Ternary carbides systems

Holleck, H., Ternary Carbide Systems of Actinoids wifli fire Transitions Metals of 4 to 8 Groups , J. Nucl Mater, 124,129-146 (1984) (Assessment, Crys. Structure, Phase Diagram, Phase Relations, 78)... 

Many ternary carbides and nitrides are known and some of these compounds have excellent properties. For instance, the hardness of ternary-carbide systems of the same group (Group IV or Group V) is considerably higher than the hardness of the binary constituents.1 1 A hardness of approximately 43.1 GPa is reported for the compound TIq 4C... 

Here again certain trends were observed, and the most influential factor was the crystal structure which the superconducting material adopted. The most fruitful system was the NaCl-type structure (also referred to as the B1 structure by metallurgists). Many of the important superconductors in this ceramic class are based on this common structure, or one derived from it. Other crystal structures of importance for these ceramic materials include the Pu2C3 and MoB2 (or ThSi2) prototypes. A plot of transition temperature versus the number of valence electrons for binary and ternary carbides shows a broad maximum at 5 electrons per atom, with a Tc maximum at 13 K. 

Mi) Actinide-Metal Group. Alloys of U-Pu-C and U-Zr-C can be used as a nuclear fuel. Both systems are characterized by extensive mutual solubility and no ternary compounds. However, U forms ternary carbides with several transition metals to give the compound UMCj, where M = Mo, W, Re, Rh, Ir, Mn, Cr, Ni, Co, Fe or Tc. 

The reaction of ternary carbides with nitrogen has attracted interest because of a novel type of phase separation occurring in double pseudobinary solid solutions of transition-metal multicomponent carbonitrides. Rudy has investigated the system Ti-Mo-C-N and has found that the homogeneous solid solution (Ti, Mo) (C, N), formed at high temperatures, disproportionates into two phases, both of which are isostructural and have nearly the same lattice parameters. One of the two phases is a Ti carbonitride rich in N and poor in Mo, the other is a Ti-Mo carbide rich in Mo hut poor in N. This type of disproportionating is bound to occur in most of the double-pseudobinary carbonitride systems... 

Phase diagrams and formation of ternary carbides in R-B-C systems 115... 

In the mixed rare earth dicarbide and the rare-earth-actinide carbide systems, the ternary compounds were found to be present in the form of a solid solution with the same structure as the component carbide. Thus, these carbides have also been called pseudobinary carbides. 

The Gd-Fe C system. In the iron gadolinium-carbon system, the liquidus projection and the 900°C isothermal section (fig. 21) were determined (Stadelmaier and Park 1981). Six ternary carbides were found in this system. Unlike the binary gadolinium carbides, they do not decompose readily in water. Two ternary carbides are metal-rich and the structures are derivatives of binary Fe-Gd structures. The crystal structures of the six ternary compounds are listed in table 16. 

Recently, Hoffmann et al. (1989) reported a series of the ErgRhjCij-type compounds present in the R-Rh-C system. These compounds RgRhjCjj (R=Y, Gd-Tm) are thermodynamically stable at 900°C and have a monoclinic structure, space group C2/m, with Z — 2 formula units per unit cell. The lattice parameters of these compounds have been measured by single-crystal X-ray diffraction. The structure contains a finite chain-like centrosymmetric polyanion [Rh5Ci2] with two Rh-Rh bonds (2.708 A) and six pairs of carbon atoms. The shortest distances between adjacent Rh5Ci2 clusters are the Rh-C distances of 2.94 A and the Rh-Rh distances of 3.27 A, and thus the Rh5Ci2 units may be treated as isolated from each other. This structure is characterized by three different kinds of C2 pairs. The C-C bond distances of 1.27, 1.32 and 1.33 A are between those of a triple bond (1.20 A) and a double bond (1.34 A) in hydrocarbons, and are the shortest found so far in ternary carbides of the rare earth metals with transition metals. 

In the rare-earth-manganese arbon systems three types of ternary carbides were found the tetragonal LaMnuC2-x for R = La-Nd (Jeitschko and Block 1985), the... 

Phase equilibria for the isothermal section at 900°C of compound compositions in the ternary gadolinium-chromium-carbon system are shown in fig. 28 (Jeitschko and Behrens 1986). Only one ternary carbide, Gd2Cr2C3, exists in this system and it was found to be isotypic with HojCrjCj. The variation of the lattice parameters of samples with different compositions indicates that the homogeneity range of Gd CrTC, seems to be small. 

The trends in ternary carbide formation in Fe base systems have been briefly reviewed by [1967Gol, 1990Ere]. Aspects of flic construction of diagrams of ternary systems formed by Cr and C with d-transition metals have been presented by [1996Bon, 1997Hil]. 

The isothermal sections at 871, 927 and 982°C in die Fe rich part of die system given in Fig. 13 were proposed by [1979Woo] based on a very detailed study. The coexistence of die ti and T2 ternary carbides with the 7 and Fc3C based phases was established. The M23C6 phase was not found. In case of treating die reported Fc3C based phase as T3 die obtained results fall in agreement widi the calculated section at 900°C, shown in Fig. 9. 

Also some ternary carbides, nitrides or oxides if necessary for the understanding of the respective binary systems these phases are treated together with the binary systems or follow them. ) Auch einige temare Carbide, Nitride oder Oxide soweit erforderlich zum Verstandnis der entsprechenden binaren Systeme diese Phasen sind mit den binaren Systemen zusammen oder unmittelbar anschliefiend behandelt. 

The linear hybrids of two structure types, CeGa2Al2 and ape, are ternary carbides SC3C0C4 and SCC0C2, which are in equilibrium with each other and occur on the isoconcentrate of 50at.% C in the Sc-Co-C system. 

Thermodynamic Data on Alloys , by Kubaschewski and Catterall, critically surveys data on some 400 binary and ternary metallic systems, with the term alloy interpreted to include transition-metal oxides, sulphides, carbides, nitrides, and phosphides. When available, values are given for the integral enthalpy and entropy of formation of the alloy, the relative partial molar enthalpy and entropy of one component, and the volume change on mixing. 

Energy states and chemical bonding in ternary carbides and nitrides formed in Ti-(AI, Ge)-(C, N) systems... 

Recent reports describe the use of various porous carbon materials for protein adsorption. For example, Hyeon and coworkers summarized the recent development of porous carbon materials in their review [163], where the successful use of mesoporous carbons as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for protein immobilization are described. Gogotsi and coworkers synthesized novel mesoporous carbon materials using ternary MAX-phase carbides that can be optimized for efficient adsorption of large inflammatory proteins [164]. The synthesized carbons possess tunable pore size with a large volume of slit-shaped mesopores. They demonstrated that not only micropores (0.4—2 nm) but also mesopores (2-50 nm) can be tuned in a controlled way by extraction of metals from carbides, providing a mechanism for the optimization of adsorption systems for selective adsorption of a large variety of biomolecules. Furthermore, Vinu and coworkers have successfully developed the synthesis of... 

Although the literature often indicates catastrophic reactions of fluorine with oxides, nitrides, carbides, silicides, borides and the like, many such species may be reacted under controlled conditions to produce oxyfluorides, nitro-fluorides such as TINF, ZrNF, HFNF, ThNF, and UNF, and other interesting ternary systems. 

From the early 1960s onwards, the use of lanthanide (Ln) based catalysts for the polymerization of conjugated dienes came to be the focus of fundamental studies [31]. The first patent on the use of lanthanides for diene polymerization originates from 1964 and was submitted by Union Carbide Corporation (UCC) [32,33]. In this patent the use of binary lanthanum and cerium catalysts is claimed. Soon after this discovery by UCC, Throckmorton (Goodyear) revealed the superiority of ternary lanthanide catalyst systems over binary catalyst systems. The ternary systems introduced by Throckmorton comprise a lanthanide compound, an aluminum alkyl cocatalyst and a halide donor [34], Out of the whole series of lanthanides Throckmorton... 

Because of the evident structmal similarities between transition metal carbides and transition metal nitrides the carbon atoms in group 4 and 5 carbides can be replaced completely by nitrogen without changing the structme of the binary phases. So far only one distinct ternary phase Cr2 (C,N)2 has been reported. Intersolubihty between the binary nitrides and carbides in the group 6 carbonitride systems Cr-C-N and Mo-C-N is not complete because of the differences in the crystal structmes of the carbide and nitride phases. 

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