OPTICAL-ABSORPTION CHARACTERIZATIONS OF POROUS AL2O3 HOST NIO NANOCOMPOSITES/

Porous Al2O3 host/NiO nanocomposites have been prepared by pyrolysis o f Ni-2(OH)(2)CO3 in the nanostructured Al2O3 hosts. Diffuse reflection spectra in the wavelength range of 200 to 800 nm were measured. Resul ts show that (1) in each spectrum exist several absorption bands of na no-NiO. With increasing the pyrolysis temperature from 550 to 1000 deg rees C, the numbers of absorption bands of NiO increase from 2 to 6 (P -1-P-6); (2) comparing with optical absorption bands of single crystal NiO, for porous nanocomposites the P-1, P-2 and P-4 present ''blue sh ift'' and the P-3, P-5 and P-6 exhibit ''red shift''; (3) when the pyr olysis temperature, T-p, is 550 degrees C, the absorption bands become so weak that only two bands (P-1 and P-6) can be observed and inverse ly, when T-p=1000 degrees C all six absorption bands of NiO are strong ; (4) for porous Al2O3/NiO nanocomposites prepared by pyrolysis at 100 0 degrees C the PF+ caused by the F+ centers in the Al2O3 host moves t owards the short wavelength at first with increasing the doping amount of NiO from 5 to 50 wt pet and then shifts to the long wavelength wit h further increasing NiO: In this paper, the above phenomena and mecha nism of the absorption bands of NiO are discussed in detail.