Graphene Nanoplatelets Nanocomposites Research Articles

Transport and magnetic properties of [formula omitted]/Graphene nanoplatelets nanocomposites

A series of Zn0.5Co0.25Cu0.25Ho0.037Fe1.963O4 (ZCCHF)/Graphene nanoplatelets (GNPs) nanocomposites (where GNPs = 0 wt%, 1.25 wt%, 2.5 wt%, 3.75 wt%, 5 wt%) were prepared via sol-gel auto-combustion (SGAC) method followed by bath sonication and studied their structural, morphological, optical, dielectric, and magnetic properties. The structural analysis confirmed a single-phase crystal matrix of all the as-prepared nanocomposites. The optical analysis revealed that the energy bandgap (Eg) lies within the range of 1.57 eV–1.62 eV. The dielectric analysis showed that the improvement in the dielectric constant (ε′) and reduction in dielectric tangent loss (tan δd) with increasing GNPs concentration from 0 wt% to 5 wt%. The real part of permeability (μ′) was improved and magnetic tangent loss (tan δM) was reduced with the addition of GNPs. Magnetic properties were studied at different temperatures (5 K, 300 K, and 400 K), and observed high saturation magnetization (MS), and coercivity (HC) at a low temperature (at 5 K). The low MS, and HC values were observed at high temperatures (300 K and 400 K). The combination of improved dielectric and tunable magnetic properties makes ZCCHF/GNPs nanocomposites promising candidates for applications in spintronics, high-frequency magnetic devices, and advanced electronic systems.

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.

Ultrasonication Influence on the Morphological Characteristics of Graphene Nanoplatelet Nanocomposites and Their Electrical and Electromagnetic Interference Shielding Behavior.

Graphene nanoplatelets (GNPs)/epoxy composites have been fabricated via gravity molding. The electrical and thermal properties of the composites have been studied with variable GNP type (C300, C500, and C750, whose surface areas are ~300, 500, and 750 m2/g, respectively), GNP loading (5, 10, 12, and 15 wt.%), and dispersion time via ultrasonication (0, 30, 60, and 120 min). By increasing the time of sonication of the GNP into the epoxy matrix, the electrical conductivity decreases, which is an effect of GNP fragmentation. The best results were observed with 10-12% loading and a higher surface area (C750), as they provide higher electrical conductivity, thereby preserving thermal conductivity. The influence of sonication over electrical conductivity was further analyzed via the study of the composite morphology by means of Raman spectroscopy and X-ray diffraction (XRD), providing information about the aspect ratio of GNPs. Moreover, electromagnetic shielding (EMI) has been studied up to 4 GHz. Composites with C750 and 120 min ultrasonication show the best performance in EMI shielding, influenced by their higher electrical conductivity.

Poly(vinyl alcohol)/graphene nanoplatelet nanocomposites: Elucidation of the nanofiller, dispersing agent, and interphase effects on thermomechanical properties

AbstractPoly(vinyl alcohol) (PVA)/graphene nanoplatelet (GnP) nanocomposite films were fabricated by a solution casting method. High loadings (30–40 wt.%) of two GnP grades, that is, xGnP C300 (low surface area/large size) and C750 (high surface area/small size), were utilized in combination with three commercial dispersing agents, that is, DISPERBYK‐161, DISPERBYK‐162 TF, and DISPERBYK‐2014, to yield films with desirable stiffness and energy dissipation characteristics (dynamic mechanical analysis, DMA), as well as thermal properties (thermogravimetric analysis, TGA) for potential impact resistance applications. The addition of GnPs and dispersing agents to PVA leads to a maximum six‐fold increase in its Young's modulus for the PVA sample containing 40 wt.% C300 GnPs and DISPERBYK‐162 TF. However, the modulus of resilience drops dramatically for the same sample (about 18‐fold decrease), as expected. Also, C300 GnPs yield nanocomposites with higher Young's moduli that those obtained using C750 GnPs. The atomic force microscopy stiffness maps illustrate that C300 GnPs disperse better in the PVA matrix. Furthermore, the average interphase thickness in the PVA‐C300 nanocomposites (~300 nm) is almost double that of PVA‐C750 nanocomposites. Based on the TGA results, the addition of GnPs and dispersing agent to the PVA matrix leads to a moderate increase (an average of 3.5%) in the value of the neat PVA, while its char yield increases by an average 8.5‐fold. Specifically, the PVA/GnP nanocomposites containing DISPERBYK‐162 TF yield the largest and char yield values than the other systems. The insights gained in this work can guide the design of coatings for impact resistance applications.

Stiffness enhancement of polymer nanocomposites via graphene nanoplatelet orientation

AbstractIn the development of National Aeronautics and Space Administration (NASA)'s Unmanned Aerial Vehicles (UAVs), lightweight and durable materials play a crucial role for extended high‐altitude flights. Nanoparticle‐reinforced polymer composites meet these requirements, exhibiting resistance to environmental degradation. Despite their potential, the outstanding specific strength, corrosion resistance, and dimensional stability at elevated temperatures of graphene–epoxy nanocomposites have not been fully realized due to inadequate dispersion and spatial orientation within epoxy matrices. Our recent research has introduced a mathematical framework aimed at optimizing alignment parameters for graphene nanoplatelets (GNPs) and Fe3O4‐attached GNP under a weak DC magnetic field. Subsequently, nanocomposites reinforced with GNP and aligned Fe3O4–GNP nanoparticles were fabricated using optimized parameters, and their alignment was characterized using various techniques. The current study examines the influence and comparative impact of alignment and weight percentage (wt%) loading of both nanoparticles on various mechanical properties, including tensile and compressive strength, along with failure mechanisms. It was observed that both GNP and aligned Fe3O4–GNP enhance the mechanical properties of nanocomposites, particularly notable improvements from aligned Fe3O4–GNP. The Young's modulus of GNP nanocomposites increased by 17%, while aligned Fe3O4–GNP contributed significantly to a 31% enhancement in the Young modulus.Highlights Epoxy nanocomposites featuring well‐dispersed GNP and Fe3O4–GNP nanoparticles. Proper alignment of Fe3O4–GNP within the epoxy nanocomposite was achieved. Mechanical properties improved with GNP and aligned Fe3O4–GNP incorporation. The aligned Fe3O4–GNP exhibits advanced potential for engineering applications.

Investigating the nanomechanical properties of polymer-graphene-titanium nitride nanocomposites for high strength application

In this work, hybrid graphene nanoplatelets (GN) and titanium nitride (TiN) were used as reinforcements to enhance nanomechanical properties of ultra-high molecular weight polyethylene (PE). The ternary nanocomposites were prepared by solvent mixing and melt-compounding processes. The nanomechanical properties of the developed nanocomposites was determined using nanoindenter. It was observed that PE-GN binary nanocomposites enhanced the nanomechanical properties, however, this was significantly pronounced with PE-GN-TiN ternary nanocomposites. For instance, the hardness and elastic modulus increased from 171 MPa and 2.5 GPa for the pure PE to 282 MPa and 3.2 GPa for PE-2 wt%GN nanocomposite, which are about 65% and 28% increments at applied load of 100 mN respectively. While PE-2 wt%GN-20 wt%TiN ternary nanocomposite revealed hardness and elastic modulus increments of about 196% and 100% compared to the pure PE and 80% and 56% compared to PE-2 wt%GN binary nanocomposite. The enhanced nanomechanical properties is attributed to the uniform distribution and interlocking of the PE molecular chains by the presence of the hybrid GN-TiN nanoparticles in the polymer matrix. The enhanced hardness, elastic modulus and other mechanical properties in this study are essential for advanced engineering applications where high mechanical features are required.

On dynamic of imperfect GNP nanocomposite joined hemisphere-cylinder shells on Winkler foundation

This paper aims to analyze the frequencies related to the poriferous nanocomposite joined hemisphere-cylinder shells (JHCS) resting on the Winkler foundation for the first time. In detail, the Winkler foundation is used to model the soil’s behavior surrounding the JHCS. Graphene nanoplatelet (GNP) is a nano-size material that enhances a matrix to make GNP nanocomposites (GNPNs). Additionally, nine different functionally graded (FG) distribution forms along the thickness of the JHCS are used to mark the efficiency of GNP through the GNPN. In addition, two distribution models along the thickness of the JHCS, covering FG and uniform models, are implemented to address the effect of the porosity along the GNPN. Supplementarily, via joining Donnell’s shell and first shear deformation theories, the primary equations of the JHCS are determined. Addedly, Hamilton’s principle finds the fundamental motion equations (FMEs) of the JHCS. The generalized differential quadrature scheme discretizes the FMEs, boundary, and joining equations. Next, via eigenvalue determination, the frequencies of the system are discovered. Finally, the influences correlated with physical values, FG forms of the GNP, edge cases, porosity models, and Winkler foundation on the frequencies correlated with the poriferous nanocomposite JHCS are evaluated.

Antistatic and antimicrobial packaging of PLA/PHBV blend‐based graphene nanoplatelets nanocomposites

AbstractGraphene nanoplatelets (GNP) were used as a filler for the preparation of antistatic and antimicrobial packaging based on biodegradable blends of poly(acid lactic)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PLA/PHBV) for the electronic components industry. These packages must have low electrical resistivity and mechanical resistance. The use of biodegradable polymers helps to reduce waste and the addition of GNP can also contribute to antimicrobial activity. In this work, the effect of the addition of GNP on the thermal, mechanical, electrical, electromagnetic properties, and antimicrobial activity of the PLA/PHVB blend was evaluated. PLA/PHBV (80/20) blends with the addition of 1, 3, and 5 wt% of GNP were prepared by melt mixing using extrusion and injection‐mold processes. The samples were characterized by mechanical tests (tensile test, and Shore D hardness), thermal (differential scanning calorimetry and thermogravimetric analysis), impedance spectroscopy, electromagnetic interference shielding efficiency (EMI SE), antimicrobial activity, and field emission gun scanning electron microscopy. In general, the addition of GNP contributes to the increase in elastic modulus and Shore D hardness. The percolation threshold was obtained with the addition of 3 or 5 wt% of GNP in the PLA/PHBV blend with a reduction of 3 orders of magnitude in the electrical resistivity, which can be applied to antistatic packaging. All the nanocomposites exhibited antimicrobial activity, and the addition of 5 wt% GNP inhibited 86% of the growth of Escherichia coli. The PLA/PHBV blend‐based GNP nanocomposite with the addition of 5 wt% of GNP presents the best balance of mechanical properties, with low electrical resistivity, greater total shielding effectiveness of EMI SE, and antimicrobial activity.

MECHANICAL BEHAVIOR OF HIGH-DENSITY POLYETHYLENE REINFORCED WITH GRAPHENE NANOPLATELETS AND JUTE FABRIC

Owing to sustainable characteristics, natural lignocellulosic fibers (FNLs) and graphene nanoplatelets (GNP)-reinforced composites are currently seeing applications in a wide range of industrial fields. Thus, in the present work, the mechanical, and flexural properties of high-density polyethylene (HDPE) reinforced with 0, 0.10, 0.25, and 0.50 wt.% of GNP combined with 50 vol.% of Juta fabric were investigated. In particular, the Juta/HDPE/0.25%GNP composite outperformed the strength of those described in the literature, even some with higher GNP. Enhancements of 38% were observed for the composite’s flexural modulus as compared to the GNP-free Juta/HDPE composite. Regarding the tensile properties, the ductility of the Juta/HDPE/0.25%GNP was increased by 112% when compared to the Juta/HDPE. Moreover, the toughness of the Juta/HDPE/0.25%GNP was 161% superior to the Juta/HDPE composite. SEM analysis of the fracture surfaces showed that, as GNP concentration rises, the fracture mechanisms change from shear band to a complex mixture of fibrillation, tearing, and crazing. Consequently, the results reveal the novel Juta/HDPE/0.25%GNP nanocomposite as a promising material for engineering applications.

Enhanced corrosion performance of ultrasonically shot peened and graphene nanoparticles reinforced squeeze-cast AZ91 magnesium alloy

The current study examined the influence of ultrasonic shot peening (USP) for 10, 20, and 30 s on the corrosion behavior of AZ91 alloy integrated with graphene nanoplatelets (GNPs) (0.5, 1.0, 2.0 wt%) by squeeze casting. The Volta potential associated with Mg17Al12 phase in the AZ91 alloy decreased with the incorporation of GNPs. All of the nanocomposites illustrate less weight loss and hydrogen evolution, which further decreases after USP. With GNPs’ addition to the AZ91 alloy, the open circuit potential increases positively and became much nobler after USP. All the nanocomposites display lesser corrosion rates contrasting to AZ91 alloy, decreasing further after USP. The 20 s ultrasonically shot-peened (USPed) AZ91–2.0GNPs demonstrates the best corrosion resistance. Mg(OH)2, MgCO3, and Al-rich compounds were the predominant corrosion products generated on the alloys and nanocomposites, with the least in the 20 s USPed AZ91–2.0GNPs nanocomposite. The smaller grains, lower Mg17Al12 phase content, and lower Volta potential betwixt the α-Mg and Mg17Al12 phases improve the cast nanocomposites’ resistance to corrosion. On the contrary, the compressive residual stress and finer grains at the surface of the USPed alloy and nanocomposites ameliorated the corrosion resistance significantly.

Diamond-like carbon graphene nanoplatelet nanocomposites for lubricated environments

The tribological behaviour of diamond-like carbon (DLC) and graphene nanoplatelets (GNP) nanocomposite has not been previously explored in a lubricated environment, with some previous studies reporting only on graphene materials on the surface of the DLC. In this study DLC-GNP nanocomposite films with various GNP coverages were synthesised by a 3 step process: spin coating a GNP suspension, heat treatment, and DLC deposition. In this study, the effect of the GNP coverage on the mechanical properties, and tribological response of the DLC-GNP nanocomposite film were studied at elevated temperatures against a cast iron pin in a base-oil lubricated environment. The study shows decrease in friction and wear of the DLC-GNP nanocomposites as the GNP coverage increased, with the lowest friction (COF ∼0.03) and wear (∼1.6 × 10−19 m3/Nm−1) achieved with a 4.5% coverage. This study reports the addition of GNP into the DLC matrix reduced both friction and wear by creating a highly graphitic transfer film on the counter-body, but for higher GNP coverages agglomeration during the spin coating of GNP islands were recorded, leading to removal of the GNP during sliding wear negating the friction reduction effect of the GNP.

Graphene nanoplatelets (GNPs): a source to bring change in the properties of Co-Ni-Gd-ferrite/GNP nanocomposites.

The nanocomposites of Co0.5Ni0.5Gd0.03Fe1.97O4/graphene nanoplatelets (CNGF/GNPs) were synthesized by a cost-effective sol-gel auto combustion (SGAC) route. The X-ray diffraction analysis confirmed the cubic structure of the as-prepared nanocomposites, and a crystallite size of 32.28 nm was observed for the 7.5 wt% GNPs. Irregular and unique nanoparticles consisting of short stacks of graphene sheets having a platelet shape were confirmed by the morphological analysis of the as-prepared nanocomposites. Raman analysis revealed a spinel crystal structure along with a new vibrational mode due to the GNPs. The energy bandgap was 3.98 eV for the composite with 7.5 wt% GNP concentration. It was observed that the percentage temperature coefficient of resistance (TCR%) rapidly decreased with an increase in temperature both in low- and high-temperature ranges. Dielectric studies carried out in the frequency range 104-107 Hz confirmed that the graphene-added composites had high values for both the real and imaginary parts of permittivity at low frequencies. A decrease in saturation magnetization with an increase in GNP concentration was observed compared with the pure CNGF samples. Hence, the as-prepared composites are useful for application in high-frequency devices as well as spintronics.

Thermal Properties of Graphene Nanoplatelets Reinforced Crosslinked and Short Chain Branched Polyethylenes for Geothermal Pipe Applications

AbstractTwo types of polyethylenes, the crosslinked high‐density polyethylene (PEX) and the short‐chain branched medium‐density polyethylene (polyethylene of raised temperature resistance [PE‐RT]), are selected as matrices for graphene nanoplatelets (GNPs) nanocomposites preparation (PEX/GNPs, PE‐RT/GNPs). The melt‐mixing technique is used to synthesize the nanocomposites containing various loadings of GNPs. Differential scanning calorimetry (DSC) is employed to study the effect of the GNPs on the melting and crystallization behavior of the prepared materials. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis (TGA). Laser flash analysis (LFA) is used to estimate the thermal conductivity of both PEX and PE‐RT/GNPs nanocomposites. TGA measurements reveal that PEX nanocomposites present decreased thermal stability with increasing filler content. The DSC results show that the crystallinity of both matrices increases with increasing filler content. PEX/GNPs nanocomposites show more significant thermal conductivity augmentation compared to the corresponding PE‐RT nanocomposites.

ICAE 2021 - Preface

One of the applicable shell structures related to underwater systems, covering riser pipes, ice-breaking equipment, underwear noise migrations, ballast water components, and gliders, can be considered Linked Hemispherical-Conical Shell (LHCS) structures. Accordingly, the ensuing investigation is provided to compute the Natural Frequency Values (NFVs) of the LHCS, with the opening angle at starting part of the hemispherical structure (which will be studied for the first time) enhanced by graphene-based nanocomposite materials containing Graphene Nano-Platelet (GNP) and Graphene Oxide-Powder (GOP) nanocomposites. For this reason, the Halpin-Tsai approach and the rule of the mixture are engrossed in determining the productive functionally graded mechanical criteria of the graphene-based nanocomposite materials. To obtain the main formulations of the LHCS, Donnell's assumptions and First-Order Shear Deformation Theory (FOSDT) are also engaged. Additionally, Hamilton's technique is involved in finding the kinetic equations coupled with the hemispherical and the conical parts of the LHCS. Next, the distinguished approach, Generalized Differential Quadrature (GDQ) program, is applied to discrete the kinetic equations. Subsequently, the standard eigenvalue problem determines the NFVs related to the GNP and GOP nanocomposites LHCSs. At termination, the exactness of the suggested scheme is confirmed by comparing the provided outputs with the NFVs of the submitted work (which can be used as the benchmark) with responses determined by FEM commercial software and the only benchmark study that exists in the literature. Furthermore, some novel cases are solved to estimate the effects of different geometric criteria of the LHCS, such as the opening angle of the hemispherical, the Half-Apex (HA) angle of the conical segment, the thickness related to the structure, and also the effect of GNP and GOP scattering models spread in conjunction with the thickness of the LHCS on the NFVs coupled with the GNP and GNP nanocomposites LHCS.

Wave frequency responses estimate of the nanocomposite linked hemispherical-conical shell underwater-like bodies with the impacts of two types of graphene-based nanofillers

One of the applicable shell structures related to underwater systems, covering riser pipes, ice-breaking equipment, underwear noise migrations, ballast water components, and gliders, can be considered Linked Hemispherical-Conical Shell (LHCS) structures. Accordingly, the ensuing investigation is provided to compute the Natural Frequency Values (NFVs) of the LHCS, with the opening angle at starting part of the hemispherical structure (which will be studied for the first time) enhanced by graphene-based nanocomposite materials containing Graphene Nano-Platelet (GNP) and Graphene Oxide-Powder (GOP) nanocomposites. For this reason, the Halpin-Tsai approach and the rule of the mixture are engrossed in determining the productive functionally graded mechanical criteria of the graphene-based nanocomposite materials. To obtain the main formulations of the LHCS, Donnell's assumptions and First-Order Shear Deformation Theory (FOSDT) are also engaged. Additionally, Hamilton's technique is involved in finding the kinetic equations coupled with the hemispherical and the conical parts of the LHCS. Next, the distinguished approach, Generalized Differential Quadrature (GDQ) program, is applied to discrete the kinetic equations. Subsequently, the standard eigenvalue problem determines the NFVs related to the GNP and GOP nanocomposites LHCSs. At termination, the exactness of the suggested scheme is confirmed by comparing the provided outputs with the NFVs of the submitted work (which can be used as the benchmark) with responses determined by FEM commercial software and the only benchmark study that exists in the literature. Furthermore, some novel cases are solved to estimate the effects of different geometric criteria of the LHCS, such as the opening angle of the hemispherical, the Half-Apex (HA) angle of the conical segment, the thickness related to the structure, and also the effect of GNP and GOP scattering models spread in conjunction with the thickness of the LHCS on the NFVs coupled with the GNP and GNP nanocomposites LHCS.

A computational model for characterizing electrical properties of flexible polymer composite filled with CNT/GNP nanoparticles

Ultrasensitive flexible sensors with a high sensitivity in a broad pressure range are required for various applications in flexible electronics era. Hybrid nanocomposites reinforced by carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) have shown improvements in cost-effectiveness and electrical properties. Simulating the hybrid nanocomposites is of vital significance since it offers an insight into the functional and electrical performance of flexible sensors. In this paper, the structural evolution of CNT and GNP nanocomposites in response to mechanical deformation is theoretically modeled to clarify the synergy mechanism of two nanofillers. The influence of the microstructure parameters including the aspect ratio (AR) and volume ratio of CNT and GNP on the conductivity and sensitivity of the flexible composites are comprehensively analyzed and discussed. Analytical simulation and experimental results show that the conductivity of the mixed filler system fails to outperform any individual system, but shows superiority regarding to the piezoresistive sensitivity. Besides, the Poisson's ratio of the polymer is innovatively introduced to characterize the elastic deformation of the nanocomposites. It was found that the Poisson's ratio of the polymer had the negative correlation with the sensitivity of the CNT/GNP nanocomposite. This work provides considerable guidance for the design and manufacture of flexible piezoresistive sensors.

Microstructure, mechanical and thermal properties of ultrafine-grained Al2024–TiC-GNPs nanocomposite

Al matrix composites (AMCs) have gained tremendous interest in the past decades due to their lightweight, superior mechanical and other physical properties. In this study, an ultrafine-grained Al2024/1 wt% TiC/1 wt% graphene nanoplatelets (GNPs) nanocomposite was fabricated through powder metallurgy. Synergetic effects of TiC and GNPs on the microstructural characteristics, mechanical properties and thermal conductivity were investigated in comparison with those of the matrix and TiC or GNPs singly reinforced Al2024 matrix nanocomposites. The Al2024/1 wt% TiC/1 wt% GNPs nanocomposite showed significantly improved mechanical properties with the compression yield strength of 370.2 MPa, ultimate compressive strength of 615.8 MPa and fracture strain of 8.6%, indicating a superior balance in the strength and ductility over TiC or GNPs singly reinforced Al matrix composite, since the distributions of both the TiC and GNPs in Al2024/1 wt% TiC/1 wt% GNPs nanocomposite were improved significantly. The significant mechanical property improvements are attributed to the synergistic reinforcing contributions from TiC and GNPs. The thermal conductivity of Al2024/1 wt% TiC/1 wt% GNPs nanocomposite stables at 55.0 W∙m-1∙K-1 without a further decrease compared with the composite singly reinforced with GNPs.

Mechanical and corrosion properties of graphene nanoplatelet–reinforced Mg–Zr and Mg–Zr–Zn matrix nanocomposites for biomedical applications

Magnesium (Mg)-based biomaterials have gained acceptability in fracture fixation due to their ability to naturally degrade in the body after fulfilling the desired functions. However, pure Mg not only degrades rapidly in the physiological environment, but also evolves hydrogen gas during degradation. In this study, Mg0.5Zr and Mg0.5ZrxZn (x = 1–5 wt.%) matrix nanocomposites (MNCs) reinforced with different contents (0.1–0.5 wt.%) of graphene nanoplatelets (GNP) were manufactured via a powder metallurgy technique and their mechanical and corrosion properties were evaluated. The increase in GNP concentration from 0.2 wt.% to 0.5 wt.% added to Mg0.5Zr matrices resulted in decreases in the compressive yield strength and corrosion resistance in Hanks’ Balanced Salt Solution (HBSS). On the other hand, a higher concentration (4–5 wt.%) of Zn added to Mg0.5Zr0.1GNP resulted in an increase in ductility but a decrease in compressive yield strength. Overall, an addition of 0.1 wt.% GNPs to Mg0.5Zr3Zn matrices gave excellent ultimate compressive strength (387 MPa) and compressive yield strength (219 MPa). Mg0.5Zr1Zn0.1GNP and Mg0.5Zr3Zn0.1GNP nanocomposites exhibited 29% and 34% higher experimental yield strength, respectively, as compared to the theoretical yield strength of Mg0.5Zr0.1GNP calculated by synergistic strengthening mechanisms including the difference in thermal expansion, elastic modulus, and geometry of the particles, grain refinement, load transfer, and precipitation of GNPs in the Mg matrices. The corrosion rates of Mg0.5Zr1Zn0.1GNP, Mg0.5Zr3Zn0.1GNP, Mg0.5Zr4Zn0.1GNP, and Mg0.5Zr5Zn0.1GNP measured using potentiodynamic polarization were 7.5 mm/y, 4.1 mm/y, 6.1 mm/y, and 8.0 mm/y, respectively. Similarly, hydrogen gas evolution tests also demonstrated that Mg0.5Zr3Zn0.1GNP exhibited a lower corrosion rate (1.5 mm/y) than those of Mg0.5Zr1Zn0.1GNP (3.8 mm/y), Mg0.5Zr4Zn0.1GNP (1.9 mm/y), and Mg0.5Zr5Zn0.1GNP (2.2 mm/y). This study demonstrates the potential of GNPs as effective nano-reinforcement particulates for improving the mechanical and corrosion properties of Mg–Zr–Zn matrices.

Graphene Nanoplatelet Nanocomposites for Lubricated Environments

Graphene Nanoplatelet Nanocomposites for Lubricated Environments

Computational prediction of electrical and thermal properties of graphene and BaTiO3 reinforced epoxy nanocomposites

Graphene based materials e.g., graphene oxide (GO), reduced graphene oxide (RGO) and graphene nano platelets (GNP) as well as Barium titanate (BaTiO3) are emerging reinforcing agents which upon mixing with epoxy provides composite materials with superior mechanical, electrical and thermal properties as well as shielding against electromagnetic (EM) radiations. Inclusion of the aforementioned reinforcing agents has shown to improve the performance, however, the extent of improvement has remained uncertain. In this study, a computational modelling approach was adopted using COMSOL Multiphysics software in conjunction with Bayesian statistical analysis to investigate the effects of including various filler materials e.g. GO, RGO, GNP and BaTiO3 in influencing the direct current (DC) conductivity (σ), dielectric constant (ε) and thermal properties on the resulting epoxy polymer matrix composites. The simulation of epoxy composites were performed for different volume percentage of the filler materials by varying the geometry of the filler material. It was observed that the content of GO, RGO, GNPs and the thickness of graphene nanoplatelets can alter the DC conductivity, dielectric constant, and thermal properties of the epoxy matrix. The lower thickness of GNPs was found to offer the larger value of DC conductivity, thermal conductivity and thermal diffusivity than rest of the graphene nanocomposites, while, the RGO showed better dielectric constant value than neat epoxy, and GO, GNP nanocomposites. Similarly, BaTiO3 nanoparticles content and diameter were observed to alter the dielectric constant, DC conductivity and thermal properties of modified epoxy in several order magnitude than neat epoxy. In this way, the higher diameter particles of BaTiO3 showed better DC conductivity properties, dielectric constant value, thermal conductivity and thermal diffusivity. Moreover, this research provides guidance for further computational examination on the selection of GNP and BaTiO3 materials for the enhancement of the electrical and thermal properties of the epoxy matrix.