Ph.D. Dissertation Defense by Ryan W. Johnson
Monday, December 3, 2004
(Dr. W. Jack Lackey, Chair)
"Process Development for the Manufacture of an Integrated Dispenser Cathode Assembly Using Laser Chemical Vapor Deposition"
Laser Chemical Vapor Deposition (LCVD) has been shown to have great potential for the manufacture of small, complex, two or three dimensional metal and ceramic parts. One of the most promising applications of the technology is in the fabrication of an integrated dispenser cathode assembly. This application requires the deposition of a boron nitride—molybdenum composite.
Georgia Tech’s LCVD system has been modified and used to characterize both boron nitride and molybdenum deposition independently. Focus has been on understanding the relations among process parameters and deposit shape. The fabrication of a boron nitride—molybdenum composite has been demonstrated.
An advanced computational model of heat and mass transport was developed and
used to investigate local phenomena in the LCVD reaction zone. The model
was applied to two different material systems and used to quantify deposition
rates and identify rate—limiting regimes. A computational structural
model was also developed to study the thermal stress state within an LCVD
deposit during growth. In sum, this work serves to both advance the general
science of Laser Chemical Vapor Deposition, and to elucidate the practicality
of fabricating ceramic—metal composites using the process.