Rare Earths
What are Rare Earth Elements?
Rare earth elements are most simply defined as those chemical elements ranging in atomic numbers between 57 and 71 and include lanthanum, from which rare earth metals get their collective name of lanthanides and range through to lutetium with an atomic number of 71. Yttrium (atomic number of 39) due to its chemical similarity to lanthanides (it is placed as a transition metal on the periodic table) is commonly found in rare earth deposits and is generally classed as a heavy rare earth metal.
Light rare earths make up the first seven elements of the lanthanide series (atomic number 57-62) and include lanthanum one of the more reactive of the rare-earth metals, cerium the most abundant of the rare earth metals, praseodymium, neodymium, promethium (not found naturally) and samarium.
Heavy rare earths are typically more valuable relative to light rare earths and have a higher atomic number ranging from 63-71. Heavy rare earths include europium (which together with terbium is the most valuable rare earth valued at US $600-700 per kilo at today’s prices) gadolinium, terbium dysprosium, holmium, erbium, thulium, ytterbium and lutetium.
The rare earths range in crustal abundance from cerium, the most abundant at 60 parts per million, which is more abundant than nickel, to thulium and lutetium which are the least abundant rare earth elements at about 0.5 parts per million.
Other metals are also often found associated with rare earth deposits and these include uranium, thorium, beryllium, niobium, tantalum and zirconium.
Periodic Table
Most rare earth deposits that are mined will comprise a complex mix of oxides that will include monazite, allanite, bastnasite and cerite which are the main rare earth minerals. These minerals then require complicated techniques to separate and to refine the metals from the oxides. The rare earth oxides are then sold at an individually negotiated contract as there is no central clearing or pricing facility for rare earth metals or oxides.
Rare earth projects often have a high value. A tonne of 98% refined ore is worth in the order of US$40 per kilogram which would rise to an average US$200 a kilogram for a fully refined 99.99% purity basket of Light Rare Earths. This value would rise even higher if the more valuable Heavy Rare Earth components are added into the calculation. Early indications from the initial RC drilling completed at Mrima Hill in Kenya by Pacific Wildcat Resources is that this rare earth deposit has a favourable proportion of the more valuable heavy rare earths (including yttrium) of almost 10%.
A Summary of the Main Uses of Rare Earths
Rare earth metals are used in a variety of modern technologies with applications in the military, medical, scientific, aerospace and consumer sectors plus in the increasingly important "green" sector. For many of their applications there is currently no known appropriate substitute. The use of rare earths as magnets in electrical motors is likely to become the major driver for growth for the whole rare earths industry and this use together with phosphors will soon make up over 65% of rare earth oxides (by value) consumed. The main uses of rare earths are the following:
· Magnets
Rare-earth alloy magnets are very powerful permanent magnets which are particularly useful in the automotive and wind power generation industries due to their light weight compared to magnetic strength. In addition these magnets are also used in computer disc drives plus in mobile phones, IPods, etc. The key rare earth metals used in magnets are neodymium, praseodymium and dysprosium.
· Phosphors
A traditional use of rare earths is to provide colour phosphors in televisions and more recently in cathode ray tubes, plasma screens and liquid crystal displays with europium, terbium and yttrium being able to emit red, green and white light respectively
· Batteries
The main battery use is in nickel metal hydride batteries (NiMH) that have a large component of lanthanum and cerium due to their hydrogen storage properties. Hybrid electric vehicles represent more than half the usage of NiMH batteries with these hybrid vehicles combining a conventional internal combustion engine propulsion system with an electric propulsion system.
· Polishing Powders
Another traditional use is as a polishing powder used in the manufacture of television and computer screens and in the production of precision optical and electronic components.
· Fluid Catalytic Cracking
Rare earths, particularly lanthanum, are used in oil refining in a process called Fluid Catalytic Cracking catalysts.
· Autocatalysts
Cerium is often used in gasoline autocatalysts as it improves vehicle performance, increases thermal stability, extends durability and will also reduce precious metals consumption.
Other uses of these metals that have an increasingly wide range of applications include metallurgical alloying agents, within the nuclear industry as control rods and in shielding, as energy efficient low temperature fluorescent lamps and within fiber-optic cables.
Lanthanum: Driving Excitement
Rare earth elements are neither rare, nor earth," says Stephen Castor, recently retired research geologist with the Nevada Bureau of Mines and Geology. The name dates to the 18th and 19th centuries, when the elements were first isolated out of actually rare minerals. "Rare earth" stuck, but the elements themselves turned out to be pretty common, mixed in small concentrations into rock the world over.
Lanthanum, first discovered in 1893, is a great example of this. There's more lanthanum on this planet than silver or lead and it's the second most abundant rare earth element, but there weren't a lot of uses for it in the early days. When Castor worked with mining companies in the late 1970s and early '80s, lanthanum mostly went into stockpile, waiting for the day when it could be sold off for higher prices. That day has come.
Today, every Prius hybrid car on the road carries with it about 10 pounds of lanthanum. And yet, most Prius owners don't even know they use this rare earth element every day. That's because the car's battery is referred to as "nickel-metal hydride." The "metal" in question is lanthanum, but what can we say, rare earth elements get no respect. A big breakthrough in battery technology, nickel-lanthanum hydride batteries pack more power into a smaller space—they're about twice as efficient as the standard lead-acid car battery.
"Toyota is the biggest car company in the world and the Prius is 8 percent of their manufacturing," Jack Lifton, an independent consultant and expert on rare earth elements, says. "Add to that other hybrid cars and the batteries used in small mopeds in China, and there's not enough lanthanum on the market today. Toyota is the first and only car company to invest in a rare earth mine."
Europium: Savior of the TV Generation
Sir William Crookes, a 19th century British chemist, once wrote that, "rare earth elements perplex us in our researches, baffle us in our speculations and haunt us in our very dreams." These weren't easy elements to isolate or to understand, and so there was a very long lag time between the discovery of the rare earths, and the discovery of practical uses for them.
It didn't help that individual rare earth elements don't occur by their lonesome—they travel in packs. To get one, you have to mine all of them. At first, industry didn't even bother to separate out individual rare earths, instead using them in a blended alloy called mischmetal. This provided the first commercial applications, says Karl Gschneidner, senior metallurgist at the Department of Energy's Ames Laboratory. In 1891, mischmetal became an ingredient in lamp mantles—devices that were hung above open flames, where they burned and produced a bright, white light you could see and work by.
Europium was the first isolated, high purity rare earth element to enter the public marketplace, in 1967, as a source of the color red in TV sets. There had been color TV before europium, but the color quality was weak. The sets relied on phosphors—substances that glow when struck with struck with electrons or other energized particles—to get their red, green and blue colors, and the early red phosphors couldn't produce a very bright color. Europium phosphors made the picture pop.
At the time, rare earth mining wasn't even a twinkle in China's eye. Up until the 1990s, most rare earth elements came from the United States, especially Mountain Pass, a mine in California near Los Angeles, which supplied most of the late 1960s europium demand. By 2003, Mountain Pass had closed and no rare earths were coming out of the United States at all. The problem, though, isn't supply. The U.S. still has plenty of rare earth elements left to mine—in Mountain Pass and elsewhere. Instead, those mines were simply driven out of business, undercut on price by Chinese companies that had lower labor costs, and also benefited from the fact that they were mining rare earth elements as a byproduct of profitable iron mining.
Today, europium is still used as a phosphor, but as cathode ray tube TVs go the way of the dodo, it's more likely to turn up in white LED-based lights, which could someday be an energy efficient replacement for both incandescent and compact fluorescent bulbs. With this technology, white light is produced by mixing various colored LEDs and europium red happens to be an ingredient in turning out a high-quality, attractive shade of white.
Lanthanum: Driving Excitement
Lanthanum, first discovered in 1893, is a great example of this. There's more lanthanum on this planet than silver or lead and it's the second most abundant rare earth element, but there weren't a lot of uses for it in the early days. When Castor worked with mining companies in the late 1970s and early '80s, lanthanum mostly went into stockpile, waiting for the day when it could be sold off for higher prices. That day has come.
Today, every Prius hybrid car on the road carries with it about 10 pounds of lanthanum. And yet, most Prius owners don't even know they use this rare earth element every day. That's because the car's battery is referred to as "nickel-metal hydride." The "metal" in question is lanthanum, but what can we say, rare earth elements get no respect. A big breakthrough in battery technology, nickel-lanthanum hydride batteries pack more power into a smaller space—they're about twice as efficient as the standard lead-acid car battery.
"Toyota is the biggest car company in the world and the Prius is 8 percent of their manufacturing," Jack Lifton, an independent consultant and expert on rare earth elements, says. "Add to that other hybrid cars and the batteries used in small mopeds in China, and there's not enough lanthanum on the market today. Toyota is the first and only car company to invest in a rare earth mine."
Europium: Savior of the TV Generation
It didn't help that individual rare earth elements don't occur by their lonesome—they travel in packs. To get one, you have to mine all of them. At first, industry didn't even bother to separate out individual rare earths, instead using them in a blended alloy called mischmetal. This provided the first commercial applications, says Karl Gschneidner, senior metallurgist at the Department of Energy's Ames Laboratory. In 1891, mischmetal became an ingredient in lamp mantles—devices that were hung above open flames, where they burned and produced a bright, white light you could see and work by.
Europium was the first isolated, high purity rare earth element to enter the public marketplace, in 1967, as a source of the color red in TV sets. There had been color TV before europium, but the color quality was weak. The sets relied on phosphors—substances that glow when struck with struck with electrons or other energized particles—to get their red, green and blue colors, and the early red phosphors couldn't produce a very bright color. Europium phosphors made the picture pop.
At the time, rare earth mining wasn't even a twinkle in China's eye. Up until the 1990s, most rare earth elements came from the United States, especially Mountain Pass, a mine in California near Los Angeles, which supplied most of the late 1960s europium demand. By 2003, Mountain Pass had closed and no rare earths were coming out of the United States at all. The problem, though, isn't supply. The U.S. still has plenty of rare earth elements left to mine—in Mountain Pass and elsewhere. Instead, those mines were simply driven out of business, undercut on price by Chinese companies that had lower labor costs, and also benefited from the fact that they were mining rare earth elements as a byproduct of profitable iron mining.
Today, europium is still used as a phosphor, but as cathode ray tube TVs go the way of the dodo, it's more likely to turn up in white LED-based lights, which could someday be an energy efficient replacement for both incandescent and compact fluorescent bulbs. With this technology, white light is produced by mixing various colored LEDs and europium red happens to be an ingredient in turning out a high-quality, attractive shade of white.
Erbium: In the Pink
The applications of erbium are both deeply important, and a little silly. For instance, adding erbium to glass is about the only way to create a stable pink shade. So erbium-doped glass pops up in novelty sunglasses and decorator vases. At the same time erbium keeps information flowing around the globe. Add a little erbium to the optical fibers that carry data in the form of light pulses, and those pulses get amplified. It can also be used as part of the gain medium that amplifies light in a laser. When you do this, you end up with a laser that can be used for dental surgery and skin treatments because it doesn't build up much heat in the human skin it's pointed at.Erbium is a great example of how rare earth elements work in practical applications. You won't find very many places where a solid chunk of a single rare earth element is being used. Instead, they tend to be things that are added, in small doses, to composites and alloys. In that way, rare earth elements work a bit like vitamins, says Daniel Cordier, mineral commodity specialist with the United States Geological Survey. "Rare earths have really unique chemical and physical properties that allow them to interact with other elements and get results that neither element could get on its own," he says.
Neodymium: Little Giant
Once upon a time, there was no such thing as a convenient way to carry your favorite tunes along on a jog. Rare earth elements changed all that. The key is magnets. Those things are everywhere, from hard drives to headphones to anything that incorporates a small electric motor—basically, if there's a component that needs to spin, magnets are probably involved. Producing a strong magnetic field used to require a big, heavy magnet and, thus, led to big, heavy pieces of technology.
Then, in the late '70s, Sony introduced the Walkman, a (relatively) small, (relatively) portable music player. Why were they able to shrink the form factor? Magnets. Specifically, magnets made from the rare earth element samarium, which were smaller and stronger than anything then available. Today, the samarium-based magnets have largely been replaced by magnets made with neodymium, which are even smaller and even stronger. We have these magnets to thank for the miniaturization of gadgetry. But they're also responsible for making necessarily chunky tech lighter and cheaper—like the turbines that turn wind into electricity, and the drills that search for oil deep below the surface of the Earth.
Then, in the late '70s, Sony introduced the Walkman, a (relatively) small, (relatively) portable music player. Why were they able to shrink the form factor? Magnets. Specifically, magnets made from the rare earth element samarium, which were smaller and stronger than anything then available. Today, the samarium-based magnets have largely been replaced by magnets made with neodymium, which are even smaller and even stronger. We have these magnets to thank for the miniaturization of gadgetry. But they're also responsible for making necessarily chunky tech lighter and cheaper—like the turbines that turn wind into electricity, and the drills that search for oil deep below the surface of the Earth.
Ref:
No comments:
Post a Comment