Modification of the physicomechanical properties of metallic materials by formation of nanoscale intermetallic phases under ion implantation

The fundamental and technological aspects of application of nanosized intermetallic compounds as implanted layers have been considered. The existing theoretical and experimental data on the effect of ion implantation on the structural state and physicomechanical properties of surface layers of metals (nickel and titanium) have been analyzed. The common features and differences in the phase composition and distribution of the phases formed by implantation over the alloyed metal layers are demonstrated.     

Role of polycrystalline titanium grain size in the formation of the concentration profiles of implanted aluminum ions

The dependence of the depth of penetration of implanted aluminum atoms into polycrystalline titanium on the grain size of initial target samples is analyzed. The irradiation was carried out by a pulse-frequency ion beam of a Diana-2 source. The increase in the modified layer thickness to 250 nm with decreasing grain size in the initial material is revealed. In the interpretation of the observed regularities, we take into account the energetically inhomogeneous composition of a beam represented by three components and probable intense sputtering of the target surface by ions. In terms of the simulation, it is found that, in samples with relatively fine grains, a significant contribution to the formation of the depth profiles of implanted atoms comes from the radiation-induced diffusion; in samples with coarse grains, it comes from the diffusion along migrating extended defects, which appear and rearrange themselves in the process of ion implantation.     

Getter formation in silicon by implantation of antimony ions

A porous silicon layer as a getter of uncontrolled impurities has been prepared by implantation of Sb⁺ into silicon and subsequent thermal treatments. The lifetime of nonequilibrium charge carriers in n- and p-type silicon wafers with a getter layer is 3–4 times longer than that without a getter.     

The formation of intermetallic phases by solid-phase reaction of Fe/Al multilayers

Thin film multilayers of Fe and Al with thicknesses ranging from 10 nm/2 nm to 10 nm/420 nm Fe/Al are used as starting structures to produce intermetallic phases by solid-phase reaction during high-vacuum thermal annealings. By measuring the relative concentrations of the reacting Fe and Al species nearby the growing interfaces and using the recently introduced concept of effective heat of mixing of binary thin-film metallic systems, a method is suggested to predict the phases to be obtained from different combinations of initial multilayer thickness and annealing temperature.     

Analysis of concentration field formation in titanium under aluminum ion implantation via a gas-and-metal film deposited on a target surface

The concentration profiles of aluminum ions in polycrystalline titanium implanted by the polychromatic beam from a vacuum arc source via a gas-and-metal film deposited on a target surface are analyzed.     

Pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium

The results from investigating the pulsed plasma-immersion ion implantation of aluminum into VT1-0 titanium are presented. It is shown that variations in the elemental and phase composition of surface layers, their microscopic characteristics, and their mechanical properties as a function of implantation time are not monotonous but follow certain patterns. The possibility of interpreting the obtained data in terms of surface modification by metallic clusters with at least ~100 atoms generated in the gas of metal atoms evaporated from cathode spots is discussed.     

Optical properties of potassium aluminum phosphate glass activated by trivalent titanium ions

Potassium aluminum phosphate glass activated by trivalent Ti ions was obtained and investigated. Some physicochemical properties of the concentration series prepared, as well as the absorption and luminescence spectra at 293 K, were investigated. The data obtained are indicative of distorted octahedral coordination of Ti³⁺ ions. The optimal concentration interval for Ti³⁺ in the glass is proposed: 0.1–1 mol/l, in which the titanium concentration can be varied without violation of the physicotechnical and luminescence-kinetic properties of the glass. As a result, Ti³⁺ can be optimally used as an activator for phosphors on its basis. In addition, the sensitizing properties of Ti³⁺ can be used to excite other ions: Ho³⁺, Er³⁺, and Yb³⁺.     

Diffusion of As ions and self-diffusion in silicon during implantation

Experimental concentration profiles of As ions in a silicon substrate at temperatures of 20, 600, and 1050°C and ion current of 40 μA/cm², as well as at 1050°C and 10 μA/cm², are presented. On the basis of our and previously published experimental data, the process of radiation-stimulated ionic diffusion and self-diffusion in silicon is simulated. A number of interesting dependences, which are discussed in the conclusion of this study, are obtained.     

Structure of intermetallic phases in Al-free galvannealed zinc coatings

Galvannealed coatings of thickness of (20–40) μm were prepared on the ultra low carbon (ULC) steel substrate. Metalography analysis was carried out to obtain the phase composition of coatings. Coatings were then transfered onto a polyacrylate foil. Transmission spectra yielding all the positions of iron within the coating thickness were measured. The doublet of zeta phase occured only after short annealing times, lower annealing temperatures and longer dipping times. Parameters of three sites of delta phase were observed to approach equilibrium values at higher annealing temperatures and longer annealing times. These changes are ascribed to diffusion transformations in the coatings during annelaing. Presented at International Colloquium “M?ssbauer Spectroscopy in Materials Science”, Všemina, Czech Republic, June 1–4, 2004.     

Intense blue luminescence of anodic aluminum oxide

The luminescence spectra of aluminum oxide with an ordered system of through pores have been studied. The diameter and density of pores were ≈ 50 nm and 1.2 × 10¹⁰ cm^?2, respectively. Amorphous aluminum oxide formed by anodization of aluminum foil in an oxalic acid electrolyte shows intense luminescence in the blue spectral region. Processing of spectra with the use of an oxalic acid approximation by Gaussian curves gives three bands peaking at ～ 382 (3.2 eV), 461 (2.7 eV), and 500 nm (2.5 eV), which correspond to different types of defects. The bands at 382 and 461 nm can be assigned to optical transitions involving F⁺ and F centers (vacancies of oxygen with one or two electrons), respectively. The lower-energy band near 500 nm can be presumably assigned to luminescence from F⁺⁺ centers (vacancy of oxygen without an electron). Analysis of the luminescence excitation spectra has revealed an inhomogeneous character of the distribution of the corresponding luminescence centers in the Al₂O₃ matrix.     

Nanoscale pore formation dynamics during aluminum anodization

A theoretical analysis of nanoscale pore formation during anodization reveals its fundamental instability mechanism to be a field focusing phenomenon when perturbations on the minima of the two oxide interfaces are in phase. Lateral leakage of the layer potential at high wave number introduces a layer tension effect that balances the previous destabilizing effect to produce a long-wave instability and a selected pore separation that scales linearly with respect to voltage. At pH higher than 1.77, pores do not form due to a very thick barrier layer. A weakly nonlinear theory based on long-wave expansion of double free surface problem yields two coupled interface evolution equations that can be reduced to one without altering the dispersion relationship by assuming an equal and in-phase amplitude for the two interfaces. This interface evolution equation faithfully reproduces the initial pore ordering and their dynamics. A hodograph transformation technique is then used to determine the interior dimension of the well-developed pores in two dimensions. The ratio of pore diameter to pore separation is found to be a factor independent of voltage but varies with the pH of the electrolyte. Both the predicted pH range where pores are formed and the predicted pore dimensions are favorably compared to experimental data. (c) 2002 American Institute of Physics.     

Volume magnetostriction in intermetallic compounds containing rare-earth ions

Substantial volume strains associated with rotation of the magnetic moment have been observed in some intermetallic compounds containing rare-earth ions. These have been calculated within the molecular field approximation using a point-charge crystal field model with specific reference to HoCo₂.     

Solid state effects during deuterium implantation into copper and titanium

Results of neutron counting experiments during deuterium implantation into titanium and copper are reported. Models for neutron yield have been developed by taking into account different solid state effects like energy degradation of incident ions, energy dependent d-d fusion cross section and diffusion of implanted deuterium possibly influenced by surface desorption and formation of metal deuterides. The asymptotic time dependence of the neutron yield during implantation has been compared with the experimental results. Using these results, solid state processes that might occur during deuterium implantation into these metals are inferred.     

Structural state and phase composition of nickel surface layers modified by high-intensity implantation of titanium ions

This paper reports on the results of experimental investigations into the microstructure and the elemental and phase compositions of ion-alloyed nickel surface layers modified by high-intensity implantation of titanium ions. It is established that the implantation of titanium ions into nickel surface layers up to 1600 nm thick leads to the formation of intermetallic phases (namely, NiTi, Ni₃Ti, and NiTi₂), a solid solution of titanium in nickel, titanium oxides of different stoichiometries, and titanium carbide TiC. It is demonstrated that the phases formed in the ion-alloyed nickel surface layers have a nanocrystalline structure. The average size of the nanocrystal grains is equal to 40 nm.     

Ordered orthorhombic phases of titanium monoxide

Symmetry analysis is carried out for the ordered phases of cubic monoxide TiO_y with relative oxygen contents y<1 and y>1. It is established that a partially ordered orthorhombic phase (space group Immm)—a derivative of the orthorhombic M₃X₂□ superstructure (at y<1.0) or the inverse superstructure M₂■X₃ (at y>1)—may arise in TiO_y. The distribution of Ti and O atoms, oxygen vacancies □, and titanium vacancies ■ in unit cells of the orthorhombic ordered phases is determined. The phases are formed through the order-disorder transition channel along two rays of a non-Lifshitz star {k ₄}, and the ordering proceeds as a first-order phase transition. The distribution functions of Ti atoms over the sites of metallic and O atoms over the sites of nonmetallic sublattices are calculated for the orthorhombic superstructures of cubic titanium monoxide TiO_y.     

The characterisation of iron-containing intermetallic phases within industrially cast aluminium

⁵⁷Fe conversion electron Mössbauer spectroscopy has been used to investigate the intermetallic phases near the surface of a D.C. cast aluminium ingot. The CEMS data is used with SAAES (selected area Auger electron spectroscopy) and SAXPS (selected area X-ray photoelectron spectroscopy) data to propose a model of the surface region above the grain boundaries.