Glass Physics and Chemistry最新文献

Compositions of heat-resistant organosilicate cold-curing composites for nuclear power plants based on OS 51-03 are developed. Deactivation coefficients are determined.

The possibility of synthesizing supramolecular composite organo-inorganic materials based on cobalt(II) ferrite and biochars from rice husk and sunflower husk is studied. It is established that the morphology of the biochar determines the structural characteristics of the composite. The synthesized materials are characterized by X-ray phase analysis, BET, and scanning electron microscopy. Cobalt(II) ferrites crystallize on the surface of the carbon carrier in the form of a film, whose crystallite size is 80–96 nm, which is lower than for CoFe₂O₄, obtained using sol-gel technology. It is established that the synthesized composites exhibit significant catalytic activity in the process of decomposition of hydrogen peroxide and sorption of chromium(VI) compounds from an aqueous solution. The increase in the sorption capacity is associated with the formation of the Fenton system Fe³⁺/Fe²⁺. The obtained results can be used for the synthesis of innovative products from agricultural waste and their use in water treatment processes.

The study object is borosilicate glass with separate and combined inclusion of Cs and/or Sr oxides in amounts of 5, 10 and 15 wt %. This can be used in the fractionation scheme of liquid high-level waste from the spent nuclear fuel reprocessing. The main attention was paid to their compliance with the quality criteria established in the regulatory document NP-019-15, when studying the physicochemical, thermophysical and mechanical properties of synthesized glass. The glass structure changes slightly relative to the structure of the initial glass frit according to Raman spectroscopy. The exception was glass containing 15 wt % Cs₂O, which contained new bands in the Raman spectra, in addition there were an increase in its molar volume and a decrease in the glass transition temperature. However, these changes had virtually no effect on the thermophysical and mechanical characteristics. The obtained data showed that the glass properties in the studied range of Cs and/or Sr oxides concentrations satisfy the current quality criteria for the product in the form of ¹³⁷Cs and ⁹⁰Sr vitrified concentrates after fractionation of liquid HLW.

The temperature dependence of the microhardness of Ag₂S is measured in the temperature range of the transition from the monoclinic to the cubic crystalline modification. The obtained experimental data are discussed, taking into account the anomalously high plasticity of this compound and the superionic nature of its cubic modification.

Fly ash is the most abundantly produced waste material from thermal power plants and steel industries. Management of this fly ash is a tedious task as it creates economic and environmental problems for society. One popular way to recycle fly ash is to produce fly ash-based bricks for construction. However, as the binding capacity of fly ash is significantly less, it pollutes the surrounding environment of the working site. Fly ash brick is usually made using cement as a binder by cold compaction technique. Cement manufacturing is an expensive industrial process that releases carbon dioxide into the atmosphere. Therefore, the scrap glass powder is used here as an alternate binder. The glass powder is mixed with the fly ash to prepare glass-ceramic brick to reduce the brick firing temperature and trap the pollutants within the silica-rich glassy phase. The glass used in this work was the scrap glass collected from the chemical laboratory of the ceramic department (NIT Rourkela). Different batches were studied concerning the glass percentage and fly ash percentage. The fabricated green bodies were sintered at 900 and 1000°C for 2 h. X-ray diffraction study revealed the presence of mullite and cristobalite phases in the sintered brick. FESEM microstructure confirms the presence of the glassy phase in the sintered brick. It is found that with an increase in glass content, the bulk density increases, and apparent porosity decreases. The mechanical properties of the glass-ceramic composite bricks are also superior to the fly ash brick.

The kinetics of silicon dioxide shell formation on metal nanoparticles by tetraethoxysilane hydrolysis in the absence of catalysts is studied. The possibility of stabilizing Au–Ag alloy nanoparticles by coating with a 5 nm thick silicon dioxide shell is shown. A model of core–shell nanoparticles consisting of a metal core and a multilayer SiO₂ shell, having a phosphor based on water-soluble porphyrin encapsulated between its layers, is proposed. It is shown that encapsulation in a multilayer SiO₂ shell leads to an increase in the intensity of porphyrin luminescence.

Foam glass based on waste glass is one of the most important ecological construction materials due to its thermal, acoustic and electromagnetic insulation powers. This work aims to study the effect of Na₂SiO₃ on the characteristics of foam glass made from soda-lime waste glass using CaCO₃ as a foaming agent. Foam glass samples were prepared by sintering at a temperature of 850°C for 10 min with a heating rate of 6.5°C/min. The first sample contains 99 wt % waste glass powder and 1 wt % CaCO₃, and the other samples were developed by replacing a quantity of glass powder with 10, 20, 30 and 40 wt % of Na₂SiO₃. The effect of this substitution on the properties of foam glass was studied using a scanning electron microscope (SEM), a differential thermal analysis (DTA), a thermal gravimetric analysis (TGA), Fourier-transform infrared analysis (FTIR), thermal insulation and mechanical strength tests. Experimental results showed that the addition of Na₂SiO₃ increases the porosity of foam glass giving it a very low thermal conductivity (0.026 Wm^–1 K^–1) by thus increasing its power of thermal insulation.

Compositions and a methodology for manufacturing composite materials for remote photoluminescent converters of LED radiation based on quartz glass and ultrafine powders of yttrium–aluminum garnet activated by cerium ions (Y₃Al₅O₁₂:Ce³⁺) are developed. The conditions for the synthesis of garnet by the method of thermochemical reactions (combustion) of nitrate salts in citric acid are optimized, and agglomerated powders with primary particle sizes of 0.8–12.3 μm are obtained for the reaction with a deficiency of acid and in the range from 49 to 207 nm for synthesis under conditions of excess citric acid. The physicochemical, structural, and spectral-luminescent characteristics of powdered samples and quartz glass–low-melting glass–phosphor composites formed at low sintering temperatures (650–700°C) are studied. It is shown that when the composite plate is illuminated with a blue LED (λ_max = 455 nm), a spot of white light is visually recorded, formed from a combination of scattered blue radiation and yellow radiation excited in YAG:Ce³⁺ particles (λ_max = 560 nm).

The phase equilibria in two three-component and one four-component salt systems based on potassium salts are studied. The influence of lower dimensional systems on the final appearance of the four-component system is shown.

Research on PbSb₂Te₄ composite material samples, obtained by the Czochralski method, is continued. The multiphase structure of the material is confirmed. Based on the analysis of X-ray studies, the predominance of PbSb₂Te₄ (70–80%) and Sb₂Te₃ (20–30%) phases is found. Traces of (CuSb)Te₂ phases with a rhombohedral structure and a hexagonal phase of Sb₂Te₂ are detected. The carrier concentration is reduced by doping the samples with copper; the impurity atoms are located in the Van der Waals gap between the layers of the main phases. With the copper content in the initial charge increasing from 0.5 to 1 at %, the carrier concentration does not decrease further.