Ternary compounds/alloys

The first belongs to space group Fm3m, and the latter to I 43m, and these two possibilities can be distinguished by comparing the X-ray diffraction intensities expected from the two structure types with those actually observed. This type of deduction is based on consideration of the roles of the individual atoms in a crystal structure, which usually finds application in compounds of inorganic composition such as binary and ternary compounds, alloys, and minerals. 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

See also Tertiary alloys Ternary aluminum alloys, 2 316—323 Ternary azeotropes, 10 476, 479, 482 Ternary compounds, nomenclature for, 17 389... 

A quantum-mechanical interpretation of Miedema s parameters has already been proposed by Chelikowsky and Phillips (1978). Extensions of the model to complex alloy systems have been considered. As an interesting application we may mention the discussion on the stabilities of ternary compounds presented by de Boer et al. (1988). In the case of the Heusler-type alloys XY2Z, for instance, the stability conditions with respect to mechanical mixtures of the same nominal composition (XY2+Z, X+Y2Z, XY+YZ, etc.) have been systematically examined and presented by means of diagrams. The Miedema s parameters, A t>, A ws1/3, moreover, have been used as variables for the construction of structural maps of intermetallic phases (Zunger 1981, Rajasekharan and Girgis 1983). 

Figure 5.41. Schemes of ternary compound formation in ternary alloys. For a few metal pairs (Al-Cu, Al-Fe, etc.) the third elements are indicated (defined by their position in the Periodic Table) with which true ternary phases are formed that is, phases are formed which are homogeneous in internal regions of the composition triangle not connected with the corners or edges. Compare these data with those shown for the formation of binary compounds in the figures relevant to the involved metals.

Just as an example about the ternary intermetallic reactivity, a few schemes of ternary compound formation for aluminium are given in Fig. 5.41, summarizing the formation capability of (true) ternary compounds. Data are generally available (although partial) about ternary aluminium alloys with selected metals (Fe, Mg, Si, etc.), owing to their relevant applications and commercial interest. With reference to the indicated metal pairs (Al-Fe, Al-Co, Al-Cu, etc.), the preferential formation of compounds with metals is evident. 

Introductory remarks. Phases related to the 1 3 stoichiometry and their derivative structures, either as point compounds or as solid solution ranges, are frequently found in binary and ternary intermetallic alloy systems. 

L. Guenee, V. Eavre-Nicolin, K. Yvon, Synthesis, crystal structure and hydrogenation properties of the ternary compounds LaNi Mg and NdNi Mg, J. Alloys Compd. 348 (2003) 129-137. 

M. Sahlberg, Y. Andersson, Hydrogen absorption in Mg-Y-Zn ternary compounds, J. Alloys Compd. 446-447 (2007) 134-137. 

After the initial attempt to prepare alloy and interstitial superconductors, several ceramists, chemists, and materials scientists joined the group of physicists and metallurgists in search of other superconducting materials. These scientists turned to ternary compounds and to more complex systems. From the mid-60 s to the mid-70 s, several new "inorganic materials" were found to exhibit the superconducting phenomenon. 

Y-Ni-Sb. Figure 1 represents the isothermal section of Y-Ni-Sb phase diagram at 870 K (0-50 at. % Sb) which was studied by Zavalii (1982). The isothermal section was constructed by means of X-ray powder analysis of alloys, which were arc melted and subsequently annealed in evacuated silica tubes for 400 h and finally quenched in water. Starting materials were Y 99.8 wt.%, Ni 99.99 wt.% and Sb 99.99 wt.%. The ternary phase equilibria diagram is characterized by the existence of two ternary compounds YNi2Sb2 (1) and YNiSb (2). 

One more ternary compound has been observed and studied by Mozharivskyj and Kuz ma (1996) from the arc melted, annealed at 1070 K for 400 h, and finally quenched in cold water alloys. It crystallizes with theMo5B2Si type structure, a = 0.7662, c = 1.3502 (X-ray powder diffraction). The starting metals were Y, not less than 99.8 wt.%, Ni and Sb 99.9 wt.%. 

A ternary compound of cerium with copper and antimony of the stoichiometric ratio 3 3 4 was identified and studied by means of X-ray analysis by Skolozdra et al. (1993). Ce3Cu3Sb4 compound was found to have the Y3Au3Sb4 type with the lattice parameters of a = 0.9721 (X-ray powder diffraction). For experimental details, see the Y-Cu-Sb system. At variance with this data, Patil et al. (1996) reported a tetragonal distortion of the cubic crystal structure Y3Cu3Sb4 for the Ce3Cu3Sb4 alloy which was prepared by arc melting the constituent ele-... 

Nd-Li-Sb. No ternary phase diagram exists for the Nd-Li-Sb system, however the formation of one ternary compound has been reported by Fischer and Schuster (1982) NdLi2Sb2 with the CaBe2Ge2 type structure, a = 0.4280, c = 1.0910 (X-ray single crystal data). The alloy was prepared by heating the elements in a Ta crucible at 870-1170 K for 24 48 h. 

The reactions in the Cu—W-S system, though similar, are simpler than those in the other systems above. For geologic reasons Moh66) has studied the system from near room temperature up to 900 °C. No ternary compounds were found. Thus, the phases which will enter into the ternary reactions are limited to the binaries. Copper and tungsten coexist at all temperatures and no binary alloys occur. 

Cohalt and copper. Ternary compounds are not formed. The alloys are hardest which oontain nickel and oohalt in equal proportions. All are attacked by nitric acid, but are fairly resistant to sulphuric acid. Waehlert, Chem. Zentr., 1914, li, 919, from Oesterr. Zeitsch. Berg- und Butten-wesen, 1914, 62, 341, 357, 374, 392, 406. 

The most common methods of preparing anhydrous binary metal fluorides in the laboratory are based on reactions of gaseous HF or F2 with suitable solid substrates. With HF, the oxidation state of the starting material is preserved, whereas with F2, the fluoride with the highest stable oxidation state is obtained. The reactions are mostly carried out in tubes of Monel (a Cu/Ni alloy) at temperatures up to about 400-600 °C. As starting materials, hydrated fluorides (obtained from aqueous HF solutions), chlorides, carbonates, or easy decomposable ternary compounds like NH4Mnp3 may be used, as shown by the following examples (2-4) ... 

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