Interaction in polysilazane/SiC powder systems [electronic resource].
- Published
- Washington, D.C. : United States. Dept. of Energy, 1992.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. - Physical Description
- Pages: (121 pages) : digital, PDF file
- Additional Creators
- Lawrence Berkeley National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
Access Online
- Restrictions on Access
- Free-to-read Unrestricted online access
- Summary
- Consolidation of ceramic precursor ceramic powder systems upon heating is investigated. A polysilazane (silicon nitride precursor) is chosen as ceramic precursor with a filler of a sub-micron SiC powder. A scheme to optimize the volume fraction of precursor is developed in order to maximize the density of the compacted samples in the green state. Different techniques are presented to improve the homogeneity of precursor distribution in the mixture. A microencapsulation technique is developed that leads to a uniform coating of precursor on individual SiC particles. Upon pyrolysis of systems with 20 wt% polysilazane, little shrinkage occurs. The SiC particles do not coarsen during the heat treatment. The precursor, upon pyrolysis, transforms into an amorphous ceramic phase that acts as a cement between SiC particles. This cement phase can remain amorphous up to 1500°C; and is best described as a siliconoxycarbide with or without traces of nitrogen. Elimination of nitrogen in the amorphous phase indicates that the filler material (SiC) has a strong influence on the pyrolysis behavior of the chosen polysilazane. The amorphous ceramic phase may crystallize between 1400 and 1500°C, and depending on the nature of the gas environment, the crystalline phases are SiC, Si or Si₃N₄. Mechanisms explaining the strength increase upon heat treatment are proposed. Redistribution of the precursor occurs by capillary forces or vapor phase diffusion and recondensation of volatile monomers. The confined pyrolysis of the precursor results in an increase of residual ceramic matter being decomposed inside the sample. Interfacial reaction between the native silica-rich surface layer on SiC particles and the precursor derived phase explains the high strength of the materials.
- Report Numbers
- E 1.99:lbl-32689
lbl-32689 - Subject(s)
- Other Subject(s)
- Organic Silicon Compounds
- Pyrolysis
- Silicon Carbides
- Synthesis
- Amorphous State
- Crystallization
- Density
- Electron Spectroscopy
- Encapsulation
- Flexural Strength
- Heat Treatments
- Interfaces
- Microstructure
- Oxycarbides
- Polymers
- Powders
- Precursor
- Processing
- Silicon Nitrides
- Silicon Oxides
- Temperature Range 0400-1000 K.
- Temperature Range 1000-4000 K.
- Transmission Electron Microscopy
- Whiskers
- X-Ray Diffraction
- Carbides
- Carbon Compounds
- Chalcogenides
- Chemical Reactions
- Coherent Scattering
- Crystal Structure
- Crystals
- Decomposition
- Diffraction
- Electron Microscopy
- Mechanical Properties
- Microscopy
- Monocrystals
- Nitrides
- Nitrogen Compounds
- Organic Compounds
- Oxides
- Oxygen Compounds
- Phase Transformations
- Physical Properties
- Pnictides
- Scattering
- Silicon Compounds
- Spectroscopy
- Temperature Range
- Thermochemical Processes
- Note
- Published through SciTech Connect.
07/01/1992.
"lbl-32689"
"DE92041178"
Boiteux, Y.P. - Funding Information
- AC03-76SF00098
View MARC record | catkey: 14460875