The Process Flow Chart of Rare Earth

INTRODUCTION

When a lanthanide mineral is processed without separation into the individual lanthanides to yield a metal termed
Mischmetal, (see the process flow chart on the left illustration).

 Mischmetal was originated from German: Mischmetall - "mixed metals" of rare earth,  it is an alloy of rare earth elements in the "natural-ratio" as they occur in the ore body. it is often usual to extract the small amount of heavy lanthanides or of high value from the precursor before metal production, consequently mischmetal contains predominantly the first four lanthanides(Cerium, Lanthanum, Praseodymium, Neodymium) of the light Ln's (Lanthanide). A typical composition includes approximately 60% cerium and 30% lanthanum, with small amounts of neodymium and praseodymium detailed as below:

Chemical Composition   Typical Guaranteed
Total Rare Earth Metals (TREM)       99.02% 98.50-99.50%
Ce/REM                                  68.70% 62.00%min
La/REM                   30.88% 30.00%min
Pr/REM                   0.31% 1.0%max
Nd/REM                   0.30% 1.0%max
Sm/REM                 <0.10% 0.1%max
Eu/REM                 <0.10% 0.1%max
Gd/REM                 <0.10% 0.1%max
Y  /REM                 <0.10% 0.1%max
Fe                   0.49% 1.0%max
Si                               0.03% 0.2%max
S                               0.02% 0.04%max
P                            <0.02% 0.02%max
Size : approx. 500 gram per piece.
(30 gr, 50 gr, 100 gr, 250gr, 500gr, 1kg gr, 3kg, 8kg is available for the ingot weight).
Packing : steel drum 250 kg net on wooden pallet of 1MT.
Chemistry, sizing and packaging requirements on Mischmetal can be tailored to the individual customers' requirements on request.
 

PROPERTY
It is prepared by electrolysis at ≈850 °C of molten rare earth chloride, as anhydrous as is practical, preferably under an inert atmosphere, see metals. The few percent of iron is present in order to lower the melting point towards the eutectic point and to make the casting of shapes easier. The material does not have a definite melting point but melts over a range near 800 °C, close to that of Ce. It is a strong reductant, comparable to magnesium, and will react with hot water plus also forming surface oxides on exposure to air.

APPLICATION
- The most common and traditional use of Mischmetal is in manufacture of Cigar & Gas lighter flints.The start of the lanthanide metals industry was the production of
lighter flints (a 1903 patent), based on a mischmetal-iron or ferrocerium (≈65 % : ≈35 %) alloy, which was invented by Carl Auer von Welsbach in 1903, lighter flints is also known as " Cereisen , Ferrocerium or "Auermetall", which nowadays is used daily in lighters by people all over the world. The first useful lighters with Cereisen were also produced by Auer von Welsbach.  1907 saw the founding of the "Treibacher Chemische Werke GesmbH" in Treibach-Althofen for the production of Ferrocerium - lighter flints under the trade name "Original Auermetall".

- The major use of mischmetal is as an additive for steel treatment, an application that is no longer as dominant for Ln usage in most countries as it once was. The prime purpose of mischmetal addition during steel alloy production is to tie up sulfur impurities, through the high affinity of Ln's for O and S, as stable lanthanide oxysulfides. A trend towards "cleaner" starting materials and more efficient use of competitive additives has reduced mischmetal consumption. In China though, with its abundant resources, mischmetal accounts for the major portion of internal lanthanide demand.

- Mischmetal is mainly used as the alloying additives of
Ferro Silicon Magnesium(FeSiMg) in ductile iron foundries, while Ferro Silicon Magnesium is used primarily in the production of ductile iron (Nodular Cast Iron) which widely applied as the ductile iron pipe, ductile iron valves, ductile iron fittings, etc. in water equipment industry.

- Mischmetal based alloys are promising electrode materials in nickel-metal-hydride rechargeable batteries that offer high capacity & long-life.

-In the manufacture of Nodular of spheroid graphite cast-iron used alongwith magnesium, after desulphurizing with Calcium Carbide bringing the sulphur content of the Iron to 0.03% Max, after the addition of Cerium Mischmetal Magnesium Alloy. Cerium Mischmetal is alloyed with cast iron of heat resistance as well as corrosion resistance type to improve  properties.  In the nodular cast iron cerium, overcomes the tendency of traces of Titanium, Bismuth, Lead, Antimony, Tin, Aluminium and Arsenic to inhibit graphitization.  Cerium Mischmetal as ladle graphitizer gives iron intermediate between gray iron and malleable iron.

-Addition of about 1% Cerium Mischmetal (up to 1% only) increases the fluidity of steel.
Cerium Mischmetal can also be added to steel to increase hardness and impact strength to improve ductility and weldability and to give cast steels having properties better than that of forged steel. It is widely used for alloying (modifying) steel to increase its strength, ductability, hardenability etc., for this purpose, 0.3 to 2.5 kg per ton Ferro Cerium Mischmetal is added to steel as per alloy steel grades. Up to 1% Cerium Mischmetal is added to steel to improve grain refinement leading to better workability. Low Alloy Austenitic Stainless Steel, such as type 308, 310, 316 etc., benefit from small additions of Cerium Mischmetal in some steel plant. Addition of Cerium Mischmetal to permanent magnets alloys like Cobalt-mischmetal; cobalt, iron, copper alloys etc. increase the coercive force and its magnetization power.


-Cerium Mischmetal increases the heat resistance properties of the Nicrome and Magnesium alloys. Magnesium alloys containing about 3% Cerium Mischmetal and about 1% Zirconium show improved creep resistance at higher temperature than is practicable for conventional magnesium alloys. Aluminum alloys containing Cerium Mischmetal have better high temperature strength and nickel alloys containing Rare Earth Metal have better high temperature oxidation resistance. Cerium Mischmetal is a powerful deoxidizer while 0.3% addition of Cerium Mischmetal of aluminum. Cerium Mischmetal is used as a hardening agent in copper alloys like brass, bronze etc., The high affinity of the Rare Earth Metals for oxygen and Nitrogen is and will be the basis for many of  their present and future application in the metallurgical fields of ferrous and non-ferrous metals.

Cerium Mischmetal

The trade names for mischmetal are sometime called as follows :

mischmetal, 28053010   Lanthanum rich mischmetal    
Cerio Mischmetal   CeMM        
MISCH metal   Mischmetall        
Misch Metal   mishmetal        
Less-Mg Misch Metal   Re mischmetal      
               
Rare Earth/misch metal   Cerium(Mischmetal)      
Cerium Misch Metal   CER-mischmetall      
Cerium (Misch) Metal   Cerium Mischmetall      
Cerio-Mischmetal   Ce-mischmetall      
Ce, mischmetal   Cer MM        
               
Ce. Mischmetal   Mm=Mischmetall      
Ce Mischmetal alloys   Ce/Fe-Mischmetall      
MM   El Mischmetal      
Mg-Zn-Misch metal alloys   Cerium rich Mischmetal      
Cerium Mischmetall   High Cerium Mischmetal      
               
Mischmetall   Rare earth metals ( Mischmetal )    
CER-Mischmetall   rare earth metals/mischmetal    
CerMM   Ce-rich mischmetal      
Cer Mischmetal   La-rich mischmetal      
Cerium-rich mischmetal   El Mischmetal es una aleación    
               
Ce-Mischmetall   Cerium MM      
Cereisen   Cerium mishmetal      
Mischmetal(Rare Earths)   Mixed rare earth metals    
michmetal   Misch metal (sometimes called Cereisen in German)
Ln Mischmetal 50% Cerium   Ce Mischmetal (alloying, deoxidizing and desulphurizing agent)
               
Lanthanide mischmetal   lanthanide (rare earth) metals    
mixed metals    pyrophoric alloy      
rare earth mischmetal   mischmetal alloy      
High Nd mischmetal   Mischmetal (lanthanide-iron-silicon)  
praseodimio   Lanthaan        
               
néodyme     lanthane        
Neodym     Lanthan        
neodimio     lantanio        
praséodyme     lantano        
Praseodym     Lantan        
               

REE   = Rare Earth Elements, lanthanum to lutetium by atomic weight plus yttrium
TREM =Total Rare Earth Metals
TREO =Total Rare Earth elements in Oxide, calculated as oxides, including lanthanum to lutetium plus yttrium
LREE = Light Rare Earth Elements, lanthanum to samarium by atomic weight
HREE = Heavy Rare Earth Elements, eur to lutetium plus yttrium
LREO = Light Rare Earth Elements in Oxide, as per LREE above, calculated as oxides
HREO = Heavy Rare Earth elements in Oxide, as per HREE above, calculated as oxides

Firesteel - survival gear

To provide an excellent firestarter in the survival kits, we use our Cerium Mischmetal and Iron, Magnesium & other metals to make Ferrocerium rod, Ferrocerium is the "flint" in lighters, and its ability to give a large number of sparks when scraped against a rough surface (pyrophoricity) is used in many other applications, such as the firestarter, camping fire, outdoor survival firestarting, etc.,  

While ferrocerium-and-steel function in a similar way to flint-and-steel in fire starting, ferrocerium actually takes on the role that steel played in traditional methods. When small shavings of it are removed quickly enough, the heat generated by friction is enough to ignite those shavings. The sparks generated are in fact tiny pieces of burning metal. FerroCerium flint rod equipped with high carbon steel scraper, then produced fireesteel, it is usually well-known as the Swedish firesteel, which was originally developed for the Swedish Department of Defense.

Swedish Fire Steel is truly "a flash of genius". Its 3,000ºC (5,000ºF) spark makes fire building easy in any weather, at any altitude. it has been approved by the International Survival Instructors Association, and it is used by a number of armies around the world.  The Swedish firesteel is a very useful fire starter in scouting and camping, sparking entertainment, clockwork toys, strikers for welding torches, etc.,  it is the best compact firestarter we can easily use, plus its dependability,made it a favorite of survival experts, hunters, fishermen and campers. It works equally well when wet or dry. Swedish Fire Steel has even found its way into cabins and backyards as a fool-proof way to light stoves and gas-barbecues.

It comes in two sizes: the larger Army Model (12,000 strikes) is ideal for camping and conventional survival kits and the Scout Model (3,000 strikes) is just barely small enough to carry on a key ring.

Ferrocerium flint rod

This emergency fire starters come under many different trade names such as artificial flint rods, Auer metal, Blastmatch, Blastmatch firesteel, blast match, Camping flints, cer/iron, Cerium flint, Cerium Mischmetal striking flint, Cerium alloy, Cerium alloys, cerium iron rods, cerium iron rod, Camp Fire Starter, Ferrocerium, Ferro-Cerium, Ferrocerium based fire-starter, Ferrocerium firestarter, Ferro mischmetal, ferocium, Ferrocerium rod, ferrocerium rods, Ferrocerium sticks, Ferro Cerium rod, ferrocium rods, ferro rod, ferro rods, Fire-Flint and Steel, Fire Steel, Firesteel, Fire and steel fire starter, Fire & Steel, Firesteels, Fire steels, Fire steel striker, Flint firestarter, Flint fire starter, Firestarter sticks, flint fire-starting, fire rod, fire bar, fire stone, firestone,  firestrikers, fire strikers, fire striker, fire starter rods, firesteel rod,  firesteel rods, firesteel sticks, firesteel stick, Flint, flints, Flint rod, flint rods, flint sticks, flint barFlint fire starter, flint and steel bushcraft fire lighters, flint striker, Flint & steel, Flint and steel, flint n' steel, Flints & Steels, Flints and Steels, Flintstone, flint stone, FC rods, iron rod, iron rods, Lighter flints, lighter flint, lighter flint misch metal (mesch metal), Magnesium-Ferrocerium Firestarter, Magnesium Ferrocerium Fire Starter, Magnesium Ferro Cerium Fire Starter, Magnesium campfire fire starter, Metal-Match, Metal-Matches, Metal match, Misch metal rods, Blast Match Fire Starter, Blast Match Flint Fire Starter, mischmetal rod, mischmetal rods, misch metal rod, mischmetal flints, mischmetal flint, pyrophoric alloys, Sparking rod, Sparking flint rods, Survival flints, survival fire starters, Swedish Army Firesteel, Camping Ultimate Survival Blast Match, etc.,

                                                  The Application of Rare Earth Metals Widening
                                                              Despite Lack of Engineering Data.
                                                           By Roman Lundin and John R. Wilson
Abstract
Uses of the pure rare earth metals or of alloys containing them as a dominant component have understandably been limited by their high cost, extreme sensitivity to contaminants, poor mechanical properties, high chemical reactivity and, most significantly, by a broad lack of physical property data and metallurgical information on these materials. Nevertheless, they are finding increasing uses as low-level but very important alloying additives for stainless steels and for aluminum alloys, silicon alloys and magnesium alloys. In addition to their historical use in spark igniters (e.g., lighter flints or ferrocerium rods) and the so-called "supermagnet" alloys such as gadolinium-cobalt, the rare earths are also finding new uses in superconducting devices, lithium/metal hydride batteries and a wide variety of ceramic and other materials. This paper reviews what is known of the physical and chemical characteristics of these unusual materials and discusses many of their current and potential future commercial uses.


Group 1 lanthanides have low melting points and high boiling points -lanthanum, cerium, praseodymium, neodymium.
Group 2 lanthanides have high melting points and high boiling points - gadolinium, terbium, yttrium, lutetium.
Group 3 lanthanides have high melting points, mid to low boiling points and a high vapor pressure at the melting point - dysprosium, holmium, erbium and scandium.
Group 4 lanthanides have low boiling points - samarium, eur , ytterbium and thulium.
Group 5 lanthanides - this group contains just one element, promethium, which really belongs in Group 1 but is highly radioactive and for that reason has no significant commercial uses.

The grouping of the lanthanides in this way also correlates with their processing characteristics. For example, the group 3 lanthanides are difficult to handle in vacuum-remelting equipment because of their high vapor pressures - they are better refined by a sublimation method. The group 2 and group 3 lanthanides are difficult to contain in metal or ceramic crucibles as liquids at high temperature because of their high melting points. The group 1 lanthanides offer some of the broadest liquid ranges (LR = BP-MP) of any of the elements. Note that the group 4 lanthanides do not have unusually high vapor pressures close to the melting point despite their relatively low boiling temperatures.
Despite the differences that permit this classification, the rare earths are chemically more similar than different, a characteristic that has presented major difficulties in their separation and purification.

1. What are the Rare Earths?
The earth elements or lanthanides consist of fourteen elements plus lanthanum. For practical reasons, the list often includes scandium and yttrium for a total of 17, since these two elements are very similar in characteristics to the lanthanides. For ease of discussion and also for convenience in assessing their potential processability and use, the rare earths are best classified into five unofficial 'groups':

Cerium Mischmetall

2. Established Rare Earth Metallurgical Uses

Rare earths have experienced gradual growth in commercial use since their discovery. Misch metal (generally referred to as Mm), a relatively impure alloy of cerium and lanthanum with other rare earth elements that is the direct result of refining RE mineral concentrates without separation of the individual elements, has been used as a flint material in lighters and firearms for many years. Both cerium and lanthanum are pyrophoric and, as a result, small particles of the alloy ignite in air when struck off the flint. Fortunately, the mischmetal usually contains a high level of both iron and interstitial elements, which make it brittle and easily able to form sparks. Mischmetal has other uses, too. Interstitial and iron-free Mm is being evaluated by a number of researchers as a lower-cost substitute for pure rare earth metals in applications where the presence of other rare earths is non-critical. The problems in applying mischmetal, however, derive from the characteristics that make it effective in flints - the material is typically embrittled by a high interstitial content and by about 5-10 wt % iron (the latter forms numerous intermetallic compounds with the rare earth metals). In addition, mischmetal varies widely in composition according to source; it may be cerium-rich mischmetal, lanthanum-rich mischmetal and may contain more or less of Nd, Pr, Sm and several other rare earths. Historically, no attempt has been made to remove the interstitials from mischmetal, which may contain several wt % of these impurities.

2.1 Improving the properties of irons and steels

Rare earth elements, most notably cerium and mischmetal, have also been used as minor alloying additives for controlling inclusions in cast irons and steels. The cerium appears to combine with the sulfide inclusions that are invariably present in these materials to form particles with a more rounded morphology that is less likely to promote cracking. The normal flake-like morphology of graphite particles in nodular irons may also be modified to a spheroidal form that promotes greater ductility. Both results may be due partly to the effect of Ce in modifying the surface properties of the metal or sulfide. The extreme chemical affinity of the rare earth elements for almost anything that they may contact suggests that they will also interact strongly with inclusions in most metals, but little is known about the mechanism by which this occurs.

A more recent discovery suggests that small additions of the lanthanides may confer even greater protection on those metals and alloys that are already well protected from corrosion by oxide films. These include the iron-chromium and iron-chromium-nickel stainless steels (i.e., both the ferritic and austenitic alloys), and most other alloys that are dependent on chromium for their corrosion/oxidation resistance. Further study may suggest that the effect is even broader - e.g., that the protection provided by all spinel-forming oxides such as Al2O3 or Cr2O3 is enhanced in this way. Use of rare earths as alloying additions for corrosion control shows promise of becoming a major growth market, for example, Mischmetal can also be used as the alloying additive of a Zinc-Aluminium alloy named Zinc-5 % Aluminum-Mischmetal (Zn-5Al-MM) alloy, having a 95% Zn-5% Al-trace mischmetal (cerium, lanthanum), which is often used to be as the coatings fore steel, to enhance the product life for certain applications.

There is also strong evidence that at least cerium acts as a grain-refining agent in some steel compositions, just as it apparently does for aluminum and magnesium alloys (see below), with corresponding improvements in mechanical properties and fatigue resistance.

2.2 Improving the properties of Non-Ferrous Metals and Alloys

High-Strength Aluminum Alloys

Lanthanide additions have been very effective in enhancing the mechanical properties (UTS, impact) and reducing the notch-sensitivity and increasing the fatigue life of a range of high-strength aluminum alloys, most notably the Al-Li alloys most commonly used for airframe construction. Good results have also been obtained for Al-Fe-V-Si alloys and more recently for the high-silicon Al-Si alloys used for (e.g.) cylinder liners. Corrosion resistance and hence resistance to stress-corrosion cracking is also greatly improved. Cerium or mischmetal are the most commonly-used additives (the amounts required are small, typically much less than 1 wt.%). The mechanism by which the lanthanides achieve this effect is not completely clear. Grain refinement is evident and it appears likely that the morphology of many of the intermetallics present is shifted from platelike toward spherical in shape, which reduces their impact as crack initiators. The effect on the corrosion resistance of these alloys is likely to be due to the effect of cerium (or other lanthanide) oxide on the protective capabilities of Al2O3, but this has not yet been shown, nor has the mechanism been studied.

Much of the recent work on the metallurgical uses of the lanthanides has been reported from China , a country that is a major rare earth metal producer, but work in Europe and in the U.S. has begun to confirm these findings. We have no reason to suspect that the data are the result of an effective PR effort!

Amorphous Alloys

Recently, as a result of work at AlliedSignal and elsewhere, interest has been growing in the production and use of amorphous aluminum, magnesium and other alloys. These are typically produced by rapid quenching of the molten alloy onto a cooled surface. The amorphous or "glassy" metals have a number of very desirable properties including, for example, unusually high corrosion resistance, thought to be due to the lack of surface/grain boundary intersects, but they are somewhat thermally unstable and will recrystallize to a more normal crystalline morphology. The addition of small amounts of rare earths, usually accompanied by transition metals, to the melt prior to 'casting' results in a material that, with carefully-controlled annealing, produces a nanocrystalline (i.e., extremely finely crystalline) structure that is more stable than the amorphous material but has better mechanical properties and equally good corrosion resistance (over-annealing to a more coarse structure offsets these advantages). New uses are rapidly developing for these materials. Once again, the mechanism by which the lanthanide additions exert their effect is not yet known. Typically, addition amounts are less than 1 wt.%, but precise control of both chemistry and processing is necessary.

Galvanizing Applications

Mischmetal is also used very effectively in an improved zinc galvanizing product called Galfan™ (developed by ILZRO/Weirton Steel). This is a zinc-5 wt.% aluminum alloy with small Mm additions that is used as a substitute for 'straight' zinc. It has been shown to be very effective in most galvanize applications with the possible exception of heavily-contaminated industrial environments. It is in extensive use in Europe as a galvanizing treatment for sheet steel.

Mischmetal or pure rare earth additions are also surprisingly beneficial in magnesium and aluminum-magnesium cast alloys. Once again, the grain structure is refined, the negative impact of intermetallics on notch sensitivity, toughness and strength is offset and corrosion resistance greatly improved. In some cases (e.g., Al8Mg5), formation of the intermetallic may be suppressed.

The beneficial effects of the lanthanides on the non-ferrous metals extends, not surprisingly, to their metal-matrix composites. Once again, the presence of the rare earths results in grain refinement, improved mechanical properties and, apparently, improved intermetallic morphology in addition to enhanced corrosion resistance.

Numerous other claims for benefits have been made, mostly in the Chinese, and occasionally in the Russian, literature. In most cases, these claims have not yet been substantiated by Western research or practice but there is no reason to doubt their validity, based on the reliability of the work discussed earlier.

2.3 Nuclear Applications of Rare Earth Metals

Eur , gadolinium and dysprosium have large capture cross-sections for thermal neutrons and thus are often incorporated into control rods to regulate reactor operation. Rare earth elements can also be used as burnable neutron absorbers to maintain the reactor flux at a more constant level. Obviously, with the relative demise of the nuclear power industry, this is a small and non-growing market for the rare earth metals.

2.4 Supermagnets and Superconductors

Although not the theme of this article, one of the most important applications of the rare earth elements is in "supermagnet" materials - usually permanent magnets based on gadolinium-cobalt, samarium-cobalt or neodymium-iron-boron with other metals in minor amounts. The cobalt alloys offer the highest permanent magnet performance known. Use of these materials continues to grow rapidly at more than 15% annually as power generating devices in automobiles and aircraft grow smaller and more compact while offering higher capacities. Tight control of purity is required to achieve optimum performance.

A number of intermetallic compounds and oxides containing rare earth metals are being evaluated as so-called high TC superconductors - materials that demonstrate superconductivity (vanishingly low electrical resistivity) at temperatures well above 0 deg. K (absolute zero). Once academic curiosities, these materials now offer considerable promise for use in future industrial high-current devices and generating equipment. Development work in this area appears to be growing exponentially and excellent progress is being made. Once again, purity seems to important in achieving optimum performance.

2.5 Other Metallurgical Applications

While there are many possible metallurgical applications for the RE metals, the high cost of these metals usually results in an alternative choice being made. However, there are some areas, such as those mentioned in sections 5.1 and 5.2, that make use of the unique characteristics of the rare earths. These include uses in thermite devices and in tracer ammunition, both of which utilize the pyrophoric characteristics of these metals to good effect. The high cost of the rare earth metals, even mischmetal, makes it unlikely that they will replace aluminum or (occasionally) magnesium in conventional thermite mixtures for steel rail welding and equivalent uses. However, in view of the favorable effect of rare earth elements on the performance of cast steels (see above), there may be an opportunity to use rare earths together with aluminum or magnesium in sophisticated thermite mixtures for welding applications in which a high performance weld is required. They could be especially valuable for underwater thermite welding systems.

Pyrophoric formulations are also used in a variety of weapons systems (mischmetal has featured in these for many years) such as tracer shells and incendiary weapons of various kinds.

The writers are frequently asked to provide fabricated rare earth samples (wire, tube, sheet) for other unspecified applications. Clearly, other uses for pure rare earth metals are also being investigated.

2.6 Other Uses of the Rare Earth Elements and their Compounds

While this article has intentionally focused on the larger-scale metallurgical uses of the rare earth metals, there are very many uses of these elements that fall into other categories. The total markets for cerium and lanthanum are large since the oxides and other compounds of these metals have found broad industrial application in products that range from camera lenses to polishing compounds. Some of these are still evolving as the technology is improved. For example (and this list is far from comprehensive):

¨ Aluminum-scandium alloys are finding uses in sporting goods such as golf clubs (along with almost any other combination of metals in this fashion-conscious sport!), baseball bats, bike frames, etc.

¨ A wide range of specialty ceramics is emerging, based on rare earth oxides. A comprehensive discussion would require a major publication of its own! Yttria (Y2O3) has long been used to stabilize zirconia (ZrO2) ceramics at high temperature but recent research has uncovered numerous additional applications for ceramics containing rare earth oxides. For example, a "second generation" family of high TC superconductors such as YBa2Cu3O7 has appeared which, while very difficult to fabricate into conductors (such as wires) offer some exciting properties. Much of the early work on high-TC oxide superconductors focused on the so-called ABO3 perovskites such as LaTiO3 and later on layered perovskites such as (La,Sr)2CuO4. Rare earths are also commonly found in solid-state zirconia-based solid electrolytes used in commercial oxygen sensors (e.g., for automotive use) and in laboratory applications. Rare earth nitride ceramics are also of interest.

¨ The rare earth oxides find wide use as components of catalysts used in chemical processing (for oxidation, amidoxidation, polymerization) and in the treatment of exhaust gases produced by internal combustion engines. They are also to be found in silicone stabilization additive packages, diesel fuel additives (for particulates control) and in corrosion inhibitors.

¨ Heated rare earth metals are used as scavengers or "getters" for oxygen and nitrogen, as well as other gases such as hydrogen, in high-vacuum systems and in nuclear applications (especially those using liquid metal coolants which are highly corrosive in the presence of even minute amounts of oxygen). Hafnium and zirconium also serve well in this application.

¨ R