Separate cobalt-copper interface smoothening under the action of low-energy argon ion bombardment

Multilayer film structures of the types “buffer gold layer (20 nm)-copper (x nm)-cobalt (y nm)-protective gold layer (10 nm)” and “buffer gold layer (20 nm)-cobalt (y nm)-copper (x nm)-protective gold layer (10 nm)” with x+y≈6 nm obtained by ion beam deposition in vacuum were studied. It was established that the smoothest surface is obtained for a structure of the second type in which the cobalt layer prior to copper deposition was additionally irradiated with a beam of argon ions at an energy below the threshold energy of sputtering in the common vacuum deposition cycle. Additional irradiation with a mixture of argon and helium ions under analogous conditions leads to the formation of a less smooth structure. It is concluded that the cobalt-copper interface is smoothened as a result of multiple collisions of the low-energy argon ion with cobalt atoms during the former ion stopping within two to three of uppermost atomic layers of the target.     

A new magnetorheological finishing process for ferromagnetic cylindrical honed surfaces

In today’s industries, the internal surface finishing of cylindrical objects is highly demanded to improve their functional performance in various engineering applications. During the traditional honing operation, the finishing forces produced by abrasives on the workpiece surface are not easily controllable and also produce various surface defects. Therefore, to further improve the surface integrity of the traditionally cylindrical honed surface made of ferromagnetic or non-ferromagnetic materials, a new magnetorheological (MR) finishing process has been used with a controlled magnetic field. The experimentation is performed on the honed surface made of gray cast iron, which is generally used as a cylinder liner. The percentage change in surface roughness values, i.e., Ra, Rq and Rz, reduced by 77.44%, 70.16% and 72.16%, respectively, with better improvement in surface after 90 minutes of finishing. The experimental results demonstrated the effectiveness of present process for improving the functional applications of ferromagnetic cylindrical honed surface after removing the various surface defects such as deeper grooves, honing grooves with shaper edges, torn and folded metals, and cavities or holes. The applications of new MR finishing process can also be useful in the internal finishing of injection barrel of a molding machine, cylindrical molds and dies, hydraulic cylinder, etc.     

Sputtering yields for low-energy Ar- and Ne-ion bombardment

The development of fluorescent lamps requires reliable experimental data of low-energy (30-300 eV) sputtering yields of the metallic components of lamps. An experimental study was carried out to measure the sputtering yields of molybdenum, tungsten and iron using the plasma chamber of a Secondary Neutral Mass Spectrometer (SNMS). The sputtering ion beam was extracted from radio frequency noble gas (Ar/Ne)-plasmas. The number of atoms sputtered was determined from the weight loss of the target by means of a microbalance. The sputtering yields data for Mo/Ar, W/Ar and Fe/Ar target/projectile combinations and their energy dependence were in good agreement with those calculated by computer simulations and measured by other groups. The sputter yield obtained for Fe/Ne target/projectile combination shows some deviation from the simulation results.     

Modification of the shape of large germanium nanoislands on silicon surface by low-energy ion bombardment

Germanium nanoislands on silicon substrates were irradiated by hydrogen and argon ions with energies below 350 eV. In the initial stage, ion bombardment leads to the division of large islands into several small islands irrespective of the ion type. The resulting surface is more homogeneous than the initial and is stable with respect to further ion irradiation.     

A mechanism of surface micro-roughening by ion bombardment

The spatial distribution of sputter-etch effects is analysed theoretically under the assumption of random slowing-down of the bombarding ions. When a surface is bombarded at locally oblique incidence the most pronounced sputtering effect is likely to be observed not at the very point of impact, but further downstream. This effect may cause a significant reduction of the local sputtering yield on top of a spike or a ridge, and an increase on the bottom of a groove or a crater. As a consequence, small irregularities on a relatively smooth surface may be enhanced during bombardment. It is concluded that a microscopically flat surface is unstable under high-dose ion bombardment unless atom migration acts as a dominating smoothing effect. Conversely, sharp cones appear to be surprisingly stable under bombardment. Even on a clean surface, cones erode more slowly than a plane surface, provided that their dimensions are of the order of, or less than, the penetration depth of the ions.     

The influence of low-energy ion bombardment on the microstructure development and mechanical properties of TiBx coatings

The influence of the deposition parameters on the growth, structure and mechanical properties of the TiB_x coatings is studied. The TiB_x coatings represent a nanocomposite system, in which random or oriented TiB₂ nanocrystallites are embedded in an amorphous matrix as is revealed by cross-sectional transmission electron microscopy. We show that low-energy ion bombardment (E_i ) of growing TiB_x coating, influences the preferred orientation of TiB₂ crystallites. The increase of ion current density (i_s) by means of negative substrate bias voltage (U_s) leads to change from random to the (0001) preferred crystal orientation whereby the electrical biasing promotes crystal growth in the coating and the (0001) texture appears gradually during the film growth. Together with the (0001) preferred orientation selection the composition B/Ti ratio was changed from 2.9 (floating potential, E_i = 8 eV) to 2.4 (E_i = 94 eV). The highest amount of oriented (0001) crystallites and highest hardness H = 53 GPa exhibit TiB_x coatings deposited at E_i = 94 eV and i_s = 2.69 mA.cm⁻².     

A new low-energy bremsstrahlung generator for GEANT4

The 2BN bremsstrahlung cross section is a well-adapted distribution to describe the radiative processes at low-electron kinetic energy (E(k) < 500 keV). In this work a method to implement this distribution in a Monte Carlo generator is developed.     

Metallurgical applications of ion implantation and ion bombardment

The physical background to the metallurgy of ion implantation is discussed. For instance, the fate of implanted atoms is considered in the content of the precipitation processes which occur as a consequence of exceeding the solubility limit during implantation.The Metallurgical applications of ion implantation and ion bombardment are discussed under the following headings: surface and interfacial energies, surface applications, superconductivity and void formation.     

Automated print inspection for cylindrical surfaces

The objective of this research was to determine the criteria for automated inspection of a string of alphanumeric characters printed directly to the surfaces of cylindrical containers. The technical problems encountered, because a curved surface was used instead of a flat surface, were container positioning for locating surface features, character position compensation due to curvature, resolution limits defined for sensor and reflected illumination. Automated print inspection requires the use of machine vision to perform the registration of characters, template comparison for correct text being produced and the interrogation of the individual characters for correctness, position, size and type.     

A simple technique for installing strain gauges on cylindrical surfaces

In this paper a simple technique for the installation of strain gauges on circular and conical cylindrical surfaces has been described. This technique may be adopted in an experimental stress analysis laboratory where sophisticated equipment is not available.     

A rotating core-based magnetorheological nano-finishing process for external cylindrical surfaces

A rotating core-based magnetorheological finishing process has been developed to finish the external cylindrical surfaces at the nano-level more efficiently. The existing MR finishing process based on the stationary curved core tool tip is found to be comparatively less effective than the present process based on a rotating flat core tool tip for finishing the external cylindrical surfaces. This is due to the fact that in the present process both the workpiece and the tool rotating rather than giving rotation to the workpiece alone as in the existing process. The carbonyl iron particle (CIP) chains are rotated along with the rotation of the tool. This results in an increase in the kinetic energy of the active abrasive particles gripped by CIP chains which causes for the better finishing performance. Finishing is done by both the processes and their corresponding results are compared. The R_a, R_q, and R_z values are reduced to 71.62%, 72.53%, and 70.73% with a stationary curved core tool tip, and 94.59%, 94.51%, and 92.68% with a rotating flat core tool tip in 90 minutes of MR finishing. The overall results revealed that the present developed process using the rotating flat tool tip is more useful in finishing the external cylindrical surfaces as compared to the stationary curved tool tip.     

Biomedical aspects of ion bombardment of polyethylene

Press-moulded ultra-high molecular weight polyethylene (UHMWPE) samples were subjected to ion bombardment and effects of the modification studied. Helium, nitrogen, argon and silver ions of energy 65–150 keV and fluences in the range of 1 × 10¹⁴ to 3 × 10¹⁶/cm² were applied. The consequences of the modification were studied with FT-IR, Raman and AFM techniques, contact angle measurements, bacteriostaticity and thrombogeneity tests. Surface layer oxidation, graphitization and changes to the surface geometry lead to increase of the surface energy. Modified surface exhibits bacteriostatic properties particularly for higher ion fluences. Aggregation of blood platelets on polymer surface subjected to ion bombardment is limited.     

A novel magnetorheological honing process for nano-finishing of variable cylindrical internal surfaces

A novel magnetorheological honing process is designed and developed for nano-finishing of cylindrical internal surfaces with the help of permanent magnets. The radial movement of magnetic tool surface is adjusted as per the internal diameter of different cylindrical components and make it fixed before start of finishing so that it can maintain constant working gap while perform finishing. The present developed magnetic tool surface always constitutes higher magnetic field than the inner surface of ferromagnetic or non-ferromagnetic cylindrical workpiece. This is an important requirement to finish the internal surface of ferromagnetic or non-ferromagnetic cylindrical components because it ensures MR polishing fluid cannot stick on the workpiece surface while performing the finishing. Hence, present developed process is useful for finishing of ferromagnetic cylindrical molds, dies, hydraulic actuators, etc. for its better functional applications after the conventional honing or grinding process. The internal surface roughness of cylindrical ferromagnetic workpiece is dropped to 90?nm from its initial value of 360?nm in 100 minutes of finishing. Further scanning electron microscopy has also been done to understand the surface characteristics of finished workpiece. The results revealed that the developed magnetorheological honing process is capable to perform nano-finishing of internal surface of the ferromagnetic cylindrical components.     

Electrical properties of CdxHg1−x Te and ZnxCdyHg1−x−y Te modified by low-energy ion bombardment

The phenomenon of conversion of the conductivity type in p-type samples of the Cd_xHg_1−x Te (0.28≤x≤0.55) and Zn_xCd_yHg_1−x−y Te solid solutions bombarded by low-energy argon ions was studied. It is shown that a necessary condition for the conversion effect in Cd_xHg_1−x Te with 0.28≤x≤0.39 is ion neutralization in the bombarding beam. The dependence of the conversion layer thickness in Cd_xHg_1−x Te on the solid solution composition agrees with that predicted by the diffusion model of ion-bombardment-induced conversion of the conductivity type.     

Helium ion bombardment of thin aluminium films

A study is presented of the effect of 5 keV helium ion bombardment on thin (about 2000 Å) aluminium films using proton backscattering, scanning and transmission electron microscopy and α particle energy loss spectroscopy. Measurements of helium content after irradiation using proton backscattering indicate low below-saturation retention for both room temperature and low temperature implantations (19% and 24% respectively). Electron microscopy examination of the films reveals a severe deformation in the form of coarse and fine-scale wrinkling whose amplitude increases with increasing helium dose. This deformation does not appear to be the result of bubble swelling. An attempt has been made to quantify the wrinkling by measuring the energy loss spectrum of α particles transmitted through irradiated films and the combination of these measurements with a simple sinusoidal deformation model indicates an increase in film area of up to 20%.     

The transport of ion bombardment induced ripples

It is demonstrated that a theory which predicts that ripples produced by ion bombardment are transported across the surface, as a result of the surface gradient dependence of the sputtering rate, is invalid and that its modification reveals their stationary behaviour. Other processes which could lead to such transport are examined.