Acetylene black surface area

Acetylene black is very pure with a carbon content of 99.7%. It has a surface area of about 65 m /g, an average particle diameter of 40 nm, and a very high but rather weak stmcture with a DBPA value of 250 mL/100 g. It is the most crystalline or graphitic of the commercial blacks. These unique features result in high electrical and thermal conductivity, low moisture absorption, and high Hquid absorption. 

The anode layer of polymer electrolyte membrane fuel cells typically includes a catalyst and a binder, often a dispersion of poly(tetraflu-oroethylene) or other hydrophobic polymers, and may also include a filler, e.g., acetylene black carbon. Anode layers may also contain a mixture of a catalyst, ionomer and binder. The presence of a ionomer in the catalyst layer effectively increases the electrochemically active surface area of the catalyst, which requires a ionically conductive pathway to the cathode catalyst to generate electric current (16). 

In recent years, there have been further improvements in the performance of zinc chloride cells. These have been brought about principally by use of laser welding to increase the internal active volume, and by improvements to materials, especially by synthesizing acetylene black with optimized surface area and water absorption characteristics. 

Both the lithium sulfur dioxide (Li-SO and lithium thionyl chloride (Li-SOCy cells may be classified as liquid cathode systems. In these systems, S02 and SOCl2 function as solvents for the electrolyte, and as the active materials at the cathode to provide voltage and ampere capacity. As liquids, these solvents permeate the porous carbon cathode material. Lithium metal serves as the anode, and a polymer-bonded porous carbon is the cathode current collector in both systems. Both cells use a Teflon-bonded acetylene black cathode structure with metallic lithium as the anode. The Li-S02 is used in a spirally wound, jelly-roll construction to increase the surface area and improve... 

In 1968 Mantell (28) described several processes for the production of carbon black. He also lists 24 distinct grades of blacks identified by their respective particle diameters (average), surface area and oil absorption (structure). These include the then common grades of channel black, gas furnace blacks, oil furnace blacks, thermal blacks, lampblack, and acetylene blacks, in language sufficient for the manufacturer to identify each grade by these three variables. 

Figure 10. B.E.T. Surface areas of heat treated Vulcan XC-72R and Shawinigan acetylene black carbons.

From the plots of BET specific surface areas as a function ofheat-treatment temperature for both Vulcan XC-72R and Shawinigan acetylene black, shown in Fig. 10, it is obvious that the latter black has experienced a much higher temperature than that for Vulcan XC-72R. It is well known that Shawinigan acetylene black is formed at a high temperature, which leads to significant surface area diminution. 

Coconut shell charcoal (average pore diameter 2.0 nm, surface area 1700 m g average particle size 10 pm) 80 wt%, acetylene black conductor 10 wt%, and poly-tetrafluoroethylene binder 10 wt% were mixed, ground, and pressed at 6 MPa to form a disk composite 10 mm in diameter and 0.55 mm thick. A pair of these disk composite electrodes were dried at 300°C below 7.5 x 10 Pa for 3 hours. Afterward they were cooled in an argon atmosphere, and an electrolyte was immersed in them under reduced pressure. By sandwiching a nonwoven polypropylene separator with the two identical immersed electrodes, a 2032 coin cell was assembled with a stainless spacer, as depicted in Figure 17.6a. 

Carbon has been used as a support material for cathodes because of its large surface area, high electric conductivity, large availability and low price. Besides, carbon materials have also catalytic activity for oxygen reduction. Active carbon materials, which have high content of mineral traces and large surface area, and different types of carbon blacks (acetylene blacks, furnace blacks) are often applied. 

---