Carbon fibers active

The original drive for the development of modem carbon fibers, in the late-1950s, was the demand for improved strong, stiff and lightweight materials for aerospace (and aeronautical) applications, particularly by the military in the West. The seminal work on carbon fibers in this period, at Union Carbide in the U.S.A., by Shindo, et al, in Japan and Watt, et al, in the U.K., is well-documented [4-7]. It is always worth pointing out, however, that the first carbon fibers, prepared from cotton and bamboo by Thomas Edison and patented in the U.S.A. in 1880, were used as filaments in incandescent lamps. 

carbon fibers are still mainly of interest as reinforcement in composite materials [7] where high strength and stiffness, combined with low weight, are required. For example, the world-wide consumption of carbon fibers in 1993 was 7,300 t (compared with a production capacity of 13,000 t) of which 36 % was used in aerospace applications, 43 % in sports materials, with the remaining 21 % being used in other industries. This consumption appears to have increased rapidly (at 15 % per year since the early 1980s), at about the same rate as production, accompanied by a marked decrease in fiber cost (especially for high modulus fibers). 

Thus in this chapter on ACF we are dealing with the overlap or intersection of two classes of carbon materials carbon fibers and active carbons. This is illustrated in the Venn diagram. Fig. 1, which is based on a classification of carbon materials recommended by lUPAC [11]. 

It is appropriate at this stage to consider active carbons generally, before leading on to introduce active carbon fibers, which are a relatively recent development of these materials. 

Traditionally, active carbons are made in particulate form, either as powders (particle size 100 pm, with an average diameter of -20 pm) or granules (particle size in the range 100 pm to several mm). The main precursor materials for particulate active carbons, PAC, are wood, coal, lignite, nutshells especially from coconuts, and peat. In 1985, 360 kt of such precursors (including 36 % wood and 28 % coal) were used to make active carbons [10], of which nearly 80 % were used in liquid-phase applications, with the rest being used in gas-phase applications. Important factors in the selection of a precursor material for an active carbon include availability and cost, carbon yield and inorganic (mainly mineral) matter content, and ease of activation. 

---

Product Hterature on KYNOL activated carbon fibers and cloths, GUN El Chemical Industry Co., Ltd., Japan, 1987 Product Hterature on... 

Fig. 1. Venn diagram illustrating where active carbon fibers lie in the classification of carbon materials.

Essentially, the technology of active carbon fibers is a combination of the technologies for carbon fibers and active carbons summarized above. This section is an outhne of the historical development of ACT. 

Fig. 2. Number of publications on active carbon fibers between 1981 and 1997 (dotted line is best fit linear trend).

Fig. 6. Breakthrough curves for aqueous acetone (10 mg 1" in feed) flowing through exnutshell granular active carbon, GAC, and PAN-based active carbon fibers, ACF, in a continuous flow reactor (see Fig. 5) at 10 ml min" and 293 K [64]. C/Cq is the outlet concentration relative to the feed concentration. Reprinted from Ind. Eng. Chem. Res., Volume 34, Lin, S. H. and Hsu, F. M., Liquid phase adsorption of organic compounds by granular activated carbon and activated carbon fibers, pp. 2110-2116, Copyright 1995, with permission from the American Chemical Society.

Economy, J., Daley, M. and Mangun. C., Activated carbon fibers - past, present and future, ACS Preprints (Fuel Chemistry Division), 1996, 41(1), 321 325. 

Maenair, R. N. and Arons, G. N., Sorptive textile systems containing activated carbon fibers. In Carbon Adsorption Handbook, ed. P. N. Cheremisinoff and F. Ellerbusch, Ann Arbor Science, Ann Arbor, 1978, pp. 819 859. 

Lin, R. Y. and Economy, J., Preparation and properties of activated carbon fibers derived from phenolic resin precursor, Appl. Polym. Symp., 1973, 21, 143 152. 

Endo, M., Takeuchi, K., Sasuda, Y., Matsubayashi, K., Oshida, K. and Drcsselhaus, M. S., Fractal analysis on pore structure for activated carbon fibers. Electron. Commun. Jpn., Part II Electron., 1994, 77(6), 98 107. 

Economy, J., Daley, M., Hippo, E. J. and Tandon, D., Elucidating the pore structure of activated carbon fibers through direct imaging using scanning tunneling microscopy (STM), Carbon, 1995, 33(3), 344 345... 

Kieffer, J., Investigation of the transitional pore stmeture of activated carbon fibers by small-angle neutron scattering, J. Appl. Phys., 1992, 72(12), 5649 5656. 

Cazorla-Amords, D., dc Lecea, C. S. M., Alcaniz-Monge, J., Gardner, M., North, A. and Dore, J., Characterization of activated carbon fibers by small-angle x-ray scattering. Carbon, 1998, 36(3), 309 312. 

Suzuki, T. and Kaneko, K., Structural change of activated carbon fibers with desorption by in situ x-ray diffraction. Carbon, 1988, 26(5), 744 745. 

Shin, S,. Jang, J., Yoon, S. H. and Mochida, I., A study on the effect of heat treatment on functional groups of pitch-based activated carbon fiber using FTIR, Carbon, 1997,35(12), 1739 1743. 

Bohra, J. N. and Saxena, R. K., Microporosity in rayon-based carbonized and activated carbon fibers. Colloid Surf., 1991, 58(4), 375 383. 

Jaroniec, M., Gilpin, R. K., Kaneko, K. and Choma, J., Evaluation of energetic heterogeneity and microporosity of activated carbon fibers on the basis of gas adsorption isotherms, Langmuir, 1991, 7(1 1), 2719 2722. 

Cazorla-Amoros, D., Alcaniz-Mongc, J. and Linares-Solano, A., Characterization of activated carbon fibers by COj adsorption, Langmuir, 1996, 12(11), 2820 2824. 

Lin, S. H. and Chen, Y. V., Adsorption and desorption characteristics of 1,1-dichloro-1-fluoroethane by granular activated carbon and activated carbon fiber, J. Environ. Sci. Health, Part A Toxic / Hazard Subst. Environ. Eng., 1996,31(6), 1279 1292. 

Xiu, G. H., Modeling breakthrough curves in a fixed bed of activated carbon fiber - exact solution and parabolic approximation, Chem. Eng. Sci., 1996, 51(16), 4039 4041. 

---