Showing papers on "Lanthanum published in 1968"

Preparation and Luminescence of Selected Eu3+‐Activated Rare Earth‐Oxygen‐Sulfur Compounds

Abstract: The hydrated sulfate, sulfate, oxysulfate, and oxysulfide compounds of yttrium, lanthanum, gadolinium, and lutetium were prepared using precipitation techniques and controlled atmosphere high temperature heat treatments. The temperature stability range in air for each compound was investigated by DTA and TGA methods. X‐ray diffraction powder data are presented for the fourteen compounds isolated. The only compounds that showed significant Eu3+‐activated luminescence were the oxy sulfates and oxysulfides. , the most efficient phosphor examined, is as bright as and distinctly more "red." Luminescence data are presented and discussed.

Different effect of cerium and gadolinium impurities on the pressure dependence of the superconducting transition temperature of lanthanum

Abstract: The different effect of cerium and gadolinium impurities on the pressure dependence of the superconducting transition temperature of lanthanum is due to different electronic structures of the rare-earth impurity. The ionic model explains the properties of gadolinium alloys, while the resonant scattering theory explains those of cerium alloys.

Rare earth activated lanthanum and lutetium oxy-chalcogenide phosphors

Abstract: A family of cathodoluminescent phosphors which consist essentially of oxy-chalcogenides of lanthanum and/or lutetium containing, for each mol of phosphor, between 0.0002 and 0.2 mol of dysprosium, erbium, europium, holmium, neodymium, praseodymium, samarium, terbium, or thulium. Up to 15 mol percent of the lanthanum and lutetium may be replaced with yttrium or gadolinium. The phosphors may be prepared by reacting the constituent elements as compounds thereof at temperatures between 900 and 1300° C. for 0.2 to 5.0 hours and then cooling the reaction product.

Preparation of rare earth metal exchanged crystalline alumino silicates

Abstract: Ammonium ion-exchanged crystalline alumino silicates are treated to exchange a given position of the ammonium cations with rare earth metal cations, by (a) the silicates and a soln. of rare earth metal salts are charged to a contact chamber comprising a plurality of stirred contact zones (b) a plug-flow of the resulting slurry through the contact chamber is maintained whereby back-mixing of the contents of one contact zone is substantially obviated, (c) the slurry is withdrawn from the contact chamber, the liquid phase separated and the rare earth-exchanged crystalline alumino silicate is recovered. Rare earth metal salts include those of cerium, lanthanum prasedymium, neodymium etc., and the solution may comprise one or more salts.

Automated neutron-activation analysis of biological material with high radiation levels

Abstract: A method has been developed for the chemical separation and subsequent γ-spectrometric analysis of the alkali metals, the alkaline earths, the rare earths, chromium, hafnium, lanthanum, manganese, phosphorus, scandium and silver in neutron-activated biological material.The separation steps, which are fully automatic, are based on a combination of ion exchange and partition chromatography and require 40 minutes for their completion.

Determination of Trace Amounts of Rare-Earth Impurities in Yttrium Oxide

Abstract: This paper discusses investigations conducted to achieve optimum sensitivity for the determination of rare earths in yttrium oxide and describes a specific technique evolved for the above analysis. A dc arc burning in a controlled atmosphere of argon and oxygen is used together with a spectrograph of very high dispersion in order to provide optimum signal-to-noise ratio. Because the excitation efficiency is not uniform along the entire height of the arc column, only the most efficient portion is transmitted to the slit. Without any treatment or concentration of the sample other than dilution with graphite powder, the above method achieves sensitivities for the rare earths in yttrium oxide ranging from about 50 ppm for the least sensitive rare earths (Pr, Ce) to about 0.5 ppm for the most sensitive rare earths (Lu, Sc, Yb).

Forming deposits within porous material

Abstract: Metal hydroxides are deposited on the interior surfaces of porous materials, e.g. woven cotton fabrics, sponges, bricks and ceramic fibre blankets, by contacting without precipitation of hydroxide the interior surfaces with (a) an aqueous solution of at least one metal salt from which the corresponding hydroxide may be precipitated at a pH of 1.7-12.5 and (b) a substance capable of decomposing at the pH of the solution to give ammonia with a consequent rise of the pH, and initiating the decomposition of the substance thereby raising the pH of the solution to a value such that the corresponding hydroxide of the metal is precipitated on the interior surfaces. The salt may be of copper, silver, beryllium, magnesium, calcium, zinc, cadmium, mercury, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, zirconium, thorium, tin, lead, chromium, uranium, manganese, iron, cobalt, nickel, ruthenium, rhodium, pelladium, iridium, or aluminium, aluminium oxychloride being preferred, and the substance decomposing to give ammonia may be hexamethylene tetramine, urea preferably in admixture with urease, urea orthophosphate and condensation products of aldehydes and ammonia. The aqueous solution of the metal salt and the ammonia producing substance may be mixed and the resulting solution adjusted to the desired pH and applied to the porous material which is then heated. The porous material may subsequently be heated to convert the precipitated hydroxide to the corresponding oxide or to a salt of the metal and if it is a carbonaceous material e.g. a cotton material or sponge, to burn away the substrate to form a material suitable for use as a catalyst. In the case of a ceramic blanket the metal hydroxide is deposited as discrete nodules around the fibres especially at the points of intersection of two or more fibres thus locking them together.ALSO:Metal hydroxides are deposited on the interior surfaces of porous materials, e.g. woven cotton fabrics and ceramic fibre blankets, by contacting without precipitation of hydroxide the interior surfaces with (a) an aqueous solution of at least one metal salt from which the corresponding hydroxide may be precipitated at a pH of 1.7-12.5 and (b) a substance capable of decomposing at the pH of the solution to give ammonia with a consequent rise of the pH, and initiating the decomposition of the substance thereby raising the pH of the solution to a value such that the corresponding hydroxide of the metal is precipitated on the interior surfaces. The salt may be of copper, silver, beryllium, magnesium, calcium, zinc, cadmium, mercury, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, zirconium, thorium, tin, lead, chromium, uranium, manganese, iron, cobalt, nickel, ruthenium, rhodium, pelladium, iridium, or aluminium, aluminium oxychloride being preferred. and the substance decomposing to give ammonia may be hexamethylene tetramine, urea preferably in admixture with urease, urea orthophosphate and condensation products of aldehydes and ammonia. The aqueous solution of the metal salt and the ammonia producing substance may be mixed and the resulting solution adjusted to the desired pH and applied to the porous material which is then heated. The porous material may subsequently be heated to convert the precipitated hydroxide to the corresponding oxide or to a salt of the metal and if it is a cotton material or sponge to burn away the substrate to form a material suitable for use as a catalyst. In the case of a ceramic fibre blanket the metal hydroxide is deposited as discrete nodules around the fibres especially at the points of intersection of two or more fibres thus locking them together.

Separation of lanthanum from barium by solvent extraction with the monooctyl ester of anilinobenzylphosphonic acid

Abstract: The extraction of the radionuclides 131barium and 140lanthanum from hydrochloric acid solution by means of the monooctyl ester of anilinobenzylphosphonic acid (MOABP) has been studied. Solutions of MOABP in three different solvents (petroleum ether, carbon tetrachloride and chloroform) were used as the organic phase and the influence of the solvents on the extraction of barium and lanthanum is discussed. It was found that lanthanum can be quantitatively extracted from certain hydrochloric acid solutions into the organic phase, whereas barium remains in the aqueous layer. A simple procedure for their separation is described. It can be carried out regardless of whether the metals are in dilute solution or in a carrier-free form. Barium chloride, even in high concentrations, does not influence the extraction of lanthanum. Lanthanum was re-extracted from the organic phase with 1 M hydrochloric acid. The purity of the separated lanthanum was checked by following its decay curve.

Lanthanum, praseodymium and neodymium chloroacetates

Abstract: The monochloroacetates of lanthanum, praseodymium and neodymium of the composition M(ClCH2COO)3·2H2O have been prepared and characterised. The compounds behave as non-electrolytes in dimethylformamide. The infrared spectra are consistent with bidentate coordination of the carboxylate group and show the presence of two types of water molecules, coordinated, and free. With six oxygen atoms from the three acetato groups and one from the water bonded to the metal, a coordination number of seven has been assigned to the rare earths in these compounds. On pyrolysis, the chloroacetates lose water at ~130 °C and yield the oxychlorides at ~500 °C. The X-ray powder patterns of the chloroacetates have been indexed for the monoclinic system, with four molecules per unit cell.

Commercial production of rare earth metals by fused salt electrolysis

Abstract: The commercial production of rare earth metals by fused salt electrolytic methods is described. These methods are used to make mischmetal, cerium, lanthanum, and didymium (Nd + Pr). The feed materials consist essentially of anhydrous chlorides of the metal to be produced, augmented by additions of nonrare earth salts to yield an electrolyte with satisfactory properties for reduction. The rare earths are derived either from monazite or from bastnasite ores. The anhydrous chlorides are manufactured from the hydrated chlorides by methods which minimize oxidation or hydrolysis. Alternatively, anhydrous chlorides may be used which result from the direct chlorination of rare earth ores by the Gold-schmidt process. These are particularly suitable for electrolysis due to their very low oxychloride content. Fluorides and oxides of the rare earths are produced by wet chemical methods to provide the relatively small quantities of these compounds now used for commercial fused salt electrolysis. Reduction cells in use today are constructed mainly from a) ceramics, b) graphite, or c) iron. The advantages and disadvantages of these types of cells are described together with the typical products which result from their use. Primary attention is given to production of mischmetal (mixed rare earth metal), which is the rare earth metal produced on the largest scale today. Brief reference is made also to production of cerium, lanthanum, and didymium (Nd + Pr) metal. Finally, a resume of the current uses of these metals is presented with reference to recent trends in the industrial applications of the rare earth metals.