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We report new class of natural nacre-like alumina toughened by zirconia fabricated by the simple two-step approach of unidirectional freeze-casting and spark plasma sintering. The biomimetic alumina-zirconia with a relative density of more than 98 % was achieved by consolidating at temperature of 1300–1425 °C with 50 MPa pressure. The resultant microstructure consists of two levels of structural hierarchy, i.e. level-1: bulk lamellar brick phase (alumina platelets) and level-2: mortar phase (yttria stabilized tetragonal zirconia polycrystals). The increase in volume fraction of zirconia (in tetragonal form) from 0 to 15 vol% was effective in progressively reducing the size of alumina platelets from 12 to 9 μm, and significantly improved the flexural strength of the composite by 60 % (from 172 to 270 MPa). By optimizing the hierarchical architecture from micro to macroscopic level, the structural performance of our synthetic nacre, where strength and toughness of 270 MPa and 13.5 MPa √ m respectively are superior to that of natural nacre and many other engineering materials (illustrated in the form of Ashby map). The exceptional damage resistance is rationalized by both intrinsic (stress induced tetragonal to monoclinic phase transformation of zirconia) and extrinsic (crack deflection, crack branching and bridging, multiple cracking, platelets interlocking) toughening mechanisms. For 15 vol% ZrO 2 composition, the contribution of intrinsic and extrinsic toughness was quantitatively evaluated as 0.9 ± 0.03 and 4.3 ± 0.07 MPa√m respectively (with experimentally measured toughness at crack initiation as 5.2 ± 0.2 MPa√m). [ABSTRACT FROM AUTHOR]

When electrophoretic deposition (EPD) is employed for fabricating alumina (Al 2 O 3)-based hydrogen barrier coatings, it becomes customary to enhance the adhesion strength by subjecting the deposited coating to high-temperature annealing. In this study, a functionally-graded Al 2 O 3 /ZrO 2 coating was designed by using the thermal stress module of Ansys software. The influence of different gradient composition distribution indices, number of layers, and layer thickness on the distribution of thermal stress was systematically investigated by simulation. Based on simulation results, the gradient parameters of the functionally-graded coating were determined as follows: a transition layer with three layers, each with a thickness of 0.13 mm; the first layer consisted of Al 2 O 3 to ZrO 2 ratio of 1:3, the second layer with a ratio of 1:1, and the third layer with a ratio of 3:1. Subsequently, the process parameters for EPD of Al 2 O 3 coating were optimized via experimental exploration. Under conditions of deposition time of 120 s, deposition voltage of 60 V, Al 2 O 3 concentration of 8 g L−1 in the electrophoretic solution, and magnesium chloride hexahydrate concentration of 0.6 g L−1, the as-fabricated Al 2 O 3 coating exhibited optimal hydrogen barrier performance. Finally, different proportions of ZrO 2 were sequentially incorporated into the prepared Al 2 O 3 coating to form functionally-graded materials (FGM). Thermal cycling experiments showed that the Al 2 O 3 coating with added ZrO 2 exhibited better stability at high temperatures. Regarding hydrogen barrier performance, the functionally-graded coating outperformed the non-functionally-graded coating. [ABSTRACT FROM AUTHOR]

In this study, joining of alumina to zirconia was conducted using a Bi 2 O 3 -Y 2 O 3 filler under a normal atmosphere. In order to prevent the possible diffusion of yttrium from zirconia substrate into the interface, yttria was added to the filler. The wettability of 97Bi 2 O 3 -3Y 2 O 3 (wt%) filler was examined, and it was found that this filler has good wettability on alumina and zirconia. The bonded samples that were brazed at 975 °C for 10, 15, and 20 min were determined to be acceptable, while the samples that underwent various process temperatures showed defects such as voids, incomplete fusion, and cracks. Three new phases were observed formed at the interface using SEM images, and the content of these phases increased with increasing holding time. The effectiveness of adding yttria to the filler was confirmed by EDS analysis, as the yttrium of the zirconia substrate did not diffuse into the interface. The fracture surfaces were studied, and XRD analysis was taken from them. Brittle fracture has occurred in all samples, and BiAlO 3 , Y 3 Al 5 O 12 , and (Bi 1.85 Zr 0.15) O 3.75 phases were identified at the interface. According to measurements of the shear strength of the joints, the sample brazed for 15 min at a temperature of 975 °C had the maximum strength of 31 MPa. [ABSTRACT FROM AUTHOR]

The corrosion of the alumina‐based refractory in coal slags would increase the Al2O3 contents of the coal slag and the influences of that on coal slag performances need to be further considered. The effects of Al2O3 on viscosities and structures of SiO2‐MgO‐CaO‐Fe2O3‐(10–22 wt%)Al2O3 coal slags were investigated in this work. The viscosity of the coal slag increased first with increasing the content of Al2O3 from 10 wt% to 14 wt% and further declined with the addition of Al2O3 content to 22 wt%. The role of Al2O3 in the present coal slag was identified. Al2O3 mainly behaved as an acidic oxide in coal slags when the Al2O3 content was less than 14 wt%, which polymerized the slag structure and increased the viscosities, and with further addition of Al2O3 to 22 wt%, a part of Al2O3 behaved as network modifiers due to the deficiency of enough metal cations for charge compensation, which could simplify the slag networks and reduce the viscosity. The variations of slag viscosities were consistent with the change tendencies of structures analyzed by spectra techniques. [ABSTRACT FROM AUTHOR]

This paper reports the design of ferroelectric nanowires using HfO2 and Al2O3. Ferroelectric nanowire transistors have drawn considerable attention recently because of their potential for use in low-power devices and non-volatile memory systems. In this work, the drain current, acceptor concentrations, and electric field are analyzed. The results obtained for the proposed device structure highlight the relevance of Al2O3- and HfO2-based nanowires as potential materials for the development of cutting-edge nanotechnology and materials science advancements. The proposed device structure has ION = 3.8 × 10−5 using HfO2 and ION = 3.48 × 10−4 using Al2O3. The significant improvements in the results make ferroelectric nanowire interesting for the scientific and research community working in this area. [ABSTRACT FROM AUTHOR]

High-performance Ox-Ox ceramics material composites (CMC) are a strategic building block in the aerospace industry and high-temperature applications. The ceramics material composites are hard to machine due to high hardness, fracture toughness, and heterogeneous structures. Furthermore, it is prone to brittle fracture during the machining process. In this study, we successfully demonstrate ultrafast laser machining technology to machine Ox-Ox CMCs. A picosecond laser has been used to machine slots to understand the impact of laser process parameters on the material removal mechanism by performing deep machining. Different scan rates and a number of over-scans have been employed to understand the material removal mechanism, which is dominated by laser ablation and aided by melting due to the residual surface temperature. The maximum material removal rate of 21.75 mm3/min has been achieved for the scan rate of 300 mm/s. This can be related to the reduction in the ablation threshold and the critical balance between the material removal mechanism by ablation and melting. It was found that, the surface roughness of the cut surface has decreased due to melting and solidification. The cross-sectional examination reveals two distinct surface structures, which are entirely resolidified and thermally eroded regions. [ABSTRACT FROM AUTHOR]

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al 2 O 3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al 2 O 3) and amorphous Al 2 O 3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue. [ABSTRACT FROM AUTHOR]

Transparent alumina ceramics produced by pulsed electric current sintering (PECS) include black dots, which can be observed with the naked eye. These black dots have porous structures caused by the aggregates in the raw powder. In order to investigate the detailed mechanism of black dot formation, transparent alumina ceramics were prepared by sintering α-alumina granules to produce large pseudo-aggregates and introducing them into α-alumina powder for PECS. Macroscopic black dots were formed in the sample. Characteristic Raman peaks of graphite were detected in porous parts of these macroscopic black dots. Analysis of gas phases generated from graphite sheets for PECS suspected to be involved in carbon contamination showed CO and CO 2 generation. In thermodynamic calculations on carbon activity during PECS, gas phase including CO and CO 2 generated from the hot graphite mold/sheet permeates the porous part of the cold sample, and the carbon activity of gases including CO and CO 2 on the porous surface theoretically exceeds unity. Then, CO is adsorbed and decomposed on the porous surface, resulting in carbon contamination. The formation of macroscopic black dots is caused by carbon deposition in agglomerates of the raw powder from CO generated by graphite sheets during PECS. [ABSTRACT FROM AUTHOR]

Ammonia borane is widely recognized as a reliable source of hydrogen. However, for efficiently generate hydrogen from ammonia borane, the use of appropriate catalysts is necessary. Transition metal catalysts, significantly enhance the hydrogen production. In our study, we focused on synthesizing a catalyst, Ru-Imine@Al 2 O 3 , by incorporating ruthenium-imine onto the surface of alumina in an ethanoic solution. We conducted this synthesis under ambient conditions. We employed advanced analytical techniques to characterize it. To better understand the structure and composition of catalyst. Notably, this is the first time that Ru-Imine and Ru-Imine@Al 2 O 3 have been used for dehydrogenation of ammonia borane. During our experiments, we found that the Ru-Imine@Al 2 O 3 catalyst exhibited excellent activity in the dehydrogenation process of ammonia borane, releasing hydrogen. We tested different levels of Ru-Imine usage and observed the best performance with 10 % Ru-Imine complex in a 10 mg catalyst. Under these conditions, the catalyst produced 19531 mL H 2 gcat.−1min−1, at 30.0 ± 1 °C. the catalytic activity of 100 % Ru-Imine was also tested under the specified conditions and produced 14183 mL H 2 gcat.−1min−1. To gain further insights into the reaction, we thoroughly determined the kinetics and proposed a mechanism for the dehydrogenation process. Our findings revealed that Ru-Imine@Al 2 O 3 catalyzed dehydrogenation of ammonia borane exhibited a lower activation energy (Ea) of 21.9 kJ mol−1. This implies that the reaction can proceed more easily and efficiently with the presence of the catalyst. Furthermore, we assessed the reusability of the catalyst and found that it demonstrated excellent performance even after eight cycles with 100 % conversion of ammonia borane. This highlights the potential of the Ru-Imine@Al 2 O 3 catalyst for repeated use without significant degradation in its activity. These findings contribute to the advancing of hydrogen generation technologies and offer promising prospects for utilizing ammonia borane as a hydrogen source. [Display omitted] • Ru-Im@Al 2 O 3 catalyst developed to enhance H 2 evolution from NH 3 BH 3 dehydrogenation. • Alumina effect, enhanced the catalytic activity with 19531 mL H 2 g−1 cat.min−1. • Kinetic studies and suggested mechanism were clearly determined for this reaction. • Ru-Im@Al 2 O 3 catalyzed hydrolysis achieved low activation energy of 21.9 kJmol-1. • Ru-Im@Al 2 O 3 displayed high stability of 100 % conversion even after the 8th run. [ABSTRACT FROM AUTHOR]

In this investigation, two distinct composites were produced using the liquid metallurgy vortex-route method with an aluminum AA6013 matrix and 0.5% and 1% nano-Al2O3 reinforcement by weight. The effects of nano-Al2O3 ceramic particles added into the AA6013 alloy to increase the hardness and strength of the composite were investigated. Samples for welding were prepared from cast composite materials with dimensions of 250 × 110 × 60 mm. The obtained specimens were joined via butt welding at 110-A and 120-A current intensities, and at a constant speed of 400 mm/min by cold metal transfer (CMT) and pulse multi-control (PMC) welding methods. Using the use of micro- and macrostructural evaluations, hardness measurements, and tensile testing, the impacts of each welding parameter on the mechanical characteristics and weld structure of the cast composites were examined. The composite material with 0.5% nano-Al2O3 reinforcement that was joined at 120 A utilizing the CMT process achieved the highest tensile strength value at 96.6 MPa. At 110-A and 120-A welding current values, 0.5% reinforced composite demonstrated the maximum strength in both welding techniques. [ABSTRACT FROM AUTHOR]

This study focuses on fabricating lattice structural Al 2 O 3 ceramics with lattice infill densities ranging from 25 % to 70 % using filament-based fused deposition modeling (FDM) technology. A specialized filament for FDM printing was developed, comprising 53 vol% Al 2 O 3 powder and ethylene vinyl acetate (EVA) as the primary binder component. The filament demonstrated excellent flexibility as assessed by a self-designed three-point bending test. The impact of lattice infill density and sintering temperature on dimensional changes, microstructure evolution, compressive strength, and strength-to-density ratio was explored. It was found that with increasing sintering temperature, the samples became more compact, resulting in higher levels of shrinkage, bulk density, and compressive strength. At a sintering temperature of 1600 °C, the sintered parts reached their maximum density through the solid-state sintering process. The sample sintered at 1600 °C with 70 % infill density exhibited the maximum compressive strength of 31.47 MPa, with a corresponding strength-to-density ratio of 20.84 MPa/g·cm−3. These findings highlight the successful fabrication of lattice structural Al 2 O 3 with low density and high compressive strength by FDM technology. • Lattice structural Al 2 O 3 ceramics were fabricated by FDM technique. • The filament for FDM with 53 vol% Al 2 O 3 was developed. • Filament demonstrated excellent flexibility. • Sintered lattice structural Al 2 O 3 ceramics at 1600 °C exhibited the maximum compressive strength of 31.47 MPa. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface grinding is a widely employed finishing process in industrial sectors dedicated to achieve desired Surface characteristics of components. This study experimentally investigates the impact of the grinding parameters pertaining to the surface characteristics of Inconel 800, which is a nickel-iron-chromium alloy extensively used in high-temperature applications. Various commercially available grinding wheels were employed to grind Inconel800 under different grinding conditions. The ground surfaces were comprehensively analyzed using surface roughness measurements, Three-dimensional profilometry, optical microscopy, findings from XRD and SEM reveal that grinding parameters and wheel characteristics significantly impact the surface texture, topographical features, residual stress, and surface morphology of the machined nickel alloy.. The insights from this investigation contribute to the understanding of the grinding behavior of nickel-based superalloys and provide a basis for optimizing the grinding process for enhanced surface integrity. The findings are valuable for industries dealing with the machining of high-performance nickel alloy components. [ABSTRACT FROM AUTHOR]

ABSTRACT Low‐temperature densification of alumina using calcium vanadate (CaV2O6, CV) having a similar dielectric constant as a liquid‐forming additive has been studied. The alumina‒CV composites containing 20‒40 vol.% CV achieve ∼94% of theoretical density at low temperatures of 1100°C‒900°C by liquid‐phase sintering. A reduction in the average size of grains from .87 to .42 µm with a surge in CV amount from 20 to 40 vol.% is observed. The permittivity decreases from 9.2 to 8.90, and the dielectric loss increases from 2.154 × 10‒3 to 4.761 × 10‒3 when the amount of CV in the alumina‒CV composite rises from 20 to 40 vol.%. The temperature coefficient of resonance frequency, thermal expansion coefficient, and thermal conductivity of the alumina‒CV composites are observed in the ranges of ‒54 to ‒72 ppm °C‒1, 6.94‒7.32 ppm °C‒1, and 13.78‒8.02 W m‒1 K‒1, respectively. The compatibility of the composites with Ag for low‐temperature co‐fired ceramics (LTCC) application is established through co‐sintering and energy‐Dispersive X‐ray spectroscopy line spectra analysis. The low‐temperature densification, acceptable range of dielectric and thermal properties, and silver compatibility make the alumina‒CV composite a candidate for LTCC application. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) based microwave dielectric composite has been widely used because of its adjustable dielectric constant and low dielectric loss, but its low thermal conductivity can not meet the heat dissipation requirements of high-power microwave devices. Therefore, it is of great significance to develop microwave dielectric composites with high thermal conductivity and low loss. In order to obtain microwave composite materials with high thermal conductivity and low losses, schistose Al 2 O 3 /PTFE (S-A/PTFE) composites and globular Al 2 O 3 /PTFE (G-A/PTFE) composites were successfully prepared. It is compared whether S-A can combine with PTFE more fully than G-A, which can promote the dielectric properties and thermal conductivity of Al 2 O 3 /PTFE composites. Surprisingly, the S-A/PTFE composites demonstrate higher thermal conductivity, lower thermal expansion and hygroscopic properties. The S-A/PTFE composites can deliver a high thermal conductivity of 0.986 W/m K. Composite substrates with 53 wt% S-A filler exhibits excellent performance, which specifically show credible dielectric constant (ε r = 4.01) and admissible dielectric loss (tanδ = 0.0014 at 10 GHz). Furthermore, the composite substrate shows a similar thermal expansion coefficient to copper, and lower water absorption rate (0.05 %). The relationship between dielectric constant of composite and filler was predicted by different theoretical modeling methods. [ABSTRACT FROM AUTHOR]

Direct Ink Writing has been demonstrated to be a promising route to produce ceramic catalysts with complex geometries and enhanced catalytic performances. To increase the catalytic performances, chemical etching can be conducted to get an interconnected and hierarchical porous structure, to increase the surface area and the contact time of the reactants. In this work, DIW alpha (α)-Al 2 O 3 catalysts were chemically etched with hydrofluoric acid (HF). Several combinations of acid concentrations and etching times were studied to find the optimal etching condition. For HF concentration of 5, 20 and 40 wt%, the optimal etching time was 48, 24 and 5 h, respectively, being 40 wt% the concentration that shows the greatest increase of surface porosity (of around 5%). HF etching can produce an interconnected porosity on 3DP α-Al 2 O 3 , but it does not yield improvement in catalytic performances when the content of fluor (F) is higher than 10 at% since it produces parasite reactions. [ABSTRACT FROM AUTHOR]

In this work, a design and additive manufacturing approach is successfully implemented to print via digital‐light‐processing cubic cellular alumina structures for antenna waveguides. Cellular structures' porosity is varied during the design phase and different dielectrics are finally produced and inserted in antenna waveguides with the aim of decreasing the cutoff frequency in the range from 1 to 10 GHz. In parallel, the electromagnetic behavior of the cellular alumina structures into the antenna waveguide as the structure porosity varies is simulated. Printed samples are then tested in a laboratory setup. In the results obtained, it is shown that the antenna cutoff frequency increases as the porosity of the alumina cellular structures increases, also evidencing a linear correlation between their average dielectric constant and porosity. In this study, it is demonstrated that the dimensional accuracy achieved after the sintering process is essential because even a small (1%) deviation of the sintered sample size from the nominal ones, due to nonlinear shrinkage, highly affects their cutoff frequencies. [ABSTRACT FROM AUTHOR]

In this study, the origins of efficiency gains in Cu(In,Ga)Se2 (CIGS) solar cells are investigated by introducing an Al2O3 passivation layer in terms of the oxidation condition of Mo back contact, alkali‐metal diffusion, minority carrier lifetimes (τ), and charge conditions. The study reveals that introduction of an Al2O3 back‐contact passivation layer into solar cells yields multiple impacts. Al2O3 deposition enhances the oxidation of the Mo back contacts, increasing Na solubility in Mo and Na diffusion from Mo into the CIGS layer, thereby modifying the metastable properties of CIGS. The charge condition at the CIGS/Al2O3 interface is not fixed negative charge but variable, dependent on whether electrons or holes are supplied. During solar cell operation, the interfacial charge condition is expected to be neutral or positive for Al2O3 grown using plasma or thermal atomic layer deposition techniques, respectively. Moreover, the mechanical peeling off of CIGS from Mo back contact enhanced τ in a similar way as with the insertion of Al2O3. Based on this study, the enhancement of alkali metal supply and the removal of direct contact of CIGS to the metal contact (Mo) can play crucial roles in improving the performance of CIGS solar cell. [ABSTRACT FROM AUTHOR]

Adding sintering additives to fabricate alumina ceramics via the binder jetting (BJ) technique effectively enhances material properties. However, it is still limited by the disadvantages of low relative density and poor mechanical properties. This study proposed reducing matrix particle size and adding nanoscale particles using binder jetting to address the poor densification and strength of printed alumina (Al 2 O 3) samples. Additionally, their effects on the mechanical properties and manufacturability of the material were explored. Numerical simulations were carried out before the experiments to predict the impact of particle stacking on the powder bed using the discrete element method (DEM). Then, filler particles with an average 40 μm size replaced the original 106 μm-sized Al 2 O 3 particles. Subsequently, Al 2 O 3 nanoparticle content in the samples was gradually increased, and the relevant properties of the sintered samples with different compositions were tested. Consequently, the size of the Al 2 O 3 particles and the addition of Al 2 O 3 nanoparticles significantly affects the physical and mechanical properties of the samples. The sample with 106 μm-sized particles has a compressive strength of 58 MPa, while reducing the particle size to 40 μm increases its compressive strength by 26 %. Moreover, the sample's compressive strength could reach up to 330 MPa, an increase of 513 %, and the hardness reaches 1215 HV (11.91 GPa) by expanding the Al 2 O 3 nanoparticles content to 30 %. Additionally, using Al 2 O 3 nanoparticles further reduces the sintering temperature, significantly improving the practicality of Al 2 O 3 printing using binder jetting. [ABSTRACT FROM AUTHOR]

The paper deals with transparent MgAl2O4 ceramics reinforced with 0.1 vol.% Al2O3 nanofibers and manufactured by spark plasma sintering at 1400°C and 100 MPa. The microstructure of MgAl2O4 ceramic samples is studied by the X-ray phase analysis and scanning electron microscopy. The optical properties are investigated in 190 to 8000 nm wavelength range. The influence of Al2O3 nanofibers on optical and mechanical properties of ceramics is discussed herein. [ABSTRACT FROM AUTHOR]

A novel sintered-joining of Al 2 O 3 and AlN is achieved for the first time using micro-Ag particle interlayers in air. In comparison with reactive air brazing, this method addresses the issue of reduced strength caused by air holes in brazed joints. Also, this sintered-joining method can be performed at a lower temperature (920 °C), improving the joint strength by relieving the residual stresses. The sintering effect of micro-Ag particles and their high density of dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of Ag and ceramic. Ag–O clusters formed at the interface can be embedded into oxygen vacancies on the ceramic surface, playing a key role in interfacial joining. By optimizing joining temperature, assembly pressure and holding time, a maximum joint shear strength of 85.2 MPa is achieved at 920 °C for 30 min with an assembly pressure of 1 MPa. This study successfully prepares Al 2 O 3 /AlN joints with excellent mechanical properties, providing a reliable foundation for the fabrication of power integrated circuits with efficient operation. [ABSTRACT FROM AUTHOR]

Zr has been widely used in high-quality steel due to its strong deoxidizing capacity and ability of improve performance of steel. ZrO2–Al2O3 inclusions with core-shell structure were observed in this study. The structure, electronic properties, and energy changes of ZrO2 and ZrO2–Al2O3 systems were studied based on first principles calculation. It indicates that ZrO2 can be used as the heterogeneous nucleation core of Al2O3. Al atoms were preferentially adsorbed on the bridge site of ZrO2 (001) and then form the ZrO2–Al2O3 interface. The template effect of ZrO2 was nine adsorption atomic layers, among which layers 1–5 was a coherent epitaxial layer, layers 5–9 was the transition layer, and the atomic ratio was 3:2. The growth mechanism of Al2O3 on ZrO2 surface was discussed. The results help understand the formation of inclusion at atomic scale and find ways to control the characteristics of inclusion in steel with Zr treatment. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) photodetectors have gained much attention due to their numerous important applications ranging from environmental monitoring to space communication. To date, most p‐NiO/n‐Si heterojunction photodetectors (HPDs) exhibit poor UV responsivity and slow response. This is mainly due to a small valence band offset (ΔEV) at the NiO/Si interface and a high density of dangling bonds at the silicon surface. Herein, an UV HPD consisting of NiO/Al2O3/n‐Si is fabricated using magnetron sputtering technique. The HPD has a large rectification ratio of 2.4 × 105. It also exhibits excellent UV responsivity (R) of 15.8 A/W at −5 V and and detectivity (D*) of 1.14 × 1013 Jones at −4 V, respectively. The excellent performance of the HPD can be attributed to the defect passivation at the interfaces of the heterojunction and the efficient separation of photogenerated carriers by the Al2O3 nanolayer. The external quantum efficiency (EQE) of the HPD as high as 5.4 × 103%, hence implying a large optical gain due to carrier proliferation resulting from impact ionization. Furthermore, the ultrafast response speed with a rise time of 80 µs and a decay time of 184 µs are obtained. [ABSTRACT FROM AUTHOR]

Multifaceted coatings are in high demand due to their remarkable tribological advantages and fortification from harsh environments. However, ceramics coatings perform well and offer excellent performance but are limited to high temperatures. In the present study, it is perceived that 0.1 wt% nanodiamonds and 1 wt% graphene nanoplatelets reinforced in Al2O3 offered improved wear-resisting properties at high temperatures from 300 to 500 °C. The measured relative density recorded was 94.45 ± 1.9, 95.45 ± 0.9, and 97.25 ± 1.9 for A-SD, AND-SD and ANDG-SD, respectively. The wear rate decrement on 10N, at 300 °C, of AND-SD was recorded at 50.12% and 74.50% in ANDG-SD. On 15N, at 400 °C, 48.35% for AND-SD and 64.31% for ANDG-SD were recorded. The highest wear rate reduction, i.e., 74.66%, was recorded in ANDG-SD at 500 °C. The COF value at an applied load of 10N at 300 °C was 0.49, 0.46, and 0.30 for A-SD, AND-SD, and ANDG-SD, respectively. At an applied load of 15N, at 400 °C, it was 0.51 for A-SD, 0.42 for AND-SD, and 0.29 for ANDG-SD. At an applied load of 20N, at 500 °C, 0.54 for A-SD, 0.40 for ANDG-SD, and 0.24 for ANDG-SD were recorded. The maximum decrement in COF value was observed at an applied load of 20N, at 500 °C, due to GNP's self-lubricating properties, which have the exceptional caliber to enhance wear resistance. Through this study, it has been supposed that developed hybrid coatings could be a robust path for developing coatings at high working temperatures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research paper has discussed the determination of mechanical, wear, and corrosion properties of the stir cast aluminium 6061 (T6) hybrid matrix composites. The reinforcements such as aluminium oxide (Al2O3), mesquite wood ash (MWA), and graphite (C) were incorporated with the Al6061 alloy and stir casted. The experimental test data has revealed that the reinforced samples have gained decent tensile strength and impact strength due to the inclusion of rigid, brittle reinforcements. Comparing the bare Al alloy, compressive strength and microhardness of sample 1 and sample 2 was maximum due to the majority of hard structured Al2O3 and MWA powder. From the wear analysis, it was inferred that the presence of maximum proportions of Al2O3 with self-lubricating graphite powder has promoted better wear resistance for the sample 1. The Tafel plot has concluded that reinforcement of M.W.A. and graphite in sample 4 has gained higher corrosion resistance with minimum current density. Finally, the introduction of bio-mesquite wood ash powder along with synthetic reinforcements has tailored the wear and corrosion properties for the composites with decent improvement in mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, we describe the mechanical characteristics of Al2O3 and TiCN thin films formed by chemical vapor deposition (CVD) and a TiAlN thin film formed by physical vapor deposition (PVD), which are used as hard coating films. A focused ion beam (FIB) was used to fabricate a microcantilever beam for strength tests and fracture toughness tests under bending. A nanoindentation system was used to apply normal force to cantilever beams. All the films showed a linear force–deflection relationship, indicating brittle fracture during elastic deformation. The Young’s modulus ranged from 340 to 379 GPa, with no significant difference among the films, whereas the fracture strength of the Al2O3 films was 5.5 GPa, which was almost twice those of the other two films. For the fracture toughness test, a precrack with various depths was made using FIB at 2 μm from the fixed end of the cantilever beam. The Al2O3 film toughness values ranged from 4.1 to 5.5 MPa√m, which were almost twice that of the TiCN film at each precrack depth. Both CVD films showed a similar trend, i.e., an increase in fracture toughness with decreasing precrack depth, However, the fracture toughness of the TiAlN film showed no precrack depth dependence. The difference in fracture toughness between the CVD and PVD films is discussed on the basis of fracture surface observation results and information on the crystal grain size and orientation. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is a process that can join many materials by causing minimal internal stress without the need for a direct electric current, contrary to traditional welding methods. The effects of SiC and Al2O3 reinforcing powders on the joining of AA6061-T6 and AA7075-T6 plates, which are difficult to join with conventional welding methods by FSW, are investigated in this study. The metallurgical properties of the combined samples are examined in terms of strength characteristics to investigate the effects of the reinforcement powder. In addition, elemental analysis is carried out for the mixing behavior of the powders. Finally, we used the TOPSIS method to select the most appropriate powder types to improve welding quality. Furthermore, a game theory application is presented to determine which powder type is suitable considering the joined aluminum plate's strength expectations. [ABSTRACT FROM AUTHOR]

The rapid advancement of high-tech technologies such as aerospace， electronic information， and biomedicine has required more demands on the properties of advanced ceramic materials. Single-characteristic structural or functional materials cannot meet the current requirements， so the high-performance composite ceramics with integrated structure and function have become global research objectives. Directionally solidified oxide eutectic composite ceramics are a class of structural and functional integrated composite materials developed in recent years for long-term service in ultra-high temperature oxidizing environments. They have characteristics such as high melting point， low density， excellent high-temperature strength， and high-temperature creep performance， while also possessing functional properties such as optics， electromagnetism， and biology. The latest development of directionally solidified structure-function integrated eutectic ceramics was reviewed， specifically focusing on Al2O3-based eutectic ceramic systems. The various preparation methods， technical principles， and growth characteristics associated with directionally solidified eutectic ceramics were summarized. Furthermore， the solidification microstructure and structural characteristics observed in a series of Al2O3-based eutectic ceramics were elaborated. The mechanical， optical， magnetic， and biological properties of composite ceramics and their influencing factors were analyzed， and their characteristics， advantages， and application scope were introduced. Finally， the review summarizes the challenges and key bottlenecks faced by directionally solidified eutectic composite ceramics in engineering applications and proposes the main directions for the development of eutectic composite ceramic materials in terms of forming technology innovation， comprehensive performance improvement， and the development of new systems.

In this investigation, two passes Constrained Groove Pressed (CGPed) Al1050 sheets went through Friction Stir Welding (FSW) by adding nano-sized Al2O3 particles. Then, the microstructure and mechanical properties of the welded joints, undergone various pass numbers and rotational to traverse speed (ω/ν) ratios, were presented. Findings showed all joints were fractured from the SZ, although HAZ softening happened due to grain growth in this region. The presence of the Al2O3 particles in the stir zone led to a fine and equiaxed grain structure, resulting from continuous dynamic recrystallization (CDRX) during the high-temperature welding process. This grain refinement contributed to an improvement in the mechanical properties of the joints, such as strength and microhardness. Employing two different ω/ν ratios resulted in a variety of thermal cycles during the welding procedure such that the peak temperature in the ω/ν of 70 and 25 r/mm reached ∼423 °C and ∼285 °C, respectively. Microstructure studies via optical observation and EBSD analysis illustrated that employing a higher ω/ν ratio and weld pass number resulted in more uniform particle distribution in the stir zone thanks to facilitating materials flow and incorporation during FSW. As a result, the three passes FSWed sample at the higher ω/ν ratio of 70 r/mm showed the most homogeneous particle distribution and finest grain structure in the SZ. This microstructure evolution was in reliable agreement with the mechanical performance of the joints. The three passes FSWed sample at the higher ω/ν ratio of 70 r/mm demonstrated the highest weld strength, microhardness, and %elongation compared to other FSWed joints. This sample showed an ultimate tensile strength (UTS) of ∼97 MPa and a %elongation of ∼16%, and its mean microhardness value had a ∼3.5% increase compared to the CGPed base metal. Conversely, the one pass FSWed sample at the lower ω/ν ratio of 25 r/mm represented the weakest mechanical properties due to cavities, defects, and agglomerated Al2O3 nanoparticles. The presence of nanoparticles was a decisive factor in microstructural evolution during the welding, thereby increasing the mechanical quality of the joints dependent upon their uniform dispersion, obtained by increasing the pass number and ω/ν ratio.

Amorphous alumina films are isotropic and have no grain boundaries, which make them have smooth surfaces, excellent properties, and wide applications in protective coatings, catalysis, and microelectronics. However, high-quality alumina films were usually prepared by vapor-phase approaches which need expensive equipment and long production time. Additionally, amorphous films are long-range disordered, which makes the study of structure–property relationships challenging. Here, a simple sol–gel method is employed to obtain high-quality amorphous Al2O3 thin films. The microstructure, morphology, and mechanical properties of amorphous Al2O3 thin films were systematically investigated. All the Al2O3 thin films heat-treated at 600–800∘C are in amorphous state with ultrasmooth surface (Ra values about 0.29–0.43 nm) and high mechanical properties (elastic modulus ∼170 GPa, hardness ∼20 GPa). The mechanical properties (E and H) of Al2O3 films gradually increase with the increase of heat-treating temperature. Additionally, the Al coordination of the amorphous alumina films are analyzed by solid-state NMR and correlated with the mechanical properties. The results show that in amorphous alumina, the presence of tetrahedral Al ([4]Al) and octahedral Al ([6]Al) is helpful to improve the mechanical properties, while the five-coordinated Al ([5]Al) is not conducive to improve the mechanical properties. The results demonstrate that sol–gel method is an attractive alternative to time-consuming and expensive vapor-phase approaches and are useful for scale-up to applications and research of amorphous alumina films. [ABSTRACT FROM AUTHOR]

Although the concept of geopolymers was proposed over 40 years ago, there still remains a lack of clarity regarding their atomic-level structure and formation. In this study, the Dmol3 quantum chemistry calculation program, based on density functional theory (DFT), was used to determine a range of electronic structural properties associated with the initial, intermediate (IM), transition (TS), and final states of Al2O3/[Al(OH)4]− conversion reactions in the alkali-activator. The properties analyzed included total energy, Gibbs free energy, electrostatic potential (ESP), Fukui functions, and frontier orbitals, comprising the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO). The simulation results indicated that electrons were transferred from the HOMO of O in H2O and OH− to the LUMO of Al in (AlO2)− or (AlO)+ , leading to an increase in the LUMO energy level of Al and a reduction in the chemical reactivity of the newly formed Al monomers. The transformation processes from Al2O3 to [Al(OH)4]− involved varying numbers of steps, energy release, and energy barriers. Notably, during the transition state conversion process, the breaking and reformation of O─ H bonds often occurred as necessary conditions for the formation of transition states. These findings have significant implications for the advancement of new technologies based on geopolymer conversion processes. [ABSTRACT FROM AUTHOR]

Abstract PMMA/PEG and PMMA/PEG doped with SiO2, TiO2, and Al2O3 were fabricated using the solution-casting technique. The composites were characterized by X-ray diffraction and scanning electron microscopy (FE-SEM), which revealed that the amorphous nature of PMMA/PEG blend doped with Al2O3 was hindered by the crystalline nature of those doped with SiO2 and TiO2. The absorption of PMMA/PEG blend doped with Al2O3 is higher, band gap energies were decreased from 4.90 eV for PMMA/PEG blend to 4.03 eV, 3.09 eV, and 2.09 eV for SiO2, TiO2, and Al2O3 doped PMMA/PEG blend, respectively. The dielectric constant, ε′ has a high value (2 × 104) for samples PMMA/PEG and SiO2/PMMA/PEG. While dielectric loss $$\left( {\varepsilon ^{{\prime \prime }} } \right)$$ ε ″ -values decreased to

Abstract The purpose of this work is to analyze the impact of reinforced Al2O3–LM6 aluminum composite made with dual mixed slurry for semi-solid casting with stirring, which is documented according to microstructure and wear properties. Under dry sliding pin-on-disk conditions, the composition and surface morphology of worn surfaces were carefully examined for the 10 N applied force, 1.2 m/s sliding speed, and sliding distances up to 750 m. Experimental findings indicate that Al2O3 reinforcement with semi-solid dual slurry effects give outstanding resistance against the adhesive wear. Microstructure, EDS, and XRD results from worn surface evaluation all show evidence of protective layers, which helps explain the reason for the rate of wear decreased due to processing. In this experiment, LM6 serves as the matrix material and Al2O3 as reinforcement. Al2O3–LM6 semi-solid cast composite was created via a dual mixed slurry technique with temperature control close to the solidus line for varying compositions. This work reports a substantial relationship between metallurgical and mechanical parameters. Mechanical properties and wear characteristics have been investigated.

Abstract The study investigates the impact of Phase Change Material (PCM) and nano Phase Change Materials (NPCM) on solar still performance. PCM and a blend of NPCM are placed within 12 copper tubes submerged in 1 mm of water to enhance productivity. Thermal performance is assessed across four major scenarios with a fixed water level of 1 mm in the basin. These scenarios include the conventional still, equipped with 12 empty copper rods and 142 g of PCM in each tube, as well as stills with NPCM Samples 1 and 2. Sample 1 contains 0.75% nanoparticle concentration plus 142 g of PCM in the first 6 tubes, while Sample 2 features 2% nanoparticle concentration plus 142 g of PCM in the subsequent 6 tubes. Aluminum oxide (Al2O3) nanoparticles ranging in size from 20 to 30 nm are utilized, with paraffin wax (PW) serving as the latent heat storage (LHS) medium due to its 62 °C melting temperature. The experiments are conducted under the local weather conditions of Vaddeswaram, Vijayawada, India (Latitude-80.6480 °E, Longitude-16.5062 °N). A differential scanning calorimeter (DSC) is utilized to examine the thermal properties, including the melting point and latent heat fusion, of the NPCM compositions. Results demonstrate that the addition of nanoparticles enhances both the specific heat capacity and latent heat of fusion (LHF) in PCM through several mechanisms, including facilitating nucleation, improving energy absorption during phase change, and modifying crystallization behavior within the phase change material. Productivity and efficiency measurements reveal significant improvements: case 1 achieves 2.66 units of daily production and 46.23% efficiency, while cases 2, 3, and 4 yield 3.17, 3.58, and 4.27 units of daily production, respectively. Notably, the utilization of NPCM results in a 60.37% increase overall productivity and a 68.29% improvement in overall efficiency.

Abstract Textile-toxic synthetic dyes, which possess complex aromatic structures, are emitted into wastewater from various branches. To address this issue, the adsorption process was applied as an attractive method for the removal of dye contaminants from water in this article. An unprecedented integrated experimental study has been carried out, accompanied by theoretical simulations at the DFT-B3LYP/6-31G (d,P) level of theory to investigate how single Maxilon Blue GRL (MxB) dye or and its mixture with MG (Malachite Green) dyes interact with the adsorbent and compare the obtained results with the data obtained through experimentation. The full geometry optimization revealed the physical adsorption of dyes on the Al2O3 surface. Non-linear optical properties (NLO) results emphasized that the complex MG-Al2O3-MxB is a highly promising material in photo-applications, and the adsorbed binary system is energetically more favorable compared to the adsorbed sole dye system. The experimental results for (MxB) dye adsorption onto γ-Al2O3 affirmed that the optimum conditions to get more than 98% uptake were at dye concentration 100 ppm, pH 10, adsorbent content 0.05 g, and equilibrium time only 20 min. The kinetic and isothermal studies revealed that the adsorption accepted with the pseudo-second-order and Freundlich isotherm model, respectively. The removal efficiency of the mixture of MxB and MG dyes was the highest but did not change clearly with increasing the % of any of them. The details of the interaction mechanisms of the sole and binary dyes were proven.

In the current study, a novel composite (Fe3O4@MnO2@Al2O3) was prepared to remove crystal violet dye and cadmium from aqueous solutions. The coprecipitation method was utilized to synthesize the composite. Batch studies are carried out using a contact period of (0.5-3) hours, an initial crystal violet and cadmium content of (50-200) mg/L, an agitation speed of (50-200) rpm, a pH of (4-12), and a composite dosage of (0.2-1) g per 50 mL of contaminated solution. The isotherm and kinetics models are formulated the experimental data. XRD, SEM-EDS, and FTIR analysis were utilized for composite characterization. The results revealed that the removal efficacy of crystal violet dye was 99.311% at 1 g of adsorbent, pH 12, 50mg/L, 1 hour, and 200rpm. The removal efficacy for cadmium (Cd) is 99.7296% at 1 g of sorbent mass at pH 6, 50mg/L, 1 hour, and 200rpm. The outcomes demonstrated that the Langmuir model could accurately depict the sorption of crystal violet dye onto the composite with R2 (0.9882) and SSE (0.7084). Based on Freundlich, the composite's capacity to reflect cadmium sorption was assessed by its highest R2 (0.8947) and lowest SSE (8.5149). The pseudo-second-order model is a more realistic way to explain how cadmium and crystal violet dye sorb onto the composite. The results showed that the composite is effective in eliminating target pollutants, since cadmium has a maximum adsorption capacity of 48.5052 mg/g and crystal violet dye has a capacity of 40.9682 mg/g. Therefore, (Fe3O4@MnO2@Al2O3) can be used as efficient sorbent for removing Cd and crystal violet dye from synthetic industrial wastewater.

All‐inorganic perovskite quantum dots (PQDs) are widely applied in photoelectronics because of their high luminous efficiency. However, PQDs have poor stability, which hinders their practical applications. In this study, controllable crystallization of PQDs is achieved by adding Al2O3 to alter the glass network. Next, Na2CO3 (aq) washing‐heating treatment is used to improve the protective mechanism. Owing to this dual strategy, the prepared CsPbBr3@glass exhibits a high photoluminescence quantum yield (PLQY > 95%) and excellent stability. In a 1000 h accelerated aging experiment, the luminous intensity remains above 96% of the initial intensity. The luminescence intensity shows almost no change after soaking in water for 20 weeks. Finally, the CsPbBr3@CsPbBr1I2@PET light‐conversion film is prepared by the sandwich method. Its color gamut covers 138% of the NTSC 1953 and 102% of the Rec. 2020. This CsPbBr3@glass with a high PLQY and ultrastability will broaden the scope of perovskite materials in displays. [ABSTRACT FROM AUTHOR]

The layered configuration of different material plates is one of the ways of achieving protection against different kinds of kinetic energy ammunitions. The thickness of each plate is one of the most important influencing parameters to prevent the penetration of the projectile. In the present study, a layered configuration of the Al2O3 and Al 7075-T651 is analysed, to prevent the perforation of 7.62 mm Lead core projectile, under normal impact conditions, by using LS-DYNA numerical simulations. Experiments were conducted on Al 7075-T651 plate and Numerical model was validated with experiment results. To achieve the objective, the validated numerical model was used to investigate influence on various Al2O3 and Al 7075-T651 combinations. Three factors led to the selection of Al 7075-T561 and Al2O3 as the target materials. First, the literature review revealed that these materials have already been employed in the construction of armour. Second, Al2O3 is a brittle material whereas Al 7075-T651 is ductile. Consequently, when combined in a layered arrangement, these materials offer the ideal destroyer-absorber arrangement. Thirdly, these materials have lower densities than steel. As a result, these materials offer a lightweight alternative for lead core 7.62 mm bullet defense. From the analysis, it is observed that two layered configurations were found to be effective in the prevention of bullet perforation: a front plate of Al2O3 that was 10mmthick and had a rear plate of Al 7075-T651 that was 06mmthick, and a front plate of Al2O3 that was 04mm thick and had a 12 mm thick layer of Al 7075-T651. [ABSTRACT FROM AUTHOR]

Hot corrosion is a severe form of industrial corrosion which occurs at high temperatures under the influence of oxidizing gases and can be prominently linked to the formation of a molten salt/ash layer over any metallic substrate. Throughout the years, several types of inhibitors and coatings have successfully been employed to reduce its devastating effects to a certain extent. In this study, two synthesized metal oxides namely Al2O3 and MnO2 were used as corrosion inhibitors and XRD, FTIR analysis were carried out to assess their structural properties. Further, TGA analysis for Al2O3 and MnO2 was carried out to determine thermal stability characteristics. The as-synthesized materials were further deposited as inhibitor coatings (Al2O3 with MnO2 bond coating, MnO2 coating and Al2O3 + 50% MnO2 coating) on T22 boiler steel specimens. All the specimens (bare T22 and coated T22 steel) were investigated for hot corrosion studies in Na2SO4-60%V2O5 environment at the temperature of 900 °C for 50 consecutive cycles. Every cycle involved a 1-h heating step in furnace followed by 20-min cooling at room temperature. Weight gain data were collected using a digital balance. XRD and (SEM–EDS) analysis were carried out to characterize the samples after exposure to hot corrosion environment. A better resistance to hot corrosion was observed for all the different types of coatings, with Al2O3 + 50% MnO2 coating representing maximum resistance. A high concentration of protective oxides such as Al2O3 and Cr2O3 present on the surface and their interaction to form dense layers on the coated samples explains the enhanced hot corrosion inhibition. [ABSTRACT FROM AUTHOR]

The impact of rare earth treatment on the chemical morphology evolution of non-metallic inclusions in bearing steel under different initial cleanliness conditions was studied through simulation. Thermodynamic calculations indicate that at an oxygen content of 0.001%, the evolution route of inclusions with increasing Ce content was Al2O3 → CeAl11O18 + CeAlO3 → CeAlO3 + Ce2O2S → Ce2O2S → Ce2O2S + CeS. As the initial oxygen content decreases, the proportion of CeAlO3 decreases, leading to easier conversion of CeAlO3 to Ce2O2S. Vacuum induction furnace experiments demonstrated that with an oxygen content of 0.001%, an increase in Ce content results in a gradual rise in the proportion of inclusions in steel sized 1~2 μm. In contrast, the proportion of inclusions sized 2~5 μm decreases. Consequently, the overall content of inclusions in steel decreases, along with a reduction in both the number density and average size of inclusions. Introducing bearing steel melt with approximately 0.01% Ce rare earth to bearing steel with initial oxygen contents of 0.0005%, 0.001%, and 0.0015% showed an evolution of inclusions from Ce2O2S and CeS to Ce2O3, CeAlO3, etc. The average inclusion size significantly increased from 0.7 μm to 2.16 μm. Morphologically, the transition of inclusions from precipitated to polymerized forms occurred as the initial oxygen content rose. High-temperature laser confocal microscopy experiments demonstrated that inclusions in low cleanliness conditions tend to agglomerate more than those in high cleanliness conditions, contributing to the increase in average size. [ABSTRACT FROM AUTHOR]

With a band gap of 2.4 eV, CdS has been extensively explored for photocatalytic applications under visible light irradiation. In this study, CdS nanoparticles have been investigated for the tribocatalytic degradation of concentrated Rhodamine B (RhB) and methyl orange (MO) solutions. For CdS nanoparticles in a glass beaker, 78.9% of 50 mg/L RhB and 69.8% of 20 mg/L MO solutions were degraded after 8 h and 24 h of magnetic stirring using Teflon magnetic rotary disks, respectively. While for CdS nanoparticles in a beaker with Al2O3 coated on its bottom, 99.8% of the RhB solution was degraded after 8 h of magnetic stirring and 95.6% of the MO solution was degraded after 12 h of magnetic stirring. Moreover, another contrast was observed between the two beaker bottoms—a new peak at 250 nm in UV–visible absorption spectra was only observed for the MO degradation by CdS in the as-received glass beaker, which indicates that MO molecules were only broken into smaller organic molecules in that case. These findings are meaningful for expanding the catalytic applications of CdS and for achieving a better understanding of tribocatalysis as well. [ABSTRACT FROM AUTHOR]

In dye-sensitized solar cells (DSSCs), materials classified as Transparent Conducting Oxides (TCOs) have the capacity to conduct electricity and transmit light at the same time. Their exceptional blend of optical transparency and electrical conductivity makes them popular choices for transparent electrodes in DSSCs. Fluorine Tin Oxide (FTO) was utilized in this experiment. The optical and electrical characteristics of TCOs may be negatively impacted by their frequent exposure to hostile environments and potential for deterioration. TCOs are coated with passivating layers to increase their performance, stability, and defense against environmental elements including oxygen, moisture, and chemical pollutants. Because of its superior dielectric qualities, strong chemical stability, and suitability with TCO materials, aluminum oxide (Al2O3) was utilized as a passivating layer for the FTO. In this research work, Al2O3 was deposited via atomic layer deposition (ALD) to form thin mesoporous layers as a passivator in the photoanode (working electrode). The work focuses on finding an appropriate thickness of Al2O3 for optimum performance of the dye-sensitized solar cells. The solar simulation and sheet resistance analysis clearly showed 200 cycles of Al2O3 to exhibit an efficiency of 4.31%, which was the most efficient performance. The surface morphology and topography of all samples were discussed and analyzed. [ABSTRACT FROM AUTHOR]

Reports of the influence of surface roughness on the adhesion and tribological performance of contemporary nitride coatings with different layer designs are still scarce in the literature. Therefore, in this study, we evaluated the behavior of a single-layer TiAlN, a bilayer TiAlN/CNx, and a nanolayer AlTiN/TiN coating. Coatings were deposited in an industrial magnetron sputtering unit on the substrates of EN 100Cr6 steel, prepared to four degrees of surface roughness (Sa = 10–550 nm). The coatings' adhesion was determined by scratch tests performed perpendicular and parallel to the machining marks. Dry reciprocating sliding tests in air were employed to evaluate the coatings' tribological behavior against an Al2O3 ball. Before and after the tests, coating properties were characterized by 3D profilometry, confocal microscopy, and energy dispersive spectroscopy. Deposition of all coatings significantly altered the surface topography and increased the roughness of the samples. No general rule could be established for the effect of surface roughness on tribological behavior and adhesion of different hard coatings. For very fine surface finishes the adhesion and tribological performance of TiAlN and TiAlN/CNx coatings was independent of the surface roughness. For the roughest surfaces, a decrease in adhesion and an increase in the wear rate were observed. The AlTiN/TiN coating exhibited the largest sensitivity of adhesion to roughness and scratching direction. The coefficient of friction and wear rate increased when AlTiN/TiN roughness exceeded Sa ≈ 100 nm. [ABSTRACT FROM AUTHOR]

Al2O3 and Ga2O3 exhibit numerous crystal phases with distinct stabilities and material properties. However, the phase transitions among those materials are typically undesirable in industrial applications, making it imperative to elucidate the transition mechanisms between these phases. The configurational similarities between Al2O3 and Ga2O3 allow for the replication of phase transition pathways between these materials. In this study, we investigate the potential phase transition pathway of alumina from the θ-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials, while extending an existing Ga2O3 phase transition path. Through this exploration, we identify a novel single-atom migration pseudomartensitic mechanism, which combines martensitic transformation with single-atom diffusion. This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases. [ABSTRACT FROM AUTHOR]

This work investigates the hybrid nanocomposites manufactured by direct mixing by dispersing varying weight percentages (wt.%) of graphene nanoparticles (GNPs) and Al2O3 NPs in epoxy resin. Their properties are then obtained using various mechanical (tensile, flexural, impact, and hardness) and thermal (thermogravimetric) analyses. Furthermore, their microstructure and functional groups are studied by SEM and FTIR, respectively. The hybrid nanocomposite, which contains 1.5 wt.% GNPs and 8.5 wt.% Al2O3 NPs, has excellent mechanical properties. Compared to a composite without GNPs, the tensile strength, flexural strength, impact strength, and shore D hardness improve by 95.12, 90.01, 171.43, and 19.75%, respectively. It is also found that hybrid nanocomposite exhibits enhanced thermal stability as GNPs increase, particularly at lower wt.% of Al2O3. The SEM of tensile fractured specimens of GNPs/Al2O3 epoxy hybrid nanocomposites reveals prominent failure mechanisms, including agglomeration of GNPs and debonding between the GNPs/Al2O3 and epoxy. The FTIR spectroscopy analysis reveals distinctive spectral peaks indicating successful incorporation of Al2O3 and GNPs into the epoxy‐based composite, with observed peaks corresponding to functional groups and bonds characteristic of each component. These findings suggest that the manufactured nanocomposite holds promise as a component in structural applications, particularly in automobiles, aerospace components, and sports equipment. [ABSTRACT FROM AUTHOR]

This work investigates the behavior and properties of corundum and mullite ceramics at high temperatures and during very long exposures in a controlled atmosphere. The motivation of the work lies primarily in advanced applications in nuclear energy technology, specifically in the search for materials for helium-cooled reactors of the 4th generation. The studied ceramic samples Al63, Al70, Al76, Al96, Al100, where the number indicates the mass percentage of Al 2 O 3 , were exposed for 1000 h at a temperature of 900 °C in gaseous atmospheres of helium, nitrogen and air. The properties of the exposed and unexposed samples were evaluated by measuring the bending strength at room temperature (CMOR), hot modulus of rupture at high temperature (HMOR), and isothermal creep, BET method, and using electron microscopy. The color changes induced by the reducing atmosphere and temperature were also interpreted using a simple thermochemical model. The CMOR measurement results show that all ceramic samples do not significantly change their properties due to long-term exposure. The detected deviations in the exposed samples from the unexposed ones can be considered random caused by the inherent heterogeneous structure. A similar conclusion also applies in the case of the HMOR measurement results, except for the results for the Al63 sample, where the drop in the strength of the exposed samples by approx. 37 MPa (20 %) may be related with the highest proportion of polyvalent oxide admixtures of all studied ceramics, i.e. 1.01 wt % Fe 2 O 3 and 0.52 wt % TiO 2. The change in color indicates that the iron and titanium present are being reduced. However, none of the conducted experiments indicate that changes in the redox state associated with the formation of oxygen vacancies would significantly reduce strength at high temperatures or increase creep in mullite ceramics. [ABSTRACT FROM AUTHOR]

The influences of the increasing content of Al 2 O 3 caused by refractory corrosion on the properties and structures of CaO–MgO-(15 wt%-27 wt%)Al 2 O 3 –SiO 2 –TiO 2 –FeO molten slags were studied at high temperature from 1923 K to 1798 K. The viscosity experimental results indicated that the slag viscosity first increased and then reduced with increasing the Al 2 O 3 content in TiO 2 -bearing slags, and the Al 2 O 3 content that reflected the inflection of the viscosity variation was about 21 wt%. From the Raman and NMR spectra analysis, when the Al 2 O 3 content in the TiO 2 -containing slag was lower than 21 wt%, Al 2 O 3 was an acidic oxide which could increase the viscosity, and with the Al 2 O 3 content in slags further increased to 27 wt%, Al 2 O 3 would behave as network modifiers to decrease the slag viscosity. From the XPS results, the amount of O2− decreased first and then raised, while the ratio of O0 and O− increased and then decreased with adding Al 2 O 3 to slags. The changing trend of the oxygens had a good accordance with the variation of slag viscosities. [ABSTRACT FROM AUTHOR]

A Cu-coated Al 2 O 3 substrates which can be used for power modules are prepared via sintering and reduction of CuO–SiO 2 film onto the surface of Al 2 O 3 ceramic without precious metal brazing filler or high-vacuum equipment. This method has a significant cost advantage over the existing technology. Effects of oxygen partial pressure from sintering atmosphere and SiO 2 content on microstructure and mechanical properties of Cu/Al 2 O 3 interface are systematically investigated. Phase compositions and morphologies of sintered Cu 2 O layer, reduced Cu layer and reactive layer are characterized via X-ray diffraction and scanning electron microscopy. In addition, physicochemical changes within CuO–SiO 2 during sintering are characterized by thermogravimetry-differential scanning calorimeter. It is found that oxygen and SiO 2 can promote the generation of Cu 2 O–CuO–SiO 2 eutectic phase with low melting point upon sintering, which increases the thickness of reaction layer and the densification of Cu layer. The shear strength between the Cu layer and the Al 2 O 3 substrate is enhanced with the increase in Cu layer densification degree, while varying in irregular manner with the thickness of reaction layer. In particular, the highest shear strength of 62.70 MPa is obtained at oxygen partial pressure of 0.02 atm and SiO 2 content of 1.5 wt%. [ABSTRACT FROM AUTHOR]