scholarly journals Characterization Of Ceramic Matrix Composites Fabricated By Chemical Vapor Infiltration

1989 ◽  
Vol 168 ◽  
Author(s):  
D. P. Stinton ◽  
D. M. Hembree ◽  
K. L. More ◽  
B. W. Sheldon ◽  
T. M. Besmann
Keyword(s):  
Elevated Temperatures ◽  
National Laboratory ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Infiltration Process ◽  
Oak Ridge ◽  
Sic Composites

AbstractA process for the preparation of fiber-reinforced SiC composites by chemical vapor deposition has been developed at Oak Ridge National Laboratory. Composites are prepared by infiltrating fibrous preforms with reactant gases that decompose at elevated temperatures to deposit silicon carbide between and around the fibers. Because the infiltration process utilizes both temperature and pressure gradients, SiC is deposited under conditions that vary considerably from the hot face to the cool face of the composite. Matrix characterization of composite samples by transmission electron microscopy and Raman spectroscopy are described.

The Stability of BN Interfacial Coatings in CFCC Systems During Oxidation and Exposure to Moisture

1997 ◽  
Vol 3 (S2) ◽  
pp. 729-730
Author(s):  
K.S. Ailey ◽  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Elevated Temperatures ◽  
Impurity Content ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Chemical Vapor Infiltration ◽  
Forced Flow ◽  
Crystallographic Structure ◽  
Matrix Composites ◽  
Sic Composites ◽  
The Stability

The mechanical reliability of ceramic matrix composites (CMCs) at elevated temperatures in oxidative environments is primarily dependent upon the chemical and structural stability of the fiber/matrix interface. Graphitic carbon coatings have traditionally been used to control the interfacial properties in CMCs, however, their use is limited in high temperature oxidative environments due to the loss of carbon and subsequent oxidation of the fiber and matrix. Thus, BN is being investigated as an alternative interfacial coating since it has comparable room temperature properties to carbon with improved oxidation resistance. The stability of BN interfaces in SiC/SiC composites is being investigated at elevated temperatures in either flowing oxygen or environments containing water vapor. The effect of several factors on BN stability, including crystallographic structure, extent of BN crystallization, and impurity content, are being evaluated.Nicalon™ fiber preforms were coated with ≈ 0.4 μm of BN by CVD using BCl3, NH3, and H2 at 1373 K. The coated preforms were densified using a forced-flow chemical vapor infiltration (FCVI) technique developed at ORNL.

scholarly journals Effect of mass transfer channels on flexural strength of C/SiC composites fabricated by femtosecond laser assisted CVI method with optimized laser power

2020 ◽  
Author(s):  
Jing Wang ◽  
Liyang Cao ◽  
Yunhai Zhang ◽  
Yongsheng Liu ◽  
Hui Fang ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Strengthening Mechanism ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Transfer Channel ◽  
Dense Band ◽  
Sic Composites ◽  
Transfer Channels

Abstract In this work, femtosecond laser assisted-chemical vapor infiltration (LA-CVI) was employed to produce C/SiC composites with 1, 3, and 5 rows of mass transfer channels. The effects of laser machining power on the quality of produced holes were investigated. The results showed that the increase in power yielded complete hole structures. The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546±15 MPa for row mass transfer channel of 3. The strengthening mechanism of the composites was linked to the increase in densification and formation of “dense band” during LA-CVI process. Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of “dense band” during LA-CVI process. In sum, LA-CVI method looks promising for future preparation of ceramic matrix composites with high densities.

scholarly journals Effect of mass transfer channels on flexural strength of C/SiC composites fabricated by femtosecond laser assisted CVI method with optimized laser power

2021 ◽  
Vol 10 (2) ◽  
pp. 227-236
Author(s):  
Jing Wang ◽  
Liyang Cao ◽  
Yunhai Zhang ◽  
Yongsheng Liu ◽  
Hui Fang ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Femtosecond Laser ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Strengthening Mechanism ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Dense Band ◽  
Sic Composites ◽  
Transfer Channels

AbstractIn this study, femtosecond laser assisted-chemical vapor infiltration (LA-CVI) was employed to produce C/SiC composites with 1, 3, and 5 rows of mass transfer channels. The effect of laser machining power on the quality of produced holes was investigated. The results showed that the increase in power yielded complete hole structures. The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546 ± 15 MPa for row mass transfer channel of 3. The strengthening mechanism of the composites was linked to the increase in densification and formation of “dense band” during LA-CVI process. Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of “dense band” during LA-CVI process. In sum, LA-CVI method is promising for future preparation of ceramic matrix composites with high densities.

A model for front evolution with a nonlocal growth rate

1999 ◽  
Vol 14 (10) ◽  
pp. 3829-3832 ◽  
Author(s):  
Shi Jin ◽  
Xuelei Wang ◽  
Thomas L. Starr
Keyword(s):  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Front Propagation ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Infiltration Process ◽  
Physical Problems ◽  
Eulerian Formulation ◽  
Continuous Filament ◽  
Vapor Infiltration

In this paper we provide a new mathematical model for front propagation with a nonlocal growth law in any space dimension. Such a problem arises in composite fabrication using the vapor infiltration process and in other physical problems involving transport and reaction. Our model, based on the level set equation coupled with a boundary value problem of the Laplace equation, is an Eulerian formulation, which allows robust treatment for topological changes such as merging and formation of pores without artificially tracking them. When applied to the fabrication of continuous filament ceramic matrix composites using chemical vapor infiltration, this model accurately predicts not only residual porosity but also the precise locations and shapes of all pores.

Microstructure and Micromechanical Property of C/C-SiC Composites

2011 ◽  
Vol 299-300 ◽  
pp. 238-241 ◽  
Author(s):  
Y. Y. Cui ◽  
Rui Cheng Bai ◽  
A. J. Li ◽  
M. S. Ren ◽  
J. L. Sun
Keyword(s):  
Polarized Light ◽  
Chemical Vapor ◽  
Pyrolytic Carbon ◽  
Chemical Vapor Infiltration ◽  
Infiltration Process ◽  
Resin Impregnation ◽  
Plastic Deformation Behavior ◽  
Digital Microscope ◽  
Sic Composites

The C/C-SiC composites are prepared by the reaction molten infiltration process of silicon powders, using porous C/C composites as preform. C/C composite frameworks with various bulk densities are prepared by the chemical vapor infiltration (CVI) combined with the resin impregnation-pyrolysis methods, using needled-carbon fiber felts as preform. Characterization of the microstructure was conducted with a digital microscope (VHX-500) and a polarized light microscopy, respectively. The hardness (H) and the elastic modulus (E) of the composites are measured using a nano indentor. The results show that the indentation behaviors of the pyrolytic carbon and resin carbon are elastic while silicon and silicon carbide show a plastic deformation behavior. The hardness of the resin carbon as well as the pyrolytic carbon is 2.1GPa and 1.3~1.6GPa, respectively. E of SiC varied from 360 to 259GPa and H from 36 to 21GPa. For Si, the value of E and H are 155-170GPa and 11.7GPa, respectively. The relationship between microstructure and mechanical properties of C/C-SiC composites were analyzed.

scholarly journals Effect of Mass Transfer Channels on Flexural Strength of C/SiC Composites Fabricated by Femtosecond Laser Assisted CVI Method with Optimized Laser Power

2020 ◽  
Author(s):  
Jing Wang ◽  
Liyang Cao ◽  
Yongsheng Liu ◽  
Yunhai Zhang ◽  
Jie Chen ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Strengthening Mechanism ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Transfer Channel ◽  
Dense Band ◽  
Sic Composites ◽  
Transfer Channels

Abstract In this work, femtosecond laser assisted-chemical vapor infiltration (LA-CVI) was employed to produce C/SiC composites with 1, 3, and 5 rows of mass transfer channels. The effects of laser machining power on the quality of produced holes were investigated. The results showed that the increase in power yielded complete hole structures. The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546±15 MPa for row mass transfer channel of 3. The strengthening mechanism of the composites was linked to the increase in densification and formation of “dense band” during LA-CVI process. Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of “dense band” during LA-CVI process. In sum, LA-CVI method looks promising for future preparation of ceramic matrix composites with high densities.

Acoustic Emission Research on Thermal Shock Behaviors of Three-Dimensional C/SiC Composites in Different Environments

2007 ◽  
Vol 546-549 ◽  
pp. 1585-1590 ◽  
Author(s):  
Peng Fang ◽  
Lai Fei Cheng ◽  
Li Tong Zhang ◽  
Hui Mei ◽  
Jun Zhang
Keyword(s):  
Acoustic Emission ◽  
Thermal Shock ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Damage Development ◽  
Damage Initiation ◽  
Sic Composites

Three-dimensional (3D) carbon fiber reinforced silicon carbide matrix composites (C/SiC) were prepared by a low-pressure chemical vapor infiltration method. The thermal shock behaviors of the composites in different environments were researched using an advanced acoustic emission (AE) system. Damage initiation and propagation were easily detected and evaluated by AE. The thermal shock damage to C/SiC composites mainly occurred at the process of cooling and was limited at argon but unlimited at wet oxygen atmosphere. Also correlations have been established between the different damage mechanisms and the characteristics of acoustic emission signals obtained during thermal shock tests. In this way, the paper contributes to the development of the acoustic emission technique for monitoring of damage development in ceramic-matrix composites.

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