Search NASA⌕ Search

SEARCH · Search NASA

Results for “synthesis (scalable processing)”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Polarization-Independent Optical Broadband Angular Selectivity

Generalizing broadband angular selectivity to both polarizations has been a scientific challenge for a long time. Previous demonstrations of the broadband angular selectivity work only for one polarization. In this paper, we propose a method that can achieve polarization-independent optical broadband angular selectivity. Our design is based on a material system consisting of alternating one-dimensionally anisotropic photonic crystal (1D PhC) stacks and half-wave plates. 1D PhC stacks have an angular photonic band gap for p-polarized light and half-wave plates can convert s-polarized light to p-polarized light. Here, by introducing alternating 1D PhC stacks and half-wave plates, we predict that one can achieve a central transmission angle at normal incidence and an angularly selective range of less than 30° across the whole visible spectrum.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Synthesis of Renewable Thermoset Polymers through Successive Lignin Modification Using Lignin-Derived Phenols

An approach to lignin-based epoxy networks from both organosolv lignin and lignin derived phenol (dihydroeugenol) are developed using multiple chemical modifications including demethylation, phenolation and phenol-formaldehyde reaction. Structures of lignin incorporated novolac polyphenols (LINPs) and epoxy networks (LINENs) were characterized using proton nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Compared to a common synthesis route in which lignin was epoxidized prior to blend with comonomers (LBEN), LINEN derivatives exhibited improved crosslink density ($ρ$), $α$-relaxation temperature ($T_α$) and storage modulus in glassy region ($E_g'$) as obtained from dynamic mechanical analysis (DMA), and increased thermal stability measured by thermogravimetric analysis (TGA). This study widens the routes of lignin modification. Renewable epoxy networks derived from both lignin and lignin derivatives are economically and ecologically attractive.

09 BIOMASS FUELS↗
DOE OSTI2018

Renewable Epoxy Thermosets from Fully Lignin-Derived Triphenols

A series of fully renewable triphenols (TPs) with various number of methoxy group substituents (n = 0–6) were synthesized using lignin-derived phenols (guaiacol and 2,6-dimethoxyphenol) and aldehydes (4-hydroxybenzaldehyde, vanillin, and syringaldehyde). The structural evolution from TPs to epoxy thermosets was followed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. Thermomechanical properties of the resulting epoxy thermosets were investigated by dynamic mechanical analysis (DMA), tensile analysis (TA), and thermogravimetric analysis (TGA). Increasing the content of methoxy groups decreased the glass transition temperature (132–118 °C) and glassy modulus (2.7–2.2 GPa). Thermal stability of high-methoxy-content thermosets was reduced due to electron-donating effects and higher oxygen content. Conversions and isolated yields of TPs significantly decreased as the number of methoxy substituents increased, which markedly determined the feasibility of TPs as precursors for polymers. This work widens the synthesis route of fully lignin-derived polyphenols, yielding polymers with thermomechanical properties comparable to bisphenol A (BPA) based materials. Finally, evaluation of methoxy substitution provides insight for the selection of lignin-derived monomers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Selective Hydrogenation of Biomass-Derived 2(5H)-Furanone to γ-Butyrolactone over Ni-Based Bimetallic Catalysts

2(5H)-Furanone was selectively hydrogenated to γ-butyrolactone (GBL) over Ni-based bimetallic catalysts, Ni-M/SiO2 (M = Fe, Co, Cu, and Zn). Catalyst characterization showed that the metal dispersion and reducibility were changed after introducing a second metal, while the physical morphology was nearly unchanged. The most active and selective bimetallic catalyst was found to be Ni–Fe/SiO2. The reaction rate constant over the 4 wt %Ni–1 wt %Fe/SiO2 bimetallic catalyst was 0.06 min–1, doubling that over 5 wt %Ni/SiO2, and the selectivity to GBL increased slightly from 86.1 to 89.5%. The Fe/(Ni+Fe) weight ratio was changed to optimize the promoting effect of Fe. The Ni–Fe bimetallic effect was further investigated using temperature-programmed desorption experiments on single crystal model surfaces with different Fe/Ni(111) structures, revealing that the enhanced catalyst activity was mainly contributed by the formation of the Ni–Fe surface alloy.

bio-inspired↗
DOE OSTI2019

Phosphoryl-Ligand Adducts of Rare Earth-TriNOx Complexes: Systematic Studies and Implications for Separations Chemistry

Phosphoryl ligands of the general formula O$=$PR 3 (R = Me, OMe, Et, $^n$Bu, Ph, $^i$Pr, NMe 2 ) were coordinated to [Nd(TriNOx)] (TriNOx 3– = ([(2-$^t$BuNO)C 6 H 4 CH 2 ] 3 N) 3– ), and the resulting complexes were characterized. Solution equilibrium constants for each complex were determined, demonstrating a large range for phosphoryl ligands’ Lewis basicity. Thermogravimetric analyses provided evidence for the qualitative thermodynamic preference of phosphoryl ligands for [Nd(TriNOx)] over the dysprosium analogue. Here, these findings were exploited for the separation of binary mixtures of neodymium/dysrosium and lanthanum/neodymium. Implementation of phosphoryl ligands in the TriNOx separation system expands its scope and demonstrates a fundamentally different mode for separating rare-earth cations based on adducts with neutral donors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Direct CO 2 Capture from Air using Poly(ethylenimine)-Loaded Polymer/Silica Fiber Sorbents

Direct CO2 capture from atmospheric air is gaining increased attention as one of the most scalable negative carbon approaches available to tackle climate change if coupled with the sequestration of CO2 geologically. Furthermore, it can also provide CO2 for further utilization from a globally uniform source, which is especially advantageous for economies without natural sources of carbon-based feedstocks. Solid-supported amine-based materials are effective for direct air capture (DAC) due to their high CO2 uptakes and acceptable sorption kinetics at ambient temperature. In this work, we describe the application of polymer/silica fiber sorbents functionalized with a primary amine-rich polymer, poly(ethylenimine) (PEI), for DAC. Monolithic fiber sorbents composed of cellulose acetate and SiO2 are synthesized via the dry-jet, wet quench spinning technique. These fibers are then functionalized with PEI (Mw 800 Da) in a simple and scalable postspinning infusion step and tested for CO2 capture under pseudoequilibrium conditions as well as under breakthrough conditions. An investigation to study the effect of feed flow rate, adsorption temperature, and presence of moisture in the feed on the CO2 breakthrough performance of a densely packed fiber sorbent module is conducted to highlight the potential application of this class of structured contactors in direct air capture. The pressure drop of these contactors at high gas velocities is also evaluated. Finally, a vacuum-assisted desorption step is demonstrated for production of high-purity CO2 from both dry and humid ambient air mixtures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effect of Different Acid Initiators on Branched Poly(propylenimine) Synthesis and CO 2 Sorption Performance

Branched poly(propylenimine) (PPI) provides an alternative to the prototypical amine polymer, commercially available branched poly(ethylenimine) (PEI), in composite adsorbents for CO 2 capture. Herein, we investigate the synthesis of PPI via cationic ring opening polymerization of azetidine using various acid initiators (HBr, HClO 4 , HCl, CH 3 SO 3 H) and polymerization times, impacting the molecular weight and CO 2 sorption behavior. The polymerization kinetics and the amine distribution (i.e., primary:secondary:tertiary ratios) are monitored with 1 H NMR during polymerization, and a basic ion-exchange resin is used to neutralize charged amine centers and to remove unreacted acid. The polymers are impregnated into the model porous oxide support, mesoporous silica SBA-15, and the CO 2 capacities under both simulated ambient air and flue gas conditions are elucidated. In parallel, the oxidative stability of the PPI-based sorbents is assessed and compared with the prototypical PEI sorbents. Sorbents with 30 wt % polymers synthesized using HBr and HClO 4 exhibit higher CO 2 capacities than those made with HCl or CH 3 SO 3 H. Sorbents from HBr polymers only lost 24% of their CO 2 capacity after 12 h of oxidation in air at 383 K. Even trace amounts of residual ClO 4 – anions in HClO 4 initiated polymers, though, accelerated oxidation (decreased CO 2 capacity by 64%). In conclusion, extended resin treatments were needed to leave undetectable Cl content in these polymers, which resulted in sorbents that are much more oxidatively stable.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗