The effect of Li2O addition on precipitation behavior of uranium in LiCl-KCl-UCl3 has been investigated in this study. 99.99% LiCl-KCl eutectic salt is mixed with 10wt% UCl3 chips at 550°C in the Pyrex tube in argon atmosphere glove box, with 10 ppm O2 and 1 ppm H2O. Then, Li2O chunks are added in mixed LiCl-KCl-UCl3 and the system has been cooled down to room temperature for 10 hours to form enough UO2 particles in the salt. The solid salt has been taken out from the glove box, and cut into three sections (top, middle and bottom) by low-speed saw for further microscopic analysis. Three pieces of solid salt are dissolved in deionized water at room temperature and the solution is filtered by a filter paper to collect non-dissolved particles. The filter paper with particles is baked in vacuum oven at 120°C for 6 hours to evaporate remaining moisture from the filter paper. Further analysis was performed for the powder remaining on the filter paper, and periphery of the powder (cake) on the filter paper. Scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), and X-ray powder diffraction (XRD) are adopted to analysis the characteristic of the particles. From SEM analysis, the powders are consisted of small particles which have 5 to 10 m diameter, and EDS analysis shows they are likely UO2 with 23 at. % of uranium and 77 at. % oxygen. Cake is also analyzed by SEM and EDS, and needle like structures are widely observed on the particle. The length of needle is distributed from 5 to 20 m, and it has 6 to 10 at. % of chlorine, which are not fully dissolved into deionized water at room temperature. From XRD analysis, the particles show the peak position of UO2, and the result is well matched with the SEM-EDS results. We are planning to add more Li2O in the system for fully reacting uranium in UCl3, and compare the results to find the effect of Li2O concentration on UO2 precipitation.

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 oC for 4 and 10 h and then the specimens are cooled by rapid quenching. The samples are aged at 300 oC 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.

This study was carried out to investigate the effect of W substitution on the precipitation behavior of χ and σ phases in super duplex stainless steel. The χ phase was precipitated at the interface of ferrite / austenite phases and inside the ferrite phase at the initial stage of aging. With an increase in the aging time, the volume fraction of the χ phase increased, and then decreased with the transformation from the χ phase to the σ phase. The σ phase was precipitated later than the χ phase, and the volume fraction of x phase increased with the increase in the aging time. The ferrite phase was decomposed into the new austenite (γ2) and σ phases by aging treatment. The decomposition of the ferrite phase into the γ2 and σ phases was retarded by W substitution for Mo. The volume fraction of the χ phase increased and that of the σ phase decreased due to W substitution. The χ and σ phases were intermetallic compounds, which had lower nickel concentration, and higher chromium, molybdenum, and tungsten concentrations. The χ phase has higher molybdenum and tungsten concentrations than those of the σ phase. The amounts of chromium and nickel in the χ and σ phases did not change, but these phases have higher concentrations of molybdenum and tungsten due to W substitution for Mo.

In this research, a precipitation method was used to synthesize β-Ga2O3 powders with various particle morphologies and sizes under varying precipitation conditions, such as gallium nitrate concentration, pH, and aging temperature, using ammonium hydroxide and ammonium carbonate as precipitants. The obtained powders were characterized in detail by XRD, SEM, FT-IR, and TG-DSC. From the TG-DSC result, GaOOH phase was transformed to β-Ga2O3 at around 742˚C, and weight loss percent was about 14 % when NH4OH was used as a precipitant. Also, β-Ga2O3 formed at 749˚C and weight loss percent was about 15 % when (NH)2CO3 was used as a precipitant. XRD results showed that the obtained Ga2O3 had pure monoclinic phase in both cases. When (NH)2CO3 was used as a precipitant, the particle shape changed and became irregular. The range of particle size was about 500nm-4μm based on various concentrations of gallium nitrate solution with NH4OH. The particle size was increased from 1-2μm to 3-4μm and particle shape was changed from spherical to bar type by increasing aging temperature over 80˚C.

The effect of Al addition on the precipitation behavior of a binary Mg-Zn alloy was investigated based on thechanges in the morphology, distribution and element concentration of precipitates formed during aging treatment. The as-castMg-6.0 mass%Zn (Mg-6Zn) and Mg-6.0 mass%Zn-3.0 mass%Al (Al-added) were homogenized at 613K for 48h and at 673Kfor 12h; they were then solid solution treated at 673K for 0.5 h and 1 h, respectively. The Mg-6Zn and Al-added alloys wereaged at 403 K and 433K. The peak hardness of the Al-added alloy was higher than that of the Mg-6Zn alloy at each agingtemperature. Rod-like, plate-like, blocky, and lath-like precipitates were observed in the Al-added alloy aged at 433K for230.4ks, although the rod-like and plate-like precipitates were observed in the TEM microstructure of the Mg-6Zn alloy agedat 433K for 360 ks. Moreover, the precipitates in the Al-added alloy were refined and densely distributed compared with thosein the Mg-6Zn alloy. The Cliff-Lorimer plots obtained by the EDS analysis of the rod-like and plate-like phases in theAl-added alloy peak aged at 433K for 230.4ks were examined. It was confirmed that the phases had higher concentrationof solute Al atom than was present in the phases, indicating that the properties of precipitates can be changed by Al addition.

The particle size of MgO was examined as a function of the Na content in Mg(OH)2 powders and the calcination temperature. Mg(OH)2 suspension was obtained by dropwise precipitation of Mg(NO3)2·6H2O and NaOH solutions. The suspension was diluted by varying the dilution volume ratio of distilled water to Mg(OH)2 suspension to change the Na salt concentration in the suspension. Mg(OH)2 slurry was filtered and dried at 60˚C under vacuum, and then its Mg(OH)2 powder was calcined to produce MgO with different amount of Na content at 500~900˚C under air. Investigation of the physical and chemical properties of the various MgO powders with dilution ratio and calcination temperature variation was done by X-ray diffraction, transmission electron microscopy, BET specific surface area and thermal gravimetric analysis. It was observed that MgO particle size could depend on the condition of calcination temperature and dilution ratio of the Mg(OH)2 suspension. The particle size of the MgO depends on the Na content remaining in the Mg(OH)2 powder, which powder was prepared by changing the dilution ratio of the Mg(OH)2 suspension. This change increased as the calcination temperature increased and decreased as the dilution ratio increased. The growth of MgO particle size according to the increase of temperature was more effective when there was a relatively high content of Na. The increase of Na content lowered the temperature at which decomposition of Mg(OH)2 to MgO took place, thereby promoting the crystal growth of MgO.

The objectives of this study were the development of a synthesis technique for highly active nanosized ITO powder and the understanding of the reaction mechanisms of the ITO precursors. The precipitation and agglomeration phenomena in ITO and precursors are very sensitive to reaction temperature, pH, and coexisting ion species. Excessive ion and ions had a negative effect an synthesizing highly active powders. However, with a relevant stabilizing treatment the shape and size of ITO and precursors could be controlled and high density sintered products of ITO were obtained. By applying the reprecipitation process (or stabilization technique), highly active ITO and powders were synthesized. Sintering these powders at for 5 hours produced 97% dense ITO bodies.

The process of coprecipitation of biocomposite hydroxyapatite/chitosan from aqueous solution at low temperature in alkali environnement was examined. We have shown that initially we have the formation of amorphous octocalcium phosphates and the transferring from OCP to amorphous calcium phosphate , and then from TCP to calcium-deficient hydroxyapatite and hydroxyapatite . The transformation of ACP to HAP was inhibited in the presence of chitosan. The result suggests that there is an affinity binding between ACP and chitosan and subsequently blocking the active growth site of ACP.

In this paper, we investigate the pozzolanic reaction of the waste glass sludge incorporating precipitation additives experimentally. The consumption of calcium hydroxide, and the compressive strength were tested for two different types of the waste glass sludge depending on whether precipitation additives were used.

유역의 물 환경을 분석하기 위해서는 수문관측 자료의 확보가 매우 중요하다. 그러나 유역의 수문 자료의 관측은 비용과 시간적인 문제도 존재하며, 정확한 관측이 어렵다는 문제 또한 존재한다. 따라서 유역의 물 환경을 분석하는데 필요한 수문 관측 자료가 부족한 상태에서는 수문반응을 간접적으로 표현할 수 있는 기후자료와 유역특성자료를 이용해야 된다. 이에 본 연구에서는 유역의 물 환경을 강수분할이라는 현상으로 대변하여 낙동강 유역의 강수분할에 기후 및 유역 특성이 미치는 영향을 분석하였다. 이 때, 강수분할은 Horton 지수로 정량화하여 연구에 적용하였다. 낙동강 유역의 Horton 지수는 기후요소 중 강수량에 의해 그 대부분이 결정되고 있음을 파악하였다. 또한 강수량 뿐 만 아니라 유역특성까지 함께 고려하여 Horton 지수를 예측한 결과, 강수량만을 이용하여 Horton 지수를 예측한 경우보다 Horton 지수의 예측력이 개선되었다. 특히 강수량과 유역의 평균경사를 함께 고려한 Horton 지수를 예측하였을 때 가장 높은 예측력을 가졌다. 이를 통하여 낙동강 유역의 강수분할에 있어서 기후특성 뿐만 아니라 유역특성 또한 일정한 영향력을 가지고 있음을 확인하였다.

1970년대 이후, 우리나라는 산업화에 따른 급격한 도시화가 이루어졌다. 본 논문에서는 우리나라의 대표적인 도시인 서울특별시 및 6대 광역시의 1973년부터 2003년까지의 31개년의 강수랑 자료를 이용하여 강수량의 변화에 대하여 분석하였다. 이와 함께 도시화에 따른 강수량의 변동성을 평가하기 위해서 비도시 지역을 선정하였으며 도시 지역의 강수량 변화와 비교하였다. 도시 지역과 비도시 지역의 연강수량, 계절별 강수량, 지속 시간 1시간 및 24시간연최대