Alumina Phase Research Articles

The spinel to garnet phase transition in the systems MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2: new experiments to resolve long-standing discrepancies

The pressure and temperature conditions of the transition from spinel to garnet as the stable aluminous phase in peridotite lithologies of the upper mantle is integral to elucidating the tectonic significance of the ‘garnet signature’ in basalts. It provides an essential constraint on models of mantle partial melting and oceanic crust formation. Existing experimental results on the univariant phase transition in the simple systems MgO-Al2O3-SiO2 (MAS) and CaO-MgO-Al2O3-SiO2 (CMAS) are mutually inconsistent. To resolve this, we have re-determined the P-T coordinates of the univariant transition in both synthetic systems by running experiments containing both systems simultaneously in the piston-cylinder apparatus, along with the MgO-ZnO pressure sensor. These experiments show a ~ 0.4 GPa difference in the pressure of the spinel/garnet phase transition between the two chemical systems at 1400 ºC, double that inferred from a compilation of existing experimental data. Absolute pressure in these experiments can be verified using the MgO-ZnO sensor. The results imply that the thermodynamic data used in recent mineral equations of state based on the Holland-Powell thermodynamic dataset are substantially correct.

Atomistic Simulation of Temperature-Dependent Interfacial Diffusion between Solid Nickel and Liquid Aluminum

The performance and durability of welded joints are directly influenced by interfacial diffusion between the metals involved, making it essential to investigate the effect of temperature on these processes. The present research examines temperature-dependent diffusion mechanisms at the interface between solid nickel and liquid aluminum using molecular dynamics simulations. Investigations were conducted at 1200, 1300, 1400, and 1500 K to explore the influence of temperature on atomic mobility and interfacial mixing. Radial distribution function analysis revealed a significant increase in the diffusion of nickel atoms into the aluminum phase with increasing temperature, indicating enhanced atomic interactions at the interface. The mean square displacement analysis supported these findings, showing that aluminum atoms were more mobile than nickel atoms at lower temperatures, while nickel atoms exhibited a faster diffusion rate with increasing temperature, surpassing aluminum in mobility. This trend is reflected in the diffusion coefficients, which exhibit a temperature-dependent increase in the diffusion rate of the nickel atoms. These results emphasize the role of temperature in controlling the diffusion dynamics at the solid–liquid interface. The insights gained from this study are critical for optimizing processes, such as dissimilar metal welding, where precise control over interfacial diffusion is essential for achieving the desired material properties and ensuring the structural integrity of nickel–aluminum joints in high-temperature applications.

Phase composition and crystal structure of alumina-zirconia ceramics with varying LaAl11O18 content

This study investigates the phase composition and structure of alumina-zirconia ceramics containing varying amounts of LaAl11O18 plates. The research addresses the significant influence of lanthanum hexaaluminate on the structural and physical properties of these ceramics, specifically focusing on its effects on crystal lattice parameters and phase volume content. Using synchrotron radiation and the Rietveld refinement method, the influence of lanthanum hexaaluminate content on the parameters of crystal lattices and phase content of the investigated materials were evaluated. Scanning electron microscopy was employed to analyze the grain size, morphology, and distribution within the material matrix. High-purity powders of α-Al2O3, 3Y-ZrO2, and La2O3 were used as initial materials. The materials were obtained by the pressureless sintering techniques in two hours at 1520 °C. A series of materials comprising 50 wt.% ZrO2 and varying percentage (0–15 wt.%) of LaAl11O18 was obtained. The coherent scattering regions of the alumina and zirconia matrix phases remained relatively unchanged in the composites. The coherent scattering regions of lanthanum hexaaluminate increased significantly with its concentration in the materials. The analysis revealed a decrease in alumina grain size with increasing LaAl11O18 content, while the size of the LaAl11O18 plates displayed a consistent increase. The best properties were observed for alumina-zirconia ceramics with the calculated content of lanthanum hexaaluminate of 12 wt.%. The relative density of this material is 95.3±0.3%, the hardness is 1490 Hv, and the indentation fracture resistance is 7.2±0.3 MPaThis study investigates the phase composition and structure of alumina-zirconia ceramics containing varying amounts of LaAl11O18 plates. The research addresses the significant influence of lanthanum hexaaluminate on the structural and physical properties of these ceramics, specifically focusing on its effects on crystal lattice parameters and phase volume content. Using synchrotron radiation and the Rietveld refinement method, the influence of lanthanum hexaaluminate content on the parameters of crystal lattices and phase content of the investigated materials were evaluated. Scanning electron microscopy was employed to analyze the grain size, morphology, and distribution within the material matrix. High-purity powders of α-Al2O3, 3Y-ZrO2, and La2O3 were used as initial materials. The materials were obtained by the pressureless sintering techniques in two hours at 1520 °C. A series of materials comprising 50 wt.% ZrO2 and varying percentage (0–15 wt.%) of LaAl11O18 was obtained. The coherent scattering regions of the alumina and zirconia matrix phases remained relatively unchanged in the composites. The coherent scattering regions of lanthanum hexaaluminate increased significantly with its concentration in the materials. The analysis revealed a decrease in alumina grain size with increasing LaAl11O18 content, while the size of the LaAl11O18 plates displayed a consistent increase. The best properties were observed for alumina-zirconia ceramics with the calculated content of lanthanum hexaaluminate of 12 wt.%. The relative density of this material is 95.3±0.3%, the hardness is 1490 Hv, and the indentation fracture resistance is 7.2±0.3 MPa.m1/2.

Amorphous Al2O3 Supported NiMo Nanocatalysts: Boosting Type 2 Sites for Hydrodesulfurization Reaction

Herein, we report superior Hydrodesulfurization (HDS) catalytic activity of ultrasmall NiMo supported on amorphous‐Al2O3 (A‐Al2O3) catalysts with enhanced type 2 sites. A‐Al2O3 was chosen as support because it has lower surface energy, better physicochemical properties, and enhanced acidic sites than the crystalline alumina phase. At 20% metal oxide composition, NiMo supported on A‐Al2O3 catalyst showed weak metal‐support interaction, higher sulfidation degree (80%) and higher amount of NiMoS sites (14.9 x 1019 sites/mg) with optimum stacking degree (2.5), leading to 1.4 and 1.2 times higher reaction rate constant and turn over frequency (TOF) respectively than wet impregnated NiMo supported on ℽ‐Al2O3 catalysts. Further, the Density Functional Theory (DFT) study supports the formation of a higher degree of type 2 sites (by confirming weaker active metal interaction for A‐Al2O3 surface than crystalline ℽ‐Al2O3), which leads to increased HDS catalytic activity.

Impact of calcium carbonate whisker on chloride migration in cementitious materials blended with calcined kaolin tailings

Cement blended with aluminate and carbonate phases has demonstrated potential as a low-carbon binding material, with limestone calcined clay cement (LC3) being a prime example. Given the growing demand for building materials, it is essential to explore alternative raw materials. This study investigates the chloride resistance of cement incorporating aluminate phases from calcined kaolin tailings (CKT) and the carbonate phase from limestone/calcium carbonate whiskers (LS/CW). The rapid chloride migration test is employed to analyze the impact of CKT and its combination with CW on chloride movement. Additionally, microstructural characteristics, phase assemblage, and morphology of the hardened paste are examined using Mercury Intrusion Porosimetry (MIP), electrochemical tests, X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Results indicate that CKT and CW combined exhibit superior chloride resistance. Beyond the filler effect, the pozzolanic and aluminate-carbonate reactions effect, the bridging effect of CW enhances microstructural properties. This study highlights the potential of modifying raw material shapes to improve long-term performance of blended cementitious materials.

An assessment of the pozzolanic potential and mechanical properties of Nigerian calcined clays for sustainable ternary cement blends

This study investigates the potential of calcined clays from Nigerian deposits as supplementary cementitious materials. Clay materials were obtained from three sites namely: Ikpeshi, Okpilla and Uzebba. The raw clay samples were then calcined at 700°C and 800°C. Chemical and mineralogical compositions were determined for the raw and calcined clay samples using XRF and XRD respectively. The chemical composition by XRF confirmed these clays as potential pozzolans with SiO2, Al2O3, and Fe2O3 collectively exceeding 70%. XRD analysis identified kaolinite and quartz as major mineral phases in the raw clays, which transformed into metakaolin upon calcination. Thermo Gravimetric Analysis (TGA) indicated varying lime consumption levels among the clays, with Ikpeshi clay displaying the highest pozzolanic reactivity and Uzebba clay the least. Compressive strength investigation on mortar cubes prepared with 50% substitution of Portland cement with the calcined clay and limestone, showed that Ikpeshi clay at 800°C had the best strength performance, with strength activity index of 0.92 (at age 28 days), demonstrating superior pozzolanic potential. Strength development was more significant between 7 and 28 days, indicating the pozzolanic reaction's contribution to long-term strength. However, initial strength at 3 days was lower than the reference Portland cement due to a delayed pozzolanic reaction. XRD analysis of blended pastes revealed typical phases of hydration like portlandite, calcium silicate hydrate phase, strätlingite, and ettringite, with the calcined clay blends showing reduced portlandite content, indicating absorption by the pozzolan's alumina phase.

Effect of Calcium Aluminate Phases in High Alumina Cements and Low Cement Castable

Effect of Calcium Aluminate Phases in High Alumina Cements and Low Cement Castable

Thermodynamic modeling of the processes of purification of primary aluminum from vanadium impurities

This article discusses the interaction of chemical elements in the three-component Al-V-B system. Vanadium reduces electrical conductivity in primary aluminum, which requires its reduction during aluminum electrolysis to values less than 0.02%. In order to reduce the concentration of vanadium impurities, thermodynamic calculations were carried out for the reactions of separation of the metallic phase of aluminum and impurities of vanadium intermetallic compounds through the use of a boron-containing flux. The calculation of thermodynamic parameters was carried out in HSC Chemistry 9.0. for AlB2 and VB2 compounds, the chemical reaction AlB2 + V = VB2 + Al within the operating temperatures of electrolysis and casting of primary aluminum of 650–950°С and the conditions of immersion of boron-containing flux into the melt to a ladle depth of 0.5, 1.0, 1.5 and 2 m, i.e. within the pressure range of 102.39–148.99 kPa. Thermodynamic analysis showed that the Gibbs energy (ΔGT) values in the entire range of operating temperatures of the electrolysis and casting of primary aluminum for VB2 are significantly lower than AlB2, therefore, they will be formed predominantly in this temperature range. The order of stability also suggests that vanadium can be easily removed from aluminum melts by adding boron. The results obtained allow us to conclude that chemical reactions of primary aluminum purification from vanadium impurities can occur due to boron additives.

Assessment of thermal behavior for storage material filled in annulus coaxial aluminum pipes and inserted in evacuated tube collector: An experimental and mathematical investigation

This research paper presents a comprehensive evaluation of an evacuated tube solar air heater (ETSAH) integrated with annulus coaxial aluminum pipe (ACALP) and phase change material (PCM). The experimental setup includes evacuated tubes and double aluminum pipes welded at the bottom and filled with PCM annularly to enhance thermal storage capacity. Experimental data and mathematical models are used to assess heat transfer techniques, power gain, and the thermal behavior of the PCM and the ETSAH. The combination of experimental results and mathematical models provides validation and reliability of the thermal characteristics by utilizing the ACALP additive. The results indicate maximum outlet temperatures of 105 °C, 97 °C, and 89 °C at flow rates of 0.006, 0.01 and 0.05 kg/s, respectively. The PCM temperature is gradually influenced by air flow rate and heat flux, which increases within the day, reaching a maximum at 14:00 of 90 °C and 93 °C of air flow rate 0.05 and 0.006 kg/s, respectively. Moreover, the maximum actual power gained from the device is 2261 W at 0.05 kg/s of air flow rate. A comparison between experimental and numerical values shows an average relative error of 3.84 %. Hence, that indicates that the mathematical model can be considered suitable for predicting the power gained by the proposed ETSAH.

Properties of multiple rare earth oxides co-stabilized YDyGdSmNd-TZP ceramics

TZP starting powders containing 0.6 mol% each of yttria, dysprosia, gadolinia, samaria and neodymia stabilizer were fabricated by a wet chemical route by coating monoclinic zirconia with rare earth nitrates and subsequent calcination. The powders were consolidated by hot pressing in the temperature range between 1250 °C–1500 °C for 1 h at 60 MPa pressure. The materials were characterized with respect to microstructure, phase composition and mechanical properties. The materials combine high fracture toughness over the whole sintering temperature range with moderate hardness and attractive strength. XRD showed that a redistribution of stabilizers takes place during sintering, an initial highly tetragonal phase containing little or no stabilizer is successively eliminated and a stabilizer saturated tetragonal phase is progressively formed. The volume fraction of cubic increases with sintering temperature as the stabilizer content increases. Above 1500 °C, a plate-shaped aluminate phase is formed from the alumina sintering aid and rare earth oxide.

A low copper content alloy Al(1-x)Cux, x≤0.1: A joint computational and experimental study

Atomistic simulation of Al1-xCux (x ≤ 0.1) alloy is performed and the mechanical properties are calculated within the framework of the density functional theory (DFT) by using of the virtual crystal approximation (VCA). The elastic matrix is calculated within the DFT using the CASTEP code and the dependences of Young's, shear and bulk moduli, Vickers hardness, Poisson's ratio, plasticity coefficient and anisotropy indices on the amount of copper are obtained. Al0.9Cu0.1 alloy was synthesized by spark plasma sintering (SPS) method. As a result, the aluminum and intermetallic CuAl2 phases were identified in the obtained sample by X-ray diffraction patterns. The microstructure (SEM) and Vickers microhardness of the sample were studied. The results of the work compensate for the lack of data for the Al-Cu alloys with a low copper content.

Effect of steel slag on rheological and mechanical properties of sulfoaluminate cement-based sustainable 3D printing concrete

The low utilisation of steel slag has led to a worsening of environmental problems. This study aims to use tri-potassium citrate (TPC) to activate the cementitious properties of steel slag and further apply sulfoaluminate cement (SAC) as supplement to design low-carbon composites. 3D printing technology can help to reduce materials consumption as well as labour cost; therefore, the advent of SS-SAC-3D printing concrete has the potential to enhance the utilisation of low-carbon composites and reduce process emissions. This study investigates the effects of steel slag and its activation on the properties of 3D-printed concrete. Workability, rheology, setting time and buildability tests were conducted. The strength differences and anisotropy between the printed and molded specimens were compared. The results demonstrate that adding aluminium-rich steel slag altered the ratios between aluminate and sulfate phases, shortened the setting time, and improved the fluidity and rheological properties of the mixture. The addition of 25 %–50 % steel slag can effectively promote the occurrence of composite hydration reactions, improve the strength to reach over 42.5 MPa (standard strength of SAC) at late ages, and significantly reduce carbon emissions. In conclusion, the SS-SAC-3DPC has the potential to become a significant building material owing to its cost-effectiveness and printability, which can meet the requirements of general building structures. More importantly, its application could contribute to a reduction in the carbon footprint of the construction industry.

Development of sol-gel synthesis and characterization of meso porous SiO2 nanopowder for improvement of nanomullite/SiC ceramic filter

The study investigates the synthesis of mesoporous SiO2 nanoparticles with uniform spherical morphology via the sol-gel method. A strategic approach of this research was to control the particle size within the sol, achieved by incorporating ammonium polycarboxylate (APC) as an additive. The primary objective of this paper is to utilize these modified particles in the fabrication of ceramic filters for metal melt filtration, aiming to enhance their functional properties. Various analytical methods, including DLS, XRD, FTIR, DTA/TG, XPS, SEM, and TEM/EDS, were employed to evaluate the product formation mechanism during the sol-gel process. It was demonstrated that by controlling the pH within an acidic range of 3, precursor particles containing the Si source formed in sizes below 10 nm within the sol, a phenomenon that is fundamental in controlling the final product size to be under 50 nm. The addition of APC, through an electrosteric mechanism, contributed to the stability of the precursor particles within the sol. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images revealed that the silica nanoparticles possess a spherical shape with a uniform size of approximately 25 nm. Nitrogen adsorption/desorption porosimetry indicated that the nanoparticles have mesoporous with an average pore size of 2.5 nm and a specific surface area of 120 m2/g. This method can be conveniently used to prepare silica nanoparticles with desirable morphology and mesostructure. Polyurethane foam filters were impregnated with nanosilica particles using a slurry casting method. Subsequently, the effects of varying percentages of nanosilica particles in the slurry on the compressive strength, density, and porosity of the ceramic foam filters were examined. Additionally, the impact of silica nanoparticles on the slurry's viscosity was studied using rheometry. The optimal sintering temperature was reported to be 1250 °C. XRD results indicated the formation of mullite phase alongside silicon carbide and alumina phases at 1250 °C. SEM microstructural analysis showed that the mullite phase formed in nanometric dimensions within the ceramic foam bodies. The emergence of the mullite phase in nanometric dimensions within the filter microstructure is one of the factors contributing to the reinforcement and enhancement of refractoriness.

Protective role of reactive aluminum phases to stabilize soil organic matter against long-term cultivation in the humid tropics under volcanic influence

ABSTRACT Cultivation can cause rapid depletion of soil organic matter (SOM), particularly in the humid tropics. Understanding the factors controlling SOM storage is a key step toward effective soil management for sustainable crop production. While clay + silt content is known to be an important factor for soil organic carbon (SOC) storage, recent studies have shown greater importance of oxalate-extracted Al (Alo; roughly corresponds to short-range-order aluminosilicate minerals and organo-Al complexes) and Fe (Feo). However, the extent to which these mineralogical factors control the response of SOM pool to land-use changes remains unclear, especially in the tropics. This study aimed to clarify the factors regulating SOM content in croplands compared to secondary forests or home gardens in Negros Occidental, Philippines. Along two line transects having a wide range of Alo contents, soil samples were collected at a depth of 0 − 10 cm from sugarcane sites (n = 33; long-term continuous cultivation of >70 years) that were paired with either secondary forests (n = 10) or home gardens (n = 20). Sugarcane sites had significantly lower SOC and total nitrogen (N) contents than secondary forest and home garden sites, whereas there was no clear difference between the latter two land uses. Both SOC and total N contents showed significant positive correlations with Alo content and, to a much less extent, with Feo content, but not with clay + silt content. The slope of the regression line between SOC and Alo was indifferent between sugarcane and the other two land uses, while the intercept was significantly lower in the sugarcane sites. These results suggest the protective role of Alo phases in both agricultural and forest soils and the presence of unprotected SOM (e.g. plant litter) in the latter sites. Furthermore, δ13C analysis suggested that the proportion of forest (C3 plant) derived carbon remaining in the sugarcane soils ranged between 10% and 50% and increased with Alo content. Together, our study showed indirect evidence of Alo-induced stabilization of SOM against long-term cultivation under the humid tropical environment.

Evaluation of engineered binderless alumina – titania beads for fluoride removal from impaired water resources

Groundwater is often contaminated with various species, with fluoride concentrations being of particular concern. Numerous studies have used adsorbents for fluoride uptake, but most are tested only as powders and not commercially acceptable engineered shapes. Therefore, it was necessary to evaluate the performance of the newly developed Al2O3/TiO2 sorbents in their beaded form to assess their efficacy in comparison to activated alumina granules. Binderless sorbent beads were self-bound with the alumina and titania phases present. The fluoride exchange kinetics of Al2O3/TiO2 beads were comparable to the powdered form. Moreover, the Al2O3/TiO2 beads had higher fluoride loading than commercially available alumina (0.17 meq/g compared to 0.13 meq/g). The Al2O3/TiO2 beads also removed: barium, calcium, lithium, magnesium, manganese, potassium, silica, and strontium from groundwater. In fixed bed column tests, the beads-maintained fluoride within acceptable limits for 42 bed volumes, which substantially outperformed activated alumina (2.5 bed volumes). This study demonstrated that Al2O3/TiO2 beads outperformed commercially available activated alumina materials. Notably, transforming the materials into beaded forms significantly improved their suitability for fluoride removal in industrially relevant fixed-bed column environments. Future studies should focus on enhancing material binding properties to increase crush strength and attrition resistance. A deeper knowledge of regeneration strategies may also facilitate cost reduction.

Effect of alumina or zirconia particles on the performance of lead-free BCZT piezoceramics

The barium titanate derivative Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) offers high dielectric and piezoelectric performance but has poor mechanical properties. Ceramic composite materials combining BCZT with tougher Al2O3 or ZrO2 could be the solution to the inherent brittleness of electroceramics. This work focuses on BCZT with 1–5 vol% addition of reinforcing phase dispersed in the microstructure. While hardness was improved in all composites, especially in ZrO2-reinforced BCZT, toughness was positively affected only by Al2O3. The chemical reactivity of BCZT during sintering resulted in the formation of new barium aluminate phases at the grain boundaries and possibly also within the grains, which affected the electrical properties of the composites. The addition of zirconia resulted in the formation of BaZrO3 or Ba(Zr,Ti)O3, which is a natural part of the BCZT solid solution and shifts the phase composition towards relaxor behaviour. ZrO2-reinforced composites exhibited higher permittivity but lower ferroelectric properties, accompanied by a substantial Curie temperature decrease.

How do reactive aluminum and iron phases control soil organic carbon and phosphate adsorption capacity in agricultural topsoils across Japan?

ABSTRACT The growing number of studies suggests that the prediction of soil organic carbon (SOC) storage and persistence can be improved by accounting for variations in soil reactive metal phases. Nevertheless, the dataset on reactive metals is often limited at a national scale. In Japan, the phosphate adsorption coefficient (PAC) has been measured for agricultural soils nationwide. PAC is known to be strongly controlled by reactive metals, and hence, it can be used as a surrogate for reactive metal content. However, the relationships between SOC, reactive metals and PAC across a wide range of agricultural soils remain unclear. We thus examined these relationships using agricultural topsoils taken from 115 sites across Japan, covering two major soil great groups, Andosols and Lowland soils, as well as various land uses and soil temperature regimes (7.2–19.1°C). For the whole dataset, PAC was strongly correlated with oxalate-extractable metals (Alox + 0.5Feox: Metalox, r = 0.83) and moderately with pyrophosphate-extractable metals (Alp + 0.5Fep: Metalp, r = 0.68). These results suggest a stronger contribution of short-range-order (SRO) minerals to PAC as the former parameter reflects the content of both SRO minerals and organically complexed metals, while the latter reflects only that of organo-metal complexes. Moreover, Metalp was the best predictor of SOC contents in both Andosols (r = 0.79) and Lowland soils (r = 0.65). When only soils at near neutral soil pH range were considered, the exchangeable Ca content also co-varied with SOC in Lowland soils (n = 17). Of the two metallic elements, reactive Al phases better explained the variation of SOC and PAC in Andosols, whereas reactive Fe phases also showed similar explanatory power for PAC in Lowland soils. Our analyses also suggested that soil group (esp. erosion intensity) and land use likely impacted the SOC-Metalox relationship in Andosols, whereas environmental factors such as soil temperature and soil redox regime affected those relationships in Lowland soils. Overall, we showed that PAC is a useful surrogate for SRO minerals and organo-metal complexes and, with careful considerations of the environmental and pedogenic factors, it is potentially useful to estimate the amounts of SOC stabilized by reactive metal phases in agricultural soils across Japan.

A closed-loop recycling of wastewater derived from aqueous carbonation of basic oxygen furnace slag in cement paste production

Aqueous carbonation (AC) treatment is a promising method for enhancing the cementitious activity of Ca- and Mg-rich solid wastes, such as basic oxygen furnace slag (BOFS), while also reducing carbon emissions. However, the carbonated filtrate (CF) solution generated during the AC process poses significant environmental challenges and limits its large-scale application. This paper, therefore, explores the feasibility of recycling CF in cement paste production as a strategy for managing AC wastewater. The study examines the impact of CF on the physico-mechanical properties, hydration behavior and microstructure of cement pastes (pure and blended with either 10% as-received or carbonated BOFS), compared to those prepared with tap water (TW) and carbonated water (CW). The results indicate that carbonated solutions (CF and CW) promote the hydration of aluminate phase in cement, with a more pronounced effect observed for CW. The solid suspensions in CF, particularly nesquehonite, restrict the growth space for calcium silicate hydrates (C-S-H) in the paste matrix, resulting in the formation of foil-like Type II C-S-H and lowering compressive strength. However, the additional nucleation sites provided by calcite crystals in carbonated BOFS (C-BOFS) accelerate cement hydration in CF-based pastes and mitigate strength loss by promoting the formation of more fibrillary C-S-H. Furthermore, the addition of a superplasticizer reduces interparticle forces in the C-BOFS-CF paste, further enhancing strength development and achieving a 28-day strength comparable to that of the control sample (OPC-TW paste).

Thermomechanical behavior of alumina–magnesia castables and numerical modeling of the steel ladle thermal process

AbstractBy experimental characterization and numerical modeling, the dependence of thermophysical properties on time and temperature as well as its influence on the thermomechanical behavior of alumina–magnesia castables has been studied in this work. The thermal conductivity, thermal expansion coefficient, and Young's modulus are the most important parameters, which evolve with temperature and piecewise change with the thermal processes of drying, preheating, and service. It is mainly related to the sintering degree and amount of formed calcium aluminate and spinel phases. The sensitivity analysis of parallel simulations for multilayer steel ladle with different numbers of temperature‐dependent thermophysical parameters demonstrates that the thermal conductivity is the most influential parameter, as it dominates the temperature distribution and affects the succeeding thermal expansion as well as deformation. The increase of thermal expansion coefficient and decrease of Young's modulus with temperature counterbalance the deformation of linings under thermal process. Meanwhile, compared with the simulation using temperature‐independent parameters, the model with temperature‐dependent thermophysical parameters exhibits more severe damage in outer surface of both the working lining and the permanent lining. This gives new insight into the adoption of temperature‐dependent parameters for actual thermomechanical behavior evaluation of refractories.

The impact of mono-ethylene glycol on ordinary Portland cement: Exploring grindability, workability, hydration, and mechanical properties

Glycol-based components are commonly used as grinding agents in ordinary Portland cement (OPC). However, their effects on the grindability and hydration mechanism have not been fully understood. In this study, the effects of mono-ethylene glycol (MEG) of various concentrations (0, 0.025, and 0.05 %) on OPC grinding characteristics as well as hydration reaction were examined. The use of MEG improved the grinding performance of OPC powder, and this effect became more noticeable with increasing quantities of MEG. Moreover, the addition of MEG substantial influenced the hydration properties of the OPC. Although there was no substantial difference in the reactivity of the aluminate phases, the reactivity of the silicate phases improved at all stages. This effect intensified with increasing concentrations of MEG. Additionally, the amount of calcium carbonate increased with the addition of MEG, indicating that MEG somehow promotes carbonation as well. With all these effects, it was concluded that the MEG proportionally enhanced the mechanical performance.