• 한국재료학회지
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• 제27권8호
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• pp.403-408
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• 2017

We investigated the effect of ZnO buffer layer on the formation of ZnO thin film by ultrasonic assisted spray pyrolysis deposition. ZnO buffer layer was formed by wet solution method, which was repeated several times. Structural and optical properties of the ZnO thin films deposited on the ZnO buffer layers with various cycles and at various temperatures were investigated by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence spectrum analysis. The structural investigations showed that three-dimensional island shaped ZnO was formed on the bare Si substrate without buffer layers, while two-dimensional ZnO thin film was deposited on the ZnO buffer layers. In addition, structural and optical investigations showed that the crystalline quality of ZnO thin film was improved by introducing the buffer layers. This improvement was attributed to the modulation of the surface energy of the Si surface by the ZnO buffer layer, which finally resulted in a modification of the growth mode from three to two-dimensional.

• 한국전기전자재료학회논문지
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• 제14권10호
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• pp.828-834
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• 2001

Zinc oxide (ZnO) films deposited on indium (In) films were post-annealed in a rapid thermal anealing (RTA) system. The ZnO/In films were RTA-treated in air or a vacuum ambient. The crystallographic properties and surface morphologies of the films were studied before and after the RTA by X-ray diffraction(XRD) and scanning electron microscopy (SEM), respectively. The resistivity variation of the films with RTA temperature and time was measured by the 4-point probe method. Auger electron spectroscopy (AES) was carried out to figure out the redistribution of indium atoms in the ZnO films. The resistivity of the ZnO/In films decreased to 2$\times$10$\^$-3/ Ωcm by diffusion of the In. The In diffusion into the ZnO films roughened the surface of ZnO films. The results of depth profile by AES showed a hump of In atoms around ZnO/In interface after the RTA at 800 $\^{C}$. The effects of temperature time and ambient during the RTA on the structural and electrical properties of the ZnO/In films were discussed.

• 한국분말재료학회지
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• 제17권4호
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• pp.263-269
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• 2010

Hexagonal barium ferrite ($BaFe_{12}O_{19}$) nano-particles have been successfully fabricated by spraypylorysis process. $BaFe_{12}O_{19}$ precursor solutions were synthesized by self-assembly method. Diethyleneamine (DEA) surfactant was used to fabricate the micelle structure of Ba-DEA complex under various DEA concentrations. $BaFe_{12}O_{19}$ powders were synthesized with addition of Fe ions to Ba-DEA complex and then fabricated $BaFe_{12}O_{19}$ powders by spray-pyrolysis process at the temperature range of $800{\sim}1000^{\circ}C$. The molar ratio of Ba/DEA and heat-treatment temperatures significantly affected the magnetic properties and morphology of $BaFe_{12}O_{19}$ powders. $BaFe_{12}O_{19}$ powders synthesized with Ba/DEA molar ratio of 1 and heat-treated at $900^{\circ}C$ showed the coercive forces (iHc) of 4.2 kOe with average crystal size of about 100 nm.

• 센서학회지
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• 제5권3호
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• pp.41-48
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• 1996

SOx 가스를 고감도로 감지할 수 있는 SAW 가스 센서를 개발하였다. 이는 SAW device 위에 SOx 가스에 감응하는 재료를 박막으로 증착함으로써 고감도의 마이크로 센서형으로 한 것이다. SOx 감응 재료로서 CdS를 선정하였으며, 이를 SAW device 위에 박막화하기 위해 초음파 분무 노즐을 이용한 분무 열분해의 박막 증착공정을 응용하였다. 초음파 분무 노즐을 통하여 생성된 균일하고 미세한 입자들은 기판위에서 안정한 열분해 환경을 조성함으로써 센서 감응막을 위한 넓은 표면적의 박막을 증착 시켰는데 기판의 온도는 $300^{\circ}C$ 내외에서 최소 50 nm수준의 결정립의 박막을 얻었다. 이렇게 하여 얻은 SAW 가스 센서는 $SO_{2}$ 가스에 감응하였으며 재현성도 보였다. 다른 가스의 존재하에서 $SO_{2}$ 가스에 대한 선택성에 관하여는 계속적인 연구가 필요하다.

• 한국재료학회지
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• 제10권3호
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• pp.204-211
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• 2000

초음파 분무법으로 $(Y,Gd)BO_3:Eu$의 PDP 적색 형광체를 제조하여 147nm VUV 여기에 따른 발광 특성을 분석하였다. 초음파 분무에 사용된 전구체 용액은 Y, Gd, Eu의 아세트산염과 $H_3BO_3$를 증류수에 용해하여 1.7MHz의 초음파 분무기로 고온의 반응관내로 분무하였다. 분무된 액적은 반응관내에서 통과시 불충분한 반응으로 C-C와 C-H를 함유한 비정질 상이었으나, $1100^{\circ}C$에서 추가 열처리 한 시편은 고상반응법으로 제조한 형광체와 동일한 결정구조와 성분을 보였다. 고상반응법으로 제조한 형광체의 분말 크기는 $3{\mu\textrm{m}}$으로 조대하고 불균일한 분포를 보인 반면, $500^{\circ}C$에서 분무한 후 $900^{\circ}C$에서 열처리하여 제조한 $(Y_{0.7}Gd_{0.3})_{0.95}BO_3:Eu_{0.05}\;^{3+}$ 형광체의 모양은 비교적 구형이었으며 평균 입자크기는 $0.7{\mu\textrm{m}}$로 미세하고 균일한 분포를 하고 있었다. 147nm VUV 여기시 초음파 분무로 제조한 $(Y_{0.7}Gd_{0.3})_{0.95}BO_3:Eu_{0.05}\;^{3+}$ 형광체의 적색 발광강도는 고상반응법으로 제조한 시편이나 상용품인 $(Y,Gd)BO_3:Eu$ 형광체에 비해 그 휘도가 증가되었다.

• 한국세라믹학회지
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• 제44권12호
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• pp.690-695
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• 2007

Scandia stabilized zirconia (ScSZ) is adapted for electrolyte material of solid oxide fuel cell (SOFC) because of its high ionic conductivity and chemical stability. ScMnSZ1 powder having a composition of $((ZrO_2)_{0.89}(Sc_2O_3)_{0.1}(MnO_2)_{0.01})$ is synthesized by ultrasonic spray pyrolysis (USP) method. Porous ScMnSZ1 powder is obtained by using a pore forming agent. Microstructure and morphology, particle size distribution of porous powder synthesized with 3wt% pore forming agent are investigated. Sintered ScMnSZ1 sample with ground fine powder are also investigated their microstructure and electrical conductivity. The electrical conductivity of sintered ScMnSZ1 samples with ground fine powder was 0.082 S/cm, 0.127 S/cm and 0.249 S/cm at $750^{\circ}C$, $800^{\circ}C$ and $900^{\circ}C$, respectively.

• 한국결정성장학회지
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• 제1권2호
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• pp.46-58
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• 1991

$Zn(NO_3)_2\cdot6H_2O$ 를 사용하여 출발용액으로 $Zn(NO_3)_2\cdot6H_2O$(aq.)용액을 각각 1M, 0.5M, 0.25M, 0.1M의 농도로 제조하여 초음파 진동자에 의해 액적을 발생시킨후, 2.3cm/sec의 유속으로 건조 및 열분해하여 ZnO분말을 합성하였다. 이때 건조 온도는 $200^{\circ}C$, 열분해 온도는 $600^{\circ}C$였다. 제조된 ZnO분말의 열적특성을 TG-DTA로 측정하였고, IR로 미분해물 및 흡착 가스의 성분을 조사하였다. 결정상 및 crystallite의 크기를 XRD로 분석하였고, 입자의 형태는 SEM과 TEM으로 관찰한 후 입자 크기와 입도분포를 SEM 사진으로부터 측정하였다. 합성 분말은 hexagonal의 결정구조를 갖는 Zinc oxide였다. 입자의 형태는 대부분 구형이고, 약 40nm 크기의 일차입자로 구성된 이차입자였다. 평규 입자 크기는 $0.28-0.61{\mu}m$ 이고 입도 분포도 좁았다.

• 한국분말재료학회지
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• 제25권1호
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• pp.1-6
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• 2018

Uniform $TiO_2$ blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating $TiO_2$ BLs of 0, 40, 70, and 100 nm, respectively, in average thickness on fluorine-doped tin oxide (FTO) glass. Compared to the other samples, the DSSC containing the uniform $TiO_2$ BL of 70 nm in thickness shows a superior power conversion efficiency of $7.58{\pm}0.20%$ because of the suppression of electron recombination by the effect of the optimized thickness. The performance improvement is mainly attributed to the increased open-circuit voltage ($0.77{\pm}0.02V$) achieved by the increased Fermi energy levels of the working electrodes and the improved short-circuit current density ($15.67{\pm}0.43mA/cm^2$) by efficient electron transfer pathways. Therefore, optimized $TiO_2$ BLs fabricated by USPD may allow performance improvements in DSSCs.

• 한국결정성장학회지
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• 제2권2호
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• pp.11-19
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• 1992

$SrTiO_3$미분말은 초음파 분무 열분해법으로 chloride와 nitrate 수용액을 출발용액으로 사용하여 농도를 0.05M과 0.1M로 하였으며 각 농도에 따른 유속의 변화를 0.5cm/sec로 변화시켜 합성하였다. 분말의 형성 과정은 0.05M, 0.05cm/sec 조건에서 단계별 분말을 합성하여 주로 morphorlogy 측면에서 고찰하였다. 출발용액이 chloride 수용액인 경우 SrTiO$_3$미분말을 합성할 수 없었으며 nitrate 수용액인 경우 모든 조건에서 (110)면을 주 peak로 하는 cubic의 순수한 구형의 $SrTiO_3$미분말을 얻을 수 있었다. 평균입자의 크기는 유속이 증가함에 따라 $0.49{\mu}m$에서 $0.55{\mu}m$로 증가하였다. 출발액적의 크기는 $14.3{\mu}m$이었으며 단계별 입자의 형태는 1, 2단계에서 용매의 증발에 의해 매우 porous하였으며 불규칙하였고, 3, 4, 5단계를 지나는 동안 점차 둥근 형태로 형성되었다.

• 한국재료학회지
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• 제29권5호
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• pp.328-335
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• 2019

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).