Non-equilibrium nitrogenation of transition-metal rich rare-earth intermetallics can be used to increase the nitrogen content beyond its equilibrium concentration. For example, nitrogenation of Sm/sub 2/Fe/sub 17/ using ammonia yields volume expansions up to 8.3 vol.%, which correspond to a composition Sm/sub 2/Fe/sub 17/N/sub x/ with x/spl ap/4. This effect is related to catalytic action at the metal surface where ammonia is decomposed into nitrogen and hydrogen, with nitrogen absorption on a site where it is weakly-bound, as an intermediate step. For overloaded Sm/sub 2/Fe/sub 17/N/sub x/ with x<3 the net reaction energy U/sub 0/=5/spl plusmn/10 kJ/mole indicates a nearly temperature-independent occupation of the non-9e sites.
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机译：富含过渡金属的稀土金属间化合物的非平衡氮化可用于增加氮含量，使其超过平衡浓度。例如，使用氨对Sm / sub 2 / Fe / sub 17 /进行氮化可产生高达8.3 vol。％的体积膨胀率，这对应于Sm / sub 2 / Fe / sub 17 / N / sub x /的组成，其中x / spl ap / 4。该作用与在金属表面上的催化作用有关，在该金属表面上，氨被分解为氮和氢，而在其弱结合的部位吸收了氮，这是中间步骤。对于x <3的超载Sm / sub 2 / Fe / sub 17 / N / sub x /，净反应能量U / sub 0 / = 5 / spl plusmn / 10 kJ / mole表示非离子的几乎与温度无关-9e网站。
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