National Institute of Standards and Technology

About: National Institute of Standards and Technology is a government organization based out in Gaithersburg, Maryland, United States. It is known for research contribution in the topics: Laser & Scattering. The organization has 26667 authors who have published 60661 publications receiving 2215547 citations. The organization is also known as: National Bureau of Standards & NIST.

PA-6 clay nanocomposite hybrid as char forming agent in intumescent formulations

Abstract: This work deals with new flame retardant (FR) intumescent formulations for ethylene-vinyl acetate copolymers (EVA) using charring polymers polyamide-6 (PA-6) and polyamide-6 clay nanocomposite hybrid (PA-6-nano) as carbonization agents. Use of PA-6 nano improved both the mechanical and fire properties of FR EVA-based materials. The part played by the clay in the improvement of the FR performance was studied using FTIR and solid state NMR. It is shown that the clay allowed the thermal stabilization of a phosphorocarbonaceous structure in the intumescent char which increased the efficiency of the shield and, in addition, the formation of a ‘ceramic’ which can act as a protective barrier. Copyright © 2000 John Wiley & Sons, Ltd.

Functionalization of carbon-based nanostructures with light transition-metal atoms for hydrogen storage

Abstract: In a recent letter [T. Yildirim and S. Ciraci, Phys. Rev. Lett. 94, 175501 (2005)], the unusual hydrogen storage capacity of Ti decorated carbon nanotubes has been revealed. The present paper extends this study further to investigate the hydrogen uptake by light transition-metal atoms decorating various carbon-based nanostructures in different types of geometry and dimensionality, such as carbon linear chain, graphene, and nanotubes. Using first-principles plane-wave method we show that not only outer but also inner surface of a large carbon nanotube can be utilized to bind more transition-metal atoms and hence to increase the storage capacity. We also found that scandium and vanadium atoms adsorbed on a carbon nanotube can bind up to five hydrogen molecules. Similarly, light transition-metal atoms can be adsorbed on both sides of graphene and each adsorbate can hold up to four hydrogen molecules yielding again a high-storage capacity. Interestingly, our results suggest that graphene can be considered as a potential high-capacity ${\mathrm{H}}_{2}$ storage medium. We also performed transition state analysis on the possible dimerization of Ti atoms adsorbed on the graphene and single-wall carbon nanotube.

Microstructural Modeling and Design of Rechargeable Lithium-Ion Batteries

Abstract: The properties of rechargeable lithium-ion batteries are determined by the electrochemical and kinetic properties of their constituent materials as well as by their underlying microstructure. In this paper a method is developed that uses microscopic information and constitutive material properties to calculate the response of rechargeable batteries. The method is implemented in OOF ,a public domain finite element code, so it can be applied to arbitrary two-dimensional microstructures with crystallographic anisotropy. This methodology can be used as a design tool for creating improved electrode microstructures. Several geometrical two-dimensional arrangements of particles of active material are explored to improve electrode utilization, power density, and reliability of the Li yC6uLixMn2O4 battery system. The analysis suggests battery performance could be improved by controlling the transport paths to the back of the positive porous electrode, maximizing the surface area for intercalating lithium ions, and

Dispersing Single-Walled Carbon Nanotubes with Surfactants: A Small Angle Neutron Scattering Study

Abstract: We have investigated the dispersion of single-walled carbon nanotubes (SWNTs) in heavy water with the surfactant octyl-phenol-ethoxylate (Triton X-100) using small angle neutron scattering. The results indicate an optimal surfactant concentration for dispersion, which we suggest results from competition between maximization of surfactant adsorption onto SWNT surfaces and a depletion interaction between SWNT bundles mediated by surfactant micelles. The latter effect drives SWNT reaggregation above a critical volume fraction of micelles. These behaviors could be general in dispersing SWNTs using amphiphilic surfactant. The data also reveal significant incoherent scattering from hydrogen in SWNTs, most likely due to acid and water residues from the purification process.