Effect of bias voltage on coating homogeneity in plasma immersion ion implantation

The paper presents research results demonstrating the influence of bias on the homogeneity of plasma immersion ion implantation. The research results allow the conclusion that plasma immersion ion implantation can be used to advantage for surface modification of medical materials, e.g., nickel-titanium (NiTi) alloys. In particular, doing of NiTi with silicon at pulsed bias provides highly homogeneous surface treatment

Effect of preliminary vacuum plasma treatment on coating adhesion

The paper presents research results on the adhesion properties of Si coatings synthesized by different methods and under different conditions of preliminary vacuum ion plasma treatment of substrates with subsequent magnetron sputtering. The substrate surface was pretreated with low-energy ion beams, high-energy ion beams, gas discharge plasma, and plasma produced by a magnetron sputtering system. The vacuum conditions (pump type, pressure, etc.), the ion current density, and the bias parameters (pulse repetition frequency and duration) were varied. The research results demonstrate a considerable effect of plasma immersion ion implantation on the adhesion of Si coatings to NiTi substrates

Characteristics of a quasi-stationary non-self-sustained pulsed gas discharge with a hot cathode

The paper presents the electrode system and main characteristics of a non-selfsustained pulsed discharge with a hot cathode operating in argon at a pulse repetition frequency of 5 kHz and pulse duration of 50 ps. It is found that during the operation at a pressure of 0.3 Pa, the discharge current can reach amplitudes of up to 300 A and more with a rather high average discharge current of ~ 100 A and low average discharge operating voltage of less than 20 V. The ion current from the discharge plasma to a Langmuir probe oscillates at frequency of about 100 kHz

Plasma immersion ion implantation for the efficient surface modification of medical materials

The paper reports on a new method of plasma immersion ion implantation for the surface modification of medical materials using the example of nickel-titanium (NiTi) alloys much used for manufacturing medical implants. The chemical composition and surface properties of NiTi alloys doped with silicon by conventional ion implantation and by the proposed plasma immersion method are compared. It is shown that the new plasma immersion method is more efficient than conventional ion beam treatment and provides Si implantation into NiTi surface layers through a depth of a hundred nanometers at low bias voltages (400 V) and temperatures (≤150°C) of the substrate. The research results suggest that the chemical composition and surface properties of materials required for medicine, e.g., NiTi alloys, can be successfully attained through modification by the proposed method of plasma immersion ion implantation and by other methods based on the proposed vacuum equipment without using any conventional ion beam treatment

Investigation of the microstructure, mechanical properties and thermal stability of nanocomposite coatings based on amorphous carbon

The Ti-C-Ni-Cr and Ti-C-Ni-Cr-Al-Si nanocomposite coatings based on amorphous carbon and the nanosized particles were synthesized by magnetron method. The results of the microstructure features and mechanical properties investigations of these coatings are presented. The thermal stability of microstructure and properties of these coatings at tempering up to 900°C were investigated. These coatings have a high (11–18 GPa) hardness, low (μ < 0.2) the coefficient of friction and high thermal stability of the microstructure and properties up to 700°C. The features of elastically stressed state of nanosized particles in these coatings were founded. A high local internal stresses in the TiC nanoscale particles do not observed

Thermal stability of Ti-C-Ni-Cr and Ti-C-Ni-Cr-Al-Si nanocomposite coatings

The results of the microstructure, mechanical and tribological properties investigations of Ti-C-Ni-Cr and Ti-C-Ni-Cr-Al-Si nanocomposite coatings based on amorphous carbon in the initial state and after the annealing to 900 °C are presented. The effect of annealing temperature on the microstructure, tribological and mechanical properties of Ti-C- Ni-Cr and Ti-C-Ni-Cr-Al-Si nanostructured coatings is discussed

Influence of surface modification of nitinol with silicon using plasma-immersion ion implantation on the alloy corrosion resistance in artificial physiological solutions

Cyclic voltammetry and potentiostatic polarization have been applied to study electrochemical behavior and to determine corrosion resistance of nitinol, which surface was modified with silicon using plasma-immersion ion implantation, in 0.9% NaCl solution and in artificial blood plasma. It was found out that continuous, and also homogeneous in composition, thin Si-containing layers are resistant to corrosion damage at high positive potentials in artificial physiological solutions due to formation of stable passive films. Breakdown potential Eb of Si-modified NiTi depends on the character of silicon and Ni distribution at the alloy surface, Eb values amounted to 0.9–1.5 V (Ag/AgCl/KCl sat.) for the alloy samples with continuous Si-containing surface layers and with decreased Ni surface concentration

Plasma immersion ion implantation for surface treatment of complex branched structures

The paper presents experimental results demonstrating the capabilities of plasma immersion ion implantation of silicon (Si) for surface treatment of complex branched structures such are self-expanding intravascular nickel-titanium (NiTi) stents. Using NiTi stents of diameter 4 and 8 mm, it is shown that plasma immersion ion implantation can provide rather homogeneous doping of their outer and inner surfaces with Si atoms. Also presented are research data on the processes that determine the thickness, composition, and structure of surface layers subjected to this type of treatment

Structural phase states in nickel-titanium surface layers doped with silicon by plasma immersion ion implantation

The paper reports on a study of NiTi-based alloys used for manufacturing self-expanding intravascular stents to elucidate how the technological modes of plasma immersion ion implantation with silicon influence the chemical an

Features of seishe initiation in the water area near Poronaisk (Sakhalin Island)

The results of studying potential sources of seiche excitation energy in the water area near Poronaisk (Sakhalin Island) using natural measurement data in 2008–2009 are presented. Time series data with a duration of about three months were collected by two autonomous sea-level recorders at one-second sample rate. Spectral analyses of time series made possible to conclude that wave processes with periods from 2 to 7 hours can be classified as seiches. Possible seiche periods calculated by numerical methods are very close to the periods of seiches detected in the Terpeniya Bay. The calculated envelopes of wave processes showed a good coincidence of the peaks of seiches with a period of 7 hours and wind waves, which confirms the transfer of energy from atmospheric disturbances to the seven-hour seiche. Seiche period of 3.5 hours is shown to be equal to the period of tidal harmonic 4M7. Thus, the resonance pass of energy transmission from tidal harmonic to seiche was revealed taking into account high for marine waters q-factor equal to 11.9 at the period of 3.5 hours. The highest seiches at a period of 2.7 hours are observed on the 6-8 day after maximum of daily tide with a period of 24.68 hours, which is close to the period of lunar tide harmonic M1. The analyses of excitation factors of seiches with 2-hour period showed that the excitation energy, or at least a part of it, is provided by atmospheric disturbances. Thus, the increasing of seiche height occurs during the winds of southern directions in the Terpeniya Bay