Papers by Author: Mieczyslaw Jurczyk

Abstract: In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites were synthesized by mechanical alloying (MA), heat treatment and nitriding of elemental microcrystalline Fe, Cr, Mn and Mo powders with addition of hydroxyapatite (HA). Microhardness and corrosion tests' results of obtained materials are presented. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Decreasing the corrosion current density is a distinct advantage for prevention of ion release and it leads to better cytocompatibility. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g. orthopedic implants.

Abstract: Ti and Ti-based alloys are preferred materials in the production of implants in both medical and dental applications. One of the methods that allow the change of biological properties of Ti alloys is the modification of their chemical composition and microstructure. In this study, new biocompatible, nanostructured Ti-x vol% SiO2, Ti-x vol% 45S5 Bioglass, and Ti-x vol% HAp (x=0, 3, 10) materials have been developed, manufactured and studied in terms of their biocompatibility. These materials give the possibility of controlling in detail the grain structure and the composition of the alloy and, consequently, the mechanical and biocompatibility performances. Our results of in vitro studies show that these bionanocomposites have excellent biocompatibility and could integrate with bone. After 1st day of incubation cells show good adhesion to the surface of studied samples in the form of filopodia. After 5 days of incubation, the typical monolayer was observed. With regard to microcrystalline Ti it could help to obtain better dental implants with better mechanical properties and corrosion resistance.

Abstract: Good mechanical properties with combination of biocompatibility and high corrosion resistance make titanium and its alloys desirable materials for medical applications. A big disadvantage of titanium connects with its poor wear characteristics, however in this work this property was modified by boride microplasma surface alloying. Plasma surface alloying gives a wide range of layer thickness, which is controlled by the amount of the placed powder and process parameters like gas flow, nozzle diameter and current. Formation of TiB phase precipitation was confirmed by XRD analysis. Additionally, the modified microstructure was observed by optical microscopy. The Vickers microhardness was significantly improved from 180HV for original titanium substrate to 900HV in obtained composite layer structure, with a smoth hardness reduction in the cross section profile. Strong heat penetration from microplasma melt-in technique, results in substrate dissolution with formation of stable composite Ti + TiB layer. The surface corrosion resistance in 0.9% NaCl solution was nearly the same as for pure titanium, showing stable behavior of created oxide layer, with no negative effect of dual phase microstructure. Wear resistance of received composite layer structures were significantly improved in comparison with initial titanium samples.

Abstract: In the present work Ti-HA (3, 10, 20, 50 vol%) nanocomposites were produced by the combination of mechanical alloying and powder metallurgical process. The experimental results show, that Ti-HA nanocomposites have better mechanical and corrosion properties in comparison with microcrystalline titanium. For example: Vickers microhardness of Ti-10 vol% HA nanocomposite is 1500 HV0.2 (pure Ti metal – 250 HV0.2) and corrosion resistance in Ringer solution is Ic = 1.19 • 10-7 A/cm2, Ec = -0.41 V for Ti-10 vol% HA and Ic = 1.31 • 10-5 A/cm2, Ec = -0.36 V for Ti. In conclusion, titanium – ceramics nanocomposite are suitable for hard tissue replacement from the point of view of both mechanical and corrosion properties.

Abstract: In the present work, a nanocrystalline nickel-free stainless steels as well as nickel-free stainless steel/hydroxyapatite nanocomposites have been synthesized by the combination of mechanical alloying (MA), heat treatment and nitriding. The microhardness of the final bulk material was studied using Vickers method. Corrosion potentiodynamic tests were performed in Ringer’s solution. The results show that nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants.

Abstract: In this work, we have synthesized LaNi5/A and Mg2Ni/A (A = graphite, copper or palladium) nanocomposites. The A elements were distributed on the surface of ball milled alloy particles homogenously and role of these particles is to catalyze the dissociation of molecular hydrogen on the surface of studied alloy. Mechanical coating with graphite or palladium effectively reduced the degradation rate of the studied electrode materials. Results showed a significant broadening of the valence bands of studied nanocomposites compared to those obtained by theoretical band calculations. The reasons responsible for the band broadening of the nanocrystalline LaNi5- and Mg2Ni-type alloys are probably associated with a strong deformation of the nanocrystals in the mechanically alloyed (MA) samples. Normally the interior of the nanocrystal is constrained and the distances between atoms located at the grain boundaries expanded. The valence band spectra of the MA samples could be also broadened due to an additional disorder introduced during formation of the nanocrystalline structure.

Abstract: The nanocrystalline Mg-based metal hydrides offer a breakthrough in prospects for practical applications. In this work, we study experimentally the structure, electrochemical properties and surface segregation effect of nanocrystalline and microcrystalline Mg2M alloys and Mg2M/M’ (M=Cu, Ni; M’=C, Ni, Pd) nanocomposites. These materials were prepared by mechanical alloying (MA). In the nanocrystalline Mg2Cu powder, discharge capacity up to 30 mA h g-1 was measured. It was found that nickel substituting copper in Mg2Cu1-xNix alloy greatly improved the discharge capacity of studied material. In nanocrystalline Mg2Ni powder, discharge capacities up to 100 mA h g-1 were measured. Additionally, it was found that mechanically coated Mg-based alloys with graphite, nickel or palladium have effectively reduced the degradation rate of the studied electrode materials. Finally, the properties of nanocrystalline alloys and their nanocomposites are compared to that of microcrystalline samples. X-ray photoelectron spectroscopy studies showed that the surface segregation of Mg atoms and valence band width in the nanocrystalline Mg2M alloy are greater compared to those observed in microcrystalline Mg2M. Especially, a strong surface segregation of Mg atoms was observed for the Mg2Ni/M’ composites. In that case, Mg atoms strongly segregate to the surface and form a Mg based oxide layer under atmospheric conditions. The lower lying Ni and M’ atoms form a metallic subsurface layer and could be responsible for the observed relatively high hydrogenation rate. Furthermore, the valence band broadening observed in the nanocrystalline Mg2Ni alloys and Mg2Ni/M’ composites could also significantly influence their hydrogenation properties.

Abstract: In this work Ni-free austenitic stainless steels with nanostructure were synthesized by mechanical alloying (MA), heat treatment and nitrogenation of elemental Fe, Cr, Mn and Mo microcrystalline powders. The phase transformation from ferritic to austenitic was confirmed by XRD analysis. The mechanical and corrosion properties of the produced biomaterials were investigated. Additionally, the biocompatibility of nickel-free austenitic stainless steels with nanostructure and microcrystalline 316L steel, were analyzed studying the behaviour of Normal Human Osteoblast (NHOst) cells from Cambrex (CC-2538). An enhancement of the properties due to the nanoscale structures in the bulk consolidated materials was observed.