I. Petkanchin et al., UNIVERSALITY IN ELECTRIC LIGHT-SCATTERING PROPERTIES OF OXIDE AGGREGATES IN AQUEOUS DISPERSIONS, Colloids and surfaces. A, Physicochemical and engineering aspects, 104(2-3), 1995, pp. 259-264
The calculated saturated electric light scattering (ELS) effect (alpha
infinity) as a function of the product qR(g) (q = k sin Theta, k = 2
pi/lambda, lambda, is the incident light wavelength, Theta is the angl
e of observation, and R(g) is the radius of gyration) is compared with
experimentally measured values of alpha infinity. Aqueous suspensions
from aggregates of SiO2 (Aerosil OX50), Al2O3 and TiO2 particles have
been investigated. The aggregates in these systems are obtained by fl
ame hydrolysis and could be described as mass fractal objects, having
a characteristic fractal dimensionality (D). D is determined by the us
e of the correlation between the time of centrifugation (t) and the fi
nal slope (S-1) of the ELS decay curve. The SiO2 and Al2O3 monodispers
e fractions were obtained by centrifugation, while the TiO2 suspension
was sonicated. The monodispersity of the fractions obtained was follo
wed through the difference between the initial and final slopes of the
ELS decay curves. As-received suspensions have characteristic mean hy
drodynamic radii, determined from the relaxation time of the ELS decay
curve. It was found that the experimental data for alpha(infinity) ve
rsus kR(g) for the different suspensions lie on a single curve; this i
s striking evidence of the universality of the regime of colloid aggre
gation.