POWDER AND DISPERSION

Abstract

A powder containing: a first particle having a first crystal composition; and a second particle having a second crystal composition different from the first crystal composition, wherein each of the first crystal composition and the second crystal composition contains at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

Claims

1. A powder comprising: a first particle having a first crystal composition; and a second particles having a second crystal composition different from the first crystal composition, wherein each of the first crystal composition and the second crystal composition comprises at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

2. The powder according to claim 1, wherein the first crystal composition comprises Ti.sub.2O.sub.3, and the second crystal composition comprises -Ti.sub.3O.sub.5.

3. The powder according to claim 1, wherein the first crystal composition comprises Ti.sub.2O.sub.3, and the second crystal composition comprises Ti.sub.4O.sub.7.

4. The powder according to claim 1, wherein the first crystal composition comprises -Ti.sub.3O.sub.5, and the second crystal composition comprises Ti.sub.4O.sub.7.

5. The powder according to claim 1, further comprising a third particle having a third crystal composition different from the first crystal composition and the second crystal composition, and comprising at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

6. A dispersion comprising: the powder according to claim 1; and a dispersion medium.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] FIG. 1 shows measurement results of X-ray diffraction of low-order titanium oxide powders in examples.

[0018] FIG. 2 shows measurement results of X-ray diffraction of low-order titanium oxide powders in examples.

DESCRIPTION OF EMBODIMENTS

[0019] An embodiment of the present invention is a powder containing a first particle having a first crystal composition and a second particle having a second crystal composition that is different from the first crystal composition.

[0020] The first crystal composition contains at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7 (hereinafter, collectively referred to as low-order titanium oxide). In an embodiment, the first crystal composition may contain only one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. In another embodiment, the first crystal composition may contain two or more selected from the group, may contain Ti.sub.2O.sub.3 and y-Ti.sub.3O.sub.5, and may contain y-Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

[0021] The second crystal composition contains at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. In an embodiment, the second crystal composition may contain only one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. In another embodiment, the second crystal composition may contain two or more selected from the group, may contain Ti.sub.2O.sub.3 and -Ti.sub.3O.sub.5, and may contain -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

[0022] It is noted that the second crystal composition different from the first crystal composition means that the second crystal composition is not completely identical to the first crystal composition. For example, if the first crystal composition is Ti.sub.2O.sub.3 and -Ti.sub.3O.sub.5 and the second crystal composition is -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7, then the second crystal composition is different from the first crystal composition. In other words, if the second crystal composition is not completely identical to the first crystal composition, the second crystal composition may have a partially common crystal structure (-Ti.sub.3O.sub.5 in the above example) to the first crystal composition.

[0023] It is confirmed that the first particle and the second particle (and third particle described later) have the first crystal composition and the second crystal composition (third crystal composition described later) respectively by measuring the powder by an X-ray diffraction method (XRD) and observing only a diffraction peak caused by at least one selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

[0024] Examples of the combination of the first crystal composition and the second crystal composition include the following combinations. [0025] (1) The first crystal composition contains Ti.sub.2O.sub.3 and the second crystal composition contains -Ti.sub.3O.sub.5. [0026] (2) The first crystal composition contains Ti.sub.2O.sub.3 and the second crystal composition contains Ti.sub.4O.sub.7. [0027] (3) The first crystal composition contains -Ti.sub.3O.sub.5 and the second crystal composition contains Ti.sub.4O.sub.7.

[0028] In these combinations (1) to (3), each of the first crystal composition and the second crystal composition may contain only one of each low-order titanium oxide described above, or may further contain another low-order titanium oxide in addition to each low-order titanium oxide described above.

[0029] The low-order titanium oxide powder may further contain a third particle having a third crystal composition different from the first crystal composition and the second crystal composition. The third crystal composition contains at least one crystal composition selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

[0030] The third crystal composition includes at least one crystal composition selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. In an embodiment, the third crystal composition may contain only one crystal composition selected from the group consisting of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7. In another embodiment, the third crystal composition may contain two or more crystal compositions selected from the group, may contain Ti.sub.2O.sub.3 and -Ti.sub.3O.sub.5, and may contain -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7.

[0031] It is noted that the third crystal composition different from the first crystal composition and the second crystal composition means that the third crystal composition is not completely identical to each of the first crystal composition and the second crystal composition. For example, if the first crystal composition is Ti.sub.2O.sub.3 and -Ti.sub.3O.sub.5, the second crystal composition is -Ti.sub.3O.sub.5 and Ti.sub.4O.sub.7, and the third crystal composition is -Ti.sub.3O.sub.5, the third crystal composition is different from the first crystal composition and the second crystal composition. In other words, if the third crystal composition is not completely identical to each of the first crystal composition and the second crystal composition, the third crystal composition may have a common crystal structure (-Ti.sub.3O.sub.5 in the above example) to each of the first crystal composition and the second crystal composition.

[0032] When the low-order titanium oxide powder further contains the third particle, for example, the first crystal composition may contain Ti.sub.2O.sub.3, the second crystal composition may contain -Ti.sub.3O.sub.5, and the third crystal composition may contain Ti.sub.4O.sub.7. In this case, each of the first crystal composition, the second crystal composition, and the third crystal composition may contain only one of each low-order titanium oxide described above, or may further contain another low-order titanium oxide in addition to the low-order titanium oxide described above.

[0033] The BET specific surface area of each of the first particles, the second particles, and the third particles may be 0.25 m.sup.2/g or more, 1 m.sup.2/g or more, 2 m.sup.2/g or more, 3 m.sup.2/g or more, or 4 m.sup.2/g or more, and may be 20 m.sup.2/g or less, 10 m.sup.2/g or less, or 8 m.sup.2/g or less. The BET specific surface area of the low-order titanium oxide powder may also be within the above range. The BET specific surface area is measured by nitrogen gas adsorption at an equilibrium relative pressure of about 0.3 using a specific surface area measuring device (for example, Macsorb HM model-1201, manufactured by Mountech Co., Ltd.), and is obtained as an average value of n=2. The degassing is performed at 200 C. for 10 minutes by a nitrogen gas flow (atmospheric pressure).

[0034] The content of impurities in each of the first particles, the second particles, and the third particles (and further in the low-order titanium oxide powder) is preferably as small as possible. The content of Al in each of the particles may be preferably 200 ppm by mass or less, 50 ppm by mass or less, or 20 ppm by mass or less. The content of B in each of the particles may be preferably 50 ppm by mass or less, 30 ppm by mass or less, or 10 ppm by mass or less. The content of Ba in each of the particles may be preferably 50 ppm by mass or less, 10 ppm by mass or less, or 5 ppm by mass or less. The content of Ca in each of the particles may be preferably 100 ppm by mass or less, 50 ppm by mass or less, or 10 ppm by mass or less. The content of Cd in each of the particles may be preferably 10 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Co in each of the particles may be preferably 10 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Cr in each of the particles may be preferably 100 ppm by mass or less, 10 ppm by mass or less, or 5 ppm by mass or less. The content of Cu in each of the particles may be preferably 200 ppm by mass or less, 50 ppm by mass or less, or 10 ppm by mass or less. The content of Fe in each of the particles may be preferably 200 ppm by mass or less, 50 ppm by mass or less, or 10 ppm by mass or less. The content of K in each of the particles may be preferably 100 ppm by mass or less, 5 ppm by mass or less, or 1 ppm by mass or less. The content of Li in each of the particles may be preferably 20 ppm by mass or less, 2 ppm by mass or less, or 0.5 ppm by mass or less.

[0035] The content of Mg in each of the particles may be preferably 100 ppm by mass or less, 10 ppm by mass or less, or 1 ppm by mass or less. The content of Mn in each of the particles may be preferably 10 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Mo in each of the particles may be preferably 10 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Na in each of the particles may be preferably 50 ppm by mass or less, 10 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Ni in each of the particles may be preferably 50 ppm by mass or less, 20 ppm by mass or less, or 10 ppm by mass or less. The content of P in each of the particles may be preferably 200 ppm by mass or less, 30 ppm by mass or less, 10 ppm by mass or less, or 5 ppm by mass or less. The content of Pb in each of the particles may be preferably 50 ppm by mass or less, 5 ppm by mass or less, or 2 ppm by mass or less. The content of Sb in each of the particles may be preferably 100 ppm by mass or less, 20 ppm by mass or less, 10 ppm by mass or less, or 2 ppm by mass or less. The content of Si in each of the particles may be preferably 1000 ppm by mass or less, 100 ppm by mass or less, 30 ppm by mass or less, 20 ppm by mass or less, or 2 ppm by mass or less. The content of Zn in each of the particles may be preferably 100 ppm by mass or less, 10 ppm by mass or less, or 2 ppm by mass or less. The content of Zr in each of the particles may be preferably 100 ppm by mass or less, 20 ppm by mass or less, or 2 ppm by mass or less.

[0036] The total content of Na, K and P in each of the particles may be preferably 2000 ppm by mass or less, 1000 ppm by mass or less, 500 ppm by mass or less, or 100 ppm by mass or less. The total content of Pb, Cd and Cr in each of the particles may be preferably 200 ppm by mass or less, 100 ppm by mass or less, 50 ppm by mass or less, or 30 ppm by mass or less.

[0037] The content of each impurity in the low-order titanium oxide powder may also be within the range described above. The content of impurities is measured by Agilent5110 ICP-OES (manufactured by Agilent Technology Co., Ltd.) using a liquid obtained by pressurizing and acid decomposing (150 C., 4 hours) 0.1 g of the sample with 1 mL addition of each of HF and HCl.

[0038] The contents of the first particle, the second particle, and the third particle in the low-order titanium oxide powder are appropriately adjusted according to the desired color tone. The content of each of the first particle, the second particle, and the third particle may be, for example, 5% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 95% by mass or more, and may be 95% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 5% by mass or less, based on the total amount of the low-order titanium oxide powder.

[0039] The low-order titanium oxide powder exhibits a black color having a specific chromaticity by containing the above particles. The L* value of the low-order titanium oxide powder in the L*a*b* color space is preferably 13.0 or less, more preferably 12.0 or less, and even more preferably 11.0 or less, and may be, for example, 4.0 or more, 5.0 or more, or 6.0 or more. The a* value of the low-order titanium oxide powder in the L*a*b* color space is preferably-3.0 or more, more preferably-2.0 or more, and is preferably 8.0 or less, more preferably 6.0 or less, still more preferably 4.0 or less. The b* value in the L*a*b* color space of the low-order titanium oxide powder is preferably-8.0 or more, more preferably-6.0 or more, and even more preferably-4.0 or more, and is preferably 1.0 or less, and more preferably 0.0 or less.

[0040] The L* value, the a* value, and the b* value in the L*a*b* color space are measured by a colorimetric color difference meter (for example, ZE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.)). More specifically, after zero point correction is performed with a cylinder for dark field, standard matching is performed with a standard white plate (X=91.71, Y=93.56, Z=110.52). Next, about 3 g of the low-order titanium oxide powder are put into a round cell of 3515H, and measurement is performed.

[0041] The above-described low-order titanium oxide powder is obtained by, for example, mixing the first particles and the second particles (and, if necessary, the third particles). The mixing may be either dry mixing or wet mixing, and is preferably dry mixing from the viewpoint that the production cost at the time of mixing can be reduced because the solvent does not need to be dried due to no use of solvent. Examples of the mixing method include mixing with a pulverizer such as an agate mortar, a ball mill, or a vibration mill, and various mixers.

[0042] The above-described low-order titanium oxide particles are suitably used as a pigment (colored filler) such as a black pigment. Such a pigment (colored filler) is suitably used as a coloring agent including, for example, cosmetics, electronic components such as semiconductors, and paints such as paints and inks.

[0043] When the low-order titanium oxide powder is used in the above-described application, the low-order titanium oxide powder is used by being dispersed in a dispersion medium, for example. That is, another embodiment of the present invention is a dispersion containing the above-described low-order titanium oxide powder and a dispersion medium dispersing the low-order titanium oxide powder.

[0044] The dispersion medium is appropriately selected depending on the application of the dispersion, and may be, for example, water, an alcohol, a ketone, an ester, a resin, or the like. Examples of the resin include an epoxy resin, a silicone resin, a phenol resin, a melamine resin, an urea resin, an unsaturated polyester, a fluororesin, a polyimide, a polyamideimide, a polyetherimide, a polybutylene terephthalate, a polyethylene terephthalate, a polyphenylene sulfide, a wholly aromatic polyester, a polysulfone, a liquid crystal polymer, a polyethersulfone, a polycarbonate, a maleimide-modified resin, an ABS (acrylonitrile butadiene styrene) resin, an AAS (acrylonitrile acrylic rubber styrene) resin, an AES (acrylonitrile ethylene propylene diene rubber styrene) resin, and the like.

[0045] The content of the low-order titanium oxide powder in the dispersion is appropriately selected depending on the application of the dispersion, and, for example, may be 5% by mass or more and may be 90% by mass or less, based on the total amount of the dispersion. The content of the dispersion medium in the dispersion is appropriately selected depending on the application of the dispersion, and, for example, may be 10% by mass or more and may be 95% by mass or less, based on the total amount of the dispersion.

EXAMPLES

[0046] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

<Preparation of Ti.sub.2O.sub.3 Particles>

[0047] A powder of TiO.sub.2 (manufactured by Toho Titanium, HT0514: purelity of 99.9%) and a powder of TiH.sub.2 (manufactured by Tohotech, TCH450: purelity of 99.8%) were mixed in an Eirich mixer (manufactured by Nippon Eirich Co., Ltd.) so that the molar ratio of TiO.sub.2/TiH.sub.2 was 3.0/1 to obtain a mixture. This mixture was transferred to an alumina crucible and heated for 12 hours in an electric furnace (HIMULTI 10000 manufactured by Fuji Electric Wave Industry Co., Ltd.) in a state in which the temperature was raised to 900 C. at 10 C./min in an Ar atmosphere. After heating, the obtained powder was pulverized in a mortar for 5 minutes to obtain particles having a crystal composition containing only one type of Ti.sub.2O.sub.3 (Ti.sub.2O.sub.3 particles).

<Production of -Ti.sub.3O.sub.5 Particles>

[0048] A powder of TiO.sub.2 (manufactured by Toho Titanium, HT0514: purelity of 99.9%) and a powder of TiH.sub.2 (manufactured by Tohotech, TCH450: purelity of 99.8%) were mixed in an Eirich mixer (manufactured by Nippon Eirich Co., Ltd.) so that the molar ratio of TiO.sub.2/TiH.sub.2 was 4.8/1 to obtain a mixture. This mixture was transferred to an alumina crucible and heated for 12 hours in an electric furnace (HIMULTI 10000 manufactured by Fuji Electric Wave Industry Co., Ltd.) in a state in which the temperature was raised to 900 C. at 10 C./min in an Ar atmosphere. After heating, the obtained powder was pulverized in a mortar for 5 minutes to obtain particles having a crystal composition containing only one type of -Ti.sub.3O.sub.5 (-Ti.sub.3O.sub.5 particles).

<Preparation of Ti.sub.4O.sub.7 Particles>

[0049] A powder of TiO.sub.2 (manufactured by Toho Titanium, HT0514: purelity of 99.9%) and a powder of TiH.sub.2 (manufactured by Tohotech, TCH450: purelity of 99.8%) were mixed in an Eirich mixer (manufactured by Nippon Eirich Co., Ltd.) so that the molar ratio of TiO.sub.2/TiH.sub.2 was 7.0/1 to obtain a mixture. This mixture was transferred to an alumina crucible and heated for 12 hours in an electric furnace (HIMULTI 10000 manufactured by Fuji Electric Wave Industry Co., Ltd.) in a state in which the temperature was raised to 900 C. at 10 C./min in an Ar atmosphere. After heating, the obtained powder was pulverized in a mortar for 5 minutes to obtain particles having a crystal composition containing only one type of Ti.sub.4O.sub.7 (Ti.sub.4O.sub.7 particles).

<Preparation of Low-Order Titanium Oxide Powders>

[0050] The Ti.sub.2O.sub.3 particles, -Ti.sub.3O.sub.5 particles, and Ti.sub.4O.sub.7 particles obtained above were weighed and placed in a plastic vessel so as to have the proportions (% by mass) shown in Table 1, and mixed for 3 minutes under the conditions of output 60 G using a low-frequency resonant acoustic mixer LabRAMII (manufactured by Resodyn Acoustic Mixers, Inc) to obtain low-order titanium oxide powders Nos. 1 to 13.

<X-Ray Diffraction Measurement>

[0051] Each of the low-order titanium oxide powders was subjected to powder X-ray diffraction measurement. Specifically, a horizontal sample multipurpose X-ray diffractometer (RINT-UltimaIV manufactured by Rigaku Corporation) was used to measure a diffraction pattern under the following measurement conditions. The obtained X-ray diffraction patterns are shown in FIGS. 1 and 2.

(Measurement Conditions)

[0052] X-ray source: Cu-K radiation (=1.54184 )

[0053] Tube voltage: 40 kV, tube current: 40 mA

[0054] Optical conditions for measurement: divergence slit=

[0055] Scattering slit: 8 mm

[0056] Light-receiving slit=0.15 mm

[0057] Position of diffraction peak=2 (diffraction angle)

[0058] Scan speed: 4.0 (2)/min, continuous scan

[0059] Measurement range: 2=10 to 80

<Measurement of Chromaticity>

[0060] The chromaticities (L*value, a*value, and b*value in the L*a*b* color space) of the Ti.sub.2O.sub.3 particles, the -Ti.sub.3O.sub.5 particles, the Ti.sub.4O.sub.7 particles, and each of the low-order titanium oxide powders were measured using a colorimetric color difference meter ZE-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). More specifically, first, zero point correction was performed with a cylinder for dark field, and then standard matching was performed with a standard white plate (X=91.71, Y=93.56, Z=110.52). Next, 3 g of the particles were put into a round cell of 3515H, and the chromaticity was measured. The results are shown in Table 1.

<Measurement of BET Specific Surface Area>

[0061] The BET specific surfaces of the Ti.sub.2O.sub.3 particles, -Ti.sub.3O.sub.5 particles, Ti.sub.4O.sub.7 particles, and each of the low-order titanium oxide powders were measured by nitrogen-gas adsorption at an equilibrated relative pressure of about 0.3 using a specific surface area measuring device (Macsorb HM model-1201, manufactured by Mountech Co., Ltd.), and averaged for n=2. Degassing was carried out by nitrogen gas flow (atmospheric pressure) at 200 C. for 10 minutes. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 BET specific Proportion surface (% by mass) Chromaticity area Ti.sub.2O.sub.3 -Ti.sub.3O.sub.5 Ti.sub.4O.sub.7 L* a* b* (m.sup.2/g) Ti.sub.2O.sub.3 particles 100 11.2 3.5 0.0 4.21 -Ti.sub.3O.sub.5 particles 100 10.8 0.4 2.1 3.56 Ti.sub.4O.sub.7 particles 100 13.2 1.5 4.3 3.21 Low-order 1 75 25 10.1 2.5 0.6 2.98 titanium 2 50 50 10.0 1.9 1.0 3.45 oxide 3 25 75 9.9 1.5 1.6 3.34 powder 4 75 25 9.8 0.1 2.6 3.21 No. 5 50 50 9.9 0.4 2.7 2.78 6 25 75 10.4 0.6 3.0 3.12 7 75 25 10.3 2.5 0.6 2.75 8 50 50 10.4 1.3 1.4 3.68 9 25 75 10.6 0.4 2.2 3.12 10 50 25 25 10.1 1.6 1.2 3.45 11 33.3 33.3 33.3 10.2 1.0 1.6 4.11 12 25 50 25 10.4 0.8 1.8 3.18 13 25 25 50 10.7 0.6 2.0 2.91

[0062] As can be seen from Table 1, the color tone can be suitably adjusted by combining the first particles and the second particles (and further the third particles) having a crystal composition of Ti.sub.2O.sub.3, -Ti.sub.3O.sub.5 or Ti.sub.4O.sub.7 and having different crystal compositions from each other. In particular, with respect to the L* value, surprisingly, the L* value of a powder containing the first particles and second particles can be lower than the L* value of the first particles themselves and the L* value of the second particles themselves. To be specific, for example, the L* values of the low-order titanium oxide powders 1 to 3 in which the Ti.sub.2O.sub.3 particles having the L* value of 11.2 and the -Ti.sub.3O.sub.5 particle having the L* value of 10.8 were mixed were expected to be between 10.8 and 11.2, but surprisingly, the L* values of the low-order titanium oxide powders 1 to 3 were lower than 10.8.

<Elemental Analysis>

[0063] The above Ti.sub.2O.sub.3 particles, -Ti.sub.3O.sub.5 particles, Ti.sub.4O.sub.7 particles, and each of the low-order titanium oxide powders were also subjected to elemental analysis using Agilent 5110ICP-OES (manufactured by Agilent Technologies, Inc.). To be specific, 0.1 g of the sample were weighed in a platinum crucible, 1 ml of each of HF and HCl were added thereto, and pressure acidolysis was performed at 150 C. for 4 hours. Thereafter, the volume was fixed at 6 ml, and after confirming that there was no unnecessary residue, ICP emission spectral analysis was performed. The results are shown in Table 2. In Table 2, ND means that the value was equal to or less than the minimum limit of detection, and the numerical value in parentheses means that the value was equal to or less than the minimum limit of quantification. The minimum limit of detection and the minimum limit of quantification are as follows.

(Minimum Limit of Detection)

[0064] Li, Na, Mg, K, and Ca: 0.5 pp, by mass

[0065] P: 5 ppm by mass

[0066] Elements other than the above: 2 ppm by mass

(Minimum Limit of Quantification)

[0067] Li, Na, Mg, K and Ca: 2 ppm by mass

[0068] P: 10 ppm by mass

[0069] Elements other than the above: 5 ppm by mass

TABLE-US-00002 TABLE 2 Results of element analysis (ppm by mass) Al B Ba Ca Cd Co Cr Cu Fe K Li Ti.sub.2O.sub.3 particles 8.2 ND ND ND ND ND 5.2 ND 5.0 ND ND -Ti.sub.3O.sub.5 particles 11.3 ND ND ND ND ND (3) ND ND ND ND Ti.sub.4O.sub.7 particles 9.5 ND ND ND ND ND (3) ND ND ND ND Low-order 1 7.4 ND ND ND ND ND (4) ND ND ND ND titanium oxide 2 8.6 ND ND ND ND ND (3) ND ND ND ND powder No. 3 6.6 ND ND ND ND ND ND ND ND ND ND 4 6.0 ND ND ND ND ND ND ND ND ND ND 5 12.8 ND ND ND ND ND 5.7 ND 7.2 ND ND 6 7.3 ND ND ND ND ND ND ND ND ND ND 7 8.7 ND ND ND ND ND (3) ND ND ND ND 8 5.5 ND ND ND ND ND ND ND ND ND ND 9 11.0 ND ND ND ND ND (5) ND (5) ND ND 10 12.1 ND ND ND ND ND 5.4 ND 6.4 ND ND 11 11.5 ND ND ND ND ND 5.0 ND 6.0 ND ND 12 10.4 ND ND ND ND ND 13.4 ND 10.1 6.8 ND 13 18.8 (4) ND ND ND ND 12.1 ND 15.0 11.8 ND Results of element analysis (ppm by mass) Mg Mn Mo Na Ni P Pb Sb Si V Zn Ti.sub.2O.sub.3 particles ND ND ND (1.8) 7.1 ND ND ND ND ND ND -Ti.sub.3O.sub.5 particles ND ND ND (1.1) (5) 13.9 ND ND ND ND ND Ti.sub.4O.sub.7 particles (1.1) ND ND 10.0 (4) 110.0 ND ND ND ND ND Low-order 1 ND ND ND (1.9) (4) ND ND ND ND ND ND titanium oxide 2 2.1 ND ND (0.8) ND ND ND ND ND ND ND powder No. 3 ND ND ND 3.2 ND ND ND ND ND ND ND 4 ND ND ND 3.6 ND (6) ND ND ND ND ND 5 ND ND ND (1.0) 8.1 ND ND ND ND ND ND 6 ND ND ND 2.8 ND ND ND ND ND ND ND 7 (0.5) ND ND (0.7) ND ND ND ND ND ND ND 8 4.1 ND ND 2.2 ND (7) ND ND ND ND ND 9 ND ND ND 3.4 7.0 (6) ND ND ND ND ND 10 ND ND ND 9.0 7.2 (7) ND ND ND ND ND 11 ND ND ND 6.2 7.1 (6) ND ND ND ND ND 12 ND ND ND 12.5 5.9 ND ND ND ND ND ND 13 (0.7) ND ND 10.4 6.0 (6) ND ND ND ND ND