Cu Precipitations at the Surface of Crystalline Cu — Zr Alloys after Annealing in Hydrogen*

Yu, Xin

doi:10.1524/zpch.1989.164.part_2.1171

Cited by 7 publications

(6 citation statements)

References 12 publications

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“…The surface Cu-enrichment upon annealing in H 2 atmosphere of both amorphous and crystalline Zr-Cu alloys was previously reported and described [59,60]; the same underlying phenomenon occurs here in all likelihood. (ii) The second stage is the formation of zirconium hydride.…”

Section: Hydrogen-induced Disproportionationsupporting

confidence: 76%

Hydrogen and Zr-based metallic glasses: Gas/solid absorption process and structure evolution

Paillier

Rongeat

Gutfleisch

et al. 2011

Journal of Alloys and Compounds

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Section: Hydrogen-induced Disproportionationsupporting

confidence: 76%

Hydrogen and Zr-based metallic glasses: Gas/solid absorption process and structure evolution

Paillier

Rongeat

Gutfleisch

et al. 2011

Journal of Alloys and Compounds

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“…19 Oxygen, either dissolved or present as a tertiary suboxide in Cu-rich alloys, also induces surface segregation of Zr with the formation of ZrO 2 when crystalline samples are annealed in ultrahigh vacuum. 20 Formation of zirconium oxide was similarly observed when a rapidly quenched amorphous Cu 30 Zr 70 alloy was exposed to CO 2 /H 2 or CO/H 2 reactant gas mixtures at 523 K. 10 Oxidation of Zr occurs despite a large excess of hydrogen, indicating that the zirconium component is highly reactive toward the carbon oxides. In sharp contrast, massive segregation of copper with the concomitant oxidation of zirconium was observed with the Cu 70 Zr 30 system.…”

Section: Discussionmentioning

confidence: 94%

“…Strong Cu segregation after annealing crystalline copper-rich alloys in hydrogen was reported. 20 No significant change in surface composition was measured, however, when amorphous Cu 30 Zr 70 and crystalline Cu 30 Zr 70 and Cu 70 Zr 30 were treated with hydrogen (473 K, 16 h). 21 In contrast, a thick Cu-enriched layer was formed at the surface of the amorphous Cu 70 Zr 30 alloy ribbon upon the same hydrogen treatment.…”

Section: Discussionmentioning

confidence: 95%

“…The results of hydrogen-induced surface segregation of Cu−Zr alloys are rather controversial. Strong Cu segregation after annealing crystalline copper-rich alloys in hydrogen was reported . No significant change in surface composition was measured, however, when amorphous Cu 30 Zr 70 and crystalline Cu 30 Zr 70 and Cu 70 Zr 30 were treated with hydrogen (473 K, 16 h) .…”

Section: Discussionmentioning

confidence: 97%

“…Preferential oxidation of Zr and Zr enrichment on the surface takes place upon oxygen exposure of amorphous Cu−Zr alloys of various compositions . Oxygen, either dissolved or present as a tertiary suboxide in Cu-rich alloys, also induces surface segregation of Zr with the formation of ZrO 2 when crystalline samples are annealed in ultrahigh vacuum . Formation of zirconium oxide was similarly observed when a rapidly quenched amorphous Cu 30 Zr 70 alloy was exposed to CO 2 /H 2 or CO/H 2 reactant gas mixtures at 523 K .…”

Section: Discussionmentioning

confidence: 98%

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Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Molnár¹,

and²,

Szépvölgyi³

et al. 1998

J. Phys. Chem. B

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X-ray photoelectron spectroscopy was used for surface characterization of amorphous Cu−M alloy powders (Cu40Ti60, Cu50Zr50, and Cu65Hf35) produced by mechanical alloying of the constituents. When used as catalyst in the dehydrogenation of alcohols Cu−Zr and Cu−Hf were found to undergo structural changes resulting in surface copper enrichment with a substantial fraction of copper being in fully reduced, metallic (Cu0) state. This result accounts for the high and stable catalytic activity of Cu−Zr and Cu−Hf in the transformations of alcohols. In contrast, when Cu−Ti is used in inert atmosphere, surface enrichment of titanium is observed. Although segregation of copper occurs in the presence of hydrogen, only oxidized copper species are detected on the surface. In either case, the catalytic activity of Cu−Ti is inferior to the other two alloy samples. TiH2 is shown by XRD to be the characteristic species formed under hydrogen. This is stable in the presence of hydrogen and, therefore, Cu acts as an oxygen scavenger and forms oxidized surface species that do not show catalytic activity.

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Changes induced in the surface characteristics and catalytic activity of amorphous Cu‐Zr by hydrogen pretreatment

Katona¹,

Molnár²,

Perczel

et al. 1992

Surface & Interface Analysis

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Hydrogen-treated amorphous Cu,,Zr,, alloy ribbon exhibits the development of characteristic formations (hemispheres) in a circular arrangement (as revealed by SEM) on both sides of the ribbon, in parallel with copper enrichment (determined by AES) and partial crystallization (determined by differential scanning calorimetry). The extrusion of pure copper is considered to be caused by hydrogen diffusing into the bulk through existing surface defects. As a consequence of the surface and structural changes, steady increases in both the copper surface area and the catalytic activity (dehydrogenation of alcohols and isomerization of allyl alcohol and 2-propyloxiane) are demonstra ted INTRODUCTION EXPERIMENTAL

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Cu Precipitations at the Surface of Crystalline Cu — Zr Alloys after Annealing in Hydrogen*

Cited by 7 publications

References 12 publications

Hydrogen and Zr-based metallic glasses: Gas/solid absorption process and structure evolution

Hydrogen and Zr-based metallic glasses: Gas/solid absorption process and structure evolution

Surface Characterization of Cu−M (M = Ti, Zr, or Hf) Alloy Powder Catalysts

Changes induced in the surface characteristics and catalytic activity of amorphous Cu‐Zr by hydrogen pretreatment

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