Due to many factors, the different basal planes in the carbonised material show different reactivities towards this gasification reaction. As a result, some plates are removed, whilst others are not. This yields a very porous structure. Figure 3 depicts the progressive steam activation reaction in the material shown in figure 2. The micropore walls are largely the flat sides of adjacent basal planes.
Progressive activation can enlarge the micropores into mesopores.
In this process, the pore shape becomes more random. See Figure 4. The chemical activation process is different from the steam activation process, in that carbonisation and activation occur at the same time, and at lower temperatures. The carbonisation temperature is relatively low, approx. The activation chemical swells the wood and opens the cellulose structure.