The devitrification of glasses with composition 50GeO2-40PbO-10PbF2-xREF3, RE = Gd, Eu, 0 3+: β-PbF2 nanocrystals embedded in a glassy oxide matrix. This transformation is investigated using thermal analysis, X-ray d...The devitrification of glasses with composition 50GeO2-40PbO-10PbF2-xREF3, RE = Gd, Eu, 0 3+: β-PbF2 nanocrystals embedded in a glassy oxide matrix. This transformation is investigated using thermal analysis, X-ray diffraction and electron microscopy. A comparison with RE3+: β-PbF2 ceramics prepared by standard ceramic techniques is performed. The Rare Earth cations show a strong nucleating effect for the precipitation of the RE3++: β-PbF2 nanocrystals. The evolution of the unit cell parameters of the REF3: β-PbF2 solid solution results from a combined effect of Pb2+-RE3+ substitution and interstitial F– introduction. In the glass ceramics, RE3+: β-PbF2 nanocrystals are constrained by the glassy matrix when they form with a pressure equivalent to 1.6 GPa. The constrained nanocrystals can return to a relaxed state by chemical dissolution of the embedding glassy matrix, followed by thermal treatments.展开更多
X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of differ...X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.展开更多
Wastes deriving from steel industry, containing large amounts of iron oxides and heavy metals, when collected in landfills are subjected to atmospheric agents, with consequent release of toxic substances in the soil a...Wastes deriving from steel industry, containing large amounts of iron oxides and heavy metals, when collected in landfills are subjected to atmospheric agents, with consequent release of toxic substances in the soil and groundwater. The reuse of these wastes as raw materials for the production of advanced materials is a viable way both to overcome the environmental impact and to reduce the disposal costs,proposing new technologically advanced materials. This work aims to simulate these interesting glassceramics by using glass cullet coming from recycled municipal waste and high amount of iron（III） oxide（from 25 wt% to 50 wt%）, the prevalent component of steel waste. The oxide was mixed with glass cullet and vitrified. The samples composition and the microstructure were investigated by scanning electron microscopy（SEM）, and X-ray diffraction（XRD） was used to evaluate the nature of the crystalline phases.The chemical stability of the materials, in terms of ionic release into saline solution, was assessed. The electrical behavior of the samples was also investigated by varying the iron ions content and controlling the crystallization process. It is possible to obtain chemically stable materials with a nearly semiconducting behavior.展开更多
文摘The devitrification of glasses with composition 50GeO2-40PbO-10PbF2-xREF3, RE = Gd, Eu, 0 3+: β-PbF2 nanocrystals embedded in a glassy oxide matrix. This transformation is investigated using thermal analysis, X-ray diffraction and electron microscopy. A comparison with RE3+: β-PbF2 ceramics prepared by standard ceramic techniques is performed. The Rare Earth cations show a strong nucleating effect for the precipitation of the RE3++: β-PbF2 nanocrystals. The evolution of the unit cell parameters of the REF3: β-PbF2 solid solution results from a combined effect of Pb2+-RE3+ substitution and interstitial F– introduction. In the glass ceramics, RE3+: β-PbF2 nanocrystals are constrained by the glassy matrix when they form with a pressure equivalent to 1.6 GPa. The constrained nanocrystals can return to a relaxed state by chemical dissolution of the embedding glassy matrix, followed by thermal treatments.
文摘X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.
文摘Wastes deriving from steel industry, containing large amounts of iron oxides and heavy metals, when collected in landfills are subjected to atmospheric agents, with consequent release of toxic substances in the soil and groundwater. The reuse of these wastes as raw materials for the production of advanced materials is a viable way both to overcome the environmental impact and to reduce the disposal costs,proposing new technologically advanced materials. This work aims to simulate these interesting glassceramics by using glass cullet coming from recycled municipal waste and high amount of iron（III） oxide（from 25 wt% to 50 wt%）, the prevalent component of steel waste. The oxide was mixed with glass cullet and vitrified. The samples composition and the microstructure were investigated by scanning electron microscopy（SEM）, and X-ray diffraction（XRD） was used to evaluate the nature of the crystalline phases.The chemical stability of the materials, in terms of ionic release into saline solution, was assessed. The electrical behavior of the samples was also investigated by varying the iron ions content and controlling the crystallization process. It is possible to obtain chemically stable materials with a nearly semiconducting behavior.
