Melt-crystallization monitoring system for the purification of 10 kg-scale LiCl salt waste

Choi, Jung-Hoon,Lee, Tae-Kyo,Lee, Ki-Rak,Han, Seung-Youb,Cho, Yung-Zun,Kim, Na-Young,Jang, Seon-Ah,Park, Hwan-Seo,Hur, Jin-Mok Elsevier 2018 Nuclear engineering and design Vol.326 No.-

<P><B>Abstract</B></P> <P>Salt waste treatment process in the pyrochemical process is under development to separate or concentrate fission products from the LiCl salt waste and to minimize waste volume by recycling the purified LiCl salt into the electrochemical process. In particular, the Cs nuclide in the LiCl salt waste is difficult to separate by chemical method, so that melt-crystallization method has been employed and engineering-scale melt-crystallization system capable of 20 kg/batch treatment has been designed and installed at the PyRoprocess Inactive integrated Demonstration (PRIDE) facility. In this study, in order to evaluate scaled-up design of melt-crystallization process, the preliminary crystallization test was conducted with 10 kg LiCl salt waste having surrogate Cs, Sr, and Ba nuclides. In consideration of temperature gradients generated inside the crystallization vessel owing to the scale-up, melt-crystallization monitoring system was developed. Using the monitoring system, we could obtain purified LiCl crystal with uniform distribution of quantity on 6 crystallization plates and high separation efficiency of over 90% at various cooling conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Engineering scale melt-crystallization monitoring system has been developed. </LI> <LI> Surrogate LiCl salt waste was used for the melt-crystallization test. </LI> <LI> Monitoring system was developed to prevent the formation of over-growing. </LI> <LI> High nuclide separation efficiency was obtained using monitoring system. </LI> </UL> </P>

탄소나노섬유가 폴리케톤의 용융결정화거동에 미치는 영향

김성혜,박진호,이상철,정영규,Kim, Sung Hae,Park, Jinho,Lee, Sang Cheol,Jeong, Young Gyu 한국섬유공학회 2016 한국섬유공학회지 Vol.53 No.4

We report the influences of carbon nanofiber (CNF) on the melt-crystallization behavior and structures of polyketone (PK) composites, which were manufactured by a solution blending process. For this purpose, melt-crystallization experiments of neat PK and its composites, including 0.5 and 1.0 wt% CNFs, were carried out at different isothermal temperatures by using a differential scanning calorimeter and the results were analyzed using the Avrami equation. For all neat PK and PK/CNF composites, the Avrami index n remained unchanged, regardless of the isothermal crystallization temperatures ($T_c$), whereas the rate constant K and the inverse of crystallization half-time (${t_{1/2}}^{-1}$) increased noticeably with decreasing ${T_c}^{\prime}s$, indicating faster melt-crystallization rates at lower ${T_c}^{\prime}s$. It was further revealed that the melt-crystallization rates of PK/CNF composites were far greater than those of neat PK owing to the nucleating effect of CNF to the melt-crystallization of PK and that the composite with 1.0 wt% CNF exhibited slightly better crystallization rates, compared to the composite with 0.5 wt% CNF. Polarized optical microscopic images and X-ray diffraction patterns also support that CNF contributes to accelerate the melt-crystallization rates of PK without influencing the crystal structure of PK ${\beta}$-form.

Effects of Humidity and Surfaces on the Melt Crystallization of Ibuprofen

Lee, Dong-Joo,Lee, Suyang,Kim, Il Won Molecular Diversity Preservation International (MD 2012 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.13 No.8

<P>Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with –CH<SUB>3</SUB>, –OH, and –COOH functional groups. Effects of the humidity were studied at room temperature (18–20 °C) with relative humidity 33%, 75%, and 100%. Effects of the surfaces were observed at −20 °C (relative humidity 36%) to enable close monitoring with slower crystal growth. The nucleation time of ibuprofen was faster at high humidity conditions probably due to the local formation of the unfavorable ibuprofen melt/water interface. The crystal morphologies of ibuprofen were governed by the nature of the surfaces, and they could be associated with the growth kinetics by the Avrami equation. The current study demonstrated the effective control of the melt crystallization of ibuprofen through the melt/atmosphere and melt/surface interfaces.</P>

Direct Observation of Interfacial Morphology in Poly(3-hexylthiophene) Transistors: Relationship between Grain Boundary and Field-Effect Mobility

Choi, Danbi,Jin, Sangwoo,Lee, Youngmin,Kim, Se Hyun,Chung, Dae Sung,Hong, Kipyo,Yang, Chanwoo,Jung, Jungwoon,Kim, Jin Kon,Ree, Moonhor,Park, Chan Eon American Chemical Society 2010 ACS APPLIED MATERIALS & INTERFACES Vol.2 No.1

<P>We investigated the effects of microstructural (crystallization and molecular orientation) and morphological alternation (grain boundary) of poly(3-hexylthiophene) (P3HT) films on the field-effect mobility (μ) before (as-spun P3HT) and after (melt-crystallized P3HT) melting of P3HT films. Although grazing incidence X-ray scattering shows that melt-crystallized P3HT has a more highly ordered edge-on structure than as-spun P3HT, the melt-crystallized P3HT reveals μ = 0.003 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>; this is an order of magnitude lower than that of as-spun P3HT (μ = 0.01 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>). In addition, the interfacial morphologies of the bottom surfaces of P3HT films, which are attached to the gate dielectric, were investigated using a film transfer technique. The melt-crystallized P3HT at this interface consists of well-developed nanowire crystallites with well-defined grain boundaries that act as trap states, as verified by analysis of the temperature-dependence of μ. The remarkable reduction of μ in low-molecular-weight P3HT film (8 kg/mol) that results from melt-crystallization is due to the increased number of well-defined grain boundaries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2010/aamick.2010.2.issue-1/am9005385/production/images/medium/am-2009-005385_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am9005385'>ACS Electronic Supporting Info</A></P>

Effects of sweating time and cooling strategy on purification of N-vinyl-2-pyrrolidinone using a melt crystallizer

강정원,Sun Hyung Kim,서명도,탁문선,김우식,양대륙 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.11

A melt crystallization process is proposed to produce high-purity n-vinyl-2-pyrrolidinone (NVP). To produce high purity products, operation strategy plays key role in the melt crystallizer. We investigated the cooling strategy and optimal sweating time using a batch-type melt crystallizer. A slow cooling followed by a slow heating was found to be an effective temperature profile to produce high purity of NVP. The optimal sweating time was found to be about 20 minutes. For industrial application, a cascade melt crystallizer which consists of four stages was constructed and the proposed crystallization/sweating scheme was applied. Using the new melt crystallizer, NVP more than 99.99%purity can be produced in semi-continuous mode.

Novel porous materials prepared by repeated directional melt crystallization

김현진,이종휘 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Porous polymeric materials have been widely used as critical components in environmental, electrical and medical applications. We fabricated novel porous structures via directional crystallization and photo crosslinking in repeated manners. The solution used in this directional crystallization was composed of dimethylsiloxane and benzene. First, a cross-linked, honeycomb-like structure was prepared by 1st directional crystallization of the solvent and subsequent photo cross-linking in freezer. In this structure, the solution was infiltrated and the 2nd directional crystallization and photo cross-linking were processed once more. Because of the 2nd directional crystallization, the structures and physical properties of the final porous materials turned out to be novel. The repeated directional crystallization resulted in increased hardness and modulus than those of the structure fabricated by single directional crystallization. On the other hand, porosity and contact angle became lower in the structure fabricated by repeated directional crystallization.

N-vinyl-2-pyrrolidone과 2-pyrrolidone 혼합물의 고-액 상평형 및 용융결정화를 이용한 N-vinyl-2-pyrrolidone의 결정성장속도 연구

김선형 ( Sun Hyung Kim ),서명도 ( Myoung Do Seo ),탁문선 ( Moon Seon Tak ),김우식 ( Woo Sik Kim ),양대륙 ( Dae Ryuk Yang ),강정원 ( Jeong Won Kang ) 한국화학공학회 2013 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.51 No.5

Solid-liquid equilibria for mixtures composed of n-vinyl-2-pyrrolidone (NVP) and 2-pyrrolidone were measured as a basic study for the melt crystallization process to remove 2-pyrrolidone as impurity included in NVP. A differential scanning calorimeter (DSC) and a crystallizer were used and the experimental results obtained from two methods were similar. The mixture showed a eutectic system which has a single composition at the minimum melting temperature. Calculation results from simple thermodynamic equations were found in general agreements with present data. To determine the growth rate of NVP crystal which is important for the design of crystallization process, thicknesses of the crystal were measured with the time using a layer melt crystallizer. The growth rates increased as cooling temperatures decreased. Heat transfer coefficient correlated from present data was found to successfully describe the crystal growth behavior.

Skull melting법에 의한 Al2O3 파우더 용융

최현민,김영출,석정원 한국결정성장학회 2019 韓國結晶成長學會誌 Vol.29 No.1

The current study demonstrates an efficient procedure to create ingots from Al2O3 powder using the skull melting method to use these ingots as a starting material in conventional methods for growing synthetic single-crystal sapphire. Dimension of the cold crucible was 24 cm in inner diameter and 30 cm in inner height, 15 kg of Al2O3 powder was completely melted within 1 h at an oscillation frequency of 2.75 MHz, maintained in the molten state for 3 h, and finally air-cooled. The areal density and components of the cooled ingot by parts were analyzed through scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The areal density and Al2O3 content of the ingot were related to the temperature distribution inside the cold crucible during high-frequency induction heating, and the area with high temperature was high tends to be high in areal density and purity. 사파이어 단결정을 성장시키는 기존 합성방법들의 원료충진율을 높이기 위한 방법으로 스컬용융법을 사용하여Al2O3 파우더를 용융시켰다. 냉각도가니 크기는 내경 24 cm, 내부 높이 30 cm로서 2.75 MHz 발진주파수에서 15 kg의 Al2O3 파우더를 1시간 내에 모두 용융시켰으며, 3시간 동안 융액상태로 유지 후 자연냉각 시켰다. 냉각된 잉곳의 부분별 면밀도및 성분은 SEM-EDS를 통해 분석하였다. 잉곳의 면밀도 및 Al2O3 함량은 고주파유도가열 시 냉각도가니 내부에 형성되는온도 분포와 관련이 있으며, 온도가 높게 형성되었던 부분이 면밀도 및 순도가 높게 나타나는 경향을 보였다.

단결정 실리콘 잉곳 결정성장 속도에 따른 고-액 경계면 형성 및 Defect 최적화

전혜준(Hye Jun Jeon),박주홍(Ju Hong Park),블라디미르 아르테미예프(Vladimir Artemyev),정재학(Jae Hak Jung) 한국태양광발전학회 2020 Current Photovoltaic Research Vol.8 No.1

It is clear that monocrystalline Silicon (Si) ingots are the key raw material for semiconductors devices. In the present industries markets, most of monocrystalline Silicon (Si) ingots are made by Czochralski Process due to their advantages with low production cost and the big crystal diameters in comparison with other manufacturing process such as Float-Zone technique. However, the disadvantage of Czochralski Process is the presence of impurities such as oxygen or carbon from the quartz and graphite crucible which later will resulted in defects and then lowering the efficiency of Si wafer. The heat transfer plays an important role in the formation of Si ingots. However, the heat transfer generates convection in Si molten state which induces the defects in Si crystal. In this study, a crystal growth simulation software was used to optimize the Si crystal growth process. The furnace and system design were modified. The results showed the melt-crystal interface shape can affect the Si crystal growth rate and defect points. In this study, the defect points and desired interface shape were controlled by specific crystal growth rate condition.

Molecular Dynamics Study on Atomistic Details of the Melting of Solid Argon

Han, Joo-Hwan The Korean Ceramic Society 2007 한국세라믹학회지 Vol.44 No.8

The atomic scale details of the melting of solid argon were monitored with the aid of molecular dynamics simulations. The potential energy distribution is substantially disturbed by an increase in the interatomic distance and the random of set distance from the lattice points, with increasing temperature. The potential energy barriers between the lattice points decrease in magnitude with the temperature. Eventually, at the melting point, these barriers can be overcome by atoms that are excited with the entropy gain acquired when the atoms obtain rotational freedom in their atomic motion, and the rotational freedom leads to the collapse of the crystal structure. Furthermore, it was found that the surface of crystals plays an important role in the melting process: the surface eliminates the barrier for the nucleation of the liquid phase and facilitates the melting process. Moreover, the atomic structure of the surface varies with increasing temperature, first via surface roughening and then, before the bulk melts, via surface melting.