TITLE:
Nanostage Alloying of Metals in Liquid Phase
AUTHORS:
Deblina Roy, Tarasankar Pal
KEYWORDS:
Alloy, Nanoparticles, Hume-Rothery Rules, Oriented Attachment, Ostwald Ripening, Digestive Ripening, Galvanic Replacement Reaction, Kirkendall Effect, Silicone Oil, High Entropy Alloys
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.11 No.1,
January
29,
2021
ABSTRACT: Alloying of metals is known from antiquity. Alloy
making i.e., homogenizing metals started in a “hit-or-miss” way. The 1st alloy from copper (Cu) and tin (Sn) was produced around 2500 BC and from then
Bronze Age began. Subsequently iron (Fe) age started after the Bronze Age.
Aluminium (Al) alloying was discovered much later because pure Al could not be
recovered easily even though Al is the most abundant metal in the earth’s
crust. Refining of Al is a very difficult job because of its strong affinity
towards oxygen. To ease alloying, melting points (mp) of the individual
constituents and reactivity of metal towards oxygen were the hurdles. Now
understanding the thermodynamics of metal mixing has paved alloying. Periodic
properties of elements concerning size, electronegativity, crystal structure,
valency, lattice spacing, etc. are considered for alloying. In this feature
article, more emphasis is given to Hume-Rothery rules in which the necessary
parameters for alloying have been illustrated. Importantly standard electrode
potential (E0) values, eutectic, phase diagram, size-related strain
in metals, etc. have been looked into in the present discussion. One elegant
example is Sn-Pb alloy, known as soft solder. Soft solder was in use for many
years to connect metals and in electric circuitry. Low melting, flowability,
and conductivity of soft solder had placed Sn-Pb alloy a unique position in
industries, laboratories and even in cottage industries. However, toxic Pb
volatilizes during soldering and hence soft solder is banned almost in all
countries. We felt the need for a viable alternative to obtain soldering
material and then silver (Ag) based highly conducting, an eco-friendly alloy of
Sn resulted in from a high boiling liquid. The discovery engenders not only a
new conducting soldering alloy but also a new concept of melting metals
together. Furthermore, new ideas of alloying have been generalized at their
nanostages from a suitable high boiling solvent.