• 한국세라믹학회지
• /
• 제32권5호
• /
• pp.635-641
• /
• 1995

The effects of A-site substitution with alkaline-earth ions (Ca, Sr and Ba) on the perovskite-phase formation and dielectric properties for Pb1-xMx(Zn1/3Nb2/3)O3 (0.0 x 0.5)-based relaxors were studied. Considerable improvements in the sinterability and the extent fo perovskite formation were observed with increasing the A-site substitution (x) and sintering temperature. The maximum dielectric permittivity appeared at x=0.1 for Sr and Ba substitutiion, while the relative dielectric permittivity was almost invariant in the case of Ca ion substitution. Curie temperature decreased with increasing relative amount of Sr and Ba ions but was almost invariant in case of Ca ion substitution. With increasing the amount of x, the diffuseness parameter ($\delta$) increased but the maximum dielectric constant decreased, demonstrating an enhanced diffuse phase transition (DPT) in the presence of alkaline-earth cations.

• 한국건축시공학회지
• /
• 제5권2호
• /
• pp.89-95
• /
• 2005

Various tests are performed with the recycled concrete including compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test. The basic data obtained from the presented test could be accumulated for the purpose of utilization in concrete structure. Most of the strength tests show that strength decrease a little extent with increasing substitution ratio of recycled coarse aggregate except splitting tensile test for the concrete with $100\%$ recycled fine aggregate. But in case of the $50\%$ substitution of recycled coarse aggregate, compressive strength, flexural strength and bonding strength are almost equal to the normal concrete. Chloride ion penetration test shows that the penetration amounts of chloride ion becomes more in proportion to the substitution ratio of recycled aggregate. But most of the results show that the permeability of recycled concrete is proper to use. The results of present study nay imply that the use of recycled aggregate for steam curing concrete is possible but the substitution ratio of recycled aggregate should be determined through further studies.

• 한국세라믹학회지
• /
• 제45권9호
• /
• pp.556-560
• /
• 2008

The effects of Nb and Co ion substitution on the dielectric and magnetic properties of the multiferroic $BiFeO_3$ thin films have been investigated. Heteroepitaxial $BiFeO_3$ thin films were deposited by Pulsed Laser Deposition method. Nb substitution decreased the leakage current by 6 orders of magnitude and Co substituted $BiFeO_3$ thin films showed an enhanced magnetization, 2 times larger than that of un-substituted $BiFeO_3$. Through the co-substitution of Co and Nb, $BiFeO_3$ thin films with a low leakage current and an enhanced magnetization could be obtained.

• Journal of Magnetics
• /
• 제4권2호
• /
• pp.65-68
• /
• 1999

The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).

• Journal of Electrochemical Science and Technology
• /
• 제7권4호
• /
• pp.245-250
• /
• 2016

The layered $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composite with well crystalized and high specific capacity is prepared by molten-salt method and using the substitution of Na for Li-ion battery. The effects of annealing temperature, time, Na contents, and electrochemical performance are investigated. In XRD analysis, the substitution of Na-ion resulted in the P2-$Na_{2/3}MO_2$ structure ($Na_{0.70}MO_{2.05}$), which co-exists in the $Na_{0.6}Li_{0.6}[Mn_{0.72}Ni_{0.18}Co_{0.10}]O_2$ composites. The discharge capacities of cathode materials exhibited $284mAhg^{-1}$ with higher initial coulombic efficiency.

• 대한화학회지
• /
• 제31권6호
• /
• pp.534-541
• /
• 1987

$Hg^{2+}$이온의 존재하에서 $[CoCl(Hedta)]^-$ 착이온에 대한 에틸렌디아민(en) 치환반응기구에 대해서 uv 및 CD스펙트럼을 이용하여 조사하였다. 속도론적인 자료로부터 $Hg^{2+}$ 이온이 금속과 작용하여 첫 en이 치환될때는 회합반응 경로를 거치며 제2, 제 3의 en은 단계적으로 치환됨을 알 수 있었다. 그리고 생성된 $[Co(en)_3]^{3+}$의 광학순도로 부터 광학수율을 결정짓는 적절한 중간체를 제시하여 치환반응에 대한 새로운 반응경로를 제시하였다.

• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
• /
• pp.53-53
• /
• 1998

Four valence of Chromium ion doped Yttrium Aluminum Garnet crystals were grown by Floating Zone and Czochralski methods. Changes of valence for Chromium (3+) ion to Chromium (4+) were achieved by substitution of Yttrium ion in dodecahedral site to Calcium and by substitution of Aluminum in octahedral site to Magnesium. Growth conditions for high quality of crystals were investigated. Grown crystals were cut and polished and then observed various types of defects. Characterizations by means of measurement of density and lattice parameter as a function of solidification fraction were performed. Results of Q-switching test using grown crystals were also reported.

• 한국막학회:학술대회논문집
• /
• 한국막학회 2001년도 춘계 총회 및 학술발표회(한국막학회)
• /
• pp.104-107
• /
• 2001

• 자원리싸이클링
• /
• 제27권4호
• /
• pp.36-43
• /
• 2018

폐 니켈-카드뮴 전지의 재활용을 위하여 효율적으로 카드뮴과 니켈을 분리할 수 있도록 이온치환 반응을 이용하여 선택적으로 카드뮴을 분리하였다. 폐 니켈-카드뮴 전지 내의 전극을 분쇄하여 얻은 전극 분말을 황산에 침출시킨 니켈-카드뮴 용액에 황화나트륨을 첨가하여 CdS로 침전시켰다. 다양한 조건에서 이온치환실험을 실시하였으며, 최적조건으로는 상온에서 용액의 pH = -0.1, $Na_2S/Cd=2.3$일 때 용액 내 잔존하는 Cd은 약 100 ppm으로 대부분 CdS로 침전된 결과를 얻을 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.578-580
• /
• 2008

Blue-emitting $CaAl_2Si_2O_8:Eu^{2+}(CAS:Eu^{2+})$ phosphor, prepared by solid-state reaction, is described in this paper. We researched the effect of boron ion substitution in the host materials. The phase and luminescent properties were investigated using the powder X-ray diffraction(XRD) and photoluminescence(PL) spectra.