700℃,^(63)Ni示踪原子在NiO+Ni_3S_2生长层中的扩散

Diffussion Of ^(63)Ni Tracer In Scale NiO+Ni_3S_2 at 700℃

利用^(63)Ni放射性同位素示踪技术,研究了在700℃、O_2-10％(SO_2+SO_3)(latm)环境下,镍被加速腐蚀过程中,^(63)Ni在(NiO+Ni_3S_2)混合产物层的分布规律。实验技术是首先在纯镍试样表面镀一层^(63)Ni,然后测量^(63)Ni在随后不同反应时间后的腐蚀产物层中的分布。实验结果表明,^(63)Ni的分布符合晶界扩散规律,即在金属初始表而位置处含量最高,并沿产物层生长方向逐渐降低。Ni_3S_2相在影响^(63)Ni传质过程特点方面所起的作用,取决于它在Ni_3S_2+NiO混合物中的分布形态。Ni_3S_2本身即可以做为一个快速扩散通道,又可通过改变Ni_3S_2+NiO混合的组织特点来影响传质过程。

^(63)Ni tracer distribution in the scale of NiO+Ni_3S_2 mixture has been determined. Expermental techniques involve electroplating a thin layer of ^(63)Ni to high purity nickel specimens, Oxidiging the specimens in latm O_2-10 %(SO_2+SO_3) at 700℃, and then counting the residual activity of ^(63)Ni in the corrosion product scale. Experimental results show that the perncipale transport mechanism for ^(63)Ni is short circuit diffusion, which means that the distribution has its maximum value close to the metal/scale interface, and decreases gradually to the scale/gas interface, It has been proposed that the way of Ni_3S_2 in influencing the transport of ^(63)Ni varies depending upon the feature of Ni_3S_2 dispersed in NiO.