Application.

The basic rhenium scope – the high-temperature and refractory steels. Alloys of rhenium with molybdenum and tungsten surpass other refractory metals and their alloys on the mechanical properties at high temperatures, they are successfully applied to manufacturing of important details of supersonic planes and rockets, in control systems of guided missiles and artificial satellites.

Wide application field of rhenium – the anticorrosive and wear-resisting alloys. Additives of rhenium to platinum metals increase it’s wear resistance. Metal rhenium and its alloys have the high resistance against wear at friction.

Owing to high chemical resistance rhenium is the valuable material for the coverings protecting products from copper, silver, nickel, tungsten, molybdenum against action of acids, alkalis, sea water, sulphurous compounds. Rhenium protective coverings are used for protection of graphite against evaporation in vacuum.

Rhenium and its alloys with tungsten are applied in electrolamps and electrovacuum devices production for manufacturing incandescent filaments, cathodes, heaters and other details.

Rhenium is applied to manufacture of thermo elements. High-temperature thermocouples from rhenium and its alloys with tungsten and molybdenum are suitable for measurement of temperatures up to 2600⁰С and keep the plasticity of electrodes after long overheating.

Rhenium and its compounds can be used as catalysts of various chemical reactions.

Sources of raw material. Rhenium on properties concerns to typical refractory metals, but on occurrence in nature it can be attributed to number of typical trace rare elements. The content of rhenium in the earth's crust (on weight) makes 1·10^-7 %. There are data about existence of three rhenium minerals - oxide, sulfide and copper sulphonate, but any of these minerals is not allocated in the pure state.

Two groups of deposits are allocated: sedimentary and molibdenic.

The cupreous sandstones (for example, the Dzhezkazgan group of deposits in Kazakhstan) represent the greatest interest in sedimentary deposits.

The rhenium content in molybdenites of various deposits changes in limits 1·10^-1-1·10^-5 %. High rhenium concentration in molybdenites is caused by identical sizes of ionic radiuses of tetravalent rhenium both molybdenum and affinity of chemical properties of these elements.

At concentration of molybdenum and copper-molybdenum ores rhenium basically follows molybdenum and at flotation it is extracted all over again in collective sulphidic concentrate, then – in molybdenum concentrate. At concentration of copper ores not containing molybdenum the most part of rhenium passes in copper concentrates.

Extraction of rhenium from molybdenum and copper concentrates.

I. The first stage of molybdenum concentrates processing is the oxidizing roasting of concentrates. At heating of material in excess air rhenium sulfide is oxidized with formation Re₂O₇. At temperature of roasting (550-600⁰С) Re₂O₇ is sublimated and carried away by a gas stream. The fullest rhenium sublimation is carried out in fluidized bed furnaces. In this case 95-97 % of rhenium passes in a gas phase. Effective catching of rhenium occurs in systems wet dust clearing (scrubbers, wet electrofilters).

At melting of copper concentrates in reverberatory furnaces about 70 % of rhenium is carried away with waste gases, at electromelting rhenium passes in a gas phase to 35-40 %. Non-sublimated part of rhenium remains in matte. At converting of matte rhenium residue is practically completely sublimated.

Thus, at molybdenum and copper concentrates processing rhenium sources are solutions of wet electrofilters and scrubbers, dust and slime of gas-clearing systems, mother liquors after allocation of calcium molybdate and ammonium, alkaline solutions after leaching of corresponding copper concentrates.

II. Processing of dust and sublimates represents oxidation of the lowest rhenium oxides up to Re₂O₇ and extraction of Re₂O₇ by water or weak sulfuric acid. Pyroluzite or air, bubbling through solution, are used as oxidizers.

The rhenium content in various solutions makes 0,01-1 g/l. All over again molybdenum as calcium molybdate is precipitated from solutions, then the solution is evaporated up to the rhenium content 10-60 g/l, then rhenium is precipitated as potassium or ammonium perrenates.

III. The manufacture of pure rhenium powder.

Titanium Ti - the chemical element with nuclear number 22, the easy metal of silver-white color.

Occurrence in nature. Titanium is on the 10th place on prevalence in the nature. The content in the earth's crust - 0,57 % on weight. In a free kind it does not meet. It is known more than 100 minerals, containing titanium. Distinguish the primary titanium ores – ilmenite-titanium-magnetite and placer ores - rutile-ilmenite-zircon. Basic ores: ilmenite (FeTiO₃), rutile (TiO₂), titanite (CaTiSiO₅), titanium-magnetite (FeTiO₃ + Fe₃O₄).

On the data for 2002, 90 % of the extracted titanium were used on manufacture of titanium dioxide TiO₂. The world production of titanium dioxide made 4,5 million tons in the year. Russia possesses the second in the world stocks of titanium after China.

Production. A concentrate of titanic ores is subjected to sulphuric acid processing or pyrometallurgical processing.

The product of sulphuric acid processing is the powder titanium dioxide TiO₂.

At pyrometallurgical method the titanium ore is sintered with coke and processed by chlorine. Received vapours of titanium tetrachloride TiCl₄ are reduced by magnesium at 850⁰С:

TiO₂ + 2C + 2Cl₂ = TiCl₄ + 2CO

TiCl₄ + 2Mg = 2MgCl₂ + Ti

Received titanic "sponge" is remelted and cleared. Titanium is refined by the iodide way or electrolysis, allocating Ti from TiCl₄. The arc, electron-beam or plasma processing is applied for production of titanic ingots.

Physical properties. Titanium – the easy silver-white metal. It exists in two crystal updatings. The melting point – 1671⁰С, the boiling point – 3260⁰С. It is plastic; it is welded in the inert atmosphere. Titanium has the high viscosity, at machining it sticks on the cutting tool, therefore tools are covered by special coverings and greasings. At usual temperature titanium is covered by protective passivating oxide film TiO₂, due to it has the high corrosion resistance in the majority of mediums (except for alkaline). The titanic dust can detonate. The flash point – 400⁰С.

Chemical properties. Titanium is steady against corrosion owing to the oxide film, but at crushing the titanium powder burns on air. Titanium is steady against the diluted solutions of many acids and alkalis (except for HF, H₃PO₄ and concentrated H₂SO₄). It easily reacts even with weak acids at presence of complex formers due to formation of complex compounds.

From solutions of titanium salts titanium hydroxide TiO(OH)₂ · H₂O is precipitated, at cautious calcination of titanium hydroxide oxide TiO₂ is received. Titanium hydroxide and oxide are amphoteric compounds.

At heating titanium cooperates with halogens. Titanium tetrachloride TiCl₄ at usual conditions is the yellowish, strongly smoking on air liquid that speaks the strong hydrolysis of TiCl₄ by containing in air water vapours and formation of the smallest droplets of HCl and suspensions of titanium hydroxide. At reduction of TiCl₄ by hydrogen, aluminium, silicon, other strong reducers, titanium trichloride TiCl₃ and titanium dichloride TiCl₂ are received. There are the solid substances with strong reducing properties. Titanium cooperates with bromine and iodine.

With nitrogen titanium forms titanium nitride TiNx (х = 0,58-1,00) at temperature above 400⁰С. At interaction of titanium with carbon titanium carbide TiCx (х = 0,49-1,00) is formed. At heating titanium absorbs hydrogen with formation of compound with structure TiH. At heating hydride is decomposed with allocation of hydrogen.

Titanium forms alloys with many metals.