Benzotriazole as an inhibitor of brass corrosion in chloride solution

The current research explores the formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys in chloride solution containing benzotriazole (BTAH), by use of electrochemical techniques, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Electrochemical reactions and surface products formed at the open circuit potential and as a function of the potential range are discussed. The addition of benzotriazole to aerated, near neutral 0.5 M NaCl solution affects the dissolution of copper, zinc, Cu-10Zn and Cu-40Zn alloys. The research also compares the inhibition efficiency and Gibbs adsorption energies of the investigated process. Benzotriazole, generally known as an inhibitor of copper corrosion is also shown to be an efficient inhibitor for copper-zinc alloys and zinc metal. The surface layer formed on alloys in BTAH-inhibited solution comprised both oxide and polymer components, namely Cu₂O and ZnO oxides, and Cu(I)-BTA and Zn(II)-BTA polymers. The formation of this mixed copper-zinc oxide polymer surface film provides an effective barrier against corrosion of both metal components in chloride solution.     

苯并三唑表面配位化学的电化学现场拉曼光谱研究

用电化学现场表面增强拉曼光谱(SERS)研究了非水体系中苯并三唑(BTAH)在银电极表面的吸附及成膜行为,结果表明非水体系中BTAH的吸附行为随电位变化而不同。较负区间主要以中性分子形式吸附;中间电位区间主要以BTA-吸附并不可逆成膜。采用直接电化学合成技术模拟电极表面过程制备了苯并三唑与Cu, Ag, Fe, Ni和Zn等金属的配合物,并研究了中性配体三苯基膦(pph₃)对其配位过程的影响,所得产物的元素分析以及拉曼光谱研究表明pph₃的加入影响了Cu和Ag与BTAH的配位过程,并出现在最终产物中,而对BTAH与Ni, Fe和Zn的配位过程未产生影响,产物未出现pph₃。     

Surface analysis of AgSn alloys by ESCA

The surface composition of AgSn alloys with low Cu and Zn contents was investigated by ESCA following various pretreatments. Exposure to air, especially at elevated temperatures, resulted in the surface being enriched, not only by Sn, but particularly by the Zn and Cu contents in the form of oxides. Zn and Cu enrichment is less pronounced when heating in a vacuum (10^?6 Torr). Any tin oxide present is partially reduced. The results obtained are compared with model concepts established by various authors from studies of binary alloys.     

Fermi surface studies of non-dilute disordered alloys by positron experiments

The technique of positron annihilation experiments as applied to the study of Fermi surfaces in metals and alloys is briefly reviewed. The angular correlation of the two annihilation photons is directly related to the momentum distribution of the positron-electron system; breaks in this distribution reflect the size and shape of the Fermi surface. Recent two-dimensional angular correlation measurements designed to study the Fermi surface of Cu?Al and Cu?Zn alloys are presented, and are compared with theoretical predictions.     

A study of Fermi surfaces of the α-phase Cu-Ge and Cu-Si alloys by positron annihilation

Angular correlation measurements on the fcc solid solutions of Cu?Ge and Cu?Si alloys have been carried out on single crystals with four crystallographic orientations by a crossed-slit geometry. The results on both the alloys are nearly the same. The 〈111〉-neck radius and the 〈100〉-radius of the Fermi surfaces increase almost linearly with increasing electron concentration in accord with previous results on Cu?Al and Cu?Zn alloys. The Fermi surface does not touch the square faces of the Brillouin zone at the solubility limit. The results agree fairly well with a calculation based on the sinking-conduction band model.     

Surface tension of liquid Cu-Ti binary alloys measured by electromagnetic levitation and thermodynamic modelling

The surface tension of liquid Cu-Ti alloys has been measured by using the containerless technique of electromagnetic levitation and theoretically calculated in the framework of the compound formation model. Measurements have been carried out on alloys covering the entire range of composition and over the temperature range 1275-2050 K. For all investigated alloys the surface tension can be described by a linear function of the temperature with negative slope.Due to the presence of different intermetallic compounds in the solid state the surface properties of liquid Cu-Ti alloys are satisfactory described by the compound formation model.     

Determination of a (4 × 4) structure formed on a Cu(0 0 1) surface by adsorption of calcium

The adsorption of calcium (Ca) atoms on a Cu(0 0 1) surface has been studied by low-energy electron diffraction (LEED) at 130, 300 and 400 K. It is found that a (4 × 4) was the only LEED pattern appeared at 400 K while a quasi-hexagonal structure was formed in a wide range of submonolayer coverage at 130 K. At 300 K, the (4 × 4) LEED spots were broad and weak. The (4 × 4) structure formed at 400 K was determined by a tensor LEED I-V analysis. It is a new-type of surface alloys consisting of five substitutional Ca atoms, nine surface Cu atoms, and two atomic vacancies in the unit cell. In spite of a quite large size-difference between Ca (3.94 Å) and Cu (2.55 Å) atoms, all Ca atoms are located at the substitutional sites. Among surface alloys so far reported, the atomic size ratio between Cu and Ca in the (4 × 4), 1.54, is the largest. Optimized structural parameters reveal that large lateral displacements of surface Cu atoms, being enabled by the appearance of the vacancies, allow the formation of the (4 × 4) structure.     

Diffusion properties of Cu(0 0 1)-c(2 × 2)-Pd surface alloys

Structural and diffusion properties of a Cu(0 0 1)-c(2 × 2)-Pd surface and sub-surface ordered alloys are studied by using interaction potentials obtained from the embedded-atom method. The calculated diffusion energies are in agreement with observed kinetics of the surface alloy formation and confirm stability of the underlayer alloy. Activation energy of planar diffusion of palladium at the initial stage of the alloy formation as well as the activation energy of the overlayer-underlayer diffusion of the Pd atoms are in good agreement with those obtained by the scanning tunneling microscopy and low energy electron diffraction measurements, respectively.     

Surface alloying of immiscible metals induced by surface state shift

By using first principles calculations, it is found that the noble metal atoms Ag, Au and Cu would like to occupy the vacancy sites of the W(0 0 1) or Mo(0 0 1) surface to form the substitutional surface alloys, despite the fact that they do not like to form alloy in the bulk. The electronic local function (ELF) for these substitutional surface alloys shows that there is no obvious chemical bonding between the noble metals and W or Mo. The analysis of electronic structures lets us conclude that the surface alloying of immiscible metals may originate from the surface state shift of W (or Mo) induced by changes of the electronic environment of surface W (or Mo) when surface W (or Mo) atoms are alternatively replaced by Ag (Au or Cu).     

Sputtering of Cu and Zn atoms from elemental and alloy targets

The energy distributions of Cu and Zn atoms sputtered from elements and Cu_xZn_1-x alloys (x=0.80, 0.24) with a 6 keV Ar⁺ beam have been measured. It was found that the collision-cascade theory properly described the flux of sputtered atoms. From the spectra the binding energies of Cu and Zn atoms in the elemental and alloy surfaces were determined. The collision-cascade theory and the experimentally adjusted values of the binding energies allowed for calculation of the total and partial sputtering yields, and the equilibrium surface composition of the ion bombarded alloys. This work was carried out as a part of Research Project M.R. I/5.     

Surface tension and density of liquid Sn-Cu alloys

The surface tension and density of Sn-Cu liquid alloys were measured with the sessile drop method, in a broad range of temperature. Total of seven compositions were investigated in the range from 0.018 to 0.5 mole fraction of Cu. With increasing concentration of Cu, both density and the surface tension are increased. With increasing temperature the density decreases linearly for all of the compositions. The surface tension exhibits similar behavior for most of the compositions, except for the alloy of 0.5 mole fractions of Cu, in which case the increase of the surface tension is observed. The obtained results are compared with existing literature data and Butler model calculations, and a relatively good agreement is observed.     

利用ICP-MASS研究有机培肥土壤重金属淋溶特征

以下辽河平原11年长期定位试验为平台,采用原状土柱淋溶实验,通过比较不同用量有机肥处理土壤重金属积累情况及其淋溶特征,探讨了雨养农业条件下有机培肥措施对土壤表层重金属（Cu,Zn,Cd和Cr）积累的影响,阐述了重金属在土壤表层(0～20 cm)中的积累特征明确了重金属元素的淋溶特点和垂直迁移规律(0～60 cm)。研究表明,随着有机肥用量增加,表层土壤中Cu,Zn,Cd和Cr的含量都随之升高,积累速度为Cd＞Cu＞Zn＞Cr。根据中国土壤环境质量标准(GB15618-1995),即使施入50 t·ha-1有机肥料,也未造成表层土壤Cr, Cu和Zn的污染,其中Cr仍符合Ⅰ类土壤质量标准,而Cu和Zn符合国家Ⅱ类土壤质量标准,但对Cd而言,此时表层土壤含量已接近国家Ⅲ类土壤质量标准阈值,存在较大风险,应引起足够重视。土柱淋溶实验表明,只有个别淋溶液Cu和Cd浓度属于国家Ⅲ类水质量标准（GB/T14848—93）,其余均符合国家Ⅱ类及以上水质标准,且所有淋溶液Cr的含量都符合国家Ⅰ类水质标准,表明在下辽河平原,即使有机肥使用量达到50 t·ha-1时,仍未对地下水构成任何风险。另外,淋溶液中的重金属含量均随土层深度增加呈现下降趋势(Cr除外),表现出重金属不易下移的特点,但相对而言,Zn和Cr向深层土壤淋溶能力较强,Cu和Cd则更易积累在表层土壤。     

The synthesis of methanol and the reverse water-gas shift reaction over Zn-deposited Cu(100) and Cu(110) surfaces: comparison with Zn/Cu(111)

The catalytic activity of Zn vapor-deposited Cu(100) and Cu(110) surfaces for methanol synthesis by the hydrogenation of CO₂ and the reverse water-gas shift reaction were studied using an XPS apparatus combined with a high-pressure flow reactor (18 atm). At a reaction temperature of 523 K, no promotional effect of Zn was observed for the methanol synthesis on both Zn/Cu(100) and Zn/Cu(110). The results were quite different from those for Zn/Cu(111), on which a significant promotion of methanol synthesis activity appeared to be due to the deposition of Zn, indicating that the promotional effect of Zn was sensitive to the surface structure of Cu. However, hysteresis was observed in the catalytic activity for methanol synthesis over the Zn/Cu(110) surface upon heating above 543 K in the reaction mixture. The activity became twice that measured before heating, which was close to the methanol synthesis activity of Zn/Cu(111) at the same Zn coverage. On the other hand, no such hysteresis was observed for the reverse water-gas shift reaction on Zn/Cu(110), indicating that the active site for methanol synthesis was not identical to that for the reverse water-gas shift reaction. In the post-reaction surface analysis, formate species was detected on both Zn/Cu(100) and Zn/Cu(110), whose coverage increased with increasing Zn coverage at 0<Θ_Zn<0.2. No correlation between the formate coverage and the methanol synthesis activity was obtained, which was in contrast to the results for Zn/Cu(111). Thus, the structure sensitivity observed in the catalytic activity of methanol synthesis over Zn-deposited Cu surfaces is ascribed to the significant difference in the reactivity of the formate intermediate.     

In-situ study of precipitates in Al–Zn–Mg–Cu alloys using anomalous small-angle x-ray scattering

In the present work,the precipitate compositions and precipitate amounts of these elements(including the size distribution,volume fraction,and inter-precipitate distance) on the Cu-containing 7000 series aluminum alloys(7150 and 7085 Al alloys),are investigated by anomalous small-angle x-ray scattering(ASAXS) at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process(120℃) by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ?A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge.     

Spin- and charge density perturbations and short-range order in Fe–Cu and Fe–Zn BCC alloys: A Mössbauer study

A model used to describe the ⁵⁷Fe Mössbauer spectra for the binary BCC iron alloys rich in iron has been extended to account for the alloy crystallographic ordering. The ordering is accounted for by introducing single order parameter. Extension of the model is described in detail. The model has been tested applying it to the Fe–Cu alloys obtained by the arc melting and to the Fe–Zn alloys prepared by the solid state reaction. Random alloys are obtained up to ∼2 at% of Cu, and up to ∼8 at% of Zn. For higher impurity (minor alloy component) concentration it has been found that Cu atoms try to avoid Fe atoms in the iron matrix as nearest neighbors, while the opposite happens to the Zn atoms, albeit at much lesser scale, i.e., Zn–Zn interactions are much weaker than Fe–Zn interactions at the nearest neighbor distance. Perturbations to the iron magnetic hyperfine field (spin density) and electron (charge) density on the iron nucleus have been obtained for both series of alloys versus impurity concentration.     

Thermodynamics and surface properties of liquid Cu–B alloys

The study of the thermodynamic and the surface properties of liquid Cu–B alloys can help better understanding of a complex interfacial chemistry related to liquid Cu–brazes in contact with boride substrates. Despite a simplicity of the Cu–B phase diagram, only a few thermodynamic data are available in the literature, while in the case of the surface properties a complete lack of data is evident. The quasi-chemical approximation (QCA) for the regular solution has been applied to describe the mixing behaviour of liquid Cu–B alloys in terms of their thermodynamic and surface properties as well as the microscopic functions. In view of joining processes related to liquid Cu–brazes/solid boride systems a particular attention is paid to the surface properties of the Cu-rich part of the system and the calculated values are substantiated by the new surface tension experimental data of liquid Cu and Cu–10 at.% B alloy. The tests have been performed by the sessile-drop method under the same experimental conditions. Considering the experimental uncertainties, the effect of oxygen on the surface tension of liquid Cu and Cu–10 at.% B alloy has been analysed by simple model that combines the physical property data included in Butler’s equation with the oxygen solubility data and it gives the same results as Belton’s adsorption equation.     

Estimation of surface tension for high temperature melts of the binary Ag-X alloys

ABSTRACT

Surface tension is a key property to materials. In this work, the surface tension of the binary alloys Ag-X (Au, Cu, Ce, Bi, Sn, Sb, In, Ni, Y, Pd) is carried out by using Butler Model over enter composition ratio at a certain temperature. According to calculation results, the increasing surface tension of the Ag-X (Cu, Au, Ni, Y, Pd) alloy is accompanied by the composition increases. For Ag-Sn alloy, the surface tension calculated by Butler model is consistent with the experimental result at temperature 1273?K. However, other Ag-X alloys can’t be compared due to the lack of the related experimental data. Although the experimental data about surface tension of the Ag-X alloy are limited, we are possible to make a comparison between the calculated results for the surface tension in this study and the available experimental data. Taken together, the surface tension calculated by Butler model that especially the Ag-Sn alloy are consistent with the experimental results at temperature 1273?K.     

A survey of surface tension,molar volume and density for Sn–Ag–Cu–Bi–Sb quinary alloys as lead-free solders

ABSTRACT

By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds.     

Micro‐Raman innovative methodology to identify Ag–Cu mixed sulphides as tarnishing corrosion products

Mixed Cu–Ag alloys with different compositions have been produced and subjected to an accelerated sulphidation process which causes the development of a mixed sulphide‐rich corroded film on their surface. It was called tarnishing, that is, the formation of a blue‐brownish patina when Cu–Ag alloys are exposed in a sulfur‐containing atmosphere. The structures of the pristine alloys have been determined by the combined analytical techniques as scanning electron microscopy energy dispersive X‐ray microanalysis and X‐ray diffraction. The experimental conclusions confirmed the occurrence of micro phase separation with the formation of different dendritic domains of about 10 µm in width. The sulphidized samples were firstly investigated by optical microscopy and X‐ray diffraction in order to verify the homogeneity of the patina and to identify the different AgCuS phases appearing on the alloy surfaces. It was observed that, despite the inherent micro‐heterogeneity of the alloys, the sulphide layer was throughout uniform in composition at the micro‐scale. The complex scenario of the relative stability of all the various mixed sulphides involved was then explored by micro‐Raman spectroscopy (μ‐RS), pointing out that the Cu‐for‐Ag substitution in the crystal lattice of the mixed Ag–Cu sulphides caused a monotonous blue shift of the vibrational wavenumbers in Raman spectra. This study has unveiled microscopic details of the tarnishing process, furnishing an innovative, cheap and non‐destructive methodology based on μ‐Raman spectroscopy for the evaluation of the silver‐copper artefacts via the compositions of their corroded products. Copyright © 2016 John Wiley & Sons, Ltd.     

A simple model to predict long-range atomic ordering temperatures in Cu-based shape memory alloys

The order–disorder and order–order phase transition temperatures in the austenitic phase of Cu-based shape memory alloys were used to obtain a set of first- and second-neighbour pair interchange energies. To this end, a mean field model was postulated. Then, the applicability to different alloys of this simple model was analysed. It was found that a good agreement with the experimental phase diagram is obtained for Cu–Zn–Al, Cu–Al–Ni and Cu–Al–Be alloys using composition-independent parameters. It was also found that for Cu–Al–Mn alloys, composition-dependent pair interchange energies need to be employed.