Khominich A. Plasmochemical synthesis and structure of carbon nanotubes layers intended for the creation of composite coatings

The thesis is devoted to the solution of the actual scientific and technical problem of creating composite coatings with a reinforcing component in the form of CNTs by the experimental study of the processes of synthesis of carbon nanostructures using CVD (chemical vapor deposition) and PECVD (plasma enhanced CVD) methods on metallic and nonmetallic substrates and studying the conditions for the formation of coatings on their separate stages. A new phenomenological model of the physicochemical processes dynamics during the carbon atoms evaporation from anode in arc discharge of high pressures (2-5∙104 Pa) is proposed. It is shown that the ion component of the carbon, metal and gas vapors mixture plays a decisive role in the evolution of composite carbon-metal nanoparticles. This idea was used in the formulation of the further experimental studies. The parameters of CNT synthesis by the CVD and PECVD methods in industrial installation of ion-plasma sputtering NNV-6,6 «Bulat» were established: the thickness of the catalyst film at which an effective desired morphology CNTs synthesis occurs is ~10-15 nm, while the sizes of catalytic centers suitable for the growth of CNTs are within the range of ~5-50 nm. It is established that the substrate temperature growth in different experiments from 500° C to 800° C leads to a more efficient synthesis of CNTs. In order to obtain the carbon ion component with a predetermined energy, the ion source based on a Penning-type discharge cell was designed, fabricated and used. The Penning source was supplemented with patented system of electrostatic control of the plasma flow from the cell. The effect of the plasma component on the CNT synthesis processes and the formation of an amorphous carbon component on the substrates and the resulting nanostructures surfaces is studied. It has been established that the addition of oxygen to the synthesis zone makes it possible to vary the thickness of the amorphous layer due to the formation of gaseous carbon oxide, which is removed by pumping out from the vacuum chamber. It is shown that the combination of adding of a working gas plasma component to the CNT synthesis zone with supplying a displacement potential to the heating stage allows obtaining the coating on the SiO2 substrate as a layer of oriented CNTs up to ~10-11 μm in height. In order to realize the synthesis of CNTs directly on substrates made of titanium alloys VT1-0 and VT6, the idea of forming a diffusion barrier on their surfaces is proposed and implemented. As a diffusion barrier, the hydride compounds, which are implementation phases and can effectively trap the diffusion of metal catalyst atoms deep into the substrate material, were chosen. Based on the results of gravimetry data, the dependence of the hydrogen penetration depth on the hydrogen saturation parameters (gas pressure, substrate temperature, hydrogenation time) was established. It is shown that the increase in the depth of the surface hydrogenated layer of the VT1-0 alloy from ~100 nm up to ~200 nm allows increasing the amount of CNT per unit of surface up to ~25 times. The device for copper vacuum evaporation was designed and manufactured. The results of copper surfaces coating with CNTs are shown. Using a comparative quantitative SEM images analysis of the initial state with the deposited layer, the coating layer thickness was established (~ 100 nm). It is shown that copper deposited by the developed method of metals sputtering on CNTs evenly covers the entire surface of the tubes, and evenly fills the space between the tubes.