Preferred Orientation Of Crystallites Research Articles

Crystallographic Texture Evolution in 3D Printed Polyethylene Reactor Blends.

In this work, crystallographic texture evolution in 3D printed trimodal polyethylene (PE) blends and high-density PE (HDPE) benchmark material were investigated to quantify the resulting material anisotropy, and the results were compared to materials made from conventional injection molded (IM) samples. Trimodal PE reactor blends consisting of HDPE, ultrahigh molecular weight PE (UHMWPE), and HDPE_wax have been used for 3D printing and injection molding. Changes in the preferred orientation and distribution of crystallites, i.e., texture evolution, were quantified utilizing the wide angle X-ray diffraction through pole figures and orientation distribution functions (ODFs) for 3D printed and IM samples. Since the change in weight-average molecular weight (Mw) of the blend was expected to significantly affect the resulting crystallinity and orientation, the overall Mw of the trimodal PE blend was varied while keeping the UHMWPE component weight fraction to 10% in the blend. The resulting texture was analyzed by varying the overall Mw of the trimodal blend and the process parameters in 3D printing and compared to the texture of conventional IM samples. The printing speed and orientation (defined with respect to the axis along the length of the samples) were used as the variable process parameters for 3D printing. The degree of anisotropy increases with an increase in the nonuniform distribution of intensities in pole figures and ODFs. All the highest intensity major texture components in IM and 3D printed samples (0° printing orientation) of reactor blends are observed to have crystals oriented in [001] or [001̅]. Overall, for the same throughput, 3D printed samples in the 0° orientation showed greater texture evolution and higher anisotropy compared to IM samples. Most notably, an increase in 3D printing speed increased the crystalline distribution closer to the 0° direction, increasing the anisotropy, while deviation from this printing orientation reduced crystalline distribution closer to the 0° direction, thus increasing isotropy. This demonstrates that tailoring material properties in specific directions can be achieved more effectively with 3D printing than with the injection molding process. Change in the overall Mw of the trimodal PE blend changed the preferential orientation distribution of the crystal planes to some degree. However, the degree of anisotropy remained the same in almost all cases, indicating that the effect of molecular weight distribution is not as significant as the printing speed and printing orientation in tailoring the resulting properties. The 3D printing process parameters (speed and orientation) were shown to have more influence on the texture than the material parameters associated with the blend.

The influence mechanisms of re-fused scanning on the surface roughness, microstructural evolution and mechanical properties of laser powder bed fusion processed AlMgScZr alloy

Laser powder bed fusion (LPBF) stands out as the foremost method for achieving intricate structure with superior design flexibility among additive manufacturing technologies. Within the LPBF process, surface roughness serves as a critical metric governing both fabrication precision and build quality. This study delves into the evolution of the top and side surface roughness as re-fused scanning times increase in LPBF-fabricated AlMgScZr alloy. Concurrently, the investigation evaluates alterations in microstructural characteristics and mechanical properties. Various characterization techniques, including confocal laser scanning microscope, scanning electron microscope, X-ray diffraction, electron backscatter diffraction, as well as tensile and microhardness tests, are employed. The findings concerning the top surface reveal that the initial application of re-fused scanning contributes to enhanced surface roughness. This improvement stems from refined grain structures and induced lattice distortions, facilitated by rapid heat dissipation and thermal recycling within the solidified layer. Consequently, microhardness increases. However, introducing the subsequent re-fused scanning exacerbates surface roughness and instigates Marongoni flow instability, magnesium depletion, and alterations in lattice structures. Moreover, with increasing the re-fused times, there is a noticeable enhancement in preferential crystallite growth orientation along the (200)α-Al crystal plane. Regarding the side surface, escalating re-fused times correlate with deteriorating roughness and alterations in molten pool shape and size, attributable to successive energy input. Despite these surface variations, minimal differences are observed in yield strength, tensile strength, and elongation. In essence, this research offers valuable insights into selecting optimal scanning methodologies during the LPBF process, thus guiding improvements in fabrication precision and component quality.

Effect of layered transition metal dichalcogenide hybrid nanomaterials on the piezoelectric performance of non‐solvent induced phase separated polyvinylidene fluoride

AbstractLayered transition metal dichalcogenides (TMDs) with high aspect ratios enhance the alignment of polymer chains and induce a preferred orientation of the polymeric crystallites when incorporated into polyvinylidene fluoride (PVDF). In addition to offering an effective charge‐transfer mechanism, TMDs give PVDF more rigidity and piezoelectric qualities. This work reports the non‐solvent induced phase separation (NIPS) introduced while developing the PVDF/MoS2 composites. During the NIPS, the PVDF chains become phase‐separated, which induces high polarization in the PVDF matrix. Phase‐separated PVDF/MoS2 composites show high porosity and charge distribution attributed to the enhanced piezoelectric output voltage. While the neat PVDF demonstrated very feeble output voltage generation, the hybrid composite containing 2 wt.% of MoS2/ZnO facilitated almost 20 times higher performance (peak‐to‐peak voltage of 2.4 V). This work yielded a phase‐separated composite that finds uses in energy harvesting, sensors, and actuators, among other fields.Highlights NIPS creates high‐porosity composites with improved charge distribution. Layered TMDs improve charge‐transfer mechanism and PVDF's electrical properties. 2 wt.% MoS2/ZnO exhibits nearly 20 times higher voltage generation than neat PVDF.

Analysis of Bone Mineral Density and Bone Quality of Cortical Bone in the Human Hyoid Body and Histological Observation of the Entheses.

The hyoid is the only bone in the human body that is completely independent, not forming a joint with any other bone; its position is maintained by the suprahyoid and infrahyoid muscles, as well as several ligaments. The purpose of this study was to ascertain the effect of the functional pressure arising from these muscles and ligaments on the hyoid body structure from its bone mineral density, bone quality, and histological observations. The area between the mesial-most part of each lesser horn and the center of the hyoid body was divided equally into four measurement regions. We conducted histological investigations at each measurement region and observed the entheses. To analyze bone mass and bone quality, we also measured bone mineral density (BMD) and analyzed biological apatite (BAp) crystallite orientation in the same regions. Histological observations identified periosteal insertions and fibrocartilaginous entheses. There was no significant difference in BMD between any of the measurement regions, but the preferential orientation of BAp crystallites was stronger in the infrahyoid muscles and ligaments, where fibrocartilaginous entheses are found, than in other places. This suggests that the functional pressure at these sites might exert a major effect not only on the morphological characteristics of the entheses but also on bone quality.

Enhanced Photoelectrochemical Activity Realized from WS2 Thin Films Prepared by RF‐Magnetron Sputtering for Water Splitting

AbstractWe report the synthesis of tungsten sulfide (WS2) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm2. The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×1021 cm−3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS2 can be suitable for PEC water splitting.

Synthesis of WS2 Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications.

Argon and oxygen pressure influence on the properties of NiO films deposited by magnetron sputtering in layer-by-layer growth regime

The influence of argon and oxygen partial pressure on the structure, morphology, and optical properties of NiO films deposited on glass substrate by radio-frequency magnetron sputtering in layer-by-layer growth regime are presented. The argon and oxygen partial pressures were varied in the range of 0.4–4 Pa. XRD measurements reveal the formation of NiO films without preferred orientation of crystallites. The average transmittance of the deposited NiO films was found to be in the range 33–73 % while the optical band gap, calculated from absorption spectra, varied from 2.9 to 3.3 eV. AFM measurements revealed that the grain size and surface roughness changed in the range of 24–55 nm and 1.4–4.3 nm, respectively. The electrical resistivity of NiO films varied from 2.4 to 880 Ohm·cm. The NiO films deposited by layer-by-layer growth regime in magnetron sputtering demonstrate a suitable structure and good optical properties for various applications.

Synthesis, microstructural and optical characterizations of sol-gel grown gadolinium doped cerium oxide ceramics.

In this study, through the utilization of the sol-gel combustion tactic, gadolinium (Gd)-doped cerium oxide (CeO2), Ce1-xGdxO2 (x = 0.00, 0.10, 0.20 and 0.30 (GDC)) ceramics were attained. The synthesized GDC ceramics were investigated using X-ray diffraction (XRD) to scrutinize their crystal structures and phase clarities. The obtained GDC ceramics have a single-phase cubic structure and belong to the crystallographic space group fm3̄m (225). The measurement of the diffraction angle of each reflection and the subsequent smearing of the renowned Bragg's relation provided coarse d-interplanar spacings. The stacking fault (SF) values of pure and Gd-doped CeO2 ceramics were assessed. To muse the degree of preferred orientation (σ) of crystallites along a crystal plane (h k l), the texture coefficient (Ci) of each XRD peak of GDC ceramics is gauged. By determining the interplanar distance (dh k l), the Bravais theory sheds light on the material's development. By exploiting Miller indices for the prime (1 1 1) plane, the lattice constants of GDC ceramics and cell volumes were obtained. Multiple techniques were employed to ascertain the microstructural parameters of GDC ceramics. A pyrometer substantiated the density of GDC ceramics. The room temperature (RT) Fourier transform infrared (FTIR) spectra of both un-doped and Gd-doped CeO2 were obtained. The UV-vis-NIR spectrometer recorded the GDC ceramics' reflectance (R) spectra at RT. For both undoped and Gd-doped CeO2, the absorption coefficient (α) spectra showed two distinct peaks. The R-dependent refractive index (η) and the α-dependent extinction coefficient (k) were determined for all GDC samples. The optical band gap (Eg) was obtained by integrating the Tauc and Kubelka-Munk approaches for GDC ceramics. For each GDC sample, the imaginary (εi) and real (εr) dielectric constants, as well as the dissipation factor (tan δ), were determined local to the characteristic wavelength (λc). Calculations were made for the Urbach energy (EU) and Urbach absorption coefficient (α0) for GDC ceramics. The minimum and maximum values of optical (σo) and electrical (σe) conductivity for GDC ceramics were determined. The volume (VELF) and surface (SELF) energy loss functions, which depend on the constants εi and εr, were used to measure electrons' energy loss rates as they travel across the surface. Raman spectroscopy revealed various vibrational modes in GDC ceramics. Finally, the implications are discussed herein.

Effect of the substrate treatment on the microstructure of CVD Ti(C,N)/α-Al2O3/TiN hard coatings

Although the use of protective Ti(C,N)/Al2O3 coatings produced by chemical vapour deposition (CVD) on cemented carbide (WC-Co) substrates is the state of the art in high-speed metal cutting, the effect of the substrate treatment on the microstructure of such coatings is not fully understood yet. In this study, the influence of the original substrate grain size (coarse-grained, fine-grained) and the substrate treatment (as-sintered, wet blasted, ground or polished) on the grain size, preferred orientation of crystallites and residual stress in Ti(C,N)/Al2O3 coatings was systematically investigated. The microstructure analyses carried out using scanning electron microscopy with electron backscatter diffraction and symmetrical X-ray diffraction (XRD) revealed that the utilization of fine-grained substrates and the substrate treatment reduce the grain size in both layers, and increase the preferred orientations 〈211〉 and 〈0001〉 of fcc-Ti(C,N) and α-Al2O3 crystallites, respectively. In α-Al2O3, the microstructure changes are mainly connected with the morphology of the bonding layer, as it follows the morphology of the fcc-Ti(C,N) facets. The residual stress analyses done using glancing angle X-ray diffraction (GAXRD) disclosed a reduction of the tensile thermal stress in α-Al2O3 layers that were deposited on coarse-grained substrates. The residual stress in fcc-Ti(C,N) was substantially less reduced in the whole fcc-Ti(C,N)/α-Al2O3 stacks than in the reference fcc-Ti(C,N) monolayers. Vice versa, fcc-Ti(C,N) in the full stacks contained less crystal structure defects and lower microstrain than in the reference fcc-Ti(C,N) monolayers, because they were exposed to higher temperatures.

Bioresorbable films of polycaprolactone blended with poly(lactic acid) or poly(lactic-co-glycolic acid)

Recent complications on the use of polypropylene meshes for hernia repair has led to the development of meshes or films, which were based on resorbable polymers such as polycaprolactone (PCL), polylactic acid (PLA) and poly(lactic-co-glycolic acid) (PLGA). These materials are able to create suitable bioactive environment for the growth and development of cells. In this research, we mainly focused on the relations among structure, mechanical performance and biocompatiblity of PCL/PLA and PCL/PLGA and blends prepared by solution casting. The films were characterized regarding the chemical structure, morphology, physicochemical properties, cytotoxicity, biocompatibility and cell growth. All the films showed high tensile strength ranging from 9.5 to 11.8 MPa. SAXS showed that the lamellar stack structure typical for PCL was present even in the blend films while the morphological parameters of the stacks varied slightly with the content of PLGA or PLA in the blends. WAXS indicated preferential orientation of crystallites (and thus, also the lamellar stacks) in the blend films. In vitro studies revealed that PCL/PLGA films displayed better cell adhesion, spreading and proliferation than PCL/PLA and PCL films. Further the effect of blending on the degradation was investigated, to understand the significant variable within the process that could provide further control of cell adhesion. The results showed that the investigated blend films are promising materials for biomedical applications.

Influence of the substrate treatment on the microstructure and properties of chemical vapour deposited Ti(C,N) coatings

The effect of the mechanical treatment on the surface morphology of cemented carbide substrates and on the microstructure and properties of chemical vapour deposited (CVD) Ti(C,N) coatings is described in terms of the functional relationships between the substrate surface roughness, and the grain size, preferred orientation of crystallites, residual stress, indentation hardness and adhesion of the coatings. The substrates were flat fine-grained and coarse-grained cemented carbides inserts that underwent different treatments – wet blasting, grinding or polishing. Although the Ti(C,N) coatings were produced in the same moderate-temperature deposition process, their microstructure characteristics and mechanical properties differed significantly. Microscopic steps and edges present on ‘rough’ substrates facilitated the growth of large V-shaped Ti(C,N) grains with a weak {211} texture. In these samples, the tensile residual stress that is typically produced during the cooling of the CVD samples was reduced. The Ti(C,N) coatings deposited on ‘smooth’ substrates were fine-grained, and possessed a pronounced {211} texture and a better adhesion to the substrate. In these samples, the thermal tensile stress was less reduced than in the samples deposited on ‘rough’ substrates. The indentation hardness of the Ti(C,N) coatings was not affected by the substrate treatment. The physical background of these relationships is explained.

Fractographic studies and tensile strength of MPG-6 graphite based on uncalcined coke, neutron-irradiated at a high temperature

This paper presents the results of studies of the mechanical properties and fracture characteristics of MPG-6 graphite in the unirradiated state and neutron-irradiated at high temperature. MPG-6 is considered as a material for future high-temperature gas-cooled reactors (HTGR). In particular, MPG-6 is considered as one of the candidate materials for prismatic fuel blocks of the Russian experimental hydrogen-producing nuclear power plant with the VTGR high-temperature reactor currently under design.It is shown that MPG-6 graphite, based on uncalcined petroleum coke, which causes a small difference in the size of crystallites in areas with different preferred orientations of crystallites, has higher radiation stability of mechanical properties than GR-280 graphite based on calcined coke.

Improvement of some physical and magnetic properties of nanocrystalline Fe15–Ni85/ITO thin films by galvanostatic pretreatment process

In this research, a comparative study on some physical and magnetic properties of nanocrystalline Fe15–Ni85 thin films with and without galvanostatic pretreatment (GPT) process deposited on conductive and transparent indium tin oxide substrates using the electrodeposition method is carried out. The films exhibit the non-preferential deposition of more noble Ni. The films, irrespective of the GPT process, show a single face-centered cubic structure with the preferential orientation of crystallites along the (111) plane. The Ni-Fe thin film with the GPT exhibits a smaller crystallite size and a stronger [111] texture than the Ni-Fe thin film without the GPT. The films exhibit in-plane magnetic hysteresis loops with a magnetic squareness ratio of about 0.10 ± 0.01 independent of the GPT. The main advantages of the Ni-Fe thin film with the GPT are the smooth surface with smaller particles and the in-plane magnetization, which shows a significant reduction of the coercive field. The results obtained in this study are expected to be useful for future experimental studies of Ni-Fe thin film materials.

Influences on the accuracy of crystallinities determined by the method of Ruland and Vonk

X-ray diffractometry is the method of choice for the determination of crystallinities in non-thermoplastic polymers, prominently in cellulose. Obtaining quantitative measures on a sound theoretical basis includes the integration of intensities scattered by the crystalline phase over volume elements in reciprocal space. This is hampered by the occurrence of diffuse scattering, whose profile is not readily distinguishable from scattering by amorphous phases. The manner of evaluating diffractograms pioneered by Ruland and refined by Vonk allows to determine crystallinities by integrating only the coherently scattered portion of crystalline-phase intensities and extrapolating their proportion to a scattering vector of 0. However, preferred crystallite orientations within measured samples, as well as the range of scattering vectors from which the data are extrapolated, have been pointed out as sources of systematic error. We investigated the influence of these factors at the examples of two crystalline structures of cellulose and two types of technically relevant thermoplastics. We found that the method of Ruland and Vonk is rather robust when applied to cellulose, but decidedly less so when applied to polymers with highly symmetric crystalline phases. We also found that there is a range of scattering vectors that leads systematically to the most accurate measures of crystallinity. We further investigated the influence of the crystallite sizes, the crystallinities themselves and the thermal displacement factors, and found that the latter had a profound effect on the accuracies of determined crystallinities.

Влияние параметров вакуумно-дугового синтеза на структурные и магнитные свойства наночастиц NiO

NiO nanoparticles were synthesized using the vacuum arc sputtering method. The influence of synthesis parameters on the structural and magnetic properties of the samples was studied. X-ray diffraction analysis confirms the polycrystalline nature of the resulting nanoparticles under all deposition conditions, but the preferred crystallite orientation depends on the deposition conditions. Magnetic behavior correlates with the crystallite size of NiO nanoparticles. Condensates with particle sizes in the range of 4–6 nm exhibit superparamagnetic behavior, which changes to antiferromagnetic behavior as the particle size increases.

Formamidinium Lead Iodide Perovskite Thin Films Formed by Two-Step Sequential Method: Solvent-Morphology Relationship.

Thin films made of formamidinium lead iodide (FAPbI3) perovskites prepared by a two-step sequential deposition method using various solvents for formamidinium iodide (FAI) - isopropanol, n-butanol and tert-butanol, were studied with the aim of finding a correlation between morphology and solvent properties to improve film quality. They were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and their photophysical properties were studied by means of absorption and photoluminescence (PL) spectroscopies. XRD patterns, absorption and PL spectra proved α-phase formation for all selected solvents. An excessive amount of PbI2 found in perovskite films prepared with n-butanol indicates incomplete conversion. Thin film morphology, such as grain and crystallite size, depended on the solvent. Using tert-butanol, thin films with a very large grain size of up to several micrometers and with preferred crystallite orientation were fabricated. The grain size increased as follows: 0.2-0.5, 0.2-1 and 2-5 µm for isopropanol, n-butanol and tert-butanol, respectively. A correlation between the grain size and viscosity, electric permittivity and polarizability of the solvent could be considered. Our results, including fabrication of perovskite films with large grains and fewer grain boundaries, are important and of interest for many optoelectronic applications.

Structure and tribological properties of sputtered Cu-modified MoS[formula omitted]:Cu films

Combining materials with a self-lubricating character is a promising approach for an environmentally friendly lubrication. Therefore, Cu was incorporated in HiPIMS synthesized non-stoichiometric MoSx thin films. By increasing the Cu concentration up from 3.09 ± 0.09at.-% to 31.93 ± 0.12at.-% by an increased target power, the structure and the tribological properties were evaluated depending on the chemical composition. The results show, that an increased Cu content in the films in combination with the target setup during the deposition process leads to a preferred (002) basal-plane crystallite orientation and a densification of the microstructure in comparison to MoSx. Due to these structural properties, the dry friction behavior is improved under humid conditions. In combination with the transferfilm formed on the surface of the 100Cr6 counterpart, the lowest coefficient of friction of μ=0.092 ± 0.003 is seen at a target power of 1.5kW. Additionally, Cu tends to agglomerate the generated wear particles, which contributes to a high amount of tribomaterial with a MoSx character in the tribo track and thus a low wear. At a target power of 2.5kW the lowest wear coefficients with k=(0.64 ± 0.22) x 10−5mm2/Nm for the coated sample and k=(0.17 ± 0.02) x10 −5 mm2/Nm for the 100Cr6 counterpart were achieved. Therefore, the modification of MoSx films with Cu is promising to reduce the sensitivity of the friction on the environment and improve the tribological properties.

Effect of SnS thin film thickness on visible light photo detection

In this study, SnS thin films of various thicknesses (500 nm–700 nm) were prepared by the thermal evaporation technique for potential photodetector application. High purity SnS prepared at 1000 °C is used to deposit thin films at room temperature. The prepared SnS thin films were characterized to assess the thickness effect on the crystallite size, morphology, transmittance, band gap, and photo-sensing properties. SnS pure phase confirmed through XRD and Raman spectral analysis. Among the fabricated SnS thin films, the sample having a thickness of 650 nm showed better crystallinity with higher crystallite size and preferred orientation of crystallites. SnS grew plate-like-columnar grain morphology of different widths and thicknesses which is confirmed by FESEM results. The UV–Vis studies showed a minimum band gap value obtained for 650 nm thickness film. The 650 nm thickness SnS films have a highest photo response of 6.72 × 10−1 AW−1, external quantum efficiency (EQE) of 157%, and detectivity of 14.2 × 109 Jones. The transient photo-response analysis showed the 650 nm SnS thin film has a 5.3 s rise and 5.1 s fall duration, which is better suitable for photodetector applications compared to other samples.

On the preferred orientation in Ti1–x Al x N and Ti1–x–y Al x Si y N thin films

Abstract The influence of the deposition geometry and the chemical composition on the form and degree of the preferred orientation of crystallites was investigated in TiN, Ti1–x Al x N, and Ti1–x–y Al x Si y N thin films deposited by cathodic arc evaporation. The deposition geometry was varied by changing the angle between the cathodes and the substrates. The chemical composition of the thin films was modified by the choice of the cathodic materials. In TiN thin films, the crystallites were preferentially oriented with the {111} direction perpendicular to the sample surface, independent of the deposition geometry. Besides, a well-pronounced in-plane texture was observed. Co-deposition of Ti, Al, and Si in nitrogen atmosphere stimulated inclination of the texture direction towards the sample surface, which can be described as a change of the texture direction related to the sample surface perpendicular direction, and reduced the amount of the in-plane texture in the coatings (the preferred orientation of crystallites in the plane of the coating).

Deposition of Al2O3 coatings in Ar-O2 low-pressure discharge plasma under a high dissociation degree of O2

The deposition of Al2O3 coating with a corundum structure was done by anodic evaporation in a low-pressure arc with a self-heated hollow cathode. The conditions were created for increasing the energy of plasma electrons and a corresponding increase in the frequency of O2 dissociation by contraction of the discharge in the anode region. The discharge was maintained in a combined mode with a constant current (70 – 100 A), on which current pulses (100 μs, 1 kHz) with adjustable amplitude (up to 220 A) were superimposed. This mode ensured a change in the degree of O2 dissociation in the range of 0.3 – 0.5 at constant average discharge current and Al evaporation rate. It is shown that an increase in the degree of O2 dissociation leads to an increase in the rate of coating deposition by a factor of 1.3 and promotion of the preferred (300) orientation of crystallites. The effect is due to the features of the adsorption of molecular and atomic oxygen on the Al2O3.