Graphite disk substrate

A simple laboratory type reactor for pyrolytic-graphite deposition is shown in Fig. 7.2.PI The substrate is a molded-graphite disk which is rotated to improve deposition uniformity. It is heated by a high-frequency (450 kHz) induction coil and deposition occurs at low pressure (500 Pa). Temperature is monitored and controlled by a sheathed thermocouple and corroborated by an optical pyrometer. 

Figure 4 Cyclic voltammograms of Fe° -btc in acid medium on two different substrates (a) platinum disk in aqueous HCl solution at concentrations of (i) 0.1, (ii) 0.2, and (iii) 0.5 M (b) basal plane pyrolytic graphite, (i) without and (ii) with Fe °-btc (scan rate 50 mV s" ). (Reproduced from Ref 52. Elsevier, 2010.)...

Monolayer graphite can be formed on the flat surfaces by heating the single-crystal carbide disks in an ethylene atmosphere. It has been found that the (111) surface is much more reactive than the (001) surface. The forming conditions on carbide surfaces (40-46) are summarized in Table 2. In the case of the TiC( 111) surface, minimal ethylene exposure is 100-200 L at 1100°C. It is very difficult to form MLG on a TiC(OOl) surface, indicating that exposures over 1 million L using ethylene gas are needed (45). In the case of the NbC(lll) surface, minimal ethylene exposure is 100 L at 1000-1100°C, and more than about 25,000 L exposure at 1100-1250°C is needed to form graphite on an NbC(lOO) substrate. 

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