ChemInform Abstract: Microstructural Evolution and Mechanical Properties of Si3N4 with Yb2O3 as Sintering Additive.

Park, H.; Kim, H.‐E.; Niihara, Koichi

doi:10.1002/chin.199725011

Cited by 13 publications

(16 citation statements)

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“…As shown in Figure , an interlocking microstructure consisting of large elongated β‐Si 3 N 4 grains was formed which is a prerequisite for achieving toughening of Si 3 N 4 by crack bridging or crack deflection mechanisms. However, the formation of elongated grains is not a sufficient condition for obtaining toughening effects . Toughening by a crack bridging or crack deflection processes occur only when cracks propagate along the prismatic faces of the elongated β‐Si 3 N 4 grain, so appropriately weak grain boundary is necessary.…”

Section: Resultsmentioning

confidence: 99%

ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics

et al. 2019

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A novel ZrSi2–MgO system was used as sintering additive for fabricating high thermal conductivity silicon nitride ceramics by gas pressure sintering at 1900°C for 12 hours. By keeping the total amount of additives at 7 mol% and adjusting the amount of ZrSi2 in the range of 0‐7 mol%, the effect of ZrSi2 addition on sintering behaviors and thermal conductivity of silicon nitride were investigated. It was found that binary additives ZrSi2–MgO were effective for the densification of Si3N4 ceramics. XRD observations demonstrated that ZrSi2 reacted with native silica on the Si3N4 surface to generate ZrO2 and β‐Si3N4 grains. TEM and in situ dilatometry confirmed that the as formed ZrO2 collaborated with MgO and Si3N4 to form Si–Zr–Mg–O–N liquid phase promoting the densification of Si3N4. Abnormal grain growth was promoted by in situ generated β‐Si3N4 grains. Consequently, compared to ZrO2‐doped materials, the addition of ZrSi2 led to enlarged grains, extremely thin grain boundary film and high contiguity of Si3N4–Si3N4 grains. Ultimately, the thermal conductivity increased by 34.6% from 84.58 to 113.91 W·(m·K)−1 when ZrO2 was substituted by ZrSi2.

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Section: Resultsmentioning

confidence: 99%

ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics

et al. 2019

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“…Y 2 O 3 , the composition of the grain‐boundary phase moves out of the Si 3 N 4 –Y 2 Si 2 O 7 –Si 2 ON 2 compatibility triangle to Y 2 O 3 ‐rich silicate and oxynitride phases. There are studies on Si 3 N 4 containing a higher amount of Y 2 O 3 or other Rare Earth (Yb 2 O 3 ) describing an excellent mechanical property behavior at temperatures >1300°C 63–68 . The problem of volume expansion during the oxidation of Y‐ or Yb‐oxynitride grain‐boundary phases like YSiO 2 N or Y 2 O 3 ·Si 3 N 4 in case of Y 2 O 3 as sintering additive 58–60 was still present.…”

Section: Silicon Nitride With Sintering Additivesmentioning

confidence: 99%

“…More detailed investigations among the Rare Earth have mainly been performed with Yb 2 O 3 as sintering additive 86–93 . A typical representative for this kind of material is the commercial Si 3 N 4 SN 88 (NGK Insulators Ltd., Nagoya, Japan) with a mixture of Yb 2 O 3 and Y 2 O 3 as sintering additives.…”

Section: Silicon Nitride With Sintering Additivesmentioning

confidence: 99%

Silicon Nitride for High‐Temperature Applications

Klemm

2010

Journal of the American Ceramic Society

401

198

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In this paper, a summary of the development of high‐temperature silicon nitride (T>1200°C) is provided. The high‐temperature capacity of various advanced commercial silicon nitrides and materials under development was analyzed in comparison with a silicon nitride without sintering additives produced by hot isostatic pressing. Based on this model Si3N4 composed of only crystalline Si3N4 grains and amorphous silica in the grain boundaries the influence of various sintering additive systems will be evaluated with focus on the high‐temperature potential of the resulting materials. The specific design of the amorphous grain‐boundary films is the key factor determining the properties at elevated temperatures. Advanced Si3N4 with Lu2O3 or Sc2O3 as sintering additive are characterized by a superior elevated temperature resistance caused by effective crystallization of the grain‐boundary phase. Nearly clean amorphous films between the Si3N4 grains comparable to that of Si3N4 without sintering additives were found to be the reason of this behavior. Benefit in the long‐term stability of Si3N4 at elevated temperatures was observed in composites with SiC and MoSi2 caused by a modified oxidation mechanism. The insufficient corrosion stability in hot gas environments at elevated temperatures was found to be the main problem of Si3N4 for application in advanced gas turbines. Progress has been achieved in the development of potential material systems for environmental barrier coatings (EBC) for Si3N4; however, the long‐term stability of the whole system EBC‐base Si3N4 has to be subject of comprehensive future studies. Besides the superior high‐temperature properties, the whole application process from cost‐effective industrial production, reliability and failure probability, industrial handling up to specific conditions during the application have to be focused in order to bring advanced Si3N4 currently available to industrial application.

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“…Silicon nitride (Si 3 N 4 ) ceramics are promising thermal structural materials for various applications at elevated temperatures because they have high strength and hardness, low coefficient of thermal expansion (CTE), and good resistance to thermal shock 1–8 . As a structural/functional material, such as radome, used at elevated temperatures, a relatively higher dielectric constant (5.6–5.8 of reactive sintered Si 3 N 4 and 7.9–8.2 of hot pressed Si 3 N 4 at 8–10 GHz) limits their wide applications 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Properties of Porous Si3N4 Ceramics with a Dense Surface

Yin

Zhang

et al. 2011

International Journal of Applied Ceramic Technology

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Porous Si3N4 ceramics with a dense surface are fabricated by a joint process of pressureless sintering and chemical vapor deposition (CVD). Before CVD, the Si3N4 ceramic shows a uniform microstructure with well‐distributed pores. During CVD, the depositions of Si3N4 in the inner surface and on the external surface of the ceramics lead to a decrease of porosities and pore sizes. As a result, both the flexural strength and fracture toughness of the Si3N4 ceramic increase by >30%, the surface hardness increases more than five times, and the dielectric constant and loss increase slightly.

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ChemInform Abstract: Microstructural Evolution and Mechanical Properties of Si3N4 with Yb2O3 as Sintering Additive.

Cited by 13 publications

References 1 publication

ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics

ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics

Silicon Nitride for High‐Temperature Applications

Microstructure and Properties of Porous Si3N4 Ceramics with a Dense Surface

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ChemInform Abstract: Microstructural Evolution and Mechanical Properties of Si3N4 with Yb2O3 as Sintering Additive.

Cited by 13 publications

References 1 publication

ZrSi2–MgO as novel additives for high thermal conductivity of β‐Si3N4 ceramics

ZrSi2–MgO as novel additives for high thermal conductivity of β‐Si3N4 ceramics

Silicon Nitride for High‐Temperature Applications

Microstructure and Properties of Porous Si3N4 Ceramics with a Dense Surface

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Product

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ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics

ZrSi₂–MgO as novel additives for high thermal conductivity of β‐Si₃N₄ ceramics