Plasma-based Implantation Research Articles

Tribochemical investigation of Cr-doped diamond-like carbon with a MoDTC-containing engine oil under boundary lubricated condition

Cr-doped diamond-like carbon (Cr-DLC) coatings were deposited and investigated for their tribological properties. A hybridized deposition technique consisted of a bipolar plasma-based ion implantation and deposition (PBII&D) and magnetron sputtering was used for the deposition. Raman spectra revealed an increase of ID/IG upon the Cr introduction, indicating the embedded CrCx act as catalysts to produce sp2 sites. The coefficients of friction (COF) were effectively reduced once MoDTC was added to the base oil. X-ray photoelectron spectroscopy (XPS) confirmed the presence of MoO3, MoS2, and MoS2−xOx in the MoDTC-derived tribofilm. The contribution of MoS2−xOx decreased with the Cr content, suggesting that the wear particles of CrCx intervenes in the process of MoDTC decomposition by preventing the oxidation of MoS2 sheets.

Gradient self-organized dislocation in expanded austenite layer during low temperature nitriding

Abstract A typical nitrogen expanded austenite layer is formed by plasma-based low-energy nitrogen ion implantation (PBLEII) on AISI 304L austenitic stainless steel at a moderate temperature of 380° C. The dislocation self-organization structure in the nitrogen expanded austenite layer is characterized as an evolution from partial and Lomer-Cottrell dislocations in the inner layer near the interface to multilayer stacking faults in the outer nitrided layer. The self-organized dislocation density and forms are essentially dependent on the plastic deformation, strain-gradient, and nitrogen-related stacking fault energies, respectively, due to the constrained expansion in the nitrided layer. As the nitrogen concentration in the austenitic matrix increases, the stacking fault energy gradually decreases, resulting in the transformation of the defect from Lamer-Cottrell dislocations to a multilayer stacking faults. The appropriate stress, which is associated with orderly stress relief during dislocation self-organization, preserves the integrity of the nitrided layer with a combinedly improved in wear and corrosion resistance. Nitriding-induced dislocation self-organization is basically explored as the formation mechanism of the nitrogen expanded austenite layer, contributing to development of the specific low-temperature nitriding austenitic steel.

Positron annihilation spectroscopy of thermally annealed hydrogenated amorphous carbon films

Hydrogenated amorphous carbon (a-C:H) films are prepared using a bipolar-type plasma-based ion implantation and deposition system, followed by thermal annealing of the films at 200 °C-800 °C. The structural and compositional changes are examined by Raman spectroscopy, Rutherford backscattering spectrometry, and elastic recoil detection analysis (ERDA). Positron annihilation spectroscopy (PAS) is also conducted to investigate the behavior of voids in the films. The results of Raman and ERDA measurement clearly show that the sp2 ring clusters increase, and hydrogen content apparently decreases at temperatures between 400 °C and 800 °C. Uncorrelated behaviors between positron lifetimes and line-shape parameters are observed in the PAS results, which can be attributed to several competing effects, such as hydrogen release, bond reconstruction, and electronic-state change of voids. Furthermore, it is suggested that the graphitization of the films begins from the surface to the inside, accompanied by the hydrogen release that is related to the void behavior.

THE INFLUENCE OF SILICON ELEMENT-ADDED DLC FILM ON Ti-6Al-4V

Silicon added diamond-like carbon films fabricated from C2H2:TMS mixture were used to study the influence of silicon content on the deposition and tribological properties of films prepared on Ti-6Al-4V substrate by using plasma-based ion implantation (PBII). The structure of the film was analyzed by Raman spectroscopy. Hardness and elastic modulus of the film were measured by nano-indentation hardness tester. Tribological propertiesof the film were performed by using ball-on-disk friction tester. The results indicate that with the increasing silicon content in the pure DLC film, the friction coefficient increases. The hardness and elastic modulus of Si-DLC film can increase to a value of up to 31.1 GPa and 200.1 GPa with a silicon content of 13.1 at.%. This is because the greater C content. The Si-DLC films with Si content of 13.1 at.% (C:Si/1:2) and 14.3 at.% (C:Si/1:6) shows a low friction coefficient of 0.2, which is considerable improvement in the tribological properties. This is due to the high hardness and elastic modulus.

Effect of plasma-nitrided titanium on mechanical properties and initial cell adhesion

Titanium alloy has been widely used as an implantable material with good biocompatibility and mechanical properties. Particularly, the titanium alloy Ti-6Al-4V with surface modification has been utilized in dental applications for decades. In this study, the plasma-based ion implantation (PBII) technique was applied on the surface of Ti-6Al-4V under gaseous mixtures of N2 and Ar with a flow rate of 30 sccm and 5 sccm, respectively. X-ray photoelectron spectroscopy (XPS) showed that the titanium nitrided layer was formed on the surface of Ti-6Al-4V at the peak of 397 eV for N 1s. The effects of plasma nitride on the Ti-6Al-4V were creating a smooth surface with hydrophilic property (RRMS = 17.93 ± 0.05 nm, θ = 61.4° ± 0.36) and increasing surface hardness by ∼42%. Direct culturing with the primary human alveolar bone cells, the plasma-nitrided Ti-6Al-4V improved cell proliferation (4 and 7 days) and showed no cytotoxicity. The DAPI/rhodamine-phalloidin staining and the scanning electron microscope (SEM) were used to examine cellular morphology and initial cell adhesion. The result demonstrated that the plasma nitride enhanced the human alveolar bone cell adhesion compared with glass slides. Overall, plasma-nitridation with nitrogen and argon on Ti-6Al-4V using the PBII technique enhanced surface properties of Ti-6Al-4V and induced adhesion and proliferation of primary human alveolar bone cells, proposing that it can be a potential surface modification for dental application.

Triboelectric nanogenerator with enhanced output and durability based on Si-DLC films

As one of the working modes of triboelectric nanogenerators (TENGs), the sliding-mode TENG has a higher charge-transfer efficiency than the contact-separation mode. However, the durability and stability of these devices remain challenging for practical applications because most dielectric materials for TENGs are organic polymers. This study used Si-incorporated diamond-like carbon (Si-DLC) films as non-polymer dielectric materials for sliding-TENGs to improve output and durability. Si-DLC films with varying Si contents were prepared using plasma-based ion implantation and deposition, and their triboelectric and tribological properties were investigated. The Si-DLC film with a higher Si content exhibited a higher triboelectric output under dry conditions owing to its stronger electron-donating ability. Furthermore, it was found that the output and durability of the Si-DLC-based sliding-TENG can be further enhanced under unsubmerged water-lubricated conditions compared with those under dry conditions. This enhanced output is attributed to the more electropositive nature of water compared with that of the Si-DLC films. Moreover, the enhanced durability and stability of the Si-DLC-based TENG under water-lubricated conditions are attributed to the anti-abrasion properties of the Si-DLC films, which prevent the formation of a transferred PTFE layer on the Si-DLC surface. This research proposed an integrated strategy to enhance output and durability simultaneously, showing great potential for designing durable self-driving sensing systems in machinery.

Effect of Water Adsorption Layers on the Friction Properties of Fluorinated Amorphous Carbon Films in Ambient Air.

Fluorinated amorphous carbon (a-C:F) films with different microstructures were prepared with bipolar-type plasma-based ion implantation and deposition method by changing the negative bias voltage, and the tribological properties were investigated in ambient air. Their surface chemistry and water adsorption properties were investigated to determine their friction properties. Microstructural analysis results showed that, as the negative bias voltage increased, the density of the films decreased with the promotion of graphitization. The water adsorption properties evaluated using a quartz crystal microbalance showed that a large adsorbed water weight was observed for the films deposited at high negative bias voltages. In contrast, these films exhibited thin water adsorption layers from the measurements with an ellipsometer. These results indicate that water molecules are adsorbed on the film surface and permeate into the films, particularly for the films deposited at high negative bias voltages. The friction properties in ambient air depend significantly on their microstructure and relative humidity (RH). Regardless of the RH, the higher the negative bias voltage during film deposition, the lower the friction coefficient. Since several water molecules existed on the surface of the film deposited with a low negative bias voltage, its surface was oxidized during sliding, which increased the friction coefficient. In addition, the friction coefficient of the films increased at high RH. The number of water molecules adsorbed on the film increased as the RH increased, causing a high shear force owing to many hydrogen bonds and/or high capillary force at the friction interface.

Sliding wear performance of TiAl-based nitride coatings deposited on ADI by cathodic arc deposition and plasma based ion implantation and deposition

ABSTRACT This work studied the sliding wear performance of TiAl-based nitride coatings synthesized on austempered ductile iron (ADI) by cathodic arc deposition (CAD) and plasma-based ion implantation and deposition (PBIID). Monolayer CAD TiAlN films and bilayer CAD and PBIID TiAl/TiAlN films deposited on an experimental device were analyzed and benchmarked against a commercial bilayer CAD film. Sliding wear was evaluated in a pin–on–disc tribometer. Two test conditions were employed, one intended to prevent damage (low load, short distance) and another intended to promote damage (higher load, longer distance). Regarding low load tests, all coated samples showed friction coefficients of 0.40–0.45 and negligible wear. Regarding high load tests, all coated variants exhibited lower or equal disc and pin wear rates with respect to uncoated ADI. In addition, coated samples displayed steady-state friction coefficients between 0.2 and 0.6 while uncoated ADI steady-state coefficients between 0.6 and 0.85.

Hybrid aging and nitriding treatment of nickel aluminum bronze by plasma-based ion implantation

Nickel-aluminum bronzes (NABs) comprise a versatile group of copper-based age hardenable quaternary alloys. Their composition usually comprises aluminum, nickel, iron, and manganese, besides copper. These alloys have a large range of applications, from architectural use to naval propellers. In the present work, a case study of a specific NAB alloy of technical importance was performed aiming to investigate the difference in wear resistance between samples that were aged and samples that received a novel hybrid aging + nitriding treatment carried out on a plasma immersion ion implantation (PIII) apparatus. Both regular aging and the hybrid treatment were carried out for solution-treated coin-shaped specimens, with martensitic matrix, in a PIII chamber under a nitrogen-based atmosphere. Three different voltage biases, 8, 10, and 12 kV, resulted in three distinct treatment temperatures, 370, 400 and 470 °C, for treatment times of 180 and 90 min, being the latter (90 min) used together with the smaller voltage (370 °C) for comparison purposes. From the coin-shaped sample, it was possible to study the two distinct treatments: i) the flat-surface-side exposed to plasma was subjected to the hybrid treatment; ii) the other flat-side (directly supported on the sample holder) was only aging-treated (hereafter termed ‘aged only’). Such methodology allowed to infer the bulk effects on the surface modification process. The XRD patterns of the hybrid-mode treated (hereafter termed ‘aged + nitrided’) surfaces showed formation of nitrogen-expanded phases, these surfaces showing hardness gains varying on the 11%–27% range when compared to the respective surfaces aged only. Scratch tests, in association with hardness and elastic modulus measurements, showed the role of the aging on the elasto-plastic response of both aged only and aged + nitrided surfaces. The nitriding resulted in significant gains of wear resistance for PIII carried out at the lowest temperatures: 43% and 41% less volume loss than the respective aged only surfaces for the treatments at 370 °C for 90 min and 180 min, respectively. Differently, the treatments at the highest temperature (450 °C) resulted in the worst wear performances, since the bulk over-aging surpassed any strength delivered by nitriding.

Spectroscopic analyses of structural alterations in diamond-like carbon films deposited on zirconia substrates

Diamond-like carbon (DLC) films represent promising surface treatments for biomedical implants. In this paper, using Raman and X-ray photoelectron spectroscopies, we analyzed the effects of secondary phases present in ZrO2 substrates on the structure of DLC films fabricated by plasma-based ion implantation and deposition method, and the structural stability of the films in response to applied indentation prints. The results revealed oxygen incorporation in DLC films from the oxide substrates during deposition, and a clear dependence of sp3 carbon content on the oxygen fraction of the substrate and on gas pressure. Moreover, a pronounced structural distortion of the DLC films at the film/substrate interface was observed, which resulted from polymorphic transformation on the zirconia surface during deposition, while a pronounced change in Raman spectral morphology of carbon induced by structural alterations could also be observed around the indentation prints. The findings clearly pointed at the need to take into considerations the structural alterations of the DLC film structure at the interface associated with interfacial defects and film adhesion, especially for biomedical applications that involve surface loading.

Reduction of Insertion Torque on Orthodontic Mini-screw Implant by means of Reduced Friction

In this article, the reduction of insertion torque on the orthodontic mini-screw implants (OMI) was studied. Three types of diamond-like carbon (DLC) films (DLC, Si-DLC, and F-DLC) were deposited on the OMIs by plasma-based ion implantation technique. The maximum insertion torque (MIT) value was measured using a physiodispenser during insertion on a mandibular pig jaw. Ten OMIs of each condition were used to evaluate the MIT values compared to the Ti-6Al-4V typed OMI. The statistical analysis of data was analyzed by One-way analysis of variance (ANOVA) and Tukey HSD. The results indicated that the Ti-6Al-4V showed the highest MIT but not significantly different from the F-DLC (P >0.05). DLC and Si-DLC showed a significant reduction in MIT comparing to the Ti-6Al-4V (P <0.05). However, the Si-DLC showed the lowest MIT among groups (P <0.05). This phenomenon was due to the decreasing friction coefficient during OMI's insertion on a mandibular pig jaw. Therefore, the DLC coating, especially Si-DLC, could reduce the MIT value of OMI. It is thought that the lowering friction coefficient yields the lowering of MIT value. Keywords: Diamond-like carbon, Friction, Insertion torque, Mini-screw implant

Stability of scattered hydrogen signals from a-C:H films during He-induced elastic recoil detection analysis

The hydrogen (H) loss of hydrogenated amorphous carbon (a-C:H) films, such as polymer-like, diamond-like, and graphite-like carbon films, was evaluated during elastic recoil detection analysis (ERDA) conducted using 3.4 MeV He2+. Films were formed on Si substrates via a plasma-based ion implantation and deposition method. The Raman scattering spectrometry of the films was then conducted, and except for the case of the polymer-like carbon film that had a strong photoluminescence background, two characteristic peaks corresponding to the disorder and graphite bands were observed in all cases. ERDA measurements indicated that there was no H loss in films with weak or negligible photoluminescence, whereas a decrease in H signals was clearly observed for the film with strong photoluminescence. The polymer polyphenylenesulfide (PPS: C6H4S), which is used as a standard material for ERDA measurements, showed a significant decrease in H signals under the same conditions. In comparison with the PPS, we concluded that a-C:H films with negligible photoluminescence can be used as standard materials for ERDA measurements.

Tribological and corrosion Behavior of Duplex Coated AISI 316L using plasma based ion implantation and deposItion

The implementation of a duplex process, which combines plasma nitriding with hard coatings obtained by cathodic arc, on stainless steel substrates has faced adhesion problems that affected the wear and corrosion behavior of the treated surfaces. One variation of the cathodic arc process, which could improve the adhesion, is its combination with plasma ion implantation.This work presents results of the wear and corrosion behavior of duplex TiTiN bilayer coatings obtained by cathodic arc deposition combined with ion implantation (PBII&D) on plasma nitrided AISI 316 L stainless steel. In order to compare the application of PBII&D in duplex processes against conventional cathodic arc deposition, other two types of samples were obtained; one group of samples was coated using the same experimental device with the substrate at floating potential and the other one with a commercial PVD system.The coatings were characterized by SEM, XRD, and nanoindentation. The adhesion was evaluated by the Scratch Test and Rockwell C indentation. The wear resistance was analyzed by the pin-on-disk test and the corrosion behavior was evaluated by means of anodic polarization tests in NaCl solution, as well as by the Salt Spray Fog Test.The PBII&D bilayer coatings showed better adhesion while the commercial PVD TiN coatings presented the smallest wear volume loss, but the delamination inside and around the track evidenced adhesion problems. Corrosion resistance was improved in all coatings benchmarked against nitride substrates, but PBII&D processes offered better protection.

Antibacterial and Antifungal Activities of PMMAs Implanted Fluorine and/or Silver Ions by Plasma-Based Ion Implantation with Argon.

The purpose of this study was to examine the anti-oral microorganism effects of fluorine and/or silver ions implanted into acrylic resin (PMMA) using plasma-based ion implantation (PBII) with argon gas. The experimental PMMA specimens were implanted with F and Ag ions alone or simultaneously by the PBII method using Ar or Ar/F2 gases and Ag mesh. The surface characteristics were evaluated by X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM). Moreover, the antibacterial activity against Streptococcus mutans (S. mutans) and the antifungal activity against Candida albicans (C. albicans) were examined by the adenosine-5’-triphosphate (ATP) emission luminescence method. XPS spectra of the modified specimens revealed peaks due to F in the Ar/F and the Ar/F+Ag groups, and due to Ag in the Ar+Ag and the Ar/F+Ag groups. The water contact angle increased significantly due to the implantation of Ar, F, and Ag. In the AFM observations, the surface roughness of the Ar/F and the Ar/F+Ag groups increased significantly by less than 5 nanometers. The presence of F and Ag was found to inhibit S. mutans growth in the Ar+Ag and the Ar/F+Ag groups. However, this method provided no significant antifungal activity against C. albicans.

Formation of large area closely packed carbon onions film by plasma-based ion implantation

A substantial quantity of carbon onions in a durable film state is indispensable for its applications. In this study, large area fabrication of closely packed homogeneous carbon onion nanoparticle film using plasma-based ion implantation was demonstrated. Ag film deposited on a Si substrate was used as the implantation target for the hydrocarbon ions accelerated at 20 kV. Nanoparticles with the mean diameter of 7.5 nm were formed at the grain boundary of the Ag film. Carbon onions with the mean diameter of 17.4 nm were synthesized and arranged to a closely packed nanoparticle film with the thickness of around 200 nm by gradual thermal vaporization of the Ag. The closely packed configuration was achieved due to the isolated growth of carbon onion nanoparticle and high uniformity of the diameter. This process can be used in principle large area formation compered to typical ion implantation technique of carbon onion nanoparticle film, which can be applicable for the practical use in mechanical and electrochemical applications.

Influence of plasma-based ion implantation and deposition on the structure, internal stress and mechanical properties of nanocrystalline ZrN coatings

Influence of plasma-based ion implantation and deposition on the structure, internal stress and mechanical properties of nanocrystalline ZrN coatings

Role of nonlocal thermoelastic peaks in the stress and texture evolution of TiN coatings formed by plasma based ion implantation and deposition

A thermodynamic approach based on the concept of nonlocal thermoelastic peaks (NTP), which are generated by implanted ions, is used to explain the structure formation and stress state in TiN coatings synthesized by plasma immersion ion implantation and deposition by filtered vacuum-arc plasma. The radius, the depth of the accumulation and the temperature in the NTP are determined, depending on the energy that the ions acquire under the action of the accelerating potential. The structure and compressive stress level in the coatings are considered together, as a result of the competition between two different atomistic processes in the NTP: radiation-induced defects formation and their removal due to thermal migration. It is supposed that the result of competition provides a minimum of free energy of the synthesized coating. A structure-stress state diagram of nitride coatings deposited under conditions of ion implantation is proposed. Relaxation processes in coatings associated with decrease of stress and change of texture from [111] to [110] or [100] are activated when the peaks temperature exceeds 1/3 of the melting point Tm.

Preparation of silicon-doped diamond-like carbon films with electrical conductivity by reactive high-power impulse magnetron sputtering combined with a plasma-based ion implantation system

Silicon-doped diamond-like carbon (Si-doped DLC) films were prepared by a reactive high-power impulse magnetron sputtering (HiPIMS) combined with a plasma-based ion implantation (PBII) system, in which tetramethylsilane (TMS) was used as a reactive gas. The preparation of the Si-doped DLC films was based on both plasma-enhanced chemical vapor deposition and physical vapor deposition. The incident energy of the reactive ions was controlled by applying negative pulse voltage to the substrate using the PBII system. The Si content was controlled by the flow rate ratio of TMS to Ar. The negative pulse voltage was crucial because the resistivity of Si-doped DLC films prepared under the conditions of an Ar flow rate of 75 sccm and a TMS flow rate of 1.5sccm exponentially decreased from 575 to 30 Ωcm with an increase in the negative pulse voltage in the voltage range up to −7 kV. Through X-ray photoelectron spectroscopy, it was estimated that the Si content in the films ranged between 4.3% and 11% in our experiment. The resistivity of the films, which were prepared at a negative pulse voltage of −5 or − 7 kV in the range of the flow rate ratio up to 0.043, markedly increased from 3 to 380 Ωcm with an increase in the Si content. Moreover, the film hardness ranged between 9 and 16 GPa.

Co-existence of γ'N phase and γN phase on nitrided austenitic Fe–Cr–Ni alloys- I. experiment

The formation of a metastable and nitrogen-supersaturated f.c.c. interstitial solid solution layer on Fe–Cr–Ni austenitic stainless steel at a moderate temperature around 650–720 K is not entirely understood. In the present work, three groups of austenitic Fe–Cr–Ni alloys, containing systematic variations of chromium, nickel and iron contents were nitrided by plasma-based low-energy ion implantation at 653 K for 4 h and investigated with light-optical microscopy (LOM), electron probe microanalysis (EPMA), (grazing incidence) X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial AISI 304L was included for comparison. For the austenitic alloys with a Cr content below 12 wt.%, a duplex layer is observed in the nitrided case where the interface between the top layer, consisting of γ'-Fe4N like ordered γ'N, and the disordered γN (nitrogen enriched austenite) zone underneath is associated with a decrease in N content. For the alloys with a Cr-content over 12 wt.%, a featureless continuous zone is observed with LOM and a gradual decrease in nitrogen content is measured with EPMA. Nevertheless, a similar duplex structure of outer γ'-Fe4N like ordered γ'N and inner γN is confirmed by XRD and TEM for all nitrided alloys, irrespective of the Cr content. The results are discussed in terms of the short-range order (SRO) promoted by the Cr–N interaction and long-range order (LRO) caused by the Fe–N interaction.

Frictional and Mechanical Properties of Surface Modified Nickel-Titanium Orthodontic Archwires

The purpose of this study was to investigate the surface hardness, frictional force and load-deflection characteristic of three types of nickel-titanium archwires; DLC-coated, CH4-PBII and CF4-PBII NiTi orthodontic archwires. The NiTi wires were deposited with DLC films and were implanted with CH4 and CF4 using Plasma-Based Ion Implantation and Deposition (PBIID) method. These archwires and upper canine brackets with slot dimension of 0.022-inch were used in this study. Surface hardness of three types of surface modified NiTi orthodontic archwires was measured using atomic force microscopy (AFM). Frictional resistance was determined using a Universal Testing Machine with a load cell of 50 N. The custom-fabricated friction-testing device was designed and bonded each bracket in an accurate position. Load-deflection characteristic was evaluated by conducting the three-point bending test with universal testing machine. The results showed that DLC-coated NiTi wires had the lowest mean of frictional force followed by CH4-PBII, CF4-PBII and conventional NiTi wires. DLC-coated NiTi wires had the highest mean of surface hardness and there was no significant difference in the unloading force at 0.5, 1.0, 2.0 and 3.0 mm of the load-deflection graphs between different types of NiTi orthodontic archwires. The results can be concluded that the surfaces of nickel-titanium orthodontic archwires can be successfully modified by the PBIID method to increase surface hardness and reduce frictional force between stainless steel brackets and NiTi archwires. The load-deflection characteristics of three types of surface modified archwires remain unchanged.