Jagannath Roy

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

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 Titanium and Vanadium on Nanomullite Derived from Diphasic Precursor Gel

To process mullite ceramics, diphasic aluminosilicate gel was synthesized from inorganic salts by employing the sol-gel route. The process of mullitization was studied by FTIR, DTA and SEM analysis. The particle size of the mullite ceramics was found to be in the nanometer range. The gel was calcined at 800°C. To the calcined gel, oxides of titanium and vanadium were mixed separately. The powder masses were compacted at 100 MPa pressure and then sintered at different elevated temperatures. The mechanical and microstructural properties of the doped samples were studied, and it was found that both the oxides influenced the process of mullitization positively.

Mullitization of aluminosilicate diphasic gel in the presence of nickel oxide additive

Aluminosilicate diphasic gel was synthesized by using inorganic salts and characterized by chemical analysis, Fourier transform infrared spectroscopy spectroscopic studies and surface area and bulk density measurements. The gel powder was compacted with nickel oxide additive in three different ratios (wt/wt). Differential thermal analysis of gel samples with additive and without additive was carried out at four different heating rates and for each sample, the activation energy of mullitization was calculated using Kissinger equation. The microstructure and phase analysis were carried out by scanning electron microscopic and X-ray diffraction studies. Observation showed that nickel oxide favored the mullitization process.