Scandium is a soft, silvery metallic element. Its atomic number is 21, making it the lightest of the transition metals. Scandium is not particularly rare - its occurrence in crustal rocks is 22 around ppm. This makes scandium generally more abundant than lead, mercury, and precious metals. Despite this fairly common occurrence, scandium rarely concentrates in nature. It does not selectively combine with the common ore-forming anions, so time and geologic forces only rarely form scandium concentrations over 100 ppm. There is currently no dedicated single mine source and it estimated that only 15 tonnes of scandium are produced globally each year.
Scandium exists in nature in its oxide form. It is very difficult to reduce to its pure elemental state. In fact, it was not isolated in pure form until 1937 and the first pound of pure elemental scandium metal was not produced until 1960. Scandium in oxide form is referred to as scandia or scandium oxide, and the chemical formula is Sc2O3. Processed scandium oxide, a white powder, is stable at ambient temperature and is the standard scandium form for commerce.
Despite scandium’s scarcity and high cost, interest in the metal is high and multiple high value commercial uses have been developed. Of particular interest is the alloy of scandium into aluminum metal products. When used in combination with other common aluminum alloys scandium can produce stronger, more corrosion resistant, heat tolerant, weldable aluminum products. Aluminum products are being increasingly incorporated into transportation applications (aircraft and automobile) in order to meet fuel efficiency requirements.
Aircraft manufacturers are particularly interested in scandium alloyed aluminum materials. Aircraft designers believe use of Al-Sc alloys can reduce aircraft weights by 15%-20%. In addition, the ability to employ weldable structures promises similar cost reduction potential.
Scandium also exhibits exceptional electrical conductivity and heat stabilization qualities and the largest volume current use is in solid oxide fuel cells (“SOFCs”). Incorporation of scandium in SOFCs enables a lower operating temperature resulting in longer lived equipment and less costly materials of construction. Bloom Energy is the leading SOFC manufacturer and currently single largest scandium user.
Al-Sc alloys may reduce aircraft weights by 15%-20%
Numerous other applications have been identified and are under research, most notably high intensity lighting (“stadium lighting”) and high voltage power transmission and additive layer parts manufacturing (“3D Printing”).
Scandium contains unique properties that when incorporated into materials of construction may create unexpected high performance product properties.
The lack of assured supply sources has slowed the adoption of scandium, but at the same time demand for high performance materials has spurred development of commercial applications. The largest of these potential applications is the use of scandium in aluminum alloys.
In general, it is possible to modify and improve aluminum base materials by alloying them with scandium. The addition of scandium with other alloy materials improves strength and heat tolerance, promotes corrosion resistance and extends weldability and weld strength to an array of aluminum alloy materials.
Currently the global mineral production value of aluminum is slightly more than $100 billion, less than only iron ore as a structural metal and slightly greater than copper. The historic growth rate of demand for aluminum is 4% and the forecast for growth through 2018 is ever stronger. Aluminum is chosen for its weight/strength advantages and ease of shaping and manufacturing. Almost all aluminum is alloyed either mildly or in advanced combinations of alloy metals.
The single largest market sector use for aluminum is transportation, primarily aircraft and automotive. Aluminum products are increasingly incorporated into these applications to meet fuel efficiency requirements. Scandium alloy characteristic can enable even greater uses for aluminum.
Aircraft makers use aluminum alloys now, and are assessing adoption of aluminum scandium alloy materials. The use of Al-Sc alloys could reduce aircraft weights by15-20%. In addition, the ability to employ weldable structures promises similar cost reduction potential.
Automotive applications could be even larger consumers of scandium-aluminum materials. Aluminum is currently widely used in drive-trains, chassis and body panels. Each pound of aluminum substituted for conventional steel materials results in a 2.5 pound weight loss for the vehicle. Scandium alloyed aluminum could also promote the adoption of aluminum for wheels and engine parts.
Additive layer manufacturing (3D Printing) is particularly suited to scandium-aluminum alloy use, where high strength, moldability and weldability are important.
If only a tiny fraction (0.1%) of the annual aluminum market absorbed scandium in alloy at a 0.5% level, it would represent 350 tonnes ($700M) in global scandia demand.
Solid Oxide Fuel Cells (SOFC) are currently the primary application for scandium, where the metal a substitute for yttrium. Scandium exhibits certain electrical and heat stabilizing qualities that make it significantly more effective than yttrium in numerous applications.
High voltage tension wires for power transmission are another potential scandium market. Aluminum-scandium alloy has much higher conductivity than other alloys, allowing the wire performance to be superior, both physically (long spans) and electrically (superior conductivity).