Development Of Nanostructures Research Articles

Carbon nanotube interweaved Fe7Se8 nanosheet/nanorod hybrids on expanded graphite for high-performance sodium storage

The construction of nano-micro scale hybrid structures by carbon materials is an effective strategy to address the issues of metal chalcogenides when used as anodes of sodium-ion batteries. Herein, we develop a carbon nanotube (CNT)-interweaved Fe7Se8/expanded graphite (EG) composite by means of a facile one-step gas-phase pyrolysis route with ferrocene, selenium and EG as the starting materials. The ex-situ monitoring of the pyrolysis process indicates that the selenium as a promoter facilitates the formation of CNTs and the carbon coated Fe7Se8 nanosheet/nanorod mixture. A competing reaction between CNT growth and the evolution of Fe7Se8 nanostructures occurs, which could be dominated by the concentration of selenium vapor. By optimizing the feeding ratio and the pyrolysis condition, the nanocomponents are homogeneously deposited on the surface of the EG matrix to realize a well-developed nano-micro hybrid configuration. The constructed three-dimensional conductive network, rich mesopores and high specific surface area (107.1 m2 g−1) contribute to substantially enhanced sodium-storage performance in ester electrolyte. Remarkably, the optimized composite electrode exhibits high reversible capacity retention of 97.5 % after 1000 cycles at 1.0 A g−1 and improved rate performance of 325 mAh g−1 at 2.0 A g−1. This study provides new avenues to develop high-performance metal chalcogenide electrodes for electrochemical energy storage.

Regulating the structure and performance of amorphous carbon-based films by introducing different interlayers for applications in PEMFC bipolar plates

In this work, the effects of inserting an interlayer on the anti-corrosion performance of amorphous carbon (a-C) films in a simulated Proton Exchange Membrane Fuel Cell (PEMFC) environment have been systematically studied. Four a-C films with different interlayers, namely CCr, C-Cr-N, CrN and Cr, were prepared on 316L stainless steel substrates using unbalanced magnetron sputtering. The surface/fractural morphologies, carbon bonding structure and the anti-corrosion performance of the 4 films were observed/characterized in detail. The nanostructure and composition evolution from the film surface down to the film-substrate interface before and after electrochemical tests were also analysed via high resolution transmission electron microscopy (HRTEM). Results indicate that a-C films with CCr and C-Cr-N interlayers display superior corrosion resistance compared to undoped samples and those lacking an interlayer, with the lowest self-corrosion current density (i.e. 2.1 × 10−7 A/cm2, C-Cr-N interlayer) being nearly two orders of magnitude lower than that of the substrate (i.e. 1.1 × 10−5 A/cm2). The doped C-Cr-N interlayer plays a vital role in the corrosion resistance of the samples by accelerating oxidation of surface defect locations, inhibiting the continuous penetration of electrolyte, and improving corrosion resistance. Additionally, a-C films with a C-Cr-N interlayer exhibited an outstanding interface contact resistance (ICR) value (~3.5 mΩ/cm2) than that with a CrN interlayer (~30 mΩ/cm2) or the 316L substrate (~100 mΩ/cm2) at a typical contact pressure of 1.5 MPa. All 4 films demonstrate obviously improved hydrophobicity (contact angles against distilled water under room temperature up to 94.2°) compared to the substrate (75.8° under identical condition). In a word, this study proves that the strategy of inserting an appropriately designed interlayer (with the ternary C-Cr-N being most promising) to a-C films could alter and enhance the anti-corrosion, ICR and hydrophobic properties of 316L, proposing valuable solutions for high-performance bipolar plates (BPs) in the PEMFC industry.

Exit wave reconstruction of a focal series of images with structural changes in high-resolution transmission electron microscopy.

High-resolution transmission electron microscopy (HRTEM) images can capture the atomic-resolution details of the dynamically changing structure of nanomaterials. Here, we propose a new scheme and an improved reconstruction algorithm to reconstruct the exit wave function for each image in a focal series of HRTEM images to reveal structural changes. In this scheme, the wave reconstructed from the focal series of images is treated as the initial wave in the reconstruction process for each HRTEM image. Additionally, to suppress noise at the frequencies where the signal is weak due to the modulation of the lens transfer function, a weight factor is introduced in the improved reconstruction algorithm. The advantages of the new scheme and algorithms are validated by using the HRTEM images of a natural specimen and a single-layer molybdenum disulphide. This algorithm enables image resolution enhancement and lens aberration removal, while potentially allowing the visualisation of the structural evolution of nanostructures.

Efficient nanopatterning of Ge surface induced by oblique argon cluster ion beam

The evolution of the self-assembled nanostructures formed on the Ge (100) surface as a result of sputtering by an obliquely incident argon cluster ion beam is studied. The bombardment was carried out with Ar1000+ ions at energy of 10 keV and angle of incidence of 60˚ from the normal while varying the ion fluence from 8 × 1014 up to 2 × 1016 ions/cm2. It is found that parallel-mode ordered ripples with significant aspect ratios can be produced on the Ge surface at a minimum sputtering depth. Such nanostructures have not previously been formed on the Ge surface with conventional argon ions. Our findings prove that argon cluster ion beam is effective for nanopatterning the surface of single-component semiconductors.

Evolution of interfacial nanostructures with temperature governing fretting wear in diamond-like carbon films

Diamond-like carbon (DLC) films are capable of offering low friction coefficient and high wear resistance when rubbed in both dry and lubricated interfaces. However, the inherent mechanisms governing fretting wear in DLC films with temperature are still not well comprehended. Herein, atomic-scale analysis was conducted to unveil the relationship between interfacial tribofilms and the fretting wear behaviors. The results emphasize the determining role of the interaction between the tribo-sintered tribofilms and the transferred carbon tribofilms, as well as the structural evolution in the DLC film with temperature. The room temperature (RT) fretting experiment establishes a bilayer nanostructured tribofilm with a C-rich transfer layer on a Fe-rich tribo-sintered layer. As the fretting temperature elevates the graphitization degree of the tribofilms exacerbates, surface oxidation and hydrogen effusion arise in the DLC film, resulting in higher friction coefficients and wear rates. Chromium outward diffusion at 500 °C establishes a Cr-rich interlayer in the tribofilm, which forms interfacial chromium-carbon bonds, promotes adhesive carbon transfer, and leads to the sharp increase of the friction force and wear rate. These findings provide new insights into the fretting wear mechanisms, and provide guidance for the application of DLC films in elevated-temperature fretting scenarios such as aero-engines tenon and spline connections.

A three-dimensional phase-field model for studying the orientation-dependent interface evolution in stress-induced martensitic phase transformation

In this study, we address the challenging task of predicting the motion of interfaces in stress-driven martensitic phase transformations within shape memory alloys. The novelty of our approach lies in the introduction of a monolithically solved thermodynamic-based phase-field method, specifically tailored for large strain conditions at the nanoscale for three-dimensional problems. To achieve this, we have developed a custom finite element software seamlessly integrated into the FEniCS open-source framework, providing a sophisticated and efficient tool for the examination of nanostructure evolution. Our investigation delves into five distinct and complex scenarios under diverse loading conditions for two– and three-dimensional problems, each presenting unique challenges: (i) a straightforward uniaxial tension scenario featuring a square domain with a pre-existing martensitic nucleus; (ii) the evolution of interfaces in a square sample incorporating a circular central nanovoid under biaxial tensile stress; (iii) the analysis of a rectangular beam subjected to horizontal and vertical compressive loads; (iv) the assessment of an initially voided rectangular beam experiencing mixed loading conditions; and (v) the three-dimensional simulations of cubic-to-tetragonal phase transformation using various orientation of the habit plane. In contrast to prior studies, our analysis not only explores the standard factors of habit plane reorientation and strain transformation values but also delves into the impact of nanovoids on austenite–martensite interface evolution.

Seeded Growth of Plasmonic Nanostructures in Deformable Polymer Confinement.

Plasmonic nanostructures exhibit optical properties highly related to their morphologies, enabling diverse applications in various areas such as biosensing, bioimaging, chemical detection, cancer therapy, and solar energy conversion. The expansive uses of these nanostructures necessitate robust and versatile synthesis methods suitable for large-scale production. Here, we introduce our recent efforts in developing a new strategy for controlling the seeded growth of plasmonic metal nanostructures, employing deformable polymer capsules to regulate the growth kinetics and the resulting particle morphology. Employing sol-gel-derived resorcinol-formaldehyde (RF) resin as a typical capsule material, we highlight its advanced features, including mechanical deformability and molecular permeability, that can be manipulated by tuning the capsule thickness and cross-linking degree. These features enable highly controllable confined seeded growth of plasmonic nanostructures. We reveal the significant role of the Ostwald ripening process of the seeds and the capsule structures in determining the morphological evolution of the plasmonic nanostructures. Moreover, we highlight some distinctive plasmonic nanostructures resulting from this unique synthesis strategy and their intriguing functionalities in various potential applications. Our discussion concludes with potential research directions to advance the development of the deformable polymer-confined seeded growth strategy into a general and robust synthesis platform for creating cutting-edge functional plasmonic nanostructures.

Thermoplastic elastomer obtained by photopolymerization‐induced concomitant macrophase and microphase separations

AbstractWe report on concomitant photoinitiated polymerization‐induced macrophase and microphase separation strategies to produce hierarchically structured recyclable poly(n‐butyl acrylate) based elastomeric materials. The investigated crosslinker‐free formulations are composed of n‐butyl acrylate monomer and a UV photo‐initiator mixed with poly(methyl methacrylate)‐b‐poly(n‐butyl acrylate)‐poly(methyl methacrylate) ABA triblock copolymers. Two different pre‐synthesized copolymers are used to control the macrophase separation. One synthesized by nitroxide‐mediated radical polymerization (NMRP), and a second by anionic polymerization (AP). Essentially, NMRP route leads to copolymer with unsaturated chain ends, activated during UV photopolymerization. On the other hand, the copolymer synthesized by AP are chemically inert. That dissimilarity is also highlighted by time‐resolved FTIR and SAXS, performed to monitor respectively monomer conversion and nanostructure evolution during photopolymerization. The experimental data demonstrate that the reactivity of the triblock copolymer impacts drastically the polymerization kinetics and the self‐assembly processes. Finally, the rheological analysis shows that the produced materials present a solid‐like behavior at low frequencies despite a large PnBA content (i.e., 85 wt%). This property is associated to the phase segregation and to the sample hierarchical morphology.

Nano-Structure Evolution and Mechanical Properties of AlxCoCrFeNi2.1 (x = 0, 0.3, 0.7, 1.0, 1.3) High-Entropy Alloy Prepared by Mechanical Alloying and Spark Plasma Sintering.

The AlxCoCrFeNi2.1 (x = 0, 0.3, 0.7, 1.0, 1.3) multi-component high-entropy alloy (HEA) was synthesized by mechanical alloying (MA) and Spark Plasma Sintering (SPS), The impact of the percentage of Al on crystal structure transition, microstructure evolution and mechanical properties were studied. Crystal structure was investigated by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results show that with the increasing of Al content, the crystal structure of the alloys gradually transformed from a nanocrystalline phase of FCC to a mix of FCC and BCC nanocrystalline. The hardness was found to increase steadily from 433 HV to 565 HV due to the increase in fraction of BCC nanocrystalline phase. Thus, the compressive fracture strength increased from 1702 MPa to 2333 MPa; in contrast, the fracture strain decreased from 39.8% to 15.6%.

The Creep‐Induced Micro‐ and Nanostructural Evolution of a Eutectic Mo–Si–Ti Alloy at 1200 °C

In the present study, the creep deformation mechanisms of a eutectic Mo–Si–Ti alloy (comprising a body‐centered solid solution and a hexagonal silicide) are verified. The microstructural changes occurring at the various microstructural length scales are correlated to the nature of the creep curve. The creep curve exhibits a transient strain‐hardening region followed by a distinct minimum and then creep rate accelerates after that. The formation of a high fraction of disperse (Ti,Mo)5Si3 precipitates in the solid solution lead to significant strengthening in the transient creep regime. By the simultaneous decrease of the initially high dislocation density in the solid solution, diffusional creep contributes to effective creep behavior. At the minimum, the load and strain are also carried by the silicide phase which undergoes plastic deformation. Continuous coarsening of precipitates and loss of precipitation strengthening in the solid solution and dynamic recovery in the silicide phase lead to creep acceleration.

Influence of environmental conditions on the morphological evolution of bismuth oxide nanostructures via pulsed laser ablation in liquids

Bismuth oxide nanomaterials are increasingly recognized for their promising electronic and optical properties, particularly in electrochemical and biomedical applications. This study demonstrates that various bismuth oxide nanostructures can be synthesized through pulsed laser ablation in liquids (PLAL) by adjusting the concentration of dissolved gases from ambient conditions. Structural and compositional analyses were performed using x-ray diffraction, Raman spectroscopy, FTIR spectroscopy, and morphological investigations were conducted using atomic force microscopy and transmission electron microscopy. Our findings indicate that factors such as dissolved gases, laser fluence, and nanoparticle aging are crucial in determining the final structure and composition of the resulting nanomaterial. The phases observed ranged from spherical metallic bismuth nanoparticles to monoclinic bismuth oxide nanowire bundles, and orthorhombic bismuth carbonate oxide nanosheets. Dissolved gases are shown to influence not only the primary particles formed immediately after ablation, but also significantly impact the aging process of the colloid as well. Additionally, fluence plays an important role in the production of reactive oxygen species, thereby influencing the reactive pathways experienced by the ablated material and its subsequent formation into nanostructures. A notable result, emphasizing the significance of factors such as liquid environment and fluence when performing PLAL on reactive targets like bismuth, is seen in high fluence (20 J/cm2) samples under ambient conditions. These samples initially display an amalgamation of α-Bi2O3 nanowire bundles and carbonate nanosheets, which upon aging, transition to predominantly bismuth oxide nanowire bundles. This contrasts with samples produced in a saturated CO2 environment where bismuth carbonate nanosheets remain highly stable in the colloid.

End-to-End Phase Field Model Discovery Combining Experimentation, Crowdsourcing, Simulation and Learning

The availability of tera-byte scale experiment data calls for AI driven approaches which automatically discover scientific models from data. Nonetheless, significant challenges present in AI-driven scientific discovery: (i) The annotation of large scale datasets requires fundamental re-thinking in developing scalable crowdsourcing tools. (ii) The learning of scientific models from data calls for innovations beyond black-box neural nets. (iii) Novel visualization & diagnosis tools are needed for the collaboration of experimental and theoretical physicists, and computer scientists. We present Phase-Field-Lab platform for end-to-end phase field model discovery, which automatically discovers phase field physics models from experiment data, integrating experimentation, crowdsourcing, simulation and learning. Phase-Field-Lab combines (i) a streamlined annotation tool which reduces the annotation time (by ~50-75%), while increasing annotation accuracy compared to baseline; (ii) an end-to-end neural model which automatically learns phase field models from data by embedding phase field simulation and existing domain knowledge into learning; and (iii) novel interfaces and visualizations to integrate our platform into the scientific discovery cycle of domain scientists. Our platform is deployed in the analysis of nano-structure evolution in materials under extreme conditions (high temperature and irradiation). Our approach reveals new properties of nano-void defects, which otherwise cannot be detected via manual analysis.

On the divergent effects of stress on the self-organizing nanostructure due to spinodal decomposition in duplex stainless steel

Duplex stainless steels suffer from serious embrittlement due to the self-organization of the nanostructure caused by phase separation (PS) in ferrite. As duplex stainless steel (DSS) components are often subjected to stress during service, the effect of elastic tensile stress (ETS) on phase separation (PS) in alloy 2507 has been investigated in this study. The alloy was aged at 400 and 450 °C for different times under an applied ETS. The nanostructure evolution and mechanical properties were analyzed using small-angle neutron scattering and analytical transmission electron microscopy as well as Vickers-hardness and nanoindentation measurements. The results show that the applied ETS can suppress spinodal decomposition (SD) in ferrite in DSS 2507, which may be due to that ETS increases the critical compositional fluctuation wavelength for SD and thus increases the diffusion distance and barrier to the occurrence of SD. The suppressive effect is more obvious at longer aging time for the same level of applied stresses. It is also indicated that the suppressive effect of ETS seems to change non-monotonically with stress levels and the medium stress level is likely to have the largest suppressive effect. The suppressive effect of ETS on PS may significantly delay the embrittlement and extend the service longevity of DSS components within the miscibility gap. These results further the understanding of the effect of ETS on PS and elastic stress should be considered in the configurations of computational simulations of PS and evaluation of the service longevity of DSS components.

Revealing Seed-Mediated Structural Evolution of Copper-Silicide Nanostructures: Generating Structured Current Collectors for Rechargeable Batteries.

Metal silicide thin films and nanostructures typically employed in electronics have recently gained significant attention in battery technology, where they are used as active or inactive materials. However, unlike thin films, the science behind the evolution of silicide nanostructures, especially 1D nanowires (NWs), is a key missing aspect. Cux Siy nanostructures synthesized by solvent vapor growth technique are studied as a model system to gain insights into metal silicide formation. The temperature-dependent phase evolution of Cux Siy structures proceeds from Cu>Cu0.83 Si0.17 >Cu5 Si>Cu15 Si4 . The role of Cu diffusion kinetics on the morphological progression of Cu silicides is studied, revealing that the growth of 1D metal silicide NWs proceeds through an in situ formed, Cu seed-mediated, self-catalytic process. The different Cux Siy morphologies synthesized are utilized as structured current collectors for K-ion battery anodes. Sb deposited by thermal evaporation upon Cu15 Si4 tripod NWs and cube architectures exhibit reversible alloying capacities of 477.3 and 477.6 mAh g-1 at a C/5 rate. Furthermore, Sb deposited Cu15 Si4 tripod NWs anode tested in Li-ion and Na-ion batteries demonstrate reversible capacities of ≈518 and 495 mAh g-1 .

Developments in Atomistic and Nano Structure Evolution Mechanisms of Molten Slag Using Atomistic Simulation Methods.

Molten slag has different properties depending on its composition. The relationship between its composition, structure, and properties has been the focus of attention in industrial manufacturing processes. This review describes the atomistic scale mechanisms by which oxides of different compositions affect the properties and structure of slag, and depicts the current state of research in the atomic simulation of molten slag. At present, the research on the macroscopic properties of molten slag mainly focuses on viscosity, free-running temperature, melting point, and desulphurization capacity. Regulating the composition has become the most direct and effective way to control slag properties. Analysis of the microevolution mechanism is the fundamental way to grasp the macroscopic properties. The microstructural evolution mechanism, especially at the atomic and nanoscale of molten slag, is reviewed from three aspects: basic oxides, acidic oxides, and amphoteric oxides. The evolution of macroscopic properties is analyzed in depth through the evolution of the atomic structure. Resolution of the macroscopic properties of molten slag by the atomic structure plays a crucial role in the development of fundamental theories of physicochemistry.

High enhancement, low cost, large area surface enhanced Raman scattering substrates all by atomic layer deposition on porous filter paper

We successfully developed an atomic layer deposition (ALD) method for making Ag noble nanoparticles on cheap, commercial filter paper consisting of three-dimensional porous glass fibers and investigated the evolution of Ag nanostructures with some key process parameters. By tuning Ag particle sizes and controlling the cycle numbers of ALD deposited Ag films, we were able to obtain high-density isolated Ag nanoparticles with average sizes in 3–9 nm without the formation of agglomerates and continuous Ag films. We proved the presence of strong localized surface plasmon resonance peaks near a target wavelength of 632 nm. We further proved the presence of surface enhanced Raman scattering (SERS) signals on the Ag coated filter paper substrates using pyridine as the test analyte. Our results demonstrate that ALD is a very promising technique for a rational design of SERS substrates and, thus, has great potential for the fabrication of large-area, low-cost SERS substrates for future commercial applications, as compared to other existing techniques.

A Study on the Nanostructural Evolution of Bi/C Anode Materials during Their First Charge/Discharge Processes.

As a candidate anode material for Li-ion batteries, Bi-based materials have attracted extensive attention from researchers due to their high specific capacity, environmental friendliness, and simple synthesis methods. However, Bi-based anode materials are prone to causing large volume changes during charging and discharging processes, and the effect of these changes on lithium storage performance is still unclear. This work introduces that Bi/C nanocomposites are prepared by the Bi-based MOF precursor calcination method, and that the Bi/C nanocomposite maintains a high specific capacity (931.6 mAh g-1) with good multiplicative performance after 100 cycles at a current density of 100 mA g-1. The structural evolution of Bi/C anode material during the first cycle of charging and discharging is investigated using in situ synchrotron radiation SAXS. The SAXS results indicate that the multistage scatterers of Bi/C composite, used as an anode material during the first lithiation, can be classified into mesopores, interspaces, and Bi nanoparticles. The different nanostructure evolutions of three types of Bi nanoparticles were observed. It is believed that this result will help to further understand the complex reaction mechanism of Bi-based anode materials in Li-ion batteries.

Surface modification and enhanced wear performance through severe shot peening treatment in 316L stainless steel manufactured by metal injection moulding

This study investigates the micro-to nanostructural evolution, hardness, and linear reciprocating wear resistance, using Al2O3 ball as a counterpart of 316L stainless steel fabricated by the metal injection moulding (MIM) process, with and without severe shot peening treatment (SSP). SSP treatment led to a slight increase in Ra but a decrease in Rz and the formation of nanocrystalline surface, α′-martensite and mechanical twin. The subsurface hardness increased significantly. Surprisingly, the coefficient of friction remained constant (0.37–0.56) and depended solely on the testing load, despite alterations in surface roughness and subsurface microstructure due to SSP treatment. Furthermore, wear resistance notably improved under 10 N and 20 N loads, attributed to the surface modification by SSP treatment, but showed no significant difference at 30 N. The wear mechanisms, including abrasive, adhesive wear, and oxidative wear, remained similar, with adhesive and oxidative wear dominating at lower testing loads (10–20 N). However, with a testing load of 30 N, the strengthening effect of SSP treatment was surpassed, leading to the dominance of severe adhesive and oxidative wear. Consequently, the wear resistance exhibited insignificant differences between specimens before and after SSP treatment.

Nanostructural Evolution of Calcium-Containing Alkali-Activated Metakaolin During High Temperature Exposure

Nanostructural Evolution of Calcium-Containing Alkali-Activated Metakaolin During High Temperature Exposure

Nanostructuring of Additively Manufactured 316L Stainless Steel Using High-Pressure Torsion Technique: An X-ray Line Profile Analysis Study.

Experiments were conducted to reveal the nanostructure evolution in additively manufactured (AMed) 316L stainless steel due to severe plastic deformation (SPD). SPD-processing was carried out using the high-pressure torsion (HPT) technique. HPT was performed on four different states of 316L: the as-built material and specimens heat-treated at 400, 800 and 1100 °C after AM-processing. The motivation for the extension of this research to the annealed states is that heat treatment is a usual step after 3D printing in order to reduce the internal stresses formed during AM-processing. The nanostructure was studied by X-ray line profile analysis (XLPA), which was completed by crystallographic texture measurements. It was found that the as-built 316L sample contained a considerable density of dislocations (1015 m-2), which decreased to about half the original density due to the heat treatments at 800 and 1100 °C. The hardness varied accordingly during annealing. Despite this difference caused by annealing, HPT processing led to a similar evolution of the microstructure by increasing the strain for the samples with and without annealing. The saturation values of the crystallite size, dislocation density and twin fault probability were about 20 nm, 3 × 1016 m-2 and 3%, respectively, while the maximum achievable hardness was ~6000 MPa. The initial <100> and <110> textures for the as-built and the annealed samples were changed to <111> due to HPT processing.