Wen-Zhi Li

Structure and properties of carbon nitride films synthesized by low energy ion bombardment

Carbon nitride films have been synthesized at low substrate temperature by Ar + sputtering a graphite target with concurrent N + assisted bombardment. It was disclosed that N + bombardment with low energies of 150–400 eV and beam densities of 0.16–0.23 mA cm −2 was favorable to grow carbon nitride films with high N/C atomic composition ratios of 0.47–0.56. The spectra of x-ray photoelectron spectroscopy and infrared spectroscopy show that the low energy N + bombardment activates nitrogen atoms to combine carbon atoms in unpolarized covalent bonds. Under the 150–300 eV and 0.16–0.23 mA cm −2 N + assisted bombardment, the formed films are identified by transmission electron microscopy to possess the β–C 3 N 4 microcrystalline structure. The films exhibit an extremely high hardness of 5260 kgf/mm 2 , a high resistivity of 4.8 × 10 12 Ω × cm, and excellent optical transmittance. Friction and wear tests show that carbon nitride films on steel substrate can perform the even wear in low friction coefficients of 0.05–0.16 while raising wear loads up to 20 N.

The effects of ion bombarding energy on the structure and properties of TiN films synthesized by dual ion beam sputtering

TiN films have been synthesized by dual ion beam sputtering (DIBS) deposition at the temperature below 100 °C. Ion bombardment influenced the metallographic morphology and crystalline orientation of TiN films. TiN film formed under N+ bombardment at low energy (<1 keV) consisted of fine crystal particles without texture. The film bombarded at 300 eV exhibited a hardness of 2750 kgf/mm2, which was an extremely high value for TiN films currently obtained by ion beam assisted deposition. The tribological tests demonstrated that TiN film synthesized by DIBS possessed good wear resistance.

Synthesis of boron carbide films by ion beam sputtering

Abstract Ion beam sputtering deposition technique was employed to prepare boron carbide (B4C) films at different substrate temperature. The structure and mechanical properties of the B4C films have been studied over the substrate temperature range of 50–350°C in order to study the temperature effect. Infrared spectroscopy, Auger electron spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy were used to evaluate the structural properties. The formation of B4C was found to strongly depend on the deposition temperature. It was shown that a higher deposition temperature was beneficial for the boron carbide synthesis. Hardness of these films was also thoroughly studied by micro-indentation facility. The hardness increased and reached a very high value of 43 GPa at a substrate temperature of 350°C.

Bonding structure and tribological properties of DLC films synthesized by dual ion beam sputtering

Abstract Results of DLC films synthesized on Si(111), glass and AISI 52100 bearing steel by dual ion beam sputtering at room temperature are presented. The carbon films deposited by ion beam sputtering were simultaneously bombarded by CH n + with energies of 0.2–25 keV. Infra-red and Raman spectroscopy revealed that films consisted of amorphous carbon with the structure of mixed sp 3 + sp 2 bonding. It appears that carbon films bombarded by CH n + with low energies of 200–400 eV have more sp 3 bonding and high microhardness. Tribological investigation of DLC films on AISI 52100 steel under a wear load of 15 N showed a constant friction coefficient of 0.1 and roughly stable wear factor of (0.436 ± 0.06) × 10 −6 mm 3 N −1 m −1 and, when the load surpassed 15 N, the friction coefficients and wear factor increased with the increase of load.

Ion beam assisted deposition of diamond-like carbon onto steel materials: preparation and advantages

Ion beam assisted deposition (IBAD) was used to prepare diamond-like carbon (DLC) film on steel materials at nearly room temperature. The films were synthesized by Ar+ beam sputtering of a chromium interlayer on the steel and concurrent bombardment by a mixture of Ne+-CHn+ with an energy of 300 eV. Owing to energetic Ar+ dynamic mixing at an early stage of chromium and carbon deposition, atomic intermixed layers at the DLC-Cr-steel interface and chromium carbide at the DLC-Cr interface were formed. Tribological experiments demonstrated that DLC films with the special interfacial structure undewent even wear under high Hertzian stresses of 2.55–3.22 GPa with low friction coefficients of 0.025–0.036. Low energy ion bombardment and gradient interfacial designs promise enhanced tribological performance of DLC films deposited onto steel substrates using IBAD. This may present a useful method for the deposition of DLC coatings onto steel devices for surface modification at room temperature.

TiC/metal nacrous structures and their fracture toughness increase

Multilayers of TiC and a series of metals have been fabricated by ion beam sputtering deposition to simulate nacre. The individual layer thickness varies from 1 to 10 nm, and the total thickness of the multilayers is about 1 μ m. Transmission electron microscopy (TEM), low-angle x-ray diffraction (LXRD), and high-resolution electron microscopy (HREM) show their periodicity and lattice images. A particular method is devised to evaluate the relative toughness of this artificial pearlite. It is shown that the toughness of these nanocomposite materials can be tremendously improved. A maximum of toughness appears at a certain modulation. Metals with high plasticity such as Al and Cu can produce a particularly spectacular effect on increasing the toughness of these multilayers.

STRUCTURAL INVESTIGATION OF DIAMOND THIN-FILMS SYNTHESIZED BY DUAL ION-BEAM DEPOSITION

The formation of diamond thin films synthesized by dual ion beam deposition at room temperature is presented. The carbon films deposited by ion beam sputtering were simultaneously bombarded by Ar+ with energies of 2–25 keV. The synthesized carbon films were characterized by TEM, AES, and XPS. Structural analyses show that the carbon films synthesized by ion beam deposition at room temperature exhibit clear diamond character.

Structure and tribology of hard carbon films synthesized by ion beam deposition

Hard carbon films were formed on Si(111) wafer and AISI 52100 steel by CHn+ ion beam deposition with energies varied from 200 eV to 15 keV. The effects of bombarding energy of CHn+ on the bonding structure and hardness of carbon films were investigated. The films were revealed to consist of amorphous carbon with the structure of mixed sp3+sp2 bonding. However, it was showed that carbon films prepared under bombarding energy of 200–550 eV were much similar to diamond in the valence band structure and had more sp3 bonds. The friction and wear properties of films deposited on AISI 52100 steel were also detected and the experimental results indicated that as wear load was less or equal to 15 N, the normal wear process can steadily last with a friction coefficient of 0.1–0.15. In addition, hard carbon films were suggested to possess the self‐lubricating function and good impact‐resistance to enhance their antiwearing ability.

Ion beam-assisted deposition of DLC films on PMMA and TiN/PMMA

Abstract Bilayered films composed of diamond-like carbon (DLC) and titanium nitride (TiN) or individual DLC films were prepared on the surface of polymethylmethacrylate (PMMA) substrates using ion beam-assisted deposition. The deposition of the DLC or the TiN films were carried out by Ar + sputtering graphite or titanium targets and CH n + or N + ion beams simultaneously bombarding the resulting films at various energies. Results of scanning electron microscopy, X-ray photoelectron and Raman spectroscopy analysis indicated that the DLC films on the PMMA and the TiN/PMMA substrates were amorphous and smooth with the structure of mixed sp 2 +sp 3 bonding. The DLC films on the TiN/PMMA system exhibited an obvious improvement in hardness and wear resistance as comparing to the PMMA only substrate.

Structure analysis of teflon-like thin films synthesized by ion beam sputtering deposition

Abstract Teflon-like thin films were synthesized by ion beam sputtering a teflon target and their structures were studied by XPS and FT-IR. XPS showed that the films consisted mainly of CF 2 bonds, a few CC bonds and CH bonds; FT-IR indicated that the absorption peaks of the thin films consisted of the strongest absorption peak of CF and the characteristic absorption peaks of teflon. These structural characteristics of the thin films correspond to the molecular structure of teflon.