Synthesis, characterization and densification of WCu nanocomposite powders

Sahoo, Prasanta Kumar; Kamal, S.S. Kalyan; Manda, Premkumar; Sreedhar, B.; Srivastava, Suneel Kumar; Durai, L.

doi:10.1016/j.ijrmhm.2011.03.011

Cited by 31 publications

(5 citation statements)

References 55 publications

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“…The binding energies at 335.7 and 341.0 eV correspond to the 3d 5/2 and 3d 3/2 levels of Pd 2+ in the form of PdO on the surface of the Pd/W 18 O 49 hybrids. , In Figure D, the W 4f doublet with the binding energies of 35.38 and 37.58 eV could be assigned to W 6+ species, ,− while the W 4f doublet with binding energies of 34.88 and 37.16 eV corresponds to W 5+ . Note that no elemental tungsten was observed in the present 2D W 18 O 49 nanosheet support. , The O 1s patterns are displayed in Figure S5, Supporting Information, to further investigate the chemical states of oxygen in W 18 O 49 and Pd/W 18 O 49 . The peak with binding energy at 530.2 eV corresponds to O 1s levels of oxygen atoms O 2– in the lattice of W 18 O 49 , and the binding energy at 533.2 eV could be assigned to the adsorbed water molecules on the free oxide surface.…”

Section: Resultsmentioning

confidence: 96%

“…Note that no elemental tungsten was observed in the present 2D W 18 O 49 nanosheet support. 46,47 The O 1s patterns are displayed in Figure S5 To elucidate the experimental conditions and the mechanism of the formation of Pd/W 18 O 49 hybrids, control experiments were performed. In the absence of W(CO) 6 , only aggregates of Pd nanoparticles with irregular shapes were obtained under otherwise the same experimental conditions, as demonstrated in Figure S6A, Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

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Strongly Coupled Pd Nanotetrahedron/Tungsten Oxide Nanosheet Hybrids with Enhanced Catalytic Activity and Stability as Oxygen Reduction Electrocatalysts

et al. 2014

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The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Strongly Coupled Pd Nanotetrahedron/Tungsten Oxide Nanosheet Hybrids with Enhanced Catalytic Activity and Stability as Oxygen Reduction Electrocatalysts

et al. 2014

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“…For an average value of x = 0.15 ± 0.05, Eq. [29] leads to Z ffi 0:022 Á T (where T is substituted in K, and Z is obtained in kJ/mol). Expressing T from this equation and substituting it into Eq.…”

Section: On a Stability Criterion And Stability Diagrams To Selmentioning

confidence: 99%

“…[20][21][22][23][24][25][26][27][28] That is why the purpose of this paper is to develop a model for thermodynamic stability of such NG alloys. Although there is plenty of previous literature on both the synthesis [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] and on modeling the stabilization of NG alloys ) (see also reviews [89][90][91][92][93] ), the present paper is novel as it puts this question into a wider framework of the nano-Calphad method, [94,95] i.e., into the thermodynamic framework originally developed by Gibbs. [96] All previous models on GB stability apply the simplest Langmuir-McLean model [97,98] (see also Reference 99) for modeling grain boundary (GB) energy.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Stability of Nano-grained Alloys Against Grain Coarsening and Precipitation of Macroscopic Phases

Kaptay

2019

Metall Mater Trans A

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Thermodynamic conditions are derived here for binary alloys to have their grain boundary (GB) energies negative, ensuring the stability of some nano-grained (NG) alloys. All binary alloys are found to belong to one of the following three types. Type 1 is the unstable NG alloy both against grain coarsening and precipitation of a macro-phase. Type 2 is the partly stable NG alloy, stable against coarsening but not against precipitation. Type 3 is the fully stable NG alloy, both against coarsening and precipitation. Alloys type 1 have negative, or low-positive interaction energies between the components. Alloys type 2 have medium-positive interaction energies, while alloys type 3 have high-positive interaction energies. Equations are derived for critical interaction energies separating alloys type 1 from type 2 and those from type 3, being functions of the molar excess GB energy of the solute, temperature (T) and composition of the alloy. The criterion to form a stable NG alloy is formulated through a new dimensionless number (Ng), defined as the ratio of the interaction energy to the excess molar GB energy of the solute, both taken at zero Kelvin. Systems with Ng number below 0.6 belong to alloy type 1, systems with Ng number between 0.6 and 1 belong to alloy type 2, while systems with Ng number above 1 belong to alloy type 3, at least at T = 0 K. The larger is the Ng number, the higher is the maximum T of stability of the NG alloy. By gradually increasing temperature alloys type 3 convert first into type 2 and further into type 1. The Ng number is used here to evaluate 16 binary tungsten-based (W-B) alloys. At T = 0 K type 3 NG alloys are formed with B = Cu, Ag, Mn, Ce, Y, Sc, Cr; type 2 is formed in the W-Ti system, while type 1 alloys are formed with B = Al, Ni, Co, Fe, Zr, Nb, Mo and Ta. For the WAg system the region of stability of the NG alloys is shown on a calculated phase diagram, indicating also the stable grain size.

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“…W-Cu is a two-phase, bi-continuous, metal-matrix composite consisting of a tungsten (W) matrix phase and a copper (Cu) reinforcement phase. Additionally, W and Cu have different atomic crystal structures (W and Cu being BCC and FCC, respectively), large atomic radii difference of >20%, and significantly different electro-negativities (W=2.36 and Cu=1.9), thus violating the Hume-Rothery rules [44,45] and making them virtually immiscible. An exception to immiscibility exists when W and Cu powders undergo high-energy ball milling.…”

Section: Tungsten-copper Composite (W-cu)mentioning

confidence: 99%

Modelling the elastic properties of bi-continuous composite microstructures captured with TriBeam serial-sectioning

Mignone

Echlin

Pollock

et al. 2017

Computational Materials Science

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The elastic and physical properties of a tungsten-copper (W-Cu) bi-continuous composite were predicted from microstructural data captured using TriBeam serial sectioning. The reconstructed 3D volume was converted into a Finite Element (FE) mesh. The minimum representative volume elements (RVEs) required for calculating phase volume fraction, Young's modulus and Poisson's ratio were determined. The predicted volume fraction of Cu and Young's modulus were found to be within 2.6%, and 3.6% of the respective experimentally determined values. The minimum RVE size is found to be dependent on the material property. The variability in the required RVE size must be considered for material properties of W-Cu and similar bi-continuous composite microstructures.

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Synthesis, characterization and densification of WCu nanocomposite powders

Cited by 31 publications

References 55 publications

Strongly Coupled Pd Nanotetrahedron/Tungsten Oxide Nanosheet Hybrids with Enhanced Catalytic Activity and Stability as Oxygen Reduction Electrocatalysts

Strongly Coupled Pd Nanotetrahedron/Tungsten Oxide Nanosheet Hybrids with Enhanced Catalytic Activity and Stability as Oxygen Reduction Electrocatalysts

Thermodynamic Stability of Nano-grained Alloys Against Grain Coarsening and Precipitation of Macroscopic Phases

Modelling the elastic properties of bi-continuous composite microstructures captured with TriBeam serial-sectioning

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