Other LI 2 Phases

A metal-rich silicide with a very simple crystal structure is NijSi with the ordered f.c.c. LI 2 structure. It has a very high potential for structural applications because of its advantageous mechanical properties and its outstanding corrosion resistance. Its deformation behavior is similar to that of other LI 2 phases, in particular NisAl, and thus NijSi has been discussed in Sec. 4.2.2 together with other LI 2 phases. 

It has been proposed by others that this B segregation produces disorder at grain boundaries, thus facilitating slip transmission across them. This view is supported by a Hall-Petch type analysis of flow stress data as a function of the grain size. There are observations on disordered grain boundary layers which indicate the formation of the y-Ni-Al phase at the grain boundaries. This is not improbable since the A1 content of Al-deficient NijAl is near the solubility limit, and in the case of the LI 2 phase CU3 Au it has been found (Tichelaar et al., 1992) that the order-disorder transition is preceded by the formation of disordered layers at the interfaces. However, such disordered layers have also been found in NijAI without B, and have not been found in many ductile NijAl alloys with B (see also Lin et al., 1993 Sun and Lin, 1993). 

Calcium is an excellent reducing agent and is widely used for this purpose. At elevated temperatures it reacts with the oxides or haUdes of almost all metallic elements to form the corresponding metal. It also combines with many metals forming a wide range of alloys and intermetaUic compounds. Among the phase systems that have been better characterized are those with Ag, Al, Au, Bi, Cd, Co, Cu, Hg, Li, Na, Ni, Pb, Sb, Si, Sn, Tl, Zn, and the other Group 2 (IIA) metals (13). 

The emulsion liquid membrane (Fig. 15.1b) is a modification of the single drop membrane configuration presented by Li [2] in order to improve the stability of the membrane and to increase the interfacial area. The membrane phase contains surfactants or other additives that stabilize the emulsion. 

The 2" phase (2006-2009) R D activities undertake a SI process optimization and the performance tests of various chemical reactors selected for the SI cycle. The 2" phase research covers a dynamic code development for the SI process, a construction of a lab. scale( l 000 NL/h) SI process, and integrated operations of the process at prototypical pressures. On the other hand, conceptual and basic designs of a pilot scale( 100 Nm /li) SI process and its equipment will also be carried out according to the optimized process established from the theoretical evaluation using a commercial-base computer code and the experiences of the lab. scale construction and operations. Preliminary performance tests of the equipment, mechanical devices, and accessories for the pilot scale SI process should be carried out to obtain the design basis. Not only the several catalysts based on non-noble metals required for section II in the SI cycle but also a membrane for the separation of the hydrogen required for section III will be developed during the 2" phase research period. 

The correlation between the total phase enthalpy and the Young s modulus, which is one of the three elastic moduli, is shown in Fig. 6 for various cubic phases, i.e. for the f.c.c. elements Al and Ni (Al), the f.c.c.-ordered NijAl (LI 2), the b.c.c. ordered FeAl, NiAl and CoAl (B2), and the cubic Laves phases CaAlj, YAI2, LaAl2, NbCr2, ZrLaves phases, i.e. there seems to be a common scatter band and the data of some other phases are near this scatter band. It has to... 

AljM with M = V, Nb, Ta, and some other phases, e.g. NijV (Bauer, 1939 Vil-lars and Calvert, 1991). The DO22 structure is derived from the close-packed cubic LI 2 structure by the stacking of LI 2 cubes with periodic antiphase boundaries in between, and thus the DO22 structure may be regarded as a tetragonally distorted, long-period ordered, cubic structure (Bauer, 1939 Yamaguchi and Umakoshi, 1990). 

Formation of superstructures of the binary rare-earth germanides The crystal structure of Ho26Pd4(Pd,Ge)i9 jc represents a substitutional variant of the Er26Ge23-j structure type. The difference between the two structures lies only in the replacement of germanium atoms by palladium atoms in positions 2(c) and 8(j) and the presence of a statistical distribution of Ce and Pd atoms in positions 2(c) and 8(i). Other isotypical ternary phases are not known. Only the compound Ce26Li5Gc23 -y, where the Li atoms occupy the 2(b) and 8(i) positions which are vacant in the previous phases, has a similar structure (table 5). 

Figure 11.21b Phase diagram of the ternary system AOT/l-octanol/H20 at 25 °C (in wt%). Isotropic water continuous phase (Li), lamellar phase (D), (bicontinuous) cubic phase (I2), isotropic oil continuous phase (L.2)> reverse hexagonal phase (F), other phase regions without symbols.

The good cyding stabihty of the tin in TCO is quite unusual, because the electrochemical cyding of li Sn and also of other Li alloy electrodes is commonly assodated with large volume changes in the order of 100-300% (Figure 15.19) [2, 7, 22, 24, 26, 349-351). Moreover, hthium alloys Li M have a highly ionic character ( Zintl-Phases, ). For this reason they are usually fairly brittle. Mechanical... 

Metallurgy. Lithium forms alloys with numerous metals. Early uses of lithium alloys were made in Germany with the production of the lead alloy, BahnmetaH (0.04% Li), which was used for bearings for railroad cars, and the aluminum alloy, Scleron. In the United States, the aluminum alloy X-2020 (4.5% Cu, 1.1% Li, 0.5% Mn, 0.2% Cd, balance Al) was introduced in 1957 for stmctural components of naval aircraft. The lower density and stmctural strength enhancement of aluminum lithium alloys compared to normal aluminum alloys make it attractive for uses in airframes. A distinct lithium—aluminum phase (Al Li) forms in the alloy which bonds tightly to the host aluminum matrix to yield about a 10% increase in the modules of elasticity of the aluminum lithium alloys produced by the main aluminum producers. The density of the alloys is about 10% less than that of other stmctural aluminum alloys. 

---