[en] A corrosion resistant and nickel free surface on NiTi (nitinol) for biomedical applications should be produced by ion implantation. Ar⁺ and/or N⁺ implantation in NiTi alloy was performed at energies of 20-40 keV and fluences of (3-5) x 10¹⁷ cm^-2 by means of plasma immersion ion implantation. The modification of the NiTi alloy and its biocompatibility properties were studied. The near surface layers were analysed by Auger electron spectroscopy (AES), grazing incidence X-ray diffraction (GIXRD) and cell culture tests, and electrochemical corrosion analysis of these layers was performed. A nickel depleted surface layer is produced by the implantation, which was sealed by the formation of TiN or Ti oxide layers at the different implantation regimes, respectively. No differences in biocompatibility were seen on the modified compared with the initial surfaces. The corrosion stability increased by this treatment

[en] Surface modification of austenitic stainless steel (SS) 316L after incubation in growing cell cultures and cell-free media as control has been studied. The following treatments were applied: mouse fibrosarcoma cells L929 for 3 and 7 days, polymorphonuclear neutrophils for 3 and 7 days and human osteosarcoma cells SAOS-2 for 7 and 14 days. Cells were enzymatically removed in all cases. The modified surfaces were probed in comparison with untreated ones by means of spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS shows the appearance of the peak of bonded nitrogen at 400.5 eV characteristic for adsorbed proteins on the surface for each type of cells and for the cell-free medium. Migration of Ni in the adsorbed layer is observed in all cases for samples after the cell cultures. The protein layer thickness is ellipsometrically determined to be within 2.5-6.0 nm for all treated samples with parameterization of its optical constants in Cauchy approach. The study showed that for such biological treatments of the SS the protein layer adsorption is the dominating process in the first 2 weeks, which could play a role in the process of corrosion by complex forming properties with metal ions

[en] The corrosion of metals is associated both with a release of ions and changes in optical surface properties. In this study, these two effects were correlated by a potentiodynamic corrosion test and in situ probing of the surface by ellipsometry. The studies were carried out with stainless steel (SS) AISI 304 and 316 in phosphate buffered saline (PBS) and in Dulbecco's modified minimal essential medium (DMEM) at pH 7.4. In both media, 304 steel is more susceptible to corrosion than 316 grade. The 316 steel shows a higher corrosion potential and higher corrosion current density in PBS than in DMEM, for 304 steel this behavior is vice versa. Ellipsometry demonstrated a higher sensitivity than potentiodynamics to surface modification in the cathodic area. In DMEM the removal of a surface layer at negative potential and a further repassivation with increasing potential was characteristic. In PBS a surface layer started to grow immediately. X-ray photoelectron spectra of this layer formed in PBS are consistent with iron phosphate. Its formation is inhibited in DMEM; the presence of amino acids is discussed as the reason

[en] The albumin adsorption on non-hydrogenated amorphous carbon films with different diamond-like character (i.e. sp³ content) is addressed. The films were produced by ion beam assisted deposition and by filtered cathodic vacuum arc deposition to obtain a wide range of sp³ contents. A combination of the spectroscopic ellipsometry, Raman spectroscopy and elastic recoil detection analysis was used for characterization of the films. It is shown that an increase of the deposition temperature leads to a decrease of the film band gap, density and a shift of the Raman G-band position. The wettability of the film is not influenced by its sp³ content. Albumin adsorption on the surface depends more on its wetting behavior than on the sp³ content. In addition, Ar ion treatment of the layers can be used to reduce the amount of adsorbed proteins

No abstract available

[en] The present work describes the surface improvement and biocompatibility of TiAl₂₄Nb₁₀ intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W

[en] The evolution of sp² hybrids in amorphous carbon (a-C) films deposited at different substrate temperatures was studied experimentally and theoretically. The bonding structure of a-C films prepared by filtered cathodic vacuum arc was assessed by the combination of visible Raman spectroscopy, x-ray absorption, and spectroscopic ellipsometry, while a-C structures were generated by molecular-dynamics deposition simulations with the Brenner interatomic potential to determine theoretical sp² site distributions. The experimental results show a transition from tetrahedral a-C (ta-C) to sp²-rich structures at ∼500 K. The sp² hybrids are mainly arranged in chains or pairs whereas graphitic structures are only promoted for sp² fractions above 80%. The theoretical analysis confirms the preferred pairing of isolated sp² sites in ta-C, the coalescence of sp² clusters for medium sp² fractions, and the pronounced formation of rings for sp² fractions >80%. However, the dominance of sixfold rings is not reproduced theoretically, probably related to the functional form of the interatomic potential used

[en] Metal plasma immersion ion implantation and deposition (MePIIID) has been proved to be an effective approach to enhance surface properties of various types of materials. In this work structure, phase composition, microhardness and surface properties, such as wettability and surface energy of layers of the ternary system Ti-N-O produced by MePIIID were investigated. To study the correlation between structure of coating and hemocompatibility the thrombocyte adhesion as well as the fibrinogen adsorption on the surface were measured. The blood compatibility of Ti oxide can be improved by the addition of nitrogen into the layer. The thrombocyte adhesion and fibrinogen adsorption were lower for TiN _xO _y than for TiO₂. This correlates with a lower hydrophobicity and higher polar component of the surface energy for TiN _xO _y. The best hemocompatibility as well as the maximal microhardness have been found for the coating TiN_0.4O_1.6