• Nuclear Engineering and Technology
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• 제51권3호
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• pp.792-799
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• 2019

The present study aims to investigate the fluorination of thorium oxide ($ThO_2$) by ammonium hydrogen difluoride ($NH_4HF_2$). Fluorination was performed at room temperature by mixing $ThO_2$ and $NH_4HF_2$ at different molar ratios, which was then left to react for 20 days. Next, the mixtures were analyzed using X-ray diffraction (XRD) at the intervals of 5, 10, 15, and 20 days, followed by the heating of the mixtures at $450-750^{\circ}C$ with argon gas flow. The characterization of $ThF_4$ was established using X-ray diffraction (XRD) and scanning electron microscopy-dispersion X-ray spectroscopy (SEM-EDX). In this study, ammonium thorium fluoride was synthesized through the fluorination of $ThO_2$ at room temperature. The optimum molar ratio in synthesizing ammonium thorium fluoride was 1.0:5.5 ($ThO_2:NH_4HF_2$) with 5 days reaction time. In addition, the heating of ammonium thorium fluoride at $450^{\circ}C$ was sufficient to produce $ThF_4$. Overall, this study proved that $NH_4HF_2$ is one of the fluorination agents that is capable of synthesizing $ThF_4$.

• 폴리머
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• 제34권4호
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• pp.386-389
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• 2010

Thermal behaviors of water in the poly(acrylic acid) (PAA)/water mixtures with 0.1 M NaCl, HCl, and NaOH were investigated by DSC. It showed that adding ions in the mixtures affected the crystallization of water evidently. Compared with the PAA/water mixtures, the $T_m$ of freezable bound water in the mixtures with ions moved to lower values and varied with different cations and anions, due to the stabilization or destabilization of the hydrogen-bonding hydration between polymers and water molecules through ionic hydration. The content of non-freezable bound water in the non-crystalline phase of the PAA/water mixtures with ions was not constant, it increased with total water content gradually, owing to the more binding sites created by ions. The ions could change the distribution of different states of water in the polymer aqueous solutions evidently.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.642-644
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• 1999

We have prepared the plasma-polymerized membrane for pervaporation of organic-liquid mixtures by the plasma polymerization technique. Plasma polymerization techniques were utilized in the development of hydrophilic composite membranes having high hydrogen ion permeability and excellent dimensional stability. To develop an organic liquid permselective Membrane, suppressing membrane swearing as well as enhancing the solubility difference is impotant. the objectives of the present study are to disign a suitable membrane for an organic-mixture system by the control of the plasma-polymer solubility.

• 한국재료학회지
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• 제27권10호
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• pp.513-517
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• 2017

An optimum route to fabricate a hybrid-structured W powder composed of nano and micro size powders was investigated. The mixture of nano and micro W powders was prepared by a ball milling and hydrogen reduction process for $WO_3$ and W powders. Microstructural observation for the ball-milled powder mixtures revealed that the nano-sized $WO_3$ particles were homogeneously distributed on the surface of large W powders. The reduction behavior of $WO_3$ powder was analyzed by a temperature programmed reduction method with different heating rates in Ar-10% $H_2$ atmosphere. The activation energies for the reduction of $WO_3$, estimated by the slope of the Kissinger plot from the amount of reaction peak shift with heating rates, were measured as 117.4 kJ/mol and 94.6 kJ/mol depending on reduction steps from $WO_3$ to $WO_2$ and from $WO_2$ to W, respectively. SEM and XRD analysis for the hydrogen-reduced powder mixture showed that the nano-sized W particles were well distributed on the surface of the micro-sized W powders.

• 대한화학회지
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• 제29권1호
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• pp.45-51
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• 1985

MeOH-DMSO 혼합용매중에서 t-butyl halide의 가메탄올 분해반응 속도상수 및 활성화 파라미터를 전기전도도법으로 측정하였고, Taft의 분광용매화 변수인 용매의 극성-편극성(${\pi}^{\ast}$), 수소결합주기산도(${\alpha}$) 및 수소결합 받기염기도(${\beta}$)를 분광법에 의해서 5가지의 지시약을 이용하여 측정계산하였다. 분광용매화변수와 반응속도상수로부터 얻은 활성화파라미터를 써서 용매의 부피조성비에 따른 가용매분해반응의 속도상수 변화를 논의한 결과, t-butyl halide의 이온화에 용매의 ${\pi}^{\ast}$, ${\alpha}$ 및 ${\beta}$가 협동적으로 기여했고, 또한 이탈기와 혼합용매사이의 이온-쌍극자 작용과 수소결합주기-받기 작용과 같은 독특한 상호작용이 전이상태의 안정화에 미치는 가장 중요한 용매효과 인자들임을 밝혔다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.336-339
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• 2006

With the steady depletion off fossil fuel reserves, hydrogen based energy sources become increasingly attractive. Therefore hydrogen production or separation technologies, such as Bas separation membrane based on adsorption technology, have received enormous attention in the industrial and academic fields. In this study, the transport mechanisms of the MTES (methyltriethoxysilane) templating silica/a-alumina composite membrane were evaluated by using unary, binary and quaternary hydrogen gas mixtures permeation experiments at unsteady- and steady-states. Since the permeation flux in the MTES membrane, through the experimental and theoretical study, was affected by molecular sieving effects as well as surface diffusion properties, the kinetic and equilibrium separation should be considered simultaneously in the membrane according to molecular properties. In order to depict the transient multi-component permeation on the templating silica membrane, the GMS (generalized Maxwell-Stefan) and DGM (dust Bas model) were adapted to unsteady-state material balance

• 한국자동차공학회논문집
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• 제14권3호
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• 한국항공우주학회지
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• 제40권10호
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• pp.901-909
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• 2012

본 논문은 연료전지 UAV를 위한 고체 상태의 $NaBH_4$ 수소 발생 및 공급 시스템의 특성에 대해 기술하고 있다. 산을 이용하여 $NaBH_4$를 분해할 경우, 발생된 수소의 유량과 압력은 급격히 변화하게 된다. 공급 수소는 자체 가압식 반응기로 안정화 되었고, 수소의 안정화 방법에 대해 소개하였다. 영하조건에서 수소를 발생시키기 위해 묽은 염산을 프로필렌 글리콜 혼합 용액으로 희석하였다. 고체 상태 $NaBH_4$ 수소 발생 및 공급 시스템을 설계하였다. 수소 발생 시스템의 특성을 밝혀내기 위한 기본 구동 실험을 수행하였다.

• 한국재료학회지
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• 제28권9호
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• pp.511-515
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• 2018

W-10 wt% Ti alloys that have a homogeneous microstructure are prepared by thermal decomposition of $WO_3-TiH_2$ powder mixtures and spark plasma sintering. The reduction and dehydrogenation behavior of $WO_3$ and $TiH_2$ are analyzed by temperature programmed reduction and a thermogravimetric method, respectively. The X-ray diffraction analysis of the powder mixture, heat-treated in an argon atmosphere, shows W- oxides and $TiO_2$ peaks. Conversely, the powder mixtures heated in a hydrogen atmosphere are composed of W, $WO_2$ and $TiO_2$ phases at $600^{\circ}C$ and W and W-rich ${\beta}$ phases at $800^{\circ}C$. The densified specimen by spark plasma sintering at $1500^{\circ}C$ in a vacuum using hydrogen-reduced $WO_3-TiH_2$ powder mixtures shows a Vickers hardness value of 4.6 GPa and a homogeneous microstructure with pure W, ${\beta}$ and Ti phases. The phase evolution dependent on the atmosphere and temperature is explained by the thermal decomposition and reaction behavior of $WO_3$ and $TiH_2$.

• Journal of Magnetics
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• 제6권1호
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• pp.13-18
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• 2001

Permalloy soft magnets have been produced by the powder injection molding process. Rheological characteristics of mixtures, debinding conditions, and the magnetic properties of permalloy after sintering have been investigated. A permalloy soft magnet with a permeability of 14200 could be obtained by preparing a mixture with a powder loading of 65.4 vol % and a PP/PEG binder systems solvent extraction, thermal debinding, and subsequent sintering at 1350$\^{C}$ in hydrogen. The permalloy soft magnet sintered in hydrogen had 95% of theoretical density and a magnetic induction of 13.2 kG in an applied magnetic field of 50 Oe.