Mössbauer spectroscopy is a nuclear analytical tool for material research. The results obtained by Mössbauer spectroscopy show high resistance to the arrangement, preparation, and macroscopic texturing of the sample. Since both paramagnetic and magnetic phases (austenite – ferrite) are well distinguished in the Mössbauer spectra, it is possible to perform basic evaluation of retained austenite in a fast way. Taking into consideration that alloying elements and significant amounts of retained austenite exhibit more complex Mössbauer spectra, they need to be analyzed by more precise approach. In basic concept, all magnetic phases that exhibit sextet (including the martensite as a supersaturate solution of carbon in ferrite) are assigned to the ferritic phases. This method is nondestructive and could find a wide application in industrial use. In the precise mode the method is able to distinguish all iron-bearing phases (ferrites, oxides, carbides, etc.).
Mössbauer spectroscopy is a nuclear resonance spectroscopic technique based on the nuclear emission and resonant absorption of gamma rays. This experimental technique provides qualitative and quantitative analysis of materials (e.g., structural, phase, and magnetic information) containing specific elements. The 57Fe isotope shows the most favorable parameters for Mössbauer spectroscopy. Backscattering geometry allows to analyze surfaces of bulk materials. Hence, 57Fe Mössbauer spectroscopy is considered as crucial experimental method in steel characterization. Scattering method utilizes the conversion X-rays registration which analyzes material surface up to the depths of 1–20 µm.
Mössbauer spectroscopy employes electric and magnetic hyperfine interactions between electrons of the iron atom and Mössbauer-active nucleus (in the source). The hyperfine parameters are isomer shift, quadrupole splitting, and hyperfine magnetic splitting. The isomer shift is a result of the Coulomb interaction between nuclear/nuclei charge and electrons charge. The charges distributed asymmetrically around the atomic nucleus (electrons, ions, and dipoles) increase the electric field gradient, which differs from zero on the site of nucleus. These electric quadrupole interactions cause a splitting of the excited nuclear level and provide information about bond properties and the local symmetry of iron site. The third hyperfine parameter is magnetic splitting. This magnetic field can originate within the atom itself, within crystals via exchange interactions, or it can be external one. The magnetic field (nuclear Zeeman effect) splits the nuclear states.
RING detector - a main part of the austenitemeter.
Ring shaped X- and gamma-ray enables analysis of specific samples without assembling of unique backscattering geometry setup and speeds up nondestructive surface analysis of large objects. Mössbauer RING detector facilitate the measurement setup. Unlike other gas detectors, RING does not require complicated geometry adjustment, is easily movable on the sample surface and due to the specific design (2π detection) enhance the count statistics.
The X-ray and gamma-ray Ring Detector offers for material scientists feasible nondestructive surface analysis of all shapes, all surface samples or large objects (ideally from 2 cm, but even smaller samples are measurable). Without a need for assembling of an unique backgscattering geometry, the Ring Detector facilitate the measurement setup. Moreover, unlike the other gas detectors, is easielly movable on the sample surface and due to the specific design allowing 2π detection enhance the count statistics and provides faster results.
Ring detector, as a toroidal proportional gas flow counter, is able to register soft X-rays (6.4 keV) and the low-energy gamma-rays (14.4 keV) utilized in the 57Fe Mössbauer spectroscopy (backgscattering mode).
There is also an ability to perform the depth selective analysis by simultaneous registration of both conversion X-rays and backscattered gamma rays, while using a proper counting gas mixture (i.e. 45% Ar + 45% Kr + 10% CH4).
Due to its design it enhace the measurement satistics and does not force the users to setup complicated geometry adjustment in the backscatteirng or emmision experiments.