The nickel HT sample is somewhat different from all the other doped samples. Its surface area and the number of pores increase when the aging temperature is increased from 65 to 80 °C, as the BJH pore volume increases from 0.17 to 0.21 cm 3 g -1 , Table . Yet the pore size changes little with the increase in the aging temperature and is similar to the HT65 sample. This suggests that the rate of agglomeration of primary crystallites in the Ni HT sample does not depend so much on temperature.