• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.114.1-114.1
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• 2010

Fe계 촉매는 FT(Fischer-Tropsch) 합성반응에 매우 유망한 촉매로 주목받고 있으며, $280^{\circ}C$ 미만의 저온 FT 합성반응의 경우, 침전법이 Fe계 촉매의 가장 전형적인 제조방법으로 알려져 있다. Fe계 촉매에 첨가되는 조촉매로는 Cu, K, $SiO_2$ 등이 가장 대표적이며, 이 중에서 특히 구조 조촉매로 첨가되는 $SiO_2$는 Fe계 촉매의 기계적 강도를 향상시킬 뿐만 아니라, 촉매의 성능에도 크게 영향을 미치는 것으로 보고되고 있다. 본 연구에서는 침전법을 이용하여 저온 FT 합성반응용 Fe계 촉매를 제조하였고, 구조 조촉매로 첨가한 $SiO_2$의 원료물질에 따른 Fe계 촉매의 성능변화를 조사하였다. $SiO_2$의 원료물질로는 콜로이드 $SiO_2$와 분말 $SiO_2$를 이용하였으며, 분말 $SiO_2$를 이용한 촉매가 콜로이드 $SiO_2$를 이용한 촉매보다 다소 높은 CO 전환율 및 중질탄화수소 선택도를 나타내는 것을 확인하였다.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.49-57
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• 2001

One of the most important considerations to braze Cu-Al dissimilar materials is control of brittle metallic compound which makes it difficult to obtain a sound brazed joint. Nowdays, several attempts were made to control the metallic compound. But effective method for controlling metallic compound was not established. In this point of view, commercially pure aluminum and copper were used as base metal and Al-Si-X and Zn-Al-X alloy systems were developed as filler metal. Brazing was carried out to find optimum conditions for Cu-Al dissimilar joint. The results obtained in this study were summarized as follows: 1) The joint brazed by Al-Si-X filler metal showed good brazeability and mechanical properties. The tensile strength of the joint brazed over solidus temperature was more than 90% of Al base metal. Especially, the joint brazed at liquidus temperature was fractured in the Al base metal. 2) Fluorides fluxes(a mixture of potassium fluoro-aluminates) were used to improve surface cleanliness of base metal and wettability of Al-Si-X filler metal. It was melted at the temperature about 1$0^{\circ}C$ lower than that of the filler metal, and made appropriate brazing environment. Therefore, it could be a proper selection as flux.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.226-230
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• 2005

In this research, magnetic properties and annealing effects of the spin valve structures were investigated, which have Ta underlayer deposited with Ar and $N_2$ gas mixture. Also, TaN underlayer as a diffusion barrier and the substrate were investigated. The structure of the spin valve was Si($SiO_2$)/Ta(TaN)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Deposition rate was decreased and resistivity and roughness of the TaN films were increased as the $N_2$ gas flow was increased. The XRD results after high temperature annealing showed that Silicides were created in Si/Ta layer, but not in Si/TaN layer. Magnetoresistance ratio (MR) and exchange coupling field ($H_{ex}$) were decreased when the $N_2$ gas flow was increased over 4.0 sccm. The MR of the spin valves with Ta and TaN films deposited with up to 4.0 sccm of $N_2$ gas flow was increased about $0.5\%$ until the annealing temperature of up to $200^{\circ}C$ and then, decreased. TaN film deposited with 8.0 sccm of $N_2$ gas flow showed twice the adhesion of the Ta film. The above results indicate that with 3.0 sccm of $N_2$ gas flow during the Ta underlayer deposition, the magnetic properties of the spin valves are maintained, while the underlayer may be used as a diffusion barrier and the adhesion between the Si substrate and the underlayer is increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.517-523
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• 2008

The microwave dielectric properties of $LiNb_3O_8-TiO_2$ based ceramics with low firing agents, CuO, $Bi_2O_3$, $B_2O_3$, $SiO_2$, $TiO_2$, were investigated to improve the sintering condition for the LTCC system. According to the X-ray diffraction and SEM, the ceramics of $LiNb_3O_8-TiO_2$ with low firing agents showed no significant second phases within a range of experiments, and fine microstructures. By adding the low firing agents, the sintering temperature decreased from $1200^{\circ}C$ to $925^{\circ}C$. Based on the results of electrical measurements, the $LiNb_3O_8-TiO_2$ ceramics showed a promising microwave dielectric properties for LTCC applications, those are ${\varepsilon}_r$ (dielectric constant) = 44, Q f (quality factor) = 18000, and ${\tau}_f$ (the temperature coefficient of resonant frequency) = $-1.5\;ppm/^{\circ}C$.

• Journal of Powder Materials
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• v.16 no.1
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• pp.33-36
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• 2009

In order to increase the magnetic loss for electromagnetic(EM) wave absorption, the soft magnetic $Fe_{73}Si_{16}B_7Nb_3Cu_1$(at%) alloy strip was used as the basic material in this study. The melt-spun strip was pulverized using an attrition mill, and the pulverized flake-shaped powder was crystallized at $540^{\circ}C$ for 1h to obtain the optimum grain size. The Fe-based powder was mixed with 2 wt% $BaTiO_3$, $0.3{\sim}0.6$ wt% carbon black, and polymer-based binders for the improvement of electromagnetic wave absorption properties. The mixture powders were tape-cast and dried to form the absorption sheets. After drying at $100^{\circ}C$ for 1h, the sheets of 0.5 mm in thickness were made by rolling at $60^{\circ}C$, and cut into toroidal shape to measure the absorption properties of samples. The characteristics including permittivity, permeability and power loss were measured using a Network Analyzer(N5230A). Consequently, the properties of electromagnetic wave absorber were improved with the addition of both $BaTiO_3$ and carbon black powder, which was caused by the increased dielectric loss of the additive powders.

• Resources Recycling
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• v.8 no.5
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• pp.19-27
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• 1999

The desilica~ilalioc~h~ar .~ctcrisocs or conveutcu dust for molten pg iron has bee11 sludled for the pulposc of converter dust reuse. Desiloconizalir~ne ff~c~encwya s observed 10 be increased with increasing feeding rate of dust, and there was 110 cffccl to Lhe des~lica~~iratiearlfli cio~cyfo r the addtioolI CaO Ln dust. In ~noslc ases, the dcs~l~conizaliornea ction was ucconlpl~shed wrthin 10 minutes regadless of thc dust cornpasilim In addition lo the desil~comzat~oenfl ect, the rzmow~lc hal-i~cteristo~fs M u, P. C, and S from mallen iron by convcrtcr dust also have been in\~esligataled. CuO m thc converlel. dust was observed to ~educc the demanganizi~tion eflect and slag laming phenomenon and make thc dephosphoriralion pn,ce*s easler.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.228-228
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• 2010

반도체 집적도의 비약적인 발전으로 각 박막 층간의 두께는 더욱 줄어들었고 이는 각 박막 층간의 확산에 대한 문제를 간과할 수 없게 하였다. 따라서 각 층간의 확산을 방지하기위한 확산방지막의 연구에 대한 관심도는 증가하게 되었다. 또한 본 연구에서 분석을 위하여 사용된 Nanoindenter는 박막 표면에 다이아몬드 팁을 이용하여 압입을 실시하여 이때 시표의 반응에 의한 팁의 위치(Z-축)를 in-situ로 측정하여 인가력과 팁의 위치에 대한 연속 압입곡선을 측정하게 된다. 이를 통하여 박막의 hardness와 elastin modulus를 측정하게 되고, 연속 압입곡선 분석을 통하여 박막의 표면응력 변화를 측정한다. 이 논문에서는 반도체의 기판으로 사용되는 Si 기판과 금속배선 물질인 Cu와의 확산을 효과적으로 방지하기 위한 W-C-N 확산방지막을 제시하였고, 시료 증착을 위하여 rf magnetron sputter를 사용하여 동일한 증착 조건에서 질소(N)의 비율을 다르게 하여 박막내 질소 비율에 따른 확산방지막을 제작하였다. 이후 시료의 열적 안정성 측정을 위하여 상온에서 $900^{\circ}C$ 까지 질소 분위기에서 30분간 열처리 과정을 실시하여 열적 손상을 인가하였고, 고온에서 확산방지막의 열적인 안정성을 Nanoindentation 분석을 이용하여 측정하였다. 측정 결과 박막내 질소 불포함된 박막의 경우 표면 강도는 9.01 GPa에서 194.01 GPa의 급격한 변화를 보였고, 질소가 포함된 박막은 9.41 GPa에서 43.01 GPa으로 상대적으로 적은 차이를 보였다. X-ray 분석 결과에서도 박막내 질소가 포함된 박막이 고온에서도 더 안정된 특성을 보이는 것을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.184-184
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• 2010

반도체 집적도의 비약적인 발전으로 각 박막 층간의 두께는 더욱 줄어들었고 이는 각 박막 층간의 확산에 대한 문제를 간과할 수 없게 하였다. 따라서 각 층간의 확산을 방지하기 위하여 두께가 수십 nm size의 확산방지막의 연구에 대한 관심도는 증가하게 되었다. 본 연구에서 분석을 위하여 사용된 Nano-indentation은 박막 표면에 다이아몬드 팁을 이용하여 압입을 실시하여 이때 시표의 반응에 의한 팁의 위치(Z-축)를 in-situ로 측정하여 인가력과 팁의 위치에 대한 연속 압입곡선을 측정하게 된다. 이를 통하여 박막의 hardness와 elastic modulus를 측정하게 되고, 연속 압입곡선 분석을 통하여 박막의 표면응력 변화를 측정한다. 이 논문에서는 반도체의 기판으로 사용되는 Si기판과 금속배선 물질인 Cu와의 확산을 효과적으로 방지하기 위한 W-C-N 확산 방지막을 제시하였고, 시료 증착을 위하여 RF-magnetron sputter를 사용하여 동일한 증착조건에서 질소(N)의 비율을 다르게 하여 박막 내 질소비율에 따른 확산방지막을 제작하였다. 이후 시료의 열적 안정성 측정을 위하여 상온, $600^{\circ}C$, $800^{\circ}C$로 각각 질소 분위기에서 30분간 열처리 과정을 실시하여 열적 손상을 인가하였다. 고온에서 확산방지막의 물리적 특성을 알아보기 위해 Nano-indentation을 이용하여 분석하였고, WET-SPM을 이용하여 표면 이미지와 거칠기를 확인하였다. 그 결과 질화물질이 내화물질에 비해 고온에서 물성변화가 적게 나타나는 것을 알 수 있었고, 균일도와 결정성 또한 질화물질에서 더 안정적이었다.

• Journal of Powder Materials
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• v.16 no.5
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• pp.316-325
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• 2009

Fe based (Fe$_{68.2}$C$_{5.9}$Si$_{3.5}$B$_{6.7}$P$_{9.6}$Cr$_{2.1}$Mo$_{2.0}$Al$_{2.0}$) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The experiment results show that the as-prepared Fe amorphous powders less than 90 $\mu$m in size has a fully amorphous phase and its weight fraction was about 73.7%. The as-atomized amorphous Fe powders had a complete spherical shape with very clean surface. Differential scanning calorimetric results of the as-atomized Fe powders less than 90 $\mu$m showed that the glass transition, T$_g$, onset crystallization, T$_x$, and super-cooled liquid range $\Delta$T=T$_x$-T$_g$ were 512, 548 and 36$^{\circ}C$, respectively. Fe amorphous powders were mixed and deformed well with 10 wt.% Cu by using AGO-2 high energy ball mill under 500 rpm.