•Ultra-light graphene aerogels (GA and CGA) were fabricated through a facile and mild approach.•The novel approach was low cost and more viable for industry with ammonia solution as single reducing agent.•The GAs showed highly repeatable compressibility.•The GAs exhibited excellent absorption performance for organic solvents.•The GAs demonstrated superior strain-sensitive electrical conductivity.A novel ultra-light graphene aerogel with highly repeatable compressibility was successfully synthesized via a low cost and viable approach. In specific, the graphene aerogel exhibited a super absorption capacity for oil and various organic solvents up to 350 times of its own mass after thermal annealing, which was much higher than the most reported absorption materials, and excellent reusable properties in absorption-combustion, absorption-distillation, and absorption-squeezing cycles. In addition to the excellent absorption capabilities, the unique graphene aerogels also possessed other significant performances, such as ideal hydrophobicity, satisfactory fire-resistance, and strain-sensitive electrical conductivity. More importantly, in comparison with the usual reduction temperature for GO, e.g. 180 °C, our fabrication approach only involved a relatively low temperature (90 °C), at which the successfully reducing GO with ammonia solution was realized assisted by freeze-drying and thermal annealing. The viable method and unique performance advantages endow the resulting graphene aerogels with important and broad applications such as oil absorption, energy devices and pressure sensitive sensors.

The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/amine system in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/amine system. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.

Biomass-derived porous activated carbon (AC) with high surface area of up to 1776.9 m2 g−1 was prepared by KOH and urea activation of Ailanthus altissima stems with unique honeycomb-like microstructure at 800 °C. As an electrode material for supercapacitors, the AC samples exhibited a remarkably large capacitance of 300.6 F g−1 at 0.5 A g−1 in 1 M H2SO4 and retained up to 213.4 F g−1 even at a current density of 20 A g−1. It is worth noting that no obvious capacitance loss was observed over 5000 charge/discharge cycles, clearly demonstrating the robust long-term stability. The excellent performance of the special carbon electrode can be attributed to the inherent honeycomb-like porous microstructure of Ailanthus altissima stems, which can offer more surfaces for activation by KOH to generate a more microporous network. This work provides a promising strategy to take full advantage of the unique microstructure of raw materials from nature via simple technologies to achieve sustainable energy development.

A facile synthesis of three-dimensional ultra-light (≈2.52 mg cm−3) graphene–poly(dopamine) modified carbon nanotube composite aerogels that needed no additional reducing agents during the forming process is reported herein. The composite aerogels exhibited highly repeatable compressibility and superior electrical conductivity, and thus will have an important application value in strain-sensitive functional devices.

Theoretical modulus of three kinds of epoxy matrices, including diethylene toluene diamine (DETDA)/4,5-epoxyclyclohexyl-1,2-diglycidyldiformate(TDE85), m-phenylenediamine (MPD)/TDE85 and single-walled carbon nanotube (SWCNT) reinforced DETDA/TDE85 were investigated via molecular dynamics (MD) simulation to establish the structure–property relationships. The flexibility and mobility of molecular chains, the packing ability of cross-linked chain segment, the fraction of free volume of epoxy resins and the cohesive energy density in different epoxy systems were analyzed in detail, respectively. The MD simulation results showed that both the slight modification in the diamine structure and the introduction of SWCNTs can result in significant changes in the microstructure parameters of epoxy matrix, however, the modulus improvement mechanisms through changing curing agents and incorporating SWCNT into epoxy matrix had similarities and differences. The MD simulation method will be of great value in predicting and analyzing some performance closely related to the microstructure parameters for the different cross-linked resin system and its composite materials.

The biodegraded cellulose acetate (CA)/poly-L-lactic acid (PLLA)/Halloysite nanotube composite nanofiber membranes were fabricated for the preparation of gel polymer electrolytes (GPEs) used in lithium-ion batteries. The microstructure, crystallization behaviour and thermal stability of nanofiber membranes were analysed. The testing results showed that the crystallization behaviour of the polymeric materials was significantly inhibited, and that the thermal stability of the polymer nanofiber membranes was improved due to the addition of the halloysite nanotubes (HNTs). The composite GPEs based on the CA/PLLA/HNT nanofiber membranes presented a satisfactory electrochemical performance, including high ionic conductivities, proper lithium-ion transference numbers, and good electrochemical stability. An ionic conductivity of 1.52 × 10−3 S cm−1 was obtained from the above mentioned GPEs, which is far greater than the existing bio-based GPEs. Moreover, the initial discharge capacities, cycle performance and rate performance of the Li/GPE/LiCoO2 cells involved with the CA/PLLA/HNT nanofiber membranes was superior to those of the commercial Celgard® 2500. Therefore, through the proper collocation of biodegradable polymer materials and functional nanoparticles, the resulting composite GPEs exhibited the recommendable integrated performance. The CA/PLLA/HNT composite nanofiber membranes can be used as novel green skeleton materials in GPEs for high performance lithium-ion batteries, which provide a perfect combination of high performance and environmental protection.

A new type of MnO/carbon composite particle with multi-modal pore structure was designed and prepared as anode materials of lithium-ion batteries through a promoted template method. The porous MnO/carbon composite anode materials exhibited the superior electrochemical performance, including excellent stability under different current density, high reversible capacity (as high as 1210.9 mA h g−1 after 700 cycles at 1.0 A g−1), good rate capability and high initial coulomb efficiency of over 80%, which had benefited from the reasonable material composition, special multi-modal pore structure, desirable micro-morphology and good structural integrity. The complex multiphase structure consisting of MnO crystal grains, abundant nanopores and uniform carbon layers can effectively improve cyclic stability and rate capability of the anode materials, and thus will have an important application value in high-performance energy supply devices.

A kind of biodegradable and well-sourced soy protein isolate (SPI)/poly(vinyl alcohol) (PVA) composite nanofiber membranes was fabricated via electrospinning and used as skeleton material in gel polymer electrolyte (GPE) of lithium-ion batteries. This study revealed that the proper material proportion, low crystallinity, sufficient porosity and good affinity between nanofiber and the electrode/electrolyte resulted in high saturated electrolyte uptake and conservation rate of the nanofiber membranes. The GPEs based on the SPI/PVA composite nanofiber membranes presented remarkable electrochemical performance, including high ionic conductivity, excellent compatibility with lithium electrode and good electrochemical stability. An ionic conductivity of 3.8 × 10–3 S cm–1 and interfacial resistance of 250 Ω for the GPEs can be obtained when the weight ratio of SPI to PVA in the spinning solution was 3:1, which was more superior to the existing biobased GPEs. In addition, the Li/GPE/LiCoO2 cells with GPEs based on the SPI/PVA (3:1) composite nanofiber membranes displayed the excellent initial discharge capacity and cycle performance. Therefore, the environmental and economical SPI/PVA composite nanofiber membranes with the optimized material proportion can be used as a green skeleton material in GPEs for high performance lithium-ion batteries.Keywords: Biodegradable; Gel polymer electrolyte; Nanofiber membranes; Skeleton materials; Soy protein isolate

An intractable problem has been revealed that the resin matrix viscosity was rising obviously after the addition of solid nano-fillers involving all kinds of surface chemical modification, causing the degraded processing properties and defective structure in the polymer composites. Therefore, the application of nano-fillers in the filament winding processing of carbon fibre composites is severely limited, in which low initial viscosity of resin matrix is required under processing temperature to ensure the impregnation of the resin to fibres. In this study, a kind of liquid-like MWCNT reinforcements (L-MWCNTs) were fabricated and explored as nano-reinforcements for T1000 carbon fibre filament winding composites. Some technical means such as transmission electron microscopy and atomic force microscopy were used to analyze the dispersion state of L-MWCNTs and interfacial interaction of the resulting composites. The mechanical properties of carbon fibre filament winding composites were characterized through Naval Ordinance Laboratory-ring burst tests and interlaminar shear strength (ILSS) tests. The results showed that the L-MWCNTs can be uniformly dispersed in an epoxy matrix without deteriorating good processing performances for the filament winding composites. The resin matrix containing the L-MWCNTs exhibited a lower surface energy and better interface bonding with T1000 carbon fibre than that of the neat epoxy. Through the addition of 6 wt% L-MWCNTs, an enhancement of 15% in tensile strength, 28% in ILSS, as well as 14.8 °C in Tg was realized for T1000 carbon fibre composites. The L-MWCNTs can exhibit important application values as a nano-reinforcement for improving interfacial, mechanical and thermal properties of the existing carbon fibre composites.

•Effects of amine/epoxy stoichiometry on curing behavior of MWCNTs-NH2/epoxy systems were studied.•The catalytic effect of MWCNTs-NH2 was weakened by increasing amine/epoxy stoichiometry.•For the system with excess epoxy, the etherification reaction was promoted by adding MWCNTs-NH2.•The moderate excess epoxy was proposed as an essential prerequisite to enhance the Tg of MWCNTs-NH2/epoxy systems.In this study, amine functionalized multi-walled carbon nanotubes (MWCNTs-NH2) with surface covalently linked ethylenediamine were prepared. The effect of amine/epoxy stoichiometry on the curing behavior, cross-linking network structure and glass transition temperature (Tg) of MWCNTs-NH2 reinforced epoxy-amine systems were investigated by using non-isothermal differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) and dynamic mechanical analysis (DMA), respectively. The results indicated the catalytic effect MWCNTs-NH2 in the curing process of epoxy was weakened with the increase of amine/epoxy stoichiometry, which can affect the formation of cross-linking network and Tg of the cured MWCNTs-NH2/epoxy nanocomposites contrasted with the corresponding neat epoxy. The MWCNTs-NH2/epoxy composites with moderate excess epoxy equivalent exhibited higher Tg than that of the neat epoxy, which was attributed to the excess epoxy groups can promote the etherification reaction as well as the interfacial interaction between MWCNTs-NH2 and epoxy resin.

•A novel 3D nanomaterial (MWCNT-PDA-POSS) with bump structure was synthesized.•Polydopamine transition layer was introduced as second modification platform.•The bump structure significantly improved the compressive performance of epoxy resin composites.A novel 3D nanomaterial (MWCNT-PDA-POSS) with bump structure was prepared by combining multi-walled carbon nanotubes (MWCNTs) and polyhedral oligomeric silsesquioxanes (POSS) via mussel-inspired chemistry. A two-step process was used for preparation of MWCNT-PDA-POSS, and the potential chemical reaction between carboxyl-functionalized MWCNT (MWCNT-COOH), polydopamine (PDA) and amino-functionalized POSS (POSS-NH2) was investigated. Furthermore, the unique bump structure of the MWCNT-PDA-POSS was observed. As nanofillers in the resin matrix, the bump structure can provide higher specific surface area while some unreacted catechol functional groups of PDA would participate in the cross-linking reaction of epoxy resin, leading to the interface strengthening between the MWCNTs and resin matrix. Therefore, the MWCNT-PDA-POSS resulted in the significantly improved compressive performances compared to the neat epoxy, and POSS-NH2 and MWCNT-COOH reinforced ones, which exhibited potential application in the multi-scale reinforced composites.

•Biodegradable filtration membranes were prepared.•Polar groups in the membrane surface helped capture fine particles.•Loading filtration efficiency can reach 99.99% in the case of small pressure drop.•Filtration membrane showed antimicrobial activity to Escherichia coli.A biodegradable and multifunctional air filtration membrane was prepared by electrospinning of soy protein isolate (SPI)/polyvinyl alcohol (PVA) system in this paper. The optimized SPI/PVA proportion in the spinning solution was determined according to the analyses of microstructure, surface chemical characteristic and mechanical property of the hybrid nanofiber membranes. Under the preferred preparation condition, two kinds of polymer materials displayed a good compatibility in the hybrid nanofibers, and a large number of polar groups existed in the membrane surface. The loading filtration efficiency of the nanofiber membrane with optimal material ratio and areal density can reach 99.99% after test of 30 min for fine particles smaller than 2.5 μm in the case of small pressure drop. Besides, this kind of filtration membrane showed an antimicrobial activity to Escherichia coli in the study. The SPI/PVA hybrid nanofiber membrane with proper material composition and microstructure can be used as a new type of high performance eco-friendly filtration materials.

Epoxy syntactic foams were prepared by introducing hollow carbon microspheres (HCMs) of micro and nano-scale. Based on the surface structure analysis of the HCMs, the effects of HCM content and particle size on the mechanical properties, dimensional stability, thermal conductivity, thermal stability and dielectric properties of the epoxy foam were investigated. The density of the epoxy foam gradually declined with the increase of the micro-scale HCM (M-HCM) content up to 9 wt%, and the compression strength of the epoxy foam just decreased slightly, while the compression modulus and flexural modulus were enhanced continuously. When 0.5 wt% and 1 wt% of HCMs were involved, the reinforcing effect of nano-scale HCMs (N-HCMs) was superior to the M-HCMs. The compression strength of the N-HCM/epoxy foams was almost equivalent to the neat epoxy, while the flexural strength of the N-HCM samples exhibited an obvious superiority. The dimensional stability and thermal stability of the epoxy foams were also improved with the addition of HCMs. Besides, the introduction of the M-HCMs and N-HCMs gave rise to different effects on the thermal conductivity, electrical conductivity and dielectric constant of the resulting epoxy foams due to the diversity in the interfacial interactions and microstructure. These results indicate that the HCM/epoxy syntactic foams show potential for application in multifunctional materials that are lightweight and of high rigidity.

The effect of epoxy resin matrix modulus on the mechanical and interfacial properties of T700 carbon fiber and T800 carbon fiber filament wound composites was investigated. Different aromatic amine curing agents were selected to change the modulus of the same kind of resin matrix. The mechanical properties of carbon fiber filament wound composites were characterized through Naval Ordinance Laboratory-ring (NOL) burst tests, and interlaminar shear strength (ILSS) tests. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic mechanical thermal analysis (DMA) were used to characterize the failure surfaces and interfacial properties of the resulting composites. The results showed that, even if carbon fibers were fully impregnated with epoxy resin, the mechanical properties of composites and the mode of interfacial failure were closely related to the modulus of the resin matrix. The resin matrix with a high modulus was found to be an essential prerequisite to excellent mechanical and interfacial properties of the resulting composites.

•The skeleton materials with optimized core–shell fibre structure were prepared.•The well-sourced polymers and facile processing techniques were involved.•The GPE had excellent electrochemical properties and cycle performance.•The GPE showed good stability and compatibility with lithium electrode.•High applicable value of the GPE in lithium-ion batteries was presented.The polyporous polymer nanofibre membranes with optimized core (polyacrylonitrile, PAN)-shell (polymethylmethacrylate, PMMA) structure are prepared by coaxial electrospinning, and then converted to gel polymer electrolytes (GPEs) after the activation process of stacked nanofibre membranes in liquid electrolyte. Based on the proper collocation of polymer materials, the desirable microstructure of polymer membranes as well as the affinity between fibre shell and the electrode/electrolyte result in a high saturated electrolyte uptake and conservation rate. The electrochemical testing results of the GPEs indicate high ionic conductivities, good electrochemical stability and appropriate lithium-ion transference numbers, which are realized through choosing optimal core–shell flow rate ratio. Furthermore, the interface impedance performance of the GPEs shows good stability and compatibility with lithium electrode, which is beneficial for long-term storage and use of the lithium-ion battery. The Li/GPE/LiCoO2 cells with GPEs based on the electrospun membranes with optimized core–shell structure present excellent cycle performance compared to the cell involved with GPEs based on PAN and commercial Celgard 2500. Thus, the polymer membranes consisting of nanofibres with well-designed core–shell structure can be used as a new type of skeleton material in GPEs used in lithium-ion batteries.

The continuous highly aligned hybrid carbon nanofibers (CNFs) with different content of acid-oxidized multi-walled carbon nanotubes (MWCNTs) were fabricated through electrospinning of polyacrylonitrile (PAN) followed by a series of heat treatments under tensile force. The effects of MWCNTs on the micro-morphology, the degree of orientation and ordered crystalline structure of the resulting nanofibers were analyzed quantitatively by diversified structural characterization techniques. The orientation of PAN molecule chains and the graphitization degree in carbonized nanofibers were distinctly improved through the addition of MWCNTs. The electrical conductivity of the hybrid CNFs with 3 wt% MWCNTs reached 26 S/cm along the fiber direction due to the ordered alignment of MWCNTs and nanofibers. The reinforcing effect of hybrid CNFs in epoxy composites was also revealed. An enhancement of 46.3% in Young’s modulus of epoxy composites was manifested by adding 5 wt% hybrid CNFs mentioned above. At the same time, the storage modulus of hybrid CNF/epoxy composites was significantly higher than that of pristine epoxy and CNF/epoxy composites not containing MWCNTs, and the performance gap became greater under the high temperature regions. It is believed that such a continuous hybrid CNF can be used as effective multifunctional reinforcement in polymer matrix composites.

Continuous polyacrylonitrile-based nano-fibres are produced by an electrospinning approach and then converted to nano-scale carbon fibres (n-CFs) with a homogeneous structure by introducing multi-step hot-stretching in this paper. The processed n-CFs are highly aligned and partially graphitic, yet obtained at a temperature range normally associated with carbonization, and show remarkably uniform structures and a quite smooth surface with a mean roughness of 0.249 nm. The electrical conductivity of the n-CFs reaches 15.5 S/cm along the fibre direction. Tensile tests demonstrate an enhancement of 21% and 60% in tensile strength and Young’s modulus, respectively, of polyetherimide composite membranes containing 1 wt% n-CFs treated with multi-step hot-stretching, which is more remarkable reinforcing effect compared to the multi-walled carbon nanotubes. It is believed that the developed approach, electrospinning and multi-step hot-stretching technique, can be a practicable means for the fabrication of continuous n-CF reinforcement with high structural integrity and desirable properties.

Curing and thermal transition behavior of two epoxy resins i.e. 2,2′-dimethyl-4,4′-diaminobiphenyl (MTB)–4,5-epoxycyclohexyl-1,2-diglycidyl diformate (TDE85) and 2,2′-bis(trifluoromethyl)-4,4′-diamino biphenyl (TFMB)–4,5-epoxycyclohexyl-1,2-diglycidyl diformate (TDE85) with different chemical structures were experimentally and theoretically investigated via molecular simulations to establish the structure–property relationships. The slight modification in the diamine structure resulted in significant changes in the curing and glass transition behavior of epoxy resin. As the side group of the diamine was changed from methyl to trifluoromethyl, the reactivity of the diamine toward epoxy decreased and the glass transition temperature increased from about 164 °C to about 191 °C. These phenomena can be illustrated by the change of the reaction energy barrier, flexibility of chains and the cohesive energy density in the molecular simulation of the curing process. The simulated values show good agreement with experimental data, and can be used to predict the related material characteristics for the different amine curing agent–epoxy systems.

Trial-and-error approaches for experimentally designing and optimizing the polymer matrix for advanced composites are time-consuming and expensive. The simulation for curing behavior and structure–property relationships of epoxy resins can provide a guideline for designing resin matrix which will possess desirable properties. So far there are few reports in which the accuracy of the molecular simulation for the different amine-epoxy systems are addressed. In this paper, an atomistic modeling technique was used to theoretically investigate the curing and thermal transition behavior of two epoxy resin matrices containing amine curing agent with different chemical structures i.e. diaminodiphenyl methane (DDM)/diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate (TDE85) and diaminodiphenyl sulfone (DDS)/TDE85 to give help for designing high heat-resistant epoxy matrix. The simulated results successfully predicted that the reaction process was catalyzed in the early stage of the curing and the slight modification in the diamine structure resulted in significant change in the curing and glass transition behavior of epoxy resin. As the bridging group of diamine changed from methylene to sulphone, the reactivity of diamine toward epoxy declined and the glass transition temperature increased from about 190 °C to about 230 °C. This simulated method presented a good agreement with experimental data, and can be used to design and predict high performance resin matrix for advanced composites.

A facile synthesis of three-dimensional ultra-light (≈2.52 mg cm−3) graphene–poly(dopamine) modified carbon nanotube composite aerogels that needed no additional reducing agents during the forming process is reported herein. The composite aerogels exhibited highly repeatable compressibility and superior electrical conductivity, and thus will have an important application value in strain-sensitive functional devices.

The biodegraded cellulose acetate (CA)/poly-L-lactic acid (PLLA)/Halloysite nanotube composite nanofiber membranes were fabricated for the preparation of gel polymer electrolytes (GPEs) used in lithium-ion batteries. The microstructure, crystallization behaviour and thermal stability of nanofiber membranes were analysed. The testing results showed that the crystallization behaviour of the polymeric materials was significantly inhibited, and that the thermal stability of the polymer nanofiber membranes was improved due to the addition of the halloysite nanotubes (HNTs). The composite GPEs based on the CA/PLLA/HNT nanofiber membranes presented a satisfactory electrochemical performance, including high ionic conductivities, proper lithium-ion transference numbers, and good electrochemical stability. An ionic conductivity of 1.52 × 10−3 S cm−1 was obtained from the above mentioned GPEs, which is far greater than the existing bio-based GPEs. Moreover, the initial discharge capacities, cycle performance and rate performance of the Li/GPE/LiCoO2 cells involved with the CA/PLLA/HNT nanofiber membranes was superior to those of the commercial Celgard® 2500. Therefore, through the proper collocation of biodegradable polymer materials and functional nanoparticles, the resulting composite GPEs exhibited the recommendable integrated performance. The CA/PLLA/HNT composite nanofiber membranes can be used as novel green skeleton materials in GPEs for high performance lithium-ion batteries, which provide a perfect combination of high performance and environmental protection.

A new type of MnO/carbon composite particle with multi-modal pore structure was designed and prepared as anode materials of lithium-ion batteries through a promoted template method. The porous MnO/carbon composite anode materials exhibited the superior electrochemical performance, including excellent stability under different current density, high reversible capacity (as high as 1210.9 mA h g−1 after 700 cycles at 1.0 A g−1), good rate capability and high initial coulomb efficiency of over 80%, which had benefited from the reasonable material composition, special multi-modal pore structure, desirable micro-morphology and good structural integrity. The complex multiphase structure consisting of MnO crystal grains, abundant nanopores and uniform carbon layers can effectively improve cyclic stability and rate capability of the anode materials, and thus will have an important application value in high-performance energy supply devices.