Two-phase Nanocomposites Research Articles

Elastic and strength properties of MXene/CNT reinforced epoxy/glass fibre based nanocomposites: Experimental and analytical study

In the current work, the strength and elastic properties of MXene/CNT reinforced epoxy/glass fibre based nanocomposites were investigated using experimental and analytical approach. To achieve this, the Halpin-Tsai model and Chamis model was employed to evaluate the mechanical properties of two -phase (MXene-CNT)/Epoxy composite and three-phase (MXene-CNT)/Epoxy/Glass fibre composite. The accuracy of the analytical model was verified by comparing the results with the experimental data. To study the strength properties of the composites in detail, experimental tensile and flexural tests were carried out. Finally, a parametric study was performed to investigate the influence of weight fractions and aspect ratios on the elastic properties of MXene/CNT reinforced composites. It was observed that the MXene/CNT reinforced glass/epoxy based composite exhibited higher load bearing capacity as compared to neat glass/epoxy composite for all the performed mechanical tests. The tensile, shear and flexural modulus of MXene/CNT reinforced laminated composite were found to be 17.2%, 15.6%, and 16.2%, higher in comparison to the neat glass/epoxy laminated composite. The addition of nano-fillers exerted positive impact on the elastic properties of both the two-phase and three-phase nanocomposites and the properties kept on improving with weight fraction of the nano-fillers. Regarding the impact of aspect ratio on elastic modulus, however, conflicting findings were noted. Increase in the aspect ratio, on one hand, resulted in an increase in the longitudinal elastic modulus; on the other hand, it resulted in a monotonous reduction in the shear modulus.

Effects of non-uniformity in thickness and volume fraction of agglomerated CNTs on the dynamics of a spinning CNT-reinforced nanocomposite truncated conical shell

In the presented work, the free vibration analysis of a rotating truncated conical shell whose thickness varies in the meridional direction is examined. The material that the shell is made of is a polymeric matrix (epoxy) enriched with carbon nanotubes (CNTs) whose volume fraction varies in the meridional direction. CNTs agglomeration is considered and the density and elastic constants of such a two-phase nanocomposite are calculated sequentially based on the Eshelby–Mori–Tanaka approach alongside the rule of mixture. The conical shell is modeled using the first-order shear deformation theory (FSDT) including the relative acceleration, Coriolis acceleration, and centrifugal acceleration along with the initial hoop tension, and the governing equations are obtained utilizing Hamilton’s principle. The solution of governing equations is performed via the combination of an analytical solution in the circumferential direction and a numerical one in the meridional direction via the differential quadrature method (DQM). The impacts of several parameters on the forward and backward natural frequencies of such a rotating shell are studied such as chirality, mass fraction and dispersion pattern of the CNTs, thickness variation parameters, and boundary conditions. It is observed that higher natural frequencies and critical rotational speeds can be achieved for CNT-reinforced conical shells when the volume fraction of the CNTs and the thickness of the shell increase from its small radius to the large one.

Photoluminescence from Two-Phase Nanocomposites Embedded in Polymers.

A set of polymer-embedded, two-colored nanocomposites were prepared where the co-existing emission peaks (~578 nm and ~650 nm) had different ratios at their emission thresholds. The nanocomposite samples were simultaneously excited by a 405 nm laser, and the growth of photoluminescence intensities was studied as a function of excitation intensity. The two peaks showed different growth evolution mechanisms. The factors impacting this difference could be (1) energy transfer between the two sized nanoparticles; (2) relaxation mechanism of smaller nanoparticles; and (3) material properties of the polymer.

Nd-doping-induced perovskite/Ruddlesden-Popper heterointerfaces boost the ORR activity and CO2 tolerance for SrFeO3-δ-based cathode

The development of cathode materials with high oxygen reduction reaction (ORR) activity is crucial to realize the wide application of solid oxide fuel cells. Nd-doped SrFeO3-δ (SNF) two-phase nanocomposite was fabricated by a dopant-induced in situ self-assembly process. The SNF nanocomposite comprises 63.4 wt% perovskite main phase (P–SNF) and 36.6 wt% Ruddlesden-Popper second phase (RP-SNF). The average thermal expansion coefficient (TEC) of SrFeO3-δ is reduced by 36.5 % and down to 13.9 × 10−6 K−1. At 750 °C, SNF demonstrates an impressive output power of 779 mW cm−2, which is twice that of the single-phase SrFeO3-δ. The superior performance stems from the heterointerface effect of the in situ self-assembled two phases. This effect increases the content of oxygen vacancies, thereby enhancing both chemical oxygen surface exchange coefficient and bulk diffusion coefficient. Moreover, the SNF composite exhibits excellent CO2 tolerance than the single-phase SrFeO3-δ. This work presents a promising avenue for exploring multifunctional materials through interface engineering, offering new possibilities for future energy conversion devices.

Self-Assembled Multiphase Nanocomposite SrCo1–xFexO3-δ Thin Films with Voltage-Controlled Magnetism for Spintronic Applications

SrCo1–xFexO3-δ (SCFO) grown on SrTiO3 substrates using pulsed laser deposition forms either a single-phase film or a two-phase self-assembled nanocomposite film depending on the oxygen partial pressure, PO2. A high PO2 of 150 mTorr during growth promotes phase separation of SCFO into a nanocomposite comprising Co oxide pillars embedded epitaxially in a Fe-rich SCFO matrix made up of brownmillerite and oxygen-deficient perovskite, despite the average composition of Sr/(Co + Fe) = 1. The SCFO matrix in the nanocomposite consists of a brownmillerite structure at a high Co content and an oxygen vacancy ordered perovskite at a high Fe content. In contrast, single-phase SCFO films grow at 20 mTorr. Ionic liquid gating of the nanocomposites oxidizes brownmillerite into perovskite with interlayer defects and renders the matrix phase magnetic with a saturation magnetization of 200 emu cm–3 at 173 K when x = 0.30.

Numerical Analysis of the Mechanical Response of Two-Phase Nanocomposites Consisting of Nanoporous Gold and Polymer.

In this work, representative volume elements (RVEs) of composites, consisting of nanoporous gold and polymer, were investigated. Gold is of great interest as a special case of nanoporous metals as it deforms to large plastic strains when compressed, whereas normally nanomaterials allow only small deformations. The nanocomposite is modeled as a nanoporous monocrystal filled with a polymer. Different models of the phase behavior of nanoporous metal composites with the addition of a polymer component were studied. Three models of the mechanical behavior of gold were implemented: elasticity, elastic-plasticity, and the model of fracture with the degradation of properties. Three types of polymers were considered: polypyrrole (PPy), epoxy resin, and polyaniline (PANI), for which elasticity and elastic-plasticity models were implemented. The effect of the morphology of the nanocomposite on their mechanical response was numerically investigated using finite element analysis.

Core-shell Structured Ag@PDA Nanowires and BT@PDA Nanoparticles for Three-phase Flexible Polymer Nanocomposites with Excellent Dielectric Properties

In this work, core-shell structured polydopamine coated silver nanowires (Ag@PDA NWs) and polydopamine coated BaTiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> nanoparticles (BT@PDA NPs) are accurately prepared. Through embedding Ag@PDA NWs and BT@PDA NPs into the P(VDF-HFP) matrix, flexible nanocomposites with high dielectric constant and low dielectric loss are prepared by constructing three-phase structure. The crystal structure, thermal properties and dielectric properties of the nanocomposites are fully investigated. Compared with two-phase nanocomposites, which are composed by Ag@PDA NWs and P(VDF-HFP), the dielectric constant of the three-phase nanocomposites is improved from 28.1 to 67.9. Additionally, owing to the presence of the polydopamine shell, the nanofillers are homogeneously dispersed and the interfacial adhesion between the nanofillers and polymer matrix is also enhanced, leading to the dielectric loss and electric conductivity of three-phase nanocomposites remain relatively low level. Furthermore, the dielectric properties of the three-phase nanocomposites exhibit weak temperature dependence.

Two modified multiscale modeling approaches for determination of two-phase and hybrid nanocomposite properties

In this paper, mechanical properties of thermoset epoxy based two-phase and hybrid nanocomposites containing carbon nanotubes (CNTs), and carbon nano diamond particles (CNPs) are determined using two different multiscale modeling approaches. The effects of resin crosslinking, interphase mechanical properties, and filler agglomeration on nanocomposite mechanical properties are investigated. First, the crosslinking between Diglycidyl ether of bisphenol A (DGEBA) resin and Diethylenetriamine (DETA) hardener is modeled considering different crosslinking forms and ratios using molecular dynamics (MD) simulations. Results indicate that resin elastic modulus increases with increasing the crosslinking ratio especially above 75%, but crosslinking form has an insignificant effect on resin modulus. Next, different nanofillers and their interphases are modeled using MD simulations to determine the representative volume element (RVE) and the effective fiber sizes and mechanical properties. The thickness of the interphase for each nano filler type is determined from the radial distribution function (RDF) diagram in order to determine the effective fiber volume more realistically. Then, the general Halpin-Tsai model is modified by adding an interphase volume factor and is used to determine two-phase and hybrid nanocomposite mechanical properties using effective nano filler properties. In addition, a new numerical multiscale modeling technique was developed which uses the MD-determined effective filler properties along with finite element method (FEM) to determine nanocomposite mechanical properties. Nanocomposites reinforced with aligned and randomly oriented reinforcements are modeled. Good agreement is observed between the two multiscale modeling techniques for the two-phase nanocomposite mechanical properties. Finally, the effect of filler agglomeration on nanocomposite properties is investigated. The results indicate that agglomeration decreases elastic modulus of CNT/epoxy nanocomposite. However, agglomeration does not have a significant effect on elastic modulus of CNP/epoxy nanocomposite.

Strong Interfacial Coupling of Tunable Ni-NiO Nanocomposite Thin Films Formed by Self-Decomposition.

The next-generation spintronic devices including memristors, tunneling devices, or stochastic switching exert surging demands on magnetic nanostructures with novel coupling schemes. Taking advantage of a phase decomposition mechanism, a unique Ni-NiO nanocomposite has been demonstrated using a conventional pulsed laser deposition technique. Ni nanodomains are segregated from NiO and exhibit as faceted "emerald-cut" morphologies with tunable dimensions affected by the growth temperature. The sharp interfacial transition between ferromagnetic (002) Ni and antiferromagnetic (002) NiO, as characterized by high-resolution transmission electron microscopy, introduces a strong exchange bias effect and magneto-optical coupling at room temperature. In situ heating-cooling X-ray diffraction (XRD) study confirms an irreversible phase transformation between Ni and NiO under ambient atmosphere. Synthesizing highly functional two-phase nanocomposites with a simple bottom-up self-assembly via such a phase decomposition mechanism presents advantages in terms of epitaxial quality, surface coverage, interfacial coupling, and tunable nanomagnetism, which are valuable for new spintronic device implementation.

Determination of mechanical properties of two-phase and hybrid nanocomposites: experimental determination and multiscale modeling

Abstract In this paper, the effects of filler content and the use of hybrid nanofillers on agglomeration and nanocomposite mechanical properties such as elastic moduli, ultimate strength and elongation to failure are investigated experimentally. In addition, thermoset epoxy-based two-phase and hybrid nanocomposites are simulated using multiscale modeling techniques. First, molecular dynamics simulation is carried out at nanoscale considering the interphase. Next, finite element method and micromechanical modeling are used for micro and macro scale modeling of nanocomposites. Nanocomposite samples containing carbon nanotubes, graphene nanoplatelets, and hybrid nanofillers with different filler contents are prepared and are tested. Also, field emission scanning electron microscopy is used to take micrographs from samples’ fracture surfaces. The results indicate that in two-phase nanocomposites, elastic modulus and ultimate strength increase while nanocomposite elongation to failure decreases with reinforcement weight fraction. In addition, nanofiller agglomeration occurred at high nanofiller contents especially higher than 0.75 wt% in the two-phase nanocomposites. Nanofiller agglomeration was observed to be much lower in the hybrid nanocomposite samples. Therefore, using hybrid nanofillers delays/prevents agglomeration and improves mechanical properties of nanocomposite at the same total filler content.

Collective magnetism of a single-crystalline nanocomposite FeCoCrMnAl high-entropy alloy

We have investigated the nature of the magnetic state of a single-crystalline FeCoCrMnAl nanocomposite high-entropy alloy (HEA), composed of crystallographically oriented magnetic nanoplatelets embedded in a magnetic matrix of different magnetic order. The two-phase nanocomposite was formed by a bcc-B2 spinodal decomposition. Due to the single-crystalline nature of the material, there is no symmetry breaking of the surface atomic monolayer at the borders between the two phases and there are no interface regions between the nanoplatelets and the matrix. The material also does not exhibit grain structure, allowing for the observation of the true intrinsic magnetism of a nanocomposite HEA. Upon cooling, the predominantly Fe‒Cr‒Mn chemically disordered bcc matrix orders first at TC1≈ 425 K in an asperomagnetic-type magnetic state. Below TC2≈ 370 K, the B2 nanoplatelets that are predominantly an Al30(Co,Mn)70 pseudo-binary intermetallic compound, start to order in a ferromagnetic (FM)-type manner. We have focused to the question whether the magnetic state of the nanocomposite below TC2 is a collective state of the interacting nanoplatelets and the matrix or their coupling is weak enough that the magnetic ordering of each of them can be treated independently. Experimental results support the development of a single collective, disordered FM-type magnetic state upon cooling due to the exchange coupling between the nanoplatelets and the matrix. The nanocomposite is magnetically soft and the strong variation of the magnetization with the temperature in a large interval ΔT≈ 125 K just above room temperature due to two successive magnetic phase transitions make this material promising for the application in magnetocaloric refrigeration.

Silicon nanoparticles with UV range photoluminescence synthesized through cryomilling induced phase transformation and etching

We report silicon nanoparticles with a particle size distribution of ~ 80 nm (mode) through controlled impact mode cryomilling of semiconductor grade silicon wafers at a temperature of 200 K under argon atmosphere. The transmission microscopic characterization of these particles establishes a partial transformation of the crystalline silicon into an amorphous phase yielding a two-phase microstructure for each of the particles. A high-speed imaging technique is utilized to understand the effect of impact energy (and milling intensity) on the phase transformation during milling. In a further development, etching of the two-phase nanocomposites leads to the dissolution of the amorphous phase yielding free nanoparticle of ~ 2 nm size that exhibit UV range photoluminescence with potential for sensors and other optical applications.

Evidence of room-temperature shear-deformation in a Cu-Al intermetallic

Lamellar eutectics are known to evidence plastic shear in otherwise brittle intermetallics, if the lamella spacing is small enough. Here we pursue this idea of confined plasticity in intermetallics further and demonstrate room-temperature shear-deformation in a two-phase CuAl2-CuAl intermetallic nano-composite. The presence of a phase with a 3-fold symmetry is also revealed after deformation. Simulation of transmission electron microscopy images shows this to be monoclinic CuAl. These observations are made in the deformation zone underneath locations of nanoindents, of which the force-displacement curves exhibit an unusual response of continuously increasing pop-in sizes with load.

Thermal transport in ZnO nanocrystal networks synthesized by nonthermal plasma

Semiconductor materials with independently controlled electrical and thermal properties have a unique promise for energy-related applications from thermoelectrics and thermophotovoltaics. Here, using nonthermal plasma synthesized, direct-contact zinc oxide (ZnO) nanocrystal (NC) networks infilled with amorphous $\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$, and amorphous ZnO-$\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ mixture, it is shown that such independent control of electrical and thermal properties is achievable. In this study, in addition to our early reports on control of the electrical properties in these two-phase nanocomposites by tailoring the contact radius between NCs, we demonstrate that the infill composition has a significant impact on the overall thermal conductivity of the NC network and can be used for thermal control. It is also shown that in these heterogeneous systems, the phonons are the dominant heat carriers, and the NC-NC contact radius has a negligible effect on thermal transport. The work suggests that this paradigm of independently controlling the electrical and thermal properties of NC-based materials through tuning the NC-NC contact radius and infill composition can be exploited even further by varying NC and infill materials with potential applications ranging from solar cells and light emitting diodes to solid-state energy converters.

Experimental observation of third-order effect in magnetic small-angle neutron scattering

A recent theory [Metlov and Michels, Phys. Rev. B 91, 054404 (2015)] predicts a qualitatively new effect in the magnetic small-angle neutron scattering (SANS) cross section of statistically-isotropic disordered ferromagnetic media. The effect is due to the third-order terms in the amplitude of the inhomogeneities. Here, its existence is demonstrated both numerically via large-scale micromagnetic simulations and analyzed experimentally in a two-phase iron-based nanocomposite. The previous model is extended to an arbitrary spatial defect profile, which allows us to describe the experimental field dependence of the third-order SANS effect quantitatively.

High proportion ZnO/CuO nanocomposites: Synthesis, structural and optical properties, and their photocatalytic behavior

High proportion ZnO/CuO nanocomposites synthesize through sol-gel method acquire structure, morphology, optical, and catalytic properties of the nanocomposites were examined with several characterization techniques. X-ray diffraction and Raman spectroscopy confirmed the formation of two-phase nanocomposites (ZnO- hexagonal wurtzite /CuO-Monoclinic) and stress was detected in the crystalline lattice of ZnO. Nanocomposites with semi-spheroidal shape were observed using scanning electron microscopy and transmission electron microscopy. Optical and photoluminescence studies show the existence of defects in the nanocomposites. Photocatalytic activity of the as-synthesized ZnO, CuO nanoparticles and ZnO/CuO nanocomposites were studied by the photodegradation of methylene blue (MB) under visible radiation. Besides, it was possible observed that the surface modification and the coupling of nanomaterials influenced photocatalysis. The results indicate that an increase in the ZnO content can improve the efficiency; however a modification in the form of incorporating the zinc oxide on copper oxide generates an increase of three times on photocatalytic activity.

Effects of arrangement and shape of MWCNT and GNP reinforcements on nanocomposite mechanical properties

In this investigation, multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets were used to prepare two-phase and hybrid epoxy-based nanocomposites. Tensile and compressive mechanical pro...

Vibration analysis of graphene oxide powder-/carbon fiber-reinforced multi-scale porous nanocomposite beams: A finite-element study

Application of the Rayleigh-Ritz method for the vibration problem of a porous multi-scale hybrid nanocomposite graphene oxide powder (GOP)/carbon fiber (CF)-reinforced beam is shown here for the first time on the basis of a new refined higher-order shear deformation beam theory. The structure consists of an initial matrix which is strengthened via both macro- and nano-scale reinforcements. Herein, GOPs and CFs are selected to be dispersed inside the resin. Moreover, the influences of porosity are included, too. The governing equations of the problem are achieved in the framework of a new refined higher-order beam model. Afterward, the Rayleigh-Ritz well-known finite-element method (FEM) is implemented to solve the problem for various boundary conditions (BCs). The validity of the presented formulation is checked by comparing the results of the employed FEM with those achieved from the Navier solution. it is shown that hybrid nanocomposites are able to support higher natural frequencies in comparison with either conventional fiber-reinforced composites or common two-phase GOP-reinforced nanocomposites.

Vertically Aligned Nanocomposite BaTiO3:YMnO3 Thin Films with Room Temperature Multiferroic Properties toward Nanoscale Memory Devices

Self-assembled epitaxial BaTiO3:YMnO3 (BTO:YMO) vertically aligned nanocomposite thin films have been fabricated on SrTiO3 (001) substrates using pulsed-laser deposition. A room temperature multiferroic response has been demonstrated in the thin films. Enormous strain has been generated in both phases (e.g., 1.4% compressive strain in BTO and 6.8% tensile strain in YMO out-of-plane) because of the large lattice mismatch. By tuning the deposition frequency, the microstructure and strain of the nanocomposite films are tailored, which leads to the property tuning in the nanocomposite films. It is found that strain plays an important role on the magnetic ordering of YMO and thus results in the room temperature ferromagnetic response. Combined with the ferroelectric response in the BTO:YMO nanocomposite thin films, a new room temperature multiferroic two-phase nanocomposite has been demonstrated. The room temperature magnetoelectric coupling has been demonstrated for this new system. Overall, the BTO:YMO thin ...

Nature of magnetic ordering in nanocomposites of Zn1-pNipO and NiO

A detailed study of the nature of magnetic exchange interactions and anisotropy in Zn1−pNipO/NiO (0 ⩽ p ⩽ 1) two-phase nanocomposites is reported. The exchange constants |J1| and |J2| have been determined using the molecular field approximation for the two sublattice model which yields |J2| ∼ 11.26 meV and |J1| ∼ 7.17 meV for p = 1, consistent with type-II antiferromagnetic ordering (i.e. |J2|≫|J1|). A novel core-shell surface layer model has been employed to explain the nature of magnetic anisotropy in these nanocomposites which yields anisotropy constants Ksurface = 2.42 erg/cm2, Kbulk = 2.61 × 106 erg/cm3 and Kshell = 9.56 × 105 erg/cm3 for shell thickness dsh ∼ 1.34 nm (p = 1).