Formation Of Structure Research Articles

Deposition of Wear-Resistant Nanocomposite Coatings from Accelerated С<sub>60</sub> Ions

Hard wear-resistant carbon coatings were deposited from accelerated C60 ions at temperatures of 200 and 300°C. It has been established that the mechanical properties of the coatings are determined by the substrate temperature (Ts) and the energy composition of the beam. The hardness of coatings deposited from C+60 ions with an energy of 7 keV exceeds 50 GPa and is virtually independent of Ts. The presence of C602+ and C603+ with an energy of ~14 and 21 keV, respectively, in the beam leads to a result that is not typical for carbon coatings – the hardness increases by more than 1.3 times with an increase in Ts from 200 to 300°C (from 31.6 GPa to 41.6 GPa). In this case, according to Raman spectroscopy data, the size of graphite nanocrystals in the coating increases with temperature up to almost 2 nm. Coatings obtained under conditions of irradiation with C602+ and C603+ ions are characterized by minimal wear (1.5×10–8 mm3/N∙m, Ts = 200°C) and minimal friction coefficient (µ = 0.05 for Ts = 300°C). We attribute the unusual dependence of hardness on Ts and the improvement in the tribological properties of coatings to the formation of a composite structure based on a diamond-like matrix and graphite nanocrystals in this range of Ts.

Ultrafast photoinduced charge carrier dynamics of L-cysteine and oleylamine stabilized CsPbBr3 perovskite quantum dots coupled with gold nanoparticles.

We have synthesized L-cysteine and oleylamine stabilized CsPbBr3 perovskite quantum dots (PQDs) and coupled them with gold nanoparticles (AuNPs). The PQDs and AuNPs, as well as their hybrid nanostructures (HNS), were characterized using UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The UV-vis spectra show absorption bands of the HNS at 503 and 520nm, attributed mainly to PQDs and AuNPs, respectively. The PQDs show a strong excitonic PL band peaked at 513nm from PQDs. The HR-TEM results show the formation of hybrid structures between PQDs and AuNPs, which is also supported by the PL quenching of the PQDs by the coupled AuNPs. Ultrafast dynamics of the exciton and charge carriers in the HNS and pristine PQD were studied using femtosecond transient absorption. Multiexponential fitting of the dynamic data revealed the existence of shallow and deep trap states in pristine PQDs and ultrafast electron transfer from PQDs to AuNPs in the HNS. A kinetic model was proposed to account for the key dynamic processes involved and to extract the time for electron transfer from PQDs to AuNPs in the HNS, found to be ∼2ps. Dynamic processes in pristine PQDs are largely unchanged by HNS formation with AuNPs.

Cooperative Load Transportation with Quadrotors using Adaptive RISE Control

The problem of transporting cable-suspended payloads using two quadrotors is analyzed in this work. The system kinematics are treated using a virtual structure formation controller, which generates the acceleration references commanded to the aerial vehicles. The disturbances caused by the payload are treated as unmodeled disturbances and a novel robust integral of the sign of the error (RISE) controller is proposed, guaranteeing the asymptotic convergence of the tracking errors. A model reference adaptive control is also incorporated into the RISE controller, combining the advantages of adaptive and robust control. The proposal is validated by numerous experiments using two quadrotors to transport a bar-shaped payload in adverse conditions. The results allow the conclusion that the proposed system is capable of performing transportation and orientation tasks with the payload, subject to translational accelerations up to 3.5 m/s2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document}.

Thermoplastic Elastomers and Their Physical Gels Electrospun into Tunable Microfibrous Nonwoven Mats: Structure Formation and Property Enhancement

AbstractThermoplastic elastomers (TPEs) based on styrenic block copolymers constitute excellent examples of self‐networking macromolecules that are employed in a wide range of contemporary technologies as molded parts. In such applications, these TPEs exist as dense (nonporous) films or other shapes. Here, it is first demonstrated that a series of commercial TPEs possessing comparable compositions can be electrospun from solution to form microfibers that are arranged into nonwoven mats that are breathable. An important consideration for microfiber formation is the copolymer molecular weight, which regulates i) the viscosity of the parent solution prior to electrospinning, ii) the ability of these copolymers to self‐assemble during electrospinning, iii) the microfiber morphology, and iv) the mechanical properties of the resultant microfibers. The addition of a midblock‐selective aliphatic oil to these TPEs yields thermoplastic elastomer gels (TPEGs), wherein the copolymer morphology and mechanical properties become highly composition‐tunable. Electrospinning TPEGs from a binary oil+solvent solution introduces a micelle inversion mechanism that begins with an oil‐rich micellar core and ends with a styrene‐rich micellar core, required for network stabilization, as the solvent dries during microfiber solidification. This work has implications for the production of controllably low‐modulus microfibrous materials possessing modestly improved toughness but exceptional extensibility and enhanced optical transparency.

Statistical analysis of Cu content effects on structural properties in CuZr metallic glasses

This study examines the effects of casting conditions on the structural properties of CuZr metallic glasses (MGs) using molecular dynamics simulations. The influence of Cu content on various structural properties was explored, finding significant power-law relationships that indicate increased Cu promotes the formation of icosahedra-like structures and enhances the population of solid-like polyhedra. In contrast, the clustering coefficient, reflecting solid-like connectivity, showed a linear relationship with Cu content, revealing that while Cu increases solid-like structures, their connectivity does not scale proportionally. No significant correlations were found for sample volume, cooling rate, or temperature within the studied ranges. This study highlights the utility of statistical analysis in elucidating material property relationships, contrasting with the less interpretable nature of machine learning models. The findings provide valuable insights into the role of Cu content in MGs and demonstrate the importance of traditional statistical approaches for material characterization.

Ultrahigh-resolution imaging of biogenic phosphorus and molybdenum in palaeoproterozoic gunflint microfossils

Phosphorus and molybdenum play important roles in the formation of microbial cell structures and specific enzymes crucial for metabolic processes. Nevertheless, questions remain about the preservation of these elements within ancient microfossils. Here, we present shape-accurate ion images capturing phosphorus and molybdenum on Palaeoproterozoic filamentous microfossils by pioneering a methodology using lateral high-resolution secondary ion mass spectrometry. Introducing electrically conductive glass for mounting isolated microfossils facilitated clearer observations with increased secondary ion yields. Phosphorus was detected along the contours of microfossils, providing direct evidence of phospholipid utilization in the cell membrane. Trace amounts of molybdenum were detected within microfossil bodies, suggesting potential remnants of molybdenum-bearing proteins, such as nitrogenase. These findings align with the hypothesized cyanobacterial origin of filamentous gunflint microfossils. Our methodology introduces a groundbreaking tool for obtaining crucial insights into the cellular evolution and metabolic pathways of microorganisms, allowing comparisons of their morphological characteristics.

First copper (II) oxo-selenite-sulfate Cu4O(SeO3)(SO4)2 and the role of a lone electron pair in open framework crystal structure formation

New copper oxo-selenite-sulfate Cu4O(SeO3)(SO4)2 was prepared by the reaction of anhydrous CuSO4, CuO, and SeO2 in a sealed silica tube. The compound crystallizes in the triclinic P1‾ space group, with cell parameters a = 8.379(3)Å, b = 8.402(4) Å, c = 8.497(3) Å, α = 82.988(14) °, β = 61.006(9) °, γ = 62.105(14)°. The selenite-sulfate features open-framework crystal structure with two types of channels, where lone electron pairs of SeO32− groups are located. DFT calculations were made to support this statement and to investigate the nature of chemical bonding in the crystal structure and estimate the band gap (3.3 eV).The crystal structure of Cu4O(SeO3)(SO4)2 was compared to the related triclinic form of Cu4O(SeO3)3. The role of sulfate groups is also discussed.

Optimization of exopolysaccharide production from the novel Enterococcus species, using statistical design of experiment

The Exopolysaccharide (EPS) producing novel strains of Enterococcus previously isolated from the vaginal source of pregnant women were selected based on ropy structure formation. The two selected strains, E.villorum SB-2 and E.rivorum S22-3, were found to be producing 2.87 g/l and 3.14 g/l EPS, respectively, in the minimal media (M17 media) after 24-hour fermentation under anaerobic condition. Both the strains have probiotic properties and have the potential to be used for industrial applications. The production media and fermentation conditions were optimized to enhance the EPS production using the one-factor method, Placket-Burman factorial designing and Central composite design (CCD) of Response surface methodology (RSM). The most relevant factors affecting the EPS yield were sucrose, yeast extract and pH for E.villorum SB2 and sucrose, yeast extract and magnesium sulfate for the E.rivorum S22-3 as determined by Placket-Burman design, whose concentrations were further optimized using CCD. The optimized fermentation conditions gave the total EPS of 9.76 g/l (4 times the initial production) from E.villorum SB-2 and 7.74 g/l (2.5 times the initial production) from E.rivorum S22-3, respectively, after 36-hour incubation at 37 °C. These optimization studies might be helpful during scale-up process for the industrial scale production of these exopolysaccharide.

Effects of Acid Dissociation and Ionic Solutions on the Aggregation of 2-Pyrone-4,6-dicarboxylic Acid.

The conversion of lignin can produce biomass-derived aromatic compounds such as 2-pyrone-4,6-dicarboxylic acid (PDC), which is a potential sustainable precursor of bioplastics. PDC is a pseudoaromatic dicarboxylic acid that can aggregate in aqueous solution. Aggregation depends upon PDC-PDC, PDC-water, and PDC-ion interactions that are representative of interactions in similar charged, aromatic compounds. These interactions both dictate PDC aggregation and the likelihood that PDC aggregates exhibit parallel stacking configurations that may promote PDC crystallization, which can be leveraged to separate PDC from solution. However, the interplay of interactions that drive aggregation and structure formation, and how these depend upon the charge of PDC and ionic species present in solution, remains unclear. In this work, we investigate PDC aggregation in diverse ionic solutions using all-atom molecular dynamics simulations and molecular clustering analysis. We consider ion-induced dipole interactions by using a modified Lennard-Jones nonbonded model for divalent ions in solutions. From molecular clustering analysis, we derive characteristic parameters to quantify aggregate sizes and parallel stacking configurations. We show that acid dissociation facilitates PDC aggregation in ionic solutions via ion-mediated interactions, and different ionic solutions influence both the likelihood of aggregation and the formation of parallel aggregates. In particular, we find that parallel stacking is primarily found in solutions with monovalent ions, whereas divalent ions promote larger, but less structured, aggregates. These results provide molecular-scale insight into the effects of specific ions on the aggregation of like-charged PDC molecules to inform understanding of related separation processes.

Janus GO/BTA/PMMA Microcapsules for Biobased Self-Healing Anticorrosion Coatings with Ultrahigh Performance.

The giant reduction of the barrier properties due to self-healing microcapsules and the lack of real-time protection during the healing remained the main challenges in self-healing anticorrosion coatings. Herein, a facile strategy using Janus graphene oxide (GO) as a dense and flexible shell has been proposed to synergistically solve these challenges. Benzotriazole (BTA) was used to synthesize Janus GO at the oil-water interface, and Janus GO/BTA/poly(methyl methacrylate) microcapsules were prepared. Energy-dispersive X-ray spectroscopy, Fourier infrared spectroscopy, Raman spectroscopy, and ultraviolet spectrophotometer analysis confirmed the formation of a Janus GO structure with one surface hydrophilic and the other hydrophobic. The surface morphology of J-GO-capsules with a high GO coverage rate was observed by scanning electron microscopy. The high biobased content coating containing J-GO-capsules showed a low-frequency impedance value above 1010 as assessed by electrochemical impedance spectroscopy after being immersed in 3.5 wt % NaCl solution for 60 days. In addition, the low-frequency impedance values of the coating were maintained after being scratched due to the self-healing properties of the J-GO-capsules as well as the real-time protective effect of the BTA. Biobased coatings with the best overall properties among all of the self-healing anticorrosion coatings were prepared.

Synthesis and characterization of epoxy resin‐polydicyclopentadiene interpenetrating polymer networks by UV‐initiated simultaneously frontal polymerization

AbstractBy combination of UV curing and frontal polymerization, interpenetrating polymer networks (IPNs) based on diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin and polydicyclopentadiene (PDCPD) were prepared by UV‐induced simultaneously frontal polymerization in this paper. Compared with the net DGEBA cured polymer, the tensile strength, elongation at break and impact strength of the IPNs were simultaneously improved. The maximum tensile strength and elongation at break of the IPNs reached 100 MPa and 4.64%, respectively, and the maximum impact strength reached 7.34KJ/m2 with an improvement of 115.2% over that of the net DGEBA cured polymer. Thermogravimetric analysis (TGA) results revealed that the IPNs could enhance the thermal stability. Data of the differential scanning calorimetry (DSC) and TGA testing shows that the IPN shows a single glass transition temperature (Tg) which is between the Tg of DGEBA and DCPD, indicating homogeneous phase and highly cross‐linked IPN formed. Morphologies and molecular structure of the IPNs polymer were observed by scanning electron microscope (SEM) and characterized by Fourier transform infrared spectroscopy (FTIR), respectively, whose results also proved the formation of ideal IPNs structures.

Euclid. I. Overview of the Euclid mission

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. is a medium-class mission in the Cosmic Vision 2015--2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14\,000\,deg$^2$ of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

Enhanced X-band microwave shielding via Fe3O4 nanoparticle-decorated few layered nitrogen-doped reduced graphene oxides: Synthesis, characterization, and performance assessment

Currently, developing lightweight with good microwave (MW) shielding efficacy materials are exceedingly challenging. The challenging task for a few layers of nitrogen-doped reduced graphene oxide (FLN-rGO) derived from thermal N-deposition with an exfoliation under the pyrolysis process. Concurrently, nitrogen-doped heteroatoms FLN-rGO structure possessing an additional electron can enhance the electrical conductivity and function as an electroactive site that enhances MW shielding effectiveness (SE). Besides, the synthesized Fe3O4-FLN-rGO NCs are self-sustaining, lightweight, and have strong chemical stability and outstanding MA performance due to the presence of chemical interaction between each other and the development of hierarchical structure formation. The structural and chemical interaction properties of pristine and Fe3O4-FLN-rGO composites are investigated using high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). These analyses confirmed that Fe3O4 NPs are homogeneously decorated on the FLN-rGO surface and revealed the chemical interactions between Fe3O4 and N-rGO, as evidenced by the Fe–O–C bonding signal observed in the Fe3O4-N-rGO (1:2) composites. The Fe3O4 NPs demonstrated remarkable saturation magnetization (Ms) and low coercivity (Hc), indicating that quantum confinement effects moderate their soft ferromagnetic characteristics. With a lightweight shielding materials thickness of 0.5 mm, these composites demonstrated an outstanding average MW SE of 44.73 dB at 8 GHz and a superb MW attenuation value (α = 845.05), indicating their excellent efficacy as materials for advanced MW shielding applications.

Bimodal structure formation and texture transition mechanism in laser remelted Mg–Al-based alloy

Texture inheritance, texture weakening, and a complete texture transition within different solidified molten pool (MP) have been achieved by manipulating various processing parameters of conduction mode in laser remelted magnesium-aluminum (Mg–Al)-based AZ31 alloy. At a low laser power (P = 100 W), restricted number of temperature gradient directions on moving solid/liquid (S/L) interfaces within small MP leads to strong texture inheritance. Tilting angles 20°–45° away from building direction (B.D.) in {0001} plane is a preferential growth direction of texture inheritance. In contrast, spontaneous texture weakening has occurred due to frequently varied temperature gradient directions within increasing MP size in higher P cases. Meanwhile, increasing scanning speed V has a significant effect on weakening the texture as well as refining grains in the solidified MP. Furthermore, fine grains formation with random orientations in MP bottom at both high P (400 W) and high V (20, 30, and 50 mm/s) leads to the occurrence of a bimodal structure, which is affected by solidification characteristics as well as thermal convection. For the case of the highest P and the highest V, a texture transition has occurred as tilting angles of 45°–90° away from B.D. in {0001} plane within MP, compared to 0°–45° texture of base material for the Mg–Al-based alloy in the study.

Comparative Analysis of Perturbed $f(R)$ Gravity and Perturbed Rastall Gravity Models in Describing Cosmic Evolution from Early to Late Universe Relative to the $\Lambda$CDM Model

Abstract This study conducts a meticulous examination of the cosmological implications inherent in Rastall gravity and $f(R)$ gravity models, assessing their efficacy across distinct cosmic epochs, from early universe structure formation to late-time acceleration. In the initial stages, both models exhibit commendable compatibility with observed features of structure formation, aligning with the established $\Lambda$CDM model. The derived Jeans' wavenumbers for each model support their viability. However, as the cosmic timeline progresses into the late universe, a discernible disparity surfaces. Utilizing the Markov Chain Monte Carlo method, we reconstruct the deceleration parameter $(q)$ and identify Deceleration - Acceleration redshift transition values. For $f(R)$ gravity, our results align closely with previous studies, emphasizing its superior ability to elucidate the recent cosmic acceleration. In contrast, Rastall gravity exhibits distinct redshift transition values. Our rigorous analysis underscores the prowess of $f(R)$ gravity in capturing the observed cosmic acceleration, positioning it as a compelling alternative to the conventional $\Lambda$CDM model. The discernible shifts observed in the peaks of the CMB power spectrum and evolution of deceleration parameter (q) for both $f(R)$ gravity and Rastall gravity models in the Early and Late universe, in relation to the $\Lambda $CDM model, provide compelling evidence supporting the proposition that these alternative gravity models can account for the anisotropy of the universe without invoking the need for dark energy.

Biomass to biofuel: Palm kernel shells as catalyst supports for enhanced biodiesel production

AbstractThe use of agricultural biomass fibers, specifically palm kernel shell (PKS), has significant potential to enhance biodiesel production. This approach overcomes economic barriers and contributes to sustainability by repurposing agricultural biomass. This study explores the effectiveness of PKS as a cost‐effective and sustainable catalyst support. Palm kernel shell was chosen due to its high carbon content, low ash presence, and abundance as a byproduct in the palm oil industry, making it an economically viable and environmentally friendly option. In this study, an optimized activated carbon from PKS biomass was fabricated as catalyst support to enhance biodiesel production efficiency. Using response surface methodology (RSM), the PKS was impregnated with phosphoric acid and synthesized at various acid concentrations, impregnation times, and activation times to enhance porosity for catalytic support capabilities. The experimental design included a central composite design (CCD) to vary these factors systematically and determine their optimal levels. Scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis revealed significant development of porosity, affirming the efficient activation process. Energy dispersive X‐ray (EDX) analysis confirmed phosphorus incorporation during activation, indicating the formation of an intricate pore structure. Fourier transform infrared (FTIR) spectroscopy highlighted the presence of functional groups pertinent to the biodiesel reaction process. The transesterification process employing PKS as a catalyst with different biobased feedstocks, such as waste frying oils from corn, palm, and sunflower, led to biodiesel yields of varying efficiencies. Notably, corn oil had the highest yield at 94.92%. This study highlights the potential of PKS as a biobased catalyst support and contributes to the broader biorefinery concept by integrating biomass utilization into renewable fuel production.

Metal-organic framework-derived hierarchical Ag/Ti3C2Tx/Co/C nanocomposite for enhanced electromagnetic wave absorption

The microwave absorption (MA) performance of 2D Ti3C2Tx is significantly restricted due to its lack of magnetic loss capacity and mismatched electromagnetic impedance. The Ag/Ti3C2Tx/Co/C (ATCC) structure, based on a unique 2D layered Ti3C2Tx, has shown exceptional electromagnetic wave absorption (EWA) properties. The addition of a silver nanoparticles enhances the polarization effect and conductance loss of Ti3C2Tx. By incorporating ZIF-67 with varying Co content, nanocomposite heterostructures and interfaces are formed in Ag/Ti3C2Tx. Moreover, the carbon source of organic ligand and the 3D network structure of Ti3C2Tx provide additional electronic transition channels and improve conductive loss. This modification results in non-uniform interfaces between Ti3C2Tx and metal nanoparticles, leading to electron accumulation and the formation of a micro-capacitance structure that generates interface polarization. Eddy current loss and magnetic loss from metal nanoparticles further enhance EWA properties. This study envisions a novel strategy for developing efficient Ti3C2Tx-based microwave absorbers modified with metal nanoparticles.

Impact of calcination technology on properties of calcined clays

Calcined kaolinitic clays are known to be very reactive pozzolans, and combined with limestone can enable significant clinker substitution in cementitious systems. Thermal activation of kaolinitic clays takes place when the hydroxyl groups are removed, leading to formation of an amorphous reactive structure. There are several technologies for clay activation, but the most used at industrial scale are flash and stationary calcination. The objective of this paper is to investigate the impact of the calcination regime on the properties of the calcined product. It presents the results of an experimental program carried out with a kaolinitic clay calcined at a flash calciner and at a laboratory furnace. Calcination brings about a drop in specific surface, and an increase of average diameter due to agglomeration, an effect more pronounced in stationary calcination. No major differences were found at the heat of hydration, CH consumption and phase assemblage for the fully dehydroxylated material. The flash calcined material had slightly better results mainly due to a finer PSD compared with the one stationary calcined. No major difference was found in water demand and compressive strength for both regimes. As expected, the main impact of the calcination regime is the agglomeration.

Optical skyrmion and its "zipper-like" topological behavior in an energy flux field.

The optical skyrmion and its topological behavior are analyzed in an energy flux field constructed by an X-type vortex in a high numerical aperture system. The conditions for the formation of a skyrmion structure in this field are discussed, showing that the vortex pattern of the transverse energy flow and the inverse energy flow are crucial for the skyrmions and also are controlled by the phase gradient of the X-type vortex. Notably, the "zipper-like" topological reaction, which is the first, to our knowledge, found in ferromagnetic materials, is observed, and the physical mechanism is also explained by the relation of orbital angular momentum density and Poynting vectors. The results will reach the topological theory and may have applications in optical traps and data storage.

Tertiary lymphoid structure formation induced by LIGHT-engineered and photosensitive nanoparticles-decorated bacteria enhances immune response against colorectal cancer

Tertiary lymphoid structures (TLSs) are known to enhance the prognosis of patients with colorectal cancer (CRC) by fostering an immunologically active tumor microenvironment (TME). Inducing TLS formation therapeutically holds promise for treating immunologically cold CRC, though it poses technical challenges. Here, we design and fabricate a photosensitive bacterial system named E@L-P/ICG. This system is engineered bacteria internally loaded with the cytokine LIGHT and surface-modified with PLGA/ICG nanoparticles (P/ICG NPs). Once accumulated in orthotopic colonic tumors in mice, E@L-P/ICG generates a mild photothermal effect under laser irradiation due to the photosensitive P/ICG NPs. This photothermal effect triggers the self-rupture of E@L-P/ICG and the death of surrounding tumor cells to release adjuvants and antigens, respectively, which in turn synergistically activate the adaptive immune responses. Furthermore, the cytokine LIGHT released from ruptured E@L-P/ICG stimulates the generation of high endothelial vessels (HEVs), promoting lymphocyte recruitment within the TME. These mechanisms lead to the TLS formation in CRC, which further boosts adaptive immune responses through effective infiltration of T cells and B cells, resulting in effectively inhibited tumor growth and extended survival of mice. Our study shows the potential of the E@L-P/ICG system in photosensitively inducing the TLS formation to treat CRC in clinic.