in Ultra Fine Particles at Clarkson University's Center for Advanced
Fine particle processing
is the first of many steps in the manufacture of numerous consumer products.
The processing of fine particles starts with their synthesis, extends
to the alteration of their chemical and physical properties, and concludes
with their incorporation into various media. Experts at CAMP, in collaboration
with faculty and industrial counterparts in the United States and overseas,
are making excellent contributions to this area of research. Highlights
of CAMP's fine particle work are provided.
Egon Matijevic' Spends One-Half Century Investigating Very Fine
has actually spent more than fifty years investigating the preparations,
properties, and interactions of very finely dispersed matter, ranging
in modal size from several nanometers to several micrometers, and
is still active in the field.
|| Professor Egon Matijevic', the holder
of the Victor K. LaMer Chair of Colloid and Surface Science
at Clarkson University,
Some people may wonder what could be sufficiently important about
tiny particles to invest so much effort in these materials. The
first and essential reason is the recognition that many properties
(optical, electric, magnetic, adsorptive, catalytic, biological,
etc.) depend not only on the chemical composition, but also on the
degree of dispersity of a given matter. Indeed, some behaviors of
the same solids change in a dramatic manner when subdivided to micrometer
and again to a nanometer size range, whereby the shape of the particles
may also play a major role.
1. Upper: extinction efficiency QE = CE/r2p
as a function of the diameter and the wavelength of very
uniform spherical hematite (a-Fe2O3)
spectra calculated using the Mie theory for the same dispersions.
2. Morin temperature (TM°) as a function of the inversed diameter
(1/d) of monodispersed hematite particles.
To illustrate this size dependence, two examples are offered. The
plot in Figure 1 displays
the experimentally determined and calculated spectra of a red pigment
(iron oxide) as a function of particle size, which clearly indicates
the importance of the uniformity of the material, if reproducible
color is to be achieved. The second example (Figure
deals with magnetic properties. It shows the strong dependence
of the Morin temperature on the diameter of colloidal hematite (a-Fe2O3)
The understanding of the relationships of the size and morphology
of finely dispersed matter is not only of theoretical interest,
but it is essential in numerous applications, especially in high
technology and medicine. In addition, the general trends in miniaturization
of sophisticated equipment and components for many uses poses demands
for ever smaller particles, yet perfectly uniform, in order to assure
the reproducibility of the products.