Preparation of Rare Earth Oxide (REExOy, REE = La, Ce, Nd) Powder from Waste NiMH Batteries: A Simple Platform for Recovery of Rare Earth Elements

( Nak-kyoon Ahn ),( Hyun-woo Shim ),( Dae-hoon Yang ),( Dae-weon Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

Nickel metal hydride batteries (NiMH) are of the important rechargeable secondary batteries. It contains the valuable metals such as Ni, Co, and rare earth metals and thus is necessary to recycle NiMH batteries when discarded after use. In particular, the rare earths are used as essential materials for high-tech products owing to their spectroscopic and magnetic properties. However, due to the most resources of rare earths are concentrated in China, the recovery of rare earths from waste resources are of crucial issues. Recently, research on the separation of rare earths from NiMH batteries has been focused on hydrometallurgy. Among them, the separation of rare earths by adding NaOH to sulfuric acid leaching solution is the simple and easy process. However, the recovered rare earth precipitates are usually in the form of NaREE(SO₄)₂·H₂O (REE: Ce, La, Nd), which is difficult to use commercially. Therefore, it is necessary to convert a form of rare earth precipitate into the rare earth oxides (REExOy). Herein, we present a route for preparing rare earth oxides from waste NiMH batteries. First, the leaching experiments, along with the control of acid concentration (M) and pulp density (g/L) were carried out for recovery of valuable metals. Then NaOH was added to the leachate to separate the rare earths. The recovered rare earths precipitate was analyzed by X-ray diffraction spectroscopy (XRD) and Microwave Plasma-Atomic Emission Spectroscopy (MP-AES), and thermal behavior was also investigated using Thermo Gravimetric Analyzer (TGA). After analyzing the raw materials, NaREE(SO4)_2·H₂O powder was added to the Na₂CO₃ solution and carbonated based on the metathesis reaction followed by heat-treatment in air. With temperature control of heat-treatment, it was confirmed that the composite rare earth was recovered as oxide at 800 ℃.

Chemistry of Rare Earth Containing Oxide-fluoride Compounds

Takashima, Masayuki,Yonezawa, Susumu,Kim, Jae-Ho,Nishibu, Shiori 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.7

The binary rare-earth oxide fluorides, Ln₂Ln'₂O₃F_(6) in which Ln and Ln' are different rare earths, were synthesized by the solid state reaction between Ln₂O₃ and Ln'F₃ at a temperature around 1000℃. Among Ln₂Ln'₂O₃F_(6) compounds, Nd₂Eu₂O₃F_(6) gave the conductivity of 3.5 Sm^(-1) at 600℃ under PO₂= 0.4 Pa, and the transport numbers of oxide ion and electron were measured to be around 0.9 and less than 0.05, respectively, at a temperature ranging from 500 to 700℃. The crystal structure of Nd₂Eu₂O₃F_(6) was determined to be the monoclinic lattice with the parameters of a_(0) = 0.396 nm, b_(0) = 1.13 nm, c_(0) = 0.562 nm, β = 134.84°, Z = 1. Ld₂Ln'₂O₃F_(6) compounds were applicable properties as an oxide ion-conducting solid electrolyte. Besides, new oxide-fluoride glasses containing large amount of rare earth elements consist of LnF₃-BaF₂-AlF₃-GeO₂ were obtained reproducibly by quenching from the melts. The glasses were found to exhibit unique optical properties such as fluorescence.

La-Gd-Y 희토류계 산화물-알루미나 세라믹스의 상안정화 영역과 내플라즈마 특성

김경범,이성민,Kim, Kyeong-Beom,Lee, Sung-Min 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.6

In this study, we have investigated new plasma resistant materials with less usage of rare-earth oxides than $Y_2O_3$ which is currently used in the semiconductor industry. We observed the stability ranges of $(Gd{\cdot}Y)_3Al_5O_{12}$ and $(La{\cdot}Y)Al_{11}O_{18}$ ternary systems, and measured their etch rates under typical fluorine plasma. $(Gd{\cdot}Y)_3Al_5O_{12}$ system showed an extensive solid solution up to 80 mol% gadolinium, but $(La{\cdot}Y)Al_{11}O_{18}$ showed a negligible substitution between rare-earth ions, which can be explained by the differences between the ionic radii. The etch rates depended on the total amount of rare-earth oxides but not on the substitution of the rare-earth ions. When the specimen was examined using XPS after the exposure to fluorine plasma, the strong surface fluorination was observed with a shift of the binding energy to higher energy.

Rare-earth oxide additives for the sintering of silicon carbide

Noviyanto, A.,Yoon, D.H. Elsevier 2013 Diamond and related materials Vol.38 No.-

The feasibility of a single component rare-earth oxide (Sc<SUB>2</SUB>O<SUB>3</SUB>, CeO<SUB>2</SUB>, Nd<SUB>2</SUB>O<SUB>3</SUB>, Sm<SUB>2</SUB>O<SUB>3</SUB>, Gd<SUB>2</SUB>O<SUB>3</SUB>, Dy<SUB>2</SUB>O<SUB>3</SUB>, Ho<SUB>2</SUB>O<SUB>3</SUB>, Er<SUB>2</SUB>O<SUB>3</SUB>, La<SUB>2</SUB>O<SUB>3</SUB>, Tm<SUB>2</SUB>O<SUB>3</SUB>, Yb<SUB>2</SUB>O<SUB>3</SUB> and Lu<SUB>2</SUB>O<SUB>3</SUB>) as a sintering additive for β-SiC was examined. The Gibbs formation free energies were first considered to identify the rare-earth oxides that would not decompose SiC at the typical hot pressing temperatures (1973-2123K). The results from the thermodynamic calculations were then tested experimentally. All rare-earth oxides examined in this study increased the density of the samples without decomposing SiC, which is in contrast to that observed with most main-group oxides reported previously. Rare-earth oxide appeared to form a eutectic composition with SiO<SUB>2</SUB> existed on the SiC surface at temperatures lower than 1700<SUP>o</SUP>C and acted as a liquid-phase sintering additive. The decrease in particle size of the sintering additive resulted in an increase in SiC density, indicating the importance of a uniform additive distribution to achieve a dense SiC.

Comparison of the Deposition Characteristics and Electrical Properties for La2O3, HfO2 and LHO Films

박종완,Woong-Sun Kim,Sang-Kyun Park,문대용,김태섭,강병우,서진규,Heon-Do Kim 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

Lanthanum oxide (La2O3), hafnium oxide (HfO2) and lanthanum hafnium oxide (LHO) films were deposited by using an electron cyclotron resonance plasma-enhanced atomic layer deposition method. Tris(isopropyl-cyclopentadienyl)lanthanum (La(iPrCp)3) and tetrakis(ethylmethy-lamino)hafnium (TEMAHf) were utilized as the lanthanum and the hafnium precursors, respectively. A self-limiting growth behavior was observed after 2-s injections of each precursor at the temperatures above the 300 ℃ deposition temperature. The growth rates of the La2O3, HfO2 and LHO film were 0.6, 0.6 and 0.5 Å/cycle. The dielectric constants of the La2O3, HfO2 and LHO films were 10.8, 12.2 and 16.3, respectively. The leakage current density of the LHO lm was 4.33 × 10-9 A/cm2 at -1 V for a film with an equivalent oxide thickness of 2.2 nm. The highest dielectric constant and the lowest leakage current obtained for the LHO film were 16.3 and 3.8 × 10-8 A/cm2, respectively. Thus, the LHO film is a promising material for a gate oxide. Lanthanum oxide (La2O3), hafnium oxide (HfO2) and lanthanum hafnium oxide (LHO) films were deposited by using an electron cyclotron resonance plasma-enhanced atomic layer deposition method. Tris(isopropyl-cyclopentadienyl)lanthanum (La(iPrCp)3) and tetrakis(ethylmethy-lamino)hafnium (TEMAHf) were utilized as the lanthanum and the hafnium precursors, respectively. A self-limiting growth behavior was observed after 2-s injections of each precursor at the temperatures above the 300 ℃ deposition temperature. The growth rates of the La2O3, HfO2 and LHO film were 0.6, 0.6 and 0.5 Å/cycle. The dielectric constants of the La2O3, HfO2 and LHO films were 10.8, 12.2 and 16.3, respectively. The leakage current density of the LHO lm was 4.33 × 10-9 A/cm2 at -1 V for a film with an equivalent oxide thickness of 2.2 nm. The highest dielectric constant and the lowest leakage current obtained for the LHO film were 16.3 and 3.8 × 10-8 A/cm2, respectively. Thus, the LHO film is a promising material for a gate oxide.

LiCl 용융염에서 NiO를 혼합한 희토류 산화물의 파이로 전해환원 특성

이민우 ( Min-woo Lee ),정상문 ( Sang Mun Jeong ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.3

LiCl 용융염에서 희토류 산화물의 환원율을 높이기 위해 NiO와 혼합하여 전해환원을 실시하였다. Cyclic voltammetry(CV) 실험을 통해 LiCl 용융염 내에서 혼합산화물의 전기화학적 환원거동을 조사하였다. 혼합산화물로 제작된 환원전극과 그라파이트 산화전극 사이에 일정한 작동전압을 인가하여 이론전하량 대비 다양한 전하량을 공급한 후 중간생성물의 결정구조를 XRD를 이용하여 분석하였다. NiO 산화물을 첨가함으로써 전기전도성이 좋은 Ni 금속 주위로 희토류 산화물이 환원되어 RE-Ni 합금형태의 금속으로 완전히 전환되었으며, 합금을 형성하는 반응 메커니즘을 제시하였다. An electrochemical reduction of a mixture of NiO and rare earth oxides has been conducted to increase the reduction degree of rare earth oxides. Cyclic voltammetry (CV) measurement was carried out to determine the electrochemical reduction behavior of the mixed oxide in molten LiCl medium. Constant voltage electrolysis was performed with various supplied charges to understand the mechanism of electrochemical reduction of the mixed oxide as a working electrode. After completion of the electrochemical reduction, crystal structure of the reaction intermediates was characterized by using an X-ray diffraction method. The results clearly demonstrate that the rare earth oxide was converted to RE-Ni intermetallics via co-reduction with NiO.

열차폐용 희토류 산화물의 상형성과 열물성

심병철,곽길호,이성민,오윤석,김형태,장병국,김성원,Shim, Byung-Chul,Kwak, Kil-Ho,Lee, Sung-Min,Oh, Yoon-Suk,Kim, Hyung-Tae,Jang, Byung-Koog,Kim, Seong-Won 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2

Thermal barrier systems have been widely investigated over the past decades, in order to enhance reliability and efficiency of gas turbines at higher temperatures. Yttria-stabilized zirconia (YSZ) is one of the most leading materials as the thermal barriers due to its low thermal conductivity, thermodynamic stability, and thermal compatibility with metal substrates. In this work, rare-earth oxides with pyrochlore phases for thermal barrier systems were investigated. Pyrochlore phases were successfully formed via solid-state reactions started from rare-earth oxide powders. For the heat-treated samples, thermo-physical properties were examined. These rare-oxide oxides showed thermal expansion of $9{\sim}12{\times}10^{-6}/K$ and thermal conductivity of 1.2~2.4 W/mK, which is comparable with the thermal properties of YSZ.

Characterization of porous sintered reaction-bonded silicon nitride containing three different rare-earth oxides

Kim Ha-Neul,Kim Mi-Ju,Park Young-Jo,Ko Jae-Woong 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.1

The eff ect of rare-earth oxides on the characteristics of porous sintered reaction-bonded silicon nitride (SRBSN) was investigated. Three types of raw Si powder mixtures containing diff erent rare-earth oxide (La 2 O 3 , Er 2 O 3 , and Yb 2 O 3 ) were prepared and nitrided in the form of compacts. The nitriding profi les of the respective raw powder mixtures with elevating temperature indicated that Yb 2 O 3 clearly promoted the nitridation of Si compacts at low temperature compared with other rare-earth oxides, and the β-Si 3 N 4 ratio after completion of the nitriding reaction was diff erent at which temperature the major nitridation occurred. Yb 2 O 3 was found to be the most eff ective additive to achieve a strong porous SRBSN, having the fl exural strength of 441 MPa. The reason why Yb 2 O 3 promotes the nitridation reaction and has excellent mechanical properties after post-sintering is that oxygen was removed during the nitriding reaction, which was supported by the analysis of oxygen content via the laser-induced breakdown spectroscopy.

BaTiO₃ 세라믹 내 희토류(Dy, Y, Ho) 첨가 효과

박금진,김창훈,김영태,허강헌 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.2

The electrical property and microstructure in BaTiO₃ ceramics doped rare-earth ions with intermediate ionic size (Dy3+, Ho3+, Y3+) were investigated. Microstructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Incorporation of rare-earth ions to BaTiO₃ ceramics depended on their ionic radius sensitively. Compared to Ho and Y ions, Dy ions provide BaTiO₃ ceramics with the high rate of densification and well-developed shell formation, due to their high solubility in the BaTiO₃ lattice, but the microstructure of Dy doped BaTiO₃ ceramics is unstable at high temperature, because Dy ions could not play a role of grain growth inhibition, leading to diffuse into BaTiO₃ lattice continuously after completion of densification during sintering. Comparing electrical property and microstructure, it is shown that the reliability of capacitor improved by high shell ratio. The electrical property and microstructure in BaTiO₃ ceramics doped rare-earth ions with intermediate ionic size (Dy3+, Ho3+, Y3+) were investigated. Microstructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Incorporation of rare-earth ions to BaTiO₃ ceramics depended on their ionic radius sensitively. Compared to Ho and Y ions, Dy ions provide BaTiO₃ ceramics with the high rate of densification and well-developed shell formation, due to their high solubility in the BaTiO₃ lattice, but the microstructure of Dy doped BaTiO₃ ceramics is unstable at high temperature, because Dy ions could not play a role of grain growth inhibition, leading to diffuse into BaTiO₃ lattice continuously after completion of densification during sintering. Comparing electrical property and microstructure, it is shown that the reliability of capacitor improved by high shell ratio.

Altering the Type of Rare-Earth Metals Used to Found Bimetallic Vanadate Phases to Tune their Surface Properties for Catalyzing NO_X/NH₃ Transformations

김동호,권동욱,( Ha Heon Phil ),김종식 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Rare-earth metal (RM) vanadates are featured by the potential to tailor their surface properties through the alteration of the type of metals/ phases or compositions, etc. For this presentation, our primary objective is to tune acidity/redox character provided by Ce₁V₁O₄ phase by substituting half of the Ce elements with Tb, Er, or Yb. This led to the formation of three RM-modified, bimetallic Ce₁V₁O₄ phases (RM_0.5 Ce_0.5V₁O₄) deployed to selectively catalyze NOX reduction (SCR) and NH3 oxidation (SCO) at a wide temperature range of 200-600°C. Herein, we corroborate how tunable the properties of the RM_0.5Ce_0.5V₁O₄ would be by varying the type of RMs with the use of a host of analytic techniques, all of which can simulate the conditions utilized to perform the SCR or SCO. The surfaces were then examined in real flue gas streams used for the SCR/SCO to further verify that the RM_0.5Ce_0.5V₁O₄ outperforms the Ce₁V₁O₄ in various aspects.