Magnetic properties and short-range structure analysis of granular cobalt silicon nitride multilayers

Jiménez-Villacorta, Félix; Espinosa, Ana; Céspedes, Eva; Prieto, C.

doi:10.1063/1.3665877

Cited by 7 publications

(3 citation statements)

References 49 publications

(56 reference statements)

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“…However, both the pre-edge and white line did not reach the same levels as those observed for the cobalt metallic foil, indicating that cobalt atoms remained partially oxidized. To the best of our knowledge, only two experimental studies have reported the XANES spectrum of Co III N, either as a rock-salt-type or a zinc-blende-type structure . The formation of CoN (ZnS type) was excluded for CoO x /Ta 3 N 5 because of the absence of the intense and well-resolved transition Co(1s) → Co(3d-4p), related to the local tetrahedral symmetry around the cobalt atoms (Wyckoff position 4a).…”

Section: Resultsmentioning

confidence: 99%

“…To the best of our knowledge, only two experimental studies have reported the XANES spectrum of Co III N, either as a rock-salt-type 63 or a zinc-blende-type structure. 64 The formation of CoN (ZnS type) was excluded for CoO x /Ta 3 N 5 because of the absence of the intense and well-resolved transition Co(1s) → Co(3d-4p), related to the local tetrahedral symmetry around the cobalt atoms (Wyckoff position 4a). A minor presence of CoN with a rock-salt-type structure cannot be ruled out because the pure compounds display a rather intense white line with a quasi-inexistent pre-edge transition (Co in O h symmetry).…”

Section: Chemistry Of Materialsmentioning

confidence: 99%

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Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

et al. 2015

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ABSTRACT:In a photocatalytic suspension system with a powder semiconductor, the interface between the photocatalyst semiconductor and catalyst should be constructed to minimize resistance for charge transfer of excited carriers. This study demonstrates an in-depth understanding of pretreatment effects on the photocatalytic O 2 evolution reaction (OER) activity of visible-lightresponsive Ta 3 N 5 decorated with CoO x nanoparticles. The CoO x /Ta 3 N 5 sample was synthesized by impregnation followed by sequential heat treatments under NH 3 flow and air flow at various temperatures. Various characterization techniques, including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS), were used to clarify the state and role of cobalt. No improvement in photocatalytic activity for OER over the bare Ta 3 N 5 was observed for the as-impregnated CoO x /Ta 3 N 5 , likely because of insufficient contact between CoO x and Ta 3 N 5 . When the sample was treated in NH 3 at high temperature, a substantial improvement in the photocatalytic activity was observed. After NH 3 treatment at 700 °C, the Co 0 -CoO x core-shell agglomerated cobalt structure was identified by XAS and STEM. No metallic cobalt species was evident after the photocatalytic OER, indicating that the metallic cobalt itself is not essential for the reaction. Accordingly, mild oxidation (200 °C) of the NH 3 -treated CoO x /Ta 3 N 5 sample enhanced photocatalytic OER activity. Oxidation at higher temperatures drastically eliminated the photocatalytic activity, most likely because of unfavorable Ta 3 N 5 oxidation. These results suggest that the intimate contact between cobalt species and Ta 3 N 5 facilitated at high temperature is beneficial to enhancing hole transport and that the cobalt oxide provides electrocatalytic sites for OER. IntroductionWater splitting using powder photocatalyst systems has attracted significant interest for the production of renewable hydrogen generation using abundant solar energy because of its simplicity, scalability, and low capital cost.1,2 To effectively convert solar energy, substantial utilization of photon energy in the visible-light range is essential. Using the AM 1.5G standard spectrum 3 , a photocatalyst with absorption from UV to 600 nm with a quantum efficiency of 30% accounts for ~5% solar to hydrogen efficiency, making the technology commercially feasible.1,4 Among the photocatalysts investigated to date, tantalum(V) nitride (Ta 3 N 5 ) has emerged as one of the most promising candidates and has been extensively investigated for more than a decade. [4][5][6][7][8][9][10][11][12][13][14][15] Ta 3 N 5 has a visible-light response (approximately 600 nm, ~2.1-eV band gap) and is capable of producing hydrogen or oxygen in the presence of appropriate sacrificial reagents and surface modifications under visible-light irradiation. 1,[5][6][7][8][9][10][11][12][13][14][15][16] Our recent work on Ta 3 N 5 thin films for the photo...

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Section: Resultsmentioning

confidence: 99%

Section: Chemistry Of Materialsmentioning

confidence: 99%

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

et al. 2015

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“…In particular, metal-ceramic multilayers show an attractive combination of electrical [3,4], magnetic [5][6][7], optical [8][9][10] and mechanical [11] properties, which are appealing for a number of engineering applications. For instance, metal-ceramic nanolaminates offer a good combination of hardness and toughness, leading to excellent wear resistance for protective coatings [11,12].…”

Section: Introductionmentioning

confidence: 99%

High temperature micropillar compression of Al/SiC nanolaminates

et al. 2013

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The effect of the temperature on the compressive stress-strain behavior of Al/SiC nanoscale multilayers was studied by means of micropillar compression tests at 23 °C and 100 °C. The multilayers (composed of alternating layers of 60 nm in thickness of nanocrystalline A1 and amorphous SiC) showed a very large hardening rate at 23 °C, which led to a flow stress of 3.1 ± 0.2 GPa at 8% strain. However, the flow stress (and the hardening rate) was reduced by 50% at 100 °C. Plastic deformation of the A1 layers was the dominant deformation mechanism at both temperatures, but the A1 layers were extruded out of the micropillar at 100 °C, while A1 plastic flow was constrained by the SiC elastic layers at 23 °C. Finite element simulations of the micropillar compression test indicated the role played by different factors (flow stress of Al, interface strength and friction coefficient) on the mechanical behavior and were able to rationalize the differences in the stress-strain curves between 23 °C and 100 °C.

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Recent advances in modeling of interfaces and mechanical behavior of multilayer metallic/ceramic composites

et al. 2017

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Magnetic properties and short-range structure analysis of granular cobalt silicon nitride multilayers

Cited by 7 publications

References 49 publications

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

High temperature micropillar compression of Al/SiC nanolaminates

Recent advances in modeling of interfaces and mechanical behavior of multilayer metallic/ceramic composites

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Magnetic properties and short-range structure analysis of granular cobalt silicon nitride multilayers

Cited by 7 publications

References 49 publications

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta3N5 Photocatalyst

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta3N5 Photocatalyst

High temperature micropillar compression of Al/SiC nanolaminates

Recent advances in modeling of interfaces and mechanical behavior of multilayer metallic/ceramic composites

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Product

Resources

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Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst

Establishing Efficient Cobalt-Based Catalytic Sites for Oxygen Evolution on a Ta₃N₅ Photocatalyst