Process for producing low valence titanium oxide

The present invention relates to low-order titanium oxide used as a conductive material such as a photocatalyst, a thin film electrode, an antistatic agent, which is useful as an environmental purification material for removing harmful substances, deodorizing and deodorizing malodorous substances, antifouling, sterilization, etc. Regarding the manufacturing method.

Titanium oxide has long been used as a white pigment with excellent hiding power and weather resistance, but in recent years, its function as a photocatalyst has attracted attention. Photocatalysts are regulated by the adsorption, oxidative decomposition, and malodorous substances (malodor prevention law) of harmful substances (aldehydes, etc.) by radical substances (hydroxy radicals, superoxide anions) generated when the surface is irradiated with ultraviolet rays. It is a substance that has functions such as deodorant decomposition, antifouling, and sterilization. In recent years, by coating this photocatalyst, developments that utilize these functions have been attempted. Many metal oxides can be used as photocatalysts, and among these, anatase-type titanium oxide having high activity is often used.

On the other hand, Ti₂O₃Low-order titanium oxide (TiOx; 0 <x <2) represented by the above is a paint that utilizes conductivity as an inorganic black pigment that can replace carbon black suspected of having carcinogenicity (see Patent Document 1). As an antistatic agent for plastics, fibers, paper, etc. (see Non-Patent Document 1), as an oxygen absorber (see Patent Document 2), as a secondary battery electrode material (see Patent Document 3), and as described above, it has a photocatalytic function. It is being studied as a material that can be extended to the visible light region (see Patent Document 4).

In the expression of each of the above characteristics, there is a range of oxidation numbers suitable for each application, for example, in the range of 0.2 <x <1.95 for a black pigment, and the conductivity is maximum near x = 1.75 (non-). (See Patent Document 2), 1.5 <x <1.9 as an oxygen absorber, x = 1,1.67,1.85 <x <2 as a secondary battery electrode material, and 1.5 <x <1.95 as a visible light response catalyst. The use of is proposed.

As a method for producing low-order titanium oxide, a method of firing metallic titanium and titanium dioxide in a nitrogen atmosphere, a method of firing titanium dioxide as a starting material in a non-oxidizing or reducing atmosphere, and the like are known. .. It is also disclosed that titanium monoxide is produced by using the pulse plasma method (see Non-Patent Document 3). Further, as a method for producing low-order titanium oxide, a method of reducing titanium dioxide at a temperature exceeding 1000 ° C. under a hydrogen atmosphere is known (Non-Patent Documents 4 to 6).

In the production of low-order titanium oxide by reduction of titanium dioxide, the oxidation number can be controlled to some extent by setting the reaction time, etc., but it takes time to proceed the reduction treatment to the inside of the particles, and sintering is performed by high temperature treatment. It produces a body, and it is difficult to obtain nano-order fine particles. Further, there is a problem such as reduction by an explosive substance such as hydrogen under high heat.

There is an example of using titanium for an electric discharge machining electrode from the viewpoint of high melting point and high strength of titanium, but in electric discharge machining, implementation conditions such as oxide formation are used. From such a technical background, it has been rarely practiced to place an electrode under conditions for producing a metal oxide, such as using a titanium-containing electrode and discharging it in water. In fact, as in Non-Patent Document 3, although there is a report on a method for obtaining titanium monoxide fine particles from metallic titanium by a pulse plasma method, there is no description on controlling the oxidation number of the titanium oxide to be produced.

For applications such as photocatalysts and conductive materials, in addition to oxidation number control, crystal morphology control and particle size distribution control have a great influence on performance development. In the above-mentioned conventional method for producing low-order titanium oxide, it is easy and stable on a scale capable of industrially producing low-order titanium oxide having a nano-order uniform particle size distribution and an arbitrary composition. It is difficult to manufacture and improvements have been sought.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-150240</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2004-137087</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2009-43679</text></patcit><patcit num="4"><text>International Publication WO2000 / 010706</text></patcit></p>

<p><nplcit num="1"><text>"Titanium Oxide" pp. 272-273, published in June 1991, published by Gihodo</text></nplcit><nplcit num="2"><text>Physical Review Vol. 187, pp. 828-833 (1969) Physical Review, 187,828-833 (1969)</text></nplcit><nplcit num="3"><text>Journal of Nanoscience and Nanotechnology Vol. 7, pp. 3157-3159 2007 J.of.Nanoscience and Nanotechnology Vol 7 3157-3159,2007</text></nplcit><nplcit num="4"><text>ISIJ International Vol. 48, No. 6, pp. 729-738 2008 ISIJ International, Vol.48 (2008), No.6, pp.729-738</text></nplcit><nplcit num="5"><text>Journal of the Electrochemical Society Vol. 155, No. 4, pp. B321-B326 2008 J. Electrochem. Soc., 155 (4), B321-B326 (2008)</text></nplcit><nplcit num="6"><text>Electrochemistry Communications Vol. 7, pp. 183-188 2005 Electrochem. Communi., 7 (2005), 183-188</text></nplcit></p>

<p> An object of the present invention is to provide a method capable of stably producing low-order titanium oxide fine particles having an arbitrary composition on an industrial scale in view of the above-mentioned problems of the prior art, particularly iron and nickel. Conductive compounds such as chlorine and sulfuric acid<u style="single">root</u>It is an object of the present invention to provide a method capable of stably producing fine particles of titanium oxide having a valence showing conductivity without containing corrosive substances such as corrosive substances on an industrial scale.</p>

<p> The present inventors have made extensive studies to achieve the above object, and have found that low-order titanium oxide can be obtained by discharging between two electrodes including at least one titanium oxide-containing electrode in an aqueous medium. , The present invention has been reached.</p><p> That is, according to the present invention, the following are provided.</p><p>[1] A method for producing low-order titanium oxide, which comprises producing low-order titanium oxide by electric discharge between two electrodes including at least one titanium-containing electrode in an aqueous medium .</p><p>[2] The method for producing low-order titanium oxide according to [1], wherein the discharge is a direct current discharge.</p><p>[3] The method for producing low-order titanium oxide according to [2], wherein the discharge is a direct current continuous discharge.</p><p>[4] The method for producing low-order titanium oxide according to [2], wherein the discharge is a DC pulse discharge.</p><p>[5] A low-order titanium oxide produced by the method according to any one of [2] to [4], which is represented by the composition formula TiOx (0.15 &lt;x &lt;2.0).</p><p>[6] The method for producing low-order titanium oxide according to [1], wherein the low-order titanium oxide is produced by electric discharge between two electrodes including at least one titanium oxide-containing electrode.</p><p>[7] The method for producing low-order titanium oxide according to [6], wherein the low-order titanium oxide is produced by electric discharge between the titanium oxide-containing electrode and the metallic titanium electrode.</p><p>[8] The method for producing low-order titanium oxide according to [6], wherein low-order titanium oxide is produced by electric discharge between two titanium oxide-containing electrodes.</p><p>[9] The method for producing low-order titanium oxide according to any one of [6] to [8], wherein the discharge is a direct current continuous discharge.</p><p>[10] The method for producing low-order titanium oxide according to any one of [6] to [8], wherein the discharge is a pulse discharge.</p><p>[11] The method for producing low-order titanium oxide according to any one of [6] to [10], wherein the titanium oxide-containing electrode contains conductive titanium oxide.</p><p>[12] The method for producing low-order titanium oxide according to any one of [6] to [10], wherein the titanium oxide-containing electrode contains metallic titanium and non-conductive titanium oxide.</p><p>[13] A low-order titanium oxide produced by the method according to any one of [6] to [12] represented by the composition formula TiOx (1.5 &lt;x &lt;2.0).</p><p>[14] Electrodes containing conductive titanium oxide.</p><p>[15] The electrode according to [14] used in the production of low-order titanium oxide.</p>

<p> According to the production method of the present invention, low-order titanium oxide fine particles having an arbitrary composition can be stably produced on an industrial scale.</p><p> According to one aspect of the present invention, low-order titanium oxide having an arbitrary composition can be produced by direct current discharge between two electrodes including at least one titanium-containing electrode.</p><p> According to another aspect of the present invention, low-order titanium oxide can be produced by electric discharge between two electrodes including at least one titanium oxide-containing electrode. In this embodiment, a reduction reaction occurs at one pole and an oxidation reaction occurs at one pole. Therefore, as compared with the conventional bipolar oxidation reaction, one of them is carried out in a reducing manner, so that there is an advantage that the production rate of the target low-order titanium oxide is increased. According to the conventional bipolar oxidation reaction, an oxidizing electrode and a reducing electrode are formed in the case of pulse or DC discharge, so that when the reducing electrode is metallic titanium, the reaction in water becomes extremely slow, and the formation rate is low. There was a problem. In this method, since the reduction reaction is caused by the electrode containing titanium oxide, such a problem that the production rate is lowered can be solved. In addition, since the reaction is promoted by generating a high current but relatively low voltage discharge in water, it does not require special equipment or danger prevention equipment, and it is not in a reducing atmosphere, so it is special. There are advantages such as no need for a material reactor.</p><p> Further, the low-order titanium oxide obtained in the present invention has excellent conductivity, and is expected to be developed as various electronic devices and photocatalyst applications. In particular, it can be expected to be used as a secondary battery electrode material.</p>

<figref num="1">It is an X-ray diffraction spectrum of Sample 1-1.</figref><figref num="2">It is a thermogravimetric analysis chart of sample 1-1.</figref><figref num="3">It is an X-ray diffraction spectrum of Sample 1-2.</figref><figref num="4">It is a thermogravimetric analysis chart of sample 1-2.</figref><figref num="5">It is an X-ray diffraction spectrum of Sample 1-3.</figref><figref num="6">It is a thermogravimetric analysis chart of Sample 1-3.</figref><figref num="7">It is an X-ray diffraction spectrum of Sample 2-1.</figref><figref num="8">It is a thermogravimetric analysis chart of sample 2-1.</figref><figref num="9">It is an X-ray diffraction spectrum of Sample 2-2.</figref><figref num="10">It is a thermogravimetric analysis chart of sample 2-2.</figref><figref num="11">It is an X-ray diffraction spectrum of Sample 2-3.</figref><figref num="12">It is a thermogravimetric analysis chart of sample 2-3.</figref><figref num="13">It is an X-ray diffraction spectrum of Sample 2-4.</figref><figref num="14">It is a thermogravimetric analysis chart of sample 2-4.</figref><figref num="15">It is a Raman spectrum of sample 1-1.</figref><figref num="16">It is a Raman spectrum of sample 1-2.</figref><figref num="17">It is a Raman spectrum of Sample 1-3.</figref><figref num="18">It is a Raman spectrum of Sample 1-4.</figref><figref num="19">It is a Raman spectrum of Samples 1-5.</figref><figref num="20">It is a Raman spectrum of sample 2-1.</figref><figref num="21">It is a Raman spectrum of sample 2-2.</figref><figref num="22">It is a Raman spectrum of sample 2-3.</figref><figref num="23">It is a Raman spectrum of sample 2-4.</figref><figref num="24">It is a Raman spectrum of sample 2-5.</figref><figref num="25">It is a Raman spectrum of sample 2-6.</figref>

The method for producing low-order titanium oxide of the present invention is characterized in that it is produced by electric discharge between two electrodes including at least one titanium oxide-containing electrode in an aqueous medium. The mechanism of low-order titanium oxide formation by electric discharge is presumed as follows. That is, when a voltage exceeding the dielectric breakdown voltage is applied between the electrodes facing each other across the aqueous medium, a discharge is generated, and the titanium oxide in the electrodes melted by the plasma generated during the discharge is dissipated to the aqueous medium and reacts with water. At the same time, it is rapidly cooled to generate fine particles.

The two electrodes need to be sufficiently conductive to cause a discharge between the electrodes. The required conductivity depends on the electrode shape, the conductivity of the medium, and the electrode voltage that can be applied deviceically, but at least the volume conductivity is 10.^-7[S / cm] or more, preferably approximately volumetric conductivity 10^-5[S / cm] or higher is preferable.

As for the two electrodes, lower-order titanium oxide can be obtained by using two metallic titanium electrodes. It is also possible to obtain a mixed oxide by a method of using an alloy containing another metal in a titanium base, or a method of using metallic titanium for one electrode and another type of electrode for the other electrode. If a titanium-containing electrode is used for at least one of them, the material of the other electrode is not particularly limited as long as it can maintain its shape at room temperature and can be discharged, and silicon, tin, aluminum, indium, etc. Main group metals such as antimony and bismuth, transition metals such as cobalt, iron, copper, silver, manganese, nickel, zinc, zirconium and tungsten, graphite and the like can be used.

In one aspect of the present invention, a titanium oxide-containing electrode is used for at least one of the electrodes. The method for imparting conductivity to the titanium oxide-containing electrode is not particularly limited, and the purity varies depending on the application, but includes (1) a method using conductive titanium oxide as an electrode, and (2) metallic titanium and titanium oxide. A method of adopting an electrode consisting of the above can be used.

When conductive titanium oxide is used as an electrode, a molded product of conductive titanium oxide alone can be used. The electrode containing conductive titanium oxide may further contain non-conductive titanium oxide.

When an electrode containing metallic titanium and titanium oxide is used, the titanium oxide may be conductive or non-conductive, and the sintered body of the mixture, the titanium oxide thin film on the metallic titanium. Can be used.

In order to ensure the conductivity of the electrode, the ratio of the conductive components such as conductive titanium oxide and metallic titanium to the non-conductive titanium oxide 1 is preferably 10 or more on a weight basis.

As a method for producing a conductive titanium oxide electrode and an electrode containing metallic titanium and conductive titanium oxide, for example, a method using high heat such as plasma spraying, arc spraying, or high-speed frame spraying of titanium oxide causes oxygen defects. There is a method of molding while making the above-mentioned method, or a method of integrally molding the conductive titanium oxide in an atmosphere of an inert gas such as nitrogen by a method such as spraying or pressing.

Examples of a method for producing an electrode containing metallic titanium and non-conductive titanium oxide include a method in which particles of both metallic titanium and non-conductive titanium oxide are mixed and integrally molded by a method such as pressing or sintering. ..

Low-order titanium oxide can be obtained by using the above titanium oxide-containing electrode as two electrodes, or by using the above titanium oxide-containing electrode and the metallic titanium electrode.

The electrode may be in any form such as a rod shape, a wire shape, and a plate shape. Regarding the sizes of both poles, they may have shapes such that either size is different.

In the present invention, lower-order titanium oxide is produced in an aqueous medium. The aqueous medium used in the present invention is not particularly limited, but the proportion of water in the medium is preferably 50% by weight or more, and usually water or a mixture of water and a water-soluble organic solvent is used. Examples of the water-soluble organic solvent include alkylene glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,4-butanediol; diethylene glycol, tetraethylene glycol, and the like. Examples thereof include oxyalkylene glycols such as polyethylene glycol and their methyl ethers and ethyl ethers. In order to simply obtain low-order titanium oxide, ion-exchanged water or the like may be used, and the oxidation number can be controlled by adding hydrogen peroxide and controlling the temperature.

The amount of the aqueous medium used is not particularly limited, but it is sufficient that the closest contact portions of the two electrodes serving as the discharge surfaces are contained in the medium and a sufficient amount is sufficient for heat diffusion for plasma sinking.

Either direct current or alternating current may be used as the current applied between the electrodes for discharge, and in the case of alternating current, rectification may be performed using a diode.

In the present invention, low-order titanium oxide is produced by discharging between two electrodes in an aqueous medium. The discharge voltage is not particularly limited, and is usually in the range of 20 to 500V, preferably in the range of 60 to 400V, more preferably in the range of 80 to 300V in consideration of safety and the need for special equipment.

The discharge current is not particularly limited, and is usually carried out in the range of 1 to 200 A. Considering the amount of production and energy efficiency, it is preferable to carry out in the range of 2 to 150 A, and more preferably in the range of 5 to 120 A.

The discharge may be continuous (continuous discharge) or pulsed (pulse discharge). Since the environment of the generated plasma differs depending on the discharge method, the oxidation number distribution, particle size distribution, and crystal morphology of the obtained low-order titanium oxide change.

The pulse interval when the pulse discharge is applied is not particularly limited, but is preferably 0.01 microsecond to 100 msec, more preferably 0.1 microsecond to 50 msec. If the interval at which the discharges are applied is too short, the rest time for plasma sinking from the immediately preceding discharge is not sufficient, which causes the distribution of products to vary, which is not preferable. Further, if the discharge interval is too long, the amount of production is significantly reduced, which is economically unfavorable.

The duration per pulse discharge varies depending on the applied voltage and current, but is usually 1 to 500 microseconds, and is preferably 5 to 300 microseconds in consideration of discharge efficiency. If the discharge time is too long, the product selectivity peculiar to pulse discharge is lowered, which is not preferable. Further, if the discharge time is too short, sufficient energy is not supplied and the production efficiency of low-order titanium oxide is lowered, which is not preferable.

The shape of the applied pulse voltage is not particularly limited, and discharge can be performed by a method such as a sine wave, a rectangular wave, or a triangular wave. Considering the efficiency with respect to the energy to be discharged, the application of a square wave is preferable.

The temperature of the water-based medium at the time of discharging is not particularly limited and depends on the type and amount of the water-based medium, but is usually carried out in the range of room temperature to 100 ° C. If the temperature is too high, the vapor pressure of the water-based medium used increases, and the time during which continuous discharge is possible is shortened, which may not be preferable. Further, if the temperature is too low, not only the viscosity of the aqueous medium increases and the reactivity decreases, but also the diffusibility of the product is impaired, which may be unfavorable.

In the present invention, it is also possible to give vibration to the electrodes. By applying vibration, there is no retention of the product deposited between the electrodes, and not only the adhesion of the reaction product on the retained product can be suppressed, but also the discharge is efficiently performed, which is preferable. The method of giving vibration is not particularly limited, and a method of giving vibration periodically or intermittently may be used.

The atmosphere in which the present invention is carried out is not particularly limited, and can be carried out under any of reduced pressure, pressure, and normal pressure. However, in consideration of safety and operability, nitrogen, argon, etc. are usually used. Conduct in an inert gas atmosphere.

Since the produced low-order titanium oxide is deposited in a liquid, the low-order titanium oxide of the present invention can be obtained as fine particles by general methods such as filtration, centrifugation, washing with water, and drying.

In the above procedure, the oxidation number of low-order titanium oxide is adjusted to TiOx (0.15 &lt;x) by appropriately adjusting the method for preparing the titanium oxide-containing electrode, the temperature of the aqueous medium, additives such as hydrogen peroxide, and the current application method. It can be any value between &lt;2.0, in particular 1.5 &lt;x &lt;2.0). Further, by keeping these conditions constant from the start to the end of the reaction, the particle size distribution and crystal morphology of the reaction products can be made uniform.

Further, the structure of the low-order titanium oxide of the present invention can be thermally changed. The low-order titanium oxide of the present invention obtained by electric discharge has a very short reaction time and is rapidly cooled, so that it may be produced in a thermally unstable structure. Therefore, it is also possible to calcin the low-order titanium oxide under an inert gas atmosphere (non-oxidizing atmosphere) within a range in which the oxidation number does not change and the particles do not increase due to aggregation. ..

The temperature of the firing process is typically in the range of 200 to 1800 ° C, preferably in the range of 300 to 1000 ° C to provide thermal stability.

The firing treatment time is not particularly limited, but may be a time sufficient for structural change, and is usually in the range of 10 minutes to 24 hours, preferably 30 minutes to 12 hours in consideration of effectiveness and economy. Is the range of.

After firing, it can be taken out into the air after being cooled in a non-oxidizing atmosphere to a temperature at which an oxidation reaction does not occur, usually 200 ° C. or lower.

<p> Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Each physical property value in the example was measured by the following method.</p><p>(Determination of composition) It was calculated from the amount of weight increase when a sufficiently dried sample was oxidized to 1000 ° C at a heating rate of 5 ° C / min in the air using a thermogravimetric analyzer.</p><p> (Example 1-1) 200 g of ion-exchanged water was placed in a 300 ml beaker and kept at 30 ° C using a bath. Two metal titanium electrodes (purity 99% or more) with a diameter of 5 mm and a length of 100 mm, whose ends are cut diagonally (about 45 degrees), are inserted into this ion-exchanged water, and the diagonally cut end face is 0.5 mm. They were arranged so as to face each other at intervals, and vibration was applied to suppress the accumulation of reaction products on the electrode surface and increase the reaction efficiency. Each electrode was connected to a DC power supply, and a 200 V, 8 A rectangular wave pulse DC voltage was applied in accordance with the electrode vibration, and the discharge was repeated with a discharge interval of 20 milliseconds and a discharge time of 200 microseconds.</p><p> At the same time as the discharge started, the formation of solid fine particles was observed. The electrodes were moved according to the wear of the electrodes, and after a discharge operation for 5 hours, the produced solid fine particles were separated by centrifugation. Then, after washing with 200 ml of ion-exchanged water, the particles were dried with hot air at 110 ° C. to obtain 11.3 g (Sample 1-1) of fine particles having a black appearance.</p><p> The composition of Sample 1-1 was estimated by thermogravimetric analysis. The weight change due to oxidation was saturated at around 900 ° C, which was a 35.6% increase from room temperature. The appearance of the sample after oxidation treatment is white, and TiO is obtained from X-ray structural analysis.₂Was identified. From this result, the average value of the composition of Sample 1-1 was estimated to be TiOx (x = 0.689).</p><p> The X-ray diffraction spectrum of Sample 1-1 is shown in FIG. 1 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 1-1 is shown in FIG.</p><p> (Example 1-2) In Example 1-1, the same operation as in Example 1-1 was performed except that the temperature of the ion-exchanged water was set to 90 ° C, and 9.0 g of fine particles having a black appearance (sample). 1-2) was obtained. Sample 1-2 was estimated to be x = 1.713 as a result of thermal analysis.</p><p> The X-ray diffraction spectrum of Sample 1-2 is shown in FIG. 3 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 1-2 is shown in FIG.</p><p> (Example 1-3) 200 g of ion-exchanged water was placed in a 300 ml beaker and kept at 30 ° C using a bath. Two metal titanium electrodes (purity 99% or more) with a diameter of 5 mm and a length of 100 mm, whose ends are cut diagonally (about 45 degrees), are inserted into ion-exchanged water, and the diagonally cut end faces are separated by 0.5 mm. It was arranged so as to face each other. Each electrode was connected to a DC power supply, and the electrodes were gradually brought closer to each other with a voltage of 200 V applied to cause a discharge. The electrode was moved according to the wear of the electrode to maintain the continuous discharge state. The direct current at the time of stable discharge was 3A.</p><p> At the same time as the discharge started, precipitation of solid fine particles was observed. After a 2-hour discharge operation, the produced solid fine particles were separated. Then, after washing with 200 ml of ion-exchanged water, it was dried with hot air at 110 ° C. to obtain 15.1 g (Sample 1-3) of a powder having a blue appearance. Sample 1-3 was estimated to be x = 1.961 as a result of thermogravimetric analysis.</p><p> The X-ray diffraction spectrum of Sample 1-3 is shown in Fig. 5 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 1-3 is shown in Fig. 6.</p><p> (Example 1-4) In Example 1-1, the same procedure as in Example 1-1 was performed except that the output current was set to 20 A.</p><p> The formation of solid fine particles was observed at the same time as the start of discharge, and after a 5-hour discharge operation, the formed solid fine particles were separated by centrifugation. Then, it was washed with 200 ml of ion-exchanged water and dried with hot air at 110 ° C. to obtain 18.6 g of fine particles having a black appearance (Sample 1-4).</p><p> This sample is TiO in the same manner as in Example 1-1.₂When oxidized to, the weight increase was 35.4%, so the average value of the composition of Sample 1-4 was estimated to be TiOx (x = 0.694).</p><p> (Example 1-5) In Example 1-1, the same procedure as in Example 1-1 was performed except that the output current was set to 60 A.</p><p> The formation of solid fine particles was observed at the same time as the start of discharge, and after a 5-hour discharge operation, the formed solid fine particles were separated by centrifugation. Then, it was washed with 200 ml of ion-exchanged water and dried with hot air at 110 ° C. to obtain 27.0 g (Sample 5) of fine particles having a black appearance.</p><p> This sample is TiO as in Example 1-1.₂When oxidized to, the weight increase was 35.7%, so the average value of the composition of Samples 1-5 was estimated to be TiOx (x = 0.686).</p><p>(Example 2-1) 200 g of ion-exchanged water was weighed in a 300 ml beaker and kept at 30 ° C in a bath. In this ion-exchanged water, two titanium oxide-containing electrodes of a metal titanium square rod having a cross section of 5 mm on both sides and a length of 200 mm and having a conductive titanium oxide film having a thickness of 0.5 mm formed on the side surface in the longitudinal direction are inserted. , The sides were arranged at an orthogonal distance of 0.1 mm between the poles. Here, the titanium oxide-containing electrode is an argon / hydrogen plasma sprayer (manufactured by Meteyu) with a power output of 45 kw, and is a normal titanium dioxide powder sized to an average particle size of 44 microns (company name: Sakai Chemical Industry, trade name). : FTR700 primary particle size 200 nm) was sprayed into argon 10 L / min and hydrogen 1 L / min, and formed on a titanium metal square rod to a thickness of 0.5 mm. The film formation time was 3 minutes. At this time<u style="single">leather</u>From the result of XRD, the titanium oxide of the film is tetravalent titanium oxide (TiO).₂) Is the main component, and it was found that it exhibits conductivity due to a slight oxygen deficiency. Each electrode was connected to a rectified AC power supply, a 200V, 8A square wave pulse voltage was applied between the electrodes, and the discharge was repeated with a discharge interval of 20 milliseconds and a discharge time of 200 microseconds. The discharge occurred only at the intersection, and the conductive titanium oxide film on the discharged part was consumed. Both electrodes were slid in the longitudinal direction while controlling so that the titanium square bar inside was not exposed due to the consumption of the conductive titanium oxide film, and electric discharge was always caused between the conductive titanium oxide films. The electrode slide speed was 5 mm / min.</p><p> Upon the start of discharge, the formation of solid fine particles was observed in the water. The electrode was moved according to the consumption of the conductive titanium oxide film used for the electrode, and after a 30-minute discharge operation, the produced solid fine particles were separated by centrifugation. Then, after washing with 200 ml of ion-exchanged water, the particles were dried with hot air at 110 ° C. to obtain 3.1 g of fine particles having a black appearance (Sample 2-1).</p><p> The composition of Sample 2-1 was estimated by thermogravimetric analysis. The weight change due to oxidation was saturated at around 900 ° C and increased by 5.54% from room temperature. The appearance of the sample after oxidation treatment is white, and TiO is obtained from X-ray structural analysis.₂Was identified. From this result, the average value of the composition of Sample 2-1 was estimated to be TiOx (x = 1.738). When the composition of the conductive titanium oxide film before discharge was similarly estimated, it was TiOx (x = 1.844).</p><p> The X-ray diffraction spectrum of Sample 2-1 is shown in FIG. 7 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 2-1 is shown in FIG.</p><p>(Example 2-2) In Example 2-1 except that a metal titanium square bar having no titanium oxide film and having two sides of 5 mm and a length of 200 mm is used as one of the electrodes. The same operation as in 2-1 was carried out to obtain 1.7 g (Sample 2-2) of fine particles having a black appearance. Sample 2-2 was estimated to be x = 1.766 as a result of thermal analysis.</p><p> The X-ray diffraction spectrum of Sample 2-2 is shown in Fig. 9 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 2-2 is shown in Fig. 10.</p><p>(Example 2-3) In Example 2-1 a non-conductive titanium oxide film having a thickness of 0.01 mm was formed on the side surface in the longitudinal direction of a metal titanium square rod having two sides of a cross section of 5 mm and a length of 200 mm. The same operation as in Example 2-1 was carried out except that two titanium oxide-containing electrodes were used, and 0.03 g (Sample 2-3) of fine particles having a blue appearance was obtained. Here, the titanium oxide-containing electrode is an ordinary titanium dioxide powder (company name: Sakai Chemical Industry Co., Ltd.) that has been sized to an average particle size of 5 microns with an argon / hydrogen plasma sprayer (manufactured by Meteyu) with a power output of 45 kw. Name: STA-100A primary particle size 10 nm) was sprayed into argon 10 L / min and hydrogen 1 L / min, and formed on a titanium metal square rod to a thickness of 0.01 mm. Sample 2-3 was estimated to be x = 1.965 as a result of thermal analysis. When the composition of the non-conductive titanium oxide film before discharge was similarly estimated, it was TiOx (x = 2.000).</p><p> The X-ray diffraction spectrum of Sample 2-3 is shown in FIG. 11 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 2-3 is shown in Fig. 12.</p><p>(Example 2-4) In Example 2-1 the discharge was the same as in Example 2-1 except that the discharge was continuous DC discharge (200V, 10A), and the appearance was blue fine particles, 2.7 g (Sample 2). -4) was obtained. The average composition of Samples 2-4 was estimated to be TiOx (x = 1.579).</p><p> The X-ray diffraction spectrum of Sample 2-4 is shown in FIG. 13 (the vertical axis is the intensity and the horizontal axis is 2θ).</p><p> The thermogravimetric analysis chart of Sample 2-4 is shown in FIG.</p><p>(Example 2-5) In Example 2-1 except that a mixed solution of 20 g of tetraethylene glycol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) and 180 g of ion-exchanged water was used instead of 200 ml of ion-exchanged water. The same procedure as in 1 was carried out to obtain 3.0 g (Sample 2-5) of fine particles having a black appearance. The average value of the composition of Sample 2-5 was estimated to be TiOx (x = 1.738), and the XRD measurement result obtained the same spectrum as that of Sample 2-1.</p><p>(Example 2-6) In Example 2-1, a titanium dioxide powder (company name: Sakai Chemical Industry, trade name: FTR700 primary particle diameter 200 nm) was used as a titanium oxide electrode in a discharge plasma sintering machine (SPS Syntex Co., Ltd.). Sintered for 20 minutes at 600 ° C and 25 MPa using SPS-1050) manufactured by the company, length 200 mm, width 5 mm, thickness 2 mm, density 3.9 g / cm.³An electrode made of conductive titanium oxide was obtained. The same procedure as in Example 2-1 was carried out except that this electrode was used, and 3.4 g (Sample 2-6) of fine particles having a black appearance was obtained. The average value of the composition of Sample 2-6 was estimated to be TiOx (x = 1.737), and the XRD measurement result obtained the same spectrum as that of Sample 2-1.</p><p> The Raman spectra of Samples 1-1 to 2-6 were measured (measured with NRS-3100 manufactured by JASCO Corporation). These spectra are shown in Figures 15 to 25 (in these figures, the vertical axis is intensity and the horizontal axis is cm.^-1Is. ). Table 1 shows the correspondence between samples 1-1 to 2-6 and FIGS. 15 to 25.</p><p><tables num="1"><img file="JP5505738B2_D0001.tif" /></tables></p><p> From the above Raman spectrum, it can be seen that the low-order titanium oxide obtained in the present invention shows a characteristic peak in the Raman spectrum.</p>

According to the production method of the present invention, low-order titanium oxide having an arbitrary composition can be stably produced on an industrial scale, and has great industrial usefulness.

Further, the low-order titanium oxide obtained in the present invention has excellent conductivity, and is expected to be developed as various electronic devices and photocatalyst applications. In particular, it can be expected to be used as a secondary battery electrode material.