Influence Of Graphene Nanoplatelets Research Articles

Influence of graphene nanoplatelets on the passivation and corrosion resistance of carbon steel bars in ordinary portland cement mortar

This study investigates the influence of adding graphene nanoplatelets (GNPs) to mortar mixtures on the corrosion behavior of embedded carbon steel rebars. Mortar mixtures were prepared with a water-to-cement ratio of 0.42 and GNP replacement levels of 0, 0.05, and 1 percent by weight of cement. After 28 days of curing in an environmental chamber, the passivity and kinetics of chloride induced corrosion initiation for the rebars were studied using a suite of electrochemical tests. The results suggest that incorporating GNPs at low concentrations may enhance the passivity and resistance to chloride-induced corrosion of carbon steel rebars; however, due to the large variability in the data, the findings are inconclusive. Potentiodynamic measurements revealed that the estimated average polarization resistance of steel rebars in 0 G (no GNP), 0.05 G, and 1 G specimens in the passive state was on average −182.3, −276.5, and −304.2 kΩ, respectively. Upon exposure to chloride solution, 0 G specimens, with an average corrosion potential of −600 mV vs. SCE, exhibited the lowest resistance, whereas 0.05 G specimens, with an average of −491 mV vs. SCE, showed the highest corrosion resistance. Results from electrical impedance spectroscopy were consistent with the potentiodynamic findings. Surface characterization also revealed that the inclusion of GNPs does not alter the surface roughness of the interface between steel rebar and paste. However, the interface between rebar ribs and mortar paste had higher surface roughness and porosity in all specimens regardless of GNPs replacement level. Visual inspections confirmed that the area around the rebar ribs at the interface is more conducive to the formation of crevice and pitting corrosion.

Influence of Graphene Nanoplatelets and Post-Curing Conditions on the Mechanical and Viscoelastic Properties of Stereolithography 3D-Printed Nanocomposites.

This study presents an innovative approach to improving the mechanical and viscoelastic properties of 3D-printed stereolithography (SLA) nanocomposites by incorporating graphene nanoplatelets (xGNP) into photopolymer matrices. Utilizing an SLA 3D printer, photopolymer formulations with xGNP concentrations of up to 0.25 wt% were successfully produced. Post-print curing was carried out using two different methods: ultraviolet (UV) curing and high-temperature curing at 160 °C. Mechanical characterization using nanoindentation showed a significant increase in elastic modulus by 104% and an increase in hardness by 85% for nanocomposites containing 0.25 wt% xGNP. Furthermore, dynamic mechanical analysis (DMA) revealed a 39% improvement in storage modulus for samples without post-curing and an improvement of approximately 30% for samples subjected to high-temperature curing. These significant improvements highlight xGNP's potential to not only increase the performance of SLA 3D-printed components but also streamline the manufacturing process by reducing or eliminating energy-intensive post-curing steps. This innovative integration of graphene nanoplatelets paves the way for the production of high-performance, functional 3D-printed products and offers significant advances for various industries with a high impact. The results highlight the transformative role of nanomaterials in additive manufacturing and position this work at the forefront of materials science and 3D printing technology.

Influence of graphene nanoplatelets on the thermal conductivity of heat transfer oils based on the developed hotwire method

The thermal conductivity measurements of graphene nanoplatelets (GNP) loaded mineral oil suspensions are obtained using an unconventional custom-made Transient Hot-Wire setup using tungsten. The presence of a few layers of graphene in the prepared GNP using a single-step ultrasonication of graphite microparticles without the use of a surfactant is verified by AFM, TEM, Raman Spectroscopy, XRD, and XPS techniques. We measured the thermal conductivity and the specific heat capacity ( Cp ) of GNP-loaded mineral oil suspensions. The experimental result shows a maximum of 45.5% increment in the thermal conductivity of the mineral oil with 1 mg ml−1 (11.481 ×10−4 weight fraction) loading of GNP at 30 °C. Despite thermal conductivity enhancements, the results indicate that the Cp is not compromised, since a low concentration of nanoplatelets was used. The experimental results agree with the Maxwell-Garnett effective medium approach (MGEMA) model for the thermal conductivity of nanofluids which we found to be suitable for lower loading of nanoparticles. We propose GNP incorporated mineral oil suspensions are effective when it comes to heat transfer fluids even with the lower volume and mass fractions.

Corrigendum to “Influence of graphene nanoplatelets (GnPs) and titanium dioxide (TiO2) hybrid fillers on the mechanical, thermal, and morphological performance of polypropylene (PP) based hybrid composites”

Corrigendum to “Influence of graphene nanoplatelets (GnPs) and titanium dioxide (TiO₂) hybrid fillers on the mechanical, thermal, and morphological performance of polypropylene (PP) based hybrid composites”

Influence of graphene nanoplatelets (GNPs) and aluminum-carbon layered double hydroxides (Al-C LDH) in polypropylene matrix of hybrid composite structures on the microstructure and mechanical performances

<p>In this study, a polypropylene (PP) matrix was reinforced with ultra-fine graphene nanoplatelets (GNPs), aluminum-carbon layered double hydroxides (Al-C LDHs), and calcium carbonate (CaCO<sub>3</sub>) as hybrid reinforcements, along with polypropylene grafted maleic anhydride (PP-g-MA) compatibilizers to create a novel thermoplastic-based hybrid composite polymer. The hybrid composite consisted of varying weight percentages of GNPs (ranging from 0.5 to 2.0 wt% in increments of 0.5), 2wt% Al-C LDH, 2wt % CaCO<sub>3</sub>, and 5wt % PP-g-MA. The bulk samples were manufactured using twin-screw extrusion followed by vertical injection molding. The developed hybrid composites were characterized using high-resolution scanning electron microscopy (HRSEM) for microstructural analysis, X-ray diffraction (XRD) for phase identification, X-ray photoelectron spectroscopy (XPS) for compositional analysis, and Fourier-transform infrared spectroscopy (FTIR) for functional group identification. Thermogravimetric analysis (TGA) was performed to assess thermal stability, crystallization, and melting behavior. Mechanical tests, including tensile, compressive, and three-point bending, were conducted to evaluate mechanical properties, while a low-velocity impact test assessed impact resistance. The results showed that the hybrid composite with a PP matrix embedded with 1.5 wt% GNPs, 2 wt% Al-C LDH, and 2 wt% CaCO<sub>3</sub> exhibited improved mechanical properties, achieving an ultimate tensile strength of approximately 45 MPa. This enhancement is attributed to the effective interconnection, bonding, and cross-linking of the reinforcements with the PP matrix, facilitating efficient load transfer, which makes it suitable for structural applications.</p>

Influence of graphene nanoplatelets on the physical and mechanical properties of hybrid natural fiber reinforced epoxy composites

Influence of graphene nanoplatelets on the physical and mechanical properties of hybrid natural fiber reinforced epoxy composites

INFLUENCE OF GRAPHENE NANOPLATELETS ON MECHANICAL AND THERMO-MECHANICAL PROPRTIES OF GLASS/EPOXY COMPOSITES

The current work focuses on the influence of graphene nanoplatelets (GPs) on the mechanical and thermo-mechanical properties of unidirectional glass/epoxy (GE) composites. GE and GP-GE composites are fabricated using the hand lay-up method followed by compression molding. Different percentages of GPs used in the fabrication of GP-GE composites are (0.1, 0.3, 0.5, and 0.7) w/% by weight of the epoxy. Tests are conducted to experimentally evaluate the uniaxial compressive properties and the coefficient of linear thermal expansion (CLTE) in the direction of fibers. Tests are also conducted to study the thermo-mechanical properties such as storage modulus (E’) and loss modulus (E’’). The variation in the storage modulus and loss modulus is measured from 15 °C to 125 °C, using a dynamic mechanical analyzer (DMA) while the CLTE is measured using a dialatometer. The results indicate that the compressive as well as thermo-mechanical properties increase with the addition of GPs up to 0.5 % and then they decrease. The addition of GPs has no effect on the CLTE of the GE composites in the fiber direction.

Influence of Graphene Nanoplatelets on the Performance of Axial Suspension Plasma-Sprayed Hydroxyapatite Coatings.

Axial suspension plasma spraying (ASPS) is an alternative technique to atmospheric plasma spraying (APS), which uses a suspension of much finer powders (<5-micron particle size) as the feedstock. It can produce more refined microstructures than APS for biomedical implants. This paper highlights the influence of incorporated graphene nanoplatelets (GNPs) on the behavior of ASPS hydroxyapatite (HAp) coatings. The characterization of the ASPS coatings (HAp + varying GNP contents) was carried out using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), confocal Raman microscopy (CRM), white light interferometry (WLI), and contact angle measurements. The evaluation of the mechanical properties such as the hardness, roughness, adhesion strength, and porosity was carried out, along with a fretting wear performance. Additionally, the biocompatibility of the Hap + GNP coatings was evaluated using cytotoxicity testing which revealed a decrease in the cell viability from 92.7% to 85.4%, with an increase in the GNP wt.%. The visualization of the cell's components was carried out using SEM and Laser Scanning Microscopy. Furthermore, the changes in the genetic expression of the various cellular markers were assessed to analyze the epigenetic changes in human mesenchymal stem cells. The gene expression changes suggested that GNPs upregulated the proliferation marker and downregulated the pluripotent markers by a minimum of three folds.

The Dose- and Time-Dependent Cytotoxic Effect of Graphene Nanoplatelets: In Vitro and In Vivo Study.

Graphene-based nanomaterials received attention from scientists due to their unique properties: they are highly conductive, mechanically resistant and elastic. These materials can be used in different sectors of society from electronic energy storage in industry to biomedical applications. This study evaluates the influence of graphene nanoplatelets in vitro and in vivo. The toxicological influence of graphene nanoplatelets (GPs) was analyzed by cytotoxic methods, the change of cell proliferation was assessed in real-time, and the effect of GPs on a living organism was evaluated in an animal model using histopathological examination. We analyzed two types of GP administration: intratracheal and peroral. We found dose- and time-dependent cytotoxic effects of GPs in vitro; the concentration above 50 μg/mL increased the cytotoxicity significantly. The real-time analysis confirmed these data; the cells exposed to a high concentration of GPs for a longer time period resulted in a decrease in cell index which indicated lower cell viability. Histopathological examination revealed thickened alveolar septa and accumulation of GPs in the endocardium after intratracheal exposure. Peroral administration did not reveal any morphological changes. This study showed the dose- and time-dependent cytotoxic potential of graphene nanoplatelets in in vitro and in vivo models.

Influence of Graphene Nanoplatelets on the Compressive and Split Tensile Strengths of Geopolymer Concrete

Geopolymer is now a more advanced alternative to cement and available substitute for OPC while graphene nanoplatelets (GnP) are new nanomaterials with extraordinary properties that can enhance and improve the strength of cementitious materials. Although graphene reinforced concrete has intriguing potential, its implementation in construction requires better knowledge of the impact of GnP on the properties of concrete related to durability. Studies on the compressive and tensile strength performance of geopolymer concrete (GPC) containing GnP are needed. The present study investigated the influence of reinforcing GPC with varying percentages of GnP on the compressive and split tensile strengths of GPC. The addition of GnP ranged from 0.0%, 0.25% and 0.5% by weight of total binder. It has been observed that the addition of GnP increased the compressive strength by 30% and the tensile strength by 22% in comparison to a reference sample with a specified composition of fly ash and sodium metasilicate. In addition, the effect of GnP on enhancing the compressive strength of the geopolymer was shown to diminish as the amount of sodium metasilicate increased.

Influence of graphene nano-platelets on thermal transport performance of carbon fiber-polymer hybrid composites: Overall assessment of microstructural aspects

This study comprehensively investigates the thermal transport behavior of unidirectional hybrid composites (UHCs) by means of a micromechanical methodology. The constructional feature of the UHC is that the continuous carbon fibers are embedded in the graphene nano-platelets (GNPs)-modified epoxy resin. The influences of volume fraction, length, thickness, and alignment of GNPs, the interfacial thermal resistance (ITR) between the nano-graphene and polymer matrix, as well as the volume fraction, arrangement type, and off-axis angle of carbon fibers on the thermal conductivities of UHCs are extensively analyzed. Further, the micromechanical model is extended to account the effect of GNP agglomeration on the UHC thermal conductivities. The results show that uniformly dispersed GNPs play a dominant role in improving the UHC thermal conductivity along the transverse direction, while the axial thermal conductivity is insignificantly influenced by the nano-graphene particles. Besides, using the GNPs with a higher aspect ratio (length/thickness) is an efficient manner to obtain much better thermal transport performance for the UHCs. It is observed that the formation of GNP agglomeration within the epoxy resin severely decreases the transverse thermal conductivity. The presence of GNP/epoxy ITR is a lowering factor of the thermal conductivity. As compared to the hexagonal and random arrays, the square array of carbon fibers within the GNP-modified epoxy produces the largest transverse thermal conductivity. On the basis of comparative studies, the model predictions agree very well with the experimental data available in the literature.

Influence of GNPs and B4C reinforcements on mechanical, thermal and wear properties of magnesium matrix composite produced by powder metallurgy

In this study, graphene nanoplatelets (GNPs) and boron carbide (B4C) nano reinforcements were incorporated to the pure magnesium (Mg). Powder metallurgy route was used to fabricate composite samples. Microstructures of specimens were examined and tensile, hardness, wear tests were performed to determine the mechanical and tribological performance of produced samples. The results indicate that the hardness was increased especially with the addition of 2% B4C and 0.5% GNPs reinforcements. A general trend was observed for the enhancements of yield and tensile strengths when nano reinforcements were added to the pure magnesium. The composite samples showed better wear resistance than the unreinforced sample. However, thermal conductivity began to decrease with the addition of B4C reinforcements. It is also observed that the porosity level was also higher for the composite samples.

The Effect of Graphene Nanoplatelets on Chloride Binding and Chloride Migration in Cement Paste

Abstract This paper aims to study the influence of graphene nanoplatelets (GNPs) on chloride binding and chloride migration in cement paste. GNPs were dispersed in cement paste in the form of a GNP solution with the help of gum Arabic powder as a dispersant. The microstructure of cement-based materials was investigated via field-emission scanning electron microscopy (FE-SEM). FE-SEM analysis indicated that GNPs can improve the compactness of the cement paste through its filling effect, bridging, and network effects. Adding 0.10 % GNP content improved the chloride binding by 32 % and reduced chloride migration by 45 %. The addition of GNPs can not only improve chloride binding within cement paste, it can also impede the in-migration of chloride from the outside.

Mechanical properties of graphene nanoplatelets reinforced epikote 828 under dynamic compression

In this experimental investigation, the influence of graphene nanoplatelets (GNPs) on the dynamic behavior of polymeric material such as diglycidyl ether of bisphenol A (DGEBA) epoxy is investigated using the Split Hopkinson Pressure Bar (SHPB). Nanocomposite samples with a different weight percentage of GNPs i.e. 0, 1, 2, 5 wt% were fabricated and tested under dynamic compression to understand the influence of nanofillers on the mechanical performance of the epoxy. The results established that changing the mass fraction of GNPs greatly influences the mechanical behavior of the epoxy and confirmed that the optimal mass fraction of GNPs was 1 wt% because of the good dispersion and viscosity. While, a further increase in the percentage of GNPs resulted in degradation of the mechanical strength of the material because of the agglomeration of graphene sheets, porosity, and their poor interfacial bonding. Moreover, each mass fraction of nanocomposites was tested at three different impact pressures i.e. 1.5, 2, and 4 bar. The main objective is to quantify the effect of the strain rate on the mechanical behavior and on the resulting damage modes. This study further confirmed that the high percentage of GNPs increases the viscosity of the epoxy resulting in porosity and void in the structure which generates high-localised stresses into the matrix causing premature failure under dynamic loading.

Influence of graphene nanoplatelets on mechanical properties and adhesive wear performance of epoxy-based composites

Epoxy resin is one of the most widely used thermoset polymers in high-performance composite materials for lightweight applications. However, epoxy has a high coefficient of friction, which limits its tribological applications. In this study, the effect was investigated of different weight fractions of solid lubricant graphene nanoplatelets (GNPs), ranging from 0 to 4.5 wt%, on mechanical and adhesive wear performance of epoxy. Adhesive wear tests covered mild and severe wear regimes. The correlation of tribological and mechanical properties was studied as well. Scanning electron microscopy (SEM) was used to observe the failure mechanisms for both tribological and mechanical samples after each test. The results revealed that the addition of GNPs to the epoxy improved its stiffness and hardness but reduced its fracture strength and toughness. Adhesive wear performance exhibited high efficiency with GNP additions and showed reductions in the specific wear rate, the coefficient of friction, and the induced interface temperature by 76%, 37%, and 22%, respectively. A fatigue wear mechanism was predominant as the applied load increased. Most importantly, severe wear signs occurred when the interface temperature reached the heat distortion temperature of the epoxy. The tribological, and mechanical properties showed only a weak correlation to each other. The addition of GNPs to epoxy by less than 4.5 wt% was highly efficient to improve the wear performance while maintaining the fracture strength and toughness. Fourier transform infrared spectroscopy (FTIR) analysis shows no chemical interaction between the epoxy matrix with GNPs, which implies its physical interaction.

The Influence of Graphene Nanoplatelets on the Tensile and Impact Behavior of Glass-Fiber-Reinforced Polymer Composites

The effect of addition of graphene nanoplatelets (GnPs) on the mechanical behavior of unidirectional S-glass fiber based composites fabricated through the hand layup technique, followed by hot compression moulding were investigated. The GnPs with varying concentrations were introduced into the composites in two different ways, i.e., (1) GnPs in matrix; (2) GnPs on the fiber surface (GnPs coated fibers fabric). The influence of method of incorporation of GnPs in the composites were evaluated from the mechanical properties, i.e., tensile, fiber pull-out and drop weight impact tests. The composite containing 0.5 wt.% GnPs on fiber surface showed the highest tensile strength with an improvement of 212% and the composite containing 0.5 wt.% GnPs in matrix showed higher energy absorption with 52% over the pristine composite. The influence of 0.5 wt.% GnPs added on the fiber surface improved the interfacial shear strength by 136% over pristine due to the enhancement of adhesion at the fiber/matrix interface.

Influence of graphene nanoplatelets on tribological properties of short carbon fibre reinforced PA-66/TCE composites

Graphene nanoplatelets (GNPs) modified thermoplastic-polymer based composite structures can be used as lightweight, damping, high strength, and tribo-elements in food processing machinery where traditional single materials become unproductive. In the present research work, novel GNPs modified polyamide 66/thermoplastic copolyester elastomer (PA 66/TCE) composite reinforced with short carbon fibres were developed. The possible structural changes of the materials by Fourier transformed infrared (FTIR) technique and the wear performance of the fabricated composites were investigated in adhesive wear and abrasive wear modes. Adhesive wear test was carried out at 1000, 3000, and 5000 m sliding distances and 50 N applied load and at 2 ms −1 sliding velocity. In case of abrasive wear, tests have been conducted at 300, 450, and 600 m abrading distances and at an applied normal load of 20 N using 425 µm silica sand particles as abrasives. For the GNPs modified PA 66/TCE hybrid composites used in this investigation, the friction coefficient increases with an increase in sliding distance and the specific wear rate decreased with an increase in sliding distance. Furthermore, superior wear performance was observed in 3 wt% GNPs modified PA 66/TCE hybrid composite. However, under three-body abrasion, the specific wear rate decreases with increase in abrading distance and the superior abrasion resistance were found in 1 wt% GNPs modified PA 66/TCE hybrid composites. Finally, the microscopy indicated significant differences in the wear mechanisms in each adhesive and abrasive wear modes.

Utilizing the Characteristics of Graphene Nano-Platelets to Improve the Cross-Linking Density of a Rubber Nano-Composite

Graphene nanoplatelets (GNP) / Acrylonitrile butadiene rubber (NBR) nanocomposites were prepared by solutions mixing method and vulcanized effectively. GNP suspension dispersed homogenously in a well-suited solution of NBR up to 2.4 phr and characterized by X-ray Diffraction (XRD). The influence of GNP on the cross-linking of GNP/NBR nanocomposites structure has been characterized and studied by the cure characteristics and swelling tests. The results showed that the cross-linking density was enhanced to 42.3% compared to that of unfilled NBR by reducing the swelling ratio to 19.7% at 1.2 phr of the GNP. Thus, the mechanical properties were investigated and revealed that the modulus at 100% elongation (M100) improved to about 155% and the hardness to about 13%. Those results were verified via the morphology analyzing using Scanning Electron Microscopy (SEM) and the enhancement of the storage modulus as a function of temperature in the rubber nanocomposite to about 100% utilizing Dynamic Mechanical Analysis (DMA) at the same content 1.2 phr of GNP.

Influence of graphene nanoplatelets on curing kinetics and rheological properties of a benzoxazine resin

The effect of two types of graphene nanoplatelets on the curing kinetics, gelation and vitrification behaviour of a benzoxazine resin was investigated by means of differential scanning calorimetry and rheological experiments. The results showed that the incorporation of graphene nanoplatelets did not change the autocatalytic nature of curing reaction. However, when benzoxazine was doped with the nanofiller supplied by XG-Sciences an acceleration effect in curing reaction was observed, especially when a 2 wt.% was added. This catalytic effect was demonstrated by the reduction of peak temperature, apparent activation energy and the shorter gelation and vitrification times.Finally, the curing kinetic equation for benzoxazine and its nanocomposites was obtained by linear model-fitting of non-isothermal experiments and it matched reasonably well with the experimental results from both non-isothermal and isothermal tests.

The influence of graphene nanoplatelets (GNPs) addition on the microstructure and mechanical properties of Cu-GNPs composites fabricated by electro-co-deposition and powder metallurgy

Copper (Cu) is the most widely used as a cost-effective material in electronic industries due to its high electrical and thermal conductivity along with good ductility. However, the low mechanical strength of the pure form of Cu limits its applications. Cu-graphene nanoplatelets (Cu-GNPs) composites could be implemented as structural materials for electrical power generation, transmission, and distribution where high mechanical strength is required. In this research, GNPs reinforced Cu matrix composite was fabricated using electro-co-deposition and powder metallurgy. The Cu-GNPs composite powder was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) to study the effect of GNPs incorporation on the surface morphology and crystallite size. Sintered samples fabricated from Cu-GNPs composite powder shows improved hardness and mechanical strength as compared to pure Cu. The improved hardness and mechanical strength of Cu-GNPs composite depend on the grain size refinement and homogeneous distribution of GNPs and their strengthening effect.