Molecular dynamics simulation of mechanical properties of Ni–Al nanowires

We employed molecular dynamics simulations to study mechanical properties of Ni–Al nanowires by calculating the stress–strain response of the wires under various loading conditions. For this purpose, nanowires were subjected to uniaxial strain at different strain rates and temperatures using embedded atom model potential. The behaviour of the wires at lower and higher strain rates was investigated, and the yield and rupture strain values and also Young’s Modulus were obtained which are essential factors for the ductility of the wires. This work indicates that how the stress–strain response of the nanowires are affected by varying strain rates and temperatures.     

Synthesis of bio-inspired Ag–Au nanocomposite and its anti-biofilm efficacy

In the present study, bio-inspired Ag–Au nanocomposite was synthesized using banana peel extract (BPE) powder. The Ag–Au nanocomposite was characterized using various techniques such as UV–vis spectrophotometry, transmission electron microscopy (TEM) attached with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Efficiency of AuNPs, AgNPs and Ag–Au nanocomposite was tested for their antibacterial activity against Pseudomonas aeruginosa NCIM 2948. The Ag–Au nanocomposite exhibits enhanced antimicrobial activity over its monometallic counterparts. Anti-biofilm activity of AgNPs, AuNPs and Ag–Au nanocomposite against P. aeruginosa was evaluated on glass surfaces. The Ag–Au nanocomposite exhibited the highest biofilm reduction (70–80%) when compared with individual AgNPs and AuNPs. Effect of AuNPs, AgNPs and Ag–Au nanocomposite on biofilm formation was evaluated in 96 wells microtiter plates. The percentage of biofilm inhibition was sharply increased with increasing concentration of AuNPs, AgNPs and Ag–Au composite. However, Au–Ag nanocomposite showed the highest biofilm inhibition when compared with individual AuNPs and AgNPs. This synergistic anti-biofilm activity of Ag–Au nanocomposite has an importance in the development of novel therapeutics against multidrug-resistant bacterial biofilm.     

One-pot synthesis of Polyindole–Au nanocomposite and its nanoscale electrical properties

Nanosized gold (Au) and polyindole (PIn) composite was prepared via in-situ polymerization of indole, using metal salt chloro-auric acid as an oxidant, in a microemulsion system. The oxidization of indole and the reduction of Au³⁺ ions occurred simultaneously in a single step, which resulted in a core shell structure having a coating of polyindole over monodispersed, size-controlled, highly populated, and stable gold nanoparticles. Indole polymerization governed by chloro-auric acid, was monitored using UV–vis absorption spectroscopy. Nanoscale electrical characterization of polyindole nanocomposite was performed using current-sensing atomic force microscopy. The investigated properties of the composite proved its enormous potential in electronic applications and fabrication of nanoscale organic devices.     

Molecular dynamics simulation of the formation of bimetallic core-shell nanostructures with binary Ni–Al nanoparticle quenching

Journal of Materials Science - Employing isothermal molecular dynamics, we simulated the self-assembly of core-shell nanostructures in the course of quenching binary Ni–Al nanoparticles (NPs)...     

Molecular dynamics simulation of the nonlinear behavior of the CNT-reinforced calcium silicate hydrate (C–S–H) composite

Calcium–Silicate–Hydrate (C–S–H), which is the major constituent of the cement at the nanoscale, is responsible for the strength and fracture properties of concrete. This research is dedicated to the numerical study of enhanced mechanical properties of C–S–H reinforced by embedding carbon nanotube (CNT) in its molecular structure. Series of molecular dynamics (MD) simulations indicate that the tensile strength of CNT-reinforced C–S–H is substantially enhanced along the direction of CNT as compared to the pure C–S–H. The results of tensile loading reveal that CNT can efficiently bridge the two sides of cracked C–S–H. In addition, CNTs can severely intensify the “transversely isotropic” response of the CNT-reinforced C–S–H. Furthermore, the pull-out behavior of CNT reveals that the force-displacement response can be estimated by a bilinear model, which can later be used for simulation of cohesive crack propagation and multiscale simulation of crack bridging at macro scale specimen of CNT-reinforced cement.     

Fracture analysis of epoxy/SWCNT nanocomposite based on global–local finite element model

A global–local multiscale finite element method (FEM) is proposed to study the interaction of nanotubes and matrix at the nanoscale near a crack tip. A 3D FE model of a representative volume element (RVE) in crack tip is built. The effects of the length and chirality of single walled carbon nanotube (SWCNT) in a polymer matrix on the fracture behavior were studied in the presence of van der Waals (vdW) interaction as inter-phase region. Detailed results show that with increasing the weight percentage of SWCNT, fracture toughness improves. Three situations of nanotube directions with respect to crack are considered. Results show that bridging condition has minimum stress intensity factor. In addition, it can be seen that the crack resistance improves by increasing the length and chirality for all kinds of nanotubes. Finally, epoxy/SWCNT 10 wt.% has lower stress intensity factor compared to epoxy/halloysite 10 wt.% in similar loading state.     

Pulse plating of Ni–B/WC nanocomposite coating and study of its corrosion and wear resistance

The aim of this study is to investigate the impact of WC content on the properties of the Ni–B/WC nanocomposites deposited by the pulse method. It is obtained that, although by addition of WC nanoparticles to the bath in initial steps (WC 4 and 8 g?l^?1), the grain size was increased and hence mechanical and electrochemical properties got worse, but at the higher amount of WC (WC 12 g?l^?1), due to the formation of the fine and packed structures, the great corrosion and wear resistance was achieved. The corrosion resistance of the Ni–B/WC12 g?l^?1 coating is 59,967?Ω and wear weight loss is 2.1 mg?cm^?2 with the friction coefficient of 0.64.     

Titanium dioxide–cellulose hybrid nanocomposite and its glucose biosensor application

This paper investigates the fabrication of titanium dioxide (TiO₂)–cellulose hybrid nanocomposite and its possibility for a conductometric glucose biosensor. TiO₂ nanoparticles were blended with cellulose solution prepared by dissolving cotton pulp with lithium chloride/N,N-dimethylacetamide solvent to fabricate TiO₂–cellulose hybrid nanocomposite. The enzyme, glucose oxidase (GOx) was immobilized into this hybrid nanocomposite by physical adsorption method. The successful immobilization of glucose oxidase into TiO₂–cellulose hybrid nanocomposite via covalent bonding between TiO₂ and GOx was confirmed by X-ray photoelectron analysis. The linear response of the glucose biosensor is obtained in the range of 1–10 mM. This study demonstrates that TiO₂–cellulose hybrid nanocomposite can be a potential candidate for an inexpensive, flexible and disposable glucose biosensor.     

Synthesis and properties of rhenium–polyethylene nanocomposite

New rhenium-containing composites were synthesized by thermodestruction of different rhenium complexes. The composites consist of rhenium-containing nanoparticles stabilized by low-density polyethylene matrix. The structure of composites was characterized by means of TEM, EDS, XRD, EXAFS and EMR. Transmission electron microscope images illustrate that the rhenium-containing nanoparticles are 15.0 ± 0.3 nm in size. The particles consist of Re, Re₂O₇, ReO₃ and ReO₂. In the electrophysical measurements it was found that permittivity and attenuation of microwave radiation correlate with composition of rhenium-containing nanoparticles.     

Synthesis and properties of rhenium–polyethylene nanocomposite

New rhenium-containing composites were synthesized by thermodestruction of different rhenium complexes. The composites consist of rhenium-containing nanoparticles stabilized by low-density polyethylene matrix. The structure of composites was characterized by means of TEM, EDS, XRD, EXAFS and EMR. Transmission electron microscope images illustrate that the rhenium-containing nanoparticles are 15.0 ± 0.3 nm in size. The particles consist of Re, Re₂O₇, ReO₃ and ReO₂. In the electrophysical measurements it was found that permittivity and attenuation of microwave radiation correlate with composition of rhenium-containing nanoparticles.     

Static and dynamic scaling of semiflexible polymer chains—a molecular dynamics simulation study of single chains and melts

A molecular dynamics study of the effect of increasing molecular chain stiffness on the dynamic properties of single linear chains and polymer melts is presented. The chain stiffness is controlled by a bending potential. By means of a normal mode analysis the systematic crossover behavior of coarse-grained linear polymer systems from Rouse modes to bending modes with increasing mode number p is presented systematically for the first time via simulation data. The magnitude and the onset of the region where crossover behavior occurs is investigated in dependence of a systematic variation of the chains’ persistence lengths. For long wavelength modes the well-known p ⁻² behavior is observed which represents the Rouse scaling, whereas for the bending modes one observes a distinct p ⁻⁴ scaling of the mean square mode amplitudes and the relaxation times. Additionally, the effect of this crossover behavior on the monomer dynamics given by their mean square displacements is investigated. The findings are contrasted with previous simulation studies of semiflexible chain behavior and it is shown that those studies—due to too small persistence lengths L _p —were actually limited to the crossover regime where both, Rouse and bending modes contribute to the chain dynamics, and no distinct p ⁻⁴ scaling can be observed. Using an expansion of the monomer position vector, a simple theory of the observed scaling behavior is proposed which allows for deriving analytic expressions that describe the presented simulation data very well.     

Design and preparation of novel Diels–Alder crosslinking polymer and its application in NLO materials

Principally novel crosslinking nonlinear optical and optoelectronics system based on Diels–Alder reaction was designed. The copolymer of methyl methacrylate and anthracen-9-ylmethyl methacrylate (PMMA-AMA) was used as a host polymer; chromophore ETO was used as guest chromophore; chromophore ETO and N,N-(methylenediphenyl)bismaleimide were used as crosslinker. The thermodynamic property of crosslinking system studied by differential scanning calorimeter (DSC) showed us that the glass transition temperature was about 65?°C and the crosslinking temperature was varied between 80 and 120?°C The crosslinking reactive speed and effectiveness were studied by ultraviolet absorption and infrared absorption spectroscopy with spectral resoluiotn 1 cm^?1. These results have indicated that the cross linking process could be finished at 110?°C for 20 min. Surprisingly, such EO polymer showed us a large EO coefficient of about 96.3 pm/V at wavelength 1 µm and excellent long term stability about 85% with respect to its initial value and can be kept after 250 h of heating at 80?°C.     

Threshold energies of atomic displacements in α-Fe under deformation: Molecular dynamics simulation

The influence of deformations on the average threshold displacement energy in α-Fe is studied by molecular dynamics simulation. Hydrostatic and several uniaxial compressive and tensile deformations are considered. It is demonstrated that the value of the threshold displacement energy is well described by the linear function of the relative change of volume caused by the deformation. The coefficient of linear approximation comes to ?1.21 eV for volume change in percent. For deformations at constant volume, changes in the displacement energy are insignificant.     

Molecular dynamics simulations of the rheological properties of graphene–PAO nanofluids

Graphene is a promising additive for lubricants. The rheological properties of graphene nanofluids have a significant impact on the tribological performance of base oil. In this case, rheological properties including viscosity, density, mean square displacement and diffusion coefficient of graphene–PAO nanofluids were investigated by using the nonequilibrium molecular dynamics simulations in order to understand the effects of graphene on the rheological properties of base oil under extreme conditions. The molecular dynamics model was validated according to the experimental and numerical statistics reported by other researchers. The simulation results reflected that the viscosity of base oil was effectively improved by adding graphene nanoparticles. As the concentration of graphene increased, the viscosity of nanofluids becomes higher. However, the diffusion coefficient reached its highest value (3.73?×?10^?9 m²/s) with nanofluids containing two pieces of graphene in the system. Furthermore, we found that the graphene played a more significant role in enhancing the viscosity of base oil at high temperature and pressure. The viscosity was especially improved by 290.2% at 0.1 MPa, 500 K. The boiling point of the base oil became higher than 800 K after adding graphene. To our best knowledge, this work is the first study of the rheological properties of graphene–PAO nanofluids using molecular dynamic simulations.     

Sol–gel auto-combustion synthesis of PVP/CoFe2O4 nanocomposite and its magnetic characterization

Poly(vinyl pyrrolidone)/CoFe₂O₄ nanocomposite has been fabricated by a sol–gel auto-combustion method. Poly(vinyl pyrrolidone) was used as a reducing agent as well as a surface capping agent to prevent particle aggregation and stabilize the particles. The average crystallite size estimated from X-ray line profile fitting was found to be 20 ± 7 nm. The high field irreversibility and unsaturated magnetization behaviours indicate the presence of the core–shell structure in the sample. The exchange bias effect observed at 10 K suggests the existence of the magnetically aligned core surrounded by spin-disordered surface layer. The reduced remanent magnetization value of 0.6 at 10 K (higher than the theoretical value of 0.5) shows the PVP/CoFe₂O₄ nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner–Wohlfarth model.     

Intense low threshold nonlinear absorption and nonlinear refraction in a new organic–polymer nanocomposite

Intense reverse saturable absorption is reported for the first time in solid films of a new organic–polymer nanocomposite, cast by doping Biebrich Scarlet dye in a vinyl polymer host polyvinyl alcohol for various concentrations, as studied employing the Z-scan technique at 442 nm under different peak incident intensities ranging from 9.37 × 10² to 104.18 × 10² W cm⁻². The sample also exhibited nonlinear refraction under the experimental conditions. The estimated values of the effective coefficients of nonlinear absorption β_eff(0.27 × 10⁻² to 45.5 × 10⁻² cm W⁻¹) as well as nonlinear refraction n₂ (−1.5 × 10⁻⁷ to −2.75 × 10⁻⁷ cm² W⁻¹) measured up to the highest reported ones for low power continuous wave excitation. The composite films were characterized as nanoclusters consisting of dye molecules encapsulated between larger molecules of the amorphous polymer and having a low average roughness (≈1 nm) for the surface. These results, together with the simple and flexible processing method for the dye–polymer composite, imply that BS–PVA composite films have promising optical properties as an efficient low threshold nanocomposite material for potential applications in nonlinear optical devices.     

Solidification behaviour and phase constituents of cast Mg–Zn–misch metal alloys

The solidification path and phase constituents of alloys in the magnesium-rich corner of the Mg–Zn–misch metal (MM) pseudo-ternary system have been investigated by a combination of differential thermal analysis, analytical electron microscopy and X-ray diffraction. The solidification behaviour diagram for this system was found to be dominated by a large two-phase (-Mg plus T-phase) field in which the lowest eutectic temperature was 500°C. T-phase has a c-centred orthorhombic crystal structure and exhibits a wide range of stoichiometry. The interdendritic eutectic phase in the pseudo-binary Mg–MM system is Mg12MM which has the same b c t structure as Mg12Ce. The eutectic temperature here is 593°C.