Journal articles: 'Graphene dispersion'

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Wu, Li Li, Xiang Lv, and Chao Can Zhang. "Preparation and Dispersion of Polyacrylamide-Grafting Graphene." Advanced Materials Research 306-307 (August 2011): 1360–63. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.1360.

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Graphene has weak interface compatibility to its solvent, and it is easy to get agglomeration in the solvent. In this paper, graphehe is modified by grafting method to improve the aqueous dispersion. Oxidized graphene is firstly prepared by modified Hummer’s method and supersonic exfoliation. Then oxidized graphene is grafted by hydrophilic polymer polyacrylamide (PAM) and deoxidized into modified graphene. The product is characterized by TEM, FTIR, Raman spectroscopy and sedimentation test. And the result demonstrates a modified graphene is successfully synthesized and its compatibility to the media is enhanced as assumption. When the ratio between PAM and graphene is 1:10, the suspension absorbance is improved as twice as common graphene’s. Meanwhile the concentration of graphene in suspension can reach 0.05mg/ml without any agglomeration.

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Касцова, А. Г., Н. В. Глебова, А. А. Нечитайлов, А. О. Краснова, А. О. Пелагейкина, and И. А. Елисеев. "Электронная спектроскопия графена, полученного методом ультразвукового диспергирования." Письма в журнал технической физики 48, no. 24 (2022): 23. http://dx.doi.org/10.21883/pjtf.2022.24.54019.19268.

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Technology of obtaining graphene by means of ultrasonic dispersion of thermally expanded graphite in the presence of a surface-active polymer Nafion is presented. The technology makes it possible to obtain large amounts of low-layer (1-3 layers) graphene in a relatively short time. An approach to control the dispersion process based on UV spectroscopy of dispersions is described. A mechanism is proposed for the effect of a surface-active polymer on the production of low-layer graphene by ultrasonic dispersion.

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Perumal, Suguna, Raji Atchudan, and In Woo Cheong. "Recent Studies on Dispersion of Graphene–Polymer Composites." Polymers 13, no. 14 (July 20, 2021): 2375. http://dx.doi.org/10.3390/polym13142375.

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Graphene is an excellent 2D material that has extraordinary properties such as high surface area, electron mobility, conductivity, and high light transmission. Polymer composites are used in many applications in place of polymers. In recent years, the development of stable graphene dispersions with high graphene concentrations has attracted great attention due to their applications in energy, bio-fields, and so forth. Thus, this review essentially discusses the preparation of stable graphene–polymer composites/dispersions. Discussion on existing methods of preparing graphene is included with their merits and demerits. Among existing methods, mechanical exfoliation is widely used for the preparation of stable graphene dispersion, the theoretical background of this method is discussed briefly. Solvents, surfactants, and polymers that are used for dispersing graphene and the factors to be considered while preparing stable graphene dispersions are discussed in detail. Further, the direct applications of stable graphene dispersions are discussed briefly. Finally, a summary and prospects for the development of stable graphene dispersions are proposed.

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Li, Liangchuan, Ming Zhou, Long Jin, Youtang Mo, Enyong Xu, Huajin Chen, Lincong Liu, Mingyue Wang, Xin Chen, and Hongwei Zhu. "Green Preparation of Aqueous Graphene Dispersion and Study on Its Dispersion Stability." Materials 13, no. 18 (September 14, 2020): 4069. http://dx.doi.org/10.3390/ma13184069.

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The large-scale preparation of stable graphene aqueous dispersion has been a challenge in the theoretical research and industrial applications of graphene. This study determined the suitable exfoliation agent for overcoming the van der Waals force between the layers of expanded graphite sheets using the liquid-phase exfoliation method on the basis of surface energy theory to prepare a single layer of graphene. To evenly and stably disperse graphene in pure water, the dispersants were selected based on Hansen solubility parameters, namely, hydrophilicity, heterocyclic structure and easy combinative features. The graphene exfoliation grade and the dispersion stability, number of layers and defect density in the dispersion were analysed under Tyndall phenomenon using volume sedimentation method, zeta potential analysis, scanning electron microscopy, Raman spectroscopy and atomic force microscopy characterization. Subsequently, the long-chain quaternary ammonium salt cationic surfactant octadecyltrimethylammonium chloride (0.3 wt.%) was electrolyzed in pure water to form ammonium ions, which promoted hydrogen bonding in the remaining oxygen-containing groups on the surface of the stripped graphene. Forming the electrostatic steric hindrance effect to achieve the stable dispersion of graphene in water can exfoliate a minimum of eight layers of graphene nanosheets; the average number of layers was less than 14. The 0.1 wt.% (sodium dodecylbenzene sulfonate: melamine = 1:1) mixed system forms π–π interaction and hydrogen bonding with graphene in pure water, which allow the stable dispersion of graphene for 22 days without sedimentation. The findings can be beneficial for the large-scale preparation of waterborne graphene in industrial applications.

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Takeda, Shimpei, and Yuta Nishina. "Structural Optimization of Alkylbenzenes as Graphene Dispersants." Processes 8, no. 2 (February 19, 2020): 238. http://dx.doi.org/10.3390/pr8020238.

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Among the several methods of producing graphene, the liquid-phase exfoliation of graphite is attractive because of a simple and easy procedure, being expected for mass production. The dispersibility of graphene can be improved by adding a dispersant molecule that interacts with graphene, but the appropriate molecular design has not been proposed. In this study, we focused on aromatic compounds with alkyl chains as dispersing agents. We synthesized a series of alkyl aromatic compounds and evaluated their performance as a dispersant for graphene. The results suggest that the alkyl chain length and solubility in the solvent play a vital role in graphene dispersion.

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Azmi, Amirul Hadi, Shaharin Fadzli Abd Rahman, and Mastura Shafinaz Zainal Abidin. "Microcrystalline Cellulose as Graphite Exfoliation Agent and its Effect on Electrical Conductivity." Solid State Phenomena 317 (May 2021): 144–51. http://dx.doi.org/10.4028/www.scientific.net/ssp.317.144.

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Graphene has drawn a lot of attention as a promising material for a conductive ink due to its high electrical conductivity and abundant source. Selection of solvent for ink formulation is crucial to obtain the desired result. In this work, microcrystal cellulose solution is investigated as alternative solvent for conductive ink formulation. Although the viability of the microcrystal cellulose solution was already presented in other works, further thorough and systematic study is highly required. Cellulose solution was prepared using microcrystalline cellulose and sodium hydroxide aqueous solution. Dispersions with different graphite-to-cellulose ratio were prepared. The exfoliation process was for sonication times of 8, 16, 24 and 32 hours. For Raman spectroscopy and 4-point probe measurement, graphene thin film was formed by drop-casting 20μl dispersion on glossy paper. Sample with low graphite-to-cellulose ratio exhibited more significant reduction in unexfoliated graphite content over the sonication time. The sufficient amount of cellulose in the dispersion leads to more effective exfoliation process. According to analysis on the Raman spectra, the exfoliated graphite could be classified as few-layer graphene with low defect content. The drop-casted thin film from dispersion with ratio of 20:1 showed sheet resistance lesser than 100 Ω/sq. The obtained results confirmed the effectiveness of microcrystal cellulose as the agent for exfoliation process.

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Liu, Hong Bo, Wu Ying Zhang, Feng Lin, and Hong Da Cao. "Comparison and Characterization of Two Preparation Methods of Graphene Oxide." Advanced Materials Research 989-994 (July 2014): 125–29. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.125.

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The graphene oxides were prepared form graphite by thermal expansion and ultrasonic dispersion. The structure of graphene oxides was characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectra. The difference of structure of graphene oxides by two preparation methods was compared. The measurement of FTIR and XRD showed the graphite was completely oxidized. The graphene oxide prepared by thermal expansion would lose large number of active functional groups, such as hydroxyl, carboxyl group, et al. However, the graphene oxide prepared by ultrasonic dispersion can retain these active functional groups. These active functional groups will be benefit to chemically modify the graphene oxides and prepare the polymer/graphene nanocomposites.

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Hung, Wei-Song, Tzu-Jen Lin, Yu-Hsuan Chiao, Arijit Sengupta, Yi-Chen Hsiao, S. Ranil Wickramasinghe, Chien-Chieh Hu, Kueir-Rarn Lee, and Juin-Yih Lai. "Graphene-induced tuning of the d-spacing of graphene oxide composite nanofiltration membranes for frictionless capillary action-induced enhancement of water permeability." Journal of Materials Chemistry A 6, no. 40 (2018): 19445–54. http://dx.doi.org/10.1039/c8ta08155g.

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Zhao, Hai Chao, Yu Lin Qiao, and Yan Zang. "Research on Graphene Preparation by Liquid Phase Ultrasonic Exfoliation and Antifriction Performance in Water." Key Engineering Materials 609-610 (April 2014): 218–24. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.218.

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The different layers of graphene were prepared by liquid ultrasonic direct exfoliation. The dispersion stability of graphene in water under different ultrasonic time, the antifriction Performance, and the elements and morphology of the wear surface are investigated. The wear mechanism of graphene solution was preliminarily discussed. The results indicate that graphene with thickness of 10nm-150nm can be produced by ultrasonic peeling expanded graphite and the dispersion stability of graphene aqueous is best when sonicating for 3h. The antifriction property and wear mechanism of graphene aqueous vary with the graphene content. When graphene content is 0.01wt%, the antifriction performance of graphene aqueous was optimum and its wear mechanism was abrasive wear.

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10

Liu, Hong Bo, Wu Ying Zhang, and Feng Lin. "Synthesis and Property of Polyurethane Acrylates Modified Graphene Oxide." Key Engineering Materials 703 (August 2016): 273–77. http://dx.doi.org/10.4028/www.scientific.net/kem.703.273.

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The graphene oxides were synthesized form graphite by ultrasonic dispersion in water, N-methylpyrrolidone (NMP), N,N-dimethyl-formamide (DMF), acetone and dimethylbenzene, and the polyurethane acrylates containing the reactive NCO (PACN) were prepared. Then the polyurethane acrylates modified graphene oxide synthesized by ultrasonic dispersion in N-methylpyrrolidone (NMP), N,N-dimethyl-formamide (DMF), acetone were prepared by NCO of PACN reacting with the hydroxyl groups of the graphene oxides. The polyurethane acrylates modified graphene oxide was characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM) and Raman spectra. The FTIR spectra showed that the NCO of PACN reacted with the hydroxyl groups of graphene oxide synthesized by ultrasonic dispersion. The measurement of SEM and Raman spectra showed that the polyurethane acrylates modification didn't change the structure and surface morphology of graphene oxide.

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Chen, Jingjing, Xiangnan Chen, Fanbin Meng, Dan Li, Xin Tian, Zeyong Wang, and Zuowan Zhou. "Super-high thermal conductivity of polyamide-6/graphene-graphene oxide composites through in situ polymerization." High Performance Polymers 29, no. 5 (June 22, 2016): 585–94. http://dx.doi.org/10.1177/0954008316655861.

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Graphene is often used to improve the thermal conductivity of polymers but usually with high amount. The key factor that limits the thermal conductivity is graphene agglomeration as well as the incompatible interface between graphene and polymer. Here, we report super-high thermal conductivity of polyamide-6 (PA6) composites achieved by adding small amounts of graphene oxide (GO)-stabilized graphene dispersions (graphene-GO). The introduction of GO not only acts as an effective dispersant for graphene due to the non-covalent π-stacking interactions but also participates in PA6 polymerization. Therefore, the issues associated with graphene dispersion in PA6 can be resolved and the interface adhesion enhanced by adding small amounts of graphene-GO. Furthermore, this approach reduces the tendency for decreased crystallinity. All these factors enhance the formation of heat conducting pathways among the graphene sheets. Thus, compared with graphene, graphene-GO enhances thermal conductivity at lower filler loading levels by enhancing graphene dispersion and interface adhesion.

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Czajka, Michael, Robert A. Shanks, and Ing Kong. "Preparation of graphene and inclusion in composites with poly(styrene-b-butadiene-b-styrene)." Science and Engineering of Composite Materials 22, no. 1 (January 1, 2015): 7–16. http://dx.doi.org/10.1515/secm-2013-0119.

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AbstractThe aim of this work was to prepare and characterize nanocomposites containing graphene from intercalated graphite. The graphene was produced by rapid thermal expansion using expandable graphite oxide or obtained commercially. The polymer used was poly(styrene-b-butadiene-b-styrene) (SBS). The SBS was dissolved in p-xylene and the graphene was ultrasonically suspended in the xylene solution. The morphology, dynamic mechanical, electrical, and thermal properties of composites were characterized. Graphene at 1% (w/w) (hydrogen atmosphere) was found to increase the storage modulus (68%) and loss modulus (147%) of the glassy state of polybutadiene in SBS. The damping factor of SBS was enhanced by 74% corresponding to the polystyrene phase of SBS using Cheap Tubes graphene. The composites were insulators at 1% (w/w). The styrene groups in SBS strongly adsorb onto the graphenes, preventing a percolation network that would enhance electrical permittivity. Graphene enhanced physical crosslinks of the polystyrene phase to increase the modulus at low concentration. Graphene dispersion using ultrasonic shear depended on π-π interactions between the aromatic rings of the solvent, graphene, and polystyrene. This is a simple, fast, cheap, and scalable way of making high-quality graphene and a new way of graphene dispersal in polymers.

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13

Luo, Kun, Xiao Gang Li, Hai Ming Wang, Peng Wang, and Chun Wei. "One-Step Synthesis of Aqueous Graphene Dispersion Stabilized by Sodium Dodecylbenzene Sulfonate." Advanced Materials Research 924 (April 2014): 46–51. http://dx.doi.org/10.4028/www.scientific.net/amr.924.46.

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Graphite oxide (GO), prepared by modified Hummer’s method from graphite, was reduced by hydrazine hydrate in the presence of sodium dodecylbenzene sulfonate (SDBS), leading to a concentrated aqueous graphene dispersion which was stable for more than one month. The analyses of XRD, UV-vis and Raman spectroscopy indicate that the reduced graphene oxide (RGO) was formed after chemical reaction, where single or multiple graphene sheets were observed by TEM and AFM, indicating that the RGO is well-dispersed in water through the operation.

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Chen, Duoli, Chaoliang Gan, Xiaoqiang Fan, Lin Zhang, Wen Li, Minhao Zhu, and Xin Quan. "Improving the Dynamic Mechanical Properties of XNBR Using ILs/KH550-Functionalized Multilayer Graphene." Materials 12, no. 17 (August 30, 2019): 2800. http://dx.doi.org/10.3390/ma12172800.

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Graphene has been considered an ideal nanoscale reinforced phase for preparing high-performance composites, but the poor compatibility and weak interfacial interaction with the matrix have limited its application. Here a highly effective and environmentally friendly method for the functionalization of graphene is proposed through an interaction between as-exfoliated graphene and (3-aminopropyl) triethoxysilane (KH550), in which 1-butylsulfonate-3-methylimidazolium bisulfate (BSO3HMIm)(HSO4) ionic-liquids-modified graphene was prepared via an electrochemical exfoliation of graphite in (BSO3HMIm)(HSO4) solution, then (BSO3HMIm)(HSO4)-modified graphene as a precursor was reacted with amine groups of KH550 for obtaining (BSO3HMIm)(HSO4)/KH550-functionalized graphene. The final products as filler into carboxylated acrylonitrile‒butadiene rubber (XNBR) improve the dynamic mechanical properties. The improvement in the dynamic mechanical properties of the nanocomposite mainly depends on high interfacial interaction and graphene’s performance characteristics, as well as a good dispersion between functionalized graphene and the XNBR matrix.

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Sahoo, Rasmita, and Rashmi Ranjan Mishra. "Phonon Dispersion for Armchair and Zigzag Carbon Nanotubes." Graphene 03, no. 02 (2014): 14–19. http://dx.doi.org/10.4236/graphene.2014.32003.

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Thema, F. T., M. J. Moloto, E. D. Dikio, N. N. Nyangiwe, L. Kotsedi, M. Maaza, and M. Khenfouch. "Synthesis and Characterization of Graphene Thin Films by Chemical Reduction of Exfoliated and Intercalated Graphite Oxide." Journal of Chemistry 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/150536.

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Commercial flakes of graphite were prepared into functionalized graphene oxide (GO) by chemical treatment. After the exfoliation and intercalation of graphene into functionalized graphene oxide that formed stable colloidal dispersion in polar aprotic solvent, the reduction process was undertaken by continuous stirring with hydrazine hydrate. The reduced material was characterized by X-ray diffraction (XRD), attenuated total reflectance (ATR) FT-IR, ultraviolet visible (UV-vis), atomic force microscopy (AFM) and Raman spectroscopy which confirm the oxidation of graphite and reduction of graphene oxide into graphene sheet.

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Zhao, Fengfeng, Hui Quan, Shijun Zhang, Yihui Xu, Zheng Zhou, Guangxin Chen, and Qifang Li. "Watered-Based Graphene Dispersion Stabilized by a Graft Co-Polymer for Electrically Conductive Screen Printing." Polymers 15, no. 2 (January 10, 2023): 356. http://dx.doi.org/10.3390/polym15020356.

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Graphene conductive inks have attracted significant attention in recent years due to their high conductivity, corrosion resistance, and environmentally friendly nature. However, the dispersion of graphene in aqueous solution is still challenging. In this work, we synthesized an amphiphilic graft copolymer, polyvinyl alcohol-g-polyaniline (PVA-g-PANI), and studied the graphene dispersion prepared with the graft copolymer by high-speed shear dispersion. The amphiphilic graft copolymer can be used as a stabilizer and adhesive agent in graphene dispersion. Given the steric hindrance of the graft copolymer, the stability of graphene dispersion is improved by decreasing the probability of π–π stacking. PVA-g-PANI has a better stability on graphene dispersion than carboxymethylcellulose sodium (CMC-Na) and a mixture of PVA and PANI. The graft copolymer has only a slight effect on the conductivity of graphene dispersion due to the existence of conductive PANI, which is beneficial for preparing the graphene dispersion with good conductivity and adhesion. Graphene dispersion is well-adapted to screen printing and is very stable with regard to the sheet resistance bending cycle.

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18

Falkovsky, Leonid A. "Phonon dispersion in graphene." Journal of the Acoustical Society of America 123, no. 5 (May 2008): 3453. http://dx.doi.org/10.1121/1.2934282.

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Falkovsky, L. A. "Phonon dispersion in graphene." Journal of Experimental and Theoretical Physics 105, no. 2 (August 2007): 397–403. http://dx.doi.org/10.1134/s1063776107080122.

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20

Li, Peng, Seon Hyeong Bae, Qing Yuan Zan, Nam Hoon Kim, and Joong Hee Lee. "One-Step Process for the Exfoliation and Surface Modification of Graphene by Electrochemical Method." Advanced Materials Research 123-125 (August 2010): 743–46. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.743.

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SDBS modified graphene was prepared by electrochemical method using Sodium dodecylbenzenesulfonate (SDBS) as electrolyte and graphite rod as electrode. The anode graphite rod was corroded and deposited at the bottom of the electrolyte solution. The obtained graphene was characterized by Atomic force microscopy (AFM), Raman and Fourier transform infrared spectra (FT-IR). AFM images indicated that most of the layers had the thickness of less than 2 nm, suggesting the fromation of single layer of graphene. The resulting graphene showed very good dispersion stability both in water and in organic solvents (ethanol, acetone).

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Marchenko, D., D. V. Evtushinsky, E. Golias, A. Varykhalov, Th Seyller, and O. Rader. "Extremely flat band in bilayer graphene." Science Advances 4, no. 11 (November 2018): eaau0059. http://dx.doi.org/10.1126/sciadv.aau0059.

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We propose a novel mechanism of flat band formation based on the relative biasing of only one sublattice against other sublattices in a honeycomb lattice bilayer. The mechanism allows modification of the band dispersion from parabolic to “Mexican hat”–like through the formation of a flattened band. The mechanism is well applicable for bilayer graphene—both doped and undoped. By angle-resolved photoemission from bilayer graphene on SiC, we demonstrate the possibility of realizing this extremely flattened band (< 2-meV dispersion), which extends two-dimensionally in a k-space area around the K¯ point and results in a disk-like constant energy cut. We argue that our two-dimensional flat band model and the experimental results have the potential to contribute to achieving superconductivity of graphene- or graphite-based systems at elevated temperatures.

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Muda, M. R., K. N. Hanim, Siti Salwa Mat Isa, Muhammad Mahyiddin Ramli, and M. F. Jamlos. "High Throughput Graphene Oxide in Modified Hummers Method and Annealing Effect on Different Deposition Method." Applied Mechanics and Materials 815 (November 2015): 141–47. http://dx.doi.org/10.4028/www.scientific.net/amm.815.141.

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Graphene sheets offer extraordinary thermal, electronic and mechanical properties which could enhance the performance of the device for various applications. However, a large quantity production and the direct dispersion of graphene or graphite sheets in water without the assistance of dispersing agent has been considered to be a challenging issue. In this study, we reported that by introducing the functional group on the graphene basal plane started from natural graphite can readily form stable graphene oxide (GO) solution in a large quantity through modified hummers method. Structural and physiochemical properties of the GO were investigated with help of Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR). The effects of the annealing treatment on a GO surface were analyzed using a Semiconductor Parameter Analyzer (SPA) in order to obtain the electrical resistance measurement. Based on the thermal reduction results, the resistance of drop casting is greater than spray coating which indicates that, the drop casting method is more reliable to be used in any application.

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Bhattacharya, Soumya, Swati Mishra, Pallawi Gupta, Pranav Pranav, Mainak Ghosh, Ashit Kumar Pramanick, Durga Prasad Mishra, and Suprabha Nayar. "Liquid phase collagen modified graphene that induces apoptosis." RSC Advances 5, no. 55 (2015): 44447–57. http://dx.doi.org/10.1039/c5ra06629h.

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The differential interference contrast (DIC) and fluorescence confocal micrographs show collagen microfibrils attacking graphite from all sides to form a stable dispersion of collagen modified graphene, but only collagen picks up a stain.

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Kanabenja, Warrayut, and Pranut Potiyaraj. "Graphene/Thermoplastic Polyurethane Composites." Key Engineering Materials 773 (July 2018): 77–81. http://dx.doi.org/10.4028/www.scientific.net/kem.773.77.

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Thermoplastic polyurethane/graphene nanocomposites were successfully prepared by mixing masterbatches with neat polymers using the melt compounding process. Graphene was obtained from graphite by the chemical mean. Graphite was initially converted into graphite oxide which was then converted to graphene oxide. Graphene oxide was then reduced by L-ascorbic acid to obtain graphene. The effects of graphene addition on thermal and morphological properties of nanocomposite were studied by a differential scanning calorimeter, a thermal gravimetric analyzer and a scanning electron microscope. TPU/graphene nanocomposites showed higher melting temperature compared to TPU. On the other hand, heat of fusion of nanocomposites was lowered. TPU and TPU/graphene nanocomposites have two steps of decomposition. The first degradation of TPU occurred at higher temperature compared with nanocomposites but the second degradation showed the opposite results. The percentage of residue after thermal degradation of nanocomposites was lower than that of TPU. For surface morphology, nanocomposite exhibited the rougher surface comparing with TPU and well graphene dispersion in TPU phase was achieved. Nevertheless, there were some agglomeration of graphene.

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Yakovleva, Elena V., Andrey V. Yakovlev, Ivan N. Frolov, Anton S. Mostovoy, and Vitaly N. Tseluikin. "ELECTROCHEMICAL DISPERSION OF GRAPHITE IN 58% NITRIC ACID TO PRODUCE MULTILAYER GRAPHENE OXIDE." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, no. 3 (March 20, 2021): 59–65. http://dx.doi.org/10.6060/ivkkt.20216403.6324.

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Electrochemical oxidation of graphite powder in 58% HNO3 was studied. Samples of oxidized graphite were obtained with a imparting of the amount of electricity 500, 700, 1500 mAh g-1. The character of the galvanostatic dependencies allows to select a region of the formation of intercalated compounds of graphite prior to the accumulation of quantity of electricity of 500 mA h g-1. It was found that when the quantity of electricity of over 700 mA h g-1 the process of electrochemical peroxidation of intercalated graphite begins with the formation of multilayer graphene oxide, as confirmed by comprehensive studies using X-ray diffraction, scanning electron microscopy, FTIR spectroscopy, laser diffraction. The synthesized multilayer graphene oxide is characterized by the presence of a spectrum of oxygen-containing functional groups, mainly hydroxyl, as well as carboxyl, epoxy and alkoxyl. X-ray images show a peak at 2θ = 11.45° which intensity increases for re-oxidized graphite compounds and also indicate the formation of a multilayer graphene oxide with an interlayer distance of 7.8 Å. The synthesized material in aqueous suspensions under the action of ultrasound is dispersed with a 7-11-fold reduction in particle size. Graphene layers remains layered structure but the degree of their deformation increases, and the thickness of the layers decreases with an increase in the imparted amount of electricity.

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Ye, Zhong-Bin, Yuan Xu, Hong Chen, Chen Cheng, Li-Juan Han, and Lin Xiao. "A Novel Micro-Nano Structure Profile Control Agent: Graphene Oxide Dispersion." Journal of Nanomaterials 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/582089.

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Graphite oxide sheet, now referred to as graphene oxide (GO), is the product of chemical exfoliation of graphite and has been known for more than a century. A GO sheet is characterized by two abruptly different length scales; the apparent thickness of the functionalized carbon sheet is approximately 1 nm, but the lateral dimensions can range from a few nanometers to micrometers. In this paper, an improved method for the preparation of graphene oxide within a mild condition is described. We have found that cancelling the high-temperature stage and prolonging the reaction time of mid-temperature can improve the efficiency of oxidation process. We utilized FTIR, XRD, Ultraviolet-visible, TGA, Raman spectrum, and XPS measurements to characterize the successfully synthesized GO. SEM images were employed to reveal the interior microstructure of as-prepared GO dispersion. We also wondrously found that the GO dispersion could be used as profile control agent in the oilfield water-flooding. Flooding experiments showed that the GO dispersion has an ability to adjust water injection profile, reduce permeability ratio, and improve conformance factor. So the GO dispersion would have potential applications in oilfield exploitation.

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Chen, Dong Zhi, and Xue Mei Lin. "Preparation of Graphene by Green Reduction Method and Characterization." Advanced Materials Research 807-809 (September 2013): 515–20. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.515.

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Graphite oxide was prepared by Hummers method and got graphene oxide by ultrasonic dispersion in water, and using a cheap and environment-friendly fructose as reductant, graphene oxide could be reduced into graphene under mild condition. Meanwhile, the structure and morphology of obtained product was characterized and analyzed by testing methods such as Fourier transform Infrared spectroscopy, X-ray diffraction, Laser Raman spectroscopy, Transmission electron microscope and so on. In addition, the electrical conductivity of obtained graphene was determinated.The experimental results show that graphite oxide can be reduced by fructose under mild conditions and can get graphene with good structure and dispersibility. And the electrical conductivity of graphene prepared by the reduction of graphite oxide with fructose is 35.7 Scm-1, which has great improvement on conducting performance compared with graphite oxide. Moreover, It is non-toxic, non-polluting and friendly to the environment in preparation process of graphene, which lays the groundwork for mass production of graphene materials.

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Wang, Baomin, Shuang Deng, and Lu Zhao. "Modification of Ultraviolet Spectrophotometry Representational Method in Graphene Nanoplates Dispersion." Journal of Nanoscience and Nanotechnology 20, no. 7 (July 1, 2020): 4015–22. http://dx.doi.org/10.1166/jnn.2020.17538.

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Graphene nanoplates (GNPs) are carbon nanomaterials with two-dimensional structure which is easy to reunite and their dispersion is necessary before using. The existing methods for dispersion characterization mainly include UV spectrophotometry, scanning electron microscope (SEM), transmission electron microscopy (TEM) and Atomic Force Microscopy (AFM). In this research study, sodium dodecyl benzene sulfonate (SDBS), polyoxyethylene (40) nonylphenyl ether, branched (CO890), polyvinyl pyrrolidone (PVP) and cetyltrimethyl ammonium bromide (CTAB) were used as dispersants, and ultrasonic treatment was employed as dispersion method. Ultraviolet spectrum for GNPs showed that some errors were attained, resulting from dispersant at 274 nm characteristic wavelength of GNPs dispersions with deionized water as controlled sample. The errors could be eliminated if dispersant solution was used as controlled sample. The microstructures of dispersed GNPs observed by SEM, TEM and AFM suggested that the GNPs were dispersed uniformly with 2.5 g/L SDBS, which showed the best dispersion effect. Raman spectrum indicated that more chaotic distribution and edge structures were achieved after dispersion.

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Becheru, Diana, George Vlăsceanu, Adela Banciu, Eugeniu Vasile, Mariana Ioniţă, and Jorge Burns. "Optical Graphene-Based Biosensor for Nucleic Acid Detection; Influence of Graphene Functionalization and Ionic Strength." International Journal of Molecular Sciences 19, no. 10 (October 19, 2018): 3230. http://dx.doi.org/10.3390/ijms19103230.

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A main challenge for optical graphene-based biosensors detecting nucleic acid is the selection of key parameters e.g. graphenic chemical structure, nanomaterial dispersion, ionic strength, and appropriate molecular interaction mechanisms. Herein we study interactions between a fluorescein-labelled DNA (FAM-DNA) probe and target single-stranded complementary DNA (cDNA) on three graphenic species, aiming to determine the most suitable platform for nucleic acid detection. Graphene oxide (GO), carboxyl graphene (GO-COOH) and reduced graphene oxide functionalized with PEGylated amino groups (rGO-PEG-NH2, PEG (polyethylene glycol)) were dispersed and characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The influence of ionic strength on molecular interaction with DNA was examined by fluorescence resonance energy transfer (FRET) comparing fluorescence intensity and anisotropy. Results indicated an effect of graphene functionalization, dispersion and concentration-dependent quenching, with GO and GO-COOH having the highest quenching abilities for FAM-DNA. Furthermore, GO and GO-COOH quenching was accentuated by the addition of either MgCl2 or MgSO4 cations. At 10 mM MgCl2 or MgSO4, the cDNA induced a decrease in fluorescence signal that was 2.7-fold for GO, 3.4-fold for GO-COOH and 4.1-fold for rGO-PEG-NH2. Best results, allowing accurate target detection, were observed when selecting rGO-PEG-NH2, MgCl2 and fluorescence anisotropy as an advantageous combination suitable for nucleic acid detection and further rational design biosensor development.

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Giovannetti, R., E. Rommozzi, M. Zannotti, C. A. D'Amato, S. Ferraro, M. Cespi, G. Bonacucina, M. Minicucci, and A. Di Cicco. "Exfoliation of graphite into graphene in aqueous solution: an application as graphene/TiO2 nanocomposite to improve visible light photocatalytic activity." RSC Advances 6, no. 95 (2016): 93048–55. http://dx.doi.org/10.1039/c6ra07617c.

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Graphene dispersion (GR) was prepared by liquid-phase sonication of graphite and evaluated by XRD, DLS and UV-Vis analysis. It was used to prepare PP@mgGR–TiO₂, showing positive effects on ARS photodegradation under visible light irradiation.

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Ghaffar, A., M. Umair, Majeed A. S. Alkanhal, and Y. Khan. "Dispersion characteristics of surface plasmon polaritons in a graphene–plasma–graphene waveguide structure." Canadian Journal of Physics 100, no. 2 (February 2022): 123–28. http://dx.doi.org/10.1139/cjp-2019-0642.

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Theoretical investigations are carried out to study surface wave propagation for a graphene parallel-plate waveguide structure filled with isotropic plasma. The extended wave propagation theory is used. The Kobo formula is used to determine graphene conductivity. Maxwell’s equations (differential form) are used to solve the analytical problem. It is concluded that surface wave propagation can be tuned and controlled by tuning the plasma parameters (plasma frequency and collisional frequency) as well as chemical potential and relaxation time of graphene. Furthermore, the effect of plasma frequency and collisional frequency on the wave attenuation is discussed, and the effect of graphene’s chemical potential, plasma frequency, and collisional frequency on propagation length are also analyzed. The normalized field distribution of plasma medium is also studied. These results may lead to potential applications in optical sensing, communication, and plasma-based optical integrated devices in the gigahertz frequency regime.

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Seo, Jeong-Min, and Jong-Beom Baek. "A solvent-free Diels–Alder reaction of graphite into functionalized graphene nanosheets." Chem. Commun. 50, no. 93 (2014): 14651–53. http://dx.doi.org/10.1039/c4cc07173e.

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A solvent-free Diels–Alder reaction between graphite as a diene and a typical dienophile, maleic anhydride or maleimide is developed. The functionalization of graphite with dienophiles is efficient enough for delamination of graphitic layers into graphene nanosheets upon dispersion in a polar solvent.

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Chen, Duhong, Fei Wang, Yijuan Li, Wei-Wei Wang, Teng-Xiang Huang, Jian-Feng Li, Kostya S. Novoselov, Zhong-Qun Tian, and Dongping Zhan. "Programmed electrochemical exfoliation of graphite to high quality graphene." Chemical Communications 55, no. 23 (2019): 3379–82. http://dx.doi.org/10.1039/c9cc00393b.

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We propose programed potential modulation strategies to balance the ion intercalation/deintercalation, surface tailoring and bubbling dispersion processes in the electrochemical exfoliation of graphite, resulting in high-quality graphene with high crystallinity, low oxidation degree, uniform size distribution and few layers.

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Jing, G. J., Z. M. Ye, X. L. Lu, J. M. Wu, S. X. Wang, and X. Cheng. "Incorporating graphene oxide into lime solution: A study of flocculation and corresponding improvement." Materiales de Construcción 68, no. 331 (June 29, 2018): 165. http://dx.doi.org/10.3989/mc.2018.05217.

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The dispersion behavior of graphene oxide in cement matrix is one important factor in enhancing cement performance. In this work, we investigated the dispersion of graphene oxide in cement by simulating alkaline environment with a solution of calcium hydroxide and studied the corresponding strategy of improving dispersion. The obtained results showed that graphene oxide would flocculate even if calcium hydroxide concentration was very low, which might be the main reason of the unstable properties of the graphene oxide-doped cement. In addition, we discovered that, compared to -OH group, the -COOH group and the long chain of polycarboxylate-based superplasticizer were more effective in delaying the flocculation of graphene oxide. Finally, we proposed a dispersion mechanism of polycarboxylate-based superplasticizer. The study provides inspiration for the design of graphene oxide-doped cement materials.

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Liu, Yue E., Cheng En He, Ren Gui Peng, Wei Tang, and Ying Kui Yang. "Ionic Liquid Assisted Dispersion of Reduced Graphene Oxide in Epoxy Composites with Improved Mechanical Properties." Advanced Materials Research 738 (August 2013): 56–60. http://dx.doi.org/10.4028/www.scientific.net/amr.738.56.

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Graphene nanosheets were prepared by chemical reduction of the exfoliated graphite oxide using sodium borohydride (NaBH4). The graphene/epoxy composites were separately fabricated in the absence or presence of imidazolium-based ionic liquids, and their dynamic thermomechanical and tensile properties were studied. TEM examinations show that graphene sheets are well dispersed in the epoxy resin and have strong interface adhesion with the matrix due to the π-π and/or cation-π interactions between graphene and imidazolium ions. The composite fabricated by assistance of ionic liquids shows larger increases in Youngs modulus, tensile strength, storage modulus and glass transition temperature compared to the composite without using ionic liquids. This work provides a method for the fabrication of multifunctional graphene-based polymer composites.

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Денисюк, И. Ю., К. Ю. Логушкова, М. И. Фокина, and М. В. Успенская. "FT-IR-спектры многослойного графена и его композиции с поверхностно-активным веществом." Журнал технической физики 126, no. 2 (2019): 177. http://dx.doi.org/10.21883/os.2019.02.47200.300-18.

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AbstractMultilayer graphene has been obtained by ultrasonic splitting of graphite microparticles in a surface-active solvent that is a mixture of nonane and water and a surface-active surfactant, which provides dispersion of graphene in hydrophilic systems, has been selected. The chemical structure of the obtained materials has been investigated by IR Fourier spectroscopy. Possible mechanisms of the influence of inorganic surfactants (sodium liquid glass) on the graphene, the type of relations that arise between it and the graphene surface, and possible areas of its application have been discussed.

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Jiang, Tianhui, Lorenza Maddalena, Julio Gomez, Federico Carosio, and Alberto Fina. "Polyelectrolytes Enabled Reduced Graphite Oxide Water Dispersions: Effects of the Structure, Molecular Weight, and Charge Density." Polymers 14, no. 19 (October 4, 2022): 4165. http://dx.doi.org/10.3390/polym14194165.

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The polyelectrolyte (PE)-based water dispersion of graphene-related materials (GRMs) represents an interesting intermediate for the development of advanced materials by sustainable processes. Although the proof of concept has been demonstrated, there is a lack of knowledge for what concerns the effects of parameters typical of PEs such as functionalization, molecular weight, and charge density. In this work, we evaluate the effects of such parameters on the quality and long-term stability of reduced graphite oxide (rGO) dispersion in aqueous media prepared by ultrasound sonication in the presence of different PEs. Four PEs were evaluated: polyacrylic acid (PAA), branched poly(ethylenimine) (BPEI), sodium carboxymethyl cellulose (CMC), and poly(sodium 4-styrenesulfonic acid) (PSS). The prepared dispersions were thoroughly characterized by means of UV-visible spectroscopy, thermogravimetric analysis, dynamic light scattering, and Raman spectroscopy. The highest concentrations of rGO were achieved by BPEI with a molecular weight of 25,000 and 270,000 Da (33 and 26 µg/mL, respectively). For other PEs, the rGO concentration was found to be independent of the molecular weight. The PAA-based dispersions displayed the best through-time stability while yielding homogeneous dispersion with a smaller average size and narrower size distribution.

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Li, Yalin, Jieling Luo, Baoquan Huang, Hongjun Jin, Xiaoli Sun, Changlin Cao, Qinghua Chen, and Qingrong Qian. "Fabrication of Graphene-Modified Styrene–Acrylic Emulsion by In Situ Aqueous Polymerization." Polymers 14, no. 18 (September 8, 2022): 3763. http://dx.doi.org/10.3390/polym14183763.

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With the aim of developing green coatings, styrene–acrylic emulsion has been widely used in architectural coatings due to its excellent environmental protection and energy conservation. Nevertheless, the lack of water and oxygen resistance of water-based styrofoam coatings has promoted various nanomaterials being studied for modification. To improve the performance of waterborne styrofoam coating, we introduced the graphene nanopowder and expected to enable it with the function of electromagnetic interference (EMI) shielding to reduce the damage of electromagnetic radiation. In this paper, the problem of poor interface compatibility between graphene and polymer resin was successfully addressed by in situ polymerization. In the process of pre-polymerization of styrene–acrylic emulsion monomer, graphene-modified styrene–acrylic emulsion was obtained by introducing graphene aqueous dispersion. The results showed that the styrene–acrylic emulsion with 4 wt% aqueous graphene dispersions exhibited the best dispersion stability, improved water and oxygen resistance, and the conductivity reached 1.89 × 10−2 S/cm. Then, the graphene-modified coating for building was prepared by using graphene-modified styrofoam emulsion. All the performance indexes of the coating are in line with the industry standards, and it still showed benign EMI shielding effect even when the graphene content was low. It is demonstrated that in situ polymerization technology and the application of graphene in resin coatings modification will promote the development of green coatings.

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Sahoo, Rasmita, and Rashmi Ranjan Mishra. "Phonon dispersion of graphene revisited." Journal of Experimental and Theoretical Physics 114, no. 5 (May 2012): 805–9. http://dx.doi.org/10.1134/s1063776112040152.

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Moiseenko, I. M., V. V. Popov, and D. V. Fateev. "Charge carriers drift induced THz amplification in dual-layer graphene structure." Journal of Physics: Conference Series 2015, no. 1 (November 1, 2021): 012094. http://dx.doi.org/10.1088/1742-6596/2015/1/012094.

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Abstract The terahertz plasmon amplification in structure based on graphene with spatial dispersion of its hydrodynamic conductivity is investigated theoretically. The spatial dispersion of graphene conductivity is related to accounting of charge carriers pressure forces and direct current in graphene. It was shown that the real part of graphene conductivity becomes negative at THz frequency range due to direct electric current in graphene.

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Roldán, Laura, Ana M. Benito, and Enrique García-Bordejé. "Self-assembled graphene aerogel and nanodiamond hybrids as high performance catalysts in oxidative propane dehydrogenation." Journal of Materials Chemistry A 3, no. 48 (2015): 24379–88. http://dx.doi.org/10.1039/c5ta07404e.

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Graphene aerogels and graphene aerogel–nanodiamond hybrids have been fabricated by a mild reduction/self-assembly hydrothermal method using graphene oxide dispersion as a precursor. The high dispersion of nanodiamonds enhances the performance in oxidative dehydrogenation of propane.

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Hopmann, Christian, and Maximilian Adamy. "Preparation of graphene-based compounds with improved dispersion by a two-stage production process." Journal of Polymer Engineering 39, no. 4 (March 26, 2019): 368–76. http://dx.doi.org/10.1515/polyeng-2018-0126.

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Abstract Graphene can be used as a functional filler in thermoplastics in order to improve the mechanical and electrical properties, among other things. In the case of high exfoliation and dispersion state, disproportionate increases in compound properties can be achieved even with the lowest filler content. Accordingly, dispersion plays a decisive role here. Up to now, it has not been possible to achieve sufficient dispersion under near-industrial conditions on a twin-screw extruder due to the achievable shear energy input and short residence times. Therefore, this study presents a two-stage compounding process with the aim of improving graphene dispersion. First of all, a predispersion step is carried out in a solvent with the aid of ultrasonic treatment. The predispersed graphene solution is then added to the twin-screw extruder for incorporation. The solvent is removed by a multi-stage degassing process. The results show an improved dispersion compared to conventional addition of the graphene in powder form. In particular, the elongation at break of graphene-based composites can be increased from 13.6% to 57.1% by the increased dispersion.

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Huang, Jing, and Jun Kang. "Two-dimensional graphyne–graphene heterostructure for all-carbon transistors." Journal of Physics: Condensed Matter 34, no. 16 (February 22, 2022): 165301. http://dx.doi.org/10.1088/1361-648x/ac513b.

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Abstract Semiconducting graphyne is a two-dimensional (2D) carbon allotrope with high mobility, which is promising for next generation all-carbon field effect transistors (FETs). In this work, the electronic properties of van der Waals heterostructure consists of 2D graphyne and graphene (GY/G) were studied from first-principles calculations. It is found that the band dispersion of isolated graphene and graphyne remain intact after they were stacked together. Due to the charge transfer from graphene to graphyne, the Fermi level of the GY/G heterostructure crosses the VB of graphene and the CB of graphyne. As a result, n-type Ohmic contact with zero Schottky barrier height (SBH) is obtained in GY/G based FETs. Moreover, the electron tunneling from graphene to graphyne is found to be efficient. Therefore, excellent electron transport properties can be expected in GY/G based FETs. Lastly, it is demonstrated that the SBH in the GY/G heterostructure can be tune by applying a vertical external electric field or doping, and the transition from n-type to p-type contact can be realized. These results show that GY/G is potentially suitable for 2D FETs, and provide insights into the development of all-carbon electronic devices.

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Shen, Ming-Yuan, Wen-Yuan Liao, Tan-Qi Wang, and Wei-Min Lai. "Characteristics and Mechanical Properties of Graphene Nanoplatelets-Reinforced Epoxy Nanocomposites: Comparison of Different Dispersal Mechanisms." Sustainability 13, no. 4 (February 7, 2021): 1788. http://dx.doi.org/10.3390/su13041788.

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The preparation of polymer-based nanocomposites requires considerable time (i.e., the dispersal of nanomaterials into a polymer matrix), resulting in difficulties associated with their commercial use. In this study, two simple and efficient dispersion methods, namely planetary centrifugal mixing and three-roll milling, were used to enable the graphene nanoplatelets to disperse uniformly throughout an epoxy solution (i.e., 0, 0.1, 0.25, 0.5, and 1.0 wt.%) and allow the subsequent preparation of graphene nanoplatelets/epoxy nanocomposites. Measurements of mechanical properties of these nanocomposites, including ultimate tensile strength, flexural strength, and flexural modulus, were used to evaluate these dispersal methods. Dispersing graphene nanoplatelets into the epoxy resin by planetary centrifugal mixing not only required a shorter process time but also resulted in a more uniform dispersion of graphene nanoplatelets than that by three-roll milling. In addition, compared with traditional dispersal methods, planetary centrifugal mixing was a more efficient dispersal method for the preparation of epoxy-based nanocomposites.

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Wang, Xuemei, Tongtong Du, Juan Wang, Haixia Kou, Xinzhen Du, and Xiaoquan Lu. "Assessment of graphene aerogel matrix solid-phase dispersion as sample preparation for the determination of chlorophenols in soil." New Journal of Chemistry 42, no. 9 (2018): 6778–84. http://dx.doi.org/10.1039/c8nj00942b.

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Three-dimensional graphene aerogels (GAs) were synthesized by hydrothermal reduction and introduced as dispersing materials of matrix solid-phase dispersion for the determination of six chlorophenols in soil via high performance liquid chromatography.

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Абдуев, А. Х., А. К. Ахмедов, А. Ш. Асваров, К. Ш. Рабаданов, and Р. М. Эмиров. "Образование композита ZnO-C с нанокристаллической структурой." Журнал технической физики 89, no. 5 (2019): 717. http://dx.doi.org/10.21883/jtf.2019.05.47474.202-18.

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AbstractThe formation of a nanocrystalline composite of a ZnO–C system with simultaneous mechanical activation of a mixture of zinc oxide and graphite powders in a ball mill in an inert atmosphere is studied. It is shown that the presence of graphite reduces the efficiency of dispersing ZnO crystallites. The following principal dispersion mechanisms of graphite are determined: the fragmentation of particles due to the impact of grinding bodies and the exfoliation of flakes by submicron zinc oxide particles. It has been established that a composite system is formed as a result of the prolonged mechanical activation effect on the ZnO–graphite mixture, which is a nanocrystalline zinc oxide powder with uniformly distributed inclusions of micro- and nanocrystalline graphite, turbostratic carbon, exfoliated graphene structures, and amorphous carbon.

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Davydov, V. N. "The recurrent relations for the electronic band structure of the multilayer graphene." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 474, no. 2220 (December 2018): 20180439. http://dx.doi.org/10.1098/rspa.2018.0439.

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The structure of the electronic energy bands for stacked multilayer graphene is developed using the tight-binding approximation (TBA). The spectra of the Dirac electrons are investigated in vicinity of the Brillouin zone minima. The electron energy dependence on quasi-momentum is established for an arbitrary number of the graphene layers for multilayer graphene having even number of layers N = 2 n , ( n = 2, 3, 4, …) with the Bernal stacking ABAB … AB; or for odd number of layers N = 2 n + 1, ( n = 1, 2, 3, …) with stacking ABAB … A. It is shown that four non-degenerate energy branches of the electronic energy spectrum are present for any number of layers. Degeneracy is considered of graphene-like energy branches with linear dispersion law. Dependences of such branches number and their degeneracy are found on number of layers. The recurrent relations are obtained for the electronic band structure of the stacked ABA…, ABC… and AAA… multilayer graphene. The flat electronic bands are obtained for ABC-stacked multilayer graphene near the K -point at the Fermi level. Such an approach may be useful in the study of multivarious aspects of graphene's physics and nanotechnologies. Also paper gives new hints for deeper studies of graphite intercalation compounds.

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Li, Shengjuan, Zhihong Yang, Jianmei Xu, Jing Xie, and Jian Sun. "Synthesis of exfoliated graphene–montmorillonite hybrids as the fillers for epoxy composites." Journal of Composite Materials 53, no. 3 (July 2, 2018): 315–26. http://dx.doi.org/10.1177/0021998318783302.

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Graphene was prepared by microwave reduction of graphite oxide and organic montmorillonite was obtained by the intercalation modification of montmorillonite. The hybrids with various mass ratios of organic montmorillonite/graphene (mOMMT:mGNS = 1:1, 5:1, 10:1, 20:1 and 30:1) were primarily prepared, following which the epoxy matrix composites incorporated with organic montmorillonite–graphene hybrids were synthesized. The results indicate that graphene sheets are further exfoliated to fewer-layer structure and organic montmorillonite interlayer has been intercalated by graphene flakes after the combination of graphene and organic montmorillonite, suggesting the synergistic dispersion of these two components. Organic montmorillonite shows completely exfoliated structure at low ratios (1:1 and 5:1) and intercalated structure at high ratios (10:1, 20:1 and 30:1). Among all the hybrids with various organic montmorillonite/graphene ratios, the hybrids at the ratio of 5:1 present better dispersion and are more beneficial to enhancing the mechanical properties of the epoxy matrix composites. Moreover, compared with graphene and organic montmorillonite fillers, the introduction of organic montmorillonite–graphene hybrids into epoxy increases the mechanical strength more efficiently, especially increasing the impact strength of epoxy by 140.8%, indicating the synergistic reinforcement of these two components. The composite filled with organic montmorillonite–graphene hybrids exhibits better thermal stability than pure epoxy, but slightly poorer than the composites incorporated with graphene, which may be attributed to the low volume fraction of the hybrids in epoxy composites.

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Wu, Pu, Xinchun Chen, Chenhui Zhang, Jiping Zhang, Jianbin Luo, and Jiyang Zhang. "Modified graphene as novel lubricating additive with high dispersion stability in oil." Friction 9, no. 1 (March 26, 2020): 143–54. http://dx.doi.org/10.1007/s40544-019-0359-2.

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Abstract Graphene is a promising material as a lubricant additive for reducing friction and wear. Here, a dispersing method which combines chemical modification of graphene by octadecylamine and dicyclohexylcarbodiimide with a kind of effective dispersant has been successfully developed to achieve the remarkable dispersion stability of graphene in base oil. The stable dispersion time of modified graphene (0.5 wt%) with dispersant (1 wt%) in PAO-6 could be up to about 120 days, which was the longest time reported so far. At the same time, the lubricant exhibits a significant improvement of tribological performance for a steel ball to plate tribo-system with a normal load of 2 N. The coefficient of friction between sliding surfaces was ~0.10 and the depth of wear track on plate was ~21 nm, which decreased by about 44% and 90% when compared to pure PAO-6, respectively. Furthermore, the analysis of the lubricating mechanisms in regard to the sliding-induced formation of nanostructured tribo-film has been contacted by using Raman spectra and TEM.

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Li, Jiehui, Gang Niu, Wei Bai, Yanjie Ma, Qingren Xiong, Changyi Qin, Junjie Zhang, Ruihua An, and Wei Ren. "Significant Improvement of Anticorrosion Properties of Zinc-Containing Coating Using Sodium Polystyrene Sulfonate Noncovalent Modified Graphene Dispersions." Coatings 10, no. 12 (November 25, 2020): 1150. http://dx.doi.org/10.3390/coatings10121150.

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High-quality graphene zinc-containing anticorrosive coatings are highly and urgently desirable for effective, economical anticorrosion of metals and alloys in industrial products. The realization of such coatings is, however, hindered by the dispersibility and compatibility of the graphene in them. This work reports a novel direct modification of graphene using sodium polystyrene sulfonate (PSS) without reduction of graphene oxide, leading to homogeneous dispersion of graphene in water. The agglomeration of graphene is prevented thanks to the formation of π−π interaction between PSS and graphene sheets. Such graphene dispersion can effectively improve the anticorrosion performance of the zinc-containing epoxy coatings. With the addition of graphene modified by PSS into the 20% zinc-containing epoxy coating (graphene is 0.05% by weight of the coating), its anticorrosion properties revealed by both electrochemical characterization and the neutral salt spray tolerance analysis are rather close to those of 60% zinc-containing epoxy coating. These results demonstrate that direct PSS modification is an effective method for graphene dispersion and thus open a pathway to achieve graphene zinc-containing anticorrosive coatings with high performance.

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Journal articles on the topic 'Graphene dispersion'

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