Examples of reactions and synthesis by melting

1 Examples of reactions and synthesis by melting. In order to give an indication of the precautions which should be taken in the preparation of alloys by melting together the component metals and of different procedures adopted, a few examples are presented in the following. 

Y-Cu alloys (Fries etal. 1994) Samples were prepared in the course of an investigation (by DTA) of the phase diagram. In this case no special difficulty is related to the differences between the melting and boiling points of the two elements these are Cu m.p. 1084.87°C, b.p. 2563°C, Y m.p. 1522°C, b.p. 3338°C. The DTA 

Hlukhyy and Pottgen (2004) prepared Pd-Mg compounds (Pd2Mg5) and Ir-Mg-In alloys. Pd2Mg5 was synthesized from cold pressed pellets prepared from Pd powder and Mg small pieces. The pellets were sealed under an argon pressure of 800 mbar in niobium tubes. The niobium tubes placed in the water-cooled sample chamber of an induction furnace were first heated at about 1000K for half a minute and then cooled down to 700 K within 30 minutes and quenched by switching off the furnace. The samples could easily be separated from the niobium tubes, and no reaction with the crucible material was observed. 

Zr Hf Ir Alloys-. An example of very high-temperature materials may be given by Ir-based (Ir melting temperature 2447°C) alloys, the mechanical properties of which can be improved by the addition of Zr and Hf. A number of Ir-rich alloys containing up to 10-15% of Zr and Hf have been prepared by Sha et al. (2006) and 

Protection of the molten metals from air and moisture The protection of the molten metals has always been an essential point. Fusion under vacuum or an inert atmosphere (pure He or Ar, possibly gettered) is systematically used. In the past, also for small scale laboratory preparations, fusion under a protective layer of molten non-reactive salts was often used. Low density salt mixtures having low-melting point and high-boiling point were generally employed (for instance eutectic mixtures of anhydrous stable alkali halides). 

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