Effect of free carbon on micro-mechanical properties of a chemically vapor deposited SiC coating

Computational thermodynamic study of SiC chemical vapor deposition from MTS‐H2*

“…Figure 1 presents equilibrium deposition diagrams at 800 ~ 2400°C, 0 ~ 26 664 Pa (0 to 200 Torr) with the H 2 / MTS ratios of 10, 30, 60, and 100. There were no predictions of phase regions with free Si, indicating co-deposition of SiC with free Si is not anticipated under the considered conditions from a purely thermodynamic perspective, which is in accord with previous experiments 24,[36][37][38][39]50 and theoretical observations. 46,48,51 However, several studies found that SiC and free Si coexisted at H 2 /MTS ratios less than 100.…”

“…Deposition diagrams show that the phase stabilities of the deposit are very sensitive to the H 2 /MTS ratio. No free Si is observed in the considered range of deposition conditions, consistent with previous experiments 24,[36][37][38][39]50 and theoretical studies. 46,48,51 As the H 2 /MTS ratio increases, the gas+SiC region expands, and the gas+graphite+SiC region shrinks.…”

“…[5][6][7][8][9] Chemical vapor deposition (CVD) and infiltration (CVI) are among the most feasible and widely studied SiC fabrication approaches because of their ability to handle complex geometry, flexible processing conditions, and the high purity, high density, and excellent crystalline morphology of the prepared SiC. [10][11][12][13][14][15][16][17][18][19][20] Methyltrichlorosilane (CH 3 SiCl 3 , MTS) is the most commonly used gas precursor for CVD and CVI of SiC [15][16][17][18][21][22][23][24] owing to its equivalent ratio of silicon (Si) to carbon (C) and the wide range of allowable deposition temperatures. Hydrogen (H 2 ) is frequently used as the carrier and diluent gas with MTS, both delivering the MTS precursor to the reactor and regulating the concentration of mixed gas precursors.…”

Bonding strength and thermal shock resistance of a novel bilayer (c‐AlPO4‐SiCw‐mullite)/SiC coated carbon fiber reinforced CMCs

“…Surface microstructure of the SiC, mullite, SiC w ‐mullite, and c ‐AlPO 4 ‐SiC w ‐mullite coatings are shown in Figure . Figure A shows the typical pebble‐like morphology on the surface of SiC coating . It is worth noting that no obvious cracks were observed on the surfaces of SiC, mullite, SiC w ‐mullite, and c ‐AlPO 4 ‐SiC w ‐mullite coatings after sintering at 1773 K for 3 hours due to the good match in thermal expansion coefficient between SiC, c ‐AlPO 4 and mullite phase.…”

“…Figure 4A shows the typical pebble-like morphology on the surface of SiC coating. 35,36 It is worth noting that no obvious cracks were observed on the surfaces of SiC, mullite, SiC w -mullite, and c-AlPO 4 -SiC w -mullite coatings after sintering at 1773 K for 3 hours due to the good match in thermal expansion coefficient between SiC, c-AlPO 4 and mullite phase. The microstructure on the surface of mullite coating is compact and smooth.…”