Main menu >> Materials Research Laboratory >> Chemical Engineering: Materials

Materials Research Laboratory

Chemical Engineering: Materials
^ Use of Very High Pressure to Investigate the Structure of Matter
H. G. Drickamer,* G. Yang, Y. Li
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory and the Departments of Physics and Chemistry)

The basic thesis of this research is that high pressure is an essential tool for understanding electronic phenomena in condensed systems. With increasing compression there is increased overlap among electronic orbitals. Different types of orbitals are perturbed to different degrees. A study of these perturbations permits one to characterize electronic states and excitations and to test theories. This work is focused on three areas: pressure effects on light-emitting polymers potentially useful as light-emitting diodes; the use of a newly developed device for controlled stretching of polymers to compare the effects of pressure and stretch on optical and related properties; and the emission characteristics of oligomers and three dimensional polymers (dendrimers) in dilute solution in various polymeric media.

^ Adsorption of Polymers on Surfaces with Chemical Heterogeneity on Nanometer Scale
V. K. Gupta,* Y. Huang
University of Illinois; U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)

Adsorption of polymers is relevant to numerous applications such as colloidal stabilization, adhesion, biochemical processes, and chromatography. Surface heterogeneity is common in these applications, and yet there is virtual nonexistence of systematic, quantitative experimental results on such surfaces. This research is focused on the kinetics of adsorption of polymers at solid surfaces and study of the influence of chemical heterogeneity. Using the tools of molecular assembly, researchers create surfaces that are well-defined and energetically heterogeneous on length-scales commensurate to typical polymer chains (RG~10-100nm). The goal is to understand the interplay between physicochemical properties of the adsorbing polymer chains and characteristics of the surface heterogeneity.

^ Fuel Cells
R. Masel,* N. Chen, I. Lee
U.S. Department of Energy, DE-FG-02-99ER14993; Defense Advanced Research Projects Office, F33615-01-C-2172

The objective of this project is to examine production of ions and facilitation of carbon monoxide shuttling in fuel cells. Researchers have developed a novel UV/HREELS technique that can look directly at the changes in the electronic structure of adsorbed molecules as the surface composition is changed. The team is using the instrument to measure the metal surface electronegativity. They have also built novel fuel cells and are testing their performance.

^ Laser Measurements of Thermal Surface Diffusion
E. G. Seebauer,* Z. Wang, E. R. Blomiley
National Science Foundation, CTS 98-06329; U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)

Surface diffusion on semiconductors is important in several aspects of microelectronic device fabrication. Researchers are making measurements of surface diffusion under real processing temperatures and pressures using a recently developed laser technique of second harmonic microscopy. Under such conditions, the research team has found that the diffusion mechanism changes from simple site hopping to a previously unknown vacancy-mediated form. The researchers are probing surface diffusion in a variety of adsorption systems to determine the precise nature of this mechanism.

^ Assembly of Nanoparticles
C. F. Zukoski,* S. Ramakrishnan
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)

Methods of manipulating the interactions of 1-nm particles are explored. Research includes a focus on the strength of attraction of heteropolymetal oxyanions controlled through ionic strength and characterized through light scattering and viscosity. Links between the strength of attraction and anion solubility are studied. Methods of building nanoporous structures of these superacid particles are developed.

^ Drying and Cracking in Ceramic Fabrication
C. F. Zukoski,* L. Brown
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)

Understanding the stresses built up in ceramic green bodies is essential to producing ceramics with low flaw density. In this study, researchers look at the role of interparticle forces in determining rates of drying and compaction in slurries. Conditions resulting in cracking are explored with the goal of generating dense, uniform, crack-free green bodies.

^ Flow of Weakly Flocculated Suspensions
C. F. Zukoski,* S. J. Yoon
U.S. Department of Energy, DE-FG02-91ER45439

(In cooperation with the Frederick Seitz Materials Research Laboratory)

In this investigation, researchers examine the flow properties of weakly flocculated suspensions. A model system has been chosen in which, by solution pH, the suspension can be reversibly gelled. By mapping out a phase boundary in pH/volume fraction space, the research team is able to explore the relationship between flocculation in colloidal suspensions and sol-gel transitions observed in molecular systems. The mechanical properties of the gelled samples are of importance in determining porosity and suspension processibility. Researchers are seeking general descriptions of yielding and flow in terms of the depth of the interparticle attractive potential.


Summary of Engineering Research