• Toxicological Research
• /
• v.35 no.3
• /
• pp.287-294
• /
• 2019

The possibility of eye exposure for workers participating in manufacturing of nanoparticles or consumers using products containing nanoparticles has been reported, but toxicity studies on the eye are scarce. In this study, cytotoxicity of five nanoparticles including silver, ceria, silica, titanium and zinc were tested using Statens Seruminstitut Rabbit Cornea (SIRC) cells. When cells were treated with nanoparticles with concentrations of $1-100{\mu}g/mL$ for 24 hr, zinc oxide nanoparticles showed higher toxicity to cornea cells. $LC_{50}$ of zinc oxide nanoparticles was less than $25{\mu}g/mL$ but those of other nanoparticles could not be calculated in this test, which means more than $100{\mu}g/mL$. Generation of reactive oxygen species was observed, and expression of apoptosis related biomarkers including Bax and Bcl-2 were changed after treatment of zinc oxide nanoparticles, while no other significant toxicity-related changes were observed in cornea cells treated with Ag, $CeO_2$, $SiO_2$ and $TiO_2$ nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1995.02a
• /
• pp.057-58
• /
• 1995

극소전자 디바이스의 고집적화에 의해 박막배선의 선폭은 0.5$mu extrm{m}$ 이하로 축소되고 있고 상대적으로 높은 전류밀도가 흐르게 된다. 높은 전류밀도하에서는 현재 일반적으로 사용되고 있는 Al을 기본으로 하는 박막배선에서의 electromigration에 의한 결함 발생 그리고 비교적 낮은 전기전도도가 심각한 문제점으로 제기된다. 본 연구에서는 Al과 고전기전도도 물질인 Ag, Cu, 그리고 Au 박막배선에 대해 electromigration에 대한 저항성, 즉 activation energy를 측정 비교함으로써 차세대 극소전자 디바이스를 위한 박막배선재료로서의 가능성을 알아보고자 한다. Electromigration test 및 activation energy를 구하기 위해 순수 Ag, Cu, Al, Au 박막배선을 0.05$\mu\textrm{m}$ 두께, 100$\mu\textrm{m}$ 선폭, 그리고 5000$\mu\textrm{m}$ 길이로 SiO2 열산화막 처리된 pp-Si(100) 기판 위에 진공 증착시켰다. 가속화 실험을 위해 인가된 d.c. 전류밀도는 2$\times$106A/$ extrm{cm}^2$ 이었고, Al과 Au에서는 6$\times$106A/$\textrm{cm}^2$이었다. 실온에서 24$0^{\circ}C$까지의 온도범위에서 d.c.인가후의 저항변화를 측정하여 Median-Time-to-Failure(MTF)를 구한 후 Black 방정식을 이용하여 activation energy를 측정하였다. Activation energy는 Cu가 1.34eV로서 가장 높게 나타났고 Au가 1.01eV, Al이 0.66eV, Ag가 0.29eV의 순으로 측정되었다. 따라서 Cu와 Au 박막배선의 경우 Al보다 electromigration에 대한 저항력이 강한 고활성화에너지 특성을 갖는 고전기전도도 재료로서 차세대 극소전자 디바이스를 위한 대체 박막배선재료로서의 가능성을 보인다.

• Journal of the Korean Applied Science and Technology
• /
• v.24 no.3
• /
• pp.272-277
• /
• 2007

Catalytic activity changes of perovskite catalysts were examined with their A-site substitution. For the preparation of catalysts, Mn was used for B-site component and La, Ce, Sr, Ba, Ca, Ag were used for A-site component of the perovskite $catalysts(ABO_3)$ The effect of calcination temperature on methane combustion and perovskite structure was also investigated. The surface area and adsorbed oxygen species were tested with BET apparatus and $O_2-TPD$, respectively. Perovskite catalysts whose A-site was partially substituted needed higher calcination temperature than un-substituted one to form the perovskite structure. From $O_2-TPD$ experiment, it was found that methane combustion activity was directly related to the oxygen desorbing ability of the catalysts. The prepared catalyst(LM-7) was stable at $600^{\circ}C$ for 72 hours of reaction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.306-306
• /
• 2008

기계적 에너지를 전기적 에너지로 변환하는 에너지 변환소자인 압전 세라믹스는 액추에이터, 변압기, 초음파모터, 초음파 소자 및 각종 센서로 응용되고 있으며, 그 응용분야는 크게 증가하고 있다. 최근에는 이러한 압전 소자를 앞으로 도래하는 ubiquitous, 무선 모바일 시대의 휴대용 전자제품, robotics, MEMS 분야 등의 대체 에너지원으로 응용하기 위한 연구가 진행되고 있다. 특히 인간의 걷기 운동 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수 가 있어서, 기존 이차전지를 대체 또는 보완 할 수 있는 방안도 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 우수한 압전특성으로 전자세라믹스 분야에서 가장 널리 사용되어지고 있지만 $1200^{\circ}C$ 이상의 높은 소결온도 때문에 $1000^{\circ}C$ 부근에서 급격히 휘발되는 PbO로 인한 환경오염과 기본조성의 변화로 인한 압전 특성의 저하가 문제시 되고 있다. 또한 적층 세라믹스의 제작 시 구조적 특성상 내부전극이 도포된 상태에서 동시 소결이 필요한데, 융점이 낮은 Ag전극 대신 값비싼 Pd나 Pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제성이 떨어지는 단점을 갖게 된다. 순수 Ag 전극을 사용하거나 Ag의 비율이 높은 내부전극을 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결되고 우수한 전기적 특성을 보이는 압전 세라믹스를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)(Ni_{1/3}/Nb_{2/3})_{0.25}(Zr_{0.35}/Ti_{0.4})O_3$ 계의 조성을 설계하고, 소걸온도를 낮추기 위해서 2 단계 하소법을 이용하였다. 또한 $MnCO_3$, $SiO_2$, $Pb_3O_4$ 등을 소량 첨가하여 액상 소결 특성을 부여하여 소결 온도를 감소시키려는 시도도 하였다. 분말을 볼 밀링 (ball milling)을 통해 24시간 동안 혼합하고, 혼합된 분말은 $800^{\circ}C$에서 2시간 동안 하소하였다. 하소한 분말을 다시 72시간 동안 볼 밀링 하여 최종 분말을 얻었다. 최종 분말에 PVB를 첨가하여 직경 15mm의 디스크 형태로 성형한 후, 850~$975^{\circ}C$ 범위에서 온도를 변화시키면서 소결을 하였다. 최종 분말 및 소결된 시편을 XRD분석을 통하여 상을 확인하였고, SEM을 이용하여 미세조직을 관찰 하였다. 전기적 특성을 평가하기 위하여 두께를 1mm로 연마한 시편에 Ag 전극을 도포하여 $650^{\circ}C$에서 열처리한 후, 분극처리 하였다. 압전특성은 $d_{33}$-meter로 측정하였고, impedance analyzer를 이용하여 압전 특성 (전기기계결합계수 및 기계적품질계수)을 측정 하였다. 또한 강유전체 특성 평가 장치 (Precision-LC)를 이용하여 분극-전계 특성을 평가하였다. 이상의 연구를 통하여 소결 온도가 $900^{\circ}C$인 경우에서도 양호한 압전 특성을 확보 할 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.10-10
• /
• 2009

Transparent BNO thin films were grown on Al-doped ZnO (AZO)/Ag/AZO/polyethersulfon (PES) (abbreviated as AAAP) transparent electrodes at a low temperature by the NCD technique. The BNO films grown on the crystallized AZO/Ag/AZO (AAA) electrodes exhibit an amorphous phase with a root mean square (rms) roughness of approximately 2 nm in the range of deposition temperature. The capacitors (Pt/BNO/AAAP) with BNO films grown at $100^{\circ}C$ show a dielectric constant of 24 and dissipation factor of 8% at 100 kHz, a leakage current density of about $8{\times}10^{-6}A/cm^2$ at an applied voltage of 1.0V. The optical transmittances of the BNO/AAAP exhibited above 80% at wavelength of 550nm at all of deposition temperature. The mechanical stability of the BNO/AAA as well as AAA electrode with the PES substrates through the bending was ensured for flexible electronic device applications. The transparent BNO capacitors grown on AAAP are powerful candidate for integration with the transparent solar cells.

• Journal of the Microelectronics and Packaging Society
• /
• v.6 no.3
• /
• pp.19-24
• /
• 1999

The multilayer chip band pass filter for mobile communication is fabricated and designed. The size, insertion loss, center frequency and band width of multilayer chip filter are 4.5$\times$4.4$\times$1.8[mm], 3.0[dB] and 700[MHz]$\pm$15[MHz] respectively. The chip filter using $BiNbO_4$with CuO 0.06wt% +$V_2O_5$.lwt% was fabricated by screen printing with Ag electrode after tape casting. Insertion loss and center frequency of the fabricated chip filter are 2.58[dB] and 692.5$\pm$15[MHz] respectively. The center frequency was lower 7.5[MHz] than design result, but other characteristics of chip filter were similar to the ruts ultras of design result.

• Journal of the Korean Ceramic Society
• /
• v.42 no.6 s.277
• /
• pp.377-383
• /
• 2005

Generally, the strength achieved of glass-ceramics is higher as is the fracture toughness, as compared with the original glass. This improvement is due to the microstructure consisting of very small crystals. In this study, Ag-doped $45SiO_2-24CaO-24Na_2O-4P_2O_5$ glasses were irradiated to strengthen by the crystallization using Femto second laser Pulses. Through the UV/VIS spectroscope, XRD, Nano-indenter and SEM etc., heat-treated and irradiation of laser pulses without heat-treated samples were analyzed. Two kinds of samples, heat-treated and laser irradiated without heat-treated samples, showed the peaks in the same wavelength near 360 nm. Especially, samples irradiated by 140 mW laser with XYZ stage having at the rate of 100$\~$l000 $\mu$m/s had the largest absorption peak among them, and heat-treated samples was shown lower absorption range than over 90 mW laser irradiated samples. Moreover, samples irradiated by laser had higher values ($4.4\~4.56{\times}10^{-3}(Pa)$) of elastic modulus which related with strength of glass than values of heat-treated samples and these are 1.2$\~$1 .5 times higher values than them of mother glass.

• Journal of the Optical Society of Korea
• /
• v.18 no.4
• /
• pp.307-316
• /
• 2014

Improved power conversion efficiency of hybrid solar cells with ITO/ZnO seed layer/ZnO NRs/ZnS QDs/P3HT/PCBM/Ag structure was obtained by optimizing the growth period of ZnO nanorods (NRs). ZnO NRs were grown using a hydrothermal method on ZnO seed layers, while ZnS quantum dots (QDs) (average thickness about 24 nm) were fabricated on the ZnO NRs by the successive ionic layer adsorption and reaction (SILAR) technique. Morphology, crystalline structure and optical absorption of layers were analyzed by a scanning electron microscope (SEM), X-ray diffraction (XRD) and UV-Visible absorption spectra, respectively. The XRD results implied that ZnS QDs were in the cubic phase (sphalerite). Other experimental results showed that the maximum power conversion efficiency of 4.09% was obtained for a device based on ZnO NR10 under an illumination of one Sun (AM 1.5G, $100mW/cm^2$).

• Journal of the Korean Chemical Society
• /
• v.33 no.1
• /
• pp.18-24
• /
• 1989

Two crystal structures of dehydrated $Ag^+$ and $Rb^+$ exchanged zeolite A, stoichiometries of $Ag_{9}Rb_{3}-A$ (a = 12.278(2)${\AA}$) and $Ag_{10}Rb_{2}-A$ (a = 12.286(2)${\AA}$) per unit cell, have been determined by single crystal x-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 21(1)$^{\circ}$C. The crystals of $Ag_{10}Rb_{2}-A$ and $Ag_{10}Rb_{2}-A$ were prepared by flow methods using exchanged solution in which mole ratios of AgNO$_3$ and RbNO$_3$ were 1:5 and 1:50, respectively, with the total concentration of 0.05 M. The structures of the dehydrated $Ag_{9}Rb_{3}-A$ and the $Ag_{10}Rb_{2}-A$ were refined to the final error indices, $R_1$ = 0.064 and $R_2$ = 0.060 with 291 reflections, and $R_1$ = 0.063 and $R_2$ = 0.080 with 416 reflections respectively, for which I >3${\sigma}$(I). In both structures, one reduced silver atom per unit cell was found inside the sodalite cavity. It may be present as a hexasilver cluster in 1/6 of the sodalite units or as an isolated Ag atom coordinated to 4 $Ag^+$ ions in each sodalite unit to give $(Ag_5)^{4+}$, symmetry 4 mm. In the structure of dehydrated $Ag_{9}Rb_{3}-A$, 8 $Ag^+$ ions lie on the threefold axis and each is nearly at the center of the 8-rings at the sites of $D_{4h}$ symmetry. In the structure of dehydrated $Ag_{10}Rb_{2}-A$, two crystallographically different eight 6-ring $Ag^+$ ions were found; $7Ag^+$ ions in the (111) planes of their O(3) framework oxygens and one $Ag^+$ ion inside of sodalite cavity. Two crystallographically different 8-ring cations were also found; two $Rb^+$ ions at the centers of the 8-oxygen rings and one $Ag^+$ ion into the large cavity. Both structures indicate that $Rb^+$ ions prefer to occupy the 8-ring sites, while $Ag^+$ ions prefer to occupy the 6-ring sites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.10
• /
• pp.923-930
• /
• 2003

We jointed Bi(Pb)-Sr-Ca-Cu-O multifilament tapes and evaluated their electrical and mechanical properties. In order to improve connectivity of multifilaments, one or two single-filament tape was inserted between two multifilament tapes. The critical current ratio(CCR) and n-value of the jointed tapes were evaluated as a function of uniaxial pressure. It was observed that critical current ratio and n-value were 24.8-29.0% and 2.5-2.8 for MM lap-jointed tape. On the other hand, the corresponding values were improved to 24.7-53.9% and 3.1-4.2 for MSM jointed tape, and 63.4-76.0% and 3.4-5.1 for double MS:vr lap-jointed tape, respectively. The highest electrical properties of double MSM lap-jointed tape are considered to be owing to the presence of single core, causing better interconnections of multifilaments between the two tapes. The mechanical property of jointed tape was evaluated and correlated to the microstructural evolution. The strength of jointed tapes was 44-64% less than that of the unjoined tape. The strain tolerance of jointed tape was also reduced compared to that of the unjoined tape. These lower mechanical properties of jointed tape are probably due to the induced nonuniform microstructure such as the existence of cracks and Ag-intrusion in the joined region.