Li Heng-De

Modification of tribological characteristics of metals after nitrogen implantation

Abstract Three steels are investigated, i.e., 0.2 carbon steel, chromium bearing steel (GCr15) and SSL316. Their tribological characteristics are compared before and after nitrogen implantations. These include hardness, coefficient of friction, wear rate and the topography of the wear tracks. Amounts of wearing are determined for both pin and disk in each run of the wear test, and a new criterion is suggested for evaluating the improvement of wear resistance by ion implantation. Nitrogen profiles determined with SIMS show that the nitrogen transports to the depth during wearing. No obvious difference is observed between implanting N + and implanting (N + + N 2 + ).

Investigation of diamondlike carbon thin films synthesized by dual ion beam assisted deposition

Abstract Diamondlike carbon films on Si(111) wafer and glass have been prepared by using dual ion beam assisted deposition at room temperature. The carbon films deposited by ion beam sputtering were simultaneously bombarded by CH n + with energies of 0.2–25 keV. These films have been characterized by RBS, AES, XPS and hardness test. The extremely high hardness and electron spectroscopy analyses showed that the diamondlike carbon films synthesized by CH n + bombardment at 200–400 eV are much more similar to diamond than the 25 keV films.

Amorphization of binary alloys by magnetron cosputtering

Abstract Magnetron cosputtering from different sources has been employed to study the metallic glass formation. Three binary systems, AlFe, BiFe and BiTi, have been studied in detail. The thin films of these three alloys were cosputtered onto various substrates cooled either with or without liquid nitrogen. The film composition of each alloy system spans the range of the phase diagram. By means of Rutherford backscattering analysis and electron microscope observation, the amorphous phases in these three binary systems were confirmed in the different composition ranges. Finally, the metallic glass forming ability by cosputtering has been compared with that by ion mixing.

Recoil implantation and interface mixing: A computer simulation study

Abstract The process of recoil implantation and interface mixing of a bilayered target (Sb/Si) is investigated by using a Monte Carlo code, TCIS. Particular attention is paid to the movements of the atoms participating m the mixing. In order to obtain some statistical knowledge of the mixing process, 1000 independent incident events have been simulated for the case of an Sb(150 A)/Si target bombarded by 100 keV Ar + . The effects of the incident ion species, the film thickness and of an interface potential are considered.

Anodic polarization studies of some ion-implanted metal surfaces

Abstract B+ and P+ implantations to SS316L and pure nickel are conducted at low temperature in a liquid nitrogen cooled chamber. Electron diffraction, SIMS analysis and polarization curves are made from the implanted surface. Results show substantial increase of corrosion resistance by implantation, particularly at doses which produce amorphous state. Multi-polarization curves of one and the same specimen seem to correlate well with concentration-depth profile of the implanted ions.

Some practical aspects of N+ implantation in various steels related to wearing

Abstract Seven steels have been investigated in order to study the effect of N implantation on their wear behavior. Factors such as matrix, heat treatment and implantation parameters and wear load are considered and found to be cross related.

Abnormal structure of titanium formed by ion beam sputtering at room temperature

Abstract Stable fcc modification of titanium ( a =0.420 nm) has been observed in ion beam sputtered films at room temperature. When the deposition rates are above 0.8 A/s, the normal hcp structure is obtained.

Surface modification of non-semiconductors by ion beams in China

Abstract The MEWA ion source has stood out for the surface modification of materials by direct ion implantation. Concurrent implantation with multiple ion species is more efficient in tailoring the surface sensitive properties of solid materials. Ion beam assisted synthesis of surface coating layers has also found increasing applications. The achievements obtained in the past few years in China will be reviewed and successful examples are introduced.

Formation of transition metal carbide thin films by dual ion beam deposition at room temperature

Abstract Transition metal carbide thin films were synthesized by dual ion beam deposition. Metal (Ta, W, Mo) and graphite targets were alternately sputtered by Ar + with an energy of 1.5 keV from a broad-beam Kaufman ion source. The resulting films were simultaneously bombarded by 15 keV Ar + from another Kaufman ion source. The arrival ratios of metal and C atoms can be conveniently controlled by adjusting the relative time of sputtering. It was observed that different phases of carbides formed at different arrival ratios. All depositions were at room temperature. XPS showed the existence of free carbon atoms even for Me/C ratios > 1. The effect of bombardment by Ar + on the phase formation was also investigated.

Ion enduced adhesion between metals and oxides

The enhancement of adhesion between deposited metal layers (Ti and Cu) and the oxide substrates at RT and 300°C respectively was studied by argon ion irradiation to various doses. The experimental results showed that the adhesive strength increased after a threshold dose irradiation and reached a saturation value at higher doses in all metal/oxide pairs. RBS spectra showed that chemical reaction had taken place in Ti/oxide case, while in Cu/oxide case, both RBS and XPS analysis showed that no evidence of such reaction had been induced.