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The nonuniform plasma caused by plasma diffusion and the incomplete plasma recovery during short pulse-off time have great influences on the sheath dynamics and the implantation efficiency in plasma-based ion implantation (PBII). In this paper, a magnetized plasma diffusion fluid model is established to describe the plasma diffusion in PBII process. Together with a magnetized sheath fluid model, the full pulse period including sheath dynamics during pulse-on time and plasma recovery during pulse-off time can be described, and the models are verified to be accurate by comparing with experimentally measured electron density profiles. The influence of process parameters on sheath dynamics, the influence of incomplete plasma recovery under multi-pulse bias on implantation efficiency are investigated by solving the presented models with considering plasma diffusion. It is found that the variations of process parameters which accelerate the plasma diffusion reduce the steady-state sheath thickness and increase the ion implantation current, and vice versa. Change the pulse frequency from 1 kHz to 100 kHz under typical PBII process parameters significantly increases the average ion implantation current density, and the limiting factor which affects the implantation efficiency is converted from duty cycle to plasma diffusion. Increasing the plasma density and decreasing the transverse magnetic field are the effective methods to improve the implantation efficiency as well. The results reported here help to provide a theoretical guidance for the parameters optimization in PBII process. [ABSTRACT FROM AUTHOR]

Abstract: Plasma-based low-energy nitrogen ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition, has emerged as a low-temperature surface engineering technique for metal and alloy. In this paper, the pure metal Ti samples have been modified by the plasma source ion nitriding process at a process temperature of 700°C for a processing time of 4h. The nitrided Ti surfaces were constructed of a continuous and dense Ti2N compound layer about 2μm thick and a 7–8μm diffused layer. During tribological test on a ball on disk tribometer against the Si3N4 ceramic counterface, a low friction coefficient of about 0.3 and the faint wear volume were obtained for the nitrided Ti samples. The cyclic polarization curves of the nitrided Ti samples in 3.5% and 6.0% NaCl solutions showed that the improved pitting corrosion resistance with an increase of corrosion potential and a decrease of passive current, compared with that of the unnitrided Ti sample. The plasma source ion nitriding of the Ti samples provided the engineering surfaces for the functional applications with the combined improvement in wear and corrosion resistance. [Copyright &y& Elsevier]

Abstract: Al ions with ion energy of 120 keV are implanted into Fe under ion current density of 3.18 μA/cm2 to implantation doses of 5×1016 and 1×1017 ions/cm2 at room temperature and elevated temperatures of 250 and 500 °C, respectively. At 250 °C, the distribution depth of implanted Al reaches 160 nm with a peak concentration of 6 at.% at the dose of 5×1016 ions/cm2, and 180 nm with 10 at.% at 1×1017 ions/cm2, analyzed by Rutherford backscattering spectroscopy, respectively. At 500 °C, the implantation depth is 200 nm and the maximum concentration of Al is 10 at.% at the dose of 1×1017 ions/cm2. With 5×1016 ions/cm2, the intermetallics Al13Fe4 is formed in the Fe samples at 500 °C, revealed by X-ray diffraction. With 1×1017 ions/cm2, the phase is also detected at 250 °C. The concentration-depth profiles of implanted Al in Fe samples at the room temperature, 250 °C and 500 °C are calculated by a mass transfer model that is built based on the transport of ions in matter and the irradiation enhanced diffusion. The calculated concentration-depth profiles are in reasonable agreement with those obtained from the experiments. [Copyright &y& Elsevier]

Abstract: The Al ion implantation into AZ31 magnesium alloy is carried out in a MEVVA 80-10 ion implantation system with an ion implantation dose ranging from 2×1016 ions/cm2 to 1×1017 ions/cm2 at an ion energy of 40–50 keV. The concentration–depth profile of implanted Al in AZ31 magnesium alloy was a Gaussian-type distribution in the depth up to about 840 nm with the maximum Al concentration up to about 10 at.% measured by using Rutherford backscattering spectrometry (RBS). The microstructure, which is composed of α-Mg phase, intermetallic β-Mg17Al12 and MgO phases is observed on the ion implanted samples by X-ray diffraction (XRD). Potentiodynamic anodic polarization curves in 0.01 M NaCl solution with pH=12 showed that the increase of corrosion potential and pitting breakdown potential and the decrease of the passive current density are obtained for the Al ion implanted samples. The Al ion implanted AZ31 magnesium alloy with the ion implantation dose of 2×1016 ions/cm2 achieved the high pitting breakdown potential to about −1000 mV(SCE). The wear rate of the Al ion implanted AZ31 magnesium alloy is approximately reduced by 30–40%, compared with that of the unimplanted sample. [Copyright &y& Elsevier]

Abstract: The Er3+-doped Al2O3 films were prepared by sintering Er-ion-implanted γ-AlOOH xerogel films on SiO2/Si(100) substrates. In a cycle, the γ-AlOOH xerogel films about 50 nm thick were dip-coated using aluminium isopropoxide-derived γ-AlOOH sols; the Er ions were then implanted into the γ-AlOOH xerogel films using an ion energy of 45 keV with different doses of 5×1014 to 1×1016 ions cm−2. Er3+-doped Al2O3 films were formed after 1, 2, and 4 cycles of dip-coating and implantation at different sintering temperatures of 800–1200 °C. The photoluminescence (PL) spectra were observed with a main peak at 1.533 μm and a side peak at 1.549 μm for all the Er3+-doped Al2O3 films. The intensity of PL peak of the Er3+-doped Al2O3 film obtained after 4 cycles with 5×1015 ions cm−2 dose at every cycle and sintered at 900 °C for 5 h, increased by about 10 and 3 times compared with that of the films obtained after 1 and 2 cycles. At the same sintering temperature of 900 °C, the intensity of PL peak of the Er3+-doped Al2O3 films first increased with the increase of dose from 5×1014 to 5×1015 ions cm−2 at every cycle, and then a saturation tendency was observed when the dose further was increased to 1×1016 ions cm−2. For the samples using 5×1015 ions cm−2 dose at every cycle, the PL intensity increased with the increase of sintering temperature from 800 to 1200 °C. [Copyright &y& Elsevier]

Abstract: 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 (γN) layer about 10μm thick at the temperature of 380°C during 4h with the high microhardness of HK0.1N 22.0GPa. 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 HK0.1N 15.5GPa. 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. [Copyright &y& Elsevier]

Abstract: A mass transfer model for metal ion implantation into a metal target at elevated temperatures has been built up based on transport of ions in matter and radiation enhanced diffusion. It is used to calculate concentration-depth profiles and compositional changes of the implanted species. The ion implantation at elevated temperatures was simulated by a dynamic Monte Carlo (MC) method, which takes into account a local saturation in the crystalline target by using a maximum atomic fraction allowed in the matrix. For the diffusion process, the transport of the implanted species was obtained from the diffusion equations for the implanted species and nonequilibrium vacancies. The radiation enhanced diffusion coefficient was obtained by taking into account linear annealing of the defects. A nonequilibrium vacancy source function and surface sputtering were introduced into the diffusion equations. Concentration-depth profiles of Cr, Fe and Ni ions implanted into Al at a temperature range from 200 to 510°C were calculated. The calculated results principally were consistent with measured concentration-depth profiles obtained by Rutherford backscattering spectroscopy (RBS). In some cases deviations occur, which are discussed. [Copyright &y& Elsevier]

Abstract: Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion-enhanced deposition, has emerged as a low-temperature surface engineering technique for steel and alloys. In this work, the effects of nitrogen alloying on the wear and corrosion resistance of the plasma source ion nitrided 1Cr18Ni9Ti austenitic stainless steel have been investigated in order to produce a combined improvement in wear and corrosion resistance. A high-nitrogen face-centered-cubic (f.c.c.) phase (γN) with the different nitrogen contents formed on the nitrided stainless steel was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing-angle X-ray diffraction and transmission electron microscopy. The wear tests were performed on a pin-on-disc tribometer in which the γN-phase samples were rubbed against a hardened Cr12MoV high-alloy steel disc (HRC 62–63) under a normal load from 2.2 to 39 N using Cr2O3 powders in machine oil as the abrasive media. The corrosion resistance was analyzed in 1% NaCl and 0.5 mol l−1 H2SO4 solutions by the electrochemical polarization technology. The γN-phase samples have a high microhardness of about HK0.1N 22 GPa and a high load-bearing capability, leading to significant improvement in wear resistance, especially under the high normal loads. The high nitrogen content in the γN phase resulted in higher wear resistance through the formation of a thicker hardened layer. The γN-phase samples have a high pitting corrosion resistance and a similar general corrosion resistance compared with those of the original stainless steel. The nitrogen content in the γN phase mainly affected the pitting corrosion resistance and slightly affected the general corrosion resistance. [Copyright &y& Elsevier]

Abstract: In order to apply the inner surface modification of the tube component by plasma-based ion implantation (PBII) technique, the tube size has been characterized by introducing a characteristic parameter – the critical radius of tube (CRT) to optimize the process parameters of a grid-enhanced PBII technique for the nitrogen ion implantation onto the inner surface of an Fe–Cr–Ni stainless steel tube under the process conditions, including the plasma density of central plasma source, the steady pulse voltage, the grid electrode radius, and the processing pressure. The temporal sheath dynamics of the ion matrix sheath on the inner surface of the tube component modified by PBII were demonstrated by the collisional fluid model using the equations of ion continuity and ion motion, Poisson’s equation, and Boltzmann’s relationship of electron to determine the effective range of the process parameters. The optimum process parameters were found by the effect factors of the CRT which was bounded by the two important process parameters, i.e. the ion implantation dose and the processing time, for the engineering practice due to the available dependence on the surface modification effect in suitable costs. [Copyright &y& Elsevier]

Abstract: The model of effective heat of formation in metal-Al binary system proposed by Pretorius et al. was developed based on characteristics of the solid-state reaction at interface to predict the formation of intermetallics during metal ion implantation into Al substrate at elevated temperature. For the Fe, Hf, Mo, Nb, Ni, Ta and Zr ion implantation with the ion energy of 50–140keV under the ion current density of 10–60μA/cm2 into Al substrate to the implantation dose of 1017–1018 ions/cm2 at the elevated temperature ranging from 300°C to 600°C, the model of effective heat of formation predicted the formation of intermetallics Al13Fe4, HfAl3, MoAl12, NbAl3, NiAl3, TaAl3 and ZrAl3, which were consistent with the experimental results. Taking the kinetic factors and the limitation of thermodynamic data into account, the model of effective heat of formation explained the formation of metastable intermetallics Cr14Al86 at the lower temperature of 400°C and of the stable intermetallics Cr2Al13 at the higher temperature of 510°C, and the formation of simple intermetallics VAl3 relative to complex intermetallics V4Al23, VAl7, and VAl10, for the Cr and V ion implantation into Al substrate, respectively, at the elevated temperature up to 510°C. [Copyright &y& Elsevier]

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'-Fe 4 N like ordered γ' N , and the disordered γ N (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'-Fe 4 N like ordered γ' N and inner γ N 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. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: A multi-purpose high voltage pulse (HVP) supply was developed for PIII&D process, to provide bias voltage of DC, HVP and HVP+DC to the workpiece. The pretreatment (sputtering cleaning) of the workpiece, ion implantation, hybrid PIII&D or normal deposition, can be finished in one vacuum cycle. In the system a vacuum bend-guide microwave ECR source is used to produce plasma. Ti/TiN x coating was prepared in this biasing manner with the PIII&D system. The result shows that the adhesion of the coating is enhanced with the HVP+DC composite biasing when the pulse amplitude and the DC voltage are chosen properly. The deposition rate can be maintained relatively high at an intermediate level between the conditions with pure HVP and DC bias. This work shows that the composite biasing is an effective method to improve the coating''s properties in PIII&D process. [Copyright &y& Elsevier]