Scientific Papers

R.B. Baksht, S.P. Vavilov, A.P. Kudinov, E.A. Litvinov, V.I. Manilov, M.N. Urbathaev, “Investigation of Cathode Flare Plasma caused by Vacuum Breakdown,” Proc. 5th Intern. Symp. Discharge and Electr. Insul. in Vacuum, Poznan, Poland, pp. 139-144 (1972).

G.P. Bazhenov, S.P. Bougaev, S.M. Chesnokov, O.B. Ladyzhenski, E.A. Litvinov, “Formation of Explosive Emission Current Flashes,” Proc. 13th Intern. Symp. Discharge and Electr. Insul. in Vacuum, Sandia Laboratories, Albuquerque, New Mexico, USA, pp. B4-1-B4-7 (1978).

E.A. Litvinov, G.A. Mesyats and D.I. Proskurovsky, “Field emission and explosive electron-emission processes in vacuum discharges,” Sov. Phys. Usp. 26(2) American institute of Physics. pp. 138-159 (1983).

E.A. Litvinov, “Theory of Explosive Electron Emission,” IEEE Transactions on Electrical Insulation Vol. EI-20 No. 4, pp. 683-689 (Aug. 1985).

E.A. Litvinov, A.G. Parfyonov, and D.L. Shmelev, “Nonstationary Model of the Cathode and near-Cathode Processes in a Vacuum Arc,” Proc. XVth Intern. Symp. Discharge and Electr.Insul.in Vacuum, Germany, Darmstadt, pp. 326-330 (1992).

V.N. Gavrilov, E.A. Litvinov, G.A. Mesyats, and D.L. Shmelev, “2-D MHD Model of the Plasma Jet Originating from a Vacuum-Arc Cathode Spit,” Proc. XVIth Intern. Symp. Discharge and Electr. Insul. in Vacuum, Moscow-St.-Petersburg, Russia, (SPIE, v. 2259), pp. 114-117 (1994).

D.L. Shmelev, E.A. Litvinov, “The Computer Simulation of the Vacuum Arc Emission Center.” pp. 783-787. (to be published in IEEE Trans. on Plasma Science) (1996).

A.V. Batrakov, L.M. Baskin, S.A. Popov, and D.I. Proskurovsky, “Electrohydrodynamic Phenomena on Explosive-emission Liquid-metal Cathode.” Proc. 16th Intern. Symp. Discharge and Electr. Insul. in Vacuum, Moscow-St.-Petersburg, Russia, (SPIE, v. 2259), pp. 2-5 (1994).

A.V. Batrakov, L.M. Baskin, S.A. Popov, and D.I. Proskurovsky. “Electrohydrodynamic Phenomenon Explosive-emission Liquid-metal Cathode,” IEEE Trans. on Dielectrics and Electr. Insul., vol. 2, No. 2, pp. 231-236 (1995).

A.V. Batrakov, C.A. Popov, and D.I. Proskurovsky, “Investigation into the erosion of explosive-emission liquid-metal cathodes,” Proc. 17th Intern. Symp. Discharge and Electr. Insul. in Vacuum, v. 2, Berkeley, California, (IEEE), pp. 752-756 (to be published in IEEE Trans. on Plasma Science) (1996).

A.V. Batrakov, C.A. Popov and D.I. Proskurovsky, “Sources of pulsed low-energy electron beams and soft X-rays based on liquid-metal explosive-emission cathodes,” Proc. 17th Intern. Symp. Discharge and Electr. Insul. in Vacuum, v. 2, Berkeley, California, (IEEE), pp. 579-583. (to be published in IEEE Trans. on Plasma Science) (1996).

Foreign Collaborators

Prof. Burkhard G. Juttner, Max-Planck-Inst. fur Plasmaphisik, Germany

№-0134 The Arc Method for Producing Powders

Full Title:	The Arc Method for Producing Powders
Technology Field(s):	MAT-SYN: Materials / Materials Synthesis and Processing

Contributors

Gennady A Mesyats

Institute of Electrophysics (Inst of Electrophysics) 34, Komsomol'skaya, GSP-387, Ekaterinburg, Sverdlovsk reg., 620219, Russia Phone: 7+3432+740223; 7+3432+745953 Fax: 7+3432+745051 mesyats@ief.intec.ru

Present Status of Research

Brief Description of Research

Nanosized particles are intermediate species between atoms and molecules constituting a matter, and are in a solid where the atoms and the molecules form more or less strong structures. In a peculiar kind of structure that is "not molecule and yet not a solid", these nanoparticles, when mixed, show unusual properties. For instance, metal may transform into semiconductors or optical materials. It seems that a great variety of possibilities might be realized with nanoparticles produced from various nonmetallic or inorganic materials and mixed with other materials to give nanocompositions. One of the long-utilized technical materials is ceramics. Ceramics produced by adding nanoparticles could made it possible to solve a great deal of problems since nanoparticles make the original material much more bulky and have much more precisely predictable properties. The raw materials for these novel technologies are nanosized powders. These powders can be produced by a variety of methods for various uses. The well-known evaporation-and-condensation method allows production of powders with an average particle size of 10 to 20 nm, but it is unsuitable for the production of powders of materials with high melting-points. The powders produced by the method of electrical explosion of conductors have an average particle size of 10 to 20 nm. However, the particle size distribution is very broad (the maximum particle size may reach 100 m) and, therefore, separation should be performed. The arc discharge method allows production of metal and metal oxide powders with an average particle size of 0.5 m to 200 nm, respectively.

The method we propose offers a number of advantages over other methods. With the arc discharge pulse duration decreased to a few hundredths of nanoseconds, and with repetitive power supply of the arc discharge, it is possible to produce metal and metal oxide powders with an average particle size of about 10 nm - with the maximum particle size at about 10 m. X-ray diffraction analysis of coarse particles has shown that they consist of nanosized blocks and, therefore, can be used immediately as a raw staff for compacting nanosized ceramics. One more important advantage of the arc method for producing powders is that the cathode material may be compounded (i.e. consisting of a mixture of any materials in their desired proportions, not necessarily alloys) and, in the powders, admixtures form that are necessary to stabilize the crystalline structure of the powder and the ceramics. The arc method also imparts other important physical properties that may diffuse more easily. The discharge chamber allows production of metal powders in vacuum or in an inert gas medium. To produce metal oxides, air or oxygen can be fed into the chamber. Metal nitrides are produced in an environment of nitrogen.

Legal Aspects

The method for production of ultrafine powders with short-pulsed arc discharges has not yet patented, but the documents required to apply for a patent are being prepared.

Special Facilities

At the Institute of Electrophysics (RAS, Ekaterinburg), a unique high-voltage pulse generator has been developed with the following specifications:

- pulse duration 30 ns - peak voltage up to 200 kV - current up to 1 kA - frequency up to 1 kHz.

Scientific Papers

G.A. Mesyats, D.I. Proskurovsky. Pulsed Electrical Discharge in Vacuum. Springer, Berlin- Heidelberg, 1989.

Y.A. Kotov, I.V. Beketov, A.M. Murzakaev, O.M. Samatov, R. Boehme, G. Schumacher. “Characteristics of ZrO nanopowders produced by electrical explosion of wires,” J.Aerosol Science, vol. 26, supplement 1, pp. 905-906 (Sept. 1995).

Y.A. Kotov, I.V. Beketov, A.M. Murzakaev, V.P. Volkov, O.M. Samatov, R. Boehme, G. Schumacher. “Synthesis of nanometersized powders of aluminia and titania using the electrical explosion of wires,” Ceramic. Science, Haly, Riccione, (Oct. 1995).

Y.A. Kotov, I.V. Beketov, A.M. Murzakaev, O.M. Samatov, R. Bothme, G. Schumacher. “Synthesis of AlO, TiO, ZrO nanopowders by electrical explosion of wires,” Material Science Forum Vols. 225-227, pp. 913-916 (1996).

№ -0135 Plasma Source Intended for Vacuum Arc Deposition of Coatings

Full Title:	Plasma Source Intended for Vacuum Arc Deposition of Coatings
Technology Field(s):	MAT-SYN: Materials / Materials Synthesis and Processing PHY-PLS: Physics / Plasma Physics

Contributors

Gennady A Mesyats

Institute of Electrophysics (Inst of Electrophysics) 34, Komsomol'skaya, GSP-387, Ekaterinburg, Sverdlovsk reg., 620219, Russia Phone: 7+3432+740223; 7+3432+745953 Fax: 7+3432+745051 mesyats@ief.intec.ru

Present Status of Research

Brief Description of Research

Arc discharges are used for deposition of metal films and coatings of metal oxide and nitride, as well as plasma sources in ion implantation facilities. The coating deposition process, combined with ion implantation, yields a more homogeneous film and stronger adhesion between the film and the substrate. The ionization degree in an arc is close to 100 percent, and multiply charged ions are present in large amounts in the arc plasma. This makes it possible to produce a high-energy beam at a comparatively low accelerating voltage.

The chief disadvantage of the arc plasma is that metal particles, sized a few micrometers or less, are present in the plasma. These particles, when adhering to the substrate, reduce the density of the coating and make it less homogeneous. The most commonly used technique for filtering off particles is to deflect the arc plasma by 90 degrees using a curved channel with a magnetic field created along the axis of the channel. Filters like this make the plasma source more complicated in design, increase its cost and give rise to plasma losses at the channel walls.

In studying the vacuum arc discharge, it has been revealed that particles are formed as the metal is splashed from the liquid pool produced by the cathode spot. The number of particles is small for an arc operating for a short period because the liquid pool appears to have no time to form. It has been proposed to develop a source for powering the discharge, and to carry out investigations of the vacuum-arc plasma source with the arc powered by a sequence of short (some tenths or hundredths of nanoseconds) current pulses. Should the project prove advantageous, a simple and low-cost source for deposition of coatings and ion implantation can be created. This will obviate the necessity to use filters where more than 90 percent of the plasma is lost, increasing the cost of the plasma sources intended for vacuum arc deposition of coatings.

Legal Aspects None.

Special Facilities None.