US 12,351,521 B2
Silicon nitride ceramic material for mobile phone rear cover and preparation method therefor
Jingxian Zhang, Shanghai (CN); Yusen Duan, Shanghai (CN); Ning Liu, Shanghai (CN); Ruixin Ma, Shanghai (CN); and Dongliang Jiang, Shanghai (CN)
Assigned to SHANGHAI INSTITUTE OF CERAMICS, CHINESE ACADEMY OF SCIENCES, Shanghai (CN)
Appl. No. 17/275,148
Filed by SHANGHAI INSTITUTE OF CERAMICS, CHINESE ACADEMY OF SCIENCES, Shanghai (CN)
PCT Filed Aug. 30, 2019, PCT No. PCT/CN2019/103757
§ 371(c)(1), (2) Date Mar. 10, 2021,
PCT Pub. No. WO2020/052453, PCT Pub. Date Mar. 19, 2020.
Claims priority of application No. 201811057057.X (CN), filed on Sep. 11, 2018.
Prior Publication US 2022/0041512 A1, Feb. 10, 2022
Int. Cl. C04B 35/591 (2006.01); C04B 35/626 (2006.01); C04B 35/634 (2006.01); H04M 1/02 (2006.01)
CPC C04B 35/591 (2013.01) [C04B 35/6342 (2013.01); H04M 1/026 (2013.01); C04B 35/6261 (2013.01); C04B 2235/3217 (2013.01); C04B 2235/3225 (2013.01); C04B 2235/3241 (2013.01); C04B 2235/6586 (2013.01); C04B 2235/77 (2013.01); C04B 2235/9607 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A preparation method of silicon nitride ceramic for a mobile phone rear cover, comprising:
(1) dispersing a mixture containing a silicon source, an oxide of a transition metal, a first sintering aid and an oxide of rare earth metal in an organic solvent to obtain a mixture of raw materials;
(2) adding a dispersant to the mixture of raw materials and then adding a binder and/or a plasticizer and mixing evenly to obtain a mixture to be shaped; and
(3) shaping the mixture to be shaped into a green body, and sintering the green body to obtain the silicon nitride ceramic,
wherein the oxide of the transition metal is chromic oxide or hafnium oxide and serves as a first colorant,
wherein the first sintering aid is selected from the group consisting of Al2O3, AlN, CaO, MgO, and SiO2,
wherein the oxide of the rare earth metal is selected from the group consisting of yttrium oxide, europium oxide, and erbium oxide and serves both as a second sintering aid and a second colorant,
wherein a mass ratio of the first sintering aid and the second sintering aid is 3:(5 to 8),
wherein the silicon source is a silicon nitride powder and/or a silicon powder, and the mass ratio of the silicon source, the first colorant, and the mixture of the first and the second sintering aid is 160:2:15, and the mass of the silicon source is converted into that of silicon nitride for calculation, and
wherein the silicon nitride ceramic has the following characteristics:
a density of 3.2 to 3.4 g/cm3;
a toughness of more than 12 MPa·m1/2;
a strength of 500 MPa to 1,100 MPa;
a thermal conductivity of 40 W/m·K to 70 w/m·K;
a dielectric constant of 7.4 to 9.4;
a dielectric loss of 10×10−4 to 15×10−4; and
a relative density of 95.0% to 99.5%.