• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제52권6호
• /
• pp.249-256
• /
• 2003

Samples with the nominal composition, Ag-$Bi_{1.84}Pb_{0.34}Sr_{1.91}Ca_{2.03}Cu_{3.06}O_{10+{\delta}}$ high $T_{c}$ superconductors containing Ag as an additive were fabricated by a solid-state reaction method. Samples with Ag of 10 wt%, 30 wt%, and 50 wt% each were sintered at $860^{\circ}C$~$870^{\circ}C$ for 24 hours. The structural characteristics, the microstructures and the critical temperature with respect to the each samples were investigated by XRD, four-prove methode, SEM and EDS respectively. The $T_{c}\;^{zero}$ of the sample with the 50 wt% Ag additive at the surface showed 94 K.

• 한국결정성장학회지
• /
• 제8권4호
• /
• pp.626-633
• /
• 1998

본 연구에서는 고유전율의 저온소성용 글라스/세라믹을 제조하고자, SiO2-TiO2-RO계 결정화 유리를 제조하고 Al2O3를 필러 물질로 혼합하여 복합체를 제조하고 그 특성을 관찰하였다. 본 유리조성으로써 $900^{\circ}C$ 이하에서 결정화되는 유리의 제조가 가능하였고, RO (BaO, CaO, SrO)의 성분에 따라 결정화 온도는 변화함을 알 수 있었다. 본 유리조성에 $Bi_2O_3$를 플럭스로 첨가하고, 세라믹 필러로써 Al2O3를 사용하여 $860^{\circ}C$에서 소성함으로써 고유전율의 저온소성용 글라스/세라믹의 제조가 가능하였고, 이때 복합체의 밀도는 3.96g/$\textrm{cm}^3$ 이었고, 유전율은 17, Q.f 값은 600이었다.

• 한국결정성장학회지
• /
• 제24권3호
• /
• pp.127-132
• /
• 2014

$Y_2O_3$-BN 세라믹 복합체를 제작하기 위해서, 분말 입도 $3{\sim}10{\mu}m$인 $Y_2O_3$ 분말을 분산한 슬러리에 pH 조절제인 NaOH를 첨가하였으며 결합제로는 PVA, 가소제로는 PEG를, BN 분말과 혼합하고, 분무건조(spray drying)공정을 거쳐 $Y_2O_3$ 혼합 분말을 제조하였다. ${\O}14mm$ 크기의 $Y_2O_3$-BN 시편을 성형하고, $1550^{\circ}C$ 및 $1600^{\circ}C$에서 소결하여 $Y_2O_3$-BN 복합체를 제작하였다. BN 투입량과 소결온도의 변수에 따른 미세구조, 순도, 꺽임강도, 열팽창계수, 밀도, 체적저항, 내플라즈마 특성을 조사하였다.

• 한국세라믹학회지
• /
• 제44권2호
• /
• pp.110-115
• /
• 2007

The effects of $TiO_2$ in the glasses on the shrinkage and dielectric properties of BNT-glass composites have been investigated. Without $TiO_2$ addition, BNT-glass composite showed two humps in the shrinkage curve, which are related with crystallization of $BaTi(BO_3)_2\;and\;Bi_4Ti_3O_{12}$. However, the increase of $TiO_2$ addition resulted in the decrease of 2nd hump in the shrinkage. The increased dielectric constant with $TiO_2$ addition might be due to the reduced crystallization of $Bi_4Ti_3O_{12}$. A dielectric constant of 52, a quality factor of 5088 GHz, and a temperature coefficient of resonant frequency of $-0.16ppm/^{\circ}C$ were obtained for a specimen containing $TiO_2$-added glasses, without sacrificing the benefits of high ${\varepsilon}_r$ and low TCF of BNT ceramics.

• 한국전기전자재료학회논문지
• /
• 제36권5호
• /
• pp.505-512
• /
• 2023

This study investigated crystal structures, microstructures, and electric-field-induced strain (EFIS) properties of Bi-based lead-free ferroelectric/relaxor composites. Bi_1/2Na_0.82K_0.18)_1/2TiO₃ (BNKT) as a ferroelectric material and 0.78Bi_1/2(Na_0.78K_0.22)_1/2TiO₃-0.02LaFeO₃ (BNKT2LF) as a relaxor material were synthesized using a conventional solid-state reaction method, and the resulting BNKT2LF powders were subjected to high-energy ball milling (HEBM) after calcination. As a result, HEBM proved a larger average grain size of sintered samples compared to conventional ball milling (CBM). In addition, the increased sintering time led to grain growth. Furthermore, HEBM treatment and sintering time demonstrated a significant effect on EFIS of BNKT/BNKT2LF composites. At 6 kV/mm, 0.35% of the maximum strain (S_max) was observed in the HEBM sample sintered for 12 h. The unipolar strain curves of CBM samples were almost linear, indicating almost no phase transitions, while HEBM samples displayed phase transitions at 5~6 kV/mm for all sintering time levels, showing the highest S_max/E_max value of 700 pm/V. These results indicated that HEBM treatment with a long sintering time might significantly enhance the electromechanical strain properties of BNT-based ceramics.

• 한국세라믹학회지
• /
• 제40권5호
• /
• pp.447-454
• /
• 2003

B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{delta}$의 출발조성비로 99.99%의 순도를 갖는 B $i_2$ $O_3$, PbO, SrC $O_3$, CaC $O_3$, CuO 분말 시약을 사용하여 고상반응법으로 합성하였다. 이렇게 합성된 Bi계 110 K 단일상의 고온초전도 물질을 다시 분말 상태로 만든 후, AgO, A $u_2$ $O_3$, MgO 금속산화물 분말을 각각 50 wt%의 비율로 혼합하였다. AgO, A $u_2$ $O_3$, MgO의 금속분말이 혼합된 시편들을 820~85$0^{\circ}C$로 각각 최종 소결시킨 후, 각 시편들에 대하여 XRD, $T_{c}$, SEM, EDS 등의 실험을 진행하였다. 얻어진 시편들의 $T_{c}$는 순수한 Bi-2223 상보다 낮지만, AgO 금속분말을 50 wt% 혼합한 시편의 임계전이온도가 99.58 K로 A $u_2$ $O_3$나 MgO를 50 wt% 혼합한 시편들보다 더 높게 나타났다. 또한, 표면 입자(grain)의 배열 상태는 AgO 금속분말을 50 wt% 혼합한 시편이 A $u_2$ $O_3$나 MgO를 50 wt% 혼합한 시편들보다 더 치밀화 되는 경향을 나타내었다.내었다.나타내었다.내었다.

• Elastomers and Composites
• /
• 제51권3호
• /
• pp.240-249
• /
• 2016

$BiVO_4$ nanomaterial was synthesized from bismuth (III) nitrate pentahydrate [$Bi(NO_3)_3{\cdot}5H_2O$] and ammonium vanadate (V) [$NH_4VO_3$]. The $BiVO_4$-graphene nanocomposite was fabricated by calcining the $BiVO_4$ nanomaterial and graphene under an oxygen-free atmosphere at $700^{\circ}C$. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize structural and morphological properties of samples. The catalytic activity of the $BiVO_4$-graphene nanocomposite was studied for the reduction of 4-nitrophenol, 3-nitrophenol and 2-nitrophenol by sodium borohydride [$NaBH_4$]. The photocatalytic activity of the $BiVO_4$-graphene nanocomposite was demonstrated by the degradation of organic dyes like BG, MB, MO and RhB under irradiation at 365 nm. The catalytic and photocatalytic activity were studied by UV-vis spectrophotometry.

• 한국전기전자재료학회논문지
• /
• 제29권6호
• /
• pp.342-347
• /
• 2016

We investigated the effect of $Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3$ (BNKT) modification on the ferroelectric and electric-field-induced strain (EFIS) properties of lead-free $0.97Bi_{1/2}(Na_{0.82}K_{0.18})_{1/2}TiO_3-0.03LaFeO_3$ (BNKTLF) ceramics as a function of BNKT content (x= 0, 0.1, 0.2, 0.3, 0.5, and 1). BNKT-modified BNKTLF powders were synthesized using a conventional solid-state reaction method. As the BNKT content x increased from 0 to 1 the normalized electric-field-induced strain ($S_{max}/E_{max}$) was observed to increase at relatively low fields, i.e., below the poling field. Moreover, BNKTLF-30BNKT showed about 460 pm/V as low as at 3 kV/mm, which is a considerably high value among the lead-free systems reported so far. Consequently, it was confirmed that ceramic-ceramic composite, a mixture of an ergodic relaxor matrix and embedded ferroelectric seeds, is a salient way to make lead-free piezoelectrics practical with enhanced EFIS at low field as well as less hysterical.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
• /
• pp.938-941
• /
• 2006

It is suggested that the bismate glass system is one of alternatives to the lead glass for barrier-ribs in PDP. Moreover it is necessary to investigate the resultant change in properties with addition of ceramic fillers. Glass frit was selected to be a $Bi_2O_3-ZnO-B_2O_3-Al_2O_3$ and two fillers, ZnO and $Al_2O_3$ were added into a glass matrix with the different content. We investigated thermal, chemical properties of bismate glass system with two different fillers. We confirmed that addition of fillers effects properties of composites such as the thermal expansion coefficient, etching mechanism.

• 한국전산구조공학회논문집
• /
• 제14권1호
• /
• pp.11-19
• /
• 2001

기능경사재(FGM)는 구성 물질의 체적분율(volume fraction)이 복합재 전체에 걸쳐 연속적 그리고 기능적으로 분포되어 있어, 기존의 이종물질 접합식(bi-material-type) 복합재보다 현저히 우수한 열기계적 특성을 가진다. 하지만, 기능경사 내열복합재의 열-탄소성 거동은 체적분율의 분포형태와 경사층이 차지하는 상대두께비에 따라 절대적으로 좌우된다. 본 연구는 기능경사 내열복합재의 열-탄소성 특성의 이들 두 설계인자에 대한 파라메트릭 FEM해석을 다룬 것이다. 열-탄소성 이론과 유한요소 근사화에 따라 연구용 2차원 FEM 프로그램을 개발하고, 대표적인 3층 구조의 2차원 기능경사 내열복합재의 열-탄소성 특성을 설계변수의 다양한 조합에 따라 분석하였다.