• 한국재료학회지
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• 제31권11호
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• pp.642-648
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• 2021

The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 ℃ for 6 h, followed by water cooling, and samples were artificially aged in air at 180 ℃ and 220 ℃ for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 ℃ and above 300 ℃, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 ℃ and 400 ℃, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 ℃ and 400 ℃ was strongly influenced by the precipitation of θ'-Al₂Cu, β'-Mg₂Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.

• 열처리공학회지
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• 제34권5호
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• pp.226-232
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• 2021

The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.

• 열처리공학회지
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• 제12권1호
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• pp.21-30
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• 1999

The present study were investigated changes of precipitation behaviour of laves phase in ferrite single phase and ferrite-martensite dual phase and precipitation of laves phase under stress. Hardness changes in ferrite phase appeared two hardness peaks by precipitation of initial fine precipitator and laves phase in 3Mo-0.3Si and 3Mo-0.3Si-C specimens, respectively. Hardness changes in martensite phase of 3Mo-0.3Si-C specimen was lower in the initial stage of aging by carbide precipitation and after this, increased by re-hardening due to precipitation of laves phase. In the ferrite phase, laves phase was mainly precipitated, whereas in the martensite phase, carbide was preferentially formed during the initial stage of aging and with increasing aging time, laves phase and carbide were simultaneously precipitated by precipitation of laves phase at around carbide. In the ferrite-martensite interface, laves phase was mainly precipitated and carbide was mainly formed at boundary of lath martensite than grain boundary. Adding the stress in aging, fine precipitator of inital precipitation of laves phase precipitated in (100) of perpendicular to tensile direction and has grown to only followed<010>direction and also, volume fraction of laves phase increased. Consequently, the stress added was accelerated initial precipitation of laves phase.

• 한국재료학회지
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• 제30권9호
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• pp.474-479
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• 2020

The effect of precipitation and dissolution of Si on the thermal diffusivity in the Al-Si alloy system is reported in this study and solution heat treatment followed by aging treatment is carried out to determine the effects of heat treatment on the thermal characteristics. The solution treatment is performed at 535 ℃ for 4 and 10 h and then the specimens are cooled by rapid quenching. The samples are aged at 300 ℃ for 4 h to precipitate Si solute. The addition of 9 wt% silicon contents makes the thermal diffusivity decrease from 78 to 74 mm/s² in the cases of solid solution treated and quenched samples. After quenching and aging, the Si solute precipitates on the Al matrix and increases the thermal diffusivity compared with that after the quenched state. In particular, the increase of the thermal diffusivity is equal to 10 mm/s² without relation to the Si contents in the Al-Si alloy, which seems to corresponded to solute amount of Si 1 wt% in the Al matrix.

• Journal of Information Display
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• 제1권1호
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• pp.35-41
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• 2000

Manganese-doped $Zn_2SiO_4$ phosphors well known as a green emitter with high luminescence efficiency were prepared by the homogeneous precipitation method, and their photoluminescence properties under vacuum-ultraviolet (VUV) excitation were investigated. $Zn_2SiO_4$:Mn phosphors obtained by this method have exhibited a high luminance of property and a spherical shape of particles. In particular, the green emission intensity of zinc orthosilicate prepared as containing around 2 mole% of manganese was much stronger than that of the commercial $Zn_2SiO_4$:Mn phosphor, while the decay time was longer. However, addition of $Al^{3+}$ and $Li^+$ into $Zn_2SiO_4$:Mn composition has significantly diminished the decay time of the phosphor without much degradation of the emission intensity.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.861-862
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• 2009

Precipitated iron-based catalysts are highly promising for the Fischer-Tropsch synthesis (FTS), in particular for the low temperature FTS below $280^{\circ}C$, because of their high activity and low cost. $SiO_2$ is an essential promoter for the precipitated iron-based catalysts to improve the attrition strength and physical stability. In this study, we carried out FTS over precipitated iron-based catalysts with and without $SiO_2$ in a fixed-bed reactor. The catalysts were prepared by a conventional co-precipitation method. In case of the catalysts with $SiO_2$, we used two comparative preparation methods, i.e., incorporation of $SiO_2$ before precipitation (denoted as precipitated $SiO_2$) and after precipitation (denoted as binder $SiO_2$), respectively. The addition of $SiO_2$ crucially affects both physico-chemical properties and catalytic peformance of precipitated iron-based catalysts.

• 한국결정성장학회지
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• 제9권1호
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• pp.84-88
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• 1999

결정성장 조건을 달리하여 공공관련 결함들의 발생영역의 크기가 다르게 형성되도록 성장한 실리콘 결정에서 반경 방향의 산소석출 거동을 고찰하였다. 반경 방향의 산소석출 거동은 결정성장 조건에 따른 공공 영역의 크기에 의존적이다. 반경 방향의 산소석출 거동은 공공우세 영역이 격자간원자 우세영역보다 산소석출이 증가한다. 또한 공공우세 영역과 격자간원자 우세영역 가장자리에서는 비정상적으로 산소석출이 크게 증가한다. 이 두 영역 경계에서는 산소석출이 거의 일어나지 않는다.

• 자원리싸이클링
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• 제30권6호
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• pp.36-42
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• 2021

폐리튬이온배터리에 함유된 유가금속을 회수하기 위해 고온에서 용융환원처리한다. 용융환원된 금속상을 염산용액으로 침출한 다음 용매추출과 침전으로 유가금속을 분리한 여과액에는 니켈(II)과 미량의 규소(IV)가 함유되어 있다. 여액으로부터 고순도 니켈화합물을 회수하기 위해 흡착법에 의한 규소(IV)의 분리와 니켈(II)의 선택적 침전에 대해 조사했다. Polyacrylamide는 규소(IV)를 선택적으로 흡착했으나 용액의 점도 역시 증가하여 여과가 어렵다. 침전제로 탄산나트륨을 첨가하면 니켈(II)과 미량의 규소(IV)가 공침되었다. 반면 옥살산나트륨은 상온에서 니켈(II)만을 선택적으로 침전시켜 순도 99.99% 이상의 니켈옥살산염 결정상을 회수할 수 있었다.

• 한국재료학회지
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• 제15권7호
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• pp.480-485
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• 2005

Sc has been known to be an very effective ppt-hardening element in Al and Al alloys and also to be effective in modification of eutectic Si in hypoeutectic Al-Si alloys. The modification mechanism of Sc is different from that of the traditional modifier Sr in Al-Si alloys. In the present study the effects of Sc on the primary and eutectic Si in hypereutectic Al-Si alloys were investigated with evaluating the microstructures with OM, EPMA and EBSD methods. The results represent that Sc has only a small effect on primary Si when added less than $0.8wt\%$. However, when Sc addition leading to the precipitation of metallic Sc within primary Si reaches $1.6wt\%$, very coarse primary Si occurs.

• 한국세라믹학회지
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• 제39권7호
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• pp.649-656
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• 2002

Zn(NO$_3$)$_2$ 수용액과 urea[CO(NH$_2$)$_2$]를 이용한 침전법과 Self-Assembled Monolayers(SAMs)를 이용한 microcontact printing 방법으로 미세 패턴화된 ZnO 박막을 Al/si0$_2$/si 기판 위에 제조하였다. Zn(NO$_3$)$_2$와 urea를 혼합하여 제조한 Zn(OH)$_2$ 박막은 침전온도와 urea 량이 증가할수록 Zn(OH)$_2$의 침전량이 증가하였고 Zn(NO$_3$)$_2$와 urea의 반응 시간이 증가함에 따라, Zn(OH)$_2$ 박막의 두께와 입자 크기가 증가하였다. Zn(NO$_3$)$_2$와 urea의 혼합비를 1 : 8, 용액의 침전 온도를 오일 bath내에서 8$0^{\circ}C$, 반응시간을 1시간으로 하여 Al/SiO$_2$/Si 기판 위에 침전된 Zn(OH)$_2$ 박막을 $600^{\circ}C$에서 1시간 동안 열처리하여, 미세 패턴을 형성하기 위한 균질한 크기의 ZnO 박막을 제조할 수 있었다. Microcontact printing방법으로 소수성과 친수성 SAMs인 Octadecylphosphonic Acid(OPA)와 2-Carboxyethylphosphonic Acid(CPA)를 각각 Al/SiO$_2$/Si 기판 위에 선택적으로 흡착한 후에 친수성 SAM인 CPA위에 Zn(OH)$_2$를 침전시켜 미세 패턴화된 ZnO 박막을 제조할 수 있었다