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Major Melt—Crucible Systems
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
Lanthanum is the least volatile of the rare earth metals; dysprosium has a vapour pressure nearly 300 times that of lanthanum at the same temperature. The metals samarium and europium are similarly very volatile. Besides, lanthanum oxide has the most negative heat of formation among the rare earth oxides. These observations led Daane et al. (1953) to devise a method for reacting the oxides of samarium, europium or ytterbium with lanthanum metal and driving this reaction to completion by distilling away in vacuum the volatile metals formed as product. The free energy of the reaction was made negative by strongly influencing the value of Q (Chapter 2). The method has since been called lanthanothermic reduction or lanthanothermy.
Electro-optic Ceramics and Devices
Published in Lionel M. Levinson, Electronic Ceramics, 2020
The optical transparency of the PLZT ceramics is highly dependent on the concentration of lanthanum oxide in the material. Both low and high concentrations are not conducive to producing high optical transparency, but in each case for a different reason. At low levels of La, the higher birefringence and the existence of ferroelectric domain walls combine to produce significant light scattering, whereas at the higher levels of La second phases precipitated in the grain boundaries lead to high opacity. The specific concentrations of La that yield high optical transparency are dependent on the Zr/Ti ratio of the compositions. For a 65:35 ratio material, the high transparency range extends from about 8 atom% La to approximately 16 atom%.
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Published in L.G. Wilson, Lorne G. Everett, Stephen J. Cullen, Handbook of Vadose Zone Characterization & Monitoring, 2018
Eric N. Koglin, Edward J. Poziomek, Mark L. Kram
Semiconducting oxides [also called metal-oxide semiconductors (MOS)] have been used for many years to detect combustible gases. The most commonly used material for the substrate is tin oxide; however, many other oxides have been used (Azad et al., 1993). In recent years, semiconducting oxide sensors have been used for the detection of NH3, H2S, CO, thiols, ethanol, hydrogen, arsine, and acetic acid, to name a few. The mechanism of detection in air is usually a catalytic oxidation at the surface of the oxide, inducing an increase in conductivity. For example, a semiconducting oxide has been developed for organochloro and organobromo compounds (Penrose et al., 1991). The sensor consists of a coil of platinum wire heat-treated with a mixture of lanthanum oxide, lanthanum fluoride, and a binder. It is used as a sensor by heating the coil to 550°C with an electric current. Conductivity is measured between the heated coil and a separate platinum electrode. When a vapor containing an organochloro compound comes in contact with the sensor, the conductivity increases. Exposure to 100 ppm concentrations of chlorobenzene, benzene, and n-hexane only gave a response to chlorobenzene.
Influence of natural leaf additive in a biodiesel-operated LHR engine on performance and NOx emission
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Senthil Ramalingam, Elangovan Murugesan, Pranesh Ganesan, Mohan Govindasamy
It has been seen that one of the best way to increase the efficiency of biodiesel-operated CI engine is to adopt LHR mode engine. Studies revealed that LHR engine has increased BTE at the expense of NOx emission. Alumina (Al2O3), zirconia (ZrO2), titanium oxide, partially stabilized zirconia (PSZ), magnesium oxide (MgO), fly ash, etc. are used as coating material in CI engine and very little studies were reported on lanthanum oxide as a coating material for CI engine. It has been reported that lanthanum oxide has higher thermal stability and lower thermal conductivity compared to that of PSZ. Lower thermal conductivity of the lanthanum oxide results in lower heat loss to the coolant and higher in-cylinder gas temperature, which may increase the BTE of the engine.
A comparative study of the solvent extraction of lanthanum(III) from different acid solutions
Published in Mineral Processing and Extractive Metallurgy, 2021
V. Agarwal, M.S. Safarzadeh, J. Galvin
Lanthanum plays an important role in nickel-metal hydride rechargeable batteries used in hybrid vehicles and is also used in oil refining as a catalyst in petroleum cracking. Lanthanum oxide is used in high-quality camera and telescope lenses, as an additive in steels and nodular cast irons, and as a component in mischmetal used in lighter flints (Corbett and Simon 1983). Lanthanum is not found as a free element in nature. Its major sources are the minerals monazite ((Ce, La, Nd, Th)PO4) and bastnäsite ((Ce, La, Y)CO3F), which are also major sources of other rare earth elements (REEs) including neodymium and cerium. Lanthanum oxide makes up ∼32.0 wt.% of the total rare earth oxide content of bastnäsite in California (Xie et al. 2014).
Critical review on lanthanum-based materials used for water purification through adsorption of inorganic contaminants
Published in Critical Reviews in Environmental Science and Technology, 2022
Koh Yuen Koh, Yi Yang, J. Paul Chen
Lanthanum oxide/hydroxide (LO/LH) can be easily synthesized through precipitation or hydrothermal treatment with an alkaline solution such as sodium hydroxide (NaOH) and ammonia solution (NH4OH). During the synthesis, hydroxyl functional group (OH) is formed on the adsorbent surface, which is responsible for the removal of certain contaminants such as phosphate, fluoride and arsenic. The adsorption mechanism has been mostly reported as ligand exchange between hydroxyl groups and anionic contaminants. Furthermore, LO/LH also adsorbs contaminants via electrostatic attraction. The adsorption performance of LO/LH is strongly dependent on solution pH and influenced by the occurrence of other components in aqueous solution (Table 1).