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

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graphite holders through multiple washings in acetone.
The average fiber
content of the resulting fiber preforms was 41.4 f 1.3 vol %.
9.3.2 Jntermediate coatine deDositioQ
The preforms next were precoated with thin layers of various
materials.
The deposition parameters and nominal thicknesses of the
films are summarized in Table 9.1.
The coating runs were carried out
using the following procedure. The preform was placed atop the graphite
spacer, and Grafoil gaskets were used to seal the injector to the spacer
and the preform to the spacer.
Hot water of 355 K average temperature
was supplied to the injector, whereas only cold water was passed through
the furnace sections and electrodes.
The apparatus was evacuated (with the exception of the MTS
reservoir) to an ultimate pressure of < 0.5 torr using a rotary
mechanical pump.
The argon purges to the furnace base, shell, and sight
port were set at appropriate levels (a total flow of 5 L/min), and argon
was allowed to flow to the preform at a rate of 500 cm3/min through the
reactant gas supply lines, subsequently flushing these lines at the
same time. The furnace was then heated to the specified deposition
temperature and the system was allowed to degas for 30 min.
After these preliminary procedures, the operation pressure of the
furnace was set on the controller and reactants were directed into the
reaction chamber. The system was allowed to stabilize and then run at
steady state for 2 hours.
On completion, the reactant gases were
replaced with argon gas flow and the furnace was cooled to room