Nanocomposite Structure Research Articles

Fabrication of composite nanostructures for impedance biosensors using anodic aluminum oxide templates and carbon nanotubes

A hybrid material consisting of an array of vertically ordered carbon nanotubes (CNTs) in porous anodic alumina was fabricated directly on oxidized Si substrates. Individual CNTs with vertical orientation were grown using the catalyst Ni nanoparticles (NPs) embedded in the pore walls of a thin template based on porous anodic alumina with a pore diameter of 40 ± 5 nm. The initial film was a two-layer Ti-Al structure on a Si/SiO2 substrate. A vertically oriented porous structure was formed by anodizing the Al layer. Electrochemical deposition was used to form the catalyst Ni-NPs with dimensions of 30 ± 5 nm. CNTs were synthesized by high-temperature chemical vapor deposition. Scanning and transmission electron microscopy, Raman spectroscopy, and X-ray diffraction were used to analyze the surface morphology and microstructure of the composite nanostructures. The CNT length was (0.6–1.5) μm, and the CNT spacing was 110 ± 10 nm. It is expected that the resulting structure will serve as a basis for the development of CNT-based electrodes for electrochemical impedance biosensors. Electrochemical impedance spectroscopy was used for the electrochemical characterization of the fabricated CNT-based electrodes. The results showed that the CNT-based electrodes are characterized by improved electron transfer kinetics.

Morphological engineering of PTAm@CNTs cathode for high-rate potassium dual-ion battery

Redox-active polymers are regarded as one of the most promising electroactive materials for non-lithium electrochemical energy storage devices due to the inherent molecular flexibility that can tolerate the structure change during the charge/discharge process. Their diverse functional groups provide abundant active sites to accommodate large-sized electrolyte ions. In this work, for the first time, the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical group, equipped at poly(TEMPO-acrylamide) (PTAm), is employed as an active cathode for potassium dual-ion batteries (KDIBs). Carbon nanotubes (CNTs) assist morphological engineering of the PTAm to create a conductive nanostructured composite, namely PTAm@CNTs. Systematic material characterizations and electrochemical evaluation suggest that the PTAm@CNTs nanocomposite possesses significant surface area and nanopores, enabling enhanced electronic and ionic conductivity. The PTAm@CNTs cathode reversibly stores hexafluorophosphate (PF6−) anions in KDIBs, delivering high energy density, rate capability, and robust cycling stability. The fast reaction kinetics of nitroxide radicals (N–O.), the redox-active groups on the PTAm, and their association with the PF6− anions contribute to the dual-ion storage. As a result, the PTAm@CNTs cathode delivers a high specific capacity of 108 mAh g−1 at 2 A g−1 (16.8C) over 300 cycles. The work suggests a promising pathway to design and synthesize functional organic electrode materials for potassium dual-ion batteries.

An experimental-analytical investigation of particle size effect on the mode I fracture behavior of polymer/graphene nanocomposites

Due to their outstanding specific mechanical and functional properties, the engineering use of polymer nanocomposites and their carbon composites is becoming increasingly pervasive. Current and potential applications include micro- and flexible electronics, energy storage devices, and the use as reinforcement for advanced carbon fiber composites for light-weighting of aerospace and mechanical structures, thereby reducing their fuel consumption and carbon footprint. While a large amount of data and models regarding the effect of the weight fraction of nanoplatelets on the mechanical properties of nanocomposites is currently available in the literature, an aspect often overlooked is the scaling of the fracture behavior and the related particle size effects. Not only is the lack of understanding of size effects in nanomaterials hindering the full exploitation of their properties, it is also a serious issue since the design of large nanocomposite structures or small-scale electronic components requires capturing the scaling of their mechanical properties and developing predictive capabilities. This paper aims at filling this knowledge gap by proposing a novel analytical and experimental approach to investigate particle size effects in nanocomposites at and leveraging the acquired knowledge to improve their fracture properties, from the nanoscale all the way to the macroscale. To this end, crack initiation fracture toughness data for graphene/epoxy nanocomposite are presented as a function of nanoparticle size and weight fraction and compared with model predictions using a novel analytical model based on enhanced crack-tip shielding effect due to the reduced nanoparticle size. Extensive fracture test data are presented for model calibration and model verification.

Novel silica coated trimetallic ferrite functionalized with amino acid-based protic ionic liquid (Mn0.5Fe0.25Ca0.25Fe2O4-SiO2@[L-Tyr][HSO4]): A versatile bio-nanostructure to catalyze green synthesis of poly-substituted hydroquinolines and pyrido[2,3-d]pyrimidine-triones

In this research a magnetized inorganic-bioorganic nanocomposite prepared through coating the Mn0.5Fe0.25Ca0.25Fe2O4 core by silica layer, and consequent functionalization by the L-tyrosinium hydrogen sulfate ionic liquid. The structure of the hybrid nanocomposite (Mn0.5Fe0.25Ca0.25Fe2O4-SiO2@[L-Tyr][HSO4]) studied by density functional theory (DFT) calculations which contains L-Tyr protonation step and the chemisorption of L-Tyr cation on silica layer. The novel synthesized bio-nanocomposite (Mn0.5Fe0.25Ca0.25Fe2O4-SiO2@[L-Tyr][HSO4]) characterized by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), vibrating-sample magnetometery (VSM), thermogravimetric (TGA/DSC), X-ray powder diffractometery (XRD), X-ray fluorescence (XRF), and transmission electron microscopy (TEM) analysis. The hybrid bio-nanocomposite applied for solvent-free diastereoselective synthesis of dispiro[tetrahydroquinoline-bis(2,2-dimethyl[1,3]dioxane-4,6-dione)] derivatives via one-pot pseudo eight-component reaction of meldrum’s acid, aromatic aldehydes, and arylamines at 50 °C. Also, the bio-nanocatalyst utilized for the aqua-mediated green synthesis of 5-aryl-5,6-dihydropyrido[2,3-d]pyrimidine-2,4,7(1H,3H,8H)-triones at 70 °C through the reaction of meldrum’s acid, aryl aldehydes, and 6-aminouracil. The recovery and reusability of the bio-nanohybrid also examined within 2 runs successfully.

Dual influence of graphene oxide/clay and electron beam radiation on the structure, mechanical, thermal, and antimicrobial properties of nitrile butadiene rubber nanocomposite

Infective diseases are becoming more popular, and managing them has become a great worry for humanity. A rubber nanocomposite based on nitrile butadiene rubber with graphene oxide (NBR/GO) and GO/nanoclay (montmorillonite, MMT) (NBR/GO/MMT) was fabricated by a simple technique, roll milling. The synergistic influence of the existence of GO, clay, and electron beam (EB)-radiation on the NBR nanocomposites was characterized using scanning electron microscopy (SEM), and Fourier-transform infrared (FT–IR) techniques to study the mechanical, thermal, and antibacterial properties. The antibacterial activity of the prepared rubber nanocomposites was estimated via the disk diffusion process against Gram-positive bacteria, Bacillus subtilis, Staphylococcus lentus, and Gram-negative bacteria ; Pseudomonas aeruginosa and Proteus mirabilis. The results demonstrated that the physico-mechanical performance was significantly reinforced by incorporating nano GO (6 phr) and clay with GO (3 phr/6 phr. NBR films have no antibacterial potential. GO increases the antibacterial efficiency of the NBR films. NBR/3% GO/3% clay film is the most effective in reducing bacterial growth and B. subtilis was the most sensitive bacteria for rubber treatments. The inhibition zone diameters of the un-irradiated and irradiated NBR/3% GO/3% clay films for B. subtilis were 18.03 ± 0.59 and 25.63 ± 0.98 mm, respectively. It could be concluded that because of its outstanding flexibility and human-body compatibility penetration, rubber in corporation with antimicrobial agents can be utilized for manufacturing medical and environmental products.

Achieving excellent mechanical and robust lubrication behavior in the CoCrNi medium-entropy alloy via in-situ graphite

The unsatisfactory wear resistance and lubrication performance of CoCrNi multi-principal elements alloys (MPEAs) have emerged as critical challenges, impeding their extensive utilization as advanced engineering materials, despite their desirable mechanical and physical properties. Incorporating graphite to obtain MPEAs-based self-lubricating composites is believed to improve the wear resistance. However, it is challenging to prepare composites with high strength, large plasticity, and excellent anti-friction performance simultaneously. The present study reports the fabrication of novel CoCrNi MPEA-based self-lubricating composites, consisting of in-situ graphite and high-hardness silicides/carbides as reinforcement, prepared by powder metallurgy and reactive sintering. The 20.6 vol% Gr@CoCrNi–SiC composite exhibits an optimal trade-off between strength and ductility, along with anti-friction and wear resistance which is superior to the reported composites with different solid lubricants. The wear mechanism is attributed to the coordinated deformation mechanism between the CoCrNi FCC matrix and silicides/carbides, and the stabile lubrication effect supported by the structural transformation from the original polycrystalline lattice structure to core-shell nanocomposite structure (similar to diamond-like carbon) of the in-situ graphite. This simple, economical and practical strategy contributes to the development of MPEA self-lubricating composites with excellent comprehensive properties.

Plasmon-Free Surface-Enhanced Raman Spectroscopy Using α-Type MoO3 Semiconductor Nanorods with Strong Light Scattering in the Visible Regime.

Recent developments in semiconductor-based surface-enhanced Raman scattering (SERS) have achieved numerous advancements, primarily centered on the chemical mechanism. However, the role of the electromagnetic (electromagnetic mechanism) contribution in advancing semiconductor SERS substrates is still underexplored. In this study, we developed a SERS substrate based on densely aligned α-type MoO3 (α-MoO3) semiconductor nanorods (NRs) with rectangular parallelepiped ribbon shapes with width measuring several hundred nanometers. These structural attributes strongly affect light transport in the visible range by multiple light scattering generated in narrow gaps between NRs, contributing to the improvement of SERS performance. Engineering the nanostructure and chemical composition of NRs realized high SERS sensitivity with an enhancement factor of 2 × 108 and a low detection limit of 5 × 10-9 M for rhodamine 6G (R6G) molecules, which was achieved by the stoichiometric NR sample with strong light scattering. Furthermore, it was observed that the scattering length becomes significantly shorter compared with the excitation wavelength in the visible regime, which indicates that light transport is strongly modified by mesoscopic interference related to Anderson localization. Additionally, high electric fields were found to be localized on the NR surfaces, depending on the excitation wavelength, similar to the SERS response. These optical phenomena indicate that electromagnetic excitation processes play an important role in plasmon-free SERS platforms based on α-MoO3 NRs. We postulate that our study provides important guidance for designing effective EM-based SERS-active semiconductor substrates.

Fabrication and characterization of an innovative g-C3N4/calcium/aloe vera enriched PVA-bacterial cellulose wound dressing: A novel approach to diabetic wound management

Nanofiber scaffolds are of particular interest due to the conducive conditions they offer for wound healing. The objective and novelty of this study was to fabricate graphitic carbon nitride/calcium/aloe vera nanocomposites and PVA/bacterial cellulose/calcium/aloe vera nanofibers via electrospinning in preparation for their application as wound dressings. Initial evaluations and production of graphitic carbon nitride (g-C3N4), g-C3N4/calcium solution, and g-C3N4/calcium/Aloe Vera solution were conducted using XRD and FTIR, which accordingly, the results confirmed the successful integration of every component within the nanocomposite structure. Moreover, the antibacterial activity of the developed materials was assessed using the bacterial growth inhibitor (MIC). The results indicated that the materials possessed sufficient antibacterial activity against both gram-positive S. aureus and gram-negative E. coli bacteria with a dilution of 1/512. The nanofibers that were generated were subsequently examined using XRD and SEM techniques with a thickness of 250 nm. Also, the evaluation of the mechanical properties was performed by subjecting PVA/BC/g-C3N4/Ca/Aloe vera nanofibers to tensile strength testing and biodegradation, which these revealed 61.0 % of elongation, and 7 % of biodegradability in 96 h. The outcomes demonstrated that the nanocomposite possessed adequate extension capacity and robust strength. Utilizing an animal model, the developed nanofibers were utilized to examine the healing of diabetic lesions. The wound healing process was observed to be accelerated by these nanofibers after a 21-day period. The area of the lesion measured 0.9891 cm2.

Electrochemical properties of novel redox active electrode coatings based on heterocyclic polyazines and its nanocomposites with carbon nanomaterials

This work aims to study electrode materials based on unsubstituted polyazines and composites which will allow further advancing both in the molecular design of redox polymers, composites and materials and evaluating their potential applicability. The polymers were prepared by two-phase chemical oxidative polymerization. Polymer-carbon nanocomposites (NC) based on unsubstituted polyphenoxazine were prepared for the first time. The physicochemical and electrochemical properties were compared for NCs based on polyphenothiazine (PPTA), polyphenoxazine (PPOA) and carbon nanomaterials (CNM). The used CNMs comprise reduced graphene oxide (RGO), single-walled and multi-walled carbon nanotubes (SWCNT and MWCNT). The NC structure and morphology were studied by means of FT IR spectroscopy, XRD, FE-SEM and TEM. The limited solubility of some monomers prevents their electrochemical deposition on electrodes. Therefore, to study the electrochemical, spectroelectrochemical behavior and electrochemical impedance of novel redox active electrode coatings, suspensions of synthesized polymers or their NCs were applied onto electrodes and dried. The effect of NC composition on the conductivity and redox activity thereof was discovered. In general, composites have a higher conductivity than individual polymers. Despite differences in electrical conductivity, all samples exhibited electrocatalytic behavior demonstrated for example of Fe(II)/Fe(III) cyanide redox transition on a planar electrode in a K3[Fe(CN)6] solution in 1 M H2SO4. The electronic absorption spectra were recorded in-situ in an electrochemical cell by varying the working electrode potential and showed an electrochromic effect for PPTA and CNM/PPTA. The proposed common equivalent electric circuit allowed explaining the different electrochemical properties of polymers and CNM composites thereof.

Application of bilateral iterative displacement control method to nonlinear free vibration analysis of dual-FG nanocomposite circular plates

This paper studies the geometrically nonlinear free vibration of a novel nanocomposite circular plate. The matrix of the nanocomposite structure is made of functionally graded (FG) polymer, and the distribution of graphene platelets (GPLs) as the reinforcement is assumed based on the five various linear FG models. Therefore, this novel nanocomposite is called dual-FG. The Voigt rule of mixture and Halpin-Tsai method are employed to homogenize FG polymer, and distribution of the GPLs within the matrix, respectively. Moreover, the whole structure is fixed on a nonlinear Kerr elastic foundation. The displacements of the plate are estimated by means of the first-order shear deformation theory (FSDT). Von-Kármán type of geometrically nonlinear relations expresses the plate's strains. The generalized differential quadrature (GDQ) technique, bilateral iterative displacement control method (BIDCM), and the weighted residual Galerkin procedure are implemented to extract the free vibration characteristics of the structure. The developed structure is validated with those reported in the open literature. A comprehensive parametric study is conducted to illustrate the effect of various parameters on the dynamic response of the dual-FG nanocomposite circular plate. It will be observed that the influence of the volume fraction and distribution model of GPL is more pronounced on the vibration frequency in the FG matrix. It was noted that the volume fraction of graphene platelets (GPL) and the power-law index of the matrix exhibit a direct and inverse relationship, respectively, with the natural frequency of the structure. Furthermore, the V-GPL model exhibits the highest percentage growth in nonlinear frequencies, while the Λ-GPL model shows the least growth. This observation is particularly pronounced for plates with hinged boundary conditions.

Fabrication and Tribological Properties of Diamond-like Carbon Film with Cr Doping by High-Power Impulse Magnetron Sputtering

The present study aims to investigate the advantages of diamond-like carbon (DLC) films in reducing friction and lubrication to address issues such as the low surface hardness, high friction coefficients, and poor wear resistance of titanium alloys. Cr-doped DLC films were deposited by high-power impulse magnetron sputtering (HiPIMS) in an atmosphere of a gas mixture of Ar and C2H2. The energy of the deposited particles was controlled by adjusting the target powers, and four sets of film samples with different powers (4 kW, 8 kW, 12 kW, and 16 kW) were fabricated. The results showed that with an increase in target power, the Cr content increased from 3.73 at. % to 22.65 at. %; meanwhile, the microstructure of the film evolved from an amorphous feature to a nanocomposite structure, with carbide embedded in an amorphous carbon matrix. The sp2-C bond content was also increased in films, suggesting an intensification of the film’s graphitization. The hardness of films exhibited a trend of initially increasing and then decreasing, reaching the maximum value at 12 kW. The friction coefficient and wear rate of films showed a reverse trend compared to hardness variation, namely initially decreasing and then increasing. The friction coefficient reached a minimum value of 0.14, and the wear rate was 2.50 × 10−7 (mm3)/(N·m), at 8 kW. The abrasive wear was the primary wear mechanism for films deposited at a higher target power. Therefore, by adjusting the target power parameter, it is possible to control the content of the metal and sp2/sp3 bonds in metal-doped DLC films, thereby regulating the mechanical and tribological properties of the films and providing an effective approach for addressing surface issues in titanium alloys.

One-step formation of synergistic ZnO/SnO2 composite nanostructures derived from annealing of crystalline ZnSn(OH)6 nanocubes for enhanced catalytic degradation of organic pollutants

Binary metal oxides/hydroxides derived primary metal oxide composites have a pivotal role in diverse applications because of the beneficial interfacial contact, good synergism, high porous nature, and high stability. The current work deals with the derived ZnO/SnO2 composite nanostructures from post-annealing crystalline ZnSn(OH)6 (ZTO-RT) nanocubes, initially synthesized via a single-step hydrothermal synthesis method. First, the pristine ZTO-RT is synthesized @ 180 °C in a hydrothermal autoclave. Further, the transformation of ZTO-RT to ZnO/SnO2 composite nanostructures is performed at two different annealing temperatures of 500 °C (ZTO-DV-500) and 750 °C (ZTO-DV-750) in the vacuum. The respective samples' physical characterization was studied and compared using various analytical techniques. The X-ray diffraction analysis affirms the amorphous nature of ZTO-DV-500 and the poly-crystalline nature of ZTO-DV-750. The nanocube morphologies of the samples are retained even at high-temperature sintering. The existence of metal-oxygen bonds on the surface of the ZnO/SnO2 composite is sustained by X-ray photoelectron spectroscopy. ZTO-DV-750 has larger pores (pore volume - 0.091 cm3 g−1) than the ZTO-DV-500 (0.051 cm3 g−1). In the presence of NaBH4 aqueous solution, the enhanced rhodamine B dye degradations of ZTO-DV-750 are observed. At low RhB concentrations (5 mg L−1), the ZTO-DV-500 and ZTO-DV-750 rate constants are determined to be 0.099 and 0.156 min−1, respectively, while at high concentration (10 mg L−1), these values are 0.043, and 0.091 min−1. Therefore, the ZTO-DV-750 composite has shown potent catalytic activity with NaBH4 over ZTO-DV-500 to decolourise organic dyes.

Exploring innovative antibacterial properties of porous ALT (Al2O3/TiO2) composite

Among all metallic materials, titanium is mostly employed in medical applications. In this study, single TiO2 layers on Ti as well as composite ALT(Al2O3/TiO2) layers on Ti for medical applications were synthesized using titanium and aluminum cathodic cages. SEM, EDX, XRD, PL, UV–Vis analyses of untreated and plasma-processed samples were used to determine the surface morphology, chemical content, microstructure, band gap, and photocatalytic behavior, respectively. E. coli and S. aureus immersion bacterial solutions were used to test the antibacterial performance of untreated and plasma-processed specimens. Comparing the composite to a single TiO2 and an untreated sample in PL spectra revealed a smaller band gap. When compared to untreated specimens, coatings made of TiO2 and composite ALT demonstrated significant antibacterial properties. The results showed that ALT-60min displayed unique antibacterial behavior because the band gap was reduced and antibacterial effectiveness was increased. This work explains the distinctive antibacterial activity of composite nanostructures made for medicinal use.

Self-cleaning and anti-corrosion superhydrophobic coatings of PA-TiO2@SiO2 copolymerized hetero compound

Inspired by leaf lotus effect, superhydrophobic surfaces have developed rapidly in recent years. In this paper, anatase nano TiO2 with particles size of about 70 nm was successfully loaded on the surface of SiO2 by sol-gel method. SiO2 and TiO2 were chemically bonded by Ti-O-Si and constructed a certain micro- and nano-composite structure. After superhydrophobic composite PA-TiO2@SiO2 was obtained by copolymerizing with acrylate and other monomers. The coating was prepared by drop coating plus spraying coating on glass substrates with water contact angles >160° and excellent self-cleaning properties, which could maintain the performance of the superhydrophobic coating by immersion in acidic solutions or water for 2 days. Meanwhile, the coating on the surface of the glass plate at −20 °C significantly delayed the freezing time of the ice. The rough structure of the surface and the presence of fluorine-containing hydrophobic groups gave the superhydrophobic coating an advantage over acrylate polymers in reducing the corrosion rate of steel surfaces.

Halogen-doped 2D reduced graphene oxide with TiO2 nanocomposite for water remediation application

Water contamination by organic and inorganic pollutants has been a challenging problem impacting living organisms. The current study explores the photocatalytic property of nanocomposite based on iodine-doped reduced graphene oxide with titanium dioxide nanoparticles (TNPs) for methyl orange (MO) dye degradation. A nanocomposite of TNPs with iodine-doped reduced graphene oxide (TIR) is prepared using the hydrothermal technique. The physicochemical properties of nanocomposite were explored by various techniques such as an X-diffractometer (XRD), Raman spectroscopy, Fourier transforms the infrared spectrum, energy-dispersive X-ray spectroscopy spectrum (EDX), and high-resolution transmission electron microscopy (HRTEM). The XRD reveals the crystalline structure of the TIR nanocomposite. The anatase TNPs with an average particle size of 9.68 ± 2.1 nm are confirmed by HRTEM. The Raman spectrum confirms the presence of iodine molecules with a peak at 101 cm−1, and the EDX spectrum confirms the presence of iodine molecules with 15.31 % elements in the TIR nanocomposite. The MO dye degradation efficiency of 96.12 % with 120 min UV exposure for TIR suggests that the iodine-doped nanocomposite is a promising photocatalyst for water remediation.

A new nanocomposite membrane based on sulfonated polysulfone boron nitride for proton exchange membrane fuel cells: Its fabrication and characterization

Sulfonated polysulfone (SPSf) polymer is an alternative raw material in producing commercially used proton exchange membranes. On the other hand, hexagonal boron nitride (hBN) is one of the additives of interest for nanocomposite PEMs. In this study, nanocomposite membranes is fabricated and characterized with SPSf and hBN nanoparticles. The degree of sulfonation of the sulfonated polysulfone is determined by titration, and sulfonic acid bonds are investigated by Proton Nuclear Magnetic Resonance (1H NMR) analysis. SPSf is dissolved with dichloromethane, and hBN nanoparticles are added. After homogenizing the prepared solution with magnetic and ultrasonic stirrers, membranes are formed using Dr. Blade. 1H NMR, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-Ray Diffractometer (XRD), and Thermogravimetric Analysis (TGA) analysis are examined the morphological, thermal, and organic compound structures of the membranes. Water uptake capacity, swelling ratio, proton conductivity, oxidative resistance, and mechanical properties of the membranes are determined. The highest water uptake capacity is obtained as 40.08 % in the membrane named SPSf-3 %hBN. Using hBN additive improved swelling ratio and thermal and mechanical strength properties. The proton conductivity values of polysulfone (PSf), SPSf, SPSf-1 %hBN, SPSf-2 %hBN, and SPSf-3 %hBN membranes are determined as 2.89, 6.84, 3.57, 10.8 and 5.12 mS cm−1, respectively. As a result of the analysis, it is observed that the nanocomposite membrane structure has both amorphous and crystalline homogeneous structure.

Sliding wear-induced compositional lamination in a VCoNi alloy at elevated temperatures, and its implications for reduced friction and wear

During tribological loading of metallic alloys at elevated temperatures, the thermo-mechanical coupling effect can lead to the development of a distinct tribolayer, profoundly influencing their tribological behavior. This study reports on the compositional lamination in the tribolayer during dry sliding wear of a VCoNi multi-principal element alloy at elevated temperatures. As the temperature increases from 25 °C to 600 °C, the alloy exhibits a remarkable 40% reduction in the coefficient of friction and a notable two-order-of-magnitude decrease in wear rate. The compositional lamination at 600 °C reveals a distinct tribolayer comprising a nanocrystalline-amorphous oxide glaze layer, a Ni-rich dealloyed layer, and a plastic deformation layer. Within the oxide glaze layer, three sublayers are identified, each featuring a nanocrystalline-amorphous nanocomposite structure with unique equiaxed nanograins. Specifically, the outermost sublayer comprises Co3O4, the intermediate sublayer contains a mixture of Co3O4 and Ni2V2O7, and the inner sublayer consists of V2O5. This multilayered structure is attributed to significant differences in the chemical affinity for oxygen among the constituent elements and their respective diffusion rates in the oxide scale. Significantly, the tribolayer formed at 600 °C exhibits a remarkable 70% increase in yield strength compared to its formation at 25 °C, correlating with a substantial reduction in wear. These findings present a novel avenue for designing self-adaptive, high-temperature wear-resistant alloys through the in-situ formation of a protective compositionally-laminated tribolayer.

Predicting mechanical heterogeneity in glassy polymer nanocomposites via an inverse computational approach based on atomistic molecular simulations and homogenization methods

Probing the mechanical behavior of the region formed between a nanoparticle reinforcement and a polymer matrix in a polymer nanocomposite structure, denoted as the “interphase”, is a main challenge as such regions are difficult to investigate by experimental methods. Here, we accurately characterize the heterogeneous mechanical behavior of polymer nanocomposites, focusing on polymer/nanofiller interphases via a combination of nanomechanical simulations and numerical homogenization techniques. Initially, the global mechanical performance of a glassy poly(ethylene oxide) polymer nanocomposite reinforced with silica nanoparticles is studied using detailed atomistic molecular dynamics simulations for 1.9% and 12.7% silica volume fractions. Next, the polymer/silica interphase thickness is identified by probing the polymer atom-based density distribution profile in the vicinity of the nanofiller at equilibrium. On the basis of this thickness, the interphase is subdivided to check the position-dependent change in mechanical properties. Then, using continuum mechanics and atomistic simulations, we proceed to compute the effective Young’s modulus and Poisson’s ratio of the polymer/nanoparticle interphase as function of the distance from the nanoparticle. In the last step, an inverse numerical homogenization model is proposed to predict the mechanical properties of the interphase on the basis of a comparison criteria with the data from MD. The results were found to be acceptable, raising the possibility of accurately and efficiently predicting interfacial properties in nanostructured materials.

Machine Learning-Based Design of Superhard High-Entropy Nitride Coatings.

Limited by the inefficiency of the conventional trial-and-error method and the boundless compositional design space of high-entropy alloys (HEAs), accelerating the discovery of superior-performing high-entropy nitride (HEN) coatings remains a formidable challenge. Herein, the superhard HEN coatings were designed and prepared using the rapidly developing data-driven model machine learning (ML). A database containing hardness and different features of HEN coatings was established and categorized into four subsets covering the information on composition, composition-physical descriptors, composition-technique parameters, and composition-physical descriptors-technique parameters. Feature engineering was employed to reduce dimensionality and interpret the impact of features on the evolution of hardness. Both root mean squared error (RMSE) and decision coefficient (R2) were applied to assess the predictive accuracy of ML models with different subsets, proportions of test set, and algorithms. The model with best predicted performance was used to explore superhard HEN coatings in a predefined virtual space. Among the generated 5-/6-/7-/8-component (excluding N) systems, the coating possessing highest hardness was individually selected for further preparation. Four newly prepared coatings achieved the superhard level with an average prediction error of 7.83%. The morphology, chemical composition, structure, and hardness of the newly prepared coatings were discussed. The nanocrystal-amorphous nanocomposite structure of the novel AlCrNbSiTiN coating with the highest hardness of 45.77 GPa was revealed. The results demonstrated that ML can effectively guide the design and composition optimization of superb-performance protective HEN coatings.

Achieving better strength-toughness synergy in heterogeneous Cu/Ni/graphene composites: A molecular dynamics simulation

The non-wetting nature of copper (Cu) and graphene, coupled with the brittle behavior of graphene, impedes the strength-toughness synergy in graphene-reinforced Cu matrix (Cu/graphene) composites, limiting their practical applications. Benefiting from interface modification engineering and heterogeneous structure strengthening effects, here a novel strengthening and toughening strategy for Cu/graphene composites by introducing a variable-thickness nickel (Ni) modification layer sandwiched between Cu and graphene (Cu/Ni/graphene) was proposed, and the influence of layer thickness-related structural heterogeneity on mechanical properties and underlying deformation mechanisms were investigated via molecular dynamics simulations. The results revealed that an optimal Ni thickness of 2.44 nm within increased Ni layer thickness enhanced the strength-toughness synergy in the Cu/Ni/graphene composites. This was attributed to altered interface structure, stress distribution, and graphene fracture behaviors due to layer thickness-related deformation behavior. In addition to common strengthening mechanisms like graphene load-bearing effect, interface dislocation nucleation, and interface dislocation blockage strengthening, the layer thickness-dependent semi-coherent Cu/Ni and Ni/graphene heterogeneous interface stress strengthening contributed to extra strength enhancement. Furthermore, cooperative deformation behavior among heterogeneous components improved toughness. The interfacial engineering strategy, achieved by tailoring the modification layer thickness, may pave the way for producing nanostructured metallic composites with extraordinary mechanical properties.