JP4035373B2 - Method for producing composite oxide of iron oxide and titanium oxide and oxide thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a substance, which is obtained by recrystallizing a mixture of iron oxide and titanium oxide after being atomized and then subjected to high-temperature treatment, and a substance having specificity in electrical characteristics.
[0002]
[Prior art]
Titanium oxide is known as a photocatalyst, and when the photocatalyst is irradiated with light having energy higher than the band cap, electrons are excited from the valence band to the conduction band, and electrons are generated in the conduction band and holes are generated in the valence band. It is known to function as a confirmed and excited photocatalyst.
On the other hand, iron oxide does not show photoactivity like the above-mentioned titanium oxide, but belongs to an n-type semiconductor and is known to be a substance having an excellent catalytic function as an iron-based catalyst.
Therefore, the present inventor came up with the idea that a new compound and function could be obtained by mixing the iron oxide and titanium oxide while researching the photocatalyst, and sought to diligently study this.
[0003]
[Problems to be solved by the invention]
As a result, after a high temperature treatment of a mixture of iron oxide and titanium oxide, a composite oxide was obtained through a recrystallization process, which changed to an oxide exhibiting a suspicious brookite structure of Fe ₂ TiO ₅ and a rutile type. was found to be TiO _2, further was studying this structure, and have reached the found present invention that a specific character Unusual electrical characteristics.
[0004]
[Means for Solving the Problems]
In the method for producing the composite oxide of the present invention, iron oxide and titanium oxide are pulverized into fine particles of about several μm, granulated into granules of about 10 to 300 μm, and the granules are obtained at 1000 ° C. to 1500 ° C. The temperature is maintained at a high temperature for about 1.5 to 2.5 hours, and this is gradually cooled to obtain a recrystallized product.
[0005]
Further, the composite oxide of iron oxide and titanium oxide of the present invention is formed by granulating iron oxide and titanium oxide pulverized into fine particles, and the granular body is heated to about 1 at a high temperature in the range of 1000 ° C to 1500 ° C. It is a composite oxide obtained by holding for about 5 to 2.5 hours and then slowly cooling and recrystallization.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
As described above, the present invention is directed to two substances: iron oxide (Fe ₂ O ₃ ) and titanium oxide (TiO ₂ ).
Titanium oxide is classified into anatase type and rutile type. The anatase type has a vertically long rectangular crystal structure in which oxygen is coordinated around the center titanium, and has a band cap of 3.23 eV. On the other hand, in the rutile type, oxygen is coordinated to the center titanium, and the band cap is 3.02 eV with a short and dense structure.
Iron oxide does not exhibit photoactivity like the above titanium oxide, but belongs to an n-type semiconductor and is a substance excellent in catalytic function as an iron-based catalyst.
[0007]
Both of these are pulverized into fine particles and, for example, put into a ball mill to be pulverized into fine particles of a micrometer unit.
In the high-temperature treatment described later, the fine particles are intended to increase the specific surface area of both to improve the treatment efficiency and to change the surface characteristics, and both become fine particles of about 0.5 to 3 μm. And mixed.
[0008]
Next, the fine particles are granulated into granular particles, and the means thereof is, for example, by a spray drying system.
The spray drying system refers to a system in which an organic solvent such as vinyl acetate is sprayed to agglomerate the original fine particles, while the fine particles are placed in a dry atmosphere and the fine particles are granulated in the drying process.
Thereby, the fine particles are formed in a granular shape of about 10 to 300 μm.
[0009]
The particles may remain in a granular form, but may be pelletized to facilitate handling, for example, a cylindrical shape having a hole with a diameter of 2 mm in a diameter of 7 mm and a height of 9 mm. be able to. At this time, pressurization is performed for pelletization, but press-contact is performed so as to maintain a hollow shape.
[0010]
The pelletized granule or granular material is subjected to high temperature treatment.
High temperature treatment refers to holding for about 2 hours at a temperature in the range of about 1000 ° C. to 1500 ° C., preferably 1320 ° C. After holding at this high temperature, it is naturally cooled and recrystallized to produce a new composite oxidation. Encourage the creation of things.
[0011]
When the structural formula of the compound obtained by the recrystallization action was determined by X-ray diffraction, the following results were obtained.
That is, a chart obtained by X-ray diffraction analysis of a sample of the compound is shown in FIG. 1, and a sharp peak is drawn at the portion marked with ■, and this was considered to be Fe ₂ TiO ₅ . In addition, a peak was drawn at the site marked with ●, which corresponds to rutile TiO ₂ .
As a result, the recrystallized product obtained by high-temperature treatment of the mixture of the two substances is presumed to be Fe ₂ TiO ₅ which is a composite oxide of iron and titanium and rutile TiO ₂ .
[0012]
Further, the surface of the composite oxide was observed with an electron micrograph (SEM) in FIGS. 2 and 3. As a result, a hollow structure in which cavities exist in the particles was confirmed in the granular sample.
[0013]
Next, temperature characteristics such as impedance and capacitance of the recrystallized product were measured with an ICZ meter, and electrical properties were examined.
Regarding the temperature characteristics of the resistance, as shown in FIG. 7, the resistance value at room temperature is about 69 kΩ, which is about 3 * 10 ² Ω · m when converted into resistivity, and can be regarded as a semiconductor region. Further, even when the temperature change of the resistance was observed, the resistance value decreased as the temperature increased, and it was proved to have semiconductor properties. The reason why the slope of the curve is small near room temperature is presumed to be due to moisture absorption in consideration of the temperature change of tan δ in FIG.
[0014]
Next, the temperature characteristics of the relative permittivity and tan δ are as shown in FIGS. 5 and 6, and the relative permittivity is calculated from the measured capacitance. The room temperature capacitance, tan δ, etc. are shown in FIG. 4 below. Street. The relative permittivity increased with increasing temperature, and this tendency was particularly large at a frequency of 10 kHz. Further, the dielectric polarization due to the frequency was large, and the dielectric loss was very large. As a result, when the equivalent circuit of the recrystallized product is estimated, it is considered that the resistor and the capacitor are connected in parallel.
[0015]
[Example 1]
4.8 kg of iron oxide (Fe ₂ O ₃ ) and 4.2 kg of titanium oxide (TiO ₂ ) were put into a ball mill and pulverized for 24 hours. Titanium oxide was anatase type. As a result, fine particles having a size of about 0.5 to 3 μm were mixed. This was subjected to a granulating and drying apparatus (Nippon Vehicle Manufacturing Co., Ltd. Atomizer), sprayed with vinyl acetate as an organic agent, and granulated in a dry atmosphere to give granules of 10 to 300 μm.
This was formed into a cylindrical pellet with a hole having a diameter of 3 mm in a diameter of 10 mm × height of 12 mm by a molding machine. This was put on a heating machine and kept at about 1320 ° C. for 2 hours, and then naturally cooled to obtain a cylindrical pellet having a hole with a diameter of 2 mm in a diameter of 7 mm × a height of 9 mm.
As a result, depending on the X-ray diffractometer, an Fe ₂ TiO ₅ suspect brookite structure as shown in FIG. 1 and a rutile TiO ₂ compound were obtained. The electrical characteristics were as shown in FIGS.
[0016]
【The invention's effect】
The present invention based on the above configuration, the composite oxide is obtained which is estimated to TiO ₂ and changed to oxide and rutile exhibiting brookite structures suspected of Fe ₂ TiO ₅ stepping the process of recrystallization of fine particles, It was also confirmed that this oxide has a unique electrical property.
A wide variety of other applications can be expected, such as the fact that it can be used as a humidity sensor by utilizing the electrical characteristics, for example, the fact that the temperature change in resistance is greatly affected by humidity.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction chart.
FIG. 2 is an electron microscope SE diagram.
FIG. 3 is an electron microscope SE diagram.
FIG. 4 is a table of dielectric specific values of frequency, capacitance, relative permittivity, and tan δ.
FIG. 5 is a graph showing a temperature change of a relative dielectric constant of electrical characteristics.
FIG. 6 is a graph showing a temperature change of tan δ of electrical characteristics.
FIG. 7 is a graph showing a temperature change in resistance of electrical characteristics.

Claims (2)

  Iron oxide and titanium oxide are pulverized into fine particles of about several μm, granulated into granules of about 10 to 300 μm, and the granules are heated to a high temperature in the range of 1000 ° C. to 1500 ° C. for about 1.5 to A method for producing a composite oxide, which is maintained for about 2.5 hours and slowly cooled to obtain a recrystallized product. The method for producing a composite oxide according to claim 1, wherein the recrystallized product is a mixture of Fe ₂ TiO ₅ and rutile TiO ₂ .

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