Metals rare-earth elements

Paramagnetism Positive Small X = constant Alkali and transition metals, rare earth elements... 

The guidelines should be adhered to as far as possible to obtain the best accuracy. It is often not possible to meet all of the guidelines with one internal standard element. For example, if the analyst is required to measure 23 trace elements in a given sample, including transition metals, rare earth elements, nonmetals such as B, S, P, and refractory metals such as Nb, W, and Zr, it is not likely that one element chosen as an internal standard will meet all of the guidelines. More than one internal standard element may be added or more than one matrix wavelength chosen, but the possibility of spectral interference must be kept in mind. The more elements present, the more emission lines there will be and the greater the possibility of spectral overlap. 

The reaction of triphenylmethyl chloride, benzyl chloride and phenyl bromide with several metallic rare earth elements like Nd, Pr, Gd and Ho in tetrahydrofuran at room temperature has been described but no pure products could be isolated (Dolgoplosk et al., 1983, Markevich et al., 1983, Yakovlev et al., 1983). The structure of the proposed compounds is unclear. In the reaction of 2,2 -diUthium biphenyl with several rare earth tribromides (R = Pr, Sm, Gd, Ho, Yb) the proposed products are metallacycles (Syutkina et al., 1983). 

Petroleum hydrocarbon cracking catalysts usually contain more than 12 elements, including transition metals, rare earth elements (REEs), and alkali and alkaline earth elements at concentrations varying from 0.005 to 35 wt%. The composition of the catalyst can be determined accurately after fusion into borate beads the total analysis takes up to 1 h. The procedure and approach is described in ASTM D7085. Lubrication oil blenders use EDXRF to check their blends and ensure that control samples from lube shops are what the products claim to be (ASTM D6481 outlines the procedure). 

Catalysis, Homogeneous Catalysis, Industrial Electron Transfer Reactions Kinetics (Chemistry) Ligand Field Concept Noble Metals Rare Earth Elements and Materials... 

Fig. 8. SEM backscattering images for AB5 alloys. Letters A, B, C, and D indicate metallic rare earth elements, LaNi, LaNis, and transition metals, respectively.

The element occurs along with other rare-earth elements in a variety of minerals. Monazite and bastnasite are the two principal commercial sources of the rare-earth metals. It was prepared in relatively pure form in 1931. 

Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earths, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible. 

D very weak or inactive many metal, alkaline-earth, and rare-earth element haUdes... 

Figure 10 presents the Curie temperature (T ) vs the TM-content (x) for Co- and Fe-based biaary alloys. Alloying rare-earth elements with small amounts of transition metals (x < 0.2) leads to a decrease ia Curie temperature. This is particularly obvious ia the Gd—Co system where it corresponds to a nonmagnetic dilution similar to that of Cu (41,42). This iadicates that TM atoms experience no exchange coupling unless they are surrounded by a minimum number j of other TM atoms. The critical number is j = 5 for Fe and j = 7 for Co. The steep iacrease of for Co-based alloys with x about 0.7 is based on this effect. 

Oxahc acid is used in various industrial areas, such as textile manufacture and processing, metal surface treatments (qv), leather tanning, cobalt production, and separation and recovery of rare-earth elements. Substantial quantities of oxahc acid are also consumed in the production of agrochemicals, pharmaceuticals, and other chemical derivatives. 

Figure 4 shows vapor pressure curves of rare-earth metals[24], clearly showing that there is a wide gap between Tm and Dy in the vapor pressure-temperature curves and that the rare-earth elements are classified into two groups according to their volatility (viz.. Sc, Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, non-volatile elements, and Sm, Eu, Tm, and Yb, volatile elements). Good correlation between the volatility and the encapsulation of metals was recently... 

SWCNT is synthesized by co-evaporation of carbon and catalyst (mostly metals) in arc discharge. In early time, Fe [3], Co [4], Ni [8, 10] or rare-earth element [10] was employed as the catalyst (see Fig. 7). In these syntheses, however, the yield of SWCNT was quite low. In the improved method, the catalyst consisting of more than one element such as Co-Pt [12,13] or Ni-Y [14] is used to increase the yield of SWCNT (e.g., more than 75 % with Ni-Y [14]). 

Figure 16 shows the charge-discharge cycle characteristics of alloys in which part of the nickel component was replaced with cobalt. Misch metal (Mm), which is a mixture of rare earth elements such as lanthanum, cerium, praseodymium, and neodymium, was used in place of lanthanum. It was found that the partial replacement of nickel with cobalt and the substi-... 

Figure 10 shows in graphic form the utility of molten salt extractions for americium removal in one, two, and three stage extractions for various salt-to-metal extraction feeds. This graph demonstrates the impressive power of molten salt extraction systems for purification of plutonium from americium and related rare earth elements. 

Figure 1. Formation of ternary borides MreMj3B2 and different structure types (Mre = rare-earth element, M-p = transition-metal element). , CeCo3B2 type ErIr3B2 type O, URujBj type El, Ndo7,Rh3 29B2 type IS, YOS3B2 type B, Laofi3Rh3B2 type , compound formation observed, but structure type unknown. Refs a , b , c , d e , f g , h , i , j ", k , 1 , m , r, s - , t u = 45 see also ref. 62.

Figure 2. Formation of ternary borides MREMT4B4 (Mre = rare-earth element, Mj = transition metal) and different structure types. B, CeCo4B4 type B, LURU4B4 type a, NdCo4B4 type H, YOS4B4 type 8, Sm,4.eFe4B4 type MRcRe4B4 type , LuRh4B4type. Refs b, c , d", e, f , g , h, il l ...

As the computational effort in the LDF approach grows, in the limit, only with the third power in the number of orbitals, it can be expected that fairly large systems with a hundred atoms, including transition metals, rare earth, and actinide elements, will become tractable. 

Almost all of the rare-earth metal/rare-earth metal tri-iodide systems, R/RI3, contain binary phases with the rare-earth element in an oxidation state lower than -1-3 ( reduced rare-earth metal iodides) [3, 7, 10-13]. More common is the oxidation state -i-2. Elements that form di-iodides RI2 are illustrated in Fig. 4.1. 

Fig. 4.1 Rare-earth elements that form di-iodides, Rl2-Light grey Metallic di-iodides, Rlz= (R )(O(l )2- grey Salt-like di-iodides, Rl2= (R )(r)2- Ambient conditions.

In each of the composition diagrams in Fig. 14.2, the numbers represent a series of reactions run at a defined composition and temperature. These are isometric sulfur slices through three-dimensional K/P/RE/S quaternary phase diagrams. As just one example of what we have studied. Table 14.1 identifies the compositions at each point and the resulting phase(s). We have rigorously studied how phase formation is dependent upon the compositions of reactions for the rare-earth elements Y, Eu, and La and we have also discovered key structural relationships between the rare-earth elements, indicating a significant dependence on rare-earth and alkali-metal size for sulfides and selenides. 

---