Nanomaterials simulation

Coarse-grained molecular dynamics simulations were used to investigate the self-assembly of polymertethered nanorods with relatively high aspect ratio. The number and location of polymer tethers were varied to determine their influence on nanorod self-assembly. We found that laterally polymer-tethered nanorods selfassemble into structures with flat interfaces; these structures include stepped ribbons, stepped lamellae and lamellae with rods packed into bilayer sheets. The stepped lamellar phase is observed for the first time in this study. End polymertethered nanorods are prone to self-assemble into structures with curved interfaces, and the assembled structures observed here include spherical micelles and nematically aligned cylinders. The cylinder phase exists at high number densities, instead of the lamellar phase typically found for end polymer-tethered nanorods with relatively lower aspect ratio.

This to certify that the presented paper is the outcome of the accomplishment of the project and thesis on "Mechanical properties of CNTs with S-W defects" carried out by Md. Zahabul Islam, student of Mechanical Engineering Department, BUET, Dhaka under the supervision of

Finite element models of single-walled and multi-walled carbon nanotubes in their perfect and fundamental forms (zigzag and armchair) were constructed. Then, after obtaining the mechanical properties of perfect carbon nanotubes, three types of imperfections, i.e., doping with Si atoms, carbon vacancy and perturbation of the ideal location of the carbon atom were introduced in different amounts to the perfect models to make them imperfect. Finally, the mechanical properties of the imperfect carbon nanotubes were numerically simulated and compared with those of perfect ones. Simple relations which predict the change of Young's modulus as a function of the imperfection percentage were derived. The results show that the existence of any kind of imperfection in the perfect models leads to lower stiffness values. This study allows to realistically judge any simulation based on perfect structures and gives for the first time a good estimate to which extend the values based on perfect structures must be lowered in order to account for common imperfections to predict the mechanical properties of carbon nanotubes which are nowadays used in the production of advanced nanocomposites and reinforced materials.

The first example of three alternative chlorination-promoted skeletal transformation pathways in the same fullerene cage is presented. Isolated-pentagonrule (IPR) C 102 (19) undergoes both Stone−Wales rotations to give non-IPR #283794 C 102 Cl 20 and C 2 losses to form nonclassical C 98 and non-IPR C 96. X-ray structural characterization of the transformation products and a theoretical study of their formation pathways are reported.

A classical fullerene is composed of hexagons and pentagons only, and its stability is generally determined by the Isolated-Pentagon-Rule (IPR). Herein, high-temperature chlorination of a mixture containing a classical IPR-obeying fullerene C 88 resulted in isolation and X-ray crystallographic characterization of non-IPR, non-classical (NC) fullerene chloride C 84 (NC2)Cl 30 (1) containing two heptagons. The carbon cage in C 84 (NC2)Cl 30 contains 14 pentagons, 12 of which form two pairs of fused pentagons and two groups of quaternary sequentially fused pentagons, which have never been observed in reported carbon cages. All 30 Cl atoms form an unprecedented single chain of ortho attachments on the C 84 cage. A reconstruction of the pathway of the chlorination-promoted skeletal transformation revealed that the previously unknown IPR isomer C 88 (3) is converted into 1 by two losses of C 2 fragments followed by two Stone-Wales rearrangements, resulting in the formation of very stable chloride with rather short CCl bonds.

The first example of three alternative chlorination-promoted skeletal transformation pathways in the same fullerene cage is presented. Isolated-pentagonrule (IPR) C 102 (19) undergoes both Stone−Wales rotations to give non-IPR #283794 C 102 Cl 20 and C 2 losses to form nonclassical C 98 and non-IPR C 96. X-ray structural characterization of the transformation products and a theoretical study of their formation pathways are reported.

A classical fullerene is composed of hexagons and pentagons only, and its stability is generally determined by the Isolated-Pentagon-Rule (IPR). Herein, high-temperature chlorination of a mixture containing a classical IPR-obeying fullerene C 88 resulted in isolation and X-ray crystallographic characterization of non-IPR, non-classical (NC) fullerene chloride C 84 (NC2)Cl 30 (1) containing two heptagons. The carbon cage in C 84 (NC2)Cl 30 contains 14 pentagons, 12 of which form two pairs of fused pentagons and two groups of quaternary sequentially fused pentagons, which have never been observed in reported carbon cages. All 30 Cl atoms form an unprecedented single chain of ortho attachments on the C 84 cage. A reconstruction of the pathway of the chlorination-promoted skeletal transformation revealed that the previously unknown IPR isomer C 88 (3) is converted into 1 by two losses of C 2 fragments followed by two Stone-Wales rearrangements, resulting in the formation of very stable chloride with rather short CCl bonds.

Though implicit representations of surfaces have often been used for various computer graphics tasks like modeling and morphing of objects, it has rarely been used for registration and matching of 3D point clouds. Unlike in graphics, where the goal is precise reconstruction, we use isosurfaces to derive a smooth and approximate representation of the underlying point cloud which helps in generalization. Implicit surfaces are generated using a variational interpolation technique. Implicit function values on a set of concentric spheres around the 3D point cloud of object are used as features for matching. Geometric-invariance is achieved by decomposing implicit values based feature set into various spherical harmonics. The decomposition provides a compact representation of 3D point clouds while achieving rotation invariance.

Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for nonselective nanorods near the domain boundary. In this case the nanorods have a certain tendency to align parallel to the interface in the boundary region and perpendicular to it inside the domains. Similar orientation ordering of spherical nanoparticles located at the lamellar interface is predicted by the molecular theory which takes into account that the nanoparticles interact with monomer units via both isotropic and anisotropic potentials. Computer simulations enable one to study the effects of the nanorod concentration, length, stiffness, and selectivity of their interactions with the copolymer components on the phase stability and orientational order of nanoparticles. If the volume fraction of the nanorods is lower than 0.1, they have no effect on the copolymer transition from the disordered state into a lamellar microstructure. Increasing nanorod concentration or nanorod length results in clustering of the nanorods and eventually leads to a macrophase separation, whereas the copolymer preserves its lamellar morphology. Segregated nanorods of length close to the width of the diblock copolymer domains are stacked side by side into smectic layers that fill domain space. Thus, spontaneous organization and orientation of nanorods leads to a spatial modulation of anisotropic composite properties creating an opportunity to align block copolymers by external fields which may be important for various applications.

Background: As cultural institutions embark in projects oriented to digitise art and archaeological collections in three dimensions, the need for developing means to access the resulting 3D models has become imperative. Shape recognition techniques developed in the field of computer vision can help in this task. Methods: This paper describes the implementation of three shape descriptors, specifically shape distributions, reflective symmetry and spherical harmonics as part of the development of a search engine that retrieves 3D models from an archaeological database without the need of using keywords as query criteria. Use case: The usefulness of this system is obvious in the context of cultural heritage museums, where it is essential to provide automatic access to archaeological and art collections. The prototype described in this paper uses, as study case, 3D models of archaeological objects belonging to Museo del Templo Mayor, a Mexican institution that preserves one of the larges...

Using dissipative particle dynamics, a refined phase diagram of the rod-coil diblock copolymer is constructed in coordinates copolymer composition-repulsion parameter of different types of units. The diagram describes the microphase separation of copolymer blocks and the orientational ordering of rigid blocks. Simulation of rodlike blocks as rigid bodies makes it possible to reduce computational costs, increase the size of the simulation cell to 32 × 32 × 32 and the total length of the copolymer chain N to 20, to vary the composition of the copolymer chain with a smaller step (up to 0.05), and to investigate the behavior of systems with high degrees of segregation of blocks (up to χN ≈ 250). Owing to this optimization, the ordering of rigid blocks not only in the lamellar but also in bicontinuous morphology can be observed for the first time. It is also shown that the zigzag and bilayer lamellas described not only in numerical but also in laboratory experiments are metastable and disappear with an increase in the size of the simulated system.

Orientational and positional ordering of nanorods in the lamellae phase of diblock copolymers has been investigated using a simple theoretical model and dissipative dynamics simulations. Orientational order parameter and local concentration profiles of nanorods are calculated numerically and extracted from computer simulations data for different values of the nanoparticle length and different number of the interaction sites in the model nanorod. The predictions of the molecular theory are compared with the results of computer simulations.. It has been found that the nanorods are orientationally ordered in the boundary region between the domains and the orientational order parameter changes its sign at the domain wall. At the same time there exists some quantitative discrepancy between theory and computer simulations which is partially removed when a similar model of a nanorod is employed both in the molecular theory and in coarse-grained molecular dynamics simulations.

Geometrical frustration exists in both metallic glasses and chiral nematic liquid crystals. Applying results from the Landau‐Ginzburg theory of liquid crystals and from polytope models for the amorphous state, a frustrated free‐energy density for metallic glasses is derived. It is expressed in terms of an order parameter that characterizes the bond orientation of neighbouring atoms.

When particles in liquid suspensions flow through channels and pipes in a laminar fashion, the resulting parabolic velocity profile gives rise to shear, which induces the particles to rotate. If flowing suspensions containing dielectric particles are immersed in an external electric field, the anisotropic polarization induced in rotating nonspherical particles will vary with the orientation of the particle with respect to the external field; what results is an uncertainty in experimental measurements that involve particle polarization. The present study establishes the limits of this uncertainty and shows that departure from spherical symmetry in individual particles can lead to a significant overlap in measurements attempting to discriminate between particle subpopulations in suspensions. For example, the uncertainty in signal amplitude for a population of activated T-lymphocytes can be as high as 20%. Such concerns arise in applications like field-flow fractionation, dielectrophoretic sorting of particles, flow impedance measurements and cytometry, and, most recently, isodielectric separation, all of which are used to separate particles in a flow based on their dielectric response. This paper considers axisymmetric particles as the first departure from the approximation of spherical symmetry, shows how to calculate an estimate of the size of the population overlap, and suggests possible strategies to minimize it.

Finite element models of single-walled and multi-walled carbon nanotubes in their perfect and fundamental forms (zigzag and armchair) were constructed. Then, after obtaining the mechanical properties of perfect carbon nanotubes, three types of imperfections, i.e., doping with Si atoms, carbon vacancy and perturbation of the ideal location of the carbon atom were introduced in different amounts to the perfect models to make them imperfect. Finally, the mechanical properties of the imperfect carbon nanotubes were numerically simulated and compared with those of perfect ones. Simple relations which predict the change of Young's modulus as a function of the imperfection percentage were derived. The results show that the existence of any kind of imperfection in the perfect models leads to lower stiffness values. This study allows to realistically judge any simulation based on perfect structures and gives for the first time a good estimate to which extend the values based on perfect structures must be lowered in order to account for common imperfections to predict the mechanical properties of carbon nanotubes which are nowadays used in the production of advanced nanocomposites and reinforced materials.

Geometrical frustration exists in both metallic glasses and chiral nematic liquid crystals. Applying results from the Landau-Ginzburg theory of liquid crystals and from polytope models for the amorphous state, a frustrated free-energy density for metallic glasses is derived, It is expressed in terms of an order parameter that characterizes the bond orientation of neighbouring atoms. Sowohl in metallischen Glasem als auch in chiralen nematischen Fliissigkristallen gibt es geometrische Frustration. Wir benutzen die Landau-Ginzburg-Theorie fiir Flussigkristalle und Polytop-Modelle fiir den amorphen Zustand urn fiir metallische Glaser eine frustrierte Dichte der freien Energie abzuleiten. Der darin enthaltene Ordnungsparameter beschreibt die Bindungsorientierung benachbarter Atome.

We apply effective-medium theory, generalized for nonlinear media, to the problem of four-wave mixing in composites consisting of conducting particles embedded in a linear dielectric medium. For spheroidal conducting particles two cases are considered: (i) the particles are oriented and (ii) the particles have a random orientation. An experiment on gold particle suspensions in glass (Schott RG6) examines the frequency dependence of the conjugate signal intensity in a four-wave mixing geometry. Analysis of these results indicates that the particles with spheroidal shapes are mixed in the glass. We find that frequency and optical depth dependence of the conjugate intensity can be used to gain insight into the shape of the particles, since a large enhancement of the conjugate reflectivity is expected at the surface plasmon resonances, which are highly sensitive to small shape distortions.

Processing and characterization of graphene (Gr)-reinforced aluminium alloy 7075 (AA7075) microcomposites and nanocomposites
are reported in this work. Composites are fabricated by mechanical alloying process at wet conditions. The bulk
composites are prepared by uniaxial die pressing to get higher densification and sintered in an inert atmosphere. Density of
the nanocomposites is higher than the microcomposites due to the reduction of grain size by increased milling time. X-ray
diffraction (XRD) analysis confirms graphene interaction with the AA7075 matrix lattice spaces. The effective distribution
of graphene with aluminium alloy is further confirmed by the Transmission Electron Microscopy (TEM) analysis. The hardness
of the composites proportionally increases with the graphene addition owing to grain refinement. Wear morphology is
characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Microcomposites reveal
abrasive and ploughing wear mechanism of material removal from the surface. Nanocomposites show adhesive wear with
delamination and particle pull-out from the material surface.

In the present investigation, a newly fabricated Al6061 reinforced with various quantity (0.4-1.6 wt%) of nano SiC in steps of 0.4 and fixed quantity (0.5 wt%) of micro graphite particle's hybrid nanocomposites were prepared by ultrasonic assisted stir casting method. The influence of nano SiC and graphite content on the mechanical and tribological properties of Al6061 hybrid nanocomposites were studied. The pin-on-disc equipment was used to carry out experiment at 10-40 N applied load, 0.5 m/s sliding speed and 1000 m sliding distance. The Al/ SiC/Gr hybrid nano-composite and matrix alloy wear surfaces were characterized by FESEM equipped with an EDS, 3D profilometer to understand the wear mechanisms. The results of Al/SiC/Gr self-lubricating hybrid nanocomposites showed improved wear resistance than the Al6061 matrix alloy. The coefficient of friction of Al/SiC/ Gr hybrid nano-composites were lower than those of the unreinforced alloy at various applied load. Compared to matrix alloy, the surface roughness of Al/SiC/Gr hybrid nano-composites had significantly reduced to 66% at low load and 75% at high load. Self-lubricating Al/SiC/Gr hybrid nanocomposites showed superior surface smoothness compared to matrix alloy. Keywords Al6061 Á Nano-SiC Á Graphite Á Ultrasonic assisted stir casting Á Self-lubricating Á Hybrid nanocomposites & I. Manivannan

The present study aims to produce graphene nanoplatelet-coated B4C ceramic particle using semi-powder method and to investigate the effect of graphene nanoplatelets on wear and corrosion performance of Al–Si-based metal matrix hybrid composites. For this purpose, first graphene nanoplatelets at different ratios (0.25, 0.5, and 1 vol.%) were coated to the surfaces of B4C particles and then the Al–Si alloy was infiltrated into the reinforcements by gas pressure infiltration method. The characterization of graphene nanoplatelet-coated B4C powders and its composites was carried out by X-ray diffraction, differential scanning calorimetry, scanning electron microscope, and transmission electron microscope analysis. Tribological properties were investigated by reciprocating ball-on-flat method under three different loads (10–20–40 N) in a dry environment. The corrosion resistance was carried out with Tafel polarization method in 3.5% NaCl solution. Characterization results show that graphe...

We report a novel observation of the tetragonal perforated layer structures in a series of rodcoil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer structure was observed at f PMPCS ≈ 0.37 in relatively low molecular weight (Mw) samples and ∼0.5 in high Mw PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod-coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The "onset" of perforation was also observed in real space in sample PS272-b-PMPCS93 (f PMPCS ≈ 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in f PS , by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at f PMPCS ≈ 0.48.

Effective utilization of carbon nanotubes (CNTs) as reinforcements in composites necessitates good interfacial bonding with the surround matrix material. The covalent functionalization of CNTs is an effective method to enhance this bonding. However, covalent bonds introduced by a functional group may alter the pristine structure of the CNT and lower its mechanical properties. Here we study the effect of hydrogen (-H), hydroxyl (-OH), carboxyl (-COOH), and amine (-NH 2) functionalization on Young's modulus of a single-wall CNT (SWCNT) using molecular mechanics (MM) simulations with the MM3 potential and the software TINKER. Both pristine and functionalized SWCNTs have been deformed in simple tension. From the strain energy of deformation vs. the axial strain curves, the value of Young's modulus has been derived as a function of the functionalization group and the amount of functionalization. It is found that Young's modulus decreases by about 30 % with 20 % of functionalization, the reduction is essentially proportional to the increase in the percentage of the functionalization material and is nearly the same for each of the four functional groups studied.

We report a detailed theoretical study of polymer nanorod composites using integral equation theory. The miscibility criteria for small amounts of nanorods in a dense polymer melt have been predicted for various polymer adsorption strengths, nanorod thicknesses, smoothnesses, and aspect ratios, for both athermally interacting and attractive rods. Close comparisons with the nanosphere limit have been made. We find that nanorods exhibit the same kinds of depletion, dispersion, bridging, and telebridging behavior previously predicted for spherical particles. However, the limits of these behaviors are a close (and sometimes nonmonotonic) function of aspect ratio, surface roughness, and nanorod thickness. The miscible region between depletiondriven phase separation and bridging driven phase separation quickly narrows with increasing aspect ratio and remains roughly constant as the nanorod radius of gyration exceeds that of the polymer. This miscible window narrows more quickly in the case of attractive rods. The polymer-mediated attractive forces between athermal rods scale with nanorod diameter, in both the bridging and depletion regimes. Telebridged structures are predicted when the range of polymer− particle attractions approaches the polymer thickness, i.e., the monomer diameter.

Iron oxide thin films have been obtained significant interest as a material that put forwards applications in photovoltaics, gas sensors, biosensors, optoelectronic and especially in spintronics. Iron oxide is one of the considerable interest due to its chemical and thermal stability. Metallic ion dopant influenced superexchange interactions and thus changed the structural, electrical and magnetic properties of the thin film. Mg dopped zinc ferrite (Mg:Zn x Fe 3Àx O 4) crystal was used to avoid the damage of Fe 3 O 4 (magnetite) crystal instead of Zn 2+ in this study. Because the radius of the Mg 2+ ion in the A-site (tetrahedral) is almost equal to that of the replaced Fe 3+ ion. Inverse-spinel structure in which oxygen ions (O 2À) are arranged to form a face-centered cubic (FCC) lattice where there are two kinds of sublattices, namely, A-site and B-site (octahedral) interstitial sites and in which the super exchange interactions occur. In this study, to increase the saturation of magnetization (M s) value for iron oxide, inverse-spinal ferrite materials have been prepared, in which the iron oxide was doped by multifarious divalent metallic elements including Zn and Mg. Triple and quaternary; iron oxide and zinc ferrite thin films with Mg metal dopants were grown by using Spray Pyrolysis (SP) technique. The structural, electrical and magnetic properties of Mg dopped iron oxide (Fe 2 O 3) and zinc ferrite (Zn x Fe 3Àx O 4) thin films have been investigated. Vibrating Sample Magnetometer (VSM) technique was used to study for the magnetic properties. As a result, we can say that Mg dopped iron oxide thin film has huge diamagnetic and of Mg dopped zinc ferrite thin film has paramagnetic property at bigger magnetic field.

In recent times, tribological properties are gaining and grabbing great attention in metal matrix composites. They can provide significant benefits such as a lower coefficient of friction, wear resistance, high strength, and stiffness. Considering all these parameters, this research article mainly focuses on developing an aluminum hybrid nanocomposite material fabricated by powder metallurgy. Then, the results were examined using a pin-on-disk apparatus. Further optimization techniques such as the Taguchi approach under Design of Experiments have been adopted to obtain a minimal outcome of various assumed parameters such as A. percentage weight fraction of graphite content (Gr), B. the sliding distance, C. the sliding speed, and D. the stress applied. In addition, we have chosen parameters such as friction and wear loss for optimizing the outcome, including the main effect plots for the S-N ratio and the Analysis of Variance (ANOVA) approach. Based on the experimental results, we ha...

In the present investigation, a newly fabricated Al6061 reinforced with various quantity (0.4-1.6 wt%) of nano SiC in steps of 0.4 and fixed quantity (0.5 wt%) of micro graphite particle's hybrid nanocomposites were prepared by ultrasonic assisted stir casting method. The influence of nano SiC and graphite content on the mechanical and tribological properties of Al6061 hybrid nanocomposites were studied. The pin-on-disc equipment was used to carry out experiment at 10-40 N applied load, 0.5 m/s sliding speed and 1000 m sliding distance. The Al/ SiC/Gr hybrid nano-composite and matrix alloy wear surfaces were characterized by FESEM equipped with an EDS, 3D profilometer to understand the wear mechanisms. The results of Al/SiC/Gr self-lubricating hybrid nanocomposites showed improved wear resistance than the Al6061 matrix alloy. The coefficient of friction of Al/SiC/ Gr hybrid nano-composites were lower than those of the unreinforced alloy at various applied load. Compared to matrix alloy, the surface roughness of Al/SiC/Gr hybrid nano-composites had significantly reduced to 66% at low load and 75% at high load. Self-lubricating Al/SiC/Gr hybrid nanocomposites showed superior surface smoothness compared to matrix alloy. Keywords Al6061 Á Nano-SiC Á Graphite Á Ultrasonic assisted stir casting Á Self-lubricating Á Hybrid nanocomposites & I. Manivannan

The lithium adsorption energies and electronic structures of pristine ((8,0)) single-walled carbon nanotube (SWCNT) and functionalized carbon nanotubes with amine and carboxyl groups (NH 2 /((8,0)) and COOH/((8,0))) were studied using density functional theory. The results show that the adsorption energies of lithium inside and outside of ((8,0)) SWCNT differ very little from each other. When the lithium is doped in carbon nanotubes, charge transfer takes place from the lithium to the nanotubes. After functionalization of carbon nanotubes with amine (ANH 2) and carboxyl (ACOOH) groups, various positions for lithium adsorption around the functional groups can be served. The adsorption energy of lithium in these positions is greater than that of lithium in pure ((8,0)) SWCNT. When the lithium was doped in NH 2 /((8,0)) and COOH/((8,0)), an energy gap between valence and conduction bands is observed, and the conductivity is reduced relative to lithium-doped non-functionalized carbon nanotubes.

Submitted for the MAR17 Meeting of The American Physical Society Coupling mesodomain positional ordering to intra-domain orientational ordering in block copolymer assembly CHRISTOPHER BURKE, ABHIRAM REDDY, ISHAN PRASAD, GREGORY GRASON, UMass Amherst-Block copolymer (BCP) melts form a number of symmetric microphases, e.g. columnar or double gyroid phases. BCPs with a block composed of chiral monomers are observed to form bulk phases with broken chiral symmetry e.g. a phase of hexagonally ordered helical mesodomains. Other new structures may be possible, e.g. double gyroid with preferred chirality which has potential photonic applications. One approach to understanding chirality transfer from monomer to the bulk is to use self consistent field theory (SCFT) and incorporate an orientational order parameter with a preference for handed twist in chiral block segments, much like the texture of cholesteric liquid crystal. Polymer chains in achiral BCPs exhibit orientational ordering which couples to the microphase geometry; a spontaneous preference for ordering may have an effect on the geometry. The influence of a preference for chiral polar (vectorial) segment order has been studied to some extent, though the influence of coupling to chiral tensorial (nematic) order has not yet been developed. We present a computational approach using SCFT with vector and tensor order which employs well developed pseudo-spectral methods. Using this we explore how tensor order influences which structures form, and if it can promote chiral phases.

We apply effective-medium theory, generalized for nonlinear media, to the problem of four-wave mixing in composites consisting of conducting particles embedded in a linear dielectric medium. For spheroidal conducting particles two cases are considered: (i) the particles are oriented and (ii) the particles have a random orientation. An experiment on gold particle suspensions in glass (Schott RG6) examines the frequency dependence of the conjugate signal intensity in a four-wave mixing geometry. Analysis of these results indicates that the particles with spheroidal shapes are mixed in the glass. We find that frequency and optical depth dependence of the conjugate intensity can be used to gain insight into the shape of the particles, since a large enhancement of the conjugate reflectivity is expected at the surface plasmon resonances, which are highly sensitive to small shape distortions.

pandemic started more than a year ago and has infected more than 115 million of people from *210 countries and [2.5 million of deaths worldwide being reported without any commercial and effective treatment or vaccine being yet released. However, recent studies on nanomaterials such as fullerenes, carbon nanotubes and graphene showed that they possess anti-inflammatory, antiviral, anti-oxidant and anti-HIV properties. Herein, the interactions which established between the fullerenes C m (m = 48, 60, 70, 80, 84 and 86) and the spike protein (SP) of SARS-CoV-2 and the human ACE2 receptor have been investigated based on the density functional theory (DFT) method with the CAM-B3LYP functional and the 6-31G* basis. The results of this study show that C48 exhibited as potential inhibitor of SARS-CoV-2. Because of the presence of heteroatoms on the surface of fullerenes which systematically reduce energy gaps, which in turn increase their reactivities. The oxygen adsorbed by fullerenes increases the number of non-covalent contacts and involves a large number of hydrogen bonds, while decreasing the binding energies. Thus, the hACE2-SP-4O 2 @C60 complex is strongly recommended for inhibiting SARS-CoV-2 in the final phase of contamination.

Nanocomposites with metallic inclusions show great promise as tunable functional materials, particularly for applications where high permittivities are desirable, such as charge-storage. These applications strain quantum mechanical computational approaches, as any representative sample of the material includes hundreds if not thousands of atoms. Many continuum methods offer some predictive power for matrix-inclusion composites, but cannot be directly applied to composites with small inclusions, for which quantum and interfacial effects dominate. Here, we develop an adjustable finite element approach to calculate the permittivities of composites consisting of a metal-oxide matrix with nanometer-scale silver inclusions, by introducing an interfacial layer in the model. The approach involves solving the Laplace equation with Dirichlet and Neumann boundary conditions. We demonstrate that such a continuum model, when appropriately informed using quantum mechanical results, can capture ma...

The purpose of this paper is examination and simulation of tribological properties of composite materials based on porous ceramic preforms infiltrated by eutectic aluminium alloy. Design/methodology/approach: The material for investigations was fabricated by pressure infiltration method of ceramic porous preforms. The eutectic aluminium alloy EN AC-AlSi12 was use as a matrix while as reinforcement were used ceramic preforms fabricated by sintering of Al 2 O 3 Alcoa CL 2500 powder with addition of pore forming agents as carbon fibres Sigrafil C10 M250 UNS manufactured by SGL Carbon Group company. The wear resistance was measured by the use of device designed in the Institute of Engineering Materials and Biomaterials. The device realize dry friction wear mechanism of reciprocating movement condition. The simulation of influence of load and number of cycles on tribological properties was by the use of neural networks made. Findings: The developed technology of manufacturing of composite materials with the pore ceramic Al 2 O 3 infiltration ensures expected tribological properties moreover those properties can by simulated by the use of neural network. Practical implications: The composite materials made by the developed method can find application as the alternative material for elements fabricated from light metal matrix composite material reinforced with ceramic fibrous preforms. Originality/value: The obtained results show the possibility of manufacturing the composite materials with expected tribological properties by the pressure infiltration method of porous preforms based on the ceramic particles with liquid aluminium alloy.

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Knowledge of materials' thermal-transport properties, conductivity and diffusivity, is crucial for several applications within areas of biology, material science and engineering. Specifically, a microsized, flexible, biologically integrated thermal transport sensor is beneficial to a plethora of applications, ranging across plants physiological ecology and thermal imaging and treatment of cancerous cells, to thermal dissipation in flexible semiconductors and thermoelectrics. Living cells pose extra challenges, due to their small volumes and irregular curvilinear shapes. Here a novel approach of simultaneously measuring thermal conductivity and diffusivity of different materials and its applicability to single cells is demonstrated. This technique is based on increasing phonon-boundary-scattering rate in nanomembranes, having extremely low flexural rigidities, to induce a considerable spectral dependence of the bandgap-emission over excitation-laser intensity. It is demonstrated ...

A design of ultrathin composite layer with metal nanoparticles on a dielectric surface is proposed for interference reduction of Fresnel reflection. The structural and material parameters of the antireflection composite are calculated within the Maxwell−Garnett effective-medium approximation. The results of the approximate analytical calculation are in good agreement with the exact numerical solution to the Maxwell equations.

Using dissipative particle dynamics, a refined phase diagram of the rod-coil diblock copolymer is constructed in coordinates copolymer composition-repulsion parameter of different types of units. The diagram describes the microphase separation of copolymer blocks and the orientational ordering of rigid blocks. Simulation of rodlike blocks as rigid bodies makes it possible to reduce computational costs, increase the size of the simulation cell to 32 × 32 × 32 and the total length of the copolymer chain N to 20, to vary the composition of the copolymer chain with a smaller step (up to 0.05), and to investigate the behavior of systems with high degrees of segregation of blocks (up to χN ≈ 250). Owing to this optimization, the ordering of rigid blocks not only in the lamellar but also in bicontinuous morphology can be observed for the first time. It is also shown that the zigzag and bilayer lamellas described not only in numerical but also in laboratory experiments are metastable and disappear with an increase in the size of the simulated system.

Stoichiometric Mn 0.2 Zn 0.8 Fe 2 O 4 monodisperse nanoparticles were prepared by the so-called polyol method. The variation of magnetization as a function of magnetic field H (up to (50 kOe) and temperature (5-320 K) were investigated, for zero-field-cooled (ZFC) and field-cooled (FC) conditions on freshly produced powder. The T variation of the low-field (H = 200 Oe) magnetic susceptibility is characteristic of superparamagnets with a blocking temperature below room temperature. The H variation of the low temperature (T = 5 K) magnetization exhibits a hysteresis loop. The coercivity is weak, about 0.2-0.3 kOe, which is typical of soft-ferrimagnetic materials. The 0 K saturation magnetization and the Curie temperature are found to be 98 emu.g-1 and 360 K, respectively. The magnetic properties of the particles are discussed in relation with their chemical composition and their cation distribution in the opportunity of using them as heating mediators for hyperthermia application in cancer therapy. In this aim, the toxicity of the particles was also evaluated by viability assays on human umbilical vein endothelial cells (HUVEC).

This is the third paper in a series devoted to the study of the volume plasmon in an ENZ slab. In the first [1], we calculated the electric field inside the slab, using the Airy formulas at the plasma resonance frequency and eliminating the singularity factors. In the second [2], we found that at plasma resonance, the volume plasmon is a null vector field. This gives the resonant plasmon properties which are both longitudinal and transversal. We present a model for a semiconducting slab, which is embedded in dielectrics and not in vacuum. This creates the possibility to describe volume and surface plasmons . Moreover, when we feed this model with the hydrodynamic Drude model, we are able to observe also longitudinal field and new resonance phenomena. We will complete the study of the volume plasmon by considering off-resonance situations in a collisional plasma. The plasmon is then no longer a null field, although longitudinal fields stay possible. More new phenomena appear, which w...

In recent years, ferrofluid has emerged as a new class of 'smart nanofluid,' whose properties are controllable by an external magnetic field. It is well known for its unique property of having both liquid and magnetic properties. Ferrofluids have been a topic of intense research during the last few decades due to their potential applications in mechanical, biomedical and optics industries. Some of the exciting applications of this material includes leak free seals, smart cooling, micro robot, micromechanical sensor, nondestructive defect sensors, tunable optical filters, actuators, optical grating, optical limiter, optical fiber modulator, magneto optical waveguide, magneto optical wavelength filter, optical switches, biosensors, hyperthermia treatment and tumor treatment, cell separation, magnetic resonance imaging based drug targeting, quantification of biomolecule agglutination etc. Besides several interesting optical effects have been observed in magnetic nanofluids under magnetic field. For example, on increasing the applied field, the transmitted intensity diminishes drastically, followed by the appearance of a 'ring' like structure in the scattered pattern, which finds applications in light limiters and switches. The scattering anisotropy factor and dipolar resonances within the scatterers are postulated as the origin for observed extinction of light. The formation of cylindrical rod-like structures, along the direction of light propagation, is manifested as a circular ring pattern in the scattered pattern. The observation of several critical fields at regular intervals in the transmitted intensity is attributed to the zippering transitions of the chains when they are in off registry. In this article, we present a critical review on various optical effects observed in ferrofluids under external magnetic field, the underlying physics and potential applications. It must be emphasized that the main focus is on scattering studies under magnetic field parallel to the incident light beam. The scattering and diffraction studies in ferrofluids (Section 4) have been elaborated for specialists.

I hereby declare that this dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration except as declared in the Acknowledgements and specified in the text. It is not substantially the same as any that I have submitted, or, is being concurrently submitted for a degree or diploma or other qualification at the University of Cambridge or any other University or similar institution except as declared in the Acknowledgements and specified in the text. I further state that no substantial part of my dissertation has already been submitted, or, is being concurrently submitted for any such degree, diploma or other qualification at the University of Cambridge or any other University or similar institution except as declared in the Acknowledgements and specified in the text. This dissertation contains fewer than 60,000 words excluding appendices, bibliography, footnotes, tables and equations.

A metal matrix composite was developed through a unique liquid pressing infiltration process to study the wear mechanism of a TiC reinforced AISI 1020 steel matrix. The microstructure, hardness, and wear behaviors of the TiC/AISI 1020 composite were compared with commercial AISI 52100 bearing steel. Microstructural analysis showed that there were no defects, such as pores or agglomeration of reinforcement particles, and about 60% of the volume of TiC was uniformly dispersed. In the case of the AISI 52100 alloy, the hardness was 62.42 HRC, which was similar to the 62.84 HRC value of the as-cast TiC/AISI 1020 composite. After the quenching heat treatment, the Rockwell hardness of the composite increased to 76.64 HRC, which was attributed to the martensitic transformation of the AISI 1020 matrix. As a result of the pin-on-disc wear test with high contact pressure, the wear width of AISI 52100 was 2937 μm, which was approximately 4.3 times wider than that of the heat-treated metal matri...

Although optical coating deposition techniques have been perfected over decades to prepare optically homogeneous dense coatings with smallest surface roughness, nanostructuring of optical coatings has proven as an effective mechanism to further enhance their performance while reducing their thickness in special cases. Therefore, nanostructure effects can be tackled as additional degrees of freedom for coating design, and can even lead to useful property combinations that are inaccessible to ' classical ' coatings prepared on the basis of the traditionally available coating materials. Examples include metal island fi lms as building blocks for spectrally selective absorber coatings for color management or solar energy conversion purposes, as well as motheye structures for antirefl ection coatings and the combined optimization of optical and non-optical coating properties.

The present study aims to study the wear behaviour of Mg reinforced with boron nitride nanocomposite. The dry sliding wear behaviour of Mg reinforced with boron nitride (0.5 wt.%) is reviewed by following ASTM standards G99, i.e., dry sliding on pin-on-disk wear test apparatus. Three wear parameters, namely load, sliding speed, and sliding distance, were considered in this study. The experiments for wear rate have been conducted as per ASTM standards G99. The wear rate obtained for Mg reinforced with boron nitride (0.5 wt.%) is predicted by the ANN toolbox of Matlab R2021a using the Levenberg-Marquardt (trainlm) algorithm, which trains the feed-forward neural network having 3-5-1 (three input neurons, five hidden neurons in the single hidden layer and one output neuron). Experimental data sets obtained from the pin-on-disk wear test have been utilized to develop ANN. The results concluded that the error for wear loss of Mg reinforced with boron nitride (0.5 wt.%) lies within 20%, wi...

Titanium carbide is the costly reinforcement nano powder mostly used in structural applications, aerospace, automobile industries and specific cutting tools where safety is main consideration factor and reasons are not difficult to understand as far as cost concerned. The primary objective in aircraft or anywhere is safety. In the present research the effect of titanium carbide particles on their mechanical properties with different aluminium matrix has been reviewed. The ultrasonic assisted stir casting is an economical and amenable process for medium to large scale production as compared to other methods such as powder metallurgy and spray forming. The objective of this paper is to study the current research and development in aluminum-based in situ and ex-situ composites by casting route. Very few work has been reported on nano TiC particulates synthesized with Al 6061 using ex-situ method. TiC particulates reinforced composites are attributed to tremendous bond reliability of TiC particulates with aluminium. Titanium carbide is proved to be a potential reinforcement for improved mechanical properties in Al MMCs.

Exfoliating graphite to graphene nanosheets by mechanical ball milling with alumina, coating alumina particles with graphene layers to enhance their electrical and thermal properties, minimizing aluminum composite's production time, and improving the adhesion between the matrix and reinforcement were the aims of this study. Ball milling (BM) followed by electroless silver coating was used to prepare the (Al 2 O 3-GNs) hybrid nanoparticles. A matrix sample from Al, 5 wt% Ni, and 0.5 wt% Mg was reinforced with different ratios of (Al 2 O 3-GNs)/Ag nanoparticles up to 7.5 wt%. The cold and hot compaction technique was used to prepare the study samples. 550 • C and 50 min were the suitable parameters for fabricating the aluminum matrix composite. Microstructure investigation has been followed by chemical analysis, hardness, compressive strength, and electrical conductivity measurements. New intermetallic phases Al 50 Mg 48 Ni 2 , AlNi, and AlMg, have been formed during the powder consolidation by the hot-pressing process. The density of the Al-5Ni-0.5Mg (3.005 g/cm 3) matrix was not significantly affected by the Al 2 O 3 /GN (3.907 g/cm 3) reinforcement density. The 7.5 wt% Al 2 O 3-GN reinforced composite exhibits the highest hardness. The electrical conductivity and the composites' compressive strength are also increased by 133% and 78%, respectively, for the 7.5 wt% sample.

The biphenylene network with periodically arranged four-, six-, and eightmembered rings has been successfully synthesized in very recent experiments. This novel two-dimensional (2D) carbon allotrope has potentials in applications of lithium storage and carbon-based circuitry. Understanding the thermal transport properties of biphenylene network is of critical importance for the performance and reliability of its practical applications. To this end, the thermal transport in biphenylene network is comprehensively investigated in this paper with the aid of molecular dynamics simulations together with first-principles calculations. For the sake of comparison, the thermal conductivities of other 2D sp2-hybridized carbon allotropes including graphene and pentaheptite are also investigated using the same method. It is found that the thermal conductivities of biphenylene network and pentaheptite are, respectively, only about one-thirteenth and one-eighth of graphene. Through the analysis of...

A drying method suitable for the study of the morphological and structural properties of colloidal magnetic systems, including a contrast agent used in Magnetic Resonance Imaging (MRI) is described. We tested three alternative ferrofluid drying methods: drying at 70 • C in nitrogen atmosphere; drying in air at 70 • C; and drying by liophylization using an MRI marker in the form of a colloidal suspension (Endorem T M-Guebert). X-ray diffraction (XRD), and transmission electron microscopy (TEM) were applied to each characterization method. The XRD allowed the observation of the possible physical-chemical changes of the stabilizers and also Fe 3 O 4 present in the system. The morphology and nanoparticles size distribution was analyzed by TEM. Among the drying methods examined in this study, the liophylization has shown to be the more adequate one for the nanoparticles (Fe 3 O 4) morphological study and nanostructural characterization, because the structure of the nanoparticles was maintained the same as in the suspension. The drying procedures performed at 70 • C in the atmospheres of nitrogen and air let to the coalescence and growth of the nanoparticles, as well as some degradation has been noticed in some of the stabilizers.