Langping Wang

Fourth-generation plasma immersion ion implantation and deposition facility for hybrid surface modification layer fabrication

The fourth-generation plasma immersion ion implantation and deposition (PIIID) facility for hybrid and batch treatment was built in our laboratory recently. Comparing with our previous PIIID facilities, several novel designs are utilized. Two multicathode pulsed cathodic arc plasma sources are fixed on the chamber wall symmetrically, which can increase the steady working time from 6 h (the single cathode source in our previous facilities) to about 18 h. Meanwhile, the inner diameter of the pulsed cathodic arc plasma source is increased from the previous 80 to 209 mm, thus, large area metal plasma can be obtained by the source. Instead of the simple sample holder in our previous facility, a complex revolution-rotation sample holder composed of 24 shafts, which can rotate around its axis and adjust its position through revolving around the center axis of the vacuum chamber, is fixed in the center of the vacuum chamber. In addition, one magnetron sputtering source is set on the chamber wall instead of the top cover in the previous facility. Because of the above characteristic, the PIIID hybrid process involving ion implantation, vacuum arc, and magnetron sputtering deposition can be acquired without breaking vacuum. In addition, the PIIID batch treatment of cylinderlike components can be finished by installing these components on the rotating shafts on the sample holder.

(Ti, O)/Ti and (Ti, O, N)/Ti composite coatings fabricated via PIIID for the medical application of NiTi shape memory alloy.

In this investigation, the plasma immersion ion implantation and deposition (PIIID) technique was used to fabricate (Ti, O)/Ti or (Ti, O, N)/Ti coatings on a NiTi shape memory alloy (SMA, 50.8 at.% Ni) to improve its corrosion, wear resistance, and bioactivity. After coating fabrication, the structure and properties of composite coatings were studied, and the coated and uncoated NiTi SMA samples were compared with each other. Scanning electron microscopic (SEM) examination of coating surfaces and cross-sections showed that (Ti, O)/Ti and (Ti, O, N)/Ti composite coatings were dense and uniform, having thickness values of 1.16 ± 0.08 μm and 0.95 ± 0.06 μm, respectively. X-ray diffraction (XRD) results revealed that there were no diffraction peaks corresponding to TiO(2) or TiN for (Ti, O)/Ti and (Ti, O, N)/Ti composite coatings, suggesting that after the PIIID treatment, TiO(2) and TiN were amorphous or nanosized in the coatings. Energy dispersive X-ray (EDX) analysis indicated that the interface between the coating and NiTi SMA substrate was gradual rather than sharp. In addition, EDX elemental mapping of coating cross-sections showed that Ni was depleted from the surface. Differential scanning calorimetry (DSC) curves revealed that the shape memory ability of NiTi SMA was not degraded by the PIIID treatment. The width of wear tracks on (Ti, O, N)/Ti coated NiTi SMA samples was reduced 6.5-fold, in comparison with that on uncoated samples. The corrosion potential (E(corr) ) was improved from -466.20 ± 37.82 mV for uncoated samples to 125.50 ± 21.49 mV and -185.40 ± 37.05 mV for (Ti, O)/Ti coated and (Ti, O, N)/Ti coated samples, respectively. Both types of coatings facilitated bone-like apatite formation on the surface of NiTi SMA in simulated body fluid (SBF), indicating their in vitro bioactivity.

Influence of Si content on structure and mechanical properties of TiAlSiN coatings deposited by multi-plasma immersion ion implantation and deposition

TiAlSiN nanocomposite coatings were prepared by multi-plasma immersion ion implantation and deposition (MPIIID). The chemical composition, microstructure and mechanical properties of these coatings were investigated by energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nano-indentation and scratch tests. XRD patterns reveal that the main reflection in the as-deposited coating corresponds to a strong TiN (200) preferred orientation. XPS results show that AlN, Si3N4, Al2O3 and Ti2O3 are also formed in the coating. Comparing with the TiN coating, when the Si content in the coating is 0.9%, the film shows an increased hardness of 32 GPa, while its fracture toughness and adhesion strength are weak. When the Si content is increased to 6.0%, the coating exhibits a super hardness of 57 GPa as well as excellent fracture toughness and adhesion strength.

DLC Film Fabrication on the Inner Surface of a Cylinder by Carbon Ion Implantation

To synthesize good diamond-like carbon (DLC) films on the inner surface of a cylinder, C2H2 plasma should be generated uniformly in the cylinder. In this study, glow discharge C2H2 plasma was generated by a high pulsed bias voltage applied on the cylinder, and ions were accelerated and implanted into the sample by the same bias. The effect of pulse frequency of the bias and working pressure on the discharge characteristics was investigated. In addition, the ball-on-disk test and Raman spectroscopy were used to characterize the as-deposited DLC films. The test results show that wear resistance of samples increases with the applied voltage, and the friction coefficient of DLC films lies in the range of 0.15-0.20

PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications.

(Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples.

Mechanical performance and corrosion behavior of TiAlSiN/WS2 multilayer deposited by multi-plasma immersion ion implantation and deposition and magnetron sputtering

Abstract To reduce the friction coefficient of the superhard TiAlSiN composite coating, TiAlSiN/WS 2 multilayers were synthesized by multiple plasma immersion ion implantation and deposition as well as radio-frequency (RF) magnetron sputtering. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectrum, nano indentation, tribological and electrochemical tests were employed to characterize the microstructure, mechanical properties and corrosion behavior of the as-deposited multilayers. SEM results reveal that the TiAlSiN/WS 2 multilayers have a good periodicity. Nano indentation results show that the nanohardness of TiAlSiN/WS 2 multilayers is between that of the TiAlSiN and WS 2 coatings. Tribological tests prove that the friction coefficient of the TiAlSiN/WS 2 multilayers is lower and more stable than that of the TiAlSiN coating. In addition, the TiAlSiN/WS 2 multilayers show excellent corrosion resistance and the corrosion current density decreases obviously at a relative small modulation period.

Characterization of polycrystalline VO2 thin film with low phase transition temperature fabricated by high power impulse magnetron sputtering

VO2 is a unique material that undergoes a reversible phase transformation around 68∘C. Currently, applications of VO2 on smart windows are limited by its high transition temperature. In order to reduce the temperature, VO2 thin film was fabricated on quartz glass substrate by high power impulse magnetron sputtering with a modulated pulsed power. The phase transition temperature has been reduced to as low as 32∘C. In addition, the VO2 film possesses a typical metal–insulator transition. X-ray diffraction and selected area electron diffraction patterns reveal that an obvious lattice distortion has been formed in the as-deposited polycrystalline VO2 thin film. X-ray photoelectron spectroscopy proves that oxygen vacancies have been formed in the as-deposited thin film, which will induce a lattice distortion in the VO2 thin film.

Limited Sheath-Collision for Plasma Immersion Ion Implantation and its Influence on Impact Energy and Dose Uniformity

To increase the efficiency of plasma immersion ion implantation (PIII) batching, a limited sheath-collision method is proposed. Sheath-collisions between three cylinders with a triangular configuration are studied using a 3-D particle-in-cell simulation. Influences of sheath-collision extent on dose uniformity are obtained, and a criteria for determining the critical that requires that sheath-collision at the center of the triangle be avoided is proposed. In addition, depth profiles of the implanted ion obtained in PIII batching demonstrate that the critical sheath-collision value has an obvious influence on the implantation depth and dose uniformity.

Theoretical Study on Dose Distributions of the Ball Bearing Treated by Plasma Immersion Ion Implantation

A two-dimensional (2-D) particle-in-cell (PIC) model was used to study plasma immersion ion implantation (PIII) process of the ball bearing. In the simulation, distributions of the normalized potential and the accumulated incident dose were calculated. In addition, the relationship among the minimum distance between neighboring ball bearings without sheath overlap, the implantation voltage, the plasma density, and the pulsewidth was obtained. When the voltage is -10 kV, the plasma density is 2.95times108 cm-3 and the pulsewidth is 10 mus; the minimum distance without sheath overlap is 38.0 cm. To evaluate the model, the potential in the sheath was measured using a probe. Experimental results are in agreement with the calculated values. The simulation results reveal that a large number of ions are implanted into the top part of the ball bearing, which shows bad dose uniformity. When the ball bearing is revolved during PIII treatment, the dose uniformity can be improved to 91.25% at least

Low-temperature fabrication of VO2 thin film on ITO glass with a Mott transition

Polycrystalline Vanadium dioxide (VO2) thin film can be fabricated on glass substrates by high power impulse magnetron sputtering at a relative high temperature. In order to apply an effective bias voltage on substrate and control the energy of the ions impinged to the substrate, conductive indium-tin oxide (ITO) glass was used as the substrate. UV-visible-near IR transmittance spectra and X-ray diffraction (XRD) patterns of the as-deposited films exhibited that M-VO2 thin film with a metal–insulator transition temperature of 37∘C was fabricated successfully at 300∘C with a bias voltage of −200V, and the calculated average crystalline size of this film was about 12nm. XRD patterns at varied temperatures showed that the structural change of MIT of the VO2 thin film was suppressed during the phase transition process, and a pure Mott transition was obtained.