It is of significant implication to fabricate high-performance, durable and low-cost catalysts toward to oxygen reduction reaction (ORR) to drive commercial application of fuel cells. In our work, we synthesize the Fe/N-CNT catalyst via one-pot grinding combined with calcination using a mixture of carbamide, CNTs and iron salts as precursors, the as-synthesized catalysts show the structure that Fe nanoparticles are encapsulated in the tube of intertwined CNTs with abundant active sites. The catalyst is synthesized at 800 °C (Fe/N-CNT-800–20) obtain high graphitization degree and high N doped content, especially the high content and proportion of Fe–N and pyridinic-N, exhibiting outstanding ORR activity. Moreover, too high calcination temperature (850 °C) and high Fe content (25%) lead to the agglomeration of Fe during the calcination, which blocked some catalytic sites, leading to poor ORR activity. This facile synergy route will provide new thoughts for the fabrication and optimization of catalysts.

Carbon fibers composites performance strengthening through graft Carbon nanotubes is a research hotspot at present. Here, a method for rapidly and effectively dispersing and removing CNT aggregates during spraying the CNTs onto CFs surface by the three-stage channel is reported. The scanning electron microscopy image characterization results shows that the three-stage channel has a significant effect on the removal of CNTs aggregates, and the obtained p-CNTs has a good dispersion morphology. Under the same condition, p-CNTs@CFs/EP and CNTs@CFs/EP composites are prepared by the three-stage channel spraying and direct spraying method respectively. Compared with no treatment CFs composites (o@CFs/EP), the tensile, compressive and interlaminar shear strength and radial thermal conductivity (λ⊥) of the CNTs@CFs/EP are increased by 7%, 11%, 9% and 80% (2452.04 MPa, 1209.37 MPa, 89.30 MPa and 1.28 W/(m·K)), the p-CNTs@CFs/EP increased by 29%, 35%, 37% and 203% (2949.06 MPa, 1471.67 MPa, 112.37 MPa and 2.15 W/(m·K)), the CNTs@CFs/EP resistivity is 72.72 Ω·m, a 64% decrease, the p-CNTs@CFs/EP is 45.45 Ω·m, a decrease of 78%. This indicates that the CFs composites prepared by the three-stage channel spraying method has better performance than direct spraying and no treatment. This method provides a new idea for CFs composites performance strengthening.

No abstract

In order to realize the goal of mass production of modification technology, CNTs would be dispersed in gas phase rapidly and then be sprayed to the surface of industrial CF that contain sizing agent. This will increase Interface shear strength (IFSS) of CF from 26MPa before processing to 35MPa maximum (increased about 33.9%). Due to the embedding function that sizing agent has on CNTs, three types of CNTs adhering to the surface of CF are formed. They are complete embedding type (σ1), partial embedding type (σ2) and sufficient exposure type (σ3). This paper analyses the relations between three formations and processing time, and the contribution to IFSS of each type. It is found that the low content of σ1 has a positive effect on IFSS which can reach 6MPa and σ2 has an even stronger effect on the improvement of IFSS compared with σ1on the same concentration. While σ3 has a negative effect on IFSS all the time.

Carbon fiber (CF) composites performance enhancement is a research hotspot at present. In this work, first, a sandwich structure composite, CF@(carbon nanotube/Fe3O4)/epoxy (CF@(CNT/Fe3O4)/EP), is prepared by the free arc dispersion-CFs surface spraying-rolling process method, herein, CFs in the middle layer and (CNT/Fe3O4)/EP as top and substrate layer. Then, CF@(CNT/Fe3O4)/EP (on both sides) and CFs (in the middle) are overlapped by structure design, forming a multilayer CF@(CNT/Fe3O4)/EP-CFs composite with a CFs core sheath. A small amount of CNT/Fe3O4 is consumed, (CNT/Fe3O4)/EP and CFs core sheath realize thermal and electrical anisotropy and directional enhancement, and multilayer sandwich structure makes the electromagnetic interference (EMI) shielding performance better strengthened by multiple absorption–reflection/penetration–reabsorption. From CF-0 to CF-8, CNT/Fe3O4 content only increases by 0.045 wt%, axial thermal conductivity (λ‖) increases from 0.59 W/(m·K) to 1.1 W/(m·K), growth rate is 86%, radial thermal conductivity (λ⊥) only increases by 0.05 W/(m·K), the maximum λ‖/λ⊥ is 2.9, axial electrical conductivity (σ‖) increases from 6.2 S/cm to 7.7 S/cm, growth rate is 24%, radial electrical conductivity (σ⊥) only increases by 0.7 × 10−4 S/cm, the total EMI shielding effectiveness (EMI SET) increases by 196%, from 10.3 dB to 30.5 dB. This provides a new idea for enhancing CFs composite properties.