*3.3. XRD Analysis*

The above SEM and EDS results were complemented with X-ray diffraction. Two measurements of the surface area of a selected sample were made (Figure 6), one with Bragg–Brentano geometry and the other one using the grazing incidence diffraction (GID) geometry. The GID geometry allows us to limit the penetration of the X-ray beam, so that diffractive information can be obtained mainly from the surface layer (in this particular case, the evidence is the almost complete disappearance of the diffraction lines from the substrate). In the figure below Figure 7, two diffractograms are superimposed on each other. The blue diffractogram was obtained using Bragg–Brentano geometry and the red diffractogram using GID geometry at a 1.5-degree tilt of the primary beam in relation to the measurement plane.

**Figure 6.** View of the loose oxide layer on a SiMo 5 sample. SEM.

**Figure 7.** Diffractogram from a sample. Blue chart, Bragg–Brentano geometry; red chart, grazing incidence diffraction (GID) geometry. SiMo 3. 1.09% Mo.

From the results of the analysis presented in Figure 7, the following components of the surface oxide layer were identified. The compounds identified were, among others: α - Fe2O3 (hematite) with a hexagonal lattice R-3c (98-002-2505), α - Fe3O4 (magnetite) with a cubic lattice Fd-3m (98-026-3007), γ - Fe2O3 (maghemite) with a cubic lattice Fd-3m (98-017-2905), and a small share of SO2 (an orthorhombic lattice).
