Systematic study of graphite encapsulated
nickel nanocrystal synthesis with formation mechanism
implicationsJ.J. Host
M-H. Teng
(
University,
By
systematically varying the carbon content, chamber pressure, arc current,
and blowing gas velocity in a tungsten-arc encapsulation setup, the
effects of each of these variables on the encapsulation of nickel in
graphite layers was observed. The data from these optimally designed
experiments revealed that the properties of the arc translate into changes
in the encapsulated product. Specifically, a larger, hotter arc results in
more encapsulation in the final sample. These findings, along with
evidence of graphite layers which have formed on pre-crystallized
particles, indicate that the graphite layers may form by two sequential
formation steps.The first step is the simple phase segregation of carbon
from a cooling liquid particle, resulting in surface graphite. The
second step is the growth of carbon on a crystallized nickel particle,
regardless of the temperature that this occurs. The proposed formation
mechanism has significant implications for both a scientific understanding
of the encapsulation phenomena, and possible commercial applications.
Order No.:
JA809-028 © 1998 MRS
Go to September 1998 Table of Contents
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