Carbon whisker

The carbon whisker mechanism can be blocked by the use of noble metal catalysts because these metals do not dissolve the carbon. 

Experimental results. Some carbon fibre specimens reveal several orders of 001 particularly in electron diffraction patterns Figure 15 shows a plot of (3 against l2, equation (3), for an electron diffraction pattern from the skin region of a high-modulus material. L(oOl)> usually referred to as Lc, is 3.5 nm and a = 2%. A full description of electron-diffraction analysis in several similarly heterogeneous carbon fibres has been published (23). Figure 15 also includes a plot from the 001 electron diffraction profiles of a carbon whisker, an exceptionally perfect graphite material. This specimen, with an Lc of 10 nm, has zero distortion, and represents the only case where we have found no distortion in a fibrous specimen. 

Tatsumi K, Zaghib K, Abe H, Higuchi S, Ohsaki T, Sawada Y. A modification in the preparation process of a carbon whisker for the anode performance of lithium rechargeable batteries. J Power Sources 1995 54 425-427. 

Hojo E, Yamashita J, Kishimoto K, Nakashima H, Kasai Y. Improved valve-regulated lead-acid batteries with carbon whisker. YUASA-JIHO. Tech Rev 1992 72 23-28. 

B) Activated Carbon Membrane (D) Carbon Whisker Membrane... 

Figure 1 Cross-sections of (A) Ceramic Substrate, (B) Activated Carbon Membrane, (C) Carbon-Coated Ceramic Membrane, and (0) Carbon Whisker Membrane...

Figure 2 (A) Top-view and (B) Side-view of Carbon whisker membrane...

Figure 3 Carbon whisker membranes with different size of carbon whiskers. The one on the top has a thicker and longer carbon whisker layer but smaller pore size of membrane compare to the rest of the two CWMs.

We reported our recent developed membranes called carbon whisker membrane (CWM) and c on-coated coamic membrane. The CWM performed a better permeant flux in the filtration process in comparison with the membrane without whiskers. Also, CWMs have a self-cleaning function which can increase the separation efficiency during die filtration and increase die lift-time of the membrane. The carbon-coated ceramic membranes with various pore sizes can be made for the puipose of nanofiltration. 

ACTIVATED CARBON MEMBRANE WITH CARBON WHISKER... 

PVC) microspheres of 0.10-0.IS pm in diameter (Asahi Kasei Co. Ltd., Japan) was used as a pre-coat reagent and precursor of the activated carbon (Sakoda et al., 1996). Preliminary experiments revealed that thermal decomposition occurs around 300 t), and that a temperature above 700 t) is needed for the complete carbonization of the polymer latex employed. The ferric sulfate (Fe2(S04) /1H2O) was used as the catalytic precursor in order to make the carbon whiskers (Li et al. 2001a, b). 

A 15-cm-Iong ceramic sample was put in a quartz tube with an i.d. diameter of 25cm, placed in an electric oven, then dried at 300 1C for 10 °C-min and kept at 300 1C for 30 minutes. The temperature was then raised again to 1000-1100 °C at a rate of 10 1C min" . The temperature was reach at 1000-1100 1C, we started to input the nitrogen/methane = (80/20) volume % mixture gas at 500 ml min, 25t in flow rate, in order to form carbon whiskers on the activated carbon layer. The hydrocarbon... 

Table 1 Preparation conditions for the Membranes A, B and C Note Membrane D is the carbon whiskers membrane reported in the previous work (Li, etal., 2001a,b)...

In this study, we made three novel membranes, labeled Membrane A, B, and C, with different formation conditions. Table I lists the preparation conditions of the membranes. Membrane D is a carbon whisker reported in Li et al. (2001), and is used for comparison. 

Figure 2 shows the SEM pictures of the prepared Membranes A, B, and C. Membrane D is also shown. It is obvious that Membranes A, B, and C have finer carbon whiskers, with diameters of approximately 0.6, 0.4, and 0.2 pm, respectively, while the whiskers of membrane D are larger, 2 pm (Li et al, 2001). As the SEM pictures show, after carbonization of polymer latex and CVD of methane, the novel membranes had thin and dense carbon whiskers compared with die conventional ones. 

In the pure water flux (PWF) of Membranes A to D that these membranes have different ranges of pore size. The PWF of Membranes, A, B, C, and D were 0.7, 2.4, 2.8, and 0.03 [m day atm ], respectively. These data indicate that the PWF of the membranes developed in this work were much better than those of carbon whisker membranes repeated in the previous works. The resultant PWF over 0.5 [m day atm ] at the pressure of 50 [kPa] is large enough for practical applications, since commercial membranes have PWF typically of 2 [m day atm" ]. 

Thus we concluded that the carbon whisker layer with high sur ce density and narrow space between the carbon whiskers has the practical effect of preventing fouling. 

Li, Y.Y., Bae, S.D., Sakoda, A., Suzuki, M. (2001a), Formation of vapor grow carbon fibers with sulfuric catalyst precursors and nitrogen as carrier gas. Carbon, 39, 91-100. Li, Y.Y., Bae, S.D., Nomura, T., Sakoda, A. and Suzuki, M. (2001b), Preparation of Custom-Tailored Carbon Whisker Membrane by Chemical Vapor Deposition, in K. Kaneko (Ed.), Fundamentals of Adsorption, 7,279-286. 

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