X-Ray Tomographic Microscopy of Nicalon Preforms and Chemical Vapor Infiltrated Nicalon/Silicon Carbide Composites

1991 ◽  
Vol 250 ◽  
Author(s):  
M. D. Butts ◽  
S. R. Stock ◽  
J. H. Kinney ◽  
T. L. Starr ◽  
M. C. Nichols ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
High Resolution Computed Tomography ◽  
X Ray ◽  
Sic Fiber ◽  
Sic Composites ◽  
And Control ◽  
Fiber Preforms ◽  
Very High

AbstractFollowing the evolving microstructure of composites through all stages of chemical vapor infiltration (CVI) is a key to improved understanding and control of the process. X-ray Tomographic Microscopy (XTM), i.e., very high resolution computed tomography, allows the microstructure of macroscopic volumes of a composite to be imaged nondestructively with resolution approaching one micrometer. Results obtained with XTM on dense SiC/SiC composites and on woven SiC fiber preforms illustrate how details of the densification process can be followed using this technique during interruptions in processing. Ways in which the three-dimensional microstructural information may be used to improve modeling are also indicated.

Complex Permittivity of 3D Textile SiC/C/SiC Composites Fabricated by Chemical Vapor Infiltration at X-Band Frequency

2008 ◽  
Vol 368-372 ◽  
pp. 1028-1030 ◽  
Author(s):  
Dong Lin Zhao ◽  
Hong Feng Yin ◽  
Yong Dong Xu ◽  
Fa Luo ◽  
Wan Cheng Zhou
Keyword(s):  
Complex Permittivity ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Pyrolytic Carbon ◽  
Chemical Vapor Infiltration ◽  
Band Frequency ◽  
Sic Fiber ◽  
X Band ◽  
Sic Composites ◽  
Vapor Infiltration

Three-dimensional textile SiC fiber reinforced SiC composites with pyrolytic carbon interfacial layer (3D-SiC/C/SiC) were fabricated by chemical vapor infiltration. The microstructure and complex permittivity of the 3D textile SiC/C/SiC composites were investigated. The flexural strength of the 3D textile SiC/C/SiC composites was 860 MPa at room temperature. The real part (ε′) and imaginary part (ε″) of the complex permittivity of the 3D-SiC/C/SiC composites are 9.11~10.03 and 4.11~4.49, respectively at the X-band frequency. The 3D-SiC/C/SiC composites would be a good candidate for structural microwave absorbing material.

Preparation and Microstructure Characterizations of Novel C/C-Zr(Hf)B2-Zr(Hf)C-SiC Composites

2014 ◽  
Vol 788 ◽  
pp. 593-597 ◽  
Author(s):  
Jie Wen Li ◽  
Xi Wei ◽  
Wei Gang Zhang ◽  
Min Ge
Keyword(s):  
High Temperature ◽  
Chemical Vapor ◽  
Pyrolytic Carbon ◽  
Carbon Composite ◽  
Chemical Vapor Infiltration ◽  
Polymeric Precursors ◽  
Ultra High Temperature Ceramics ◽  
Sic Composites ◽  
Fiber Preforms ◽  
Very High

A series of novel C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were prepared by chemical vapor infiltration (CVI) of pyrolytic carbon and polymeric impregnation and pyrolysis (PIP) with hybrid polymeric precursors of SiC (polycarbosilane), Zr (Hf)C and Zr (Hf)B2 in carbon fiber preforms. The formed ultra-high temperature ceramics (UHTCs) matrix of SiC-ZrC-ZrB2 and SiC-HfC-HfB2 were designed to improve the oxidation resistance of carbon/carbon composite at very high temperatures above 2000°C. The pyrolysis process of Zr (Hf)C and Zr (Hf)B2 polymeric precursors was investigated, and the results showed that the hybrid precursors could be successfully transformed into Zr (Hf)C and Zr (Hf)B2 ceramic particles with the sizes of nanometer with temperatures above 1500°C. Furthermore, the multiscale structure of C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were also characterized , showing that the carbon fibers were covered by pyrolytic carbon, and the continuous ceramic matrix was well dispersed, formed by Zr (Hf)C and Zr (Hf)B2 nanoparticles distributing homogeneously in the continuous SiC matrix. This homogeneous dispersion of composite ceramics of Zr (Hf)C and Zr (Hf)B2 with SiC plays excellent protection of C/C composites from oxidation at high temperature via formation of stable oxides coatings.

Emissivity of Silicon Carbide Composites as a Function of Temperature and Microstructure

1995 ◽  
Vol 410 ◽  
Author(s):  
Ming Sun ◽  
Isabel K. Lloyd
Keyword(s):  
Oxide Layer ◽  
Intelligent Control ◽  
Chemical Vapor ◽  
Sample Surface ◽  
Spectral Emissivity ◽  
Chemical Vapor Infiltration ◽  
Layer Formation ◽  
Microwave Assisted ◽  
Sic Fiber ◽  
Sic Composites

ABSTRACTSpectral emissivity normal to the sample surface was investigated as a potential intelligent control parameter for the manufacture of SiC fiber reinforced SiC composites by chemical vapor infiltration (CVI) and microwave assisted CVI. Results indicated that at temperatures between 600 and 1000°C and wavelengths between 1500 and 2100 nm emissivity was sensitive to the sample porosity. It also appeared to be sensitive to the thickness of the oxide layer on the composites. The emissivity was not very sensitive to temperature in this region. It was concluded that emissivity is promising as a probe of density during manufacturing. It may also be useful as a probe of oxide layer formation.

Studying SiC/SiC Composites by X-Ray Tomography

2014 ◽  
Vol 602-603 ◽  
pp. 416-421 ◽  
Author(s):  
Xin Gui Zhou ◽  
Shuang Zhao ◽  
Paul Mummery ◽  
James Marrow
Keyword(s):  
Three Dimensional ◽  
Matrix Composites ◽  
Displacement Fields ◽  
Damage Development ◽  
X Ray ◽  
Sic Fiber ◽  
Mesh Free ◽  
Sic Composites ◽  
The University ◽  
Polymer Impregnation

Continuous SiC fiber reinforced SiC matrix composites (SiC/SiC) have been studied and developed for high temperature applications and nuclear applications. In this study, SiC/SiC composites were fabricated via polymer impregnation and pyrolysis (PIP) process and studied by X-ray tomography. The SiC/SiC composites were first scanned using a Metris X-tek 320 kV source at the Henry Moseley X-ray Imaging Facility at the University of Manchester, the closed porosities were investigated after three dimensional (3D) imaging of the samples. Furthermore, high-resolution synchrotron X-ray tomography was applied to the SiC/SiC composite at Diamond Light Source. Digital volume correlation was employed for Hertzian indentation testing of the SiC/SiC composite, quantifying damage by measurement of the displacement fields within the material. A Cellular Automata integrated with Finite Elements (CAFE) method was developed to account for the effect of microstructure on the fracture behavior of the SiC/SiC composite. Graded microstructures, textures and multiple phases were simulated and a mesh-free framework was developed to compute the damage development through the microstructure. The results indicated that we could study the development of discontinuous cracking and damage coalescence, and its sensitivity to microstructure with this method.

Comparison of Two Methods for Testing the In-Plane Shear Property of 3D Stitched Plain Woven C/SiC Composites

2015 ◽  
Vol 1110 ◽  
pp. 3-6
Author(s):  
Hua Jie Xu ◽  
Li Tong Zhang ◽  
Lai Fei Cheng
Keyword(s):  
Shear Strength ◽  
Reliable Method ◽  
Ceramic Matrix Composite ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Ceramic Matrix ◽  
Chemical Vapor Infiltration ◽  
Plane Shear ◽  
Shear Property ◽  
Sic Composites

Three types of three-dimensional stitched carbon fiber reinforced silicon carbide composites (3DS C/SiCs) with 4, 9 and 16 Z-yarn/cm2 were fabricated by chemical vapor infiltration, respectively. Both iosipescu specimens without enough representative volume elements (RVEs) and ±45° tension specimens containing enough RVEs were tested to attain the in-plane shear properties of 3DS C/SiCs. The results showed that these two methods produced similar results. This demonstrated that the dimensions of iosipescu specimens were not necessary to cover enough RVEs for 3DS ceramic matrix composite in-plane shear testing. With respect to the shear modulus, both two methods would be regarded as the effective methods. However, in terms of the in-plane shear strength, iosipescu method would be a more reliable method.

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.

Microstructures, Strength and Toughness of 2D Cf/(C-SiC) Composites by Chemical Vapor Infiltration

2009 ◽  
Vol 24 (5) ◽  
pp. 939-942 ◽  
Author(s):  
Zhi-Xin MENG ◽  
Lai-Fei CHENG ◽  
Li-Tong ZHANG ◽  
Yong-Dong XU ◽  
Xiu-Feng HAN
Keyword(s):  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Sic Composites ◽  
Strength And Toughness ◽  
Vapor Infiltration
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