Rhenium metal. Rhenium: application and properties Rhenium in liquid state

Effect of Rhenium Doping on the Deformation Behavior and Mechanical Properties of Heterophase Single Crystals of a Doped Heat-Resistant Alloy Based on No. 3A1

G.P. Grabovetskaya, Yu.R. Kolobov, V.P. Buntushkin1, E.V. Kozlov2

1 Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634021 Russia 2 All-Russian Institute Aviation Materials, Moscow, 107005 Russia 3 Tomsk State University of Architecture and Civil Engineering, Tomsk, 634003 Russia

Raster methods electron microscopy the structure and phase composition of single crystals were studied<001 >alloy type VKNA. The influence of alloying with rhenium on the deformation behavior and temperature dependence of the mechanical properties of single crystals in the temperature range 293–1373 K is studied. Possible physical reasons for the change in the nature of the deformation behavior of single crystals doped with rhenium are discussed.<001 >alloys of the VKNA type in the temperature range 2931 073 K.

The effect of Re alloying on deformation behavior and mechanical properties of heterophase single crystals of doped high temperature Ni3Al-based alloy

G.P. Grabovetskaya, Yu.R. Kolobov, V.P. Buntushkin, and E.V. Kozlov

The structure and phase composition of single crystals<001>of VKHA-type alloy have been investigated by scanning electron microscopy. The effect of Re alloying on deformation behavior and temperature dependence of mechanical properties of the above-mentioned single crystals in the temperature range of 293-1 373 K has been examined. Consideration are given to possible physical reasons of changing deformation behavior characteristics of Re alloying of single crystals<001>of VKHA-type alloy in the temperature range of 293-1 073 K.

1. Introduction

Promising materials for turbine blades

at present, there are poly- and single crystals of heat-resistant (y + y") nickel alloys with a large

volume fraction of the -phase (intermetallic compound No. 3A1) with super-

structure L12. Such alloys have high heat resistance and can operate at high temperatures for a long time. Polycrystalline alloys based on Na3A1 have been fairly well studied.

In particular, it has been established that in such materials the processes of deformation and fracture during high-temperature creep are localized at the grain boundaries. This leads to the initiation and diffusion-controlled growth of grain-boundary wedge-shaped cracks.

With the simultaneous development of slip along the grain boundaries. The absence of grain boundaries in single crystals of these alloys eliminates the negative consequences of grain boundary processes and allows

significantly improve the performance characteristics of the alloys under consideration.

It has been shown in the papers that in the process of deformation of single crystals of (y + y/)-alloys, when the shear stresses in the operating slip system reach a critical value, slip nucleation takes place at the y/y interfaces. Slip develops first in the y-phase, and then occurs cutting of particles of high-strength y"-phase by dislocations. Subsequently, with increasing deformation, slip also develops in the y-phase. In this case, it is mainly localized in the less strong y-phase. + y")-alloy. Another way to increase the strength of single crystals (y + y") alloys is alloying with elements that increase the strength characteristics of the y- and y7-phases.

In this work, we study the effect of rhenium alloying on the deformation behavior and temperature dependence of the mechanical properties of complexly alloyed single crystals of an alloy based on Ni3Al.

2. Material and test method

Single crystals were used as a material for the study.<001 >alloy based on Ni3Al containing elements Cr, Ti, W, Mo, Hf, C, the total amount of which did not exceed 14 wt. % (VKNA type alloy).

The microstructure of the alloy was examined using a scanning (Philips SEM 515) microscope. The phase composition was determined by X-ray diffraction analysis on a DRON-2 setup.

Mechanical tensile tests were carried out on a modernized PV-3012M unit in the temperature range 293-1373 K at a rate of 3.3*10-3 s1. Samples for mechanical testing in the form of a double blade with dimensions of the working part 10x2.5x1 mm were cut out by the electrospark method. Before testing, a layer about 100 μm thick was removed from the surfaces of the samples by mechanical grinding and electrolytic polishing.

3. Results of the experiment and their discussion

Structural studies have shown that original state(state 1) single crystals<001 >alloy

VKNA type contains two phases - y and y7. In the bulk of the alloy, there are large precipitates of irregular shape of the y"-phase with a size of 30-100 μm and a finely dispersed mixture of plates of y7- and y-phases, with dimensions of the order of several micrometers in length and ~ 1 μm in width (Fig. 1, a). The main volume occupies the Y-phase (-90%), a solid solution based on Ni3Al, while the volume fraction of large precipitates of the Y-phase is -22%.

The introduction into the alloy of a small (less than 2 wt. %) amount

quality of rhenium (state 2) leads to the appearance in

volume of single crystals of the third phase - A1^e. However, its volume fraction does not exceed 0.5%. The bulk of the material is still occupied by the γ7 phase (-75%). At the same time, the volume fraction of large segregations of the y7-phase decreases to 10%, and their sizes to 5–30 µm (Fig. 1, b).

On fig. Figures 2 and 3 show typical flow curves and the temperature dependence of the tensile mechanical properties of single crystals.<001 >alloy VKNA in state 1 in the temperature range 293–1373 K. From fig. It can be seen from Fig. 2 that the flow curves of these single crystals at temperatures below 1073 K exhibit an extended stage of strain hardening with a high strain hardening coefficient, which is characteristic of multiple slip in the octahedral planes of single crystals with the L12 superstructure. This character of slip is also confirmed by the presence of single crystals on the pre-polished surface.<001 >alloy type VKNA in state 1 after testing in the temperature range 293-1073 K fine and/or coarse slip marks in two mutually perpendicular slip systems that pass through both phases without interruption.

On the flow curves of single crystals<001 >In the alloy of the VKNA type in state 1 at temperatures of 1273 and 1373 K, a platform or a sharp yield tooth is observed, followed by an extended stage of strain hardening with a low strain hardening coefficient. This type of stretching curves is characteristic of single crystals with the L12 superstructure if the deformation is carried out by dislocation glide in the cube plane. After testing at temperatures above 1073 K, no slip traces are observed on the pre-polished surface of the samples, which is typical for cubic slip in single crystals.<001 >intermetallic compound No. 3A1. Cracks appear near the fracture site. They are located along the interface between large dendrites of the y7 phase and a finely dispersed mixture of (y + y7) phases. The crack density p is not high. For example, after testing

Rice. Fig. 1. Structure of single crystals of the VKNA alloy in states 1 (a) and 2 (b)

Deformation, %

Rice. 2. Flow curves of single crystals<001>alloy VKNA in state 1, calculated in the approximation of uniform elongation: 293 (1); 873(2); 1073(3); 1273(4); 1373 K (5)

Temperature, K

Rice. Fig. 4. Dependence of the tensile strength (1), yield strength (2) and strain to failure (3) on the test temperature of single crystals<001 >alloy type VKNA in condition 2

at 1373 K p is -10 mm-2. The crack length ranges from 20 to 150 µm.

Special flow curves for single crystals<001 >alloys of the VKNA type in state 1 are observed at a temperature of 1073 K. This temperature is characterized by a very short stage of strain hardening with a maximum strain hardening coefficient, which is replaced by a softening stage. On the surface of the samples after stretching at a temperature of 1073 K, both traces of slip in two mutually perpendicular slip systems and cracks are observed.

From fig. 3 shows that for single crystals< 001 >A VKNA-type alloy in state 1 is characterized by a monotonic increase in the yield strength a0 2 in the temperature range 293-1073 K, and then, after reaching a maximum in at a temperature close to 1073 K, its sharp drop. Plasticity of single crystals<001 >alloy

of the VKNA type in state 1 decreases with increasing temperature, reaches a minimum at a temperature of 1073 K, and then increases. The value of the ultimate strength av of single crystals<001 >alloy type VKNA in state 1 in the temperature range 293-873 K practically does not change. As the temperature increases, av initially slightly increases and, reaching a maximum at 1073 K, drops sharply.

Thus, the temperature dependence of the deformation behavior, strength and plastic characteristics of single crystals<001 >alloy type VKNA in state 1 is similar to the anomalous dependence of those for single crystals of intermetallic No. 3A1.

Doping with rhenium leads to a significant increase in the values of a 02 and a in single crystals<001 >alloy of the VKNA type in the temperature range from room temperature to 873 K (Fig. 4), which may be associated with hard

Rice. Fig. 3. Dependence of the value of the tensile strength (1), the flow limit 5. Flow curves of single crystals<001>VKNA alloy in co-

honor (2) and deformation to failure (3) from the standing test temperature 2, calculated in the uniform elongation approximation:

single crystals<001>alloy type VKNA in condition 1 293 (1); 1073(2); 1173(3); 1273(4); 1373 K (5)

solution hardening. In this case, in the specified temperature range, the values of а0 2 and а are practically constant. At temperatures above 873 K, the values of a02 and a in single crystals<001 >alloy type VKNA in state 2 sharply decrease to values corresponding to state 1. The value of 8 single crystals<001 >alloy type VKNA when alloyed with rhenium, on the contrary, decreases compared to the corresponding values of 8 for state 1. However, in the entire temperature range studied, it monotonically increases with increasing temperature from 16 to 33% (Fig. 4).

On fig. Figure 5 shows typical tensile flow curves for single crystals.<001 >alloy of the VKNA type in state 2 in the temperature range 2931373 K. From fig. 5 it can be seen that on the flow curve of these single crystals at room temperature, an extended stage of strain hardening is observed with a higher strain hardening coefficient than that corresponding to state 1. With increasing test temperature, the length of the stage of strain hardening of single crystals<001 >alloy type VKNA in state 2 increases monotonically, while the strain hardening coefficient decreases monotonically. While the strain hardening coefficient for single crystals<001 >VKNA-type alloy in state 1 changes with increasing temperature along a curve with a maximum (Fig. 2).

On the pre-polished surface of single crystals<001 >alloy VKNA in state 2, as well as on the surface of single crystals<001 >alloy type VKNA in state 1, after stretching in the temperature range of 293–1073 K, there are thin and/or coarse slip marks in two mutually perpendicular slip systems, and after testing at temperatures above 1073, there are no slip traces. In this case, the density and length of cracks on the surface near the fracture site in single crystals<001 >of the VKNA alloy in state 2 is less than in state 1. Thus, after stretching at 1373 K, the density of cracks on the surface of single crystals<001 >of the VKNA alloy in state 2 is -3 mm-2, and the crack length ranges from 15 to 30 µm.

Thus, the above data show that doping with rhenium leads to a qualitative change in the deformation behavior of single crystals<001 >alloys of the VKNA type in the temperature range 2931073 K.

The anomalous dependence of the deformation behavior and strength characteristics of intermetallic No. 3A1 on temperature, in accordance with

rye in a certain temperature range are practically not destroyed. Dislocation barriers of the Kira-Wilsdorf type are two split superparticle dislocations interconnected by an antiphase boundary strip in the cube plane. The activation energy for the formation and destruction of these barriers is largely determined by the energies of the antiphase boundary and stacking fault. It is known that the energies of the antiphase boundary and the stacking fault of the Ni3Al intermetallic compound depend significantly on the type and amount of alloying elements. Hence, it can be assumed that the change in the nature of the temperature dependences of the values of st02, hf, and s of single crystals<001 >alloys of the VKNA type when alloyed with rhenium is associated with a change in the energies of the antiphase boundary and the stacking fault in the Y-phase.

4. Conclusion

Thus, doping with rhenium leads to a change in the nature of the deformation behavior of single crystals<001 >alloys of the VKNA type in the temperature range 293-1073 K. In this case, an increase in the strain hardening coefficients and strength characteristics of these single crystals is observed while maintaining satisfactory plasticity.

Literature

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2. Kolobov Yu.R. Diffusion-controlled processes at the boundary

grain quality and plasticity of metallic polycrystals. - Novosibirsk: Nauka, 1998. - 173 p.

3. Kolobov Yu.R., Kasymov M.K., Afanasiev N.I. The study of laws

Numbers and Mechanisms of High-Temperature Fracture of an Alloyed Intermetallic // Phys. - 1989. - T. 66. - Issue. 5. -S. 987-992.

4. Grabovetskaya G.P., Zverev I.K., Kolobov Yu.R. Development of plastic deformation and fracture during creep of alloyed alloys based on Ni3Al with different boron content // Phys. -1994. - T. 7. - Issue. 3. - S. 152-158.

5. Shalin R.E., Svetlov I.L., Kachanov E.B. and other Monocrystals of nickel heat-resistant alloys. - M.: Mashinostroenie, 1997. -333 p.

6. Poirier J.P. High temperature creep crystalline bodies. - M.: Metallurgy, 1982. - 272 p.

7. Kablov E.N., Golubovsky E.R. Heat resistance of nickel alloys. - M.: Mashinostroenie, 1998. - 463 p.

8. Popov L.E., Koneva N.A., Tereshko I.V. Strain hardening of ordered alloys. - M.: Metallurgy, 1979. -255 p.

9. Grinberg B.F., Ivanov M.A. Intermetallics: microstructure, deformation behavior. - Ekaterinburg: NISO UrO RAN, 2002. - 359 p.

10. Thornton P.H., DaviesP.G., Johnston T.I. The temperature dependence of the flow stress of the Y phase based upon Ni3Al // Metallurgical Transactions. - 1970. - No. 1. - P. 207-212.

11. Liu C.T, Pope D.P. Ni3Al and its alloys // Intermetallic Compounds. -1994. - V. 2. - P. 17-51.

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APPLICATION OF RHENIUM AS ALLOYING ELEMENT IN ALLOYS AND METAL MATERIALS

A positive impact on the growth of rhenium production in the 1970s-1980s was its wide and large-scale use in high-temperature nickel alloys and in platinum-rhenium catalysts for various purposes. At the same time, the need for new materials in traditional areas of application of rhenium - electronics and special metallurgy - stimulates interest in this metal from industry and science. According to the technical classification, rhenium is a typical refractory metal, however, in a number of properties it differs significantly from other refractory metals such as molybdenum or tungsten. In terms of characteristics, rhenium to some extent approaches noble metals such as platinum, osmium, and iridium. It can be conditionally considered that rhenium occupies an intermediate position between refractory metals, on the one hand, and platinum group metals, on the other. For example, unlike tungsten, rhenium does not enter the so-called water cycle - a negative phenomenon that causes damage to the filament of vacuum tubes. That is why a vacuum lamp made with rhenium filament is practically “eternal” (its service life is up to 100 years).

By analogy with platinum metals, rhenium has a high corrosion resistance in a humid atmosphere and in aggressive environments. It almost does not interact at ordinary temperatures with hydrochloric and sulfuric acids. Like tungsten and molybdenum, rhenium is paramagnetic, but its electrical resistivity is ~3.5 times greater than that of these metals.

The mechanical properties of rhenium are especially different. It is characterized by high plasticity at room temperature and, in terms of the modulus of normal elasticity, ranks third after osmium and iridium. This is due to the structure of the metal: rhenium is the only element among the refractory metals of the fifth and sixth groups of the Periodic Table of D.I. Mendeleev (vanadium, niobium, tantalum, chromium, tungsten, molybdenum), which has a hexagonal close-packed lattice (hcp), similar to the lattice of noble metals, such as osmium or ruthenium. Other refractory metals (tungsten, molybdenum) are characterized by a different structural type based on a body-centered cubic lattice (BCC).

The properties of rhenium at elevated temperatures also compare favorably with the properties of other refractory metals. So, although the hardness of rhenium, like that of tungsten and molybdenum, decreases with increasing temperature, however, softening is not so fast and at a temperature of 1000 ° C, rhenium has a hardness ~ 2 times greater than tungsten under similar conditions. In addition, at high temperatures, rhenium is characterized by increased long-term strength compared to tungsten and especially molybdenum and niobium. In terms of abrasion resistance, rhenium is in second place after osmium.

These unique properties of rhenium, as well as a number of others, are discussed in detail in the works. They determine the efficiency of rhenium alloying of various metals and alloys in order to increase their ductility, wear resistance and other parameters.

A large number of binary and multicomponent alloys of rhenium with various metals are described in the scientific and technical literature. These are widely known alloys such as nickel-rhenium, tungsten-rhenium, molybdenum-rhenium, nickel-molybdenum-rhenium, nickel-tantalum-rhenium, nickel-tungsten-rhenium and a number of others.

At present, nickel-rhenium, tungsten-rhenium and molybdenum-rhenium alloys are most widely used in terms of production, and in some properties, rhenium alloys with tungsten and molybdenum surpass the properties of individual metals. Such alloys have high mechanical characteristics at room and elevated temperatures, dimensional stability and vibration strength, do not become brittle after crystallization, and weld well, forming a dense plastic seam. They are distinguished by high corrosion resistance in aggressive environments.

Rhenium alloys are used as a structural material in various operating conditions at high temperatures (>1800 °C) and voltage, as critical parts of electrovacuum devices, as a material for electrical contacts, elastic elements of various devices and mechanisms, etc. The properties of rhenium alloys with refractory metals and nickel are described above (see table. 9), and in table. 88 some physical and mechanical properties of tungsten-rhenium and molyb-den-rhenium alloys are summarized.

Nickel-rhenium alloys are used in aviation, they are used as oxide cathode cores, which are characterized by increased reliability and durability. Alloying nickel with rhenium leads to an improvement in its strength characteristics while maintaining ductility. These alloys also have high heat resistance, vibration strength and dimensional stability.

V last years Russian scientists have developed new superheat-resistant rhenium-containing nickel alloys with unique properties for rotor blades and disks of aviation and power gas turbines. These are the three groups of nickel-rhenium alloys.

1. Heat resistant nickel alloys containing 9-12% Re , for the manufacture of turbine blades operating at temperatures up to 1100 ° C.

2. Intermetallic nickel alloys (1-2% Re ) based on connection Ni 3 Al for the manufacture of turbine blades operating at temperatures up to 1250 °C.

3. Heat resistant nickel alloys (1-2% Re ) for the manufacture of turbine disks operating at temperatures of 850-950 ° C.

Table 88

Some physical and mechanical properties of rhenium alloys with tungsten and molybdenum

Indicator	Alloy Mo-Re	Alloy W-Re
Indicator	(47% Re)	(27% Re)
Crystal cell	BCC	BCC
Density, g / cm 3	13,3	19,8
Recrystallization start temperature, °C	1350	1500
Melting point, °С	2500	3000
Linear thermal coefficient expansion, KG 6 * 1/deg (0-1000 °С)

Atomic number - 75, Re. The name takes from the Rhine - a river in Germany. The metal was discovered in 1925. The first batch of rhenium was obtained in 1928. Last discovered element with a known stable isotope.

Rhenium - metal with a white tint. Rhenium Powder opposite is black. It is a very hard and dense metal. Melting - 3186º C, boiling - 5596º C. It has paramagnetic properties.

natural mineral rhenium photo below:

At temperatures above 300º C, the metal begins to oxidize intensively, depending on the temperature increase. The reactions of rhenium are more resistant to oxide than, for example, those of tungsten. Almost no reactions with hydrogen and nitrogen occur, only adsorption with hydrogen.

During heating, interaction with chlorine, fluorine and bromine begins to occur. Insoluble in acids other than nitric acid. When rhenium reacts with an amalgam is formed.

Interacting with hydrogen peroxide (more precisely, its aqueous solution), it forms rhenium acid. The only element representing refractory metals that does not form carbides.

It is known that rhenium is not involved in biochemistry. There are quite a few facts about its possible effects, but its toxicity is reliable, so in any case it is poisonous to living beings.

Mining and origin of rhenium

This is an extremely rare metal. Most common in natural deposits combination of tungsten - rhenium- molybdenum. An admixture of this element is also found in the minerals of its neighbors. Main rhenium mining comes from deposits, where it is extracted along the way.

Also, rhenium is extracted from the rarest natural mineral called dzhezkazganite - after the name of the Kazakh city near which it was found. Rhenium is also found in columbite (niobium), pyrites, zircon and some rare earth minerals.

Rhenium is dispersed throughout the world, in negligible concentrations. Only one serious deposit of this metal is reliably known - Iturup, a small island in the Kuriles, Russia. It was discovered in 1992. Rhenium there is represented by the mineral rhenite ReS2, which has a structure similar to molybdenite.

The field is a small area on top of a dormant volcano, where thermal springs are active. This suggests that the deposit continues to grow, and according to preliminary estimates, it annually releases about 37 tons of this metal into the atmosphere.

The second source of rhenium, more or less suitable for industrial development, can be considered the Hitura deposit, located in Finland. There, rhenium is found in the mineral tarkianite.

How to receive rhenium? Production of this metal occurs through the processing of primary raw materials with a fairly low percentage of metal. Copper and molybdenum sulfides are mainly used.

The stages of the pyrometallurgical process used when working with ores containing rhenium include the procedure of melting, converting and oxidative roasting.

At high melting temperatures, the highest oxide Re2O7 is first obtained, which is retained by special traps. Often, some of the rhenium remains in the soot after firing, from which it can be obtained using hydrogen. Next, the resulting powder is melted into rhenium.

During smelting, most of the rhenium is sublimated from the ore, the remainder settles in the matte. During the conversion of the matte, the rhenium contained in it is released by means of a gas.

Rhenium is concentrated with sulfuric acid, after which rhenium acid is obtained. Using certain purification methods, rhenium is separated from the acid solution.

Based on the rather low productivity this method- the output can be no more than 65% of the metal contained in the ore, scientific research is constantly being carried out to identify more productive alternative methods of metal production.

Modern technologies already imply the use of an aqueous solution, instead of an acid one. This will allow much more metal to be captured during cleaning.

Application of rhenium

The main advantages of rhenium, for which it is so valued all over the world, are refractoriness, low corrosion when exposed to various chemicals, etc. In view of the high on this metal, they try to use it only in extreme and exceptional cases.

Not so long ago, the main area of its application was heat-resistant rhenium alloys with various metals used in rocket and aircraft industries.

In particular, the alloys were used to produce spare parts for supersonic fighters. Such alloys include at least 6% rhenium metal in their composition.

This aspect quickly made jet engines a major source of consumption of the world's rhenium reserves. In addition, due to this, he began to be considered a military-strategic reserve.

Special thermocouples containing rhenium make it possible to measure enormous temperatures. Rhenium allows platinum metals to extend their service life. Rhenium is also used to make springs for precision instruments and filaments for spectrometers and pressure gauges.

More precisely, it is used there with a rhenium coating. Due to its resistance to chemical attack, rhenium is used to create protective coatings against acidic and alkaline environments.

Rhenium has found application in the manufacture of special contacts that self-clean after a short-term short circuit. Oxide remains on ordinary contacts, which sometimes does not pass current. It also remains on rhenium, but soon disappears. Therefore, rhenium contacts have a very long service life.

But especially important aspect its application has become use of rhenium in special catalysts, with the help of which certain components are produced. Participation in the process of processing petroleum products increased the demand for rhenium several times. The world market is already seriously interested in this rare earth metal.

Rhenium price

The world reserve of this metal is about 13 thousand tons, mostly in molybdenum and copper deposits. They are its main sources in the metallurgical industry.

In principle, this is not surprising, more than 2/3 of all rhenium on the planet is contained in them. And the remaining third is secondary material.

According to some estimates, these reserves will last another three hundred years at least. Moreover, in this report, secondary use was not taken into account. And such projects have been developed for a long time, and some projects have proven their worth in practice.

Prices for any product are set based on the availability of the product. How to become clear rhenium, buy which not everyone can afford, by no means affordable metal. In addition, there is a strong demand for rhenium. Price he naturally corresponding.

As of 2011, to purchase rhenium, the price per gram was about $4.5. Significant downward trends in prices were not observed. In addition, the price depends on the degree of purification of the metal, so rhenium can cost as much as $ 1,000 per kilogram, or ten times more expensive.

Rhenium, the application of which will be discussed below, is an element of the chemical periodic table under the atomic index 75 (Re). The name of the substance comes from the river Rhine in Germany. The year of discovery of this metal is 1925. The first significant batch of material was obtained in 1928. This element belongs to the last analogue with a stable isotope. By itself, rhenium is a metal with a white tint, and its powder mass is black. Melting and boiling points range from +3186 to +5596 degrees Celsius. It has paramagnetic properties.

Peculiarities

The use of rhenium is not so widespread due to its exceptional parameters and high cost. At +300 °C, the metal begins to actively undergo oxidation, the process of which depends on a further increase in temperature. This element is more stable than tungsten, practically does not interact with hydrogen and nitrogen, providing only adsorption.

When heated, a reaction with chlorine, bromine and fluorine is noted. Rhenium does not dissolve only in nitric acid, and when interacting with mercury, an amalgam is formed. Reaction with an aqueous composition of hydrogen peroxide causes the formation of rhenium acid. This element is the only one among refractory metals that does not form carbides. The use of rhenium has no participation in biochemistry. There is little information available about all of its possible effects. Among the reliable facts - toxicity and toxicity to living organisms.

Mining

Rhenium is a metal that is extremely rare. In nature, it is most often found in combination with tungsten and molybdenum. In addition, impurities are present in the mineral deposits of its neighbors in the table. Predominantly, rhenium is mined from molybdenum deposits by associated extraction.

In addition, the element in question is extracted from dzhezkazganite, a very rare natural mineral, which is so named after the Kazakh settlement near the deposit. Rhenium can also be isolated from pyrite, zirconium, columbite.

The metal is dispersed throughout the world in negligible concentration. Among the known mining sites, where it is found in significant quantities, is the Kuril in Russia. The deposit was discovered in 1992. Here, the metal is presented in the form of a structure similar to molybdenum (ReS 2).

Mining is carried out on a small platform located on top of a dormant volcano. Thermal springs are active there, which indicates the expansion of the deposit, which, according to preliminary estimates, emits about 37 tons of this metal per year.

The second in terms of production is the rhenium deposit, suitable for the industrial extraction of the element. It is located in Finland and is called Hitura. There, the metal is extracted from another mineral - tarkyanite.

Receipt

Rhenium is obtained by processing primary raw materials, which initially have a low percentage of this material. Most often, the element is extracted from copper and molybdenum sulfides. Rhenium alloys are subjected to pyrometallurgical action, which is used when working with ores that are smelted, converted and roasted.

Excessive melting temperatures make it possible to obtain Re-207, which is retained by special trapping devices. It happens that part of the element settles in soot after firing. Pure material can be obtained from this substance with the help of hydrogen. Then the resulting powder substance is melted directly into rhenium ingots. The use of ore for the extraction of the element in question is accompanied by the appearance of sediment in the matte. Further conversion of this composition makes it possible to isolate rhenium by exposure to certain gases.

Technological moments

It is possible to achieve the desired concentration during production due to the properties of rhenium and the use of sulfuric acid. After passing through special purification methods, it is possible to isolate a pure element from the ore.

This method is not very productive; the yield of a pure product is no more than 65%. This indicator varies depending on the metal content in the ore. On this basis, scientific research is regularly carried out to identify more advanced and alternative methods of production.

Modern technologies make it possible to optimize the properties of artificially obtained rhenium. This solution allows the use of an aqueous solution instead of an acid one. This makes it possible to capture significantly more pure metal during cleaning.

Application

First, consider the main characteristics of the element in question, for which it is especially appreciated:

Infusibility.
Minimal susceptibility to corrosion.
No deformation when exposed to chemicals and acids.

Since the price of this metal is extremely high, it is used mainly in rare cases. The main area of application of this element is the production of heat-resistant alloys with various metals, which are used in the construction of rockets and the aviation industry. As a rule, rhenium is used for the production of spare parts for supersonic fighters. Such compositions include at least 6% metal.

Such a source quickly turned into the main means for creating jet power units. At the same time, the material began to be considered a military-strategic reserve. Specially provided thermal couples allow to measure temperatures in huge ranges. The element in question makes it possible to extend the service life of most of the aggregated metals. From rhenium, the use of which is discussed above, springs are also made for precision equipment, platinum metals, spectrometers, pressure gauges.

More specifically, it uses rhenium-coated tungsten. Due to its resistance to chemical influences, this metal is included in the composition of protective coatings against acidic and alkaline environments.

Rhenium is also used to make special contacts. They have the property of self-cleaning in the event of a short circuit. On ordinary metals, oxide remains, which does not allow the passage of current. Current also passes through rhenium alloys, but it does not leave any traces behind itself. In this regard, contacts made of this metal have a long service life.

The most important aspect of the use of rhenium was the possibility of using it to create catalysts that help produce certain components of gasoline fuel. The possibility of using a chemical element in the oil products industry led to an increase in its demand in the corresponding market by several times. The world is seriously interested in this unique material.

Stocks

It should be noted that the world stock of rhenium is at least 13 thousand tons only in molybdenum and copper deposits. They are the main sources of this component in the metallurgical industry. More than 2/3 of all rhenium on the planet is found in such configurations. The remaining third is secondary residues. If we reduce all calculations of reserves to a single denominator, they should be enough for at least three hundred years. In the calculation of scientists, recycling was not taken into account. Similar projects have been developed for a long time, some of them have proven their worth.

Price

Prices for the product of most categories are formed due to the availability and demand of the product. A component such as rhenium is one of the most expensive metals in the world, so not every manufacturer can afford it, although it has unique properties that make it possible to offset the costs of its expensive use. At the same time, rhenium has parameters that no other metal has. For the creation of space and aviation structures, its characteristics are ideal. It is not surprising that the price of rhenium is high, although it corresponds to all indicators characteristic of this unique material.

Already in 2011, the average cost of rhenium was about 4.5 US dollars per gram. Subsequently, no downward trend in prices was observed. Often the final cost depends on the degree of purification of the metal. The price of the material can reach thousands of dollars and more.

Discovery history

This element was discovered by German chemists Ead and Walter Noddack in 1925. They conducted research using columbispectral analysis in the laboratory of the Siemens and Shake group. After this event, a corresponding report was held at a meeting of German chemists in Nuremberg. A year later, a team of scientists isolated the first two milligrams of rhenium from molybdenum.

In relatively pure form the element was obtained only in 1928. To obtain one milligram of the substance, it was necessary to process over 600 kilograms of Norwegian molybdenum. industrial production of this metal also started in Germany (1930). The capacity of processing plants made it possible to obtain about 120 kg of metal annually. At that time, this fully satisfied the need for rhenium in the entire world market. In America, the first industrial 4.5 kg of a unique metal were obtained in 1943 by processing concentrated molybdenum. It was this element that became the last discovered metal with a stable isotope. All other analogues discovered earlier, including artificially, did not have similar properties.

Natural reserves

To date, according to the natural reserves of the metal in question, the list of deposits can be arranged in the following order:

Chilean mines.
United States of America.
Iturup Island, whose deposits are estimated at up to 20 tons per year (in the form of volcanic gas eruptions).

V Russian Federation semi-element deposits of the hydrogen type are assessed as areas that have the maximum potential for porphyry copper and copper-molybdenum ores. In total, according to experts' forecasts, rhenium deposits in Russia amount to 2900 tons (76% of the state's resource). The lion's share of these deposits is located in (82%). The next field in terms of reserves is the Briketno-Zheltukhinsky basin in the Ryazan region.

Outcome

Rhenium - chemical element, which belongs to the group of rare metals with unique characteristics. Its properties, places of extraction, areas of application are described above.

D. I. Mendeleev in 1869 predicted the existence and properties of two elements of the VII group - analogues of manganese, which he tentatively called "eka-manganese" and "dwi-manganese". They correspond to the currently known elements - technetium (serial number 43) and rhenium (serial number 75).

In the next 53 years, many researchers reported the discovery of analogues of manganese, but without convincing evidence. Now we know that the search for element 43 in natural compounds could not be successful, since it is unstable. It was only in 1937 that this element was obtained artificially by E. Segre and K. Perrier by bombarding molybdenum nuclei with deuterons and called technetium (from the Greek "techno" - artificial).

In 1922, German chemists Walter and Ida Noddack began a systematic search for analogues of manganese in various minerals. From 1 kg of columbite, they isolated 0.2 g of a product enriched in molybdenum, tungsten, ruthenium and osmium. In this product, an element with the atomic number 75 was detected from the characteristic X-ray spectra. The Noddacks reported their discovery in 1925 and named the element rhenium. Later, in 1927, the Noddacks found that significant concentrations (up to hundredths of a percent) of rhenium are contained in molybdenite, from which the element was isolated in quantities that made it possible to study Chemical properties its compounds and get the metal.

The production of rhenium and its compounds in small quantities first arose in Germany in 1930 at the Mansfeld plant, where rhenium was extracted from furnace scales formed during the smelting of cuprous shales containing an admixture of molybdenite. In the USSR, the production of rhenium began in 1948.

Properties of rhenium

Rhenium is a refractory heavy metal appearance looks like steel. Some physical properties rhenium are listed below:

Atomic number 75

Atomic mass 186.31

Type and periods of the grating. . . . Hexagonal,

Close-packed a = 0.276, c = 0.445 nm

TOC \o "1-3" \h \z Density, g/cm3 21.0

Temperature, °С:

Melting........ 3180±20

Boiling ~5900

Specific heat capacity is average at

0-1200 °С, J/(g" °С) .... 0.153

Electrical resistivity

R * 10 ", OM" cm 19.8

State transition temperature

Superconductivity, K. . . . 1.7

Electron work function, zV 4.8 Thermal neutron capture cross section

P "1024, cm2 85

Hardness HB of the annealed metal, MPa 2000

Then annealed bars) bv, MPa 1155

Modulus of elasticity E, GPa. . . 470

In terms of melting point, rhenium ranks second among metals, second only to tungsten, and fourth in density (after osmium, iridium and platinum). The electrical resistivity of rhenium is almost 4 times higher than that of tungsten and molybdenum.

Unlike tungsten, rhenium is ductile in the cast and recrystallized state and can be deformed in the cold. Due to the high modulus of elasticity, after a slight deformation, the hardness of rhenium increases greatly - strong hardening appears. However, after annealing in a protective atmosphere or in a vacuum, the metal regains plasticity.

Rhenium products (unlike tungsten products) withstand repeated heating and cooling without loss of strength. Welds are not brittle. The strength of rhenium up to 1200 ° C is higher than that of tungsten, and significantly exceeds the strength of molybdenum.

Rhenium is stable in air at ordinary temperatures. Significant oxidation of the metal begins at 300°C and proceeds intensively above 600°C with the formation of the higher oxide Re2O7.

Rhenium does not react with hydrogen and nitrogen up to the melting point and does not form carbide. The eutectic in the rhenium-carbon system melts at 2480°C.

Rhenium reacts with fluorine and chlorine when heated, practically does not interact with bromine and iodine. Rhenium is stable in hydrochloric and hydrofluoric acids

Cold and hot. In nitric acid, hot concentrated sulfuric acid and hydrogen peroxide, the metal dissolves.

Rhenium is resistant to the action of molten tin, zinc, silver and copper, slightly corroded by aluminum and easily soluble in liquid iron and nickel.

With refractory metals (tungsten, molybdenum, tantalum and niobium), rhenium forms solid solutions with a limiting rhenium content of 30-50% (by mass).

Properties of chemical compounds

The most characteristic and stable compounds of rhenium are the highest degree +7. In addition, compounds are known that correspond to the oxidation states 6;5;4;3;2;1; as well as -1.

Oxides. Rhenium forms three stable oxides: rhenium anhydride, trioxide and dioxide.

Rhenium anhydride Re207 is formed during the oxidation of rhenium with oxygen. Color - light yellow, melts at 297 ° C, boiling point 363 C. It dissolves in water to form rhenium acid HRe04.

Rhenium trioxide Re03 is an orange-red solid formed by incomplete oxidation of rhenium powder. It is sparingly soluble in water and dilute hydrochloric and sulfuric acids. At temperatures above 400 ° C, it exhibits noticeable volatility.

Rhenium dioxide Re02 dark brown solid, obtained by reduction of RejO; hydrogen at 300 °C. Dioxide is insoluble in water, dilute hydrochloric and sulfuric acids. When heated in vacuum (above 750°C), it disproportionates to form Re207 and rhenium.

Rhenic acid and its salts are perrheates. Rhenic acid is a strong monobasic acid. Unlike permanganic acid, HRe04 is a weak oxidizing agent. When interacting with oxides, carbonates, alkalis, it forms perrhenates. Potassium, thallium and rubidium perrhenates are sparingly soluble in water, ammonium and copper perrhenates are sparingly soluble, sodium, magnesium and calcium perrhenates are well soluble in water.

Rhenium chlorides. The most studied chlorides are ReCl3 and ReCl3. Rhenium pentachloride is formed by the action of chlorine on metallic rhenium at temperatures above 400 °C. The substance is dark brown. Melts at 260°C, boiling point 330°C. Decomposes in water to form HRe04 and Re02 "xH20.

ReCl3 trichloride is a red-black substance obtained as a result of thermal dissociation of ReCl5 at temperatures above 200 °C. Melting point 730 °C, sublimes at 500-550 °C

Two oxychlorides are known: ReOCl4 (melting point 30 °C, boiling point 228 °C) and ReOjCl (liquid, boils at 130 °C).

Rhenium sulfides. Two sulfides are known - RejS? and ReS2. Higher sulfide is a dark brown substance that is precipitated by hydrogen sulfide from acidic and alkaline solutions. Rhenium disulfide ReS2 is obtained by thermal decomposition of Re2Sy (above 300 °C) or direct interaction of rhenium with sulfur at 850-1000 °C. ReS2 crystallizes in a layered lattice identical to that of molybdenite. In air at temperatures above 300 °C, it oxidizes to form Re2O7.

Applications of rhenium

At present, the following effective areas of application of rhenium have been identified.

Catalysts. Rhenium and its compounds are used as catalysts for a number of processes in the chemical and oil industry. This is the largest area of application for rhenium. Rhenium-containing catalysts have acquired the greatest importance in oil cracking. The use of rhenium catalysts made it possible to increase the productivity of installations, increase the yield of light fractions of gasoline, and reduce the exhaust gas. rats on catalysts by replacing most of the platinum with rhenium.

Electric lighting and electrovacuum equipment. In a number of crucial cases, when it is necessary to ensure the durability of the operation of electric lamps and electronic devices (especially under dynamic load conditions), rhenium or rhenium alloys with tungsten and molybdenum are used instead of tungsten in this area. The advantages of rhenium and its alloys over tungsten are better strength characteristics and retention of plasticity in the recrystallized state, less tendency to evaporate in a vacuum in the presence of traces of moisture (resistance to the hydrogen-water cycle), higher electrical resistance. Rhenium and tungsten alloys with rhenium (up to 30% Re) are used to make filaments, cathode and heater cores, and radio tube grids. V electronic appliances Mo-50% Re alloy is also used, which combines high strength with ductility.

Heat-resistant alloys are one of the important uses of rhenium. Alloys of rhenium with other refractory metals (tungsten, molybdenum and tantalum), along with heat resistance and refractoriness, are characterized by plasticity. They are used in aviation and space technology (parts of thermionic engines, rocket nose nozzles, parts of rocket nozzles, gas turbine blades, etc.).

Alloys for thermocouples. Rhenium and its alloys with tungsten and molybdenum have a high and stable thermoelectromotive force (TEF). In the USSR, thermocouples made of alloys (W-5% Re) - (W - 20% Re) are widely used. T.e.d. With. this thermocouple in the range of 0-2500 ° C is linearly dependent on temperature. At 2000 °C t.e.d. With. is equal to 30 mV. The advantage of a thermocouple is the preservation of plasticity after prolonged heating at high temperature.

Electrocongancts. Rhenium and its alloys with tungsten. are distinguished by high wear resistance and resistance to electro-corrosion in the conditions of formation electric arc. They are more durable than tungsten in tropical environments. Tests of contacts made of alloys W - 15-% Re in voltage regulators and engine ignition devices showed their advantages over tungsten.

Instrumentation. Rhenium and its alloys, which are distinguished by high hardness and wear resistance, are used for the manufacture of parts for various devices, for example, supports for scales, axes of geodetic equipment, hinged supports, and springs. Operation tests of flat springs made of rhenium at a temperature of 800 °C and multiple heating cycles showed the absence of residual deformation and the preservation of the initial hardness.

The scale of rhenium production in foreign countries in 1986 they were at the level of 8 tons/year. The main producers are the USA and Chile; in 1986, 6.4 tons of rhenium were used in the USA.

2. RHENIUM SOURCES

Rhenium is a typical trace element. Its content in the earth's crust is low - 10 7% (by mass). Elevated concentrations of rhenium, which are of industrial importance, are observed in copper sulfides and especially in molybdenite.

The bond between rhenium and molybdenum is due to the isomorphism of MoS2 and ReS2. The content of rhenium in molybdenites of various deposits ranges from 10-1 to 10 "5%. Molybdenites of copper-molybdenum deposits, in particular copper-porphyry ores, are richer in rhenium. Thus, molybdenite concentrates obtained by enriching porphyry copper ores of the USSR contain 0, 02-0.17% rhenium.Significant resources of rhenium are concentrated in some copper deposits, belonging to the type of cuprous sandstones and cuprous shales.This type includes the ores of the Dzhezkazgan deposit of the USSR.The ores with a high content of CuFeS4 bornite are richer in rhenium.In the copper concentrates obtained by flotation contains 0.002-0.003% Re. It is assumed that rhenium is in them in the form of a finely dispersed mineral CuReS4 - dzhezkazganite.

The behavior of rhenium during the processing of molybdenite concentrates

During oxidative roasting of molybdenite concentrates, carried out at 560-600 °C, the rhenium contained in the concentrate forms Re207 oxide, which is carried away with the gas flow (the boiling point of Re207 is 363 °C). The degree of sublimation of rhenium depends on the firing conditions and the mineralogical composition of the concentrate. So, when roasting concentrates in multi-hearth furnaces, the degree of sublimation of rhenium is not higher than 50-60% From Fig. 60

Ras.60. Changes in the content of sulfur, rhenium and the degree of oxidation of molybdenite (dashed line) along the hearths of an eight-hearth furnace

It can be seen that rhenium sublimates with gases at 6-8 hearths (during firing in an 8-hearth furnace), when most of the molybdenite is oxidized. This is explained by the fact that low-volatile rhenium dioxide is formed in the presence of MoS2 according to the reaction:

MoS2+2Re207 = 4Re02+ Mo02+2S02. (5.1)

In addition, incomplete sublimation of rhenium may be due to the partial interaction of Re2O7 with calcite, as well as iron and copper oxides, with the formation of perrhenates. For example, with calcite, a reaction is possible:

CaC03+Re207 = Ca(Re04)2+C02. (5.2)

Pod number

Soviet researchers have established that rhenium sublimates most completely during the roasting of molybdenite concentrates in a fluidized bed. The degree of sublimation is 92-96%. This is due to the absence during firing in furnaces

COP conditions for the formation of lower oxides of rhenium and perrhenates. Efficient capture of rhenium from the gas phase is achieved in wet dust collection systems, consisting of scrubbers and wet electrostatic precipitators. Rhenium in this case is contained in sulfuric acid solutions. To increase the concentration of rhenium, the solutions are repeatedly circulated. Solutions containing, g/l, are removed from the wet collection system: Re 0.2-0.8; Mo 5-12 and H2SO 80-150. A small part of the rhenium is contained in the sludge.

In the case of incomplete sublimation of the rhenium concentrate during roasting, the rhenium remaining in the cinder passes into ammonia or soda solutions for leaching cinders and remains in the mother liquors after precipitation of molybdenum compounds.

When used instead of oxidative roasting, the decomposition of molybdenite with nitric acid (see Chap. 1), rhenium passes into nitric-sulfuric acid mother liquors, which contain, depending on the adopted modes, g / l: H2SO4 150-200; HN03 50-100; Mo 10-20; Re 0.02-0.1 (depending on the content in the raw material).

Thus, sulfuric acid solutions of wet dust collection systems and mother (waste) solutions after hydrometallurgical processing of cinders, as well as nitric-sulfuric acid mother solutions from the decomposition of molybdenite with nitric acid can serve as a source of obtaining rhenium during the processing of molybdenite concentrates.

Behavior of rhenium in copper production

When smelting copper concentrates in reverberatory or ore - nothermal electric furnaces, up to 75% of rhenium flies with gases, while blowing matte in converters, all the rhenium contained in them is removed with gases. If furnace and converter gases containing SOz are sent to sulfuric acid, then rhenium is concentrated in the washing circulating sulfuric acid of electrostatic precipitators. 45-80% of rhenium contained in copper concentrates passes into the washing acid. Washing acid contains 0.1-0.5 g/l of rhenium and ~500 g/l of H2SO4, as well as impurities of copper, zinc, iron, arsenic, etc., and serves as the main source of rhenium in the processing of copper concentrates.