Shape Of Nanofillers Research Articles

Enhanced dielectric properties of titanium dioxide/epoxy nanocomposites with different nanofiller shape

In this study, three different shapes of titanium dioxide, namely nanoparticles, nanowires, and nanosheets, were blended into a bisphenol-A epoxy resin. The dielectric properties of the epoxy nanocomposites were measured to investigate whether the shape of the nanofiller affects the behavior of the epoxy resin. Firstly, titanium dioxide nanowires and titanium dioxide nanosheets were synthesized. Secondly, three different fillers were added to the epoxy resin to obtain three types of nanocomposites. Finally, the performance of these epoxy nanocomposites were evaluated including complex permittivity dependence on frequencies, DC volume resistivity, AC breakdown strength, and thermally stimulated discharge current. Results indicate that different shapes of titanium dioxide fillers have varying effects on the characteristics of the epoxy resin. It was observed that the shape of the nanofiller influences the amount of trapped charge in samples which subsequently impacts the overall performance of the epoxy composite.

Phase field model for electric-thermal coupled discharge breakdown of polyimide nanocomposites under high frequency electrical stress

In contrast to conventional transformers, power electronic transformers, as an integral component of new energy power system, are often subjected to high-frequency and transient electrical stresses, leading to heightened concerns regarding insulation failures. Meanwhile, the underlying mechanism behind discharge breakdown failure and nanofiller enhancement under high-frequency electrical stress remains unclear. An electric-thermal coupled discharge breakdown phase field model was constructed to study the evolution of the breakdown path in polyimide nanocomposite insulation subjected to high-frequency stress. The investigation focused on analyzing the effect of various factors, including frequency, temperature, and nanofiller shape, on the breakdown path of Polyimide (PI) composites. Additionally, it elucidated the enhancement mechanism of nano-modified composite insulation at the mesoscopic scale. The results indicated that with increasing frequency and temperature, the discharge breakdown path demonstrates accelerated development, accompanied by a gradual dominance of Joule heat energy. This enhancement is attributed to the dispersed electric field distribution and the hindering effect of the nanosheets. The research findings offer a theoretical foundation and methodological framework to inform the optimal design and performance management of new insulating materials utilized in high-frequency power equipment.

Influence of TiO2 nanofiller geometry on the rheological and optical properties of poly(acrylic acid)‐based nanocomposite hydrogels

AbstractThe properties of macroscopic polymer nanocomposites are highly dependent on the nanoparticle–polymer interfacial region, which varies with the morphology of the nanoparticles. Herein, we used TiO2 nanofillers with very low aspect ratio, the same chemical composition, and surface functions, but different geometries (nanospheres and nanoplates) dispersed in a poly(acrylic acid) matrix to analyze the influence of the nanoparticle geometry on the properties of nanocomposite hydrogels. The geometry was found to affect the swelling and rheological properties of the nanocomposite polymers. Particularly, the yield strain (from 25% to 130%), modulus (from 17,500 to 25,000 Pa), and brittleness of nanoplates based nanocomposite increased more significantly. Finite‐difference time‐domain simulations demonstrated that nanoplates increased the wavelength of the absorption maxima (224 nm for NS to 240 nm for NP) and charge distribution. The results obtained in this research indicate that the nanofiller shape markedly influences the rheological properties of the nanocomposite polymers, opening the door to further research focused on polymer–nanofiller interactions, and their effect on the macroscopic properties of the nanocomposites.

Theoretical models for gas separation prediction of mixed matrix membranes: effects of the shape factor of nanofillers and interface voids

Abstract In this work, a new model is developed by modifying the existing Maxwell–Wagner–Sillars (MWS) model to predict the gas separation properties of mixed matrix membranes (MMMs). The new modified MWS model, for the first time, provides the simultaneous exploration of the role of nanofillers/matrix interface voids and the exact geometrical shape of nanofillers in predicting the gas separation properties of MMMs. To unveil the crucial role of nanofillers/matrix interface voids, a mixed matrix membrane is considered a three-component system composed of the polymer matrix as the continuous component, nanofillers as the dispersed component and the interface voids between the two components. Moreover, the new model elucidates the role of the exact ellipsoidal shape of nanofillers within the membrane on the gas separation of MMMs by considering the shape factor of nanofillers. The newly developed modified MWS model is accurately able to predict the gas permeation of MMMs with a lower average absolute relative error (%AARE) of around 8% compared with the around 30% for conventional models such as the Maxwell model, Bruggeman model, Lewis–Nielsen model and Pal model and even compared with the modified Maxwell model (∼24%).

Effect of shape of titanium dioxide nanofillers on the properties of dental composites

The main objective of the present study was to evaluate the effect of the morphology of titanium dioxide nanofillers on the flexural strength and shear bond strength of the dental composite. Spherical and rhombic-shaped nano titanium dioxide fillers were synthesized via solvothermal method and were characterized. Subsequently, these fillers were incorporated into a flowable composite (Filtek™ Z350 XT Flowable Restorative) at 0.5 wt.% and 1.5 wt.% and the prepared specimens were stored in water for 24 h. The specimens were then evaluated for flexural strength using a universal testing machine. Similarly, the shear bond strength of modified composites to the tooth was evaluated and bond failures were analyzed using stereomicroscope magnification. Incorporation of nanofillers significantly enhanced the flexural strength of flowable composite (p = 0.009) with a significant increase at 0.5wt.% of spherical (p = 0.015) and rhomboidal-shaped fillers (p = 0.010). However, no statistically significant difference in flexural strength was observed among the different shapes of nanofillers. The results of our study did not show a significant effect on the shear bond strength of the composites. Thus the reinforcing ability of titanium dioxide nanofillers on dental composite was confirmed in this study, although the effect of using nanofillers with different morphology was not significant.Graphical abstract

Effect of size and shape of nanofillers on electrostatic and thermal behavior of epoxy-based composites

The role of nanodielectrics in the electrical power system is becoming crucial owing to its superior properties and potential applications in the field. Yet, the materials face limited breakdown strength and thermal properties. Further, the nanodielectrics have not found a comprehensive commercial platform because of the costly manufacturing process, and characterization and testing facilities. Therefore, to reduce the involved cost, in this work, an FE (finite element) based computational technique has been implemented to visualize the effect of shape, size, and filler concentration under the application of high voltage (HV). The epoxy-based nanodielectrics have been modeled incorporating a range of different shapes and size nanofillers—Al2O3, BN, BeO, SiO2, and TiO2. The paper discusses the 2D-analysis of the modeled nanodielectric in the steady-state electrostatic fields and thermal domains. It shows the insights of the nanofillers’ choice to ensure a perfect blend of electrical and thermal properties. The epoxy with square-shaped BeO fillers showed a rise in the electric field of nearly 1.5 times than unfilled neat epoxy, which indicates a significant surge in thermal conductivity at specific filler loading.

Interfacial tuning and designer morphologies of microporous membranes based on polypropylene/natural rubber nanocomposites

AbstractMicroporous polypropylene (PP) nanocomposite membranes are in great demand in various fields such as energy harvesting, water purification, and other industrial applications. Thin films of PP/natural rubber (NR) blend nanocomposite have been prepared by melt mixing and the membranes are made porous by extracting the NR phase from the blend. The present study gives a better insight into the nanoparticle shape and localization‐tailored porous morphology of PP membrane. Thermodynamic prediction of nanofiller localization and its impact on morphology were studied. 2D clay platelets in PP matrix tune the morphology of the porous membrane into lamellar, whereas spherical nanofillers give elongated spherical pores. The localization of nanoparticles was observed using transmission electron microscope, which is also confirmed from theoretical prediction of localization of nanofillers with the help of interfacial energy and surface tension. Thermal studies reveal that nanofillers enhance the thermal stability of polymers. Mechanical studies reveal that nanoparticles improve the mechanical properties of the system. 2D platelet shaped‐nanofillers enhance the mechanical strength of the polymer up to 39%, which is higher than that obtained for 3D spherical nanofillers. Nanofiller shape and localization have a great influence in deciding the properties and porosity of the membrane.

Understanding the cavitation and crazing behavior in the polymer nanocomposite by tuning shape and size of nanofiller

It is very crucial to understand the fracture mechanism of the polymer nanocomposites (PNCs) on the molecular level. In this work, the effect of the shape and size of nanofillers on it has been investigated in details by adopting a coarse-grained molecular dynamics simulation. First, the fracture energy of PNCs is found to be much higher for rod fillers than for sheet fillers and sphere fillers. Then it is reduced with increasing the nanofiller size much faster for sphere fillers than for sheet fillers and rod fillers which results from their interface and network. To better understand it, the bond orientation degree is characterized which can reflect the elongation. By calculating the stress contribution of matrix chains and nanofillers, the stress borne by matrix chains gradually decreases with the increase of nanofiller size for sphere fillers and sheet fillers while it is nearly same for rod fillers. In addition, the stress borne by sphere filler is gradually reduced with the nanofiller size while it borne by rod fillers and sheet fillers rises. The former is closely related to the number of the interfacial beads which bear the high stress while the latter is attributed to the stress contribution by the bond/angle energy. Furthermore, the number of voids is quantified which first increases and then decreases with the strain which reflects the generation and coalescence of voids. Meanwhile, the voids prefer to nucleate in the matrix which is a weak region at the strong interfacial interaction. Last, the maximum number of voids gradually increases with the nanofiller size for sphere fillers and sheet fillers while it is nearly unchanged for rod fillers which is consistent with the matrix region. In summary, this work could provide a further understanding how the nanofiller shape affects the fracture properties of PNCs.

Effect of Nanoparticle Shape on the Electrical and Thermal Properties of Solid Polymer Electrolytes

The effect of nanoparticle shape on the ionic conductivity and thermal properties of solid polymer electrolytes is reported. Poly(ethylene oxide) (PEO) and LiClO4 electrolytes with an ether oxygen to Li+ molar ratio of 10:1 are filled with TiO2 nanorods and elliptical-shaped fillers in the concentration ranges of 1–2.5 and 1–10 wt %, respectively. The filler concentration that provides the maximum improvement in the ionic conductivity scales inversely with aspect ratio (AR): 10 wt % for spherical nanoparticles (AR = 1), 5 wt % for ellipses (AR ≈ 4.4), and 1–2 wt % for nanorods (AR ≈ 6.6). The same trend is true for Fe2O3 nanofillers, suggesting that the observation is independent of the chemical identity of the metal oxide filler. While the filler concentration required to maximize the conductivity improvement is correlated to the nanofiller shape, the magnitude of the improvement is correlated to the surface-to-volume ratio of the filler. Specifically, the conductivity increases 1 order of magnitude by i...

Increasing the electrical conductivity of polymer nanocomposites under the external field by tuning nanofiller shape

It is very important to improve the electrical conductivity of polymer nanocomposites (PNCs), which can be used under the external field. In this work, by employing a coarse-grained molecular dynamics simulation, the effect of the external fields (tensile field and shear field) on the conductive probability of PNCs has been investigated in details by tuning the nanofiller shape. By carefully analyzing the conductive network, compared with the rod filler and the sphere filler, the Y filler and the X filler can protect the conducive networks well from their breakage perpendicular to the external fields, which thus can significantly enhance the conductive probability under the external fields. In other words, compared with under the quiescent state, the decrease or the increase of the conductive probability under the external fields depends on the nanofiller shape. Meanwhile, it is interesting to find that both the directional conductive probabilities parallel to the shear field and perpendicular to the shear field increase with the shear rate for the Y fillers, which further reflects their high conductive probability under the shear field. The reason can be attributed to two aspects: (1) the gradual aggregation of Y fillers under the external field; (2) the multi-arm structures of Y fillers. In summary, this work presents some further understanding how to improve the electrical conductivity of PNCs under the external fields by tuning the nanofiller shape.

EFFECT OF THE NANOFILLER SHAPE ON THE CONDUCTIVE NETWORK FORMATION OF POLYMER NANOCOMPOSITES VIA A COARSE-GRAINED SIMULATION

ABSTRACT It is very important to improve the electrical conductivity of polymer nanocomposites, which can widen their application. The effect of the nanofiller shape on the relationship between the nanofiller microstructure and the conductive probability of the nanofiller filled polymer nanocomposites (PNCs) has been investigated in detail by employing a coarse-grained molecular dynamics simulation. Four kinds of nanofiller shapes are considered: rod filler, Y filler, X filler, and sphere filler. First, the mean square radius of gyration gradually decreases from rod filler, Y filler, X filler, to sphere filler, which reflects the highest aspect ratio for rod filler. Meanwhile, the dispersion state of the nanofiller is relatively uniform in the matrix. The conductive probability (denoted by the formation probability of the conductive network) is adopted to stand for the conductive property. The results show that the conductive probability gradually decreases from rod filler, Y filler, X filler, to sphere filler, which is attributed to their gradually decreased size. In summary, the nanofiller shape affects the electric conductive property of PNCs.

Comparative tribological and corrosion resistance properties of epoxy composite coatings reinforced with functionalized fullerene C60 and graphene

Abstract This study investigated the effects of incorporation of two different shapes functionalization fullerene C60 (FC60) and functionalization graphene (FG), into the polymer matrix on the tribological and anti-corrosion performances of epoxy coating. The structural and morphological characterization was examined using Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. It was found that the functional groups had been grafted on the surface of C60 and G. The tribological and anti-corrosion results indicated that composite coatings showed a lower friction coefficient, wear traces area and higher anti-corrosion in comparison with neat epoxy, owing to the balance of reinforcement, lubrication and barrier properties of nanofillers and cracks generated by them, and optimal additive concentration of FC60 and FG both were 0.5 wt.%. Furthermore, this work opens up that FC60/EP coatings exhibited better tribological performance but worse corrosion resistance ability compared with FG/EP coatings due to the different shapes of nanofillers. Different tribological and anti-corrosion mechanisms were analyzed in details.

Effect of nanofiller shape on viscoelasticity of rubber nanocomposite investigated by FEA

Abstract Based on the micromechanical theory, the effect of the shapes of nanofillers on the viscoelasticity of rubber nanocomposites was evaluated by the finite element analysis. The shapes of nanofillers we discussed included sphere, cylinder, tube, plate, ring, and spring. Two types of interphase – “bonding interphase” and “frictional interphase” – which represented the strong interphase and the weak interphase respectively were assumed to discuss the effect of interphase on the viscoelasticity of rubber nanocomposites. The dissipation and loss factors were calculated and discussed. The predicted results show that the shapes of nanofillers have great effect on the viscoelasticity of rubber nanocomposite. Including the spring nanofillers in the rubber matrix can greatly decrease the loss factor of the nanocomposite when the interphase is a “bonding interphase,” while including the ring nanofillers in the rubber matrix can greatly increase the loss factor of the nanocomposite when the interphase is a “frictional interphase.”

Effect of nanofiller shape on effective thermal conductivity of fluoropolymer composites

Filler particle shape and size influence interconnectivity within a polymer matrix and both play a significant role in controlling the effective thermal conductivity of a composite. This study examines the effect of nanofiller particle shape in a polytetrafluoroethylene (PTFE) matrix on thermal energy transport. Experimental measurements using a laser flash analysis method are performed on PTFE with three different shaped carbon fillers: nano-diamond spheres, carbon nanotubes (CNT) and graphene flakes. Filler concentration ranged from 0 to 30%. The experimental results are coupled with a particle connectivity model to understand the relationship between energy transport and filler connectivity. Results show filler particles with more micron scale dimensions form better interconnected networks at lower volume concentrations than fillers with fewer micron scale dimensions. Filler connectivity influences effective conductivity: specifically, nano-diamond spheres showed negligible interconnectivity and result in negligible change in thermal conductivity. The CNT, with one-micron scale dimension (i.e., length) and flakes, with two-micron scale dimensions (i.e., length and height), both exhibited linear increases in interconnectivity and effective thermal conductivity. Graphene interconnectivity in PTFE is six times that of CNT and thermal conductivity is 0.5 W/mK, two times that of CNT, respectively. These results provide new insights on how to optimize nanoparticle structure to enhance thermal energy transport.

Modeling the electrical percolation behavior of hybrid nanocomposites based on carbon nanotubes and graphene nanoplatelets

An improved three-dimensional percolation model taking into account the random dispersion of nanofillers in a polymer matrix has been developed in order to study the effect of the nanofiller shape and aspect ratio (AR) on the electrical percolation behavior characteristic of nanocomposites. In this new model, two nanofillers of different shape and AR have been considered separately—carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs)—while hybrid systems with different relative ratio of the fillers and various AR have also been investigated. The numerical model is able to predict the electrical percolation threshold assuming a perfect random dispersion and orientation of the nanofillers, while tunneling effects are also accounted for, resulting in a percolation volume of 0.023 and 1.628 vol% for CNTs and GNPs nanocomposites, respectively, showing a quantitative agreement with existing experimental observations. The percolation volume was found to decrease with the AR of CNT and GNP according to different relationships. Hybrid systems incorporating CNTs and GNPs exhibited significant synergistic effects when the two fillers were properly combined. The numerical predictions confirm the applicability of the model to predict the percolation behavior and percolating network morphology by indicating the probability of contact patterns between same and different elements.

Correlation of electrical conductivity, dielectric properties, microwave absorption, and matrix properties of composites filled with graphene nanoplatelets and carbon nanotubes

The DC electrical conductivity, percolation threshold, and dielectric properties of Graphene Nanoplatelets (GNPs) filled epoxy composites are studied and correlated with microwave absorption. The properties of GNPs filled composites are also compared with multiwalled carbon nanotubes (MWCNTs) composites, and GNPs are observed to have superior conductivity than MWCNTs. In all batches, the nanofillers have 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 wt. %. All composites irrespective of the type of nanofiller and viscosity of the matrix have shown electrical percolation threshold at 3.0 wt. %. The dielectric properties, i.e., complex permittivity, tan loss, and AC conductivity, are studied in 100 Hz–5.5 MHz. The DC and AC electrical conductivities (at and below the percolation) measured in 100 Hz–5.5 MHz are correlated to the GNPs and MWCNTs epoxy composites in the microwave frequency range (11–17 GHz). The maximum return loss of −12 dB and −6 dB was determined for MWCNTs and GNPs, respectively. The effects of nanofiller shape and the viscosity of the matrix on the dispersion and interparticle spacing of the conductive fillers within the polymer matrix have been discussed based on the results of conductivity, dielectric, and absorption properties.

Nano-ZnO embedded mixed matrix polyethersulfone (PES) membrane: Influence of nanofiller shape on characterization and fouling resistance

Two different kinds of nano-ZnO (nanoparticle and nanorod) were synthesized, characterized, and embedded in a PES membrane matrix to investigate the effects of a nanofiller shape on the mixed matrix membrane characteristics and the antifouling capability. The mixed matrix membranes were fabricated by mixing different amounts of nanofillers with dope solution followed by a phase inversion precipitation technique. The effect of the shape of the embedded nanofillers on the morphology and performance of the fabricated membranes was studied in terms of pure water flux, fouling resistance, hydrophilicity, surface, and bulk morphology by means of permeation tests, milk powder solution filtration, water contact angle and porosity measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. Water flux of the mixed matrix membranes significantly improved after the addition of both types of ZnO nanofillers due to a higher hydrophilicity and porosity of the prepared membranes. The water contact angle measurements confirmed the increased hydrophilicity of the modified membranes, particularly in the ZnO nanorod mixed membranes. Fouling resistance of the membranes assessed by powder milk solution filtration revealed that 0.1wt% ZnO nanorod membrane has the best antifouling property. The prepared mixed matrix membranes embedded with 0.1wt% of both types of ZnO nanofillers showed a remarkable durability and reusability during the filtration tests; however, the best performance came from membrane prepared with ZnO nanorods.

Correlation between Thermo-mechanical Reliability and Superhydrophobic Nature of CNT Composite Coatings

One of the most important applications for superhydrophobic coatings is anti-frosting for safety and energy conservation. Safety concerns are especially critical in cold-climate regions where the daily temperature fluctuation is large. However, superhydrophobic coatings have not been studied in terms of their thermomechanical reliability. In this study, wetting characteristics and stress relaxation behavior were quantitatively investigated with multi-walled carbon nanotube (MWNT)–silicone composite films under thermal cycling condition. It is concluded that an open structure with numerous nanopores among the fillers, constituting air pockets described as the “Cassie structure,” is of great importance not only for developing a film's superhydrophobic nature but also for accommodation of thermal stress that evolved from different coefficients of thermal expansion between the coating and the substrate. The amount of stress relaxation for a 30 vol% MWNT–silicone composite film with open structure reaches ~80% of the value for its counterpart with a closed structure and no pores. A superhydrophobic MWNT–silicone composite film that can endure over 4000 thermal cycles (−30°C to room temperature) is fabricated by controlling the composition and microstructure of the composite. In addition, the importance of size and shape of nanofillers in delaying nucleation and growth of frost on superhydrophobic coatings is also discussed.

Influence of Fe2O3 Nanofiller Shape on the Conductivity and Thermal Properties of Solid Polymer Electrolytes: Nanorods versus Nanospheres

The influence of nanofiller shape on the ionic conductivity and thermal properties of solid polymer electrolytes is investigated. Electrolytes of polyethylene oxide (PEO) and LiClO4 filled with 1–20 wt % spherical Fe2O3 nanoparticles and 0.5–10 wt % Fe2O3 nanorods are measured at an ether oxygen to Li ratio of 10:1. Nanorods improve the ionic conductivity to a similar extent as spherical nanoparticles, except at concentrations 10–20 times lower. The maximum conductivity improvement occurs at a spherical metal oxide nanoparticle loading of 10 wt %; however, an equivalent nanorod loading decreases the conductivity below that of the unfilled electrolyte. This result suggests that the long-range morphology of the two nanocomposites differs widely, where high concentrations of nanorods will inhibit instead of enhance Li transport. The shape of the nanofiller also affects the crystallization rate and resulting crystal structure. Differential scanning calorimetry measurements show that samples containing nanorod...

Sepiolite needle-like clay for PA6 nanocomposites: An alternative to layered silicates?

This paper presents a study of polyamide 6/sepiolite clay nanocomposite, obtained by melt compounding in a mini twin-screw extruder, and characterised in terms of morphology (SEM and TEM analysis) and mechanical properties of the composite, along with their crystallinity and crystal structure of the semi-crystalline matrix. The tensile test results are interpreted in terms of two micromechanical models: the Halpin–Tsai model for stiffness and the Pukanszky equation for yield stress, and compared with the results on polyamide 6/smectite montmorillonite (MMT) clay nanocomposites from selected publications. This comparison between sepiolite (fibre-like shape, 1D) and smectite (platelet-like, 2D) clays offers an interesting model-study on the effect of nanofiller shape and orientation on final mechanical properties. It shows that 1D fillers are expected to provide better reinforcement in the case of oriented systems, whereas platelets should be more efficient in isotropic composites. It was demonstrated that sepiolite has a higher reinforcing efficiency (higher effective aspect ratio) than MMT in PA6 and a good filler-matrix interface, due to strong hydrogen bonds between silanol groups on the sepiolite surface and amide groups of PA6.