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 & Thin film. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

Self-trapping of helium in metals

Abstract: Atomistic calculations are presented which demonstrate that helium atoms in a metal lattice are able to cluster with each other, producing vacancies and nearby self-interstitial defects. Even a small number of helium atoms is found to be sufficient to create these large distortions. As few as five interstitial helium atoms can spontaneously produce a lattice vacancy and nearby self-interstitial. An eight-helium-atom cluster gives rise to two such defects, and 16 helium atoms to more than five self-interstitial vacancy pairs. It was noted that the self-interstitials prefer to agglomerate on the same "side" of the helium cluster rather than to spread themselves out uniformly. The binding energy of each additional helium atom to these clusters increases with helium concentration and the trap is apparently unsaturable. A rate theory using these atomistic binding energies has been used to calculate the kinetics of helium-bubble nucleation and growth. The results are consistent with measurements of the properties of helium resulting from tritium decay.

Solidification in direct metal deposition by LENS processing

Abstract: Thermal imaging and metallographic analysis were used to study Laser Engineered Net Shaping (LENS™) processing of 316 stainless steel and H13 tool steel. The cooling rates at the solid-liquid interface were measured over a range of conduction conditions. The length scale of the molten zone controls cooling rates during solidification in direct metal deposition. In LENS processing, the molten zone ranges from 0.5 mm in length to 1.5 mm, resulting in cooling rates at the solid-liquid interface ranging from 200–6,000 Ks−1.

Poly(Arylene Ether Sulfone) Copolymers and Related Systems from Disulfonated Monomer Building Blocks: Synthesis, Characterization, and Performance – A Topical Review

Abstract: Research and development efforts have been focussed over the last five years towards the preparation of new, but potentially commercially viable low-cost copolymers for use as proton exchange membrane for fuel cell and other membrane applications. Our primary efforts centered on the direct synthesis of disulfonated copolymers via step-polycondensation methods. These novel series of disulfonated copolymers include optionally fluorinated poly(arylene ethers), poly(thioethers), polyimides, polybenzimidazoles, and polybenzoxazoles, as well as multiblock copolymer systems. The first generation of alternative proton exchange membranes (PEMs) has focused on wholly aromatic, disulfonated poly(arylene ether sulfone) random copolymers. Detailed herein are the development and current state of these disulfonated poly(arylene ether sulfone) copolymers and their fuel cell performance in both hydrogen-air PEMFCs and direct methanol fuel cells (DMFC).