Glass and Ceramics最新文献

The preparation and identification of microstructure features as well as the texturing of the thermoelectric material Bi₂ Te_2.7 Se_0.3 doped with dysprosium are considered. The textured compounds Bi_2–x Dy_x Te_2.7 Se_0.3 with x = 0.0000; 0.0010; 0.0025; 0.0050; 0.0100, and 0.0200 were obtained by means of solvothermal synthesis of the original powders and their subsequent spark plasma sintering. Dysprosium doping effects several interrelated phenomena. The first one is particle size reduction of the original powder with increasing x. This effect is explained by an increase in the ionicity of the covalently polar bonds Bi(Dy)–Te with increasing Dy content on account of the difference in the electro-negativity of Bi and Dy. The second effect is associated with average grain size reduction with increasing x in bulk samples, which is determined by a corresponding change in the particle size in the original powder with different amounts of alloying. This phenomenon also effects greater texturing in the samples.

The possibility of producing geometrically complex mechanical-engineering products based on reaction-sintered silicon carbide using two methods was investigated — mechanical processing of polymerized workpieces before sintering and molding by hot slip casting under pressure. The resulting silicon carbide ceramic materials are characterized by low density of the order of 3.04 – 3.07 g/cm³, porosity ≤ 1%, and bending strength 320 – 360 MPa. Materials based on silicon carbide modified with boron carbide have density 2.72 g/cm³, porosity about 1%, and bending strength of 280 MPa.

The characteristics of glass-ceramic materials prepared by means of thermal plasma were investigated. The influence of the ash content of a thermal power plant (TPP) on the properties of glass-ceramic materials is considered. Samples of glass-ceramic materials with an ash mass content of 70% and the following characteristics were obtained: compressive strength 530 MPa, bending strength 115 MPa, and density 2700 kg/m³.

The influence of the float-tank operating regime on the adhesion of tin oxides to the bottom surface of the manufactured glass strip was studied. Statistical analysis of the experimental data and modeling made it possible to quantify the influence of the formation regime of a glass strip and the chemical composition of the glass on the amount of adhesion of tin oxides.

In the present study, we built predictive models of the mechanical properties (Young’s modulus, fracture strength and toughness) of α-Al₂O₃. Experiments carried out on samples produced by spark plasma sintering (SPS). The experimental results were the basis for the evaluation of mathematical models and predictions by both the radial basis function neural network (RBFNN) and multiple linear regression (MLR) models. The results of the comparison of MLR and RBFNN models showed good agreement between the experimental data and the RBFNN model predictions whereas the MLR model reveals modest agreement with the studied mechanical properties.

The results of investigations of the chemical and mineralogical composition and main characteristics are presented to determine the suitability of trachybasalt porphyrite of the Karabulak section of the Gavasai deposit in Uzbekistan for preparing thermal insulation material, in particular mineral fiber. It was found that this new deposit of igneous rock can be used as the main raw material component in the manufacture of basalt fiber products, a widely demanded and modern material in the construction industry.

The amounts of large-tonnage mineral waste that are generated raise serious misgivings at environmental protection agencies. Most mineral waste is a valuable secondary raw material, but the lack of integrated technologies for their processing substantially slows down their processing. An assessment was made of the possibility of joint processing of quartz-leucoxene concentrate (waste from oil extraction) and brucite-containing waste from the production of refractories. Joint pyrometallurgical processing of two wastes made it possible to obtain magnesium titanate, a valuable product for different industries. In hydrometallurgical processing of magnesium titanate, a complex magnesium-titanium containing coagulant was obtained, which showed high efficiency in the process of treating high-pH wastewater (concrete mixing unit). In addition to increasing the purification efficiency (reducing the residual concentrations of pollutants), the use of a complex reagent made it possible to reduce reagent costs and intensify the sedimentation and filtration of coagulation sludge (simplification of the instrumentation).

The most promising method for the manufacture of metal parts with complex forms is casting according to lost-wax or burnt-out models. The melted material used is a complex composition of wax with other organic compounds, characterized by high constancy of physicochemical and mechanical properties, since the accuracy of repeated reproduction of critical parts, for example, turbojet engine blades, depends on this. A wax model is necessary to grow a ceramic shell around it, whose manufacturing accuracy is decisive for obtaining a high-quality casting. Since the surface of the wax model is hydrophobic and the ceramic slurry applied to the model is water-based, a critical factor in shell technology is the ideal wettability of the model surface by the slurry applied to it. Improving wettability can be achieved not only by introducing special surfactant wetting agents into the aqueous phase, but also by changing the properties of the wax surface itself, i.e., giving it hydrophilic properties. A method of physically modifying the surface of a wax model is presented — application to it of a thin layer of ceramic powder, which is well wetted by aqueous ceramic suspensions.

The results of an investigation of glass formation on frit production by mans of induction heating are presented. According to x-ray phase analysis, the resulting frit is completely amorphous. The frit meets standard spreadability requirements — 45 mm and linear thermal expansion coefficient [LTEC] 120 × 10^–7 K^–1. The enamel coating has a high chemical resistance to acids and alkalis. A comparative analysis of frit synthesis in a laboratory electric furnace by means of induction heating demonstrated that the frit induction melting time is reduced by two-fold, energy consumption is reduced by 23%, and the process efficiency is increased on average by four-fold.

Ceramic-vermiculite thermal insulation with a wollastonite binder was prepared from chalk, diatomite, and expanded vermiculite by means of solid-phase synthesis of the components. The influence of the granulometric composition of expanded vermiculite and the influence of the composition of the batch on the phase composition and the physicomechanical and thermophysical properties of ceramic materials were studied. The main crystalline phase of the ceramic samples is biotite and wollastonite. The developed ceramic-vermiculite thermal insulation has an apparent density 310 – 510 kg/m3 and can be operated at temperatures up to 1050°C inclusively. The developed materials can be used as fire-resistant thermal insulation for industrial furnaces, equipment, and so on.