-
Details
-
Hits: 33
In this paper, we show fast femtosecond laser writing of birefringent waveplates in nanoporous glass (NPG) volume. The possibility of laser writing acceleration on the order of magnitude is shown in NPG relative to fused silica. In situ measurements of birefringent plate retardance are performed for heating and cooling stages in the 20…650 ?С temperature range. Femtosecond laser-written birefringent elements are found to have greater thermal stability relative to conventional crystal quartz plates in highly varying temperature environments. The obtained results are of particular interest to the industrial fabrication of laser-written phase optics elements in NPG.
-
Details
-
Hits: 37
The influence of diamond grinding modes on the structure and mechanical properties of ceramics based on zirconium dioxide stabilized with magnesium oxide has been studied. Powders of the composition ZrO2 – 6 mol. % MgO was obtained by chemical co-precipitation from solutions of zirconium and magnesium chloride salts. The blanks of the samples were made by cold isostatic pressing at maximum pressures of 55 and 200 MPa, followed by sintering at a temperature of 1700 ?C for 4 hours. The resulting blanks (both porous and high-density) were machined with different cutting depths in the range of 0.003…0.010 mm. It was found that the surface roughness of the samples increased with increasing cutting depth. After mechanical processing of high-density samples obtained at a maximum pressure of 200 MPa, conditions are created on their surface for the implementation of a phase transition. Grinding promotes the transition of the tetragonal phase of zirconium dioxide (t-ZrO2) to the monoclinic phase (m-ZrO2) on the surface of the samples, which leads to an increase in the critical stress intensity coefficient (K1c) from 4.3 to 6.4 MPa·m1/2. Mechanical processing of samples with an open porosity of 3.0…3.5 % obtained by pressing at a maximum pressure of 55 MPa does not lead to phase transformations on their surface and K1c remains within the margin of error.
-
Details
-
Hits: 41
This article describes the process of obtaining VK94-1 ceramics modified with zirconium dioxide ZrO2, in order to determine and compare such properties of the resulting composite material as: apparent density, mechanical bending strength and Vickers hardness (microhardness) with the properties of ceramics VK94-1, as well as the effect on these properties of changes in the percentage of zirconium dioxide in the samples. The influence of the firing temperature on the sintering of samples has been studied. Samples with different component ratios VK94-1/ZrO2 (90/10, 80/20, 70/30) were pressed on an isostatic press at a pressure of 150 MPa. The firing was carried out at different temperatures: 1500, 1550 and 1600 ?C in different firing mediums.
-
Details
-
Hits: 35
The technology of plasma synthesis of ceramic pigment based on vanadium waste has been developed. The chemical and phase composition of the pigment has been studied. The effect of a pigment based on waste on the aesthetic and consumer properties of wall ceramics has been studied. The CIE L*a*b* system defines the color characteristics of wall ceramics.
-
Details
-
Hits: 35
The paper presents the results of investigation of polycrystalline powders and films of CsCu?Br? and CsCu?I? compounds obtained by vacuum thermal evaporation. X-ray phase analysis confirmed the formation of single-phase films which correspond well to the initial compositions. The microstructure of the films was studied by scanning electron microscopy. It was found that CsCu?I? and CsCu?Br? films consist of rounded crystals ranging in size from tens nanometers to 200 nm. The obtained results confirm the potential of compounds CsCu?Br? and CsCu?I? for its application in the field of optoelectronics, however, it is necessary to increase the duration of sputtering of materials to form thicker and more continuous films.
-
Details
-
Hits: 61
The paper investigates the possibility of thermal processing of waste from the chemical industry – phosphogypsum. It is shown that when phosphogypsum is dried, partial dehydration of dihydrous calcium sulfate occurs, and when calcined at temperatures of 600…1200 ?C, complete dehydration occurs. It was found that after heat treatment below 800 ?C, the samples actively absorb moisture. During the heat treatment of phosphogypsum in the presence of a reducing agent, two endothermic effects are observed associated with the sequential dehydration of CaSO4?2H2O, and a wide peak of the exothermic effect associated with the thermal destruction of the reducing agent and the formation of calcium sulfide from phosphogypsum. Phosphogypsum samples heat-treated in the presence of a reducing agent acquire the ability to emit a yellow-orange glow under the influence of ultraviolet radiation. Synthesized pigments can be used to produce water-based paints and varnishes.
-
Details
-
Hits: 52
The possibilities of obtaining fireclay crucibles for fire assay of ores with high quality indicators based on the highest-grade local raw materials of Uzbekistan – AKF-78 kaolin and fireclay obtained from this brand of kaolin were studied. In order to improve the physical and technical indicators of fireclay crucibles, pre-fired waste catalyst of the Shurtan Gas Chemical Complex (SGCC), containing 90.22 % Al2O3, was introduced into the composition of the masses. The optimal mass with a content of 8 % alumina waste withstands more than 11 – 13 melting without corrosion, and the heat resistance of the samples increases to 8 thermal cycles. At the same time, the amount of mullite formed after firing at 1420 ?C increases noticeably. The research promotes the use of local materials and recycling of industrial waste, which is environmentally friendly. This aligns with the goals of sustainable development by reducing waste and utilizing resources efficiently.
-
Details
-
Hits: 52
Using the sintering method near the softening temperature of the glass employed, glass-ceramic composites consisting of low-alkali aluminoborosilicate glass and barium titanate mixed in various proportions were successfully synthesized. The electrical properties of the samples were investigated in the microwave range. According to X-ray phase analysis, the synthesized samples are a mixture of barium titanate and an amorphous phase, as well as, under certain heat treatment conditions, products of glass crystallization (SiO2 – quartz and tridymite) and its interaction with the ferroelectric filler (Ba2TiSi2O8 – fresnoite). The dielectric permittivity level of the studied glass composite samples, measured at a frequency of 1 GHz, ranged from 9.2 to 25.0 with a dielectric loss tangent of 0.007…0.012.
-
Details
-
Hits: 57
Ceramics based on yttrium-aluminum garnet doped with ruthenium ions were synthesized. Ceramic samples were obtained by non-reactive sintering of nanocrystalline powders formed by chemical co-precipitation. The results indicated that the yttrium-aluminum garnet matrix can accommodate up to 0.5 аt. % of ruthenium cations without the formation of secondary phases or impurities. A slight deviation from the stoichiometry of the composition did not hinder the incorporation of ruthenium into the structure of the yttrium-aluminum garnet. Additionally, changes in the valence of the sintering additive did not influence the solubility of ruthenium ions in the ceramic material.
-
Details
-
Hits: 49
Phase and elemental analysis were performed for amorphous nanosized thin films of (InSe)20(GaSe)80 and (InSe)50(GaSe)50 compositions, and surface morphology studies were conducted. Optical transmission studies of thin films allowed us to establish that absorption corresponds to indirect allowed transitions for these compositions in accordance with the Tauc model, while the values of the optical band gap are Eg = 1.26 eV for (InSe)20(GaSe)80 and 1.07 eV for (InSe)50(GaSe)50 thin films.
