Sintering/Crystallization and Viscosity of Sealing Glass-Ceramics

Two glass-ceramics sealants for solid-oxide fuel cells (SOFC) in the system BaO/SrO-MgO-B2O3-SiO2 have been analysed according to relevant sealing parameters such as sintering and crystallization of the glass powders and dilatation and viscosity evolution with crystallization of glass-ceramic compacts. Special emphasis is given to the crystallization kinetics and mechanism, crystalline phases formed and the role of viscosity in the whole sealing process. The slower crystallization rate of the strontium-containing glass composition results in good joining with the interconnect steel before the glass starts to crystallize and increases its viscosity. This avoids and excessive sealing temperature and offers better compatibility with the start up and working temperature of an SOFC (750–850 °C).

Glass-Ceramic Synthesis of Cr-substituted Strontium Hexaferrite Nanoparticles with Enhanced Coercivity

Magnetically hard ferrites attract considerable interest due to their ability to maintain a high coercivity of nanosized particles and therefore show promising applications as nanomagnets ranging from magnetic recording to biomedicine. Herein, we report an approach to prepare nonsintered single-domain nanoparticles of chromium-substituted hexaferrite via crystallization of glass in the system SrO–Fe2O3–Cr2O3–B2O3. We have observed a formation of plate-like hexaferrite nanoparticles with diameters changing from 20 to 190 nm depending on the annealing temperature. We demonstrated that chromium substitution led to a significant improvement of the coercivity, which varied from 334 to 732 kA m−1 for the smallest and the largest particles, respectively. The results provide a new strategy for producing high-coercivity ferrite nanomagnets.

Ferrosilicate glass ceramics based on wastes from ore concentration

We showed in this work that there is a possibility of recycling the wastes derived from iron ore concentration by using glass technology. The compositions of new glass ceramics with high technological and decorative properties were developed. The influence of Al2O3, MgO and Na2O additives to the waste from ore benefication on the parameters of the synthesized glass and its crystallization products was studied. The optimal temperatures of synthesis, annealing and crystallization of glass samples in the systems (Fe2O3–FeO)–SiO2–Al2O3–Na2O and (Fe2O3–FeO)–SiO2–Al2O3–MgO were shown to be 1450100С, 500–6000С and 700–8000C, respectively. It was established that the redox conditions of crystallization of glasses in the system (FeO–Fe2O3)–SiO2–Al2O3–Na2O strongly affect the nature of the iron-containing phases that are formed: oxidative conditions favors the formation of hematite (Fe2O3) and aegirinite (Na2OFe2O34SiO2), whereas reducing conditions contributes to the formation of wustite (FeO) and fayalite (2FeOSiO2). In the system (FeO–Fe2O3)–SiO2–Al2O3–MgO under both oxidative and reducing conditions of crystallization, the same crystalline phases appear: olivine (2(Mg,Fe)OSiO2), hercin (FeOAl2O3) and iron metasilicate (FeOSiO2). It was shown that the crystallization of samples under reducing conditions allows producing materials with higher microhardness. The surface layer of glasses and glass ceramics exhibited less microhardness than their deep layers.

Space-selective crystallization of glass by an optical vortex beam

We report on the improvement of ultrafast laser-written track quality by using an optical vortex.