The problem?
The objective of this study is to characterize the outer surface of a zirconium tube at three circumferential positions in order to verify the homogeneity of the coatings over the entire circumference of the tube.
The customer wants to verify the uniformity of the coatings on the entire length of the tube. To do this, FILAB offers the customer a comparative study using XPS technology. The idea is to perform an elemental, structural, and quantitative analysis of the surface layer (a few nm deep) of a sample from three different areas of the tube in order to meet the customer's needs.
Characterizing the surface of a zirconium tube using XPS
Objective :
Determine whether the coating on the customer's zirconium tube is uniform across its entire surface. To do this, the outer surface of the tube is characterized using XPS analysis on three different areas.
Approach :
Study three areas of the tube to verify whether or not these three areas are identical. To do this, we used XPS. XPS analyses revealed that the zirconium tube was not homogeneous throughout. It consists primarily of a partially oxidized layer of chromium, followed by a layer of zirconium. For the three circumferential positions, the chromium detected on the surface is in the form of Cr2O3 oxide and in metallic form, while the zirconium is only in oxide form (ZrO2).
In-depth analysis at approximately 60 nm, coupled with analysis of the extreme surface, revealed heterogeneities between the different positions.
For all three positions, the oxygen content appears to stabilize at around 20% after 60 nm of abrasion.
Analysis and interpretation of results obtained by XPS
Observations :
On each profile, over the first few nanometers, a very rapid decrease in the carbon content is observed. This change corresponds to the removal of the thin layer of atmospheric pollution present on most samples.
Underneath this layer, there is always a layer of chromium followed by a layer of zirconium. However, the thickness of these layers varies significantly depending on their position. In addition to this difference in chromium thickness, a difference in oxygen content can also be observed.
Conclusion of the comparative study of the three areas
Each sample exhibits distinct chemical stratification comprising a thin layer of surface contamination, followed by layers of chromium and zirconium. Variations in layer thickness and composition depending on position reveal significant differences in the chemical structure of the samples.
For all three positions, the oxygen content appears to stabilize at around 20% after 60 nm of abrasion. The base metal has therefore not been reached, and the zirconium oxide layer in all three areas appears to be greater than 30 nm.
