Carbon onions constituents

The carbon onions present a Unk between the fullerenes and the multiwalled nanotubes. From one point of view, they may be considered fullerene cages concentrically contained one inside another and constantly increasing in size toward the outside. On the other hand, they might just as weU be interpreted as multiwalled nanotubes with length zero so only the caps of the constituent tubes remain. With irregular caps, carbon nanoparticles of uneven shape result. 

FIGURE 10.3 Two different projections of a carbon onion consisting of four fullerene molecules, each of which contains 60n carbon atoms, where n is the number of the fullerene shell in the carbon onion. The carbon onion has evident icosahedral shape due to the presence of 12 pentagons in each of the constituent fullerene shells. 

The sp -hybridized constituents of the nanodiamond sample (mostly the outer layers of the particles and, in parts, the material in the interstices of the agglomerates under examination) are characterized by two bands that have already been mentioned in the carbon nanotubes and onions the G- and the D-band. The exact position of the G-band (observed at about 1580 cm" ) depends on both the excitation wavelength (dispersion) and the particle size. With decreasing wavelength of... 

Gay-Lussac supposed that when sulphuric acid acts upon borax the base is partitioned between the two acids in proportion to the numbers of their atoms , but later he supposed that if sulphuric acid is added until the colour of litmus is that of onion skin, the sulphuric acid has completely neutralised the soda. In 1839 he recognised the law of mass action (see p. 579). He showed that the active constituent of Homberg s pyrophorus (see Vol. Ill, p. 43) is potassium sulphide, since he prepared a pyrophorus by heating a mixture of potassium sulphate and carbon. He described the pyrophosphates discovered by Clark and metaphosphoric acid discovered by Berzelius and Engelhart (see p. 272). 

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