JP7338881B2 - NEGATIVE THERMAL EXPANSION MATERIAL PARTICLE GROUP, COMPOSITE MATERIAL AND METHOD FOR MANUFACTURING SAME - Google Patents

Description

TECHNICAL FIELD The present invention relates to a negative thermal expansion material fine particle group, a composite material, and a method for producing the same.

Generally, it is known that a substance thermally expands as its temperature rises. However, the advanced development of industrial technology in recent years calls for controlling even thermal expansion, which can be said to be the fate of solid materials. Even if the length change rate is about 10 ppm (10 ^-5 ), even if it is a slight change from the general sense, it is necessary to manufacture semiconductor devices that require high precision at the nanometer level. It is a big problem in fields such as precision instruments that have an effect. In addition, in devices that combine multiple materials, other problems such as interfacial peeling and wire breakage may occur due to differences in thermal expansion of the constituent materials.

On the other hand, there is also known a negative thermal expansion material (having a negative coefficient of linear expansion) in which the lattice volume decreases as the temperature rises. For example, a composite material is known in which thermal expansion is suppressed by mixing α-Cu ₂ V ₂ O ₇ having a negative coefficient of linear expansion and Al having a positive coefficient of linear expansion (for example, non-patent literature 1.).

α-Cu ₂ V ₂ O ₇ is known to exhibit negative thermal expansion with a coefficient of linear expansion of -5 to -6 ppm/K in the temperature range from room temperature to 200°C.

Especially in the field of electronic devices, where miniaturization, sophistication, and complexity are rapidly progressing, the difference in thermal expansion between constituent materials creates serious problems such as peeling and disconnection, making thermal expansion control an urgent issue. (For example, Non-Patent Document 2). Thermal expansion control of materials such as resin films, adhesives, interlayer fillers, and substrates is essential for thermal expansion control in the field of electronic devices, and it is assumed that these materials will be used in sizes of several micrometers. In order to achieve this, it is necessary to reduce the size of the thermal expansion inhibitor from submicrons to about 1 μm.

N. Zhang et al., "Tailored thermal expansion and electrical properties of α-Cu2V2O7/Al," Ceramics International, 2016, 42, p.17004-17008 H. Kino, T. Fukushima, and T. Tanaka, Proceedings of 2017 IEEE 67th Electronic Components and Technology Conference, 1523 (2017). DOI: 10.1109/ECTC.2017.209 Toagosei, "Negative thermal expansion filler 'Ultea'", grade table, [online], [searched on January 13, 2019], Internet <URL: http://www.toagosei.co.jp/products/ performance_chemicals/amenity/pdf/ultea_01.pdf>

However, even in the case of a bulk material or a coarse powder material exhibiting a huge negative thermal expansion, the negative thermal expansion is often significantly impaired as the particles are made finer. For example, commercially available negative thermally expandable fine particles (Non-Patent Document 3) mainly composed of zirconium phosphate are known, but they have a particle size of about 1 μm and α = -2 ppm/K, and the ability to suppress thermal expansion is not sufficient. I had a problem.

Therefore, an object of the present disclosure is to provide a negative thermal expansion material fine particle group, a composite material, and a method for producing the same, which exhibit a large negative thermal expansion in a wide temperature range even when finely divided.

In order to achieve the above object, one aspect of the present disclosure provides the following negative thermal expansion material fine particle group, composite material, and method for producing the same.

Represented by the general formula (1) Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga, and Fe), has a negative coefficient of linear expansion, and has a laser diffraction/scattering formula Provided is a negative thermal expansion material fine particle group comprising fine particles having a volume frequency center particle size (median diameter) of 30 nm to 5 μm according to a particle size distribution evaluation method.
Also provided is a composite material containing the negative thermal expansion material fine particle group in a thermosetting resin.
Also provided is a metal-based composite material of a metal and the negative thermal expansion material fine particle group.
In addition, an aqueous solution consisting of a raw material of a compound represented by Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga, and Fe) and an organic acid, or an inorganic salt aqueous solution, an organic metal A preparation step of preparing an aqueous compound solution;
A misting step of misting the solution obtained in the preparation step;
and a heating step of heat-treating the mist obtained in the misting step in a temperature range of 600° C. to 1000° C. while circulating it with a carrier gas.

According to the present disclosure, it is possible to achieve a negative thermal expansion material that exhibits a large negative thermal expansion over a wide temperature range even when microparticulated.

FIG. 1 is a schematic diagram for explaining a method for producing a group of negative thermal expansion material fine particles according to an embodiment. FIG. 2 is a graph showing linear thermal expansion of a negative thermal expansion material, an epoxy resin, and a composite material thereof in Examples. FIG. 3A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 3B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 3B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 4A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 4B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 4C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 5A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 5B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 5B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 6 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example. FIG. 7A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 7B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 7C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 7D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 7E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 8A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 8B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 8C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 8D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 8E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 9A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 9B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 9C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 9D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 9E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 10 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example. FIG. 11A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 11B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 11C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 11D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 11E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 12A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 12B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 12C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 12D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 12E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 13A is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 13B is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 13C is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 13D is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 13E is an FE-SEM (Field Emission Scanning Electron Microscope) image showing the structure of the negative thermal expansion material fine particle group in the example. FIG. 14 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example. FIG. 15A is an SEM image of the negative thermal expansion material fine particle group in Example, showing the measurement points. FIG. 15B is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15C is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15D is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15E is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15F is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15G is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 15H is an image obtained by the EBSD method in the SEM corresponding to the measurement points. FIG. 16 is a schematic diagram for explaining the structure of fine particles of a negative thermal expansion material. FIG. 17 is a graph showing linear thermal expansion of negative thermal expansion materials, aluminum, and composite materials thereof in Examples.

[Embodiment]
(Structure of Negative Thermal Expansion Material Fine Particle Group)
In the disclosure of the present application, the inventors focused on the Cu ₂ V ₂ O ₇ system as a candidate for a substance exhibiting negative thermal expansion. α-Cu ₂ V ₂ O ₇ , which has a cubic crystal structure, is of interest as a multiferroic material in which ferroelectricity and weak paramagnetism coexist. Anisotropic thermal deformation of the crystal lattice is observed in the region, probably due to pyroelectricity. As a result, negative thermal expansion occurs in which the unit cell volume shrinks as the temperature rises over a wide temperature range.

By substituting Cu ₂ V ₂ O ₇ with various elements, it can take a cubic α-phase, a monoclinic β-phase, and a triclinic γ-phase. Therefore, the present inventors have found that when part of the Cu site is replaced with another element, negative thermal expansion characteristics that cannot be realized in the conventional α-Cu ₂ V ₂ O ₇ system are exhibited. A group of negative thermal expansion material particles having such a configuration, a composite material containing the group of negative thermal expansion material particles, and a method for producing these have been devised.

Here, the term "fine particles" refers to aggregates composed of even smaller single crystal grains (see Fig. 16), and the term "fine particles group" refers to the volume frequency according to the laser diffraction/scattering particle size distribution evaluation method. It is assumed to be an aggregate of fine particles having a center particle diameter (median diameter) of 5 μm or less. In the following, the "volume frequency median particle size (median size) determined by the laser diffraction/scattering particle size distribution evaluation method" may be simply referred to as "particle size". Also, the particle size of the fine particles can be appropriately changed by changing the conditions of the manufacturing method described below. The negative thermal expansion material particle group of the present disclosure has a negative linear expansion coefficient at the above particle diameter in the temperature range of 100 to 700 K, preferably less than α = -3.5 ppm/K, more preferably α = It has a coefficient of linear expansion of -6 ppm/K or less, more preferably α=-10 ppm/K.

The method for producing the negative thermal expansion material utilizes a method for producing fine particles of metal oxide by a spray pyrolysis method (see, for example, Japanese Patent No. 5413898). Details are described below.

(Method for producing negative thermal expansion material fine particle group)
Next, a method for producing the negative thermal expansion material fine particle group according to the present embodiment will be described.

FIG. 1 is a schematic diagram for a manufacturing process of a group of negative thermal expansion material fine particles.

Negative thermal expansion material manufacturing apparatus 100 includes a mist generator (not shown) that generates mist 10 (aerosol) from a raw material solution, a flow passage 101 through which carrier gas CG containing mist 10 flows, and mist 10 at 150 to 400 ° C. A drying furnace 102 that heats and dries, a thermal decomposition furnace 103 that heats and thermally decomposes the dried mist 13 at 600 to 1000° C., and a collection device (not shown) that collects fine particles 16 generated as a result of thermal decomposition. and

Various raw material reagents can be used as the raw material solution in order to produce the negative thermal expansion material. Specifically, an aqueous solution or an inorganic salt aqueous solution consisting of raw materials of a compound represented by Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga and Fe) and an organic acid , to prepare and use an aqueous organometallic compound solution (preparation step).

When Zn is used for R in Cu _2-X R _X V ₂ O ₇ , a stable β-phase (monoclinic) crystal structure is obtained at room temperature. When Zn is used for R, X is 0.1 to 1, preferably 0.15 to 0.5, more preferably 0.15 to 0.3. As a result, the coefficient of linear expansion has a larger absolute value than the coefficient of linear expansion of α-Cu ₂ V ₂ O ₇ in which Cu is not substituted with R. The numerical range of X is based on the following facts.

First, it is known that the crystal system becomes the β phase under the condition of X=0.2 in the examples of the present disclosure, which will be described later. In addition, although non-patent literature (J. Pommer et al., Physical Review B 67, 214410 (2003)) does not report thermal expansion characteristics, Cu _2-x Zn _x V ₂ O ₇ has a wide range of x and is known to become a β phase when x>0.15. Combining these, it is reasonably inferred from knowledge of condensed matter physics that similar properties are exhibited in the vicinity of X=0.2. It should also be considered that the x value of 0.15 at the phase boundary between the α phase and the β phase varies depending on the sample synthesis conditions and the like.

Furthermore, as shown in Non-Patent Document 1, the bulk body exhibits negative thermal expansion characteristics even in the α phase, so even if the crystal structure of the α phase is obtained, the negative thermal expansion material of the present disclosure A method for producing a microparticle group is effective. That is, the crystal structure obtained in the present disclosure is not necessarily limited to the β-phase, and may be the α-phase as long as other requirements such as the coefficient of linear expansion are satisfied. This point should also be considered.

Next, as the raw material compounds, oxides such as copper oxide, zinc oxide, and vanadium pentoxide can be used. Moreover, the organic acid of aqueous solution can use a citric acid, an acetic acid, etc., for example. Inorganic salt aqueous solutions and organometallic compound aqueous solutions include, for example, metal nitrates, metal acetates, metal sulfates, metal chlorides, metal fatty acids, metal alkoxides, and metal acetylacetonates. , sulfuric acid, etc. may be used.

The solution obtained in the preparation step is turned into mist 10 by a mist generator such as an ultrasonic vibrator or a two-fluid nozzle (mist formation step). The diameter of the droplets forming the mist 10 is adjusted by changing the mist generation method or the like.

The mist 10 generated in the misting process is heat-treated in the temperature range of 150° C. to 400° C. while flowing the carrier gas CG through the heating space corresponding to the drying furnace 102 in the flow path 101 (drying process). The mist 10 flowing through the heating space of the drying furnace 102 is heated in the temperature range of 150° C. to 400° C., and is gradually dried into mist 11, mist 12, and mist 13. FIG. Air, for example, is used as the carrier gas CG for circulating the mists 10-13. In addition to air, an inert gas such as nitrogen gas or argon gas, or a reducing gas such as hydrogen gas may be used.

Next, heat treatment is performed in a temperature range of 600° C. to 1000° C. while the carrier gas CG is circulated in the heating space corresponding to the pyrolysis furnace 103 in the flow path 101 (heating step). The dried product 14 flowing through the heating space of the pyrolysis furnace 103 is further heated in the temperature range of 600° C. to 1000° C., thermally decomposed and undergoes a solid phase reaction, and most of the particles 15 during pyrolysis are fine particles after pyrolysis. 16.

Next, the resulting product obtained in the heating step is heat-treated (fired) again at a temperature range of, for example, 600° C. to 1000° C. (secondary firing step). The secondary firing process is performed in a predetermined atmosphere using an electric furnace or the like. As a result, the dried product 14 incompletely pyrolyzed and the particles 15 in the process of pyrolysis contained in the resulting product, that is, the organic acid salt particles, are decomposed into fine particles 16 and collected as a fine particle group.

In addition, the secondary baking process is not necessarily required. For example, by securing a larger heating space corresponding to the pyrolysis furnace 103 in the heating process and adjusting the flow rate of the carrier gas CG, the same effect as in the case of going through the secondary firing process without going through the secondary firing process can be achieved. Fine particles 16 of negative thermal expansion material can be obtained. In this case, since it is a one-process process, the manufacturing cost can be reduced compared to the case where the secondary baking process is performed separately from the heating process.

By adjusting the temperature during spray pyrolysis, the flow rate of the carrier gas CG, the residence time in the mist furnace, the raw material solution concentration, etc., it is possible to obtain the fine particles 16 having a desired composition, microstructure, internal structure, and particle size. can be done.

The structure of the microparticles contained in the microparticle group produced by the above manufacturing method is schematically shown in FIG.

FIG. 16 is a schematic diagram for explaining the structure of the fine particles 16. As shown in FIG.

The microparticles 16 are aggregates of a plurality of crystal grains 160 to 163 and are polycrystalline. The crystal structure of grains 160-163 will be described later in FIGS. 15A-15H.

Next, a composite material is obtained by mixing a fine particle group of the obtained fine particles 16 with a thermosetting resin such as an epoxy resin in a desired volume ratio. As a mixing method, a blade mixer, a rotation-revolution stirrer, or the like is adopted.

[Example]
A microparticle group of β-Cu _1.8 Zn _0.2 V ₂ O ₇ was produced (x=0.2) based on the manufacturing method of the negative thermal expansion material described in the above embodiment.

First, as a preparation process, raw reagents (powder) of CuO, ZnO and V ₂ O ₅ weighed in a stoichiometric ratio were mixed in a mortar and fired in the air at a temperature of 670° C. for 10 hours. The resulting powder was ground in a mortar and dissolved in pure water together with anhydrous citric acid. At that time, 3 g of anhydrous citric acid and 100 mL of pure water were added to 1 g of the sample powder, and the mixture was stirred using a magnetic stirrer until the sample powder was dissolved. Note that, for example, V ₂ O ₃ may be used instead of V ₂ O ₅ .

Next, the obtained aqueous solution was misted into droplets with a diameter of 3 μm, and the drying furnace temperature was 400° C., the pyrolysis furnace temperature was 600° C., the flow rate of the carrier gas CG was 3.8 L/min, and the residence time in the mist furnace was 7 sec. By heating, particles of the negative thermal expansion material having an average particle size of 2 μm were produced. Next, the obtained particles were subjected to secondary firing at 670° C. for 10 minutes to obtain a negative thermal expansion material fine particle group. The obtained β-Cu _1.8 Zn _0.2 V ₂ O ₇ fine particle group had an average particle size of 2 μm.

Next, the obtained fine particles and the epoxy resin were mixed at a ratio of 50:50 by volume, respectively, to form a composite material.

FIG. 2 is a graph showing linear thermal expansion of a negative thermal expansion material, an epoxy resin, and a composite material thereof in Examples.

The linear thermal expansion of the negative thermal expansion material was measured for a sample in which fine particles were sintered. Since the linear thermal expansion of negative thermal expansion materials is not linear with temperature, the numerical values of the coefficient of linear expansion α shown below are average values. The prediction of the rule of composition (broken line in the graph) is a proportion by volume ratio assuming that the negative thermal expansion material and the epoxy resin each exhibit their own thermal expansion in the composite material. As shown in FIG. 2, the linear expansion coefficient α of the negative thermal expansion material composed of β-Cu _1.8 Zn _0.2 V ₂ O ₇ obtained in the above example was -10 ppm/K. On the other hand, the linear expansion coefficient of the epoxy resin is 70 ppm/K, and the linear expansion coefficient of the composite material of the negative thermal expansion material and the epoxy resin is about 26.7 ppm/K, which is suppressed more than the linear expansion coefficient of the epoxy resin. It can be seen that the prediction of the compound rule is somewhat suppressed.

The above composite material is a mixture of an epoxy resin and a negative thermal expansion material at a volume ratio of 50:50, respectively. Non-patent literature (K. Takenaka and M. Ichigo, Composites Science and Technology 104, 47-51 (2014)) reports a detailed analysis of how the thermal expansion of the resin is suppressed. From the results of the examples of the present disclosure (blended at a volume ratio of 50:50), it can be easily inferred that thermal expansion is suppressed according to the blending ratio even at other blending ratios.

In addition, after mixing the obtained fine particle group and aluminum powder at a ratio of 30 to 70 by volume, respectively, it was inserted into a carbon die and a discharge plasma sintering apparatus (Syntex Lab; manufactured by SPS Syntex). sintered to form a composite material. The sintering conditions were 40 MPa, 375° C., and 5 min in a vacuum or argon atmosphere.

FIG. 17 is a graph showing linear thermal expansion of negative thermal expansion materials, aluminum, and composite materials thereof in Examples.

The linear thermal expansion of the negative thermal expansion material is the same as in FIG. The prediction of the rule of composition (broken line in the graph) is a proportion by volume ratio, assuming that the negative thermal expansion material and aluminum each exhibit their own thermal expansion in the composite material. As shown in FIG. 17, the linear expansion coefficient α of the negative thermal expansion material composed of β-Cu _1.8 Zn _0.2 V ₂ O ₇ obtained in the above example was −10 ppm/K. On the other hand, the linear expansion coefficient of aluminum is about 20 ppm/K, and the linear expansion coefficient of the composite material of the negative thermal expansion material and aluminum is about 17 ppm/K, which is suppressed more than the linear expansion coefficient of aluminum, and the prediction of the rule of combination It can be seen that it is slightly larger than

The above composite material is a mixture of a negative thermal expansion material and aluminum in a volume ratio of 30:70, respectively. Therefore, it can be inferred that thermal expansion is suppressed depending on the compounding ratio even at other compounding ratios. Compositing of aluminum and a negative thermal expansion material is not limited to sintering, and any method may be used as long as a metal matrix composite material is obtained as a result of compositing.

Next, the fine particles obtained under the conditions of the above Examples were subjected to the secondary firing process under a plurality of conditions, with different secondary firing conditions. In addition, unless otherwise stated below, fine particles are placed in an electric furnace and the temperature is raised from room temperature to the target firing temperature at a temperature rate of 10 ° C./min, then secondary firing is performed while maintaining the stated temperature, and then room temperature. was performed by lowering the temperature to

(Secondary firing step-temperature condition 1)
The following scanning microscope images of FIGS. 3A to 3C were obtained by photographing fine particle groups obtained by performing the secondary firing process under the conditions of 670° C. and 5 hours in an air atmosphere. The scanning microscope images of FIGS. 4A to 4C were obtained by photographing fine particle groups obtained by performing the secondary firing process under the conditions of 620° C. and 5 hours in an air atmosphere. The scanning microscope images of FIGS. 5A to 5C were obtained by photographing fine particle groups obtained by performing the secondary firing process under the conditions of 580° C. and 5 hours in an air atmosphere. Furthermore, FIG. 6 is a graph showing the diffraction intensity distribution obtained from the X-ray diffraction of the negative thermal expansion material fine particle group when the temperature conditions of the secondary firing process are changed.

3A to 3C are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

3A to 3C are scanning electron microscope images of the negative thermal expansion material fine particle group observed at different magnifications (3,000 times, 5,000 times, and 10,000 times). was found to be well controlled. For observation, a scanning electron microscope manufactured by JEOL Ltd. was used.

4A to 4C are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

4A to 4C are scanning electron microscope images of negative thermal expansion material fine particle groups observed at different magnifications (3,000 times, 5,000 times, and 10,000 times). was found to be well controlled.

5A to 5C are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

5A to 5C are scanning electron microscope images of negative thermal expansion material fine particle groups observed at different magnifications (3,000 times, 5,000 times, and 10,000 times). was found to be well controlled.

FIG. 6 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example.

It can be seen that the crystal structure is good under any temperature conditions in the secondary firing step.

From the above, it was found that the particle shape of the fine particle group was well controlled at least at 670° C. or lower as the temperature condition of the secondary firing by changing the temperature conditions of the secondary firing step.

(Secondary baking step-time conditions)
The following scanning microscope images in FIGS. 7A to 7E show that the secondary firing process was performed at 670° C. in an air atmosphere for 2 hours; 5° C./min, 1 hour; 5° C./min, 20 min; /min, 10 min; 5°C/min, 10 min; 10°C/min. The scanning microscope images of FIGS. 8A to 8E and FIGS. 9A to 9E are obtained by changing the photographing magnification under the same conditions as in FIGS. 7A to 7E. Furthermore, FIG. 10 is a graph showing the diffraction intensity distribution obtained from the X-ray diffraction of the negative thermal expansion material fine particle group when the temperature conditions of the secondary firing process are changed.

7A to 7E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

7A to 7E are scanning electron microscope images of negative thermal expansion material microparticles observed at 3,000 times. For observation, a scanning electron microscope manufactured by JEOL Ltd. was used.

8A to 8E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

8A to 8E are scanning electron microscope images of negative thermal expansion material microparticles observed at a magnification of 5,000.

9A to 9E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

9A to 9E are scanning electron microscope images of negative thermal expansion material fine particles observed at a magnification of 10,000.

As described above, by changing the time conditions of the secondary firing process, under the conditions of 670 ° C., the particle shape of the fine particle group is well controlled with little sintering under the conditions of 20 minutes or less firing time. However, it was found that when the firing time was 1 hour or more, sintering occurred frequently and the particle shape of the fine particle group was not well controlled.

FIG. 10 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example.

It can be seen that the composition is good under any temperature conditions in the secondary firing process.

(Secondary firing step-temperature condition 2)
The following scanning microscope images of FIGS. C./min, 670.degree. C.; 10 min; 40.degree. C./min, 670.degree. C.; 10 min; 10.degree. Also, the scanning microscope images of FIGS. 12A to 12E and FIGS. 13A to 13E are obtained by changing the photographing magnification under the same conditions as those of FIGS. 11A to 11E. Furthermore, FIG. 14 is a graph showing the diffraction intensity distribution obtained from the X-ray diffraction of the negative thermal expansion material fine particle group when the temperature conditions of the secondary firing process are changed.

11A to 11E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

11A to 11E are scanning electron microscope images of negative thermal expansion material microparticles observed at 3,000 times. For observation, a scanning electron microscope manufactured by JEOL Ltd. was used.

12A to 12E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

12A to 12E are scanning electron microscope images of negative thermal expansion material microparticles observed at 5,000 times.

13A to 13E are FE-SEM (Field Emission Scanning Electron Microscope) images showing the structure of the negative thermal expansion material fine particle group in the example.

13A to 13E are scanning electron microscope images of negative thermal expansion material microparticles observed at 10,000 times.

As described above, by changing the time conditions of the secondary firing process, under the condition of the firing time of 10 minutes and the firing temperature of 670 ° C. or less, there is little sintering and the particle shape of the fine particle group is well controlled. However, it was found that when the firing temperature is 720° C. or higher, sintering occurs frequently and the particle shape of the fine particle group cannot be well controlled.

FIG. 14 is a graph showing the diffraction intensity distribution by X-ray diffraction of the negative thermal expansion material fine particle group in the example.

It can be seen that the composition is good under any temperature conditions in the secondary firing process.

FIG. 15A is an SEM (Scanning Electron Microscope) image (tilt 0°) of the negative thermal expansion material fine particle group in the example, showing measurement points p ₁ to p ₇ . 15B to 15H are images obtained by the EBSD method in a SEM (scanning electron microscope) corresponding to the measurement points p ₁ to p ₇ (lower image; upper image shows the measurement points; SEM image at 70°).

15A to 15H, the heating process is performed under the conditions of a drying furnace temperature of 400° C., a thermal decomposition furnace temperature of 600° C., a carrier gas CG flow rate of 3.8 L/min, and a residence time in the mist furnace of 7 sec. A secondary firing process is performed under the conditions of 10 min and 10° C./min, and the generated fine particle group of the negative thermal expansion material is embedded in epoxy resin, a cross-sectional sample is prepared by ion milling, and the acceleration voltage is 20 kV. I took a picture.

According to the image of FIG. 15A, it can be seen that the fine particles are composed of a plurality of crystal grains. Measuring points p ₁ to p ₃ belong to the first grain, measuring point p ₄ belongs to the second grain, measuring point p ₅ belongs to the third grain, measuring points p ₆ to p ₇ belong to It belongs to the fourth grain.

According to the images of FIGS. 15B to 15D, the crystal structures of the measurement points p ₁ to p ₃ in the first crystal grain are the same, so it can be seen that the first crystal grain is a crystal grain. According to the images of FIGS. 15G to 15H, it can be seen that the fourth crystal grain is a crystal grain because the crystal structures of the measurement points p ₆ to p ₇ in the fourth crystal grain are the same. Furthermore, it can be seen that the crystal structures of the first crystal grains, the second crystal grains, the third crystal grains, and the fourth crystal grains are different from each other. In other words, the fine particles have a structure in which a plurality of different crystal grains are aggregated.

(Effect of Embodiment)
According to the above-described embodiments and examples, Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga, and Fe; X is 0.1 to 1). An aqueous solution or the like consisting of the raw material of the compound represented and an organic acid was prepared, turned into a mist, dried with a carrier gas, and heated to produce a fine particle group, so the volume frequency by the laser diffraction/scattering particle size distribution evaluation method A negative thermal expansion material having a negative coefficient of linear expansion in a wide temperature range of 100 to 700K can be produced even when the central particle diameter (median diameter) is in the range of 30 nm to 5 μm. Furthermore, a linear expansion coefficient of α=-10 ppm/K could be achieved in the example.

In addition, since the negative thermal expansion material is produced as a fine particle group, it can be easily mixed with the desired resin, and since it is fine particles, it is possible to obtain a composite material that is uniformly dispersed throughout the resin. It is possible to obtain the effect of uniformly suppressing thermal expansion over the entire length.

[Other embodiments]
In addition, the present disclosure is not limited to the above embodiments, and changes, deletions, additions, etc. of the combinations of each process and each material described in the above embodiments are possible within the scope of not changing the gist of the present disclosure. .

Provided are a group of negative thermal expansion material fine particles, a composite material, and a method for producing the same, which exhibit large negative thermal expansion over a wide temperature range and have desired particle characteristics.

10 to 13: Mist 14: Dried product 15: Particles 16: Fine particles 100: Negative thermal expansion material manufacturing device 101: Flow path 102: Drying furnace 103: Pyrolysis furnace CG: Carrier gas

Claims (9)

Represented by the general formula (1) Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga and Fe , X is 0.1 to 1 ), and the temperature range is 100 to 700 K Negative thermal expansion material fine particle group having a linear expansion coefficient of −6 ppm/K or less as an average value at , and a volume frequency median particle diameter (median diameter) of 30 nm to 5 μm according to a laser diffraction/scattering particle size distribution evaluation method . 2. The group of negative thermal expansion material fine particles according to claim 1 , wherein said R is Zn. 3. The negative thermal expansion material fine particle group according to claim 1 or 2, characterized in that it is a monoclinic β phase. A composite material containing the negative thermal expansion material fine particle group according to any one of claims 1 to 3 in a thermosetting resin. A metal-based composite material comprising a metal and the negative thermal expansion material fine particle group according to any one of claims 1 to 3 . Cu _2-X R _X V ₂ O ₇ (R is at least one element selected from Zn, Ga and Fe , X is 0.1 to 1 ) and an aqueous solution consisting of a raw material of a compound represented by an organic acid, or a preparation step of preparing an aqueous inorganic salt solution and an aqueous organometallic compound solution;
A misting step of misting the solution obtained in the preparation step;
A heating step of heat-treating the mist obtained in the misting step in a temperature range of 600 ° C. to 1000 ° C. while circulating it with a carrier gas. A method for producing a negative thermal expansion material fine particle group of /K or less. 7. The method for producing a negative thermal expansion material fine particle group according to claim 6 , further comprising a drying step of heat-treating the mist in a temperature range of 150° C. to 400° C. after the misting step and before the heating step. 8. The method for producing a group of negative thermal expansion material fine particles according to claim 6 , further comprising a secondary firing step of heat-treating the negative thermal expansion material fine particles obtained in the heating step at a temperature in the range of 580.degree. C. to 1000.degree. 9. The method for producing a negative thermal expansion material fine particle group according to claim 8 , wherein the secondary firing step is a heat treatment at a temperature range of 580° C. to 670° C. for 10 to 600 minutes.

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