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CLARKSON UNIVERSITY · POTSDAM · NEW YORK 13699 · VOLUME 17 NO 2 · DECEMBER 2001

Research in Ultra Fine Particles at Clarkson University's Center for Advanced Materials Processing

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.

 

Professor Egon Matijevic' Spends One-Half Century Investigating Very Fine Particles

Professor Egon Matijevic', the Victor K. LaMer Chair in Colloid and Surface Science Professor Egon Matijevic', the holder of the Victor K. LaMer Chair of Colloid and Surface Science at Clarkson University,
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.

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.

 

 

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Figure 1

Figure 1. Upper: extinction efficiency QE = CE/r2p as a function of the diameter and the wavelength of very uniform spherical hematite (a-Fe2O3) particles.

Lower: spectra calculated using the Mie theory for the same dispersions.

Fgure 2

Figure 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 2) deals with magnetic properties. It shows the strong dependence of the Morin temperature on the diameter of colloidal hematite (a-Fe2O3) spheres.

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.


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