鉬、鎢活化燒結機構之探討
Date Issued
2002
Date
2002
Author(s)
黃坤祥
DOI
902216E002042
Abstract
Molybdenum and tungsten are known as
refractory metals and need high sintering
temperature to achieve high sintered densities.
Previous literatures have shown that addition
of a small amount of Ni can lower their
sintering temperature, however, the sintering
mechanism to explain the enhancement
phenomenon is still not clear. The objective
of this study was thus to investigate the cause
of the activated sintering in Mo-Ni system in
more detail. The dilatometer analysis in this
study suggests that the solid-state activated
sintering proceeds at the temperature below
the peritetic point of 1362 ℃. No eutectic
was formed at 1317 ℃ which suggests that
no free nickel or nickel solution was present
in the system. The field emission TEM and
the scanning Auger analysis indicate that a
ä-NiMo intermetallic film, about 2 nm thick,
was present at the grain boundaries. This
finding excludes the possibility that the
activated sintering is caused by the
amorphous layer at the grain boundaries. The
experiment of the Mo/Ni-Mo diffusion
couple shows that the diffusivity of Mo in the
ä-NiMo layer is about 30,000 times of the
self-diffusivity of Mo. This suggests that the
thin ä-NiMo layer serves as a fast diffusion
path and impart the activation effect for the
sintering of Ni-doped molybdenum.
Subjects
Molybdenum
Activated sintering
δ-NiMo intermetallic compound
Publisher
臺北市：國立臺灣大學材料科學與工程學研究所
Type
report
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