文档介绍：7 Particle Size Distribution
and Monodisperse Sols
Monodisperse systems are those containing particles of almost the same size with-
in a deviation of about 10 percent. The chemical structure, shape, etc. are in gen-
eral the same and the system may be treated as a standard or basic disperse sys-
tem for understanding general disperse systems. However, the systems that usual-
ly appear are polydisperse, having various particle sizes.
Particle Size Distribution
In Chapt. 6, experimental methods are described to determine a particle size. But,
if the solution is polydisperse, some of the methods provide only a kind of aver-
age representing the particle size. For example, the turbidity of Eq. is related
to the weight-averaged molecular weight of the system under observation, or the
square of the particle mass averaged over the size distribution. Conversely, these
data can hardly be analyzed for the size distribution function unless a well pre-
pared set of monodisperse systems is used. This is true with sedimentation.
As noted in Sec. , if the Debye factor has to be introduced in Eq. ,
the anguleular intensity distribution of scattered light from noninteracting particles
is influenced by the size, shape, and optical contrast of the particles. We may as-
sume that the shape of the particles is known, as given by the Debye factor listed
in Table . The size distribution function, G(M), where M is the particle mass,
can appear in the expression of the scattered intensity as given by
Z1
I
q p2
1 cos2 h
h 2 G
MM2P
q; MdM
7:1
I 2 4 2 0
i;u 2e0k R
0
where 0 is the particle polarizability per unit mass so that = 0 M. By inversion
of the Fredholm equation, Eq. , G(M) can be experimentally determined from
the measurement of the scattered intensity as a function of the scattering angle.
Schnablegger and Glatter (1993) describe putational procedures.
Particle Size Distribution 129
On the other hand