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Brief Description of Current Research
Dispersions of fine particles are in fact complex fluids that have applications in a wide range of fields, including coatings, electronic pastes, food, cosmetics, drilling fluids, paints and pigments, cements, emulsions, and ceramics. Our goal is to correlate the properties of colloidal dispersions to physical and chemical characteristics of the system for the purpose of producing engineered slurries of controlled stability and fluidity. Of primary interest is the study of the effect of key factors, such as type of the stabilizing method, adsorption density of the polymers and surfactants, conformation, molecular weight, and chemistry of functional groups. Through a systematic engineering of the dispersion it should be possible to maximize the solids loadings and improve process efficiency.
We are also addressing the rheological behavior, microstructure development, and morphology of polymer nanocomposites, a novel class of materials where nano-sized particles are dispersed in a polymer matrix. We are using a combination of rheological experiments (stress-strain, steady shear viscosity, viscoelasticity, yield) and characterization techniques such as AFM, optical microscope, SEM, TEM, XRD, TGA, DSC, and FTIR. The ultimate goal is to design materials of optimal properties for novel applications.
Another major area of work is the synthesis and study of core particles coated with shells of different chemical composition and a variety nano sizes for use in drug delivery systems. As the multilayered particles are prepared they are characterized using various methods to verify the realization of induced changes in surface charge, diameter, and surface properties. Because these core-shell particles exhibit properties different than those of the uncoated core particles (for example, different surface chemical composition, increased stability, higher surface area, and different magnetic and optical properties), they are extremely attractive as a subject of scientific inquiry.
We are also interested in understanding the colloidal behavior of dispersions of particles of heterogeneous surfaces, the adsorption mechanism of polymers and surfactants on the surface of heterogeneously charged particles, and the reaction mechanism between different dispersants and the dissolved metal ions in supernatant. A primary goal is to understand the effect of dissolved ions in governing the colloidal behavior of dispersions. This would enable us to engineer the active sites and/or functionality of the dispersants to control the rate and amount of adsorption and dissolution capacity. It would also make it possible to synthesize effective dispersants for the control of the most critical rheological features of dispersions, and to develop flocculants for separation strategies effective to levels of parts per billion.
Selected Publications
- “Adsorbents and Desiccants”, Zaman, A. A. Industrial Minerals and
Rocks, 7 (to appear 2005).
- “Influence of Dispersing Agents and Solution Conditions on the
Solubility of Crude Kaolin”, Zaman, A. A., and Mathur, S., J. of Colloid
and Interface Science, Vol. 271 (1), 124-130 (2004).
- “Clay Loading and Dispersion Effects on the Rheological Properties of
Unsaturated Polyester Nanocomposites”, Nguyen, A. and Zaman, A. A.,
Journal of Undergraduate Research, University of Florida, Vol. 5, Issue
3 (2003).
- “Effect of Filler Fraction on Strength Viscosity and Porosity of
Experimental Compomer Materials”, Schulze, K, Zaman, A. A., and Soderholm,
K.-J., Journal of Dentistry, Vol. 31, 373-382 (2003).
- “Effects of Polymer Bridging and Electrostatics on the Rheological
Behavior of Aqueous Dispersion”, Zaman, A. A., Particle & Particle
Systems Characterization, 20(5): 342-350 (2003).
- “Effects of Process Variables and Their Interactions on Solubility of
Metal Ions from Crude Kaolin Particles: Results of A Statistical Design of
Experiments”, Zaman, A. A., Demir, F., and Finch, Earnie, Applied Clay
Science, Vol. 22, 237-250 (2003).
- Functional Fillers and Nanoscale Minerals, Zaman, A. A., Moudgil,
B. M., and El-Shall, H., Edited by J. J. Keller, B. Moudgil, and M. A.
Herpfer, pp. 165-173 (2003).
- “Effect of polymer bridging on rheological properties of concentrated silica suspensions in the presence of low molecular weight physically adsorbed poly (ethylene oxide)”, Zaman, A. A., and Delorme, N., Rheologica Acta, Vol. 41(5): 408-417 (2002).