ELECTRICALLY CONDUCTIVE GRADES OF CARBON-BLACK - STRUCTURE AND PROPERTIES

Carbon structure of nine commercial conductive blacks, comprising benzene- and acetylene-based blacks was analyzed. This series was selected for its use in dry cells (Leclanche type). TEM (transmission electron microscopy) and X-ray diffraction were employed. First, it has been confirmed that the classical ''crystallite'' as defined by L(a) and L(c) is not the basic building unit of the black structure. This unit is seen to be the carbon layer itself as defined by its size and state by means of TEM phase contrast mode. First, the sizes of the distorted layers were seen to range at three different scales [i.e., less than 1 nm, about 5 nm or over (few tens and over)]. Then taking into account the distortions as a second parameter, five different types were discriminated, say five different turbostratic stacking orders. Type I is defined by a layer size of 0.8 nm and a coherent stack of three layers. In type II, layer size is larger: 1 nm in average and perfect enough to stack by four. Type III has the largest layer size compatible with a concentric texture of the particle: about 5-nm large. The number of layers stacked together is ten in average. Type IV has distorted layers over 5 nm in diameter and stacked by 5/6, whereas type V has the largest layer sizes (few tens) often straight and stacked by 7/8. Those largest layer sizes exist exclusively with the ''hollow-shell'' morphology. Following this model, all the productions were actually characterized by one or few populations of aggregates with a typical turbostratic stacking order and related to properties.