Thick Aluminum Research Articles

VALIDATION OF CORROSION STATUS OF SOME ROOFING SHEETS UTILIZED IN GOMBE METROPOLIS

The study was aim at investigation the level of corrosion on roofing sheets utilized in Gombe where acid and alkaline medium immersion test of 25 days showed that light zinc (0.15 mm) sample decreased in weight from 0.03g to 0.04 g while the 2.0mm zinc decreased in weight range of 0.01g to 0.04 g in the alkaline solution. Samples of thick aluminum (5.5 mm) and light aluminium(4.5mm) showed insignificant weight range 0.0g to 0.03 g after immersion in alkaline. In acidic medium both light and thick zinc showed greater weight lost 0.05g to 0.08g. However both the thick and light aluminium showed loss of their shiny appearance only with no renowned significant corrosion throughout the twenty-five days of immersion. XRF analysis of the oxides on the corrosion samples of 0.15mm zinc showed decreasing pattern of: Fe2O3 > SiO2.> Na2O >Al2O3 > MnO > CaO respectively. The decreasing order of the percentage of oxides on 2.0mm zinc: Fe2O3 > SiO2 .>Al2O3 > CaO > MnO oxides on 4. 5mm. Aluminium is in decreasing order of; Al2O3 > SiO2.> Fe2O3 > CaO > K2O . On the other side percentage of the oxides of 5.0mm Aluminium is Al2O3 > SiO2 > MnO respectively. Aluminium samples are more durable and resistant which indicates suitability for roofing than zinc sheets.

Online tensile strength prediction considering geometric and physical characteristics during FSW 2219-T8 aluminum alloy plate

Tensile strength of joints of friction stir welded (FSW) thick 2219-T8 aluminum alloy plates, is affected by multiple geometric and physical characteristics, such as axial force, welding temperature, gap, and mismatch of the butt face, which makes it difficult to predict the tensile strength with high precision on line. At present, simple welding process prediction based on temperature or force is difficult to achieve accurate control of complex welding process. In this paper, a multi-information fused one-dimensional Convolutional Neural Network (1DCNN), combining geometric and physical characteristics of welding process, was proposed to predict the tensile strength of joints. Firstly, the experiments of FSW thick 2219-T8 aluminum alloy plates were conducted and the axial force, welding temperature, gap and mismatch of the butt face are measured. Then, the measured multi-source data was fused through down-sampling technology. Before training, the Particle Swarm Optimization (PSO) and Long Short-Term Memory (LSTM) were adopted to optimize the initial learning rate and layer structure of the model. The experiment results showed that the proposed model can accurately and quickly predict the tensile strength of thick 2219-T8 aluminum alloy joints with the mean absolute percentage error less than 2%. In addition, metallographic analysis revealed that the joint tensile strength is interlocked with weld defects and fine grain strengthening. The research lays a foundation for welding quality control of FSW.

Effects of laser shock peening on silicon nitride ceramic with varying sintering additive ratios

Silicon nitride ceramic (Si3N4) for industrial applications is conventionally manufactured with sintering additives, and the properties of Si3N4 change significantly based on the contents of these additives. In this study, we investigate the effects of laser shock peening (LSP) on Si3N4 sintered with varying ratios of sintering additives.The Si3N4 samples were sintered with a mixture of Y2O3, MgO, and SiO2 sintering additives at 5, 7, 9, and 11 wt%. A Nd:YAG laser (wavelength = 532 nm, maximum pulse energy = 1.4 J, repetition rate = 10 Hz, pulse duration = 8 ns, beam diameter = 11 mm, top-hat profile) was used to irradiate the Si3N4 samples. The samples were coated with a protective layer (100 μm thick aluminum foil) and a water layer to confine plasma. LSP of Si3N4 with 5% sintering additives resulted in a slight change in surface hardness but a 77% decrease in surface compressive residual stress. In contrast, LSP of Si3N4 with 11% sintering additives led to a simultaneous increase in surface hardness (7.3%) and surface compressive residual stress (67%), indicating a significant difference in the effectiveness of LSP depending on the ratio of sintering additives. Additionally, the surface of Si3N4 with 11% sintering additives showed evidence of grain refinement after LSP. It was demonstrated that the bending strength of Si3N4 with 11% sintering additives increased by 15.2%, and the depth of the fracture origin was significantly deepened.

Impact response of pseudoelastic nitinol

The response of polycrystalline nitinol with solely austenite structure was studied in three series of planar impact tests characterized by loading of the nitinol samples of 0.5–10 mm thickness by 1 mm thick aluminum impactor accelerated up to velocities of about 387, 429, and 567 m/s. In all the tests, the velocities of the free surfaces of the samples were monitored by a laser velocity interferometer. It was found that in all three test series, the amplitude of elastic precursor wave, being initially greater than 4 GPa, rapidly decays with the propagation distance down to ∼2.5 GPa, below which the decay is hindered by atomic clusters of the nanometer size. Based on the part of the velocity histories indicating the shock-induced austenite–martensite transformation, the initial, of about 2.5 × 103 s−1, and the maximum, up to 1 × 105 s−1, rates of the transformation were determined. As well, the impact stress slightly greater than 4 GPa was determined as that required for the onset of the B2 → B19′ transformation under shock loading. The unloading parts of the same velocity histories allowed a rough estimate of the fraction of the shock-transformed martensite and the elucidation of the virtually complete reversibility of the transformation.

Investigation On Barrier Layers Of PT/BaTiO3/PT Based Thin Film Capacitors

AbstractBarium titanate is a ferroelectric material used as a dielectric in thin film capacitors owing to its high dielectric constant. Barrier layers are utilized in these capacitors to improve the capacitors’ performance by controlling the microstructure and creating thin resistive films. In this paper, the effect of barrier layers in Pt/BT/Pt capacitors is studied using zinc oxide and aluminium oxide. The performance parameters such as capacitance density, leakage current, equivalent series resistance, dielectric loss and dielectric strength of Pt/BT/Pt thin film capacitors with barrier layers of different sizes are simulated using COMSOL Multiphysics modeling software. 2 nm thick aluminum oxide as Pt ‐ BT barrier layer gives optimal performance. The leakage current, dielectric loss, capacitance density, equivalent series resistance and dielectric strength of Pt/BT/Pt capacitor are found to be 0.519 mA, 9.62×10−12, 172.8 fF/μm2, 9.62 kΩ, 108 V/m respectively whereas that of Pt/ALO/BT/ALO/Pt capacitor are found to be 1.56×10−18 A, 7.81×10−18, 11.6 fF/μm2, 9.01×1015 Ω, 5.05×109 V/m respectively. The low capacitance in Pt/ALO/BT/ALO/Pt capacitor is due to the low dielectric constant of aluminium dioxide barrier layer. The reduced leakage current and increased equivalent series resistance is due to the low conductivity of the aluminium oxide barrier layer. The use of aluminium oxide barrier layer between the conductive surfaces can reduce the electric field and increase the breakdown voltage, leading to improved dielectric strength and reduced dielectric loss.

Effect of Relative Density on the Lateral Response of Piled Raft Foundation: An Experimental Study

The population surge has led to a corresponding increase in the demand for high-rise buildings, bridges, and other heavy structures. In addition to gravity loads, these structures must withstand lateral loads from earthquakes, wind, ships, vehicles, etc. A piled raft foundation (PRF) has emerged as the most favored system for high-rise buildings due to its ability to resist lateral loads. An experimental study was conducted on three different piled raft model configurations with three different relative densities (Dr) to determine the effect of Dr on the lateral response of a PRF. A model raft was constructed using a 25 mm thick aluminum plate with dimensions of 304.8 mm × 304.8 mm, and galvanized iron (GI) pipes, each 457.2 mm in length, were used to represent the piles. The lateral and vertical load cells were connected to measure the applied loads. It was found that an increase in Dr increased the soil stiffness and led to a decrease in the lateral displacement for all three PRF models. Additionally, the contribution of the piles in resisting the lateral load decreased, whereas the contribution of the raft portion in resisting the lateral load increased. With an increase in Dr from 30% to 90%, the percentage contribution of the raft increased from 42% to 66% for 2PRF, 38% to 61% for 4PRF, and 46% to 70% for 6PRF.

On the role of local reinforcement in an adhesively bonded AL/CFRP energy absorber under axial loading: A theoretical investigation and optimization

AbstractThis paper aims to develop a novel theoretical model that incorporates the effects of local composite reinforcement using adhesive bonding on the energy absorption of aluminum structures under axial loading. The goal is to optimize energy absorption prior to any connection failures and to prevent uneven structural deformation. Moreover, it strives to reduce the structure's weight and material usage, achieving superior results compared to traditional global reinforcement techniques. The theoretical model was validated through experimental testing and finite element analysis, demonstrating good agreement with the predicted results. The results reveal that increasing the CFRP fiber angle, layer thickness, and number of layers generally leads to improved energy absorption capacity. An optimization analysis was performed to determine the optimal design parameters, yielding a fiber angle of 80°–90°, composite thickness of 1.5 mm, and aluminum thickness of 2.5 is the best configuration, offering the highest specific energy absorption and adequate peak load capacity for maximized energy absorption. The proposed model offers significant improvements over existing approaches, enhancing the predictive capabilities and practical applicability of energy absorption predictions in engineering design.Highlights A novel theoretical model for energy absorption in locally reinforced hybrid AL/CFRP structures. The influence of design parameters, such as CFRP layer count, fiber orientation, and thickness ratio. Optimization to maximize the average crushing force while meeting weight and geometric constraints. Findings can inform the design of safer and more efficient energy‐absorbing structures in various applications.

Effect of Process Parameters on the Mechanical Properties of Simultaneous Double-Sided Friction Stir Welding Joints

Currently, conventional single-sided friction stir welding is primarily suitable for joining thin plate aluminum alloys, and its application to thick plates is still challenging in terms of welding efficiency and joint mechanical properties. Simultaneous double-sided friction stir welding (SDS-FSW) is a high-efficiency joining technique specifically developed for welding thick plates. However, there is little research on the influence of SDS-FSW process parameters on the joint mechanical properties. In this study, a 12 mm thick AA6061-T6 aluminum alloy and dual robot welding equipment are used to conduct SDS-FSW experiments exploring the influence of rotational speed ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega$$\\end{document} and welding speed v on the mechanical properties and microstructure. The results show that when the welding parameters are ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega$$\\end{document} = 800 r/min and v = 60–80 mm/min, smooth and defect-free thick plate aluminum alloy SDS-FSW joints can be obtained, and the macroscopic morphology of the joints is distributed in a “dumbbell” shape. The grain size in the weld nugget zone increases with increasing welding heat input. The microhardness distribution in the joint displays a “W” shape, and the hardness value of the weld nugget zone can reach 67% to 86% of that of the base metal (BM). The junction between the thermo-mechanically affected zone and the heat affected zone is the weakest region of the joint, with the lowest hardness being approximately 51% of that of the BM. When the welding parameters are ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\omega$$\\end{document} = 800 r/min and v = 140 mm/min, the SDS-FSW joint has the highest tensile strength, reaching 78.43% of the BM strength and exhibiting ductile fracture characteristics. This research indicates that acceptable weld strength in thick aluminum alloys can be achieved via the SDS-FSW joining mechanism, highlighting its significant potential for industrial applications.

Dissimilar unbeveled aluminum to steel butt joint achieved by laser-arc hybrid welding-brazing

In this study, unbeveled butt joints of 2 mm thick steel and aluminum plates were welded using a laser-arc hybrid process. The influence of welding speed and wire feed speed on joint weld formation, microstructures, and mechanical properties were investigated. The results indicate that using a laser-arc hybrid heat source enables good weld formation of steel/aluminum dissimilar metals without groove preparation, even under high welding speed conditions. The steel side interface formed Fe₂(Al,Si)₅ near the steel and Fe(Al,Si)₃ near the aluminum. As the welding heat input decreased, the thickness of the intermetallic compounds gradually reduced. With an increase in welding speed or wire feed speed, the tensile strength of the joint first increased and then decreased, reaching a maximum of 104.47 MPa. Cracks propagated rapidly along the intermetallic compound region, resulting in brittle fracture characteristics. The three-point bending test showed a maximum longitudinal bending angle of 53.82° and a maximum transverse bending angle of 36.54°.

Acoustic emission detection and modal decomposition using a relaxor ferroelectric single crystal linear array.

This paper reports on an acoustic emission (AE) sensor based on relaxor ferroelectric single crystal (RFSC) transduction. The sensor crystal is arranged into a Linear Array for Modal Decomposition and Analysis (LAMDA), with the sensor interrogated by a bespoke high-bandwidth instrument. The efficacy of RFSC LAMDA sensors is showcased through a series of comparative experiments, which include the simultaneous acquisition of pencil lead break (PLB) AEs in a 1.6mm thick aluminium plate using RFSC LAMDA, a wideband commercial sensor, and laser vibrometry. Subsequent modal decomposition and analysis of the PLB AE signals, as detected by RFSC LAMDA, identified the guided wave modes below 1.4MHz. Furthermore, it was found that RFSC LAMDA exhibits, on average, 26.6 times greater improvement in sensitivity compared with polyvinylidene fluoride LAMDA variant with near-identical geometry.

Achieving microstructural homogeneity in the stir zone across thick AA6061 welds using self-reacting bobbin tool friction stir welding

This study focuses into strategizing the usage of self-reacting bobbin tool friction stir welding (SRBT-FSW) to obtain consistent microstructural homogeneity along the thickness of AA6061 aluminium alloy (AA) thick plates during welding. The SRBT-FSW technology, distinguished by its dual-shoulder design, represents a significant step forward in FSW by eliminating the requirement for a backing anvil and promoting balanced heat distribution. This study seeks to address the issues of maintaining uniform microstructural characteristics throughout the weld zone, which is crucial for the mechanical performance and durability of welded joints in structural applications. The experimental study entails the systematic welding of AA6061 plates of 6 mm thickness using a self-reacting bobbin tool under a fixed processing condition. Electron backscatter diffraction (EBSD) was used to characterize the grain structure and phase distribution over the weld. Mechanical parameters like as tensile strength and hardness were determined to establish correlations between microstructure and mechanical performance. The results demonstrated that SRBT-FSW significantly enhances microstructural homogeneity across the weld zone, leading to improved mechanical properties. In the Bottom Zone (BZ), a refined grain structure with an average grain size (AGS) of 3.53 µm and a random or weak texture was observed, contributing to enhanced hardness and mechanical performance, with an ultimate tensile strength (UTS) of 220 MPa. In contrast, the Top Zone (TZ) exhibited a coarser AGS of 4.33 µm with a pronounced {111} crystallographic texture, resulting in a slightly lower UTS of 205 MPa. The Middle Zone (MZ), influenced by the greater heat input from both the TZ and BZ, showed an intermediate AGS of 3.99 µm, predominantly oriented along the {101} plane, and achieved a UTS of 194 MPa, with a slight reduction in ductility. This study highlights the potential of self-reacting bobbin tool friction stir welding as a reliable method for making high-quality, homogeneous welds in thick aluminium plates and paving way for their wider application in the aerospace, automotive, and shipbuilding industries, where homogeneous microstructural qualities are of significant importance.

Stepwise double-sided friction stir welding: an alternative for root defect mitigation in aluminium plates with lower gauge numbers

Penetration-induced fractional unbonded defects and flow-induced root flaws are part of the discontinuities of the conventional friction stir welded (FSW’ed) aluminium alloys with limited impact assessment/clarification in literature. The novelty of this study lies in the attempt to eliminate penetration-aided root defect via a stepwise double-sided welding process as well as identify its impact on loadbearing. As a result, the stepwise double-sided FSW welding of a thick aluminium plate (6 mm) was carried out while the microstructure, strength, and fracture modes of the ensuing welds were compared with the conventional (single-sided) friction stir welded counterparts. The stepwise double-sided FSW-welded joint demonstrated better tensile strength relative to the single-sided FSW-welded counterparts owing to its material flow consolidation (two-side deformation) and elimination of penetration-induced fractional unbonded region/root defect. The welding processes do not have a noteworthy influence on the fracture location of the welds as failure ensued via the stir zones of the respective welds. Transient breaking/brittle appearance, and ductile fracture modes were noticed in the single-sided and stepwise double-sided FSW-welded samples respectively. The stepwise double-sided FSW process is recommended as a better choice for thick workpieces relative to conventional FSW to improve the weld’s loadbearing resistance.

Ultrasonic Welding Parameter Optimization for Electric Component Welding

Industrial requirements to establish metallic joints between dissimilar metals in the electric area. The ultrasonic welding process is an optimal process to joint thin sheets or foils. The goal of the research was to optimize the ultrasonic welding parameters to join thin nickel-coated copper sheets and aluminium sheets. It used a 0.5 mm thick high-purity copper (Cu-OF-R200) sheet coated with a 10 μm pure nickel layer and a 0.5 mm thick aluminium (1050A H24) sheet. The ultrasonic welding is made by a Branson Ultraweld L20 ultrasonic welder equipment. The mechanical properties and exacting geometrical tolerance of the joint were required. The welding parameter optimization is made empirically, with several welding tests. The optimal welding parameters were confirmed by non-destructive and destructive tests of the joints. The non-destructive tests were the visual inspection and geometrical measurements of the joint sizes. The destructive tests were tensile tests and macroscopic and microscopic tests. The completed test results confirmed the process applicability and the quality of the joint.

Optimizing performance of hybrid fiber reinforced overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) offer significant weight advantages over traditional all-metal vessels particularly in industries like aerospace, automotive and pharmaceutical, but pose unique challenges in mechanical design, fabrication, and testing. Despite their benefits, COPVs are susceptible to stress rupture failure, which can lead to catastrophic consequences during operation. This failure mode is not fully understood, with burst pressure-induced extreme stress concentrations and dynamic loading primarily contributing to rapid deformation and strain. To address these concerns, a comprehensive investigation was conducted, focusing on optimizing and examining the effects of optimum winding angle and lay-up pattern configuration on burst pressure in vessels under internal pressure. Finite element modeling analyzed the burst pressure behavior of COPVs with a 4 mm thick aluminum core cylinder and varying layers of carbon/fiber epoxy, each with a constant thickness. ABAQUS composite modeler generated 18 COPV models with carbon fiber/epoxy plies, ensuring uniform thicknesses while exploring different fiber orientations. The effects of ply stacking sequence were analyzed through finite element analysis for all models, comprising varying layers with uniform thicknesses. Attention was paid to failure criteria, methodically evaluating the burst strength of the Al/CFRPC COPVs This exhaustive analysis yielded an optimal COPV design profile characterized by a precisely calibrated ply stacking sequence of [24.50, −24.50] PP winding pattern and six (6) arranged layers. The stress-strain distribution analysis of the Composite Overwrapped Pressure Vessel (COPV) revealed both a uniform distribution of stress across its surface and extreme stress concentration, particularly peaking towards the polar boss region. This concentration is discernible due to variations in ply thickness induced by the overwrapped fiber orientation. This investigation provides valuable insights for optimizing COPV design and enhancing its performance and reliability in various applications.

Study on the fatigue properties of SPR-bonded aluminum-steel sheet joints

This study deals mainly with the influence of adhesive layer on the fatigue behavior and fretting of self-piercing riveted (SPR) joint joining differing thicknesses of AlSi10MnMg aluminum and DP590 steel sheets in lap shear geometry. Fatigue life, failure modes, crack propagation and fretting behaviors of the SPR and SPR-bonded joints were investigated and compared. The results showed that the static strength and fatigue life of SPR-bonded joints were significantly enhanced than that of SPR joints, but the fatigue failure mode of SPR-bonded and SPR joints differed. The SPR-bonded joints all failed in a rivet tail pull-out mode at all tested loads, which accompanied with small cracking in the aluminum sheet in contact with the rivet tail at lower test load. However, the failure mode of the SPR joints shifted from the aluminum sheet cracking to rivet tail pull-out as the fatigue test load increased. And during the aluminum sheet cracking failure, the fatigue crack originated from the faying interface of aluminum and steel sheet at the vicinity of the rivet shank and propagated along the width direction of aluminum sheet. Fretting wear analysis showed that the overall extent of fretting decreased and the location of fretting areas varied due to the adhesive bonding. Fretting of SPR joints mostly existed at the faying interface between aluminum and steel about 1.5 mm away from the rivet shank and resulted in fatigue crack initiation, while the fretting region of SPR-bonded joints shifted to the faying interface between rivet tail and aluminum sheet.

Experimental and Numerical Evaluation of Calcium-Silicate-Based Mineral Foam for Blast Mitigation

Cellular materials such as aluminum and polyurethane foams are recognized for their effectiveness in energy absorption. They commonly serve as crushable cores in sacrificial cladding for blast mitigation purposes. This study delves into the effectiveness of autoclaved aerated concrete (AAC), a lightweight, porous material known for its energy-absorbing properties as a crushable core in sacrificial cladding. The experimental set-up features a rigid frame made of steel measuring 1000 × 1000 × 15 mm3 with a central square opening (300 × 300 mm2) holding a 2 mm thick aluminum plate representing the structure. The dynamic response of the aluminum plate is captured using two high-speed cameras arranged in a stereoscopic configuration. Three-dimensional digital image correlation is used to compute the transient deformation fields. Blast loading is achieved by detonating 20 g of C4 explosive set at 250 mm from the plate’s center. The study assesses the mineral foam’s absorption capacity by comparing out-of-plane displacement and mean permanent deformation of the aluminum plate with and without the protective solution. Six foam configurations (A to F) are tested experimentally and numerically, varying in the foam’s free space for expansion relative to its total volume. Results show positive protective effects, with configuration F reducing maximum deflection by at least 30% and configuration C by up to 70%. Foam configuration influences energy dissipation, with an optimal lateral surface-to-volume ratio (ζ) enhancing protective effects, although excessive ζ leads to non-uniform foam crushing. To address the influence of front skin deformability, a non-deformable front skin has been adopted. The latter demonstrates an increased effectiveness of the sacrificial cladding, particularly for ζ values above the optimal value obtained when using a deformable front skin. Notably, using a non-deformable front skin increases maximum deflection reduction and foam energy absorption by up to approximately 30%.

Parameter dependence of depth and lateral resolution of transmission Kikuchi diffraction

The spatial resolution of transmission Kikuchi diffraction (TKD) depends on experimental parameters such as atomic number, accelerating voltage, sample backtilt and thickness. In this work, the dependence of spatial resolution on these parameters is explored by using bilayered coarse-grained/nanocrystalline samples to determine the depth resolution. Digital image correlation of the Kikuchi patterns across grain boundaries is used to measure the lateral resolution. The depth resolutions of TKD in aluminium, copper and platinum at 30 kV for an untilted sample were 80, 32 and 14 nm respectively. These worsened with increasing sample backtilt and slightly improved with decreasing accelerating voltage. The best physical lateral resolution obtained was 6 nm, at 30 keV in a 41 nm thick aluminium sample with no backtilt. The lateral resolution worsened with increasing sample thickness and backtilt, contrasting with some previous reports. Accelerating voltage and atomic number did not have a significant impact on the measured lateral resolution within the scatter in the data.

Rapid α-Al2O3 Growth on an Iron Aluminide Coating at 600 °C in the Presence of O2, H2O, and KCl.

In this work, a slurry iron aluminide-coated ferritic steel SVM12 was subjected to a laboratory experiment mimicking superheater corrosion in a biomass-fired power boiler. The samples were exposed under model Cl-rich biomass conditions, in a KCl + O2 + H2O environment at 600 °C for 168, 2000, and 8000 h. The morphology of corrosion and the composition of the oxide scale and the coating were investigated by a combination of advanced analytical techniques such as FESEM/EDS, SEM/EBSD, and XRD. Even after short-term exposure, the coating developed a very fast-growing and up to 50 μm thick α-Al2O3 scale in contrast to the spontaneous formation of a protective, thin, dense, slow-growing, and very adhesive α-Al2O3 layer usually formed on metallic materials after high-temperature oxidation. In view of the literature on the formation of oxide scales on alloys and coatings, the formation of an α-Al2O3 scale at this relatively low temperature is very surprising in itself. The thick alumina scale was not protective as its formation resulted in fast degradation of the coating and rapid Fe2Al5 → FeAl phase transformation, which in turn generated porosity inside the coating. In all cases, the resulting thick Al2O3 scale was porous and consisted of both equiaxed α-Al2O3 grains and randomly oriented aggregated alumina whiskers. Potassium is concentrated in the outer part of the Al2O3 scale, while chlorine is concentrated close to the scale/aluminide interface. The unexpected formation of rapidly growing α-Al2O3 at relatively low temperature is attributed to the hydrolysis of aluminum chloride generated in the corrosion process.

Assessment of the Radiopacity of Different Fissure Sealants Compared to Dental Hard Tissues

Aim: The radiopacity of dental materials is crucial for assessing the radiographic success of restorations and can significantly influence clinicians' choice of materials. The objective of our study is to compare the radiopacity of five fissure sealants with that of compomer, composite, glass ionomer filling, and dental hard tissues using digital imaging techniques. Material and Method: Five different fissure sealants (Fuji Triage, BeautiSealant, Grandio Seal, Helioseal F Plus, Embrace Wetbond), compomer (Compoglass F), composite (Solare X), and glass ionomer filling (Equa Forte) materials were prepared as 5 samples each in disk form with a thickness of 2 mm. As controls, sections of primary and permanent teeth with a thickness of 2 mm, along with an aluminum step wedge were utilized. The mean gray values of the samples were measured using Image J software, and the equivalent aluminum thickness was subsequently determined. Statistics analysis using Kruskal-Wallis test at p<0.05. Results: The equivalent aluminum thicknesses related to the radiopacity of fissure sealants are ranked as follows: Fuji Triage (5.2±0.2) > Grandio Seal (3.9±0.2) = permanent tooth enamel (3.7±0.2) = Embrace Wetbond (3.6±0.6) = primary tooth enamel (3.6±0.3) = BeautiSealent (2.1±0.3) > Helioseal F Plus (1.1±0) (p<0.05). The radiopacity equivalent aluminum thicknesses of restorative materials are ranked as follows: Compoglass F (7.3±0.4) > Solare X (4.7±0.3) = Equa Forte (4.4±0.4) = permanent tooth enamel (3.7±0.2) = primary tooth enamel (3.6±0.3) (p<0.05). Conclusion: Materials like Fuji Triage and Compoglass F exhibit high radiopacity values, which can significantly aid clinical monitoring and restoration success.

Measurements of fluctuation-induced in-plane magneto-conductivity of granular aluminum film

The phenomenon of Berezinskii–Kosterlitz–Thouless (BKT) phase fluctuations and the superconducting fluctuations is investigated in a 40 nm thick granular aluminum film using magneto-transport measurements. The transport measurements suggest the possibility of strong electron–phonon (el–ph) interactions in contrast to a Bardeen–Cooper–Schrieffer superconductor. It shows a BKT transition of 2.304 K and a superconducting mean-field transition at 2.32 K. The presence of the resistive tail even before the BKT transition reflects the abundance of thermally activated free vortices. By analyzing the excess conductivity, Gaussian–Ginzburg–Landau superconducting fluctuations are observed above the superconducting transition, which causes rounding of the transition region even before the superconducting transition. The temperature dependence of the fluctuation conductivity in zero magnetic field exhibits distinct signatures of the two-dimensional direct Aslamazov–Larkin theory, with a significant contribution from the Maki–Thompson (MT) model. Furthermore, the anomalous behavior of the fluctuation conductivity at higher temperatures and perpendicular magnetic fields (up to 700 mT) is explained in terms of the total-energy cutoff (=0.72) in the low-wavelength region of the superconducting fluctuations and a pair-breaking parameter (∼0.031). Further studies on the pair-breaking parameter indicate the presence of the el–ph scattering, which diminishes the MT contribution. Our study carries important bearings on how the BKT phase fluctuations and superconducting amplitude fluctuations control the conductivity of granular superconductor near and above the transition region as non-equilibrium properties of weakly disordered granular superconductors. This research is of significance, offering insights into the fundamental properties of granular superconductivity and aiding in the comprehension of nano-structured thin film devices.