Avoiding water reservoir effects in ALD of functional complex alkali oxides by using O3 as the oxygen source

Toxic Pb-containing piezo-, pyro- and ferroelectrics continue to dominate the market even though they were banned from use in consumer products more than a decade ago. There is a strong...

Analysis of Alkali Oxides Influence on the Microstructure of Refractory Grog

The development and subsequent production of these special kind of grog from raw materials available in the Czech Republic is one of the possibilities how to reduce income costs for the production of refractory materials with specific properties. The experimental work is focused on verifying the possibility of producing grog with increased alumina content from available raw materials. The raw materials are kaolins and claystones. To achieve a higher content of alumina in the grog, waste mullite dust is used. In order to improve the physical and mechanical properties of the grog, modifiers are used. Selected modifiers are expected to affect positively on the resulting density while maintaining the heat properties.

Combustion characteristics of coal, petroleum coke, biomass and their ternary blends

This work presents the combustion characteristics of coal, petroleum coke (PC), rice straw (RS), mustard cake (MC) and their blends to assess the applicability of blended fuel for thermal power generation. Characterization results show that PC has the highest GCV (35990 kJ/kg) to improve the overall energy density of the blend significantly. Higher VM present in RS and MC improved the ignition behavior and combustion efficiency of the blend. For 10 OC/min heating rate at 350 OC, with the increase in RS in blends from 10% to 30%, combustion efficiency increased from 12.85% to 32.66%. Synergistic analysis signifies that higher biomass content enhances blends' combustion characteristics through catalytic effects of alkali oxides present in RS/MC. Thermodynamic analysis (ΔH, ΔG and ΔS) inferred that RS and MC combustion is easier than coal and PC. With the increase in MC in blends from 10% to 30%, ΔH decreased from 114.81 to 82.31 kJ/mol, ΔG declined from 159.33 to 122.86 kJ/mol and ΔS improved from −63.59 to −58.14 J/mol.K, indicating blending of biomass improved the combustion.

RESEARCH OF THE POSSIBILITY OF REDUCING THE CIRCULATION OF SULFUR OXIDE IN THE PRODUCTION OF WHITE CEMENT

The article discusses the possibility of reducing the circulation of sulfur oxide in the production of white cement by introducing alkaline potassium oxides K2O and sodium Na2O. A decrease in the circulation of sulfur oxide SO3 is achieved by increasing its yield in the clinker by transferring SO3 from a more sublimated compound of calcium sulfate CaSO4 to less sublimated potassium sulfates K2SO4 and sodium Na2SO4. Potassium and sodium oxides are introduced in the composition of carbonates and feldspar. The amount of introduced alkali oxides is controlled by the molar ratio A/S between sulfur oxide SO3 and alkaline oxides K2O and Na2O. It is shown that with the same molar ratio between sulfur oxide and alkaline oxides, the amount of SO3 removed with clinker depends on the ratio between potassium and sodium oxides. The higher the sodium oxide content, the more sulfur oxide comes out with the clinker and less remains to circulate in the kiln. The sublimation of sulfur oxide decreases from 70.5% - without the introduction of alkaline oxides, to 38,5 % at the maximum A/S ratio with the addition of potassium and sodium oxides in a ratio of 80:20 %. When potassium and sodium oxides are added in a ratio of 20:80%, the sublimation of sulfur oxide is reduced to 7,7 % at the same A/S ratio.

The Influence of Ferrous Metallurgy Waste in the Aktobe Region on the Frost Resistance of Ceramic Bricks Based on Low-Melting Clay

The research objective is studying the effect of tailing slurry of chromite ore beneficiation on the phase composition and frost resistance of ceramic bricks obtained based on low-melting clay. For the study, two compositions were taken, % wt.: 1) the optimal composition ─ low-melting clay of the Ilek deposit - 70, tailing slurry of chromite ore beneficiation, 2) the reference composition ─ low-melting clay of the Ilek deposit - 100. Raw materials were crushed to pass through a sieve No. 1.0 mm; then, the components were thoroughly mixed. The bricks were prepared by melting at a batch moisture content of 22 %. The mold bricks were dried to a residual moisture content of 5 % max. The dried bricks were fired at temperatures, оС: 950 (the glass phase emergence), and 1,050 (the final brick firing temperature). The increased content of iron oxide (Fe2O3=12.3 %) and alkali oxides (R2O=3.2 %) in the tailing slurry of chromite ore beneficiation contributed to the liquid phase emergence at 950 оС. Colorless, yellowish, and brown glasses with refractive indices N within 1.50-1.54, forming as a result of melting of spars and mixed-layer clayey formations, were observed under the microscope in the studied prototypes of composition No. 1 at a firing temperature of 950 °C. In the composition No. 2, a liquid phase also emerges, but in smaller quantities. Adding tailing slurry of chromite ore beneficiation to ceramic masses contributes to the formation of anorthite and glass phase in prototypes based on low-melting clay at a firing temperature of 950 °C. An increase in the firing temperature to 1,050 °C increases the content of the glass phase and anorthite, which significantly improves the frost resistance of ceramic bricks.

The relationship of phase and chemical compositions of a durable ceramic material of the fortification wall of the city of Thessaloniki (Greece) age more than 1000 years

A ceramic material with an age of more than 1000 years has been studied. Plinth was used as a ceramic material for the construction of the fortress wall. In addition, the element analysis determined an increased content of carbon in the samples - 9,50 %. Increased carbon content in inclusions indicates the introduction of fuel into the raw material. The introduction of fuel into the raw material not only increases the porosity of the products, but also contributes to the uniform sintering of the ceramic shard and with an increased content of alkali oxides (R2O > 4 %), the formation of a glass phase up to 1000 oC.

Pore Structure Regulation in Refractory Grog with Alumina Content over 45 %

Increased alumina content in refractory grog is a product of the grog’s firing and, at the same time, it is a raw material used for the production of dense or insulating, shaped or monolithic refractories. Grog characteristics determine the properties of the final product. The specific characteristics of the grog are therefore optimized to suit the refractory product as close as possible. The basic characteristics determining the nature of the grog include its mineralogical composition, chemical composition, and apparent porosity. The present study focuses on ways of reducing the porosity of a high-alumina grog and thus obtaining a raw material suitable for the production of dense refractory materials. The experiments have shown that it is possible to regulate porosity by using clay with better sinterability and phosphoric acid in the production of grog from claystone with alumina content over 40 %, a minimal Fe2O3 content, a minimal content of CaO and alkali oxides.