Volume 26 (2018): Issue 43 (September 2018)

The new Ion Beam Centre (IBC) equipped with 6 MV tandem ion accelerator and 500 kV ion implanter systems was built at the Slovak University of Technology, Faculty of Materials Science and Technology (STU MTF). The facility provides Ion Beam Modification of Materials (IBMM) and Ion Beam Analysis (IBA), which includes Rutherford Backscattering Spectrometry (RBS), Particle Induced X-ray Analysis (PIXE), Elastic Recoil Spectrometry (ERDA) and Nuclear Reaction Analysis (NRA). Presented are selected experimental procedures carried out in the IBC during the first year of operation. They present examples of a typical IBA performed, such as thin film characterisation in nm to tens of µm range, elemental depth profiles and sensitivity to the light elements enhancement by non-Rutherford cross-section regime application along with the crystalline sample channelling spectra and boron content measurement.

Exact determination of energy loss of ion in materials is still a non-trivial task because of relatively complicated changes of the ion`s stopping power S(E) during transport of the probing ion inside the material structure. Energy loss of ion in the material structure always depends on the current value of continually decreasing energy of the ion, indeed. A purely theoretical approach can be applied to the energy loss calculation in some typical cases. Average energy loss of ion can be determined by means of the Bethe-Bloch analytical theory (1-6) (in high velocity region) and the Lindhard-Scharff-Schiøtt (LSS) theory (7-10) (in low velocity region). Currently, there is no acceptable exact theory to determine the energy loss of ion in intermediate-velocity region (11) and experimental data must be used in that case. Basically, only a finite number of discrete experimental data is always available. Therefore, if the problem how much energy the projectile ion loses in a certain distance travelled is solved, the modelling of function S(E) based on some acceptable assumptions must be applied.

In this contribution, we present the energy loss calculations in intermediate-velocity region of ion based on linear interpolation of experimental data. Calculation was carried out for a kapton foil using the data taken from Ziegler, Biersack (12). Energy values of an ion along its trajectory inside the foil were found, and the mean projected range of ion penetrating into the foil was calculated. Finally, the energy resolution was evaluated taking into account straggling provided that the foil is used as an absorber in the ERDA experiment.

The trace element analysis system is presented using Proton Induced X-ray Emission (PIXE) analysis at a new Ion Beam Centre in Trnava. Standard PIXE system dedicated to the measurement of thick solid samples was extended by a new application for trace element analysis in aerosol samples. The sample holder was modified with respect to the dimensions of the aerosol filters, and a new sample holder and a Faraday cup (FC) were made. The first results of the PIXE aerosol analysis are presented in this paper. Furthermore, the geometric efficiency of the detection system was verified using 55Fe radioactive source emitting monoenergetic Mn X-ray lines. The measured data were compared with the Monte Carlo simulations regarding/disregarding the X-ray attenuation.

The influence of increased Cu and Ag contents on the microstructure evolution in the utilized Sn-0.3Ag-0.7Cu (wt. %) solder was studied. The utilized solder was exploited in the wave soldering process at the temperatures of about 260 °C for several days. The samples investigation involved the differential scanning calorimetry, the scanning electron microscopy including the energy dispersive X-ray spectroscopy, and the X-ray diffraction techniques. To predict phase equilibria at various temperatures and temperature dependences of heat capacity, the Thermo-Calc software and the COST531 lead-free solder database were used. The original and the utilized solders were found to be very similar regarding the phase occurrence, but slightly differ from one another in microstructure evolution due to higher bulk contents of Cu in the latter solder. The obtained results contribute to both the better understanding of the microstructure evolution in low-silver Sn-Ag-Cu solders and the determination of compositional limits for those solders used in the wave soldering process.

Borated austenitic stainless steel is used in nuclear industry due to the high neutron absorption efficiency. The plasma, laser and electron beam welding experiments were used for the study of the weld joints microstructure. The microstructure changes caused by welding process were observed by light optical microscopy and transmission electron microscopy. The microstructural characterization and microchemical analysis showed significant changes of the phase composition in the weld metal mainly. The austenitic dendrites were surrounded by eutectics, which were the mixture of the M₂(C,B) and M₂₃(C,B) borocarbides, δ-ferrite and austenite.

The activities of the young STU MTF research team focused on the material properties of superconductors were reviewed for the first time. We performed structural analyses on multiple types of superconducting tapes in order to get deeper insight into the correlation between their structure and electromagnetic properties, both experimentally and by modelling. We also addressed the joining of tapes by lead-free solders.

The contribution deals with analysis of the influence of the substrate surface laser ablation before deposition process to improve the adhesion of coating-substrate system. The coatings were applied to the high-speed steel 6-5-2-5 (STN 19 852) and WC-Co cemented carbide with cobalt content of 10 wt%. LAteral Rotating Cathodes (LARC^®) process was chosen for evaporation of individual CrN layers. Influence of laser ablation on the substrate morphology, structure, roughness, presence of residual stresses inside the substrates and layers and their adhesion behavior between the layers and the base material was studied. Scanning electron microscopy fitted with energy dispersive spectroscopy was utilized to investigate morphology and fracture areas of substrates with CrN layers. X-ray diffraction analysis was employed to detect the residual stresses measurements. Adhesion between the coatings and substrate was analyzed using “Mercedes” testing.