Interfacial modification of basalt fiber filling composites with graphene oxide and polydopamine for enhanced mechanical and tribological properties

Due to the chemical inertness of the basalt fiber (BF) surface, the weaker interfacial bonding between BF and polymer matrices will seriously affect the further application of basalt fiber enhanced composites. In this study, a continuous and compact graphene oxide (GO) layer was grafted onto the surface of basalt fiber (BF) using biomimetic polydopamine (PDA) as a bridge to improve the mechanical and tribological properties of polyamide 6. The impact and flexural strength of the PA6 composites filled by the GO grafting BF (GO–PDA–BF/PA6) indicated that the introduction of GO has made a larger improvement in interface bonding performance between BF and PA6 matrix. The friction and wear tests showed the wear rate of the GO–PDA–BF/PA6 composite decreased by 51% compared with BF/PA6 composites and it also showed the best wear resistance and load-carrying capacity under various applied loads and sliding speeds, explained by the improved interface bonding between GO–PDA–BF and PA6 matrix and the anti-wear protective transfer film formed by GO in the worn surface. This study provided a considerable flexibility strategy of tailoring the interfacial compatibility between reinforcement and matrix for effectively improving the comprehensive performance of composites.

Graphene oxide was grafted onto the surface of basalt fiber via polydopamine to enhance the interfacial adhesion of PA6 composites.     

PEGylated polyvinylidene fluoride membranes via grafting from a graphene oxide additive for improving permeability and antifouling properties

Polyvinylidene fluoride (PVDF) porous membranes with enhanced hydrophilicity and antifouling performance were developed via surface PEGylation (PEG, polyethylene glycol) via a reactive graphene oxide (GO) additive. PVDF/GO blended membranes were first fabricated via a non-solvent-induced phase separation process. Then the carboxyl groups of GO sheets immobilized on the membrane surface acted as initiating sites for grafting amine-functionalized PEG (PEG-NH₂) chains via an amination reaction. Analysis of the X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy-attenuated total reflectance results confirmed the successful grafting of hydrophilic PEG molecular chains on PVDF membrane surfaces. The water contact angle of the PEGylated PVDF membrane decreased to 59.9°, indicating improved hydrophilicity. As a result, the antifouling performance was enhanced significantly. After surface PEGylation, the flux recovery rate is reached 90.2%, the total fouling ratio was as low as 20.7%, and reversible fouling plays a dominant role during the membrane fouling process. This work provides a valuable strategy to fabricate PEGylated membranes via the introduction of a reactive GO additive.

Polyvinylidene fluoride (PVDF) porous membranes with enhanced hydrophilicity and antifouling performance were developed via surface PEGylation (PEG, polyethylene glycol) via a reactive graphene oxide (GO) additive.     

Coordinating capillary infiltration with anodic oxidation: a multi-functional strategy for electrochemical fabrication of graphene

Electrochemical exfoliation of graphite stands out as a promising alternative to the existing methods for scalable graphene fabrication. However, factors governing the electrochemical process and the underlying mechanism are complex and how to effectively control the exfoliation process is far from completely clear despite many attempts in previous works. Herein, for the first time, capillary infiltration, anodic oxidation and their dependence on temperature were found to be critical in determining the electrolyte infiltration and the anodic oxidation process. On this basis, we achieved tuning of sheet dimensions (both thickness and lateral size) and surface chemistry of graphene by facilely controlling the temperature (5–95 °C). Four kinds of graphene materials featuring small size, porosity, water dispersibility and large size can be selectively fabricated in the same electrolyte system at different temperatures. Especially, low-temperature exfoliation results in high yields (99.5%) of small-sized graphene, which is a new breakthrough for electrochemical methods. The finding and associated mechanism of temperature''s influence on both capillary infiltration and anodic oxidation not only deepen our understanding of the electrochemical exfoliation, but also make electrochemistry a versatile technique for graphene fabrication.

Coordinating the capillarity infiltration with anodic oxidation enables electrochemical fabrication of various graphene materials at different temperatures.     

Correction: Molecular dynamics simulation of the mechanical properties of multilayer graphene oxide nanosheets

Correction for ‘Molecular dynamics simulation of the mechanical properties of multilayer graphene oxide nanosheets’ by Xu Zhang et al., RSC Adv., 2017, 7, 55005–55011.

The authors regret that Hang Liu’s name was spelled incorrectly in the original article. The correct author names are as presented above.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Enhancing the mechanical and tribological properties of epoxy composites via incorporation of reactive bio-based epoxy functionalized graphene oxide

The high rigidity and brittleness of traditional thermosetting resin based on bisphenol epoxy limits its many potential technical applications. Here, a novel tertiary amine containing cardanol-based epoxy resin (NC-514-DEA) was synthesized by reaction of diethanolamine (DEA) with cardanol epoxy resin (NC-514). Moreover, NC-514-DEA modified graphene oxide (GOND) was prepared and used as a reactive nano-reinforcing filler for epoxy composites. The results show that, compared with neat epoxy resin, the fracture toughness of the epoxy composite with 0.5 wt% GOND is increased by nearly 10%, and the friction coefficient is reduced from 0.567 to 0.408, demonstrating the best performance among specimens. The improved mechanical and wear resistance properties of prepared composites were attribute to the synergistic effect of NC-514-DEA and GO, which inhibited the generation and propagation of cracks by enhancing the interfacial interaction and distributing stress. In addition, the synthetic process of GOND is green, simple and efficient, providing a novel way for designing epoxy composite materials with many potential applications.

Superior mechanical and tribological properties of epoxy nanocomposites were obtained by introducing novel reactive bio-based epoxy-modified graphene oxide nanomaterials.     

Graphene as a nanofiller for enhancing the tribological properties and thermal conductivity of base grease

During mechanical processes, violent friction and wear between the friction contact surfaces not only causes wear to mechanical components, reducing the instrument life, but also causes friction heat, reducing the working efficiency of machines during operation. The addition of graphene-reinforced grease to the mechanical friction surface can effectively reduce the friction coefficient and improve the thermal conductivity. In this work, the tribological properties and thermal conductivity of base grease with graphene were investigated systematically. The tribological results showed that the grease with 2 wt% graphene had the best tribological properties among all these greases. The wear scar diameter and average friction coefficient of graphene grease with 2 wt% graphene reached 0.43 mm and 0.10 (the values for base grease are 0.50 mm and 0.118), respectively. In addition, the average friction coefficient and wear scar diameter increased proportionally with the increasing load and frequency. The thermal conductivity of the grease with 4 wt% graphene reached 0.28 W (m K)⁻¹, an increase of 55.5% in comparison with the base grease. It is proposed that the addition of graphene into the base grease effectively enhanced the tribological properties and thermal conductivity.

The addition of graphene-reinforced grease to the mechanical friction surface can effectively reduce the friction coefficient and accelerate heat transportation.     

Facile fabrication of long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites for enhanced tribological performance

Due to their ultrathin 2D laminated structure as well as excellent mechanical and thermal stabilities, ultrafine graphene-based nanoparticles exhibit fascinating advantages as highly-efficient lubricant additives. However, it remains a daunting challenge to achieve good and durable dispersion of these graphene-based nanoparticles in lubricating oils. Herein, we report a facile and efficient integration strategy involving particle size miniaturization, surface grafting with octadecyl alcohol (OA), and partial chemical reduction to prepare a novel long-chain alkyl functionalized ultrafine reduced graphene oxide (RGO-g-OA) with highly-dispersive capacity and superior tribological performance. The chemical composition and structural characteristics, microstructural morphology, and particle size distribution of RGO-g-OA were systematically investigated. Combining significantly improved lipophilicity derived from the long-chain alkyl grafting and partial chemical reduction with the small-size effect gave rise to outstanding long-term dispersion stability (as long as one month) of RGO-g-OA in the finished oil. Moreover, the friction coefficient and wear volume of finished oil with merely 0.005 wt% RGO-g-OA greatly reduced to 0.065 and 10 316 μm³, decreased by 9.7% and 44%, respectively, compared to those of pristine finished oil, demonstrating remarkable friction reduction and anti-wear performances. Consequently, owing to the characteristics of facile fabrication, durable dispersion stability, and superior tribological performance at an extremely low content, this novel nanoadditive shows a promising application potential in the tribology field.

Long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites with outstanding dispersibility and enhanced lubricating performances.     

Graphene platelet reinforced copper composites for improved tribological and thermal properties

In this work, investigations were conducted to evaluate a type of graphene platelet–reinforced copper (GPL/Cu) composite for enhanced tribological and thermal properties. The pin-on-disc (steel) results show that the wear loss and the friction coefficient of the composites decrease by nearly 80% and 70%, respectively, in comparison with those of pure Cu. Thermal conductivity of the composites initially improves substantially by approximately 30% with a slight loading of 0.25 vol% GPLs and decreases gradually with a higher content of GPLs. Microstructural analysis reveals that the enhancement in the tribological property is attributed to both the self-lubricating property of GPLs and grain refinement while the improvement in the thermal property is closely associated with the uniform dispersion of GPLs.

The uniform dispersion and self-lubricating property of GPLs enhance both the tribological and thermal performances.     

Facile synthesis of porous Fe3O4@C core/shell nanorod/graphene for improving microwave absorption properties

Porous Fe₃O₄@C core/shell nanorods decorated with reduced graphene oxide (RGO) were fabricated through a facile one-pot method. The microwave absorption properties of the samples can be adjusted by the weight ratio of RGO. The addition of RGO not only effectively reduces the agglomeration of Fe₃O₄@C, but also has a great effect on impedance matching and dielectric loss, resulting in enhanced microwave absorption abilities. The thickness corresponding to optimum reflection loss (R_L) decreases as the weight ratio of RGO increases. For the Fe₃O₄@C/RGO composite, a maximum R_L value of −48.6 dB can be obtained at 13.9 GHz with a thickness of 3.0 mm, and the absorption bandwidth with R_L below −10 dB is 7.1 GHz from 10.9 GHz to 18 GHz. These results demonstrate a facile method to prepare a highly efficient microwave absorption material with special microstructure.

Porous Fe₃O₄@C core/shell nanorods decorated with reduced graphene oxide were synthesized by a facile one-pot method, and exhibit high microwave absorption performance: maximum reflection loss reaches −48.6 dB.     

Fe3O4 nanoclusters highly dispersed on a porous graphene support as an additive for improving the hydrogen storage properties of LiBH4

Fe₃O₄ nanoclusters anchored on porous reduced graphene oxide (Fe₃O₄@rGO) have been synthesized by a one-step hydrothermal route, and then ball milled with LiBH₄ to prepare a hydrogen storage composite with a low onset dehydrogenation temperature, and improved dehydrogenation kinetics and rehydrogenation reversibility. The LiBH₄–20 wt% Fe₃O₄@rGO composite begins to release hydrogen at 74 °C, which is 250 °C lower than for ball-milled pure LiBH₄. Moreover, the composite can release 3.36 wt% hydrogen at 400 °C within 1000 s, which is 2.52 times as high as that of pure LiBH₄. Importantly, it can uptake 5.74 wt% hydrogen at 400 °C under 5 MPa H₂, and its hydrogen absorption capacity still reaches 3.73 wt% after 5 de/rehydrogenation cycles. The activation energy (E_a) of the hydrogen desorption of the composite is decreased by 79.78 kJ mol⁻¹ when 20 wt% Fe₃O₄@rGO is introduced into LiBH₄ as a destabilizer and catalyst precursor, showing enhanced thermodynamic properties. It could be claimed that not only the destabilization of Fe₃O₄, but also the active Li₃BO₃ species formed in situ, as well as the wrapping effect of the graphene, synergistically improve the hydrogen storage properties of LiBH₄. This work provides insight into developing non-noble metals supported on functional graphene as additives to improve the hydrogen storage properties of LiBH₄.

Fe₃O₄ nanoclusters highly dispersed on a porous graphene support were fabricated and significantly improved the dehydrogenation kinetics and rehydrogenation reversibility of LiBH₄.     

Self-lubrication and tribological properties of polymer composites containing lubricant

The purpose of this study was to improve the tribological properties of polydimethylsiloxane (PDMS) by mixing lubricants into it. The chemical composition, physical/chemical bonding state, and mechanical properties of the PDMS/lubricant composites (PLCs), prepared by mixing PDMS and lubricants at different ratios, were analyzed. With increasing lubricant content, the friction coefficient initially decreased, reaching a minimum value at a PDMS/lubricant ratio of 100 : 10; however, it gradually increased with a further increase in the lubricant content. The mechanical properties of PLCs with lubricant contents of 10% and higher decreased owing to the lubricant addition, so that the contact area with the sliding counter tip increased with lubricant content, but the frictional resistance was still decreased owing to the self-lubricating effect. In addition, owing to the effect of the lubricating film, there was no direct contact between the PLC surface and counter tip, and almost no damage was done to the PLC surface. Finite element analysis of the changes in stress during indentation and sliding confirmed that the stress applied to the PLCs was lower than that for bare PDMS.

The purpose of this study was to improve the tribological properties of polydimethylsiloxane (PDMS) by mixing lubricants into it.     

Diaminopyrene modified reduced graphene oxide as a novel electrode material for excellent performance supercapacitors

In this paper, novel reduced graphene oxide (rGO) composites (DAPrGOs) modified by diaminopyrene (DAP) were successfully synthesized via a facile solvothermal reaction method and used for supercapacitors. Compared with the pristine rGO, the DAPrGO1 electrode showed distinctly better performance (397.63 F g⁻¹vs. 80.29 F g⁻¹ of pristine rGO at 0.5 A g⁻¹) with small charge transfer resistance. When a symmetric device was fabricated using DAPrGO1 as the active material, it also exhibited a high capacitance of 82.70 F g⁻¹ at 0.5 A g⁻¹ with an energy density of 25.84 W h kg⁻¹ at a power density of 375 W kg⁻¹, and even offered a high power density of 7500 W kg⁻¹ (18.71 W h kg⁻¹) at 10 A g⁻¹. Moreover, the device possessed good electrochemical stability up to 20 000 cycles, implying promising applications in energy storage fields.

Schematic illustration of the facile synthesis process of DAPrGOs nanocomposites, Ragone plots and the superior cyclic stability of the assembled DAPrGO1//DAPrGO1 SSS.     

CuO nanorods grown vertically on graphene nanosheets as a battery-type material for high-performance supercapacitor electrodes

This work reports the preparation and characterization of the CuO nanorods grown vertically on graphene nanosheets, denoted as CuO/rGO@NF. Graphene is deposited by electrostatic attraction showing the morphology of folded nanosheets, which improves the electrical conductivity of the electrode, while CuO is modified by filtered cathodic vacuum arc technology and subsequent electrochemical oxidation presenting the morphology of nanorods, which increases the contact area of active sites and shortens the ion and electronic diffusion path. The results show that the CuO/rGO@NF electrode deliver an ultrahigh specific capacity (2.51 C cm⁻² at 2 mA cm⁻²), remarkable rate performance (64.6%) and improved conductivity. A symmetrical supercapacitor is assembled by two identical electrodes, presenting the maximum energy density of 38.35 W h kg⁻¹ at a power density of 187.5 W kg⁻¹. Therefore, the CuO/rGO@NF electrode can be used as a prospective electrode for energy storage devices. In addition, the whole electrode preparation process is short in time, safe and environmentally friendly, which provides a new idea for the preparation of other electrode materials.

The CuO/rGO@NF electrode is prepared by a simple and time-saving method, which has ultrahigh area capacity and excellent rate performance.     

一种新型活组织材料的组织学及力学特性**☆

背景：异物诱发包裹产生的包裹组织是一种自体活组织材料,理论上完全避免了非自体植入物所面临的免疫排斥反应和破坏作用,具有合成材料及脱细胞所无法比拟的生物学优势。
　　目的：试图开发出一种只含有自体细胞和细胞外基质成分的自体活组织生物材料,并评价其组织结构及力学特征。
　　方法：将硅胶管植入犬腹腔1个月,获得包裹形成的荚囊样生物组织,然后经过体外修整形成管型结构即自体活组织生物管。对标本进行了力学测定、组织学观察及表面结构分析。
　　结果与结论：腹腔内植入硅胶管形成的自体活组织生物管取材方便,主要由富含Ⅰ型和Ⅲ型胶原的细胞外基质构成,成肌纤维细胞排列在胶原纤维间,呈同心圆样结构,培养1个月时,管壁厚度可达70-250μm,可耐受(1100±187) mm Hg (1 mm Hg=0.133 kPa)的静水压,具有很好的可缝合性。提示自体活组织生物管形态可塑性大,由自体细胞及细胞外基质成分构成,避免了免疫排斥反应的发生,且具有足够的力学强度,有希望用于组织工程化血管的体外构建。     

Conjugation of a smart polymer to doxorubicin through a pH-responsive bond for targeted drug delivery and improving drug loading on graphene oxide

Polymeric nanoparticles have emerged as efficient carriers for anticancer drug delivery because they can improve the solubility of hydrophobic drugs and also can increase the bio-distribution of drugs throughout the bloodstream. In this work, a computational study is performed on a set of new pH-sensitive polymer–drug compounds based on an intelligent polymer called poly(β-malic acid) (PMLA). The molecular dynamics (MD) simulation is used to explore the adsorption and dynamic properties of PMLA–doxorubicin (PMLA–DOX) interaction with the graphene oxide (GOX) surface in acidic and neutral environments. The PMLA is bonded to DOX through an amide bond (PMLA-ami-DOX) and a hydrazone bond (PMLA-hz-DOX) and their adsorption behavior is compared with free DOX. Our results confirm that the polymer–drug prodrug shows unique properties. Analysis of the adsorption behavior reveals that this process is spontaneous and the most stable complex with a binding energy of −1210.262 kJ mol⁻¹ is the GOX/PMLA-hz-DOX complex at normal pH. On the other hand, this system has a great sensitivity to pH so that in an acidic environment, its interaction with GOX became weaker while such behavior is not observed for the PMLA-ami-DOX complex. The results obtained from this study provide accurate information about the interaction of the polymer–drug compounds and nanocarriers at the atomic level, which can be useful in the design of smart drug delivery systems.

Polymeric nanoparticles have emerged as efficient carriers for anticancer drug delivery because they can improve the solubility of hydrophobic drugs and also can increase the bio-distribution of drugs throughout the bloodstream.     

Tin-selenide as a futuristic material: properties and applications

SnSe/SnSe₂ is a promising versatile material with applications in various fields like solar cells, photodetectors, memory devices, lithium and sodium-ion batteries, gas sensing, photocatalysis, supercapacitors, topological insulators, resistive switching devices due to its optimal band gap. In this review, all possible applications of SnSe/SnSe₂ have been summarized. Some of the basic properties, as well as synthesis techniques have also been outlined. This review will help the researcher to understand the properties and possible applications of tin selenide-based materials. Thus, this will help in advancing the field of tin selenide-based materials for next generation technology.

SnSe/SnSe₂ has diverse applications like solar cells, photodetectors, memory devices, Li and Na-ion batteries, gas sensors, photocatalysis, supercapacitors, topological insulators, resistive switching devices due to its optimal band gap.     

Li2ZnTi3O8/graphene nanocomposite as a high-performance anode material for lithium-ion batteries

An Li₂ZnTi₃O₈/graphene (LZTO/G) anode is successfully synthesized by a two-step reaction. The results show that LZTO particles can be well dispersed into the graphene conductive network. The conductive structure greatly improves the electrochemical performance of LZTO/G. When cycled for 400 cycles, 76.4% of the capacity for the 2nd cycle is maintained at 1 A g⁻¹. Also, 174.8 and 156.5 mA h g⁻¹ are still delivered at the 100th cycle for 5 and 6 A g⁻¹, respectively. The excellent cyclic performance and the large specific capacities at high current densities are due to the good conductive network of the LZTO active particles, large pore volume, small particle size, low charge-transfer resistance and high lithium diffusion coefficient.

The structure of G modifying LZTO is beneficial for the diffusion of Li⁺ ions and transportation of electrons.     

Cu oxidation kinetics through graphene and its effect on the electrical properties of graphene

The oxidation kinetics of Cu through graphene were evaluated from the surface coverage of Cu oxide (F_ox) by varying the oxidation time (t_ox = 10–360 min) and temperature (T_ox = 180–240 °C) under an air environment. F_ox, as a function of time, well followed the Johnson–Mehl–Avrami–Kolmogorov equation; thus, the activation energy of Cu oxidation was estimated as 1.5 eV. Transmission electron microscopy studies revealed that Cu₂O formed on the top of the graphene at grain boundaries (G-GBs), indicating that Cu₂O growth was governed by the out-diffusion of Cu through G-GBs. Further, the effect of Cu oxidation on graphene quality was investigated by measuring the electrical properties of graphene after transferring. The variation of the sheet resistance (R_s) as a function of t_ox at all T_ox was converted into one curve as a function of F_ox. R_s of 250 Ω sq⁻¹ was constant, similar to that of as-grown graphene up to F_ox = 15%, and then increased with F_ox. The Hall measurement revealed that the carrier concentration remained constant in the entire range of F_ox, and R_s was solely related to the decrease in the Hall mobility. The variation in Hall mobility was examined according to the graphene percolation probability model, simulating electrical conduction on G-GBs during Cu₂O evolution. This model well explains the constant Hall mobility within F_ox = 15% and drastic F_ox degradation of 15–50% by the concept that the electrical conduction of graphene is disconnected by Cu₂O formation along with the G-GBs. Therefore, we systematically developed the oxidation kinetics of Cu through graphene and simultaneously examined the changes in the electrical properties of graphene.

The oxidation kinetics of Cu through graphene were evaluated from the surface coverage of Cu oxide (F_ox) by varying the oxidation time (t_ox = 10–360 min) and temperature (T_ox = 180–240 °C) under an air environment.     

Fabrication and simulation of a layered ultrahigh thermal conductive material made of self-assembled graphene and polydopamine on a copper substrate

A composite material of graphene (G) and polydopamine (PDA) on a copper (Cu) substrate (G/PDA@Cu) was fabricated successfully by sequential immersion deposition in a dopamine solution and an aqueous graphene oxide suspension before annealing. Optimum preparation conditions were explored by the orthogonal experimental method. The morphology and chemical composition of G/PDA@Cu were studied systematically by a series of characterization techniques. The thermal-conductive performance was evaluated by a laser flash thermal analyser. The thermal conductivity of G/PDA@Cu was 519.43 W m⁻¹ K⁻¹, which is ultrahigh and 30.50% higher than that of the Cu substrate. The adhesion force between G/PDA and the Cu substrate was 4.18 mN, which means that G bonds to the Cu substrate tightly. The model simulation also showed that G/PDA@Cu exhibits excellent thermal conductivity, allowing it to play a significant role in the thermal management of advanced electronic chips. The thermal-conductive devices using this material were prepared for practical applications.

A composite material of graphene (G) and polydopamine (PDA) on a copper (Cu) substrate (G/PDA@Cu) was fabricated successfully by sequential immersion deposition in a dopamine solution and an aqueous graphene oxide suspension before annealing.     

Design and simulation of a multilayer Halbach magnet for NMR

Halbach magnet is a type of permanent magnet generating a relatively high and homogeneous magnetic field. It is suitable for Nuclear Magnetic Resonance (NMR) studies of small volume chemical or biological samples. In this article, the model of a Halbach magnet made from an odd number of cylindrical layers is proposed for the first time. Then after the optimization of interlayer distances for odd layers Halbach cylinders, the model is verified by the simulation with a magnet inner radius of 30 mm and an outer radius of 49 mm. Moreover, the disturbance of uniformity in 5 mm DSV (Diameter of Spherical Volume) is presented with errors in magnetic strength and angular variation. As a result, a minimum uniformity of 46 ppm inside a 5 mm DSV is achieved, while it increases practically in the presence of magnetic blocks errors. The good performance of the Halbach magnet with odd layers may find potential applications in NMR. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 134–141, 2015