**7. Conclusion**

416 Thermodynamics – Interaction Studies – Solids, Liquids and Gases

(Fig. 5 a,b, curves 3). Temperature boundary shown at the Fig. 5 is shifted in reverse direction for the W-Ta system (Fig. 5 c, curves 3). It should be noted, that the calculation results performed for cases (2) and (3) (for ideal and nonideal solid solution) for the W-Ta

The influence of rhenium and molibdenium on the equilibrium yield of tungsten in the M-W-F-H systems is observed for W-Re and W-Mo alloys deposition. The ReF6 addition to the gas mixture with WF6 increase insignificantly the yield of tungsten in spite of strong atom interaction during the crystallization according to thermodynamic calculations (Fig. 6). This effect is still smaller for the case of W-Mo co-deposition. However equilibrium yield of metals for their co-deposition with tungsten and the energy of the interaction of metallic components during the crystallization have the common tendency. The knowledge of

The thermodynamic background presented above is very useful for production of the coatings based on tungsten, tungsten alloys with Re, Mo, Nb, Ta, V and tungsten compounds (for example tungsten carbides). The tungsten coatings have found wide application in thin-film integral circuits when preparing the Ohmic contacts in the production of the silicon-, germanium-, and gallium-arsenide-based Schottky-barrier diodes. The tungsten selective deposition technology is perspective in the production of conducting elements at dielectric substrates [36]. Tungsten films are used for covering hot cathodes, improving their emission characteristics, and as protective coatings for anodes in extra-highpower microwave devices. The CVD-tungsten coatings are used as independent elements in

The X-ray bremsstrahlung in modern clinical tomographs and other X-ray units is obtained by using tungsten or W–Re coatings at rotating anodes made of molybdenium or carbon– carbon composite materials. In the nuclear power engineering, tungsten was shown to be a good material for enveloping nuclear fuel particles because of low diffusion permeability of the envelope for the fuel. The tungsten- and W–Re alloy-coatings [2, 3, 5] are extremely stable in molten salts and metals used as coolants in high-temperature and nuclear machinery, e.g., in heat pipes with lithium coolant and in thermonuclear facilities. Tungsten emitters with high emission uniformity, elevated high-temperature grain orientation and

High-temperature technical equipment cannot go without tungsten crucibles, capillaries, and other works that can be easily prepared by the CVD techniques. Tungsten is used as a coating for components of jet engines, fuel cell electrodes, filters and porous components of ion engines, etc. [2] The CVD-alloying of tungsten coatings with rhenium allows to improve significantly their operating ability, especially under the temperature or load cycling. Tungsten compounds have a wide field of application. The tungsten-carbide composites deposited by using the fluoride technology occupy a niche among coatings with a thickness of 10 to 100 mkm; they are unique in respect of strengthening practically any material, starting with carbon, tool, and stainless steels, titanium alloys, and finishing with hard alloys. CVD method permits to coat complicated shape components (which cannot be coated using PVD-method or plasma sputtering of carbide powders with binder). Below we

In the first place we can mention the strengthening of the oil and gas and drilling equipment (pumps, friction and erosion assemblies). The problems of hydrogen- sulfide corrosion,

microstructure stability are of interest for their use in thermionic energy converters.

refined data of process energies will allow us to obtain a more realistic situation.

system are almost identical due to the small enthalpy of mixing [35].

**6. The application fields of the coatings** 

list the most promissing fields of applications [37].

electronics.


Thermodynamic Aspects of CVD Crystallization of Refractory Metals and Their Alloys 419

[1] Korolev Yu. M., Stolyarov V. I., Vosstanovlenie ftoridov tugoplavkikh metallov

[2] Krasovskii A.I., Chuzshko R.K., Tregulov V.R., Balakhovskii O.A., Ftoridnii process

[3] Pons M., Benezech A., Huguet P., et all, J. Phys. France, Vol. 5, N. 8 (1995) pp. 1145-1160. [4] Lakhotkin Yu.V., Krasovskii A.I., Volfram-renievie pokritij (Nauka, Moskva, 1989) 158 p.

[6] Blokhinzev D.I. Osnovi kvantovoii mekhaniki (Nauka, Moskva, 1983) 664 p. (in Russian). [7] Malandin M.B., Lakhotkin Yu.V., Kuzmin V.P., Problemi fizicheskogo metallovedenij

[8] Bersuker I.B., Elektronnoe stroenie i svoistva koordinatsionnikh soedinenii. Vvedenie v

[9] Charkin O.P., Stabilnost i struktura gasoobrasnikh neorganicheskikh molekul, radikalov

[10] Termicheskie konstanti vezhestv. Spravochnik (Izd. AN SSSR, Moskva, 1962-1981) 10 t.

[11] Gurvich L.V., Veiz I.V., Medvedev V.A. et al., Termodinamicheskie svoistva individualnikh vezsestv (Nauka, Moskva, 1978-1982) 4 t. (in Russian). [12] Molekulyarnie postoyannie neorganicheskikh soedinenii. Spravochnik (Chmiya,

[15] Gusarov A.V., Pervov V.S., Gotkis I.S. et al., DAN SSSR, T. 216,, N. 6 (1974) pp. 1296-

[18] Alikhanyan A.S., Pervov V.S., Malkerova N.P. et al., J. Neorganicheskoii chimii, T. 23,

[20] Gotkis I.S., Gusarov A.V., Pervov V.S., et al., Koordinasionnaij chimij T. 4, Vip. 5 (1978)

[22] Burgess J., Fawcett J., Peacock R.D. et al., J. Chem Soc., Dalton Trans., N. 14, (1976) pp.

[23] Politov Yu.A., Alikhanyan A.S., Butzki V.D., et al., DAN SSSR, T. 309, N. 4 (1989) pp.

[24] Politov Yu.A., Alikhanyan A.S., Butzki V.D., et al., J. Neorganicheskoii chimii, T. 32, N.

[26] Stull D.R., Prophet H. JANAF Thermochemical Tables. NSRDS-NBS 37 US, (NBS,

[13] Sidopov L.N., Sholz V.B., J. Fiz. Chimii, T. 45, N. 2 (1971) pp. 275-280 (in Russian). [14] Sidopov L.N., Denisov M.Ya., Akishin P.A. et al., J. Fiz. Chimii, T. 40, N. 5 (1966) pp.

[16] Lau K.H., Hildenbrand D.L. J. Chem. Phys., Vol. 71, N. 4 (1979) pp. 1572-1577.

[19] Nuttal R.L., Kilday M.Y., Churney K.L., Natt. Bur. Stand. Rep. 73-281, (1973).

[17] Hildenbrand D.L. J. Chem. Phys., Vol. 65, N. 2 (1976) pp. 614-618.

[21] Hildenbrand D.L. J. Chem. Phys., Vol. 62, N. 8 (1975) pp. 3074-3079.

[25] Stout J.W., Boo W.O.J. J. Chem. Phys., Vol. 71, N. 1 (1979) pp. 1-8.

[27] Arara R., Pollard R. J. Electrochem. Soc., Vol. 138, N. 5 (1991) pp. 1523-1537.

vodorodom (Metallurguij, Moskva, 1981) 184 p. (in Russian).

[5] Lakhotkin Yu.V., Protection of Metals, Vol. 44, N. 4 (2008) pp. 319-332.

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(MIFI, Moskva, 1991) pp. 35-47. (in Russian).

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**10. References** 

(in Russian).

(in Russian).

components and the atom intraction on the growing surface during the crystallization. It was established that only an introduction in the thermodynamic calculation of atom interaction on the growing surface, which increase in the following sequence: Ta, W, Re, Nb, V, Mo, results in a rise of yield of VB group metals under their co-deposition with tungsten, excepting W-Ta system. This may explain the experimentally observed tungsten yield rise under its alloying with rhenium and molibdenium.

