Intermetallic compound, formation

There is no intermetallic compound formation and the electrodeposit behaves as a simple mixture of the two metals. It can be considered as basically a stable wick of tin through which zinc is fed to be consumed at a rate lower than its consumption from a wholly zinc surface. If the conditions are such that zinc is rapidly consumed, and no protective layer of corrosion products is formed, the coating may break down, but in mildly corrosive conditions some of the benefits of a zinc coating, without some of its disadvantages, are obtained. 

The alkali metals do not form intermetallic compounds with the transition metals. Both Na and Li dissolve only ppm quantities of most transition metals, although the solubilities are greater in Li. Nickel is very soluble in Li (900 ppm at 600°C), but no intermetallic compound forms. Intermetallic compound formation is, however, observed between Li and the noble metals Rh, Ir, Pd and Pt, so this section concentrates on the preparation of these compounds. 

Beryllium forms intermetallic compounds with transition metals and phase diagrams are available Some 26 phase diagrams have also been published for Mg-transition metal systems, and intermetallic compound formation is widespread in these systems also. The extent of intermetallic compound formation decreases down group IIA, such that Ca, Sr and Ba show much less tendency for compound formation to the extent that compounds are observed only in the Ba-Pd system. 

H. Chan, A. Butler, D.M. Falk and M.S. Freund, Artificial neural network processing of stripping analysis responses for identifying and quantifying heavy metals in the presence of intermetallic compound formation. Anal. Chem., 69 (1997) 2373-2378. 

Intermetallic compound formation may be observed as the result from the diffusion across an interface between the two solids. The transient formation of a liquid phase may aid the synthesis and densification processes. A further aid to the reaction speed and completeness may come from the non-negligible volatility of the component(s). An important factor influencing the feasibility of the reactions between mixed powders is represented by the heat of formation of the desired alloy the reaction will be easier if it is more exothermic. Heat must generally be supplied to start the reaction but then an exothermic reaction can become self-sustaining. Such reactions are also known as combustion synthesis, reactive synthesis, self-propagating high-temperature synthesis. 

Aluminium is known to form a number of binary142 145 221 and tema-ry intermetallics with iron and nickel or chromium. In this section, the intermetallic compound formation at the interface between a solid iron-nickel or iron-chromium alloy and the aluminium melt saturated with alloy constituents at 700°C, will be described. Also, the effect of dissolution on the process of layer growth will be illustrated.344 345... 

K.N. Tu, G. Ottaviani, U. Gosele, H. Foil. Intermetallic compound formation in thin-film and bulk samples of the Ni-Si binary system // J.Appl.Phys.- 1983.- V.54, No.2.-P.758-763. 

The solubilities of uranium, plutonium, and thorium in magnesium at 650°C are 0.002 wt %, 55 wt %, and 44 wt %, respectively. Thus, assuming no solute interaction, uranium is essentially insoluble in magnesium, while plutonium is quite soluble and good separation may be effected. While precipitation of an insoluble phase from solution would appear to be a straightforward process, the behavior of a solute in a given metal or alloy may differ from its behavior when influenced by the inclusion of other solutes. One element may increase or suppress the solubility of another through coprecipitation or intermetallic compound formation. Such effects must be determined experimentally. 

Figure 1. Periodic table showing intermetallic compound formation from the reaction of clean metal surfaces with -5000L of SiH4. Temperature required to grow thin films are indicated above the table. Solid areas indicate metals studied in our laboratory, while the cross-hatched areas refer to elements which should be employable based on thin film interdiffusion precedents.

Figure 4. Schematic view of intermetallic compound formation, oxidation (encapsulation), and subsequent reduction of (a) Ni on Si and (b) Pt on Ti02. We note that the oxidation states of Pt and Ti in PtTi Oy are not known (i.e., y may be 0) this figure is intended to indicate qualitative phase formation characteristics only.

Figure 3 also shows conversion and selectivity to C2H4 with Sn added to the Pt catalyst[15]. Both the alkane conversion and the selectivity to olefins increase significantly with added Sn. X-ray diffraction and XPS of the Pt-Sn catalyst indicate intermetallic compound formation rather than fee metal, and this surface evidently increases the alkane conversion and reduces the decomposition of olefins. 

The classification of Brenner is now represented by different values of the selectivity constants. The composition reference line introduced by Brenner is given by AB BA = 1- If the component A is the less noble component, curve 5 would represent normal and curve 4 anomalous co-deposition. Curve 3 represents segregation and curve 2 intermetallic compound formation AB. 

H, Chan, A. Buter, D. M. Falck, and M. S. Freund, Anal. Chem., 69, 2373 (1997). Artificial Neural Network Processing of Stripping Analysis Responses for Identifying and Quantifying Heavy Metals in the Presence of Intermetallic Compound Formation. 

FIGURE 48.2 Soldering steps required for first-pass soldering of a bottomside component on a PWB and success reflow steps encountered during first-pass soldering and repair. Note that the intermetallic compound formation thickness is not truly linear with each step. Thickness depends on materials of the soldering system, time above solder alloy liquidus, peak temperature, etc. The illustration is meant to show that with each reflow cycle, there is increased intermetallic layer thickness. 

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