SPHERICAL EUCRYPTITE PARTICLES AND METHOD FOR PRODUCING SAME

Abstract

The present invention addresses the problem of providing: spherical eucryptite particles which have higher circularity than in the prior art, have a large negative thermal expansion and a high thermal conductivity, have high flowability, dispersibility, and filling capability, and are also applicable in the field of semiconductors; and a method for producing the spherical eucryptite particles. As a means for solving the problem, the present invention provides: the method for producing the spherical eucryptite particles characterized by heat treating, at 600 to 1100 C., spherical particles which have been thermally sprayed with a feedstock powder that includes 45 to 55 mol % of SiO.sub.2, 20 to 30 mol % of Al.sub.2O.sub.3, and 20 to 30 mol % of Li.sub.2O, and obtaining spherical particles that include 89% or more of a eucryptite crystalline phase; and the spherical eucryptite particles obtained by this method.

Claims

1. Spherical eucryptite particles comprising a eucryptite crystalline phase containing 45 to 55 mol % of SiO.sub.2, 20 to 30 mol % of Al.sub.2O.sub.3 and 20 to 30 mol % of Li.sub.2O, and having a circularity of 0.90 to 1.0.

2. The spherical eucryptite particles according to claim 1, wherein said particles have a thermal expansion coefficient is 210.sup.6/K to 1010.sup.6/K.

3. The spherical eucryptite particles according to claim 1, wherein the average particle diameter (D50) is more than 1 m to 100 m.

4. A method for producing spherical eucryptite particles according to claim 1, wherein said spherical particles are obtained by thermally spraying a feedstock powder containing 45 to 55 mol % of SiO.sub.2, 20 to 30 mol % of Al.sub.2O.sub.3 and 20 to 30 mol % of Li.sub.2O, and heat treated to obtain spherical particles containing 89% or more of a eucryptite crystalline phase.

5. The method for producing spherical eucryptite particles according to claim 4, wherein the thermally sprayed spherical particles are heat treated at 500 to 1000 C. for 1 to 48 hours.

6. The spherical eucryptite particles according to claim 2, wherein the average particle diameter (D50) is more than 1 m to 100 m.

7. A method for producing spherical eucryptite particles according to claim 2, wherein said spherical particles are obtained by thermally spraying a feedstock powder containing 45 to 55 mol % of SiO.sub.2, 20 to 30 mol % of Al.sub.2O.sub.3 and 20 to 30 mol % of Li.sub.2O, and heat treated to obtain spherical particles containing 89% or more of a eucryptite crystalline phase.

8. A method for producing spherical eucryptite particles according to claim 3, wherein said spherical particles are obtained by thermally spraying a feedstock powder containing 45 to 55 mol % of SiO.sub.2, 20 to 30 mol % of Al.sub.2O.sub.3 and 20 to 30 mol % of Li.sub.2O, and heat treated to obtain spherical particles containing 89% or more of a eucryptite crystalline phase.

Description

EXAMPLES

[0071] Hereinafter, the present invention will be described in more details with reference to Examples and Comparative Examples. However, the present invention is not construed as being limited to the following examples.

[0072] Particles obtained by thermally spraying feedstock powders having various compositions and different particle diameters were heated to 700 C. at a rate of temperature increase of 100 C./hour in the atmosphere and held for 6 h and then cooled to a room temperature at a temperature lowering rate of 100 C./hour.

[0073] The average particle diameter, composition, circularity and thermal expansion coefficient of the obtained particles are shown in Table 1.

[0074] Here, the average particle diameter of the obtained particles was measured by particle size distribution measurement by a laser diffraction method, the composition was analyzed by an atomic absorption method, and the crystalline phase was measured by X-ray diffraction. The circularity was measured using a flow type particle image analyzer. Further, the obtained particles were mixed with an epoxy resin to prepare a resin mixture, and the thermal expansion coefficient of the resin composition at RT to 300 C. was measured. Assuming that the thermal expansion coefficient of the epoxy resin is 11910.sup.6/K, the thermal expansion coefficient of the particles was calculated.

[0075] It was confirmed by X-ray diffraction that each of Sample Nos. 1 to 6 according to the present invention contained 90% or more of eucryptite crystalline phase. In Sample Nos. 1 to 6, spherical particles having a circularity as high as 0.91 to 0.97 were obtained, and their thermal expansion coefficients were negative values of 2.6 to 7.610.sup.6/K. In Sample No. 7, since the particles had a small diameter, they formed a strong agglomerate by the heat treatment and could not be used as particles. In the case of Sample Nos. 8 to 10 which are outside the composition range of the present invention, only those with a thermal expansion coefficient having positive values of 0.4 to 2.110.sup.6/K were obtained. Also, the particles obtained by thermally spraying a feedstock which is the same as

[0076] Sample No. 2 were heated in the atmosphere to 450 to 1100 C. at a rate of temperature increase of 100 C./hour and maintained for a predetermined time and then cooled to a room temperature at a cooling rate of 100 C./hour. The composition, circularity and thermal expansion coefficient of the obtained particles are shown in Table 2. Sample Nos. 11 to 16, which were heat treated at 500 to 1000 C., had a high circularity of 0.91 to 0.97 and a thermal expansion coefficient of negative values of 2.1 to 9.110.sup.6/K. In Sample No. 17, which was heat treated at 450 C., an amorphous pattern was observed by X-ray diffraction, and its thermal expansion coefficient was a positive value of 2.110.sup.6/K. In addition, in Sample No. 18, which was heat treated at 1100 C., agglomeration of particles occurred, and spherical particles could not be obtained.

TABLE-US-00001 TABLE 1 Ex. Ex. Ex. Ex. Ex. No. 1 2 3 4 5 Ave. Dia.(D50) m 1.4 6.5 29 91 118 SiO.sub.2 mol % 50.6 50.4 54.7 53.7 45.8 Al.sub.2O.sub.3 mol % 24.1 21.3 20.8 25.6 27.2 Li.sub.2O mol % 25.3 28.3 24.5 20.7 27.0 Circularity 0.92 0.97 0.95 0.93 0.91 Thermal 10.sup.6/K 7.6 4.9 2.6 3.1 2.8 Expansion Coefficient Comp. Comp. Comp. Comp. Ex. Ex. Ex. Ex. Ex. No. 6 7 8 9 10 Ave. Dia.(D50) m 24 0.8 15 23 21 SiO.sub.2 mol % 49.6 56.4 44.1 56.1 54.7 Al.sub.2O.sub.3 mol % 29.1 21.2 31.2 25.9 19.1 Li.sub.2O mol % 21.3 22.4 24.7 18.0 26.2 Circularity 0.94 agglo. 0.91 0.90 0.92 Thermal 10.sup.6/K 3.4 1.4 2.1 0.4 Expansion Coefficient

TABLE-US-00002 TABLE 2 Ex. Ex. Ex. Ex. Ex. No. 11 12 13 14 15 Heat Treat. C. 500 600 700 800 900 Temp. Heat Treat. h 48 24 6 6 4 Hold. Time SiO.sub.2 mol % 50.4 50.4 50.4 50.4 50.4 Al.sub.2O.sub.3 mol % 21.3 21.3 21.3 21.3 21.3 Li.sub.2O mol % 28.3 28.3 28.3 28.3 28.3 Circularity 0.97 0.97 0.97 0.96 0.94 Thermal 10.sup.6/K 2.1 3.3 4.9 6.4 8.3 Expansion Coefficient Ex. Comp. Ex. Comp. Ex. No. 16 17 18 Heat Treat. C. 1000 450 1100 Temp. Heat Treat. h 1 48 1 Hold. Time SiO.sub.2 mol % 50.4 50.4 50.4 Al.sub.2O.sub.3 mol % 21.3 21.3 21.3 Li.sub.2O mol % 28.3 28.3 28.3 Circularity 0.91 0.97 agglo. Thermal 10.sup.6/K 9.1 2.1 7.8 Expansion Coefficient