The particle growth and size distribution of nickel supported on alumina model catalyst were observed under hydrogen atmosphere at 600℃ to 800℃.
Using the transmission electron microscope, the particles were clearly found to grow in either way of crystallite migration or atomic diffusion (ostwald ripening), broadening the particle size distribution and increasing the mean size with the age of hydrogen exposure and with the increase of temperature.
In particular, the sample sintered for 40hr at 800℃ exhibited the very large, faceted nickel crystallites locally.
A sintering power-law, which can delineate the mechanisms of particle growth, i.e., crystallite migration and ostwald ripening, correlates the mean size with exponent above 10 at 600℃ and 700℃, but with significantly lower value at 800℃, indicating the change of controlling mechanism.
However, the small standard deviation values of the particle size, compared with the results of Kuo et al's commercial catalyst(15), may be due to the difference of support geometry.