Influence of reduced graphene oxide on mechanical behaviors of sodium carboxymethyl cellulose

Sodium carboxymethyl cellulose/reduced graphene oxide (NaCMC/rGO) nanocomposite films were prepared by a simple solution mixing-evaporation method. The NaCMC/rGO nanocomposite films were characterized and compared with sodium carboxymethyl cellulose/graphene oxide (NaCMC/GO) nanocomposite films. The stability of the rGO dispersion, and the structural and mechanical properties of the composite films were investigated by UV–Vis spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and using a universal testing machine (UTM). The results revealed that CMC and rGO were able to form a homogenous mixture. Compared with pure CMC, the tensile strength and Young's modulus of the CMC/rGO nanocomposite films were considerably enhanced (by 72.52% and 131.79%, respectively) upon incorporation of 2 wt% rGO.     

石墨烯微片表面接枝PMMA及其环氧树脂复合材料性能

利用石墨烯微片（GNPs）表面羟基与硅烷偶联剂反应,并通过原子转移自由基聚合（ATRP）方法在GNPs表面接枝了聚甲基丙烯酸甲酯（PMMA）。应用扫描电子显微镜、透射电子显微镜、红外光谱和X射线衍射方法分析了化学接枝前后GNPs的微观结构变化。将接枝PMMA的GNPs加入环氧树脂中,研究其对环氧树脂力学性能与尺寸稳定性的影响。研究结果表明,与原始GNPs相比,表面接枝PMMA的GNPs对环氧树脂力学性能的增强作用更明显。添加质量分数为0.5%的GNPs-PMMA可以使环氧树脂拉伸强度和模量分别提高17.4%和75%,弯曲强度和模量也分别增加了6%和12%,同时可以使环氧树脂在低于玻璃化转变温度的线性热膨胀系数（CTE）降低25%。     

Influence of surfactant type on the dispersion state and properties of graphene nanoplatelets reinforced aluminium matrix nanocomposites

Graphene dispersion in aluminium matrix is a critical concern for the attainment of composite improved mechanical and tribological properties which hinders broad applications of Al nanocomposites. Herein, graphene nanoplatelets (GNPs) dispersion in Al matrix achieved by colloidal processing, i.e., combining sonication and surfactant dispersing aid. In this work, the performance of the two types of surfactant (anionic, sodium dodecyl benzene sulfonate (SDBS), and nonionic polymeric, ethyl cellulose (EC)) were evaluated for effective GNPs dispersion in a solvent and Al matrix. Surfactant assisted GNPs solvent dispersion characterized through sedimentation test and UV-vis spectroscopy to optimize surfactant concentration. Density, hardness, wear properties and microstructural characterizations of GNPs/Al powder and sintered discs were performed to gauge the effect of surfactant type. It was found that surfactant addition enhances dispersion ability of GNPs than neat GNPs but at low GNPs fractions. The results show that EC assisted GNPs/Al nanocomposites of 0.5 wt% GNPs concentration has shown an increase in hardness (31%) and reduce wear rate (98%). Whereas, 0.3 wt% SDBS assisted GNPs/Al nanocomposites shown maximal increases in hardness (18%) and reduce wear rate (98%) as compared to pure aluminium, respectively. Conclusively, it has been revealed that polymeric EC based surfactant GNPs owing to steric repulsion shows better dispersion effect resulting in high density and improved wear resistance and performed better than SDBS based surfactant GNPs in Al matrix.     

氧化纳米纤维素增强再生纤维素全纤维素复合薄膜的制备及性能

以2,2,6,6-四甲基哌啶-氮-氧化物(TEMPO)氧化松木粉纳米纤维素(TOCNs)为增强相、α-纤维素粉制备再生纤维素(RC)为基体,采用溶胶-凝胶法制备氧化纳米纤维素增强再生纤维素(TOCNs/RC)全纤维素复合薄膜。对不同TOCNs添加量下TOCNs/RC全纤维素复合薄膜的力学性能、光学性能、氧气阻隔性能和热稳定性能进行研究,并通过FTIR、SEM、TEM、XRD和流变仪对TOCNs和TOCNs/RC全纤维素复合薄膜的结构、形貌及纤维素溶液流变性能进行表征。结果表明,TOCNs添加量对TOCNs/RC全纤维素复合薄膜的力学性能有显著影响,当TOCNs添加量(与纤维素基体的质量比)为1.0%时,TOCNs/RC全纤维素复合薄膜的拉伸强度和断裂能分别可达134.3 MPa和21.51 MJ·m?3,具有最佳的综合力学性能;TOCNs/RC全纤维素复合薄膜的透光率随TOCNs添加量的增加而下降,雾度随TOCNs添加量的增加而增大,但仍保持较高的透光率(>85%)和较低的雾度(<14%);TOCNs/RC全纤维素复合薄膜还具有优异的氧气阻隔性,TOCNs添加量为1.6%时,其透氧系数仅为1.47×10?17cm3·cm/cm2·s·Pa。TOCNs/RC全纤维素复合薄膜有优于一般塑料薄膜的拉伸强度和氧气阻隔性,并有可媲美于塑料薄膜的透明度,可作软包装复合材料的强度层和阻隔层,在绿色高性能包装材料领域具有广阔的应用前景。      

纳米TiO2 / 再生纤维素复合薄膜的制备及光催化性能

在1-烯丙基-3-甲基咪唑氯室温离子液体中, 将纳米TiO₂粉末与纤维素浆粕进行溶液共混, 所得纤维素用水再生后, 经过超临界CO₂干燥处理, 制备了不同TiO₂ 含量的纳米TiO₂ / 再生纤维素复合膜。通过扫描电子显微镜(SEM) 、X 射线衍射(XRD) 、傅立叶变换红外光谱( FTIR) 对所得薄膜的形貌、结构进行表征。利用PCC-2 型光催化活性检测仪测试薄膜在紫外光下光催化降解亚甲基蓝的能力, 评价薄膜的光催化活性。讨论了纳米TiO₂ 含量、超临界CO₂ 干燥和真空干燥对薄膜性能的影响。结果表明: 复合膜的光催化活性达到所用TiO₂粉体的90 %; 经超临界CO₂ 干燥处理所得复合膜的光催化活性明显高于真空干燥所得复合膜的活性; 纳米复合膜的光催化活性随TiO₂ 含量的增加先升高后降低, 含量为5 %时光催化活性最高。      

Preparation of transparent and conductive cellulose nanocrystals/graphene nanoplatelets films

The manufacture of emerging products such as photovoltaic devices requires combinations of various novel materials to be leveraged into successful, scalable approach. In order to develop new electronic devices, it is necessary to find innovative solutions to the eco-sustainability problem of materials as substrates for circuits. We report on the demonstration of polymer solar cells fabricated on optically transparent and conductive graphene nanoplatelets (GNPs)–cellulose nanocrystals (CNC) film. The solar cells fabricated on the GNPs/CNC films display good rectification in the dark. Such GNPs–CNC functional films are expected to be attractive for eco-friendly electronics.     

Development of Al- and Cu-based nanocomposites reinforced by graphene nanoplatelets: Fabrication and characterization

Aluminum and copper matrix nanocomposites reinforced by graphene nanoplatelets (GNPs) were successfully fabricated by a wet mixing method followed by conventional powder metallurgy. The uniform dispersion of GNPs within the metal matrices showed that the wet mixing method has a great potential to be used as a mixing technique. However, by increasing the GNPs content, GNPs agglomeration was more visible. DSC and XRD of Al/GNPs nanocomposites showed that no new phase formed below the melting point of Al. Microstructural observations in both nanocomposites reveal the evident grain refinement effect as a consequence of GNPs addition. The interfacial bonding evaluation shows a poor interfacial bonding between GNPs and Al, while the interfacial bonding between Cu and GNPs is strong enough to improve the properties of the Cu/GNPs nanocomposites. In both composites, the coefficient of thermal expansion decreases as a function of GNPs while, their hardness is improved by increasing the GNPs content as well as their elastic modulus.     

Processing-structure-property relations of chemically bonded phosphate ceramic composites

Mechanical properties and microstructures of a chemically bonded phosphate ceramic (CBPC) and its composite with 1.0 wt% graphite nanoplatelets (GNPs) reinforcement have been investigated. Microstructure was identified by using optical and scanning electron microscopes, X-ray tomography, and X-ray diffraction. In addition, weight loss of the resin at room temperature was studied. The microstructure characterization shows that CBPC is itself a composite with several crystalline (wollastonite and brushite) and amorphous phases. SEM and micro tomography show a homogeneous distribution of crystalline phases. Bending and compression strength of the CBPC was improved by reducing bubbles via preparation in vacuum.     

Effects of functional groups on the graphene sheet for improving the thermomechanical properties of polyurethane nanocomposites

Dispersibility of graphene sheets in polymer matrices and interfacial interaction are challenging for producing graphene-based high performance polymer nanocomposites. In this study, three kinds nanofillers; pristine graphene nanoplatelets (GNPs), graphene oxide (GO), and functionalized graphene sheet (FGS) were used to prepare polyurethane (PU) composite by in-situ polymerization. To evaluate the efficacy of functional groups on the graphene sheets, PU reinforced with GNPs, GO, and FGS were compared through tensile testing and dynamic mechanical thermal analysis. The Young's moduli of 2 wt% GO and FGS based PU nanocomposites were found significantly higher than that of same amount of GNPs loading as an evidence of the effect of functional groups on graphene sheets for the mechanical reinforcement. The strong interaction of FGS with PU was responsible to exhibit notably high modulus (25.8 MPa) of 2 wt% FGS/PU composite than the same amount of GNPs and GO loading even at elevated temperature (100 °C).     

Studying the surface of UHMWPE films modified with graphene nanoplatelets using a Raman mapping method

Abstract

This article discusses the nature of the distribution of intact polyaniline-functionalized graphene nanoplatelets (GNPs) in the surface layer of nanomodified films of ultra-high molecular weight polyethylene (UHMWPE) using a Raman mapping method. On the Raman maps, D, G, and 2D peaks can be observed for the 0.1?wt.% GNPs content in the UHMWPE. In the surface layer of the films containing 1.0?wt.% GNPs, these signals are not detected, thereby indicating the displacement of the nanomodifier into the polymer bulk. In contrast, the polyaniline-functionalized GNPs tend to migrate to the surface of the UHMWPE nanocomposite film and evenly distribute in the surface layer as the concentration increases from 0.1 to 2.0?wt.%.     

兼具阻燃和导热性能的环氧树脂复合材料：石墨烯纳米片杂化三聚氰胺磷酸盐的作用

研发制备低成本、少缺陷及高效率的石墨烯纳米片杂化阻燃剂对实现复合材料多功能性具有重要意义。以三聚氰胺为助剥离剂将微粉石墨(GRA)经机械球磨后与磷酸液相反应得到一种阻燃导热的石墨烯纳米片杂化三聚氰胺磷酸盐(GMP),在表征GMP形貌、结构、组成和热稳定性的基础上,研究了添加GMP环氧树脂(EP)复合材料的阻燃、热分解和导热性能。GMP的热失重分析结果表明：与三聚氰胺磷酸盐(MP)相比,初始分解温度提升了29.3℃,与环氧树脂的热分解温度更匹配,有助于提高阻燃效率。氧指数仪、锥形量热仪和导热性能研究表明,GMP添加30wt%时,EP复合材料的极限氧指数达到了30.4%,UL 94垂直燃烧达到V-0级,峰值热释放速率(PHRR)和峰值烟释放速率(PSPR)分别下降69%和74.0%;导热系数提升至2.10 W·m^-1·K^-1,相对于EP提升了708%。这是由于GMP中石墨烯纳米片(GNPs)与MP的相互作用促进了EP形成了致密的膨胀炭层,有效提高了EP复合材料的阻燃性;随着GMP添加量的增加,GNPs和石墨微片传热通道的形成改善了EP复合材料的导...     

Nanocomposite films and coatings produced by interaction between graphite oxide and Congo red

Nanocomposite films and coatings were produced from the aqueous solutions containing different proportions of graphite oxide (GO) and Congo red by filtering through a polycarbonate membrane filter into alkaline media. They were examined by electron microscopy, Raman and FTIR spectroscopy, XRD, contact angle, and electrical conductivity measurements. It was established that the Congo red is able to interact through its amino groups with different functional groups of GO to form larger moieties composed of the nanoplatelets of GO. Raman spectroscopy revealed quinoid-like ring structure for dye adhering to the GO. In the case when the interaction occurs with the terminal functional groups located on the edges of the nanoplateletes of GO, larger crystallites in the nanocomposite are formed. The interaction between the Congo red and functional groups of GO situated in a basal plane leads to more compact structure of the nanocomposite. Pulsed laser treatment was used to reduce GO to graphene. Raman spectra of laser treated areas show positive effect of addition of the Congo red on the graphene yield in nanocomposite coatings after the laser treatment.     

Structural and photoluminescence investigation of ZnSe nanocrystals dispersed in organic and inorganic matrices

In this work, we report on the investigation of the effect of dispersion of zinc selenide (ZnSe) nanocrystallites into polystyrene (PS) and silica (SiO₂) thin films on their structural, morphological and photoluminescence properties. The ZnSe/PS nanocomposites thin films were synthesized by a direct dispersion of ZnSe crystallites into polymers solution, whereas the ZnSe–SiO₂ films were prepared on glass substrates by the sol–gel dip-coating technique. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-rays (EDX), UV–visible spectrophotometry and photoluminescence spectroscopy (PL) techniques have been used to study the structural, morphological and optical properties of the prepared nanocomposite thin films. XRD patterns have demonstrated the incorporation of cubic ZnSe in both organic and inorganic matrices. SEM micrographs have indicated that ZnSe dispersion in the films is homogeneous. UV–visible absorption spectra of the nanocomposite thin films have put into evidence that the dispersion of ZnSe nanocrystals in the thin film matrices improved their optical absorption. Room temperature PL spectra have shown that the addition of ZnSe enhanced the UV emission of PS and all the emission of SiO₂ thin films.     

Influence of graphene nanoplatelets content on the structure and properties of macroporous carbon foams prepared by organic colloidal templates

Graphene nanoplatelets (GNPs)-reinforced carbon foams have been fabricated by polycondensation of resorcinol–formaldehyde resin as a carbon precursor and GNPs as a reinforcing material. The pore structure, mechanical properties, and electrical conductivity were investigated in terms of the amount of the GNPs. The results show that the amount of GNPs has a considerable influence on compressive strength, electrical conductivity, and specific capacitance. Although the amount of GNPs added does not influence the pore structure, the mechanical properties, electrical conductivity, and specific capacitance of carbon foams were improved with increasing the GNPs content. With 5 wt% addition of GNPs, the compressive strength, electrical conductivity, and specific capacitance increased by 75.2, 240.26, and 53.36 %, respectively.     

Electrical properties of graphene nanoplatelets/ultra-high molecular weight polyethylene composites

Graphene nanoplatelets (GNPs)/ultra-high molecular weight polyethylene (UHMWPE) composites with a segregated structure had been fabricated using ethanol-assisted dispersion and hot compression at 180 °C. A percolation threshold of 3.5 wt% was achieved because of the formation conductive network. The positive temperature coefficient (PTC) and the negative temperature coefficient (NTC) effects of GNPs/UHMWPE composites had been investigated. The PTC behavior enhanced with increasing GNPs content but this was not always the case. The maximum PTC effect was observed in GNPs/UHMWPE composites (GNPs, 3.8 wt%) with the relatively low room temperature resistivity and the relatively high peak resistivity. The structure for GNPs/UHMWPE composites was examined by the SEM. The fact revealed that the slight interaction between GNPs and UHMWPE matrix may be changed by thermal cycles, and this can explain why thermal cycles could increase PTC and NTC intensity.     

壳聚糖/纤维素生物质发泡复合材料多孔结构的表征

以壳聚糖微粒为增强体,离子液体为纤维素溶剂,采用冷冻干燥法成功制备了壳聚糖/纤维素生物质发泡复合材料。利用SEM、XRD和TGA表征多孔复合材料微观结构、结晶性能以及热稳定性,测试了其孔隙率和吸水性能。实验结果表明:壳聚糖/纤维素多孔复合材料具有三维相互贯通的微孔结构,壳聚糖粉体有助于孔洞结构的形成,TGA结果显示纤维素多孔材料的热稳定性能得以提高。XRD结果显示纤维素经离子液体溶解再生后晶型结构由纤维素I转化为纤维素II。纤维素含量较低(≤4wt%)时,随1wt%壳聚糖粉体的加入,孔隙率明显提高。壳聚糖/纤维素多孔复合材料的力学性能随纤维素含量的增加而不断提高,而吸水性能有所下降。壳聚糖与纤维素质量比为1∶3时,壳聚糖/纤维素多孔复合材料孔隙率为72.7%,吸水率和相对保湿率分别为28.0g/g和17.6g/g,断裂强度和断裂伸长率分别为0.32 MPa和25.4%,能够作为一种优良的吸附材料用于制备高性能的医用敷料。     

Water dispersible graphene noncovalently functionalized with tryptophan and its poly(vinyl alcohol) nanocomposite

Graphene sheets functionalized noncovalently with aromatic amino acid, tryptophan (Tryp), were prepared by reducing graphene oxide through hydrazine hydrate. Tryp-functionalized graphene is water dispersible and can be stabilized for several months. Atomic force microscopy (AFM), X-ray diffraction (XRD), UV–vis absorption and Raman spectroscopy were used to investigate the nanostructures and the properties of graphene. Application of the graphene dispersion to poly(vinyl alcohol) (PVA) with the help of tryptophan to prepare nanocomposite was also carried out. And the PVA/graphene nanocomposite was characterized by thermogravimetric analysis (TGA) and tensile testing. A 23% improvement in tensile strength and moderate increases in Young’s modulus and thermal stability for PVA were achieved by adding only 0.2 wt% graphene sheets.     

聚乳酸/乙基纤维素复合膜的制备及其性能

以烯基琥珀酸酐( ASA) 作为新型增塑剂, 使用三氯甲烷作为聚乳酸( PLA) 和乙基纤维素( EC) 的共溶剂, 采用溶液浇铸法成功制备了聚乳酸/ 乙基纤维素复合膜。用红外光谱( FT IR) 、X 射线衍射(XRD) 表征了复合膜结构, 并测试了其吸水性和力学性能。FTIR 测试结果显示, 复合膜中存在强烈的氢键相互作用。XRD 表明,ASA 显著提高了PLA 和EC 2 种高聚物的界面黏合性。力学测试结果表明, ASA 对该复合膜具有良好的增塑效果。当膜中PLA 质量分数[ 37%时, PLA 对复合膜起增强作用。复合膜的吸水性随ASA 含量的增大而降低, 随PLA 含量的增大而提高。该复合膜作为一种潜在的药物缓释材料, 将具有广阔应用前景。      

Effect of multiwalled carbon nanotubes on the crystallization and dielectric properties of BP-PEN nanocomposites

In this work, polymer-based nanocomposite films formed from biphenol poly(arylene ether nitrile) (BP-PEN) and multiwalled carbon nanotubes (MWCNTs) were successfully prepared by the solution casting method combined with continuous ultrasonic dispersion technology. The micromorphology, thermal, mechanical and dielectric properties of the nanocomposite films were investigated in detail. Non-isothermal crystallization behavior studies indicate that the presence of MWCNTs enhances the crystallization of BP-PEN in the nanocomposites, which is consistent with the XRD analysis. Most importantly, it could be observed that the film containing 0.8 wt% MWCNTs reached the maximum crystallinity. Although, incorporation of MWCNTs did not obviously increase the mechanical of the films, all the nanocomposite films still exhibited excellent mechanical strength. The SEM micrographs of the nanocomposite films showed that the MWCNTs were uniformly coated by BP-PEN crystals, and indicating significantly improved nucleation ability of MWCNTs for polymer crystallization.     

Hydrogen storage studies of palladium decorated nitrogen doped graphene nanoplatelets

Hydrogen storage in materials is of significant importance in the present scenario of depleting conventional energy sources. Porous solids such as activated carbon or nanostructured carbon materials have promising future as hydrogen storage media. The hydrogen storage capacity in nanostructured carbon materials can be further enhanced by atomic hydrogen spillover from a supported catalyst. In the present work, the hydrogen storage properties of nitrogen doped graphene nanoplatelets (N-GNP) and palladium decorated nitrogen doped graphene nanoplatelets (Pd/N-GNP) have been investigated. The results show that hydrogen uptake capacity of nitrogen doped graphene nanoplatelets and palladium decorated nitrogen doped graphene nanoplatelets at pressure 32 bar and temperature 25 degrees C is 0.42 wt% and 1.25 wt% respectively. The dispersion of palladium nanoparticles increases the hydrogen storage capacity of nitrogen doped graphene nanoplatelets by 0.83 wt%. This may be due to high dispersion of palladium nanoparticles and strong adhesion between metal and graphene nanoplatelets over the surface of N-GNP, which enhances the spillover mechanism. Thus, an increase in the hydrogen spillover effect and the binding energy between metal nanoparticles and supporting material achieved by nitrogen doping has been observed to result in a higher hydrogen storage capacity of pristine GNP.