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     

Solvothermally reduced graphene oxide/polyimide composites: Structures and thermal and mechanical properties

Solvothermally reduced graphene oxide (SRGO)/polyimide (PI) composites were prepared by in situ polymerization. The structures and components were carefully investigated by X-ray diffraction. Thermal properties were measured by thermogravimetry and dynamic thermomechanical analysis. Mechanical properties were carefully evaluated by tensile testing and scanning electron microscopy. The SRGO/PI composites exhibit extremely high tensile strength and elastic modulus, which is 30% higher than that of pure PI film. Meanwhile, the thermal stability of SRGO/PI composites also displays an obvious enhancement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47164.     

Multifunctional polyimide/graphene oxide composites via in situ polymerization

In this article, we detail an effective way to improve electrical, thermal, and gas barrier properties using a simple processing method for polymer composites. Graphene oxide (GO) prepared with graphite using a modified Hummers method was used as a nanofiller for r‐GO/PI composites by in situ polymerization. PI composites with different loadings of GO were prepared by the thermal imidization of polyamic acid (PAA)/GO. This method greatly improved the electrical properties of the r‐GO/PI composites compared with pure PI due to the electrical percolation networks of reduced graphene oxide within the films. The conductivity of r‐GO/PI composites (30:70 w/w) equaled 1.1 × 10¹ S m^?1, roughly 10¹⁴ times that of pure PI and the oxygen transmission rate (OTR, 30:70 w/w) was reduced by about 93%. The Young's modulus of the r‐GO/PI composite film containing 30 wt % GO increased to 4.2 GPa, which was an approximate improvement of 282% compared with pure PI film. The corresponding strength and the elongation at break decreased to 70.0 MPa and 2.2%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40177.     

Investigation of thermomechanical properties and matrix–filler interaction on polyimide/graphene oxide composites

We report, the preparation of nanocomposites having polyimide (PI) as matrix and graphene oxide (GO) as filler, analyses of matrix–filler interactions, and enhancements in thermomechanical properties of PI/GO as compared with pristine PI. The matrix–filler interactions were analyzed by ¹H NMR, X‐ray photoelectron spectroscopy, and density functional theory calculations. The data suggested stronger matrix–filler interactions in PI/GO as compared with PI/G composites. The stronger matrix–filler interactions and homogeneous dispersion of fillers lead to a significant enhancement in mechanical properties in PI/GO nanocomposites. Thus, with just 1 wt% GO content, the modulus of PI/GO composite increased by ～106% as compared with pristine PI. Finally, thermal expansion coefficients of the nanocomposites are also investigated. A plausible hypothesis has been proposed in the text to explain the observed matrix–filler interactions and the subsequent property enhancements in nanocomposites. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Electrical properties of flexible graphene reinforced polyimide composites

The electrical properties of polyimide and the composite at different volumes fractions were studied in the frequency range 200–20 kHz and in the temperature range 30–200 °C. Increasing the volume fraction of graphene up to 10%, resulted in an extremely large increase in the dielectric constant, which indicates the composites remarkable ability to store electric potential energy under the effect of alternating electric field. An increase in dielectric constant was also observed with increasing temperature and decreasing frequency. The outstanding dielectric properties of polyimide graphene nanocomposites are attributed to the large volume fraction of interfaces in the bulk of the material. The measured increase in dielectric constant with increasing temperature was attributed to the segmental mobility of the polymer chains. The AC conductivity for polyimide and the composites was calculated from the loss factor and a remarkably high conductivity was obtained for the composites due to the formation of conducting paths in the matrix by the graphene sheets. Also this study showed that the thermal conductivity of the composites increased sharply with increasing graphene concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45372.     

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.     

金刚烷胺/氧化石墨烯复合材料的制备及其吸附性能

以氧化石墨烯和金刚烷为原料，通过水相合成法制备了金刚烷胺功能化氧化石墨烯复合材料A/GO，以FT-IR、XRD和XPS对A/GO进行了结构表征，并考察了A/GO对有机染料的吸附性能。结果表明，与氧化石墨烯相比，A/GO对甲基蓝（AB93）表现出高效吸附性，其吸附动力学和吸附等温模型分别符合拟二级动力学和Langmuir模型，理论最大吸附容量（qm）为1250.0 mg/g。热力学分析表明，A/GO吸附AB93是自发的放热过程。A/GO吸附AB93对盐（NaCl和KCl）表现出良好的耐盐性，而CaCl2能有效地促进A/GO吸附AB93。对于刚果红和AB93等的混合染料体系，A/GO能选择性吸附AB93。     

聚吡咯/氧化石墨烯复合材料的制备及电化学性能研究

分别采用物理球磨混合法、化学原位聚合法和化学原位聚合-还原法制备了聚吡咯/氧化石墨烯混合物、聚吡咯/氧化石墨烯(PPy/GO)和聚吡咯/还原氧化石墨烯(PPy/RGO)复合材料。通过三电极测试其电化学性能(循环伏安、恒流充放电和交流阻抗)。结果表明,通过化学原位聚合法制备的PPy/GO(304. 5 F/g)比电容远高于物理混合(16 F/g)和聚吡咯/还原氧化石墨烯(126. 4 F/g)。化学法原位聚合法制备PPy/GO最佳条件是冰浴条件下和加入表面活性剂对羟基苯磺酸钠。并通过X射线衍射(XRD)和扫描电子显微镜(SEM)对化学原位制备的PPy/GO组成、结构和形貌进行了表征。     

氧化石墨烯/天然橡胶复合材料的制备与性能

采用己内酰胺（CPL）改性氧化石墨烯（GO）（CPL-GO）,与天然橡胶（NR）复合后通过熔融共混法制备了CPL-GO/NR复合材料。考察了CPL-GO用量对CPL-GO/NR复合材料物理机械性能、界面相互作用和气体阻隔性能的影响。结果表明,CPL改性GO后,X射线衍射层间距增加,片层堆砌更为松散,CPL-GO与水接触角增至91.2°。当CPL-GO的质量分数为2.0%时,CPL-GO/NR复合材料的拉伸强度为26.1 MPa,较纯NR提高了50.9%。随着CPL-GO用量的增加,复合材料的储能模量增加,损耗因子的峰值减小,表明GO经CPL表面改性后与NR复合,增强了两相界面间的相互作用,从而提高了复合材料抵抗变形的能力。在40 ℃下,当CPL-GO的质量分数为3.0%时,CPL-GO/NR复合材料的气体渗透系数较纯NR下降了57.1%。     

ZnO/石墨烯复合材料的制备及性能研究

本文将采用溶胶-凝胶法制备纳米ZnO和通过Hummers法制备的石墨烯进行简单的一步超声复合,得到ZnO/石墨烯复合材料。利用XRD、TEM以及紫外可见分光光度计对所制备的ZnO和石墨烯样品进行测试表征,并以亚甲基蓝的降解效率来评价ZnO/石墨烯复合材料的光催化活性能。研究表明:ZnO/石墨烯的光催活性较纯氧化锌提高了4倍有余,当石墨烯质量比为15%时,ZnO/石墨烯的光催化活性最强。     

一步水热法合成铜改性的介孔γ-Al_2O_3及其吸附脱硫性能研究

采用一步水热合成法,以Al(NO3)3为铝源,P123为模板剂,Na OH、Na2CO3和K2CO3分别为沉淀剂,Cu(NO3)2为铜源,制备出负载铜的金属有序介孔γ-Al2O3,并运用N2吸附-脱附和XRD等技术对其结构进行表征,同时探讨了铜改性的介孔γ-Al2O3对模型燃油中的噻吩的吸附性能。结果表明,这3种沉淀剂都能制备出比表面积大(>226 m2/g),孔径分布中心为3.3 nm,孔体积为0.27⁰.35 cm3/g的负载铜的介孔γ-Al2O3,且样品都保持了较好的介孔结构。样品对模型燃油中噻吩的吸附脱硫性能表明,用Na OH作为沉淀剂且负载铜的介孔γ-Al2O3样品对噻吩的吸附性能较好,原因在于此样品具有较大的比表面积且铜在此样品中的分散性较好。     

Influence of structure of amines on the properties of amines‐modified reduced graphene oxide/polyimide composites

Graphene oxide (GO), as an important precursor of graphene, was functionalized using alkyl‐amines with different structure and then reduced to prepare reduced amines grafted graphene oxide (RAGOs) by N₂H₄ · H₂O. The successful chemical amidation reaction between amine groups of alkyl‐amines and carboxyl groups of GO was confirmed by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). Then RAGOs/polyimide nanocomposites were prepared via in situ polymerization and thermal curing process with different loadings of RAGOs. The modification of amine chains lead to homogenous dispersion of RAGOs in the composites and it formed strong interfacial adhesion between RAGOs and the polymer matrix. The mechanical and electrical properties of polyimide (PI) were significantly improved by incorporation of a small amount of RAGOs, the influence of structure of amines grafted on RAGOs on the enhancement effects of composites was discussed. The research results indicated that the proper structure of amine could effectively enhance the properties of composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43820.     

Preparation and electrochemical properties of polyaniline/reduced graphene oxide composites

Polyaniline (PANI)/reduced graphene oxide (rGO) composites were synthesized by in situ oxidative polymerization of aniline on reduced graphene sheets. Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscopy were used to characterize the composites. The results indicated PANI/rGO composites were produced and contained covalent bonds between the functional groups of PANI and rGO. A uniform coating of PANI on the rGO sheets had a synergistic effect on the properties of the composites. The electrochemical properties of the PANI/rGO composites produced using different feed ratios of aniline to rGO were studied. The results showed that the composites exhibited a maximum specific capacitance of 797.5 F/g at 0.5 A/g and minimum charge transfer resistance of 0.98 Ω when the feed ratio of aniline to rGO was 2:1. These values were superior to those of pure PANI and rGO. The composites also displayed excellent cycling stability, with specific capacitance retention of 92.43% after 1000 cycles. These stable structural composites show promise for the development of new supercapacitor applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46103.     

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.     

Bifunctional ternary manganese oxide/vanadium oxide/reduced graphene oxide as electrochromic asymmetric supercapacitor

A bifunctional ternary manganese oxide/vanadium oxide/reduced graphene oxide (MnO₂/V₂O₅/rGO) was developed for asymmetric electrochromic supercapacitor (EC-SC) application. The elemental mapping revealed uniformly distributed MnO₂, V₂O₅ and rGO, depicting homogenous synthesis of the hybrid composite. The phase composition, vibration modes and valance state of the ternary composite were analyzed via X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis, respectively. Interestingly, the as-prepared MnO₂/V₂O₅/rGO composite disclosed tremendous C_sp of 1403.5 F/g, which was higher compared to MnO₂/V₂O₅ (801.1 F/g), V₂O₅ (613.1 F/g), MnO₂ (126.7 F/g) and rGO (60.7 F/g). MnO₂/V₂O₅/rGO that appeared in dark green switched its visual color to orange at the charged state, confirming the electrochromic property. The bifunctional manganese oxide/vanadium oxide/reduced graphene oxide//copper-based metal-organic framework/reduced graphene oxide (MnO₂/V₂O₅/rGO//MrGO) asymmetrical EC-SC device revealed outstanding cycling stability (90.3% charge retention over 5000 cycles), tremendous specific capacitance (652.7 F/g) and maximum specific energy (60.4 Wh/kg). MnO₂/V₂O₅/rGO//MrGO asymmetrical EC-SC device demonstrated reversible color changes from dark green to orange at the discharged and charged states, respectively. The significantly great electrochromic and supercapacitive performance revealed that MnO₂/V₂O₅/rGO//MrGO is an outstanding electroactive candidate for the next generation of electrochromic supercapacitors.     

PET石墨烯复合材料的制备及性能研究

将氧化石墨烯(GO)与精对苯二甲酸(PET)、乙二醇(EG)进行原位聚合,制备了氧化石墨烯/PET(GO/PET)复合材料,研究了氧化石墨烯对PET聚酯的热性能、结晶性能的影响,并制备复合材料纤维,测试了其力学性能.结果表明:GO的加入提高了PET的热稳定性、结晶温度及结晶速率但没有改变PET的成核方式和生长方式.与纯PET相比,加入GO后纤维的拉伸强度降低,断裂伸长率提高,但与低GO含量的PET纤维相比,GO含量较高的PET纤维的拉伸强度更高.     

Dielectric properties of graphene–iron oxide/polyimide films with oriented graphene

The preparation of high‐dielectric‐constant (k) materials is important in the field of electronics. However, how to effectively use the function of fillers to enhance k is still a challenge. In this study, anisotropic graphene (GNS)–iron oxide (Fe₃O₄)/polyimide (PI) nanocomposite films with oriented GNSs were prepared by the in situ polymerization of 4,4′‐oxydianiline and pyromellitic anhydride in the presence of GNS–Fe₃O₄. Films of the precursors were fabricated, and this was followed by stepwise imidization under a magnetic field at a higher temperature to orient the magnetic sheets. The orientation of GNS–Fe₃O₄ and the relationships of the GNS–Fe₃O₄ content and measurement frequency with the dielectric properties of the GNS–Fe₃O₄/PI films were studied in detail. The dielectric property differences of the GNS–Fe₃O₄/PIs with GNS–Fe₃O₄ parallel or perpendicular to the film surface were not obvious, when the content of GNS–Fe₃O₄ was lower than 5 wt %. However, at the percolation threshold, the k values of GNS–Fe₃O₄/PI films with horizontal GNS–Fe₃O₄ were much higher than those of the other two kinds of films at 10³ Hz; this was derived from the contribution of more effective microcapcitors parallel to the film surface. So, making the GNS–Fe₃O₄ parallel to the film surface greatly enhanced k of GNS–Fe₃O₄. However, switching the charges on the large lateral surface of the parallel GNSs with the electric field also caused a higher dielectric loss and the frequency dependence of k and the dielectric loss at low frequency. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43041.     

氧化石墨烯复合TiO2-B薄膜的制备及其电致变色性能

目前具有一维纳米结构的TiO₂薄膜在电致变色领域应用主要受限于材料光调制幅度小、响应时间长、循环稳定性差等缺点。为了解决上述问题,本文采用沉积法将B型二氧化钛纳米管（TiO₂-B）与氧化石墨烯复合,以TiO₂粉末为原料,采用水热法得到钛酸纳米管后,利用沉积法在氟掺杂的氧化锡玻璃（FTO）基底上制备了高透明度、大光调制范围以及优良循环性能的氧化石墨烯复合B型二氧化钛纳米管电致变色薄膜（GO/TiO₂）。借助XRD、XPS、Raman、FESEM、HR-TEM等分析手段研究了氧化石墨烯用量对GO/TiO₂复合薄膜电致变色性能的影响。研究结果表明,当GO与钛酸纳米管的质量比（GO/钛酸）为7％时,GO/TiO₂复合薄膜离子扩散系数为1.46×10^-8cm²/s,着色效率值为38.1cm²/C,具有良好的电致变色性能。在-1.6V、633nm处,GO/TiO₂电致变色薄膜的光调制幅度可达77％,GO/TiO₂薄膜的着色和漂白时间分别为28.6s和4.8s,100次循环后的光调制幅度保持率为96.1％。     

氧化石墨烯/密胺树脂导电复合材料的制备与性能研究

采用的改进的Hummers法和组合剥离技术制备了氧化石墨烯(GO),并以氧化石墨烯、甲醛溶液、三聚氰胺为原料,采用原位合成技术制备石墨烯/密胺树脂导电复合材料(GO/MF)及含有水合肼的氧化石墨烯/密胺树脂复合材料(GO/MF+N_2H_4),并对其结构、热稳定性和导电性等进行研究分析。试验结果表明:GO/MF+N_2H_4试样的热稳定性最佳,氧化石墨烯的加入,提高了密胺树脂材料的导电性,且添加质量分数0.9%GO的GO/MF+N_2H_4试样出现导电临界值,体积电阻率达到1.5×10~4Ω·m,为制备具有抗静电性能和导电性能的密胺树脂新型复合材料提供一定的基础理论参考。     

Mechanical properties of graphene oxide reinforced alumina matrix composites

Graphene oxide (GO) reinforced alumina matrix composites have been fabricated by using graphene oxide synthesized by a modified Hummer's method. Samples were prepared by powder metallurgy and consolidated by Spark Plasma Sintering (SPS). The influence of GO addition on the microstructure and mechanical properties of the composites was investigated. Results show a significant increase (almost 35%) of the fracture toughness for composites containing 0.5 wt% graphene oxide compared to sintered pure alumina. In order to find reasons for this improvement Scanning/Transmission Electron Microscopy (SEM/TEM) observations were carried out. They reveal a good interface between the reinforcement and the matrix as well as such mechanisms like branching, deflection and bridging of crack propagation.