• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.39 no.1
• /
• pp.1-8
• /
• 2002

The effects of the addition of either monoclinic $ZrO_2$($ZrO_2$(m)) or tetragonal $ZrO_2$($ZrO_2$(t)) containing 5.35wt% $Y_2O_3$ on the physical properties and electrical conductivity of TEX>$Al_2O_3$ were investigated. The addition of $ZrO_2$(m) and $ZrO_2$(t) increased sintered density of $Al_2O_3$. The Vickers hardness also increased as addition of >($ZrO_2$(t) increased going through a maximum at 20wt% and the hardness of the specimens was found to be dependent on the sintered density. The addition of $ZrO_2$(t) improved the hardness of $Al_2O_3$-$ZrO_2$ systems and the $ZrO_2$(m) addition showed the better effect on the thermal shock property of $Al_2O_3$-$ZrO_2$ systems than that of the $ZrO_2$(t) addition. Above 15wt% addition of $ZrO_2$(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of $ZrO_2$(m).

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.11.2-11.2
• /
• 2009

Au-Ag 합금 박막에서 화학적으로 덜 안정한 Ag를 선택적으로 에칭하는 dealloying 기법을 통하여 crack-free 나노기공 gold 박막을 Si 기판에 제조하였다. Au-Ag 합금 박막은 두 가지 방법을 이용하였다: 1) thermal 또는 electron beam 증착법을 이용하여 Au 와 Ag 다층 박막을 Si 기판에 증착시킨 후 열처리를 통한 합금 박막제조; 2) co-thermal 증착법을 이용하여 Au-Ag 합금박막을 Si 기판에 직접 증착. Crack-free 나노기공 gold 박막 제조에 적합한 합금조성을 얻기 위하여 증착 속도, 열처리조건, dealloying 조건등을 조절하였다. Perchloric acid, HClO4 전해질을 이용한 전기화학적 dealloying을 통하여 crack-free 나노기공 gold 박막을 제조하였고, 기공크기를 조절할 수 있었다. 이에 더하여, electrophoretic 방법을 이용하여 나노기공 gold와 semiconductive 양자점 (CdTe 또는 CdSe)의 나노복합박막을 형성시킨 후 특성을 분석하였다.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1997.10a
• /
• pp.77-78
• /
• 1997

1. 서론 : Polyimide는 내열성과 기계적, 화학적 특성이 다른 고분자막에 비해 뛰어나며 선택도 또한 비교적 높기 때문에($\alpha$= 3-7) 최근 많은 연구가 대상이 되고 있다. 그러나 trade-off현상으로 알려진 바와 같이 선택도가 우수한 고분자 재료는 투과계수가 떨어지고 투과계수가 높은 고분자 재료는 낮은 선택도를 갖고 있기 때문에 보다 광범위한 분야에 실용적인 막으로 사용하기 위해서는 이를 개선하는 연구가 필요하다. 최근의 연구는 높은 투과계수와 선택도를 가진 새로운 고분자 재료의 합성에 관한 연구, 뛰어난 투과계수를 가지고 있지만 선택도가 낮은 고분자막을 대상으로 여러가지 수식방법을 이용하여 투과계수를 감소시키지 않으면서 동시에 선택도를 향상시키기 위한 연구, 우수한 화학적 특성과 선택도를 가진 물질을 대상으로 복합막이나 비대칭막으로 만들어 투과 저항을 극소화시키기 위한 연구 등의 방향으로 진행되고 있다. 본 연구는 Polyimide중 가장 큰 투과계수를 가진 것으로 보고된 6FDA-p-TeMPD막(P$_{O_2}$ = 122Barrer, $\alpha$$_{O_2/N_2}$ = 3.4)을 제조하여 분리 투과 특성을 향상시키려는 목적으로 UV처리를 하고 UV조사 시간과 강도(Intensity)를 변수로 투과 특성을 조사하여 가장 뛰어난 투과 특성을 나타내는 최적조건을 찾고자 하였다.

• Journal of the Korean Chemical Society
• /
• v.50 no.4
• /
• pp.315-320
• /
• 2006

manganese oxides have been prepared by Chimie Douce redox reaction between permanganate and chalcogen element fine powder under acidic condition (pH = 1). According to powder X-ray diffraction analyses, the S- and Se-doped manganese oxides are crystallized with layered birnessite and tunnel-type -MnO2 structures, respectively. On the contrary, Te-doped compound was found to be X-ray amorphous. According to EDS analyses, these compounds contain chalcogen dopants with the ratio of chalcogen/manganese = 4-7%. We have investigated the chemical bonding character of these materials with X-ray absorption spectroscopic (XAS) analysis. Mn K-edge XAS results clearly demonstrated that the manganese ions are stabilized in octahedral symmetry with the mixed oxidation states of +3/+4. On the other hand, according to Se K- and Te L1-edge XAS results, selenium and tellurium elements have the high oxidation states of +6, which is surely due to the oxidation of neutral chalcogen element by the strong oxidant permanganate ion. Taking into account their crystal structures and Mn oxidation states, the obtained manganese oxides are expected to be applicable as electrode materials for lithium secondary batteries.

• Journal of Life Science
• /
• v.23 no.8
• /
• pp.1019-1024
• /
• 2013

The aims of this study were to determine antioxidation effect and neuroblastoma cell protection effect of donkey's bone and skin extracts (DBSE). DBSE was extracted by a pressure-cooker for 48 h and lyophilized. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was significantly increased with increased doses of DBSE and 40 mg/ml of DBSE showed 95.43% of the DPPH scavenging effect, which was equivalent to 1 mg/ml of vitamin C. The 2,2'-azino-bis (3-ethylbenzothiazoline-6- sulphonic acid) (ABTS) radical scavenging activity was also increased in a dose-dependent manner, and 20 mg/ml of DBSE showed 88.73% of the ABTS scavenging effect. The oxygen radical absorbance capacity (${\mu}M$ Trolox equivalent) of DBSE was significantly increased at a concentration of 10 mg/ml, which showed $132.53{\mu}M$ TE. The viability of oxidatively stressed brain cells induced by $500{\mu}M\;H_2O_2$ was protected by DBSE at concentrations greater than $50{\mu}M$. Cell viability after DBSE treatment at 50 and $100{\mu}g/ml$ was 53.78 and $54.34{\mu}M$ TE, respectively. There was no significant difference between both doses; however, 200 and $500{\mu}g/ml$ of DBSE showed 59.74 and 66.08% of cell viability, respectively indicating that DBSE protected SK-N-SH from oxidation stress. These results suggest that DBSE may have potential to be used as natural antioxidants in food industry, while in vivo evidence is necessary to support DBSE's in vitro-based antioxidative efficiency.

• Journal of Fisheries and Marine Sciences Education
• /
• v.24 no.2
• /
• pp.203-209
• /
• 2012

We investigated the effect on dietary EPA (eicosapentaenoic acid) source (EP) into formulated diets for growth of brackish flea, Diaphanosoma celebensis. The highest density and specific growth rate (SGR) of brackish fleas were observed on Tetraselmis suecica (TE) trial, but these of trial were not significantly differed with that of Chlorella (CH) + Crypthecodinium sp. (CR) + EP trial, contained EPA oil (P>0.05). Contrastively, CH trial showed the lowest SGR. And in the RNA/DNA ratio, 0.08 of TE trial was the highest ratio out of whole trials, but the trial not significantly differed with that of CH + CR + EP trial (P>0.05). But, the ratio of CH trial was the lowest ratio at 0.05 out of whole trials (P<0.05). Through out results, the EPA source for flea culture was showed a positive effect through their growth and SGR. Therefore, we suggested that a usage of the source with CH could replace T. suecica as good diet for culture of the brackish flea.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.1
• /
• pp.69-74
• /
• 2015

Cadmium telluride (CdTe) is being developed for thin film of the X-Ray detector recently. But a rough surface of the CdTe should be improved for resolution and signal speed. This paper shows the study on the improvement of surface roughness and removal rate by applying Chemical Mechanical Polishing. The conventional potassium hydroxide (KOH) based colloidal silica slurry could not realize a mirror surface without physical defects, resulting in low material removal rate and many scratches on surface. In order to enhance chemical reaction such as form oxidized layer on the surface of cadmium telluride, we used hydrogen peroxide ($H_2O_2$) as an oxidizer. Consequently, in case of 3 wt% concentration of hydrogen peroxide, the highest MRR (938 nm/min) and the lowest surface roughness ($R_{p-v}=10.69nm$, $R_a=0.8nm$) could be obtained. EDS was also used to confirm the generated oxide of cadmium telluride surface.

• Journal of Acupuncture Research
• /
• v.15 no.2
• /
• pp.455-478
• /
• 1998

The result as following one was founded that investigate cause and acupuncture point for symptoms of headache; 1. Headache in distinction from doo-pung(頭風.) was defined that it' period is short and treatment is easy. 2. The cause of headache was classified according to the interior and exterior cause of the body. 3. Total number of used acupuncture point was one hundred and six, and in order of using time acupuncture point was appeared as LI4(15), LU7(12), GB20(12), BL2(11), GV20(9), TE23(9), SI3(7), GV24(7), GV23(7) 4. The meridian distribution of acupuncture point is appeared as Bladder Meridian(21points), Gallbladder Meridian(18points), Governer vesseI(14points), Triple Energizer meridian(12points), Large Intestine Meridian(9points), Small Intestine Meridian(7points), Stomach Meridian(7points) 5. According to headache position, the distribution of acupuncture point $Yangmy\check{o}ng\;Ky\check{o}ng$ and Governer vessel was used to frontal headache, Soyang $Ky\check{o}ng$ to migraine, Taeyang $Ky\check{o}ng$ and Governer vessel to occipital headache. 6. LI4(合谷) and LU7(列缺) was used to general headache as basic acupuncture point.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.39 no.4
• /
• pp.341-349
• /
• 2002

Electrical, mechanical and sinterability properties of yttria-stabilized zirconia doped with 5.35wt% $Y_2$O$_3$(Y$_2$O$_3$- containing stabilized zirconia : YSZ) were studied as a function of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ addition. The ratio of monoclinic phase to tetragonal phase was changed by the addition of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ to 8.00 wt% and sintered density decreased with increasing $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ addition. Fracture toughness increased with the increase of monoclinic to tetragonal phase ratio and was maximum at about 18%. When transition metals such as CoO, Fe$_2$O$_3$ or MnO$_2$ was added more than 1.5 wt%, the electrical conductivity of YSZ increased. But $Al_2$O$_3$ hardly affected the electrical conductivity of YSZ. The addition of $Al_2$O$_3$, CoO, Fe$_2$O$_3$ and MnO$_2$ into YSZ resulted in the more complex behavior of fracture toughness and hardness variation and the specimen with 1.5wt%-Fe$_2$O$_3$, 3.0wt%-Al$_2$O$_3$ and 1.5wt%-CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$^{1}$2/ and Vickers hardness of 1201 kgf/mm$^2$.

• Journal of Powder Materials
• /
• v.30 no.2
• /
• pp.130-139
• /
• 2023

Thermoelectric materials and devices are energy-harvesting devices that can effectively recycle waste heat into electricity. Thermoelectric power generation is widely used in factories, engines, and even in human bodies as they continuously generate heat. However, thermoelectric elements exhibit poor performance and low energy efficiency; research is being conducted to find new materials or improve the thermoelectric performance of existing materials, that is, by ensuring a high figure-of-merit (zT) value. For increasing zT, higher σ (electrical conductivity) and S (Seebeck coefficient) and a lower κ (thermal conductivity) are required. Here, interface engineering by atomic layer deposition (ALD) is used to increase zT of n-type BiTeSe (BTS) thermoelectric powders. ALD of the BTS powders is performed in a rotary-type ALD reactor, and 40 to 100 ALD cycles of ZnO thin films are conducted at 100℃. The physical and chemical properties and thermoelectric performance of the ALD-coated BTS powders and pellets are characterized. It is revealed that electrical conductivity and thermal conductivity are decoupled, and thus, zT of ALD-coated BTS pellets is increased by more than 60% compared to that of the uncoated BTS pellets. This result can be utilized in a novel method for improving the thermoelectric efficiency in materials processing.