Graphene Fillers Research Articles

Effect of Graphene Fillers on the Water Absorption and Mechanical Properties of NaOH‐Treated Kenaf Fiber‐Reinforced Epoxy Composites

This paper is focused on developing composites using kenaf fibers, epoxy polymer, and incorporation of graphene fillers. The kenaf fibers are treated with 5% NaOH to remove the hydrophilic nature and reinforced it with the hydrophobic matrix. The composites are fabricated using the compression moulding technique by keeping 60 wt.% epoxy as constant, and the graphene and kenaf fiber weights are changed accordingly. The samples for tensile, flexural, impact, hardness, and water absorption tests are prepared as per the ASTM D3039, D790, D256, D2240, and D572 standards, respectively. The effect of graphene fillers in the 5% NaOH‐treated kenaf fibers reinforced with the epoxy matrix is tested. Among the various samples, sample 4 which has 6% graphene addition in the epoxy matrix reinforced with 5% treated kenaf fiber displayed the highest tensile strength of 63 MPa, flexural strength of 97 MPa, impact strength of 9.56 kJ/m2, hardness value of 97, and lower water absorption of 5.13%. This is due to the proper dispersion of graphene fillers in the matrix which caused better interfacial adhesion between the fiber and matrix. The water absorption test showed the lowest value in sample S5 as the graphene fillers obstruct water penetration in the fibers. SEM analysis is done on the prepared samples to study the surface flaws and structural changes.

Investigation of mechanical properties and free vibration behavior of graphene/basalt nano filler banana/sisal hybrid composite

This research work addresses the influence of graphene and basalt filler on mechanical properties and free vibration behavior of banana/sisal hybrid composite. Banana/sisal hybrid composites were prepared with three weight percentage (wt.%), 6 wt.% of graphene, and basalt filler by a compression molding process. The improvement in tensile strength of 24.8% and 30% was noticed for the basalt (6 wt.%) and graphene (6 wt.%) filler addition, respectively. Comparing with basalt addition, graphene addition provides an 1.5 times improvement in flexural strength. The tensile fractography was also carried out and studied the interfacial bonding of the composite. From the morphology, it was observed that there was a good interfacial adhesion between the fiber and the matrix which enhance the mechanical property of the hybrid composite. The free vibrational behavior of the hybrid composite has also been analyzed. The modal analysis shows the enhanced natural frequencies and modal damping for the addition of 6 wt.% of graphene filler in the hybrid composite.

ПОВЫШЕНИЕ ЭКСПЛУАТАЦИОННЫХ СВОЙСТВ ПЛАСТИЧНЫХ СМАЗОК ГРАФЕНОВЫМИ ДОБАВКАМИ

It is known that commercial lubricants do not always meet high performance requirements in terms of their tribological characteristics. In particular, it was found that at high loads in worn mechanisms, Litol-24 grease does not always provide high anti-wear properties that help extend the service life of plain bearings. In order to improve the performance properties, studies were carried out on the modification of the lubricant with numerous graphenes and comparative tests were carried out on the MI-1M friction machine. The structure of the carbon film was determined by Raman scattering on a DXR Raman Microscope Thermo Scientific spectrometer. As a result of the research, it was found that the modification of the lubricant with graphenes makes it possible to form a film on the friction surface. At the same time, the wear of parts is reduced from 0.0138 mg on the Litol-24 commercial lubricant to 0.0079 on the graphene-modified lubricant. As a result of spectral analysis, it was determined that the spectrum of the carbon film contains approximately the same intensity G-line - 1565 cm-1 and D-line - 1340 cm-1 and a low-intensity 2D line - 2700 cm-1. This spectrum is identical to the Raman spectrum of amorphous carbon. In the spectrum from the metal surface of the roller, the listed lines of the Raman spectrum are absent. In the process of testing on a friction machine of Litol 24 plastic lubricant with multilayer graphene filler, the destruction of the graphene structure and its transformation into amorphous carbon is observed. As a result of determining the roughness of the roller and the thickness of the carbon film with a profilometer, it was found that the surface roughness with a carbon film is less compared to the clean metal surface of the roller: (0.176 - 0.168 = 0.008 μm) and (0.566 - 0.485 = 0.071 μm), the depth of the profile depressions on the surface with carbon film decreased by 0.116 µm. The height of the protrusions of the profile on the surface with the carbon film increased by 0.161 µm. At the same time, it was determined by calculation that the approximate thickness of the carbon film is 0.138 μm. On the basis of the conducted studies, it can be argued that the modification of Litol-24 commercial lubricant with graphenes contributes to the formation of a protective anti-wear film on the friction surface, thereby reducing wear and increasing the service life of machine parts.

Investigation of Ceramic Based Composites by Using 2D Graphene Filler

The ceramic composites of sodium bismuth titanate with reduce graphene oxide NBT/rGO of different compositions were fabricated by solid state sintering method and characterized. In this work, the graphene oxide (GO) and reduce graphene oxide (rGO) was successfully synthesized by Hummer’s modified method which is confirmed by FTIR and XRD results. The reduce graphene oxide used as 2D filler in piezoelectric creamic material. The crystalline structure of NBT/rGO composite was confirmed by X-ray diffraction with rhombohedral symmetry. The dispersion of rGO in the ceramic can be detect by the optical microcopy images. The electrical conductivity of sodium bismuth titanate shows increase at higher values of frequency and conductivity nanocomposites of different wt% were start decreases up to certain value of frequency. The broadening of peaks in frequency explicit plots of electrical conductivity with the help of LCR Meter (Impedance Capacitance and Resistance). The crystalline size of reduced graphene oxide and NBT is calculated by Scherrer’s formula of XRD peaks.

Influence the Graphene Filler Addition on the Tensile Behavior of Natural Kenaf Fiber‐Based Hybrid Nanocomposites

In current centuries, emphasis has moved from previous resources and compounds to lightweight substances to generate softer, most effective components for particular needs. Using organic kenaf fibers with nanoreinforced epoxy polymers in a blended microbially nanocomposite can improve properties and be environmentally friendly. Adding graphene powder to the epoxy resin increases barrier and mechanical properties while maintaining rigidity without compromising toughness. To explore the impression of such parameters on the materials’ properties of the construction, a mechanical test on nanocomposite features, such as size, filler content, and treatment effect, may be utilized. The elastic behavior, tension characteristics, and stress at vintage for three types of nanobased materials were calculated using the test results: graphite raw kenaf, nanosheets and sun‐bleached kenaf fibers, salinized graphene oxide, and epoxy reinforced with salinized kenaf fibers. The impact of nanocomposite magnitude, filler concentration, and filler processing on mechanical properties is carefully investigated. According to the findings, the three‐weight proportion of 75 nm‐sized particles with salinized filler and kenaf fiber produces the maximum mechanical performance. Compared to other combinations, these combinations increase tensile strength by 16%. However, it appears to be beneficial when it comes to strength properties and deflection. Because of flaws and cavities at the micrometer level, the framework was less robust and distorted quickly after including a nanoparticle filler.

Optimisation of Graphene Nanofiller Addition on the Mechanical and Adsorption Properties of Woven Banana/Polyester Hybrid Nanocomposites by Grey-Taguchi Method

Throughout history, techniques have shifted from mainstream metals and minerals to nanocomposites to generate smaller, more practical elements for particular purposes. Natural fibres have greater advantages than glass fibres, such as being cheaper, recyclable, and nonflammable. The main objective of the current experiment is to determine how the accumulation of graphene to hybrid polyester composites reinforced with woven banana fibre affects their mechanical properties. Composites were constructed utilising the hand lay-up process with the following limitations: (i) graphene filler weightiness, (ii) woven banana fibre thickness in gsm, and (iii) number of woven banana layers, all at three different levels. Using the L9 (33) orthogonal design, nine composite samples are generated and tested according to the ASTM standard. According to the grey research, hybrid composites having 5% graphene powder and 350 grammes per square metre of woven banana fibre in three layers have high mechanical strength. Adding fibre content to immaculate polyester increased its mechanical properties in general. As the fibre and filler concentrations grew, more energy was required to break the fibre bundles between the matrix and its resin. The confirmation test by the optimal process value utilising the grey relation analysis is considerably better than the actual test data. Tension strength has improved by 17.14%, bending strength has improved by 96.75%, and impact energy has increased by 16.17%.

Experimental and modeling analysis of p-type Bi0.4Sb1.6Te3 and graphene nanocomposites

The state-of-the-art Bismuth-Telluride (Bi2Te3) based systems are promising thermoelectric materials for efficient thermoelectric applications. In this study, the effect of graphene nanosheets (GNS) integrity on thermoelectric properties of a p-type Bi0.4Sb1.6Te3 alloy has been studied using high-energy ball milling and SPS sintering techniques. The synthesized pristine Bi0.4Sb1.6Te3 and 0.05wt% GNS/Bi0.4Sb1.6Te3 nanocomposites at different addition times of GNS have exhibited a single-phase and artifact-free bulk nanocrystalline Bi0.4Sb1.6Te3 with nanocrystals size of 17 nm. The TEM analysis confirmed the mechanical exfoliation of graphene filler in 5m nanocomposite into a single-layered nanostructure with an interplanar spacing of 0.343 nm. The prominent Raman features of the monolayered graphene sheet have appeared in the synthesized 5m-GNS/Bi0.4Sb1.6Te3 nanocomposite. This highlighted the crucial rule of graphene addition time on its structure and morphology of the synthesized nanocomposites. The ZT profile of 5m nanocomposite reached 0.801 at 348 K till 398 K. This resulted in 65% of improvements to the pristine Bi0.4Sb1.6Te3 pellet at 323 K. The obtained results were used to simulate a thermoelectric (TE) device module using ANSYS Workbench. The GNS nanocomposites have shown an ultrahigh output power of 95.57 W compared to 89.96 W for the pristine module at ΔT of 150 °C. The GNS addition has increased the output power of pristine Bi0.4Sb1.6Te3 by 7%, leading to comparable TE performance to other simulated Bi2Te3 systems.

Electrical, Piezoresistive and Electromagnetic Properties of Graphene Reinforced Cement Composites: A Review.

Due to their excellent combination of mechanical and physical properties, graphene and its derivatives as reinforcements have been drawing tremendous attention to the development of high-performance and multifunctional cement-based composites. This paper is mainly focused on reviewing existing studies on the three material properties (electrical, piezoresistive and electromagnetic) correlated to the multifunction of graphene reinforced cement composite materials (GRCCMs). Graphene fillers have demonstrated better reinforcing effects on the three material properties involved when compared to the other fillers, such as carbon fiber (CF), carbon nanotube (CNT) and glass fiber (GF). This can be attributed to the large specific surface area of graphene fillers, leading to improved hydration process, microstructures and interactions between the fillers and the cement matrix in the composites. Therefore, studies on using some widely adopted methods/techniques to characterize and investigate the hydration and microstructures of GRCCMs are reviewed and discussed. Since the types of graphene fillers and cement matrices and the preparation methods affect the filler dispersion and material properties, studies on these aspects are also briefly summarized and discussed. Based on the review, some challenges and research gaps for future research are identified. This review is envisaged to provide a comprehensive literature review and more insightful perspectives for research on developing multifunctional GRCCMs.

Mechanical and electrical characterization of elastomer based pressure sensors containing graphene filler material under cycled load.

Grafen(GrF) katkılı elastomer esaslı basınç sensörleri (PgS) iki aşamada elde edilmiştir. Bu malzemeler SEM cihazında analiz edilerek dolgu malzemelerinin dağılımı ile direnç arasındaki etkileşimi incelenmiştir. PgS’lere, farklı deplasman değerleri için çevrimli yüklemeler uygulanarak, numunelerin iç yapısına bağlı direnç değerlerinde oluşan değişiklikler gözlemlendi. Matris içindeki iletken dolgu malzemesinin yüzey alanı, mekanik özellikleri ve dağılım şekli PgS’lerin iletkenliğini belirlemektedir. Basınç-Direnç ilişkisine bağlı olarak dirençteki azalma ve iletkenlikteki artış, 3 mm sıkıştırmada daha yüksektir. GrF katkılı PgS’lerin direnç değişimi yükün bir fonksiyonu olarak değişkenlik göstermektedir.. Uygulanan kuvvet artışı ile bir miktar direnç artsa da, yükün dolgu malzemesine aktarılması sonucu direnç düşme eğilimindedir. PgS’lere, 1mm, 2mm ve 3mm’lik deplasmanlarda çevrimli yükleme-boşaltma testleri yapılmış, sırasıyla 85 N, 273 N ve 805 N sıkıştırma kuvvetleri elde edilmiştir. En yüksek direnç değeri 3 mm sıkıştırma sonucunda 5,29Ex06 Ω olarak tespit edilmiştir. Çalışmamızda PgS’nin bu eşsiz özelliğinden yararlanarak hava süspansiyon körüklerinin ikincil süspansiyon elemanı olan sönümleme takozu üzerine uygulaması ile yaptığımız testlerde, körüğün çalışma şartları ile ilgili tahminler yapılmıştır.

High pressure homogenization of graphene and carbon nanotube for thermal conductive polyethylene composite with a low filler content

AbstractThermal conductive polymer composite pipes have been used to replace metal pipes that are easy to be corroded. However, the low thermal conductivity of the matrix is the critical factor limiting their applications. Here, large‐size exfoliation of graphene and carbon nanotube (CNT) are proposed to prepare thermal‐conductive polyethylene nanocomposites with a low filler content. Expanded graphite and CNT are co‐dispersed by high pressure homogenizer in presence of polyvinyl pyrrolidone. Such a dispersion method can maintain the high aspect ratio and reduce generation of defects of graphene and CNTs, which is vital for building a long‐range thermal conductivity pathway in the nanocomposites. In addition, the graphene and CNT fillers can be obtained with high yield and efficiency. When the fillers are dispersed into the polyethylene by optimizing the composition, thermal conductive composites can be obtained with enhanced mechanical properties. The nanocomposite with 5.22 wt.% filler can reach a thermal conductivity of 1.265 W·m−1·K−1, 3.94 times to that of the neat polyethylene, and the mechanical strength can be increased by 42%, supporting improvement of the thermal conductivity and mechanical strength at the same time.

Exploring graphene and graphene/nanoparticles as fillers to enhance atomic oxygen corrosion resistance of polyimide films

Graphene and graphene/nanoparticles were explored to enhance the atomic oxygen (AO) corrosion resistance of polyimide (PI) composites. Graphene flakes (EGs) were produced by electrochemical method using alternating current (AC). A series of EGs/PI composite films were prepared by in-situ polymerization. After exposure to AO, although all EGs/PI composite films were resistant to AO, we found a much greater enhancement, i.e. adding 1.5 wt% EGs can reduce the mass loss of the composite by 42%. On this basis, EGs/SiO 2 and EGs/Al 2 O 3 co-doping fillers were firstly used to further enhance the AO corrosion resistance of PI. The sample co-doped 1.5 wt% EGs with 3 wt% SiO 2 could achieve a 71% decrease in the composite’ mass loss. Bonding effect and barrier effect of graphene fillers are responsible for the enhanced protective performance. At the same time, the “synergistic effect” between EGs and nanoparticles also plays a role in the enhancement. These preliminary but interesting results pave a novel way for the study of AO corrosion resistance. • High-quality few-layer graphene was successfully exfoliated by electrochemical method via alternating current. • A series of EGs/PI composite films were compared. • EGs/SiO 2 and EGs/Al 2 O 3 co-doping fillers were firstly used to further enhance the AO corrosion resistance of PI. • The “synergistic effect” between EGs and nanoparticles plays a role in the enhancement.

Electrical Breakdown Voltage of Palm Oil and Nano Graphene Filler in Nanofluids Application on Transformer Insulating Oil

Generally, power transformers have been using mineral oil as a liquid insulator due to its availability and excellent dielectric property. However, petroleum sources are depleting, which implies that mineral oil is going to be limited in availability. So, this research is to investigate on vegetable oil with nanographene filler as a substitution. Vegetable insulating oil is considered as environment-friendly insulating oil due to their superiority of biodegradable, nature-friendly, high fire-point, and good level of breakdown voltage (BV). Nevertheless, vegetable insulating oil have high viscosity, leading to a slow flow rate on the cooling performance of power transformers. To solve this problem, a process of transesterification was used to produce palm oil methyl ester (POME) from a refined bleached deodorized palm olein (RBDPO) to reduce its viscosity. RBDPO and POME were used as two kinds of fluid-based to combine with graphene nanoparticles (GNPs). Electrical breakdown voltage tests were performed by the IEC60156 standard. The results shown that POME have higher BV than RBDPO but adding GNPs may lead to lower BV even with a small amount of concentration. Nevertheless, every nanofluid has a higher BV than 30 kV.

Specifics of Thermal Transport in Graphene Composites: Effect of Lateral Dimensions of Graphene Fillers.

We report on the investigation of thermal transport in noncured silicone composites with graphene fillers of different lateral dimensions. Graphene fillers are comprised of few-layer graphene flakes with lateral sizes in the range from 400 to 1200 nm and the number of atomic planes from 1 to ∼100. The distribution of the lateral dimensions and thicknesses of graphene fillers has been determined via atomic force microscopy statistics. It was found that in the examined range of the lateral dimensions, the thermal conductivity of the composites increases with increasing size of the graphene fillers. The observed difference in thermal properties can be related to the average gray phonon mean free path in graphene, which has been estimated to be around ∼800 nm at room temperature. The thermal contact resistance of composites with graphene fillers of 1200 nm lateral dimensions was also smaller than that of composites with graphene fillers of 400 nm lateral dimensions. The effects of the filler loading fraction and the filler size on the thermal conductivity of the composites were rationalized within the Kanari model. The obtained results are important for the optimization of graphene fillers for applications in thermal interface materials for heat removal from high-power-density electronics.

Influence of the Graphene Filler Nature on the Morphology and Properties of Melt Blended EVOH Based Nanocomposites.

In this study, ethylene vinyl alcohol (EVOH) nanocomposites elaborated by melt blending with four different fillers were investigated. Two graphene and two graphite fillers displaying various shapes were selected. The morphology, microstructure, thermal, mechanical, and barrier properties of the nanocomposite films prepared for 2 wt% fillers were analyzed with the aim to establish structure–function properties relationships. The nanocomposites properties significantly depended on the nature of the incorporated filler. The nanocomposite film prepared with the expanded graphite filler exhibited the highest Young modulus value (E = 1430 MPa) and the best barrier properties. Indeed, barrier properties, rarely studied at high water activities, evidenced a significant improvement with a decrease of the water vapor permeability by a factor 1.8 and of the oxygen permeabilities by a factor close to 2, for a critical water activity higher than 0.95. An increase of the thermal stability was also evidenced for this nanocomposite. It was shown that for all studied nanocomposites, the properties could be related to the dispersion state of the fillers and the simultaneous increase of the crystallinity of the matrix. A specific equation was proposed to take into account these both parameters to accurately predict the nanocomposite barrier properties.

Influence of graphene fillers on vibration characteristics of tapered hybrid GFRP composite beams under elevated temperature condition: Numerical and experimental study

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid uniform and tapered configurations with 0.25 wt.% of graphene are greater than those of the glass fiber–reinforced polymer beams without graphene reinforcement and observed lesser for 0.5 and 0.75 wt.% of graphene under fixed-fixed and fixed-free end supports, respectively, due to unavoidable agglomeration effects. Furthermore, the parametric study was performed with the influence of weight fraction of graphene and temperature on the transverse response of the tapered composite beam. Hence, it can be concluded that the use of graphene filler in the glass fiber–reinforced polymer composites in the tapered composite beams improves the bending natural frequencies significantly when the weight fraction of the graphene is used lesser as agglomeration is unavoidable in practical condition. Therefore, the comprehensive numerical and experimental work presented in this study will be useful to the designers while using graphene fillers to improve the bending characteristics of the tapered composite beams.

Композиты графен-полиэтилен высокого давления и их свойства

A method for the introduction graphene into high-pressure polyethylene (HPPE) has been developed. Samples of graphene-HPPE were obtained with the content of graphene filler: 0.25%; 0.5%; 1.0%; 1.5%; 3.0%; 5.0% wt. The structural, morphological and deformation-strength properties of the obtained samples have been investigated. It was established that the increase of the elastic modulus value for the samples with the filler concentration of 3% wt and more.

Mechanical anisotropy of graphene nanocomposites induced by graphene alignment during stereolithography 3D printing

Stereolithographically 3D-printed graphene-PMMA nanocomposites were previously found to be mechanically stiffer and stronger in the print axis, suggesting that the graphene filler was selectively oriented. Here, using polarized light microscopy, we confirm experimentally for the first time the presence of aligned graphene platelets in these nanocomposites. The alignment appears to be weak, however, as anisotropy of the storage modulus and quasistatic failure strength was only ~ 10% – 30%, about 100 × lower than the maximum anisotropy possible and 10 × smaller than that of other 3D-printed anisotropic composites. The optimal graphene concentration for maximum anisotropy was 0.02wt%– 0.05wt%, as graphene agglomeration at higher concentrations reduced anisotropy and beyond 0.2wt% it prevented 3D printing altogether. Using finite element simulations, which were experimentally verified, it was also shown that the anisotropy of the bulk nanocomposites could be fully imparted to more complex 3D-printed parts such as Octet Truss structures.Graphic abstract

Mesoscopic simulation of thermal conductivities of 3D carbon nanotubes, graphene and their epoxy resin based composites

The thermal conductivities of the 3D carbon nanotubes (CNTs), CNT/epoxy resin (CNT/EP) composites, graphene/EP composites and CNT/graphene/EP composites are systematically investigated via mesoscopic simulations using smoothed particle hydrodynamics (SPH) and dissipative particle dynamics (DPD). The effects of the CNT length and overall mass density on the thermal conductivity of the CNTs are discussed. Moreover, the influences of the loading and size of the fillers on the thermal conductivities of the CNT/EP, graphene/EP and CNTs/graphene/EP composites are investigated. The results have shown that introducing the CNT and graphene fillers simultaneously to the epoxy resin can improve the thermal conductivity of the composites most effectively. The study demonstrates that coupled DPD and SPH model is a viable approach to understand the thermal conductivities of nanocomposites at a reduced computational cost compared to full atomistic simulation.

Mechanochemical functionality of graphene additives in ultralow wear polytetrafluoroethylene composites

Poly-tetrafluoroethylene (PTFE) is a well-known solid lubricant, but its poor wear resistance limits its tribological applications. Certain carbonaceous fillers reduce PTFE wear rate by up to 4000-fold with no sacrifice of the friction coefficient; whereas the responsible mechanisms remain unclear. We systematically studied the effects of three graphene fillers with different aggregate strengths (graphene nanoplates, few-layer graphene and single-layer graphene) on the wear resistance of graphene-PTFE composites. The results found (1) graphene of weak aggregate strength outperform that of strong aggregate strength by 100 times in wear reduction, (2) strong correlations between wear rate, tribofilm carboxylate signal intensity and filler-matrix area per unit composite mass. The carboxylate signals likely correspond to chemical bonding between mechanochemically degraded PTFE, graphene and the steel counterface within highly crosslinked and adherent transfer films and worn polymer surfaces. Results in this study support two independent (primary versus secondary) wear reduction hypotheses in literature which were further backed by DFT simulations of filler-matrix interactions, TEM/EDS analysis of wear debris, SEM/EDS images of the polymer surfaces, and environmental test results in a dry argon (Ar) atmosphere. The results of this paper are also of instructive value for the development of solid lubricants with highly controllable wear characteristics.

Ultrahigh Thermal Conductivity of Epoxy Composites with Hybrid Carbon Fiber and Graphene Filler

Ultrahigh Thermal Conductivity of Epoxy Composites with Hybrid Carbon Fiber and Graphene Filler