Powder manufacturing method and powder manufacturing apparatus

Abstract

To provide a technique for producing powder having excellent characteristics.SOLUTION: The powder manufacturing method includes a step of introducing the powder into the heating unit, a step of heating the powder while dispersing the powder by causing the fluid inside the heating unit to flow, and a step of cooling the powder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a powder manufacturing method and a powder manufacturing apparatus. [Background technology]

[0002] It is generally known that materials expand thermally as the temperature rises. However, the recent advances in industrial technology have made it necessary to control even the thermal expansion that is the fate of solid materials. The rate of change in length (linear strain) is 10 ppm (10 -5 ), which is considered to be a small change in shape by ordinary standards, can be a major problem in fields such as semiconductor device manufacturing, which requires high precision at the nanometer level, and precision equipment, where even the slightest distortion in a component can have a significant impact on its function. Furthermore, in devices made from multiple materials, differences in the thermal expansion of the constituent materials can cause other problems such as interfacial peeling and disconnections.

[0003] On the other hand, negative thermal expansion materials are also known, whose lattice volume decreases with increasing temperature (having a negative thermal expansion coefficient). For example, zinc magnesium pyrophosphate, Zn 2-x Mg x P2O7 exhibits a large negative thermal expansion over a wide temperature range, centered around room temperature, and is low cost and has a small environmental impact, making it a promising industrial thermal expansion inhibitor (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] “Structural phase transition and giant negative thermal expansion in pyrophosphate Zn2-xMgxP2O7”, Y. Kadowaki, R. Kasugai, Y. Yokoyama, N. Katayama, Y. Okamoto, and K. Takenaka, Appl. Phys. Lett. 119, 201906 (2021) Summary of the Invention [Problem to be solved by the invention]

[0005] In the field of electronic devices, which are rapidly becoming smaller, more functional, and more complex, differences in thermal expansion between constituent materials can cause serious problems such as peeling and disconnection, making thermal expansion control an urgent issue. Controlling the thermal expansion of components such as resin films, adhesives, interlayer fillers, and substrates is considered essential for controlling thermal expansion in the electronic device field, but these components are expected to be used at sizes of around several microns, and to achieve this, it is necessary to miniaturize thermal expansion inhibitors from submicron to around 1 micron.

[0006] However, even for materials that exhibit large negative thermal expansion in bulk or coarse powder form, the negative thermal expansion properties are often significantly impaired when the material is atomized. This is thought to be due in part to the introduction of strain and defects into the crystal during the atomization process.

[0007] The present disclosure has been made in light of these circumstances, and one of its objectives is to provide a technique for producing powder having excellent properties. [Means for solving the problem]

[0008] In order to solve the above problems, a method for producing powder according to one aspect of the present disclosure includes the steps of introducing powder into a container, heating the powder while dispersing the powder by flowing a fluid inside the container, and cooling the powder.

[0009] Another aspect of the present disclosure is a powder manufacturing apparatus including a powder introducing unit that introduces powder into a container, a heating unit that heats the powder in the container, and a flow generating unit that causes a fluid in the container to flow when the powder is heated by the heating unit. [Effects of the Invention]

[0010] According to the present disclosure, a technique for producing powder with excellent properties can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram schematically illustrating a configuration of a powder manufacturing apparatus according to an embodiment of the present disclosure. [Figure 2] 1 is a diagram schematically illustrating a configuration of a powder manufacturing apparatus according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a graph showing the particle size distribution of the powder of Example 1. [Figure 4] FIG. 2 is a diagram showing the linear thermal expansion of the powder of Example 1. [Figure 5] FIG. 10 is a graph showing the particle size distribution of the powder of Example 2. [Figure 6] FIG. 10 is a diagram showing the linear thermal expansion of the powder of Example 2. [Figure 7] FIG. 10 is a diagram showing the particle size distribution of the powder of Example 3. [Figure 8] FIG. 10 is a diagram showing the linear thermal expansion of the powder of Example 3. [Figure 9] FIG. 10 is a graph showing the particle size distribution of the powder of Example 4. [Figure 10] FIG. 10 is a diagram showing the linear thermal expansion of the powder of Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] In the powder manufacturing method of the present disclosure, the powder obtained by microparticulating a bulk or coarse powder is recrystallized to improve the deterioration of properties caused by the crystal distortion and defects introduced during microparticulation, thereby producing a fine powder that has the excellent properties of the bulk or coarse powder.

[0013] Heating powder is an effective way to promote recrystallization. Conventionally, powders are heated in a container such as a crucible. However, heating powders can cause problems such as the bonding of fine particles, resulting in an increase in particle size or unevenness. Such an increase in particle size or unevenness can sometimes contribute to a deterioration in the properties of the powder.

[0014] To solve this problem, the powder manufacturing method of the present disclosure involves heating the powder while dispersing it by flowing a fluid in which the powder is dispersed. This promotes recrystallization of the powder while suppressing bonding between fine particles, thereby suppressing the effects of particle size increase and non-uniformity and improving the properties of the powder.

[0015] Here, the term "fluid" refers to a continuous medium, such as a gas or a liquid, that has fluidity and does not generate shear stress in a stationary state, regardless of whether it is in a flowing state. Therefore, the powder production method of the present disclosure includes both a case where a fluid in a non-flowing state is made to flow, and a case where a fluid in a flowing state is made to continue to flow.

[0016] Fig. 1 shows a schematic configuration of a powder manufacturing apparatus according to an embodiment of the present disclosure. Fig. 2 shows another example configuration of a powder manufacturing apparatus according to an embodiment of the present disclosure. The powder manufacturing apparatus 1 includes a heating unit 10, a powder introducing unit 11, a fluid delivery unit 12, an inlet flow rate adjusting unit 13, an outlet flow rate adjusting unit 16, a cooling unit 17, a powder recovery unit 18, and a control unit 20 that controls these components.

[0017] The powder introduction unit 11 introduces powder into the heating unit 10. The fluid delivery unit 12 delivers a fluid that functions as a dispersion medium for dispersing the powder to the heating unit 10. The powder introduction unit 11 may mix the powder into the fluid delivered from the fluid delivery unit 12 and introduce the powder together with the fluid into the heating unit 10. In this case, the fluid also functions as a carrier for transporting the powder to the heating unit 10. The powder introduction unit 11 may deliver the powder together with the carrier fluid to mix the powder into the fluid delivered from the fluid delivery unit 12. As shown in FIG. 1, the powder introduction unit 11 and the fluid delivery unit 12 may be provided in parallel. Alternatively, as shown in FIG. 2, the fluid delivery unit 12 may be provided directly upstream of the powder introduction unit 11. In the latter case, the amount of powder delivered from the powder introduction unit 11 may be adjusted by the flow rate of the fluid delivered from the fluid delivery unit 12. The fluid delivery unit 12 may be configured by a pump or the like. The powder introduction section 11 and the fluid delivery section 12 may be configured by a powder blow gun used for powder coating, etc. The powder introduction section 11 may introduce powder into the heating section 10 separately from the fluid delivered from the fluid delivery section 12.

[0018] The inlet-side flow rate adjustment unit 13 adjusts the flow rate of the fluid flowing into the heating unit 10. The outlet-side flow rate adjustment unit 16 adjusts the flow rate of the fluid discharged from the heating unit 10. The inlet-side flow rate adjustment unit 13 and the outlet-side flow rate adjustment unit 16 may be configured by a valve with an adjustable opening, an orifice with an opening with an adjustable inner diameter, or the like. The inlet-side flow rate adjustment unit 13 and the outlet-side flow rate adjustment unit 16 are controlled by the control unit 20 to adjust the flow rate and fluidity of the fluid inside the heating unit 10 and to adjust the time the powder remains inside the heating unit 10 (heating time).

[0019] The heating unit 10 has a space capable of accommodating powder and heats the powder present in the space. The heating unit 10 may be constituted by any type of electric furnace. The heating unit 10 may also be constituted by a container and an electric heating wire provided on the inner wall or inside the container.

[0020] The powder introduced into the heating unit 10 is heated and recrystallized in the heating unit 10. This makes it possible to produce powder with a higher degree of crystallinity than the powder before heating. The powder introduced into the heating unit 10 is dispersed by the flow of the fluid delivered from the fluid delivery unit 12 into the heating unit 10, thereby suppressing bonding between fine particles. This makes it possible to produce powder with fine particles having small and uniform particle sizes. The fluid delivery unit 12 functions as a flow generation unit that causes the fluid inside the heating unit 10 to flow.

[0021] The fluid inside the heating unit 10 also flows due to convection caused by heating. Therefore, the heating unit 10 also functions as a flow generating unit. If the bonding of fine particles is sufficiently suppressed by the fluid flow caused by convection alone, the fluid delivery unit 12 may deliver the fluid at a flow rate necessary to introduce the powder into the heating unit 10. Alternatively, the fluid delivery unit 12 may not be provided.

[0022] An inlet 14 for introducing powder and fluid into the heating unit 10 may be provided in the lower part of the heating unit 10, and an outlet 15 for discharging powder and fluid from the heating unit 10 may be provided in the upper part of the heating unit 10. This allows the powder to be discharged from the upper outlet 15 together with the heated and rising fluid without having to suck the fluid from outside the heating unit 10, thereby simplifying the configuration of the powder manufacturing apparatus 1. Note that a suction unit for sucking the fluid from inside the heating unit 10 may be provided. In this case, the suction unit may function as the flow generating unit.

[0023] The heating unit 10 may heat the powder to a temperature lower than the melting point of the substance contained in the powder. This prevents the substance contained in the powder from melting and bonding together, and the heating unit 10 may heat the powder to a temperature close to the melting point of the substance contained in the powder. This further promotes recrystallization of the powder, thereby shortening the heating time. The heating unit 10 may heat the powder to a temperature slightly higher than the melting point of the substance contained in the powder. This melts the substance on the surface of the fine particles and causes them to become spherical due to surface tension, thereby improving the sphericity of the powder.

[0024] The heating unit 10 may heat the powder preferably to 800 to 1200° C., more preferably 1000 to 1100° C. The heating temperature of the powder may be 100° C. or higher, 200° C. or higher, 300° C. or higher, 400° C. or higher, 500° C. or higher, 600° C. or higher, 700° C. or higher, 800° C. or higher, 900° C. or higher, 1000° C. or higher, 1100° C. or higher, 1200° C. or higher, 1300° C. or higher, 1400° C. or higher, or 1500° C. or higher. The heating temperature of the powder may be 2000°C or less, 1900°C or less, 1800°C or less, 1700°C or less, 1600°C or less, 1500°C or less, 1400°C or less, 1300°C or less, 1200°C or less, 1100°C or less, 1000°C or less, 900°C or less, 800°C or less, 700°C or less, 600°C or less, 500°C or less, 400°C or less, 300°C or less, or 200°C or less.

[0025] The cooling unit 17 cools the powder heated by the heating unit 10. The cooling unit 17 may cool the powder by air cooling, water cooling, or other methods. A part of the flow path from the outlet 15 of the heating unit 10 to the powder recovery unit 18 may be open to the atmosphere. The powder recovery unit 18 recovers the powder cooled by the cooling unit 17.

[0026] The control unit 20 controls the flow generating unit so as to cause the fluid in which the powder is dispersed to flow when the powder is heated inside the heating unit 10. For example, the control unit 20 controls the fluid delivery unit 12, the inlet-side flow rate adjustment unit 13, and the outlet-side flow rate adjustment unit 16 to control the flow rate of the fluid so that the fluid flows inside the heating unit 10.

[0027] Although the above description has been given of a case where powder is continuously introduced into the heating unit 10 from the powder introduction unit 11 and powder is produced by a continuous operation method, powder may also be produced by a batch operation method. In this case, the fluid delivery unit 12, the inlet-side flow rate adjuster 13, and the outlet-side flow rate adjuster 16 may not be provided. As a flow generating unit for causing the fluid inside the heating unit 10 to flow, a stirring blade, a fan, or the like that stirs the fluid inside the heating unit 10 may be provided.

[0028] The powder produced by the powder production device 1 is measured using a laser diffraction / scattering particle size distribution evaluation method to determine the volume frequency median particle size (median diameter) D 50 The particle size may be an aggregate of fine particles having a diameter of 30 nm or more and less than 10 μm. Here, "fine particles" includes an aggregate of even smaller single crystal grains. Hereinafter, the "volume frequency median particle size (median diameter) determined by the laser diffraction / scattering particle size distribution evaluation method" may be simply referred to as "particle size." The particle size of a powder can be appropriately changed by changing the manufacturing conditions. For example, the volume frequency median particle size D of a powder 50 may be 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, 1.3 μm or less, 1.2 μm or less, 1.1 μm or less, 1 μm or less, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, 0.6 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, 0.2 μm or less, or 0.1 μm or less. 90 may be 20 μm or less, 18 μm or less, 16 μm or less, 14 μm or less, 12 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, 0.9 μm or less, or 0.8 μm or less.

[0029] The powder may include a negative thermal expansion material.

[0030] The negative thermal expansion material is represented by the general formula (1) Zn 2-x T x P 2-y A y O7 (T includes at least one element selected from Mg, Al, Si, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, and Bi, and A includes at least one element selected from Al, Si, V, Ge, and Sn, and satisfies 0≦x<2 and 0≦y≦2, excluding (x,y)=(0,0) and (0,2)).

[0031] In general formula (1), x may satisfy 0 < x ≤ 1.6. More preferably, x is from 0.05 to 1.6. x may be 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more. x may be 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less.

[0032] In general formula (1), y may satisfy 0 ≤ y ≤ 1.8. More preferably, y is 0 ≤ y ≤ 1.6, and even more preferably, y is from 0 to 1.2. y may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more. y may be 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less.

[0033] It is known that there are many stoichiometric compositions of pyrophosphates, such as Mg2P2O7, Ca2P2O7, Mn2P2O7, Fe2P2O7, Co2P2O7, Ni2P2O7, Cu2P2O7, Zn2P2O7, etc., and they have a flexible crystal structure. Therefore, many elements close to Zn in the periodic table are preferable as T in general formula (1). For example, Mg, Al, Mn, Fe, Cu, etc. are preferable as T.

[0034] The negative thermal expansion material has the general formula (2) Cu 2-x R x V 2-y P yIt may contain a compound represented by O7 (R contains at least one element selected from Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Zn, Sn, and satisfies 0 ≦ x ≦ 2, 0 < y < 2).

[0035] In the general formula (2), x may be 0 < x ≦ 2, 0 ≦ x < 2, or 0 < x < 2. x may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more. x may be 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less.

[0036] In the general formula (2), y may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more. y may be 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less.

[0037] The negative thermal expansion material is of the general formula (3) Ti 2-x M x It may contain a compound represented by O3 (M contains at least one element selected from Mg, Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, Bi, and satisfies 0 ≦ x < 2).

[0038] In general formula (3), x may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, or 1.6 or more. x may be 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0039] The powder of the present disclosure has a negative linear expansion coefficient at the above particle size in at least a portion of the temperature range from 200 K to 380 K, preferably α = -3.5 ppm / K or less, more preferably α = -6 ppm / K or less, even more preferably α = -10 ppm / K or less, and even more preferably α = -20 ppm / K or less. The linear expansion coefficient of the powder may be -1 ppm / K or less, -2 ppm / K or less, -3 ppm / K or less, -4 ppm / K or less, -5 ppm / K or less, -7 ppm / K or less, -8 ppm / K or less, -9 ppm / K or less, -12 ppm / K or less, -15 ppm / K or less, -30 ppm / K or less, or -40 ppm / K or less. It is sufficient for the powder to have the negative linear expansion coefficient in at least a portion of the temperature range from 200 K to 380 K; it is not necessary for the powder to have the negative linear expansion coefficient in a portion of the temperature range from 200 K to 380 K. "At least a portion of the temperature range" may be any temperature range, for example, 1K, 10K, 20K, 30K, 40K, 50K, or 100K.

[0040] In the present disclosure, the linear expansion coefficient of a powder is evaluated as follows. Measuring the thermal expansion characteristics of a single particle is technically difficult, and attempting to measure the thermal expansion characteristics of sintered particles could result in the negative thermal expansion material being altered during the sintering process. Given that negative thermal expansion materials are primarily used to suppress thermal expansion by combining them with materials such as resins, it is reasonable to evaluate the thermal expansion coefficient of a powder by measuring the degree to which thermal expansion is suppressed in a composite material obtained by combining the powder with a common resin such as epoxy resin. Therefore, in the present disclosure, the linear expansion coefficient of a powder is evaluated according to the rule of composition, which predicts the linear expansion coefficient of a composite material by proportionally dividing the thermal expansion coefficients of the base material and the powder dispersed in the base material based on the volume ratio of each material.

[0041] The composite rule is that the volume ratio of the base and the linear expansion coefficient are respectively ν m , α m , the volume ratio of the particles and the linear expansion coefficient are ν f , α f , the linear expansion coefficient of the composite material is α c As, α c =ν m α m +ν f α f The linear thermal expansion of the composite material is predicted from the relational expression. m +ν f =1. Based on this formula, α f =(α c -ν m α m ) / ν f The coefficient of linear expansion of the powder is evaluated by α f All of these can be easily measured. By using this method, the linear expansion coefficient α of the powder can be measured regardless of the type of base. f Therefore, the linear expansion coefficient α mAny material can be used as the base material as long as its α is known or measurable. However, when metals or ceramics are used as the base material, the heat treatment temperature for compounding is higher than that of resins, and the negative thermal expansion material may be altered during the compounding process, resulting in a negative thermal expansion value lower than the original value. This has been reported in previous literature (e.g., "Matrix-filler interfaces and physical properties of metal matrix composites with negative thermal expansion manganese nitride," K. Takenaka, K. Kuzuoka, and N. Sugimoto, J. Appl. Phys. 118, 084902 (2015)). This is not desirable for evaluating the linear expansion coefficient of powder. For this reason, it is preferable to use epoxy resin as the base material. In the examples described below, the linear expansion coefficient of powder was evaluated using a composite material obtained by compounding powder with an epoxy resin as the base material. α at 200K to 380K f The average value of these is taken as the coefficient of linear expansion of the powder in the range of 200K to 380K. The temperature range in which a powder exhibits large negative thermal expansion may vary depending on the chemical composition, so the temperature range in which thermal expansion is evaluated may be changed as appropriate to properly evaluate the powder's ability to suppress thermal expansion. For example, 250K to 350K, 200K to 350K, or 300K to 380K may be preferable. f The average value of these may be used as the linear expansion coefficient of the powder in that temperature range.

[0042] Negative thermal expansion materials may be manufactured by a solid-state reaction method or a spray-drying method. In the former method, raw material powders such as oxides containing the constituent elements of the compounds represented by general formulas (1) to (3) are weighed out in a specified molar ratio, mixed in an agate mortar and pestle, and then placed in an alumina crucible and fired. In the latter method, an aqueous solution containing at least one of the compounds represented by general formulas (1) to (3) and their raw materials, and at least one of an acid, a salt, and an organometallic compound, is spray-dried.

[0043] The spray drying method can produce particles with smaller particle size, narrower particle size distribution, and isotropic particle shape compared to conventional solid-state reaction methods. This allows the powder to be pulverized with an overwhelmingly smaller mechanical load than when pulverizing the large crystals obtained by conventional solid-state reaction methods, resulting in a group of fine particles that maintains the negative thermal expansion properties. By incorporating a classification process such as sieving, the particle size and particle size distribution can be further adjusted.

[0044] The acid may be an organic acid or an inorganic acid. Examples of organic acids that can be used include citric acid and acetic acid. The salt may be a salt of an organic acid and an alkali, or a salt of an inorganic acid and an alkali. Examples of salts that can be used include metal nitrates, metal acetates, metal sulfates, metal chlorides, and metal fatty acids. Examples of organometallic compounds that can be used include metal alkoxides and metal acetylacetonates. An aqueous solution of a metal dissolved in nitric acid, hydrochloric acid, sulfuric acid, or the like may also be used.

[0045] When preparing the aqueous solution, the compounds represented by the general formulae (1) to (3) themselves may be dissolved, or raw materials for the compounds represented by the general formulae (1) to (3) may be dissolved.

[0046] In the powder production method of the present disclosure, the fluid may be a gas or a liquid. The fluid may be one that does not react with or has low reactivity to the substances contained in the powder in a temperature range from room temperature to the temperature inside the heating unit 10. The gas may be air or oxygen, or an inert gas such as nitrogen or a noble gas. The noble gas may be helium, neon, argon, xenon, or the like. The liquid may be one in which the substances contained in the powder do not dissolve or have low solubility in a temperature range from room temperature to the temperature inside the heating unit 10. The liquid may be an inorganic solvent or an organic solvent. The liquid may be a polar solvent such as water, methanol, ethanol, propanol, formic acid, acetic acid, tetrahydrofuran, acetone, acetonitrile, or dimethyl sulfoxide, or a nonpolar solvent such as hexane, diethyl ether, benzene, or ethyl acetate.

[0047] The powder manufacturing method of the present disclosure may include a step of pulverizing the recrystallized powder as described above. The step of pulverizing the powder may involve pulverizing the powder using a jet mill that uses compressed air or high-pressure gas to pulverize the materials by causing them to collide with each other, thereby reducing the particle size of the powder. This makes it possible to further reduce and uniform the particle size of the powder.

[0048] The powder production technology disclosed herein can produce inexpensive powder of a negative thermal expansion material that exhibits large negative thermal expansion at around room temperature. Furthermore, the use of this powder of negative thermal expansion material enables precise control of thermal expansion of microcomponents or localized areas at the 1 μm level. Furthermore, when the powder of the negative thermal expansion material is dispersed in a base such as a resin, sedimentation of the powder of the negative thermal expansion material can be suppressed, thereby achieving a uniform dispersion. Furthermore, because the median diameter of the powder of the negative thermal expansion material is equal to or smaller than the wavelength of visible light (300 nm to 800 nm), visible light transmittance can be maintained even when the powder of the negative thermal expansion material is blended with a transparent or translucent material such as glass or acrylic.

[0049] The powder of the present disclosure includes a negative thermal expansion material having a negative linear expansion coefficient in at least a part of a temperature range, and has a volume frequency median particle size (median diameter) D measured by a laser diffraction / scattering particle size distribution evaluation device. 50 is 1.3 μm or less. D 50 may be 1.2 μm or less, 1.1 μm or less, 1.0 μm or less, 0.9 μm or less, 0.8 μm or less, 0.7 μm or less, 0.6 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, 0.2 μm or less, or 0.1 μm or less. This makes it possible to provide a powder with a small particle size.

[0050] The powder of the present disclosure includes a negative thermal expansion material having a negative linear expansion coefficient in at least a part of a temperature range, and has a volume frequency 90% diameter D 90 is 3 μm or less. D 90 may be 2.9 μm or less, 2.8 μm or less, 2.7 μm or less, 2.6 μm or less, 2.5 μm or less, 2.4 μm or less, 2.3 μm or less, 2.2 μm or less, 2.1 μm or less, 2.0 μm or less, 1.9 μm or less, 1.8 μm or less, 1.7 μm or less, 1.6 μm or less, 1.5 μm or less, 1.4 μm or less, 1.3 μm or less, 1.2 μm or less, 1.1 μm or less, or 1.0 μm or less. This makes it possible to provide a powder having a small particle size and containing almost no particles with a large particle size.

[0051] The powder of the present disclosure may contain any compound. For example, the powder of the present disclosure may contain a negative thermal expansion material such as a compound represented by the above general formulas (1) to (3). The powder production technique of the present disclosure is particularly suitable for producing powder whose bulk properties deteriorate when pulverized.

[0052] [Example] By the powder production method of the present disclosure, Zn 1.6 Mg 0.4 Powder of P2O7 (in general formula (1), T=Mg, x=0.4, y=0) was produced.

[0053] (Adjustment of raw powder) The powder as the raw material may be prepared by a solid-phase reaction method or by spray drying.

[0054] In the solid-state reaction method, ZnO, MgO, and NH4H2PO4 powders were weighed out in a specified molar ratio and mixed in an agate mortar and pestle, then placed in an alumina crucible and fired in air at 800-850°C for 2-6 hours. After firing, the mixture was removed and mixed again in an agate mortar and pestle, then placed in an alumina crucible and fired in air at 850-900°C for 2-10 hours.

[0055] In the case of spray drying, Zn was synthesized in advance using a solid-state reaction method. 1.6 Mg 0.4 A citric acid solution of P2O7 powder or a citric acid solution of ZnO, MgO, NH4H2PO4, or (NH4)2HPO4 was dried and granulated using a spray dryer, and the resulting citrate powder was placed in an alumina crucible and heated in air at 400°C for 5 hours to decompose the citrate. The resulting powder was pulverized using a planetary ball mill, placed in an alumina crucible, and fired in air at 850-900°C for 2-10 hours.

[0056] (Fine particle formation by grinding) The prepared powder was further pulverized in a planetary ball mill for 10 minutes to 6 hours, which reduced the median diameter to less than 1 μm.

[0057] Examples 1 and 2 The pulverized raw material powder was introduced into the powder production apparatus 1 and recrystallized to produce the powders of Examples 1 and 2. For the powder of Example 1, the temperature of the heating section 10 was set to 1050°C, the flow rates of the inlet-side flow rate adjuster 13 and the outlet-side flow rate adjuster 16 were set to low, 22.9 g of raw material powder was introduced into the heating section 10 over 2.5 hours, and 8.1 g of powder was recovered. For the powder of Example 2, the temperature of the heating section 10 was set to 1050°C, the flow rates of the inlet-side flow rate adjuster 13 and the outlet-side flow rate adjuster 16 were set to high, 52.4 g of raw material powder was introduced into the heating section 10 over 5.5 hours, and 29.2 g of powder was recovered.

[0058] Examples 3 and 4 The pulverized raw material powder was introduced into the powder production apparatus 1 and recrystallized. The powders of Examples 3 and 4 were then pulverized using a jet mill pulverizer (Seishin Enterprise Co., Ltd., CO-JET system α MARK III). For the powder of Example 3, the temperature of the heating section 10 was set to 1050°C, the flow rate of the inlet-side flow rate adjuster 13 was set to low, and the flow rate of the outlet-side flow rate adjuster 16 was set to high. 62.1 g of raw material powder was introduced into the heating section 10 over 5 hours, and 27.2 g of powder was recovered. The powder was then pulverized using compressed air at 0.1 to 0.69 MPa in the jet mill pulverizer. For the powder of Example 4, the temperature of the heating section 10 was set to 1070 to 1080°C, the flow rates of the inlet-side flow rate adjuster 13 and the outlet-side flow rate adjuster 16 were set to high. 76.25 g of raw material powder was introduced into the heating section 10 over 4 hours, and 75.0 g of powder was recovered. Thereafter, the powder was pulverized in a jet mill pulverizer using compressed air at 0.1 to 0.69 MPa.

[0059] FIG. 3 shows the particle size distribution of the powder in Example 1. The particle size distribution of the powder was measured using a laser diffraction / scattering particle size distribution evaluation device (LA-950V2) manufactured by Horiba, Ltd. The same applies to the subsequent Examples. In the figure, circles indicate the particle size distribution of the powder in Example 1, and triangles indicate the particle size distribution of the powder in the comparative example described in Non-Patent Document 1. The volume frequency median particle size D of the powder in Example 1 50 is 1.17 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of the comparative example was 2.68 μm. 50 is 1.32 μm, and the volume frequency 90% diameter D 90 The particle size of the powder of Example 1 was smaller and more uniform than that of the powder of the comparative example.

[0060] Figure 4 shows the linear thermal expansion of the powder of Example 1. The hollow circles represent the linear thermal expansion of a composite material in which the powder of Example 1 was blended in an epoxy resin (Adeka (registered trademark) EP-4100E / EH-105L) at a volume ratio of 30%, while the solid circles represent the linear thermal expansion of the powder of the comparative example described in Non-Patent Document 1. The volume ratio was calculated using the true specific gravity of the epoxy resin as 1.16 and Zn 1.6 Mg 0.4The true specific gravity of P2O7 was 3.17. The thermal expansion of a solid material is evaluated by linear thermal expansion ΔL / L. The linear thermal expansion ΔL / L on the vertical axis of Figure 3 represents the change in length based on the length L at 250K. The change in length was measured using a laser thermal dilatometer (LIX-2, manufactured by ULVAC, Inc.). The slope of the linear thermal expansion, i.e., the temperature derivative, is the linear expansion coefficient α. For isotropic materials with no directional dependency, linear thermal expansion essentially represents bulk thermal expansion, and the relationship is ΔV / V = 3ΔL / L (V is volume). The thermal expansion suppression ability of the powder of Example 1 was comparable to that of the powder of the comparative example at temperatures between 250K and 300K, 340K and 370K and 390K and 400K, but slightly superior to that of the powder of the comparative example at temperatures between 300K and 340K and 370K and 390K.

[0061] Based on the measurement results of the linear thermal expansion, the linear expansion coefficient of the powder of Example 1 was calculated by the method described above. m =0.7, ν f =0.3, α m As mentioned above, the calculated value of the linear expansion coefficient may vary depending on the temperature, but the average value in the range of 200K to 380K was used as the linear expansion coefficient α of the powder. f The α of the composite material in Example 1 was calculated as follows: c The measured value of α of the powder of Example 1 was +29.92 ppm / K. f The calculated value of α was -46.91 ppm / K. c The measured value of α was +31.90 ppm / K, and the α of the powder of the comparative example f The calculated value of was -40.31 ppm / K. When the temperature range was 250 K to 350 K, the α c The measured value of α of the powder in Example 1 was +24.49 ppm / K. f The calculated value of α was -64.99 ppm / K. c The measured value of α was +25.88 ppm / K, and the α of the powder of the comparative example f The calculated value was -60.38 ppm / K.

[0062] Figure 5 shows the particle size distribution of the powder of Example 2. In the figure, squares indicate the particle size distribution of the raw material powder of Example 2, circles indicate the particle size distribution of the powder of Example 2, and triangles indicate the particle size distribution of the powder of the comparative example described in Non-Patent Document 1. The volume frequency median particle size D of the raw material powder of Example 2 50 is 0.44 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of Example 2 was 1.46 μm. 50 is 0.82 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of the comparative example was 2.16 μm. 50 is 1.32 μm, and the volume frequency 90% diameter D 90 The particle size of the powder of Example 2 was 3.10 μm. The particle size of the powder of Example 2 was smaller and more uniform than that of the powder of the comparative example. Furthermore, the powder of Example 2 maintained the maximum particle size of the raw material powder of Example 2.

[0063] FIG. 6 shows the linear thermal expansion of the powder of Example 2. The hollow circles indicate the linear thermal expansion of a composite material in which the powder of Example 1 is mixed with an epoxy resin at a volume ratio of 30%, and the solid circles indicate the linear thermal expansion of the powder of the comparative example described in Non-Patent Document 1. The thermal expansion suppression ability of the powder of Example 2 is comparable to that of the powder of the comparative example at temperatures between 320K and 400K, and slightly exceeds that of the powder of the comparative example at temperatures between 250K and 320K. The α of the composite material of Example 2 c The measured value of α of the powder of Example 2 was +31.17 ppm / K. f The calculated value was -42.72 ppm / K.

[0064] 7 shows the particle size distribution of the powder of Example 3. In the figure, squares represent the particle size distribution of the raw material powder of Example 3, triangles represent the particle size distribution of the powder of Example 3 before pulverization with the jet mill pulverizer, and circles represent the particle size distribution of the powder of Example 3 after pulverization with the jet mill pulverizer. The volume frequency median particle size D of the raw material powder of Example 3 50 is 1.16 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of Example 3 before being pulverized by the jet mill pulverizer was 2.47 μm. 50 is 1.50 μm, and the volume frequency 90% diameter D 90The volume frequency median particle size D of the powder of Example 3 after pulverization by the jet mill pulverizer was 3.49 μm. 50 is 0.77 μm, and the volume frequency 90% diameter D 90 The particle size was 1.49 μm. The powder of Example 3 before being pulverized in the jet mill pulverizer maintains the maximum particle size of the raw material powder of Example 3. The powder of Example 3 after being pulverized in the jet mill pulverizer has a particle size that is significantly smaller and more uniform than the raw material powder of Example 3 and the powder of Example 3 before being pulverized in the jet mill pulverizer.

[0065] FIG. 8 shows the linear thermal expansion of the powder of Example 3. The triangles indicate the linear thermal expansion of a composite material in which the powder of Example 3 was blended in an epoxy resin at a volume ratio of 30% before being pulverized in a jet mill pulverizer, the hollow circles indicate the linear thermal expansion of a composite material in which the powder of Example 3 was blended in an epoxy resin at a volume ratio of 30% after being pulverized in a jet mill pulverizer, and the solid circles indicate the linear thermal expansion of the comparative powder described in Non-Patent Document 1. The thermal expansion suppression ability of the powder of Example 3 before being pulverized in a jet mill pulverizer is slightly superior to that of the comparative powder at 250 to 400 K. The thermal expansion suppression ability of the powder of Example 3 after being pulverized in a jet mill pulverizer is similar to that of the comparative powder at 250 to 300 K and is comparable to that of the comparative powder at 300 to 400 K, and was able to suppress the thermal expansion of the epoxy resin. For the powder of Example 3 before being pulverized in a jet mill pulverizer, the α of the composite material was c The measured value of α of the powder of Example 3 was +30.07 ppm / K. f The calculated value of was -46.41 ppm / K. For the powder of Example 3 after being pulverized by the jet mill pulverizer, the α of the composite material was c The measured value of α of the powder of Example 3 was +34.60 ppm / K. f The calculated value was -31.28 ppm / K.

[0066] 9 shows the particle size distribution of the powder of Example 4. In the figure, squares indicate the particle size distribution of the raw material powder of Example 4, triangles indicate the particle size distribution of the powder of Example 4 before pulverization with the jet mill pulverizer, and circles indicate the particle size distribution of the powder of Example 4 after pulverization with the jet mill pulverizer. The volume frequency median particle size D of the raw material powder of Example 4 50 is 1.16 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of Example 4 before being pulverized by the jet mill pulverizer was 2.47 μm. 50 is 1.32 μm, and the volume frequency 90% diameter D 90 The volume frequency median particle size D of the powder of Example 4 after pulverization by the jet mill pulverizer was 2.81 μm. 50 is 0.63 μm, and the volume frequency 90% diameter D 90 The maximum particle size of the powder of Example 4 after pulverization in the jet mill pulverizer was 1.08 μm. The powder of Example 4 before pulverization in the jet mill pulverizer had a particle size similar to that of the raw material powder of Example 4. The powder of Example 4 after pulverization in the jet mill pulverizer had a particle size significantly smaller and more uniform than the raw material powder of Example 4 and the powder of Example 4 before pulverization in the jet mill pulverizer. The maximum particle size of the powder of Example 4 after pulverization in the jet mill pulverizer was 2.976 μm, which was able to suppress the maximum particle size to 3 μm or less.

[0067] FIG. 10 shows the linear thermal expansion of the powder of Example 4. The hollow circles indicate the linear thermal expansion of a composite material in which the powder of Example 4 after being pulverized in a jet mill pulverizer was blended in an epoxy resin at a volume ratio of 30%, and the solid circles indicate the linear thermal expansion of the powder of the comparative example described in Non-Patent Document 1. The thermal expansion suppression ability of the powder of Example 4 after being pulverized in a jet mill pulverizer was comparable to that of the powder of the comparative example at 250 to 300 K, and was comparable to that of the powder of the comparative example at 300 to 400 K, and was able to suppress the thermal expansion of the epoxy resin. For the powder of Example 4 after being pulverized in a jet mill pulverizer, the α of the composite material was c The measured value of α of the powder of Example 3 was +34.13 ppm / K. f The calculated value was -32.87 ppm / K.

[0068] From the above, it has been demonstrated that the powder manufacturing method of the present disclosure can manufacture powder with small and uniform particle size while maintaining excellent negative thermal expansion properties comparable to those of a bulk material.

[0069] Although the examples describe an example in which part of the Zn in Zn2P2O7 is replaced with Mg, it is believed that similar negative thermal expansion properties will be exhibited when part of the Zn is replaced with elements such as Al, Si, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, Bi, etc. It is also believed that similar negative thermal expansion properties will be exhibited when part of the P is replaced with elements such as Al, Si, V, Ge, Sn, etc.

[0070] The present disclosure has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and the respective treatment processes, and that such modifications are also within the scope of the present disclosure. [Explanation of symbols]

[0071] 1 powder manufacturing apparatus, 10 heating section, 11 powder introduction section, 12 fluid delivery section, 13 inlet side flow rate adjustment section, 14 inlet, 15 outlet, 16 outlet side flow rate adjustment section, 17 cooling section, 18 powder recovery section, 20 control section.

Claims

1. introducing powder into the heating section; heating the powder while dispersing the powder by causing a fluid inside the heating unit to flow; cooling the powder; A method for producing powder comprising:

2. The powder contains a negative thermal expansion material that has a negative linear expansion coefficient in at least a part of a temperature range. The method of claim 1.

3. The powder has the general formula (1) Zn ２－ｘ T ｘ P ２－ｙ A ｙ O ７ (T includes at least one element selected from Mg, Al, Si, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, and Bi, and A includes at least one element selected from Al, Si, V, Ge, and Sn, and satisfies 0≦x<2 and 0≦y≦2, excluding (x, y)=(0,0) and (0,2)). The method of claim 2.

4. The powder has the general formula (2) Cu ２－ｘ R ｘ V ２－ｙ P ｙ O ７ (R contains at least one element selected from Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Zn, and Sn, and satisfies 0≦x≦2 and 0<y<2.) The method of claim 2.

5. The powder is represented by the general formula (3) Ti ２－ｘ M ｘ O ３ (M includes at least one element selected from Mg, Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, La, Ta, W, and Bi, and satisfies 0≦x<2.) The method of claim 2.

6. The volume frequency median particle size (median diameter) measured by a laser diffraction / scattering particle size distribution evaluation device is 30 nm or more and less than 10 μm.

6. The method according to any one of claims 1 to 5.

7. 90% volume frequency diameter D measured by a laser diffraction / scattering particle size distribution evaluation device ９０ is 20 μm or less 6. The method according to any one of claims 1 to 5.

8. In the step of heating the powder, the powder is heated to a temperature close to the melting point of a substance contained in the powder.

6. The method according to any one of claims 1 to 5.

9. In the step of heating the powder, the powder is heated to 800°C to 1200°C.

6. The method according to any one of claims 1 to 5.

10. A step of pulverizing the heated powder is provided.

6. The method according to any one of claims 1 to 5.

11. In the pulverizing step, the powder is pulverized by a jet mill. The method of claim 10.

12. a powder introduction section that introduces powder into the container; a heating unit that heats the powder inside the container; a flow generating unit that causes the fluid inside the container to flow when the powder is heated by the heating unit; A powder manufacturing apparatus comprising:

13. a fluid delivery section for injecting the fluid into the container; The powder manufacturing apparatus according to claim 12.

14. The fluid flows in from the bottom of the container and flows out from the top of the container. The powder manufacturing apparatus according to claim 13.

15. a flow rate adjusting unit that adjusts at least one of the flow rate of the fluid flowing into the container and the flow rate of the fluid flowing out of the container; The powder manufacturing apparatus according to claim 13 or 14.

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