Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics

Abstract Densification and mechanical properties (hardness, fracture toughness and flexural strength) of the SiC-TiB2 composite were studied. Pressureless sintering experiments were carried out on samples containing 0 to 50 vol % of TiB2 created by an in-situ reaction between TiO2 and C: 2TiO2 + B4...

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Main Author: Bucevac, DUSAN
Other Authors: Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))
Format: Others
Language:en
en
Published: 2009
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Online Access:http://hdl.handle.net/1974/5266
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spelling ndltd-LACETR-oai-collectionscanada.gc.ca-OKQ.1974-52662013-12-20T03:39:30ZMicrostructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite CeramicsBucevac, DUSANSiC TiB2 composite pressureless in-situAbstract Densification and mechanical properties (hardness, fracture toughness and flexural strength) of the SiC-TiB2 composite were studied. Pressureless sintering experiments were carried out on samples containing 0 to 50 vol % of TiB2 created by an in-situ reaction between TiO2 and C: 2TiO2 + B4C + 3C 2TiB2 + 4CO Al2O3 and Y2O3 were used as sintering additives to create a liquid phase and promote densification at sintering temperatures ranging from 1820 to 1940oC. The sintered samples were subsequently heat-treated at temperatures ranging from 1850 to 1970oC It was found that the presence of TiB2 formed by the above reaction serves as an effective obstacle to crack propagation thus increasing both the strength and fracture toughness of SiC while maintaining high a hardness of the sintered samples. Densities higher than 98 % TD were achieved depending on both the sintering temperature and heat treatment conditions. From a density viewpoint, the optimum volume fraction of TiB2 was from 12 to 24 vol %. Typical microstructures for samples with this volume fraction of TiB2 consist of TiB2 particles (< 5m) uniformly dispersed in a matrix of elongated SiC plates. The presence of TiB2 particles in the matrix of SiC inhibited exaggerated grain growth of the SiC grains and activated additional toughening mechanisms. The subsequent heat treatment of the sintered samples improved mechanical properties. The optimum sintering and heat treatment temperatures were 1940 and 1970oC, respectively. The maximum flexural strength of 593 MPa was obtained in sample with 12 vol % TiB2. A maximum fracture toughness of 6.6 MPa•m1/2 was measured in samples containing 24 vol % TiB2. While both fracture toughness and strength increased with the presence of TiB2 particles, hardness on the other hand decreased from ~18 GPa in samples without TiB2 to 16.4 and 15.9 GPa in samples with 12 and 24 vol % TiB2, respectively. A theoretical analysis was conducted to model the effect of microstructure on the fracture toughness of SiC-TiB2 composites and was experimentally verified.Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-09-30 23:04:32.565Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))2009-09-30 23:04:32.5652009-10-07T15:58:41Z2009-10-07T15:58:41Z2009-10-07T15:58:41ZThesis53468599 bytesapplication/pdfhttp://hdl.handle.net/1974/5266enenCanadian thesesThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
collection NDLTD
language en
en
format Others
sources NDLTD
topic SiC TiB2 composite pressureless in-situ
spellingShingle SiC TiB2 composite pressureless in-situ
Bucevac, DUSAN
Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
description Abstract Densification and mechanical properties (hardness, fracture toughness and flexural strength) of the SiC-TiB2 composite were studied. Pressureless sintering experiments were carried out on samples containing 0 to 50 vol % of TiB2 created by an in-situ reaction between TiO2 and C: 2TiO2 + B4C + 3C 2TiB2 + 4CO Al2O3 and Y2O3 were used as sintering additives to create a liquid phase and promote densification at sintering temperatures ranging from 1820 to 1940oC. The sintered samples were subsequently heat-treated at temperatures ranging from 1850 to 1970oC It was found that the presence of TiB2 formed by the above reaction serves as an effective obstacle to crack propagation thus increasing both the strength and fracture toughness of SiC while maintaining high a hardness of the sintered samples. Densities higher than 98 % TD were achieved depending on both the sintering temperature and heat treatment conditions. From a density viewpoint, the optimum volume fraction of TiB2 was from 12 to 24 vol %. Typical microstructures for samples with this volume fraction of TiB2 consist of TiB2 particles (< 5m) uniformly dispersed in a matrix of elongated SiC plates. The presence of TiB2 particles in the matrix of SiC inhibited exaggerated grain growth of the SiC grains and activated additional toughening mechanisms. The subsequent heat treatment of the sintered samples improved mechanical properties. The optimum sintering and heat treatment temperatures were 1940 and 1970oC, respectively. The maximum flexural strength of 593 MPa was obtained in sample with 12 vol % TiB2. A maximum fracture toughness of 6.6 MPa•m1/2 was measured in samples containing 24 vol % TiB2. While both fracture toughness and strength increased with the presence of TiB2 particles, hardness on the other hand decreased from ~18 GPa in samples without TiB2 to 16.4 and 15.9 GPa in samples with 12 and 24 vol % TiB2, respectively. A theoretical analysis was conducted to model the effect of microstructure on the fracture toughness of SiC-TiB2 composites and was experimentally verified. === Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2009-09-30 23:04:32.565
author2 Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))
author_facet Queen's University (Kingston, Ont.). Theses (Queen's University (Kingston, Ont.))
Bucevac, DUSAN
author Bucevac, DUSAN
author_sort Bucevac, DUSAN
title Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
title_short Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
title_full Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
title_fullStr Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
title_full_unstemmed Microstructure-Mechanical Properties Relations in Pressureless Sintered SiC-TiB2 Composite Ceramics
title_sort microstructure-mechanical properties relations in pressureless sintered sic-tib2 composite ceramics
publishDate 2009
url http://hdl.handle.net/1974/5266
work_keys_str_mv AT bucevacdusan microstructuremechanicalpropertiesrelationsinpressurelesssinteredsictib2compositeceramics
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