Changes in surface properties of nitrogen-implanted AISI316L stainless steel

The effect of nitrogen ion implantation with an energy of 125 keV and doses of 1 × 10¹⁷–1 × 10¹⁸ at/cm² on such tribological characteristics of AISI316L stainless steel as the friction coefficient, wear resistance, and microhardness was studied. The steel surface layer composition was studied by the methods of RBS, XRD, GXRD, SEM, and EDX. The friction coefficient and abrasion resistance of AISI316L stainless steel were measured in air, oxygen and argon atmospheres, and in vacuum. An increase in the abrasion resistance after implantation was detected, which was different for various media. The largest increase in the wear resistance was observed during testing in air. The largest decrease in the friction coefficient was observed for all implanted samples in argon atmosphere. Tribological tests resulted in an increase in nitrogen, carbon, and oxygen concentrations in worn sample fragments in comparison with their concentrations in surface layers immediately after implantation.     

Surface engineering of biomedical metallic materials by plasma-based low-energy ion implantation

Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition of thin films, for surface engineering of metallic materials was emerged as low-temperature, low-pressure surface modification technique. Plasma source ion nitriding onto AISI 316L austenitic stainless steel produced a high nitrogen face-centered-cubic phase (γ_N) layer about 10 μm thick at the temperature of 380 °C during 4 h with the high microhardness of HK_0.1 N 22.0 GPa. The microhardness of the nitrided surface from the titanium nitride phase [(Ti, Al, V)N] layer on Ti6Al4V alloy at 750 °C during 4 h achieved up to about HK_0.1 N 15.5 GPa. No pitting corrosion in the Ringer’s solution at 37 °C was detected by electrochemical polarization measurement for the nitrided AISI 316L stainless steel and Ti6Al4V alloy, respectively. Plasma source ion nitriding of the metallic materials provided the engineering surfaces with combined improvement in hardness and corrosion resistance.     

Biocompatible film deposition by using Nd:YAG pulsed laser

A Nd:YAG laser operating at the fundamental wavelength (1064 nm) and at the second harmonic (532 nm), with 9 ns pulse duration, 100–900 mJ pulse energy, and 30 Hz repetition rate mode, was employed to ablate in vacuum (10^?6 mbar) biomaterial targets and to deposit thin films on substrate backings. Titanium target was ablated at the fundamental frequency and deposited on near-Si substrates. The ablation yield increases with the laser fluence and at 40 J/cm ² the ablation yield for titanium is 1.2×10¹⁶ atoms/pulse. Thin film of titanium was deposited on silicon substrates placed at different distance and angles with respect to the target and analysed with different surface techniques (optical microscopy, scanning electron spectrosopy (SEM), and surface profile).

Hydroxyapatite (HA) target was ablated to the second harmonic and thin films were deposited on Ti and Si substrates. The ablation yield at a laser fluence of 10 J/cm ² is about 5×10¹⁴ HA molecules/pulse. Thin film of HA, deposited on silicon substrates placed at different distance and angles with respect to the target, was analysed with different surface techniques (optical microscopy, SEM, and Raman spectroscopy).

Metallic films show high uniformity and absence of grains, whereas the bio-ceramic film shows a large grain size distribution. Both films found special application in the field of biomaterial coverage.     

CEMS study of stainless steel films deposited by pulsed laser ablation of AISI316

Thin stainless steel films deposited on SiO₂/Si wafer were prepared by a pulsed laser ablation of austenite stainless steel (AISI316), and characterized by conversion electron Mössbauer spectrometry (CEMS) using a He gas proportional counter. As-deposited films were composed of a magnetic phase. When deposited films were heated in air at various temperatures, the hyperfine field of the magnetic phase increased. Hematite was produced on the surface, and the magnetic orientation changed from parallel to in-plane at random with the increase of heating temperatures. The metallic iron and magnetite were produced at 400°C in dry Ar + 5%H₂ atmosphere. When the film was heated in wet Ar + 5%H₂ atmosphere at 600°C, maghemite was produced on the surface, and austenite phase was produced in the inner film.     

Studies of some physical properties of PrFe0.7Ni0.3O3 thin films after 200 MeV Ag15+ irradiation

PrFe_0.7Ni_0.3O₃ thin films (thickness ~ 200 nm) were prepared by pulsed laser ablation technique on LaAlO₃ substrate. These films were irradiated with 200?MeV Ag¹⁵⁺ ions at various fluencies, ranging from 1 × 10¹¹ to 1 × 10¹² ions/cm². These irradiated thin films were characterized by using X-ray diffraction, dc conductivity, dc magnetization and atomic force microscopy. These films exhibit orthorhombic structure and retain it even after irradiations. The crystallite size (110–137?nm), micro strain (1.48 × 10^?2–1.75 × 10^?2 line^?2?m^?4) and dislocation density (79.7 × 10¹⁴–53.2 × 10¹⁴ line/m²) vary with ion fluencies. An enhancement in resistivity at certain fluence and then a decrease in its value (0.22175–0.21813?Ω?cm) are seen. A drastic change in observed magnetism after ion irradiation is seen. With ion irradiation, an increase in surface roughness, due to the formation of hillocks and other factors, is observed. Destruction of magnetic domains after irradiation can also be visualized with magnetic force microscopy and is in close agreement with magnetization data. The impact on various physical properties in these thin films after irradiation indicates a distortion in the lattice structure and consequently on single-particle band width caused by stress-induced defects.     

TiCN thin films grown by reactive crossed beam pulsed laser deposition

In this work, we used a crossed plasma configuration where the ablation of two different targets in a reactive atmosphere was performed to prepare nanocrystalline thin films of ternary compounds. In order to assess this alternative deposition configuration, titanium carbonitride (TiCN) thin films were deposited. Two crossed plasmas were produced by simultaneously ablating titanium and graphite targets in an Ar/N₂ atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates whilst keeping the ablation conditions of the Ti target constant. By varying the laser fluence on the carbon target it was possible to study the effect of the carbon plasma on the characteristics of the deposited TiCN films. The structure and composition of the films were analyzed by X-ray Diffraction, Raman Spectroscopy and non-Rutherford Backscattering Spectroscopy. The hardness and elastic modulus of the films was also measured by nanoindentation. In general, the experimental results showed that the TiCN thin films were highly oriented in the (111) crystallographic direction with crystallite sizes as small as 6.0 nm. It was found that the hardness increased as the laser fluence was increased, reaching a maximum value of about 33 GPa and an elastic modulus of 244 GPa. With the proposed configuration, the carbon content could be easily varied from 42 to 5 at.% by changing the laser fluence on the carbon target.     

Electrochemical recycling of cell phone Li-ion batteries: application as corrosion protector of AISI 430 stainless steel in artificial seawater

This article aims to present a new alternative to waste management of spent Li-ion batteries from cell phones. In this sense, the proposed is recycling the cobalt from Li-ion cathode by electrodeposition and apply it as corrosion protector of AISI 430 stainless steel. Thus, two greatest environmental problems can be solved, producing a low-cost and high-corrosion-resistant stainless steel. The cobalt electrodeposition bath came from acid dissolution of spent Li-ion cathode with chemical formula LiCoO₂. The charge efficiency for cobalt electrodeposition in ?1.0 V and pH = 3 reaches 95 %. A protective layer of Co₃O₄ was successfully obtained by treatment of AISI 430 stainless steel with cobalt electrodeposited at 800 °C for 200 h in air atmosphere. The corrosion current of AISI 430 stainless steel in artificial seawater was reduced from 30 to 0.76 μA cm^?2. The treatment proposed produces a AISI 430 stainless steel with double of corrosion resistance and half of cost if compared with AISI 304 stainless steel.     

Evaluation of bacterial adhesion on Si-doped diamond-like carbon films

Diamond-like carbon (DLC) films as biomaterial for medical devices have been attracting great interest due to their excellent properties such as hardness, low friction and chemical inertness. It has been demonstrated that the properties of DLC films can be further improved by the addition of silicon into DLC films, such as thermal stability, compressive stress, etc. However no research work on anti-bacterial properties of silicon-doped diamond-like carbon films has been reported. In this paper the surface physical and chemical properties of Si-doped diamond-like carbon films with various Si contents on 316 stainless steel substrate prepared by a magnetron sputtering technique were investigated, including surface topography, surface chemistry, the sp³/sp² ratio, contact angle, surface free energy, etc. Bacterial adhesion to Si-doped DLC films was evaluated with Pseudomonas aeruginosa, Staphylococcus epidermidis and Staphylococcus aureus which frequently cause medical device-associated infections. The experimental results showed that bacterial adhesion decreased with increasing the silicon content in the films. All the Si-doped DLC films performed much better than stainless steel 316L on reducing bacterial attachment.     

Influence of ion bombardment on growth and properties of PLD created DLC films

A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J?cm^?2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp² “graphitic” and sp³ “diamond” bonds was measured using XPS. Sp³ bonds changed from 60 % to 81 %. We found the highest sp³ content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented.     

Corrosion behavior of low energy,high temperature nitrogen ion-implanted AISI 304 stainless steel

This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate temperature of about 500°C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion current density of 100 μA cm⁻². Nitrogen ion concentration of 6 × 10¹⁷, 8 × 10¹⁷ and 10¹⁸ ions cm⁻², were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry (SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing nitrogen ion concentration.      

Electrochemical synthesis and characterization of polyaniline-coated PEMFC metal bipolar plates with improved corrosion resistance

This article reported the electrochemical deposition of polyaniline (PANI) on 316-L stainless steel (316LSS) to improve the anti-corrosion performance as PEMFC metal bipolar plates. The results indicate that PANI can increase the corrosion potential of 316LSS by more than 410.57 mV and effectively decrease the corrosion current density by four orders of magnitude in comparison with the uncoated 316LSS. The experimental results showed that the PANI increased the open-circuit potential of the steel by about 140 mV. The polarization current value of PANI-coated 316LSS reduced to 2.3 × 10^?7 A/cm² under the PEMFC cathode working condition. During exposure for 12 h, Nyquist plots of PANI-coated 316LSS did not change substantially. This indicates that the PANI coating was an effective barrier against the inward penetration of corrosive species.     

Geometric dynamic recrystallization of austenitic stainless steel through linear plane-strain machining

ABSTRACT

Type 316L austenitic stainless steel was severely plastically deformed at room temperature using linear plane-strain machining in a single pass that imparted shear strains up to 2.2 at strain rates up to 2?×?10³ s^?1. The resulting microstructures exhibited significant grain size refinement and improved mechanical strength where geometric dynamic recrystallization was identified as the primary microstructural recrystallization mechanism active at high strain rates. This mechanism is rarely observed in low to medium stacking fault energy materials. The critical stress required for twin initiation is raised by the combined effects of refined grain size and the increase in stacking fault energy due to the adiabatic heating of the chip, thus permitting geometric dynamic recrystallization. The suppression of martensite formation was observed and is correlated to the significant adiabatic heating and mechanical stabilisation of the austenitic stainless steel. A gradient of the amount of strain induced martensite formed from the surface towards the interior of the chip. As the strain rate is increased from 4?×?10² s^?1–2?×?10³ s^?1, a grain morphology change was observed from a population of grains with a high fraction of irregular shaped grains to one dominated by elongated grain shapes with a microstructure characterised by an enhanced density of intragranular sub-cell structure, serrated grain boundaries, and no observable twins. As strain rates were increased, the combination of reduction in strain induced martensite and non-uniform intragranular strain led to grain softening where a Hall-Petch relationship was observed with a negative strengthening coefficient of ?0.08?MPa m^1/2.     

Diamond deposition on siliconized stainless steel

Silicon diffusion layers in AISI 304 and AISI 316 type stainless steels were investigated as an alternative to surface barrier coatings for diamond film growth. Uniform 2 μm thick silicon rich interlayers were obtained by coating the surface of the steels with silicon and performing diffusion treatments at 800 °C. Adherent diamond films with low sp² carbon content were deposited on the diffused silicon layers by a modified hot filament assisted chemical vapor deposition (HFCVD) method. Characterization of as-siliconized layers and diamond coatings was performed by energy dispersive X-ray analysis, scanning electron microscopy, X-ray diffraction and Raman spectroscopy.     

Correlation of plume dynamics and oxygen pressure with VO2 stoichiometry during pulsed laser deposition

Vanadium dioxide thin films have been deposited on Corning glass substrates by a KrF laser ablation of V₂O₅ target at the laser fluence of 2 J?cm^?2. The substrate temperature and the target-substrate distance were set to 500 ^°C and 4 cm, respectively. X-ray diffraction analysis showed that pure VO₂ is only obtained at an oxygen pressure range of 4×10^?3–2×10^?2 mbar. A higher optical switching contrast was obtained for the VO₂ films deposited at 4×10^?3–10^?2 mbar. The films properties were correlated to the plume-oxygen gas interaction monitored by fast imaging of the plume.     

Influence of the ion energy on the structure of Bi and Fe2O3 thin films

Compounds containing bismuth, iron and oxygen (BFO) can result in materials with important magnetic and electrical properties for high-technology applications. We plan to prepare such compounds using the simultaneous ablation of bismuth and iron oxide targets. For that reason in the first part of this work we study the plasmas and the materials produced by ablation of bismuth or Fe₂O₃ targets, and then the two plasmas are combined in order to deposit the BFO compounds. The individual plasmas were characterized using a Langmuir probe, in order to measure the mean kinetic ion energy (E _p) and plasma density (N _p). Bismuth and magnetite-Fe₃O₄ thin films were obtained in high vacuum (2.7×10^?4 Pa). Meanwhile for the deposition of α-Fe₂O₃ (hematite) or amorphous bismuth oxide thin films a reactive atmosphere (Ar/O₂=80/20) was used. All depositions were made at room temperature. The bismuth thin films crystallized in the rhombohedral metallic system with preferential orientations that depended on the Bi-ion energy used. Bismuth oxide phases were only obtained after annealing of the Bi thin films at different temperatures. Iron oxide thin films reproducing the target stoichiometry were obtained at a certain value of iron-ion energy. Preliminary structural results of the BFO thin films obtained by the combination of the individual plasmas are presented.     

Modified structural,morphological and photoelectrochemical properties of 120 MeV Ag9+ ion irradiated BaTiO3 thin films

The effects of high electronic energy deposition on the structure, surface topography, optical property and photoelectrochemical behavior of barium titanate thin (BaTiO₃) films have been investigated by irradiating films with 120 MeV Ag⁹⁺ ions at different ion fluences in the range of 1 × 10¹¹–3 × 10¹² ions cm^?2. Barium titanate thin films were deposited on indium tin oxide-coated glass substrate by sol–gel spin coating method. The structure of the film was crystalline with tetragonal phase. Surface topography was studied by atomic force microscopy detailing the values of roughness of the films. Maximum photocurrent density of 1.78 mA cm^?2 at 0.4 V/SCE and applied bias photon-to-current efficiency (ABPE) of 0.91% was observed for BaTiO₃ film irradiated at 1 × 10¹¹ ions cm^?2.     

Optical and electrical properties of swift heavy ion beam-irradiated polycarbonate/polystyrene bilayer films

Polycarbonate/polystyrene bilayer films prepared by solvent-casting method were irradiated with 55 MeV carbon ion beam at different fluences ranging from 1×10¹¹ to 1×10¹³ ions cm^?2. The structural, optical, surface morphology and dielectric properties of these films were investigated by X-ray diffraction (XRD), UV–visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, optical microscopy and dielectric measurements. The XRD pattern shows that the percentage of crystallinity decreases while inter-chain separations increase with ion fluence. UV–visible spectroscopy shows that the energy band gap decreases and the number of carbon atoms in nanoclusters increase with the increase in ion fluences. The refractive index is also found to decrease with the increase in the ion fluence. Optical microscopy shows that after irradiation polymeric bilayer films color changes with ion fluences. The FTIR spectra evidenced a very small change in cross-linking and chain scissoring at high fluence. Dielectric constant decreases while dielectric loss and AC conductivity increase with ion fluences.     

Production of TiN thin films by N2-laser-ablated Ti atoms in nitrogen gas atmospheres

Laser ablation has proven to be an important technique for thin film deposition because of the high velocity heating and quenching of materials. We have used a nitrogen laser, which is capable of producing nanosecond pulses of intense UV (337.1 nm) radiation to generate high-temperature and high-electron-density plasmas when strongly focused on titanium targets. Laser beam pulses with a peak energy of 32 J/cm² and a power density of 1.6 GW/cm² were used in this experiment. As ablated Ti species are allowed to expand further in a nitrogen atmosphere, they cool down and eventually dissipate. In this sequence, they meet a substrate where condensation, nucleation, and growth processes yield TiN thin films because of the reaction with the nitrogen gas. Thin film depositions were made on stainless steel (AISI 1020 and AISI 304) substrates at nitrogen gas pressures ranging from 10^-1 Pa to 200 Pa and for different distances between the substrate and the spot where the laser beam was focused upon the target. For rather short distances (less than 7 mm), optical microscopy shows the effect of a further plasma-thin film interaction, while at larger distances, the depositions exhibit a regular film condensation from the vapor. Microstructure characterization of the thin film deposited was done by several techniques. The typical cubic TiN phase was identified by transmission electron microscopy (TEM) and energy dispersion spectroscopy (EDS).     

The effect of TiN nanoparticles deposition with different number of shots on SS316L by plasma focus device

In this paper, we present the result of TiN nanocrystalline deposition on SS316L, using a 4 kJ plasma focus (PF) device for 10, 20, and 30 focus shots. The effect of different number of focus shots on micro-structural changes of thin film is characterized by field emission scanning electron microscope. Existence of grains in different size confirms the formation of TiN nanocrystals on the surface of SS316L substrate. X-ray diffraction (XRD) reveals the formation of a nanocrystalline titanium nitride coating on the surface of SS316L samples. The crystalline size of TiN obtained from XRD data is strongly dependent on the number of focus shots. Thickness of the elements found on the surface of the treated sample that obtain by Rutherford backscattering spectroscopy (RBS) analysis is in the range of 150×10¹⁵?200×10¹⁵ atoms/cm². All the existence elements in the coated samples are identified by Particle Induced X-ray Emission (PIXE) spectra. Investigation on the corrosion resistance of TiN coatings was performed using an electrochemical potentiodynamic polarization. Our results suggest that TiN nanocrystalline implantation with proper ion fluences using PF can significantly improve the corrosion resistance of SS316L.     

Simulation of high fluence fast neutron damage with heavy ion bombardment

316 stainless steel has been irradiated with 5 MeV Cu ions to a fluence of 2 × 10¹⁶ ions/cm² at 500°C. Transmission electron microscopy of this sample reveals that 6 × 10¹⁵ voids/cm² of average diameter equal to 180 Å were produced. A method for correlating the fluence of ions with equivalent neutron fluences is described. This method predicts that the Cu bombardment in this study should produce a microstructure similar to that found in steel irradiated with 2–5 × 11²² neutrons/cm². A comparison of the ion produced voids with those found after previous neutron irradiation experiments confirms this prediction.