Surface modification of silica glass by CHF3 plasma treatment and carbon negative-ion implantation for cell pattern adhesion

We have investigated a method for the patterning of cell adhesion on a silica glass by using two-steps of surface modification processes of CHF₃ plasma treatment and negative-ion pattern implantation. For the first step, exposure of CHF₃ plasma to silica glass (SG) was used to obtain hydrophobic surface, leading to eliminate cell-adhesion property. After treatment with RF power of 20 W and exposure time of 120 s, the hydrophobicity was occurred from the increase in contact angle of SG from 43° to 88° and its reason based on XPS analysis was due to formations of C―F, C―F₂, and C―F₃ bonds, so-called fluorocarbonated bonds. Culture of mesenchymal stem cells (MSC) and rat adrenal pheochromocytoma cells (PC12h) showed the degradation of cell adhesion property on the plasma-treated SG surface. For the second step, carbon negative-ion implantation into the hydrophobic fluorocarbonated-SG surface was used to pattern the hydrophilic region, leading to enhance cell adhesion property. The contact angle of C-modified surface decreased to 76° at conditions of 15 keV and 1 × 10¹⁵ ions/cm². XPS showed that the hydrophilicity was due to reduction of C―F_x bonds and formation of C―O and C═O bonds. After 3 days culture of MSC and PC12h on the C-implanted surface of the plasma-treated SG, a fairly good adhesion patterning of both cells was obtained on the ion-implanted regions.     

X-ray photoelectron spectroscopy study of the corrosion behaviour of galvanised steel implanted with rare earths

The present paper studies the effect of ion implantation of 2 × 10¹⁶ ions/cm² of Ce⁺ and 2 × 10¹⁶ ions/cm² of La⁺ at 150 keV on the corrosion behaviour of hot-dip galvanised steel. After implantation, galvanised steel was characterised by means of XPS previous to and following immersion in the medium. The results revealed incorporation of cerium and lanthanum on the surface as Ce₂O₃ and La₂O₃, respectively. Electrochemical impedance spectroscopy was carried out in order to evaluate its corrosion behaviour in 0.6 M NaCl during 1 month of immersion. The corrosion resistance was improved by an increase in the charge transfer resistance of the implanted specimens in the medium. This effect could be associated with changes in the morphology/microstructure of the corrosion products layer rather than in its composition variations.     

Effect of nitrogen ion irradiation on the nano-tribological and surface mechanical properties of ultra-high molecular weight polyethylene

Generation of wear debris is the principal obstacle limiting the durability of ultra-high molecular weight polyethylene (UHMWPE) in biomedical applications. Aiming to enhance UHMWPE wear resistance, surface modification with swift heavy ion irradiation (SHI) appears as a potential and attractive methodology. Contrary to ion implantation techniques, the swift heavy ions range can reach tens to hundreds microns and its extremely high linear energy is able to induce effective chemical modifications using low fluence values. Nano-wear performance and surface mechanical properties of samples of pristine and SHI irradiated (using N₂⁺ ions at 33 MeV and a fluence of 1 × 10¹² ions/cm²) were characterized by depth sensing indentation (DSI) and scanning probe microscopy (SPM). It turned out that modifications induced by irradiation at the surface layers were successful to reduce nano-wear volume and creep deformation. These improvements were related to beneficial changes in hardness, elastic modulus, hardness to elastic modulus ratio and friction coefficient.     

Surface characteristics, nano-indentation and corrosion behavior of Nb implanted NiTi alloy

NiTi shape memory alloy has been modified by Nb implantation with different implantation parameters including incident dose and current. The surface morphology and chemical components are determined by atomic force microscopy (AFM), Auger Electron Spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results show that Nb implantation leads to the formation of compact Nb₂O₅/TiO₂ thin film about 30 nm in thickness on the surface of the NiTi alloy and decreases the surface concentration of Ni. A larger incident dose or incident current causes a higher surface roughness and a higher Nb content in the implantation layer of NiTi alloy. The nano-indentation measurements indicate the obvious reduction of both nano-hardness and Young's modulus of the Nb implanted NiTi alloy in the implantation layer and even in deeper NiTi matrix. The results of potentiodynamic polarization test show that the corrosion resistance of NiTi alloy in Hanks's solution has been evidently improved by Nb implantation. The NiTi alloy with a moderate implantation parameter of 1.5 × 10¹⁷ ions/cm² and 2 mA exhibits the best corrosion resistance ability.     

Nano-wear, nano-hardness and corrosion-resistance of electroplated nickel surfaces after co-implantation of Cr and N2 ions

In this work, a successful sequential co-implantation treatment of Cr⁺ and N₂⁺ ions into electrodeposited nickel plates is presented. The goal of this treatment is the simultaneous enhancement of the wear resistance, mechanical stability and corrosion-protection properties of the Ni surfaces. The ion-implanted surfaces have been characterized by glow-discharge optical-emission spectroscopy, X-ray diffraction, nano-hardness, roughness, nano-wear and potentio-dynamic corrosion tests. It has been observed that the implantation of Cr⁺ or N₂⁺ alone is not sufficient to achieve simultaneously the enhancement of both the wear-resistance and the corrosion-protection properties. Conversely, the sequential implantation of Cr⁺ and N₂⁺ at 140 keV and fluencies of 3 × 10¹⁷ and 1.5 × 10¹⁷ ions/cm² respectively, permits the formation of a functional surface capable of reducing both the corrosion rate and the wear rates, with respect to those exhibited by the un-implanted Ni surfaces.This treatment can be used to protect the surfaces of micro-embossing/stamping dies based on electroformed Nickel, as an alternative to other coating strategies. Furthermore, the ion implantation assures the non-modification of the net-shape and surface finish of these types of dies, which is of crucial importance when they are used for high-precision micro-texturing/imprinting applications.     

Plasma processing for surface modification of trivalent chromium as alternative to hexavalent chromium layer

Plasma source ion implantation (PSII) treatment was undertaken to improve the mechanical properties of electrodeposited trivalent chromium layers. Nitrogen ions were implanted, with energies of − 15 to − 25 keV and doses of 1, 5 and 10 × 10¹⁷ atoms cm^− 2, to modify the surface properties of Cr plating layer. The surface properties of the films were characterized by XRD, SEM, ruby-ball on disk type tribometer and nanoindenter. Polycrystalline CrN films with (200), (220) and (222) orientations were preferentially grown and numbers of surface cracks were increased by N⁺-PSII onto trivalent chromium layers. The surface hardness of the Cr³⁺ plating layer was increased from 16 to 25 GPa by N⁺-PSII. Severe wear and higher friction was observed on N⁺-PSII treated trivalent Cr plating. It seemed that the wear debris from hardened and cracked surface of the N⁺-PSII treated specimen prompted abrasive wear in the wear test. Roughness of the Cr³⁺ plating layers was smoothed with increasing implantation doses.     

Characterization of expanded austenite developed on AISI 316L stainless steel by plasma carburization

Expanded austenite generation through ion carburizing of AISI 316L using two different reactive gas mixtures (Ar 50%, H₂ 45%, CH₄ 5% and Ar 80%, H₂ 15%, CH₄ 5%) has been studied. It was found that an ∼ 14 µm surface layer of expanded austenite was developed with 30 min processing for both gas mixtures. Nevertheless, AES analyses have shown that on the ∼ 150 nm surface layer carbon in a concentration of ∼ 12% was diffused and located as carbide. For longer periods of processing, while for the gas mixture with 50% of Ar no significant modifications within those 150 nm surface layer were produced, for the gas mixture with 80% of Ar a gradual increase in the carbon concentration with time was found, with the extra carbon remaining as free carbon. The difference between both situations can be attributed to the different resulting current densities that have been of 7.0 mA cm^− 2 and 8.1 mA cm^− 2 for 50% and 80% of Ar respectively. Higher current densities result in higher carbon and Ar ions fluxes inducing, from one side surface element concentration modification through sputtering, and from the other the enhancement of carbon diffusion on the first hundred nanometers of the surface layers. This free carbon on top of the surface layers can act as solid lubricant reducing wear rate. Nevertheless, and in spite of the fact that expanded austenite was proved to be corrosion resistant, a reduction against NaCl solution corrosion in relation to the base material was observed. This lost to corrosion resistance can be attributed to carbide development on the layers closer to the surface that can work as a trigger for localized corrosion.     

Selective single pulse femtosecond laser removal of alumina (Al2O3) from a bilayered Al2O3/TiAlN/steel coating

We studied surface modification of a double layer protective coating on steel induced by single fs laser pulse irradiation in ambient air. The outer alumina (Al₂O₃) layer, which protects against aggressive environments, was 1.7 μm thick and the titanium aluminum nitride (TiAlN) layer in contact with the steel surface had a thickness of 1.9 μm. The pulses (λ = 775 nm, τ = 200 fs) were generated by a Ti:sapphire laser source. The pulse energy was varied from 0.32 μJ to 50 μJ, corresponding to an incident laser fluence of 0.11 J cm^− 2 to 16.47 J cm^− 2. The surface damage threshold was found to be 0.20 J cm^− 2 and the alumina layer removal was initiated at 0.56 J cm^− 2. This selective ablation of alumina was possible in a wide range of fluences, up to the maximum applied, without ablating the TiAlN layer beneath.     

Study on implantation of Co ions in ZrCuNiAl bulk metallic glass

A bulk metallic glass Zr₅₅Cu₃₀Ni₅Al₁₀ with a dimension of 70 × 10 × 1 mm was prepared using copper mold suction casting. Co ion implantation was carried out in a MEVVA source system. XRD and DSC were utilized to determine the alloy's structure and thermal stability. XPS was adopted to analyze the surface composition and Co atomic concentration distribution. Micro-hardness was examined using a micro-hardness tester. The results showed, after Co ion implantation, that the alloy sample was still in an amorphous state on the whole. Ion implantation changed the thermodynamic parameters and enhanced the thermal stability of the amorphous alloy. Along the depth of the as-implanted amorphous alloy, the Co atomic concentration profile presented an M-like shape. Surface micro-hardness of the amorphous alloy was enhanced from 575.8 Hv to 662.6 Hv. In short, ion implantation can be used as an effective means of surface modification for bulk metallic glasses.     

Surface transformation of Ti-45Al-2Nb-2Mn-1B titanium aluminide by electron beam melting

Microstructure and phase evolution on the surface of Ti-45Al-2Nb-2Mn-1B (at.%) gamma based titanium aluminide was investigated by a series of electron beam melting with different beam energies and scanning speeds. X-Ray Diffraction (XRD), Glow Discharge Spectroscopy (GDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) were performed to characterize the phase modification and morphology after the EBM treatment.At beam energies of 250 W and scanning speed of 16 mm s⁻¹, the lamellar structure of Ti-45Al-2Nb-2Mn-1B transformed into a dendritic structure composed of initial α₂ (Ti₃Al) dendrites and an interdendritic phase of the γ (TiAl). While at higher energies of 350 W and lower beam speeds of 7 mm s⁻¹, mainly B2 and α₂ (Ti₃Al) phases with higher titanium formed on the surface.All Phase transformations increased the hardness of the surface to a maximum of 600 HV if compared to 330 HV for untreated material. Lower energies and higher speeds induced cracks in the surface layers, while higher energies and lower speeds produced hard surface layers without cracking.     

The beneficial role of Y-implantation on the aqueous corrosion of stainless steel

The corrosion behaviour of Y-implanted austenitic stainless steel AISI 321 samples was investigated in 0.5 M H₂SO₄ at ambient temperature using potentiodynamic polarization and cyclic voltammetry. The implantation of 1 × 10¹⁶ Y-ions/cm² of 40 keV energy did not lead to an improvement of the corrosion resistance of the material because of sputtering effects. On the other hand, a significant improvement of the corrosion resistance was observed by increasing of the dose (2 × 10¹⁷ Y-ions/cm² implanted in the presence of oxygen) and the implantation energy (55 and 80 keV). The elemental composition of the near-surface layers of the implanted steel samples prior and after the corrosion attack was determined by Rutherford backscattering spectrometry (RBS) and Nuclear Reaction Analysis (NRA) using alpha particles, protons and deuterons as projectiles. The surface morphology and microstructure of the non-corroded and corroded samples were examined by Scanning Electron Microscopy (SEM). The corrosion resistance of the implanted materials was found to be related with the thickness and the composition of the implanted layer.     

Effect of plasma surface treatment and heat treatment ambience on mechanical and corrosion protection properties of hybrid sol-gel coatings on aluminum

Hybrid sol-gel coatings derived from a base catalyzed hydrolysis of tetraethylorthosilicate and methyltriethoxysilane were deposited on aluminum substrates by a dip coating technique. Some of the coatings were deposited on substrates whose surfaces were pre-treated using atmospheric-air plasma prior to coating in order to study the effect of surface activation by plasma pre-treatment. The coated substrates were heat treated in different ambiences like air, flowing N₂ and vacuum to see the effect of heat treatment ambience on the properties of the coatings. Characterization of the coatings after heat treatment was carried out with respect to coating thickness, pencil scratch hardness, adhesion, water contact angle and their microstructure. Corrosion testing for all the coatings was carried out by electrochemical polarization measurements as well as electrochemical impedance spectroscopy in 3.5% NaCl solution for 1 h exposure time to investigate on their corrosion resistance. Coating thicknesses ranging from 1 μm-5 μm were obtained by varying the withdrawal speeds. Heat treatment in a controlled atmosphere with low oxygen content was seen to improve the hydrophobicity of coated surface, as measured by water contact angles (20^o — air; 71^o — N₂; 95^o — vacuum), thereby improving the corrosion resistance. Surface pre-treatment using open-air plasma was seen to improve the adhesion of the sol-gel coatings thus making it possible to obtain adherent and thick coatings in a single dip coating process. Both the methods of processing the coatings reduced the corrosion rate of aluminum from 1.95 mpy to 0.004 mpy in case of coatings densified in nitrogen and to 0.00068 mpy for coatings deposited on a plasma treated substrate and densified in air.     

Development and irradiation performance of stencil masks for heavy-ion patterned implantation

Heavy-ion implantation is a powerful tool to conduct atomic injection and to create buried nanoparticles with good depth-controllability in dielectric material. Metal nanoparticle composites, especially, the metal ion implanted insulators (e.g. SiO₂) with patterned nanoparticles are promising for plasmonic applications, possessing an enhanced surface plasmon resonance and nonlinear optical property as compared with randomly implanted specimens [1]. Contact masked implantation is one practical method for patterned implantation, which has advantage of reliable 2D nanoparticle spatial controllability without any abreactions. In this experiment, the Si stencil mask was made from top Si layer of SOI wafer by using e-beam lithography and plasma deep etching. The mask can be fabricated with required aspect ratio (from 3 up to 100), fine pore shape, surface flatness, and mechanical hardness. 60 keV Cu ion irradiation damage test shows that, below the fluence of 1 × 10¹⁷ ions/cm², Si stencil mask can keep dimensional stability.     

Hydrogen permeation behavior in pure nickel implanted with phosphorus, sulphur and their mixture

The entry and transport of hydrogen in phosphorus (P)-, sulphur (S)- and their mixture (P + S)-implanted nickel specimens with a fluence range of 1 × 10¹⁵ to 1 × 10¹⁷/cm² have been investigated using an electrochemical permeation technique and etching treatment (0.2% HF solution). From the hydrogen permeation transients obtained, the effective hydrogen concentration (C_H), apparent hydrogen diffusion coefficient (D_lag) and breakthrough time (t_lag) were estimated by using the time lag method in addition to the steady state permeation current density (P_∞). It was found that at a fluence of less than 1 × 10¹⁶/cm² almost all hydrogen permeation transients of the implanted nickel specimens were affected by the defects (vacancy, compressive stress and so on) generated during ion implantation process. At a high fluence of 1 × 10¹⁷/cm² the hydrogen permeation transient had a specific behavior because of the formation of amorphous phase for P, the structure change from fcc-structure to bcc-structure for S and both of them for the mixture (P and S). However, a synergistic effect of P and S was not observed on the hydrogen permeation transient. The behavior of these parameters depending on fluence and implanting element was discussed in terms of an amount of hydrogen entry site, the degree of defects, the properties of amorphous phase and structure and so on.     

Laser surface alloying of aluminium with WC + Co + NiCr for improved wear resistance

In the present study, laser surface alloying of aluminium with WC + Co + NiCr (in the ratio of 70:15:15) has been conducted using a 5 kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003 m), with the output power ranging from 3 to 3.5 kW and scan speed from 0.012 m/s to 0.04 m/s by simultaneous feeding of precursor powder (at a flow rate of 1 × 10^− 5 kg/s) and using He shroud at a gas flow rate of 3 × 10^− 6 m³/s. The effect of laser power and scan speed on the characteristics (microstructures, phases and composition) and properties (wear and corrosion resistance) of the surface alloyed layer have been investigated in details. Laser surface alloying leads to development of fine grained aluminium with the dispersion of WC, W₂C, Al₄C₃, Al₉Co₂, Al₃Ni, Cr₂₃C₆, and Co₆W₆C. The microhardness of the alloyed zone is significantly improved to a maximum value of 650 VHN as compared to 22 VHN of the as-received aluminium substrate. The mechanism of microhardness enhancement has been established. The fretting wear behavior of the alloyed zone was evaluated against WC by Ball-on-disc wear testing unit and the mechanism of wear was established.     

Corrosion behavior of electroless Ni-P alloy coatings containing tungsten or nano-scattered alumina composite in 3.5% NaCl solution

The corrosion protection performance of electroless deposited nickel-phosphorus (Ni-P) alloy coatings containing tungsten (Ni-P-W) or nano-scattered alumina (Ni-P-Al₂O₃) composite coatings on low carbon steel was studied. The effect of heat treatment on the coating performance was also studied. The optimum conditions under which such coatings can provide good corrosion protection to the substrate were determined after two weeks of immersion in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance before and after heat treatment. The Ni-P-W coatings showed the highest surface resistance compared with Ni-P-Al₂O₃ and Ni-P. The surface resistance of Ni-P-W coatings was 12.0 × 10⁴ Ω cm² which is about the double of the resistance showed by Ni-P-Al₂O₃ (7.00 × 10⁴ Ω cm²) and twenty times greater than the surface resistance of Ni-P (0.78 × 10⁴ Ω cm²). XRD analysis of non-heat-treated samples revealed formation of a protective tungsten phosphide phase. Heat treatment has an adverse effect on the corrosion protection performance of tungsten and alumina composite coatings. The surface resistance decreased sharply after heat treatment.     

PEO coatings obtained on an Mg-Mn type alloy under unipolar and bipolar modes in silicate-containing electrolytes

Protective surface layers with high corrosion resistance (R_p = 3.3·105 ohm cm²) and significant microhardness (H = 4.8 GPa), as compared to the substrate material, were obtained on MA8 magnesium alloy by bipolar Plasma Electrolytic Oxidation (PEO) in a silicate-fluoride electrolyte. The phase and elemental composition and morphology of the coatings were investigated. It was found that the application of the bipolar PEO mode enables one to synthesise on the alloy's surface a high-temperature phase of magnesium silicate, forsterite (Mg₂SiO₄) having good anticorrosion and mechanical properties.     

Corrosion behaviour of nitrogen ion implanted AISI type 304L stainless steel in nitric acid medium

The effects of nitrogen ion implantation on corrosion behaviour of 304L stainless steel in 1 N HNO₃ medium were investigated using surface analytical and electrochemical techniques. Nitrogen ion was implanted at 70 keV in the dose range of 1 × 10¹⁵, 1 × 10¹⁶, 1 × 10¹⁷ and 2.5 × 10¹⁷ N⁺/cm², respectively. Grazing incidence X-ray diffraction results for unimplanted and up to dose of 1 × 10¹⁶ N⁺/cm² showed co-existence of γ-Fe and α′-Fe and, at higher doses (1 × 10¹⁷ and 2.5 × 10¹⁷) preferential formation of chromium nitride was observed. X-ray photoelectron spectroscopy investigation confirmed the formation of chromium nitride at higher doses. Electrochemical corrosion investigation revealed nobler open circuit potential, decrease in corrosion current densities, passive current densities and increase in polarization resistance with increase in dose rate. Surface morphology analysis after polarization study using atomic force microscope showed grain boundary dissolution for unimplanted specimens and resistance to surface dissolution with increase in dose rate for implanted specimens.     

Ion beam modification of ePTFE for improving the blood compatibility

Expanded polytetrafluoroethylene (ePTFE), which is a durable biomaterial because of its excellent biological inertness, is now widely used for prostheses in clinical medicine. However, conversely, the inert nature of ePTFE results in poor adaptability to the surrounding tissue due to lack of a cell-adhesive property. In this study, the surface of ePTFE was modified with ion beam irradiation to improve the blood compatibility. The surface modification of ePTFE sheets by He⁺, Ne⁺, Ar⁺ and Kr⁺ ion beams was performed at an energy of 150 keV with fluences of 1 × 10¹⁴, 5 × 10¹⁴ and 1 × 10¹⁵ ions/cm². To investigate anti-thrombogenicity, Ca²⁺-replenished platelet-rich plasma (PRP) was placed in contact with the surfaces for 10 min. Compared to the non-modified ePTFE surface, platelet response was inhibited on the surfaces modified with He⁺, Ne⁺ and Ar⁺: 5 × 10¹⁴ and 1 × 10¹⁵ ions/cm², and Kr⁺: 5 × 10¹⁴ ions/cm²; however, platelet response was promoted on the surfaces modified with He⁺, Ne⁺ and Ar⁺: 1 × 10¹⁴ ions/cm², and Kr⁺: 1 × 10¹⁴ and 1 × 10¹⁵ ions/cm². The significant morphological changes in ePTFE surface associated with ion beam modification are thought to be one of the reasons for the inhibition of platelet response. Endothelial cells were cultured on the surfaces for 3 days to evaluate the cellular response. Endothelial cell growth was significantly promoted on all of the surfaces of ion beam-modified ePTFE, although the non-modified ePTFE surface dramatically inhibited this growth. It is concluded that ion beam modification of ePTFE surface can improve the blood compatibility through not only the promotion of endothelial cell growth but also the inhibition of platelet response.     

Corrosion behavior and surface characterization of tantalum implanted TiNi alloy

TiNi shape memory alloy has been modified by Ta plasma immersion ion implantation technology to improve corrosion resistance. The results of the polarization tests show that the corrosion resistance of TiNi alloy in Ringer's solution at 310 K has been improved by the Ta ion implantation and the Ta/TiNi sample with a moderate incident dose of 1.5 × 10¹⁷ ions/cm² exhibits the best corrosion resistance ability. The surface characterization and chemical composition of the Ta/TiNi samples were determined by Auger electron spectroscopy (AES), Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) methods. AFM images reveal that compact aggregates of nano-grains uniformly disperse on the surface of the Ta/TiNi samples. AES and XPS analyses on the Ta/TiNi sample show that the component of the surface layer is mainly composed of TiO₂ and Ta₂O₅, which is benefit to the corrosion resistance ability and biocompatibility.