• Title/Summary/Keyword: Conventional sintering

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Structure and Properties for 28 GHz Microwave Sintered PZT Nanocomposites

  • Tajima, Ken-ichi;Hwang, Hae-Jin;Sando, Mutsuo;Niihara, Koichi
    • The Korean Journal of Ceramics
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    • v.4 no.4
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    • pp.352-355
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    • 1998
  • Dense $ Pb(Zr, Ti)O_3(PZT)/Al_2O_3$ nanocomposites were prepared by the 28 GHz microwave heating method and conventional electric furnace sintering. Electrical and mechanical properties of the composites were investigated. The fracture strength of the PZT composites with 0.1vol% $Al_2O_3$ was significantly improved in both sintering methods. Smaller grain size and effective reinforcement of the PZT matrix by the second phase were considered to be responsible for the excellent fracture strength. Planar electromechanical coupling factor Kp of the composites sintered by 28GHz microwave heating was higher than that of the materical prepared by the conventional route. It seemed that the control of the reaction between PZT and $Al_2O_3$ by the microwave rapid sintering resulted in the high piezoelectric properties.

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Effect of Pyrochlore Phase on Electric Properties for PNN-PT-PZ Piezoelectric Ceramics (PNN-PT-PZ계 압전세라믹스의 전기적 특성에 미치는 Pyrochlore 상의 영향)

  • 이기태;남효덕
    • Journal of the Korean Ceramic Society
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    • v.31 no.9
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    • pp.1030-1036
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    • 1994
  • The ceramics in the system 0.5[Pb(Ni1/3Nb2/3)O3]-0.5[0.65PbTiO3-0.35PbZrO3] were prepared by conventional solid state reaction method, double calcined method (columbite precursor method) and flux method using NaCl-KCl. Amount of pyrochlore phase for the calcined powders, sintering charateristrics, dielectric and piezoelectric properties were then investigated. Sintering temperature was 1000~120$0^{\circ}C$ and in case of flux method, the amount of flux to oxide was 1 : 1 mole ratio. The dielectric and piezoelectric properties of ceramics prepared by double calcined method and flux method were found to be better than those by conventional method. It was also possible to lower sintering temperature and reduce the amount of pyrochlore phase either by double calcined method or flux method. But with increasing sintering temperature, the difference in characteristrics due to diffrent fabrication method gradually.

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Dielectric and Piezoelectric Properties of Microwave Sintered BNT-ST Ceramics (마이크로파 소성법으로 제조한 BNT-ST 세라믹스의 유전 및 압전 특성)

  • Lee, Sang-Hun;Kim, Seong-Hyun;Erkinov, Farrukh;Nguyen, Hoang Thien Khoi;Duong, Trang An;Han, Hyoung-Su;Lee, Jae-Shin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.33 no.1
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    • pp.37-44
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    • 2020
  • This study investigated the microstructure and piezoelectric properties of lead-free 0.74(Bi1/2Na1/2)TiO3-0.26SrTiO3 (BNST26) piezoelectric ceramics sintered using a microwave furnace. For comparison, specimens were also prepared using a conventional furnace sintering (CFS). Average grain sizes of 2.4 ㎛ and 3.2 ㎛ were obtained in the sample sintered at 1,100℃ for 5 min using microwave sintering (MWS) and at 1,175℃ for 2 h using CFS, respectively. To quantify the changes in the microstructures and electrical properties according to the sintering conditions, the polarization hysteresis, bipolar and unipolar strain curves, and temperature dependence of permittivity were evaluated. As a result, it was determined that the Pmax (maximum polarization), Pr (remanent polarization) and Smax (maximum strain) values tend to increase with the average grain size. Based on these results, it is concluded that the MWS method can produce lead-free ceramics with superior performance in a relatively short time compared to the conventional CFS method.

Effect of Carbon Addition and Sintering Temperature on Densification and Microstructural Evolution of Sinter-Hardening Alloys Steels

  • Verma, N.;Anand, S.;Upadhyaya, A.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.557-558
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    • 2006
  • In all conventional sintered PM products, the pores present are of two types, primary and secondary. Primary pores forming during compaction and latter during sintering, due to penetration of formed liquid through the matrix grain boundary. Effect of carbon addition on diffusion of Cu in SH737-2Cu system was investigated. After compaction and transient liquid phase sintering at $1120^{\circ}C$ and $1180^{\circ}C$, samples were characterized for densification, showing rise in sintering density and reduction in swelling on carbon addition. Quantitative microstructural characterization (shape factor and pore size) revealed bimodal distribution for 0% carbon, more rounded pores for 0.9% carbon and higher sintering temperature, and pore coarsening at higher sintering temperature.

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Low Temperature Sintering and Dielectric Properties of $Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ Ceramics ($Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ 세라믹스의 저온소성과 유전특성)

  • 남효덕
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1994.11a
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    • pp.8-12
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    • 1994
  • Solid solutions $Sr_2$($Ta_{1-x}$$Nb_{x}$)$_2$$O_{7}$ (x = 0.0 - 1.0) composed of strontium-tantalate (low Curie temperature) and strontium-niobate (high Curie temperature) were prepared by the conventional mixed oxide method and the molten salt synthesis method (flux method). Phase relation, sintering temperature, grain-orientation and dielectric properties were investigated for sintered ceramic samples with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. Single phase $Sr_2$$Nb_2$$O_{7}$ powder was synthesized by using flux method at lower temperatures, and sintering temperature was also reduced by using flux method derived powder than using mixed-oxide derived powder. Sintering characteristics and dielectric properties of specimens prepared by flux method were better than those derived through the conventional method.

Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy

  • Kim, Mijoo;Kim, Jaewon;Mai, Hang-Nga;Kwon, Tae-Yub;Choi, Yong-Do;Lee, Cheong-Hee;Lee, Du-Hyeong
    • The Journal of Advanced Prosthodontics
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    • v.11 no.5
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    • pp.280-285
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    • 2019
  • PURPOSE. The present study was designed to examine the clinical fit of fixed dental prosthesis fabricated by the milling-sintering method using a presintered cobalt-chromium alloy. MATERIALS AND METHODS. Two single metal-ceramic crowns were fabricated via milling-sintering method and casting method in each of the twelve consecutive patients who required an implant-supported fixed prosthesis. In the milling-sintering method, the prosthetic coping was designed in computer software, and the design was converted to a non-precious alloy coping using milling and post-sintering process. In the casting method, the conventional manual fabrication process was applied. The absolute marginal discrepancy of the prostheses was evaluated intraorally using the triple-scan technique. Statistical analysis was conducted using Mann-Whitney U test (${\alpha}=.05$). RESULTS. Eight patients (66.7%) showed a lower marginal discrepancy of the prostheses made using the milling-sintering method than that of the prosthesis made by the casting method. Statistically, the misfit of the prosthesis fabricated using the milling-sintering method was not significantly different from that fabricated using the casting method (P=.782). There was no tendency between the amount of marginal discrepancy and the measurement point. CONCLUSION. The overall marginal fit of prosthesis fabricated by milling-sintering using a presintered alloy was comparable to that of the prosthesis fabricated by the conventional casting method in clinical use.

The Fabrication and Their Properties of Zirconia-spinel COmposites by Reaction Sintering (반응소결에 의한 지르코니아-스피넬 복합체의 제조 및 성질)

  • 황규홍;김상모
    • Journal of the Korean Ceramic Society
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    • v.33 no.7
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    • pp.779-784
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    • 1996
  • The spinel/cubic stabilized zirconia composites were fabricated via, The reaction sintering of monoclinic zirco-nia(baddeleyite) added with MgAl powder. During heating Mg and Al were oxidizedfirst and subsequently the oxides formed spinel (MgAl2O4) and finally remained MgO stabilized the zirconia, Because the oxides formed during the oxidation process would have very fine grain size (order of submicron) mainly due to the effects of attrition milling the reaction sintering was more effective in densification and improvement of strength and fracture toughness than conventional sintering with direct addition of MgO. The sintering behavior phase transformation during firing and mechanical properties of sintered body were investigated with emphasis on the relations between spinel formation due to MgAl addition and sintering and mechanical properties.

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Influence of Sintering Parameters on the Mechanical Performance of PM Steels Pre-alloyed with Chromium

  • Bergman, Ola;Lindqvist, Bjorn;Bengtsson, Sven
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.280-281
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    • 2006
  • Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature $1120^{\circ}C$ although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range $1120-1250^{\circ}C$, due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density $7.1\;g/cm^3$, after sintering at $1250^{\circ}C$ followed by cooling at $2.5^{\circ}C/s$ and tempering.

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Enhanced Sintering Behavior and Electrical Properties of Single Phase BiFeO3 Prepared by Attrition Milling and Conventional Sintering

  • Jeon, Nari;Moon, Kyoung-Seok;Rout, Dibyranjan;Kang, Suk-Joong L.
    • Journal of the Korean Ceramic Society
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    • v.49 no.6
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    • pp.485-492
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    • 2012
  • Dense and single phase $BiFeO_3$ (BFO) ceramics were prepared using attrition milled calcined (coarse) powders of an average particle size of ${\approx}3{\mu}m$ by conventional sintering process. A relative density of ${\approx}96%$ with average grain size $7.3{\mu}m$ was obtained when the powder compacts were sintered at $850^{\circ}C$ even for a shorter duration of 10 min. In contrast, densification barely occurred at $800^{\circ}C$ for up to 12 h rather the microstruce showed the growth of abnormal grains. The grain growth behavior at different temperatures is discussed in terms of nonlinear growth rates with respect to the driving force. The sample sintered at $850^{\circ}C$ for 12 h showed enhanced electrical properties with leakage current density of $4{\times}10^{-7}A/cm^2$ at 1 kV/cm, remnant polarization $2P_r$ of $8{\mu}C/cm^2$ at 20 kV/cm, and minimal dissipation factor (tan ${\delta}$) of ~0.025 at $10^6$ Hz. These values are comparable to the previously reported values obtained using unconventional sintering techniques such as spark plasma sintering and rapid liquid phase sintering.

Effects of the Whisker Orientation and Sintering Temperature on Mechanical Properties of the Si$_3$N$_4$ based Composites (Si$_3$N$_4$ Whisker의 배열방향과 소결온도가 Si$_3$N$_4$ 복합체의 기계적 성질에 미치는 영향)

  • 김창원;박동수
    • Journal of the Korean Ceramic Society
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    • v.36 no.5
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    • pp.483-489
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    • 1999
  • Gas pressure sintered silicon nitride based composites with 3 wt% $\beta$-Si3N4 whiskers were prepared and change of properties according to the whisker orientation and sintering temperature was studied. The tapes with whiskers were fabricated by two different method ; conventional tape casting and a modified tape casting by using guide pins,. Orientations of the whiskers were controlled by different stacking sequences of the sheets cut from the tape. Samples were fully densified by gas pressure sintering at 2148-2273K. As the sintering temperature increased size of the large elongated grains increased. In case of unidirectional samples sintering shrinkage normal to the whisker alignment direction was larger than that of parallel to the direction and the shrinkage anisotropy increased slightly as sintering temperature increased. As sintering temperature increased the crack length parallel to whisker alignment direction became shorter but that normal to the direction did not depend on sintering temperature. In case of cross-plied samples the anisotropy of mechanical properties disappeared.

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