Xiaoji Zhang

Electrical properties of polymer modified by metal ion implantation

Abstract Polyethylene terephthalate (PET) has been modified by Ag, Cr, Cu and Si ion implantation with a dose range from 1×10 16 to 2×10 17 ions cm −2 using a metal vapor vacuum arc (MEVVA) source. The electrical properties of PET have been changed after metal ion implantation. The resistivity of implanted PET decreased obviously with an increase of ion dose. When metal ion dose of 2×10 17 cm −2 was selected, the resistivity of PET could be less than 10 Ω cm, but when Si ions are implanted, the resistivity of PET would be up to several hundred Ω cm. The results show that the conductive behavior of a metal ion implanted sample is obviously different from Si implantation one. The changes of the structure and composition have been observed with transmission electron microscope (TEM) and X-ray diffraction (XRD). The surface structure is varying after ion implantation and it is believed that the change would cause the improvement of the conductive properties. The mechanism of electrical conduction will be discussed.

Formation of complex carbon films on implanted carbon layers by pulsed V=C and Ti+C dual implantation into steel

Abstract Thin carbon films and implanted C complex layers are formed using pulsed V + C and Ti + C dual implantation into H13 steel. The thickness of the C films on the implanted layers were observed by Auger analysis to be 20–50 nm. The C film can reduce the surface friction factor and induce surface lubrication. The surface hardening properties of pulsed Ti + C and V + C were studied. Solid solution hardening was obtained for implanted atom concentrations of 20–45 at.%. Fine grains and dense dislocations were observed by transmission electron microscopy, so fine grain hardening and dislocation hardening are expected. The dispersion hardening phases were distinguished by X-ray diffraction and electron spectroscopy to be Fe 2 Ti, FeV, TiC and VC.

Behavior of PET implanted by Ti, Ag, Si and C ion using MEVVA implantation

Abstract Polyethylene terephthalane (PET) has been modified with Ti, Ag, Si and C ions from a metal vapor arc source (MEVVA). Ti, Ag, Si and C ions were implanted with acceleration voltage 40 kV to fluences ranging from 1×1016 to 2×1017 cm−2. The surface of implanted PET darkened with increasing ion dose, when the metal ion dose was greater than 1×1017 cm−2 the color changed to metallic bright. The surface resistance decreases by 5–6 orders of magnitude with increasing dose. The resistivity is stable after long-term storage. The depth of Ti- and Ag-implanted layer is approximately 150 and 80 nm measured by Rutherford backscattering (RBS), respectively. TEM photos revealed the presence of Ti and Ag nano-meter particles on the surface resulting from the high-dose implantation. Ti and Ag ion implantations improved conductivity and wear resistance significantly. The phase and structural changes were obtained by X-ray diffraction (XRD). It can be seen that nano-meter particles of Ti precipitation, TiO2 and Ti-carbides have been formed in implanted layer. Nano-hardness of implanted PET has been measured by a nano-indenter. The results show that the surface hardness, modulus and wear resistance could be increased.

Measurement of some parameter on MEVVA ion source

The charge density and the charge state distribution of ions extracted from metal vapor vacuum arc ion source have been measured by single, double probe, and time of flight systems, and the ion beam density distributions near the extracting electrode have been measured with and without a cusped magnetic field in order to improve the performance of ion beams. The charge state distributions as a function for many operational cathode materials were investigated.

Mevva ion source for the application of material surface modification

Several versions of Mevva ion sources have been developed in our institute since 1988. It operates in a pulsed mode with a pulse length of 1.2 ms and a repetition rate of up to 50 pps. A time‐averaged beam current of 10 or 50 mA has been extracted at 30–80 kV from Mevva IIA‐H and Mevva IIB, respectively. In order to develop surface modification of materials by ion implantation we have constructed three kinds of Mevva ion source implantation systems. High dose (3–5×1017 cm−2) implantation with Ti, Ce, Y, and Ti+C, etc. has been carried out for improving the lifetime of metal cutting tools, relay contacts, dies, and some sophisticated components.

TRIBOLOGICAL BEHAVIORS OF DUPLEX DLC/Al2O3 COATINGS FABRICATED USING MICRO-ARC OXIDATION AND FILTERED CATHODIC VACUUM ARC SYSTEM

Micro-arc oxidation technique (MAO) treatment produces a layer of alumina film on the surface of the aluminum alloy. A hard and uniform tetrahedral amorphous carbon film (diamond-like carbon, DLC) was deposited on the top of the alumina layer of the 2024 aluminum alloy by a pulsed filtered catholic vacuum arc (FCVA) deposition system with a metal vapor vacuum arc (MEVVA) source. The morphology and tribological properties of the duplex DLC/Al2O3 coating were investigated by a scanning electron microscope (SEM) and a ball-on-disk sliding tester. These results suggested that the duplex DLC/Al2O3 coating had good adhesion and a low friction coefficient, which improved significantly the wear resistance of aluminum alloys.

Structural and mechanical properties of amorphous carbon films deposited by the dual plasma technique

Abstract Direct current metal filtered cathodic vacuum arc (FCVA) and acetylene gas (C2H2) were wielded to synthesize Ti-containing amorphous carbon films on Si (100). The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the (111) preferential crystallographic orientation exists in the film, and the main existing pattern of carbon is sp2. With increasing the acetylene flow rate, the contents of Ti and TiC phase of the film gradually reduce; however, the thickness of the film increases. When the substrate bias voltage reaches −600 V, the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa, respectively, and the friction coefficient of the film is 0.25.

NANOCOMPOSITE nc-TiC/a-C:H FILMS FABRICATED BY DUAL PLASMA TECHNIQUE

Nanocomposite nc-TiC/a-C:H films have been deposited via filtered cathodic vacuum arc technique, employing Ti target and C2H2 gas as material precursors. The composition and nanostructure of film, correlated to mechanical and tribological properties of film, are varied by changing C2H2 flow rate and filter coil current. Glancing angle X-ray diffraction has been used to show that salient TiC (111) peak exists in film with grain size of order of 8–10 nm, as a function of filter coil current. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) investigations demonstrate that the nc-TiC/a-C:H films mainly contain nanocrystalline graphite and sp2-bonded carbon, both as a function of C2H2 flow rate. Mechanical tests confirm that the nc-TiC/a-C:H films possess superior hardness of 33.9 GPa and elastic modulus of 237.6 GPa.

Property improvement of multilayer TiN/Ti films with C+ implantation

Using the MEVVA ion source, carbon ions have been implanted in TiN coatings deposited by multiarc ion plating. The Vickers microhardness of the C+-implanted TiN films increased with the increase in the ion flux and dose. X-ray diffraction (XRD) analysis showed that the TiC phases had been formed in the films. In addition, the films had the preferred growth orientations of TiN and TiC, both of which were (111) orientation after annealing at 500°C for 30 min. Auger electron spectra analysis indicated that C+-implanted profile was in typical Gaussian-like distribution in single films. The distribution with multipeaks of C atoms was obtained in multi-layer TiN/Ti. The possibility of the multilayer films (Ti(C,N)/TiN/Ti(C,N)/TiN and Ti(C,N)/TiC/Ti(C,N)/TiC) forming using the C-implanted TiN/Ti films is presented for the first time.