Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications
We completed the development of a method for preparing smooth vapor deposited polyimide (PI) up to 160 {micro}m thick for NIF target capsules. The process consists of two steps. The first step is vacuum chemical vapor deposition (CVD) of monomer species, pyromelletic dianhydride and oxidianaline, which react on the surface of a shell to form short chain oligomers of polyamic acid. In the second step solvent vapor exposure in a gas levitation apparatus swells and fluidizes the outer surface. Roughness in the outer fluid layer is reduced by surface-tension-driven flow. The shells are cured in the final smoothing step by heating to 300 C reacting the polyamic acid to polyimide. Recent experiments using x-ray radiography have allowed us to determine the depth of solvent penetration and the solvent concentration over a range of solvent exposure conditions. We found that the rate of penetration is a function of the solvent partial pressure in the flowing vapor stream. The concentration of solvent in the swollen layer is 0.45 g/cc and is independent of exposure conditions. Using the penetration information we were able to improve the smoothing process by increasing the solvent partial pressure. The optimized vapor smoothing process allowed us to consistently meet the smoothness specifications of NIF capsules.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 888625
- Report Number(s):
- UCRL-JRNL-214285; TRN: US200618%%450
- Journal Information:
- Fusion Science And Technology, Vol. 49
- Country of Publication:
- United States
- Language:
- English
Similar Records
Solution Based Deposition of Polyimide Ablators for NIF Capsules
Fabrication of polyimide shells by vapor phase deposition for use as ICF targets