280 



THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



a fixed duration of pyrolysis. It will be noted that the rate of deposition is 

 not proportional to the concentration, a change in concentration by a 



7000 

 6000 

 5000 



2000 



1500 



=10.002x10-* 



- 0.003 p 



0.004 



965 



970 975 980 985 990 



TEMPERATURE OF PYROLYSIS IN DEGREES CENTIGRADE 



Fig. 4 — Dependence of the rate of carbon deposition on pyrolyzing temperature at 4.5 

 per cent methane concentration and for constant duration of pyrolysis. Rate of deposition 

 expressed in terms of film resistance. 



8000 



< 2000 



1500 



800 



600 

 500 

 400 



0.002X10-* 



z 



0.005 IJJ 



0.02 



2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

 METHANE CONCENTRATION IN COATING GASES IN PER CENT 



Fig. 5 — Dependence of the thickness of carbon films on hydrocarbon concentration in 

 continuous furnace. Film thickness expressed in terms of film resistance. 



given percentage producing a greater change in rate of deposition at low 

 concentrations than at high. 



The rate of carbon deposition with temperature, concentration, and dura- 

 tion of pyrolysis all held constant is a function of the geometry of the system, 

 being dependent, for example, on the distance between the furnace wall and 



