The growth and structure of ultrathin vanadium oxide films on Rh(111) has been studied by scanning tunneling microscopy, low-energy electron diffraction, high-resolution x-ray photoelectron spectroscopy, high-resolution electron energy-loss spectroscopy, and ab initio density-functional-theory calculations. For submonolayer coverages $[\Theta <0.6\mathrm{}\mathrm{MLE}$ (monolayer equivalents)], depending on the oxide preparation route (reactive evaporation vs postoxidation), two well-ordered V-oxide phases with $(\sqrt{7}\times \sqrt{7})R19.1\mathrm{}°$ and $(\sqrt{13}\times \sqrt{13})R13.8\mathrm{}°$ structures and similar electronic and vibrational signatures have been observed. The $\sqrt{7}$ and $\sqrt{13}$ phases are interface stabilized and exhibit high formal oxidation states $\left(\sim 5^{+}\right).\mathrm{}$ In the oxide coverage range $0.6<\mathrm{}\Theta <1.2\mathrm{}\mathrm{MLE},$ i.e., after the completion of the first oxide layer, the $\sqrt{7}$ and $\sqrt{13}$ structures are replaced by several coexisting V-oxide phases, where the oxidation state of the V atoms progressively decreases from $4^{+}$ to $2^{+}$ with increasing oxide coverage. For coverages exceeding 2 MLE a bulk-type ${\mathrm{V}}_2{\mathrm{O}}_3$ phase with corundum structure grows epitaxially on the Rh(111) surface. The observed growth mode is examined by assessing kinetic and energetic effects in the ultrathin oxide film growth. The importance of the oxide-free areas of the metal support for the formation of highly oxidized V-oxide layers at the initial stages of growth is discussed.

The reduction of vanadium oxide monolayer structures on Rh(111) has been investigated by variable-temperature scanning tunneling microscopy, low energy electron diffraction, photoelectron spectroscopy of the core levels, and the valence band, and by probing the phonon spectra of the oxide structures in high-resolution electron energy loss spectroscopy. A sequence of oxide phases has been observed following the reduction from the highly oxidized $(\sqrt{7}\times \sqrt{7})\mathrm{R}19.1°$ V-oxide monolayer: $(5\times 5)$, $(5\times 3\sqrt{3})\mathrm{rect}$, $(9\times 9)$, and “wagon-wheel” oxide structures are formed with decreasing chemical potential of oxygen ${\mu }_{\mathrm{O}}$. The structures have been simulated by ab initio density functional theory, and structure models are presented. The various V-oxide structures are interrelated by common $\mathrm{V}\mathrm{O}$ coordination units, and the reduction progresses mainly via the removal of $\mathrm{V}\mathrm{O}$ vanadyl groups. All oxide structures are stable at the appropriate ${\mu }_{\mathrm{O}}$ only in the two-dimensional V-oxide/Rh(111) phase diagram and are thus stabilized by the metal-oxide interface. The results demonstrate that oxides in ultrathin layer form display modified physical and chemical properties as compared to the bulk oxides.

Inductive thermography is a non-destructive testing method, whereby the specimen is slightly heated with a short heating pulse (0.1–1 s) and the temperature change on the surface is recorded with an infrared (IR) camera. Eddy current is induced by means of high frequency (HF) magnetic field in the surface ‘skin’ of the specimen. Since surface cracks disturb the eddy current distribution and the heat diffusion, they become visible in the IR images. Head checks and squats are specific types of damage in railway rails related to rolling contact fatigue (RCF). Inductive thermography can be excellently used to detect head checks and squats on rails, and the method is also applicable for characterizing individual cracks as well as crack networks. Several rail pieces with head checks, with artificial electrical discharge-machining (EDM)-cuts and with a squat defect were inspected using inductive thermography. Aiming towards rail inspection of the track, 1 m long rail pieces were inspected in two different ways: first via a ‘stop-and-go’ technique, through which their subsequent images are merged together into a panorama image, and secondly via scanning during a continuous movement of the rail. The advantages and disadvantages of both methods are compared and analyzed. Special image processing tools were developed to automatically fully characterize the rail defects (average crack angle, distance between cracks and average crack length) in the recorded IR images. Additionally, finite element simulations were used to investigate the effect of the measurement setup and of the crack parameters, in order to optimize the experiments.