Hydrogen in amorphous metals

The solid lines represent a fit of the two-state model to these data. Inset magnification of the small Q behaviour of the linewidths at 373 K dashed line HWHM oc q2) (from Ref [34]). 

From the Q dependence a mobility range of about 10 A is obtained. For the mobile state the isotropic Chudley-Elliott model is assumed. The result of a fit with this two-state model is shown by the solid line in Fig. 26.8 obviously a reasonable agreement between model and fit is achieved. In particular, the diffusion process in between traps is considerably faster than in crystalline Pd, whereas, as a consequence of trapping, the long-range diffusion coefficient is of the same order. At small Q the character of the narrow mode already crosses over from diffusive to localized behavior this explains a Q exponent smaller than 

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The absence of a plateau has been reported by all previous workers and seems to be a general feature of hydrogen in amorphous metals. In crystalline systems the formation of the hydride can be viewed as a cooperative phase transition of the first order in which the hydrogen condenses from a vapour like state into a liquid like state. The... 

R. Kirchheim, F. Sommer and G. Schluckebier, Hydrogen in Amorphous Metals-I, Acta Metall. 30 1059 (1982). 

A solid solution of hydrogen in technetium metal is formed during the electrodcpo-sition of technetium from acid aqueous solutions of pcrtechnctate. The maximum hydrogen content of the amorphous phase corresponded to TcHo.27 [6]. 

The thermal decomposition of silanes in the presence of hydrogen into siUcon for production of ultrapure, semiconductor-grade siUcon has become an important art, known as the Siemens process (13). A variety of process parameters, which usually include the introduction of hydrogen, have been studied. Silane can be used to deposit siUcon at temperatures below 1000°C (14). Dichlorosilane deposits siUcon at 1000—1150°C (15,16). Ttichlorosilane has been reported as a source for siUcon deposition at >1150° C (17). Tribromosilane is ordinarily a source for siUcon deposition at 600—800°C (18). Thin-film deposition of siUcon metal from silane and disilane takes place at temperatures as low as 640°C, but results in amorphous hydrogenated siUcon (19). 

This work is a contribution to the understanding of the effect of spillover hydrogen in a type of catalyst of considerable industrial importance, namely that composed of transition metal sulfides and amorphous acidic solids. This is typically the case of sulfided CoMo supported on silica-alumina used for mild hydrocracking. 

R. Kirchheim, Solubility, diffusivity and trapping of hydrogen in dilute alloys, deformed and amorphous metals-II, Acta Metallurgica, 30(6) (1982) 1069-1078. 

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