Nondestructive thickness measurement of silica scale using cathodoluminescence

Susumu Imashuku, Wataru Hashimoto, Kazuaki Wagatsuma

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


The knowledge of the composition, morphology, and thickness of surface protective scales, such as SiO2 and Al2O3, is important to control the performance of heat-resistant alloys operated at high temperatures above 1000 °C. Cathodoluminescence (CL) analysis is one of the most promising methods to acquire such information nondestructively. Unlike Al2O3 scale, the use of the brightness of CL image to determine SiO2 scale thickness is difficult because the brightness and color of its acquired CL image depend not only on the thickness of the scale but also on its oxygen potential and impurity concentration. In this study, we investigated the CL spectra of SiO2 scales formed on Fe-20%Si alloy, Si, and MoSi2 to present a method for measuring the thickness of SiO2 scale on silica-forming materials from their CL spectra. A linear calibration curve was obtained from the intensity of the CL peak at 445 nm which originated from the intrinsic defects in SiO2 and the thickness of the SiO2 scale for each heat-treatment temperature (1000 °C, 1200 °C, 1300 °C, and 1400 °C). Data in this study can be adequately employed to derive CL calibration curves at different temperatures because the CL intensity and heat-treatment temperature were fitted according to Arrhenius relationship at different SiO2 scale thickness, regardless of the type of base materials. These results indicated that the thickness of the SiO2 scale formed on silica-forming alloys can be determined by acquiring their CL spectra. Therefore, CL analysis has the potential to be employed as a novel analytical method to control the performance of silica-forming alloys.

Original languageEnglish
Article number119022
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Publication statusPublished - 2021 Feb 5


  • Cathodoluminescence
  • Nondestructive analysis
  • SiO scale
  • Thickness

ASJC Scopus subject areas

  • Analytical Chemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Spectroscopy


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