Developments In the Tantalum Market
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1. I should like to thank Metal Events for the opportunity to talk about tantalum.
2. The Tantalum-Niobium International Study Center, or T.I.C., is an association with eighty-one member companies in twenty different countries across the world.
3. Tantalum in your life
Tantalum is probably best known for its use in electronics, in situations like these:
If you need a heart pacemaker, or an insulin injector
If you brake hard in your car and avoid an accident, using the automatic braking system
In an impact, tantalum capacitors open the air bag in a split second
But tantalum is used in other ways:
Implanted in the body, it can reconstruct joints and tissue,
It is in the hottest part of jet engines
Tantalum carbides cut through steel like butter
In the chemical industry, tantalum equipment keeps corrosive acids confined, and safe.
This paper will review the sources of raw materials, touch on the chemical processing methods which extract the metal, comment on the products which result, and give an idea of the applications and uses of tantalum metal and compounds.
Tantalum is an element. It is a grey metal, classed as a refractory metal because it is resistant to attack. For industrial use, its important properties are a high melting point, ductility which allows it to be drawn into wire, malleability which allows sheets and tubes to be made. Once exposed to air, the metal is covered with a thin layer of oxide which allows it to resist fluids in the human body, and also acids and other corrosive liquids, in the chemical industry. It has a high dielectric, which makes it so valuable in capacitors for the electronics industry.
6. Sources of minerals
The chief mineral containing tantalum is tantalite, and its main source is Australia. The company Sons of Gwalia operates the two largest tantalum mines in the world, producing at least half of world mine output.
The only underground mine working is in Canada, although it produces relatively little compared with ten or fifteen years ago, now less than 5% of world output. Other mines are open cut. There are several mines in Brazil, and some in China, notably the Yichun mine. There are traditional sources in Africa, such as those in Nigeria, Democratic Republic of Congo and Rwanda, which have supplied minerals for half a century, in variable quantities.
In the Democratic Republic of Congo the mineral is columbite-tantalite, known locally as 'coltan', and it has been the subject of trading by militias in the civil war. The T.I.C. continues to call on its members to take care in purchasing minerals in Central Africa, as harm to local populations, wildlife or the environment is not acceptable. The mining and trading of minerals is a way of producing an income, and Central Africa has exported tantalum minerals for many years, so putting an embargo on all such trade is not the whole answer. Supply from DRC is probably not more than 10% of world mine output.
Still in Africa, Ethiopia has a productive mine at Kenticha, and in Mozambique the Marropino mine is going back into operation.
Looking at the near future, there are known reserves in Egypt and Saudi Arabia which are being actively investigated, and numerous deposits in Canada, in Greenland, and in other countries in South America and in Africa. These factors show that there is no reason for tantalum raw materials to be in short supply in the foreseeable future. Estimates of supply requirements indicate growth at 7% per annum, and these can be covered by the raw materials suppliers. They can also be covered by the processing companies which refine the metal from the minerals.
7. Wodgina Mine
This is the Wodgina mine in the desert in the north of Western Australia, run by Sons of Gwalia. This mine can continue to supply at its current rate for the next twenty years, and as exploration around the site is successfully finding increasing reserves, the life of the mine is likely to be longer than twenty years. Its sister at Greenbushes, in the south of Western Australia, can run at full capacity for twenty-five years, and here also exploration is showing that more resources are present and the mine could be expanded. It could be extended into an underground mine by working the hard rock deposits already known. In 2003 these two mines produced 2.1 million pounds of tantalum pentoxide contained, the measure of production used in this industry. The T.I.C. has estimated that member companies in the association produced 3.1 million pounds of tantalum pentoxide in minerals in 2003. But even this is not total world production, as there are other mines which are run by companies not in our membership.
8. Raw materials production, T.I.C. members
In addition to the tantalum which is mined, there are also sources in the slag left after tin has been smelted from some of the minerals of tin. The tin slag does still provide some tantalum, as you can see from this slide. Twenty years ago the majority of tantalum came from tin slag and this situation has now changed. There are two other sources of supply to mention. The Defense Logistics Agency National Stockpile in the United States releases raw materials on to the market. And there is also recycling: about 20-25% of supply comes from recycling of materials from within the industry. With expansion of existing mines, and new potential sources, there should be no shortage of tantalum even if growth increases to two or three times the forecast 7% per annum.
9. Processors of tantalum minerals
The metal has then to be extracted from the minerals and slag, of course, and there are processing plants in Germany, China, Japan, Thailand, Kazakhstan, and in the United States where two of the major groups are established, H.C. Starck and Cabot Supermetals. You will recognise that these are not the same countries where the minerals were mined and where physical processing or concentration takes place. So it is necessary to transport the concentrates, mostly by sea but occasionally by air.
10. Transport difficulties
Recent changes to the regulations recommended by the International Atomic Energy Agency, the IAEA, have resulted in a lowering of the limit of the level of radioactivity in materials which can be transported as normal goods. There is a very small content of uranium and thorium in tantalum minerals, and as these elements are in the crystal lattice they are not removed by the initial physical treatment at or near the mine site. A survey we have carried out indicates that the majority of concentrates have radioactivity levels of up to 40 Bq/g. The regulations have moved the limit from 70 to 10 Bq/g, so many of our concentrates have been re-classified as 'dangerous goods' and some carriers refuse to take them. Some concentrates at the higher end of the range do need particular packaging and documentation, but we do not believe that the majority of materials pose any risk during transport, and the T.I.C. is therefore making representations to various authorities to request that the limit be reviewed.
11. Refining metal from minerals
I mentioned that this is a refractory metal, with a high melting point. Smelting is not a possibility, and the minerals have to be treated with a mixture of hydrofluoric acid and concentrated sulphuric acid in order to dissolve the tantalum oxide or other compounds in the mineral concentrates. The solution is mixed with MIBK to effect solvent extraction, and after stages of washing and drying tantalum oxide can be obtained, or if potassium hydroxide is added to neutralise the solution the product is K-salt, potassium tantalum fluoride. In order to obtain metal, the tantalum oxide is reduced with molten sodium. These are difficult processes and the reagents have to be carefully kept and used, so they are strictly controlled and environmental regulations are observed.
Tantalum Australia is responsible for research into a new method of separating metal, by a method involving osmosis, but this is still in an experimental phase.
12. T.I.C. members 2003: estimated processors' receipts, processors' shipments
For the processing companies which do this work, the T.I.C. has estimated that its members received 3.2 million pounds of tantalum contained in the various materials with which they were supplied in 2003, and the output by members contained 3.33 million pounds of tantalum. This indicates a slight drawdown of inventory, which is reasonable after the inventory was built up in 2001 and not immediately required.
13. Processors' shipments, by categories
Almost half the tantalum processed emerged as tantalum capacitor powder, as you can see from this pie chart. In addition to the use of powder in capacitors, the wire which is part of the mill products category was also used for capacitors.
The capacitor manufacturers also use even more of the mill products in the form of trays and bars to hold the capacitor anodes during sintering, so that as the materials are heated there is no contamination.
Tantalum chemicals can be used as chemicals - for example tantalum oxide can be purified and used in glass as it increases the refractive index, so that lenses will be more powerful for less size and weight - or the chemicals can be intermediates and processed again. Tantalum carbide goes into cutting tools, and tantalum ingot can be turned into chemical processing equipment or specialised items such as sputtering targets, after purification by electron beam melting.
14. Tantalum capacitors
More than half the tantalum consumed in 2003 went into the manufacture of tantalum capacitors, those small components of electronic circuits which store and release electrical energy as application demands. The vast majority of that tantalum powder and wire was used by T.I.C. member capacitor firms, which include the major manufacturers in the world, and some more was used by non-members.
World tantalum capacitor production for the year was estimated by the EIA as over 19 thousand million capacitors.
15. Applications for capacitors
When space is limited and reliability is vital, then tantalum capacitors come into their own. Here are some examples we all see around us. Cell phones with camera and video functions built into them can have 22 or 23 tantalum capacitors. Tantalum is not only in the handsets, it is in the infrastructure, the far larger pieces of electronic equipment which convert and transmit the signals, making the system work.
Laptop computers have more programmes and functions while being smaller and slimmer, so tantalum capacitors save space and also save your batteries because they work at low voltage, another advantage for the new generation of batteries Mr Amazutsumi told us about yesterday. Digital cameras and video cameras benefit from the same advantages - cases are smaller, the cameras can do more and work longer.
16. Electronics: capacitors and other uses
The more luxurious the car, the more features it has which are governed by computerised circuits, but even cars which are not so expensive also have these circuits. When the temperature in the engine compartment can rise from freezing point to running temperatures in a matter of seconds, tantalum capacitors remain reliable and tolerate the cold and the heat. The electronics industry in general is already coming back from the doldrums in which it languished in 2001 and 2002, according to observers. Demand for PCs and cell phones is starting to increase. As Neil Buxton said, Japan is emerging from the electronics bubble which burst.
But even in electronic equipment, tantalum has uses which are not in capacitors. In those pieces of equipment with multiple circuits squeezed into a restricted volume, the semiconductors can be protected from short circuits between conducting materials by a barrier film of insulating tantalum oxide, for example.
Tantalum is also used as a thin film coating print heads on laser printers, as it can withstand the high temperatures.
More and more uses for thin films are being discovered, with the film usually being applied by means of sputtering.
17. Medical applications
Reliability and extended life are paramount in heart pacemakers, and tantalum capacitors are therefore chosen as they can be implanted and left for a long time. Tantalum can also be used in the form of the metal, since, as I mentioned, it is impervious to body fluids.
Clips and implants made of tantalum can be used without problems of rejection.
If an injury has to be treated, or tissue replaced after removal by an operation, a form of tantalum mesh can be used which becomes absorbed into the body and the tissues re-grow around it.
Alternatively the implant can be made of steel or an alloy, which would be less dense, coated with tantalum, and the properties of tantalum would be imparted to the implant.
In an exciting piece of research, we have heard that tantalum is used in muscle stimulation in two ways: a tiny pellet of tantalum is attached to muscle which has been detached from its nerve in an accident, and this can be stimulated by an electronic circuit with tantalum capacitors which cause the muscle to contract, allowing the patient to move a leg or arm, this is in an experimental stage but gives hope for future success.
18. Other industries
The alloys in the hottest section of jet engines contain tantalum. As passenger journeys are now reaching the numbers they achieved in the first half of 2001, orders for aircraft are beginning to show improvement. Both Boeing and Airbus say that their engines will work at higher temperatures, with more efficiency and lower emissions, and this will require highly resistant alloys.
The use of tantalum carbide in cutting tools is at a stable level. Tool makers have carried out research and development on various combinations of carbides of tungsten with additions of niobium and tantalum and other metals, and now use smaller amounts of carbides for tips rather than larger tools. The materials bring their own economies by cutting steel sheet into car doors or washing machine cases quickly and with reduced waste.
Tantalum is good for heat exchangers.
In the chemical industry reaction vessels are made of tantalum metal sheet when other materials would be dissolved by the acids being produced in the plant. Accessory parts of the equipment would also be made of tantalum, so that when the product is pumped out it does not corrode the pipes and valves.
T.I.C. member companies range from miners and smelters and traders which supply raw materials, through processors which provide metal and compounds to capacitor manufacturers, and also assaying companies which serve the others. In recent years we have had several companies from China join the association, we have nine Chinese members, and one from Korea. Also several of the established capacitor firms, have moved some of their activities to China, Kemet has its Asian headquarters in China now, and AVX is there as well, among others.
Tantalum is a remarkable metal, which has many uses in other fields as well as in electronics, and I encourage you to contact the members of our association, or the T.I.C. office, for even more information.