2013, Vol.14, No.1

Carbon Letters 2023 KCI Impact Factor : 1.35 KCI-WoS Impact Factor : 4.82

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

Carbon nanotubes (CNTs) are increasingly attracting scientific and industrial interest because of their outstanding characteristics, such as a high Young’s modulus and tensile strength, low density, and excellent electrical and thermal properties. The incorporation of CNTs into polymer matrices greatly improves the electrical, thermal, and mechanical properties of the materials. Surface modification of CNTs can improve their processibility and dispersion within the composites. This paper aims to review the surface modification of CNTs, processing technologies, and mechanical and electrical properties of CNT-based epoxy composites.

Physically and chemically activated carbons (ACs) exhibited high adsorption capacities for organic and inorganic pollutants compared with other adsorbents due to their expanded surface areas and wide pore volume distribution. In this work, seven steam-ACs with different burn-off have been prepared from cotton stalks. The textural properties of these sorbents were determined using nitrogen adsorption at -196°C .The chemistry of the surface of the present sorbents was characterized by determining the surface functional C-O groups using Fourier transform infrared spectroscopy, surface pH, pHpzc, and Boehm’s acid-base neutralization method. The textural properties and the morphology of the sorbent surface depend on the percentage of burn-off. The surface acidity and surface basicity are related to the burn-off percentage. A theoretical model was developed to find a mathematical expression that relates the % burn-off to ash content, surface area, and mean pore radius. Also, the chemistry of the carbon surface is related to the % burn-off. A mathematical expression was proposed where % burn-off was taken as an independent factor and the other variable as a dependent factor. This expression allows the choice of the value of % burn-off with required steam-AC properties.

The effects of heat treatment temperature (HTT) of polyacrylonitrile-based carbon fiber (CF) on the mechanical, thermal, and tribological properties of C/C composites were investigated. It was found that HTT (graphitization) of CF affects the thermal conductivity and mechanical and tribological characteristics of C/C composites. Thermal treatment of fibers at temperatures up to 2800°C led to a decrease of the wear rate and the friction coefficient of C/C composite-based discs from 7.0 to 1.1 μm/stop and from 0.356 to 0.269, respectively. The friction surface morphology and friction mechanism strongly depended on the mechanical properties of the CFs. The relief of the friction surface of composites based on CFs with final graphitization was also modified, compared to that of composites based on initial fibers. This phenomenon could be explained by modification of the abrasive wear resistance of reinforcement fibers and consequently modification of the friction and wearing properties of composites. Correlation of the graphitization temperature with the increased flexural and compressive strength, apparent density, and thermal conductivity of the composites was also demonstrated.