JP6431124B2 - Reduction method of titanium oxide using microwave - Google Patents

Description

  The present invention relates to a method for directly reducing titanium oxide using microwaves.

The crawl method is known as a method for smelting (reducing) titanium ore, and the method is disclosed in many documents such as Japanese Patent No. 4537727 (Patent Document 1).
In the crawl method, first, TiO _{2 in} titanium ore is reacted with Cl in the presence of C at a temperature of about 900 ° C., and TiO ₂ + 2Cl ₂ + 2C (or C) = TiC ₄ + 2CO (or CO ₂ ) In this method, TiCl ₄ is produced by a reaction formula, and then TiCl ₄ is refined and reacted with metal Mg, and a spongy metal Ti is produced by a metal thermal reduction method.

This can be represented by the reaction formula as follows: TiCl ₄ (l, g) + 2Mg (l, g) = Ti (s) + 2MgCl ₂ (l). Industrially, it takes several days in a steel reaction vessel (“s” in parentheses represents solid, “l” represents liquid, and “g” represents gas).
However, this method for producing titanium metal by the crawl method has a problem that it takes a long time to produce and the production cost is high.

Next, a method for directly reducing titanium oxide has also been proposed (Non-Patent Document 1).
In the reduction method proposed here, a raw material TiO ₂ powder is placed on a molybdenum plate in a reaction vessel, powdered calcium metal is placed on the bottom of the reaction vessel, and the reaction vessel is heated to a high temperature in this state. Thus, calcium vapor is generated, and this calcium vapor is reacted with titanium oxide.

  However, in this method, it takes a long time to heat the calcium metal to a temperature at which it evaporates, and furthermore, electricity, heavy oil, gas, or the like is used as a heat source for heating the reaction vessel. At the same time, there is a problem that the environmental load is large.

  By the way, as a means for heating a substance, a technique for irradiating a substance with microwaves is known. In Non-Patent Document 1, a means using microwave heating can be considered as a means for efficiently heating and evaporating calcium metal. .

However, generally, since metal reflects microwaves, it can be heated only in the mode of induction heating (means for heating a conductor by passing an electric current through electromagnetic induction). Therefore, there is a problem that the metal is heated and evaporated and induction heating cannot be continued. Further, in the microwave band induction heating, only a single mode can be used, and there is a problem that the induction heating area is narrow.
From these problems, for example, when the metal is heated to continuously evaporate the metal to generate metal vapor, the microwave cannot be used as the heating source. there were.

  That is, even if a microwave is used as the heating source of the technique according to Non-Patent Document 1, calcium metal reflects the microwave and cannot be heated unless the induction heating mode is used, that is, cannot generate steam. The problem remains.

Japanese Patent No. 4537727

A paper published in the Journal of Iron and Steel, published by the Japan Iron and Steel Association, in 1976 (No. 4), pages 86-93, "Production of powdered titanium by the calcium thermal reduction method of titanium oxide" Method "(Author, Katsutoshi Ono et al.)

  Therefore, the subject of the present invention is microwave heating, which has not been suitable for heating metal, but a means for efficiently heating a metal material and generating metal vapor using this microwave heating is proposed. The present invention also proposes a method for directly reducing titanium oxide using this metal vapor with less energy, in a short time and at low cost.

The object of the present invention is achieved by the following means.
1. A mixture of a metal material and a ceramic body is irradiated with microwaves and heated, thereby evaporating the metal material, thereby generating metal vapor,
The metal vapor is configured to react with titanium oxide ,
The metal material is calcium, magnesium, sodium or potassium,
The method for reducing titanium oxide , wherein the ceramic body is zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, or aluminum nitride .

2. The method according to claim 1, wherein the method is performed under vacuum.

3 . The method for reducing titanium oxide according to claim 1 or 2 , wherein the titanium oxide is irradiated with microwaves and heated.

4). The method for reducing titanium oxide according to claim 1, wherein the shape of the metal material is powder, granular, and / or thin film.

5. 5. The method for reducing titanium oxide according to claim 4, wherein the length of the longest portion of the metal material is ¼ or less of the wavelength of the microwave ceramics to be irradiated.

6 . The length of the longest portion of the mixture is, the method of reducing a titanium oxide according to any one of claims 1 to 5, characterized in that an integral multiple of a quarter of the wavelength in the ceramic of the microwave irradiation .

7 . The method for reducing titanium oxide according to any one of claims 1 to 6 , wherein a heat insulating material is disposed around the mixture.

8 . The metallic material and by mixing the ceramic body, further comprising preparing the mixture, the reduction method of the titanium oxide according to any one of claims 1-7.

According to the invention shown in 1 above, although it is a metal material that has been difficult to heat even by microwave irradiation, if microwaves are irradiated to a mixture of a metal material and a ceramic body, the microwaves are mixed. It is also absorbed by the metal that became part of the body and can be heated. When the temperature of the metal material reaches near the boiling point by this heating, the metal material evaporates (or sublimates), and metal vapor can be generated.

The effect of the invention shown in the above 1 will be described in detail as follows.
Conventionally, when microwaves are used to heat and evaporate metals, the inside of an applicator (referred to as “heating chamber”, especially “microwave irradiation chamber”, hereinafter the same)) is generally used as microwave heating. It had to be in the mode of unintentional induction heating.

  However, if the method according to the above 1 is used, since the microwave irradiation is applied to the mixture of the metal material and the ceramic body, electric field heating is possible in addition to induction heating. Absorption is increased, and the metal can be efficiently heated under vacuum and can be continuously evaporated even if the state of the material changes. That is, it can be heated using a multi-mode applicator. Even in a place where the electric field strength in the single mode is high, even if the metal material is reduced, electromagnetic wave energy can be continuously applied by the electric field.

Therefore, according to the invention shown in the above 1, since the metal can be heated by microwave irradiation regardless of the type of applicator, metal vapor can be generated with high efficiency and low energy.
By using this metal vapor generation method, titanium oxide can be reduced with less energy, in a short time and at low cost.

According to the invention shown in 2 above, since the microwave is irradiated to the mixture under vacuum, the partial pressure of metal vapor to be generated (ratio of metal vapor in the atmosphere) can be increased. Thereby, the reactivity of titanium oxide and the metal vapor | steam which plays the role of a reducing agent can be improved.
Furthermore, by reducing the titanium oxide by generating metal vapor under vacuum, the oxidation of the metal material can be prevented or suppressed before the reaction, and the reduced titanium metal is oxidized again after the reaction. Can be prevented or suppressed.
In the present invention, “vacuum” refers to a state where the pressure is lower than atmospheric pressure, and there is no limitation by atmospheric pressure.

According to the invention described in 1 above, by adopting calcium or magnesium as the metal material, the generated metal vapor of calcium or magnesium serves as a reducing agent in the reaction with titanium oxide, reducing titanium oxide. can do.
TiO ₂ (s) + 2Ca (g) → Ti (s) + 2CaO (s)
TiO ₂ (s) + 2Mg (g) → Ti (s) + 2MgO (s)
(In the above reaction formula, the state of each substance indicates that (s) is solid and (g) is gas. The same applies hereinafter.)
The metal containing calcium or magnesium means a pure metal of calcium or magnesium, an alloy which is a compound containing calcium or magnesium, a calcium or magnesium metal containing other impurities, or the like.

According to the invention shown in 3 above, the reactivity with metal vapor can be enhanced by irradiating not only the metal material but also titanium oxide as a raw material with microwaves and heating them.

According to the invention shown in 5 above, the mixture of the metal material and the ceramic body resonates by setting the length of the longest portion of the metal material to ¼ or less of the wavelength in the microwave ceramic to be irradiated. It becomes a condition that the microwave to the metal material is easily absorbed. Thereby, a metal material can be heated efficiently and a metal vapor | steam can be generated.
The wavelength of the ceramic described above is derived from λ ₀ / √ε ₁ (λ ₀ : wavelength of electromagnetic wave in vacuum, ε ₁ : dielectric constant of ceramic).

  Here, the longest part of the metal material is, for example, the longest diagonal line in the case of a rectangular parallelepiped, the diameter in the case of a sphere, the longest diameter in the case of a distorted sphere (granular body), and the plate or a thin film. The longest side or diagonal line, if cylindrical, is the longer of the diameters or sides. In other words, it indicates the diameter of the largest true sphere that circumscribes the metal material at two or more points.

Invention shown in the above 4, the individual shape of the metal material, a powder, are defined as particulate and / or thin film, i.e., powdered, of the shape of the particulate or thin film, a shape alone Alternatively, two or more shapes may be mixed and used.
With this configuration, it becomes easy to mix with the ceramic body, and it becomes easy to arbitrarily adjust the mixing condition, such as uniform or non-uniform, so that the production of the mixed body can be facilitated. Furthermore, by adopting these shapes, as in the case of the invention shown in 5 above, it becomes a condition that microwaves are easily absorbed into the metal material by resonance, and the heating efficiency can be increased.
The granular shape includes a spherical shape and a distorted spherical shape (hereinafter the same).

According to the invention shown in 6 above, the length of the longest part of the mixture is set to an integral multiple of 1/4 of the wavelength of the microwave to be irradiated, so that the mixture resonates with the antenna. Energy can be confined in the mixture, and heating efficiency can be increased.

According to the invention shown in the above 7 , since heat generated by irradiating the mixture with microwaves is confined by the heat insulating material, the heating efficiency of the mixture can be increased, and as a result, metal vapor is generated with less energy. Can be made.

According to the invention shown in 1 above, by employing zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide or aluminum nitride as the ceramic body forming the mixture, Heating efficiency can be stabilized.
In other words, these ceramic bodies have high heat resistance and are easy to transmit electromagnetic waves (less loss to electromagnetic waves), so that the ceramic body can be prevented from collapsing and deforming by irradiating microwaves, so that the heating efficiency is stable. Can be made.
Furthermore, these ceramics can maintain the optimally set conditions for heating the metal material without affecting the microwave output and wavelength even when irradiated with microwaves, and improving the heating efficiency. It can be stabilized.

The invention shown in 8 is the method described in 1 to 7 above, and further includes a step of mixing a metal material and a ceramic body to produce a mixture. With this configuration, the mixture can be easily manufactured.

Schematic explanatory drawing showing an embodiment of the mixture according to the present invention (example of non-uniform mixing) Schematic explanatory view showing another embodiment of the mixture according to the present invention (example of uniform mixing) 1 is a schematic configuration diagram showing an embodiment of an apparatus according to the present invention. Schematic configuration diagram showing another embodiment of the apparatus according to the present invention Schematic configuration diagram of equipment used for verification experiment Temperature change graph showing the result of verification experiment (Reduction of titanium oxide using Ca vapor) X-ray analysis graph showing results of verification experiment (reduction of titanium oxide using Ca vapor) Temperature change graph showing the result of verification experiment (reduction of titanium oxide using Mg vapor) X-ray analysis graph showing the result of verification experiment (reduction of titanium oxide using Mg vapor) A photograph of the product obtained from the verification experiment Other photos of products taken from verification experiments

The present invention relates to a method for reducing metal oxide by generating metal vapor by heating and evaporating a metal material, reacting the metal vapor with titanium oxide as a raw material.
As described above, in order to heat the metal material and generate the metal vapor, conventionally, the metal material is heated by heating the entire heating chamber using an electric furnace or the like. However, with this heating means, it is necessary to heat up to other parts that do not require heating, and furthermore, since the electric furnace used as a heating source consumes a lot of energy, there is a problem that the heating efficiency is poor.

The inventors have conceived a means of using microwave heating to improve heating efficiency.
Microwave heating is a heating means in which irradiated microwaves are absorbed by a substance due to dielectric loss and its energy becomes heat. Unlike heating by an external heat source, the effects of heat conduction and convection are almost negligible, and only specific substances can be selectively, rapidly and uniformly heated.

  However, since the metal reflects the microwave, the microwave is not absorbed by the metal, so that the metal cannot be evaporated by the microwave heating and the metal vapor cannot be obtained by the conventional technique.

  Therefore, the present inventors mixed a metal material and ceramics, and by irradiating the mixture with microwaves under a vacuum, the microwaves were also absorbed by the metal material that became part of the mixture, It has been found that this metal material generates heat. When the temperature reaches near the boiling point of the metal material (a temperature lower than the boiling point under vacuum) by this heating, the metal material is evaporated (or sublimated), and metal vapor can be generated.

  Note that the microwaves used in the present invention include electromagnetic waves having a frequency of 300 MHz to 3 THz, but a generally usable frequency range is 900 MHz to 5.8 GHz. In addition, the vacuum or under vacuum in the present invention means a state where the pressure is lower than the atmospheric pressure, and the atmospheric pressure is not limited.

  These effects are thought to be due to the absorption of electromagnetic wave energy into the metal material when the mixture of the metal material and the ceramic body is irradiated with microwaves. The metal is efficiently heated and evaporated under vacuum. It is considered possible.

In other words, if microwaves are applied to a mixture of a metal material and a ceramic body, in addition to induction heating, electric field heating is also possible. Below, the metal can be heated efficiently and continuously evaporated even if the state of the metal material changes. That is, it can be heated using a multi-mode applicator. Even in a place where the electric field strength in the single mode is high, even if the metal material is reduced, electromagnetic wave energy can be continuously applied by the electric field.
Therefore, regardless of the type of applicator, the metal can be heated by microwave irradiation, so that metal vapor can be generated with high efficiency and low energy.

  In the present invention, the metal vapor includes atoms that are in a gaseous state, atoms that are excited by microwaves, and atoms that are excited by radicals.

The mixture 1 according to the present invention will be described in detail.
As shown in FIG. 1, the mixture 1 is an aggregate obtained by mixing a metal material 11 and a ceramic body 12.

  The metal material 11 is a substance to be evaporated in the present invention, and is a solid metal that attempts to generate steam. In the case where the metal material 11 is a single substance, the microwave is not reflected and absorbed by the surface, and therefore, the metal material 11 is not heated sufficiently even when irradiated with the microwave.

The metal forming the metal material 11 is a metal that can be an oxide reducing agent.
For example, a metal containing calcium, magnesium, sodium or potassium can be used. The above-mentioned metal containing calcium or the like means a pure metal such as calcium, an alloy which is a compound containing calcium or the like, a metal such as calcium containing other impurities, or the like.
In particular, in the present invention aiming at reduction of titanium oxide, it is preferable to use calcium or magnesium serving as a reducing agent as the metal material 11.

The shape of the metal material 11 is not limited, and may be any shape such as powder, granular (including spherical and distorted spherical bodies), rectangular parallelepiped, thin film, or coil. However, considering the ease of mixing with the ceramic body 12, it is preferably in the form of powder or granules. In addition, metal materials are often marketed in the form of a plate, which may be finely chopped and used in a thin film or plate shape, or may be wound in a spiral shape and used in a coil shape. Also good.
There is no limitation also about the magnitude | size of the metal material 11. FIG. However, in consideration of ease of mixing with the ceramic body 12, it is preferable to use a metal material 11 having a uniform size such as powder, granule, sphere, or cuboid.

  The size of the metal material 11 is preferably such that the length of the longest portion of the metal material is ¼ or less of the wavelength of the microwave ceramics to be irradiated. With this configuration, the mixture composed of the metal material and the ceramic body resonates, and the microwave is easily absorbed into the metal material, and the metal material can be efficiently heated to generate metal vapor.

Note that it is not preferable to set the length of the longest part of the metal material to ¼ of the wavelength of the microwave ceramics to be irradiated because the antenna becomes an antenna with respect to the microwave.
The wavelength of the ceramic is derived from λ ₀ / √ε ₁ (λ ₀ : wavelength of electromagnetic wave in vacuum, ε ₁ : dielectric constant of ceramic).

  Here, the longest part of the metal material is, for example, the longest diagonal line in the case of a rectangular parallelepiped, the diameter in the case of a sphere, the longest diameter in the case of a distorted sphere (granular body), and the plate or a thin film. If it is the longest side or diagonal line, or cylindrical, it is the longer of the diameters or sides. In other words, it indicates the diameter of the largest true sphere that circumscribes the metal material at two or more points.

  For example, if the metal material 11 is powdery or granular, the shape is often spherical (including distorted spherical). In this case, the longest diameter of the shape, that is, the diameter in the case of a sphere and the longest diameter in the case of a distorted sphere correspond to the longest portion of the metal material.

  For example, when the metal material 11 is in the form of a plate such as a thin film, the longest side is the longest when the planar shape is a triangle, and the longest when the planar shape is a quadrilateral or more polygon. The length of the diagonal line corresponds to the longest part of the metal material.

  The ceramic body 12 is a sintered body in which an inorganic material is heat-treated and baked. Ceramics having dielectric properties and heat resistance have low dielectric loss with respect to electromagnetic waves and transmit microwaves, so that they are not sufficiently heated even when irradiated with microwaves.

  Examples of the ceramic body 12 include heat-resistant zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, or aluminum nitride. This is because these materials are excellent in heat resistance and easily transmit electromagnetic waves, so that the loss with respect to the electromagnetic waves is small. In other words, even when these ceramics are irradiated with microwaves, they do not react to the microwaves and do not affect the microwaves irradiated under the optimum conditions for heating the target.

The form of the ceramic body 12 is not limited, and may be any shape such as powder, granular (including spherical and distorted spherical bodies, the same applies hereinafter), and a rectangular parallelepiped. However, considering the ease of mixing with the metal material 11, it is preferably in the form of powder or granules. Among them, it is preferable to employ spherical ceramics that are also called ceramic balls.
Further, the size of the ceramic body 12 is not limited. However, considering the ease of mixing with the metal material 11, it is preferable to use a ceramic body 12 having a uniform powder size, granular shape, spherical shape, cubic shape, or the like.

  Although there is no limitation about the preparation means of the mixture 1, For example, the metal material 11 and the ceramic body 12 which are both powdery, granular, or spherical forms are put in the same container (the first container 2 in the figure), and these are placed. The method of mixing moderately can be mentioned. At this time, it is not necessary to mold the mixture 1 by pressing it.

For the mixed body 1, there are a method of mixing the metal material 11 and the ceramic body 12 non-uniformly and a method of mixing uniformly. The embodiment of the mixture 1 shown in FIG. 1 is an example in which the metal material 11 and the ceramic body 12 are mixed non-uniformly. Another embodiment of the mixture 1 shown in FIG. 2 is an example in which the metal material 11 and the ceramic body 12 are uniformly mixed.
Which mixing method should provide good heating efficiency should be appropriately determined according to the specific properties of the metal material 11 and the ceramic 12, the microwave setting, and the like.

By setting the length of the longest part of the mixture to an integral multiple of 1/4 of the wavelength of the microwave to be irradiated, the mixture resonates with the antenna, so that the microwave energy can be confined in the mixture. , Heating efficiency can be increased.
Even if the size of the mixture deviates from the condition of an integral multiple of 1/4, heating with microwaves is possible. The condition that is an integral multiple of 1/4 is a condition that allows the mixture to be heated most efficiently. It can be said that the heating efficiency decreases as the condition deviates from this condition.

  Here, the longest part of the mixture is, for example, the longest diagonal line for a rectangular parallelepiped, the diameter for a spherical body, the longest diameter (longest diameter) for a distorted spherical body (granular body), In the case of a thin film, it is the longest side or diagonal line, and in the case of a cylindrical shape, it is the longer one of diameters or sides. In other words, it indicates the diameter of the largest sphere that circumscribes the mixture at two or more points. .

  When the mixture 1 manufactured as described above is placed in a heating chamber (microwave irradiation chamber) and irradiated with microwaves, the metal material 11 in the mixture 1 absorbs microwaves and generates heat. . When the temperature of the metal material 11 reaches a boiling point (a temperature lower than the boiling point under vacuum), the metal material 11 can be evaporated (or sublimated) to generate a metal vapor 11 '.

  And when the metal vapor | steam 11 'generate | occur | produced in the above-mentioned way and titanium oxide react, this titanium oxide can be reduce | restored and a titanium metal can be obtained.

In order to react these and reduce titanium oxide, titanium oxide may be exposed to and contacted with metal vapor 11 '. The means for contacting is not limited, and publicly known means can be adopted without any particular limitation. For example, the metal material 11 and titanium oxide are installed in the same space, and the metal vapor 11 generated from the metal material 11 is used. Both may be arranged in the same space so that 'reaches titanium oxide. Moreover, even when the space where the metal vapor 11 ′ is generated from the metal material 11 and the space where the titanium oxide is installed are different, the metal vapor 11 ′ can reach the space where the titanium oxide is installed. It is good also as a structure which contacts.

These reactions are represented by the following reaction formulas.
・ When calcium is used as the metal material
TiO ₂ (s) + 2Ca (g) → Ti (s) + 2CaO (s)
(s): Solid, (g): Gas ・ When magnesium is used as the metal material
TiO ₂ (s) + 2Mg (g) → Ti (s) + 2MgO (s)
(s): Solid, (g): Gas

  In addition, about the titanium oxide used for this invention, there is no limitation in the aspect and magnitude | size. In general, titanium oxide is solid at room temperature and is in the form of white powder (powder) or granular form. In the present invention, titanium oxides in these forms can be used.

Subsequently, the apparatus 3 for reducing the oxide by generating the metal vapor 11 ′ by the above-described method and bringing the metal vapor 11 ′ into contact with the oxide will be described.
The present invention is based on the proposal of means for reducing titanium oxide by generating metal vapor by the above-described method and reacting the metal vapor 11 ′ generated thereby with titanium oxide. Is not limited to the configuration of the apparatus 3 described below or a reduction method using the apparatus 3.

FIG. 3 shows an embodiment of an apparatus 3 for carrying out the titanium oxide reduction method according to the present invention.
The apparatus 3 includes at least a heating chamber 4, a first container 2, a second container 6, and a microwave source 7.

  The heating chamber 4 is a space that irradiates the mixture 1 with microwaves and heats it. The form of the heating chamber 4 and the material forming the heating chamber 4 are not limited, but the heating chamber 4 is preferably formed of a material that can withstand high temperatures, does not absorb microwaves, and does not react with metal vapor. For example, it can be formed of alumina refractories, zirconia refractories, magnesia refractories, or may be formed of heat resistant steel or stainless alloy.

The heating chamber 4 is preferably provided with a configuration for installing and fixing a first container 2 and a second container 6 described later. For example, mention may be made of a configuration in which a mounting table 9 (not shown in FIG. 3 but shown in FIG. 5 showing an apparatus used in a verification experiment) is provided as a mounting table for installing and fixing the first container 2 and the like. Can do.
Further, in FIG. 3, the first container 2 and the second container 6 are arranged vertically in series, and the microwave source 7 is arranged in the heating chamber 4, but the first container 2, the second container 6, and the micro in the heating chamber 4. The position of the wave source 7 is not limited. For example, the first container 2 and the second container 6 may be arranged in parallel.

The first container 2 is a container that stores the metal material 11 and the ceramic body 12, that is, the container 1. In other words, the metal material 11 and the ceramic body 12 can be mixed in the first container 2 to produce the mixture 1.
The metal material 11 to be used is preferably calcium or magnesium.
Although the shape of the first container 2 is not limited, for example, as shown in FIG. 3, a bowl-shaped container having an open top, a quartz tube or a crucible having a publicly known shape can be used.

The 2nd container 6 is a container which accommodates the raw material 5 containing an oxide.
The raw material 5 accommodated in the second container 6 is titanium oxide.
Although there is no limitation in the shape of the 2nd container 6, as shown in FIG. 3, the bowl-shaped container by which upper direction was open | released, and the crucible of the publicly known shape can be mentioned, for example.

  In the embodiment shown in FIG. 3, the mixture 1 is stored in the first container 2 and the raw material 5 is stored in the second container 6. However, the mixture 1 and the raw material 5 are stored in the same container. It may be adopted.

The microwave source 7 is a device that includes a microwave oscillator 71 and oscillates microwaves for irradiating the mixture 1 in the heating chamber 4.
As shown in FIG. 3, the microwave source 7 has a configuration in which microwaves oscillated by a microwave oscillator 71 are irradiated from the microwave introduction port 73 to the heating chamber 4 via the waveguide 72.
For the microwave source 7, a publicly known configuration can be adopted, for example, a magnetron can be adopted.

A heat insulating material 8 can be provided in the heating chamber 4.
The heat insulating material 8 is preferably installed around the first container 2 and the second container 6. Thereby, the heat of the mixture 1 generated by the microwave irradiation is not released to the space in the heating chamber 2, and the temperature rise of the mixture 1 can be accelerated and the generation of metal vapor can be accelerated.
However, it is not preferable to install the heat insulating material 8 on the upper part of the first container 2. This is because the metal vapor 11 ′ generated from the first container 2 may be prevented from reaching the second container 6 when installed on the upper part.

A vacuum pump V can be connected to the heating chamber 4.
By reducing the pressure in the heating chamber 4 or the first container 2 and the second container 6 by the vacuum pump V, the metal material 11 can be evaporated at a temperature lower than the boiling point. In addition, impurities and the like in the second container 6 can be removed.

Further, if the mixture is irradiated with microwaves under vacuum, the partial pressure of the metal vapor to be generated (ratio occupied by the metal vapor in the atmosphere) can be increased, whereby the metal vapor 11 ′ and titanium oxide are increased. The reactivity with can be increased.
Furthermore, before the reaction, the oxidation of the metal material can be prevented or suppressed, and after the reaction, the reduced titanium metal can be prevented or suppressed from being oxidized again.
In the present invention, “vacuum” refers to a state where the pressure is lower than atmospheric pressure, and there is no limitation by atmospheric pressure.

  In the heating chamber 4, the microwave is preferably irradiated not only on the mixture 1 accommodated in the first container 2 but also on the raw material 5 (titanium oxide) accommodated in the second container 6. Thereby, if the raw material 5 is also heated to a high temperature, the reactivity with the metal vapor 11 ′ increases.

However, the heating means for the raw material 5 accommodated in the second container 6 is not limited.
In the above-described means, the mixture 1 accommodated in the first container 2 and the raw material 5 accommodated in the second container 6 are installed in a common space called the heating chamber 4 in FIG. 3, and this space is irradiated. Both are heated by microwaves irradiated from the same microwave source.

  On the other hand, it is possible to adopt a configuration in which the space in which the mixture 1 accommodated in the first container 2 is installed and the space in which the raw material 5 accommodated in the second container 6 is installed are different spaces. .

  For example, as in an apparatus 3 ′ shown in FIG. 4, a space (heating chamber 4a) in which the mixture 1 accommodated in the first container 2 is installed and a raw material 5 accommodated in the second container 6 are installed. A configuration in which microwave sources 7a and 7b are provided in each of the spaces (heating chamber 4b) can be given. The microwave source 7a or 7b can oscillate the optimum matching microwave for each of the mixture 1 or the raw material 5 to be heated.

  The heating chambers 4 a and 4 b are connected by a steam passage 41. This steam passage 41 is an opening through which the metal vapor 11 ′ generated in the heating chamber 4 a can pass to the heating chamber 4 b. Thereby, the metal vapor | steam 11 'generate | occur | produced in the heating chamber 4a can pass the vapor | steam channel | path 41, reaches | attains the heating chamber 4b, and can reach the raw material 5 of the heating chamber 4b.

  On the other hand, the steam passage 41 can be configured such that microwaves do not pass through the choke structure. In this case, the microwave energy irradiated to the heating chamber 4a is confined in the heating chamber 4a, and the microwave energy irradiated to the heating chamber 4b is confined in the heating chamber 4b. The irradiated microwave does not affect the other heating chambers 4b and 4a. According to this structure, the heating chamber 4a has an optimum matching microwave for heating the mixture 1 installed therein, and the heating chamber 4b has an optimum matching microwave for heating the raw material 5 installed here. Each wave can be irradiated, and the mixture 1 and the raw material 5 can be efficiently heated with different settings (mainly output and irradiation time).

The position, shape, and material of the vapor passage 41 are not limited, but the side wall can be formed of a conductive material such as metal, and the shape is preferably, for example, a cylindrical shape.
By setting the diameter of the vapor passage 41 to 1/8 or less of the wavelength of the microwave oscillated from the microwave sources 7a and 7b, the microwave can be prevented from passing through the vapor passage 41, and the diameter is preferably Is 1/64 or more, and the length is also 1/4 or more of the wavelength of the microwaves oscillated from the microwave sources 7a and 7b, and preferably 1 wavelength or less. By forming the steam passage 41 in such a size, a choke structure is formed, and the microwave does not leak from the steam passage 41.

  Moreover, as another example of the heating means of the raw material 5 accommodated in the second container 6, a configuration in which a different heat source using an electric furnace or the like is employed for the second container 6 or the raw material 5 accommodated therein. Can be mentioned. In the case of this configuration, the mixture 1 accommodated in the first container 2 is heated by microwaves, and the raw material 5 accommodated in the second container 6 is heated by another heat source using an electric furnace or the like. In this configuration, the configuration in which the mixture 1 and the raw material 5 are installed in the same space (configuration shown in FIG. 3) and the configuration in which the mixture 1 and the raw material 5 are installed in different spaces (shown in FIG. 4). Any one of (configuration) may be adopted.

The above-described titanium oxide reduction method is represented by the following reaction formula.
・ When calcium is used as the metal material
TiO ₂ (s) + 2Ca (g) → Ti (s) + 2CaO (s)
(s): Solid, (g): Gas ・ When magnesium is used as the metal material
TiO ₂ (s) + 2Mg (g) → Ti (s) + 2MgO (s)
(s): Solid, (g): Gas

Although there is no limitation on the aspect of the titanium metal reduced by the above-described method, it is often obtained in a powdery (powdered) or granular form. In this case, the titanium metal adheres or stays as a product together with CaO or MgO on the wall surface of the second container 6 or the heating chamber 4 (including not only the side surfaces but also the top and bottom surfaces). This product is often in the form of a black powder (powdered) or granular, and depending on conditions, it may be obtained as a lighter color than white.

  The method for recovering the reduced titanium metal is not limited. For example, the powdery (powdered) or granular product adhering or staying on the wall of the second container 6 or the heating chamber 4 is scraped off and collected. Can be mentioned. Also, as a tool for collecting, when the apparatus is large, a shovel or a scoop may be used. When the apparatus is small, a teaspoon may be used, and the product adheres or stays. The entire container can also be collected.

<Verification experiment 1>
"Reduction method of titanium oxide using calcium vapor"
A verification experiment was conducted on the method for reducing titanium oxide according to the present invention.

-Outline of apparatus The schematic block diagram of the apparatus 3 used for verification experiment is shown in FIG.
As shown in FIG. 5, a commercially available microwave heating furnace was used in the verification experiment. A microwave source 7 and a vacuum pump V are connected to the heating furnace.

A microwave introduction port 73 is provided in the heating chamber, and a cylindrical heat insulating material 8 is installed on the mounting table 9.
In the heat insulating material 8, a first container 2 in which a mixture 1 made of a metal material 11 and a ceramic body 12 is accommodated is installed. In the first container 2, on the upper part of the mixture 1, A second container 6 containing a raw material 5 (titanium oxide) is installed.

-Mixture and raw material The mixture was prepared by storing the metal material 11 and the ceramic body 12 together in the first container 2 and mixing them.
Here, calcium (Ca) was used as the metal material 11, and zirconia (ZrO ₂ ) was used as the ceramic body.
The calcium used was a spherical granule, and a plurality of these were used. The zirconia used was a spherical granular material also called a ceramic ball, and a plurality of these were used. The diameter of this zirconia is about several hundred μm to 1 mm, and the diameter of calcium is smaller than that of zirconia.

The mixing ratio is 2.00 g (0.05 mol) for calcium and 10.0 g for zirconia.
Since calcium and zirconia are both spherical particles, they were accommodated in the same crucible (first container 2) and mixed to prepare the mixture 1.

  A quartz tube was used as the first container 2, and an alumina crucible was used as the second container 6. The alumina crucible of the second container 6 is slightly smaller than the quartz tube of the first container 6, and the second container 6 is housed in the first container 2.

The second container 6 contained anatase-type titanium oxide as the raw material 5.
The titanium oxide used is a powder having a diameter of 45 μm or less.

Subsequently, the heating chamber 4 was irradiated with microwaves. The inside of the first container 2 and the second container 6 is depressurized to about several tens Pa by the vacuum pump V.
The frequency of the used microwave was 2.45 GHz, the output was controlled in the range of 800 W to 1600 W so that the temperature of the second container 6 was around 1050 degrees, and the microwave was irradiated for 60 minutes.

-Verification result While irradiating the microwave, the temperature course in the 2nd container 6 was measured (refer FIG. 6).
As shown in FIG. 6, about 2 to 3 minutes have passed since the microwave irradiation was started, the temperature in the second container 6 suddenly increased, and reached about 1050 degrees after about 5 minutes. did. Thereafter, the same temperature was maintained until the microwave irradiation was completed.

  Since it is difficult to think that the titanium oxide accommodated in the second container 6 reaches 1000 degrees or more by microwave irradiation, these temperature changes cause the calcium in the first container 2 to evaporate by microwave heating, This is considered to be due to the metal vapor 11 ′ reaching the second container 6.

Therefore, it was verified that by irradiating the above-described mixture 1 with microwaves, calcium constituting the mixture 1 was heated and eventually evaporated to generate metal vapor.
Although the boiling point of calcium is 1484 degrees, the vapor pressure under reduced pressure is considered to be about 1000 ° C.

Here, the first container 2 and the second container 6 were also visually observed together with the measurement of the temperature change.
After irradiation with microwaves, it was confirmed that the inside of the first container 2 became light purple (slightly lighter than light red). This light purple color is known as color development in the plasma state of calcium, and it was confirmed that calcium, which is a metal material, became plasma.
Note that, as described above, in the present invention, the metal vapor includes atoms that are excited by microwaves and atoms excited by microwaves in addition to atoms that are in a gaseous state. Therefore, it has been confirmed that the use of the method according to the present invention generates calcium metal vapor.

Then, after finishing microwave irradiation, the component adhering to the 2nd container 6 or this upper part was taken out, and the X-ray analysis (XRD) was performed.
The result of the X-ray analysis is shown in FIG.
As FIG. 7 shows, the peak which shows titanium (Ti) appeared in the vicinity of the peak which shows CaO. From this result, it was found that titanium oxide was successfully reduced.

The reaction in this verification experiment is expressed as follows.
TiO ₂ (s) + 2Ca (g) → Ti (s) + 2CaO (s)
(s): Solid, (g): Gas

<Verification experiment 2>
"Reduction method of titanium oxide using magnesium vapor"
The verification experiment 2 was implemented about the reduction method of the titanium oxide which concerns on this invention.

The apparatus used in the verification experiment 2 and the manufacturing method of the mixture are the same as those in the verification experiment 1. Magnesium was used as the metal material 11 instead of calcium.
The frequency of the used microwave was 2.45 GHz, the output was controlled so that the temperature of the second container 6 was around 1100 degrees in the range of 800 W to 1000 W, and the microwave was irradiated for 60 minutes.

-Verification result While irradiating the microwave, the temperature course in the 2nd container 6 was measured (refer FIG. 8).
As shown in FIG. 8, when 7 to 8 minutes have elapsed since the start of the microwave irradiation, the temperature in the second container 6 suddenly increased and reached 1000 degrees. After that, around 1100 degrees was maintained until the microwave irradiation was completed.

  Since it is difficult to think that the titanium oxide accommodated in the second container 6 reaches 900 degrees by microwave irradiation, these temperature changes cause the magnesium in the first container 2 to evaporate by microwave heating, and the metal This is considered to be due to the vapor 11 ′ reaching the second container 6.

  Therefore, it was verified that by irradiating the above-described mixture 1 with microwaves, magnesium constituting the mixture 1 was heated and eventually evaporated to generate metal vapor.

Here, the first container 2 and the second container 6 were also visually observed together with the measurement of the temperature change.
After the microwave irradiation, it was confirmed that the inside of the first container 2 became green. This green color is known as the color development in the plasma state of magnesium, and it was confirmed that magnesium as a metal material became plasma.
Note that, as described above, in the present invention, the metal vapor includes atoms that are excited by microwaves and atoms excited by microwaves in addition to atoms that are in a gaseous state. Therefore, it was confirmed that the metal vapor of magnesium was generated by using the method according to the present invention.

Then, after finishing microwave irradiation, the component adhering to the 2nd container 6 or this upper part was taken out, and the X-ray analysis (XRD) was performed.
The result of the X-ray analysis is shown in FIG.
As FIG. 9 shows, the peak which shows titanium (Ti) appeared in the vicinity of the peak which shows MgO. From this result, it was found that titanium oxide was successfully reduced.

The reaction in this verification experiment is expressed as follows.
TiO ₂ (s) + 2Mg (g) → Ti (s) + 2MgO (s)
(s): Solid, (g): Gas

As described above, verification experiments 1 and 2 were performed, and titanium oxide was successfully reduced using the method according to the present invention.
It was found that the resulting reduced titanium obtained by these experiments differed in morphological characteristics from the titanium reduced by the conventional method.

Titanium reduced by a conventional method (a method of heating and evaporating calcium and magnesium in a heating chamber at a high temperature using an electric furnace or the like) is in a molten form, and when it is taken out of the heating chamber The melt was solidified by natural cooling and became a solid.
As a reason for the melt, the conventional method uses means for heating the entire heating chamber at a high temperature using an electric furnace or the like, so that not only calcium which is a metal material but also titanium oxide which is a raw material It is considered that these were heated to a high temperature and reached melting.

  On the other hand, the titanium obtained by using the method according to the present invention is often in the form of powder (powder) and in the form of dry sand. In order to form this as a lump, it is necessary to melt the obtained powder once and then form it by cooling or compressing it.

10 to 11 show photographs taken of the product obtained in the verification experiment 1. FIG. As described above, in the verification experiment 1, calcium metal vapor is used.
FIG. 10 is a photograph of the product taken out after taking out the product adhering to the second container 6 (using an alumina crucible in the verification experiment) after the reaction. In addition, it was confirmed by the said X-ray analysis that the reduced titanium was contained in this product (refer FIG. 7).
According to FIG. 10, since the product containing the reduced titanium was adhered to the wall surface of the second container 6, it is also observed as a solid material imitating its shape. However, when this was closely observed, it was found that fine powdery forms (powder) gathered to form this solid substance.

FIG. 11 is a photograph of the appearance of the product in FIG. 10 in a fine powder form (powder). The solid matter in FIG. 10 collapsed into a powder when a slight force was applied. The solids in FIG. 10 are considered to have extremely weak bonding between the powders forming the solids, and the product obtained by the verification experiment 1 was confirmed to be in a fine powder form (powder). .
In addition, this product contains calcium oxide (CaO) in addition to the reduced titanium (see the XRD result shown in FIG. 7).

  The reason why it is obtained as a powder is that since the present invention uses microwave heating for calcium, which is a metal material, titanium oxide, which is a raw material, melts even when irradiated with microwaves. It is thought that it was not heated so much. Even if a heating means other than microwaves is adopted for the raw material titanium oxide, unlike the conventional technology, the temperature of the raw material can be controlled in the present invention, so the raw material does not reach a high temperature, The raw material or the resulting product does not melt. Therefore, it is considered that the titanium metal obtained using the method according to the present invention was obtained in a powder form (powder).

DESCRIPTION OF SYMBOLS 1 Mixture 11 Metal material 12 Ceramic body 2 First container 3 Apparatus 4 Heating chamber 5 Raw material 6 Second container 7 Microwave source 71 Microwave oscillator 72 Waveguide 73 Microwave inlet 8 Heat insulating material 9 Mounting base V Vacuum pump

Claims (8)

A mixture of a metal material and a ceramic body is irradiated with microwaves and heated, thereby evaporating the metal material, thereby generating metal vapor,
The metal vapor is configured to react with titanium oxide ,
The metal material is calcium, magnesium, sodium or potassium,
The method for reducing titanium oxide , wherein the ceramic body is zirconia, quartz, alumina, boron nitride, silicon carbide, silicon oxide, silicon nitride, aluminum oxide, or aluminum nitride .   The method according to claim 1, wherein the method is performed under vacuum. The method for reducing titanium oxide according to claim 1 or 2 , wherein the titanium oxide is irradiated with microwaves and heated. The shape of the metal material, powdered, reduction method of the titanium oxide according to claim 1 to 3, characterized in that a granular and / or thin film. 5. The method for reducing titanium oxide according to claim 4, wherein the length of the longest portion of the metal material is ¼ or less of the wavelength of the microwave ceramics to be irradiated. The length of the longest portion of the mixture is, the method of reducing a titanium oxide according to any one of claims 1 to 5, characterized in that an integral multiple of a quarter of the wavelength in the ceramic of the microwave irradiation . The method for reducing titanium oxide according to any one of claims 1 to 6 , wherein a heat insulating material is disposed around the mixture. The metallic material and by mixing the ceramic body, further comprising preparing the mixture, the reduction method of the titanium oxide according to any one of claims 1-7.