Synthesis and Characterization of Glass and Glass-Ceramic Materials of the System SiO 2 -Fe 2 O 3 -BaO-Al 2 O 3
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Synthesis and Characterization of Glass and Glass-Ceramic Materials of the System SiO2Fe2O3-BaO-Al2O3 O.I. Pánuco-Valdés, J. López-Cuevas, J.L. Rodríguez-Galicia Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Carretera SaltilloMonterrey, km 13.5, Ramos Arizpe, Coahuila, México, C.P. 25900 ABSTRACT The effect of mechanical activation on the crystallization of glasses of the system SiO2Fe2O3-BaO-Al2O3 is investigated. The ceramic-glasses are synthesized from silica and iron-rich Ferro-Titanium-Zirconiferous (FTZ) sands available in the state of Coahuila, Mexico. The parent glass is subjected to mechanical activation in a high-energy attrition mill during 4 or 8h. Then, both milled and non-milled glasses are subjected to a thermal crystallization treatment at temperatures of 900 or 1000ºC during 2 or 5h. It is found that, in the case of the thermal treatment carried out at 900°C/5h, an increment in the time employed for both the mechanical activation and the crystallization treatment enhanced the crystallization of the parent glasses and produced an increase in the compressive strength of the synthesized glass-ceramics. INTRODUCTION Iron is one of the elements present in large quantity in natural volcanic rocks; some basalts contain as much as 10 -15 wt% iron oxides; Ferro-Titanium-Zirconiferous (FTZ) sand contains ~15 wt% Fe2O3. Iron-rich glass-forming compositions are well known and widely used for the production of glass fibers and glass-ceramic tiles by melting, fibering or casting/rolling natural basalt rocks. Petrurgic products are characterized by high abrasion and corrosion resistance as well as high mechanical strength. Some of the iron-bearing silicate glasses also possess special optical and magnetic properties. In these glasses, iron can exist either in the ferrous or the ferric oxidation state. In the amorphous structure, Fe3+ can be considered as an intermediate ion, whereas Fe2+ is typically a modifying ion [1]. Controlled crystallization of glass is commonly employed to produce glass-ceramics with desirable properties. Glass-ceramic materials have a number of outstanding characteristics in comparison with traditional ceramics and glasses, which determine their application in advanced technology. The controlled crystallization of iron-rich glass is commonly employed to produce glass–ceramics with desirable properties [2]. Among the glass compositions that precipitate a magnetic phase are B2O3-Al2O3-SiO2-Fe2O3-CaO, Li2O-SiO2-Fe2O3 and Li2O-SiO2-Fe2O3-MnO, BaO-B2O3-Fe2O3, SiO2-Al2O3-Fe2O3-K2O, CaO-Fe2O3-Al2O3-B2O3 and BaO-Fe2O3-SiO2 [3]. The compositions with high iron content are peculiar since they show a tendency toward spontaneous crystallization and in some cases the amorphous structure can be obtained only after quenching in water [4]. The aim of this work is to synthesize and characterize glass and glass-ceramic materials with compositions in the SiO2-Fe2O3-BaO-Al2O3 system and potential for structural applications. Silica and iron-rich FTZ sands available in the state of
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