High Alumina Research Articles

Characterization and properties of Chinese red clay for use as ceramic and construction materials.

This study involves the characterization and analysis of a Chinese red clay obtained from Hunan province to determine its suitability for manufacturing ceramic products. X-ray fluorescence analysis showed the clay has high silica (63.25 weight percent) and alumina (21.38 weight percent) content along with iron oxide, alkalis, and calcium acting as fluxes. X-ray diffraction (XRD) confirmed the presence of quartz, kaolinite, illite, and hematite as the major mineralogical phases. Scanning electron microscopy revealed loosely stacked, plate-shaped kaolinite particles exhibiting pseudohexagonal morphology. Particle size distribution shows a d50 of 12.7 μm and specific surface area is 21.3 m2/g. Differential thermal analysis-thermogravimetric analysis showed mass losses between 450-600°C and 950-1050°C corresponding to dehydroxylation and formation of a liquid phase, respectively. Dilatometry traced the onset of viscous flow sintering around 1000°C. Test bars produced from the clay were fired at 800°C, 900°C, 950°C, 1000°C, and 1050°C. The firing shrinkage increased from 2.5% at 800°C to 12.8% at 1050°C. Strength improved from 11.2 megapascals at 800°C to 42.3 megapascals at 1050°C due to densification and mullite formation. Hematite content caused the color to change from orange-red at 950°C to dark red at 1050°C. XRD analysis of fired specimens confirmed the presence of hematite and newly formed mullite and cristobalite phases. The results indicate the suitability of the clay for manufacturing bricks, roof tiles, and wall tiles using appropriate firing temperatures and cycles.

ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ ГАББРОИДОВ И ГРАНИТОИДОВ НЯТЫГРАНСКОГО КОМПЛЕКСА (БУРЕИНСКИЙ МАССИВ)

Gneissic gabbros, gabbrodiorites, granodiorites, and granites of the Late Proterozoic Nyatygransky Complex, exposed by erosion in the eastern part of the Bureya massif, form small intrusive bodies within the boundaries of the Melgin metalliferous trough, as well as around it. Analysis of chemical and trace-element compositions of rocks from the Nyatygransky Complex revealed their geochemical features. The calculated agpaitic index values for gabbroids are very low and range from 0.11 to 0.33. Granodiorites have slightly higher index values ranging from 0.5 to 0.38, and only gneiss-granites are plumasitic with agpaitic index values between 0.45 and 0.75. Both gabbroids and granitoids are assigned to calc-alkaline rocks by their agpaitic index. Gneissic gabbros, dominated by dark-colored minerals (labradorite, hornblende), show enhanced alkalinity not common to gabbros (4%); in them, the magnesium content prevails over the iron content. They are characterized by high alumina content (15–18%), reaching 20.38%. Geochemically, they are interpreted as I-type igneous rocks. Gneissic granitoids with a slight predominance of the iron content over the magnesium content are less aluminous (Al2O3 12–15%). They are interpreted as S-type (sedimentary) and I-type (igneous) granitoids, formed in sedimentary and granitic layers of the earth’s crust. According to petrochemical diagrams, the gabbroids and granitoids of the Nyatigransky Complex belong to the volcanic arcs of the active continental margin.

The Study on Inclusions in Casting High Manganese Steel Smelted with High Alumina Furnace Crucible

The Study on Inclusions in Casting High Manganese Steel Smelted with High Alumina Furnace Crucible

Effect of the titanium-dioxide addition on the structural, dielectric, and mechanical properties of different cement-based mortars with corundum aggregate

The primary objective of this study was to look into the role of titanium dioxide in the production of corundum-based mortars, with a focus on finding the optimal mortar composition for achieving improved mechanical and dielectric performances. Changes in the mix design (different binders, different additive dosages), as well as their effects on the hydration pathway, chemical bonds, phase modifications, and microstructure, were examined. These findings were then correlated to the designed mortars' mechanical strengths and dielectric properties. Experimental mortars were produced with binders made from ordinary Portland cement, high alumina cement, and their mixtures, and corundum as aggregate. Titanium dioxide was employed as an additive (3 and 5wt.%). Nine different mortars were submitted for comprehensive mineralogical and microstructural characterization upon curing and solidification. The compressive and flexural strengths were monitored throughout the 28-day period. The dielectric constant (εr), dielectric loss tangent (tanδ), and electrical resistivity (ρ) were measured over a frequency range of 100Hz to 1MHz. XRD analysis highlighted the appearance of mayenite as a dielectric-prone phase in the samples doped with titanium dioxide. Differential thermal analysis and FTIR spectroscopy identified a higher amount of extra-low crystalline phase in OPC and HAC mortars with TiO2 addition, which accelerated hydration mechanisms, created a surplus of hydration products and made a more compact cement matrix. TiO2 added in 3wt.% amount led to higher mechanical strengths in OPC-based mortars, while it improved the dielectric properties of HAC mortars.

Applicability of the Teetered Bed Separator for Beneficiating Indian Iron Ore Fines: An Experimental Study

Higher alumina and lower iron content in Indian iron ore fines is a major problem for its effective utilization in the ironmaking process. India is the second largest steel producer in the world with an annual production of 200 million tons in the year 2020, whereas iron ore beneficiation of this country is highly derisory. Only 52 concentrators are required to produce 220 MTPA of iron ore. Most of the concentrator's benefits are limited to sizing and washing. In recent years, the Teetered Bed Separator (TBS) has gained significant importance and appeared as a viable option for beneficiating a variety of fine minerals. So, a systematic study has been carried out to verify the suitability of the TBS to reduce the alumina content and improve the iron grade in Indian iron ore fines. As the performance of gravity separation processes strongly depends on the feed particle size, a size-by-size beneficiation study was carried out to delineate the role of particle size on the performance of the TBS. Based on this study, the TBS is established to be a possible alternative to the other conventional equipment used for the beneficiation of iron ore fines.

Effect of calcium aluminate-based additive on properties of periclase-carbon refractories for steelteeming ladles

Premature decommissioning of steel-teeming ladle lining due to critical localized damage, whichi significantly reduces the functional properties of the lining, is one of the most acute problems in modern metallurgy. The main type of products used for steel-teeming ladle lining is periclase-carbon. In order to improve corrosion resistance and resistance to thermomechanical loads, additional additives, such as spinel, and high alumina CMA cement, are introduced into the periclase-carbon products. In this paper, the effect of calcium aluminate-based additive on the properties of periclasecarbon refractories is investigated. It is assumed that there is a potential for the formation of magnesium aluminate spinel (MA) in periclase-carbon products with calcium-aluminate additives during heat treatment. Fused periclase was used as the raw material, the carbon component was represented by natural flake graphite in an amount of 10 wt% and a combined binder. An additive based on calcium aluminates was introduced, with a fractional size from 0 to 3 mm, while the amount of main fractions of fused periclase was reduced by the corresponding amount of the additive introduced. The compressive strength, apparent porosity, and bending strength values before and after coking firing were analyzed. The thermal coefficient of linear expansion, phase composition and microstructure of the products were also investigated.

Oxidation and dissolution behavior of FeCrNiAl based high entropy alloy and alumina-forming austenitic steel exposed to lead-bismuth eutectic (LBE)

Developing corrosion-resistant alloys is essential for the application of lead-cooled fast reactors. Herein, two types of FeCrNiAl alloys (high entropy alloy, HEA and alumina forming austenitic steel, AFA) are fabricated and their long-term corrosion (up to 3000 h) in lead-bismuth eutectic (LBE) at high temperature are investigated. Both alloys illustrate oxidation and dissolution behaviors, a Cr-Al enriched layer forms on AFA and the B2-NiAl phase in HEA demonstrates outstanding oxidation resistance and stability in LBE. This work offers guidelines for alloy design, especially optimizing the phase distribution of new nuclear materials that to be used in LBE.

4-year monitoring of degradation mechanisms of seawater sea-sand concrete exposed to tidal conditions: development of chemical composition and micro-performance

In tidal zones, the transfer of conductive ions accelerates concrete deterioration due to dry-wet cycles, temperature, and humidity gradients over time. Thus, this study investigates the effects of ground granulated blast furnace slag (GGBS), silica fume (SF), and metakaolin (MK) on the deterioration rate of seawater Sea-sand concrete (SWSSC) exposed to tidal conditions for four years caused by carbonation, sulphate and chloride penetration. Results showed continuous exposure to MgSO4, reduced Fe content and converted AFm into AFt, contributing to an increase in total SWSSC porosity of 12.9% while reduced to 10.2%, 7.4% and 7.3% with the optimal addition of GGBS, SF and MK. In combined sulphate and chloride-rich conditions, enhanced gel phase physical properties were more influential than AFm phases in increasing chloride binding capacity. SF suppressed AFt expansion, formed dense C−S−H with optimal Ca/Si ratio and physically increased the chloride binding capacity of SWSSC. Similarly, despite its high alumina content, MK restricted chloride mobility mainly through C−S−H and, subsequently, AFm phases. Additionally, through its initial acceleration of calcium-hydroxide consumption, SF reduced alkalinity and minimized the formation of CaCO3, outperforming MK in mitigating carbonation. Higher CaO and MgO in GGBS-mixed samples led to dolomite formation in severely carbonated zones, causing long-term mechanical strength reduction. In summary, SF significantly enhanced SWSSC durability and served as an effective additive in tidal-exposed SWSSC.

First-principles lattice dynamics and thermodynamic properties of α-, θ-, κ- and γ-Al2O3 and solid state temperature-pressure phase diagram

γ-Al2O3 is a commonly observed high temperature alumina phase during Al-based alloy oxidation. Due to the partially ordered, defective nature of the spinel structure arising from the partial occupancy in the Al sites, first-principles prediction of the thermodynamic properties of γ-Al2O3 has been challenging. In this work, employing the first-principles quasiharmonic approach, we obtain the finite temperature thermodynamic properties of γ-Al2O3, including entropy, chemical potential, heat capacity, thermal expansion coefficient, and elastic constants and the results are compared with those calculated for the other three alumina phases, i.e., α-Al2O3, θ-Al2O3, and κ-Al2O3. The calculated lattice constants and the predicted relative phase stability under 0 K and 0 GPa, α>κ>θ>γ, are consistent with experimental values and existing calculations, respectively. Based on the results, we constructed the temperature-pressure phase diagram covering the four Al2O3 phases (α, κ, θ, γ), which could provide for experimentally synthesizing the different alumina phases.

Characteristics of Fly Ash as a Constituent Material for Geopolymer

Fly ash waste from the Asam-Asam Power Plant in South Kalimantan continues to increase. Various attempts have been made to utilize fly ash waste, among others. as a basic material for making geopolymers. Geopolymer is environmentally friendly because it replaces all cement with high Silica (Si) and Alumina (Al) wastes such as fly ash. This study aims to characterize fly ash as a raw material of geopolymer. Fly ash was filtered using 200 mesh and then heated in an oven at 105°C for 24 hours. The prepared fly ash was then tested for physical properties and compound analysis using XRF, identification of chemical bonds and functional groups using FTIR, morphology, and elements using SEM EDX. Initial and final setting time was investigated using the Vicat apparatus to determine e whether cement is undergoing proper hydration. The results indicated that the fly ash was classified to class F. That was based on the amount of SiO2 + Al2O3 + Fe2O3 of 85.91%, and the CaO content was less than 10%. Moreover, fly ash’s initial and final setting time was 1072.5 and 3180 minutes, respectively. Fly ash in this research can be used as a raw material for geopolymers.

Thermodynamic analysis of the corrosion of high alumina cement by carbon dioxide

The integrity of the wellbore cement sheath plays a crucial role in the geological utilization and sequestration of carbon dioxide. Although high alumina cement (HAC) is a specialized cement with exceptional performance, additional research is required to assess its capability for long-term carbon dioxide sequestration. In this study, the effects of various corrosion conditions and pozzolanic materials on the corrosion of HAC were investigated by using the Gibbs energy minimization method. And the corrosion resistance of minerals was analyzed based on the multiphase chemical equilibrium theory. The results indicate that C3AH6 in HAC is the most susceptible to corrosion. As the temperature increases, more carbon dioxide is consumed for the complete reaction of the primary minerals in HAC. However, the corrosion of HAC is largely unaffected by system pressure. The high concentration of carbon dioxide in formation water accelerates mineral corrosion rates. In addition, the presence of Mg2+ and SO42− increases the formation of intermediate products during the corrosion of HAC, whereas the rate of mineral corrosion decreases as salinity increases. Fly ash can enhance the corrosion resistance of HAC during the initial stage of carbonization. Increasing the replacement ratio of fly ash to HAC reduces the generation of C3AH6 and increases the formation of C2ASH8. The corrosion resistance of each mineral is different, following the order: Al(OH)3 > C2ASH8 > C4AcH11 > C4Ac0.5H12 > C3AH6.

Preliminary Investigation on the Application of a Semi-Lightweight Mullite Spherical Solid Waste Material in Ladle Permanent Layer

The heat dissipation of high alumina castables for ladle permanent layer is a topic worthy of attention and solution. It is proposed to use spherical porous mullite (a solid waste) instead of irregular M70 mullite aggregate in castable to reduce the thermal conductivity and realize a high-strength and lightweight design. The effect of spherical porous mullite content in castables on thermal conductivity, service strength and thermal shock resistance were discussed. The results demonstrated that the substitution amount of spherical porous mullite increased, the bulk densities of the castables dropped from 2.68 to 2.38 g.cm−3, the apparent porosity rose from 15.5 to 25.0%. The thermal conductivities reduced from 1.174 to 0.585 W.m−1.K−1 (1000°C), which can be ascribed to the increased porosity extending the heat transfer path. Furthermore, owing to the high strength of spherical mullite and its excellent bonding with matrix, the mechanical strength of castable was at a high strength level, with modulus of rupture of 18 M Pa and cold crushing strength of 76 MPa at the spherical porous mullite completely substituting M 70 mullite. The semi-lightweight and low thermal conductivity castable containing spherical porous mullite show great application potential in the ladle permanent layer.

Influence of partial substitution of metakaolin by palm oil fuel ash and alumina waste ash on compressive strength and microstructure in metakaolin-based geopolymer mortar

Geopolymer is recognized as an alternate binder that compounds silica-rich and alumina-rich materials as raw materials and is produced by alkaline activation. In general, biomass ashes in particular for palm oil fuel ash (POFA) is an ideal starting material on the grounds of its high silica concentration, while industrial by-products, especially alumina waste (AW) is also employed as starting material due to its high alumina content. The objective of this research is to address the effects on the compressive strength and also the microstructure of metakaolin-based geopolymer mortar studied through the adaptability of the substitution of metakaolin (MK) by POFA and AW. In order to investigate the effects of POFA and AW substitution on the polymerization reaction and its outcomes, metakaolin-based geopolymers were produced. The most recent data suggests that POFA and AW probably serve as feedstocks for geopolymers with a little strength reduction. The partial substitution of MK by POFA reduces the polymerization reaction rate while maintaining the same water/binder ratio. However, because of the long-lasting polymerization reaction, it is still obtainable to reach a significant degree of polymerization reaction and also provides a comparable 28-day curing age compressive strength for 20 % replacement of MK by POFA. Considering 10 % substitution of POFA by AW, it results in 22.08 % improvement in the compressive strength after 28 curing days. On top of that, the compressive strength development of the geopolymer sample was investigated using scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). It was discovered that the density and the compressive strength were induced by the particle morphologies, the surface area of POFA and AW, and the chemical composition as a result of the geopolymerization.

Utilization of nanoparticles and waste materials in cement mortars

Abstract Cement has shaped the modern built environment, but its production generates substantial carbon dioxide emissions. Consequently, there is an urgent need to identify alternative cementitious building materials for sustainable construction. In this study, cement mortars (CMs) were produced by partially replacing cement with nanoclay (NC) and granite dust (GD). The replacement proportions (% by weight of cement) of these materials were 1.5, 3, and 4.5% for NC and 10, 20, and 30% for GD. For mortars containing NC but not GD, the strength was maximized when the NC replacement proportion was 3%. To evaluate the combined effect of partially replacing cement with both NC and GD on the fresh and hardening properties of cement-blended mortars, ternary binder mixtures containing 3% NC together with 10, 20, or 30% GD were prepared, and their workability, bulk density, compressive strength (at 7, 28, and 90 days), and flexural strength were measured. Increasing the content of NC and/or GD reduced the flowability of these mortars relative to that of the reference mortar mix because it increased the content of fine materials. CM containing 3% NC and 10% GD had the highest compressive strength at 7, 28, and 90 days while also having the greatest flexural strength when compared to the control mix. This is most likely due to the high silica and alumina content of NC and GD, as well as their high specific surface area, which would improve the maturity and density of the matrix when compared to cement alone.

Investigation of the influence of impurities typical in secondary raw materials on the behavior of high alumina castables – Part 1: Design of the castables, setting properties and high temperature fracture behavior

The research was carried out using a primary high alumina raw material that was selectively spiked with typical elements found in secondary raw materials. These artificially spiked raw materials were processed into cement-free high alumina monolithics by 1:1 substitution of the corresponding high alumina matrix fraction in the formulation. Regardless of the impurity, the rheology and setting behavior of the developed model refractory castables showed a very high degree of comparability with the reference material. The same workability allowed the production of comparable test pieces for hot wedge splitting tests. The effects on high temperature fracture behavior observed in this study can therefore be attributed solely to the impurities.

Changes in the physicochemical properties of calcium aluminate cement paste with high alumina content under deep seas

Changes in the physicochemical properties of calcium aluminate cement paste with high alumina content under deep seas

Self-healing capability of engineered cementitious composites with calcium aluminate cement

The reduced heating temperatures required for producing calcium aluminate cement (CAC) make it highly suitable for reducing CO2 emissions in engineered cementitious composites (ECCs) known with their significant amount of cement. However, it is not clear to what extent this can influence the advanced mechanical and self-healing ability of control ECC, especially with the risk of conversion in CAC reaction products. This study investigates the self-healing capability of ECCs produced using CAC instead of conventional ordinary Portland cement (OPC). It also assesses the impact of incorporating fly ash (FA) into CAC-ECC blends at different FA/CAC ratios. In addition to the mechanical characterisation of sound specimens, flexural properties, cracking behavior, ultra-sonic pulse velocity (UPV) and rapid chloride permeability test (RCPT) were performed on preloaded OPC- and CAC-ECCs. The study also analyzed the microstructural changes of self-healing products associated with the high alumina content of CAC. The results show that CAC can be used to produce high mechanical strengths ECCs, with more than 34% and 7% higher compressive and flexural strengths respectively than those of ECC-CTL at early age, though the addition of FA was important to reach improved patterns of mechanical properties at advanced ages. In addition, significant improvements were recorded for the recovery rates of CAC-ECCs, reaching more than 29% for flexural strengths, 11% for UPV and 75% for RCPT than the ECC-CTL. The self-healing products characterized with SEM-EDS confirmed the occurrence of conversion when FA was not included in CAC-ECCs, nevertheless with limited effect on the self-healing efficiency of these mixtures.

Investigation of the role of impurities typical in secondary raw materials on the behaviour of high alumina castables - Part II: Influence on thermomechanical behaviour

The present work investigated the effect of relatively small additions of impurities originating in secondary raw materials on the thermomechanical properties of alumina castables bonded with active alumina. Castable compositions containing impurities for testing were selected on the basis of predictions from thermochemical calculations of their phase composition and the formation of large amounts of liquid phase at the temperature of 1600 °C. Viscosity of the emerging liquid phase was also calculated. The selected alumina castables with impurities from the systems: CaO–SiO2. Na2O–SiO2. Fe2O3–CaO. Fe2O3–CaO–SiO2 and TiO2–CaO–SiO2 were tested for thermomechanical properties by analysing the effect of impurities on refractoriness under load (RUL) creep in compression (CiC) and resonant frequencies and damping changes versus temperature (RFDA). Real composition of tested material via high temperature X-ray diffraction (HT-XRD) were verified. The obtained results indicate that impurities introduced into the refractory castables in a total amount of 0,18 wt% (2% in the fraction 0–45 μm) and in the most unfavourable ratio from the point of view of phase equilibria have an observable effect on the properties of the material at elevated temperature. The obtained results show that in the case of introducing impurities into the material with mutual proportions of shares limiting the formation of the liquid phase. It will be possible to maintain the thermomechanical properties of alumina castables at a satisfactory level (compared to the pure one) from the industrial process perspective in which it will be used. The obtained results shed new light on the possibilities of the conscious use of secondary raw materials in refractory monolithics technology.

Alkali Methods for Alumina Extraction from the By-products of High Alumina Coal: A Review

Alkali Methods for Alumina Extraction from the By-products of High Alumina Coal: A Review

Phase evolutions, microstructure and physico-mechanical properties of ceramics from Meiganga kaolin: effect of Na/K2O and CaO addition

ABSTRACT This paper examines the potential use of pegmatite and marble as additives in amalgamation with Meiganga kaolin to produce stoneware products capable to resist high temperatures as well as enhancement the mechanical characteristics. Two series of ceramic products were formulated by partly replacing kaolin with 0, 3, 5 and 7 wt% of both pegmatite and marble wastes. The specimens were sintered at 1000°C, 1050°C and 1100°C. Fired ceramic samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and the microstructure of the products was determined using an environmental scanning electron microscope and energy-dispersive X-ray spectroscopy. Also, the physico-mechanical properties were evaluated. Results divulged that, the addition of pegmatite or marble to kaolin enhances the strength of the ceramic body and act as a fluxing agent by promoting vitrification and glassy phase in clay after firing. The highest flexural strength results were observed with 7 wt% of pegmatite added at 1100 °C, with an increase ~ 35% compared to the control sample. High silica and alumina contents in pegmatite fill in voids, providing densification matrices. The incorporation of pegmatite allows to obtain a ceramic with better mechanical properties and energy saving as compared by the conventional ceramic.