Graphite tube coated with pyrolytic graphite is formed by the pyrolysis of organic matter, pyrolytic graphite, on the inner surface of an ordinary graphite tube.

Siemer and Woodriff et al. Have introduced a very simple method for depositing pyrolytic graphite on carbon elements. In a diameter of 17 mm heat insulation glass tube outer wall, wrapped about 50 turns of nichrome wire as the sample room. In the pipe is energized with ordinary nitrogen, adjustable transformer heating nickel wire, the temperature reached 1000 degrees. The object to be covered in the tube, stop the nitrogen gas flow, the conversion of methane (39 ~ 200 mL / min). The rate of methane varies depending on the body. According to the size and shape of the components, the deposition rate of pyrolytic graphite is generally 0.01 ~ 0.1mm / h. The pyrolytic carbon was deposited on the graphite tube by the method introduced by Kntlensky. Gas hydrocarbon (methane generally) diffusion through the porous graphite L slowly deposited pyrolytic carbon coating on the larvae L gap. At high temperature (2300 DEG C), graphite surface was first coated, at low temperature (1400 DEG C) and low pressure, the internal pore is preferentially coated graphite, until the gap completely closed so far. The graphite produced by this method has a density of 2.1 g / cm3, close to the theoretical density. Also available with 10% methane argon or nitrogen, with a flow rate of 0.3 L / min ordinary graphite tube (2300 C) 60 s, after 2350 DEG C to 6 s of ventilation, cooling, so repeated 10 times.

It is suggested that before or after each analysis, on the graphite tube coated with pyrolytic graphite coating. C1vburn et al. Proposed at each atomic stage, the methane in argon blowing, it can continuously re coated with pyrolytic graphite coating. Allen et al. Acetylene was added into the nitrogen gas flow, claiming a lower detection limit, and the life of the graphite tube was prolonged by 10 times. Steinev and Kramer improved the conventional CRA-90 type graphite tube gas entrance and coat protection system, so that it can carry out continuous pyrolysis of coated graphite tube.

Scanning electron microscopy was used to study the surface of pyrolytic graphite tube. The test results of HGA-2100 graphite tube show that the deposition temperature must be higher than 2300. It is pointed out that the ability of graphite to eliminate interference is related to its surface smoothness.