JP6543753B2 - Method of densifying and spheroidizing solution precursor droplets of solid materials and materials using plasma - Google Patents

Description

  The present invention is generally directed to methods of obtaining and processing feedstocks to produce high density spherical products. The feed material consists of powder particles, or solution precursor droplets from spray drying technology, which comprises a ceramic or metal material. More particularly, the present invention is directed to a method of using a microwave plasma torch capable of creating a laminar flow pattern while processing material to produce a high density spherical product. Laminar flow in the axisymmetric hot zone of uniform temperature profile in the torch enables the generation of uniform spherical particles by homogeneous material distribution, whereby the final product has excellent characteristics.

  One of the most important aspects when making industrial powders is the spheronization process. The spheronization process transforms the powder produced by spray drying and sintering techniques or the angular powder produced by conventional grinding methods into spheres. Spherical particles are more homogeneous in shape, more dense, have fewer holes, provide more flowability, and have less friability. These features make the powder excellent for applications such as injection molding, thermal spraying of coatings, and also result in parts having near net shape.

  The current spheroidizing method includes the method using thermal arc plasma described in US Pat. No. 4,076,640 issued Feb. 28, 1978, and the radio described in US Pat. No. 6,919, 527 issued Jul. 19, 2005. There is a method of using frequency generated plasma. However, these two methods have limitations due to radio frequency plasma features and thermal arc plasma features.

  In the case of a thermal arc plasma, an electric arc is generated between the two electrodes, which is then blown away from the plasma channel using a plasma gas. The powder is then sprayed from the side vertically into the plasma plume or at an angle. The powder is exposed to high temperature plasma in the plasma plume and collected as spheres in the filter during subsequent processing. A problem with thermal arc plasmas is that the high temperature of the electrode causes the electrode to erode, which causes contamination of the plasma plume by the electrode material, which results in contamination of the powder to be treated. Furthermore, the temperature gradients in the thermal arc plasma plume are essentially non-uniform. Thus, spraying the powder from the side into the plasma plume exposes the powder to a non-uniform temperature gradient, which results in particles of non-uniform size, density or porosity.

  In the case of radio frequency plasma spheroidisation, the plasma is generated in the dielectric cylinder by induction at ambient pressure. Radio frequency plasma is known to have low coupling efficiency of radio frequency energy into the plasma, and lower plasma temperatures as compared to arc and microwave generated plasmas. The magnetic field that plays a role in generating the plasma in the radio frequency plasma is a non-uniform profile, which causes a non-uniform temperature gradient, thus making the heat treatment of the particles non-homogeneous. This causes inhomogeneities in the size, microstructure and density or porosity of the final product.

  Therefore, there is a need to provide a homogeneous and uniform high temperature thermal path for all feeds to be processed, such as high purity, contamination free, homogeneous spherical particles. However, no such method has been reported.

  Thus, it can be seen from the above that there is a need in the art to overcome the drawbacks and limitations described and described herein.

U.S. Pat. No. 4,076,640 U.S. Pat. No. 6,919,527 US Patent Application Publication No. 2008/0173641 International Publication No. 2014/052833

  Prior art by using a microwave-generated plasma torch device capable of producing laminar flow patterns to spheroidize and densify geometrically non-uniform powder particles and solution precursor droplets of ceramic materials The disadvantages of are overcome and provide further advantages.

  According to one embodiment of the present invention, a pressurized powder feeder is used to axially inject powder particles into the plasma chamber. The powder particles are entrained in a laminar gas flow pattern in the plasma chamber and subjected to uniform heat treatment by being exposed to a uniform temperature profile in the microwave generated plasma. The result is spherical pearl-like particles with uniform density.

  According to another embodiment of the present invention, a droplet preparation or atomization device is used to eject solution precursor droplets. Solution precursor droplets are entrained in a laminar gas flow pattern and heat treated uniformly by exposure to a uniform temperature profile in a microwave-generated plasma, whereby spherical pearl-like particles having a uniform density are formed It is generated.

  Another feature of the present invention is the use of a microwave generated plasma according to U.S. patent application Ser.

  Thus, the object of the present invention is the effect of turbulence on the feed material to be treated by the microwave-generated plasma so as to be dense spherical particles of uniform size and shape and characterized by homogeneous material distribution. There is no laminar flow environment.

  Another object of the invention is to improve the plasma treatment of the material to provide the product with improved thermal properties, improved corrosion wear resistance and higher resistance to interfacial stress.

  Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the present invention are considered as part of the present invention as described and claimed in detail herein.

  The recitations herein set forth desired objectives met by the various embodiments of the present invention, any or all of these objectives, in the most general embodiments of the present invention, or more specific implementations thereof It does not imply or imply that it is present as an essential feature, either individually or collectively, in any of its forms.

  The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. However, the present invention, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

A microwave generating source as described in US Patent Application Publication No. 2008/0173641 A1, a dielectric plasma torch as described in US Patent Application No. 13445947, and a powder feeder or solution for dispensing powder particles according to the present invention FIG. 6 illustrates a preferred embodiment of an apparatus used to make high density spherical particles using a material feeder such as a solution precursor reservoir to dispense drops. It is a diagram of a dense spherical MgO-Y ₂ O ₃ particles obtained by spray drying the powder is microwave plasma processing after being injected. It is a diagram of a dense spherical MgO-Y ₂ O ₃ particles obtained by spray drying the powder is microwave plasma processing after being injected. FIG. 6 is a diagram of a method of atomizing droplets using a spray device. FIG. 7 is a diagram of a 20 to 38 micrometer diameter dense, spheroidized 7% by weight Y ₂ O ₃ -ZrO ₂ (7YSZ) ceramic particle after ejection of 7YSZ precursor droplets by use of an atomizing injector. . FIG. 10 is a diagram of dense, spheroidized 7YSZ ceramic particles 38 to 53 micrometers in diameter after ejection of 7YSZ precursor droplets by use of an atomizing injector. FIG. 10 is a diagram of a high density spheroidized 8YSZ ceramic particle of 15 to 35 micrometers in diameter after jetting of 9YSZ precursor droplets using a droplet preparation apparatus. FIG. 8 is an illustration of an alternative embodiment that includes an additional treated plasma gas that controls the velocity and residence time of the feed in the plasma zone. FIG. 7 is an illustration of an alternative embodiment that includes the addition of a passivated feed in the form of a gas or mist through the central or middle tube of the plasma torch. FIG. 7 is an illustration of an alternative embodiment that includes the addition of one or more inlets to introduce the passivating feed to coat the spherical product particles after the plasma zone. FIG. 10 is a diagram of a 10 to 50 micrometer diameter dense spheroidized mixed ceramic particle of alumina-titania and cobalt oxide after spraying of the correspondingly mixed spray-dried powder. FIG. 10 is a diagram of a 10 to 50 micrometer diameter dense spheroidized mixed ceramic particle of alumina-titania and cobalt oxide after spraying of the correspondingly mixed spray-dried powder. FIG. 1 is a diagram of a method of spheroidizing by injection of solid powder using a powder feeder. FIG. 2 is a diagram of a method of spheroidizing by spraying a mist of droplets using a spray nozzle. FIG. 7 is a diagram of a method of spheroidization by continuous flow uniform droplet injection using a frequency driven droplet preparation device.

Referring to FIG. 1, a method for producing a high density spherical product comprising a microwave radiation generator 1, a plasma chamber 2, a dielectric sheath plasma torch 3 and a powder feeder or solution precursor injector 4 The device is illustrated. The microwave radiation generating device 1 described in US Patent Application Publication No. 2008/0173641 A1 is combined with 2 and 3. The plasma chamber 2 and the dielectric sheath plasma torch 3 are both described in US patent application Ser. The particle feeder 4 is an injection device including a pressure source 5 and can supply solid powder particles 6 to the dielectric plasma torch 3. When a powder jet is used, the particles 6 may be products by spray drying techniques or other techniques. Alternatively, the particles 6 may be droplets of a solution precursor which is jetted using a sprayer or a droplet preparation device actuated by a high frequency electrical device. Pressurization sources 7 and 8 are used to introduce process gas into 3 as an input that entrains and accelerates particles 6 towards the plasma 14 along the axis 11. First, the particles 6 are accelerated by entrainment using the central laminar gas flow 10 created in the annular gap 9. The cooling laminar flow 13 created in the annular gap 12 flows at 100 standard cubic feet per hour or more per solid powder supply or in the form of a spray to provide a laminar sheath on the inner wall of the dielectric torch 3 and the inner wall from the plasma 14 Not to melt by heat radiation of High flow rates are also necessary to prevent the particles 6 from reaching the inner wall of the dielectric torch 3 where plasma attachment may occur. A relatively slow gas flow is required when using a droplet production injector since the particle flow is more uniform and flows closer to the axis 11. The particles 6 are directed by the laminar flow 10 and 13 towards the microwave plasma 14 where they are heat treated homogeneously into dense spherical product particles 15. Dense spheronization of spray dried ceramic solid particles 6 or droplets of solution precursor material can maintain appropriate experimental parameters that can maintain a stable microwave generated plasma 14 to produce dense spherical particles 15 Achieved by selecting. These parameters include: 1 microwave power, jet flow rate of powder particles or solution precursor droplets along axis 11, carrier flow rate of laminar entrained flow 10, laminar cooling flow 13 in dielectric sheath torch 3, plasma A heating rate within 15 and a cooling rate of 10 ³ ° C./sec or more when leaving the plasma 15.

Referring to FIG. 2, the method is obtained by spray-drying techniques from INFRAMAT Corporation, commercial magnesia - applies to spherical particles 6 made from yttria _(MgO-Y 2 _{O 3)} solid powder particles. In the case of INFRAMAT powder, the particles 6 have a closed or hemispherical morphology, are low density, porous and fragile particles. A powder feeder 4 comprising a reservoir comprising a low pressure gas stream (<20 PSI) from a pressurized source 5 provides a fluidized bed for particles 6. The particles 6 are moved by the gas flow towards the inlet of the plasma torch 3 through the powder feeder 4. The particles 6 are initially at a diameter ranging from 38 micrometers (μm) to 73 μm. Removal of small particles (particles less than 37 μm in diameter) prior to injection reduces any material recirculation above the hot zone. Also, the removal of large particles (greater than 75 μm) reduces the diameter range of the collected particle product. A sieve of mesh size 400 (38 μm) and 200 (74 μm) is used to carry out this classification operation. The particles 6 are then entrained and accelerated along the axis 11 by the laminar gas flow 10 towards the microwave plasma 14 a minimum distance of 2 (2) inches. The laminar flow 10 is important to make the flow path of the particles 6 into a cylindrical area as close as possible to the axis 11. Penetration into plasma 14 is achieved such that the directional path of particles 6 is at the center of plasma 14 along axis 11. The particles 6 are in part again accelerated by the second laminar gas flow 13 a minimum distance of 3⁄4 inch before reaching the top of the plasma flame 14. The main function of the laminar flow 13 is to ensure sufficient cooling of the dielectric tube sheath 3 containing the plasma. The laminar flow 13 needs to be high enough to travel over the remainder of the length of the outer tube of the dielectric plasma torch 3. The processing means combining the axisymmetric laminar gas flows 10 and 13 together with the uniform temperature profile of the plasma 14 volumetrically heat-treat the particles 6 so as to obtain the dense spherical product 15 shown in FIG. 2a. Make sure to be done. The two large graduations of the ruler in FIG. 2b correspond to 100 micrometers and indicate that the diameter of the particles 15 falls in the range of 15 micrometers to 50 micrometers. The high density spherical particles 6 exhibit "pearl" like texture and morphology.

  Referring to FIG. 3, particles 6 are produced using a spray device 16 for solution precursor injection. The spray device 16 consists of two concentric quartz tubes 17 and 18 fused together. The 7YSZ solution precursor in a stainless steel pressure tank or one containing yttrium in any other weight concentration ranging from 3% to 20% is introduced into the inlet 19 of the tube 17. The jet flow rate of the solution precursor is on the order of 4 milliliters per minute, and the gas tank pressure is about 20 pounds per square inch (PSI). The length of the tube 18 is more than 2 inches and not more than 1 foot. Via the input pipe 20, the pressurized gas source 21 pushes the atomizing gas stream 22 into the annular gap between the concentric pipe 18 and the pipe 17 in the spray device 16. The jetted solution precursor exits orifice 23 where it is atomized by gas stream 22 and exits orifice 24 of tube 18 as an aerosol of droplet particles 6. The distance between the orifices 23 and 24 should not exceed 1 millimeter (mm). The end of the tube 18 is tapered so that the gas stream 22 enters the jet of solution precursor at an angle close to 90 degrees. After exiting, the particles 6 are also entrained by the laminar flow 10 in the dielectric plasma torch 3, as also seen in FIG. 1, and then reach the axisymmetric heat treatment means in the dielectric plasma torch 3, the plasma It is heated volumetrically in 14.

  Referring to FIGS. 4 and 5, dense, spheroidized 7YSZ product particles 15 from atomization of the 7YSZ solution precursor using the spray device 16 are illustrated. The particles 15 exhibit a "pearl" -like texture and morphology. The particles 15 are shown in FIG. 4 (20 to 38 μm) and FIG. 5 (38 to 53 μm) after classification performed by sieves having mesh sizes of 635 (20 μm), 400 (38 μm) and 270 (53 μm) respectively. As shown, measurements result in diameters ranging from about 20 micrometers (μm) to 53 micrometers (μm).

  In still other embodiments, a feeder different from the spray device may be used to generate the atomized precursor droplets. In this case, a piezoelectrically driven drop making device is used, which produces a stream jet of uniform drops of 8 wt% YSZ, which is then subjected to the plasma hot zone of the microwave plasma device described above in FIG. It is injected inside. This droplet production device is described in WO2014052833A1. Referring to FIG. 6, spherical high density 8YSZ product particles in the size range of 15 to 35 micrometers are produced as measured using an optical microscope. FIG. 6 contains a 50 micrometer scale. These spheres are pearly, indicating that the spherical high density particles have a smooth surface that enhances flow.

  In yet another embodiment, a carrier gas is added to the central feed tube to entrain the powder particulate matter into the plasma and to control the velocity of the powder particulate matter and the residence time in the plasma. The entrained gas may be selected to be compatible with the purpose of processing the powder particulate matter. For example, if it is necessary to ensure that the material to be treated is not oxidized or reduced, an inert gas such as argon may be selected. If the material to be spheroidized is to be oxidized, oxygen gas is used, and if it is to be reduced, hydrogen or ammonia may be used.

  Referring to FIG. 7, the pressurization source 25 is used to introduce additional entrained gas into a tube inlet 26 in communication with the outlet nozzle 27 of the powder feeder 4 containing the feed particles 6. The feed particles 6 are accelerated in the central tube 28 in the plasma torch 3. The flow rate of the injected gas 25 is determined according to the size and morphology of the injected particle powder so as to optimize the melting state of these particles in the plasma zone. The additional gas 25 can be injected so as to be in line with the flow direction of the feed particles 6 by explicitly changing the communication between the inlet 26 and the powder feeder outlet nozzle 27 and the central tube 28 of the plasma torch 3. Are known to those skilled in the art.

  In still other embodiments, a fluid that induces passivation is added to the process to passivate and / or coat the spherical powder. The passivating fluid may be either a gaseous solution or an atomized solution. Referring to FIG. 8, the pressurization source 25 is used to introduce the passivating fluid 29 in gas phase form into the injection pipe 26 in communication with the outlet nozzle feeder 27 of the powder feeder 4 containing the supply particles 6. . Referring again to FIG. 8, the passivating material 29 is introduced into the inlet pipe 26 in communication with the outlet nozzle feeder 27 of the powder feeder 4 containing the feed particles 6 as a mist using the atomizing gas source 30 and the atomizer 31. It can be introduced. The mixture of passivating material and feed particles move together in the central tube 28 towards the plasma zone, where the passivating material and feed particles 6 react chemically.

  Referring to FIG. 8, further, a fluid 32 inducing immobilization may be added from the injection tube 33 in communication with the intermediate tube 34 of the plasma torch 3. The passivating fluid 32 is introduced as a gas using a pressurized gas source 35 or as a mist using a combination of an atomizing gas 36 and a spray device 37. The mixture of passivating material 32 and feed particles 6 is mixed together in the middle tube 34 at the outlet end of the central tube 28 and entrained together towards the plasma zone where the passivating material 32 And feed particles 6 react chemically.

  In yet another embodiment, the passivating fluid is injected into the process after the microwave injection port, ie via an additional injection port located downstream of the plasma hot zone. In this case, the powder is first spheroidized and then exposed to a passivating fluid which may be in the form of a gas or a misty solution. The object of the present invention is to provide means for producing core-shell like microstructured spherical particle products. See Figure 9a. The passivated fluid material is injected into the inlet 38 of the plasma gas discharge chamber 39 as a gas phase or atomized droplet and is deposited on the plasma treated particles 15, thereby producing the coated particles 40. Ru. The passivated fluid material may be introduced as a gas or mist droplet using the means described in paragraphs [0026] and [0027]. The second tube inlet 41, and even multiple injection tubes, can be used to introduce the same passivating fluid material, or a combination of different coating fluid materials. It will be apparent to those skilled in the art that the number of these inlets to the evacuation chamber 39 can be increased to be compatible with complex mixing for the desired passivation layer or coating layer, depending on the application. is there. Referring to FIG. 9b, a passivated or coated particle 40 comprising a spherical core 15 and a shell-like passivation coating 42 is shown enlarged.

The method as described in paragraph [0020] was applied to spherical particles made of a mixture of commercially available alumina-titania and cobalt oxide powders shown in FIG. 10a. The mixture is obtained by spray drying techniques, an average 37 diameter micrometer alumina - consists titania _{(Al 2 O 3 -13TiO 2)} 80 wt% cobalt oxide (CoO) 20 wt% of the agglomerated powder particles. The scale with a white scale on the background (ruler) shows 100 micrometers between two long scale bars and the distance between two consecutive small scale bars is 10 micrometers. FIG. 10 b shows spherical high density product particles after treatment with microwave plasma. From the figure it can be seen that the majority of the product particles exhibit a pearl-like texture of diameter size ranging from 10 microns to 50 microns.

  Electrodeless microwave generated plasma can be used for the purification of a wide variety of materials. When there is an electrode for generating plasma as in the arc plasma method, impurities are introduced while the processing material melts and flies. The impurities are made of electrode material. The high operating temperature of the arc plasma causes the electrodes to wear out. The generation of the microwave plasma used in the present method does not require electrodes, thus eliminating contamination and achieving the production of high purity processed material.

  Referring to FIG. 11, high density spherical particles are made according to the procedure described in the figure. The powder particles to be treated are first screened and classified according to their diameter to a minimum diameter of 20 μm and a maximum diameter of 74 μm. Thereby, light particles are not recirculated above the high temperature zone of the plasma chamber, and furthermore, the processing energy present in the plasma is sufficient to melt the particles. The powder is then placed in the inner chamber, which is within the powder feeder to which the fluidized bed is directed, using a relatively low pressurized air source not exceeding 20 pounds per square inch (PSI). The powder feeder is constantly shaken using a shaker operated by another pressurized air source having a minimum pressure of 20 pounds per square inch (PSI) so that the powder flows better. The powder is carried from inside the powder feeder towards the inlet of the feed tube of the dielectric plasma torch, under pressure which makes it possible to inject the particles constantly into the plasma treatment. Before this, referring to the right side of FIG. 11, microwave radiation is introduced into the waveguide towards the plasma chamber in which the dielectric plasma torch is placed and placed perpendicular to the waveguide Be done. Two annular flows, one of which is for entrainment of the jetted particles and the other of which prevents the inner wall of the outer tube of the plasma torch from melting under the action of high heat from the plasma. A stream is introduced. When both flows are introduced into place, the plasma is ignited in the dielectric plasma torch. The appropriate combination of entrained and cooling flows is selected to stabilize the plasma. In addition, these entrained and cooled flows allow smooth flow of particles towards the plasma and to avoid turbulence that may create powder recirculation and backflow above the hot zone of the chamber. It is selected. Furthermore, these entrained and cooling flows are selected to minimize any non-uniformities in the heat path radially outward from the axis 11. Once the particles reach the plasma that is now in the high temperature zone, they are brought into a homogeneous molten state in the high temperature zone, characterized by the uniform thermal profile of the plasma along with the uniform thermal profile of the particles. The particles are treated volumetrically and uniformly and exit into the rapid cooling chamber with the atmosphere under the outlet nozzle of the plasma. The product, after solidification, is collected in a nylon or stainless steel filter or, in some applications, cooled in distilled water and analyzed for its microstructure and mechanical, optical and thermal properties .

  Referring to FIG. 12, a procedure for producing high density spherical particles using solution droplets is illustrated. First, the desired chemical composition is mixed according to the specified proportions of reactants. The mixture is then agitated sufficiently to obtain a homogeneous molecular mixture of reactants. The solution is then poured into a stainless steel tank. Air is injected into the tank by use of a pressurized air source, whereby the solution is pushed towards the spray nozzle similar to the sprayer and is injected into the central feed of the sprayer and emerges as a jet. At the same time, air is pushed into the concentric outer tube of the sprayer and penetrates the solution jet in the vertical direction, by using another pressurized source. As a result, the air atomizes the jets, causing droplets of various diameter sizes to mix and direct them toward the plasma. Before that, referring to the right side of FIG. 12, the procedure of igniting the plasma is repeated as described in the paragraph referring to FIG. Microwave radiation is introduced into the waveguide towards a plasma chamber in which a dielectric plasma torch is disposed and placed perpendicular to the waveguide. Two annular flows, one for entrainment of injected particles and the other for preventing the inner wall of the outer tube of the plasma torch from melting under the action of high heat from the plasma , Two annular flows are introduced. When both flows are introduced into place, the plasma is ignited in the dielectric plasma torch. The appropriate combination of entrained and cooling flows is selected to stabilize the plasma. In addition, these flows allow smooth flow of droplets towards the plasma, avoiding turbulence that may create powder recirculation and backflow over the high temperature zone of the plasma chamber, and heat It is chosen to avoid bursting in the pathway. When the droplets reach the plasma, which is now in the high temperature zone, it is brought into a homogeneous molten state in the high temperature zone, characterized by a uniform thermal profile with a uniform temperature profile of the plasma. The droplets are treated volumetrically and uniformly as the solvent material produced by the redox reaction is burned off. The treated particles exit into the rapid cooling chamber by the atmosphere under the outlet nozzle of the plasma. The product, after solidification, is collected in a filter or, in some applications, cooled in distilled water and analyzed for its microstructure and mechanical, optical and thermal properties.

  Referring to FIG. 13, a procedure for producing high density spherical particles using uniform solution precursor droplets generated using a droplet preparation apparatus is illustrated. First, the chemical composition of the desired solution is prepared by mixing the specified proportions of reactants. The solution is then stirred thoroughly to obtain a homogeneous molecular mixture of reactants. The solution is then pumped into the reservoir of the drop making device by a peristaltic pump or pressurized tank. Once the reservoir is full, the piezoelectric transducer is activated and the liquid solution in the reservoir is appropriately perturbed. When the perturbations satisfy the Rayleigh's breakdown law, the solution flows through the capillary nozzle continuously in a uniform stream of uniform droplets exiting at a constant velocity for a given drive frequency by the piezoelectric. Appears as. The nature of the droplet flow is monitored so that it is in the form of a uniform droplet jet, not a burst mode or an accidental mode. This droplet stream is then injected into the feed tube of the dielectric plasma torch where it undergoes the same plasma treatment and then aggregates of dense spherical particles as described in the paragraph referring to FIGS. 11 and 12 It is transformed into the body.

EXAMPLE 1 Spheronization of MgO-Y ₂ O ₃ Spray-Dried Particles Referring to FIG. 2, this method is a commercially available magnesia-yttria (MgO-Y ₂ O ₃ ) solid powder obtained by spray-drying technology from Inframat Corporation. Applied to spherical particles made from particles. Dense spherical particles exhibit a "pearl" -like texture and morphology.

Example 2 Spheroidization of a Atomized 7YSZ Solution Precursor Referring to FIGS. 4 and 5, this method is from the spraying of an atomized droplet of a 7 wt% yttria stabilized zirconia (7YSZ) solution precursor using a sprayer. Applied to produce high density spherical particles directly.

Example 3: Spheroidization of a Stream Droplet with a Uniform Droplet of 8YSZ Solution Precursor Referring to FIG. 6, this method uses 8% by weight yttria stabilized zirconia (8YSZ) using a high frequency piezoelectric driven drop preparation apparatus. It was applied to produce high density spherical particles directly from the spray of uniform droplets of solution precursor.

Example 4: Alumina - Referring to spheroidizing view 10 of the powder particles in the mixture of titania _{(Al 2} O 3 -13TiO ₂₎ and cobalt oxide (CoO), the method, the alumina obtained by spray-drying techniques - titania oxide It was applied to spherical particles made of agglomerated powder particles of a mixture consisting of 80% by weight of (Al ₂ O ₃ -13TiO ₂ ) and 20% by weight of cobalt oxide (CoO). Dense spherical particles exhibit a "pearl" -like texture and morphology.

Claims (12)

A method of producing passivated spherical high-density powder product particles using microwave plasma, which is extracted from the exhaust gas from the plasma after injecting the feed material consisting of powder particles with the feed material for surface coating There,
a) axial introduction of the feed material into the axisymmetric microwave plasma torch via the material feeder;
b) entraining the feed using axisymmetric laminar entrained flow;
c) directing the feed towards the microwave plasma using an axisymmetric laminar cooling flow;
d ) introducing a passivating material next to the feed material;
The e) the feed material and the surface coating for supplying material, the method comprising treatment in a microwave-generated plasma,
and a extracting the powdered product from f) prior Sharing, ABS outlet gas, a method of producing a passivated spherical dense powder product particles. The method of claim 1 , wherein the passivating material is a gas phase material. The method according to claim 1 , wherein the passivating material is a misty liquid material. The method of claim 1 , wherein the product particles are spherical and have a shell-core structure. The method according to claim 4 , wherein the core structure is made of a feed material. The method according to claim 4 , wherein the shell structure is made of a coating material. A method of producing passivated spherical high-density powder product particles using microwave plasma, which is extracted from the exhaust gas from the plasma after injecting the feed material consisting of powder particles with the feed material for surface coating There,
a) axial introduction of the feed material into the axisymmetric microwave plasma torch via the material feeder;
b) entraining the feed using axisymmetric laminar entrained flow;
c) directing the feed towards the microwave plasma using an axisymmetric laminar cooling flow;
and to process the d) the feed material in a microwave-generated plasma,
and introducing the passivating material into the plasma discharge in Perth downstream of e) microwave energy input,
f) the plasma discharge picture output scan or et including and extracting the overturned powder products, a method of producing a passivated spherical dense powder product particles. 8. The method of claim 7 , wherein the passivating material is a gas phase material. The method according to claim 7 , wherein the passivating material is a misty liquid material. 8. The method of claim 7 , wherein the product particles are spherical and have a shell-core structure. The method according to claim 10 , wherein the core structure is made of a feed material. The method according to claim 10 , wherein the shell structure is made of a coating material.

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