• 전자공학회논문지A
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• 제32A권11호
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• pp.35-43
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• 1995

To obtain high quality of $Ta_{2}O_{5}$ film, two dielectric layers of $Si_{3}N_{4}$ and $Ta_{2}O_{5}$ were subsequently formed on Si wafer. Silicon nitride films were thermally grown in 10 Torr ammonia ambient by R.F induced heating system. The thickness of thermally grown $Si_{3}N_{4}$ film was able to be controlled in the range of tens $\AA$ due to the self-limited growth property. $Ta_{2}O_{5}$ film of 200$\AA$ thickness was then deposited on the as-grown $Si_{3}N_{4}$ film about 25$\AA$ thickness by sputtering method and annealed at $900^{\circ}C$in $O_{2}$ ambient for 1hr. Stoichiometry film was prepared by the annealing in oxygen ambient. Despite the high temperature anneal process, silicon oxide layer was not grown at the interface of the layered films because of the oxidation barrier effect of Si$_{3}$N$_{4}$ film. The fabricated $Ta_{2}O_{5}$/$Si_{3}N_{4}$ film showed low leakage current less than several nA and high dielectric breakdown strength.

• 한국전기전자재료학회논문지
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• 제23권5호
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• pp.379-382
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• 2010

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition enhanced density, electromechanical coupling factor($k_p$) piezoelectric constant $d_{33}$ and mechanical quality factor($Q_m$). At the 0.9 mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum values of 0.46, 471, and 148 pC/N, respectively.

• 한국표면공학회지
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• 제29권6호
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• pp.628-633
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• 1996

Large saturation magnetization $4pM_s$ is essentially required for soft magnetic thin layers used in magnetic recording devices. Amorphous Co-based alloys and Fe-Co alloys may be regarded as one of the candidates for soft magnetic materials which possess large $4\piM_s$. Some preparation process to improve soft magnetism of these films were performed in this study. Addition of Ta seemed to be effective to change the magnetostriction constant $\lambda$ from positive value to negative one. The magnetoelastic energy $K_e$ is strongly dependent on $\lambda$. $(Co_{95.7}Zr_{4.3})_{100-x}Ta_x$ films with $K_e$ of negative value have sufficiently soft magnetic characteristics. $Fe_{90}Co_{10}$ alloy exhibits extremely large $4\piM_s$, of about 24 kG. Addition of N and Ta to $Fe_{90}Co_{10}$ films improved the soft magnetism of them. The $Fe_{82.0}Co_{7.6}Ta_{10.4}$:N/Ti multilayered films exhibit better soft magnetic properties and better thermal stability than Fe-Co-Ta:N singlelayer films.

• 한국세라믹학회지
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• 제31권11호
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• pp.1299-1306
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• 1994

Effect of MgO content on microstructural evolution and microwave dielectric properties of Ba(Mg1/3Ta2/3)O3 system was investigated. MgO content was varied from 10 mol% deficiency to 10 mol% excess of stoichiometric composition, respectively. It was found that MgO-deficient specimen showed faster grain growth rate than stoichometric and MgO excess BMT system. Besides, sandwich type precipitates of Ba5Ta4O15 which was formed within the BMT grain, might lead to the anisotropic grain growth of BMT grain. On the contrary, in MgO excess specimen, BMT grain growth rate was retarded by precipitations of MgO phase in grain boundary. Besides, the Q values of MgO-deficient showed lower than MgO-excess due to precipitations of Ba5Ta4O15 within BMT grain.

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.831-834
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• 1995

The nature of hydrogen bonding between thioacetamide and azines has been thoroughly investigated using near IR absorption spectroscopy. The νN-H + amide II combination band in thioacetamide (TA) has been analyzed to determine the thermodynamic constants for the formation of hydrogen bonded 1:1 TA:azine complexes in CCl4 and CHCl3 solutions. The relative stabilities of TA-azine complexes (pyridine->1,2-diazine->1,3-diazine->1,4-diazine-TA) are in good agreement with the relative proton affinities of azines in the gas phase. The results serve as a basis for analyzing the factors which influence the hydrogen bonding formation of TA in nonaqueous solutions.

• 한국식품영양과학회지
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• 제37권4호
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• pp.410-415
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• 2008

본 연구는 Ames test와 SRB assay를 통해 SK와 SDK 메탄올 추출물을 이용하여 항돌연변이원성과 세포독성 효과에 대해 살펴보았다. S. Typhimurium TA98과 TA100 균주를 사용하여 돌연변이원성을 실시한 결과 SK와 SDK 메탄올 추출물 자체의 돌연변이원성은 없었으며, MNNG와 4NQO를 유도하여 높은 항돌연변이 효과를 나타내었다. S.Typhimurium TA98에서 4NQO를 유도하여 SDK($200{\mu}g$/plate) 메탄올 추출물 처리 시에 71.4%의 억제효과를 나타내었으며, 반면에 S. Typhimurium TA100에 4NQO와 MNNG의 돌연변이를 유도하였을 때 각각 56.1%와 83.6%의 억제율을 보였다. 암세포 성장 억제효과를 검토한 결과 샘플처리 시 농도 의존적 증가를 보였으며, SDK 메탄올 추출물 1 mg/mL 첨가 시 HeLa, Hep3B, MCF-7, AGS 및 A549에서 각각 61.5%, 61.3%, 51.4%, 57.9% 및 77.7%의 억제효과를 나타내었다. SK 메탄올 추출물 첨가 결과 $51{\sim}58%$ 정도의 억제효과를 보였다. 대조적으로 SDK 메탄올 추출물을 1mg/mL 첨가 시 293에서 $2{\sim}38%$의 세포독성을 나타내었다.

• Corrosion Science and Technology
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• 제8권4호
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• pp.139-142
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• 2009

Recently, quaternary titanium alloys of the system Ti-Nb-Ta-Zr received considerable research interest as potential implant materials because of their excellent mechanical properties and biocompatibility. However, only few reported works were available on the corrosion behavior of such alloys. Hence, in the present work, electrochemical corrosion of Ti-35Nb-5Ta-7Zr alloy, which has been fabricated by arc melting and heat treatment, was studied in 0.9 wt% NaCl at $37\pm1^{\circ}C$, along with biomedical grade Ti-6Al-4V and CP-Ti. The phase and microstructure of the alloys were investigated employing XRD and SEM. The results of electrochemical studies indicated that the corrosion resistance of the quaternary alloy was inferior to that of Ti-6Al-4V and CP Ti.

• Tribology and Lubricants
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• 제32권4호
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• pp.125-131
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• 2016

In recent years, thick ta-C coating has attracted considerable interest owing to its existing and potential commercial importance in applications such as automobile accessories, drills, and gears. The thickness of the ta-C coating is an important parameter in these applications. However, the biggest problems are achieving efficient coating and uniformity over a large area with high-speed deposition. Feasibility is confirmed for the ta-C coating thickness of up to 9.0 µm (coating speed: 3.0 µm/h, fixed substrate) using a single FCVA cathode. The thickness was determined using multiple coating cycles that were controlled using substrate temperature and residual stresses. In the present research, we have designed a coating system using FCVA plasma and produced enhanced thick ta-C coating. The system uses a specialized magnetic field configuration with stabilized DC arc plasma discharge during deposition. To achieve quality that is acceptable for use in automobile accessories, the magnetic field, T-type filters, and 10 pieces of a multi-cathode are used to demonstrate the deposition of the thick ta-C coating. The results of coating performance indicate that uniformity is ±7.6 , deposited area is 400 mm, and the thickness of the ta-C coating is up to 5.0 µm (coating speed: 0.3 µm/h, revolution and rotation). The hardness of the coating ranges from 30 to 59 GPa, and the adhesion strength level (HF1) ranges from 20 to 60 N, depending on the ta-C coating.

• 한국전기전자재료학회논문지
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• 제24권8호
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• pp.627-631
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• 2011

[ $[Li_{0.04}(Na_{0.54}K_{0.46})_{0.96}](Nb_{1-0.04-X}TaxSb_{0.04})O_3$ ]lead-free piezoelectric ceramics have been prepared by normal sintering at $1,100^{\circ}C$ for 5 h. X-ray diffraction analysis indicated that specimens demonstrate orthorhombic symmetry when $Ta\leq5$ mol%. While transforming into tetragonal symmetry when $x\geq20$ mol%. These suggest that the orthorhombic and tetragonal phases co-exist in the ceramics with 5 mol% $cm^3$. As the result of SEM images, the grain growth was decreased with the increase of Ta substitution. The ceramics become 'softening', leading to improvements in $k_p$, $\varepsilon_r$ and $d_{33}$, but a decrease in $Q_m$. Excellent properties of $k_p$= 0.46, $d_{33}$= 293 pC/N, ${\varepsilon}_r$= 1,583 and Tc= $340^{\circ}C$ were obtained when Ta= 15 mol%.

• 한국세라믹학회지
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• 제40권4호
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• pp.354-359
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• 2003

The microwave dielectric characteristics of (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ (0$\leq$x$\leq$1.0) ceramics were investigated by crystalstructure, variations of ionic polarizability, and microstructures. As x increased, (1-x)(Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)O$_2$-x(Mg$\_$1/3/Ta$\_$2/3/)O$_2$ transformed to tetragonal structure. Because the ionic radius of (Mg$\_$1/3/Ta$\_$2/3/)$\^$4+/was slightly bigger than one of (Al$\_$$\frac{1}{2}$/Ta$\_$$\frac{1}{2}$/)$\^$4+/, the cell parameters increased with increase of (Mg$\_$1/3/Ta$\_$2/3/)O$_2$concentration and coincided with prediction of the molecular additivity rule. As x increased, the compositions revealed ordered phase and were of single phase above 60 mol%. The increase of the ordered phase and grain size enhanced the Q and when ordering was completed at x over 0.6, the grain size was major factor for the increase in the a. Though the grain size increased, however, the porosity deteriorated the q. Therefore, the a depended on the order/disorder, the porosity, and the grain size in regular order.