Magnetic Phase Transition of Amorphous Alloys FeNiSiB

Static and dynamical behaviour of amorphous ferromagnets FeNiSiB was investigated by the Mössbauer spectroscopy and magnetostatic methods below and above T$\text{}_{C}$. The distributions of hyperfine magnetic field in the ferromagnetic phase and quadrupole splitting in the paramagnetic one were extracted by means of the constrained Hesse-Rübartch method. The static critical exponents were determined using the power laws and the Kouvel-Fisher method. The results of the Mössbauer investigations were compared with those obtained by magnetic measurements

Structure of friction products and the surface of tribological system elements

The goal of the paper is to identify characteristic features of the surfaces of rubbing bodies and friction products, which come into being when friction processes are realized under optimal conditions, regarding wear resistance. Mössbauer investigations carried out both in scattering and transmission arrangement have evidenced, between others, differences in oxides content and their phase composition, depending on the temperature of tribological system in the course of friction test. It has been found that the wear products obtained at the optimal temperature are composed of the much smaller particles than those produced at lower or at higher temperature

Phase Composition of the Surface Zone of Nitrided Cast Steels and Their Mechanical Properties

Conversion electron Mössbauer spectroscopy and structural X-ray diffractometry have been used to study nitrides formation in the surface layer of cast steels subjected previously to low-temperature nitriding. It has been found that creation of iron-nitrogen phases strongly depends on sample composition. Nitrides: $γ^\prime-Fe_{4}N$ and $\epsilon-Fe_{2-3}N$ arise in the course of the nitriding procedure in most investigated cast steels. Moreover, considerable changes in their microstructure and tribological properties occur. The depth profile of nitrides has been derived for selected cast steel

Modelling of thermomagnetic curves obtained with Mössbauer spectrometry for two-phase nanocrystalline alloys

Thermomagnetic curves obtained with Mössbauer spectrometry for two-phase nanocrystalline alloys have been analyzed theoretically. The main goal was to understand a slope jump in the temperature dependence of the hyperfine field for crystalline phase of higher Curie temperature at the Curie point of the amorphous phase. We propose a simple model introducing an effective exchange integral for one phase depending on mean spin value in the other phase. We also consider a strong spin polarization of the amorphous phase by penetrating field originating from nanocrystallites. Results of numerical calculations within the mean field approximation (MFA) reproduce qualitatively the experimental curves for nanocrystalline FINEMET and Fe-Nb-B alloys

Structure of the superficial region and mechanical properties of nitrided cast steels

A series of cast steels were subjected to two-stage low-temperature nitriding. Mossbauer, XRD and mechanical investigations were carried out for both as-cast and nitriding materials in order to determine phase composition (especially the content of gamma'-Fe4N and epsilon-Fe2-3N), microhardness of the superficial region as well as tribological properties. It has been stated that the relative content of iron-nitrogen phases strongly depends on chemical composition of the cast steel and the effective thickness of the surface layer comprising iron nitrides is less than 0.015 mm. Considerable increase of surface microhardness and wear resistance of nitrided specimens in comparison with their as-cast counterparts has been observed. It has been found that the values of microhardness of nitrided samples at the surface are above twice larger than those in the core

Surface Effects in Fe-Based Nanocrystalline Alloys

The microstructural and Mossbauer investigations of FeZrBCu nanocrystalline alloy are presented. The results obtained indicate that fine bcc-Fe grains do possess identifiable surface properties which arise from the symmetry restriction at grain boundary

Novel designs and technologies for cell engineering

Microfluidic devices, such as lab-on-a-chip systems, are highly advantageous for cell engineering and cell based assays. It is a particularly useful approach for development of the in vitro cellular systems mimicking the in vivo environment. In this paper, a novel lab-on-a-chip device for three-dimensional human cell culture and anticancer drug testing is presented. Cells were cultured as Multicellular Tumor Spheroids (MCTS) — the best cancer tumor model developed so far. Diff erent designs were tested and novel technique of microfabrication in poly(dimethylsiloxane) was developed. MCTS were cultured in a system of polymeric microwells, with the network of microfluidic channels for culture medium flow. Design included optimal shear stress and proper nutrients supply for cultured cells. Final design provided MCTS culture for four weeks with the homeostasis-like state achievement, which is characteristic for the in vivo situation