Microstructure and Mechanical Properties of 2D C/SiC Composites Fabricated by CVI Combining with Slurry Infiltration
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2D C/SiC composites were fabricated by chemical vapor infiltration(CVI)combining with slurry infiltration(SI)process.Effects of content of SI-SiC particles on the microstructure and mechanical performances were investigated.The particles can be infiltrated into inter-bundle pores of fiber preform after CVI SiC for 80h.The density and mechanical strength of the as-fabricated composites increase not only with increasing the CVI SiC time before SI process,but also with decreasing content of the particles.The SI process greatly reduces the interlaminar shear strength,and has little influence on the tensile strength.Keywords:
Chemical vapor infiltration
Infiltration (HVAC)
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Chemical vapor infiltration
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For long term structural service, the upper temperature capability for slurry-cast melt infiltrated (MI) SiC/SiC composites is limited to approx. 1315 C because of silicon reaction with the SiC fibers. For applications requiring material temperatures in excess of 1315 C, alternate methods of manufacturing the SiC matrices without silicon are being investigated, such as a hybrid combination of CVI and PIP. In this study, stacked fabric plies of Sylramic i-BN SiC fibers were coated with a CVI BN interface layer followed by a partial CVI SiC matrix. The remaining porosity in the SiC/SiC preforms was then infiltrated with silicon carbide matrix by PIP. Thermo-mechanical property measurements indicate that these composites are stable to 1700 C in inert environments under no load conditions for 100 h and under load conditions to 1450 C in air for 300 h. The advantages, disadvantages, and potential of this composite system for high temperature applications will be discussed.
Ceramic matrix composite
Inert
Chemical vapor infiltration
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CVI (Chemical Vapor Infiltration) and pulse CVI process are reviewed. CVI is prominent in tight bonding between reinforcing fiber and matrix, however, is inferior in tedious processing time, nonuniformity of infiltration along the thickness and a limitation of the shapes of preform. On the contrary, powder-and fiber-preforms and porous materials with free shape can be infiltrated by pulse CVI. Pulse CVI of SiC from CH3SiCl3-H2 to porous carbon resulted in oxidation resistance over 1070h at 1573K in an air flow, and also increase of flexural strength by 2-3 times. RF-heated carbon fiber wound around carbon plate was effectively infiltrated by SiC. SiC powder preform, average particle size of 10μm, was strengthened to flexural strength of 240MPa after 30000 pulse of CVI. A combination of Si3N4 powder and BN matrix is also refered.
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Chemical vapor infiltration
Ceramic matrix composite
Infiltration (HVAC)
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Chemical vapor infiltration
Brittleness
Ceramic matrix composite
Infiltration (HVAC)
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In order to increase the densification rate of C/SiC composites fabricated by CVI process, a continuous synchronous chemical vapor infiltration (CSCVI) technologic route for fabrication of C/SiC composites reinforced by carbon cloth was brought forward. C/SiC composites were fabricated, and their microstructure were observed and analyzed. The results indicate that, in CSCVI process, deposition rate of SiC matrix is faster, therefore the densification degree is greater and SiC solid is more uniform. At the same time, that deposition rate of SiC is controlled only by the deposition temperature and the MTS (CH 3SiCl 3) flux enhances the maneuverability of CSCVI process, and enlarges the variety range of processing parameters.
Chemical vapor infiltration
Deposition
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Reinforced carbon–carbon
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Sintered porous SiC ceramics are modified with SiC nanowires prepared via chemical vapor infiltration (CVI). SiC nanowires are successfully grown within sintered porous SiC ceramics following vapor–liquid–solid growth. The diameter of the SiC nanowires is in the range of 200 nm–1 μm, and first decreases with increasing input gas ratio (α = 50, 60, 70, and 80) and increases thereafter. The diameter of the nanowires decreases from the surface to the interior areas of the porous SiC ceramics. SiC nanowires effectively improve the mechanical properties of the porous SiC ceramics, and sample Ni‐50 has the highest flexural strength of 33.91 MPa and fracture toughness of 0.79 MPa · m 1/2 , which increases by 90.4% and 49.1% compared to an unmodified sample, respectively. Additionally, the presence of SiC nanowires leads to porous SiC ceramics with altered porosity and microstructure, and higher thermal conductivity. The porous SiC ceramics modified by CVI SiC nanowires satisfy the requirements of gas filtration applications and the pressure drop increases with decreasing apparent porosity. The porous SiC ceramics modified with CVI SiC nanowire has higher permeability than those resulting from the introduction of CVI‐SiC matrix or CVD‐SiC coating into porous SiC ceramics.
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C f/SiC composites were fabricated by Self heating Chemical Vapor Infiltration (SHCVI) , Mechanical properties of the composites were investigated, Microstructure and fracture morphologies were observed under SEM It showed that: SHCVI can have faster infiltration rate than other CVI methods Increase of gas flow rate will improve the composites, properties The thickness of carbon coating has great influence on their mechanical properties , the appropriate value of which is within 0 35～0 55μm
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Pyrolytic carbon coating and successive SiC matrix were respectively prepared by chemical vapor infiltration(CVI) in T700 kind integer felt.The subsequent reactive melt infiltration(RMI) method was adopted to densify it further and C/SiC composites were successively prepared.The microstructure and effect of interface on flexural properties were thoroughly investigated.The results show that C/SiC composites fabricated by CVI-RMI methods have high density and low porosity(10%),in which CVI-SiC and RMI-SiC distribute uniformly.The flexural strength of the composites is 133 MPa.The composites are damaged layer by layer with good pseudo-plasticity.C fibers are damaged lightly because of pyrolytic carbon coating and CVI-SiC.Pyrolytic carbon coating moderates the interface strength between C fibers and SiC,which is beneficial to the pulling out of C fibers.
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SiC matrix composites reinforced by continuous carbon fibers were fabricated using an improved chemical vapor infiltration (Continuous Synchronous CVI, CSCVI) process, so that the weaving of continuous carbon fibers and deposition of SiC go along synchronously. Under different processing condition, C/SiC composites were fabricated and their microstructures were observed. The size of remnant pores of CSCVI-C/SiC composites is very small and less than that of ICVI-C/SiC composites. CSCVI process has a capacity for fabrication of C/SiC with low porosity and high density. Some characters of C/SiC composites, such as open porosity, thickness of SiC matrix and final density, are directly effected by the winding linear velocity of carbon tows.
Chemical vapor infiltration
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Carbon fibers
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