A Cu-Al alloy

Since many experimental studies of 7-Fe were performed for 7-Fe particles in a Cu matrix (or Cu alloy, including Cu-Al) [113], [114], it is important to probe the electronic structure of the particle-matrix systems. Embedded-cluster methods are ideally taylored to treat small particles of a metal in a host matrix, a system that would require a very large supercell in band-structure calculations. DV calculations were performed for the 14-atom Fe particle in copper shown in Fig. 21 [118]. Spin-density contour maps were obtained to assess the polarization of the Cu matrix by the coherent magnetic 7-Fe particle. Examples are given in Figs. 22 and 23 for a Fe particle in Cu and 7-Fe in Cu with two substitutional Al. If the matrix is a Cu-Al alloy, this element is known to penetrate the Fe particle [114]. 

Abstract. The Thermal Analsysis (TA) applies a great variety of techniques suitable for determining the thermophysical properties of solids. Here after a wide and detailed review on more conventional methods of differential thermal analysis (DTA) and differential scanning calorimetry (DSC) to study non-equilibrated materials, the experimental results obtained from Short-Range Ordering (SRO) in a Cu-Al alloys is presented and discussed. The kinetic parameters and laws in these materials are deeply discussed focusing attention also to vacancy behavior and effects of quenching conditions. 

Part II Experimental Results of Short-Range Ordering in a-Cu-Al Alloys... 

The investigation by differential scanning calorimetry of the ordering process in a-Cu-Al alloys leads to the following conclusions ... 

Roberts-Austen connected two Pt-Pt/10%-Ir thermocouples in parallel which, in turn, were connected to a galvanometer. One thermocouple was inserted into a reference sample consisting of a Cu-Al alloy or of an alumimun silicate clay (fireclay). The other thermocouple was embedded into a steel sample of the same shape and dimensions as the reference. Both the sample and reference were placed in an evacuated furnace. A second galvanometer monitored the temperature of the reference. The purpose of the experiments was to construct a phase diagram of carbon steels and, by extension, railway lines. Since his method was atme differential technique, it was much more sensitive than Le Chatelier s. The DTA design used today is only a slight modification of Roberts-Austen s, and the only major improvements are in the electronics of temperature control and in the data processing, which is now handled by computers (see Fig. 1). 

Crystallization of Be from a Be-Al alloy is effective for removing Fe, Mn and Ni but leads to an enrichment in Al, Cu and Mg typical analytical data are included in Table l . 

Fig. 14. Fraction of A1 in Cu-Al alloy, 1 — x, as a function of potential from the sampled-current voltam-mograms in Figure 13 (O) 10.0, ( ) 25.0, and (A) 50.0 mmol L 1 Cu(I) ( ) 10.0 mmol L-1 Cu(I), from RRDE-ALSV experiments and ( ) AAS analysis of bulk electrodeposits. Adapted from Tierney et al. [45] by permission of The Electrochemical Society.

Figure 2.25. SEM micrograph of a cross-section perpendicular to the interface of a Cu-Cr alloy on vitreous carbon cooled from 1373K at steady state contact angle. From (Landry et al. 1997) [8].

The results show that catalytic activity is higher when the catalyst is reduced in a N -Hj mixture between 500 and 573 K and that it decreases when steam is present in the reduction mixture. For samples reduced in H -HjO flow, treated at high temperature or taken from an industrial reactor, lower activity is evident for the LTWGS reaction. Such deactivation in the samples reduced in Hj-HjO stream may be caused by the formation of a Cu-Zn alloy and by changes in the Cu oxidation state, as determined by XRD characterization. However, the deactivation observed here in the reoxidized-aged samples could not have been caused by the observed decrease in Cu crystal size. In this case, the decrease in activity may be related to a spinel surface species observed in the XRD pattern (Fig. 2d). Laine et al. [14] have proposed that an increase in dispersion accompanied by deactivation can be explained by the formation of a highly dispersed but less active phase, possibly a CUAI2O4 surface spinel . 

The data on differential thermal desorption spectra of the reduction of NiO and CuO proved to be very important. Despite the differences in reduction temperatures of individual oxides (320°C and 270°C), a maximum ee was observed at that reduction when mixture of oxides were reduced at a lower temperature, 220°C, because Ni-Cu catalysts contain two phases a Cu phase and a Cu-Ni-alloy phase. With increase of the copper content, the Ni-Cu phase is enriched in the bulk with Ni and on the surface with Cu. According to Klabunovskii et al. the Ni-Cu (70 30) catalyst is five times more active than the pure Cu catalyst, but after modification of this catalyst with TA, its enantioselectivity in the hydrogenation of EAA was lower than either the modified pure Cu catalyst ee 50%) or pure Ni-TA catalyst ee 33%) under the same conditions. Thus the bimetallic Ni-Cu catalysts revealed S5mergism in catalytic activity but not in enantioselectivity. 

The first report of a CuInSe2/CdS heteroj unction solar cell-based on single-crystal CulnSe2-appeared in 1974 [72]. The cell achieved an efficiency of 5%. In 1983 the first electrochemical approach to produce a polycrystalline thin film of CuInSe2 was reported by Bhattacharya [73] in which Cu, In, and Se were deposited simultaneously from an acidic solution. Other approaches to the synthesis of polycrystalline CuIn(S,Se)2 thin films appeared quickly after the first report for example, Hodes et al. annealed an electrodeposited Cu-In alloy [74], Kapur et al. annealed stacked Cu-In layers [75], and Bhattacharya et al. annealed In-Se Cu-Se stacks [28]. The EDA routes which currently produce the most efHcient CuIn(S,Se)2 solar cells involve co-deposition of all of the constituent elements [76] followed by annealing in a sulfur atmosphere, and the electrodeposition of a Cu-In alloy with a small amount of Se, again followed by annealing in sulfur [34]. Both routes produce devices with around 11% power conversion efficiency. 

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