7,207 research outputs found
Fe-Cluster Pushing Electrons to N‑Doped Graphitic Layers with Fe<sub>3</sub>C(Fe) Hybrid Nanostructure to Enhance O<sub>2</sub> Reduction Catalysis of Zn-Air Batteries
No full textNon-noble metal catalysts with catalytic
activity toward oxygen reduction reaction (ORR) comparable or even
superior to that of Pt/C are extremely important for the wide application
of metal–air batteries and fuel cells. Here, we develop a simple
and controllable strategy to synthesize Fe-cluster embedded in Fe3C nanoparticles (designated as Fe3C(Fe)) encased
in nitrogen-doped graphitic layers (NDGLs) with graphitic shells as
a novel hybrid nanostructure as an effective ORR catalyst by directly
pyrolyzing a mixture of Prussian blue (PB) and glucose. The pyrolysis
temperature was found to be the key parameter for obtaining a stable
Fe3C(Fe)@NDGL core–shell nanostructure with an optimized
content of nitrogen. The optimized Fe3C(Fe)@NDGL catalyst
showed high catalytic performance of ORR comparable to that of the
Pt/C (20 wt %) catalyst and better stability than that of the Pt/C
catalyst in alkaline electrolyte. According to the experimental results
and first principle calculation, the high activity of the Fe3C(Fe)@NDGL catalyst can be ascribed to the synergistic effect of
an adequate content of nitrogen doping in graphitic carbon shells
and Fe-cluster pushing electrons to NDGL. A zinc–air battery
utilizing the Fe3C(Fe)@NDGL catalyst demonstrated a maximum
power density of 186 mW cm–2, which is slightly
higher than that of a zinc–air battery utilizing the commercial
Pt/C catalyst (167 mW cm–2), mostly because of the
large surface area of the N-doped graphitic carbon shells. Theoretical
calculation verified that O2 molecules can spontaneously
adsorb on both pristine and nitrogen doped graphene surfaces and then
quickly diffuse to the catalytically active nitrogen sites. Our catalyst
can potentially become a promising replacement for Pt catalysts in
metal-air batteries and fuel cells
Precipitation of supersaturated solute in H ion irradiated Fe-Au and Fe-Au-W alloys studied by positron annihilation spectroscopy
No full textThe effect of thermal aging of homogenized Fe-Au and Fe-Au-W alloys, irradiated at room temperature with hydrogen ions, was studied for an aging treatment at 300 °C for aging times up to 100 h. The aging behavior of the Fe-based alloys is compared to the results for pure Fe. The precipitation behavior of Au-rich and W-rich precipitates and its correlation to the H+ irradiation-induced defects is investigated by variable energy positron annihilation spectroscopy (VEPAS). The formation of open-volume defects after irradiation is monitored by an increase in the S parameter, while the recovery of the vacancy-like defects and the formation of precipitates are signalled by an increase in the W parameter. Au-rich precipitation continuously develops during long-term aging, as indicated by the increase in the W parameter. The change of the W parameter in the Fe-Au-W alloy is not only due to the effect of solute W on the Au precipitates, but also because of the interface of W-rich Laves phase with matrix.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Novel Aerospace MaterialsRST/Fundamental Aspects of Materials and Energ
General Sheman's Visit to Santa Fe
No full textComments on an article by the Jesuits, concerning General Sherman's visit to Santa Fe, from Revista Catolica, October 12, 1878. Fight against the Jesuits, Catholic Church, comment on Bishop Lamy, St. Francis Cathedral, Protestants. Translated from Spanish to English. No sure of author? Document in English, 1 pp/fr, two pages per frame
Direct promotion effect of Fe on no reduction by activated carbon loaded with Fe species
No full textActivated carbon materials loaded with Fe species were prepared via an impregnation method and studied. Various analyses showed good dispersion of Fe species on the activated carbon surface when the loading amount did not exceed 2 g of iron(III) nitrate nonahydrate on 10 g of activated carbon. Additionally, the simultaneously existing forms of Fe species on the activated samples were found to be Fe3O4, FeO, and elemental Fe(0). NO reduction experiments under anaerobic conditions showed that the loading of Fe species enhanced the NO reducing ability from an NO conversion of (28 to 86)% at 850 degrees C, which is a more remarkable influence on NO reduction than that of the well-known C-O complexes. Thermodynamic analysis and detailed experimental results led to a new mechanism with two independent routes, both of which require Fe participation and proceed at temperatures below and above 800 degrees C, respectively, and generate different COx products. Furthermore, one of the routes was more efficient in reducing NO than the other. This mechanism explained the experiments much better than the existing C-O theory of complexes. (C) 2015 Elsevier Ltd. All rights reserved
Simultaneously Improved Bendability and Strength of Al–Mg–Si–Cu–Zn Alloys by Controlling the Formation and Evolution of Primary Fe-Rich Phase
No full textIn present work, the formation, evolution, and distribution of the primary Fe-rich phase in an Al–Mg–Si–Cu–Zn–Fe–Mn alloy are coupling controlled by ultrasonic melt treatment (USMT) and thermomechanical processing (TMP). It is shown in the results that the size of grains and Fe-rich phase in the as-cast state can be greatly reduced by the applied optimum USMT at 680 °C. Additionally, the transformation rate of β-Fe-rich phase to α-Fe-rich phase can be also enhanced. After the coupling control of USMT and TMP, the number density and distribution uniformity of multiscale Fe-rich particles can be greatly increased or improved, which contributes to the fine-grained recrystallization microstructure and weakened texture. Finally, compared with the 6xxx series Al alloys (such as AA6016 and AA6111), the alloy sheet in the pre-aging state exhibits substantially improved bendability and strength (the plastic strain ratio and tensile strength are 0.67 and 304 MPa, respectively). The effect of USMT on the formation and transformation of primary Fe-rich phase and the mechanisms of improved bendability and strength are deeply discussed.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Maria Santofimia Navarr
Fe incorporation in cement hydrates: experiments and thermodynamic modeling
No full textCurrent understanding of the state of Fe during the hydration of cement is very limited and further studies are necessary to find out the possible incorporation of Fe in cement hydrates. Moreover, it is important to understand the hydration reaction and properties development of ferrite-rich cement. Our previous study [1] reported the hydration reaction and properties of ferrite-rich Portland cement by various experimental techniques and thermodynamic modelling and compared with ordinary Portland cement. However, we could not quantify the Fecontaining hydrates in the cements and the uptake of Fe by C-S-H. Therefore, the objective of this study is to quantify the Fe-containing hydrates during the hydration of ordinary Portland cement and ferrite-rich Portland cement. Ordinary Portland cement and ferrite-rich Portland cement were hydrated for 3 months and the hydration products were quantified with XRD/Rietveld analysis. The selective dissolution was used to determine the amount of Fe-containing phases. It was found that Fe-siliceous hydrogarnet was the primary Fe-containing phase. From the hydration of ferrite and amount of formed Fesiliceous hydrogarnet, the Fe uptake in C-S-H was determined. The distribution ratio for Fe uptake in C-S-H and chemical composition of Fe-siliceous hydrogarnet were incorporated into the thermodynamic model to predict the hydration reaction of ordinary Portland cement and ferrite-rich Portland cement and the results were compared with experimental data of XRD/Rietveld analysis and selective dissolution. The successful agreement of the experimental results with the model demonstrates the state of Fe in the hydrated cements
Self healing of radiation-induced damage in Fe–Au and Fe–Cu alloys: Combining positron annihilation spectroscopy with TEM and ab initio calculations
No full textSelf healing of early stage radiation damage by site selective solute segregation is a promising approach to extend the lifetime of nuclear reactor components. In the present study, the creation and autonomous healing of irradiation-induced damage is investigated in pure Fe and high purity Fe–Au and Fe–Cu model alloys. To create radiation damage samples are irradiated at 550 °C by 120 keV He+ ions with fluences of 5.0 × 1015, 1.0 × 1016 and 5.0 × 1016 ions/cm2. The observed increase in the S and W parameters determined in the variable energy positron annihilation spectroscopy measurements indicates the formation of vacancy-like defects, precipitates and vacancy-solute complexes. The presence of substitutionally dissolved Au is found to reduce the formation of radiation defects more efficiently than solute Cu. Site-specific Au precipitation at defect sites is indicated, which results in damage healing with a reduced swelling, whereas Cu precipitates and radiation damage only show weak interaction. Ab initio calculations show that the binding energies of Au solutes to vacancy clusters (Au-Vn) are significantly larger than those of Cu solutes (Cu-Vn) whereas the binding energies of helium filled vacancy clusters Au-HenVn and Cu-HenVn are comparable.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Fundamental Aspects of Materials and EnergyNovel Aerospace Material
Surface Oxidation and Wettability of Fe–Mn and Fe–Mn–Si-Alloyed Steel After Annealing
No full textThe surface oxidation and wettability of Mn and Si-alloyed steel after annealing at different conditions are studied with scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and a so-called de-wetting method. After exposure at 950 °C for 1 hour in an Ar + 5 vol pct H2 gas atmosphere with dew points (DP) ranging from – 40 °C to 10 °C, oxides were observed along the grain boundaries or dispersed on the surface for the Fe–1.8 Mn steels while a continuous oxides layer was formed on Fe–1.9 Mn–0.94 Si steels (composition in weight fractions). The oxides formed at different DPs were predicted based on thermodynamic calculations. (Fe,Mn)O was formed on Fe–1.8 Mn steel at the whole range of DPs, while the oxide phase on Fe–1.9 Mn–0.94 Si steel depends on the DP. At low-DP SiO2 were formed and with increasing the DP (Fe,Mn)SiO3 or (Fe,Mn)SiO3 + (Fe,Mn)2SiO4 were formed and finally (Fe,Mn)2SiO4 were formed. An increase of the fraction of Fe in the oxide with increasing DP for both steels was observed with XPS analysis. As a measure for the surface wettability, the contact angle of Pb droplets on the annealed steels surfaces was determined with SEM and image analysis software. Also, the contact angle of Pb on pure Fe and on the Mn and Si alloyed steels free of surface oxides was measured for comparison. The results show that the contact angle of Pb on the steel surfaces after annealing decreases with increasing DP. This improved wettability with increasing dew point is related to the Fe fraction of the oxides formed on the surface.Team Kevin RossiTeam Maria Santofimia NavarroTeam Marcel Herman
Enhanced reversibility of the magnetoelastic transition in (Mn,Fe)<sub>2</sub>(P,Si) alloys via minimizing the transition-induced elastic strain energy
No full textMagnetocaloric materials undergoing reversible phase transitions are highly desirable for magnetic refrigeration applications. (Mn,Fe)2(P,Si) alloys exhibit a giant magnetocaloric effect accompanied by a magnetoelastic transition, while the noticeable irreversibility causes drastic degradation of the magnetocaloric properties during consecutive cooling cycles. In the present work, we performed a comprehensive study on the magnetoelastic transition of the (Mn,Fe)2(P,Si) alloys by high-resolution transmission electron microscopy, in situ field- and temperature-dependent neutron powder diffraction as well as density functional theory calculations (DFT). We found a generalized relationship between the thermal hysteresis and the transition-induced elastic strain energy for the (Mn,Fe)2(P,Si) family. The thermal hysteresis was greatly reduced from 11 to 1 K by a mere 4 at.% substitution of Fe by Mo in the Mn1.15Fe0.80P0.45Si0.55 alloy. This reduction is found to be due to a strong reduction in the transition-induced elastic strain energy. The significantly enhanced reversibility of the magnetoelastic transition leads to a remarkable improvement of the reversible magnetocaloric properties, compared to the parent alloy. Based on the DFT calculations and the neutron diffraction experiments, we also elucidated the underlying mechanism of the tunable transition temperature for the (Mn,Fe)2(P,Si) family, which can essentially be attributed to the strong competition between the covalent bonding and the ferromagnetic exchange coupling. The present work provides not only a new strategy to improve the reversibility of a first-order magnetic transition but also essential insight into the electron-spin-lattice coupling in giant magnetocaloric materials.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.RST/Fundamental Aspects of Materials and Energ
Workshop on the Open Archives Initiative (OAI) and peer review journals in Europe : a report
No full textA workshop on the Open Archives Initiative and Peer Review Journals in Europe was held at CERN, in Geneva, from March 22nd to 24th. The purpose of this workshop was to mobilise a group of European scientists and librarians who want to play an active role in organizing a self-managed system for electronic scholarly communication. Such a system should be compliant with the technical standards proposed by the Open Archives Initiative (OAI). The immediate deployment of OAI-compliant e-print repositories was a concrete objective of the workshop. The workshop had a second (exploratory) objective, related to the certification of writings submitted to archives
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