Amorphous intermetallic compounds

For the spectra of Ni, peaks corresponding to Ni oxide and Ni metal are observed in the as-prepared sample [28-30]. After the etching with Ar, however, the peak of Ni metal is predominant. This implies that the state of Ni in the Ni-Zn nanoclusters is metallic, although their surface was oxidized under the atmospheric conditions. On the other hand, the identification of Zn state is difficult because the peak positions of Zn and ZnO in ESCA spectra are very close to each other. Furthermore, the B/Ni ratio determined by ESCA was increased with increasing Zn added e.g., Ni B = 73.3 26.7 and 60.6 39.4 for Zn/Ni = 0.0 and 1.0, respectively. Because no crystalline structure was found except for Ti02 from both electron and X-ray diffraction patterns of the respective samples, it can be concluded that formed nanoclusters were amorphous. Ni-Zn nanoclusters would be composed of amorphous intermetallic compounds through the... 

In order to describe the magnetic order behavior of amorphous intermetallic compounds containing rare-earth atoms with nonzero orbital momentum, such as a-TbFe2, Harris et al. (1973) have introduced the random anisotropy-axis ... 

X.L. Yeh, K. Samwer, W.L. Johnson, Formation of an amorphous metallic hydride by reaction of hydrogen with crystalline intermetallic compounds - a new method of synthesizing metallic glasses, Appl. Phys. Lett. 42 (1983) 242-244. 

D.E. Luzzi, M. Meshii, The crystalline to amorphous transition of intermetallic compounds under electron irradiation -a review, Res. Mechanica 21(3) (1987) 207-247. 

R.A. Varin, T. Czujko, J. Mizera, The effect of MgNi2 intermetallic compound on nanostructurization and amorphization of Mg-Ni alloys processed by controlled mechanical milling ,... 

The mechanisms of radiation-induced amorphization have been investigated for more than three decades, and a variety of models have been developed to describe the processes that lead to radiation-induced amorphization of different types of materials. Early work was mainly based on the results for irradiated intermetallic compounds and semiconductors. In general, these models have been applied to ceramics with only minor modifications (Weber 2000). The models are of two types the direct impact or cascade quenching models (Morehead and Crowder 1970, Gibbons 1972) and defect accumulation models (Gibbons 1972, Jackson 1988, Ziemann 1985, Ziemann et al. 1993, Titov and Carter 1996, Motta and Olander 1990, Okamoto et al. 1999). 

Motta AT (1997) Amorphization of intermetallic compounds under irradiation—a review. J Nucl Mater 244 227-250... 

Pabst A, Hutton CO (1951) Huttonite a new monoclinic thorium silicate. Am Mineral 36 60-69 Pedraza DF (1986) Mechanisms of the electron irradiation-induced amorphous transition in intermetallic compounds. J Mater Res 1 425-441... 

Table 2.2. Hydrogen-induced amorphization of several types of the AB2 type intermetallic compounds with C15 structure (Laves phase RM2)...

Fig. 2.10. C ross-sectionnl electron micrograph of a Ni/Zr ilifTusion couple reacted at (a) 200 ( for 6 It, showing 80ntm thick amorphous interlayer which has grown by interdilTusion (h) the same diffusion couple reacted tit 300 "C for 18 It. showing both an amorphous interlayer and it layer of the crystalline intermetallic compound Ni/Zr (2/KIJ...

Now suppose that intermetallic compounds are suppressed in Fig. 2.16. Consider the metastable equilibrium between an amorphous phase and the terminal solutions of a-Zr (bcc Zr) and Ni. Under these conditions, the common tangent construction yields a metastable equilibrium state which consists of a single-phase a-solution for xZr > x4, a two-phase region of liquid (glass)/a-... 

Fig. 2.16. Free-energy diagram for the Ni/Zr system at 300°C showing the free energy of mixing as a function of composition for the hep, bcc, fee, and liquid/amorphous phases. Intermetallic compounds are shown by dots and are assumed to be line compounds. The common tangents for the hep/liquid, and liquid/fee metastable equilibrium are shown. These define compositions XLXj.X3.X4 [2.76]...

Nucleation and the phase sequence problem. We showed above that many possible reactions can occur in a diffusion couple. Any new phase for which AG < 0 is thermodynamically allowed. In fact, the thermodynamic driving force for intermetallic compounds (e.g., crystalline NiZr) is greater than that for the formation of an amorphous phase... 

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