scholarly journals Probability of detection of internal voids in structural ceramics using microfocus radiography

1986 ◽  
Vol 1 (3) ◽  
pp. 457-467 ◽  
Author(s):  
George Y. Baaklini ◽  
Don J. Roth
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Focal Spot ◽  
Probability Of Detection ◽  
Structural Ceramics ◽  
Structural Ceramic ◽  
X Ray ◽  
Low X ◽  
Statistical Results ◽  
Sintered Silicon

The reliability of microfocus x radiography for detecting internal voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low x-ray photon energies (<20 keV) and a 10 μm focal spot. The statistics were developed for implanted internal voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation and characterization are discussed. Statistical results are given as probability-of-detection curves at a 95% confidence level for voids ranging in size from 20–528 μm in diameter.

scholarly journals Probability of Detection of Internal Voids in Structural Ceramics Using Microfocus Radiography

1985 ◽  
Vol 60 ◽  
Author(s):  
George Y. Baaklini ◽  
Don J. Roth
Keyword(s):  
Silicon Carbide ◽  
Focal Spot ◽  
Probability Of Detection ◽  
Structural Ceramics ◽  
Structural Ceramic ◽  
X Ray ◽  
Percent Confidence Level ◽  
Low X ◽  
Statistical Results ◽  
Sintered Silicon

AbstractThe reliability of mlcrofocus x-rad1ogrphy for detecting Internal voids 1n structural ceramic test specimens was statistically evaluated. The micro-focus system was operated in the projection mode using low x-ray photon energies (≤;20 keV) and a 10 μm focal spot. The statistics were developed for Implanted Internal voids 1n green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Statistical results are given as probability-of-detection curves at a 95 percent confidence level for voids ranging in size from 20 to 528 μm in diameter.

NDE of Structural Ceramics

1986 ◽  
Author(s):  
Stanley J. Klima ◽  
Alex Vary
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Ultrasonic Velocity ◽  
Detection Probability ◽  
Ultrasonic Attenuation ◽  
Acoustic Microscopy ◽  
Modulus Of Rupture ◽  
Structural Ceramics ◽  
X Ray ◽  
Microscopy Techniques

Radiographic, ultrasonic, scanning laser acoustic microscopy (SLAM), and thermo-acoustic microscopy techniques were used to characterize silicon nitride and silicon carbide modulus-of-rupture test specimens in various stages of fabrication. Conventional and microfocus x-ray techniques were found capable of detecting minute high density inclusions in as-received powders, green compacts, and fully densified specimens. Significant density gradients in sintered bars were observed by radiography, ultrasonic velocity, and SLAM. Ultrasonic attenuation was found sensitive to microstructural variations due to grain and void morphology and distribution. SLAM was also capable of detecting voids, inclusions, and cracks in finished test bars. Consideration is given to the potential for applying thermo-acoustic microscopy techniques to green and densified ceramics. The detection probability statistics and some limitations of radiography and SLAM also are discussed.

Sintered silicon nitride/nano-silicon carbide materials based on preceramic polymers and ceramic powder

2012 ◽  
Vol 32 (9) ◽  
pp. 1893-1899 ◽  
Author(s):  
Ulrich Degenhardt ◽  
Frank Stegner ◽  
Christian Liebscher ◽  
Uwe Glatzel ◽  
Karl Berroth ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Ceramic Powder ◽  
Preceramic Polymers ◽  
Nano Silicon ◽  
Sintered Silicon

scholarly journals Determination of trace impurities in sintered silicon carbide and silicon nitride by the pressure acid decomposition/ICP-AES.

1992 ◽  
Vol 41 (12) ◽  
pp. T151-T156 ◽  
Author(s):  
Yoshinori UWAMINO ◽  
Hisashi MORIKAWA ◽  
Akira TSUGE ◽  
Kiyoshi NAKANE ◽  
Yasuo IIDA ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Acid Decomposition ◽  
Trace Impurities ◽  
Sintered Silicon

X-ray line-broadening study of a liquid-phase-sintered silicon carbide

2002 ◽  
Vol 22 (14-15) ◽  
pp. 2677-2687 ◽  
Author(s):  
A.L. Ortiz ◽  
F. Sánchez-Bajo ◽  
A. Hernández-Jiménez ◽  
F. Guiberteau ◽  
F.L. Cumbrera
Keyword(s):  
Silicon Carbide ◽  
Liquid Phase ◽  
Line Broadening ◽  
X Ray ◽  
Sintered Silicon

scholarly journals Influence of the substitution of Y2O3 for CeO2 on the mechanical and microstructural properties of silicon nitride

Cerâmica ◽  
2005 ◽  
Vol 51 (319) ◽  
pp. 285-288
Author(s):  
J. V. C. de Souza ◽  
C. A. Kelly ◽  
M. R. V. Moreira ◽  
M. V. Ribeiro ◽  
C. dos Santos ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Cost Reduction ◽  
Nitrogen Atmosphere ◽  
Microstructural Properties ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Nitride Ceramics ◽  
Mechanical And Microstructural Properties ◽  
Sintered Silicon

This work investigated the substitution of Y2O3 for CeO2 in liquid-phase sintered silicon nitride ceramics. Cost reduction as well as good physical, mechanical and microstructural properties are the main objectives of the present study. Two powder mixtures were prepared, varying the contents of alpha-Si3N4, Al2O3, AlN, Y2O3 and CeO2. The mixtures were homogenized in ethanol, dried in a rotating evaporator and kiln, respectively, and then uniaxially (100 MPa) and cold isostatically pressed (300 MPa). The samples were sintered at 1850ºC for 1 h in a graphite resistive furnace under nitrogen atmosphere. After sintering the density of the samples was higher than 97% of the theoretical value. The fracture toughness and hardness were higher than 5.28 MPa.m½ and 17.12 GPa, respectively. Phase analysis by X-ray diffraction and scanning electron microscopy revealed the presence of alpha-SiAlON and beta-Si3N4.

Effect of additives on the polytypic transformation of pressureless sintered silicon carbide

1984 ◽  
Vol 42 ◽  
pp. 414-415
Author(s):  
S. Shinozaki ◽  
W. T. Donlon ◽  
C. R. Peters ◽  
R. M. Williams ◽  
B. N. Juterbock
Keyword(s):  
Silicon Carbide ◽  
Analytical Electron Microscopy ◽  
Metallic Aluminum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Effect Of Additives ◽  
Heat Treated ◽  
Analytical Electron ◽  
Boundary Chemistry ◽  
Sintered Silicon

The influence of metallic aluminum (Al) and silicon (Si) additives on the polytype distributions in silicon carbide (SiC) has been investigated. Tajima and Kingery and Shinozaki and Kinsman have shown, respectively, that 4H polytype becomes predominant when SiC materials are heat-treated in Al- or Si-rich environments. Quantitative x-ray diffraction analysis of polytype distributions has revealed that when β-SiC powder with an Al addition is sintered near 1950°C, the 15R polytype increases considerably and the 4H polytype becomes predominant above 1950°C. The correlations between polytype distributions in SiC grains and grain boundary chemistry have been studied using analytical electron microscopy.

Joining Ceramics Using Microwave Energy

1993 ◽  
Vol 314 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Richard Silberglitf
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Processing Time ◽  
Single Mode ◽  
Microwave Energy ◽  
Internal Heating ◽  
The Past ◽  
Complex Shapes ◽  
Microwave Applicator ◽  
Sintered Silicon

AbstractIn the past several years there has been an explosive growth in the use of microwave energy for the processing of a host of materials. Microwave energy provides rapid internal heating which results in an overall reduction in the processing time. The important features of microwave processing are described, as well as several applications.Microwave energy has been used by a few groups for the joining of alumina, mullite, silicon nitride and silicon carbide. The work performed by these groups will be reviewed. Typically, a single mode microwave applicator has been used to join ceramics at temperatures ranging between 1250°C - 1800°C. Microwave joining of ceramics was achieved in a matter of minutes, in contrast to hours reported by conventional methods. The strength of the joints was equal to or greater than the as-received materials. Joining of specimens of sintered silicon carbide (Hexoloy ™ ) using interlayers, and direct joining of reaction bonded silicon carbide (RBSC) to itself and Hexoloy™ has been accomplished recently. Both single mode and multimode microwave applicators were used and larger specimens of RBSC having complex shapes were joined using hybrid heating. The paper describes microwave joining apparatus, techniques and results.

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