Scandium – metal of cosmic century

 

Dr O.N.Novikov

 

This article is written under thorough serious analysis of scientific and technical development trends. Between them is a search of new materials, which are required for design of perspective equipment models. One of such materials is scandium, what has a key position between them. Scandium is monoisotopic element and consists of atoms for 100%.

Scandium – Sc45. Mostly rich with scandium mineral – thortveitite – is one of the rarest mineral. Largest significant deposits of thortveitite are located on the south of Norway and on the island of Madagascar.

How “rich” this resources one may just by such digitals: during more than 40 years, from 1911 till 1952, on Norwegian mines only 23 kg of thortveitite were produced. Frankly to admit during the next ten years in respect to high interest to scandium from many industrial and scientific branches output of thortveitite was extremely increased and resulted in sum to 50 kg. A bit more wide other minerals rich with scandium are populated: these are sterrettite, kolbekit, bolzit. But in hundredths (0,01) and thousandths (0,001) of a percent this element is attended in a number of ore such as iron, uranium, tin, wolfram, in low-grade coal, even in sea water and seaweeds. Despite this variation technological production of scandium and its compounds from various raw materials were developed. For example, here the method of scandium oxide production, designed by czech and slovak scientists, has been described below.

First stage – roasting on the fire of production wastes of wolfram ore. Volatile components have been roasted by this procedure. Solid residue shall be disintegrated by concentrated sulfuric acid, after water is added, scandium hydrooxide has been precipitated by ammonium from solution. Then, sediment has been dried and calcinated in gas oven at temperature of 600-700ºC. As a result light pink powder of scandium oxide (Sc2O3) with significant admixture of solid silicic acid and various oxidants, first iron oxides, has been produced. This admixtures may be avoided by leaching powder in pure hydrochloric acid with further separation of various fractions. Silicic acid has been avoided by gelatin solution, and created ferric chloride – by ether extraction method. Then, serial of chemical operations, in that various acids, toxic ammonium, water and ether participate, has been followed. Procedure is that: steam – wash - dry. Purified scandium oxide has been proceeded by hydrochloric acid and scandium oxalate has been proceeded by oxalic acid for sediment. It has been roasted at 1100ºC and made to oxide.

Second stage – metal scandium producing from oxide – is also laborious process. Accordingly to research data of Ames Laboratory of the USA it's mostly recommended to make scandium oxide to fluoride. It has been effected by reaction with hydrogen fluoride or ammonium bifluoride - NH4F • HF. For full chemical transaction of scandium oxide Sc2O3  into scandium fluoride ScF3  reaction has been duplicated. Scandium fluoride has been regenerated by metal calcium in tantalum cricibles (melting pots). Process begins at temperature 850 °C and goes in argon content. After that, temperature has been increased to value of 1600 °C. Resulted metal scandium and slag have been separated by melting in vacuum conditions. And nevertheless scandium bar is not enough pure after such procedure. The main admixture in the bar - tantalum with relative part 3 - 5 %.

Finally, third stage of purification - vacuum distillation. Physical conditions: temperature - 1650-1750 °C, pressure - 10 - 15 mm Hg (hydrargyrum). Operation has been resulted with aprx. 95% of scandium in the bar. Further cleanup step is purification of scandium part to the level of 99%, what is a more complicated multistep process.

Despite this scientists insist on further researches, stream to achieve maximal purity of rare metal, study properties of its compounds, develop new methods of its producing. In recent times simultaneous method of scandium extraction from uranium ore becomes significant importance.

 

Significant content of scandium - up to 10 g/t - in ash of various stone coal sorts is also worth to be stressed. Scandium extraction from such raw material is possible in complex coal pieces processing for synthetic liquid fuel, that is analogue of motor and Diesel trading fuel. After extraction of liquid fuel components slag is a subproduct, which is usable for scandium extrating also. Method of "Ecological Group" Ltd. for resolving this problem is a process of selective sorption by "Alpa-9M" equipment. With this complex micro-component extration has been simplified and cheapened significantly. This is a reason for low cost effectiveness of its extraction.

 

Our reference:

In scandium production the main problem is a technological process of its full extraction from processing ore. With progressive development of metallurgy of scandium containing ore, its annual production output will increase. Here are basic ore mineralss and possible part of scandium in the table:

 

Scandium in natural minerals

Mineral, t

(annual production)

Scandium ratio, t (annual production)

Bauxites — 71 Mio

710—1420

Uranium ore — 50 Mio

50—500

Ilmenites — 2 Mio

20—40

Wolframites

30—70

Cassiterites — 200 000

20—25

Zirconium — 100 000

5—12

Total resources are shown. The most part of them has been absolutely not applied. Indicated digitals show that these resources are very huge. In this connection it's worth to indicate coal scandium too. And as a first step of its mining - processing of slags by iron-foundry method using blast furnace, that has begun recently in many industrialized contries.

 

Production and consumption of scandium

 

Annual world production of scandium oxide, 1988:

China - 50-60 kg

France - 100 kg

Norway - 120 kg

USA - 500 kg

Japan - more than 30 kg

Kazakhstan - more than 700 kg

Ukraine - more than 610 kg

Russia - more than 958 kg

 

It's recommended to take note of enormous scandium resources in Russia and former Soviet Union (output production data are significantly differ, but quantity amounts of mining output, by independent experts opinions, are equal and exceed official data of world production). Generally, by independent experts opinions, main producers of scandium (scandium oxide) are currently Russia, China, Ukraine and Kazakhstan. Published in press scandium (scandium oxide) production data in the USA, Japan, France is more secondary metal and metal from world trade market than own original production. In certain degree significant amount of scandium raw material will be directed from Australia, Canada and Brazil in the next years.

It's adviced also to take into account deports of rare earth minerals, containing scandium, in Mongolia. This is also perspective scandium source for metal industry and for scandium metallurgy development as well. By the way, scandium is practically available everywhere, but economically it's advisable to extract it by our technology. It is recommended as exclusive method.

 

Scientific interest have alternative resources of scandium also. These are fair oil waters with scandium content 0,012 mg/l and sea water with scandium content 4x10-5 mg/l.

 

Cost

 

Scandium may be for sure called metal of the XXI century. Its mining output will increase very fast as well as its cost because of processing of huge amounts of coal crowds (especially in Russian industry) into liquid fuel. Unfortunately, very high cost of scandium will be actual for relatively long time (the last 5 years prices for metal scandium differ from $12 000 till $20000 for kg in the world stock market). Time to time prices for scandium and its oxide alternate suddenly, what is little understandable as for experts. For example, by the US Bureau of Mines (USBM) 1991 scandium oxide cost $3 500 for kg (99,9%), $10000 for kg, metal powder with fragments up to 250 microns (99,9% distillate) - $296 000 for kg, dendrites pieces (99,9%) - $248 000 for kg. Price decrease (as for that of pure beryllium) will happen as far as industry supplied enough and scandium recycling technology developed, what has been awaited to the middle and the second half of the XXI century.

 

Practical employment

 

1) Light sources. Amount of 80 kg scandium (in compound of Sc2O3) for a year has been used for production of high intensity light elements. Scandium iodide has been added as element of mercury gas lamps, designed as natural sources of synthetic light close to the solar by its structure and well suitable for color transferring by television camera.

 

2) Ferrites production. Scandium oxide (melt temperature 2450oC) has an important significance for production of supercomputers (low induction ferrites).

 

3) Scandium isotopes. Radioactive isotope Sc46 (half life about 84 days) is usable in petroleum industry as “a bench mark” for metallurgical process control and oncological deseases therapy.

Isotope Sc47 (half life about 3,5 days) is a one of the best sources of positrons.

 

4) Scandium alloys. Employment priority of scandium by usable amount are aluminium-scandium alloys, which have been used in air-space field, for sport equipment (motocycles, baseball bats etc.) - i.e. everywhere as high-strength material. In compound with aluminium scandium provides with additional strength and ductility. Extreme ductility significance at rupture strength for pure scandium is about 400 MPa (40 kg/mm), for titanium, for example, is 250-350 MPa, for unalloyed yttrium – 300 MPa. Use of scandium alloys in aviation and air-space technologies will provide significant decrease of costs for transportation and sharp increase of exploited systems reliability. At the same time cost decrease for scandium and its employment for car engines production will increase their (car engines) servicelife and partially efficiency factor. It's very important to take into account that scandium strengthens aluminium fusions alloyed by hafnium.

 

5) Alloying of scandium is one of the most important industrial interests, which is not learned enough for practical use. Both aluminium alloying by yttrium and pure aluminium alloying by scandium enhance electrical conductivity of material. High effectiveness of strengthening has wide perspectives for use of such alloyage in electricity transmission lines (ETL). Scandium alloys are most perspective materials for production of guided rockets and military weaponary as well as for technologies of high strength metal cables (space Elevator).

 

6) A number of special scandium alloys – composites with scandium - are rather perspective for constucion of cyborgs skeleton. Last years scandium (partially yttrium and lutecium) were important for producing of some durable and super reliable by its compositions martensitically wearest steels. Some examples of that proved durability more than 700 kg/mm (above 7 000 MPa)!

 

7) Supersolid materials. Scandium has been used for supersolid materials fusion. For example, titanium carbide alloying by scandium carbide increase microsolidity very significantly (twice), what makes this new material the 4th after diamond by solidity (solidity significance about 98,7 – 120 GPa), boron nitride (borazon) (about 77 – 87 GPa), alloy of boron, carbon, silicon (about 68 – 77 GPa) and makes its solidity significantly more than that of boron carbide (43,2 – 52 GPa), silicon carbide (37 GPa). Micro-solidity of scandium carbide and titanium carbide alloyage is about 53,4 GPa (for example, titanium carbide has solidity 29,5 GPa). Specially interesting are alloys of scandium and beryllium, which have unique characteristics on strength and heat resistance. As for example, scandium beryllide (1 scandium atom and 13 beryllium atoms) possesses most effective combination of such significances as density, strength and melting temperature. It may be the best material for air-space equipment and techniques build-up, outdoing in this relation best alloys of titanium, known for people society, and a number of composed materials (including materials based on carbon and boron atomic chains).

 

8) Nuclear power industry. In atomic power industry is usable succesfully scandium hydride and deuteride – excellent moderator of fast neutrons and buster in powerful and compact neutron generators. Scandium diboride (melting temperature 2250oC) is usable as a component of heat resistance alloys as well as material of cathode in electronic devices. In atomic power industry scandium beryllide is suitable as neutrons reflector.

 

9) Medicine. Scandium oxide may be used as material for high quality dental prosthesis.

 

10) Laser materials. Able for high temperature super conductivity scandium is useful for laser material production (LMP). Gallium scandium gadolinium garnet allowed 4,5% efficiency factor and record parameters in mode of frequent generation of ultra-short impulses at alloying it by chrome and neodymium ions, what is optimistic background for construction of super power laser systems, that may be usable for thermonuclear microblasts just by pure deuterium (inertial synthesis) in the next future already. For example, it's been awaiting in the next 10 -13 years that laser materials on the basis of LMP and scandium borates will take leading place in development of laser equipments and outfit with them active defense systems of aircraft and helicopters in industrialized countries. On the way with this process thermonuclear power industry will be developed involving gelium 3 (produced on the Moon). Thermonuclear microblast has been already exercised using mixtures with gelium 3.

 

11) Metallurgy. Scandium usage as microalloying admixture influences significantly on the number of practically important alloys. For example, adding 0,4% scandium to alloys of aluminium and magnesium increase temporal resistance for 35% and fluidity significance limit for 65 - 84%. Herewith relative elongation is 20 – 27 %. Adding scandium in amount 0,3 – 0,67 % to chrome increase its resistance for oxidation even at temperature conditions up to 1290oC. Analogical but more powerful effectiveness additional scandium makes on heat resistance alloys such as “nichrome”. For this aim scandium is more effective than yttrium. Scandium oxide is prefferable for high temperature ceramics production relatively to other oxides. Heating increases strength of scandium oxide, that gets its maximum at 1030oC. At the same time scandium oxide has minimal heat-conductivity and the highest thermodynamical resistance. Yttrium scandate is one of the best materials for high temperature resistance devices or constructions, which are resistable to high temperatures. Scandium oxide has been used for production of hermanatic glasses in optical electronics. Scandium-gallium as a bound material is one of the best metal glues and special coverage substances.

 

  • Solar batteries production. Scandium oxide and holmium oxide as alloyage is usable in production of photography transducers with silicon as coverage substance. This cover has a wide spectrum of optical clarity (400 – 930 nm) and decrease spectral coefficient of light reflection from silicon up to 1 – 4 %. Use of this modified photoelement makes current power at short circuit to increase for 35 – 70 %, what allows in its turn to increase output power of phototransducers for 1,4 times.

 

  • MHD-generator (MHD - magnetic hydro-dynamical). Scandium chromite has been used as one of the best and most longlife materials in MHD-GENERATOR electrodes. Production method: to the overall ceramics mass previously oxidized chrome has been added and sintered, what increases strength and electroconductivity of material. Besides zirconium dioxide as electrode material for MHD-GENERATOR, scandium chromite possesses a higher resistance to erosion by cesium compounds (usable as plasma forming admixture).

 

  • Roentgen mirrors. Scandium has been used widely for production of multilayer Roentgen mirrors (compositions: scandium-wolfram, scandium-chrome, scandium-molybdenum). Scandium telluride is a very perspective material for thermoelements production (high thermoelectromotive force (EMF) up to 255 µV/K with low density and high strength). In recent years refrectory alloys (intermetal compounds) of scandium and renium (melting temperature up to 2575 oC), rutenium ( melting temperature up to 1840 oC), iron ( melting temperature up to 1600 oC) have been very important for air-space and atomic equipment. These compounds are heatproof, have medium density etc.

 

  • Refrectory materials. Scandium oxide as a refrectory material of special purpose (melting point 2450 oC) is important for production of casting ladles, designed for high-alloy steel spilling. Scandium oxide is more resistable to erosion in liquid metal flow than all known and popular materials (for example, almost resistable yttrium oxide is low for 8,5 times by this significance relatively to scandium oxide) and probably not replacable in this field. Its wide use is restricted by high expensiveness, thus alternative decision is use of yttrium scandates, reinforced by thready crystals of aluminium oxide for strength increase, and use of scandium tantalate as well.

 

16) Rhinestones. Scandium oxide plays an important role for producing of rhinestones, where it's the best stabilizer. Some scandium amount has been used for producing heatproof material as nickel-chrome alloy and ferrum-chrome-alluminium alloy (nichromes and fechrals), what increases significantly their lifetime as heat winding in resistance furnaces.

 

  • Luminophores. Scandium borate as well as yttrium borate has been used in radioelectronics as matrix for luminophores.

 

As shown above, scandium is a key element for development of new equipment and engineering techniques. Without scandium no hi-tech is possible. It's time for business to pay attention on it. Scandium extraction is a business-plan element for wastes processing, what makes any business-plan to be attractive for invesment politics. For example, ash wastes contain scandium up to 10 g/t. Taking into account scandium cost it may be estimated as a bonus to income - $200/t of ash. Coal itself costs lower!

 

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