Lecture 4 Modern technology in the processing of

Lecture 4. Modern technology in the processing of tantalum and niobium containing rare-metal raw materials. Yerbolat Sailaukhanuly, Ph. D

Ta, Tantalum, 1802 • • • Named for the Greek mythological figure Tantalus. Tantalum was discovered by Anders Gustaf Ekenberg, a Swedish chemist, in 1802 in minerals obtained from Ytterby, Sweden. In 1866 when, Jean Charles Galissard de Marignac, a Swiss chemist, proved that tantalum and niobium were two distinct elements. The first relatively pure samples of tantalum were first produced in 1907. Today, tantalum is primarily obtained from the minerals columbite ((Fe, Mn, Mg)(Nb, Ta)2 O 6), tantalite ((Fe, Mn)(Ta, Nb)2 O 6) and euxenite ((Y, Ca, Er, La, Ce, U, Th)(Nb, Ta, Ti)2 O 6). Tantalum is a strong, ductile metal that is nearly immune to chemical attack at room temperatures. Tantalum is used to make components for chemical plants, nuclear power plants, airplanes and missiles. Tantalum does not react with bodily fluids and is used to make surgical equipment, surgical sutures as well as implants, such as artificial joints and cranial plates. Tantalum is alloyed with steel to increase steel's ductility, strength and melting point. Tantalum pentoxide (Ta 2 O 5), one of tantalum's compounds, is a dielectric material and is used to make capacitors. It is also used to make a glass with a high index of refraction that is used in camera lenses. A composite consisting of tantalum carbide (Ta. C) and graphite is one of the hardest materials known and is used on the cutting edges of high-speed machine tools.

Nb, niobium, 1864 • • Named for the Greek mythological figure Niobe. The story of niobium's discovery is a bit confusing. In 1809 when William Hyde Wollaston, an English chemist and physicist, compared the minerals columbite and tantalite ((Fe, Mn)(Ta, Nb)2 O 6) and declared that columbium was actually the element tantalum. This confusion arose because tantalum and niobium are similar metals, are always found together and are very difficult to isolate. Niobium was rediscovered and renamed by Heinrich Rose in 1844 when he produced two new acids, niobic acid and pelopic acid, from samples of columbite and tantalite. Metallic niobium was finally isolated by the Swedish chemist Christian Wilhelm Blomstrand in 1864. Today, niobium is primarily obtained from the minerals columbite and pyrochlore ((Ca, Na)2 Nb 2 O 6(O, OH, F)). Niobium is used as an alloying agent and for jewelry, but perhaps its most interesting applications are in the field of superconductivity. Superconductive wire can be made from an alloy of niobium and titanium which can then be used to make superconductive magnets. Pure niobium is itself a superconductor when it is cooled below 9. 25 K (-442. 75°F).

Properties of Ta and Nb Ta Nb Atomic Number: 73 Atomic Weight: 180. 94788 Melting Point: 3290 K (3017°C or 5463°F) Boiling Point: 5731 K (5458°C or 9856°F) Density: 16. 4 grams per cubic centimeter Phase at Room Temperature: Solid Element Classification: Metal Key isotopes: 180 Ta, 181 Ta Atomic Number: 41 Atomic Weight: 92. 90638 Melting Point: 2750 K (2477°C or 4491°F) Boiling Point: 5017 K (4744°C or 8571°F) Density: 8. 57 grams per cubic centimeter Phase at Room Temperature: Solid Element Classification: Metal Key isotopes: 93 Nb

Ta and Nb minerals Ta Nb Tantalite, (Fe, Mn)Ta 2 O 6 Columbite(niobite) (Fe, Mn)Nb 2 O 6 Microlite, (Na, Ca)2 Ta 2 O 6(O, OH, F) Coltan(columbite– tantalite) (Fe, Mn)(Nb, Ta)2 O 6 Wodginite, Mn 2+(Sn, Ta)Ta 2 O 8 Pyrochlore (Na, Ca)2 Nb 2 O 6(OH, F) Loparite (Ce, Na, Ca)(Ti, Nb)O 3 6

Processing Ta and Nb ores • • • Ta and Nb ores are poor. (Ta. Nb)2 O 5 – 0. 003 - 0. 2%. Ta and Nb minerals are extracted simultaneously with other valuable minerals. The basic method of Ta nad Nb ores enrichment – gravitational, which gives concentrate consisting tantalite or columbite. Further enrichment of minerals separation is carried out by electromagnetic and flotation. Tantalite concentrate 1 st category – 60 -65% Ta 2 O 5, 2 nd category – 40% Ta 2 O 5 Columbite concentrate 1 st category - 60% Nb 2 O 5, 2 nd category – 40% Nb 2 O 5 Pyrochlore concentrate should contain 38 % (Ta. Nb)2 O 5 Loparite concentrate should contain 38 % (Ta. Nb)2 O 5

Decomposition of Tantalite and columbite concentrate with sodium hydroxide Na. OH: Ta. Nb concentrate = 300: 100 kg 750 -800 °C fusion Na 3 Ta. O 4 and Na 3 Nb. O 4 H 2 O Na 5 Ta 6 O 19*25 H 2 O and Na 14 Nb 12 O 37*32 H 2 O HCl Ta 2 O 5*n. H 20 and Nb 2 O 5*n. H 20 Obtaining pure Ta and Nb 8

Decomposition with hydrofluoric acid (HF 60 -70% t ≥°C) Where, Э - Ta and Nb H 2 Sn. F 6, H 2 Ti. F 6, H 2 WF 6, H 2 Si. F 6

Chlorination of loparite concentrate Cl 2 (g) 750 -850 °C in presence of C (coal) or cox Nb. Cl 5 Nb. OCl 3 Al. Cl 3 Ta. Cl 5 Ti. Cl 4 t°C, melt 204. 7 - - 216. 5 -23 t°C, boil 248 400 180 234 136 90 % (Ta, Nb)2 O 5 Chlorination of Loparite concentrate gives 93 -94 % Nb and 86 -88 % Ta tech oxide

Separation Ta and Nb 1. Fractional crystallization of the complex fluorides 23 -40% HF, 70 -80 °C, KCl K 2 Ta. F 7 and K 2 Nb. OF 5*H 20 have different crystal structure 2. Extraction. Tributyl phosphate (TBF) or methylisobuthylketon (MIBK) 3. Rectification. Ta. Cl 5 t°C, boil Nb. Cl 5 234 248

Production of Ta and Nb powder 1 Metallothermy (Na) 800 -900 °C 2. Carbothermy (C) 1800 – 1900 °C 3. Alumothermy (Al) 2200 °C 4. Reduction Ta. Cl 5 and Nb. Cl 5 with H 2

The tantalum facility of "Ulba Metallurgical Plant" JSC provides the following products to the world market: TANTALUM PRODUCTS: • • 3 N 2, 3 N 5, 3 N 7, 4 N and 4 N 5 pure Tantalum ingot produced by double and triple electron beam melting Chips Tantalum mill products of flat and round forms Powders Materials for сapacitors Ingots Ta. Y and products Alloy ingots Ta. W-10, Ta. W-2. 5 and products 4 N 5 pure Tantalum ingot produced by vacuum arc melting NIOBIUM PRODUCTS: • Niobium pentoxide • Ingots • Chips • Mill Products • Rods, wire • Powders • Ingots from Nb. Ti alloy. Nb. Ti products • Ingots from Nb. Zr alloy and products • Niobium Pentoxide