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Title: Si3N4/SiC Nanocomposites from Precursor Derived Ceramics.

Abstract

Abstract not provided.

Authors:
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1425299
Report Number(s):
SAND2017-2022PE
651295
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the NM Tech MSE Seminar held February 22, 2017 in Socorro, NM, United States.
Country of Publication:
United States
Language:
English

Citation Formats

Strong, Kevin. Si3N4/SiC Nanocomposites from Precursor Derived Ceramics.. United States: N. p., 2017. Web.
Strong, Kevin. Si3N4/SiC Nanocomposites from Precursor Derived Ceramics.. United States.
Strong, Kevin. Wed . "Si3N4/SiC Nanocomposites from Precursor Derived Ceramics.". United States. doi:. https://www.osti.gov/servlets/purl/1425299.
@article{osti_1425299,
title = {Si3N4/SiC Nanocomposites from Precursor Derived Ceramics.},
author = {Strong, Kevin},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}

Conference:
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  • Al{sub 2}O{sub 3}/5wt% SiC nanocomposites were prepared using a polysilazane precursor for the SiC. This polymer produces a mixture of {alpha} and {gamma} SiC after heat treatment at high temperatures. The preparation steps for the nanocomposite involved the mixture of either the as-received or the heat treated polymer with MgO doped alumina, followed by sintering at 1700{degrees}C under protective atmosphere. Microstructure observations using TEM showed that comparing with materials produced by the mechanical mixture of commercial powders, the precursor derived material have smaller particle size and the better distribution of the SiC particles, but present lower sintered density.
  • Polymer-based routes to ceramic oxides take advantage of precursor chemistry and structure to produce materials with a range of pore sizes. Polymer precursor routes to non-oxide ceramics offer products with superior thermal and chemical stability in many cases. Polymethylsilane (PMS), a versatile cross linked SiC precursor, [(MeHSi){sub x}(MeSi){sub y}], was synthesized using published procedures to yield fluid precursors with a low (20--40%) degree of cross linking. Unique, highly cross linked (60--70%), solid polymers were produced under reaction conditions which carefully conserve the volatile monomer. These two polymers were converted to SiC to determine the relative importance of the various contributionsmore » to porosity, and to assess the role of precursor structure on porosity development in non-oxides. Initial results indicate that precursor structure has little effect on porosity. The development of the porosity appears to be dominated by high temperature thermochemistry and/or microstructural changes.« less
  • As part of a development program for a high-temperature, dry-lubricated bearing technology and lubricant system, a high-speed high-temperature disk-on-disk tribometer was utilized and a matrix of traction data covering a range of load, speed, and temperature was obtained. The influence of dry powder lubricants, TiO2 and MoS2, on the traction coefficients between two ceramic materials, Si3N4 and SiC, was investigated. The results of this investigation are characteristic curves for the traction coefficient vs the slide/roll ratio with dry powders which are reminiscent of fluids, and the observation of dry powder lubricants' lower traction coefficients and wear. Measured tractions are foundmore » to be a strong function of powder-lubricant type, and values decrease moderately with slide-to-roll ration and load. The data show a weak sensitivity to temperature. 9 refs.« less
  • Unidirectional SiC monofilament-reinforced Si3N4 matrix composites were fabricated by the slurry-coating and filament-winding process, followed by hot pressing. Fracture strength and toughness parameters were assessed in comparison with the matrix material. Composite strengths were controlled by processing-related flaws in the SiC filaments. Moderate improvement in apparent fracture toughness (KQ) and significant improvement in work-of-fracture text (R) were also observed for the unidirectional composites relative to the matrix ceramic. 30 references.