• Korean Journal of Chemical Engineering
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• 제36권2호
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• pp.191-196
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• 2019

The phase of Cu,Zn,Al precursors strongly affects the activity of their final catalysts. Herein, the Cu,Zn,Al precursor was prepared by precipitation of $Al^{3+}$ onto primitive, amorphous Cu,Zn precipitate. This precursor turned out to be a phase mixture of zincian malachite and hydrotalcite in which the latter phase was less abundant compared to the co-precipitated precursor. The final catalyst derived from this precursor exhibited a little higher copper surface area and methanol synthesis activity than the co-precipitated counterpart. Therefore, the two precursor phases need to be mixed in an adequate proportion for the preparation of active $Cu/ZnO/Al_2O_3$ catalyst.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1241-1246
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• 2010

Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.

• 한국수소및신에너지학회논문집
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• 제23권3호
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• pp.207-212
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• 2012

This study was performed to observe the change of stainless steel pipe interacting with alkaline solution. We used STS316L and STS304 as samples which were soaked in alkaline solution. We measured the samples by use of FE-SEM, EDX, SIMS to observe the surface and depth profile of both samples. The result showed that the precipitate appeared on the surface of both samples from 5 days. but the precipitate was confirmed to be decreased as time passes. but the quantitative change of precipitates at both samples was different as time passed. The EDX showed that the precipitate is Potassium from solution of Electrolysis. The result also showed that the primary elements of stainless steel pipeline and of Alkaline Solution were changed. The change of primary elements was severe between 5 days to 16 days and was stable around 40 days at both samples. The reaction of STS316L with alkaline solution was lower than STS304. We hoped that this study would be the foundation of developing the electrode of the alkaline hydrogen generator.

• 열처리공학회지
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• 제33권5호
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• pp.226-231
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• 2020

The Cu-Co-Si alloy shows high strength by forming precipitates by aging precipitation heat treatment of supersaturated solid solution treated with solution treatment such as Cu-Ni-Si alloy, and the Co₂Si precipitated phase is dispersed in the copper matrix. The effect of aging treatment on the microstructure, mechanical and electrical properties of Cu-Co-Si alloys for electronic devices was investigated. As a results of SEM/EDS analysis, it was found that Co₂Si precipitates of 30~300 nm size were distributed in grains. By performing the double aging treatment, it was possible to improve the strength and electrical conductivity by dispersing the fine precipitate evenly.

• 한국결정성장학회지
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• 제28권2호
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• pp.85-90
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• 2018

폐니켈수소전지에 함유되어 있는 희토류를 회수하기 위하여 $H_2SO_4$로 침출한 용액에 10 M NaOH를 첨가하여 희토류를 pH 2.0 이하에서 약 98 % 침전시켰다. 이후 회수된 희토류 복합 침전물은 $800^{\circ}C$에서 4시간 동안 열처리를 통해 $HNO_3$에 대한 침출률을 증가시켰으며, 희토류 복합 침전물이 용해된 용액에 oxalic acid를 첨가하여 2차 침전을 실시하였다. 재침전된 희토류는 다시 $800^{\circ}C$에서 4시간 열처리를 통해 산화물 형태로 변환되었으며, 이때 희토류 산화물의 순도는 약 99.5 %를 나타내었다.

• 열처리공학회지
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• 제9권2호
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• pp.79-90
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• 1996

Transmission electron microscopy(TEM) investigation on the phase decomposition of B2-ordered (Ni,Co)Al supersaturated with Ni and Co has revealed the precipitation of $(Ni,Co)_2Al$ which has not been expected from the reported equilibrium phase diagram. The $(Ni,Co)_2Al$ phase has a hexagonal struture and takes a rod-like shape with the long axis of the rod parallel to the <111> directions of the B2 matrix. By aging at temperatures below 873 K, a long period Superlattice Structure appears in the hexagonal $(Ni,Co)_2Al$ Phase. The orientation relationship between the $(Ni,Co)_2Al$ Precipitates and the B2-(Ni,Co)Al matrix is found to be$(0001)_p$ // $(111)_{B2}$ and $[\bar{1}2\bar{1}0]_P$ // $[\bar{1}10]_{B2}$, Where the suffix p and B2 denote the $(Ni,Co)_2Al$ precipitate and the B2-(Ni,Co)Al matrix, respectively. (Ni,Co)Al hardens appreciably by the fine precipitation of the $(Ni,Co)_2Al$ phase. Energy dispersive spectroscopy was used to analyze the compositions of each phase formed in B2-(Ni,Co)Al.

• 한국재료학회지
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• 제30권12호
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• pp.678-686
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• 2020

Microstructural characteristics of directionally solidified René 80 superalloy are investigated with optical microscope and scanning electron microscope; solidification velocity is found to change from 25 to 200 μm/s under the condition of constant thermal gradient (G) and constant alloy composition (Co). Based on differential scanning calorimetry (DSC) measurement, γ phase (1,322 ℃), MC carbide (1,278 ℃), γ/γ' eutectic phase (1,202 ℃), and γ' precipitate (1,136 ℃) are formed sequentially during cooling process. The size of the MC carbide and γ/γ' eutectic phases gradually decrease with increasing solidification velocity, whereas the area fractions of MC carbide and γ/γ' eutectic phase are nearly constant as a function of solidification velocity. It is estimated that the area fractions of MC carbide and γ/γ' eutectic phase are determined not by the solidification velocity but by the alloy composition. Microstructural characteristics of René 80 superalloy after solid solution heat-treatment and primary aging heat-treatment are such that the size and the area fraction of γ' precipitate are nearly constant with solidification velocity and the area fraction of γ/γ' eutectic phase decreases from 1.7 % to 0.955 %, which is also constant regardless of the solidification velocity. However, the size of carbide solely decreases with increasing solidification velocity, which influences the tensile properties at room temperature.

• 한국결정성장학회지
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• 제33권1호
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• pp.15-21
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• 2023

산화아연 분말을 제조하기 위해 3종류의 나트륨계 알칼리 침전제인 수산화나트륨, 탄산나트륨, 수산화나트륨/탄산수소나트륨을 이용하여 반응에 따른 열역학적 고찰과 아연 침전생성물로부터 산화아연 분말 제조 공정의 차이점을 비교하였다. 나트륨계 알칼리 침전제와의 반응으로 생성된 아연 침전생성물은 각각 히드록시염화아연(Zn₅(OH)₈Cl₂·H₂O)과 탄산아연수산화물 (Zn₅(OH)₆(CO₃)₂·H₂O)임을 XRD를 통해 확인하였다. 나트륨계 알칼리 침전제에 따라 800℃에서 열처리하여 생성된 산화아연 입자 크기를 비교하였다. 혼합된 수산화나트륨 및 탄산수소나트륨의 알칼리 침전제 반응으로 보다 균일한 산화아연 입자를 제조할 수 있었다.

• 분석과학
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• 제5권4호
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• pp.425-431
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• 1992

$La(OH)_3$ 공침에 의한 극미량 인산이온의 부선 및 농축에 관한 연구를 가시/자외선 분광광도법을 이용하여 수행하였다. 암모니아용액으로 조절한 pH 9.5의 1.0L 시료용액 중 인산 이온을 수산화란탄 침전에 공침시켰다. 1:8의 sodium oleate와 sodium dodecyl sulfate 혼합 계면활성제를 가하고 질소기체를 bubbling하여 침전들을 용액 표면으로 띄웠다. 뜬 침전들을 감압 플라스크에 모은 다음 용액을 걸러 버리고 침전을 묽은 암보니아용액으로 씻고 황산에 녹였다. 몰리브덴 청색법으로 농축된 용액 중 인산이온을 정량하였다. 이상의 방법으로 수도물과 강물 중 인산이온을 분석하였고 각 시료에 인산이온을 20.0ng/mL 가하여 분석한 결과 각각 93%와 86%의 회수율을 얻었다.

• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2001년도 제31회 학술심포지움 및 춘계학술대회
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• pp.59-59
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• 2001