Oak Ridge National Laboratory

About: Oak Ridge National Laboratory is a facility organization based out in Oak Ridge, Tennessee, United States. It is known for research contribution in the topics: Neutron & Ion. The organization has 31868 authors who have published 73724 publications receiving 2633689 citations. The organization is also known as: ORNL.

Introduction of π-Complexation into Porous Aromatic Framework for Highly Selective Adsorption of Ethylene over Ethane

Abstract: In this work, we demonstrate for the first time the introduction of π-complexation into a porous aromatic framework (PAF), affording significant increase in ethylene uptake capacity, as illustrated in the context of Ag(I) ion functionalized PAF-1, PAF-1-SO3Ag. IAST calculations using single-component-isotherm data and an equimolar ethylene/ethane ratio at 296 K reveal that PAF-1-SO3Ag shows exceptionally high ethylene/ethane adsorption selectivity (Sads: 27 to 125), far surpassing benchmark zeolite and any other MOF reported in literature. The formation of π-complexation between ethylene molecules and Ag(I) ions in PAF-1-SO3Ag has been evidenced by the high isosteric heats of adsorption of C2H4 and also proved by in situ IR spectroscopy studies. Transient breakthrough experiments, supported by simulations, indicate the feasibility of PAF-1-SO3Ag for producing 99.95%+ pure C2H4 in a Pressure Swing Adsorption operation. Our work herein thus suggests a new perspective to functionalizing PAFs and other types ...

Increasing cellulose accessibility is more important than removing lignin: A comparison of cellulose solvent‐based lignocellulose fractionation and soaking in aqueous ammonia

Abstract: While many pretreatments attempt to improve the enzymatic digestibility of biomass by removing lignin, this study shows that improving the surface area accessible to cellulase is a more important factor for achieving a high sugar yield. Here we compared the pretreatment of switchgrass by two methods, cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF) and soaking in aqueous ammonia (SAA). Following pretreatment, enzymatic hydrolysis was conducted at two cellulase loadings, 15 filter paper units (FPU)/g glucan and 3 FPU/g glucan, with and without BSA blocking of lignin absorption sites. The hydrolysis results showed that the lignin remaining after SAA had a significant negative effect on cellulase performance, despite the high level of delignification achieved with this pretreatment. No negative effect due to lignin was detected for COSLIF-treated substrate. SEM micrographs, XRD crystallinity measurements, and cellulose accessibility to cellulase (CAC) determinations confirmed that COSLIF fully disrupted the cell wall structure, resulting in a 16-fold increase in CAC, while SAA caused a 1.4-fold CAC increase. A surface plot relating the lignin removal, CAC, and digestibility of numerous samples (both pure cellulosic substrates and lignocellulosic materials pretreated by several methods) was also developed to better understand the relative impacts of delignification and CAC on glucan digestibility.

The Effect of Fluoroethylene Carbonate as an Additive on the Solid Electrolyte Interphase on Silicon Lithium-Ion Electrodes

Abstract: Fluoroethylene carbonate (FEC) has become a standard electrolyte additive for use with silicon negative electrodes, but how FEC affects solid electrolyte interphase (SEI) formation on the silicon anode’s surface is still not well understood. Herein, SEI formed from LiPF6-based carbonate electrolytes, with and without FEC, were investigated on 50 nm thick amorphous silicon thin film electrodes to understand the role of FEC on silicon electrode surface reactions. In contrast to previous work, anhydrous and anoxic techniques were used to prevent air and moisture contamination of prepared SEI films. This allowed for accurate characterization of the SEI structure and composition by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling. These results show that FEC reduction leads to fluoride ion and LiF formation, consistent with previous computational and experimental results. Surprisingly, we also find that these species decrease lithium-ion solubility and increas...

Reversible redox reactions in an epitaxially stabilized SrCoO(x) oxygen sponge.

Abstract: Fast, reversible redox reactions in solids at low temperatures without thermomechanical degradation are a promising strategy for enhancing the overall performance and lifetime of many energy materials and devices. However, the robust nature of the cation's oxidation state and the high thermodynamic barrier have hindered the realization of fast catalysis and bulk diffusion at low temperatures. Here, we report a significant lowering of the redox temperature by epitaxial stabilization of strontium cobaltites (SrCoO(x)) grown directly as one of two distinct crystalline phases, either the perovskite SrCoO(3-δ) or the brownmillerite SrCoO(2.5). Importantly, these two phases can be reversibly switched at a remarkably reduced temperature (200-300 °C) in a considerably short time (< 1 min) without destroying the parent framework. The fast, low-temperature redox activity in SrCoO(3-δ) is attributed to a small Gibbs free-energy difference between two topotatic phases. Our findings thus provide useful information for developing highly sensitive electrochemical sensors and low-temperature cathode materials.

Review of Atom Probe FIB-Based Specimen Preparation Methods

Abstract: Several FIB-based methods that have been developed to fabricate needle-shaped atom probe specimens from a variety of specimen geometries, and site-specific regions are reviewed. These methods have enabled electronic device structures to be characterized. The atom probe may be used to quantify the level and range of gallium implantation and has demonstrated that the use of low accelerating voltages during the final stages of milling can dramatically reduce the extent of gallium implantation.