Acetylene black structure

Acetylene black is very pure with a carbon content of 99.7%. It has a surface area of about 65 m2/g, an average particle diameter of 40 nm, and a very high but rather weak structure 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 liquid absorption. 

The primary particles of acetylene black have different shapes than those of other carbon blacks (Fig. 58). As the increased order in the c direction of the crystalline regions indicates, folded sheets of carbon layers are the main structural component. Their application is limited to special uses, e.g., in dry cells, because of their relatively high price. Total worldwide production is ca. 40 000 t/a. 

Acetylene black is the carbon material of choice for the cathode of Leclanche cells. Acetylene black serves a dual purpose (1) it provides a conducting path between the carbon rod current collector and the particle of active Mn02 material and (2) it absorbs and holds, or retains, the electrolyte for ionic conductivity throughout the cathode structure. Carbons, used as the conductive diluent, do not participate in the redox reactions that generate current and voltage. 

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. 

The reinforcement by fillers increases as the filler concentration increases since the reinforcing mechanism is related to the presence of active sites on the filler surface which are available for reaction or interaction with matrix polymer. But this increase is limited by the effect a filler has on the rheological properties of a mixed material. There is a certain filler concentration above which the reinforcing effect of the dispersed filler is lost. Carbon black can serve as a simple example. Acetylene black has many useful properties but it cannot be used effectively for reinforcement because its structure does not permit high loadings whereas some furnace blacks can be loaded to high concentrations. 

The anode of a Ni-Cd battery typically consists of a mix of Cd and CdO powders with the addition of a conductive additive (acetylene black). The impedance of the anode-particle surface is determined by the activated adsorption of OH anions first on the metal surface, with subsequent conversion into Cd(OH)2 and hydrated CdO layers (Duhirel et al. [1992])). Reaction products are also present in a partly dissolved Cd(OH)3" state. The activated adsorption mechanism of the anode reaction, as well as porous structure of the electrode, makes it appropriate to use for its analysis the equivalent circuit shown in Figure 4.5.14. It was shown by Xiong et al. [1996], by separate impedance measurements on the anode and cathode, that most of the impedance decrease during discharge is due to the anode, as the initial formation of a Cd(OH)Jrate limiting step of the reaction. The... 

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