Search for: All records

Abstract A polycrystalline Cu foam with sub-micron ligament sizes was formed by creating a non-woven fabric via electrospinning with a homogeneous mixture of polyvinyl alcohol(PVA)-and copper acetate(Cu(Ac) 2 ). Thermogravimetric measurement of the electrospun fabric of the precursor solution is reported. Oxidizing the precursor fabric at 773K formed an oxide nano-foam; subsequent heating at 573K with a reducing gas transformed the CuO nano-foam to Cu with a similar ligament and meso-scale pore size morphology. A cross-section prepared by focused ion beam lift-out shows the polycrystalline structure with multi-scale porosity. The mechanical property of the Cu nano-foam is measured by nano-indentation. The load-depth curves and deduced mechanical properties suggest that additional intra-ligament pores lead to unique structure-property relations in this non-conventional form of metal. 

ABSTRACT Composite nanostructured foams consisting of a metallic shell deposited on a polymeric core were formed by plating copper via electroless deposition on electrospun polycaprolactone (PCL) fiber mats. The final structure consisted of 1000-nm scale PCL fibers coated with 100s of nm of copper, leading to final core-shell thicknesses on the order of 1000-3000 nm. The resulting open cell, core-shell foams had relative densities between 4 and 15 %. By controlling the composition of the adjuncts in the plating bath, particularly the composition of formaldehyde, the relative thickness of copper coating as the fiber diameter could be controlled. As-spun PCL mats had a nominal compressive modulus on the order of 0.1 MPa; adding a uniform metallic shell increased the modulus up to 2 MPa for sub-10 % relative density foams. A computational materials science analysis using density functional theory was used to explore the effects pre-treatment with Pd may have on the density of nuclei formed during electroless plating. 

The El Niño–Southern Oscillation (ENSO), which originates in the Pacific, is the strongest and most well-known mode of tropical climate variability. Its reach is global, and it can force climate variations of the tropical Atlantic and Indian Oceans by perturbing the global atmospheric circulation. Less appreciated is how the tropical Atlantic and Indian Oceans affect the Pacific. Especially noteworthy is the multidecadal Atlantic warming that began in the late 1990s, because recent research suggests that it has influenced Indo-Pacific climate, the character of the ENSO cycle, and the hiatus in global surface warming. Discovery of these pantropical interactions provides a pathway forward for improving predictions of climate variability in the current climate and for refining projections of future climate under different anthropogenic forcing scenarios.