Nanofilled Composites Research Articles

Recent Progress in Graphene/Polymer Nanocomposites.

Nanocomposites, multiphase solid materials with at least one nanoscaled component, have been attracting ever-increasing attention because of their unique properties. Graphene is an ideal filler for high-performance multifunctional nanocomposites in light of its superior mechanical, electrical, thermal, and optical properties. However, the 2D nature of graphene usually gives rise to highly anisotropic features, which brings new opportunities to tailor nanocomposites by making full use of its excellent in-plane properties. Here, recent progress on graphene/polymer nanocomposites is summarized with emphasis on strengthening/toughening, electrical conduction, thermal transportation, and photothermal energy conversion. The influence of the graphene configuration, including layer number, defects, and lateral size, on its intrinsic properties and the properties of graphene/polymer nanocomposites is systematically analyzed. Meanwhile, the role of the interfacial interaction between graphene and polymer in affecting the properties of nanocomposites is also explored. The correlation between the graphene distribution in the matrix and the properties of the nanocomposite is discussed in detail. The key challenges and possible solutions are also addressed. This review may provide a constructive guidance for preparing high-performance graphene/polymer nanocomposite in the future.

Color and translucency stability of contemporary resin-based restorative materials.

To determine color and translucency stability of present-day resin-based restorative materials. Disk-shaped (1.0 × 10 mm) resin composites (Filtek Universal, 3M ESPE; Spectra ST, Dentsply Sirona; Gradia Direct X, GC America; Estilite Quick, Tokuyama; Harmonize, Kerr; ACTIVA Bioactive-Restorative, Pulpdent) were prepared and divided into four staining groups (n=5); coffee (55°C), grape juice (5°C), deionized water (25°C) and thermocycling (20 000 cycles, 5°C to 55°C with a 30-second dwell time). Spectrophotometer measurements were taken at baseline and 14 days for each group and the color stability (CIEDE2000) and changes in the translucency parameter (RTPCIEDE2000 ) and luminous transmittance of each composite were determined. A 2-way analysis of variance (ANOVA) using maximum likelihood estimations was used for analysis for these changes, with subsequent pairwise comparisons using Bonferroni-corrected Student's t tests and an experiment-wise α=0.05. A significant interaction (P < .0001) between material and treatment was found for each change in the esthetic property tested over 14 days. Multiple significant differences between materials for each treatment and between treatments for each material were identified. The severity of color change and translucency of resin-based materials are dependent on their type, mostly affected by the coffee staining medium. Nano-filled resin composite is most resistant to color change and with stable translucency after artificial aging. Nano-filled resin composite may be the most esthetically durable resin- based restorative material. Micro-hybrid resin composite and resin-modified glass ionomer restorative material are susceptible to color change and losing their translucency. Hot coffee solution may shorten the esthetic lifespan of a resin-based material.

Enhancement of energy density in novel Ba0.67Sr0.33TiO3 nanorod array nanocomposites

The majority of the previously reported nanocomposites obtainable with higher energy density (>15 J cm−3) relies strongly on much higher breakdown strength (>4000 kV cm−1). The operation of capacitors in such higher applied electric field brings challenges because of the substantially increased the failure probability. In this study we explored the dispersibility and the orientation of fillers in nanocomposites as they play vital roles in the energy density. Based on the infinite element modulation results, an original design of 1–3 type composite structure was employed in the current study. This design adopts the one-dimensional (110)-oriented monodispersed barium strontium titanate Ba0.67Sr0.33TiO3 (BST) nanorod array as fillers embedded in the three-dimensional poly (−vinylidene fluoride) (PVDF) polymer matrix. With these originally designed BST/PVDF nanocomposites, we have demonstrated a significant enhancement of energy density at a lower applied electric field. For example, an energy density of 13.10 J cm−3 at electric field of 3400 kV cm−1 can be obtained, an enhancement of 3 times larger than that of bare PVDF. Moreover, the discharge efficiency is maintained at 69% at 3400 kV cm−1. The high performance of this originally designed nanacomposite demonstrated its potential application in the next generation energy storage devices.

Electromagnetic Shielding Effectiveness of X-Type Hexaferrite-C3N4 Binary Nanofiller-Incorporated Poly(vinylidene fluoride) Multiphase Composites

The significant influence of magnetic X-type hexaferrite-C3N4 binary nanofillers on the shielding effectiveness of poly(vinylidene fluoride) heterostructure composite materials has been displayed in the present report. The overall improvement in shielding effectiveness of these multiphase composite structures is immensely important for the prevention of electromagnetic pollution in the GHz frequency range. The uniqueness of this magnetic-semiconducting binary composite system helps improve the shielding effectiveness due to absorption (SEA) and reflection (SER) as well as total shielding effectiveness (SET) of the X-type hexaferrite-C3N4-PVDF heterostructure composite materials. The high magnetic loss in terms of domain wall resonance together with the eddy current loss produced by these X-type hexaferrite-C3N4 binary composite nanofillers inside the polar structure of β-phase reaches the PVDF matrix and the dielectric loss of the composite materials helps improve SEA to a maximum value of approximately −62 dB at 13.95 GHz as well as SET to a maximum value of approximately −73 dB in the X-band and approximately −88 dB in the Ku-band of the resultant composite structures. The high attenuation (>99.999999%) of these X-type hexaferrite-C3N4-PVDF heterostructure composite materials makes them the most useful for the applications in the microwave/GHz frequency region.

Reduced graphene oxide/silica nanocomposite‐reinforced anticorrosive fluorocarbon coating

AbstractReduced graphene oxide‐silica (rGO/SiO2) nanocomposite filler was prepared with a ball milling process and then modified using a coupling agent of NH2C3H6Si(OC2H5)3(KH‐550) to improve its dispersion in the fluoroethylene vinyl ether (FEVE) coating. The surface properties and morphologies of the modified rGO/SiO2(M‐rGO/SiO2) nanocomposite filler and M‐rGO/SiO2‐reinforced FEVE coating were characterized by using Fourier transform infrared spectroscopy (FT‐IR) and scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and Tafel polarization curves were applied to illustrate the corrosion resistance of the coating. The results showed that the M‐rGO/SiO2composite can disperse well in the coating and efficiently extend the corrosion path, enhancing the anti‐corrosion property of the FEVE coating. Therefore, the |Z|0.01 Hzof M‐rGO/SiO2reinforced FEVE coating maintained at around 1010 Ω·cm2in the 30 days test cycle and a protection efficiency of up to 95.18% was achieved.

Non-silicate nanoparticles for improved nanohybrid resin composites

ObjectiveZirconia and alumina nanoparticles were coated with a silica-rich layer (ALSI and ZRSI) and used to prepare experimental nanohybrid resin composites, which were characterized and compared to a control commercial resin composite (Filtek Z350 XT). MethodsSilica nanoparticles with sizes compatible to ALSI (Aerosil 150) and ZRSI (Aerosil OX 50) were tested as references. The volume of nanoparticles was equivalent across the composites, which also had consistent content of glass microparticles. CC conversion, viscosity, depth of cure, surface topography, hardness, opacity, radio-opacity, and edge chipping resistance (ReA) were tested after 24 h. Flexural strength (σf) and fracture toughness (KIC) were also tested after 15 K thermal cycles. Data were analyzed using one-way or two-way ANOVA and Tukey’s test (α = 0.05). ResultsALSI and ZRSI yielded resin composites with lower viscosity and more irregular nanoagglomerates compared to nanosilica-based composites. CC conversion and depth of cure were lower for ZRSI composite, which had higher opacity, radio-opacity, and hardness. ReA was higher for ALSI composite. Composites with ALSI and ZRSI showed stable σf after aging, whereas the control and Aerosil 150 resin composites showed significant degradation. The commercial and nanosilica-based composites showed up to 42% reduction in KIC after aging, whereas resin composites with ZRSI and ALSI showed a more stable KIC. SignificanceALSI and ZRSI generated nanohybrid resin composites with improved and/or more stable physical properties compared with nanosilica-based and commercial composites. This study suggests that changing the composition of nanofillers is a simple method to enhance the performance of nanohybrid composites.

The WS2 dependence on the elasticity and optical band gap energies of swollen PAAm composites

New generation nano-filler polymer composites have many applications including biomedical, electronic and maritime related applications because of their mechanical, electronic and optical properties. The properties of composites were investigated as a function of nano-filler content. Among these, tungsten disulfide (WS2) has the potential to be used as a component in electronic devices owing to its high electron mobility and easily tunable optical band gap energy. Tungsten disulfide (WS2)- Polyacrylamide (PAAm) composite was prepared using free radical co-polymerization and wet laboratory methods with WS2 content. Composites were characterized for mechanical and optical properties using an Elasticity Instrument and UV-vis Spectrophotometer, respectively. Elastic modulus was modeled by a statistical thermodynamics model. Tauc’s and Urbach’s Tail model for direct transition were used to model for the optical band gap. In this study, the swelling and WS2 effect on the optical band gap and elasticity of WS2 - PAAm composites were investigated. It was observed that the elasticity presented a reversed behavior of optical band gap energies with respect to WS2 content. For the applications of nano-filler doped polymer composites in flexible electronic devices, WS2 content strongly influences the mechanical and optical properties.

Multifunctional inkjet printed sensors for MMOD impact detection

The sensitivity of the electronic properties of carbon nanotubes to gases, chemicals, temperature, and mechanical strain enables their use as fillers in nanocomposites for sensing applications. In this paper, the authors develop a low-cost and scalable process based on inkjet printing technology to fabricate printed flexible sensors used for strain and damage detection. A well-dispersed conductive water-based ink is fabricated with functionalized multiwall carbon nanotubes (MWCNT) and deposited onto paper and Kapton substrates to obtain a sheet resistance as low as 500 Ω sq−1 with about 30 printed layers. The number of printed layers, the direction of the electrical resistance measurement, and the type of substrate have clear effects on the sensor’s electrical performances related to the detection of mechanical strain and impact damage. This work demonstrates the effectiveness of the printed sensors for micrometeoroid and orbital debris (MMOD) impact damage detection through hypervelocity testing.

A sustainable dynamic redox reaction passive film for long-term anti-corrosion of carbon steel surface

CeO2 was used as the only oxidant for aniline polymerization, and polyaniline (PANI) was grown on CeO2 surface to form CeO2@PANI nanocomposites. SEM and TEM showed that the CeO2@PANI composites were nanorods in a core-shell structure. XPS indicated that CeO2-core was reduced by aniline into Ce3+, which was then captured by the PANI-shell. Then the passive ability of CeO2@PANI coating on steels was explored. EIS showed that the impedance modulus of the CeO2@PANI coating exceeded 108 Ω·cm2 after accelerated immersion. The SVET and XPS confirmed that PANI polarized the anodic reaction, Ce3+ suppressed the cathodic reaction, and PO43− formed complex precipitation. Some high-valent metal oxides can directly oxidize the aniline polymerization to form MO@PANI hybrid particles. The cations obtained by the metal oxide reduction can be captured by PANI and participate in passivation together with dopants. This study provides a new kind of nanocomposite fillers that can effectively passivate steel substrates within epoxy coatings for long-time protection.

FRACTAL ANALYSIS OF STRUCTURAL AND MECHANICAL CHARACTERISTICS OF AN INTERFACIAL REGION IN EPOXY POLYMER NANOCOMPOSITES

It is shown on the basis of the micromechanical tensile strength model of a polymer composite, that the strength of an interfacial region material in polymer–high modulus filler nanocomposites decreases as its thickness increases, which contradicts the case of adhesion between two polymers, in which the thickness of an interfacial region is linearly dependent on the degree of interfacial adhesion. A fractal model of phase interactions is used to estimate the threshold values of the nanocluster volume ratio of an epoxy polymer matrix and the metal nanoparticles of a filler, with the mechanical stress transfer from the polymer matrix to the filler being weakened upon reaching these values. It is shown that exceeding a threshold value of the filler volume ratio violates the aggregate stability of the filler and reduces the values of the dimensionless parameter of the micromechanical model, which characterizes the degree of interfacial adhesion. With a further increase in the filler volume ratio, the values of this parameter become negative, while the composite strength virtually does not increase.

Nitrene functionalization as a new approach for reducing the interfacial thermal resistance in graphene nanoplatelets/epoxy nanocomposites

Conventional functionalization methods, such as oxidation, can be very damaging for the nanocarbons microstructure and therefore detrimental for their intrinsic thermal conductivity. In this study, nitrene chemistry was investigated as a non-disruptive approach for the covalent functionalization of graphene nanoplatelets (GNP). The nitrene precursor was synthesized and thermally decomposed in situ to functionalize GNP (cm-GNP). Temperature and solvents of reaction were found to have profound impact on the functionalization yield. Epoxy nanocomposites were then prepared with pristine, oxidized and cm-GNP. Influence of dispersion methodology was crucial for cm-GNP, as sonication was found to damage the functionalization. Oxidation caused a dramatic drop in thermal conductivity compared to pristine GNP. By contrast, nitrene chemistry produced the highest thermal conductivity enhancement. Finally, epoxy nanocomposites thermal conductivity results were correlated and discussed in light of SEM and micro-computed X-ray tomography (μCT) analyses. The μCT highlighted new features, such as micro-voids surrounding pristine GNP in epoxy nanocomposites, which are invisible with conventional methods. It was found that functionalization not only enhanced the dispersion but also improved GNP/polymer interactions. Moreover, μCT clearly demonstrated that nitrene functionalization eliminated the micro voids surrounding the fillers in the epoxy nanocomposites.

Surface charge density and diffuse layer properties of highly defined 2:1 layered silicate platelets

Clays are not only ubiquitous in nature, but they are also used in huge quantities in a broad range of industrial applications, such as thixotropic drilling fluids, ore pelletizers, waste disposal sealants, or fillers in polymer nanocomposites. In order to model environmental processes or to design new materials on a rational base, it is of prime importance to determine and possibly modify the interfacial properties of clay platelets at the solid/electrolyte interface. In this context, the fundamental question rises how far the stoichiometric interlayer charges as determined by the composition of the silicate layer correlates with the diffuse double-layer properties. Here, this question is addressed by means of a series of purposely synthesized sodium 2:1 layered silicates with defined composition and hence interlayer charge densities, respectively. Platelets of layered silicates of large enough diameter to perform AFM colloidal probe measurements were produced by melt synthesis. For comparison also, a natural muscovite mica has been included in this study. The diffuse layer properties in electrolyte solution have been determined by direct force measurements using the colloidal probe AFM technique and by electrokinetic measurements, respectively. We find that the diffuse layer potential decreases with increasing interlayer charge of the 2:1 layered silicates. This counterintuitive finding is attributed to ion adsorption and was further corroborated by determining the quantitative adsorption of polyelectrolytes, namely poly(amidoamine) dendrimers.Graphical abstract

Photomechanical actuation of polydimethylsiloxane/carbon black nanocomposite

Materials such as carbon black (CB), carbon nanotube, graphene, etc. have been found to deform on exposure to the light source. Introducing these materials into polymers could convert them to photo-responsive composites. This is demonstrated by the experiment in which polydimethylsiloxane (PDMS) polymer containing CB nanofiller composites is prepared, and its photomechanical actuation from exposure to IR light source is recorded using a laser displacement sensor. The particle size analysis reveals the size of the CB, which is verified by the dynamic light scattering method. The UV-vis-IR spectrophotometer study shows that an increase in the light absorbance capacity of nanocomposites compared to the plain polymer. The PDMS/CB nanocomposite beam exhibited a significant deformation compared to plain PDMS. Deformation of the order of 10-11 mm is observed for a given IR source. The deformation found to have good repeatability but with some thermal hysteresis in cyclic actuation and de-actuation.

Effect of Polymeric In Situ Stabilizers on Dispersion Homogeneity of Nanofillers and Thermal Conductivity Enhancement of Composites

Boron nitride (BN) nanofiller-based polymer composites have been considered promising candidates for efficient heat-dissipating packaging materials because of their superior thermal conductivity, mechanical strength, and chemical resistance. However, strong aggregation of the BN nanofillers in the composite matrix as well as the difficulty in the modification of the chemically inert surface prevents their effective use in polymer composites. Herein, we report an effective method by using in situ stabilizers to achieve homogeneous dispersion of boron nitride (BN) nanofillers in an epoxy-based polymeric matrix and demonstrate their use as efficient heat-dissipating materials. Poly(4-vinylpyridine) (P4VP) is designed and added into the epoxy resin to produce in situ stabilizers during preparation of hexagonal BNs (h-BNs) and BN nanotubes (BNNTs) dispersion. In-depth experimental and theoretical studies indicated that the homogeneous distribution of BN nanofillers in epoxy composites achieved by using the in situ stabilizer enhanced the thermal conductivity of the composite by ∼27% at the same concentration of the BN nanofillers. In addition, the thermal conductivity of the h-BN/epoxy composite (∼3.3 W/mK) was dramatically improved by ∼48% (4.9 W/mK) when the homogeneously dispersed BNNTs (∼1.8 vol %) were added. The concept of the proposed in situ stabilizer can be further utilized to prepare the epoxy composites with the homogeneous distribution of BN nanofillers, which is critical for reproducible and position-independent composite properties.

Influence of uniaxial orientation of fluorinated polymer/phosphonate‐modified needle‐like nanofiller composite by drawing

AbstractThe orientation effect of sepiolite natural clay, a needle‐shaped nanoparticle, in a polymer matrix was investigated. Uniaxial drawing was performed on polymer‐based nanocomposites containing organo‐modified sepiolite, achieving uniform dispersion in the crystalline polymer by modifying the surface with organic molecular chains. Fluorinated polymer was used as the matrix, and sepiolite was modified using fluorinated chains. High‐temperature drawing was conducted to increase the density of amorphous chains in the fluoropolymer. Observations confirmed the orientation of the nanofiller in the drawing direction. When the filler content was intentionally increased, it was as if it were a nanosized mille‐feuille. As a result of 5× drawing, a 20% improvement in crystallinity was calculated. Small‐angle X‐ray scattering (SAXS) analysis showed a 32 Å increase in long‐period values. When high‐drawing was conducted, some amorphous parts transformed into crystals, and the difference in electron densities between the two regions widened, increasing the long‐period value while decreasing the SAXS intensity. The crystallization temperature increased by 1.8°C, and the Young's modulus calculated from the strain‐stress curve showed a nearly 4× increase. The mechanical strength doubled when the neat fluoropolymer was drawn five times. This provides a clear understanding of the enhancement behavior of the structural and physical properties of a uniform dispersible polymer/needle nanoparticle nanocomposite using uniaxially oriented nanofillers.

Influence of Bulk-fill Restoration on Polymerization Shrinkage Stress and Marginal Gap Formation in Class V Restorations

Restoring Class V cavities with a regular bulk-fill composite presents a more favorable biomechanical behavior than restoring with a regular nano-filled composite.

A synthesis of AgNP-rGO-PANI nanocomposite and its use in fabrication of chipless RFID sensor: current research progress

Chipless RFID (Radio Frequency Identification) tag has attracted significant attention due to the low manufacturing cost. By eliminating the use of integrated circuit (IC), chipless RFID tag can offer competitive price in order to completely replace barcode systems. Besides, integration of physical parameter sensors with chipless RFID will open up a new domain for controlling and monitoring perishable items. It can also be fully printable by using inkjet-printed technology. The inkjet-printed technique is one of the most promising technological solutions for the realization of chipless RFID with low-cost advantage. Various types of conductive inks with different fillers such as metal nanoparticles, carbon nanotubes (CNT), and polymer have been developed for printed electronics. It needs deep investigation and study in designing low-cost but robust by using conductive ink on a low-cost substrate. The aim of this review is to claim research gap related to how AgNP-rGO-PANI (Silver Nanoparticle - Reduced Graphene Oxide - Polyaniline) nanocomposite has both scientific and economic advantages. The inkjet-printed method using conductive inks with nanocomposite fillers synthesized from semiconductor materials such as graphene, silver nanoparticles, and polyaniline on a thin sheet of low-cost substrate. This review provides an overview of synthesis methods of AgNP-rGO-PANI nanocomposite, structure and design of chipless RFID sensor, and chipless RFID sensor fabrication methods.

Tribological properties of compatabilizer and graphene oxide-filled polypropylene nanocomposites

Effect of maleic-anhydride-grafted-polypropylene (PP-g-MA) and graphene oxide (GO) addition on the tribological properties of polypropylene (PP) nanocomposites were investigated in this study. Graphene oxides with different levels (0.05 and 0.15 wt%) were used as reinforcing filler for PP nanocomposites. Maleic-anhydride-grafted-polypropylene (3 wt%) was added as a compatibilizer agent to increase the interaction between the GO and PP matrix. GO-filled PP nanocomposites with and without PP-g-MA were produced by a twin-screw extruder followed by injection moulding. Wear tests were carried out under dry sliding conditions against AISI 1040 steel disc using a pin-on-disc device at 0.4–1.6$$\hbox { m s}^{-1}$$ sliding speed and 10–40 N loads. The tribological test results showed that the coefficient of friction and wear rate of PP nanocomposites increased with applied loads and sliding speeds. The coefficient of friction decreased by 8.2, 14.2, 37.3 and 74.7% under $$1.2\hbox { m s}^{-1}$$ sliding speed and 40 N load with the addition of PP-g-MA and GO to the PP nanocomposites. The wear rate of PP and its nanocomposites was $$10^{-13}\hbox { m}^{2}\hbox { N}^{-1}$$. The minimum wear rate was obtained for 0.15 wt% GO and 3 wt% PP-g-MA-filled PP nanocomposites with a value of $$5.7537\hbox {E}^{-14}\hbox { m}^{2}\hbox { N}^{-1}$$ at $$0.4\hbox {m s}^{-1}$$ sliding speed and 10 N load in this study.

Applying the ultrasonic vibration during TIG welding as a promising approach for the development of nanoparticle dispersion strengthened aluminum weldments

Abstract In the present work, an innovative approach by adding the filler materials containing ZrO2/TiO2 hybrid nanoparticles to the weld pool during tungsten inert gas (TIG) welding under ultrasonic vibration (UV) was developed to fabricate nanostructured welds. Nanocomposite filler materials were manufactured from Al–Si alloy strips and ZrO2/TiO2 hybrid nanoparticles using accumulative roll bonding. After TIG welding, the influence of UV on the nanoparticle dispersion as well as the microstructure of welds was assessed using electron microscopes (SEM and TEM). When UV treatment was applied, the morphology of α-Al grains was changed from a coarse dendritic structure to a fine and globular shape and Al–Si eutectic phase was significantly refined. The results depict that the addition of nanoparticles together with application of UV can improve the grain refinement and as a result increases the mechanical properties than that of conventional TIG welding.

Two-body Wear and Hardness of New Generation Artificial Resin Teeth.

The purpose of this study was to evaluate two-body wear and hardness of new generation artificial resin teeth. Ten specimens of four different artificial resin teeth (nanofill composite, nanohybrid composite, microfiller reinforced acrylic and highly modified acrylic) were prepared. Specimens were thermodynamically loaded in a dual-axis chewing simulator (50N, 240,000 cycles, 1.6 Hz, 5/55°C thermocycle). The wear loss was analyzed by using plaster replicas and 3D laser scanner. Vickers hardness was determined before and after thermodynamic loading. Mean Vickers hardness values of highly modified acrylic resin teeth were statistically significantly lower than nanohybrid composite (p⟨0.001), nanofilled composite (p⟨0.001) and microfiller reinforced acrylic resin teeth (p⟨0.001). Mean wear loss of highly modified and microfiller reinforced acrylic resin teeth were statistically significantly lower than nanohybrid composite (p⟨0.001) and nanofilled composite (p⟨0.001) resin teeth. There was a statistically significant difference in wear among the materials. The correlation between hardness and wear was not statistically significant.