Intermetallic compounds

The first intermetallic compound that could reversibly absorb hydrogen (ZrNi) was reported by Libowitz et al. [60]. A magnesium-based hydride with relatively high capacity (Mg2Ni) was reported by Reilly and Wiswall in 1968 [61]. Later, room-temperature hydrides such as the ternary hydrides TiFeH2 and LaNisHfi were 

In most cases, intermetallic compounds are built by alloying a metal which easily forms stable hydrides (A) and another element which does not form stable hydrides (B). The intermetallics thus formed could then be grouped according to their stoichiometry such as AB5 (LaNis, CaNis), AB2 (ZrMn2, ZrV2), AB (TiFe) and A2B (Mg2Ni). 

In some cases, empirical rules can also relate thermodynamic properties to crystal structures. One of the best-known cases is in the AB5 systems where the equilibrium pressure is linearly correlated to the cell volume. As the cell volume increases, the equilibrium plateau pressure decreases, following a InPn law [64]. However, some exceptions exist to this rule such as in LaPts where electronic effects make the smaller unit cell more stable [65[. Nevertheless, generally, for intermetallic compounds the stability of the hydride increases with the size of the interstices [66]. A limitation of this empirical rule is that comparison between different types of intermetallics is impossible. For example, the stabilities of AB2 alloys cannot be compared with those of AB5 alloys [43]. 

In order to meet the requirements of a practical application, a metal hydride must first satisfy the thermodynamic requirements operation temperature and hydrogen pressure. As the entropy term of Eq. (1.11) is effectively the same for all compounds, this means that the heat of formation (AH) is the principal parameter of a given alloy for hydrogen storage applications. Unfortunately, first principles calculations of AH for ternary alloys are still lacking [47]. However, semi-empirical models can be applied for some systems and give useful physical insight on the hydride formation. 

In Seetion 3.2.2, I briefly introduced the family of ordered intei metallic compounds, of which CU3AU was the first to be identified, early in the 20th century. We saw in the discussion of superalloys that such phases, Ni AI in particular, have a crucial role 

Much attention was paid to slruelures, superconducting properties, magnetic susceptibilities, Knight shifts, and specific heats of intermetallic compounds of technetium. Their structure types and lattice constants arc presented in Table 9.3. A. 

The TcAl6 phase was shown to be isoslructural with MnAlf, and ReAle- TcAli2 exhibits the same structure as M0AI12 and ReAli2 [51]. No new intermediate phases were found to exist in alloys of technetium with rhodium, palladium or platinum. The solubility of technetium in these metals increases in the given sequence ]71]. The group Vlll transition elements Co, Ni, Rh, Pd, Ir. and Pt show extensive solid solubility in technetium metal at 1050 C [72]. The solid solubility of technetium in nickel is 

Phase Composition Structure Lattice constants [A] References 

Strictly speaking an intermetallic compound is a compound formed by two metals, such as NiaAl, AI2C, etc., although the definition has been broadened to include metal-metalloid (Si, Ge, and As) and even nonmetals (FeaC). There are over 11,000 known intermetallic compounds, discovered primarily from their phase diagrams. It is estimated that there could be as many as 500,000 possible ternary systems and 10 quaternary systems with only a small fraction actually known (see Villars, 1994). Intermetallic compounds possess 

Solutions of up to 0-8 at. % Fe in beryllium show a small quadrupole splitting ( 0-58 mm s ) which is a function of concentration [77]. 

The ferromagnetic iron borides are often referred to as interstitial compounds because the boron atoms occupy interstices in an otherwise close-packed iron lattice. The internal fields at room temperature of Fe2B and FeB are 242 and 118 kG respectively compared with a value of 330 kG for iron itself [79, 80]. Data available concerning the detailed band structure of these compounds are consistent with 3i/-populations on the iron atoms of and 

A reinvestigation of the magnetic structure of FejB has shown the existence of two superimposed magnetic splittings of 244 and 252 kG at 4-2 K 

Manganese doping of Fc2B produces little broadening of the outer peaks 

The borocarbides FesB jCi also have the cementite structure. As x increases to 0-54 the average magnetic field increases to 240 kG (partly due to an increase in Tq) and the lines broaden and indicate some structure [86]. The effect of boron or carbon neighbours on the iron atoms are predominantly short-range, and the effective 3 /-population remains constant. 

Essentials of Inorganic Materials Synthesis, First Edition. C.N.R. Rao and Kanishka Biswas. 2015 John Wiley Sons, Inc. Published 2015 by John Wiley Sons, Inc. 

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The intermetallic compound layer shown in Fig. 10 are thought of FerTi and TiC[5]. This Tie is so called though is weak cause of the strength decrease [ 5]. 

The tensile strength in the joint part shown Fig.ll has less than the maetrial strength. As for this, joint strength is thought to be a decrease more than the strength of Ti because of an increase in the intermetallic compound of TiC that a little brittle. 

Intermetallic compounds with gallium are used as semiconductors. Indium is used to coat other metals to protect against corrosion, especially in engine bearings it is also a constituent of low-metal alloys used in safety sprinklers. The toxicity of thallium compounds has limited the use of the metal, but it does find use as a constituent of high-endurance alloys for bearings. 

Reference has already been made to the high melting point, boiling point and strength of transition metals, and this has been attributed to high valency electron-atom ratios. Transition metals quite readily form alloys with each other, and with non-transition metals in some of these alloys, definite intermetallic compounds appear (for example CuZn, CoZn3, Cu3,Sng, Ag5Al3) and in these the formulae correspond to certain definite electron-atom ratios. 

Intermetallic Compounds. Numerous intermetalhc galhum—transition element compounds have been reported (17). The principal compounds ate hsted in Table 4 (18—23). There ate probably several Cs and Rb compounds however, none is well known. 

E. L. Schlapback, ed.. Hydrogen in Intermetallic Compounds, Spriager-Vedag, Berlin, 1988, Chapt. 5, pp. 197—237. 

Selenium occurs in the slimes as intermetallic compounds such as copper silver selenide [12040-91 -4], CuAgSe disilver selenide [1302-09-6], Ag2Se and Cu2 Se [20405-64-5], where x < 1. The primary purpose of slimes treatment is the recovery of the precious metals gold, silver, platinum, palladium, and rhodium. The recovery of selenium is a secondary concern. Because of the complexity and variabiUty of slimes composition throughout the world, a number of processes have been developed to recover both the precious metals and selenium. More recently, the emphasis has switched to the development of processes which result in early recovery of the higher value precious metals. Selenium and tellurium are released in the later stages. Processes in use at the primary copper refineries are described in detail elsewhere (25—44). 

The numerous intermetallic compounds of zirconium, from ZrAl to ZrZn, are reviewed in References 120—123. 

Intermetallic compounds of zirconium with kon, cobalt, and manganese absorb and desorb considerable amounts of hydrogen, up to ZrMri2 [68417-38-9] (128) and ZrV2H 2 [63440-37-9] (129). These and other zirconium intermetallic compounds are being extensively studied for possible hydrogen storage appHcations (130). 

The intermetallic compounds with Group 16 (VIA) elements including CdS, CdSe, and CdTe have interesting semiconductor properties for photoconductors, photovoltaic cells, and ir windows. Cadmium sulfide is widely used as a phosphor in television tubes. 

Whereas finely divided cobalt is pyrophoric, the metal in massive form is not readily attacked by air or water or temperatures below approximately 300°C. Above 300°C, cobalt is oxidized by air. Cobalt combines readily with the halogens to form haUdes and with most of the other nonmetals when heated or in the molten state. Although it does not combine direcdy with nitrogen, cobalt decomposes ammonia at elevated temperatures to form a nitride, and reacts with carbon monoxide above 225°C to form the carbide C02C. Cobalt forms intermetallic compounds with many metals, such as Al, Cr, Mo,... 

Sohd rocket propellants represent a very special case of a particulate composite ia which inorganic propellant particles, about 75% by volume, are bound ia an organic matrix such as polyurethane. An essential requirement is that the composite be uniform to promote a steady burning reaction (1). Further examples of particulate composites are those with metal matrices and iaclude cermets, which consist of ceramic particles ia a metal matrix, and dispersion hardened alloys, ia which the particles may be metal oxides or intermetallic compounds with smaller diameters and lower volume fractions than those ia cermets (1). The general nature of particulate reinforcement is such that the resulting composite material is macroscopicaHy isotropic. 

N.N. Thadhani, Shock-Induced Chemical Synthesis of Intermetallic Compounds, in Shock Compression of Condensed Matter—1989 (edited by S.C. Schmidt, J.N. Johnson, and L.W. Davison), Elsevier Science, Amsterdam, 1990, pp. 503-510. 

Thadhani, N.N., Shock-Induced Chemical Synthesis of Intermetallic Compounds, presented at the American Physical Society Topical Conference on Shock Compression of Condensed Matter, Albuquerque, NM, August 14-17, 1989. 

The phase diagram for the copper-antimony system is shown on the next page. The phase diagram contains the intermetallic compound marked "X" on the diagram. Determine the chemical formula of this compound. The atomic weights of copper and antimony are 63.54 and 121.75 respectively. 

Solution hardening is not confined to 5000 series aluminium alloys. The other alloy series all have elements dissolved in solid solution and they are all solution strengthened to some degree. But most aluminium alloys owe their strength to fine precipitates of intermetallic compounds, and solution strengthening is not dominant... 

Figure A1.37 shows the iron-carbon phase diagram up to 6.7 wt% carbon (to the first intermetallic compound, FejC). Of all the phase diagrams you, as an engineer, will encounter, this is the most important. So much so that you simply have to learn the names of the phases, and the approximate regimes of composition and temperature they occupy. The phases are ...

Figure A 1.52 shows the Ti-Al phase diagram (important for the standard commercial alloy Ti-6% Al-4% V. It shows two peritectic reactions, at each of which liquid reacts with a solid phase to give an intermetallic compound, (a) Ring the peritectics and give the (approximate) chemical formula for the two compounds, (b) Shade all... 

Westbrook, J.H. and Fleischer, R.L. (1995) Intermetallic Compounds Principles and Practice (Wiley, Chichester, UK). 

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