Electron Microscopy Investigations Research Articles

Adapting Conductivity and Mechanical Properties through Layer Thickness Variation in Copper Niobium Laminated Metallic Composites

Cu/Nb laminated metallic composites (LMCs) exhibit extraordinary mechanical strength while electrical conductivity is maintained at a high level. In this research, Cu‐based LMCs with varying volume fraction of niobium are produced via accumulative roll bonding (ARB) and additionally cold‐rolled and heat‐treated to identify the role of these heterogeneous phase boundaries on the overall sheet properties. Deformation structures in these layered materials are studied through scanning transmission electron microscopy investigations. The existence of an interface‐affected zone at the phase boundaries and mechanical intermixing is attributed to decreasing electrical and increasing mechanical properties, especially in very thin layered LMCs. Atom probe tomography measurements show that mechanical alloying occurs due to severe plastic deformation during ARB processing of the laminates. An additional subsequent heat treatment leads to chemical demixing at the interfaces of the phase boundaries.

Effects of aging on the microstructure and mechanical properties of metastable β-type Ti-23.6Nb-5.1Mo-6.7Zr alloy with low elastic modulus

In this study, the influence of thermomechanical treatments on the microstructure and mechanical properties of a new metastable β-titanium Ti-23.6Nb-5.1Mo-6.7Zr alloy was assessed. The objective was to determine if the alloy is a potential candidate for a future fabrication of orthopedic implants, in particular prosthetic hip stems with a functional gradient of mechanical properties. Two thermomechanical processing routes were investigated: (a) 90% cold-rolled, (b) 90% cold-rolled, followed by annealing at 950 °C for 1 h. After these initial processing steps, samples were aged between 300 °C and 500 °C from 0.5 h to 4 h. Microstructural characterization was conducted by optical microscopy, transmission electron microscopy and x-ray diffraction. Young's modulus and microhardness were measured. Young's modulus of the sample annealed after cold rolling is lower than that after the cold rolled one. Aging was effective at increasing hardness but also increasing Young's modulus. The hardening during aging resulted from fine ωiso and α precipitation. The transmission electron microscopy investigations indicated that an aging treatment at 500 °C leads to a fine (α + β) microstructure, avoiding brittle ωiso precipitation. For these reasons, this alloy is a potential candidate for the manufacture of a hybrid hip prosthetic stem by employing localized aging treatment at 500 °C in the neck region, creating a functional strength gradient and maintaining a low Young's modulus in the distal part, which is needed to mitigate the stress shielding of the bone.

Microstructural and mechanical properties of Al-Al2O3 micro and nanocomposite fabricated by stir casting

ABSTRACT The current study examines the relationship between the microstructure and tribological characteristics of Al-Si alloy composites reinforced by secondary phase nano SiC particulates synthesis via the stir casting process. The results of wear testing of stir-cast SiC metal matrix composites including up to 12 weight percent fine (75–100 µm) and coarse (125–150 µm) size particles were obtained from cast aluminium alloy. It was discovered via microstructural investigation that the aluminium alloy and SiC particles have good interface bonding. However, at greater amounts (12 wt.%) of fine size reinforcement, clustering of reinforced particles is observed. In addition, results state that finer size particles agglomerate more in the matrix than coarser size particles at greater reinforcement levels. In addition, increasing the amount of SiC particles in the matrix enhanced the hardness of the base alloy. However, when the size of the SiC particles was reduced, the hardness of the composite increased dramatically. Better wear resistance was observed for higher SiC reinforcement levels, while higher forces were also associated with a corresponding increase in wear rate. A combined mode of adhesive and abrasive wear mechanisms is responsible for composite wear, according to a scanning electron microscopy (SEM) investigation of worn surfaces.

Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li4Ti5O12 spinel lattice upon lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron-beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of spinel lattice.

Teak leaf biochar production for sustainable forest waste management at low temperatures

This study investigates the possibilities of producing biochar from teak leaves as an environmentally beneficial approach to managing forest waste in a sustainable manner. Teak leaves, a readily available forest by-product, were converted into biochar through a low-temperature pyrolysis process using a top-lit updraft mechanism. The results demonstrate the efficiency of this approach, yielding a substantial biochar output of 37.4 wt%, with its thermal field modelled perfectly via Levenberg-Marquardt algorithm in ANN topology. Elemental analysis of the teak leaf biochar revealed a high carbon content of 64.40%, positioning it as a valuable carbon-rich material suitable for various applications. Textural properties analysis indicated a significant surface area of 371.78 m2/g and a total pore volume of 0.175 cm³/g, enhancing its potential for various applications. Scanning Electron Microscopy (SEM) investigations showed a diverse network of pores and a rough surface structure, reinforcing the biochar’s versatility. This study shows the environmental benefits of low-temperature teak leaf biochar production, because it provides a carbon-content-preserving, sustainable alternative for handling forest wastes.

Microstructure and mechanical response of as-built and solution-annealed LPBF Hastelloy X under high-temperature fatigue loading

This study investigates the microstructural characteristics and the high-temperature mechanical behavior of Hastelloy X, fabricated via laser powder-bed fusion (LPBF) technology. Hastelloy X, a solid solution-strengthened nickel-based superalloy known for its high strength and oxidation resistance at elevated temperatures, has gained significant interest for the fabrication of complex aerospace components through LPBF technology. The study initially focuses on the impact of solution annealing heat treatment at 1227 °C on the alloy microstructure, based on scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations. It then explores the fatigue and cyclic deformation response of the alloy at 750 °C across different strain ranges, comparing the as-built and solution-annealed conditions. To understand the observed differences in the cyclic mechanical response of as-built and solution-annealed LPBF HX, for a particular condition, a set of dedicated tests have been performed and interrupted at selected numbers of cycles in the different stages of the mechanical response. At each interruption point, specimens have been examined by TEM to provide an in-depth understanding of the effect of dislocation microstructural evolution on the high-temperature cyclic mechanical response of the alloy.

Comparison of kink-band structures and specificities of cell wall polysaccharides in modern and ancient flax fibres

Flax (Linum usitatissimum L.) is a plant of industrial importance, its fibres being presently used for high-value textile applications, composite reinforcements as well as natural actuators. Human interest in this fibre-rich plant dates back several millennia, including to Ancient Egypt where flax was used extensively in various quotidian items. While the recent technical developments of flax fibres continue to diversify through scientific research, the historical use of flax also has rich lessons for today. Through careful examination of ancient Egyptian and modern flax fibres, this study aims to conduct a multi-scale characterization from the yarn to the fibre cell wall scale, linking differences in structure and polysaccharide content to the mechanical performance and durability of flax. Here, a multi-scale biochemical study is enriched by scanning electron microscopy and nanomechanical investigations. A key finding is the similarity of cellulose features, crystallinity index and local mechanical performances between ancient and modern fibres. Biochemically speaking, monosaccharides analysis, deep-UV and NMR investigations demonstrate that ancient fibres exhibit less pectins but a similar hemicellulosic content, especially through uronic acids and galactose, suggesting the sensitivity of these non-crystalline components.

Compressive behavior of thermoplastic polyurethane with an active agent foaming for 3D-printed customized comfort insoles

The primary objective of this study was to investigate the compressive behavior of 3D-printed specimens made of a thermoplastic polyurethane filament, specifically colorFabb varioShore TPU, which incorporates a foaming agent. The foaming technology makes it possible to manipulate 3D prints’ properties by adjusting process parameters that affect the level of expansion, such as printing temperature, printing speed or flow ratio. This capability opens new possibilities for 3D-printed personalized foot orthotics or for static comfort-oriented applications by tailoring the stiffness of the print based on the application requirements. Since infill density and infill pattern also affect the compressive characteristics of 3D prints, this research took these two parameters into account as independent variables, alongside the printing temperature. Thus, the specimens with printing temperatures set at 190°C, 220°C, and 240°C, gyroid and honeycomb patterns, and infill variations from 10% to 35% in 5% increments were experimentally investigated in compression testing. The evaluation was conducted to determine the influence of these factors on the stiffness of prints at 10% and 20% strains, in accordance with established standard. The findings had an important practical value as they provide data for adjusting the variable stiffness based on peak plantar pressure measurement data when developing tailored foot orthoses (insoles), which was the second objective of the research. The most influential factor affecting the compressive strength was the printing temperature, followed by infill density and pattern type. The difference in compression modulus between 10% and 20% strains did not exhibit statistical significance. Moreover, the main effects plots indicated minimal variations in compression modulus effects at 220°C and 240°C, whereas an important difference was observed at 190°C printing temperature, which was confirmed by scanning electron microscopy investigations showing foamed layers at 220°C and unfoamed layers at 190°C. Furthermore, interaction plots revealed no significant interaction effect among the studied variables. Additionally, a comparison of samples’ sizes and densities before and two months after testing indicated no observable modifications When applied to custom orthotics (five pairs of insoles were customized and tested), the experimental findings documented variations in the reduction and distribution of peak plantar pressure based on the infill variability.

Gomphonemavancampianum sp. nov. (Gomphonemataceae, Bacillariophyceae), a new large Gomphonema species from Europe.

During a French biomonitoring survey of the lakes in the region Rhône-Méditerranée-Corse, a large, unknown Gomphonema taxon was observed in a lake in the vicinity of the City of Lyon (Département du Rhône, France), that could not be identified using the currently available literature. Detailed light and scanning electron microscopy investigations revealed the presence of two types of valves, one bearing a thick marginal crest and valves lacking the crest. Following comparison with similar, mostly tropical Gomphonema species, the unknown taxon is described as new: Gomphonemavancampianum sp. nov. Discriminating features of the new species include the peculiar valve shape resembling a Chinese spoon, the broad upper valve part with acuminate tip, the presence of shallow depressions in the axial area, distinctly punctate striae and the occasional presence of the marginal crest. The new species was observed in several samples collected in an oligo- to mesotrophic, calcium-carbonate rich lake with a high ecological quality.

Synergistic and potential antifungal properties of tailored, one pot multicomponent monoterpenes co-delivered with fluconazole encapsulated nanostructure lipid carrier

Frequent and variant infections are caused by the virtue of opportunistic fungi pathogens. Candidiasis, aspergillosis, and mucormycosis are pathogenic microorganisms that give rise to vast fungal diseases that alternate between moderate to fatal in severity. The use of fluconazole as an antifungal drug was limited due to the acquired resistance in some types of Candida and other fungal species. This study aims to consolidate fluconazole’s biological effectiveness against several pathogenic fungi. Six active monoterpenes (MTs) of carvacrol, linalool, geraniol, α-terpinene, citronellal, and nerolidol were selected and encapsulated in nanostructure lipid carrier (NLC) with (NLC-Flu-MTs) and/without (NLC-MTs) fluconazole in one nanoformulation to determine if they will act synergistically or not? The synthesized nanoformulation NLC-Flu-MTs and NLC-MTs exhibited very good particle size of 144.5 nm and 138.6 nm for size and zeta potential values of (− 23.5 mV) and (− 20.3 mV), respectively. Transmission electron microscope investigation confirmed that the synthesized NLCs have regular and spherical shape. The abundance and concentration of the six released monoterpenes were determined, as a novel approach, using GC–MS with very good results and validity. In-vitro antifungal screening was done before and after nano co-delivery against seven pathogenic, and aggressive fungi of Candida tropicalis, Candida krusei, Candida glabrata, Geotrichum Candidum, Candidaalbicans, Aspergillus Niger, and mucor circinelloides. Inhibition Zone diameter (IZD) and the minimum inhibitory concentration (MIC) were measured. Nanoformulations NLC-Flu-MTs and NLC-MTs manifested potential and unique biological susceptibility against all the tested microorganisms with reduced (MIC) values, especially against Candida Tropicalis (MIC = 0.97 µg/ml) which represents 16-fold of the value shown by NLC-MTs (MIC = 15.6 µg/ml) and 64-fold of fluconazole free before nanoformulation (MIC = 62.5 µg/ml). The efficiency of nanomaterials, particularly NLC-Flu-MTs, has become evident in the diminishing value of MIC which affirmed the synergism between fluconazole and the other six monoterpenes.

Improving photocatalytic efficiency of ZnO nanoflowers through gold incorporation for Rhodamine B photodegradation

In this study, we reported the synthesis and characterization of Au-doped ZnO hybrid nanostructures via a wet chemical approach and assessed their photocatalytic efficiency for the removal of Rhodamine (Rh–B). X-ray powder diffraction (XRD) has been done to verify the crystal structure, i.e. phase identification, crystallite size, texture, stress, and strain. The XRD patterns demonstrate that the wurtzite structure has been retained and that Au nanoparticles were effectively ingested into the ZnO nanoflowers lattice. This demonstrates that Au nanoparticles are effectively absorbed into the ZnO nanoflowers lattice, considering that peaks shifted in the direction of smaller Bragg's angles. As a result, the size of the crystallites increases from (20.7–25.3) nm, and their microstrain decreases from (0.92–0.72) x 10−3 A0 for pure-ZnO to Au-doped ZnO heterostructures, respectively. Scanning Electron Microscopy (SEM) investigation reveals flower-like structures of pure ZnO while a further closed look indicates that these flowers are made up of a variety of oriented, thorn-like branched NWs with diameters ranging from (50–90) nm and lengths ranging from a few microns. The corresponding EDS evaluation of pure ZnO nanoflowers and Au-doped ZnO heterostructures clearly shows that the noble metal Au NPs are deposited, and enormously safeguard the surface of ZnO nanoflowers. Reducing the Au-doped ZnO band gap which generated a red shift in light absorption, was confirmed by the PL spectra which in turn increased the photocatalytic efficiency and reduced the dye degradation time of Rh–B. The photocatalytic ability of Au-doped ZnO heterostructures considerably increased the photodegradation efficiency of Rh–B molecules from 28 min for pure ZnO to 10 min for Au-doped ZnO heterostructures. Due to their wide surface area and distinct morphology as compared to pure ZnO nanoflowers.

Atomic and electronic structures of domain boundaries in LaTiO3 thin films

Domain boundaries in perovskite oxides often exhibit abundant physical properties and phenomena. Here, epitaxial LaTiO3 thin films on (100) SrTiO3 substrates are prepared by pulsed-laser deposition. X-ray diffraction and transmission electron microscopy investigations reveal that the epitaxial LaTiO3 thin films have good crystallinity but a high density of domain boundaries. Atomic-scale scanning transmission electron microscopy observations reveal that two types of domain boundaries are formed in the LaTiO3 thin films. The type I domain boundaries are formed on the {100} crystal planes, while the type II domain boundaries on the {110} crystal planes. Electron energy-loss spectroscopy analyses suggest that the valence states of Ti ions at the type I domain boundaries are +3, while those at the type II domain boundaries are +4. First-principles calculations reveal that the bandgap decreases at both domain boundaries compared to the bulk. The carrier concentration at the type I domain boundaries is significantly higher than that of the bulk, while the carrier concentration at the type II domain boundaries is lower. These findings suggest that domain boundaries play an important role in tailoring the electrical properties of the LaTiO3 thin films, thereby promoting the potential applications and property modulation of related materials and devices.

Structural, bandgap tailoring, photoluminescence and electrochemical characteristics of Sm3+-doped ZnS quantum dots prepared in Ar-atmosphere

Sm3+-doped ZnS quantum dots were prepared by a cost-effective, simple co-precipitation technique under an argon atmosphere. The prepared Sm3+-doped QDs exhibited a cubic structure with an average particle size of ∼ 2 nm, as confirmed through X-ray diffraction and high-resolution transmission electron microscopic investigations. The crystallite was reduced and strain produced due to the larger ionic radius of Sm3+ ions. The Sm (at. 2 %)-doped ZnS exhibited a blue shift, and the optical transmittance was enhanced. A highly intense red emission was obtained in photoluminescence investigations, and this is due to the transfer of photons from 4G5/2 → 6H11/2 for f-f transitions of the Sm3+ in the 4f5 configuration. The obtained photoluminescence emissions lead to red phosphor applications. The cyclic voltammogram analysis showed that adding Sm to ZnS QDs made their specific capacitance value higher and it found potential applications in supercapacitors.

Detection of water pollutants using super-hydrophobic porous silicon-based SERS substrates.

Super hydrophobic porous silicon surface is prepared using a wet chemical synthesis route. Scanning electron microscopic investigation confirms a correlation between pore size and reaction time. SERS substrates are prepared by silver nanoparticle deposition on porous silicon surface. They exhibit excellent characteristics in terms of sensitivity, reproducibility, stability, and uniformity. They could detect rhodamine 6G in femtomolar range with SERS enhancement factor of ~ 6.1 × 1012, which is best ever reported for these substrates. Molecule-specific sensing of water pollutants such as methylene blue, glyphosate, andchlorpyrifos, is demonstrated for concentrations well below their permissible limits along with excellent enhancement factors. Porous silicon substrate functionalized with Ag nanoparticles demonstrates to be a promising candidate for low-cost, long-life, reliable sensors for environmental conservation applications.

Effect of Microsphere Concentration on Catechin Release from Microneedle Arrays.

In this work, microspheres were developed by cross-linking glutaraldehyde in an aqueous gelatin solution with a surfactant and solvent. A poly(vinyl alcohol) (PVA) solution was produced and combined with catechin-loaded microspheres. Different microsphere concentrations (0%, 5%, 10%, and 15%) were applied to the PVA microneedles. The moisture content, particle size, swelling, and drug release percentage of microneedles were studied using various microsphere concentrations. Fourier transform infrared and scanning electron microscopy (SEM) investigations validated the structure of gelatin microspheres as well as their decoration in microneedles. The SEM scans revealed that spherical microspheres with a wrinkled and folded morphology were created, with no physical holes visible on the surface. The gelatin microspheres generated had a mean particle size of 20-30 μm. Ex vivo release analysis indicated that microneedles containing 10% microspheres released the most catechin, with 42.9% at 12 h and 84.4% at 24 h.

Neuron mapping in the Molly fish optic tectum: An emphasis on the adult neurogenesis process.

Teleost fish exhibit the most pronounced and widespread adult neurogenesis. Recently, functional development and the fate of newborn neurons have been reported in the optic tectum (OT) of fish. To determine the role of neurogenesis in the OT, this study used histological, immunohistochemical, and electron microscopic investigations on 18 adult Molly fish specimens (Poecilia sphenops). The OT of the Molly fish was a bilateral lobed structure located in the dorsal part of the mesencephalon. It exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. The stratum opticum (SO) was supplied by optic nerve fibers, in which the neuropil was the main component. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). Furthermore, oligodendrocytes with their processes wrapped around the nerve fibers could be observed. The stratum album centrale (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. The neuronal cells of the SO and large tectal cells of the SAC expressed autophagy-related protein-5 (APG5). Interleukin-1β (IL-1β) was expressed in both neurons and glia cells of SGC. Additionally, inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventriculare (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. In all strata, S100 protein and Oligodendrocyte Lineage Transcription Factor 2 (Olig2) were expressed by microglia, oligodendrocytes, and astrocytes. In conclusion, it was possible to identify different varieties of neurons in the optic tectum, each with a distinct role. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT. RESEARCH HIGHLIGHTS: The OT of the Molly fish exhibited a laminated structure made up of alternating fiber and cellular layers, which were organized into six main layers. Radial bipolar neurons that possessed bundles of microtubules were observed in the stratum fibrosum et griseum superficiale (SFGS). The stratum album central (SAC) consisted mainly of the axons of the stratum griseum centrale (SGC) and the large tectal, pyriform, and horizontal neurons. Inducible nitric oxide synthase (iNOS) was expressed in the neuropil of the SAC synaptic layer and granule cells of the stratum periventricular (SPV). Also, transforming growth factor beta (TGF-β), SRY-box transcription factor 9 (SOX9), and myostatin were clearly expressed in the proliferative neurons. The existence of astrocytes, proliferative neurons, and stem cells highlights the regenerative capacity of OT.

Creep anisotropy of additively manufactured Inconel-738LC: Combined experiments and microstructure-based modeling

The current lack of quantitative knowledge on processing-microstructure–property relationships is one of the major bottlenecks in today’s rapidly expanding field of additive manufacturing. This is centrally rooted in the nature of the processing, leading to complex microstructural features. Experimentally-guided modeling can offer reliable solutions for the safe application of additively manufactured materials. In this work, we combine a set of systematic experiments and modeling to address creep anisotropy and its correlation with microstructural characteristics in laser-based powder bed fusion (PBF-LB/M) additively manufactured Inconel-738LC (IN738LC). Three sample orientations (with the tensile axis parallel, perpendicular, and 45° tilted, relative to the building direction) are crept at 850 °C, accompanied by electron backscatter secondary diffraction (EBSD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations. A crystal plasticity (CP) model for Ni-base superalloys, capable of modeling different types of slip systems, is developed and combined with various polycrystalline representative volume elements (RVEs) built on the experimental measurements. Besides our experiments, we verify our modeling framework on electron beam powder bed fusion (PBF-EB/M) additively manufactured Inconel-738LC. The results of our simulations show that while the crystallographic texture alone cannot explain the observed creep anisotropy, the superlattice extrinsic stacking faults (SESF) and related microtwinning slip systems play major roles as active deformation mechanisms. We confirm this using TEM investigations, revealing evidence of SESFs in crept specimens. We also show that the elongated grain morphology can result in higher creep rates, especially in the specimens with a tilted tensile axis.

Se Inter-Diffusion Limits Absorber Layer Grain Growth in CdSe - CdTe Photovoltaics

Diffusion of Se from the CdSe window layer into the CdTe absorber improves the short circuit current density by narrowing the band gap and increasing the carrier lifetime. Thicker CdSe layers, however, show a dramatic loss in photocurrent collection due to Se over-alloying. Electron microscopy investigations show that this decrease in performance is due to the formation of small grains (∼783 nm average diameter), which exhibit grain boundary porosity in the Se inter-diffusion region. The larger grain boundary area and void free surfaces give rise to higher levels of nonradiative recombination, and therefore, a lower photocurrent. It is proposed that the small grain size is due to a drag force exerted by segregated Se solute atoms on a moving grain boundary, while faster Se diffusion along the grain boundaries results in vacancy build up and porosity due to the Kirkendall effect. The results indicate that the device processing conditions must be carefully controlled such that the negative effects of Se alloying (i.e., smaller grains, Kirkendall voids) do not undermine its benefits. Published by the American Physical Society 2024

Comparative study between oxide/soft ferrite, oxide/hard ferrite, and soft/hard ferrite nanocomposites: structural, electrical, and magnetic properties

Three binary nanocomposites (NCs): (0.5NiO/0.5Ni0.5Zn0.5Fe2O4), (0.5NiO/0.5BaFe12O19), and (0.5Ni0.5Zn0.5Fe2O4/0.5BaFe12O19) were prepared using the co-precipitation method followed by the wet ball-milling technique. X-ray diffraction analysis showed the production of NiO and Ni0.5Zn0.5Fe2O4 single phases, while the α-Fe2O3 secondary phase appeared in the BaFe12O19 and the 0.5Ni0.5Zn0.5Fe2O4/0.5BaFe12O19 nanocomposite. The transmission electron microscopy investigation and the selected area electron diffraction demonstrated the presence of the nanocomposites’ constituent phases. x-ray photoelectron spectroscopy identified the oxidation states found in the prepared samples (Ba2+, Ni2+, Ni3+, Zn2+, Fe3+, and O2−). The bandgap values (Eg) of the nanocomposites are in the range between 2.79 and 3.66 eV, which indicates their semiconductor nature. The DC conductivity experiment confirmed the semiconducting nature of all samples, and the activation energies ( EaH ) and ( EaL ) at high and low-temperature regions, respectively, were calculated from the Arrhenius equation. According to the vibrating sample magnetometer, the NCs exhibited ferromagnetic (FM) as showed by the M-H loops. In the oxide/soft ferrite NC, the dM/dH curve indicated strong exchange coupling interactions, while the hard and the soft magnetic phases in the oxide/hard ferrite and the soft/hard ferrite NCs were weakly exchanged coupled. Significant uses had been found for each of the three nanocomposites according to their constituent phases and properties.

Assessing lunar paleointensity variability during the 3.9 - 3.5 Ga high field epoch

Numerous paleomagnetic studies suggest that a lunar dynamo, with surface field intensities potentially as high as 40-100 µT, existed between ∼3.9 Ga and ∼3.5 Ga. This period is referred to as the High Field Epoch (HFE). However, the debate over the origin of magnetization recorded in lunar rocks still persists. In addition, whether the Moon could have sustained a continuously strong dynamo during the HFE remains unclear. To unravel the origin of magnetization preserved in lunar rocks and to better characterize the evolution of the ancient lunar dynamo, we conducted a comprehensive set of experiments including rock magnetic tests, electron microscopy, and paleomagnetic investigations on four HFE-aged Apollo 11 mare basalt samples: 10003, 10044, 10069, and 10071. Rock magnetic experiments and electron microscopy indicate that the remanence carriers are kamacite grains of varying sizes and domain states. Sample 10003 recorded a paleointensity of 54.10 ± 4.66 µT. Sample 10044, which was shocked (peak pressure >5 GPa), did not preserve a stable high coercivity remanent magnetization. Samples 10069 and 10071 recorded paleointensities of 61.46 ± 26.09 µT and 10.69 ± 2.87 µT, respectively. A series of hydrostatic pressure experiments, isothermal remanent magnetization (IRM) acquisition experiments, and viscous remanent magnetization (VRM) tests preclude the possibility of our samples containing shock remanent magnetization from transient impact-generated fields, IRM acquisition from exposure to spacecraft fields, and VRM acquisition from exposure to the Earth magnetic field. Overall, our study suggests that the source of these magnetizations was likely the lunar dynamo and may indicate nearly order-of-magnitude magnetic field fluctuations during the HFE.