Effect of Y2O3 addition on the properties of reaction-bonded porous SiC ceramics

et al. 2011

J. Ceram. Soc. Japan

Porous mullite-bonded silicon carbide (SiC) ceramics were prepared from SiC and aluminum hydroxide [Al(OH) 3 ] powders. The Al(OH) 3 content was varied from 14.5 to 47.3 wt %, and porous SiC ceramics were fabricated via reaction sintering at 1450 1550°C for 2 h. The microstructure showed large SiC grains embedded in a matrix of small and loosely packed mullite/alumina particles. It was demonstrated that the porosity decreased and flexural strength increased with increase in Al(OH) 3 content. The porosity varied from 46 to 54%, and flexural strength varied from 3 to 14 MPa with the variation in Al(OH) 3 content and sintering temperature. Typically, porous mullite-bonded SiC ceramics of 14 MPa strength and 47% porosity were obtained when SiC and 47.3 wt % Al(OH) 3 powders were sintered at 1500°C.

Section: Resultsmentioning

confidence: 99%

Effect of aluminum hydroxide content on porosity and strength of porous mullite-bonded silicon carbide ceramics

Kumar

Eom

et al. 2011

J. Ceram. Soc. Japan

“…20) A flexural strength of 28 MPa at 44% porosity was reported for reaction-bonded porous SiC ceramics. 29) Some further lower strengths were also reported in oxidation-bonded 30) and reaction-bonded porous SiC ceramics. 31), 32) In contrast, typical strengths of the AYC5 and AYC10 specimens with a toughened microstructure were 56 MPa at 47% porosity and 61 MPa at 44% porosity, respectively.…”

Section: )mentioning

confidence: 99%

Processing of porous silicon carbide with toughened strut microstructure

Eom

Narisawa

2010

J. Ceram. Soc. Japan

Porous SiC ceramics were fabricated by the carbothermal reduction of polysiloxane-derived SiOC containing hollow microspheres followed by sintering. The effect of the Al 2 O 3 Y 2 O 3 CaO (AYC) content on the microstructure and flexural strength of the porous SiC ceramics were investigated. The growth of large platelet ¡-SiC grains increased with increasing additive content due to enhanced grain growth and the ¢ ¼ ¡ phase transformation of SiC. In situ toughened microstructures consisting of large platelet grains and fine equiaxed grains were obtained when 10 or 20 wt% AYC was added. The porosity generally decreased with increasing the additive content, whereas the flexural strength increased. The typical flexural strength of the porous SiC ceramics sintered with 10 wt% AYC was 61 MPa at a porosity of 44%.

“…When hollow microspheres were used as templates, carbothermal reduction and subsequent sintering of carbon-filled polysiloxane rendered porous SiC ceramics with a flexural strength of 60 MPa and a compressive strength of 240 MPa at ∼40% porosity [100]. For comparison, flexural strengths of ∼10 MPa at ∼50% porosity [140] and ∼28 MPa at ∼44% porosity [141] were reported in reaction-bonded porous SiC ceramics and 17 MPa at ∼61% porosity in sintered porous SiC ceramics [142]. A compressive strength of ∼160 MPa was also reported at 40% porosity in porous SiC ceramics prepared using polymer microbeads as the sacrificial templates [143].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Processing of polysiloxane-derived porous ceramics: a review

Kumar

Science and Technology of Advanced Materials

2010

112

Because of the unique combination of their attractive properties, porous ceramics are considered as candidate materials for several engineering applications. The production of porous ceramics from polysiloxane precursors offers advantages in terms of simple processing methodology, low processing cost, and easy control over porosity and other properties of the resultant ceramics. Therefore, considerable research has been conducted to produce various Si(O)C-based ceramics from polysiloxane precursors by employing different processing strategies. The complete potential of these materials can only be achieved when properties are tailored for a specific application, whereas the control over these properties is highly dependent on the processing route. This review deals with processing strategies of polysiloxane-derived porous ceramics. The essential features of processing strategies-replica, sacrificial template, direct foaming and reaction techniques-are explained and the available literature reports are thoroughly reviewed with particular regard to the critical issues that affect pore characteristics. A short note on the cross-linking methods of polysiloxanes is also provided. The potential of each processing strategy on porosity and strength of the resultant SiC or SiOC ceramics is outlined.