Al2O3 TiO2 Research Articles

Principles of ensuring thermal stability in innovative technology of periclase-spinel refractories

This article presents the results of research on the structural-phase regularities and behavior of periclase-spinel refractories under high-gradient thermal loads. The findings from the analysis of structural-phase variability in the refractory samples are used to achieve the desired thermal resistance. Based on the investigation of the subsolidus structure of the MgO–FeO–Al2O3–TiO2 system, predictions were made regarding the characteristics of solid-phase exchange reactions, considering the existence of solid solutions with various types of crystal structures in specific areas of the system. This enabled the application of new principles for ensuring thermal stability in the developed periclase-spinel refractories, specifically through organizing a fragmented, micro-cracked structure by combining solid-phase exchange reactions with the establishment of mobile equilibrium upon reaching stationary-state temperatures. An additional feature is the possibility of phase invertibility of solid spinel solutions, including changes in the type of spinel structure, in particular quandilite. Physicochemical research methods confirmed the enhanced ability of the material to flexibly adapt its phase composition and microstructure to thermal loads. The feasibility of these principles for achieving the structural-phase adaptability of the material to thermal shocks was validated by electron microscopy analysis.

Enhancement of sodium ion conductivity in phosphate-based glass-ceramics by chemical substitution approach

A NASICON-type sodium-ion conducting material was synthesized via the glass-ceramic route by investigating the zinc doped Na2O–Al2O3–TiO2–P2O5 system. The glasses and glass-ceramics corresponding to the formula Na2+xAl1-xZnxTi(PO4)3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1), labeled as (NAZTP-Gx) and (NAZTP-GCx) respectively, were characterized using different techniques. Differential Scanning Calorimetry (DSC) measurements were carried out to identify the characteristic temperatures, the glass transition (Tg) and the crystallization temperature (Tc). X-ray Diffraction (XRD) analysis of the glass-ceramics confirmed the formation of a solid solution Na2+xAl1-xZnxTi(PO4)3 NASICON phase, Theoretical calculations employing the Perdew–Burke–Ernzerhoff generalized gradients approximation (PBE-GGA) model supported the potential substitution of aluminum by zinc in the octahedral site in the NASICON-phase. Further structural insights were obtained through Infrared (IR) and Raman spectroscopies. Scanning electron microscopy (SEM) analysis revealed a distinct flower-like shape of the formed crystallites in the glass-ceramic NAZTP-GC0.2. Electrical characterization using electrochemical impedance spectroscopy (EIS) demonstrated that the NAZTP-GC0.2 sample exhibited the highest ionic conductivity at 300 °C, reaching 4.1 × 10−5 (Ω−1 cm−1) with an activation energy of 0.25 eV. The DC polarization was performed on the NAZTP-GC0.2 glass-ceramic, revealing that the ions are the main charge carriers in the sample. This comprehensive analysis provides valuable insights into the partial zinc doping of NASICON glass-ceramics, offering potential for improved performance as solid electrolytes in various applications.

Catalytically ultrathin titania coating to enhance energy storage and release of aluminum hydride via atomic layer deposition

Aluminum hydride (AlH3) has attracted much attention owing to its extraordinary hydrogen storage performance, yet AlH3 is prone to hydrogen release reaction during long-term storage, leading to a decrease in energy and hindering its practical application. Herein, AlH3 particles are stabilized by catalytically ultrathin TiO2 coating via atomic layer deposition (ALD), the hydrogen content of which is controllable and reduces only 0.0026 wt% per ALD cycle of TiO2 coating. 30 cycles of TiO2 (2.4 nm) coated AlH3 exhibits a peak decomposition temperature of 203.42 ℃ and decomposition activation energy of 112.21 kJ/mol, which are 7.83 ℃ and 22.64 kJ/mol higher than those of bare AlH3. The hydrogen content loss of TiO2 coated AlH3 under hydrothermal aging conditions is much lower than that of bare AlH3 due to the passivation of defects on native Al2O3 by forming inert Al2O3 and catalytic TiO2 double-shell coating structure. TiO2 coated AlH3 exhibits enhanced combustion performance with stronger flame radiation intensity compared to bare AlH3. The density functional theory calculations indicate that the contact between AlH3 and TiO2 can weaken the strength of Al-H ion bond and promote the release of hydrogen. Our work offers a feasible method for simultaneously improving the stability and energy release of AlH3.

WVOx Supported on Industrial Al2O3, SiO2, AC, TiO2–Al2O3 for Catalytic Dehydration of Gas-Glycerol to Acrolein

WVOx Supported on Industrial Al2O3, SiO2, AC, TiO2–Al2O3 for Catalytic Dehydration of Gas-Glycerol to Acrolein

Study of hybrid nanoscatterer for enhancing light efficiency of quantum dot-converted light-emitting diodes

Optical scatterer additives play a critical role in enhancing the light conversion efficiency and uniformity of quantum dot-converted light-emitting diodes (Qc-LEDs). This study investigates the impact of optical characteristics and morphology of nanoscatterer on the light conversion and extraction efficiency of Qc-LEDs. Various metal oxides and boron nitride nanoparticles and nanoplates with different diffraction index were selected to carry out the study. Finite-Difference Time-Domain (FDTD) simulation was employed to evaluate the scattering effect of various nanosphere and nanoplate scatterers on the optical performance of the Qc-LEDs. The simulation results revealed that the hybrid nanoscatterer integrates the forward-scattering from the nanosphere and backward-scattering of blue light from the nanoplate. Spectral analysis was conducted to examine the optical performance of Qc-LEDs with varying combinations and concentrations of nanoscatterers. TiO2 nanoparticles and Al2O3 nanoplates were found to be the best combination for maximal light conversion and extraction efficiency within Qc-LEDs. The results indicate an optimal light efficiency is obtained with the optimal ratio of 1:2:2 for quantum dots, TiO2 nanoparticles, and Al2O3 nanoplates. These findings reveal the relationship between optical properties, morphology, and light conversion efficiency in Qc-LEDs, highlighting the advantages of the hybrid nanoscatterers for improving optical performance of Qc-LEDs.

Biocompatible Mg–Al2O3–TiO2 hybrid nanocomposites: Influence of fillers on mechanical and corrosion properties

A hybrid Mg composite filled with micro Al2O3 and nano TiO2 is manufactured through a blend press sinter powder metallurgy route. To appraise the significance of filler incorporation on the mechanical and corrosion strength, the composite is undergoing a series of characterizations. Initially the filler distribution was analyzed through electron microscopes. Static mechanical tests as per ASTM are conducted to measure the influence of fillers on the tensile and compression properties. The corrosion characteristics were studied by immersing the composites into the laboratory synthesized stimulated body fluid (SBF). Through the Tafel Polarization, the corroded surfaces are examined. The corrosion resistance of the composites exhibited a change that closely resembled that of pure magnesium. Based on the experimental findings, it appears that the composite being examined is well-suited for various biomedical applications, particularly in the field of dental implants.

A comparative analysis on the magnetohydrodynamic mixed convective flow of a hybrid nanofluid with radiative heat transfer using bagging regression

Hybrid nanofluids exhibit enhanced attributes such as increased mechanical strength, chemical inertness, thermal diffusivity, and structural robustness compared to traditional nanofluids. In connection with this, the current study explores a comparative analysis of the mixed convection phenomenon in a magnetohydrodynamic flow of a hybrid nanofluid with radiative heat transfer. The originality of the current illustration is to scrutinise the hybrid nanofluids with combinations of Copper–sliver (Cu–Ag), Aluminium oxide–Titanium dioxide (Al2O3–TiO2 ), and Copper–Aluminium oxide (Cu–Al2O3 ) on flow and heat transfer. Here, the basis fluids are assumed to be kerosene and water. The perturbation approach is used to solve the governing equations, and bagging regression is used to show the velocity characteristics of the hybrid nanofluid magnetohydrodynamic flow. The outcomes are scrutinised using tables and figures. The results reveal that the shear stress on a surface rises as the radiation parameter increases. The shear stress on a surface typically decreases as the magnetic field strength rises. However, shear stress escalates with the increase in radiation parameter due to heat absorption.

Phase equilibria in the low-TiO2 part of the CaO–MgO–SiO2–Al2O3–TiO2 system at a fixed MgO/CaO mass ratio of 0.2 and Al2O3/SiO2 mass ratio of 0.4

Adding titanium oxide has become a common practice in modern blast furnace operating procedures. The blast furnace slag is based on the CaO–MgO–Al2O3–SiO2–TiO2 low titanium slag system rather than CaO–MgO–Al2O3–SiO2 system. Phase equilibria in the CaO–SiO2–Al2O3–MgO–TiO2 system in the low-TiO2 part have been experimentally determined by means of high temperature equilibration and quenching technique followed by electron probe X-ray microanalysis. Introducing a small quantity of titanium-bearing materials can lower the liquidus temperature. The TiO2 content in the slag should be controlled below 4.6 wt%, otherwise it will enter the perovskite phase region where the liquidus temperatures increases rapidly. The compositions of the solid solutions corresponding to the liquidus have been precisely measured and should be utilized for developing the thermodynamic database.

Thermophysical properties, crystallization behavior and structure of CaO–SiO2–MgO–Al2O3–TiO2–FeO slag with varying TiO2 contents

This study investigated the effect of TiO2 content on the viscosity, free running temperature, electrical conductivity, crystallization behavior, and structure of high-titanium CaO–SiO2-10 wt% MgO-13 wt%Al2O3–TiO2-4 wt.% FeO slag by experiments and molecular dynamics simulations. The results revealed that increasing TiO2 weakened the overall bonding energy and simplified the slag structure, leading to a decrease in viscosity and an increase in electrical conductivity. Thermodynamic calculations revealed a continuous enrichment of the slag towards the pseudobrookite region with increasing TiO2 content. The precipitation of pseudobrookite phase during cooling resulted in short-slag characteristics and a rising free running temperature. Additionally, the peak intensity of pseudobrookite phase gradually enhanced and its morphology changed from elongated strips to plates with higher TiO2 concentration. Structural analysis demonstrated that the poorly stabilized [TiO6] octahedron was the major form of Ti atoms in the slag, and its proportion progressively increased with increasing TiO2 content.

Exploring innovative antibacterial properties of porous ALT (Al2O3/TiO2) composite

Among all metallic materials, titanium is mostly employed in medical applications. In this study, single TiO2 layers on Ti as well as composite ALT(Al2O3/TiO2) layers on Ti for medical applications were synthesized using titanium and aluminum cathodic cages. SEM, EDX, XRD, PL, UV–Vis analyses of untreated and plasma-processed samples were used to determine the surface morphology, chemical content, microstructure, band gap, and photocatalytic behavior, respectively. E. coli and S. aureus immersion bacterial solutions were used to test the antibacterial performance of untreated and plasma-processed specimens. Comparing the composite to a single TiO2 and an untreated sample in PL spectra revealed a smaller band gap. When compared to untreated specimens, coatings made of TiO2 and composite ALT demonstrated significant antibacterial properties. The results showed that ALT-60min displayed unique antibacterial behavior because the band gap was reduced and antibacterial effectiveness was increased. This work explains the distinctive antibacterial activity of composite nanostructures made for medicinal use.

Geochronology and Petrogenesis of Late Carboniferous to Early Permian Basalts in the Central Lhasa Subterrane, Southern Tibet: Implications for the Evolution of the Sumdo Paleo‐Tethys Ocean

AbstractBasalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane, southern Tibet. Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo‐Tethys Ocean and its dynamic mechanism. Basalt samples from the Luobadui Formation in the Leqingla area, NW of Linzhou City in the central Lhasa subterrane, southern Tibet exhibit arc‐like geochemical signatures in a subduction‐zone tectonic setting characterized by high Al2O3 and low TiO2 contents, fractionated REE patterns with low Nb/La ratios and high LREE concentrations, and negative HFSE anomalies. Based on their higher Th/Ce, Nb/Zr, and lower Ba/Th, Pb/Nd ratios, slightly negative to positive εNd(t) values, and the relatively high Sr‐Pb isotopic compositions, these samples were probably derived from partial melting of a depleted mantle source of garnet + spinel lherzolite, metasomatized by subducted sediments around 297 Ma. Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine, clinopyroxene and minor plagioclase during magma ascent and eruption. It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo‐Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.

Effect of Nb2O5 doping on low-temperature sintering of TiO2-Al2O3 ceramics

This study investigates the effects of Nb2O5 as a dopant in TiO2–Al2O3 ceramics to lower sintering temperature and enhance performance, including the physical, mechanical, and dielectric properties of the ceramics at sintering temperatures 1250 °C–1350 °C. Specifically, TiO2–Al2O3 ceramics doped with 1.5 wt% Nb2O5 and sintered at 1350 °C exhibit remarkable density 94 %, compressive strength 1372 MPa, and abrasion resistance 1.36 × 10−4 mm3/N·m, surpassing those of pure alumina ceramics. This improvement is attributed to enhanced grain boundary diffusion and strain energy resulting from Nb5+ cation substitution. The incorporation of Nb2O5 in TiO2–Al2O3 ceramics reduce sintering temperatures by 150–200 °C. The dielectric constant of TiO2–Al2O3 ceramics doped with 1.5 wt% Nb2O5 sintered at 1350 °C is found to be 13.4, with a dielectric loss of 2.56 × 10−2 and insulation resistance 7.3 × 1012 Ω. Nb2O5 is an effective additive for reducing sintering temperatures in Al2O3 based ceramic.

Critical evaluation and thermodynamic assessment of the Al2O3–TiO2–CaO ternary system

Knowledge about the thermodynamic equilibria of the Al2O3–TiO2–CaO system is important for the design of refractory and ceramic materials. The Al2O3–TiO2, Al2O3–CaO and CaO–TiO2 binary systems were reoptimized and the Al2O3–TiO2–CaO ternary system was assessed by CALPHAD (CAlculation of PHAse Diagram) approach due to the reliability of phase diagram and thermodynamic property data. The liquid phase was described by the ionic two-sublattice model with the formula (Al+3,Ti+2,Ti+3,Ca+2)P(O−2,AlO1.5,Va,O,TiO2)Q. A set of self-consistent thermodynamic parameters for the Al2O3–TiO2–CaO ternary system was finally obtained, reproducing well the phase diagram and thermodynamic properties, predicting the Ca4Ti3O10 primary crystallization field. The present thermodynamic description is of interest for the design of refractory and ceramic materials as well as the development of thermodynamic databases for multicomponent aluminosilicate system.

The static corrosion behaviors of gelcasted MAX phases in contaminated lead-bismuth eutectic (LBE) at 600 °C with low oxygen

The deployment of gelcasted MAX phase ceramic components in nuclear reactors is critical due to their exceptional performance. This study explores the corrosion behaviors of three gelcasted MAX phase ceramics (Ti3AlC2, Ti2AlC, and Ti3SiC2) in liquid lead-bismuth eutectic (LBE) at 600 °C under low oxygen conditions. Unique corrosion layers formed on the samples: Ti₃AlC₂ developed an Al2O3 inner layer and TiO2 outer layer, Ti₂AlC showed TiO2 grains coated with FeCr2O4 spinel, and Ti3SiC2 exhibited a composite layer of TiO2, Fe3O4, SiO2, PbO, and TiO2. LBE caused slight matrix enrichment in Ti₃AlC₂ and Ti₂AlC samples. Corrosion resistance was ranked as Ti3SiC2 > Ti3AlC2 > Ti₂AlC. Additionally, a coupled corrosion phenomenon resembling electrolytic electrodeposition between MAX phase ceramics and stainless steel was observed in contaminated LBE. This research provides novel insights into the corrosion mechanisms of MAX phases, paving the way for their application in advanced nuclear systems.

Corrosion behavior of low melting glass modified potassium silicate coating under the synergy of solid NaCl deposit and water vapor at 700 °C

The effects of LMG (SiO2–BaO–Al2O3–TiO2–Na2O–K2O–ZnO) modification on the performance of potassium silicate coatings on Ti–6Al–4V alloy during tests of either H2O/O2- or NaCl/H2O/O2- corrosion were investigated at 700 °C for 500 h using thermogravimetric, SEM, EPMA, and XRD. Adding 10-30 wt% LMG particles into the potassium silicate solution did not impair the intact and the surface roughness of the coatings and improved the resistance of the coatings against humid oxygen corrosion and NaCl/H2O/O2-induced corrosion. For the humid oxygen corrosion, the improvement was enhanced when the amounts of LMG was increased. However, the LMG10 coating with 30 vol% LMG had the most excellent corrosion resistance, the formation of titanate was prohibited; the coatings with more LMG additions were less protective than LMG10 though better than the coating without LMG.

Middle Silurian–Middle Devonian Magmatic Rocks in the Eastern Segment of the Northern Margin of the North China Craton: Implications for Regional Tectonics

This paper presents a detailed study including LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope, and whole rock Sr-Nd isotope analysis of magmatic rocks from the Yitong County, Jilin Province, NE China. These data are used to better constrain the Middle Silurian–Middle Devonian tectonic evolution in the eastern segment of the northern margin of the North China Craton (NCC). Zircon U-Pb dating results show that the Ximangzhang tonalite formed in the Late Silurian (425 ± 6 Ma); the basalt, andesite, and metamorphic olivine-bearing basalt in the Fangniugou volcanic rocks formed in the Middle Silurian (428 ± 6.6 Ma) and Middle Devonian (388.4 ± 3.9 Ma, and 384.1 ± 4.9 Ma). The Late Silurian tonalites are characterized by high SiO2 and Na2O and low K2O, MgO, FeOT, and TiO2, with an A/CNK ratio of 0.91–1.00, characteristic of calc-alkaline I-type granite. They are enriched in Rb, Ba, Th, U, and K, and depleted in Nb, Sr, P, and Ti, with positive εNd(t) (+0.35) and εHf(t) (+0.44 to +6.31) values, suggesting that they mainly originated from the partial melting of Meso–Neoproterozoic accretionary lower crustal material (basalt). The Middle Silurian basalts are characterized by low SiO2, P2O5, TiO2, and Na2O and high Al2O3, FeOT, and K2O, enriched in Rb, Ba, Th, U, and K and depleted in Nb, Ta, Sr, P, and Ti, indicative of shoshonitic basalt. The Late Silurian tonalites have positive εNd(t) (+4.91 to +6.18) values and primarily originated from depleted mantle magmas metasomatized by subduction fluids, supplemented by a small amount of subducted sediments and crustal materials. The Middle Devonian volcanic rocks exhibit low SiO2, TiO2, and Na2O and high K2O, and MgO, enriched in Rb, K, and LREEs and depleted in Nb, Ta, Sr, and HREEs, characteristic of shoshonitic volcanic rocks. Their εNd(t) (+2.11 to +3.77) and εHf(t) (+5.90 to +11.73) values are positive. These characteristics indicate that the Middle Devonian volcanic rocks primarily originated from depleted mantle magmas metasomatized by subduction fluids, with the addition of crustal materials or subducted sediments during their formation. Based on regional geological data, it is believed that the study area underwent the following evolutionary stages during the Silurian–Devonian period: (1) active continental margin stage of southward subduction of the Paleo–Asian Ocean (PAO) (443–419 Ma); (2) arc-continent collision stage (419–405 Ma); (3) post-collision extension stage (404–375 Ma); (4) active continental margin stage, with the PAO plate subducting southward once again (375–360 Ma).

Non-Darcian MHD flow of ternary-hybrid Cu-TiO2-Al2O3/H2O nanofluid over an inclined sheet with activation energy

This study has been carried out to understand the unsteady MHD slip flow of a water-based ternary hybrid nanofluid including spherical Cu, titanium dioxide TiO2 and cylindrical Al2O3 nanoparticles across an angled sheet. The complicated scenario above investigates how ternary-hybrid nanofluid behaves when it is stretched across an inclined surface in the existence of a magnetic field. In complex thermal systems such as energy-generating technologies and cooling mechanisms, an understanding of this relationship is essential. In the existence of first-order velocity slip, the heat transfer has been examined taking into account the non-Darcy Porous media, activation energy, and heat source. The study is more accommodating because of the Soret effect. The relevant similarity transformations are applied in primary equations and a built-in bvp4c program is employed for solutions. The effectiveness of the numerical approach is demonstrated by a thorough agreement with results that have been published in the past. The key conclusions are as follows: greater values of the first order slip parameter cause the flow to slow down; an increase in Soret number causes the flow to speed up; and in both scenarios—that is, with and without velocity slip, fluid movement drops caused by higher values of the chemical reaction. The Forchheimer parameter lowers fluid velocity while activation energy enhances the fluid concentration.

The effect of adding hybrid nanoparticles (Al2O3–TiO2) on the performance of parabolic trough solar collectors using different thermal oils and molten salts

Enhancing the operational efficiency of parabolic trough solar collector (PTSC) systems is key to the advancement of solar energy technologies that enhance power generation sustainability. In the quest for efficient, environmentally friendly energy sources, solar energy systems have been a major focus of both researchers and industry. Adding hybrid nanoparticles (Al2O3–TiO2) to different base fluids of thermal oil or molten salts and then simulating the PTSC's energetic and exergetic performance is pivotal to efficiency enhancement. The focus of this paper will be on three thermal oils Syltherm-800, Therminol VP-1, and Therminol 75 that are used as base fluids with the addition of hybrid nanoparticles. Molten salts such as Solar Salt, Hitec, and HitecXL, which are considered different base fluid types, are also simulated with the same hybrid nanoparticle combination. The inlet temperature is found to be a determining factor in the choice of the base fluid. Inlet temperatures in the range of 300–650 K for thermal oils with the addition of Al2O3–TiO2 have improved the thermal and exergy efficiency of the PTSC by approximately 0.99 % and 0.59 %, respectively. Therminol VP-1/Al2O3–TiO2 has the highest average thermal efficiency among other thermal oils, with an average percentage of 71.68 %, while Syltherm-800/Al2O3–TiO2 has recorded the highest exergy efficiency of 24.1 %. At higher inlet temperatures above 500 K mixing Al2O3–TiO2 with molten salts has increased both energetic and exergetic PTSC performance by approximately 0.60 %. Solar Salt/Al2O3–TiO2 has the highest average thermal and exergy efficiency of 61.8 % and 36.1 %, respectively.

Systematic analysis of the gallium ions and structure-directing agents in the preparation of NiW HDS catalysts over mixed oxides of Al2O3-TiO2

In this study, we prepared Al2O3-TiO2 (AT) mixed oxides to synthesize NiW catalysts for sulfur removal reactions. The AT support samples were prepared with various surfactants. Additionally, gallium atoms (2.4 wt%) were introduced as an additive to coat the outer surface layers of AT support that lacked Al3+ or Ti2+ cations. Characterization results showed substantial differences in textural properties, chemical composition, and surface acidity. The x-ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HR-TEM) results demonstrated that the NiW/AT-L-Ga sample has a better combination of dispersion, sulfidation, and promotion among materials. The sulfided NiW/AT-L-Ga catalyst had the highest catalytic activity. After incorporating Ga, XPS observed that the activity could be associated with an increase in the NiWS active phase; however, including a surfactant in the synthesis of the support allowed an increase in the amount of NiWS phase. The active phase was modeled considering the HR-TEM results for the slab length, revealing the atoms at the border susceptible to promotion.

Dissolution behavior of Al2O3 inclusions into CaO–MgO–SiO2–Al2O3–TiO2 system ladle slags

Dissolution behavior of Al2O3 inclusions into CaO–MgO–SiO2–Al2O3–TiO2 system ladle slags