Cristalización de Cordierita en vidrios derivados del sistema cuaternario CaO-MgO-Al₂O₃-SiO₂. Influencia de la composición del vidrio

Abstract

Se ha estudiado el efecto del calcio en la cristalizaci-n de cordierita para la obtenci-n de un material vitrocer ‡mico dentro del sistema cuaternario CaO-MgO-Al 2 O 3 -SiO 2 . Con este objetivo se han seleccionado seis composiciones dentro del campo primario de cristalizaci-n de la cordierita y se han obtenido por fusi-n sus correspondientes vidrios. Se han analizado las muestras obtenidas tras un tratamiento tŽrmico en tres etapas (transformaci-n v'trea, nucleaci-n y crecimiento) por difracci-n de rayos-X (DRX), as' como las microestructuras correspondientes a las fases cristalinas obtenidas, por microscop'a electr-nica de barrido (MEB). Las microestructuras fueron asociadas a los materiales cristalizados con la ayuda del microan ‡lisis de dispersi-n de energ'as de rayos X (DEX). La cantidad de CaO en los vidrios est ‡ directamente relacionada con la cristalizaci-n de anortita, sugiriendo la gran cantidad de anortita cristalizada en relaci-n al bajo contenido en CaO de los vidrios originales, la formaci-n de una soluci-n s-lida de anortita (CaO.Al 2 O 3 .2SiO 2 )-diopsido (MgO.CaO.2SiO 2 ), lo cual fue corroborado tambiŽn mediante MEB/DEX. A la temperatura de crecimiento, casi todas las muestras hab'an cristalizado parcialmente cordierita, ya sea como fase mayoritaria o como fase secundaria. La microestructura de la anortita se mostr-muy particulada en forma de esferolitos de un di ‡metro pr-ximo a los 500 nm, mientras la cordierita mostr-morfolog'as dispares, desde noecleos de cristalizaci-n cuasi-esferol'ticos (rosetones) de m-cordierita por cristalizaci-n directa desde el vidrio a dendritas densificadas procedentes de la transformaci-n de µ-cordierita a α-cordierita, detect ‡ndose finalmente bloques homogŽneos de α-cordierita de tama-os superiores a 10x10 µm 2 . Palabras clave: cordierita , anortita, vitrocer ‡micos, microestructura.Cordierite crystallization in glasses derived from the CaO-MgO-Al 2 O 3 -SiO 2 quaternary system. Influence of the glass composition.It has been studied the calcium effect on the crystallization of cordierite for obtaining a glassceramic material into the CaOáMgOáAl 2 O 3 áSiO 2 quaternary system. With this propose it has been selected six compositions into de cordierite primary field of crystallization and obtained the original glasses. The obtained samples have been analysed after a thermal treatment in three steps (glass transformation, nucleation and growth) by X-ray diffraction (XRD). The composition of phases in microstructures have been analysed by scanning electron microscopy (SEM). The microstructures have been related with the crystalline phases by energy dispersive X-ray microanalysis (EDX). The amount of CaO in glasses is directly related with the anorthite crystallization, suggesting that the great amount of crystallized anorthite in relation with the low amount of CaO in the original glasses is due to the formation of one anorthite-diopside solid solution, what was tested by EDX. At growth temperature almost every samples partly crystallized, as primary or secondar...

Pyroxene-based glass-ceramics as glazes for floor tiles

“…This approach has been used successfully for the development of cordierite-based glass-ceramic glazes. 8,9 The main target of this work is, therefore, to know the action of some additives, fluxes and nucleants, on the crystallization of diopside (pyroxene) in glasses in the MgO-CaO-Al 2 O 3 -SiO 2 quaternary system. We will pay close attention to two points, the formation of the maximum amount of well-formed crystals of pyroxene and the suitable maturation (development) of the glass-ceramic glaze.…”

Microstructural Evolution in Fast‐Heated Cordierite‐Based Glass‐Ceramic Glazes for Ceramic Tile

“…The glass was prepared using a previously reported procedure. 11,12 The basic composition of the pattern glass, hereafter named G11, was derived from glasses A10 and A11 prepared in a previous work. 11,12 Basically, these compositions were within the cordierite primary crystallization field on the 5% CaO plane of the CaO-MgO-Al 2 O 3 -SiO 2 The glass was prepared using commercial chemicals (SiO 2 , Al 2 O 3 , CaCO 3 , MgCO 3 , TiO 2 , and BO 3 H 3 ; Merck, Barcelona, Spain).…”

“…11,12 The basic composition of the pattern glass, hereafter named G11, was derived from glasses A10 and A11 prepared in a previous work. 11,12 Basically, these compositions were within the cordierite primary crystallization field on the 5% CaO plane of the CaO-MgO-Al 2 O 3 -SiO 2 The glass was prepared using commercial chemicals (SiO 2 , Al 2 O 3 , CaCO 3 , MgCO 3 , TiO 2 , and BO 3 H 3 ; Merck, Barcelona, Spain). The calculated batches were mixed and melted in an alumina crucible at 1600°C for 2 h. The melt was poured into water, and the small flakes of glass (frit) formed then were crushed and milled.…”

“…Recently, we have studied the effect of some additives on the microstructural evolution of glass-ceramic glazes from glasses with compositions in the quaternary system. 11,12 The presence of CaO in the base glass has allowed us to mature the glass-ceramic glaze easily, i.e., to avoid crawling of the coating or other faults on firing at lower temperatures and, therefore, to be used on conventional bodies. The results show that additions of TiO 2 and B 2 O 3 to a chosen glass in the cordierite primary phase field of the CaO-MgO-Al 2 O 3 -SiO 2 quaternary system favors the crystallization of well-shaped cordierite crystals after controlled thermal treatment.…”