Ion implantation manufacture of superconducting magnesium diboride films of the MgB2 stoichiometry (B:Mg=2:1 composition) by boron implantation in Mg wafers requires a precise knowledge of the implantation process properties, in particular of the partial sputtering yields of Mg atoms by B ions. To verify these yields experimentally we deposited thin Mg films on glassy carbon platelets and implanted them with high fluences of 40, 60, and 80 keV B+ ions. He-backscattering (RBS) spectrometry was used to determine before- and after-implantation depth profiles of Mg and B. The sputtering yields turned out to be small enough (<0.1 atoms per ion) to neglect sputtering in simulations of the implanted profiles. The results of the simulations have been compared to RBS spectra recorded on samples treated with 3 energies/fluencies optimised for a wide plateau of the B:Mg=2:1 stoichiometric composition.

AISI-304 austenitic stainless steel has been nitrocarburized in N2 and C2H2 ambient using high-voltage plasma immersion ion implantation (PIII) technology. The use of different PIII treatment times revealed important hints with respect to the microstructural, mechanical and corrosion properties of the nitrocarburized layer. Grazing incidence X-ray diffraction (GIXRD) shows the presence of nitride (γN and CrN) and carbide (γC and Fe3C) phases. Glow discharge optical spectroscopy (GDOS) has been used to characterize the elemental depth profiles in which the thickness of the modified layers is derived. Dynamic microindentation method is used for the study of mechanical performance of the nitrocarburized layer as well as the untreated material. The microhardness has been increased to a maximum value of more than nine times compared to that of the untreated one. The corrosion performance is characterized by potentiodynamic polarization technique and was found to be treatment time dependent.

To improve the biocompatibility of polyurethane (PUR), we modified the surface by irradiation with different ions (Carbon; C, Oxygen; O, Nitrogen; N, or Argon; Ar) at 0.3-50 keV energy and doses of 1,00E+13 - 1,00E+15 ions/cm(2). The effects of ion implantation using different ion energies and densities were observed on adhesion, proliferation, and viability of human umbilical vein endothelial cells (HUVECs). The long-term in vitro stability of ion-implanted PUR was also investigated. Ion irradiation moderately affected the surface roughness (R(a)), but strongly enhanced the work of adhesion (W(a)). Cell adhesion was markedly improved on O-, N-, and Ar-, but not on C-implanted PUR surfaces. Medium ion energies and lower ion doses produced the best HUVEC attachment and proliferation, indicating the importance of choosing the proper range of energy applied during ion irradiation. In addition, apoptosis rates were significantly reduced when compared with unmodified PUR (uPUR). N implantation significantly protected the surface, although C implantation led to stronger surface erosions than on uPUR. In total, ion implantation on flexible PUR surfaces strongly improved the material surface characteristics and biocompatibility. Electron beam ion implantation within an appropriate energy window is thus a key to improving flexible PUR surfaces for clinical use to support endothelial cell performance. Thus, it can contribute to designing small-diameter grafts, which are in great demand, towards vascular tissue engineering applications.

The aim of this study was to develop and characterize novel metal-polymer constructs to improve the biocompatibility of flexible but hydrophobic polyurethane (PUR) implants. Using a physical vapor deposition (PVD) technique, thin films (< or =100 nm) of zirconium (Zr) or titanium (Ti) were deposited on the polyurethane surface. Both coatings displayed good stability when subjected to cross-cutting test and especially Zr showed only minor and superficial cracks in the scanning electron microscopy analysis. PVD coating resulted in significantly lowered contact angles and the standard surface free energy of wetting (Delta(wet)G degrees ) turned to more favorable negative values (Ti: -40; Zr: -30; untreated PUR (uPUR): +10.1 mN/m). This may lead to the highly enhanced adhesion and proliferation properties observed with human umbilical vein endothelial cells (HUVECs). In addition, the novel coatings had no toxic effect and even drastically reduced apoptosis rates of HUVECs. Cell morphology, nitric oxide production, and mitochondrial membrane potential--both at static and flow conditions--were superior compared with uPUR, thus demonstrating intact physiological functions. Therefore, we suggest that combining PUR as a flexible material with a thin coating of Zr or Ti as the improved biocompatible surface may have advantages for use, for example, vascular graft material.

Doping TiO2 with nitrogen is recognized as a procedure to get sensitization of this material with visible light. In the present work, incorporation of nitrogen within the structure of TiO2 thin films has been accomplished by N2+ ion implantation in TiO2 anatase thin films (50 keV ion energy for doses of 3 x 1011, 6 x 1 016, and 1.2 x 10(17) ions cm(-2)) and during preparation by metalorganic chemical vapor deposition (MOCVD) using nitrogen as carrier gas. The analysis of the samples by X-ray photoemission spectroscopy (XPS) and for the MOCVD samples also by secondary ion mass spectroscopy (SIMS) has shown that nitrogen, in the form of nitride-like species, (N/Ti ratios of 0.03 and 0.12 for the MOCVD and the implanted samples, respectively) has become effectively incorporated within the structure of TiO2. The water contact angle on the implanted thin films varied from about 80 degrees to around 30 degrees when illuminated with visible light, depending on the ion dose. Similarly, the MOCVD samples showed a sharp decrease in wetting contact angle under visible light from about 80 degrees to 55 degrees. In the two cases, the thin films reach total hydrophilicity by posterior UV irradiation. To account for these results, the possible existence of specific excitation mechanisms for visible or UV photons, the former involving the incorporated nitrogen atoms, is discussed.

Plasma immersion ion implantation (PIII) of nitrogen on AISI 316L austenitic stainless steel has been investigated at four different negative implantation biases (5, 10, 15, 20 kV) and two different pulse-on-times (5 and 10 mu s) for developing a nitrogen/nitride-rich corrosion resistive layer. Post implanted specimens were examined by X-ray diffraction, and subjected to potentiodynamic polarization tests in 1 wt.% NaCl solution. PIII at - 15 kV shows significant and optimum improvement in corrosion resistance. (C) 2006 Elsevier B.V. All rights reserved.

For hardness measurements, the indentation depth is about 10% of the effective information depth under static loading. A change of the wear mechanism is observed under lateral loading conditions in oscillating ball-on-disc tests for nitrided austenitic stainless steel with an expanded austenite surface layer from abrasive to a subsurface plastic flow with a redistribution of the inserted nitrogen. This leads to an effective nitriding depth about 3–5 larger than the actual nitrided zone.

Thin YSi2-x layers are formed by 195 keV Y ion implantation in Si(111) substrates to a dose of 2 x 10(17) Y+/cm(2) at 500 degrees C followed by annealing in nitrogen atmosphere at different temperatures for I h. The investigation of the phase composition is carried out by Rutherford backscattering spectrometry (RBS), whereas the structural characterization is accomplished by means of both X-ray diffraction (XRD) pole figure and cross-sectional transmission electron microscopy (XTEM). The results show that the YSi2-x layers grown on the Si has the epitaxial relationship of YSi2-x (0 0 0 1)//Si(111) and YSi2-x [11- 20]//Si [110]. (C) 2006 Elsevier B.V. All rights reserved.

Superconducting regions of magnesium diboride (MgB2) on magnesium substrate were formed by the combined methods of ion implantation and transient annealing using three different ion fluences and three different energy density of Ar plasma pulses. The samples were characterized by Rutherford back scattering (RBS) and superconductivity detection techniques. The results of these characterizations are presented and discussed. The highest critical temperature observed TC=33.8K.

Plasma immersion ion implantation (PIII) using halogen or oxygen plasmas has been employed for the surface passivation of advanced alloys with a view to their applications for high-temperature oxidation protection and in medicine. Special devices have been designed to ensure efficient plasma generation and reduce sample contamination arising from the interaction of the aggressive plasmas with the chamber components under bias. The paper addresses two main applications of PIII, namely oxidation protection of gamma-titanium aluminides (gamma-TiAl), and modification of the surface properties of shape-memory superelastic nickel-titanium (NiTi) alloys. TiAl intermetallics are of great interest for advanced automobile, aerospace and power generation applications due to their low specific weight and high strength. However, excessive oxidation occurring in these materials at temperatures above 700 degrees C has hindered their widespread use. Samples of technical gamma-TiAl alloys have been treated by both beamline implantation of Cl or F, and PIII of Cl using an Ar/Cl gaseous blend or alternative precursor gases. High-temperature oxidation behavior has been examined under conditions of either isothermal or thermocyclic oxidation at 900 degrees C. Optimized implantation processing produces marked improvement in the oxidation behavior of the gamma-TiAl samples. On the basis of these results, a commercially viable process for enhancing the high-temperature oxidation resistance of gamma-TiAl alloys using PIII of halogens is being developed. NiTi alloys are promising materials for use in biomedicine, provided that the release of Ni ions into the body environment can be sufficiently reduced. Oxygen PIII at substrate temperatures below 250 degrees C results in the formation of a transparent rutile TiO2 surface layer with a Ni content down to below I at.%. This layer in turn serves as a barrier to the corrosion and out-diffusion of Ni ions. Biocompatibility tests show superior in vitro blood compatibility in comparison with untreated NiTi samples. (c) 2006 Elsevier B.V All rights reserved.

Outstanding wear resistance of austenitic stainless steel after nitrogen insertion and formation of expanded austenite in the temperature range below 420 degrees C is a well established phenomena. However, detailed information on the wear mechanism for the modified surfaces is still missing. This paper presents the results of wear experiments performed in a dry oscillating geometry against a WC ball (diameter 3 mm, load 3 N), together with metallographic investigations of the resulting cross-sections, both with and without nitriding. Comparisons with calculated stress distributions indicate that those nitrided samples showing a specific wear reduction by a factor of about 100 were subjected to a combination of stress maxima within the surface layer and below the layer in the bulk material. (c) 2007 Elsevier B.V. All rights reserved.

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 TiNxOy than for TiO2. This correlates with a lower hydrophobicity and higher polar component of the surface energy for TiNxOy. The best hemocompatibility as well as the maximal microhardness have been found for the coating TiN0.4O1.6.

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 400W to 650W 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 400W.

The technical TiAl-alloy γ-MET (Ti–46.5Al–4(Cr, Nb, Ta, B)) was oxidised thermocyclically (24h-cycle-test) at 900°C in wet and dry air. In this paper results of untreated and fluorine treated TiAl-samples are presented. Their oxidation behaviour will be shown. Several methods were used to apply the halogens to the surface, e.g. beamline ion implantation, spraying of or dipping into a halogen containing liquid. A pure protective alumina scale was found, e.g. after treatment with a fluorine containing polymer and thermocyclic oxidation up to 1 year at 900°C in laboratory air. On the other side thick fast growing and non-protective mixed oxide scales were found on the untreated samples.

The results of investigation of the MgB 2 inter-metallic compound with the use of boron ions implantation and plasma pulse treatment are presented.The samples were characterized by: four-probe electric conductivity measurements, magnetically modulated microwave absorption, and magnetic measurements.For hydrogen and argon pulsed plasma treatment the samples with T c ranging from 10 K to 32 K were obtained.The superconducting phase does not form a continuous layer since the resistivity does not fall down to zero.Apparently, separate islands of superconducting phase are connected through metallic Mg paths.All samples are still below the percolation threshold.

A. Arazi,1 T. Faestermann,2 J. O. Fernández Niello,1 K. Knie,2 G. Korschinek,2 M. Poutivtsev,2 E. Richter,3 G. Rugel,2 and A. Wallner4 1Laboratorio TANDAR, Comisión Nacional de Energı́a Atómica, Avenida del Libertador 8250, 1429 Buenos Aires, Argentina 2Technische Universität München, Am Coulombwall 6, D-85748 Garching, Germany 3Forschungszentrum Rossendorf, Postfach 510119, D-01314 Dresden, Germany 4Vienna Environmental Research Accelerator, Institut für Isotopenforschung und Kernphysik, Universität Wien, Währinger Str. 17, A-1090 Wien, Austria (Received 3 April 2006; published 11 August 2006)

Mechanical and tribological properties of successive C and N ion implantation into Al were studied in the present work. Ion sequence, substrate temperature and subsequent thermal treatment were performed in order to understand the involved mechanisms on the surface hardening. The results showed that independent of the ion sequence, a higher surface hardness is obtained for room temperature ion implantation (approximate to 10 GPa). At high substrate temperature the hardness decreases to 7 GPa. The hardening mechanisms are discussed in terms of solid solution, hard embedded precipitates in the soft Al matrix and the damage produced by the ion implantation process. Adhesive and abrasive regimes are identified from the friction coefficient profiles and are function of the ion implantation parameters. Wear resistance is improved if subsequent thermal treatment at high temperature is performed. Wear improvement is correlated to the presence of a high concentration of carbon clusters in the Al matrix. (c) 2006 Published by Elsevier B.V.

The results of investigation of the polycrystalline boron implanted by magnesium and argon plasma pulse treatment are presented. The four-probe electric conductivity measurements and magnetically modulated microwave absorption showed the presence of superconducting islands below the temperature of 25 K. Below T = 23 K we detected the Kondo effect, a logarithmic increase in the resistivity as the temperature is lowered, due to iron impurity.