Sintering method and sintering aid

Abstract

To provide a method for efficiently sintering sinter ceramics and a sintering aid used in the method.SOLUTION: The present invention includes a step of irradiating a mixture containing ceramic particles for sintering and a sintering aid containing a metal fluoride with a laser. The wavelength of the laser is preferably 350 to 2500 nm, and the output is preferably 1 to 1000 W / cm2. As the metal fluoride, yttrium fluoride, barium fluoride, etc. are preferably used.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for sintering ceramics using a laser and a sintering aid used in the method. [Background technology]

[0002] Ceramic sintered bodies obtained by sintering an aggregate of ceramic particles have excellent electrical conductivity or electrical insulation, heat resistance, mechanical properties, corrosion resistance, abrasion resistance, etc., and are therefore widely used in substrates for various electronic products, heat-resistant components, tools, etc.

[0003] For example, when producing a plate-shaped ceramic sintered body, there is a method in which a slurry, paste or powder prepared by mixing ceramic particles with a binder solution in which a polymer binder is dissolved in a medium is subjected to press molding, slurry casting, injection molding, extrusion molding, screen printing, etc., and then sintered. In this method, the sintering temperature must usually be 1200°C or higher, which is not economical, and therefore a sintering method using a laser has been considered.

[0004] Patent Document 1 discloses a method for sintering ceramics to be sintered, which comprises forming a layer containing carbon powder on the surface of an article made of ceramics to be sintered, and then irradiating the carbon powder-containing layer in the resulting laminate with a laser under an inert gas atmosphere or vacuum condition, characterized in that a laser-transmitting member is placed on the surface of the carbon powder-containing layer. Furthermore, Patent Document 2 discloses a method for producing a ceramic sintered body, which includes a mixing step of mixing ceramic powder and carbon powder to obtain a mixed powder, a molding step of molding the mixed powder to obtain a molded body, and a sintering step of irradiating the molded body with laser light to form a ceramic sintered part. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6959790 [Patent Document 2] Patent Publication No. 2023-29060 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for efficiently sintering ceramics for sintering and a sintering aid for use in said method. [Means for solving the problem]

[0007] The present invention is illustrated below. 1. A sintering method comprising a step of irradiating a laser onto a mixture containing ceramic particles to be sintered and a sintering aid containing a metal fluoride. 2. The wavelength of the laser is 350-2500 nm and the output is 1-1000 W / cm 2 2. The sintering method according to item 1, wherein 3. The above metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, titanium fluoride 2. The sintering method according to item 1, wherein the fluoride is at least one selected from the group consisting of fluorine, niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride. 4. The sintering method according to item 1, wherein the content of the ceramic particles for sintering and the content of the sintering aid constituting the mixture are 90 to 97 mass % and 3 to 10 mass %, respectively, when the total of the two is taken as 100 volume %. 5. A sintering aid used in the sintering method according to item 1 above, which contains a metal fluoride. 6. The above metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, titanium fluoride Item 6. The sintering aid according to item 5, which is at least one selected from the group consisting of fluorine, niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride. Effect of the Invention

[0008] According to the sintering method of the present invention, the metal fluoride has a higher laser absorption rate than the sintering ceramic, and this makes it possible to efficiently sinter the sintering ceramic by simply irradiating the mixture with a laser. The sintering aid of the present invention is suitable for producing a ceramic sintered body. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the sintering method of the present invention, in which (A) is an example of a sintering apparatus, and (B) and (C) are examples of an article having a sintered part obtained after laser irradiation. [Diagram 2] 1 is an image showing the inside of a sintered product obtained in Example 1. [Diagram 3] This is an enlarged image of Figure 2. [Figure 4] 2 shows X-ray diffraction images of a precursor molded body before laser irradiation and a sintered product after laser irradiation in Example 1. [Diagram 5] 1 is an image showing the inside of the sintered product obtained in Example 2. [Figure 6] FIG. 6 is an enlarged image of FIG. [Figure 7] 1 is an image showing the inside of a sintered product obtained in Example 3. [Figure 8] FIG. 8 is an enlarged image of FIG. [Figure 9] 1 is an image showing the inside of the sintered product obtained in Example 4. [Figure 10] FIG. 10 is an enlarged image of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The sintering method of the present invention is characterized by comprising a step of irradiating a mixture containing ceramic particles to be sintered and a sintering aid containing a metal fluoride with a laser. A typical sintering method will be described below with reference to FIG.

[0011] FIG. 1(A) is a schematic diagram of a sintering device 10 that irradiates a laser oscillated from a laser light source 13 onto the surface of a molded product 11 (e.g., a plate-shaped molded product) made of a mixture containing ceramic particles for sintering and a sintering aid containing a metal fluoride in a chamber 17. For example, when a laser having a wavelength of 350 to 2500 nm is irradiated onto the ceramic particles for sintering and the metal fluoride, respectively, the metal fluoride has a higher energy absorption rate of the laser, so that when the laser is irradiated onto the molded product 11, the laser irradiated portion of the molded product 11 instantly reaches a temperature at which the ceramic particles for sintering are sintered, and a sintered portion 20 shown in FIG. 1(B) or (C) is formed. The sintered portions 20 in FIG. 1(B) and (C) have different sintering depths, and the sintering depths can be adjusted, for example, by the shape or size (thickness, etc.) of the molded product 11, the laser irradiation conditions, etc.

[0012] The ceramics constituting the ceramic particles to be sintered are not particularly limited, and may be oxides, nitrides, oxynitrides, or the like. Examples of the oxide include aluminum oxide, mullite, magnesium oxide, zinc oxide, titanium oxide, iron oxide, yttrium oxide, zirconium oxide, stabilized zirconia, and barium titanate. Examples of the nitride include silicon nitride, aluminum nitride, titanium nitride, zirconium nitride, tantalum nitride, and iron nitride. Examples of the oxynitride include sialon and silicon oxynitride.

[0013] The shape and size of the ceramic particles for sintering are not particularly limited. The particle shape can be a solid body, such as a sphere, an oval sphere, a polyhedron, a line, a plate, or an irregular shape. The particle diameter is preferably 10 nm to 100 μm, more preferably 100 nm to 10 μm. In general, as in the molded product 11 in FIG. 1, a raw material molded body consisting of a mixture of ceramic particles for sintering and a sintering aid is irradiated with a laser, so that if the raw material packing density of the raw material molded body is high, a dense ceramic sintered body can be produced. Therefore, by using a raw material molded body containing ceramic particles for sintering having a wide particle size distribution between 100 nm and 10 μm, for example, a raw material molded body containing two or more types of ceramic particles for sintering having different average particle sizes, a dense ceramic sintered body can be efficiently produced.

[0014] The sintering aid contains a metal fluoride, and depending on the type of ceramic to be sintered that constitutes the ceramic particles to be sintered, may further contain conventionally known sintering aids (hereinafter referred to as "other sintering aids"), but typically consists of one or more types of metal fluorides.

[0015] Metal fluorides include calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, and Examples of fluoride include antimony, titanium fluoride, niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride, and lutetium fluoride. The above metal fluorides are treated with a compound having the general formula MF n When expressed as (M: metal atom), MF contains M different from the metal atom of the ceramic to be sintered that constitutes the ceramic particle to be sintered. n It is preferable to use:

[0016] The other sintering aids include ceramics different from the ceramics to be sintered that constitute the ceramic particles to be sintered.

[0017] The shape and size of the sintering aid are not particularly limited.

[0018] In order to ensure efficient sintering, the contents of the sintering ceramic particles and sintering aid contained in the molded product 11 before laser irradiation are preferably 90 to 97 volume % and 3 to 10 volume %, more preferably 92 to 96 volume % and 4 to 8 volume %, and even more preferably 93 to 95 volume % and 5 to 7 volume %, respectively, assuming the total of both to be 100 volume %.

[0019] The type of laser to be irradiated onto the molded product 11 containing the ceramic particles to be sintered and the sintering aid is not particularly limited, and a solid-state laser, a gas laser, a semiconductor laser, a fiber laser, etc. can be used. Among these, a fiber laser is preferred. A fiber laser is a laser that is transmitted in a state in which a laser is confined in the fiber by generating an induced discharge in a core doped with a rare earth element or the like in an optical fiber. A device that oscillates a fiber laser may be connected to a device that oscillates another laser such as a solid-state laser to form a laser oscillation device with a higher output.

[0020] The conditions for irradiating the molded product 11 with the laser are appropriately selected depending on the type of ceramic constituting the ceramic particles to be sintered, the type of sintering aid, the content ratio of the ceramic particles to be sintered and the sintering aid, and the like.

[0021] The wavelength of the laser is not particularly limited and can be 300 to 10,000 nm, but is preferably 350 to 2,500 nm, and more preferably 500 to 1,500 nm. As described above, when a laser having a wavelength of 350 to 2,500 nm is irradiated, the laser irradiated portion of the molded product 11 instantaneously reaches the sintering temperature, and sintering proceeds. The present inventors believe that when a laser having a wavelength of 350 to 2,500 nm in particular is irradiated to the molded product 11, oxygen in the air, or oxygen in the case where the ceramic particles for sintering are oxide particles, reacts with fluorine in the metal fluoride, and at this time, the laser absorbency is improved for anion deficiency, and the sintering reaction proceeds more easily.

[0022] From the viewpoint of smooth sintering, the laser output is preferably 1 to 1000 W / cm 2 , more preferably 500 to 1000 W / cm 2 It is.

[0023] There is no particular limitation on the method of irradiating the molded product 11 with a laser. When forming a large-area sintered portion on the molded product 11, a method of irradiating the molded product 11 with a laser while scanning it or changing the optical path via a light diffusion lens while the molded product 11 is fixed, or a method of irradiating the molded product 11 with a laser with a fixed optical path while moving the molded product 11 can be applied.

[0024] When the molded product 11 is irradiated with a laser, the atmosphere is not particularly limited and may be air, nitrogen, argon, helium, etc. In the sintering apparatus of Fig. 1(A), the laser irradiation may be performed in a state in which the chamber 17 is filled with the above gas, or in a state in which the introduction and exhaust of the above gas are repeated.

[0025] When irradiating the laser, the molded article 11 may be preheated as necessary. The preheating method is not particularly limited, and may be an infrared lamp, a halogen lamp, resistance heating, high-frequency induction heating, microwave heating, or the like.

[0026] According to the sintering method of the present invention, sintering progresses in the depth direction from the surface of the molded product 11 irradiated with the laser, and depending on the type of sintering ceramics contained in the molded product 11, the formed sintered part has laser transparency, and as long as the laser attenuation is not large, sintering can be performed deep into the irradiated part of the molded product 11. Therefore, by appropriately setting the laser irradiation conditions, it is possible to obtain an article 30 having a sintered part 20 having the structure shown in Fig. 1(C), for example.

[0027] The sintering aid of the present invention is a sintering aid for laser sintering used in the sintering method of the present invention. Depending on the type of ceramic constituting the ceramic particles for sintering or the type of metal fluoride, the grain boundaries of the ceramic sintered body obtained by laser irradiation may be filled with the reaction product of the ceramic constituting the ceramic particles for sintering and the metal fluoride, so the metal fluoride can act not only as a sintering aid but also as a grain boundary forming material. EXAMPLES

[0028] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0029] In the following experiments, a fiber laser emitting a laser with a wavelength of 1070 nm was used to irradiate a disk-shaped molded body (outer diameter: 15 mm, thickness: 1.8 mm) consisting of α-alumina particles or yttria-stabilized zirconium oxide particles and metal fluoride powder (sintering aid) via a galvanometer mirror.

[0030] Example 1 "AA-3" (trade name, median particle size: 3.5 μm) and "AA-03" (trade name, median particle size: 0.40 μm) from the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. were mixed in a volume ratio of 7:3, and then this mixed powder was mixed with yttrium fluoride powder in a volume ratio of 95:5. Thereafter, this mixed raw material was subjected to powder compaction to obtain a disk-shaped compact (hereinafter referred to as "raw material compact (P1)"). Next, the laser power was increased to 1000W / cm 2 The laser was irradiated with a beam diameter of 8 mm while scanning the entire surface of the raw material compact (P1) at a speed of 100 mm per second, to obtain a ceramic sintered body (hereinafter referred to as "sintered body (X1)").

[0031] The obtained sintered body (X1) was broken, and the microstructure inside the sintered body was observed by an electron microscope (see Figure 2). From Figure 2, it was found that the sintered body (X1) was a dense sintered body. Furthermore, from Figure 3, which is an enlarged image of Figure 2, it was found that the grain boundary crystal phase was dispersed in the alumina crystal phase. The relative density was measured by the Archimedes method and was found to be 92%. Furthermore, when the sintered body (X1) was subjected to X-ray diffraction measurement, as shown in FIG. 4, the diffraction image of the raw material compact (P1) before the laser irradiation included a pattern of α-alumina and yttrium fluoride, and the diffraction image of the sintered body (X1) included a pattern of α-alumina and Y3Al5O 12 (hereinafter referred to as "YAG") pattern.

[0032] Example 2 Laser power is set to 700W / cm 2 A ceramic sintered body (hereinafter, referred to as "sintered body (X2)") was obtained by the same operation as in Example 1, except for changing the above. The obtained sintered body (X2) was broken and the microstructure inside the sintered body was observed. It was found from Figures 5 and 6 that the sintered body (X2) was slightly coarser than the sintered body (X1), but was sufficiently sintered. The relative density was 78%.

[0033] Example 3 A ceramic sintered body (hereinafter referred to as "sintered body (X3)") was obtained by the same operation as in Example 1, except that barium fluoride powder manufactured by Kojundo Chemical Laboratory was used instead of yttrium fluoride powder, and the volume ratio of α-alumina single crystal mixed particles and barium fluoride powder was 90:10. The obtained sintered body (X3) was broken and the microstructure inside the sintered body was observed. From Figs. 7 and 8, it was found that the sintered body (X3) was sufficiently sintered.

[0034] Example 4 A ceramic sintered body (hereinafter referred to as "sintered body (X4)") was obtained by the same operation as in Example 1, except that yttria-stabilized zirconium oxide particles (average particle size: 1 μm) manufactured by Tosoh Corporation were used instead of the α-alumina single crystal mixed particles, and the volume ratio of the yttria-stabilized zirconium oxide particles and yttrium fluoride powder was set to 95:5. The obtained sintered body (X4) was broken and the microstructure inside the sintered body was observed. From Figs. 9 and 10, it was found that the sintered body (X4) was sufficiently sintered. [Industrial Applicability]

[0035] According to the sintering method of the present invention, the ceramic to be sintered can be sintered in a shorter time than when the laser is directly irradiated only to the ceramic particles to be sintered. Therefore, a sintered product or a shaped product can be produced with high accuracy and speed by using a desired portion of the non-sintered part containing the ceramic particles to be sintered as the sintered part. [Explanation of symbols]

[0036] 10: Sintering equipment 11: Mixture of ceramic particles for sintering and sintering aids (molded product) 13: Laser light source 15: Pedestal 17: Chamber 20: Sintering section 30: Article having a sintered part (sintered product)

Claims

1. A sintering method comprising the step of irradiating a laser onto a mixture containing ceramic particles to be sintered and a sintering aid containing a metal fluoride.

2. The wavelength of the laser is 350 to 2500 nm, and the output is 1 to 1000 W / cm ２ The sintering method according to claim 1,

3. The metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, or titanium fluoride.

2. The sintering method according to claim 1, wherein the fluoride is at least one selected from the group consisting of niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride.

4. The sintering method according to claim 1, wherein the content ratios of the sintering ceramic particles and the sintering aid constituting the mixture are 90 to 97% by volume and 3 to 10% by volume, respectively, when the total of the two is 100% by volume.

5. A sintering aid used in the sintering method according to claim 1, comprising a metal fluoride.

6. The metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, or titanium fluoride.

6. The sintering aid according to claim 5, which is at least one selected from the group consisting of niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride.

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