REVEALING SPECIFIC FEATURES OF STRUCTURE FORMATION IN COMPOSITES BASED ON NANOPOWDERS OF SYNTHESIZED ZIRCONIUM DIOXIDE

The study of composites based on zirconium dioxide, especially partially stabilized ones, is relevant for a number of reasons. It is promising as a tool or structural material, for example, in designing hydro abrasive nozzles with improved mechanical properties [1] and is of great functional importance. In particular, it is used in medicine as a material for endoprostheses [2, 3] and dentures [4, 5]. This explains numerous publications on methods of obtaining and processing these composites [6, 7]. Another important factor is that zirconium compounds are widespread in the lithosphere. According to various data, Clark of zirconium is from 170 to 250 g/t. Therefore, expansion of technological capabilities for the use of this material, obtaining products with a competitive market price will contribute to the promotion of zirconium products on the world market. Materials based on nanopowders of partially stabilized zirconium dioxide with various additives of refractory compounds are especially promising [8, 9]. It should be noted that some countries where the greatest deposits of zirconium are concentrated have no own mass production of powder of this type so far. Therefore, the study of new methods of obtaining nanopowders and products based on this material will promote the creation of preconditions for the large-scale production of zirconium dioxide nanopowders.

The paper presents the results of computer modeling and prediction of the mechanical properties of composite materials with a polycarbonate matrix filled with short glass inclusions. At the microlevel, the influence of the volume of inclusions on the mechanical properties of the designed composite based on polycarbonate matrix is studied in the DIGIMAT (France) program. It was found that with a ratio of the sizes of inclusions in the range of 468÷60, the par-  ticles have a needle shape, and the material with such inclusions has a higher stress limit and elastic modulus than with a shape coefficient less than 50. The components of the fiber orientation tensor were also determined, at which the values of computer modeling are in good agreement with experimental data. The influence of the size of the finite element grid on the characteristics of the composite at the macro level was studied, and recommendations were given for choosing the size of the face of the finite element. The adequacy of computer models was confirmed by the results of field tests. The paper presents the results of testing flat samples made by injection molding technology.
Mechanical tests were carried out for three variants of samples made of composite material based on a polycarbonate matrix with 10 %, 20 % and 30 % inclusions. The discrepancy between the experimental and computer results for samples with 10 %, 20 % content of short chopped fibers is explained by the influence of technological factors on the properties of the material at the macro-level. The conducted research allowed us to develop a computer modeling technique used at the stage of development of polymer composites based on thermoplastic matrices with short glass inclusions.
Keywords: composite material, polycarbonate, short glass fibers, DIGIMAT, elastic modulus. 5/12 ( 113 ) 2021 trochromic material. In this case, the volume of polyvinyl alcohol in the composite was approximately equal to the volume of nickel hydroxide, and the efficiency of Ni(OH) 2 deposition and colorationbleaching processes was approximately 100 %.
Keywords: electrochromism, electrodeposition, nickel hydroxide, polyvinyl alcohol, deposition duration, coating thickness, adhesion. The use of electrochromic elements in "smart" windows leads to significant savings in electricity required for cooling premises. However, the high cost of these devices does not allow the technology to be widely used. Since the cost is determined by costly vacuum deposition methods, the development of other cheaper methods of deposition of electrochromic element layers is urgent.

Vadym Kovalenko
Aspects of alternative to vacuum formation methods -cathode template electrochemical deposition of composite electrochromic Ni(OH) 2 -PVA films were investigated.
The study is devoted to determining the effect of the duration of deposition of the electrochromic layer on their physicochemical characteristics, in particular, on the optical and electrochemical properties. The deposition was carried out on fluorine-doped tin oxide glasses (FTO glasses). The time of deposition was chosen equal to 5, 10, 20, 40, 60, and 80 minutes.
As a result of the experiments, it was shown that the optimal duration of deposition under the selected conditions of the electrochromic layer formation was the interval from 5 to 20 minutes, inclusive. The deposition time of 40 minutes did not improve the optical characteristics of the film. At the same time, with the deposition duration of 60 and 80 minutes, the electrochemical and optical parameters sharply decreased, the coloration depth and irreversibility during bleaching, as well as the specific capacitances of the processes decreased.
In the course of data processing, the film thickness was calculated depending on the duration of deposition in several ways. Comparison of the graphs obtained made it possible to determine the approximate amount of polyvinyl alcohol in the electrochromic composite coating, as well as to estimate the current efficiency of the electrodeposition and oxidation-reduction process of the elec- The procedure for the identification of white jewelry alloys based on precious metals, in particular, silver, platinum and platinum group metals with different contents of alloying components, by testing on an assay stone and by the method of X-ray fluorescence analysis has been considered. The methodology for assessing the compliance of silver and platinum fineness in white jewelry alloys of different component composition with the requirements of regulatory documents and the procedure for their identification has been improved.
It has been established that the silver fineness in precious alloys of the AgCu, AgZnCu system, determined using the potassium dichromate reagent on the test stone, depends on the manifestation of the contrast of the qualitative reaction from the standard sample (assay needle).
It has been proven that for testing silver alloys containing palladium, the "Acid reagent for gold 750" is effective, which works to determine the qualitative and approximate content of silver in alloys.
It was determined that the reagent "Ferrous-cyanide potassium" is very sensitive to changes in the alloy composition of silver alloys and makes it possible to establish the silver content with an accuracy Hardness testing using the Vickers method and SEM was used to analyze the microstructure. X-ray diffraction (XRD) testing was conducted to ensure the Fe-11Al-Mn alloy phase and corrosion testing was carried out using the three-electrode cell polarization method. With the addition of Mn, the Vickers hardness of the Fe-11Al-Mn alloy decreased from 331. 50  respectively. An important factor for improving the performance of cryogenic materials is the impact mechanism. The resulting impact toughness increased by 2.85 J/mm 2 to 3.30 J/mm 2 for F. 15 and F25, respectively. The addition of the element Mn increases of 5 %. The presence in silver alloys of such impurities as zinc, cadmium, nickel, gold, palladium and others increases the error in determining the fineness of silver and forms a different color and shade.
It has been proven that testing of silver alloys on an assay stone with silver nitrate is effective only for the СрМ system. The presence of zinc in 925 sterling silver alloys visually increases the color intensity of the sediment, which indicates a higher overestimated fineness.
It has been found that the identification of the content of precious alloys based on platinum for the presence of ligature components is carried out with a potassium iodide reagent at t=120 °C by the color and shade of the sediment.
The procedure for using potassium iodide during testing of precious platinum-based alloys has been optimized.
Keywords: assay control, precious metals based on silver and platinum, assay stone. the corrosion resistance of the Fe-11Al-Mn alloy. The lowest corrosion rate occurs at 25 % wt Mn to 0.016 mm/year. Based on the results, the F25 alloy has the highest mechanical and corrosion resistance of the three types of alloys equivalent to SS 304 stainless steel. The microstructure of Fe-11Al-Mn alloy was similar between before and after cryogenic temperature treatment, this condition showed that the microstructure did not change during the process. From the overall results, the Fa-11Al-Mn alloy is a promising candidate for material applications working at cryogenic temperatures by optimizing the Mn content.
Keywords: Fe-11Al-Mn, Microstructure, Mechanical characteristics, Impact, Corrosion resistance, Cryogenic temperature. 5/12 ( 113 ) 2021 (IMPs) between the steel and titanium layer. The barrier layers (height ~0.5 mm) of vanadium and copper alloys were surfaced by arc techniques while minimizing the level of thermal influence on the base metal. To this end, plasma surfacing with a current-driving wire and pulsed MAG surfacing were used. The obtained samples were examined by methods of metallography, X-ray spectral microanalysis, durometric analysis. It has been established that when a layer of vanadium is plated on the surface of titanium, a defectfree structure of variable composition (53.87-65.67) wt % Ti with (33.93-45.54) wt % V is formed without IMPs. The subsequent surfacing of steel on a layer of vanadium leads to the formation of eutectics (hardness up to 5,523 MPa) in the fusion zone, as well as to the evolution of cracks. To prevent the formation of IMPs, a layer of bronze CuBe 2 was deposited on the surface of vanadium. The formed layer contributed to the formation of a grid of hot cracks. In the titanium-vanadium-copper transition zones (0.1-0.2 mm wide), a fragile phase was observed. To eliminate this drawback, the bronze CuBe 2 was replaced with bronze CuSi 3 Mn 1 ; a defect-free junction was obtained. When using a barrier layer with CuSi3Mn1, a defectfree junction was obtained (10-30 % Ti; 18-50 % Fe; 5-25 % Cu). The study reported here makes it possible to recommend CuSi 3 Mn 1 as a barrier layer for welding bimetallic sheets "steel-titanium". One of the applications of the research results could be welding of longitudinally welded pipes of main oil and gas pipelines formed from bimetallic sheets of steel clad with titanium.
Keywords: steel-titanium bimetal, barrier layer, structure, intermetallic phases, interface boundary. samples treated by electrical discharge machining forms a thin film on the surface of friction of steel samples, which leads to a change in the relief of surfaces with an increase in the height of the microprotrusions, as well as the structuring of the transfer film in the direction of sliding. The effect of machining steel surfaces by electrical discharge on the wear resistance of metal-polymer tribosystem was established. The implementation of the devised technology could provide a significant increase in the wear resistance of metal-polymer tribojunctions.
Keywords: alloying electrode, wear resistance of metal polymers, tribojunction, electrical discharge machining, steel modification. This paper considers the technology of electrical discharge machining of steel friction pairs and reports the results of experimental studies. Analysis of the experimental studies has shown that increasing the "anode-cathode" voltage leads to a sharp decrease in the micro-hardness of the surface layer. The study has also made it possible to determine the characteristic dimensions of the structural elements, the height parameters of surface roughness. The elemental composition of the resulting surface of a steel 15KHGN2TA sample differs from the composition of coatings and the surface layers of samples modified by electrical discharge machining involving various electrodes. Under the "anode-cathode" system operation mode, a thin layer of coating with a stable modified structure forms on the surface of the cathode due to dissipative processes. It is shown that the height of surface irregularities on sections after friction is higher than on the surface sections outside the friction flow, which is associated with the formation of a friction transfer film on the samples' surface. It was established that the interaction of friction of steel Розглянуто особливості формування мікроструктури композитів на основі синтезованих хімічним способом методом розкладу з фторидних солей нанопорошків діоксиду цирконію. При цьому було використано фтороводневу кислоту, концентровану азотну кислоту, водний розчин аміаку, металевий цирконій, полівініловий спирт. Встановлено, що зменшення пористості нанопорошків в процесі спікання є головним завданням на шляху формування високощільних матеріалів.