Purpose of this work is to establish the features in the microstructure and thermoelectric properties of composites consisting of Bi2Te2.7Se0.3-based matrix and a Fe filler. The composition with a filler content of 0.3 wt. % Fe has a higher thermolectric figure of merit as compared to the Bi2Te2.7Se0.3 matrix. For this composition, the maximum value of ZT reaches ~0.75, while for Bi2Te2.7Se0.3 ZT does not exceed ~0.63. Thus, in the composite of the Bi2Te2.7Se0.3 + Fe system, the thermoelectric figure of merit can be increased by about 20 %.
Using absorption spectroscopy, differential scanning calorimetry, and X-ray powder diffraction, we studied the effect of a small addition of CeO2 on the process of thermally stimulated formation of plasmonic Au nanoparticles in the glass of the ZnO–MgO–Al2O3–SiO2 system containing TiO2 and ZrO2 as nucleating agents. It is shown that when the glass is heated from temperatures slightly above Tg to temperatures in the region of the exothermic peak, the plasmon resonance band of Au nanoparticles undergoes a nonlinear shift; however, the addition of CeO2 significantly expands the the shift to the long wavelength region of the spectrum. We performed the computer simulation of the experimental optical absorption spectra, estimated the sizes of the formed nanoparticles and proposed the mechanism of the effect of the CeO2 addition on the formation of plasmonic Au nanoparticles.
The formation of microtracks in the volume of porous glass samples by femtosecond laser pulses which is of importance for laser writing of active optical waveguides was studied. It was found that impregnation of nanoporous glass in bismuth nitrate solution leads to the appearance of an orange luminescence band under 488 nm light excitation and this luminescence band is enhanced in the laser-wriiten tracks. It is shown that increasing the laser pulse energy to 200 nJ allows increasing the phase contrast of the tracks laser-written in nanoporous glass doped with bismuth compared to the ones formed in nanoporous glass without additives.
The technology of glass concrete based on dispersed container and sheet glass has been developed. It is shown that when Portland cement and cullet are ground together, when a specific surface area of 5890 – 6450 cm2/g and a particle size of 3.4 – 3.6 microns with a dispersed glass content in the composite of 20 – 50 wt. % with hyperplasticizer glass concrete corresponds to class B30 – B40, which meets the requirements of regulatory documents. The microstructure of glass concrete and the features of its dehydration when heated to 1000 °C investigated. Using X-ray phase analysis, it was found that sodium-calcium hydroaluminosilicates such as gmelenite and thomsonite are formed in glass concrete.
Powders of hydroxyapatite (HA) Ca10(PO4)6(OH)2 treated in 0.25M aqueous solutions of ammonium NH4H2PO4, sodium NaH2PO4 and potassium KH2PO4 dihydrophosphates for 1 hour under stirring were used for ceramics production. According to the XRD data, there was no changes in the phase composition of the powders after such treatment. After firing in the range of 900 – 1100 ?С, the phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with an aqueous solution of NH4H2PO4 included ?-tricalcium phosphate ?-Ca3(PO4)2 and HA Ca10(PO4)6(OH)2; The phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with NaH2PO4 aqueous solution included sodium-substituted tricalcium phosphate Ca10Na(PO4)7 and HA Ca10(PO4)6(OH)2; the phase composition of ceramics based on HA Ca10(PO4)6(OH)2 powder treated with an aqueous solution of KH2PO4 included potassium-substituted tricalcium phosphate Ca10K(PO4)7 and HA Ca10(PO4)6(OH)2. The formation of biphasic ceramics occurred due to a decrease in the molar ratio Ca/P of HA powder after treatment in aqueous solutions of ammonium NH4H2PO4, sodium NaH2PO4 and potassium KH2PO4 dihydrophosphates. HA-particle surface adsorption of cations and anions from the solution, slight dissolution of HA in solutions of dihydrophosphates with acidic pH, as well as ion exchange of cations and anions of HA for cations and anions from solutions, were possible processes providing change in the ratio of cations and anions in the HA powder. The resulting ceramic composites contain biocompatible phases, and can be recommended for the creation of bone implants.
Samples of Zr0.9Y0.1O2–?–BiScO3 and Сe0.9Y0.1O2–?–BiScO3 solid solutions were obtained by solid-phase synthesis. X-ray diffraction revealed that the Zr0.9Y0.1O2–?–BiScO3 system corresponds to a tetragonal structure with space symmetry group P42/nmc. The Сe0.9Y0.1O2–?–BiScO3 ceramics is two-phase and is characterized by a cubic structure with space symmetry groups and Ia–3. Using the impedance spectroscopy method, it was found that the Сe0.9Y0.1O2–?–BiScO3 system has the highest electrical conductivity, however, the activation energy is lower in the Zr0.9Y0.1O2–?–BiScO3 ceramics, amounting to 0.3 eV in the temperature range of 300–420 ?С and 0.7 eV in the temperature range 420–680 ?С. The activation energy of the Сe0.9Y0.1O2–?–BiScO3 solid solution is 1.0 eV.
The results of diamond-abrasive treatment of the reverse side of silicon carbide semiconductor plates of polytypes 4H and 6H are presented. Dimensions of surface microcracks of ceramic plates after abrasive treatment with pastes with diamond powder of different grain size are investigated, and also relationship between length of surface microcrack and rate of material removal depending on technological modes of diamond-abrasive treatment is established. As a result, a new method of single-sided abrasion treatment of thin ceramic plates is proposed, which ensures reduction of crack formation.
The results of studying the behavior of analcime-bearing rocks of the Timan region (Komi Republic) under high-temperature firing (1200 – 1280 ?С) were presented. The mineral composition and physical characteristics (apparent density, water absorption, open porosity, thermal conductivity) of the resulting ceramics were determined. The influence of the mineral composition of the initial analcime-containing rocks on the bloating and physical characteristics of fired ceramics was shown. Porous materials with low apparent density (0.37 – 0.39 kg/m3), water absorption (up to 4.3 %), and thermal conductivity (0.09 – 0.10 W/m??С) were obtained. The obtained results show the prospects of using analcime-bearing rocks with a certain mineral composition for producing heat-insulating materials.
The results of an investigations into the effect of filamentous striae with birefringence from 3 to 15 nm/cm in SO-115M glass-ceramic on the manufacturing quality of optical parts for ring lasers and the exact characteristics of laser gyroscopes based on them are presented. It is shown that the presence of striaes with stresses of no more than 15 nm/cm in SO-115M glass-ceramic does not depend on the speed of manufacturing the resonator optical circuit and the quality of its assembly. The presence of striaes in the output mirror additional backscattered of a ring laser may have the destination of lock-in zone. Correct adjustment of the output mirror allows to reduce scattering and reveal the growth of the lock-in zone in laser gyroscope. It is shown that the accuracy of the laser gyroscope improves by the quality mirror substrates, the geometry of the resonator body, and increases the accuracy of scattering inside the resonator.
