TWI868340B - Titanium oxide, powder, powder composition, solid composition, liquid composition, and molded body - Google Patents

Abstract

A titanium oxide that meets the following requirements 1 to 3: Requirement 1: When T = 25°C, A(T) does not reach 0.3780; A(T) is (lattice constant of the a-axis (short axis) of the above titanium oxide)/(lattice constant of the c-axis (long axis) of the above titanium oxide) at temperature T, and the above lattice constants are obtained by X-ray diffraction measurement of the above titanium oxide; Requirement 2: Contains metals and/or semi-metallic elements other than titanium; Requirement 3: The total molar content of metals and semi-metallic elements other than titanium is less than the molar content of titanium.

Description

Titanium oxide, powder, powder composition, solid composition, liquid composition, and molded body

The present invention relates to a titanium oxide, a powder, a powder composition, a solid composition, a liquid composition, and a formed body.

It is known that in order to reduce the thermal expansion coefficient of a solid composition, a filler having a smaller thermal expansion coefficient is added.

For example, Patent Document 1 discloses tungsten zirconium phosphate as a filler material, which exhibits a negative thermal expansion coefficient. [Prior Art Document] [Patent Document]

Patent document 1: Japanese Patent Publication No. 2018-2577

[The problem the invention is trying to solve]

However, previous materials may not necessarily be able to sufficiently reduce the thermal expansion coefficient.

In addition, it is important to control the thermal expansion coefficient in accordance with the temperature range used in each application. For example, since the resin material for semiconductor sealing is usually used below 200°C, when added to the resin material for semiconductor sealing, it is better to use a material with a negative thermal expansion coefficient with a large absolute value below 200°C. In particular, if the temperature at which the material has the largest absolute negative thermal expansion coefficient can be adjusted, a composite material with a thermal expansion coefficient that matches the application can be designed by adjusting the amount of the material added.

The present invention is completed in view of the above situation, and its purpose is to provide a material having a negative thermal expansion coefficient with the largest absolute value in a relatively low temperature range. [Technical means to solve the problem]

The inventors of the present invention have conducted various studies and have completed the present invention as a result. That is, the present invention provides the following inventions.

The titanium oxide of the present invention meets the following requirements 1 to 3: Requirement 1: When T = 25°C, A(T) does not reach 0.3780; A(T) is (lattice constant of the a-axis (short axis) of the above-mentioned titanium oxide)/(lattice constant of the c-axis (long axis) of the above-mentioned titanium oxide) at temperature T, and the above-mentioned lattice constants are obtained by X-ray diffraction measurement of the above-mentioned titanium oxide; Requirement 2: Contains metals and/or semi-metallic elements other than titanium; Requirement 3: The total molar content of metals and semi-metallic elements other than titanium is less than the molar content of titanium.

Here, when T=25°C, A(T) of the above requirement 1 can be less than 0.3774.

The metal and/or semi-metal element other than titanium mentioned above can be selected from the element group belonging to the 3rd to 6th periods.

The powder of the present invention is the powder of the titanium oxide mentioned above.

The powder composition of the present invention comprises the above-mentioned powder.

The solid composition of the present invention comprises the above-mentioned powder or the above-mentioned powder combination.

The liquid composition of the present invention comprises the above-mentioned powder or the above-mentioned powder composition.

The molded body of the present invention is a molded body of the above-mentioned powder or the above-mentioned powder combination. [Effect of the invention]

According to the present invention, a material having a negative thermal expansion coefficient with a maximum absolute value in a relatively low temperature region can be provided.

The following describes the preferred embodiments of the present invention in detail. However, the present invention is not limited to the following embodiments.

<Titanium oxide> The titanium oxide of the present invention satisfies the following requirements 1 to 3.

Requirement 1: When T = 25°C, A(T) does not reach 0.3780. A(T) is (lattice constant of the a-axis (short axis) of the above-mentioned titanium oxide)/(lattice constant of the c-axis (long axis) of the above-mentioned titanium oxide) at temperature T. The above-mentioned lattice constants are obtained by X-ray diffraction measurement of the above-mentioned titanium oxide.

Requirement 2: Contains metals and/or semi-metallic elements other than titanium.

Requirement 3: The total molar content of metals and semi-metallic elements other than titanium is less than the molar content of titanium.

The lattice constant in the definition of A(T) is determined by powder X-ray diffraction measurement. There are two analytical methods: the Rietveld method and the least squares method.

In this specification, the axis corresponding to the minimum lattice constant in the crystal structure determined by powder X-ray diffraction is referred to as the a-axis, and the axis corresponding to the maximum lattice constant is referred to as the c-axis. The length of the a-axis and the length of the c-axis of the lattice are referred to as the a-axis length and the c-axis length, respectively.

A(T) is a parameter that indicates the anisotropy of the length of the crystal axis at temperature T. The larger the value of A, the longer the length of the a-axis is relative to the length of the c-axis, and the smaller the value of A, the smaller the length of the a-axis is relative to the length of the c-axis.

When T = 25 ° C, the value of A(T) of the titanium oxide of the present invention is less than 0.3780, preferably less than 0.3778, more preferably less than 0.3776, further preferably less than 0.3774, and further preferably less than 0.3772. By making the value of A(T) within this range, the temperature of the negative thermal expansion coefficient with the maximum absolute value can be effectively reduced.

When T=25°C, the lower limit of the value of A(T) is preferably 0.3500 or more, more preferably 0.3600 or more, and further preferably 0.3710 or more. By setting the lower limit of the value of A(T) within this range, the structural stability is increased, and a thermally stable structure is formed.

Furthermore, when T=100°C, the value of A(T) is preferably 0.3780 or less, more preferably 0.3769 or less, and further preferably 0.3765 or less. By making the value of A(T) within this range, the temperature at which the absolute maximum negative thermal expansion coefficient is obtained can be effectively reduced.

When T=100°C, the lower limit of the value of A(T) is preferably 0.3500 or more, more preferably 0.3600 or more, and further preferably 0.3710 or more. By setting the lower limit of the value of A(T) within this range, the structural stability is increased, and a thermally stable structure is formed.

Depending on the type of titanium oxide crystal, the crystal structure changes due to structural phase transition within a specific temperature range. In this specification, in the crystal structure at a certain temperature T, the axis with the largest crystal lattice constant is set as the c-axis, and the axis with the smallest crystal lattice constant is set as the a-axis. In any of the triclinic system, monoclinic system, rectangular system, tetragonal system, hexagonal system, and rhombohedral system, the a-axis and c-axis are defined as above.

The titanium oxide of the present invention contains metals other than titanium and/or semi-metallic elements. That is, the titanium oxide may contain one or more metal elements other than titanium, may contain one or more semi-metallic elements, or may contain a combination of one or more metal elements other than titanium and one or more semi-metallic elements.

The metal and/or semi-metal element other than titanium contained in the titanium oxide of the present invention is preferably selected from the element group belonging to the 3rd to 6th period, and more preferably selected from the element group belonging to the 3rd to 5th period. By selecting from these element groups, a thermally stable compound can be obtained.

From the viewpoint of being able to effectively reduce the temperature of the negative thermal expansion coefficient with the largest absolute value, the elements belonging to the third period are preferably Mg and Al; the elements belonging to the fourth period are preferably Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Ge; the elements belonging to the fifth period are preferably Sr, Y, Zr, Nb, Mo, In, Sn, Sb, and Te; the elements belonging to the sixth period are preferably Cs, Ba, La, Ce, Pr, Nd, W, and Bi. In particular, Al, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, and Sb are preferred, and Al, Cr, and Nb are particularly preferred.

The total molar content of metals and semi-metallic elements other than titanium in the titanium oxide of the present invention is less than the molar content of titanium.

From the viewpoint of showing a negative thermal expansion coefficient with a relatively large absolute value, the total molar content of metals and semi-metallic elements other than titanium in the titanium oxide of the present invention is preferably less than 50% of the molar content of titanium, more preferably less than 30%, further preferably less than 20%, and particularly preferably less than 15%.

Furthermore, from the perspective of effectively lowering the temperature at which the negative thermal expansion coefficient with the largest absolute value can be obtained, the total molar content of metals and semi-metallic elements other than titanium in the titanium oxide of the present invention is preferably greater than 0.5% of the molar content of titanium, more preferably greater than 1%, more preferably greater than 3%, and even more preferably greater than 5%.

The titanium oxide of the present invention preferably has a corundum structure. By having a corundum structure, it can exhibit a negative thermal expansion coefficient with a relatively large absolute value.

The crystal system is not particularly limited, but a rhombohedral system is preferred in order to exhibit a negative thermal expansion coefficient with a relatively large absolute value. The space group is preferably R-3c.

The composition formula of the titanium oxide of the present invention is preferably represented by Ti _{2 - x} M _x O _{3 - δ} (x = 0.02 to 0.66, δ = -0.32 to 0.40), more preferably represented by Ti _{2 - x} M _x O _{3 - δ} (x = 0.06 to 0.40, δ = -0.20 to 0.20), and particularly preferably represented by Ti _{2 - x} M _x O _{3 - δ} (x = 0.10 to 0.30, δ = -0.10 to 0.10). However, M refers to a metal and/or semi-metal element other than titanium. By making x and δ within the above range, the thermal stability of the titanium oxide of the present invention is improved, and the absolute value of the negative thermal expansion coefficient becomes larger. Furthermore, when M includes two or more elements selected from the group consisting of metals and semi-metallic elements other than titanium, the subscript x under M represents the total molar ratio of the elements. When M includes two or more elements, the molar ratio between the elements of M is not particularly limited.

In the present invention, the above δ represents the oxygen deficiency amount of titanium oxide, which can be calculated by thermogravimetric analysis. The method for measuring the oxygen deficiency amount δ by thermogravimetric analysis is shown below. Titanium oxide is heated under the flow of dry air to oxidize it until the weight does not increase substantially. δ can be calculated based on the weight increase until the end of heating. As a measuring device, for example, a thermogravimetric analyzer TGDTA6300AST-2 (manufactured by Seiko Nanotech Corporation) can be used.

According to the titanium oxide of this embodiment, the temperature showing the absolute maximum negative thermal expansion coefficient can be relatively lowered, for example, it can be set to less than 190°C, below 180°C, and below 175°C. According to the titanium oxide of this embodiment, the absolute maximum negative thermal expansion coefficient can also be set to below -5 ppm/°C, below -10 ppm/°C, below -15 ppm/°C, below -20 ppm/°C, and below -25 ppm/°C.

The titanium oxide of the present invention can be in the form of powder. The powder can be suitably used as a filler added to a solid composition in order to control the thermal expansion rate of the solid composition.

The D90 of titanium oxide powder is preferably 0.5 μm to 70 μm. D90 is preferably 0.6 μm to 0.7 μm or more, and more preferably 60 μm to 40 μm or less. If D90 is within this range, the coating property is improved. If D90 is 0.5 μm or more, it is difficult to produce agglomerated particles, and the uniformity when kneading with a matrix material such as a resin is easier to improve. D50 is preferably 0.5 μm to 60 μm or less. If D50 is 60 μm or less, there is a tendency that the coating property is easier to improve. If D50 is 0.5 μm or more, it is difficult to produce agglomerated particles, and the uniformity when kneading with a matrix material such as a resin is easier to improve.

However, D50 and D90 in this manual refer to the cumulative frequency calculated from the smallest particle size in the volume-based cumulative particle size distribution curve obtained by the laser diffraction scattering method, with the particle size with a cumulative frequency of 50% being D50 and the particle size with a cumulative frequency of 90% being D90. The volume-based particle size distribution is measured by the laser diffraction scattering method. For example, the laser diffraction particle size distribution measuring device Mastersizer 2000 manufactured by Malvern Instruments Ltd. can be used. The refractive index is 2.40 for measurement.

The BET specific surface area of the titanium oxide powder of the present invention is preferably not less than 0.1 m ² /g and not more than 20.0 m ² /g.

<Method for producing titanium oxide and its powder> The method for producing titanium oxide of the present invention is not particularly limited. For example, it can be obtained by sintering the raw material powder of titanium oxide. The sintering method is not particularly limited, and can be a normal pressure sintering method using a heating machine such as an electric furnace, a hot pressing method or a hot isostatic pressure sintering (HIP) method in which pressure is applied while heating, or a discharge plasma sintering method in which pressure is applied while electricity is applied for heating. In particular, the discharge plasma sintering method is more suitable.

In the discharge plasma sintering, a mixture of raw materials of titanium oxide of the present invention is pressurized while a pulse current is passed through the mixture, thereby generating discharge in the raw material mixture to heat and sinter.

In order to prevent the obtained compound from being deteriorated by contact with air, the plasma sintering step is preferably performed under an inert gas atmosphere such as argon, nitrogen, or vacuum.

The pressure applied in the plasma sintering step is preferably in the range of more than 0 MPa and less than 100 MPa. In order to obtain a high-density first material, the pressure applied in the plasma sintering step is preferably set to be greater than 10 MPa, and more preferably set to be greater than 30 MPa. The heating temperature in the plasma sintering step is preferably sufficiently lower than the melting point of the target titanium oxide.

The raw material powder includes a titanium source, a metal and/or semi-metal source other than titanium, and an oxygen source. Examples of the titanium source include titanium oxides such as Ti ₂ O ₃ and TiO ₂ , and metallic titanium. Examples of the metal and/or semi-metal source other than titanium include oxides, hydroxides, and monomers of metal and/or semi-metal elements other than titanium. The oxygen source is usually titanium oxide or an oxide of a metal and/or semi-metal other than titanium. That is, at least one of the titanium source and the metal and/or semi-metal source other than titanium is preferably an oxide, and more preferably both are oxides. Furthermore, when the titanium source and/or the metal and/or semi-metal source other than titanium are oxides, they may all be oxides, or a part of each may be an oxide, and the rest may be a non-oxide such as a metal. In this way, the oxygen ratio in the product, i.e., δ in the above formula, can be controlled. In addition, by adjusting the ratio of the molar content of titanium and the content of metals and/or semi-metallic elements other than titanium in the raw material powder, x in the above formula in the obtained titanium oxide can be adjusted.

The plasma sintering step can be performed in two stages. That is, discharge plasma sintering can be performed by the method shown below. By performing such two-stage discharge plasma sintering, impurity phases can be removed and metals and/or semi-metallic elements other than titanium can be more easily dissolved, so it is more suitable.

First, a first mixing step is performed, i.e., titanium oxide is mixed with a metal and/or semi-metal source other than titanium to obtain a first mixed powder. Then, a first discharge plasma sintering step is performed, i.e., the first mixed powder is subjected to discharge plasma sintering to obtain a first sintered body. Then, a second mixing step is performed, i.e., the obtained first sintered body is crushed and metallic titanium and a metal and/or semi-metal source other than titanium are mixed therein to obtain a second mixed powder. Thereafter, a second discharge plasma sintering step is performed, i.e., the second mixed powder is subjected to discharge plasma sintering to obtain a second sintered body.

The obtained titanium oxide block is crushed, screened, pulverized, etc. to adjust the particle size distribution, thereby obtaining titanium oxide powder.

<Powder composition containing titanium oxide powder> One embodiment of the present invention is a powder composition containing the above-mentioned titanium oxide powder and other powders, and the powder composition is a powder composition. This powder composition can be suitably used as a filler to control the thermal expansion rate of the solid composition described later. The content of titanium oxide in the powder composition is not limited, and the function of controlling the thermal expansion amount can be exerted according to the content. From the perspective of efficiently controlling the thermal expansion amount, the content of the above-mentioned titanium oxide can be 75% by mass or more, 85% by mass or more, or 95% by mass or more.

Examples of other powders in the powder composition other than the titanium oxide powder include calcium carbonate, talc, mica, silica, clay, wollastonite, potassium titanium, hard silicate, gypsum fiber, aluminum borate, aromatic polyamide fiber, carbon fiber, glass fiber, glass flakes, polyoxybenzoyl whisker Crystal, glass balloon, carbon black, graphite, aluminum oxide, aluminum nitride, boron nitride, ceria, ferrite, iron oxide, barium titanate, lead zirconate titanate, zeolite, iron powder, aluminum powder, barium sulfate, zinc borate, red phosphorus, magnesium oxide, aluminum magnesium carbonate, antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc carbonate, TiO ₂ , TiO.

The D90, D50 and BET specific surface area of the powder composition can be set to be the same as the D90 and D50 of the above-mentioned titanium oxide powder.

The method for preparing the powder composition is not particularly limited. For example, the titanium oxide powder mentioned above is mixed with other fillers, and the particle size distribution is adjusted by crushing, screening, pulverizing, etc. as needed.

<Molded body> The molded body of this embodiment is a molded body of the above-mentioned titanium oxide powder or powder combination. The molded body in this embodiment can be a sintered body obtained by sintering the titanium oxide powder or powder combination.

Usually, the molded body is obtained by sintering the powder or powder composition. In this case, it is more appropriate to sinter within a temperature range that maintains the crystal structure of titanium oxide.

Various known sintering methods can be applied to obtain a sintered body. As a method for obtaining a sintered body, conventional heating, hot pressing, the above-mentioned discharge plasma sintering, etc. can be used.

The heating temperature for plasma sintering is preferably sufficiently lower than the melting point of titanium oxide.

Furthermore, the formed body of the present embodiment is not limited to a sintered body, and for example, may be a pressurized powder obtained by pressurizing a powder or a powder composition.

The powder or powder composition molded body according to the present embodiment can provide a component with less thermal expansion, which can greatly reduce the dimensional change of the component when the temperature changes. Therefore, it can be suitably used in various components used in devices that are particularly sensitive to dimensional changes caused by temperature.

Furthermore, by combining the powder or the molded body of the powder composition with other materials having a positive thermal expansion coefficient, the thermal expansion coefficient of the entire component can be controlled to be lower. For example, if a portion of the length direction of the rod is formed using the molded body of the powder of this embodiment, and the other portion is formed using a component of a material having a positive thermal expansion coefficient, the thermal expansion coefficient of the rod in the length direction can be freely controlled according to the existence ratio of the two materials. For example, the thermal expansion of the rod in the length direction can be substantially zero.

<Solid composition> The solid composition of this embodiment includes the above-mentioned titanium oxide powder or powder composition, and the first material.

[First material] The first material is not particularly limited, and examples thereof include resins, alkaline metal silicates, ceramics, metals, etc. The first material may be an adhesive material that bonds the above-mentioned titanium oxides to each other, or a matrix material that keeps the above-mentioned titanium oxides in a dispersed state.

Examples of resins include thermoplastic resins, and hardened products of thermosetting resins or active energy ray-hardening resins.

Examples of thermosetting resins include epoxy resins, cyclobutane resins, unsaturated polyester resins, alkyd resins, phenolic resins (phenolic varnish resins, soluble phenolic resins, etc.), acrylic resins, polyurethane resins, polysilicone resins, polyimide resins, and melamine resins. Examples of active energy ray-curing resins include ultraviolet-curing resins and electron beam-curing resins, such as acrylic urethane resins, epoxy acrylate resins, acrylic acrylate resins, polyester acrylate resins, and phenol methacrylate resins. Other examples of resins include silicone-based, urethane-based, rubber-based, acrylic-based adhesives, etc.

Examples of thermoplastic resins include polyolefins (polyethylene, polypropylene, etc.), ABS resin, polyamide (nylon 6, nylon 6,6, etc.), polyamide imide, polyester (polyethylene terephthalate, polyethylene naphthalate), liquid crystal polymer, polyphenylene ether, polyacetal, polycarbonate, polyphenylene sulfide, polyimide, polyetherimide, polyether sulfone, polyketone, polystyrene, and polyetheretherketone.

The first material may include one of the above-mentioned resins, or may include two or more of the above-mentioned resins.

From the perspective of improving heat resistance, the first material is preferably epoxy resin, polyether sulfone, liquid crystal polymer, polyimide, polyamide imide, or silicone.

Examples of alkali metal silicates include lithium silicate, sodium silicate, and potassium silicate. The first material may include one alkali metal silicate or two or more alkali metal silicates. These materials have higher heat resistance and are therefore preferred.

The ceramics are not particularly limited, and examples thereof include oxide ceramics such as aluminum oxide, silicon dioxide (including silicon oxide and silicon dioxide glass), titanium dioxide, zirconium oxide, magnesium oxide, vanadium oxide, yttrium oxide, zinc oxide, and iron oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; and ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, barium sulfate, aluminum hydroxide, potassium titanium oxide, talc, kaolin clay, kaolinite, kaolinite, pyrophyllite, montmorillonite, sericite, mica, chlorite, bentonite, sponge, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and quartz sand. The first material may include one ceramic or two or more ceramics. Ceramics are preferred because they can improve heat resistance. The sintered body can be produced by discharge plasma sintering or the like.

The metal is not particularly limited, and examples thereof include: single metals such as aluminum, tantalum, niobium, titanium, molybdenum, iron, nickel, cobalt, chromium, copper, silver, gold, platinum, lead, tin, and tungsten; alloys such as stainless steel (SUS); and mixtures thereof. The first material may include one metal or two or more metals. Such metals are preferred because they can improve heat resistance.

[Other components] The solid composition may contain other components in addition to the first material and the titanium oxide powder or powder composition. For example, a catalyst may be listed. As the catalyst, there is no particular limitation, and examples thereof include acidic compounds, alkaline compounds, and organic metal compounds. As acidic compounds, acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, phosphoric acid, formic acid, acetic acid, and oxalic acid may be used. As alkaline compounds, ammonium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide may be used. As organic metal compound catalysts, examples thereof include those containing aluminum, zirconium, tin, titanium, and zinc.

The content of titanium oxide in the solid composition is not particularly limited, and the function of controlling thermal expansion can be exerted according to the content. The content of titanium oxide in the solid composition can be set to, for example, 1% by weight or more, or 3% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 40% by weight or more, or 70% by weight or more. If the content of titanium oxide increases, it is easier to exert the effect of reducing the thermal linear expansion coefficient. The content of titanium oxide in the solid composition can be set to, for example, 99% by weight or less. The content of titanium oxide in the solid composition can be 95% by weight or less, or 90% by weight or less.

The content of the first material in the solid composition can be, for example, 1% by weight or more. The content of the first material in the solid composition can be 5% by weight or more, or 10% by weight or more. The content of the first material in the solid composition can be, for example, 99% by weight or less. The content of the first material in the solid composition can also be 97% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 60% by weight or less, or 30% by weight or less.

The solid composition of the present embodiment can have a sufficiently low thermal expansion coefficient by including the titanium oxide of the present embodiment. According to the solid composition, a component with extremely small dimensional change when the temperature changes can be obtained. Therefore, it can be suitably used in optical components or components for semiconductor manufacturing devices that are particularly sensitive to dimensional changes caused by temperature.

In particular, since the absolute value of the maximum negative thermal expansion coefficient of the titanium oxide is large enough, a solid composition (material) with a negative thermal expansion coefficient can also be obtained. The so-called negative thermal expansion coefficient means that the volume shrinks with thermal expansion. In a plate formed by joining the end surface (side surface) of a plate of a solid composition with a negative thermal expansion coefficient to the end surface of a plate of another material with a positive thermal expansion coefficient, the thermal expansion coefficient of the entire plate in a direction perpendicular to the thickness direction can be made substantially zero.

Furthermore, the temperature at which the titanium oxide shows the maximum absolute negative thermal expansion coefficient can be relatively lowered, for example, it can be set to less than 190°C. Therefore, the thermal expansion coefficient of the solid composition in the temperature range less than 190°C can be reduced. In addition, if the titanium oxide powder and a _material such as _Ti2O3 showing the maximum absolute negative thermal expansion coefficient at around 200°C are added to the solid composition, the thermal expansion coefficient of the solid composition is reduced in a wide temperature range, which is preferred.

<Liquid composition> The liquid composition of this embodiment includes the above-mentioned titanium oxide powder or powder composition, and a second material. The liquid composition is a composition that is fluid at 25°C. The liquid composition can be a raw material for the above-mentioned solid composition. The so-called "fluid at 25°C" means that after the liquid composition is supplied to a specified container and the liquid surface is horizontal, the container is tilted 45 degrees, and the liquid surface will move or deform after 1 hour.

[Second material] The second material is in liquid form and can be a dispersion of the above-mentioned titanium oxide powder or powder composition. The second material can be the raw material of the first material.

For example, when the first material is an alkali metal silicate, the second material may include the alkali metal silicate and a solvent that can dissolve or disperse the alkali metal silicate. When the first material is a thermoplastic resin, the second material may include the thermoplastic resin and a solvent that can dissolve or disperse the thermoplastic resin. When the first material is a cured product of a thermosetting resin or an active energy ray-curing resin, the second material is the thermosetting resin or active energy ray-curing resin before curing.

The thermosetting resin before curing is fluid at room temperature, and when heated, it is cured by a cross-linking reaction, etc. The thermosetting resin before curing may contain one resin or two or more resins.

The active energy ray-curing resin before curing is fluid at room temperature, and is cured by causing a crosslinking reaction, etc., by irradiation with active energy rays such as light (UV, etc.) or electron beams. The active energy ray-curing resin before curing contains a curable monomer and/or a curable oligomer, and may further contain a solvent and/or a photoinitiator as needed. Examples of curable monomers and curable oligomers are photocurable monomers and photocurable oligomers. Examples of photocurable monomers are monofunctional or multifunctional acrylate monomers. Examples of photocurable oligomers include: urethane acrylate, epoxy acrylate, acrylic acrylate, polyester acrylate, and phenol methacrylate.

Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, glycol solvents, hydrocarbon solvents, aprotic polar solvents and other organic solvents and water. In the case of alkali metal silicates, the solvent is, for example, water.

[Other components] The liquid composition of this embodiment may also contain other components in addition to the second material and the titanium oxide powder or powder combination. For example, it may contain other components listed in the first material.

The content of titanium oxide in the liquid composition is not particularly limited and can be appropriately set from the perspective of controlling the thermal expansion of the solid composition after hardening. Specifically, it can be the same as the first material.

<Method for producing liquid composition> The method for producing the liquid composition is not particularly limited. For example, the liquid composition can be obtained by stirring and mixing the powder or powder composition of the above-mentioned titanium oxide with the second material. As a stirring method, for example, stirring using a stirrer can be cited. Alternatively, the titanium oxide can be dispersed in the second material by ultrasonic treatment.

As mixing methods used in the mixing step, for example, there can be listed: ball milling, self-rotating and revolving mixer, impeller rotation method, blade rotation method, rotary film method, rotor/stator mixing method, colloid milling method, high-pressure homogenization method, ultrasonic dispersion method. In the mixing step, multiple mixing methods can be performed in sequence or simultaneously. By homogenizing the composition and applying shear in the mixing step, the fluidity and deformability of the composition can be improved.

<Method for producing a solid composition> After the liquid composition is formed into a desired shape, a solid composition can be produced by converting the second material in the liquid composition into the first material, which is obtained by compounding titanium oxide and the first material.

For example, when the second material comprises an alkali metal silicate and a solvent that can dissolve or disperse the alkali metal silicate, and when the second material comprises a thermoplastic resin and a solvent that can dissolve or disperse the thermoplastic resin, after the liquid composition is formed into a desired shape, the solvent is removed from the liquid composition, thereby obtaining a solid composition comprising titanium oxide and the first material (alkali metal salt or thermoplastic resin).

The solvent can be removed by evaporating the solvent by natural drying, vacuum drying, heating, etc. From the viewpoint of suppressing the generation of coarse bubbles, it is appropriate to remove the solvent while maintaining the temperature of the mixture below the boiling point of the solvent.

When the second material is a thermosetting resin or an active energy ray-curing resin, after the liquid composition is formed into a desired shape, the liquid composition can be cured using heat or active energy rays (UV, etc.).

The method of forming the liquid composition into a predetermined shape includes, for example, injecting the liquid composition into a mold; and applying the liquid composition on the surface of a substrate to form a film.

Furthermore, when the first material is a ceramic or a metal, the following steps may be performed. A mixture of a raw material powder of the first material and titanium oxide is prepared, and the mixture is heat-treated to sinter the raw material powder of the first material, thereby obtaining a solid composition containing the first material and titanium oxide as a sintered body. If necessary, the pores of the solid composition may be adjusted by heat treatment such as annealing. As a sintering method, conventional heating, hot pressing, discharge plasma sintering, etc. may be used.

Discharge plasma sintering refers to applying pressure to a mixture of raw material powder of the first material and titanium oxide while passing a pulsed current through the mixture. This generates discharge between the raw material powder of the first material, thereby heating the raw material powder of the first material for sintering.

In order to prevent the obtained compound from being deteriorated by contact with air, the plasma sintering step is preferably performed under an inert gas atmosphere such as argon, nitrogen, or vacuum.

The pressure applied in the plasma sintering step is preferably in the range of more than 0 MPa and less than 100 MPa. In order to obtain a high-density first material, the pressure applied in the plasma sintering step is preferably set to be greater than 10 MPa, and more preferably set to be greater than 30 MPa.

The heating temperature in the plasma sintering step is preferably sufficiently lower than the melting point of the first material as the target.

Furthermore, by heat treating the obtained solid composition, the size and distribution of the pores can be adjusted. [Example]

Hereinafter, the present invention will be described in more detail with reference to embodiments.

<Analysis of the crystal structure of titanium oxide> For the analysis of the crystal structure, the powder X-ray diffraction measurement device SmartLab (manufactured by Rigaku) was used to change the temperature under the following conditions to measure the powder X-ray diffraction and obtain the powder X-ray diffraction pattern. Based on the obtained pattern, the lattice constant was refined using the least square method using the PDXL2 (manufactured by Rigaku) software, and the lattice constant of the a-axis and the lattice constant of the c-axis were obtained in the range of 25℃ to 400℃, thereby calculating A(T). Measuring device: Powder X-ray diffraction measuring device SmartLab (manufactured by Rigaku) X-ray generator: CuKα radiation source, voltage 45 kV, current 200 mA Slit: Slit width 2 mm Scanning step: 0.02 deg Scanning range: 5-80 deg Scanning speed: 10 deg/min X-ray detector: One-dimensional semiconductor detector Sample preparation: Powdered by mortar grinding Measurement gas atmosphere: Ar 100 mL/min Sample stage: Made of dedicated glass substrate _SiO2 The space group of the corundum structure of the titanium oxide in Examples 1 to 5 and Comparative Examples 1 to 3 all have a diffraction peak of Ti ₂ O ₃ belonging to R-3c.

<Evaluation of thermal expansion control characteristics> The thermal expansion control characteristics were evaluated by the following method. The thermal expansion coefficient of the obtained titanium oxide sintered body (molded body) sample was measured using the following device. Measurement device: Thermo plus EVO2 TMA series Thermo plus 8310 Temperature range: 25℃-320℃ Reference solid: Alumina The typical size of the sintered body sample is 15 mm×4 mm×4 mm. For the sintered body of 15 mm×4 mm×4 mm, the longest side is taken as the sample length L, and the sample length L(T) at temperature T is measured. The dimensional change rate ΔL(T)/L(30℃) relative to the sample length (L(30℃) at 30℃ is calculated by the following formula. ΔL(T)/L(30℃)＝(L(T)－L(30℃))/L(30℃) Within the range of 40℃～300℃, the dimensional change rate ΔL(T)/L(30℃) is used as a function of T. In the range of (T-10℃ ) to (T + 10 ° C) by the least square method, and the obtained slope is regarded as the thermal expansion coefficient α (1/ ° C) at temperature T ° C. The value of the negative thermal expansion coefficient with the largest absolute value among the thermal expansion coefficients at each temperature and the temperature at that time are calculated. The case where the temperature with the largest absolute value of the negative thermal expansion coefficient is lower than 190 ° C is evaluated as good.

<Evaluation of oxygen deficiency amount δ> For the titanium oxides of Examples 1 to 5 and Comparative Examples 1 and 2, the oxygen deficiency amount δ was evaluated by thermogravimetric analysis of each titanium oxide. According to the thermogravimetric analysis, assuming that the oxidation reaction of the titanium oxide will proceed, the oxygen deficiency amount δ is calculated according to the following formula (1). The titanium oxide after the oxidation reaction is called the final oxide. Measuring apparatus: Thermogravimetric analyzer TGDTA6300AST-2 (manufactured by Seiko Instruments NanoTech Co., Ltd.) Heating program: Raise the temperature from 30°C to 100°C at 10°C/min, and keep at 100°C for 5 minutes. Thereafter, raise the temperature from 100°C to 1300°C at 10°C/min, and keep at 1300°C for 10 minutes. Measuring gas atmosphere: Dry air 200 mL/min [number 1] δ: oxygen deficiency W _F : maximum value of the weight of titanium oxide at 100℃～1300℃ W _I : weight of titanium oxide immediately after being kept at 100℃ for 5 minutes M _F : molecular weight of the final oxide M _O : atomic weight of O 16.00 g/mol M _I : average atomic weight of metal and/or semi-metal elements in titanium oxide

In formula (1), M _F is calculated based on the oxidation state of each metal contained at 1300°C after being normalized so that the sum of the coefficients of the composition formula of Ti and metal or semi-metal elements other than Ti relative to each added composition of titanium oxide becomes _1. Ti is oxidized to TiO ₂ , Nb is oxidized to Nb ₂ O ₅ , Al is oxidized to Al ₂ O ₃ , Cr is oxidized to Cr ₂ O ₃ , and Si is oxidized to SiO ₂ , and M _F is calculated as a mixture thereof. In Example 1, M _F is calculated using (0.935TiO ₂ + 0.0325Nb ₂ O ₅ ) as the final oxide. In Example 2, _MF was calculated using (0.90TiO ₂ +0.05Al ₂ O ₃ ) as the final oxide. In Example 3, _MF was calculated using (0.915TiO ₂ +0.0425Cr _{2 O 3 ) as the final oxide. In Example 4, MF was calculated using (0.95TiO 2 +0.025Cr 2 O 3 ) as the final} oxide. In Example 5, _MF was calculated using (0.875TiO ₂ +0.0625Nb ₂ O ₅ ) as the final oxide. In Comparative Example 1, _MF was calculated using TiO ₂ as the final oxide. In Comparative Example 2, M _F was calculated using (0.995TiO ₂ +0.005SiO ₂ ) as the final oxide.

In Example 1, _MI is calculated as (0.935Ti+0.065Nb). In Example 2, _MI is calculated as (0.90Ti+0.10Al). In Example 3, _MI is calculated as (0.915Ti+0.085Cr). In Example 4, _MI is calculated as (0.95Ti+0.05Cr). In Example 5, _MI is calculated as (0.875Ti+0.125Nb). In Comparative Example 1, the atomic weight of Ti is _MI . In Comparative Example 2, _MI is calculated as (0.995Ti+0.005Si).

<Example 1> 5.53 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemical Co., Ltd., 150 μm pass, purity 99.9%) and 0.47 g of Nb ₂ O ₃ powder (manufactured by High Purity Chemical Co., Ltd.; particles, 2-5 mm; purity 99.9%) were weighed and pulverized in a mortar to obtain a first mixed powder. The obtained first mixed powder was placed in a special carbon mold and discharged plasma sintered under the following conditions to obtain a first sintered body.

Device: Doctor Sinter Lab SPS-511S (manufactured by Fuji Denpa Koki Co., Ltd.) Sample: 6.0 g of mixed powder Mold: Carbon mold for the device, inner diameter 20 mmφ Gas atmosphere: Argon 0.05 MPa Pressure: 40 MPa (12.8 kN) Heating: 1500°C, 10 minutes

The first sintered body obtained was pulverized in a mortar to obtain a first titanium oxide powder. 5.56 g of the first titanium oxide powder was weighed, and 0.10 g of Ti powder (manufactured by Kojun Chemical Co., Ltd., 300 μm Pass, purity 99.95%) and 0.17 g of Nb ₂ O ₃ powder (manufactured by Kojun Chemical Co., Ltd.; particles, 2-5 mm; purity 99.9%) were weighed and placed in the above 5.56 g of the first titanium oxide powder, and pulverized in a mortar to obtain a second mixed powder. The obtained second mixed powder was placed in a special carbon mold and discharged plasma sintered under the following conditions to obtain the sintered body of Example 1. The crystal structure of the sintered body of Example 1 was analyzed. As a result, A (25°C) was 0.3773 and A (100°C) was 0.3756. Furthermore, according to the addition amount, the addition composition of the sintered body of Example 1 was Ti _1.87 Nb _0.13 O _2.92 .

Device: Doctor Sinter Lab SPS-511S (manufactured by Fuji Denpa Koki Co., Ltd.) Sample: 6.0 g of mixed powder Mold: Carbon mold for the device, inner diameter 20 mmφ Gas atmosphere: Argon 0.05 MPa Pressure: 40 MPa (12.8 kN) Heating: 1350°C, 10 minutes

<Example 2> 3.71 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemicals, 150 μm Pass, purity 99.9%) and 0.29 g of Al ₂ O ₃ powder (manufactured by High Purity Chemicals, average particle size about 1 μm, purity 99.9%) were weighed and pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold and subjected to discharge plasma sintering under the following conditions to obtain a sintered body of Example 2. The crystal structure of the obtained sintered body of Example 2 was analyzed, and the result was that A (25°C) was 0.3772. In addition, according to the addition amount, the addition composition of the sintered body of Example 2 was Ti _1.80 Al _0.20 O ₃ .

Device: Doctor Sinter Lab SPS-511S (manufactured by Fuji Denpa Koki Co., Ltd.) Sample: 4.0 g of mixed powder Mold: Carbon mold for the device, inner diameter 20 mmφ Gas atmosphere: Argon 0.05 MPa Pressure: 40 MPa (12.8 kN) Heating: 1500°C, 10 minutes

<Example 3> 5.46 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemicals, 150 μm Pass, purity 99.9%) and 0.54 g of Cr ₂ O ₃ powder (manufactured by High Purity Chemicals, average particle size 3 μm, purity 99.9%) were weighed and pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold, and the amount of mixed powder in the conditions of Example 2 was changed to 6.0 g. Discharge plasma sintering was performed under these conditions to obtain a sintered body of Example 3. The crystal structure of the sintered body of Example 3 was analyzed, and the results showed that A (25°C) was 0.3769 and A (100°C) was 0.3761. Furthermore, according to the addition amount, the addition composition of the sintered body of Example 3 is Ti _1.83 Cr _0.17 O ₃ .

<Example 4> 3.79 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemicals, 150 μm Pass, purity 99.9%) and 0.21 g of Cr ₂ O ₃ powder (manufactured by High Purity Chemicals, average particle size about 3 μm, purity 99.9%) were weighed and pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold, and the heating temperature in the conditions of Example 2 was changed to 1300°C. Discharge plasma sintering was performed under this condition to obtain a sintered body of Example 4. The crystal structure of the sintered body of Example 4 was analyzed, and the result was that A (25°C) was 0.3772. Furthermore, according to the addition amount, the addition composition of the sintered body of Example 4 is Ti _1.90 Cr _0.10 O ₃ . <Example 5> 4.75 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemicals, 150 μm Pass, purity 99.9%), 0.10 g of Ti powder (manufactured by High Purity Chemicals, 300 μm Pass, purity 99.95%), and 1.14 g of Nb ₂ O ₃ powder (manufactured by High Purity Chemicals; particles, 2-5 mm; purity 99.9%) were weighed and pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold, and the heating temperature in the conditions of Example 2 was changed to 1350°C. Discharge plasma sintering was performed under this condition to obtain a sintered body of Example 5. The crystal structure of the sintered body of Example 5 was analyzed, and the results showed that A (25°C) was 0.3758 and A (100°C) was 0.3752. Furthermore, according to the addition amount, the addition composition of the sintered body of Example 5 was Ti _1.75 Nb _0.25 O _2.92 .

<Comparative Example 1> 6.60 g of Ti ₂ O ₃ powder (manufactured by High Purity Chemical Co., Ltd., 150 μm Pass, purity 99.9%) was crushed in a mortar to obtain a powder. The obtained powder was placed in a special carbon mold, the amount of powder in the conditions of Example 2 was changed to 6.60 g, the heating temperature was changed to 1350°C, and discharge plasma sintering was performed under these conditions to obtain a sintered body of Comparative Example 1. The crystal structure of the sintered body of Comparative Example 1 obtained was analyzed, and the results showed that A (25°C) was 0.3779 and A (100°C) was 0.3770. In addition, in terms of the added amount, the added composition of the sintered body of Comparative Example 1 is Ti ₂ O ₃ .

<Comparative Example 2> 1.00 g of Ti powder (manufactured by High Purity Chemicals, 300 μm Pass, purity 99.95%), 6.00 g of TiO2 _powder (manufactured by High Purity Chemicals, average particle size of about 2 μm, purity 99.99%), and 0.03 g of SiO2 _powder (manufactured by High Purity Chemicals, average particle size of 0.8 μm, purity 99.9%) were weighed and pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold, the amount of the mixed powder in the conditions of Example 2 was changed to 6.0 g, the heating temperature was changed to 1100°C, and the sintering time was changed to 45 minutes. Discharge plasma sintering was performed under these conditions to obtain a sintered body of Comparative Example 2. The crystal structure of the sintered body of Comparative Example 2 was analyzed, and the result showed that A (25°C) was 0.3786. Furthermore, according to the addition amount, the addition composition of the sintered body of Comparative Example 2 was Ti _1.99 Si _0.01 O _3.14 .

<Comparative Example 3> Weigh 1.96 g of Ti ₂ O ₃ powder (produced by High Purity Chemical Company, 45 μm Pass, purity 99%), 2.23 g of Cr ₂ O ₃ powder (average particle size of about 3 μm, purity 99.9%), and 1.96 g of ZrO ₂ powder (produced by High Purity Chemical Company, particle size 20-40 μm, purity 98%), and grind them in a mortar to obtain a mixed powder. The obtained mixed powder was placed in a special carbon mold, and the amount of the mixed powder in the conditions of Example 2 was changed to 6.0 g, the heating temperature was changed to 1200°C, and the sintering time was changed to 1 hour. Discharge plasma sintering was performed under these conditions to obtain a sintered body of Comparative Example 3. The crystal structure of the sintered body of Comparative Example 2 was analyzed, and the result showed that A (25°C) was 0.3711. In addition, according to the addition amount, the addition composition of the sintered body of Comparative Example 3 was Ti _0.72 Cr _0.77 Zr _0.38 O ₃ .

The results of the Examples and Comparative Examples are shown in Table 1. [Table 1] Table 1 Join the group Oxygen deficiency δ Sintering temperature Ratio of a-axis to c-axis Absolute maximum negative thermal expansion coefficient The temperature at which the absolute value of the negative thermal expansion coefficient is the largest A(25℃) A(100℃) ppm/℃ Embodiment 1 Ti _1.87 Nb _{0.1 3} O _2.92 0.02 1350℃ 0.3773 0.3756 -twenty one 153℃ Embodiment 2 Ti _1.80 Al _0.20 O ₃ -0.01 1500℃ 0.3772 - -29 174℃ Embodiment 3 Ti _1.83 Cr _0.17 O ₃ -0.04 1500℃ 0.3769 0.3761 -26 165℃ Embodiment 4 Ti _{1.90 Cr 0.10} O ₃ -0.06 1300℃ 0.3772 - -35 177℃ Embodiment 5 Ti _1.75 Nb _{0. 25} O _2.92 0.06 1350℃ 0.3758 0.3752 -31 155℃ Comparison Example 1 Ti ₂ O ₃ -0.02 1350℃ 0.3779 0.3770 -43 190℃ Comparison Example 2 _{Ti 1.99} Si _{0.01 O 3.14} -0.28 1100℃ 0.3786 - -0.2 190℃ Comparison Example 3 Ti _{0. 72} Cr _{0. 77} Zr _{0. 38} O ₃ - 1200℃ 0.3711 - - No negative thermal expansion shown

FIG. 1 shows the temperature dependence of the dimensional change rate ΔL(T)/L(30° C.) of Examples 1, 2, 5 and Comparative Examples 1, 2, 3.

FIG. 2 shows the thermal expansion coefficient α(T)(1/°C) of Examples 1 to 5 and Comparative Examples 1, 2, and 3, that is, the temperature differential of the dimensional change rate ΔL(T)/L(30°C).

FIG3 shows the relationship between temperature and A(T) in Examples 1, 5 and Comparative Example 1.

It has been confirmed that the titanium oxide of the embodiment shows an absolute maximum negative thermal expansion coefficient at a temperature lower than 190°C.

FIG1 is a graph showing the temperature dependence of the dimensional change rate ΔL(T)/L(30°C) of Examples 1, 2, 5 and Comparative Examples 1, 2, 3. FIG2 is a graph showing the temperature differential of the thermal expansion coefficient α(T) (1/°C) of Examples 1 to 5 and Comparative Examples 1, 2, 3, i.e., the dimensional change rate ΔL(T)/L(30°C). FIG3 is a graph showing the relationship between temperature and A(T) of Examples 1, 5 and Comparative Example 1.

Claims (8)

A titanium oxide, which satisfies the following requirements 1 to 3 and is represented by Ti _2-x M _x O _3-δ (x=0.02~0.66, δ=-0.32~0.40) (wherein a metal and/or semi-metal element other than titanium is set as M), and M is at least one selected from the group consisting of Mg, Al, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, In, Sn, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, W, and Bi : Requirement 1: When T = 25 ° C, A (T) does not reach 0.3780; A (T) is (the lattice constant of the a-axis (short axis) of the above-mentioned titanium oxide) / (the lattice constant of the c-axis (long axis) of the above-mentioned titanium oxide) at temperature T, and the above-mentioned lattice constants are obtained by X-ray diffraction measurement of the above-mentioned titanium oxide; Requirement 2: Contains metals and/or semi-metallic elements other than titanium; Requirement 3: The total molar content of metals and semi-metallic elements other than titanium is less than the molar content of titanium. For example, the titanium oxide in claim 1, when T=25℃, A(T) is less than 0.3774. The titanium oxide of claim 1 or 2, wherein the metal and/or semi-metal element other than titanium is selected from the element group belonging to the 3rd to 6th period. A powder, which is a powder of titanium oxide as claimed in any one of claims 1 to 3. A powder composition comprising the powder as claimed in claim 4. A solid composition comprising a powder as in claim 4 or a powder composition as in claim 5. A liquid composition comprising a powder as in claim 4 or a powder composition as in claim 5. A shaped body, which is a powder as in claim 4 or a shaped body of a powder composition as in claim 5.