S. Kąc

Crystalline hydroxyapatite coatings synthesized under hydrothermal conditions on modified titanium substrates

Hydroxyapatite coatings were successfully produced on modified titanium substrates via hydrothermal synthesis in a Ca(EDTA)(2-) and (NH4)2HPO4 solution. The morphology of modified titanium substrates as well as hydroxyapatite coatings was studied using scanning electron microcopy and phase identification by X-ray diffraction, and Raman and FTIR spectroscopy. The results show that the nucleation and growth of hydroxyapatite needle-like crystals with hexagonal symmetry occurred only on titanium substrates both chemically and thermally treated. No hydroxyapatite phase was detected on only acid etched Ti metal. This finding demonstrates that only a particular titanium surface treatment can effectively induce the apatite nucleation under hydrothermal conditions.

Properties and microstructure of the (Fe, Ni)-Cu-(P, Si, B) melt-spun alloys.

The work presents the microstructure characterization of the new (Fe, Ni)–Cu–(P, Si, B) melt‐spun glass forming alloys investigated by means of transmission electron microscope. The results are compared with the data obtained by other complementary methods such as XRD and Mössbauer spectroscopy. The phases occurring during the crystallization of the glassy matrix are identified and characterized in terms of a long‐range order and a short‐range order. The thermal stability of the alloy is characterized by differential scanning calorimetry. The study describes the mechanical and magnetic properties of the new alloys at room temperature as well as characteristics resulting from heating the as‐cast melt‐spun alloy at elevated temperatures. The changes of the properties of the alloy at elevated temperatures are correlated with the microstructural changes.

Digital image correlation of coated and uncoated Religa Heart_Ext ventricular assist device

The digital image correlation is used to estimate influence of deposited heamocompatible coatings (gold and titanium nitride) on mechanical response of ventricular assist device Religa Heart_Ext made of Bionate II (thermoplastic polycarbonate urethane) under working conditions by comparison of the coated Religa Heart_Ext with uncoated Religa Heart_Ext. The DIC is applied for experimental investigation of the strains and displacements distribution on external surface of the blood chamber of ventricular assist device during loading. The experiment was conducted in a hydraulic system with water at operating temperatures of 25 and 37 °C, as well as under static pressures: 80, 120, 180, 220 and 280 mmHg, and static underpressures: -25, -45, -75 mmHg. The subsequent images were taken after stabilization of pressure on a set level. The applied research method shows that the nano-coating of 30 nm in thickness significantly affects deformation of the blood chamber of Religa Heart_Ext in macro scale. The proposed composition of coatings increases strain on external surface of the ventricular assist device.

Fractal-like behaviour of the BCC/FCC phase separation in the iron-gold alloys

Iron‐gold alloys with compositions Fe70Au30 and Fe50Au50 were prepared by arc melting. The alloys were investigated by means of the high‐resolution scanning electron microscopy (SEM‐FEG) in the as‐cast state and upon annealing in two steps, i.e. at 250°C for 24 h and subsequently at 500°C for 48 h. The alloys were composed of two phases, i.e. a BCC phase rich in iron and a FCC phase rich in gold. The single‐phase regions have equivalent diameter of about 50 nm. SEM images show self‐similar structure for the spatial distribution of the above phases on scales ranging from about 1 mm till about 100 nm. The roughness of the images has been used to estimate a fractal dimension of the phase mixture. For larger scales of the as‐cast samples one finds fractal dimension of about 1.7 for Fe70Au30 composition, i.e. very close to the dimension of typical diffusion limited aggregation (DLA) fractals. For annealed samples, dimension 1.1 was found.

Modification of Al-Si alloy surface layer using Nd: YAG laser

The paper describes the laser cladding of hypereutectic Al-Si alloy with chromium. An impulse Nd:YAG laser was employed for laser cladding process. The article presents the changes of microstructure, chemical composition, microhardness of the obtained clad layers, which were depended on the effect of the laser processing parameters and the thickness of chromium coatings. The laser cladding produced the very fine microstructure and higher hardness of clad layers.