Turbostratic disorder

Graphitic carbon normally refers to soft carbon heated above about 2100°C. The probability of finding turbostratie disorder begins to decrease as the heat-treatment temperature increases to above 2100°C. When the heating temperature reaehes above 3000°C, graphite forms. Coneeptually, graphite is a graphitic carbon with no or very little turbostratic disorder. 

Figure 15. Arrangement of the Mn - O layers and separating sheets according to Giovanoli [3]. The layer structure can be (a) completely ordered or (d) completely disordered (turbostratic disorder). The cases (h) and (c) represent situation between the two extremes, (b) Disorder of the interlayer atoms or molecules but an ordered stacking of the Mn - O layers with constant layer distance, (c) Disorder of the interlayer atoms and an incommensurate shift of the complete Mn - O sheet within the layer plane, resulting in an incommensurate superstructure along the r -direction (perpendicular to the layer) and in a diffuse distribution of the electron density in this layer, resulting in a lower contribution of this layer to the 0 0 / reflections. (Adapted from Ref. [47]).

The basic building block of carbon is a planar sheet of carbon atoms arranged in a honeycomb structure (called graphene or basal plane). These carbon sheets are stacked in an ordered or disordered manner to form crystallites. Each crystallite has two different edge sites (Fig. 2) the armchair and zig-zag sites. In graphite and other ordered carbons, these edge sites are actually the crystallite planes, while in disordered soft and hard carbons these sites, as a result of turbostratic disorder, may not... 

As in many other anthracitic substances, diffuse bands also appear near 43° and 80° 26. These represent two-dimensional (hk) reflections only since the turbostratic disorder of graphitic layers which characterizes amorphous carbons does not permit (hkl) three-dimensional atomic planes other than (001). Hirsch (19) proposed that the position of the (11) band was a function of carbon content of the sample, related to the crystallite layer diameter (L ). With increasing rank, the (11) reflection shifts towards smaller 26 values, representing greater bond lengths and larger crystallite size. Using values... 

The asymmetry of peak shape is preserved in anthraxolite heated to 1200°C. showing that turbostratic disorder persists in spite of a general enhancement of ordering. The band is also sharper and narrower. This may be interpreted to mean either that fewer class intervals are represented in the crystallite size distribution or that increased ordering of aromatic lamellae has reached the point where graphite (hid) planes are more common. Diffraction peaks of both (100) and (101) fall with the 2-A. band. 

With increasing temperature above 2273 K, the probability of turbostratic disorder decreases and the fraction of the stacked layer with graphitic order increases hence the reversible capacity also increases. Figure 26.12 shows the variation of reversible capacity of carbons in region III with the probability of turbostratic disorder F), emphasizing the fact that the reversible capacity decreases with increasing turbostratic disorder with a relation of 372(1 - P). Thermal treatments of soft carbons at temperatures greater than 2673 K form... 

FIGURE 26.12 Variation of reversible capacity of region III carbons with the probability of turbostratic disorder (P). (Reprinted with permission from J.R. Dahn, T. Zheng, Y. Liu, and J.S. Xue, Mechanisms for lithium insertion in carbonaceous materials. Science, 270, 590, 1995. Copyright 1995 AAAS.)... 

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