Natural resources are the foundation for our lives and lifestyles.
What would our lives be like without mining? Imagine a world without transportation such as jet planes or railroads, without communications such as cell phones or radar, without decorative items such as art or jewelry, without buildings such as skyscrapers or parking garages, without defense systems items such as missiles or submarines, without medical care items such as X-rays or surgical tools. We wouldn’t have any of these things without mining and minerals.
Sources: Hafnium is retrieved as a by-product from zirconium ore minerals. In a typical zirconium ore, there is a Zr:Hf ratio of about 50:1. The mineral zircon is the primary ore source of hafnium. Most zircon (and, therefore, hafnium) is mined from titanium-rich, heavy-mineral sand deposits. Hafnium and zirconium are both used in nuclear reactors. In this application, each must be pure and free from the other. The manufacture of nuclear-grade zirconium therefore produces hafnium as a by-product and, the manufacture of nuclear-grade hafnium produces zirconium as a by-product. This processing actually produces more hafnium than is consumed. Unused hafnium is stored as hafnium oxide or hafnium metal. Geologists estimate the hafnium resources in the United States total 130,000 tons. (By comparison, zirconium resources are about 14 million tons.) World resources of hafnium are estimated at over 1 million tons. Hafnium is imported to the United States in a variety of forms, including hafnium oxide and scrap metals containing hafnium. The majority of the hafnium imported comes from France. Other world producers of hafnium-bearing minerals include Germany, the United Kingdom, Brazil, China, India, Russia, South Africa, Ukraine, and the United States.
Uses: The most significant use of hafnium is in the production of special alloys known as superalloys. Superalloys are alloys (mixtures) of metals that are designed to withstand high-stress situations, such as very high temperatures and pressures. Such metals can include iron, nickel, chromium, titanium, niobium, hafnium and other metals. Because of its ability to absorb neutrons, it is used to control nuclear reactions in fission reactors, including the nuclear reactors that power nuclear submarines. Hafnium is also used as a “scavenger” metal in the retrieval of oxygen and nitrogen. A scavenger metal is one which aids in the collection of gases without reacting with them to form other compounds.
Substitutes and Alternative Sources: Silver-cadmium-indium alloys can be used in place of hafnium as control rods in nuclear reactors. In the production of superalloys, zirconium can often be used in place of hafnium. In some applications, only hafnium gives the desired qualities and so no substitute is possible. However, the abundance of hafnium in storage (and the fact that its production outpaces its consumption) means there is no immediate danger of running short of this rare element.
Background: Hafnium is a bright silver, ductile, lustrous metallic element with a very high melting point. Its atomic number is 72 and its symbol is Hf. Hafnium is the 45th most abundant element in the Earth’s crust with an average crustal abundance of 3 ppm (parts per million). The element was discovered by Dirk Coster and George Charles von Hevesey by separating it from zirconium in 1923.
Hafnium does not react with air, water, acids or bases. It is similar to the element cadmium in that it absorbs neutrons. This feature makes hafnium useful as a control rod material in nuclear reactors.
There is no biological use or benefit for hafnium. It is present in ocean water in very small amounts, specifically 0.008 ppb by weight (parts per billion). For comparison, hafnium is far more concentrated in the Earth’s crust at 3,300 ppb by weight.