Structure

The main types of carbon filaments have been introduced in the previous chapter, and a brief description has been given of their principal structural features. This chapter considers the main types of measurements that have been carried out to elucidate their structure. In all cases, unless otherwise stated, it is assumed that the basic structural unit is the hexagonal plane of carbon atoms in the honeycomb arrangement. In highly perfect filaments, these planes are stacked in a regular ABAB (graphitic) sequence, while in less perfect filaments, the stacking is random (turbostratic). For disordered filaments, the planes are bent, or twisted, and defects such as vacancies, interstitials, dislocations, grain boundaries, voids, impurities, etc., are present. The purpose of structural information is, as far as possible, to characterize the basic structural unit and the defects which are present. This chapter will therefore attempt to show in each case what structural information can be achieved by each of the characterization techniques.