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A Model of Gas‐Phase Transport During the Initial Stages of Sintering of Silicon Carbide
Author(s) -
Kaza Anil,
Matthewson M. John,
Niesz Dale,
Haber Richard L.,
Rossi Mark A.
Publication year - 2009
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.1551-2916.2009.03252.x
Subject(s) - sintering , silicon carbide , materials science , porosity , phase (matter) , silicon , gas phase , particle (ecology) , chemical engineering , carbon fibers , carbide , microstructure , composite material , metallurgy , chemistry , composite number , oceanography , organic chemistry , engineering , geology
Carbon, which is often used as an additive to silicon carbide powder, is thought to facilitate densification during sintering by aiding the removal of the native SiO 2 layer, which is present on the starting SiC powder. The mechanism is the reduction of SiO 2 to SiC with the formation of primarily CO gas, which diffuses out from the porous compact at a temperature below the normal sintering temperature. It has been found beneficial to hold the compact at an intermediate temperature to allow time for the CO and other gases to diffuse out before the pores close. We investigate this process using a computational model based on codiffusion of multiple gas species, which enables prediction of the gas and condensed phase compositions as a function of time and position in the specimen. The results are used to determine the optimum holding time for complete SiO 2 removal as a function of key parameters, such as specimen thickness, particle size, temperature, etc., as well as the necessary amount of C additive. The results of the modeling are consistent with the experimentally observed spatial variation of density and composition in SiC compacts.