Abdul- Qader Dawood Faisal
Abstract
A Pyrolytic graphite (PG) shell was produced by Chemical Vapor Deposition (CVD) using a new modified vacuum furnace. The deposition experiments of (PG) were achieved on a substrate ...
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A Pyrolytic graphite (PG) shell was produced by Chemical Vapor Deposition (CVD) using a new modified vacuum furnace. The deposition experiments of (PG) were achieved on a substrate of solid rods and slabs of commercial graphite. This was selected as a miniaturized mandrel for deposition experiments. The substrate was heated at temperature range of (1500ºC-2300ºC) and a hydrocarbon gas (liquid benzene) was used with a pressure range of (1.5mbar- 2.5 mbar).A flow of hydrocarbon gas was admitted into the chamber and the PG was deposited by decomposition of the gas at high temperature on preheated graphite mandrel as previously mentioned. Methane gas was also used for deposition experiments at high temperature range (1700ºC-2000ºC) and pressure range of (100mbar-200mbar) .The thickness of the prepared material was measured as a function of T, P and time. An x-ray diffraction analysis has been done for the prepared PG shell and compared with standard grid electrode for high power electronic tubes made of PG. The calculated density of the deposited layer produced in this work at maximum temperature was about (2.1±0.1 g/cm3) .A high temperature calibration was achieved using Stephan -Boltzmann's law for different melting point metals (Cu, Ni, Ta, Mo).In addition an optical pyrometer was also used for this calibration. Finally, the prepared PG shell of this work was exposed to a high temperature oxyacetylene burner test at the atmosphere. The test shows no visual deformation of the external material
