Script for Cheltenham U3A. 9 September 2011


RARE EARTHS.

Members will recall that the Noble gases had similar and unique properties which as their position at the right side of the PT shows, have all of the possible “orbital shells” occupied by electrons; there is no opportunity for wandering (valence) electrons to join them and create further chemical reactions. They are inert.

The Lanthanides + 2 (Sc and Y), today’s grouping, are much reactive chemically. They sit in Group 3 (of the PT) their construction , their electron shell orbits, are less occupied than say Noble gases, so there is opportunity for valence electrons to cause chemical reactions and they do. The group has a trivial name, Rare Earths , which I shall use freely as a shorthand. These elements are reactive, one Pm, is very radioactive, another Lu the hardest and densest, is rare and expensive and has a radioactive isotope too. These elements, not Pm, are processed into metals, that are cosmetically shiny silvery-white in colour (as is Scandium and Yttrium.) They are malleable, ductile, have high melting temperatures, 900 K typically, a boiling point of 3700K, are good electrical conductors, magnetic. The world uses about 20 million tonnes a year, small by comparison with say iron, copper.

Why Lanthanides? Taken from the Greek word (lanthanein) which means hidden. That is a clue its perceived elusiveness and trivial name. These elements do not exist as single blocks to dig out of the ground in nature like lumps of coal. But when you think about it, not many do?

I have produced a handout of the elements, their everyday uses, for you to keep if you want. This will posted on our website as well.

The International Union of Pure and Applied Chemistry, the authority in everything chemical , earlier deprecated the term rare earths, but currently itself uses it. A full chemical description of rare earths is clearly beyond the scope and time available in this brief session, but I would like to at least skim over the parameters, the how and where we get them from, maybe briefly how they are processed, and importantly how they are used in our world. Unlike Noble gases, which you understand well, rare earth uses are probably less obvious to you. You will rarely hear a lanthanide used as a example element described in a TV or radio programme. They are truly hidden. Today then is different, this is all lanthanides and no Hydrogen Helium or Carbon !


Rarity

Are they rare? The absolute straight answer is yes and no! Some are rarish, but for the most part not, nor is the description accurate. The common description (RE) is an obsolete term for water-insoluble, strongly basic oxides of electro-positive materials which were ,and are, incapable of being smelted into metal using late 18th century technology.


How rare ?– give us a number!

The world needs about 20 million tonnes of RE annually. Lu the rarest of RE, about 10 tonnes a year are mined. Cerium is the 26th rarest element in the earth’s crust, at 68ppm similar to Copper (Cu.), Nd is more common than gold (Au), Th is more plentiful than Iodine ( 47th rarest)

Pm (Promethium, derived chiefly from nuclear fission) { has a half life of 17.7 years, so the element only exists in nature in negligible amounts. (approximately 572 g in the earth’s crust.)

Workings of mining outflow (tailings) where gadolinite, xenotime,  ( samarskite,  euxenite, fergusonite ) are found yields Yttrium and other RE . Broadly the residue of , or slurry tailings, of ore mining.

IN definition then is a grouping of the Lanthanides, 15 of them ( Atomic numbers 57-71) plus two from earlier in the PT, Scandium and Yttrium (Atomic numbers 21 and 39. For the technocrats, this group of elements’ atoms or ions can be found in the 4f block of orbitals. Some call them inner transition elements. (note, some US web sites split the Lanthanides off at AN 70; for the moment they are wrong)


Importance?

The properties of these elements are a benefit in the production of a wide number of devices in everyday use.

Here is a paragraph-length sentence; Widely in telecommunications, lasers, precise measurement devices, critical airport luggage -scanning devices, high quality metal and glass industrial processes, detection and scanning in special medical scanners and portable X ray kit, special lighting devices, in special glass, lenses, cameras, mobile phones, high performance special purpose permanent super-strength magnets, in glass and ceramics often for colouration, catalysts in car-exhaust purification devices, computer memories, night vision glasses, sunglasses, hybrid and electric motor vehicles, in so-called green products and processes. The new wind turbines that increasingly cover the landscape would be much larger and less efficient but for rare earth magnets used in the electric motors.

I have tried to capture most of this in a tabulated list which you have.


Where are rare earths found? Where are they mined?

Found widely in the world, Brazil, USA, Sweden, India, Russia, S. Africa, Vietnam, Canada, Greenland. However since 2000 when China began producing REs in large quantities mining in other countries has all but stopped. New investment ventures in USA, Greenland, Vietnam, Australia, Canada, Brazil, S Africa. Japan has millions of tonnes in discarded electronic equipment.

New Scientist, 09 July 'a single kilometre of ocean floor could provide 20% of annual world consumption' & 'Two regions near Hawaii and Tahiti might contain as much as 100 billion tonnes' cf US geological Survey estimate world reserves at 100 million tonnes.

Mined in China, in small facilities, often in crude illegal, dangerous, privately owned mines. China accounts for about 97% of world production, in 2011 where it is has disastrous consequences for the local environment, and for people who work and live there.

(picture of mining in China to pass round)

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{Optional depending on time}

Mining, refining, and recycling of rare earths can have serious environmental consequences if not properly managed. A particular hazard is mildly radioactive slurry tailings resulting from the common occurrence of thorium and uranium in rare earth element ores.  Additionally, toxic acids are required during the refining process.  Improper handling of these substances can result in extensive environmental damage. In May 2010, China announced a major, five-month crackdown on illegal mining in order to protect the environment and its resources. This campaign is expected to be concentrated in the South,[39] where mines are commonly small, rural, and illegal operations particularly prone to release toxic wastes into the general water supply.[11][40] However, even the major operation in Baotou, in Inner Mongolia, where much of the world's rare earth supply is refined, has suffered major environmental damage

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La

Ce

Pr

Nd

Pm

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

Sc

Y

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

21

39





®














The elements. Just for me this bit.

Silvery-white metals ( except Pm) ,

Sc. Y.

Lanthanum

How is it produced? {vvv short Narrative and slide}

Uses of La.

First used in gas mantles. ( shorter Narrative)


This is a little bit of a story for those who don’t care for chemistry!

There is an oddball in the set, this is after all nature, so if there is two minutes let’s mention it since it links to Dr Oppenheimer who I like(d) . Tell the story about Dr JR Oppenheimer’s disgraceful treatment at the hands of the US anti communist zealots.


Prometheum, Pm named after Prometheus the mythological Greek Titan who stole fire from Mt Olympus and brought it back to mankind. (cf Dr JR Oppenheimer whose biographers called him the American Prometheus. Recall that Dr Oppenheimer, whose college, and colleague’s names are immortalised in elements, Seaborgium, Lawrencium, Fermium, Californium, Berklium, etc. No Opperheimerum there. )


Probably won’t use this.

{Discovered in 1945, it is radioactive, at Oak Ridge and later Los Alamos during processing of Uranium fission fuel. It occurs naturally in minute quantities in pitchblende 4 pp quintillion (10 to 18th ) and as a product of spontaneous and induced U and Pu fission. ( Its most stable isotope has a half life of 17 years)

It is used as a source of electrical power in nuclear batteries, lasting 5+ years, as a luminous green light source, in thickness gauges, as a portable heat source in space vehicles., and in portable x-ray kit.

Try to use this – a few of us might be glad to know this when we are “on the operating table, a more informed patient so to speak”


Lu is performing a life-saving role in PET (positron emission tomography) scanners , where records of a molecular level medical tests can be made. PET involves the collection of images based on detection of radiation from positrons emitted by short-lived radioactive substance.


Rare earth, cost at market. Price per pound weight,

La,Y, Ce, Pr. Gd, Sm, Er, Nd, $100+

Dy, Yb, Ho, Eu, Tb, $200-999

Sc , Tm, Lu, $1000+,

Conclusion.

Rare earths, 15 plus Sc and Y, in total a surprisingly small amount globally, are critical components in modern technological processes, chemistry, chemical engineering, automobile-emissions, space vehicles, medicine, high flux permanent magnets, telecommunications, computer memories, computing, measurement tools, high quality lighting, in hostile environments, weapon systems, health products, protective health and safety equipment, environmental/green engineering products, solar panels, chemical storage, night vision equipment, glass products.


End.

Below left for now; I will use this when we are hard up for something to talk about.

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The modern world’s worriers think we can not live without rare earths. But that is not true, China can hardly hold the world to ransom since its own factories are making many of the products, and its citizens are using them as well. But. Neodymium is at the heart of super strong permanent magnets, and its price has quadrupled as electric motors (cars, wind turbines) that use magnets instead of magnetic windings for smaller, cheaper, more powerful motors.

Kind of Top Gear, but too complex! OK if generalised.

The Lotus Roadster uses no rare earths, nor the BMW Mini E. AC propulsion of California has steered clear. Now Toyota is devoloping a Ne-free electric motor, reported to be based on the electromotive industrial mainstay, the cheap and rugged AC induction motor patented by Nikola Tesla in 1888. Think of it as a rotating transformer with the secondary windings residing in a stationary casing (stator) and the secondary conductors attached to an inner shaft (rotor) AC applied to the stator windings creates a rotating magnetic field whilst inducing a current in the separate conductor surrounding the rotor. With the AC now circulating within it, the rotor creates a rotating magnetic field of its own, which procreeeds to chase the stator’s rotating field, causing the rotor to spin in the process and generate torque. Modern AC induction motors have 3 or more sets of stator winding, which smooths things out and allows more torque. These are call asynchronous motors because the rotor’s magnetic field never catches up with the stator’s field. That distinguishes them from synchronous motors that use permanent magnets in their rotors instead of a set of conductors. In synchronous motors the stators’s rotating magnetic field imposes an electromagnetic torque directly on the fixed magnetic field of the rotor causing the latter assembly to spin on its axis in sync with the stator field.

The problem with asynch. motors was varying their speed. No longer problematic because of semiconductor controls. The big advantages apart from simplicity and ruggedness has always been its tolerance of temperatures. The Prius’s permanent magnet motor needs significant cooling, adding to the weight, an induction motor by contrast can be cooled passively (just like VW Beetles) removing the need for radiator, cooling fan, water pump, plumbing.

The hybrids need a petrol engine for extra zip; an induction motor can briefly be pushed to much higher output, and uses only one gear. The Roadster 3 phase induction motor is no bigger than a watermelon, weighs 52kg, packs 288hp (215kw) giving 295lb of torque from rest to 6000 revs. Battery to wheels efficiency is 88%, three times better than a conventional car.

This is science from 1888 re-applied to 2015 use.

The end.