Microstructure and Properties of Si-Ti-C-O Fiber-Bonded Ceramics.

Kajii

Int J Applied Ceramic Tech

et al. 2010

Self Cite

The stress–temperature‐lifetime response of Si–Ti–C–O fiber‐bonded ceramic (Tyrannohex™) and sintered SiC fiber‐bonded ceramic (SA‐Tyrannohex™) materials as investigated in air from 500 to 1150°C and 500 to 1400°C, respectively. The apparent threshold stress in bending of Si–Ti–C–O fiber‐bonded ceramic with a lifetime of more than 1000 h was about 175 MPa in the 500–1150°C temperature range. In the case of sintered SiC fiber‐bonded ceramic, when the applied stress was below an apparent threshold stress in bending (e.g., ∼225 MPa) for tests conducted ≤1150°C, no failures were observed for lifetimes up to≥1000 h. While, at the temperature of ≥1300°C, the apparent threshold stress in bending decreased to 175 MPa. The decrease in strength was caused by grain growth, which was confirmed from scanning electron microscopic fractography. Both fiber‐bonded ceramics exhibited much higher durability than a commercial SiC/SiC composite at temperatures above 500°C. In addition, results suggested that the sintered SiC fiber‐bonded ceramic (SA‐Tyrannohex) exhibited better mechanical performance than a Hi‐Nicalon/MI SiC composite with BN/SiC fiber coating at temperatures above 1300°C.

Section: Methodssupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Thermomechanical Performance of Si–Ti–C–O and Sintered SiC Fiber‐Bonded Ceramics at High Temperatures

Kajii

Int J Applied Ceramic Tech

et al. 2010

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Journal of the American Ceramic Society

“…Furthermore, ceramics produced by hot-pressing preoxidized fibers have been found to have excellent high-temperature characteristics. 13 However, oxidation of longer durations, particularly at higher temperatures, causes the formation of imperfections and the resultant degradation of fiber strength. 9,14 -17 Therefore, the most suitable conditions for producing a SiO 2 film must be established to maximize the strength of oxidized silicon carbide fibers.…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of Low‐Oxygen Silicon Carbide Fiber (Hi‐Nicalon) Subjected to Selected Oxidation Treatment

Shimoo

Toyoda

Okamura

2000

Low-oxygen silicon carbide fibers (Hi-Nicalon) were oxidized at temperatures from 1073 to 1773 K under an oxygen partial pressure of 0.25 atm. The strength of the unoxidized core was practically unaffected by the oxidation temperatures. The strength of the as-oxidized fibers with an SiO 2 film decreased markedly with increasing oxidation temperature. When exposed subsequently to 1773 K in argon, the fibers with a SiO 2 film of 0.3-0.5 m thickness had the best thermal stability.

Journal of the European Ceramic Society

“…The oxide layer also contains small amounts of TiO2 due to the initial Ti content in the fibers that react with the free carbon to form TiC particles. The final, dense ceramic consists of pressed Si-Ti-C-O fibers surrounded by a mostly amorphous SiO2 layer with TiC precipitates [18,19].…”

Section: Si-ti-c-o Fiber Bonded Ceramicsmentioning

confidence: 99%

“…Ceramic laminates and fibrous monoliths [11] represent a low cost alternative with many of the advantages of CMCs such as increased toughness [12,13], thermal shock resistance [14], lower creep rates [15], good wear behavior [16] or in-plane fracture resistance [17]. Fiber bonded ceramics are obtained by hot-pressing of ceramic mats, resulting in materials that can be considered halfway between CMCs and fibrous monoliths [18][19][20][21][22]. A significant advantage of this approach is that their production requires fewer processing steps than CMCs and they can be shaped into complex forms by means of molds and spacers, significantly reducing manufacturing costs.…”

Section: Introductionmentioning

confidence: 99%

High temperature compressive strength and creep behavior of Si Ti C O fiber-bonded ceramics

Vera

Martı́nez-Fernández

Singh

et al. 2017

Fiber bonded silicon carbide ceramic materials provide cost-advantage over traditional ceramic matrix composites and require fewer processing steps. Despite their interest in extreme environment thermostructural applications no data on long term mechanical reliability other than static fatigue is available for them. We studied the high temperature compressive strength and creep behavior of a fiber bonded SiC material obtained by hotpressing of Si-TiC -O fibers. The deformation mechanism and onset of plasticity was evaluated and compared with other commercial SiC materials. Up to 1400 °C, plasticity is very limited and any macroscopic deformation proceeds by crack formation and damage propagation. A transient viscous creep stage is observed due to flow in the silica matrix and once steady state is established, a stress exponent ~4 and an activation energy Q ~ 700 kJ mol-1 are found. These results are consistent with previous data on creep of polymer derived SiC fibers and polycrystals.