Publications

Results 51–75 of 171

Search results

Jump to search filters

Highly porous ceramic foams from magnesium oxide stabilized pickering emulsions

AIChE Annual Meeting, Conference Proceedings

Roberts, Christine C.; Hughes, Lindsey G.; Mondy, L.A.; Grillet, Anne M.; DiAntonio, Christopher D.; Chavez, Tom C.; Ingersoll, David I.

Ceramic foams with porosities over 90% are created by drying and sintering particle stabilized oil-water emulsions. This technique is optimized for the creation of magnesium oxide (MgO) porous scaffolds. Processing parameters such as emulsion mixing speed, particle concentration, and drying time are related to final properties such as porosity, permeability, and mechanical strength. The hydroxylation of magnesium oxide to form a gel can also be used to create green ceramics with very low densities directly without the additional steps to form an emulsion. The quality of these ceramic foams compares well to porous ceramics produced by other methods, specifically tape casting of an MgO slip with added poreformers and sponge impregnation of reticulated foam with a slip in a replication process.

More Details
TYPE Conference YEAR 2012
OSTIScopus

First-principles flocculation as the key to low energy algal biofuels processing

Hewson, John C.; Mondy, L.A.; Murton, Jaclyn K.; O'Hern, Timothy J.; Parchert, Kylea J.; Pohl, Phillip I.; Williams, Cecelia V.; Wyatt, Nicholas B.; Barringer, David A.; Pierce, Flint P.; Brady, Patrick V.; Dwyer, Brian P.; Grillet, Anne M.; Hankins, M.G.; Hughes, Lindsey G.; Lechman, Jeremy B.

This document summarizes a three year Laboratory Directed Research and Development (LDRD) program effort to improve our understanding of algal flocculation with a key to overcoming harvesting as a techno-economic barrier to algal biofuels. Flocculation is limited by the concentrations of deprotonated functional groups on the algal cell surface. Favorable charged groups on the surfaces of precipitates that form in solution and the interaction of both with ions in the water can favor flocculation. Measurements of algae cell-surface functional groups are reported and related to the quantity of flocculant required. Deprotonation of surface groups and complexation of surface groups with ions from the growth media are predicted in the context of PHREEQC. The understanding of surface chemistry is linked to boundaries of effective flocculation. We show that the phase-space of effective flocculation can be expanded by more frequent alga-alga or floc-floc collisions. The collision frequency is dependent on the floc structure, described in the fractal sense. The fractal floc structure is shown to depend on the rate of shear mixing. We present both experimental measurements of the floc structure variation and simulations using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). Both show a densification of the flocs with increasing shear. The LAMMPS results show a combined change in the fractal dimension and a change in the coordination number leading to stronger flocs.

More Details
TYPE SAND Report YEAR 2012
DOIOSTI

Finite element analysis of multilayer coextrusion

Rao, Rekha R.; Mondy, L.A.; Schunk, Randy; Hopkins, Matthew M.

Multilayer coextrusion has become a popular commercial process for producing complex polymeric products from soda bottles to reflective coatings. A numerical model of a multilayer coextrusion process is developed based on a finite element discretization and two different free-surface methods, an arbitrary-Lagrangian-Eulerian (ALE) moving mesh implementation and an Eulerian level set method, to understand the moving boundary problem associated with the polymer-polymer interface. The goal of this work is to have a numerical capability suitable for optimizing and troubleshooting the coextrusion process, circumventing flow instabilities such as ribbing and barring, and reducing variability in layer thickness. Though these instabilities can be both viscous and elastic in nature, for this work a generalized Newtonian description of the fluid is used. Models of varying degrees of complexity are investigated including stability analysis and direct three-dimensional finite element free surface approaches. The results of this work show how critical modeling can be to reduce build test cycles, improve material choices, and guide mold design.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI
Results 51–75 of 171
Results 51–75 of 171