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SEM images of (a) as received TEGO sheets, (b) sonicated TEGO sheets in DMF, and (c) electrosprayed TEGO sheets in DMF without polymer.
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Two dimensional graphene oxide sheets are converted into three dimensional (3D) hollow and filled microspheres by using three different carrying polymers through one-step core-shell electrospraying technique without applying any post treatments. Electrospraying process prevents the aggregations and crumbling of graphene sheets by constructing 3D in...
Contexts in source publication
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... exfoliation process of TEGO sheets Electrospraying process enables graphene sheets to get dispersed homogeneously in polymer solution, prevents their agglomeration under electric eld and enhances the intercala- tion of polymer chains into graphene layers. SEM images of TEGO sheets aer the sonication and electrospraying processes are given in Fig. 2 to promote understanding the effect of electric eld on the morphological changes of TEGO sheets. Untreated TEGO has worm-like structure (Fig. 2a). Aer Paper RSC Advances sonication in DMF, layers are separated from each other, and hence, ake dimension decreases (Fig. 2b); however, the structure still has multi-layered graphene. 35 ...
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... their agglomeration under electric eld and enhances the intercala- tion of polymer chains into graphene layers. SEM images of TEGO sheets aer the sonication and electrospraying processes are given in Fig. 2 to promote understanding the effect of electric eld on the morphological changes of TEGO sheets. Untreated TEGO has worm-like structure (Fig. 2a). Aer Paper RSC Advances sonication in DMF, layers are separated from each other, and hence, ake dimension decreases (Fig. 2b); however, the structure still has multi-layered graphene. 35 Upon the being subjected to applied electric eld, the layers become more attened whereby more transparent sheet formation is observed (Fig. 2c). ...
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... TEGO sheets aer the sonication and electrospraying processes are given in Fig. 2 to promote understanding the effect of electric eld on the morphological changes of TEGO sheets. Untreated TEGO has worm-like structure (Fig. 2a). Aer Paper RSC Advances sonication in DMF, layers are separated from each other, and hence, ake dimension decreases (Fig. 2b); however, the structure still has multi-layered graphene. 35 Upon the being subjected to applied electric eld, the layers become more attened whereby more transparent sheet formation is observed (Fig. 2c). Electric eld deforms the working uid during electrospraying which causes loosely broad graphene ...
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... structure (Fig. 2a). Aer Paper RSC Advances sonication in DMF, layers are separated from each other, and hence, ake dimension decreases (Fig. 2b); however, the structure still has multi-layered graphene. 35 Upon the being subjected to applied electric eld, the layers become more attened whereby more transparent sheet formation is observed (Fig. 2c). Electric eld deforms the working uid during electrospraying which causes loosely broad graphene ...
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... porous core structure. The average diameter of spheres changes from 3.4 mm to 4.6 mm by increasing the ow rate of core material because higher ow rate speeds up the evaporation process of solvent. Spraying methanol with a high ow rate of 5 mL min À1 totally changes the morphology and ber formation is detected among spheres, which are shown in Fig. S2. † In addition, FIB-SEM technique is used for the observation of porous core in PMMA spheres produced by using atmo- spheric air in core syringe. Fig. 12 displays FIB-SEM images of these spheres aer the ion bombardment. The structure of spheres is noticeably porous even at longer bombardment ...
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Citations
... Poudeh and colleagues introduced a novel design for creating 3D graphene-based hollow and filled polymeric spheres through a one-step core-shell electrospraying technique (Figure 2) [12]. To achieve the desired spherical morphology, the study determined the optimal polymer concentration using Mark-Houwink-Sakurada equations [12]. ...
... Poudeh and colleagues introduced a novel design for creating 3D graphene-based hollow and filled polymeric spheres through a one-step core-shell electrospraying technique (Figure 2) [12]. To achieve the desired spherical morphology, the study determined the optimal polymer concentration using Mark-Houwink-Sakurada equations [12]. Proper polymer concentration and solution viscosity are crucial for obtaining the desired spherical shape. ...
... The interactions that occur between polymeric chains and graphene sheets throughout the sphere formation process are essential in determining the characteristics and capabilities of the subsequently formed materials. The core-shell electrospraying method unveils novel prospects for creating sophisticated graphene-centric structures characterized by customized properties, thus presenting a promising Preparation of 3D graphene-based spheres by tri-axial electrospraying technique [12]. ...
Materials based on 3D graphene, such as aerogels, hydrogels, sponges, and foams, are attracting substantial interest due to their superb electrical conductivity, remarkable mechanical properties, and expedited mass and electron transport. These substances preserve the inherent characteristics of 2D graphene sheets and introduce enhanced features like low density, substantial surface area, high porosity, and steadfast mechanical properties. The applications for 3D graphene-based materials are vast, ranging from flexible electronics, sensors, absorbents, and composites to catalysis, energy storage devices, agricultural uses, water purification, biomedical applications, and solar steam generation devices, among others. In this book chapter, we consolidate the latest advancements in the fabrication of 3D graphene-based materials, discussing their properties and the emerging uses in composites and energy storage apparatuses. The synthesis of 3D graphene-based materials on a larger scale poses substantial challenges, the discussion of which might spur innovation and novel approaches in this domain. We aim to provide a comprehensive overview of the contemporary progress in this field, emphasizing the synthesis, properties, and diverse applications of these advanced materials. Our research is anticipated to establish a groundwork for the widespread preparation, understanding of structure-property relationships, and utilization of 3D graphene-based architectures (3DGAs) across various fields, including but not limited to tissue engineering, electronics, supercapacitors, composites, and energy storage devices.
... Furthermore, the technique employed for the accumulation of dual droplets in the external phase is utilized in the production of hollow alginate microparticles, which are recognized as an exceptional carrier for encapsulating water-soluble substances [23]. This method is significantly simpler compared to previous studies that have documented the generation of 3D hollow structures using various techniques, including electrospinning [24], elimination of the core through calcination [25], and emulsification [18]. ...
This study includes an examination of the design, fabrication, and experimentation of a rudimentary droplet generator. The device has potential applications in on-demand double and higher-order emulsions as well as tailored emulsions with numerous cores. The phenomenon of a pendant double droplet creation is observed when an inner phase is transported through a capillary, while a middle phase envelops the external surface of the capillary. This leads to the occurrence of a pinching-off process at the tip of the pulled capillary. Following this, the double droplet is introduced into a container that is filled with the outer phase. The present study examines the force equilibrium throughout the droplet break-up process and aims to forecast the final morphology of the droplets within the container by considering the impact of interfacial tension ratios. The shell thickness in a core–shell formation can be calculated based on the inner and middle phase flow rates as well as the middle droplet formation period. The present platform, which enables the simple production of double and higher emulsions, exhibits promising prospects for the controlled manufacturing of complex emulsions. This technology holds potential for various applications, including the experimental exploration of collision behavior or electro-hydrodynamics in emulsions as well as millimeter-size engineered microparticle fabrication.
... Thus, macroscopically and efficiently generating 3D graphene-based porous adsorbents with high adsorption capacity and low toxicity has not been possible. Various 3D graphene forms were created, including graphene networks [50], graphene fibers [51], and graphene spheres [52]. For the 3D graphene architectures, great surface area, durability, and quick electron and mass transfer are provided 3D structures with intrinsic graphene characteristics. ...
Carbon materials and their diverse allotropes have played important roles in our daily lives and the advancement
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significant attention since 2004 because of their unique and exciting properties. Over the last decade, 3D-graphene nanomaterials have been developed to efficiently use 2D-graphene nanosheets in applications like energy storage, environmental remediation, and electrochemical catalysis. We describe 3D graphene materials,
classify them, briefly discuss their history, and cover this review’s basic synthesis chemical procedures. Special
attention is given to their bibliometric analysis, advancement, synthesis, technical applications of energy storage
devices, environmental applications, and supercapacitor-based applications. The CiteSpace (6.1. R3) software is
used for the bibliometric analysis findings from 2012 to 2023 for keywords, countries, journals, co-occurrence,
and co-author networks. Data were taken from 1142 papers, 71 review articles, and 1071 article proceedings
over 12 years, from 2012 to 2023. The date of retrieval, November 10, 2022, was the latest.
... The concentration of TEGO in the oil was 0.5 Wt.%. The average number of graphene layers was 27, confirmed by scanning electron microscopy (SEM) and Raman spectroscopy (Poudeh et al., 2015). Engine tests were carried out for 75 h with graphene oxide (TEGO) Grade-1 nanoparticles added in 5W-40 fully synthetic commercial engine oil. ...
Purpose
This study aims to investigate the tribological characteristics of a Napier-type second piston ring against a cylinder liner in the presence of graphene nano-additives mixed into 5W40 fully synthetic engine oil.
Design/methodology/approach
Wear tests were carried out in the boundary lubrication condition using a reciprocating tribometer, and real engine tests were performed using a single spark ignition Honda GX 270 test engine for a duration of 75 h.
Findings
The experimental results of the tribometer tests revealed that the nano-additives formed a layer on the rubbed surfaces of both the piston ring and the cylinder liner. However, this layer was only formed at the top dead center of the cylinder liner during the engine tests. The accumulation of carbon (C) from the graphene was heavily detected on the rubbed surface of piston ring/cylinder liner, mixed with other additive elements such as Ca, Zn, S and P. Overall, the use of graphene nano-additives in engine oil was found to improve the frictional behavior in the boundary and mixed lubrication regimes. Abrasive wear was found to be the main mechanism occurring on the surface of both piston rings and cylinder liners.
Originality/value
Though many researchers have discussed the potential benefits of graphene as a nano-additive in oil to reduce the friction and wear in laboratory tests using tribometers, to date, no actual engine tests have been performed. In this paper, both tribometer and real engine tests were performed on a piston ring and cylinder liner using a fully formulated oil with and without graphene nano-additives in the boundary lubrication condition. It was found that a graphene nano-additive plays an active role in lowering the coefficient of friction and increasing surface protection and lubrication by forming a protective layer on the rubbing surfaces.
... However, in practical applications, 2D graphene sheets tend to restack together due to strong π-π interactions and van der Waals forces, which lead to a significant decrease in electrical conductivity and surface area, and this affects negatively the utilization of graphene in many fields. To overcome this problem and provide advanced functions with improved performance, several 3D graphene structures such as graphene networks [6], graphene fibers [7], and graphene spheres [8] have been constructed. The combination of 3D structures and intrinsic properties of graphene provide high surface area, excellent mechanical strength, and fast mass and electron transport for the 3D graphene architectures. ...
... Compared to self-assembly strategy, with this technique, it is possible to obtain more controlled structure with desirable morphology [37]. However, the size of architectures directly depends on the size of templates [8]. So far, considerable amounts of work have focused on the production of 3D graphene-based materials using template-assisted method. ...
... More recently, core-shell electrospinning/electrospraying has received great attention due to its possibility to attain multifunctionality and utilize different materials in one-step process by eliminating deposition steps as in the self-assembly and template-assisted methods, and thus it expands the potential applications of fabricated structures in many areas including drug delivery, energy storage, sensors, and nanocomposites [8,55]. In this technique, the final morphology is affected by various solution properties (such as viscosity and electrical conductivity) and process parameters (such as voltage and flow rate) [56]. ...
Graphene, a two-dimensional (2D) sp 2-hybridized carbon sheet, shows excellent chemical, mechanical , and physical properties owing to its unique structure, which makes it a great potential in the energy storage devices, sensors, composite materials, and biotechnology. The utilization of graphene sheets into the macroscopic structures is one of the important issues since 2D graphene sheets tend to restack together in bulk materials due to strong π-π interactions and van der Waals forces. The aggregation of graphene sheets and their crumbling lead to a significant decrease in electrical conductivity , surface area, and mechanical strength which negatively affects the utilization of graphene in the practical applications. Recently, three-dimensional (3D) graphene materials have been attracting much attention since they not only preserve the intrinsic properties of 2D graphene sheets by inhibiting the agglomeration behavior of 2D graphene sheets but also provide advanced functions with improved performance in various applications. The content of this chapter covers (i) a brief summary of production techniques of 2D graphene and its drawbacks, (ii) main strategies for the development of 3D graphene structures, (iii) production methods, and (iv) possible applications of 3D graphene architectures in composites and energy-storage devices. Graphene, a two-dimensional (2D) hexagonal lattice of sp 2 carbon atoms, has been the interest of many studies. The long-range π-conjugation in graphene yields intriguing properties such as high electrical and thermal conductivity [1, 2], large surface area [3], good chemical stability [4], and excellent mechanical strength [5], which make it a great candidate in various applications such as energy storage systems, polymer composites, and sensors [3]. However, in practical applications, 2D graphene sheets tend to restack
... The effect of rheological properties and process parameters on the final morphology of electrospun structures have been investigated and optimized in details in our previous studies. [14,15] The electrospinning process was performed with an applied voltage of 12 kV, flow rate of 9 μL/min with the nozzle to collector distance of 10 cm while atmospheric air was used as core material. For two different graphene solutions, electrospinning parameters were kept same. ...
... [20] A sharp peak at 2θ = 26°belongs to the 200 graphitic plane of both TEGO and GNP. [15] In Figure 5a, small reflection peaks at 2θ = 15.5°, 20°and 31°indicate the presence of manganese chloride hydrate in the electrospun fiber structure (PDF 25-1043). ...
... In the FTIR spectrum of electrospun PAN/ MnCl 2 /TEGO in Figure 6a, the bands at 2930 cm À 1 , 2243 cm À 1 , 1452 cm À 1 are attributed to the CÀ H bonds in CH 2 , nitrile bond (C�N), and tensile vibration of CH 2 of PAN polymer, respectively. [15] A peak at 1631 cm À 1 is related to the C=C aromatic vibration of TEGO. [8] Moreover, OÀ H vibration at 3375 cm À 1 corresponds to the MnCl 2 .H 2 O in the electrospun fiber. ...
Three‐dimensional (3D) urchin‐shaped free‐standing composite electrodes were produced by the integration of single‐ and multi‐layer graphene and manganese oxide in a step‐wise procedure. The strong interactions between the components were confirmed by spectroscopic characterization techniques. The influence of single‐ and multi‐layer graphene on the electrochemical performance of composite electrodes was investigated in details. Single‐layer graphene with higher oxygen functional groups showed better interfacial interactions between each component by providing exfoliated structure. The electrode containing single‐layer graphene exhibited 28% higher specific capacitance of 452 F/g at a scan rate of 1 mV/s compared to that of multi‐layer graphene. After 1000 cycles of charging‐discharging, single platelet graphene‐based electrode with a high capacitance retention of 89% showed improved synergistic effects by the combination of conductive PANI, single platelets graphene, and manganese oxide. This study indicated the importance of intercalated and exfoliated state of graphene in electrochemical behavior of supercapacitor electrodes.
... However, in these aforementioned processes, it is not easy to control structural properties such as porosity and hollowness since the morphology directly depends on the chosen templates. At this point, electrospinning is an alternative and easy method for the production of graphene-based structures in the form of spheres 12,13 and fibers 14 by adjusting the polymer concentration and surface tension of a droplet. The electrodes produced by electrospinning have an ability to form a continuous network, which is essential for the charge transport and provides conducting framework and excellent interconnectivity. ...
... The greater the viscosity is, the more stable is the polymeric jet to be able to travel through the grounded collector. 20 In our previous work, 12 we showed the effect of polymer concentration and molecular weight on the formation of different polymeric structures by using the Mark−Houwink− Sakurada equation (Table S1). Figure 2 represents the concentration as a function of the molecular weight of PAN, where the solid line shows the concentration threshold of PAN polymer where above and on the line, fiber formation is dominant (see the Supporting Information). On moving toward lower regions, spherical and foamlike structures start to form. ...
... On the other hand, each point in the graph corresponds to the different PAN concentrations with different molecular weights, which are selected for the fabrication of fibers, spheres, and foam, colored red, purple, and blue, respectively. Hence, it is possible to obtain the structures with the desired morphology and size, such as spheres, 12 foams, and fibers, 21 by tailoring the system (e.g., flow rate, applied voltage, and working distance between the nozzle and collector) and solution parameters (e.g., polymer concentration). ...
Platinum (Pt)-decorated graphene-based carbon composite electrodes with controlled dimensionality were successfully fabricated via core−shell electrospinning/electro-spraying techniques. In this process, multilayer graphene sheets were converted into the three different forms, fiber, sphere, and foam, by tailoring the polymer concentration, molecular weight of polymer, and applied voltage. As polymer concentration increased, continuous fibers were produced, whereas decreasing polymer concentration caused the formation of graphene-based foam. In addition, the reduction in polymer molecular weight in electrospun solution led to the creation of three-dimensional (3D) spherical structures. In this work, graphene-based foam was produced for the first time by utilizing core−shell electrospraying technology instead of available chemical vapor deposition techniques. The effect of morphologies and dimensions of carbonized graphene-based carbon electrodes on its electrochemical behavior was investigated by cyclic voltammetry and galvanostatic charge−discharge methods. Among the three different electrodes, Pt-supported 3D graphene-based spheres showed the highest specific capacitance of 118 F/g at a scan rate of 1 mV/s owing to the homogeneous decoration of Pt particles with a small diameter of 4 nm on the surface. After 1000 cycles of charging−discharging, Pt-decorated graphene-based structures showed high cyclic stability and retention of capacitance, indicating their potential as high-performance electrodes for energy storage devices.
... Recent electrospray review articles give detailed accounts of the functional materials and polymers used in electrospray research (Bock et al., 2012;Nguyen et al., 2016;Xie et al., 2015). Here we just mention a few additional examples of such materials: cyan-nanopigment in PMMA, ( Widiyandari et al., 2007); photoluminescent Cerium doped Y 3 Al 5 O 12 encapsulated in PMMA ( Hogan et al., 2007); magnetite in PLGA (Faramarzi, Barzin, & Mobedi, 2017); graphene in PS, PMMA, and PAN (Haghighi Poudeh, Saner Okan, Seyyed Monfared Zanjani, Yildiz, & Menceloglu, 2015); (−)-epigallocatechin gallate (a bioactive compound in green tea) in chitosan ( Gómez-Mascaraque, Sanchez, & López-Rubio, 2016), cisplatin in chitosan ( Qu et al., 2014). The polymers used for pharma and food applications must be biocompatible and optionally biodegradable. ...
Polymer solution electrospray is a relatively recent research area which has become increasingly active due to its potential for engineering particle morphologies at the micro- and nanoscales, which can be useful for pharmaceutical applications, energy devices, and other fields. Despite significant efforts in this research area, and the fact that electrospray (ES) theory for pure solvents is well-established, improved understanding is still needed on how polymeric structures form during electrospray, to be able to predict the diversity of particle morphologies encountered. This situation is due partly to the complexity of the mechanisms involved, which combine the rich behavior of polymer solutions with the unique physics of ES (with disparate temporal and spatial scales). In this article, we start by reviewing which application fields have driven research in polymer solution electrospraying, and which morphologies matter. We then develop a theoretical framework on the mechanisms responsible for the transformation of a polymer solution droplet made by ES into a solid morphology. We discuss the applicability of a droplet drying model used in Spray Drying to the case of electrospray droplets. We further highlight the importance of Coulombic instabilities in developing polymeric structures. These structures include particles with pointed ends, sometimes with long nanofilaments, as well as other elongated shapes, and globular shapes with a broad size distribution. We identify the conditions necessary to prepare monodisperse globular particles (e.g. spheres). Finally, we analyze the roles played by the presence of nonsolvent vapors during droplet drying. This includes ambient humidity when electrospraying non water-soluble polymers, whose effects on particle porosity have often been overlooked. We close with recommendations and clarifications of practical importance for practitioners.
... The incorporation of carbon particles into electrospun solution can cause the instabilities in electrified jet during electrospinning, thus leading to structural deformations in electrospun fiber due to the changes in solution viscosity, physical forces and aggregations of particles. It is possible to control the shape of fiber and the distribution of reinforcing particles by adjusting the polymer and filler concentrations, and polymer-drying time [2,17]. In addition to solution and processing parameters, functionalization of particles surface improves their dispersion and wettability in the chosen polymeric matrix [5]. ...
... Viscosity is one of critical solution parameters during electrospinning that directly affects fiber morphology [17]. It is possible to tailor the viscosity by adjusting polymer concentration and controlling polymer molecular weight. ...
... The average diameters of fibers are given in Table 1. The results indicate that the average diameters of FMD based fibers are slightly smaller than pristine diamond based fibers because the average size of FMD particles are relatively smaller than pristine diamond and amine groups on the surface of diamond are able to interact with the solvent during electrospinning process which increases the drying time of the polymeric jet and thus fiber diameter decreases [17,32]. For instance, neat PMMA fibers have an average fiber diameter of 940 ± 95 nm. ...
Diamond in polymeric composites provides superior mechanical and thermal properties due to its controllable surface chemistry and large accessible surface area. Homogeneous dispersion of diamond in matrix and improved interfacial bondings between diamond and matrix are two important issues to achieve high performance and prevent structural failures in composite manufacturing. In the present work, the surface of submicron scale mono-crystalline diamond was functionalized by hydrazine hydrate and then dispersed in polymethyl methacrylate (PMMA) matrix homogenously by electrospinning technique. This process circumvented aggregations of diamond particles and provided homogeneous dispersion in polymer matrix. Structural morphologies of diamond reinforced PMMA electrospun fibers were adjusted by tailoring polymer concentration, diamond content, flow rate and applied voltage to attain an ideal fiber structure having continuous network without beads. PMMA was used as a polymeric carrier to improve the bonding interactions with epoxy matrix. Flexural tests indicated that the addition of 1 wt% functionalized diamond based electrospun fiber in epoxy matrix improved flexural modulus by 36.4% and flexural strength by 28.1%. Therefore, controlling the surface chemistry of diamond provides better interfacial interactions in reinforcing agent and thus load transfer was realized efficiently in epoxy specimen. In addition, thermal stability of epoxy composites was improved by the addition of diamond particles in electrospun structure.
... During the electrospinning process, the viscoelastic force and Coulombic forces are acting against each other by causing the sample jet to stretch to fibers along the electric field. 37 For dilute polymer solutions, the low viscoelastic forces are not strong enough to act against the electric force and as a result spheres are formed. These spherical droplets are formed due to surface tension and in low concentrations hollow spheres are formed. ...
Using the core-first growth strategy, we have synthesized a tris-Ni(II) initiator which bears three initiating sites for the ensuing polymerization of N-1-phenethyl-N′-methylcarbodiimide. The arms of these star polymers bearing chiral side chains adopt single-handed helical rod-like conformations. The polymerization occurs in a controlled, living fashion, and this multiarm architecture imparts a new set of intriguing properties including their self-assembly into diverse nanostructures when cast from different solvents. These assemblies, characterized by AFM, TEM, and DLS, include the formation of nanofiber networks and twisted superhelical nanostructures. Interestingly, by processing these polymers via electrospraying method, hollow and uniform platelet-like particles were obtained. These solvent-dependent morphologies of microparticles were observed by using SEM. The kinetic studies of polymerizations, inspection of self-aggregation behaviors, and electrosprayed architectures will open up possibilities for a variety of potential biomedical applications.
