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The damage induced in GaAs crystals irradiated with dual-ion beam (low-energy I2+ and high-energy Fe9+), producing simultaneous nuclear ( Sn) and electronic ( Se) energy depositions, was investigated using several characterization techniques. Analysis of the damage buildup shows that Sn alone (single 900 keV ion beam) leads, in a two-step process, to full amorphization of the irradiated layer (at a fluence of 1.5 nm−2) and to the development of a high (2.2%) elastic strain. Conversely, only one step in the disordering process is observed upon dual-ion beam irradiation (i.e., 900 keV I2+ and 27 MeV Fe9+, Sn& Se); hence, amorphization is prevented and the elastic strain remains very weak (below 0.2%). These results provide a strong evidence that, in GaAs, the electronic energy deposition can induce an efficient dynamic annealing of the damage created in collision cascades formed during nuclear energy deposition.

The role on filiform corrosion (FFC), after an automotive painting process with a phosphate treatment, of the near surface deformed layer (NSDL) formed during mechanical processing on AA8006 aluminium alloys is investigated. Samples subjected to specific surface pretreatments are examined before and after different steps of the phosphating process in order to identify the characteristics of the NSDL that are responsible for the susceptibility to FFC. The thickness, the structure and the composition of this NSDL are determined by SEM, RBS, XPS and transmission electron microscopy. The presence of a 200-nm thick NSDL which is not completely eliminated during the degreasing step of the phosphating process increases dramatically the FFC susceptibility of AA8006 aluminium alloys compared with beforehand etched samples. The influence of Pb and Mg segregation on top of the surface is found to be negligible whereas the specific microstructure of the NSDL characterised by nanograins with boundaries decorated by nano-sized oxide intermetallic particles seems to play a major role on FFC. Copyright © 2014 John Wiley & Sons, Ltd.

This paper reports modifications of the chemical and structural properties of MgAl2O4 single crystals implanted with Cs ions and submitted to high-temperature annealing. The composition changes, the damage created in the three sublattices (Al, Mg and O) of the crystals, and the behavior of implanted ions were studied by Rutherford backscattering and channeling experiments as a function of the Cs fluence and annealing temperature. The data show that annealing above 700–800 °C induces a huge modification of the stoichiometry of the material, a decrease of the lattice disorder, and an increase of the fraction of Cs atoms located in substitutional lattice sites. These results have to be taken into account for the future use of spinel as a matrix for the transmutation of nuclear waste.

Damage accumulation in irradiated solids reveals a complex character which contains essential information about the mechanisms governing the formation of defects and their transformations. A detailed discussion of the different types of damage build-up is presented, which clearly emphasizes the discontinuous character of the damage accumulation in the elastic collision regime. The paper discusses the advantages and drawbacks of existing models, compares them with experimental damage accumulation results and proposes an alternative description based on the discontinuous character of the damage build-ups.

Ni-P alloys were formed by P ion implantation into pure Ni single crystals at low (15 K) and high (300 K) temperature up to a metalloid ion concentration (≈0.12) such that the fractions of amorphous volume obtained at the maximum disorder depth were ≈0.5 for both temperatures. The samples were then heated up or cooled down to the reverse temperature (300 and 15K) and implanted up to total amorphization. The disordering kinetics was followed by RBS and channeling at the different stages of the experiments. The results demonstrate that the implantation temperature entirely governs the amorphization kinetics and the final state of the sample: the amorphous phase formed before the temperature change is transformed by the subsequent implantation into a new amorphous phase with a mean metalloid concentration characteristics of the final implantation temperature.

A vegetação original de Morro Azul, região serrana a noroeste da cidade do Rio de Janeiro, era constituída de Mata Atlântica. Sofreu modificações antrópicas e atualmente apresenta áreas de pastagens e manchas de mata remanescente. Ocorrem ainda áreas de reflorestamento com Pinus, Eucalyptus e outras espécies não nativas. O presente trabalho tem como objetivo avaliar, através da análise polínica, a contribuição de cada tipo de vegetação no fornecimento de néctar e pólen para as abelhas Apis mellifera. Onze amostras mensais de mel e nove de cargas de pólen foram obtidas de uma colméia-controle e preparadas para análise palinológica seguindo a metodologia padrão européia, sem aplicação de acetólise. Seis amostras de mel foram consideradas monoflorais, Baccharis (março), Gochnatia (abril e novembro), Eucalyptus (setembro e outubro) e Castanea (agosto). Três foram consideradas biflorais, caracterizadas como mel de Mimosa scabrella tipo polínico e Piptadenia (janeiro), Eucalyptus e Eupatorium (junho) e Phytolacca e Machaerium tipo polínico (outubro). Os méis heteroflorais ocorreram em julho (Arecaceae, Eucalyptus e Allophylus) e dezembro (Anadenanthera, Eupatorium e Eucalyptus). As amostras de cargas de pólen indicaram dominância dos tipos polínicos Arecaceae, Baccharis, Castanea, Cecropia, Eucalyptus e Mimosa caesalpiniifolia Benth. Os resultados forneceram um espectro polínico que refletiu a contribuição nectarífera e polinífera das plantas ruderais e das espécies introduzidas na região. The original vegetation in the Morro Azul mountain region, northwest of Rio de Janeiro city, was the Atlantic tropical rain forest. Anthropic activities transformed the vegetation into pastureland and patches of the original forest. In addition, there are reforested areas of Pinus, Eucalyptus and others of non native plant species. The aim of the present research was to estimate the contribution of nectar and pollen from each type of vegetation for Apis mellifera bees, using pollen analysis. Eleven monthly collected honey samples and nine samples of pollen loads were obtained in a control-hive and prepared for pollen analysis following the standard European methodology without application of acetolysis. Six honey samples were considered monofloral, as of Baccharis (March), Gochnatia (April and November), Eucalyptus (September and October) and Castanea (August). Three were considered bifloral ones, as of Mimosa scabrella pollen type and Piptadenia (January), Eucalyptus and Eupatorium (June) and Phytolacca and Machaerium pollen type (October). Heterofloral honeys occurred in July (Arecaceae, Eucalyptus and Allophylus) and in December (Anadenanthera, Eupatorium and Eucalyptus). The dominant pollen loads comprised the pollen types of Arecaceae, Baccharis, Castanea, Cecropia, Eucalyptus and Mimosa caesalpiniifolia Benth. The results provided a pollen spectrum that reflected the nectariferous and polliniferous contribution of field vegetation and of introduced plant species in the study region.

Expérience GANIL; The effect of external irradiation on $\beta$-thorium phosphate-diphosphate (tetravalent actini des bearing storage matrix) and the influence on its dissolution in aqueous media were studied. Highly energetic heavy ions were used to get the amorphization of the crystalline structure of the ceramic. The ex-situ dissolution expenments showed an increase of the dissolution versus amorphous fraction in several pH and temperature conditions. The in-situ dissolution experiments highlighted the primordial importance of radiolytic produced free radical species. From these results, the ceramic presents a good resistance to aqueous alteration even in amorphous state.

The mixing mechanism of thin layers of Au, Pt or W embedded in silica when irradiated with 4.5 MeV Au ions was studied as a function of the ion fluence , temperature T and layer thickness d. Analysis of the diffusion process by means of Rutherford backscattering spectrometry showed that the spreading of metal peaks was anisotropic and that their variance varied as at room temperature or 2 at 100 K. This behavior is attributed to an association of metal atoms with diffusing defects.

We report a study of the impurity-radiation damage interaction for In in silver. Time-differential perturbed angular correlation experiments were carried out on111Cd, the radioactive daughter of111In produced and recoiled in Ag following the109Ag(α, 2n)111In nuclear reaction. All irradiations were performed at 80 K. The dose-rate and annealing temperature dependences of the defect-induced quadrupole interaction on111Cd were investigated. Clear differences are observed between the effects of correlated damage (the impurity interacting with the damage created by its own recoil) and uncorrelated damage (where the impurity is submitted to the influence of other damage cascades). In the former case (low dose-rate experiments), about 6% of the111In impurities are subject to a well-defined quadrupole interaction which is ascribed to a near-neighbor vacancy. This proportion is temperature-independent up to 500 K, but the amplitude of the quadrupole frequency is reduced by a factor of three between 300 and 400 K. Assuming vacancy release by the impurity, this would lead to a binding energy of 0.34(15) eV. The remainder of the111In nuclei are subject to a distribution of quadrupole interactions presumably due to a statistical repartition of lattice defects at some distance from the impurities. The width of the distribution changes upon annealing: a clear transition takes place at 200 K, which is the divacancy mobility threshold in Ag deduced from resistivity experiments. When cascade overlap occurs (high dose-rate experiments), no impurity-defect trapping is evidenced but a distribution of quadrupole interactions due to surrounding damage is still found. From these experiments, an order of magnitude of the damage cascade “size” is deduced. Our results are discussed in terms of available information on the impurity-damage interaction in various hosts; a compilation of all results on the impurity-vacancy interaction known to us is also presented in the paper.

A simple method of analysis of channeling data, which allows to determine quantitatively the fraction of amorphous volume at the maximum disorder depth in ion bombarded single crystals, is presented. the final expression for the amorphous fraction contains four parameters easily deducted from experimental spectra.

Nickel hydrides $\mathrm{Ni}{\mathrm{H}}_{x}$ in the composition range $0lxl2.00$ were produced by low-temperature ion implantation. Their magnetic properties were studied via time-differential perturbed angular correlation (TDPAC) experiments on $^{111}\mathrm{In}$ implanted into the Ni host before hydrogenation. At low H concentration ($x\ensuremath{\lesssim}0.10$) beats are observed in the TDPAC pattern, due to the reduction in hyperfine interaction (HFI) at the probe site by screening from neighboring H atoms. Excellent fits to the TDPAC spectra over the whole concentration range $0lxl0.70$ are obtained under the assumption that the H atoms randomly occupy the interstitial octahedral sites in the Ni lattice and that the probe HFI reductions due to H atoms in the first-, second-, and third-neighbor shell are simply additive (albeit different for each shell). The absolute magnitudes of the HFI reduction corresponding to each shell are the only free parameters in the analysis. We conclude that a supersaturated $\ensuremath{\alpha}$ phase is formed by implantation at least up to $x\ensuremath{\sim}0.85$. The magnetization H concentration dependence of the implanted hydride is deduced from that of the average HFI. It is linear, and falls to zero at $x=(0.83\ifmmode\pm\else\textpm\fi{}0.10)$. This result is identical to the one found in electrolytically charged samples, in spite of the fact that the latter's magnetism is determined by a combination of two phases (the magnetic $\ensuremath{\alpha}$ phase and the non-magnetic $\ensuremath{\beta}$ phase). The TDPAC of $^{111}\mathrm{In}$ in electrolytically charged and implanted samples at $x=0.70$ are entirely different, as expected from the structural differences. The magnetization result for the implanted sample is discussed in terms of recent band-structure calculations.

A partially amorphous (the fraction of amorphous volume in the implanted layer was about 0.7) Ni 0.90 B 0.10 alloy formed by 15 K boron implantation into a nickel single crystal was annealed, above the crystallization temperature and post-irradiated at 15 K with low fluences of boron ions. The disordering behaviour was monitored at the different steps of the experiment using Rutherford backscattering and channelling techniques. The results show that, as postulated in a recent model, the simultaneous presence of radiation damage and chemical short-range order is required for amorphization. Annealing has led to the formation of a multiphased alloy in which only the boron-rich crystalline Ni 3 B phase undergoes an amorphous transition by boron post-irradiation.

We have shown that, in contrast to what is observed when hydrogen is diffused into Ni (formation of a two-phased alloy up to a saturation concentration x∼0.70), a unique supersaturated α-phase is formed by low-temperature H implantation up to x=1.0. The magnetism of this phase decreases linearly and reaches zero at x=(0.83±0.10), as predicted by recent band structure calculations and as also found in the case of a diffused alloy.

Rutherford backscattering and time-differential perturbed angular correlation experiments were performed on In-implanted nickel foils annealed up to 900 K. The impuritydamage interaction is shown to anneal out just at (or very slightly below) the In diffusion temperature.

Single crystals of NiAl and FeAl B2 type ordered intermetalhc compounds were irradiated at 90 K with xenon ions and the radiation damage studied by in situ Rutherford backscattering and channeling experiments. After a first stage (up to 5 x 1013 Xe cm-−2) where a strong increase in the dechanneling rate of the analyzing ions is obtained, an unexpected reordering effect (i.e. a decrease in the channeling rate) is observed in both alloys. This process is discussed in relation with defect rearrangements or induced crystalline structural phase transformation. Finally for irradiation fluences higher than 2.5 x 1015 Xe CM−2 complete dechanneling occurs, confirming that total amorphization takes place in NiAl, while the disorder level remains at a very low and constant value in FeAl.

The possibility of “internal oxidation” in Yb-implanted iron is studied via 18 O tracing experiments. For a 400 keV Yb-implantation in iron single crystals, no oxygen diffusion occurs at the Yb depth under implantation or annealing up to 520°C.

Integral perturbed angular correlation measurements of the hyperfine field at 175 Lu isotope-separator implanted in Fe and Ni yield fields of −(575 ± 41) kOe and −(130 ± 27) kOe, respectively. A clear annealing stage is found around 450°C.