Layer Deposition Research Articles

Clinical and Genetic characteristics of patients with Peripheral Retinal Fleck in Koreans.

To describe the clinical and genetic features of Korean patients with peripheral retinal flecks unrelated to aging. A retrospective analysis was conducted on the clinical characteristics of patients with symmetric peripheral retinal flecks. Age-related deposits such as reticular pseudodrusen were excluded, as well as secondary deposits related to intraocular inflammation, tumor, and drug toxicity. Multimodal imaging, electrophysiological examinations, and genetic testing were analyzed. A total of 10 patients (2 males and 8 females) with bilateral peripheral flecks were enrolled in this study. A mean age at diagnosis was 30.5±19.6 years (4-59 years). Within the 10 patients, 6 were genetically confirmed with monogenic retinal disorders. Biallelic pathogenic variants in RDH5 were found in 5 patients, and 1 patient was diagnosed with retinopathy related to Alport syndrome due to a pathogenic variant in COL4A5. Although not genetically confirmed, one case associated with nanophthalmos and another case showing chorioretinal mottling in a carrier of ocular albinism have been identified. In one patient, genetic testing also revealed unknown causes. The mean logMAR initial visual acuity was 0.12±0.18 and 0.07±0.18 in right and left eyes, respectively. Night blindness was reported by 4 patients (40%), with 3 showing decreased or delayed rod response in electroretinogram, particularly those with RDH5 mutations. Differences in the deposit layers and the patterns of flecks were observed on multimodal imaging. In the study population, we observed various causes and clinical differences in the retinal fleck patterns among Koreans, including RDH5-related fundus albipunctatus and Alport syndrome. Despite reports of night blindness symptoms in some cases, all patients demonstrated satisfactory corrected visual acuity.

Modeling the formation of toma hills based on fluid dynamics with a modified Voellmy rheology

Abstract. Toma hills are perhaps the most enigmatic morphological feature found in rock avalanche deposits. While it has been proposed that toma hills might emerge from the fluid-like behavior of rock avalanches, there still seems to be no consistent explanation for their occurrence. This paper presents numerical results based on a modified version of the Voellmy rheology, which was recently developed to explain the long runout of rock avalanches. In contrast to the widely used original version, the modified Voellmy rheology defines distinct regimes of Coulomb friction at low velocities and velocity-dependent friction at high velocities. When movement slows down, returning to Coulomb friction may cause a sudden increase in friction. Material accumulates in the region upstream of the point where this happens. In turn, high velocities may persist for some time in the downstream and lateral ranges, ultimately resulting in a thin deposit layer. In combination, both processes generate more or less isolated hills with shapes and sizes similar to those of toma hills found in real rock avalanche deposits. Thus, the modified Voellmy rheology suggests a simple mechanism for the formation of toma hills.

Investigating the effects of powder feeding rate on microstructure transformation in linear laser beam additive manufactured thick-walled structures

The coarse columnar crystals that grow through multiple layers are commonly observed in laser additive manufactured structures, with fractures tending to occur in regions where there are abrupt changes in grain morphology. This can lead to a degradation of the mechanical properties of the samples. In this study on laser additive manufacturing, thick-walled structures made of 304 stainless steel were created using a linear beam spot with a rectangular powder feeding nozzle. By adjusting the powder feeding rate to influence the thermal cycling characteristics during the laser additive manufacturing process, a hierarchical grain structure that combines coarse and fine equiaxed grains was achieved, enhancing the forming efficiency and overall mechanical performance of the structure. The results from the thermal cycling characteristics and microstructure analysis indicate that increasing the powder feeding rate during the additive manufacturing process can decrease the hierarchical cooling rate, temperature gradient, and heat accumulation effect. This reduction in turn decreases the grain size and facilitates the transformation of columnar crystals into equiaxed crystals. Furthermore, the transformation of low-angle grain boundaries into high-angle grain boundaries in the interlayer region helps to reduce stress concentration, weaken anisotropic tendencies, and mitigate intergranular fracture tendencies, ultimately improving the mechanical properties of the overall structure. In actual engineering applications, the powder flow can be adjusted to control the temperature gradient and cooling rate of the deposition layer, thereby altering the grain morphology and optimizing the mechanical properties of additive manufacturing parts.

Effect of cathodic current density on hydrogen embrittlement susceptibility of X70 steel girth weld in different soil simulation solutions

PurposeIn this paper, the authors aim to study the relationship between hydrogen embrittlement (HE) susceptibility and cathodic current density applied on the X70 steel girth welds.Design/methodology/approachThe HE susceptibility of X70 steel girth welds were investigated through slow strain rate tensile test and observed and analyzed by optical microscope and scanning electron microscope methods.FindingsThe results show that HE susceptibility of X70 girth weld was basically unchanged with increasing of ion concentration while gradually increased and maintain at a specific value with the increase of cathodic current density. As for same ion content, a dense calcareous deposit layer generated on the sample surface in soil simulation solution with Ca2+ and Mg2+ resulted a decreased HE susceptibility while the porous calcareous deposit layer resulted a increased HE susceptibility.Originality/valueA logistic regression model was established to describe the correlation between HE index and the cathodic current density.

Effect of mechanical vibration on microstructure and performance of Fe-based composite coatings fabricated by underwater laser deposition technology

To solve the problem of the uneven composition and poor performance caused by water environment during the underwater laser deposition process, the mechanical vibration assisted underwater laser deposition technology was innovatively proposed, and Fe-based composite layer was successfully prepared. The microstructure, grain type and properties of Fe-based composite layer with and without mechanical vibration were studied and compared. The results showed that the mechanical vibration broke the grain and promoted the formation of more nuclei, which reduced the average grain size by 13.48 %. The solute located in the grain gap was transferred to the liquid molten pool by mechanical vibration, which reduced the Ti content in the intergranular precipitated phase Fe2Ti and made the Fe2Ti from coarse continuous distribution to fine discontinuous distribution. Additionally, the mechanisms of mechanical vibration promoting the performance of the composite were analyzed comprehensively. Compared with the composite without mechanical vibration, the composite with mechanical vibration had good corrosion resistance after 30 days of immersion, and the tribo-corrosion resistance was also improved. With the aid of mechanical vibration, the ultimate tensile strength and elongation of the composite were increased by 11.30 % and 22.08 %, respectively, due to the formation of recrystallized grains, high density high-angle grain boundaries, and fine intergranular precipitate. This study was expected to provide a new way to regulate the microstructure and properties of the underwater laser deposition layer, and promote the application of underwater laser deposition technology in marine engineering equipment.

ZnO Nanoparticle Assisted Liquid Metal for Dendrite-Free Zn Metal Anodes.

Dendrite growth and interfacial side reactions on Zn anode seriously affect the safety and service life of Zn ions batteries. Interface engineering is an effective way to solve these problems. Here, a liquid metal-ZnO composite coating with high ionic conductivity is creatively designed, which not only reduces the Zn2+ diffusion barrier but also increases the hydrogen evolution overpotential, thereby eliminating dendrite growth behavior and corrosion on the modified Zn anode. Moreover, its unique structure induces Zn deposition into the inner of coating, which can effectively avoid the volume expansion in the deposit layer of Zn anode. Therefore, it can cycle for 3000 h at an ultra-small polarization of 28 mV at 1 mA cm-2, and the microbattery assembled in combination with the MnO2 cathode also maintains 2000 cycles with high Coulomb efficiency, providing a general idea for the development of the next generation of rechargeable metal batteries.

Post-mortem analysis of the deposit layers on the lower divertor after the 2023 high particle fluence campaign of WEST

We analysed deposits collected on the lower divertor of WEST after the first high fluence campaign performed in 2023. Deposits were collected on the high field side (thick deposition area) of 2 ITER-grade plasma facing units (PFUs), located on different toroidal positions. Using focused ion beam cross sectioning, the deposits were found to be very thick (12–55 µm). A significant difference was observed in the toroidal direction with thicker deposits for the PFU located at the maximal heat load in the inner side, showing a deposition pattern due to the toroidal magnetic field modulation. Deposits present a complex layer-by-layer structure with dense layers, some melted parts and porosities within the layers. The deposition is mainly composed of tungsten with oxygen, boron, carbon and traces of nitrogen whose composition vary along the radial direction. We identified W-rich deposits in the high plasma flux area near the inner strike point and deposits rich in O, B, C and N in the low plasma flux area further away from this strike point. W dense layers of about 5 up to 40 µm thick in the thick deposit area near the strike point were attributed to the high fluence campaign. Pure boron layers resulting from wall conditioning and processed by plasma wall interactions were also observed.

Performance of yellow and pink oyster mushroom dyes in dye sensitized solar cell

A solar photovoltaic (PV) cell, is an electrical device that uses the PV effect to convert light energy into electricity. The application of oyster mushroom dyes in dye sensitized solar cell (DSSC) is a novel strategy to substitute the costly chemical production process with easily extractable, environmentally acceptable dyes. Both dyes of yellow and pink oyster mushrooms were extracted using the same process but dried into powder form using two techniques, warm drying and freeze drying. The characterization was carried out utilizing current-voltage (I-V) characterization for electrical properties, Ultraviolet-Visible (UV-Vis) spectrophotometer for optical properties, Field Emission Scanning Electron Microscopy (FESEM), and Atomic Force Microscopy (AFM) for the structural properties. It was found that freeze-dried pink and yellow oyster mushroom had shown the good properties for DSSC application as it produced energy bandgap which lies within the range of efficient dye sensitizer; 1.7 eV and 2.2 eV, the most uniform distribution of pores and a nearly spherical form in FESEM analysis, and AFM result obtained with the highest root mean square (RMS) roughness value (26.922 and 34.033) with stereoscopic morphologies. The data proved that mushroom dyes can be incorporated in DSSC with the optimization of drying method in the extraction process, dilution of dye and the layer of deposition on the glass substrate. The current density-voltage (J–V) characteristics of fabricated DSSC was characterized using Newport Oriel Sol3A solar simulator under AM 1.5 Sun condition (100 mW/cm2, 25 oC). From the result obtained by solar simulator, the fabricated FTO/TiO2/Pleurotus djamor dye/Pt indicated the Voc of 0.499 V and Jsc of 0.397 mA/cm2.

Improving the Bioactivity and Antibiofilm Properties of Metallic Implant Materials via Controlled Surface Microdeformation.

Although metallic implants provide most of the required properties for bone-related applications, especially orthopedic implants, insufficient osseointegration, which may lead to loosening of the implant or prolonged healing time, is still an issue to be resolved. Osseointegration can be improved via application of various surface treatments on the metal surface. The current study focuses on a novel surface microdeformation method, which enables the formation of controlled surface patterns of various parameters. With this purpose, a surface microdeformation procedure was applied on 316L stainless steel surfaces, forming four different patterns which affected various surface parameters such as roughness, surface energy, dislocation activities close to the surface, and wettability. Static immersion tests in a simulated body fluid (SBF) environment showed that modifying the surface parameters via controlled surface patterning promoted the formation of a stable oxide layer and calcium-phosphate (CaP) deposition on the metal surfaces, improving bioactivity. Moreover, the higher amount of CaP deposition and oxide layer formation on the modified surfaces led to reduced ion release, which contributed to improved corrosion resistance. Finally, the effect of the formed surface patterns on antibiofilm formation was investigated via incubation with C. albicans for 24 h, which exhibited that microdeformation patterns remarkably inhibited the biofilm formation. Throughout the experiments, certain patterns yielded outstanding results among the four patterns formed. Overall, it was concluded that forming controlled patterns on stainless steel surfaces via surface microdeformation significantly contributed to the metal's biocompatibility via improving bioactivity, corrosion resistance, and antibiofilm formation properties. Especially, the specific surface properties such as increased surface energy, high surface roughness, and dislocation density close to the metal surface as well as increased hydrophilicity obtained via forming the pattern with relatively deeper and narrowly spaced indents yielded the most promising outcomes. These methodologies constitute novel approaches to be used while designing new methodologies for the surface modification of metallic implant materials for improved osseointegration.

Helium retention feature in the boron deposited layer on tungsten substrate by laser-induced breakdown spectroscopy and machine learning approach

ITER is designed for a burning plasma operation in which Tungsten (W) tiles are used as the first wall and diverter materials. Studying He dynamics in B-coated W wall is essential to understanding the effect of boronized plasma-facing components in fusion reactors, as these post-conditioning materials significantly influence helium retention and release. Plasma-wall interactions (PWI) are an important issue in ITER fusion reactors. PWI would lead to wall erosion and impurity redeposition. As a product of the D-T burning plasma, helium (He) ash would be retained or co-deposited on plasma-facing components (PFCs), affecting the stable operation of burning plasma. Laser-induced breakdown spectroscopy (LIBS) is proposed as a promising in-situ diagnostic approach for monitoring D/T and He retention and impurity deposition on PFCs of tokamak devices. In this study, the LIBS technique was used to investigate the helium retention feature in the boron (B) layer on tungsten substrate in 10−5 mbar. Five He-retention samples on the boron deposition layer on tungsten substrates were prepared by pulsed laser deposition (PLD) method at different ambient pressures in our lab. The investigations indicate that the atomic spectral line of helium (He-I 587.56 nm) was observed in the spectra of the first three laser shots. The depth profiles of He, B, and W in the boron-deposited layer on tungsten substrate were performed by LIBS to determine the co-deposition layer thickness. The concentration of He in the co-deposition layer samples measured by TDS is 7 × 1020 He/m2. The plasma parameters, such as plasma electron temperature and electron number density, were calculated to validate the local thermodynamic equilibrium. Machine learning (ML) algorithms are used to classify the co-deposits and substrates. The first three principal components (PC1, PC2 & PC3) of the unsupervised ML algorithm (PCA) give a classification accuracy of 91.7 %. The supervised ML algorithm neural network achieved training and testing accuracy of 100 % and 96.7 %, respectively.

Modeling fiber alignment in 3D printed ultra-high-performance concrete based on stereology theory

This paper introduces a theoretical model for forecasting fiber orientation in 3D-printed ultra-high-performance concrete (3DP-UHPC). Initially, the dynamic evolution process of fiber alignment in 3DP-UHPC was characterized using X-ray computed tomography (X-CT) and image analysis. The results indicated that fiber alignment during extrusion process was primarily constrained by the rigid boundary of nozzle. Leveraging stereology theory, the regularity of fiber alignment affected by boundary effects was elucidated. Following layer deposition, the flattening effect resulting from the nozzle's extrusion force and gravity of upper layers influenced fiber alignment along printing direction. To quantify this impact, a flattening correction coefficient was introduced to modify fiber orientation coefficient in an ideal state. Finally, considering the overlapping effect of boundary and flattening on fiber orientation in 3DP-UHPC, a theoretical model was developed to predict fiber orientation. The model demonstrated robust adaptability, providing valuable insights into the design of 3DP-UHPC with improved fiber reinforcement efficiency.

Structural, Morphological, and Optical Properties of TiO2/CdS Core-Shell System Prepared by Two Method for Photoelectrocatalytic Application

Abstract The present study utilized the hydrothermal technique to carry out the deposition of films of TiO2. The deposition of CdS on the TiO2 films was accomplished using the chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) methods. The morphological and structural characteristics of the TiO2/CdS thin films were investigated using a combination of XRD, SEM, EDX, and AFM techniques. Additionally, the optical properties of the nanostructures were examined using UV-Visible and PL spectroscopic techniques. The X-Ray Diffraction pattern of all TiO2 films revealed the formation of the anatase phase. The CdS present in the Ti/TiO2/CdS samples exhibited a hexagonal structure. The hydrothermal technique employed in the preparation of the TiO2 thin films resulted in the formation of nanofiber morphology, which was evident from the SEM images. The absorption edge data for the TiO2/CdS films demonstrated a shift towards the visible region, indicating a decrease in the bandgap as compared to the TiO2 nanostructure. Significantly improved photoelectrocatalytic performance was observed in the Ti/TiO2/CdS samples prepared using the CBD method, surpassing that of the Ti/TiO2/CdS samples prepared using the SILAR method.

Investigation on Microstucutres and properties of ion nitriding layer of Al0.5CoCrFeNiTi0.25 HEAs cladding coating

To investigate the effect of ion nitriding on the microstructures and properties of high entropy alloy coatings, the Al0.5CoCrFeNiTi0.25 high entropy alloy coating was fabricated via laser cladding and subsequently subjected to ion nitriding treatment. A comparative analysis were conducted to investigate the phase compositions, microstructures and properties of cladding coatings and ion nitriding layer. Furthermore the formation mechanism of the nitriding layer was studied. XRD results revealed that Al0.5CoCrFeNiTi0.25 HEA coatings consisted of duplex FCC and BCC phases, whereas the nitriding layer was composed of high-nitrogen FCC solid solutions and nitrides such as AlN, CrN, Fe4N and TiN. Following ion nitriding, the surface morphology of nitriding layer presented “cauliflower-like” nitride particles, which became denser with the extended nitriding time. Notably, the microhardness of nitriding layer was approximately four times that of HEA coating, and the wear resistance and the corrosion resistance of cladding coating were improved significantly after ion nitriding. During ion nitriding process, N atoms reacted with the alloying elements to form nitrides, which preferentially deposited at grain boundaries and BCC phases and grew horizontally. As the deposition layer spread across the entire surface, the nitriding mechanism shifted from reaction -controlled to diffusion-controlled, with N atoms diffusing inward to form a diffusion layer with high nitrogen solid solutions. With the prolong of nitriding time from 1h to 12h, the thickness of the diffusion layer increased from 11.77 μm to 96.07 μm.

Molecular Dynamics Analysis of Multi-Factor Influences on Structural Defects in Deposited Mg-Matrix Zn Atom Films.

Mg metal vascular stents not only have good mechanical support properties but also can be entirely absorbed by the human body as a trace element beneficial to the human body, but because Mg metal is quickly dissolved and absorbed in the human body, magnesium metal alone cannot be ideally used as a vascular stent. Since the dense oxide Zn film formed by Zn contact with oxygen in the air has good anti-corrosion performance, the Zn nanolayer film deposited on the Mg matrix vascular scaffold by magnetron sputtering can effectively inhibit the rapid dissolution of Mg metal. However, there are few studies on the molecular dynamic structural defects of Mg-matrix Zn atomic magnetron sputtering, and the atomic level simulation of Mg-matrix Zn thin-film depositions can comprehensively understand the atomic level structural defects in the deposition process of Zn thin films from a theoretical perspective to further guide experimental research. Based on this, this research first studied and analyzed the atomic layer structure defects, surface morphology, surface roughness, atomic density of different deposited layers, radial distribution function, and residual stress of the thin-film deposition layer of 1500 deposited Zn atoms at the initial deposition stage, during and after deposition under Mg-matrix thermal layer 500K and a deposited velocity 5 Å/ps by molecular dynamics. At the same time, the effects of temperature and deposited velocity of the Mg-matrix thermal layer on the surface morphology, roughness, and biaxial stress of the deposited films were studied.

A Novel Flow‐Balanced Friction Stir Channeling Technology: High Rectangularity Design and Channel Formation Mechanisms

Friction stir channeling (FSC) presents a promising approach for achieving continuous channels in heat exchangers, which are considered as leading candidates for high‐efficiency thermal dissipation. However, the irregular cross‐sectional shape of prepared channels induces stress concentration and compromises the load‐bearing capacity and structural integrity. Herein, flow‐balanced FSC (FB‐FSC) technology is proposed to fabricate channels with enhanced rectangularity. This technique allows for precise control over the shape, path, position, and arrangement of the channels. The channel formation in FB‐FSC is affected by material overflow–reflux behaviors and stick–slip conditions. Material overflows onto the shoulder due to shearing and extraction then refluxes under axial pressure to close the channel. The material stuck to the probe rotates accordingly and is pulled out into the channel cavity to form a deposition layer. By regulating channel formation mechanisms, channel rectangularity of 90.8%, continuous formation of 14 m, minimum spacing of 2 mm, variable arc radius, and gradient distribution are directly achieved via FB‐FSC. The FB‐FSC technology enables the efficient formation of cooling channels with high quality, which is significant for the design of heat exchangers to realize desired performances.

Effect of external surface barriers over hierarchical ZSM-5 zeolite on n-heptane catalytic cracking

To better understand external surface barriers on hierarchical ZSM-5 zeolite, SiO2 layers were constructed over zeolite nanocrystal by using chemical liquid depositions (CLD). Diffusion measurement showed that the apparent diffusion rate over the zeolite was increased by up to 142 % after SiO2 deposition, indicating that the external surface barriers had been significantly reduced. The performance of hierarchical ZSM-5 zeolite for n-heptane catalytic cracking indicated that the catalytic activity (TOF) was increased from 0.55 to 0.91 s−1 after 3 nm layer of SiO2 deposition, leading to a total yield increase of ethylene and propylene by up to 23 %. The strong positive correlation of catalytic activity with apparent diffusion rate suggests that reducing external surface barriers can improve the utilization efficiency of active sites in micropores and enhance the catalytic activity of the zeolite. These results demonstrate that CLD of SiO2 can reduce external surface barriers on hierarchical zeolite, thereby improving its cracking performance.

Production of low-sulphur tailings by hydrocycloning

Acid mine drainage (AMD) is an environmental problem in gold mines containing sulphur minerals. The potential for acid drainage in tailings facilities must be considered when studying their dry closure. Therefore, controlling the sulphur content in the final layer of tailings deposition has the potential to prevent AMD after closure. In this context, the rougher flotation tailings were hydrocycloning in a pilot plant in a gold mining company to assess the potential for generating modified tailings with low-sulphur content. A total of 10 samples were composited over one hour of pilot plant operation. The hydrocyclone overflow showed an average reduction of 36.2% in sulphur content and an average metallurgical recovery of 20.0%. The underflow had an average increase in sulphur content of 16.8% and 80.0% metallurgical recovery. These results demonstrated the possibility of generating modified tailings with reduced sulphur content through hydrocycloning.

Effects of Carbon Deposition on Deuterium Plasma-Driven Permeation Through Tungsten-Coated RAFM Steel

In steady-state operation of fusion reactors, eroded materials and contaminations, especially carbon (C), may deposit on the surface of plasma-facing components. In this work, the effects of C deposition on hydrogen isotope permeation behavior through tungsten (W)–coated reduced activation ferritic/martensitic (RAFM) steel were systematically investigated by plasma-driven permeation (PDP) measurements in the temperature range of 633 to 893 K. A C deposition layer with thickness of ~200 nm was prepared by magnetron sputtering to simulate the formation of C impurities in the first-wall area of tokamaks. The implantation depth of incident deuterium (D) ions was estimated to be <10 nm at incident energy of 114 eV. Deuterium effective diffusion coefficients (Deff’s) for W-coated RAFM steel with/without a C layer were obtained. It was found that the C layer tended to increase Deff in the low-temperature region of ~675 to 820 K. At high temperature, however, Deff was measured be lower than that without a C layer. Nevertheless, the addition of a C layer had no significant effect on Deff compared to the W coating alone with respect to bare RAFM steels. For steady-state D-PDP flux, it was found that the C layer significantly decreased D permeation flux at low temperature. But, the permeation flux difference between the samples with/without a C layer became smaller with increasing temperature, indicating that the influence of C deposition on D permeation was negligible at high temperature. Similar D-PDP behavior was detected as increasing the incident ion flux by means of increasing plasma discharge power. Surface reemission of absorbed D as well as the D concentration gradient throughout the sample was found to be influenced by C deposition; therefore, D permeation flux changed correspondingly.

The Ain Dibba and Ain Kissa phosphorites, Tebessa (NE Algeria): REE depletion versus shallow, open depositional environment during the Paleocene-Eocene phosphogenesis in North Africa

The Ain Dibba and Ain Kissa phosphorites, located north of Tebessa town, NE Algeria, belong to the Upper Cretaceous-Paleocene-Eocene Afro-Arabian phosphatic province that extends from Morrocco to the Middle East. These two phosphorite showings, which were partly exploited at the beginning of the 20th century, were deposited during the Late Paleocene (Thanetian) times on the northern basin of the Kasserine Paleo-Island. Although they are not yet economically very important, the present petrological and geochemical study contribute highly to the knowledge of their critical trace and REE contents as well as the understanding of their paleo-depositional environment. Petrographic and XRD data show that these phosphorites are mainly composed of pellets, coprolites, bioclasts and rare glauconite, gypsum, quartz grains and zeolites. These constituents are cemented by calcareous, siliceous or rarely clayey matrix. The pellets and coprolites are composed mainly of cryptocrystalline carbonate fluor-apatite (CFA). The XRF and ICP-MS chemical analyses of these phosphorites, show they are not as rich as those from Kef Essenoun and Bled El Hadba southern basin, neither in P2O5 nor in REE contents. P2O5 concentrations range from 14.16 to 26.57 wt% (average = 20.24 ± 4.33 wt%, n = 15), with only one sample having 31.89 wt% P2O5, whereas ΣREE contents range from 171 to 344 ppm (average = 252 ± 69 ppm, n = 9) and, therefore, considered as moderately REE-enriched phosphorites. Ce anomaly values display a decrease from the lower to the upper phosphorite sub-layers (from −0.57 down to −0.72), suggesting an increase from relatively sub-oxic to more oxic conditions. The Eu anomalies range from 0.89 to 1.35 for Ain Dibba and from 0.93 to 1.35 for Ain Kissa phosphorites. The highest Ce/Ce∗ and lowest Eu/Eu∗ anomalies are recorded in the lower layers, often enriched in both REE and glauconite contents, whereas the lowest Ce/Ce∗ and highest Eu/Eu∗ anomalies, reflecting more oxic conditions, are characteristics of the glauconite-free and REE-poor upper layers. The gradual timewise transition from relatively sub-oxic to oxic conditions (from the lower to the upper layers) is also recorded in the redox-sensitive (Cr, Ni, V, U) trace element data. This implies that during early diagenesis, the sedimentary environment became slightly reduced, which enabled intensive uptake of both REE and some trace element (e.g., Cr, V, Ni, U) mainly from pore-water through substitution and adsorption mechanisms onto apatite and glauconite minerals. This is noticed especially in the lower phosphorite layers of both Ain Dibba and Ain Kissa deposits. In a larger scale, the Ain Dibba and Ain Kissa phosphorites show lower REE contents, lower Ce and Eu anomalies, and lower redox-sensitive trace element contents than those of the southern (Kef Essenoun and Bled El Hadba) and eastern (Tunisian) basins of the Kasserine paleo-Island. These geochemical features indicate that phosphorites from the northern basin were deposited, through upwelling current, in a more open, shallower, oxygenated and agitated environment during the Paleocene-Eocene phosphogenesis in North Africa and Middle East.

Magnetic-assisted alignment of nanofibers in a polymer nanocomposite for high-temperature capacitive energy storage applications.

Flexible polymer-based dielectrics with high energy storage characteristics over a wide temperature range are crucial for advanced electrical and electronic systems. However, the intrinsic low dielectric constant and drastically degraded breakdown strength hinder the development of polymer-based dielectrics at elevated temperatures. Here, we propose a magnetic-assisted approach for fabricating a polyethyleneimine (PEI)-based nanocomposite with precisely aligned nanofibers within the polymer matrix, and with Al2O3 deposition layers applied on the surface. The resulting polymer nanocomposite exhibits simultaneously increased dielectric constant and enhanced breakdown strength at high temperatures compared to pristine PEI. The enhanced dielectric constant is contributed by the depolarization effect of out-of-plane orientated nanofibers in composite films, while the surficial Al2O3 layers, with a wide bandgap, effectively prevent charge injection and transport at the electrode/dielectric interface. The optimally aligned composite films exhibit a significantly enhanced discharged energy density of 6.5 J cm-3 at 150 °C, with approximately 41% and 132% enhancement compared to random films and pristine PEI films, respectively. Additionally, a metalized multilayer polymer-based capacitor utilizing this composite film produces a high capacitance of 88 nF, while demonstrating excellent cyclability and flexibility at 150 °C. This work offers an effective strategy for developing polymer-based composite dielectrics with superior capacitive performance at elevated temperatures and demonstrates the potential of fabricating high-quality flexible capacitors.