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Title: High resolution energy loss research: Si compounds and ceramics. Progress report, January 1, 1988--January 1, 1989

Abstract

Analytical and high resolution electron microscopes are used to investigate interfaces, grain boundaries and triple junctions in a number of materials. Interfaces between silicon carbide whiskers and either aluminum oxide or silicon nitride grains in two different ceramic matrix composites were found to be mostly crystalline, and did not contain a continuous amorphous phase. The amount of amorphous phase in these interfaces depended primarily on the amount of sintering aid used. Amorphous multiphase regions at triple grain junctions in several structural ceramics were shown to consists of fibrous graphite microcrystals in an oxygen containing amorphous matrix. We consider it likely that these regions act as fracture nuclei for structural ceramics and composites. Grain boundaries from a large silicon bicrystal with {Sigma}13 (32) structure were examined by atomic resolution and electron energy loss microscopy; this boundary is composed of theoretically perfect regions and regions to which oxygen had segregated during crystal growth. Detailed microstructural analysis of a liquid phase sintered body made from silicon dioxide, aluminum oxide and silicon nitride showed that silicon oxynitride is apparently nucleated at the liquid/silicon nitride interface; the structure of the silicon oxynitride/silicon nitride interface is strongly anisotropic. Instrumentation and theory are also discussed.

Authors:
Publication Date:
Research Org.:
Arizona State Univ., Tempe, AZ (United States). Center for Solid State Science
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10119657
Report Number(s):
DOE/ER/45305-2
ON: DE92007118
DOE Contract Number:
FG02-87ER45305
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1989]
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CERAMICS; ENERGY-LOSS SPECTROSCOPY; MICROSTRUCTURE; SILICON COMPOUNDS; PROGRESS REPORT; ELECTRON MICROSCOPY; INTERFACES; GRAIN BOUNDARIES; SILICON CARBIDES; SILICON NITRIDES; COMPOSITE MATERIALS; 360202; STRUCTURE AND PHASE STUDIES

Citation Formats

Carpenter, R.W. High resolution energy loss research: Si compounds and ceramics. Progress report, January 1, 1988--January 1, 1989. United States: N. p., 1989. Web. doi:10.2172/10119657.
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Carpenter, R.W. High resolution energy loss research: Si compounds and ceramics. Progress report, January 1, 1988--January 1, 1989. United States. doi:10.2172/10119657.
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Carpenter, R.W. Sun . "High resolution energy loss research: Si compounds and ceramics. Progress report, January 1, 1988--January 1, 1989". United States. doi:10.2172/10119657. https://www.osti.gov/servlets/purl/10119657.
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@article{osti_10119657,
title = {High resolution energy loss research: Si compounds and ceramics. Progress report, January 1, 1988--January 1, 1989},
author = {Carpenter, R.W.},
abstractNote = {Analytical and high resolution electron microscopes are used to investigate interfaces, grain boundaries and triple junctions in a number of materials. Interfaces between silicon carbide whiskers and either aluminum oxide or silicon nitride grains in two different ceramic matrix composites were found to be mostly crystalline, and did not contain a continuous amorphous phase. The amount of amorphous phase in these interfaces depended primarily on the amount of sintering aid used. Amorphous multiphase regions at triple grain junctions in several structural ceramics were shown to consists of fibrous graphite microcrystals in an oxygen containing amorphous matrix. We consider it likely that these regions act as fracture nuclei for structural ceramics and composites. Grain boundaries from a large silicon bicrystal with {Sigma}13 (32) structure were examined by atomic resolution and electron energy loss microscopy; this boundary is composed of theoretically perfect regions and regions to which oxygen had segregated during crystal growth. Detailed microstructural analysis of a liquid phase sintered body made from silicon dioxide, aluminum oxide and silicon nitride showed that silicon oxynitride is apparently nucleated at the liquid/silicon nitride interface; the structure of the silicon oxynitride/silicon nitride interface is strongly anisotropic. Instrumentation and theory are also discussed.},
doi = {10.2172/10119657},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 1989},
month = {Sun Dec 31 00:00:00 EST 1989}
}
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Technical Report:
View Technical Report (0.62 MB)
DOI:  10.2172/10119657
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  • ;
    This report discusses both experimental and theoretical work on silicon compounds and ceramics. High resolution energy loss research on liquid-phase reaction zones in wurtzite silicon carbide alloys, energy loss and x-ray analysis of major constituents in silicon oxynitride ceramics, instrumentation, electron energy loss core edge theory for crystals, electronic structure of amorphous solids, and proposed research are some of the topics summarized in this report. (JL)

  • ;
    Our current investigation of the structure and chemistry of whisker/matrix interfaces and matrix grain boundaries in SiC whisker reinforced Si{sub 3}N{sub 4} composites has been completed. We examined these interfaces and boundaries in four composites whose starting materials and processing were identical except for the SiC whiskers themselves, which were from four different sources: American matrix, Nikkei, Huber and Tokai. Thus, differences in interfaces among the composites are attributable to differences in the whiskers. The results showed that oxygen-rich amorphous interfacial layers were discontinuous in all whisker/matrix interfaces and continuous in all matrix grain boundaries. Further, we used position-resolved highmore » spatial resolution electron energy loss spectroscopy to show that the ``chemical interface width`` is much wider than the ``geometric or structural interface width`` at both types of interfaces in all four composites. The geometric interface widths were determined from high resolution transmission electron microscope images of edge-on interfaces.« less

  • ;
    Our current investigation of the structure and chemistry of whisker/matrix interfaces and matrix grain boundaries in SiC whisker reinforced Si{sub 3}N{sub 4} composites has been completed. We examined these interfaces and boundaries in four composites whose starting materials and processing were identical except for the SiC whiskers themselves, which were from four different sources: American matrix, Nikkei, Huber and Tokai. Thus, differences in interfaces among the composites are attributable to differences in the whiskers. The results showed that oxygen-rich amorphous interfacial layers were discontinuous in all whisker/matrix interfaces and continuous in all matrix grain boundaries. Further, we used position-resolved highmore » spatial resolution electron energy loss spectroscopy to show that the chemical interface width'' is much wider than the geometric or structural interface width'' at both types of interfaces in all four composites. The geometric interface widths were determined from high resolution transmission electron microscope images of edge-on interfaces.« less

  • Analytical and high resolution electron microscopes are used to investigate interfaces, grain boundaries and triple junctions in a number of materials. Interfaces between silicon carbide whiskers and either aluminum oxide or silicon nitride grains in two different ceramic matrix composites were found to be mostly crystalline, and did not contain a continuous amorphous phase. The amount of amorphous phase in these interfaces depended primarily on the amount of sintering aid used. Amorphous multiphase regions at triple grain junctions in several structural ceramics were shown to consists of fibrous graphite microcrystals in an oxygen containing amorphous matrix. We consider it likelymore » that these regions act as fracture nuclei for structural ceramics and composites. Grain boundaries from a large silicon bicrystal with {Sigma}13 (32) structure were examined by atomic resolution and electron energy loss microscopy; this boundary is composed of theoretically perfect regions and regions to which oxygen had segregated during crystal growth. Detailed microstructural analysis of a liquid phase sintered body made from silicon dioxide, aluminum oxide and silicon nitride showed that silicon oxynitride is apparently nucleated at the liquid/silicon nitride interface; the structure of the silicon oxynitride/silicon nitride interface is strongly anisotropic. Instrumentation and theory are also discussed.« less

  • ;
    This report discusses both experimental and theoretical work on silicon compounds and ceramics. High resolution energy loss research on liquid-phase reaction zones in wurtzite silicon carbide alloys, energy loss and x-ray analysis of major constituents in silicon oxynitride ceramics, instrumentation, electron energy loss core edge theory for crystals, electronic structure of amorphous solids, and proposed research are some of the topics summarized in this report. (JL)