RU2492027C1 - Plasmachemical method of producing modified superdispersed powder - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to plasma technology. Proposed method comprises producing superdispersed powder by subjecting the stock to effects of plasma of high-frequency induction discharge of H-shape at voltage at inductor of 100-200 V and temperature in the discharge of 2000-10000°C. Then powder modified at the first step is modified by plasma of high-frequency induction discharge of atmospheric pressure of E-shape at voltage at inductor of 3.0-3.5 kV and temperature in the discharge of 300-1000°C at simultaneous feed of modifying reagent into plasma. At both steps the processes are realised on feeding plasma-forming gas at flow rate of 8-15 m³/h and that of carrier gas of 0.2-1.0 m³/h. Proposed method is realised in a wide temperature range to expand the range of produced powders. Note here that temperature conditions are controlled by adjusting the anode voltage on selecting H- or E-shape of high-frequency induction discharge.

EFFECT: production of modified superdischarge powders in single process cycle.

3 cl, 9 ex, 2 tbl, 13 dwg

Description

The invention relates to plasma technology and can be used to obtain modified ultrafine powders (UDP) in a single technological cycle.

Known methods and devices for producing and modifying various products by plasma methods (US patent No. 6409851 B01J 19/12, 2002; patent RU No. 2252817, B01J 19/08, H05B 6/80, 2003; patent RU No. 2266866, C01B 31/02 , 2004; Dresvin S.V. Low-temperature plasma - Novosibirsk, 1992). Known methods allow modification either by changing the geometric shapes and sizes of the modified products (patent RU No. 2128148, C03B 19/10, 1997), or by surface treatment of the material (JP patent No. 58-12349, H01L 27/08, H01L 29/01, 1983 ; US patent No. 4425210, C23F 1/00, 1984). In the application US No. 20090293675, B22F 9/14, 2009 describes methods for producing nanoparticles, including the supply of atomized droplets in the torch RF discharge.

In messages (US patent No. 6994837, C01G 23/047, B01J 23/00, C01G 25/02, C01G 27/02, 2006; US patent No. 6409851, B01J 19/12, B22F 9/30, B22F 1/00, C01B 31/00, H01J 37/32, 2002; patent RU No. 2311225, B01J 19/00, 2007; IM Ulanov, MV Isupov and A.Yu. Litvinsev. - Experimental study of transformer-coupled toroidal discharge in mercury vapor. J Phys. D .: Appl. Phys. 40 (2007) 4561-4567) describes methods and devices that can be used to synthesize nanoparticles of metals, semiconductors, ceramics, or other classes of materials.

There is also known a method and apparatus for producing nanodispersed powders in microwave discharge plasma (patent RU No. 2252817, B01J 19/08, H05B 6/80, 2003), in which the starting reagents are introduced into the plasma gas stream at a temperature of 1475-3500 ° C in any aggregate state (vaporous, powdery, liquid droplet or in any combination thereof). The reagents in a powder state are then introduced in the form of an aerosol with a carrier gas. The powers of the currently used magnetrons limit the ability to receive a microwave discharge in a wide temperature range. Therefore, discharges of this type are used either to obtain dispersed powders, or to modify them, but they do not allow both processes to be carried out simultaneously.

A known method of plasma processing of dispersed refractory materials and a device for its implementation (patent RU No. 2128148, C03B 19/10, 1997), which includes introducing the material into the high-temperature region of the plasma stream. A device for implementing the method comprises a discharge chamber of a plasma torch, a gas distribution element, and a material feeder. The feeder is installed with the possibility of feeding material into the flow area adjacent to the outer side of the cut of the discharge chamber.

The above methods and devices do not allow the production of modified ultrafine powders in a single technological cycle; additional stages are required: unloading the obtained powders, their packaging, and subsequent loading into the modification unit. The difficulty in carrying out these operations is the need to take into account aggregation processes in which ultrafine powders are involved because of their highly developed surface and reactivity. This problem is relevant for all materials of the new generation, which include, in particular, fullerenes, ultra- and nanopowders, nanotubes, ultrafine diamonds, etc., obtained not only by plasma methods.

The objective of the invention is to obtain modified ultrafine powders in a single technological cycle, expanding the range of the resulting target products.

The technical problem is solved by the plasma-chemical method of obtaining a modified ultrafine powder, characterized in that in a single technological cycle, first exposure to the raw materials with a plasma by a high-frequency induction discharge of atmospheric pressure of H-form at an inductor voltage of 100-200 V and a temperature in the discharge of 2000-10000 ° C produces ultrafine powder, which is then exposed to the plasma of a high-frequency induction discharge of atmospheric pressure of the E-form at an inductor voltage of 3.0-3.5 kV and tempera Ur in the discharge 300-1000 ° C while supplying a plasma in the modifying reagent, wherein both stages are processes when applying the plasma gas at a flow rate of 8-15 ^m3 / h, carrier gas at a flow rate of 0.2-1.0 m ³ / h.

The solution of the technical problem allows to obtain modified ultrafine powders in a single technological cycle, to expand the range of the target products obtained from metal oxides to composite materials with desired properties.

The proposed method is based on the properties of a high-frequency induction discharge (RFI-discharge) to exist in two forms: E and N. For the E-form of the discharge, low plasma temperatures of 300-1000 ° C are characteristic, which allows using the discharge when modifying and processing the surface of bodies of various physical nature (synthetic fibers, capillary-porous materials of animal and vegetable origin, metal coatings). The H-form of an RFI discharge is characterized by high plasma temperatures of 2000-10000 ° C, which makes it possible to use this form of discharge in the preparation of powders of the class r.h. nano and ultrafine sizes.

The invention is illustrated by the following drawings.

Figure 1 shows photographs illustrating the forms of a high-frequency induction discharge: the E-form (a, b) and the H-form (c).

Figure 2 shows the dependence of the voltage at the inductor U _ind from the voltage at the anode of the generator lamp U _anode .

Figure 3 shows a circuit for measuring voltage across an inductor.

Figure 4 shows the spectra of the RFI discharge for the E-form (Mode 1), the H-form (Mode 3) and the transition form (Mode 2) (a) and the H-form of the discharge at P _p = 7.8 kW (b).

Figure 5 is a block diagram of a device for implementing the method.

Figure 6 shows the dispersion of the feedstock.

7 illustrates the dimensions of the obtained dispersed SiO ₂ powder in a modification reactor 4.

Figure 8 shows an electronic photograph of a silicon oxide SiO ₂ powder after modification.

Fig.9 illustrates the dispersion of a powder of silicon oxide SiO ₂ obtained from tetraethoxysilane.

Figure 10 - the dispersion of the powder of TiO ₂ obtained from TBT.

11 - dispersion of the modified powder of TiO ₂ .

12 shows the size distribution of the composition (TiO ₂ ) _x (SiO ₂ ) _1-x .

On Fig shows a photograph of the obtained powder (TiO ₂ ) _x (SiO ₂ ) _1-x after modification in the E-discharge.

On figa shows a characteristic view of the E-form of RFI-discharge: in the region of the extreme turns of the inductor there is a brighter glow, and the discharge itself in shape resembles an hourglass. The voltage at the inductor is 3.0-3.5 kV (figure 2). As the amplitude of high-frequency oscillations increases, the plasma conductivity increases, and the discharge fills the discharge chamber along its entire length (Figs. 1, 6). With a further increase in the voltage on the generator lamp to 5.8-6.3 kV, the conductivity of the load (plasma) with increasing E-field reaches a critical value, the magnetic energy of the inductor begins to be released in the discharge zone, a ring current appears, there is a sharp decrease in the voltage on the inductor of less than 1 kV (Fig. .2), and the discharge goes into the H-form (figv). The circuit for measuring the voltage across the inductor is shown in FIG. 3. The voltage at the inductor was measured with an S-50 kilovoltmeter relative to the grounded midpoint. The power in the discharge P _p and in the plasma jet P _{p was} measured by calorimetry. Plasma temperature was determined by spectral studies of the discharge with a USB4000 fiber-optic spectrometer. Figure 4 shows the full discharge spectra recorded in the UV range for E, H and the transition form of the discharge. An analysis of the results of spectral measurements showed that in the regimes for the E-form of the RFI discharge, the gas temperature was 200-1000 ° C, for the H-form of the RFI discharge - 2000-8000 ° C.

The essence of the claimed method lies in the fact that the receipt of the modified ultrafine powder is carried out in two stages in a single technological cycle. At the first stage, an ultrafine powder is obtained by exposing the feedstock with plasma to a high-frequency induction discharge of atmospheric pressure of the H-form at an inductor voltage of not more than 1.0 kV, a discharge temperature T _p = 2000-8000 ° C, a discharge temperature T _p = 2000- 3000 ° C. At the second stage, the ultrafine powder obtained in the first stage is modified by exposing it to a plasma of a high-frequency induction discharge of atmospheric pressure of the E-form at an inductor voltage of 3.0-3.5 kV, a discharge temperature T _p = 300-1000 ° C, and a temperature in the discharge jet T _str = 200-500 ° C while feeding a modifying reagent into the plasma. In both stages of the processes is conducted at a feed rate of a plasma gas G _at = 8-15 m ³ / hour, a flow rate of carrier gas G _n = 0.2-1.0 m ³ / h. The indicated costs of the plasma-forming and transporting gas (with a total flow rate in the range of 8.2-16 m ³ / h) are associated with the possibility of producing an RF induction discharge. At lower costs, an RF breakdown does not occur and the discharge is not ignited. At high costs, the discharge is "blown away", it is not supported by the electromagnetic field and goes out. The method is carried out in a single cycle, without reloading the ultrafine powder obtained in the first stage, excluding its contact with the external environment.

The proposed method allows the use of raw materials and a modifying reagent (modifier) in any aggregate state, while it is possible to introduce the raw material or modifier into the discharge chamber (plasma clot) or under a plasma torch cut (in a plasma stream), which extends the temperature range of the proposed method (table 1 -2).

Table 1 Options for the place of input of raw materials and modifier No. Getting UDP Modification of UDP Discharge chamber Jet of plasma Discharge chamber Jet of plasma one + + 2 + + 3 + + four + +

table 2 Variants of the aggregate state of raw materials and modifier Getting UDP Modification of UDP powder liquid gas powder liquid gas 5 + + 6 + + 7 + + 8 + + 9 + + 10 + + eleven + + 12 + + 13 + +

A diagram of a device for producing modified ultrafine powders is shown in Fig.5.

The composition of the device and the purpose of the individual nodes:

- High-frequency generator (VCHG) with an RF plasmatron (VChP): for receiving a high-frequency induction discharge of the E - and H-forms.

- Gas-forming device (HFC): for organizing the necessary expenses of the transporting gas (Ar, O ₂ , air) for supplying raw materials and a modifier; for adjusting the flow rate of a plasma-forming gas (Ar, O ₂ , N ₂ , CO ₂ , air, other gases).

- Dosing feeder 1: for supplying raw materials and a modifier to the discharge chamber (RC) of the plasma torch.

- Flange 2: for supplying raw materials and a modifier to the discharge stream. The design of the reactor flange connecting with the RFI plasmatron provides for the introduction of cold gases into the plasma-chemical reactor for quenching or dilution of reaction products during modification.

- Reactor Expander 3: due to a sharp expansion in the reactor, quenching and powder formation occur. From the reactor 3, by controlling the valves 5 and 6 ("open" - "closed"), the powder is supplied to the reactor 4 or to the reactor 5.

- Reactor 4: the resulting powder is collected in the reactor for use in the future for modification.

- Reactor 5: the finished modified product is collected in the reactor.

- Raw material supply device (UPS) and modifier supply device (UPM). The devices provide the supply of raw materials and a modifier in any aggregate state: powder, liquid, gaseous into the discharge chamber and into the plasma stream, depending on the chosen method implementation option (Tables 1, 2).

- Adjustable valves B1-B7. The purpose of the valves: B1 and B2 - adjustment of the flow of raw materials and modifier, respectively, when they are fed into the discharge chamber of the plasma torch; B3 and B4 - adjustment of the flow of raw materials and modifier, respectively, when they are fed into the plasma stream; B5 and B6 - connecting or disconnecting reactors 4 and 5, respectively; B7 - for supplying the obtained powder to UPM.

The method is as follows.

The starting position of all valves is closed. Depending on the mode, the gas-forming device provides the necessary flow rate of the transporting and plasma-forming gas.

In the first stage, an ultrafine powder is obtained.

Turn on the high-frequency generator and set the anode voltage C _anode = 6.0-7.0 kV to ignite the discharge. Establish the required gas flow: plasma _of G = 8-15 m ³ / hour; transporting G _tg = 0.2-1.0 m ³ / hour.

Set the anode voltage U _anode = 6.2-9.5 kV. The voltage at the inductor U _ind = 0.2-0.9 kV. An H-shape RF discharge arises. The plasma temperature in the inductor zone T _p = 2000-8000 ° C, in the jet zone T _p = 2000-3000 ° C.

Open valve B1 for supplying raw materials to the discharge chamber (PK). In case of supply of raw materials under the plasma torch cut (into the discharge stream), valve B3 is opened, while valve B1 is closed.

Open valve B6 to supply the resulting powder to the reactor 4.

When a gas, liquid, or powder substance, hereinafter referred to as the “material”, is introduced into the plasma (into the inductor zone or into the plasma jet), the following processes occur:

- heating the material to T _melting ;

- melting of the material at T _melting ;

- heating to an evaporation temperature T of _evaporation ;

- heating and dissociation of vapor dispersed material.

When material enters the “expander-cooler” reactor (item 3), the material vapor cools and condenses. The resulting ultrafine powder is collected in a reactor 4.

In the second stage, the obtained powder is modified. Without stopping the generation of plasma, reduce the anode voltage to U _anode = 4.0-5.8 kV, the voltage on the inductor with U _ind = 3.0-3.5 kV. An E-shape discharge occurs. The temperature in the discharge bunch is T _p = 300-1000 ° C. The temperature at the cutoff of the plasma torch T _p = 200-500 ° C. Then establish the required gas flow: plasma _of G = 8-15 m ³ / hour; transporting G _tg = 0.2-1.0 m ³ / hour.

Close valve B6 and open valve B5. When using the obtained powder for modification or as a modifying reagent, valve B7 is opened - the powder obtained in the first stage is fed from the reactor 4 to the modifier supply device (UPM). To supply raw materials and a modifying reagent to the RK, valves B1 and B2 are opened, respectively. In the discharge chamber of the plasma torch (in a plasma clot), the obtained powder is modified.

To modify the powder in a plasma jet:

open valves B1 and B4 in case of supply of raw materials to the Republic of Kazakhstan, and the modifier in the plasma stream or

open valves B3 and B4 in the case of supply of raw materials and a modifier to the plasma stream or

open valves B3 and B2 in the case of supplying raw materials to the plasma jet, and the modifier in the Republic of Kazakhstan.

When using liquid or gaseous raw materials, the raw materials are supplied from a raw material supply device (UPS). When using a liquid or gaseous modifier, the modifier is supplied from a modifier feed device (UPM). Valve B6 is closed. The collection of the modified ultrafine powder comes from reactor 5.

The invention is illustrated by the following examples of specific performance.

Example 1. Obtaining an ultrafine silica powder modified with nanosized silica (the raw materials and modifier are powders, are supplied to the Republic of Kazakhstan, see table 1, clause 3 and table 2, clause 5). As raw materials used ultrafine powder SiO ₂ plant quartz products Gus-Khrustalny (Vladimirovsk region). Determination of the dispersion of the powders was carried out on a laser analyzer ANALYSETTE-22 (Fig.6). The main mass fraction of fractions of the feedstock is 250-500 microns (82.88%).

Process parameters: U _anode = 8.5 kV, U _ind = 0.4 kV (H-discharge). The flow rate of the plasma gas of air G _by = 10 m ³ / hour. The flow rate of the argon transporting gas G _tg = 0.15 m ³ / hour. The consumption of raw materials G _c - 6 kg / hour. The feed was carried out in the discharge chamber of the plasma torch. In the reactor 4 (FIG. 5), the dispersed SiO ₂ powder is collected. The dispersion of the obtained powder was determined on a Veeco MultiMode V scanning probe microscope (Fig. 7). The obtained powder was used as a modifier of the initial powder.

Powder modification: supply of a modifier to the discharge chamber from reactor 4 (valves B6 are closed, B5 and B7 are open). Supply of the initial powder to the discharge chamber. Voltages: U _anode = 5.5 kV, U _ind = 3.4 kV (E-discharge). The consumption of plasma-forming gas G _by = 10 m ³ / hour. The flow rate of the transporting gas G _tg = 0.15 m ³ / hour. Raw material consumption G _c = 6 kg / h. Modifier Consumption G _modif = 90 g / hour. In the plasma zone, the initial powder interacted with a finer modifier powder. Due to the developed surface of the obtained modifier (particle size ~ 250-350 nm), larger particles are enveloped by small ones. A core of SiO _{2 is formed} with a shell of SiO ₂ nanopowders with more active surface properties (Fig. 8).

Example 2 (the raw materials and the modifier are powders, the raw materials are fed into the plasma jet, the modifier is in the Republic of Kazakhstan, see table 1, paragraph 1 and table 2, paragraph 5). Obtaining a dispersed powder is analogous to example 1, but the feed is fed into the plasma stream (valve B1 - closed, valve B3 - open). Process parameters: U _anode = 9.5 kV, U _ind = 0.35 kV (H-discharge). Other parameters of Example 1. The modification process is similar to Example 1. The result is a modified nanodispersed powder SiO ₂ SiO ₂ soot.

Example 3 (raw materials and modifier - powders, are fed into the plasma jet, see table 1 p. 4 and table 2 p. 5). The process is similar to example 2, but the modifier ultrafine powder SiO ₂ is fed into the plasma stream (valves B2 - closed, B4 - open). In the E-discharge voltage U _anode = 5.8 kV, U _ind = 0.38 kV. Modification process is similar to Example 1. The result is a modified nanodispersed powder SiO ₂ SiO ₂ soot.

Example 4 (raw materials and modifier - powders, see table 1 p. 2 and table 2 p. 5). Obtaining ultrafine powder is similar to example 1, and the modifier is fed into the plasma stream (B2 - closed, B4 - open). Process parameters: U _anode = 9.5 kV, U _ind = 0.35 kV (H-discharge). The remaining parameters in example 1. The modification process is similar to example 3. The result is an ultrafine SiO ₂ powder modified with nanosized SiO ₂ powder.

Example 5 (raw materials - liquid, modifier - powder, raw materials and modifier served in the Republic of Kazakhstan, see table 1 p. 3 and table 2 p. 8). As raw materials, tetraethoxysilane C ₈ H ₂₀ O ₄ Si (TEOS, TU 6-09-11-2153-94) is used, which is fed from a modifier supply device to the discharge chamber of the plasma torch. The consumption of TEOS G _teos = 0.1 l / h. The flow rate of the carrier gas Ar G _tg = 0.15 m ³ / h. The remaining modes are similar to example 1. During processing in plasma, tetraethoxysilane droplets evaporate. Homogeneous reactions occur in the gas phase and, when the gases formed as a result of the reaction are cooled, particles of SiO ₂ powder are formed. The resulting powder is sent to the plasma torch. Due to the higher specific surface area and chemical activity of the obtained modifier powder, the larger SiO ₂ powder obtained from tetraethoxysilane is mixed and enveloped to give new properties to the newly formed compound.

Example 6 (raw material - liquid is supplied to the Republic of Kazakhstan, the modifier - powder is fed into the discharge stream, see table 1 p. 2 and table 2 p. 8). The experiment is similar to example 5, but the modifying reagent is fed into the discharge stream.

Example 7. Obtaining a modified powder of SiO ₂ (raw material - liquid, modifier - powder, raw material and modifier are fed into the discharge stream). The feedstock tetraethoxysilane (TEOS) C ₈ H ₂₀ O ₄ Si (TU 6-09-11-2153-94). Supply from UPS to discharge stream. Process parameters: U _anode = 6.5 kV, U _ind = 0.8 kV (H-discharge). The flow rate of the plasma gas of air G _by = 8 m ³ / hour. The flow rate of argon transporting gas G _tg = 0.2 m ³ / h, the flow rate of raw materials G _c = 0.2 l / h. In plasma, TEOS decomposes under the influence of high plasma temperature into the gas phase and, when cooled in reactor 3 (Fig. 5), SiO ₂ powder is formed with the dispersion distribution shown in Fig. 9. The dispersion of the obtained powders was determined using a Veeco MultiMode V scanning probe microscope. The modification of the obtained powder (in the E-discharge) was carried out by feeding the obtained SiO ₂ powder from reactor 7 into the discharge jet as a modifying reagent.

Example 8. Obtaining a modified ultrafine titanium dioxide powder (raw material - liquid is supplied into the plasma jet, modifier - gas is supplied to the SC, see table 1, paragraph 1 and table 2, paragraph 10). The feedstock is tetrabutoxytitanium (TBT) C ₁₆ H ₃₆ O ₄ Ti (TU 6-09-2738-89). The supply of raw materials in the discharge stream (T _p = 2000 ° C). U _anode = 6.5 kV, U _ind = 0.8 kV, TBT flow rate G _TBT = 100 ml / min. The flow rate of the transporting gas G _Ar = 0.3 m ³ / h The consumption of plasma-forming oxygen gas G _O2 = 10 m ³ / h. As a result of the interaction of the feedstock with the plasma, the formation of amorphous particles of titanium dioxide TiO ₂ (Fig. 10). Studies of the obtained powder were carried out on a Malvern instrument. For modification, the obtained TiO ₂ powder from reactor 4 is fed into the discharge chamber of the plasma torch, where a mixture of gases Ar (20%) + O ₂ (80%) with a total flow rate of 0.8 m ³ / h (T _p = 500 ° C, U _anode = 5.0 kV, U _ind = 3.3 kV - E-discharge). X-ray diffraction patterns of the obtained modified TiO ₂ powder showed that upon modification a crystal structure of the particles is formed and a noticeable amount of a rutile (TiO ₆ ) type lattice is observed. The dispersion of the modified TiO ₂ powder is shown in FIG. 11.

Example 9. Obtaining a modified powder (TiO ₂ ) _x (SiO ₂ ) _1-x (raw material - liquid is supplied to the Republic of Kazakhstan, modifier - gas is fed into the discharge stream, see table 1, clause 2 and table 2, clause 10) . Raw materials - a mixture of tetrabutoxy titanium C ₁₆ H ₃₆ O ₄ Ti and tetraethoxysilane C ₈ H ₂₀ O ₄ Si in a 1: 4 ratio is fed from the OPS to the discharge chamber (T _p = 2200 ° C, U _anode = 6.5 kV, U _ind = 0.8 kV , mixture flow rate G _mixture = 80 ml / min, flow rate of argon transport gas G _Ar = 0.3 m ³ / h, plasma oxygen gas flow rate G _O2 = 12 m ³ / h (H-discharge). The obtained powder was modified in an E-discharge gas mixture: U _anode = 5.0 kV, U _ind = 3.3 kV with a total flow rate of 0.4 m ³ / h of transporting gas Ar: O ₂ - 1: 4 and a plasma-forming oxygen gas flow rate G _O2 = 11 m ³ / h. The resulting powder (TiO ₂ ) _x (SiO ₂ ) _1-x and a mixture of gas Ar: O ₂ For modification, they are fed into the discharge jet. Investigations of the IR spectra showed an increase in adsorption peaks corresponding to Si-O-Si and Ti-O-Ti bonds. This indicates the formation of separate phases of titanium dioxide and silicon dioxide. Size distribution of the composition (TiO ₂ ) _x (SiO ₂ ) _{1-x is} shown in Fig. 12. The appearance of the obtained composite powder from the reactor 6 is shown in Fig. 13.

Thus, the proposed method allows to obtain modified ultrafine powders in a single technological cycle using the properties of H- and E-forms of high-frequency induction discharge. The method is carried out in a wide temperature range, which allows to expand the range of powders obtained. In this case, the temperature regime is actually controlled by adjusting the anode voltage when choosing the H- and E-forms of a high-frequency induction discharge.

Claims (3)

1. Plasma-chemical method for producing a modified ultrafine powder, characterized in that in a single technological cycle, ultrafine powder is first obtained by exposing the raw materials to the plasma to be introduced by a high-frequency induction discharge of atmospheric pressure of H-form at a voltage across the inductor of 100-200 V and a temperature in the discharge of 2000-10000 ° C, and then the resulting powder is exposed to the plasma of a high-frequency induction discharge of atmospheric pressure of the E-form at an inductor voltage of 3.0-3.5 kV and a temperature in p zryade 300-1000 ° C while supplying a plasma in the modifying reagent, wherein both stages plasma gas is fed at a rate of 8-15 m ³ / h and a carrier gas - at a rate of 0.2-1.0 m ³ / h. 2. The plasma-chemical method for producing the modified ultrafine powder according to claim 1, characterized in that the feedstock and the modifying reagent are introduced into the plasma under the plasma torch cut-off or into the discharge chamber of the plasma torch. 3. The plasma-chemical method for producing the modified ultrafine powder according to claim 1 or 2, characterized in that the raw material and the modifying reagent are supplied in powder, liquid or gaseous state.

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