Interfacial Chemistry-Structure and Fracture of Ceramic Composites

Jones, R.H.; Henager, C.H.; Schilling, Chris; Schoenlein, L. H.; Weber, William J.; Gac, Frank D.

doi:10.1002/9780470310496.ch15

Cited by 4 publications

(4 citation statements)

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“…The as-received Nicalon fibers consist of ultrafine beta SiC crystals (10 to 25 A dia.) which are homogeneously distributed in an amorphous phase containing C and Sio 2 (Andersson and Warren 1984;Chaim, Heuer, and Chen 1988;Schoenlein et al 1988;Jones et al 1988). Based on reaction thermodynamic arguments, it is plausible that the C and Si0 2 originally present in the fibers reacted with Al to produce more stable phases such as Al 4 c 3 and Al 2 o 3 (Brondyke 1953;Standage and Gani 1967;Kubaschewski and Alcock 1979).…”

Section: Alcoa High-purity Tibmentioning

confidence: 99%

Immersion tests of TiB/sub 2/-based materials for aluminum processing applications

Schilling¹,

Graff²

1988

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The behavior of four types of TiB 2-based materials exposed to molten Al at 970'C was evaluated for time durations of up to 20 wk. These materials are prime candidates for cathodes in advanced Al smelters and include I) high-purity polycrystalline titanium diboride (TiB 2), 2) TiB 2-graphite (TiB 2-G) composites, 3) composites of woven ceramic fiber mesh coated with high-purity TiB 2 , and 4) composites of 50 vol% TiB 2-so val% aluminum nitride (AlN). The evaluations primarily involved optical ceramographic comparisons of samples before and after nonpolarized immersion in molten Al. The samples of TiB 2-AlN and high-purity TiB 2 exhibited superior resistance to chemical attack by molten Al; no visible microcracking or intergranular penetration by Al was observed. A reaction layer grew to 20 ~ in thickness at the surfaces of the TiB 2-AlN after exposure to Al for 20 wk; additional analyses are needed to determine the chemistry of the reaction lQ~. The TiB 2-ceramic fiber mesh samples exhibited mixed results; the TiB 2 coatings remained largely intact after 20 wk of exposure to Al, but the SiC-based fibers were attacked within 4 wk of exposure to molten Al. Fiber deterioration may be attributed to chemical reactions between molten Al and reactive constituents of the SiC-based fibers. An evaluation of composites with ceramic fibers that are less susceptible to degradation is recommended. The TiB 2-G composites exhibited poor resistance to chemical attack by molten Al. The experiments indicate that the surfaces of the composites are attacked by a three-step process: 1) removal of graphite accompanied by penetration of the TiB 2 pores by Al, 2) formation of Al-filled microcracks along TiB 2 grain boundaries, and 3) disruption of the microstructure by extension of large Al-filled cracks. Samples that were exposed for 4 to 20 wk were completely disrupted by Al-filled crack systems and TiB 2 grain boundary penetration by Al. Such catastrophic deterioration does not agree with the satisfactory performance observed with TiB 2-G cathodes during Hall-Herault cell electrolysis. Additional research is needed to elucidate the chemical reactions causing the difference in performance during polarized

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Section: Alcoa High-purity Tibmentioning

confidence: 99%

Immersion tests of TiB/sub 2/-based materials for aluminum processing applications

Schilling¹,

Graff²

1988

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“…The most pertinent references are discussed in further detail in the following sections. Correlations between the mechanical properties and fiber-matrix phases in Nicalon-fiber-reinforced Si 3 N 4 (a) have been reported by Jones et al (1988) and . Based on analyses by transmission electron microscopy (TEM), two layers of C were observed at fiber-matrix interfaces, which allowed some pullout to occur during fracture.…”

Section: Review Of Processing and Mechanical Propertiesmentioning

confidence: 87%

“…by CVD techniques, may be more desirable." SiC-Whisker-Reinforced Si 3 N 4 Room temperature mechanical properties and microstructures of whiskermatrix interfaces were correlated by Jones et al (1988) and for reaction-bonded Si 3 N 4 reinforced with VLS whiskers. (a) The samples were prepared with various coatings applied to the whiskers, including s;o 2 , BN, and C. Alterations to processing parameters resulted in significant changes to the microstructures of whisker-matrix interfaces, based on analyses by TEM with x-ray energy dispersive spectroscopy and Auger electron spectroscopy.…”

Section: Shetty Et Al (I985) Evaluated Room Temperature Mechanical Pmentioning

confidence: 99%

“…Reports pertaining to whisker-coating technology are not so prevalent in the literature. Chemical vapor deposition has been used to produce ceramic coatings on SiC whiskers in reports by Jones et al (1988), Schoenlein et al (!988), and . However, the latter reference cites difficulties with the chemical vapor deposition process based on a personal communication with 0.…”

Section: Review Of Filament Coating Techniquesmentioning

confidence: 99%

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Effects of filament-matrix interfaces on the mechanical properties of SiC-reinforced Si sub 3 N sub 4: A Review

Schilling¹

1989

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DISCLAIMER This program was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any or their employees, makes <~ny warranty, expressed or implied, or usumes my leg;tl li;ability or responsibility for the .J.ccur;acy, completeness, or usefulness of any information, appu.dus, product, or process disclosed, or represents lhill its use would not infringe pri\'ately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government of any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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Interface modification and characterization of silicon carbide platelets coated with alumina particles

Pei

Kelly

Malghan

1993

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Interfacial Chemistry-Structure and Fracture of Ceramic Composites

Cited by 4 publications

References 0 publications

Immersion tests of TiB/sub 2/-based materials for aluminum processing applications

Immersion tests of TiB/sub 2/-based materials for aluminum processing applications

Effects of filament-matrix interfaces on the mechanical properties of SiC-reinforced Si sub 3 N sub 4: A Review

Interface modification and characterization of silicon carbide platelets coated with alumina particles

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