Materiales vitrocerámicos del sistema MgO-Al₂O₃-SiO₂ a partir de ceniza de cáscara de arroz

Abstract

En este trabajo se muestran los resultados de un estudio de valorización de la ceniza de cáscara de arroz como materia prima en la obtención de materiales vitrocerámicos. Se ha formulado un vidrio en el sistema base MgO-Al 2 O 3 -SiO 2 incorporando B 2 O 3 y Na 2 O para facilitar los procesos de fusión y colado del vidrio. El vidrio se ha caracterizado mediante la determinación de su composición química. Su comportamiento frente a la sinterización se ha llevado a cabo mediante Microscopía de Calefacción (MC). La estabilidad térmica de las muestras y el mecanismo de cristalización preferente se ha estudiado mediante Análisis Térmico Diferencial (ATD). La mineralogía de los materiales vitrocerámicos se ha llevado a cabo por Difracción de rayos-X (DRX). Los resultados obtenidos muestran que es posible utilizar ceniza de cáscara de arroz para producir materiales vitrocerámicos mediante un proceso de sinterización seguido de cristalización, con nefelina (Na 2 O·Al 2 O 3 ·2SiO 2 ) como fase cristalina mayoritaria en el intervalo de temperatura 700º-950ºC y forsterita (2MgO·SiO 2 ) a temperaturas superiores a 950ºC. Palabras Clave: ceniza de cáscara de arroz, vidrio, vitrocerámico, nefelina, forsterita Glass-ceramic materials of system MgO-Al 2 O 3 -SiO 2 from rice husk ashThis wok shows the results of a valorisation study to use rice husk ash as raw material to develop glass-ceramic materials. An original glass has been formulated in the base system MgO-Al 2 O 3 -SiO 2 with addition of B 2 O 3 and Na 2 O to facilitate the melting and poring processes. Glass characterization was carried out by determining its chemical composition. Sintering behaviour has been examined by Hot Stage Microscopy (HSM). Thermal stability and crystallization mechanism have been studied by Differential Thermal Analysis (DTA). Mineralogy analyses of the glass-ceramic materials were carried out using X-ray Diffraction (XRD). Results show that it is possible to use ash rice husk to produce glass-ceramic materials by a sintercrystallization process, with nepheline (Na 2 O·Al 2 O 3 ·SiO 2 ) as major crystalline phase in the temperature interval 700-950ºC and forsterite (2MgO·SiO 2 ) at temperatures above 950ºC. Keywords: rice husk ask, glass, glass-ceramic, nepheline, forsterite INTRODUCCIÓNEl desarrollo económico y social experimentado por el ser humano a lo largo de su evolución ha estado asociado a su capacidad para explotar los recursos energéticos disponibles. El modelo energético actual, basado en la utilización a gran escala de combustibles fósiles (petróleo, carbón y gas), no es sostenible, ya que presenta graves problemas asociados al agotamiento de los recursos energéticos y al deterioro medioambiental provocado por la utilización de estos combustibles. Por tanto, es necesario encontrar fuentes de energía alternativas. En los últimos años se han desarrollado diversos procesos eficientes para convertir la biomasa en energía. Sin embargo, estos procesos no son completamente "limpios" ya que en el proceso de combustión de la materia orgánic...

Recycling of Glass Fibers from Fiberglass Polyester Waste Composite for the Manufacture of Glass-Ceramic Materials

“…These results confirm that surface crystallisation plays a major role in the formation of the glass-ceramic. Similar findings have been reported for other materials [30][31][32]. Figure 8 illustrates the appearance the glass-ceramic tiles obtained by sintering + crystallization of mixtures of glass powders of different particle sizes at 1013˚C for 60 min: (a) 1600 -2000 µm, 160 -250 µm and 80 -100 µm, (b) 80 -100 µm.…”

Crystallisation and microstructure of nepheline–forsterite glass-ceramics

“…Ceramics International, 39(2013) The figure shows that the devitrification process of RHA glass occurred through a surface crystallisation mechanism [35]. Thus, the most effective method for manufacturing glassceramic materials from RHA glass is by a sinter-crystallisation process, which involves the sintering and subsequent crystallisation of powdered glass.…”

“…Finally, an endothermic reaction starting at 1100ºC indicates the formation of liquid phases. The XRD patterns collected on glass samples that were thermally treated for 60 min [35] indicate that the first exothermic effect (745ºC) corresponds to the crystallisation of nepheline (Na 2 O·Al 2 O 3 ·2SiO 2 ) from the parent glass, whereas the formation of forsterite (2MgO·SiO 2 ) is responsible for the crystallisation effect centred at 900ºC. TTT curves, the lower heat treatment temperatures require longer times to initiate crystallisation; thus, the glass begins to devitrify after 40 minutes at 700ºC.…”

“…In a recent paper [35], the authors have demonstrated the feasibility of producing forsteritenepheline-based glasses from a RHA mixture that incorporates B 2 O 3 and Na 2 O to facilitate the melting process. Significant environmental benefits are attained by using RHA as source of silica: (a) avoided landfill disposal of the residue; (b) minimization of the natural raw materials consumption.…”

“…This ash, which is known as RHA, is a carbon neutral green product that contains approximately 85-90 (wt%) amorphous silica. Worldwide, approximately 120 Mt of rice husk are produced annually, which gives rise to a global production of 21 Mt/year of RHA [35]. In general, RHA is dumped as a waste [36,37]; however, because of its composition, it may be used as a source of silica in the steel industry [38] and as a pozzolanic material for the cement industry [39,40].…”