• 한국자기학회지
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• 제18권2호
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• pp.58-62
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• 2008

칩인덕터용 $Ni_{0.4}Zn_{0.4}Cu_{0.2}Fe_2O_4$ ferrite(NiZnCu ferrite)를 고상반응법 및 졸겔법으로 제조하였다. 고상반응법에 의해 제조된 마이크론크기의 NiZnCu ferrite 분말과 졸겔법에 의해 제조된 나노크기의 분말을 혼합하여 소결성 및 자기적 특성을 증가 시켰다. 나노크기의 분말을 20wt%첨가한 토로이달 코아 시편의 초투자율은 1 MHz에서 $880^{\circ}C$ 소결시 78.1에서 $920^{\circ}C$ 소결시 178.2의 값을 가졌으며 소결온도가 증가할수록 초투자율값이 증가하였다. 소결 밀도, 수축율 및 포화자화값도 소결온도가 증가함에 따라 증가하였으며 이것은 grain사이즈 효과 및 소결성이 증가 되었기 때문이다. 고상반응법에 의해 제조한 ferrite에 졸겔법에 의해 제조한 나노크기의 ferrite 분말을 혼합하여 소결성을 향상시키고 자기적 특성을 향상시킬 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.420-420
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• 2012

ZnO seed layer were deposited on quartz substrate by sol-gel method and prism-like Al-doped ZnO nanorods (AZO nanorods) were grown on ZnO seed layer by hydrothermal method with various Al concentration ranging from 0 to 2.0 at.%. Structural and optical properties of the AZO nanorods were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL). The diameter of the AZO nanorods was smaller than undoped ZnO nanorods and its diameter of the AZO nanorods decreased with increasing Al concentration. In XRD spectrum, it was observed that stress and full width at half maximum (FWHM) of the AZO nanorods decreased and the 'c' lattice constant increased as the Al concentration increased. From undoped ZnO nanorods, it was observed that the green-red emission peak of deep-level emission (DLE) in PL spectra. However, after Al doping, not only a broad green emission peak but also a blue emission peak of DLE were observed.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.64-68
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• 2012

We have successfully demonstrated a bandgap alteration of transparent zinc oxide (ZnO) thin film with Mg dopant by using sol-gel spin coating technique. By increasing the dopant from 0 to 30 atomic percent (at.%), a decrement value in the cutoff is observed, where the absorption edge shifts continuously to the shorter wavelength side, towards 300 nm. This resulted in a significant bandgap increment from 3.28 to 3.57 eV. However, the transmittance of the thin film at 350-800 nm gradually downgraded, from 93 to 80 % which is most probably due to the grain size that becomes bigger, and it also affected the electrical properties. The decrement from 45 to 0.05 mA at +10 V was observed in the I-V characteristics, concluding the significant relationship; where higher optical bandgap materials will exhibit lower conductivity. These findings may be useful in optoelectronics devices.

• Environmental Engineering Research
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• 제19권3호
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• pp.205-214
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• 2014

Petroleum a vital commodity affecting every aspect of 21st century. Toxicity and adverse effects of sulphur as catalyst in petroleum products is of great concern required development of techniques for desulphurization in compliance with the International standards. Installation of desulphurizing units costs over $200 million per unit placing economic burden on developing countries like Pakistan. Present study analysis of commercial fuels (station petrol and jet fuel JP8) on gas chromatography-mass spectrometry (GC-MS) identified sulphur concentration of 19.94 mg/L and 21.75 mg/L, respectively. This scenario urged the researcher to attempt synthesis of material that is likely to offer good adsorption capacity for sulphur. Following protocol of sol-gel method, transition metals (Ni, Cu, Zn) solution is gelated with tetraethoxysilane (TEOS; silica precursor) using glycerol. Fourier transform infrared spectroscopy (FTIR) spectra revealed bonding of Zn-O, Cu-O, and Ni-O by stretching vibrations at $468cm^{-1}$, $617cm^{-1}$, and $468cm^{-1}$, respectively. Thiophene and Benzothiophene mixed in n-heptane and benzene (4:1) for preparation of Model Fuels I and II, respectively. Each of silica based metal was applied as adsorbent in batch mode to assess the removal efficiency. Results demonstrated optimal desulphurization of more than 90% following efficacy order as Si-Ni > Si-Zn > Si-Cu based adsorbents. Proposed multilayered (Freundlich) adsorption mechanism follows ${\pi}$-complexation with pseudo secnd order kinetics.

• 한국재료학회지
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• 제18권11호
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• pp.628-633
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• 2008

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of $C_2H_5OH$, $CH_3COCH_3$, $H_2$, $C_3H_8$, 100 ppm of CO, and 5 ppm of $NO_2$) were measured at $300\;{\sim}\;400^{\circ}C$. The prepared ZnO nanopowders showed high gas responses to $C_2H_5OH$ and $CH_3COCH_3$ at $400^{\circ}C$. The sensing materials prepared at the compositions of [$ZnCl_2$]:[$N_2H_4$]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses ($S\;=\;R_a/R_g,\;R_a$ : resistance in air, $R_g$ : resistance in gas) to 200 ppm of $C_2H_5OH$($S\;=\;102.8{\sim}160.7$) and 200 ppm of $CH_3COCH_3$($S\;= 72.6{\sim}166.2$), while they showed low gas responses to $H_2$, $C_3H_8$, CO, and $NO_2$. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.

• 한국진공학회지
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• 제19권6호
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• pp.483-488
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• 2010

스핀코팅 방법을 이용하여 다양한 농도의 전구체로 ZnO 나노 섬유질 박막(ZnO nano-fibrous thin films)을 성장하였고, 그에 따른 표면 및 광학적 특성 변화를 scanning electron microscopy (SEM)와 photoluminescence (PL)을 이용하여 측정하였다. 전구체 농도가 0.4 mol (M) 이하 일 때는 성장률이 낮아 ZnO 핵생성만이 되었고, 0.6 M 이상일 때 ZnO 박막은 나노섬유질 구조가 되었다. 전구체 농도가 더욱 증가함에 따라 ZnO 나노 섬유질의 굵기가 굵어졌고 ZnO 박막의 두께도 단계적으로 두꺼워졌다. 전구체 농도가 증가함에 따라 ZnO 나노 섬유질 박막의 photoluminescence (PL)의 근밴드가장자리 광방출(near-band-edge emission) 피크 세기와 full-width at half-maximu (FWHM)이 증가하였고, 깊은 준위 광방출(deep-level mission) 피크는 적색편이(red-shift)하였다.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.45-50
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• 2015

Glycine-nitrate와 citric acid를 이용하여 단상의 Ni-Zn ferrite, Ba-ferrite 나노입자와 두 나노복합체 ferrite의 전구체를 제조하고 이를 열처리하여 XRD 및 FT-IR로 각각의 상 분석을, SEM으로 분말의 형상과 크기를, VSM으로 자기적 특성과 합성된 나노복합체 ferrite에서의 exchange-coupling 상호작용을 확인하였다. XRD 분석 결과, 자전 연소법으로 얻은 전구체로 단상의 Ni-Zn ferrite와 Ba-ferrite 나노 입자 및 $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ 나노복합체 페라이트가 합성되었으며, 나노복합체에는 $BaFe_{12}O_{19}$와 $Ni_{0.5}Zn_{0.5}Fe_2O_4$가 잘 분포되어 있어 경자성과 연자성이 공존하고 있음을 확인하였고, 나노복합체 페라이트의 히스테리시스 곡선의 형상을 통해 경자성과 연자성 사이에 exchange-copuling이 잘 이루어졌음을 확인할 수 있었다. VSM으로 측정한 나노복합체의 경우. GNP로 제조한 precursor를 $900^{\circ}C$에서 하소한 $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ 나노복합체는 포화자화 81.69 emu/g, 잔류자화 38 emu/g, 보자력 2598.48G를 나타내었다. $Ni_{0.5}Zn_{0.5}Fe_2O_4/BaFe_{12}O_{19}$ 복합체에서 $BaFe_{12}O_{19}$의 무게비가 증가 할수록 보자력은 증가하였고, 포화자화값과 잔류자화 값은 감소하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.200-200
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• 2010

In recent times, metal oxide semiconductors thin films transistor (TFT), such as zinc and indium based oxide TFTs, have attracted considerable attention because of their several advantageous electrical and optical properties. There are many deposition methods for fabrication of ZnO-based materials such as chemical vapor deposition, RF/DC sputtering and pulsed laser deposition. However, these vacuum process require expensive equipment and result in high manufacturing costs. Also, the methods is difficult to fabricate various multicomponent oxide semiconductor. Recently, several groups report solution processed metal oxide TFTs for low cost and non vacuum process. In this study, we have newly developed solution-processed TFTs based on Ti-related multi-component transparent oxide, i. e., InTiO as the active layer. We propose new multicomponent oxide, Titanium indium oxide(TiInO), to fabricate the high performance TFT through the sol-gel method. We investigated the influence of relative compositions of Ti on the electrical properties. Indium nitrate hydrate [$In(NO^3).xH_2O$] and Titanium isobutoxide [$C_{16}H_{36}O_4Ti$] were dissolved in acetylacetone. Then monoethanolamine (MEA) and acetic acid ($CH_3COOH$) were added to the solution. The molar concentration of indium was kept as 0.1 mol concentration and the amount of Ti was varied according to weighting percent (0, 5, 10%). The complex solutions become clear and homogeneous after stirring for 24 hours. Heavily boron (p+) doped Si wafer with 100nm thermally grown $SiO_2$ serve as the gate and gate dielectric of the TFT, respectively. TiInO thin films were deposited using the sol-gel solution by the spin-coating method. After coating, the films annealed in a tube furnace at $500^{\circ}C$ for 1hour under oxygen ambient. The 5% Ti-doped InO TFT had a field-effect mobility $1.15cm^2/V{\cdot}S$, a threshold voltage of 4.73 V, an on/off current ratio grater than $10^7$, and a subthreshold slop of 0.49 V/dec. The 10% Ti-doped InO TFT had a field-effect mobility $1.03\;cm^2/V{\cdot}S$, a threshold voltage of 1.87 V, an on/off current ration grater than $10^7$, and a subthreshold slop of 0.67 V/dec.

• 마이크로전자및패키징학회지
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• 제2권1호
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• pp.49-58
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• 1995

출발물질은 cordierite 유리와 borosilicate/Si3N4 복합분말을 사용하였다. Cordierite 유리조성은 무게비로 17.8MgO-23.1Al2O3-48.1ASiO2-5.0ZnO-1.0B2O3를 선택하였다. Borosilicate/Si3N4복합분말은 sol-gel법으로 a-si3N4 core 분말에 borosilicate 겔을 코팅하여 얻었다. 복합분말과 cordierite 유리 분말을 부피비로 0/100, 12.5/87.5 및 25/75의 조성으로 혼합하여 tape casting 에 의해 green sheet를 제작하였다. 이들 sheet들을 800~100$0^{\circ}C$에서 2시간 소성하여 얻은 시편을 SEM, XRD, 밀도, 유전상수 등을 측정하여 저 유전율의 저온 소성 기판재료를 제조하기 위한 조건들을 검토하였다.

• 한국안광학회지
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• 제13권1호
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• pp.71-76
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• 2008

목적: 저온에서 열처리에 의해 소다-라임-실리카 유리 위에 강한 UV방사 나노결정 ZnO박막을 단순하고 효율적 방법으로 개선하고자 한다. 방법: 소다-라임-실리카 유리 위에 코팅되고 전열처리 및 300$^{\circ}C$의 후열처리를 행하여 제조된 나노 결정질 ZnO 박막의 결정 구조적, 표면 형상적 및 광학적 특성을 X-선 회절 분석, 전계방사 주사형 전자 현미경, 원자간력 현미경, ultra violet - visible - near infrared spectrophotometer 및 photoluminescence를 이용하여 분석하였다. 결과: 가시광 영역에서 높은 투과율과 자외부에서 뚜렷한 흡수밴드를 갖는 c-축으로 고배향된 ZnO 박막을 300$^{\circ}C$의 후열처리를 통하여 얻을 수 있었다. 비교적 뚜렷한 near band edge 발광을 보이는 photoluminescence 스펙트럼이 나타났으며, 결함에 의한 완만한 녹색 발광은 거의 관찰되지 않았다. 결론: 앞으로 본 연구는 300$^{\circ}C$ 이하의 저온에서 저렴하고 쉽게 ZnO을 기초로한 광전기 소자에 적용될 것이다.