• 한국세라믹학회지
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• 제28권1호
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• pp.11-18
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• 1991

A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics, and the effects of stress-induced phase transformation of ZrO2 on thermal shock behavior of Al2O3-ZrO2 ceramics were investigated. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent. Metal hydroxides were obtained by single precipitation(process A) and co-precipitation(process B) method at the condition of pH=7, and the composition of Al2O3-ZrO2 composites was fixed as Al2O3-15v/o ZrO2(+3m/o Y2O3). Critical temperature difference showing rapid strength degradation by thermal shock showed higher value in Al2O3/ZrO2 composites(process A : 20$0^{\circ}C$, process B : 215$^{\circ}C$) than in Al2O3(175$^{\circ}C$). The improvement of thermal shock property for Al2O3/ZrO2 composites was mainly due to the increase of strength at room temperature by adding ZrO2. The strength degradation was more severe for the sample with higher strength at room temperature. Crack initiation energies by thermal shock showed higher values in Al2O3/ZrO2 composites than in Al2O3 ceramics due to increase of fracture toughness by ZrO2.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.11-11
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• 2008

ZnO has a very large exciton binding energy (60 meV) as well as thermal and chemical stability, which are expected to allow efficient excitonic emission, even at room temperature. ZnO based electronic devices have attracted increasing interest as the backplanes for applications in the next-generation displays, such as active-matrix liquid crystal displays (AMLCDs) and active-matrix organic light emitting diodes (AMOLEDs), and in solid state lighting systems as a substitution for GaN based light emitting diodes (LEDs). Most of these electronic devices employ the electrical behavior of n-type semiconducting active oxides due to the difficulty in obtaining a p-type film with long-term stability and high performance. p-type ZnO films can be produced by substituting group V elements (N, P, and As) for the O sites or group I elements (Li, Na, and K) for Zn sites. However, the achievement of p-type ZnO is a difficult task due to self-compensation induced from intrinsic donor defects, such as O vacancies (Vo) and Zn interstitials ($Zn_i$), or an unintentional extrinsic donor such as H. Phosphorus (P) doped ZnO thin films were grown on c-sapphire substrates by radio frequency magnetron sputtering with various Ar/ $O_2$ gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio with out post-annealing. The P-doped ZnO films grown at a Ar/ $O_2$ ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of $10^{-17}cm^{-3}$ and $2.5cm^2/V{\cdot}s$, respectively. X-ray diffraction showed that the ZnO (0002) peak shifted to lower angle due to the positioning of $p^{3-}$ ions with a smaller ionic radius in the $O^{2-}$ sites. This indicates that a p-type mechanism was due to the substitutional Po. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/n-Si heterojunction LEO showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission.

• 한국진공학회지
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• 제9권2호
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• pp.150-154
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• 2000

Impurity-free vacancy diffusion 방법을 이용하여 압축 응력을 가진 InGaAs/InGaAsP 다중 양자 우물 구조에서 열처리 온도에 따른 무질서 정도를 조사하였다. InGaAs/SiO$_2$ cap 구조가 InP/$SiO_2$ cap 구조보다 급속열처리 (rapid thermal annealing : RTA) 과정에서 더 많은 청색 천이를 나타내었다. 열처리 온도 $700^{\circ}C$에서, InGaAs/$SiO_2$ cap 구조의 경우 다중양자우물의 밴드갭 파장은 1.55 $\mu\textrm{m}$대역에서 1.3 $\mu\textrm{m}$ 대역으로 이동하였으며, InGaAs/$SiO_2$ cap 구조와 InP/$SiO_2$ cap 구조의 밴드갭 파장차이는 195 nm (123 meV)로 높은 선택성을 나타내었다. 또한, DCXRD 스펙트럼으로부터 다중양자우물 구조에서 균일한 합금형태로 완전히 무질서화되는 것을 볼 수 있었다.

• Advances in materials Research
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• 제1권2호
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• pp.161-168
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• 2012

Nanoflake composite multi core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole was synthesized by in situ polymerization method. In this paper, the fabrication of $SrFe_{12}O_{19}$ nanoflake is as first core by solgel method. Then fabricated a shell layer from magnetic nanoparticles of $Fe_3O_4$, which synthesized by coprecipitation technique, onto the $SrFe_{12}O_{19}$ nanoflake. Polyethylene glycol (PEG) as a polymer layer and as second shell was coated onto the before core-shell. Than core-shell $SrFe_{12}O_{19}/Fe_3O_4$/PEG was used as template for the preparation of $SrFe_{12}O_{19}/Fe_3O_4$/PEG/Polypyrrole composite. Final composite has a conductive property among $4.23{\times}10^{-2}Scm^{-1}$ and magnetic property about $M_s$=2.99 emu/g. Also final composite in soluble at organic solvent such as DMF and DMSO and has a flake structure. Conductivity and magnetic property respectively determine by four-probe instrument and vibrant sample magnetometer (VSM), morphology and article size determined by FE-SEM, TEM and XRD.

• 전자공학회논문지 IE
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• 제43권2호
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• pp.7-10
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• 2006

일반적인 산화 절연 게이트 대신 $BaTa_2O_6$를 사용한 GaN metal-insulator-semiconductor(MIS) 구조를 제작하였다. $Al_2O_3$(0001) 기판 위에서와 GaAs(001) 기판 위에서의 GaN 막의 누설 전류는 각각 $10^{-12}-10^{-13}A/cm^2$와 $10^{-6}-10^{-7}A/cm^2$로 측정되었다. 이 막의 누설전류는 각각 $Al_2O_3$(0001) 기판 위의 GaN인 경우는 45 MV/cm가 넘는 공간전하 제한전류에 의하여, GaAs(001) 기판 위의 GaN인 경우는 Poole-Frenkel 방출에 따른다는 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제30권12호
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• pp.762-767
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• 2017

Mullite ($3Al_2O_3{\cdot}2SiO_2$) has emerged as a promising candidate for high-temperature structural materials due to its erosion resistance, chemical and thermal stabilities, relatively low thermal expansion coefficient, excellent thermal shock and creep resistances, and low dielectric constant. However, since the pure mullite sintering temperature is as high as $1,600{\sim}1,700^{\circ}C$, there is an increasing need for a sintering additive capable of improving the strength characteristics while lowering the sintering temperature. Herein we have tried to obtain the optimal sintering additive composition by adding MgO, $Cr_2O_3$, and $Y_2O_3$ to mullite, followed by sintering at $1,325{\sim}1,550^{\circ}C$ for 2 h. With additives of 2 wt% of MgO, 2 wt% of $Cr_2O_3$, 4 wt% of $Y_2O_3$, A density of $3.23g/cm^3$ was obtained for the sintered body at $1,350^{\circ}C$ upon using 2 wt% MgO, 2 wt% $Cr_2O_3$, and 4 wt% $Y_2O_3$ as additives. The three-point flexural strength of that was 275 MPa and the coefficient of thermal expansion (CTE) was $4.15ppm/^{\circ}C$.

• 한국조리학회지
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• 제23권7호
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• pp.97-111
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• 2017

As a single-person household emerges as an important consumer group, an Online-to-Offline or Offlineto-Online(O2O) service market is rapidly growing. This study attempted to verify the effects of convenience and webrooming characteristics of O2O service using the Technology Acceptance Model (TAM). The purpose of this study was to investigate the effects of the convenience and webrooming of food O2O service on users' perceived ease of use and perceived usefulness, and the effects of perceived ease of use and perceived usefulness on purchase intention of O2O services. Using a convenience sampling technique, an online survey was conducted through Google survey from April 16 to April 30, 2017 and was distributed to 447 O2O service users. A total of 320 questionnaires were included in the final analysis. The results showed that convenience had a significant effect on users' perceived ease of use as well as perceived usefulness. In addition, users' perceived ease of use had a significant impact on users' perceived usefulness. Finally, both perceived ease of use and perceived usefulness positively affected users' purchase intention of O2O services. These findings suggest that differentiated events, promotions, and store information should be provided when launching O2O service because webrooming is a more important factor in enhancing perceived usefulness than the perceived ease of use.

• 한국진공학회지
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• 제9권3호
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• pp.263-266
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• 2000

본 논문에서는 낮은 구동 전압에서 동작하고 안정된 on/off 상태를 갖는 Al/$TiO_2-SiO_2$/Mo 형태의 안티퓨즈를 제작하였다. 하부전극으로 사용된 Mo 금속은 표면상태가 부드럽고 녹는점이 높은 매우 안정된 금속으로, 표면 위에 제조된 $SiO_2$ 특성을 매우 안정되게 유지시켰다. 또한 $TiO_2$절연막을 $SiO_2$절연막 위에 복층 구조로 증착하여, Ti 금속의 침투로 인한 $SiO_2$ 절연막의 약화로 동일 두께(100 $\AA$)의 $SiO_2$, 단일막에 비하여 향상된 절연파괴 전압을 얻을 수 있었다. $TiO_2-SiO_2$ 이중절연막을 사용하여 적정 절연파괴전압 및 ON-저항을 구현하였으며, 두께가 두꺼워짐으로 인해 바닥금속의 거칠기의 영향을 최소화시킬 수 있었다. 이중 절연막의 두께는 250 $\AA$이고 프로그래밍 전압은 9.0 V이고 약 65 $\Omega$의 on 저항을 얻을 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.54-54
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• 2010

Zinc oxide is metal oxide semiconductor with the 3.37 eV bandgap energy. Zinc oxide is very attractive materials for many application fields. Zinc Oxide has many advantages such as high conductivity and good transmittance in visible region. Also it is cheaper than other semiconductor materials such as indium tin oxide (ITO). Therefore, ZnO is alternative material for ITO. ZnO is attracting attention for its application to transparent conductive oxide (TCO) films, surface acoustic wave (SAW), films bulk acoustic resonator (FBAR), piezoelectric materials, gas-sensing, solar cells and photocatalyst. In this study, we synthesized ZnO nanoparticles and defined their physical and chemical properties. Also we studied about the application of ZnO nanoparticles as a photocatalyst and try to find a enhancement photocatalytic activity of ZnO nanorticles.. We synthesized ZnO nanoparticles using spray-pyrolysis method and defined the physical and optical properties of ZnO nanoparticles in experiment I. When the ZnO are exposed to UV light, reduction and oxidation(REDOX) reaction will occur on the ZnO surface and generate ${O_2}^-$ and OH radicals. These powerful oxidizing agents are proven to be effective in decomposition of the harmful organic materials and convert them into $CO_2$ and $H_2O$. Therefore, we investigated that the photocatalytic activity was increased through the surface modification of synthesized ZnO nanoparticles. In experiment II, we studied on the stability of ZnO nanoparticles in water. It is well known that ZnO is unstable in water in comparison with $TiO_2$. $Zn(OH)_2$ was formed at the ZnO surface and ZnO become inactive as a photocatalyst when ZnO is present in the solution. Therefore, we prepared synthesized ZnO nanoparticles that were immersed in the water and dried in the oven. After that, we measured photocatalytic activities of prepared samples and find the cause of their photocatalytic activity changes.

• 한국세라믹학회지
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• 제33권8호
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• pp.928-934
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• 1996

X-선 형광분석법을 사용하여 표준검정곡선법으로 시멘트 중의 주, 부성분들을 정량하고 습식법과 분석결과를 비교하였다. 이때, 표준시료 및 미지시료는 용융 케스트 비드법으로 준비하였다. 표준시멘트(227A372)의 오차분석결과 주성분인 CaO, SiO2, Al2O3, Fe2O3 및 부성분중의 MgO, SrO는 상대오차가 1% 이내이었으며, 부성분중 So3, K2O, TiO2, Na2O P2O5 및 Mn2O3는 5% 이하의 상대오차를 가졌다. 부성분의 상대오차는 시료준비오차가 가장 큰 부분을 차지하였다. X-선 형광분석과 습식분석을 비교한 결과 시멘트 분석의 측정값간의 최대혀용범위를 만족하므로, X-선 형광분석법을 시멘트 화학분석에 적용할 수 있을 것으로 판단된다. 그리고, 기존의 습식법으로 분석하기 어려운 시멘트내에 존재하는 미량성분인 P2O5, SrO 및 Mn2O3 의 정밀정확한 분석 또한 가능하였다.