• Toxicological Research
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• v.31 no.2
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• pp.181-189
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• 2015

In recent years, the use of both nano- and micro-sized lanthanum has been increasing in the production of optical glasses, batteries, alloys, etc. However, a hazard assessment has not been performed to determine the degree of toxicity of lanthanum. Therefore, the purpose of this study was to identify the toxicity of both nano- and micro-sized lanthanum oxide in cultured cells and rats. After identifying the size and the morphology of lanthanum oxides, the toxicity of two different sized lanthanum oxides was compared in cultured RAW264.7 cells and A549 cells. The toxicity of the lanthanum oxides was also analyzed using rats. The half maximal inhibitory concentrations of micro-$La_2O_3$ in the RAW264.7 cells, with and without sonication, were 17.3 and 12.7 times higher than those of nano-$La_2O_3$, respectively. Similar to the RAW264.7 cells, the toxicity of nano-$La_2O_3$ was stronger than that of micro-$La_2O_3$ in the A549 cells. We found that nano-$La_2O_3$ was absorbed in the lungs more and was eliminated more slowly than micro-$La_2O_3$. At a dosage that did not affect the body weight, numbers of leukocytes, and concentrations of lactate dehydrogenase and albumin in the bronchoalveolar lavage (BAL) fluids, the weight of the lungs increased. Inflammatory effects on BAL decreased over time, but lung weight increased and the proteinosis of the lung became severe over time. The effects of particle size on the toxicity of lanthanum oxides in rats were less than in the cultured cells. In conclusion, smaller lanthanum oxides were more toxic in the cultured cells, and sonication decreased their size and increased their toxicity. The smaller-sized lanthanum was absorbed more into the lungs and caused more toxicity in the lungs. The histopathological symptoms caused by lanthanum oxide in the lungs did not go away and continued to worsen until 13 weeks after the initial exposure.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.741-749
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• 1994

The planar solid oxide fuel cell(SOFC) contains several ceramic materials depending on its structure and has rdfractory metal parts for manifolds, shrouds and current leads. Among ceramic materials for planar SOFC, joining of lanthanum chromite separator and yttria stabilized zirconia(YSZ) electoyte in planar SOFC stack to give strong gas tight seals is necessary for satisfactory operation and high performance. Nevertheless, for planar SOFC/sub s/, how to seal the cell stack and gas manifold remains as one of the unsolved problems. Therefore, in this study. we investigated the joining of sintered lanthanum chromite and YSZ pellets using unsintered lanthanum chromite green films as sealent. Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDX) revealed that Ca in the sealing material diffused and dissolved into YSZ and sintered lanthanum chromite, and unsintered lanthanum chromite green films reacted with YSZ to from a new phase at the interface. Also, the densification of unsintered lanthanum chromite green films was inpeded by the Ca migration.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1023-1031
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• 1996

A new synthetic route for the lanthanum β-diketonate compounds via in-situ formed lanthanum alkyl complexes was developed in the process for the development of suitable MOCVD (metal-organic chemical vapor deposition) precursors of PLT, one of the promising material for the ferroelectric film. A series of lanthanum β-diketonate compounds were successfully synthesized by this method. This new method is found to have some merits; versatile method for almost every β-diketone, β-hydroxyketone, and β-hydroxyaldehyde, short reaction time, easy purification for high purity, moderate to high yield, and easy access to anhydrous compounds. In some cases, anhydrous oligomeric products fail to show the higher volatility. On the other hand, some lanthanum β-diketonates with aromatic groups such as La(1,3-biphenyl-l,3-propandione)3 are found to have favorable properties for a precursor of lanthanum oxide, one of major components of PLT, such as low melting point, and much higher decomposition temperature. A plausible pyrolysis mechanism is proposed by the TGA, where consecutive dissociation of R, CO, CH, C, and O fragments occurs.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.50-56
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• 2012

In this study, loess composites, loess with lanthanum and with aluminum, were made and evaluated for treatment of phosphorus removal in natural water system. Desiccation method for production of loess composite was superior to centrifugation method in obtaining high concentrated composites of lanthanum and aluminum. Washing of loess lanthanum composite by water did not deteriorat the lanthanum concentration in the composite, but this lowered the aluminum concentration of loess aluminum composite. Total of 15 and 37.5% of aluminum contents were removed after first washing treatment in aluminum loess of 0.05% and 0.1% respectively. However, no more aluminum loss was monitored with increase of washing times. Phosphorus removal efficiencies were not decreased with washed loess aluminum composite. Phosphorus removal was successfully achieved by adsorption of phosphate to loess composite at pH range of 5.0 ~ 8.0. Freundlich and Langmuir adsorption isotherm was observed in the adsorption of phosphate for loess composite. Dosages of 0.05% and 0.1% lanthanum composite for 95% of phosphorus removal could reduce its usage amount to 25% and 50%, respectively, comparing with dosage of loess alone. Dosages of 0.05% and 0.1% aluminum composite could reduce its usage amount to 48% and 63%, respectively.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.2
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• pp.50-56
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• 2013

Objectives: The present study investigated cytotoxicity and DNA damage in human lung cells in vitro. Methods: Neodymium oxide and lanthanum oxide were dispersed by ultrasonic treatments. The assay was performed with MRC-5 (Human male fetus lung cell). Cytotoxicity and comet assay of lanthanum oxide and neodymium oxide were measured after 24 and 48 hours incubation. Results: After 24 hours of exposure to rare earth metals, the cytotoxicities of lanthanum oxide in more than $1{\mu}M$ concentration groups were significantly increased when compared to the control group, but the cytotoxicities of neodymiun oxide in more than $100{\mu}M$ concentration groups were statistically increased. After 48 hours exposure, cytotoxicities of both materials were statistically increased in $100,000{\mu}M$ concentration groups. Olive tail moments of the lanthanum oxide treated group were significantly increased when compared to the control group. Conclusions: The cytotoxicity of lanthanum oxide was higher than that of neodymium oxide. The DNA of MRC-5 cells treated with lanthanum oxide for 48 hours were significantly damaged.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3163-3168
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• 2014

Three kinds of lanthanum oxides ($La_2CO_3$) were synthesized from different methods and used as a catalyst in the transesterification of dimethyl carbonate (DMC) with glycerol for the synthesis of glycerol carbonate (GLC). Lanthanum oxide synthesized using a surfactant (S-La) showed a much higher GLC yield of 89.9% compared to other lanthanum oxides synthesized by calcination (C-La) and precipitation (P-La) at the reaction conditions of $90^{\circ}C$, DMC/glycerol = 2, and catalyst/glycerol = 5 wt %. The best catalyst was obtained when the surfactant/La weight ratio was 12. XRD study revealed that S-La has large amount of monoclinic and hexagonal $La_2O_2CO_3$ phases, which are assumed as active sites of the catalyst for the reaction.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.624-628
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• 2003

Lanthanum oxyfluoride can be synthesized by mechanochemical (MC) reaction between lanthanum oxide ($La_2O_3$) and polytetrafluoroethylene (PTFE, ($({CF_2CF_2}_n)$) in air using a planetary mill. MC reaction between the two materials induced from intensive grinding operation. The MC reaction is almost finished by 240min, and the products ground for 240min or more are composed of LaOF, amorphous $La(CO_3)F$ and amorphous carbon (C). Heating this MC reaction products at $600^{\circ}C$ enables us to eliminate amorphous C and decompose $La(CO_3)F$ into LaOF, so that pure LaOF material can be obtained as the final product. The average particle size of the final product (purified LaOF) is around few ten nanometers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.287-287
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• 2007

The ferroelectric and electric properties of UV-irradiated bismuth lanthanum titanate (BLT) films prepared using photosensitive starting precursors were characterized. The effects of lanthanum doping on ferroelectric and electric properties were investigated by polarization-electric field hysteresis loops and leakage current-voltage measurements. X-ray diffractometer and ellipsometry were served to provide the information about the crystalline structure and thickness of the films after annealing. The images of the surface microstructure and direct-patterned BLT films were observed by using scanning electron microscopy. The effects of lanthanum doping on the electric properties of direct-pattern able BLT films and their direct-patterning were studied.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1347-1352
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• 1996

• Journal of Powder Materials
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• v.22 no.6
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• pp.413-419
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• 2015

Lanthanum zirconate, $La_2Zr_2O_7$, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a $La_2Zr_2O_7-4YSZ$ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.