2014, Vol.15, No.1

Carbon Letters 2023 KCI Impact Factor : 1.35 KCI-WoS Impact Factor : 6.04

pISSN : 1976-4251 / eISSN : 2233-4998
https://journal.kci.go.kr/carbon

Carbon nanofibers (CNFs) with diameters in the submicron and nanometer range exhibit highspecific surface area, hierarchically porous structure, flexibility, and super strength which allowthem to be used in the electrode materials of energy storage devices, and as hybrid-typefiller in carbon fiber reinforced plastics and bone tissue scaffold. Unlike catalytic synthesis andother methods, electrospinning of various polymeric precursors followed by stabilization andcarbonization has become a straightforward and convenient way to fabricate continuous CNFs. This paper is a comprehensive and brief review on the latest advances made in the developmentof electrospun CNFs with major focus on the promising applications accomplished byappropriately regulating the microstructural, mechanical, and electrical properties of as-spunCNFs. Additionally, the article describes the various strategies to make a variety of carbonCNFs for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedicalapplications. It is envisioned that electrospun CNFs will be the key materials of green scienceand technology through close collaborations with carbon fibers and carbon nanotubes.

As a part of the electromagnetic spectrum, microwaves heat materials fast and efficientlyvia direct energy transfer, while conventional heating methods rely on conduction and convection. To date, the use of microwave heating in the research of carbon-based materialshas been mainly limited to liquid solutions. However, more rapid and efficient heating ispossible in electron-rich solid materials, because the target materials absorb the energy ofmicrowaves effectively and exclusively. Carbon-based solid materials are suitable for microwave-heating due to the delocalized pi electrons from sp2-hybridized carbon networks. Inthis perspective review, research on the microwave heating of carbon-based solid materialsis extensively investigated. This review includes basic theories of microwave heating, andapplications in carbon nanotubes, graphite and other carbon-based materials. Finally, priorityissues are discussed for the advanced use of microwave heating, which have been poorlyunderstood so far: heating mechanism, temperature control, and penetration depth.

A microstructure analysis is carried out to optimize the process parameters of a randomlyoriented discrete length hybrid carbon fiber reinforced carbon matrix composite. The compositeis fabricated by moulding of a slurry into a preform, followed by hot-pressing andcarbonization. Heating rates of 0.1, 0.2, 0.3, 0.5, 1, and 3.3°C/min and pressures of 5, 10, 15,and 20 MPa are applied during hot-pressing. Matrix precursor to reinforcement weight ratiosof 70:30, 50:50, and 30:70 are also considered. A microstructure analysis of the carbon/carbon compacts is performed for each variant. Higher heating rates give bloated compactswhereas low heating rates give bloating-free, fine microstructure compacts. The compactsfabricated at higher pressure have displayed side oozing of molten pitch and discrete lengthcarbon fibers. The microstructure of the compacts fabricated at low pressure shows a lack ofdensification. The compacts with low matrix precursor to reinforcement weight ratios haveinsufficient bonding agent to bind the reinforcement whereas the higher matrix precursor toreinforcement weight ratio results in a plaster-like structure. Based on the microstructureanalysis, a heating rate of 0.2°C/min, pressure of 15 MPa, and a matrix precursor to reinforcementratio of 50:50 are found to be optimum w.r.t attaining bloating-free densificationand processing time.