Journal of the Korea Institute of Military Science and Technology (한국군사과학기술학회지)

The Korea Institute of Military Science and Technology (한국군사과학기술학회)
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Tailoring the Dielectric and Mechanical Properties of Si3N4 Ceramics

질화규소 세라믹의 유전 및 기계적 특성 제어에 관한 연구

  • Lee, Seung Jun (The 4th Research and Development Institute, Agency for Defense Development) ;
  • Yong, Seok-Min (The 4th Research and Development Institute, Agency for Defense Development) ;
  • Park, Jin-Woo (The 4th Research and Development Institute, Agency for Defense Development) ;
  • Choi, Jaeho (The 4th Research and Development Institute, Agency for Defense Development) ;
  • Baek, Seungsu (The 4th Research and Development Institute, Agency for Defense Development)
  • 이승준 (국방과학연구소 제4기술연구본부) ;
  • 용석민 (국방과학연구소 제4기술연구본부) ;
  • 박진우 (국방과학연구소 제4기술연구본부) ;
  • 최재호 (국방과학연구소 제4기술연구본부) ;
  • 백승수 (국방과학연구소 제4기술연구본부)
  • Received : 2018.05.18
  • Accepted : 2018.10.05
  • Published : 2018.12.05
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Abstract

The present study investigates the effect of PMMA and BN content on microstructure, mechanical and dielectric properties of silicon nitride($Si_3N_4$) ceramics in $Y_2O_3-Al_2O_3$ additive system. The total additive content was fixed at 8 wt.% and the amount of PMMA varies from 0 to 40 wt.% and BN varies from 0 to 36 wt.%, respectively. The crystalline phases of the samples were determined by X-ray diffraction analysis. All the sintered sample shows complete transformation of ${\alpha}$ to ${\beta}-Si_3N_4$ during the sintering process indicated that the phase transformation was unaffected by the PMMA or BN content. However, the microstructure shows that the residual porosity increased with increasing PMMA and BN content. In addition, the flexural strength and the dielectric constant decrease with addition of PMMA and BN due to the residual porosity. This article provides empirical study of design parameters for $Si_3N_4$-based radome materials.

Keywords

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Fig. 1. Scanning electron microscopy images of the Si3N4 ceramics. (a) Plasma-etched surface of SP0, (b) Polished surface of SP16, (c) magnified image of SP16 and (d) fracture surface of SB16

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Fig. 2. X-ray diffraction(XRD) patterns of the SP16 and SB16. Comparison with the JCPDS data of Si3N4 and BN

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Fig. 3. Effect of PMMA and BN content on the flexural strength of the Si3N4 ceramics

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Fig. 4. Effect of PMMA and BN content on the dielectric constant of the Si3N4 ceramics. The inset table lists the loss tangent of the composition

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Fig. 5. Data map of flexural strength and dielectri cconstant of SP and SB compositions

Table 1. Identification, PMMA contents, density and porosity of the SP compositions

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Table 2. Identification, BN contents, density and porosity of the SB compositions

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