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Hoang Thien Khoi Nguyen,Trang An Duong,에르키노프 파루크,강형원,Byeong-Woo Kim,안창원,한형수,JAE SHIN LEE 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.5
This study investigated the structures, dielectric, ferroelectric and piezoeletric properties of lead-free (0.99 x ) Bi 0.5 Na 0.5 TiO 3 0.01CaTiO 3 x SrTiO 3 (BNT CT 100 x ST, x = 0.22–0.30) piezoelectric ceramics. These piezoceramics were successfully prepared using the conventional solid-state reaction method sintered at 1175 °C for 2 h. It was found that a phase transition from nonergodic relaxor to ergodic relaxor was induced by ST modifi cation in BNT CT ceramics. Consequently, a large electromechanical strain of 0.20% corresponding to high normalized strain d∗ 33 of 667 pm/V was obtained even under 3 kV/mm for BNT CT 28ST ceramics. Therefore, it is noted that lead-free BNT CT 100 x ST ceramics can be promising candidates for actuator applications.
Phuong Thien Thuong,Tran Manh Hung,Nguyen Minh Khoi,Hoang Thi My Nhung,Nguyen Thi Chinh,Nguyen Thi Quy,장태수,나민균 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.3
Four lignans, meso-dihydroguaiaretic acid(DHGA), macelignan, fragransin A2 and nectandrin B,were isolated from the seeds of Myristica fragrans (Vietnamesenutmeg) and investigated for their cytotoxicactivity against eight cancer cell lines. Of these, DHGAexhibited potent cytotoxicity against H358 with IC50 valueof 10.1 lM. In addition, DHGA showed antitumor activityin allogeneic tumor-bearing mice model.
Thuong, Phuong Thien,Hung, Tran Manh,Khoi, Nguyen Minh,Nhung, Hoang Thi My,Chinh, Nguyen Thi,Quy, Nguyen Thi,Jang, Tae Su,Na, MinKyun 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.3
Four lignans, meso-dihydroguaiaretic acid (DHGA), macelignan, fragransin $A_2$ and nectandrin B, were isolated from the seeds of Myristica fragrans (Vietnamese nutmeg) and investigated for their cytotoxic activity against eight cancer cell lines. Of these, DHGA exhibited potent cytotoxicity against H358 with $IC_{50}$ value of $10.1{\mu}M$. In addition, DHGA showed antitumor activity in allogeneic tumor-bearing mice model.
마이크로파 소성법으로 제조한 BNT-ST 세라믹스의 유전 및 압전 특성
이상훈,김성현,에르키노프 파루크,Hoang Thien Khoi Nguyen,Trang An Duong,한형수,이재신 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.1
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 μm and 3.2 μm 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. 본 연구에서는 마이크로파 소성법으로 제조한 0.74(Bi1/2Na1/2)TiO3-0.26SrTiO3 (BNST26) 무연 압전 세라믹스의 유전 및 압전 특성을 살펴보았다. BNST26 시료의 경우 일반 전기로 소성법의 경우 1175°C에서 2시간 동안 소결하면 충분한 치밀화가 진행되었으며 평균입도는 3.2 μm이었다. 반면에 마이크로파 소성법으로 제조한 경우 1100°C에서 5분간 소성하여도 충분히 치밀화가 진행되었으며 평균입도는 보다 작은 2.4 μm으로 나타났다. 특히 전계유기 변형 특성면에서 CFS 방법으로 제조한 시료의 경우 4 kV/mm의 전계 하에서 정규화 변형률이 509.5 pm/V를 나타내었고, MWS 방법으로 1100°C에서 5분간 소결하여 제조한 시료는 491.7 pm/V를 나타내어 대등한 수준의 특성을 보였다.
( Trang An Duong ),( Hoang Thien Khoi Nguyen ),( Sang-sub Lee ),( Chang Won Ahn ),( Byeong Woo Kim ),( Jae Shin Lee ),( Hyoung Su Han ) 한국센서학회 2021 센서학회지 Vol.30 No.6
This study analyzes the phase transition behavior and electrical properties of lead-free (1-x)K<sub>0.5</sub>Na<sub>0.5</sub>NbO<sub>3-x</sub>BaZrO<sub>3</sub> (KNN-100xBZ) piezoelectric ceramics. The stabilized crystal structures in BaZrO<sub>3</sub>-modified KNN ceramics is clarified to be pseudocubic. The polymorphic phase transition from the orthorhombic to pseudocubic phases can be observed with KNN-6BZ ceramics considering the optimized piezoelectric constant (d<sub>33</sub>). Electromechanical strain behaviors are discussed. Accordingly, the enhancement of strain value at x = 0.08 (composition) may originate from the coexistence of ferroelectric domains and polar nanoregions. A schematic of domains for KNN, KNN-8BZ, and KNN-15BZ ceramics has been proposed to describe the relationship between the stabilized relaxor and changes in electrical properties.
Giant Strain in Lead-free Relaxor/Ferroelectric Piezocomposite Ceramics
Thi Hinh Dinh,Jin-Kyu Kang,Hoang Thien Khoi Nguyen,Trang An Duong,Jae-Shin Lee,Vu Diem Ngoc Tran,Ky Nam Pham 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12
The crystal structural, ferroelectric, and electric-field-induced-strain (EFIS) properties of leadfree relaxor/ferroelectric piezocomposites were investigated. The relaxor-matrix phases were mixed with the ferroelectric-seed phases by using a conventional ceramic processing route. The addition of the ferroelectric seed phase dramatically enhanced the EFIS of the relaxor matrix phase at low electric fields. Giant strains of 745 pm/V at 4 kV/mm and 466 pm/V at 3 kV/mm were obtained when the seed contents were 30 wt% and 50 wt%, respectively, which are much higher than those of the relaxor matrix phase without ferroelectric seeds (575 pm/V at 4 kV/mm and 327 pm/V at 3 kV/mm).
이상섭,이창헌,즈엉 짱 안,웬 호앙 티엔 코이,한형수,이재신,Lee, Sang Sub,Lee, Chang-Heon,Duong, Trang An,Nguyen, Hoang Thien Khoi,Han, Hyoung-Su,Lee, Jae-Shin 한국전기전자재료학회 2021 전기전자재료학회논문지 Vol.34 No.1
This study investigated the structural, dielectric, ferroelectric, and strain properties of (0.98-x)Bi1/2Na1/2TiO3-0.02BiFeO3-xSrTiO3 (BNT-BF-100xST, x=0.20, 0.22, 0.24, 0.26, and 0.28). All samples were successfully synthesized using the conventional solid-state reaction method and sintered at 1,175℃ for 2 h. The average grain size of the BNT-BF-100x ceramics decreased with increasing ST content. Furthermore, we observed that the ferroelectric- relaxor transition temperature (TF-R) decreased with increasing ST content, which eventually vanished in the BNT-BF-24ST ceramics. The results indicated that a ferroelectric to relaxor phase transition could be induced by ST modification. Consequently, a large electromechanical strain of 633 pm/V at 4 kV/mm was observed for the BNT-BF-26ST ceramics. These results imply that our materials have the competitive advantage of larger strain under lower operating field conditions compared with other BNT-based lead-free piezoelectric ceramics. We expect that BNT-BF-ST lead-free piezoelectric ceramics are promising candidates as a novel ternary BNT-based system and can find potential applications in actuators.