Formation Of Nanocomposite Structure Research Articles

Establishing patterns in the structure formation of polymer nanocomposites based on polyamide 6 during their crystallization processes

This paper reports experimental and computational studies on patterns in the structure formation of polymer nanocomposites when different types of fillers are used. The study was conducted for nanocomposites based on polyamide 6 filled with carbon nanotubes or silicon dioxide nanoparticles. In the course of research, the mass fraction of the filler varied from 0.2 % to 4.0 %, and the cooling rate of the melt composite varied from 0.5 K/min up to 20 K/min. Data on experimental and theoretical studies into the mechanisms of structure formation of composites according to the method, which includes two stages, are given. According to the first stage, crystallization exotherms of nanocomposites were experimentally obtained when they are cooled from the melt at a given constant rate. The dependence of various characteristics of the crystallization process on the mass fraction of the filler and the cooling rate of the composite was established. At the second stage, based on the analysis of the obtained crystallization exotherms, theoretical studies were performed to determine the mechanisms of structure formation of nanocomposites at different stages of crystallization. For the initial stage, according to the nucleation equation, the presence of two mechanisms of structure formation – planar and volumetric – has been shown. Within the framework of the Kolmogorov-Avrami equation, the mechanisms of structure formation at the next stage of crystallization were established, which corresponds to the formation of ordered structures in the material within the volume of the polymer composite as a whole. The research was carried out assuming the existence of a mechanism of crystallization of the polymer matrix itself, which is realized on fluctuations in the density of the polymer, and a mechanism of crystallization, the centers of which are filler particles. The use of the proposed nanocomposites is promising for the manufacture of parts of energy equipment, electronic equipment, elements of chemical, processing, defense industry installations, etc.

Antibacterial and Anticandidal Activity of the Nanostructural Composite of a Spirothiazolidine-Derivative Assembled on Silver Nanoparticles.

Our aims in this work are the preparation of an ionic liquid based on heterocyclic compounds with Ag nanoparticles and the investigation of its application as an antibacterial and anticandidal agent. These goals were achieved through the fabrication of an ionic liquid based on Ag nanoparticles with 5-Amino-3-(4-fluorophenyl)-N-hexadecyl-7-(4-methylphenyl)-2-H spiro[cyclohexane1,2'-[1,3]thiazolo [4,5-b]pyridine]-6-carbonitrile (P16). The nanostructure of the prepared ionic liquid was characterized using techniques such as FTIR, 1HNMR, 13CNMR, UV, SEM, and TEM. The biological activity of the prepared compound (P16) and its nanocomposites with Ag nanoparticles was tested using five clinical bacteria (Pseudomonas aeruginosa 249; Escherichia coli 141; Enterobacter cloacae 235; Staphylococcus epidermidis BC 161, and methicillin-resistant S. aureus 217), and three Candida species (Candida utilis ATCC 9255; C. tropicalis ATCC 1362, and C. albicans ATCC 20402). The FTIR, 1HNMR, and 13CNMR results confirmed the chemical structure of the synthesized P16 compound. The nanostructure of the prepared ionic liquid was determined based on data obtained from the UV, SEM, and TEM tests. The antibacterial and anticandidal results showed that the biological activity of the compound (P16) was enhanced after the formation of nanocomposite structures with Ag nanoparticles. Moreover, the biological activity of the compound itself (P16) and that of its nanocomposite structure with Ag nanoparticles was higher than that of ampicillin and amphotericin B, which were used as control drugs in this work.

R-GO coated magnetic high entropy alloy/oxide nanocomposites as highly efficient Fenton and photo-Fenton catalysts

To utilize the synergistic effect of high entropy alloy, high entropy oxide and r-GO (reduced graphene oxide), we prepared r-GO coated nanocomposites comprising bcc high entropy alloy/spinel high entropy oxide (H730) and bcc high entropy alloy/hexagonal high entropy oxide (H725), encompassing elemental constituents such as Aluminum (Al), Chromium (Cr), Manganese (Mn), Iron (Fe), and Cobalt (Co). The samples were meticulously synthesized using the sol-gel technique followed by subsequent calcination at a temperature of 700 °C under nitrogen or air atmospheres. The assessment through X-ray diffraction and electron diffraction methodologies conclusively confirmed the successful formation of nanocomposite structures. The electron microscopy and Raman spectroscopy confirmed the r-GO coating over both the composites. The saturation magnetization values of 32 and 10 emu/g were noticed at 30 kOe for H730 and H725 samples, respectively. In-depth analysis using X-ray photoelectron spectroscopy revealed the coexistence of diverse oxidation states within the constituent elements of the samples. Notably, the H730 nanocomposite exhibited superior catalytic efficacy in comparison to its H725 counterpart for the degradation of p-nitrophenol (PNP) under both Fenton and photo-Fenton reaction conditions. Impressively, complete degradation of PNP was achieved within a remarkably short span of 18 min. Furthermore, the H730 nanocomposite alongwith stronger magnetic attributes, demonstrated a notable 86 % degradation efficiency even after undergoing five consecutive cycles.

The effect of low-energy high-current pulsed electron beam irradiation on the structure, phase composition and mechanical properties of Ni3Al and Ni3Al-TiC composites

Using scanning and transmission electron microscopy, X-ray diffraction, indentation and bending tests we studied the evolution of microstructure, phase composition and mechanical properties of TiC-free Ni3Al and Ni3Al-TiC composites (TiC content was 10 and 30 vol%) fabricated by self-propagating high-temperature synthesis (SHS) under pressure induced by low-energy high-current pulsed electron beam (LEHCEB) irradiation with the surface energy density of 8, 12 and 18 J/cm2. It was found that the irradiation results in the improvement of phase composition of the near-surface layer by way of the increase of yield of SHS reaction. LEHCEB irradiation enables formation of nanocomposite structure in the near-surface layer of Ni3Al-TiC composites with decreased grain size of Ni3Al matrix, refined TiC particles and increased volume fraction of TiC. This structure leads to the increase of microhardness but decrease of strength under bending. Two mechanisms of TiC particles refining are suggested. The effect of surface energy density on the manifestation degree of the found phenomena is discussed. The contribution of different hardening mechanisms to the overall hardening is considered.

Integration of hardness and toughness in (CuNiTiNbCr)Nx high entropy films through nitrogen-induced nanocomposite structure

The high-entropy alloy films show excellent comprehensive properties and have great application prospects in space, polar, deep-sea exploration. Compared with traditional ceramic films, the application of high-entropy alloy films is limited by the relative low hardness. In this paper, based on the nanocomposite structure formation principle in thermodynamics, we design the nanocomposite (CuNiTiNbCr)Nx films (HEFs). The introduced N atoms react with Ti, Nb, Cr to form (TiNbCr)N phase (accompanied by Cu and Ni segregation), and the structure of the HEFs changes from amorphous to a nanocomposite structure of CuNi-rich amorphous matrix-(TiNbCr)N nanocrystalline phase. The nanocomposite HEFs exhibit high hardness, high toughness, and excellent wear performance. These results indicate that nanocomposite HEFs have potential applications in the field of extreme environmental wear protection.

Formation of Nanocomposite Structures under Laser Irradiation λ = 1.064 µm DVD-R Coated with Aluminum Foil

Purpose. Obtaining, characterization and mathematical description of atomic force microscopic images of 1D-dimensional whisker-like nanocomposite structures formed under the conditions of high-intensity laser processing using.Formation of polycarbonate with inner thin layers of Al, semiconductor metals Si, Sb, Te, Ge, and ZnS and SiO2 compounds in a DVD-R-5 disc covered with aluminum foil.Methods. Applied pulsed laser radiation for laser processing of DVD-R-5 was used. The methods of confocal, atomic force and scanning electron microscopy to study microand nanostructuring after laser processing of DVD-R-5 patterns were used. The direct and inverse Fourier transforms atomic force images were carried out. Analysis of solutions to the heat balance equation as applied to the results of laser processing was performed.Results. Under high-speed exposure to laser radiation (TEM01 or TEM10 modes) on a DVD-R-5 sample coated with aluminum foil, VNS were detected and studied. With the help of direct and inverse Fourier transforms on atomic force images of the surface after laser processing, the periodicity of the formed VNS was confirmed. It is shown that the process of DVD-R-5 laser processing is adiabatic, the propagation velocity of the melting wave front exceeds the sonic one in polycarbonate. The conclusion about the formation of VNS due to self-focusing and filamentation of laser radiation in the reflected diffracting beams of each of the mode components is substantiated.Conclusion. Under conditions of high-intensity laser processing by repetitively pulsed laser radiation with the TEM01 or TEM10 modes, 1D-dimensional VNSs are formed with a thickness at the base of up to 0.5 μm and a height of more than 1 μm, the composition of which can include both conductors, semiconductors, and their compounds. The resulting WNSs have a highly developed ordered surface structure, which may indicate that their application is promising.

Thermoelectric properties and microstructure of nanocomposite Sb-GeO2 and Sb–TiO2 thin films

This work reports on fabrication and thermoelectric properties of Sb-GeO2 and Sb–TiO2 nanocomposite thin films. The formation of nanocomposite structure includes the precipitation of Sb phase and the amorphous GeO2 or TiO2 phase. In the Sb-GeO2 nanocomposite, the formation of large rhombohedral Sb grains is observed, where monoclinic Sb are formed as intermediate phase. This contributes remarkably to the elevation of conductivity, while results in the reduction of Seebeck coefficient and power factor. Contrary, the effective inhibition of Sb crystallization caused by TiO2 leads to the smaller monoclinic and rhombohedral Sb grains with homogeneous distribution in annealed Sb–TiO2 thin film. The existence of monoclinic Sb facilitates to acquire excellent thermoelectric properties. Tiny grains within the films introduce more grain boundaries, making it possible to scatter and filter low energy carriers. This leads to high conductivity, remarkable rise of the Seebeck coefficient, and excellent power factor of 765.5 μW/mK2 at 650 K. The results demonstrate that the Sb–TiO2 nanocomposite materials with high power factor can be a candidate for thermoelectric devices.

Structure of AlNiGd nanocomposites with enhanced ductility produced by high pressure torsion processing

The fully consolidated bilayer (consisting of two amorphous Al86Ni9Gd5 melt-spun ribbons) disks with a diameter of 5 mm were produced using unconstrained high pressure torsion (HPT) processing subjecting for 2–5 turns at applied pressures of 2 and 4 GPa. The structure and mechanical properties of the disks as well as those of the as-prepared and heated up to 479 K ribbon samples were studied by X-ray diffraction analysis, transmission and scanning electron microscopy, three-point bending tests and measurements of microhardness. It was established that the heat treatment and consolidation resulted in formation of nanocomposite structures consisting of Al nanocrystals 21 and 6 nm in size, respectively, with enhanced microhardness. It was shown that the heat treatment of the ribbon led to a loss of the plastic strain (from 2 to 0.4%) while the consolidated disks retained the same level of plasticity as that in the as-cast amorphous ribbon. The possible reason of the enhanced plasticity of the nanophase composites obtained by deformation-induced crystallization was discussed.

Effect of Arc Currents on the Mechanical, High Temperature Oxidation and Corrosion Properties of CrSiN Nanocomposite Coatings

In methods for multi-arc ion plating technology, the behavior and characteristics of the arc spot determine the physical characteristics of arc plasma and the properties of the subsequent deposited coatings. In this paper, the effect of arc currents on the hardness, friction coefficient, high temperature oxidation, and corrosion properties of the CrSiN coatings was studied. According to the XRD and SEM results, with the increase of arc currents, the coatings grew preferentially to the CrN (111) crystal direction, and the CrN (220) crystal phase appeared at high currents of 90 A. In addition, the number of large particles increased when the current exceeded 70 A. The HR-TEM results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4 as explored by XRD. The maximum hardness was achieved at 3120 Hv when the coatings were deposited under currents around 70 A. However, the hardness values decreased with further increase of arc currents. From the contact of ceramic balls with the wear of coatings, the surface of coatings gradually produced friction marks, and the friction force increased from a steady friction force to a dynamic friction force. The high temperature oxidation results showed that fewer oxides were formed on the surface of the coatings when oxidized at 800 °C. It was also found that CrSiN nanocomposite coatings prepared at an arc current of 70 A had a larger corrosion potential and polarization impedance, which could effectively protect the tool matrix.

The Effect of Reactive Electric Field-Assisted Sintering of MoS2/Bi2Te3 Heterostructure on the Phase Integrity of Bi2Te3 Matrix and the Thermoelectric Properties.

In this work, a series of Bi2Te3/X mol% MoS2 (X = 0, 25, 50, 75) bulk nanocomposites were prepared by hydrothermal reaction followed by reactive spark plasma sintering (SPS). X-ray diffraction analysis (XRD) indicates that the native nanopowders, comprising of Bi2Te3/MoS2 heterostructure, are highly reactive during the electric field-assisted sintering by SPS. The nano-sized MoS2 particles react with the Bi2Te3 plates matrix forming a mixed-anion compound, Bi2Te2S, at the interface between the nanoplates. The transport properties characterizations revealed a significant influence of the nanocomposite structure formation on the native electrical conductivity, Seebeck coefficient, and thermal conductivity of the initial Bi2Te3 matrix. As a result, enhanced ZT values have been obtained in Bi2Te3/25 mol% MoS2 over the temperature range of 300–475 K induced mainly by a significant increase in the electrical conductivity.

Co3O4 quantum dots-polyoxometalate nanocomposites as visible light photoelectrocatalysts for selective oxidation of benzyl alcohol

Highly efficient visible-light photoelectrocatalysts were developed for mild oxidation of benzyl alcohol and its derivatives to related aldehydes with air as a safe and environmental friendly oxidant. The photoelectrocatalysts were designed by electrostatic association of the amino acids and [PMo12O40]3- for achieving (amino acid)3PMA followed by covalent attachment to Co3O4-QDs. The prepared Co/(ABA)3PMA and Co/(gly)3PMA nanocomposites were immobilized on charcoal using an alternate electrophoretic approach. Interestingly, the formation of nanocomposite structures remarkably enhanced the photo-generated charge separation and photoelectrocatalytic performance. Comparison of the results of photoelectrocatalytic oxidation of benzyl alcohol with that of photocatalytic and catalytic ones revealed that no reaction occurred during the catalytic tests, while the photocatalytic performance was positively affected by the utilization of a small bias (0.9 V vs. saturated calomel electrode). The Co3O4-QDs increases the visible light absorption and H3PMo12O40 with appropriate energy levels increases the charge mobility in nanocomposites structures. A plausible mechanism for the photoelectrocatalytic oxidation was suggested and illustrated using the results of scavenger tests and energy level determination.

Fabrication of ZIF-8 decorated copper doped TiO2 nanocomposite at low ZIF-8 loading for solar energy applications

The effects of crystallization time and amount of Zeolitic Imidazolate Framework-8 (ZIF-8) on the photocatalytic activity of ZIF-8 decorated copper (Cu) doped titania (TiO2) (ZIF-8/Cu-TiO2) powders were investigated in this study. The formation of nanocomposite structure of ZIF-8 crystals grown over the surface of core Cu-TiO2 particles containing heterojunction sites was observed at low ZIF-8 level. Powders containing ZIF-8 in the 5–46% range (weight basis) were synthesized and their activities in the photocatalytic degradation of an organic dye molecule were evaluated. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) analyses indicated that ZIF-8/Cu-TiO2 nanocomposite can be prepared at low levels of ZIF-8. HR-TEM images of 46% ZIF-8/Cu-TiO2 showed that Cu-TiO2 particles act as a core and ZIF-8 crystals grow over the surface of Cu-TiO2 particles during crystal growth and Cu-TiO2 particles were almost completely covered with ZIF-8 crystals. Photocatalytic activity increased with decreasing ZIF-8 level which was attributed to the formation of heterojunctions due to partial coverage of TiO2 surface. The 1st order reaction rate constant of ZIF-8/Cu-TiO2 nanocomposite containing 5% ZIF-8 was found to be 4 and 1.4 times that of bare ZIF-8 and Cu-TiO2, respectively. Partial coverage of TiO2 surface with ZIF-8 crystals lead to the formation of light exposed ZIF-8/Cu-TiO2 heterojunction sites for the enhanced degradation of the dye molecule. The presence of ZIF-8 in the nanocomposite also increased the adsorption of the organic dye by the interaction with open Zn2+ metal sites of ZIF-8 on the nanocomposite surface. This study revealed that ZIF-8/Cu-TiO2 nanocomposites could be prepared at low ZIF-8 levels and short growth times with higher photocatalytic activities than their constituents and nanocomposites prepared at higher ZIF-8 levels and longer growth times.

Структура и механические свойства композитных аморфно-кристаллических материалов на основе алюминия, синтезированных кручением под высоким давлением.

The results of the structural studies and hardness measurements of bi-and three-layer samples obtained by high pressure torsion of melt-spun ribbons of Al-based alloys with amorphous and crystalline structures have been presented. It has been established that straining of amorphous ribbons results in formation of nanocomposite structure while that refinement of crystalline structure and increase of microstrains takes place in crystalline ribbon. It has been found that the hardness of the consolidated samples increases with the increase of the deformation level up to 4,7 GPa.

PVA Treated PEDOT-PSS: TiO2 Nanocomposite Based High-Performance Sensors Towards Detection of Relative Humidity and Soil Moisture Content for Agricultural Applications

In this work, we authors report the investigation of polyvinyl alcohol (PVA) modified poly(3,4-ethylene-dioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS): titanium dioxide (TiO2) nanocomposite sensors towards relative humidity and soil moisture measurements at room temperature for agricultural applications. The morphological and structural features of the nanocomposite films were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR) and theromogravimetric analysis (TGA). These characterizations reveal the successful formation of nanocomposite structures with improved thermal stability. The conductivity of nanocomposite film shows significant improvement compared to pure PEDOT-PSS by three orders of magnitude. Sensitive layer of PEDOT-PSS:PVA doped TiO2 thin films were fabricated on ITO substrate using the spin coating technique to study relative humidity and soil moisture response. The nanocomposite film was subjected to varying levels of relative humidity (%RH) ranging from 5 to 95% and varied moisture content in soils of Montmorillonite and Kaolinite at room temperature. The resistance was found to decrease with increasing RH and gravimetric moisture content in Montmorillonite and Kaolinite soils. The humidity sensing response of PEDOT-PSS: PVA doped TiO2 (8 wt%) composite thin film shows higher sensitivity of 96% with fast response and recovery times of 10 and 50 s respectively. Further, the sensitivities of 10.5 and 8.32 kΩ with 0.2% variation in gravimetric water content were achieved upon exposure of the prepared sensor to red and black soils respectively. Due to being relatively inexpensive, simple fabrication technique, excellent sensitivity, good repeatability and reproducibility these PVA modified PEDOT-PSS: TiO2 nanocomposites sensors could be potentially useful in quantification of soil moisture content and relative humidity for agricultural applications.

Effects of Bias Voltages on the Structural, Mechanical and Oxidation Resistance Properties of Cr–Si–N Nanocomposite Coatings

Cr–Si–N nanocomposite coatings were deposited by multi-arc ion plating under different bias voltages. The influences of bias voltage on composition, microstructure, surface morphology and mechanical properties of Cr–Si–N nanocomposite coatings were investigated in detail. The HR-TEM, XRD, and XPS results confirmed the formation of nanocomposite structure of nanocrystalline of CrN embedded into the amorphous phase of Si3N4. The particle radius of CrN can be calculated from the half-width of the diffraction peak of CrN (200) and the value was about 20–60 nm. In addition, no diffraction peaks of CrSi2, Cr3Si, or Si3N4 were found in all the Cr–Si–N coatings. With the increasing of bias voltages from 0 to −200 V, the number and size of large droplets on the coating surface decreased, and the growth mode of the coatings changed from loose to dense. However, with the increasing of bias voltages from 0 to −200 V, the micro-hardness of the coatings increased and then decreased, reaching its maximum value at negative bias voltages of 100 V. It was found that the friction coefficient of Cr–Si–N coatings is almost the same except for the Cr–Si–N coatings deposited under bias voltage of 0 V. When the oxidation temperature was at 800 °C, the Cr–Si–N coating was only partially oxidized. However, with the increase of oxidation temperature to 1200 °C, the surface of the coating was completely covered by the oxide generated. The results showed that the bias voltages used in multi-arc ion plating had effects on the structure, mechanical, and high temperature oxidation resistance properties of Cr–Si–N nanocomposite coatings.

Prepare of nanocomposite structures through the magnetron deposition of material on the colloidal silica films and investigation of their properties

The paper presents a study of nanocomposite structures prepared by magnetron sputtering of titanium on a template formed during the deposition of colloidal silica particles on a metal substrate. The effect of power and spraying time on the formation of nanocomposite structures was studied. The features of the processes of growth of a metal film on an opal matrix and the Implantation of metal into its structure are revealed.

The Features of Nanocomposite Structure Formation on the Surface of Metal Products under the Influence of Low-Temperature Plasma

The work presents the study of technological considerations of the nanocomposite structure formation on complex profile surfaces under the influence of low-temperature plasma aimed at wear resistance increase of metal products, the research being conducted on the novel plant.

Structural and mechanical properties of carbon incorporation in DC/HiPIMS CrAlN coatings

Incorporating carbon into ternary nitride coatings to tune the mechanical and tribological properties of thin films is of great interest in order to improve the performance of tools and components. Especially, the approach to tailor CrAlN coatings by doping transition metals has been extensively studied in recent years. Nevertheless, the microstructural changes, induced by carbon incorporation, especially into Al-rich CrAlN coatings, are not yet fully understood. Thus, detailed investigations of the microstructure, performed by means of synchrotron radiation, using x-ray diffraction and x-ray photoelectron spectroscopy and Raman scattering with different laser excitation (355 nm and 532 nm), were conducted to understand the evolution of the mechanical properties of CrAlCN coatings depending on the carbon content.The results prove that an increasing carbon content significantly influences the microstructure, residual stresses, as well as the mechanical properties of the coatings. The presence of CC and CN bonds was proven by investigating the C 1s orbital. Furthermore, the increasing amount of carbon forms amorphous CrC structures, which were detected by analyzing the Cr 3p orbital. These results were confirmed for the amorphous phases by Raman scattering additionally indicating the formation of nanocomposite structures due to the formation of carbon nano-onoin like structures. The investigations of the crystalline structure using XRD reveal the existence of a fcc structure for the CrAlN phase as well as small amounts of hexagonal AlN in the CrAlCN coating with the highest carbon content.

Structure and properties of detonation gun sprayed coatings from the synthesized FeAlSi/Al2O3 powder

Structure and properties of detonation gun sprayed (DS) coatings from the synthesized FeAlSi/Al2O3 powder have been investigated. The powder was manufactured through a mechanically assisted self-propagating high-temperature synthesis route. A small addition of nanosized SiO2 particles to the reaction mixture for the synthesis of FeAl-FeAl2 eutectoid refines the thickness of B2-FeAl lamellar grains in the synthesized powder. Silicon arisen from the aluminothermic reduction of SiO2 during the synthesis is preferentially located in the B2-phase. High-quality coatings with porosity less than 1 vol% and nanocomposite structure have been obtained from the synthesized powder using a computer-aided ‘Perun-S’ detonation gun complex. Phase composition of the coatings includes B2-FeAl, hercinite FeAl2O4, FeAl2, A2-Fe-based solid-solution, Al2O3, and probably complex Fe2.95Si0.05O4 oxide. It is formation of nanocomposite structure with the mean crystallite size of main components in the range of ≈9–15 nm that seems to be responsible for the lower microhardness of the coatings from the FeAlSi/Al2O3 powder than that of the basic Fe-Al eutectoid composition. As-sprayed coatings from the synthesized FeAlSi/Al2O3 powder demonstrate good room and elevated temperature erosion behavior. Oxide dominated erosion with mixed brittle-ductile wear behavior is thought to occur in the coatings at 550 °C. The proposed powder modification is found to be beneficial for the oxidation resistance of DS coatings in air at 950 °C. Promoting of alumina formation during oxidation and the corresponding decline in Fe2O3 content in the oxide scale are considered as the main reasons for the slower oxidation kinetics of the FeAlSi/Al2O3 coatings as compared with those of the basic Fe-Al eutectoid composition.

Формирование и исследование химической чувствительности нанокомпозитных структур на основе облученных углеродных нанотрубок и оксидов металлов

Формирование и исследование химической чувствительности нанокомпозитных структур на основе облученных углеродных нанотрубок и оксидов металлов