Silicon Carbide Platelet/Silicon Carbide Composites

Mitchell, T. E.; Jonghe, Lutgard C. De; MoberlyChan, Warren J.; Ritchie, Robert O.

doi:10.1111/j.1151-2916.1995.tb08366.x

Cited by 33 publications

(9 citation statements)

References 21 publications

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“…Clear examples are SiC nanoceramics for superplasticity 1,2 and in situ-toughened SiC ceramics for improved toughness. [3][4][5][6][7][8] Several attempts to control the microstructure of SiC have been reported, including control of the initial ␣-SiC content in the starting powder, 9 seeding for favored preferential grain growth, 10,11 the incorporation of ␣-SiC platelets, 12 the addition of liquid-forming additives such as AlN-Y 2 O 3 13 and Al-B-C, 14 and heat treatment for controlled grain growth. 15,16 A fracture toughness of ∼8 MPaиm 1/2 has been reported in SiC ceramics with yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) 3 as a grain-boundary phase, and a higher fracture toughness (∼9 MPaиm 1/2 ) has been reported in SiC ceramics with Al-B-C. 14 However, the correlation between the chemistry of the glassy phase and the properties of the resulting ceramics is not well established.…”

Section: Introductionmentioning

confidence: 99%

Fine‐Grained Silicon Carbide Ceramics with Oxynitride Glass

Kim

Mitomo

1999

Journal of the American Ceramic Society

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By using an oxynitride glass composition from the Y-MgSi-Al-O-N system as a sintering additive, the effect of atmosphere on densification was investigated during the liquidphase sintering of SiC, and the resulting microstructure and mechanical properties of the sintered and subsequently annealed materials were investigated. SiC ceramics that were densified with 10 wt% oxynitride glass showed higher sinterability in a nitrogen atmosphere. Oxynitride glass enlarged the stability region of ␤-SiC and suppressed ␤ → ␣ phase transformation, which resulted in an equiaxed microstructure. Grain growth of fine-grained SiC in some extent (up to ∼300 nm) was beneficial in improving both room-temperature strength and toughness. The best results were obtained when the ceramics were hot-pressed at 1800°C for 1 h in a nitrogen atmosphere and subsequently annealed at 1900°C for 3 h in an argon atmosphere. The room-temperature flexural strength and fracture toughness of the material were 847 MPa and 3.5 MPaؒm 1/2 , respectively.

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Section: Introductionmentioning

confidence: 99%

Fine‐Grained Silicon Carbide Ceramics with Oxynitride Glass

Kim

Mitomo

1999

Journal of the American Ceramic Society

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“…However, one principal factor which limits their application is their low fracture toughness, which in commercial material is typically on the order of 2-3 MPa√m. In light of this, much recent research on SiC [1][2][3][4][5][6][7][8][9][10][11] has focused on ways to increase this toughness. Of these, the approach of in situ toughening with aluminum, boron and carbon additions to produce so-called ABC-SiC [3] has been particularly successful in increasing the ambienttemperature fracture toughness to above 9 MPa√m [7], which is the highest toughness ever reported for SiC.…”

Section: Introductionmentioning

confidence: 99%

Ambient to high-temperature fracture toughness and cyclic fatigue behavior in Al-containing silicon carbide ceramics

et al. 2003

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Abstract-A series of in situ toughened, Al, B and C containing, silicon carbide ceramics (ABC-SiC) has been examined with Al contents varying from 3 to 7 wt%. With increasing Al additions, the grain morphology in the as-processed microstructures varied from elongated to bimodal to equiaxed, with a change in the nature of the grain-boundary film from amorphous to partially crystalline to fully crystalline. Fracture toughness and cyclic fatigue tests on these microstructures revealed that although the 7 wt.% Al containing material (7ABC) was extremely brittle, the 3 and particularly 5 wt.% Al materials (3ABC and 5ABC, respectively) displayed excellent crack-growth resistance at both ambient (25°C) and elevated (1300°C) temperatures. Indeed, no evidence of creep damage, in the form of grain-boundary cavitation, was seen at temperatures at 1300°C or below. The enhanced toughness of the higher Al-containing materials was associated with extensive crack bridging from both interlocking grains (in 3ABC) and uncracked ligaments (in 5ABC); in contrast, the 7ABC SiC showed no such bridging, concomitant with a marked reduction in the volume fraction of elongated grains. Mechanistically, cyclic fatigue-crack growth in 3ABC and 5ABC SiC involved the progressive degradation of such bridging ligaments in the crack wake, with the difference in the degree of elastic vs. frictional bridging affecting the slope, i.e., Paris law exponent, of the crack-growth curve.

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“…21 The remaining sintering additives form bulk secondary phases. 10,22,23 The SiC grains exhibit a high degree of stacking faults, because the energy difference between the various stacking sequences is typically very small. The grains also show sporadic dislocations after hot pressing.…”

Section: (3) Microstructural Changesmentioning

confidence: 99%

Flexural Creep of an in Situ‐Toughened Silicon Carbide

Sixta

Zhang

Jonghe

2001

Journal of the American Ceramic Society

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Flexural creep behavior is reported for an in situ-toughenedSiC between 1100°and 1500°C in four-point bending. The flexural creep rate of this SiC, sintered with aluminum, boron, and carbon (ABC-SiC), exhibits linear stress dependence, low apparent activation energy, and low incidence of cavitation and dislocation production. Most grain boundaries in this ceramic contain 1-5 nm intergranular films. The creep rate is consistent with a grain-boundary transport mechanism involving diffusion along the grain-boundary film-SiC interfaces. The microstructure and grain boundaries have been examined using transmission electron microscopy to assess possible changes during creep, particularly in relation to the applied stress direction.

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Silicon Carbide Platelet/Silicon Carbide Composites

Cited by 33 publications

References 21 publications

Fine‐Grained Silicon Carbide Ceramics with Oxynitride Glass

Fine‐Grained Silicon Carbide Ceramics with Oxynitride Glass

Ambient to high-temperature fracture toughness and cyclic fatigue behavior in Al-containing silicon carbide ceramics

Flexural Creep of an in Situ‐Toughened Silicon Carbide

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