JP4420611B2 - Titanium oxide powder surface modification method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder surface modification treatment method and an apparatus used therefor.
[0002]
[Prior art]
Various technologies for handling powder have been systematically developed as fine particle engineering. For example, elemental technologies such as grinding, classification, transportation, drying, granulation, stirring, dispersion, and surface modification are magnetic tape, magnetic fluid, It has been used in the production of powders in a wide range of fields such as catalysts, catalyst carriers, abrasives, pigments, paints, copy toners, pharmaceuticals, foods, and others. In recent years, composite powders, nanoparticles or nanopolymers with new functions have attracted attention, and nano-level powders that are compounded by altering the surface of the core particles or coating various substances. Surface modification technology is becoming necessary.
[0003]
The technology prepared by conventional fine particle engineering is premised on treatment under atmospheric pressure or at most Torr order pressure, and cannot sufficiently remove moisture and impurities adhering to the powder.
Therefore, when handling fine particles at the nano level, the fine particles aggregate due to the attached water, so it is difficult to reliably modify the surface of each particle, and because of the attached water and impurities, the entire powder surface is at the nano level. There is a problem that it is difficult to form a high quality coating film with less impurities and contamination.
[0004]
Further, Patent Document 1 discloses a surface treatment method of powder using atmospheric pressure plasma, and surface treatment is performed by atmospheric pressure glow discharge while the powder is suspended and conveyed by a rare gas or a mixed gas of a rare gas and a reactive gas. A method of performing is disclosed.
Since this disclosed method is a treatment under atmospheric pressure as in the conventional method, removal of moisture and impurities adhering to the powder is not sufficient. Further, in glow discharge, high-energy electrons are unlikely to exist and gas dissociation efficiency is small, so that it is difficult to obtain higher-order active species and decomposition products. For example, the dissociation rate of nitrogen in glow discharge is as small as about 1%. When glow discharge is applied to methane gas CH _4, it is difficult to obtain higher-order decomposition products such as CH ₂ ions, CH ions, and C ions other than CH ₃ ions.
As described above, the above disclosed method has a drawback in that it is difficult to obtain a high-quality product because there are restrictions on the gas types that can be used for surface modification and the reforming reaction does not proceed easily.
[0005]
In order to reliably remove the adhering moisture and obtain a high-quality surface-modified powder, it is required to use a vacuum process.
Patent Document 2 discloses a fine powder coating method in which a rotating barrel type container is installed in a vacuum chamber, a sputtering source is installed in the container, and the powder in the container is coated by a sputtering method.
Further, Patent Document 3 uses an ion plating method to ionize a vapor supplied from a melt evaporation source by applying a discharge plasma flow from a plasma gun and deposit it on the surface of a granular material from above. A method of producing a half-coated particle by forming a film is disclosed.
However, in sputtering and ion plating coatings, particles ejected from a sputtering source or evaporation source adhere to the powder with directionality, making uniform coating difficult, and sputtering generally has a low coating speed. There is a problem that it is difficult to reduce the processing cost in practical use.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-228739 [Patent Document 2]
JP-A-2-153068 [Patent Document 2]
Japanese Patent Laid-Open No. 2000-336473
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide is to provide a powder surface modification how to perform surface modification treatment of the powder to uniformly and faster. In particular, it is to provide a titanium oxide powder surface modification method for nitriding modification of titanium oxide powder.
[0008]
[Means for Solving the Problems]
To solve the above problems, the first powder surface modification method of the present invention, the electron beam gun to a molecule composed include nitrogen of active elements in gas mixed with the gas and an argon gas having containing Electron beam-excited plasma is generated by irradiating electrons accelerated from the dissociation, ionization, and excitation, and this plasma is caused to act on the titanium oxide powder, resulting in a chemical reaction involving the active element nitrogen contained in the plasma. The body surface is modified by nitriding .
How the present invention, the active elements contained in the plasma is involved, nitride, oxide, oxynitride, reduction, hydrogenation, fluoride, powder by causing the plasma reactions and chlorinated at the powder surface This is a surface modification method, particularly a titanium oxide powder surface modification method for nitriding modification of titanium oxide powder .
[0009]
In the second powder surface modification method of the present invention, an electron beam excited plasma is generated from an electron beam gun to a molecular gas containing a constituent element of a thin film to be formed on the powder surface, and this plasma is converted into a powder. A thin film is coated on the powder surface by acting.
In this method, a thin film of ceramic, semiconductor, metal, or organic material can be formed on the powder surface by chemical vapor deposition (CVD).
[0010]
In the first and second inventions, the electron beam excited plasma is formed by electrons emitted from an electron beam gun and accelerated by an acceleration electrode colliding with a gas in a vacuum chamber. Is disclosed in detail in specifications such as Japanese Patent Nos. 2871675 and 2868120 owned by the present applicant.
Electron beam excited plasma is generated with an electron beam accelerated to an energy of about 60 eV to 100 eV, which maximizes the gas cross-sectional area. Therefore, it has excellent gas excitation and ionization efficiency, and generates high-density plasma even at low pressure. Can be made.
[0011]
For example, nitrogen gas exhibits a high dissociation rate of about 10% and generates higher-order active species and decomposition products, so that the surface modification reaction can be performed efficiently. For example, from methane gas, in addition to CH ₃ ions, higher-order decomposition products such as CH ₂ ions, CH ions, and C ions are obtained.
In this way, since various active species can be obtained, the surface modified layer that cannot be formed by the reaction according to the equilibrium condition under atmospheric pressure may be formed by electron beam excited plasma. Can be enriched.
[0012]
Further, when generating the electron beam excited plasma, for example, after evacuating to about 10 ⁻⁶ Torr, a process gas is introduced and electrons are irradiated to form plasma.
Therefore, the water adhering to the fine particles is almost completely removed. In addition, by performing pretreatment using oxygen or hydrogen plasma before the surface modification treatment, impurities attached to the powder can be efficiently removed.
[0013]
Furthermore, since the plasma acting on the powder is supplied to the entire surface, surface modification such as chemical reaction and coating is performed uniformly on the surface.
Further, the electron beam excitation plasma is a high-density plasma, and the surface modification reaction proceeds at a high speed, so that high processing efficiency can be achieved.
Furthermore, the electron beam excited plasma can easily increase the high density plasma region, and can increase the reaction field with the powder to improve the productivity.
[0014]
In addition, it is preferable that the powder is stirred while the plasma acts. This is because the individual particles are uniformly exposed to the plasma on the surface and subjected to a uniform treatment.
Further, it is preferable to apply a negative bias voltage to the container for storing the powder. Reaction can be promoted by ions in the plasma being accelerated by the bias potential and colliding with the powder stored in the container.
The powder may be heated before the plasma acts or while the plasma acts. In particular, the powder may be dried or impurities removed by heating from 100 ° C. to 1000 ° C. before the plasma acts. By heating in vacuum, moisture and impurities can be efficiently removed including crystal water. By removing moisture and impurities, not only can homogeneous reaction and formation of a homogeneous film be performed, but cross-linked and agglomerated powder particles can be separated and dispersed to perform a more homogeneous and high-quality surface modification treatment. Can do.
[0015]
In order to solve the above problems, the powder surface modification apparatus of the present invention generates plasma by maintaining an electron beam gun for generating an electron beam, an acceleration electrode, and a vacuum between the electron beam gun and the acceleration electrode. Equipped with a vacuum chamber and a container with a stirring mechanism that is provided in the vacuum chamber and stores the powder to be processed in the container, stirs it, introduces gas into the vacuum chamber, and accelerates electrons from the electron beam gun. Electron beam excited plasma is generated by irradiating gas in a vacuum chamber to dissociate, ionize, and excite, and this plasma is applied to the powder to be treated to modify the surface of the powder.
[0016]
The gas is a single or mixed gas of molecules containing the active elements nitrogen, oxygen, hydrogen, fluorine, chlorine, etc., and performs plasma reactions such as nitridation, oxidation, oxynitridation, reduction, hydrogenation, fluorination, and chlorination. You may make it produce on the powder surface. Further, it may be a mixed gas containing a molecular gas composed of inert elements argon and helium.
Further, by selecting a molecular gas composed of an element that forms a thin film in the gas, the powder surface can be coated with a thin film of ceramic, semiconductor, metal, or organic material.
[0017]
A DC power source or a high-frequency power source may be connected to the vessel with a stirring mechanism so that a negative bias voltage can be applied.
Moreover, the heater with a stirring mechanism may be installed in proximity. The heater for heating has a function of removing moisture and impurities adhering to the powder and performing a homogeneous reaction and formation of a homogeneous film with high quality.
[0018]
In addition, the container with a stirring mechanism is a dish-type container disposed upward under the electron beam excitation plasma, and the container itself vibrates or by mixing pulverized balls into the powder in the container, Alternatively, the stored powder may be stirred by installing a scraper in the container and rotating the scraper. When the electron beam excitation plasma is generated using a ring-shaped electron emission type electron beam gun, the region where high-density plasma is formed is increased by increasing the diameter of the ring, so that productivity is improved.
[0019]
Further, the container with the stirring mechanism is a barrel-type container surrounding the electron beam excited plasma, and the container rotates or swings, or a pulverized ball is mixed into the powder in the container, or both of them. The stored processing target powder may be agitated by this measure. By increasing the distance between the electron beam gun and the accelerating electrode, the plasma reaction region can be enlarged and productivity can be improved.
Note that the barrel-type container may be configured such that the powder stored by opening a part of the wall can be easily discharged from the container. By stopping rotation and swinging when the opening is located on the lower side and opening it to drop the contents down, the powder stored in the barrel-type container can be easily recovered. .
Further, a part of the wall may be inclined to discharge the contents.
[0020]
Furthermore, a barrel type container is attached with an inclination, and a powder supply mechanism for continuously supplying the powder into the container is arranged in the upward opening of the container, and the treated powder is placed at the bottom of the container. A powder discharge mechanism that continuously discharges to the outside is provided so that surface modification treatment can be performed continuously. The processing target powder supplied to the container stays in the container for a predetermined time, is subjected to surface modification treatment, becomes a product, and is collected from the lower side of the container.
In addition, a partition plate is provided on the wall of the rotating container so that the powder received in the container can easily flow out and the residence time in the container is not sufficient, so that the powder is properly retained to allow sufficient processing time. Configure to ensure.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the powder surface modification method and apparatus of the present invention will be described in detail using some examples.
[0022]
[Example 1]
FIG. 1 is a conceptual diagram of a powder surface modifying apparatus according to a first embodiment.
The powder surface modification apparatus 11 of the present embodiment is provided with a pressure gradient type electron beam gun 13 for introducing an electron beam 21 on the side of a vacuum chamber 12 and an acceleration electrode 14 at a position facing the electron beam gun. A barrel type powder container 15 is provided so as to surround the plasma 22 excited by the electron beam 21.
The vacuum chamber 12 is provided with a nozzle for introducing gas and a vacuum pipe nozzle for evacuating.
[0023]
The electron beam gun 13 includes a cathode 16 and a discharge electrode 17 provided with holes through which electrons pass, and a nozzle for introducing a working gas such as argon.
Further, the output voltage of the discharge power source 18 is applied between the cathode 16 and the discharge electrode 17, and the output voltage of the acceleration power source 19 is applied between the discharge electrode 17 and the acceleration electrode 14.
The powder container 15 is a cylindrical barrel type container having a diameter of 400 mm and a length of 400 mm, for example, and rotates around a horizontal axis passing near the center of the plasma 22 generated in the container. A gutter 20 is provided so that 23 does not spill out during rotation.
[0024]
In this embodiment, an example in which nitriding treatment of titanium oxide powder is performed using the apparatus shown in the drawing will be described.
About 1 kg of titanium oxide powder 23 is charged into the barrel-type powder container 15.
Argon gas is introduced as the working gas of the electron beam gun 13, a direct discharge of argon is caused in the discharge space using the thermal electrons emitted from the cathode 16 of the electron beam gun 13 as a trigger, and nitrogen gas and argon gas are introduced from the nozzle of the vacuum chamber 12. The pressure is set to 3 mTorr.
[0025]
Next, by applying an acceleration voltage between the discharge electrode 17 and the acceleration electrode 14, the electron beam 21 is drawn from the discharge space of the electron beam gun 13 into the vacuum chamber 12, and a spindle-shaped electron beam is placed inside the barrel-type container 15. An excitation plasma 22 is generated. The electron beam excited plasma 22 has a central axis that substantially overlaps the rotational axis of the barrel-type container 15.
The discharge current indicated by the discharge power source 18 was 10 A, and the acceleration voltage indicated by the acceleration power source 19 was 90V. The barrel-type container 15 was rotated or rocked to continuously process the powder for 60 minutes while stirring the powder 23.
[0026]
It was estimated that the titanium oxide powder 23 after the treatment had a light yellow color and surface nitridation was performed. In order to investigate the composition ratio and chemical bonding state of the powder surface, X-ray photoelectron spectroscopy (XPS) was performed, and a wide scan spectrum and a narrow scan spectrum of main elements were measured.
When the component ratio of each element was determined from the narrow scan spectrum, about 9 atomic% of nitrogen was detected. FIG. 2 shows the nitrogen peak (N1s) in the XPS analysis result, with the horizontal axis representing the binding energy and the vertical axis representing the number of counts.
[0027]
According to the figure, a main peak is observed at a position of 396 eV, and a broad peak considerably smaller than the main peak is observed in a range of 398 to 403 eV. In these peaks, 396 eV relates to Ti—N, 400 eV relates to C—N and N—H, and 402 eV relates to a bond of N—N and —NO. Thus, it can be seen that most of the nitrogen is bound to titanium.
[0028]
Titanium oxide is chemically stable and it is considered extremely difficult to replace oxygen with nitrogen. However, according to the surface modification method using the electron beam excited plasma apparatus of the present invention, Ti-N is efficiently used. Could be converted into a bond.
The size of the plasma formed in the vacuum chamber can be adjusted according to the distance between the electron beam gun 13 and the acceleration electrode 14 and the conditions of the electron beam, so that the capacity of the powder container 15 and the amount of powder to be stored are appropriately set. The size can be selected, and further improvement in productivity can be expected.
[0029]
FIG. 3 and FIG. 4 are conceptual diagrams for explaining an example of an apparatus for taking out the processed powder from the barrel-type powder container 15, respectively. 4A is a side sectional view, and FIG. 4B is an elevation sectional view.
The apparatus of FIG. 3 forms a damper 24 in which a part of the wall of the powder container 15 is lifted around one end, and when the surface modification reaction ends and the rotation or swing of the powder container 15 stops, To be on the lower side. Then, since all the powder 23 in the powder container 15 is collected on the damper 24, when the back side of the damper 24 is lifted, the powder 23 spills out from the opening on the near side, so that it is received in another container and taken out. be able to.
[0030]
In the apparatus of FIG. 4, an extraction slit 25 is provided in a part of the wall of the powder container 15, and a lid 26 for opening and closing the extraction slit 25 is provided.
When the surface modification reaction is completed and the rotation or swinging of the powder container 15 is stopped, the position of the take-out slit 25 is set to be on the lower side. When the lid 26 is opened when the take-out slit 25 comes to the lower side, the powder 23 spills out from the take-out slit 25 and is received and taken out by another container.
When the powder container 15 only swings, the extraction slit 25 is on the upper side during the swinging, and when the processing is completed, the extraction slit 25 is brought to the lower side to spill the contents. May be. In this case, a lid is not required.
[0031]
[Example 2]
FIG. 5 is a conceptual diagram of a powder surface modifying apparatus according to a second embodiment of the present invention.
In the powder surface modification device 31 of this embodiment, a ring-shaped radiation electron beam gun 33 for generating an electron beam 41 is provided on the upper surface of the vacuum chamber 32, and a dish-shaped powder container 35 is provided under the electron beam gun. Is. A discharge cup 37 of the electron beam gun 33 is provided so as to protrude into the vacuum chamber 32, and a plurality of holes for emitting electrons in the horizontal outward direction are formed in the side surface of the cylindrical discharge cup 37 so as to surround the discharge cup. The electron beam 41 is accelerated toward the ring-shaped acceleration electrode 34.
[0032]
The vacuum chamber 32 is provided with a nozzle for introducing a gas and a vacuum pipe nozzle for evacuating, and when an accelerated electron beam 41 is irradiated to the gas, an electron beam excited plasma 42 is generated.
The dish-shaped container 35 faces vertically upward so as to contain the powder 43, and holds the powder 43 under the electron beam excited plasma 42 formed in the vacuum chamber 32. The dish-shaped container 35 includes an ultrasonic vibrator, and the powder 43 stored by stirring is stirred so that a new surface always comes into contact with the plasma 42.
[0033]
Thus, using the apparatus 31 using the ring-shaped radiation electron beam gun 33, the surface nitriding treatment of the titanium oxide powder was performed in the same manner as in the first example.
About 1 kg of titanium oxide powder is charged in a dish-shaped container 35 having a diameter of 600 mm, the vacuum chamber 32 is evacuated, argon gas is introduced into the electron beam gun 33, and the hot electrons emitted from the cathode 36 are used as a trigger for argon in the discharge space. A direct current discharge was generated, nitrogen gas and argon gas were introduced into the vacuum chamber 32, and the pressure was set to 3 mTorr. By applying an accelerating voltage between the discharge electrode in the discharge cup 37 and the ring-shaped acceleration electrode 34, the electron beam 41 is drawn from the discharge cup 37 into the vacuum chamber 32, and is formed in a disk shape on the dish-shaped container 35. An electron beam excitation plasma 42 was generated.
The powder was processed for 60 minutes while vibrating the dish-shaped container 35 at a discharge current of 10 A and an acceleration voltage of 90 V.
[0034]
It was confirmed that the titanium oxide powder after the treatment had a light yellow color as in the case of the first example. As a result of performing X-ray photoelectron spectroscopy, the nitrogen content on the powder surface was about 7 atomic%. Further, from the result of observing the nitrogen peak (N1s), it was confirmed that there was a main peak at a position of 396 eV and that there were many titanium-nitrogen bonds.
In addition, since the area of the annular plasma generated in the vacuum chamber can be expanded relatively freely, productivity can be further improved.
[0035]
[Example 3]
FIG. 6 is a conceptual diagram of a powder surface modifying apparatus according to a third embodiment of the present invention.
In the present embodiment, a heater and a bias voltage applying mechanism are added to the configuration of the first embodiment, and there is no difference in others. Therefore, in FIG. 6, the same reference numerals are assigned to the components having the same functions as those in FIG.
The powder surface reforming apparatus 51 of this embodiment is provided with a lamp heater 52 below a barrel-type powder container 15 provided in a vacuum chamber 12 with a rotating shaft horizontal. In addition, an RF power source 54 is connected to the powder container 15 via a matching unit 53 so that self-bias application can be performed.
[0036]
When performing powder surface modification using the powder surface modification apparatus 51 of the present embodiment, the powder 23 in the powder container 15 is heated and dried by the lamp heater 52 before the treatment. be able to. By drying the powder, it is possible to remove the adhering moisture and disperse the crosslinked and agglomerated powder to perform a more homogeneous and high-quality surface modification treatment. Impurities and water of crystallization can be removed by heating at a high temperature.
In particular, when a crystalline thin film is coated, crystal growth can be promoted by heating the powder during the treatment.
Considering removal of impurities, removal of crystal water or crystal formation, it is preferable that the heating temperature can be set in the range of 100 ° C. to 1000 ° C.
[0037]
When a bias voltage is applied to the powder container 15 using the RF power source 54, cleaning can be performed by applying appropriate ions to the powder before the surface modification treatment. When a thin film is coated on the powder surface, a high-functional thin film can be deposited on the powder surface by applying a bias voltage.
In addition, by applying an appropriate bias voltage, the reactivity of chemical reactions such as nitriding, oxidation, oxynitriding, reduction, hydrogenation, and chlorination on the powder surface can be improved.
[0038]
[Example 4]
FIG. 7 is a conceptual diagram of a powder surface modifying apparatus according to a fourth embodiment of the present invention.
The powder surface modification device 61 of this embodiment is a device in which the surface modification process is continued.
The powder surface modification device 61 is provided with a pressure gradient type electron beam gun 62 for generating an electron beam 71 at an oblique direction on the side of a vacuum chamber (not shown in the figure), and an acceleration electrode 63 at a position facing the electron beam gun. A barrel type powder container 64 is provided so as to be rotated so as to surround the plasma 72 excited by the electron beam 71, and the discharge nozzle 66 of the powder supply hopper 65 is inserted into the upward opening of the powder container 64. The powder 73 is disposed so as to be supplied to the end of the powder container 64, and a powder take-out container 67 is provided so as to receive the powder 73 spilling from the lower end of the powder container 64. ing.
[0039]
The powder supply hopper 65 is provided with a heater 68 on the wall, and the powder is heated and dried and impurities are removed before being supplied to the powder container 64 subjected to the powder surface modification treatment. it can.
Further, baffle plates 69 are provided on the side wall of the powder container 64 at appropriate intervals so that the surface modification is performed in the powder container 64 so that the powder 73 does not flow down in a short time on the inclined wall surface. The residence time for receiving processing is secured. The baffle plate 69 may be any one that appropriately inhibits the flow of the fluidized powder and has a stirring effect, and may be an annular partition plate or a large number of screen-like plates arranged.
[0040]
When the dried powder 73 is supplied from the powder supply hopper 65 into the powder container 64 through the discharge nozzle 66, the powder 73 gets over the baffle plate 69 and slowly flows down the inner wall surface. During this time, the gas generated in the powder container 64 is subjected to the action of the electron beam excitation plasma 72 and subjected to surface modification treatment. Finally, the powder is removed from the lower end of the powder container 64 to the powder extraction container 67. Drop and store.
Thus, the powder surface modification apparatus 61 of the present embodiment can recover the powder by continuously performing the surface modification treatment on the powder.
[0041]
【The invention's effect】
As described above, the powder surface modification method and apparatus according to the present invention perform powder surface modification processing uniformly and at high speed, and economically produce and provide fine powder with new characteristics. Can now.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a powder surface modifying apparatus according to a first embodiment of the present invention.
FIG. 2 is a drawing showing a part of the result of X-ray photoelectron spectroscopy when nitriding is performed with the apparatus of the first embodiment.
FIG. 3 is a drawing for explaining an example of an apparatus for taking out powder from the powder container of the first embodiment.
FIG. 4 is a drawing for explaining another example of an apparatus for taking out powder from the powder container of the first embodiment.
FIG. 5 is a conceptual diagram of a powder surface modifying apparatus according to a second embodiment of the present invention.
FIG. 6 is a conceptual diagram of a powder surface modifying apparatus according to a third embodiment of the present invention.
FIG. 7 is a conceptual diagram of a powder surface modifying apparatus according to a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Powder surface modification apparatus 12 Vacuum chamber 13 Pressure gradient type electron beam gun 14 Acceleration electrode 15 Barrel type powder container 16 Cathode 17 Discharge electrode 18 Discharge power source 19 Acceleration power source 20 鍔 21 Electron beam 22 Electron beam excitation plasma 23 Powder 24 Damper 25 Extraction slit 26 Lid 31 Powder surface modification device 32 Vacuum chamber 33 Ring-shaped radiation type electron beam gun 34 Ring-shaped acceleration electrode 35 Dish-shaped powder container 36 Cathode 37 Discharge cup 41 Electron beam 42 Electron beam excitation plasma 43 Powder 44 Ultrasonic vibrator 51 Powder surface modification device 52 Lamp heater 53 Matching device 54 RF power supply 61 Powder surface modification device 62 Pressure gradient type electron beam gun 63 Accelerating electrode 64 Barrel type powder container 65 Powder supply hopper 66 Discharge Nozzle 67 Powder container 68 Heater 69 Baffle plate 71 Arm 72 electron-beam excited plasma 73 powder

Claims (5)

Electron beam-excited plasma is generated by irradiating a mixture of nitrogen gas and argon gas with electrons accelerated from an electron beam gun to dissociate, ionize, and excite, and this plasma is included in the titanium oxide powder. A titanium oxide powder surface modification method characterized by nitriding and modifying the surface of the powder by a chemical reaction of nitrogen as an active element. The powder of titanium oxide powder surface modification method according to claim 1 Symbol mounting, characterized in that it is agitated while the plasma acts. The titanium oxide powder surface modification method according to claim 1 or 2, wherein a negative bias voltage is applied to the container for storing the powder. The titanium oxide powder surface modification method according to any one of claims 1 to 3 , wherein the powder is heated before or during the action of the plasma. The powder of titanium oxide powder surface modification according to any one of claims 1 to 3, characterized in that it is heated and dried and impurity removal to 1000 ° C. from 100 ° C. prior to the plasma acts Quality method.

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