A high strength, high toughness, high thermal conductivity silicon nitride ceramic material and preparation method thereof
A technology of silicon nitride ceramics and raw materials, applied in the field of high toughness, high thermal conductivity silicon nitride ceramic materials and its preparation, and high strength, can solve the problems of restricting large-scale application, low thermal conductivity of ceramics, and poor mechanical properties , to achieve the effect of improving thermal conductivity, improving thermal conductivity, bending strength and fracture toughness
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[0034] As an example of the preparation of mixed powder, including: 3 N 4 The powder is mixed with the sintering aid, and the powder is uniformly mixed after ball milling, drying and sieving. Ball milling can use vacuum ball milling tank wet ball milling, and the atmosphere in the ball mill tank can be vacuum or filled with Ar, N 2 , the wet ball milling uses alcohol as the solvent, the material: solvent ratio can be (1:1) ~ (3:1), the material: ball ratio can be (1:1) ~ (5:1), and the number of ball milling revolutions is 200 ~500rpm, ball milling time is 4 ~ 20h. Drying can be carried out by rotary evaporation drying or vacuum drying. The whole drying process can be carried out in vacuum, Ar, N 2 in a protective atmosphere. Wherein, the drying temperature may be 50°C to 100°C, and the drying time may be 8 to 24 hours. The mesh number of the sieve can be 60-300 meshes.
[0035] The mixed powder is pressed into shape to obtain a green body. Compression molding may inclu...
Embodiment 1
[0046] With 0.5wt% Y and 1.5wt% MgO as sintering aids, and 98wt% α-Si 3 N 4 The powder is mixed by ball milling, dried and sieved to obtain a uniformly mixed powder; then dry-pressed under 20MPa pressure, and then cold isostatic pressing under 250MPa pressure; the obtained body is placed in a BN crucible , pre-sintered at 800 °C for 4 h in an Ar atmosphere; then the pre-sintered body was pressure-sintered at 1900 °C, where the heating rate was 10 °C / min, N 2 The pressure is 1MPa, and the holding time is 4h; after sintering, it is cooled to 1200°C at a cooling rate of 10°C / min, and then cooled to room temperature with the furnace.
[0047] The thermal conductivity of the silicon nitride ceramic material prepared in Example 1 is 95.2W / (m·K), the three-point bending strength is 713±21MPa, and the fracture toughness is 9.91±0.19MPa·m 1 / 2 .
Embodiment 2
[0049] With 2.5wt% Y and 1.5wt% MgO as sintering aids, and 96wt% α-Si 3 N 4 The powders are mixed by ball milling, sieved after drying to obtain uniformly mixed powders; then dry-pressed under 30MPa pressure, and then cold isostatic pressing under 300MPa pressure; the obtained body is placed in a BN crucible , pre-sintered at 1400 °C for 6 h in an Ar atmosphere; then the pre-sintered green body was pressure-sintered at 1850 °C, where the heating rate was 5 °C / min, N 2 The pressure is 1MPa, and the holding time is 4h; after sintering, it is cooled to 1000°C at a cooling rate of 10°C / min, and then cooled to room temperature with the furnace.
[0050] The thermal conductivity of the silicon nitride ceramic material prepared in Example 2 is 87.6W / (m·K), the three-point bending strength is 1018±29MPa, and the fracture toughness is 8.51±0.21MPa·m 1 / 2 .
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