We continue to review some of the most important materials in heat treatment and metallurgy.
Lithium (chemical symbol: Li)
Lithium is believed to be one of only three elements – the others are hydrogen and helium – produced in significant quantities by the “Big Bang.” Synthesis of these elements took place within the first three minutes of the universe’s existence. Lithium is also the only alkali metal (Li, Na, K, Rb, Cs, Fr) that reacts with nitrogen.
Johann August Arfvedson in 1817 discovered lithium in the mineral petalite (LiAl(Si2O5)2). However, it was first isolated by William Thomas Brande and Sir Humphrey Davy through the electrolysis of lithium oxide (Li2O). Today, larger amounts of the metal are obtained through the electrolysis of lithium chloride (LiCl). Lithium is not found free in nature and makes up only 0.0007% of the Earth's crust. Lithium, like sodium, reacts violently with water but to a lesser degree.
Lithium based batteries (Fig. 1) used in computers and cellphones have extended battery life and revolutionized these consumer devices. For a given battery weight, lithium batteries deliver more energy than batteries based on lead or other metals. In other words, lithium batteries have high energy density. Lithium also has the highest specific heat of any solid element and is used in heat-transfer applications.
It is used to make special glasses and ceramics, including the Mount Palomar telescope's 200-inch mirror found in the Hale telescope (Fig. 2). It was built between 1934 and 1948, funded by a $6 million gift from the Rockefeller Foundation. The primary mirror is the largest single-piece mirror in any working telescope and many feel it could never be replicated. As cast by Corning Glass, the Pyrex honeycomb mirror weighed 20 tons. Caltech scientists ground the mirror to shape and polished it to optical smoothness, removing about 10,000 pounds of glass. The mirror is cleaned weekly and re-coated with aluminum about once a year. This image shows the mirror before (top) and after re-coating.
Lithium is the lightest metal and can be alloyed with aluminum, copper, manganese and cadmium to make strong, lightweight metals for aircraft. Lithium hydroxide (LiOH) is used to remove carbon dioxide from the atmosphere of spacecraft. Lithium stearate (LiC18H35O2) is used as a general-purpose and high-temperature lubricant. Lithium carbonate (Li2CO3) is used as a drug to treat manic-depression disorder.
Here are a few important facts about lithium.[2,5]
- Atomic number: 3
- Atomic weight: 6.941
- Melting point: 453.65 K (180.50°C or 356.90°F)
- Boiling point: 1615 K (1342°C or 2448°F)
- Density: 0.534 grams per cubic centimeter
- Phase at room temperature: Solid
- Element classification: Metal
- Period number: 2
- Group number: 1
- Group name: Alkali metal
- Electron configuration: 1s22s2
- KnowledgeDoor (www.knowledgedoor.com)
- Jefferson Lab (https://www.jlab.org)
- Chemicool (ww.chemicool.com)
- Guide to the Cosmos Newsletter (http://guidetothecosmos.com)
- Periodic Table of the Elements, Sargent-Welch Catalog No. WLS-18806-10, 2004
- Wikipedia (www.wikipedia.org)
- Royal Society of Chemistry (rsc.org)