共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Seo Y. Ishikawa A. Sugimoto M. Watanabe R. Minamitani A. Nishikata 《Corrosion Science》2005,47(8):2079-2090
The cathodic reduction of duplex air-formed oxide film on copper was performed at a constant current density of ic = −50 μA cm−2 in deaerated 0.1 M KCl solution to investigate the sequence of cathodic reduction of each oxide layer and its mechanism. The single-phase thick CuO film on copper was also cathodically reduced at ic = −50 μA cm−2 or −2.5 mA cm−2. The surface characterizations of the air-formed oxide film and single-phase CuO film before cathodic reduction and after partial or complete cathodic reduction were performed by XPS and X-ray diffraction, respectively.The two plateau regions appeared in the potential vs. time curve during cathodic reduction of the duplex air-formed oxide film on copper, while one plateau region was observed in the potential-time curve during cathodic reduction of the single-phase CuO film on copper. The potential in the first plateau region for the air-formed film coincided with that in the plateau region for the CuO film. The results of XPS and X-ray diffraction suggested that in the first plateau region, the outer CuO layer is directly reduced to metallic Cu, while in the second plateau region, the inner Cu2O layer is reduced to metallic Cu. 相似文献
2.
Erika HodúlováMarián Palcut Emil Lechovi?Beáta Šimeková Koloman Ulrich 《Journal of Alloys and Compounds》2011,509(25):7052-7059
The effects of Bi and In additions on intermetallic phase formation in lead-free solder joints of Sn-3.7Ag-0.7Cu; Sn-1.0Ag-0.5Cu-1.0Bi and Sn-1.5Ag-0.7Cu-9.5In (composition given in weight %) with copper substrate are studied. Soldering of copper plate was conducted at 250 °C for 5 s. The joints were subsequently aged at temperatures of 130-170 °C for 2-16 days in a convection oven. The aged interfaces were analyzed by optical microscopy and energy dispersive X-ray spectroscopy (EDX) microanalysis. Two intermetallic layers are observed at the interface - Cu3Sn and Cu6Sn5. Cu6Sn5 is formed during soldering. Cu3Sn is formed during solid state ageing. Bi and In decrease the growth rate of Cu3Sn since they appear to inhibit tin diffusion through the grain boundaries. Furthermore, indium was found to produce a new phase - Cu6(Sn,In)5 instead of Cu6Sn5, with a higher rate constant. The mechanism of the Cu6(Sn,In)5 layer growth is discussed and the conclusions for the optimal solder chemical composition are presented. 相似文献
3.
Copper thin films were deposited on oxidized silicon at a substrate temperature of 70 °C and 150 °C using EB-PVD technique. The morphology and crystal orientation of the deposited film were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Corrosion behavior of films was studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, immersion test, and cathodic chronopotentiography. Additionally, the crystalline structure of corroded samples immediately after polarization was examined by XRD. Corrosion current density for copper deposits was higher than copper sheet by polarization tests, while the data obtained by the EIS technique emphasized higher corrosion current density for copper sheet. However there was a conflict between polarization and EIS data, the other results obtained by immersion and cathodic chronopotentiography tests proved that the corrosion resistance of copper deposits was higher than copper sheet in the same alkaline media, which can be attributed to chemical composition and higher thickness of the passive layer formed on copper deposits. On the other hand, breakdown potential (Ebp) for copper sheet was about 0.3 VSCE, while a distinct Ebp was not found for copper deposits. This was a sign of higher stability of the passive layer formed on copper deposits. The XRD patterns of samples immediately after polarization showed a higher content of Cu(OH)2 on copper deposits in comparison with copper sheet. The stable morphology formed on the surface of copper after polarization was monoclinic CuO, which is assumed to have a significant effect on copper protection in alkaline media. This morphology was more compact on copper deposits in comparison with copper sheet. This was due to higher ability of deposits to react with hydroxyl ions. 相似文献
4.
F. Moura E.C. Aguiar E. Longo J.A. Varela A.Z. Simões 《Journal of Alloys and Compounds》2011,509(9):3817-3821
Calcium copper titanate, CaCu3Ti4O12 (CCTO), thin film has been deposited by the soft chemical method on Pt/Ti/SiO2/Si (1 0 0) substrates at 700 °C for 2 h. The peaks were indexed as cubic phase belonging to the Im−3 space group. The film exhibited a duplex microstructure consisting of large grains of 130 nm in length and regions of fine grains (less than 80 nm). The CCTO film capacitor showed a dielectric loss of 0.031 and a dielectric permittivity of 1020 at 1 MHz. The J-V behavior is completely symmetrical, regardless of whether the conduction is limited by interfacial barriers or by bulk-like mechanisms. Based on impedance analyses, the equivalent circuit of CCTO film consisting of a resistor connected in series with two resistor-capacitor (RC) elements. 相似文献
5.
Didier Dentel Hussein MortadaMickael Derivaz Jean-Luc BischoffEmmanuel Denys Francisco M. MoralesMiriam Herrera J.M. MánuelR. García 《Acta Materialia》2012,60(5):1929-1936
We report on the initial growth mechanisms of Ge on LaAlO3(0 0 1), a crystalline oxide with a high dielectric constant (high-κ material). Chemical and structural properties were investigated in situ, through X-ray photoelectron spectroscopy and reflection high-energy electron diffraction, and ex situ by using high-resolution transmission electron microscopy. Ge was deposited by molecular beam epitaxy at 600 °C on a c(2 × 2) reconstructed LaAlO3(0 0 1) surface. At this temperature, a Volmer-Weber growth mode is observed due to a lower LaAlO3(0 0 1) surface free energy. It is characterized by the immediate formation of crystalline nano-islands. The Ge islands are relaxed and present an abrupt interface with the substrate. Some of them exhibit a preferential relationship in their heteroepitaxy, where the Ge(0 0 1) planes are parallel to the LaAlO3(0 0 1) ones, but rotated by 45° in the [0 0 1] direction. An additional rotation of 6° with respect to the growth axis is also observed, which compensates partially for the strain produced by the high lattice parameter mismatch (∼5%) between the semiconductor and the oxide. 相似文献
6.
Effects of blending on surface characteristics of copper corrosion products in drinking water distribution systems 总被引:1,自引:0,他引:1
Copper scales formed over 6-months during exposure to ground, surface and saline waters were characterized by EDS, XRD and XPS. Scale color and hardness were light red-brown-black/hard for high alkalinity and blue-green/soft for high SO4 or Cl waters. Cl was present in surface or saline copper scales. The Cu/Cu2O ratio decreased with time indicating an e transfer copper corrosion mechanism. Cu2O, CuO, and Cu(OH)2 dominated the top 0.5-1 A° scale indicating continuous corrosion. Cu2O oxidation to CuO increased with alkalinity, and depended on time and pH. Total copper release was predicted using a Cu(OH)2 model. 相似文献
7.
L.C. Tsao 《Journal of Alloys and Compounds》2011,509(33):8441-8448
This study investigated the effects of adding 0.5 wt.% nano-TiO2 particles into Sn3.5Ag0.5Cu (SAC) lead-free solder alloys on the growth of intermetallic compounds (IMC) with Cu substrates during solid-state isothermal aging at temperatures of 100, 125, 150, and 175 °C for up to 7 days. The results indicate that the morphology of the Cu6Sn5 phase transformed from scallop-type to layer-type in both SAC solder/Cu joints and Sn3.5Ag0.5Cu-0.5 wt.% TiO2 (SAC) composite solder/Cu joints. In the SAC solder/Cu joints, a few coarse Ag3Sn particles were embedded in the Cu6Sn5 surface and grew with prolonged aging time. However, in the SAC composite solder/Cu aging, a great number of nano-Ag3Sn particles were absorbed in the Cu6Sn5 surface. The morphology of adsorption of nano-Ag3Sn particles changed dramatically from adsorption-type to moss-type, and the size of the particles increased.The apparent activation energies for the growth of overall IMC layers were calculated as 42.48 kJ/mol for SAC solder and 60.31 kJ/mol for SAC composite solder. The reduced diffusion coefficient was confirmed for the SAC composite solder/Cu joints. 相似文献
8.
An in-situ photoacoustic (PAS) technique, using a piezoelectric detector with high sensitivity was applied to the study on duplex oxide films anodically formed on copper in pH 8.4 borate solution. The PAS signals from the copper electrode were produced by an irradiation of light beam with a wavelength of 514.5 nm. The PAS amplitude during cathodic reduction of the outer oxide layer to Cu2O changed in the opposite direction, depending on the anodic potential of film formation and oxidation time. Assuming that the change in PAS amplitude is proportional to both optical absorption coefficient and film thickness, it was deduced from comparison of the estimated absorption coefficients for Cu (OH)2, CuO and CuO0.67 films that dehydration of the outer layer having an average composition of CuOx (OH)2?2x proceeded with increasing anodic potential of film formation and oxidation time during growth of the duplex oxide film. Moreover, it was found that the change in PAS amplitude during cathodic reduction of the total Cu2O film involving the inner layer to metallic copper was proportional to the electric charge required for cathodic reduction, i.e., the film thickness, irrespective of anodic potential of film formation and oxidation time, which proved the validity of the above assumption. 相似文献
9.
To explain the very slow growth rate of the CuO scale during copper oxidation at high temperatures above 850 °C as reported in the literature, the influence of the morphology of the CuO grains on scale growth was investigated by oxidizing copper with different purities in 0.1 MPa oxygen atmosphere at 600-1000 °C. Oxidation of 99.99% copper shows that the growth of the CuO scale depends on the morphology of the CuO grains. The very thin CuO scale observed at 1000 °C is related to flat CuO grains resulted from fast lateral growth of the CuO grains, whereas the thicker CuO scale at lower temperatures results from the fine CuO grains. This dependence of scale growth on oxide grain morphology was confirmed by oxidizing 99.9999% and floating zone refined (>99.9999%) copper at 800 °C. It reveals that grain boundary diffusion can favour the growth of the CuO scale, and its contribution is related to the morphology of the CuO grains depending on the purity of copper specimens. 相似文献
10.
The formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole was studied using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Benzotriazole (BTAH), generally known as an inhibitor of copper corrosion, also proved to be an efficient inhibitor for copper-zinc alloys and zinc metal. The surface layers formed on alloys in BTAH-inhibited solution comprised both polymer and oxide components, namely Cu(I)BTA and Zn(II)BTA polymers and Cu2O and ZnO oxides, as proved by the in-depth profiling of the layers formed. A tentative structural model describing the improved corrosion resistance of Cu, Cu-xZn alloys and Zn in BTAH containing chloride solution is proposed. 相似文献
11.
During anodising of Al-Cu alloys, copper species are incorporated into the anodic alumina film, where they migrate outward faster than Al3+ ions. In the present study of an Al-1at.% Cu alloy, the valence state of the incorporated copper species was investigated by X-ray photoelectron spectroscopy, revealing the presence of Cu2+ ions within the amorphous alumina film. However, extended X-ray irradiation led to reduction of units of CuO to Cu2O, probably due mainly to interactions with electrons from the X-ray window of the instrument and photoelectrons from the specimen. The XPS analysis employed films formed on thin sputtering-deposited alloy/electropolished aluminium specimens. Such an approach enables sufficient concentrations of copper species to be developed in the anodic film for their ready detection. 相似文献
12.
CuO nanoparticles with average diameter of about 20 nm were accumulated on surface of sol-gel silica thin films heat treated at 300 °C in air. Heat treatment of the CuO nanoparticles at 600 °C in a reducing environment resulted in effective reduction of the nanoparticles and penetration of them into the film. While the thin films heat treated at 300 °C exhibited a strong antibacterial activity against Escherichia coli bacteria, the reducing process decreased their antibacterial activity. However, by definition of normalized antibacterial activity (antibacterial activity/surface concentration of coppers) it was found that Cu nanoparticles were more toxic to the bacteria than the CuO nanoparticles (by a factor of ∼ 2.1). Thus, the lower antibacterial activity of the reduced thin films was assigned to diffusion of the initially accumulated copper-based nanoparticles into the film. The CuO nanoparticles also exhibited a slight photocatalytic activity for inactivation of the bacteria (∼ 22% improvement in their antibacterial activity). Instead, the normalized antibacterial activity of the Cu nanoparticles covered by a thin oxide layer highly increased (∼ 63% improvement) in the photocatalytic process. A mechanism was also proposed to describe the better antibacterial activity of the Cu than CuO nanoparticles in dark and under light irradiation. 相似文献
13.
To clarify the initial oxidation mechanism of copper, the oxidation was carried out at 400 °C in 0.1 MPa oxygen using 99.9999% (6 N) and 99.5% (2 N) pure specimens. Oxidation of 6 N copper after 60 s showed that the number density of the oxide nuclei varied with the face of copper crystals, while the nucleation occurred preferentially at the grain boundaries. A metallographic examination indicated that the products of initial oxidation consist of both CuO and Cu2O. CuO is firstly formed as a thin uniform film on the copper surface, and then Cu2O nucleates and grows beneath the CuO film. This result is different from the conclusion reached in the literature that CuO does not appear until the laterally growing Cu2O nuclei have covered the whole surface using other methods. In contrast to 6 N copper, nucleation of Cu2O was much delayed for 2 N copper, though a thin CuO film was similarly formed on 2 N copper surface. Impurities in 2 N copper should be responsible for slow nucleation of Cu2O and slow growth of nuclei. 相似文献
14.
Semiconductor properties of passive films formed on the Fe-18Cr alloy in a borate buffer solution (pH = 8.4) and 0.1 M H2SO4 solution were examined using a photoelectrochemical spectroscopy and an electrochemical impedance spectroscopy. Photo current reveals two photo action spectra that derived from outer hydroxide and inner oxide layers. A typical n-type semiconductor behaviour is observed by both photo current and impedance for the passive films formed in the borate buffer solution. On the other hand, a negative photo current generated, the absolute value of which decreased as applied potential increased in the sulfuric acid solution. This indicates that the passive film behaves as a p-type semiconductor. However, Mott-Schottky plot revealed the typical n-type semiconductor property. It is concluded that the passive film on the Fe-18Cr alloy formed in the borate buffer solution is composed of both n-type outer hydroxide and inner oxide layers. On the other hand, the passive film of the Fe-18Cr alloy in the sulphuric acid consists of p-type oxide and n-type hydroxide layers. The behaviour of passive film growth and corrosion was discussed in terms of the electronic structure in the passive film. 相似文献
15.
The surface tension of silver-copper binary liquid alloys is calculated, in the frame work of Eyring theory. The calculations were made for different compositions (mole fraction, xCu = 0, 0.2, 0.4, 0.6, 0.8 and 1), in the temperature range 1100-1800 K. The surface tension decreases with temperature increase, at a fixed copper fraction xCu, and increases with increasing copper content. The calculated results are appropriately compared with existing literature data. 相似文献
16.
Effect of copper on the defect density of Fe–20Cr–xCu (x?=?0, 4) stainless steel alloys was investigated in deaerated pH 8·5 borate buffer solution at room temperature using Mott–Schottky analysis. Mott–Schottky analysis revealed that the addition of copper increased the acceptor density (NA, VCr?3), i.e. decreased the Cr+3 content of the passive film. Also the donor densities, shallow donor (ND1, VO+2) and deep donor (ND2, VCr+6), of the passive films formed were increased. XPS analysis confirmed the decrease in Cr content and enrichment of copper in the passive film of Cu containing alloys, which ultimately dictated their lower corrosion resistance, i.e. decreased film protectiveness and stability. 相似文献
17.
The Fe1−xPtx-C granular films with different Pt atomic fractions (0.09 ≤ x ≤ 0.52) and film thicknesses (5 nm ≤ t ≤ 100 nm) were deposited on MgO(1 0 0) and SiO2/Si(1 0 0) substrates by facing-target sputtering and post-annealing. With the increasing x, the ordered L10 FePt grains form. All of the films are ferromagnetic, and the easy axis is in the film plane. With the decrease of t, the films turn from hard ferromagnetic to soft ferromagnetic. The maximum coercivity of the 100-nm thick Fe1−xPtx-C granular films measured at a 10-kOe field is 3.7 kOe at x = 0.48. The coercivity of the Fe0.56Pt0.44-C granular films increases, and the magnetization measured at a 10-kOe field decreases with the increasing t. The reversal mechanism of the 100-nm thick Fe1−xPtx-C granular films turns from the domain wall motion to the Stoner-Wohlfarth rotation mode as x increases. However, the reversal mechanism of the Fe56Pt44-C granular films with different t approaches the Stoner-Wohlfarth rotation mode, and is film-thickness independent. 相似文献
18.
The corrosion process in the Cu/CuSO4 + H2SO4 system is considered as the sum of two coupled single-electron electrochemical reactions that occur simultaneously and independently on the surface of the copper electrode. Our numerical model incorporates diffusion and migration of solution species including cuprous ions, as well as the chemical equilibria for copper sulphate and sulphuric acid dissociation. Numerical simulations are compared with the trends discovered during experimental investigation of copper corrosion in similar systems. 相似文献
19.
L Santinacci G.I Sproule D Landheer A Banu T Djenizian M.J Graham 《Corrosion Science》2004,46(8):2067-2079
Anodic oxide films were galvanostatically grown on n-InSb(1 0 0) surfaces at various pH in sodium hydroxide (0.1 M NaOH, pH=13), borate buffer (0.075 M Na2B4O7 + 0.3 M H3BO3, pH=8.4) and phosphate buffer (0.3 M NH4H2PO4, pH=4.4). Thickness, composition and morphology of the oxide films were determined by various surface analytical techniques such as Auger electron spectroscopy, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and atomic force microscopy. The oxides comprise mainly In2O3 and Sb2O3 and the oxide thickness increases with pH. Electrical properties of oxides indicate that the films may be useful as insulators in some device applications. 相似文献
20.
The anodic oxidation and cathodic reduction processes of the Cu/Cu2O multilayer film and pure Cu film in pH 8.4 borate buffer solution were analyzed by electrochemical quartz crystal microbalance (EQCM) for gravimetry and bending beam method (BBM) for stress measurement. The mass loss of the multilayer film during anodic oxidation at 0.8 V (SHE) in the passive region was less than that of the pure Cu film. The comparison between current transients and mass changes during anodic oxidation has succeeded in separating the anodic current density into two partial current densities of oxide film growth, iO2-, and of Cu2+ dissolution through the passive film, iCu2+. As a result, in the case of the pure Cu film, the anodic current density was mainly due to iCu2+, while in the case of the multilayer film, iCu2+ was almost equal to iO2-. The compressive stress for the multilayer film was generated during anodic oxidation, while the tensile stress for the pure Cu film was generated.The mass loss of the multilayer film during cathodic reduction at a constant current density (ic = −20 μA cm−2) was significantly less than that estimated from coulometry, suggesting that H2O produced by cathodic reduction remained in the multilayer film. The compressive stress was generated during cathodic reduction of the multilayer film, which was ascribed to H2O remained in the multilayer film. 相似文献