Alumina Inclusions Research Articles

Innovative recycling and conversion of aluminum waste to hydrogen and aluminum chloride: Enhancing economic feasibility and sustainability in Saudi Arabia

The rapid industrialization and urbanization in Saudi Arabia have led to significant challenges in waste management, particularly in recycling aluminum waste. This study explores an innovative approach for converting aluminum waste, specifically beverage cans, into valuable products such as aluminum chloride (AlCl3) and hydrogen (H2). The process involves the chemical reaction of aluminum with hydrochloric acid (HCl), producing AlCl3 and H2, and is modeled using Aspen Plus software. Two scenarios are evaluated: one without recycling and one incorporating recycling processes. In the first scenario, the direct conversion process yields 355 tons of AlCl3 and 9 tons of H2 per day from 100 metric tons of aluminum waste. The minimum selling price (MSP) of AlCl3 is calculated to be $764 per ton, with an annual profit of $25 million, assuming a market price of $1000 per ton. However, the economic viability of this scenario is highly sensitive to conversion efficiencies and market conditions. The second scenario integrates a recycling loop, processing 90 % of the aluminum waste back into aluminum, significantly enhancing economic stability. This scenario produces 35 tons of AlCl3 and 1 ton of H2 per day, with an MSP of $1068 per ton. Despite the higher MSP, the inclusion of recycled aluminum, sold at $2400 per ton, results in a higher annual profit of $38 million, demonstrating greater economic resilience and sustainability. This study provides a comprehensive techno-economic analysis, highlighting the dual benefits of waste reduction and resource recovery. By optimizing reaction conditions and incorporating recycling, the proposed process aligns with Saudi Arabia's Vision 2030 sustainability goals, offering a viable pathway for enhancing economic feasibility and environmental sustainability in aluminum waste management.

Heteromultimetallic Platform for Enhanced C-H Bond Activation: Aluminum-Incorporated Dicopper Complex Mimicking Cu-ZSM-5 Structure and Oxidative Reactivity.

Bimetallic complexes have sparked interest across various chemical disciplines, driving advancements in research. Recent advancements in this field have shed light on complex reactions in metalloenzymes and unveiled new chemical transformations. Two primary types of bimetallic platforms have emerged: (1) systems where both metals actively participate in reactivity, and (2) systems where one metal mediates the reaction while the other regulates reactivity. This study introduces a novel multinucleating ligand platform capable of integrating both types of bimetallic systems. To demonstrate the significance of this platform, we synthesized a unique dicopper complex incorporating aluminum in its coordination environment. This complex serves as the first structural model for the active site in copper-based zeolites, highlighting the role of aluminum in hydrogen atom abstraction reactivity. Comparative studies of oxidative C-H bond activation revealed that the inclusion of aluminum significantly alters the thermodynamic driving force (by -11 kcal mol-1) for bond activation and modifies the proton-coupled electron-transfer reaction mechanism, resulting in a 14-fold rate increase. Both computational and experimental data support the high modularity of this multinucleating ligand platform, offering a new approach to fine-tune the reactivity of bimetallic complexes.

Bubble Characteristics Required for the Complete Removal of Alumina Inclusions from Steel Melts

Gas bubbling can be an effective means to float out alumina inclusions from liquid steel in a ladle. However, large spherical cap bubbles are formed when using porous plugs, as the liquid steel is nonwetting to the porous refractory. These bubbles rise rapidly through the liquid steel, forming a fast‐moving bubble plume, restricting contact times. Sized microbubbles, by contrast, have now been generated in liquid metals by shearing methods, involving linear crossflows to an entering flow of gas, or alternatively by rotational shearing. Combined with these convective shearing forces, local kinetic energy of turbulence can also play an important part in determining final microbubble size distributions. As microbubbles have much smaller rise velocities and present a far greater inclusion capture surface area than those of a single large bubble of the same gross volume, this will allow us to remove sub‐50 μm inclusions from liquid steel. It is expected that this goal will require a redesign of current ladle shrouds.

SEM Image Processing Assisted by Deep Learning to Quantify Mesoporous γ-Alumina Spatial Heterogeneity and Its Predicted Impact on Mass Transfer.

The pore network architecture of porous heterogeneous catalyst supports has a significant effect on the kinetics of mass transfer occurring within them. Therefore, characterizing and understanding structure-transport relationships is essential to guide new designs of heterogeneous catalysts with higher activity and selectivity and superior resistance to deactivation. This study combines classical characterization via N2 adsorption and desorption and mercury porosimetry with advanced scanning electron microscopy (SEM) imaging and processing approaches to quantify the spatial heterogeneity of γ-alumina (γ-Al2O3), a catalyst support of great industrial relevance. Based on this, a model is proposed for the spatial organization of γ-Al2O3, containing alumina inclusions of different porosities with respect to the alumina matrix. Using original, advanced SEM image analysis techniques, including deep learning semantic segmentation and porosity measurement under gray-level calibration, the inclusion volume fraction and interphase porosity difference were identified and quantified as the key parameters that served as input for effective tortuosity factor predictions using effective medium theory (EMT)-based models. For the studied aluminas, spatial porosity heterogeneity impact on the effective tortuosity factor was found to be negligible, yet it was proven to become significant for an inclusion content of at least 30% and an interphase porosity difference of over 20%. The proposed methodology based on machine-learning-supported image analysis, in conjunction with other analytical techniques, is a general platform that should have a broader impact on porous materials characterization.

Hybridization of concrete by the inclusions of kaolin, alumina and silica fume: Performance evaluation

Concrete is the prime source, which fulfils the applications for construction in various forms. The prime roles of concrete industries are reducing material usage, enrichment of compressive strength, and flexural strength of concrete usage. This research focuses on recycling kaolin (mining waste) and silica fume, a great potential material for replacing coarse aggregate gravel stone and fine aggregate sand in conventional concrete as a hybrid. The developed concrete contained 5% nano alumina (Al2O3), 10% of kaolin waste (KW), and 5, 10, and 15% of silica fume (SF), and its behavior like compressive strength, flexural strength, water absorption, and acid attack behavior is studied. The molecular structure of crystalline is analyzed via X-ray diffraction (XRD). The 15% SF blended with 5% alumina and 10% KW cured within 28 and 90 days recorded high compressive and flexural strength (44 ± 1.76 MPa and 4.3 ± 0.17 MPa). XRD pattern proved their alumina, SF, and KW and found that the concrete blended with 5% alumina, 10% KW, and 15 wt% SF(90 days cured concrete) showed low water absorption (3.1 ± 0.12%). The effect of sulfuric acid behavior on weight reduction was 0.78% compared to CC1 (concrete cube without Al2O3, SF, and KW).

Interactions Between Alumina Inclusions at the Liquid Iron/Argon Gas Interface: Role of Contact Line Undulation

A deep understanding of the behavior of nonmetallic inclusions is essential for steel cleanliness control. The behavior of alumina inclusions at the liquid iron/argon gas interface is investigated using a high‐temperature confocal scanning laser microscope. The obtained images are used to determine the moving velocity of the inclusions on the interface. The obtained experimental data are quantitatively evaluated using the lateral capillary interaction model for multipole orders established by Danov–Kralchevsky while taking into account the resistive drag force. The attraction forces calculated from these data are in the range between ≈10−13 and ≈10−11 N. The best‐fitting model is assigned for each case. The multipole models almost counterbalance the drag force, indicating a good interpretation of the interaction between the inclusions. Moreover, the acting length of this interaction is examined and compared to the previous work on Ce2O3 inclusions. It is found that alumina inclusions generally exhibit a larger acting length at a large critical radius and a smaller acting length at a small critical radius when comparing them to their counterpart cerium oxide inclusions. Considering the particle shapes, high shape irregularity is better interpreted by higher orders of the multipoles.

CFD simulation and water model experiments with overflow-type supergravity reactor set up for continuously removing inclusions from aluminum melt

In this work, an overflow-type supergravity reactor has been tested for removal of inclusions from aluminum melt. A combination of numerical and physical simulations was employed to investigate the continuous separation process of recycled aluminum melt and inclusions, with a focus on evaluating the effects of reactor structures, process parameters, and inclusion characteristics on the inclusion separation efficiency. The results of numerical simulation indicate that the inclusion separation efficiency is positively related to overflow pipe length (L), overflow pipe installation height (H), gravity coefficient (G), inclusion density (ρ) and inclusion diameter (d), and negatively related to overflow pipe diameter (Φ) and melt inflow rate (Q). The overflow-type supergravity reactor exhibited excellent performance in separating inclusions from recycled aluminum melt. Under the conditions of L = 40 mm, H = 108 mm, Φ = 10 mm, G = 500, and Q = 0.5 kg/s, the separation efficiency of 18 μm Al2O3 inclusions reached nearly 100 %. The high consistency between the results of numerical and physical simulations provided full verification of the reliability and accuracy of the numerical simulation.

The Influence of the Phase Arrangement of ATZ Composites on Their Wear Rate Under Ball-on-Disc Tests

An alumina-toughened zirconia (ATZ) material, fabricated using a procedure consisting of the common sintering of two different zirconia powders, was tested using the ball-on-disc method in a temperature range between 20 and 400 °C. Tetragonal zirconia balls were used as a counterpart. Three different types of microstructure were designed, one consisting in separated alumina inclusions in zirconia matrix, the second one containing alumina inclusion in the amount close to the percolation point and another one which was a combination of two continuous phases, penetrating the whole volume of the composite. It was detected that at elevated temperatures all materials showed distinct decrease of measured wear rate. Composite with a low alumina content showed minimal wear rate at 300 °C and composites with higher amount of alumina were the most wear resistant at 400 °C. There are some evidences that this minimal wear rate is connected with a pseudoplastic behavior of a layer formed between co operating elements of tribological pair.

Effects of alumina addition on electrical properties of alumina-toughened zirconia for application in low- and intermediate-temperature solid oxide fuel cells

One of the priorities in the field of hydrogen energy is the development of intermediate-temperature (IT-SOFCs) and low-temperature solid oxide fuel cells (LT-SOFCs), which are capable of highly efficient operation in the range of 500–800 °C. The currently applied 8-YSZ electrolytes are expected to be replaced by one based on tetragonal zirconia (3Y-TZP), which is characterized not only by high ionic conductivity below 700 °C, but also significantly higher mechanical strength. One of the candidates is alumina-toughened zirconia (ATZ) with extraordinary mechanical properties (flexural strength of up to 1 GPa and outstanding fracture toughness (KIc) in excess of 10 MPa m0.5). A series of composites with a nanometric alumina content of 2.3, 10, and 20 vol% were obtained and investigated to evaluate the effects of aluminum addition on the electrical properties of the materials in relation to their microstructure, chemical and phase composition. Measurements performed by means of electrochemical impedance spectroscopy over the range of 300–650 °C showed that the total electrical conductivity of the obtained ATZ samples decreased slightly with increasing content of alumina inclusions and it was around one-third of an order of magnitude lower than that of the reference 3Y-TZP sinter prepared from the commercially available oxide powder containing 3 mol% of yttrium oxide (TOSOH). This is a consequence of the fact that ATZ sinters exhibited a lower specific conductivity of grain boundaries than 3Y-TZP whilst having comparable electrical conductivity of grain interiors. The total electrical conductivity values determined for the ATZ sinters at 700 and 800 °C are approximately the same as the electrical conductivity of 3Y-TZP, and they can therefore be considered a viable alternative to 8-YSZ electrolytes in applications such as IT-SOFCs or LT-SOFCs.

Experimental Study on the Environmental Effects and Mechanical Characteristics of Solidified Cr(VI)-Contaminated Soil Based on Slag and Desulfurization Gypsum

This study proposed a new curing agent consisting of slag and desulfurization gypsum industrial waste to solidify Cr(VI)-contaminated soils and prevent its migration and bioaccumulation in the ecosphere. The curing agent dosage of 10–30% resulted in a Cr(VI) toxic leaching concentration, compressive strength, and hydraulic conductivity range of 0.118–5.824 mg/L, 2.70–10.22 MPa, and 1.70 × 10−9–1.37 × 10−6 cm/s, respectively. Following four dry and wet cycles, the dosage of the curing agent was found to be 20–30% to achieve minimum environmental safety requirements. Cr(VI) in the cured specimens mainly existed as CrO42−, or acid salt, in which a portion was changed to Cr(III) during precipitation or directly was encased in the silica-alumina mesh structure. The adsorption capacity of hexavalent chrome on the outer of the hydration product groups was insignificant owing to the electronegativity. Hence, the Cr(VI) was solidified by hydrides such as C-S(A)-H and calcium alumina inclusions. Calcite, quartz, and several zeolite-like substances were also found to be colloidal in the pores to block Cr(VI).

Removal behavior of Al–Ti–O inclusions in aluminum deoxidized molten steel containing titanium by microporous magnesium foam ceramic filters

Al–Ti–O inclusions in aluminum deoxidized and titanium (Ti)-alloyed steel aggravate the submerged nozzle clogging and instability of the continuous casting process, lowering the cleanliness of casting billet. In the present investigation, the removal behavior of the oxide inclusions in aluminum deoxidized IF steel and Ti-alloyed welding wire steel by microporous/fused MgO foam ceramic filter (PMF/FMF) and the improvement of the steel cleanliness were comparatively investigated. It is found that MgO foam ceramic filters immersed in Al deoxidized steel effectively reduced its number density of Al2O3 inclusions and total oxygen (TO) content, by use of forming Al–Mg–O spinel interface reaction layer between the filters and tested steel. Furthermore, the cleanliness increase of Ti-alloyed steel immersed by the filters, due to formation of a more complete and continuous Al–Mg–Ti–O spinel layer on their surface, was bigger compared with that in Ti-free steel, with sporadically distributed Al–Mg–O spinel of interface layer on the surface of filters immersed in Ti-free steel. This is ascribed to the higher Ti content and some liquid inclusion of MgO–Al2O3-TiOX in Ti-alloyed steel, enhancing the reaction of the MgO of aggregates in the filters with Al, Ti, and O and deposition of other solid MgO–Al2O3-TiOX on the surface of the filter, respectively. In addition, the better purification efficiency of the PMF on tested steel compared with the FMF, was due to its higher porosity, roughness and more liquid phase components of the matrix in PMF, which improve the reaction of filter with liquid steel, and raise its adsorption capacity with Al2O3-based inclusions in the steel, forming Al–Mg–O spinel interface layer to removal the oxide inclusions.

Effect of α-Al2O3 content on microstructures, mechanical properties and purification efficiency on molten steel of MgO-based filters

In this study, five sets of MgO-based ceramic filters were prepared using porous MgO powder and α-Al2O3 micro-powder as raw materials. The effect of α-Al2O3 content on the microstructures, mechanical properties and purification efficiency of MgO-based filters were investigated via SEM, EDS, and immersion test in molten steel, etc. The results indicate that the reactive sintering between α-Al2O3 and MgO promoted the formation and growth of neck connections of magnesium aluminate spinel between grains, increased the density of the filter skeleton, and decreased the pore size inside the skeleton. The higher density and smaller pore size of the skeleton, as well as the neck connection of spinel and crack deflection effect caused by magnesium aluminate spinel, comprehensively improved the strength and thermal shock resistance of MgO-based ceramic filters. Furthermore, the results from the immersion test in molten steel revealed that an appropriate amount of high-temperature liquid phase, smaller pore size, and in-situ generated spinel were beneficial for the filters to adsorb dissolved aluminum, dissolved oxygen, alumina inclusions, and secondary spinel inclusions in the steel. The filter with 20 wt.% α-Al2O3 had the best overall performance with a compressive strength of 2.35 MPa, a compressive strength after thermal shock test of 1.91 MPa and an efficiency of 77.3% in reducing the total oxygen content of the steel.

Phase analysis of complex non-metallic inclusions in Al-deoxidized 42CrMo4 steel after contact with MgO–C refractories

This study extensively investigated characteristic non-metallic inclusions in oxidized and deoxidized 42CrMo4 steel after contact to MgO–C refractories, proposing possible formation and modification mechanisms of non-metallic inclusions. The structures and compositions of different inclusion species were analyzed, revealing various types: crystalline, amorphous, and complex inclusions containing both crystalline and amorphous phases. The latter always consisted of an amorphous Mn–Si–Al–O matrix containing various crystalline phases such as Al2O3, MnAl2O4 and/or MnTiO3. The formation of amorphous Mn–Si–Al–O inclusions was attributed to steel melt oxidation, while pure crystalline corundum inclusions resulted from both the steel melt oxidation and deoxidation. Alumina inclusions exhibited different shapes, likely because of variations in aluminum and oxygen supersaturation in the steel melt during their formation. Complex inclusions were suggested to form through precipitation on existing inclusions and mutual collision of pre-existing inclusions, facilitated by the non-wetting behavior of solid alumina inclusions in the steel melt.

Effect of oxygen and sulfur on alumina particle behavior in front of solid–liquid interface of steel liquid

In this work, the interface characteristics between alumina and the steel liquid with different sulfur and oxygen concentrations were measured by an improved sessile drop method. And the behavior of alumina inclusions in front of the solid–liquid interface of steel liquid with different oxygen and sulfur concentrations was investigated by in-situ observation. Furthermore, the behavior of alumina particles in front of the solid–liquid interface on the surface of the steel liquid was discussed from the interface characteristics between alumina and the steel liquid with different sulfur and oxygen concentrations based on the interface gradient force, coulombic force, and Marangoni effect viewpoints. The results show that the large and small inclusion particles were engulfed and pushed, respectively, at the interface of solid–liquid, while the critical average radius for engulfed inclusion particles decreased from 7.73 μm to 6.21 μm and 4.84 μm, respectively, with sulfur and oxygen concentrations increasing. And the behavior can be described by a function formula concerning the interface characteristics between alumina and the steel liquid with the different sulfur and oxygen concentrations based on the interface gradient force, coulombic force, and Marangoni effect viewpoints. Further, it is found that the aggregation ability due to capillary force is weakened and even dispersed at the solid–liquid interface, which leads to the inclusion being easily pushed away from the front of the solid–liquid interface with the increase in sulfur and oxygen concentrations.

Effect of Al–Ti Concentration on Alumina Inclusions Aggregation Floating Behavior in Molten IF Steel

Understanding the aggregation‐floating behavior of alumina inclusions, which is influenced by the interface properties between inclusions and molten steel, is crucial to control the purity of interstitial‐free (IF) steel in the refining process. In this work, it is attempted to investigate the effect of aluminum and titanium concentrations on the aggregation‐floating behavior of alumina inclusions in the interior of IF molten steel based on the interface properties between molten steel and alumina inclusions. The interface properties between the molten steel and alumina inclusions are measured using an improved sessile drop method. And, the aggregation‐floating behavior of inclusions in the interior of molten steel is quantitatively discussed by an aggregation model based on the attractive force between alumina inclusions, which was combined with the interface properties. In the results, it is shown that the attractive forces between alumina inclusions, ranging from 6.96 × 10−6 to 5.41 × 10−5 N, increase and decrease, respectively, with increasing aluminum and titanium concentrations. Furthermore, the terminal floating speeds of alumina inclusions, ranging from 0.0510 to 0.0873 m s−1, increase and decrease, respectively, with increasing aluminum and titanium concentrations.

TiN Inclusions Formation in Ti-Al Deoxidized Ultra-low Carbon Steel

TiN inclusion in steel is easy to cause surface defects in ultra-low carbon steel. TiN was studied by analyzing their formation mechanisms, compositions, and morphology through SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectroscopy). Thermodynamic analysis through kinetic simulations of the different stages of RH degassing was conducted by the FactSageTM software package. TiN inclusions can distribute either randomly or in clusters with exogenous inclusions. Most of the TiN inclusions are regular cubic shapes. Some of them have a black center which is alumina inclusion. The alumina inclusions formed by reoxidation can catch TiN inclusions and combine with them because of the strong combining affinity between them. Ti is a strong nitride former in liquid steel, and TiN mostly forms during cooling or solidification. The maximum temperature is approximately 1, 430 °C. The growth of TiN inclusions can be controlled by adjusting the Ti and N contents (N< 30 ppm).

Agglomeration behavior of alumina inclusions and calcium aluminate inclusions on molten nickel-based superalloy surface

Agglomeration behavior of alumina inclusions and calcium aluminate inclusions on molten nickel-based superalloy surface

Effect of Al–Ti Concentration on the Alumina Inclusions Agglomeration Behavior on the Surface of Molten Steel

Effect of Al–Ti Concentration on the Alumina Inclusions Agglomeration Behavior on the Surface of Molten Steel

Effects of tri-ethylene glycol mono methyl ether and alumina on the performances of enriched hydrogen dual fuel diesel engine

The present study is focused on the combustion behavior, performance and emissions of a modified diesel engine working on dual fuel mode with hydrogen as a gaseous fuel by the inclusion of tri-ethylene glycol mono methyl ether and alumina nanoparticles as fuel additives. The inclusion of tri-ethylene glycol mono methyl ether, alumina and hydrogen separately and simultaneously improved the net heat release with reduced cylinder pressure at high loads as compared with neat diesel. The brake thermal efficiency increased by 22.5% and 11.6% by the inclusion of tri-ethylene glycol mono methyl ether and hydrogen respectively at 50% load, when combined together, it was improved remarkably by 28.15%. The addition of alumina was responsible for a slight reduction in NOx formation at all loads, while it was incremented by hydrogen enrichment at the highest load as compared to pure diesel. The CO formation was incremented by the addition of alumina, while the CO2 and HC formations were reduced up to 50% load, increased at 70% load. The CO, CO2, HC and smoke opacity were reduced with TGME and hydrogen enrichment, while the NOx formation was reduced up to 50% load, then increased at the higher load.

Alumina Nucleation, Growth Kinetics, and Morphology: A Review

The reaction between aluminum and the dissolved oxygen in liquid steel yields the precipitation of alumina crystals with characteristic morphologies and size distributions. Alumina precipitation and growth involve a wide spectrum of time, length, velocity, and thermodynamic supersaturation scales throughout the refining processes. The smallest length and time scales are those quantifying the nucleation kinetics and the initial growth at the highest supersaturation. Further growth and crystal morphology depend on the concentration of surface tension elements which inhibit the crystal's faces suffering further modifications due to washing effects provided by turbulent flows. This step involves longer time, velocity, length, and moderate supersaturations. The final step involves the growth of alumina inclusions through collision–agglomeration–sintering, and capillary processes on the surfaces of argon bubbles under low supersaturations. Jumps of supersaturation, due to late aluminum additions or steel reoxidation, lead to alumina crystals changing their morphology to dendritic‐type growth. The present contribution reviews each one of these kinetic phenomena closing with the consequences that alumina precipitation has on the continuous casting process. The content of this review is useful to practitioners and theorists alike.