Articoli di riviste: "Graphite"

1

Gholamalizadeh, Naghmeh, Saeedeh Mazinani, Majid Abdouss, Ali Mohammad Bazargan e Fataneh Fatemi. "Efficient and Direct Exfoliation of High-Quality Graphene Layers in Water from Different Graphite Sources and Its Electrical Characterization". Nano 16, n. 07 (24 giugno 2021): 2150079. http://dx.doi.org/10.1142/s179329202150079x.

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Green and efficient mass production of graphene sheets with high quality and electrical conductivity is intriguing for both academic scientists and industry. Among numerous production methods suffering from complexity or harsh chemical media, direct and high-yield exfoliation of graphite in water seems to be the best choice. In this study, efforts were made to prepare high-quality and stable graphene dispersions with the highest possible concentrations through an ultrasound-assisted liquid-phase exfoliation (LPE) in water directly from two types of natural graphites. The rigorous structural, morphological and electrical analyses were conducted on both graphite and graphene samples to quantitatively identify the effect of graphite sources on the LPE yield and the quality of the graphene nanosheets produced in the presence of an ionic surfactant. The results obtained by TEM, AFM, XRD and Raman spectroscopy indicated the successful and efficient production of single and few layer graphene sheets with the remarkable concentration of 3.18[Formula: see text]mg.ml[Formula: see text] in water. Moreover, the results signified that the structural quality, electrical conductivity and production yield of the graphene layers undoubtedly depend on the structural properties of graphite source. In fact, the graphite source greatly influences the final properties and potential applications of the produced graphene layer and the results are so important for the future graphene industry.

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Kausar, Ayesha. "Avant-Garde Polymer and Nano-Graphite-Derived Nanocomposites—Versatility and Implications". C 9, n. 1 (19 gennaio 2023): 13. http://dx.doi.org/10.3390/c9010013.

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Graphite (stacked graphene layers) has been modified in several ways to enhance its potential properties/utilities. One approach is to convert graphite into a unique ‘nano-graphite’ form. Nano-graphite consists of few-layered graphene, multi-layered graphene, graphite nanoplatelets, and other graphene aggregates. Graphite can be converted to nano-graphite using physical and chemical methods. Nano-graphite, similar to graphite, has been reinforced in conducting polymers/thermoplastics/rubbery matrices to develop high-performance nanocomposites. Nano-graphite and polymer/nano-graphite nanomaterials have characteristics that are advantageous over those of pristine graphitic materials. This review basically highlights the essential features, design versatilities, and applications of polymer/nano-graphite nanocomposites in solar cells, electromagnetic shielding, and electronic devices.

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3

Lu, Yan. "Size Effect of Expandable Graphite". Advanced Materials Research 499 (aprile 2012): 72–75. http://dx.doi.org/10.4028/www.scientific.net/amr.499.72.

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Using three natural graphites with different particle size, 35, 50 and 80 mesh, as raw materials, expandable graphites were prepared by intercalating, water-washing and drying the natural graphites. The products were characterized by X-ray diffraction, Infrared spectroscopy, scanning electron microscope and Raman spectroscopy. Results show that the structure of expandable graphite is affected strongly by the particle size of natural graphite. With increasing the particle size of natural graphite, for expandable graphite, the expansion degree of graphite flakes along the c-axis and the relative ratio of intercalating agents increase, while the structural disorder increases.

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Cao, Ning, e Yuan Zhang. "Study of Reduced Graphene Oxide Preparation by Hummers’ Method and Related Characterization". Journal of Nanomaterials 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/168125.

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As a novel two-dimensional carbon material, graphene has fine potential applications in the fields of electron transfer agent and supercapacitor material for its excellent electronic and optical property. However, the challenge is to synthesize graphene in a bulk quantity. In this paper, graphite oxide was prepared from natural flake graphite by Hummers’ method through liquid oxidization, and the reduced graphene oxide was obtained by chemical reduction of graphene oxide using NH3·H2O aqueous solution and hydrazine hydrate. The raw material graphite, graphite oxide, and reduced graphene oxide were characterized by X-ray diffraction (XRD), attenuated total reflectance-infrared spectroscopy (ATR-IR), and field emission scanning electron microscope (SEM). The results indicated that the distance spacing of graphite oxide was longer than that of graphite and the crystal structure of graphite was changed. The flake graphite was oxidized to graphite oxide and lots of oxygen-containing groups were found in the graphite oxide. In the morphologies of samples, fold structure was found on both the surface and the edge of reduced graphene oxide.

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Jeon, In Yup, Seo Yoon Bae e Jong Beom Baek. "Exfoliation of Graphite via Edge-Functionalization with Carboxylic Acid-Terminated Hyperbranched Poly(ether-ketone)s". Advanced Materials Research 123-125 (agosto 2010): 671–74. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.671.

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Because the complete restoration of graphene oxide into graphene is unsuccessful, the “direct” exfoliation of graphite into graphene is still remaining challenge. Here, we report in-situ grafting of carboxylic acid-terminated hyperbranched poly(ether-ketone) (HPEK) onto the edge of graphite to afford “edge-functionalized” HPEK grafted graphite (HPEK-g-graphite). The HPEK plays as a macromolecular wedge to exfoliate graphite. The degree of exfoliation of the resultant HPEK-g-graphite was estimated by wide-angle x-ray diffraction (WAXD), transmission electron microscopy (TEM). Due to the macromolecular wedge effect, the resultant HPEK-g-graphite was dispersible well in common organic solvents. Hence, HPEK-g-graphite could be potentially useful for graphene-based materials.

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Johnsen, Rune E., Poul Norby e Matteo Leoni. "Intercalation of lithium into disordered graphite in a working battery". Journal of Applied Crystallography 51, n. 4 (28 giugno 2018): 998–1004. http://dx.doi.org/10.1107/s1600576718007756.

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The structural transformations occurring during the intercalation of lithium into disordered graphite in a working battery were studied in detail by operando X-ray powder diffraction (XRPD). By using a capillary-based micro-battery cell, it was possible to study the stacking disorder in the initial graphite as well as in lithiated graphites. The micro-battery cell was assembled in its charged state with graphite as positive electrode and metallic lithium as counter electrode. The battery was discharged until a stage II compound (LiC12) was formed. The operando XRPD data reveal that the graphitic electrode material retains a disordered nature during the intercalation process. A DIFFaX+ refinement based on the initial operando XRPD pattern shows that the initial graphite generally has an intergrown structure with domains of graphite 2H and graphite 3R. However, the average stacking sequence of the initial graphite also contains a significant concentration of AA-type stacking of the graphene sheets. DIFFaX+ was further used to refine structure models of a stage III type compound and the final stage II compound. The refinement of the stage II compound showed that it is dominated by AαAAαA-type stacking, but that it also contains a significant concentration of AαABβB-type slabs in the average stacking sequence.

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Wang, Meng Lu, e Li Ji. "Expansion Mechanism of Expandable Graphite Formed by Natural Graphite with Different Particle Size". Advanced Materials Research 499 (aprile 2012): 16–19. http://dx.doi.org/10.4028/www.scientific.net/amr.499.16.

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Using three natural graphites with different particle sizes, 80, 50 and 35 mesh, as raw material, three expanded graphites were prepared by irradiating expandable graphite in a microwave oven. Results show that the particle size of natural graphite influences strongly the expansion ratio of expanded graphite, and the larger the particle size, the larger the expansion ratio. In addition, the expansion mechanism of expandable graphite is discussed.

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Li, Jinghao, Qiangu Yan, Xuefeng Zhang, Jilei Zhang e Zhiyong Cai. "Efficient Conversion of Lignin Waste to High Value Bio-Graphene Oxide Nanomaterials". Polymers 11, n. 4 (4 aprile 2019): 623. http://dx.doi.org/10.3390/polym11040623.

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Lignin graphene oxide was oxidized after Kraft lignin was graphitized by thermal catalytic conversion. The reduced lignin graphene oxide was derived from lignin graphene oxide through thermal reduction treatment. These Kraft lignin, lignin graphite, lignin graphene oxide, and reduced lignin graphene oxide were characterized by scanning electron microscopy, raman microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy and thermogravimetric analysis. The results showed lignin graphite converted from Kraft lignin had fewer layers with smaller lateral size than natural graphite. Moreover, lignin graphene oxide was successfully produced from lignin graphite by an oxidation reaction with an hour-long reaction time, which has remarkably shorter reaction time than that of graphene oxide made from natural graphite. Meanwhile, this lignin-derived graphene oxide had the same XRD, FTIR and Raman peaks as graphene oxide oxidized from natural graphite. The SEM, TEM, and AFM images showed that this lignin graphene oxide with 1–3 average layers has a smaller lateral size than that of graphene oxide made from natural graphite. Moreover, the lignin graphene oxide can be reduced to reduced lignin graphene oxide to fabricate graphene-based aerogel, wire, and film for some potential applications.

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9

Panteleimonov, R. A., О. V. Boichuk, K. D. Pershina e V. M. Ogenko. "Structural and electrochemical properties of N-doped graphene–graphite composites". Voprosy Khimii i Khimicheskoi Tekhnologii, n. 6 (dicembre 2022): 61–67. http://dx.doi.org/10.32434/0321-4095-2022-145-6-61-67.

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This work studied the impact of graphene content and heat treatment on the structural changes and electrical parameters of graphite/N-doped graphene mixtures. Using photoelectron spectroscopy the appearance of two types of carbon-containing phases was detected in the visible range of the N-doped graphene samples synthesized from liquid nitrogen. The following features of the samples were shown: one typical structure of graphene (sp2C–sp2C), two atypical structures (sp3C–N and the C–O bond), and graphene components modified with nitrogen (pyridine–N, pyrrole–N, graphite–N and oxidized N–O). The dependence between the ratio of components in graphite–graphene mixtures and their electrochemical properties was found. The effect of graphite content and heat treatment on the change in the type of conductivity in a graphite–graphene mixture was determined by comparison of resistance and capacitance distribution in the frequency range of 100–900 Hz. The change of the graphite concentration in the graphene–graphite mixture allows governing the type of doping and electrical parameters of the mixtures.

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Ni, Chengyuan, Chengdong Xia, Wenping Liu, Wei Xu, Zhiqiang Shan, Xiaoxu Lei, Haiqing Qin e Zhendong Tao. "Effect of Graphene on the Performance of Silicon–Carbon Composite Anode Materials for Lithium-Ion Batteries". Materials 17, n. 3 (4 febbraio 2024): 754. http://dx.doi.org/10.3390/ma17030754.

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(Si/graphite)@C and (Si/graphite/graphene)@C were synthesized by coating asphalt-cracked carbon on the surface of a Si-based precursor by spray drying, followed by heat treatment at 1000 °C under vacuum for 2h. The impact of graphene on the performance of silicon–carbon composite-based anode materials for lithium-ion batteries (LIBs) was investigated. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) images of (Si/graphite/graphene)@C showed that the nano-Si and graphene particles were dispersed on the surface of graphite, and thermogravimetric analysis (TGA) curves indicated that the content of silicon in the (Si/graphite/graphene)@C was 18.91%. More bituminous cracking carbon formed on the surface of the (Si/graphite/graphene)@C due to the large specific surface area of graphene. (Si/Graphite/Graphene)@C delivered first discharge and charge capacities of 860.4 and 782.1 mAh/g, respectively, initial coulombic efficiency (ICE) of 90.9%, and capacity retention of 74.5% after 200 cycles. The addition of graphene effectively improved the cycling performance of the Si-based anode materials, which can be attributed to the reduction of electrochemical polarization due to the good structural stability and high conductivity of graphene.

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Arao, Yoshihiko, Jonathon D. Tanks, Kojiro Aida e Masatoshi Kubouchi. "Exfoliation Behavior of Large Anionic Graphite Flakes in Liquid Produced by Salt-Assisted Ball Milling". Processes 8, n. 1 (24 dicembre 2019): 28. http://dx.doi.org/10.3390/pr8010028.

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Functionalization of graphite is crucial for efficient and effective exfoliation to graphene. When negative charges are fixed to the edges of natural graphite, the resulting anionic graphite shows negative charging in a polar solvent. This enhanced negative charging is assumed to contribute the exfoliation of graphite during liquid-phase exfoliation (LPE). In this study, we prepared large anionic graphite flakes (~10 μm) by salt-assisted ball milling, as well as natural graphite flakes of the same size for comparison. During the LPE process, centrifugation speed and solvent type have dominant effects on graphene concentration and quality (e.g., size and thickness), so we investigated these factors for anionic graphite flakes in detail. The anionic graphite showed higher exfoliation efficiency in every type of solvent (isopropanol, methyl ethyl ketone, acetone, and water-based cosolvent) compared with the natural graphite. Monolayer graphene, with an average size of 80–200 nm, was obtained with relatively high yield (>10%) at only 3 min of sonication. The small size of graphene was due to edge fragmentation during the LPE process. The recyclability of the sediment and the characterization of the exfoliated powders for anionic graphene were also investigated.

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12

Li, Pei Pei, e Bao Xiang Deng. "Research on Carbon Materials with Synthesis and Characterization of Graphene-Based". Advanced Materials Research 1003 (luglio 2014): 100–104. http://dx.doi.org/10.4028/www.scientific.net/amr.1003.100.

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Carbon materials has been a popular application materials, especially in graphene. Graphene, the mother of all graphitic materials, has emerged to become an exciting two-dimensional material with wondrous properties. Atomic and electronic structures of graphene have been investigated by employing a variety of micro-scopic, spectroscopic, and other techniques. The results show it has better thermal stability, and larger surface area than graphite, graphite oxide. Keywords: graphite; oxidation-reduction method; graphite oxide; graphene

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13

Lei, Yun, Jun Xu, Rong Li e Fei Fei Chen. "Acidification Assisted Preparation of Graphite Oxide and Graphene". Advanced Materials Research 988 (luglio 2014): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.988.36.

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Graphite oxide was prepared by acidification assisted Hummers method, which contains acidification, medium temperature and high-temperature three stages. Traditional Hummers low-temperature process was replaced by acidification process. The dosages of acid, graphite and potassium permanganate were investigated, and the produced graphite oxide was treated by ultrasonic oscillation and reduced to graphene by refluxing the reaction mixture at 100°C under open-air conditions. The structure of natural graphite, graphite oxide and graphene were characterized by X-ray diffractometry and infrared spectrum, the morphology of graphene was observed on a scanning electron microscope and the electrochemical properties of graphene were analyzed by the three-electrode cyclic voltammetry test system.

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14

Duan, Wen Yan. "Effect of Expansion Temperature of Expandable Graphite on Anti-Friction Effect of Graphite Nonasheets from Sonicating Expanded Graphite". Applied Mechanics and Materials 80-81 (luglio 2011): 225–28. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.225.

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Three graphite nanosheets were prepared by sonicating three expanded graphites that were formed by rapidly heating expandable graphite at 600, 800 and 1000 °C, respectively. The graphite nanosheets were characterized by scanning electron microscope. The anti-friction effects of the graphite nanosheets used as lubricating additives were investigated. The results show that the size of the graphite nanosheets decreases with increasing the temperature of expandable graphite. The graphite nanosheets have an obvious anti-friction effect, and the effect is related to the heating temperature.

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Bastiurea, Marian, Dumitru Dima e Gabriel Andrei. "Effect of Graphene Oxide and Graphite on Dry Sliding Wear Behavior of Polyester Composites". Materiale Plastice 55, n. 1 (30 marzo 2018): 102–10. http://dx.doi.org/10.37358/mp.18.1.4973.

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Graphene oxide and graphite filled polyester composites were prepared by using conventional melt-mixing methods in order to improve tribological performance of polyester. It was investigated friction stability, microhardness, friction coefficient, and specific wear rate of the composites in details. It was found that the presence of graphite and graphene oxide influenced friction coefficient and wear rate of the composites. Graphene oxide decreased wear rate with increasing of test speed and graphite decreased wear rate for composite for all speeds. Tribological performance of the polyester/graphene composites is mainly attributed to bigger thermal conductivity for graphene, which can easily dissipate the heat which appears during the friction process at bigger forces. The positive influence of graphite on coefficient of friction (COF) of the composites is the result of the clivage of graphite layers during the loadings due to van der Waals weak bonds between the graphite layers.

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Ji, Li, e Meng Lu Wang. "Effect of Particle Size of Natural Graphite on Methyl Blue Sorption Behavior of Expanded Graphite". Advanced Materials Research 499 (aprile 2012): 12–15. http://dx.doi.org/10.4028/www.scientific.net/amr.499.12.

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Using three natural graphites with different particle sizes, 80, 50 and 35 mesh, as raw material, expanded graphite was prepared by rapidly heating expandable graphite in a muffle and by irradiating it in a microwave oven, respectively. The resulting expanded graphites were used for adsorbing methyl blue in water. The results show that the removal rate of methyl blue is influenced by the treatment method of solution, the particle size of natural graphite and expansion method of expandable graphite. After selection of desired operation parameters, a higher removal rate is achieved.

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Minitha, Cherukutty Ramakrishnan, e Ramasamy Thangavelu Rajendrakumar. "Synthesis and Characterization of Reduced Graphene Oxide". Advanced Materials Research 678 (marzo 2013): 56–60. http://dx.doi.org/10.4028/www.scientific.net/amr.678.56.

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Reduced graphene oxide is an excellent candidate for various electronic devices such as high performance gas sensors. In this work Graphene oxide was prepared by oxidizing graphite to form graphite oxide. From XRD analysis the peak around 11.5o confirmed that the oxygen was intercalated into graphite. By using hydrazine hydrate, the epoxy group in graphite oxide was reduced then the solution of reduced graphite oxide (rGO) is exfoliated. Raman spectrum of rGO contains both G band (1580 cm-1), D band (1350 cm-1). The remarkable structural changes reveals that reduction of graphene oxide from the values of ID/IG ratio that increase from 0.727 (GO) to 1.414 (rGO). The exfoliated reduced graphite oxide solution is spin coated on to the SiO2/Si substrates.

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Guo, Qiaoqin, Zhong Yang, Ding Guo, Dong Tao, Yongchun Guo, Jianping Li e Yaping Bai. "Research on the Oxidation Mechanism of Vermicular Graphite Cast Iron". Materials 12, n. 19 (25 settembre 2019): 3130. http://dx.doi.org/10.3390/ma12193130.

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The oxidation mechanism of vermicular graphite cast iron was studied. The oxidation reaction starts from graphites and diffused slowly. Graphites in vermicular graphite are interconnected, coral-like clusters, providing the main oxidation core and channel. The worm-like graphites on the surface are mostly oxidized and form oxide affected zones. The oxide films are composed of a loose oxide layer with the phases of Fe3O4, Fe2O3, and FeO, and a dense passivation layer with FeO and Fe2SiO4. After oxidation, pearlites in the vermicular graphite cast iron are decomposed into ferrite and cementite at high temperatures.

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Рутьков, Е. В., Е. Ю. Афанасьева, Н. П. Лавровская e Н. Р. Галль. "Интеркалирование натрием графеновых пленок на Re(10(1)0)". Физика твердого тела 60, n. 5 (2018): 1024. http://dx.doi.org/10.21883/ftt.2018.05.45807.301.

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AbstractIt is shown that during low-temperature (300–500 K) intercalation of sodium atoms into thin multilayer graphene and graphite films on rhenium the first graphene layer plays the role of a trap to which atoms coming on the surface diffuse through a graphite film. The intercalation phase of the interlayer space in the graphite bulk is actively filled at a sodium atoms concentration under the first graphene layer close to the maximum possible (2 ± 0.5) × 10^14 cm^–2. This phase capacity is proportional to the graphite film thickness that can be varied in this work from one graphene layer to ~50 atomic layers. The diffusion energy E _ d of Na atoms through the graphite film was estimated to be E _ d ≈ 1.4 eV.

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Alinejad, Babak, e Korosh Mahmoodi. "Synthesis of graphene nanoflakes by grinding natural graphite together with NaCl in a planetary ball mill". Functional Materials Letters 10, n. 04 (agosto 2017): 1750047. http://dx.doi.org/10.1142/s1793604717500473.

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Natural graphite is a soft material that conventional milling methods fail to grind into nanoparticles. We found that adding NaCl into graphite during milling allows obtaining graphene nanoflakes of about 50[Formula: see text][Formula: see text][Formula: see text]200[Formula: see text]nm2 as evidenced by Transmission Electron Microscope (TEM). NaCl particles are substantially brittle and harder than graphite, serving as milling agents by both helping to chop graphite into smaller pieces and preventing graphite particles from agglomeration. After milling, NaCl can be easily washed away by water. Probable mechanism for exfoliation of graphene during the modified ball milling may be explained by NaCl and graphene slipping or sliding against and over each other, exfoliating the graphene particles into thin layers.

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Yürüm, Yuda, Burcu Saner Okan, Firuze Okyay, Alp Yürüm, Fatma Dinç, Neylan Görgülü e Selmiye Alkan Gürsel. "An Improved Technique for the Exfoliation of Graphene Nanosheets and Utilization of their Nanocomposites as Fuel Cell Electrodes". Key Engineering Materials 543 (marzo 2013): 9–12. http://dx.doi.org/10.4028/www.scientific.net/kem.543.9.

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Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional 2D honeycomb lattice. The graphene sheets in graphite interact with each other through van der Waals forces to form layered structure. The first graphene sheets were obtained by extracting monolayer sheets from the three-dimensional graphite using a technique called micromechanical cleavage in 2004 [. There are numerous attempts in the literature to produce monolayer graphene sheets by the treatment of graphite. The first work was conducted by Brodie in 1859 and GO was prepared by repeated treatment of Ceylon graphite with an oxidation mixture consisting of potassium chlorate and fuming nitric acid [. Then, in 1898, Staudenmaier produced graphite oxide (GO) by the oxidation of graphite in concentrated sulfuric acid and nitric acid with potassium chlorate [. However, this method was time consuming and hazardous. Hummers and Offeman found a rapid and safer method for the preparation of GO and in this method graphite was oxidized in water free mixture of sulfuric acid, sodium nitrate and potassium permanganate [.

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Lv, Ya Nan, Jian Fang Wang, Yin Long, Cheng An Tao, Lin Xia e Hui Zhu. "How Graphene Layers Depend on Drying Methods of Graphene Oxide". Advanced Materials Research 554-556 (luglio 2012): 597–600. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.597.

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Abstract: Graphite oxide is of great importance in preparing graphene, the average layer of graphene depends on that of graphene oxide in some extent. In this paper, we prepared graphite oxide via H3PO4/H2SO4mixed acid, then which were dried by vacuum drying in a freezer dryer and drying oven respectively, the graphite oxide powder and thin film were obtained correspondingly. After dispersing the above two forms of graphite oxide in water by shaking, stirring or supersonic wave, they were reduced in the same condition. According to the XRD, AFM results, vacuum freeze-drying was inclined to gain few-lay graphene.

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Rubanik, V. V., V. O. Savitsky, V. V. jr Rubanik, V. F. Lutsko, I. V. Nikiforova, Hung Thang Bui e Dinh Phuong Doan. "OBTAINING GRAPHENE STRUCTURES AND NANOPOLYMERS USING ULTRASONIC VIBRATIONS". Vektor nauki Tol'yattinskogo gosudarstvennogo universiteta, n. 3 (2021): 74–83. http://dx.doi.org/10.18323/2073-5073-2021-3-74-83.

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Graphene-based polymer nanocomposites are considered a promising class of future materials. The degree of filling, the filler and binder nature, and the shape, size, and mutual arrangement of filler particles determine the properties of a polymer composite material. The destruction of nanoparticles aggregates occurs most effectively in liquid media under the action of ultrasonic vibrations. The authors proposed the technique and designed laboratory equipment for ultrasonic treatment of the finely-dispersed graphite suspension, carried out the ultrasonic treatment (UST) of finely-dispersed graphite powder. The suspensions based on graphite with a solvent were obtained. The authors carried out the experiments on producing graphene using the graphite liquid-phase exfoliation method at the ultrasonic treatment with different ultrasonic treatment times, analyzed experimental data, and selected the UST optimal time. The paper contains the results of the study of the effect of the graphite suspension base on the degree of ultrasonic liquid-phase exfoliation of graphite. The most effective synthesis of graphene structures using UST is synthesis from graphite suspensions based on dichloroethane, benzol, and dichlorobenzene. Graphene structures’ output ratio amounts to up to 66 %. The authors developed the technology for producing polymers modified with graphene structures using ultrasonic dispersion. Based on graphene synthesized by the graphite liquid-phase exfoliation, the authors obtained nanopolymers using ultrasonic vibrations, carried out DSC measurements, and studied their strength properties. The limit strength of elastic polymers is from 1.9 to 3.6 MPa at different concentrations of graphene inclusions. The residual elongation of samples within the deviation did not change and amounted to 200 %.

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Rubanik, V. V., V. O. Savitsky, V. V. jr Rubanik, V. F. Lutsko, I. V. Nikiforova, Hung Thang Bui e Dinh Phuong Doan. "OBTAINING GRAPHENE STRUCTURES AND NANOPOLYMERS USING ULTRASONIC VIBRATIONS". Vektor nauki Tol'yattinskogo gosudarstvennogo universiteta, n. 3 (2021): 74–83. http://dx.doi.org/10.18323/2073-5073-2021-3-74-83.

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Graphene-based polymer nanocomposites are considered a promising class of future materials. The degree of filling, the filler and binder nature, and the shape, size, and mutual arrangement of filler particles determine the properties of a polymer composite material. The destruction of nanoparticles aggregates occurs most effectively in liquid media under the action of ultrasonic vibrations. The authors proposed the technique and designed laboratory equipment for ultrasonic treatment of the finely-dispersed graphite suspension, carried out the ultrasonic treatment (UST) of finely-dispersed graphite powder. The suspensions based on graphite with a solvent were obtained. The authors carried out the experiments on producing graphene using the graphite liquid-phase exfoliation method at the ultrasonic treatment with different ultrasonic treatment times, analyzed experimental data, and selected the UST optimal time. The paper contains the results of the study of the effect of the graphite suspension base on the degree of ultrasonic liquid-phase exfoliation of graphite. The most effective synthesis of graphene structures using UST is synthesis from graphite suspensions based on dichloroethane, benzol, and dichlorobenzene. Graphene structures’ output ratio amounts to up to 66 %. The authors developed the technology for producing polymers modified with graphene structures using ultrasonic dispersion. Based on graphene synthesized by the graphite liquid-phase exfoliation, the authors obtained nanopolymers using ultrasonic vibrations, carried out DSC measurements, and studied their strength properties. The limit strength of elastic polymers is from 1.9 to 3.6 MPa at different concentrations of graphene inclusions. The residual elongation of samples within the deviation did not change and amounted to 200 %.

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Li, Jihui, Huiqing Shi, Ning Li, Mei Li e Jing Li. "Facile preparation of graphite intercalation compounds in alkali solution". Open Chemistry 8, n. 4 (1 agosto 2010): 783–88. http://dx.doi.org/10.2478/s11532-010-0048-5.

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AbstractGraphite intercalation compounds are often prepared by flake graphite, oxidants, inorganic acids, organic acids and intercalated ions which are usually hydrogen protons between the graphene planes. They are also known as the acid-treated graphite intercalation compounds. In this work, alkaline graphite intercalation compounds were prepared by flake graphite, K2Cr2O7, concentrated H2SO4 and NaOH, and the morphology and structure were characterized by Electron microscopy and X-ray techniques. The results display that the combination of neutralisation heat and oxidation capability produced by K2Cr2O7 can break the bonds to produce the spaces between the graphene planes and hydroxyl ions also intercalate into the graphene planes to form alkaline graphite intercalation compounds in alkali solution. The morphology and structure of alkaline graphite intercalation compounds are analogous to the ones of the acid-treated graphite intercalation compounds, but the intercalated ions and the expansion volume are different. The results show that the method is an innovation.

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Wang, Ziming, Yiyang Cao, Decai Pan e Sen Hu. "Vertically Aligned and Interconnected Graphite and Graphene Oxide Networks Leading to Enhanced Thermal Conductivity of Polymer Composites". Polymers 12, n. 5 (14 maggio 2020): 1121. http://dx.doi.org/10.3390/polym12051121.

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Natural graphite flakes possess high theoretical thermal conductivity and can notably enhance the thermal conductive property of polymeric composites. Currently, because of weak interaction between graphite flakes, it is hard to construct a three-dimensional graphite network to achieve efficient heat transfer channels. In this study, vertically aligned and interconnected graphite skeletons were prepared with graphene oxide serving as bridge and support via freeze-casting method. Three freezing temperatures were utilized, and the resulting graphite and graphene oxide network was filled in a polymeric matrix. Benefiting from the ultralow freezing temperature of −196 °C, the network and its composite occupied a more uniform and denser structure, which lead to enhanced thermal conductivity (2.15 W m−1 K−1) with high enhancement efficiency and prominent mechanical properties. It can be significantly attributed to the well oriented graphite and graphene oxide bridges between graphite flakes. This simple and effective strategy may bring opportunities to develop high-performance thermal interface materials with great potential.

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27

Lakshani, S. D. M., D. B. H. I. Bandara, R. C. L. De Silva, A. M. K. L. Abeykoon, M. H. T. Dulaj e I. R. M. Kottegoda. "Mass scale production and purification of graphite oxide from Sri Lankan vein graphite and spectroscopic characterization". Sri Lankan Journal of Physics 24, n. 2 (31 dicembre 2023): 98–109. http://dx.doi.org/10.4038/sljp.v24i2.8134.

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Abstract (sommario):

Discovery of graphene has enhanced attention on industrial scale production of graphene using natural graphite which involves oxidation followed by reduction processes. Aiming for the first time, mass scale production of graphite oxide from Sri Lankan vein graphite of natural purity 99.5% carbon, following an improved Hummer’s method was experimented at optimized conditions minimizing chemical, energy and time wastage. The present study further aimed at determination of pH and manganese ions on successive purification processes of graphite oxide. The X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) characterizations were followed for verification of products. The wastewater produced from graphite oxide preparation process was systematically tested for Mn2+ ion using Atomic Absorption Spectroscopy (AAS). XRD peaks verified the formation of graphite oxide successfully through a complete oxidation of graphite. FTIR spectrum exhibited characteristic peaks related to typical graphite oxide while SEM shows the typical morphological features. XPS analysis verified complete removal of Mn from graphite oxide after purification. AAS analysis reveals entire removal of Mn after several washing cycles using only water. The investigation concludes that even mass scale production of quality graphite oxide is possible from Sri Lankan pure vein graphite which can subsequently be used to produce precious graphene and derivatives for various high-end applications.

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28

Yao, Yu Qin, Yin Jie Cen, Richard D. Sisson e Jian Yu Liang. "A Synthesize Protocol for Graphene Nanosheets". Materials Science Forum 880 (novembre 2016): 3–6. http://dx.doi.org/10.4028/www.scientific.net/msf.880.3.

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Abstract (sommario):

Chemical synthesis is cheap and easy to be tailored. Reduction of graphite oxide to form graphene nanosheets is a necessary step that determines yield, quality, chemical and surface properties of graphene nanosheets. In this report, the reduction of graphite oxides by chemical and thermal methods has been employed to convert graphite oxide synthesized by the same wet chemical method using KMnO4 and H2O2. The characterization results from the two reduction methods indicate that a combination of wet oxidation of graphite and thermal reduction method is an efficient and environmental friendly way to produce graphene.

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29

Meng, Long Yue, e Soo Jin Park. "Synthesis of Graphene Nanosheets via Thermal Exfoliation of Pretreated Graphite at Low Temperature". Advanced Materials Research 123-125 (agosto 2010): 787–90. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.787.

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Abstract (sommario):

In this work, we synthesized graphene nanosheets via a soft chemistry synthetic route involving pre-exfoliation treatment, strong oxidation, and post thermal exfoliation. X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM) confirmed the ordered graphite crystal structure and morphology of graphene nanosheets. N2 adsorption was used to determine the specific surface area of graphene nanosheets. As a result, pre-treatment of the graphite with HNO3/H2SO4 mixture produced the exfoliated graphite nanoplates, and the post thermal exfoliation of the graphite oxide nanosheets at low temperature led to produce a large number graphene nanosheets. The specific surface area of obtained graphene nanosheets was 333 m2/g.

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30

Loryuenyong, Vorrada, Krit Totepvimarn, Passakorn Eimburanapravat, Wanchai Boonchompoo e Achanai Buasri. "Preparation and Characterization of Reduced Graphene Oxide Sheets via Water-Based Exfoliation and Reduction Methods". Advances in Materials Science and Engineering 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/923403.

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Abstract (sommario):

This research studied the synthesis of graphene oxide and graphene via a low-cost manufacturing method. The process started with the chemical oxidation of commercial graphite powder into graphite oxide by modified Hummer’s method, followed by the exfoliation of graphite oxide in distilled water using the ultrasound frequency from a laboratory ultrasonic bath. Finally, the oxygen functional groups on exfoliated graphite oxide or graphene oxide were eliminated by stirring in hot distilled water at 95°C, as a replacement for highly toxic and dangerously unstable hydrazine. The results assured that stirring in hot distilled water could give the product of graphene or reduced graphene oxide. The samples were characterized by FTIR, XRD, TGA, Raman spectroscopy, SEM, and TEM methods.

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31

Yu, Hui Jiang, Zheng Guang Zou, Fei Long, Chun Yan Xie e Hao Ma. "Preparation of Graphene with Ultrasound-Assisted in the Process of Oxidation". Applied Mechanics and Materials 34-35 (ottobre 2010): 1784–87. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.1784.

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Abstract (sommario):

To get single-layer of graphene, exfoliating fully intercalated graphite oxide into single- layer graphene oxide is one of the important factors. In this paper, graphite oxide prepared by the Improved Hummers Method, and ultrasound was added to the Low-temperature Reaction of this oxidation process to improve the efficiency of intercalation. Then the obtained graphene oxide was dispersed with surfactant and reduced with Hydrazine Hydrate. XRD patterns indicated that the layer distance of graphite oxide did increased at the aid of the ultrasound, and the obtained reduced products were single- and few-layer. FT-IR analysis further confirmed the preparation of graphite oxide and graphene.

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32

Ilnicka, Anna, Malgorzata Skorupska, Piotr Kamedulski e Jerzy P. Lukaszewicz. "Electro-Exfoliation of Graphite to Graphene in an Aqueous Solution of Inorganic Salt and the Stabilization of Its Sponge Structure with Poly(Furfuryl Alcohol)". Nanomaterials 9, n. 7 (3 luglio 2019): 971. http://dx.doi.org/10.3390/nano9070971.

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Abstract (sommario):

We demonstrate an accessible and effective technique for exfoliating graphite foil and graphite powder into graphene in a water solution of inorganic salt. In our research, we report an electrochemical cathodic exfoliation in an aqueous solution of Na2SO4. After electro-exfoliation, the resulting graphene was premixed with furfuryl alcohol (FA) and an inorganic template (CaCO3 and Na2CO3). Once FA was polymerized to poly(furfuryl alcohol) (PFA), the mixture was carbonized. Carbon bridges originating in thermally-decomposed PFA joined exfoliated graphene flakes and stabilized the whole sponge-type structure after the nano-template was removed. Gases evolved at the graphite electrode (cathode) played an important role in the process of graphene-flake splitting and accelerated the change of graphite into graphene flakes. Starting graphite materials and graphene sponges were characterized using Raman spectroscopy, SEM, high-resolution transmission electron microscopy (HRTEM), elemental analysis, and low-temperature adsorption of nitrogen to determine their structure, morphology, and chemical composition. The discovered manufacturing protocol had a positive influence on the specific surface area and porosity of the sponges. The SEM and HRTEM studies confirmed a high separation degree of graphite and different agglomeration pathways. Raman spectra were analyzed with particular focus on the intensities of ID and IG peaks; the graphene-type nature of the sponges was confirmed.

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33

Paul, Abigail, Regan Magee, Warren Wilczewski, Nathan Wichert, Caleb Gula, Rudolph Olson, Eric Shereda et al. "Characterization and Analysis of Coal-Derived Graphite for Lithium-Ion Batteries". ECS Meeting Abstracts MA2024-01, n. 4 (9 agosto 2024): 670. http://dx.doi.org/10.1149/ma2024-014670mtgabs.

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Abstract (sommario):

Graphite is a critical material used as the negative electrode in lithium-ion batteries. Both natural and synthetic graphites are utilized, with the latter obtained from a range of carbon raw materials. In this work, efforts to synthesize graphite from coal as a domestic feedstock for synthetic graphite are reported. The performance in lithium-ion coin cells of this coal derived graphite is compared to commercial battery-grade graphite. This includes characterization of the thermodynamics of the coal derived graphite using the multi-species, multi-reaction (MSMR) model, characterization of the entropy and enthalpy of the material, and estimation of the rate capability. This enables modeling of synthetic coal-derived graphites and virtual evaluation[1] of these materials towards electric vehicle and grid storage applications. References 1. T. R. Garrick, Y. Zeng, J. B. Siegel, and V. R. Subramanian, "From Atoms to Wheels: The Role of Multi-Scale Modeling in the Future of Transportation Electrification." Journal of The Electrochemical Society 170.11 (2023): 113502.

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34

Panteleimonov, Radyslav, Oleksandr Boichuk, Katherine Pershina e Volodymyr Ogenko. "IMPACT OF THE GRAPHENE SYNTHESIS AND CONCENTRATION CONDITIONS ON ELECTRICAL PARAMETERS OF GRAPHENE — GRAPHITE SYSTEM". Ukrainian Chemistry Journal 87, n. 8 (24 settembre 2021): 127–37. http://dx.doi.org/10.33609/2708-129x.87.08.2021.127-137.

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Abstract (sommario):

Electrochemical impedance spectroscopy was used to study the electrical parameters of graphite-graphene systems with different mass concentrations of graphene. Graphene was synthesized using two methods of plasma arc discharge from aqueous and non-aqueous medium (water and liquid nitrogen) to determine the impact of graphite concentration, water, and heat treatment of graphene on electrical parameters (conductivity and electrostatic capacity) of the graphite-graphene mixture. The average values of active resistance and electrostatic capacity of these systems are obtained. The optimal ratio of components with high capacitance and conductivity, which was 1: 1. The influence of heat treatment adsorbed on the graphene surface of the water and mass fraction of graphite on the change of electrical parameters of the system is shown. Comparison of the values of capacity and active resistance of the samples showed that the presence of water in graphene reduces the average values of capacity relative to graphene without water by 10 times and symbolically increases the active resistance at a mass ratio of graphene to graphite 1: 3, and at a ratio of 1: 1 values are proportional. Comparison of resistance, capacitance, and charge distribution calculations in a graphite-graphene mixture in the frequency range 10–2 ÷ 103 Hz established the effect of heat treatment on increasing the values of capacitance and active resistance. Heat treatment at 2500C of graphene, synthesized from an aqueous medium, leads to an increase in the values of capacitance and conductivity, which occurs due to a different distribution of charges on the surface. Analysis of charge distribution maps shows that water adsorbed on the surface of graphene in the presence of a significant amount of graphite can be a factor in interfering with the distribution of charge carriers and significantly reduce the conductivity and electrostatic capacity of the system.

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35

Long, Yin, Jian Fang Wang, Ya Nan Lv, Cheng An Tao, Lin Xia e Hui Zhu. "Preparation and Characterization of Graphene by the Oxidation Reduction Method". Advanced Materials Research 554-556 (luglio 2012): 624–27. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.624.

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Abstract (sommario):

We prepared graphite oxide (GO) from natural graphite by the modified Hummers method. Then graphene was prepared by ultrasonically dispersing GO in the presence of hydrazine hydrate. The samples were characterized by FTIR, Raman, Scanning electron microscope (SEM) and Transmission electron microscope (TEM). The results suggest that the graphite is oxidized to covalent bond-type graphite intercalation compounds with various oxygen functional groups (C=O, C-OH, -COOH and C-O-C). Results show that the functional groups on graphite oxide surface are mostly removed by hydrazine hydrate and graphene presents translucent slide with curly edge.

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36

Barjasteh, E., C. Sutanto, T. Reddy e J. Vinh. "A graphene/graphite-based conductive polyamide 12 interlayer for increasing the fracture toughness and conductivity of carbon-fiber composites". Journal of Composite Materials 51, n. 20 (19 aprile 2017): 2879–87. http://dx.doi.org/10.1177/0021998317705707.

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Abstract (sommario):

A conductive thermoplastic material was developed to increase the interlaminar fracture toughness and through-the-thickness conductivity of carbon-fiber-reinforced plastics materials. A polyamide 12 nonwoven fabric was coated with graphene/graphite particles in a solution of hexane, water, and graphite particles. The graphite powders were exfoliated in the sonication bath and the resulting layers of graphene resided at the interface of the immiscible solvents, where the graphene layers/graphite simultaneously infused into the polyamide 12. The sonication time and graphite content were optimized to maximize the surface conductivity of conductive polyamide 12 fabric. The presence of pristine graphene flakes and graphite on the polyamide 12 fabric was confirmed by X-ray diffraction and scanning electron microscopy. The dry fabric preform was interleaved with the conductive polyamide 12 and the composite laminates were manufactured by a vacuum-assisted resin transfer molding process. The resulting composite laminate resulted in a significant increase in Mode I and Mode II fracture toughness up to 42% and 141%, respectively, and a decrease in the volume resistivity from 100 MΩm to 402 Ωm.

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37

Lei, Xiao-Wen, Shungo Shimizu e Jin-Xing Shi. "The Theoretical Study of Kink Deformation in Graphite Based on Differential Geometric Method". Nanomaterials 12, n. 6 (9 marzo 2022): 903. http://dx.doi.org/10.3390/nano12060903.

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Abstract (sommario):

Kink deformation is often observed in materials with laminated layers. Graphite composed of stacked graphene layers has the unique laminated structure of carbon nanomaterials. In this study, we performed the interlayer deformation of graphite under compression using a simulation of molecular dynamics and proposed a differential geometrical method to evaluate the kink deformation. We employed “mean curvature” for the representativeness of the geometrical properties to explore the mechanism of kink deformation and the mechanical behaviors of graphite in nanoscale. The effect of the number of graphene layers and the lattice chirality of each graphene layer on kink deformation and stress–strain diagrams of compressed graphite are discussed in detail. The results showed that kink deformation occurred in compressed graphite when the strain was approximately equal to 0.02, and the potential energy of the compressed graphite proportionately increased with the increasing compressive strain. The proposed differential geometric method can not only be applied to kink deformation in nanoscale graphite, but could also be extended to solving and predicting interlayer deformation that occurs in micro- and macro-scale material structures with laminated layers.

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38

Ramirez-Barria, Carolina S., Diana M. Fernandes, Cristina Freire, Elvira Villaro-Abalos, Antonio Guerrero-Ruiz e Inmaculada Rodríguez-Ramos. "Upgrading the Properties of Reduced Graphene Oxide and Nitrogen-Doped Reduced Graphene Oxide Produced by Thermal Reduction toward Efficient ORR Electrocatalysts". Nanomaterials 9, n. 12 (11 dicembre 2019): 1761. http://dx.doi.org/10.3390/nano9121761.

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Abstract (sommario):

N-doped (NrGO) and non-doped (rGO) graphenic materials are prepared by oxidation and further thermal treatment under ammonia and inert atmospheres, respectively, of natural graphites of different particle sizes. An extensive characterization of graphene materials points out that the physical properties of synthesized materials, as well as the nitrogen species introduced, depend on the particle size of the starting graphite, the reduction atmospheres, and the temperature conditions used during the exfoliation treatment. These findings indicate that it is possible to tailor properties of non-doped and N-doped reduced graphene oxide, such as the number of layers, surface area, and nitrogen content, by using a simple strategy based on selecting adequate graphite sizes and convenient experimental conditions during thermal exfoliation. Additionally, the graphenic materials are successfully applied as electrocatalysts for the demanding oxygen reduction reaction (ORR). Nitrogen doping together with the starting graphite of smaller particle size (NrGO325-4) resulted in a more efficient ORR electrocatalyst with more positive onset potentials (Eonset = 0.82 V versus RHE), superior diffusion-limiting current density (jL, 0.26V, 1600rpm = −4.05 mA cm−2), and selectivity to the direct four-electron pathway. Moreover, all NrGOm-4 show high tolerance to methanol poisoning in comparison with the state-of-the-art ORR electrocatalyst Pt/C and good stability.

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39

Yurov V.M., Zhangozin K.N., Zhanabergenov T.K. e Kargin D.B. "Surface phenomena in graphite and obtaining graphene from it". Novosti nauki Kazahstana, n. 1 (15 marzo 2024): 19–42. http://dx.doi.org/10.53939/1560-5655_2024_1_19.

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Abstract (sommario):

The article offers an overview of our latest theoretical work on graphite and graphene. A model is proposed for determining the thickness of the surface layer of graphite, from which the strength of graphite and graphene can be calculated and the length of nanocracks in the surface layer of these materials can be determined.

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40

Usuda, Teruki, K. Matsuno, Hisao Matsunaga, Keiji Yanase e Masahiro Endo. "Hydrogen-Induced Ductility Loss in Cast Irons". Materials Science Forum 750 (marzo 2013): 260–63. http://dx.doi.org/10.4028/www.scientific.net/msf.750.260.

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Abstract (sommario):

Effect of hydrogen-charging was investigated with respect to the tensile properties of three types of cast irons: JIS FCD400, FCD450 and FCD700. In this study, hydrogen charging led to a marked ductility loss in all the cast irons. The thermal desorption spectroscopy and the hydrogen microprint technique revealed that, in the hydrogen-charged specimens, most of solute hydrogen was diffusive and mainly segregated at graphite, graphite/matrix interface zone and pearlite. In the fracture process of non-charged specimen, neighboring graphites were interconnected with each other mainly by ductile dimple fracture. On the other hand, in the fracture process of hydrogen-charged specimen, the graphites were interconnected by cracks. The difference in the fracture morphology between the non-charged and the hydrogen-charged specimens is attributed to the presence of diffusive hydrogen in graphite and graphite/matrix interface. During early stage of fracture process in hydrogen-charged specimen, the interspace between graphite and matrix is filled with hydrogen gas, which leads to the ductility loss of matrix in the vicinity of graphite. Even after the initiation of crack from graphite, hydrogen is continuously outgassed from graphite and supplied to the crack tip. Therefore, concerning the hydrogen effect on the strength of cast irons, a role of subsurface graphite as a “local hydrogen supplier” should be taken into consideration.

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41

Al-Jarah, R. A., A. M. Al-Mashkhadani, V. Mansur, S. S. Aldavud, A. A. Osipov e V. F. Pershin. "Production of Graphene-Containing Suspensions and Concentrates by Cascade Exfoliation of Graphite". Vestnik Tambovskogo gosudarstvennogo tehnicheskogo universiteta 28, n. 1 (2022): 139–52. http://dx.doi.org/10.17277/vestnik.2022.01.pp.139-152.

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Abstract (sommario):

Various technologies and equipment for the production of graphene-containing suspensions by liquid-phase exfoliation of graphite are considered. The prospects of using liquid-phase graphite shear exfoliation in a continuous mode are shown. Taking into account the analyzed shortcomings of existing technologies, a technology for the production of graphene-containing suspensions and concentrates by cascade exfoliation of graphite and a device for its implementation are proposed. In particular, the following are proposed: a new method for two-stage dosing of graphite powder; new design of rod drum mill for mechanical activation of graphite; a new design of the rotary apparatus with compound movable blades, providing an increase in shear forces acting on graphite particles in the process of exfoliation. The kinetics of the exfoliation process has been studied. Experimental studies on the modification of concrete with graphene have been carried out and an increase in compressive strength of at least 33% has been proven.

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42

Pajarito, Bryan, Amelia Jane Belarmino, Rizza Mae Calimbas e Jillian Rae Gonzales. "Graphite Nanoplatelets from Waste Chicken Feathers". Materials 13, n. 9 (2 maggio 2020): 2109. http://dx.doi.org/10.3390/ma13092109.

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Abstract (sommario):

Graphite nanoplatelets (GNPs), a functional 2D nanofiller for polymer nanocomposites, utilize natural graphite as a raw material due to its stacked graphene layers and outstanding material properties upon successful exfoliation into nano-thick sheets. However, the increasing demand for natural graphite in many industrial applications necessitates the use of graphite from waste resources. We synthesized GNPs from waste chicken feathers (WCFs) by graphitizing carbonized chicken feathers and exfoliating the graphitic carbon by high-speed homogenization and sonication. We then separated GNP from non-exfoliated carbon by centrifugation. This paper describes the morphology, chemical, and crystalline properties of WCF and its carbon derivatives, as well as the structural features of WCF-derived carbons. We obtained GNPs that have a 2D structure with huge variations in particle size and thickness. The GNP shows the presence of carbonyl groups, which are mostly attached at the edges of the stacked graphene sheets. Defects in the GNP are higher than in graphene synthesized from direct exfoliation of natural graphite but lower than in graphene oxide and reduced graphene oxide. To produce GNP of high quality from WCF, restacking of graphene sheets and concentration of carbonyls must be minimized.

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43

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

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Abstract (sommario):

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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44

Liu, Li Lai, Mao Zhong An, Shan Chao Xing, Xiao Jun Shen, Chen Yang e Xin Long Xu. "Preparation of Graphene Oxide Based on Expanded Graphite". Advanced Materials Research 881-883 (gennaio 2014): 1083–88. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1083.

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Abstract (sommario):

Graphene oxide with high degree of oxidation and peelable has been prepared by two-step oxidation method used large flake graphite. The expanded graphite was prepared firstly and then prepared graphene oxide via further oxidation. The influence of oxidation time, oxidant dosage and high temperature reaction on the structure and degree of oxidation were studied. The morphology and structure of graphene oxide were characterized by X-ray diffraction, fourier transform infrared spectra, scanning electron microscope and transmission electron microscope. It was found that high degree of oxidation and large specific surface area graphene oxide was prepared at the ratio of sulfuric acid and expanded graphite was 75 mL : 1 g, the ratio of potassium permanganate and expanded graphite was 4 g : 1 g and the oxidation time at 35 °C was 24 h. This technology is simple without high-temperature reaction process, and solved the problem of low oxidation efficiency when used the large flake graphite as raw materials.

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45

Altay, L., G. S. Tantug, H. Cekin, Y. Seki e M. Sarikanat. "Thermal and mechanical behavior of graphene loaded synthetic graphite/polyphenylene sulfide (PPS) composites". High Temperatures-High Pressures 50, n. 4-5 (2021): 415–32. http://dx.doi.org/10.32908/hthp.v50.1089.

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Abstract (sommario):

Thermoplastics when they become thermally conductive, have a great potential to be used in thermal management applications due to their low cost, lightweight, and flexibility. Here, synthetic graphite and graphene are used as thermally conductive fillers to fabricate Polyphenylene Sulfide- (PPS) based composite materials with high thermal conductivity. Graphene and graphite added PPS composites were manufactured by using a twinscrew extruder and injection molding machine. Physical, thermal, mechanical, and morphological properties of the composites were investigated by several characterization methods including thermogravimetric analysis, differential scanning calorimetry, thermomechanical analysis, scanning electron microscopy, thermal diffusivity measurement, and tensile and flexural tests, The in-plane and through-plane thermal conductivity coefficient of graphene (5 wt. %) loaded synthetic graphite (40 wt. %)/PPS composites are greatly improved to 26.45 and 5.02 W/mK, respectively compared to that of neat PPS. The outstanding in-plane thermal conductivity of graphene loaded graphite/PPS composites is attributed to the formation of an effective thermal conductive pathway due to the alignment of the layered structure of graphene and graphite fillers in the flow direction.

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46

Kaburagi, Yutaka, Akira Yoshida e Yoshihiro Hishiyama. "Microtexture of highly crystallized graphite as studied by galvanomagnetic properties and electron channeling contrast effect". Journal of Materials Research 11, n. 3 (marzo 1996): 769–78. http://dx.doi.org/10.1557/jmr.1996.0093.

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Abstract (sommario):

The relationship between microtexture and crystallinity of highly crystallized graphites with the residual resistivity ratio ρ300K/ρ4.2K of 3.45–5.50 was investigated. The graphite crystals studied were kish graphite (KG), highly oriented pyrolytic graphite (HOPG), and highly crystallized graphite films prepared from carbonized aromatic polyimide films. The study was made by the observations of an electron channeling pattern and electron channeling contrast image (ECI) under scanning electron microscope and the measurements of x-ray diffraction, magnetoresistance, and Hall coefficient. The values of the mean free path of the carriers λ, which approximates the mean crystal grain size, were estimated to be 2.6–6.1 μm from the magnetoresistance at 4.2 K for the highly crystallized graphites. The values of the average crystal grain diameter D in the basal plane evaluated from ECI were several hundred microns or more for KG, 60 μm for HOPG, and 6 and 12 μm for the graphite films. The difference between the values of λ and D for each crystallized graphite was discussed in relation to other results obtained.

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47

Bae, Seo Yoon, In Yup Jeon e Jong Beom Baek. "Highly Transparent and Conductive Graphene Electrode". Advanced Materials Research 123-125 (agosto 2010): 113–16. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.113.

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Abstract (sommario):

The solvent-based exfoliation of graphite, including into graphene and/or graphene-like platelets, is an important challenge. Here, we report a “direct” Friedel-Crafts acylation reaction between graphite and 4-ethylbenzoic acid (EBA) to afford edge-functionalized graphite (EFG). Unlike, for example, graphite oxide (GO), the functionalization is at the edges of the graphite and thus, the basal plane of individual layers in EFG is not functionalized. The EFG can be easily dispersed and exfoliated in common organic solvents to concentrations as high as 0.8 mg/mL. Large-are uniform films can be produced by solution-casting such dispersions on substrates and conductivities as high as 125 S/cm can be obtained by subsequent heat treatment at 900 °C under argon atmosphere. Hence, a few layers graphene obtained from annealing under argon atmosphere show the potential to replace Indium tin oxide (ITO).

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48

Joorab Doozha, Amir, e Kristin M. Poduska. "Graphite oxidation chemistry is relevant for designing cleaning strategies for radiocarbon dating samples". Analytical Methods 11, n. 22 (2019): 2880–87. http://dx.doi.org/10.1039/c9ay00046a.

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Abstract (sommario):

We demonstrate that mixtures of graphite and lab-oxidized graphenic carbon materials can be separated into three individual components (graphite, graphene/graphite oxide and oxidative debris) by a series of aqueous treatments.

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49

Liang, Chaoping, Feilong Wang e Sai Tang. "Two-dimensional ordering governs the overpotential of Li intercalation and plating on graphene and its variants". Journal of Applied Physics 131, n. 16 (28 aprile 2022): 165001. http://dx.doi.org/10.1063/5.0083852.

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Abstract (sommario):

In this work, the Li ordering and its influence on Li intercalation and plating on graphite, bilayer, and single-layer graphene are investigated by first-principles calculation with two-dimensional cluster expansion and van der Waals corrections. The results show that Li intercalation has a multistage feature for graphite and bilayer graphene at Li concentrations from C2 to LiC6. Beyond LiC6, Li atoms are crowded in graphite and bilayer graphene, resulting in a negative discharge voltage. The calculated overpotential indicates Li plating easily happens on graphite but is unlikely on bilayer graphene. For single-layer graphene, Li atoms uniformly cover the graphene surface from C2 to LiC4 with the presence of voltage stages, while forming an atomic island at a higher Li concentration. Our findings not only give a good recount on recent Li plating phenomena in Li-ion batteries but also provide a rationale for circumventing those side reactions on graphene and its variants.

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50

Jiang, Yan Li, Mei Tian, Ying Hui Yu, Jia Yao Liu e Shuang Liu. "Preparation and Property of Reduced Graphene for Hummers". Key Engineering Materials 591 (novembre 2013): 301–4. http://dx.doi.org/10.4028/www.scientific.net/kem.591.301.

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Abstract (sommario):

Graphene material has ideal lattice structure and unique electrical, optical and other properties. In the electronics, composite materials, and other fields it has a broad application prospect. In this paper, using the Hummers method, to prepare oxidized graphite and graphene , to optimize the conditions of the preparation of graphite oxide. With two kinds of reductors, glucose and hydrazine hydrate, reduction graphite oxide, and dropped silver ions in the process of reduction. Using XRD, SEM and Raman spectra to character and analyze the products. The result showed that the graphite and silver ions in the oxidation reaction process were both restored by glucose, hydrazine hydrate. This structure that silver nanoparticles are uniformly distributed in the graphene sheet layers, can effectively prevent the reunion of graphene layers, and also upset the rules of the pile of the graphene layers.

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