• 수산해양교육연구
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• 제15권2호
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• pp.176-183
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• 2003

Recently, with the tendency of lightening, high-strength and high-speed in the marine industries such as marine structures, ships and propellers, it is rapidly enlarged the use of the aluminium alloy. Therefore, there occurs much interest in the study on corrosion characteristics of aluminium alloy. This paper was studied on the corrosion characteristics of Al-Mg alloy propeller used for a coasting vessel. Under the various pH of marine environment, the corrosion test of Al-Mg alloy was carried out. And thus polarization resistance, corrosion potential, and current density behavior of Al-Mg alloy and galvanic corrosion behavior of Al-brass and Al-Mg alloy coupled Al 5086 and SS 400 for hull were investigated. The main results are as following: 1. The corrosion potential of Al-brass propeller is more nobel than materials for hull, but that of Al-Mg alloy propeller is low or similar to materials for hull. Therefore, the galvanic corrosion of hull due to Al-Mg propeller don't occur. 2. The polarization resistance of Al-Mg alloy in sea water of pH 4 is highest, and corrosion current density of Al-Mg propeller is the most controlled. 3. As pH value decreases, potential showed Evans polarization diagram approaches cathodic potential. The corrosion current density of Al-Mg alloy is controlled to anodic reaction rate, therefore, the corrosion reaction of Al-Mg alloy is anodic control.

• 청정기술
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• 제3권2호
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• pp.87-93
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• 1997

본 실험은 알루미나 시멘트와 산화칼슘을 이용해 염기성 조건에서 질산염을 침전시킴으로써 오염수를 처리하는 공정에 관한 것이다. 시중에 시판되고 있는 알루미나 시멘트 중 알루미나 함량이 낮은 시멘트가 높은 질산염 제거를 보였다. 알루미늄과 칼슘의 성분비는 침전반응에 가장 중요한 요소임을 알 수 있었다. 고농도의 질산염 폐수의 처리를 위해 다단계의 침전반응이 효과적이었다. 질산염 뿐만 아니라 황산, 인산 및 염소의 제거에도 침전반응에 의한 제거가 가능하였다. 반응 후에 탄산나트륨의 첨가와 산을 이용한 중화를 포함한 후처리로 처리수내에 용출된 알루미늄과 칼슘의 제거가 가능하였다.

• 한국세라믹학회지
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• 제47권5호
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• pp.401-406
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• 2010

For the lower-temperature preparation of calcium monoaluminate(CA, C:CaO, A:$Al_2O_3$) clinker which is hard to synthesize purely within its melting point, an equimolar hydrate was obtained and then used as a starting raw material of clinker burning. The hydrate was prepared from a mixture of waste oyster shell and industrial aluminium hydroxide by heating to $1200^{\circ}C$, grinding and mixing with water. The hydrate was composed of amorphous aluminium hydroxide and $C_3AH_6$(H:$H_2O$) formed by resolution-precipitation mechanism of the system C-A-H. By heating the hydrate, nearly pure and porous calcium monoaluminate clinker was formed at $1400^{\circ}C$ which is fairly lower temperature than that of its melting point. The formation of calcium monoaluminate was performed mainly by the reaction between amorphous alumina and $C_{12}A_7$ caused by the decomposition of $C_3AH_6$. The immediate and earlier formation of $C_{12}A_7$ seemed to be accelerated by not only high surface area and instability of the thermally decomposed hydrate but also the catalytic effect of water decomposed from the hydrate. The final calcium monoaluminate clinker was very porous because of the influence of highly porous shape of the thermally decomposed hydrate.

• 대한토목학회논문집
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• 제26권2C호
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• pp.89-98
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• 2006

본 연구에서는 해성점토의 전단강도를 증진시킬 목적으로 철과 알루미늄 전극을 직접 삽입한 후 전극을 분해하여 지반 고결화 효과를 유발하였다. 이를 위해 남해안에서 채취한 실제 해성점토에 대해 실내 토조를 이용한 파일럿 실험을 실시하였고, 각각 철과 알루미늄을 삽입한 후 일정 고전류(2.5A)를 적용시켰다. 고결화에 의한 영향을 파악하고자 실험 종료 후에는 콘관입시험기를 이용하여 비배수 전단강도를 측정하였으며, 위치별 함수비와 pH 및 전기전도도를 측정하여 철과 알루미늄의 전극분해에 의한 고결화 효과를 간접적으로 판단하였다. 철 전극 전기분해 실험 결과, 양(+)극부 근처에서의 함수비는 초기에 비해 35% 감소하였고, 음극부 근처에서는 13% 증가하였으나, 양극부에서 용출된 철 이온과 흙 입자의 고결화 작용에 의해 전체적으로 측정된 전단강도는 초기에 비해 상당히 증가하였다. 또한 알루미늄 전극을 이용하였을 경우, 철에 비해 비교적 균일한 전단강도 증진효과가 나타났으며, 그 개량정도 역시 더 크게 나타났다.

• 분석과학
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• 제37권2호
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• pp.87-97
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• 2024

The appropriate intake of fluoride (F^-) is beneficial to human health; however, the over-consumption can result in various potentially harmful effects. This study compared different colorimetric reagents, i.e., aluminium-xylenol orange (Al-XO), zirconium-xylenol orange (Zr-XO), and zirconium-alizarin red S (Zr-ARS), for fluoride measurements by the UV-Vis, in terms of reaction mechanisms, method sensitivity, and interferences from aluminium and ferric ions. The colorimetric procedures were optimized, and the analytical methods were evaluated. The goodness of linearity (R² > 0.998) was obtained for all three assays within the concentration range of 1.0-20.0 mg/L fluoride in deionized water, in which the method sensitivity followed the descending order of Zr-XO > Al-XO > Zr-ARS. The Zr-XO was applied for determining the fluoride in different tea extracts in water (90 ℃ and 60-minute-brewing) and black tea demonstrated the highest fluoride content (3.0-3.6 mg/L). The effects of brewing time and temperature on the release of fluoride in the tea extracts were also investigated, indicating these are critical factors for the fluoride extraction. This study highlighted the application potentials of the UV-Vis measurement as a simple, convenient, and cheap analytical approach and discussed different colorimetric reagents used for fluoride determination in tea extracts in the context that the UV-Vis spectrophotometers are commonly equipped in most laboratories.

• 대한기계학회논문집A
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• 제21권7호
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• pp.1058-1072
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• 1997

A head-neck complex dummy, for measuring brain pressure and reaction force in the cervical spine was developed for experimental study related in injury mechanism. Dummy comprised aluminium-casted head with water filled cavity for simulating brain and mechanical neck assembled with six motion segments. Several kinds of experiments (compression, bending, cyclic modulus, relaxation and constant velocity profile) for the developed mechanical neck showed that this neck model is biomechanically reliable compared with in-vitro test results. As an application of developed head-neck complex dummy, shock absorbing properties of protective helmet was chosen. The experiments showed that the maximum pressure increment of brain after impact was tolerable compared with the guide line for mild brain injury pressure (25psi). Constrast to this results, the reaction force in the neck was high enough to produce failure in the cervical spine.

• 한국물환경학회지
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• 제28권2호
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• pp.197-201
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• 2012

The objective of this study was to evaluate the removal efficiency of arsenite and arsenate using composite adsorbents with various mixing ratio of recycled aluminum oxides and $TiO_2$. From batch adsorption experiments, while the removal of As(III) was almost same with 4 different composite samples in the entire pH range, the removal of As(V) was substantially increased as the weight ratio of $TiO_2$ in composite samples reduced and showed anionic adsorption characteristics. Both adsorption of As (III) and As(V) on composite samples followed pseudo-second-order adsorption equation and C-3 showed faster reaction rate for the removal of arsenic. From the adsorption isotherm experiments, Langmuir isotherm explained well and the maximum adsorption capacities of arsenic were obtained with C-1.

• 대한환경공학회지
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• 제33권3호
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• pp.212-221
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• 2011

우리나라의 공공하수처리시설은 생물학적 인 제거공정을 운전하고 있으나, '12년부터 지역구분(I, II, III)에 따라 각각 0.2, 0.3 및 0.5 mg/L로 강화되는 방류수수질기준을 준수하기 위해서는 화학물질을 이용한 추가적인 인 처리시설을 적용할 필요성이 대두되었다. 강화된 총인의 수질기준을 만족하기 위해 적용된 물리화학적 처리기술 성능의 구체적인 운영자료 구축을 위하여, 화학적 응집제 사용 중인 인 처리시설 중 모범적으로 가동하고 있는 국내 시설의 운영 데이터를 분석하여 처리성능을 평가하였다. 또한, jar 테스트를 이용해 물리화학적 인 제거공정 적용 시 최적 응집제 주입율 도출, 인 제거 및 슬러지 발생특성을 관찰하고 약품비용과 슬러지 발생증가량을 산정하여 실처리장에 응집제 적용 시 예상되는 경제성 분석을 하였다. 활성슬러지를 이용한 jar 테스트 결과, 0.5와 0.2 mg/L 이하의 총인 농도를 달성하기 위해 필요한 최소한의 응집제(황산알루미늄, 폴리염화알루미늄)의 주입농도는 각각 25와 30 mg/L (as $Al_2O_3$)이며, 2차 처리수의 경우에는 동일한 총인 농도를 달성하기 위해 요구되는 응집제 주입농도가 활성슬러지에 비해 약 1/12~1/3 수준으로 감소하였다. jar 테스트 결과, 활성슬러지에 응집제를 주입할 경우에 고형물 농도가 약 10~11%가 증가할 것으로 예측되었다. 한편, 활성슬러지에 응집제를 주입하는 경우의 응집제(황산알루미늄) 구입비는 2차 처리수에 주입하는 경우에 비해 약 4~10배 정도가 증가할 것으로 산정되었다. 또한, 슬러지 발생량은 약 4~10배 정도 증가할 것으로 예측되었다.

• 한국세라믹학회지
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• 제51권2호
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• pp.72-81
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• 2014

The main mineral phases of natural hydraulic lime (NHL) as a hydraulic lime binderare $Ca(OH)_2$, $C_2S$, $C_3S$, $C_3A$, and $SiO_2$ residues. Also, NHL has the characteristic of setting and hardening by a hydration reaction with water and by carbonation reactions with carbon dioxide from the air. In this study, in an effort to investigate changes of the mineral phases by NHL hydration and carbonation reactions, transitions of mineral phases and the microstructures of hardened pastes were analyzed by XRD, DSC, SEM, and by pore size distributions using domestic and foreign-sourced NHL pastes after curing at 1, 3, 7, and 28 days. On the basis of the analysis results, it was confirmed that domestic low-grade limestone can be used for the manufacturing of NHL. The main hydration mineral phases were $Ca(OH)_2$, $CaCO_3$, $C_2S$, and $SiO_2$ residues, while in the case of foreign-sourced NHL, a small amount of an aluminium hydration phase formed. Also, the $CaCO_3$ content after the carbonation reaction increased with an increase in the curing time. After hydration for 28 days, NHL containing considerable amounts of $C_2S$ and $C_3S$ showed higher carbonation ratios than others types.

• 공업화학
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• 제17권2호
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• pp.188-193
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• 2006

용액의 pH, 주입방법, 온도, 유량의 변화를 주면서 질산알루미늄($Al_{3}(NO_{3})_3{\cdot}9H_{2}O$)을 암모니아수($NH_{4}OH$)로 침전시켜 베마이트(Boehmite)를 합성하였다. 베마이트 상이 형성되는 pH 범위와 입자의 형상과 기공특성에 미치는 합성 조건의 영향을 조사하였다. 베마이트는 반응 용액의 pH가 7.5~9일 때 형성되었고, P2jet 주입방법은 침전이 일어나는 동안 pH를 일정하게 유지할 수 있어 용액내의 반응에 참여하는 이온의 농도가 일정하게 유지되어 균일한 크기의 입자와 기공을 형성할 수 있게 하였다. 따라서 비표면적과 기공부피 두 가지 동시에 향상되었다. 온도가 올라갈수록, 유량이 감소할수록 비표면적과 기공부피가 증가함을 보이고, $60^{\circ}C$ 이상에서는 미세섬유모양의 입자를 얻을 수 있었다. 최적의 조건은 pH 9에서 P2jet 방법으로 주입하고 반응온도 $90^{\circ}C$와 유량 2.5 mL/min을 유지하였을 경우로 비표면적은 $385.46m^2/g$이고 기공 부피는 1.0252 mL/g을 가지는 평균 10 nm의 기공이 형성된 다공성 베마이트를 얻을 수 있었다.