La 2 O 3 •SrO•5B 2 O 3 were studied by hot stage microscopy (HSM) and simultaneous thermal analysis (DTA-TG) under non-isothermal regime at 10°C/min and by optical contactless dilatometer under isothermal conditions at 700 °C up to 10 hours for different times. After the thermal treatments, specimens were characterized by gas pycnometry, X-ray Powder Diffraction (XRD) and Field Emission Scanning Electron Microscopes (FE-SEM). The results demonstrate that the densification completed before the crystallization process, thus forming well sintered samples. Then, during the phase formation gas is released, which leads to foaming process. After holding of 160 minutes at 700°C the degree of crystallization reached about 0.8 and the foaming stopped. The obtained sample had high closed porosity and quite intriguing structure composed of two fairly different crystal arrangements. The first was "sponge-like", while the second was denser and consisted of "sheets", 10-30 nm thick. The subsequent holding led to re-crystallization, formation of larger denser zones that reached even 10-15 µm and an increase in open porosity. These results highlight that in the case of sinter crystallization of nano powders, some intriguing features can be expected. [ABSTRACT FROM AUTHOR]

Melt-quenching method was employed for obtaining a glass-ceramic with the following composition 42P 2 O 5 ·40CaO·5SrO·10Na 2 O·3TiO 2 (mol%) glass. The crystallization and sintering behavior of glass have been studied by using DTA, HSM, XRD, FTIR and SEM methods. It was determined that the surface and volume crystallization mechanisms act simultaneously in bulk glass samples. The comparison of DTA and HSM data revealed that the sintering and crystallization processes are independent. The sintered calcium phosphate glass-ceramic which contained bioactive β-Ca 3 (PO 4 ) 2 and β-Ca 2 P 2 O 7 phases was successfully prepared. It was determined that during crystallization the primary phase in the precipitate was β-Ca(PO 3 ) 2. Other phases appearing in the resulting glass-ceramic were: α-Ca 2 P 2 O 7 , γ-Ca 2 P 2 O 7 , Ca 4 P 6 O 19 and CaHPO 4 (H 2 O) 2 . Crystalline phases containing Sr and Ti were not detected. SEM analysis of the glass-ceramic microstructure revealed surface crystallization of glass particles and plate-like morphology of crystal growth. The result of the in vitro bioactivity showed that no apatite layer was formed on the surface of the as-prepared glass-ceramic samples after immersion in the simulated body fluid (SBF). [ABSTRACT FROM AUTHOR]

In this work, the dissolution behavior of a polyphosphate glass, with the composition 45P2O5·3SiO2·25K2O·15CaO·10MgO·ZnO·MnO (mol %), in simulated body fluid (SBF) at a temperature of 37 °C for different times was studied. Two powder sizes of the glass (granulation: 0.1-0.3 and 0.3-0.65 mm) and the bulk glass were investigated. The dissolution experiments were conducted under stationary conditions. Changes in the normalized mass release, normalized concentration of ions, pH values, and surface morphology were determined as a function of the dissolution time. The initial rates of glass powder dissolution and leaching of ions, as well as the diffusion coefficient of cations and the releasing rate of ions, during the hydrolysis process of glass were determined. It was shown that the investigated phosphate glass dissolves in SBF incongruently, with neither precipitation nor the formation of newly potentially toxic compounds, in a dissolution period 720 h. [ABSTRACT FROM AUTHOR]

In this work, the dissolution behavior of a polyphosphate glass, with the composition 45P2O5·3SiO2·25K2O·15CaO·10MgO·ZnO·MnO (mol %), in simulated body fluid (SBF) at a temperature of 37 °C for different times was studied. Two powder sizes of the glass (granulation: 0.1-0.3 and 0.3-0.65 mm) and the bulk glass were investigated. The dissolution experiments were conducted under stationary conditions. Changes in the normalized mass release, normalized concentration of ions, pH values, and surface morphology were determined as a function of the dissolution time. The initial rates of glass powder dissolution and leaching of ions, as well as the diffusion coefficient of cations and the releasing rate of ions, during the hydrolysis process of glass were determined. It was shown that the investigated phosphate glass dissolves in SBF incongruently, with neither precipitation nor the formation of newly potentially toxic compounds, in a dissolution period 720 h. [ABSTRACT FROM AUTHOR]

The crystallization and sintering behaviors of polyphosphate glass doped with trace elements Zn and Mn were examined. The heating experiments on bulk and powder glass samples were performed. The parent glass revealed low crystallization ability and the glass crystallization carried out under simultaneous acting of the surface and volume mechanisms. The bulk glass sample isothermally heated at T = 500 °C commences to crystallize after 12 h, and KPO and CaKPO crystalline phases appeared. The dendritic morphology of the crystals growing on sample surface was determined. The DTA and HSM results showed that the sintering and crystallization processes are independent. Phosphate glass-ceramics containing KPO, KMg(PO), Ca(PO) and KCa(PO) crystalline phases has been prepared by sintering of the glass powder compacts at T = 500 °C for t = 12 h. A plate-like morphology of crystals which grow on glass grains surface was observed. The activation energies of crystal growth, E = (246.6 ± 19.74) kJ mol (Kissinger) and E = (258.80 ± 19.70) kJ mol (Ozawa), were calculated. [ABSTRACT FROM AUTHOR]