Effect of Chemical Vapor Deposition Pressure on Preferred Orientation, Microstructure, and Oxidation Resistance of Pyrolytic Graphite

Pyrolytic Graphite (PyG) is the candidate material for pyrochemical reprocessing of spent fuels involving corrosive molten salts, metals and high temperatures. The properties of PyG synthesized by the chemical vapor deposition process depend on process conditions like temperature, pressure and gas dynamics. In the present investigation, the influence of pressure on the texture and microstructure of PyG synthesized between 2.5 and 10 mbar at 2200 °C pyrolysis is studied. The density measurement shows a marginal reduction from 2.22 to 2.19 g/cm³ while the growth rate decreased from 24 to ~ 15 μm/h with increasing pressure from 2.5 to 10 mbar. The texture analysis by various characterization techniques reveals a decrease in the degree of preferred orientation with increasing pressure. The deposition mechanism based on the concept of gas dynamics, nucleation and growth contributing to the above results are briefly discussed.