Excerpts taken from abstracts in CMQ, Vol. 50, No. 3.
To subscribe – www.cmq-online.ca
Leaching of lanthanides from various weathered elution deposited ores
G. A. Moldoveanu and V. G. Papangelakis, Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
ABSTRACT Lanthanides adsorbed on clay minerals were easily recovered by ion exchange leaching with inorganic monovalent salt solutions under ambient conditions. The leaching efficiency (as per cent extraction) of various salts at 0·5M and 25°C was investigated as a function of cation type and salt system (sulphates versus chlorides). The selected lixiviant concentration was based on a 3:1 stoichiometric ratio between total lanthanide content and the exchange cation. Leaching efficiency decreased in the order Cs+>NH4+>Na+>Li+, from 90% to ∼60% respectively, with sulphates exhibiting ∼10% higher extraction than chlorides; differences in lanthanide desorption were explained in terms of differences in cation hydration energies. (NH4)2SO4 was identified as the optimum lixiviant and a procedure was established to investigate the influence of temperature, pH and agitation on desorption kinetics and lanthanide extraction levels. It was determined that maximum extraction required a pH level below 5 and moderate temperatures (<50°C).
Mineralogical characterisation using QEMSCAN of the Nechalacho heavy rare earth metal deposit, Northwest Territories, Canada
T. Grammatikopoulos, SGS Canada Inc, Advanced Mineralogy Facility, Lakefield, Ontario, Canada; W. Mercer, Avalon Rare Metals Inc., Toronto, Ontario, Canada; and C. Gunning, SGS Canada Inc., Advanced Mineralogy Facility, Lakefield, Ontario, Canada
ABSTRACT The Nechalacho rare metal deposit, located in the Northwest Territories, Canada, is currently being taken through a feasibility study by Avalon Rare Metals Inc. QEMSCAN analysis, coupled with supplementary mineral chemistry, and major and trace element analyses, were utilised to identify and quantify the mineralogy of the deposit, and determine REE distribution among the minerals. Geologically, the analysis illustrates distinct styles of REE-Zr mineralization. Fergusonite and zircon are the primary HREE, whereas monazite, allanite, synchysite and bastnaesite the LREE carriers, and identification of fergusonite poor and rich zones. Metallurgically, the QEMSCAN analysis quantifies the liberation of the REE, which is adequate for mineral beneficiation at a K80 below 75 μm, and predicts a range of REE grades and recoveries that can be compared to the actual metallurgical values.
Effects of La addition on microstructure and mechanical properties of SN-58BI solders joints with OSP pads
Y. Y. Shiue and T. H. Chuang, National Taiwan University, Taipei, Taiwan
ABSTRACT Rapid whisker growth was significantly alleviated in a Sn‐58Bi alloy doped with 0·5 wt-% La. Experimental results showed that many thin, plate form intermetallic phases appeared in the solder matrix. The absence of tin whiskers was correlated to the shape effect of RE containing intermetallic plates. After reflowing, Cu6Sn5 intermetallic compounds appeared at the solder/pad interfaces of Sn‐58Bi and Sn‐58Bi‐0·5La packages with OSP pads, which grow linearly during the aging at 75 and 100°C for various times ranging from 100 to 1000 h. In addition, the interfacial intermetallics layers in Sn‐58Bi‐0·5La solder joints were also observed thinner than those in undoped Sn‐58Bi joints. However, RE containing interfacial intermetallic compounds in Sn‐58Bi‐0·5La solder joints led to lower bonding strengths in both ball shear tests (0·4 mm s−1) and high speed ball shear tests (2000 mm s−1). All the reflowed and aged solder joints of both packages were ruptured through the solder balls indicating brittle characteristic.
Thermodynamic modelling of Mn-Y and Mn-Gd systems for application of RE in Mg alloy development
J. Kim and I.-H., Jung, Department of Mining and Materials Engineering, McGill University, Montreal, Quebec, Canada
ABSTRACT Mg alloys are extensively used as light structural materials in the modern industry. Mn and RE metals are effectively used as alloying elements to enhance the properties of Mg alloys. Therefore, the thermodynamic database of those alloys is important in the design and processing of Mg alloys. Critical evaluation and optimisation of all available literature data for the Mn-Y and Mn-Gd systems were conducted to obtain reliable thermodynamic functions of all solid and liquid phases. Recent experimental data were taken into account and the phase diagram and thermodynamic properties were slightly revised for the Mn-Y system and considerably altered for the Mn-Gd one from previous studies. Both systems have quite similar thermodynamic properties and phase diagrams. The systematic trend observed in RE elements for Mn-RE systems is discussed.