Plasma Immersion Ion Implantation And Deposition Research Articles

Surface characteristics and electrochemical corrosion behavior of NiTi coated with diamond-like carbon

Diamond-like carbon (DLC) films were produced on NiTi substrate by plasma immersion ion implantation and deposition (PIIID) at room temperature. Surface morphology and roughness were analyzed by atomic force microscopy. Film microstructure and hardness were characterized by Raman scattering spectroscopy and nano-indentation, respectively. The corrosion resistance in Hank's solution was evaluated by means of open-circuit potential (OCP) and potentiodynamic polarization techniques. It was found that, according to the corrosion potential ( E OCP), the coated sample is always more noble than the uncoated one. For the polarization curves, the shift of the breakdown potential to more positive values and the reduction of the current densities give evidence that the coating with DLC is a useful method for reducing the corrosion attack of the NiTi alloy in Hank's solution.

Surface modification of NiTi alloys using diamond-like carbon (DLC) fabricated by plasma immersion ion implantation and deposition (PIIID)

DLC films with various bias voltages were deposited on polished NiTi alloys by plasma immersion ion implantation and deposition (PIIID) using graphite as plasma precursor. Microstructure and nano-hardness of the DLC films were characterized by Raman spectroscopy and nano-indentation system, respectively. The electrochemical corrosion behavior of DLC coated and uncoated NiTi alloys is investigated in Hank’s solution by means of potentiodynamic polarization tests. The results show that on the one hand the corrosion resistance and surface hardness and elastic modulus of the NiTi alloys are remarkably improved due to the deposition of the DLC films, and on the other hand the sp 3/sp 2 ratio inferred from Raman spectra, hardness, elastic modulus and the corrosion resistance of the DLC films on the NiTi alloys first increase and then decrease with the increase of the bias voltage. It can be concluded that the corrosion resistance of the DLC films is influenced by their microstructure.

Formation of diamond-like carbon (DLC) film on the NiTi alloys via plasma immersion ion implantation and deposition (PIIID) for improving corrosion resistance

NiTi alloys are potentially useful in biomedical application due to their unique superelasticity and shape memory effect. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, Diamond-like carbon (DLC) film is fabricated on the NiTi alloys using plasma immersion ion implantation and deposition (PIIID) at room temperature to improve their corrosion resistance and block the out-diffusion of the Ni ions. The results show that the DLC films cannot only improve the corrosion resistance of the NiTi substrate, but also effectively suppress the Ni ions release from the substrate. The reason that the corrosion resistance of the coated samples is markedly improved due to the DLC films formation is systematically investigated.

Effect of diamond-like carbon (DLC) on the properties of the NiTi alloys

NiTi alloy has found wide application in the biomedical field due to its unique shape memory effect, superelasticity and biocompatibility. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, NiTi alloys were coated with diamond-like carbon (DLC) fabricated by plasma immersion ion implantation and deposition (PIIID) to improve their corrosion resistance and blood compatibility without sacrificing their shape memory effect and superelasticity. The structure of the films and the depth profiles between the films and substrate were studied using Raman spectroscopy and XPS, respectively. The phase transformation temperature, superelasticity, anticorrosion behavior and Ni ions release of the coated and uncoated sample were investigated by DSC, tensile tests, potentiodynamic polarization and AAS, respectively. The hemocompatibilty of the coated and uncoated samples was measured using clotting time and platelet adhesion. The results shows that the films is DLC accompanying with the formation of the mixing layer, and the DLC films can markedly improve the corrosion resistance and the hemocompatibility, obviously increase the ratio of albumin-to-fibrinogen and effectively block the Ni ions release of the NiTi alloys without sacrificing its superelasticity and changing its phase transformation temperature. The research results suggest DLC films prepared by PIIID could improve the in vivo performance of NiTi alloys implanted into the human body.

Effect of plasma immersion ion implantation and deposition on high temperature oxidation of titanium alloy IMI 834-aluminizing

Aluminium plays a significant role in high temperature construction materials and coatings. It helps to form continuous, protective and thermodynamically stable alumina oxide scale over their surfaces upon high temperature exposure and enhances their life significantly. However, the performance of coatings depends on the surface engineering technique that is used for application of coatings. In the present paper, plasma immersion ion implantation and deposition (PIII-D) was used to deposit aluminium coating on the titanium alloy IMI 834 under varying conditions. Subsequently, the oxidation behaviour of the alloy has been studied at elevated temperatures. The weight change data showed that the specimen that is aluminium coated followed by implantation exhibits minimum weight gain and extended period of oxide spallation when compared to uncoated and other coated specimens. XRD was used to identify the phases that formed during oxidation process. Oxide morphology was observed by SEM and the composition of oxide scales was analysed by EDS. A suitable degradation mechanism for Al coatings have been proposed based on the results obtained with different techniques.

Antithrombogenic investigation and biological behavior of cultured human umbilical vein endothelial cells on Ti-O film

Our previous research results have shown that the Ti-O films with appropriate characteristics possess great potentials for biomaterials application. In this paper, using plasma immersion ion implantation and deposition (PIII-D), titanium oxide thin films are fabricated onto silicon wafer. The antithrombogenesis of films is evaluated in vitro through the platelet adhesion investigation. The biological behavior of human umbilical vein endothelial cells (HUVEC) on the film surface is investigated in vitro by endothelial cell (EC) culture. Our results reveal that the crystalline Ti-O films exhibit attractive blood compatibility. The in vitro HUVEC-cultured investigation of Ti-O film surface has justified that the biological behavior of HUVECs on different structure surfaces is significantly different. The adherence, growth and proliferation of HUVECs to the crystalline Ti-O film surface are in order, by forming a perfect single layer, preserving the natural original shape and displaying the cobblestone road metal rank, and obviously superior to that on the amorphous Ti-O film surface. According to our study, the crystalline Ti-O film, with proper microstructure, is helpful for seeding ECs and can be used as a functional surface for the adherence and growth of ECs.

Surface Characterization and Blood Compatibility of Diamond-Like Carbon (DLC) Films on the NiTi Alloys

Diamond-like carbon (DLC) films are fabricated on the NiTi alloys at room temperature using plasma immersion ion implantation and deposition (PIIID). The effects of the substrate bias on the characteristics of the DLC films are systematically examined to correlate to the blood compatibility. The results show both the ID⁄IG ratio (inverse trend in the sp3⁄sp2 ratio) and the G peak position first decrease and then increase, while the nano-hardness first increases and then decreases with the increase of the substrate bias, and the blood compatibility of the coated sample is better than that of the uncoated sample and the DLC films on the NiTi alloys deposited at the substrate bias of 25 kV possesses better blood compatibility than the films deposited at other substrate bias. It can be concluded that the blood compatibility of the DLC films on the NiTi alloys is influenced by the sp3⁄sp2 ratio.

Characteristics and surface energy of silicon-doped diamond-like carbon films fabricated by plasma immersion ion implantation and deposition

Diamond-like carbon (DLC) films doped with different silicon contents up to 11.48 at.% were fabricated by plasma immersion ion implantation and deposition (PIII-D) using a silicon cathodic arc plasma source. The surface chemical compositions and bonding configurations were determined by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The results reveal that the sp 3 configuration including Si–C bonds increases with higher silicon content, and oxygen incorporates more readily into the silicon and carbon interlinks on the surface of the more heavily silicon-doped DLC films. Contact angle measurements and calculations show that the Si-DLC films with higher silicon contents tend to be more hydrophilic and possess higher surface energy. The surface states obtained by silicon alloying and oxygen incorporation indicate increased silicon oxycarbide bonding states and sp 3 bonding states on the surface, and it can be accounted for by the increased surface energy particularly the polar contribution.

Structure and properties of Ca-plasma-implanted titanium

Plasma immersion ion implantation and deposition (PIII-D) has been proven to be an effective approach to enhance the surface properties of various types of materials and applied in many industrial areas, such as semiconductor and biomaterials. In this work, calcium ions were implanted into and deposited onto titanium using PIII-D to improve its surface bioactivity. Based on secondary ion mass spectrometry (SIMS) results, the Ca implantation depth increases with higher bias voltages. After exposure to air, the outermost surface is found to comprise calcium hydroxide and calcium carbonate. The bioactivity of the implanted titanium was evaluated using a simulated body fluid (SBF) soaking test. After the sample was soaked in the simulated body fluid for a period of time, the calcium hydroxide on the surface dissolved gradually into the solution. At the same time, hydroxyapatite formed on the surface indicating the implantation of calcium into titanium indeed improves the bioactivity of the surface.

Behavior of cultured human umbilical vein endothelial cells on titanium oxide films fabricated by plasma immersion ion implantation and deposition

Our previous research results have shown that Ti–O films with appropriate characteristics possessed good blood compatibility. In this paper, we synthesized Ti–O films using plasma immersion ion implantation and deposition (PIII-D) and investigated the characteristics and the biological behavior of cultured human umbilical vein endothelial cells (HUVEC) onto film surface. The structure and composition of the Ti–O films were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atom force microscopy (AFM). The surface energy was measured by a contact angle method. The in vitro HUVEC-cultured investigation of Ti–O film surface justified that the biological behavior of HUVEC on different structure surfaces was significantly different. The adherence and growth of HUVEC to crystalline Ti–O film surface were much better than that of amorphous Ti–O film. The mechanism based on the relationship between the film characteristics and biological behavior of endothelial cells (ECs) is discussed.

Adhesion strength of TiN films synthesized on GCr15-bearing steel using plasma immersion ion implantation and deposition

TiN films were synthesized on GCr15-bearing steel by plasma immersion ion implantation and deposition (PIIID). During the experiments, the bias voltage was varied from −10 to −30 kV, and the ratio of implantation to deposition was adjusted from 1:10, 1:20, 1:30 to 1:40 by changing the pulse durations of the bias voltage and the vacuum arc discharge. Adhesion strength tests were carried out by scratch test. The results reveal that the adhesion strength between the film and the substrate is influenced by the bias voltage and the ratio of implantation to deposition significantly. In addition, the pretreatment of substrates and the interface layer have some impacts on the final adhesion strength.

Fabrication of titanium carbide film on bearing steel by plasma immersion ion implantation and deposition

Titanium carbide films have been synthesized by plasma immersion ion implantation and deposition (PIIID) on 9Cr18 bearing steel. During the experiments, acetylene (C 2H 2) and titanium plasmas were generated simultaneously. Acetylene plasma was produced by a radio-frequency plasma source, and titanium plasma was generated by cathodic arc plasma source. Influences of gas pressure and pulse width of the bias voltage on properties of the thin film were investigated. The as-deposited films were characterized by X-ray diffraction (XRD), micro-hardness tester, pin-on-disc tribological facility and electrochemistry corrosion equipment. XRD pattern proves that TiC phase is formed in the film. Compared with uncoated substrates, micro-hardness results reveal that the maximum micro-hardness is increased by 70.8%. In addition, the friction coefficient decreases to about 0.1, and the corrosion resistance of coated substrate surfaces is improved significantly.

Synthesis of aluminum nitride films by plasma immersion ion implantation–deposition using hybrid gas–metal cathodic arc gun

Aluminum nitride (AlN) is of interest in the industry because of its excellent electronic, optical, acoustic, thermal, and mechanical properties. In this work, aluminum nitride films are deposited on silicon wafers (100) by metal plasma immersion ion implantation and deposition (PIIID) using a modified hybrid gas–metal cathodic arc plasma source and with no intentional heating to the substrate. The mixed metal and gaseous plasma is generated by feeding the gas into the arc discharge region. The deposition rate is found to mainly depend on the Al ion flux from the cathodic arc source and is only slightly affected by the N2 flow rate. The AlN films fabricated by this method exhibit a cubic crystalline microstructure with stable and low internal stress. The surface of the AlN films is quite smooth with the surface roughness on the order of 1/2 nm as determined by atomic force microscopy, homogeneous, and continuous, and the dense granular microstructures give rise to good adhesion with the substrate. The N to Al ratio increases with the bias voltage applied to the substrates. A fairly large amount of O originating from the residual vacuum is found in the samples with low N:Al ratios, but a high bias reduces the oxygen concentration. The compositions, microstructures and crystal states of the deposited films are quite stable and remain unchanged after annealing at 800 °C for 1 h. Our hybrid gas–metal source cathodic arc source delivers better AlN thin films than conventional PIIID employing dual plasmas.

Intrinsic stress and preferred orientation in TiN coatings deposited on Al using plasma immersion ion implantation assisted deposition

TiN coatings were deposited on Al substrates using the plasma immersion ion implantation and deposition (PIIIAD) technique, employing a filtered Ti cathodic arc in a nitrogen atmosphere. Negative pulsed bias voltages between 0 to −4.0 kV were applied with varying duty cycles, at a constant time-averaged bias. Stress measurements using X-ray diffraction reveal an increase and then a decrease in the intrinsic compressive stress at increasing on-time bias. A bias-dependent preferred orientation of TiN is observed, i.e. {111}, {200} and {220} at low bias and predominantly {200} at higher bias. The hardness reduces from 29 GPa at lower bias to 20 GPa at higher bias. Thus, the time averaged energy of ion bombardment does not uniquely determine the properties of the growing coating, which can be adjusted by the on-time substrate bias applied for very short durations. A simplified subplantation model of stress development is formulated for the case of pulsed bias, the predictions of which are in reasonable agreement with the experimental data.

Substrate bias effects in plasma immersion ion implantation assisted deposition from a TiAl cathodic arc

Ti 1− x Al x thin films were deposited on stainless steel substrates using plasma immersion ion implantation and deposition (PIIIAD). A cathodic arc was employed as a source of metallic ions from Ti 0.5Al 0.5 cathode and the arc plasma was guided by a curved magnetic field filter. The resultant thin films were analyzed using Auger electron spectroscopy (AES) and X-ray diffraction techniques. A dynamic profile simulation code, TRIDYN, based on binary collision approximation was applied to understand the Ti and Al profiles in the deposited thin film. The results indicate that the film composition and phase formation depend on the applied bias, duty cycle and off time energy of the bombarding ions. The results also indicate that in PIIIAD conditions, the assumption of time averaged d.c. bias is improper to describe pulsed biasing, with deposition, resputtering and ion implantation all occurring simultaneously.

Deformation behavior of titanium nitride film prepared by plasma immersion ion implantation and deposition

Plasma immersion ion implantation and deposition (PIIID) provides a novel approach to fabricate high quality films by means of utilizing particle filtrated metal plasma and varying acceleration pulse voltages. In this work, investigation on plastic deformation of TiN films synthesized by PIIID was performed by pulling the TiN film-coated stainless steel sheet samples. The surface morphology during the pulling was observed in situ by scanning electron microscopy. No delaminating, peeling or cracking were found on the coating surfaces. The structure of the films was identified by transmission electron microscopy and atom force microscopy. It is considered that the excellent deformation behavior of the TiN film was related with the nanocrystal structure of the films and the broader film/matrix interface achieved by the PIII process.

Controlling synthesis of Ti–O/Ti–N gradient films by PIII

Titanium oxide and titanium nitrogen gradient films were synthesized using plasma-immersion ion implantation and deposition (PIIID). A intelligent control system was developed to control pushing of the metal cathode source and variation of the gas composition by programmable logical control (PLC); cathode pushing rules can be conveniently set, multi-channel gas composition control was achieved by D/A and mass flow control (MFC), and gas change has quick dynamic response velocity and a good degree of linearity. The results show that the whole system is stable and reliable, has strong anti-interference capacity and sets flexibly correlative technological parameters. The mechanical properties of the films synthesized on silicon wafer, titanium and low-temperature isotropic carbon (LTIC) were analyzed by microhardness tests, pin-on-disc wear experiments and scratch adhesion tests. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate the properties. Good mechanical properties were achieved by controlling the synthesis of the Ti–O/Ti–N gradient films discussed in this paper.

Increasing the retained dose by plasma immersion ion implantation and deposition

The retained dose of ions can be increased by Plasma Immersion Ion Implantation and Deposition (PIIID). A substrate is immersed in a metal or carbon plasma and a negative repetitively pulsed bias voltage is applied. During the pulses, an electric sheath is formed around the substrate and ions are accelerated through the sheath and implanted into the substrate. Direct and recoil ion implantation and sputtering take place during the pulses whereas low-energy deposition occurs between the pulses. The condensable plasma can be produced using a cathodic arc plasma source combined with a magnetic macroparticle filter. PIIID can be applied to perform fast high-dose implantations or to deposit thin films with broad intermixing at the film-substrate interface. The bias voltage duty cycle can be tuned to sputter away the film deposited during pulse off-time (similar to the method of sacrificial layer). We have simulated the PIIID process using the Monte Carlo code T-DYN 4.0. This code allows a calculation of the dose-dependent depth profile for a process with deposition and implantation phases, taking sputtering into account. Predicted retained doses and experimentally obtained retained doses measured by Rutherford backscattering spectrometry are compared.

Increasing the retained dose by plasma immersion ion implantation and deposition

The retained dose of ions can be increased by Plasma Immersion Ion Implantation and Deposition (PIIID). A substrate is immersed in a metal or carbon plasma and a negative repetitively pulsed bias voltage is applied. During the pulses, an electric sheath is formed around the substrate and ions are accelerated through the sheath and implanted into the substrate. Direct and recoil ion implantation and sputtering take place during the pulses whereas low-energy deposition occurs between the pulses. The condensable plasma can be produced using a cathodic arc plasma source combined with a magnetic macroparticle filter. PIIID can be applied to perform fast high-dose implantations or to deposit thin films with broad intermixing at the film-substrate interface. The bias voltage duty cycle can be tuned to sputter away the film deposited during pulse off-time (similar to the method of sacrificial layer). We have simulated the PIIID process using the Monte Carlo code T-DYN 4.0. This code allows a calculation of the dose-dependent depth profile for a process with deposition and implantation phases, taking sputtering into account. Predicted retained doses and experimentally obtained retained doses measured by Rutherford backscattering spectrometry are compared.