Thermal Oxidation Resistance of Rare Earth-Containing Composite Elastomer

Institute of Scientific and Technical Information of China (English)

邱关明; 张明; 周兰香; 中北里志; 井上真一; 冈本弘

2001-01-01

The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.

Rare earth oxide doping in oxide cathodes

International Nuclear Information System (INIS)

Engelsen, Daniel den; Gaertner, Georg

2006-01-01

The effect on life performance and poisoning with O 2 by doping oxide cathodes with rare earth oxides and pseudo rare earth oxides, notably yttria, is qualitatively explained in terms of electrolysis of BaO during emission of electrons. Doped cathodes show less electrolysis and consume therefore less Ba during life: consequently, doped cathodes have a better life performance. However, the lower Ba-production makes doped cathodes more sensitive to oxygen poisoning. The experimentally found relation between conductivity and yttria concentration was the motive to propose a new model for the crystal imperfections in BaO. In this new imperfection model most Y 3+ -ions will combine with barium vacancies, therefore, the increase of the conductivity is modest and also the effect on the position of the Fermi level is modest. By assuming a combination of bulk and surface conductivity, the agreement between experiment and theory can be improved further

Composite catalyst for carbon monoxide and hydrocarbon oxidation

Science.gov (United States)

Liu, Wei; Flytzani-Stephanopoulos, Maria

1996-01-01

A method and composition for the complete oxidation of carbon monoxide and/or hydrocarbon compounds. The method involves reacting the carbon monoxide and/or hydrocarbons with an oxidizing agent in the presence of a metal oxide composite catalyst. The catalyst is prepared by combining fluorite-type oxygen ion conductors with active transition metals. The fluorite oxide, selected from the group consisting of cerium oxide, zirconium oxide, thorium oxide, hafnium oxide, and uranium oxide, and may be doped by alkaline earth and rare earth oxides. The transition metals, selected from the group consisting of molybdnum, copper, cobalt, maganese, nickel, and silver, are used as additives. The atomic ratio of transition metal to fluorite oxide is less than one.

Rare Earth Oxide Thin Films

CERN Document Server

Fanciulli, Marco

2007-01-01

Thin rare earth (RE) oxide films are emerging materials for microelectronic, nanoelectronic, and spintronic applications. The state-of-the-art of thin film deposition techniques as well as the structural, physical, chemical, and electrical properties of thin RE oxide films and of their interface with semiconducting substrates are discussed. The aim is to identify proper methodologies for the development of RE oxides thin films and to evaluate their effectiveness as innovative materials in different applications.

Rare earths 1998 market update

International Nuclear Information System (INIS)

Tourre, J.M.

1998-01-01

The rare earth industry has always been a world of rapid change with the emergence of new markets, new ores and new players, as well as the disappearance of old applications. Rare earth based products are used in a great diversity of applications such as hard disk drives, CD drives, batteries, capacitors, pigments, ceramics, polishing powders, fuel cells, flints, catalyst converter, fluid cracking catalysts, etc. South East Asia holds the largest share of the known reserve of rare earth ores and is one of the major markets for rare earth compounds; in the last ten years, China has become the largest producer of rare earth intermediates as well as an important exporter of separated rare earth elements. Today, China has approximately 150 factories producing rare earth compounds, most of which are experiencing financial difficulties due to the lack of knowledge of true market needs, lack of control of their distribution channels and production over-capacity. Recently the Chinese rare earth producers have recognized the situation and efforts are underway to rationalize rare earth production. Japan has dominated many of the major application markets, and is by far the largest market for metal and alloy products. This will remain the case for the next five years; however, new countries are emerging as significant users of rare earth products such as Korea, Taiwan and Malaysia. During the last ten years rare earth producers adjusted to several radical changes that affected the raw materials, the application mix and the price structure. New producers have emerged, especially from China; some have subsequently stopped their activities while others have focused their efforts in a specific market segment

Syntheses of rare-earth metal oxide nanotubes by the sol-gel method assisted with porous anodic aluminum oxide templates

International Nuclear Information System (INIS)

Kuang Qin; Lin Zhiwei; Lian Wei; Jiang Zhiyuan; Xie Zhaoxiong; Huang Rongbin; Zheng Lansun

2007-01-01

In this paper, we report a versatile synthetic method of ordered rare-earth metal (RE) oxide nanotubes. RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction (XRD) have been employed to characterize the morphology and composition of the as-prepared nanotubes. It is found that as-prepared RE oxides evolve into bamboo-like nanotubes and entirely hollow nanotubes. A new possible formation mechanism of RE oxide nanotubes in the AAO channels is proposed. These high-quantity RE oxide nanotubes are expected to have promising applications in many areas such as luminescent materials, catalysts, magnets, etc. - Graphical abstract: A versatile synthetic method for the preparation of ordered rare-earth (RE) oxide nanotubes is reported, by which RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates

Influence of rare earth additions on the oxidation resistance of chromia forming alloys

International Nuclear Information System (INIS)

Pillis, Marina Fuser

1995-01-01

The addition of rare earths to alloys, either in elemental form or as surface coatings reduces the oxidation rate of chromia forming alloys. The rare earths either act as nucleation sites for surface oxides or get incorporates into the surface oxide and diffuse to oxide grain boundaries. If the latter occurs, a change in the defect structure close to the grain boundaries, probably takes place. In this manner, the rare earths inhibits the movement of chromium ions to the oxide/gas interface. The influence of rare earth additions to AISI 316, AISI 316L and Ni-20 Cr on their oxidation behavior has been studied., AISI 316+Ce, AISI 316+Y, Ni-20 Cr and Ni-20 Cr-2 Al-1 Ce were prepared by melting and AISI 316L, AISI 316L+Ce O 2 and AISI 316L+Y 2 O 3 by powder compaction. The effect of superficial deposits of rare earth oxides was also studied. The alloys were coated with rare earth oxides by high temperature conversion of the respective rare earth nitrates. Isothermal oxidation tests were carried out at 900-1100 deg C and the cyclic oxidation tests consisted of 6 cycles of 2 hours each at 900 deg C, followed by cooling to room temperature. All the tests were carried out in air. Oxidation behavior was evaluated gravimetrically. Scanning electron microscopy was used to study surface morphology. Energy dispersive analysis and X-ray diffraction techniques were used to identify oxide constituents. Overall, it has been observed that with the addition of rare earths, oxidation resistance increases by decreasing oxidation rates and increasing oxide adhesion. Addition of rare earths to AISI 316 prepared by melting resulted in rapid formation of a chromium rich oxide layered near the metal/oxide interface which reduced overall oxidation rate. The addition of Ce O 2 to AISI 316L was found to improve oxidation behavior after 10 hours at 1100 deg C and also inhibit the formation of volatile Cr O 3 . The isothermal oxidation behavior of rare earth oxide covered Ni-20 Cr at 900 deg C

Novel precursors for the deposition of rare earth oxides

International Nuclear Information System (INIS)

Ahlers, Mareike

2010-01-01

During this work rare earth solvates with nitrate and perchlorate anions have been investigated. All compounds have been structurally characterized and analyzed using thermal gravimetric analysis. The decomposition residues were analyzed using powder diffraction methods. Almost all compounds showed a characteristically intense exothermic decomposition step during the thermal decomposition, most likely caused by an intramolecular redox reaction between the nitrate or perchlorate anion respectively and the organic solvent molecules. The nitrates RE(NO 3 ) 3 (CH(OCH 3 ) 3 ) 2 (RE = Sm, Eu) were isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. The known compound group of dimethoxyethane solvates was then expanded with RE(NO 3 ) 3 (O 2 C 4 H 10 ) (RE = La, Sm, Eu). Considering the possible use as precursor material the already described neodymium compound is also discussed. The thermal decomposition of these compounds yields the respective cubic rare earth oxide and shows the typical intense exothermic decomposition reaction. A variety of different precursor system based on nitrate solvates for the deposition of rare earth oxide layers on a silicon surface was developed and investigated in collaboration with the group of Prof. Dr. Al-Shamery (Univ. Oldenburg). Ultra thin films on a H-Si(111) surface were obtained via the deposition of the precursor, which was dissolved in organic solvents. An oxide layer was detected after the heating of the sample. The film thickness was measured as < 10 nm, whereas the thickness of the film was controlled by the concentration of the precursor solution. Sm(ClO 4 ) 3 (CH(OCH 3 ) 3 ) 3 was isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. Eu(ClO 4 ) 3 (CH(OCH 3 ) 3 ) 2 (MeOH) 2 was obtained without recrystallization. The methanol molecules, formed during the hydrolysis of the trimethyl

Rare Earth Oxide Fluoride Nanoparticles And Hydrothermal Method For Forming Nanoparticles

Science.gov (United States)

Fulton, John L.; Hoffmann, Markus M.

2003-12-23

A hydrothermal method for forming nanoparticles of a rare earth element, oxygen and fluorine has been discovered. Nanoparticles comprising a rare earth element, oxygen and fluorine are also described. These nanoparticles can exhibit excellent refractory properties as well as remarkable stability in hydrothermal conditions. The nanoparticles can exhibit excellent properties for numerous applications including fiber reinforcement of ceramic composites, catalyst supports, and corrosion resistant coatings for high-temperature aqueous solutions.

The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems

Science.gov (United States)

Zhu, Dongming; Harder, Bryan James

2014-01-01

Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.

Research and development of tungsten electrodes added with rare earth oxides

International Nuclear Information System (INIS)

Zuoren Nie; Ying Chen; Meiling Zhou; Tieyong Zuo

2001-01-01

The recent research and development of tungsten electrodes used in TIG and Plasma technologies are introduced, and the tungsten materials as well as the effects of rare earth oxides are specially discussed. in W-La 2 O 3 , W-CeO 2 , W-Y 2 O 3 and W-ThO 2 electrode materials, the W-2.2mass%La 2 O 3 electrode exhibited the best properties when the current is of little or middle volume, and when the electrodes are used in large current, the W-Y 2 O 3 electrode is the best. By a comparative study between the tungsten electrodes activated with single metal oxides, as above-mentioned, and those containing two or three rare earth oxides, namely La 2 O 3 , CeO 2 and Y 2 O 3 , it was indicated that the welding arc properties of the tungsten electrodes activated with combined rare earth oxides additions is superior than that of the electrodes containing single oxides as above mentioned. It was also shown that the operating properties of tungsten electrodes depend intensively on the rare earth oxides contained in the electrodes, and the actions of rare earth oxides during arcing are the most important factors to the electrodes' operating properties, temperature, work function as well as the arc stability. (author)

Thin-film method-XRF determination of the composition of rare earth oxides

International Nuclear Information System (INIS)

Xiao Deming

1992-01-01

The author describes the thin-film sample preparation by precipitation-pumping filtering method and the composition of rare earth oxide materials by XRF determination. The determination limits are 0.01% to 0.17%. The coefficients of variation are in the range of 0.85% to 14.9%. The analytical results of several kinds of rare earth oxide materials show that this method can be applied to the determination of the composition of rare earth oxide mixtures

Rare earths: occurrence, production and applications

International Nuclear Information System (INIS)

Murthy, T.K.S.; Mukherjee, T.K.

2002-01-01

The mining and processing of rare earth minerals, particularly of monazite, began in a modest way in 1880s for commercialized production of mantle for gas lighting. For all major applications up to mid-twentieth century- production of lighter flints, misch metal as a metallurgical alloying agent, colouring, decolourizing and polishing agents for glass, petroleum cracking catalysts and arc-carbons, unseparated or partially separated rare earths were adequate. These applications continue till today. With the development and industrial application of powerful techniques like ion exchange and solvent extraction for the separation of rare earths, the decades after 1960 saw increasing utilization of the specific properties of the individual rare earths. Some of these advanced technological applications include: special glass for optical systems including camera lenses, phosphors for colour television, cathode ray tubes and fluorescent lighting, X-ray intensification screens, high intensity permanent magnets, electro optical devices, lasers, hydrogen storage materials, hydride rechargeable batteries, photomagnetic data storage systems, autoexhaust catalysts, special ceramics of unusual toughness, artificial diamonds and nonpoisonous plastic colorants. The topics covered in the book include rare earths: their story identity, rare earth resources, processing of ores and recovery of mixed rare earths products, separation and purification of rare earths, nonmetallic applications of rare earths, rare earth metals: production and applications, rare earth alloys and their applications, analysis of rare earth, processing of rare earth resources in India by Indian Rare Earth Ltd. and availability and market conditions

Recycling of the rare earth oxides from spent rechargeable batteries using waste metallurgical slags

Directory of Open Access Journals (Sweden)

Tang K.

2013-01-01

Full Text Available A high temperature process for recycling spent nickel-metal hydride rechargeable batteries has been recently developed at SINTEF/NTNU. The spent battery modules were first frozen with liquid nitrogen for the de-activation and brittle fracture treatment. The broken steel scraps and plastics were then separated by the mechanical classification and magnetic separation. The remaining positive and negative electrodes, together with the polymer separator, were heated to 600-800oC in order to remove the organic components and further separate the Ni-based negative electrode. XRF analyses indicate that the heat-treated materials consist mainly of nickel, rare earth and cobalt oxides. The valuable rare earth oxides were further recovered by the high-temperature slagging treatment. The waste metallurgical slags, consist mainly of SiO2 and CaO, were used as the rare earth oxide absorbent. After the high temperature slagging treatment, over 98% of nickel and cobalt oxides were reduced to the metal phase; meanwhile almost all rare earth oxides remain in the molten slags. Furthermore, EPMA and XRF analyses of the slag samples indicate that the rare earth oxides selectively precipitate in the forms of solid xSiO2•yCaO•zRe2O3. The matrix of slag phase is Re2O3 deficient, typically being less than 5 wt%. This provides a sound basis to further develop the high-temperature process of concentrating the Re2O3 oxides in slags.

Effect of rare earth oxide additives on the performance of NiMH batteries

International Nuclear Information System (INIS)

Tanaka, Toshiki; Kuzuhara, Minoru; Watada, Masaharu; Oshitani, Masahiko

2006-01-01

To date, we have performed research on nickel-metal hydride (NiMH) batteries used in many applications and have found that addition of rare earth oxides to the nickel electrode and the hydrogen-storage alloy (MH) electrode improves battery performance significantly. Because heavy rare earth oxides of such as Er, Tm, Yb and Lu have remarkable properties that shift the oxygen evolution overpotentials of nickel electrodes to more noble potentials, it is possible to improve high-temperature charge efficiency of nickel-metal hydride secondary batteries by adding them to nickel electrodes. Furthermore, addition of heavy rare earth oxides to MH electrodes depresses an acceleration of the alloy corrosion and improves service life of the battery at high temperatures. Accordingly, addition of heavy rare earth oxides is effective for NiMH batteries used in high-temperature applications such as electric vehicles (EVs), hybrid vehicles (HEVs) and rapid charge devices. In this study, we discussed how the addition of heavy rare earth oxides affects NiMH battery characteristics

Study of NiO cathode modified by rare earth oxide additive for MCFC by electrochemical impedance spectroscopy

International Nuclear Information System (INIS)

Huang Bo; Chen Gang; Li Fei; Yu Qingchun; Hu Keao

2004-01-01

The preparation and subsequent oxidation of nickel cathodes modified by impregnation with rare earth oxide were evaluated by surface and bulk analysis. The electrochemical behaviors of rare earth oxide impregnated nickel oxide cathodes were also evaluated in a molten 62 mol% Li 2 CO 3 +38 mol% K 2 CO 3 eutectic at 650 deg. C by electrochemical impedance spectroscopy (EIS) as a function of rare earth oxide content and immersion time. The rare earth oxide-impregnated nickel cathodes show almost the similar porosity, pore size, and morphology to the reference nickel cathode. The stability tests of rare earth oxide-impregnated nickel oxide cathodes show that the rare earth oxide additive can dramatically reduce the solubility of nickel oxide in a eutectic carbonate mixture under the standard cathode gas condition. The impedance response of all cathode materials at different immersion time is characterized by the presence of depressed semicircles in the high frequency range changing over into the lines with the angles of which observed with the real axis differing 45 deg. or 90 deg. in the low frequency range. The experimental Nyquist plots can be well analyzed theoretically with a modified model based on the well-known Randles-Ershler equivalent circuit model. In the new model, the double layer capacity (C d ) is replaced by the parallel combination of C d and b/ω; therefore, this circuit is modified to be the parallel combination of (C d ), b/ω, and the charge transfer resistance (R ct ) based on the Randles-Ershler equivalent circuit, to take into consideration both the non-uniformity of electric field at the electrode/electrolyte interface owing to the roughness of electrode surface, and the variety of relaxation times with adsorbed species on the electrode surface. The impedance spectra for all cathode materials show important variations during the 200 h of immersion. The incorporation of lithium in its structure and the low dissolution of nickel oxide and rare

The effects of rare earths on activity and surface properties of Ru/γ-Al2O3 catalyst for water gas shift reaction

Directory of Open Access Journals (Sweden)

Laitao Luo

2007-04-01

Full Text Available A series of Ru-RE/γ- Al2O3 (RE = Ce, Pr, La, Sm, Tb or Gd and Ru/γ- Al2O3 catalysts were prepared by impregnation method. The influence of rare earths on the catalytic performance of Ru/γ- Al2O3 catalyst for the water gas shift reaction was studied. The catalysts were characterized by X-ray diffraction (XRD, temperature programmed reduction (TPR, temperature programmed desorption (TPD, and CO chemisorption. The results show that the addition of rare earths increases the catalytic activity of Ru based catalyst. Among these cerium is the most remarkably. The addition of cerium increases the active surface area, improves the dispersion of ruthenium, and weakens the interaction between ruthenium and the support. Cerium also affects the adsorption and reduction properties of Ru/γ-Al2O3 catalyst.

Rare earth germanates

International Nuclear Information System (INIS)

Bondar', I.A.; Vinogradova, N.V.; Dem'yanets, L.N.

1983-01-01

From the viewpoint of structural chemistry and general regularities controlling formation reactions of compounds and phases in melts, solid and gaseous states, recent achievements in the chemistry of rare earth germanates are generalized. Methods of synthesizing germanates, systems on the base of germanium oxides and rare earths are considered. The data on crystallochemical characteristics are tabulated. Individual compounds of scandium germanate are also characterized. Processes of germanate formation using the data of IR-spectroscopy, X-ray phase analysis are studied. The structure and morphotropic series of rare earth germanates and silicates are determined. Fields of their present and possible future application are considered

Development of reduction technology for oxide fuel. Behaviour of rare-earth in lithium reduction process

International Nuclear Information System (INIS)

Kato, Tetsuya; Usami, Tsuyoshi; Yuda, Ryoichi; Kurata, Masateru; Moriyama, Hirotake

2000-01-01

Solubility measurements of rare-earth oxides in molten LiCl-Li 2 O salt and reduction tests of UO 2 doped with rare-earth oxides were carried out to determine the behavior of rare-earths in lithium reduction process. The solubility of rare-earth oxides increases in the order of Gd 2 O concentration. In multi-element systems including 6 rare-earth oxides, the solubility of each element is smaller than that in the individual systems. In the reduction tests, more than 90% of UO 2 was reduced within 1 hour after starting reduction and about 7% of rare-earths eluded into the LiCl molten salt bath containing Li 2 O which is formed by the reduction of UO 2 . The rare-earth concentrations in the bath were evaluated using the solubility data, assuming that rare-earth oxides in multi-element systems form solid solution as the equilibrium solid phase and that the activity coefficients in the solid phase are independent of the compositions. The calculated concentrations are consistent with the experimental ones obtained in the reduction tests. (author)

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

Science.gov (United States)

Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.

2014-11-01

Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

OXIDATIVE DEHYDROGENATION OF PROPANE BY RARE EARTH PHOSPHATES SUPPORTED ON AL-PILC

Directory of Open Access Journals (Sweden)

Carolina De Los Santos

2012-12-01

Full Text Available Catalytic activity in propane oxidative dehydrogenation of rare earth phosphates LnPO4 (where Ln = La, Ce, Pr, Nd, Sm and of the same supported by an aluminum pillared clay, of high specific surface area, is presented. The solids were characterized by TGA, XRD, nitrogen adsorption and immediate analysis after reaction in order to determine eventual carbon formation. Catalytic assays were performed at temperatures in the range 400oC-600oC, the reaction mixture was C3H8/O2/Ar = 10/10/80. All the catalysts were active. The reaction products were H2, CO, CO2, CH4, C2H4 and C3H6 and there were no organic oxygenated compounds detected. Although all the investigated systems were active, the Al-PILC supported catalysts presented a higher activity than the bulk materials. In this context, the samarium supported catalyst showed a propene yield increase from 4% to 10% compared with bulk samarium phosphate at 600°C. This effect was attributed to the increase in the specific surface area.

Optimization of leaching process for sum of rare earth and calcium oxides

International Nuclear Information System (INIS)

Troyanier, L.S.; Elunkina, Z.A.; Nikonov, V.N.; Lobov, V.I.

1978-01-01

Presented are the results of investigation of leaching process for rare earth and calcium oxides by sulfuric acid. The method of planning experiment has been used for this investigation. Mixtures of cerium, yttrium and neodyum oxides, taken in the relation of 1:1:0.5, have been used as rare earth elements. Received are adequate models characterizing dependence of solubility of rare earth and calcium oxides on some factors (H 2 SO 4 concentration, CaO:R 2 O 3 relation, liquid to solid ratio, solution temperature, mixing time). Dependences of solubility of rare earth elements and calcium on the process parameters are received and presented in a form of regression equations. Dependences received can be used for choice of optimum regime of the process as well as for its control

Hydrogen Production from Water by Photolysis, Sonolysis and Sonophotolysis with Solid Solutions of Rare Earth, Gallium and Indium Oxides as Heterogeneous Catalysts

Directory of Open Access Journals (Sweden)

Marta Penconi

2015-07-01

Full Text Available In this work, we present the hydrogen production by photolysis, sonolysis and sonophotolysis of water in the presence of newly synthesized solid solutions of rare earth, gallium and indium oxides playing as catalysts. From the experiments of photolysis, we found that the best photocatalyst is the solid solution Y0.8Ga0.2InO3 doped by sulphur atoms. In experiments of sonolysis, we optimized the rate of hydrogen production by changing the amount of water, adding ethanol and tuning the power of our piezoelectric transducer. Finally, we performed sonolysis and sonophotolysis experiments in the presence of S:Y0.8Ga0.2InO3 finding a promising synergistic effect of UV-visible electromagnetic waves and 38 kHz ultrasound waves in producing H2.

Rare earth germanates

International Nuclear Information System (INIS)

Bondar', I.A.; Vinogradova, N.V.; Dem'yanets, L.N.

1983-01-01

Rare earth germanates attract close attention both as an independent class of compounds and analogues of a widely spread class of natural and synthetic minerals. The methods of rare earth germanate synthesis (solid-phase, hydrothermal) are considered. Systems on the basis of germanium and rare earth oxides, phase diagrams, phase transformations are studied. Using different chemical analysese the processes of rare earth germanate formation are investigated. IR spectra of alkali and rare earth metal germanates are presented, their comparative analysis being carried out. Crystal structures of the compounds, lattice parameters are studied. Fields of possible application of rare earth germanates are shown

Nano rare-earth oxides induced size-dependent vacuolization: an independent pathway from autophagy.

Science.gov (United States)

Zhang, Ying; Yu, Chenguang; Huang, Guanyi; Wang, Changli; Wen, Longping

2010-09-07

Four rare earth oxides have been shown to induce autophagy. Interestingly, we often noticed plentiful vacuolization, which was not always involved in this autophagic process. In this study, we investigated three other rare-earth elements, including Yttrium (Y), Ytterbium (Yb), and Lanthanum (La). Autophagic effect could be induced by all of them but only Y(2)O(3) and Yb(2)O(3) could cause massive vacuolization. Y(2)O(3) and Yb(2)O(3) treated by sonication or centrifugation to reduce particle size were used to test vacuolization level in HeLa cell lines. The results showed that rare earth oxides-induced vacuolization is size-dependent and differs from autophagic pathway. To further clarify the characteristics of this autophagic process, we used MEF Atg-5 (autophagy associated gene 5) knockout cell line, and the result showed that the autophagic process induced by rare earth oxides is Atg-5-dependent and the observed vacuolization was independent from autophagy. Similar results could also be observed in our tests on 3-methyladenine(3-MA), a well-known autophagy inhibitor. In conclusion, for the first time, we clarified the relationship between massive vacuolization and autophagic process induced by rare earth oxides and pointed out the size effect of rare earth oxides on the formation of vacuoles, which give clues to further investigation on the mechanisms underlying their biological effects.

Preparation and characterization of Pt Sn / C-rare earth and PtRu / C-rare earth using an alcohol reduction process for ethanol electron-oxidation

International Nuclear Information System (INIS)

Rodrigues, Rita Maria de Sousa

2011-01-01

The electro catalyst PtRu / C-rare earth and PtSn/C-rare earth (20 wt%) were prepared by alcohol reduction method using H 2 PtCl 6 .6H 2 O Ru Cl xH 2 O, SnCl 2 .2H 2 O as a source of metals 85 % Vulcan - 15 % rare earth as a support and, finally, ethylene glycol as reducing agent. The electrocatalysts were characterized physically by X-ray diffraction (XRD), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM). Analyses by EDX showed that the atomic ratios of different electrocatalysts, prepared by alcohol reduction method are similar to the nominal starting compositions indicating that this methodology is promising for the preparation of electrocatalysts. In all the XRD patterns for the prepared electrocatalysts there is a broad peak at about 2θ = 25 o , which is associated with the carbon support and four additional diffraction peaks at approximately 2θ = 40 o , 47 o , 67 o e 82 o , which in turn are associated with the plans (111), (200), (220) e (311), respectively, of face-centered cubic structure (FCC) platinum. The results of X-ray diffraction also showed average crystallite sizes between 2.0 and 4.0 nm for PtSn e 2,0 a 3,0 para PtRu. The studies for the electrochemical oxidation of ethanol in acid medium were carried out using the technique of chronoamperometry in a solution 0,5 mol.L-1 H 2 SO 4 , + 1,0 mol.L-1 de C 2 H 5 OH. The polarization curves obtained in the fuel cell unit, powered directly by ethanol, are in agreement with the results of voltammetry and chronoamperometry noting the beneficial effect of rare earths in the preparation of electrocatalysts and attesting that the electrocatalysts PtSn/C are more effective than PtRu/C for the oxidation of ethanol.

Analysis of “Favorable Growth Element” Based on Rare Earth-aluminum Composite Mechanism of Compound Process

Science.gov (United States)

Hao, Baohong; Zeng, Qihui; Zhao, Jin

2018-01-01

Under the background that failure resulted in by high temperature once only aluminum oxide is used as the gasoline additive. This paper, with the purpose to solve this problem, is to synthesize AcAl oxide for gasoline additive. In order to get the rare-earth-aluminum oxide, first, a complex model of rare earth oxide based on theories about ion coordination is established. Then, by the complex model, the type of “compound growth unit” when rare earth elements join the hydrothermal conditions and the inclination that “diversification” might probably happen are deduced. Depending on the results got by complex model, this paper introduces the type of compound and its existence conditions of “Compound growth unit” owned by stable rare-earth-aluminum oxide. By adjusting the compositions of modifier, compound materials of rare earth-aluminum oxide used for gasoline additive is made. By XRD test, aperture test, adsorption test and desorption test, the theoretical deduction is proved to be right. From the experiment, it is concluded that: a dense environment is the pre-condition to form rare-earth-aluminum polymer, which is also an essential condition for the polymer to update to a favorable growth unit and produce mesoporous rare-earth-aluminum oxide with high activity.

Research on manufacturing aluminum - rare earth alloy with a high content of rare earth (> 20% RE) from total rare earth oxides by thermit reduction

International Nuclear Information System (INIS)

Ngo Trong Hiep; Dam Van Tien; Tran Duy Hai; Ngo Xuan Hung and Ly Thanh Vu

2004-01-01

In this report, several theoretical principles of thermit reduction method used for metal oxides to obtain metals, ferroalloys and ligatua with technical purity are presented. Manufacture of aluminum-rare earth alloys by thermit reduction is also described in the report. Data that are generalized based on thermo-kinetic calculation of the thermit reduction and selection of technological flow-sheet based on thermal effect will partly clarify research results in investigating typical features of the process and identify measures to reduce metal loss in discharged slags. (author)

A study on the separation method of total rare earth oxides in Xenotime

International Nuclear Information System (INIS)

Shim, Sang Kwon; Park, Hea Kyung; Kim, Kyung Lim

1990-01-01

This study is concerned with the separation method of total rare earth oxides in Xenotime by acid digest method. Thioacetamide was used as a carrier, tartaric acid was used as a masking agent and oxalic acid was used as a precipitant. So the effects of three acid digest methods, pH of the solution, digesting time,tartaric acid, oxalic acid and aging time were oberved. The results showed that the best acid digest method was sulfuric acid leaching and mixed acid digest method, and that pH of the solution was 2, digesting time was 4 hours, tartaric acid was 100 ml of 2% solution, oxalic acid was 8 gr. and aging time was 1 hour. Through this experiment, it was confirmed by X-ray diffractometer that the separated total rare earth oxides consisted of the Yttrium and the other rare earth elements : Gadolinium, Dysprosium, Erbium, Ytterbium and trace rare earth elements. The pure rare earth oxides being separated by this method were dried and ignited at 900 deg C (Author)

Biodiesel production using alkali earth metal oxides catalysts synthesized by sol-gel method

Directory of Open Access Journals (Sweden)

Majid Mohadesi

2014-03-01

Full Text Available Biodiesel fuel is considered as an alternative to diesel fuel. This fuel is produced through transesterification reactions of vegetable oils or animal fat by alcohols in the presence of different catalysts. Recent studies on this process have shown that, basic heterogeneous catalysts have a higher performance than other catalysts. In this study different alkali earth metal oxides (CaO, MgO and BaO doped SiO2 were used as catalyst for the biodiesel production process. These catalysts were synthesis by using the sol-gel method. A transesterification reaction was studied after 8h by mixing corn oil, methanol (methanol to oil molar ratio of 16:1, and 6 wt. % catalyst (based on oil at 60oC and 600rpm. Catalyst loading was studied for different catalysts ranging in amounts from 40, 60 to 80%. The purity and yield of the produced biodiesel for 60% CaO/SiO2 was higher than other catalysts and at 97.3% and 82.1%, respectively.

Microstructure-property relationships of rare-earth--zinc-oxide varistors

International Nuclear Information System (INIS)

Williams, P.; Krivanek, O.L.; Thomas, G.; Yodogawa, M.

1980-01-01

The microstructure and properties of ZnO varistors containing Ba, Co, and rare-earth--metal oxides, which give values of α [α=d(log I)/d(log V)] as high as 29, are examined. Mean ZnO grain size is 11 μm, and the grains are uniformly doped with Co. The barium and rare earth metals concentrate into 1.5-μm-wide particles embedded in a matrix of ZnO grains. Within the grains and at grain boundaries, the barium and rare-earth--metal concentration is below the detection limit of the energy-dispersive spectrometer technique (about 0.5%). No intergranular films, amorphous or crystalline, are detected, to within 10 A resolution. These results are shown to be consistent with the grain boundary charge depletion model for the voltage barrier formation and breakdown

Radiological aspects in a monazite based rare earth production facility

International Nuclear Information System (INIS)

Harikumar, M.; Sujata, R.; Chinnaesakki, S.; Tripathi, R.M.; Puranik, V.D.; Nair, N.N.G.

2011-01-01

One of the largest reserves of monazite in the world is present in the Indian subcontinent. Monazite ore has around 8-9% thorium oxide and nearly 60% Rare earth oxides. Selective acid extraction is used to separate the composite rare earths. The main radiological hazard arises from the presence of thorium and its daughter products. Monitoring of the radiation field and air activity in the rare earths plant is done routinely to reduce the radiation exposure to plant personnel. The separation of uranium and rare earths from Thorium concentrate separated from Monazite is being done as a part of the THRUST (Thorium Retrieval, Recovery of Uranium and Re-storage of Thorium) project from 2004 at Indian Rare Earths Limited, Udyogamandal. The radiological aspect for this extraction of uranium and rare earths was studied. The general radiation field in the rare earth production plant was 0.3-5.0 μGyh -1 and the average short lived air activity was 46 ± 7 mWL. The long lived air activity arising from 232 Th is very insignificant radiologically. The occupational radiation exposure for the rare earths separation plant is only 6 % of the total dose and the estimated average individual dose is 1.6 mSv per year. Studies were also done to estimate the residual radioactivity in the separated rare earth compounds using gamma spectrometry and the results showed significant presence of 227 Ac arising due to the protactinium fraction in the thorium concentrate. This activity is not detectable in a freshly separated rare earth compound but can buildup with time. (author)

A divalent rare earth oxide semiconductor: Yttrium monoxide

Science.gov (United States)

Kaminaga, Kenichi; Sei, Ryosuke; Hayashi, Kouichi; Happo, Naohisa; Tajiri, Hiroo; Oka, Daichi; Fukumura, Tomoteru; Hasegawa, Tetsuya

Rare earth sesquioxides like Y2O3 are known as widegap insulators with the highly stable closed shell trivalent rare earth ions. On the other hand, rare earth monoxides such as YO have been recognized as gaseous phase, and only EuO and YbO were thermodynamically stable solid-phase rock salt monoxides. In this study, solid-phase rock salt yttrium monoxide, YO, was synthesized in a form of epitaxial thin film by pulsed laser deposition method. YO possesses unusual valence of Y2+ ([Kr] 4d1) . In contrast with Y2O3, YO was narrow gap semiconductor with dark-brown color. The electrical conductivity was tunable from 10-1 to 103 Ω-1 cm-1 by introducing oxygen vacancies as electron donor. Weak antilocalization behavior was observed indicating significant spin-orbit coupling owing to 4 d electron carrier. The absorption spectral shape implies the Mott-Hubbard insulator character of YO. Rare earth monoixdes will be new platform of functional oxides. This work was supported by JST-CREST, the Japan Society for the Promotion of Science (JSPS) with Grant-in-Aid for Scientific Research on Innovative Areas (Nos. 26105002 and 26105006), and Nanotechnology Platform (Project No.12024046) of MEXT, Japan.

Rare earth elements: end use and recyclability

Science.gov (United States)

Goonan, Thomas G.

2011-01-01

Rare earth elements are used in mature markets (such as catalysts, glassmaking, lighting, and metallurgy), which account for 59 percent of the total worldwide consumption of rare earth elements, and in newer, high-growth markets (such as battery alloys, ceramics, and permanent magnets), which account for 41 percent of the total worldwide consumption of rare earth elements. In mature market segments, lanthanum and cerium constitute about 80 percent of rare earth elements used, and in new market segments, dysprosium, neodymium, and praseodymium account for about 85 percent of rare earth elements used. Regardless of the end use, rare earth elements are not recycled in large quantities, but could be if recycling became mandated or very high prices of rare earth elements made recycling feasible.

Influence of rare earth oxides in the oxidation of chromia forming alloys

International Nuclear Information System (INIS)

Ramanathan, L.V.

1989-01-01

The influence of superficial application of rare earth oxides such as CeO sub(2), La sub(2)O sub(3), Nd sub(2)O sub(3), Sm sub(2)O sub(3), and Gd sub(2)O sub (3) to AISI 304 and 310 stainless steels, on their isothermal oxidation behavior at 900 sup(0) and 1000 sup(0)C, and cyclic oxidation behavior between 20 sup(0) and 1000 sup(0)C has been studied. The application of rare earth oxides (REO) has been found to increase the oxidation resistance at AISI 304. No significant improvements in oxidation resistance of AISI 310 were noted. The oxidation resistance of AISI 304 was highest in the presence of CeO sub(2) on its surface. The other REO in decreasing order of influence on oxidation resistance are La sub(2)O sub(3), Nd sub(2)O sub(3), Sm sub(2)O sub(3) and Gd sub(2)O sub(3). SEM investigations of the oxide scale morphology revealed that the improved resistance is probably due to the formation of a thin layer of fine grained compact Cr sub(2)O sub(3) and the higher adhesion of the scale to its increased plasticity. (author)

Rare earth-iron-boron premanent magnets

International Nuclear Information System (INIS)

Ghendehari, M.H.

1988-01-01

This patent describes a method for producing rare earth-iron-boron permanent magnets containing added rare earth oxide, comprising the steps of: (a) mixing a particulate alloy containing at least one rare earth metal, iron, and boron with at least one particulate rare earth oxide; (b) aligning magnetic domains of the mixture in a magnetic field; (c) compacting the aligned mixture to form a shape; and (d) sintering the compacted shape

Microstructure and mechanical properties of multi-components rare earth oxide-doped molybdenum alloys

International Nuclear Information System (INIS)

Zhang Guojun; Sun Yuanjun; Zuo Chao; Wei Jianfeng; Sun Jun

2008-01-01

Pure molybdenum and molybdenum alloys doped with two- or three-components rare earth oxide particles were prepared by powder metallurgy. Both the tensile property and fracture toughness of the pure molybdenum and multi-components rare earth oxide-doped molybdenum alloys were determined at room temperature. The multi-components rare earth oxide-doped molybdenum alloys are fine grained and contain a homogeneous distribution of fine particles in the submicron and nanometer size ranges, which is why the molybdenum alloys have higher strength and fracture toughness than pure molybdenum. Quantitative analysis is used to explain the increase in yield strength with respect to grain size and second phase strengthening. Furthermore, the relationship between the tensile properties and microstructural parameters is quantitatively established

Process for obtaining sintered conglomerates with a high density of rare earth oxides and actinides

International Nuclear Information System (INIS)

Pasto, A.E.

1974-01-01

The invention concerns a method to produce agglomerates of actinide and rare earth oxides possessing a cubic-monoclinic transformation in order to obtain high densities close to the theoretical density, and the articles produced by the method. The process is based on the use of a rare earth or actinide oxide, in particular Eu 2 O 3 , with a cubic-monoclinic phase transformation, the oxide being sintered by hot compression at a temperature 50 deg C to 100 deg C above the transformation temperature. The sintered agglomerates obtained can have a purity of at least 99.9% and a density of practically 100%. These agglomerates are suitable in particular for the formation of nuclear reactor control rods [fr

Rare earths production and marketing opportunities

International Nuclear Information System (INIS)

Falconnet, P.G.

1988-01-01

The rare earths (RE) market is relatively small. The total production during 1968 was only 10000 tons (REO) which rose to 27000 tons (REO) during 1985. The three major areas of application, which are volume market for ceric rare earths are catalysts, glass ceramics and metallurgy. Among the other uses of rare earths, the permanent magnets, lamp phosphors and fine ceramics have registered significant growth in RE consumption. Monazite and bastnasite are the main natural source for rare earths and processing of these for one of the rare earths in high demand leads to over production of some others not in demand, thus creating a balance problem. The growth in RE market has always been influenced by the technology shifts and product substitution. For example, the RE consumption during 1974/76 for desulfurization of steel had substantially decreased due to the usage of calcium. Similarly, 1985 had witnessed a drastic cut in the use of REs in fluid cracking due to the introduction of stabilized zeolites which contain less REO. Thus, the overall compound growth rate of demand was only 3.9 % per year during the period 1970-1985. At present, 37 % of the rare earths production goes to the glass/ceramics industry, 33 % for catalyst and 25 % to metallurgy. The price of REs constantly shows a downward trend. This trend coupled with the rapid changes taking place in the various technological fields, demands greater flexibility and high marketing skills from the RE producers. The key factor for future expansion of RE market will be the development of 'high volume' application of ceric rare earths. (author) 2 figs., 8 tabs

Preparation and characterization of PT-rare earth/C electrocatalysts for PEM fuel cells

International Nuclear Information System (INIS)

Santoro, Thais Aranha de Barros

2009-01-01

Pt-rare earth/C electrocatalysts (rare earth = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, and Lu) were prepared (20 wt.% and Pt-to-RE atomic ratio of 50:50) by an alcohol reduction process using H 2 PtCl 6 .6H 2 O (Aldrich) and rare earth (III) chlorides (Aldrich) as metal sources, ethylene glycol as solvent and reducing agent, and Vulcan XC72 as support. The electrocatalysts were characterized by Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffractometry (XRD) and Transmission Electron Microscopy (TEM). The energy dispersive x-ray spectroscopy analysis showed that the Pt-Rare Earth atomic ratios obtained for all electrocatalysts were similar to those used in the preparations. In all diffractograms, it was observed a broad peak at about 25 degree which was associated to the Vulcan XC72 support material and four peaks at approximately 28=40 degree, 47 degree, 67 degree and 82 degree, which were associated to the (111), (200), (220), (311), and (222) planes, respectively, of the face-centered cubic (fcc) structure characteristic of platinum and platinum alloys. For the Pt-Rare Earth/C electrocatalysts, it was also observed peaks related to the rare earth oxides on the X ray diffractograms. PtLa/C electrocatalysts were prepared at different atomic ratio. Transmission electronic microscopy micrographs of electrocatalysts showed a reasonable distribution of the Pt particles on the carbon support with some agglomerations, which is in agreement with x-ray diffractometry result. The performance for CO, methanol and ethanol oxidation was investigated by cyclic voltammetry, chronoamperometry and Fourier transform infrared spectroscopy spectroscopy. The electrocatalytic activity of the Pt-Rare Earth/C electro catalyst, specially PtLa/C, were higher than that of the Pt/C electrocatalyst. Fourier transform infrared spectroscopy studies for ethanol oxidation on Pt-Rare Earth/C electrocatalyst showed that acetaldehyde and acetic acid were the main products. The PtLa/C (30

Effect of additives on lithium doped magnesium oxide catalysts used in the oxidative coupling of methane

NARCIS (Netherlands)

Korf, S.J.; Roos, J.A.; Veltman, L.J.; van Ommen, J.G.; Ross, J.R.H.

1989-01-01

It has been found that it is possible to improve the activity and stability for the oxidative coupling of methane of a Li/MgO catalyst by the addition of small amounts of the oxides of various transition and rare earth metals. A number of these additives, e.g. SnO2, TiO2, Dy2O3 and Tb4O7, caused

Selectivities of rare earth oxide catalysts for dehydration of butanols

International Nuclear Information System (INIS)

Bernal, S.; Trillo, J.M.

1980-01-01

The catalytic dehydration of 2-propanol, 1-butanol, and 2-butanol over La 2 O 3 , CeO 2 , Pr 6 O 11 , Sm 2 O 3 , Eu 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , and Yb 2 O 3 is studied. Because of the gradual variation of the general properties of 4f oxides, the former group has been considered a likely series to analyze the existence of definite correlations between alkene distribution and catalyst properties, often reported in the literature. According to our study, the effect of temperature on product distribution may strongly restrict the validity of such correlations. This point is discussed on the basis of the linear relationships found here between the activation energy (E/sub a/) and the log of the preexponential factor

Extraction studies on rare earths using dinonyl phenyl phosphoric acid

International Nuclear Information System (INIS)

Anitha, M.; Singh, D.K.; Kotekar, M.K.; Vijayalakshmi, R.; Singh, H.

2011-01-01

Rare earths are widely used in phosphor materials, magnetic substances, alloys, catalyst, lasers, superconductors, solid oxide fuel cells and in nuclear applications. The high value of these elements depends on their effective separation into high purity compounds. The separation into individual rare earths is very difficult to achieve, due to the very low separation factors between two adjacent rare earths arising due to similar chemical properties. Taking the advantage of variation in basicity, the separation is generally accomplished by solvent extraction or ion exchange. There are several references on the separation of rare earth in different media employing various types of extractants such as 2-ethylhexyl 2-ethyhexylphosphonic acid (EHEHPA) and di-2-ethyl hexyl phosphoric acid (D2EHPA) which have been widely used for the separation and purification of rare earths. Dinonyl phenyl phosphoric acid (DNPPA) is an organo phosphorus extractant (pKa = 2.54) and is an aromatic analogue of D2EHPA, which extracts metal ion by cation exchange mechanism. DNPPA was explored to recover rare earths from phosphate media such as wet process phosphoric acid and merchant grade acid. However, there is no information available in literature on DNPPA for RE extraction from chloride medium. Therefore, an attempt has been made in the present study to investigate the feasibility of using DNPPA for extraction of La(III), Dy(III) and Y(III) from chloride medium

in vivo EFFECTS OF RARE-EARTH BASED NANOPARTICLES ON OXIDATIVE BALANCE IN RATS

Directory of Open Access Journals (Sweden)

V. K. Klochkov

2016-12-01

Full Text Available The purpose of the research was to find the influence of rare-earth based nanoparticles (CeO2, GdVO2: Eu3+ on the oxidative balance in rats. We analyzed biochemical markers of oxidative stress (lipid peroxidation level, nitric oxide metabolites, sulfhydryl groups content and enzyme activities (superoxide dismutase, catalase in tissues of rats. It has been found that administration of both types of the nanoparticles increased nitric oxide metabolites and products of lipid peroxidation in liver and spleen within 5 days. At injections of GdVO2: Eu3+ lipid peroxidation products, nitric oxide metabolites in serum at 5, 10 and 15 days of the experiment was also increased whereas the level of sulfhydryl groups decreased compared to the intact state and the control. In contrast, under the influence of nanoparticle CeO2 level diene conjugates were not significantly changed and the level of nitric oxide metabolites within 15 day even decreased. During this period, under the influence of both types of nanoparticles the activity of superoxide dismutase was increased, catalase activity was not changed. Oxidative stress coefficient showed the less pronounced CeO2 prooxidant effect (2.04 in comparison to GdVO2: Eu3+ (6.89. However, after-effect of both types of nanoparticles showed complete restoration of oxidative balance values.

Microstructure and emission ability of rare earth oxides doped molybdenum cathodes

International Nuclear Information System (INIS)

Yang Jiancan; Nie Zuoren; Wang Yiman

2003-01-01

We adopted high-resolution transmission electron microscopy (TEM) and scanning electron microscopy (SAM) to observe and analyze the microstructure of rare earth oxide (La 2 O 3 , Sc 2 O 3 ) doped molybdenum cathodes. The results show that there are many nanometer particles in the molybdenum matrix besides some sub-micrometer particles in the crystal interfaces. All these particles are rare earth oxides as determined through calculating the electron diffraction pattern. Then we determined the electron work function and the zero-field emission current of molybdenum cathodes by the electron emission measurement. To correlate the emission data with surface composition, we use Auger electron spectroscopy (AES) to analyze the elements on the activated cathode surface and their depth profiles. We found that there were about 20 nm thick layers on an activated cathode surface, which have a high content of rare earth elements. We also use AES to analyze the elements diffusion to the cathode surface from cathode body during heating up to its operating temperature to find out which element positively affects the electron emission

High purity samarium oxide from mixed rare earth carbonates

International Nuclear Information System (INIS)

Queiroz, Carlos A. da S.; Seneda, Jose A.; Vasconcellos, Mari E. de; Pedreira Filho, Walter dos R.

2013-01-01

A simple and economical chemical process for the production of highly pure samarium oxides is discussed. The raw material, which was used in the form of rare earth carbonates was produced industrially from the chemical treatment of Brazilian monazite. Ion exchange chromatography was performed using a strong cationic resin that is typically employed in water treatment processes to fractionate rare earth elements (REE) without the use of retention ions. Under these conditions, 99.9% pure Sm 2 O 3 was eluted using the ammonium salt of ethylenediaminetetraacetic acid (EDTA) at a controlled pH. The EDTA-samarium complex was separated from EDTA and then precipitated as oxalate and fired to samarium oxide. Molecular absorption spectrophotometry was used to monitor the samarium content during the proposed process, and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the samarium oxide. Typical samarium oxide obtained from the proposed procedure contained the following contaminants in micrograms per gram: Sc (20.90); Y (11.80); La (8.4); Ce (4.3); Pr (2.5); Nd (5.1); Eu (94); Gd (114); Tb (3.6); Dy (2.5), Ho (2.3); Er (3.0); Tm (2.3); Yb (38,2); Lu (25.6). The high-purity samarium oxides produced in the present study can be used as an alternative to imported products in research and development applications. (author)

A divalent rare earth oxide semiconductor: Yttrium monoxide

Energy Technology Data Exchange (ETDEWEB)

Kaminaga, Kenichi; Sei, Ryosuke [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Department of Chemistry, Tohoku University, Sendai 980-8578 (Japan); Hayashi, Kouichi [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Happo, Naohisa [School of Information Sciences, Hiroshima City University, Hiroshima 731-3194 (Japan); Tajiri, Hiroo [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Sayo 679-5198 (Japan); Oka, Daichi; Fukumura, Tomoteru, E-mail: tomoteru.fukumura.e4@tohoku.ac.jp [Department of Chemistry, Tohoku University, Sendai 980-8578 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan)

2016-03-21

Rare earth oxides are usually widegap insulators like Y{sub 2}O{sub 3} with closed shell trivalent rare earth ions. In this study, solid phase rock salt structure yttrium monoxide, YO, with unusual valence of Y{sup 2+} (4d{sup 1}) was synthesized in a form of epitaxial thin film by pulsed laser deposition method. YO has been recognized as gaseous phase in previous studies. In contrast with Y{sub 2}O{sub 3}, YO was dark-brown colored and narrow gap semiconductor. The tunable electrical conductivity ranging from 10{sup −1} to 10{sup 3} Ω{sup −1 }cm{sup −1} was attributed to the presence of oxygen vacancies serving as electron donor. Weak antilocalization behavior observed in magnetoresistance indicated significant role of spin-orbit coupling as a manifestation of 4d electron carrier.

Rare Earth-Activated Silica-Based Nanocomposites

Directory of Open Access Journals (Sweden)

C. Armellini

2007-01-01

Full Text Available Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i Er3+-activated SiO2-HfO2 waveguide glass ceramic, and (ii core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

Stepwise hydrochloric acid extraction of monazite hydroxides for the recovery of cerium lean rare earths, cerium, uranium and thorium

International Nuclear Information System (INIS)

Swaminathan, T.V.; Nair, V.R.; John, C.V.

1988-01-01

Monazite sand is normally processed by the caustic soda route to produce mixed rare earth chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earth chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earth chloride rather than the natural rare earth chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earth chloride, cerium, thorium and uranium from rare earth + thorium hydroxide obtained by treating monazite, based on stepwise hydrochloric acid extraction, was developed in the authors laboratory. The process involves drying of the mixed rare earth-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions

Morphology and pore structure of rare earth oxides

International Nuclear Information System (INIS)

Bruce, L.A.; Hoang, M.; Hardin, S.; Turney, T.W.

1991-01-01

The morphology observed by transmission electron microscopy of rare earth oxides, prepared by two different routes, has been related to adsorption, characteristics for nitrogen at 77 K. The most common morphology was that of thin sheets, then small equiaxed particles, and, more rarely, rod-like particles. The presence of small equiaxed particles was found to be a prerequisite for adsorption hysteresis. Evaluation of linear 't' plots indicated freedom from micropores in all samples, but positive deviations in the presence of sheet morphology at high relative pressures left open the possibility of wedge-like pores in these samples. 14 refs., 3 tabs., 5 figs

Isotope exchange in oxide-containing catalyst

Science.gov (United States)

Brown, Kenneth G. (Inventor); Upchurch, Billy T. (Inventor); Hess, Robert V. (Inventor); Miller, Irvin M. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Hoyt, Ronald F. (Inventor)

1989-01-01

A method of exchanging rare-isotope oxygen for common-isotope oxygen in the top several layers of an oxide-containing catalyst is disclosed. A sample of an oxide-containing catalyst is exposed to a flowing stream of reducing gas in an inert carrier gas at a temperature suitable for the removal of the reactive common-isotope oxygen atoms from the surface layer or layers of the catalyst without damaging the catalyst structure. The reduction temperature must be higher than any at which the catalyst will subsequently operate. Sufficient reducing gas is used to allow removal of all the reactive common-isotope oxygen atoms in the top several layers of the catalyst. The catalyst is then reoxidized with the desired rare-isotope oxygen in sufficient quantity to replace all of the common-isotope oxygen that was removed.

Reducible oxide based catalysts

Science.gov (United States)

Thompson, Levi T.; Kim, Chang Hwan; Bej, Shyamal K.

2010-04-06

A catalyst is disclosed herein. The catalyst includes a reducible oxide support and at least one noble metal fixed on the reducible oxide support. The noble metal(s) is loaded on the support at a substantially constant temperature and pH.

The role of rare earth oxide nanoparticles in suppressing the photobleaching of fluorescent organic dyes

Science.gov (United States)

Guha, Anubhav; Basu, Anindita

2013-03-01

Organic dyes are widely used for both industrial as well as in scientific applications such as the fluorescent tagging of materials. However the process of photobleaching can rapidly degrade dye fluorescence rendering the material non-functional. Thus exploring novel methods for preventing photobleaching can have widespread benefits. In this work we show that the addition of minute quantities of rare earth (RE) oxide nanoparticles can significantly suppress the photobleaching of dyes. The fluorescence of Rhodamine and AlexaFluor dyes was measured as a function of time with and without the addition of CeO2 and La2O3 nanoparticle additives (two RE oxides that contain an oxygen vacancy based defect structure), as well as with FeO nanoparticles (which has an oxygen excess stoichiometry). We find that the rare earth oxides significantly prolonged the lifetimes of the dyes. The results allow us to develop a model based upon the presence of oxygen vacancies defects that allow the RE oxides to act as oxygen scavengers. This enables the RE oxide particles to effectively remove reactive oxygen free radicals generated in the dye solutions during the photoabsorption process. Current affiliation: Harvard University

Determination of trace elements in high pure rare earth oxide by double focusing inductively coupled plasma mass spectrometry (HR ICP-MS) and high performance liquid chromatography (HPLC) techniques

International Nuclear Information System (INIS)

Pedreira Filho, Walter dos Reis

2000-01-01

Rare earth oxides are used in several technological fields whose applications can be observed in several areas of modern technology, among which are included: lasers, semiconductors semi, high purity materials and metallic alloys. The field of applications of the rare earth elements is quite wide. Several important industrial applications are ceramics, catalysts and metallurgical as well as research areas and high technology sectors. Such applications have been presenting an accentuated growth in the last years. Chemical characterization of rare earth oxides of high purity has been constituting one of the major challenges of analytical chemistry. Several analytical techniques were used for chemical characterization of high purity rare earth the oxides. Even so, those techniques present limitations when one needs to characterize materials of a high level of purity, as in the case of rare earth oxides. Some of those limitations are associated, for example, to spectral interference. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a powerful analytical tool for quantitative analysis of metal impurities in high purity materials. The Instituto de Pesquisas Energeticas e Nucleares (IPEN) has an unit of production and purification of rare earth oxides, with above 99,9% level of purity. In this work, the rare earth impurities were characterized in samples (La 2 O 3 ; CeO 2 ; Pr 6 O 11 ; Nd 2 O 3 ; Sm 2 O 3 ; Gd 2 O 3 ; Y 2 O 3 ) produced at the IPEN and certified standard materials produced by Johnson Matthey Chemical (JMC). The technique of high performance liquid chromatography (HPLC) was used in the separation of the impurities. Quantification of metallic impurities was carried out as inductively coupled plasma mass spectrometer (HR-ICP MS). In this work it is presented a new analytical methodology in the chemical characterization of metallic impurities in rare earth oxides of high purity (> 99,9%) with and without separation of the matrix. Analyses of standard

Simultaneous determination of dysprosium, holmium and erbium in high purity rare earth oxides by second order derivative spectrophotometry

International Nuclear Information System (INIS)

Anbu, M.; Prasada Rao, T.; Iyer, C. S. P.; Damodaran, A. D.

1996-01-01

High purity individual rare earth oxides are increasingly used as major components in lasers (Y 2 O 3 ), phosphors (YVO 3 , Eu 2 O 3 ), magnetic bubble memory films (Gd 2 O 3 ) and refractive-index lenses and fibre optics (La 2 O 3 ). The determination of individual lanthanides in high purity rare earth oxides is a more important and difficult task. This paper reports the utilization of higher order derivative spectrophotometry for the simultaneous determination of dysprosium, holmium and erbium in high purity rare earth oxides. The developed procedure is simple, reliable and allows the determination of 0.001 to 0.2% of dysprosium, holmium and erbium in several rare earth. (author). 9 refs, 2 figs, 2 tabs

Role of the acid-base properties of gallium-antimony oxide catalyst in oxidative ammonolysis of propane to acrylonitrile (AN)

Energy Technology Data Exchange (ETDEWEB)

Osipova, Z.G.; Sokolovskii, V.D.

1979-07-01

The role of the acid-base properties of gallium-antimony oxide catalyst in oxidative ammonolysis of propane to acrylonitrile (AN) was studied in a differential flow reactor at 550/sup 0/C, with the reaction mixture containing 5 3< by vol propane, 6 3< ammonia, and 18.6Vertical Bar3< oxygen diluted in helium, over ebulliated beds of a 5Vertical Bar3< Ga/Sb or a 1:3:1.5:1 Ga/Sb/Ni/P catalysts, the basicity of which was varied by adding 5 mole Vertical Bar3< of an alkaline earth metal (added as the nitrate and calcined). Both the rate of propane conversion and that of AN formation increased with increasing concentration of the basic sites (determined by back titration with benzoic acid) on both types of the catalysts and linearly correlated with the amount of nitrous oxide desorbed from the catalysts after the reaction. The presence of ammonia in the reaction mixture increased the activity and selectivity of the catalysts and the concentration of the active basic sites. Apparently, the reaction rate is limited by proton abstraction from a propane molecule with the formation of a carbanion stabilized on alkaline-earth metal cations. The rate-determining proton abstraction occurs on nucleophile basic sites, formed by dissociative adsorption of ammonia to form species such as NH, NH/sub 2/, and HNO, which are then oxidized to N/sub 2/ and N/sub 2/O.

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.

2014-11-05

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system p-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts.

Study on recovering directly the commercial cerium oxide and total of residue rare earths from Dongpao bastnasite concentrate

International Nuclear Information System (INIS)

Nguyen Trong Hung; Nguyen Thanh Chung; Luu Xuan Dinh

2003-01-01

A technology for decomposition roasting and sequential leaching processes of Dong Pao bastnasite concentrate to recover directly commercial cerium oxide and total of residue rare earth elements from the leaching solution of the roasted product have been investigated. The bastnasite concentrate is initially roasted at temperature range of 600 - 650 degC and for time of 4 hrs in order to decompose and convert the hardly soluble carbonate forms of ore into easily soluble oxide. The roasted solid is then leached with sulfuric acid solution of 6N at 60 degC for 4 hrs to convert rare earths in oxide and fluoride form into rare earth sulfate. The recovery yield of rare earths of these stages is more than 95%. The attention has especially been paid on recovering directly the commercial cerium oxide and total of residue rare earth element from the above leaching solution. Complex ions of CeSO 4 2+ , Ce(SO 4 ) 2 , Ce(SO 4 ) 3 2- and Ce(SO 4 ) 4 4- exist in aqueous solution of cerium (IV) sulfate. Based on the property, the method of ion - sieve with DOWEX cation resin column has been applied to estimating separation of the ceric complex anions from Ln(III). The survey showed that most of the ceric complex anions are separated from total of residue rare earths. The latter which are absorbed in the cation column are recovered by elution of HCl of 4N. The recovery yield of cerium can only be reached 20% but the purity of that is very high, can be reached 99.6%. About 5 kg of CeO 2 of high grade and 5 kg of TREO of commercial specification have been produced. (author)

Investigations on fabricating strategies and utilization of rare earth based multicomponent oxide powders in radiation detection

International Nuclear Information System (INIS)

Shinde, Seema; Pitale, S.S.; Banthia, S.; Ghosh, M.; Tyagi, M.; Sen, S.; Gadkari, S.C.

2014-01-01

Materials containing rare earths demonstrate a broad field of applications as high energy radiation detectors, mainly due to their fascinating optical properties. Currently, Ce 3+ -doped rare earth silicates and garnets dominate the scintillator market because they show a high light yield, fast decay time, and high chemical stability. Moreover, the emission wavelength of silicates (410-440 nm) matches the wavelength sensitivity of conventional PMTs while, Si-photo-detector readouts are possible with garnets (emission near 550 nm). The composition, structure and phase of rare earth silicates are rather complex. For example, there are many phases like oxyorthosilicate R 2 SiO 5 , disilicate R 2 Si 2 O 7 , hexagonal R x (SiO 4 ) 6 O 2 oxyapatite etc (where R= Rare earth element). The controlled synthesis of single phase rare earth silicates and garnets nanomaterials is not easy and can only be reached with precisely controlled experimental conditions. In this work, we provide a broad overview of our recent scientific developments linked to a few aspects of synthesizing cerium activated rare earth based silicates and garnet materials, namely Gd 2 SiO 5 :Ce 3+ , Gd 4.67 (SiO 4 ) 3 O, Gd 2 Si 2 O 7 :Ce 3+ and Gd 3 Al x Ga 1-x O 12 :Ce 3+ (where 0≤x≤5) exploiting the advantages of solution combustion, chemical co-precipitation and hydrothermal techniques. A brief summary of results based on synthesis strategy adopted, composition, size shape and corresponding luminescence features of Gd based compounds are tabulated. The room temperature photoluminescence (PL) features of compounds listed. Efforts towards finding new properties and new materials will be continued and several applications, in particular energy-conversion and scintillator detectors, will benefit from these rare earth materials

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li2O Salt

International Nuclear Information System (INIS)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon; Sohn, Jung Min

2016-01-01

In this study, the electrochemical reduction of RE 2 O 3 (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li 2 O. The electrochemical reduction behavior of the mixed RE 2 O 3 -NiO oxide has been investigated and the reduction path of RE 2 O 3 has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl 3 in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li 2 O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE 2 O 3 on the produced Ni to form intermetallic RENi 5 . The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd 2 O 3 was successfully converted to the metal in the presence of NiO.

Determination of rare earth elements in high purity rare earth oxides by liquid chromatography, thermionic mass spectrometry and combined liquid chromatography/thermionic mass spectrometry

International Nuclear Information System (INIS)

Stijfhoorn, D.E.; Stray, H.; Hjelmseth, H.

1993-01-01

A high-performance liquid chromatographic (HPLC) method for the determination of rare earth elements in rocks has been modified and used for the determination of rare earth elements (REE) in high purity rare earth oxides. The detection limit was 1-1.5 ng or 2-3 mg/kg when a solution corresponding to 0.5 mg of the rare earth oxide was injected. The REE determination was also carried out by adding a mixture of selected REE isotopes to the sample and analysing the collected HPLC-fractions by mass spectrometry (MS) using a thermionic source. Since the matrix element was not collected, interference from this element during the mass spectrometric analysis was avoided. Detection limits as low as 0.5 mg/kg could then be obtained. Detection limits as low as 0.05 mg/kg were possible by MS without HPLC-pre-separation, but this approach could only be used for those elements that were not affected by the matrix. Commercial samples of high purity Nd 2 O 3 , Gd 2 O 3 and Dy 2 O 3 were analysed in this study, and a comparison of results obtained by HPLC, combined HPLC/MS and direct MS is presented. (Author)

Rare-earth hafnium oxide materials for magnetohydrodynamic (MHD) generator application

Energy Technology Data Exchange (ETDEWEB)

Marchant, D. D; Bates, J. L.

1979-01-01

Several ceramic materials based on rare-earth hafnium oxides have been identified as potential high-temperature electrodes and low-temperature current leadouts for open cycle coal-fired MHD generator channels. The electrode-current leadouts combination must operate at temperatures between 400 and 2000K with an electrical conductivity greater than 10/sup -2/ ohm/sup -1/ cm/sup -1/. The electrodes will be exposed to flowing (linear flow rates up to 100 m/s) potassium seeded coal combustion gases (plasma core temperatures between 2400 to 3200/sup 0/K) and coal slag. During operation the electrodes must conduct direct electric current at densities near 1.5 amp/cm/sup 2/. Consequently, the electrodes must be resistant to electrochemical decompositions and interactions with both the coal slag and potassium salts (e.g., K/sub 2/SO/sub 4/, K/sub 2/CO/sub 3/). The current leadout materials are placed between the hot electrodes and the water-cooled copper structural members and must have electrical conductivities greater than 10/sup -2/ ohm/sup -1/ cm/sup -1/ between 1400 and 400/sup 0/K. The current leadouts must be thermally and electrochemically compatible with the electrode, copper, and potassium salts. Ideally, the electrodes and current leadouts should exhibit minimal ionic conductivity. The fabrication, electrical conductivity, and electrochemical corrosion of rare-earth hafnium oxide materials are discussed. (WHK)

Rare Earth Elements - A New Challenge for the World Economy

Directory of Open Access Journals (Sweden)

Cristina Bumbac

2013-01-01

Full Text Available Rare Earth Elements or Rare Earth Metals (REM are a collection of seventeen chemical elements in the periodic table, namely scandium, yttrium and fifteen lanthanides. The term "rare earth" arises from the rare earth minerals from which they were first isolated. They are uncommon oxide-type minerals (earths found in Gandolinite extracted from one mine in Sweden. The first discovery was made in 1794, but it was only in 1940 that the scientist Frank Spedding developed an ion exchange procedure for separating and purifying the REM. For the next decades, they were hardly used in some "minor" industrial fields. Only after 2000 their importance grew, once the multitude of possibilities to use them was discovered due to technological progress. Now REM are incorporated into almost all modern technological devices: superconductors, magnets, electronic polishers, refining catalysts hybrid car components and military techniques. They are used in small quantities, but due to their extraordinary properties the prices are very high. The main problem is that China dominates this market, with 97% of total global supply. The highest concentration of rare earth metals are in Inner Mongolia in China, Mountain Pass in California U.S.A. and in Mount Weld in Australia. The developed countries are far behind China regarding production and are indeed depending on Chinese exports. Hence, there is a difficult situation on this particular market, with an uncertain future.

Effects of rare-earths additions on the breakdown of protective oxide scales in the presence of sulfur

International Nuclear Information System (INIS)

Srinivasan, V.; Goodman, D.E.

1989-01-01

Minor additions of rare-earths improve oxide scale adhesion in simple oxidation at high temperatures. The efficacy of such improvements and the role of such additions are not well understood in the presence of sulfur at 500-700 degrees C. Therefore, mixed gas corrosion tests were performed on model Fe-based alloys, with minor additions of rare-earths in an H 2 /H 2 S/H 2 O/Ar gas mixture at 700 degrees C up to 192 hours. The scale breakdown mechanisms were studied on preoxidized samples. The scales and the substrates were characterized by SEM/EDS, and scanning Auger microscopy (AES). The results are discussed

Structural/surface characterization and catalytic evaluation of rare-earth (Y, Sm and La) doped ceria composite oxides for CH{sub 3}SH catalytic decomposition

Energy Technology Data Exchange (ETDEWEB)

He, Dedong; Chen, Dingkai; Hao, Husheng; Yu, Jie; Liu, Jiangping; Lu, Jichang; Liu, Feng [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Wan, Gengping [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Research Center for Analysis and Measurement, Hainan University, Haikou, 570228 (China); He, Sufang [Research Center for Analysis and Measurement, Kunming University of Science and Technology, Kunming, 650093 (China); Luo, Yongming, E-mail: environcatalysis222@yahoo.com [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China)

2016-12-30

Highlights: • Ce{sub 0.75}RE{sub 0.25}O{sub 2-δ} (RE = Y, Sm and La) were synthesized by citrate complexation method. • Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ} exhibited the best stability for the decomposition of CH{sub 3}SH. • Cation radius played a key role in determining structure and surface characteristics. • Catalytic behavior depended on synergistic role of oxygen vacancies and basic sites. • Ce{sub 2}S{sub 3} accumulation on the surface was responsible for the deactivation of catalyst. - Abstract: A series of rare earth (Y, Sm and La) doped ceria composite oxides and pure CeO{sub 2} were synthesized and evaluated by conducting CH{sub 3}SH catalytic decomposition test. Several characterization studies, including XRD, BET, Raman, H{sub 2}-TPR, XPS, FT-IR, CO{sub 2}-TPD and CH{sub 3}SH-TPD, were undertaken to correlate structural and surface properties of the obtained ceria-based catalysts with their catalytic performance for CH{sub 3}SH decomposition. More oxygen vacancies and increased basic sites exhibited in the rare earth doped ceria catalysts. Y doped ceria sample (Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ}), with a moderate increase in basic sites, contained more oxygen vacancies. More structural defects and active sites could be provided, and a relatively small amount of sulfur would accumulate, which resulted in better catalytic performance. The developed catalyst presented good catalytic behavior with stability very similar to that of typical zeolite-based catalysts reported previously. However, La doped ceria catalyst (Ce{sub 0.75}La{sub 0.25}O{sub 2-δ}) with the highest alkalinity was not the most active one. More sulfur species would be adsorbed and a large amount of cerium sulfide species (Ce{sub 2}S{sub 3}) would accumulate, which caused deactivation of the catalysts. The combined effect of increased oxygen vacancies and alkalinity led to the catalytic stability of Ce{sub 0.75}Sm{sub 0.25}O{sub 2-δ} sample was comparable to that of pure Ce

Pyro-Electrochemical Reduction of a Mixture of Rare Earth Oxides and NiO in LiCl molten Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun [Department of Chemical Engineering, Chungbuk National University, Cheongju (Korea, Republic of)

2017-06-15

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.

XAS study of V2O5/Al2O3 catalysts doped with rare earth oxides

International Nuclear Information System (INIS)

Centeno, M.A.; Malet, P.; Capitan, M.J.; Benitez, J.J.; Carrizosa, I.; Odriozola, J.A.

1995-01-01

This paper reports on XAS studies of well dispersed V 2 O 5 /Al 2 O 3 and V 2 O 5 /Sm 2 O 3 /Al 2 O 3 samples. XAS spectra at V-K and Sm-L III edges show that the rare earth oxide favours the formation of regular tetrahedral units, [VO 4 ], over the surface of the support. Positions of the preedge peak at the V-K edge, and intensities of the white line at the Sm-L III edge also suggest modifications in the electronic density around V and Sm atoms when they are simultaneously supported over Al 2 O 3 . ((orig.))

Forecasting of physicochemical properties of rare earth sesquioxides on the base of their electronic structure in condensed state using electronic computer

International Nuclear Information System (INIS)

Kutolin, S.A.; Kotyukov, V.I.; Komarova, S.N.; Smirnova, E.G.

1980-01-01

A functional dependence between physicochemical properties of rare earth sesquioxides and energy state of rare earth atom sublattice valent electrons in sesquioxides is found out. The results of calculation of a simplified zone strucrure of rare earth sesquioxides are presented. The energy of the band of metal sublattice valent electrons for rare earth oxides is presented by the Chebyshev coefficients and polynomials and is calculated in the atomic units of mass. The density, melting points, standard change of enthalpy entropy, free energy, specific heat, standard entropy, forbidden zone width, static permitivity with a relative error of 10-12%, and thermal value of seeming activation energy, tangent of a dielectric losses angle, puncture voltage in rare earth oxides with a relative error of 20% are calculated on the base of calculation of electronic structure of rare earth sesquioxide in a condensed state and regression equations of calculation of oxide physicochemical properties. It is shown that only the Chebyshev coefficients determining the metal sublattice electronic structure in an oxide are ''information'' ones, i e. they contribute into the quantitative description of the system

Autothermal reforming catalyst having perovskite structure

Science.gov (United States)

Krumpel, Michael [Naperville, IL; Liu, Di-Jia [Naperville, IL

2009-03-24

The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

Some major aspects of the chemical behavior of rare earth oxides: An overview

International Nuclear Information System (INIS)

Bernal, S.; Blanco, G.; Calvino, J.J.; Omil, J.A. Perez; Pintado, J.M.

2006-01-01

The chemical behavior of sesquioxides and higher rare earth oxides is briefly reviewed. In the first case processes implying no change in the lanthanoid oxidation state are considered, whereas in the second one the analysis is focused on their redox behavior

Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media

Science.gov (United States)

Blasco-Ahicart, Marta; Soriano-López, Joaquín; Carbó, Jorge J.; Poblet, Josep M.; Galan-Mascaros, J. R.

2018-01-01

Water splitting is a promising approach to the efficient and cost-effective production of renewable fuels, but water oxidation remains a bottleneck in its technological development because it largely relies on noble-metal catalysts. Although inexpensive transition-metal oxides are competitive water oxidation catalysts in alkaline media, they cannot compete with noble metals in acidic media, in which hydrogen production is easier and faster. Here, we report a water oxidation catalyst based on earth-abundant metals that performs well in acidic conditions. Specifically, we report the enhanced catalytic activity of insoluble salts of polyoxometalates with caesium or barium counter-cations for oxygen evolution. In particular, the barium salt of a cobalt-phosphotungstate polyanion outperforms the state-of-the-art IrO2 catalyst even at pH < 1, with an overpotential of 189 mV at 1 mA cm-2. In addition, we find that a carbon-paste conducting support with a hydrocarbon binder can improve the stability of metal-oxide catalysts in acidic media by providing a hydrophobic environment.

China's rare-earth industry

Science.gov (United States)

Tse, Pui-Kwan

2011-01-01

Introduction China's dominant position as the producer of over 95 percent of the world output of rare-earth minerals and rapid increases in the consumption of rare earths owing to the emergence of new clean-energy and defense-related technologies, combined with China's decisions to restrict exports of rare earths, have resulted in heightened concerns about the future availability of rare earths. As a result, industrial countries such as Japan, the United States, and countries of the European Union face tighter supplies and higher prices for rare earths. This paper briefly reviews China's rare-earth production, consumption, and reserves and the important policies and regulations regarding the production and trade of rare earths, including recently announced export quotas. The 15 lanthanide elements-lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium (atomic numbers 57-71)-were originally known as the rare earths from their occurrence in oxides mixtures. Recently, some researchers have included two other elements-scandium and yttrium-in their discussion of rare earths. Yttrium (atomic number 39), which lies above lanthanum in transition group III of the periodic table and has a similar 3+ ion with a noble gas core, has both atomic and ionic radii similar in size to those of terbium and dysprosium and is generally found in nature with lanthanides. Scandium (atomic number 21) has a smaller ionic radius than yttrium and the lanthanides, and its chemical behavior is intermediate between that of aluminum and the lanthanides. It is found in nature with the lanthanides and yttrium. Rare earths are used widely in high-technology and clean-energy products because they impart special properties of magnetism, luminescence, and strength. Rare earths are also used in weapon systems to obtain the same properties.

Cerium concentrate and mixed rare earth chloride by the oxidative decomposition of bastnaesite in molten sodium hydroxide

International Nuclear Information System (INIS)

Iijima, Toshio; Kato, Kazuhiro; Kuno, Toyohiko; Okuwaki, Akitsugu; Umetsu, Yoshiaki; Okabe, Taijiro

1993-01-01

Bastnaesite was treated in molten NaOH at 623-777 K for 10-60 min under atmosphere. Cerium-(III) in the ore was easily oxidized 95% or more within 30 min to give an oxidation product composed of solid solutions of CeO 2 -rich and CeO 2 -lean phases and Ce-free rare earth oxide phase. Simultaneously fluoride ion was removed 97% or more. Cerium concentrate was prepared from the oxidation product by leaching with 0.1-3 M HCl solution. The yield of cerium concentrate and the CeO 2 content reached 55-57% and 70-72%, respectively. Mixed rare earth chloride is composed of about 90% rare earth chloride and 10% alkaline earth chloride, and the contents of CeCl 3 , LaCl 3 , NdCl 3 , and PrCl 3 are 11.5, 58.5, 14.4, and 5.4%, respectively. The particle size of resulting cerium concentrate was fairly uniform and about 0.1 μm

Rare earth impurities in high purity lanthanum oxide determined by neutron activation analysis

International Nuclear Information System (INIS)

Nguyen Van Suc; Desai, H.B.; Parthasarathy, R.; Gangadharan, S.

1992-01-01

Individual rare earth impurities in high purity La 2 O 3 (≥99.9%) have been determined by NAA after pre-separation of the matrix (La). The separation is carried out on an anion exchanger (Dowex 1x8) using different mixtures of methanol/nitric acid as eluants. The rare earth elements from Dy to Lu are eluted quantitatively using a 10% 1M HNO 3 - 90% methanol mixture, while the light rare earths from Ce to Gd are eluted quantitatively using a 10% 0.05M HNO 3 - 90% methanol mixture. La, which is retained on the column, is eluted using 0.1M HNO 3 . The recoveries of the various rare earth elements have been checked using radiotracers and also by spiking the sample with known amount of elements, and the recoveries are found to be quantitative. Results obtained on a typical high purity lanthanum oxide are reported here. (author) 5 refs.; 1 fig

An Overview of Rare Earth Science and Technology

Science.gov (United States)

Gschneidner, Karl, Jr.

2012-02-01

Currently rare earth science and technology is robust: this includes all the major branches of science -- biochemistry, chemistry, materials and physics. There are, however, currently some anomalies and distortions especially in the technology and applications sector of the rare earth field, which is caused by the dominance of China on the sales of rare earths and rare earth containing products. For the past 5 to 10 years ˜95% of rare earths utilized in commerce came from China. Although Chinese actions have lead to sudden and large price spikes and export embargoes, the rare earths are still available but at a higher cost. The start up of production in 2011 at mines in the USA and Australia will alleviate this situation in about two years. Basic and applied research on the condensed matter physics/materials science has hardly been impacted by these events, but new research opportunities are opening up especially with regard to the USA's military and energy security. Magnets seems to be the hottest topic, but research on battery materials, phosphors and catalysts are also (or should be) strongly considered.

Processing of monazite at the rare earth division,Udyogamandal

International Nuclear Information System (INIS)

Narayanan, N.S.; Thulasidoss, S.; Ramachandran, T.V.; Swaminathan, T.V.; Prasad, K.R.

1988-01-01

The processing techniques adopted at the Rare Earth Division of the Indian Rare Earths Limited at Udyogamandal, for the production of rare earth compounds of various compositions and purity grades are reviewed. Over 100 different compounds are produced and marketed, and these include mixed rare earths chloride, crude thorium concentrate, cerium oxide, cerium hydrate, rare earths carbonate, didymium salts and individual rare earth oxides and salts. Also, the trisodium phosphate obtained as byproduct in the processing of monazite, is recovered and marketed. The process scheme for monazite essentially involves alkaline digestion of ground monazite, removal of the by-product trisodium phosphate, separation of thorium through preferential dissolution of rare earths hydroxide in hydrochloric acid under controlled pH and temperature conditions followed by purification, and evaporation of the chloride solution to yield pure rare earths chloride. Part of the chloride is utilised for the production of individual rare earth compounds after separation by solvent extraction and ion exchange processes. Individual rare earth compounds of 99.99 %+ purity are regularly produced to cater to the demand within the country. (author) 8 figs., 1 tab

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li{sub 2}O Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon [Chungbook National University, Chungju (Korea, Republic of); Sohn, Jung Min [Chonbuk National University, Jeonju (Korea, Republic of)

2016-05-15

In this study, the electrochemical reduction of RE{sub 2}O{sub 3} (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li{sub 2}O. The electrochemical reduction behavior of the mixed RE{sub 2}O{sub 3}-NiO oxide has been investigated and the reduction path of RE{sub 2}O{sub 3} has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl{sub 3} in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li{sub 2}O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE{sub 2}O{sub 3} on the produced Ni to form intermetallic RENi{sub 5}. The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd{sub 2}O{sub 3} was successfully converted to the metal in the presence of NiO.

Quantification of trace amounts of rare earth elements in high purity gadolinium oxide by sector field inductively coupled plasma mass spectrometry (ICP-MS)

International Nuclear Information System (INIS)

Pedreira, W.R.; Silva Queiroz, C.A. da; Abrao, A.; Pimentel, M.M.

2004-01-01

In recent years, rare earth elements (REEs) have received much attention in the fields of geochemistry and industry. Gadolinium oxide is used for many different high technology applications such as infrared absorbing automotive glass, petroleum cracking catalyst, gadolinium-yttrium garnets, microwave applications, and color TV tube phosphors. It can also be used in optical glass manufacturing and in the electronic industry. Rapid and accurate determinations of the rare earth elements are increasingly required as industrial demands expand. In general, the inductively coupled plasma mass spectrometry (ICP-MS) presents some advantages for trace element analysis, due to high sensitivity and resolution, when compared with other analytical techniques. In this work, sector field inductively coupled plasma mass spectrometry was used. Sixteen elements (Sc, Y, and 14 lanthanides) were determined selectively with the ICP-MS system using a concentration gradient method. The detection limits with the ICP-MS system were about 0.2-8 pg ml -1 . The recovery percentage ranged from 95 to 100% for different rare earth elements. The %R.S.D. of the methods varying between 1.5 and 2.5% for a set of five (n=5) replicates was found for the IPEN's material and for the certificate reference sample. Determination of trace REEs in two high pure gadolinium oxides samples (IPEN and JMC) was performed. IPEN's material is highly pure (>99.99%) and was successfully analyzed without spectral interference

Supramolecular water oxidation with Ru-bda-based catalysts.

Science.gov (United States)

Richmond, Craig J; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni

2014-12-22

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda=2,2'-bipyridine-6,6'-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s(-1) , respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bragg-grating-based rare-earth-ion-doped channel waveguide lasers and their applications

NARCIS (Netherlands)

Bernhardi, Edward

2012-01-01

The research presented in this thesis concerns the investigation and development of Bragggrating-based integrated cavities for the rare-earth-ion-doped Al2O3 (aluminium oxide) waveguide platform, both from a theoretical and an experimental point of view, with the primary purpose of realizing

Determination of active oxygen content in rare earth peroxides

International Nuclear Information System (INIS)

Queiroz, Carlos A.S.; Abrao, Alcidio

1993-01-01

The content of active oxygen in rare earth peroxides have been determined after the dissolution of the samples with hydrocloridic acid in the presence of potassium iodide. The free generated iodine is titrated with sodium thiosulfate using starch as indicator. The oxidation of iodide to the free iodine indicates the presence of a higher valence state rare earth oxide, until now specifically recognized for the oxides of cerium (Ce O 2 ), praseodymium (Pr 6 O 1 1) and terbium (TB 4 O 7 ). recently the authors synthesized a new series of rare earth compounds, the peroxides. These new compounds were prepared by precipitating the rare earth elements complexed with carbonate ion by addition of hydrogen peroxide. the authors demonstrated that all rare earth elements, once solubilized by complexing with carbonate ion, are quantitatively precipitated as peroxide by addition of hydrogen peroxide. (author)

A problem in gravimetric method for the determination of rare earth elements as oxide after the fluoride separation

International Nuclear Information System (INIS)

Takada, Kunio

1979-01-01

For the gravimetric determination of lanthanum, it was precipitated as fluoride and converted to oxide by igniting (ca. 930 0 C) in a town gas flame. However, the oxidation of lanthanum fluoride by ignition was incomplete, the major part of the precipitate being converted to oxyfluoride (LaOF) and a mixture of oxide and oxyfluoride resulted. Therefore, analytical results were generally (5 -- 7)% higher than theoretically expected. The lanthanum fluoride became converted into the oxide by repeating ignition (ca. 1070 0 C) three times, each for (30 -- 40)min. However, the weight was lower than that of the corresponding sesquioxide, La 2 O 3 . Except for ytterbium and lutetium, gravimetric results as oxides for the other rare earth elements (Y, Pr, Nd, Sm, Eu and Gd) were higher than theoretical values. Therefore, the precipitation of the rare earth elements as fluoride and the subsequent determination as oxide by ignition of the fluoride could not be recommended as the gravimetric method for the rare earths. In order to obtain accurate results for major to minor amounts of the rare earth elements, an EDTA titration at pH 6 should be used after the dissolution of fluoride in acid, if the fluoride precipitation separation is involved. (author)

Preliminary study on the existence characteristics of rare earth elements in the interstratified oxidized zone

International Nuclear Information System (INIS)

Wang Jinping

2006-10-01

There were few of studies on rare earth elements (REE) in sandstone hosted uranium deposits, except the study of sediments source tracing and REE distribution modalities. Based on the study of existence characteristics of REE in subzones of interstratified oxidized zone in Shihongtan uranium deposit, Tuha basin, the possible migration features of REE was traced, and the significance of ΣREE, LREE/HREE ratios and δEu, δCe value during the interstratified oxidation were illustrated. (authors)

THE EFFECTS OF RARE EARTHS ON ACTIVITY AND SURFACE ...

African Journals Online (AJOL)

A series of Ru-RE/γ-AL2O3 (RE = Ce, Pr, La, Sm, Tb or Gd) and Ru/γ-AL2O3 catalysts were prepared by impregnation method. The influence of rare earths on the catalytic performance of Ru/γ-AL2O3 catalyst for the water gas shift reaction was studied. The catalysts were characterized by X-ray diffraction (XRD), ...

Rare-earth-free high energy product manganese-based magnetic materials.

Science.gov (United States)

Patel, Ketan; Zhang, Jingming; Ren, Shenqiang

2018-06-14

The constant drive to replace rare-earth metal magnets has initiated great interest in an alternative. Manganese (Mn) has emerged to be a potential candidate as a key element in rare-earth-free magnets. Its five unpaired valence electrons give it a large magnetocrystalline energy and the ability to form several intermetallic compounds. These factors have led Mn-based magnets to be a potential replacement for rare-earth permanent magnets for several applications, such as efficient power electronics, energy generators, magnetic recording and tunneling applications, and spintronics. For past few decades, Mn-based magnets have been explored in many different forms, such as bulk magnets, thin films, and nanoparticles. Here, we review the recent progress in the synthesis and structure-magnetic property relationships of Mn-based rare-earth-free magnets (MnBi, MnAl and MnGa). Furthermore, we discuss their potential to replace rare-earth magnetic materials through the control of their structure and composition to achieve the theoretically predicted magnetic properties.

A study of emission property and microstructure of rare earth oxide-molybdenum cermet cathode materials made by spark plasma sintering

International Nuclear Information System (INIS)

Wang Jinshu; Li Hongyi; Yang Sa; Cui Ying; Zhou Meiling

2004-01-01

A fast sintering method, spark plasma sintering (SPS) was used for the synthesis of rare earth oxide-molybdenum cathode material. The secondary emission property, microstructure, and phase constitution of materials have been studied in this paper. The experimental results show that the maximum secondary emission coefficient of this material can be high to 3.84, much higher than that of rare earth oxide-molybdenum cathode made by traditional sintering method. The grain size is less than 1 μm and rare earth distributed evenly in the material. After the material was activated at 1600 deg. C, a 4 μm layer of rare earth oxide which leads to the high secondary emission coefficient of the material, is formed on the surface of the cathode

Mechanism-Based Design of Green Oxidation Catalysts

Energy Technology Data Exchange (ETDEWEB)

Rybak-Akimova, Elena [Tufts Univ., Medford, MA (United States)

2015-03-16

In modern era of scarce resources, developing chemical processes that can eventually generate useful materials and fuels from readily available, simple, cheap, renewable starting materials is of paramount importance. Small molecules, such as dioxygen, dinitrogen, water, or carbon dioxide, can be viewed as ideal sources of oxygen, nitrogen, or carbon atoms in synthetic applications. Living organisms perfected the art of utilizing small molecules in biosynthesis and in generating energy; photosynthesis, which couples carbohydrate synthesis from carbon dioxide with photocatalytic water splitting, is but one impressive example of possible catalytic processes. Small molecule activation in synthetic systems remains challenging, and current efforts are focused on developing catalytic reactions that can convert small molecules into useful building blocks for generating more complicated organic molecules, including fuels. Modeling nature is attractive in many respects, including the possibility to use non-toxic, earth-abundant metals in catalysis. Specific systems investigated in our work include biomimetic catalytic oxidations with dioxygen, hydrogen peroxide, and related oxygen atom donors. More recently, a new direction was been also pursued in the group, fixation of carbon dioxide with transition metal complexes. Mechanistic understanding of biomimetic metal-catalyzed oxidations is critical for the design of functional models of metalloenzymes, and ultimately for the rational synthesis of useful, selective and efficient oxidation catalysts utilizing dioxygen and hydrogen peroxide as terminal oxidants. All iron oxidases and oxygenases (both mononuclear and dinuclear) utilize metal-centered intermediates as reactive species in selective substrate oxidation. In contrast, free radical pathways (Fenton chemistry) are common for traditional inorganic iron compounds, producing hydroxyl radicals as very active, non-selective oxidants. Recent developments, however, changed this

Metal Phosphate-Supported Pt Catalysts for CO Oxidation

Directory of Open Access Journals (Sweden)

Xiaoshuang Qian

2014-12-01

Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

Production of rare earth-silicon-iron alloys

International Nuclear Information System (INIS)

Mehra, O.K.; Bose, D.K.; Gupta, C.K.

1987-01-01

At Metallurgy Division, BARC, improved procedures for producing rare earth-silicon alloys have been investigated. In these methods, reduction of mixed rare earth oxide by a ferro-silicon and aluminium mixture in combination with CaO-MgO flux/CaO-CaF 2 flux have been tried to prepare an alloy product with a higher rare earth recovery at a higher rare earth content than the present commercial production method. The rare earth recovery using CaO-CaF 2 was 85 per cent while in the case of CaO-MgO flux it was 76 per cent. The corresponding rare earth contents in the alloy correspond to 40 per cent and 55 per cent by weight respectively. (author)

Chemical engineering design of CO oxidation catalysts

Science.gov (United States)

Herz, Richard K.

1987-01-01

How a chemical reaction engineer would approach the challenge of designing a CO oxidation catalyst for pulsed CO2 lasers is described. CO oxidation catalysts have a long history of application, of course, so it is instructive to first consider the special requirements of the laser application and then to compare them to the characteristics of existing processes which utilize CO oxidation catalysts. All CO2 laser applications require a CO oxidation catalyst with the following characteristics: (1) active at stoichiometric ratios of O2 and CO, (2) no inhibition by CO2 or other components of the laser environment, (3) releases no particulates during vibration or thermal cycling, and (4) long lifetime with a stable activity. In all applications, low consumption of power is desirable, a characteristic especially critical in aerospace applications and, thus, catalyst activity at low temperatures is highly desirable. High power lasers with high pulse repetition rates inherently require circulation of the gas mixture and this forced circulation is available for moving gas past the catalyst. Low repetition rate lasers, however, do not inherently require gas circulation, so a catalyst that did not require such circulation would be favorable from the standpoint of minimum power consumption. Lasers designed for atmospheric penetration of their infrared radiation utilize CO2 formed from rare isotopes of oxygen and this application has the additional constraint that normal abundance oxygen isotopes in the catalyst must not exchange with rare isotopes in the gas mixture.

Life cycle inventory of the production of rare earths and the subsequent production of NdFeB rare earth permanent magnets.

Science.gov (United States)

Sprecher, Benjamin; Xiao, Yanping; Walton, Allan; Speight, John; Harris, Rex; Kleijn, Rene; Visser, Geert; Kramer, Gert Jan

2014-04-01

Neodymium is one of the more critical rare earth elements with respect to current availability and is most often used in high performance magnets. In this paper, we compare the virgin production route of these magnets with two hypothetical recycling processes in terms of environmental impact. The first recycling process looks at manual dismantling of computer hard disk drives (HDDs) combined with a novel hydrogen based recycling process. The second process assumes HDDs are shredded. Our life cycle assessment is based both on up to date literature and on our own experimental data. Because the production process of neodymium oxide is generic to all rare earths, we also report the life cycle inventory data for the production of rare earth oxides separately. We conclude that recycling of neodymium, especially via manual dismantling, is preferable to primary production, with some environmental indicators showing an order of magnitude improvement. The choice of recycling technology is also important with respect to resource recovery. While manual disassembly allows in principle for all magnetic material to be recovered, shredding leads to very low recovery rates (<10%).

Proceedings of the national conference on rare earth processing and utilization - 2014: abstracts

International Nuclear Information System (INIS)

Anitha, M.; Dasgupta, Kinshuk; Singh, D.K.

2014-01-01

The rare earth elements (REEs) are becoming increasingly important in the transition to a low-carbon, circular economy, considering their essential role in permanent magnets, lamp phosphors, rechargeable nickel metal hydride batteries and catalysts and other green applications. The increasing popularity of hybrid and electric cars, wind turbines and compact fluorescent lamps is causing an increase in the demand and price of REEs. The European Commission considers the REEs as the most critical raw materials group, with the highest supply risk. According to the medium-term criticality matrix of the U.S. Department of Energy (DOE), the five most critical REEs are neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy) and yttrium (Y). China is presently producing more than 90% of all rare earths, although they possess less than 40% of the proven reserves. Due to large and increasing domestic demands, China tightened its REE export quota from 2012 onwards. These export quotas caused serious problems for REE users outside of China. To tackle the REE supply challenge, several approaches have been proposed. Fortunately India is blessed with large resources of rare earths in the form of monazite found in the beach sands of Kerala, Tamil Nadu and Odisha. Indian Rare Earths Limited at Aluva near Kochi used to produce mainly mixed rare earths chloride and export to USA, UK, France, Japan, etc. During the 1990s and early 2000s this plant exported pure oxides of samarium, neodymium, etc. to developed countries. This national conference has expanded its canvas by including newer emerging areas in rare earths recycling, environmental issues, recent advances in rare earth material science, rare earth research and development initiatives around the world which provide a platform for the growth of rare earth Industry. Papers relevant to INIS are indexed separately

Thermogravimetric study of rare earth concentrates

International Nuclear Information System (INIS)

Delyagejd, V.V.; Anisimova, V.N.; Eremenko, Z.V.; Kutsev, V.S.

1974-01-01

Methods of thermogravimetric, chemical and phase analysis were used in measuring the concentration of rare-earth elements of different origins. At temperatures 400-800 deg C a gradual decomposition of fluorocarbonates takes place leading to the formation of derivatives of corresponding oxides and oxyfluorides. For concentrates containing siderite the process takes place at 550-600 deg C followed by oxidation of bivalent iron into trivalent state. Reaction of rare-earth elements with sodium carbonate and the increase in the concentration of the latter results in a narrowing down of the interval of temperatures at which decomposition takes place. Under these conditions an intense reaction and a fusion take place leading to the formation of eutectic at 500-600 deg C and further synthesis of sodium fluoride and oxyfluoride derivatives of calcium and rare-earth elements

The industry of metallic rare earths (R.E.)

International Nuclear Information System (INIS)

Poirier, P.

1979-01-01

The following subjects are discussed: rare earths resources (rare earths abondance and world reserves, main ores). Rare earths separation and purification (ionic exchange, solvent extraction). Metallic rare earths and their mixtures, metallothermic reduction of oxides or fluorides (Ca, Mg, Al, Si or rare earth metals), Co-reduction process for intermetallic compounds (SmCo 5 ). Industrial applications of metallic rare earths (traditional applications such as flints, nodular cast iron, steel refining, magnesium industrie, applications under development such as rare earths/cobalt magnets, LaNi 5 for hydrogen storage, special alloys (automotive post combustion), magnetostrictive alloys). Economical problems: rare earth are elements relatively abundant and often at easily accessible prices. However, this group of 15 elements are liable to certain economical restraints. It is difficult to crack ore for only one rare earth. Availability of one given rare earth must be associated with the other corresponding rare earths to absorb all the other rare earths in other applications. Rare-earth industry has a strong expanding rate. 20% per year average for 6 years with Rhone-Poulenc. Thanks to their exceptional, specific characteristics rare earths have a bright future particularly for their metals

Rare metal and rare earth pegmatites of Western India

International Nuclear Information System (INIS)

Maithani, P.B.; Nagar, R.K.

1999-01-01

Rajasthan Mica Belt in western India is one of the three major mica-producing Proterozoic pegmatite belts of India, the others being in Bihar and Andhra Pradesh. The pegmatites of these mica belts, in general, are associated with the rare metal (RM) and rare earth element (REE)-bearing minerals like columbite-tantalite, beryl, lepidolite and other multiple oxides. RM-REE pegmatites of Gujarat are devoid of commercially workable mica. These pegmatites are geologically characterised in this paper, based on their association with granite plutons geochemistry, and RM and REE potential. In addition to RM and RE-bearing pegmatites, granites of the Umedpur area, Gujarat also show anomalous concentration (0.97 wt%) of rare metals (6431 ppm Nb, 1266 ppm Ta, 454 ppm Sn, 173 ppm W), (1098 ppm Ce 1.36% Y 2 O 3 ) rare earths, and uranium (0.40% eU 3 O 8 ). Eluvial concentrations in the soil and panned concentrate (0.04-0.28 wt%) analysed up to 7.4%Nb 2 O 5 , 836 ppm Ta, and 1.31% Y. Discrete columbite-tantalite and betafite have been identified in these concentrates in addition to other minerals like zircon, rutile, sphene and xenotime. This area with discrete RM R EE mineral phases could be significant as a non-pegmatite source for rare metal and rare earths. (author)

Chemical analysis of rare earth elements

International Nuclear Information System (INIS)

Tsukahara, Ryoichi; Sakoh, Takefumi; Nagai, Iwao

1994-01-01

Recently attention has been paid to ICP-AES or ICP-MS, and the reports on the analysis of rare earth elements by utilizing these methods continue to increase. These reports have become to take about 30% of the reports on rare earth analysis, and this is because these methods are highly sensitive to rare earth elements, and also these methods have spread widely. In ICP-AES and ICP-MS, mostly solution samples are measured, therefore, solids must be made into solution. At the time of quantitatively determining the rare earth elements of low concentration, separation and concentration are necessary. Referring to the literatures reported partially in 1990 and from 1991 to 1993, the progress of ICP-AES and ICP-MS is reported. Rare earth oxides and the alloys containing rare earth elements are easily decomposed with acids, but the decomposition of rocks is difficult, and its method is discussed. The separation of the rare earth elements from others in geochemical samples, cation exchange process is frequently utilized. Also solvent extraction process has been studied. For the separation of rare earth elements mutually, chromatography is used. The spectral interference in spectral analysis was studied. The comparison of these methods with other methods is reported. (K.I)

Thermodynamics of rare earths in steelmaking

International Nuclear Information System (INIS)

Vahed, A.; Kay, D.A.R.

1976-01-01

The standard free energies of formation of the oxides, sulfides and oxysulfides of cerium and lanthanum under steelmaking conditions have been calculated and used to predict the behavior of rare earths in steelmaking. Deoxidation and desulfurization constants, expressed in terms of Henrian activities, have been used to construct a precipitation diagram which indicates the sequence of rare earth inclusion formation. An enrichment of lanthanum in (RE)-oxysulfide and cerium in (RE)-sulfide is predicted. It is also predicted that rare earths should be able to reduce the soluble oxygen and sulfur contents of liquid steel well below the contents presently found in most industrial and laboratory practices. A simple method of calculating steelmaking additions for complete rare earth control of inclusion composition is presented

Chlorination of UO2, PuO2, and rare-earth oxides using ZrCl4

International Nuclear Information System (INIS)

Sakamura, Yoshiharu; Inoue, Tadashi; Iwai, Takashi; Moriyama, Hirotake

2001-01-01

A new chlorination method using ZrCl 4 , which has a high reactivity with oxygen, has been investigated for more efficient oxide treatment. After actinide oxides are chlorinated and dissolved in a molten salt bath, actinide metals can be selectively collected using the electrorefining process. This process is well suited for pyrochemical reprocessing of metallic fuels. In LiCl-KCI eutectic melts, rare-earth oxides (Y 2 O 3 , La 2 O 3 , CeO 2 , and Nd 2 O 3 ) and actinide oxides (UO 2 and PuO 2 ) were chlorinated by adding ZrCl 4 . As a result, rare-earth and actinide elements were dissolved into the salt as trivalent ions and ZrO 2 was precipitated. When an excess of ZrCI 4 was added, oxides in powder form were completely chlorinated in five hours. It was demonstrated that the ZrCI 4 chlorination method, free from corrosive gas such as chlorine, was very simple and useful. (author)

Rare-earth elements

Science.gov (United States)

Van Gosen, Bradley S.; Verplanck, Philip L.; Seal, Robert R.; Long, Keith R.; Gambogi, Joseph; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

2017-12-19

The rare-earth elements (REEs) are 15 elements that range in atomic number from 57 (lanthanum) to 71 (lutetium); they are commonly referred to as the “lanthanides.” Yttrium (atomic number 39) is also commonly regarded as an REE because it shares chemical and physical similarities and has affinities with the lanthanides. Although REEs are not rare in terms of average crustal abundance, the concentrated deposits of REEs are limited in number.Because of their unusual physical and chemical properties, the REEs have diverse defense, energy, industrial, and military technology applications. The glass industry is the leading consumer of REE raw materials, which are used for glass polishing and as additives that provide color and special optical properties to the glass. Lanthanum-based catalysts are used in petroleum refining, and cerium-based catalysts are used in automotive catalytic converters. The use of REEs in magnets is a rapidly increasing application. Neodymium-iron-boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys.China, which has led the world production of REEs for decades, accounted for more than 90 percent of global production and supply, on average, during the past decade. Citing a need to retain its limited REE resources to meet domestic requirements as well as concerns about the environmental effects of mining, China began placing restrictions on the supply of REEs in 2010 through the imposition of quotas, licenses, and taxes. As a result, the global rare-earth industry has increased its stockpiling of REEs; explored for deposits outside of China; and promoted new efforts to conserve, recycle, and substitute for REEs. New mine production began at Mount Weld in Western Australia, and numerous other exploration and development projects noted in this chapter are ongoing throughout the world.The REE-bearing minerals are

Liquidus temperature and chemical durability of selected glasses to immobilize rare earth oxides waste

Energy Technology Data Exchange (ETDEWEB)

Mohd Fadzil, Syazwani, E-mail: mfsyazwani86@postech.ac.kr [Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, 790784 Pohang, Gyeongbuk (Korea, Republic of); School of Applied Physics, Faculty of Science and Technology, The National University of Malaysia, 43650 Bandar Baru Bangi, Selangor (Malaysia); Hrma, Pavel [Division of Advanced Nuclear Engineering, Pohang University of Science and Technology, 790784 Pohang, Gyeongbuk (Korea, Republic of); Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA (United States); Schweiger, Michael J.; Riley, Brian J. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA (United States)

2015-10-15

Pyroprocessing is are processing method for managing and reusing used nuclear fuel (UNF) by dissolving it in an electrorefiner with a molten alkali or alkaline earth chloride salt mixture while avoiding wet reprocessing. Pyroprocessing UNF with a LiCl–KCl eutectic salt releases the fission products from the fuel and generates a variety of metallic and salt-based species, including rare earth (RE) chlorides. If the RE-chlorides are converted to oxides, borosilicate glass is a prime candidate for their immobilization because of its durability and ability to dissolve almost any RE waste component into the glass matrix at high loadings. Crystallization that occurs in waste glasses as the waste loading increases may complicate glass processing and affect the product quality. This work compares three types of borosilicate glasses in terms of liquidus temperature (T{sub L}): the International Simple Glass designed by the International Working Group, sodium borosilicate glass developed by Korea Hydro and Nuclear Power, and the lanthanide aluminoborosilicate (LABS) glass established in the United States. The LABS glass allows the highest waste loadings (over 50 mass% RE{sub 2}O{sub 3}) while possessing an acceptable chemical durability. - Highlights: • We investigated crystallization in borosilicate glasses containing rare earth oxides. • New crystallinity and durability data are shown for glasses proposed in the literature. • Both liquidus temperature and chemical durability increased as the waste loading increased.

Preparation of ammonium sulfate, calcium oxide and rare earth concentrate from phospho-gypsum

International Nuclear Information System (INIS)

Andrianov, A.M.; Rusin, N.F.; Dejneka, G.F.; Zinchenko, T.A.; Burova, T.I.

1978-01-01

A technological scheme is proposed which gives ammonium sulfate, purified (from admixtures of silicon, iron, titanium, aluminium) calcium oxide with direct yield of calcium 91% and rare-earth concentrate, containing 5.6% of Ln 2 O 3 with direct yield of 99.5%

Radioluminescence of rare-earth doped aluminum oxide

Energy Technology Data Exchange (ETDEWEB)

Santiago, M.; Molina, P. [Universidad Nacional del Centro de la Provincia de Buenos Aires, Instituto de Fisica Arroyo Seco, Pinto 399, 7000 Tandil (Argentina); Barros, V. S.; Khoury, H. J.; Elihimas, D. R., E-mail: msantiag@exa.unicen.edu.ar [Universidade Federal de Pernambuco, Departamento de Energia Nuclear, Av. Prof. Luiz Freire 1000, Recife, PE 50740-540 (Brazil)

2011-10-15

Carbon-doped aluminum oxide (Al{sub 2}O{sub 3}:C) is one of the most used radioluminescence (Rl) materials for fiberoptic dosimetry due to its high efficiency and commercial availability. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, the radioluminescence response of rare-earth doped Al{sub 2}O{sub 3} samples has been evaluated. The samples were prepared by mixing stoichiometric amounts of aluminum nitrate, urea and dopants with different amounts of terbium, samarium, cerium and thulium nitrates varying from 0 to 0.15 mo 1%. The influence of the different activators on the Rl spectra has been investigated in order to determine the feasibility of using these compounds for Rl fiberoptic dosimetry. (Author)

Radioluminescence of rare-earth doped aluminum oxide

International Nuclear Information System (INIS)

Santiago, M.; Molina, P.; Barros, V. S.; Khoury, H. J.; Elihimas, D. R.

2011-10-01

Carbon-doped aluminum oxide (Al 2 O 3 :C) is one of the most used radioluminescence (Rl) materials for fiberoptic dosimetry due to its high efficiency and commercial availability. However, this compound presents the drawback of emitting in the spectral region, where the spurious radioluminescence of fibers is also important. In this work, the radioluminescence response of rare-earth doped Al 2 O 3 samples has been evaluated. The samples were prepared by mixing stoichiometric amounts of aluminum nitrate, urea and dopants with different amounts of terbium, samarium, cerium and thulium nitrates varying from 0 to 0.15 mo 1%. The influence of the different activators on the Rl spectra has been investigated in order to determine the feasibility of using these compounds for Rl fiberoptic dosimetry. (Author)

[Synergetic effects of silicon carbide and molecular sieve loaded catalyst on microwave assisted catalytic oxidation of toluene].

Science.gov (United States)

Wang, Xiao-Hui; Bo, Long-Li; Liu, Hai-Nan; Zhang, Hao; Sun, Jian-Yu; Yang, Li; Cai, Li-Dong

2013-06-01

Molecular sieve loaded catalyst was prepared by impregnation method, microwave-absorbing material silicon carbide and the catalyst were investigated for catalytic oxidation of toluene by microwave irradiation. Research work examined effects of silicon carbide and molecular sieve loading Cu-V catalyst's mixture ratio as well as mixed approach changes on degradation of toluene, and characteristics of catalyst were measured through scanning electron microscope, specific surface area test and X-ray diffraction analysis. The result showed that the fixed bed reactor had advantages of both thermal storage property and low-temperature catalytic oxidation when 20% silicon carbide was filled at the bottom of the reactor, and this could effectively improve the utilization of microwave energy as well as catalytic oxidation efficiency of toluene. Under microwave power of 75 W and 47 W, complete-combustion temperatures of molecular sieve loaded Cu-V catalyst and Cu-V-Ce catalyst to toluene were 325 degrees C and 160 degrees C, respectively. Characteristics of the catalysts showed that mixture of rare-earth element Ce increased the dispersion of active components in the surface of catalyst, micropore structure of catalyst effectively guaranteed high adsorption capacity for toluene, while amorphous phase of Cu and V oxides increased the activity of catalyst greatly.

Solid state chemistry of rare earth oxides. Final report, September 1, 1950--July 31, 1977

International Nuclear Information System (INIS)

Eyring, L.

1977-07-01

Work under Contract E(11-1)-1109 and its antecedents has been primarily for the purpose of obtaining detailed thermodynamic, kinetic and structural information on the complex rare earth oxides of praseodymium and terbium. These systems exhibit homologous series of ordered phases, order-disorder transformations, wide-range nonstoichiometric phases, chemical hysteresis in two-phase regions and many other solid state reaction phenomena. Fluorite-related materials of importance to ERDA occur as nuclear fuels, radiation power sources, insulators and solid electrolytes. The rare earth oxides serve directly as model systems for such similar materials and, in a more general sense, they serve as models of solids in general since they exhibit nearly the full range of solid state properties

Rare Earth Garnet Selective Emitter

Science.gov (United States)

Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

1994-01-01

Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional

Uses of extraction and ion exchange chromatography in the thorium and rare earths separation from industrial residue generated in thorium purification unity at IPEN. Application of rare earths as catalysts for generation of hydrogen

International Nuclear Information System (INIS)

Zini, Josiane

2010-01-01

In the 70's a pilot plant for studies of different concentrates processing obtained from the chemical processing of monazite was operated at IPEN / CNEN-SP, with a view to obtaining thorium of nuclear purity. This unity was operated on an industrial scale since 1985, generating around 25 metric tons of residue and was closed in 2002. This waste containing thorium and rare earths was named Retoter (Rejeito de Torio e Terras Raras, in portuguese) and stored in the IPEN Safeguards shed. This paper studies the treatment of the waste, aimed at environmental, radiological and technology. Were studied two cases for the chromatographic separation of thorium from rare earths. One of them was the chromatographic extraction, where the extracting agent tributyl phosphate was supported on polymeric resins Amberlite XAD16. The other method is studied for comparison purposes, since the material used in chromatographic extraction is unprecedented with regard to the separation of thorium, was the ion-exchange chromatography using DOWEX 1-X8 strong cationic resin. Was studied also the chromatographic process of extraction with the extracting agent DEHPA supported on Amberlite XAD16 for the fractionation in groups of rare earths elements. Thorium was separated with high purity for strategic purposes and rare earths recovered free from thorium, were tested as a catalyst for ethanol reforming to hydrogen obtaining which is used in fuel cells for power generation. (author)

Component-Customizable Porous Rare-Earth-Based Colloidal Spheres towards Highly Effective Catalysts and Bioimaging Applications.

Science.gov (United States)

Li, Cheng Chao; Rui, Xianhong; Wei, Weifeng; Chen, Libao; Yu, Yan

2017-11-16

Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effects. However, a combination of different components in a single porous sphere is still greatly challenged due to the different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres with customizable elemental compositions and a uniform element distribution. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and a subsequent ion-exchange process, which steers clear of obstacles, such as differences in solubility product constant, that are to be found in traditional co-precipitation methods. Our approach provides a new mixing mechanism to realize homogeneous distribution of each element within the porous spheres. An array of binary, ternary, and even senary RE colloidal porous spheres with diameters of 500 nm to 700 nm has been successfully synthesized. Taking advantage of their good dispersibility, porosity, and customizable components, these porous RE oxide spheres show excellent catalytic activity for the reduction of 4-nitrophenol, and promising application in single-phase multifunctional bioprobes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel precursors for the deposition of rare earth oxides; Neuartige Precursor zur Abscheidung von Selten-Erd-Oxiden

Energy Technology Data Exchange (ETDEWEB)

Ahlers, Mareike

2010-02-22

During this work rare earth solvates with nitrate and perchlorate anions have been investigated. All compounds have been structurally characterized and analyzed using thermal gravimetric analysis. The decomposition residues were analyzed using powder diffraction methods. Almost all compounds showed a characteristically intense exothermic decomposition step during the thermal decomposition, most likely caused by an intramolecular redox reaction between the nitrate or perchlorate anion respectively and the organic solvent molecules. The nitrates RE(NO{sub 3}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2} (RE = Sm, Eu) were isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. The known compound group of dimethoxyethane solvates was then expanded with RE(NO{sub 3}){sub 3}(O{sub 2}C{sub 4}H{sub 10}) (RE = La, Sm, Eu). Considering the possible use as precursor material the already described neodymium compound is also discussed. The thermal decomposition of these compounds yields the respective cubic rare earth oxide and shows the typical intense exothermic decomposition reaction. A variety of different precursor system based on nitrate solvates for the deposition of rare earth oxide layers on a silicon surface was developed and investigated in collaboration with the group of Prof. Dr. Al-Shamery (Univ. Oldenburg). Ultra thin films on a H-Si(111) surface were obtained via the deposition of the precursor, which was dissolved in organic solvents. An oxide layer was detected after the heating of the sample. The film thickness was measured as < 10 nm, whereas the thickness of the film was controlled by the concentration of the precursor solution. Sm(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 3} was isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. Eu(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2}(MeOH){sub 2} was obtained without

Laser cladding in-situ carbide particle reinforced Fe-based composite coatings with rare earth oxide addition

Institute of Scientific and Technical Information of China (English)

吴朝锋; 马明星; 刘文今; 钟敏霖; 张红军; 张伟明

2009-01-01

Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...

Investigation of catalytic oxidation of diamond by water vapor and carbon dioxide in the presence of alkali melts of some rare earth oxides

International Nuclear Information System (INIS)

Kulakova, I.I.; Rudenko, A.P.; Sulejmenova, A.S.; Tolstopyatova, A.A.

1978-01-01

The results of an investigation of the catalytic oxydation of diamond by carbon dioxide and water vapors at 906 deg C in the presence of melts of some rare earth oxides in potassium hydroxide are given. The ion La 3+ was shown to possess the most catalytic activity. The earlier proposed mechanisms of the diamond oxidation by CO 2 and H 2 O were corroborated. The ions of rare earth elements were found to accelerate the different stages of the process

Obtainment of zirconium oxide and partially stabilized zirconium oxide with yttrium and rare earth oxides, from Brazilian zirconite, for ceramic aim

International Nuclear Information System (INIS)

Ribeiro, S.

1991-05-01

This work presents experimental results for processing of brazilian zirconite in order to obtain zirconium oxide with Yttrium and Rare Earth oxide by mutual coprecipitation for ceramics purposes. Due to analysis of experimental results was possible to obtain the optimum conditions for each one of technological route stage, such as: alkaline fusion; acid leaching; sulfactation and coprecipitation. (author)

Sc, Y, La-Lu - Rare Earth Elements

International Nuclear Information System (INIS)

Anon.

1987-01-01

At present extensive efforts are being made in completing work on system number Rare Earth Elements. Part A is devoted to the occurrence of these elements on the earth and in the universe. Part B deals with the pure metals; the 7 volumes published cover the description of the separation from the raw materials, the preparation of pure metals,their uses and toxicology, the physical properties of nuclei, atoms, molecules, and isotopes; in addition the behavior of ions in solution and the electrochemical behavior of rare earth elements are described. The compounds are described in Part C. Part D with 6 volumes has been devoted to the description of coordination compounds and is completed. The volume ''Rare Earth Elements C 10'' deals with the rare earth tellurides, oxide tellurides, tellurates, telluride halides, tellurate halides, sulfide tellurides, selenide tellurides, and alkali rare earth tellurates. Another topic of this volume are the compounds of the rare earth elements with polonium. So far as meaningful and in accordance with all earlier volumes of ''Rare Earth Elements'' Series C, comparative data are presented in sections preceding treatment of the individual compounds and systems

High purity neodymium acetate from mixed rare earth carbonates

International Nuclear Information System (INIS)

Queiroz, Carlos A. da Silva; Rocha, Soraya M. Rizzo da; Vasconcellos, Mari E. de; Lobo, Raquel M.; Seneda, Jose A.; Pedreira, Walter dos R.

2011-01-01

A simple and economical chemical process for obtaining high purity neodymium acetate is discussed. The raw material in the form rare earth carbonate is produced industrially from the chemical treatment of Brazilian monazite. Ion exchange chromatography technique with a strong cationic resin, proper to water treatment, and without the use of retention ions was used for the fractionating of the rare earth elements (REE). In this way, it was possible to obtain 99.9% pure Nd 2 O 3 in yields greater than or equal 80%, with the elution of the REE using ammonium salt of ethylenediaminetetraacetic acid (EDTA) solution in pH controlled. The complex of EDTA-neodymium was transformed into neodymium oxide, which was subsequently dissolved in acetic acid to obtain the neodymium acetates. Molecular absorption spectrophotometry was used to monitor the neodymium content during the process and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the neodymium acetates. The typical neodymium acetates obtained contain the followings contaminants in μg g -1 : Sc(5.1); Y (0.9); La (1.0); Ce (6.1); Pr (34,4); Sm (12.8); Eu (1.1); Gd (15.4); Tb (29.3); Dy (5.2), Ho(7.4); Er (14.6); Tm (0.3); Yb (2.5); Lu (1.0). The high purity neodymium acetates obtained from this procedure have been applied, replacing the imported product, in research and development area on rare earth catalysts. (author)

Rare earth elements and permanent magnets (invited)

Science.gov (United States)

Dent, Peter C.

2012-04-01

Rare earth (RE) magnets have become virtually indispensible in a wide variety of industries such as aerospace, automotive, electronics, medical, and military. RE elements are essential ingredients in these high performance magnets based on intermetallic compounds RECo5, RE2TM17 (TM: transition metal), and RE2TM14B. Rare earth magnets are known for their superior magnetic properties—high induction, and coercive force. These properties arise due to the extremely high magnetocrystalline anisotropy made possible by unique 3d-4f interactions between transition metals and rare earths. For more than 40 years, these magnets remain the number one choice in applications that require high magnetic fields in extreme operating conditions—high demagnetization forces and high temperature. EEC produces and specializes in RECo5 and RE2TM17 type sintered magnets. Samarium and gadolinium are key RE ingredients in the powder metallurgical magnet production processes which include melting, crushing, jet milling, pressing, sintering, and heat treating. The magnetic properties and applications of these magnets will be discussed. We will also briefly discuss the past, current, and future of the permanent magnet business. Currently, over 95% of all pure rare earth oxides are sourced from China, which currently controls the market. We will provide insights regarding current and potential new magnet technologies and designer choices, which may mitigate rare earth supply chain issues now and into the future.

Rare earths: critical elements for various applications and challenges in their separation

International Nuclear Information System (INIS)

Singh, D.K.; Chakravartty, J.K.

2015-01-01

High purity rare earths oxides, metal and alloys find wide applications in high tech area such as nuclear energy, permanent magnets, materials for storing hydrogen, phosphors, laser, etc. Rare earths consists a group of 15 elements from La to Lu in the periodic table and it also includes Sc and Y. Due to similar chemical nature owing to common oxidation state of +3, rare earths are very difficult to separate from each other. They have very low separation factors with acidic extractants like D2EHPA and EHEHPA and hence require large number of stages in various cascade of extraction process. Monazite (a source of rare earths, thorium and uranium) is processed at IREL to separate rare earths from thorium and uranium. The rare earths are fractionated into three groups namely light rare earths (LRE), middle rare earths (MRE) and heavy rare earths (HRE) by solvent extraction method employing EHEHPA as extractant

The formation of crystals in glasses containing rare earth oxides

Energy Technology Data Exchange (ETDEWEB)

Fadzil, Syazwani Mohd [Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Hrma, Pavel [Pohang University of Science and Technology (POSTECH), Pohang, South Korea and Pacific Northwest National Laboratory, Richland, Washington (United States); Crum, Jarrod [Pacific Northwest National Laboratory, Richland, Washington (United States); Siong, Khoo Kok; Ngatiman, Mohammad Fadzlee; Said, Riduan Mt [National University of Malaysia, Bandar Baru Bangi, Selangor (Malaysia)

2014-02-12

with 5%, 10% and 15% addition of mixed rare earth oxides. The component coefficients T{sub B2O3}, T{sub SiO2}, T{sub CaO}, and T{sub RE2O3} were also evaluated using a recently published study.

Contribution towards ALD and MOCVD of rare earth oxides and hafnium oxide. From precursor evaluation to process development and thin film characterization

International Nuclear Information System (INIS)

Xu, Ke

2013-01-01

This PhD thesis is consisted of two major parts: precursor development for ALD and MOCVD applications as well as thin film deposition using ALD and MOCVD with self developed precursors. The first part of this work presents the synthesis, characterization and detailed thermal property investigations of different novel group IV and rare earth precursor classes (guandinate, guanidine and ketoiminate). The second part of this work presents the ALD and MOCVD depositions using various guanidinate precursors for forming corresponding metal oxide thin films. The overall motivation of this work is to fulfill the lack of precursors of rare earth and group IV elements for ALD and MOCVD applications that satisfy the stringent requirements for the modern microelectronic and optoelectronic technologies. The aspect of the precursor engineering part is focusing on influence of ligand sphere on precursors' chemical and thermal properties. In this way, we successfully introduced guanidine and ketoiminate as potential ligands for the precursor design. The thin film deposition part of this work is ALD of rare earth oxides and group IV oxides employing literature known compounds which were previously developed in our research group. The main focus was dedicated to the process optimization, the characterization of the structural, morphological, compositional and functional properties of the deposited thin films. Certain film properties were discussed comparatively with the corresponding thin films deposited with literature known precursors. It was already shortly demonstrated in Chapter 6 that the guanidine ligand showed potential interest as suitable ligand for precursor engineering. This titan guanidine precursor [Ti(NC(NMe 2 ) 2 ) 4 ] (GD1) possesses higher thermal stability compared to its parent amide, [Ti(NMe 2 ) 4 ], while reactivity against water is not significantly affected. It could be very interesting to transfer this ligand for the precursor development of rare earth

Preparing rare earth-silicon-iron-aluminum alloys

International Nuclear Information System (INIS)

Marchant, J.D.; Morrice, E.; Herve, B.P.; Wong, M.M.

1980-01-01

As part of its mission to assure the maximum recovery and use of the Nation's mineral resources, the Bureau of Mines, investigated an improved procedure for producing rare earth-silicon alloys. For example, a charge consisting of 681 grams of mixed rare-earth oxides, 309 grams of ferrosilicon (75 wt-pct Si), and 182 grams of aluminum metal along with a flux consisting of 681 grams of CaO and 45 grams of MgO was reacted at 1500 0 C in an induction furnace. Good slag-metal separation was achieved. The alloy product contained, in weight-percent, 53 RE, 28 Si, 11 Fe, and 4 Al with a rare earth recovery of 80 pct. In current industrial practice rare earth recoveries are usually about 60 pct in alloy products that contain approximately 30 wt-pct each of rare earths and silicon. Metallurgical evaluations showed the alloys prepared in this investigation to be as effective in controlling the detrimental effect of sulfur in steel and cast iron as the commercial rare earth-silicon-iron alloys presently used in the steel industry

Recovering heavy rare earth metals from magnet scrap

Science.gov (United States)

Ott, Ryan T.; McCallum, Ralph W.; Jones, Lawrence L.

2017-08-08

A method of treating rare earth metal-bearing permanent magnet scrap, waste or other material in a manner to recover the heavy rare earth metal content separately from the light rare earth metal content. The heavy rare earth metal content can be recovered either as a heavy rare earth metal-enriched iron based alloy or as a heavy rare earth metal based alloy.

MICROBIALLY MEDIATED LEACHING OF RARE EARTH ELEMENTS FROM RECYCLABLE MATERIALS

Energy Technology Data Exchange (ETDEWEB)

Reed, D. W.; Fujita, Y.; Daubaras, D. L.; Bruhn, D. F.; Reiss, J. H.; Thompson, V. S.; Jiao, Y.

2016-09-01

Bioleaching offers a potential approach for recovery of rare earth elements (REE) from recyclable materials, such as fluorescent lamp phosphors or degraded industrial catalysts. Microorganisms were enriched from REE-containing ores and recyclable materials with the goal of identifying strains capable of extracting REE from solid materials. Over 100 heterotrophic microorganisms were isolated and screened for their ability to produce organic acids capable of leaching REE. The ten most promising isolates were most closely related to Pseudomonas, Acinetobacter and Talaromyces. Of the acids produced, gluconic acid appeared to be the most effective at leaching REE (yttrium, lanthanum, cerium, europium, and terbium) from retorted phosphor powders (RPP), fluidized cracking catalyst (FCC), and europium-doped yttrium oxide (YOEu). We found that an Acinetobacter isolates, BH1, was the most capable strain and able to leach 33% of the total REE content from the FCC material. These results support the continuing evaluation of gluconic acid-producing microbes for large-scale REE recovery from recyclable materials.

Thermochemistry of rare earth doped uranium oxides LnxU1-xO2-0.5x+y (Ln = La, Y, Nd)

Science.gov (United States)

Zhang, Lei; Navrotsky, Alexandra

2015-10-01

Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10-50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO1.5, UO2 and UO3 in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of LnxU1-xO2-0.5x+y is similar to that of UO2 to UO3 for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U5+, U6+, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements.

A simple enrichment correction factor for improving erosion estimation by rare earth oxide tracers

Science.gov (United States)

Spatially distributed soil erosion data are needed to better understanding soil erosion processes and validating distributed erosion models. Rare earth element (REE) oxides were used to generate spatial erosion data. However, a general concern on the accuracy of the technique arose due to selective ...

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni A.

2014-01-01

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses

Extraction of rare earths and hydrochloric acid by trialkylphosphine oxide

International Nuclear Information System (INIS)

Mikhajlichenko, A.I.; Karmannikov, V.P.; Klimenko, M.A.; Fedulova, T.V.

1983-01-01

Extraction of rare earth chlorides and hydrochloric acid by trialkylphosphine oxide with different radicals (POR) (RR' 2 PO-POR, where RR'=alkyl of a normal structure, containing 7 to 9 carbon atoms, R=isoamyl) has been studied. Distribution of lanthanum-, neodymium-, lutetium- and yttrium chlorides during extraction with 1.28 mol/l POR solution in white spirit is investigated in the salt concentration range in the equilibrium aqueous phase from 0 to 2.8 mol/l. Lanthanide distribution coefficients increase with an increase in the order number of elements, with the separation coefficients of two extreme members of the series (Lu and La) for chlorides and nitrates constituting 100 and 80, respectively microquantities of Ln against the background of macroquantities of La is 2.6 mol/l. According to the results of measurements of viscosity, electric conductivity and water content in the extracts a conclusion is made on the state of salt in the organic phase. In the systems POR-LnCl 3 -HCl-H 2 O the hydrochloric acid extraction increases with an increase in the rare earth chloride concentration and order number of the element

Catalyst for Decomposition of Nitrogen Oxides

Science.gov (United States)

Schryer, David R. (Inventor); Jordan, Jeffrey D. (Inventor); Akyurtlu, Ates (Inventor); Akyurtlu, Jale (Inventor)

2015-01-01

This invention relates generally to a platinized tin oxide-based catalyst. It relates particularly to an improved platinized tin oxide-based catalyst able to decompose nitric oxide to nitrogen and oxygen without the necessity of a reducing gas.

Bench scale studies on separation of rare earths by ion exchange

International Nuclear Information System (INIS)

Aroonrung-Areeya, A.

1976-01-01

The method of ion exchange was applied to the separation of mixtures of rare earth oxides into the pure components. The method consists of eluting a band of mixed rare earths adsorbed on a cation-exchange resin through a second cation-exchange bed in the copper II state. The eluent consists of an ammonia buffered solution of ethylenediamine tetraacetic acid. The mixed rare earth oxide used as testing material was obtained from the digestion of Thai monazite. The amounts varied from 1, 5 to 50 grams. The purity of the rare earth fractions were analyzed either by neutron activation of X-ray fluorescence. The Cu.EDTA was recovered by the addition of lime. It was found that gram quantities of pure rare earths could be obtained by this method

Influence of rare earth additions on the oxidation resistance of chromia forming alloys; Influencia da adicao de terras raras sobre a resistencia a oxidacao de ligas formadoras de cromia

Energy Technology Data Exchange (ETDEWEB)

Pillis, Marina Fuser

1995-12-31

The addition of rare earths to alloys, either in elemental form or as surface coatings reduces the oxidation rate of chromia forming alloys. The rare earths either act as nucleation sites for surface oxides or get incorporates into the surface oxide and diffuse to oxide grain boundaries. If the latter occurs, a change in the defect structure close to the grain boundaries, probably takes place. In this manner, the rare earths inhibits the movement of chromium ions to the oxide/gas interface. The influence of rare earth additions to AISI 316, AISI 316L and Ni-20 Cr on their oxidation behavior has been studied., AISI 316+Ce, AISI 316+Y, Ni-20 Cr and Ni-20 Cr-2 Al-1 Ce were prepared by melting and AISI 316L, AISI 316L+Ce O{sub 2} and AISI 316L+Y{sub 2} O{sub 3} by powder compaction. The effect of superficial deposits of rare earth oxides was also studied. The alloys were coated with rare earth oxides by high temperature conversion of the respective rare earth nitrates. Isothermal oxidation tests were carried out at 900-1100 deg C and the cyclic oxidation tests consisted of 6 cycles of 2 hours each at 900 deg C, followed by cooling to room temperature. All the tests were carried out in air. Oxidation behavior was evaluated gravimetrically. Scanning electron microscopy was used to study surface morphology. Energy dispersive analysis and X-ray diffraction techniques were used to identify oxide constituents. Overall, it has been observed that with the addition of rare earths, oxidation resistance increases by decreasing oxidation rates and increasing oxide adhesion. Addition of rare earths to AISI 316 prepared by melting resulted in rapid formation of a chromium rich oxide layered near the metal/oxide interface which reduced overall oxidation rate. The addition of Ce O{sub 2} to AISI 316L was found to improve oxidation behavior after 10 hours at 1100 deg C and also inhibit the formation of volatile Cr O{sub 3}. The isothermal oxidation behavior of rare earth oxide covered

Rare earth sulfates

International Nuclear Information System (INIS)

Komissarova, L.N.; Shatskij, V.M.; Pokrovskij, A.N.; Chizhov, S.M.; Bal'kina, T.I.; Suponitskij, Yu.L.

1986-01-01

Results of experimental works on the study of synthesis conditions, structure and physico-chemical properties of rare earth, scandium and yttrium sulfates, have been generalized. Phase diagrams of solubility and fusibility, thermodynamic and crystallochemical characteristics, thermal stability of hydrates and anhydrous sulfates of rare earths, including normal, double (with cations of alkali and alkaline-earth metals), ternary and anion-mixed sulfates of rare earths, as well as their adducts, are considered. The state of ions of rare earths, scandium and yttrium in aqueous sulfuric acid solutions is discussed. Data on the use of rare earth sulfates are given

Environmental Defects And Economic Impact On Global Market Of Rare Earth Metals

Science.gov (United States)

Charalampides, G.; Vatalis, K.; Karayannis, V.; Baklavaridis, A.

2016-11-01

Rare earth elements include the 14 lanthanides as well as lanthanium and often yttrium. Actually, most of them are not very rare and occur widely dispersed in a variety of rocks. Rare earth metals are vital to some of the world's faster growing industries: catalysts, Nd-magnets, ceramics, glass, metallurgy, battery alloys, electronics and phosphors. Worldwide, the main countries for distribution of rare earths deposits include China, USA, Russia, Brasil, India, Australia, Greenland and Malaysia. The mining and processing of rare earth metals usually result in significant environmental defects. Many deposits are associated with high concentrations of radioactive elements such as uranium and thorium, which requires separate treatment and disposal. The accumulation of rare earth elements in soils has occurred due to pollution caused by the exploitation of rare earth resources and the wide use of rare earths as fertilizers in agriculture. This accumulation has a toxic effect on the soil microfauna community. However, there are large differences in market prices due to the degree of purity determined by the specifications in the applications. The main focus of this article is to overview Rare Earth Metals’ overall impact on global economy and their environmental defects on soils during processing techniques and as they are used as fertilizers.

Rare Earth Elements: Overview of Mining, Mineralogy, Uses, Sustainability and Environmental Impact

Directory of Open Access Journals (Sweden)

Nawshad Haque

2014-10-01

Full Text Available Rare earths are used in the renewable energy technologies such as wind turbines, batteries, catalysts and electric cars. Current mining, processing and sustainability aspects have been described in this paper. Rare earth availability is undergoing a temporary decline due mainly to quotas being imposed by the Chinese government on export and action taken against illegal mining operations. The reduction in availability coupled with increasing demand has led to increased prices for rare earths. Although the prices have come down recently, this situation is likely to be volatile until material becomes available from new sources or formerly closed mines are reopened. Although the number of identified deposits in the world is close to a thousand, there are only a handful of actual operating mines. Prominent currently operating mines are Bayan Obo in China, Mountain Pass in the US and recently opened Mount Weld in Australia. The major contributor to the total greenhouse gas (GHG footprint of rare earth processing is hydrochloric acid (ca. 38%, followed by steam use (32% and electricity (12%. Life cycle based water and energy consumption is significantly higher compared with other metals.

Oxidation catalyst

Science.gov (United States)

Ceyer, Sylvia T.; Lahr, David L.

2010-11-09

The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

Electro-kinetic separation of rare earth elements using a redox-active ligand

Energy Technology Data Exchange (ETDEWEB)

Fang, Huayi; Cole, Bren E.; Qiao, Yusen; Bogart, Justin A.; Cheisson, Thibault; Manor, Brian C.; Carroll, Patrick J.; Schelter, Eric J. [Department of Chemistry, University of Pennsylvania, Philadelphia, PA (United States)

2017-10-16

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare-earth-metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare-earth-element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox-active ligand [{2-(tBuN(O))C_6H_4CH_2}{sub 3}N]{sup 3-}. Using this method, a single-step separation factor up to 261 was obtained for the separation of a 50:50 yttrium-lutetium mixture. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Metal-free carbon materials-catalyzed sulfate radical-based advanced oxidation processes: A review on heterogeneous catalysts and applications.

Science.gov (United States)

Zhao, Qingxia; Mao, Qiming; Zhou, Yaoyu; Wei, Jianhong; Liu, Xiaocheng; Yang, Junying; Luo, Lin; Zhang, Jiachao; Chen, Hong; Chen, Hongbo; Tang, Lin

2017-12-01

In recent years, advanced oxidation processes (AOPs), especially sulfate radical based AOPs have been widely used in various fields of wastewater treatment due to their capability and adaptability in decontamination. Recently, metal-free carbon materials catalysts in sulfate radical production has been more and more concerned because these materials have been demonstrated to be promising alternatives to conventional metal-based catalysts, but the review of metal-free catalysts is rare. The present review outlines the current state of knowledge on the generation of sulfate radical using metal-free catalysts including carbon nanotubes, graphene, mesoporous carbon, activated carbon, activated carbon fiber, nanodiamond. The mechanism such as the radical pathway and non-radical pathway, and factors influencing of the activation of sulfate radical was also be revealed. Knowledge gaps and research needs have been identified, which include the perspectives on challenges related to metal-free catalyst, heterogeneous metal-free catalyst/persulfate systems and their potential in practical environmental remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

International Nuclear Information System (INIS)

Bazuev, G.V.; Makarova, O.V.; Shvejkin, G.P.

1983-01-01

A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln 3 + cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm 3 size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balancewith electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti 3 + cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled π*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility

Recent developments in the MOCVD and ALD of rare earth oxides and silicates

International Nuclear Information System (INIS)

Jones, Anthony C.; Aspinall, Helen C.; Chalker, Paul R.; Potter, Richard J.; Kukli, Kaupo; Rahtu, Antti; Ritala, Mikko; Leskelae, Markku

2005-01-01

Lanthanide, or rare-earth oxides are currently being investigated as alternatives to SiO 2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high-κ dielectric oxides and in this paper some of our recent research into the MOCVD and ALD of PrO x , La 2 O 3 , Gd 2 O 3 , Nd 2 O 3 and their related silicates are reviewed

Investigations on the determination of traces of some rare earths (Eu, Sm, Gd, Y) in oxides of rare earths (Y2O3, Sm2O3, Gd2O3) by emission spectrography in d.c. arc

International Nuclear Information System (INIS)

Dittrich, K.; Gajek, M.; Luan, P.

1978-01-01

The evaporation of traces and matrices of rare earth elements was investigated in different atmospheres. It was found, that low-boiling rare earths elements, because of their extended formation of carbides evaporate more slowly than high-boiling rare earths elements. The evaporation of the traces depends on the matrices. 3 cases for the determination of traces of rare earths elements in oxides of other rare earths elements are derived from the results of the evaporation: Low- to high-boiling traces of rare earths elements in low-boiling matrices of rare earths elements, low-boiling traces in medium- to high-boiling matrices, and medium- to high-boiling traces in medium- to high-boiling matrices. The results of the determination are: in Y 2 O 3 : 14 ppm Sm, 2 ppm Eu; in Gd 2 O 3 : 18 ppm Y, 3 ppm Sm, 2 ppm Eu; in Sm 2 O 3 : 70 ppm Y, 370 ppm Gd, 16 ppm Eu. (author)

A Comparative Study of Mn/Co Binary Metal Catalysts Supported on Two Commercial Diatomaceous Earths for Oxidation of Benzene

Directory of Open Access Journals (Sweden)

Marco Tomatis

2018-03-01

Full Text Available Two commercial diatomaceous earths were used as supports for the preparation of Mn/Co binary metal catalysts at different metal loads (5 to 10 wt % Mn and 5 to 15 wt % Co by incipient wetness deposition. The activity of the prepared catalysts towards the complete oxidation of benzene to CO2 and water was investigated between 100 and 400 °C. Raw supports and synthesized catalysts were characterized by XRD, N2 physisorption, SEM-EDS, H2-TPR, and TPD. The purification treatment of food-grade diatomite significantly affected the crystallinity of this support while reducing its specific surface area (SSA. A loss of SSA, associated with the increase in the metal load, was observed on samples prepared on natural diatomite, while the opposite trend occurred with food-grade diatomite-supported catalysts. Metal nanoparticles of around 50 nm diameter were observed on the catalysts’ surface by SEM analysis. EDS analysis confirmed the uniform deposition of the active phases on the support’s surface. A larger H2 consumption was found by TPR analysis of natural diatomite-based samples in comparison to those prepared at the same metal load on food-grade diatomite. During the catalytic oxidation experiment, over 90% conversion of benzene were achieved at a reaction temperature of 225 °C by all of the prepared samples. In addition, the formation of coke during the oxidation tests was demonstrated by TGA analysis and the soluble fraction of the produced coke was characterized by GC-MS.

Magnetic properties of rare earth oxides with perovskite structure

International Nuclear Information System (INIS)

Hinatsu, Yukio

2008-01-01

A perovskite composite oxide is represented by the general formula of ABO 3 . Cations at the B site characterize magnetic properties of the oxide. Many studies have been accumulated for transition metal elements at the B sites. In this report the studies of rare earth elements at the B sites are reviewed. In rare elements, tetravalent ions such as Ce 4+ , Pr 4+ and Tb 4+ can occupy the B sites with Ba and Sr ions at the A sites. Both the SrTbO 3 and BaTbO 3 have an orthorhombic structure and show the antiferromagnetic transition at about 33 K, which is originated from terbium ions coupled antiferromagnetically with the six neighboring terbium ions. A tetravalent praseodymium perovskite SrPrO 3 shows no existence of the magnetic ordering down to 2.0 K. This is in contrast to the result of isomorphous BaPrO 3 , which shows an antiferromagnetic transition at 11.5 K. A double perovskite structure is represented by the formula A 2 LnMO 6 (A=Ba, Sr, Ca; M=Ru, Ir). In a double perovskite compound Ba 2 PrRuO 6 , the Pr 3+ and Ru 5+ ions are arranged with regularity over the six-coordinate B sites. This compound transforms to an antiferromagnetic state below 117 K. Antiferromagnetic transition temperatures T N for isomorphous Sr and Ca show a clear tendency, T N (A=Ba)>T N (Sr)>T N (Ca), in the compounds with the same rare earth elements (Ln). The 6H-perovskite structure Ba 3 LnRu 2 O 9 consists of linkages between LnO 6 octahedra and Ru 2 O 9 dimers made from face-shared RuO 6 octahedra. The 6H-perovskite structure Ba 3 MRu 2 O 9 (M=Sc, Y, La, Nd-Gd, Dy-Lu) have the valence state of Ba 3 M 3+ Ru 2 4.5+ O 9 . The magnetic susceptibilities show a broad maximum at 135-370 K. This magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru 2 O 9 dimer and to the magnetic interaction between the Ru 2 O 9 dimers. (author)

Analysis of electrical and microstructural characteristics of a ZnO-based varistor doped with rare earth oxide

International Nuclear Information System (INIS)

Andrade, J.M. de; Dias, R.; Furtado, J.G. de M.; Assuncao, F.C.R.

2010-01-01

Varistor is a semiconductor device, used in the protection of electrical systems, characterized to have a high no-linear electric resistance. Its properties are directly dependents of its chemical composition and microstructural characteristics. In this work were analyzed microstructural and electrical characteristics of a ZnO-based varistor doped with rare earth oxide, with chemical composition (mol%) 98,5.ZnO - 0,3.Pr 6 O 11 - 0,2.Dy 2 O 3 - 0,9.Co 2 O 3 - 0,1.Cr 2 O 3 . X-ray diffraction for phase characterization, scanning electron microscopy and energy dispersive X-ray spectroscopy were used for microstructural analysis. Measurement of average grain size and electrical and dielectric characteristics complete the characterization. The results show the formation of biphasic microstructure and with high densification, presenting relevant varistors characteristics but that would need improvements.(author)

Possibility study of use rare earth deposit from Araxa, Minas Gerais State

International Nuclear Information System (INIS)

Fernandes, M.D.

1975-01-01

Prospecting work done by Instituto de Pesquisas Radioativas on the Barreiro area (Araxa, M.G.) has shown the existence of a rare earth deposit of about 700.000 ton, averaging 13,5 % rare earth oxide, mainly associated to the mineral monazite. In a first stage, the conventional mineral dressing methods were tried to treat the monazite. This was followed by a study of a chemical process for the production of rare earth compounds of commercial grade. The conventional methods of mineral dressing tested did not lead to satisfactory results. This was assumed to be due to insufficient liberation of the monazite. However, the application of the chemical process to the natural material, using concentrated sulfuric acid in the initial attack, allowed more than 90% rare earth extraction and a subsequent yield of commercial grade rare earth oxide, with over 75% rare earth recovery. (author)

Rare earths in iron and steelmaking and gaseous desulphurisation

International Nuclear Information System (INIS)

Kay, D.A.R.; Subramanian, S.V.; Meng, V.; Kumar, R.V.

1985-01-01

Rare earth (RE) additions, either as mischmetal or rare earth silicide, are used in many ladle treatment processes in modern ferrous metallurgy. In ironmaking they provide the basis for the control of graphite morphology in cast irons and in steelmaking additions are made to aluminum-killed steels for desulphurisation and the control of inclusion composition and morphology. Rare earth oxides may also be used in the desulphurisation of medium calorific value gaseous fuels and stack gases. In this paper, Ce-S-O and La-S-O phase stability diagrams are used to determine the role of the rare earths in the external processing of iron and steel, and gaseous desulphurisation

The structural priciples that underlie the higher oxides of the rare earths

International Nuclear Information System (INIS)

Kang, Z.C.; Zhang, J.; Eyring, L.

1996-01-01

The structural principle that accounts for the anion-deficient, fluorite-related homologous series of higher rare earth oxides has awaited the determination of a sufficient number of their structures to test hypotheses. Recent structure refinement of five additional members has permitted extraction of a number of generalizations concerning their crystallization behavior. These general principles are outlined. Furthermore, based on the fluorite structure itself, a phenomenological structural principle is outlined that (1) unifies all known and possible phases in these fluorite-related systems under one generic formula, (2) models all known structures correctly and (3) enables modeling of any unknown structure or polymorph in the series. All that is required are electron diffraction patterns adequate to determine the supercell and a knowledge of its composition. (orig.)

Solar furnace experiments for thermophysical properties studies of rare-earth oxide MHD materials

International Nuclear Information System (INIS)

Coutures, J.P.

1978-01-01

Some high temperature work performed with solar furnaces on rare earth oxides is reviewed. Emphasis is on the thermophysical properties (refractoriness, vaporization behavior) and the nature of solid solution on materials which could be used as electrodes for the MHD process. As new sources of energy are being developed due to the world energy crisis, MHD conversion could be useful. The development of MHD systems requires new efforts to develop and optimize materials properties. These materials must have good mechanical and electrical properties (if possible, pure electronic conduction with good emission). Because of the high temperature in MHD generators, the materials for electrodes must have good refractoriness and also must resist vaporization and corrosion at high temperature (T approx. 2000 0 C). Rare-earth oxides are the basic components for most of the MHD electrode materials and it is important to know their thermophysical properties (solidification point phase transitions, heat of fusion and of phase transition, vapor pressure). Because of the high temperature range and the nature of the atmosphere in which these experiments must be performed, special equipment adapted to solar furnaces was developed

Rare earth industries: Strategies for Malaysia

International Nuclear Information System (INIS)

2011-01-01

Evidently, many reports cite Malaysia as having reasonably substantial amounts of rare earths elements. In fact, based on the rare earths found in the residual tin deposits alone, Malaysia has about 30,000 tonnes. This does not take into account unmapped deposits which experts believe may offer more tonnages of rare earths. Brazil which is reported to have about 48,000 tonnes has announced plans to invest aggressively in the rare earths business. China has on record the largest reserves with about 36 million tonnes. This explains why China has invested heavily in the entire value chain of the rare earths business. Chinas committed investment in rare earths started many years ago when the country's foremost leaders proclaimed the strategic position of rare earths in the world economy. That forecast is now a reality where the rise in the green high-tech economy is seen driving global demand for rare earths in a big way. Malaysia needs to discover and venture into new economic growth areas. This will help fuel the country's drive to achieve a high income status by 2020 as articulated in the New Economic Model (NEM) and the many supporting Economic Transformation Plans that the Government has recently launched. Rare earths may be the new growth area for Malaysia. However, the business opportunities should not just be confined to the mining, extraction and production of rare earths elements alone if Malaysia is to maximise benefits from this industry. The industry's gold mine is in the downstream products. This is also the sector that China wants to expand. Japan which now controls about 50 % of the global market for downstream rare earths-based high-tech components is desperately looking for partners to grow their stake in the business. Malaysia needs to embark on the right strategies in order to build the rare earths industry in the country. What are the strategies? (author)

Optical emission spectrographic analysis of thulium oxide for rare earth impurities

International Nuclear Information System (INIS)

Chandola, L.C.; Khanna, P.P.; Dixit, V.C.

1988-01-01

An optical emission spectrographic method has been developed for the analysis of high purity thulium oxide to determine rare earth elements Er, Yb, Lu and Y. A 1200 groove/mm grating blazed at 3300 A is used to record the spectrum on Kodak SA-1 photographic plates after the excitation of the graphite-sample (1:1) mixture in DC arc. The determination range is 0.008 per cent to 0.1 per cent and the relative standard deviation is 17.6 per cent. (author). 15 refs., 5 tables, 5 figs

Scintillation property of rare earth-free SnO-doped oxide glass

OpenAIRE

Masai, Hirokazu; Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Yoko, Toshinobu

2012-01-01

The authors have demonstrated scintillation of rare earth (RE)-free Sn-doped oxide glass by excitation of ionizing radiation. It is notable that light emission is attained for RE-free transparent glass due to s[2]-sp transition of Sn[2+] centre and the emission correlates with the excitation band at 20 eV. We have also demonstrated that excitation band of emission centre can be tuned by the chemical composition of the host glass. The present result is valuable not only for design of RE-free i...

Rare-earth doped boron nitride nanotubes: Synthesis and characterization

Energy Technology Data Exchange (ETDEWEB)

Silva, Wellington Marcos; Sousa, Edesia Martins Barros de, E-mail: wellingtonmarcos@yahoo.com.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2016-07-01

Full text: Boron nitride is a heat and chemically resistant refractory compound of boron and nitrogen atoms with the chemical formula BN. This structure exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form (h-BN) corresponding to graphite is the most stable and soft among BN polymorph. However, boron nitride nanotubes (BNNTs) were first time synthesized in 1995 [1] and have a type of one-dimensional (1D) nanostructure. Recently the BNNTs have attracted significant interest for scientific and technological applications due to their Wide bandgap. The Wide-bandgap semiconductors doped with rare-earth are considered as a new type of luminescent material, combining special Wide bandgap semiconducting properties with the rare-earth luminescence feature. BNNTs have a stable wide bandgap of 5.5 eV and super thermal and chemical stabilities, which make BNNTs an ideal nanosized luminescent material [2]. In this study, we report a simple and efficient route for the synthesis of BNNTs doped with samarium and europium. High quality BNNTs doped was produced via CVD technique using NH{sub 3} and N{sub 2} gases as source. Boron amorphous, catalyst and oxides rare-earth powder were used as precursor. Detailed studies involving energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM) were performed in order to characterize the BNNTs as grown. [1] Chopra, N. G.; Luyken, R. J. et al. Science, v. 269, p. 966-967, 1995. [2] Chen, H.; Chen, Y. et al. Adv. Matter. v. 19, p. 1845-1848, 2007. (author)

Rare-earth doped boron nitride nanotubes: Synthesis and characterization

International Nuclear Information System (INIS)

Silva, Wellington Marcos; Sousa, Edesia Martins Barros de

2016-01-01

Full text: Boron nitride is a heat and chemically resistant refractory compound of boron and nitrogen atoms with the chemical formula BN. This structure exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form (h-BN) corresponding to graphite is the most stable and soft among BN polymorph. However, boron nitride nanotubes (BNNTs) were first time synthesized in 1995 [1] and have a type of one-dimensional (1D) nanostructure. Recently the BNNTs have attracted significant interest for scientific and technological applications due to their Wide bandgap. The Wide-bandgap semiconductors doped with rare-earth are considered as a new type of luminescent material, combining special Wide bandgap semiconducting properties with the rare-earth luminescence feature. BNNTs have a stable wide bandgap of 5.5 eV and super thermal and chemical stabilities, which make BNNTs an ideal nanosized luminescent material [2]. In this study, we report a simple and efficient route for the synthesis of BNNTs doped with samarium and europium. High quality BNNTs doped was produced via CVD technique using NH 3 and N 2 gases as source. Boron amorphous, catalyst and oxides rare-earth powder were used as precursor. Detailed studies involving energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM) were performed in order to characterize the BNNTs as grown. [1] Chopra, N. G.; Luyken, R. J. et al. Science, v. 269, p. 966-967, 1995. [2] Chen, H.; Chen, Y. et al. Adv. Matter. v. 19, p. 1845-1848, 2007. (author)

A process for the recovery of mixed rare-earth oxides from monazite

International Nuclear Information System (INIS)

Te Riele, W.A.M.

1982-01-01

A simple process has been demonstrated in the laboratory for the production of mixed rare-earth oxides from monazite concentrate. The product is substantially free from radioactive materials and has a purity of more than 98 per cent. The process involves leaching, filtration, ion exchange by use of a cation resin, precipitation, and calcination. The design, materials, consumption and cost of chemicals, and labor requirements are discussed, and a recommendation is made for pilot-plant tests

Sol-gel based oxidation catalyst and coating system using same

Science.gov (United States)

Watkins, Anthony N. (Inventor); Leighty, Bradley D. (Inventor); Oglesby, Donald M. (Inventor); Patry, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor)

2010-01-01

An oxidation catalyst system is formed by particles of an oxidation catalyst dispersed in a porous sol-gel binder. The oxidation catalyst system can be applied by brush or spray painting while the sol-gel binder is in its sol state.

Changes of fluorescent spectral features after successive rare earth doping of gadolinium oxide powders

Energy Technology Data Exchange (ETDEWEB)

Kuznik, W. [Chemical Department, Silesian University of Technology, Gliwice (Poland); Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Brik, M.G. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Cieslik, I.; Majchrowski, A.; Jaroszewicz, L. [Institute of Applied Physics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); AlZayed, N.S. [Physics and Astronomy Dept., College of Science, P.O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); El-Naggar, A.M. [Physics and Astronomy Dept., College of Science, P.O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); Permanent address: Physics department, Faculty of Science, Ain Shams University, Abassia, Cairo 11566 (Egypt); Sildos, I.; Lange, S.; Kiisk, V. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Kityk, I.V., E-mail: ikityk@el.pcz.czest.pl [Electrical Engineering Department, Czestochowa University of Technology, Armii Krajowej 17, Czestochowa (Poland); Physics and Astronomy Dept., College of Science, P.O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia)

2012-01-15

Highlights: > Principally new phosphors based on rare earth moped Gd{sub 2}O{sub 3} are obtained. > The time-resolved fluorescent spectra show drastic changes with the doping. > Temperature measurements were done. - Abstract: We present a complex fluorescence study of a series of gadolinium oxide polycrystalline powders singly, doubly and triply doped with trivalent rare earth ions (Er{sup 3+}, Tb{sup 3+}, and Dy{sup 3+}), to explore a possibility of their use as materials for white light emitting diodes. The excitation and luminescence spectra along with the decay kinetics were measured in the temperature range from 6 to 300 K. The luminescence efficiency was studied within the visible spectral range, i.e. -400 nm to 750 nm under excitation by 355 nm third harmonic Nd:YAG laser pulses. Singly doped Er{sup 3+} sample gave stronger luminescence signals, but others showed significantly larger decay lifetimes. The successive rare earths doping leads to substantial changes of the spectral positions due to the up-conversion processes. In the singly (Er{sup 3+}) doped sample, following the time resolved spectrum and decay curves, there are two different types of emissions: at 660 nm and at shorter wavelengths (below 640 nm) the red emission's lifetime is ten times longer than at shorter wavelengths. The singly doped sample shows unclear temperature-dependence of luminescence with lifetime at 550 nm (the longest at 100 K, similarly at 6 K and 300 K) and achieved luminous efficacy 73.5 lm/W.

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

Directory of Open Access Journals (Sweden)

Robert Wojcieszak

2017-11-01

Full Text Available The oxidation of bio-based molecules in general, and of carbohydrates and furanics in particular, is a highly attractive process. The catalytic conversion of renewable compounds is of high importance. Acids and other chemical intermediates issued from oxidation processes have many applications related, especially, to food and detergents, as well as to pharmaceutics, cosmetics, and the chemical industry. Until now, the oxidation of sugars, furfural, or 5-hydroxymethylfurfural has been mainly conducted through biochemical processes or with strong inorganic oxidants. The use of these processes very often presents many disadvantages, especially regarding products separation and selectivity control. Generally, the oxidation is performed in batch conditions using an appropriate catalyst and a basic aqueous solution (pH 7–9, while bubbling oxygen or air through the slurry. However, there is a renewed interest in working in base-free conditions to avoid the production of salts. Actually, this gives direct access to different acids or diacids without laborious product purification steps. This review focuses on processes applying gold-based catalysts, and on the catalytic properties of these systems in the base-free oxidation of important compounds: C5–C6 sugars, furfural, and 5-hydroxymethylfurfural. A better understanding of the chemical and physical properties of the catalysts and of the operating conditions applied in the oxidation reactions is essential. For this reason, in this review we put emphasis on these most impacting factors.

Electric and magnetic properties of oxidic titanium bronzes of rare earths Lnsub(2/3+x)TiOsub(3+-y) with perovskite structure

Energy Technology Data Exchange (ETDEWEB)

Bazuev, G V; Makarova, O V; Shvejkin, G P [AN SSSR, Sverdlovsk. Inst. Khimii

1983-01-01

A study was made on electric and magnetic properties of oxidic titanium bronzes of rare earths and their dependence on rare earth nature and the degree of rare earth sublattice filling was followed. Data on Lnsub(2/3)TiOsub(3-y) (Ln-Ce, Nd) anion-deficient perovskites are given as well. Investigated Cesub(2/3)TiOsub(2.985) and Ndsub(2/3)TiOsub(2.875) phases as well as defectless with respect to oxygen Lnsub(2/3)TiOsub(3) phases have rhombic structure of perovskite type with ordered position of Ln/sup 3 +/ cations and vacancies. Specific electric resistance and thermoelectromotive force factor were determined in vacuum at 290-1173 K for samples in the form of parallelepiped of 3x5x25 mm/sup 3/ size. Magnetic susceptibility chi was determined at 77-300 K by Faraday method using a device based on magnetic balance with electromagnetic compensation. Relative error during chi measuring didn't exceed +-2%. Collectivized behaviour of d-electrons of Ti/sup 3 +/ cations in oxidic titanium bronzes of rare earths: Lnsub(2/3+x)TiOsub(3+-y) (Ln-La, Ce, Nd; 0 < x < 1/3), conditioned by formation of narrow, partly filled ..pi..*-zone, was established on the basis of measuring specific electric resistance and magnetic susceptibility.

Interstitial pressure dependence of the thermal conductivity of some rare earth oxide powders

International Nuclear Information System (INIS)

Pradeep, P.

1997-01-01

Thermal transport properties of powdered materials depend upon interstitial gas pressure. The present study reports the experimental results for the effective thermal conductivity of three rare earth oxide powders viz. yttrium oxide, samarium oxide, and gadolinium oxide, at various interstitial pressures by using transient plane source (TPS) method. A theoretical model is also proposed for the interpretation of the variation of the effective thermal conductivity with interstitial gas pressure. Its validity is found to be good in low pressure range of 45 mm Hg to normal pressure when compared with the experimental results. Also an attempt has been made to calculate the variation of thermal conductivity with interstitial pressure in the high pressure range up to 2 kbar using the proposed model. (author)

Rare earths: harvesting basic research for technology

International Nuclear Information System (INIS)

Jagatap, B.N.

2014-01-01

In recent years, rare earths are increasingly becoming a versatile platform for basic research that presents enormous technological potentials. A variety of nano-sized inorganic matrices varying from oxides, phosphates, gallates and aluminates, tungstates, stannates, vanadates to fluorides doped with different lanthanide ions have been synthesized and their optical properties have been investigated in the Chemistry Group, BARC. Another interesting application is laser cooling of solids using rare earth doped glasses with potential applications in remote cooling of electronic devices. Combining the luminescence properties of rare earths with photonic crystals is yet another potent area with wide ranging applications. In this presentation we provide an overview of these developments with examples from the R and D programs of the Chemistry Group, BARC

Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Martin, Madhavi Z [ORNL; Fox, Dr. Richard V [Idaho National Laboratory (INL); Miziolek, Andrzej W [United States Army Research Laboratory; DeLucia, Frank C [United States Army Research Laboratory; Andre, Nicolas O [ORNL

2015-01-01

There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in realworld complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

Spectral Analysis of Rare Earth Elements using Laser-Induced Breakdown Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Martin, Madhavi Z [ORNL; Fox, Dr. Richard V [Idaho National Laboratory (INL); Miziolek, Andrzej W [United States Army Research Laboratory; DeLucia, Frank C [United States Army Research Laboratory; Andre, Nicolas O [ORNL

2015-01-01

There is growing interest in rapid analysis of rare earth elements (REEs) both due to the need to find new natural sources to satisfy increased demand in their use in various electronic devices, as well as the fact that they are used to estimate actinide masses for nuclear safeguards and nonproliferation. Laser-Induced Breakdown Spectroscopy (LIBS) appears to be a particularly well-suited spectroscopy-based technology to rapidly and accurately analyze the REEs in various matrices at low concentration levels (parts-per-million). Although LIBS spectra of REEs have been reported for a number of years, further work is still necessary in order to be able to quantify the concentrations of various REEs in real-world complex samples. LIBS offers advantages over conventional solution-based radiochemistry in terms of cost, analytical turnaround, waste generation, personnel dose, and contamination risk. Rare earth elements of commercial interest are found in the following three matrix groups: 1) raw ores and unrefined materials, 2) as components in refined products such as magnets, lighting phosphors, consumer electronics (which are mostly magnets and phosphors), catalysts, batteries, etc., and 3) waste/recyclable materials (aka e-waste). LIBS spectra for REEs such as Gd, Nd, and Sm found in rare earth magnets are presented.

Quantitative analysis or rare earths by X-ray fluorescence spectrometry

International Nuclear Information System (INIS)

Taam, Isabel; Mantovano, J.L.; Gante, Valdir; Jesus, Camila S.

2013-01-01

Rare earths ores and compounds are of growing importance to the worldwide industry. Its applications range from raw material to catalysts, manufacturing of electronics and even super magnets. Therefore, the demand for quick and accurate quantitative analysis methods is continuously growing. Current quantification methods of rare earths involve the separation of these elements by ion exchange and liquid-liquid extraction prior to the analysis itself, processes both time and reagent consuming. In the present work, we propose a method that directly quantifies by XRF technique the following rare earths: La, Pr, Nd, Sm and Gd in a concentrated liquor whose matrix also contains Ca, Y, PO4, U and Th. We evaluated the analytical interference of each element present on the sample on X-rays spectrum. The studied samples are certified standards and the obtained results have been compared to EDTA titration results, an already well-established and widely trusted method.We also measured the matrix effect thus using a complex rare earths standard. Results show that quantification by XRF technique is as accurate as the results in dose titration with EDTA for the same elements, with the advantage of exempting the previous separation step from each rare earth and from other elements present in the matrix (such as U and Th). (author)

Rare earths

International Nuclear Information System (INIS)

1984-01-01

The conference was held from September 12 to 13, 1984 in Jetrichovice, Czechoslovakia. The participants heard 16 papers of which 4 were inputted in INIS. These papers dealt with industrial separation processes of rare earths, the use of chemical methods of separation from the concentrate of apatite and bastnesite, the effect of the relative permittivity of solvents in the elution of rare earth elements from a cation exchanger, and the determination of the content of different rare earth elements using X-ray fluorescence analysis and atomic absorption spectroscopy. (E.S.)

X-ray fluorescence analysis of terbium oxide for rare earth impurities

International Nuclear Information System (INIS)

Chandola, L.C.; Machado, I.J.; Mohile, A.N.

1975-01-01

A method for the determination of Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Dy 2 O 3 , Ho 2 O 3 and Y 2 O 3 in terbium oxide is described. The sample is converted to terbium oxalate, mixed with boric acid binder in the ratio 2:1, pelleted at a pressure of 20 tons over a boric acid backing pellet and irradiated with x-rays from a tungsten tube operated by Philips PW 1140 generator. The secondary x-rays thus generated are analysed by a LiF (200) crystal in Philips PW 1220 x-ray fluorescence spectrometer using suitable detectors. The minimum determination limit (MDL) is 0.01% for all rare earth oxides determined except for Y 2 O 3 for which it is 0.005%. (author)

Extraction-differential-photometric method to determine rare earths of cerium subgroup

International Nuclear Information System (INIS)

Askerov, D.N.; Gusejnov, I.K.; Melikov, A.A.

1985-01-01

The extraction - photometric method to determine great quantities of rare earths of the cerium subgroup as a complex with antipyrine A and diphenylguanidine is developed. Isobutyl and n-butyl alcohols are used as extractants. It is established that proportional dependence between relative optical density and concentration of rare earths of the cerium subgroup in the solution takes place in the concentration interval of 10.3-14.7 μg of rare earths in 1 ml of the solution. Determination error is+-1.12%. The technique is used to determine rare earths of the cerium subgroup in rare earth oxides of a mixed composition, as well as in monozite and loparite

Effects of rare earth oxide nanoparticles on root elongation of plants.

Science.gov (United States)

Ma, Yuhui; Kuang, Linglin; He, Xiao; Bai, Wei; Ding, Yayun; Zhang, Zhiyong; Zhao, Yuliang; Chai, Zhifang

2010-01-01

The phytotoxicity of four rare earth oxide nanoparticles, nano-CeO(2), nano-La(2)O(3), nano-Gd(2)O(3) and nano-Yb(2)O(3) on seven higher plant species (radish, rape, tomato, lettuce, wheat, cabbage, and cucumber) were investigated in the present study by means of root elongation experiments. Their effects on root growth varied greatly between different nanoparticles and plant species. A suspension of 2000 mg L(-1) nano-CeO(2) had no effect on the root elongation of six plants, except lettuce. On the contrary, 2000 mg L(-1) suspensions of nano-La(2)O(3), nano-Gd(2)O(3) and nano-Yb(2)O(3) severely inhibited the root elongation of all the seven species. Inhibitory effects of nano-La(2)O(3), nano-Gd(2)O(3), and nano-Yb(2)O(3) also differed in the different growth process of plants. For wheat, the inhibition mainly took place during the seed incubation process, while lettuce and rape were inhibited on both seed soaking and incubation process. The fifty percent inhibitory concentrations (IC(50)) for rape were about 40 mg L(-1) of nano-La(2)O(3), 20mg L(-1) of nano-Gd(2)O(3), and 70 mg L(-1) of nano-Yb(2)O(3), respectively. In the concentration ranges used in this study, the RE(3+) ion released from the nanoparticles had negligible effects on the root elongation. These results are helpful in understanding phytotoxicity of rare earth oxide nanoparticles. Copyright 2009 Elsevier Ltd. All rights reserved.

X-ray fluorescence analysis of high purity rare earth oxides for common trace rare earth impurities

International Nuclear Information System (INIS)

Chandola, L.C.; Dixit, R.M.; Khanna, P.P.; Deshpande, S.S.; Machado, I.J.; Kapoor, S.K.

1990-01-01

Methods for the determination of individual trace common rare earth (RE) elements have been developed for fifteen RE oxide matrices viz. La 2 O 3 to Lu 2 O 3 and Y 2 O 3 . In general, for each matrix, two or three neighbouring elements on both sides of the matrix element are determined. The minimum determination limit (MDL) achieved is 0.002% for most of the elements. Special efforts were made to use a small amount of sample (as low as 400 mg) for the analysis by the use of double layer pellet technique and critical thickness studies. Practical experiences with 15 RE matrices, most of which are investigated for the first time, are discussed. Details of selection of instrumental parameters and analysis lines, precision and accuracy and preparation of samples and synthetic standards are given. Theoretical minimum detection limit (TMDL) for each analyte element is calculated in all the 15 matrices. (author). 50 tabs., 2 figs

Effect of catalysts on heterogeneous oxidation of coal

Energy Technology Data Exchange (ETDEWEB)

Glazkova, A P; Kazarova, Yu A; Suslov, A V

1978-01-01

Analyzes the effects of catalysts on the heterogeneous oxidation of coal in deflagration processes of stoichiometric mixtures. The following substances are studied as catalysts: alkali and alkaline-earth metals, and compounds of copper, lead, chromium, iron, and sulfur. In the first case the catalysts are used in the form of nitrates and the nitrate simultaneously plays the role of an oxidizer. In the second case the catalysts are added to stoichiometric mixtures of ammonium nitrate with carbon. It is shown that during carbon oxidation by nitrates the catalytic efficiency of the metals studied forms the following order: sodium > lead > potassium > barium > aluminium > calcium > magnesium > copper. The calculated and experimental parameters of combustion are given. The problem of dependence of combustion rate on combustion heat, the mechanism of the combustion reaction and the catalytic effects of the additives are discussed. Features of heterogeneous catalysis in the oxidation process of carbon by various oxidizers are analyzed. The investigations on the combustion process are important as the process takes place during explosion of coal dust in underground coal mines and during burning of coal in industrial furnaces. (34 refs.) (In Russian)

Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts

Directory of Open Access Journals (Sweden)

R. Prasad

2011-05-01

Full Text Available CuO-CeO2 systems have been proposed as a promising catalyst for low temperature diesel-soot oxidation. CuO-CeO2 catalysts prepared by various methods were examined for air oxidation of the soot in a semi batch tubular flow reactor. The air oxidation of soot was carried out under tight contact with soot/catalyst ratio of 1/10. Air flow rate was 150 ml/min, soot-catalyst mixture was 110 mg, heating rate was 5 0C/min. Prepared catalysts were calcined at 500 0C and their stability was examined by further heating to 800 0C for 4 hours. It was found that the selectivity of all the catalysts was nearly 100% to CO2 production. It was observed that the activity and stability of the catalysts greatly influenced by the preparation methods. The strong interaction between CuO and CeO2 is closely related to the preparation route that plays a crucial role in the soot oxidation over the CuO-CeO2 catalysts. The ranking order of the preparation methods of the catalysts in the soot oxidation performance is as follows: sol-gel > urea nitrate combustion > Urea gelation method > thermal decomposition > co-precipitation. Copyright © 2011 BCREC UNDIP. All rights reserved.(Received: 27th June 2010, Revised: 7th August 2010; Accepted: 13rd October 2010[How to Cite: R. Prasad, V.R. Bella. (2011. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 15-21. doi:10.9767/bcrec.6.1.822.15-21][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.822.15-21 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/822 | View in 

The determination of minor amounts of rare earth elements in high purity earth oxides by HPLC/IDMS

International Nuclear Information System (INIS)

Stijfhoorn, D.E.; Stray, H.; Hjelmseth, H.

1991-05-01

Since the early seventies isotopic dilution mass spectrometry (IDMS) has been used at Institutt for energiteknikk, Kjeller, Norway for determination and certification of rare earth elements in high purity Y 2 O 3 . These lanthanides have, during the last few decades, become more widely used in highly specialized technology. High purity, quality 4 N (99.99%) or even 5 N materials are needed for phosphors, lasers, optical fibers, X-ray films, and in contrast fluids for magnetic resonance imaging (MRI). However, in a matrix constisting primarily of a single lanthanide, IDMS alone will not be effective due to isobaric interferences from the main elements or the mono-oxides formed in the ion source. On the other hand, high performance liquid chromatography (HPLC) may be used, but the detection limit will be in the order of 5 to 10 ppm/W. In this work a combination of HPLC and IDMS has been used to lower the detection limit to 1 ppm/W, where the sample is spiked before separation by HPLC, followed by IDMS analysis of the HPLC- fractions. In some cases the HPLC-process has to be repeated to remove the main element completly. Results are presented for Dy 2 O 3 and Nd 2 O 3 , but similar separating procedures can be applied for other rare earth oxides. 3 refs., 2 figs. 2 tabs

China’s Rare Earths Supply Forecast in 2025: A Dynamic Computable General Equilibrium Analysis

Directory of Open Access Journals (Sweden)

Jianping Ge

2016-09-01

Full Text Available The supply of rare earths in China has been the focus of significant attention in recent years. Due to changes in regulatory policies and the development of strategic emerging industries, it is critical to investigate the scenario of rare earth supplies in 2025. To address this question, this paper constructed a dynamic computable equilibrium (DCGE model to forecast the production, domestic supply, and export of China’s rare earths in 2025. Based on our analysis, production will increase by 10.8%–12.6% and achieve 116,335–118,260 tons of rare-earth oxide (REO in 2025, based on recent extraction control during 2011–2016. Moreover, domestic supply and export will be 75,081–76,800 tons REO and 38,797–39,400 tons REO, respectively. The technological improvements on substitution and recycling will significantly decrease the supply and mining activities of rare earths. From a policy perspective, we found that the elimination of export regulations, including export quotas and export taxes, does have a negative impact on China’s future domestic supply of rare earths. The policy conflicts between the increase in investment in strategic emerging industries, and the increase in resource and environmental taxes on rare earths will also affect China’s rare earths supply in the future.

Thermoemission properties of tungsten with additions of rare earth oxides

International Nuclear Information System (INIS)

Gural'nik, N.I.; Evstifeev, V.V.; Imangulova, N.G.

1988-01-01

Thermoemission properties of tungsten with addition of rare earth oxides are studied in the superhigh vacuum set with oil-free pumping system. Electronic work function eφ is determined by the method of total saturation current. Temperature dependences are obtained of the work function for three types of cathodes: W+La 2 O 3 ; W+φ 2 O 3 and W+Dy 2 O 3 . It is stated, that the first two types eφ decreases approximately from 4.2 to 3.3 eV and from 4.5 to 3.8 eV, respectively, after activation at proper temperatures. These cathodes are the most effective ones at the temperature of 1700 (W+La 2 O 3 ) and 1900-2100 K (W+ φ 4 O 3 ). The work function of cathodes with addition of dysprosium oxide did not practically vary (4.55-4.3 eV) within the whole studied temperature interval (1500-2100 K)

Redox reactions in rare earth chloride molten electrolytes

International Nuclear Information System (INIS)

Khokhlov, V.A.; Novoselova, A.V.; Nikolaeva, E.V.; Tkacheva, O.Yu.; Salyulev, A.B.

2007-01-01

Rare earth (REM, Ln) solutions in chloride melts including MCI+LnCl 3 mixtures, where M - alkali metals, were investigated by potentiometry, voltammetry, conductometry in wide concentration and temperature intervals. Findings present complete and trusty information on the valent state of rare earths, structure and composition of complex ions affecting essentially on properties of electrolytes. It is demonstrated that the coexistence of rare earth ions with different oxidation level formed as a result of possible redox reactions: 2Ln 3+ + Ln ↔3Ln 2+ , Ln 2+ + Ln↔2Ln + and nM + + Ln↔nM + Ln n+ appears sharply in thermodynamic and transport properties of molten Ln-LnCl 3 and Ln-LnCl 3 -MCl systems [ru

Spectral determination of individual rare earths in different classes of inorganic compounds

International Nuclear Information System (INIS)

Karpenko, L.I.; Fadeeva, L.A.; Shevchenko, L.D.

1979-01-01

The conditions are found allowing to analyze various inorganic compounds for rare-earth elements without separation from non-rare-earth components. The influence of the plasma composition on the intensity of spectral lines of rare-earth elements is studied. The relative intensity of homologous spectral lines of various rare-earth elements remains constant regardless of the plasma composition. The conditions are found for the determination of individual rare-earth elements acting as both alloying additives (Csub(n) -- n x 10 -1 -n x 10 -3 %), and basic components (up to tens of per cent) in different classes of inorganic compounds of 1-7 elements. The general method is developed for the determination of individual rare-earth elements in mixtures of oxides of rare-earth elements, complex fluorides of rare-earth elements and elements of group 2, gallates, borates, germanates, vanadates of rare-earth elements and aluminium; zirconates-titanates of lead and barium, containing modifying additives of rare-earth elements, complex chalcogenides of rare-earth elements and elements of group 5

Extraction of rare earths from iron-rich rare earth deposits

OpenAIRE

Bisaka, K.; Thobadi, I.C.; Pawlik, C.

2017-01-01

Rare earth metals are classified as critical metals by the United Nations, as they have found wide application in the fabrication of magnets, particularly those used in green energy technologies which mitigate global warming. Processing of ores containing rare earth elements is complex, and differs according to the nature of each ore. In the conventional process, run of mine (ROM) ores are processed in a physical separation plant to produce a concentrate from which rare earth elements are ext...

Giant magnetic anisotropy of rare-earth adatoms and dimers adsorbed by graphene oxide.

Science.gov (United States)

Zhang, Kai-Cheng; Li, Yong-Feng; Liu, Yong; Zhu, Yan; Shi, Li-Bin

2017-05-24

Nowadays, transition-metal adatoms and dimers with giant magnetic anisotropy have attracted much attention due to their potential applications in data storage, spintronics and quantum computations. Using density-functional calculations, we investigated the magnetic anisotropy of the rare-earth adatoms and dimers adsorbed by graphene oxide. Our calculations reveal that the adatoms of Tm, Er and Sm possess giant magnetic anisotropy, typically larger than 40 meV. When the dimers of (Tm,Er,Sm)-Ir are adsorbed onto graphene oxide, the magnetic anisotropy even exceeds 200 meV. The magnetic anisotropy can be tuned by the external electric field as well as the environment.

Yttrium and rare earths separation by ion exchange resin

International Nuclear Information System (INIS)

Pinatti, D.G.; Ayres, M.J.G.; Ribeiro, S.; Silva, G.L.J.P.; Silva, M.L.C.P.; Martins, A.H.

1988-01-01

The experimental results of yttrium and rare earths separation from Brazilian xenotime are presented. The research consist in five stage: 1) Preparation of yttrium, erbium and lutetium standard solutions, from solubilization of pure oxides 2) yttrium and rare earths separation by ion exchange chromatrography 3) Separation and recovery of EDTA 4) Precipitation and calcination and 4) Analytical control of process. (C.G.C.) [pt

Characteristics of the behavior of rare-earth oxides and composites on their base by charged particles and neutrons irradiated

International Nuclear Information System (INIS)

Tuseev, T.; Aksenova, T.I.; Berdauletov, A.K.

2000-01-01

In this work the results of comparative investigation of adsorption curves versus REM order number (La, Ce, Nd, Pr, Gd) and dose neutron irradiation are presented. It is discovered that the original REM oxides have high adsorption capacity both for donor gases and for acceptor ones. The adsorption capacity for oxygen and hydrogen becomes lower when the REM order number is higher, but it is contrary for water molecules. The obtained results showed that adsorption properties of REM oxides were changing on identical laws. But oxides of metals, having anomalous properties (variable valency, high cross-section capture) revealed especial adsorption properties under irradiation. In the time of consideration of possible mechanism of radiation - stimulated gas adsorption on oxide surface it is necessary to take in attention both the formation of radiation defects in crystal lattice and the characteristics of electron structure and presence of 4 f - cover in rare-earth metals

Novel online security system based on rare-earth-doped glass microbeads

Science.gov (United States)

Officer, Simon; Prabhu, G. R.; Pollard, Pat; Hunter, Catherine; Ross, Gary A.

2004-06-01

A novel fluorescent security label has been produced that could replace numerous conventional fluorescent dyes in document security. This label utilizes rare earth ions doped in a borosilicate glass matrix to produce sharp spectral fluorescence peaks with characteristic long lifetimes due to the rare earth ions. These are subsequently detected by an online detection system based on fluorescence and the long lifetimes to avoid any interference from other fluorophores present in the background. Security is further enhanced by the interaction of the rare earth ions with each other and the effect of the host on the emission spectra and therefore the number of permutations that could be produced. This creates a very secure label with various applications for the security market.

Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers

Science.gov (United States)

Schryer, David R.; Upchurch, Billy T.; Hess, Robert V.; Wood, George M.; Sidney, Barry D.; Miller, Irvin M.; Brown, Kenneth G.; Vannorman, John D.; Schryer, Jacqueline; Brown, David R.

1990-01-01

Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed.

Advances in the hydrometallurgical separation techniques of high purity rare earth elements

International Nuclear Information System (INIS)

Vijayalakshmi, R.; Kain, V.

2017-01-01

Rare Earths are a series of 15 chemically similar elements that occur together in monazite mineral found in the beach sands of Kerala, Tamil Nadu and Orissa. The rare earth elements (REE) are becoming increasingly strategically important considering their essential role in permanent magnets such as, SmCo_5, Sm_2Co_1_7 and Nd_2Fe_1_4B, phosphors for LED screens and lamps, rechargeable nickel metal hydride batteries and catalysts and other green applications. The increasing popularity of hybrid and electric cars, wind turbines and compact fluorescent lamps is causing an increase in the demand and price of REE. The European Commission considers the REE as the most critical raw materials group, with the highest supply risk. According to the medium-term criticality matrix of the U.S. Department of Energy (DOE), the five most critical REE are neodymium (Nd), europium (Eu), terbium (Tb), dysprosium (Dy) and yttrium (Y). China is presently producing more than 90% of all rare earths, although they possess less than 405 of the proven reserves. Due to large and increasing domestic demands, China tightened its REE export quota from 2012 onwards. These export quotas caused serious problems for REE users outside of China. Fortunately India is blessed with large resources of rare earths in the form of monazite found in the beach sands of Kerala, Tamil Nadu and Orissa. Indian Rare Earths Limited at Aluva near Kochi produces mainly mixed rare earths chloride and till recent past exporting to USA, UK, France, Japan, etc. They have revived their rare earth separation plant to meet the in-house demands of the strategic, defense and nuclear industry. This paper discusses the recent advances made in hydrometallurgical separation techniques based on solvent extraction technique, ion-exchange resins, hollow fibre membrane extractor, solvent encapsulated polymeric beads, etc for the production of high purity rare earth elements from both primary (Monazite, xenotime) and secondary sources

Determination of the composition of surface optical layers prepared with the use of rare earth and zirconium oxides

International Nuclear Information System (INIS)

Mishchenko, V.T.; Shilova, L.P.; Shkol'nikova, T.M.

1991-01-01

Simple titrimetric and gravimetric methods for determination of optical oxide layers (rare earth and zirconium oxides), sputtered on glass or quartz sublayer, have been developed. The minimal determined oxide mass in surface layers is equal to 0.01 mg in titrimetric determination and 0.1 mg - in gravimetric one. It is shown that composition of films and pellets, used for film sputtering, is identical

Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts.

Science.gov (United States)

Yamazaki, Shin-ichi; Yamada, Yusuke; Takeda, Sahori; Goto, Midori; Ioroi, Tsutomu; Siroma, Zyun; Yasuda, Kazuaki

2010-08-21

Electrochemical CO oxidation by several carbon-supported rhodium tetraphenylporphyrins with systematically varied meso-substituents was investigated. A quantitative analysis revealed that the p-substituents on the meso-phenyl groups significantly affected CO oxidation activity. The electrocatalytic reaction was characterized in detail based on the spectroscopic and X-ray structural results as well as electrochemical analyses. The difference in the activity among Rh porphyrins is discussed in terms of the properties of p-substituents along with a proposed reaction mechanism. Rhodium tetrakis(4-carboxyphenyl)porphyrin (Rh(TCPP)), which exhibited the highest activity among the porphyrins tested, oxidized CO at a high rate at much lower potentials (means that CO is electrochemically oxidized by this catalyst when a slight overpotential is applied during the operation of a proton exchange membrane fuel cell. This catalyst exhibited little H(2) oxidation activity, in contrast to Pt-based catalysts.

In situ cyclization modification in polymerization of butadiene by rare earth coordination catalyst

International Nuclear Information System (INIS)

Wang Chaoyang

2005-01-01

Butadiene was polymerized to a certain extent in the presence of a rare earth coordination catalyst, neodymium compound of neodymium chloride and i-propyl alcohol and triethyl aluminum (NdCl 3 ·3i-PrOH-AlEt 3 ) in toluene and the allyl chloride was then added to the reactive solution in order to in situ cyclize the formed polybutadiene and cyclopolymerize the unreacted butadiene monomers. Effects of molar ratio of allylchloride to AlEt 3 (Cl/Al), cyclization reaction time and temperature, butadiene and NdCl 3 ·3i-PrOH concentrations on the cyclization reaction have been investigated. The cyclization reaction is very quick, only several minutes. The cyclization reaction temperature has few effects on the properties of the cyclized product. Cl/Al is a very important condition for this reaction system. Cyclized polybutadiene has a low value of intrinsic viscosity, free gelling and high yield at high Cl/Al. The microstructures and properties of the cyclized products have been characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and gel permeation chromatography. The cyclization mechanism is put forward

Rare earth industry in India

International Nuclear Information System (INIS)

Singh, D.S.

2016-01-01

Rare Earths (RE) comprises of 17 elements i.e. elements from atomic No. 57-71 (lanthanide series) along with yttrium (atomic No. 39) and scandium (atomic No. 21). They exhibit special electronic, magnetic, optical and catalytic properties. The first 7 elements in the lanthanide series from atomic Nos. 57 to 63 (La to Eu) are called Light Rare Earths (LRE), while the remaining elements from atomic Nos. 64 to 71 (Gd to Lu) are grouped as Heavy Rare Earths (HRE). Scandium and Yttrium have properties similar to HRE. The concentration of the REs in the earth's crust is as high as some other elements including that of copper. The only difference is that REs do not occur as separate minerals amenable for easy exploration and mining and are widely distributed across the earth's surface, hence they are called as REs. Resources In India, monazite has been the principal source of RE. It occurs in association with other heavy minerals, such as ilmenite, rutile, zircon etc. in the beach sands and inland placer deposits. The monazite content in this assemblage varies from negligible quantity to as high as 5%. As per AMD resource estimation, the reported resource of monazite in India is about 11.93 million tons which corresponds with about 6.9 million tons of RE oxides. Although India possesses large deposits of monazite, the heavier RE are not present in sufficient quantities in this mineral. (author)

Rare earth element recycling from waste nickel-metal hydride batteries

International Nuclear Information System (INIS)

Yang, Xiuli; Zhang, Junwei; Fang, Xihui

2014-01-01

Highlights: • Leaching kinetics of REEs has rarely been reported. • A new method, including hydrochloric acid leaching and oxalic acid precipitation, was proposed. • REEs recovery rate of 95.16% and pure rare earth oxides of 99% were obtained. • Leaching process was controlled by chemical reaction. • The kinetic equation was determined. - Abstract: With an increase in number of waste nickel-metal hydride batteries, and because of the importance of rare earth elements, the recycling of rare earth elements is becoming increasingly important. In this paper, we investigate the effects of temperature, hydrochloric acid concentration, and leaching time to optimize leaching conditions and determine leach kinetics. The results indicate that an increase in temperature, hydrochloric acid concentration, and leaching time enhance the leaching rate of rare earth elements. A maximum rare earth elements recovery of 95.16% was achieved at optimal leaching conditions of 70 °C, solid/liquid ratio of 1:10, 20% hydrochloric acid concentration, −74 μm particle size, and 100 min leaching time. The experimental data were best fitted by a chemical reaction-controlled model. The activation energy was 43.98 kJ/mol and the reaction order for hydrochloric acid concentration was 0.64. The kinetic equation for the leaching process was found to be: 1−(1−x) 1/3 =A/ρr 0 [HCl] 0.64 exp((−439,800)/(8.314T) )t. After leaching and filtration, by adding saturated oxalic solution to the filtrate, rare earth element oxalates were obtained. After removing impurities by adding ammonia, filtering, washing with dilute hydrochloric acid, and calcining at 810 °C, a final product of 99% pure rare earth oxides was obtained

Titrimetric determination of Zr, Hf, Sn, Ta and rare earths in binary oxide systems

International Nuclear Information System (INIS)

Flyantikova, G.V.; Chekirda, T.N.; Lasovskaya, O.N.; Migun, N.P.

1989-01-01

Proximate method of titrimetric determination of oxides of Zr(4), Hf(4), Sn(4), Ta(5) and rare earths (La, Lu, Nd, Eu, Yb, Y) in binary systems (BS) with high accuracy was developed. A study was made on conditions of decomposition and dissolution of BS by means of their treatment by the mixture of solutions of concentrated sulfuric acid and ammonium sulfate during 2h boiling eith successive complexonometric determination of their components by direct EDTA titration in the presence of xylenol orange. The relative standard deviation when titrating 0.3-9.7mg oxides in BS does not exceed 0.02

Concentration of rare earths ore from Pocos de Caldas - MG, Brazil

International Nuclear Information System (INIS)

Sampaio, J.A.; Lins, F.F.; Porphirio, N.H.

1990-01-01

The objective of this research was to concentrate, mainly by flotation, a rare-earth ore body. The valuable mineral is bastnaesite which occurs intimately associated with iron oxides and other gangue minerals, making difficult to get a concentrate of commercial grade. The use of oleic acid at a pulp temperature of -80 sup(0)C gave a concentrate of 23% rare-earth oxides at 72% overall recovery. The magnetic separation could enhance the grade of the flotation feed. (author)

Mechanochemical decomposition of monazite to assist the extraction of rare earth elements

Energy Technology Data Exchange (ETDEWEB)

Kim, Wantae; Bae, Inkook; Chae, Soochun [Korea Institute of Geoscience and Mineral Resources, 92 Gwahang-no, Yuseong-gu, Daejeon 305-350 (Korea, Republic of); Shin, Heeyoung, E-mail: hyshin@kigam.re.k [Korea Institute of Geoscience and Mineral Resources, 92 Gwahang-no, Yuseong-gu, Daejeon 305-350 (Korea, Republic of)

2009-11-03

Mechanochemical decomposition by milling a mixture of monazite and sodium hydroxide powder and subsequent leaching by sulfuric acid for the extraction of rare earth elements at room temperature has been investigated. The milling of the mixture allows the mechanochemical formation of rare earth hydroxides and sodium phosphate as milling progresses. Nearly all the monazite is decomposed within 120 min under the present milling conditions. A 0.05N sulfuric acid solution enables us to improve the yield of each of La, Nd and Sm to around 85% or more in the powder milled for 120 min. Also, respective Ce and Pr yields of about 20% and 70% remain un-dissolved since they are changed into oxide forms during and after the milling operation. These rare earth oxides are mostly dissolved as the acid concentration increases to 5N. The yield of rare earth elements increases with increasing milling time. Thus mechanochemical milling plays a significant role in achieving high yield of rare earth elements from the leaching of the milled powder.

Mechanochemical decomposition of monazite to assist the extraction of rare earth elements

International Nuclear Information System (INIS)

Kim, Wantae; Bae, Inkook; Chae, Soochun; Shin, Heeyoung

2009-01-01

Mechanochemical decomposition by milling a mixture of monazite and sodium hydroxide powder and subsequent leaching by sulfuric acid for the extraction of rare earth elements at room temperature has been investigated. The milling of the mixture allows the mechanochemical formation of rare earth hydroxides and sodium phosphate as milling progresses. Nearly all the monazite is decomposed within 120 min under the present milling conditions. A 0.05N sulfuric acid solution enables us to improve the yield of each of La, Nd and Sm to around 85% or more in the powder milled for 120 min. Also, respective Ce and Pr yields of about 20% and 70% remain un-dissolved since they are changed into oxide forms during and after the milling operation. These rare earth oxides are mostly dissolved as the acid concentration increases to 5N. The yield of rare earth elements increases with increasing milling time. Thus mechanochemical milling plays a significant role in achieving high yield of rare earth elements from the leaching of the milled powder.

Radiological Impacts and Regulation of Rare Earth Elements in Non-Nuclear Energy Production

Directory of Open Access Journals (Sweden)

Timothy Ault

2015-03-01

Full Text Available Energy industries account for a significant portion of total rare earth usage, both in the US and worldwide. Rare earth minerals are frequently collocated with naturally occurring radioactive material, imparting an occupational radiological dose during recovery. This paper explores the extent to which rare earths are used by various non-nuclear energy industries and estimates the radiological dose which can be attributed to these industries on absolute and normalized scales. It was determined that typical rare earth mining results in an occupational collective dose of approximately 0.0061 person-mSv/t rare earth elements, amounting to a total of 330 person-mSv/year across all non-nuclear energy industries (about 60% of the annual collective dose from one pressurized water reactor operated in the US, although for rare earth mining the impact is spread out over many more workers. About half of the collective dose from non-nuclear energy production results from use of fuel cracking catalysts for oil refining, although given the extent of the oil industry, it is a small dose when normalized to the energy equivalent of the oil that is used annually. Another factor in energy industries’ reliance on rare earths is the complicated state of the regulation of naturally occurring radiological materials; correspondingly, this paper also explores regulatory and management implications.

X-ray fluorescence analysis of neodymium oxide/oxalate for rare earth impurities

International Nuclear Information System (INIS)

Chandola, L.C.; Mohile, A.N.

1977-01-01

An X-ray fluorescence method for the determination of cesium, praseodymium, samarium, europium and gadolinium in pure neodymium oxide and oxalate is described. The oxide sample is converted to oxalate and mixed with a binder (boric acid) to obtain a pressed circular pellet. The amount of sample needed for analysis is reduced by making use of the double layer pellet technique. A tungsten target X-ray tube is employed to irradiate the sample and a Philips PW 1220 semiautomatic X-ray spectrometer with a LiF (200) crystal is used to analyse the fluorescent X-rays. The minimum determination limit is 0.01 percent for all rare earths determined except for europium for which the limit is 0.005 percent. Three sigma detection limits have been calculated. (author)

Catalysts for synthetic liquid fuels

Energy Technology Data Exchange (ETDEWEB)

Bruce, L.A.; Turney, T.W.

1987-12-01

Fischer-Tropsch catalysts have been designed, characterized and tested for the selective production of hydrocarbons suitable as synthetic liquid transport fuels from synthesis gas (i.e., by the reduction of carbon monoxide with hydrogen). It was found that hydrocarbons in the middle distillate range, or suitable for conversion to that range, could be produced over several of the new catalyst systems. The various catalysts examined included: (1) synthetic cobalt clays, mainly cobalt chlorites; (2) cobalt hydrotalcites; (3) ruthenium metal supported on rare earth oxides of high surface area; and (4) a novel promoted cobalt catalyst. Active and selective catalysts have been obtained, in each category. With the exception of the clays, reproducibility of catalyst performance has been good. Catalysts in groups 2 and 4 have exhibited very high activity, with long lifetimes and easy regeneration.

Rare earth octacyanomolybdates(4)

International Nuclear Information System (INIS)

Zubritskaya, D.I.; Sergeeva, A.N.; Pisak, Yu.V.

1980-01-01

Optimal conditions for synthesis of rare-earth octacyanomolybdates(4) of the Ln 4 [Mo(CN) 8 ] 3 xnH 2 O composition (where Ln is a rare-earth element, other than Pr, Pm, Lu, Tb) have been worked out. The synthesis has been accomplished by neutralization with octacianomolybdic acid with rare-earth carbonates. The composition and structure of the compounds synthesized have been studied by infrared-spectroscopy. It has been established that rare-earth octacyanomolybdates(4) form three isostructural groups

Rare earth metal alloy magnets

International Nuclear Information System (INIS)

Harris, I.R.; Evans, J.M.; Nyholm, P.S.

1979-01-01

This invention relates to rare earth metal alloy magnets and to methods for their production. The technique is based on the fact that rare earth metal alloys (for e.g. cerium or yttrium) which have been crumbled to form a powder by hydride formation and decomposition can be used for the fabrication of magnets without the disadvantages inherent in alloy particle size reduction by mechanical milling. (UK)

Rare earths and rare earth alloys electrolytic preparation process and device for this process

International Nuclear Information System (INIS)

Seon, F.; Barthole, G.

1986-01-01

Electrolysis of a molten salt of rare earth or rare earth alloy for preparation of the metal or alloy is described. The molten salt bath comprises at least a rare earth chloride, at least an alkaline or alkaline earth chloride and at least an alkaline or alkaline earth fluoride [fr

Separation of pure Cerium oxides from rare earth compounds. Homogeneous precipitation using Urea-Hydrogen Peroxide

International Nuclear Information System (INIS)

Umeda, K.; Abrao, E.

1975-01-01

The obtainment of ceric oxide (CeO 2 ) of purity higher than 97% by application of homogeneous precipitation technique is described. The selective separation of cerium was reached by hydrolysis of urea in the presence of hydrogen peroxide, using a rare earths concentrate named rare earths chloride, a natural mixture of all lanthanides provenient from the industrialization of monazite. The best conditions for the preparation of CeO 2 of 94% purity are: 35-70g R 2 O 3 /1 and pH2,0 hydrolysis temperature: 88-90 0 C, urea/R 2 O 3 ratio: 4, H 2 O 2 /Ce 2 O 3 ratio: 1,5-5,0 and hydrolysis duration: 4 hours. A leaching procedure of the precipitate with 0,25-0,75M NHO 3 leads to a product of 97-99,5% CeO 2

Alloys of Pt and Rare Earths for the Oxygen Electroreduction Reaction

DEFF Research Database (Denmark)

Malacrida, Paolo

This thesis presents the development and characterization of a new class of Pt alloys for catalyzing the Oxygen Reduction Reaction (ORR), in perspective of a future substitution of traditional Pt-based catalysts at the cathode of Polymer Electrolyte Membrane Fuel Cells (PEMFCs). Focused on spectr....... A number of bimetallic alloys based on Pt and a rare earth, like the Pt-Y system or more recently proposed Pt-lanthanide phases, have been tested and characterized. Polycrystalline Pt5La and Pt5Ce exhibited more than a factor of 3 enhancement in specific activity relative to state......-Y nanoparticles are among the most active ORR catalysts ever reported, although they lose 37 % of this activity after stability test. Similar to the case of polycrystals, after immersion in the acidic electrolyte and testing the active phase consists of a Pt shell surrounding an alloyed core. Also in this case...

Rare earths as a future resource

International Nuclear Information System (INIS)

Cornell, D.H.

1988-01-01

The fourteen rare earth or lanthanide elements have recently emerged as an important natural resource because of the rapidly growing demand in the electronic, chemical and metallurgical industries. The Symposium on rare earth elements as a future resource presented a multidisciplinary review of rare earth chemistry, geology, beneficiation, industrial applications and marketing. Papers by experts in many fields were presented on the following topics: chemical properties of the rare earth elements; the analysis of rare earth elements and minerals; beneficiation and extraction of rare earth elements; economic geochemistry and mineralogy of rare earths; present industrial uses of rare earth elements; the role of rare earth elements in high-temperature superconductors; the technical application of high-temperature superconductors; supply and demand for rare earth products - now and in the future, and the geology of rare earth deposits

The structural basis of the fluorite-related rare earth higher oxides

International Nuclear Information System (INIS)

Kang, Z.C.; Eyring, LeRoy

1996-01-01

In this paper phenomenological structural principles, and rules for their application are advanced for predicting the ideal structures of the higher oxides of the rare earths. These principles allow to establish a generic formula incorporating all known phases, guide the correct modelling of the established structures and demonstrate that structures previously proposed but proven incorrect do not follow the structural principles. They also can be used to predict the structures not yet established for known phases, including polymorphs, and provide rationalization for phases fitting the generic formula that have not yet been found. The structural principles flow naturally from the fluorite substructure characteristic of all established phases. 39 refs., 5 tabs., 16 figs

Optical emission spectrographic analysis of lutetium oxide for rare earth impurities

International Nuclear Information System (INIS)

Chandola, L.C.; Dixit, V.S.

1986-01-01

An optical emission spectrographic (OES) method has been developed for the analysis of high purity lutetium oxide to determine rare earths Er, Tm, Yb and Y. The spectra are excited by a d.c. arc run at 10 A current after mixing the sample with graphite buffer in the weight ratio 1:1. A 1200 grooves/mm grating blazed at 3300 A is used for dispersion and a Kodak SA-1 plate for recording the spectrum. The detection limit is 0.001 per cent for Tm, Yb and Y while it is 0.005 per cent for Er. The relative standard deviation of the method is ± 13.4 per cent. (author)

Photostability of solutions of rare earth chelates in organic solvents and polymers

International Nuclear Information System (INIS)

Karasev, V.E.; Mirochnik, A.G.; Lysun, T.V.; Vovna, V.I.

1990-01-01

Consideration is given to results of comparative study of photochemical properties of rare erath chelate complexes (adducts of rare earth β-diketonates with triphenylphosphine oxide, hexamethylphosphotriamide, phenanthroline) in organic solvents and polymers. Effect of excitation conditions, composition, solvent, nature of ligand and rare earth ion on photolysis rate was investigated. 9 refs.; 2 figs.; 4 tabs

Global recovery process of thorium and rare earths in a nitrate medium

International Nuclear Information System (INIS)

Cailly, F.; Mottot, Y.

1993-01-01

The aqueous solution of thorium and rare earth nitrates, obtained by leaching the ore with nitric acid, is extracted by an organic phosphorous compound (phosphate, phosphonate, phosphinate or phosphine oxide) and a cationic extractant chosen among phosphoric acid di-esters. Extraction of thorium and rare earths is possible even in presence of phosphate ions in the aqueous solution. Thorium and rare earths are separated by liquid-liquid extraction of the organic phase

Comparison of Elemental Mercury Oxidation Across Vanadium and Cerium Based Catalysts in Coal Combustion Flue Gas: Catalytic Performances and Particulate Matter Effects.

Science.gov (United States)

Wan, Qi; Yao, Qiang; Duan, Lei; Li, Xinghua; Zhang, Lei; Hao, Jiming

2018-03-06

This paper discussed the field test results of mercury oxidation activities over vanadium and cerium based catalysts in both coal-fired circulating fluidized bed boiler (CFBB) and chain grate boiler (CGB) flue gases. The characterizations of the catalysts and effects of flue gas components, specifically the particulate matter (PM) species, were also discussed. The catalytic performance results indicated that both catalysts exhibited mercury oxidation preference in CGB flue gas rather than in CFBB flue gas. Flue gas component studies before and after dust removal equipment implied that the mercury oxidation was well related to PM, together with gaseous components such as NO, SO 2 , and NH 3 . Further investigations demonstrated a negative PM concentration-induced effect on the mercury oxidation activity in the flue gases before the dust removal, which was attributed to the surface coverage by the large amount of PM. In addition, the PM concentrations in the flue gases after the dust removal failed in determining the mercury oxidation efficiency, wherein the presence of different chemical species in PM, such as elemental carbon (EC), organic carbon (OC) and alkali (earth) metals (Na, Mg, K, and Ca) in the flue gases dominated the catalytic oxidation of mercury.

Emission Properties, Solubility, Thermodynamic Analysis and NMR Studies of Rare-Earth Complexes with Two Different Phosphine Oxides

Directory of Open Access Journals (Sweden)

Hiroki Iwanaga

2010-07-01

Full Text Available The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs and security media. The thermodynamic properties of Eu(III complexes are correlated with the solubility. Correlations between coordination structures and emission intensity were explained by NMR analysis. The luminous flux of red LED devices with Eu(III complexes is very high (20 mA, 870 m lumen. A new white LED has its largest spectra intensity in the red region and a human look much more vividly under this light.

Electrocatalytic Water Oxidation by a Homogeneous Copper Catalyst Disfavors Single-Site Mechanisms.

Science.gov (United States)

Koepke, Sara J; Light, Kenneth M; VanNatta, Peter E; Wiley, Keaton M; Kieber-Emmons, Matthew T

2017-06-28

Deployment of solar fuels derived from water requires robust oxygen-evolving catalysts made from earth abundant materials. Copper has recently received much attention in this regard. Mechanistic parallels between Cu and single-site Ru/Ir/Mn water oxidation catalysts, including intermediacy of terminal Cu oxo/oxyl species, are prevalent in the literature; however, intermediacy of late transition metal oxo species would be remarkable given the high d-electron count would fill antibonding orbitals, making these species high in energy. This may suggest alternate pathways are at work in copper-based water oxidation. This report characterizes a dinuclear copper water oxidation catalyst, {[(L)Cu(II)] 2 -(μ-OH) 2 }(OTf) 2 (L = Me 2 TMPA = bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine) in which water oxidation proceeds with high Faradaic efficiency (>90%) and moderate rates (33 s -1 at ∼1 V overpotential, pH 12.5). A large kinetic isotope effect (k H /k D = 20) suggests proton coupled electron transfer in the initial oxidation as the rate-determining step. This species partially dissociates in aqueous solution at pH 12.5 to generate a mononuclear {[(L)Cu(II)(OH)]} + adduct (K eq = 0.0041). Calculations that reproduce the experimental findings reveal that oxidation of either the mononuclear or dinuclear species results in a common dinuclear intermediate, {[LCu(III)] 2 -(μ-O) 2 } 2+ , which avoids formation of terminal Cu(IV)═O/Cu(III)-O • intermediates. Calculations further reveal that both intermolecular water nucleophilic attack and redox isomerization of {[LCu(III)] 2 -(μ-O) 2 } 2+ are energetically accessible pathways for O-O bond formation. The consequences of these findings are discussed in relation to differences in water oxidation pathways between Cu catalysts and catalysts based on Ru, Ir, and Mn.

Development of a methodology for the separation of europium and samarium from a mixture of rare earth oxides by electroreduction/ precipitation

International Nuclear Information System (INIS)

Chepcanoff, Vera

2006-01-01

The rare earths (RE) were first used in 1903, when Welsbach developed a lighter that is still used today. Nowadays, the RE are employed in many different fields, as in the production of super-alloys , as catalysts for petroleum industry, in the manufacture of non-ferrous alloys, color television tubes, x-ray screens, special glasses, ceramics, computer industries, nuclear medicine, lasers, pigments, etc., moving, in the last decade , a market of US$ 2 billions per year. Due to their similar properties, the RE elements are very difficult to separate, requiring complex processes, what make the products very expensive. Elements like Eu and Sm, which contents in the minerals are low (0.05% and 2.0%, respectively, in monazite) are extremely expensive, but their field of application justifies the research for looking for other processes, more simple and/or more effective. Trivalent state is a characteristic of all RE, but some of them presents oxidation state +2, like Ce, Eu, Sm and Yb. In the case of Eu and Sm, the focus of the present work, the divalent state is achieved by electro-reduction in the potentials -0.65 and -1.55 (SCE), respectively. This makes possible the separation of these elements from the other rare earths and from each other. Thus, making use of this characteristic, a process for the individual separation of Eu and Sm in (NH 4 ) 2 SO 4 solution by electro-reduction/precipitation is proposed, where Sm is first separated from the solution as sulfate, and Eu, that remains in the solution, is precipitated after the decrease of temperature and potential applied. The process developed from a synthetic Eu and Sm solution was applied to a mixture of semi-heavy RE oxide, produced at IPEN-CNEN/SP, obtaining the separation of Sm. This product was analyzed by spectrophotometry, showing high purity. (author)

Radiochemical studies in chemical separation and spectrographic determination of rare earths in thorium oxide matrix (Preprint No. RA.06)

International Nuclear Information System (INIS)

Adya, V.C.; Dhawale, B.A.; Rajeshwari, B.; Bangia, T.R.; Sastry, M.D.

1989-01-01

A chemical separation procedure was standardised for the separation of traces of rare earths from ThO 2 matrix using HDEHP (Di 2-ethyl hexyl phosphoric acid). The studies were carried out using both nitric acid and hydrochloric acid medium in different concentrations. The extraction studies were also carried out using radioactive isotopes of rare earths viz. 141 Ce, 152-154 Eu, 153 Gd, 170 Tm etc. The extraction was effective in both media. In 0.1 M HDEHP/xylene and 3 M HNO 3 , Ce was partially extracted into organic phase. So HCl/xylene medium was chosen for extraction purposes. The recovery was confirmed by both gamma counting and emission spectropgraphic method. It was found to be quantitative within experimental error. The separation procedure development here was used for determination of rare earths in thorium oxide matrix by emission spectrographic method. (author)

Microwave-assisted Extraction of Rare Earth Elements from Petroleum Refining Catalysts and Ambient Fine Aerosols Prior to Inductively Coupled Plasma - Mass Spectrometry

Science.gov (United States)

Mittlefehldt, David W.; Kulkarni, Pranav; Chellam, Shankar

2006-01-01

In the absence of a certified reference material, a robust microwave-assisted acid digestion procedure followed by inductively coupled plasma - mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM2.5). High temperature (200 C), high pressure (200 psig), acid digestion (HNO3, HF, and H3BO3) with 20 minute dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst, and PM2.5. This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb, and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy, and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using 115In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu, and Dy in ambient PM2.5 in an industrial area of Houston, TX.

Microwave-assisted extraction of rare earth elements from petroleum refining catalysts and ambient fine aerosols prior to inductively coupled plasma-mass spectrometry

International Nuclear Information System (INIS)

Kulkarni, Pranav; Chellam, Shankararaman; Mittlefehldt, David W.

2007-01-01

A robust microwave-assisted acid digestion procedure followed by inductively coupled plasma-mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM 2.5 ). High temperature (200 deg. C), high pressure (200 psig), acid digestion (HNO 3 , HF and H 3 BO 3 ) with 20 min dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst and PM 2.5 . This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using 115 In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu and Dy in ambient PM 2.5 in an industrial area of Houston, TX

Cerium and rare earth separation process

International Nuclear Information System (INIS)

Martin, M.; Rollat, M.

1986-01-01

An aqueous solution containing cerium III and rare earths is oxidized in the anodic compartment of an electrolytic cell, cerium IV is extracted by an organic solvent, the organic phase containing Ce IV is reduced in the catodic compartment of the same electrolytic cell and cerium III is extracted in a nitric aqueous phase [fr

Oil-refinery and automotive emissions of rare earth elements

International Nuclear Information System (INIS)

Kitto, M.E.; Gordon, G.E.; Anderson, D.L.; Olmez, I.

1991-01-01

The concentration pattern of rare-earth elements (REEs) in emissions from oil refineries and newer-model automobiles shows a distortion from the crustal abundance pattern. The REEs arise from the zeolite cracking catalysts used in petroleum refining and emission-control substrates used in automobile catalytic converters, respectively. Ten petroleum cracking catalysts from four countries and 12 catalytic converters from five automobile manufacturers were characterized for their REE content. The cracking catalysts are highly enriched in light REEs, whereas the automobile catalysts are enriched primarily in Ce. Incorporation of zeolite catalysts into refined oil provides new atmospheric elemental signatures for tracing emissions from refineries and oil-fired power plants on a regional scale. Though both have enhanced La/REE ratios, emissions from these two sources can be distinguished by their La/V ratios. Although REE demand by the petroleum industry has dropped considerably in recent years, automobile catalytic converters containing REEs are expected to increase dramatically as more stringent emission regulations are adopted in Europe, Japan and the US

Rare Earth Polyoxometalates.

Science.gov (United States)

Boskovic, Colette

2017-09-19

Longstanding and important applications make use of the chemical and physical properties of both rare earth metals and polyoxometalates of early transition metals. The catalytic, optical, and magnetic features of rare earth metal ions are well-known, as are the reversible multielectron redox and photoredox capabilities of polyoxomolybdates and polyoxotungstates. The combination of rare earth ions and polyoxometalates in discrete molecules and coordination polymers is of interest for the unique combination of chemical and physical properties that can arise. This Account surveys our efforts to synthesize and investigate compounds with rare earth ions and polyoxometalates (RE-POMs), sometimes with carboxylate-based organic coligands. Our general synthetic approach is "bottom-up", which affords well-defined nanoscale molecules, typically in crystalline form and amenable to single-crystal X-ray diffraction for structure determination. Our particular focus is on elucidation of the physical properties conferred by the different structural components with a view to ultimately being able to tune these properties chemically. For this purpose, we employ a variety of spectroscopic, magnetochemical, electrochemical, and scattering techniques in concert with theoretical modeling and computation. Studies of RE-POM single-molecule magnets (SMMs) have utilized magnetic susceptibility, inelastic neutron scattering, and ab initio calculations. These investigations have allowed characterization of the crystal field splitting of the rare earth(III) ions that is responsible for the SMM properties of slow magnetic relaxation and magnetization quantum tunneling. Such SMMs are promising for applications in quantum computing and molecular spintronics. Photophysical measurements of a family of hybrid RE-POMs with organic ligands have afforded insights into sensitization of Tb(III) and Eu(III) emission through both organic and polyoxometalate chromophores in the same molecule. Detailed

Calcium-based mixed oxide catalysts for methanolysis of Jatropha curcas oil to biodiesel

International Nuclear Information System (INIS)

Taufiq-Yap, Y.H.; Lee, H.V.; Hussein, M.Z.; Yunus, R.

2011-01-01

Calcium-based mixed oxides catalysts (CaMgO and CaZnO) have been investigated for the transesterification of Jatropha curcas oil (JCO) with methanol, in order to evaluate their potential as heterogeneous catalysts for biodiesel production. Both CaMgO and CaZnO catalysts were prepared by coprecipitation method of the corresponding mixed metal nitrate solution in the presence of a soluble carbonate salt at ∼ pH 8-9. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed desorption of CO 2 (CO 2 -TPD), scanning electron microscopy (SEM) and N 2 adsorption (BET). The conversion of JCO by CaMgO and CaZnO were studied and compared with calcium oxide (CaO), magnesium oxide (MgO) and zinc oxide (ZnO) catalysts. Both CaMgO and CaZnO catalysts showed high activity as CaO and were easily separated from the product. CaMgO was found more active than CaZnO in the transesterification of JCO with methanol. Under the suitable transesterification conditions at 338 K (catalyst amount = 4 wt. %, methanol/oil molar ratio = 15, reaction time = 6 h), the JCO conversion of more than 80% can be achieved over CaMgO and CaZnO catalysts. Even though CaO gave the highest activity, the conversion of JCO decreased significantly after reused for forth run whereas the conversion was only slightly lowered for CaMgO and CaZnO after sixth run.

Ultrafast Transient Absorption Spectroscopy of Polymer-Based Organophotoredox Catalysts Mimicking Transition-Metal Complexes

Science.gov (United States)

Jamhawi, Abdelqader; Paul, Anam C.; Smith, Justin D.; Handa, Sachin; Liu, Jinjun

2017-06-01

Transition-metal complexes of rare earth metals including ruthenium and iridium are most commonly employed as visible-light photocatalysts. Despite their highly important and broad applications, they have many disadvantages including high cost associated with low abundance in earth crust, potential toxicity, requirement of specialized ligands for desired activity, and difficulty in recycling of metal contents as well as associated ligands. Polymer-based organophotoredox catalysts are promising alternatives and possess unique advantages such as easier synthesis from inexpensive starting material, longer excited state life time, broad range of activity, sustainability, and recyclability. In this research talk, time-resolved photoluminescence and femtosecond transient absorption (TA) spectroscopy measurements of three novel polymer-based organophotoredox catalysts will be presented. By our synthetic team, their catalytic activity has been proven in some highly valuable chemical transformations, that otherwise require transition metal complexes. Time-resolved spectroscopic investigations have demonstrated that photoinduced processes in these catalysts are similar to the transition metal complexes. Especially, intramolecular vibrational relaxation, internal conversion, and intersystem crossing from the S1 state to the T1 state all occur on a sub-picosecond timescale. The long lifetime of the T1 state ( 2-3 microsecond) renders these polymers potent oxidizing and reducing agents. A spectroscopic and kinetic model has been developed for global fitting of TA spectra in both the frequency and time domains. Implication of the current ultrafast spectroscopy studies of these novel molecules to their roles in photocatalysis will be discussed.

Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

Science.gov (United States)

Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

2015-07-21

The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven

The Chinese Society of Rare Earth is Studying The Feasibility of Marketing Rare Earth Futures

Institute of Scientific and Technical Information of China (English)

2015-01-01

Lin Donglu,secretary-general of the Chinese Society of Rare Earth recently said,the Chinese Society of Rare Earth undertook the research on subject of the National Social Science Fund Foundation on the reform of Chinese rare earth trading pricing mechanism on promoting RMB globalization,and is focusing on studying the feasibility of marketing rare earth futures variety.

Yttrium aluminum garnet (YAG) obtained by rare-earth mixed oxide (RE2O3)

International Nuclear Information System (INIS)

Castro, D.F.; Daguano, J.K.M.F.; Rodrigues Junior, D.; Suzuki, P.A.; Silva, O.M.M.

2010-01-01

In this work, the substitution of commercial Y 2 O 3 by a rare earth mixed oxide, RE 2 O 3 , to form Yttrium aluminum Garnet-Y 3 Al 5 O 12 , was investigated. Al 2 O 3 :Y 2 O 3 and Al 2 O 3 :RE 2 O 3 powder-mixtures, in a molar ratio of 60:40, were milled and subsequently cold uniaxially-pressed. Compacts were sintered at 1000, 1400 or 1600 deg C, for 120 minutes. RE 2 O 3 oxide was characterized by high-resolution synchrotron X-ray diffraction (HRXRD) and compared to Y 2 O 3 . X-ray diffraction pattern of the RE 2 O 3 indicates a true solid solution formation. Rietveld refinement of the sintered YAG and (RE)AG reveled a similar crystal structure to the YAGs obtained by the use of Al 2 O 3 -Y 2 O 3 or Al 2 O 3 -RE 2 O 3 respectively. Microstructural analysis of both, YAG or (RE)AG, revealed similar grain sizes of about 2.5 μm besides mechanical properties, with hardness of 400HV and fracture toughness of 3.8MPa.m1/2. It could be, thus, demonstrated that pure Y 2 O 3 can be substituted by the rare-earth solid solution, RE 2 O 3 , in the formation YAGs, presenting similar microstructural and mechanical properties. (author)

Influence of Catalyst Acid/Base Properties in Acrolein Production by Oxidative Coupling of Ethanol and Methanol.

Science.gov (United States)

Lilić, Aleksandra; Bennici, Simona; Devaux, Jean-François; Dubois, Jean-Luc; Auroux, Aline

2017-05-09

Oxidative coupling of methanol and ethanol represents a new route to produce acrolein. In this work, the overall reaction was decoupled in two steps, the oxidation and the aldolization, by using two consecutive reactors to investigate the role of the acid/base properties of silica-supported oxide catalysts. The oxidation of a mixture of methanol and ethanol to formaldehyde and acetaldehyde was performed over a FeMoO x catalyst, and then the product mixture was transferred without intermediate separation to a second reactor, in which the aldol condensation and dehydration to acrolein were performed over the supported oxides. The impact of the acid/base properties on the selectivity towards acrolein was investigated under oxidizing conditions for the first time. The acid/base properties of the catalysts were investigated by NH 3 -, SO 2 -, and methanol-adsorption microcalorimetry. A MgO/SiO 2 catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Potential rare-earth modified CeO{sub 2} catalysts for soot oxidation. Part III. Effect of dopant loading and calcination temperature on catalytic activity with O{sub 2} and NO + O{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Krishna, K.; Bueno-Lopez, A.; Makkee, M.; Moulijn, J.A. [Catalysis Engineering, DelftChemTech, Delft University of Technology, Julianalaan 136, NL 2628 BL Delft (Netherlands)

2007-09-26

CeO{sub 2} and CeReO{sub xy} catalysts are prepared by the calcination at different temperatures (y = 500-1000 C) and having a different composition (Re = La{sup 3+} or Pr{sup 3+/4+}{sub ,} 0-90 wt.%). The catalysts are characterised by XRD, H{sub 2}-TPR, Raman, and BET surface area. The soot oxidation is studied with O{sub 2} and NO + O{sub 2} in the tight and loose contact conditions, respectively. CeO{sub 2} sinters between 800-900 C due to a grain growth, leading to an increased crystallite size and a decreased BET surface area. La{sup 3+} or Pr{sup 3+/4+} hinders the grain growth of CeO{sub 2} and, thereby, improving the surface catalytic properties. Using O{sub 2} as an oxidant, an improved soot oxidation is observed over CeLaO{sub xy} and CePrO{sub xy} in the whole dopant weight loading and calcination temperature range studied, compared with CeO{sub 2}. Using NO + O{sub 2}, the soot conversion decreased over CeLaO{sub xy} catalysts calcined below 800 C compared with the soot oxidation over CeO{sub 2y}. CePrO{sub xy}, on the other hand, showed a superior soot oxidation activity in the whole composition and calcination temperature range using NO + O{sub 2}. The improvement in the soot oxidation activity over the various catalysts with O{sub 2} can be explained based on an improvement in the external surface area. The superior soot oxidation activity of CePrO{sub xy} with NO + O{sub 2} is explained by the changes in the redox properties of the catalyst as well as surface area. CePrO{sub xy}, having 50 wt.% of dopant, is found to be the best catalyst due to synergism between cerium and praseodymium compared to pure components. NO into NO{sub 2} oxidation activity, that determines soot oxidation activity, is improved over all CePrO{sub x} catalysts. (author)

Cobalt oxide-based catalysts deposited by cold plasma for proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Kazimierski, P.; Jozwiak, L.; Sielski, J.; Tyczkowski, J., E-mail: jacek.tyczkowski@p.lodz.pl

2015-11-02

In proton exchange membrane fuel cells (PEMFC), both the anodic hydrogen oxidation reaction and the cathodic oxygen reduction reaction (ORR) require appropriate catalysts. So far, platinum-based catalysts are still the best option for this purpose. However, because these catalysts are too expensive for making commercially viable fuel cells, extensive research over the past decade has focused on developing noble metal-free alternative catalysts. In this paper, an approach based on cobalt oxide films fabricated by plasma-enhanced metal-organic chemical vapor deposition is presented. Such a material can be used to prepare catalysts for ORR in PEMFC. The films containing CoO{sub X} were deposited on a carbon paper thereby forming the electrode. Morphology and atomic composition of the films were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The possibility of their application as the electro-catalyst for ORR in PEMFC was investigated and the electro-catalytic activities were evaluated by the electrochemical measurements and single cell tests. It was found that the fuel cell with Pt as the anode catalyst and CoO{sub X} deposit as the cathode catalyst was characterized by the open circuit voltage of 635 mV, Tafel slope of approx. 130 mV/dec and the maximum power density of 5.3 W/m{sup 2}. - Highlights: • Cobalt oxide catalyst for proton exchange membrane fuel cells was plasma deposited. • The catalyst exhibits activity for the oxygen reduction reaction. • Morphology and atomic composition of the catalyst were determined.

Afganistan and rare earths

Directory of Open Access Journals (Sweden)

Emilian M. Dobrescu

2013-05-01

Full Text Available On our planet, over a quarter of new technologies for the economic production of industrial goods, are using rare earths, which are also called critical minerals and industries that rely on these precious items being worth of an estimated nearly five trillion dollars, or 5 percent of world gross domestic product. In the near future, competition will increase for the control of rare earth minerals embedded in high-tech products. Rare minerals are in the twenty-first century what oil accounted for in the twentieth century and coal in the nineteenth century: the engine of a new industrial revolution. Future energy will be produced increasingly by more sophisticated technological equipment based not just on steel and concrete, but incorporating significant quantities of metals and rare earths. Widespread application of these technologies will result in an exponential increase in demand for such minerals, and what is worrying is that minerals of this type are almost nowhere to be found in Europe and in other industrialized countries in the world, such as U.S. and Japan, but only in some Asian countries, like China and Afghanistan.

Nanoparticular metal oxide/anatase catalysts

DEFF Research Database (Denmark)

2010-01-01

The present invention concerns a method of preparation of nanoparticular metal oxide catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular metal oxide catalyst precursors comprising combustible crystallization seeds upon which...... the catalyst metai oxide is co-precipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step. The present invention also concerns processes wherein the nanoparticular metal oxide catalysts of the invention are used, such as SCR (deNOx) reactions...

Oxidation performance of a Fe-13Cr alloy with additions of rare earth elements

International Nuclear Information System (INIS)

Martinez-Villafane, A.; Chacon-Nava, J.G.; Gaona-Tiburcio, C.; Almeraya-Calderon, F.; Dominguez-Patino, G.; Gonzalez-Rodriguez, J.G.

2003-01-01

The influence of rare earth elements (REE's) i.e. Neodymium (Nd) and Praseodymium (Pr) on the oxidation behavior of a Fe-13Cr alloy has been studied, and its role on the oxidation rate and oxide morphology and formation is discussed. Specimens were isothermally oxidized in oxygen at 800 deg. C for 24 h. It was found that a small addition (≤0.03 wt.%) of either Nd or Pr, reduced the oxidation rate of the Fe-13Cr base alloy. Moreover, the simultaneous addition of both elements to the alloy produced a dramatic reduction in the oxidation kinetics. Analysis by scanning electronic microscope (SEM) revealed that the morphology of oxides formed on Fe-13Cr specimens with and without REE's specimens was very different. In fact, a fine-grained oxide morphology was observed for alloys with REE's addition. For these alloys only, chromium enrichment at the metal/scale interface was observed. From transmission electronic microscope (TEM) analysis, it was found the following: at the early stages of oxide formation, after 0.25 h, Cr 2 O 3 , Fe 3 O 4 , α-Fe 2 O 3 and γ-Fe 2 O 3 were formed; at 6 h, Cr 2 O 3 , FeCr 2 O 4 and α-Fe 2 O 3 were identified and, for exposure times greater than 6 h, Cr 2 O 3 , α-Fe 2 O 3 and a spinel which was presumably transformed into a solid solution (Fe 2 O 3 ·Cr 2 O 3 ) were found

Rare earths and actinides

International Nuclear Information System (INIS)

Coqblin, B.

1982-01-01

This paper reviews the different properties of rare-earths and actinides, either as pure metals or as in alloys or compounds. Three different cases are considered: (i) First, in the case of 'normal' rare-earths which are characterized by a valence of 3, we discuss essentially the magnetic ordering, the coexistence between superconductivity and magnetism and the properties of amorphous rare-earth systems. (ii) Second, in the case of 'anomalous' rare-earths, we distinguish between either 'intermediate-valence' systems or 'Kondo' systems. Special emphasis is given to the problems of the 'Kondo lattice' (for compounds such as CeAl 2 ,CeAl 3 or CeB 6 ) or the 'Anderson lattice' (for compounds such as TmSe). The problem of neutron diffraction in these systems is also discussed. (iii) Third, in the case of actinides, we can separate between the d-f hybridized and almost magnetic metals at the beginning of the series and the rare-earth like the metals after americium. (orig.)

Modelling of the partial oxidation of {alpha}, {beta}-unsaturated aldehydes on Mo-V-oxides based catalysts

Energy Technology Data Exchange (ETDEWEB)

Boehnke, H.; Petzoldt, J.C.; Stein, B.; Weimer, C.; Gaube, J.W. [Technische Univ. Darmstadt (Germany). Inst. fuer Chemische Technologie

1998-12-31

A kinetic model based on the Mars-van Krevelen mechanism that allows to describe the microkinetics of the heterogeneously catalysed partial oxidation of {alpha}, {beta}-unsaturated aldehydes is presented. This conversion is represented by a network, composed of the oxidation of the {alpha}, {beta}-unsaturated aldehyde towards the {alpha}, {beta}-unsaturated carboxylic acid and the consecutive oxidation of the acid as well as the parallel reaction of the aldehyde to products of deeper oxidation. The reaction steps of aldehyde respectively acid oxidation and catalyst reoxidation have been investigated separately in transient experiments. The combination of steady state and transient experiments has led to an improved understanding of the interaction of the catalyst with the aldehyde and the carboxylic acids as well as to a support of the kinetic model assumptions. (orig.)

Safety aspects in rare earths recovery

International Nuclear Information System (INIS)

Bhattacharya, R.

2014-01-01

Recovery of rare earths involves mining of beach sands, mineral separation to obtain monazite and its chemical processing to obtain rare earth composites. The composites are then subjected to further chemical treatment to obtain individual rare earths. Although the separated out rare earths are not radioactive, the process for recovery of rare earths involve both radiological as well as conventional hazards. This paper highlights the safety aspects in the mining, mineral separation and chemical processing of monazite to obtain rare earths

Magnetic Partitioning Nanofluid for Rare Earth Extraction from Geothermal Fluids

Energy Technology Data Exchange (ETDEWEB)

McGrail, Bernard P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thallapally, Praveen K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Liu, Jian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nune, Satish K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2017-08-21

Rare earth metals are critical materials in a wide variety of applications in generating and storing renewable energy and in designing more energy efficient devices. Extracting rare earth metals from geothermal brines is a very challenging problem due to the low concentrations of these elements and engineering challenges with traditional chemical separations methods involving packed sorbent beds or membranes that would impede large volumetric flow rates of geothermal fluids transitioning through the plant. We are demonstrating a simple and highly cost-effective nanofluid-based method for extracting rare earth metals from geothermal brines. Core-shell composite nanoparticles are produced that contain a magnetic iron oxide core surrounded by a shell made of silica or metal-organic framework (MOF) sorbent functionalized with chelating ligands selective for the rare earth elements. By introducing the nanoparticles at low concentration (≈0.05 wt%) into the geothermal brine after it passes through the plant heat exchanger, the brine is exposed to a very high concentration of chelating sites on the nanoparticles without need to pass through a large and costly traditional packed bed or membrane system where pressure drop and parasitic pumping power losses are significant issues. Instead, after a short residence time flowing with the brine, the particles are effectively separated out with an electromagnet and standard extraction methods are then applied to strip the rare earth metals from the nanoparticles, which are then recycled back to the geothermal plant. Recovery efficiency for the rare earths at ppm level has now been measured for both silica and MOF sorbents functionalized with a variety of chelating ligands. A detailed preliminary techno-economic performance analysis of extraction systems using both sorbents showed potential to generate a promising internal rate of return (IRR) up to 20%.

Enzymatic determination of rare earth elements using pyrophosphatases

International Nuclear Information System (INIS)

Shekhovtsova, T.N.; Pirogova, S.V.; Fedorova, O.M.; Dolmanova, I.F.; Bajkov, A.A.

1993-01-01

A highly sensitive(determination limit 8x10 -6 -4x10 -4 μ g/m) and selective enzymatic method for determination of rare earth elements has been developed. The method is based on inhibition action of rare earths on the catalytic activity of pyrophosphates isolated from bakery geast and E.Coli. The mechanism of the rare earth element action, corresponding to competitive inhibition, has been established

Heterobimetallic transition metal/rare earth metal bifunctional catalysis: a Cu/Sm/Schiff base complex for syn-selective catalytic asymmetric nitro-Mannich reaction.

Science.gov (United States)

Handa, Shinya; Gnanadesikan, Vijay; Matsunaga, Shigeki; Shibasaki, Masakatsu

2010-04-07

The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)(2)/Sm(O-iPr)(3)/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)(3), we reoptimized the catalyst preparation method, and a catalyst derived from Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(O-iPr)(13) was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66-99% ee and syn/anti = >20:1-13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm(5)O(O-iPr)(13).

Preparation of Pt Ru/C + rare earths by the method of reduction by alcohol for the electro-oxidation of ethanol

International Nuclear Information System (INIS)

Tusi, M.M.; Rodrigues, R.M.S.; Spinace, E.V.; Oliveira Neto, A.

2010-01-01

PtRu/C electrocatalyst was prepared in a single step, while that PtRu/85%C-15%Ce, PtRu/85%C-15%La, PtRu/85%C-15%Nd and PtRu/85%C-15%Er electrocatalyst were prepared in a two step. In the first step a Carbon Vulcan XC72 + rare earth supports were prepared. In the second step PtRu electrocatalyst were prepared by an alcohol-reduction process using ethylene glycol as solvent and reducing agent and supported on Vulcan XC72 + earth rare. The obtained electrocatalysts were characterized by EDAX, XRD and chronoamperometry. The electro-oxidation of ethanol was studied by chronoamperometry at room temperature. PtRu/85%C- 15%Ce electrocatalyst showed a significant increase of performance for ethanol oxidation compared to PtRu/C electrocatalyst. (author)

MOCVD and ALD of rare earth containing multifunctional materials. From precursor chemistry to thin film deposition and applications

International Nuclear Information System (INIS)

Milanov, Andrian Petrov

2010-01-01

The present thesis deals with the development of metal-organic complexes of rare elements. They should be used as novel precursors for the production of rare earth thin films by metal-organic chemical vapor deposition (MOCVD) and Atomic Layer Deposition (ALD). Within the work two precursor classes were examined, the tris-Malonato-complexes as well as the tris-Guanidinato-complexes of a series of rare earth metals. The latter showed excellent properties regarding to their volatility, their thermal stability, the defined decomposition and high reactivity towards water. They have been successfully used as precursors for the MOCVD of rare earth oxide layers. By using of a gadolinium guanidinate it could also be shown that the rare earth guanidinates are promising precursors for ALD of rare earth oxide and MOCVD of rare earth nitride layers. [de

Monazite upgradation and production of high pure rare earths

International Nuclear Information System (INIS)

Asnani, C.K.; Mohanty, D.; Kumar, S.S.

2014-01-01

Rare earth extraction from monazite and further processing of mixed rare earth chlorides for producing individual high pure rare earths involves a complex flowsheet based on solvent extraction process. Apart from involving multiple extractions, scrubbing and stripping operations, the flowsheet requires optimization of critical parameters such as solvent molarity, solvent saponification level and recycling of product solutions as reflux to ensure preferential upload of required rare earths to generate high purity product. This paper tracks monazite flow from the raw sand feed through to the monazite product and its processing to generate rare earths of internationally acceptable quality

Use of rare earth oxides as tracers to identify sediment source areas for agricultural hillslopes

Directory of Open Access Journals (Sweden)

C. Deasy

2010-11-01

Full Text Available Understanding sediment sources is essential to enable more effective targeting of in-field mitigation approaches to reduce diffuse pollution from agricultural land. In this paper we report on the application of rare earth element oxides to arable soils at hillslope scale in order to determine sediment source areas and their relative importance, using a non-intrusive method of surface spraying. Runoff, sediments and rare earth elements lost from four arable hillslope lengths at a site in the UK with clay soils were monitored from three rainfall events after tracer application. Measured erosion rates were low, reflecting the typical event conditions occurring at the site, and less than 1% of the applied REO tracers were recovered, which is consistent with the results of comparable studies. Tracer recovery at the base of the hillslope was able to indicate the relative importance of different hillslope sediment source areas, which were found to be consistent between events. The principal source of eroded sediments was the upslope area, implying that the wheel tracks were principally conduits for sediment transport, and not highly active sites of erosion. Mitigation treatments for sediment losses from arable hillslopes should therefore focus on methodologies for trapping mobile sediments within wheel track areas through increasing surface roughness or reducing the connectivity of sediment transport processes.

China’s Rare Earths Production Forecasting and Sustainable Development Policy Implications

Directory of Open Access Journals (Sweden)

Xibo Wang

2017-06-01

Full Text Available Because of their unique physical and chemical properties, Rare earth elements (REEs perform important functions in our everyday lives, with use in a range of products. Recently, the study of China’s rare earth elements production has become a hot topic of worldwide interest, because of its dominant position in global rare earth elements supply, and an increasing demand for rare earth elements due to the constant use of rare earth elements in high-tech manufacturing industries. At the same time, as an exhaustible resource, the sustainable development of rare earth elements has received extensive attention. However, most of the study results are based on a qualitative analysis of rare earth elements distribution and production capacity, with few studies using quantitative modeling. To achieve reliable results with more factors being taken into consideration, this paper applies the generic multivariant system dynamics model to forecast China’s rare earth elements production trend and Hubbert peak, using Vensim software based on the Hubbert model. The results show that the peak of China’s rare earth elements production will appear by 2040, and that production will slowly decline afterwards. Based on the results, the paper proposes some policy recommendations for the sustainable development of China’s—and the world’s—rare earth elements market and rare earth-related industries.

A study on dehydration of rare earth chloride hydrate

International Nuclear Information System (INIS)

Cho, Yong Zun; Eun, Hee Chul; Son, Sung Mo; Lee, Tae Kyo; Hwang, Taek Sung

2012-01-01

The dehydration schemes of rare earth (La, Ce, Nd, Pr, Sm. Eu, Gd, Y) chloride hydrates was investigated by using a dehydration apparatus. To prevent the formation of the rare earth oxychlorides, the operation temperature was changed step by step (80→150→230 degree C) based on the TGA (thermo-gravimetric analysis) results of the rare earth chloride hydrates. A vacuum pump and preheated Ar gas were used to effectively remove the evaporated moisture and maintain an inert condition in the dehydration apparatus. The dehydration temperature of the rare earth chloride hydrate was increased when the atomic number of the rare earth nuclide was increased. The content of the moisture in the rare earth chloride hydrate was decreased below 10% in the dehydration apparatus.

Recovery of rare earths from used polishes by chemical vapor transport process

International Nuclear Information System (INIS)

Ozaki, T.; Machida, K.; Adachi, G.

1998-01-01

Full text: Rare earth oxide polishes are widely used in the glass industry because of its mechanical and chemical polishing action. The Japanese glass industry use 2000 tons per year of the polishes, and a large portion of them are thrown away after their polishing lifetime. A dry recovery processes for rare earths from the used polishes have been investigated by using a chemical vapor transport method via the formation of vapor complexes RAl n Cl 3+3n (R = rare earths). A flow type reactor with various temperature gradients was employed for the process. The used polishes were mixed with active carbon, and chlorinated with N 2 + Cl 2 mixture at 1273 K. Aluminium oxide were also chlorinated at lower temperature and the resulting AlCl 3 were introduced to the reactor. The rare earth chlorides and AlCl 3 were converted to the vapor complexes. These were driven along the temperature gradient, decomposed according to the reverse reaction, and regenerated RCl 3 . About 90 % of the used polish were chlorinated after 2 hours. Rare earth chlorides, AlCl 3 , and FeCl 3 were fully transported after 82 hours. The rare earth chlorides were mainly condensed over the temperature range 1263-903 K. On the other hand, AlCl 3 and FeCl 3 were deposited at the temperature range below 413 K. CaCl 2 and SrCl 2 were hardly transported and remained in the residue. When the temperature gradient with the smaller slope was used, mutual separation efficiencies among the rare earths was improved. The highest CeCl 3 purity of 80% was obtained in the process

Rare earth oxyhalogenide base thermoluminescent material

International Nuclear Information System (INIS)

Rabatin, J.G.

1976-01-01

A process is described that consists to expose a thermoluminescent material to ionizing radiations, the material being a rare earth oxyhalogenide with terbium additions, to heat this material up to the emission of visible radiations and to measure the emitted radiations which are proportional to the ionizing radiation dose [fr

Solvent extraction of uranium, thorium, and rare earths with dialkyldithiophosphoric acids

International Nuclear Information System (INIS)

Haiduc, I.; Curtui, M.

1986-01-01

The separation conditions for throium (IV) in the presence of trivalent rare earths was investigated. The distribution ratios (D), extraction effectivity values (E%) and separation factor(S) were calculated for binary systems Th-La, Th-Ce, Th-Pr, Th-Sm. Di-(2-ethyl-hexyl)dithiophosphoric acid (HEhdtp) alone or mixtures of HEhdtp and trioctylphosphoshine oxide (TOPO) can be successfully used for separation of Thorium (IV) and rare earths

Plasma and catalyst for the oxidation of NOx

Science.gov (United States)

Jõgi, Indrek; Erme, Kalev; Levoll, Erik; Raud, Jüri; Stamate, Eugen

2018-03-01

Efficient exhaust gas cleaning from NO x (NO and NO2) by absorption and adsorption based methods requires the oxidation of NO. The application of non-thermal plasma is considered as a promising oxidation method but the oxidation of NO by direct plasma remains limited due to the back-reaction of NO2 to NO mediated by O radicals in plasma. Indirect NO oxidation by plasma produced ozone allows to circumvent the back-reaction and further oxidize NO2 to N2O5 but the slow reaction rate for the latter process limits the efficiency of this process. Present paper gives an overview of the role of metal-oxide catalysts in the improvement of oxidation efficiency for both direct and indirect plasma oxidation of NO x . The plasma produced active oxygen species (O, O3) were shown to play an important role in the reactions taking place on the catalyst surfaces while the exact mechanism and extent of the effect were different for direct and indirect oxidation. In the case of direct plasma oxidation, both short and long lifetime oxygen species could reach the catalyst and participate in the oxidation of NO to NO2. The back-reaction in the plasma phase remained still important factor and limited the effect of catalyst. In the case of indirect oxidation, only ozone could reach the catalyst surface and improve the oxidation of NO2 to N2O5. The effect of catalyst at different experimental conditions was quantitatively described with the aid of simple global chemical kinetic models derived for the NO x oxidation either by plasma or ozone. The models allowed to compare the effect of different catalysts and to analyze the limitations for the efficiency improvement by catalyst.

Complex catalysts from self-repairing ensembles to highly reactive air-based oxidation systems

Science.gov (United States)

Craig L. Hill; Laurent Delannoy; Dean C. Duncan; Ira A. Weinstock; Roman F. Renneke; Richard S. Reiner; Rajai H. Atalla; Jong Woo Han; Daniel A. Hillesheim; Rui Cao; Travis M. Anderson; Nelya M. Okun; Djamaladdin G. Musaev; Yurii V. Geletii

2007-01-01

Progress in four interrelated catalysis research efforts in our laboratory are summarized: (1) catalytic photochemical functionalization of unactivated CeH bonds by polyoxometalates (POMs); (2) self-repairing catalysts; (3) catalysts for air-based oxidations under ambient conditions; and (4) terminal oxo complexes of the late-transition metal elements and their...

Rare earth element recycling from waste nickel-metal hydride batteries.

Science.gov (United States)

Yang, Xiuli; Zhang, Junwei; Fang, Xihui

2014-08-30

With an increase in number of waste nickel-metal hydride batteries, and because of the importance of rare earth elements, the recycling of rare earth elements is becoming increasingly important. In this paper, we investigate the effects of temperature, hydrochloric acid concentration, and leaching time to optimize leaching conditions and determine leach kinetics. The results indicate that an increase in temperature, hydrochloric acid concentration, and leaching time enhance the leaching rate of rare earth elements. A maximum rare earth elements recovery of 95.16% was achieved at optimal leaching conditions of 70°C, solid/liquid ratio of 1:10, 20% hydrochloric acid concentration, -74μm particle size, and 100min leaching time. The experimental data were best fitted by a chemical reaction-controlled model. The activation energy was 43.98kJ/mol and the reaction order for hydrochloric acid concentration was 0.64. The kinetic equation for the leaching process was found to be: 1-(1-x)(1/3)=A/ρr0[HCl](0.64)exp-439,8008.314Tt. After leaching and filtration, by adding saturated oxalic solution to the filtrate, rare earth element oxalates were obtained. After removing impurities by adding ammonia, filtering, washing with dilute hydrochloric acid, and calcining at 810°C, a final product of 99% pure rare earth oxides was obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

Raman scattering of rare earth hexaborides

International Nuclear Information System (INIS)

Ogita, Norio; Hasegawa, Takumi; Udagawa, Masayuki; Iga, Fumitoshi; Kunii, Satoru

2009-01-01

Raman scattering spectra were measured for the rare-earth hexaborides RB 6 (R = Ce, Gd, or Dy). All Raman-active phonons due to B 6 vibrations were observed in the range 600 - 1400 cm -1 . Anomalous peaks were detected below 200 cm -1 , which correspond to vibrations of rare-earth ion excited by second-order Raman scattering process. The intensity and energy of the rare-earth mode decrease with decreasing temperature. This suggests that the rare-earth ion vibrates in a shallow and anharmonic potential due to the boron cage. Using the reported values of mean square displacement of rare-earth ion, we estimated the anharmonic contribution for the rare-earth vibrations.

Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

Energy Technology Data Exchange (ETDEWEB)

Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

2015-09-14

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co₃O₄ or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

Procedure for the separation of cerium from rare earth phosphate mixtures

International Nuclear Information System (INIS)

Richter, H.; Grauss, H.; Schmitt, A.; Schade, H.; Lindeholz, M.; Lorenz, E.; Weickart, J.

1986-01-01

The invention is concerned with a procedure for the separation of cerium from rare earth concentrates originating from the partial neutralization of nitric crude phosphate decomposition solutions without preceding elimination of impurities from the raw material. The rare earth phosphates are treated with an excess of concentrated nitric acid through which the Ce 3+ , contained in the solution, is oxidized to Ce 4+ and precipitated as cerium(IV) phosphate by neutralization with alkalis

Effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel - Part 1

International Nuclear Information System (INIS)

Kim, Soon-Tae; Jeon, Soon-Hyeok; Lee, In-Sung; Park, Yong-Soo

2010-01-01

To elucidate the effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel, a metallographic examination, potentiodynamic and potentiostatic polarization tests, a SEM-EDS and a SAM analysis of inclusion, austenite phase and ferrite phase were conducted. The addition of rare earth metals to the base alloy led to the formation of (Mn, Cr, Si, Al, Ce) oxides and (Mn, Cr, Si, Ce) oxides, which improved the resistance to pitting corrosion and caused a decrease in the preferential interface areas for the initiation of the pitting corrosion.

Rare earth ion controlled crystallization of mica glass-ceramics

International Nuclear Information System (INIS)

Garai, Mrinmoy; Karmakar, Basudeb

2016-01-01

In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO_2, Nd_2O_3, Sm_2O_3 and Gd_2O_3 doped K_2O−MgO−B_2O_3−Al_2O_3−SiO_2−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm"−"3) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T_g) and crystallization temperature (T_c). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg_3(AlSi_3O_1_0)F_2 by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10"−"6/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque fluorophlogopite mica glass-ceramics by single-step heat treatment. • Nanocrystalline glass

Multielement determination of rare earth elements by liquid chromatography/inductively coupled plasma atomic emission spectrometry

International Nuclear Information System (INIS)

Sawatari, Hideyuki; Asano, Takaaki; Hu, Xincheng; Saizuka, Tomoo; Itoh, Akihide; Hirose, Akio; Haraguchi, Hiroki

1995-01-01

The rapid determination of rare earth elements (REEs) has been investigated by an on-line system of high performance liquid chromatography/multichannel inductively coupled plasma atomic emission spectrometry. In the present system, all REEs could be detected simultaneously in a single chromatographic measurement without spectral interferences. Utilizing a cation exchange column and 2-hydroxy-2-methylpropanoic acid aqueous solution as the mobile phase, the detection limits of 0.4-30 ng ml -1 for all REEs were obtained. The system was applied to the determination of REEs in geological standard rock samples and rare earth impurities in high purity rare earth oxides. The REEs in standard rocks could be determined by the present HPLC/ICP-AES system without pretreatment after acid digestion, although the detection limits were not sufficient for the analysis of rare earth oxides. (author)

Mammography with rare earth intensifying screens

International Nuclear Information System (INIS)

Maurer, H.J.; Goos, F.

1987-01-01

Screens basing on rare earth phosphors with suitable films green or blue sensitive may be used in mammography with grids without diagnostic losses. Highest definition will be obtained with medium densities on film. High-speed screens may reduce dose, but definition is poor. Best compromise between speed and high definition may be reached with relative low thickness of phosphor layers. A system of high definition films (Medichrome) and special rare earth screens give best results. (orig.) [de

Rare earth industries: Downstream business

International Nuclear Information System (INIS)

2011-01-01

The value chain of the rare earths business involves mining, extraction, processing, refining and the manufacture of an extensive range of downstream products which find wide applications in such industries including aerospace, consumer electronics, medical, military, automotive, renewable wind and solar energy and telecommunications. In fact the entire gamut of the high-tech industries depends on a sustainable supply of rare earths elements. The explosive demand in mobile phones is an excellent illustration of the massive potential that the rare earths business offers. In a matter of less than 20 years, the number of cell phones worldwide has reached a staggering 5 billion. Soon, going by the report of their growth in sales, the world demand for cell phones may even exceed the global population. Admittedly, the rare earths business does pose certain risks. Top among the risks are the health and safety risks. The mining, extraction and refining of rare earths produce residues and wastes which carry health and safety risks. The residues from the extraction and refining are radioactive, while their effluent waste streams do pose pollution risks to the receiving rivers and waterways. But, as clearly elaborated in a recent report by IAEA experts, there are technologies and systems available to efficiently mitigate such risks. The risks are Rare Earth manageable. However, it is crucial that the risk and waste management procedures are strictly followed and adhered to. This is where effective monitoring and surveillance throughout the life of all such rare earths facilities is crucial. Fortunately, Malaysia's regulatory standards on rare earths follow international standards. In some areas, Malaysia's regulatory regime is even more stringent than the international guidelines. (author)

Production of rare earth polishing powders in Russia

International Nuclear Information System (INIS)

Kosynkin, V.D.; Ivanov, E.N.; Kotrekhov, V.A.; Shtutza, M.G.; Grabko, A.I.

1998-01-01

Full text: Russia is a potent producer of polishing powders made of rare earth material presented as an extensive and well developed base. Considering the reserves, the facilities predisposition and the polishing agent (cerium dioxide) content the chief mineral source is loparite, apatite and monazite. The production of rare earth polishing powders is based on specially developed continuous technological processes, corrosion-proof equipment, ensuring a high and stable production quality. A special attention is paid to the radiation safety of the powders. The initial material for the rare earth polishing powders based on loparite is the fusion cake of rare earth chlorides obtained at that mineral chlorination. The technology of the polishing powder production from the REE fusion cake includes the following stages: dissolution of the REE fusion cake chlorides; - thorough cleaning of the REE fusion cake chlorides from radioactive and non-rare-earth impurities; chemical precipitation of REE carbonates, obtaining middlings with proper material and granulometric composition, thermal treatment of precipitated carbonates followed with the operations of drying and roasting; classification of roasted oxides, obtaining end products - polishing powders. The production of fluorine-containing powders includes the stage of their fluorination after the stage of carbonate precipitation. The stabilizing doping can be introduced both into the middlings during one of the technological process of powders manufacturing and into the end product. Rare earth polishing powders are manufactured in Russia by the Share Holding Company 'Chepetz Mechanical Plant' (ChMP Co.), the city of Glasov. The plant produces a number of polishing materials, such as; polishing powder Optinol, containing at least 50% by mass of cerium dioxide, used in the mass production of optical and other articles; polishing powder Optinol-10 with doping to improve the sedimentary and aggregate stability of the solid phase

Global demand for rare earth resources and strategies for green mining

Energy Technology Data Exchange (ETDEWEB)

Dutta, Tanushree [Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763 (Korea, Republic of); Kim, Ki-Hyun, E-mail: kkim61@hanyang.ac.kr [Department of Civil & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763 (Korea, Republic of); Uchimiya, Minori [USDA-ARS Southern Regional Research Center, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124 (United States); Kwon, Eilhann E. [Department of Environment and Energy, Sejong University, Seoul 05006 (Korea, Republic of); Jeon, Byong-Hun [Department of Natural Resources & Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763 (Korea, Republic of); Deep, Akash [Central Scientific Instruments Organisation (CSIR-CSIO), Sector 30C, Chandigarh 160030 (India); Yun, Seong-Taek [Department of Earth and Environmental Sciences and KU-KIST Green School, Korea University, Seoul 02841 (Korea, Republic of)

2016-10-15

Rare earth elements (REEs) are essential raw materials for emerging renewable energy resources and ‘smart’ electronic devices. Global REE demand is slated to grow at an annual rate of 5% by 2020. This high growth rate will require a steady supply base of REEs in the long run. At present, China is responsible for 85% of global rare earth oxide (REO) production. To overcome this monopolistic supply situation, new strategies and investments are necessary to satisfy domestic supply demands. Concurrently, environmental, economic, and social problems arising from REE mining must be addressed. There is an urgent need to develop efficient REE recycling techniques from end-of-life products, technologies to minimize the amount of REEs required per unit device, and methods to recover them from fly ash or fossil fuel-burning wastes.

Structural, magnetic and electronic properties of rare earth ternary oxides Li Ln(II) 2 Ln(III)O4

International Nuclear Information System (INIS)

Malki, M.

1987-06-01

Properties of a new class of rare earth ternary oxides Li Ln(II) 2 Ln(III)O 4 where Ln(II) is a divalent metal (Sr, Eu) and Ln(III) a trivalent rare earth (Eu, Gd, Dy, Er and Y). These orthorhombic compounds (type Li Eu 3 O 4 ) allow the study of many magnetic phenomena and their evolution in function of the nature of Ln(II) and Ln(III): diamagnetic ions Sr 2+ , Y 3+ ; isotrope magnetic ions: Eu 2+ , Gd 3+ and anisotrope magnetic ions Dy 3+ , Er 3+ . Magnetic and electric properties are obtained by classical techniques and from hyperfine interaction by Moessbauer spectroscopy. The possibility to use several Moessbauer resonance (nuclei Eu 151, Gd 155, Dy 161 and Er 166) completes informations obtained by the macroscopic study [fr

Oxidation of Commercial Petronas Diesel with Tert-Butyl Hydroperoxide Over Poly molybdate Alumina Supported Catalyst Modified With Alkaline Earth Metals

International Nuclear Information System (INIS)

Wan Nazwanie Wan Abdullah; Rusmidah Ali; Wan Azlee Wan Abu Bakar

2016-01-01

Due to strict environmental legislation for ultra-low sulfur diesel fuels, increasing technical and operational challenges are imposed to conventional hydrodesulfurization (HDS) technology. Therefore, catalytic oxidative desulfurization (Cat-ODS) has been suggested to be an alternative method to replace a conventional method which is hydrodesulfurization. In this study, catalytic oxidation of commercial diesel was performed using an oil-soluble oxidant, tert-butyl hydroperoxide (TBHP), over poly molybdate supported on alumina MoO_3-PO_4/ Al_2O_3 catalyst. A commercial Petronas diesel with 440 ppm of total sulfur was employed to evaluate the elimination of sulfur compounds. Besides, the percentage of sulfur removal was measured by (GC-FPD). Alkaline earth metals, such as Calcium (Ca), Barium (Ba) and Strontium (Sr) were introduced on the surface of MoO_3-PO_4/ Al_2O_3. The results showed that the catalytic activity decreased in the order, Ca/ MoO_3-PO_4/ Al_2O_3>Sr/ MoO_3-PO_4/ Al_2O_3> Ba/ MoO_3-PO_4/ Al_2O_3. The Ca/ MoO_3-PO_4/ Al_2O_3 catalyst was characterized by XRD and FESEM. XRD results showed that the best catalyst was highly amorphous while FESEM micrograph illustrated an aggregation and agglomeration of various particle sizes. The catalytic activity of Ca/ MoO_3-PO_4/ Al_2O_3 catalyst with various Ca/ Mo ratios were also studied. When the Ca/ Mo ratio was 15:85, the sulfur removal was the highest (79 %) at 45 degree Celsius, 30 min and O/ S molar ratio 3.0 with solvent = dimethylformamide (DMF), diesel/ solvent ratio = 1.0. (author)

Catalyst for Ammonia Oxidation

DEFF Research Database (Denmark)

2015-01-01

The present invention relates to a bimetallic catalyst for ammonia oxidation, a method for producing a bimetallic catalyst for ammonia oxidation and a method for tuning the catalytic activity of a transition metal. By depositing an overlayer of less catalytic active metal onto a more catalytic...

Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

NARCIS (Netherlands)

Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

2013-01-01

Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

Flotation process of lead-, copper-, uranium-, and rare earth minerals

International Nuclear Information System (INIS)

Broman, P.G.; Kihlstedt, P.G.; Du Rietz, C.

1977-01-01

This invention relates to a flotation process of oxide or sulfide ores containing lead-, copper-, uranium-, and rare earth minerals applicating a new collector. Flotation is in the presence of a tertiary amine

Rare earth industries; Moving Malaysia's Green Economy Forward

International Nuclear Information System (INIS)

2011-08-01

There is a famous saying, Where there is risk, there is opportunity. Rare earths present both health and environmental risks as well as potential economic opportunities. However, the risks are manageable thanks to improved technologies and a better understanding of the implications on health and the environment. This explains why there is a rush by many countries to reopen old mines and increase investment in the production of rare earths concentrate and their high value downstream products. Why is there such a scramble to risk money on rare earths? What have ignited global demand? Where are the opportunities? How are the risks associated with rare earths managed? Can Malaysia benefit from this new growth industry? What should be our strategies? This report, produced by the joint Working Group of the Academy of Sciences Malaysia (ASM) and the Majlis Professor Negara (MPN), discusses the science of rare earths and their business prospects; and proposes some strategic directions for Malaysia. The analysis is based on information culled from various secondary sources as well as the groups engagement with experts from the Rare Earths Society of China. (author)

Rare Earths and Clean Energy: analyzing China's upper hand

International Nuclear Information System (INIS)

Seaman, J.

2010-01-01

An ominous but avoidable resource crunch in the so-called 'rare earth elements' is now threatening the development of a number of key industries from energy to defense to consumer electronics. As key components in the latest generation of technologies, including specialized magnets for windmills and hybrid cars, lasers for range finders and 'smart' munitions, and phosphors for LCD screens, demand for these rare metals is expected to grow rapidly in the years to come. But decades of under-investment in the mining and separation of these elements across the globe has left the industry ill-prepared to meet thi s growing demand. Over the years, only China has recognized the strategic significance of these resources and has succeeded in gaining a near monopoly on production, currently churning out 97% of the world' s rare earth oxides. Faced with problems of its own, and eager to use its resource advantage to master higher levels of value-added production of rare earth-dependent products, China has increasingly limited the rest of the world's access to these raw materials. This only complicates what was already projected to be a problematic resource shortage. This issue demands a higher quality of public debate. Rare earth consuming countries outside of China have only recently become aware of their dependence and started to take stock of the risks. Time is of the essence. Bringing new supplies online to meet growing demand is a long, complicated and risky process but is nevertheless necessary to ensure the development of high tech industries, notably clean energy. Accessible reserves of rare earths do exist outside of China and mitigating the effects of the looming shortage requires opening up these reserves to production. Yet, as the Chinese experience attests, there are substantial risks to the environment associated with mining and separating rare earths. Care must be taken to ensure responsible mining practices across the globe. Longer-term solutions, such as

A study on artificial rare earth (RE2O3) based neutron absorber

International Nuclear Information System (INIS)

KIM, Kyung-O; Kyung KIM, Jong

2015-01-01

A new concept of a neutron absorption material (i.e., an artificial rare earth compound) was introduced for criticality control in a spent fuel storage system. In particular, spent nuclear fuels were considered as a potential source of rare earth elements because the nuclear fission of uranium produces a full range of nuclides. It was also found that an artificial rare earth compound (RE 2 O 3 ) as a High-Level Waste (HLW) was naturally extracted from pyroprocessing technology developed for recovering uranium and transuranic elements (TRU) from spent fuels. In this study, various characteristics (e.g., activity, neutron absorption cross-section) were analyzed for validating the application possibility of this waste compound as a neutron absorption material. As a result, the artificial rare earth compound had a higher neutron absorption probability in the entire energy range, and it can be used for maintaining sub-criticality for more than 40 years on the basis of the neutron absorption capability of Boral™. Therefore, this approach is expected to vastly improve the efficiency of radioactive waste management by simultaneously keeping HLW and spent nuclear fuel in a restricted space. - Highlights: • Quantitative analysis of rare earth elements in PWR spent fuels. • Extraction of artificial rare earth compound using pyroprocessing technology. • Characteristic analysis of artificial rare earth elements. • Performance evaluation of artificial rare earth for criticality control.

Oxidative desulfurization of synthetic diesel using supported catalysts. Part 3. Support effect on vanadium-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Cedeno-Caero, Luis; Gomez-Bernal, Hilda; Fraustro-Cuevas, Adriana; Guerra-Gomez, Hector D.; Cuevas-Garcia, Rogelio [UNICAT, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Cd. Universitaria 04510, Mexico D.F. (Mexico)

2008-04-15

Oxidesulfurization (ODS) of benzothiophenic compounds prevailing in diesel was conducted with hydrogen peroxide in presence of various catalysts, using a model diesel and actual diesel fuel. ODS activities of dibenzothiophenes (DBTs) in hexadecane for a series of V{sub 2}O{sub 5} catalysts supported on alumina, titania, ceria, niobia and silica, were evaluated. Results show that the oxidation activity of DBTs depends on the support used. It was observed that the sulfone yield is not proportional to textural properties or V content. For all catalysts, ODS of benzothiophene (BT), dibenzothiophene (DBT), 4-methyl dibenzothiophene (4-MDBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) decreased in the following order: DBT > 4-MDBT > 4,6-DMDBT > BT. This trend does not depend on the catalyst used or the textural properties of the catalysts and supports. In presence of indole ODS activities diminish, except with catalysts supported on alumina-titania mixed oxide, whereas with V{sub 2}O{sub 5}/TiO{sub 2} catalyst the performance is the highest. ODS of Mexican diesel fuel was carried out in presence of this catalyst and S level was diminished in about 99%. (author)

Chemical nature of catalysts of oxide nanoparticles in environment

Indian Academy of Sciences (India)

Carbon nanostructures (CNS) are often grown using oxide nanoparticles as catalyst in chemical vapour deposition and these oxides are not expected to survive as such during growth. In the present study, the catalysts of cobalt- and nickel oxide-based nanoparticles of sizes varying over a range have been reduced at 575 ...

Uranium-oxide-based catalysts for the destruction of volatile chloro-organic compounds

International Nuclear Information System (INIS)

Hutchings, G.; Heneghan, C.S.; Taylor, S.H.

1996-01-01

The industrial release of hydrocarbons and chlorine-containing organic molecules into the environment continues to attract considerable public concern, which in turn has led to governmental attempts to control such emissions. The challenge is to reduce pollution without stifling economic growth. Chlorine-containing pollutants are known to be particularly stable, and at present the main industrial process for their destruction involves thermal oxidation at 1,000 o C, an expensive process that can lead to the formation of highly toxic by-products such as dioxins and dibenzofurans. Catalytic combustion at lower temperatures could potentially destroy pollutants more efficiently (in terms of energy requirements) and without forming toxic by-products. Current industrial catalysts are based on precious metals that are deactivated rapidly by organochlorine compounds. Here we report that catalysts based on uranium oxide efficiently destroy a range of hydrocarbon and chlorine-containing pollutants, and that these catalysts are resistant to deactivation. We show that benzene, toluene, chlorobutane and chlorobenzene can be destroyed at moderate temperatures ( o C) and industrially relevant flow rates. (Author)

Micromagnetics of rare-earth efficient permanent magnets

Science.gov (United States)

Fischbacher, Johann; Kovacs, Alexander; Gusenbauer, Markus; Oezelt, Harald; Exl, Lukas; Bance, Simon; Schrefl, Thomas

2018-05-01

The development of permanent magnets containing less or no rare-earth elements is linked to profound knowledge of the coercivity mechanism. Prerequisites for a promising permanent magnet material are a high spontaneous magnetization and a sufficiently high magnetic anisotropy. In addition to the intrinsic magnetic properties the microstructure of the magnet plays a significant role in establishing coercivity. The influence of the microstructure on coercivity, remanence, and energy density product can be understood by using micromagnetic simulations. With advances in computer hardware and numerical methods, hysteresis curves of magnets can be computed quickly so that the simulations can readily provide guidance for the development of permanent magnets. The potential of rare-earth reduced and rare-earth free permanent magnets is investigated using micromagnetic simulations. The results show excellent hard magnetic properties can be achieved in grain boundary engineered NdFeB, rare-earth magnets with a ThMn12 structure, Co-based nano-wires, and L10-FeNi provided that the magnet’s microstructure is optimized.

General geochemical properties and abundances of the rare earth elements

International Nuclear Information System (INIS)

Henderson, P.

1984-01-01

This chapter reviews some of the fundamental aspects of rare earth elements (REE) geochemistry and gives data on abundances in the solar system, the bulk Earth and the Earth's crust. It describes the state of knowledge on the partitioning of the REE, especially in igneous rock systems, and cites reference works concerned with the REE. Several chemical properties of REE are discussed (oxidation states; redox conditions; element coordination and ionic radii; element substitution). (Auth.)

Electrostatic tuning of Kondo effect in a rare-earth-doped wide-band-gap oxide

KAUST Repository

Li, Yongfeng; Deng, Rui; Lin, Weinan; Tian, Yufeng; Peng, Haiyang; Yi, Jiabao; Yao, Bin; Wu, Tao

2013-01-01

As a long-lived theme in solid-state physics, the Kondo effect reflects the many-body physics involving the short-range Coulomb interactions between itinerant electrons and localized spins in metallic materials. Here we show that the Kondo effect is present in ZnO, a prototypical wide-band-gap oxide, doped with a rare-earth element (Gd). The localized 4f electrons of Gd ions do not produce remanent magnetism, but interact strongly with the host electrons, giving rise to a saturating resistance upturn and negative magnetoresistance at low temperatures. Furthermore, the Kondo temperature and resistance can be electrostatically modulated using electric-double-layer gating with liquid ionic electrolyte. Our experiments provide the experimental evidence of tunable Kondo effect in ZnO, underscoring the magnetic interactions between localized and itinerant electrons and the emergent transport behaviors in such doped wide-band-gap oxides.

Electrostatic tuning of Kondo effect in a rare-earth-doped wide-band-gap oxide

KAUST Repository

Li, Yongfeng

2013-04-29

As a long-lived theme in solid-state physics, the Kondo effect reflects the many-body physics involving the short-range Coulomb interactions between itinerant electrons and localized spins in metallic materials. Here we show that the Kondo effect is present in ZnO, a prototypical wide-band-gap oxide, doped with a rare-earth element (Gd). The localized 4f electrons of Gd ions do not produce remanent magnetism, but interact strongly with the host electrons, giving rise to a saturating resistance upturn and negative magnetoresistance at low temperatures. Furthermore, the Kondo temperature and resistance can be electrostatically modulated using electric-double-layer gating with liquid ionic electrolyte. Our experiments provide the experimental evidence of tunable Kondo effect in ZnO, underscoring the magnetic interactions between localized and itinerant electrons and the emergent transport behaviors in such doped wide-band-gap oxides.

The determination of the rare earth elements in naturally-occurring materials zy flame spectroscopy

International Nuclear Information System (INIS)

Watts, J.C.

1975-01-01

Because the quantitative collection of the rare-earth elements retains natural abundance ratios, adequate analytical methodology incorporates their individual sensitivities, and tolerates their mutual contamination. To achieve these ends, the sensitivities of 15 rare-earths in flame emission were determined in the unseparated nitrous oxide/acetylene flame, their mutual interference ascertained at practical concentrations, and useful emission lines selected for their determination in natural materials. Sources of atomic emission interference were extraneous in origin. Fe in the determination of Dy and Zr in the determination of Nd. Inter-element interferences of the rare-earth elements were minimal after wavelength selection and reduction of the spectral band width. For comparison, five rare earths were determined by flame AAS. (author)

Rare earth ion controlled crystallization of mica glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Garai, Mrinmoy; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in

2016-09-05

In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO{sub 2}, Nd{sub 2}O{sub 3}, Sm{sub 2}O{sub 3} and Gd{sub 2}O{sub 3} doped K{sub 2}O−MgO−B{sub 2}O{sub 3}−Al{sub 2}O{sub 3}−SiO{sub 2}−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm{sup −3}) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T{sub g}) and crystallization temperature (T{sub c}). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg{sub 3}(AlSi{sub 3}O{sub 10})F{sub 2} by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10{sup −6}/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque

Plasma and catalyst for the oxidation of NOx

DEFF Research Database (Denmark)

Jögi, I.; Erme, K.; Levoll, E.

2017-01-01

The removal of NOx from the exhaust gases requires the oxidation of most abundant NO to NO2 or N2O5. The oxidation can be done by non-thermal plasma but the efficiency is limited due to the back-reaction of NO2 to NO by O radicals. Present contribution investigates the role of catalysts in the im......The removal of NOx from the exhaust gases requires the oxidation of most abundant NO to NO2 or N2O5. The oxidation can be done by non-thermal plasma but the efficiency is limited due to the back-reaction of NO2 to NO by O radicals. Present contribution investigates the role of catalysts...... in the improvement of oxidation efficiency based on the stationary and time-dependent studies of the NOx oxidation at different reactor configurations and experimental conditions. The plasma produced active oxygen species (O, O3) were shown to play an important role in the reactions taking place on the catalyst...... surfaces while the exact mechanism and extent of the effect depended on the reactor configuration. The effect of catalyst at different experimental conditions was quantitatively described with the aid of analytical lumped kinetic models derived for the NOx oxidation when the catalyst was directly...

Oxidation of methyl heterocyclic compounds on vanadium oxide catalysts

International Nuclear Information System (INIS)

Shimanskaya, M.V.; Lejtis, L.A.; Iovel', I.G.; Gol'dberg, Yu.Sh.; Skolmejstere, R.A.; Golender, L.O.

1985-01-01

Data on vapor-phase oxidation of methyl derivatives of thiophene, Δ 2 - thiazo line, pyridine, pyrazine and pyramidine on oxide vanadium-molybdenum catalysts to corresponding heterylaldehydes are generalized. The dependence of catalytic properties of oxide vanadium-molybdenum systems in oxidation reactions of methylheterocyclic compounds on V:Mo ratio in the catalyst is revealed. It is shown that heterocyclic compounds are coordinated by a heteroatom on Lewis centres of V-Mo-O-catalyst primarily with partially reduced vanadium ions

Effect of rare earth elements yttrium and lanthanum on high temperature oxidation resistance of Mo-Si-B alloys

International Nuclear Information System (INIS)

Majumdar, Sanjib

2014-01-01

In the present investigation, 0.2 to 2 at% Y and La alloyed Mo-9Si-8B were consolidated using mechanical alloying followed by spark plasma sintering. Isothermal oxidation studies were conducted in a wide temperature range from 650 to 1300℃. Detailed characterization studies of the oxide scale using SEM, EDS, FIB, TEM reveal the formation of Y x Mo 18 O 32 and 3La 2 O 3 ·MoO 3 oxide phases, respectively, for Y and La-containing alloys reduce the evaporation of MoO 3 . The growth rate of protective silica scale is also enhanced due to faster formation of Y and La rich oxide particles which probably act as nucleation sites for silica. At higher temperatures (at 1100℃), the oxidation behavior of unalloyed and RE-alloyed Mo-9Si-8B are comparable. A transient weight loss followed by a steady state is reached due to protective amorphous silica-rich scale formation beyond 1100℃. Therefore, alloying with rare earth elements provides a broader application temperature window for silicide based materials starting from 750℃ to 1300℃

Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts

Science.gov (United States)

MURAHASHI, Shun-Ichi

2011-01-01

This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. PMID:21558760

Processing of Pakistani carbonatites for separation of cerium from adjacent rare earths

International Nuclear Information System (INIS)

Akram, M.; Qazi, N.K.; Khan, M.F.; Hasan, G.H.; Ahmed, N.; Chughtai, N.A.

2003-01-01

Carbonatite rock of Loe-Shilman area in North Western Frontier Province (NWFP) of Pakistan contains rare earth elements. This rock was upgraded in terms of its rare earths content from 2,000 ppm to 10,000 ppm rare earths oxide (REO) by crushing, calcination at 1000 deg. C for 3 hrs and cold leaching with 2% HCl for 1 hr. 80% to 95% of rare earths present in carbonatite powder were digested in nitric acid at 60 deg. C after 2 hrs stirring. Tributyl phosphate (TBP), diluted with dodecane, was used as extractant for extraction of rare earths. Since extraction is dependent on pH of the aqueous feed solution, the role of nitrate ions concentration in the solvent extraction of rare earth elements (REEs) was studied. It was observed that extraction of REEs was maximum at pH 1.1. The solvent had been unable to extract REEs from high acidic feed solutions. Solvents of different molarities were also tried against aqueous phase of pH 1.1. Studies showed a poor gain at 0 M and 0.5 M of organic phase while no gain observed beyond 2 molar solvent. 1 M organic phase gave maximum yield of rare earths salt, Ln(OH)/sub 3/, when stripped solution precipitated with ammonium hydroxide solution. It was also observed that if aqueous solution of 3.0 N was treated with blank solvent (i.e. Molarity = 0), it gave almost the same result. It was further established that optimum quantity of caging agent, Al(NO/sub 3/)/sub 3/-9H/sub 2/O added to aqueous solution prior to pH adjustment (i.e. 10 gm/100 gm powder dissolved) suppressed fluoride ions (F') which were hindering the extraction of rare earths. This improved the extraction efficiency of desired elements. To optimise the process parameters like solvent dilution, aqueous to organic ratio and extraction/stripping times, a' series of experiments were performed. Recovery for the desired elements had been between 78% to 86%. The optimum extraction parameters were found to be TBP concentration 40% (v/v) for aqueous to organic ratio 1:5 and 50

Catalytic wet air oxidation of 2-chlorophenol over sewage sludge-derived carbon-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Tu, Yuting [Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON), CNRS – Université Claude Bernard Lyon 1, 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex (France); School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Xiong, Ya; Tian, Shuanghong [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275 (China); Kong, Lingjun [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Descorme, Claude, E-mail: claude.descorme@ircelyon.univ-lyon1.fr [Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON), CNRS – Université Claude Bernard Lyon 1, 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex (France)

2014-07-15

Highlights: • A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared. • FeSC exhibited high catalytic activity in the wet air oxidation of 2-chlorophenol. • A strong correlation was observed between the 2-CP conversion, the iron leaching and the pH. • Using an acetate buffer, the iron leaching was suppressed while keeping some catalytic activity. • A simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst. - Abstract: A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared and used in the Catalytic Wet Air Oxidation (CWAO) of 2-chlorophenol (2-CP). The catalysts were characterized in terms of elemental composition, surface area, pH{sub PZC}, XRD and SEM. The performances of the FeSC catalyst in the CWAO of 2-CP was assessed in a batch reactor operated at 120 °C under 0.9 MPa oxygen partial pressure. Complete decomposition of 2-CP was achieved within 5 h and 90% Total Organic Carbon (TOC) was removed after 24 h of reaction. Quite a straight correlation was observed between the 2-CP conversion, the amount of iron leached in solution and the pH of the reaction mixture at a given reaction time, indicating a strong predominance of the homogeneous catalysis contribution. The iron leaching could be efficiently prevented when the pH of the solution was maintained at values higher than 4.5, while the catalytic activity was only slightly reduced. Upon four successive batch CWAO experiments, using the same FeSC catalyst recovered by filtration after pH adjustment, only a very minor catalyst deactivation was observed. Finally, based on all the identified intermediates, a simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst.

Rare-Earth Oxide Ion (Tm3+, Ho3+, and U3+) Doped Glasses and Fibres for 1.8 to 4 Micrometer Coherent and Broadband Sources

Science.gov (United States)

2006-07-24

oxide ( TeO2 ) , fluorine- containing silicate (SiOF2) and germanate (GeOF2) glass hosts for each dopant by characterising the spectroscopic properties...Earth Oxide Ion (Tm3+, Ho3+, And U3+) Doped Glasses And Fibres For 1.8 To 4 Micrometer Coherent And Broadband Sources 5c. PROGRAM ELEMENT NUMBER 5d...Rare-earth oxide ion (Tm3+, Ho3+, and U3+) doped glasses and fibres for 1.8 to 4 micrometer coherent and broadband sources Report prepared

Nanocarbons as catalyst for selective oxidation of acrolein to acrylic acid

Energy Technology Data Exchange (ETDEWEB)

Frank, B.; Blume, R.; Rinaldi, A.; Trunschke, A.; Schloegl, R. [Fritz Haber Institute of the Max Planck Society, Berlin (Germany). Dept. of Inorganic Chemistry

2011-07-01

Selective oxidations are key steps of industrial oil and gas processing for the synthesis of high-value chemicals. Mixed metal oxides based on redox active V or Mo are frequently used for oxidative C-H bond activation. However, multiple processes require precious metals or suffer from low product selectivity demanding an ongoing search for cost-effective alternatives. Recently, the nanostructured carbon was reported to catalyze the metal-free selective alkane activation by oxidative dehydrogenation (ODH). Electron-rich surface carbonyls coordinate this reaction and mimic the active oxygen species in metal oxide catalysts. Here we show that the graphitic carbon, beyond ODH, has the potential to selectively mediate the insertion of an oxygen atom into an organic molecule, i.e., acrolein. Multi-step atom rearrangements considerably exceed the mechanistic complexity of hydrogen abstraction and were so far believed to be the exclusive domain of metal (oxide) catalysis. In the carbon catalyzed process, the nucleophilic oxygen atoms terminating the graphite (0001) surface abstract the formyl hydrogen and the activated aldehyde gets oxidized by epoxide-type mobile oxygen, thus the sp{sup 2} carbon acts as a bifunctional catalyst. Substantial similarities between the metal oxide- and carbon-catalyzed reactions could be identified. Our results shed light on a rarely known facet of applications of nanostructured carbon materials being decorated with diverse oxygen functionalities to coordinate complex catalytic processes. We could successfully transfer the results obtained from the graphite model to carbon nanotubes (CNTs) providing a higher surface area, defect density, and intrinsic activity, to substantially increase the reactivity per catalyst volume. Indeed, low dimensional nanostructured carbon is a highly flexible and robust material which can be modified in a multiple manner to optimize its properties with respect to the intended application. The exploration of

Calcium-borosilicate glass-ceramics wasteforms to immobilize rare-earth oxide wastes from pyro-processing

Energy Technology Data Exchange (ETDEWEB)

Kim, Miae [Department of Materials Science and Engineering and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784 (Korea, Republic of); Heo, Jong, E-mail: jheo@postech.ac.kr [Department of Materials Science and Engineering and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 790-784 (Korea, Republic of); Department of Materials Engineering, Adama Science and Technology University (ASTU), PO Box 1888, Adama (Ethiopia)

2015-12-15

Glass-ceramics containing calcium neodymium(cerium) oxide silicate [Ca{sub 2}Nd{sub 8-x}Ce{sub x}(SiO{sub 4}){sub 6}O{sub 2}] crystals were fabricated for the immobilization of radioactive wastes that contain large portions of rare-earth ions. Controlled crystallization of alkali borosilicate glasses by heating at T ≥ 750 °C for 3 h formed hexagonal Ca–silicate crystals. Maximum lanthanide oxide waste loading was >26.8 wt.%. Ce and Nd ions were highly partitioned inside Ca–silicate crystals compared to the glass matrix; the rare-earth wastes are efficiently immobilized inside the crystalline phases. The concentrations of Ce and Nd ions released in a material characterization center-type 1 test were below the detection limit (0.1 ppb) of inductively coupled plasma mass spectroscopy. Normalized release values performed by a product consistency test were 2.64·10{sup −6} g m{sup −2} for Ce ion and 2.19·10{sup −6} g m{sup −2} for Nd ion. Results suggest that glass-ceramics containing calcium neodymium(cerium) silicate crystals are good candidate wasteforms for immobilization of lanthanide wastes generated by pyro-processing. - Highlights: • Glass-ceramic wasteforms containing Ca{sub 2}Nd{sub 8-x}Ce{sub x}(SiO{sub 4}){sub 6}O{sub 2} crystals were synthesized to immobilize lanthanide wastes. • Maximum lanthanide oxide waste loading was >26.8 wt.%. • Ce and Nd ions were highly partitioned inside Ca–Nd–silicate crystals compared to glass matrix. • Amounts of Ce and Nd ions released in the material characterization center-type 1 were below the detection limit (0.1 ppb). • Normalized release values performed by a PCT were 2.64• 10{sup −6} g m{sup −2} for Ce ions and 2.19• 10{sup −6} g m{sup −2} for Nd ions.

Mechanical Properties of Magnesium-Rare Earth Alloy Systems: A Review

Directory of Open Access Journals (Sweden)

Sravya Tekumalla

2014-12-01

Full Text Available Magnesium-rare earth based alloys are increasingly being investigated due to the formation of highly stable strengthening phases, activation of additional deformation modes and improvement in mechanical properties. Several investigations have been done to study the effect of rare earths when they are alloyed to pure magnesium and other Mg alloys. In this review, the mechanical properties of the previously investigated different magnesium-rare earth based binary alloys, ternary alloys and other higher alloys with more than three alloying elements are presented.

Sintered cobalt-rare earth intermetallic product

International Nuclear Information System (INIS)

Benz, M.C.

1975-01-01

A process is described for preparing novel sintered cobalt--rare earth intermetallic products which can be magnetized to form permanent magnets having stable improved magnetic properties. A cobalt--rare earth metal alloy is formed having a composition which at sintering temperature falls outside the composition covered by the single Co 5 R intermetallic phase on the rare earth richer side. The alloy contains a major amount of the Co 5 R intermetallic phase and a second solid CoR phase which is richer in rare earth metal content than the Co 5 R phase. The specific cobalt and rare earth metal content of the alloy is substantially the same as that desired in the sintered product. The alloy, in particulate form, is pressed into compacts and sintered to the desired density. The sintered product is comprised of a major amount of the Co 5 R solid intermetallic phase and up to about 35 percent of the product of the second solid CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase

Enzymatic determination of rare earth elements by use of pyrophosphotases

International Nuclear Information System (INIS)

Shekhovtseva, T.N.; Pirogova, S.V.; Fedorova, O.M.; Dolmanova, I.F.; Bajkov, A.A.

1993-01-01

A highly sensitive (determination limit 8 x 10 -6 - 4 x 10 -4 μg/ml) and selective enzymatic method for determination of rare earth elements has been developed. The method is based on inhibition action of rare earths on the catalytic activity of pyrophosphates isolated from bakery geast and E. Coli. The mechanism of the rare earth element action, corresponding to competitive inhibition, has been established

Processes for the production of rare earths from monazite (Paper No. 36)

International Nuclear Information System (INIS)

Murthy, T.K.S.

1979-01-01

A few typical cases are briefly described to illustrate different methods available for rare earth concentration and separation from mixed rare earths chloride obtained for monazite. In the case of cerium, rare earths chloride mixture is treated with sodium sulphate to precipitate rare earths as double sulphates from which hydroxide cake is prepared. The cake is dried to oxidise cerium. Trivalent rare earths are selectively leached and the product is treated with HNO 3 . The resulting ceric nitrate solution is purified by liquid-liquid extraction using TBP. The scrubbed extract is reduced with H 2 O 2 and cerous nitrate is recovered by evaporation. Lanthanum is first concentrated by selective precipitation of hydroxides from rare earths chloride using air-ammonia mixture. The hydroxyde cake is dissolved in HNO 3 and NH 4 NO 3 to get the double nitrate which is subjected to counter current crystallisation for purification. Europium is present at a concentration of 0.01% in the rare earths chloride. It is concentrated in several steps by liquid-liquid extraction using di-2-ethyl hexyl phosphoric acid. The product is purified by selective reduction and europium is obtained as europium sulphate. In the same solvent extraction process samarium and gadolinium are also concentrated to about 25%. They are further upgraded to above 90% purity by repetion of liquid-liquid extraction technique. Cerium, lanthanum and europium obtained by the above processes analyse > 99% as oxides. (M.G.B.)

Development of biomimetic catalytic oxidation methods and non-salt methods using transition metal-based acid and base ambiphilic catalysts.

Science.gov (United States)

Murahashi, Shun-Ichi

2011-01-01

This review focuses on the development of ruthenium and flavin catalysts for environmentally benign oxidation reactions based on mimicking the functions of cytochrome P-450 and flavoenzymes, and low valent transition-metal catalysts that replace conventional acids and bases. Several new concepts and new types of catalytic reactions based on these concepts are described. (Communicated by Ryoji Noyori, M.J.A.).

Study of rare earth elements as material for control rods

International Nuclear Information System (INIS)

1975-03-01

The properties of rare earth elements as the material for control rods were studied. The rare earth elements, especially europium oxide, has the nuclear property corresponding to boron carbide, and its neutron absorption process does not emit alpha particles. The elements produced as a result of neutron capture also have large capture cross sections. This paper presents survey report on the properties and nuclear properties of rare earth elements, and comparison with other materials. Preliminary experiment was performed to make the pellets of europium oxide, and is described in this paper. Because of large density, the crystal form to be made was monoclinic system. Europium hydroxide was decomposed at 1000 0 C and 10 -5 torr. The obtained powder was dipped into benzene, and dryed in the air at 450 0 C. This powder was pressed and sintered in the air for one hour at 1500 0 C. The density of the obtained pellets was 97.0% of the theoretical density. The cross section of europium for fast neutron absorption is not yet accurately obtained, and is in the range between 4.65 and 8.5 barn for 151 Eu(n,γ) reaction. Since chain absorption reaction is caused in Eu, the overall capability of neutron absorption is not much changed by the loss of original material due to absorption. The pellets of europium oxide may be handled in air, but must be kept in dry atmosphere. The reactions of europium oxide with various metals were also investigated. The characteristic behavior in case of irradiation depends on the amount of silicon contained, and it was very good if the amount was less than 0.03%. (Kato, T.)

Thermochemistry of rare earth doped uranium oxides Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} (Ln = La, Y, Nd)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei; Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.edu

2015-10-15

Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO{sub 1.5}, UO{sub 2} and UO{sub 3} in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3} for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U{sup 5+}, U{sup 6+}, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements. - Highlights: • We synthesize, characterize Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} solid solutions (Ln = La, Y, Nd). • Formation enthalpies become more exothermic with increasing rare earth content. • Oxidation enthalpy of Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3}. • Direct calorimetric measurements are in good agreement with free energy data.

Application of 241Am EDXRF to the determination of rare earth samples of solvent extraction processes

International Nuclear Information System (INIS)

Yan Chunhua; Jia Jiangtao; Liao Chunsheng; Li Biaoguo

1998-01-01

A rapid energy dispersive X-ray fluorescence spectroscopy (EDXRF) analysis system is established to determine rare earth concentrations. The characteristic K-shell series X-rays of rare earths were excited by a 1.1 x 10 9 Bq 241 Am radioisotope source. The spectra were recorded and analyzed using a multi-channel analyzer, employing a high-purity Ge detector. In this method, the Compton scattering peak, absorption of elements, and specific simplification are considered. Samples of light, middle and heavy rare earths during separation processes in both hydrochloride solution and rare earth loaded organic phases were analyzed off-line. Some comparative results measured by ICP are also given. The results show that the method can be used for a wide range of rare earth concentrations (0.1-300 g l -1 rare earth oxide). Being rapid, effective, precise and non-destructive, the method can be applied to on-line analysis to determine rare earth concentrations during separation by solvent extraction. (orig.)

Study of treatment of a thorium and rare earths residue by extraction chromatography

International Nuclear Information System (INIS)

Zini, Josiane; Abrao, Alcidio; Carvalho, Fatima Maria Sequeira de; Freitas, Antonio Alves de; Scapin, Marcos Antonio

2005-01-01

In the 70's was established at IPEN the project of a thorium compounds purification pilot plant that had the goal of fulfilling the nuclear technology purity standards. The used method was the purification by extraction with solvents in pulsed columns. The thorium remaining in the organic phase was back extracted as thorium nitrate with a high degree of purity. Impurities, thorium non-extracted and practically all rare earths in aqueous phase of this chemical process were precipitated as hydroxide, generating a product containing thorium and rare earths, that was denominated RETOTER (residue of thorium and rare earths). This residue was accumulated and today there are 25 (twenty-five) metric tons of this by product stored in the safeguard storage shed at IPEN that must to be treated due to the radiation of the thorium and mainly his daughters. The average composition of this residue is, 68% in thorium oxide (ThO 2 ), 5% in rare earths oxides (R 2 O 3 ), 0,3% in uranium oxide (U 3 O 8 ) and common impurities such as phosphorus, iron, titanium, lead and sodium. In this work a new method is presented for separation and purification of thorium from this residue, obtaining a concentrate with high degree of purity for nuclear and non-nuclear use. This process will contribute to establish a decreasing of residue volumes, to have a mind to the minimization of environmental impacts, the reduction of worker's exposition and reduction of the storage costs. In this process the separation and purification of uranium and thorium is done by chromatography extraction, being used polymeric resins, that are previously functionalized with organic solvent (extractor agent). The effluent of this process is a concentrate of rare earths that can be reprocessed in a subsequent fractionating for to obtaining the individual fractions. (author)

Recovery of rare earths from spent NdFeB magnets of wind turbine: Leaching and kinetic aspects.

Science.gov (United States)

Kumari, Aarti; Sinha, Manish Kumar; Pramanik, Swati; Sahu, Sushanta Kumar

2018-05-01

Increasing demands of rare earth (RE) metals for advanced technological applications coupled with the scarcity of primary resources have led to the development of processes to treat secondary resources like scraps or end of life products that are often rich in such metals. Spent NdFeB magnet may serve as a potential source of rare earths containing around ∼30% of neodymium and other rare earths. In the present investigation, a pyro-hydrometallurgical process has been developed to recover rare earth elements (Nd, Pr and Dy) from the spent wind turbine magnet. The spent magnet is demagnetized and roasted at 1123 K to convert rare earths and iron to their respective oxides. Roasting of the magnet not only provides selectivity, but enhances the leaching efficiency also. The leaching of the roasted sample with 0.5 M hydrochloric acid at 368 K, 100 g/L pulp density and 500 rpm for 300 min selectively recovers the rare earth elements almost quantitatively leaving iron oxide in the residue. Leaching of rare earth elements with hydrochloric acid follows the mixed controlled kinetic model with activation energy (E a ) of 30.1 kJ/mol in the temperature range 348-368 K. The leaching mechanism is further established by characterizing the leach residues obtained at different time intervals by scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Individual rare earth elements from the leach solution containing 16.8 g/L of Nd, 3.8 g/L Pr, 0.28 g/L of Dy and other minor impurity elements could be separated by solvent extraction. However, mixed rare earth oxide of 99% purity was produced by oxalate precipitation followed by roasting. The leach residue comprising of pure hematite has a potential to be used as pigment or can find other applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Rare earth mobility in hydrothermal ore-forming systems

International Nuclear Information System (INIS)

Cornell, D.H.; Schade, J.; Scheepers, R.; Watkeys, M.K.

1988-01-01

Rocks and ores which form by magmatic processes display a range of chondrite-normalised rare earth profiles. One REE (rare earth elements) profile feature which seems unrelated to magmatic processes is the birdwing profile, in which both heavy and light rare earths are enriched relative to the middle rare earths. Birdwing rare earth profiles are an easily identified geochemical anomaly. It is proposed that rare earth geochemistry could be applied in geochemical prospecting for ore formed by hydrothermal processes. 5 figs

Replacing critical rare earth materials in high energy density magnets

Science.gov (United States)

McCallum, R. William

2012-02-01

High energy density permanent magnets are crucial to the design of internal permanent magnet motors (IPM) for hybride and electric vehicles and direct drive wind generators. Current motor designs use rare earth permanent magnets which easily meet the performance goals, however, the rising concerns over cost and foreign control of the current supply of rare earth resources has motivated a search for non-rare earth based permanent magnets alloys with performance metrics which allow the design of permanent magnet motors and generators without rare earth magnets. This talk will discuss the state of non-rare-earth permanent magnets and efforts to both improve the current materials and find new materials. These efforts combine first principles calculations and meso-scale magnetic modeling with advance characterization and synthesis techniques in order to advance the state of the art in non rare earth permanent magnets. The use of genetic algorithms in first principle structural calculations, combinatorial synthesis in the experimental search for materials, atom probe microscopy to characterize grain boundaries on the atomic level, and other state of the art techniques will be discussed. In addition the possibility of replacing critical rare earth elements with the most abundant rare earth Ce will be discussed.

Two Catalysts for Selective Oxidation of Contaminant Gases

Science.gov (United States)

Wright, John D.

2011-01-01

Two catalysts for the selective oxidation of trace amounts of contaminant gases in air have been developed for use aboard the International Space Station. These catalysts might also be useful for reducing concentrations of fumes in terrestrial industrial facilities especially facilities that use halocarbons as solvents, refrigerant liquids, and foaming agents, as well as facilities that generate or utilize ammonia. The first catalyst is of the supported-precious-metal type. This catalyst is highly active for the oxidation of halocarbons, hydrocarbons, and oxygenates at low concentrations in air. This catalyst is more active for the oxidation of hydrocarbons and halocarbons than are competing catalysts developed in recent years. This catalyst completely converts these airborne contaminant gases to carbon dioxide, water, and mineral acids that can be easily removed from the air, and does not make any chlorine gas in the process. The catalyst is thermally stable and is not poisoned by chlorine or fluorine atoms produced on its surface during the destruction of a halocarbon. In addition, the catalyst can selectively oxidize ammonia to nitrogen at a temperature between 200 and 260 C, without making nitrogen oxides, which are toxic. The temperature of 260 C is higher than the operational temperature of any other precious-metal catalyst that can selectively oxidize ammonia. The purpose of the platinum in this catalyst is to oxidize hydrocarbons and to ensure that the oxidation of halocarbons goes to completion. However, the platinum exhibits little or no activity for initiating the destruction of halocarbons. Instead, the attack on the halocarbons is initiated by the support. The support also provides a high surface area for exposure of the platinum. Moreover, the support resists deactivation or destruction by halogens released during the destruction of halocarbons. The second catalyst is of the supported- metal-oxide type. This catalyst can selectively oxidize ammonia to

Rare earth metals-primary resources and prospects of processing secondary resources in India

International Nuclear Information System (INIS)

Pandey, B.D.

2015-01-01

The importance of Rare earth metals (REMs) in modern technological applications is associated with their spectroscopic and magnetic properties. The occurrence of rare earths in mixed form is commonly reported and their separation to the individual metal is a challenging task because of the similar chemical properties. The economical processing of the primary ores of rare earths is limited to a few countries and their supply at the international level is currently dominated by China. Hence assessing the present scenario of the primary resources of rare earths vis-à-vis their applications and demand is crucial at this stage, besides looking at the alternate resources to ensure availability of REMs; such aspects are covered in the manuscript. In view of the environmental concerns in the processing of ores such as monazite, xenotime, bastnasite, etc, and increasing demand of REMs, corresponding increase in demand of the raw materials has been recorded. It is therefore, necessary to utilize the end-of the-life rare earth containing materials as a rich resource by developing an appropriate recycling technology, which is emerging as a high priority area. To recover the REMs, major secondary resources such as electronic wastes, industrial wastes, spent catalysts and magnets, and phosphors powder, etc, have been considered for now. This will not only open the prospects of utilizing the wastes containing REMs, but will also limit the imports while lowering the production cost and decreasing the load on the primary reserves. The paper also examines the efficient recycling methods to recover a fairly good amount of rare earths which are relevant to India in view of the limited exploitation of the ores. Recovery of REMs from secondary resources using mechanical treatment followed by hydrometallurgical methods is prevalent and the same is reviewed in some detail. The recent R and D work pursued at CSIR-NML to extract (leaching and metal separation using some phosphatic reagents

Study of interaction of uranium, plutonium and rare earth fluorides with some metal oxides in fluoric salt melts

International Nuclear Information System (INIS)

Gorbunov, V.F.; Novoselov, G.P.; Ulanov, S.A.

1976-01-01

Interaction of plutonium, uranium, and rare-earth elements (REE) fluorides with aluminium and calcium oxides in melts of eutectic mixture LiF-NaF has been studied at 800 deg C by X-ray diffraction method. It has been shown that tetravalent uranium and plutonium are coprecipitated by oxides as a solid solution UO 2 -PuO 2 . Trivalent plutonium in fluorides melts in not precipitated in the presence of tetravalent uranium which can be used for their separation. REE are precipitated from a salt melt by calcium oxide and are not precipitated by aluminium oxide. Thus, aluminium oxide in a selective precipitator for uranium and plutonium in presence of REE. Addition of aluminium fluoride retains trivalent plutonium and REE in a salt melt in presence of Ca and Al oxides. The mechanism of interacting plutonium and REE trifluorides with metal oxides in fluoride melts has been considered

The Rare Earth Magnet Industry and Rare Earth Price in China

Directory of Open Access Journals (Sweden)

Ding Kaihong

2014-07-01

Full Text Available In the past four years, the price of rare earth metal fluctuates sharply for many reasons. Currently, it has become more stable and more reasonable. This presentation is focused on the effect about the rare earth metal price. Some motor manufacturers have shifted from rare earth permanent magnet to ferrite magnet. Many motor manufacturers changed the design for the motor cooling system to make the motor function at a lower temperature. Thus the consumption of Dy can be markedly reduced. As for manufacturer of NdFeB magnet, we are also trying to optimize our process to reduce to dependence of HREE such as Dy and Tb. HS process have been introduced to solve the problem. With more and more people focusing and engaging on the REE industry, the price of REE will be more transparent without too many fluctuations. China is considering the problems of balancing the environment, energy sources, and labor sources. The application field about NdFeB such as wind turbine generator, HEV/EV, FA /OA is flourishing.

The Rare Earth Magnet Industry and Rare Earth Price in China

Science.gov (United States)

Ding, Kaihong

2014-07-01

In the past four years, the price of rare earth metal fluctuates sharply for many reasons. Currently, it has become more stable and more reasonable. This presentation is focused on the effect about the rare earth metal price. Some motor manufacturers have shifted from rare earth permanent magnet to ferrite magnet. Many motor manufacturers changed the design for the motor cooling system to make the motor function at a lower temperature. Thus the consumption of Dy can be markedly reduced. As for manufacturer of NdFeB magnet, we are also trying to optimize our process to reduce to dependence of HREE such as Dy and Tb. HS process have been introduced to solve the problem. With more and more people focusing and engaging on the REE industry, the price of REE will be more transparent without too many fluctuations. China is considering the problems of balancing the environment, energy sources, and labor sources. The application field about NdFeB such as wind turbine generator, HEV/EV, FA /OA is flourishing.

Study of rare earth elements, uranium and thorium migration in rocks from Espinharas uranium deposit, Paraiba - Brazil

International Nuclear Information System (INIS)

Conceicao, Cirilo C.S.

2009-01-01

The determination of rare earth elements as natural analogue in patterns geologic has grown as a tool for predicting the long-term safety of nuclear disposal in geological formation. Migration of natural radionuclides is one of the most serious problems in the waste deposit from nuclear fuel cycle. Rare earth elements show the same kinetic behavior in rocks as natural radionuclides. This similar property of the analogues allows perform studies and models on the subject of radionuclides migration. The aim of this study was to determine the distribution of rare earth elements in rocks located at Espinharas - Paraiba - Brazil, uranium deposit. In this work are presented the results from the study above the distribution of rare earth elements in function of the degree of mineralized rocks, composition and the conditions of radioactive equilibrium of the uranium and thorium in some fractures on the rocks from radioactive occurrence of Espinharas-Brazil. The results show that there is a correlation of heavy rare earth elements, uranium and Thorium concentrations to oxidation factor of the rocks. However this correlation was not observed for light rare earth elements. It means that heavy rare earth elements follow the natural radionuclides in oxidation process of rocks. The samples were analyzed by ICP-MS, alpha and gamma spectrometry, X-ray diffraction and fluorimetry. (author)

Recovery and separation of rare-earth elements, barium, and strontium from bastnasite with sulfuric acid

International Nuclear Information System (INIS)

Eisele, J.A.; Bauer, D.J.

1974-01-01

A bench-scale investigation was made of a concentrated H 2 SO 4 reaction for recovering and separating rare earth elements, barium, and strontium from a bastnaesite ore and byproduct. Barium and strontium were dissolved in the concentrated acid and precipitated as a mixed product by water dilution. Separation of strontium from barium was effected by reaction with Na 2 CO 3 solution, followed by a dilute acid leach of the SrCO 3 formed. After removing the barium and strontium from bastnaesite ore, the rare-earth elements were roasted to water-soluble sulfates. The rare earth sulfate solution was subsequently processed by solvent extraction to produce rare-earth oxides low in lead and magnesium. (U.S.)

Rare earth elements behavior in Peruibe black mud

International Nuclear Information System (INIS)

Torrecilha, Jefferson K.; Carvalho, Leandro P.; Gouvea, Paulo F.M.; Silva, Paulo S.C. da

2015-01-01

Rare earth elements in sediments have been used as powerful tools for environmental studies because of their behavior during geochemical processes and are also widely accepted as reliable provenance tracers because they are largely water-immobile and thus behave conservatively during sedimentary processes. The Peruibe Black Mud (PBM) is a sedimentary deposit originated from the interactions of marine sediments and organic matter in an estuarine environment that originates a peloid currently used for medicinal purposes. The objective of this study was to examine rare earth elements pattern distribution in the Peruibe black mud sedimentary deposit as a proxy for its geochemical development. Elemental ratios such as LaN/YbN, Th/U and La/Th were determined and a normalization of the mean rare earth elements concentrations in the samples related to NASC indicates that the light (La to Eu) rare earth elements present values close to the unity while the heavy (Tb to Lu) rare earth elements are depleted related to NASC. It can be observed that the light rare earth elements present enrichment values slightly enriched over the unity while the heavy rare earth elements present values generally below the unity reflecting the enrichment of the light rare earth elements over the heavy rare earth. Rare earth elements concentrations determined in Peruibe black mud samples showed a distribution similar to that found in the NASC for the light rare earth elements and depleted for the heavy rare earth elements. (author)

Rare earth elements behavior in Peruibe black mud

Energy Technology Data Exchange (ETDEWEB)

Torrecilha, Jefferson K.; Carvalho, Leandro P.; Gouvea, Paulo F.M.; Silva, Paulo S.C. da, E-mail: jeffkoy@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2015-07-01

Rare earth elements in sediments have been used as powerful tools for environmental studies because of their behavior during geochemical processes and are also widely accepted as reliable provenance tracers because they are largely water-immobile and thus behave conservatively during sedimentary processes. The Peruibe Black Mud (PBM) is a sedimentary deposit originated from the interactions of marine sediments and organic matter in an estuarine environment that originates a peloid currently used for medicinal purposes. The objective of this study was to examine rare earth elements pattern distribution in the Peruibe black mud sedimentary deposit as a proxy for its geochemical development. Elemental ratios such as LaN/YbN, Th/U and La/Th were determined and a normalization of the mean rare earth elements concentrations in the samples related to NASC indicates that the light (La to Eu) rare earth elements present values close to the unity while the heavy (Tb to Lu) rare earth elements are depleted related to NASC. It can be observed that the light rare earth elements present enrichment values slightly enriched over the unity while the heavy rare earth elements present values generally below the unity reflecting the enrichment of the light rare earth elements over the heavy rare earth. Rare earth elements concentrations determined in Peruibe black mud samples showed a distribution similar to that found in the NASC for the light rare earth elements and depleted for the heavy rare earth elements. (author)

Easy and General Synthesis of Large-Sized Mesoporous Rare-Earth Oxide Thin Films by 'Micelle Assembly'.

Science.gov (United States)

Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Dai, Pengcheng; Yamauchi, Yusuke

2015-12-01

Large-sized (ca. 40 nm) mesoporous Er2O3 thin films are synthesized by using a triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er(3+) is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare-earth oxide (Sm2O3, Dy2O3, Tb2O3, Ho2O3, Yb2O3, and Lu2O3) thin films with potential uses in electronics and optical devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study on Yen Phu rare earth ore concentrate treatment technology and separation of major heavy rare earth elements by solvent extraction method

International Nuclear Information System (INIS)

Le Ba Thuan; Pham Quang Trung; Vu Lap Lai

2003-01-01

1. Yenphu rare earth ore concentrate treatment by alkali under pressure: On the base of studying mineral and chemical compositions of Yenphu rare earth ore concentrate containing 28% TREO and conditions for digestion of ore concentrate by alkali under pressure such as ore concentrate/ NaOH ratio, alkali concentration, pressure and temperature at bench scale (100 gram and 5 kg per batch), the optimal conditions for decomposition of REE ore concentrate have been determined. The yield of the decomposition stage is about 90%. The studies on alkali washing, REE leaching by HCl, pH for leaching process, and iron and radioactive impurities removing by Na 2 S + Na 2 PO 4 have been carried out. The obtained results show that mixture of Na 2 S 5% + Na2PO 4 1% is effective in iron and radioactive impurities removing. The obtained REE oxides get purity of > 99% and meet the need of solvent extraction (SX) individual separation of rare earth elements. The schema for recovery of REEs from Yenphu REE ore concentrate by alkali decomposition under high pressure has been proposed. 2. Fractionation of Yenphu rare earth mixture into subgroups by solvent extraction with PC88A: On the base of simulation program, the parameters for fractional process of rare earths mixture into subgroups by solvent extraction with PC88A have been proposed and determined by experimental verification on mixer-settler set. According to this process, rare earths mixture fractionated into yttrium and light subgroups. In their turn, the light subgroup was separated into light (La, Ce, Pr, Nd) and middle (Sm, Eu, Gd) subgroups. The average yield of the process reached value > 95%. The composition of light subgroup meets the needs for individual separation of Gd, Eu, and Sm. 3. Separation and purification of yttrium: The process for recovery of yttrium consists of two stages: upgrade to get high quality Y concentrate by PC88A and purification by Aliquat 336 in NH 4 SCN-NH 4 Cl medium. The process parameter for

Electro-catalytic oxidation of reactive Orange 107 using cerium doped oxides of Nd3+ nanoparticle

International Nuclear Information System (INIS)

Rajkumar, K.; Muthukumar, M.; Mangalaraja, R.V.

2011-01-01

A new rare earth doped cerium oxide powder was used as a catalyst to investigate the removal of colour and TOC from simulated wastewater of Reactive Orange 107. The electro oxidation process was carried out in the reactor in presence of an electrolyte NaCl. Graphite electrode was used as anode and cathode and electrolysis were carried out at a current density of 34.96 mAcm -2 with a catalyst concentration of 0.05g L -1 . In order to find the efficiency of nanocatalyst, experiments were also conducted without catalyst. From the experiment, it was found that complete colour removal was achieved on electrocatalytic oxidation as well as electro oxidation. When comparing the above processes, catalytic oxidation shows more efficient than electro oxidation. With respect to the degradation of the dye, catalytic oxidation shows more TOC removal than the oxidation taken place without catalyst. It infers that even though the electro-catalytic oxidation process achieves complete decolouration but it does not achieve complete mineralisation. The FTIR and GCMS studies confirmed the formation of by-products. (author)

Rare earth elements and oxides in liquid phase epitaxy

Czech Academy of Sciences Publication Activity Database

Procházková, Olga; Grym, Jan; Zavadil, Jiří; Kopecká, M.

2006-01-01

Roč. 100, č. 8 (2006), s. 640-- ISSN 0009-2770. [Sjezd chemických společností /58./. Ústí nad Labem, 04.09.2006-08.09.2006] R&D Projects: GA ČR(CZ) GA102/06/0153 Institutional research plan: CEZ:AV0Z20670512 Keywords : semiconductor technology * rare earth metals Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.431, year: 2006

Synthesis and photoluminescence properties of novel Schiff base type polymer-rare earth complexes containing furfural-based bidentate Schiff base ligands

Science.gov (United States)

Gao, Baojiao; Zhang, Dandan; Li, Yanbin

2018-03-01

Luminescent polymer-rare earth complexes are an important class of photoluminescence and electroluminescence materials. Via molecular design, two furfural-based bidentate Schiff base ligands, furfural-aniline (FA) type ligand and furfural-cyclohexylamine (FC) type ligand, were bonded on the side chains of polysulfone (PSF), respectively, forming two functionalized macromolecules, PSF-FA and PSF-FC. And then through respective coordination reactions of the two functionalized macromolecules with Eu(Ⅲ) ion and Tb(Ⅲ) ion, novel luminescent binary and ternary (with 1,10-phenanthroline as the second ligand) polymer-rare earth complexes were synthesized. For these complexes, on basis of the characterization of their chemical structures, they photoluminescence properties were main researched, and the relationship between their luminescent properties and structures was explored. The experimental results show that the complexes coming from PSF-FA and Eu(Ⅲ) ion including binary and ternary complexes emit strong red luminescence, indicating that the bonded bidentate Schiff base ligand FA can sensitize the fluorescence emission of Eu(III) ion. While the complexes coming from PSF-FC and Tb(Ⅲ) ion produce green luminescence, displaying that the bonded bidentate Schiff base ligand FC can sensitize the fluorescence emission of Tb(Ⅲ) ion. The fluorescence emission intensities of the ternary complexes were stronger than that of binary complexes, reflecting the important effect of the second ligand. The fluorescence emission of the solid film of complexes is much stronger than that of the solutions of complexes. Besides, by comparison, it is found that the furfural (as a heteroaromatic compound)-based Schiff base type polymer-rare earth complexes have stronger fluorescence emission and higher energy transfer efficiency than salicylaldehyde (as a common aromatic compound)-based Schiff base type polymer-rare earth complexes.

Aerobic Oxidation of Alcohols over Gold Catalysts: Role of Acid and Base

DEFF Research Database (Denmark)

Klitgaard, Søren Kegnæs; DeLa Riva, Andrew T.; Helveg, Stig

2008-01-01

Gold nanoparticles are deposited on potassium titanate nanowires and used as heterogeneous catalysts in the aerobic oxidation of benzyl alcohol in methanol to methyl benzoate at ambient conditions. The presence of a catalytic amount of base promotes the reaction and the formation of free benzoic...

A rare earth-based metal-organic framework for moisture removal and control in confined spaces

KAUST Repository

Eddaoudi, Mohamed

2017-04-13

A method for preparing a metal-organic framework (MOF) comprising contacting one or more of a rare earth metal ion component with one or more of a tetratopic ligand component, sufficient to form a rare earth-based MOF for controlling moisture in an environment. A method of moisture control in an environment comprising adsorbing and/or desorbing water vapor in an environment using a MOF, the MOF including one or more of a rare earth metal ion component and one or more of a tetratopic ligand component. A method of controlling moisture in an environment comprising sensing the relative humidity in the environment comprising a MOF; and adsorbing water vapor on the MOF if the relative humidity is above a first level, sufficient to control moisture in an environment. The examples relate to a MOF created from 1,2,4,5-Tetrakis(4-carboxyphenyl )benzene (BTEB) as tetratopic ligand, 2-fluorobenzoic acid and Y(NO3)3, Tb(NO3)3 and Yb(NO3)3 as rare earth metals.

Naphthenic acid removal from HVGO by alkaline earth metal catalysts

Energy Technology Data Exchange (ETDEWEB)

Ding, L.; Rahimi, P.; Hawkins, R.; Bhatt, S.; Shi, Y. [National Centre for Upgrading Technology, Devon, AB (Canada); Natural Resources Canada, Devon, AB (Canada). CanmetENERGY

2009-07-01

This poster highlighted a study that investigated naphthenic acid removal from bitumen-derived heavy vacuum gas oil (HVGO) by thermal cracking and catalytic decarboxylation over alkaline earth-metal oxides and ZnO catalysts in a batch reactor and a continuous fixed-bed reactor. X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA) temperature-programmed desorption (TPD) of carbon dioxide (CO{sub 2}-TPD), and scanning electron microscopy were used to characterize the fresh and spent catalysts. With MgO and ZnO, naphthenic acid removal proceeded via catalytic decarboxylation. No crystalline phase changes were observed after reaction. With CaO, multiple pathways such as catalytic decarboxylation, neutralization, and thermal cracking were responsible for naphthenic acid conversion. The spent catalysts contained Ca(OH){sub 2} and CaCO{sub 3}. With BaO, naphthenic acid conversion occurred through neutralization. All BaO was converted to Ba(OH){sub 2} during the reaction. tabs., figs.

Yttrium separation of Xenotime waste in Pitinga (Brazil), in order to obtain rare earth elements

International Nuclear Information System (INIS)

Melo.

1996-01-01

The xenotime (YPO 4 and rare earth elements) found in the mine of Pitinga, Amazonas State, Brazil, has its origin in a primal depository ('eluvio' kind) of cassiterite, having considerable quantities of zirconite, ilmenite, topaz and niobates-tantalates. This xenotime has different characteristics in relation of the depositories that exist in other countries for presenting more concentration of rare earth heavy oxides. The mineralization of this cassiterite is problematic, because of the high level of radioactive elements. In the present work, we will process only the xenotime. The separation of rare earth elements is very difficult due to their great chemical similarity. For a more exactly determination, it is necessary to separate them at least of the macron constituents of the sample. As the Yttrium is considerate one of the rare earth elements, due to its chemical similarity, we can understand the difficulty of a chemical separation, mainly when this one is also a macro constituent of the sample, as in the case of xenotime. The process of separation will be based on the little difference that exists between the constants of complexation and the fluoride. (authors). 5 refs., 1 fig., 2 tabs

Rare Earth Metals: Resourcefulness and Recovery

Science.gov (United States)

Wang, Shijie

2013-10-01

When we appreciate the digital revolution carried over from the twentieth century with mobile communication and the Internet, and when we enjoy our high-tech lifestyle filled with iDevices, hybrid cars, wind turbines, and solar cells in this new century, we should also appreciate that all of these advanced products depend on rare earth metals to function. Although there are only 136,000 tons of annual worldwide demand, (Cho, Rare Earth Metals, Will We Have Enough?)1 rare earth metals are becoming such hot commodities on international markets, due to not only to their increasing uses, including in most critical military hardware, but also to Chinese growth, which accounts for 95% of global rare earth metal production. Hence, the 2013 technical calendar topic, planned by the TMS/Hydrometallurgy and Electrometallurgy Committee, is particularly relevant, with four articles (including this commentary) contributed to the JOM October Issue discussing rare earth metals' resourcefulness and recovery.

Ternary rare-earth based alternative gate-dielectrics for future integration in MOSFETs

Energy Technology Data Exchange (ETDEWEB)

Schubert, Juergen; Lopes, Joao Marcelo; Durgun Oezben, Eylem; Luptak, Roman; Lenk, Steffi; Zander, Willi; Roeckerath, Martin [IBN 1-IT, Forschungszentrum Juelich, 52425 Juelich (Germany)

2009-07-01

The dielectric SiO{sub 2} has been the key to the tremendous improvements in Si-based metal-oxide-semiconductor (MOS) device performance over the past four decades. It has, however, reached its limit in terms of scaling since it exhibits a leakage current density higher than 1 A/cm{sup 2} and does not retain its intrinsic physical properties at thicknesses below 1.5 nm. In order to overcome these problems and keep Moore's law ongoing, the use of higher dielectric constant (k) gate oxides has been suggested. These high-k materials must satisfy numerous requirements such as the high k, low leakage currents, suitable band gap und offsets to silicon. Rare-earth based dielectrics are promising materials which fulfill these needs. We will review the properties of REScO{sub 3} (RE = La, Dy, Gd, Sm, Tb) and LaLuO{sub 3} thin films, grown with pulsed laser deposition, e-gun evaporation or molecular beam deposition, integrated in capacitors and transistors. A k > 20 for the REScO{sub 3} (RE = Dy, Gd) and around 30 for (RE = La, Sm, Tb) and LaLuO{sub 3} are obtained. Transistors prepared on SOI and sSOI show mobility values up to 380 cm{sup 2}/Vs on sSOI, which are comparable to such prepared with HfO{sub 2}.

Investigation of recovery and recycling of rare earth elements from waste fluorescent lamp phosphors

Science.gov (United States)

Eduafo, Patrick Max

Characterization techniques and experimental measurements were used to evaluate a process for recycling rare earth elements (REEs) from spent fluorescent lamp phosphors. QEMSCAN analysis revealed that over 60% of the rare earth bearing minerals was less than 10 microm. A representative sample of the as-received feed contained 14.59 wt% total rare earth elements (TREE) and upon sieving to below 75 microm, the grade increased to 19.60 wt% REE with 98.75% recovery. Based on experimental work, a new process for extracting the chief REEs from end of life fluorescent lamps has been developed. The proposed flowsheet employs a three-stage leaching and precipitation process for selective extraction and recovery of the REEs. Hydrochloric acid was used as lixiviant in batch leach experiments on the phosphor powder. The maximum extraction obtained was 100% for both yttrium and europium under the following leaching conditions: 2.5 M HCl, 70°C, 1 hour, 180 g/L and 600 rpm. However, the solubility of cerium, lanthanum and terbium remained low at these conditions. Kinetic data of the leaching of yttrium and europium showed best fit to the logarithmic rate expression of the empirical model of leaching. Activation energy was calculated to be 77.49 kJ/mol for Y and 72.75 kJ/mol for Eu in the temperature range of 298 to 343 K. Precipitation tests demonstrate that at least 50% excess the stoichiometric amount of oxalic acid is needed to recover yttrium and europium efficiently to produce a pure (Y, Eu) mixed oxide. Total recovery of the REEs was achieved even at very low pH or without any base added. Over 99% pure mixed rare earth oxide at 99% recovery has been attained. An economic assessment of the developed process using operating and capital cost have be undertaken and based on the analysis of the three economic scenarios, two are economic and one is non-economic.

A family of rare-earth-based single chain magnets: playing with anisotropy.

Science.gov (United States)

Bernot, Kevin; Bogani, Lapo; Caneschi, Andrea; Gatteschi, Dante; Sessoli, Roberta

2006-06-21

The first family of rare-earth-based single chain magnets is presented. Compounds of general formula [M(hfac)3(NITPhOPh)], where M = Eu, Gd, Tb, Dy, Ho, Er, or Yb, and PhOPh is the nitronyl-nitroxide radical (2,4'-benzoxo-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), have been structurally characterized and found to be isostructural. The characterization of both static and dynamic magnetic properties of the whole family is reported. Dy, Tb, and Ho compounds display slow relaxation of the magnetization, and ac susceptibility shows a thermally activated regime with energy barriers of 69, 45, and 34 K for Dy, Tb, and Ho compounds, respectively, while only a frequency-dependent susceptibility is observed for Er below 2.0 K. In Gd and Yb derivatives, antiferromagnetic interactions dominate. The pre-exponential factors differ by about 4 orders of magnitude. Finite size effects, due to naturally occurring defects, affect the static and dynamic properties of the compounds differently.

Cathodoluminescent characteristics and light technical parameters of thin-film screens based on oxides and oxysulfides of rare-earth elements

Science.gov (United States)

Bondar, Vyacheslav D.; Grytsiv, Myroslav; Groodzinsky, Arkady; Vasyliv, Mykhailo

1995-11-01

Results on creation of thin-film single-crystal high-resolution screens with energy control of luminescence color are presented. In order to create phosphor films ion-plasma technology for deposition of yttrium and lanthanum oxides and oxysulfides activated by rare earth elements has been developed. The screen consists of phosphor film on phosphor substrate with different colors of luminescence (e.g. Y2O3-Eu film with red color on Y3Al5O12- Tb, Ce substrate with green color of luminescence). Electron irradiation causes luminescence with color that depends on energy of the electron beam. The physical reason for color change is that electron beam energy defines electron penetration depth. If the energy is weak, only the film is excited. More powerful beam penetrates into the substrate and thus changes the color of luminescence.

Preparation of rare earth fluorides from apatite concentrate

International Nuclear Information System (INIS)

Mulyarchuk, I.F.; Voloshchenko, M.V.; Zen'kovich, E.G.; Sumenkova, V.V.; AN Ukrainskoj SSR, Kiev. Inst. Problem Lit'ya)

1980-01-01

The processes of preparation of the rare earths element sum from apatite concentrate of the Khibins, connected with preliminary extraction of rare earth phosphates from nitric acid extract using solvent extraction or direct precipitation from the extract by solution of potassium and ammonium fluorides. The sequence of the processes of the first variant is the following: solvent extraction of rare earths by tributylphosphate from clarified nitric acid extract of apatite with subsequent reextraction of rare earths with water and precipitation of rare earth phosphates from aqueous solution during neutralization by ammonia. In case of fluoride preparation from rare earth phosphate the main attention is paid to precipitation and filtration of fluorides. Technological scheme and cost price of industry for the production of 1800 t of rare earth trifluorides a year are calculated. When taking account of TBP losses according to its solubility the industry cost price is 1O times lower the modern cost of rare earth fluorides

Catalytic Oxidation of Phenol over Zeolite Based Cu/Y-5 Catalyst: Part 1: Catalyst Preparation and Characterization

Directory of Open Access Journals (Sweden)

K. Maduna Valkaj

2015-01-01

Full Text Available The necessity to remove organic pollutants from the industrial wastewater streams has forced the development of new technologies that can produce better results in terms of pollutant removal and process efficiency in combination with low investment and operating costs. One of the new emerging processes with a potential to fulfil these demands is catalytic wet peroxide oxidation, commonly known as the CWPO process. The oxidative effect of the hydrogen peroxide is intensified by the addition of a heterogeneous catalyst that can reduce the operating conditions to atmospheric pressure and temperatures below 383 K. Zeolites, among others, are especially appealing as catalysts for selective oxidation processes due to their unique characteristics such as shape selectivity, thermal and chemical stability, and benign effect on nature and the living world. In this work, catalytic activity, selectivity and stability of Cu/Y-5 zeolite in phenol oxidation with hydrogen peroxide was examined. Catalyst samples were prepared by ion exchange method of the protonic form of commercial zeolite. The catalysts were characterized with powder X-ray diffraction (XRD, scanning electron microscopy (SEM, and AAS elemental analysis, while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and in the temperature range from 323 to 353 K. The catalyst was prepared in powdered form and the mass fraction of the active metal component on the zeolite was 3.46 %. The initial concentration of phenol solution was equal to 0.01 mol dm−3 and the concentration of hydrogen peroxide ranged from 0.01 to 0.10 mol dm−3. The obtained experimental data was tested to a proposed kinetic model for phenol oxidation r = k1 cF cVP and hydrogen peroxide decomposition rHP = k2 cHP. The kinetic parameters were estimated using the Nelder

Thermochemistry of rare-earth trifluorides

International Nuclear Information System (INIS)

Kim, K.Y.; Johnson, C.E.

1981-01-01

Using the most recent crystallographic data, the Born-Lande equation was employed to calculate lattice energies of the rare-earth trifluorides. The excellent agreement ( 0 sub(f)(MX 3 ,c,298.15K) can be estimated. The magnitude of the monotonic change of ΔH 0 sub(f)(MX 3 ) for the rare-earth trihalides series (14 4f electrons) is comparable to the energy change between Sc and Ti in which only one 3d electron is added. This energy change is consistent with the chemical evidence that the electrons in the f-orbitals of rare earths contribute negligibly to the bonding. (author)

Rare earth minerals and resources in the world

Energy Technology Data Exchange (ETDEWEB)

Kanazawa, Yasuo [Human Resource Department, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8568 (Japan)]. E-mail: y.kanazawa@aist.go.jp; Kamitani, Masaharu [Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8567 (Japan)

2006-02-09

About 200 rare earth (RE) minerals are distributed in a wide variety of mineral classes, such as halides, carbonates, oxides, phosphates, silicates, etc. Due to the large ionic radii and trivalent oxidation state, RE ions in the minerals have large coordination numbers (c.n.) 6-10 by anions (O, F, OH). Light rare earth elements (LREEs) tend to occupy the larger sites of 8-10 c.n. and concentrate in carbonates and phosphates. On the other hand, heavy rare earth elements (HREEs) and Y occupy 6-8 c.n. sites and are abundant in oxides and a part of phosphates. Only a few mineral species, such as bastnaesite (Ce,La)(CO{sub 3})F, monazite (Ce,La)PO{sub 4}, xenotime YPO{sub 4}, and RE-bearing clay have been recovered for commercial production. Bayan Obo, China is the biggest RE deposit in the world. One of probable hypotheses for ore geneses is that the deposit might be formed by hydrothermal replacement of carbonate rocks of sedimentary origin. The hydrothermal fluid may be derived from an alkaline-carbonatite intrusive series. Following Bayan Obo, more than 550 carbonatite/alkaline complex rocks constitute the majority of the world RE resources. The distribution is restricted to interior and marginal regions of continents, especially Precambrian cratons and shields, or related to large-scale rift structures. Main concentrated areas of the complexes are East African rift zones, northern Scandinavia-Kola peninsula, eastern Canada and southern Brazil. Representative sedimentary deposits of REE are placer- and conglomerate-types. The major potential countries are Australia, India, Brazil, and Malaysia. Weathered residual deposits have been formed under tropical and sub-tropical climates. Bauxite and laterite nickel deposit are the representative. Ion adsorption clay without radioactive elements is known in southern China. Weathering processes concentrate REE in a particular clay mineral-layer in the weathered crusts whose source were originally REE-rich rocks like granite

Rare earth minerals and resources in the world

International Nuclear Information System (INIS)

Kanazawa, Yasuo; Kamitani, Masaharu

2006-01-01

About 200 rare earth (RE) minerals are distributed in a wide variety of mineral classes, such as halides, carbonates, oxides, phosphates, silicates, etc. Due to the large ionic radii and trivalent oxidation state, RE ions in the minerals have large coordination numbers (c.n.) 6-10 by anions (O, F, OH). Light rare earth elements (LREEs) tend to occupy the larger sites of 8-10 c.n. and concentrate in carbonates and phosphates. On the other hand, heavy rare earth elements (HREEs) and Y occupy 6-8 c.n. sites and are abundant in oxides and a part of phosphates. Only a few mineral species, such as bastnaesite (Ce,La)(CO 3 )F, monazite (Ce,La)PO 4 , xenotime YPO 4 , and RE-bearing clay have been recovered for commercial production. Bayan Obo, China is the biggest RE deposit in the world. One of probable hypotheses for ore geneses is that the deposit might be formed by hydrothermal replacement of carbonate rocks of sedimentary origin. The hydrothermal fluid may be derived from an alkaline-carbonatite intrusive series. Following Bayan Obo, more than 550 carbonatite/alkaline complex rocks constitute the majority of the world RE resources. The distribution is restricted to interior and marginal regions of continents, especially Precambrian cratons and shields, or related to large-scale rift structures. Main concentrated areas of the complexes are East African rift zones, northern Scandinavia-Kola peninsula, eastern Canada and southern Brazil. Representative sedimentary deposits of REE are placer- and conglomerate-types. The major potential countries are Australia, India, Brazil, and Malaysia. Weathered residual deposits have been formed under tropical and sub-tropical climates. Bauxite and laterite nickel deposit are the representative. Ion adsorption clay without radioactive elements is known in southern China. Weathering processes concentrate REE in a particular clay mineral-layer in the weathered crusts whose source were originally REE-rich rocks like granite and

Theory of Rare-Earth Alloys

DEFF Research Database (Denmark)

Lindgård, Per-Anker

1977-01-01

A mean-field random alloy theory combined with a simple calculation of the exchange interaction J(c,Q) is shown to quantitatively account for the phase diagrams for alloys of rare-earth metals with Y, Lu, Sc, and other rare-earth metals. A concentration-dependent J(c,Q) explains the empirical 2...

Effects of rare earth oxide addition on NdFeB magnets

International Nuclear Information System (INIS)

Ohashi, K.; Yokoyama, T.; Tawara, Y.

1988-01-01

The effects of addition of rare-earth oxides on the magnetic properties of Nd-Fe-B sintered magnets are studied. The addition of Dy 2 O 3 and Tb 4 O 7 leads to an increase in intrinsic coercivity. For addition of Dy 2 O 3 , the optimum conditions for powder mixing and the optimum Dy 2 O 3 particle size were determined. A mixing time of more than 10 minutes, and a Dy 2 O 3 particle size of less than 3 μm, are required to obtain a high intrinsic coercivity. EPMA measurements of NdFeBAl magnets with Dy 2 O 3 added reveal an inhomogeneous distribution of Dy in the Nd 2 Fe 14 B matrix: the material is Dy-rich near grain boundaries, but Dy-poor within the matrix. The appearance of such an inhomogeneous distribution of Dy is attributed to the reduction of Dy 2 O 3 in the Nd-rich phases, followed by diffusion of the resulting Dy atoms into the matrix

Heterogeneous Metal Catalysts for Oxidation Reactions

Directory of Open Access Journals (Sweden)

Md. Eaqub Ali

2014-01-01

Full Text Available Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.