Alloying with Transition Metals

The information on the effect of alloy formation on the catalytic activity is generally conflicting. The effect of Sc during superheating of the catalyst is interpreted as an activity increase due to reduction of SC2O3 to Sc followed by an activity decrease due to Sc + Fe alloy formation [271]. Small amounts of Co increases the rate of NH3 synthesis and N2-chemisorption [123]. Small amounts of Ni increases only the rate of NH3 synthesis, not the rate of N2 chemisorption [123]. 

A promising technique for the study of the catalytic activity of alloys is the study of chemisorption on iron overlayers on single crystals of other metals such as Fe/Ru [375], Fe/Re [376], and Fe/W [377]. 

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The activation of aluminum with ultrasound or dispersion of liquid aluminum. The suspension of powder aluminum in petrol or n-geptane without oxygen is subjected to ultrasound the tough oxide film on the surface of aluminum is removed and aluminum becomes reactive. The second activation technique is the dispersion of liquid aluminum with argon or purified nitrogen flow into a finely dispersed state. It should be noted, however, that the most reactive aluminum powder for direct synthesis is the powder alloyed with transition metals (titanium, zirconium, niobium, tantalum) with the size of particles from 10 to 125 pm. 

Fig. 12.57. Correlation between pitting potential and pzc. (Reprinted from J. O M. Bockris and J. Kang, The Pro-tectivity of Aluminum and its Alloys with Transition Metals, J. Solid State Elec-trochem. 1 28,1997, with permission from Springer-Verlag.)...

Bockris and J. Kang, The Protectivity of Aluminum and its Alloys with Transition Metals, J. Solid State Electrochem. 

For example, in the Al— 12.0Zn—3.3Mg— 1.2Cu—0.13Zr—0.4Mn—0.49Sc alloy high mechanical properties were obtained, i.e. YS = 790 MPa and UTS = 820 MPa. This high strength was achieved due to additional combined alloying with transition metals, such as Sc, Zr, Cr and Mn, which retard... 

However, numerous studies reported that Pt and Pd alloys, with transition metals as Co, Ni, Cr, and Fe, showed the enhancement factor up to 10 for ORR if compared with pure metal (Table 2) [33]. 

The magnetic transition temperatures of RMn2X2 compounds are plotted in fig. 32 against the Mn-Mn distances within the layer and between two Mn-Mn layers R. It appears that the respective temperatures follow a curve that is a function of R but it is not a function of R. . It is seen that there is a critical distance of R of about 0.285 nm. Antiferromagnetic coupling exists when R is less than 0.285 nm and ferromagnetism appears for R >0.285 nm. Similar critical distances were observed in many Mn alloys with transition metals (Tebble and Craik 1969). 

In the following, we will attempt to derive some trends in the behavior of rare earths and actinides alloyed with transition metals ... 

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