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Results for “REGENERATION”
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.
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Regeneration of Active Surface Alloys during Cyclic Oxidation and Reduction: Oxidation of H 2 on Pd/Ag(111)
The surface morphology and composition of a catalyst during excursions between oxidizing and reducing conditions can change substantially, especially in bimetallic alloys. Both thermodynamic and kinetic factors play a role in determining the properties of alloy surfaces where the active phase may be a metastable state. Previously, Ag oxide reduction was shown to be dramatically enhanced when Pd is on the surface; however, Pd is more stable when dissolved in Ag, raising the question as to whether a highly active Pd surface state will persist over multiple reaction cycles—a requirement for catalytic function. Experiments herein demonstrate that the enhanced chemical functionality due to the presence of Pd on the surface is retained, based on the enhanced rate of silver oxide reduction over multiple oxidation/reduction cycles for a Pd/Ag(111) model. Repeated oxidation and reduction promote PdAg alloying and reversible structural and compositional changes are detected using X-ray photoelectron spectroscopy. Furthermore, this study establishes that metastable phases can persist in reactive processes on surfaces, indicating their potential in heterogeneous catalysis.
Modeling Electrochemical Vacancy Regeneration in Single-Walled Carbon Nanotubes
Not provided.
Regenerable Multifunctional Sorbent Development for Sulfur and Chloride Removal from Coal-Derived Synthesis Gas
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Regenerable Manganese-Based Sorbent for Cleanup of Simulated Biomass-Derived Syngas
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Effect of Additives on Decomposition of Sodium Carbonate: Precombustion CO2 Capture Sorbent Regeneration
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Carbon Dioxide Capture from the Air Using a Polyamine Based Regenerable Solid Adsorbent
Easy to prepare solid materials based on fumed silica impregnated with polyethylenimine (PEI) were found to be superior adsorbents for the capture of carbon dioxide directly from air. During the initial hours of the experiments, these adsorbents effectively scrubbed all the CO(2) from the air despite its very low concentration. The effect of moisture on the adsorption characteristics and capacity was studied at room temperature. Regenerative ability was also determined in a short series of adsorption/desorption cycles.
Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent
A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load 1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.
The chemistry of metal–organic frameworks for CO2 capture, regeneration and conversion
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A Membraneless Electrochemically Mediated Amine Regeneration for Carbon Capture
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Sulfur-resistant and regenerable Ni/Co spinel-based catalysts for methane dry reforming
Oxide-supported metal catalysts were prepared in this study by thermal impregnation of highly crystalline and highly-faceted starting spinels of the form (M 0.75 Mg 0.25 )Al 2 O 4 , where M = Ni, Co, or Cu and mixtures thereof. In situ reduction at 900°C extracts the transition metals from the oxide, and the resulting catalysts contain metal crystallites with particle sizes of ~100 nm and exceedingly low dispersion, but show high activity for dry reforming of methane with turnover frequencies as large as 3.9 at 850°C. The Ni 0.37 5Cu 0.375 Mg 0.25 Al 2 O 4 catalyst shows stable methane conversion out to 12 hours on stream without performance-degrading coking. For the Ni/Co catalysts, the reforming activity and sulfur tolerance are both functions of the Ni/Co ratio and the synthesis temperature of the starting spinel, with Ni 0.375 Co 0.375 Mg 0.25 Al 2 O 4 synthesized at 1500°C displaying fast reaction kinetics even in the presence of 20 ppm H 2 S. High reforming activity is attributed to long linear lengths of high-perfection facet edges and corners on the metal crystallites. Sulfur tolerance seems to be improved by a combination of the oxygen storage capacity of the defective spinel support and its faceting that provides additional reaction sites for activation of CO 2 .
Polyester functional graphenic materials as a mechanically enhanced scaffold for tissue regeneration
Traditional metal implants such as titanium, cobalt, and chromium have found wide utility in medicine; however, these come with a risk of toxicity. To overcome metal-related toxicity and enable degradability, polyesters including polycaprolactone (PCL), polylactic acid (PLA), and polyglycolic acid (PGA) show promise for the replacement of various biomedical applications of metals due to their accepted biocompatibility and FDA approval. However, polyesters are less stiff than their metallic counterparts, limiting their application to non-load bearing injury sites, such as fixation hardware for fingers. To improve mechanical properties, graphene oxide (GO)-polyester composites are a promising class of biodegradable scaffolds. Initial reports of these composites are encouraging, but mechanical properties still fall short. Traditional composites rely on non-covalent association between GO and the polyesters, which often leads to failure at the interface and weakens the overall strength of the material. Herein, we present a strategy for attachment of these FDA-approved polyesters onto a derivative of GO using a robust covalent bond. By covalently functionalizing the graphenic backbone with polyesters and without metal catalysts, we create functional graphenic materials (FGMs) to not only simultaneously retain biodegradability and compatibility, but also mechanically strengthen PCL, PLA, and PGA; we observed an average increase in the Young's modulus of over 140% compared to the graphenic backbone. These polyester-functionalized FGMs are a promising platform technology for tissue implants.