Chunzhi Gong

Microstructure and mechanical properties of TiN/TiAlN multilayer coatings deposited by arc ion plating with separate targets

Abstract TiN/TiAlN multilayer coatings were prepared by arc ion plating with separate targets. In order to decrease the unfavorable macroparticles, a straight magnetized filter was used for the low melting aluminium target. The results show that the output plasmas of titanium target without filter and aluminium target with filter reach the substrate with the same order of magnitude. Meanwhile, the number of macroparticles in TiN/TiAlN multilayer coatings deposited with separate targets is only 1/10–1/3 of that deposited with alloy target reported in literature. Al atom addition may lead to the decrease of peak at (200) lattice plane and strengthening of peak at (111) and (220) lattice planes. The measured hardness of TiN/TiAlN multilayer coatings accords with the mixture principle and the maximum hardness is HV2495. The adhesion strength reaches 75 N.

Novel plasma immersion ion implantation and deposition hardware and technique based on high power pulsed magnetron discharge

A novel plasma immersion ion implantation technique based on high power pulsed magnetron sputtering (HPPMS) discharge that can produce a high density metal plasma is described. The metal plasma is clean and does not suffer from contamination from macroparticles, and the process can be readily scaled up for industrial production. The hardware, working principle, and operation modes are described. A matching circuit is developed to modulate the high-voltage and HPPMS pulses to enable operation under different modes such as simultaneous implantation and deposition, pure implantation, and selective implantation. To demonstrate the efficacy of the system and technique, CrN films with a smooth and dense surface without macroparticles were produced. An excellent adhesion with a critical load of 59.9 N is achieved for the pure implantation mode.

Flexible system for multiple plasma immersion ion implantation-deposition processes

Multiple plasma immersion ion implantation-deposition offers better flexibility compared to other thin film deposition techniques with regard to process optimization. The plasmas may be based on either cathodic arc plasmas (metal ions) or gas plasmas (gas ions) or both of them. Processing parameters such as pulsing frequency, pulse duration, bias voltage amplitude, and so on, that critically affect the film structure, internal stress, surface morphology, and other surface properties can be adjusted relatively easily to optimize the process. The plasma density can be readily controlled via the input power to obtain the desirable gas-to-metal ion ratios in the films. The high-voltage pulses can be applied to the samples within (in-duration mode), before (before-duration mode), or after (after-duration mode) the firing of the cathodic arcs. Consequently, dynamic ion beam assisted deposition processes incorporating various mixes of gas and metal ions can be achieved to yield thin films with the desirable prop...

Oxygen Plasma Ion Implantation of Biomedical Titanium Alloy

Titanium alloys have attracted more attention as biomaterials. Plasma ion implantation is utilized in this paper to improve the bioactivity, wear resistance, and corrosion resistance of Ti6Al4V alloy. As an effective surface-modification technique, plasma ion implantation eliminates the limitation of light of sight compared to conventional beam ion implantation. The plasma is excited by an RF power ranging from 200 to 400 W with sample bias of 20 kV. The results show the improvement in hardness, corrosion resistance, and tribological properties. Longer treatment time or higher RF power leads to a higher wear resistance. The friction coefficient rapidly increases at 500 s with the sample treated with the RF power of 400 W, while it changes abruptly at 1500 s with the sample processed with the RF power of 600 W. After the treatment, the corrosion resistance is considerably improved, which demonstrate that the potential of the samples shift positively while the corrosion current decreases substantially. The corrosion current may decrease by a factor of six compared to that of the control sample. The precipitates containing phosphorous and calcium appear, indicating a better activity while nothing grows on the untreated sample

Low energy-consumption plasma electrolytic oxidation based on grid cathode

Plasma electrolytic oxidation (PEO) has attracted widespread attention owing to the simplicity of operation and the excellent properties of the formed coating. However, wider applications of PEO have been limited due to the high power consumption. This work describes the design and performance of a novel technique named shorter distance PEO (SD-PEO), which is intended for lowering the energy consumption. The key feature of the method is the application of grid cathode to eliminate the gaseous envelope effect and to block of the exchange of charge carries during SD-PEO process. Compared to PEO carried out at a normal electrode distance, e.g., 50 mm, both the voltage drop and the joule heat consumed in the electrolyte at a shorter distance, e.g., of 5 mm (SD-PEO) are relatively small. Consequently, the energy consumption rendered by the novel SD-PEO method may decrease by more than 25%. Our results reveal that SD-PEO is a low energy-consumption microarc oxidation technique with more potential in industry applications.

High voltage pulser with a fast fall-time for plasma immersion ion implantation

A novel high voltage (HV) modulator that offers a short fall time to minimize sputtering effects and allow more precise control of the incident ion fluence in plasma immersion ion implantation is described. The use of 36 insulated-gate bipolar transistors in the 30 kV hard-tube pulser reduces the HV fall time to 3.5 μs, compared to a fall time of 80 μs if a pull-down resister is used. The voltage balance is achieved by a voltage-balancing resistor, clamped capacitance, and the synchronization of drive signals. Compared to the traditional method employing a pull-down resister or an additional hard tube, our design consumes less power and is more economical and reliable.

Plasma Immersion Ion Implantation Into Inner Surface of Cylindrical Bore Using Moving Auxiliary Electrode

Plasma immersion ion implantation into inner surfaces of tubes has practical importance, but intrinsic drawbacks such as poor dose uniformity and small equivalent ion flux have limited wider applications. In this paper, a new technique utilizing a moving auxiliary electrode inside the tube to improve the dose uniformity and ion implantation efficiency is described. The effects of the moving auxiliary electrode are investigated by 2-D particle-in-cell simulation. The results show that, when the grounded auxiliary electrode is withdrawn along the axis of the tube, external ions are continuously attracted into the tube and implanted into the interior wall. It is verified by the incident dose peak when the auxiliary electrode is kept at a certain location inside the tube. Uniform ion implantation into a cylindrical bore can be accomplished by physical translation of the electrode, and this technique is suitable for implantation of long tubes without an internal plasma source.

Direct coupling of pulsed radio frequency and pulsed high power in novel pulsed power system for plasma immersion ion implantation

A novel power supply system that directly couples pulsed high voltage (HV) pulses and pulsed 13.56 MHz radio frequency (rf) has been developed for plasma processes. In this system, the sample holder is connected to both the rf generator and HV modulator. The coupling circuit in the hybrid system is composed of individual matching units, low pass filters, and voltage clamping units. This ensures the safe operation of the rf system even when the HV is on. The PSPICE software is utilized to optimize the design of circuits. The system can be operated in two modes. The pulsed rf discharge may serve as either the seed plasma source for glow discharge or high-density plasma source for plasma immersion ion implantation (PIII). The pulsed high-voltage glow discharge is induced when a rf pulse with a short duration or a larger time interval between the rf and HV pulses is used. Conventional PIII can also be achieved. Experiments conducted on the new system confirm steady and safe operation.

Surface Treatment of Polyethylene Terephthalate Using Plasma Ion Implantation Based on Direct Coupling of RF and High-Voltage Pulse

Plasma immersion ion implantation employing hybrid radio-frequency (RF) and high-voltage (HV) pulses via a single feedthrough is an effective surface modification method. In this technique, the sample holder is connected to both the RF generator and the HV modulator in order to generate a high-density plasma in the vicinity of the sample. HV pulses are applied to the sample in between the RF pulses to conduct ion implantation. Polyethylene terephthalate (PET) samples were modified using an C2H2 plasma generated by this technique, and diamond-like-carbon films were successfully deposited. In this process, the pulsed HV changed from 2.5 to 10 kV with an RF power ranging from 0 to 150 W and an RF of 13.56 MHz. The C2H2 gas pressure was maintained at 1.0 Pa with a processing time of 15 min. Cleaning effects were observed without arcing damage with increasing sample bias from 2.5 to 10 kV. The negative bias and RF were observed to influence the water contact angles of treated PET samples. The plasma-implanted surface became more hydrophilic with increasing sample bias and RF power, respectively.

A Specially Designed PLC-Based High-Voltage Pulse Modulator for Plasma Immersion Ion Implantation

A novel high-voltage pulse power system based on a programmable logic controller (PLC) is developed for plasma immersion ion implantation (PIII). The PLC unit with strong anti-interference ability is utilized to optimize both electrical parameters and ion-implantation processes with manual or/and procedure modes. Specially designed periphery circuits are developed to realize the arbitrary adjustment of pulsing frequency and width which is impossible for conventional PLC systems. The electrical protection can also work rapidly in the case of a sudden short circuit. In the main power circuit, a tetrode hard tube is employed to switch the dc high voltage. In order to reduce the rise time of the pulse as much as possible, the potentials on the tetrode grids are optimized. A closed-loop system is also designed to ensure implantation voltage not to depend on the plasma load during the PIII processes. With the help of numerical calculation or simulation, the expected ion energy-number spectrum can be easily obtained.