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 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.

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.

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.

scholarly journals Chemical Vapor Infiltration of Non-Oxide Ceramic Matrix Composites

1993 ◽  
Vol 327 ◽  
Author(s):  
Theodore M. Besmann ◽  
David P. Stinton ◽  
Richard A. Lowden
Keyword(s):  
State Of The Art ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Ceramic Composites ◽  
Chemical Vapor Infiltration ◽  
Oxide Ceramic ◽  
Matrix Composites ◽  
Aerospace Applications ◽  
Structural Applications ◽  
Vapor Infiltration

AbstractContinuous fiber ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being investigated, with the complexity of filament weaves and deposition chemistry merged with standard heat and mass transport relationships. Silicon carbide-based materials are, by far, the most mature, and are already being used in aerospace applications. This paper addresses the state-of-the art of the technology and outlines current issues.

A Pre-Stitching Method to Manufacture Z-Pins Reinforced Woven Ceramic Matrix Composite Laminates

2013 ◽  
Vol 721 ◽  
pp. 117-120
Author(s):  
Wei Liu ◽  
Gui Qiong Jiao ◽  
Jing Guo ◽  
Hao Tian Jiang
Keyword(s):  
Carbon Fibers ◽  
Composite Laminates ◽  
Impact Resistance ◽  
Ceramic Matrix Composite ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Chemical Vapor Infiltration ◽  
Matrix Composites ◽  
Delamination Resistance

Z-pins reinforced 2D ceramic matrix composites (CMCs), integratedly designed new materials, are developed to enhance 2D CMCs through-thickness in the form of Z-pins and to ensure significant increase in interlaminar fracture toughness, delamination resistance and impact resistance, and Z-pins reinforced 2D CMCs have much application. A manual pre-stitching method is developed to make holes in the graphite fixture to control Z-pins row spacings and to introduce yarns of 3000 T300 carbon fibers bundle into a preform. Z-pins reinforced woven CMCs for research were manufactured successfully by repeatedly using chemical vapor infiltration (CVI) to infiltrate SiC matrix into woven preform and carbon fiber sutures. It is shown that this method of manufactured Z-pins reinforced woven CMC is feasible.

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.

scholarly journals Design, Fabrication, and Testing of Ceramic Joints for High Temperature SiC/SiC Composites

2000 ◽  
Author(s):  
M. Singh ◽  
Edgar Lara-Curzio
Keyword(s):  
Silicon Carbide ◽  
Shear Strength ◽  
Elevated Temperatures ◽  
Stress Rupture ◽  
Ceramic Matrix Composites ◽  
Matrix Composites ◽  
Carbide Matrix ◽  
Sic Composites ◽  
Stress Rupture Testing

Various issues associated with the design and mechanical evaluation of joints of ceramic matrix composites are discussed. The specific case of an affordable, robust ceramic joining technology (ARCJoinT) to join silicon carbide (CG-Nicalon™) fiber-reinforced-chemically vapor infiltrated (CVI) silicon carbide matrix composites is addressed. Experimental results are presented for the time and temperature dependence of the shear strength of these joints in air up to 1200°C. From compression testing of double-notched joint specimens with a notch separation of 4 mm, it was found that the apparent shear strength of the joints decreased from 92 MPa at room temperature to 71 MPa at 1200°C. From shear stress-rupture testing in air at 1200°C it was found that the shear strength of the joints decreased rapidly with time from an initial shear strength of 71 MPa to 17.5 MPa after 14.3 hours. The implications of these results in relation to the expected long-term service life of these joints in applications at elevated temperatures are discussed.

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