7 research outputs found
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Magnetostriction of field-structured magnetoelastomers.
Field-structured magnetic particle composites are an important new class of materials that have great potential as both sensors and actuators. These materials are synthesized by suspending magnetic particles in a polymeric resin and subjecting these to magnetic fields while the resin polymerizes. If a simple uniaxial magnetic field is used, the particles will form chains, yielding composites whose magnetic susceptibility is enhanced along a single direction. A biaxial magnetic field, comprised of two orthogonal ac fields, forms particle sheets, yielding composites whose magnetic susceptibility is enhanced along two principal directions. A balanced triaxial magnetic field can be used to enhance the susceptibility in all directions, and biased heterodyned triaxial magnetic fields are especially effective for producing composites with a greatly enhanced susceptibility along a single axis. Magnetostriction is quadratic in the susceptibility, so increasing the composite susceptibility is important to developing actuators that function well at modest fields. To investigate magnetostriction in these field-structured composites we have constructed a sensitive, constant-stress apparatus capable of 1 ppm strain resolution. The sample geometry is designed to minimize demagnetizing field effects. With this apparatus we have demonstrated field-structured composites with nearly 10,000 ppm strain
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Directed self -assembly of nanoparticles
Nanotechnology promises to revolutionize the way we think about, but more importantly create new materials. The key to making this promise a reality is a commitment to fundamental research in critical areas including synthesis, fabrication, and characterization of nanoscale components. Nanoparticles have attracted wide attention as such components due to their unique size dependent properties including, superparamagnetism, chemilumiescents, and catalysis. To fully harness the potential capabilities of nanoparticles we need to develop new methods to assemble them into useful patterns or structures. Directed self-assembly using noncovalent interactions can be used to achieve this goal. This dissertation outlines experiments demonstrating several methods of polymer-mediated assembly of gold and iron oxide nanoparticles. Directed self-assembly using various polymer architectures provided a direct means to: (1) control the overall size of nanoparticle aggregates, (2) control interparticle spacing between particles, (3) control the collective behavior in nanoparticle ensembles
Highly fluorinated comb-shaped copolymers as proton exchange membranes (PEMs): improving PEM properties through rational design
Peer reviewed: YesNRC publication: Ye
Exploiting Interfacial Water Properties for Desalination and Purification Applications
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