Progress Toward Meeting NIF Specifications for Vapor Deposited Polyimide Ablator Coatings

Letts, Stephan A.; Anthamatten, Mitchell; Buckley, Steven R.; Fearon, E. M.; Nissen, April; Cook, Robert

doi:10.13182/fst04-a447

Cited by 10 publications

(5 citation statements)

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“…7 An important advantage of CVD is the ability to coat onto curved surface and complex geometries such as particles 6 and spheres. 10 Cross-linking polymers such as hydrogels 1 can also be fabricated using this technique.…”

Section: Introductionmentioning

confidence: 99%

“…This process is capable of retaining chemical functional groups, and this has enabled a variety of linear polymers to be vapor-grown, including, for example, hydrophobic, hydrophilic, and antimicrobial coatings . An important advantage of CVD is the ability to coat onto curved surface and complex geometries such as particles and spheres . Cross-linking polymers such as hydrogels can also be fabricated using this technique.…”

Section: Introductionmentioning

confidence: 99%

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Solvent-Assisted Dewetting during Chemical Vapor Deposition

Chen

Anthamatten

2009

Langmuir

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This study examines the use of a nonreactive solvent vapor, tert-butanol, during initiated chemical vapor deposition (iCVD) to promote polymer film dewetting. iCVD is a solventless technique to grow polymer thin films directly from gas phase feeds. Using a custom-built axisymmetric hot-zone reactor, smooth poly(methyl methacrylate) films are grown from methyl methacrylate (MMA) and tert-butyl peroxide (TBPO). When solvent vapor is used, nonequilibrium dewetted structures comprising of randomly distributed polymer droplets are observed. The length scale of observed topographies, determined using power spectral density (PSD) analysis, ranges from 5 to 100 microm and is influenced by deposition conditions, especially the carrier gas and solvent vapor flow rates. The use of a carrier gas leads to faster deposition rates and suppresses thin film dewetting. The use of solvent vapor promotes dewetting and leads to larger length scales of the dewetted features. Control over lateral length scale is demonstrated by preparation of hierarchal "bump on bump" topographies. Vapor-induced dewetting is demonstrated on silicon wafer substrate with a native oxide layer and also on hydrophobically modified substrate prepared using silane coupling. Autophobic dewetting of PMMA from SiOx/Si during iCVD is attributed to a thin film instability driven by both long-range van der Waals forces and short-range polar interactions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solvent-Assisted Dewetting during Chemical Vapor Deposition

Chen

Anthamatten

2009

Langmuir

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“…VDP enables uniform coatings to be formed when the presence of a solvent is unacceptable or when coatings are required to conform well to nonplanar substrates. Vapor‐deposited polyimide films are being investigated for use as gas barriers,11–13 conformal dielectric coatings,14–16 and inertial confinement fusion laser targets 17–22…”

Section: Introductionmentioning

confidence: 99%

Solid‐state amidization and imidization reactions in vapor‐deposited poly(amic acid)

Anthamatten

Letts

Day

et al. 2004

J. Polym. Sci. A Polym. Chem.

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The condensation polymerization of 4,4Ј-oxydianiline with pyromellitic dianhydride for the formation of poly(amic acid) and the subsequent imidization for the formation of polyimides were investigated for films prepared with vapor-deposition polymerization techniques. Fourier transform infrared spectroscopy, thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of films at different temperatures indicated that additional solid-state polymerization occurred before imidization. The experiments revealed that, upon vapor deposition, poly(amic acid) oligomers formed that had a number-average molecular weight of about 1500 Da. Between 100 -130°C, these chains underwent an additional condensation reaction and formed slightly higher molecular weight oligomers. Calorimetry measurements showed that this reaction was exothermic [enthalpy of reaction (⌬H) ϳ Ϫ30 J/g] and had an activation energy of about 120 kJ/mol. The experimental ⌬H values were compared with results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 -300°C), the imidization of amide linkages occurred as an endothermic reaction (⌬H ϳ ϩ120 J/g) with an activation energy of about 130 kJ/mol. The solid-state kinetics depended on the reaction conversion as well as the processing conditions used to deposit the films.

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“…1,2 Previous efforts have made possible the fabrication of aromatic polyimide capsules from pyromellitic dianhydride ͑PMDA͒ and 4 , 4Ј-oxydianiline ͑ODA͒ by employing a technique based upon vapor-phase polymerization, [3][4][5] or by an emulsion technique, 6 and the properties of the capsules critical to the ICF application were assessed. [7][8][9][10] It was verified that the PMDA-ODA polyimide capsules, prepared via the vapor-deposition technique, possessed comparable yet distinct properties from the commercial PMDA-ODA polyimide ͑Kapton͒, produced by solutionbased methods. Prior works have yet to examine one attribute of the capsules vital to the ICF application: their resistance to ␤ radiation emitted by tritium, a main component of the fuel mixture currently used in ICF.…”

Section: Introductionmentioning

confidence: 90%

Properties and structure of vapor-deposited polyimide upon electron-beam irradiation

Tsai

Kuo

Harding

2006

Journal of Applied Physics

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Vapor-deposited polyimide capsules from pyromellitic dianhydride and 4,4′-oxydianiline were irradiated with an electron beam that mimicked the β-radiation emitted by tritium, a fuel that the capsules are to contain during the inertial confinement fusion process. The mechanical properties and gas permeability of the irradiated capsules were measured to examine their radiation resistance. Upon electron-beam irradiation at an energy of 8keV and a dose of 120MGy, the capsules showed 15% and 56% decrease in tensile strength and elongation at break, respectively, without significant change in gas permeability and Young’s modulus. Analyses using x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy indicated that the chain cleavage and carbonization occurred but were confined in a thin layer at the top surface of the capsules. The shallow penetration of the low-energy electron beam used, as well as the existence of cross-linking in the vapor-deposited polyimide, may have led to the smaller magnitude of property degradation in the capsules compared to that reported for solution-cast polyimide.

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Progress Toward Meeting NIF Specifications for Vapor Deposited Polyimide Ablator Coatings

Cited by 10 publications

References 0 publications

Solvent-Assisted Dewetting during Chemical Vapor Deposition

Solvent-Assisted Dewetting during Chemical Vapor Deposition

Solid‐state amidization and imidization reactions in vapor‐deposited poly(amic acid)

Properties and structure of vapor-deposited polyimide upon electron-beam irradiation

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