Hydroxylation Studies on High-Solid Load Magnesia Aqueous Suspensions

Autor(es)

Rafael Salomão ^[1] ; Leandro Fernandes ^[2]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Escola de Engenharia de São Carlos. Departamento de Engenharia de Materiais - Brasil

^[2] Universidade de São Paulo. Escola de Engenharia de São Carlos. Departamento de Engenharia de Materiais - Brasil

• Tipo de documento: Artigo Científico
• Fonte: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 26, 2023-01-06.

Resumo

Abstract The magnesia (MgO) hydroxylation behavior in dilute suspensions (below 50% volumetric solid loads) has been extensively studied over the past decades due to its role in refractory castables. However, its equivalent effects on concentrated systems have not been analyzed in such a systemic way, although they are known to be as or more deleterious than those observed in dilute systems. This study focuses on the hydroxylation behavior of different sources of magnesia (sinter and caustic magnesia) in aqueous suspensions prepared at various solids concentrations (17-96 vol%) and shaped by distinct methods. They were analyzed by thermogravimetry, apparent volumetric expansion measurements, X-ray diffraction, scanning electron microscopy, and in situ temperature measurements during curing. The ratio between experimental and theoretical extents of the hydroxylation degree resulted in the reaction yield. A comparison between samples containing the same water amount revealed those with caustic magnesia showed a faster evolution of hydroxylation degree, apparent volumetric expansion, and higher maximum internal temperature during curing. In both systems, the yield levels of compositions of heavier solid loads were higher, despite the small quantity of hydroxylation products formed. Significant differences in the products’ microstructure were observed and related to the ions' mobility toward crystallization nuclei. (AU)

• Processo FAPESP: 18/19773-3 - Refratários microporosos moldáveis no sistema Al2O3-MgO-CaO para isolamento térmico acima de 1200ºC
• Beneficiário: Rafael Salomão
• Modalidade de apoio: Bolsas no Exterior - Pesquisa
• Processo FAPESP: 10/19274-5 - Nova rota de sínteses de hidrotalcita (Mg6Al2(OH)16CO3.4H2O) a partir de suspensões aquosas de óxido de magnésio (MgO) e hidróxido de alumínio (Al(OH)3) e sua utilização em cerâmicas porosas para isolamento térmico em alta temperatura
• Beneficiário: Rafael Salomão
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores