Abstract
Simultaneous thermogravimetric analysis and thermo-Raman spectroscopy (TRS) measurements for in situ monitoring of wet chemical reaction of Ni(OH) 2 ·4H 2 O and Al(OH) 3 forming NiO-Al 2 O 3 nanoparticles is studied and compared with the solid-state reaction. Herein, a different approach of synthesis and monitoring of NiO-Al 2 O 3 by TRS is presented, in which, in situ thermo-Raman spectra are recorded at every degree interval from 25 to 800 °C to understand the structural and compositional changes in NiO-Al 2 O 3 as a function of temperature. Slow controlled heating of the sample as in TRS, enables better control over morphology and particle size distribution (∼10-20 nm diameter). The X-ray diffraction (XRD) shows that smaller particle size is obtained using wet chemical reaction than the solid-state reaction (∼25 nm diameter). TRS studies also reveal that, the bulk NiAl 2 O 4 forms at temperatures above 800 °C, although, the onset of formation is around 600 °C. Condensation of Al(OH) 3 forming Al 2 O 3 is also monitored, wherein, presence of hydrocarbon is found to contribute to the observed fluorescence background. Based on the TRS and complementary characterizations using XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis, the formation of supported NiO-Al 2 O 3 is discussed. © 2009 Elsevier B.V. All rights reserved.