Surface Of Graphite Nanosheets Research Articles

Research on the high thermal conductivity composite phase change materials with graphite nanosheets for battery thermal safety

Composite phase change material (CPCM) as an efficient battery thermal management strategy has been widely utilized owing to its promising performance, but its thermal conductivity and stability still need to be improved in battery module. Herein, three different kinds of CPCM have been successfully prepared and utilized in battery module, which are composite with PEG, epoxy resin (ER), silver nanoparticles (AgNP) modified with dopamine hydrochloride (PDA) self-assembled on the surface of graphite nanosheets (GNS), denoted as PEE (PEG/ER), PEG(PEG/ER/GNS), and PEGA (PEG/ER/GNS/Ag), respectively. Among them, the AgNP with super-high thermal conductivity has been distributed on the surface of GNS to form laminated nanostructures, promoting the construction of thermal conduction network. The thermal conductivity and latent heat of CPCM are 3.1 W∙m−1∙K−1 and 105.8 J∙g−1, respectively. Furthermore, even under 35 °C ambient temperature, the application of PEGA for battery module can effectively control the maximum temperature below 52 °C and maintained a temperature difference within 6 °C at a 3C discharge rate, which is better than those of battery modules with PEE and PEG. It reveals that the battery module with designed high thermal conductivity CPCM can provide insights into the passive thermal management and other energy storage fields.

Introducing graphite nanosheets to change the microscopic morphology of CoS nanoparticles to obtain ultra-thin and excellent electromagnetic wave absorption performance

The composite material of metal sulfide and dielectric material has always been regarded as a research hotspot in the field of electromagnetic wave absorption. In this work, the cobalt sulfide (CoS) particles were successfully grown on the modified graphite nanosheets (GNs) by the two-step hydrothermal method to obtain excellent CoS/GNs EM wave absorption materials. SEM images show that after adding GNs, the morphology of CoS particles will change from micron-scale regular spheres to irregular nano-fragments which attached to the surface of GNs. The reason is that the binding sites on the surface of GNs will limit the growth of CoS particles. Fortunately, the introduction of GNs not only adjusted the impedance matching performance of CoS, but also perfectly combined the dielectric loss and magnetic loss mechanisms. EM analysis showed that the minimum reflection loss (RLmin) of CoS/GNs materials is −52 dB at an ultra-thin thickness of 1.1 mm, and the effective absorption bandwidth (EAB) is 3.7 GHz (14.3 GHz–18 GHz). Therefore, this ultra-thin nanocomposite material is expected to have broad market application prospects.

Spherical shape Co@Co3O4 core-shell composites grown on surface of graphite nanosheets with ultra-thin and excellent electromagnetic absorption performance

In this work, graphite nanosheets (GNs)/Co composites with excellent electromagnetic (EM) absorption performance was designed by a one-step hydrothermal method, and the surface of Co particles were coated with Co3O4 shell layer by a second hydrothermal method to obtain the expected core-shell GNs/Co@Co3O4 structure, and the microtopography, structure and magnetic properties of core-shell GNs/Co@Co3O4 structure were characterized in detail. EM analysis revealed that core-shell GNs/Co@Co3O4 structure has an excellent EM wave absorption performance. For GNs/Co@Co3O4, the excellent reflection loss (RL) is −55.16 dB with an ultra-thin matching thickness of 1.6 mm, and the effective absorption bandwidth (EAB) is 3.84 GHz (from 14.16 GHz to 18.00 GHz) with the ultra-thin matching thickness of only 1.2 mm. In this work, the two hydrothermal methods replaced the conventional core-shell structure method and obtained EM wave absorption core-shell Co@Co3O4/GNs with ultra-thin thickness, strong EM wave absorption capability, and broad absorption bandwidth.

Synergistic effect of polyhedral iron-cobalt alloys and graphite nanosheets with excellent microwave absorption performance

Fast development of industry and technology has led to electromagnetic harm in the civil and military field, which has been obtained much attention and can be effectively weakened with the help of microwave absorbing materials. Hence, based on the route that multiple materials can optimize the impedance matching to further improve the microwave absorption performance, the polyhedral iron-cobalt alloy (FeCo)/graphite nanosheets (p-FCG) binary composites were prepared by the speedy and facile liquid reduction method. SEM results show polyhedral FeCo alloys with the size of 100–200 nm are located on the surface of graphite nanosheets (GNS), forming the stable three-dimensional structure. When the filled ratio is 40 wt% in the epoxy resin, the maximum reflection loss reaches −53.96 dB and the efficient bandwidth is 4.3 GHz with a thin thickness of 1.3 mm. More importantly, the effective bandwidth of p-FCG is able to cover the entire C, X and Ku bands with the matching thicknesses in the range from 1.3 mm to 4.2 mm. The microwave absorption performance of p-FCG is remarkable, which is superior to the single GNS and FeCo on account of synergistic effect and moderate impedance matching. Thus, the binary composites p-FCG may be expected as an engineering microwave absorber with the strong absorption, thin thickness, and wide frequency.

Ultrasmall HKUST-1 nanoparticles decorated graphite nanosheets for highly sensitive electrochemical sensing of DNA damage biomarker 8-hydroxy-2’-deoxyguanosine

Herein, graphite nanosheets (GN) were first prepared through simple liquid-phase exfoliation of graphite powder in N, N-dimethylacetamide (DMAC). After then, ultrasmall Cu-based metal organic frame (HKUST-1) nanoparticles (less than 5 nm) were in-situ anchored on the surface of graphite nanosheets with high degree of dispersion. Due to the intrinsic structural advantages of the as-synthesized HKUST-1 nanoparticles decorated graphite nanosheets (HKUST-1/GN) hybrids, including superior electron transfer ability and the greatly enhanced adsorption property, HKUST-1/GN shows excellent electrochemical sensing performance toward DNA damage biomarker 8-hydroxy-2’-deoxyguanosine with fast detection speed (∼240 s), wide linear window (10 nM–1 μM), high sensitivity (346857 μA mM−1 cm−2), low detection limit (∼2.5 nM), and good reproducibility. As a result, a highly sensitive electrochemical sensing platform for the detection of DNA damage biomarker 8-hydroxy-2’-deoxyguanosine was fabricated basing the as-prepared HKUST-1/GN hybrids. What is more, the developed electrochemical method was successfully used for the detection of real samples and exhibited satisfied result.

Polymer nanocomposite films with thicknesses (≤ 30 μm) corresponding to the lateral dimension of graphite nanosheets as straightforward thermal conducting pathways

Herein, Polysiloxane-based nanocomposite films with controlled assembly of modified graphite nanosheets (GNs) are fabricated, and their thermal and optical properties are evaluated as potential thermal interface materials (TIMs). The micro-dimensional thickness of the composite films is chosen to be the same as the average lateral dimension of GNs in order to create straightforward thermal conducting pathways with oriented GNs and to minimize heat loss through the polymer matrix. Paramagnetic iron oxide nanoparticles are deposited on the surface of GNs, which were obtained by the exfoliation of graphite flakes via chemical vapor deposition, and their anisotropic orientation inside a pre-polymer of polysiloxane is controlled by application of a magnetic field (0.45 T). The analysis revealed that the modified GNs were perpendicularly-oriented and anchored the film surfaces of the composite with high anisotropy under the application of a magnetic flux. The controlled assembly of GNs (5 wt%) enhanced the thermal diffusivity of the composites by 330% and 200% compared to a pristine polymer and a corresponding composite with a random distribution of GNs, respectively. The enhancements of the optical and thermal properties were elucidated in terms of variations in the magnetic susceptibility of GNs as well as the increased thermal conduction.

Electrically conductive adhesives based on acrylate resin filled with silver-plated graphite nanosheets and carbon nanotubes

Using the electroless plating method, the silver particles were successfully coated on the surface of graphite nanosheets (GNs) and carbon nanotubes (CNTs). Energy-dispersive spectrometer images showed that the content of silver was about 30–55 wt%, which were supported by the X-ray diffraction images and scanning electron microscopy images. Taking advantage of the ‘Synergistic Effects’ occurring between fillers with different morphologies, we were able to obtain silver-plated graphite nanosheets (Ag/GNs) and silver-plated carbon nanotubes (Ag/CNTs) filled polyacrylate-based electrically conductive adhesives (ECAs). Through the study, we found that the overall properties of the ECAs are optimum when the composite filler is at 30 wt% concentration, consisting of 21 wt% Ag/GNs and 9 wt% Ag/CNTs. Photograph of transmission electron microscope showed that the Ag/GNs and Ag/CNTs dispersed within the polymer matrix homogeneously. The conductivity of the ECAs reaches 8.71 S/cm and the shear strength is 0.47 MPa.

Miniemulsion polymerization of styrene in the presence of graphite nanosheets

Miniemulsion polymerization of styrene was performed in the presence of carbon nanosheets. As a result, PS particles were introduced onto the surface of graphite nanosheets by the miniemulsion polymerization. The formation of SDS surface micelles is influenced by the concentration of graphite nanosheets. Therefore, the composites show three different surface morphologies of graphite nanosheets surfaces; (1) the surface attached with PS particles, (2) the surface covered with PS thin film, and (3) the bare exposed surface. The crosslinked PS particles strongly stick to the surface of graphite nanosheets and the graphite nanosheet/ crosslinked PS composites show much improved dispersion stability in toluene.

Preparation and characterization of nickel-coated graphite nanosheets

Nickel-coated graphite nanosheets have been fabricated by simple oxidation and reduction process. The resulting products have a homogeneous and consecutive distribution of nickel coated on the surface of graphite nanosheets. The addition of polyvinylpyrrolidone (PVP) can control the size of nickel particles. Scanning electron microscopy (SEM) images, XRD pattern of the composites all confirm the deposition of nickel. The magnetic property of the coated GNs was characterized by Magnetic Property Measurement System (MPMS).

Surface modified graphite nanosheets used as adsorbent to remove 1,2-dichlorobenzene from water

The surface of graphite nanosheets (GNs) prepared by wet ball milling from expanded graphite (EG) was surface modified during the preparation process. The SEM images shown were employed to analyze the morphology of surface modified graphite nanosheets. The XPS date and Raman spectroscopy show that the milling process gives graphene surface more defects and phenolic groups compared to that of expanded graphite and graphite nanosheets. It was found that after ball milling, the surface modified GNs can be used as an effective adsorbent to remove 1,2-dichlorobenzene from water. Their adsorption capacity reaches 28.3 mg/g, which is comparable to that of carbon nanotubes (CNTs).

Instant modification of graphite nanosheets by the grafting of a styrene oligomer under microwave radiation

AbstractInstant grafting polymerization of styrene initiated by microwave radiation on the surface of graphite nanosheets (GNs) was carried out. The stability of the modified GN dispersions in different solvents indicated significant changes in the surface properties of GNs. In comparison with GNs without modification, the modified GNs showed more stable suspensions in a nonpolar organic solvent such as toluene and were more likely to form a precipitate when dispersed in distilled water, a polar solvent. Fourier transform infrared and thermogravimetric analysis were used to confirm the functionalized GNs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008