Steklo i Keramika (Glass and Ceramics). Monthly scientific, technical and industrial journal

 

ISSN 0131-9582 (Online)

Based on calculations, spatial distribution of the local electric field (LEF) for various structural configurations of silver nanoparticles (NPs) in silicate and zinc-phosphate glasses was studied. The features of this distribution determine
the efficiency of energy transfer from plasmonic NPs to rare earth (RE) ions located in particles vicinity. The mechanism of energy transfer through field enhancement, caused by the surface plasmon resonance of particles, is a dominant for NPs of sizes of ?5 nm and is determined by several factors. To clarify their roles and significance, the dependences of LEF upon the size, spatial distribution and degree of agglomeration of silver NPs in glass were studied. With this aim, a visual representation of the spatial distribution of the LEF in the vicinity of agglomerates of plasmonic NPs was proposed,
which allows to perfom an effective, comparative analysis of the nature of the field enhancement in places of hypothetical location of RE ions. Based on simulations, the dependencies of LEF intensity enhancement, spatial distribution of such places in relation to the nearest plasmonic particle, upon concentration of NPs, their size, degree of agglomeration and the presence of small (?5 nm) particles in the sample along with the relatively large ones, were determined. It was revealed that the optimal configuration of silver particles in glass for obtaining of the maximum average enhancement of LEF intensity per the site of possible location of RE ion is an agglomerate of NPs with sizes slightly larger than 25 nm and average distances between particle centers ~30 nm.
Zinc magnesium aluminosilicate (ZMAS) glasses have been obtained with the addition of Na2O (from 1.1 to 7.0 mol. %). Influence of the Na2O content on glass forming ability and effectiveness of the ion-exchange treatment in molten KNO3 was studied. Dependences of depth and strain of subsurface layer on treatment duration have been also studied, concentration shifts of alkaline cations in result of ion-exchange process have been evaluated. It was showed that glass Vickers hardness increases both with the Na2O content in glass and with the duration of ion-exchange. Vickers hardness
of the ion-exchanged glasses with 7 mol. % of Na2O treated duration for 72 h reaches 900 HV. Possibility of ion-exchange process usage with glass-ceramics, obtained from glasses of ZMAS system modified with sodium oxide, has been discussed.
Refractory and heat-resistant materials with a coarse-grained and large-porous structure were obtained using silica glass suspensions with mullite, spinel, corundum and quartz fillers. The influence of sintering temperature on the phase composition, structure, porosity and density of the materials were studied. It was found that the strength of the ceramics increases in the temperature range 1300…1400 ?C and decreases at 1500…1600 ?C due to the crystallization of the silica glass. The composites in the silica glass–corundum system have the most stable strength characteristics.
The processes of obtaining hafnium diboride by the carbothermic reduction of hafnium oxide by heat treatment in a vacuum furnace and a spark plasma sintering installation have been studied. When the charge was heat treated in a vacuum furnace, hafnium diboride powder was obtained in the temperature range 1500...1700 °C, but it is characterized by the presence of secondary crystalline phases. Monophase hafnium diboride powder with a fine-grained uniform structure was obtained using the spark plasma sintering method at a temperature of 1500 °C.
During the study using electron microscopy, the structural features of ceramic brick samples with minimum and maximum slag content at the micro-, macro- and meso-level were determined. The method of mercury porosimetry revealed the influence of nickel production slag on reducing the number of the most dangerous pores with a size of 0.002...0.050 microns (mesolevel) of a ceramic shard, which ensures regulation of the formation of the pore phase during the firing process and increases the frost resistance of products. At the same time, it has been established that an increase
in the mass content of slag in the composition of the raw material charge, starting from 5 %, determines the increase in the volume of pores larger than 0.050 microns (macro level) in the volume of the finished product. This causes a decrease in the strength of the samples. The results of electron microscopy of samples with a minimum and maximum content of nickel slag confirmed the identified structural features of the composite ceramic material at the micro-, macro- and meso-level and were used in the development of technology for the production of ceramic bricks with the addition of technogenic products of nickel production.
The possibility of obtaining a new alternative source of clay raw materials for obtaining ceramic materials based on silt deposits of reservoirs, which has functional properties, is considered. The physicochemical properties of silty bottom sediments of the Tuyamuyun reservoir in Uzbekistan have been studied. It has been established that the developed ceramic masses based on the “silt-kaolin” double composition can be used for the production of ceramic materials for building purposes.
Calcium monoaluminate was synthesized using the sol-gel method and the effect of europium and neodymium oxides on the synthesis and kinetics of structure formation in the temperature range of 500 – 1000 ?С was studied
It has been established that the formation of the structure of calcium monoaluminate occurs at a temperature of 1000 ?C and with exposure for 4 hours of a xerogel obtained on the basis of a mixture of Al(NO3)3 + Ca(NO3)2 at a ratio of compounds of 2 : 1, respectively. In the sample obtained, the intermediate mineral is mayenite Ca12Al14O33. With the introduction of mineralizing europium oxide Eu2O3 in an amount of 1.5 wt. % over 100 wt. % into the Al(NO3)3 + Ca(NO3)2 composition, at a synthesis temperature of 1000 ?C, the exposure time for the maximum formation of calcium monoaluminate is reduced to 1 hour. In samples containing Nd2O3, for the maximum formation of calcium monoaluminate at the same exposure time, it is required to introduce it in an amount of 5 wt. %.
The publication presents general information about calcium zirconate and the physical/chemical properties of products based thereon. Methods for CaZrO3 production, such as solid-phase synthesis, electric arc melting, codeposition, hydrothermal synthesis etc. are studied.
The influence of the technological parameters of glass melting of the selected composition in the SrO–Al2O3–P2O5–SiO2–F system on the value of the refractive index and the amount of fluorine that remains in the glass structure after melting is investigated. The use of a joint lowering of the melting temperature and tableting of the charge leads to an increased absorption of fluorine in the glass up to 17 wt. % at the same time, the value of the refractive index decreases to nD = 1.49. It has been experimentally established that in the selected multicomponent glass for glass ionomer cements with two glass-forming oxides SiO2 and P2O5 with a high content of Al2O3, each mass percentage of fluorine reduces the refractive index ?3.5•10–4 units.
The technology of facing material based on mechanically activated cullet modified with potassium hydroxides has been developed. The phase composition, macro- and microstructure of the lining material are investigated.
It is established that the structure of the composite modified with potassium hydroxide is represented in the interstitial space by needle-like and columnar crystals of potassium silicates. The physical and mechanical characteristics of the facing material are investigated.