S. Lo Russo

Effect of nitrogen‐ion implantation on the unlubricated sliding wear of steel

The effect of 30‐keV nitrogen‐ion implantation on the unlubricated sliding wear of type‐38 NCD4 steel has been investigated. The effect of implants is seen to reduce the amount of wear for nitrogen doses above 1017 ions/cm2. The reduction in the wear persists also after removal of a material thickness greater than the penetration depth of the implanted nitrogen ions.

Lattice disorder in implanted insulators: Pb implantation in α-Al2O3

Abstract The effects of 20, 50 and 100 keV Pb ion implantation on α-A12O3 single crystals have been investigated using the Rutherford backscattering channeling technique. Lattice disorder is observed to reach saturation at Pb doses greater than 1015 ions/cm2. Analysis of the implantation and damage profiles reveals that migration of defects occurs during implantation. It is found that the average threshold displacement energy, obtained from the measured number of displaced lattice atoms using the Kinchin-Pease equation, is dependent on implantation energy. This is discussed in terms of lattice reordering during ion bombardment which depends on the substrate temperature. The lowest value of the average displacement energy, obtained from the 20 keV samples, is 14 ± 2 eV, in reasonable agreement with the calculated Frenkel pair formation energy in α-A12O3. Lattice locations for {0110} and {1212} configurations show that the implanted Pb atoms are almost substitutional along the A1 rows. The substituti...

Sodium surface concentration analysis on glass by 23Na(p,α)20Ne nuclear reaction

Abstract The 23Na(p, α)20Ne nuclear reaction has been used to investigate the depth profile of Na near the surface of commercial soda-lime-silicate glasses. The depth profile of Na has been quantitatively determined (with a depth resolution of about 120 A) without migration effects due to the measurement method. Such perturbations, which make other analysis techniques difficult to use, appear only with very high current densities of the incident beam. A brief review of the principles of nuclear reaction used to analyse the concentration profile near the surface of samples is presented. A comparison with the traditional methods is discussed.

Optical, chemical and mechanical modifications induced by ion implantation on glass surfaces

Abstract Soda-lime glasses have been implanted with 50 keV Az ions. Modifications induced on the glass surface have been studied as a function of implanted dose, with particular regard to optical, chemical and mechanical properties. Optical measurements indicate a reduction of the refractive index, connected to the surface sodium content. The sodium profile has been measured using the Na23(p, α)Ne20 nuclear reaction. An improvement of the mechanical resistance has been observed at low implantation dose, together with a change of the chemical durability. An expansion of glass has been observed by S.E.M. and interpherometric microscopy for 80 keV implantation energy.

Transmission energy loss of light channeled particles in thin silicon crystals

Abstract The energy losses of light ions channeled through Si were investigated by studying the energy distribution of the transmitted particles. Beams of protons, deuterons and helium ions have been used in the energy range from 0.9 to 5.0 MeV. Measurements of the energy losses were made for the , , axial and {111}, {110} planar directions. Comparison of the energy loss for different particles shows a correlation with a simple velocity dependent function. The energy loss as a function of the incident energy is discussed in terms of localized and non localized components of the stopping power.

MAGNETIC PROPERTIES OF Co AND Ni BASED ALLOY NANOPARTICLES DISPERSED IN A SILICA MATRIX

Abstract A comparative study of the magnetic properties of Co and Ni based alloy nanoparticles (Ni–Co, Ni–Cu and Co–Cu) formed in a silica matrix by ion implantation is presented. Different ion doses and implantation sequences were realized in order to obtain different nanostructures. The structural and magnetic properties observed for the Cu50Ni50 nanoparticles are similar to those of the Cu60Ni40 bulk alloy. The crystal structure of CoxNi1−x (0⩽x⩽1) nanoparticles is similar to that of the corresponding bulk alloy. The magnetic properties depend on the ion-implanted dose and on the alloy composition. The samples prepared by implanting a 15×10 16 ions / cm 2 total dose contain nanoparticles, which are superparamagnetic at room temperature and their magnetic behavior is influenced by dipolar interparticle interactions. The magnetization of the CoNi samples at high magnetic field is larger than that of the corresponding bulk alloy and follows the same composition dependence of that quantity measured in the alloy.

Hydrogen sorption properties of vanadium- and palladium-implanted magnesium films

Abstract Magnesium films prepared by vacuum evaporation were implanted with vanadium and palladium ions in order to study their hydrogenation characteristics. It was found that the hydrogenation kinetics depend on the ion species and on the ion dose implanted. Indeed, the vanadium-implanted magnesium films have faster kinetics than the palladium-implanted ones. However, low vanadium concentration (∼0.3 at.%) seems to inhibit the absorption reaction. Among the ion-implanted magnesium films, the fastest kinetics were obtained with the vanadium-implanted film at a dose of 1×1016 ions/cm2: at 623 K and under a hydrogen pressure of 10 bar, a concentration of 6 wt.% of hydrogen was reached in 270 min during the first hydrogenation and in 45 min during the second one.

The thermal oxidation of ion-implanted zirconium

Abstract The thermal oxidation of polycrystalline zirconium implanted with 21 different ion species has been studied by using the nuclear reaction 16 O( d , p 1 ) 17 O. A very good agreement has been found between the oxidation kinetics of unimplanted zirconium as determined by the nuclear reaction and those previously measured gravimetrically. Oxidation kinetics show a time dependence which is cubic or parabolic depending upon the surface treatment before oxidation. Ion implantation produces significant changes in oxidation rate but the time dependence remains the same. A strong correlation has been found between the behaviour of ion implanted systems and that reported for binary alloys, confirming the hypothesis that the ionic size of the additive is the major parameter governing the influence upon the oxidation of zirconium. The implanted species which inhibit oxidation possess ionic radii lying between 80% and 100% of that of Zr 4+ . An explanation of their beneficial effect based on an increase of the plasticity of the growing oxide is presented.

Thermal effect of nitrogen implantation on high carbon steels

Abstract Quenched and annealed samples of a high carbon steel implanted with 105 keV nitrogen at a nominal dose of 3 × 1017 ions cm-2 and current densities of 50, 100 and 200 μA cm-2 were analysed by a nuclear technique to measure the retained dose. The dose thus measured depends on the beam current density as well as on the initial steel structure: it decreases with the beam current density and is systematically lower in quenched steel than that in the annealed steel. Microhardness measurements and conversion electron Mossbauer scattering were used to study the structural modifications induced by various implantation conditions. The mean implantation temperature of the samples, as evaluated on the basis of the microhardness values and checked by a thermocouple, lies in the tempering range of hardened structures at the above implantation current densities. The metallurgical transformations observed can account for the different amount of retained implanted ions in the first 200 nm below the surface.

The pitting behavior of Al-3103 implanted with molybdenum

Abstract The pitting corrosion of Al-3103 (Al–Mn alloy) implanted with molybdenum was investigated in solutions containing 0.1 M NaCl using potentiodynamic polarization tests. The Mo ion implantation in Al-3103 was performed with ion energies from 50 to 100 keV at doses ranging from 5×10 16 to 2×10 17 ions/cm 2 . The Mo depth profiles were measured by Rutherford backscattering spectrometry. Polarization tests were performed in the presence and absence of a bicarbonate (HCO 3 − )/carbonate (CO 3 2− ) buffer. Compared to the unimplanted ones, the implanted samples showed an increase of corrosion potentials from 170 to 240 mV in the unbuffered solution and an increase of pitting potentials from 90 to 160 mV in the buffered solution. The surface chemical states and corrosion morphology of the samples were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively.