Both X-ray diffraction patterns and transmission electron microscopy images verified the dispersion morphology of OMMT in the copolymer matrix. Then, the effect of the introduction of OMMT layers on the copolymer properties was studied by comparing with pure copolymer AM/SSS/DOAAB (ADOS). The thermal degradation results demonstrated that the thermal stability of the ADOS/OMMT were better than pure copolymer ADOS. During the solution properties tests, ADOS/OMMT nanocomposite was superior to ADOS in viscosifying ability, temperature resistance, salt tolerance, shear resistance and viscoelasticity, which was because OMMT contributed to enhance the hydrophobic association structure formed between polymer molecules. Additionally, the ADOS/OMMT nanocomposite exhibited more excellent interfacial activity and crude oil emulsifiability in comparison to pure copolymer ADOS. These performances indicated ADOS/OMMT nanocomposite had good application prospects in tertiary recovery.In this research, a novel amphiphilic hydrophobically associative polymer nanocomposite (ADOS/OMMT) was prepared using acrylamide (AM), sodium 4-vinylbenzenesulfonate (SSS), N, N′-dimethyl octadeyl allyl ammonium bromide (DOAAB) and organo-modified montmorillonite (OMMT) through  Over Hydrophobic associating polymer is a kind of water-soluble polymer with a few hydrophobic groups in the hydrophilic main chain ,13. When+ and K+ ions between its layers. Therefore, in order to increase the compatibility of MMT platelets with hydrophobic polymer bulk, the original MMT needs to carry out organic pre-modification by cation exchange technology  dihydrochloride (AIBI) were produced by Shanghai Macklin Biochemical Co., Ltd. Octadecyl dimethyl tertiary amine were obtained from Shandong Xiya Chemical Industry Co., Ltd. Allyl bromide was bought from Aladdin Industrial Corporation (China). CTAB was obtained from Tianjin Guangfu Fine Chemical research institute. Na-MMT with a cationic exchange capacity of 1 mol 1 kg2.2.a.First, 1000 mmol N, N-dimethyl-octadecyl tertiary amine was dissolved in a three-mouth flask containing 300 ml of ethanol, and 150 mmol allyl bromide was added to the three-mouth flask for stirring. Then, the reaction was conducted under the protection of nitrogen at 60°C for 24 h. Third, the reaction mixture was distilled under reduced pressure to remove the ethanol thereby obtaining the crude product. Finally, the crude product needed to be recrystallized using acetone and ether and then put in the refrigerator for 48 h. The solvent in the product was filtered out to obtain the pure white powder product, which was put into the oven to dry for later use. The synthetic scheme is demonstrated in figure 12.3.− ion could be detected by solution of AgNO3. The finished samples were dried for one day in a drying oven at 70°C, dry samples were ground to powder (around 65 ∼ 75 µm) and put into self-sealing bags for later use. The process of organic modification of MMT is demonstrated in figure 1b.OMMT was obtained by cation exchange reaction, and the details are as follows. Firstly, 5 g pure natural Na-MMT powders was added into 100 ml of deionized water in a flat bottom three-mouth flask. Then, the mixture was stirred continuously for 1.5 h at 80°C in a water bath. At the same time, 1.2 CEC intercalation agent (CTAB) was dissolved in 40 ml of deionized water in a 150 ml beaker for later use. Finally, intercalation agent solution was slowly dripped into the swollen montmorillonite dispersion system above, and the dispersion system continued to react for 10 h at 80°C with stirring. After the intercalation reaction, the prepared suspension of OMMT was allowed to stand for 12 h in a separatory funnel. Then, the upper parts of samples were collected by filtering and lavation was carried out several times with deionized water until no Br2.4.In situ polymerization was used for synthesizing ADOS/OMMT nanocomposites. In a 150 ml beaker, 12 g AM, 0.42 g N′-dimethyl octadeyl allyl ammonium bromide (DOAAB), and 0.385 g SSS were dissolved in 40 ml deionization water in sequential order forming a uniform solution. After that the different quantities of prepared OMMT  were added into the above monomers solution slowly under high speed magnetic stirring and kept stirring for 2.5 h at 40°C. This was done to make sure that monomers adsorbed onto the MMT nanolayers adequately to synthesize composite material with better performance. An initiator AIBI (0.25 wt%) was added into the mixed suspension by injector, then, the mixture was stirred for another 30 min. The two steps were done under nitrogen protection. Subsequently, copolymerization was carried out for 6.5 h at 55°C. The resulting gel copolymer was cut into small pieces and washed in ethyl alcohol repeatedly, and dried them in a vacuum oven at 75°C. The scheme for the preparation of ADOS/OMMT nanocomposite is demonstrated in Pure copolymer (ADOS) was synthesized by almost the same process and condition. The only difference was that OMMT was not needed in the synthesis process.2.5.−1 was carried out for OMMT, Na-MMT, pure copolymer and nanocomposite by a FTS-3000 spectrophotometer (American Digilab) at room temperature. The 1H-NMR spectra of pure copolymer and surfactant monomer was measured by a Bruker ASCEND-400 NMR instrument, and deuterium oxide (D2O) was used as solvent. The interlayer spacing of the samples was characterized on a Bruker D8 Advance X-ray diffraction instrument  and calculated by Bragg's Law. During the testing, the system operated at a voltage of 40 KV and current 40 mA. Also the scanning speed was 1° min−1 from 1° to 10° with a step distance of 0.02°.FTIR spectrometric analysis in the spectral range of 4000–400 cm−1 under nitrogen flow rate of 140 cm3 min−1. Dispersion morphology of the OMMT layers in the nanocomposite was observed by TEM  at 200 kV. Meanwhile, the microscopic observation of pure copolymer matrix was obtained as blank control.The weight losses of the samples from room temperature to 700°C were recorded on a NETZSCH TGA (STA409PC) from Germany, and the samples were heated at the rate of 10°C min2.6.−1 flowing through the capillary tube of Ubbelohde viscometer (diluted) was measured with a stopwatch. Then the original sample solution was diluted by 1 mol l−1 NaCl aqueous solution several times and the flow time of sample solutions with different dilutions was obtained. Also the flow time of 1 mol l−1 NaCl aqueous solution was measured by the same method as above. Finally, the intrinsic viscosity of samples was calculated by the dilution extrapolation method and using the Mark-Houwink equation with experimental data  was the intrinsic viscosity (ml g−1).The intrinsic viscosity of copolymers and nanocomposites was obtained by the dilution extrapolation method at 30°C. First, the time of the sample solution with NaCl concentration of 1 mol ltal data :2.1ηr=tt2.7.−1 in the process of the measurements of salt resistance, temperature resistance and rheological properties.The correlation between the apparent viscosity and solution concentration, salinity and temperature was acquired by a Brookfield viscometer  and the test was carried out at the rotor speed of 20 r.p.m. The rheological behaviour of the copolymer was measured by a physical MCR 301 rotated rheometer (Austria). The shear resistance and viscoelasticity of the sample solution was tested under steady and oscillatory shear mode respectively. And all solutions of samples used for test were prepared with deionized water under room temperature conditions. The concentration of the sample solution was 6000 mg l2.8.The measurements of interfacial tension between crude oil and the copolymer solution and the nanocomposite solution were carried on a TX-500c spinning drop interface tensiometer . All sample solutions were tested for 35 min at the condition of 45°C, 6000 r.2.9.Equal volumes of crude oil and sample solution were measured, respectively, into a 50 ml centrifugal tube, then an electric mixer was used to stir the mixture at a speed of 5000 r for 10 min to turn the mixture into a uniform emulsion. The prepared emulsion was poured into a measuring cylinder with a plug, and then the total volume of emulsion was recorded. Afterwards, the volume of emulsion layer was recorded at regular intervals. The emulsification property of the sample solution was evaluated by the emulsification index, it could be calculated by the following formula ,5:2.4EI, OMMT (b), pure copolymer (c) and its nanocomposite (d) was gained and is presented in figure 3a, the small peak at 3626 cm−1 corresponded to the O─H stretching vibrations for SiO─H and AlO─H of silicate layers. The characteristic peak at 1624 cm−1 was attributed to H─O─H bending vibrations in the water molecules, which existed in the montmorillonite interlamellar  of the copolymer sample reflects the contribution of an individual copolymer molecule to the solution viscosity and it doesn't change with the concentration of sample solution  of ADOS, ADOS/1% OMMT and ADOS/2% OMMT nanocomposites were respectively 701.583 ml g−1, 825.25 ml g−1, 630.00 ml g−1 using dilution extrapolation.The intrinsic viscosity [solution ,50. As f3.7.−1, which was the critical micelle concentration (CMC) of the samples. Obviously, the apparent viscosity increased slowly as the polymer concentration increased before the turning point. This was because at low concentrations, the polymer macromolecules were mainly in the form of intramolecular association in the solution, which led to the curl of the molecular chain and the reduction of the hydrodynamic volume. After the turning point, intermolecular association played a dominant role, and supramolecular aggregates with network structure formed, leading to the sharp increase of apparent viscosity [In order to study the difference between the influence trend of the concentration of the nanocomposites solutions and the pure copolymer solution on the apparent viscosity, the apparent viscosity of the pure polymer solution and the nanocomposites solutions with different concentrations was tested at room temperature, as shown in iscosity . Howeveriscosity ,52. Howe3.8.−1 is shown in The influence of temperature from 25°C to 95°C on viscosity of ADOS solution and ADOS/OMMT solution for the concentrations of 6000 mg lIt can be seen from the 3.9.2Cl for both ADOS and ADOS/OMMT solutions was tested and recorded. The apparent viscosity of the sample solution as a function of different salt ions (NaCl and Ca2Cl) concentration is summarized in 2 concentrations, the apparent viscosities of the samples solutions decreased first, then increased, and then decreased. And similar phenomenon could be seen in previous literature [− and ─SO3H−) on the polymer backbone were shielded by salt ions (Na+ or Ca2+), leading to the reduction of electrostatic repulsion and the contraction of polymer chains. This resulted in the decline of the sample's apparent viscosities [+ and Ca2+ on the charge on the polymer chain. In addition, MMT platelets could promote and participate in formation of stronger intermolecular association networks [2 solutions exceeds 40%. Moreover, when the concentration of NaCl and CaCl2 solutions was about 290 000 mg l−1 and 330 000 mg l−1, respectively, the apparent viscosity of the samples reached the maximum value. Above all, both ADOS and ADOS/OMMT nanocomposites had excellent salt resistance, and the introduction of OMMT has a synergistic effect on the salt resistance of pure polymer.Salt ions are known to affect the apparent viscosity of polymer solutions. Therefore, the apparent viscosity in the presence of different concentrations of NaCl and Caterature . These ccosities ,56. At tcosities ,58. At hcosities . Howevernetworks . Also, a3.10.−1 to 1000 s−1, the apparent viscosity of the sample solution decreased gradually, showing the behaviour of shear thinning. However, under the same shearing rate, the shear degradation of ADOS/1% OMMT and ADOS/2% OMMT was lower as compared with that for ADOS. This was because the introduction of nano-OMMT enhanced the intermolecular hydrophobic association, which made the three-dimensional network structure more stable and less vulnerable to shear damage. Consequently, ADOS/OMMT nanocomposites had more excellent shear resistance performance than ADOS.Variation curves of ADOS and ADOS/OMMT solutions apparent viscosity versus shear rate are demonstrated in 3.11.fc) corresponding to the crossing point (Gc) was the characteristic relaxation time (tc) [tc of ADOS, ADOS/1% OMMT and ADOS/2% OMMT were 0.12, 2.7 and 13.7 s, respectively. Moreover, the longer tc was, the better the elastic efficiency. So, compared with ADOS, ADOS/OMMT had better elastic properties. These results could be interpreted as, the original intermolecular hydrophobic association was strengthened by electrostatic interaction and hydrogen bonding between molecular chains of matrix and exfoliated MMT layers, forming a more complex and stable physical network structure [The viscoelastic property of the polymer solution is of great significance to the displacement of oil trapped in pore dead angles. The viscoelasticity test results of ADOS and ADOS/OMMT solutions are reported in ime (tc) . Therefotructure .Figure 3.12.−1, respectively. Furthermore, the ADOS and ADOS/OMMT nanocomposite had a relatively good ability to decrease the interfacial tension between crude oil and water. Interestingly, ADOS/OMMT nanocomposites could contribute to more decrease than ADOS in the interfacial tension at the crude oil–water interface. These phenomena attributed to the fact that the hydrophilic and hydrophobic segments existing in copolymers had good orientation at the crude oil–water interface, which led to reduction of interfacial tension [Interfacial tension (IFT) of both ADOS and ADOS/OMMT nanocomposites at the oil–water interface have been tested. The relation curves between IFT of ADOS and ADOS/OMMT nanocomposite solution and their solution concentration at 45°C are demonstrated in  tension ,61. Addi tension ,62.Figu3.13.−1 or 5000 mg l−1, the emulsification index of ADOS/1% OMMT nanocomposites was greater than pure polymer and ADOS/2% OMMT nanocomposites throughout the test, that is, the emulsifying capacity of ADOS/1% OMMT nanocomposites was more superior than the other two samples. Moreover, it could be noticed that pure polymers had a better ability to stabilize emulsions in aqueous solutions than ADOS/2% OMMT nanocomposites. This was because the amphiphilic structure of the copolymer gave the copolymer the ability to emulsify crude oil. The hydrophobic groups of the copolymer could form network structure by intermolecular association, which could trap oil droplets into network structure thereby forming stable O/W emulsion with the interface membrane [The emulsifying capacity of the ADOS and ADOS/OMMT nanocomposites at room temperature was investigated by recording emulsification index against time. The results of emulsifying crude oil with these samples in aqueous solution are displayed in membrane . Additiomembrane . Neverth4.in situ polymerization. TEM and XRD analysis proved that OMMT was successfully dispersed in an ADOS copolymer matrix in the form of exfoliation and intercalated structure. The TGA results showed that the thermal stability of the ADOS/OMMT was better than pure ADOS. Meanwhile, the solution properties investigation indicated that ADOS/OMMT had higher apparent viscosity than pure ADOS. Besides, at the same condition, the temperature resistance, shear resistance and viscoelasticity of the ADOS/OMMT solution were enhanced relative to ADOS. Also, compared with pure ADOS, the copolymer ADOS with introduction of an appropriate amount of OMMT could demonstrate superior interfacial activity and crude oil emulsifiability. Therefore, ADOS/OMMT nanocomposites possess good application prospects in tertiary recovery and oil drilling.A amphoteric hydrophobically associative polyacrylamide/organic MMT nanocomposite (ADOS/OMMT) was prepared with


Polymer-composite materials have the characteristics of light weight, high load, corrosion resistance, heat resistance, and high oil resistance. In particular, graphene composite has better electrical conductivity and mechanical performance. However, the raw materials of graphene composite are processed into semi-finished products, directly affecting their performance and service life. The electromagnetic pulse compaction was initially studied to get the product Graphene/PEKK composite powder. Simultaneously, spark plasma sintering was used to get the bars to determine the electrical conductivity of Graphene/PEKK composite. On the basis of this result, conducting Graphene/PEKK composite powder can be processed by electromagnetic pulse compaction. Finite element numerical analysis was used to obtain process parameters during the electromagnetic pulse compaction. The results show that discharge voltage and discharge capacitance influence on the magnetic force, which is a main moulding factor affecting stress, strain and density distribution on the specimen during electromagnetic pulse compaction in a few microseconds. With the rapid development of automobile, aviation, aerospace, and rail transit, lightweight materials have become a relatively important topic as an effective measure to pursue global energy conservation and environmental protection ,2,3. PolPEEK composite is a lightweight material that can bear the main load-bearing structure of an aircraft. As a torsion box with a span of 12 m, carbon fibre with 6 m length and 28 mm thickness can be realized by fibre-reinforcement technology to strengthen the upper beam of a PEEK engine pylon ,8,9. AppIn some harsh service environments, polymer-composite materials can replace traditional metal materials. They are an important means to solve the problem of corrosion and light weight. If polymer composites have high strength and conductivity, then they can replace metal materials for use in harsh environments. Graphene is known to be the thinnest and strongest material that can be separated from graphite materials ,11,12. IThe conductive mechanism of conductive Graphene/PEEK polymer-composites is primarily through the formation of conductive passage . GraphenGraphene/PEKK composite materials are processed into semi-finished and finished products such as plates, bars, pipes, test parts, structural parts, and skin. To ensure the performance of Graphene/PEKK composite materials and to improve the quality of finished products, the moulding process is one of the most commonly used techniques. Graphene has been combined with the higher-performance thermoplastic PEKK to improve its electrical conductivity ,21. For In general, the moulding process can be divided into hot and cold moulding. Hot moulding can improve the quality of products primarily by adjusting the temperature, whereas cold moulding refers to finished and semi-finished products obtained from powder at room temperature, and cold moulding mainly depends on pressure and pressure holding time to obtain specimens with high density, and it is easy to control the moulding size. Thermoforming includes hot pressing, extrusion, injection moulding, calendering, secondary moulding, and casting moulding. With the rapid development of computer technology, 3D-printing technology has been gradually applied in various fields ,24,25. IThe use of 3D printing to form conductive Graphene/PEKK composite powder has certain problems. Firstly, the dispersion problem of graphene in the polymer matrix still needs to be solved to maximize its excellent mechanical properties and functionality . SecondlSome researchers have also used spark plasma sintering (SPS) to form specimens for polymer composite powder. SPS  is used 2 and PZT powders in an indirect way. After selecting the appropriate processing parameters, TiO2 and PZT ceramics with higher density and better electrical properties than those produced by traditional static compaction are generated [The powder-moulding process at room temperature is called cold moulding. Previous research showed an important cold-moulding method  named loenerated . Low-volB. Chelluri  describeFew studies have focused on the moulding of Graphene/PEKK composites, especially the moulding of self-prepared Graphene/PEKK composites . IdentifIn the present study, Graphene/PEKK composite powder was synthesized in the laboratory by way of in situ polymerization, and then it was called self-prepared Graphene/PEKK composite powder. Firstly, SPS was used to obtain a Graphene/PEKK composite compressed column with high electrical conductivity in order to determine the feasibility of electromagnetic pulse compaction conductive powder. Secondly, cold moulding-electromagnetic pulse compaction technology was primarily proposed to realize the moulding process of self-prepared Graphene/PEKK polymer powder at room temperature. In this paper, the finite element numerical analysis was used to determine process parameters during the electromagnetic pulse compaction moulding. The loose coupled FE analysis method with ANSYS and MSC.Marc was proposed, and it used ANSYS to obtain the magnetic force. Additionally, the magnetic-force distribution on different points was regarded as the boundary conditions of the MSC.Marc software. The FE numerical analysis method was initially used to determine the change law of process parameters during the cold moulding electromagnetic pulse compaction process and guided future theoretical and experimental research.Graphene used in this study was bought from Shenzhen Yuewang Energy Saving Technology Service Co. Ltd, Shenzhen, China. Terephthalyl chloride, diphenyl ether, aluminum trichloride (anhydrous), dimethylformamide, and dichloromethane were purchased from Sinopharmaceutical. The graphene was dispersed in dichloromethane, and then diphenyl ether, p-benzoyl chloride, N, N-dimethylformamide and anhydrous aluminum trichloride were added successively. After stirring evenly, the composite powder was obtained after cleaning, filtering, grinding and drying. According to the above technological process, Graphene/PEKK composite powder with 3.8% mass percentage of graphene was prepared. Among them, the molar ratio of diphenyl ether, terephthalyl chloride, N,N-dimethylformamide and aluminum trichloride is 1:1:2:6.Thermal properties including thermogravimentric analysis (TGA) and differential scanning calorimetry (DSC) of self-prepared Graphene/PEKK composite powder were characterized before moulding of conductive Graphene/PEKK composite materials. The TGA test  was conducted from 50 to 1000 °C at a ramp rate of 10/min. The DSC test  was carried out between 0 and 450 °C at a heating/cooling rate of 10 °C/min.gT) of this Graphene/PEKK composite may be defined as 125.5 °C. It should be noted that melting temperature and the corresponding viscosity of the polymer composite directly determines the difficulty and quality of flow forming process in engineering application. According to Graphene/PEKK composite powder samples were obtained by in situ polymerisation. Commercial graphene was satisfactory dispersed in high-performance thermoplastic PEKK polymer to improve its electrical properties. However, higher temperature moulding decreases the graphene performance, whereas lower temperature influences dispersion, tool life, and porosity. Thus, the suitable moulding temperature is a key factor influencing the quality of the electrode bar. The self-prepared Graphene/PEKK composite material is a thermoplastic composite material, which has the characteristics of light weight, high toughness, low energy consumption, corrosion resistance, good formability, and conductivity. In this research, SPS equipment  was usedSPS is a new powder-metallurgy sintering technology in which metals and other powders are placed in a mould made of graphite and other materials. The specific sintering power supply and pressing pressure are applied to the sintered powder by using upper and lower die-punched and electrified electrodes. High-performance materials are produced by discharge activation, thermoplastic deformation, and cooling. A previous article discussed how to process powder electrodes , as wellTo reduce the fitting time and evaluate the computation results, an effective experimental design method was needed. Several different factors and levels needed to be considered when optimizing the parameters during SPS moulding. The purpose of the optimisation of parameters during SPS moulding was to reach the maximum conductivity. Orthogonal design is a kind of design method that is primarily used to study multiple factors and multiple levels . The suiFive electrode bars were obtained based on the parameters in Graphene/PEKK composite with 3.8% graphene content had strong electrical conductivity by using the SPS moulding bar; The above research confirmed the electrical conductivity and matrix structure of self-prepared Graphene/PEKK composites and some shortcomings about SPS moulding technology. Compared with hot-press-moulding SPS moulding technology, it can save time as it needed only 30 min. Normally, the temperature can change the grain size. In particular, high temperature can produce toxic gases and influence the molecular structure, whereas low temperature sintering can affect the density of specimens. In other words, it influenced electrical conductivity and strength. At the same time, during SPS, the geometrical properties of the tool limited the specimen size.Moulding pressure directly affected the density, and at the same time increased the hardness and electrical conductivity by increasing the pressure; increasing the temperature can reduce the flow resistance and shear force between the material particles, as well as reduce the friction coefficient between particles to overcome mould cracks. Although increased temperature reduced the external force, it also reduced the mechanical properties of the material. Therefore, balancing the moulding pressure and moulding temperature was the key to mould polymer composites. On the basis of the above research, we have reason to believe that the product of conducting Graphene/PEKK composite can be obtained by electromagnetic pulse compaction. Accordingly, the following research is discussed.Electromagnetic pulse processing equipment is a new technology equipment which uses electromagnetic energy to process metal materials and is applicable in the field of special processing technology. It is especially suitable for processing non-ferrous materials, such as aluminium, magnesium, and copper. It can weld all kinds of homogeneous or heterogeneous metal materials with conductive properties, which cannot be achieved by traditional technology.Herein, electromagnetic moulding experiments were performed with a machine, and the technological parameters are given in The electromagnetic moulding powder pressing machine used is shown in Graphene composite materials have high electrical conductivity, and local welding can be achieved during the process of electromagnetic pulse compaction. The electromagnetic pulse compaction of Graphene/PEKK composite materials was primarily divided into four stages as shown in During the electromagnetic-moulding process, the energy-conversion process was more complicated, and the mutual coupling of complex energy fields realized powder moulding. Previous research focused on the electromagnetic moulding of metal powder, whereas self-prepared Graphene/PEKK composite material with high electrical conductivity was studied in the current work. Theoretically, the moulding mechanism of a polymer composite powder is similar to that of electromagnetically formed metal powder. This research firstly determined the process parameters of electromagnetically formed conductive Graphene/PEKK composite powder through FE simulation analysis; that provided basic guidance for future experiments. This research used a loosely coupled method with the ANSYS/Multiphysics module to establish the current excitation. The electromagnetic field model was used to study the influence of discharge current on the magnetic field and magnetic pressure with magnetic pressure as the boundary condition in the MSC.Marc software (2019), as shown in The discharge time of the electromagnetic pulse compaction was shorter than the compaction moulding time. The influence of the elastoplastic deformation of powder on the magnetic-field distribution and the magnetic force was ignored. The FE model was established by the loose coupling method . FirstlyIn fact, during the electromagnetic pulse compaction processing, the electromagnetic force and discharge current had a pulse signal, as shown in Electromagnetic pulse compaction can achieve the parameters of the macroscopic powder-compaction process through experimental methods, but it cannot accurately describe the powder-compaction process. This research used a loosely coupled method with the ANSYS/Multiphysics module to establish current excitation. The electromagnetic-field model was used to study the influence of discharge current on magnetic field and magnetic pressure. With magnetic pressure as the boundary condition, in MSC.MARC, the powder module and Shima–Oyane yield criterion were used to establish the powder-compaction model.Yield criterion: Shima–Oyane (1)F=1γ. With increased discharge energy, densification also increased as shown in In the current research, the magnetic-pressure distribution on the bar was obtained using ANSYS. Magnetic pressure was used as the boundary condition of electromagnetic moulding to realize FE numerical simulation analysis. In general, through the simulation analysis of the electromagnetic pulse compacted Graphene/PEKK composite powder, determining the change trend of the process parameters during moulding was possible, but there was a problem of stress distribution at each node in the simulation, especially in the electromagnetic distribution. In the decay stage after the maximum pressure, the positions of different nodes rose to different degrees. This finding showed that when the powder was sintered and the discharge was over, the elastoplastic properties of the material itself changed, and the impulse force acquired inertia, the phenomenon of falling after rising. Therefore, in future research, a constitutive model research should be conducted for self-prepared composite-material powder to further optimize the simulation boundary conditions and improve the simulation accuracy.On the basis of above research, the following conclusions were obtained.The spark plasma sintering technique was used to process the self-prepared Graphene/PEKK polymer composite specimens to get the electrical conductivity of Graphene/PEKK composite; the specimen with diameter 12 mm and height 11 mm was polished off 0.5 mm  in the axial direction, and the electrical conductivity was about 0.014S/cm. Thus, 3.8% of the content of graphene in the Graphene/PEKK composite can be regarded as the conducting graphene composite electrode.The moulding of self-prepared Graphene/PEKK polymer composite powder, discharge voltage, discharge capacitance, and material constitutive model of self-prepared Graphene/PEKK composite powder were important factors affecting the moulding quality. According to the inherent adjustable range of the experimental equipment, four fixed parameters of discharge voltage  and discharge capacitance  were selected.Simulation analysis using ANSYS and MSC.Marc was proposed, and it used ANSYS to obtain the magnetic force. Additionally, the magnetic-force distribution on different points was regarded as the boundary conditions of MSC.Marc software. It obtained 16 groups of simulation results regarding the discharge current and magnetic force. The different stresses, strains, and density distributions on the electrode bar were determined by simulation analysis. When the energy was the maximum, the stress, strain, and density also arrived at the maximum within a few microseconds.The self-prepared Graphene/PEKK composite powder will be modified and commercialized, so the material constitutive model must be reconstructed, and the existing constitutive model cannot accurately predict stress, strain and compaction density during the moulding process, especially considering the lack of accuracy in the law of stress changes. Subsequently, we will finish the electromagnetic pulse compaction experiment for self-prepared Graphene/PEKK composite powder based on the process parameters supported by finite element numerical analysis.NoOriginal WordsAbbreviation1Poly (ether-ketone-ketone)PEKK2Poly (ether-ether-ketone)PEEK3Spark Plasma SinteringSPS4Lead Zirconate TitanatePZT5Magnetic Pulsed CompactionMPC6Dynamic Magnetic ConsolidationDMC7Direct CurrentDC8Differential Scanning CalorimetryDSC9Scanning Electron MicroscopySEM10Finite ElementFE


The possibility of graphene synthesis (the bottom-up approach) in plasma and the effective control of the morphology and electrical properties of graphene-based layers were demonstrated. Graphene flakes were grown in a plasma jet generated by a direct current plasma torch with helium and argon as the plasma-forming gases. In the case of argon plasma, the synthesized graphene flakes were relatively thick (2–6 nm) and non-conductive. In helium plasma, for the first time, graphene with a predominance of monolayer flakes and high conductivity was grown in a significant amount using an industrial plasma torch. One-dimensional (1D) flow modeling shows that the helium plasma is a less charged environment providing the formation of thinner graphene flakes with low defect density. These flakes might be used for a water-based suspension of the graphene with PEDOT:PSS : polystyrene sulfonate) composite to create the structures employing the 2D printing technologies. Good structural quality, low layer resistance, and good mechanical strength combined with the ability to obtain a large amount of the graphene powder, and to control the parameters of the synthesized particles make this material promising for various applications and, above all, for sensors and other devices for flexible electronics and the Internet of things ecosystem. Graphene, due to its unique electronic characteristics ,2, is on2-carbon atoms) the material for the printed electronics should have, in addition to good electronic characteristics (high conductivity and carrier mobility), (a) proven and scalable technology for producing graphene flakes; (b) a low cost of starting materials and manufacturing of the graphene suspension and ink; (c) high physical and mechanical stability of the starting materials and devices under the operating conditions; (d) formation, after the solvent evaporation, of the entire printed layer with good adhesion and interaction between the particles. Compliance of most of these properties is conditioned by the production of thin (preferably monolayer) flakes. However, the graphite exfoliation does not, as a rule, satisfy this important requirement. The way out of this contradiction is in changing the approach: in the transition from graphite exfoliation to the synthesis of the graphene flakes.Unlike the ideal graphene  ,18,19. GThe authors of  show thaThe present work is aimed at searching for the conditions for efficient bottom-up synthesis of the graphene flakes utilizing the DC plasma torch as well as at investigation of the structural and the electrical properties of the conducting layers produced via the printing technologies. As a result, we show that the graphene powder with a predominance of monolayer flakes might be successfully applied in the 2D printing technologies and, as an example, in the production of the conductive layers for a wide spectrum of applications: various sensors and other devices of flexible electronics.3.To synthesize the graphene, we applied the plasma-chemical approach based on the use of a 40 kW DC plasma torch with the expanding channel of the output electrode and the vortex stabilization of the plasma jet. The design feature of the plasma torch (expanding channel of the output electrode) and the tangential input make it possible to obtain stable plasma jets within a wide range of parametric studies . A more To study morphology and the local properties with high spatial resolution, we employed electron microscopy and Raman spectroscopy. We used the Hitachi S5500 scanning electron microscope (Hitachi High-Technologies Corp (Microscopy), Japan) with in-lens technology (STEM mode) and a Nova NanoSem 650 raster electron microscope  with the standard processing technique (SEM mode). We recorded the Raman spectra at room temperature on a INTEGRA Spectra spectrometer  using λ = 532 nm exciting radiation. We applied X-ray element microanalysis (EDAX)  to identify the chemical elements and to determine their quantitative content as well as the dynamic light scattering (DLS) method)  to measure the nanoparticle size. The DLS method makes it also possible to determine the diffusion coefficient of the dispersed particles in the liquid using analysis of the correlation function of the scattered light-intensity fluctuations. Then, from the diffusion coefficient, we calculated the nanoparticle radii. We employed a Solver PRO NT-MDT  scanning microscope to obtain atomic force microscopy (AFM) images from the surface of the examined films and substrates and to evaluate the sample thicknesses. The measurements were carried out in contact and semi-contact modes. A X-ray photoelectron spectroscopy (XPS) measurements were carried out in an ultrahigh-vacuum chamber equipped with an X-ray source  and a hemispherical energy analyzer Phoibos .We printed the films on DMP-2831 Dimatix FUJIFILM jet printer . After printing a layer, the film was subjected to a drying procedure at 60 °C to exclude the possible mixing effects. Then we studied the layer resistance of the fabricated films using a four-probe JANDEL equipment and the HM21 Test Unit at room temperature . To measure the current-voltage (I-V) characteristics of the fabricated structures, we employed a high-precision Keithley picoampere-meter  at room temperature, with Ag alloy contacts.When studying the cyclic deformations, we performed simultaneous testing of the electrical parameters of the material or structures utilizing the home-made installations applying tensile and compressive loads to the tested films. The strain was estimated using the well-known equation ε = (d + t)/2r where d is the flexible substrate thickness (d = 100 mm), t is the film thickness, and r is the substrate bending radius. The film thickness t < 500 nm is negligible as compared to that of the substrate.The EDAX results for both types of sample see b show th2/g. For comparison, [2/g.The specific surface area for both types of flakes measured by the standard Brunauer–Emmett–Teller (BET) method was ~500 mparison,  presents2/Si substrate.To prepare the suspensions, we mixed 10 mg of the dry graphene flakes powder with 50 mL of the 0.7:0.3 ethyl alcohol-water solution, and added the surfactant . After sonication and centrifugation aimed at separation into individual flakes, we deposited the suspension on the silicon surface. −1), G (1585 cm−1) 2D (2700 cm−1). Note that the D-line structure for the C-Ar film attests to the fact that the synthesized flakes contain not one but several layers [D/IG > 1 for the C-Ar film indicates a significantly higher defect concentration than the C-He film where ID/IG < 1.l layers ,35. The The C-He film created by the drops turned out to be loose and crumbled. The C-Ar suspension made it possible to form denser and truly solid film. The thickness of the films was large, of the order of a micron. After drying, we measured the layer resistance of the films using the four-probe head. The values obtained were 1.3 MΩ/sq and 5.0–5.6 MΩ/sq for the C-Ar and the C-He suspensions, respectively. Our attempt to consolidate the film by a mechanical action did not lead to a change in the C-Ar film resistance and destroyed the C-He film. Thus, in the C-He film flakes do not form a unified material due to the relatively high concentration of surfactants on the surface of the fine flakes; that very fact was the reason for the high resistance. In contrast, the C-Ar film was formed as a singular layer and its high resistance is most likely related to the high resistance of the particles themselves.2 hybridization. Also the C1s spectra of the both graphene flakes includes peaks centered at about 286.4, 287, and 289 eV, corresponding to C–O, –C=O and –COO− groups, respectively [Crystal phase of the obtained materials were determined by XPS. XPS spectra for C-Ar and C-He samples are given in ectively ,37,38. TTo improve the conditions for the C-He film formation from the individual particles, we added to the above-described suspension a 1% PEDOT:PSS : polystyrene sulfonate composite) water solution, the total composition being 2:1 or 0.05 weight% in the film. This led to radical changes in the formed film quality. Here, for the C-He film, we obtained the layer resistance of 600–800 Ω/sq (for the film of submicron thickness) and 1.4–2.6 kΩ/sq for the thin (about 200 nm) film. For comparison, a thick PEDOT:PSS film (more than a micron) had the resistance of 3.6–4.2 kΩ/sq, and the thinner films (~200 nm) with the resistance of ~10 kΩ/sq. For the composite film with the C-Ar suspension, the resistance coincided with that of the PEDOT:PSS, that is, the contribution of the C-Ar particles was not noticeable.n = 3.1 × 1015 cm–2: it corresponds to the volume plane of ~7 × 1018 cm–3. For a thinner film, n = 3 × 1013 cm–2. The carrier mobility in the films turned to be relatively high: μ = 6–90 cm2/Vs. The carrier mobility values of ~90 cm2/Vs are usually obtained for the 1–2 monolayer thick graphene particle films [We performed the Hall measurements  for the C-He based composite film, its thickness being about 5 μm, the sheet concentration was le films .Numerical simulation of the plasma flow was performed using the quasi-one-dimensional approach when the two-dimensional system of equations was transformed into the one-dimensional system employing integration along with one of two coordinates under the given profiles of velocity and temperature . Plasma 2, C3, C3H, C2H2, and later at the temperature 3270 K the condensation of carbon into graphene/graphite (CGr) commences. Similar curves for the case of argon plasma are also given in 3, and Cgr). The condensation begins a little bit earlier at 3304 K. It means a longer sojourn of particles under high temperatures. As a result, temperature profiles along the jet axis and corresponding equilibrium plasma compositions were calculated. To print on the 2D printer, we prepared the ink from the C-He: PEDOT:PSS conductive composite suspension. We printed using the composite ink made of the C-He suspension kept for 8 months. Here, to obtain a homogeneous composite suspension, we only applied a brief ultrasound and centrifuge treatment. As a result, we printed the resistive structures on two types of substrate . The insert in It is an important fact that printing of the films and practically transparent layer using the C-He suspension without PEDOT:PSS (five printing layers) on the paper results in obtaining the conductive track, several nanometers thick, with the resistance of 470 GΩ/sq, without transition to the composite films.2/Si substrate. Note that the layers are porous and straight. In general, mechanical testing of such layers, both on the paper and on the PET (bends of the printed structures) demonstrates the formation of the unified layer. Deformations did not lead to the printed film destruction. A comparison of the resistances of the films obtained from the C-M particles with the C-He-based composite films  and some scattering in the resistance values (10–15%) at the repeated measurements.To obtain graphene or multigraphene within a short period, various plasma generators are engaged ,40,41,42The bottom-up synthesis method implies that the nanostructures are synthesized by stacking atoms onto each other: this gives rise to the crystal planes; and the crystal planes further stack onto each other resulting in the nanomaterial synthesis. Despite its short history (compared to the other techniques), the plasma-based technologies have already achieved successes for the synthesis of the carbon-based materials ,46,47. IAnalysis of electrical properties and the search for electronic applications are very poorly represented in the available literature. The exception is an electrochemical application in fuel cells , lithiumThe study of their structural flexibility shows both good adhesion to the composite film, to PET, and the stable layer properties under the bending up to 1.5 mm (tensile strain ~3%), thus providing the prospects of such a material and structures for flexible electronics. The flexibility of films created from C-M suspension was studied where changes in the resistance and some scattering in the resistance values under repeated measurements (within 30% for strain ~2%)  were deTo the best of our knowledge, this work paves the path to use of these kind graphene flakes in printed flexible sensors, logics, and other devices aimed at use in the continuously expanding Internet of Things ecosystem.We show that graphene flakes synthesized in helium plasma with the propane-butane mixture addition can be used to obtain a water-based graphene suspension or a composite suspension with PEDOT:PSS to create structures using the 2D printing technologies. The low thickness (from a monolayer to 2 nm) and the high conductivity of the layers obtained from such particles is one of the important and attractive parameters of such particles. For a bottom-up synthesis approach, the formation of a material with that low density of defects is not an easy task. On the contrary, the particles synthesized in argon plasma are thicker, more defective, and non-conductive.One-dimensional flow modeling shows that in the case of argon the environment encloses more radicals, electrons, and ions compared with helium. This is the precondition to increase the number of condensed cycles and side reactions, favoring the increase in size and thickness of flakes and defect density. In contrast, helium plasma leads to the creation of graphene flakes C-He with more promising application properties.Some test structures were fabricated from C-He suspension with the use of 2D printed technologies. The predominance of monolayer graphene flakes created in helium plasma provides the unique stability of the water-based graphene inks (at least 8 months). The composite graphene: PEDOT:PSS films have a smooth surface and a uniform structure. The layer resistance of the relatively thick composite layers obtained by droplets equals 600–800 Ω/sq for the submicron thickness film and to 1.4–2.6 kΩ/sq for a thin film (about 200 nm). The resistance of the ~80–500 nm thick layers created by the 2D printing on the PET was equal to 70–2000 Ω/sq: significantly lower than that of the graphene flakes created by graphite exfoliation. In general, good structural quality, low layer resistance, sufficiently high carrier mobility, and good mechanical strength combined with the possibility to obtain a large amount of the graphene powder, and the possibility to control the parameters of the synthesized particles, makes this material promising, above all, for resistive sensors. Our results contribute to the direct integration of the graphene structures into the 2D printing technology on flexible substrates for nanoelectronics, sensors, biomedical, and optoelectronic components and nanodevices.


As pump intensity increased from 0 to 15 W/mm2, we observed a loss–gain–loss transition process, which was discussed in detail through coupled-mode theory. In addition, amplification at different frequencies was achieved by merely re-optimizing the geometric parameters of the dielectric resonators. This study offers an effective solution for enhancing terahertz radiation and developing terahertz lasers.Graphene under optical pump has been shown to be an attractive gain medium with negative dynamic conductivity at terahertz frequencies. However, the amplification over a monolayer graphene is very weak due to its one-atom thickness. In this paper, the proposed graphene-dielectric reflective metasurface effectively improved terahertz field localization and enhanced coherent amplification. The amplification coefficient of 35 was obtained at 3.38 THz at room temperature with an infrared pump intensity of 8 W/mm Terahertz (THz) radiation from 0.1 to 10 THz is the least studied subrange on the electromagnetic spectrum. Many efforts have been devoted to the generation and detection of THz waves, which promotes the rapid development of THz imaging, THz non-invasive detection, and next-generation wireless communication technology . Among ohν < 2EF), is slightly absorbed by graphene due to the intraband carrier transition. In contrast, graphene shows universal absorption of 2.3% from the interband carrier transition when hν > 2EF. Besides the absorption modulation in graphene, the study by Otsuji, T., et al. showed that a sufficiently strong optical pump [EF−ħω/2 through carrier–carrier scattering, after which they occupy the energy states closer to the Dirac point through the emission of a series of optical phonons [Graphene, composed of two-dimensional (2D) carbon atoms arranged in a hexagonal lattice, exhibits many fascinating properties ,8, inclucal pump ,13 or cucal pump  may inve phonons ,16,17. T phonons  and infr phonons , indicate2/2ħ. The one-atom thickness further limits the interaction of graphene with the THz waves, leading to a negligible amplification effect. The amplification can be enhanced by using multiple layers of graphene [However, the negative dynamic conductivity is one or two orders smaller than the characteristic conductivity graphene ,19,20, bgraphene , and by graphene ,23,24. Tgraphene . HoweverIn this paper, we studied the enhanced THz amplification when the optically pumped graphene was combined with dielectric metasurfaces. Without material loss, the high-Q resonance of the dielectric resonator together with the back mirror significantly enhanced the field intensity around and outside of the graphene, leading to power amplification coefficient of 35 at room temperature with monolayer graphene. The complex conductivity of graphene was always considered. The transition from absorption to gain, with different pump intensity, was studied in detail based on the coupled-mode theory. The gain frequency was changed by optimizing the geometry of the dielectric resonators.kB is the Boltzmann constant, ħ is the Planck’s constant, ω is the electromagnetic wave frequency, T is the temperature, and Fermi energy EF is related to the pump intensity byα is the fine-structure constant, νf is the Fermi velocity, and I is the pump intensity. Here, the relaxation time λ was 1.5 μm.The dynamic conductivity of graphene under optical pump can be described by : (1)σ=σiσintra is always positive. The real part of σinter in the Equation (3) assumes negative values when the photon energy is less than twice that of the Fermi energy (ħω < 2EF). The conductivity met this condition when graphene was pumped at high pump intensity I (see Equation (4)). When the negative σinter is large enough to cancel the positive σintra, the total conductivity becomes negative. However, with a further increase in pump intensity, σinter tended to saturation and σintra increased. The total conductivity became positive again. −5 S. At a fixed THz frequency, such as 4 THz  with the requirement of a slightly higher pump intensity.As one can see from Equation (2), the real part of the conductivity hd. The transmission line model of this structure is shown in hd (air was considered for simplicity) was set at 28 μm. The transmission line was shorted by the back mirror. The reflection coefficient of the normal excitation can be calculated by [We first considered a simple structure of optically pumped graphene sheet on top of a back mirror. The graphene and the mirror were separated by a distance of lated by :(5)r=1η0Bd = cos (khd)/((tan (khd/2) − 2η0 × sin (khd))) is the susceptance of the short-circuited transmission line, whose variation with frequency is shown in r1 from Equation (5) is shown in the dB = 0, i.e., the air thickness hd = λ/4. The peak reflection coefficient is a finite number instead of infinity due to the limited precision of the data points. However, the actual conductivity −5 S . The periodic boundary conditions were applied at the x and y boundaries and perfect electric conductor (PEC) at the −z boundary, while the Floquet port was adopted at the +z boundary for both incidence and detection of the electric field Ey. The simulation results perfectly agreed with the theoretical ones in Here,  −10−5 S , which ip = 51.5 μm. The dielectric resonator was a split-ring resonator (SRR) made of silicon, with inner radius rin = 6.8 μm, outer radius rout = 13.7 μm, thickness hSi = 28 μm, and opening angle θ = 14°. The opening was symmetric with respect to y = 0. The surrounding medium was air and would later be replaced with low-index dielectric toward the end of the study. This graphene-dielectric metasurface was illuminated by y-polarization  plane wave. The transmission responses of the pure SRR array without graphene and the back mirror is investigated in f1 = 3.36 THz and f2 = 3.5 THz. The corresponding near-field distributions at f1 and f2 were investigated. The electric fields at both frequencies were well confined in the opening gap of SRR as can be seen in f1 than at f2, as the Q factors of the two resonances were around 170 and 17, respectively. The high-Q resonance at f1 showed great potential to enhance the interaction of THz waves and graphene once the graphene was attached to the dielectric metasurface.In order to enhance the interaction between the gain medium and the THz waves, the monolayer graphene was attached to an array of dielectric resonators , and thef1. Graphene was lossy with positive f1. The corresponding field intensity at the top interface  as ,30,31: rin = 7.59 μm, rout = 12.36 μm (2), rin = 10.43 μm, rout = 15.96 μm (3), rin = 18.29 μm, and rout = 23.00 μm. All of them had the same opening angle of 14°. The reflection amplitude as a function of frequency is plotted in I = 0.35 W/mm2 and T = 77 K, an amplification coefficient of 55.6 was obtained at 1.75 THz; after, we re-optimized the lattice constant and radius . As the temperature moved away from 77 K, the gain effect gradually decreased, and the operating frequency also shifted slightly. As mentioned earlier, this is mainly due to the temperature dependence of both the real and imaginary parts of graphene conductivity.In the last step, we embedded the silicon SRRs into poly(methyl methacrylate) (refractive index of 1.48) in the reflective metasurface, and kept their top interfaces aligned so that the monolayer graphene could still touch the top interface of SRRs. We optimized the structure to maximize the reflection gain when the pumping intensity was 8 W/mm2. Within the coupled-mode theory, we analyzed the mechanism of loss and gain of the hybrid metasurface with different pump intensities. In addition, THz amplification frequency was widely designable by controlling the split-ring dimensions.In summary, we proposed and numerically investigated the amplification of terahertz (THz) radiation based on photo-pumped graphene-dielectric hybrid metasurface. The initial study showed that the monolayer graphene with back mirror was not enough to stimulate sufficient amplification no matter the pump intensity. Graphene was then attached to the high-Q silicon split-ring reflective metasurface, so that the strong field localization enhanced the interaction between terahertz wave and graphene. The amplification coefficient of 35 was obtained at the resonance frequency of 3.38 THz at room temperature with an infrared pump intensity of 8 W/mm


Since its discovery in 2004 by Novoselov et al., graphene has attracted increasing attention in the scientific community due to its excellent physical and chemical properties, such as thermal/mechanical resistance, electronic stability, high Young's modulus, and fast mobility of charged atoms. In addition, other remarkable characteristics support its use in analytical chemistry, especially as sorbent. For these reasons, graphene-based materials (GBMs) have been used as a promising material in sample preparation. Graphene and graphene oxide, owing to their excellent physical and chemical properties as a large surface area, good mechanical strength, thermal stability, and delocalized π-electrons, are ideal sorbents, especially for molecules containing aromatic rings. They have been used in several sample preparation techniques such as solid-phase extraction (SPE), stir bar sorptive extraction (SBSE), magnetic solid-phase extraction (MSPE), as well as in miniaturized modes as solid-phase microextraction (SPME) in their different configurations. However, the reduced size and weight of graphene sheets can limit their use since they commonly aggregate to each other, causing clogging in high-pressure extractive devices. One way to overcome it and other drawbacks consists of covalently attaching the graphene sheets to support materials . Also, graphene-based materials can be further chemically modified to favor some interactions with specific analytes, resulting in more efficient hybrid sorbents with higher selectivity for specific chemical classes. As a result of this wide variety of graphene-based sorbents, several studies have shown the current potential of applying GBMs in different fields such as food, biological, pharmaceutical, and environmental applications. Within such a context, this review will focus on the last five years of achievements in graphene-based materials for sample preparation techniques highlighting their synthesis, chemical structure, and potential application for the extraction of target analytes in different complex matrices. Over the last decades, nanotechnology has become a promising tool in relevant scientific fields, allowing humanity to reach top levels of quality in several areas such as engineering, chemistry, medicine, and sports, among others  distributed along with the thinnest structure of the negligible mass, but high Young's modulus, as already discovered , transparency, and impermeability to gases must be underscored  still represents a hurdle to its broad implementation. This occurs because the most utilized manufacturing approach is based on the graphite top-down mechanical exfoliation process by adhesive tape , only the external surface is available for such interaction, which potentially diminishes extraction performance due to this steric hindrance associated. Additionally, the delocalized π-electron system favors electrostatic interaction between the graphene and molecules that possess aromatic rings in its structure.For this reason, prevalent contaminants such as pesticides, preservatives, pharmaceuticals, and veterinary drugs can be remediated from the environment by using GBMs  is a 2D monolayer of carbon atoms covalently bonded in a honeycomb pattern, displaying a flat sheet conformation  can take off the graphene layers from the surface of a graphite piece. One of the advantages of mechanical exfoliation is the possibility of different pile-up layers of other 2D materials with several graphene heterostructures  is the most popular method to obtain graphene. As shown in Conversely, the bottom-up approaches are another alternative to synthesize high-quality graphene layers. The leading methods used include pyrolysis, chemical vapor deposition (CVD), plasma synthesis, and epitaxial growth  is like a graphene sheet functionalized on both sides with several oxygenated functions such as hydroxyl, carboxyl, and epoxy. These functions impose a hydrophilic character to GO; as a consequence, the interaction between layers is weaker compared to graphene, making GO an easily exfoliated material. GO structure depends principally on the purification methods . Thus, they can be currently used in several applications  yields a low substitution degree due to their stable carbon conjugation. However, covalent functionalization can be done by taking advantage of the oxygenated reactive groups of the graphene oxide (GO) sheets. Therefore, in the same way as the chemical reduction of graphene oxide, the hydroxyl, carboxyl, and epoxy groups can be covalently replaced by other functional groups. The GO surface modification with aliphatic amines to form an amide bond is one of the most common strategies  are by far the most commonly used sorbent in solid-phase extraction (SPE) and chromatographic separations. Apart from the conventional C8/C18 reversed phases, today mixed-mode polymeric sorbents are widely used in SPE because they present interactions with several compounds and better performance compared to the conventional ones, and they are also commercially available  for catechins being 11 times higher compared to GO sheets (18.7 mg g−1) and other rGO-amino groups . Hence, tributylamine-rGO was employed as a sorbent in a modified QuEChERS  method achieving a higher clean-up performance compared to traditional sorbents as PSA, C18, and graphitized carbon black (GCB), regularly used in QuERChERS , which allows the use of graphene sorbents in small quantities (<100 mg)  for the extraction of aflatoxins in corn samples. Calix[4]arene is a macrocyclic molecule of four phenol units bonded by methylene bridges, which can favor the extraction of aflatoxins by H-bonding, hydrophobic, and π-π interactions. The recoveries of aflatoxins (AFs) obtained employing cellulose acetate CFs (35–41%), polydopamine coated CFs (PDA-CFs) (45–55%), calix[4]arene-GO-CFs (60–72%), GO/PDA-CFs (63–82%), and calix[4]arene-GO/PDA-CFs (86–94%) as SPE sorbents showed that together calix[4]arene and GO increased the efficiency of the sorbent phase , which are cyclic oligosaccharides formed by starch enzymatic degradation, and are linked by several α-1,4-anhydroglucopyranose. In nature, they are made up of 6, 7, or 8 glucose units and categorized as α, β, and γ-CD, respectively. CDs have cone shapes with a hydrophobic cavity and a hydrophilic external surface. This specific structure allows them to form inclusion complexes with specific molecules such as polyphenolics compounds through hydrogen bonding, hydrophobic, and Van der Waals interactions  ranging from 0.9955 to 0.9998. The LODs and LOQs for the nine analytes ranged from 1.1–60.4 to 2.7–170.5 ng L−1, respectively; RSD was 2.2–9.6%, and enrichment factors obtained from 22.5 to 1307.5. This high enrichment factor is attributed to the combined advantages of β-CD and GO. When compared with the commercial fibers and some published methods, the GO/β-CD sol-gel coating fiber showed a higher extraction efficiency, except for those organophosphate flame retardants containing a benzene ring. Similarly, Cao et al. combined the advantages of graphene and cyclodextrins with ionic liquids and ILs , which was used as a sorbent to extract plant growth regulators from vegetable samples using magnetic solid-phase extraction (MSPE) followed by UHPLC-MS/MS analysis. This approach showed fast separation, high surface area, high adsorption capability, and environmental friendliness. The comparison between Fe3O4@SiO2/GO, Fe3O4@SiO2/GO/β-CD, and Fe3O4@SiO2/GO/IL showed that Fe3O4@SiO2/GO/β-CD/IL had higher extraction efficiency and selective adsorption capacity.The combination of graphene and cyclodextrins properties becomes the resulting material attractive to be employed in sample preparation techniques. An interesting application was carried out by Deng et al. The novel β-CD–GO-coated SPME fiber was prepared using a sol-gel technique and immobilizing onto a pre-functionalized stainless steel wire  below 8.1%.For food analysis, β-CD combined with GO were used in the sample preparation during the analysis of organochlorine pesticide residues in honey . This trend is justified by the presence of epoxy and -COOH groups on the GO surface, favoring the bonding with the CDs. Although some works reported the employment of graphene combined with cyclodextrins as sorbent, these materials were obtained by graphene oxide reduction  which is considered an efficient and environment-friendly sample preparation technique  and maghemite (γ-Fe2O3) as the magnetic nanoparticles (MNPs) more frequently used , cobalt, (Co), and nickel (Ni) oxides, highlighting the magnetite . As an example, Chandra et al. prepared an rGO/Fe3O4 for arsenic removal from surface water samples  the chemical co-precipitation and (ii) the hydrothermal synthesis. The chemical co-precipitation is based on the deposition of iron ions over the nanosheets by adding an alkaline solution to an aqueous dispersion of graphene Fesolution . As Fe3+3O4 particles on the nanosheets. Within such a context, hydrothermal synthesis has been proposed as an alternative to yield sorbents with better Fe3O4 particles distribution with more G exposed adsorption sites and then, improved adsorption capacity. This method is based on the reduction of Fe3+ and GO in sodium acetate and polyethyleneglycol in an autoclave at elevated temperature . In this case, before graphene anchoring, Fe3O4 particles are modified with a silane coupling agent, consisting of tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) , deep eutectic solvents, boronate affinity materials (BAM), supramolecules , aptamers, polymers, and metal-organic frameworks (MOFs). For those magnetic GBMs, their preparation and applications were recently comprehensively reviewed by Li et al. They provided a summary of the state of the art of them, highlighting application as MSPE sorbents of organic compounds, biomolecules, and metal ions  combined with GBMs. In this context, MIPs are prepared from a template (mold) which behaves structurally similarly as the target analytes, to achieve a selective interaction through a template-complementary binding site . In this section, their application in the field of sample preparation combined with GBMs is covered, highlighting preparation strategies of aqueous-recognition MIPs cleverly to achieve such functionalization  on magnetic graphene oxide (GO-Fe3O4) surface to remove 17β-estradiol (17β-E2) from food samples. The resulting sorbent has shown a functional extraction recovery of 84.20% at a low concentration level of 0.5 μmol L−1. Furthermore, due to the magnetic properties of the GO-MIP-Fe3O4, a simple, fast, and efficient separation of 17β-E2 were achieved, suggesting the combination between these materials as an excellent way to obtain hybrid sorbents. Following the same trend, Barati et al. (3O4 particles (GO-MIP-Fe3O4). In this case, the author worked with natural samples, specifically alkaloids (evodiamine and rutaecarpine) extract from Evodiae Fructus, suggesting a great versatility of such magnetic GO-MIP sorbent. Also, its analytes' recovery achieves values over 82% considering as good values from our viewpoint.An attractive approach to obtain high performative material involves the use of the graphene-based MIP functionalized with a magnetic particle to favor the extraction and sorbent isolation. Within such a context, Ning et al.  proposedi et al.  synthesiMoreover, In 1914, a work with ionic liquids (ILs) was reported for the first time, although at that time, the author had no idea of the importance that these would take in the scientific area almost a century later Walden, . From thThe ILs are compounds with a dual nature acting as nonpolar for nonpolar analytes and, inversely, for those with a strong proton donor group, depending on the separation mechanism that it presents  of controlled size by a co-precipitation method to obtain the Fe3O4-SiO2-G-PIL hybrid sorbent; the obtained material was used to determine preservatives in vegetables by QuEChERS following GC-MS analysis. In this study, it was possible to take advantage of the functional properties related to magnetic nanoparticles and also by its coupling to the GO with the polymeric ILs . Moreover, the method's detection limits varied between 0.82 and 6.64 μg kg−1 for the 20 preservatives studied. Similarly, Tashakkori et al. (−1) and the lab-made SPME fibers being used more than 120 times, which is a useful feature when compared with the commercially available ones such as PA and CAR/PDMS. These results reinforce the great interest in developing hybrid GBMs combined with ILS.Other interesting applications based on IL-GBMs include work published by Chen Y. et al. . They syi et al.  synthesi+Br−)-GO-Sil] as a hybrid IL sorbent to extract flavonoids in urine samples. They synthesized the material by an interesting process consisting of an in situ radical chain-transfer polymerization and then in situ anion exchange. In this case, the procedure started with the silica coating by GO, using a manufacturing layer by layer fabrication method. Then, the poly (VHIm+Br−)-GO-Sil anion was transformed into hexafluorophosphate (PF6−) by in situ anion exchange. The method based on SPE-HPLC-UV showed acceptable extraction recoveries for four flavonoids, with limits of detection in the range of 0.1–0.5 μg L−1. The proposed material showed ecological and cost-effective advantages. It can be applied successfully to the extraction and enrichment of flavonoids in human samples, even allowing the study of metabolic kinetics.Additionally, biological samples were analyzed by Ding et al. . They fuFinally, considering other types of samples, an interesting study published by Zhou et al.  was carrApart from the interesting application herein discussed, other relevant studies based on hybrid sorbents combining IL and GBMs are shown in 30) between the graphene oxide (GO) nanosheets and further support this onto polycaprolactone nanofibers, aiming to enhance temperature, and pH resistance to the sorbent phase. This novel material was applied in SPE extraction of four statin drugs showing acceptable analytical performance. The author emphasized the excellent ability of this sorbent to interact with acidic polar species, possibly due to the resistance to pH variations. Another interesting application was performed by Li et al. , due to the hydroxy and amine groups to which the ions bind metallic. This result demonstrates the potential of this hybrid sorbent material in the cleaning processes of contaminating metal ions in complex matrices such as water. Additionally, the authors emphasize its low producing cost as a useful characteristic since commercially available sorbents often are expensive and non-reusable.This section aims to present some alternative graphene-based materials that could be an alternative for the sample preparation in the future. For this reason, there are not many publications apart from the materials already discussed in the previous sections. An original example recently published by Tahmasebi  consistei et al.  whose sy30 insertions, can enhance the interaction with the π-electron system onto the GO surface, resulting in enhanced extraction performance. Similarly, Amiri et al.  selectivity for specific analytes and thus present chemical inertia for matrix interferents; (ii) good recovery and enrichment factors; and (iii) simple and non-expensive production. Once fulfilling these requirements, graphene-based materials have increasingly seemed to be the right candidate since their first application in sample preparation around 2011. Its large surface area, together with the π-π delocalized electron system, aid in improving so much the extraction performance of target compounds possessing aromatic rings as several chemical classes  as herein discussed on section Graphene and Graphene Oxide.in silica reported this result.Although the successful application in its “bare” form (G and GO), sometimes the functionalization of them seems to enhance even more the performance of such sorbents. For this reason, in this work, we have shown several different applications based on the use of hybrid materials consisting of GBMs anchored to other extractive sorbents such as alkyl and aryl groups, cyclodextrins, magnetic particles, molecularly imprinted polymers, ionic liquids, and among others. The functionalization is often achieved by forming covalent or hydrogen bondings, using sol-gel or polymerization router, or even electrochemical deposition. This interesting approach is encouraged by the possibility to ally the advantages of each class in only one. Apart from this goal, the clogging and backpressure problems often related to G and GO when packed in sorbent-based sample preparation techniques are overcome by the addition of other compounds. For example, several works underscored in sections Alkyl and Aril Groups, Cyclodextrins, and Magnetic Materials based on magnetic particles, or anchoring Similarly, increasing on extraction selectivity and by consequence, performance is observed when GBMs were functionalized with both MIPS or the tunable-ILs, as can be seen in sections Molecularly-Imprinted Polymers and Ionic Liquids. This background explains the significant tendency to work with hybrid graphene-based materials instead of its bare form. GBMs are an excellent sorbent, often surpassing the commercially available phases such as C8 and C18.After all, by assessing the recent literature and considering the vast number of applications involving graphene in the sample preparation arena, as herein discussed, an increasing tendency to expand the footprint of GBMs functionalized with several classes must continue in the years to come. This conclusion is mainly supported by the unique favorable GBMs physical-chemical properties, which—together with the advancements on the materials synthesis routes, extraction techniques, and related subjects—evidenced this field as one of the most critical developments in the sample preparation area nowadays. Also, an increasing number of papers reporting the employment of hybrid GBMs and miniaturized sample preparation techniques must be expected. This trend can be projected considering the high potential obtained by combining the well-established benefits of automation/miniaturization with the use of more selective and performative materials, possibly leading to greener sample preparation techniques by following the Green Chemistry concept.EM wrote sections Introduction, Miscellaneous, and Concluding Remarks, as well as edited the whole manuscript. KM-C wrote sections Graphene and Graphene Oxide and Alkyl and Aril Groups, built The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.