Graphene Nanoparticles Research Articles

Brownian and thermal diffusivity impact due to the Maxwell nanofluid (graphene/engine oil) flow with motile microorganisms and Joule heating

Abstract Nanofluids have many applications in industries as well as engineering such as biomedicine, manufacturing, and electronics. Nanofluid is used for improvement of thermal and mass transmission. Based on the aforementioned applications, in the present study, a two-dimensional Maxwell nanofluid with thermal radiation effect on the existence of motile microorganisms over a vertically stretchable surface is explored. The consequence of heat absorption, the efficiency of heat flux in a porous medium, viscous dissipations, and Joule heating impacts are considered. The Brownian and thermophoretic diffusion effects have been evaluated. In addition, the binary chemical reaction is taken into account to evaluate the magnetohydrodynamics (MHD) mixed convection flow. Graphene nanoparticles are suspended in so-called engine oil (base fluid). The proposed liquid model depends on the governing nonlinear equations of velocity, temperature, the concentration of nanoparticles, and motile gyrotactic microorganisms. In order to transform highly nonlinear partial differential equations into nonlinear ordinary differential equations, an appropriate similarity transformation is exploited. For the solution of the present study, the homotopy analysis method-technique in Mathematica-12 is used. The fluctuation of velocity, temperature, concentration, and gyrotactic microorganisms’ characteristics for numerous flow parameters is discussed in detail. Some important fallouts of the existing study are that the Maxwell liquid parameter, Eckert number, and magnetic parameter lessen the nanoliquid velocity. But the fluid temperature becomes higher for growing estimates of the Brownian motion and thermophoretic factors. The radiation and chemical reaction parameters have declining impacts on the solutal profile. The motile microorganism profile shows a decrement in bioconvection Lewis and Rayleigh numbers. The nanofluid thermal profile is improved but the nanofluid velocity declined through the augmentation of volume fraction. Also, the coefficient of skin friction and Nusselt number are obtained versus various flow parameters.

Influence of GNP nanoparticles on shear and dynamic behaviour of flat-joggle-flat composite joints

The focus of the current research is to examine the effects of adding graphene nanoparticles (GNP) to GFRP flat-joggle-flat (FJF) composite joints made with the co-cure manufacturing process on their mechanical and vibrational properties. The experimental results show that adding 0.25, 0.50, and 0.75 wt% GNP reinforcement to the resin greatly improved the strength properties of composite joints by 8.30%, 26.37%, and 34.73%, respectively. However, a higher percentage of GNPs (1%) reduced the strength of joints by 3.90% due to agglomeration. Field emission scanning electron microscopy (FESEM) reveals that 0.75 wt% of GNP reinforced enhanced interfacial interaction and created coarser interfaces in the bond line to postpone failure. Cutting-edge internal failure and damage progression modes are incorporated by the ultrasonic C-scan method. The modal analysis confirmed that the 0.75 wt% GNP reinforcement had the maximum fundamental natural frequency of 918.1 Hz compared to other weight percentages. The obtained experimental results and used methods are in good agreement.

Detection of two markers for pancreatic cancer (CEA, CA199) based on a nano-silicon sphere-cyclodextrin recognition platform

The detection of tumor markers has significant importance in the early diagnosis of cancer. It is an important indicator for evaluating the extent of the disease and monitoring the efficacy of tumor treatment. Therefore, it is meaningful to find a convenient, fast, and sensitive method to detect tumor markers. Carbohydrate antigen 19–9 (CA19-9) is the first discovered carbohydrate antigen tumor marker with the highest sensitivity and specificity for pancreatic cancer. Carcinoembryonic antigen (CEA), as the most widely spectrum carbohydrate antigen tumor marker, can show an upward trend in many tumors. In this work, an electrochemical immunosensing platform was proposed for the detection of CEA and CA199. Nano-silicon sphere-cyclodextrin was synthesized for antibody capture. Graphene and gold nanoparticles were used to modify the electrode, improving the electronic conductivity of the electrode. The synthesized sensor can be used for highly sensitive detection of two tumor markers. This method also provides a new platform for clinical immune analysis of other biomolecules.

Magnetically Stimulable Graphene Oxide/Polypropylene Nanocomposites.

Core-shell magnetic air-stable nanoparticles have attracted increasing interest in recent years. Attaining a satisfactory distribution of magnetic nanoparticles (MNPs) in polymeric matrices is difficult due to magnetically induced aggregation, and supporting the MNPs on a nonmagnetic core-shell is a well-established strategy. In order to obtain magnetically active polypropylene (PP) nanocomposites by melt mixing, the thermal reduction of graphene oxides (TrGO) at two different temperatures (600 and 1000 °C) was carried out, and, subsequently, metallic nanoparticles (Co or Ni) were dispersed on them. The XRD patterns of the nanoparticles show the characteristic peaks of the graphene, Co, and Ni nanoparticles, where the estimated sizes of Ni and Co were 3.59 and 4.25 nm, respectively. The Raman spectroscopy presents typical D and G bands of graphene materials as well as the corresponding peaks of Ni and Co nanoparticles. Elemental and surface area studies show that the carbon content and surface area increase with thermal reduction, as expected, following a reduction in the surface area by the support of MNPs. Atomic absorption spectroscopy demonstrates about 9-12 wt % metallic nanoparticles supported on the TrGO surface, showing that the reduction of GO at two different temperatures has no significant effect on the support of metallic nanoparticles. Fourier transform infrared (FT-IR) spectroscopy shows that the addition of a filler does not alter the chemical structure of the polymer. Scanning electron microscopy of the fracture interface of the samples demonstrates consistent dispersion of the filler in the polymer. The TGA analysis shows that, with the incorporation of the filler, the initial (Tonset) and maximum (Tmax) degradation temperatures of the PP nanocomposites increase up to 34 and 19 °C, respectively. The DSC results present an improvement in the crystallization temperature and percent crystallinity. The filler addition slightly enhances the elastic modulus of the nanocomposites. The results of the water contact angle confirm that the prepared nanocomposites are hydrophilic. Importantly, the diamagnetic matrix is transformed into a ferromagnetic one with the addition of the magnetic filler.

Effect of nickel and rGO on the photocatalytic properties of Co3−xNixO4 prepared with citric acid and CTAB

This work summarizes the research about Co3−xNixO4 x = 0.0 (0%), 0.01 (1%), and 0.04 (4%) conducted with the addition of reduced graphene oxide, rGO, using two routes: with citric acid R1 (C₆H₈O₇, CA) and cetyltrimethylammonium R2 (C19H42BrN, CTAB) by sol-gel technique. The results show that the composite material —with rGO— enhanced the photocatalytic degradation of methylene blue (MB). According to the results, incorporating rGO into samples with low Ni concentrations of 1% and 4% and processed at 400 °C with R1, significantly increased their specific surface area to 31.372 m2.g−1 and 84.743 m2.g−1, respectively. The XRD technique shows the formation of pure cobalt spinel without associated secondary phases and with complete insertion of Ni into the structure. The presence of CA allows the formation of the oxide at lower temperatures. The results of the magnetic tests suggest that the samples obtained by the two synthesis routes present a paramagnetic behavior. The use of CTAB permits the formation of nanoparticles with low agglomeration. TEM images indicate that the sizes of the nanoparticles obtained in the synthesis are less than 20 nm. Thus, based on Raman spectroscopy, the vibrational modes corresponding to the Co3−xNixO4 structure were studied, identifying a broadening and displacement of the peaks with the addition of Ni.Moreover, the disappearance of the peaks corresponding to rGO and attributed to the coating of Co3−xNixO4 graphene nanoparticles was observed. The adsorption isotherms show the behavior of a mesoporous textured material. The diffuse reflectance indicates that R2 with a 1.72 eV value obtained the material with the smallest gap. In addition, the process identified that the existence of reduced graphene oxide increases the material’s specific surface area, which plays a crucial role in MB degradation, outperforming the 4% Ni sample that degraded 39.65% in a two-hour treatment.

Influence of Variable Viscosity on Entropy Generation Analysis Due to Graphene Oxide Nanofluid Flow

Conventional investigations on fluid flows are undertaken with an assumption of constant fluid properties. But in reality, the properties such as viscosity and thermal conductivity vary with temperature. In such cases, considering these variabilities aids in modelling the flows with accuracy. Particularly, studying the flow of graphene based nanofluids with variable properties makes the best of both the advantageous thermophysical properties of graphene nanoparticles in heat transfer and the variable fluid properties in accuartely modelling the flow. In this article, the flow of graphene oxide nanofluid along a linearly stretching cylinder under no-slip and convective boundary conditions is investigated, by taking the base fluid viscosity to be a temperature dependant function. Buongiorno model is adapted to develop the flow of graphene nanofluids including the influence of variable heat source, cross-diffusion effects and the effects of nanoparticle characteristics such as thermophoresis and Brownian motion. The modelled equations are transformed and are numerically solved using linearization method. The impacts of embedded parameters including the Dufour and Soret numbers on temperature, concentration and velocity profiles of the chosen nanofluid and their consequent impacts on the predominant cause for the generated entropy are studied. The obtained results are depicted and interpreted in detail. From the tabulated values of skin friction and the values of Sherwood and Nusselt numbers, it is inferred that the conductive heat and mass transfer can be enhanced by variable viscosity parameter and skin friction can be reduced by Soret number. Furthermore, entropy generation is analysed and Bejan number is calculated to be lesser than 0.5, thus demonstrating the dominance of irreversibilty to fluid friction and mass transfer.

Electrically conductive PDMS/Clay nanocomposites assembled with graphene, copper and silver nanoparticles for flexible electronic applications

Electrically conductive PDMS/Clay nanocomposites assembled with graphene, copper and silver nanoparticles for flexible electronic applications

Simulation of melting paraffin with graphene nanoparticles within a solar thermal energy storage system

In this paper, applying new structure and loading Graphene nanoparticles have been considered as promising techniques for enhancing thermal storage systems. The layers within the paraffin zone were made from aluminum and the melting temperature of paraffin is 319.55 K. The paraffin zone located in the middle section of the triplex tube and uniform hot temperatures (335 K) for both walls of annulus have been applied. Three geometries for the container were applied with changing the angle of fins (α = 7.5°, 15° and 30°). The uniform concentration of additives was assumed involving a homogeneous model for predicting properties. Results indicate that loading Graphene nanoparticles causes time of melting to decrease about 4.98% when α = 7.5° and the impact of ϕ improves about 5.2% with reduce of angle from 30° to 7.5°. In addition, as angle declines, the period of melting decreases around 76.47% which is associated with augmentation of driving force (conduction) in geometry with lower α.

Fused Filament Fabricated Poly(lactic acid) Parts Reinforced with Short Carbon Fiber and Graphene Nanoparticles with Improved Tribological Properties.

This study investigated the mechanical and tribological properties of 3D-printed Poly (lactic acid) (PLA) composites reinforced with different concentrations of carbon fibers (SCF) and graphene nanoparticles (GNP) (0.5 to 5 wt.% of each filler). The samples were produced using FFF (fused filament fabrication) 3D printing. The results showed a good dispersion of the fillers in the composites. SCF and GNP promoted the crystallization of the PLA filaments. The hardness, elastic modulus, and specific wear resistance grew with the increase in the filler concentration. A hardness improvement of about 30% was observed for the composite with 5 wt.% of SCF + 5 wt.% GNP (PSG-5) compared to PLA. The same trend was observed for the elastic modulus with an increase of 220%. All the composites presented lower coefficients of friction (0.49 to 0.6) than PLA (0.71). The composite PSG-5 sample showed the lowest value of specific wear rate (4.04 × 10-4 mm3/N.m), corresponding to about a five times reduction compared to PLA. Therefore, it was concluded that the addition of GNP and SCF to PLA made it possible to obtain composites with better mechanical and tribological behavior.

Properties and tribological evaluation of graphene and fullerene nanoparticles as additives in oil lubrication

In this study, SAE-0W20 engine oil was mixed with graphene and fullerene nanoparticles. The goal of this study was to evaluate and compare the effects of different carbon nanoparticles on the thermal, rheological, and tribological properties of engine oil, such as thermal degradation, viscosity, friction, and wear. Using a two-step process, graphene and fullerene nanostructures were dispersed in low-viscosity SAE-0W20 engine oil at a concentration of 0.05 wt.%. The friction and wear characteristics were evaluated in a customized cylindrical block-on-ring tribology test according to the ASTM G77 standard. Graphene and fullerene nanoparticles protect contact surfaces by forming a very thin protective film between moving mechanical parts thus resulting in wear and friction reduction. The results showed graphene nanoparticles have improved significantly the tribological performance of SAE-0W20 engine oil.

Molecular dynamics simulation and experimental investigation of mechanical properties of calcium carbonate and graphene reinforced polylactic acid nanocomposites.

The use of Molecular Dynamics (MD) simulations to examine the mechanical characteristics of polymer compositesreinforced with calcium carbonate (CaCO3) and graphene (GR) is represented in this work. The effects of CaCO3 andGR nanoadditives in polylactic acid (PLA) matrix in different concentrations were evaluated using the results of MDsimulations. Experimental analyses have been conducted to validate the results of MD based on the mechanicalproperties of fabricated nanocomposites, including modulus of elasticity, shear modulus, and Poisson's ratio. Themodeling, computation, and analysis of several simulations on the improved mechanical characteristics ofPLA/CaCO3 and PLA/GR nanocomposites are introduced and discussed. The results revealed that the addition ofGR nanoparticles were more effective in enhancing the mechanical properties of PLA components as compared withthat of CaCO3 nanoparticles, as the modulus of elasticity, shear modulus and Poisson's ratio increased byapproximately 21%, 17%, and 16% for addition of 3 wt% GR nanoparticles in the PLA matrix, respectively. The mechanical behavior of PLA/CaCO3 and PLA/GR nanocomposites have been simulated based on the moleculardynamic technique using material studio (MS) that enabled the analyses of synergy between the polymer moleculesand the nanoparticles. Molecular models for a system of nanocomposites were built by embedding the nano-clustersinto an amorphous PLA matrix. Nanoparticles have been modeled as spherical nanoclusters of graphite and calciteunit cells. Molecular models of the pure PLA matrix were also developed for comparison. The relaxed systems of MDsimulations have been carried out to calculate the mechanical properties of nanocomposites containing 1, 3 and 5wt% nanofiller contents. To validate the results of the simulations, the PLA/CaCO3 and PLA/GR nanocompositegranules, containing different weight ratios of the nanofillers in the matrix, have been synthesized by melt-blendingtechnique. These granules have been used to produce tensile test samples by injection molding technique, withdifferent fractions of nanoparticles in the matrix, to study the effects of such nanoadditives on the mechanicalproperties of the PLA nanocomposites.

FEM treatments for MHD highly mixed convection flow within partially heated double-lid driven odd-shaped enclosures using ternary composition nanofluids

A highly mixed convection due to the movements of two perpendicular walls of odd-shaped enclosures is examined. The upper and right boundaries are partially heated, and several heating situations based on the positions of the active parts are considered. Also, several directions of the lid-walls movements are examined. The inner medium is a heat generating and the considered Lorentz force is inclined with angle Φ. The mathematical formulations are based on the Brinkman-extended non-Darcy model. The containers are filled with ternary composition nanofluids. The components of the ternary nanofluids are spherical Al2O3 nanoparticles, MWCNT cylindrical nanoparticles and platelet graphene nanoparticles and suitable correlations for the thermophysical properties are introduced. The numerical simulations are carried out using the finite element method (FEM) based on the characteristics–based split (CBS) algorithm. The major outcomes revealed that the ternary composition nanofluids cause an enhancement in the heat transfer rate by 17.65% comparing to the mono-nanofluids. Also, to get the best mixed convection situation, it is recommended to locate the heat sources in the middle of the outer perpendicular walls, set Re≥100 and make the lower perpendicular walls move in anticlockwise direction to get the best mixed convection situation.

Graphene and Fe2O3 filled composites for mitigation of electromagnetic pollution and protection of electronic appliances

With extensive advancement and abundant availability of telecommunication and electronic devices, electromagnetic pollution has become a serious concern not only for human health but also for much sensitive electronic equipment which may fail or malfunction due to electromagnetic interference. Therefore, effective and lightweight electromagnetic interference (EMI) shielding structures are of vital importance for human protection as well as for safeguarding sensitive electronic equipment from interference. In this regard, carbon fiber reinforced composite structures (CFRCS) have proven as one of the best options due to their light weight, extraordinary mechanical properties, and excellent durability. This study explored the synergistic incorporation of graphene and ferric oxide nanoparticles in the CFRCS at various loading concentrations to enhance their electromagnetic shielding effectiveness (EMI SE). According to the results, maximum EMI shielding effectiveness of 95.57 dB was attained at a 4% loading concentration of graphene and a 6% loading concentration of ferric oxide, over a broader frequency range of 0.1 GHz–13.6 GHz. In light of these results, different EMI shielding structures can be developed, including EMI shielding rooms for better protection of humans as well as any sensitive electronic equipment from the harmful effect of electromagnetic radiation. The obtained results are outstanding and may be employed commercially for the protection of electronic equipment and human individuals.

Role of graphene nanoparticles on the electrophysical processes in PVP and PVP:ZnTiO3 polymer layers at Schottky diode (SD)

In this paper, a polyvinyl pyrrolidine (PVP) polymer layer is inserted between the metal–semiconductor (MS) structure to manufacture a metal–polymer–semiconductor (MPS) structure or Schottky diode (SD). The zinc titanate and graphene nanostructures were doped into the PVP layer individually and together to improve the electrical performance of the MPS-type SD. The crystalline size, surface morphology, and band gap energy of the ZnTiO3 nanostructures are examined by the x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and ultraviolet–visible (UV–Vis) spectroscopy, respectively. It is common to measure the current–voltage (I–V) features (at ±3 V) of these five structures for calculating the reverse saturation current (I 0), barrier height, ideality factor (n), series (R s), and shunt (R sh) resistances as the main electrical parameters utilizing the thermionic emission, Norde, and Cheung models. Also, the forwarded-bias energy-dependent surface states density (N ss) and the forward/reverse biased current conduction mechanisms are studied and discussed. The rectifying ratio (RR) of Al/PVP:Gr-ZnTiO3/p-Si SD has the highest increase among these five SDs while the lowest I 0 and highest R sh are related to the Al/PVP:Gr/p-Si (MPS2) and Al/PVP:ZnTiO3/p-Si (MPS3) SDs, respectively. Therefore, doping Gr into the PVP interlayer increases the electrical conduction in the SDs although PVP:Gr-ZnTiO3 polymer layer improves the RR of SDs.

Fabrication and Characterization of Ag-Graphene Nanocomposites and Investigation of Their Cytotoxic, Antifungal and Photocatalytic Potential.

In the present study, we aimed to synthesize (Ag)1-x(GNPs)x nanocomposites in variable ratios (25% GNPs-Ag, 50% GNPs-Ag, and 75% GNPs-Ag) via an ex situ approach to investigate the incremental effects of GNPs (graphene nanoparticles) on AgNPs (silver nanoparticles). The prepared nanocomposites were successfully characterized using different microscopic and spectroscopic techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet spectroscopy, and Raman spectroscopic analysis. For the evaluation of morphological aspects, shape, and percentage elemental composition, SEM and EDX analyses were employed. The bioactivities of the synthesized nanocomposites were briefly investigated. The antifungal activity of (Ag)1-x(GNPs)x nanocomposites was reported to be 25% for AgNPs and 66.25% using 50% GNPs-Ag against Alternaria alternata. The synthesized nanocomposites were further evaluated for cytotoxic potential against U87 cancer cell lines with improved results (for pure AgNPs IC50: ~150 µg/mL, for 50% GNPs-Ag IC50: ~12.5 µg/mL). The photocatalytic properties of the nanocomposites were determined against the toxic dye Congo red, and the percentage degradation was recorded as 38.35% for AgNPs and 98.7% for 50% GNPs-Ag. Hence, from the results, it is concluded that silver nanoparticles with carbon derivatives (graphene) have strong anticancer and antifungal properties. Dye degradation strongly confirmed the photocatalytic potential of Ag-graphene nanocomposites in the removal of toxicity present in organic water pollutants.

Bottom‐Up Synthesis, Dispersion and Properties of Rectangular‐Shaped Graphene Quantum Dots

AbstractCarbon nanomaterials have attracted the attention of the scientific community for more than 30 years now; first with fullerene, then with nanotubes and now with graphene and graphene related materials. Graphene quantum dots (GQDs) are nanoparticles of graphene that can be synthesized following two approaches, namely top‐down and bottom‐up methods. The top‐down synthesis used harsh chemical and/or physical treatments of macroscopic graphitic materials to obtain nanoparticles, while the second is based on organic chemistry through the synthesis of polycyclic aromatic hydrocarbons exhibiting various sizes and shapes that are perfectly controlled. The main drawback of this approach is related to the low solubility of carbon materials that prevents the synthesis of nanoparticles containing more than few hundreds of sp2 carbon atoms. Here we report on the synthesis of a family of rectangular‐shaped graphene quantum dots containing up to 162 sp2 carbon atoms. These graphene quantum dots are not functionalized on their periphery in order to keep the maximum similarity with nanoparticles of pure graphene. We chose water with sodium deoxycholate surfactant to study their dispersion and their optical properties (absorption, photoluminescence and photoluminescence excitation). The electronic structure of the particles and of their aggregates are studied using Tight‐Binding (TB). We observe that the larger particles (GQD 3 and GQD 4) present a slightly better dispensability than the smaller ones, probably because the larger GQDs can accommodate more surfactant molecules on each side, which helps to stabilize their dispersion in water.

Performance enhancement and emissions reduction in a diesel engine using oleander and croton biodiesel doped with graphene nanoparticles

Biodiesel is considered a suitable substitute for petroleum diesel because it is renewable, environment-friendly, and has a low carbon footprint. However, its high density, high viscosity and low heating value prevents it from replacing petroleum diesel completely. This study investigates the performance and emission characteristics of a compression ignition engine operating on oleander and croton biodiesel doped with graphene nanoparticles. Five fuel samples are used, including diesel (D100), diesel - 80% blended with oleander and croton biodiesel - 20% (OCB20) and OCB20 dosed with graphene nanoparticles at mass fractions of 50 ppm (mg/L), 75 ppm (mg/L) and 100 ppm (mg/L), respectively. The chemical composition of biodiesel and graphene nanoparticles is analyzed using Fourier Transform Infrared (FTIR) spectroscopy while the morphology of the nanoparticles is analyzed using Scanning Electron Microscope (SEM). Engine tests reveal a significant improvement in brake thermal efficiency, especially at 75 ppm concentration which is 2.76% and 18.93% higher than diesel and OCB20, respectively, and a reduction in brake specific fuel consumption by 2.44% and 16.67% compared to diesel and OCB20, respectively. Carbon monoxide (CO) and unburnt hydrocarbon emissions (UHC) decreases for the 50 ppm sample, recording 8.58% and 21.65% reduction in CO and 52.2% and 50% in UHC compared to the diesel and OCB20, respectively. However, Oxides of Nitrogen (NOx) emissions increase. The results indicate that graphene nanoparticle-enhanced biodiesel can adequately substitute petroleum diesel, albeit with NOx reduction techniques.

Comparative Study of Conducting and Antimicrobial Behaviour of Graphene and Silver based Nano-Materials

Instantaneous and rapid developments in nanotechnology stimulated innovative ideas across many fields of day-to-day life. Carbon-based nanomaterials have developed many platforms for an extensive range of applications due to their unique mechanical, electrical and biological properties. Nanoparticles of noble metals and their compounds are also playing an enormous role in many aspects of our life i.e. medical devices, pharmaceuticals, polymer industry, biomedical field, coating of kitchen appliances, food packing, clothes and gifts. Silver and carbon-based nanoparticles are being used diversely in food, fitness and health care, therapeutic, manufacturing and optical devices industries due to their distinctive chemical and physical characteristics. This study provides a short review of antibacterial and conducting activities of graphene and silver nanoparticles (AgNPs) both. These are well known conducting nanomaterials applied in many areas and a wide literature is available on these characteristics. Thermal conducting behaviour of both materials also has a noteworthy standing. Thus, it becomes interesting to utilize these features to create new composite materials with improved electrical, thermal and antimicrobial properties; comparative study is also an interesting field to do innovations.

Heat and fire-resistant nanofiber networks: Towards tailoring the new generation of lightweight intermeshing polymer composite systems

Safe use of materials is a primary focus of emerging low-carbon industry. Catastrophic fire incidents due to high flammability of polymers as versatile materials necessitate developing fire-proof polymer composites. In this study, a novel and robust strategy is implemented to fabricate non-flammable and fire-proof thermoplastics with remarkably lower flame retardant (FR) content leading to outstanding limiting oxygen index (LOI) of 30% and UL 94-V0. This can be achieved using nano-fibrillation by forming networks of heat-resistant polymeric nanofibers (polyphenylene ether (PPE) or polyphenylene sulfide (PPS)) within polystyrene (PS). Formation of heat-resistant nanofibers creates a continuous network-structured layer/shield to preserve the matrix against burning and suppresses dripping by boosting the melt-strength. Nanofibers also lead to promoting a graphitized char layer to thoroughly protect the polymer against fire. These synergistic effects enhance FR efficiency, as demonstrated by a 30% reduction in fire growth rate and peak heat release rate, upon inclusion of 15 wt% PPE nanofibers, compared to an equivalent composite with spherical particles. Only the PS sample containing 25 wt% FR and 15 wt% heat-resistant nanofibers meets UL 94-V0 while presence of a similar content of spherical PPE or PPS, graphene nanoparticles, or carbon nanotubes does not provide this feature. Nanofibers also strengthen energy absorption leading to high impact strength of PS composites (120%). Hence, this novel strategy can be extended to a wide range of polymer systems to fabricate novel generation of fire-proof devices with tunable properties for various potential applications including energy storages packs, electronic equipment, and robotics.

Exact solutions via Prabhakar fractional approach to investigate heat transfer and flow features of hybrid nanofluid subject to shape and slip effects

The core devotion of this study is to develop a generalized model by means of a recently proposed fractional technique in order to anticipate the enhancement in the thermal efficiency of engine oil because of the dispersion of graphene and magnesia nanoparticles. In addition to investigating the synergistic attributes of the foregoing particles, this work evaluates shape impacts for column, brick, tetrahedron, blade, and lamina-like shapes. In the primary model, the flow equation is coupled with concentration and energy functions. This classical system is transmuted into a fractional environment by generalizing mathematical expressions of thermal and diffusion fluxes by virtue of the Prabhakar fractional operator. In this study, ramped flow and temperature slip conditions are simultaneously applied for the first time to examine the behavior of a hybrid nanofluid. The mathematical analysis of this problem involves the incorporation of dimension-independent parameters into the model and the execution of the Laplace transform for the consequent equations. By doing so, exact solutions are derived in the form of Mittag–Leffler functions. Multiple illustrations are developed by dint of exact solutions to chew over all aspects of temperature variations and flow dynamics. For the preparation of these illustrations, the details of parametric ranges are as follows: 0.00 le varUpsilon le 0.04, 2.0 le Gr_1 le 8.0, 0.5 le Sc le 2.0, 0.1 le uptau le 4.0, 0.1 le d le 0.6, 0.2 le lambda _1 le 1.5, and 1.0 le Gr_2 le 7.0. The contribution of differently shaped nanoparticles, volume proportions, and fractional parameters in boosting the heat-transferring attributes of engine oil is also anticipated. In this regard, results for Nusselt number are provided in tabular form. Additionally, a brief analysis of shear stress is carried out for fractional parameters and various combinations of magnesia, graphene, and engine oil. This investigation anticipates that engine oil’s hybridization with magnesia and graphene would result in a 33% increase in its thermal performance, which evidently improves its industrial significance. The enhancement in Schmidt number yields an improvement in the mass transfer rate. An increment in collective volume fraction leads to raising the profile of the thermal field. However, the velocity indicates a decreasing behavior. Nusselt number reaches its highest value (Nu=8.1363) for the lamina shape of considered particles. When the intensity of the buoyancy force augments, it causes the velocity to increase.