Studies on copper-semiconducting layer-electrolyte systems—I. Electrode potentials of copper and electrodeposited copper sulphide in S2− and Cu2+ media

Copper sulphide layers electrodeposited from a Na₂S bath consist chiefly of cuprous sulphide. Calculated values of the specific conductance of the deposited sulphide average around 3·8 × 10^?5 ohm^?1.cm^?1.Electrode potentials, E_H, of the Cu/Cu_2?δS in unbuffered Na₂S solutions and in solutions buffered at pH 9, correspond to the behaviour of a Cu/Cu_2?δS, overlayered with CuS/electrolyte. Steady reproducible potentials are obtained with the above electrodes in 0·5–10^?3M CuSO₄ solutions, closely comparable with those of the reversible Cu/Cu²⁺ couple.     

The anodic dissolution of mild steel in solutions containing both Cl− and NO3− Ions

The electrochemical machining of mild steel in Cl^?/NO₃^? mixed electrolytes is slow and produces an extremely rough and ragged appearance. From steady-state polarization, film stripping and current efficiency measurements made on mild steel anodes in these mixed solutions, it was concluded that Cl^? ions produce only localized dissolution of the passive anode film formed on steel anodes in the presence of NO₃^? ions. For this reason, a severe cratering of the surface results. The mechanism of film dissolution in the presence of Cl^? ion is much different than in the presence of ClO₃^? ion.     

Effect of WC and CeO2 on microstructure and properties of W–Cu electrical contact material

W–Cu alloys with an individual addition of WC and CeO₂ particles were prepared by means of powder metallurgy and infiltration, and the effect of WC and CeO₂ individual addition on microstructure and properties of W–Cu alloys was investigated. The results show that W–Cu alloys with a separate addition of 1.5 wt% WC and 0.5 wt% CeO₂ have desired properties, but an excessive addition decreases hardness and electric conductivity. The vacuum electrical breakdown tests show that the individual addition of WC and CeO₂ results in the enhancement of the breakdown strength and decrease of the chopping current. The microstructual analysis of W–Cu alloys with WC or CeO₂ addition after vacuum electrical breakdown 50 times shows that the vacuum electrical arcs spread on the cathode surface. Meanwhile, W–Cu alloys with WC or CeO₂ addition has a slight splash of molten copper, a less amount of cathode craters, and fine dispersed cathode craters on the entire surface of W–Cu alloys.     

Atomic-scale structure and chemistry of ceramic/metal interfaces—II. Solute segregation at MgO/Cu (Ag) and CdO/Ag (Au) interfaces

The first quantitative measurements of solute segregation at ceramic/metal (C/M) heterophase interfaces are presented for the MgO/Cu (Ag) and CdO/Ag (Au) systems. Interfaces are produced by internal oxidation of ternary alloys. Solute segregation at C/M interfaces is induced by intermediate-temperature annealing treatments. The Gibbsian interfacial excess of solute, Γ_solute, at these interfaces is determined in a direct, quantitative manner by atom-probe field-ion microscopy (APFIM). These measurements are complemented in the MgO/Cu (Ag) system by a composition analysis of this interface employing electron energy loss spectroscopy (EELS). Analyses of 15 {222} MgO/Cu (Ag) interfaces by APFIM show an average segregation level of (4.0±1.9)×10¹⁴ atoms/cm² or 0.22±0.10 effective monolayers at 500°C. Analyses of three {222} CdO/Ag (Au) interfaces show an average segregation level of (3.0±1.0)×10¹⁴ atoms/cm² or 0.22±0.07 effective monolayers at 400°C. Whereas {222} CdO/Ag (Au) interfaces in unannealed specimens show no evidence of gold segregation. These results are discussed in view of recent models of interfacial segregation.     

Effects of Cu,Mo and C on the corrosion of deformed 18Cr8Ni stainless steels in H2SO4/NaCl solutions

The effects of Mo, Cu and C on the rate and type of corrosion of 18Cr8Ni stainless steels after deformation into U-shaped specimens have been investigated in 5N H₂SO₄ solutions containing up to 0·4M NaCl at 40°C. General corrosion, intergranular corrosion, and/or transgranular stress-corrosion cracking were found to occur, the type of attack depending on the contents of Mo, Cu and C in the steel, the concentration of NaCl in the solution, and the degree of deformation. In particular, it was observed that carbon has an effect on intergranular corrosion in these solutions, which is quite different from that observed in Strauss and Huey tests.     

The hot corrosion of nickel-based ternary alloys and superalloys for gas turbine applications—II. The mechanism of corrosion in SO2/O2 atmospheres

A stage-by-stage mechanism is proposed for the corrosion of Ni-20Cr-X ternary alloys in SO₂/O₂ (in equilibrium with SO₃) atmospheres. Stage 1 represents the building of the initial oxide layer which takes place immediately. Stage 2 elaborates on the build-up of external oxide layers and sulphide areas and can be applied to both NiSO₄ or non-NiSO₄ forming conditions. Stage 3 elucidates the development of the internal striated sulphide structure. The beneficial effect of the ternary additions of Al, V and Si is related to the mechanism.