Inorganic Materials: Applied Research最新文献

Experimental studies were conducted on the high-temperature forming of materials based on TiB/TiAl(Nb, Mo)B under process conditions that combine combustion in the mode of self-propagating high-temperature synthesis (SHS) of the initial powder components and their shear deformation following the passage of the combustion wave—free SHS compression. The objects of study were composites consisting of 100% TiB–(20–40) wt % Ti (TiB layer) and TiAl(Nb, Mo)B alloy (at %: 51.85 Ti–43 Al–4 Nb–1 Mo–0.15 B), as well as two-layer composite materials with the following layer proportions, vol %: 70TiB/30TiAl(Nb, Mo)B, 50TiB/50TiAl(Nb, Mo)B, 30TiB/70TiAl(Nb, Mo)B. The degree of deformation was chosen as the criterion for formability of the composites during shear deformation. It was established that, by varying the composition of each layer in the composite and the technological parameters of free SHS compression, it is possible to regulate the degree of deformation from 0.2 to 0.55. It was shown that the technological parameters of free SHS compression (holding time, pressing pressure, deformation rate) and the initial composition affect the formability and structure of the composites. The structural features and phase composition of the composites obtained were studied. It was demonstrated that a diffusion zone forms between the ceramic and intermetallic layers as a result of chemical interaction, the size of which can be regulated within the range of 30–150 μm.

A method for obtaining europium and gadolinium hafnates with the general formula Eu_2–xGd_xHf₂O₇ at x = 0–2 using microwave radiation is considered. The influence of the duration of microwave treatment and the temperature of subsequent calcination on the phase composition of europium and gadolinium hafnate powders is investigated. The optimum microwave treatment time for powder systems that ensures the maximum content of europium hafnate and gadolinium hafnate in the phase composition of the material is established. Deviations from the found optimal duration of microwave exposure result in samples containing phases of individual oxides of the initial metals, namely, hafnium dioxide and rare earth element oxides. Heat treatment at 1350°C intensifies the process of ordering the crystal structure, facilitating the transition from the metastable fluorite phase to the stable pyrochlore phase. This conclusion is supported by the calculated unit cell parameters of Eu_2–xGd_xHf₂O₇ compositions at x = 0 and 2 that underwent heat treatment at 1200–1450°C. In systems with x = 0.5–1.5 annealed at 1500°C, the dependence of the structural type in which they crystallize on the duration of microwave treatment is determined.

Abstract—This research studied the effect of centrifugal casting on the mechanical properties of deformable semi-finished products made of aluminum alloys of the Al–Zn–Mg–Cu and Al–Mg systems for space technology products. The study was carried out on sheets with a thickness of 3 mm and a rolling ring with a thickness of 10 mm. The samples were obtained from annular cast blanks measuring 350/240 mm (outer/inner diameter) cast by centrifugal casting. Hardness measurements were carried out along the width of the cast ring. The measurement results showed that the hardness practically did not change over the entire width, except for a zone at a distance of 5 to 7 mm from the inner edge of the ring. In this zone, the hardness decreases sharply. It has been determined that deformed semi-finished products obtained from blanks cast by centrifugal casting have minimal anisotropy of strength properties. The properties of the rolling ring of the Al–Mg alloy system exceed the properties of similar products manufactured using standard technologies. The proposed technology for manufacturing solid-rolled rings from blanks obtained by centrifugal casting will not only increase the reliability of products with a significant reduction in labor intensity, but also reduce their weight by increasing their mechanical characteristics.

Analysis of the mechanical behavior of aluminum reinforced with metallized spheres is carried out. Samples of reinforced aluminum obtained by improved casting technology are tested for bending. The role of metallized spheres in resistance to deformation is studied. The dependence of the bending strength on the diameter of the reinforcing spheres is determined. It is established that the use of spheres of minimum size is preferable, since the maximum load is achieved with low deformation and elongation of the sample. The use of polystyrene foam spheres coated with a copper–graphite layer results in a lightening of the product by up to 30% of the total weight.

The structure and thermal stability of the amorphous alloy Al₈₅Ni₅Fe₇La₃ in the initial rapidly quenched state and after xenon ion irradiation with energy of 167 MeV in the range of fluence values of 10¹²–2 × 10¹⁴ ions/cm² were studied. On the basis of the modeling of defect formation profiles, the heterogeneity of the defect distribution over the thickness of the irradiated sample was found. The mean free path of xenon ions was determined, which determines the zone of maximum accumulation of radiation defects. It is in this zone that nanocrystallization with the primary precipitation of the metastable intermetallic Al₈(Fe,Ni)₂La was detected by electron microscopy methods. A comparative analysis of the alloy structure after quenching, irradiation and annealing was carried out using complex structural research methods. It is shown that irradiation leads to a decrease in the degree of short-range order in an amorphous matrix and increases the thermal stability of an amorphous nanocrystalline structure partially crystallized as a result of irradiation.

Abstract—To obtain a composite with interpenetrating intermetallic/ceramic phases (of type IPC, interpenetrating phase composites) by the self-propagating high-temperature synthesis (SHS) method, the Ni–Al–Ti–2B powder system was used. It consisted of mechanically activated composite particles-granules (Ni + Al) and a mixture of finely dispersed boron and titanium powder. The quantitative ratio between the granules and the Ti + 2B mixture was varied. For all compositions, the synthesis was carried out in the combustion mode without heating. In the combustion wave front, the chemical reactions occurred in the composite granules and in the mixture around the granules, between titanium and boron. As a result of combustion a porous framework of titanium diboride was formed; a melt of nickel aluminides penetrated into the pores of the framework. The metal–ceramic combustion product is characterized by developed porosity and a composite structure with diboride and intermetallic phases located like interpenetrating frameworks. The TiB₂–NiAl structure depends on the ratio of components in the mixture. The pores formed in place of the granules, repeating their shape.

Metallic zinc of grade Ts3 is not widely used because of its lead content of up to 2.0–2.5%. The possibility of synthesizing a new alloy based on the zinc alloy TsAM4-1 using off-grade zinc of grade Ts3 and additional alloying with metallic sodium was evaluated (as a result, the alloy designation TsAM4-1 was changed to TsAMSv4-1-2.5). The effect of sodium addition on the corrosion-electrochemical behavior of the zinc alloy TsAMSv4-1-2.5 in a NaCl electrolyte was studied using a pulse potentiostat PI-50-1.1 by the potentiodynamic method at a potential scan rate of 2 mV/s. It was shown that alloying the TsAMSv4-1-2.5 alloy with sodium shifts the potentials of free corrosion, pitting formation, and repassivation toward the positive region. With increasing chloride ion concentration in the NaCl electrolyte, the corrosion rate of the alloys increases regardless of their composition. The addition of sodium to the TsAMSv4-1-2.5 alloy reduces its corrosion rate by 10–15%. The improvement in corrosion resistance of the zinc alloy TsAMSv4-1-2.5 by 10% allows for an equivalent reduction in the thickness of protective coatings on protected products, as well as a decrease in environmental contamination by lead.

The comprehensive investigation results of surface morphology, the internal structure, and the physical and physicomechanical properties (thermal conductivity coefficient, specific electrical resistance, tensile strength, Young’s modulus) of carbon fiber obtained from isotropic pitch based on heavy oil pyrolysis resin are shown in this paper. The pristine isotropic pitch was doped with ultralong double-walled carbon nanotubes with a single filament length exceeding 10 000 nm, with their content varying from 0 to 1.0 wt %. The moulded carbon fiber, after stabilization by thermal oxidation unfusible state, was exposed to various heat treatment regimes: carbonization at 2000°C, as well as graphitization at 2500 or 2800°C. It was shown that carbon nanotubes content increase leads to different effects. Compared to undoped carbon fiber, there is an increase in the thermal conductivity coefficient (from 6.61 to 12.72 W/(m K)) and a decrease in specific electrical resistance (from 33.90 to 5.41 μΩ m). However, this is accompanied by inhomogeneities formation in doping component distribution within the carbon fiber filament, resulting in a significant degradation of the physicomechanical properties. Typical surface and structural defects of the final filament (overstretching, protrusions, hollows) that appear during its moulding and depending on the carbon nanotube content in the pitch material are discussed.

The influence of the purity of the initial components on the mechanical and thermoelectric properties of extruded samples based on Sb₂Te₃–Bi₂Te₃ (p-type conductivity) and Bi₂Te₃–Bi₂Se₃ (n-type conductivity) solid solutions is studied. Powders of materials (with a purity of 99.99, 99.999, and 99.9999 wt % of the main substance) obtained by rapid crystallization of the melt in water or by grinding ingots fused in an ampoule are used. The samples are finely crystalline, the grain sizes do not exceed 10 μm, and materials with p-type conductivity contain inclusions of the second phase (tellurium-based eutectics). The mechanical and thermoelectric properties are determined; the ultimate strength during compressive deformation at room temperature of these samples is 170 ± 20 MPa for material with p-type conductivity and 241 ± 17 MPa for material with n-type conductivity. The thermoelectric parameters (electrical conductivity, Seebeck coefficient, thermal conductivity, and thermoelectric figure of merit) of samples are measured in the range from 100 to 600 K. The purity of initial components does not have a significant effect on the thermoelectric figure of merit (ZT) of samples with p-type conductivity. For samples with n-type conductivity obtained from the purest materials, the maximum of thermoelectric figure of merit ZT is shifted towards higher temperatures. The maximum thermoelectric figure of merit is ZT_max ~ 1.1 at 340 K for material with p-type conductivity and ZT_max ~ 1.0 at 420 K for material with n-type conductivity.

This work is devoted to the synthesis and determination of physicochemical properties of biochars obtained by hydrothermal carbonization (HTC) of plant biomass, in particular, peach waste. The influence of material processing modes on the physicochemical properties of materials was assessed; namely, the features of changes in the crystal structure and chemical composition depending on the carbonization temperature of samples were determined. Scanning electron microscopy, energy-dispersive elemental analysis, IR Fourier spectroscopy, Raman spectroscopy, and X-ray phase analysis were used to analyze the physical, chemical and morphological characteristics. It is shown that, with an increase in the carbonization temperature, the concentration of elemental carbon in samples increases and the content of functional groups decreases. Sorption studies were carried out under static conditions on model solutions of organic dyes—methylene blue (MB) and Congo red (CR). It was found that carbonization increases the adsorption capacity of HTC coals by 2.5–3 times, but, in general, does not affect the sorption absorption rate. The equilibrium time for both dyes was 15 min.