We present an investigation of the influence of four dopant lithium concentrations on the electrical properties of CuO. X-ray measurements have revealed a single phase formed up to 4.2 at. % of Li, and a second phase formed, Li2CuO2, in the case of 10.5 at. % of Li concentration. The log(ρ/T) vs 1/T data are better represented by two straight lines than by one and show an initial strong decrease of the conduction activation energies for small contents of Li (<1.7 at. %), which becomes weak for larger contents. The change in slope observed in the resistivity measurements as a function of temperature has also been investigated by calorimetric measurements, revealing a specific heat anomaly which can be associated with the antiferromagnetic order transition.

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Hastelloy alloys combine good mechanical properties with excellent resistance to corrosion. One of their potential applications is in deep gas wells where there is a high concentration of H 2 S. [1] In such conditions, mechanical resistance to very high pressures in combination with chemical resistance to the acidic environment is required. However, use of Hastelloy is limited by the cost. Therefore, it appeared interesting to study the feasibility of covering a less expensive base material with a coating of Hastelloy of appropriate thickness, recognizing that the corrosion resistance is essentially a surface property. An economic evaluation indicates that a cost reduction of 50±60 % is expected if using tubes coated with Hastelloy instead of tubes fully made of Hastelloy. [2] Various techniques exist for coating a metal surface with another metal, like manual welding, laser cladding, diffusion bonding, plasma spraying, or chemical vapor deposition. The first two techniques have the advantage that the bond between the coating and the substrate is a fusion bond, which in general is the strongest bond. The other techniques have the advantage that the possible mixing of the coating with the substrate material is negligible. The problem of mixing with substrate material is less severe in the case of laser cladding because of its more localized heat input than manual welding. Also, since the heat input in the case of laser cladding is controllable, an attempt can be made to apply the coating without melting the substrate. Further, using multiple laser passes it is possible to reach a composition close to that of the alloy used for coating formation at the outer surface of the total layer. The corresponding gradual change in composition from bottom to top of the layer may contribute to the strength of the layer/substrate bond.Hastelloy shows its best corrosion resistance when the secondary phases are homogeneously dispersed in the microstructure of the alloy. This can be achieved by annealing at 1200 C followed by quenching in water. [3] When a coating is applied with laser cladding to a massive steel plate, it is subjected to rapid solidification, which produces a very fine microstructure, and thus very small secondary phase particles. The rapid solidification could also lead to an enhanced (non-equilibrium) solid solubility of the alloying elements in the matrix, and a correspondingly smaller amount of secondary phase.In this communication the composition and microstructure of a Hastelloy coating produced by laser cladding of a stainless-steel substrate have been investigated, in particular to reveal the effect of mixing with substrate material.Coatings of Hastelloy C-276 (composition (wt.-%): C 0.02, Co 2.5, Cr 15, Mo 16, W 3.7, Fe 5.5, Ni) were applied to an AISI 316 (composition (wt.-%): Mn 0.5, Mo 2.5, Cr 17, Ni 11, Fe) stainless-steel substrate using a Rofin Sinar CO 2 laser, which emits a continuous beam at a maximum power of 5 kW. To this end a Hastelloy C276 wire of diameter 1.2 mm was fed continuously using ...

The resistivity of Li doped CuO polycrystalline samples is discussed following the variable-range hopping mechanism (VRH) form, exp ((T0/T)1/4), between 80 and 300 K. The T0 have been measured to be in the range of 107 − 108 K . In the CuO undoped system, the VRH mechanism does not fit appreciably the resistivity data in the range of temperature considered. However, when Li is introduced, this behaviour is followed, leading us to suggest that the Li doped CuO could be view as a disordered system. At higher temperatures, the thermal activation mechanism takes place.

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