• 소성∙가공
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• 제3권4호
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• pp.427-439
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• 1994

The high temperature deformation behavior of $SiC_p/Al-Si$ composites and Al-Si matrix was studied by hot torsion test in a range of temperature from $270^{\circ}C$ to $520^{\circ}C$ and at strain rate range of $1.2{\times}10_{-3}~2.16{\times}10_{-1}/sec$. The hot restoration mechanisms for both matrix and composites were found to be dynamic recrystallization(DRX) from the investigation of flow curves and microstructural evolutions. The Si precipitates and SiC particles promoted DRX, and the peak strain$({\varepsilon}_p)$ of the composites was smaller than that of the matrix. Flow stresses of $SiC_p/Al-Si$ composites were found to be generally higher than the matrix, but the difference was quite small at higher temperature due to the decrease of capability of load transfer by SiC particles. With increasing temperature, failure strain of matrix and composites are inclined to increase, the increasing value of failure strain for the $SiC_p/Al-Si$ composites was small compared to that of matrix. The stress dependence of both materials on strain rate() and temperature(T) was examined by hyperbolic sine law, $\.{\varepsilon}=A_1[sinh({\alpha}{\cdot}{\sigma})]_n$exp(-Q/RT)

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제2권2호
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• pp.149-158
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• 1998

Biomass of non-living brown seaweed Sargassun fluitans pretreated with NaOH is capable of taking up more than $10\%$ $(q_{max}$ : 3.85 mmol/g for Al and 1.48 mmol/g for Cu) of its dry weight in the Al and Cu at pH of 4.5. However, the maximum Al and Cu uptakes calculated from Langmuir isotherm were 1.58 mmol/g for Al and 1.35 mmol/g for Cu at pH 3.5. Equilibrium batch sorption study was performed using two-metal system containing Al and Cu. The mathematical model of the two-metal sorption system enabled quantitative estimation of one-metal biosorption inhibition due to the influence of a second metal. NaOH-treated S. fluitans contained 2.19 mmol $(43\;wt.\%)$ carboxyl groups per gram of biomass. A modified form of Langmuir, which assumes binding of Cu as $Cu^{2+}$ and Al as $Al(OH)_2^+,$ was used to model the experimental data. This result agrees with the one of mono-valent sorption for Al in single-metal system. The modified Langmuir model gives the following affinity correlated coefficients: 0.196 for Cu and 6.820 for Ah at pH 4.5, and 2.904 for Cu and 3.131 for Al at pH 3.5. The interference of Al in Cu biosorptive uptake was assessed by `cutting' the three dimensional uptake isotherm surfaces at constant second-metal final concentrations. Equimolar final equilibrium concentrations of Cu and Al of 1 mM at pH 4.5 give Cu and hi uptakes reduced by $82.5\%\;and\;5.4\%,$ respectively. However, these values at pH 3.5 were $55\%\;(Cu)\;and\;31\%$ (Al).

• 한국주조공학회지
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• 제24권2호
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• pp.85-93
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• 2004

Mechanical property of hypereutectic Al-Si alloy is changed according to size and distribution of primary Si. Consequently, the study on the refinement for primary Si is progressed for a long time. But such effect of refinement comes out fading phenomena with the lapse of time. Therefore, this study investigated the optimum condition of primary Si refinement for hypereutectic Al-Si alloy. And we observed various primary Si size with P's fading phenomena. The experiment results were as follows. For experiment of primary Si refinement, we made hypereutectic Al-Si alloy with various amounts of P addition. As a result of experiment, we obtained the fine microstructure at 0.01wt.%P. And the optimum condition of P addition, for preventing from growth of primary Si by P fading, is estimated 0.1wt.%P.

• 한국세라믹학회지
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• 제51권5호
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• pp.392-398
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• 2014

$Al_2O_3$-SiC composites reinforced with SiC whisker ($SiC_w$) were fabricated using three different methods. In the first, $Al_2O_3-SiC_w$ starting materials were used. In the second, $Al_2O_3-SiC_w$-SiC particles ($SiC_p$) were used, which was intended to enhance the mechanical properties by $SiC_p$ reinforcement. In the third method, reaction-sintering was used with mullite-Al-C-$SiC_w$ starting materials. After hot-pressing at $1750^{\circ}C$ and 30 MPa for 1 h, the composites fabricated using $Al_2O_3-SiC_w$ and $Al_2O_3-SiC_w-SiC_p$ showed strong mechanical properties, by which the effects of reinforcement by $SiC_w$ and $SiC_p$ were confirmed. On the other hand, the mechanical properties of the composite fabricated by reaction-sintering were found to be inferior to those of the other $Al_2O_3$-SiC composites owing to its relatively lower density and the presence of ${\gamma}-Al_2O_3$ and ${\gamma}-Al_{2.67}O_4$. The greatest hardness and $K_{1C}$ were 20.37 GPa for the composite fabricated using $Al_2O_3-SiC_w$, and $4.9MPa{\cdot}m^{1/2}$ using $Al_2O_3-SiC_w-SiC_p$, respectively, which were much improved over those from the monolithic $Al_2O_3$.

• 자원환경지질
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• 제42권5호
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• pp.501-507
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• 2009

본 연구에서는 단일 벽(Single-wall) 구조를 갖는 나노크기의 속이 빈(hollow) 볼(Ball)형(NBs; Nano-balls), 짧은 길이 튜브(S-NTs; Short-fiber Nano-tubes)형 및 긴 길이 튜브(L-NTs; Long-fiber Nano-tubes) 물질을 동일한 조성 Al/Ge=1.33을 갖는 Aluminogermanate(ALGE) Precursor 최초 혼합용액의 단순한 pH 조절 과정에서 자기조합(Self-assembly)을 통해 성공적으로 합성하였다. 먼저 pH=13으로의 염기성화(Na/Al=28~30) 및 최종 pH=9 조건에서 5 nm의 균질한 크기를 갖으며, 화학조성인 Al/Ge=1.5~1.6인 속이 빈 구조의 NBs가 합성되었다. pH=13으로의 염기성화 및 최종 pH=4 조건에서는 3.3 nm 지름, 길이 15~20 nm, Al/Ge=2.6~2.8의 S-NTs가 합성되었다. 그러나 pH=9로 염기성화(Na/Al=3.8) 시킨 후 최종 pH=4조건에서는 나노-튜브의 길이가 100 nm 이상인 L-NTs가 처음으로 합성되었다. 이러한 결과는 ALGE Precursor로부터 -Ge-OH 표면에서의 $H^+$-dissociation 정도 차이, 즉, $Na^+$ 양 및 최종 pH 조건을 달리함으로써 의도하는 형태의 ALGE 나노물질 유도가 가능함을 시사한다.

• 대한환경공학회지
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• 제35권7호
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• pp.495-502
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• 2013

본 연구는 UF공정의 전처리로써 Al(III)계 응집제인 alum과 PACl을 사용한 응집공정 적용 시 두 응집제의 효율 비교 및 잔류 알루미늄 농도를 고려한 최적 운전 조건을 알아보기 위해 응집제 주입농도, 완속교반의 적용 그리고 해수 원수의 pH를 변화하여 UF막 flux 및 잔류 알루미늄 이온 농도를 조사했다. 그 결과 pH 8.0 조건에서 alum의 주입농도가 증가할수록 flux 또한 증가하였으며 완속교반은 UF막 flux를 오히려 감소시킨 것으로 조사된 반면 PACl의 경우 주입농도가 증가할수록 flux는 일부 감소하는 경향을 보였으며 alum과는 반대로 완속교반 적용시 flux 또한 증가하였다. 반면에 pH 6.5 조건에서 alum 주입량이 0.7 mg/L (as Al)일 때 UF막 flux의 효율이 가장 좋았고 잔류 알루미늄 농도는 0.05 mg/L (as Al) 이하로 측정되었다. PACl의 경우 UF막 flux 측면에서는 최적 조건은 pH 8.0, 주입농도 1.2 mg/L (as Al) 그리고 완속교반 시간을 적용하였을 때였으며 잔류 알루미늄 농도를 고려한 최적 주입조건은 pH 6.5 조건에서 주입농도를 1.2 mg/L (as Al)일 때로 조사되었다.

• 한국환경과학회지
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• 제18권5호
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• pp.589-594
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• 2009

The goals of this study were conducted to investigate the effects of applying liquid aluminum chloride ($AlCl_3$) to rice hulls on pH and soluble reactive P (SRP). A total of 800 broiler chicks (4 treatments $\times$ 4 replicates $\times$ 50 birds) were housed into 16 floor pens in a single house for 5 weeks. The treatments were divided into 4 groups: control, 100 g of liquid $AlCl_3/kg$ of rice hulls, 200 g of liquid $AlCl_3/kg$ of rice hulls, and 300 g of liquid $AlCl_3/kg$ of rice hulls. Liquid $AlCl_3$ was sprayed on the rice hulls surface at a rate of 100 g, 200 g, and 300 g liquid $AlCl_3$ per kg rice hull. pH values and SRP contents were significantly decreased (P<0.05) with the increased liquid $AlCl_3$ levels in comparison with control. However, no significant differences in SRP contents were observed among all treatments at 3 and 4 weeks. Applying 100 g, 200 g, and 300 g liquid $AlCl_3$ to rice hulls reduced SRP contents by 18, 25, and 52% for 5 weeks, respectively, compared with the controls. In conclusion, these results suggest that using liquid $AlCl_3$ on rice hulls should be promising for reducing water contamination and resulted in a reduction in SRP contents, which reduced pH.

• 소성∙가공
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• 제13권7호
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• pp.608-613
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• 2004

Mechanical properties of hypereutectic Al-Si alloy are influenced by the size and distribution of primary Si. To investigate the effects of P addition and holding time, hypereutectic Al-Si alloys with various amount of P content were produced in the lab. Then, the size and distribution of primary Si were examined respectively. Mechanical properties of hardness, tensile strength and wear resistance were analyzed in conjunction with the microstructural variations in alloys.

• 한국토양비료학회지
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• 제21권1호
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• pp.21-29
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• 1988

인산(燐酸) 축적지(畜積地) 토양(土壤) 149점(點)(시건설원예지(施設園藝地) 60점(點), 마늘, 양파, 고추 재배지(栽培地) 89점) 에 대한 무기태인산(無機態燐酸)의 형태별(形態別) 조성(造成)과 유효인산(有效燐酸) 함량(含量)과의 관계(關係)를 검토(檢討)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 총(總) 인산(燐酸)에 대한 무기태인산(無機態燐酸)의 분포비(分布比)는 68.9%(Sa-p 2.7, Al-p 26.4, Fe-p 27.6, Ca-p 12.2), 유기태인산(有機態燐酸)은 6.7%, 유효인산(有效燐酸)은 26.0%이었따. 2. 유효인산함량(有效燐酸含量)과 무기태인산(無機態燐酸) 함량(含量)과의 상관관계(相關關係)에서 Al-p와는 0.1%에서 유의성(有意性)있는 상관관계(相關關係)를 나타내었으며, Sa-p, Ca-p 순으로 유의성(有意性)을 보였고 Fe-p와는 일정한 상관관계(相關關係)를 나타내지 않았다. 3. 유효인산함량(有效燐酸含量)과 무기태인산(無機態燐酸) 함량(含量)과의 다중회귀분석(多重回歸分析) 결과(結果) $Av.P=81.694+0.858Sa-p^{***}+0.648Al-p^{***}+0.091Ca-p^{**}(R=0.826^{***})$의 관계식(關係式)을 얻었으며, 각 성분(成分)의 기여도(奇與度)는 Sa-p 26.1, Al-p 65.2, Ca-p 8.7%이었다. 4. 유효인산함량(有效燐酸含量)과 수용성인산(水溶性燐酸), 수용성인산(水溶性燐酸)과 $0.01M-CaCl_2-p$와는 고도(高度)의 유의성(有意性) 있는 상관관계(相關關係)를 나타내었고, $0.01M-CaCl_2$ 용액(溶液)에 의한 30분(分) 추출법(抽出法)은 토양용액(土壤溶液) 인산(燐酸)을 신속(迅速) 간편(簡便)하게 추정(推定)할 수 있는 방법(方法)으로 생각되었다.

• 한국광물학회지
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• 제13권4호
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• pp.186-195
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• 2000

To study phosphate adsorption on kaolinite, $^{31}$ P MAS NMR(magic angle spinning nuclear magnetic resonance spectroscopy)has been used for kaolinite reacted in 0.1 M phosphate solutions at pH’s from 3 to 11. There are at least 3 different forms of phosphate on kaolinite. One is the phosphate physically adsorbed on kaolinite surface (outer-sphere complexes) or species left after vacuum-filtering. The second is the phosphate adsorbed by ligand exchange (inner-sphere complexes), and the third is Al-phosphate precipitates which are pH dependent. Most of the inner-spherer complexes and surface precipitates are mainly on hydroxided Al(aluminol) rather than hydroxided Si(silanol). These are pertinent with the results obtained from the phosphate adsorption experiments on silica gel and ${\gamma}$-Al$_2$O$_3$ as model compounds, respectively. The two peaks with more negative chemical shifts(more shielded) than the ortho-phosphate peak (positive chemical shift) are assigned to be the inner-sphere complexes and surface precipitates. The $^{31}$ P chemical shifts of the Al-phosphate precipitates are more negative than those of inner-sphere complexes at a given pH due to the larger number of P-O-Al linkages per tetrahedron. The chemical shifts of both the inner-sphere complexes and surface precipitates are more negative than those of inner-sphere complexes at a given pH due to the larger number of P-O-Al linkages per tetrahedron. The chemical shifts of both the inner-sphere complexes and surface precipitates become progressively less shielded with increasing pH. For the inner-sphere complexes, decreasing phosphate protonation combined with peak averaging by rapid proton exchange among phosphate tetrahedra with different numbers of protons is though to be the reason for the peak change. The decreasing shielding with increasing pH for surface precipitates is probably due to the decreasing average number of P-O-Al linkages per tetrahedron combined with decreasing protonation like inner-sphere complexes.