• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.277-277
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• 2007

$(Bi,La)_4Ti_3O_{12}$ (BLT) 물질은 결정 방향에 따른 강한 이방성의 강유전 특성을 나타낸다. 따라서 BLT 박막을 이용하여 FeRAM 소자 등을 제작하기 위해서는 결정의 방향성을 세심하게 제어하는 것이 매우 중요하다. 현재까지 연구된 BLT 박막의 방향성 조절 결과를 보면, BLT 박막을 스핀 코팅 법 (spin coating method)으로 중착하고, 핵생성 열처리 단계를 조절하여 무작위 방향성 (random orientation)을 갖는 박막을 제조하는 방법이 일반적이었다. 그런데 이러한 스핀 코팅법에서의 핵생성 단계의 제어는 공정 조건 확보가 너무 어려운 단점이 있다. 이러한 어려움을 극복할 수 있는 대안은 스퍼터링 증착법 (sputtering deposition method), PLD법 (pulsed laser deposition method) 등과 같은 PVD (physical vapor deposition) 법의 증착방법을 적용하는 것이다. PVD 법으로 증착하는 경우에는 이미 박막 내에 무수한 결정핵이 존재하기 때문에 핵생성 단계가 필요 없게 된다. PVD 증착법의 적용을 위해서는 타겟 (target)의 제조 및 평가 실험이 선행되어야 한다. 그런데 벌크 BLT 재료의 소결공정 조건과 전기적 특성에 관한 연구 결과는 거의 발표 되지 않고 있다. 본 실험에서는 $Bi_2O_3$, $TiO_2$ and $La_2O_3$ 분말을 이용하여 최적의 조성을 구하기 위하여 Bi양을 변화시키며 타겟을 제조 하였다. 혼합된 분말을 하소 후 pallet 형태로 성형하여 소결을 실시하였다. 시편을 1mm 두께로 연마하고, 표면에 silver 전극을 인쇄하여 전기적 특성을 측정하였다. Bi양이 3.28몰 첨가된 조성에서 최대의 잔류분극 (2Pr) 값을 얻었고, 이때의 값은 약 $18{\mu}C/cm^2$ 정도였다. 최적화된 조성 ($Bi_{3.28}La_{0.75}Ti_3O_{12}$)으로 BLT 타겟을 제조하여 PLD법으로 박막을 제조하였다. 박막 제조 시 압력은 $1{\times}10^{-1}\;{\sim}\;1{\times}10^{-4}\;Torr$ 범위에서 변화시켰다. $1{\times}10^{-1}\;Torr$ 압력을 제외하고는 모든 압력에서 BLT 박막이 증착되었다. 중착된 박막을 $650\;{\sim}\;800^{\circ}C$에서 30분간 열처리를 실시하고 전기적 특성을 평가한 결과, $1{\times}10^{-2}\;Torr$에서 증착한 박막에서 양호한 P-V (polarization-voltage) 이력곡선을 얻을 수 있었고, 이때의 잔류분극 (2Pr) 값은 약 $6\;{\mu}C/cm^2$ 이었다. 주사전자현미경 (SEM)을 이용하여 BLT 박막 표면의 미세구조도 관찰하였는데, 스핀코팅 법으로 증착한 경우에 관찰되었던 조대화된 입자들은 관찰되지 않았고, 상당히 양호한 입자 크기 균일도를 나타내었다.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.221-226
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• 2016

Production of eco-friendly and biologically harmless materials is strongly required in all industries. In particular, reducing volatile organic compounds in coating processes is extremely important to secure worker's safety. During recent two decades, extensive research works on water-borne polyurethane dispersion (PUD) have been continuously developed as an alternative to solvent-borne polyurethane. However, PUD was shown inferior mechanical properties to the organic solvent-borne polyurethane due to a limit to the molecular weight increase, which resulted in the limit of applications. To overcome this drawback, several approaches have been examined such as polymer blends and thermal/radiation induced crosslinking. Among these methods, the radiation curing system was suitable for industrialization because of the high crosslinking density and fast curing speed. In this study, we overcame the drawback for PUD via introducing benzophenone radiation curable units to PUD. We synthesized PUD films which possessed good dispersion in water for 30 days, increased Tg and Td more than $5^{\circ}C$ after UV curing film as well as improved young's modulus more than double.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.380-387
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• 1998

In this paper, a sensor material with Fe/Zr multilayer thin film, in which the change in the magnetization and strain with hydrogenation is maximized, were developed. Compositionally modulated (CM) Fe/Zr multilayers with a $Fe_{80}Zr_{20}$ composition and modulation wavelengths ($\lambda$) $3~50{\AA}$ were deposited by sequentially sputtering (RF diode) elemental Fe and Zr targets. The films were electrolytically hydrogenated to select the optimum Fe/Zr multilayers that show the maximum increases in the magnetization and strain with hydrogenation. The changes in the magnetic properties of the thin films after hydrogenation, were measured using a hysteresis graph and a vibrating sample magnetometer (VSM), and the strains induced in the films by hydrogenation were also measured using a laser heterodyne interferometer (LHI). The optimum sensor material selected was incorporated in a fiber-optic hydrogen sensor (that can sense indirectly amount of hydrogen injected) by depositing it directly on the sensing arm of a single-mode fiber Michelson interferometer. The developed sensor holds significant promise for non-destructive test evaluation (NDE) applications because it is expected to be useful for detecting easily and accurately the subsurface corrosion in structural systems.

• Fire Science and Engineering
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• v.32 no.6
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• pp.1-6
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• 2018

This study is to analyze the characteristics of the yellow insulation ring type of the CSST used for tubing when it is artificially deteriorated and damaged by burning. The CSST for tubing consists of a tube, protective coating, nut, yellow insulation ring, packing, and socket. In addition, it is thought that a yellow insulation ring and rubber packing were used to connect the tube and socket in order to improve the airtightness and insulation performance. The result of the verification of the data acquired from the tests in the 95% confidence interval shows that the Anderson-Darling (AD) and P value were analyzed to be 0.945 and 0.015, respectively. This confirms that the test data of the CSST for tubing is reliable. The analysis of the arithmetic mean of the insulation resistance of a CSST showed that the CSST damaged by burning by a torch, and the one damaged by electrical burning, was $16.7k{\Omega}$ (the greatest relatively) and $208{\Omega}$ (the lowest), respectively, while it was $1.72k{\Omega}$ in the case of a normal product. Therefore, the analysis result of the insulation resistance of the CSST collected from the scene of a fire can be utilized to examine the cause of damage by burning. In addition, it was found that when the maximum current of 97 A was applied to the CSST for about 5 s using a Primary Current Injection Test System (PCITS) the protective film and insulation ring of the CSST has no difference from that of a normal product. However, a part of the metal tube was melted.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.129-137
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• 2009

Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.

• Clean Technology
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• v.27 no.2
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• pp.132-138
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• 2021

Research is being conducted on graphene to provide graphene having both excellent physical as well as electrical properties in addition to unique physical properties. In this study, Hummer's method, which is a representative method for chemical exfoliation, was applied in order to investigate the possibility of the mass production of high-quality graphene oxide. Three types of graphite (graphite, crystalline graphite, and expanded graphite) were used in the preparation of graphene oxide with variations in the amount of potassium permanganate added, reaction temperature, and reaction time. Then a Fourier transform infrared spectroscopy (FT-IR), a Raman spectrometer, and a transmission electron microscope (TEM) were used to measure the quality of the prepared graphene oxide. Of the three types of graphite used in this experiment, crystalline graphite showed the highest quality. The prepared graphene oxide was then purified with an organic solvent, and an analysis conducted using energy dispersive X-ray spectroscopy (EDS). From the results of the residual values, we were able to confirm that both acid wastewater and wastewater were best purified using cyclohexane. The method for manufacturing graphene oxide as well as the method of purification using organic solvents that are presented in this study are expected to have less of an environmental impact, making them environmentally friendly. This makes them suitable for use in various industrial fields such as the film industry and for heat dissipation and as coating agents.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.29-34
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• 2022

A fabrication process of smart windows with controllable visible light transmittance by using retardation films is proposed. The 𝛌/4-phase retardation films that can convert a linearly polarized light into circularly polarized light are achieved through photo-alignment layers and reactive mesogen (RM) coating process. Two sheets of the fabricated retardation films with different orientation angles induced to light transmission mode (45°/-45°) and light blocking mode (45°/45°) for visible wavelength. We evaluated retardation characteristics according to the thickness of the birefringent RM material and found out the optimal condition for the film with 𝚫n·d of 𝛌/4-phase. The proposed structure of the smart window exhibited the light blocking ratio improved by more than 20% in the visible wavelength (380 nm to 780 nm). Finally, it was confirmed that the feasibility of the window structure by applying to a prototype for a smart window with a size of 150 × 150 mm².

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.1-7
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• 2002

To study the increased resistance in fish against Vibrio vulnificus known as an important agent of vibrio septicemia in human, we analyzed specific and nonspecific immune response in flounder after administration of V. vulnificus bacterins by oral route. It contained the comparison of antibody concentrations in the sera of flounder after oral administration by two different protocols with uncoated heat killed bacterin of V vulnificus (UHKB, 20 mg/kg body weight), i.e., 4 weeks continuously (group 4W) and taking 2 weeks resting period between the 1st and last week of administration (group 1-2-1W). Even though, 1-2-1W group showed significantly increased level of specific antibody in serum, it did not reach to that of 4W group. Certainly, flounder vaccinated twice a week for four weeks (20 mg/kg b.w.) showed increased concentration of specific antibody against V. vulnificus at week 2 after last administration by oral route and maintained throughout the experimental period. It also was confirmed by the increased numbers of specific antibody secreting cells (SASC) in the leukocytes isolated from the splenocytes of the flounder of 4W group at week 1 after last administration until the end of experimental period. However, enteric, acid-resistant film coated heat killed bacterin (ECHB) did not show both greater immune reaction for antibody production and faster elimination of a challenge dose of V. vulnificus compared with those of the UHKB. These results suggested that UHKB administered by oral route was very effective method to prevent the contamination of V vulnificus in flounder, and did not show the increased antigenicity by coating the surface with acid-resistant film.