CAMP Professor Igor Sokolov Models the Shaping Mechanism of Nanoporous Colloidal Silica Particles

CAMP Professor Igor Sokolov, of Clarkson University's Department of Chemistry, is modeling the shaping mechanism of nanoporous colloidal silica particles. After the discovery of the liquid crystal templating [1, 2] of hexagonal, cubic and lamellar mesostructured silica, materials chemistry leaped into the realm of design and synthesis of inorganics with complex forms. Never before has it been possible to synthesize inorganics with structural features of a few nanometers and architectures over such large length scales, up to hundreds of microns. The anticipation for discovery from mesoscale synthesis is comparable to high T_c superconductors, porous silicon, conducting organic polymers, fullerenes and carbon nanotubes. This mesochemistry is inspiring research in materials science, solid state chemistry, semiconductor physics, biomimetics and biomaterials. It represents a new way of thinking about templated synthesis of materials over length scales that have never been seen before in solid state chemistry.

Figure 5. Variety of mesoporous shapes: (a) tubes, (b) discoids with protrusions, (c) "seashell," (d) discoid of sunken shape, (e) "Moebius strip" shape, (f) spin, (g) fat tube, (h) cone, (i) helix.

As a more detailed understanding of supramolecular templating developed, it became apparent that it also provided a vital and inspirational link with nature's processing of bio-minerals. Many of these shapes can be some parts for future nanomachines( Figure 5). Professor Sokolov is studying the mechanisms of formation of these fascinating shapes [3, 4]. Together with his graduate student Y.Kievsky, he is synthesizing the shapes under diverse conditions using different temperatures, different chemicals, and various mixing conditions. Figures 6 and 7 show a nice agreement between his theory and experimental results.

In addition to this modeling work, Professor Sokolov is involved in the modeling of atomic structures of crystalline surfaces. He also models the long-range force interaction between nano/micro particles and various surfaces such as bacterial cell walls used for bioremediation and wafer surfaces used in semiconductor technology.

Figure 7. 3 D simulation of the discharge of internal stress inside a growing discoid. Due to differential contraction a flat discoid (a) evolves into either "sunken" (b) or "protruding" (c) shapes (reference 3). For example, shape (b) closely resembles the experimental shape in Figure 5c.

For more information about Professor Igor Sokolov and his research, you may call him at 315-268- 2375 or send email to isokolov@clarkson.edu.

References:

1. Kresge C.T., Leonowicz M., Roth W.J., Vartuli J.C., and Beck J.C., "Ordered Mesoporous Molecular Sieves Synthesized by a Liquid-Crystal Template Mechanism," Nature, 359, 710 (1992).

2. Ozin G.A., Kresge C.T., Yang S.M., Yang H., Sokolov I. Yu., and Coombs N., " Morphokinetics: Growth of Mesoporous Silica Curved Shapes," Adv. Materials, 11, 52 (1999).

3. Yang M., Sokolov I.Yu, Coombs N., Kresge C.T., and Ozin G.A., " Supramolecular Origami: Hollow Helicoids of Mesoporous Silica," Adv. Mater., 11, 1427 (1999).

4. Sokolov I.Yu, Yang H., Ozin G.A., and Kresge C.T., " Radial Patterns in Mesoporous Silica ," Adv. Mater., 11, 636 (1999).

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CAMP Professor Cetin Cetinkaya is Modeling Acoustic Wave Propagation in Thin-Layered Structures for Nondestructive Evaluation Applications

CAMP Professor Cetin Cetinkaya, of Clarkson University's Department of Mechanical and Aeronautical Engineering, and his research group have been developing mathematical models for acoustic wave propagation in thin-layered structures for nondestructive evaluation. Coating substrates with thin layers of materials is a common practice in a wide spectrum of applications. Uncertainties in the deposition process require measurements and verification of the coating layer materials and their geometric properties. The characterization of bonding quality and the determination of the post-deposition bonding material properties are also of great interest.

Professor Cetinkaya's modeling work is being directed towards layered structures made of polymeric materials with an arbitrary number of layers. The typical layer thicknesses of the structures under investigation are in the range of 10 mm to 500 mm. However, the modeling work can be up- and down-scaled for thinner or thicker layers without any modifications. His modeling efforts are based on continuum mechanics. Using Navier's equations of motion and integral transforms, a transfer matrix formulation between the stress and displacement components on the surfaces of a layer has been developed. See Figure 8. The main advantage of the transfer matrix approach is that it allows the development of a consistent formulation for structures with an arbitrary number of layers. Professor Cetinkaya's research group has generalized this formulation for layers with varying material properties and thermoelastic layers. The varying layer formulation has great potential in evaluating bonding quality of the interfacial layers. The thermoelastic formulation has been developed for pulsed laser generated acoustic wave applications.

In addition, an experimental program has been developed to enhance the modeling work. Professor Cetinkaya's research lab has state-of-the-art ultrasonic testing equipment. An important aspect of the research program is to verify the mathematical models with experimental studies. He uses ultrasonics to address the evaluation needs and laser research to target applications where non-contact operations are required.

For more information about Professor Cetin Cetinkaya and his research, you may call him at 315-268-6514 or send email to cetin@clarkson.edu.