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Results for “Percolation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Nanoporous Thermosets with Percolating Pores from Block Polymers Chemically Fixed above the Order–Disorder Transition

A lamellar diblock polymer combining a cross-linkable segment with a chemically etchable segment was cross-linked above its order–disorder temperature (TODT) to kinetically trap the morphology associated with the fluctuating disordered state. After removal of the etchable block, evaluation of the resulting porous thermoset allows for an unprecedented experimental characterization of the trapped disordered phase. Through a combination of small-angle X-ray scattering, nitrogen sorption, scanning electron microscopy, and electron tomography experiments we demonstrate that the nanoporous structure exhibits a narrow pore size distribution and a high surface to volume ratio and is bicontinuous over a large sample area. Together with the processability of the polymeric starting material, the proposed system combines attractive attributes for many advanced applications. In particular, it was used to design new composite membranes for the ultrafiltration of water.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Percolating porosity in ultrafine grained copper processed by High Pressure Torsion

Defect structures in copper of different purity (nominally 99.99 and 99.999 wt. %) deformed via High Pressure Torsion (HPT) with varying processing parameters are investigated utilizing the radiotracer diffusion technique. While the degree of deformation is kept constant, the effects of applied quasi-hydrostatic pressure, processing temperature, post-deformation annealing treatments, and of the impurity concentration on the deformed samples are analyzed in terms of the formation of interconnected internal porosity. Furthermore, the anisotropy of the developing porosity network is examined. The porosity channels occurred to be interconnected along the direction parallel to the surface normal with a volume fraction of the order of a few ppm while no long-range penetration along the internal porosity could be detected when measured along the azimuthal or radial directions of a HPT processed sample.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

36 MATERIALS SCIENCE↗