Required Diffusion Time for in-situ Measurement of Diffusion Coefficients in Liquid Alloys by X-ray Fluorescence Analysis

抄録

This study establishs a method to determine the diffusion time required for diffusion measurement by using the long capillary technique and through in-situ X-ray fluorescence analysis. A diffusion couple of pure Sn (60 mm height) and Sn90Bi10 (3 mm height) was set to provide stable density layering and maintained at 573 K. The X-ray source was positioned 10 mm above the bottom of the sample. The detected intensity of Lβ emission line of Bi (Bi Lβ) changed mainly because of the diffusion of Bi in liquid Sn. The apparent diffusion coefficients (𝐷𝑎𝑝𝑝) were calculated by fitting the analytical solution for the diffusion to the temporal distribution of Bi Lβ intensity by varying the fitting time range from 0 to 𝑡𝐷 (diffusion time). The change in 𝐷𝑎𝑝𝑝 was large at short 𝑡𝐷, but decreased with increasing 𝑡𝐷. The deviation of 𝐷𝑎𝑝𝑝 from the value corresponding to the longest 𝑡𝐷 and the maximum range scale of the confidence interval of 𝐷𝑎𝑝𝑝 were determined. The largest calculated value is considered to be the systematic error in the diffusion measurement (𝛥𝐷). For the required value of 𝑡𝐷, 𝛥𝐷 becomes less than the acceptable systematic error in the diffusion measurement. The convergent 𝐷𝑎𝑝𝑝 [(2.16±0.09)×10-9 m2/s] agreed with the microgravity reference data in the error range.