Ceramics in the CaO–SiO2 and Na2O–CaO–SiO2 systems were obtained from powders synthesized from aqueous solutions of silicic acid and calcium nitrate at a molar ratio of Ca/Si = 0.5 by direct precipitation with the addition of an aqueous solution of ammonia. Solutions of silicic acid prepared via the dynamic ion exchange method passing an aqueous solution of sodium silicate Na2SiO3 through a column with KU-2x8 sulfopolysterol cationite from top to bottom or from bottom to top were used for the synthesis of the starting powders. High-purity silicic acid, which does not contain sodium ions, was obtained by feeding an aqueous solution of sodium silicate Na2SiO3 from the bottom to top. The powders after synthesis contained hydrated calcium silicates and hydrated silicon dioxide. The powder synthesized from acid containing sodium ions included a reaction by-product - sodium nitrate NaNO3. Ceramics with a phase composition including cristobalite SiO2, tridymite SiO2, and sodium calcium silicate Na2Ca3Si6O16 were obtained after firing at 800…1000 °C from a synthesized powder containing sodium nitrate NaNO3. Ceramics with a phase composition including SiO2 (cristobalite, quartz) and CaSiO3 (wollastonite, pseudowollastonite) were obtained after firing at 1000...1200 °C from powder synthesized from high purity silicic acid. The obtained ceramic materials, whose phase composition contains biocompatible phases in CaO–SiO2 and Na2O–CaO–SiO2 oxide systems, can be used to create bone implants after the necessary in vitro and in vivo studies.
This paper describes the process of obtaining VK94-1 ceramics with various TTB (temporary technological bonds) in order to assess the effect of the binder on properties such as apparent density, total porosity and linear shrinkage of the samples. Ceramics obtained using 8 wt. % PEG as a binder showed the best results compared to the material molded using 5 wt. % PVA. This is due to the fact that polyethylene glycol gives a more dense semi-finished product due to the formation of thinner boundary layers.
The article presents X-ray diffraction, dielectric, and pyroelectric results of a PbZrO3 ceramic synthesized from nanodispersed PbO and ZrO2 powders with the addition of BaTiO3 nanoparticles. It was found that the addition of barium titanate results in the formation of a rhombohedral ferroelectric phase in lead zirconate. Pyroelectric measurements showed that the spontaneous polarization of the solid solutions for x = 0,10 is 45…55 ?C/cm2.
The paper presents the results on the formation of boron-based coatings by precipitation of target material from a vapor-plasma phase formed by electron beam exposure to a solid-state target in the forevacuum pressure range. The physicomechanical properties of coatings formed when inert, active, and reactive gases are injected into the region of interaction between an electron beam and a target are investigated. It is shown that a change in the gaseous medium in the region of vapor deposition of the boron target on a titanium substrate does not significantly affect the hardness during nanoindentation (H) and the modulus of elasticity (E) of the formed coatings. At the same time, the obtained hardness values during nanoindentation vary from 19.5 to 20.3 GPa, and the modulus of elasticity varies from 182.5 to 207.7 GPa. Nevertheless, the injection of reactive and active gases into the working volume of the vacuum chamber has a significant effect on the adhesion resistance and roughness of such coatings. It was found that the use of N2 in the deposition of boron-containing vapors increases the adhesive properties of coatings (critical load 22.78 N), while the coating roughness is the highest Ra = 0.306 microns. The injection of O2 into the deposition area contributes to the formation of coatings with the lowest roughness (Ra = 0.045 microns) and adhesive resistance (critical load 0.6 N).
This study presents the development and experimental validation of nanomodified cement obtained by joint grinding of clinker, gypsum, microsilica, polycarboxylate superplasticizer, and dune sand. The optimal composition and technological parameters providing increased strength and performance properties of the binder were studied. A series of cement systems with varying clinker and sand content was prepared, while the amount of gypsum (5 %) and modifier (10 %) remained constant. The results showed that mechanical activation in a ball mill for 110 minutes provided a nanostructured material with a specific surface area of 5500…5700 and an average particle size of 3.5…3.7 ?m. Strength tests have shown that the optimal clinker content is 70...80 %, while replacing up to 20 % of clinker with dune sand does not reduce strength. In this composition, the 28-day compressive strength reached 110…115 МПа, exceeding the control samples by 25…30 %. It was also established that the optimal water-to-cement ratio (W/C = 0.18…0.20) ensures dense microstructure and maximum strength, while higher W/C values lead to increased porosity and strength loss. The findings highlight the potential of nanomodified cement technology for reducing clinker consumption, improving performance, and enhancing the environmental sustainability of cement production.
The microstructure and dielectric properties of manganese-doped zinc titanate (MnxZn1–xTiO3) ceramic samples were investigated as a function of manganese concentration (x = 0.1; 0.3, & 0.5). XRD analysis confirmed that the samples exhibited an ilmenite hexagonal structure, indicating the structural evolution of the material. The dielectric constant was influenced by the Mn content and increased with increasing temperature and decreased with increasing frequency. According to the findings, the dielectric loss and dielectric constant increased with temperature and decreased with frequency. The addition of trace amounts of zinc to the manganese titanate ceramics resulted in a substantial increase in the dielectric constant. The substitution of zinc ions for manganese ions effectively enhanced the dielectric properties of the ceramic samples, which highlights their potential for advanced applications.
The formation of waveguides in the bulk of sintered nanoporous glass pre-impregnated in a bismuth nitrate solution was demonstrated. The influence of laser irradiation regimes on the refractive index change and luminescence intensity in fs laser beam-written tracks was studied. It was shown that the relative luminescence intensity of the formed waveguides depends significantly on the impregnating bismuth nitrate solution concentration. The waveguides exhibit broadband (FWHM ~150 nm) luminescence in the near infrared region (1200…1500 nm) when pumped at a wavelength of 808 nm. This indicates potential for using the formed waveguides as the active medium of waveguide laser amplifiers.
The electrical properties of bidoped oxide pyrochlore Bi6/5Mn1/3Ni1/3Ta4/3O6+? (sp. gr. Fd-3m, a = 10.5038(9) ?), synthesized for the first time by the solid-phase method, were studied. According to scanning electron microscopy data, the ceramics is characterized by a porous microstructure formed by randomly oriented grains of an elongated shape. The average crystallite size determined by X-ray diffraction is 65 nm. The electrical properties of the samples were studied using an immittance analyzer at temperatures of 100…450 °C in the frequency range of 25…106 Hz. An electrical model of the sample was constructed in the form of an equivalent circuit, on the basis of which the relative permittivity (?25), the dielectric loss tangent (4 10–3 at a frequency of 106 Hz) and the activation energy of through conductivity (0.7 eV) were calculated. Two polarization mechanisms were established. Electronic polarization dominates in the high-frequency region. At low frequencies, ion-migration polarization is observed, with parameters close to the Warburg theoretical model.
In this paper the effect of chemical modification of the surface of monolithic polycarbonate on the adhesive strength of heterogeneous laminated glass are considered. The effect of chemical modification of the surface on ensuring stable adhesion between transparent chemically and physically incompatible materials is shown. The use of chemical surface modification in the production of heterogeneous aircraft glazing is proposed to improve its operational reliability and safety.
Lead-germanate glasses are a promising material for creating optical elements. However, producing such glasses with a high degree of homogeneity is associated with several technological challenges. During synthesis, phase separation can occur, in which the glass separates into several amorphous phases with different chemical compositions, negatively affecting its optical properties (scattering, absorption). Determining the exact composition is further complicated by the high lead content, which can distort analytical results. Uneven evaporation of components from the glass surface and insufficient mixing of the melting during synthesis can also lead to local variations in composition. To address these issues, a method for chemical composition mapping based on laser-induced breakdown spectroscopy (LIBS) is proposed, allowing for the visualization of the spatial distribution of elements on the sample surface. This paper presents the results of a LIBS study of lead-germanate glass samples of various compositions and demonstrates the differences in the results obtained depending on the spectral data processing method.
