The synthesis of a novel first stage GIC containing simultaneously lithium, potassium and barium through a solid–liquid reaction by molten salts method is described. Such a route has been largely developed in our laboratory for intercalation of metals into graphite. The interplanar distance of this quaternary compound reaches 950 pm and exhibits poly-layered intercalated sheets defined by X-ray measurements. The Li0.2K0.75Ba0.6C6 chemical formula of the compound is determined by ion beam analysis and this GIC is remarkably homogeneous. This GIC is the first poly-layered one containing barium.

This study provides an assessment on a proposed method for separation of cesium, strontium, and barium using electrochemical reduction at a liquid bismuth cathode in LiCl-KCl eutectic salt, investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS). CV studies were performed at temperatures of 723-823 K and concentrations of the target species up to 4.0wt%. Redox reactions occurring during potential sweeps were observed. Concentration of BaCl2 in the salt did not seem to influence the diffusivity in the studied concentration range up to 4.0wt%. The presence of strontium in the system affected the redox reaction of lithium; however, there were no distinguishable redox peaks that could be measured. Impedance spectra obtained from EIS methods were used to calculate the exchange current densities of the electroactive active redox couple at the bismuth cathode. Results show the rate-controlling step in deposition to be the mass transport of Cs+ ions from the bulk salt to the cathode surface layer. Results from SEM-EDS suggest that Cs-Bi and Sr-Bi intermetallics from LiCl-KCl salt are not thermodynamically favorable.

본 연구에서는 기존의 CDI (capacitive deionization)를 이용해 산업 폐수에 함유되어있을 수 있는 바륨 이온 제거에 관해서 연구하였다. Feed 용액은 30 mg/L의 BaCl2 (barium chloride dihydrate) 수용액을 사용하였고, 유속은 10 mL/min 설정하였다. 흡착 조건을 1.2 V에서 3, 5, 7분으로, 탈착 조건은 각각 -1, -1.5, -2 V 및 1, 2, 3분으로 다양하게 조정하여 가장 효율이 높은 조건을 선정하는 실험을 진행하였고, 그 결과 흡착 1.2 V/7분 탈착 -1 V/1분의 조건에서 64.4%의 바륨 이온 제거효율을 나타내었다. 동일한 실험 조건으로 바륨과 같은 농도인 30 mg/L NaCl 수용액에 대하여 CDI의 제거효율과 비교 분석한 결과 흡착 1.2 V/7분 탈착 -1 V/1분의 조건에서 69.9%의 제거효율을 나타내었다.

The properties of powder metallurgy products are related to their densities. In the present work, we demonstrate a method to apply artificial neural networks (ANNs) trained on experimental data to predict the bulk density of barium titanates. The density is modeled as a function of pressure, press rate, heating rate, sintering temperature, and soaking time using the ANN method. The model predictions with the training and testing data result in a high coefficient of correlation (R2 = 0.95 and Pearson’s r = 0.97) and low average error. Moreover, a graphical user interface for the model is developed on the basis of the transformed weights of the optimally trained model. It facilitates the prediction of an infinite combination of process parameters with reasonable accuracy. Sensitivity analysis performed on the ANN model aids the identification of the impact of process parameters on the density of barium titanates.

본 연구는 고방사성해수폐액 (HSW)으로부터 Barium (Ba)이 함침된 4A 제올라이트 (BaA)에 의한 고방사성핵종 중에 하나인 Sr의 흡착 제거를 수행하였다. BaA에 의한 Sr의 흡착 (BaA-Sr)은 Ba의 함침농도 20.2wt% 이상에서 Ba의 함침농도가 증가 할수록 감소하며 Ba 함침농도는 20.2wt% 정도가 적당하였다. 그리고 BaA-Sr 흡착은 BaA 내 4A에 의한 Sr 흡착 (4A-Sr)에 BaSO4 침전에 따른 Sr 공침이 첨가되어, Sr의 농도가 0.2 mg/L 이하 (HSW 내 실제 Sr 농도 수준)에서 BaA는 m/V (흡착제 량/용액 부피)=5 g/L, 4A는 m/V >20 g/L에서 99% 이상의 Sr 제거가 가능하였다. 이는 흡착제 단위 g 당 Sr의 처리용량 및 2 차 고체폐기물 (폐흡착제 등) 발생량 저감화 차원에서 BaA-Sr 흡착이 4A-Sr 흡착보다 우수함을 나타낸다. 또한 BaA-Sr 흡 착이 증류수보다 해수폐액에서 Sr의 제거능이 우수하여 HSW로부터 직접 Sr을 제거하는 데 효과적일 것으로 보인다. 반면 에 BaA에 의한 Cs의 흡착 (BaA-Cs)은 주로 BaA 내 4A에 의해서 이루어지고 있어 함침 Ba의 영향은 거의 없는 것 같다. 한 편 BaA-Sr 흡착속도는 유사 2차 속도식으로 표현할 수 있으며, Sr의 초기농도 및 V/m 비 증가에 따라서 속도상수 (k2)는 감 소하지만 평형흡착량 (qe)은 증가하고 있다. 그러나 용액의 온도증가에 따라서는 반대로 k2는 증가하지만 qe는 감소하고 있 다. BaA-Sr 흡착 활성화에너지는 약 38 kJ/mol 로 강력한 결합 형태를 이룬 화학흡착은 아니더라도 물리적 흡착보다 화학적 흡착이 지배적일 것으로 보인다.

A magnetic powder, M-type barium hexaferrite (BaFe12O19), was consolidated with the spark plasma sin-tering process. Three different holding temperatures, 850℃, 875℃ and 900℃ were applied to the spark plasma sinteringprocess with the same holding times, heating rates and compaction pressure of 30 MPa. The relative density was mea-sured simultaneously with spark plasma sintering and the convergent relative density after cooling was found to be pro-portional to the holding temperature. The full relative density was obtained at 900℃ and the total sintering time wasonly 33.3 min, which was much less than the conventional furnace sintering method. The higher holding temperaturealso led to the higher saturation magnetic moment (σs) and the higher coercivity (Hc) in the vibrating sample magne-tometer measurement. The saturation magnetic moment (σs) and the coercivity (Hc) obtained at 900℃ were 56.3 emu/g and541.5 Oe for each.

The growing conditions of barium nitrate Ba(NO3)2 single crystals using the aqueous solution method have been studied. Supersaturation can be calculated by measuring the temperature of the solution and its equilibrium temperature. Supersaturation of Ba(NO3)2 was 0.7% at 32.0˚C and about 3% at 34.0˚C. The obtained single crystals have three kind of morphology: tetrahedral, cubic, and, rarely, dodecahedral. The normal growth rate is proportional to the supersaturation; it is necessary to make the solution below 5% supersaturation in order to obtain transparent Ba(NO3)2 single crystals. The normal growth rate for 1ar11 faces was 2.51×10-6 mm/s for the 0.7% supersaturation condition (32.0˚C), 6.43×10-6 mm/s for the the condition of 3.0% supersaturation, and 7.01×10-6 mm/s for the condition of 5.0% supersaturation. The quality of the grown crystals depends on the nature of the seed, the cooling rate employed, and the agitation of the solution. The faces of the obtained crystals have been identified uising an X-ray diffractometer. The surface diffusion is responsible for the low growth rates of the 1ar11 faces.

BaTiO3 powders were prepared by sol-gel method from different concentration of KOH aqueous solution and Ba/Ti molar ratio. Particle shape, size and crystal structure of prepared BaTiO3 powders were analyzed by SEM, XRD, and FT-IR. As the result of KOH concentration changing, spherical particles were obtained by condition more than 3 M and particle size decreased as concentration increasing. Different appearance showed between dried and sintered powders against changing of Ba/Ti molar ratio. In case of dried powders, the crystallinity decreased as molar ratio increasing. On the other hand, increased as molar ratio increasing in case of sintered powders.

Y-type barium ferrite was prepared by the glass-ceramic method. Glasses with composition of were prepared, and the precipitation behavior of Y-type ferrite from the glass matrix was investigated by heating glass specimens at various temperature. which is a precursor of M-type ferrite was precipitated at about 813 K and an unknown compound, phase X, was precipitated at about 850 K. M-type ferrite and Y-type ferrite started to form at about 923 K and 1103 K, respectively. The formation of Y-type ferrite was int erpreted as the result of the reaction of M-type ferrite with a melt of phase X.

Y-type barium ferrite ( Me=Zn, Co, Cu) expected as an electromagnetic wave absorber were prepared by the glass-ceramic method. The glasses with composition of were prepared. Single-phase powders of Y type barium ferrite were obtained with the composition . The shape of Y-type crystals depended strongly on the heating temperature and changed from a plate-like hexagon to a complex polyhedron with increasing heating temperature. Correlation was recognized between saturation magnetization and crystal shape. Electromagnetic wave absorption characteristics was affected by the saturation magnetization and crystal shape.

Sr2Ta2O7, a layered perovskite compound, has been reported to possess most excellent photocatalytic properties among the layered perovskite materials. Recently, we have demonstrated that Ba5Ta4O15 that was prepared under a mol ratio of Ba: Ta=1:1 has high photocatalytic performance as well as Sr2Ta2O7. In this study, the photocatalyst samples with a mol ratio of Sr: Ba: Ta = (1-x): x: 1 were prepared. The maximum photocatalytic performance was obtained for x= 0.2, which is three times as high as that of undoped Sr2Ta2O7.

Multilayer ceramic capacitor (MLCC) miniaturization has increased the demand for superfine powder due to its thin dielectric layer. Hydrothermally synthesized powder a pseudo-cubic phase resulting in poor dielectric properties due to size effect and hydroxyl ion inclusion in the lattice. We attempted a superfine (lower than 100 nm) highly tetragonal powder via a solvothermal method without precipitating agent. The lattice parameters and the relative amounts of tetragonal and cubic phases were determined using Rietveld refinement.

In this study, high purity fine powders were prepared by SHS (Self-propagating High-temperature Synthesis). We would examinate the study of sintering properties and characteristics as a function of temperature with various additives (binder, sintering agent). In separately binder addition, the green and sintered density of specimen were increased as binder content increases. The increased porosity resulted in fine grain size due to the inhibition of grain boundary moving. The and MgO playa role of increasing dielectric constants at room temperature. These values were decreased at curie temperature. In case of , the Curie temperature was decreased. In this study, a high dielectric ceramic capacitor material with temperature stability was synthesized by using various additives

The ferroelectric properties of barium titanate strongly depend on its microstructure, in particular, grain size and distribution. During sintering, usually exhibits abnormal grain growth, which deteriorates considerably the ferroelectric properties. A typical technique to suppress the abnormal grain growth is the addition of dopants. Dopant addition, however, affects the ferroelectric properties and thus limits the application of . Here, we report a simple but novel technique to prevent the abnormal grain growth of and to overcome the limitation of dopant use. The technique consists of stepwise sintering in a reducing atmosphere and in an oxidizing atmosphere. The materials prepared by the present technique exhibit uniform grain size and high dielectric properties. The technique should provide opportunities of having -based materials with superior ferroelectric properties.

졸-겔 dip coating법에 의해 제조한 바륨페라이트 박막의 미세구조와 결정학적인 구조 특성에 관해 조사하였다. 기판에 형성된 바륨페라이트 입자는 침상 형태의 입자들로 구성되어 있었으며, C축은 장축 방향이었고, 막 두께가 증가함에 따라 침상형 입자들은 기판에 평행하게 배향하는 경향을 나타내었다. 박막은 바륨페라이트층, Ba, Fe, SiO2로 구성되어 있는 중간층, 그리고 기판층인 SiO2층으로 구성되어 있었으며, 중간층과 SiO2층간의 계면은 Ba 와 SiO2간의 화합물로 구성되어 있었다. 침상 형태의 입자는 950˚C에서 3시간 열처리하므로써 완전히 소실하였고, 1300˚C에서 3시간 열처리하므로써 c면이 기판에 평행하게 위치하는 완전한 육각판상 형태의 입자로 변화되었다.