Inorganic Materials: Applied Research最新文献

The microstructure and thermoelectric properties of materials based on p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.4Se_0.6 solid solutions doped with graphene are studied. The samples are obtained by spark plasma sintering of powders prepared by melt spinning and crushed in a ball mill together with graphene plates, which are introduced in an amount of 0.05, 0.1, and 0.15 wt %. Scanning electron microscopy is used to study the composition and microstructure. The samples with p-type conductivity have a fine-grained (on the order of hundreds of nanometers) structure with microsized tellurium-based eutectic inclusions. The samples with n-type conductivity contain grains with melted edges. The thermoelectric parameters are measured: Seebeck coefficient, electrical conductivity, thermal conductivity at room temperature and in the temperature range from 100 to 700 K; and the thermoelectric figure of merit is calculated. When adding 0.15 wt % of graphene plates to a p-type solid solution, the maximum thermoelectric figure of merit (ZT)_max of the material increases by 13% and is equal to 1.3 at 420 K. For a sample with n-type conductivity doped with graphene, the highest value of (ZT)_max = 0.83 at 470 K is obtained by adding 0.1 wt % of graphene plates.

On the basis of the research conducted, it is proposed to use the waste of the enrichment of ferruginous quartzites from KMA as the main raw material for the production of fire-polished glass-crystalline cladding material (glass silica). The regularities of the formation of the phase composition of glass silica with the formation of crystalline phases such as hematite and hypersthene are established. On the basis of the experimental studies using X-ray diffraction analysis, differential thermal analysis, and IR spectroscopy, a mechanism for the formation of the phase composition of glass silica is proposed. The advantages of the developed technology in comparison with those of the analogs are shown. It is found that, after plasma chemical modification, performance indicators of the front surface of glass silica, such as water resistance, acid resistance, alkali resistance, and hardness, increase significantly.

Synthesis of complex oxide ceramic materials in a fast electron beam is discussed. Powder reagents, along with irradiation, are exposed to air currents, which prevent gases and particles from entering the accelerator. To keep ultrafine powder mixtures in the irradiation zone, they were granulated. Two methods for granulation of an ultrafine powder with the composition 80 wt % Al₂O₃ + 20 wt % (ZrO₂–3Y₂O₃) were used. The first method involved moistening, drying, and subsequent sifting through a coarse sieve. In the second method, the powder mixture was supplemented with a binding additive, which gave a stable volumetric shape to the sample. For the granulation methods used, the features of short-term heating of the oxide powders in air with a fast electron beam with energy of 2 MeV and the zirconia corundum synthesis under these conditions were studied. Granulation of the ultrafine powder made it possible to minimize its weight loss under irradiation. During irradiation of the powder mass, the latter was locally melted, which was accompanied by an intense gas release leading to the formation of hollow ceramic droplets. It has been shown by X-ray diffraction analysis that the oxides do not mutually dissolve in the droplet walls and the recrystallization processes are accompanied by the formation of cubic aluminum oxide microcrystallites and the transition of aluminum oxide in them from the monoclinic to corundum phase. The presence of microcrystallites of evenly distributed fine zirconia dioxide particles in the intergrain spacings indicates the synthesis of zirconia corundum under irradiation. At the same time, the phase composition of zirconium dioxide after irradiation does not change as compared with the initial powder.

We explored the physical and mechanical properties of ceramic material containing complex oxide solid Zr_{1– n}[YbNd]_nO₂ solution and corundum micro phase and its potential use in prosthetic dentistry practice meeting aesthetic and strength requirements. The ceramic obtained is shown to have a static bending strength of 850 MPa. According to the international standard ISO 6872: 2015, “Dentistry–Ceramic Materials,” the materials belong to the fourth and fifth class. This makes it possible to apply the material not only for making single crowns but also to manufacture four-unit bridgework having no localization and fixing restrictions. The new ceramics meet the requirements set forth in prosthetic dentistry and feature required color characteristics and has high opacity which makes it possible to mask the supporting structures.

Abstract—The effect of nanofiller (NF) additives containing nickel oxide nanoparticles (NPs) stabilized by a polymer matrix of high-pressure polyethylene (PE) obtained by the mechanochemical method on the peculiarities of the structure and properties of metal-containing nanocomposites based on isotactic polypropylene (PP) and high-pressure polyethylene (PE) is studied. Differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used. Improvement of the strength, deformation, and rheological parameters as well as thermo-oxidative stability of the obtained nanocomposites is found. This is apparently associated with the synergistic effect of the interfacial interaction of nickel-containing nanoparticles in the PE matrix with the components of the PP/PE polymer composition. It is shown that nanocomposites based on PP/PE/NF can be processed by both the method of pressing and the methods of injection molding and extrusion, which expands the scope of their application.

The microstructure and thermophysical properties (specific heat capacity, thermal diffusivity, thermal conductivity) of fine-grained ceramic composites based on yttrium-aluminum garnet Y_2.5Nd_0.5Al₅O₁₂ (YAG:Nd) with different molybdenum contents (10, 20 and 40 vol %) were studied. Submicron garnet powders of Y_2.5Nd_0.5Al₅O₁₂ were obtained by the coprecipitation method; YAG:Nd + Mo powder compositions with the YAG:Nd core–Mo shell structure were obtained by deposition of molybdenum onto the surface of garnet particles; samples of ceramic composites were obtained by the method of spark plasma sintering (SPS). Electron microscopy and X-ray phase analysis were used to study the microstructure and phase composition of the composites. YAG:Nd + Mo composites have a high relative density (98.1–99%) and a uniform fine-grained microstructure with a garnet grain size of 2–3 μm. Sintered YAG:Nd + Mo composites at room and elevated temperatures (up to 1100°C) have a high thermal conductivity coefficient exceeding the thermal conductivity coefficient of uranium dioxide UO₂, which allows using these materials as heat-resistant inert fuel matrices. It was shown that higher thermal conductivity of composites is ensured at a content of at least 20 vol % Mo. In composites with the addition of 20 and 40% Mo, the thermal conductivity coefficient at 1100°C reaches 7.0 and 8.8 W m^–1 K^–1, respectively.

Synthesis of highly porous ceramic materials for catalytic converters based on coarse-dispersed αAl₂O₃ using a combination of compaction and thermochemical synthesis with the participation of active ultrafine binders is carried out. Using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), it is established that the morphology of the synthesized material simultaneously includes large pores between filler particles (dominant αAl₂O₃ phase) and submicron pores in transboundary regions that appeared during the processes of liquid-phase sintering and gas evolution. A significant amount of indialite (Mg₂Al₄Si₅O₁₈) and spinel (MgAl₂O₄) formed as a result of thermochemical synthesis on surfaces and in the gaps between coarse-dispersed particles is revealed. The dominant pore size (according to the volume of mercury intrusion) is from 20 to 60 μm (about 73%), as well as pores with size from 0.4 to 2 μm (about 6%).The average pore size is about 9 μm. Highly porous materials with these characteristics of the pore space can be effectively used after modification as catalytic converters for the dehydrogenation of alkyl aromatic hydrocarbons with large molecular sizes (about 400 nm) with a long mean free path on the order of ~3–4 μm.

Abstract—The reliability of numerical modeling of crack growth in a laminate glass-epoxy composite under combined loading by opening (mode I) and shear (mode II) of an interlaminar crack was assessed. According to experimentally determined standard (DCB and ENF) and nonstandard (SLB and OLB) methods for the values of interlayer crack resistance parameters under individual and combined loading modes I and II, the exponent in the Benzeggagh-Kenane equation was calculated as a material constant of a laminated epoxy glass composite. Using this parameter and using the ANSYS application software package within the framework of linear elastic fracture mechanics and the virtual crack closure method, the numerical finite element modeling of interlaminar crack resistance of SLB and OLB type specimens was carried out under a combined loading mode with a different fraction of modes. With an optimal number of elements in a finite element mesh corresponding to a given length of the crack growth trajectory, the numerical modeling provides sufficient accuracy in calculating the limit load of the beginning of crack growth with a minimum amount of calculations and good agreement between the experimentally determined and calculated crack resistance parameters.

Abstract—The possibility of a conglomeration of elemental powders in the mechanical synthesis of a high-entropy 30Fe–30Cr–20Ni–10Mo–10W alloy has been determined. The distribution of particles of elemental powders in conglomerates formed during mechanical alloying has been studied. The influence of mechanical alloying modes on the content of conglomerates of a fraction of more than 32 μm in the powder charge is determined. The phase composition of the conglomerates after hydrogen heat treatment has been studied. The resulting conglomerates can be used in the process of additive manufacturing of parts of oil and gas equipment for operation in conditions of high temperatures and corrosive effects.

A technique for obtaining SiO₂–Cr₂O₃ coatings on a Y-TZP (ZrO₂ stabilized by Y₂O₃) zirconia ceramic substrate is proposed. The coating has been created in three stages: (i) forming a SiO₂ adhesion layer by applying a 5% solution of 3-aminopropyltriethoxysilane alcohol onto the ceramic substrate surface with the subsequent heat treatment at 450 ± 5°C for 30 min, (ii) deposition of Cr (purity 99.9%) by pulse magnetron sputtering onto the prepared ceramic substrate with the formed SiO₂ layer, and (iii) diffusion oxidation of Cr deposited onto the ceramic substrate to Cr₂O₃ in a muffle furnace at a temperature of 450 ± 5°C for 30 min. The mechanical characteristics of the coating have been examined depending on the preliminary and finishing operations (abrasive-jet machining and polishing). Samples with the coating of a submicron thickness of 150 ± 20 nm having the lamellar nanostructure, an open porosity value of 1.3%, a microhardness of 2000 HV, roughness Ra of 0.32–0.63, a friction coefficient of 0.175, and an abrasion resistance against loadings 184% higher than for pure zirconia ceramics have been obtained.