石墨烯/玻璃块体复合材料的制备及性能

本文报道了还原氧化石墨烯/钠钙硅(rGO/SLS)玻璃块体复合材料的热压制备和力学性能。首先以3-氨基丙基三乙氧基硅烷为表面活性剂修饰玻璃粉微粒;然后在水溶液中带负电的氧化石墨烯(GO)纳米片通过静电自组装与被氨基修饰过带正电的玻璃颗粒相结合生成复合颗粒。通过高温真空热压烧结,GO被还原成rGO,从而原位生成rGO/SLS玻璃块状复合材料。结果表明,rGO均匀分布在玻璃基质中,并明显增强了复合材料的机械性能。rGO/SLS玻璃块体复合材料中rGO的含量为0.5%(质量分数)时,复合材料的弯曲强度比纯的SLS玻璃提高了约一倍。     

Preparation and characterization of reduced graphene oxide-reinforced boron carbide ceramics by self-assembly polymerization and spark plasma sintering

A self-assembly polymerization process was used to prepare graphene oxide/boron carbide (GO/B₄C) composite powders, spark plasma sintering (SPS) was used to fabricate reduced graphene oxide/boron carbide (rGO/B₄C) composites at 1800 °C and 30 MPa with a soaking time of 5 min. The effects of rGO addition on mechanical properties of the composites, such as Vickers hardness, flexural strength and fracture toughness, were investigated. The results showed that GO/B₄C composite powders were successfully self-assembled and a network structure was formed at high GO contents. The flexural strength and fracture toughness of rGO/B₄C composites were 643.64 MPa and 5.56 MPa m^1/2, respectively, at 1 and 2.5 wt.% rGO content, corresponding to an increase of 99.11% and 71.6% when compared to B₄C ceramics. Uniformly dispersed rGO in rGO/B₄C composites played an important role in improving their strength and toughness. The toughening mechanisms of rGO/B₄C composites were explained by graphene pull-out, crack deflection and bridging.     

聚偏氟乙烯/石墨烯复合材料的制备及性能研究

用溶液共混法制备出聚偏氟乙烯/氧化石墨烯复合材料(PVDF/GO),经高温热压将GO还原得到聚偏氟乙烯/还原氧化石墨烯复合材料(PVDF/rGO)。研究了填料种类及含量对复合材料电学性能、热稳定性和力学性能的影响。结果表明：随GO和rGO的添加,两种复合材料的介电常数(ε _r)均变大、介电损耗(tanδ)变化不大;低含量下GO和rGO均能提高PVDF的热稳定性,但rGO对PVDF性能的改善效果更好;随填料含量从0增加到8%(质量),100 Hz下PVDF/rGO复合材料的ε _r从3.60增加到38.30,PVDF/rGO[4%(质量)]复合材料失重率为5%的分解温度较纯PVDF提高了6.44℃。rGO增强了PVDF的刚性,PVDF/rGO复合材料的拉伸强度先增大后减小,杨氏模量逐渐增大,当rGO含量为4%(质量)时拉伸强度最大,拉伸强度和弹性模量分别较纯PVDF提高了35.30%、22.58%。但GO和rGO都降低了复合材料的击穿场强。     

In Situ Processing of Graphene/Leucite Nanocomposite Through Graphene Oxide/Geopolymer

Graphene/leucite nanocomposites (rGO/leucite) were prepared through in situ reduction of graphene oxide/geopolymer (rGO/KGP) composites. The effects of rGO on the microstructure and mechanical properties with respect to the geopolymer matrix after the high‐temperature treatment were investigated systematically. The results show that GO is first partially reduced in the geopolymeric solution and then completely under the post high‐temperature treatment. The rGO sheets undergo no interfacial reactions with the matrix even after thermal treatment. The rGO/geopolymer composites fully transform to rGO/leucite composites after being treated at 1000°C for 30 min in an argon atmosphere. Significant improvements in mechanical properties were achieved through rGO reinforcement giving flexural strength, elastic modulus, and fracture toughness of 91.1 MPa, 60.5 GPa, and 2.04 MPa·m^1/2, increased by 120%, 8%, and 1.5%, respectively, compared with the leucite matrix alone.     

Preparation and properties of reduced graphene oxide/fused silica composites

An in situ strategy for fabrication of reduced graphene oxide/fused silica (rGO/FS) composites using 3-aminopropyltriethoxysilane as surfactant is reported. GO nanosheets were bound to FS particles by an electrostatic assembly between ultra thin negatively charged GO sheets and positively charged amino-modified FS particles. After spark plasma sintering, rGO/FS bulk composites have been produced from the GO and FS composite particles with GO being reduced to rGO in vacuum at high temperatures. Results show that rGO sheets were well dispersed in the matrix, and conductivity of these rGO/FS composites at room temperature was strongly dependent on the rGO nanosheet concentration. i.e., the conductivity of rGO/FS was increased to 10⁻⁴ S/cm when a conducting network was formed inside the composites. The effect of GO nanosheets on the mechanical properties of rGO/FS bulk composites was also investigated. The addition of 1 wt.% GO sheets to FS resulted in 72% increase in Vickers hardness, indicating the stress transfering from the FS matrix to the rigid rGO sheets. With the same rGO content, the fracture toughness of the as-prepared composites was increased by 74%. The main toughening mechanisms were thought to be crack deflection, crack branching, pulling-out and bridging of the rGO sheets.     

Effects of substitution for carbon black with graphene oxide or graphene on the morphology and performance of natural rubber/carbon black composites

In this study, nanosheets including graphene oxide (GO) and reduced graphene oxide (rGO), were incorporated into natural rubber (NR), to study the effects of substituting GO or rGO for carbon black (CB) on the structure and performance of NR/CB composites. The morphological observations revealed the dispersion of CB was improved by partially substituting nanosheets for CB. The improvements in static and dynamic mechanical properties were achieved at small substitution content of GO or rGO nanosheets. With substitution of rGO nanosheets, significant improvement in flex cracking resistance was achieved. NR/CB/rGO (NRG) composites has a much lower heat build‐up value compared with NR/CB/GO (NG) composites at a high load of nanosheets. However, both GO and rGO tended to aggregate at a high concentration, which led to the poor efficiency on enhancing the dynamic properties, or even deteriorate the performance of rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41832.     

Functionalized graphene‐reinforced rubber composite: Mechanical and tribological behavior study

A functionalized graphene, fluorinated graphene nanosheets (FGS), and SiO₂ nanoparticles as reinforcing fillers were employed to improve the mechanical properties of the solution styrene butadiene and butadiene rubber composites (SSBR‐BR). The results showed that the mechanical properties of SSBR‐BR composite filled with FGS were substantially improved than those of the unfilled and equivalent filler loaded graphene oxide (GO) and reduced graphene oxide (rGO) filled SSBR‐BR composites. It can be ascribed to the fact that the hydrophobic surface of FGS can be endowed the good dispersion in rubber matrix and stronger interfacial interaction between rubber and fillers. The tribological properties of these composites are also investigated. The results reveal that incorporation of GO, rGO, and FGS in SSBR‐BR composites can decrease antiwear properties because the existence of layered graphene promotes to tear and peel off. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44970.     

Mechanical,thermal conductive,and dielectric properties of fluoroelastomer/reduced graphene oxide composites in situ prepared by solvent thermal reduction

Fluoroelastomer (FKM)/reduced graphene oxide (rGO) composites are in situ prepared by solvent thermal reduction method in N,N‐dimethylformamide (DMF) solution. The reduction of graphene oxide (GO) is characterized by X‐Ray photoelectron (XPS), ultraviolet–visible (UV–vis), and Fourier transform infrared (FTIR) spectra. GO and rGO are both efficient fillers to improve the mechanical properties of FKM. The dispersibility of rGO is improved after solvent thermal reduction which is confirmed by scanning electron micrograph (SEM) and X‐ray diffraction (XRD). The homogenous suspension of FKM/rGO composites in DMF can stay stable for more than a month. The dielectric permittivity of FKM/rGO (5 phr) is 26.4 at the frequency of 10⁻¹ Hz, higher than the pure FKM (8.1). The thermal conductivity of rGO/FKM composites increases. POLYM. COMPOS., 35:1779–1785, 2014. © 2013 Society of Plastics Engineers     

Investigation of thermal properties and mechanical properties of reduced graphene oxide/polyimide resin composites

In this article, reduced graphene oxide/polyimide resin composites which exhibited enhancements in mechanical properties were successfully fabricated by hot‐pressing, and reduced graphene oxide nanosheets were synthesized by thermal reduced method, which can readily mix with PI powders in aqueous solution by sonication process. The chemical structures of rGO were carefully characterized by X‐ray diffraction, Fourier transfer infrared spectroscopy and X‐ray photoelectron spectroscopy. The field emission scanning electron microscopy observations showed that the rGO displayed excellent dispersibility and compatibility with the PI matrix. The mechanical analysis indicated that the tensile and flexural strength values of the rGO/PI resin composite with 1.5 wt% rGO loading reached 80.7 and 133.3 MPa, respectively. Compared with pure PI, the optimized rGO/PI resin composite exhibited an enhancement of 30% in tensile strength, 19% in flexural strength and 27% in impact strength, due to the fine dispersion of high specific surface area of graphene nanosheets and the good adhesion between the rGO and the matrix. In addition, thermogravimetric analysis, dynamic mechanical analysis, and dielectric properties were also investigated. POLYM. COMPOS., 38:2321–2331, 2017. © 2015 Society of Plastics Engineers     

Impact of enhanced interfacial strength on physical,mechanical and tribological properties of copper/reduced graphene oxide composites: Microstructural investigation

Copper/reduced graphene oxide (rGO) composites were prepared to improve the mechanical and tribological properties of copper without adversely affecting its physical properties in any significant manner. No hazardous chemicals were used for reduced graphene oxide production, which maintained the integrity of layers. For better dispersibility of rGO in the copper matrix, electroless deposition of copper was done on the activated and sensitized rGO surfaces. Different amounts of prepared Copper/rGO nanocomposites were then dispersed in bulk copper using ethanol and finally compacted using spark plasma sintering. The coefficient of friction of copper reinforced with 0.5 wt% of nanocomposite reduced by 77.5% compared to neat copper. The flexural strength of copper reinforced with 0.75 wt% of nanocomposite and modulus of 1 wt% of nanocomposite reinforced copper increased by 15.2% and 31.3%, respectively, with different strengthening mechanisms before and after yield point. The increase in hardness and strength of the material along with thin rGO films in the wear track accounted for the sharp decrease in the coefficient of friction for the composites. There was a minimal and gradual decrease in the physical properties (electrical and thermal conductivities) of the composites with an increase in the amount of reinforcement. The two-step composite fabrication process ensured better dispersion of rGO in the copper matrix, which resulted in even properties throughout the composite.     

Simultaneous in situ reduction,self-alignment and covalent bonding in graphene oxide/epoxy composites

Graphene oxide (GO)/waterborne epoxy (EP) composites are prepared using an easy, all aqueous, in situ polymerization method. GO is reduced in situ using hydrazine to achieve highly stable reduced graphene oxide (rGO)/EP dispersions, leading to the formation of composites with a self-aligned layered structure and highly anisotropic properties between the direction of alignment and that perpendicular to it. The strong covalent bonding between the epoxy and rGO and the highly aligned, ultralarge rGO sheets give rise to a remarkable percolation threshold of 0.12 vol.%, as well as much improved mechanical, electrical and thermal properties of the composites in the alignment direction. They outperform those containing GO sheets that are bonded to the epoxy matrix through a weaker π–π stacking mechanism.     

Preparation of functional reduced graphene oxide and its influence on the properties of polyimide composites

Homogeneous dispersion and strong filler–matrix interfacial interactions were vital factors for graphene for enhancing the properties of polymer composites. To improve the dispersion of graphene in the polymer matrix and enhance the interfacial interactions, graphene oxide (GO), as an important precursor of graphene, was functionalized with amine‐terminated poly(ethylene glycol) (PEG–NH₂) to prepare GO–poly(ethylene glycol) (PEG). Then, GO–PEG was further reduced to prepare modified reduced graphene oxide (rGO)–PEG with N₂H₄·H₂O. The success of the modification was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. Different loadings of rGO–PEG were introduced into polyimide (PI) to produce composites via in situ polymerization and a thermal reduction process. The modification of PEG–NH₂ on the surface of rGO inhibited its reaggregation and improved the filler–matrix interfacial interactions. The properties of the composites were enhanced by the incorporation of rGO–PEG. With the addition of 1.0 wt % rGO–PEG, the tensile strength of PI increased by 81.5%, and the electrical conductivity increased by eight orders of magnitude. This significant improvement was attributed to the homogeneous dispersion of rGO–PEG and its strong filler–matrix interfacial interactions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45119.     

Preparation of well‐dispersed reduced graphene oxide and its mechanical reinforcement in polyvinyl alcohol fibre

The current work reports the preparation and characterization of polyvinyl alcohol (PVA) composite fibres reinforced with graphene reduced from graphene oxide (GO) by using oligomeric proanthocyanidin (OPC) as a reductant. After reduction, most of the oxygen‐containing groups were removed from the GO and reduced graphene oxide (rGO) was prepared. As a result of combined OPC as a dispersant, rGO could be well dispersed in a dimethyl sulfoxide/H₂O mixed solvent and in PVA matrix, and the PVA/rGO dispersion was wet spun followed by hot drawing to prepare continuous PVA/rGO composite fibres. The PVA/rGO composite fibres exhibited a significant enhancement of mechanical properties at low rGO loadings; in particular the tensile strength and Young's modulus of the 2.0 wt% rGO and PVA composite fibre increased to 244% and 294% respectively relative to neat PVA fibre. Moreover, the storage modulus (?10 °C) and T_g increased to 300% and 7.2 °C, respectively. © 2016 Society of Chemical Industry     

Enhanced toughness and strength of boron carbide ceramics with reduced graphene oxide fabricated by hot pressing

Boron carbide (B₄C) hybrids with different contents of graphene oxide (GO) were prepared by a heterogeneous co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as the cationic surfactant. The as-obtained mixtures were further hot-pressed at 1950 °C for 60 min under 30 MPa, by which B₄C–reduced GO (rGO) composites were fabricated. It was found that the addition of only 0.5 wt% rGO could alter the predominance of trans-granular fracture in monolithic B₄C ceramic material to mixed trans-granular and inter-granular modes in B₄C–rGO composites. The flexural strength and fracture toughness of the B₄C–2 wt% rGO were increased by 31% (from 350 to 455 MPa) and 83% (from 3.20 to 5.85 MPa·m^1/2), respectively, compared with those of pure B₄C. The improved mechanical properties are attributed to the mechanisms of pull-out and bridging of rGO and crack deflection, as evidenced by microstructural observations. The energy dissipation in the present B₄C–rGO composites was further verified using two micromechanical models.     

一段混炼时间对石墨烯/天然橡胶/溶聚丁苯橡胶复合材料性能的影响

采用一段密炼和二段开炼的两段混炼工艺制备氧化石墨烯(GO)/天然橡胶(NR)/溶聚丁苯橡胶(SSBR)和还原氧化石墨烯(rGO)/NR/SBR复合材料,研究一段混炼时间对GO/NR/SSBR和rGO/NR/SSBR复合材料性能的影响。结果表明:随着一段混炼时间的延长,GO/NR/SSBR和rGO/NR/SSBR复合材料的Fmax和FL增大,t90缩短;邵尔A型硬度、300%定伸应力、拉伸强度和撕裂强度呈先增大后减小的趋势,导电性能和导热性能呈先提高后降低的趋势,气密性能呈先提高后平稳再降低的趋势。     

Effect of oxidation debris on spectroscopic and macroscopic properties of graphene oxide

Oxidation debris (OD) and graphene oxide (GO) before and after OD removal were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, mass spectroscopy, X-ray diffraction, transmission electron microscopy and potentiometric titration, respectively. OD removal decreased GO absorption intensity in UV/Vis spectra, caused changes in peak position and absorption intensity in FTIR spectra, and resulted in the decrease of I_D/I_G in Raman spectra. OD was amorphous and had higher content of acidic groups than purified GO. OD contributed 10–25% of overall surface charge density to unpurified GO in spite of small amount (ca. 1% mass). OD removal decreased significantly GO dispersibility in aqueous solution, but increased obviously the electrical conductivity of reduced graphene oxide (rGO) and the apparent density of compacted rGO. The removal of OD was necessary because of its striking effects on both GO spectroscopic and macroscopic properties. Batch desorption in NaOH solution was recommended for OD removal from as-prepared graphite oxide because of slow OD desorption kinetics.     

Enhanced mechanical properties of glass fibre epoxy composites by 2D exfoliated graphene oxide filler

Graphene oxide (GO) received a significant attention in the scientific community due to their excellent mechanical properties identifying themselves as an alternative and combinatory to various other metals and composites. Though GO possess excellent strength, it was observed from the literature that graphene oxide consisting of hydroxyl group elements ensue in poor bonding. Thus reduced functional group density (rFGD) graphene is preferred which has an advantage of good bonding, alongside very small quantity as a filler is required to achieve the enhancement equivalent to graphene oxide which forms the novelty of the current work. In current case, 3, 6 and 9 wt% of rFGD is dispersed into E-glass fibre reinforced composite by traditional hand layup technique. The obtained results revealed that, the tensile, flexural and impact strength have shown superior enhancement with 3 and 6 wt% of rGO than neat E-glass epoxy (0 wt% rGO), whereas an asymptotic decrement is noticed at 9 wt% when tested with ASTM standards except for impact strength. The microstructural studies also indicated the proper adhesion and alignment of fibres without any agglomerations corroborate the enhancement of properties. These overall finding supports the suitability of the developed laminates for potential use in structural applications in aerospace industry.     

CE/BMI/GO复合材料的制备与性能

以双马来酰亚胺树脂(BMI)预聚体改性氰酸酯树脂(CE)(CE/BMI)作为基体树脂,以氧化石墨烯(GO)作为增强体,通过浇铸成型工艺制备了CE/BMI/GO复合材料。研究了GO的质量分数对CE/BMI/GO复合材料力学和摩擦学性能的影响。结果表明,GO的加入有益于复合材料力学性能和摩擦学性能的提高。GO的质量分数为0.8%时复合材料获得最好的韧性和耐磨性。对比基体树脂,CE/BMI/GO复合材料的冲击强度和弯曲强度分别提高了33.6%和27.6%;摩擦系数和磨损率分别降低了22.5%和77.6%。     

Conversion of pencil graphite to graphene/polypyrrole nanofiber composite electrodes and its doping effect on the supercapacitive properties

Graphene platelets were synthesized from pencil flake graphite and commercial graphite by chemical method. The chemical method involved modified Hummer's method to synthesize graphene oxide (GO) and the use of hydrazine monohydrate to reduce GO to reduced graphene oxide (rGO). rGO were further reduced using rapid microwave treatment in presence of little amount of hydrazine monohydrate to graphene platelets. Chemically modified graphene/polypyrrole (PPy) nanofiber composites were prepared by in situ anodic electropolymerization of pyrrole monomer in the presence of graphene on stainless steel substrate. The morphology, composition, and electronic structure of the composites together with PPy fibers, graphene oxide (GO), rGO, and graphene were characterized using X‐ray diffraction (XRD), laser‐Raman, and scanning electron microscopic (SEM) methods. From SEM, it was observed that chemically modified graphene formed as a uniform nanocomposite with the PPy fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge–discharge process when used as supercapacitor electrodes. A specific capacitance of supercapacitor was as high as 304 F g^?1 at a current density of 2 mA cm^?1 was achieved over a PPy‐doped graphene composite. POLYM. ENG. SCI., 55:2118–2126, 2015. © 2014 Society of Plastics Engineers     

Preparation and properties of acrylonitrile–butadiene rubber–graphene nanocomposites

The graphene oxide (GO) was prepared by sonication‐induced exfoliation from graphite oxide, which was produced by oxidation from graphite flakes with a modified Hummer's method. The GO was then treated by hydrazine to obtain reduced graphene oxide (rGO). On the basis of the characterization results, the GO was successfully reduced to rGO. Acrylonitrile–butadiene rubber (NBR)–GO and NBR–rGO composites were prepared via a solution‐mixing method, and their various physical properties were investigated. The NBR–rGO nanocomposite demonstrated a higher curing efficiency and a change in torque compared to the gum and NBR–GO compounds. This agreed well with the crosslinking density measured by swelling. The results manifested in the high hardness (Shore A) and high tensile modulus of the NBR–rGO compounds. For instance, the tensile modulus at a 0.1‐phr rGO loading greatly increased above 83, 114, and 116% at strain levels of 50, 100, and 200%, respectively, compared to the 0.1‐phr GO loaded sample. The observed enhancement was highly attributed to a homogeneous dispersion of rGO within the NBR matrix; this was confirmed by scanning electron microscopy and transmission electron microscopy analysis. However, in view of the high ultimate tensile strength, the NBR–GO compounds exhibited an advantage; this was presumably due to strong hydrogen bonding or polar–polar interactions between the NBR and GO sheets. This interfacial interaction between GO and NBR was supported by the marginal increase in the glass‐transition temperatures of the NBR compounds containing fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42457.