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Shell‐derived materials are promising heterogeneous catalysts for biodiesel production due to their nontoxic and renewable nature, but they have the disadvantage of being highly leachable. To overcome this issue, Ca(OCH3)2 formed through the reaction of CaO with methanol, and supported in turn on Al2O3 is proposed as a catalytic system for the transesterification of fresh soybean oil and waste cooking oil (WCO). First, catalysts with several Al/Ca molar ratios (0.2, 0.5, and 0.8‐AC), as well as their precursors (CaO and Al2O3) alone, were tested at 60 °C, catalyst loading 6% wt, methanol‐to‐oil molar ratio (MOR) 10, for 1 h for fresh oil, and 3 h for WCO. The 0.2‐AC catalyst generated the highest biodiesel yield for both oils. The optimum operating conditions for WCO transesterification, determined by using a univariable approach, were 60 °C, 9 wt% catalyst loading, MOR of 12.5, and a reaction time of 3 h. These improved conditions led to yields higher than 90% for pure CaO and the 0.2, 0.5, and 0.8‐AC catalysts. The density, kinematic viscosity, and refractive index of the biodiesel obtained were measured. [ABSTRACT FROM AUTHOR]

Porous alumina structures were developed by indirect Powder Bed Fusion with Laser Beam (PBF-LB), employing a novel feedstock (composite granules) based on alumina (Al 2 O 3), bio-renewable polyamide 612 (PA612), and micron-sized graphite (MG) using a commercial PBF-LB machine that operates with a low-power visible light diode laser. Regular and slightly rounded composite granules were prepared via the thermally induced phase separation (TIPS) process in dimethyl sulfoxide (DMSO) using 0.05 vol% of PA612, 40/60 vol% of Al 2 O 3 /PA612 and 6.25 wt% of MG, and then characterized via density measurements, Hausner's ratio, SEM-EDS, particle size distribution, Raman spectroscopy, DSC, and TGA. Experimental conditions to be used in the PBF-LB process were determined in order to obtain high-quality green porous structures with a controlled geometry. After the heating treatments, sintered components with good structural integrity, a high open porosity associated with interconnected pores in the struts, and a ceramic matrix with microsized-equiaxial grains were obtained. The evaluation of the mechanical properties was performed by diametral compression testing. In order to improve these properties, a vacuum infiltration process involving a low-concentration alumina-ethanol suspension was used on pre-sintered discs. As a consequence of the infiltration process, the discs showed improved mechanical properties after sintering without the porosity having been significantly affected. [ABSTRACT FROM AUTHOR]

Highlights In the present work, the impact of corona aging on the dielectric, thermal, and surface properties of silicone rubber filled with different nanofillers such as alumina (Al2O3), aluminum trihydrate (ATH), boron nitride (BN), and titania (TiO2) are studied. The surface degradation of the silicone rubber nanocomposites after corona aging is evaluated through contact angle measurement, atomic force microscopy (AFM) studies, and by water droplet‐initiated corona inception voltage studies. Alumina filled silicone rubber shows less reduction in surface and hydrophobic properties after corona aging. Water droplet initiated corona inception voltage (CIV) under negative DC voltage is much higher than under positive DC and AC voltages. Al2O3/TiO2‐ filled silicone rubber samples show better CIV performance. The Dielectric Response Spectroscopy (DRS) indicates that TiO2 filled silicone rubber insulating material possesses higher permittivity at lower frequencies. Boron nitride added composites have high thermal conductivity whereas ATH filled silicone rubber composites shows higher decay rate, as observed through laser‐induced thermography studies. A significantly high surface leakage current is observed in all samples after corona aging. The Space Charge Limited Current (SCLC) studies clearly indicate that inclusion of nano‐fillers resulted in an increase in crossover voltage and trap density values compared to base silicone rubber. Al2O3 filled silicone rubber exhibits lower surface roughness even after corona aging. High thermal conductive composites show better performance even after corona aging. ATH, and BN filled silicone rubber have improved thermal conductivity by 35.2% and 76.3%. TiO2 filler added silicone rubber exhibits high permittivity with low tan δ. Al2O3 filled silicone rubber has minimal surface and volume leakage current Crossover voltage and the trap density get enhanced on addition of fillers to the base polymer. [ABSTRACT FROM AUTHOR]

Currently, with the gradual development of anticorrosive coatings, the pursuit of simple preparation methods and the improvement of anticorrosive coatings' properties have become the major research trends. This study successfully prepared a hydrophilic super anticorrosive coating through a simple mixing method. The coating has a contact Angle of 67.8° and a rolling Angle greater than 20°. This coating can withstand 180 days of salt spray test with no bubble or rust formation when placed on a Q 235 substrate in a 3.5 wt % NaCl solution, demonstrating the excellent corrosion resistance of the AO0.4AN0.6EP coating. Furthermore, after being immersed in a 3.5 wt % NaCl solution for 3 days, the AO0.4AN0.6EP coating exhibited the largest impedance diameter (2.07×108 Ω⋅cm2), almost three times larger than other coatings, and possessed the highest Bode modulus value, one order of magnitude higher than other coatings. After immersion in a 3.5 wt % NaCl solution for 7 days, the AO0.4AN0.6EP coating had the largest Ecorr and the smallest icorr, indicating its superior corrosion resistance. In addition to corrosion resistance, the AO0.4AN0.6EP coating showed no signs of cracking, discoloration, or decomposition after being exposed to ultraviolet aging lights for 30 days, demonstrating its excellent UV resistance. Moreover, neither dry soil particles nor muddy water could adhere to the coating surface, proving its good self‐cleaning ability. Therefore, this coating holds promising applications in the field of super corrosion‐resistant coatings. [ABSTRACT FROM AUTHOR]

In this study, the effects of different silicon carbide (SiC) particle sizes on the viscosity and curing behavior of alumina (Al 2 O 3) ceramic suspensions were thoroughly investigated. The findings revealed that increasing the size of SiC particles led to a noticeable decrease in the viscosity of the suspension. The Al 2 O 3 ceramic suspension with 0.6 μm SiC powder demonstrated a shallower cure depth and wider excess width compared to the suspension with 1.0 μm SiC powder. Sintering tests demonstrated that the properties of the SiC–Al 2 O 3 ceramics improved at higher sintering temperatures. Moreover, a high-performance honeycomb ceramic was successfully designed and fabricated with a porosity and compressive strength of 30.8 % and 188 MPa, respectively. Finally, the SiC–Al 2 O 3 honeycomb ceramics were effectively applied in heat insulation and oil-water separation applications, demonstrating their remarkable capabilities. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) provides a promising avenue for constructing ceramic parts with high precision and complex shapes, yet the inherent brittleness and strength‐toughness trade‐off hinder their wide applications. Here, according to DLP 3D printing, the textured alumina ceramic components with horizontally aligned textured microstructure were successfully created by adding anisotropically shaped platelets. As a critical process in the preparation of textured ceramics, the alumina platelets were aligned horizontally during printing by using the special shear fields and forming capabilities of DLP technology. The shrinkage, density, microstructure, mechanical performance, and damage‐tolerance behavior of alumina parts with different platelet concentrations were examined, and the toughening mechanisms were investigated. The strength and toughness of ceramics with 5 vol.% platelet addition are increased by 22% and 43%, respectively, as compared with those without platelets. The improved damage tolerance capabilities were primarily ascribed to the collaborative toughening mechanisms stimulated by the platelet addition, including crack branching, crack deflection, uncracked‐ligament bridging, and platelet pull‐out, which increased the crack tortuosity and consumed more fracture energy. The strategy opens up new opportunities to design complex 3D ceramic geometries with bio‐inspired layered or textured architectures, providing optimized damage tolerance. [ABSTRACT FROM AUTHOR]

Due to their high hardness at elevated temperatures and chemical stability, alumina-based ceramic cutting tools have been successfully applied in the machining of ferrous materials, especially quenched and tempered steels. Their low fracture toughness, however, makes it difficult to finish them by grinding, as cracks and defects can occur. In addition, its application in machining processes demands appropriate edge preparation to avoid tool failure. Within this context, the paper aims to demonstrate the applicability of an experimental Al2O3 + MgO ceramic cutting insert in hard turning. For this, grinding tests were performed to determine the most appropriate conditions to improve its surface and edge quality. The effects of cutting and feed speeds, grinding wheel bonding material, and abrasive grain size were investigated. Moreover, different cutting-edge geometries were prepared in this tool material and tested in turning a hardened AISI 4140 steel (50 HRC) to determine their performance regarding tool life and workpiece roughness. The results demonstrated that a finer grinding wheel (D15) combined with high cutting (60 m/s) and feed (10 mm/min) speeds leads to the lowest surface roughness and edge chipping. In addition, both symmetric (Κ = 1) and asymmetric (Κ = 2) edge roundings led to higher tool lives in hard turning in comparison to a single chamfered tool, as they contributed to better load distribution in the cutting region. The paper provides information for the manufacture and application of alumina-based ceramic cutting inserts in the metalworking industry, as it disseminates good manufacturing practices and recommendations for appropriate cutting-edge geometry. [ABSTRACT FROM AUTHOR]

Hierarchical cellular ceramics have attracted considerable interest due to their versatility and unique physico-mechanical effectiveness for advanced applications. Tailorable alumina foams with low shrinkage were fabricated through an innovative combination of 3D printing and sacrificial templating with low environmental footprint. The viscoelastic pastes were formulated using the aqueous-based solution of binder, dispersant, and plasticizer with different volumes of α-alumina and lightweight hollow microspheres (HMs) as a template. The solid-to-liquid ratio increased 53–80 vol% with the inclusion of HMs for printable rheology. Cellular architectures of alumina were structured through a material extrusion-based technique and then thermally treated at 1200 °C. Finally, the alumina monoliths achieved a ∼55–93 % porosity with three different types of adjustable pores, produced by combining 3D printing, burning of templates, and inter-particle voids. The HMs generated spherical pores (7–47 µm) in the printing struts with reduced CO 2 emissions compared to conventional sacrificial porogens during the burnout process. [Display omitted] • Alumina monolith appears a density of 0.31 g/cc with tailorable pores of 93 %. • Aqueous-based pastes are designed using lightweight hollow microspheres template. • The 3D printing paste is formulated with a solids-loading of up to 80 vol%. • Foam with three different sizes pore is fabricated by 3D printing and microspheres. • The study is an ecological approach for lightweight low shrinkage alumina foam. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) provides the opportunity to perform fundamental and mechanistic observations of complex, dynamic, and transient systems and ultimately link material microstructure and its evolution during tribological interactions. This investigation focuses on the evolution of a dynamic fluoropolymer tribofilm formed during sliding of polytetrafluoroethylene (PTFE) mixed with 5 wt% alpha-phase alumina particles against 304L stainless steel. Sliding was periodically interrupted for AFM topography scans. The average film roughness, the average friction coefficient, and polymer wear rate based on sample height recession were recorded as a function of increasing sliding cycles. Topographical maps suggested tribofilm nucleates in grooves of the steel countersample, spreads, and develops into a uniform film through sliding. Prominent nanoscale features were visible around 10,000 sliding cycles and thereafter. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed good correlations between these features and aluminum-rich domains, suggesting the presence of alumina particles on the surface. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) is advancing technologically towards the production of components for high-demand mechanical applications with stringent dimensional accuracy, leveraging metallic and ceramic raw materials. The AM process for ceramic components, known as Ultraviolet Laser Stereolithography (SLA), enables the fabrication of unique parts or small batches without substantial investments in molds and dies, and avoids the problems associated with traditional manufacturing, which involves multiple stages and final machining for precision. This study addresses the need to produce reference elements or targets for metrological applications, including verification, adjustment, or calibration of 3D scanners and mid- to high-range optical sensors. Precision spheres are a primary geometry in this context due to their straightforward mathematical definition, facilitating rapid and accurate error detection in equipment. Our objective is to exploit this novel SLA process along with the advantageous optical properties of technical ceramics (such as being white, matte, lightweight, and corrosion-resistant) to materialize these reference objects. Specifically, this work involves the fabrication of alumina hemispheres using SLA. The manufacturing process incorporates four design variables (wall thickness, support shape, fill type, and orientation) and one manufacturing variable (the arrangement of spheres on the printing tray). To evaluate the impact of the design variables, dimensional and geometric parameters (GD&T), including diameters, form errors, and their distribution on the surface of the sphere, have been characterized. These measurements are conducted with high accuracy using a Coordinate Measuring Machine (CMM). The study also examines the influence of these variables in the dimensional and geometric accuracy of the spheres. Correlations between various parameters were identified, specifically highlighting critical factors affecting process precision, such as the position of the piece on the print tray and the wall thickness value. The smallest diameter errors were recorded at the outermost positions of the tray (rear and front), while the smallest shape errors were found at the central position, in both cases with errors in the range of tens of micrometers. In any case, the smallest deformations were observed with the highest wall thickness (2 mm). [ABSTRACT FROM AUTHOR]

Functionally graded ceramic systems consisted of Al2O3/(Al2O3–ZrO2) and Al2O3/(Al2O3–Nd2Ti2O7) have been produced by gel casting. In Al2O3/ZrO2 systems, Al2O3 was gathered with three different Al2O3/ZrO2 mixtures with varying ZrO2 contents. For Al2O3/Nd2Ti2O7 system, Al2O3 layer was combined with 3 mol% Nd2Ti2O7‐doped Al2O3. All samples sintered at 1480 and 1540°C showed strong adhesion between layers without any crack formation. In the Al2O3/ZrO2 systems, both layers were intact; a distinct separation was observed, whereas a large reaction zone was observed for the Al2O3/Nd2Ti2O7 system as a consequence of reaction between both phases. The separation between layers for both systems was identified by SEM–EDX analyses. The hardness and wear tests of the samples showed that functional grading approach ensures combining various physical properties in a monolithic body. [ABSTRACT FROM AUTHOR]

Zirconia/alumina composites are a family of structural ceramics with excellent mechanical properties. In order to improve the engineering reliability of this kind of composites, the uniform spatial distribution of the two phases is necessary. One of the effective methods to achieve this goal is to synthesize uniform zirconia–alumina composite nano powders. Here, we report mechanochemical synthesis of zirconia–alumina composite nano powders, in which dehydration and crystallization of Zr–Y–Al hydroxide can be achieved under milling conditions, leading to the formation of the tetragonal zirconia phase with supersaturated Al3+. The mechanochemically synthesized powders have the uniform element distribution and a fine primary crystallite size of around 11 nm. After sintering at 1400°C, t‐ZrO2/α‐Al2O3 composite with the uniform phase distribution and grain size distribution could be obtained. To uncover the full benefits of these supersaturated composite powders in ceramic processing, future work could be done to break up the deagglomerations and improve the sinterability of the mechanochemically synthesized zirconia/alumina powders. [ABSTRACT FROM AUTHOR]

Ceramic saggars of mullite‐cordierite are currently used to produce cathode powders for lithium‐ion batteries. Strong interactions occur between the LiNi0.8Mn0.1Co0.1O2 (NMC) precursor in the temperature range of calcination (750–1000°C) leading to corrosion and formation of cracks in the saggar. The frequent failure of saggar causes a lot of waste, which could be reduced by choosing corrosion‐resistant materials. To understand the corrosion mechanism in the system MgO–Al2O3–SiO2, the materials MgO, Al2O3, MgAl2O4, and SiC (instead of SiO2) were embedded in premixed NMC precursor and calcined at T = 780°C for 50, 100, 150 and 200 h. The formed phases were determined by phase and microstructure analysis. Finally, the formation of LiAlO2 and Li5AlO4 is associated with a lower growth rate of the corrosion layer compared with Li4SiO4, while MgO is inert. The reactivity with NMC can be ordered as follows: SiO2 > Al2O3 > MgO. [ABSTRACT FROM AUTHOR]

ABSTRACT It is demonstrated by means of ultra high vacuum (UHV) surface‐sensitive techniques and periodic density functional theory (DFT) calculations that the electronic and NO− adsorption properties of nanosized Ni clusters deposited onto the α‐Al2O3 (0001) surface significantly depend upon the size of the cluster. The properties of the Ni cluster of the size of 2 nm and lower are predominantly determined by the formation of the Ni/Al2O3 interface bond notably polarized towards the oxide. As a result, the metal cluster acquires a net positive charge manifested by the bond strengthening of adsorbed NO compared to the bulk Ni substrate. With the increasing size of the cluster, the Ni/Al2O3 interfacial bond depolarizes due to the growing of lateral Ni–Ni interaction. With a mean coverage of Ni on the alumina surface exceeding 0.25 equivalent monolayers, their properties in terms of adsorption behavior of NO resemble those that are characteristic for the bulk Ni substrate. Such a size dependence offers an opportunity to tune the properties of metal clusters and the metal/oxide system as a whole, for example, to achieve the required electronic and adsorption‐reaction properties. [ABSTRACT FROM AUTHOR]

Thick and dense graphite anodes used in lithium‐ion batteries (LIBs) suffer from sluggish reaction kinetics at the electrode level, causing Li metal plating on their surfaces and significant capacity decay at high charging currents. Thus, it is crucial to tailor electrodes based on a comprehensive understanding of the complex reaction kinetics to realize fast‐charging LIBs. A multi‐interface strategy is proposed for electrode tailoring using Al2O3 nanoparticles to enhance fast‐charging capability while suppressing Li metal plating. Molecular dynamics simulations suggest that the incorporated Al2O3 nanoparticles perturb the charge and molecule distributions in the boundary layer, forming an "interfacial highway" for facile Li+ transport at the Al2O3/electrolyte interface. This pushes Li+ deeper into the electrode and homogenizes the Li+ flux across the electrode's top surface. A full cell assembled with the Al2O3‐decorated graphite electrode (areal capacity of 4.4 mAh cm−2) exhibits excellent cyclability with a capacity retention of 83.4% over 500 cycles even at a 2C rate without any noticeable signal for undesirable Li plating. The role of interfacial highways predicted by theoretical computations is further validated using a pouch‐type full cell (500 mAh). These findings provide insights into the interfacial and microstructural design of high‐capacity graphite electrodes for fast‐charging, long‐cycling LIBs. [ABSTRACT FROM AUTHOR]

To improve the strength of Al 2 O 3 specimens produced using the water-stabilized plasma spraying technique (WSPSAO), this study investigates the effect of structural modification on the mechanical properties of WSPSAO using the Al-Cu-O reaction between the metal, atmospheric oxygen, and base material. A Cu-powder layer is applied to the specimen surface, melted, and oxidized at high temperatures. It penetrates into the specimen, resulting in significant microstructural modification deep in the specimen. After modification, uniaxial Al 2 O 3 , CuO, Cu 2 O, and CuAl 2 O 4 are formed in the specimen, resulting in a denser and more uniform structure than that of the original material. The bending strength of the coated surface is 145 MPa, and that on the opposite side of the coated surface is 118 MPa, which is 130%–180% higher than the original strength of the base material. [ABSTRACT FROM AUTHOR]

The mechanical behavior and cracking patterns of thermally‐shocked additively manufactured alumina were investigated. The flexural strength of test specimens that had been heated to temperatures ranging from 200°C to 1000°C and then rapidly quenched in water was determined at ambient temperature by four‐point bending. Results indicated that the surface cracking patterns had a multifractal structure and that an increase in the thermal shock temperature led to an increase in the density and uniformity of the crack network. The flexural strength results were analyzed with Weibull statistics, where the Weibull moduli for most of the thermal shock conditions tested were found to be statistically indistinguishable. It was also found that a significant decrease (∼50%) in flexural strength occurred for heating temperatures ≥300°C. The effect of the manufacturing method on cracking patterns is discussed, as well as the implication of the material behavior for practical applications of these materials. [ABSTRACT FROM AUTHOR]

The bulk and surface properties of materials based on nickel and aluminum oxides and hydroxides, as such or after reduction processes, are reviewed and discussed critically. The actual and potential industrial applications of these materials, both in reducing conditions and in oxidizing conditions, are summarized. Mechanisms for reactant molecule activation are also discussed. [ABSTRACT FROM AUTHOR]

In this work, the morphology of zirconia, alumina, and silicas was studied, and static sorption of the repellents N, N-diethyl-3-methylbenzamide and ethyl-3-[acetyl(butyl)amino]propionate on these oxides was carried out. ZrO2, Al2O3, and SiO2 phenyl were shown to have high sorption activity to the repellents N, N-diethyl-3-methylbenzamide (239 mg/g for SiO2 phenyl) and ethyl-3-[acetyl(butyl)amino]propionate (251 mg/g for ZrO2). Pointedly, it was found that despite having the largest pore volume and high specific surface area (compared to the other studied oxides), SiO2 C2 has a significantly inferior sorption capacity in respect to other oxides, in particular SiO2 phenyl, which can be explained by the presence of the phenyl group in the latter that has chemical affinity for repellent molecules. Obtained isotherms of SiO2 300 also confirm the low sorption activity towards N, N-diethyl-3-methylbenzamide. The sorption equilibrium for both repellents, in most cases, is described by the Langmuir monomolecular adsorption model. The obtained results suggest that the studied zirconia, alumina, and silica can be used as carrier components of repellents. [ABSTRACT FROM AUTHOR]

The Bi 2 O 3 –B 2 O 3 –SiO 2 –ZnO–Al 2 O 3 (BBSZA) glass/Al 2 O 3 composites are prepared by quenching and quenching-free methods and conducted a comparative analysis of their microstructures and properties. The results reveal that the BBSZA/Al 2 O 3 composite obtained by quenching free method has smaller pores and superior performance. Specifically, at a BBSZA content of 50 wt%, the composite exhibits a thermal conductivity of 5.352 W/m·K and a flexural strength of 193.54 MPa, which are 1.38 times and 2.08 times those obtained using the quenching method, respectively. XRD and TEM analyses, along with parallel experiments using other glasses, suggest that presintering crystallization may be the prerequisite for achieving denser composites via the quenching-free method. BBSZA glass reacts with Al 2 O 3 at the presintering process to generate a great amount of ZnAl 2 O 4 crystals, which enhances grain boundary energy and increases sintering density. This work provides insights into the low-cost and high-performance development of low temperature co-fired ceramics (LTCC). [ABSTRACT FROM AUTHOR]

A range of techniques for the coating of high purity alumina (HPA) on porous polypropylene battery separators has been investigated. A slurry was prepared by dispersion of the alumina powder in acetone solvent and poly (vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) as the binder to obtain an excellent adhesion to the membrane. Doctor blade, spin coating, and electro‐spin coating techniques were utilized to coat a thin layer of HPA on the separator that was followed up with a calendering step to improve compactness, decrease thickness and enhance adhesion. Furthermore, the effect of HPA particle size, distribution, and the use of a calendering step on coating thickness, compactness, and electrochemical performance were investigated using three HPA sources. The doctor blade technique was found to give the most uniform coating with the best mechanical properties and high‐temperature resistance. The coated separators were incorporated into lithium‐ion coin cells to evaluate the rate capability and long‐term cycling performance. [ABSTRACT FROM AUTHOR]

Miniaturization is governed by the precise and accurate micro-machining operations of various applications. Micro-EDM has emerged as a feasible method for attaining microscale high-precision drilling. The present paper aims to conduct an experimental investigation for drilling micro-holes on copper using the Alumina (Al2O3) powder mixed Micro-EDM technique. Process parameters, including voltage, feed rate, and powder concentration, are varied in experimentation to evaluate their impact on response measures like MRR, TWR, taper angle, and aspect ratio. ANOVA determines the individual contribution of process parameters on each response measure. Voltage is the primary factor influencing MRR (93.5%), TWR (58.24%), and aspect ratio (67.3%), whereas the interaction effect of voltage with powder concentration primarily affects the taper angle (32.36%). Furthermore, the GRA method has optimized the multiple parameters for different responses. The optimum combination of parameters was obtained at a voltage of 125 V, powder concentration of 0.8 g/L, and tool travel speed of 9 µm/s at which better responses are received. The results obtained from FESEM analyses indicate that utilizing alumina (Al2O3) Nano-powder in the dielectric fluid leads to improved effectiveness and reduces the formation of micro-cracks, and micro-voids. Furthermore, the formation of recast layer is reduced by 36.49% as compared to without powder mixed EDM oil during micro-drilling operations. [ABSTRACT FROM AUTHOR]

The unique mechanical, chemical, and tribological properties of members of graphene family make them a consummate reinforcement candidate for improving the wear resistance properties of matrices. The present work conveys the tribological behavior of the plasma-sprayed alumina (Al2O3) coatings in various conditions, such as at high temperature as well as in marine condition by reinforcing carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) into it. Synergistic reinforcement of CNTs and GNPs decreased the coefficient of friction (CoF) by 45% at room temperature and by ~ 50% at high temperature as well as in simulated seawater. Additionally, weight loss after wear almost decreased by 6–7 folds for ACG coating. The key reasons attributed for these improvements are: (a) formation of stable film during the wear; (b) lubricative properties of the reinforcement; and (c) higher fracture toughness of ACG coating as compared to others. Elemental mapping of the worn track of the ACG tracks showed a uniform distribution of elements over them which assisted in improving the wear performance of ACG in all the adverse ambiences. [ABSTRACT FROM AUTHOR]

AbstractThe need for alternative green energy to fossil fuels has increased research interest in creating energy storage technologies. One of the important components of an energy storage device is electrolytes. Previously, the use of liquid electrolytes (LEs) was dominant; nevertheless, LEs were reported to be flammable. Recently, attempts have been made to switch out the LEs for solid polymer electrolytes (SPE). SPE has a variety of merits; however, their limited ionic conductivity and high operating temperatures impede their development into practical application. Thus, fillers such as alumina (Al2O3) as an additive are introduced to enhance their performance. Recent progress in the use of Al2O3 has shown promising advancements in enhancing the electrochemical performance of SPEs while the future direction includes examining the cost-effectiveness of Al2O3-filled SPEs for large-scale applications, thereby paving the way for their integration into commercial energy storage technologies. This article provides a discussion on the effect of Al2O3 on the conductivity, and electrochemical stability of SPEs. Additionally, the review discusses the impact of various factors such as functionalization on the overall performance of SPEs-filled Al2O3. The review concluded by highlighting the potential applications, prospects, challenges, and recommendations for using Al2O3-filled SPEs in advanced energy storage devices. [ABSTRACT FROM AUTHOR]

Alternative binders offer an avenue for advancing ultra-low-cement and cement-free castables while reducing carbon emissions and energy consumption. In this study, geopolymer binders partially or fully replaced calcium aluminate cement (CAC) in high-alumina castables. The formulations underwent diverse testing, including flowability, physico-thermo-mechanical measurements, and XRD, ATR-FTIR, and SEM analyses. The findings highlighted the feasibility of utilizing geopolymers to craft innovative refractories. The formulation comprising 2.7 wt% CAC and 1.3 wt% geopolymer (AT-3 C-1 G*) exhibited the most successful performance. At 1400 °C, these samples displayed shrinkage of 1.18%, elastic modulus of 135 GPa, flexural strength of 39.1 MPa, and high thermal shock resistance (∆T∼1000 °C). The interaction between CAC and geopolymer inhibited cement hydration while enhancing the geopolymerization process. Moreover, firing the samples at 800–1400 °C led to liquid phase and nepheline formation from the geopolymeric gel, resulting in viscous sintering and improved ceramic densification. These developments produced refractories with remarkable overall performance, surpassing the reference material. [ABSTRACT FROM AUTHOR]

In this work we show how the addition of a third element, namely Fe or Ni, influences the interfacial behaviour of liquid TiAl alloys on polycrystalline alumina. Wetting of these alloys was studied by the sessile drop method at 1500 °C and the interfacial microstructures were characterised to determine the relation between the contact angle and the interfacial reaction with the aid of the relevant phase diagrams. The equiatomic TiAl intermetallic wetted the alumina substrate forming a contact angle of 60°. On the other hand, increasing concentrations of Fe and Ni were found to improve the wetting behaviour of ternary TiAl-X alloys: for third-element atomic concentrations of 5 at. %, contact angles decreased to 32° and 29° by adding Fe and Ni, respectively. Neither reactive-formed interlayers nor newly formed phases were observed for any binary or ternary composition as confirmed by thermodynamic calculations. A slight dissolution of the ceramic occurred during liquid/solid contact and became more evident with the increase of concentration of the third element. The introduction of oxygen into the melt provided by the dissolution of alumina improved the wetting behaviour. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the internal and external stabilities of a p–i–n methylammonium lead iodide perovskite solar cell (PSC) are improved. Polystyrene (PS) is introduced into the perovskite layer to form a cross‐linked polymer–perovskite network, which enhances the nucleation and growth of the perovskite grains. Moreover, for the first time, 60 nm thick ZnO/AlOx nanolaminate (NL) thin‐film encapsulation (TFE) is deposited directly on the PSC using an atmospheric‐pressure (AP) spatial atomic layer deposition system operated in AP spatial chemical vapor deposition (AP–SCVD) mode. The rapid nature of AP–SCVD enables encapsulation of the PSCs in open air at 130 °C without damaging the perovskite. The PS additive improves the performance and internal stability of the PSCs by reducing ion migration. Both the PS additive and the ZnO/AlOx NL TFEs improve the external stability under standard test conditions (dark, 65 °C, 85% relative humidity [RH]) by preventing water ingress. The number and thickness of the ZnO/AlOx NL layers are optimized, resulting in a water–vapor transmission rate as low as 5.1 × 10−5 g m−2 day−1 at 65 °C and 85% RH. A 14‐fold increase in PSC lifetime is demonstrated; notably, this is achieved using PS, a commodity‐scale polymer, and AP–SCVD, a scalable, open‐air encapsulation method. [ABSTRACT FROM AUTHOR]

Highlights The performance of multi‐layer ceramic/composite ballistic armor consisting of Alumina, Carbon fiber, and Ultra High Molecular Weight Polyethylene (UHMWPE) under the impact of 7.62 × 51 M61 caliber armor‐piercing (AP) bullets was examined by experimental and finite element methods. The alumina ceramic thickness used in the experiments is 12 mm. The composite structure thickness used in all samples is 10 mm. Explicit dynamic analyses were also conducted using the Ls‐Dyna to verify the experimental studies. The analysis results were compared with experimental studies and evaluated by considering the damage status of the bullet and armor. According to ballistic test results, partial penetration was observed in all armor produced. The front ceramic layer caused corrosion of the bullet, and a mushrooming effect occurred on it. The carbon fiber layer has dramatically helped as an alternative or support to UHMWPE. Since the results obtained with the carbon fiber ratios used remain within the standards, it will not pose a problem regarding usage. On the contrary, using carbon fiber, which is relatively easier to produce and supply than UHMWPE and more economically suitable, will provide more significant benefits. Experimental and numerical studies have revealed consistent results for all armors. The effect of a 7.62 × 51 armor‐piercing bullet on ceramic/composite armor was examined. Carbon fiber and UHMWPE hybrid structure was created in different thicknesses. The carbon fiber layer has dramatically helped as an alternative or support to UHMWPE. Using carbon fiber, which is relatively easier to produce and supply than UHMWPE and is more economically suitable. Experimental and numerical studies have revealed consistent results for all armors. [ABSTRACT FROM AUTHOR]

The conversion of bioethanol to ethylene in gas phase and atmospheric pressure was investigated over γ‐Al2O3 supported copper and nickel catalysts. These catalysts were prepared by co‐precipitation and pre‐treated with hydrogen at 450 °C. Six catalysts were studied at 450 °C under a nitrogen atmosphere. It was found that the monometallic Cu/γ‐Al2O3 catalyst exhibited the highest ethylene concentration, with a selectivity of around 90 %. The bioethanol conversion obtained was between 57 %‐86 %. Another catalyst that exhibited high concentration values was the NiCu1 : 7 bimetallic catalyst. The catalysts were characterised using XRD, SEM, EDS, TEM, TGA, FTIR, Raman, and N2‐physisoption techniques. Furthermore, the Cu/γ‐Al2O3 catalyst was studied under different reduction temperatures and gas flow conditions. It was found that the catalysts reduced at 350 °C and 35 ml/min N2 flow presented ethylene concentrations between (0.18–0.21) g/L. Moreover, the catalyst deactivation was identified to be first order and the equation of the Cu/γ‐Al2O3 catalyst deactivation model was determined. Carbonaceous deposits over the used sample were not detected by Raman and FTIR. It was determined that the Cu/γ‐Al2O3 catalyst deactivation could be mainly attributed to the blocking of the catalytic sites by strongly adsorbed compounds and hydroxylation of the catalyst surface. [ABSTRACT FROM AUTHOR]

Ceramic stereolithography 3D printing technology has demonstrated great potential in alumina core manufacturing for advanced turbine blade casting. However, there have been very few photosensitive material formulas specifically designed for alumina core fabrications. Herein, we present the design of a 3D printable ceramic paste based on bimodal particle size distributions for additive manufacturing of high‐quality alumina cores. The coarse particles in the paste remain in their original shape while the fine particles transform into platelet‐like particles during sintering. The effects of coarse particles, platelet‐like particles, and grain growth on maintaining porosity and limiting shrinkage rates are studied. Furthermore, the vacuum sintering process is found to be beneficial for core material properties. The physical properties tests verify that the newly designed alumina paste in this work can meet the application requirement, which is superior to the previous research. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous Zn ion batteries (AZIBs) have attracted significant attention as a promising alternative to Li‐ion batteries due to the use of water‐based electrolytes, high energy density per volume, and cost‐effectiveness. However, various parasitic reactions relating to hydrogen evolution reaction, corrosion, and dendrite growth in the Zn anode can result in the degradation of the electrochemical performance of AZIBs. Therefore, understanding the mechanisms underlying these various phenomena and their role in the electrochemical performance of AZIBs provides valuable insights for the development of anode and cathode materials. In this study, we investigate the effect of the MnO2 cathode and Al2O3‐coated Zn anode on the electrochemical performance of the AZIBs. The experimental results show that Al2O3‐coated Zn anodes efficiently suppress the dendrite growth on the Zn. However, significant cycling fade of the full cell comprising of an Al2O3‐coated Zn anode and MnO2 cathode was observed during continuous charge/discharge cycles. The poor cycle performance can be mainly attributed to the phase transformation of MnO2–Mn2O3 and the formation of various byproducts, which highlights the importance of the electrochemical stability of cathode materials in AZIBs to improve the cycle performance. [ABSTRACT FROM AUTHOR]

High-performance ceramics are recognized as key enabling materials because of their very high thermal, chemical and mechanical resistance in combination with a lower density compared to most metals. These properties apparently predestine ceramics for many different applications, e.g. propulsion engines. Within the present work, the high potential of additive manufacturing in the field of ceramic materials (CerAMfacturing) could be demonstrated. It is possible to produce high-resolution ceramic aerospike engines using CerAM VPP. The manufactured components not only combine the typical ceramic properties, but also exhibit: - high geometric complexity, - very good surface properties, and - very good manufacturing accuracy. These developments will pave the way for a new generation of propulsion engines. • Ceramic aerospike engine additively manufactured by CerAM VPP. • No critical defects or deformations visible with NDT. • Very high resolution (slit width approx. 500 μm) and very good surface quality (R a < 2 μm). • Measurements on specific impulse showed very good reproducibility. [ABSTRACT FROM AUTHOR]

The increase in demand for petroleum fuels attracted the attention of the research community to identify a control measure for petroleum source depletion. On the other hand, the heavy usage and burning of petroleum products cause environmental pollutants like oxides of nitrogen, carbon monoxide, hydrocarbons, etc. Therefore, it is important to control all the problems caused by the increasing use of petroleum products, such as diesel, petrol, Kerosene, fuel oil, etc. This investigation aims to reduce the usage of fossil-based petroleum diesel by producing an effective substitute bio-diesel from Juliflora seeds, which exhibit similar properties to diesel. Furthermore, the operational and emission behaviors of the biodiesel in the Reactive Controlled Compression Ignition (RCCI) engine are analyzed by including nanoadditives such as ZnO, Al 2 O 3 and CeO 2 . Furthermore, the obtained performance and emission results are optimized using a hybrid deep neural network (DNN) using the Aquila optimization algorithm (AOA). The algorithm chooses the diesel-biodiesel blend with 75 ppm of alumina nanoparticle as the optimum blend. This considered blend provided better performance and emission results at 72.86% loading condition. The obtained results are 28.19% for brake thermal efficiency (BTE), 446.14 g/kWh for brake-specific fuel consumption, 0.105% for carbon monoxide emission, 19.82 ppm of unburnt hydrocarbon, 457 ppm of NO x emission and 21.98% of smoke emission. [ABSTRACT FROM AUTHOR]

Controlling the preparation process is essential to ensure the quality of the ceramics. Previous research on the ceramic process concentrated on a certain part of powder synthesis, forming, or sintering. Herein, we propose a novel process, foam precursor–derived Al2O3 ceramics, to realize particle rearrangement, assembly, and sintering and find that this method has a marvelous influence on the microstructure and mechanical properties. Alumina foams prepared by the particle‐stabilized foam method are used as ceramic precursors, and after pre‐sintering, crash, and hot pressing, foam precursor–derived Al2O3 ceramics can be obtained. It has fine grains (1/5 of the traditional process) and uniform grain size without any additional sintering aid, realized by the high grain growth exponent of foams. Ultrahigh dislocation density (∼1010 mm−2) is discovered in (0 0 0 1) plane of foam precursor–derived ceramics, comparable to the dislocation density of high‐entropy ceramics. Besides, transgranular fracture mode is observed in the ceramics prepared by the new method rather than the intergranular fracture in the control group, and the comprehensive mechanical properties are promoted accordingly. The unusual microstructure and fracture mode caused by the foam precursor process reveal the influence of the microstructure such as dislocation and grain boundary on the fracture behavior of ceramics, which is less considered in conventional research. This preparation process may be applied in the preparation of other high‐performance ceramics. [ABSTRACT FROM AUTHOR]

Aluminum foams have emerged as a remarkable engineering material, exhibiting exceptional structural performance and many excellent properties. This has led to a rise in their application in various fields. The investigation and development of aluminum foam have led to the discovery of multiple applications in numerous industries, including the aerospace, automotive, petrochemical, and building materials industries. Foam made of aluminum, one of the most well-known examples of metallic foams, is a significant technological advancement in the foams industry. This article aims to comprehensively analyze the manufacturing techniques that employ blowing agents, such as alumina, titanium hydride, and sodium chloride. This article explores the unique properties and diverse applications of aluminum foams. In addition, the current status of research and development in aluminum foam is discussed. It accomplishes this by providing an overview of existing developments and identifying future opportunities in this industry. This review article is an invaluable resource for academics and industry professionals interested in aluminum foams, as it provides valuable insights into production procedures, properties, applications, and ongoing research. [ABSTRACT FROM AUTHOR]

The hydroprocessing of gasoline on modified alumina catalysts makes it possible to obtain high-octane products. The implementation and development of the process have largely become possible due to the development of modified alumina catalysts that do not contain noble metals and exhibit special catalytic properties. This article discusses topical issues of petrochemistry, namely the creation of catalysts with improved characteristics for the production of high-octane gasoline with low sulfur content. New catalytic systems based on alumina and other carriers modified with transition metals, lanthanum and phosphorus were synthesized. By physico-chemical methods of analysis TPD of ammonia, TEM and XRD, we studied the acid–base and structural characteristics of the developed catalysts. The activity of the developed catalysts in the studied process of hydrotreating gasoline fractions depends on the structure and condition of the active centers. The process of hydrotreating straight-run gasoline in the presence of synthesized catalysts was carried out on a laboratory flow unit. It was shown that, during the hydrotreating of straight-run gasoline on the NiO-MoO3-La-P-HZSM-HY-Al2O3 catalyst, the octane number in the final product increased to 88.6, and the sulfur content decreased from 0.0088 to 0.001%. It was found that the minimum sulfur content in the gasoline hydrotreating product of 0.0005% was achieved on the catalyst CoO-WO3-La-P-HZSM-HY-Al2O3, which is significantly lower than for other studied catalytic systems. The obtained results of the sulfur content in the hydrotreating products fully comply with the Euro-5 standard. Thus, the efficiency of hydrotreating the gasoline fractions studied in this work was mainly determined by the nature of the carriers and modifiers used for the synthesis of catalysts and the technological parameters of the process. The synthesized catalysts showed high activity and selectivity, resulting in high-octane gasoline with a low sulfur content that meets international quality standards. [ABSTRACT FROM AUTHOR]

Recycled materials, especially scrap aluminum alloy wheels with reinforcement castings, are gaining applications in various fields such as aerospace, naval, military, and automobile. In this research, Honda car alloy wheels are stir-cast with 5% alumina as reinforcement and subjected to corrosion, wear, and machinability studies. Corrosion studies were conducted to evaluate the corrosion current density (ICorr), corrosion potential (ECorr), and corrosion rate for the cast aluminum metal matrix composite. The wear studies with different loads, i.e., 50 N, 60 N, 70 N, and 80 N, were performed on the specimen and investigated the coefficient of friction, frictional force, and pin temperature. The sliding load has a significant effect on wear performance, and for the sliding load of 80 N, the wear recorded was 2574.83 µm. The electrochemical machinability studies with voltage, duty cycle, and concentration of citric acid electrolyte are performed on the machining rate and surface corrosion factor. Analysis of the electrochemical machining process with PROMETHEE-II shows that 7 V, 60% duty cycle, and 30 g/L electrolyte concentration are estimated to be the best combination for a higher machining rate and a lower surface corrosion factor. [ABSTRACT FROM AUTHOR]

In this study, α-Al 2 O 3 was sintered by dynamic sinter forging (DSF). The grain growth, mechanical properties and microstructures of the resultant ceramics were investigated in detail. The results showed that the grain growth during DSF was dominated by a dynamic grain growth process, in which grain size increased with an increase in pressure. The flexural strength of the ceramics increased with increasing pressure and reached 770 MPa in the sample prepared at 1300oC and 100 ± 10 MPa, which was significantly higher than that of the samples prepared by hot pressing and hot oscillatory pressing. The high strength was contributed to the severe plastic deformation induced by the oscillatory pressures, which strengthened both grain boundaries and grains. The current study suggests that DSF is a promising technique for preparation of high-performance Al 2 O 3 ceramics, better than hot pressing and hot oscillatory pressing. [ABSTRACT FROM AUTHOR]

The use of alumina-containing nepheline raw materials as an alternative source of alumina is relevant in the context of the limited bauxite reserves in Kazakhstan. Nepheline processing can result in products such as alumina, sodium and potassium salts, silicate products and rare metals. In terms of economic value, alumina is the most important. This article considers an advanced technology for nepheline processing for the extraction of alumina that is first purified from potassium. The application of calcium sulphate and calcium oxide as additives to the nepheline raw materials is studied. The optimal conditions for two-stage leaching with calcium additives in the form of calcium sulphate and calcium hydroxide are determined. [ABSTRACT FROM AUTHOR]

This article presents the results of studies on the distribution of rare metals among the products of the alkali sulfate processing of nepheline syenites. In response to the limited reserves of Bayer bauxite in the alumina industrial production region of Kazakhstan, the feasibility of using alternative alumina-containing nonbauxite raw materials was investigated. The most promising nonbauxite raw materials in Kazakhstan are nepheline and kaolinite clays. At present, there is no effective technology for processing nepheline ores. This article describes a proposed complex technology involving nepheline processing with the associated extraction of gallium and vanadium. The technology includes the activation of raw materials, followed by two-stage leaching, where potassium is extracted in the first stage. The sludge and solution obtained from the second stage of the leaching process are utilized for calcium silicate production and two-stage carbonization, respectively. In the first stage, aluminum hydroxide is extracted, and, in the second stage, a concentration of rare metals, such as gallium and vanadium, is obtained. Vanadium is extracted from the solution via crystallization, and gallium is extracted via electrodeposition. Overall, 38.48% of the Ga2O3 and 56.12% of the V2O5 are recovered from raw nepheline syenite. A technological scheme of the developed technology is presented in this article. [ABSTRACT FROM AUTHOR]

Secondary aluminum (Al) dross (SAD) is a hazardous waste discharged from Al production, processing and recycling. Over 6.7 million tons of SAD was discharged on the planet in 2023. SAD is consisted of 40–60 wt% of alumina (Al2O3), 10–30 wt% of AlN, 5–15 wt% of salts and 3–10 wt% of heavy metal oxides. Currently, recycling of SAD to make Al2O3 by hydrometallurgy is a promising method for disposal of SAD. Hydrometallurgy method is mainly divided into acid leaching and alkali leaching. In acid leaching, Al, AlN and Al2O3 react with acid to form aluminum sulfate and aluminum chloride. In alkali leaching, Al, AlN and Al2O3 react with alkali to form sodium aluminate. High-purity Al2O3 is obtained after precipitation, washing, drying and calcination from the leachate. Resource consumption and emission was calculated to evaluate the economic and environmental benefits. About 147.9 and 172.6 dollars was earned after making Al2O3 from a ton of SAD by alkali and acid leaching process, respectively. And carbon emissions of a ton of Al2O3 was risen about 596.5 and 2216.0 kg CO2, respectively, compared with the Bayer process with bauxite. We proposed a calcination pre-treatment with quicklime on SAD to reduce the carbon emission. The Al and AlN are oxidized into Al2O3 after calcination, and the Al2O3 reacts with CaO to form CaO·Al2O3. The Al in CaO·Al2O3 can be leached out easily with a low concentration of alkali. This review provides a guidance for the recycling of SAD by hydrometallurgy, and proposes a novel idea for the energy and consumption reduction in alumina (Al₂O₃) production.

Purpose: To assess utility, benefits, and risks of 4th-generation alumina–zirconia ceramic pairings in elective total hip arthroplasty (THA). Methods: A comprehensive mixed-methods best-evidence synthesis using data from systematic reviews, randomized controlled trials (RCTs), prospective and retrospective cohort studies, as well as joint replacement registries, was conducted to estimate overall revision and survival rates, periprosthetic infection, bearing fractures, and noise phenomena with 4th-generation alumina–zirconia ceramic versus other tribological couplings in elective THA. The systematic review part across multiple databases was registered with PROSPERO (CRD42023418076), and individual study data were extracted for statistical re-analysis. Results: Twenty overlapping systematic reviews, 7, 17, and 8 references from RCTs, cohort studies, and joint replacement registries form the basis of this work. According to current best evidence, it is (i) 15–33 times more likely that 4th-generation alumina–zirconia pairings avoid a revision for infection than causing a revision for audible noise, (ii) 38–85 times more likely that 4th-generation alumina–zirconia pairings avoid a revision for infection than causing a revision for ceramic head fractures, and (iii) three to six times more likely that 4th-generation alumina–zirconia pairings avoid a revision for infection than cause a revision for ceramic liner fractures. Conclusion: Fourth-generation alumina–zirconia pairings in THA show a favorable benefit–risk ratio, with rare compound-specific adverse events and complications significantly outbalanced by long-term advantages, such as a markedly lower incidence of revision for infection.