Novel Colloidal Silica Technology For In Situ Spinelization in MgO-Containing Refractories

Author(s)

Salomao, Rafael ; Fernandes, Leandro ; Sundblom, Andreas ; Greenwood, Peter ; Martinatti, Isabela Santos ; Tiba, Paulo Roberto Teruo

• Document type: Journal article
• Source: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 27, p. 13-pg., 2024-01-01.

Abstract

This study used an aqueous dispersion of silanized colloidal silica (SCS), whose particles' surfaces were modified with an epoxysilane-based coupling agent, as the liquid medium and binder for MgO-Al2O3-containing suspensions. Fine calcined alumina and magnesia sinter particles were dispersed in SCS to form a 65 vol% solids suspension. Equivalent silica-free compositions containing calcium aluminate cement or unsilanized colloidal silica were tested as references. After mixing, the SCS-suspension showed low viscosity and suitable workability and, after curing, a thin protective coating of magnesium silicate hydrate (MSH) was formed, thus preventing MgO hydroxylation and improving bonding strength, generating green-dried structures of significant flexural strength (8 MPa). During initial heating, the decomposition of MSH and the softening of amorphous silica particles reduced the overall expansion of spinel (MgAl2O4) formation. After sintering at 1600oC, the structure showed intense densification (total porosity of 8%) high flexural strength (73 MPa) and large spinel crystals surrounded by a thin layer of amorphous silica and magnesium silicates. (AU)

• FAPESP's process: 18/19773-3 - Microporous castable refractories in the Al2O3-MgO-CaO system for thermal insulation above 1200ºC
• Grantee: Rafael Salomão
• Support Opportunities: Scholarships abroad - Research
• FAPESP's process: 22/03655-7 - Reducing energy losses in industrial processes with high-efficiency thermal insulation of microporous castable calcium silicate produced from elements of biomass: eggshells and rice husk ash
• Grantee: Rafael Salomão
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants