Characterization and control of the fiber-matrix interface in ceramic ...

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temperature by simply switching off the power. Finally, the sample was
removed from the furnace after evacuating the system for another 30 min
at room temperature.
9.3.3 Densification
The coated preforms were densified using the FCVI process. The
composites were infiltrated with Sic produced by the decomposition of
methyltrichlorosilane (MTS) in hydrogen. The deposition parameters used
were as follows: a top surface temperature of 12OO0C, an MTS flow of
0.333 g/min, a hydrogen flow of 500 cm3/min, and atmospheric pressure.
The infiltration procedure is the same as for the deposition of
intermediate layers, with a few exceptions. All infiltration runs were
performed at atmospheric pressure, approximately 740 torr for the
majority of the experiments.
The samples were heated to 1475 K with the
full 500 cm3/min of hydrogen flowing through the vaporizer by pass.
When
the temperature stabilized, flow was diverted to the evaporator using a
set of pneumatic valves and diluent flow was supplied by a mass flow
controller in series with the vapor contoller.
A predetermined pressure
differential across the sample (170 KPa) designated complete
infiltration. At this point, system control is switched to a programmer.
The programmer diverts the hydrogen flow back to the vaporizer bypass and
slowly cools the furnace to room temperature.
The hydrogen flow is
replaced by argon below 500 K.
The samples were removed from the furnace
once the system had reached ambient temperature. The MTS reservoir was
weighed after every run to verify actual reactant usage and flow.