Nitrogen-doped carbon/graphene (NCG) hybrid materials were prepared by an in-situ polymerization and followed pyrolysis for sodium-ion batteries. The NCG has a large interlayer distance (0.360 nm) and a high nitrogen content of 7.54 at%, resulting in a high reversible sodium storage capacity of 336 mAh g -1 at 30 mA g -1 .The NCG shows a sandwich-like structure, i.e. nitrogen-doped carbon nanosheets closely coated on both sides of graphene. The carbon nanosheets shorten the ion
A vinyl isocyanate (VI) synthesized from toluene diisocyanate and 2-hydroxyethyl methacrylate was used as a novel coupling agent to obtain strong chemical interfacial adhesion and therefore, improve the tensile properties of Kraft fiber-reinforced unsaturated polyester (UPE) composites. Results characterized by fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and scanning electron microscope (SEM) indicated that the novel coupling agent VI had a significant effect on the tensile properties of composites due to the formation of chemical bonds between the VI-Kraft interfaces and the VI-UPE interfaces. The tensile properties of composites modified by VI were much better than those of the control composite without VI modification. The VI-modified composites after severe hygrothermal aging exhibited lower losses of tensile properties and desirable tensile durability. The improvement in tensile properties, less interfacial separation after severe hygrothermal aging, lower damping values, and higher glass transition temperature are sufficient to show that the interfacial adhesion between the Kraft fiber and the UPE matrix was significantly improved because the coupling agent VI has both active isocyano groups which react with the Kraft fiber and vinyl groups which are copolymerizable with the UPE resin.
Purpose -The purpose of this paper is to investigate the effect of thermal-oxidative aging at 1508C on the mechanical properties of carbon fibre reinforced bismaleimide composites. Design/methodology/approach -Composites specimens after thermo-oxidative aging at 1508C for various times (up to 1,000 h) were investigated by scanning electron microscopy (SEM) for fracture morphology, Fourier transform infrared (FTIR) spectroscopy for chemical structures, and flexural strength test and inter-laminar shear strength (ILSS) test for mechanical properties. Findings -The results indicated that the mechanical properties of carbon fibre/BMI composites were affected significantly by testing temperature rather than by aging time. SEM results showed that the good adhesion of fibre and matrix resulted in the better mechanical properties. The composites showed lower flexural strength and ILSS at 1508C due to the viscoelastic behaviour of matrix resin. The FTIR spectra confirmed the decomposition of crosslinked maleimide occurred just on the surface of composites during various aging times. Research limitations/implications -Results indicated that carbon fibre/BMI composites had excellent heat resistance and aging resistance. Practical implications -Due to their excellent thermal and mechanical properties, the carbon fibre/BMI composites show greater potential for their applications in some extreme fields such as aerospace and machine. Originality/value -The paper investigates the relationships of the fracture morphologies of composites and chemical structures of matrix resin to the mechanical properties after thermo-oxidative aging.
With the aim to obtain robust electrochemical cycling stability which is crucial for application of smart electrochromic devices (ECD), we propose an effect strategy by introducing three-dimensional (3D) star-shaped triptycene...
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