Silicon carbide particles

Abstract

To provide a silicon carbide particle made of α-SiC particles and suitably used as a material for "filters for removing solid substances of a specific size" and "lightweight components" used in harsh environments.SOLUTION: A silicon carbide particle that is made of particles of α-SiC, has a specific surface area of 1.18 m2 / g or more, has a loose bulk density of 0.7 g / cm3 or less, and has a cumulative pore volume of 0.35 cm3 / g or more with respect to pores having a diameter of 0.1 μm or more and 5.0 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to silicon carbide particles and a method for producing the same. [Background technology]

[0002] Silicon carbide particles have excellent heat and chemical resistance, making them suitable for use in harsh environments as filters for removing solid matter of a specific size and as lightweight components. However, there are currently no silicon carbide particles with the low bulk density and specific pore size desired for these applications. Patent Document 1 describes secondary particles obtained by sintering only silicon carbide powder (primary particle diameter D50: 0.26 μm) without using any sintering aids or binders, which have a D50 of 43.2 μm and a specific surface area of ​​0.98 m 2 / g. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2020 / 194974 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide silicon carbide particles that are composed of secondary particles of α-SiC and are suitable for use as a material for "filters for removing solid substances of a specific size" and "lightweight members" that are used in harsh environments. [Means for solving the problem]

[0005] In order to solve the above problems, one aspect of the present invention is a method for producing a silicon carbide (SiC) composite material comprising secondary particles of α-SiC and having a specific surface area of ​​1.18 m 2 / g or more, loose bulk density is 0.7g / cm 3 The cumulative pore volume of pores with diameters of 0.1 μm to 5.0 μm is 0.35 cm3 / g or more. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide silicon carbide particles that are composed of secondary particles of α-SiC and are suitable for use as a material for "filters for removing solid substances of a specific size" and "lightweight members" that are used in harsh environments. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph showing differential pore volume distributions of silicon carbide particles of Examples and Comparative Examples. [Figure 2] 1 shows SEM images of the surfaces of silicon carbide particles of Examples 1 and 2 and Comparative Example 1. [Figure 3] 1 is an SEM image of the surface of silicon carbide particles of Comparative Examples 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below. In the embodiments described below, technically preferable limitations are imposed for implementing the present invention, but these limitations are not essential requirements for the present invention.

[0009] 〔composition〕 The silicon carbide particles of this embodiment are made of secondary particles of α-SiC and have a specific surface area of ​​1.18 m 2 / g or more, loose bulk density is 0.7g / cm 3 The cumulative pore volume of pores with diameters of 0.1 μm to 5.0 μm is 0.35 cm 3 / g or more.

[0010] The silicon carbide particles of this embodiment have a specific surface area of ​​1.18 m 2 / g or more 5.00m 2 / g or less. 2If it is less than 5.00 m / g, the porosity will be insufficient and the specific surface area will be less than 5.00 m 2 / g or less, it is easy to prevent granule collapse (the collapse of part of the primary particles that form the secondary particles). Note that a primary particle is a single particle, and a secondary particle is a particle formed by the aggregation and bonding of multiple primary particles. In addition, the specific surface area is 1.21 m 2 / g or more 4.00m 2 / g or less is more preferable, and 1.24m 2 / g or more 3.00m 2 It is particularly preferable that the saturation coefficient is 1 / g or less.

[0011] In the silicon carbide particles of this embodiment, the loose bulk density is 0.3 g / cm 3 More than 0.7g / cm 3 It is preferable that the loose bulk density is 0.3 g / cm or less. 3 At this level, granule collapse is easily suppressed, and the density is 0.7 g / cm 3 If the density exceeds 0.3 g / cm, the voids will be insufficient. 3 More than 0.65g / cm 3 More preferably, it is 0.3 g / cm or less. 3 More than 0.60g / cm 3 It is particularly preferred that:

[0012] In the silicon carbide particles of this embodiment, the cumulative pore volume of pores having a diameter of 0.1 μm or more and 5.0 μm or less is 0.35 cm 3 / g or more 1.00cm 3 / g or less. The cumulative pore volume of pores with diameters of 0.1 μm or more and 5.0 μm or less is preferably 0.35 cm 3 / g or more, the pores are sufficient. The cumulative pore volume of pores with diameters of 0.1 μm to 5.0 μm is 1.00 cm 3 / g or less, it is easy to suppress granule collapse. In addition, the cumulative pore volume of pores with diameters of 0.1 μm or more and 5.0 μm or less is 0.40 cm 3 / g or more 0.90cm 3 / g or less is more preferable, and 0.45 cm 3 / g or more 0.80cm 3 It is particularly preferable that the saturation coefficient is 1 / g or less.

[0013] The silicon carbide particles of this embodiment preferably have a D50% particle size of 10 μm or more and 100 μm or less. A D50% particle size of 10 μm or more tends to improve fluidity when producing a molded product, and a D50% particle size of 100 μm or less can prevent the gaps between secondary particles from becoming large. Furthermore, the D50% particle size is more preferably 20 μm or more and 80 μm or less, and particularly preferably 30 μm or more and 60 μm or less.

[0014] The silicon carbide particles of this embodiment can be produced by granulating primary particles of α-SiC with an optimized particle size using a pore-forming material without using a sintering aid or binder, and then sintering the resulting granules. More specifically, the process is preferably carried out using a raw material comprising α-SiC primary particles with a D50% particle size of 0.05 μm to 1.0 μm and a pore-forming material, the raw material containing the pore-forming material at a content of 30% by volume or more.

[0015] By setting the D50% particle size of the α-SiC primary particles used in the above manufacturing method to 0.05 μm or more, voids can be suitably formed between the primary particles. By setting the D50% particle size of the α-SiC primary particles to 1.0 μm or less, voids formed between the primary particles can be prevented from becoming too large, voids with the desired pore size can be obtained, and a decrease in adhesive force between the primary particles can be prevented, allowing the pore-forming material to be suitably incorporated. Furthermore, the D50% particle size of the α-SiC primary particles used in the above manufacturing method is more preferably 0.10 μm to 0.80 μm, and particularly preferably 0.20 μm to 0.60 μm.

[0016] The content of the pore-forming material in the raw materials used in the above manufacturing method is preferably 30% by volume or more and 75% by volume or less. When the content of the pore-forming material is 30% by volume or more, the voids formed between the primary particles have an appropriate size, and when it is 75% by volume or less, granule collapse is easily suppressed. Furthermore, the content of the pore-forming material is more preferably 35% by volume or more and 70% by volume or less, and particularly preferably 40% by volume or more and 65% by volume or less.

[0017] [Action, effect] The silicon carbide particles of this embodiment are made of secondary particles of α-SiC and have a specific surface area of ​​1.18 m 2 / g or more, and the loose bulk density is 0.7g / cm 3 The cumulative pore volume of pores with diameters of 0.1 μm to 5.0 μm is 0.35 cm 3 / g or more. Therefore, the silicon carbide particles of the present embodiment can be suitably used as a material for "filters for removing solid substances of a specific size" or "lightweight members" used in harsh environments. [Example]

[0018] The present invention will be described in more detail below with reference to examples and comparative examples. [Production of silicon carbide secondary particles] Example 1 The primary particles of α-SiC prepared were those with a D50% particle size of 0.26 μm (manufactured by Fujimi Incorporated). This D50% particle size was measured by a laser diffraction scattering method using an MT-3300 manufactured by Microtrackbell Co., Ltd. The D50% particle size refers to the particle size at which the cumulative frequency from the small particle size side in the cumulative particle size distribution based on volume of the powder is 50%. As the pore-forming material, cross-linked acrylic monodisperse particles (manufactured by Soken Chemical & Engineering Co., Ltd.) with an average particle size of 3 μm were prepared.

[0019] First, the α-SiC primary particles and the pore-forming material were mixed so that the content of the pore-forming material was 45% by volume to obtain a raw material powder. Next, the raw material powder was dispersed in a solvent such as water to obtain a slurry, which was then supplied to a spray dryer for granulation, to obtain a granulated product consisting of a mixed powder of α-SiC primary particles and a pore-forming material. Next, the obtained granules were sintered to produce sintered granules (secondary particles) using a resistance heating sintering furnace FVS-R manufactured by Fuji Denpa Kogyo Co., Ltd. The operating conditions of the sintering furnace were an argon atmosphere, a sintering temperature of 1850°C, and a sintering time of 4 hours. The particle size of the obtained sintered granules was adjusted using sieves with mesh openings of 32 μm and 75 μm, thereby obtaining silicon carbide secondary particles of Example 1.

[0020] <Example 2> The α-SiC primary particles and the pore-forming material were mixed so that the content of the pore-forming material was 60% by volume to obtain a raw material powder. Silicon carbide secondary particles of Example 2 were obtained in the same manner as in Example 1, except for the content of the pore-forming material.

[0021] <Comparative Example 1> A raw material powder was obtained by mixing only the α-SiC primary particles without using a pore-forming agent. α-SiC secondary particles of Comparative Example 1 were obtained in the same manner as in Example 1, except that this raw material powder was used.

[0022] <Comparative Example 2> Primary particles of α-SiC with a D50% particle size of 6.9 μm (manufactured by Fujimi Inc.) were prepared for Comparative Example 2. This D50% particle size was measured by an electrical resistance method using a Multisizer III manufactured by Beckman Coulter, Inc. A raw material powder was obtained by mixing the α-SiC primary particles, sintering aid, and binder without using a pore-forming agent. Sintered granules (secondary particles) were produced in the same manner as in Example 1, except that a granulated product consisting of a mixed powder of the α-SiC primary particles, sintering aid, and binder was obtained using this raw material powder and that the operating temperature of the sintering furnace was set to 1900°C. The sintering aid used was aluminum nitrate nonahydrate (Al(NO3)3·9H2O). The amount of sintering aid added was 30 parts by mass or less per 100 parts by mass of α-SiC primary particles. An alkali-soluble polymer was used as the binder, and the amount of binder added was 2 parts by mass or less per 100 parts by mass of the α-SiC primary particles. The particle size of the obtained sintered granules was adjusted using sieves with mesh openings of 32 μm and 53 μm, thereby obtaining secondary silicon carbide particles of Comparative Example 2.

[0023] <Comparative Example 3> A raw material powder was obtained by mixing the same α-SiC primary particles and sintering aid as in Example 1 without using a pore-forming agent. Sintered granules (secondary particles) were produced in the same manner as in Example 1, except that this raw material powder was used to obtain a granulated product consisting of a mixed powder of α-SiC primary particles and sintering aid, and the operating temperature of the sintering furnace was set to 1800°C. The sintering aid used was the same as in Comparative Example 2, and the addition ratio relative to the α-SiC primary particles was the same as in Comparative Example 2. The obtained sintered granules were crushed using a centrifugal crusher manufactured by Verder Scientific. The rotation speed of the centrifugal crusher was 14,000 rpm. Then, particle size adjustment was performed using sieves with mesh openings of 32 μm and 53 μm. In this way, silicon carbide secondary particles of Comparative Example 3 were obtained.

[0024] [Measurement of physical properties of silicon carbide secondary particles] <Particle size> The particle sizes (D10% particle size, D50% particle size, D90% particle size) of each of the obtained silicon carbide secondary particles were measured using a laser diffraction / scattering particle size distribution analyzer LA-300 manufactured by Horiba, Ltd. For Comparative Example 3, only the D50% particle size was measured. Note that D10% is the particle size at which the cumulative particle volume from the small particle size side in the volume-based cumulative particle size distribution is 10% of the total particle volume, and D90% is the particle size at which the cumulative particle volume from the small particle size side is 90%.

[0025] <Loose bulk density> The loose bulk density of each of the obtained silicon carbide secondary particles was measured using a bulk density measuring device (JIS K-5101) manufactured by Tsutsui Rikagaku Kikai Co., Ltd. The powder was allowed to fall naturally into a measuring container until the container was full, and the powder that protruded from the top of the container was scraped off with a plate, after which the powder mass was measured and the measured mass was divided by the container volume to calculate the loose bulk density.

[0026] <Specific surface area> The specific surface area of ​​each of the obtained silicon carbide secondary particles was measured using a fully automatic BET specific surface area measuring device "Macsorb (registered trademark)" manufactured by Mountech Co., Ltd.

[0027] <Cumulative pore volume> The differential pore volume distribution of each obtained silicon carbide secondary particle was measured using a POREMASTER-60 manufactured by Quantachrome, and the graph shown in FIG. 1 was obtained. Also, the cumulative pore volume (cm 3 / g) with a pore diameter of 0.1 μm or more and 5.0 μm or less was measured.

[0028] <SEM image> SEM images of the surfaces of the obtained silicon carbide secondary particles were taken at magnifications of 1000 times, 2000 times, 3000 times, and 10000 times for Examples 1 and 2 and Comparative Example 1, and at magnifications of 1000 times and 2000 times for Comparative Examples 2 and 3. The results are shown in FIGS. 2 and 3.

[0029] The manufacturing methods and measurement results of the physical properties of each silicon carbide secondary particle are shown in Table 1.

[0030]

Table 1

[0031] From the results in Table 1, "α-SiC primary particles with a D50% particle diameter of 0.26 μm (0.05 μm or more and 1.0 μm or less), a pore-forming material with an average particle diameter of 3 μm, without a sintering aid and a binder, and a raw material with a pore-forming material content of 45% by volume or more and 60% by volume or less (30% by volume or more)" was used. By granulating and sintering the α-SiC primary particles, "secondary particles composed of α-SiC, with a specific surface area of 1.29 m 2 / g (1.18 m 2 / g or more), a loose bulk density of 0.34 g / cm 3 or more and 0.51 g / cm 3 or less (0.7 g / cm 3 or less), and a cumulative pore volume with a pore diameter of 0.1 μm or more and 5.0 μm or less of 0.48 cm 3 / g or more and 0.59 cm 3 / g or less (0.35 cm 3 / g or more and a D50% particle size of 44.04 μm or more and 45.83 μm or less (10 μm or more and 100 μm or less),” that is, the silicon carbide particles of Examples 1 and 2, can be obtained.

[0032] 2, it can be seen that the silicon carbide particles of Examples 1 and 2 have pores formed by the pore-forming material in addition to pores formed by the gaps between the primary particles, resulting in a low bulk density. In contrast, it can be seen that the silicon carbide particles of Comparative Example 1 have a higher bulk density than the silicon carbide particles of Examples 1 and 2. It can also be seen from the SEM image of FIG. 3 that the silicon carbide particles of Comparative Examples 2 and 3 also have a higher bulk density than the silicon carbide particles of Examples 1 and 2.

[0033] Furthermore, because the silicon carbide particles of Examples 1 and 2 have the above physical properties, they can be suitably used as materials for "filters for removing solid substances of a specific size" and "lightweight components" used in harsh environments. Furthermore, the silicon carbide particles of Examples 1 and 2 do not contain any sintering aids or binders, and therefore have a high purity of α-SiC, making them suitable for use in applications where the inclusion of impurities is a problem.

Claims

1. It consists of secondary particles of α-SiC and has a specific surface area of ​​1.18 m 2 / g or more, loose bulk density is 0.7g / cm 3 The cumulative pore volume of pores with a diameter of 0.1 μm or more and 5.0 μm or less is 0.35 cm 3 / g or more.

2. 2. The silicon carbide particles according to claim 1, wherein the D50% particle size is 10 μm or more and 100 μm or less.

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