• Resources Recycling
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• v.13 no.6
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• pp.9-15
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• 2004

The optimum conditions were studied for the preparation of transparent iron oxide with the air oxidation of FeOOH. The FeOOH obtained by mixing NaOH and FeSO$_4$ solution in various conditions such as R(=2NaOH/FeSO$_4$), FeSO$_4$ concentration. reaction temperature and air flow rate. When the FeSO$_4$ increased gradually, the concentration of iron ion in the solution became high. So, particle size increased precipitating Fe$_3O_4$. Goethite dehydrate at about 200$^{\circ}C$ and ended the reaction at about 320$^{\circ}C$ forming hematite. The lower the reaction temperature was, the shorter the particle length of goethite and particle size decreased. When the flow rate of air as an oxidant increased, the amount of dissolved oxygen in the solution increased, which made oxidation rate increased. And then particle size of goethite decreased.

• Korean Journal of Materials Research
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• v.8 no.3
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• pp.256-262
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• 1998

산소이온전도체 13mol% CaO안정화 $ZrO_{2}$에 대한 $AI_{2}$$O_{3}$의 첨가효과를 살펴보기 위해 출발원료분말을 ($Zr_{0.87}$ $Ca_{0.13}$ O$1.87_{1-x}$ $AI_{2}$$O_{3}$)x,(x=0,0.01,0.02,0.03,0.05)와 같은 조성이 되도록 공침법으로 합성하고 $1400^{\circ}C$에서 소결시켜, $AI_{2}$$O_{3}$의 첨가에 따른 /grain size의 변화, $AI_{2}$$O_{3}$의 형태 및 존재위치, 소결밀도의 변화, 그리고 저항률의 변화를 살펴보았다. 그 결과, 결정립의 크기는 1mol% A $I_{2}$$O_{3}$첨가까지는 증가하였고, 2mol%첨가이상에서는 입계로 석출하기 시작한 $AI_{2}$$O_{3}$의 pinning효과에 기인되어 감소하였다. 또 1mol% $AI_{2}$$O_{3}$첨가시에 격자상수값의 급격한 감소가 보여지고, 그 이상에서는 변화가 별로 없어 13mol%CaO안정화 $ZnO_{2}$의 고용도한은 최대 1mol%임을 알 수 있었다. 전기전도도 또한 1mol% $AI_{2}$$O_{3}$첨가시에 증가됨을 나타냈다. $ZrO_{2}$에의 고용도한까지의 $AI_{2}$$O_{3}$첨가는 결정립성장을 촉진시키며 밀도값의 증대를 가져오고 전기전도도의 증가를 가져오는 긍정적인 효과를 나타냈다.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.7
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• pp.779-785
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• 2015

Cathodic protection is recognized as the most cost-effective and technically appropriate corrosion prevention method for the submerged zone of offshore structures, ships, and deep-sea facilities. When cathodic protection is applied, the cathodic currents cause dissolved oxygen reduction, generating hydroxyl ions near the polarized surface that increase the interfacial pH and result in enhanced carbonate ion concentration and precipitation of an inorganic layer whose principal component is calcium carbonate. Depending on the potential, magnesium hydroxide can also precipitate. This mixed deposit is generally called "calcareous deposit." This layer functions as a barrier against the corrosive environment, leading to a decrease in current demand. Hence, the importance of calcareous deposits for the effective, efficient operation of marine cathodic protection systems is recognized by engineers and scientists concerned with cathodic protection in submerged marine environments. Calcareous deposit formation on a marine structure depends on the potential, current, pH, temperature, pressure, sea-water chemistry, flow, and time; deposit quality is significantly influenced by these factors. This study determines how calcareous deposits form in sea water, and assesses the interrelationship of formation conditions (such as the sea water temperature and surface condition of steel), deposited structure, and properties and the effectiveness of the cathodic protection.