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Thermophoretic Deposition of Small Particles in the Modified Chemical Vapor Deposition (MCVD) Process
Author(s) -
WALKER K. L.,
GEYLING F. T.,
NAGEL S. R.
Publication year - 1980
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1980.tb10763.x
Subject(s) - thermophoresis , deposition (geology) , chemical vapor deposition , volumetric flow rate , chemistry , temperature gradient , analytical chemistry (journal) , materials science , thermodynamics , nanotechnology , meteorology , chromatography , organic chemistry , nanofluid , paleontology , physics , sediment , nanoparticle , biology
Thermophoresis is conclusively established as the particulate deposition mechanism in the MCVD process by comparing experimental measurements and quantitative theoretical predictions. The deposition efficiency, E , is defined as the fraction of the silica in the gas stream (initially as SiCl 4 ) that is deposited. For normal MCVD operating conditions, the deposition efficiency is only a function of the equilibrium temperature, T e , at which the gas and walls equilibrate downstream of the torch and the temperature, T r , at which reaction occurs. The deposition efficiency is ∼0.8[1‐( T e / T r )]. It is determined that T e is a strong function of the torch traverse velocity, the traverse length, the temperature of the ambient environment, and the tube wall thickness but only a weak function of the gas flow rate. At high gas flow rates, the efficiency is limited by incomplete reaction.