V-Cr-Ti alloys

As we see in Table 1, CaO can be fabricated as a corrosion product between residual oxygen in metals, such as V-Cr-Ti alloys and dissolved Ca in Li. It is probable that CaO is intact in liquid Li. As we see in the screening test results in Table 1. O is mostly an interstitial impurity (especially, in BCC metals like V-alloys). When it is exposed to liquid-Li-bearing Ca, the... 

Fig. 6 Thermodynamic stability of several possible oxide phases that can form on V-Cr-Ti alloys with Li, and Ca in oxygen-containing environments.

Research has focused on V—Cr—Ti—Si alloys, having 0.15 wt % Cr, 0—20% Ti, and less than 1% Si. Titanium additions above 3 wt % drastically reduce the magnitude of radiation-induced sweUing. The alloy of greatest interest is V—5Ti—5Cr (31). 

BCC Alloys Hydrogen-absorbing alloys with bcc (body-centered-cubic) structures, such as Ti-V-Mn, Ti-V-Cr, Ti-V-Cr-Mn, and Ti-Cr-(Mo, Ru), have been developed since 1993 [43]. These alloys offer more interstitial sites than fee and hep structures and have a higher hydrogen capacity (about 3.0 mass%) than conventional intermetallic hydrogenabsorbing alloys. 

In metals the electrons lose their association with individual atoms and the number of valence electrons is often used in rationalization schemes. Estimated enthalpies of formation for equi-atomic alloys, MM, of two elements of the first transition metal series are given as a function of the difference in number of valence electrons in Figure 7.13 [8], Compounds of a given common metal are given a specific symbol. For example, the scandium compounds ScM where M = Ti, V, Cr, Mn, Fe, Co, Ni and Zn, are given by open circles. The metal M of the compound MM is... 

As an example for the specific case of vanadium alloys with palladium, the trend of the average atomic volume of the alloys is shown in Fig. 4.20 and compared with the phase diagram. These data were obtained by Ellner (2004) who studied the solid solutions of several metals (Ti, V, Cr, Mn, Fe, Co and Ni) in palladium. The alloys were heat treated at 800°C and water-quenched. From the unit cell parameters measured by X-ray diffraction methods, the average atomic volume was obtained Vat = c 14 (see Table 4.3). These data together with those of the literature were reported in a graph, and the partial molar (atomic) value of the vanadium volume in Pd solid solution (Fv)... 

These different interrelated structures, with special attention to their occurrence in Al-X-Y ternary alloys (X = Ti, Zr, Hf, V, Nb, Ta, Mo Y = V, Cr, Mn, Fe, Co, Ni, Cu, Zn) have been considered by Kumar (1990). According to differences in chemical bonding, mechanical and physical properties, Kumar considered (for various stoichiometries) three main groups of structures ... 

An accurate determination of copper and zinc traces in human serum samples from the International Measurement Evaluation Programme-17 launched by IRMM (Geel) has been made by isotope dilution TIMS.38 An analytical method for the multi-element determination of metals (Ti, V, Cr, Co, Ni and Mo) potentially released from dental implants and prostheses into human body fluids (in blood and urine) by ICP-MS (double-focusing sector field instrument and quadrupole instrument with octopole collision cell) for medical studies was developed in Sanz-Medel s group.39 The Cr and Co concentrations found in blood samples of patients with chromium-cobalt based alloy varied in the sub-p,gl 1 range and were not significantly higher than the basal levels found by other authors.40... 

Although the pure titanium-hydrogen system exhibits the normal isotope effect, many titanium alloys show the inverse effect. The exchange of pro-tium-tritium mixture with the hydrided phase of these alloys has demonstrated an inverse protium-tritium isotope effect in Ti-V, Ti-Mo, Ti-Cr, Ti-Mn, and the ternary alloy TiCrMn (1). On the other hand, Ti-Co, Ti-Fe, and Ti-Ni systems exhibit the normal isotope effect. Clearly much can be learned from a study of these systems. 

Figure 8. Maximum hydrogen solubility as a function of atom % alloy partner exhibited by V/Cr and Ti/Mo alloys. Data obtained at 40°C for a hydrogen charging pressure of 60 atm. (O) V/Cr, Ref. 52 (a) Ti/Mo, Ref. 56 (A) Ti/Mo, this work.

The phosphoric acid cell has been under research for a longer time than that of any other kind of fuel cell. Alloys of Pt with Cr, V, and Ti and other non-noble metals are better than Pt (Appleby, 1986). The particle size of the catalyst has been reduced to that of tens of atoms (Stonehart, 1993).10 Much attention has been given to the search for non-noble (hence cheaper) catalysts that are stable in hot acids. The best are the porphyrins, the formulas for which are shown in Fig. 13.20. They are applied to a base of graphite. These electrocatalysts are more effective in alkaline fuel cells than in those with acid electrolytes. Curiously, these substances are more stable and give better catalysis after pyrolysis in He at 800 °C, a process that would decompose the organic part of the structure. Perhaps the only active part of the porphyrin catalyst is the central... 

Fig. 80. Simplified density of states curve for metallic chromium. Energy scale is referred to bottom of s-p band. The Fermi level relative to the d bands is also shown for b.c.c. Ti, V, and Mn given the same relative positions of d and s-p bands. Ferromagnetic, simple-cubic sublattices are coupled antiferro-magnetically in b.c.c. Cr-Mn alloys.

One of the important materials problems in this design is the corrosion of metal alloys when Li-Pb is used as the breeder-moderator. The dual wall structure used in the Cauldron Blanket Module should apply equally well here, so that V can be used for the plasma first wall to provide structural strength with minimum activation. The choice of a material for the wall membrane in contact with liquid Li-Pb becomes difficult. Ti alloys cannot be used because of reaction with Pb. Pure iron and iron-rich alloys appear marginal because of a solubility of Fe in Pb of 10-5 atom fraction at 900 K (12). Use of Ni or Cr as alloying constituents in iron do not improve the situation, since Ni and Cr have solubilities in Pb of 0.03 and v 10" atom fraction at 900 K (13). The refractory metals Nb, Ta, Mo,... 

The aim of this chapter is to review our understanding of the fundamental processes that yield improved electrocatalytic properties of bimetallic systems. Three classes of bimetallic systems will be discussed bulk alloys, surface alloys, and overlayer(s) of one metal deposited on the surface of another. First, we describe PtjM (M=Ni, Co, Fe, Cr, V, and Ti) bulk alloys, where a detailed and rather complete analysis of surface structure and composition has been determined by ex situ and in situ surface-sensitive probes. Central to our approach to establish chemisorption and electrocatalytic trends on well-characterized surfaces are concepts of surface segregation, relaxation, and reconstruction of near-surface atoms. For the discussion on surface alloys, the emphasis is on Pd-Au, a system that highlights the importance of surface segregation in controlling surface composition and surface activity. For exploring adsorption and catalytic properties of submonolayer and overlayer structures of one metal on the surface of another, we summarize the results for Pd thin metal films deposited on Pt single-crystal surfaces. For all three systems, we discuss electrocatalytic reactions related to the development of materials... 

A major reason why Zr (rather than Cr, Mn, V or Ti) has become the preferred choice as the recrystallization inhibiting element relates to its relatively low effect on quench sensitivity in commercial aluminum alloys [6],... 

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