Role of Cr2O3 on the mullittization of di-phasic Al2O3-SiO2 gel

Abstract

Diphasic Al2O3-SiO2 gel was synthesized by sol-gel route from inorganic salts following aqueous phase colloidal interaction and the effect of Cr2O3 additive on the formation of mullite ceramics from this diphasic gel was investigated. The gel powder was thoroughly characterized by chemical analysis, measurement of surface area, bulk density and FTIR spectroscopy. The calcined gel was compacted with Cr2O3 additives in three different proportions (ca. 1, 2 and 3 wt%) and heat treated at different elevated temperatures (ca, 1400, 1500 and 1600 ºC). The analyses of microstructure and phase composition of the sintered masses were carried out by scanning electron microscopy and XRD technique. The morphology of the mullite crystals changed significantly in the presence of the additives. It has been observed that more than 7% more mullite has been formed with the addition of maximum 3% additive only. Using the additive, the maximum reduction in apparent porosity was about 30% and maximum improvement in density in the sintered compacts was about 14%. The flexural strength and fracture toughness of the sintered compacts also improved by 16% and 6% respectively in the presence of the Cr2O3 additive under the experimental condition.

Effect of vanadic anhydride and copper oxide on the development of hard porcelain composite and its antibacterial activity

“…In addition to the strength, Hideki Yoshida et al observed that triaxial porcelain glaze with incorporated silver-clay as antimicrobial agent also showed a good antimicrobial activity using Escherichia coli (E. coli) as test organism [15]. In several literatures, authors reported the enhancement of mullite growth during the high temperature sintering of different clay materials (most important constituents of porcelain) [10][11][12]16,17] and alumino-silicate precursors [18][19][20][21][22][23] in the presence of different oxides and metal ions. The effect of the copper ions and oxides of vanadium and copper on the formation of mullite from both clay and alumino-silicate precursor and their effect on the strength of mullite were very well studied [11,12,[21][22][23].…”

The formation of Cr(VI) compound at the interface between metal and heat-insulating material and the approach to prevent the formation by sol–gel process

“…Ca-free insulators consisting of high-purity alumina or mullite are commercially available, 11),12) but they are much more expensive than CaSiObased compounds. Therefore, insulators consisting of CaSiO are widely used especially in the field of large-scale heating apparatuses.…”