Pyrolytic graphite, oxidation rates

Pyrolytic BN in the form of a pure, dense, anistropic film can be deposited at high temperatures from a mixture of ammonia and boron halide. It has a higher electrical resistivity than hot-pressed BN (see Fig. 2.24), but its dielectric constant and loss tangent are about the same. The dielectric strength of BN is rated at 4,000 volts/mil at room temperature, which makes it an excellent insulator. As is illustrated in Fig. 2.25, the oxidation rate of pyrolytic BN is significantly less that that of pyrolytic graphite below 2000°C. 

Figure 7.5 (A) Oxygen reduction and hydrogen peroxide oxidation on a bare pyrolytic graphite disk-Pt ring electrode (B) Oxygen reduction and hydrogen peroxide oxidation on an oxidized pyrolytic graphite disk-Pt ring electrode in Oa-saturated 0.1 M KOH and (C) Proposed ORR mechanism. Potential scan rate 5 mV s ring potential 1.34 V vs 1 M NaOH//Hg/HgO. Reprinted with permission from Ref. 24.

Atomic absorption spectrometry furnace tubes are supplied with a hard pyrolytic graphite surface. This helps to reduce the porosity of the tube, which minimizes adsorption of hot metal vapors and slows down the rate of oxidation of the graphite and the accompanying mechanical degradation of the furnace tube. 

FIGURE 12, In situ Mossbauer spectra of a 50% w/w Fe-enriched hydrated ferric oxide precipitated on Shawinigan black high-area carbon in the form of a Teflon-bonded electrode in 4 M KOH at (a) -0.3 V and (b) -1.1 V versus Hg/HgO, OH". Inset Cyclic voltammogram of the same, although nonenriched, material as in (a) in the form of a thin porous Teflon-bonded coating electrode deposited on an ordinary pyrolytic graphite electrode, in 4 M KOH. Scan rate 10 mV s" ... 

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