Oxygen In Cu Research Articles

Ordering of oxygen into chains and distribution of hole density in YBa 2Cu 3O 1+ x

A series of Y 0.999Gd 0.001Ba 2Cu 3O 6+ x compounds is studied by Gd 3+ EPR in the full range of oxygen content. The fine structu re is modified by the hole distribution in the Cu(2)O 2 layers mirroring oxygen chains in the Cu(1)O x layers. The fine structure of 5 differently occupied first-neighbour Cu(1)O x oxygen chain configurations surrounding the Gd 3+ ions is resolved. Formation of chain begins at a threshold oxygen content x 0=0.14. For x>0.14 oxygen in Cu(1)O x planes is ordered mainly into chains, the amount of disordered oxygen decreases with increasing x. The EPR intensities are in quantitative agreement with a model calculation of 2-dimensionally ordered oxygen chains.

KINETICS OF OXYGEN EXCHANGE IN HIGH TEMPERATURE SUPERCONDUCTOR YBa2Cu3O6+x

Kinetics of oxygen absorption in YBa 2 Cu 3 O 6+x has been described. Experiments were performed in the high pressure reactor with constant volume in the temperature range of 150–700°C and oxygen pressure 1.4–10.7 atm. Two stages of oxygen absorption in tetraphase have been discovered. The first is related to the formation of a solid solution of oxygen in Cu(I) layers with the activation energy 0.07 ± 0.01 eV . The second one is oxygen diffusion in the system of short disordered chains ( Cu − O )n with the activation energy 0.30 ± 0.01 eV . Growths of chains and their interaction during the second stage results in the formation of ortho-phase accompanied by further decrease of the reaction rate. Structure-chemical reasons for the multistage mechanism of oxygen absorption are discussed.

酸化物超電導体粉末のガス吸脱着特性

Temperature programmed desorption (TPD) measurements in vacuum were examined for the oxide superconducting powders of synthesized high Tc Bi-Pb-Sr-Ca-Cu (Bi system) and YBa2Cu3O7-y (Y system). Oxygen desorption peak was observed around 470°C for the powder of Bi system after annealing at 400°C in oxygen atmosphere. Oxgen desorption peaks of Y system have been separated in four peaks. The desorption peak at 400-460°C is owing to the desorption of oxygen in Cu(1) plane. Two desorption peaks at 650-670°C and at 790°C seem to originate from impurity phases. The desorption peak at 900°C arises from phase separation reaction.To estimate sensitivity to water and carbon dioxide of the powders of Bi and Y system, TPD measurements were carried out after exposure to water vapor or carbon dioxide. TPD spectra of Bi system show no remarkable difference from those after annealing in oxygen atmosphere. However, two water desorption peaks were observed for the powders of Y system after exposure to water vapor at room temperature, which suggests that chemical reaction have proceeded.

Deuterium Interactions with Ion-Implanted Oxygen in Cu and Au

ABSTRACTThe interactions of deuterium (D) with oxygen in Cu and Au were examined using ion implantation, nuclear-reaction analysis, and transmission electron microscopy. In Cu, the reduction of Cu2O precipitates by D to produce D20 was shown to occur readily down to room temperature, at a rate limited by the transport of D to the oxides. The reverse process of D2O dissociation was characterized for the first time below the temperature range of steam blistering. The evolution of the Cu(D)-Cu2O-D2O system was shown to be predicted by a newly extended transport formalism encompassing phase changes, trapping, diffusion, and surface release. In Au, buried 0 sinks were used to measure the permeability of D at 573 and 373 K, thereby extending the range of measured permeabilities downward by about six orders or magnitude.

The Copper-catalyzed Autoxidation of Cysteine.The Amount of Hydrogen Peroxide Produced under Various Conditions and the Stoichiometry of the Reaction

Abstract Hydrogen peroxide is shown to be produced as an intermediate from oxygen in the copper-catalyzed autoxidation of cysteine. The amounts of cysteine oxidized and of hydrogen peroxide formed varied depending on the reaction conditions employed. The perpxide upon forming was spontaneously utilized for the oxidation of cysteine. As a result, the ratio of the concentration of hydrogen peroxide formed to cysteine oxidized is variable depending on the conditions. But, in dilute solutions, where the oxidation by the peroxide was slow, a stiochiometric relation of 2:1 was obtained between cysteine consumed and hydrogen peroxide produced. The rate of autoxidation is dependent on the concentration of oxygen dissolved. The double reciprocal plot of the rate against the concentration of oxygen gives a straight line, which indicates a possibility of the Michaelis-Menten type mechanism concerning the reoxidation or oxygenation of Cu(I) species.

The annealing and re-oxidation of oxidized Cu [sbnd]Ni alloys

A study has been made of the effects of an intermediate, isothermal annealing treatment in argon on the oxidation kinetics in dry oxygen of Cu 10%Ni and Cu 24%Ni at 800°C and Cu 80%Ni at 1000°C using a semi-automatic microbalance. Changes in scale morphology and composition have been investigated using various techniques. Oxidation of Cu 10%Ni and Cu 24%Ni produces external scales consisting of a thick, inner Cu 2O layer and a thin, outer CuO layer, together with nickel-rich internal oxide in the adjacent alloy. Oxidation of Cu 80%Ni yields an external scale consisting of a thick, inner NiO layer and a thin, outer CuO layer, together with a few nickel-rich internal oxide particles in the adjacent alloy. During annealing, the outer CuO layers on the three alloys dissociate to give Cu 2O and oxygen. With Cu 80%Ni only, further dissociation to give copper metal takes place after long annealing times. In all cases, the annealing treatment leads to a reduction in the cation vacancy gradient across the scale and a reduction in the total vacancy level in the scale due to the reduction in oxygen activity at the oxide-gas interface. In Cu 10%Ni and Cu 24%Ni, internal oxide formation during annealing stimulates dissociation of the Cu 2O scale near the oxide-alloy interface to give copper metal and oxygen. Similarly, internal oxide formation stimulates dissociation of the NiO layer on Cu-80%Ni, although to a lesser extent than for the copper-rich alloys. During re-oxidation, the kinetics are partly determined by the extent of scale thinning during the prior annealing treatment, giving more rapid weight gains than expected from those recorded during the initial oxidation period. Nevertheless, particularly for Cu-80%Ni, where the scale thinning is relatively small, the reduction in the cation vacancy gradient across the scale and the reduction in the total vacancy level in the scale do result in a reduced oxidation rate compared with the rate recorded during the initial oxidation period.

The annealing and re-oxidation of oxidized Cu [sbnd]Ni alloys

A study has been made of the effects of an intermediate, isothermal annealing treatment in argon on the oxidation kinetics in dry oxygen of Cu 10%Ni and Cu 24%Ni at 800°C and Cu 80%Ni at 1000°C using a semi-automatic microbalance. Changes in scale morphology and composition have been investigated using various techniques. Oxidation of Cu 10%Ni and Cu 24%Ni produces external scales consisting of a thick, inner Cu 2O layer and a thin, outer CuO layer, together with nickel-rich internal oxide in the adjacent alloy. Oxidation of Cu 80%Ni yields an external scale consisting of a thick, inner NiO layer and a thin, outer CuO layer, together with a few nickel-rich internal oxide particles in the adjacent alloy. During annealing, the outer CuO layers on the three alloys dissociate to give Cu 2O and oxygen. With Cu 80%Ni only, further dissociation to give copper metal takes place after long annealing times. In all cases, the annealing treatment leads to a reduction in the cation vacancy gradient across the scale and a reduction in the total vacancy level in the scale due to the reduction in oxygen activity at the oxide-gas interface. In Cu 10%Ni and Cu 24%Ni, internal oxide formation during annealing stimulates dissociation of the Cu 2O scale near the oxide-alloy interface to give copper metal and oxygen. Similarly, internal oxide formation stimulates dissociation of the NiO layer on Cu 80%Ni, although to a lesser extent than for the copper-rich alloys. During re-oxidation, the kinetics are partly determined by the extent of scale thinning during the prior annealing treatment, giving more rapid weight gains than expected from those recorded during the initial oxidation period. Nevertheless, particularly for Cu 80%Ni, where the scale thinning is relatively small, the reduction in the cation vacancy gradient across the scale and the reduction in the total vacancy level in the scale do result in a reduced oxidation rate compared with the rate recorded during the initial oxidation period.