• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.1
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• pp.49-58
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• 2018

For the immobilization of high-radioactive nuclides such as Cs and Sr by high-temperature thermal decomposition, this study was carried out to investigate the phase transformation with calcined temperature by using TGA (thermogravimetric analysis) and XRD (X-ray diffraction) in the Cs-adsorbed CHA (chabazite zeolite of K type)-Cs and CHA-PCFC (potassium cobalt ferrocyanide)-Cs zeolite system, and Sr-adsorbed 4A-Sr and BaA-Sr zeolite system, respectively. In the case of CHA-Cs zeolite system, the structure of CHA-Cs remained at up to $900^{\circ}C$ and recrystallized to pollucite ($CsAlSi_2O_6$) at $1,100^{\circ}C$ after undergoing amorphous phase at $1,000^{\circ}C$. However, the CHA-CFC-Cs zeolite system retained the CHA-PCFC-Cs structure up to $700^{\circ}C$, but its structure collapsed in $900{\sim}1,000^{\circ}C$, and then transformed to amorphous phase, and recrystallized to pollucite at $1,100^{\circ}C$. In the case of 4A-Sr zeolite system, on the other hand, the structure of 4A-Sr maintained up to $700^{\circ}C$ and its phase transformed to amorphous at $800^{\circ}C$, and recrystallized to Sr-feldspar ($SrAl_2Si_2O_8$, hexagonal) at $900^{\circ}C$ and to $SrAl_2Si_2O_8$ (triclinic) at $1,100^{\circ}C$. However, the BaA-Sr zeolite system structure began to break down at below $500^{\circ}C$, and then transformed to amorphous phase in $500{\sim}900^{\circ}C$ and recrystallized to Ba/Sr-feldspar (coexistence of $Ba_{0.9}Sr_{0.1}Al_2Si_2O_8$ and $Ba_{0.5}Sr_{0.5}Al_2Si_2O_8$) at $1,100^{\circ}C$. All of the above zeolite systems recrystallized to mineral phase through the dehydration/(decomposition) ${\rightarrow}$ amorphous ${\rightarrow}$ recrystallization with increasing temperature. Although further study of the volatility and leachability of Cs and Sr in the high-temperature thermal decomposition process is required, Cs and Sr adsorbed in each zeolite system are mineralized as pollucite, Sr-feldspar and Ba/Sr-feldspar. Therefore, Cs and Sr seen to be able to completely immobilize in the calcining wasteform/(solidified wasteform).

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.2
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• pp.147-154
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• 1984

Two Fe-hydrous oxide A,B and one Al-hydroxide minerals were synthesized precipitating Fe $Cl_3$ and $AlCl_3$ with alkali solution(NaOH) at pH 6.0, 12.0 and 4.5 respectively, for precise understanding of physico-chemical and surface charge characteristics of soils in which these minerals are dominant. Identification of these final products, effect of free and amorphous materials on X-ray diffraction analysis, particle size distribution and surface change characterics of these minerals were performed. Fe-hydroxide A and B were identified as great deal of X-ray amorphous material and as goethite with large amount of X-ray amorphous material, respectively. Dehydration by oven at $105^{\circ}C$ of these minerals exhibited akaganeite peaks with low X-ray amorphous hump and pure goethite peaks for Fe-hydroxide A and B, respectively. Both minerals, however, turned into hematite upon firing at $550^{\circ}C$. On the other hand, Al-hydroxide identified as mixture of gibbsite and bayerite of around 7:3 ratio. Application of sodium dithionite and ammonium oxalate solutions for removal of free or amorphous Fe and Al from these minerals revealed that only peak intensities of Al-hydroxide system were enhanced upon Al-extraction by oxalate solution even though dithionite solution was much powerful to extract Fe from Fe-hydrous oxide systems. Original(wet) Fe-hydrous oxide A has the highest specific surface and surface charge development(negative and positive), and the greatest amount of less than $2{\mu}m$ sized particles. Specific surface and clay sized particles(less than $2{\mu}m$) of Fe-hydrous oxide A, however, were drastically reduced upon dehydration($P_2O_5$ and oven drying) compare to the rest minerals. The Z.P.C. of these synthetic minerals were 8.0-8.5, 7.5-8.0 and 5.5-6.0 for Fe-hydrous oxide A, B and Al-hydroxide, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.2
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• pp.95-101
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• 1991

The results of relationships between colloidal stability and soil pH on three Hawaii's volcanic ash soils developed under the three different rainfall conditions can be summarized as follows: 1. The Hilo soil only revealed the increase of colloidal stability by becoming for from Z.P.C point to either side of pH. 2. Hilo and Kawaihae soils, however, showed the increase of colloidal stability only in the higher pH range than their Z.P.C. 3. $P_2O_5$ drying procers decreased colloidal stability kof these soils because of so called irreversible drying characteristics of amorphous materials and the decrement was in order of: Akaka>Hilo>Kawaihae expressing positive correlation with content of amorphous materials in them. 4. The difference of colloidal stability curves among three soils can easily be interpreted by DLVO theory considering 0.1N-HCl amount added to decrease their soil pH, respectively. The addition of large amount of 0.1N-HCl into Akaka and Kawaihae soils did not effectively develop the positive charge but resulted in the shrink of diffuse double layer thickness inducing large attraction forces among soil particles.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.2
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• pp.168-178
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• 1983

Influence of several dehydration treatments on original structure and water behavior in the process of drying were investigated employing three hawaiian volcanic ash soils and four synthetic minerals. These three soils were developed under different rainfall condition and contained three different amount of amorphous materials in them. Measurement of water losses by oven drying at $105^{\circ}C$, $P_2O_5$ drying, freeze drying, and critical point drying revealed that more water losses were noted by oven drying than by three other drying techniques and the differences of water losses between oven and $P_2O_5$-drying were closely related to amoun: of amorphous materials in them, showing the order of Kaiwiki > Hilo > Kawaihae. This indicates that dehydration of amorphous materials by elevated temperature ($105^{\circ}C$) excluded water beyond that in the adsorbed (hygroscopic) state. The effect of dehydration treatments on initial structure was visualized by scanning electron microscopy. The micrographs showed that oven-and $P_2O_5$-dried samples formed into large mass of sub-angular blocky, dense, and closed crumbs, while the freeze dried and critical point dried samples resulted in less shrinkage, and small, fluffy and open spongy structure. However, critical point drying technique produced bulkier, softer, and greater open structure samples than even freeze drying. Additional Index Words: original structure, synthetic minerals, critical point drying, $P_2O_5$ drying. 1. This is a part of author's Ph.D. dissertation submitted to the University of Hawaii, Honolulu, Hawaii 96822 in 1979. 2. Professor of Agricultural Chemistry, Korea University.

• Journal of Sericultural and Entomological Science
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• v.38 no.2
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• pp.160-167
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• 1996

The middle silk gland, that is a liquid silk thread gland consisting of silk protein, was taken out and a silk monofilament was made by drawing rapidly to approximately 3 times. In order to deteriorate the inter molecular hydrogen bonding force and to stretch in, the drawn silk filament was swoolen in boiling water. The results obtained are as follows ; The silk gland sample that just dried silk gland was occupied in crystalline region of silk-I type and random amorphous region. According to the examination of X-ray diffraction and thermal analysis, silk-II type crystal begins to appear partially in monofilament sample and spread to almost complet silk-II type crystal in 65.2% drawn sample. And, orientation of silk fibroin mlecule increased suddenly in early stage with a rise of drawing ratiofrom birefringence and density, and it was found that orientation of fibroin molecule was completed. As drawing ratio increases relation with time of hydrolysis, birefringence appeared almost fixed a tendency. Crystallization collapse by hydrolysis was not found in X-ray diffraction and thermal analysis. But, amorphous region began to flow by treated hydrolysis, that orientation of crystallization part was disturbed was supposed.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.597-608
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• 1994

A new process for the production of high purity ${\alpha}-Al_2O_3$ from ammonium aluminium sulfate solution abtained through the sulfation of low grade bauxite ore with $(NH_4)_2SO_4$, and leaching of the sulfated product was investigated. This process is consisted of solvent extraction for Fe component removal from ammonium aluminum sulfate solution and homogeneous precipitation of Al containing precipitate from the refined ammonium aluminium sulfate solution by using urea as precipitator. The optimum conditions of solvent extraction with Alamine 336 as extractant were shaking time of 4min, organic phase ratio to aqueous phase of 0.25. The types of precipitation products from this precipitation were amorphous alumina gel, pseudo-boehmite and crystalline boehmite in the lower temperature of $100^{\circ}C$, in the range from $125^{\circ}C$ to $150^{\circ}C$, and above $150^{\circ}C$, respectively. And also amorphous alumina gel hydrate in $1000^{\circ}C$ and crystalline boehmite in $1250^{\circ}C$ were tranfered to ${\alpha}-Al_2O_3$, respectively. This alumina was identified as ${\alpha}-Al_2O_3$ of purity 99.7%.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.411-417
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• 2013

To use as an anode material of lithium secondary battery, graphite-silicon composite powders are prepared by ball-milling with silicon nanoparticles (average diameter 100 nm, 0~50 wt%) and graphite powder (average diameter $15{\mu}m$) and their electrochemical properties are examined. As the silicon content increases, the graphite becomes smaller by the ball-milling and amorphous phase appears whereas the silicon do not suffer the change of nanocrystalline phases and embeds within the amorphous phase of graphite. Cyclic voltammetry at low scan rate reveals that typical oxidation peaks of graphite and silicon appear at 0.2~0.35 and 0.55~0.6 V, respectively, with higher reversibility for repeated cycles. In contrast, the high-scan-rate redox behavior is very irreversible for repeated cycles. High irreversible capacity is exhibited in the initial charging-discharging cycles, but it diminishes as the cycle number increases. The saturated discharge capacity achieves about 485 mAh $g^{-1}$ at 50th cycle for the composite of Si 20 wt%. This is due to the formation of amorphous graphite morphology by the adequate composition (C:Si=8:2 w/w), which efficiently buffers the volume change during alloying/dealloying between silicon and lithium.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.263-264
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• 2002

무정형 고분자인 폴리카보네이트는 투명하고 뛰어난 기계적 성질(특히 내충격성) 내열성 내한성ㆍ전기적 성질을 균형 있게 갖추고, 무독하고 자기소화성(自己消火性)도 있는 엔지니어링 플라스틱이다. 본 연구의 목적은 이러한 특성을 가지는 폴리카보네이트를 이용하여 전기방사법으로 sub-micron의 섬유직경으로 구성된 부직포를 제조하는데 있다. (중략)

• Polymer Science and Technology
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• v.15 no.3
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• pp.296-302
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• 2004

최근 분자들의 자기조립 현상을 나노-바이오 소자 개발에 응용하는 연구가 활발히 진행되고 있으며, 이러한 응용을 위한 대표적인 자기조립체로는 양친성 계면활성제, 블록공증합체, 콜로이드와 초분자체를 들 수 있다. 대부분의 콜로이드가 구형 모양으로 vander Waals interaction에 의하여 3-D결정 (crystal) 형태의 자기조립구조를 형성하는 반면에, 콜로이드를 제외한 대부분의 자기조립체는 적정 조건에서 액정 (liquid crystals), 결정 (crystal) 및 무정형 (amorphous)을 형성한다. 적용하고자 하는 응용의 범위와 재료의 특성에 따라서 각 상태 (phase)를 이용할 수 있으나, 액정상을 이용하는 것과 결정상을 이용하는 경우가 대부분이다. (중략)

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1366-1368
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• 2001

In this study it can be confirmed that the formula by the free-rotational dipole theory is similiar with that by the phenomenological theory and the non-linear permittivity is determined only with the third harmonic conponent of polarization. Various parameters of VDCN copolymers were obtained from fitting results with the related formula.