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Abstract: CoCr alloys are widely used in some specific hip and knee prosthesis. In particular, they are used in advanced metal on metal (MoM) prostheses. However, while these new implants have an intermediate wear rate between low wear ceramic–metal and high wear polymer–metal prostheses, a high risk of metalosis produced by wear debris, originated in the metal–metal sliding contact, is still present. Oxygen plasma immersion ion implantation (PI3) provides a practical method to improve wear resistance of CoCr alloys, thus reducing the amount of wear particles. This paper describes the tribological and wear resistance improvements of CoCr alloy implanted by PI3. Friction and wear tests were performed to investigate the modifications obtained by oxygen implantation. Glow Discharge Optical Emission Spectrometry (GD-OES) analysis was employed to evaluate the oxide layer thickness and compositional changes of the metallic alloying elements produced by the oxygen treatment. Moreover, SEM analysis was carried out for detecting wear particles after ball on disk tests in a biological solution simulating the human body fluid. The reported results indicate that PI3 improves the wear resistance of CoCr alloy to be used in human body implants. [Copyright &y& Elsevier]

Kapton samples were implanted with aluminum in order to create a metal oxide layer for protection against atomic oxygen degradation in space environment. Three different approaches were used. First, an aluminum plasma was created by vacuum arc discharge in a magnetic field, and samples were implanted by plasma immersion. Although sample charging problems prevented implantation at significant depths, an ion mixing layer was formed, as shown by X-ray Photoelectron Spectroscopy (XPS) depth profile analysis, giving superior adhesion of the aluminum film to the substrate. In a second approach, a 20-nm aluminum film was deposited on a Kapton sample by electron beam, followed by nitrogen plasma immersion ion implantation. Rutherford Backscattering Spectroscopy (RBS) analysis did not show significant recoil implantation of aluminum, and the process resulted in a cracked film, possibly due to the formation of a stressed aluminum nitride layer. In a third approach, direct aluminum implantation by plasma immersion was made without a confining magnetic field. Charging problems are minimized in this low-density plasma, but an increase of a factor of 10 in treatment time was not enough to compensate the much lower dose implanted per pulse. This was revealed by oxygen degradation tests made by submitting the treated samples to RF oxygen plasmas and measuring the mass loss. The sample implanted in magnetically confined plasmas conserved its transparency and had negligible mass loss. Unconfined plasmas also resulted in a degradation protection layer but only in small patches of the substrate since the low dose and possibly a misalignment resulted in poor uniformity. Thermal transients followed by adhesion tests showed that direct implantation gives the necessary adhesion of the protective layer in order to withstand the harsh space environment. [Copyright &y& Elsevier]

In order to apply the protective effect of Cl doping for high-temperature oxidation resistance of TiAl alloys of complex-shaped parts, plasma immersion ion implantation (PI3) of chlorine into technical TiAl alloys was investigated. A specialized PI3 apparatus was optimized for the strongly etching electronegative Cl plasma. Plasma diagnostics was performed using a Langmuir probe. In order to sustain a sufficiently dense plasma, different RF antenna configurations are discussed and the resulting densities are compared. The influence of plasma pulsing on the surface interaction of Cl during the process was evaluated. Two different commercial alloys were implanted and tested. The resulting depth profiles of the modified surface layer were investigated using depth profiling with Auger electron spectroscopy (AES). After implantation, the Cl is located close to the surface. Oxidation tests at 900 °C in air for 100 h showed a strong decrease in oxidation, which is comparable to conventional beamline implantation of Cl. The effect is rather independent of the alloy composition. [Copyright &y& Elsevier]

Implantation of oxygen in stainless steel (15% Cr) via plasma-based ion implantation in a distributed ECR plasma reactor has been studied as functions of ion energy and dose. Due to the formation at the surface of dielectric films with optical index and thickness depending on the implantation time and pulse voltage (up to 44 kV), various colorations can be obtained. The experimental results demonstrate the feasibility of uniform processing, the possibility of reaching perfect control of the coloring through the dose and energy of implanted ions, and that the resulting coloration varies monotonically when increasing the dose and penetration depth of implanted oxygen. Characterization of the films by scanning electron microscopy and X-ray microanalysis shows that oxygen implantation results in strong surface oxidation, but without any significant degradation of the surface aspect. The thickness and composition profiles of the oxide layers determined using X-ray photoelectron spectroscopy combined with ellipsometry indicate that the thickness, of course, increases with ion energy and dose, but that the composition of the oxide layer resulting from the implantation process is not uniform. A uniform iron oxide layer (with a stoichiometry closed to Fe2O3), free from chromium, is formed in the near-surface region, while chromium segregates at the interface between the oxide layer and the bulk stainless steel to form chromium oxide Cr2O3. [Copyright &y& Elsevier]

The lifetime of metallic components can be drastically increased by surface treatments ensuring a low friction coefficient, surface hardening and an anticorrosion coating. A promising method for such surface modifications is plasma-based ion implantation (PBII) of nitrogen. In order to improve and to obtain a better understanding of such a treatment, we have performed nitrogen implantation in different materials at various ion energy values using pure nitrogen and N2/H2 gas mixture plasmas. Fe and Ti samples were simultaneously treated in a large-volume PBII reactor in which the plasma is excited at the distributed electron cyclotron resonance. Si substrates were also implanted in order to characterize the nitrogen implantation efficiency by Fourier-transform infrared (FTIR) analysis. Profiles of the relative concentration of elements in the samples were deduced from X-ray photoelectron spectroscopy (XPS) analysis as a function of depth. The absolute concentration of implanted nitrogen was also obtained by nuclear reaction with 15N atoms implanted in metals via PBII from a 15N2/14N2 gas mixture. These results can be very useful for calibrating and improving PBII surface treatments of materials. [Copyright &y& Elsevier]

Abstract: Ion bombardment of biological cellular material has been used as a tool for the transfer of exogenous DNA macromolecules into the cell interior region. The precise physical mechanisms associated with this transfer of macromolecules through the cell envelope remain unexplained, however it has been observed that the ion bombardment is accompanied by the formation of “microcraters” on the wall of plant cells, and it is possible that these features provide channels for the macromolecule transfer. Thus the nature and origin of the microcraters are of importance to understanding the DNA transfer phenomenon as well as being of fundamental interest. We report here on the formation of microcraters on onion skin cell walls by plasma immersion ion implantation (PIII) using ~20keV Ar+ ions at a dose of about 1×1015 ions/cm2. The results indicate that PIII provides a tool for carrying out ion bombardment of living biological materials previously done using beam-line implantation methods. [Copyright &y& Elsevier]