A roller electrospinning technique is combined with sol-gel chemistry to fabricate silica and polymeric materials on conductive and nonconductive substrates to verify its ability for controlling the long-range periodic structure of the final product. According to the experimental results, formation of the one-dimensional periodic silica structure was dependent on the electrical conductivity of the collector substrate. The periodic density seems to be related to the width of silica product. No effect from the electrical conductivity of collector substrate on the structure of polymeric system was observed. An energy transformation model was proposed to investigate the formation mechanism of this periodic structure. The theoretical simulation indicates that large width-to-thickness ratio of the product and high-energy transformation efficiency favor the formation of the long-range periodic structure.
With the development of electromagnetic technology, there is an urgent need for further research on highly efficient and lightweight microwave absorption materials. Transition metal carbides have drawn tremendous attention due to their strong microwave dissipation ability and perfect stability in extreme environments. However, owing to carburization under high temperatures, synthesizing metal carbides with specified morphology is still a challenge. Here, titanium carbide (TiC) with a flake-like structure was prepared through a carbothermic reduction method guided by two-dimensional graphene sheets. The prepared flake-like TiC sheets show excellent microwave absorption properties in 1–40 GHz compared with TiC spherical particles. A minimum reflection loss (RL) of −57.0 dB at 11.8 and 3.2 GHz effective absorption bandwidth (RL < −10 dB) was achieved. Meanwhile, an optimal RL of −57 dB is also achieved at 35.8 GHz together with an even broader absorption bandwidth from 34.2 to 40 GHz (5.8 GHz in total). This excellent microwave absorption performance is attributed to the flake-like morphology, which dramatically enhances the multiple polarization loss. The method of utilizing graphene sheets as a guide to fabricate flake-like TiC not only illuminates a new strategy for fabricating transition metal carbides with specified morphology but also provides an attractive candidate for microwave absorption applications.
The creation of stiff yet multifunctional three-dimensional porous carbon architecture at very low cost is still challenging. In this work, lightweight and stiff carbon foam (CF) with adjustable pore structure was prepared by using flour as the basic element via a simple fermentation and carbonization process. The compressive strength of CF exhibits a high value of 3.6 MPa whereas its density is 0.29 g/cm3 (compressive modulus can be 121 MPa). The electromagnetic interference (EMI) shielding effectiveness measurements (specific EMI shielding effectiveness can be 78.18 dB·cm3·g–1) indicate that CF can be used as lightweight, effective shielding material. Unlike ordinary foam structure materials, the low thermal conductivity (lowest is 0.06 W/m·K) with high resistance to fire makes CF a good candidate for commercial thermal insulation material. These results demonstrate a promising method to fabricate an economical, robust carbon material for applications in industry as well as topics regarding environmental protection and improvement of energy efficiency.
A unique porous TiO2 with Co3O4 nanoparticles anchored in (Co3O4@TiO2) is prepared by a dual-templating method for promoting electromagnetic microwave absorption (EMA). The as-prepared Co3O4@TiO2 possesses a three-dimensional (3D) ordered macroporous TiO2 skeleton and plenty of mesopores, as well as small Co3O4 nanoparticles that coexisted in the macropore walls of the TiO2 skeleton. The introduction of Co3O4 can increase the magnetic loss as well as suppress impedance mismatch, resulting in the regulation of the EMA performance. The synergetic effect of the TiO2 porous framework and Co3O4 nanoparticles with proper ratio promote microwave absorption performance. Therefore, Co3O4@TiO2-2 with 25 wt % Co3O4 nanoparticles content displays a strong and ultrawide effective absorption band (EAB) performance. The Co3O4@TiO2-2 presents a strong reflection loss of -53.9 dB at 2.95 mm. Moreover, it obtains a super broad EAB of ∼12.5 GHz at 5.0 mm. This dual-templating approach for a well-controlled porous structure could be a facial strategy for the development of high-performance electromagnetic wave absorbers.
Tailoring the structure and properties of graphene fibers is an important step toward practical applications. Here, we report macroscopic, long graphene ribbons formed by combining electrostatic interaction and shear stress during the wet-spinning process. The graphene ribbons are flexible and can be woven into complex structures, and the ribbon morphology can be tailored by controlling the orientation of wrinkles to obtain elasticity within a modest strain. We demonstrate several potential applications of pure or Pt-graphene hybrid ribbons as elastic strain sensors, counter electrodes for dye-sensitized fiber solar cells with cell efficiencies reaching 4.69% under standard illumination and 6.41% with a back reflector, and woven fabric supercapacitor electrodes. Our method can directly fabricate meter-long graphene ribbons with controlled structure and high performance as both energy conversion and energy storage materials.
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