Sandia National Laboratories

About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Combustion. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode

Abstract: We report the creation of a nanoscale electrochemical device inside a transmission electron microscope--consisting of a single tin dioxide (SnO(2)) nanowire anode, an ionic liquid electrolyte, and a bulk lithium cobalt dioxide (LiCoO(2)) cathode--and the in situ observation of the lithiation of the SnO(2) nanowire during electrochemical charging. Upon charging, a reaction front propagated progressively along the nanowire, causing the nanowire to swell, elongate, and spiral. The reaction front is a "Medusa zone" containing a high density of mobile dislocations, which are continuously nucleated and absorbed at the moving front. This dislocation cloud indicates large in-plane misfit stresses and is a structural precursor to electrochemically driven solid-state amorphization. Because lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical effects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, our observations provide important mechanistic insight for the design of advanced batteries.

Complex and oriented ZnO nanostructures

Abstract: Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

Size-dependent fracture of silicon nanoparticles during lithiation.

Abstract: Lithiation of individual silicon nanoparticles was studied in real time with in situ transmission electron microscopy. A strong size dependence of fracture was discovered; that is, there exists a critical particle diameter of ∼150 nm, below which the particles neither cracked nor fractured upon first lithiation, and above which the particles initially formed surface cracks and then fractured due to lithiation-induced swelling. The unexpected surface cracking arose owing to the buildup of large tensile hoop stress, which reversed the initial compression, in the surface layer. The stress reversal was attributed to the unique mechanism of lithiation in crystalline Si, taking place by movement of a two-phase boundary between the inner core of pristine Si and the outer shell of amorphous Li–Si alloy. While the resulting hoop tension tended to initiate surface cracks, the small-sized nanoparticles nevertheless averted fracture. This is because the stored strain energy from electrochemical reactions was insuffic...

Visualizing knowledge domains

Abstract: L'A. passe en revue les techniques de visualisation utilisees pour representer de facon cartographique la structure de domaine des disciplines scientifiques, et pour soutenir la recherche d'information et la classification. Un bref historique montre que la visualisation des domaines de connaissances s'enracine dans des disciplines telles que la scientometrie, la bibliometrie et l'analyse de citations, ainsi que la visualisation scientifique. L'A. analyse les principales etapes du processus de visualisation des domaines de connaissances : unites d'analyse, mesures, similarites entre unites. Differentes techniques couramment utilisees pour l'analyse et la visualisation des connaissances sont passees en revue : techniques de reduction de la dimensionnalite, analyse par clusters, configuration spatiale, visualisation et conception d'interaction. Differentes approches sont appliquees pour engendrer et comparer diverses representations cartographiques de la recherche sur la visualisation des domaines de connaissances. Ces cartes mettent en valeur les relations entre l'analyse de citations, la bibliometrie, la semantique et la visualisation de l'information. Augmenter l'accessibilite de la visualisation des domaines aupres des non-experts, appliquer la visualisation des domaines de connaissances pour mieux repondre a des questions pragmatiques, favoriser la collaboration et la diffusion des resultats entre chercheurs, developper des algorithmes plus robustes, comptent parmi les directions de recherche les plus prometteuses.