REM Handling Procedures

Below are recommended handling procedurs for the Rare Earth Metals.  Keep in mind that these procedures are intened for very high purity metals, and alternative procedures may exiist or be better suited to your facilities capabilities.  Please consult with your safety officer(s) before employing any of these procedures. The procedures are groupe by element: 

(La, Ce, Pr & Nd), (Sc, Y, Gd, Tb, Dy, Ho, Er, Tm and Lu), (Sm & Yb), and Eu

 

RECOMMENDED HANDLING PROCEDURES FOR: La, Ce, Pr and Nd
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  1. Storage These metals will oxidize slowly at room temperature in air. They should be stored under 10-3 torr or better vacuum or in sealed jars under an inert gas. For long term storage the best method is to seal these metals in evacuated Pyrex tubes with the ends sealed by fusion. Oils should not be used.
  2. Cleaning Even when stored as described above, some surface oxidation will occur. The oxidation should be removed by filing. A wire-brush wheel may also be used, but filing is preferred. If the surface has already turned white, at least one mm of metal should be removed to ensure the removal of intergranular corrosion products which are present near the surface. After filing, the cold worked surface can be removed by electropolishing (see below) which also passivates the surface.
  3. Electropolishing An electrolyte of 1% (or up to 6%) perchloric acid in absolute methanol is stirred and cooled continuously in a dry ice-acetone bath. A platinum cylinder (cup) serves as the cathode. A current density of about 0.5 amps/cm2 usually is required. A variable voltage supply should be used and the amperage controlled to give small bubbles at the surface of the sample. The electrolyte should not be allowed to bubble excessively. The sample should be rinsed while cold in the dry-ice acetone bath, then rinsed with copious quantities of methanol. [If pure fcc cerium is required, a room temperature etch should be used since some dhcp cerium will form on cooling to dry-ice temperatures. Roman's solution is recommended: Koch and Picklesimer, Trans. Met. Soc. AIME 239 759 (1967).]
  4. Cutting A metal saw (hack saw or jeweler's saw), or a low speed diamond saw, or a spark cutter may be used. The metal should be electropolished after cutting since the freshly cut surface is quite reactive. Shearing is not recommended unless the sheared surface is filed off. The low speed diamond saw or the spark cutter are recommended as the best method for obtaining a strain-free surface.
  5. Cold Working These metals can be cold swaged or rolled about 30% reduction in cross section without heat treatment. To prevent contamination they should be wrapped or (even better) sealed in tantalum.
  6. Handling Since these metals react primarily with moisture, they should not be touched with bare hands. Plastic gloves are recommended. They can be handled in air, but an oxide layer does form quite quickly. This layer can be removed and the surface passivated by electropolishing (see 3 above).
  7. Stress Relief The surface should be freshly cleaned by electropolishing just prior to heat treatment. A vacuum of 10-8 torr or better is required to prevent contamination. Minimal contamination will occur at 10-6 torr if the samples are wrapped in clean tantalum. The recommended temperature is half of the melting point in K for about 8 hours. (If pure d-hcp La is required, a special procedure must be used)
  8. Melting These metals may be arc or electron beam melted. Levitation and induction heating in outgassed tantalum or tungsten crucibles are also suitable. If these metals are heated in tantalum or tungsten to temperatures significantly above their melting points, tantalum and tungsten will dissolve in the molten rare earth [for details see Dennison, Tschetter, Gschneidner, J. Less-Common Metals 11, 423-35 (1966)].

 

RECOMMENDED HANDLING PROCEDURES FOR: Sc, Y, Gd, Tb, Dy, Ho, Er, Tm and Lu
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  1. Storage These metals do not oxidize at room temperature in air. However, for long term storage, closed containers are recommended. Oil should not be used.
  2. Cleaning If surface oxidation has occurred due to exposure to acid fumes or slightly elevated temperatures, the major portion should be removed by filing and the final polishing done electrolytically (see below).
  3. Electropolishing An electrolyte of 1% (or up to 6%) perchloric acid in absolute methanol is stirred and cooled continuously in a dry ice-acetone bath. A platinum cylinder (cup) serves as the cathode. A current density of about 0.5 amps/cm2 usually is required. A variable voltage supply should be used and the amperage controlled to give small bubbles at the surface of the sample. The electrolyte should not be allowed to bubble excessively. The sample should be rinsed while cold in the dry-ice acetone bath, then rinsed with copious quantities of methanol.
  4. Cutting A metal saw (hack saw or jeweler's saw), or a low speed diamond saw, or a spark cutter may be used. The metal should be electropolished after cutting since the freshly cut surface is quite reactive. Shearing is not recommended unless the sheared surface is filed off. The low speed diamond saw or the spark cutter are recommended as the best method for obtaining a strain-free surface.
  5. Cold Working These metals can be cold swaged or rolled about 30% reduction in cross section without heat treatment. To prevent contamination they should be wrapped or (even better) sealed in tantalum.
  6. Handling Since these metals react primarily with moisture, they should not be touched with bare hands without cleaning the surface before they are heated. Plastic gloves are recommended. They can be handled in air. However, as mentioned above, strained surfaces from cutting or filing should be removed by electropolishing (see 3 above).
  7. Stress Relief The surface should be freshly cleaned by electropolishing just prior to heat treatment. A vacuum of 10-8 torr or better is required to prevent contamination. Minimal contamination will occur at 10-6 torr if the samples are wrapped in clean tantalum. The recommended temperature is half of the melting point in K for about 8 hours.
  8. Melting These metals may be arc or electron beam melted. (Due to its high pressure, Thulium can not be melted and can be arc melted only with great losses of metal). Levitation or induction heating in outgassed tantalum or tungsten crucibles are also suitable. If these metals are heated in tantalum to tungsten or a temperature above their melting points, tantalum and tungsten will dissolve in the molten rare earth [for details see Dennison, Tschetter, Gschneidner, J. Less-Common Metals 10, 108-15 (1966) and 11, 423-35 (1966)].

 

RECOMMENDED HANDLING PROCEDURES FOR: Sm and Yb
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  1. Storage These metals will oxidize very slowly at room temperature in air. They should be stored under 10-3 torr or better vacuum or in sealed jars under an inert gas. For long term storage the best method is to seal these metals in evacuated Pyrex tubes with the ends sealed by fusion. Oil should not be used.
  2. Cleaning If surface oxidation has occurred due to exposure to acid fumes or slightly elevated temperatures, the major portion should be removed by filing and the final polishing done electrolytically (see below).
  3. Electropolishing For Sm: An electrolyte of 1% (or up to 6%) perchloric acid in absolute methanol is stirred and cooled continuously in a dry ice-acetone bath. A platinum cylinder (cup) serves as the cathode. A current density of about 0.5 amps/cm2 usually is required. A variable voltage supply should be used and the amperage controlled to give small bubbles at the surface of the sample. The electrolyte should not be allowed to bubble excessively. The sample should be rinsed while cold in the dry-ice acetone bath, then rinsed with copious quantities of methanol. For Yb: A chemical polis of 5-8 ml HNO3, 58 ml H3PO4 and 22 ml of methanol swabbed on for 10 seconds works well. Electropolishing with 10 vol.% HCl in methanol at room temperature also works. See Beaudry and Gschneidner in Handbook on the Physics and Chemistry of Rare Earths, Vol. 1, 209 (1978) North Holland Publishing Co., Amsterdam.
  4. Cutting A metal saw (hack saw or jeweler's saw), or a low speed diamond saw, or a spark cutter may be used. The metal should be electropolished after cutting since the freshly cut surface is quite reactive. Shearing is not recommended unless the sheared surface is filed off. The low speed diamond saw or the spark cutter are recommended as the best method for obtaining a strain-free surface.
  5. Cold Working Sm can be cold swaged or rolled only about 10% reduction in cross section, while Yb can be cold worked 50% or more without heat treatment. To prevent contamination both should be wrapped or (even better) sealed in tantalum.
  6. Handling Since these metals react primarily with moisture, they should not be touched with bare hands, especially if they are to be heated. Plastic gloves are recommended. They can be handled in air, but an oxide layer does form slowly. This layer can be removed by electropolishing (see 3 above).
  7. Stress Relief The surface should be freshly cleaned by electropolishing just prior to heat treatment. A vacuum of 10-8 torr or better is required to prevent contamination. Minimal contamination will occur at 10-6 torr if the samples are wrapped in clean tantalum. The recommended temperature is half of the melting point in K for about 8 hours.
  8. Melting Sm may be arc melted but not Yb. Induction heating in sealed outgassed tantalum or tungsten crucibles is most suitable. If these metals are heated in tantalum or tungsten to a temperature significantly above their melting points, tantalum and tungsten will dissolve in the molten rare earth [for details see Dennison, Tschetter, Gschneidner, J. Less-Common Metals 11, 423-35 (1966)].

 

RECOMMENDED HANDLING PROCEDURES FOR: Europium
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  1. Storage Europium reacts quickly with moist air. It should be stored in sealed Pyrex tubes or under 10-6 torr vacuum or better. Sealing in a Pyrex jar under an inert atmosphere is all right for short term storage.
  2. Cleaning The only method recommended is scraping the surface with a sharp instrument.
  3. Cutting A sharp knife or razor blade works the best for small pieces. A hack saw may be used, but blades must be changed frequently.
  4. Cold Working Eu is soft and can be extruded, swages or cold rolled. However, the surface must be protected from the air at all times.
  5. Handling All handling should be done under an inert atmosphere. However, the surfaces of extruded Eu react slowly in air and short time exposure to air does not contaminate the sample excessively.
  6. Stress Relief Must be heated under 10-8 torr or sealed in clean, outgassed tantalum containers. A temperature of 275- 300°C for about 8 hours is recommended.
  7. Melting Europium should be melted in sealed, outgassed tantalum crucibles. Open crucibles under an inert atmosphere will work.
  8. Electropolishing, Metallography Little is known about electropolishing Eu or preparing Eu for metallographic examination. If this is necessary we suggest that procedures developed for alkali or alkaline earth metals may work for Eu.