The Experts below are selected from a list of 51708 Experts worldwide ranked by ideXlab platform
Christoph Kenel - One of the best experts on this subject based on the ideXlab platform.
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hierarchically porous metallic scaffolds via 3d extrusion and reduction of Oxide Particle inks with salt space holders
Additive manufacturing, 2020Co-Authors: Christoph Kenel, Nicholas R Geisendorfer, Ramille N Shah, David C DunandAbstract:Abstract 3D ink-extrusion of powders followed by sintering is an emerging additive manufacturing method capable of creating metallic microlattices. Here, we study the creation of hierarchically porous Fe or Ni scaffolds by 3D extrusion of 0/90° lattices from inks consisting of fine Oxide powders (Fe2O3 or NiO,
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microstructure and Oxide Particle stability in a novel ods γ tial alloy processed by spark plasma sintering and laser additive manufacturing
Intermetallics, 2017Co-Authors: Christoph Kenel, Karl Dawson, Josh Barras, Carl Hauser, Georgia Dasargyri, Thomas Bauer, Alberto Colella, Adriaan B Spierings, G J TatlockAbstract:Abstract In this work, a novel Oxide dispersion strengthened titanium aluminide alloy (Ti-45Al-3Nb- 2 O 3 at.%) was developed for powder-based processing technologies with a focus on spark plasma sintering and additive manufacturing. Titanium aluminides are promising structural intermetallics for weight reduction and an increased performance of high temperature components. The alloy design and selection process was supported by computational thermodynamics based on the CALPHAD approach, taking into account requirements for processing as well as long term alloy behavior under service conditions. Processing trials using spark plasma sintering, direct metal deposition and selective laser melting were conducted to study the alloy behavior, microstructure formation and introduction as well as stability of the ODS Particles. Additionally, thermal annealing on the sintered and laser consolidated material was performed. Conventional dual phase α 2 -Ti 3 Al and γ-TiAl duplex and near-lamellar microstructures were obtained from the processed material. The ODS Particles were homogeneously distributed in the alloy matrix after processing in the liquid state. For the direct metal deposition process, the novel alloy was compared to the established GE48-2-2 alloy (Ti-48Al-2Cr-2Nb) in terms of phases, microstructure and texture after processing. A significantly reduced texture formation was observed with the novel alloy. The hardness of the consolidated material shows superior properties for ODS-containing TiAl compared to ODS-free material. This work provides a first step towards tailored alloys for AM and the production of ODS TiAl alloys.
Vicki H Grassian - One of the best experts on this subject based on the ideXlab platform.
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surface catalyzed chlorine and nitrogen activation mechanisms for the heterogeneous formation of clno no no2 hono and n2o from hno3 and hcl on aluminum Oxide Particle surfaces
Journal of Physical Chemistry A, 2012Co-Authors: Gayan Rubasinghege, Vicki H GrassianAbstract:It is well-known that chlorine active species (e.g., Cl2, ClONO2, ClONO) can form from heterogeneous reactions between nitrogen Oxides and hydrogen chloride on aerosol Particle surfaces in the stratosphere. However, less is known about these reactions in the troposphere. In this study, a potential new heterogeneous pathway involving reaction of gaseous HCl and HNO3 on aluminum Oxide Particle surfaces, a proxy for mineral dust in the troposphere, is proposed. We combine transmission Fourier transform infrared spectroscopy with X-ray photoelectron spectroscopy to investigate changes in the composition of both gas-phase and surface-bound species during the reaction under different environmental conditions of relative humidity and simulated solar radiation. Exposure of surface nitrate-coated aluminum Oxide Particles, from prereaction with nitric acid, to gaseous HCl yields several gas-phase products, including ClNO, NO2, and HNO3, under dry (RH 20%), NO and ...
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xps study of nitrogen diOxide adsorption on metal Oxide Particle surfaces under different environmental conditions
Physical Chemistry Chemical Physics, 2009Co-Authors: Jonas Baltrusaitis, P M Jayaweera, Vicki H GrassianAbstract:The adsorption of nitrogen diOxide on gamma aluminium Oxide (γ-Al2O3) and alpha iron Oxide (α-Fe2O3) Particle surfaces under various conditions of relative humidity, presence of molecular oxygen and UV light has been investigated. X-Ray photoelectron spectroscopy (XPS) is used to monitor the different surface species that form under these environmental conditions. Adsorption of NO2 on aluminum Oxide Particle surfaces results primarily in the formation of surface nitrate, NO3− with an oxidation state of +5, as indicated by a peak with binding energy of 407.3 eV in the N1s region. An additional minority species, sensitive to the presence of relative humidity and molecular oxygen, is also observed in the N1s region with lower binding energy of 405.9 eV. This peak is assigned to a surface species in the +4 oxidation state. When irradiated with UV light, other species form on the surface. These surface-bound photochemical products all have lower binding energy, between 400 and 402 eV, indicating reduced nitrogen species in the range of N oxidations states spanning +1 to −1. Co-adsorbed water decreases the amount of these reduced surface-bound products while the presence of molecular oxygen completely suppresses the formation of all reduced nitrogen species on aluminum Oxide Particle surfaces. For NO2 on iron Oxide Particle surfaces, photoreduction is enhanced relative to γ-Al2O3 and surface bound photoreduced species are observed under all environmental conditions. Complementing the experimental data, N1s core electron binding energies (CEBEs) were calculated using DFT for a number of nitrogen-containing species in the gas phase and adsorbed on an Al8O12cluster. A range of CEBEs is calculated for various nitrogen species in different adsorption modes and oxidation states. These calculated values are discussed in light of the peaks observed in the XPS N1s region and the possible species that form following NO2 adsorption and photoreaction on metal Oxide Particle surfaces under different conditions of relative humidity, presence of molecular oxygen and UV light.
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photochemistry of adsorbed nitrate on aluminum Oxide Particle surfaces
Journal of Physical Chemistry A, 2009Co-Authors: Gayan Rubasinghege, Vicki H GrassianAbstract:Nitrogen Oxides, including nitrogen diOxide and nitric acid, react with mineral dust Particles in the atmosphere to yield adsorbed nitrate. Although nitrate ion is a well-known chromophore in natural waters, little is known about the surface photochemistry of nitrate adsorbed on mineral Particles. In this study, nitrate adsorbed on aluminum Oxide, a model system for mineral dust aerosol, is irradiated with broadband light (λ > 300 nm) as a function of relative humidity (RH) in the presence of molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products including NO2, NO, and N2O, with NO being the major product. The relative ratio and product yields of these gas-phase products change with RH, with N2O production being highest at the higher relative humidities. Furthermore, an efficient dark reaction readily converts the major NO product into NO2 during post-irradiation. Photochemical processes on mineral dust aerosol surfaces have the pot...
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spectroscopic study of nitric acid and water adsorption on Oxide Particles enhanced nitric acid uptake kinetics in the presence of adsorbed water
Journal of Physical Chemistry A, 2001Co-Authors: A L Goodman, E T Bernard, Vicki H GrassianAbstract:In this study, the heterogeneous reactivity of nitric acid on Oxide Particles of some of the most abundant crustal elements is investigated at 296 K. The Oxide Particles are used as models for mineral dust aerosol found in the atmosphere. Transmission FT-IR spectroscopy is used to probe changes in the spectrum of the Oxide Particle surface following adsorption of HNO3 on SiO2, α-Al2O3, TiO2, γ-Fe2O3, CaO, and MgO. It is found that HNO3 molecularly and reversibly adsorbs on SiO2. For the other Oxides investigated, HNO3 dissociatively and irreversibly adsorbs to form surface nitrate. There is also a small amount of molecularly adsorbed nitric acid (<10% of the adsorbed nitrate) on the Oxide Particle surface in the presence of gas-phase nitric acid. Because adsorbed water may play a role in the heterogeneous uptake of nitric acid in the atmosphere, transmission FT-IR spectroscopy is used to investigate H2O adsorption on SiO2, α-Al2O3, TiO2, γ-Fe2O3, CaO, and MgO Particles as well. Uptake of water on the oxid...
Chunfu Zhang - One of the best experts on this subject based on the ideXlab platform.
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prolonged in vivo circulation time by zwitterionic modification of magnetite nanoParticles for blood pool contrast agents
Contrast Media & Molecular Imaging, 2012Co-Authors: Wangchuan Xiao, Yuxin Chen, Mingli Li, Chunfu Zhang, Dan Li, Hongchen GuAbstract:Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron Oxide Particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the Particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoParticles via EDC/NHS [N-(3-dimethylaminopropyl)-N′-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic Particles demonstrated five times lower macrophage cell uptake than the original Particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoParticles had much longer in vivo circulation time than the original Particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoParticles with carboxyl surface and to prolong their circulating time. Copyright © 2012 John Wiley & Sons, Ltd.
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prolonged in vivo circulation time by zwitterionic modification of magnetite nanoParticles for blood pool contrast agents
Contrast Media & Molecular Imaging, 2012Co-Authors: Wangchuan Xiao, Yuxin Chen, Jiang Lin, Chunfu ZhangAbstract:Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron Oxide Particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the Particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoParticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic Particles demonstrated five times lower macrophage cell uptake than the original Particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoParticles had much longer in vivo circulation time than the original Particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoParticles with carboxyl surface and to prolong their circulating time.
Cesar Pulgarin - One of the best experts on this subject based on the ideXlab platform.
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iron Oxide mediated semiconductor photocatalysis vs heterogeneous photo fenton treatment of viruses in wastewater impact of the Oxide Particle size
Journal of Hazardous Materials, 2017Co-Authors: Stefanos Giannakis, Siting Liu, Anna Carratala, Sami Rtimi, Masoud Talebi Amiri, M Bensimon, Cesar PulgarinAbstract:The photo-Fenton process is recognized as a promising technique towards microorganism disinfection in wastewater, but its efficiency is hampered at near-neutral pH operating values. In this work, we overcome these obstacles by using the heterogeneous photo-Fenton process as the default disinfecting technique, targeting MS2 coliphage in wastewater. The use of low concentrations of iron Oxides in wastewater without H2O2 (wustite, maghemite, magnetite) has demonstrated limited semiconductor-mediated MS2 inactivation. Changing the operational pH and the size of the Oxide Particles indicated that the isoelectric point of the iron Oxides and the active surface area are crucial in the success of the process, and the possible underlying mechanisms are investigated. Furthermore, the addition of low amounts of Fe-Oxides (1mgL-1) and H2O2 in the system (1, 5 and 10mgL-1) greatly enhanced the inactivation process, leading to heterogeneous photo-Fenton processes on the surface of the magnetically separable Oxides used. Additionally, photo-dissolution of iron in the bulk, lead to homogeneous photo-Fenton, further aided by the complexation by the dissolved organic matter in the solution. Finally, we assess the impact of the presence of the bacterial host and the difference caused by the different iron sources (salts, Oxides) and the Fe-Oxide size (normal, nano-sized).
Wangchuan Xiao - One of the best experts on this subject based on the ideXlab platform.
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prolonged in vivo circulation time by zwitterionic modification of magnetite nanoParticles for blood pool contrast agents
Contrast Media & Molecular Imaging, 2012Co-Authors: Wangchuan Xiao, Yuxin Chen, Mingli Li, Chunfu Zhang, Dan Li, Hongchen GuAbstract:Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron Oxide Particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the Particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoParticles via EDC/NHS [N-(3-dimethylaminopropyl)-N′-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic Particles demonstrated five times lower macrophage cell uptake than the original Particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoParticles had much longer in vivo circulation time than the original Particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoParticles with carboxyl surface and to prolong their circulating time. Copyright © 2012 John Wiley & Sons, Ltd.
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prolonged in vivo circulation time by zwitterionic modification of magnetite nanoParticles for blood pool contrast agents
Contrast Media & Molecular Imaging, 2012Co-Authors: Wangchuan Xiao, Yuxin Chen, Jiang Lin, Chunfu ZhangAbstract:Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron Oxide Particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the Particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoParticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic Particles demonstrated five times lower macrophage cell uptake than the original Particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoParticles had much longer in vivo circulation time than the original Particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoParticles with carboxyl surface and to prolong their circulating time.
