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 Patterns of Phase Composition and Properties of High-Calcium Low-Density Ceramics Formation Based on Argillous Raw Materials of Various Chemical and Mineralogical Composition

The post-sintering properties of walling high-calcium ceramics based on clay-containing raw materials in low-temperature roasting depend on the chemical-mineralogical composition of clay with different contents of iron, calcium-containing and alkaline oxides that contribute to the formation of new crystalline phases, which provide for the production of low-density ceramic material with high-strength properties.

Phase composition, microstructure and properties of aluminosilicate lightweight materials obtained by the method of burnable additives

The nature of phase formation and the properties of aluminosilicate lightweight materials created from raw materials from the Angren and Samarkand deposits of Uzbekistan are studied. The phase composition, microstructure, and physicotechnical properties of the compositions with the addition of plastic black clay and a burnable additive in the form of coke of various fractional composition were determined. It is shown that the materials of the Angrenskoye deposit are more prone to cristobalitization, which is due to the low content of alkaline oxides and a fine-grained structure. The optimum complex of properties is possessed by lightweights based on cracked clay with a burnable additive in the form of polyfraction coke. Ill. 3. Ref. 13. Tab. 2.

Characterization of Ornamental Stones Wastes for Use in Ceramic Materials

Ornamental stones processing produces large amounts of wastes, which without treatment, are disposed in deposits, constituting the major environmental problem in this sector in Brazil. There is a great variety of rocks and different technologies in the ornamental stones processing. Rock block sawing can be performed using multi-blade gangsaw, the conventional technology, or multiwire gangsaw, latest technology which uses only diamond wire and water to cut blocks. In recent years there has been a great change in the use of ornamental stones sawing technologies, where currently almost 50% of the sawed materials are processed by the multi wire technology. The ornamental stones wastes have compounds that can collaborate in the processing of the ceramic. Due to the great variety of Brazilian ornamental stones and technologies in addition to the growth of de sector in recent years, there is a need for new studies regard to the characterization and environmental classification of waste, for a better management and application. Therefore, the objective of this work was the characterization and environmental classification of ornamental stones wastes aiming their use in red ceramics. The wastes were characterized with the determination of its chemical composition and mineralogical analysis, particle size, morphological analysis and environmental, the latter by means of the leaching and solubilization tests, for subsequent classification. The wastes are composed mainly of SiO2, Al2O3, alkaline oxides, earth alkaline oxides and iron, and those which were submitted to the leaching and solubilization tests are classified as non-inert.

Influence of Annealing Temperature on Electrical Properties of Unmodified Bentonite

In this work, influence of annealing temperature on the electrical properties of unmodified bentonite has been investigated. It is concluded that, by the increase of annealing temperature, the values of permittivity and conductivity are decreased, but the electric resistance and the density of the bentonite are increased. It is also shown that the basic reason for this is the presence of water molecules and alkaline oxides such as Na2O, K2O in bentonite.

Alteration Processes and Deterioration Phenomena of Faience Tiles in the Complex of King Djoser at Saqqara, Egypt

The Complex of King Djoser (2667-2648 BC) at Saqqara was the earliest stone building of its size in the world. Some of the walls of the substructure of the Step Pyramid and the so-called "Southern Tomb" were covered with panels of blue-green faience tiles. The present work aims to study causes of decay the faience tiles which coated Southern Tomb of Step Pyramid. Investigations and analytical techniques including scanning electron microscopy combined with energy-dispersive X-ray microanalysis (SEM/EDX), X-ray diffraction (XRD), X-ray florescence (XRF) and polarizing microscopy were used. Results show that body of faience tiles contains high ratio of silicon oxide SiO2 and low amounts of alkaline oxides (Na2O, MgO), copper was used to obtain the blue colour in an oxidizing atmosphere and fixing mortar of faience tiles consists mainly of calcite, quartz, gypsum, in addition to halite. High content of moisture and crystallization of salts mainly halite salt were the main factors of faience tiles degradation.Keywords: Alteration processes; Faience tiles; Step Pyramid; Mortars.eISSN 2398-4295 © 2018. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open-access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia.

Valorization of rice straw waste: an alternative ceramic raw material

In the production of rice a large amount of solid residue is produced, for which alternative utilizations are scarce or are not commonly applied in industry. Rice straw (RS) is a waste product of rice harvest that is generated in equal or greater quantities than the rice itself. RS is frequently burned in open air, which makes it a significant source of pollution. In the search for possible uses of RS, it should be noted that its ash (RSA) is particularly rich in silica, alkaline and alkaline earth metals and may be used as a source of alkalis and silica for the production of triaxial ceramics. The present research work proposes the production of a ceramic raw material from RS for its use in the fabrication of ceramic materials for the construction industry. Based on the chemical and mineralogical composition of RSA created under different thermal conditions, the most suitable RSA for this purpose was that obtained from treating RS at a temperature of 800 ºC for a time of 2 h. The resulting RSA presented high contents of SiO2 (79.62%), alkaline oxides (K2O) (10.53%) and alkaline earth oxides (CaO) (2.80%). It is concluded that RSA is a new alternative ceramic raw material that can be used as a replacement for the fluxing (mainly feldspar) and inert (quartz) materials that are used in the production of triaxial ceramics.

Growth and Characterization of Ce3+doped Calciumferrate(III) Type Crystals

Ce3+ ions in oxide hosts show broad optical emission in the green spectral range, because of a strong ligand field. Substances such as Ce3+ doped CaSc2O4 and SrY2O4 crystallizing in the calciumferrate(III) structure type are used as ceramic phosphors for white LED's. However, under ambient conditions cerium prefers the 4-valent state, e.g. CeO2. For the ceramics, charge compensation and incorporation of Ce3+ can be reached by adding alkaline oxides, where e.g. (Na+, Ce3+) are substituting (2 Ca2+). Unfortunately, this option is not feasible for single crystal growth from the melt, because at the very high melting points near 21000C (CaSc2O4, [1]) or even 22000C (SrY2O4, [2]) alkaline oxides are evaporating completely. It will be shown that nevertheless efficient Ce3+ doping of both hosts can be obtained if melt crystal growth is performed in a suitable atmosphere with sufficiently low oxygen fugacity. First crystal growth experiments where performed by LHPG (Laser Heated Pedestal Growth), but meanwhile bulk growth by the Czochralski technique is feasible too. The figure shows such Ce3+:CaSc2O4 single crystal. Especially Ce3+:CaSc2O4 shows efficient broad band green emission, and no foreign phases indicating Ce4+ (CeO2) can be detected by X-ray diffraction. TEM analysis hints on incorporation of Ce3+ on a Ca2+ site.

Ce3+:CaSc2O4 Crystal Fibers for Green Light Emission: Growth Issues and Characterization

ABSTRACTCe3+ is known to show broad optical emission peaking in the green spectral range. For the stabilization of 3-valent cerium in ceramic phosphors such as calcium scandate CaSc2O4, often co-doping with sodium for charge compensation is performed (Na+, Ce3+ ↔ 2 Ca2+). At the melting point of CaSc2O4 (≈2110°C), however, alkaline oxides evaporate completely and co-doping is thus no option for crystal growth from the melt. It is shown that even without co-doping Ce3+:CaSc2O4 crystal fibers can be grown from the melt by laser-heated pedestal growth (LHPG) in a suitable reactive atmosphere. Reactive means here that the oxygen partial pressure is a function of temperature and pO2(T) rises for this atmosphere in such a way that Ce3+ is kept stable for all T. Crystal fibers with ≈1 mm diameter and ≤50 mm length were grown and characterized. Differential thermal analysis (DTA) was performed in the pseudo-binary system CaO–Sc2O3, and the specific heat capacity cp(T) of CaSc2O4 was measured up to 1240 K by differential scanning calorimetry (DSC). Near and beyond the melting point of calcium scandate significant evaporation of calcium tends to shift the melt composition towards the Sc2O3 side. Measurements and thermodynamic calculations reveal quantitative data on the fugacities of evaporating species.