JP5649060B2 - Titanium oxide particles and method for producing the same - Google Patents

Description

  The present invention relates to titanium oxide particles and a method for producing the same.

  Photocatalysts are attracting a great deal of attention in general society, including the fields of chemistry, physics, engineering and medicine.

In particular, photocatalysts made of titanium oxide (TiO ₂ ) have been put into practical use and are widely used as antibacterial coating materials, materials for decomposing outer walls, and sterilizing materials for operating room walls and floors (non-) Patent Documents 1 and 2).

  In addition, titanium oxide is expected to play an important role in generating fuel cells and clean energy sources as a photocatalyst that generates hydrogen by decomposition of water.

G. K. Mor, K. Shankar, M. Paulose, O. K. Varghese, and C. A. Grimes, “Enhanced Photocleavage of Water Using Titania Nanotube Arrays,” Nano Lett., 5, 191-195, (2005). The Chemical Society of Japan Akira Fujishima (responsible editing) “Ability Training Chemistry School Photocatalyst” Maruzen

  However, when conventional titanium oxide is used as a photocatalyst, there is a problem that the reaction rate is slow.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide titanium oxide particles capable of increasing the reaction rate.

  Another object of the present invention is to provide a method for producing titanium oxide particles capable of increasing the reaction rate.

According to the embodiment of the present invention, the titanium oxide particles are titanium oxide particles having a particle size on the order of nanometers. The titanium oxide particles include titanium oxide composed of an amorphous phase, titanium oxide composed of a polycrystalline phase, and TiZrO ₄ . Including.

  According to the embodiment of the present invention, the method for producing titanium oxide particles includes a first step of putting a pulverized ball, polycrystalline titanium oxide powder, and a solvent into a pulverization container, A second step of rotating and revolving the crushing container for a period of time, and after the second step, the rotation and revolution of the crushing container are stopped and in the crushing container for a second time different from the first time A third step of cooling the contents of the second step and a fourth step of performing the second and third steps a desired number of times.

  Since the titanium oxide particles according to the embodiment of the present invention include titanium oxide composed of an amorphous phase and titanium oxide composed of a polycrystalline phase, there are more defects than titanium oxide composed of only a polycrystalline phase. As a result, when the titanium oxide particles are used as a photocatalyst in the decolorization reaction of the methylene blue aqueous solution, the reduction reaction of the menthylene blue aqueous solution is promoted through defects contained in the amorphous phase.

  Therefore, the reaction rate when titanium oxide particles are used as a photocatalyst can be increased.

It is a conceptual diagram of the titanium oxide particle by embodiment of this invention. It is a perspective view of the planetary ball mill which manufactures the titanium oxide particle shown in FIG. It is a top view of the turntable and the crushing container shown in FIG. It is process drawing which shows the manufacturing method of the titanium oxide particle by embodiment of this invention. It is a figure which shows the measurement result of the X-ray diffraction of the titanium oxide particle shown in FIG. It is a figure which shows the relationship between the ratio of the amorphous in a titanium oxide particle, and total grinding | pulverization time. It is a figure which shows the relationship between the ratio of an amorphous | non-crystalline substance, and rotational speed. It is a figure which shows the relationship between the ratio of Zr atom, and the total grinding | pulverization time. It is a figure which shows the relationship between the ratio of Zr atom, and a rotational speed. It is a figure which shows the relationship between the correlation function measured using dynamic light scattering, and time. It is a figure which shows the correlation function of the dynamic light scattering before and behind the grinding | pulverization by the planetary ball mill shown in FIG. It is the schematic of the ultraviolet irradiation device for verifying photocatalytic ability. It is the schematic of the stirring element shown in FIG. It is a figure which shows the wavelength dependence of a light absorbency. It is a figure which shows the relationship between a light absorbency and the irradiation time of a laser beam. It is a figure which shows the relationship between a light absorbency and the grinding | pulverization time. It is a figure which shows the relationship between the reaction rate of a decoloring reaction, and total grinding | pulverization time. It is a figure which shows the relationship between the reaction speed of a decoloring reaction, and the rotational speed of the revolution at the time of a grinding | pulverization.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

FIG. 1 is a conceptual diagram of titanium oxide particles according to an embodiment of the present invention. Referring to FIG. 1, titanium oxide particles 10 according to an embodiment of the present invention include an amorphous phase 1, a polycrystalline phase 2, and TiZrO ₄ . In FIG. 1, TiZrO ₄ is not shown.

The titanium oxide particles 10 have a particle diameter of, for example, 400 nm and are spherical. Each of the amorphous phase 1 and the polycrystalline phase 2 is made of TiO ₂ . The proportion of the amorphous phase 1 may be smaller or larger than the proportion of the polycrystalline phase 2, but is preferably larger than the proportion of the polycrystalline phase 2.

  FIG. 2 is a perspective view of a planetary ball mill for producing the titanium oxide particles 10 shown in FIG. Referring to FIG. 2, planetary ball mill 100 includes a main body portion 11, a control portion 12, a turntable 13, and a pulverization container 14. The planetary ball mill 100 is a premium line P-7 manufactured by Fritsch.

  The control unit 12 is disposed on the main body 11 on one end side of the main body 11. The control unit 12 includes a touch panel type operation panel 121.

  The turntable 13 is disposed in the space 111 of the main body 11. Then, the turntable 13 rotates at a desired rotation speed, for example, clockwise.

The crushing container 14 has, for example, a volume of 45 cc and is made of zirconia (ZrO ₂ ). The crushing container 14 is installed on the turntable 13 and is attachable to and detachable from the turntable 13. The grinding container 14, for example, rotated at a desired rotational speed counterclockwise.

  The pulverization container 14 is a container for containing a raw material for producing nanoparticles, balls for pulverizing the raw material, and a solvent.

  Although not shown in FIG. 2, a motor for rotating the turntable 13 and the crushing container 14 is built in the main body 11 below the turntable 13.

  The operation panel 121 receives the rotational speed of the rotating disk 13 (= revolving rotational speed Vrev) and the rotational speed of the grinding container 14 (= rotational rotational speed Vrot) from the operator of the planetary ball mill 100. Then, operation panel 121 outputs the received rotation speeds Vrev and Vrot to the motor.

  Then, the motor rotates the turntable 13 and the crushing container 14 at the rotation speeds Vrev and Vrot, respectively.

  And when desired time passes, the operation panel 121 will receive the stop instruction | indication for stopping rotation of the turntable 13 and the crushing container 14, from an operator, and will stop a motor.

  Thus, when the turntable 13 and the crushing container 14 rotate at the rotation speeds Vrev and Vrot, respectively, the crushing container 14 revolves at the rotation speed Vrev and rotates at the rotation speed Vrot. The direction of revolution is opposite to the direction of rotation.

FIG. 3 is a plan view of the turntable 13 and the crushing container 14 shown in FIG. Referring to FIG. 3, the rotating disk 13 is rotated at a rotational speed Vrev clockwise, grinding container 14 is rotated at a rotational speed Vrot counterclockwise.

  Then, the centrifugal force Fct1 is generated by the rotation (= revolution) of the turntable 13, and the centrifugal force Fct2 is generated by the rotation (= rotation) of the crushing container 14. Then, gravity F in which the centrifugal force Fct1 and the centrifugal force Fct2 are combined is generated in the pulverization container 14.

  As a result, the raw material (not shown) put in the crushing container 14 collides with the crushing ball 15 and the wall of the crushing container 14 by gravity F, and continuously receives a strong impact and is crushed.

  In this case, the maximum value of gravity F is 97G (G: gravity acceleration).

  FIG. 4 is a process diagram showing a method of manufacturing titanium oxide particles 10 according to the embodiment of the present invention. Referring to FIG. 4, when the production of titanium oxide particles 10 is started, pulverized balls 15 having a desired diameter, polycrystalline titanium oxide powder, and a solvent are placed in pulverization container 14 (step). S1).

In this case, the pulverized ball 15 is made of, for example, zirconia (ZrO ₂ ) having a diameter of 1 mm. Further, the titanium oxide powder is made of commercially available anatase or P25 and has a particle size on the order of microns. Furthermore, a solvent consists of methanol, for example.

  Then, 40 g of zirconia grinding balls 15, 1.0 g of titanium oxide, and 6.0 g of methanol are placed in the grinding container 14.

  In step S1, the pulverized ball 15, titanium oxide, and the solvent are preferably put in the pulverization container 14 in the order of the pulverized ball 15, titanium oxide, and the solvent.

  When the grinding ball 15, titanium oxide, and the solvent are put into the grinding container 14, n = 1 is set (step S2), and the grinding container 14 is rotated and revolved during the first time (step S3). In this case, the revolution speed Vrev of the grinding container 14 is set to, for example, 600 rpm, and the rotation speed Vrot of the grinding container 14 is set to, for example, 1200 rpm. The first time is 20 minutes or 1 hour.

  After step S3, the rotation and revolution of the crushing container 14 are stopped (step S4), and the contents in the crushing container 14 are cooled during the second time (step S5). In this case, the second time is, for example, 10 minutes or 15 minutes. Further, the contents in the pulverization container 14 are cooled to room temperature by air cooling. Thus, the first time that is the pulverization time is longer than the second time that is the cooling time.

  Thereafter, it is determined whether n = N (N is a desired number of times) (step S6).

  When it is determined in step S6 that n = N is not satisfied, n = n + 1 is set (step S7). And a series of operation | movement returns to step S3, and step S3-step S6 mentioned above are repeatedly performed until it determines with it being n = N in step S6.

  Thereafter, when it is determined in step S6 that n = N, the production of the titanium oxide particles 10 is completed. In addition, when the process shown in FIG. 4 is completed, methanol remains in the pulverization container 14, and the titanium oxide particles 10 are stored in a separate container together with methanol.

  By executing step S3 described above, the titanium oxide powder is pulverized. Further, N is set so that the total time for executing step S3 is in the range of 0.5 hours to 12 hours. For example, when the first time is 1 hour and the total time for executing step S3 is 3 hours, N is set to N = 3 times.

  As described above, by pulverizing the titanium oxide in step S3 and cooling the contents in the pulverization container 14 in step S5, as described later, the reaction rate when the titanium oxide particles 10 are used as a photocatalyst. Can be faster.

  When the first time is 1 hour, the temperature of the contents of the pulverization container 14 is raised to a temperature higher than 40 ° C. when Step S3 is completed. Therefore, by cooling the contents heated to a temperature higher than 40 ° C. in step S5, defects in the amorphous phase 1 can be increased, and the reaction rate when the titanium oxide particles 10 are used as a photocatalyst is increased. Can be fast.

  FIG. 5 is a diagram showing a measurement result of X-ray diffraction of the titanium oxide particles 10 shown in FIG. In FIG. 5, the vertical axis represents the diffraction intensity of X-ray diffraction, and the horizontal axis represents the scattering angle 2θ.

  Curve k1 shows the measurement result of X-ray diffraction of the titanium oxide particles 10, curve k2 shows the measurement result of X-ray diffraction of titanium oxide before pulverization using the planetary ball mill 100, and curve k3 shows The curve k2 is normalized so that the peak at the 25.4 degree scattering angle of the curve k2 matches the peak at the 25.4 degree scattering angle of the curve k1, and the normalized data is subtracted from the curve k1. Indicates.

  Furthermore, the grinding conditions when grinding titanium oxide using the planetary ball mill 100 are as follows. The grinding ball 15 is made of 40 g of zirconia (diameter 1 mmφ), the sample is made of 1.0 g of titanium oxide, the solvent is made of 6.0 g of methanol, and the first time in step S3 shown in FIG. 1 hour, the second time in step S5 shown in FIG. 4 is 15 minutes, the total grinding time is 8 hours, the revolution speed Vrev of the revolution of the grinding container 14 is 600 rpm, and the grinding container 14 The rotation speed Vrot of the rotation is 1200 rpm.

  Referring to FIG. 5, only the peak due to the polycrystalline phase was observed in the titanium oxide before pulverization using planetary ball mill 100 (curve k2).

On the other hand, in the titanium oxide particles 10, the peak due to the polycrystalline phase was remarkably reduced (strength was 1/18), and the signal due to the broad amorphous phase became remarkable (curve k1). Peaks P1 to P3 are peaks caused by TiZrO ₄ . Then, Zr is due to zirconia (ZrO ₂₎ which is a material of the grinding container 14 and grinding balls 15.

Therefore, titanium oxide particles 10, it has been demonstrated that consists of TiO ₂ and TiZrO ₄ Metropolitan consisting consisting TiO ₂ and an amorphous phase consisting of polycrystalline phase.

  FIG. 6 is a graph showing the relationship between the amorphous ratio in the titanium oxide particles 10 and the total pulverization time.

  In FIG. 6, the vertical axis represents the amorphous ratio, and the horizontal axis represents the total grinding time. The pulverization conditions are the same as the pulverization conditions described in FIG. 5, except that the total pulverization time is changed to 0.5, 0.75, 1, 3, 6, 8, and 12 hours. The conditions are as described above. In this case, when the total pulverization time was 0.5 hour and 0.75 hour, the first time in step S3 shown in FIG. 4 was set to 0.5 hour and 0.75 hour, respectively. Further, the amorphous ratio was calculated by dividing the area of the curve k3 shown in FIG. 5 by the area of the curve k1.

  Referring to FIG. 6, the ratio of amorphous increases as the total pulverization time becomes longer, and saturates when the total pulverization time is 8 hours or more. More specifically, the proportion of amorphous increases to about 40% when the total grinding time is up to 1 hour, and increases from about 40% to about 80% when the total grinding time is increased from 1 hour to 3 hours. If it grows rapidly and the total grinding time is longer than 3 hours, it gradually increases and saturates at about 90%. Thus, when the total pulverization time is within 1 hour, the proportion of amorphous is smaller than the proportion of the polycrystalline phase, and when the total pulverization time is 3 hours or more, the proportion of amorphous is less than the proportion of the polycrystalline phase. Also grows.

  Therefore, it was found that the amorphous ratio in the titanium oxide particles 10 increases as the grinding time by the planetary ball mill 100 increases.

  FIG. 7 is a diagram showing the relationship between the amorphous ratio and the rotation speed. In FIG. 7, the vertical axis represents the ratio of amorphous, and the horizontal axis represents the rotational speed of revolution during pulverization by the planetary ball mill 100. Further, the pulverization conditions are those in which the revolution speed Vrev of the pulverization container 14 is changed to 100, 300, 600, 800, and 1000 (rpm) under the pulverization conditions described in FIG. The conditions are as described above. Further, the amorphous ratio was calculated by dividing the area of the curve k3 shown in FIG. 5 by the area of the curve k1.

  Referring to FIG. 7, the amorphous ratio increases as the revolution speed Vrev of the grinding container 14 increases. This is presumably because the impact force applied to the titanium oxide increases as the rotational speed Vrev increases.

  FIG. 8 is a diagram showing the relationship between the ratio of Zr atoms and the total grinding time. In FIG. 8, the vertical axis represents the proportion of Zr atoms, and the horizontal axis represents the total grinding time. The pulverization conditions are the same as those described in FIG. Furthermore, the ratio of Zr atoms was measured by EPMA (Electron Probe Micro Analyzer).

Referring to FIG. 8, the proportion of Zr atoms increases as the total grinding time becomes longer. This is because the collision between the powder of titanium oxide as a raw material and the zirconia (ZrO ₂ ) as the material of the grinding container 14 and the grinding ball 15 increases due to the increase in the total grinding time, and Zr in ZrO ₂ is increased. It is thought that atoms were taken into titanium oxide. Further, the increase in Zr atoms due to the increase in the total pulverization time is in good agreement with the fact that the amorphous ratio increases as the total pulverization time becomes longer as shown in FIG.

  FIG. 9 is a diagram showing the relationship between the ratio of Zr atoms and the rotation speed. In FIG. 9, the vertical axis represents the ratio of Zr atoms, and the horizontal axis represents the rotational speed of revolution during grinding by the planetary ball mill 100. The pulverization conditions are the same as those described in FIG. Furthermore, the proportion of Zr atoms was measured by EPMA.

  Referring to FIG. 9, the ratio of Zr atoms is substantially constant up to a rotational speed Vrev of about 400 rpm, but increases as the rotational speed Vrev increases as the rotational speed Vrev reaches 400 rpm or more. This is because the pulverization of titanium oxide proceeds until the rotational speed Vrev is about 400 rpm. However, since the particle size of the pulverized titanium oxide is relatively large, the amount of Zr atoms taken into the titanium oxide is almost constant. However, when the rotational speed Vrev is 400 rpm or more, the pulverization of the titanium oxide further proceeds, and the particle size of the titanium oxide becomes relatively small, so that the amount of Zr atoms taken into the titanium oxide increases. It is done.

  A method for measuring the particle size of the titanium oxide particles 10 manufactured according to the process shown in FIG. 4 will be described. The particle size of the titanium oxide particles 10 was measured using dynamic light scattering.

  FIG. 10 is a diagram showing the relationship between the correlation function measured using dynamic light scattering and time. The methanol solution containing the titanium oxide particles 10 is irradiated with laser light having a wavelength of 532 nm, and the scattered light scattered by the titanium oxide particles 10 performing Brownian motion is detected by a photomultiplier tube. As a result, the relationship between the correlation function and time shown in FIG. 10 is obtained.

And the correlation function shown in FIG. 10 is analyzed using the cumulant method (Formula (1)). That is, fitting is performed so that G ₁ (τ) shown in Expression (1) matches the correlation function shown in FIG.

  In Equation (1), Γ is the reciprocal of the correlation time, and μ is the polydispersity.

  The diffusion coefficient D is calculated using Γ obtained by the analysis using the equation (1) and the following equation (2).

In Equation (2), k is a scattering vector, n ₀ is the refractive index of the solvent (methanol), λ ₀ is the wavelength of the laser beam (532 nm), and θ is the titanium oxide particle. 10 is a scattering angle of laser light by 10.

  The particle size d was calculated by substituting the diffusion coefficient D calculated using the equation (2) into the following equation.

In Equation (3), k _B is the Boltzmann constant, T is the absolute temperature, and η ₀ is the viscosity of the solvent (methanol).

  FIG. 11 is a diagram showing a correlation function of dynamic light scattering before and after pulverization by the planetary ball mill 100 shown in FIG. 11A shows a correlation function of dynamic light scattering before pulverization by the planetary ball mill 100, and FIG. 11B shows dynamic light after pulverization by the planetary ball mill 100. It is a figure which shows the correlation function of scattering.

The particle diameter of the titanium oxide calculated by the method described above using the correlation function shown in FIG. 11A is 1.011 μm, and the surface area of one grain is 3.21 × 10 ⁻¹² m ² . The volume of one grain was 5.41 × 10 ⁻¹⁹ m ³ .

Moreover, the particle diameter of the titanium oxide particle 10 calculated by the method described above using the correlation function shown in FIG. 11B is 402 nm, and the surface area of one particle is 5.08 × 10 ⁻¹³ m ² . Yes, the volume of one grain was 3.04 × 10 ⁻²⁰ m ³ .

  As described above, the titanium oxide particles 10 manufactured according to the process shown in FIG. 4 using the planetary ball mill 100 have a particle size smaller than that of the titanium oxide powder before pulverization. And the volume of one grain becomes small. The titanium oxide particles 10 are made of nanometer order particles.

  Next, the photocatalytic ability of the titanium oxide particles 10 will be described.

  FIG. 12 is a schematic view of an ultraviolet irradiation apparatus for verifying the photocatalytic ability. Referring to FIG. 12, measurement apparatus 200 includes a stirrer 210, a stirrer 220, a container 230, mirrors 240 and 250, and a laser device 260.

  The container 230 has a quadrangular prism shape and is made of either quartz or sapphire. Note that the container 230 may have a shape other than a quadrangular prism. The stirrer 220 is installed inside the container 230. The container 230 in which the stirrer 220 is placed is installed on the stirrer 210.

  The laser device 260 is composed of, for example, a He / Cd laser, and emits laser light having a wavelength of 325 nm. This laser beam has a light intensity of 8 mW.

  The mirrors 240 and 250 are made of an aluminum mirror. The mirror 240 reflects the laser light emitted from the laser device 260 toward the mirror 250. The mirror 250 irradiates the container 230 with the laser light reflected by the mirror 240.

  The stirrer 220 receives a magnetic force from the stirrer 210 and rotates by the received magnetic force to stir the solution 270 in the container 230. In this case, the rotation speed of the stirrer 220 is 1150 rpm. The stirrer 210 rotates the stirrer 220 by magnetic force.

  FIG. 13 is a schematic view of the stirrer 220 shown in FIG. Referring to FIG. 13, stirrer 220 includes a magnet 221, a protective film 222, and a belt-like member 223. The magnet 221 has a prismatic shape, and has, for example, a hexagonal cross-sectional shape. The magnet 221 has the same polarity as the magnet held by the stirrer 210.

  The protective film 222 is made of, for example, Teflon (registered trademark) and covers the magnet 221. The reason why the protective film 222 covers the magnet 221 is to prevent the magnet 221 from damaging the inner wall of the container 230. The belt-like member 223 is made of Teflon (registered trademark), and is disposed so as to cover the protective film 222 at a substantially central portion in the length direction of the magnet 221.

  Since the magnet 221 of the stirrer 220 has the same polarity as the magnet of the stirrer 210, for example, when the magnet of the stirrer 210 rotates counterclockwise, the magnet 221 receives a magnetic force in the direction of the arrow 224 from the magnet of the stirrer 210. The stirrer 220 rotates in the direction of the arrow 224. As a result, the stirrer 220 stirs the solution 270 in the container 230. In this case, since the stirrer 220 has the strip-shaped member 223, the portion of the protective film 222 other than the portion covered by the strip-shaped member 223 does not contact the bottom surface of the container 230. A gap is formed between the two. As a result, the stirrer 220 easily rotates in the direction of the arrow 224 when the magnet of the stirrer 210 rotates counterclockwise.

  Referring to FIG. 12 again, when measuring the photocatalytic ability of the titanium oxide particles 10, the solution 270 is composed of a methylene blue aqueous solution containing methylene blue represented by the following chemical formula (1).

The methylene blue aqueous solution contains a methanol solution in which about 2 mg of titanium oxide particles 10 are dispersed and 2.94 × 10 ⁻⁵ mol of methylene blue, and the solvent is water. The volume of the methylene blue aqueous solution is 3.0 ml.

  When the laser device 260 irradiates the methylene blue aqueous solution with laser light having a wavelength of 325 nm, the reduction reaction in the following chemical formula (2) proceeds, and the color of the methylene blue aqueous solution changes from blue to colorless. When the laser beam irradiation is stopped, the oxidation reaction of chemical formula (2) proceeds, and the color of the methylene blue aqueous solution changes from colorless to blue.

  After irradiating the methylene blue aqueous solution with a laser beam having a wavelength of 325 nm using the measuring apparatus 200, the absorbance of the methylene blue aqueous solution was measured while changing the wavelength. Absorbance measurement conditions were a bandwidth of 5.0 nm, a scanning speed of 400 nm / min, a start wavelength of 900 nm, an end wavelength of 400 nm, and a data capture interval of 1.0 nm.

  FIG. 14 is a diagram showing the wavelength dependence of absorbance. (A) of FIG. 14 is a figure which shows the wavelength dependence of the light absorbency in the dark state, ie, when not irradiating a laser beam of 325 nm. FIG. 14B is a diagram showing the wavelength dependence of absorbance when a methylene blue aqueous solution containing titanium oxide that is not pulverized using a planetary ball mill 100 is irradiated with a 325 nm laser beam. Further, FIG. 14C is a diagram showing the wavelength dependence of absorbance when a 325 nm laser beam is irradiated to a methylene blue aqueous solution containing titanium oxide particles 10 pulverized using the planetary ball mill 100.

  Curves k4 to k11 in FIG. 14 (b) indicate that the irradiation time of the laser beam having a wavelength of 325 nm is 15 minutes, 30 minutes, 45 minutes, 60 minutes, 75 minutes, 90 minutes, 105 minutes and 120 minutes, respectively. The wavelength dependence of absorbance at a certain time is shown.

  Curves k12 to k19 in FIG. 14 (c) are respectively in the dark state, the irradiation time of laser light having a wavelength of 325 nm is 0.25 minutes, 0.5 minutes, 0.75 minutes, 1 minute, 2 minutes, The wavelength dependence of the absorbance at 5 minutes and 10 minutes is shown.

  Note that the pulverization conditions for producing the titanium oxide particles 10 used for the absorbance measurement shown in FIG. 14C are 1 hour in Step S3 shown in FIG. The time of 2 is 15 minutes, the total time of grinding (= total of the first time) is 6 hours, the revolution speed Vrev of the grinding container 14 is 600 rpm, and the rotation speed Vrot of the grinding container 14 is 1200 rpm. is there.

  Referring to (a) of FIG. 14, when the laser beam having a wavelength of 325 nm is not irradiated, the absorbance spectrum hardly changes even after the lapse of time from 15 minutes to 120 minutes, and is about 662 nm. It has an absorption peak at the wavelength.

  Referring to FIG. 14B, the absorbance has an absorption peak at a wavelength of about 662 nm, and decreases as the irradiation time of the laser light becomes longer (see curves k4 to k11). The decrease in absorbance means that the reduction reaction of chemical formula (2) proceeds and methylene blue is decolorized. Therefore, titanium oxide that has not been pulverized using the planetary ball mill 100 acts as a photocatalyst that takes about 120 minutes to advance the reduction reaction of methylene blue.

  Referring to (c) of FIG. 14, the absorbance has an absorption peak at a wavelength of about 662 nm. The absorbance rapidly decreases when the laser light irradiation time is increased from 0.25 minutes to 0.5 minutes, and further decreases as the laser light irradiation time is longer than 0.5 minutes.

  Thus, the titanium oxide particles 10 pulverized using the planetary ball mill 100 act as a photocatalyst that promotes the reduction reaction of methylene blue in a very short time of 10 minutes or less.

  FIG. 15 is a diagram showing the relationship between the absorbance and the irradiation time of the laser beam. In FIG. 15, the vertical axis represents the absorbance at the wavelength of 662 nm shown in FIG. 14, and the horizontal axis represents the irradiation time of the laser light. A straight line k20 shows the relationship between the absorbance in the dark state and the irradiation time of the laser beam, and a curve k21 shows a case where the methylene blue aqueous solution containing titanium oxide that is not pulverized using the planetary ball mill 100 is irradiated with 325 nm laser light. The curve k22 shows the relationship between the absorbance of the methylene blue aqueous solution containing titanium oxide particles 10 pulverized using the planetary ball mill 100 and the laser light when irradiated with 325 nm laser light. The relationship with irradiation time is shown.

  Referring to FIG. 15, in the dark state, the absorbance hardly changes with the irradiation time of the laser beam (see straight line k20).

  When titanium oxide that is not pulverized using the planetary ball mill 100 is used as a photocatalyst, the absorbance decreases as the irradiation time of the laser light increases (see curve k21).

  On the other hand, when the titanium oxide particles 10 pulverized using the planetary ball mill 100 are used as a photocatalyst, the absorbance decreases very steeply with respect to the irradiation time of the laser light (see curve k22).

If the curve k21 is ₁ the time constant tau when expressed by a function of exp (-t / τ), the time constant in the case of the curve k22 expressed by a function of exp (-t / τ) was tau _2, τ ₂ / τ ₁ = 0.00765. Therefore, it was found that when the titanium oxide particles 10 were used as a photocatalyst, the reduction reaction of methylene blue proceeded 132 times faster than when titanium oxide not pulverized was used as the photocatalyst.

  FIG. 16 is a diagram showing the relationship between the absorbance and the irradiation time of the laser beam. In FIG. 16, the vertical axis represents absorbance at a wavelength of 662 nm, and the horizontal axis represents laser beam irradiation time.

  Moreover, the curves k23 to k30 shown in FIG. 16 (a) are respectively the absorbance and pulverization time of the methylene blue aqueous solution containing Sample 1 to Sample 8 (titanium oxide particles) pulverized using the pulverization conditions in Table 1. Show the relationship.

  In Table 1, sample 1 is titanium oxide having an anatase type crystal structure and is not pulverized. Sample 2 is titanium oxide dedicated to the photocatalyst and is not pulverized. Further, in each of the samples 3 to 8, one grinding time (first time of step S3 shown in FIG. 4) is 1 hour, and cooling time (second time of step S5 shown in FIG. 4). Is 15 minutes.

  Further, FIG. 16B is an enlarged view of the curves k25 to k30 shown in FIG.

  Referring to FIG. 16, the absorbance of the methylene blue aqueous solution containing titanium oxide that has not been crushed decreases as the irradiation time of the laser beam becomes longer (see curves k23 and k24).

  On the other hand, the absorbance of a methylene blue aqueous solution containing crushed titanium oxide decreases sharply with respect to the irradiation time of the laser beam. And the reduction ratio of the absorbance of the methylene blue aqueous solution containing pulverized titanium oxide is larger when the pulverization time is longer (see curves k25 to k30).

  FIG. 17 is a diagram showing the relationship between the reaction rate of the decolorization reaction and the total pulverization time. In FIG. 17, the vertical axis represents the reaction rate, and the horizontal axis represents the total grinding time.

  The black rhombus indicates the relationship between the reaction rate of the methylene blue aqueous solution containing titanium oxide of Samples 1 and 4 to 8 shown in Table 1 and the total grinding time. The white rhombus indicates the samples 2 and 3 shown in Table 1. The relationship between the reaction rate of the methylene blue aqueous solution containing titanium oxide and the total grinding time is shown.

  Furthermore, the reaction rate was calculated by calculating the reciprocal of the time constant τ when the curves k23 to k30 shown in FIG. 16 were expressed by a function of exp (−t / τ).

  Referring to FIG. 17, the reaction rate of the methylene blue aqueous solution containing titanium oxide of P25 increases as the pulverization time becomes longer (see white rhombus).

  Moreover, the reaction rate of the methylene blue aqueous solution containing the titanium oxide of anatase increases as the pulverization time becomes longer (see black diamonds).

Furthermore, the reaction rate increases dramatically when the total pulverization time is 1 hour or more (see white rhombus and black rhombus). This is because, as shown in FIG. 6 , when the total pulverization time is 1 hour or more, the titanium oxide particles 10 contain an amorphous phase, and defects in the titanium oxide particles 10 increase.

  Table 2 shows the rate of increase in the reaction rate of the decolorization reaction with the total grinding time.

In Table 2, the ratio of P25 to the reaction rate is the ratio of the rate of the reaction of anate to the reaction rate of P25 (= 0.03355 (min ⁻¹ )) where the total grinding time is zero.

  From the results shown in Table 2, it is understood that the reaction rate is remarkably increased by pulverizing the titanium oxide composed of anatase, which is about 135 times at the maximum. Moreover, by pulverizing the titanium oxide made of anate, the reaction rate becomes about 29 times or more faster than the reaction rate of P25 used exclusively for the photocatalyst. Furthermore, by pulverizing P25 titanium oxide, the reaction rate is about 37 times that of non-pulverized P25 titanium oxide.

  Thus, by using the titanium oxide particles pulverized according to the process shown in FIG. 4 as a photocatalyst, the reaction rate of the decolorization reaction of methylene blue can be remarkably increased.

  FIG. 18 is a diagram showing the relationship between the reaction speed of the decolorization reaction and the rotation speed of revolution during pulverization. In FIG. 18, the vertical axis represents the reaction speed of the decolorization reaction, and the horizontal axis represents the rotational speed of revolution of the pulverization container 14. The pulverization conditions are those in which the total pulverization time is set to 1 hour and the revolution speed Vrev of the pulverization container 14 is changed to 450 rpm, 600 rpm, 800 rpm, and 1000 rpm in the pulverization conditions shown in Table 1.

  Referring to FIG. 18, the reaction speed increases as the revolution speed Vrev increases. As shown in FIG. 7, the amorphous ratio in the titanium oxide particles 10 increases as the revolution speed Vrev increases. Therefore, considering the results shown in FIG. 7 and the results shown in FIG. 18 together, it was found that the reaction rate of the decolorization reaction increases as the amorphous ratio in the titanium oxide particles 10 increases.

  Table 3 shows the rate of increase in the reaction speed of the decolorization reaction due to the rotational speed of revolution during grinding.

In Table 3, the ratio of P25 to the reaction rate is the ratio of the reaction rate of anatase to the reaction rate of P25 (= 0.03355 (min ⁻¹ )) where the total grinding time is zero.

  From the results shown in Table 3, it can be seen that by pulverizing titanium oxide composed of anate, the reaction speed increases as the revolution speed increases, and is about 91 times at maximum. Moreover, by pulverizing the titanium oxide made of anate, the reaction rate becomes about 21 times or more faster than the reaction rate of P25 used exclusively for the photocatalyst.

  As described above, the titanium oxide particles 10 manufactured according to the process shown in FIG. 4 include the amorphous phase 1 and the polycrystalline phase 2. When the titanium oxide particles 10 are used as the photocatalyst in the decolorization reaction of the methylene blue aqueous solution, the reduction reaction of the methylene blue aqueous solution is promoted through the defects of the amorphous phase 1. Therefore, the reaction rate of the decolorization reaction of the methylene blue aqueous solution can be dramatically increased.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to titanium oxide particles and a method for producing the same.

  DESCRIPTION OF SYMBOLS 1 Amorphous phase, 2 Polycrystalline phase, 10 Titanium oxide particle | grains, 11 Main-body part, 12 Control part, 13 Turntable, 14 Grinding container, 15 Grinding ball, 100 Planetary ball mill, 121 Operation panel, 200 Measuring apparatus, 210 Stirrer, 220 Stirrer, 221 Magnet, 222 Protective film, 223 Strip member, 230 Container, 240, 250 Mirror, 260 Laser device.

Claims (5)

Titanium oxide particles with a particle size of nanometer order,
Titanium oxide consisting of an amorphous phase;
Titanium oxide comprising a polycrystalline phase;
Titanium oxide particles containing TiZrO ₄ . A first step of putting a pulverized ball, polycrystalline titanium oxide powder, and a solvent into a pulverization vessel;
A second step of rotating and revolving the grinding vessel during a first time;
After the second step, the third step of stopping rotation and revolution of the pulverization container and cooling the contents in the pulverization container for a second time different from the first time;
And a fourth step of performing the second and third steps a desired number of times.   3. The oxidation according to claim 2, wherein in the first step, the pulverized ball, the titanium oxide powder, and the solvent are put into the pulverization container in the order of the pulverized ball, the titanium oxide powder, and the solvent. A method for producing titanium particles.   The method for producing titanium oxide according to claim 2 or 3, wherein the first time is longer than the second time.   The method for producing titanium oxide particles according to any one of claims 2 to 4, wherein the rotation speed of the rotation is larger than the rotation speed of the revolution.

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