Mirela Contulov

Surface Engineering of the Hydrogenated DLC (a-C:H) Coatings with Optimized Mechanical Performance

The aim of this contribution is to present the properties of the hydrogenated DLC (a-C:H) films and to study their growth carried out in a special deposition technique based on Gaseous Thermionic Vacuum Arc (G-TVA) method. The mechanical properties were investigated on cross-sectional samples using the Fischerscope HM 2000 depth sensing indentation (DSI) tester.

Surface Activation of the Polycarbonate in Atmospheric Pressure Plasma Generated in Air and Helium by Surface Dielectric Barrier Discharge (SDBD)

Surface Dielectric Barrier Discharges (SDBD) plasma treatment has been performed to produce uniform atmospheric plasmas in He and in open air in order to functionalize the polycarbonate surface. SDBD is used for different application, processing especially of low-cost polymeric materials, combining the advantages of non-equilibrium plasma properties with the ease of atmospheric-pressure operation. Contact angle measurements were used to record the short-and long - term variations in wettability of treated and untreated polycarbonate sheets. The modification process was determined with hydrophilic measurements evaluated by means of the SEE system drop test.

Investigation of Composition-Properties’ Relations on Silicon and Carbon Based Nanomaterials

Multicomponent thin films (binary-SiC and ternary-SiCAl) as well as single thin films (silicon Si) were deposited using Thermionic Vacuum Arc (TVA) technology. The thin films were characterized using X-ray diffractometer (XRD, Philips PW1050, Cu K), scanning electron microscope (SEM, Zeiss EVO 50 SEM) accompanied with energy dispersive spectrometer and transmission electron microscope (TEM, Phillips CM 120 ST, 100 kV). The film is composed of nanoparticles very smoothly distributed of 15-30 nanometer size embedded in amorphous matrix film. The results reveal high hardness for SiC (10-40 GPa) and for SiCAl: low wear rate (6.16E-05 mm3/Nm).

Application of carbon-aluminum nanostructures in divertor coatings from fusion reactor

Nanostructured carbon materials have increasingly attracted the interest of the scientific community, because of their fascinating physical properties and potential applications in high-tech devices. In the current ITER design, the tiles made of carbon fiber composites (CFCs) are foreseen for the strike point zone and tungsten (W) for other parts of the divertor region. This choice is a compromise based mainly on experience with individual materials in many different tokamaks. Also Carbon-Aluminum composites are the candidate material for the First Wall in ITER. In order to prepare nanostructured carbon-aluminum nanocomposite for the divertor part in fusion applications, the original method thermionic vacuum arc (TVA) was used in two electronic guns configuration. One of the main advantages of this technology is the bombardment of the growing thin film just by the ions of the depositing film. Moreover, the energy of ions can be controlled. Thermo-electrons emitted by an externally heated cathode and focused by a Wehnelt focusing cylinder are strongly accelerated towards the anode whose material is evaporated and bright plasma is ignited by a high voltage DC supply. The nanostructured C-Al films were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM). Tribological properties in dry sliding were evaluated using a CSM ball-on-disc tribometer. The carbon - aluminum films were identified as a nanocrystals complex (from 2nm to 50 nm diameters) surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films. The friction coefficients (0.1 - 0.2, 0.5) of the C-Al coatings was decreased more than 2-5 times in comparison with the uncoated substrates proving excellent tribological properties. C-Al nanocomposites coatings were designed to have excellent tribological properties while the structure is composed by nanocrystals complex surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films.

Electron microscopy characterization of some carbon based nanostructures with application in divertors coatings from fusion reactor

Nanostructured carbon materials have increasingly attracted the interest of the scientific community, because of their fascinating physical properties and potential applications in high-tech devices. In the current ITER design, the tiles made of carbon fiber composites (CFCs) are foreseen for the strike point zone and tungsten (W) for other parts of the divertor region. This choice is a compromise based mainly on experience with individual materials in many different tokamaks. Also Beryllium is the candidate material for the First Wall in ITER. In order to prepare nanostructured carbon-tungsten nanocomposite for the divertor part in fusion applications, the original method thermionic vacuum arc (TVA) was used in two electronic guns configuration. One of the main advantages of this technology is the bombardment of the growing thin film just by the ions of the depositing film. The nanostructured C-W and C-Be films were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). The C-W films were identified as a nanocrystals complex (5 nm average diameter) surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films. The C-Be films are polycrystalline with mean grain size about 15 nm. The friction coefficients (0.15 - 0.35) of the C-W coatings was decreased more than 3-5 times in comparison with the uncoated substrates proving excellent tribological properties. C-W nanocomposites coatings were designed to have excellent tribological properties while the structure is composed by nanocrystals complex surrounded by amorphous structures with a strong graphitization tendency, allowing the creating of adherent and wear resistant films.&updat

HRTEM Images of a-C:H Thin Films Deposited by G-TVA Technique

The aim of this paper is to an report analysis of the different characteristics of the coatings obtained by an extension in applicability of the thermionic vacuum arc method, i.e., gaseous thermionic vacuum arc using gases as precursors, instead of solid materials. The morphology and structure of the film were investigated by transmission electron microscopy (TEM) provided by high-resolution TEM with 1.4-Å resolution and 1.2-M magnification.

Synthesis and characterization of some carbon based nanostructures

The aim of present paper is to present the latest results on investigations of the carbon thin film deposited by Thermionic Vacuum Arc (TVA) method and laser pyrolysis. X-ray photoelectron spectroscopy (XPS) and X-ray generated Auger electron spectroscopy (XAES) were used to determine composition and sp2 to sp3 ratios in the outer layers of the film surfaces. The analyses were conducted in a Thermoelectron ESCALAB 250 electron spectrometer equipped with a hemispherical sector energy analyser. Monochromated Al K X-radiation was employed for the XPS examination, at source excitation energy of 15 KeV and emission current of 20 mA. Analyzer pass energy of 20 eV with step size of 0.1 eV and dwell time of 100 ms was used throughout.