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Title: Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications

Abstract

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 consistentlymore » meet the smoothness specifications of NIF capsules.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
888625
Report Number(s):
UCRL-JRNL-214285
TRN: US200618%%450
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Fusion Science And Technology
Additional Journal Information:
Journal Volume: 49
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; CHEMICAL VAPOR DEPOSITION; COATINGS; HEATING; LEVITATION; MONOMERS; PARTIAL PRESSURE; ROUGHNESS; SOLVENTS; SPECIFICATIONS; TARGETS; X-RAY RADIOGRAPHY

Citation Formats

Letts, S, Fearon, E, Anthamatten, M, Buckley, S, King, C, and Cook, R. Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications. United States: N. p., 2005. Web.
Letts, S, Fearon, E, Anthamatten, M, Buckley, S, King, C, & Cook, R. Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications. United States.
Letts, S, Fearon, E, Anthamatten, M, Buckley, S, King, C, and Cook, R. Wed . "Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications". United States. https://www.osti.gov/servlets/purl/888625.
@article{osti_888625,
title = {Preparation Of Polyimide Ablator Coatings Meeting The NIF Specifications},
author = {Letts, S and Fearon, E and Anthamatten, M and Buckley, S and King, C and Cook, R},
abstractNote = {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.},
doi = {},
journal = {Fusion Science And Technology},
number = ,
volume = 49,
place = {United States},
year = {2005},
month = {7}
}