Papers by Keyword: Graphene

Abstract: At present, the distributed long-gauge optical sensor on fiber reinforced polymer(FRP) bar cannot be manufactured through integrated production. On the other hand, the point-sensing technology of the self-sensing bar will cause deviations in structural health monitoring (SHM). To solve these issues, applying the graphene/epoxy on FRP members is a feasible method for the piezoresistive characteristics of graphene. In this paper, basalt FRP (BFRP) bars with graphene/epoxy film were tested under static tensile load and the resistance was measured at the same time until they were broken down. The results suggested that the changing rate of resistance was linearly correlated to the strain. This fact indicated that the graphene-modified BFRP bar can well reflect the stress condition of the structural member within a safe range.

Abstract: Terahertz technology can be used in sensing and communication applications. We designed a polarization-sensitive photodetector specially for Terahertz frequency based on cross-shaped graphene sheet. The shaped graphene excites localized surface plasmon which can enhance the absorption of incident light. From the Finite Difference Time Domain Solutions (FDTD), we figured out that transmission of incident light relates to the size of photodetector, polarization angle and physical properties of graphene such as chemical potential and layers. The transmission can be tuned as low as 8.3 ×10^-5 when we set the size at 14×6µm and 14×5µm for two different graphene pieces and polarization angle as 0°, at room temperature. This device we designed can absorb Terahertz at a wavelength around 126 µm, which can be used in THz application applied in future high-tech communication or safety inspection.

Abstract: In this paper, graphene oxide (GO) was obtained by oxidation of powdered graphite foil wastes (pGFW) at 0 - 40°C. Oxidizing reagents can easily penetrate the layers of graphite foil and thus, the intercalation or functionalization-oxidation processes may occur resulting in graphite oxide formation. The methods of synthesis of GO and its separation from the reaction mixture were partially corrected. GO was reduced, also, to the reduced graphene oxide (rGO) by using hydroiodic acid, ascorbic acid, zinc powder, hydrazine, and Alnus extract. Thermal treatment of GO powders and GO films, obtained from pGFW was implemented at 20-300° C in air and at 20-1000° C under argon flow and in a vacuum. At high-temperature treatment (1000°C) of GO graphene was obtained with a defective structure.

Abstract: A facile and effective approach to assemble graphene hybridized multiple manganese oxides /graphene ((m-MnO₂/Gr) was explored. The structure varied from two-dimensional (2D) to one-dimensional (1D) club-shaped manganese oxides via blending of Gr into the molten salt precursor. Compared to the m-MnO₂ and pristine Gr electrode, the m-MnO₂/Gr composites displayed a superior synergistic effect in promoted capacitive performance, cycle performance, with capacity retention of about 90% after 2000 charge-discharge cycles. It expects to supply a promising strategy to synthesize large scalable production of hybrid supercapacitor electrode.

Abstract: Epoxy coatings and Reduced Graphene Oxide (RGO) modified epoxy coatings were prepared on N80 tubing steel. The influence of temperature on the corrosion resistance of RGO modified epoxy coatings was studied. And the corrosion behavior of epoxy coatings and RGO modified epoxy coatings in 10.0 wt% NaCl solution at different temperatures was compared. The results showed that the corrosion resistance of both coatings decreased with the increase of temperature. However, the corrosion resistance of RGO modified epoxy coating was two to three orders of magnitude higher than that of epoxy coating at different test temperature. The addition of RGO nanosheets greatly enhanced the corrosion resistance of epoxy composite coatings in 10.0 wt% NaCl solution at high temperature due to their high impermeability and negative coefficient of thermal expansion.

Abstract: In order to obtain the alloy composite material with high hardness, good anti-friction property and low friction coefficient, the electrodeposition technology was used to prepare nanocrystalline Co-Ni-graphene composite coating on the surface of low carbon steel by means of ultrasonic dispersion combined with mechanical agitation. The influence of graphene content in electrolyte on composite coating was studied. The surface microstructure, composition, phase structure, micro-hardness and micro-wear properties of composite coating were measured by scanning electron microscopy, energy spectrometer, X-ray diffractometer, micro-hardness tester and UNMT-1 comprehensive mechanical testing system for micro-nanometer materials. The results show that with the increase of the content of graphene in the electrolyte the graphene particles were embedded in the alloy coating, which changes the crystal structure of the alloy coating and improves the microhardness and micro friction resistance of the coating. When the content of graphene in the electrolyte was 0.9g/L the microstructure of the composite coating was fine and uniform, the highest microhardness value was 678 HV, the minimum average friction coefficient was 0.15, and the composite coating had good wear resistance.

Abstract: Graphene(Gr) reinforced copper matrix composites(Gr/Cu) were prepared by powder metallurgy process, and the effects of graphene content on microstructure and properties of the composites were investigated. The microstructure, density, hardness and electrical conductivity of the composites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), density measurement, hardness tester and conductivity meter. The results show that the interface bonding of the composite is good, there is no crack and no obvious interface reaction; there are a lot of dislocations and twins in Cu matrix. With the increase of graphene content, the density, heat capacity and thermal conductivity of the composites decrease, but the hardness increases first and then decreases.

Abstract: The microstructure of coatings with different graphene content and the hardness of cladding layer under different distance between coil and samples were investigated. The results showed that with the increase of graphene, the mean particle size of the powder did not get significantly coarser. The defects and oxides were appeared in the cladding layer and graphene diffused into the substrate. Distance between induction coil and sample has great impact on the hardness of coating, the higher hardness was measured in the distance between 6-8cm. The thermodynamic analysis of coating nucleation was carried out.

Abstract: The selective adsorption of CH₄, H₂S, SO₂ and H₂O by alkali earth metal (AEM) decorated double vacancy graphene (DVG) was investigated with the first principles method. The most stable adsorption configurations, adsorption energy of CH₄, H₂S, SO₂ and H₂O on AEM_DVG have been discussed.

Abstract: 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.