Effect of Charge Voltage on the Microstructural, Mechanical, and Tribological Properties of Mo–Cu–V–N Nanocomposite Coatings

As an important high-power impulse magnetron sputtering (HIPIMS) parameter, charge voltage has a significant influence on the microstructure and properties of hard coatings. In this work, the Mo–Cu–V–N coatings were prepared at various charge voltages using HIPIMS technique to study their mechanical and tribological properties. The microstructure was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The mechanical and tribological properties were investigated by nano-indentation and ball-on-disc tribometer. The results revealed that all the coatings showed a solid-solution phase of B1-MoVN, the V atoms dissolved into face-centered cubic (FCC) B1-MoN lattice by partial substitution of Mo, and formed a solid-solution phase. Even at a high Cu content (~8.8 at. %), the Cu atoms existed as an amorphous phase. When the charge voltage increased, more energy was put into discharge, and the microstructure changed from coarse structure into dense columnar structure, resulting in the highest hardness of 28.2 GPa at 700 V. An excellent wear performance with low friction coefficient of 0.32 and wear rate of 6.3 × 10−17 m3/N·m was achieved at 750 V, and the wear mechanism was dominated by mild abrasive and tribo-oxidation wear.

Production of Thin PbxSn1–xTe Films by “Hot Wall” Method for Creating IR-Photodetectors

Alloys of lead and tin telluride (PbxSn1–xTe) are materials with good thermoelectric properties, as well as semiconductors that can be used as long-wave infrared detectors. Polycrystalline telluride of PbxSn1–xTe (0.05 £ x £ 0.80) alloys has been synthesized by direct fusion technique. Thin films of these materials have been obtained by the hot wall method depositing Сorning 7059 on glass substrates at Tsub = (200–350) oC and vacuum of about 10–5 Torr. The microstructure of the films has been investigated by XRD, SEM and EDX methods. The X-ray spectra of thin films have been in satisfactorily agreement with the spectra of the powder target and indicated the absence of binary phases. The films have shown a natural cubic crystalline structure. While increasing the lead content, the unit cell parameter of the crystal also increases. The established linear relationship between the unit cell parameter and the elemental composition corresponds to Vegard's law. The SEM analysis has shown that the films are polycrystalline, have a columnar structure, are tightly packed and have good mechanical adhesion. The grain size depends on the chemical composition and temperature of the substrate. The electrical measurements have shown that the grown films are non-degenerate semiconductors of p-type conductivity. The conductivity of the films was in the range of σ = (3 × 101)–(1 × 104) Ω–1×cm–1. An increase of lead concentration leads to a decrease in electrical conductivity. Hall mobility in the grown thin films increases in the range of changes in the lead content from ~10 to ~23 at. %, and decreases with a further increase to ~33 at. %. At the same time, the strongest dependence of the decrease in mobility on an increase in temperature increase is observed for films with a high lead content and is explained by the predominant scattering of charge carriers by vibrations of the crystal lattice. For a sample with an average lead concentration, an alternative effect of two scattering mechanisms is observed in the temperature dependence of the mobility: by impurity ions and by phonons.

Modeling of protective plasma spray ceramic coating made of clad powder mixture

To solve the problem of increasing the adhesive-cohesive strength of plasma multifunctional coatings used to protect parts of power and mechanical engineering equipment components from wear and corrosion, a ceramic coating of the “Al2O3 - Ni” system, obtained from a powder mixture based on corundum clad with nickel, is proposed for use and studied. The coating was applied by high-energy plasma powder deposition (on the “Thermoplasma-50” installation) to the intermetallic sublayer of the “Ni-Co-Cr-Al-Y” system. The aim of this work was to study the micro structure and phase composition of the powder mixture of oxide ceramics clad with a refractory metal component (nickel), as well as the plasma coating formed from this powder material. According to the results of the research, it was found that the powder mixture clad with nickel has a multiphase composition (Ni+l-Al2O3+r-Al2O3), a spherical morphology of particles. From this powder material, a coating with a phase composition (Ni+L -Al2O3+J ’-L J u Ll) is formed, characterized by a layered microstructure with a columnar structure of oxide grains and nickel interlayers. The coating has high hardness and adhesive-cohesive strength, low coefficient of friction and is recommended for protection against wear of energy and mechanical engineering parts.

Obliquely Bideposited TiN Thin Film with Morphology-Dependent Optical Properties

TiN thin films were obliquely bideposited with different subdeposit thicknesses. The morphology of the bideposited film was varied from a nano-zigzag array to a vertically grown columnar structure by reducing the subdeposit thickness. The principal index of refraction and extinction coefficient were obtained to explain the measured reflectance and transmittance spectra. The loss of the bideposited thin film decreased as the thickness of the subdeposit decreased. The principal indices for normal incidence were near or under unity, indicating the low reflection by the bideposited thin films. A TiN film with a subdeposit thickness of 3 nm demonstrated an average index of refraction of 0.83 and extinction coefficient of below 0.2 for visible wavelengths. The retrieved principal refractive indexes explained the anisotropic transmission and reflection. For most normal incident cases, the analysis offers the tunable anisotropic property of a TiN nanostructured film for multilayer design in the future.

Enhanced Ferroelectric, Dielectric Properties of Fe-Doped PMN-PT Thin Films

Fe-doped 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT) thin films were grown in Pt/Ti/SiO2/Si substrate by a chemical solution deposition method. Effects of the annealing temperature and doping concentration on the crystallinity, microstructure, ferroelectric and dielectric properties of thin film were investigated. High (111) preferred orientation and density columnar structure were achieved in the 2% Fe-doped PMN-PT thin film annealed at 650 °C. The preferred orientation was transferred to a random orientation as the doping concentration increased. A 2% Fe-doped PMN-PT thin film showed the effectively reduced leakage current density, which was due to the fact that the oxygen vacancies were effectively restricted and a transition of Ti4+ to Ti3+ was prevented. The optimal ferroelectric properties of 2% Fe-doped PMN-PT thin film annealed at 650 °C were identified with slim polarization-applied field loops, high saturation polarization (Ps = 78.8 µC/cm2), remanent polarization (Pr = 23.1 µC/cm2) and low coercive voltage (Ec = 100 kV/cm). Moreover, the 2% Fe-doped PMN-PT thin film annealed at 650 °C showed an excellent dielectric performance with a high dielectric constant (εr ~1300 at 1 kHz).

Characteristics of the Structure, Mechanical, and Tribological Properties of a Mo-Mo2N Nanocomposite Coating Deposited on the Ti6Al4V Alloy by Magnetron Sputtering

Mo-Mo2N nanocomposite coating was produced by reactive magnetron sputtering of a molybdenum target, in the atmosphere, of Ar and N2 gases. Coating was deposited on Ti6Al4V titanium alloy. Presented are the results of analysis of the XRD crystal structure, microscopic SEM, TEM and AFM analysis, measurements of hardness, Young’s modulus, and adhesion. Coating consisted of a-Mo phase, constituting the matrix, and g-Mo2N reinforcing phase, which had columnar structure. The size of crystallite phases averaged 20.4 nm for the Mo phase and 14.1 nm for the Mo2N phase. Increasing nitrogen flow rate leads to the fragmentation of the columnar grains and increased hardness from 22.3 GPa to 27.5 GPa. The resulting coating has a low Young’s modulus of 230 GPa to 240 GPa. Measurements of hardness and Young’s modulus were carried out using the nanoindentation method. Friction coefficient and tribological wear of the coatings were determined with a tribometer, using the multi-cycle oscillation method. Among tested coatings, the lowest friction coefficient was 0.3 and wear coefficient was 10 × 10−16 m3/N∙m. In addition, this coating has an average surface roughness of RMS < 2.4 nm, determined using AFM tests, as well as a good adhesion to the substrate. The dominant wear mechanism of the Mo-Mo2N coatings was abrasive wear and wear by oxidation. The Mo-Mo2N coating produced in this work is a prospective material for the elements of machines and devices operating in dry friction conditions.

Influence of oxygen fraction on the characteristics of titanium oxide coatings obtained by the magnetron method

Titanium oxide coatings were obtained by magnetron sputtering on a glass substrate with different oxygen fraction in the plasma. Studies were carried out by scanning electron microscopy of the obtained coating samples establishing the role of oxygen in the process of crystallization of TiOx-coatings. It was found that with increasing the oxygen fraction in the vacuum arc discharge plasma the crystal grain size increases, the time of coating on the substrate increases, and the crystal layer has a columnar structure. The presence of amorphous and crystalline phase for all coating samples was revealed, with the predominance of the former. On the surface microphotographs of the coatings microcraters were found, on the surface of the samples obtained at the concentration of O2 in the plasma 14% of their concentration is maximum, this can be explained by changes in the state of the plasma, starting to occur at this concentration of reaction gas. Vacuum photonic annealing of the obtained coatings was performed. Vacuum radiation annealing in the furnace led to modification of coatings: sintering of coatings, increase of their crystallinity. An increase in crystallite size in a sample with an oxygen fraction of 12% was detected.

Microstructure of the coating obtained by magnetron sputtering of a Ni-Cr-B4C composite target

This paper presents data on obtaining a composite coating by radio frequency (RF) magnetron sputtering of a Ni-Cr-B4C composite target in an inert gas (argon) environment. To make the target, Ni-Cr-B4C composite powder was applied to the copper base of the target by detonation gas-thermal spraying. The obtained targets served as a source of coating material during high-frequency magnetron sputtering. This method of coating production ensures the reproducibility of their properties, as well as the uniformity of coating thickness and good adhesion to various target backings. The data of the study of the structure and morphology of the composite coating are presented. The resulting composite coating Ni-B/Cr7C3 with a thickness of 2 microns has a dense homogeneous structure with expressed textured polycrystallinity. The surface of the resulting coating is represented by nanoscale and homogeneous grains. There is no columnar crystal growth in the coating, which has a positive effect, as the columnar structure reduces the mechanical characteristics of the coatings due to faster oxygen diffusion along the grain boundaries. It is established that the combined use of the Ni-B and Cr7C3 binary phases in composite coatings leads to an increase in operational properties.

The Effect of Al and Ti Transition Metals on the Wear Resistance of Ceramic Based CrN Coatings; Investigation under Ambient Air and Vacuum Conditions

In the present study, CrN, CrAlN and CrAlTiN coatings were deposited using the cathodic arc evaporation technique. The structural investigations of these CrN based coatings were performed by scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, X-ray diffractometer. The hardness and adhesion strength values of coatings were determined via Vickers type microhardness tester and progressive load scratch tester, respectively. The wear performance of samples was established at ambient air and vacuum condition. All coatings grew in the “T zone” growth model and had a dense and columnar structure. The XRD patterns presented predominantly (220), (110), and (111) reflections. It was demonstrated that the quaternary coating had a higher texture parameter as 0.68, which was related to the highest thickness and hardness. Also, CrAlTiN coatings with the smallest mean crystallite size of ∼87 nm showed the best hardness, and this ensured relatively high scratch resistance. CrN and CrAlTiN coatings improved wear performance under ambient air condition but were not striking as under vacuum condition. The quaternary coating had a superior performance in the vacuum condition, but due to the high sensitivity of Ti to oxygen, it fell behind the CrN coating under ambient air condition.

Intermolecular interactions of layers octa-phenyl-2,3-naphthalocyaninato zinc

The orientation of octa-phenyl-2,3-naphthalocyaninato zinc molecules is modeled by the atom-atom potential method. The dependence of the interaction energy of octa-phenyl-2,3-naphthalocyaninato zinc molecules on the angles characterizing their orientation relative to each other is established. It is shown that the obtained values of the interaction energy allow us to qualitatively explain the formation of molecules in a columnar structure.