Effects of treatment temperature on the reduction of GO under alkaline solution during the preparation of graphene/geopolymer composites

Homogeneously dispersed reduced-graphene-oxide (rGO) reinforced geopolymer composites were successfully prepared through in-situ reduction of graphene oxide (GO) under alkaline geopolymeric condition. The effects of treatment temperatures on the reduction of GO under the alkaline solution during the rGO/geopolymer preparation process were characterized systematically. The results showed that GO could be in situ reduced under alkaline geopolymer solution at various temperatures (25–80 °C) for 3 h. The reduction degree of rGO was improved with increasing the reaction temperature. The rGO was well dispersed, and the rGO/geopolymer composites showed amorphous structure.     

Fabrication of polymer/microwave‐reduced graphite oxide nanocomposites by ball‐milling assisted wet compounding

Microwave‐induced reduction of graphite oxide (GO) is a promising method for rapid and scalable production of graphene. However, homogeneous incorporation of thus prepared graphene into polymer matrix is still a hard task. In this article, we present a ball‐milling assisted wet compounding method for the fabrications of microwave‐reduced GO (MRGO)/polymer composites. MRGO powders were added into a solution of polystyrene (PS) and then mechanically exfoliated in a stirring mill. Scanning electron microscopy and transmission electron microscopy investigations show that the graphene sheets have been homogeneously dispersed in the PS matrix. The composites show pronouncedly improved properties. The thermal degradation temperature of composites increased by 34°C with the addition of 5wt% MRGO in PS. Up to 76% improvement of storage modulus (at 30°C) is achieved by compounding with 10wt% MRGO.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

高电活性石墨烯/聚苯胺纳米复合材料的制备和表征

采用了一种简单有效地方法制备了高电活性的石墨烯/聚苯胺复合材料。首先,将苯胺在氧化石墨烯（GO）的水性分散液中氧化聚合,制备了氧化石墨烯/聚苯胺（GO/PANI）,再将GO/PANI与水合肼反应,制得还原-氧化石墨烯/聚苯胺（R（GO/PANI））。利用透射电子显微镜（TEM）,热失重分析（TGA）和循环伏安法（CV）对GO/PANI和R（GO/PANI的形貌,热稳定性和电化学性能进行了分析研究。结果表明,GO表面存PANI,且R（GO/PANI）的热稳定性和电活性都明显高于GO/PANI。     

还原氧化石墨烯增强水泥基复合材料微观结构及力学性能

采用水热还原法制备了不同还原程度的还原氧化石墨烯(RGO),并将其添加到水泥浆体中,制得石墨烯增强水泥基复合材料。采用傅里叶变换红外光谱(FT-IR)、力学性能测试仪、扫描电子显微镜(SEM)对氧化石墨烯(GO)还原程度及水泥基复合材料的力学性能和微观结构进行测试。结果表明,在120℃水热条件下,控制不同还原时间可以得到不同还原程度的RGO;随着GO还原程度的提高,复合材料力学强度不断增加;RGO可使水泥更加密实,降低了水泥浆体的孔隙率,对水泥基复合材料起到增强增韧的作用。     

氧化石墨烯-壳聚糖纤维制备及其对染料吸附性能

选取壳聚糖和聚乙烯醇与氧化石墨烯共混复合,通过湿法纺丝工艺技术,制备不同氧化石墨烯含量的氧化石墨烯-壳聚糖复合纤维。利用扫描电镜和红外光谱表征了复合纤维的微观结构和化学组成,结果表明:复合纤维成形较好,氧化石墨烯与壳聚糖之间形成了稳定的氢键。通过染料吸附试验可知:氧化石墨烯可明显提高复合纤维对染料的吸附能力,当氧化石墨烯质量分数为1%时,吸附效果最理想,吸附量可达407 mg/g,有望用于印染废水的综合处理。     

In-situ synthesis and characterization of electrically conductive polypyrrole/graphene nanocomposites

Polypyrrole (PPy)/graphene (GR) nanocomposites were successfully prepared via in-situ polymerization of graphite oxide (GO) and pyrrole monomer followed by chemical reduction using hydrazine monohydrate. The large surface area and high aspect ratio of the in-situ generated graphene played an important role in justifying the noticeable improvements in electrical conductivity of the prepared composites via chemical reduction. X-ray photoelectron spectroscopy (XPS) analysis revealed the removal of oxygen functionality from the GO surface after reduction and the bonding structure of the reduced composites were further determined from FTIR and Raman spectroscopic analysis. For PPy/GR composite, intensity ratio between D band and G band was high (∼1.17), indicating an increased number of c-sp² domains that were formed during the reduction process. A reasonable improvement in thermal stability of the reduced composite was also observed. Transmission electron microscopy (TEM) observations indicated the dispersion of the graphene nanosheets within the PPy matrix.     

Preparation and properties of octadecylamine modified graphene oxide/styrene‐butadiene rubber composites through an improved melt compounding method

Octadecylamine modified graphene oxide/styrene‐butadiene rubber (GO‐ODA/SBR) composites are prepared by a novel and environmental‐friendly method called “Improved melt compounding”. A GO‐ODA/ethanol paste mixture is prepared firstly, and then blended with SBR by melt compounding. GO‐ODA sheets are uniformly dispersed in SBR as confirmed by scanning electron microscope, transmission electron microscopy, and X‐ray diffraction. The interfacial interaction between GO‐ODA and SBR is weaker than that between GO and SBR, which is proved by equilibrium swelling test and dynamic mechanical analysis. GO‐ODA/SBR show more pronounced “Payne effect” than GO/SBR composites, indicating enhanced filler networks resulted from the modification of GO with ODA. GO‐ODA/SBR composite has higher tensile strength and elongation at break than SBR and GO/SBR composite. The tensile strength and elongation at break for the composite with 5 parts GO‐ODA per hundred parts of rubber increase by 208% and 172% versus neat SBR, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42907.     

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     

Fabrication of polypyrrole/graphene oxide nanocomposites by liquid/liquid interfacial polymerization and evaluation of their optical,electrical and electrochemical properties

A novel route has been developed to synthesize polypyrrole (PPy)/graphene oxide (GO) nanocomposites via liquid/liquid interfacial polymerization where GO and initiator was dispersed in the aquous phase and the monomer was dissolved in the organic phase. The synthesized samples were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), ultraviolet–visible absorption (UV–vis), X-ray diffraction (XRD), electrochemical and electrical conductivity measurements. A good dispersion of the GO sheets within the PPy matrix was observed from the morphological analysis. The composites exhibited noticeable improvement in thermal stability and electrical conductivity in comparison to pure polypyrrole. The composites showed excellent electrochemical reversibility at the scan rate of 0.1 V/s and good cyclic stability even up to 100th cycle. Newly developed graphene oxide based polypyrrole composite could be applied in electrochemical energy storage device.     

Graphene/nanosized silicon composites for lithium battery anodes with improved cycling stability

Graphene/nanosized silicon composites were prepared and used for lithium battery anodes. Two types of graphene samples were used and their composites with nanosized silicon were prepared in different ways. In the first method, graphene oxide (GO) and nanosized silicon particles were homogeneously mixed in aqueous solution and then the dry samples were annealed at 500 °C to give thermally reduced GO and nanosized silicon composites. In the second method, the graphene sample was prepared by fast heat treatment of expandable graphite at 1050 °C and the graphene/nanosized silicon composites were then prepared by mechanical blending. In both cases, homogeneous composites were formed and the presence of graphene in the composites has been proved to effectively enhance the cycling stability of silicon anode in the lithium-ion batteries. The significant enhancement on cycling stability could be ascribed to the high conductivity of the graphene materials and absorption of volume changes of silicon by graphene sheets during the lithiation/delithiation process. In particular, the composites using thermally expanded graphite exhibited not only more excellent cycling performance, but also higher specific capacity of 2753 mAh/g because the graphene sheets prepared by this method have fewer structural defects than thermally reduced GO.     

Improvement of mechanical properties of graphene oxide/poly(allylamine) composites by chemical crosslinking

Graphite oxide was prepared by oxidation of graphite using the Hummers method, and its ultrasonication in water yielded dispersed graphene oxide (GO) sheets. These sheets were then crosslinked with a water soluble polymer, namely poly (allylamine) hydrochloride (PAH), by carbodiimide coupling. Free standing composite films were obtained by filtration. These crosslinked composites showed better mechanical properties than unmodified GO films and those of composites that were made by simple mixing of GO and PAH. The filtration process was optimized to produce strong GO films which were subsequently crosslinked with PAH in-situ to produce very strong composites with tensile strengths up to146 MPa.     

Synthesis of conducting graphene/Si3N4 composites by spark plasma sintering

Graphene/silicon nitride (Si₃N₄) composites with high fraction of few layered graphene are synthesized by an in situ reduction of graphene oxide (GO) during spark plasma sintering (SPS) of the GO/Si₃N₄ composites. The adequate intermixing of the GO layers and the ceramic powders is achieved in alcohol under sonication followed by blade mixing. The reduction of GO occurs together with the composite densification in SPS, thus avoiding the implementation of additional reduction steps. The materials are studied by X-ray photoelectron and micro-Raman spectroscopy, revealing a high level of recovery of graphene-like domains. The SPS graphene/Si₃N₄ composites exhibit relatively large electrical conductivity values caused by the presence of reduced graphene oxide (∼1 S cm⁻¹ for ∼4 vol.%, and ∼7 S cm⁻¹ for 7 vol.% of reduced-GO). This single-step process also prevents the formation of highly curved graphene sheets during the thermal treatment as the sheets are homogeneously embedded in the ceramic matrix. The uniform distribution of the reduced GO sheets in the composites also produces a noticeable grain refinement of the silicon nitride matrix.     

Assessment on the mechanical,structural, and thermal attributes of green graphene-based water soluble polymer electrolyte composites

In the current study, graphene oxide (GO) was prepared using green chemistry with modified Hummer's method without incorporating sodium nitrate (NaNO₃). Solvent casting was employed to fabricate GO-doped poly(ethylene oxide) (PEO), that is, PEO/GO composites with various proportion of Na₂SO₄ and were then subjected to characterization via advanced spectroscopic techniques for different physicochemical aspects to estimate their potential applications as marketable products. XRD analysis explored that fabricated composites are more crystalline than neat PEO. PEO/GO/Na₂SO₄ composite films offered maximum crystallinity. SEM displayed the same trend. TG/DTA thermogram exposed better thermal stability than pristine polymer. FTIR studies confirmed complexation among hybrid's components. Elongation-at-break and Young's modulus displayed an enhancing behavior with an incremental loading of salt and filler. In terms of mechanical performance, composite of PEO with 0.37 wt % GO and 0.08 g salt was found to be an ideal composition during the course of study. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48376.     

Fabrication of semiconducting graphene oxide/polyaniline composite particles and their electrorheological response under an applied electric field

Semiconducting graphene oxide/polyaniline (GO/PANI) composite particles for potential electrorheological (ER) fluid applications were synthesized by the in situ dispersion polymerization of aniline in the presence of GO particles, which were prepared using a modified Hummers method. The electroresponsive ER characteristics of the composite when dispersed in silicone oil exhibited a phase transition from a liquid-like to solid-like state under an applied electric field. The morphology and composition of the composite particles were characterized by scanning and transmission electron microscopy and Raman spectroscopy. Its fibrillation phenomenon was observed by optical microscopy during the application of an external electric field. The bulk rheological characteristics of both the flow curve and yield stress were examined using a rotational rheometer equipped with a high voltage generator. The GO/PANI composite showed typical ER behavior, which demonstrated its potential applications as an ER smart material.     

石墨烯负载二氧化钛复合材料及光催化降解甲基橙

以天然鳞片石墨为原料,用改进的Hummers法氧化制备氧化石墨烯,然后用葡萄糖还原制得石墨稀,再用溶胶一凝胶法复合制备了TiO2／2;墨烯的复合材料。用FI-IR、Raman、AFM、SEMvR）3LTGA对石墨烯和TiO2／2;墨烯复合材料进行了表征,并在紫外光照射条件下对比石墨烯、TiO2、TiO：／2;墨烯复合材料对甲基橙的降解效果。结果表明,在紫外光照射下,TiO2的负载率为35％时,TiO2／2;墨烯复合材料光催化降解甲基橙的催化效率明显大于单纯TiO2及石墨烯,光催化4小时后,脱色率达到85％。TiO2／2;墨烯复合材料不失为一种有潜力的光催化降解染料废水催化材料。     

Pulsed laser assisted reduction of graphene oxide

We report a simple approach to reduce graphene oxide (GO) solution by pulsed laser irradiation. The reduction was rapidly carried out at room temperature in only 5 min. The reduced graphene oxide (r-GO) was characterized with UV–visible spectroscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, thermo-gravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. Based on this reducing method, an r-GO conductive film with a sheet resistance of 53.8 kΩ/sq was obtained. The pulsed laser reduction of GO in solution creates a new way to produce graphene composites for a variety of applications.     

镍负载二氧化钛/PEI/石墨烯纳米复合催化剂的制备与研究

首先采用改进的Hummers法制备了氧化石墨烯(GO),再以聚乙烯亚胺(PEI)修饰的氧化石墨烯为载体,并以硫酸钛和氯化镍为前驱体,利用水热法在180 ℃下以PEI为交联剂制得镍负载的TiO2/PEI/石墨烯纳米复合催化剂。通过紫外可见分光光度计(UV-vis)、傅里叶变换红外光谱(FTIR)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)等测试手段对催化剂进行了表征。结果表明,Ni-TiO2/PEI/RGO纳米复合催化剂中镍负载TiO2纳米粒子与石墨烯能够均匀复合,并具有较小的晶粒尺寸。以对硝基苯酚(4-NP)为降解目标物,考察了该催化剂在NaBH4存在下还原4-NP的催化活性。结果表明,镍负载的TiO2/PEI/石墨烯纳米复合催化剂具有良好的重复催化活性,其降解率为98%,催化剂重复使用10次后,降解率仍能保持90%以上。     

HDPE/功能化石墨烯复合材料制备及性能研究

氧化石墨烯(GO)具有较高的比表面积,层间距大,表面拥有丰富的官能团,可以很好地分散到聚合物中,但GO导电性差。研究对GO进行还原和表面修饰,以改善石墨烯和HDPE的相容性。采用熔融混炼法制备了HDPE/石墨烯复合材料,结合力学性能、导电性能、微观结构测试,考察不同HDPE/石墨烯复合材料的导电阈值,分析影响复合材料导电性的因素,进而得出较优化的制备工艺。研究发现石墨烯添加量为7.5%时,导电通路开始形成,当石墨烯含量达到7.5%时,拉伸强度提升22.14%,拉伸模量提升21.19%。     

Characterization and performance of dodecyl amine functionalized graphene oxide and dodecyl amine functionalized graphene/high‐density polyethylene nanocomposites: A comparative study

Dodecyl amine (DA) functionalized graphene oxide(DA‐GO) and dodecyl amine functionalized reduced graphene oxide (DA‐RGO) were produced by using amidation reaction and chemical reduction, then two kinds of well dispersed DA‐GO/high‐density polyethylene (HDPE) and DA‐RGO/HDPE nanocomposites were prepared by solution mixing method and hot‐pressing process. Thermogravimetric, X‐ray photoelectron spectroscopy, Fourier transforms infrared spectroscopy, X‐ray diffractions, and Raman spectroscopy analyses showed that DA was successfully grafted onto the graphene oxide surface by uncleophilic substitution and the amidation reaction, which increased the intragallery spacing of graphite oxide, resulting in the uniform dispersion of DA‐GO and DA‐RGO in the nonpolar xylene solvent. Morphological analysis of nanocomposites showed that both DA‐GO and DA‐RGO were homogeneously dispersed in HDPE matrix and formed strong interfacial interaction. Although the crystallinity, dynamic mechanical, gas barrier, and thermal stability properties of HDPE were significantly improved by addition of small amount of DA‐GO or DA‐RGO, the performance comparison of DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites indicated that the reduction of DA‐GO was not necessary because the interfacial adhesion and aspect ratio of graphene sheets had hardly changed after reduction, which resulting in almost the same properties between DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39803.     

Preparation of graphene by the rapid and mild thermal reduction of graphene oxide induced by microwaves

Rapid and mild thermal reduction of graphene oxide (GO) to graphene was achieved with the assistance of microwaves in a mixed solution of N,N-dimethylacetamide and water (DMAc/H₂O). The mixed solution works as both a solvent for the produced graphene and a medium to control the temperature of the reactive system up to 165 °C. Fourier transform infrared spectrometry, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis confirmed the formation of graphene under this mild thermal reduction condition. The reduction time is found to be in the scale of minutes. The as-prepared graphene can be well dispersed in DMAc to form an organic suspension, and the suspension is stable for months at room temperature. The conductivity of graphene paper prepared by the microwave reduced product is about 10⁴ times than that of GO paper.