High-Rate Sputter Deposition of Ultrathick Boron Carbide Coatings on Rolling Spherical Substrates

Merlo, J. B.; Forien, J. B.; Kawasaki, K.; Gonzalez, S.; Shin, S. J.; Sohngen, L. R.; Taylor, G. V.; Rodriguez, Z. R.; Kucheyev, S. O.

doi:10.1080/15361055.2025.2478342

High-Rate Sputter Deposition of Ultrathick Boron Carbide Coatings on Rolling Spherical Substrates

Journal Article · Mon Apr 28 20:00:00 EDT 2025 · Fusion Science and Technology

DOI:https://doi.org/10.1080/15361055.2025.2478342· OSTI ID:2564544

^[1]; Forien, J. B. ^[1]; Kawasaki, K. ^[1]; Gonzalez, S. ^[1]; Shin, S. J. ^[1]; Sohngen, L. R. ^[1]; Taylor, G. V. ^[1]; Rodriguez, Z. R. ^[1]; Kucheyev, S. O. ^[1]

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Amorphous boron carbide (B₄C) is a promising next-generation ablator material for inertial confinement fusion. However, the deposition of ultrathick B4C coatings with submicron-scale density uniformity on spherical substrates, as required for ablator shell fabrication, remains challenging. Here, in this study, we use direct current magnetron sputtering to deposit B₄C onto 2-mm-diameter Si spheres rolling in a dish-shaped substrate holder. High deposition rates of ∼3 μm/h are achieved. Ultrathick films have a columnar microstructure, with the column width determined by the density of nodular defects. Nodular defect nucleation is dominated by the pickup of particulates from the holder during substrate rolling. We demonstrate the fabrication of a hollow B₄C spherical shell with a wall thickness of 80 μm. Also demonstrated is the laser machining of holes in the B₄C coating, which is necessary for both the chemical removal of the Si template and the attachment of a fusion fuel fill tube.

View Accepted Manuscript (DOE)

Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: AC52-07NA27344

OSTI ID:: 2564544

Report Number(s):: LLNL--CONF-871458; 1109218

Journal Information:: Fusion Science and Technology, Journal Name: Fusion Science and Technology; ISSN 1943-7641; ISSN 1536-1055

Publisher:: Taylor & FrancisCopyright Statement

Country of Publication:: United States

Language:: English

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