Effect of mechanical activation on the crystallization and properties of iron-rich glass materials
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Effect of mechanical activation on the crystallization and properties of iron-rich glass materials Claudia M. García-Hernández, Jorge López-Cuevas and José L. Rodríguez-Galicia Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Carr. SaltilloMonterrey, Km. 13.5, C.P. 25900, Ramos Arizpe, Coahuila, México. ABSTRACT The effect of mechanical activation (MA) of the precursor mixture of raw materials and/or the parent glass, on the microstructure and physical and mechanical properties of iron-rich glassceramic materials of the system SiO2-B2O3-BaO-Fe2O3, has been studied. MA of the materials is conducted for 0, 2 or 6h using a high energy attrition milling device. Crystallization treatments are given to the parent glass at 650, 750 or 850°C for 5h. Crystallization of the samples is promoted by increased treatment temperature, and especially also by double MA at 850ºC. With increasing crystallization temperature, both the density and the compressive strength increase, while porosity decreases. However, at 850ºC, prolonged MA decreases both the density and the compressive strength due to an increment in porosity caused by the growth of the BaFe12O19 crystals. INTRODUCTION Mechanical activation (MA) is a process that involves prolonged high energy milling of a material. Its use can lead to many interesting applications, ranging from waste processing to the production of advanced materials. During MA, several structural changes take place in the materials being ground, which modify their physicochemical properties [1]. An important feature of this processing route is the refinement of the microstructure (grain and particle size) associated with the particle fracture and deformation caused by the collision events occurring between the grinding medium and the powder. It can also increase the reactivity of the milled powders, leading to a reduction in the temperature conventionally required to carry out a posterior solid state reaction process for the synthesis of a material with particular chemical and phase composition. MA has been widely associated with the amorphization of crystalline materials, but its use to promote the crystallization of amorphous materials is a less studied case [2-3]. The main aim of this work is to study the effect of MA of the precursor mixture of raw materials and/or the parent glass, on the microstructure, and physical and mechanical properties of iron-rich glass-ceramics of the system B2O3-SiO2-BaO-Fe2O3, for potential structural applications, intending to obtain in them barium hexaferrite (BeFe12O19) crystals dispersed in a borosilicate glass matrix. High purity raw materials as well as an iron oxide husk are used to obtain the desired glass and glass-ceramic materials. The iron oxide husk is a byproduct of the knurling of the surface of low carbon steel tubes prior to their coating with a refractory lining during the production of oxygen lances for steel making.
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EXPERIMENTAL DETAILS The studied parent glass is based on one of the materials investigated by A. Mirkazem
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