Nanoplatelet Composites Research Articles

Uncovering the thermal conductivity of graphene nanoplatelet composites with interlayers using a Monte Carlo model

Abstract This paper uses Monte Carlo (MC) method to study the thermal conductivity of graphene nanoplatelet (GNP) composites. Firstly, a large number of GNPs are randomly set in a representative volume element (RVE). Then, based on the temperature field satisfying the Laplace equation in the matrix, a coated surface (CS) is set up on each GNP surface, and the temperature of CS and GNP are obtained by a Walk-on-Spheres (WoS) method. Finally, the WoS method continues to be applied to calculate the heat flux density of composite materials, further obtaining the thermal conductivity of the composite. We have incorporated the influence of interlayers in the WoS process and pointed out that walk onto the interlayer surface have a very low probability of getting to GNP due to the extremely low thermal conductivity of the interlayer. The calculated results are consistent with the experimental data. The model also studied the effects of size, orientation, and aggregation of GNP on the thermal conductivity of the composite.

Enhancing the thermal conductivity of polystyrene/polyamide 6/graphene nanoplatelets composites through elongational flow

Migration and distribution of thermal conduct fillers in polymer blend are key factors in the preparation of enhanced thermal conductivity composite. In this study, polystyrene(PS)/polyamides 6(PA6)/graphene nanoplatelets(GNPs) composites with enhanced thermal conductivity were prepared under elongational flow, and the migration and distribution of GNPs were investigated by molecular dynamics simulation and experiments. The results showed that when GNPs immigrate from PA6 phase to PS phase, the elongational flow caused the orientation of the PS phase and GNPs, reducing the migration rate of GNPs from the PA6 phase to the PS phase. At the same time, the stretching viscosity of the PS phase increases, which prevents GNPs entering the PS phase. As a result, GNPs remain within the PA6 phase near the interface of the two phases. The effective distribution density of GNPs increased, making it easier for them to interconnect and form thermal conduction paths, thereby improving the thermal conductivity of the composites. Particularly, the composite prepared under the elongational flow with the 50/50 vol ratio of PS/PA6, the in-plane thermal conductivity of PS/PA6/GNPs composites reached a maximum of 1.64 W/(m·K).

Graphene nanoplatelet reinforced Al-based composites prepared from recycled powders via mechanical alloying and pressureless sintering

This study reports on the powder metallurgy preparation and characterization of aluminum-graphene nanoplatelet (Al-GNP) composites synthesized using recycled Al powders. Recycled Al and GNP powders (0.1–1 wt%) were mechanically alloyed (MA'd) for 4 h, followed by cold pressing (at 450 MPa) and pressureless sintering at 590 °C for 2 h. Starting powders were analyzed using an optical emission spectrometer (OES) and a Raman spectrometer. Also, MA'd powders and sintered samples were characterized using an X-ray diffractometer (XRD), a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a differential scanning calorimeter (DSC). Particle size analyses, pycnometer, and Archimedes' densities, Vickers microhardness, dry-sliding wear, and compression tests were also conducted. The Al4C3 formation was observed in the XRD patterns of sintered compositions. The highest and lowest relative densities were measured for the 1 wt% and 0.1 wt% GNP reinforced samples as 97 % and 92 %, respectively. The highest hardness value was obtained as approximately 1.31 GPa for 1 wt% GNP reinforced. With the addition of reinforcement GNP, the wear rate developed to approximately 0.00225 mm3/Nm. The compressive strength increased from nearly 70 MPa to 162 MPa.

Effective Young’s modulus of highly porous 3D printed mono-material and coaxial structures

The dynamic elastic response of 3D macroporous scaffolds is crucial to determine their performance under operating conditions. In this work, the elastic behaviour of 3D printed bar-shaped scaffolds of γ-Al2O3 and γ-Al2O3/graphene nanoplatelets (GNP) composites (18 vol%), fabricated by Direct Ink Writing (DIW), is investigated. Dynamic Young’s modulus (E) is studied by the Impulse Excitation Technique (IET) and compared with theoretical results obtained by Finite Element Methods (FEM) and the multi-scale material simulator GeoDict®. In addition, Resonant Ultrasound Spectroscopy (RUS) is used to characterize E of single- and bi-material coaxial struts. While additions of GNP to γ-Al2O3 lead to an increase in E, it decreases in the coaxial struts due to the development of thermal residual stresses at the core/shell interface. The suitability of combining experimental and theoretical methods for the analysis of the elastic properties and the anisotropy associated with the lattice pattern is demonstrated.

Impact of Rheology-Based Optimum Parameters on Enhancing the Mechanical Properties and Fatigue of Additively Manufactured Acrylonitrile-Butadiene-Styrene/Graphene Nanoplatelet Composites.

This study investigates the interaction between static and fatigue strength and the rheological properties of acrylonitrile-butadiene-styrene (ABS) polymer reinforced with graphene nanoplatelets (GNPs) in both filament and 3D-printed forms. Specifically focusing on the effects of 1.0 wt.% GNPs, the study examines their influence on static/fatigue responses. The rheological behaviour of pure ABS polymer and ABS/GNPs nanocomposite samples, fabricated through material extrusion, is evaluated. The results indicated that the addition of 1.0 wt.% GNPs to the ABS matrix improved the elastic modulus of the nanocomposite filaments by up to about 34%, while reducing their ductility by approximately 60%. Observations revealed that the static and fatigue responses of the composite filament materials and 3D-printed parts were not solely attributed to differences in mechanical properties, but were also influenced by extrusion-related process parameters. The shark-skin effect, directly related to the material's rheological properties, had a major impact on static strength and fatigue life. The proposed method involved adjusting the temperature of the heating zones of the extruder during filament production to enhance the static response of the filament and using a higher nozzle temperature (270 °C) to improve the fatigue life of the 3D-printed samples. The findings reveal that the proposed parameter optimisation led to filaments with minimised shark-skin effects, resulting in an improvement in ultimate tensile strength compared to pure ABS. Moreover, the 3D-printed samples produced with a higher nozzle temperature exhibited increased fatigue lives compared to those manufactured under identical conditions as pure ABS.

In situ three-roll mill exfoliation approach for fabricating asphalt/graphite nanoplatelet composites as thermal interface materials

Thermal interface materials (TIMs) are vital to dissipate excess heat generated by electronic components with ever-growing power density to ensure their reliability and performance. However, the limited dispersibility of nano-sized thermal conductive fillers hinders further enhancement of thermal conductivity in TIMs. It remains challenging to manufacture high-performance TIMs with simultaneous high thermal conductivity, low cost, and capability of large-scale production. Herein, a solvent-free and scalable approach was adopted to fabricate asphalt/graphite nanoplatelets (GNPs) composites by in situ exfoliating graphite in asphalt melt using a three-roll mill. During exfoliation, asphalt was adsorbed onto the surface of GNPs via π-π interaction and improved their dispersibility. Hence, GNPs formed integrated thermal conductive pathways with reduced interfacial thermal resistance, which significantly improved the thermal conductivity of asphalt/GNP composites. At 25 vol% loading, the asphalt/GNP composite displayed a thermal conductivity of 1.95 W m−1 K−1, showing a 114 % increase compared to the asphalt/commercial GNP (c-GNP) composite prepared by conventional mechanical mixing. Moreover, the heat-resistant and mechanical properties of the asphalt/GNP composites were also enhanced due to the improved filler dispersion and filler-matrix interactions. Thus, the asphalt/GNP composites fabricated by in situ three-roll milling possessed remarkable advantages as TIMs compared with asphalt/c-GNP composites and commercial silicone rubber thermal pads.

Fatigue response of multiscale extrusion-based additively manufactured acrylonitrile butadiene styrene-graphene nanoplatelets composites

This study investigates the effect of varying concentrations of graphene nanoplatelets (GNPs) on the mechanical and fatigue characteristics of acrylonitrile butadiene styrene (ABS)/GNPs nanocomposites, both in filament form and as 3D-printed parts with different raster orientations. Quasi-static and cyclic loading tests were performed on specimens containing 0.1 wt%, 0.5 wt%, 1.0 wt%, and 2.0 wt% GNPs. The results indicated that the addition of 0.1 wt% GNPs to the ABS polymer matrix increased the ultimate tensile strength (UTS) of the filament by 18 %. Addition of 1.0 wt% and 2.0 wt% GNPs to the matrix improved the Young's modulus of the filament by up to about 35 % but did not enhance the UTS. The filament containing 0.5 wt% GNPs demonstrated the highest fatigue life, even higher than that of the standard samples fabricated through injection molding technique. This was due to its high static strength, Young's modulus, and ductility. However, when the ABS/GNPs nanocomposites were 3D-printed, the addition of GNPs had no major impact on their fatigue life, especially in the higher load levels. Inadequate adhesion and reduced interlayer bonding strength resulted in a detrimental impact on fatigue life of 3D-printed objects. The extrudate-swell phenomenon seems to significantly affect this reduction in fatigue life. To address this, larger nozzle diameter (0.6 mm) was used in fabricating 3D-printed samples. Results indicated that samples with less distortion and smaller extrudate-swell had higher fatigue life. It highlights the importance of considering GNP concentration and printing parameters for optimal fatigue properties in ABS/GNPs composites.

Composites with aligned and plasma-surface-modified graphene nanoplatelets and high dielectric constants

We have developed a method for designing polymer and graphene nanoplatelet (GNP) composites that show high dielectric constants over a wide range of GNP contents. GNPs are dispersed in the composites through plasma-surface modification and aligned by applying an electric field (EF). This creates a large number of microcapacitor structures of GNPs separated by the polymer. The maximum dielectric constant of the sample to which the EF is applied is approximately twice that of the sample to which the EF is not applied. Furthermore, the maximum dielectric constants of the samples with plasma-surface modified GNPs are higher than those of the samples with unmodified GNPs. The composites show high dielectric constants (∼500 at 100 Hz) over a wide range of GNP contents (6 ∼ 10 wt%) while maintaining mechanical flexibility (Young’s modulus:12 ± 4 MPa).

Utilizing Upcycled Graphene Nanoplatelet-Coated Glass Fibers as a Performance Booster and Compatibilizer for Enhanced Mechanical Performance of Polypropylene/Glass Fiber/Graphene Nanoplatelet Composites.

The high usage ratio and elevated density of glass fibers (GFs), often surpassing twice that of polymers, can contribute to undesired increases in the overall density of polymeric materials. One potential solution is the incorporation of graphene as a secondary additive, offering a lower specific gravity and exceptional mechanical properties. In light of this, waste tire-derived graphene nanoplates (GNPs) were optimized for coating onto GFs by considering factors such as surface treatment of the fiber, the dispersion quality of GNP, and the coating technique. The resulting GNP-coated GF (GNP-c-GF) was initially incorporated into pure polypropylene (PP) at low weight percentages (0.1-1 wt %), and 31% increase in the tensile modulus was achieved compared to neat PP. Subsequently, 1 wt % GNP-c-GF was utilized as a compatibilizer in PP/GF/GNP composites to enhance the compatibility between GNP and GF. By strategically incorporating GNP and GNP-c-GF at a lower GF ratio, the detrimental impact on the tensile modulus of 30% GF-filled PP was effectively mitigated, leading to a remarkable enhancement to an impressive value of 5658 MPa. The successful integration of GNP and GNP-c-GF exemplifies their promising potential as additives for achieving superior mechanical properties in composite materials, while concurrently promoting the utilization of recycled content.

Fused Deposition Modeling of Isotactic Polypropylene/Graphene Nanoplatelets Composites: Achieving Enhanced Thermal Conductivity through Filler Orientation.

High-performance thermally conductive composites are increasingly vital due to the accelerated advancements in communication and electronics, driving the demand for efficient thermal management in electronic packaging, light-emitting diodes (LEDs), and energy storage applications. Controlling the orderly arrangement of fillers within a polymer matrix is acknowledged as an essential strategy for developing thermal conductive composites. In this study, isotactic polypropylene/GNP (iPP/GNP) composite filament tailored for fused deposition modeling (FDM) was achieved by combining ball milling with melt extrusion processing. The rheological properties of the composites were thoroughly studied. The shear field and pressure field distributions during the FDM extrusion process were simulated and examined using Polyflow, focusing on the influence of the 3D printing processing flow field on the orientation of GNP within the iPP matrix. Exploiting the unique capabilities of FDM and through strategic printing path design, thermally conductive composites with GNPs oriented in the through-plane direction were 3D printed. At a GNP content of 5 wt%, the as-printed sample demonstrated a thermal conductivity of 0.64 W/m · K, which was 1.5 times the in-plane thermal conductivity for 0.42 W/m · K and triple pure iPP for 0.22 W/m · K. Effective medium theory (EMT) model fitting results indicated a significantly reduced interface thermal resistance in the through-plane direction compared to the in-plane direction. This work shed brilliant light on developing PP-based thermal conductive composites with arbitrarily-customized structures.

Correlation between structural and improved magneto-dielectric behaviour of Li-Mg-Dy ferrite/Graphene nanoplatelet composites and their potential applications

The tenacity of the current study was to prepare Li0.2Mg0.6Fe2.17Dy0.03O4/Graphene nanoplatelet (LMFD/GNP) composites with different Graphene nanoplatelets (GNPs) contents, including 0 wt% GNPs, 1.25 wt% GNPs, 2.5 wt% GNPs, 3.75 wt% GNPs, and 5 wt% GNPs using an economical chemical sol–gel auto combustion (SGAC) process, with a balance among the structural, and magneto-dielectric order parameters for potential applications. The structural study indicated all the LMFD/GNP composites have single-phase spinel matrix and maximum crystallite size was 53.32 nm, while Lorentz fit Raman spectra also confirmed the spinel matrix along with the existence of GNPs in the composites. The LMFD/GNP composites revealed a decrease in dielectric constants and tangent loss with increasing frequency and higher values at low frequencies, while lower values at high frequencies. The quality factor was maximum and tangent loss was the minimum for LMFD/GNP composite with GNPs doping 1.25 wt% GNPs. The LMFD/GNP composites were found to have a soft magnetic nature and the composite with GNPs concentration of 2.5 wt% GNPs has the highest saturation magnetization (104.59 emu/g) and microwave operating frequency (23.12 GHz). Moreover, the retentivity and high coercivity were 32.85 emu/g and 107.99 Oe for 1.25 wt% GNPs composite. Due to a comparatively high crystallite size, large saturation magnetization, and microwave operating frequency along with high coercivity the LMFD/GNP composites are well suited for potential applications including high-frequency devices, transformer cores, and hyperthermia.

THE EFFECT OF GRINDING ON OPTICAL BAND GAP AND URBACH ENERGY OF POLYPYRROLE/GRAPHENE COMPOSITES

The goal of this study is to better understand the effect of grinding on the Eg of polypyrrole (PPy)/commercial graphene nanoplatelets (xGnP) composites with varying amounts of xGnP. The Eg for direct transition as a function of the xGnP amount was calculated from the Tauc plot. While the average particle size of the composites decreased between 6% and 30%, there was a slight decrement in the Egs. These values changed between 4.02 to 3.87 eV with the increasing amount of xGnP before grinding, and they reached between 3.97 to 3.88 eV after grinding. Moreover, it was determined that the EU was inversely proportional to Eg. These findings suggest that the PPy/xGnP composites could be suitable for several applications, such as photocatalytic and optoelectronic.

Application of computer simulation to model transient vibration responses of GPLs reinforced doubly curved concrete panel under instantaneous heating

In this article for the first time, with the aid of computer simulation, transient vibration responses of the concrete doubly curved panel exposed to immediate heating are reported owing to the significance of concrete panels used in civil applications. The substrate includes spring element, shear, torsion, and substrate-structure friction factor. A novel model of a two-parameter substrate is introduced in this research with enough flexibility to involve three forms of polynomial, sinusoidal, and cosinusoidal expansion with various terms in its stiffness. With the aid of Halpin-Tsai micromechanics and the well-known rule of mixtures, the material properties of the graphene nanoplatelet (GPLs) composites reinforced doubly curved concrete panels are modeled. As well as this, for accurate modeling of the current work, the thermal conductivity of each continuous GPLs layer along with thickness direction using mathematical simulation is presented. Finally, entropy, the constitutive heat conduction equation, the Heaviside unit step function, and thermal shock loading are used in the final governing equations. The Laplace transform is employed to solve the temporal variation of the system’s response, while its spatial response is determined with the aid of the harmonic differential quadrature approach (HDQA). For more verification of the current work results and due to the lack of research in the field of the transient response of thermally induced vibrations of the panel, the results of the current work are verified with a Machine learning algorithm. Then, in the results section, some recommendations for enhancing the transient vibrations of the present concrete structure will be thoroughly examined.

A theoretical approach for thermomechanical shock analysis of doubly curved panel with respect to geometrical and physical parameters using machine-leaning-based algorithm

In this work, for the first time, bending information of the doubly curved panel under thermo-mechanical shock loading (MSL) with respect to geometrical and physical parameters via both numerically, and machine-leaning-based algorithms is presented. The graphene nanoplatelets composites are used to reinforce the current composite curved panel along with latitudinal direction. It should be note that the current curved panel is reinforced in latitudinal direction with GPLs due to thermo-MSL in the latitudinal direction. The material properties of the current doubly curved structure are obtained with the aid of role of mixture and Halpin–Tsai micromechanics model. As well as this, GPL distribution’s thermal conductivity for each pattern of GPL is considered for high accuracy of the current work’s model. Three-dimension (3D) elasticity theory, linear thermo-elasticity principle, constitutive heat conduction equation, and relaxation time equation are used to present the mathematical modeling of the current work. After obtaining the governing equations, the equations are solved via numerical solution using Chebyshev–Gauss–Lobatto function, and spatial and Laplace latitudinal methods. Deep neural networks (DNNs) as a machine learning method are used to train and test the obtained results from mathematical modeling. After predicting the results, the results are compared with the outcomes of mathematical modeling and show that with the low computational cost of DNNs algorithm, the results can be predicted instead of other high computational cost methods. Finally, some suggestions for improving the thermo-mechanical behavior of the current doubly curved panel under external shock loading.

Preparation of antistatic and biodegradable packaging of PLA/PHBV blend‐based glassy carbon and graphene nanoplatelets composites

AbstractGlassy carbon (GC) and graphene nanoplatelets (GNP) were used as fillers for the preparation of antistatic and biodegradable composites based on poly (lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PLA/PHBV) blend. In this work, PLA/PHBV (80/20) blends with the addition of different GC contents (0.1, 0.3, and 0.5 wt%) were prepared by melt mixing using a twin‐screw extruder, and specimens were injection molded. Furthermore, hybrid composites were prepared with the addition of 5 wt% of GNP and different GC contents (0.1, 0.3, and 0.5 wt%) using the same processing. The effect of the addition of GC and GNP on the mechanical, electrical, and electromagnetic properties and its effect on the biodegradability of the PLA/PHVB blend was evaluated. The simultaneous addition of GC (0.3 and 0.5 wt%) and GNP (5 wt%) significantly increases the elastic modulus and decreases the electrical resistivity, becoming suitable for electrostatic discharge protection packaging applications. The hybrid composite GC0.5/GNP5 reached a maximum value of total attenuation (4.5 dB), which corresponds to 60% EMI shielding. The degree of crystallinity affects biodegradability more than the type or presence of carbon material. After 110 days of anaerobic biodegradation, the hybrid composite exhibited 10% biodegradability due to the high degree of crystallinity that hinders the biodegradability process. The hybrid composites with the addition of GC and GNP are very promising for use in antistatic packaging.

Microstructural Characteristics of Al4C3 Phase and the Interfaces in Al/Graphene Nanoplatelet Composites and their Effect on the Mechanical Properties

Microstructural Characteristics of Al4C3 Phase and the Interfaces in Al/Graphene Nanoplatelet Composites and their Effect on the Mechanical Properties

Study on the removal of Rhodamine B of Iron(III)-dicarboxylic framework/graphene nanoplatelets composites

In this study, Iron(III)-dicarboxylic framework/graphene nanoplatelets (Fe-BDC/GNPs) composites were synthesized by the ultrasonic method in a water/ethanol mixture solvent. As-prepared composite materials were characterized by XRD, SEM, BET, and laser light scattering techniques. The sorption behaviors of Rhodamine B by the prepared material were studied. The results showed that the material could effectively remove chromogenic organic compounds (RhB) by the adsorption process. The prepared Fe-BDC/GNPs composite revealed high adsorption toward RhB with removal percentage of higher 90% at an RhB initial concentration of 10 ppm after 2 hours. The Freundlich isotherm was more suitable than the Langmuir isotherm and Temkin isotherm for the adsorption process of Rhodamine B onto the synthesized material with R2 = 0,9955. The analytical outputs also revealed that the adsorption kinetics were more accurately represented by the second-order model as both R2 = 0,9974 and qe,cal was approximate to qe,exp.

Efficient Removal of Representative Chemical Agents by Rapid and Sufficient Adsorption via Magnetic Graphene Oxide Composites

Chemical agents pose a significant threat to social security, highlighting the crucial role of representative chemical agents adsorption in ensuring the safety our environment. This study explored the application of Magnetic Graphene Oxide Nanoplatelet Composites (MGONCs) in adsorbing the representative chemical agents such as Lewisite (L), O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX), Sarin (GB), and Soman (GD). MGONCs were synthesized through a physical blending method, with the combination of graphene oxide (GO) and Fe3O4 nanoparticles at a mass ratio of 1:1. Optimization of the adsorption process involved investigating the effects of contact time, temperature, and adsorbent dosage. Remarkably, the adsorption rate of L and VX exceeded 99% when the dosage of MGONCs was 2.5 mg, with a contact time of 30 s at room temperature. Furthermore, GB and GD achieved maximum adsorption rates after a contact time of 20 min, with the dosages of MGONCs at 10 mg and 20 mg, respectively. Characterization of the magnetic composite was accomplished through XRD, TEM, VSM, FTIR, TGA, and BET analyses. Kinetical analysis revealed that the adsorption mechanism of GB and GD on MGONCs followed pseudo-second-order (PSO) kinetics, exhibiting a high regression coefficient. The calculated qe values were 0.103125 mg/g and 0.081349 mg/g, respectively. This research demonstrated the feasibility of utilizing MGONCs as highly efficient adsorbents for representative chemical agents, particularly in on-site sampling scenarios.

Sodium alginate/hydroxyapatite/graphene nanoplatelets composites for bone tissue engineering

Sodium alginate/hydroxyapatite/graphene nanoplatelets composites for bone tissue engineering

Biocompatible 3D-Printed Tendon/Ligament Scaffolds Based on Polylactic Acid/Graphite Nanoplatelet Composites.

Three-dimensional (3D) printing technology has become a popular tool to produce complex structures. It has great potential in the regenerative medicine field to produce customizable and reproducible scaffolds with high control of dimensions and porosity. This study was focused on the investigation of new biocompatible and biodegradable 3D-printed scaffolds with suitable mechanical properties to assist tendon and ligament regeneration. Polylactic acid (PLA) scaffolds were reinforced with 0.5 wt.% of functionalized graphite nanoplatelets decorated with silver nanoparticles ((f-EG)+Ag). The functionalization of graphene was carried out to strengthen the interface with the polymer. (f-EG)+Ag exhibited antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), an important feature for the healing process and prevention of bacterial infections. The scaffolds' structure, biodegradation, and mechanical properties were assessed to confirm their suitability for tendon and ligamentregeneration. All scaffolds exhibited surface nanoroughness created during printing, which was increased by the filler presence. The wet state dynamic mechanical analysis proved that the incorporation of reinforcement led to an increase in the storage modulus, compared with neat PLA. The cytotoxicity assays using L929 fibroblasts showed that the scaffolds were biocompatible. The PLA+[(f-EG)+Ag] scaffolds were also loaded with human tendon-derived cells and showed their capability to maintain the tenogenic commitment with an increase in the gene expression of specific tendon/ligament-related markers. The results demonstrate the potential application of these new 3D-printed nanocomposite scaffolds for tendon and ligament regeneration.