Microstructure and Mechanical Properties of Si3N4/hBN Composites Prepared by Hot-Pressing Using Nitrided Si3N4 Powders

In order to produce Si3N4/hBN composite with low cost, it seems necessary to use nitrided Si3N4 powders since the cost of Si powder is much cheaper than that of Si3N4 powder. The purpose of the present work is to investigate the nitride conditions, and in particular, we focused on the relationship between microstructures and mechanical properties of hot-pressed Si3N4/hBN ceramic composite using nitrided Si3N4 powders. The mixed powders of Si3N4 and hBN were prepared by nitriding Si powders at 1380oC for 24 h, and subsequently sintered by hot-pressing at 1800oC for 2 h in N2 atmosphere. The microstructure and mechanical properties of the Si3N4/hBN composites were investigated. Flexural strength, Young’s modulus, and hardness decreased by the addition of 20 vol% hBN. The addition of BN resulted in a decrease in the modulus as well as an increase in the size of fracture source, both contribute to the observed decrease in mechanical properties. The Si3N4/BN based ceramic composites revealed enhanced crack deflection. The Vickers indentation crack paths in specimens are sinusoidal due to pull-out of grains during crack propagation.

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Microstructure and Mechanical Properties of Hot Pressed ZrC-SiC-ZrB2 Composites

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.434-435.173 ◽

2010 ◽

Vol 434-435 ◽

pp. 173-177 ◽

Cited By ~ 3

Author(s):

Bao Xia Ma ◽

Wen Bo Han ◽

Xing Hong Zhang

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Grain Size ◽

Flexural Strength ◽

Hot Pressing ◽

Ceramic Composites ◽

Strong Function ◽

Slight Tendency ◽

Microstructure And Mechanical Properties

Ternary ZrC-SiC-ZrB2 ceramic composites were prepared by hot pressing at 1900 °C for 60 min under a pressure of 30 MPa in argon. The influence of ZrB2 content on the microstructure and mechanical properties of ZrC-SiC-ZrB2 composites was investigated. Examination of SEM showed that the microstructure of the composites consisted of the equiaxed ZrB2, ZrC and SiC grains, and there was a slight tendency of reduction for grain size in ZrC with increasing ZrB2 content. The hardness increased considerably from 23.3 GPa for the ZS material to 26.4 GPa for the ZS20B material. Flexural strength was a strong function of ZrB2 content, increasing from 407 MPa without ZrB2 addition to 627 MPa when the ZrB2 content was 20vol.%. However, the addition of ZrB2 has little influence on the fracture toughness, ranging between 5.5 and 5.7 MPam1/2.

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Microstructure and mechanical properties of TiB2–SiC ceramic composites by Reactive Hot Pressing

International Journal of Refractory Metals and Hard Materials ◽

10.1016/j.ijrmhm.2013.10.007 ◽

2014 ◽

Vol 42 ◽

pp. 36-41 ◽

Cited By ~ 46

Author(s):

Guolong Zhao ◽

Chuanzhen Huang ◽

Hanlian Liu ◽

Bin Zou ◽

Hongtao Zhu ◽

...

Keyword(s):

Mechanical Properties ◽

Hot Pressing ◽

Ceramic Composites ◽

Microstructure And Mechanical Properties ◽

Sic Ceramic ◽

Reactive Hot Pressing

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Microstructure and Mechanical Properties of Silicon Nitride/h-BN Based Machinable Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.287.340 ◽

2005 ◽

Vol 287 ◽

pp. 340-345 ◽

Cited By ~ 5

Author(s):

Won Seung Cho ◽

Jae Hyung Lee ◽

Myeong Woo Cho ◽

Eun Sang Lee ◽

Dong Sam Park ◽

...

Keyword(s):

Mechanical Properties ◽

Ceramic Composites ◽

Drilling Process ◽

Sintered Compact ◽

Pull Out ◽

Indentation Crack ◽

Micro Drilling ◽

Crack Paths ◽

Thrust Forces ◽

Si3n4 Ceramics

The effects of h-BN content on the microstructure, mechanical properties, and machinability of Si3N4 ceramics were investigated. The relative density of the sintered compact decreased with increasing BN content. The flexural strength also decreased with h-BN content, mainly due to lower Young’s modulus of h-BN compared to Si3N4. With increasing h-BN content, Si3N4/h-BN based ceramic composites revealed enhanced crack resistance (R-curve) behavior. The Vickers indentation crack paths in specimens are sinusoidal due to bridging and pull out of grains during crack propagation. The grain size of ß-Si3N4 slightly decreased with h-BN content. During milling and micro-drilling process, monolithic Si3N4 ceramic could not be machined, due to brittle fracture. However, thrust forces measured for Si3N4/h-BN composites decreased with increasing h-BN content, showing the excellent macro and micro machinabilty.

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Microstructure and mechanical properties of novel ternary electroconductive ceramics

Journal of Materials Research ◽

10.1557/jmr.2004.0428 ◽

2004 ◽

Vol 19 (11) ◽

pp. 3343-3352 ◽

Cited By ~ 7

Author(s):

Diletta Sciti ◽

Stefano Guicciardi

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Oxidation Resistance ◽

Hot Pressing ◽

Room Temperature ◽

Matrix Material ◽

Ceramic Composites ◽

Microstructure And Mechanical Properties ◽

Electrical Conductors ◽

Poor Oxidation Resistance

Electroconductive ceramic composites, constituted of an insulating matrix (a composite AlN-SiC) containing 30 vol% of an electroconductive phase (MoSi2, ZrB2, or ZrC), were densified through hot-pressing. Microstructure and mechanical properties were compared to those of the AlN-SiC matrix material. All the ternary composites are good electrical conductors, with resistivities in the range 0.3 × 10-3to 4 × 10-3Ω·cm. Room temperature properties are improved by the addition of the electroconductive particles. Strength and toughness measurements at high temperature show that MoSi2-containing composite is stable up to 1300 °C (strength 611 MPa, toughness 3.7 MPa·m1/2), whereas ZrB2-containing composite is stable up to 1000 °C. ZrC-containing composite is not suitable for high-temperature applications due to poor oxidation resistance.

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Effect of Oxidation on the Mechanical Properties of Nextel™ 312/BN/Blackglas™ Composites

MRS Proceedings ◽

10.1557/proc-365-429 ◽

1994 ◽

Vol 365 ◽

Cited By ~ 1

Author(s):

K. Ranji Vaidyanathan ◽

W. Roger Cannon ◽

Stephen C. Danforth ◽

Albert G. Tobin ◽

John W. Holmes

Keyword(s):

Mechanical Properties ◽

Surface Layer ◽

Gas Turbine ◽

Low Cost ◽

Ceramic Composites ◽

Continuous Fiber ◽

Turbine Engine ◽

Preceramic Polymers ◽

Pull Out ◽

Near Net Shape

ABSTRACTPreceramic polymers are attractive precursor materials for the production of low cost continuous fiber reinforced ceramic composites (CFCC) into near net shape components. Currently, CFCC components based upon a Blackglas™ matrix reinforced with Nextel™ 312 fibers with a BN rich surface layer are being investigated for gas turbine engine applications. The effects of oxidation on tensile and bend properties were investigated after exposure to flowing air at 600°C for 20–1000h. A significant reduction in the tensile properties accompanied by increases in fiber pull-out was observed after oxidation for 96 hours. After 500 hours oxidation, strength decreased by 50% relative to as-prepared composites. These results indicate that oxidation beyond 200 hours may be embrittling the composite.

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