EBSD Analysis of Tungsten-Filament Carburization During the Hot-Wire CVD of Multi-Walled Carbon Nanotubes

Abstract

Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation.

Structure and Interface Analysis of Diamond on an AlGaN/GaN HEMT Utilizing an in Situ SiNx Interlayer Grown by MOCVD

“…Additionally, Figure (b) shows a dark contrast region above the SiN x layer that is due to nanometer scale material from the filament depositing at the initial stage of diamond deposition. This filament material is known to occur in HFCVD diamond, and the details of this phenomena will be discussed in a separate report.…”

The Stability of Straightened Ta Filament During Chemical Vapor Deposition of Diamond Film

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Plateholder design for deposition of uniform diamond coatings on WC-Co substrates by microwave plasma CVD for efficient turning application

“…One can avoid this problem using HFCVD and DC electrical discharge systems with more uniform temperature distribution [3,[10][11][12] to produce diamond films on complex shape substrates. However, there are technical difficulties because of filament carburization [13], moreover, typical growth rates in the HFCVD method are by an order of magnitude lower compared to that for MPCVD [14]. The heating uniformity becomes to be a problem upon MPCVD deposition scaling.…”