TEM Investigations Research Articles

Structural, microstructural characterization and luminescence spectroscopy of europium-doped strontium titanate prepared by the sol-gel method

In this work, we report on the polycrystalline Sr1-3x/2EuxTiO3, x = 0.01–0.07 materials prepared by the sol-gel route and their optical properties. The Sr1-3x/2EuxTiO3 powders calcined at 1000 °C showed a microstructure consisting of nanograins with average particle size decreasing from 86.32 nm to 51.87 nm with the increase of Eu amount from 1 at% to 7 at% Eu, as revealed SEM and TEM investigations. Optimized sintering conditions of Eu-doped SrTiO3 ceramics (1400 °C, 4h in air) led to materials with a single phase of cubic SrTiO3. The high purity and uniform distribution of the chemical elements of as-fabricated SrTiO3 doped with Eu guaranteed good optical properties. The emission of the Eu3+ ion mainly occurs for the transitions from the 5D0 level to the levels of the 7Fj (j = 1, 2) term, more precisely, the 5D0 → 7F2 electric dipole transition (∼615 nm) or the 5D0 → 7F1 magnetic dipole transition (∼595 nm). The CIE coordinates of all samples calculated from the emission spectra obtained under the 395 nm and 465 nm excitation wavelength are located in the orange-red region. Therefore, this europium-doped SrTiO3 phosphor is a promising candidate for application as a red-emitting component in solid-state light sources.

Ultrahigh adsorption capacity of a new metal sieve-like structure nanocomposite-based chitosan-graphene oxide nanosheet coated with poly-o-toluidine for the removal of Acid Red dye from the aquatic environment

This article describes an easy and simple method to remove a toxic Acid Red dye from aqueous solution. Ternary poly(O-toluidine)/graphene oxide/chitosan P(OT)/GO/CS nanocomposites (NCs) were fabricated by an oxidative polymerization technique to remove Acid Red (A.R.) dye from aqueous solutions using solid-phase extraction. The P(OT)/GO/CS NCs exhibit a metal sieve-like structure consisting of GO nanosheets and a core shell-shell porous structure, which provides several adsorption sites and channels for the transport of dye molecules. FTIR, XRD, RAMAN, TEM, SEM, BET, and TGA-DTG investigations were carried out on NCs. To investigate the removal effectiveness of the NCs using adsorbent dose, pH and solution temperature, shaking time, and ionic strength. Experimental adsorption findings, utilizing 15 mg of solid-phase NCs, can remove the majority of the A.R. dye in 75 min at pH 2.0 with an adsorption efficiency and an adsorption capacity of 99.6% and 169.5 mg/g, respectively. The pseudo-second-order kinetic model best captures the adsorption process of A.R. dye on the NC solid phase, according to experimental data. Thermodynamically, the removal process was endothermic, spontaneous, and associated with increasing randomness. Finally, NCs were tested by removing A.R. dye from real samples. NCs removed A.R. dye from aqueous solutions for four cycles.

Evaluation of curcumin-loaded chitosan nanoparticles for wound healing activity.

Wound healing is a biological process that can be difficult to manage clinically. In skin wound healing, the interaction of many cells, growth factors, and cytokines reveals an outstanding biological function mechanism. Wound healing that occurs naturally restores tissue integrity, however, it is usually restricted to wound repair. Curcumin synthesised in a chitosan matrix can be used to heal skin sores. The ionotropic gelation procedure required crosslinking chitosan with a tripolyphosphate (TPP) crosslinker to generate curcumin nanoparticles encapsulated in chitosan. The nanoparticles were between 200 and 400 nm in size, with a strong positive surface charge and good entrapment efficacy, according to SEM and TEM investigations. Curcumin and chitosan compatibility was investigated using FTIR spectroscopy. All batches showed consistent drug release, with the F5 batch having the highest curcumin release, at 75% after 16 hours. On L929 cells, scratch assays were utilised to assess wound healing. Wound closure with widths of 59 and 65 mm with curcumin and 45 and 78 mm with curcumin-loaded chitosan nanoparticles was seen after 24 and 48 hours of examination. According to the findings, prepared curcumin chitosan nanoparticles are beneficial in healing skin damage.

Exploring Kinnow mandarin's hidden potential: Nature's key to antimicrobial and antidiabetic gold nanoparticles (K-AuNPs)

This pioneering study aims to address the paradox of the highly regarded Kinnow mandarin fruit, whose valuable peels have been considered undesired remnants from industrial fruit juice production. The study proposes the utilization of these discarded peels to synthesize ecologically safe gold nanoparticles (K-AuNPs) through a one-pot method. The objectives of this research are to synthesize K-AuNPs using an ecologically safe single-step approach, utilizing discarded Kinnow mandarin fruit peels, and to assess their antibacterial and antidiabetic potential.The validation of K-AuNPs involved various techniques including UV–visible spectroscopy, TEM, DLS, and zeta-potential investigations. The antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis was compared to levofloxacin and Kinnow mandarin aqueous peel extract (KAPE). Furthermore, the anti-diabetic efficacy was evaluated through α-amylase and α-glucosidase experiments, comparing K-AuNPs to pure KAPE and the standard inhibitor acarbose.The results confirmed the successful synthesis of K-AuNPs from KAPE, as evidenced by UV-spectral profiles (527 nm), TEM micrographs (∼21 d. nm), dynamic light scattering (65 d.nm), and zeta-potential (-12 mV). The K-AuNPs demonstrated a superior zone of inhibition and lower MIC values against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis, surpassing levofloxacin and KAPE alone. Additionally, the K-AuNPs exhibited potent anti-diabetic efficacy, outperforming both pure KAPE and acarbose at a lower dosage.To sum up, the process of producing K-AuNPs utilizing Kinnow mandarin peel extracts demonstrates a powerful antibacterial and antidiabetic remedy sourced from previously discarded materials. These findings signify a significant leap forward in the domain of natural product exploration, with the potential to fundamentally reshape modern healthcare approaches.

Evolution of dislocation loops and voids in post-irradiation annealed ThO2: A combined in-situ TEM and cluster dynamics investigation

The effect of isochronal annealing on the evolution of dislocation loop and void population in proton irradiated ThO2 has been investigated. Post-irradiation annealing in other actinide oxides like UO2 shows significant loop coarsening. ThO2 samples were irradiated with 2 MeV protons up to a dose of 0.1 dpa at 600 °C. Post-irradiation isochronal annealing was performed at 600, 800, 1000 and 1100 °C for 1 h at each temperature using in-situ TEM. Only faulted 1/3<111> type dislocation loops were observed, and their sizes and distribution were characterized. The population of self-interstitial atom (SIA) dislocation loops did not show any significant growth and coarsening. Additionally, nanometric voids were observed at annealing temperatures of 1000 and 1100 °C. Using cluster dynamics (CD), we have studied the nucleation and growth of point defects and defect clusters, i.e., SIA prismatic dislocation loops and nanometric and sub-nanometric voids in proton irradiated ThO2. The CD model was further utilized to predict the growth and coarsening of loops and voids during isochronal annealing at the experimental and higher temperatures. The model did not predict significant SIA loop growth which closely corresponds to the TEM observations. CD predicted SIA loop coarsening is insignificant even at high annealing temperature of 1500 °C because the model only considers the growth of defect clusters by absorption of like point defects, i.e., SIA loops absorb interstitials and voids absorb vacancies, and cannot account for their migration and coalescence due to elastic interaction. The CD model also predicts the evolution of nanometric voids having mean size within the error bounds of TEM observations.

Reductive Treatment of Pt Supported on Ti0.8Sn0.2O2-C Composite: A Route for Modulating the Sn-Pt Interactions.

The composites of transition metal-doped titania and carbon have emerged as promising supports for Pt electrocatalysts in PEM fuel cells. In these multifunctional supports, the oxide component stabilizes the Pt particles, while the dopant provides a co-catalytic function. Among other elements, Sn is a valuable additive. Stong metal-support interaction (SMSI), i.e., the migration of a partially reduced oxide species from the support to the surface of Pt during reductive treatment is a general feature of TiO2-supported Pt catalysts. In order to explore the influence of SMSI on the stability and performance of Pt/Ti0.8Sn0.2O2-C catalysts, the structural and catalytic properties of the as prepared samples measured using XRD, TEM, XPS and electrochemical investigations were compared to those obtained from catalysts reduced in hydrogen at elevated temperatures. According to the observations, the uniform oxide coverage of the carbon backbone facilitated the formation of Pt-oxide-C triple junctions at a high density. The electrocatalytic behavior of the as prepared catalysts was determined by the atomic closeness of Sn to Pt, while even a low temperature reductive treatment resulted in Sn-Pt alloying. The segregation of tin oxide on the surface of the alloy particles, a characteristic material transport process in Sn-Pt alloys after oxygen exposure, contributed to a better stability of the reduced catalysts.

High-Temperature Mechanical Properties of NbTaHfTiZrV0.5 Refractory High-Entropy Alloys.

The NbTaHfTiZrV0.5 is a refractory multi-principal-element alloy with high strength and good ductility at room temperature. It is important for possible high-temperature applications to investigate the deformation mechanism of the NbTaHfTiZrV0.5 alloy at different temperatures using tensile tests. In this investigation, the tensile tests were conducted at room temperature to 1273 K on sheet materials fabricated by cold rolling combined with annealing treatments. At 473 K, the NbTaHfTiZrV0.5 alloy exhibited a high tensile ductility (12%). At a testing temperature range of 673~873 K, the ductility was reduced, but the yield strength remained above 800 MPa, which is rare in most other alloys. The TEM investigations revealed that a dislocation slip controlled the plastic deformation, and the degree of deformation was closely related to the dislocation density. The true stress-strain curves of the alloy under different deformation conditions were obtained by tensile deformation at different deformation temperatures (673~873 K) and strain rates (0.001~0.0005 s-1). Experimental results were utilized to construct the parameters of a constitutive model based on a traditional mathematical model to predict the flow behavior at high temperatures. The excellent high-temperature mechanical properties of the NbTaHfTiZrV0.5 alloy will enable it to be used in several engineering applications.

Influence of Dy3+ ion concentration on structural, photoluminescence and energy transfer mechanism of promising GdSr2AlO5 nanophosphors for white light applications

Influence of the trivalent dysprosium ion on the structure and luminescent properties of Gd1-xSr2AlO5:xDy3+ (x = 1–6 mol %) phosphors were examined. Creation of structures, photoluminescence efficacy, optical characteristics and energy transfer were all carefully inspected. X-ray diffraction patterns endorse single phase formation of all fabricated samples with tetragonal structure having space-symmetry of I4/mcm (space group No. 140). SEM and TEM investigation validates the good morphology which having particle in nanorange. EDX analysis affirms the formation of material with proper stoichiometry. The excitation spectrum of the optimum sample contains absorption peaks corresponding to the Gd3+ as well as Dy3+ ions and sharp and intense peak of Gd3+ ion in comparison to the Dy3+ ion, confirms the occurrence of significant energy transfer between Gd3+ and Dy3+ ions. The Dy3+ ions transitions 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 were identified in the PL spectra at an excitation of 351 nm as bluish, yellowish and reddish bands at 488, 582 and 669 nm respectively. Due to charge transference from Gd3+ to Dy3+ ions, fabricated materials under Gd3+ excitation (272 nm) showed emission peaks owing to both the Gd3+ and Dy3+ transition. Concentration quenching with respect to the luminescence performance occurs due to the quadrupole-quadrupole interactions between nearest activator ions. Photometric characteristics were also evaluated in order to define whether the phosphors are appropriate for white light emitting diodes.

Steering the Au−FexCo1Oy interface for efficient imine synthesis at low temperature via oxidative coupling reaction

Low-temperature imine formation through oxidative coupling of alcohols with amines under base-free conditions is very important for fine-chemical synthesis. Supported-Au catalysts show superior performances toward selective oxidation reactions but are scarcely reported for the above application. In this work, the finely-dispersed Au nanoparticles (ca. 2.4 nm) loaded on magnetic FexCo1Oy oxides were developed as novel, efficient and reusable heterogeneous catalyst. Varying the Fe/Co molar ratio allowed tuning the Au−FexCo1Oy interface and further boosting the selective oxidation performance of Au. The optimum Au/Fe0.25Co1Oy catalyst showed >99% yield of benzylideneaniline and 20.1 molimine molAu−1 h−1 productivity using the model reaction at 30 °C under air atmosphere without alkaline additives. This was the best result compared to benchmark Au-based catalysts in the literature. In addition, this catalyst exhibited superior performances towards gram-scaled synthesis and diverse substrates. XRD, N2-physisorption, TEM, H2-TPR, O2-TPD, EPR, pyridine-adsorbed FT-IR, and kinetic investigations were used to study this Au catalytic system. It was found that the synergy between Fe2O3 and Co3O4 can induce formation of abundantly mobile and reactive oxygen species (i.e., O2− and O− related to oxygen vacancies) and electron-rich metallic Au species on the surface of mesoporous FexCo1Oy oxides. These interfacial features were disclosed to be vital to activating molecular O2 and O H bond in an alcohol. Besides, it was demonstrated that the surface Lewis acidic sites associated with coordinatively unsaturated Co3+ ions can help facilitate the tandem oxidation-condensation reactions.

Green Synthesis of Zinc Oxide Nanoparticles Using Viscum album Extracts: Unveiling Bioactive Compounds, Antibacterial Potential, and Antioxidant Activities.

The current study explored the antioxidant and antibacterial capabilities of zinc oxide nanoparticles (ZnONPs) synthetized using methanolic leaf extracts of the medicinal herb Viscum album. Through TEM investigation and UV-Vis analysis, which peaked at 406 nm, the synthesis of ZnONPs was verified. TEM analyses showed that the synthesized ZnONPs had a size distribution with an average of 13.5 nm and a quasi-spherical shape. Forty-four phytoconstituents were found in the methanolic leaf extracts of V. album. Additionally, a comparison of the antibacterial effectiveness and antioxidant capacity of aqueous and methanolic extracts of wild-grown V. album phytomedicine and green-manufactured ZnONPs was conducted. The green-generated ZnONPs were examined against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa and shown to have superior antibacterial activity by 22%, 66%, and 44%, respectively, as compared to wild herbal medicinal extracts. Since the ZnONPs' aqueous extracts had higher concentrations of DNA gyrase-B inhibitory components, they were shown to be more effective in limiting bacterial growth. In contrast to the percentages of 49% and 57% for a wild plant extract, the aqueous- and methanolic-extract-mediated green ZnONPs, with a 100 g/mL concentration, showed 94% and 98% scavenging capacity for DPPH free radicals, respectively. However, methanolic extracts were more effective than aqueous extracts in terms of the antioxidant analyses. This study establishes that greenly produced ZnONPs have the potential to be used in nanomedicine to treat bacteria that are resistant to a variety of drugs, as well as those with reactive oxygen species toxicity.

Facile Synthesis of Vanadium Oxide/Carbon Spheres-Doped Nickel Oxide Functioned as a Nanocatalyst and Bactericidal Behavior with Molecular Docking Analysis.

Vanadium oxide (V2O5) and carbon spheres (Cs)-doped NiO2 nanostructures (NSs) were prepared using the co-precipitation approach. Several spectroscopic and microscopic techniques, including X-ray diffraction (XRD), UV-vis, FTIR, TEM, and HR-TEM investigations, were used to describe the as-synthesized NSs. The XRD pattern exhibited the hexagonal structure, and the crystallite size of pristine and doped NSs was calculated as 29.3, 32.8, 25.79, and 45.19 nm, respectively. The control sample (NiO2) showed maximum absorption at 330 nm, and upon doping, a redshift was observed, leading to decreased band gap energy from 3.75 to 3.59 eV. TEM of NiO2 shows agglomerated nonuniform nanorods exhibited with various nanoparticles without a specific orientation; a higher agglomeration was observed upon doping. The (4 wt %) V2O5/Cs-doped NiO2 NSs served as superior catalysts with a 94.21% MB reduction in acidic media. The significant antibacterial efficacy was estimated against Escherichia coli by measuring the zone of inhibition (3.75 mm). Besides their bactericidal analysis, V2O5/Cs-doped NiO2 was shown to have a binding score of 6.37 for dihydrofolate reductase and a binding score of 4.31 for dihydropteroate synthase in an in silico docking study of E. coli.

In-situ TEM investigation of void swelling in nickel under irradiation with analysis aided by computer vision

Understanding the stability of irradiation-induced voids in materials is important for engineering material's swelling behavior under irradiation. In-situ TEM offers a spatial and temporal resolution that is suitable for investigating the evolution of voids under irradiation. However, the in-situ videos have often been too large to be analyzed manually, leaving the valuable data underutilized. We developed a deep learning-based semantic segmentation model to consistently study the growth and shrinkage of voids in nickel under 1 MeV krypton ion irradiation at various temperatures from 525 °C to 650 °C. With a foil thickness near 100 nm and ion flux of 6.3 × 1011 ions⋅ cm−2⋅s−1, the pre-existing voids, which were created beforehand by irradiation at 600 °C to 0.5 dpa, shrank at low temperatures and grew at high temperatures under irradiation, where the transition occurred at 575 °C (∼0.5 TM). The observed stability transition provided new insight for the shrinkage mechanism of voids under irradiation. In addition, an annealing experiment on nickel, previously irradiated at 600 °C to 3 dpa, was performed sequentially at 650 °C to 720 °C to reveal the shrinkage rate of void as a function of temperature and void size. The advantage of combining computer vision and in-situ TEM to obtain comprehensive void evolution was demonstrated.

A hierarchically porous MOF confined CsPbBr3 quantum dots: Fluorescence switching probe for detecting Cu (II) and melamine in food samples

The hypersensitivity of Perovskite quantum dots (PeQDs) towards external environmental conditions and the water quenching of their fluorescence have limited their practical analytical applications. In this work highly luminescent CsPbBr3 was confined into a hierarchically porous ZIF-8 metal organic framework (HZIF-8) through a simple two step in situ growth method. XRD, FTIR, SEM, TEM, and XPS investigations confirmed the successful synthesis of the CsPbBr3/HZIF-8 nanocomposite. CsPbBr3 PeQDs are uniformly distributed within the HZIF-8 MOF matrix and exhibited intense green emission at 510 nm with a FWHM value of 25 nm in ambient conditions. The nanocomposite showed enhanced stability against moisture and UV light. The intense PL emission of the nanocomposite was well maintained in an aqueous solution also, with no noticeable change in fluorescence characteristics for 15 days of storage in aqueous solution. The CsPbBr3/HZIF-8 composite was then utilized as an on–off-on luminescent probe for the detection of Cu2+ metal ions and melamine in real samples. Because of the porous nature of the MOF, the target analytes can be quickly located and this nanosensor is found to be very sensitive toward Cu2+ and melamine detection. A linear relationship from 3 to 500 nM and 30–1500 nM was found for melamine and Cu2+ under an optimal experimental condition, with a limit of detection value of around 4.66 nM and 2.64 nM for Cu2+ and melamine respectively.

Highly efficient AgVO3/WO3 photocatalyst n-n heterojunction toward visible-light induced degradation antibiotic

In the present work, WO3 NPs were fabricated using a facile hydrothermal method assisted by polyvinylpyrrolidone (PVP) for the first time, and AgVO3 with different weight percentages (3%, 6%, 9% and 12%) was uniformly distributed on the surface of mesoporous WO3 by impregnation - calcination processes to construct n-n heterojunction AgVO3/WO3 nanocomposites. The obtained AgVO3/WO3 nanocomposites were utilized for the effective Ciprofloxacin (CIP) degradation during visible illumination. The XRD and TEM investigations verified the formation of AgVO3 and WO3 in a monoclinic crystal structure with a particle size of 40 nm. XPS and TEM measurements evidenced the existence of Ago and Ag+ in the heterostructure AgVO3/WO3 system. 9%AgVO3/WO3 nanocomposite exhibited larger photocatalytic performance, i.e., 100% with 120 min of illumination, than the other nanocomposite photocatalysts. The apparent rate constant of 9% AgVO3/WO3 nanocomposite (0.0162 min−1) was enhanced 18 times greater than the WO3 NPs (0.0009 min−1). The efficient photocatalytic performance could correlate with the close contact between AgVO3 and WO3 NPs, which enhanced the visible light absorption and efficacious separation of the carriers during degradation reactions. The AgVO3/WO3 nanocomposite obeyed the S-scheme mechanism for charge transfer to achieve promising redox abilities in both AgVO3 and WO3. The optimized 9% AgVO3/WO3 photocatalyst showed high reusability and photostability for five consecutive runs without loss its efficiency. This study provides a new mechanism for addressing highly effective nanocomposites with excellent photocatalytic ability that exhibit practical applications in the environmental remediation of antibiotics.

TEM investigation of reduced activation ferritic/martensitic alloys developed by thermodynamic modeling

Two reduced activation ferritic/martensitic (RAFM) alloys with chemical compositions guided by thermodynamic modelling were designed, fabricated, and mechanically tested in previous work. The experimental alloys demonstrated significantly refined grain and subgrain size with a high density of dislocations leading to higher yield and tensile strength with respect to EUROFER97–2 without sacrificing the impact toughness. This improvement has been achieved thanks to the dedicated chemical and thermal treatment that alternates the nucleation, growth and coarsening as well as enables the presence of high-density small precipitates as compared to EUROFER97 steel. In this work, TEM investigation was performed to quantitatively describe the microstructural parameters such as the average sizes of M23C6 and MX particles, number density of the particles and dislocation density. Furthermore, the strengthening contribution of each microstructural feature was calculated, and the correspondence of the total strength derived via microstructure to the measured yield strength is discussed.

The synergistic effects of nano-sized α-Al(Mn,Cr,Fe)Si and Al–Si–Zr dispersoids on the creep behavior Al–Si–Mg–Cu (Mn, Cr, Zr) diesel engine alloy

The influence of Mn, Cr and Zr on the creep behavior of an Al–Si–Mg–Cu alloy intended for Diesel engine applications was studied. Two alloys, base alloy Al–7Si-0.3Mg-0.5Cu (MG1) and Al–7Si-0.3Mg-0.5Cu-0.15Mn-0.25Cr-0.15Zr (MG2-1) were creep tested at 300–350 °C and 28 MPa in the T7 heat-treated and soaked (100 h at 300 °C) condition. The apparent activation energy for creep for MG1 was 184 kJ mol−1 and for the MG2-1 was 234 kJ mol−1. The two alloys exhibited differing rate controlling creep mechanisms. The minimum creep rates of the MG2-1 alloy were 3–5 times lower than the MG1 alloy at 300 °C and 325 °C, respectively and only 1.3 times lower at 350 °C. The TEM investigation indicated creep deformation in the MG2-1 alloy was due to thermally activated restoration processes where grain boundary migration experienced Zener pinning by coherent and ∼5 nm αMG2-1-Al(Mn,Cr,Fe)Si. In the MG1 alloy, the creep mechanism was identified as climb over nano-sized (∼50 nm) non-coherent α-Al(Mn,Fe) dispersoids. EDS analysis showed that semi coherent Q’ phase (near equilibrium version of Q phase) existed in the MG1 alloy that had a nucleating role for nano-sized non-coherent α-Al(Mn,Fe) dispersoids.

Microstructure and phase composition of transition zone between low alloyed steel boiler tube and an austenitic stainless steel weld overlay produced by cold metal transfer method

The microstructural characterization, as well as phase and chemical composition of the transition zone between the 16Mo3 steel boiler tube and 310 austenitic stainless steel weld overlay produced by the Cold Metal Transfer method, were studied.It was showed that the transition zone has a complex structure related to the changing composition. Two separate areas are noticeable in the transition zone. The area near the fusion boundry is two phased (martensite and austenite). Detailed TEM investigation of this area disclosed martensitic–austenitic structure with the Kurdjumov-Sachs relationship between martensite and austenite. The microstructure of the part of the transition zone with Ms temperature lower than room temperature is austenite.The investigations showed that by using low energy welding method we can significantly reduce the width of the martensite area in the transition zone of weld overaly.

Microstructure and properties of an AZ61 alloy after extrusion with a forward-backward oscillating die without preheating of the initial billet

We have investigated the microstructure, mechanical and corrosion properties of an AZ61 alloy that was extruded using a newly developed technique with an oscillating die (KoBo). The KoBo method allows the extrusion of AZ61 without preheating of the initial billet at high deformation ratios. The combined SEM, EBSD and TEM investigations of the microstructure revealed significant microstructure refinement as well as changes to the intensity of the texture and the distribution of the Mg17Al12 phase. The size of grains was reduced from coarse (davg 20.4 µm for the initial billet) to fine (davg 6.6 µm for the extrusion ratio of R1 7:1 and davg 4.5 µm for R2 10:1). However, in this study, it does not improve the strength and the corrosion properties of the AZ61 alloys. The continuously precipitated Mg17Al12 phase along the grain boundaries overwhelms the strengthening due to grain refinement. Intense corrosion occurs in the case of the KoBo-extruded samples, and the main mechanism of the corrosion is microgalvanic, taking place between the matrix and the Mg17Al12 formed at grain boundaries.

Microstructure and Mechanical Property Evolution of Robotic Friction Stir-Welded Al–Li Alloys

2198 aluminum–lithium alloy was friction stir-welded with a KUKA Robot integrated with a compact friction stir-welding head with a rotation speed of 800 rpm at different welding speeds. The real-time tool force in the three directions of Fx, Fy and Fz was measured with a load sensor. Mechanical properties and microstructure evolution were investigated systematically. The results showed that Fz force increased from 3.2 kN to 8.5 kN as welding speed increased from 50 mm/min to 500 mm/min. Ultimate tensile strength of 383 MPa, 88% of base metal, was obtained when the welding speed was 100 mm/min. The nugget zone consisted of refined grains with an average size of 4 μm. TEM investigation demonstrates that T1 precipitation predominated in the base metal and disappeared in the nugget zone, as a small amount of δ’ was retained. The W-shape hardness profile in all weldments and higher welding speed lead to a higher hardness value.

Sustainable Cauliflower-Patterned CuFe2O4 Electrode Production from Chalcopyrite for Supercapacitor Applications.

The primary purpose of this study was to produce an ore-based high-capacity supercapacitor electrode. For this, chalcopyrite ore was first leached with nitric acid, and then metal oxide synthesis was carried out immediately on nickel foam using a hydrothermal technique from the solution. Cauliflower-patterned CuFe2O4 with a wall thickness of about 23 nm was synthesized on the Ni foam surface, characterized by XRD, FTIR, XPS, SEM, and TEM investigations. The produced electrode also displayed a feature of a battery-like charge storage mechanism with a specific capacity of 525 mF cm-2 at 2 mA cm-2 current density, energy of 8.9 mWh cm-2, and a power density of 233 mW cm-2. Additionally, even after 1350 cycles, this electrode still performed at 109% of its original capacity. The performance of this finding is 255% higher than that of the CuFe2O4 in our earlier investigation; despite being pure, it performs far better than some of its equivalents in the literature. Obtaining such performance from an electrode made from ore indicates that the use of ore has a lot of potential for supercapacitor production and property improvement.