Homogeneous Distribution of Sintering Additives in Liquid‐Phase Sintered Silicon Carbide

Lidén, Eva; Carlström, Elis; Eklund, Lars; Nyberg, B.; Carlsson, Roger

doi:10.1111/j.1151-2916.1995.tb08886.x

Cited by 59 publications

(25 citation statements)

References 13 publications

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“…The glue between these factors is in the microstructure. A homogeneous green structure greatly improves the LPS response [18]. The amount and placement of the liquid phase have significant impact on the sintering trajectory.…”

Section: Typical Microstructuresmentioning

confidence: 99%

Review: liquid phase sintering

2009

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Liquid phase sintering (LPS) is a process for forming high performance, multiple-phase components from powders. It involves sintering under conditions where solid grains coexist with a wetting liquid. Many variants of LPS are applied to a wide range of engineering materials. Example applications for this technology are found in automobile engine connecting rods and high-speed metal cutting inserts. Scientific advances in understanding LPS began in the 1950s. The resulting quantitative process models are now embedded in computer simulations to enable predictions of the sintered component dimensions, microstructure, and properties. However, there are remaining areas in need of research attention. This LPS review, based on over 2,500 publications, outlines what happens when mixed powders are heated to the LPS temperature, with a focus on the densification and microstructure evolution events.

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Section: Typical Microstructuresmentioning

confidence: 99%

Review: liquid phase sintering

2009

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“…Only a few papers showed the successful densification of SiC ceramics with a smaller amount of sintering additives via liquid-phase sintering. Liden et al 16) sintered SiC ceramics with 3 wt % additives (2 wt % Al 2 O 3 and 1 wt % Y 2 O 3 ) by collidal processing. Hirata et al 17) also sintered SiC ceramics with 2.86 wt % additives (1.44 wt % Al 2 O 3 and 1.42 wt % Y 2 O 3 ) by collidal processing.…”

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confidence: 99%

Effect of in situ-synthesized nano-size SiC addition on density and electrical resistivity of liquid-phase sintered silicon carbide ceramics

Lim

Kim

et al. 2011

J. Ceram. Soc. Japan

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Submicron-size SiC ceramics were sintered to densities >97% of the theoretical density by adding 5 wt % in situ-synthesized nano-size SiC and 2 wt % AlNRE 2 O 3 (RE = Y, Er). The SiC ceramics showed very low electrical resistivity in an order of 10 ¹4 ³·m. This low electrical resistivity was attributed to the smaller amount (2 wt %) of sintering additives addition and their microstructural characteristics, i.e., growth of nitrogn-doped SiC grains and the confinment of non-conducting Y-and Er-containing phases in the junction areas.©2011 The Ceramic Society of Japan. All rights reserved.Key-words : SiC, Sintering, Electrical resistivity [Received June 15, 2011; Accepted September 20, 2011] Silicon carbide (SiC) ceramics with a small amount of additives or without additives have attracted considerable attention for use in semiconductor processing, nuclear fusion reactors, and high temperature thermomechanical applications because of their excellent chemical and thermal stability and good mechanical properties.1)8) In the early 1980 s, Omori and Takei 9) reported an innovative approach to fully densify SiC at temperatures as low as 1850°C via liquid-phase sintering by adding rare earth oxides to the starting powder. Since this innovative work, interest in liquidphase sintered (LPS)-SiC has grown continuously, becausae LPSSiC ceramics show better mechanical properties than solid-state sintered SiC ceramics. sintered SiC ceramics with 3 wt % RE 2 O 3 AlN additives (RE = Sc, Lu, Y). SiC ceramics sintered with a smaller amount of additives would be more beneficial for applications in semiconductor processing and nuclear fusion reactors because of their better chemical and thermal stability.In this study, the sinterability of SiC ceramics with 2 wt % additives (RE 2 O 3 AlN, RE = Y, Er) was investigated with or without 5 wt % in-situ-synthesized nano-size SiC addition. The electrical resistivity of the resulting SiC ceramics was also investigated.For SiC with 2 wt % additives, submicron ¢-SiC (Ultrafine, Betarundum, Ibiden Co. Ltd.), polysiloxane (1036 kg/m 3 , GE Toshiba Silicones Co., Ltd., Tokyo, Japan), phenol resin (1090 kg/m 3 , Kangnam Chemical Co. Ltd., Incheon, Korea), Y 2 O 3 (99.9%, Kojundo Chemical Lab Co. Ltd., Sakado, Japan), Er 2 O 3 (99.9%, Kojundo Chemical Lab Co. Ltd., Sakado, Japan) and AlN (grade B, H. C. Starck, Berlin, Germany) were mixed at the weight ratio shown in Table 1 by ball milling using SiC balls and a polypropylene jar for 24 h in ethanol. The AlN:RE 2 O 3 molar ratio was 3:2. The mixtures were dried, sieved (60 mesh), pressed uniaxially and heat-treated at 200°C for 2 h in air to cross-link the polysiloxane in the mixture. The compact was heat-treated at 1450°C for 1 h and hot-pressed at 2050°C for 6 h under 40 MPa in an atmospheric pressure of nitrogen.The relative densities of the hot-pressed specimens were determined using the Archimedes method. The theoretical densities of each specimen were calculated according to the rule

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“…2),6),13)17) Methods for the successful densification of SiC ceramics with a smaller amount of sintering additives via liquid-phase sintering include (1) the use of colloidal processing for the homogeneous distribution of sintering additives 18), 19) and (2) the addition of in situsynthesized nano-sized SiC into submicron-sized SiC powders. 20) In this study, the sinterability of four different commercially available SiC powders was investigated with the addition of 1 wt % AlNDy 2 O 3 additives by hot pressing.…”

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Influence of powder characteristics on the electrical resistivity of SiC ceramics

Lim

Kim

2012

J. Ceram. Soc. Japan

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Four types of commercially available SiC powders were hot-pressed with 1 wt % Dy 2 O 3 AlN additives in a 3:2 molar ratio. Three submicron-sized SiC powders could be densified so as to have a relative density higher than 98%, whereas a micron-sized SiC powder showed limited densification up to 93.5%. SiC ceramics fabricated from ¢-SiC powders exhibited electrical resistivities (³10 ¹1 ³·cm) that were lower than those from ¡-SiC powders (³10 1 ³·cm). The lower electrical resistivity of the SiC ceramics fabricated from ¢-SiC powders could be attributed to a higher carrier density and enhanced charge mobility when compared to the SiC ceramics from ¡-SiC powders.©2012 The Ceramic Society of Japan. All rights reserved.Key-words : SiC, Sintering, Electrical resistivity [Received January 5, 2012; Accepted February 28, 2012] Silicon carbide (SiC) is considered to be a suitable material for various structural applications such as mechanical seals, bearings, cylinder liners, armor plates, and mirror materials for astronomical telescopes due to its superior properties of high hardness, high temperature strength, and excellent resistance to wear and corrosion.1)6) In addition, SiC ceramics with or without a small amount of additives have attracted considerable attention for use in semiconductor processing, nuclear fusion reactors, and high temperature thermomechanical applications because of their excellent chemical and thermal stability and good mechanical properties.7)11) In the mid 1970s, Lange 12) first reported on the successful densification of SiC by liquid-phase sintering with the addition of Al 2 O 3 as a sintering additive. Since this innovative work, interest in liquid-phase sintered (LPS)-SiC has grown continuously because such materials exhibit better mechanical properties than solid-state sintered SiC ceramics.2),6),13)17) Methods for the successful densification of SiC ceramics with a smaller amount of sintering additives via liquid-phase sintering include (1) the use of colloidal processing for the homogeneous distribution of sintering additives 18),19) and (2) the addition of in situsynthesized nano-sized SiC into submicron-sized SiC powders. 20) In this study, the sinterability of four different commercially available SiC powders was investigated with the addition of 1 wt % AlNDy 2 O 3 additives by hot pressing. The effect of the SiC powder characteristics on the electrical resistivity of the hot-pressed SiC ceramics was also investigated. The AlNDy 2 O 3 additive system was selected because of the success of previous research on the densification of SiC with AlN-rare earth oxide systems 4),11) and the good chemical stability of Dy 2 O 3 at high temperatures in the presence of SiC. 21)Four types of commercially available SiC powders were used as starting materials; their characteristics are shown in Table 1. The crystalline phase of powders A1 and A2 is ¡-SiC, while that of B1 and B2 is ¢-SiC. 22) The mixtures were dried, sieved (60 mesh), pressed uniaxially, and heat-treated at 200°C for 2 h in air so ...

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Homogeneous Distribution of Sintering Additives in Liquid‐Phase Sintered Silicon Carbide

Cited by 59 publications

References 13 publications

Review: liquid phase sintering

Review: liquid phase sintering

Effect of in situ-synthesized nano-size SiC addition on density and electrical resistivity of liquid-phase sintered silicon carbide ceramics

Influence of powder characteristics on the electrical resistivity of SiC ceramics

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